A method of accommodating an element in a building equipment component. The presence of the element may be detected, and whether the element is required may be determined. The building equipment component may be operated if the element is present and required, or if the element not required. If the element is absent but required, the building equipment component may be stopped. In some instances, the building equipment component may include a required first sensor, and the element may be an optional second sensor.

Commercial and residential buildings employ a variety of different building equipment components. Examples of typical building equipment components include heating and cooling equipment such as furnaces, boilers, heat pumps and the like. Other examples of typical building equipment components include water heaters, air exchangers and other ventilation equipment and similar equipment. A variety of HVAC equipment employ dampers, zone valves and the like.
In particular, water heaters are used in homes, businesses and just about any establishment having the need for heated water. Water heaters often heat water using the simple "heat rises" principle. In operation, water heaters typically heat cold or ambient temperature water entering at or near the bottom of the water heater to a desired temperature using a gas-fired burner, an electric heater or some other heater element. During a heating cycle, the cold or ambient temperature water at or near the bottom of the water heater becomes hotter and begins to rise towards the top of the water heater. Cooler and denser water, once on top of the water being heated, falls toward the bottom of the water heater so that it can be heated or reheated to the desired temperature. After the temperature of the water at the bottom of the water heater reaches a certain desired temperature, the water heater typically stops heating the water for a period of time.
When demand for hot water arises (e.g., someone turns on a faucet to run a shower), fresh, cold or ambient temperature water enters the water heater and "pushes out" or supplies the hotter water at or near the top of the water heater. When a sufficient amount of the hotter water exits from the top of the water heater so that the fresh, cold or ambient temperature water entering the bottom causes the temperature of the water at the bottom of the tank to drop below a set point temperature, the water heater typically turns on and repeats the heat cycling described above.
A conventional water heater typically has at least one heating element or "heater," such as a gas-fired and/or electric burner. To take advantage of the "heat-rises" principle, the heater is typically located at or near the bottom of the water heater tank. Each water heater typically also has at least one thermostat or controller for controlling the heater.
To facilitate the heating of water, the controller often receives signals related to the temperature of the water. When these signals indicate that the water temperature is below a first set point, for example, when the water temperature is below 120 degrees Fahrenheit, the controller turns on the heater and the water at or near the bottom of the water heater begins to heat. After some time, the temperature of the water at the bottom of the water heater will increase to a second set point, which, for example, may be about 140 degrees Fahrenheit. When the water temperature at the bottom of the tank is indicated as being greater than the second set point, the controller typically causes the heater to reduce its heat output or, alternatively, causes the heater to turn off. The heat cycle begins again when the temperature of the water at the bottom of the water heater drops below the first set point.
Some water heaters rely upon a single water temperature sensor, while others employ two water temperature sensors. In some cases, using two water temperature sensors, such as one at or near the top of a water heater and a second at or near the bottom of a water heater, may provide improved temperature control resulting in energy savings, higher hot water capacity, and greater potential safety.
As described above, the hottest water in a water heater may typically be found at or near the top of the water heater tank. As a result, the water at or near the top of the water heater tank may be substantially hotter than the water at or near the bottom of the water heater tank, such as where a single water temperature sensor may be located. This means that the water at or near the top of the water heater tank may be hotter or even substantially hotter than a lower, safer temperature, such as may be indicated by the water temperature sensor at or near the bottom of the water heater tank.
Thus, in some cases a water heater includes a second temperature sensor that may be positioned at or near the top of the water heater tank, in order to provide the controller with information pertaining to the water temperature at or near the top of the water heater tank. The second temperature sensor positioned at or near the top of the water heater tank may also be useful in reducing or eliminating stratification, which may occur as a result of frequent small hot water withdrawals from the water heater tank.

Building equipment component control with automatic feature detection


A headset (1) comprising a switch (15; 19) and an actuating member (13), which is turnable in relation to the housing (2) about a first axis (A1). An ear hook (3; 32) is attached to the actuating member (13). The ear hook (3; 32) can be arranged in a right ear mode for wearing the headset (1) at the right ear and a left ear mode for wearing the headset at the left ear. The switch (15; 19) switches the headset electronics from an active state to a passive state, when the ear hook (3) is turned about the first axis (A1) in a first direction (P1) from an active position to a first passive position. The switch (15; 19) switches the headset electronics from the active state to the passive state when the ear hook (3) is turned about the first axis (A1) in the second direction (P2) from the active position to a second passive position.

Communication headsets are becoming more and more widely used. Especially, small Bluetooth headsets to be used with cellular phones have become increasingly popular the recent years.
A modern headset is a small compact unit with small operating buttons on the surface. In order to change mode of the headset, e.g. switching the headset on/off or answering a telephone call, the user typically presses a small momentary button. As the headset is a small unit, the button is often very small and it can be cumbersome to press it correctly. Thus, it is desirable to provide switching function of a headset without this disadvantage.
U.S. Pat. No. 7,046,799 discloses a headset with a pivotally mounted ear hook and an activation switch that activates the headset when the ear hook is in an open position and deactivates the headset when the ear hook is in a closed position.
WO 2008/145127 discloses a headset with a turnable speaker tower wherein the headset can be switched on and off by turning the speaker tower about an axis. According to an embodiment, an ear hook can be attached to the speaker tower. When the ear hook is arranged for right ear use, the ear hook is turned into a compact position, when the headset is switched off. This is very advantageous, as the headset takes up less space. Furthermore, the risk of unintended switching "on" is small, as it requires that the ear hook must be turned into an active and less compact position. However, when the ear hook is arranged for left ear use, the ear hook is not turned into a compact position when the headset is switched off. Thus, the ear hook points away from the headset housing, which is disadvantageous, if the user wants to keep the headset in his pocket or the like. Furthermore, the risk of unintended switching "on" can be higher when the ear hook is not kept in a compact position.

Headset with turnable ear hook with two off positions


A reset signal generating circuit is provided between a power supply voltage terminal for supplying an electric voltage and ground for being maintained at a given potential. A CR time constant circuit has a first transistor and a first capacitor connected in series. A control circuit sets the start of operation for the first transistor. A discharge circuit discharges the electric charge stored on the first capacitor when electric power supply is turned off. A protection circuit against a negative over-voltage applied to the first transistor by the discharge circuit. To this end, a reset signal generating circuit provides a reset signal when restarting a power supply and positively outputting a reset signal even where the power supply has an abrupt rising characteristic, without consuming electric current in a steady state.

This invention relates to a reset signal generating circuit for generating a reset signal during turning on a power supply. More particularly, the invention is concerned with a reset signal generating circuit which is adapted to reduce consumption of electric power by a reset circuit during operating a system circuit, and generate a reset signal without fail regardless of a rising characteristic in power supply voltage during resetting the system circuit.
Conventionally, there have been reset signal generating circuits for resetting a system circuit during turning on a power supply, as shown in FIG. 4(a) and FIG. 4(b).
The circuit of FIG. 4(a) is a reset signal generating circuit that uses a CR time constant circuit adapted to supply to an output terminal R.sub.OUT a low level signal lower than a power supply voltage V.sub.cc for a time period determined by the on-resistance R of a transistor Q5 and the capacitance of a capacitor C5. That is, the transistor Q5 formed for example by a PMOSFET and the capacitor C5 are connected in series between a terminal of power supply V.sub.cc and a ground GND. While the capacitor C5 is being charged after turning on the transistor Q5, a low level signal lower in voltage than a power supply voltage V.sub.cc is outputted through the output terminal R.sub.OUT. Here, the transistor Q5 has a gate connected to the ground GND.
This circuit utilizes the on-resistance of the active-element transistor Q5 as a resistance instead of a passive-element resistance. Consequently, the transistor Q5 will not be turned on until the gate-to-source voltage of the transistor Q5 is raised to a threshold voltage. Here, the threshold voltage means a minimum voltage for turning on a transistor that is applied between the gate and the source of the transistor. As a result, the charging electricity to the capacitor C5 is not started until the threshold voltage of the transistor is reached, even where the slant of rising in the power supply voltage V.sub.cc is smaller than the slant of electricity charging given by the CR time constant, ensuring time period for voltage lower than the power supply voltage V.sub.cc.
The circuit shown in FIG. 4(b) includes voltage-divisional resistances R5, R6 connected in series between a power supply voltage V.sub.cc terminal and a ground GND, and a comparator COM connected to a connection point between these resistances. The divisional voltage V.sub.R6 taken out of the connection point is compared with a constant voltage V.sub.C by the comparator COM. The comparator COM outputs a low level signal as a reset signal to an output terminal R.sub.OUT, before the power supply voltage V.sub.cc becomes to such a level that the divisional voltage V.sub.R6 is higher than the constant voltage V.sub.C.
In the circuit of FIG. 4(a), however, the gate of the transistor Q5 is fixedly connected to the ground GND. Consequently, even after the power supply voltage V.sub.cc is turned off and becomes a zero voltage, there remains a potential corresponding to the threshold voltage V.sub.th of the transistor Q5. To this end, the capacitor C5 is not completely discharged and the potential on the output terminal R.sub.OUT is not to be reduced down to a zero voltage. As a result, where performing resetting by once turning off the power supply, there are cases that no reset signal be available on the output terminal R.sub.OUT.
Meanwhile, in the circuit of FIG. 4(b), if the power supply voltage V.sub.cc is abrupt in rising, there encounters a case that the time period for generating a reset signal to the output terminal R.sub.OUT is too brief to stably performing a reset operation. Further, this circuit has an electric current steadily flowing through the resistances R5, R6 connected between the power supply voltage V.sub.cc terminal and the ground GND. There is a problem that it is inconvenient for use in an integrated circuit for portable electric appliances and devices because of relatively high electric power consumption.

Low-power reset signal generating circuit improved in voltage rising characteristic


A gas booster system in which a variable frequency drive is used to control, by means of a variable speed motor, the compression rate of a pump in a gas turbine combustion engine. The rate of the variable speed motor, and thus the rate of compression, is controlled by monitoring turbine temperature. The gas turbine system responds to the turbine temperature to regulate the rate of compression of the fuel.

This invention relates to a system and a method for increasing the efficiency and for improving the control of gas turbines and associated gas booster systems.
Gas booster systems for gas turbine (e.g. microturbine) systems are well known. A conventional gas turbine system typically includes a gas booster system to supply pressurized gaseous fuel to a combustion chamber that generates high temperature exhaust for the turbine. Various parameters have been used to control the flow rate and pressure of the fuel being supplied to the gas turbine engine. An example of a conventional system is disclosed in U.S. Pat. No. 4,178,754. This system includes a positive displacement gear type fuel pump. The fuel pressure is controlled by bypassing flow using a pressure regulator. The fuel flow rate is controlled using a metering valve. The regulator and the metering valve operate in response to turbine operating conditions as represented by the following parameters: turbine inlet temperature, compressor inlet temperature, and compressor exit pressure. Similarly, in U.S. Pat. No. 5,850,733, which is incorporated herein by reference, the fuel flow to a gas turbine is controlled, in part, based on the gas turbine exhaust temperature.
In some conventional gas turbine systems, a reciprocating type compressor is used to compress the natural gas being used as fuel in the gas turbine combustion engine. These reciprocating compressors normally operate at a fixed rate of displacement. Accordingly, to regulate the fuel flow rate into the compressor, a system of valves is opened or closed in response to various system parameters. These systems are generally disfavored because the number of valves required in such a system require many pipe connections, resulting in an increased risk of leaks due to the intense vibrations generated by reciprocating compressors. Moreover, such systems include a significant lag-time between the time when the parameter is detected and the time when the system adequately responds by opening or closing one of the valves in the system.
U.S. Pat. No. 5,606,853 describes a system in which the rate of compression in a screw type compressor can be changed using a variable speed motor. By changing the compression rate, the fuel flow rate into the combustion chamber can be adjusted thereby eliminating the need for a system of valves which are opened and closed in response to a measured system parameter. The speed of the motor driving the compressor is dependant on a computer signal generated in response to a measurement of the power output of the turbine. However, measurements of turbine power output do not provide as accurate a measure of system conditions as do measurements of the turbine temperature. Specifically, fuel demand is more accurately determined by measuring turbine inlet and exhaust temperatures. Thus, there remains a need to provide a gas booster system that automatically supplies the appropriate amount of fuel at the appropriate pressure to the combustion chamber based on either the turbine inlet or exhaust temperature.
The present invention addresses this need and provides other benefits as described further below.
The system provides a gas turbine system comprising: a pump for providing a gaseous fuel to a combustion chamber which produces an exhaust; an electric motor which drives the pump; a turbine which receives the exhaust from the combustion chamber; a sensor which measures a parameter of the temperature of the turbine; and a controller which adjusts the speed of said electric motor in response to the turbine temperature.
Preferably, the pump is a positive displacement pump, and among positive displace pumps it is ideally a rotary screw pump. Additionally, the sensor is preferably a thermocouple. The sensor may be positioned to measure the turbine temperature at an inlet or at an outlet of the turbine. The sensor may measure the turbine temperature by measuring the temperature of the combustion chamber exhaust before it enters the turbine inlet or by measuring the temperature of turbine exhaust which exits through the turbine outlet. Alternatively, the sensor may measure the turbine temperature by measuring the temperature of a metal part of the turbine inlet or outlet.
The controller controls the speed of the variable speed motor by sending a control signal, which is responsive to the temperature measured by the sensor, to a variable frequency drive. The variable frequency drive, in turn, adjusts the speed of the variable speed motor in response to the control signal sent by the controller. The control signal from the controller may be generated in numerous ways. In a first embodiment, a difference between the turbine temperature and a predetermined second temperature may be determined by the controller. A control signal corresponding to the difference between the temperatures may then be sent to the variable frequency drive which, in turn, adjusts the speed of the variable speed motor.
In this first embodiment, if the sensor is positioned at the turbine inlet, the predetermined second temperature may be between 1400xc2x0 and 1700xc2x0 F., and is preferably approximately 1600xc2x0 F. If, on the other hand, the sensor is positioned at the turbine outlet, the predetermined second temperature may be between 1175xc2x0 and 1550xc2x0 F.
In a second embodiment, the controller may send a control signal which is responsive to the measured turbine temperature (rather than to a difference between the turbine temperature and a predetermined second temperature) to the variable frequency drive. The variable frequency drive may then adjust the speed of the variable speed motor in response to the control signal.
Finally, the system may include a hermetically sealed passage connecting the pump to the combustion chamber. In this case, the hermetic seal ideally comprises a magnetic coupling.
A method for controlling a gas turbine system is also contemplated. The method includes: compressing a gaseous fuel with a pump controlled by an electric motor; forcing the compressed gaseous fuel into a combustion chamber; igniting the compressed gaseous fuel in the combustion chamber and thereby producing an exhaust which enters a turbine; measuring a temperature of the turbine; and controlling the speed of the electric motor in response to the turbine temperature.
In following this method, the step of compressing of the gaseous fuel is preferably completed by a positive displacement pump, and among positive displacement pumps it is ideally a rotary screw pump. The step of measuring the temperature of the turbine includes positioning a sensor, which is preferably a thermocouple, either at an inlet or at an out of the turbine. Moreover, the step of measuring the turbine temperature, contemplates either measuring the temperature of the combustion chamber exhaust before the exhaust enters the turbine through the turbine inlet or measuring the temperature of an exhaust which exits the turbine through the turbine outlet. In the alternative, the step of measuring the turbine temperature can be completed by measuring the temperature of a metal part of either the turbine inlet or the turbine outlet.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.


An example of a system that provides notary services on behalf of an application client running on a mobile device is described. The application client requests a notarization token from an application notary service client running on the same mobile device. The application notary service client utilizes a SIM card of the mobile device to generate a notarization token request which is sent to an application notary service server. The application notary service server utilizes a SIM signature validator server to validate the notarization token request and generates the notarization token for delivery to the application client via the application notary service client. The application client includes the notarization token in a request to an application server, which uses the notarization token to validate the application client for access to a function or data of the server.

In recent years, the popularity of smart mobile devices, such as smartphones and tablets, has exploded. Many of the functions that device users utilize on such devices are supported by mobile apps. A mobile app typically involves an application program stored on and executed by the mobile device. Many mobile applications, however, involve an interaction with a server program stored on and executed by server hardware in a network, such as a mobile communications network and/or the Internet. The application program on the mobile device serves as a client to obtain or consume a service offered by a server application running on a network computer platform. Although some types of such client programs, such as browsers, may communicate with a variety of servers to obtain different services, many mobile apps involve interaction of the client program with a specific corresponding server program. A mobile shopping app, for example, might utilize the shopping service vendor's client application program running on the mobile device to enable the mobile device to obtain information from and conduct transactions with a server of that same shopping service vendor. The client application in turn provides the user interface functionalities on the device, albeit as configured by the particular vendor for the shopping service.
Where the service provider offers a mobile app, with a mobile client configured to correspond to and specifically access that provider's server application, it may be undesirable for client applications of other parties to access information from and/or on that provider's server. By way of an example, consider a mobile network service provider that offers a mobile app allowing its device user-customers to access their usage and other account information on-line. Such a provider operates a server application on-line and offers for download a corresponding client application program for execution on the customers' mobile devices. The service provider in our example intends to allow users of its client application program access to the information but may prefer not to allow third party client applications access to the on-line information at the server, even if the other client applications are running on devices of customers of the service provider.
Currently, the backend services accessed via the server are able to check whether a client request originates from a customer device, but not from which application running in the device. For example, third party data meter apps exist in the marketplace for execution on mobile devices. These data meter apps are able to utilize a network service provider's backend service to obtain usage data corresponding to the user of the mobile device (e.g., minutes of use, data transferred, etc.), even if the provider's application server would desire such apps not to be able to access the usage data, because the backend service on the provider's application server cannot distinguish those third party data meter apps from the provider's own mobile app client program.

System for mobile application notary service


A threaded connection between adjacent tubular members includes a pin member providing an external wedge thread and a box member providing an internal wedge thread, wherein the internal wedge thread corresponds with the external wedge thread. Further, the threaded connection includes at least one interruption along a helical thread length of one of the external wedge thread and the internal wedge thread and at least two regions along an axial length of the threaded connection where the external wedge thread and the internal wedge thread form a thread seal.

1. Field of the Disclosure
The present disclosure generally relates to wedge-threaded tubular connections. More particularly, the present disclosure relates to wedge-threaded tubular connections having a plurality of thread interruptions along a helical thread length of at least one of a pin member and a box member.
2. Background Art
Casing joints, liners, and other oilfield tubulars are frequently used to drill, complete, and produce wells. For example, casing joints may be placed in a wellbore to stabilize and protect a formation against high wellbore pressures (e.g., wellbore pressures that exceed a formation pressure) that could otherwise damage the formation. Casing joints are sections of pipe (e.g., steel or titanium), which may be coupled in an end-to-end manner by threaded connections, welded connections, or any other connection mechanisms known in the art. As such, connections are usually designed so that at least one seal is formed between an interior of the coupled casing joints and the annulus formed between exterior walls of the casing joints and the interior walls of the wellbore (i.e., the formation). The seals may be elastomeric (e.g., an o-ring seal), thread seals, metal-to-metal seals, or any other seals known to one of ordinary skill in the art.
It should be understood that certain terms are used herein as they would be conventionally understood, particularly where threaded tubular joints are connected in a vertical position along their central axes such as when making up a pipe string for lowering into a wellbore. Typically, in a male-female threaded tubular connection, the male component of the connection is referred to as a "pin" member and the female component is called a "box" member. As used herein, "make-up" refers to engaging a pin member into a box member and threading the members together through torque and rotation. Further, the term "selected make-up" refers to the threading of a pin member and a box member together with a desired amount of torque or based on a relative position (axial or circumferential) of the pin member with respect to the box member. Furthermore, the term "box face" is understood to be the end of the box member facing outward from the box threads and the term "pin nose" is understood to be the end of the pin member facing outward from the threads of the connection. As such, upon make-up of a connection, the nose of the pin is stabbed or inserted into and past the face of the box.
Referring to the geometry of threads, the term "load flank" designates the side wall surface of a thread that faces away from the outer end of the respective pin or box member on which the thread is formed and supports the weight (i.e., tensile load) of the lower tubular member hanging in the wellbore. Similarly, the term "stab flank" designates the side wall surface of the thread that faces toward the outer end of the respective pin or box member and supports forces compressing the joints toward each other such as the weight of the upper tubular member during the initial make-up of the joint or such as a force applied to push a lower tubular member against the bottom of a bore hole (i.e., compressive force).
One type of threaded connection commonly used in oil country tubular goods is known as a wedge thread. Referring initially to FIGS. 1A and 1B, a prior art tubular connection 100 having a wedge thread is shown. As used herein, "wedge threads" are threads, regardless of a particular thread form, that increase in width (i.e., axial distance between load flanks 225 and 226 and stab flanks 232 and 231) in opposite directions on a pin member 101 and a box member 102. The rate at which the threads change in width along the connection is defined by a variable known as the "wedge ratio." As used herein, "wedge ratio," although technically not a ratio, refers to the difference between the stab flank lead and the load flank lead, which causes the width of the threads to vary along the connection. Furthermore, as used herein, a thread "lead" refers to the differential distance between a component of a thread on consecutive threads. As such, the "stab lead" is the distance between stab flanks of consecutive thread pitches along the axial length of the connection. A detailed discussion of wedge ratios is provided in U.S. Pat. No. 6,206,436, issued to Mallis, assigned to the assignee of the present disclosure, and incorporated by reference in its entirety herein. Furthermore, wedge threads are extensively disclosed in U.S. Pat. No. RE 30,647 issued to Blose, U.S. Pat. No. RE 34,467 issued to Reeves, U.S. Pat. No. 4,703,954 issued to Ortloff, and U.S. Pat. No. 5,454,605 issued to Mott, all assigned to the assignee of the present disclosure and incorporated herein by reference in their entirety.
Referring still to FIGS. 1A and 1B, a pin thread crest 222 in a wedge thread coupling is narrow towards a distal end 108 of pin member 101 while a box thread crest 291 is wide. Moving along an axis 105 (from right to left), pin thread crest 222 widens while box thread crest 291 narrows as it approaches a distal end 110 of box member 102. As shown in FIG. 1A, the threads are tapered, meaning that a pin thread 106 increases in diameter from beginning to end while a box thread 107 decreases in diameter in a complimentary manner. Having a thread taper may improve the ability to stab pin member 101 into box member 102 and distribute stress throughout the connection.
Generally, thread seals are difficult to achieve in non-wedge (i.e., free-running) threads. However, thread forms that are unable to form a wedge seal in a free-running configuration may create thread seals when used in a wedge thread configuration. As should be understood by one of ordinary skill, as wedge threads do not require any particular type or geometry of thread form, a variety of thread forms may be used. One example of a suitable thread form is a semi-dovetailed thread form disclosed in U.S. Pat. No. 5,360,239, issued to Klementich and incorporated herein by reference in its entirety. Another thread form includes a multi-faceted load flank or stab flank, as disclosed in U.S. Pat. No. 6,722,706, issued to Church and incorporated herein by reference in its entirety. Each of the above thread forms is considered to be a "trapped" thread form, meaning that at least a portion of the corresponding load flanks and/or corresponding stab flanks axially overlap.
An open (i.e., not trapped) thread form with a generally rectangular shape is disclosed in U.S. Pat. No. 6,578,880, issued to Watts and incorporated herein by reference in its entirety. As such, the above thread forms (i.e., those of Klementich, Church, and Watts) are examples of thread forms that may be used with embodiments of the present disclosure. Generally, open thread forms such as buttress or stub are not suitable for wedge threads, as they would impart a large radial force on the box member. However, a generally square thread form, such as that disclosed by Watts, or a trapped thread form, may be used, as they do not impart an outward radial force on the box member. As such, those having ordinary skill in the art will appreciate that the teachings contained herein are not limited to particular thread forms.
Referring again to FIGS. 1A and 1B, in wedge threads, a thread seal may be accomplished through contact pressure caused by interference that occurs at make-up over at least a portion of connection 100 between pin load flank 226 and box load flank 225 and between pin stab flank 232 and box stab flank 231. Close proximity or interference between roots 292 and 221 and crests 222 and 291 complete the thread seal when occurring proximate to such flank interference. Generally, higher pressures may be contained either by increasing interference between the roots and crests ("root/crest interference") on pin member 101 and box member 102 or by increasing the aforementioned flank interference.
Although various wedge thread connections exist having positive-stop torque shoulders (e.g., Klementich, referenced above), wedge threads typically do not have torque shoulders, so their make-up is "indeterminate," and, as a result, the relative position of the pin member and box member may vary more during make-up for a given torque range to be applied than for connections having a positive-stop torque shoulder. For wedge threads designed to have flank interference and root/crest interference at a selected make-up, the connection is designed such that both the flank interference and root/crest interference increase as the connection is made-up (i.e., an increase in torque increases flank interference and root/crest interference). For tapered wedge threads having root/crest clearance, the clearance decreases as the connection is made-up.
Regardless of the design of the wedge thread, corresponding flanks come closer to each other (i.e., clearance decreases or interference increases) during make-up. Indeterminate make-up allows for the flank interference and root/crest interference to be increased by increasing the make-up torque on the connection. Thus, a wedge thread may be able to thread-seal higher pressures of gas and/or liquid by designing the connection to have more flank interference and/or root/crest interference or by increasing the make-up torque on the connection. However, increased interference and make-up torque may increase stress on the connection during make-up, which may lead to premature failure of the connection.
Furthermore, as shown, connection 100 includes a metal-to-metal seal 112 created by contact between corresponding seal surfaces 103 and 104, respectively located on pin member 101 and box member 102. Metal-to-metal seal 112 provides an additional measure of seal integrity (i.e., when a wedge thread seal is not sufficient) for threaded connection 100, and is particularly useful where connection 100 is intended to contain high-pressure gases. While metal-to-metal seal 112 is shown located proximate to the distal end 108 of pin member 102, it should be understood by one of ordinary skill in the art that metal-to-metal seal 112 may be positioned anywhere along the length of connection 100, including, but not limited to, a location proximate to distal end 110 of box member 102.
Nonetheless, seal surfaces 103 and 104 of metal-to-metal seal 112 are usually constructed as corresponding frustoconical surfaces characterized by a low angle (e.g., an angle less than about 4 or 5 degrees) of intersection with their corresponding remaining pin 101 and box 102 surfaces. Typically, low-angle metal-to-metal seal surfaces 103 and 104 are used in conjunction with wedge thread connections (e.g., 100) because the indeterminate make-up thereof necessitates a seal capable of less precise axial alignment. As wedge threads make-up indeterminately, the relative axial position of pin member 101 and box member 102 will vary over successive make-up and breakout cycles. However, one disadvantage of a low-angle metal-to-metal seal is that seal surfaces 103 and 104 have larger friction contact areas than higher-angle seals, and as such, have less resistance to galling upon make-up. Furthermore, as low-angle metal-to-metal seals engage slowly (i.e., low radial displacement per revolution), the seals must be in contact for several revolutions. As such, in a wedge thread connection including a metal-to-metal seal, the seal is typically the first thing to "make-up," such that the initial engagement of the seal marks the "hand tight" state of such a threaded connection. Therefore, while low-angle seals are beneficial in that they accommodate the indeterminate make-up characteristics of wedge threads, they may become ineffective over repeated make-up and break-out cycles as seal surfaces 103 and 104 are deformed and/or are cold-worked out of specification.
In contrast, free-running threads used in oilfield tubular connections typically do not form thread seals when the connection is made-up. Referring now to FIG. 2, a prior art connection 200 having free-running threads is shown. The free-running threads include load flanks 254 and 255, stab flanks 257 and 258, crests 259 and 262, and roots 260 and 261. As is typical of a connection with free-running threads, connection 200 relies on a positive-stop torque shoulder formed by the contact of surfaces 252 and 251 disposed on a pin member 201 and a box member 202, respectively. The positive-stop torque shoulder shown in FIG. 2 is commonly referred to as a "pin nose shoulder." In other connections, the positive-stop torque shoulder may instead be formed by a box face 263 and a mating shoulder (not shown) on pin member 201. The positive-stop torque shoulder may also provide a seal. Unlike wedge threads (e.g., those shown in FIGS. 1A-B), which make-up by the wedging of the pin thread 106 and the box thread 107, free-running threads rely on the positive-stop torque shoulder to load connection 200 during make-up. To make-up connection 200, pin member 201 and box member 202 are screwed together until surfaces 251 and 252 are brought into abutment, at which point pin load flank 254 and box load flank 255 are also in abutment. Additional torque is applied to pin member 201 and box member 202 to load surfaces 252 and 251 and pin load flank 254 and box load flank 255 until the desired amount of make-up torque (i.e., the selected make-up) has been applied to connection 200.
Because a large gap 253 exists between pin stab flank 257 and box stab flank 258, connection 200 does not accomplish a thread seal. Gap 253 occurs as a result of how free-running threads with positive-stop torque shoulders are loaded. Applying torque to connection 200 during make-up against the positive-stop torque shoulder causes pin member 201 to be compressed while box member 202 is stretched in tension. Note that when a box face shoulder is used, box member 202 is compressed while pin member 201 is stretched in tension. The force between pin member 201 and box member 202 is applied through pin load flank 254 and box load flank 255. Notably, pin stab flank 257 and box stab flank 258 are not loaded during make-up. This results in contact pressure between load flanks 254 and 255 and gap 253 between stab flanks 257 and 258. As discussed above, a wedge thread (e.g., FIGS. 1A-B) forms a thread seal in part because of the interference between load flanks 225 and 226 and stab flanks 232 and 231. In wedge threads, this occurs near the end of the make-up of the connection because of the varying width of pin thread 106 and box thread 107. To have similar interference between load flanks 254 and 255 and stab flanks 257 and 258 on a cylindrical (i.e., non-tapered) free-running thread, the interference would exist substantially throughout the make-up of the connection because pin thread 106 and box thread 107 have a continuous width. Furthermore, root/crest interference, if any, would exist substantially throughout the make-up of the connection. This could lead to galling of the threads and difficulty in making-up the connection.
The variance in thread width for a wedge thread occurs as a result of the load flanks having different leads than the stab flanks. A thread lead may be quantified in inches per revolution or by the commonly used inverse term "thread pitch," (i.e., threads per inch). A graph of the leads for a wedge thread is shown in FIG. 3. For this connection, the load lead 14 is constant over the length of the connection and greater than the stab lead 12, which is also constant. The nominal lead is shown as item 10. As used herein, "nominal lead" refers to the average of load lead 14 and stab lead 12. The thread will widen with each revolution by the difference in load lead 14 and stab lead 12. As described above, the difference in the load lead 14 and the stab lead 12 is the "wedge ratio." For a free-running thread (i.e., non-wedge thread), load lead 14 and stab lead 12 would be substantially equal, thus causing the free-running thread to have a substantially constant thread width (i.e., a zero wedge ratio).
Prior to make-up, a joint compound commonly referred to as "pipe dope" is typically applied to components of a threaded connection. Pipe dope provides lubrication to aid the make-up of the connection, thus allowing for the connection to be repeatedly made-up and broken-out over time. In oilfield tubular applications, pipe dope may contain metallic particle additives, such as copper, to protect the threads of the pin and box members from friction galling during make-up and break-out. Furthermore, the base (e.g., a grease) of the pipe dope may assist a wedge-threaded connection in achieving a thread seal between load and stab flanks thereof.
Because of the close-fitting manner in which wedge threads make-up, less pipe dope is required. Typically, the pipe dope is only applied to the pin thread of a wedge thread connection with that application being performed with a brush instead of a large swab, as would be typical of other thread connections. When a wedge thread connection is made-up, excess pipe dope may become trapped between the pin thread and the box threads, which may either cause falsely elevated torque readings (leading to insufficient make-up or "stand off") or, in rare circumstances, damage the connection. Typically, problems associated with excess pipe dope on wedge-threaded connections may be avoided by restricting the amount of pipe dope applied and by controlling the speed at which the wedge-threaded connection is made-up. Limiting the make-up speed of a wedge-threaded connection allows the pipe dope to travel and squeeze out before it becomes trapped within the connection at high pressures.
Even though damage to threaded connections from over-pressurized pipe dope is rare, the damage sustained thereby remains a significant concern for operators. Particularly, the connection may be damaged if the pipe dope applied is too viscous to "flow" and squeeze out of the connection. A more common scenario that may occur when making up wedge-threaded connections is pipe stand-off. Pipe stand-off refers to the situation where the connection produces a false torque reading that indicates the connection is fully made-up when it is not. Because operators make-up wedge threads based on a selected make-up torque, the connection may not be fully made-up when the relative position of the pin member and the box member is taken into account. Often, pipe stand-off is difficult to detect on the rig at the time of make-up, and even a small amount of stand-off can threaten the integrity of the connection.
In cold weather locations such as North Slope Alaska or the North Sea, failures due to inviscid pipe dope flow is more likely to occur than in warmer environments. In cold environments, a pipe dope having a lower metal content and reduced kinematic viscosity may be used to reduce the likelihood of such failures. The kinematic viscosity is the ratio of the viscosity of a fluid to its density, wherein a "centistoke" is a commonly used unit of measure for kinematic viscosity. Thus, if a pipe dope having a high kinematic viscosity is used and the connection is made-up too quickly, as may occur when using a power frame to make-up threaded connections, the pipe dope may become trapped between the pin thread and the box thread, thus causing a high pressure build-up that may either expand the box member or result in pipe stand off.
In wedge thread connections, pipe stand-off due to inadequate evacuation of pipe dope is common. As the pressure build-up may bleed off during use, the connection is at risk of accidentally backing-off during use. Therefore, stand-off in wedge-threaded connections is of particular concern as it may lead to loss of seal integrity or even mechanical separation of two connected members. Furthermore, it should be noted that pipe stand-off is of particular concern for larger diameter threaded connections, including, but not limited to tubulars greater than or equal to about 9⅝ inches diameter (24.4 cm). Because of the long helical thread length (i.e., the total length of the thread if the helix were "unraveled" and straightened out) associated therewith, dope evacuation is more difficult for larger diameter threaded connections. It has been determined that pipe dope evacuation is difficult for threaded connections having helical thread lengths in excess of 200-250 inches.
Further still, larger diameter tubulars used for threaded connections are more susceptible to ovalization from their relatively high outer diameter ("OD") to wall thickness ("t") ratios. For large diameter tubulars, (e.g., the 9⅝ inch pipe described above) the OD/t ratio may exceed 20. It has been observed that as the outer diameter (and thus the OD/t ratio) increases, it becomes increasingly difficult to manufacture tubular stock within the same cylindricity tolerance used for smaller diameter tubulars. As a result, many large diameter tubulars suffer from ovalization as they are manufactured. Furthermore, large diameter tubulars are also increasingly susceptible to ovalization resulting from extended periods of storage following manufacturing.
To combat such ovalization during the thread machining process, the chuck of a machine tool (e.g., a lathe) may be used to temporarily "straighten" out an ovalized end while the precision wedge threads are cut. However, once released from the chuck, the end of the tubular may return to its ovalized state, thus leaving the threaded portion of the stock eccentrically (i.e., non-cylindrically) shaped. Because of the loading characteristics of wedge threads, ovalized pin and box members may re-straighten themselves upon selected make-up. However, prior to selected make-up, the eccentrically shaped wedge threads may operate (in a manner similar to a scroll compressor) to dramatically pressurize the pipe dope trapped therein, thus increasing the risk of stand-off at selected make-up.
Furthermore, pipe stand-off may be particularly problematic in strings used at elevated downhole service temperatures (i.e., the temperature a tubular would expected to experience in service). Particularly, in high-temperature service (e.g., temperatures greater than 250° F., a steam-flood string, or a geothermal string), even a small amount of stand-off may be deleterious. For example, if a made-up wedge connection having even an infinitesimal amount of stand-off is deployed to a high-temperature well, the pipe dope may flow out of the wedge thread connection, thus reducing the integrity of the thread seal.
A wide range of pipe dopes is commercially available. Pipe dope is typically a proprietary formulation of lubricant(s) and particulates. In general, higher particulate concentrations result in more viscous pipe dope, which helps to provide a thread seal in wedge thread connections. The base grease is also largely determinative of the final kinematic viscosity of the pipe dope. One company providing pipe dope for threaded connections is JET-LUBE®, Inc. (Houston, Tex., USA). One type of pipe dope provided by JET-LUBE®, Inc. is KOPR-KOTE®, which contains less than 10 percent by weight of copper as the particulate additive. KOPR-KOTE® is provided in an alternative formulation for arctic use, as are several other JET-LUBE® formulations. Higher temperature pipe dopes ("thermal grade") from JET-LUBE® utilize a petroleum oil with a kinematic viscosity of 414 to 506 centistokes at 40 degrees C. The "arctic grade" pipe dopes utilize a calcium base grease with a kinematic viscosity of about 20 to 24 centistokes at 40 degrees C., which is much lower than the thermal grade. Another pipe dope is JET-LUBE® NCS-30, which is specifically marketed for use with wedge thread connections. That pipe dope does not contain metallic particulates. Instead, JET-LUBE® NCS-30 uses a proprietary formulation of chemically inert fibers as a particulate additive. Also, JET-LUBE® NCS-30 uses a calcium base grease similar to the arctic grade compounds to provide reduced kinematic viscosity.
Although many of the problems with making-up a wedge thread may be avoided by using a pipe dope with lower kinematic viscosity and/or reduced metal content, using such a compound may disadvantageously affect the sealing ability of a wedge thread. Particularly, the downhole operating environment may be much hotter than the surface, thus enabling the pipe dope to flow more easily and not aid in thread seal maintenance. In general, the higher the kinematic viscosity of the pipe dope, the better the resulting thread seal in wedge threads.
Furthermore, alternative solutions exist to temporarily modify the kinematic viscosity for the purposes of making-up a threaded connection. Such a solution is disclosed in U.S. patent application Ser. No. 11/420,441 entitled "Dope Relief Method for Wedge Thread Connections," filed on May 25, 2006, by Harris A. Reynolds, et al., and incorporated herein by reference in its entirety. In the '441 application, methods and apparatus to apply heat and/or vibration to a wedge thread connection prior to and during make-up are disclosed. As such, the applied heat will temporarily reduce the kinematic viscosity of the pipe dope so that it will flow through the connection more effectively during make-up. Similarly, the application of vibration to the connection during makeup will also temporarily reduce the kinematic viscosity of the pipe dope at make-up. The benefit of such methods and apparatus is that the kinematic viscosity may be reduced for the purpose of making-up the connection but return to the desirable properties thereafter. However, such a solution requires additional equipment to perform the heating and/or vibration that may be difficult to locate and handle in remote locations.
In addition to modifying the properties of the pipe dope compound itself, mechanical solutions for relieving pressure build-up of wedge thread connections during make-up have been proposed. An example of a mechanical solution is disclosed in U.S. Pat. No. 6,050,610, issued to Enderle, assigned to the assignee of the present disclosure, and incorporated herein by reference in its entirety. The '610 patent discloses a wedge thread connection having a groove in a thread root to provide a pipe dope escape path during make-up. Similarly, U.S. Pat. No. 6,905,149 issued to DeLange discloses a groove in a thread crest to provide a pipe dope escape path. However, it should be noted that the groove in the thread crest may prevent a wedge thread so equipped from sealing, as the groove may provide a continuous leak path for the pipe dope. Alternatively, in a two-step wedge thread, the thread crest groove may be provided on only one step such that seal integrity is not compromised.
Furthermore, the pressure-relief grooves disclosed in the '610 and '149 patents are limited in depth and width because larger grooves would reduce the strength of the threaded connection. Furthermore, such grooves work poorly because the cross-sectional areas of the grooves are too small to have an adequate flow coefficient (e.g., Cv) or an adequate volume to serve as an effective dope reservoir. Because of the limited size, pressure-relief grooves and other former mechanical solutions to pressure build-up of wedge thread connections during make-up may fail to prevent connection damage and pipe stand-off for problematic connections, such as larger diameter wedge thread connections.


An image forming apparatus includes a first photosensitive member and a second photosensitive member that form images having different colors, a transfer belt that transfers the images formed on the first photosensitive member and the second photosensitive member onto a recording sheet, a first motor that rotatingly drives the first photosensitive member and the transfer belt, and a second motor that rotatingly drives the second photosensitive member. After the startup process of the first and second motors has been completed, the rotation speed of the second motor is controlled while maintaining the rotation speed of the first motor unchanged so that the second rotation phase of the second photosensitive member rotatingly driven by the second motor is the same as the first rotation phase of the first photosensitive member rotatingly driven by the first motor.

1. Field of the Invention
The present invention relates to an image forming apparatus that controls the rotation phases of a plurality of photosensitive members.
2. Description of the Related Art
In recent years, electrophotographic color image forming apparatuses of a tandem type have been in widespread use. In image forming apparatuses of a tandem type, toner images of individual colors are formed on a plurality of photosensitive drums, and the toner images of the individual colors are overlaid and transferred onto a recording sheet. Electrophotographic color image forming apparatuses of a tandem type have an advantage over color image forming apparatuses that form an image using a single photosensitive drum in terms of the productivity of image formation. However, color image forming apparatuses of a tandem type may cause color misregistration in which the relative positions of the toner image of individual colors are shifted when the toner images formed on the photosensitive drums are overlaid. In such a case, an unclear and low-quality image is formed on a recording sheet.
One of the reasons for causing color misregistration is a shift of rotation phase among the plurality of photosensitive drums. The eccentricity of the photosensitive drum with respect to the rotation shaft causes the peripheral speed to periodically vary. If the phases of periodical variations in the peripheral speeds of the photosensitive drums are not the same, increases or decreases in the peripheral speeds of the photosensitive drums are not the same. Therefore, shifts of the relative positions of toner image of individual colors become noticeable. To address such an issue, U.S. Pat. No. 6,173,141 describes an image forming apparatus that prevents color misregistration by performing control so that the rotation phases of the photosensitive drums are the same. In the image forming apparatus described in U.S. Pat. No. 6,173,141, a microprocessor receives the rotation speed of a photosensitive drum for color image formation and the rotation speed of a photosensitive drum for monochrome image formation and controls a drive motor for driving the photosensitive drum for color image formation, a drive motor for driving the photosensitive drum for monochrome image formation, and a drive motor for driving a transfer conveyer belt so that the variation cycles of the two drums are synchronized with each other.
A variety of techniques for phasing two photosensitive drums have been proposed. One of the techniques is to increase or decrease one of the rotation speeds of the two photosensitive drums after the rotation speeds have reached the rotation speed for image formation. If the intention is only to make two photosensitive drums be in phase, the rotation speed of either photosensitive drum can be changed. However, when the drive motor that drives the photosensitive drum for monochrome image formation also drives the transfer conveyer belt and if the two photosensitive drums are made to be in phase, the following problems arise.
That is, if the photosensitive drum for monochrome image formation is accelerated, a roller for driving the transfer conveyer belt is also accelerated. The transfer conveyer belt is stretchable. Accordingly, if the roller for driving the transfer conveyer belt is accelerated, part of the transfer conveyer belt that is pulled by the roller stretches, and part of the transfer conveyer belt that is fed by the roller is loosened. This gradually disappears due to the restoration force of the transfer conveyer belt. However, the restoration force serves as a disturbance and is applied to the roller. Therefore, it takes a relatively long time until the rotation speed of the roller reaches a predetermined stable speed through feedback control. Such a problem also arises when, in image forming apparatuses that transfer a toner image formed on a photosensitive drum onto a recording sheet via an intermediate transfer belt, the phase of the photosensitive drum is made the same as that of another photosensitive drum by increasing or decreasing the rotation speeds of drive motor for driving the photosensitive drum and the intermediate transfer belt. As described above, in order to make the two photosensitive drums be in phase, which one of the photosensitive drums is selected for increasing or decreasing the rotation speed needs to be determined.


An apparatus and method for adjusting a desired expression section according to input bit values in a mobile communication system that expresses only a defined partial section of the input bit values in order to make the number of output bits be less than the number of the input bits, and maps bit values included in unexpressed sections to a specific value is provided. In the apparatus and method, a measurer divides possible output bit values into at least three sections, and measures output frequencies of output bits for the respective sections for a predetermined time. A controller adjusts the desired expression section, when an output frequency for a specific section is greater than output frequencies for other sections.

1. Field of the Invention
The present invention relates generally to a decoder in a mobile communication system. In particular, the present invention relates to an apparatus and method for adjusting an input range of data input to a decoder for performance improvement of a soft-decision decoder.
2. Description of the Related Art
A mobile communication system wirelessly transmits/receives data. However, because data is wirelessly transmitted/received in the mobile communication system, it is difficult for a receiver to correctly receive data transmitted from a transmitter. In order to solve this problem, the transmitter encodes transmission data before transmission, and the receiver decodes the encoded data to receive the original data.
FIG. 1 is a block diagram illustrating a structure of a general transceiver in a mobile communication system. With reference to FIG. 1, a description will be made of a structure of a transceiver in a mobile communication system.
Referring to FIG. 1, in a transmitter, input bits comprising a binary signal are input to an encoder 100. The encoder 100 encodes the input bits, and outputs coded bit streams to a matcher 102. The matcher 102 performs rate matching on the serial coded bit streams taking the number of output bits transmitted over a radio frame into consideration, and delivers the rate-matched bit streams to an interleaver 104. The interleaver 104 performs interleaving on the rate-matched bit streams such that the coded bit streams should be robust against a burst error, and outputs the interleaved bit streams to a modulator 106. The modulator 106 symbol-maps the interleaved bit streams according to a symbol mapping constellation. The modulator 106 supports Quadrature Phase Shift Keying (QPSK), 8-ary Phase Shift Keying (8PSK), 16-ary Quadrature Amplitude Modulation (16QAM) and 64QAM as its modulation scheme. The number of bits constituting the symbol is defined depending on the modulation scheme. A symbol comprises 2 bits for the QPSK modulation, 3 bits for the 8PSK modulation, 4 bits for the 16QAM modulation, and 6 bits for the 64QAM modulation. The modulated symbols output from the modulator 106 are transmitted via a transmission antenna 108.
In a receiver, symbols transmitted via the transmission antenna 108 are received by a reception antenna 110. The symbols received by the reception antenna 110 are input to a demodulator 112. The demodulator 112 has the same symbol mapping constellation as that of the modulator 106, and converts the received symbols into binary bit streams according to the symbol mapping constellation. That is, the demodulation scheme is determined by the modulation scheme. The binary bit streams demodulated by the demodulator 112 are delivered to a deinterleaver 114. The deinterleaver 114 deinterleaves the demodulated binary bit streams according to the same scheme as the interleaving scheme of the interleaver 104, and outputs the deinterleaved binary bit streams to a dematcher 116. The dematcher 116 removes repeated bits when the matcher 102 performed bit repetition, and reproduces punctured bits when the matcher 102 performed puncturing, and outputs the result bit streams to a decoder 118. The decoder 118 decodes the rate-dematched binary bit streams into binary bits.
FIG. 2 is a block diagram illustrating a structure of a general receiver using a Viterbi decoder. The receiver of FIG. 2 is made by adding a range adjuster 206 to the receiver of FIG. 1. The range adjuster will be described below. Generally, one modulation symbol output from a demodulator 200 comprises 10 bits or less. Here, a decoder 208 can estimate a signal from a transmitter with less-than-10 bits. Generally, the decoder 208 can correctly estimate a signal from the transmitter with only 3 or 4-bit information. When the number of bits input to the decoder 208 (or output from the range adjuster 206) is 3, there are 8 possible expressions. When the number of bits input to the decoder 208 is 4, there are 16 possible expressions. Table 1 illustrates possible expressions for the case where the number of bits input to the decoder 208 is 3.
TABLE 1Bits input to decoderDecimal expression100−4101−3110−2111−10000001101020113
Table 2 illustrates possible expressions for the case where the number of bits input to the decoder 208 is 4.
TABLE 2Bits input to decoderDecimal expression1000−81001−71010−61011−51100−41101−31110−21111−10000000011001020011301004010150110601117
According to Table 1, the 8 possible expressions include −4 to 3, and according to Table 2, the 16 possible expressions include −8 to 7. The range adjuster 206 has a function of adjusting an expression form of one symbol delivered to the decoder 208. A description will now be made of the reason why the range adjuster 206 adjusts an expression form of one symbol.
As described above, a binary bit stream for one symbol delivered to the range adjuster 206 is generally comprises about 10 bits, and a binary bit stream for one symbol output from the range adjuster 206 is generally comprises 3 or 4 bits. Therefore, values that cannot be expressed with the 3 or 4 bits among the input bit values should be mapped to values that can be expressed with the 3 or 4 bits. Table 3 illustrates possible expressions for the case where the number of bits input to the range adjuster 206 is 6 and the number of bits output from the range adjuster 206 is 4.
TABLE 3DecimalDecimalexpression ofexpression ofInput bitsinput bitsOutput bitsoutput bits100000−321000−8  100001−311000−8  ............111000−81000−8  111001−71001−7  ............000000000000............000110601106000111701117............01111030011170111113101117
As illustrated in Table 3, the values that cannot be expressed with the output bits are mapped to the smallest value and the largest value among the values that can be expressed with the output bits. That is, according to Table 3, when the input bit value is smaller than −8, the output bit value is expressed with −8 (1000), and when the input bit value is larger than 7, the output bit value is expressed with 7 (0111).
However, a soft-decision decoder can obtain its maximum performance when as many input values as possible can be expressed. That is, the soft-decision decoder can perform more accurate decoding when all of the input bits, including −32 (100000) and 31 (011111), are input. Therefore, it is necessary to express, with the 4 output bits, even the possible maximum value that can be expressed with the 6 input bits.
In a conventional method, an adjustment constant 'k' of the range adjuster is set to one fixed value so that as many input values to the soft-decision decoder as possible can be expressed, or the adjustment constant 'k' is adjusted according to an arithmetic mean value. However, when the range adjuster uses the one fixed value, it cannot efficiently express its input values. Referring to Table 3, when values smaller than −8 and values larger than 7 among input values to the range adjuster are more frequently input to the range adjuster as compared with other values, it is necessary to express the values smaller than −8 and the values larger than 7 in detail. For example, a method capable of distinguishing −10 and −23 should be provided. However, when the adjustment constant is fixed, there is no way to distinguish −10 and −23. Therefore, when the adjustment constant has a fixed value, the range adjuster cannot flexibly operate according to the input bit values.
Also, when the range adjuster adjusts the number of bits delivered to the decoder according to an arithmetic mean value, it has the following disadvantage. The range adjuster arithmetically averages its output bit values for a predetermined time. When the arithmetic mean value is close to −8 or 7, the adjustment constant is adjusted, and even when the arithmetic mean value is close to 0, the adjustment constant is adjusted. However, the operation of arithmetically averaging the output bit values causes an increase in memory capacity, calculations and complexity. For example, when the number of output bits is 4, 9-bit memories are required in order to perform arithmetic calculation (summation) on the output bits 128 times, increasing the complexity. In addition, in order to increase the accuracy of the arithmetic mean value, it is necessary to use a value obtained by performing arithmetic averaging calculation for a long time. However, the memory capacity increases in proportion to the number of calculations on the output bits, causing an increase in circuit complexity.

Apparatus and method for adjusting an input range for a soft-decision decoder


Various apparatuses and methods for protecting a transmitter from electrostatic discharge are disclosed herein. For example, some embodiments provide an apparatus including a first ESD clamp connected to an antenna input, a first reactive component connected to the first ESD clamp, a second ESD clamp connected to the first reactive component, and a second reactive component connected between the second ESD clamp and the transmitter.

Electronic circuits include conductors and semiconductors that can be damaged when exposed to too much electrical current. When a current passes through a conductor that is too small for the current, the conductor may be heated and can be damaged or destroyed. The intense heat can melt or vaporize parts of the circuit and cause the circuit to immediately fail, or may leave latent damage that will cause the circuit to fail in the future. A very common cause of this type of damage is electrostatic discharge (ESD), due for example to static electricity, which can be generated during normal movement of a person carrying an electronic device.
Electronic devices are typically designed to protect circuits from ESD by enclosing them in insulating housings. Any electrical conductors that are exposed to the user, such as those in headphone jacks, universal serial bus (USB) connectors, memory slots, etc, may be protected by buffers that are relatively robust and resistant to ESD. ESD protection circuits may also be applied to electrical conductors that are exposed to the user.
Some electronic circuits that may be exposed to the user, however, are more difficult to protect using traditional ESD protection circuits without degrading normal function. For example, some cellular telephones include frequency modulation (FM) transmitters having a relatively large antenna located on the battery cover. The battery cover is removed from the cellular telephone each time the battery is accessed, exposing an FM transmitter connector pin that is normally connected to the FM antenna on the battery cover. If static electricity reaches the FM transmitter pin, either by contact with the user or by an electrical strike through the air, the FM transmitter could easily be damaged or destroyed. Standards bodies such as the International Electrotechnical Commission (IEC) specify stringent test requirements for electronic devices which attempt to ensure that the devices are robust enough for normal use. In one such test, the FM transmitter pin is required to withstand an 8 kV contact ESD strike and a 15 kV air ESD strike. Traditional ESD protection circuits applied to the FM transmitter pin that can withstand these ESD levels would degrade normal function of the FM transmitter. For example, because the FM transmitter is designed to operate with a high Q inductive antenna, resistive or lossy components used in a traditional ESD protection circuit would cause a severe power penalty. The characteristic impedance of the FM transmitter and antenna must also be carefully controlled based on the target FM frequencies, and resistive or lossy components may impact characteristic impedances as well as direct power losses.

Asymmetric ESD protection for FM transmitter


A molding member for an automobile window plate includes an extruded elongate member with upper and side portions to continuously extend along upper and side edges of the window plate, respectively, and having a main section for covering a gap between the window plate and an adjacent automobile body panel, a lip section projecting from the main section to cover an outer periphery of the window plate, and a leg section extending from the main section into the gap for retaining the molding member in place. The lip section is provided with a first groove portion adjacent to the lip section and extending along the upper portion of the elongate member, and a second groove portion spaced from the lip section and extending along the side portion of the elongate member, to define between the lip section and the outer periphery of the window plate a weir solely along the side portion of the elongate member. The elongate member is adapted to be subjected to a permanent plastic deformation such that the first and second groove portions are aligned with each other substantially in a common plane to form a continuous single groove for receiving upper and side edges of the window plate.

1. Field of the Invention:
The present invention relates to a molding member for an automobile window plate, with a longitudinally variable cross-section.
2. Description of the Related Art:
An automobile generally employs various kinds of window molding members which extend along the periphery of a front or rear window plate, i.e. along a pair of front or rear pillars and the front or rear edge of the roof panel of the automobile body. A variety of requirements have been imposed on such molding members mainly from design and/or functional viewpoint, resulting in an increased demand in the automobile industry for the window molding members whose cross-sectional shape varies in the longitudinal direction.
Specifically, there has been proposed a window molding member having an upper portion of a first predetermined cross-section, a side portion of a second predetermined cross-section, and a corner portion arranged between the side and upper portions, where the cross-section changes gradually from the first to the second. When the molding member is arranged along the periphery of a front window plate, the first cross-section of the upper portion contributes to realize a so-called flush outer surface of the automobile body, while the second cross-section of the side portion serves to define a weir along the side edge of the window plate. During driving in rainy conditions, the weir serves to prevent rain water on the window plate from flowing across the side portion of the molding member toward the side window, thereby effectively preserving the driver's and/or navigator's sight through the side windows.
For producing a window molding member with longitudinally variable cross-section, various methods are known. A typical method is to physically divide each molding member into first and second extruded portions with the respectively predetermined cross-sectional shapes, which are connected with each other either by an injection molding process or by using a separate corner connection-piece. However, connection of these two portions by means of the injection molding accompanies formation of undesirable burrs along the junctions and resultant deterioration in the appearance, while use of the corner connection-piece results in increased number of the required components and assembly steps.
These problems can be more or less overcome by a method disclosed e.g. in U.S. Pat. Nos. 4,757,659 and 4,757,660 to Miyakawa et al., which includes extrusion of a continuous elongate preform body with a constant cross-section throughout the entire length. In this case, the preform body portion forming the upper portion of the molding member is subjected to cutting at the base end of a first arm section and at an area of a leg section from where a second arm section extends, to allow removal of these arm sections from the relevant body portion, and provide the upper portion with a glass plate receiving groove between the top and third arm section. On the other hand, the preform body portion forming the side portion of the molding member is subjected to cutting at the base end of the third arm section, to allow removal of that arm section from the relevant body portion, and provide the molding side portion with another glass plate receiving groove between the first and second arm sections.
Such a method is still disadvantageous in that the molding member cannot be produced accurately and efficiently, due mainly to the above-mentioned local cutting of the arm sections to form two glass plate receiving grooves along the upper and side portions of the molding member, respectively. Moreover, there are substantial difficulties in securing the molding member to the periphery of the glass plate as well, since the first arm section along the corner portion between the upper and side portions has to be formed with a receiving groove into which the glass plate must be carefully inserted, requiring delicate and time-consuming manual operations.

Molding member for automobile window plate


The invention relates to an LED lamp (L), having a light-emitting means with at least one LED, and a heat sink (K1-K6), characterized in that the heat sink (K1-K6) is configured such that a plurality of channels (1, 1′, 1″, 1′″) are formed through said heat sink for transporting away air which is heated by operation of the light-emitting means, wherein the channels (1, 1′, 1″, 1′″) are arranged in the form of a ring around an axis (A), and wherein the length of at least one channel (1, 1′, 1″, 1′″) is at least half the shortest diagonal or transversal in the transverse extent of the corresponding one channel. The arrangement according to the invention and in particular the configuration of the channels (1, 1′, 1″, 1′″) make it possible to achieve particularly effective dissipation of heat.

The invention relates to an LED lamp (LED: light-emitting diode), which comprises a light-emitting means with at least one LED and a heat sink.
During operation of an LED lamp, in principle heat is generated, to be precise by the LED or LEDs themselves, but also by a supply circuit ("driver circuit") for the LED(s). This heat is at least partially transferred from said components to surrounding components or the surrounding air. In order to enable as high an efficiency of the lamp as possible, colour stability, possibly colour temperature stability in the case of white LEDs and as long a life of the LED(s) as possible, it is desirable for the heat to be transported away from said components (supply circuit, LED chip) effectively and efficiently, with the result that the temperature of the LED does not rise beyond a certain extent.
The prior art WO 2006/118457 A1 has disclosed a heat sink for an LED lamp. The efficiency of heat dissipation is limited with this heat sink.
The invention is based on the object of specifying LED lamps with improved heat sinks.


A process for patching a crack or other defect in a thick-walled steel component, such as the wall of a pressure vessel, is provided. Stacked sheets of pre-impregnated carbon fiber-reinforced epoxy are bonded together and cured by interposed layers of a second resin. A structural adhesive is used to bond the stack to the steel to form the patch.

It is common to have stress fatigue cracks or corrosion damage (collectively referred to herein as "defects") in structural steel components, such as the body of a beam or the wall of a pressure vessel. These defects often eventually require repair.
The conventional technique used involves removing defected metal and replacing it with a compatible alloy through a welding process. The welding can cause undesirable embrittlement, distortion and the imposition of residual stresses, which can lead to further failure.
The research underlying the present invention was undertaken with the aim of devising an alternative technique for repairing such defects, particularly in thick walled steel components.
The research centered on experimenting with carbon fiber-reinforced polymer sheets to form a patch over the defect. More particularly, the commercial product used in the experimentation was one offered by Mitsubishi Chemical Corporation, of Japan, under the trade mark REPELARK.
This technology involves the use of thin, flat, substantially rigid sheets of partly cured epoxy resin having parallel carbon fibers embedded therein and oriented along the length of the sheet. These sheets are referred to in the art by the term "pre-pregs", which is a short-hand term for "pre-impregnated carbon fiber reinforced resin sheet". A liquid epoxy resin (referred to herein as "the curing resin") is used to initiate curing of the resin of the pre-preg and to bond it to the substrate to which it is to be attached. Curing and bonding occur over time when the two resins are brought into contact. Otherwise stated, the Mitsubishi system is characterized by the use of compatible resins which interact chemically at atmospheric temperature to effect complete curing of the pre-preg resin and bonding of the curing resin with the pre-preg resin and the substrate.
This contrasts with other known systems in which carbon fiber-reinforced epoxy sheets are cured using a combination of high temperature (e.g 350.degree. F.) and pressure.
The Mitsubishi system lends itself to use in the field, where it is impractical to use high temperature and pressure-inducing equipment.
In practice, it has been used to clad and reinforce concrete structures, such as bridge beams. In this application, a skin, comprising a single thickness of contiguous pre-pregs, is bonded to the flat concrete surfaces of the beam by a layer of curing resin. The pre-preg resin slowly cures at ambient temperature to a completely hardened state, over a period of about a week, by interaction with the curing resin.
Applicant speculated that the Mitsubishi or a similar pre-preg system might be useful in connection with patching defects in a structural steel component, such as the boom of a crane or the wall of a pressure vessel. However, on carrying out experimentation and obtaining familiarity with the Mitsubishi system, several problems became evident and required solution. More particularly:
The interface strength contributed by the layer of curing resin, when cured at ambient temperature, was very low--in tests, failure would occur in this layer at about 200 N, whereas a failure characteristic in the order of perhaps 10,000 N was needed; PA1 A patch having a thickness of just one pre-preg had insufficient strength in the context of thick-walled steel structures--but using a stack of several pre-pregs required the use of several curing resin layers, which introduced further weakness; PA1 The time required to cure at the conventional ambient temperature in field applications to a fully cured state, (typically a week), was impractical for use with a component that needed to go back into service as soon as possible, fully repaired; and PA1 It was a requirement in many cases that the patch had to conform to a substrate surface that was something other than a flat surface. For example, the surface might be arcuate or irregular (as would occur where a crack extended from a bulging weld). PA1 It was found that mild heating of the pre-preg/curing resin assembly resulted not only in accelerated curing but also in sufficient strengthening of the layer of curing resin so that the latter was no longer a weak point in the end product; PA1 It was further found that use of heat-shrinkable tape was effective to uniformly contain and apply pressure to such an assembly, when mildly heated; PA1 It was found that the provision of wrap-around heating pads and heat-shrinkable tape provided suitable means for applying sufficient pressure and heat to a partly cured pre-preg/curing resin assembly mounted on a steel component in the field to achieve satisfactory bonding and curing within a period in the order of 2 hours; PA1 As a result of the foregoing, it was now possible to use a stack of pre-pregs (perhaps three or more), separated by layers of curing resin, to create an assembly suitable for heat and pressure treatment to produce an end product having the necessary patch strength; PA1 The stack could be satisfactorily contained by a combination of release film and peel-ply fabric (referred to singly or collectively as "release means") at the top and bottom; PA1 To cope with forming problems and to minimize time consumption in the field, advantage was taken of the fact that, in the early stages of curing, the resin of the pre-preg softens and the pre-preg/curing resin assembly can be formed. As curing continues over time, the softened resins harden and begin to rigidify. Therefore, the process preferably incorporates first forming the pre-preg/curing resin laminate stack, including release means, on a prepared form or mould, under controlled conditions at a site removed from the component and then, after about 3 days of curing, conveying the formed, partly cured and shape-retaining laminate stack to the component, mounting it thereon, and rapidly completing curing using mild heat and pressure as previously described; PA1 It was further found desirable to abrade or roughen and clean the surface of the component and to texture the bottom of the stack, after removal of the release means, to ensure good bonding; and PA1 Finally it was found desirable to use a high strength structural adhesive to unite the base of the stack with the surface of the steel component. The bond strength of this layer is the most important parameter in transferring load from the steel substrate to the patch. PA1 The patch/component composite structure had a greater failure strength than the original unreinforced component; PA1 The final steps of applying, bonding and completely curing the stack on the component could be accomplished in about 2 hours; and PA1 Additional crack initiation or growth was effectively arrested.

Carbon fiber-reinforced polymer patch for defect repair of a structural steel component


In a calibration reference light source and a sensitivity calibration system using the same, a plurality of single-wavelength light sources for emitting reference lights having mutually different single-wavelengths are used instead of a black body radiation source for radiating a white light, and not only the intensities of the single-wavelength reference lights, but also the wavelengths thereof are measured to obtain sensitivity correction coefficients of intensity-to-radiance conversion data. Thus, obtained reference radiance are highly reliable and sensitivity correction of spectrophotometers and spectral illuminometers can be performed with high accuracy and reliability at a user side, whereby the calibration reference light source and the calibration system using the same can be obtained at low cost.

1. Field of the Invention
The present invention relates to a calibration reference light source and a calibration system using the same, which enable a user side to recalibrate wavelengths and sensitivities of a spectrophotometer and a spectral illuminometer.
2. Description of the Background Art
The spectrophotometer and spectral illuminometer are widely used to measure and evaluate radiances and colors of various light sources and display devices and normally have a construction as shown in FIG. 8. In this spectrophotometer, a light 201 to be measured is gathered by an objective optical system 202 to be incident on an incident slit 211 of a polychrometer 210. The beam incident on the slit forms a wavelength dispersed image of the incident slit 211 on a sensor array 214 via a diffraction grating 212 and an imaging optical system 213. Pixel intensity distributions En (n is a pixel number of 1, 2, . . . ) of the sensor array 214 according to the spectral intensity of the incident light are sent to a controller 204 via a processing circuit 203 to be converted into spectral radiances L(λ).
Calibrations of such a spectrophotometer includes a wavelength calibration and a sensitivity calibration. The wavelength calibration is performed by saving a correspondence table (n-λn correspondence table) of the pixel number n of the respective pixels of the sensor array 214 and a centroid wavelength λn. The pixel intensity distributions En in an actual light to be measured are converted into spectral intensity distributions E(λ) based on the above n-λn correspondence table. Further, the sensitivity calibration is performed by saving a ratio of a spectral radiance reference value L0(λ) to the spectral intensity distribution E0(λ) in the case where a reference light source including a known black body radiation source that is obtained a spectral radiance reference value L0(λ) such as an A-light source (2856 K) is measured , as a correction coefficient C0(λ). In other words,C0(λ)=L0(λ)/E0(λ)  (1).
At the time of a light measurement by the thus calibrated spectrophotometer, the spectral intensity distributions E(λ) obtained from the pixel intensity distributions En in accordance with the above n-λn correspondence table are converted into spectral radiances L(λ) as below using the above calibration coefficient C0(λ).L(λ)=C0(λ)·E(λ)  (2)
Even if being calibrated as above at the time of manufacturing, the spectrophotometer cannot avoid a sensitivity change due to a wavelength change caused by a change in the optical arrangement of the built-in polychrometer 210 and characteristic changes of optical elements and circuit elements such as the objective optical system 202 and the diffraction grating 212. Thus, recalibration (correction) needs to be performed at a sufficient frequency in order to maintain accuracy over a long term. However, a radiation exitance M(λ, T) of the A-light source, which has been conventionally used in the sensitivity calibration of the spectrophotometer, is given by Planck's law of radiation using C1, C2 as constants:M(λ, T)=C1·λ−5·exp[1−C2/(λ·T)]  (3)and relatively and absolutely largely depends on color temperature T.
Accordingly, it is necessary to control or monitor the color temperature to use this A-light source as a calibration reference. In order to maintain a radiation intensity of ±1% of the A-light source having a color temperature of 2856 K at 400 nm, the color temperature needs to be controlled with an accuracy of ±2 K. Thus, sufficient attentions need to be paid to the driving of the A-light source such as stabilization of a power supply voltage. On the other hand, at least two monitoring sensors having different spectral sensitivities are necessary for the monitoring of the color temperature. Filters, which are normally unavoidably temperature-dependent, are provided in these sensors, and wavelength errors of the filters need to be 0.5 nm or shorter. Further, attentions need to be paid to changes of the A-light source and the filters with time (e.g. wear damage of a filament in the A-light source).
Due to this difficulty to handle, the sensitivity recalibration (sensitivity correction) of the spectrophotometer is frequently performed by returning the spectrophotometer to a factory or service deposits of a manufacturer. Thus, it takes cost and time to return and recalibrate and it is difficult to recalibrate at a frequency necessary to maintain the accuracy. Accordingly, the present inventors previously proposed a calibration reference light source constructed by a plurality of single-wavelength light sources with stable wavelengths and semiconductor monitoring sensors with stable characteristics in Japanese Unexamined Patent Publication No. 2006-177785 (D1). Thus, this calibration reference light source using no A-light source is easy to handle and calibration at the user side is possible.
The wavelength stability of the single-wavelength light sources is essential even in the above prior art, relatively high-cost wavelength stabilized lasers such as gas lasers and temperature-controlled semiconductor lasers need to be used as the single-wavelength light sources. Further, lasers have a limit in usable wavelengths, single-wavelength reference lights of only about three wavelengths (408 nm, 532 nm and 635 nm) can be obtained within a visible range (380 to 780 nm) which is a general measurement wavelength range of spectrophotometers. The accuracy of correction coefficients at all the measurement wavelengths estimated based on data on the correction coefficients at these few wavelengths by interpolation or the like is low.

Calibration reference light source and calibration system using the same


A fully automatic servovalve analyzer system includes a data processing system, a transducer system, and a transducer interface system connecting the data processing system to the transducer system. The data processing system stores data defining characteristics of transducers connected to a unit under test as well as characteristic data for the unit under test itself and test procedures which are to be performed. After a unit under test has been hydraulically and electrically connected to the analyzer system, the system automatically performs any defined tests, analyzes the results and outputs the results in a preselected human recognizable form.

Servovalves are very widely used in aircraft as well as in industrial processes and machine systems because they enable a great deal of power or large forces to be exerted in response to an electrical signal. In the present state of the art, however, extremely high precision is required, and this in turn demands that precise information be gained as to the performance of the servovalve under a great many different static and dynamic conditions. To this end, therefore, there have been developed servovalve analyzers which enable a number of parameters of a unit under test (UUT) to be measured. For a time, a product made by industrial measurements and controls, and described generally in U.S. Pat. No. 2,934,938 was widely used throughout the industry to derive essential servovalve analysis information. A knowledgeable operator could, using preset sequences and potentiometer settings, perform an allotted number of tests on a servovalve, the results of which were recorded on an XY plotter, the plots from which could be measured to derive certain essential values.
Subsequently, a data processor-based version of this system was introduced by industrial measurements and controls that was called the "Image 2000". This system was based upon the concept of making available a fixed number of predetermined programs and hardwired circuits for a specific set of servovalves and transducers. With all servovalve characteristics known in advance, this system could accommodate perhaps 20 different servovalves. Present needs, however, demand far more versatility and capability, as well as higher ranges of precision than have heretofore been available. There is a need for what is essentially a generic or universal servovalve analyzer, which can be utilized to analyze many different UUTs having widely varying pressure, flow rate and actuation requirements. It is desirable to accommodate these different servovalves without requiring the generation of new programs, without requiring dedicated systems requiring highly skilled operators for each different valve type, and without requiring readjustment of the system.
For example, servovalve characteristics are dependent on a number of principal factors, including pressure, flow rate, drive signal and the dimensional system (English or Metric) that is used. Analysis is then made of a number of principal parameters, such as flow gain, hysteresis, nonlinearity, asymmetry and saturation. Today, moreover, some or practically all of a number of other specific parameters have to be measured, including (but not limited to) null shift, null area flow gain, threshold, resolution, internal leakage, pressure gain, null pressure, dynamic response at preset points and proof pressure. Because servovalves range widely in size, power demands, pressure levels involved and other characteristics, various servo amplifiers having different current and power characteristics must be used to provide electrical stimuli, and different physical stimuli might also be utilized. Furthermore, because pressure, displacement (position) and flow rates must be measured, each possibly requiring sensing in a plurality of different ranges, many different transducers may have to be made available for each of these ranges. To be able to analyze a thousand or more different UUTs with the accuracy and versatility needed, but without requiring system reconfiguration by the operator or extensive additional programming or computational work, requires that problems be overcome that have not heretofore been faced.


A method can include selecting integrated circuit (IC) device fabrication process source variations; generating relationships between each process source variance and a device metric variance; and calculating at least one IC device metric value from the process source variations and corresponding relationships between each process source variance and a device metric variance.

Conventional integrated circuit (IC) design methods utilize "hardware-based" approaches to predict device metrics (such as transistor performance metrics). For example, performance data can be collected from various dies on a number of fabricated wafers and then analyzed. Based on such analysis, models (e.g., transistor models) can then be created, which can serve as basis for simulating circuit behavior.
Such conventional approaches can suffice for mature fabrication processes. However, for processes still under development, such hardware data is generally unreliable as fabrication steps can be subject to change or the fabrication process drifts, making the initial metrics inaccurate thereby necessitating multiple rounds of design as the circuit behaviors evolve with the progression of the process development. Also, conventional approaches may only present performance data, making it difficult to obtain comprehensive information on how the sources of particular process variations can impact different device metrics.
Fabricated IC devices tend to encounter failures or underperforming components due to fabrication process variations, for instance, variations in threshold voltage. As a result, designers may elect to design conservatively, that is, to a wider set of process corners for the sake of ensuring a robust design but then sacrificing certain design targets. As semiconductor process advances to support Moore's law, the challenges of designing ICs in the context of process development only increase as the processes become more complex and therefore difficult to develop and implement. Design compensations for the ever-widening corners only increase. The trend continues with putting more and more burdens on design teams to tape out new chip products with satisfactory designs and meeting timelines for customers.

Integrated circuit device methods and models with predicted device metric variations


Advertisements over a network, such as the Internet, by extracting an index file of suppliers of search result sets for a plurality of keywords and/or an index of ads to be placed. A keyword in a received query may be matched to the suppliers of related search result sets and/or the ads to be placed in the index file(s). The search results may be ranked based on various criteria such as yield, click through rates and history of dealings. Search result sets for the keywords from the matching suppliers and the ads to be placed may be combined to produce a search result set ranked in accordance with estimated yields for advertisements associated with each result in the search result set and delivered in response to the received query. The search results in the combined set may be reranked and/or repriced.

1. Field of the Invention
This invention is related to ad delivery systems for placing Internet advertising in response to queries from search engine sites.
2. Description of the Prior Art
Conventional ad delivery systems have had problems, for example, with slow response, pricing which discouraged higher bids and limited matching. What is needed is an improved ad delivery system which avoids or reduces the problems inherent in known systems.