A cruise control governor which is able to dynamically define and switch between various goal droop curves in order to find the best goal droop curve for use with the current vehicle driving situation. For instance, the present invention will dynamically define and select different goal droop curves when the vehicle is lugging up a hill, coasting down a hill, cruising on level ground, preparing to crest a hill, or preparing to transition off of a downhill slope.

As is known in the art, a cruise control governor attempts to maintain a user-selected vehicle speed. Referring to FIG. 1(a), if the vehicle speed maintained by the cruise control governor is plotted as a function of time, it is apparent that the actual vehicle speed is not perfectly maintained at the cruise control set speed, because the controller can only attempt to maintain the desired set speed by measuring deviation of the actual speed from the set speed. The governor attempts to maintain a constant vehicle speed by controlling the amount of fuel which is provided to the engine, which is roughly proportional to the amount of torque that the engine will generate. FIG. 1(b) plots the engine torque vs. time which corresponds to the vehicle speed plot of FIG. 1(a). If the vehicle speed is plotted against engine torque, as in FIG. 2, a convenient paradigm is provided for visualizing the action of the cruise control governor. Viewing the cruise control governor from the perspective of FIG. 2 indicates that the engine will produce whatever engine torque is required to maintain a constant vehicle speed. Since the torque that goes into the vehicle varies with the terrain, the torque generation from the engine must also vary in order to maintain a constant vehicle speed.
Cruise control governors are devices that attempt to maintain a desired set speed condition by monitoring the system that they are trying to control. The cruise control governor monitors the road speed of the vehicle and reacts by changing the fuel command to the engine. For example, when the governor detects an underspeed condition, the governor increases the torque generation of the engine in order to increase the speed of the vehicle, thereby compensating for the undesirable underspeed situation. Thus, the governor is not capable of reacting until it recognizes that the vehicle has already deviated from the set speed. Once the vehicle has deviated from the set speed, it is too late for the governor to provide a perfect response, therefore the governor attempts to return the vehicle to the set speed as quickly as possible. Because the vehicle must deviate from the set speed before the governor reacts, it is impossible for the governor to provide a perfect response. This is why the plot of vehicle speed vs. time in FIG. 1(a) exhibits slight deviations both above and below the vehicle set speed. FIG. 3 is a process flow diagram which illustrates the interaction of the governor 22 with the vehicle/engine combination 24. The actual measured vehicle speed is subtracted from the desired set speed (which is set by the driver using the cab interface 20) in order to create a speed error signal. This speed error signal is input to the governor 22, which adjusts the fuel command signal to the vehicle/engine combination 24 in response thereto.
The plot of engine torque vs. vehicle speed in FIG. 2 is referred to as a "droop" curve. Such a droop curve is realized because the controller is attempting to follow a goal droop curve. The controller adjusts its response, and thus the response of the engine, as a function of the current operating conditions of the vehicle and as a function of the goal droop curve. FIGS. 4a-f illustrate examples of various goal droop curves. The shape of the goal droop curve used with any particular controller depends upon the particular response that is desired from the controller.
The ability for the controller to follow the goal droop curves depends upon the gain of the governor. The governor's gain is an indication of the aggressiveness of the controller. A high gain provides a very aggressive governor that will adjust engine torque generation rapidly in an attempt to follow the goal droop curve. However, aggressive gain governors also have a tendency to be unstable. In summary, the goal droop curves define where the controller attempts to maintain vehicle operation, and the governor gains define how aggressively the goal droop curves are followed.
Because vehicle speed determines where on the goal droop curve the controller attempts to operate, environmental factors which affect the speed of the vehicle affect the performance of the controller. One such environmental factor is the grade of the road surface upon which the vehicle travels. Gradability is a concept that allows one to consider the relationship between vehicle speed, the grade of a hill, the full torque curve of the engine, aerodynamic drag, gearing and torque requirements. This concept utilizes a grade curve as illustrated in FIG. 5. The grade curve denotes the torque needed, at every speed, to remain at an equilibrium for a certain combination of hill grade, aerodynamic drag, and gearing selection. FIG. 6 shows some examples of how various hill grades affect the placement of the grade curve. Such grade curves are useful because they provide an easy means to determine if the vehicle is going to accelerate or decelerate. If, at the current vehicle speed, the grade curve is higher than the torque curve, then the vehicle will slow down to the point of intersection between the grade curve and the torque curve. If, at the current vehicle speed, the grade curve is lower than the torque curve, then the vehicle will accelerate to a vehicle speed where the grade curve and the torque curve intersect. FIG. 7 shows an example of such movement.
When the vehicle goes over a hill, the grade varies depending upon where on the hill the vehicle is placed. FIG. 8 shows the various grades which are encountered by the vehicle on a symmetrical hill. As illustrated in FIG. 9, the grade curve for a vehicle progressing to the top of a hill will move to the left as the maximum percent grade is reached, and then move back to the right as the grade is decreased back to zero. If the vehicle slows down at all before the crest of the hill, due to the higher torque requirements, then the vehicle will accelerate before the top of the hill because the grade curve moves to the right as the vehicle approaches the crest of the hill (0% grade). The exact location of the start of the acceleration will depend upon the shape and length of the hill, the rating of the engine, and the aerodynamics of the vehicle.
Because most hills are relatively symmetrical and follow the model of FIG. 8, acceleration of the vehicle as it nears the crest of the hill is undesirable due to the fact that the vehicle will accelerate automatically on the downside of the hill due to the negative grade. Conversely, a vehicle entering a valley will decelerate on the downside of the hill prior to its eventual automatic deceleration when it encounters the upside of the hill on the opposite side of the valley. When a vehicle accelerates prior to a point where the terrain will cause the vehicle to accelerate automatically, or when a vehicle decelerates prior to a point where the terrain will cause the vehicle to decelerate automatically, fuel is wasted.
In the interest of increasing fuel economy of the vehicle, it is therefore desirable to design a controller which is able to recognize that the vehicle is cresting a hill or approaching the bottom of a valley and thereby alter the performance of the cruise control governor in order to obtain maximum fuel economy throughout the entire hill or valley event. The present invention is directed toward meeting these needs.

Cruise control governor using optimal droop selection logic


A coping system for parapet is comprised of three separate components, a plurality of cleats, a plurality of chairs and a plurality of caps. The cleats are secured to the parapet at spaced intervals and each cleat supports a corresponding chair. Each cap extends between at least two cleats and chairs. Adjacent caps are spaced from each other forming a gap between the caps with the gap being located directly above the chair. The chair forms a gutter for routing water away from the top of the parapet. The chair biases the cap away from the parapet to maintain the engagement between the cap and the cleat. All three components are made entirely of metal providing a sealed joint between adjacent caps without the use of organic compounds.

Buildings, particularly those having flat roofs, generally include parapets or comparable structures extending above the roof line on one or more sides. The parapets perform two functions. First, they enhance the aesthetic appearance of the building. Second, they prevent rain water and other fluids from flowing from the roof and onto the face of the building. Eliminating the flow of fluids onto the face of the building helps to maintain the appearance of the building by reducing discoloration of the face as well as helping to maintain the structural integrity of the components used for the building face.
Parapets extend above the roof line and usually terminate in a flat ledge extending the length of the parapet. The flat edge is exposed to the atmosphere and thus requires protection from moisture and the other elements of nature. Copings have been developed to cover, or cap, the flat ledge of the parapets. Generally, these copings are manufactured from metal or plastic and are designed to extend over the entire width of the flat ledge and redirect any fluids such as rain away and off of from the flat ledge.
One of the simplest copings is a single sheet of material extending the length of the parapet. While this type of coping provides some protection, designs which allow a varying width of the flat ledge and designs which provide an inclined surface for the fluid run off have significantly improved the performance of copings. These newer designs for copings include a plurality of anchoring elements or hold down cleats which are attached at predetermined spaced intervals along the flat ledge of the parapet by screws, bolts, nails or other means known in the art. Usually, some type of sealing device is attached to the hold down cleats and a cover or coping element is assembled to adjacent hold down cleats with additional sealing being provided between the cleat and the coping element. The hold down cleat usually includes some type of spacer which will provide for the inclining of the top surface of the coping element to direct fluid flow away from the building face and onto the roof top.
While the newer designs for copings have significantly improved the performance of copings, the interface between the hold down cleats and the coping element has proven to be an area requiring additional development. The hold down cleat can sag due to its own weight or form the weight of water and ice allowing deterioration of the sealing between the components and thus the leaking of fluid onto the parapet itself. In addition, the use of organic supports (plastic chairs, foam inserts and the like) is not compatible with long term durability of the coping system. Organic components can deteriorate over many years due to the high temperatures generated under the coping cover in hot sunny climates. In cold climates, low temperatures make organic components venerable to embrittlement and cracking. In intermediate climates, the continued cycling between high temperatures and low temperatures also has a detrimental effect on the durability of the organic compounds.
Accordingly, continued development of coping systems has been directed towards improved systems for holding the coping plate on the parapet and improving the interface between the coping cover plate and the hold down cleats especially at the joining of adjacent coping cover plates.


An In-phase/Quadrature phase (I/Q) mismatch compensation method of a transceiver is provided. The method includes establishing a first loopback path between a transmitter and a receiver, transmitting a training sequence from the transmitter to the receiver through the established first loopback path, acquiring, at the receiver, a first correlation result value by correlating the training sequence received through the established first loopback path, establishing a second loopback path between the transmitter and the receiver, transmitting the training sequence from the transmitter to the receiver through the established second loopback path, acquiring, at the receiver, a second correlation result value by correlating the training sequence received through the second loopback path, and estimating I/Q mismatch values of the transmitter and the receiver using the first and second correlation result values.

1. Field of the Invention
The present invention relates generally to an In-Phase/Quadrature Phase (I/Q) mismatch calibration method and apparatus, and more particularly, to a transceiver for use in any of Wireless Local Area Network (WLAN), Wireless Personal Area Network (PAN), and 3rd Generation (3G) and 4G cellular mobile communication systems.
2. Description of the Related Art
A mobile communication system can adopt Quadrature Modulation which uses orthogonal In-Phase (I) and Quadrature Phase (Q) simultaneously for up-conversion of a signal from baseband to passband and down-conversion from passband to baseband. The quadrature modulation is advantageous in terms of two-fold increase of transmission on a single carrier but disadvantageous in that a mismatch between the In-Phase and Quadrature Phase of the Local Oscillator (LO) causes mutual interference between I-phase and Q-phase signals and, thus, degrades system performance.
The I/Q mismatch may be divided into two categories, gain mismatch and phase mismatch. The gain mismatch denotes the difference in magnitude between I and Q components of the LO. The phase mismatch denotes the loss of the orthogonality in phase between I and Q components.
If the I/Q mismatch occurs at the quadrature modulator of a transceiver, this degrades Error Vector Magnitude (EVM) and increases Packet Error Rate (PER), resulting in degradation of entire system. Particularly, radio communication systems such as WLAN, WPAN, 3G and 4G cellular communication systems adopt high order modulation schemes including 16 Quadrature Amplitude Modulation (QAM), 64QAM, and 256QAM, which requires calibration of the transceiver I/Q due to the I/Q mismatch, i.e., the radio communication systems become more sensitive to the transceiver I/Q mismatch as the modulation order increases.

I/Q mismatch compensation method and apparatus


A written document (hereinafter referred to as a “work,” on electronic format which includes, stories, novels, education texts, biographies, compilations, collections, anthologies, tracts, and any other traditional format for relatively extensive texts) provides access to reference, bibliography and/or definition material through an electronic software capability associated with the work. Depending upon reader access information or characteristics (e.g., age, grade, proficiency, or position within the work or any other identifiable reader characteristic or access limitation), any request for reference material, definitions, explanations, translations, or other material provided in the associated software capability is automatically limited by system acknowledgement of the reader access information or characteristics. As the reader's access information or characteristics change, the quality and/or quantity and/or format of requested information with respect to a work changes.

1. Field of the Invention
The present invention relates to the field of media, such as text, video, graphics, and sound, containing terms, ideas, images, and information for which background references, footnotes, translations or definitions may be desirable to the reader.
2. Background of the Art
When individuals use primary text such as written, video, film, graphic, or sound recording matter (which includes hard copy material and electronic material), there may be a need or desire to provide reference material to a reader, upon request, to enable the reader to appreciate or understand the text, graphics, or sound. In a learning or scholastic environment, it may also be necessary to limit access to reference or definition material, or, at least, to limit the degree to which terms can, or should be, explained to specific readers depending on their particular, and distinguishable, levels of progress. These levels of progress, for example, may be defined by the reader's age, grade level, program level (e.g., Advanced Placement versus Basic study tracks), stage of study within an ongoing course (e.g., first semester versus second semester), the user's place in the sequence of the (written, video, graphic, or sound recording) material, and the like. At the present time, when a reader requests reference material or definition from within material (a text, sound recording, video game or video), a uniform reference or uniform (single) definition for the requested term is provided. This system has limited informational and educational options both for the providers and users of written, graphic, video, videogames, and sound recordings.

Progressive reference system, method and apparatus


The invention discloses an electronic apparatus comprising a motherboard, a connector, a card member and a first holder. The connector is disposed on the motherboard and the card member is disposed on the connector. The motherboard comprises a first fixing portion and the card member comprises a second fixing portion. The first holder comprises a third fixing portion fixed to the first fixing portion of the motherboard and a fourth fixing portion fixed to the second fixing portion of the card member. Accordingly, once the motherboard or the card member is hit or pulled by an external force, since two ends of the first holder respectively fix the card member and the motherboard, the card member will not be detached from the connector, such that the card member can be connected to the connector well.

1. Field of the Invention
This invention relates to an electronic apparatus, and more particularly to an electronic apparatus which fixes a card member on a motherboard with a holder.
2. Description of the Prior Art
With the rising and flourishing of technologies and information nowadays, computers have been popularized electronic apparatuses. Presently, all of the electronic apparatuses sold in the market (e.g., desktops, laptops, or severs) are connected to peripheral hardware via various kinds of card members. For example, those card members can be interface cards for the hosts that connect to peripheral hardware, to let the hosts communicate and transmit signals with the peripheral hardware and perform the functions of the peripheral hardware. In a traditional electronic apparatus, many interface cards are usually inserted into the motherboard, such as a VGA (Video Graphic Array) card, an audio card, a network card, a USB (Universal Serial Bus) interface card, memory, etc., to expand functions or increasing the performance of the electronic apparatus.
Generally, one or more interface card connectors will be disposed on a motherboard. An interface card is inserted in a corresponding interface card connector with the side which has signal terminals on the interface card. Concurrently, the interface card is fixed on the motherboard with the clamping force of the interface card connector. However, the method of fixing is not firm. If the motherboard is hit or pulled by an external force during transportation or usage of the motherboard, the interface cards will not stay fixed on the interface card connector, which means the interface card will not be electrically connected to the motherboard efficiently.


A numbering scheme is disclosed for implementation in the context of an application display. A user is able to select an item on the display by speaking a number corresponding to a desired control item. In some cases, the screen can include so many numbers that the user loses context and is unable to identify which number they want to select. For this reason, in one embodiment, a temporal switching mechanism is implemented wherein periodic switches (e.g., second-long intervals) occur between showing numbered items and showing a non-numbered screen. In one embodiment, an optional secondary confirmation step is implemented wherein the user sees only the item they just selected and has the chance to (a) learn the programmatic name of the item they selected and/or (b) either confirm and proceed with their selection, or cancel. In one embodiment, the optional secondary confirmation step is omitted if the user speaks a number followed by a predetermined command word.

The present invention generally pertains to user interaction with a computing system. More specifically, the present invention pertains to interactions implemented in the context of a speech recognition system.
There is a trend toward implementation of a natural user interface (NUI) as the next generation of user interface. Much attention has been paid to the improvement of related speech recognition technology. However, additional challenges lie in addressing the usability of such an interface, particularly in the context of a visual interface associated with an application or desktop that supports user interactions implemented in the context of a speech recognition system. There remains a need for a system that enables a user to utilize speech recognition to select any visually indicated control (menu, button, hyperlink, text field, etc.) on a display screen in an efficient and controlled manner, and in a way that is not dependent on traditional physically initiated interaction.
One way to configure a speech recognition input system is to enable a user to select an item displayed on a screen by saying the name of that item. For example, "File" will open the file menu or "OKAY" will initiate action associated with an OK button. One way to implement such functionality is to configure an application to use Accessible Interfaces to programmatically expose GUI controls to assistive technologies, such as speech recognition. For example, the file menu would be exposed by the application declaring that there is an item called "File" located at coordinates 30, 10 to 70, 35. The speech recognition software then reads which GUI controls are available, and uses this information to construct a list (i.e., a grammar) of user statement expectations. For example, the list might contain "File", "Edit", "View" (menu item buttons), as well as "Open", "Bold", "Bullets" (tool bar buttons), or "scroll up", "scroll down" (scroll bar items), and/or other items. When a user speaks a listed item (e.g., "bold"), the speech recognition software calls the application via the Accessible Interfaces to 'click' the appropriate item (e.g., click the "bold" button) thereby initiating an appropriate response.
The described functionality works well in many cases as an efficient way to manipulate GUI controls by voice, but it breaks down under certain scenarios. In one such scenario, if an application omits a programmatic name for a control, the user cannot use voice to manipulate that control since they have no way to identify it (e.g., a name for a particular text box is omitted).
Another scenario that can present a challenge arises when an application has a mismatched name between what the user expects to say and the actual programmatic name of the control. Under these circumstances, the user will not typically speak the name of the control and thus not be able to manipulate it. For example, if an image in an Internet browser has a name of "Flag" yet the image depicts an emblem with the text "House of Windsor", the user will naturally try and say "House of Windsor" and never know that they were meant to say "Flag". In another example, if a button in a media player application is programmatically called "WnEqBtn1" yet the text on the label reads "Equalizer settings," the user will never know to say "WnEqBtn1".
Yet another scenario presenting a challenge arises when an application depicts something graphically yet the user does not know what it is called (even if it is named 'appropriately'). In this case, the user will not know how to speak the name of the control to manipulate it. For example, a round button with an arrow therein on an operating system task bar may be called "Show Hidden Icons" but all the user can see is the graphical representation. In another example, an icon is presented on a toolbar presenting a graphical representation indicating a functionality of drawing a border around a table. The majority of users may not know that the icon is called "Outside Border", even if they do know that it is a button they need to press to draw a border around something.
In all the scenarios discussed above, even users dependent on speech recognition can use voice-enabled keyboard emulation ("Computer Press Tab Tab Tab Enter") or mouse simulation ("Mousegrid 1 3 4 7 Click") to select the item they want to manipulate. Such methods enable the user to solve each of the challenges associated with the described scenarios, though at a cost of (a) a significant decrease in efficiency and (b) an increased chance of error due to a limited capacity for precision.
One way to overcome the described challenges associated with speech recognition selection would be to draw a static set of numbers over everything on a display. The user could then simply select a number that corresponds to a desired item for selection. A disadvantage associated with this approach is that it is not uncommon for an application display to incorporate so many numbers that a user cannot clearly determine which number corresponds to an item they want to select. One solution for the crowded numbering problem is to incorporate multiple layers of numbering (e.g., choose word processing application, then choose toolbar area, then choose toolbar, then choose a button on the toolbar, wherein each selection incorporates identification from a limited set of numbers). The layers enable a user to step through a GUI to the item they wish to select. This described method of selection is relatively inefficient and attempts to reduce the number of layers can require solving problems having great mathematical complexity.

Graphic user interface schemes for supporting speech recognition input systems


A converter 10 has an IGBT power switch 34. A resonant tank circuit 30 couples the IGBT to a voltage source. A gate controller turns the IGBT on and off by applying a suitable gate control voltage to the gate. The resonant tank circuit imposes a sinusoidal waveform on the emitter current. After the emitter current reverses direction, the gate signal is terminated and the IGBT is shut off. Minority carriers in the emitter are swept away by the tank circuit and are further deposited in a transformer that is coupled to the tank circuit.

This invention relates to DC-to-DC converters and, in particular, to quasi-resonant converters using Insulated Gate Bipolar Transistors (IGBT).
Quasi-resonant switching converters are used to convert one level of DC voltage and current to another level of DC level and current. They provide a similar function for direct current conversion that transformers provide for AC current and voltage converters use power semiconductor devices that turn off and on at relatively high rates. DC output is modulated by the time that the power devices are either on or off. This time is typically referred to as the xe2x80x9cduty cyclexe2x80x9d. The devices can be rapidly switched on or off and the resulting output is applied to an output filter for smoothing out the variations and switching waveforms.
Modern switching converters frequently use techniques that were pioneered by Edward J. Miller in his U.S. Pat. No. 4,138,715 issued Feb. 6, 1979. In that patent the basic problem of switching losses in DC converters is solved by applying a tank circuit to the switch. When power semi-conductor devices are switched at full current or full voltage, it takes a significant amount of time for the device to return to zero current or zero volts. In that time, the device and the circuit can experience short transients with relatively high peaks. These transients represent a waste of power and also a source of unwanted electromagnetic interference. In addition, rapid switching at high currents and high voltages creates thermal stresses on the power semi-conductors and thereby limits their useful life.
IGBTs are popular switching devices. One of their benefits is that they provide very low resistance in their on state. In addition, they can be rapidly switched on and off using their MOS controlled gate. In general, their on resistance is substantially less than power MOSFETs and they can handle higher currents for similar size devices. However, one drawback of the IGBT is that it includes minority carriers. If there is a high voltage or a high current in the collector when the IGBT is switched off, those carriers must be removed. Unfortunately, the minority carriers decay by recombination over a period of time. In effect, the presence of minority carriers in the collector resembles the discharge of a capacitor. When there are a large number of minority carriers, they can generate a substantial amount of heat until they are removed from the collector. This feature of IGBTs has limited their usefulness in DC-to-DC converters.
The invention overcomes the defects of the prior art and solves the problem of the slow decay of minority carriers in IGBTs by providing a quasi-resonant circuit for an IGBT in a DC-to-DC converter. A resonant tank circuit is coupled to the collector of the IGBT. The resonant tank circuit generates a quasi-sinusoidal waveform for the collector voltage and for the emitter current. After the collector voltage falls below ground, the gate pulse is terminated and the IGBT turns off. Then, the minority carriers on the collector are swept away by the inductor of the tank circuit. Those minority carriers are stored in a capacitor that is coupled across the primary winding of the transformer. In this way, the minority carriers are rapidly removed from the collector thereby quickly discharging the IGBT and making it ready for its next cycle.


In a sector servo type magnetic disk apparatus having a carriage lock mechanism for locking a carriage by using magnetic force of a magnet, when a magnetic head placed on a CSS (contact start and stop) zone in contact with a disk is unlocked and moved to a data zone, a driving current supplied to a voice coil motor for driving the carriage is increased at a predetermined rate, until servo data recorded in the data zone is detected.

1. Field of the Invention
This invention relates to a data recording/reproducing apparatus such as a magnetic disk apparatus, and more particularly to a data recording/reproducing apparatus having a carriage lock mechanism using a magnet.
2. Description of the Related Art
In a magnetic disk apparatus employing the CSS (Contact Start and Stop) method, a CSS zone, i.e., an area other than the data zone, is formed in the innermost portion of a disk (recording medium), to protect the surface of the disk from damage. The magnetic head is placed in contact with the CSS zone when a power source of the magnetic disk apparatus is turned off. The magnetic head is included in a carriage and moves over the disk in accordance with the movement of the carriage. When the power source of the magnetic disk apparatus is turned on and the disk is rotated, the magnetic head is flown from the CSS zone, and then toward the outer portion of the disk, i.e., the data zone.
When the power source of the magnetic disk apparatus is turned off, if the apparatus vibrates, thereby moving the carriage, the magnetic head in contact with the CSS zone may be moved, resulting in damage to the surface of the disk. To prevent this, a lock mechanism for locking the carriage is provided in the magnetic disk apparatus, so that the carriage including the magnetic head on the CSS zone is not easily moved.
For this purpose, a carriage lock mechanism which locks the carriage by utilizing magnetic force of a magnet may be used. This carriage lock mechanism locks the carriage including the magnetic head on the CSS zone by the magnetic force of, for example, the magnet of a voice coil motor (VCM) for moving the carriage. In the carriage lock mechanism, when the magnetic head is moved from the CSS zone to the data zone (this movement is hereinafter referred to as an initial seek operation), the force which releases the carriage from the locked state is applied to the carriage.
In a conventional apparatus, a constant current necessary to generate force for releasing the carriage from its locked state is continuously supplied to the voice coil motor during an initial seek operation. However, as shown in FIG. 1, since the magnetic force (hereinafter referred to as offset force) does not affect the carriage which includes the magnetic head on the data zone relatively large force is applied to the carriage in the direction toward the outer portion of the disk. As a result, the magnetic head cannot detect servo data in the data zone, and may run out of control. Therefore, since the magnetic head and the surface of the disk may be damaged, data recorded on the disk will be destroyed.
Under the circumstances, it is demanded to develop a data recording/reproducing apparatus wherein the carriage is released from the locked state at an initial seek operation without causing the magnetic head to run out of control.


This document describes systems, devices, and methods that measure a distance between ultrasound or other acoustic transducers to provide a contractility or other therapy efficacy indication. In one example, the indication is communicated to a caregiver for assisting in the caregiver's determination of particular therapy settings. In another example, the indication is used in a feedback controller to automatically adjust one or more therapy parameters based at least in part on the indication.

When functioning properly, the human heart maintains its own intrinsic rhythm. Its sinoatrial node generates intrinsic electrical cardiac signals that depolarize the atria, causing atrial heart contractions. Its atrioventricular node then passes the intrinsic cardiac signal to depolarize the ventricles, causing ventricular heart contractions. These intrinsic cardiac signals can be sensed on a surface electrocardiogram (ECG) obtained from electrodes placed on the patient's skin, or from electrodes implanted within the patient's body. The surface ECG waveform, for example, includes artifacts associated with atrial depolarizations ("P-waves") and those associated with ventricular depolarizations ("QRS complexes").
A normal heart is capable of pumping adequate blood throughout the body's circulatory system. However, some people have irregular cardiac rhythms, referred to as cardiac arrhythmias. Moreover, some patients have poor spatial coordination of heart contractions. In either case, diminished blood circulation may result. For such patients, a cardiac rhythm management system may be used to improve the rhythm and/or spatial coordination of heart contractions. Such systems are often implanted in the patient and deliver therapy to the heart.
Cardiac rhythm management systems include, among other things, pacemakers, also referred to as pacers. Pacers deliver timed sequences of low energy electrical stimuli, called pace pulses, to the heart, such as via an intravascular lead wire or catheter (referred to as a "lead") having one or more electrodes disposed in or about the heart. Heart contractions are initiated in response to such pace pulses (this is referred to as "capturing" the heart). By properly timing the delivery of pace pulses, the heart can be induced to contract in proper rhythm, greatly improving its efficiency as a pump. Pacers are often used to treat patients with bradyarrhythmias, that is, hearts that beat too slowly, or irregularly. Such pacers may also coordinate atrial and ventricular contractions to improve pumping efficiency.
Cardiac rhythm management systems also include cardiac resynchronization therapy (CRT) devices for coordinating the spatial nature of heart depolarizations for improving pumping efficiency. For example, a CRT device may deliver appropriately timed pace pulses to different locations of the same heart chamber to better coordinate the contraction of that heart chamber, or the CRT device may deliver appropriately timed pace pulses to different heart chambers to improve the manner in which these different heart chambers contract together.
Cardiac rhythm management systems also include defibrillators that are capable of delivering higher energy electrical stimuli to the heart. Such defibrillators include cardioverters, which synchronize the delivery of such stimuli to sensed intrinsic heart activity signals. Defibrillators are often used to treat patients with tachyarrhythmias, that is, hearts that beat too quickly. Such too-fast heart rhythms also cause diminished blood circulation because the heart isn't allowed sufficient time to fill with blood before contracting to expel the blood. Such pumping by the heart is inefficient. A defibrillator is capable of delivering a high energy electrical stimulus that is sometimes referred to as a defibrillation countershock, also referred to simply as a "shock." The countershock interrupts the tachyarrhythmia, allowing the heart to reestablish a normal rhythm for the efficient pumping of blood. In addition to pacers, CRT devices, and defibrillators, cardiac rhythm management systems also include devices that combine these functions, as well as monitors, drug delivery devices, and any other implantable or external systems or devices for diagnosing or treating the heart.
One problem presented by some cardiac patients is determining the extent of any benefit obtained from a particular cardiac resynchronization therapy (e.g., left ventricular pacing, bi-ventricular pacing, and/or multisite pacing within the same heart chamber), or parameter settings controlling such therapy. This may include determining whether a patient is actually benefitting from the CRT or other therapy being received. This may also include determining whether a particular CRT or other therapy benefits a particular patient more or less than another different CRT or other therapy. For these and other reasons, the present inventors have recognized that there exists an unmet need for improved techniques of determining the efficacy of such therapy.

Cardiac rhythm management systems and methods using acoustic contractility indicator


A system and method allows a debugging tool to operate in an environment differently from an expected environment of an application being debugged, yet allows the application to be debugged in an environment in which it is expected to operate. Debugging commands are communicated to an application environment from the debugger running in a different environment and debugging information is communicated from the application environment to the debugger.

Development of application programs can involve a development stage and then a debugging stage, during which problems with the application program may be detected and/or solved. Specialized debugging tools can simplify and speed up the debugging stage of an application program. Such debugging tools can allow a user to see or even change the value of variables at certain stages of program execution so that a developer can find potential problems in the application program and attempt to solve these problems.
During the operation of the debugging tool, the application program is executed in an environment that operates identically or nearly identically to at least one environment in which the application program is expected to be operated. Identical or nearly identical operation can be important to the debugging process, because if an application runs differently on the debugger than it does in the environments in which it is expected to operate, problems with can occur in such expected environments either might not appear when the application is run by the debugger or can exhibit different behaviors in the debugger than they do in the normal operating environment of the application program, making problems reported by users of the application program more difficult to track and solve. Still other problems might appear when the application is run on the debugger may not appear in any expected operating environment, causing the developer to waste time solving problems that may never appear. This can cause the developer to lose confidence in the debugger.
When the runtime environment is the same environment in which the debugging tool operates, the debugging tool can be used to accurately operate the application program and perform certain debugging functions such as showing the value of variables, allowing the user to change the value of variables and other similar functions.
However, if the debugging tool does not operate in one or more of the environments in which an application program is expected to operate, the debugging tool can not execute the application program in its native environment, causing the difficulties described above. An example of a debugging tool that does not operate in the native environment of the application program is the conventional Flash 5 authoring tool commercially available from Macromedia, Inc., of San Francisco, Calif. Flash 5 operates in a Microsoft Windows or Apple Macintosh environment and contains a debugging tool. Flash 5 is used to develop applications for the Flash 5 player, which operates as a plug-in to a browser, such as the conventional Microsoft Internet Explorer commercially available from Microsoft Corporation of Redmond, Wash. or the Navigator program commercially available from the Netscape Corporation of Mountain View Calif. and owned by America Online of Dulles, Va. Because Flash 5 applications are executed in an environment of the browser, but the Flash 5 debugging tool operates natively under the operating system, the problems described above can result if the Flash 5 debugging tool is used to debug a Flash 5 application.
One potential solution to this problem is for the user to program the functionality of the debugger into the application program. This potential solution is suboptimal because, although the user can program some of this functionality into the application program, such programming takes time that the programmer could use to solve problems with the application program.
One potential solution to the problems that arise if the debugging tool operates in an environment that is different from the environment expected by the application program would be for the debugging tool to simulate the environment in which the application program is expected to operate. However, a simulation of this type can involve anticipating how an inordinately large number of circumstances would be anticipated by the expected operating environment of the application, a task that would be prone to inaccuracies even if it could be attempted. If there is more than one environment in which the application program being developed operates, the debugging tool would have to be able to simulate all of the environments, compounding the difficulties of simulation. Furthermore, if the environments are evolving, the debugging tool must be constantly updated to accurately simulate the ever evolving environments. These factors can make the simulation of multiple evolving environments a seemingly insurmountable task.
What is needed is a system and method that can allow a debugging tool to accurately assist with debugging an application program even if the application program operates in one or more environments that are different from the environment in which the debugging tool operates.

System and method for debugging programs run in a variety of environments


A method for operating a display system in a vehicle (03) when driving into a parking space (06), uses a camera (01) with an image processing unit in which the image data obtained by the camera (01) can be processed and a display screen (02) in the interior of the vehicle. After the vehicle has moved to the vehicle position in which the first parking-space icon (07) has been brought to overlay the parking space (06) shown in the real-time image, a second parking-space icon (09) is faded into the real-time image on the display screen (02) by the image processing unit, with this second parking-space icon (09) in the real-time image in true scale indicating a region which after moving along a first segment (15) of the travel path (14) towards the parking space (06) must be brought to overlay the parking space (06) shown in the real-time image. After the vehicle has moved to the vehicle position in which the second parking-space icon (09) has been brought to overlay the parking space (06) shown in the real-time image, a third parking-space icon (11) is faded into the real-time image on the display screen (02) by the image processing unit, with said third parking-space icon (11) in the real-time image in true scale indicating a region which after moving along a second segment (16) of the travel path towards the parking space (06) must be brought to overlay the parking space (06) shown in the real-time image.

From the state of the art, many approaches are known for supporting the driver when parking a vehicle.
DE 100 45 616 A1 describes a method for operating a display system. In this method, additional distance sensors are provided by means of which the parking space is measured. Based on this measured data, a control device assesses whether the parking space found is sufficiently large for parking the vehicle. If this is the case, a parking strategy by means of which the vehicle can be steered into the parking space is automatically calculated. This known method is associated with a disadvantage in that the system of distance sensors that are required for reliably measuring the size of the parking space is extremely expensive. Furthermore, this system leaves open a number of product liability issues, since, in the case of any errors made by the distance sensors during the measuring process, damage to other vehicles or the vehicle being parked can easily occur.
From DE 101 61 316 A1 a further parking-maneuver support system is known. In this system, the driver can select a correspondingly suitable mode depending on the given parking situation, with a pre-stored situation being displayed on the screen, depending on the respective mode selected. Depending on the subsequent vehicle movements, on the display screen, the position of the vehicle being parked changes relative to the pre-stored situation. However, the support system only functions in a satisfactory manner if the actual starting position of the vehicle agrees with the vehicle's starting position in the situation in the intermediate storage system. To ensure this, it is proposed that corresponding sensor systems for measuring the parking space be used. Alternatively, it is proposed by means of suitable position locating devices to enable the driver to bring the actual starting position into agreement with the starting position of the situation in the intermediate storage system. This system is associated with the disadvantage that it is not possible to reliably ensure truly adequate agreement between the actual starting position and the starting position of the situation in the intermediate storage system.
From DE 100 65 327 A1 a method is known in which the image data from a camera is displayed to the driver as an image on a display screen in the interior of the vehicle. A parking-space icon is faded into this image, which for example shows the real-time situation at the rear of the vehicle, wherein this parking-space icon in the real-time image in true scale indicates a region which the vehicle can be moved into from its actual starting position, taking into account the vehicle's characteristics, in particular vehicle size, maximum steering angle and maximum angle of steering in the opposite direction, during the parking procedure. In order to find a suitable parking place which is large enough for parking the vehicle, the driver then maneuvers the vehicle until the faded-in parking-space icon is essentially congruently superimposed on the parking space shown in the real-time image. As soon as this is the case, the vehicle is in a suitable starting position to drive into the parking space that is suitable for parking.
Starting from the proposal for finding a suitable parking space as disclosed in DE 100 65 327 A1, DE 102 50 021 proposes a method with which the found parking space can subsequently be driven into by the vehicle, with the aid of the display system in the vehicle. In the method described in DE 102 50 021, the defined starting point is the position of the vehicle in which the first parking-space icon has been made to overlay the parking space shown on the display screen. The image which is displayed at this starting point in time is put into the intermediate storage system and subsequently, during the following parking procedure is permanently displayed on the display screen. During the actual parking procedure, commencing with the starting position, a vehicle icon is faded into this fixed image, with the position of the vehicle icon being calculated, relative to the situation on screen, based on the movement data for the vehicle since the time the vehicle left the starting position. This provides the driver with the opportunity of controlling his/her own steering movements during the parking procedure, relative to the situation at the starting point. This method is associated with the disadvantage in that during the parking procedure no updated image of the external environment is displayed to the driver. Consequently, it can happen that the situation in the external environment changes without this being detectable on the screen of the display system during the parking procedure. Furthermore, this method still requires the driver to make the suitable steering movements during parking, without direct support being provided by the display system.

Method for operating a display system in a vehicle for driving into a parking space


An incandescent bulb having a looped filament within an evacuated bulb containing a gas mixture including a halogen employs magnetic means external to the bulb to provide inductive heating of the filament so that there are no connections passing through the bulb envelope. Alternative embodiments include a toroidal bulb wherein a second arm of a magnetic circuit passes normally through the center of the bulb toroid, alternating voltage excitation being supplied to a first arm of the magnetic circuit; and an elliptical bulb that is disposed between oppositely facing ends of a two-part second magnetic arm that is similarly excited. In a further embodiment, an additional arm of the magnetic circuit serves to form a non-uniform field in the vicinity of the filament, thereby to provide a lift force against the force of gravity so as to minimize filament sagging.

1. Field of the Invention
This invention relates generally to illumination devices, especially light bulbs, and more particularly to illumination devices in which a filament is made incandescent so as to provide light, and for which a principle design element has been the attainment of a longer useful life.
2. Background Information
Incandescent light bulbs can become non-functional, or "burn out," as a result of breakage or other loss of structural integrity. Such bulbs include metallic filaments that become broken, or there may occur a rupture in the hermetic seal by which the lead-in conductors that provide power to the device are passed into the interior of the bulb. Typically, such breakage or loss of integrity results from simple evaporation of the filament material and a resultant loss of mechanical strength. Breakage may also result from heat stress, both from heat cycling in being turned on and off, and from temperature gradients established at the juncture of various internal structures with the glass or glass-like envelope that surrounds those internal parts and provides the support required to hold those parts in position.
To counteract such filament evaporation, such bulbs may include, along with a filling of inert gas such as argon, a small amount of halogen or compounds thereof, the latter acting to re-deposit evaporated filament material back onto the filament at the hottest parts thereof. While this procedure is quite effective in permitting hotter filament temperatures and hence more efficient light emission, a consequence of having the halogen gas present is that filament material is "scavenged" thereby from the colder ends of the filament near to the lead-in conductors and the seal with the surrounding glass envelope, whereby such colder ends similarly may become weak and eventually break.
Another source of bulb failure involves the interface between the glass envelope and the lead-in conductors. For example, U.S. Pat. No. 3,420,944 issued Jan. 7, 1969 to Holcomb describes a lead-in conductor having a thin intermediate foil or ribbon portion made of a refractory metal such as molybdenum at the point of the seal. Such metal is subject to oxidation at its outer end and ultimately to breakage as a result of the infusion of oxygen from the surrounding atmosphere into the seal, hence one solution to the problem has been to provide to the foil a coating of an oxidation-resistant material such as chromium. However, such coatings have been found to undergo chemical reaction with the internal halogen atmosphere, hence to avoid that occurrence Holcomb limits the application of the oxidation-resistant material to an outer segment of the foil, the inwardly extending uncoated molybdenum being unaffected by the interior halogen atmosphere.
In addition to chemical attacks on such intermediate ribbon portions, as was previously noted active halogens such as bromine also cause corrosion of the filament coils themselves near the ends of the filament, as a result of sharp temperature gradients both between adjacent coils of the filament and between the filament and a connecting spud that attaches the filament to the lead-in connectors. In U.S. Pat. No. 3,431,448 issued Mar. 4, 1969 to English, that effect is sought to be minimized or eliminated through use of a structural design wherein sharp temperature gradients are reduced. U.S. Pat. No. 4,568,854 issued Feb. 4, 1986 to Westlund et al., uses a particular ceramic base for improved heat dissipation in a type of high temperature tungsten halogen lamp.
Yet another cause of filament breakage lies in a "sagging" effect whereby an initially horizontally disposed filament having the usual coiled structure will become elongated upon being incandesced, the center portion thereof will sag downwardly from the effect of gravity, and the resulting curvature in the filament may ultimately bring adjacent turns of the coils thereof into contact so as to short out, or contact may similarly be made between a coil and a mounting structure. Even in the absence of such breakage, such sagging serves to move downwardly the central source of light from the bulb, thereby requiring adjustment in the position of the bulb when it is used as a light source in a focused system of lenses. As described in U.S. Pat. No. 3,789,255 issued Jan. 29, 1974 to Sell et al., inclusion within the filament material of dopants in the form of alkali silicates, or in the Sell et al. patent itself of means for producing helium-filled bubbles within the filament, will result upon incandescence of the filament in the growth of elongated and interlocked grains or crystals that are axially disposed and serve to minimize sagging.
U.S. Pat. No. 4,451,760 issued May 29, 1984 to Griffin et al. addresses the issues of filament sag and halogen corrosion through the introduction into the envelope of a quantity of copper, e.g., as one of the lead-in wires, a plating on the lead-in wires, a separate copper insert, or a coating on the filament. One source of filament sag is understood to lie in grain boundary slippage within the filament material, particularly in halogen lamps that will have present some amount of gaseous oxygen, since such slippage is thought to be facilitated by free oxygen. That oxygen is also thought to exacerbate metal corrosion by the halogen gas. The copper serves to remove oxygen and thereby minimize both grain boundary slippage and corrosion.
In U.S. Pat. No. 4,449,398 issued Feb. 12, 1985 to Munroe, an elongate incandescent bulb is described that has relatively massive terminals at each end thereof, and one or more elongate helical coils, supported on a stiff refractory central element, extending therebetween. This structure permits use of filament coils of a size larger than is customary and is thus less susceptible to breakage.
As opposed to such direct energy input to a filament, fluorescent bulbs of the type described in U.S. Pat. No. 3,987,335 issued Oct. 19, 1976 to Anderson operate not by means of a heated filament but rather by the fluorescence of a phosphor that has been excited by radiation from a contained, ionized gas. As described by Anderson, previous efforts to provide excitation of the contained gas so as to produce that ionization have included coupling electrical energy thereinto by means either of ordinary induction using an electrical air transformer or by electromagnetic induction, i.e., an rf energy source, but such efforts have proved to be too inefficient and also become sources of possibly dangerous rf radiation. It is also known to use rf fields for the purpose of "flashing" a "getter," i.e., a piece of magnesium or the like within the bulb is brought to incandescence by an rf field so as to react with residual gases left within an evacuated bulb and thereby effectively remove the same.
Efforts based upon the use of iron or ferromagnetic transformer cores have likewise proved to be too inefficient, i.e., at the frequencies required for useful energy transfer to the gas the eddy current heating losses occurring in such cores become too great, resulting not only in a loss of energy but also in creating unacceptable heat levels within the bulb. The Anderson patent describes a device in which ionization in the gas is induced by a transformer that is only partially contained within the bulb envelope, the portion of the transformer that is open to the atmosphere serving as a means for cooling of the transformer as a whole.
Lamps that provide fluorescence energy by means of a spark discharge within a gas are described in U.S. Pat. No. 4,187,446 issued Feb. 5, 1980 to Gross et al. and in U.S. Pat. No. 4,311,942 issued Jan. 19, 1982 to Skeist et al. Both such patents employ ballast designs that employ diverging magnetic fields which serve to expand the arc volume for increased gas excitation while also limiting the arc current. U.S. Patent No. 4,855,635 issued Aug. 8, 1989 to Grossman et al., describes the use of permanent magnets in manipulating the arc shape.
From the foregoing, it is apparent that heating of a filament to incandescence by direct electrical connection to an external current source must necessarily involve numerous technical problems arising principally from the presence of heat gradients in passing from inside to outside of the bulb envelope and within the filament itself. Sagging of that filament introduces another cause of breakage. Fluorescent bulbs avoid such filament problems, and moreover provide light with substantially greater efficiency than do incandescent bulbs. However, the fluorescent bulb introduces its own inefficiencies, commencing with the need to achieve a transformation of electrical energy from a conducting environment to a gas; secondly, ionization of that gas; thirdly, ionic de-excitation to provide radiation; fourthly, application of that radiation to the excitation of a phosphor; and finally, emission of light from that phosphor. In particular, the process of exciting the gas by means either of inductive coupling or an arc discharge must be inherently inefficient, given the volume-extended and spaced-apart nature of any gas relative to any particular means for exciting the same. Such inefficiency is exacerbated by the fact that energy absorption by a gas is at least quasi-quantized in nature, and the relatively crude, macroscopic methods of inductive or arc excitation cannot take account of the most efficient energy absorption profile of the gas as defined, e.g., by its frequency-dependent Einstein absorption coefficient. Such processes may be improved by the use of appropriate magnetic fields to control and shape the excitation process, but yet it remains as a substantial barrier to the efficient production of light. What is needed and would be useful, therefore, is a method and apparatus by which a filament within an evacuated envelope could be brought to incandescence while avoiding the problems of heat gradients inherent in the use of lead-in conductors. It would also be useful if means could be provided by which sagging of the filament could be avoided. No such method and apparatus being otherwise available, they are now provided by the present invention.

Inductively coupled incandescent light bulb


The nucleoside analog 2'-fluoro-5-methyl-1-.beta.-D-arabinofuranosyluracil (FMAU) has been found to have an especially desirable combination of properties for use as an imaging agent, including in particular limited in vivo catabolism. Methods for the preparation of the .sup.11 C!-labelled FMAU and for the use of the labelled material are also provided.

This invention relates generally to the fields of biochemistry and medicine. More particularly, the present invention relates to compositions for use in imaging cancer or infectious disease.
Imaging of cellular proliferation in vivo using radiolabeled analogues of nucleosides such as .sup.13 I!-IUdR and .sup.11 C!-thymidine is plagued by extensive catabolism of the parent compounds following intravenous administration, limiting uptake into the DNA of tumor tissues. Such catabolic events include dehalogenation, cleavage of the sugar moieties from the base, and ring opening of the base. In vivo assessment of such events requires complex mathematical models to interpret kinetic data obtained in imaging studies.
Mathematical models currently being designed to interpret positron emission tomography (PET) kinetic data obtained from .sup.11 C! thymidine studies in tumors are generally cumbersome, in large measure due to the presence of significant levels of short-term catabolism of thymidine with subsequent production of several radiolabeled byproducts in plasma and tissue Martiat P. H., Ferrant A., Labar D., et al. (1988) In vivo measurement of carbon-11 thymidine uptake in non-Hodgkin's lymphoma using positron emission tomography. J. Nucl. Med. 29, 1633-1637; Shields A. F., Larson S. M., Grunbaum A., and Graham M. M. (1984). Short-term thymidine uptake in normal and neoplastic tissues: Studies for PET. J. Nucl. Med. 25, 759-764; Shields A. F., Coonrod D. U., Quakenbush R. C., et al. (1987) Cellular sources of thymidine nucleotides: Studies for PET. J. Nucl. Med. 28, 1435-1440; Wong C. Y. O., Yue N., Chan B., et al. (1994) .sup.11 C!-Thymidine PET imaging as a measure of DNA synthesis rate: A preliminary quantitative study of human brain glioblastoma. J. Nucl. Med. 35, 9P; Mankoff D. A., Graham M. M., and Shields A. F. (1994a) Graphical analysis method for estimating blood-to-tissue transfer constants for tracers with labeled metabolites. J. Nucl. Med. 35, 34P, 1994; Mankoff D. A., Shields A. F., Lee T. T., and Graham M. M. (1994b) Tracer kinetic model to quantitative imaging of thymidine utilization using .sup.11 C!-thymidine and PET. J. Nucl. Med. 35, 138P!. Though potentially less complex, modeling of the kinetic behavior of ring labeled thymidine is likewise non-trivial Shields ASF., Graham M. M., and O'Sullivan F. (1992) Use of .sup.11 C!-thymidine with PET and kinetic modeling to produce images of DNA synthesis. J. Nucl. Med. 33, 1009-1010; Mankoff et al., 1994a,b, supra!. In the case of imaging studies with radioiodinated IUdR using conventional nuclear medicine techniques, in addition to significant dehalogenation it has also been demonstrated that UdR, once formed, may be converted to TdR in mammalian systems and subsequently incorporated into DNA Commerford S. L. and Joel D. D. (1979) Iododeoxyuridine administered to mice is de-iodinated and incorporated into DNA primarily as thymidylate. Biochem. Biophys. Res. Comm. 86, 112-118!.
The short-term catabolism of .sup.11 C and .sup.14 C-methyl!-thymidine have been extensively studied Conti P. S., Hilton J., Magee C. A., and Anderson J. H. (1989) Tumor imaging with positron-emission tomography (PET) and .sup.11 C!-thymidine: Determination of radiolabeled thymidine metabolites by high pressure liquid chromatography (HPLC) for kinetic data analysis. Radiology 173, P402; Conti P. S., Hilton J., Magee C. A., and Anderson J. H. (1990) Analysis of nucleoside metabolism during positron emission tomography (PET) imaging studies of brain tumors with carbon-11 labeled thymidine (TdR). 199th Meeting of American Chemical Society, Boston, Mass. April 22-27!. Such studies have demonstrated that significant catabolism occurs once thymidine has been administered intravenously, with the notable radiolabeled products being thymine, dihydrothymine, beta-ureidoisobutyric acid, and beta-aminoisobutyric acid. The latter constitutes the most abundant radiolabeled species in plasma and tissues by 10 minutes post-injection. While .sup.11 C!-CO.sub.2 is the most abundant radiolabeled species in plasma following administration of ring labeled thymidine Shields A. F., Kozell L. B., Link J. M., et al. (1990b) Comparison of PET imaging using .sup.11 C!-thymidine labeled in the ring-2 and methyl positions. J. Nucl. Med. 31, 794; Shields A. F., Swenson E. R., and Bassingthwaighte J. B. (1990c) Contribution of labeled carbon dioxide to PET imaging of .sup.11 C!-labeled compounds. J. Nucl. Med. 31, 909!, radiolabeled thymine, dihydrothymine, and beta-ureidoisobutyric acid also are present, albeit in lesser amounts. Despite its extensive catabolism, it has been demonstrated that .sup.11 C!-thymidine has utility in tumor imaging in both animal models and patients Larson S. M., Weiden P. L., Grunbaum A., et al. (1981) Positron imaging feasibility studies. I: Characteristics of .sup.3 H!-thymidine uptake in rodent and canine neoplasms: Concise Communication. J. Nucl. Med. 22, 869-874; Conti P. S., Kleinert E. L., Schmall B., et al. (1984a) Potential use of carbon-11 labeled thymidine (TdR) for studying the effect of therapy on prostatic adenocarcinoma in vivo. 32nd Annual Meeting of the Radiation Research Society, Orlando, Fla., March 25-29; Conti P. S., KIeinert E. L., Schmall B., Whitmore W. F., Jr. (1984b) Comparative uptake studies of radiolabeled thymidine in the Dunning R3327H fast-growing and R3327H slow-growing prostate adenocarcinomas in vivo. 79th Meeting of the American Urological Association, New Orleans, La., May 6-10; Conti, P. S., Schmall, B., Herr, H. W., et al. (1985) Carbon-11 labeled alpha-aminoisobutyric acid, 2-deoxy-D-glucose and thymidine as potential imaging agents for prostatic and renal malignancies. Surgical Forum 36, 635-637; Conti P. S., Camargo E. E., Grossman S. A., et al. (1991) Multiple radiotracers for evaluation of intracranial mass lesions using PET. J. Nucl. Med. 32, 954; Shields et al., 1984, 1987, 1990b,c, supra; Shields A. F., Lim K., Grierson J., et al. (1990a) Utilization of labeled thymidine in DNA synthesis: Studies for PET. J. Nucl. Med. 31, 337-342; Martiat et al. 1988, supra; Strauss L. G. and Conti P. S. (1991) The applications of PET in clinical oncology. J. Nucl. Med. 32, 623-648; Schmall B., Conti P. S., Schaeffer D. J., and KIeinert E. L. (1992) Tumor and organ biochemical profiles determined in vivo following uptake of a combination of radiolabeled substrates: Potential applications for PET. Amer. J Phys. Imag. 7 , 2-11; Wong et al. 1994, supra; Vander Borght T., Pauwels S., Lambotte L., et al. (1994) Brain tumor imaging with PET and 2-.sup.11 C!-thymidine. J. Nucl. Med. 35: 974-982!.
There is thus a long-felt need in the art for a suitable partially or non-catabolized imaging agent (e.g., nucleoside analog) for use in, e.g., tumor proliferation studies with PET. Except for limited catabolism, an ideal tracer should share the other in vivo characteristics of thymidine, including cell transport, phosphorylation by mammalian kinase, and incorporation into DNA. In particular, development of a partially or non-catabolized thymidine analog would greatly simplify imaging and modeling approaches and potentially provide higher tumor to target ratios due to more selective incorporation of radiotracer.
It is an object of the present invention to provide compositions and methods which do not suffer from the drawbacks of the heretofore-known compositions.

Imaging agents and methods for the preparation and use thereof

University Advanced Bio-Imaging Associates


In accordance with one embodiment, apparatus are provided, which include a digital continuous-tone two-dimensional authentic image and an image processor. Tamper message data is provided which represents a tamper message when viewed. Two halftoning screens are provided to be applied to at least a portion of the continuous-tone two-dimensional authentic image, to embed the tamper message data within a portion of the authentic image, in a manner so as to be substantially not visible in a printed or displayed version of the authentic image absent image processing or tampering of the authentic image. The screens include a first screen to apply first elements arranged in a first way, and a second screen to apply second elements arranged in a second way. A halftoner applies the two halftoning screens to visibly portray desired information of the continuous-tone authentic image. The first screen is applied in a limited area of the authentic image and in a form defined by the tamper message data. The second screen is applied in an area abutting the limited area.

Various known techniques exist for embedding information into a printed work, for example, a legal document or currency. The embedded information may be visual information, which can be embedded into the document by treating the document. For example, micro printing produces an image that is too small to be discerned by the naked eye. The size, for example, of the image may be one hundredth of a normal type size. While features of this size can be easily printed, they are difficult to copy or scan. The printed feature is thus covert, and may be viewed using a magnifying glass to confirm the fact that the printed item is an original.
Another technique that is used to authenticate documents is called the void pantograph. Printed dots of different sizes are utilized to create an effect. Smaller dots visible to the human eye dominate the appearance of the form. However the smaller dots are lost when a facsimile is produced in copying or scanning. Then, larger, less frequently printed dots become visible in the copy, and spell out the word "void".

Tools to embed tampering indicator into digital visual works using two screens with halftoning elements of different size dots or shapes


A digital filter circuit is described. The digital filter circuit includes at least one signal input and at least one finite impulse response (FIR) filter associated with the at least one signal input. The at least one signal input is configured to receive an input signal, wherein the input signal includes a product of at least two input signal samples. The at least one FIR filter is established as a short-length FIR filter. Further, a signal processing method is described.

Digital filters are known in a large variety in the state of the art. In general, digital filters are configured to process a digital signal, thereby altering the digital signal in a predefined manner depending on the filter coefficients of the digital filter.
In certain applications, the digital signal may comprise products of two or more signal samples. However, known digital filters may not have a sufficient processing speed in order to process such product signals at high sample rates in real time.
Thus, there is a need for a digital filter circuit as well as for a signal processing method that allow for processing product signals in real time at high sample rates.

Digital filter circuit and signal processing method


A hydrostatic pad for use in holding a semiconductor wafer during grinding of the wafer by grinding wheels. The pad includes hydrostatic pockets formed in a face of the body directly opposed to the wafer. The pockets are adapted for receiving fluid through the body and into the pockets to provide a barrier between the body face and the workpiece while still applying pressure to hold the workpiece during grinding. The hydrostatic pads allow the wafer to rotate relative to the pads about their common axis. The pockets are oriented to reduce hydrostatic bending moments that are produced in the wafer when the grinding wheels shift or tilt relative to the hydrostatic pads, helping prevent nanotopology degradation of surfaces of the wafer commonly caused by shift and tilt of the grinding wheels.

This invention relates generally to simultaneous double side grinding of semiconductor wafers and more particularly to a wafer-clamping device for use with a double side grinder.
Semiconductor wafers are commonly used in the production of integrated circuit chips on which circuitry is printed. The circuitry is first printed in miniaturized form onto surfaces of the wafers, then the wafers are broken into circuit chips. But this smaller circuitry requires that wafer surfaces be extremely flat and parallel to ensure that the circuitry can be properly printed over the entire surface of the wafer. To accomplish this, a grinding process is commonly used to improve certain features of the wafers (e.g., flatness and parallelism) after they are cut from an ingot.
Simultaneous double side grinding operates on both sides of the wafer at the same time and produces wafers with highly planarized surfaces. It is therefore a desirable grinding process. Double side grinders that can be used to accomplish this include those manufactured by Koyo Machine Industries Co., Ltd. These grinders use a wafer-clamping device to hold the semiconductor wafer during grinding. The clamping device typically comprises a pair of hydrostatic pads and a pair of grinding wheels. The pads and wheels are oriented in opposed relation to hold the wafer therebetween in a vertical orientation. The hydrostatic pads beneficially produce a fluid barrier between the respective pad and wafer surface for holding the wafer without the rigid pads physically contacting the wafer during grinding. This reduces damage to the wafer that may be caused by physical clamping and allows the wafer to move (rotate) tangentially relative to the pad surfaces with less friction. While this grinding process significantly improves flatness and parallelism of the ground wafer surfaces, it can also cause degradation of the topology of the wafer surfaces.
In order to identify and address the topology degradation concerns, device and semiconductor material manufacturers consider the nanotopology of the wafer surfaces. Nanotopology has been defined as the deviation of a wafer surface within a spatial wavelength of about 0.2 mm to about 20 mm. This spatial wavelength corresponds very closely to surface features on the nanometer scale for processed semiconductor wafers. The foregoing definition has been proposed by Semiconductor Equipment and Materials International (SEMI), a global trade association for the semiconductor industry (SEMI document 3089). Nanotopology measures the elevational deviations of one surface of the wafer and does not consider thickness variations of the wafer, as with traditional flatness measurements. Several metrology methods have been developed to detect and record these kinds of surface variations. For instance, the measurement deviation of reflected light from incidence light allows detection of very small surface variations. These methods are used to measure peak to valley (PV) variations within the wavelength.
A typical wafer-clamping device 1′ of a double side grinder of the prior art is schematically shown in FIGS. 1 and 2. Grinding wheels 9′ and hydrostatic pads 11′ hold the wafer W independently of one another. They respectively define clamping planes 71′ and 73′. A clamping pressure of the grinding wheels 9′ on the wafer W is centered at a rotational axis 67′ of the wheels, while a clamping pressure of the hydrostatic pads 11′ on the wafer is centered near a center WC of the wafer. As long as clamping planes 71′ and 73′ are held coincident during grinding (FIG. 1), the wafer remains in plane (i.e., does not bend) and is uniformly ground by wheels 9′. A general discussion regarding alignment of clamping planes may be found in published European Appl. No. 1,118,429. However, if the two planes 71′ and 73′ become misaligned, the clamping pressures of the grinding wheels 9′ and hydrostatic pads 11′ produce a bending moment, or hydrostatic clamping moment, in the wafer W that causes the wafer to bend sharply generally adjacent peripheral edges 41′ of the grinding wheel openings 39′ (FIG. 2). This produces regions of high localized stress in the wafer W.
Misalignment of clamping planes 71′ and 73′ is common during double side grinding operation and is generally caused by movement of the grinding wheels 9′ relative to the hydrostatic pads 11′ (FIG. 2). Possible modes of misalignment are schematically illustrated in FIGS. 2 and 3. These include a combination of three distinct modes. In the first mode there is a lateral shift S of the grinding wheels 9′ relative to the hydrostatic pads 11′ in translation along an axis of rotation 67′ of the grinding wheels (FIG. 2). A second mode is characterized by a vertical tilt VT of the wheels 9′ about a horizontal axis X through the center of the respective grinding wheel (FIGS. 2 and 3). FIG. 2 illustrates a combination of the first mode and second mode. In a third mode there is a horizontal tilt HT of the wheels 9′ about a vertical axis Y through the center of the respective grinding wheel (FIG. 3). These modes are greatly exaggerated in the drawings to illustrate the concept; actual misalignment may be relatively small. In addition, each of the wheels 9′ is capable of moving independently of the other so that horizontal tilt HT of the left wheel can be different from that of the right wheel, and the same is true for the vertical tilts VT of the two wheels.
The magnitude of hydrostatic clamping moments caused by misalignment of clamping planes 71′ and 73′ is related to the design of the hydrostatic pads 11′. For example, higher moments are generally caused by pads 11′ that clamp a larger area of the wafer W (e.g., pads that have a large working surface area), by pads in which a center of pad clamping is located a relatively large distance apart from the grinding wheel rotational axis 67′, by pads that exert a high hydrostatic pad clamping force on the wafer (i.e., hold the wafer very rigidly), or by pads that exhibit a combination of these features.
In clamping device 1′ using prior art pads 11′ (an example of one prior art pad is shown in FIG. 4), the bending moment in wafer W is relatively large when clamping planes 71′ and 73′ misalign because the wafer is clamped very tightly and rigidly by the pads 11′, including near peripheral edges 41′ of grinding wheel opening 39′. The wafer cannot adjust to movement of grinding wheels 9′ and the wafer bends sharply near opening edges 41′ (FIG. 2). The wafers W are not uniformly ground and they develop undesirable nanotopology features that cannot be removed by subsequent processing (e.g., polishing). Misalignment of clamping planes 71′ and 73′ can also cause the grinding wheels 9′ to wear unevenly, which can further contribute to development of undesirable nanotopology features on the ground wafer W.
FIGS. 5A and 5B illustrate undesirable nanotopology features that can form on surfaces of a ground wafer W when clamping planes 71′ and 73′ misalign and the wafer bends during the grinding operation. The features include center-marks 77′ and B-rings 79′ (FIG. 5A). The center-marks 77′ are generally caused by a combination of lateral shift S and vertical tilt VT of the grinding wheels 9′, while the B-rings 79′ are generally caused by a combination of lateral shift S and horizontal tilt HT of the wheels. As shown in FIG. 5B, both features 77′ and 79′ have relatively large peak to valley variations associated with them. They are therefore indicative of poor wafer nanotopology and can significantly affect ability to print miniaturized circuitry on wafer surfaces.
Misalignment of hydrostatic pad and grinding wheel clamping planes 71′ and 73′ causing nanotopology degradation can be corrected by regularly aligning the clamping planes. But the dynamics of the grinding operation as well as the effects of differential wear on the grinding wheels 9′ cause the planes to diverge from alignment after a relatively small number of operations. Alignment steps, which are highly time consuming, may be required so often as to make it a commercially impractical way of controlling operation of the grinder.
Accordingly, there is a need for a hydrostatic pad usable in a wafer-clamping device of a double side grinder capable of effectively holding semi-conductor wafers for processing but still forgiving to movement of grinding wheels so that degradation of wafer surface nanotopology is minimized upon repeated grinder operation.

Wafer clamping device for a double side grinder


A swash-plate plunger-type hydraulic device has a cylinder block with a plurality of plungers slidably fitted in cylinder bores, a swash plate confronting one end of the cylinder block, and a distribution valve plate slidably held against the other end of the cylinder block. The cylinder block has an even number of circularly arrayed connecting ports communicating with the cylinder bores and opening at the other end thereof. The distribution valve plate has inlet and outlet ports. The cylinder block is rotatable through an angular displacement .theta.1 in which the hydraulic pressure in one connecting port between the inlet and outlet ports increases from a lower pressure to a higher pressure, through an angular displacement .theta.2 in which the hydraulic pressure in one connecting port between the inlet and output ports decreases from the higher pressure to the lower pressure, and through an angular displacement .theta.3 from a position where the hydraulic pressure starts to increase to a position where the hydraulic pressure starts to decrease. The inlet and outlet ports are defined such that the angular displacements .theta.1, .theta.2, .theta.3 are expressed by: EQU .theta.1=.theta.2 and .theta.3=180.degree..

1. FIELD OF THE INVENTION
The present invention relates to a swash-plate plunger-type hydraulic device such as a swash-plate plunger-type hydraulic pump, a swash-plate plunger-type hydraulic motor, or the like.
2. DESCRIPTION OF THE PRIOR ART:
One known swash-plate plunger-type hydraulic device for use as a pump or a motor is disclosed in Japanese Laid-Open Patent Publication No. 61-118566, for example. Such a swash-plate plunger-type hydraulic device generally has an odd number of plungers that are movable in discharge and suction strokes at different times, or out of phase with each other, for reducing flow rate and torque fluctuations.
Swash-plate plunger-type hydraulic pump and motor may be combined into a hydraulically operated continuously variable transmission. In such a hydraulically operated continuously variable transmission, each of the pump and the motor has an odd number of plungers that are also actuatable in discharge and suction strokes out of phase.
When a plunger shifts in a cylinder from the discharge stroke (compressing stroke) to the suction stroke (expanding stroke), it develops an abrupt change in the hydraulic pressure in the cylinder. The change in the hydraulic pressure is transmitted as vibrating forces to the plunger, the swash plate, and the casing of the hydraulic device. It is known that the transmitted vibrating forces are responsible for the generation of noise from the hydraulic device and the hydraulically operated continuously variable transmission employing the same.
Various attempts have heretofore been proposed to lessen the above change in the hydraulic pressure. For example, pre-compressing and pre-expanding intervals are provided between the discharge and suction strokes, and a restriction passage such as a V-shaped groove, a recess, a regulator valve, or the like is defined to reduce the pressure variation. For details, see Japanese Laid-Open Utility Model Publication No. 63-96372 and Japanese Laid-Open Patent Publication No. 2-129461, for example.
However, the conventional proposals are only effective to attenuate the change in the hydraulic pressure in the cylinder which houses each plunger. The total value of thrust loads imposed on all the plungers is still subject to fluctuations that are applied as vibrating forces. Therefore, it is difficult to lower the noise level to a sufficiently low level.
The fluctuations of the total thrust load will be described below with reference to FIG. 24 of the accompanying drawings. FIG. 24 shows thrust loads F1 through F9 that are applied to respective nine plungers of a swash-plate plunger-type hydraulic pump, and a total thrust load Ft which is the sum of the thrust loads F1 through F9, when the cylinder block rotates. The graph of FIG. 27 has a horizontal axis which is indicative of time, but which may be indicative of the angular displacement of the cylinder block since the angular displacement varies with time. Study of FIG. 27 indicates that the thrust load exerted to each plunger smoothly varies in load increasing and decreasing zones, and the total thrust load Ft fluctuates as shown.
In the case where a swash-plate plunger-type hydraulic pump or motor is of the variable displacement type and has a support shaft by which the swash plate is tiltably supported, or a swash-plate plunger-type hydraulic pump or motor is of the fixed displacement type and has a support shaft similar to the support shaft by which the swash plate is tiltably supported, even if changes in the hydraulic pressure in the cylinder housing each plunger are lessened, variations in the moment about the support shaft, which are also responsible for vibrating forces, cannot sufficiently be suppressed. Therefore, it is difficult to sufficiently lower the noise produced by such a pump or motor.
In such a swash-plate plunger-type hydraulic pump or motor, if it has an even number of plungers, then the pulsating ratio of a discharged flow from the hydraulic device is calculated as follows:
FIG. 25 of the accompanying drawings shows a hydraulic pump model in which a cylinder block 101 has an odd number of angularly spaced cylinder bores 111 defined therein and a number of plungers 112 slidably disposed respectively in the cylinder bores 111, with a swash plate 106 held against the tip ends of the plungers 112. The total stroke L of a plunger 112 is given by: EQU L=2R tan .alpha. (a)
where R is the radius of a circle passing through the centers of the cylinder bores 111, and .alpha. is the angle at which the swash plate 106 is tilted. The displacement D of the plungers 112 is expressed as follows: EQU D=ZAL=2ZAR tan .alpha. (b)
where A is the pressure-bearing surface area of the plungers 112, and Z is the number of the plungers 112.
While a plunger 112 is being angularly moved an angle .theta. from the bottom dead center (BDC), the plunger 112 axially moves a distance x: EQU x=L/2-R cos .theta.tan .alpha.=L/2.times.(1-cos .theta.) (c)
Therefore, the speed v at which the plunger 112 axially moves is given as follows: EQU v=dx/dt=(L.omega./2).times.sin .theta. (d)
where .omega. is the angular velocity of the cylinder block 101.
It is assumed that the number of plungers 112 that are in the discharge stroke is expressed by ZO. From the equation (d), the instantaneous discharge rate Qt of the hydraulic pump is given by: EQU Qt=.SIGMA.Avi=(AL.omega./2).SIGMA.sin .theta.i (e)
The equation (e) can be modified into: EQU Qt=(AL.omega./2).times.sin (.pi.Z0/Z).times.sin {.theta.+.pi.(Z0-1)/Z}/sin (.pi./Z) (f).
Since the number Z of the plungers 112 is even, the equation (f) is therefore modified into: EQU Qt=(AL.omega./2).times.cos (.theta.-.pi./Z)/sin (.pi./Z) (g)
The instantaneous discharge rate Qt is shown in FIG. 26 of the accompanying drawings. As can be understood from FIG. 26, if the number of the plungers 112 is even, then the discharged flow pulsates Z times while the cylinder block 101 makes one revolution. The pulsating ratio .SIGMA. of the instantaneous discharge rate is expressed by: EQU .SIGMA.=.pi./Z.times.tan (.pi./2Z) (h).
According to this equation, actual pulsating ratios .SIGMA. with different numbers of plungers are calculated as follows:
______________________________________ Z 6 8 10 12 .epsilon. (%): 14.0 7.81 4.97 3.45 ______________________________________
The above theoretical study is based on Hydraulic Engineering written by Tsuneo Ichikawa and Akira Hibi.
The foregoing analysis of the pulsating ratio assumes that the hydraulic pressure in the cylinder bores varies according a rectangular pattern as shown in FIG. 27(A) of the accompanying drawings. In actual swash-plate plunger-type hydraulic pumps or motors, however, pre-compressing and pre-expanding zones or restriction passages are employed to cause the hydraulic pressure to vary according to a trapezoidal pattern for thereby preventing the hydraulic pressure from abruptly varying upon a plunger transition from the suction stroke to the discharge stroke and a plunger transition from the discharge stroke to the suction stroke. Consequently, actual pressure changes are indicated by a trapezoidal pattern as shown in FIG. 27(B) of the accompanying drawings. As a result, the actual pulsating ratio differs from the theoretically determined pulsating ratio.
While the trapezoidal pressure pattern is effective in preventing abrupt pressure changes to reduce vibrating forces applied to the swash plate and other components, it rather increases the pulsating ratio, giving rise to abnormal vibration (torque fluctuations), as evidenced by various experiments.

High efficiency reduced-noise swash-plate-type hydraulic device


There is provided a zoom lens in which the load on the driving system for wobbling operation can easily made low and an image pickup apparatus equipped with the same. A zoom lens in which each of distances between a plurality of lens units changes during zooming from the wide angle end to the telephoto end, includes a focus lens unit that shifts along an optical axis to effect focusing from infinity to a close distance and a plurality of wobbling lens units that wobble after a shift of the focus lens unit at an amplitude smaller than the shift of the focus lens unit in focusing operation, wherein a combination of the wobbling lens units caused to operate changes in the middle of the zooming from the wide angle end to the telephoto end.

1. Field of the Invention
The present invention relates to a zoom lens having a plurality of wobbling lens units and an image pickup apparatus equipped with such a zoom lens.
2. Description of the Related Art
A zoom lens having a wobbling lens unit has already been known. The wobbling lens unit is a lens unit which minutely oscillates (wobbles) at high speed along the direction of the optical axis to change the contrast of the image to an extent that is not recognizable in the reproduced image, and the focus state on the image pickup element is detected utilizing the oscillation (wobbling) of the wobbling unit.
For example, when an object is in focus, while the contrast of a formed image changes slightly with oscillation (wobbling) of the wobbling lens unit, the image shows substantially the same contrast at both ends of the wobbling range.
On the other hand, when the object shifts forward or backward to be out of focus, the image has different contrasts at both ends of the wobbling range. The object's going out of focus is detected from this change in the contrast, and the focus lens unit is shifted along the optical axis to bring the object into focus again. Thereafter, the wobbling lens unit is caused to oscillate minutely at high speed again to maintain the in-focus state.
The period of oscillation of the wobbling lens unit depends on the frame rate of the system including the image pickup element. Japanese Patent Application Laid-open Publication No. 2007-293146 describes a technique of changing the amplitude of oscillation of the wobbling lens unit in accordance with the zoom state to cause an appropriate change in contrast irrespective of the zoom state.

Zoom lens and image pickup apparatus equipped with same


A hole-cutting device for attachment to a portable electric drill or similar rotating machine. The device has a cylindrical body with a rearward edge and a forward edge; a mounting plate is affixed across the rearward edge, and a series of chipper teeth are affixed about the forward edge. Each chipper tooth has a transverse cutting edge and a second cutting edge in substantial alignment with the wall of the cylinder, but alternate chipper teeth have second cutting edges displaced inwardly and outwardly from the cylindrical member.

The present invention relates generally to a hole-saw device for cutting holes in wood material; more particularly, the invention relates to a hole saw having chipper teeth for facilitating the cutting operation.
Hole-cutting saw devices are well known in the art, the most typical prior art device being one which merely constrains a saw-toothed blade in a circular loop. The tooth pattern of such devices usually adapts conventional saw-toothed techniques to provide a series of sharpened metal points aligned around a circular path wherein each toothed point may be aligned slightly outwardly or inwardly from the vertical in order to widen the cutting pattern. A widened cutting pattern offers the advantage of cutting a circular groove which is wider than the thickness of the cutting blade, and therefore it eases the frictional forces of the wood against the side surfaces of the blade. The cutting effectiveness of such a device depends upon the force applied against the cutting tool so that the sharpened saw blade points are forced to bite into the wood material and thereby to remove particles of material. If no axial force is applied against the cutting tool, devices of this type will generally merely turn in the saw groove without removing material from the bottom of the saw groove.
The foregoing operation of conventional hole-cutting saws is to be contrasted with the operation of other cutting tools, such as chain saws. The chain saw cutting tool utilizes a series of aligned links which are propelled in an endless loop via a chain drive mechanism but always along a linear cutting path. Each link comprises a small wood chipper wherein the link has a forward gauge plate to restrain the depth of chipping and cutting, followed by a rearward curved and sharpened blade edge which is positioned at an elevation higher than the gauge member. The elevation distance between the sharpened blade edge and the gauge member determines and limits the depth of chipping; i.e., the chipper blade's natural propensity to bite deeply into the wood surface is limited by the gauge which rides along the bottom of the groove just ahead of the chipper cutting edge. Chain saws utilize this principle to rapidly and efficiently cut through wood materials, principally trees; and if each of the chipper teeth are well sharpened, there is no external force required to facilitate the cutting operation. The weight of the chain saw blade and guide bar by itself, together with the natural propensity of the chipper to dig into the wood material, enables the chain saw to guide itself through a cut in a wood material.
Because a certain axial force is required to drive a hole cutting saw through wooden materials, it becomes increasingly difficult to cut holes of increasing diameter. In the construction trades, particularly the plumbing and heating/ventilating trade, it frequently becomes necessary to cut enlarged holes for the passage of pipes and heating ducts. Such hole saws as required for these operations may be required to cut up to six-inch diameter holes; the axial force and torque required against the cutting tool for a six-inch diameter hole is quite large and may be beyond the capabilities of some workmen and power drills. It, therefore, would be a significant advantage to provide a hole-cutting device which operates with substantially lowered axial force in order to complete a cutting operation.