In a wheel supporting rolling bearing unit in which pitch circle diameters of balls 6a, 6b in an outside row and an inside row are made different, contact angles αOUT, αIN of the balls 6a, 6b in the two rows in a completed state are equal to each other. Initial contact angles βOUT, βIN of the two rows are smaller than predetermined contact angles αOUT, αIN. The extent [αIN−βIN] to which the initial contact angle βIN of the balls 6b, 6b in the inside row is made smaller than the predetermined contact angle αIN of the balls 6b, 6b is made larger than the extent [αOUT−βOUT] to which the initial contact angle βOUT of the balls 6a, 6a in the outside row is made smaller than the predetermined contact angle αOUT of the balls 6a, 6a {[αIN−βIN]>[αOUT−βOUT]}. By this configuration, imparting the predetermined contact angles αOUT, αIN to the balls 6a, 6b in the two rows in the completed state, and the preloads and contact angles of the balls 6a, 6b in the two rows are made proper.

A wheel and a brake rotary member of a motor vehicle are supported rotatably on a suspension system by a wheel supporting rolling bearing unit. Since a large moment is exerted on a wheel supporting rolling bearing unit like this when the motor vehicle turns, rigidity against such a large moment or moment rigidity needs to be ensured in order to ensure the running stability. For this purpose, conventionally, as the wheel supporting rolling bearing unit, a construction has generally been used in which rolling elements are arranged in double rows and preload and a back-to-back type contact angle are imparted to the rolling elements in each of the two rows. For supporting wheels on suspension systems of motor vehicles, wheel supporting rolling bearing units of various types of constructions are known as are described in, for example, Patent Documents Nos. 1 to 6.
FIGS. 4 to 5 show a construction described in Patent Document No. 1 of those patent documents. A wheel supporting rolling bearing unit 1 of a first example shown in FIG. 4 of these figures includes a hub main body 3 and an inner ring 4 which make up a hub 2 which is an inside diameter side raceway ring member, an outer ring 5 which is an outside diameter side raceway ring member and a plurality of rolling elements 6, 6. A flange 7 which supports a wheel is formed at an outer end portion of an outer circumferential surface of the hub main body 3 of those constituent components. (Outer with respect to an axial direction means a side which lies transversely outwards when the bearing unit is assembled on a motor vehicle, which is a lower side in FIG. 3 and a left-hand side in FIGS. 4 to 7. On the contrary, a side which lies transversely centrally means inner with respect to the axial direction, which is an upper side in FIG. 3 and a right-hand side in FIGS. 4 to 7. This is true throughout the description.)
An inner ring raceway 8a for an outside row is formed on the outer circumferential surface at an intermediate portion and a small-diameter stepped portion 9 whose outside diameter is decreased are formed at an inner end portion of the hub main body 3. Then, the inner ring 4 having an inner ring raceway 8b for an inside row formed on an outer circumferential surface thereof is fitted on this small-diameter stepped portion 9 so as to make up the hub 2 above. An inner end face of this inner ring 4 is pressed by a clamping portion 10 which is formed by clamping to expand diametrically outwards a cylindrical portion formed at the inner end portion of the hub main body 3, so as to fix the inner ring 4 to a predetermined position on the hub main body 3. Double rows of outer ring raceways 11a, 11b are formed on an inner circumferential surface of the outer ring 5, and the respective rolling elements 6, 6 are disposed between the two outer ring raceways 11a, 11b and the two inner ring raceways 8a, 8b so that pluralities of rolling elements 6, 6 are provided in the two rows, respectively.
Next, in a wheel supporting rolling bearing unit 1a of a second example shown in FIG. 5, a hub 2a, which is an outside diameter side raceway ring member and has a flange 7a for support a wheel, is disposed around a pair of inner rings 4a, 4a, which is an inside diameter side raceway ring members and do not rotate when fitted outwardly to a support shaft (not shown). Then, pluralities of rolling elements 6, 6 are provided, respectively, between outer ring raceways 11a, 11b formed on an inner surface of the hub 2a and respective inner ring raceways 8a, 8b formed on outer circumferences of the respective inner rings 4a, 4a.
In addition, FIG. 6 shows a construction described in Patent Document No. 5. A wheel supporting rolling bearing unit 1b of a third example includes a hub 2, an outer ring 5, and a plurality of balls 6, 6 which are individually rolling elements. In these components, the hub 2 is formed by combining a hub main body 3 and an inner ring 4. The hub 2 has a mounting flange, which supports a wheel and a brake rotary member and is formed at an axially outer end side of an outer circumferential surface thereof and double rows of inner ring raceways 8a, 8b, which are formed at axially intermediate portion and an inner end portion thereof, respectively. In these two inner ring raceways 8a, 8b, the diameter of the inner ring raceway 8a as an axial outside row is made larger than the diameter of the inner ring raceway 8b as an axial inside row. Distal end portions of a plurality of studs 12 are fixed to the mounting flange 7, so that a brake rotary member such as a disc and a wheel which makes up a road wheel are allowed to be fixedly supported on the mounting flange 7.
In the construction shown in FIG. 6, to make different the diameters of the two inner ring raceways 8a, 8b, an outer circumferential surface side inclined stepped portion 14 is formed at an axially intermediate portion on the outer circumferential surface of the hub main body 3 in a position which lies slightly further axially inwards than the inner ring raceway 8a of the outside row. The outer circumferential surface side inclined stepped portion 14 is inclined so that an outside diameter thereof decreases as it extends axially inwards. A small-diameter stepped portion 9 is formed at an axial inner end portion of the hub main body 3 which lies further axially inwards than the outer circumferential surface side inclined stepped portion 14.
Then, the inner ring 4 having the inner ring raceway 8b of the axial inside row on an outer circumferential surface thereof is fitted on this small-diameter stepped portion 9, and this inner ring 4 is pressed against a rising surface 13 which lies at an axial outer end portion of the small-diameter stepped portion 9. In this state, the inner ring 4 is fixedly connected to the hub main body 3. Both the two inner ring raceways 8a, 8b have a circular arc-shaped cross section (a generatrix shape) and their outside diameters decrease as they approach each other (as they extend towards an axial center of the hub 2).
The outer ring 5 has double rows of outer ring raceways 11a, 11b on an inner circumferential surface thereof and a connecting flange 15 which fixedly connects the outer ring 5 to a suspension system and formed on an outer circumferential surface. In these two outer ring raceways 11a, 11b, the diameter of the axially outside outer ring raceway 11a is made larger than the diameter of the axially inside outer ring raceway 11b. For this purpose, in the construction in FIG. 6, an inner circumferential surface side inclined stepped portion 16 is formed at an axially intermediate portion on the outer circumferential surface of the outer ring 5 in a position which lies slightly further axially inwards than the outside outer ring raceway 11a. The inner circumferential surface side inclined stepped portion 16 is inclined so that an inside diameter thereof decreases as it extends axially inwards, The two outer ring raceways 11a, 11b have a circular arc-shaped cross section (a generatrix shape) and their outside diameters decrease as they approach each other (as they extend towards an axial center of the hub 2).
The respective balls 6, 6 are provided rollingly between the two inner ring raceways 8a, 8b and the two outer ring raceways 11a, 11b so that pluralities of balls 6, 6 are disposed therebetween, respectively. In this state, a preload and a contact angle of back-to-back type (DB type) are imparted to the balls 6, 6 which are disposed in the double rows. Pitch circle diameters of the balls 6, 6 in the two rows are made different according to a difference in diameter between the inner ring raceways 8a, 8b and the outer ring raceways 11a, 11b. Namely, the pitch circle diameter PCDOUT of the respective balls 6, 6 (outside row) in the axially outside row is made larger than the pitch circle diameter PCDIN of the respective balls 6, 6 (inside row) in the axially inside row (PCDOUT>PCTIN). In the illustrated example, although the balls 6, 6 are used as rolling elements, if a rolling bearing unit for a heavy motor vehicle, tapered rollers may be used as the rolling elements.
Heretofore, the constructions of the wheel supporting rolling bearing units described in Patent Documents Nos. 2 to 6 in which the pitch circle diameters of the rolling elements in the two rows are made different are explained. In these constructions, the moment rigidity is made large by such an extent that the pitch circle diameter PCDOUT of the outside row can be made large, and this facilitates the design to realize improvements in running stability when the vehicle turns and durability of the wheel supporting rolling bearing unit. On the other hand, since the pitch circle diameter PCDIN of the inside row does not have to be made large, part (knuckle mounting hole) of the suspension system dose not have to particularly be increased in diameter. Consequently, even though this part of the suspension system is not particularly made large in size, the improvement in both running stability and durability can be realized.
While in the construction shown in FIG. 6, the diameters of the rolling elements 6, 6 which are disposed in the double rows are made equal, as with a wheel supporting rolling bearing unit 1c shown in FIG. 7, there has conventionally been known a construction in which the diameter of rolling elements 6a, 6a in an outside row is made smaller than the diameter of rolling elements 6b, 6b in an inside row. In this construction, as a fourth example, shown in FIG. 7, the number of rolling elements 6a, 6a in the outside row is made sufficiently larger than the number of rolling elements 6b, 6b in the inside row, whereby the rigidity of the outside row is made much higher than the rigidity of the inside row. Although the balls are used as the rolling elements in the respective illustrated examples, tapered rollers may be used as rolling elements for a rolling bearing unit for use on a heavy motor vehicle.
While any of the constructions shown in FIGS. 4 to 7 is automatically assembled on a production line of a bearing factory, if a defect such as a flaw exists somewhere in the construction, noise and vibrations generated while driving the vehicle and also a sufficient durability cannot be ensured. Thus, in a bearing factory, all or part of assembled wheel supporting rolling bearing units are inspected (a total inspection or a sampling inspection) to determine on the existence of defects. If there should be a defect, then, the production line is repaired or modified to eliminate a cause which generates the defect.
In general, a flaw on a rolling contact portion is considered as a type of defect which triggers a repair or modification of the production line. Namely, if flaws exist on the rolling contact portions between the rolling surfaces of the respective rolling elements 6, 6a, 6b and the respective raceways 8a, 8b, 11a, 11b, immoderate vibrations are generated when operating the wheel supporting rolling bearing unit and also early flaking originated from the flaws is generated, and then leading to a possibility of remarkably shorten the durability of this wheel supporting rolling bearing unit. Flaws which constitute a cause for the drawback like this are singly generated by a contamination of foreign matters or caused by a trouble on the production line side such as a failure in controlling the production facility. If such a trouble occurs, unless the production line is repaired immediately, plural defective products are produced, thus deteriorating the yield of products.
Thus, it becomes necessary to determine the existence of flaws on the rolling contact portions through inspection. As an inspection method for determining the existence of flaws like this, as is described in Patent Document No. 7, it is general practice to measure vibrations of a rolling bearing unit and to measure whether or not vibrations of a large amplitude (remarkably large vibrations compared with vibrations generated during normal driving) are contained in a specific frequency in the vibrations so measured. The revolving speed of the respective rolling elements which make up the rolling bearing unit (the rotational speed of the cages) is expressed bync=(ni/2)·{1−cos α/(dm /d)}when the inside diameter side raceway ring member rotates, and is expressed bync=(ne/2)·{1+cos α/(dm /d}when the outside diameter side raceway ring member rotates. In both the expressions, d denotes the diameter of the rolling elements, dm the pitch circle diameter of the rolling elements, α the contact angle [°] of the rolling elements, ni the rotational speed [s−1] of the inside diameter side raceway ring member and ne the rotational speed [s−1] of the outside diameter side raceway ring member.
For example, assuming that the number of rolling elements is Z, if a flaw exists in one location on an outer ring raceway in a circumferential direction thereof with an inside diameter side bearing ring rotating, vibrations in a frequency of Z·nc[Hz] are generated, while if a flaw exists in one location on an inner ring raceway in a circumferential direction thereof with the inside diameter side bearing ring rotating, vibrations in a frequency of Z·(ni−nc) [Hz] are generated. Vibrations in specific frequencies are similarly obtained when an outside diameter side raceway ring member rotates. Further, if a flow exists on the rolling surface of the rolling element, a frequency of vibrations based on the flaw is obtained based on the rolling speed of the rolling element itself.
Thus, by rotating the inside diameter side raceway ring member (or the outside diameter side raceway ring member) of the assembled rolling bearing unit, measuring vibrations of this rolling bearing unit and determining whether vibrations in the frequencies described above exist in the measured vibrations, whether or not a flaw exists on the rolling contact portions of this rolling bearing unit can be determined.
The determination in the way is implemented without any specific problem if the rolling bearing unit is a single row rolling bearing unit. However, if a double row rolling bearing unit like the wheel supporting rolling bearing units shown in FIGS. 4 to 7, it is not possible to know on which rolling contact portion of the row the flaw exists without any modifications to the flaw inspecting configuration for single row rolling bearing units. Namely, in the conventional wheel supporting rolling bearing units shown in FIGS. 4 to 5 which are used generally, since the specifications (the diameter, number, pitch circle diameter and contact angle of the rolling elements) of the two rows are the same, whether a flaw exists in the outside row or in the inside row, vibrations in the same frequency are generated. Therefore, it is not possible to specify in which of the rows the flaw exists, and hence, the repair of the production line cannot be started immediately. Namely, until disassembling the wheel supporting rolling bearing unit on which the flaw is determined to exist through analysis of the frequencies of vibrations to observe the raceway surfaces and the rolling surfaces, the row on which the flaw exists can not be specified. However, disassembling the wheel supporting rolling bearing is troublesome. In particular, in the constructions shown in FIGS. 4, 6, 7 in which the hub main body 3 and the inner ring 4 are fixedly connected together by the clamping portion 10, the clamping portion 10 needs to be ground off, and hence, time taken from confirmation of existence of the flaw to identification of the position where the flaw exists becomes long. When this time is taken long, time during which the production line is stopped to prevent the manufacture of defective products becomes long, and production efficiency becomes lower.
Further, in the wheel supporting rolling bearing units 1b, 1c shown in FIGS. 6 and 7, respectively, the contact angle of the balls 6, 6, 6a, 6b needs to be controlled properly as well as imparting a proper preload to the respective balls 6, 6, 6a, 6b so that the performances with respect to low torque characteristic, rigidity, durability and the like are exhibited as desired. It is general practice that the contact angle of the respective balls 6, 6, 6a, 6b is controlled to be equal (e.g., on the order of 20 to 45 degrees) between the outside row and the inside row. The larger the preload becomes, although the higher the rigidity of the wheel supporting rolling bearing units 1b, 1c, however, the higher the dynamic torque and shorter the fatigue life of the rolling surface. On the other hand, the larger the contact angle becomes, although the higher the axial rigidity, however, lower the radial rigidity and larger the spin at the rolling contact portion to thereby reduce the fatigue life of the rolling contact surface.
As is obvious from these facts, it is important to set the preload and the contact angle properly. Even in the wheel supporting rolling bearing units described in Patent Documents Nos. 2 to 6 in which the pitch circle diameters of the rolling elements in the two rows are made different, it is important to control the preload imparted to the respective rolling elements and the contact angle properly from the viewpoint that the performances with respect to low torque characteristic, rigidity, durability and the like are exhibited as desired.
However, in the wheel supporting rolling bearing units in which the pitch circle diameters of the rolling elements in the two rows are made different, since the rigidities of the two rows are different, unless a consideration, which is different from that to be taken for the general wheel supporting rolling bearing units in which the pitch circle diameters of the rolling elements in the two rows are equal, is taken, it is not possible to control properly the contact angles and the preloads of the two rows. The reason for this will be described below.
It is already known from, for example, Non-Patent Document No. 1 that when an axial load is exerted on a radial rolling bearing, the contact angle of respective rolling elements becomes large. In the wheel supporting rolling bearing unit which is intended by the invention, by imparting axial load to the rolling elements which are disposed in the double rows, a predetermined preload is imparted to the respective rolling elements. For example, in the construction shown in FIG. 6, the preload is imparted to the respective balls 6, 6, 6a, 6b which are disposed between the pair of inner ring raceways 8a, 8b and the double rows of outer ring raceways 11a, 11b by pressing the inner ring 4 outwards in the axial direction by the clamping portion 10 so as to shorten the pitch between the two inner ring raceways 8a, 8b. The magnitude of the preload (the quantity of the preload) becomes the amount of displacement of the inner ring 4 towards the outside in the axial direction from a state that the rolling surfaces of the rolling elements which are the respective balls 6, 6, 6a, 6b are brought into light contact with the two inner ring raceways 8a, 8b and the two outer ring raceways 11a, 11b (without imparting any preload to the respective balls 6, 6, 6a, 6b)
From this fact that imparting the preload to the rolling elements in the two rows (the balls 6, 6, 6a, 6b) in the wheel supporting rolling bearing unit which is intended by the invention is similar to the state in which the axial load is exerted on the radial rolling bearing, whereby the contact angle of the rolling elements in the two rows becomes large. In the general conventional wheel supporting bearing unit, since the specifications (the pitch circle diameter, the rolling element diameter, the number of rolling elements) of the two rows are equal to each other, amounts of changes in contact angle of the rolling elements in the two rows which occur in association with impartation of the preload are the same. Therefore, it has been relatively easy to control the preload and contact angle of the rolling elements in the two rows to proper values when the wheel supporting rolling bearing unit is completely assembled.
In contrast to this, in the wheel supporting rolling bearing unit which is intended by the invention in which the pitch circle diameters of the rolling elements in the two rows are made different, since the rigidities of the two rows are different, to control the preload to be imparted to the rolling elements (the balls 6, 6, 6a, 6b) in the two rows and contact angle properly, a special consideration is necessary. Namely, in the construction in which the pitch circle diameter of the axially outside row is larger than the pitch circle diameter of the axially inside row, the axial rigidity of the axially outside row becomes larger than the axial rigidity of the axially inside row. On the other hand, a force axially pushing the rolling elements in the two rows for imparting preload becomes equal, of course. Thus, when the inner ring 4 is pushed axially outwards to impart the preload, elastic deformation of the respective portions (the respective raceways and the rolling surfaces of the rolling elements) which is linked with impartation of the preload to the respective rolling elements becomes more on the outside row than on the inside row. As a result, degree at which the contact angle is increased in association with impartation of the preload becomes larger on the outside row than on the inside row.
Thus, in the wheel supporting rolling bearing unit which is intended by the invention in which the pitch circle diameters of the rolling elements in the two rows are made different, if the contact angles (initial contact angles) of the rolling elements in the two rows are made identical in a state that no preload has been imparted yet, as done on the conventional wheel supporting rolling bearing, the contact angles of the two rows become different after completion of assembling of the bearing unit (after the impartation of the preload). Furthermore, in association with generation of the difference in contact angle between these two rows, the preload imparted to the rolling elements in the two rows becomes different from the desired value (because the axial load that is generated in association with the axial displacement of the inner ring due to the impartation of the preloads is not generated as desired). As a result, the preload and the contact angle of the rolling elements in the two rows become improper.
In the construction shown in FIG. 6, while the construction is illustrated in which the inner ring 4 fitted on the axial inner end portion of the hub main body 3 is pressed by the clamping portion 10, the aforesaid problem is generated irrespective of the construction in which the inner ring is pressed or not. For example, although a construction is also known in which an axial inner end face of an inner ring is pressed by a nut which is thread fitted on an externally threaded portion provided on an axial inner end portion of a hub main body, the same problem is also generated in the construction like this. In addition, also in a construction in which an inner ring is pressed by a housing of a constant velocity joint, the problem is caused in a similar manner. Furthermore, even in the event that rolling elements are tapered elements, the same problem is generated.                Patent Document No. 1: JP-A-2004-142722        Patent Document No. 2: JP-A-2003-232343        Patent Document No. 3: JP-A-2004-108449        Patent Document No. 4: JP-A-2004-345439        Patent Document No. 5: JP-A-2006-137365        Patent Document No. 6: International Publication WO 2005/065077 pamphlet        Patent Document No. 7: JP-A-2004-361390
Non-Patent Document No. 1: pages 62 to 65 of "Rolling Bearing, Dynamic Load Capacity of Rolling bearing," written and published by Junzo Okamoto, and printed by Seibun-sha Ltd. Printing, in September, 1987

Method for manufacturing wheel supporting rolling bearing unit and method for inspecting double row rolling bearing unit


An alternative billing system for communication service, comprising a gateway comprising a processor and a memory, and an application stored in the memory that, when executed by the processor, receives a text message from an originating electronic device, determines that an account balance associated with the originating electronic device lacks sufficient funds to pay for origination of the text message, sends a message to a terminating electronic device identified by the text message to inquire if the terminating electronic device wants to be billed for the origination of the text message, when a message accepting billing for the origination of the text message is received from the terminating electronic device, sends the text message to the terminating electronic device, and when a message rejecting billing for the origination of the text message is received from the terminating electronic device, does not send the text message to the terminating electronic device.

Mobile devices may pay for carrier service in several ways. Two common ways are to post-pay for service or pre-pay for service. Post-paying involves subscribers paying for services that have been rendered, for example, paying for mobile services consumed during a prior period of time. As long as the subscriber pays the periodic bill according to an agreement, services may continue. Pre-paying involves establishing an account balance with a service provider to then draft against as services are utilized by the mobile device. When prepaid service funds become exhausted, the subscriber may add funds to the account in order to continue using the mobile service for the mobile device.

Alternative text billing system and method


A read channel equalizer of a magnetic tape drive which equalizes digitally sampled magnetic signals detected by a read head is dynamically adapted. A detector of equalizer dynamic adaptation logic compares equalizer output signals to desired values that are based on the decoding scheme (such as +2, 0 and −2 for PR4) to sense equalizer output signals that are offset from at least one desired value, and signals the fact of each offset and its polarity as amplitude independent error signals. The signaled sensed amplitude independent error signals are fed back to adjustable taps of the equalizer. The simplified error signals thus avoid complex calculations of waveform errors, such as least mean square calculations. The error signals may be weighted and may be adjusted to align synchronously provided error signals with asynchronous taps of the equalizer.

Magnetic tape cartridges provide a means to store data on magnetic tape to be saved and read back at a subsequent time. A magnetic tape drive writes the data to magnetic tape, typically as a set of parallel tracks, and subsequently a magnetic tape drive reads back the data. To read back the data, a magnetic tape drive typically comprises parallel read heads to read each of the parallel tracks, a drive system for moving a magnetic tape with respect to the read heads such that the read heads may detect magnetic signals on the magnetic tape, and a read channel for digitally sampling magnetic signals detected by the read heads and for providing digital samples of the magnetic signals. The digital samples are then decoded into data bits, and the data bits from the parallel tracks are combined to provide the read back data. The read channel typically requires an equalizer for each of the read heads to compensate for the change in the signal due to the magnetic recording properties of the write head, the magnetic tape, and the read head. Magnetic tapes may be interchanged between tape drives, such that a magnetic tape written on one tape drive will be read by another tape drive. Variation in the response of the read heads to the variously written magnetic tapes may result in unacceptably poor read back of the recorded signals.
Adaptive equalizers have been implemented in magnetic tape drives, and have been based on solving a set of equations to find the equalizer characteristic that reduces the error between the desired and actual amplitudes. The set of equations may be highly complex and require some amount of time to calculate. Thus, the equalizer might be computed at the beginning of use with respect to a magnetic tape, or recomputed a few times during use. Further, the desired amplitudes may be difficult to estimate. Hence, in many instances, the desired amplitudes are best estimated by employing a signal having known characteristics, such as a synchronization signal, or a data set separator signal, and not the random data signals.
In magnetic tape, the recording characteristics may not only vary from track to track, but may as well vary in a continuous fashion along a track or tracks. Thus, a selected equalizer characteristic, although satisfactory at the beginning or at some specific track location of a magnetic tape, may lead to an increase in data read errors at some point along the track.
Further, in magnetic tape, an equalizer typically equalizes signals in the asynchronous domain, which means that the digital samples that are processed by the equalizer are taken asynchronously with respect to the clock that is used to write the data on the magnetic tape. This makes a determination of a desired amplitude at the point of the asynchronous sample a difficult task.

Dynamically adapting a magnetic tape read channel equalizer

International Business Machines Corporation


A multi-band spectral subtraction scheme is proposed, comprising a multi-band filter architecture, noise and signal power detection, and gain function for noise reduction. In one embodiment, the gain function for noise reduction consists of a gain scale function and a maximum attenuation function providing a predetermined amount of gain as a function of signal to noise ratio (xe2x80x9cSNRxe2x80x9d) and noise. In one embodiment, the gain scale function is a three-segment piecewise linear function, and the three piecewise linear sections of the gain scale function include a first section providing maximum expansion up to a first knee point for maximum noise reduction, a second section providing less expansion up to a second knee point for less noise reduction, and a third section providing minimum or no expansion for input signals with high SNR to minimize distortion. According to embodiments of the present invention, the maximum attenuation function can either be a constant or equal to the estimated noise envelope. The disclosed noise reduction techniques can be applied to a variety of speech communication systems, such as hearing aids, public address systems, teleconference systems, voice control systems, or speaker phones. When used in hearing aid applications, the noise reduction gain function according to aspects of the present invention is combined with the hearing loss compensation gain function inherent to hearing aid processing.

1. Field of the Invention
The present invention relates to electronic hearing devices and electronic systems for sound reproduction. More particularly the present invention relates to noise reduction to preserve the fidelity of signals in electronic hearing aid devices and other electronic sound systems. According to the present invention, the noise reduction devices and methods utilize digital signal processing techniques.
The current invention can be used in any speech communication device where speech is degraded by additive noise. Without limitation, applications of the present invention include hearing aids, telephones, assistive listening devices, and public address systems.
2. The Background Art
This invention relates generally to the field of enhancing speech degraded by additive noise as well as its application in hearing aids when only one microphone input is available for processing. The speech enhancement refers specifically to the field of improving perceptual aspects of speech, such as overall sound quality, intelligibility, and degree of listener fatigue.
Background noise is usually an unwanted signal when attempting to communicate via spoken language. Background noise can be annoying, and can even degrade speech to a point where it cannot be understood. The undesired effects of interference due to background noise are heightened in individuals with hearing loss. As is known to those skilled in the art, one of the first symptoms of a sensorineural hearing loss is increased difficulty understanding speech when background noise is present.
This problem has been investigated by estimating the Speech Reception Threshold (xe2x80x9cSRTxe2x80x9d), which is the speech-to-noise ratio required to achieve a 50% correct recognition level, usually measured using lists of single-syllable words. In most cases, hearing impaired people require a better speech-to-noise ratio in order to understand the same amount of information as people with normal hearing, depending on the nature of the background noise.
Hearing aids, which are one of the only treatments available for the loss of sensitivity associated with a sensorineural hearing loss, traditionally offer little benefit to the hearing impaired in noisy situations. However, as is known to those skilled in the art, hearing aids have been improved dramatically in the last decade, most recently with the introduction of several different kinds of digital hearing aids. These digital hearing aids employ advanced digital signal processing technologies to compensate for the hearing loss of the hearing impaired individual.
However, as is known to those skilled in the art, most digital hearing aids still do not completely solve the problem of hearing in noise. In fact, they can sometimes aggravate hearing difficulties in noisy environments. One of the benefits of modern hearing aids is the use of compression circuitry to map the range of sound associated with normal loudness into the reduced dynamic range associated with a hearing loss. The compression circuitry acts as a nonlinear amplifier and applies more gain to soft signals and less gain to loud signals so that hearing impaired individuals can hear soft sounds while keeping loud sounds from becoming too loud and causing discomfort or pain. However, one of the consequences of this compression circuitry is to reduce the signal-to-noise ratio (xe2x80x9cSNRxe2x80x9d). As more compression is applied, the signal-to-noise ratio is further degraded. In addition, amplification of soft sounds may make low-level circuit noise audible and annoying to the user.
As is known to those skilled in the art, the general field of noise reduction, i.e., the enhancement of speech degraded by additive noise, has received considerable attention in the literature since the mid-1970s. The main objective of noise reduction is ultimately to improve one or more perceptual aspects of speech, such as overall quality, intelligibility, or degree of listener fatigue.
Noise reduction techniques can be divided into two major categories, depending on the number of input signal sources. Noise reduction using multi-input signal sources requires using more than one microphone or other input transducer to obtain the reference input for speech enhancement or noise cancellation. However, use of multi-microphone systems is not always practical in hearing aids, especially small, custom devices that fit in or near the ear canal. The same is true for many other small electronic audio devices such as telephones and assistive listening devices.
Noise reduction using only one microphone is more practical for hearing aid applications. However, it is very difficult to design a noise reduction system with high performance, since the only information available to the noise reduction circuitry is the noisy speech contaminated by the additive background noise. To further aggravate the situation, the background may be itself be speech-like, such as in an environment with competing speakers (e.g., a cocktail party).
Various noise reduction schemes have been investigated, such as spectral subtraction, Wiener filtering, maximum likelihood, and minimum mean square error processing. Spectral subtraction is computationally efficient and robust as compared to other noise reduction algorithms. As is known to those skilled in the art, the fundamental idea of spectral subtraction entails subtracting an estimate of the noise power spectrum from the noisy speech power spectrum. Several publications concerning spectral subtraction techniques based on short-time spectral amplitude estimation have been reviewed and compared in Jae S. Lim and Alan V. Oppenheim, xe2x80x9cEnhancement and Bandwidth Compression of Noisy Speech,xe2x80x9d PROC. IEEE, Vol. 67, No. 12, pp. 1586-1604, December 1979.
However, as is known to those skilled in the art, there are drawbacks to these spectral subtraction methods, in that a very unpleasant residual noise remains in the processed signal (in the form of musical tones), and in that speech is perceptually distorted. Since the review of the literature mentioned above, some modified versions of spectral subtraction have been investigated in order to reduce the residual noise. This is described in SAEED V. VASEGHI, ADVANCED SIGNAL PROCESSING AND DIGITAL NOISE REDUCTION (John Wiley and Sons Ltd., 1996).
According to these modified approaches, the noisy received audio signal may be modeled in the time domain by the equation:
x(t)=s(t)+n(t),
where x(t), s(t) and n(t) are the noisy signal, the original signal, and the additive noise, respectively. In the frequency domain, the noisy signal can be expressed as:
X(ƒ)=S(ƒ)+N(ƒ),
where X(ƒ), S(ƒ), and N(ƒ) are the Fourier transforms of the noisy signal, of the original signal, and of the additive noise, respectively. Then, the equation describing spectral subtraction techniques may be generalized as:
|Ŝ(ƒ)|=|H(ƒ)|xc2x7|X(ƒ)|,
where |S{circumflex over ( )}(ƒ)| is an estimate of the original signal spectrum |S(ƒ)|, and |H(ƒ)| is a spectral gain or weighting function for adjustment of the noisy signal magnitude spectrum. As is known to those skilled in the art, the magnitude response |H(ƒ)| is defined by:
|H(ƒ)|=G(R(ƒ))=[1xe2x88x92xcexc(R(ƒ))xcex1]xcex2,
            R                    (        f        )              =                  "LeftBracketingBar"                              N            ^                                          (            f            )                          "RightBracketingBar"                    "LeftBracketingBar"                  X                                (            f            )                          "RightBracketingBar"              ,
where N{circumflex over ( )}(ƒ) is the estimated noise spectrum. Throughout this document, the signal-to-noise ratio (xe2x80x9cSNRxe2x80x9d) is defined as the reciprocal of R(ƒ). For magnitude spectral subtraction techniques, the exponents used in the above set of equations are xcex1=1, xcex2=1, xcexc=1, and for power spectral subtraction techniques, the exponents used are xcex1=2, xcex2=0.5, xcexc=1. The parameter xcexc controls the amount of noise subtracted from the noisy signal. For full noise subtraction, xcexc=1, and for over-subtraction, xcexc greater than 1.
The spectral subtraction technique yields an estimate only for the magnitude of the speech spectrum S(ƒ), and the phase is not processed. That is, the estimate for the spectral phase of the speech is obtained from the noisy speech, i.e., arg[S{circumflex over ( )}(ƒ)]=arg[X(ƒ)].
Due to the random variations in the noise spectrum, spectral subtraction may produce negative estimates of the power or magnitude spectrum. In addition, very small variations in SNR close to 0 dB may cause large fluctuations in the spectral subtraction amount. In fact, the residual noise introduced by the variation or erroneous estimates of the noise magnitude can become so annoying that one might prefer the unprocessed noisy speech signal over the spectrally subtracted one.
To reduce the effect of residual noise, various methods have been investigated. For example, Berouti et al. (in M. Berouti, R. Schwartz, and J. Makhoul, xe2x80x9cEnhancement of Speech Corrupted by Additive Noise,xe2x80x9d in Proc. IEEE Conf. on Acoustics, Speech and Signal Processing, pp. 208-211, April 1979) suggested the use of a xe2x80x9cnoise floorxe2x80x9d to limit the amount of reduction. Using a noise floor is equivalent to keeping the magnitude of the transfer function or gain above a certain threshold. Boll (in S. F. Boll, xe2x80x9cReduction of Acoustic Noise in Speech Using Spectral Subtraction,xe2x80x9d IEEE Trans. Acoust., Speech, Signal Process., vol. ASSP-27, pp. 113-120, April 1979) suggested magnitude averaging of the noisy speech spectrum. Soft-decision noise reduction filtering (see, e.g., R. J. McAulay and M. L. Malpass, xe2x80x9cSpeech Enhancement Using a Soft Decision Noise reduction Filter,xe2x80x9d IEEE Trans. on Acoust., Speech, Signal Proc., vol. ASSP-28, pp.137-145, April 1980) and optimal Minimum Mean-Square Error (xe2x80x9cMMSExe2x80x9d) estimation of the short-time spectral amplitude (see, e.g., Y. Ephraim and D. Malah, xe2x80x9cSpeech Enhancement Using a Minimum Mean-square Error Short-time Spectral Amplitude Estimator,xe2x80x9d IEEE Trans. on Acoust., Speech, Signal Proc., vol. ASSP-32, pp. 1109-1121, December 1984) have also been introduced for this purpose.
In 1994, Walter Etter (see Walter Etter and George S. Moschytz, xe2x80x9cNoise Reduction by Noise-Adaptive Spectral Magnitude Expansion,xe2x80x9d J. Audio Eng. Soc., Vol. 42, No. 5, May 1994) proposed a different weighting function for spectral subtraction, which is described by the following equation:
G(R(ƒ))=[A(ƒ)xc2x7R(ƒ)]1xe2x88x92"sgr"(ƒ).
The underlying idea of this technique is to adapt the crossover point of the spectral magnitude expansion in each frequency channel based on the noise and gain scale factor A(ƒ), so this method is also called noise-adaptive spectral magnitude expansion. Similarly the gain is post-processed by averaging or by using a low-pass smoothing filter to reduce the residual noise.
U.S. Pat. No. 5,794,187 (issued to D. Franklin) discloses another gain or weighting function for spectral subtraction in a broad-band time domain. In that document, the gain transfer function is modeled as:       G    =                  X                  r                                xe2x80x83                              m                                xe2x80x83                              s                                      X                      rm                                      xe2x80x83                                    s                          +        α              ,
where Xrms is the RMS value of the input noisy signal, and xcex1 is a constant.
Recently, a psychoacoustic masking model has been incorporated in spectral subtraction to reduce residual noise or distortion by finding the best tradeoff between noise reduction and speech distortion. For further information, see N. Virag. xe2x80x9cSpeech Enhancement Based on Masking Properties of the Auditory System,xe2x80x9d Proc. ICASSP, pp. 796-799, 1995, Stefan Gustafsson, Peter Jax and Peter Vary, xe2x80x9cA Novel Psychoacoustically Motivated Audio Enhancement Algorithm Preserving Background Noise Characteristics,xe2x80x9d Proc. ICASSP, pp. 397-400, 1998, and T. F. Quatieri and R. A. Baxter, xe2x80x9cNoise Reduction Based on Spectral Change,xe2x80x9d IEEE workshop on Applications of Signal Processing to Audio and Acoustics, 1997.
It is well-known that a human listener will not perceive any additive signals as long as their power spectral density lies completely below the auditory masking threshold. Therefore, complete removal of noise is not necessary in most situations. Referring to the publications mentioned above, N. Virag attempted to adjust the parameters xcex1, xcex2 and xcexc adaptively in the spectral subtraction equation so that the noise was reduced to the masking threshold. Stefan Gustafsson suggested that a perceptually complete removal of noise is neither necessary, nor desirable in most situations. In a telephone application, for example, a retained low-level natural sounding background noise will give the far end user a feeling of the atmosphere at the near end and will also avoid the impression of an interrupted transmission. Therefore, noise should only be reduced to an expected amount. In his noise-spectrum subtraction method, the weighting function is chosen in such a way that the difference between the desired and the actual noise level lies exactly at the masking threshold.
Applications of noise reduction in hearing aids have been investigated. As mentioned above, hearing aids are very sensitive to power consumption. Thus, the most challenging problem of noise reduction in hearing aids is the compromise between performance and complexity. In addition, a hearing aid inherently has its own gain adjustment function for hearing loss compensation. Cummins (in U.S. Pat. No. 4,887,299) developed a gain compensation function for both noise reduction and hearing loss compensation, which is a function of the input signal energy envelope. The gain consists of three piecewise linear sections in the decibel domain, including a first section providing expansion up to a first knee point for noise reduction, a second section providing linear amplification, and a third section providing compression to reduce the effort of over range signals and minimize loudness discomfort to the user. Finally, U.S. Pat. No. 5,867,581 discloses a hearing aid that implements noise reduction by selectively turning on or off the output signal or noisy bands.
Spectral subtraction for noise reduction is very attractive due to its simplicity, but the residual noise inherent to this technique can be unpleasant and annoying. Hence, various gain or weighting functions G(ƒ), as well as noise estimation methods in spectral subtraction have been investigated to solve this problem. It appears that the methods which combine auditory masking models have been the most successful. However, these algorithms are too complicated to be suitable for application in low-power devices, such as hearing aids. Hence, a new multi-band spectral subtraction scheme is proposed, which differs in its multi-band filter architecture, noise and signal power detection, and gain function. According to the present invention, spectral subtraction is performed in the dB domain. The circuitry and method of the present invention is relatively simple, but still maintains high sound quality.
Thus, it is an object of the present invention to provide a simple spectral subtraction noise reduction technique suitable for use in low-power applications that still maintains high sound quality. These and other features and advantages of the present invention will be presented in more detail in the following specification of the invention and the associated figures.
A multi-band spectral subtraction scheme is proposed, comprising a multi-band filter architecture, noise and signal power detection, and gain function for noise reduction. In one embodiment, the gain function for noise reduction consists of a gain scale function and a maximum attenuation function providing a predetermined amount of gain as a function of signal to noise ratio (xe2x80x9cSNRxe2x80x9d) and noise. In one embodiment, the gain scale function is a three-segment piecewise linear fuinction, and the three piecewise linear sections of the gain scale function include a first section providing maximum expansion up to a first knee point for maximum noise reduction, a second section providing less expansion up to a second knee point for less noise reduction, and a third section providing minimum or no expansion for input signals with high SNR to minimize distortion. According to embodiments of the present invention, the maximum attenuation function can either be a constant or equal to the estimated noise envelope. The disclosed noise reduction techniques can be applied to a variety of speech communication systems, such as hearing aids, public address systems, teleconference systems, voice control systems, or speaker phones. When used in hearing aid applications, the noise reduction gain function according to aspects of the present invention is combined with the hearing loss compensation gain function inherent to hearing aid processing.


Disclosed are a communication system, a communication device, a communication method, and a program all for preventing disconnection of communication during re-transmission in response to an automatic repeat request in a confirmation mode. The communication system is provided with a first communication device including data transmitting means and data re-transmitting means and a second communication device connected to the first communication device and including data receiving means for receiving data transmitted from the first communication device and data re-transmission requesting means for requesting re-transmission of data not normally received by the data receiving means. The data receiving means determines whether or not the re-transmission data requested by the data re-transmission requesting means will be re-transmitted from the first communication device.

In a mobile communication system such as a cellular phone, a communication system of an LTE (Long Term Evolution type) method which reduces transmission delay and connection delay than usual is spreading.
An entire structure of a radio access network in the mobile communication system of the related LTE method (E-UTRAN: Evolved Universal Terrestrial Radio Access Network) will be described with reference to FIG. 12.
A mobile communication system 1001 of the LTE method includes: a mobile station 1050 called as UE (User Equipment), and a radio base station 1060 called as eNB (E-UTRAN Node B). Between the mobile station 1050 and the base radio station 1060, communication is performed via a radio link (RL) 70.
The mobile station 1050 includes: a PDCP (Packet Data Convergence Protocol) sublayer 1051, an RLC (Radio Link Control) sublayer 1052, an MAC (Medium Access Control) sublayer 1053, a Physical layer 1054 and a radio unit 1055. The radio base station 1060 includes: a PDCP sublayer 1061, an RLC sublayer 1062, a MAC sublayer 1063, a physical layer 1064 and a radio unit 1065.
Next, a structure of the RLC sublayer 1062 in the radio base station 1060 and the RLC sublayer 1052 in the mobile station 1050 of the related mobile communication system 1001 will be described with reference to FIGS. 13 and 14.
The RLC sublayer 1062 in the radio base station 1060 includes: an RLC_SDU (Service Data Unit) receiving unit 1080, a transmission buffer 1081, an RLC_PDU (Protocol Data Unit) generating unit 1082, an RLC_PDU transmitting unit 1083, a re-transmission buffer 1084, an RLC_PDU receiving unit 1085, a reception buffer 1086, an RLC_SDU generating unit 1087, an RLC_SDU transmitting unit 1088, a transmission control information memory unit 1089 and a reception control information memory unit 1090.
Also, the RLC sublayer 1052 in the mobile station 1050 includes: an RLC_PDU receiving unit 1100, a reception buffer 1101, an RLC_SDU generating unit 1102, an RLC_SDU transmitting unit 1103, a re-transmission buffer 1104, an RLC_SDU receiving unit 1105, a transmission buffer 1106, an RLC_PDU generating unit 1107, an RLC_PDU transmitting unit 1108, a transmission control information memory unit 1109 and a reception control information memory unit 1110.
Next, processing of the RLC sublayer 1052 in the mobile station 1050 and the RLC sublayer 1062 in the radio base station 1060 of the mobile communication system 1001 shown in FIG. 12 will be described with reference to FIGS. 12 to 14. Concerning the processing of the RLC sublayers 1052 and 1062, although there are TM (Transparent Mode), UM (Unacknowledged Mode) and AM (Acknowledged Mode), it will be described with AM below.
As shown in FIG. 12, in a part in which transmission processing is performed in the mobile station 1050 (a part shown with down arrow in the figure), for transmitted C/U plane data, that is, control plane data or user plane data (hereinafter, referred to as data), PDCP processing by the PDCP sublayer 1051, RLC processing by the RLC sublayer 1052, MAC processing by the MAC sublayer 1053 and physical processing by the physical layer 1054 are applied in turn, and data to be transmitted is created. The transmission data is transmitted to the radio link 70 by the radio unit 1055 as a radio signal.
Also, in a part in which reception processing is performed in the mobile station 1050 (a part shown with up arrow in the figure), the radio signal from the radio link 70 is received by the radio unit 1055, and for the received signal, physical processing by the physical layer 1054, MAC processing by the MAC sublayer 1053, RLC processing by the RLC sublayer 1052 and PDCP processing by the PDCP sublayer 1051 are applied to the received data in turn. From the data to which a series of processing is applied, data transmitted from the transmission-side is extracted (received).
Also in a part in which transmission processing is performed in the radio base station 1060 (a part shown with up arrow in the figure), for the data transmitted, PDCP processing by the PDCP sublayer 1061, RLC processing by the RLC sublayer 1062, MAC processing by the MAC sublayer 1063 and physical processing by the physical layer 1064 are applied in turn. Data to which a series of processing is applied is transmitted to the radio link 70 by the radio unit 1065 as a radio signal.
Also in a part in which reception processing is performed in the radio base station 1060 (a part shown with down arrow in the figure), the radio signal from the radio link 70 is received by the radio unit 1065, and for the received data physical processing by the physical layer 1064, MAC processing by the MAC sublayer 1063, RLC processing by the RLC sublayer 1062 and PDCP processing by the PDCP sublayer 1061 are applied in turn. From the data to which a series of processing is applied, data transmitted from transmission-side is extracted (received).
As shown in FIGS. 13 and 14, the RLC_SDU receiving unit 1080 of the RLC sublayer 1062 in the radio base station 1060 receives RLC_SDU from the PDCP sublayer 1061 and stores it in the transmission buffer 1081. The RLC_PDU generating unit 1082 acquires data required for transmission from the transmission control information memory unit 1089, the re-transmission buffer 1084 and the transmission buffer 1081, and generates RLC_PDU.
When the RLC_PDU generating unit 1082 generates RLC_PDU, the RLC_PDU generating unit 1082 adds RLC_SN (Sequence Number) to an RLC header. The RLC header includes a polling bit. By setting the polling bit, a report of receiving condition of the mobile station 1050 is requested.
Generated RLC_PDU is, in preparation for ARQ (Automatic Repeat request) re-transmission, stored in the re-transmission buffer 1084 and transmitted to the MAC sublayer 1063 in the radio base station 1060 by the RLC_PDU transmitting unit 1083. RLC_PDU transmitted to the MAC sublayer 1063 is sent to the radio unit 65 via the physical layer 1064. RLC_PDU is sent to the mobile station 1050 via the radio link 70 from the radio unit 1065.
In the mobile station 1050, RLC_PDU sent from the radio base station 1060 is received by the radio unit 1055 via the radio link 70. Received RLC_PDU is received, via the physical layer 1054, by the RLC_PDU receiving unit 1100 of the RLC sublayer 1052 from the MAC sublayer 1053 in the mobile station 1050.
The RLC_PDU receiving unit 1100 stores, among RLC_PDU received from the MAC sublayer 1053, transmission control information from the radio base station 1060 in the reception control information memory unit 1110 and stores other information in the reception buffer 1101.
The RLC_SDU generating unit 1102 acquires RLC_PDU from the reception buffer 1101 and generates RLC_SDU. Generated RLC_SDU is transmitted to the PDCP sublayer 1051 in the mobile station 1050 from the RLC_SDU transmitting unit 1103.
Also, in case received RLC_PDU includes a request to report receiving condition, or in case it includes a request to detect reception failure and to report receiving condition, the reception buffer 1101 stores information of "request to report receiving condition" or "request to detect reception failure and to report receiving condition" among the received RLC_PDU in the transmission control information memory unit 1109.
Also, the transmission control information memory unit 1109 forwards information of "request to report receiving condition" or "request to detect reception failure and to report receiving condition" stored in the transmission control information memory unit 1109 to the RLC_PDU generating unit 1107.
When the RLC_PDU generating unit 1107 receives information of "request to report receiving condition" or "request to detect reception failure and to report receiving condition" forwarded from the transmission control information memory unit 1109, it prepares for generation of transmission control information. The RLC_PDU generating unit 1107 generates, while generating RLC_PDU, transmission control information which replies to "request to report receiving condition" or "request to detect reception failure and to report receiving condition".
As stated above, in the RLC_PDU generating unit 1107, transmission control information which notifies whether or not the mobile station 1050 has received RLC_PDU by using RLC_SN as ACK (ACKnowledgement)/NACK (Negative ACKnowledgement) is generated.
Processing in data transmission from the mobile station 1050 to the radio base station 1060 is similar to the processing in data transmission from the radio base station 1060 to the mobile station 1050. That is, the RLC_SDU receiving unit 1105 of the RLC sublayer 1052 in the mobile station 1050 receives RLC_SDU from the PDCP sublayer 1051 in the mobile station 1050 and stores it in the transmission buffer 1106. The RLC_PDU generating unit 1107 acquires data required for transmission from the transmission control information memory unit 1109, the re-transmission buffer 1104 and the transmission buffer 1106 and generates RLC_PDU.
When the RLC_PDU generating unit 1107 generates RLC_PDU, the RLC_PDU generating unit 1107 adds RLC_SN to an RLC header. The RLC header includes a polling bit. By setting the polling bit, a report of receiving condition of the radio base station 1060 is requested.
Generated RLC_PDU is, in preparation for ARQ re-transmission, stored in the re-transmission buffer 1104 and transmitted to the MAC sublayer 1053 in the mobile station 1050 by the RLC_PDU transmitting unit 1108. RLC_PDU transmitted to the MAC sublayer 1053 is sent to the radio unit 1055 via the physical layer 1054. RLC_PDU is sent to the radio base station 1060 via the radio link 70 from the radio unit 1055.
In the radio base station 1060, RLC_PDU sent from the mobile station 1050 is received by the radio unit 1065 via the radio link 70. Received RLC_PDU is received, via the physical layer 1064, by the RLC_PDU receiving unit 1085 of the RLC sublayer 1062 from the MAC sublayer 1063.
The RLC_PDU receiving unit 1085 stores, among RLC_PDU received from the MAC sublayer 1063, transmission control information from the mobile station 1050 in the reception control information memory unit 1090 and stores other information in the reception buffer 1086.
The RLC_SDU generating unit 1087 acquires RLC_PDU from the reception buffer 1086 and generates RLC_SDU. Generated RLC_SDU is transmitted to the PDCP sublayer 1061 in the radio base station 1060 from the RLC_SDU transmitting unit 1088.
Also, in case received RLC_PDU includes a request to report receiving condition, or in case it includes a request to detect reception failure and to report receiving condition, the reception buffer 1086 stores information of "request to report receiving condition" or "request to detect reception failure and to report receiving condition" among the received RLC_PDU in the transmission control information memory unit 1089.
Also, the transmission control information memory unit 1089 forwards information of "request to report receiving condition" or "request to detect reception failure and to report receiving condition" stored in the transmission control information memory unit 1089 to the RLC_PDU generating unit 1082.
When the RLC_PDU generating unit 1082 receives information of "request to report receiving condition" or "request to detect reception failure and to report receiving condition" forwarded from the transmission control information memory unit 1089, it prepares for generation of transmission control information. The RLC_PDU generating unit 1082 generates, while generating RLC_PDU, transmission control information which replies to "request to report receiving condition" or "request to detect reception failure and to report receiving condition".
As stated above, in the RLC_PDU generating unit 1082, transmission control information which notifies whether or not the radio base station 1060 has received RLC_PDU by using RLC_SN as ACK/NACK is generated.
Above is a communication procedure between the mobile station 1050 and the radio base station 1060 in the related mobile communication system.
A data transmission method which adopts, as mentioned above, automatic repeat request (ARQ) as an error control technology is disclosed, for example, in patent document 1.

Communication system, communication device, communication method and program


An apparatus includes a housing, defining an inner volume, and an actuator mechanism movably disposed therein. The actuator mechanism is configured to be transitioned from a first configuration to a second configuration to define a pre-sample reservoir fluidically couplable to receive a pre-sample volume of bodily-fluid via an inlet port of the housing. The actuator mechanism is movable from a first position to a second position within the housing after the pre-sample reservoir receives the pre-sample volume such that the housing and the actuator mechanism collectively define a sample reservoir to receive a sample volume of bodily-fluid via the inlet port. The outlet port is in fluid communication with the sample reservoir and is configured to be fluidically coupled to an external fluid reservoir after the sample volume is disposed in the sample reservoir to transfer at least a portion of the sample volume into the external fluid reservoir.

Embodiments described herein relate generally to the parenteral procurement of bodily-fluid samples, and more particularly, to devices and methods for parenterally procuring bodily-fluid samples with reduced contamination from microbes or other contaminants exterior to the bodily-fluid source (e.g., dermally-residing microbes) via syringe-based fluid transfer and/or the like.
Health care practitioners routinely perform various types of tests (including microbial tests, tuberculosis tests, and the like) on patients using parenterally-obtained bodily-fluids. The in vitro diagnostics industry has expanded the types of approaches employed to identify, categorize, type, determine sensitivity and suitability (e.g., to specific antibiotics), and/or to otherwise discern desired information about bodily-fluid samples with increased speed, specificity, and accuracy. For example, some such approaches include DNA/RNA sequencing, biological marker identification, mass spectrometry, centrifuging, magnetic separation, microfluidic isolation, molecular analysis, polymerase chain reaction (PCR) analysis, interferon-gamma release assays, and/or the like. In some instances, such approaches can be used, for example, in microbial testing of parenterally obtained bodily-fluids to determine the presence of one or more potentially undesirable microbes, such as bacteria, fungi, or yeast (e.g., Candida).
In some instances, microbial testing may include diagnostic methods including but not limited to incubating patient samples in one or more sterile vessels containing culture media that is conducive to microbial growth, molecular sample analysis, gene sequencing, PCR-based approaches, mass spectrometry, and/or the like as noted above. Generally, when such microbes are present in the patient sample, the microbes flourish over time in the culture medium or can be detected and/or identified by one of the aforementioned technological approaches. When culture medium is utilized for microbial testing, after a variable amount of time (e.g., a few hours to several days), organism growth can be detected by automated, continuous monitoring (e.g., by detecting carbon dioxide and/or the like). The culture medium can then be tested for the presence of the microbes, which if present, suggests the presence of the same microbes in the patient sample and thus, in the bodily-fluid of the patient from which the sample was obtained. When other technologies are used for microbial testing, the amount of time required to determine a presence of microbes may vary (e.g. from nearly instantaneously to several minutes, hours, or days). These technologies, however, are still sensitive to the inherent quality and/or integrity of the specimen that is being analyzed. Accordingly, when microbes are determined to be present in the culture medium or identified by another diagnostic test, the patient may be prescribed one or more antibiotics or other treatments specifically designed to treat or otherwise remove the undesired microbes from the patient.
Patient samples, however, can become contaminated during procurement and/or otherwise can be susceptible to false positive results. For example, microbes from a bodily surface (e.g., dermally-residing microbes) that are dislodged during needle insertion into a patient, either directly or indirectly via tissue fragments, hair follicles, sweat glands, and other skin adnexal structures, can be subsequently transferred to a culture medium with the patient sample and/or included in the specimen that is to be analyzed for non-culture based testing. Another possible source of contamination is from the person drawing the patient sample. For example, a doctor, phlebotomist, nurse, etc. can transfer contaminants from their body (e.g., finger, arms, etc.) to the patient sample and/or to the equipment containing the patient sample. Specifically, equipment and/or devices used during a patient sample procurement process (e.g., patient to needle, needle/tubing to sample vessels, etc.) often include multiple fluidic interfaces that can each introduce points of potential contamination. In some instances, such contaminants may thrive in a culture medium and/or may be identified by another diagnostic technology and eventually yield a positive microbial test result, thereby falsely indicating the presence of such microbes in vivo.
In some instances, false positive results and/or false negative results can be attributed to a specific volume of the patient sample. For example, overfilling of volume-sensitive blood culture bottles can lead to false positive results as noted in the instructions for use and/or warning labeling from manufacturers of such culture bottles, as well as associated automated continuous monitoring microbial detection systems. On the other hand, insufficient patient sample volume within a culture medium can result in false negative results. By way of example, in a study performed by the Mayo Clinic entitled, Optimized Pathogen Detection with 30- Compared to 20-Milliliter Blood Culture Draws, Journal of Clinical Microbiology, December 2011, a patient sample volume of 20 milliliters (mL) can result in detection of about 80% of bacteremias present in a patient sample, a patient sample volume of 40 mL can result in detection of about 88% of the bacteremias, and a patient sample volume of 60 mL can result in detection of about 99% of the bacteremias. In some instances, such as in patients with sepsis, a concentration of colony forming units (CFUs) in the septic patient's bloodstream can be highly variable (including very low levels of less than 1 CFU per 10 ml of blood). Thus, ensuring that a sufficient amount of blood is collected and analyzed is desired for clinical confidence in the accuracy of the microbial test result.
While placing blood in a culture medium is a 'standard of care' today, a number of new technologies (examples of which are noted above) hold promise in increasing the pace with which microbes (and antibiotic susceptibility and/or sensitivity) can be identified in a bodily-fluid sample. However, procuring a sufficient volume of blood that is analyzed remains desirable as a small volume of blood may not contain a CFU that is actually present in the patient's bloodstream, thereby falsely indicating that a patient is not septic.
Such inaccurate results because of contamination, insufficient patient sample volume, and/or the like are a concern when attempting to diagnose or treat a suspected illness or condition. For example, false negative results from microbial tests may result in a misdiagnosis and/or delayed treatment of a patient illness, which, in some cases, could result in the death of the patient. Conversely, false positive results from microbial tests may result in the patient being unnecessarily subjected to one or more anti-microbial therapies, which may cause serious side effects to the patient including, for example, death, as well as produce an unnecessary burden and expense to the health care system due to extended length of patient stay and/or other complications associated with erroneous treatments. Additionally, the use of diagnostic imaging equipment attributable to these false positive results is also a concern from both a cost as well as patient safety perspective as unnecessary exposure to concentrated radiation associated with a variety of imaging procedures (e.g., CT scans) has many known adverse impacts on long-term patient health.
As such, a need exists for improved bodily-fluid transfer devices and methods that reduce microbial contamination in bodily-fluid test samples particularly in syringe-based fluid transfers.

Devices and methods for syringe-based fluid transfer for bodily-fluid sampling


The present invention provides a software storage unit, a backup method, and a backup control program capable of completing data transfer to a data backup destination in a shorter time. The software storage unit includes a software storage section constructed across a plurality of physical machines and a switch section coupled to an external network, wherein the software storage section grasps data to back up, among stored data, which is to be transferred to a data backup destination, splits the grasped data into a plurality of data parts, and issues a command to transfer the split data parts from respective ones of the plurality of physical machines to the data backup destination via the switch section.

In recent years, great importance has been placed on backup of data used in an operation system, as a countermeasure not only against system troubles or failures but also against disasters. Accordingly, a system is configured to be provided with a backup system separately from an operation system, and data used in the operation system is backed up into the backup system. The system is thereby enabled to continue operation even when, by any chance, operation of the operation system becomes difficult to continue owing to its system trouble or failure or owing to a disaster, by starting up the backup system as an operation system using the backup data and thereby recovering the system.
There is a system in which a backup system is connected with an operation system via a network and, in preparation for a case where operation of the operation system becomes difficult to continue owing to its system trouble, failure or the like, backup transfer of data to the backup system is performed on the operation system. In the system, storages each using an HDD (Hard Disk Drive) or an SSD (Solid State Drive) are employed for storing data, and data stored in a storage on the operation system side is transferred to a storage on the backup system side via the network.
A description will be given of such a system of background art where the backup transfer is performed. A system shown in FIG. 8 includes an operation system 100, a backup system 200, and a network 300 connecting the operation system 100 and the backup system 200. The operation system 100 includes a storage 101, a server 102 and a switch 103. As shown in FIG. 9, the storage 101 has a configuration including, within a storage 400, an interface unit 401, a control unit 402 and an above-described HDD or SSD 403. The backup system 200 includes a storage 201, a server 202 and a switch 203.
Next, a description will be given of a data backup technique from the storage 101 of the operation system 100 to the backup system 200 in FIG. 8. In the data backup technique using the storage 101 of background art, data to back up has been written into the storage 101 constituting the operation system 100. Then, according to a command from the storage 101 or the server 102, data transmission of the data written in the storage 101 to the storage 201 of the backup system 200 is performed. The data transmission is performed via the switch 103 constituting the operation system 100, the network 300 and the switch 203 constituting the backup system 200. By such data transmission, data in the operation system 100 can be backed up into the backup system 200.
Patent Literature 1 (PTL1) relates to a computer system, and describes that, for data backup, a method of storing into a disc device or a magnetic tape device connected to a computer system and a method of storing into another computer via a network are used.

Software storage unit, backup method, and recording medium storing backup control program


An exemplary copper-silver alloy wire includes a conductive core containing copper, and a copper-silver cladding layer surrounding the conductive core. A ratio of silver to copper by weight in the copper-silver cladding layer is in a range from 1% to 30%. An exemplary method for manufacturing the copper-silver alloy wire includes steps of: providing a conductive core containing copper; forming a silver layer surrounding the conductive core; and heating the silver layer and peripheral portions of the conductive core so as to form a copper-silver cladding layer at an interface between the silver layer and the conductive core. The copper-silver alloy wire has high electrical conductivity, low current loss and high anti-interference.

Wires and cables are very important for diversified electrical appliances to input or output electrical power and data signals. Therefore, it is necessary for wires and cables to have high electrical conductivity, low current loss and high anti-interference.
In order to enhance the electrical conductivity of wires and cables, materials with high electrical conductivity such as pure copper and pure silver are used as a conductive core. However, not only are pure copper and pure silver fairly soft materials, but also it is very difficult to refine them, thus their use leads to a considerable increase in cost. Therefore, it has been believed for a long time that copper-based alloys such as brass are better for use as conductive core material for wires and cables, brass being an alloy of copper and zinc.
Brass, however, does have some draw-backs when used in wires and cables. Firstly, the electrical conductivity of a brass core is relatively low compared to other conducting metals, as a result wires and cables made from brass exhibit relatively high levels of eddy current loss. Eddy current is caused by self inductance in the conductor core when carrying current. Moreover, eddy current loss can increase with increasing diameter of wires and cables. Wires and cables with brass cores suffer from relatively high levels of interference, which can affect transmission of high frequency signals.
What is needed, therefore, is a wire with copper-silver alloy core having high electrical conductivity, low current loss and high anti-interference. What is also needed, therefore, is a method for manufacturing the wire.

Copper-silver alloy wire and method for manufacturing the same


A CMOS multiplexing circuit is provided for selecting one of a plurality of input signals under control of a digital select signal for providing an output signal inverted with respect to the selected input signal. A plurality of processing channels one for each input signal and each having exactly first, second, third and fourth transistors serially connected between first and second sources of operating potential are repsonsive to the digital select signal whereby only the second and third transistors in the selected processing channels are enabled. The other processing channels supporting the remaining input signals are disabled. The first and fourth transistors of the selected processing channel are alternately enabled by one of the plurality of input signals for providing the inverse state thereof at the output formed at the interconnection of the second and third transistors. The first and second sources of operating potential need pass through only two transistors which improves the propagation delay and since only the second and third transistors of the selected processing channels are conducting, the transistors forming the remaining non-selected processing channels are effectively removed from the output terminal thereby reducing the capacitive load thereon and improving the propagation delay in the select path.

This invention relates in general to multiplexer circuits, and more particularly, to a high speed CMOS multiplexer circuit having reduced propagation delay in the data path and selected path.
A multiplexing circuit is a common and useful component of many modern digital systems wherein there is a need to select between one of a plurality of input signals under control of a digital select signal. For example, in a four-to-one digital multiplexer, four digital input signals are applied at four data inputs while 2-bit digital select signal is applied at the select inputs thereof. The four possible combinations of the 2-bit digital select signal propagates the inverse state of the selected digital input signal to the output terminal. Other multiplexing circuits can accommodate a greater number of input signals with additional select bits. For example, an eight-to-one multiplexer requires a 3-bit digital select signal and a sixteen-to-one multiplexer uses a 4-bit digital select signal.
The conventional multiplexing circuit comprises a parallel combination of processing channels, one for each input signal, coupled between a positive source of operating potential such as V.sub.CC and a ground potential terminal. Each processing channel typically includes at least six serially couple CMOS transistors, three upper P-channel CMOS transistors, and three lower N-channel CMOS transistors. The drain of the lower P-channel CMOS transistor and the drain of the highest N-channel CMOS transistor in each conduction channel are coupled together to the output node. The gates of the CMOS transistors are coupled for receiving the digital select signals and input signals such that the digital select signal enables four of the six serially coupled transistors in one conduction path while the data input signal enables one of the remaining two transistors whereby either the three upper P-channel CMOS transistors or the three lower N-channel CMOS transistors are conducting. The output terminal is thus pulled toward V.sub.CC or ground potential through the three upper transistors or the three lower transistors depending on the digital input signal for providing the inverse state thereof.
The aforedescribed conventional multiplexer circuit includes a propagation delay through the six transistor conduction paths wherein the positive supply V.sub.CC or ground potential must pass through the three upper P-channel CMOS transistors or the three lower N-channel CMOS transistors, respectively, to reach the output terminal. The drain-to-source resistance and the ever present junction capacitance of each transistor creates an undesirable RC time constant for the propagating signal. Hence, the greater the number of transistors in a conduction path, the greater resistance and capacitance and associated propagation delay therethrough. Thus, it would be desirable to reduce the number of transistors in the data conduction path for each processing channel of the multiplexer.
Another concern in achieving reduced propagation delay through the multiplexer circuit is the parasitic drain capacitances associated with the P.sup.+ diffusion to N.sup.- bulk junction of the P-channel CMOS transistors and the N.sup.+ diffusion to P.sup.- bulk junction of the N-channel CMOS transistors. Theses junction capacitances are affixed to the output terminal at the junction of the lowest P-channel CMOS transistor and the highest N-channel CMOS transistor. Depending on the state of the digital input signals, it is common for the P-channel CMOS and N-channel CMOS transistors on either side of the output terminal in the non-selected processing channels to be conducting thereby adding the parasitic junction capacitances of the P-channel and N-channel CMOS transistors next in line in the conduction paths which serves to further load the output terminal slowing the charge and discharge rate thereof and increasing the propagation delay through the multiplexer circuit.
Previous attempts at speeding up the multiplexer circuit have included increasing size of the CMOS transistors for increasing the drive capacity thereof. This technique is often ineffective since the increase in size of the CMOS transistors also increases the parasitic drain capacitance of each transistor connected to the output terminal of which only one is attempting to drive the capacitive load. To maintain symmetry it is necessary to increase the size of all the CMOS transistors equally effectively increasing the parasitic drain capacitance by a factor of four and defeating the attempt at higher speed by driving the capacitive loads harder. A more desirable approach would be to reduce the capacitive load on the output terminal rather than drive it with additional power.
Hence, what is needed is an improved CMOS multiplexing circuit having fewer transistors in the conduction paths of each processing channel while reducing the capacitive load on the output terminal.

High speed CMOS multiplexer having reduced propagation delay


An electromagnetic clutch according to the present invention includes a first rotatable member which is rotatably supported on a first bearing. The first rotatable member is connected to an external driving source and has an axial magnetic end plate. A second rotatable member is connected to a driven member. An annular magnetic member is supported on the second rotatable member through a plurality of leaf springs so as to be capable of axial movement and faces the axial end plate of the rotatable member with an axial gap therebetween. A third rotatable member is connected to the second rotatable member to limit the axial movement of the annular magnetic member. An electromagnet is associated with one of rotatable members and the annular magnetic member for transmitting rotational force from the external driving source to the other of the rotatable members by pulling the annular magnetic member into contact with the end plate. A coupling device couples the annular magnetic member to the third rotatable member. An elastic member is disposed between the coupling device and the outer end surface of the third rotatable member for reducing vibration and impact noise at the time of attraction in the axial direction of said annular magnetic member to the magnetic end plate of said first rotatable member.

1. Field of The Invention
The present invention generally relates to an electromagnetic clutch, such as for use in controlling the transmission of power from an automobile engine to a refrigerant compressor in an automotive air conditioning system, and, more particularly, to an electromagnetic clutch having a structure for reducing impact noise when an armature plate is attracted to a rotor.
2. Description of The Prior Art
Generally, there are two types of well-known electromagnetic clutches which include a structure to transfer rotational and attractive forces: one type includes a plurality of leaf springs to transfer the forces and the other type includes a plurality of rubber members to transfer the forces. For example, U.S. Pat. No. 4,694,945 discloses a plurality of leaf springs which transfer rotational force from a clutch rotor to an armature plate as the armature plate engages the clutch plate of the clutch rotor. Issued Japanese Utility Model No. 58-8997 discloses a plurality of rubber members which transfer rotational force from the clutch rotor to the armature plate as the armature plate engages the clutch plate of the clutch rotor.
In systems such as that described in above-mentioned U.S. Pat. No. 4,694,945, when the electromagnet associated with the clutch is excited, the armature plate is attracted to one end surface of a rotor against the recoil strength of the leaf springs. As the axial air gap between the armature plate and the rotor is made smaller, the attractive force attracting the armature plate to the rotor increases. Accordingly, the kinetic energy of the armature plate is large just before the armature plate contacts the clutch plate. This kinetic energy of the armature plate is converted to sound energy and vibration as the armature plate contacts the clutch plate. Therefore, when the armature plate is attracted to the rotor, large impact noise and vibration is produced between the armature plate and the rotor. Systems such as that described in the above-mentioned Issued Japanese Utility Model No. 58-8997 reduce this noise and vibration by the use of rubber members. However, the effectiveness and durability of these rubber members is decreased by the rotational stress applied thereto immediately after the armature plate engages the clutch plate.
U.S. Pat. No. 4,808,870 discloses an improved connecting structure between an armature plate and a stopper plate for reducing impact noise when the armature plate is attracted to a rotor. This structure is an improvement over the above-described systems in that impact noise is reduced and the durability of the elastic members is increased. However, in this system, the connecting structure includes an elastic member fixedly secured to an associated pin member. While the elastic member is not subject to rotational force, the absorption of impact noise is accomplished by the elastic member receiving shearing stress produced by the axial movement of the pin member. This shearing stress has a detrimental effect on the durability of the elastic member.

Electromagnetic clutch having a structure for reducing impact noise


A silver halide photographic light-sensitive material is disclosed. The light-sensitive material comprises a support having thereon a photographic layer including a silver halide emulsion layer wherein the outermost surface of said photographic layer has a pH value of from 5.4 to 5.9 and said silver emulsion layer contains a compound represented by the following formula I; ##STR1## wherein R.sub.1 is an alkyl group, a cycloalkyl group or an aryl group; R.sub.2 is an alkyl group, a cycloalkyl group, an acyl group or an aryl group; R.sub.3 is a substituent, n is 0 or 1; X.sub.1 is a substituent capable of splitting off upon coupling reaction with the oxidation product of a color developing agent; and Y.sub.1 is an organic group. The light-sensitive material is excellent in stability during storage and gives stable photographic characteristics even when pH value of developer is varied.

Light-sensitive materials are distributed to users via various routes after production thereof. In the case of color printing paper, the light-sensitive material is often subject to various temperatures before reaching the photo-finisher and stored under non-refrigerating conditions due to the limited space even in the photo-finishing laboratory, even thougt an instruction for refrigerating storage is given. For this reason, the sensitivity and fogging at the time of use by the user often differ from those at delivery from the factory, which can hamper the obtainment of satisfactory performance. This is critical at increased levels of fogging, which can spoil the commercial value. Thus, there has been demand for a light-sensitive material with excellent storage stability at various temperatures in the photographic industry. In recent years, rapid processing of color photographic paper has been achieved by the use of silver halide grains with high silver chloride contents, as disclosed in WO87-04534; however, such silver halide grains are also known to be poor in the abovementioned storage stability. Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) No. 6940/1990 discloses a technique for making the surface pH on the emulsion layer side of a light-sensitive material fall between 4.0 and 5.3 to solve the above problem. Specifically, each coating solution is adjusted with respect to pH and a carbamoylpyridium hardener and a bisformazinium hardener are used. However, analyses by the present inventor revealed that this method has no effect on sensitivity fluctuation, though it has a slight effect on fogging fluctuation. Also, the use of a large amount of a 1,3,5-triazine hardener has been found to improve fogging fluctuation in storage by making the surface pH of the emulsion layer fall in the range specified above, but the problem of sensitivity fluctuation remains unsolved. Another finding was that the use of a large amount of hardener tends to form an aggregate with gelatin, which damages the coating quality.
Generally, a silver halide color photographic light-sensitive material, hereinafter referred to as a color light-sensitive material, has a silver halide emulsion layer which has been spectrally sensitized to the desired sensitivity, wherein dye images are formed by reaction of yellow, magenta and cyan dye forming couplers in the silver halide emulsion and a color developing agent.
5-pyrazolone couplers, which have traditionally been used as magenta dye forming couplers, have major problems that yellow staining forms in the undeveloped portion in response to heat and moisture and the dye formed has undesirable absorption at around 430 nm which is undesirable from the viewpoint of color reproduction. The pyrazolobenzimidazoles described in British Patent No. 1,047,612, the indazolones described in U.S. Pat. No. 3,770,447 and the pyrazoloazoles described in U.S. Pat. No. 3,334,515, British Patent Nos. 1,252,418 and 1,334,515 and Japanese Patent O.P.I Publication Nos. 162548/1984 and 171956/1984 have very little undesirable absorption at around 430 nm and causes little Y staining due to heat or moisture.
On the other hand, there have recently been used yellow dye forming couplers which have little undesirable absorption on the long wavelength side of the spectral absorption characteristic of the dye and which offer good color reproduction, including the compound described in Japanese Patent O.P.I. Publication No. 123047/1988.
However, these magenta and yellow couplers change their color developability with changes in color developer pH, thus significantly affecting the properties, particularly gradation, of the color light-sensitive material.

Silver halide photographic light-sensitive material


A suspension system for a backpack includes a rocker arm pivotally connected to the backpack. A first hip stay has a first end connected to a first end of the rocker arm and a second end opposite the first end. A second hip stay has a first end connected to a second end of the rocker arm and a second end opposite the first end. A waist belt is attached to the second end of the first hip stay and to the second end of the second hip stay. The first and second hip stays distribute the load of the backpack between a wearer's left and right hips. A backpack incorporating the suspension system is also disclosed.

Backpacks are commonly used in recreational activities, such as hiking, climbing and skiing, to carry clothing, food, water, shelter, equipment and various other items. Backpacks are also used in everyday activities to carry items such as books, files and computers. Conventional backpacks typically employ a shoulder harness that extends over one or both of the wearer's shoulders in conjunction with a waist belt that wraps around the wearer's waist. The shoulder harness and waist belt allow the load of the backpack (and its contents) to be distributed over both the wearer's shoulders and waist.
Various movements of the backpack wearer may cause the load of the backpack to undesirably shift to one side of the body or the other. For example, rocking of the wearer's hips during walking or hiking (as a result of the wearer's natural gait) may cause the backpack and/or the load to shift with respect to the wearer's body, undesirably emphasizing the load on one of the hips, and/or on one or both of the shoulders. This shifting is often emphasized in situations where the wearer is traveling uphill, downhill, or across off-camber, rough and/or uneven terrain.
Numerous backpack suspension systems have been developed to reduce the shifting of the load on the wearer's body. For example, backpacks have been developed with semi-rigid frames that flex along with the wearer's body to reduce the shifting of the load. In addition, backpacks have been developed with pivoting hip belts that pivot to compensate for movement of the wearer's hips relative to the rest of their body. These packs, however, fail to adequately compensate for the shifting of the load. Therefore, there remains a need in the art for a backpack suspension system that evenly distributes the backpack's load over the wearer's body throughout various movements and shifting of the body.


A multi-shot crossbow includes a crossbow arm, bowstrings, and a crossbow body, wherein the crossbow arm is provided with a slider which is slidably connected with the crossbow arm along a longitudinal direction of the crossbow arm, a top of the crossbow arm is fixed with an arrow chamber which is provided with a plurality of longitudinally extending arrow holes, each of the arrow holes is provided with a slidably connected hammer, each hammer is fixedly connected to the slider, the bowstrings are located below the crossbow arm, and when the slider is at a back end point, the slider is movably attached to the crossbow body. Multiple arrows can be simultaneously shot, and the hammers can be arranged side by side and can shoot all the arrows at the same time. All the arrows are evenly driven and are shot with small radius and high hit accuracy.

Crossbow is a weapon used to shoot arrows. Crossbow is a kind of bow with an arm, and is mainly composed of a crossbow arm, a crossbow arch, a bowstring and a crossbow body. The crossbow bow is provided transversally to the front end of the crossbow arm. The crossbow arm is provided with an arrow groove, and the crossbow body is placed at the rear end of the arrow groove. The bowstring is located above the crossbow arm, the two ends of the bowstring are hooked on two crossbows, and the string is hung on the hook of the crossbow body. When shooting, the arrow is placed in the arrow groove, the hook is pulled open, the open crossbow is used to drive the bowstring to form a kinetic energy of rapid rebound, and the arrow is shot at a high speed. As recorded in the history, Zhugeliannu can shoot ten arrows at a time. Zhugeliannu is in a state of loss, and many people want to reproduce it. However, as to the existing imitated Zhugeliannu, the difference is only the number of arrow grooves on the crossbow arm, and the rest of the structure is roughly the same as the structure of the ordinary crossbow. Since after is string is hooked, the portions of the string on both sides of the hook are inclined at an angle, and thus the arrows within the arrow grooves on the two sides are shot first and the arrows within the arrow grooves in the middle are shot later. The kinetic energy of the bowstring is attenuated, resulting in a large spread radius of the arrows and low shooting accuracy. In order to ensure the initial velocity of the arrows, the existing stringer usually uses a bowstring of larger pounds to hit multiple arrows. However, it is difficult to get the string ready, the arrows need to be arranged in the arrow grooves one by one, the shooting interval is long, and repeated shooting is performed very slowly.