Showing papers on "Offset (computer science) published in 1991"

Method for providing video programming nearly on demand

Abstract: A method for providing video programming in a nearly on demand basis is disclosed. A video network (10) includes a video server (11) that operates several video recorders (17) to simultaneously exhibit video performances or programs on a plurality of channels. The video server (11) is controlled in real time in accordance with data presented to it in an exhibition plan (19). The exhibition plan (19) calls for two or more channels to show the same program on a time offset basis. Due to the offset in exhibiting a given program, a subscriber may view a program at any time, from the beginning of a program, by waiting for a period of time that is no longer than the offset.

System for modifying relocatable object code files to monitor accesses to dynamically allocated memory

Abstract: An object code expansion program inserts new instructions and data between preexisting instructions and data of an object code file; offsets are modified to reflect new positions of the preexisting instructions and data. For each item of preexisting object code (instructions or data), the following steps are performed: making a new code block comprising any desired new instructions and the item, and storing it as new object code; tracking the location of the item and the new code block within the new object code; and tracking items that contain inter-item offsets. Then, each inter-item offset is updated using the new location of the item or new code block, as required. Finally, offsets in symbol tables and relocation structures are updated with the new location of the item. This expansion program is used to add instructions to object code files of a second program, to monitor substantially all of the memory accesses of the second program. The added instructions establish and maintain a memory status array with entries for memory locations that are validly accessibly by the second program; entries indicate the status of corresponding memory locations. The memory status array is used to check for the errors of writing to unallocated memory and reading from unallocated or uninitialized memory. Also, the data section of the object code files are expanded with extra dummy entries to aid in the detection of array bounds violations and similar data errors. Furthermore, watchpoints can be established for more comprehensive monitoring.

D.C. offset compensation in a radio receiver

Abstract: A zero-IF radio receiver eliminates DC offset without distortion or loss of the low-frequency and DC components of the received or desired signal by initially differentiating the received signal to filter out the DC offset. The signal is amplified to a suitable level and then integrated to recapture the original DC and low frequency signal components. The integration essentially restores the filtered components to the original value in the amplified signal using an arbitrary constant of integration of bounded magnitude to generate a restored signal. Using various techniques that exploit predetermined signal patterns or inherent signal properties of the desired signal, the DC offset can be reasonably estimated. The DC offset estimate is then subtracted out of the restored signal leaving the amplified, received signal substantially free from distortion. An advantageous method for differentiating and digitizing the received, signal uses the technique of companded delta modulation.

Cellular tdm communication system employing offset frame synchronization

Abstract: An RF cellular TDM communication system employing offset frame synchronization between cells, any cell being omni-directional or directional, such that a frame at one cell is offset by an integral number of frames from another cell; the system incorporating multiplexed speech transcoding of traffic channels from multiple cells while supporting stringent delay requirements. Offset frame synchronization (255) for providing rapid mobile assisted handoff.

Error bounded variable distance offset operator for free form curves and surfaces

Abstract: Most offset approximation algorithms for freeform curves and surfaces may be classified into two main groups. The first approximates the curve using simple primitives such as piecewise arcs and lines and then calculates the (exact) offset operator to this approximation. The second offsets the control polygon/mesh and then attempts to estimate the error of the approximated offset over a region. Most of the current offset algorithms estimate the error using a finite set of samples taken from the region and therefore can not guarantee the offset approximation is within a given tolerance over the whole curve or surface. This paper presents new methods to globally bound the error of the approximated offset of freeform curves and surfaces and then automatically derive new approximations with improved accuracy. These tools can also be used to develop a global error bound for a variable distance offset operation and to detect and trim out loops in the offset.

Method of and apparatus for controlling modulation of digital signals in frequency-modulated transmissions

Abstract: A signal amplitude shaping circuit (31) is interposed between a signal source (32) and a signal input terminal (16) of a frequency modulation circuit of a typical voice radio transmitter or transceiver unit. The amplitude shaping circuit (31) includes a high-impedance sampling circuit (34) which senses the steady state bias voltage at the signal input terminal during periods when no data are being transmitted. Upon receipt of a transmit-enable signal (53), the most recently sensed bias voltage is stored and positive and negative offset voltages (74, 69) are generated with respect to the stored voltage (40). One of the offset voltages (74, 69) is adjusted as a precisely determined voltage with respect to the stored voltage (40). The other of the offset voltages (69) is generated by inverting the first, adjusted voltage, such that the two offset voltages (74, 69) are offset by equal values in opposite directions. An analog switch (46) is adapted to receive a sequence of digital signals and to apply the positive and negative offset voltages (74, 69) to the signal input terminal in a sequence corresponding to the binary signal sequence of the received data signals.

Speckle ensemble statistics of logarithmically scaled data (radar)

Abstract: It is shown that statistics of logarithmically scaled (averaged) radar data can be described by simple analytical expressions using Riemann's zeta function and Eule's psi function. This achievement makes possible the proper qualification of the impact of such transformation on the physical interpretation of remote sensing data and derived data (i.e. field-averaged mean and standard deviation). The standard deviation for Rayleigh-fading objects is a constant at a logarithmic scale and depends on the number k only. Averaging at a logarithmic scale of radar data, which themselves result from the linear averaging over k independent samples or looks, introduces an offset dependent on the number k only. This offset does not depend on the mean level of the signal and therefore is the same for all Rayleigh-fading objects in the scene. >

Method of and apparatus for obtaining vehicle heading information

Abstract: When fewer than three of the satellites of a satellite global positioning system (GPS) such as NAVSTAR are visible to a user (15), the user cannot obtain independent positional information from the system. Since a satellite (11) in such a system is moving with respect to a user (15), its signals are received with a Doppler offset from their normal centre frequency and the frequency offset due to the satellite motion alone is calculable for a user at an approximate location from a given satellite. An additional Doppler frequency offset will result from any movement of the user. The magnitude of the additional frequency shift, in conjunction with the known speed (m) of the user, can be used to calculate the angle between the satellite motion (V 1 ) and the user's motion and since the direction of the former is known, the user's heading from local North (N) can be calculated in instances where only one or two GPS satellites (11,12) are visible to a user.

Highway traffic signal local controller

Abstract: A highway traffic control method is shown in which the control method (80) and phasing scheme (82) are defined and recall switches are set (84) every cycle of operation. In time-of-day control methods (FIGS. 14 and 15) timing parameters (86) also are defined every cycle, and common cycle length and planned offset are computed (90) at the local master controller (16). Offset deviation is measured (94) and used along with the computed cycle length for adjustment of the local signal timing (96). Following execution of signal control, the control method, phasing scheme and timing parameters are defined and recall switches set in preparation for the next cycle of operation. In the traffic-responsive method, traffic data from local detectors are obtained and processed (100) and, using this data, signal timing parameters are computed using linear programming (102). In the traffic-adaptive method (FIG. 20 ) real-time detector information is processed (226) and used for further adjustment of signal timing parameters (228). Inputs for the linear programming solution (114) include incoming and saturation flow rates (110) and data from a movement-phase matrix M (126) which defines the relationship between movements and phases. Matrix M is generated using data from a green-green conflict matrix G (128) which identifies conflicting traffic movement. Linear program constraints for less preferred movements (118) are made equalities to reduce the number of multiple solutions. Linear programming is used to obtain maximum, optimum, and minimum cycle lengths and green times. Provision is made for adjustment of linear program solutions if the solution is not acceptable (178, 192 and 206). If the linear program has no solution (172, 188 and 202) maximum, optimum and minimum cycle lengths and green times from time-of-day tables are used.

Dual parallel cone beam circular scanning trajectories for reduced data incompleteness in three-dimensional computerized tomography

Abstract: A configuration of three-dimensional cone beam computerized tomography imaging which minimizes the incompleteness of the data set acquired, while providing fast data acquisition to minimize motion artifacts. An object within a field of view is scanned, preferably simultaneously, along a pair of circular source scanning trajectories spaced a distance selected to minimize the amount of missing data. A procedure is disclosed for calculating the spacing distance between the scanning trajectories which minimizes the amount of missing data. In one embodiment, a pair of cone beam x-ray sources are employed and a corresponding pair of two-dimensional array detectors. In order to reduce interference caused by x-rays from one source interacting with the detector corresponding to the other source, the cone beam x-ray sources are angularly offset, for example by 90°.

Synchronous communication between execution environments in a data processing system employing an object-oriented memory protection mechanism

Abstract: A subsystem call mechanism for communicating between a first execution environment associated with a first domain object, and a second execution environment associated with a second domain object. An environment table object is associated with a process object. The environment table object includes a control stack which is an array of control stack entries which entries save the state of the first calling execution environment to be restored on a return from the second execution environment. A subsystem entry in the subsystem table specifies the object that defines region 2 of the target execution environment and the frame pointer of the topmost stack frame in the target environment, a supervisor Stack Pointer that is a linear address for the supervisor stack used when involving a supervisor call in the user mode (instead of the stack pointer in the current frame) to locate the new frame. The first domain object further includes Procedure Entries that specify the type and address of the target procedure. Each of the procedure entries includes a Procedure Entry Type field that indicates the type of procedure to be invoked, either a supervisor procedure or a subsystem procedure, and an offset into the target execution environment. The offset specifies the first instruction of the target procedure.

Vehicle trim assembly and fastener therefor

Abstract: A rotatable fastener for attaching trim strips to vehicle window assemblies and other vehicular trim supports includes a pair of trim engaging flanges at one end of a central shaft and a retaining head at the other end. The flanges are beveled to engage the edges of a trim strip slot upon one-quarter turn rotation after insertion through an aperture in the window assembly or trim support. The retaining head includes recesses for engaging projections on the window assembly or trim support after rotation to resist removal. The flanges are preferably offset and the aperture shaped to receive the offset flanges and central shaft to resist fastener movement in the aperture and slot. Alternately, the fastener may include a planar head while the flanges may each include a flexible portion and slot for reducing the width of the flanges upon insertion.

Method and means for ensuring single pass small read/write access to variable length records stored on selected DASDs in a DASD array

Abstract: Write update of variable length records stored in row major order on an array of N DASDs is facilitated by utilizing the correlation between byte offsets of a variable length record and the byte offset of a byte level parity image of data stored on the same track across N-1 other DASDs.

Disc drive with offset address field

Abstract: An offset address field in a magnetic disc storage system which uses a dual gap head and a rotary actuator. The dual gap head has two gaps, one for reading information and the other for writing information. Prior to a write operation, an address field which precedes a data field is read. The rotary actuator introduces a skew angle between the head and a data track. The skew angle causes the two gaps to travel along different radii of the storage disc. A read address field is aligned with the data field and a write address field is offset from the data field. Prior to writing data on the disc surface, the head is offset so that the write address field is read. Since the write address field is offset, a write operation can proceed without any further offset to the magnetic head.

Trim correction circuit with temperature coefficient compensation

Abstract: An op amp bias system that provides input offset voltage trim current with minimum offset thermal drift The bias system includes a bias generator that provides bias current to the op amp and correction circuitry responsive to the bias current for providing an input offset trim current that compensates for offset drift error with changes in temperature

Method of correcting image signal

Abstract: Disclosed herein is a method of correcting an image signal, which is suitable for use in reading an image by an image sensor having a black reference pixel and effective pixels. This method comprises a first process for determining initial offset data from the black reference pixel and determining such first correction data that values outputted from all the effective pixels of the image sensor are identical to each other at the exposure greater than the minimum value of an exposure range required to read the image and smaller than the maximum value of the exposure range necessary to read the same; a second process for determining the latest offset data from the black reference pixel; a third process for determining offset correction data from the difference between the latest offset data and the initial offset data; a fourth process for determining image data from the effective pixels of the image sensor upon reading the image borne by an original; a fifth process for adding the first correction data to the offset correction data to obtain second correction data; and a sixth process for subtracting the second correction data from the image data to obtain image data subsequent to correction processing. In addition, this method includes a seventh process for performing shading correction of the image data obtained in the sixth process.

Offset correction apparatus of turning angular velocity sensor

Abstract: An offset correction apparatus comprising a turning angular velocity sensor, a vehicle speed sensor for outputting a pulsed signal every constant distance traveled by a vehicle, a stop determining unit for determining that the vehicle is at a stop, an offset calculation unit for integrating an output of the turning angular velocity sensor during a period of time that the stop of the vehicle is determined by the stop determining unit and then calculating an offset value of the output of the turning angular velocity sensor, a storage unit to store the offset value calculated by the offset calculation unit, and a heading correction unit for correcting heading data obtained from the output of the turning angular velocity sensor, with the offset value, wherein when the pulsed signal from the vehicle speed sensor disappears and the output from the turning angular velocity sensor is less than a threshold, the stop determining unit determines that the vehicle is at a stop.

The resolution of narrow low-velocity zones with the generalized reciprocal method

Abstract: The depth to the surface of a refractor and the seismic velocity within the refractor are very often intimately related. In the shallow environment, increased thicknesses of weathering occur in areas of jointing, shearing or lithological variations, and these zones of deeper weathering can have lower subweathering refractor velocities. This association is important in geotechnical investigations and in the measurement of weathering thicknesses and sub-weathering velocities for statics corrections for reflection seismic surveys. Algorithms, which employ forward and reverse traveltime data and which explicitly accommodate the offset distance through the process known as refraction migration, are necessary if detailed structure on a refractor and rapid lateral variations of the seismic velocity within it are to be resolved. These requirements are satisfied with wavefront construction techniques, Hales’ method and the generalized reciprocal method (GRM). However, these methods employ refraction migration in fundamentally different manners. Most methods compute an offset distance with an often imprecise knowledge of the seismic velocities of the overlying layers. In contrast, the GRM uses a range of offset distances from less than to greater than the optimum value, with the optimum value being selected with a minimum-variance criterion. The approach of the GRM is essential where there are undetected layers and where there are rapid variations in the depth to a refractor and the seismic velocity within it. In the latter situations the offset distance necessary to define the seismic velocities can differ considerably from the value required to define depths. The efficacy of the GRM in resolving structure and seismic velocity is demonstrated with three model studies and two field examples.

Pixel by pixel offset and gain correction in analog data from scanning arrays

Abstract: Method and apparatus for a correction of photosite offset and gain in the analog domain. Correction of offset and gain in the analog domain, prior to conversion of the analog signals to digital signals, allows the use of the maximum dynamic range of the system for pixel information, once the image is converted.

How to Compute Offsets Without Self-Intersection

Abstract: Traditional t.echniques for computing offsets are local in nature and lack good criteria for eliminating possible self-intersections of the offset. Methods based on integrating differential equations or on image processing do not lack such criteria, but seem to require constructing the solution in the ambient space, i.e., in one dimension larger than the offset. We investigate such methods.

Methods of controlling dot size in digital halftoning with multi-cell threshold arrays

Abstract: A method of equalizing the shape and size of halftone dots in a supertile having digital cells, corresponding ideal cells and pixels to faithfully reproduce an image having predetermined gray levels. Various techniques include: (1) adding offset vectors to the coordinates of pixels in digital cells; (2) determining twice as many smaller digital cells as original digital cells; and (3) determining a model digital cell and ranking pixels in remaining digital cells to mimic the ranking of pixels in the model cell.

Functional measurement of data head misregistration

Abstract: The present invention demonstrates a rotating media storage system which quickly measures and accurately compensates for thermal and mechanical errors in the position of the data detector with respect to the written data. This is accomplished by measuring the error rate of the written data as a function of the read offset of the detector. Error rates become increasingly large as the sensed noise to signal ratio becomes large. The present invention counts the number of errors detected in reading written data for various read offsets when the data storage system is initially activated. When the number of errors reaches a target rate, the read offset required to produce the target rate is saved. This procedure is performed on either side of the data track. The detector is then centered between the two offsets. During the operation of the storage system, thermal and mechanical errors are introduced into the detector position compensation means. The present invention compensates for this by periodically determining a new offset for each side of the data track. The new offset which corresponds to the target error rate is found by interpolating between measured offsets for error rates which are higher and lower respectively than the target error rate. The new measured read offsets are obtained by reading back written data in a similar manner as was used to obtain the initial read offsets. The detector is then recentered with respect to the write transducer position between the new offsets on either side of the data track.

Hard-disk storage apparatus with memory storing data-head control information

Abstract: A hard-disk storage apparatus is provided with a plurality of stacked magnetic recording disks each of which is provided with a plurality of tracks Each of the tracks is specified by a cylinder address and a physical data-head address Logical data-head addresses applied to the hard-disk are converted into the corresponding physical data-head address according to a conversion table pre-recorded within a non-volatile memory Further, offset parameters of each data-head over two selected cylinders at predetermined temperatures are previously stored within the non-volatile memory A microprocessor unit calculates offset parameters of all the data-heads over each of the tracks at a given temperature preferably measured within the hard-disk storage assembly These offset parameters are utilized to correct the displacement of each data-head over a given track due to temperatures

Offset compensation CMOS operational amplifier

Abstract: An amplifier circuit with internal offset cancellation receives a differential input signal and provides differentially related currents which flow through first and second conduction paths of a differential-to-signal-ended converter for providing an output signal. Although ideally the differentially related currents should be equal with a zero differential input signal, the inherent mismatches between the transistors of the amplifier produce error currents causing the offset error. During an auto-zero phase, the differential input signal is zeroed while first and second capacitors are connected to the first and second conduction paths of the differential-to-single-ended converter for storing a charge representative of the input offset voltage. During the operational phase, the capacitor voltages control first and second transistors operating in parallel with the first and second conduction path for removing any error current thereby providing compensation of the offset error for the differential input signal.

Amplitude, phase and frequency versus offset applications1

Abstract: In a layered earth the seismic reflection response for incidence at non-normal angles is dependent upon the elastic constants and thicknesses of the layers. The possibility is investigated of increasing the diagnostic value of seismic data by using the phase and the frequency v. offset information in addition to that from the amplitude v. offset. The combined amplitude, phase and frequency versus offset (APF.VO) analysis is carried out through the computation of amplitude, phase and frequency indicators based on the analytical description of seismic traces. Both synthetic and actual data are examined. From the analyses of synthetic seismograms, it is shown that modifying the velocities and thicknesses of a given target layer, by introducing different pore fluids or lithological conditions, produces changes in APF.VO plots. In particular, the effects related to interference among reflections and to critical angle phenomena are clearly detected by both the phase and amplitude v. offset indicators in terms of phase shifts and amplitude variations. The frequency indicator is mainly controlled by the spectrum of the propagating wavelet. Since the basic synthetic model is derived from an existing well, located close to a seismic line, some actual CDP gathers are analysed. Features related to interference and critical angle are again evident in the APF.VO plots of the actual data. The amplitude indicator appears to be reasonably stable while the phase shows a higher spatial variability and a stronger sensitivity to noise. Differential interference with offset often occurs in actual layered structures and distorts seismic data significantly. Therefore AVO interpretation and AVO inversion procedures must also tackle this problem. Knowledge of phase and frequency variations v. offset may help classical AVO interpretation and yield further information for use in inversion techniques.

Ratiometric A/D converter with non-rationometric error offset

Abstract: A ratiometric converter is provided that is comprised of a dual converter system utilizing a first converter (36) and a second converter (38). The second converter (38) is operable to receive the input voltage from a load cell (10) on sense lines (12) and (14) and compare them with an internal reference. Similarly, the first A/D converter (36) is operable to receive the reference voltage to the load cell (10) and compare it with the internal reference. The output of each of the converters (36) and (38) is then input to subtraction circuits (78) and (84), respectively, in the digital domain. In a calibration mode, switches (72) and (73) shorts the reference nodes in the load cell (10) together to determine the non-ratiometric offsets., These offsets are then stored in registers (80) and (86) for the reference voltage and the input voltage, respectively. During operation, the offsets are then input to the subtraction blocks (78) and 84) and a digital subtraction performed on the output of both converters (36) and (38). The output of the subtraction blocks (78) and (84) are then input to a ratiometric operator block (52) to perform a digital division thereon. This results in a ratiometric output that has the non-ratiometric offsets removed. Thereafter, the signal is input to a system calibration block (32) to remove ratiometric errors.

Parameter estimation in a one‐dimensional anelastic medium

Abstract: Surface seismic data with a known source pulse are used to estimate parameters in a stack of homogeneous layers. The unknown parameters in each layer are the P wave velocity, the S wave velocity, the density, the layer thickness, and the quality factor. The forward problem is solved by dynamic ray tracing. Primary and multiple P wave reflections are considered. The S wave velocities are estimated from the PP transmission and reflection coefficients. The model is fitted to the data using a stabilized least squares procedure. The Jacobian is computed analytically in each step. By introducing the layer thicknesses as unknown parameters, it is possible to keep the number of unknowns at a tractable level, and the Gauss-Newton approximation to the Hessian matrix can be inverted exactly at each iteration. When only one event is considered, the scheme provides a nonlinear solution to the amplitude versus offset problem, where offset dependent corrections for absorption, geometrical spreading, and transmission losses are automatically included. All parameters are successfully estimated from synthetic data. We also perform a sensitivity analysis for the different parameters and discuss the reliability for the estimates in each parameter group.

Reduced offsets for minimization of binary-valued functions

Abstract: A modified approach to two-level logic minimization is described which obviates the need to compute the offset, yet provides the same global picture available with the offset. This approach is based on a new concept called the reduced offset. It is shown that reduced offsets can be computed without using the offset. This scheme has been implemented in ESPRESSO with an interface to the multilevel minimization environment MIS, where it is used to minimize individual nodes (representing two-level functions with single outputs) in multilevel networks. Such functions usually have very large offsets because of a large number of variables in their don't care sets. The modified approach is up to 8.5 times faster than ESPRESSO on a set of benchmark examples. >

Sensor with programmable temperature compensation

Abstract: A sensor provides an electrical signal in response to occurrence of a condition and is programmed in accordance with tested temperature characteristics of the sensor to provide selected gain and/or offset in the output signal and to compensate for change in gain and/or offset of the output signal due to change in device temperature.