Showing papers on "Offset (computer science) published in 2017"

OTIDS: A Novel Intrusion Detection System for In-vehicle Network by Using Remote Frame

Abstract: Controller Area Network (CAN) is a bus communication protocol which defines a standard for reliable and efficient transmission between in-vehicle nodes in real-time. Since CAN message is broadcast from a transmitter to the other nodes on a bus, it does not contain information about the source and destination address for validation. Therefore, an attacker can easily inject any message to lead system malfunctions. In this paper, we propose an intrusion detection method based on the analysis of the offset ratio and time interval between request and response messages in CAN. If a remote frame having a particular identifier is transmitted, a receiver node should respond to the remote frame immediately. In attack-free state, each node has a fixed response offset ratio and time interval while these values vary in attack state. Using this property, we can measure the response performance of the existing nodes based on the offset ratio and time interval between request and response messages. As a result, our methodology can detect intrusions by monitoring offset ratio and time interval, and it allows quick intrusion detection with high accuracy.

Neural offset min-sum decoding

Abstract: Recently, it was shown that if multiplicative weights are assigned to the edges of a Tanner graph used in belief propagation decoding, it is possible to use deep learning techniques to find values for the weights which improve the error-correction performance of the decoder. Unfortunately, this approach requires many multiplications, which are generally expensive operations. In this paper, we suggest a more hardware-friendly approach in which offset min-sum decoding is augmented with learnable offset parameters. Our method uses no multiplications and has a parameter count less than half that of the multiplicative algorithm. This both speeds up training and provides a feasible path to hardware architectures. After describing our method, we compare the performance of the two neural decoding algorithms and show that our method achieves error-correction performance within 0.1 dB of the multiplicative approach and as much as 1 dB better than traditional belief propagation for the codes under consideration.

Beam Pattern Synthesis for an FDA Radar with Hamming Window-Based Nonuniform Frequency Offset

Abstract: A frequency diverse array (FDA) with uniform inter-element frequency offset generates an “S-shaped” beam pattern with maxima at multiple range and angle values. This property allows a number of reflectors positioned at any of the maxima to interfere with the target-returns, thus weakening the signal-to-interference-plus-noise ratio. In this letter, a uniformly spaced symmetric FDA with Hamming window-based tapering interelement frequency offsets has been proposed. The proposed design produces a single maximum beam pattern toward the desired range and angle values. This approach is mathematically analyzed and verified by numerical results. Moreover, it outperforms the existing forms of FDA with uniform interelement offset, e.g., conventional FDA, as well as the FDA with nonuniform interelement offset, e.g., Log-FDA in terms of side-lobe suppression and transmit energy focusing.

Integral Action in Output Feedback for Multi-Input Multi-Output Nonlinear Systems

Abstract: We address a particular problem of output regulation for multi-input multi-output nonlinear systems. Specifically, we are interested in making the stability of an equilibrium point and the regulation to zero of an output robust to (small) unmodelled discrepancies between design model and actual system in particular those introducing an offset. We propose a novel procedure which is intended to be relevant to realistic scenarios, as illustrated by a (non academic) example.

Series and Parallel Elastic Actuation: Influence of Operating Positions on Design and Control

Abstract: It is well-established that properly tuned elastic elements can make robotic actuators more energy-efficient, especially in cyclic tasks. Considering a drive train topology, two important subcategories of elastic actuators are series elastic actuation (SEA) and parallel elastic actuation (PEA). There is still no definite answer to the fundamental question which topology consumes less energy in a given task. This paper approaches the problem by studying oscillatory motions of a single degree-of-freedom link in a gravitational field. The imposed motion is a sinusoid with a nonzero offset requiring a static torque that needs to be compensated by the actuation system. Simulations and experiments show that the SEA consumes less energy up to certain offset angles. At high offsets, the PEA becomes the more energy-efficient alternative, provided that its no-load angle is properly tuned. Inverse dynamics simulations show how a threshold offset angle can be determined for a given task.

Joint Transceiver and Offset Design for Visible Light Communications With Input-Dependent Shot Noise

Abstract: In this paper, we investigate the problem of the joint transceiver and offset design for point-to-point multiple-input–multiple-output (MIMO) and multiple user multiple-input–single-output visible light communication (VLC) systems. Both uplink and downlink multi-user scenarios are considered. The shot noise induced by the incoming signals is considered, leading to a more realistic MIMO VLC channel model. Under key lighting constraints, we formulate non-convex optimization problems aimed at minimizing the sum mean squared error. To optimize the transceiver and the offset jointly, a gradient projection-based procedure is resorted to. When only imperfect channel state information is available, a semidefinite programming-based scheme is proposed to obtain robust transceiver and offset. The proposed method is shown to non-trivially outperform the conventional scaled zero forcing and singular. value decomposition-based equalization methods. The robust scheme works particularly well when the signal is much stronger than the noise.

Offset optimization in signalized traffic networks via semidefinite relaxation

Abstract: We study the problem of selecting offsets of the traffic signals in a network of signalized intersections to reduce queues of vehicles at all intersections. The signals in the network have a common cycle time and a fixed timing plan. It is assumed that the exogenous demands are constant or periodic with the same period as the cycle time and the intersections are under-saturated. The resulting queuing processes are periodic. These periodic processes are approximated by sinusoids. The sinusoidal approximation leads to an analytical expression of the queue lengths at every intersection as a function of the demands and the vector of offsets. The optimum offset vector is the solution of a quadratically constrained quadratic program (QCQP), which is solved via its convex semidefinite relaxation. Unlike existing techniques, our approach accommodates networks with arbitrary topology and scales well with network size. We illustrate the result in two case studies. The first is an academic example previously proposed in the literature, and the second case study consists of an arterial corridor network in Arcadia, California.

Seismic Behavior of Concentrically Braced Steel Frames with Out-of-Plane Offset Irregularity

Abstract: Braced steel frames are sometimes designed with out-of-plane shifted bracing members on the first story due to architectural or functional considerations. Such frames are classified and designated as frames having the Type-4 horizontal structural irregularity entitled “frames with out-of-plane offset irregularity” as per the Minimum Design Loads for Building and Other Structures (ASCE 7-10). The purpose of this study is to investigate the nonlinear seismic behavior of ordinary steel concentrically braced frames with out-of-plane offset irregularity and evaluate their seismic design parameters. To this end, two 3-story and 6-story three-dimensional ordinary concentrically braced frames (OCBFs) with and without out-of-plane offset of one of the vertical elements on the first story were considered (i.e. irregular and regular configurations). The seismic design parameters considered in this study includes: frame overall overstrength factor, column overstrength factor and the inelastic dynamic inter-story drift demands. Nonlinear time-history dynamic analysis of the frames showed that overall overstrength factor of the lowand mid-rise irregular frames studied in this research is lower than that of the regular ones. Moreover, it was found that the Seismic Provisions prescribed overstrength factor (i.e. Ωo=2.0) to amplify columns axial seismic forces in OCBFs is not conservative for the studied regular frames’ columns as well as the columns in the vicinity of the shifted bracing members on the first story of the irregular frames. Also, it was shown that the studied lowand mid-rise regular and irregular concentrically braced frames experience greater inter-story drift demands than predicted by the amplified elastic analysis proposed in the codes.

An adaptive multiscale algorithm for efficient extended waveform inversion

Abstract: Subsurface-offset extended full-waveform inversion (FWI) may converge to kinematically accurate velocity models without the low-frequency data accuracy required for standard data-domain FWI. However, this robust alternative approach to waveform inversion suffers from a very high computational cost resulting from its use of nonlocal wave physics: The computation of strain from stress involves an integral over the subsurface offset axis, which must be performed at every space-time grid point. We found that a combination of data-fit driven offset limits, grid coarsening, and low-pass data filtering can reduce the cost of extended inversion by one to two orders of magnitude.

The Thermal Phase Curve Offset on Tidally and Nontidally Locked Exoplanets: A Shallow Water Model

Abstract: Using a shallow water model with time-dependent forcing, we show that the peak of an exoplanet thermal phase curve is, in general, offset from the secondary eclipse when the planet is rotating. That is, the planetary hot spot is offset from the point of maximal heating (the substellar point) and may lead or lag the forcing; the extent and sign of the offset are functions of both the rotation rate and orbital period of the planet. We also find that the system reaches a steady state in the reference frame of the moving forcing. The model is an extension of the well-studied Matsuno–Gill model into a full spherical geometry and with a planetary-scale translating forcing representing the insolation received on an exoplanet from a host star. The speed of the gravity waves in the model is shown to be a key metric in evaluating the phase curve offset. If the velocity of the substellar point (relative to the planet's surface) exceeds that of the gravity waves, then the hot spot will lag the substellar point, as might be expected by consideration of forced gravity wave dynamics. However, when the substellar point is moving slower than the internal wave speed of the system, the hottest point may lead the passage of the forcing. We provide an interpretation of this result by consideration of the Rossby and Kelvin wave dynamics, as well as, in the very slowly rotating case, a one-dimensional model that yields an analytic solution. Finally, we consider the inverse problem of constraining planetary rotation rate from an observed phase curve.

Optimum design of a double-tail latch comparator on power, speed, offset and size

Abstract: Transistor sizing is one of the most critical parts of comparator design which has a significant influence on comparator specifications. This paper presents an optimum design of a double-tail latch comparator based on transistor sizing with a great certainty to reach the best possible design due to using Hspice (as a software simulator) linked with a heuristic algorithm. To achieve a low-power, high-speed, low offset and, small size comparator, the multi-objective inclined planes optimization and Hspice were linked and several Pareto-fronts were obtained. As a result of analyzing the Pareto-fronts, power and total sizes of transistors have a tradeoff with delay and offset voltage. Meanwhile, the results comparison with a recent work shows the superiority of the present approach performance.

Observation of spin and orbital rotation of red blood cell in dual-beam fibre-optic trap with transverse offset

Abstract: The spin and orbital rotation of the red blood cell (RBC) are achieved simultaneously by introducing a transverse offset to the dual-beam fibre-optic trap. The motion type of the captured RBC could be controlled by adjusting the offset distance. When the offset distance is relatively small, the RBC is observed to spin in the trap centre, with the spin frequency increasing linearly with the offset distance. Once the offset distance is above a critical value, the RBC will rotate along an elliptic orbit, together with the spin motion. The orbital rotation frequency and spin frequency both decrease with the increased offset distance. This technique allows mixing and viewing living cells from different perspectives concurrently without exposing them to any mechanical contact, and is generally applicable to biological and medical research.

Compressed convolutional neural network-oriented parallel convolution operation method and apparatus

Abstract: The invention provides a compressed convolutional neural network-oriented parallel convolution operation method and apparatus. The method comprises the steps of determining an adopted operation mode according to input control signal convolution data shift chain length selection, accumulated offset enabling and convolution calculation enabling; and by adopting two serial shift register chains, inputting convolution data, convolution parameters and channel offset, and performing 3X3 and 1X1 convolution operation at the same time for a same input convolution data stream. According to the method, a multiplier, an accumulator, a parameter register and an offset register are added only based on original serial shift register chain-based 3X3 convolution operation; the realization method is simple; the executive efficiency is high; and the convolution operation in a compressed neural network algorithm can be effectively accelerated. According to the apparatus, a plurality of characteristic graphs can be output at the same time through simple hardware unit expansion and copying; and the apparatus has the advantages of low power consumption, high function unit utilization rate and high processing speed.

Multi-stage coherence drift based sampling rate synchronization for acoustic beamforming

Abstract: Multi-channel speech enhancement algorithms rely on a synchronous sampling of the microphone signals. This, however, cannot always be guaranteed, especially if the sensors are distributed in an environment. To avoid performance degradation the sampling rate offset needs to be estimated and compensated for. In this contribution we extend the recently proposed coherence drift based method in two important directions. First, the increasing phase shift in the short-time Fourier transform domain is estimated from the coherence drift in a Matched Filter-like fashion, where intermediate estimates are weighted by their instantaneous SNR. Second, an observed bias is removed by iterating between offset estimation and compensation by resampling a couple of times. The effectiveness of the proposed method is demonstrated by speech recognition results on the output of a beamformer with and without sampling rate offset compensation between the input channels. We compare MVDR and maximum-SNR beamformers in reverberant environments and further show that both benefit from a novel phase normalization, which we also propose in this contribution.

On the propagation of gravity currents over and through a submerged array of circular cylinders

Abstract: The propagation of full-depth lock-exchange bottom gravity currents past a submerged array of circular cylinders is investigated using laboratory experiments and large eddy simulations. Firstly, to investigate the front velocity of gravity currents across the whole range of array density (i.e. the volume fraction of solids), the array is densified from a flat bed ( ) towards a solid slab ( ) under a particular submergence ratio , where is the flow depth and is the array height. The time-averaged front velocity in the slumping phase of the gravity current is found to first decrease and then increase with increasing . Next, a new geometrical framework consisting of a streamwise array density and a spanwise array density is proposed to account for organized but non-equidistant arrays ( ), where and are the streamwise and spanwise cylinder spacings, respectively, and is the cylinder diameter. It is argued that this two-dimensional parameter space can provide a more quantitative and unambiguous description of the current–array interaction compared with the array density given by . Both in-line and staggered arrays are investigated. Four dynamically different flow regimes are identified: (i) through-flow propagating in the array interior subject to individual cylinder wakes ( : small for in-line array and arbitrary for staggered array; : small); (ii) over-flow propagating on the top of the array subject to vertical convective instability ( : large; : large); (iii) plunging-flow climbing sparse close-to-impermeable rows of cylinders with minor streamwise intrusion ( : small; : large); and (iv) skimming-flow channelized by an in-line array into several subcurrents with strong wake sheltering ( : large; : small). The most remarkable difference between in-line and staggered arrays is the non-existence of skimming-flow in the latter due to the flow interruption by the offset rows. Our analysis reveals that as increases, the change of flow regime from through-flow towards over- or skimming-flow is responsible for increasing the gravity current front velocity.

A 0.2-1.45-GHz Subsampling Fractional-$N$ Digital MDLL With Zero-Offset Aperture PD-Based Spur Cancellation and In Situ Static Phase Offset Detection

Abstract: A digital fractional-N subsampling multiplying delay-locked loop is proposed in this paper. A zero phase-offset latch-based aperture phase detector is introduced in a reference spur cancellation loop to precisely cancel any static phase offset (SPO) between the injected reference and the digitally controlled oscillator (DCO) phases. An in situ detection scheme is employed to directly measure this phase offset accurately by obviating the requirement of a high-speed off-chip measurement setup. Moreover, a mathematical expression is derived for the calculation of reference spur generated from a given SPO. A uniformly distributed switched capacitor-based DCO frequency tuning achieves highly linear gain. The chip prototype is fabricated in a 1.2-V supply, 65-nm LP CMOS technology and covers an output frequency range of 0.2-1.45 GHz while occupying a core area of 0.054 mm 2 . Measured phase noise at 1.4175 GHz is -95 dBc/Hz at 100-kHz offset, which is 9 dB lower than in phase-locked loop mode of operation.

Multi-view rotoscope contour propagation

Abstract: A video stream may be captured, and may have a plurality of frames including at least a first frame and a second frame. Each of the frames may have a plurality of views obtained from viewpoints that are offset from each other. A source contour, associated with a source view of the first frame, may be retrieved. Camera parameters, associated with the image capture device used to capture the video stream, may also be retrieved. The camera parameters may include a first offset between the source view and a destination view of the first frame. At least the first offset may be used to project the source contour to the destination view to generate a destination contour associated with the destination view.

New Approaches for Increasing Accuracy in Readout of Resistive Sensor Arrays

Abstract: One of the most efficient ways to connect a resistive sensor array is using columns and rows in a 2-D structure. The main problem in this implementation is crosstalk appearing due to non-idealities in the readout circuits. Crosstalk causes measurement errors which restrict the usable range in array size or resistive sensors values. This paper analyses the way in which these factors affect accuracy, setting out a new approach to eliminate or reduce their influence based on just an additional operational amplifier and some calibration resistors without a significant increase in readout time. The first method involves introducing an additional column in order to eliminate the combined effect of the output resistance buffers for row selection, offset voltages and bias current of the operational amplifier. In the second method, a row of resistors is added in order to reduce the effect of finite gains. Theoretical analysis has been performed and validated by simulation. Results show that an improvement in accuracy compared with other proposals in the literature is possible.

DC-link capacitor voltage offset suppression with no filters for three-phase four-switch inverter fed PMSM drives

Abstract: The adjustable speed range for three-phase four-switch inverter (TPFSI) fed permanent magnet synchronous motor (PMSM) drives is seriously limited by the DC-link capacitor voltage offset in TPFSI. For the traditional offset suppression schemes, the low-pass filters or notch filters are necessary to extract the capacitor voltage offset, which will deteriorate the control performance of the offset suppression schemes severely, especially for the low-speed range. Thus, a novel offset suppression scheme with no filters is proposed to improve the situation. For the proposed scheme, to extract the offset with no filters, a new static coordinate is defined, the relationships between the fundamental/offset components of capacitor voltages and the load currents are revealed, based on which a simple algorithm is developed. Then, the desired compensatory current is obtained by a closed-loop control and injected into the stator current control loop. Experimental results have validated the proposed scheme.

Time Series Analysis of Very Slow Landslides in the Three Gorges Region through Small Baseline SAR Offset Tracking

Abstract: Sub-pixel offset tracking has been used in various applications, including measurements of glacier movement, earthquakes, landslides, etc., as a complementary method to time series InSAR. In this work, we explore the use of a small baseline subset (SBAS) Offset Tracking approach to monitor very slow landslides with centimetre-level annual displacement rate, and in challenging areas characterized by high humidity, dense vegetation cover, and steep slopes. This approach, herein referred to as SBAS Offset Tracking, is used to minimize temporal and spatial de-correlation in offset pairs, in order to achieve high density of reliable measurements. This approach is applied to a case study of the Tanjiahe landslide in the Three Gorges Region. Using the TerraSAR-X Staring Spotlight (TSX-ST) data, with sufficient density of observations, we estimate the precision of the SBAS offset tracking approach to be 2–3 cm on average. The results demonstrated accord well with corresponding GPS measurements.

Reliable underwater dipole source characterization in 3D space by an optimally designed artificial lateral line system.

Abstract: Inspired by the lateral line of aquatic vertebrates, an artificial lateral line (ALL) system can localize and track an underwater moving object by analyzing the ambient flow caused by its motion. There are several studies on object detection, localization and tracking by ALL systems, but only a few have investigated the optimal design of the ALL system, the one that on average provides the highest characterization accuracy. Design optimization is particularly important because the uncertainties in the employed flow model and in sensor measurements deteriorate the reliability of sensing. This study investigates the optimal design of the ALL system in three-dimensional (3D) space for dipole source characterization. It highlights some challenges specific to the 3D setting and demonstrates the shortcomings of the designs in which all sensors and their sensing directions are in the same plane. As an alternative, it proposes two design concepts, called 'Offset Strategy' and 'Angle Strategy' to overcome these shortcomings. It investigates potentials of having a swarm of cooperative ALLs as well. It performs design optimization in the presence of sensor and model uncertainties and analyzes the trade-off between the number of sensors and characterization accuracy. The obtained solutions are analyzed to reveal their strategies in solving the problem efficiently. The dependency of the optimized solutions on the uncertainties is also demonstrated.

Adaptive material deposition for additive manufacturing

Abstract: A closed-loop adaptive material deposition apparatus and method uses a scanning system to monitor an additively manufactured object as it is being fabricated and adapting the geometric shape and material composition of the subsequent layers based on the scan data. The scanning system repeatedly captures geometric and/or material information of a partially manufactured object with optional auxiliary objects inserted during the manufacturing process. Based on this information, the actual surface geometry and/or actual material composition is computed. Surface geometry may be offset and used as a slicing surface for the next portion of the digital model. The shape of the slicing surface may then be recomputed each time the system scans the partially fabricated object.

A method for the evaluation and magnified representation of two-dimensional contouring error

Abstract: The method of evaluating two-dimensional contouring error between the reference trajectory and the trajectory measured with a cross-grid encoder and magnifying the error is widely used. However, this method has a problem in that the inner cornering error is discontinuously magnified and represented and thus is not accurately detected. Several methods have been proposed to solve this problem, but they have limitations, such as the requirement that an offset value be set or the imposition of conditions on the reference trajectory. Therefore, by calculating errors in the inward direction from a longer trajectory to a shorter trajectory, this paper proposes a new method to continuously magnify and represent the inner cornering error including the corner vertex without the need to set an offset or the imposition of conditions on the reference trajectory. The proposed method was applied to the measurement results at an actual machining center. Consequently, the inner cornering error was continuously magnified and represented, and the error at a corner was accurately calculated using the proposed method.

Low Offset Drift–Low-Noise Orthogonal Fluxgate With Synchronized Polarity Flipping

Abstract: In this paper, we present an orthogonal fluxgate in fundamental mode with extremely stable offset and low noise. The typical solution to stabilizing the offset in this type of sensor is to flip the dc bias of its excitation current and subtract the output obtained with opposite polarities. In this case, on the contrary, we flip both the ac and dc components of the excitation current and sum the output voltages. This is performed using fast solid-state switches with low on-resistance. In this way, we achieved a large suppression of the dependence of the offset on temperature, obtaining an average offset drift of 0.012 nT/K, making this sensor on the top class for offset stability. We digitally sampled and numerically demodulated the output voltage of the sensor to extract the first harmonic. The value of the first harmonic shows noise right after switching of the current. Therefore, we numerically erased those few noisy values of the first harmonic before integrating it. In this way, we managed to limit the noise growth given by switching of the current. Finally, we strongly improved the offset stability with minor increment of noise.

Static clutter elimination for frequency-modulated continuous-wave radar displacement measurement based on phasor offset compensation

Abstract: The displacement measurement with frequency-modulated continuous-wave radar based on radar interferometry technique has attracted growing interest in recent years. One of the main challenging issues is the static clutter interference in the same range bin, which results in amplitude shrinkage. A novel approach from signal processing side is proposed, i.e. implementing a post-processing procedure based on phasor offset compensation, which can be formulated as a circle fitting problem regarding phasor representation. Both simulated and experimental results are provided to validate the effectiveness and superiority of the proposed technique.

A Low-Voltage SRAM Sense Amplifier With Offset Cancelling Using Digitized Multiple Body Biasing

Abstract: With continued CMOS technology scaling down, transistors exhibit higher degrees of variation and mismatch, resulting in a larger offset voltage. A large offset voltage will enlarge bitline swing, increasing dynamic power consumption during a read operation and degrading the sensing decision correct rate and operation speed. Thus, the offset voltage is the most critical metric for static random access memory sense amplifiers (SAs), mainly arising from transistor threshold voltage mismatch. Here we propose an offset-cancelling technique with digitized multiple body biasing. In this scheme, SA transistor threshold voltage mismatch is compensated by adjusting the body bias voltage digitally and repeatedly. Simulation results in 130-nm CMOS technology show that the proposed calibration technique can reduce the standard deviation of the offset voltage by over four times comparing to a conventional SA, with about 6.5% and 1.6% area power overhead of a 6-kbit prototype chip introduced.