Showing papers on "Offset (computer science) published in 2015"

Mono-Exponential Fitting in T2-Relaxometry: Relevance of Offset and First Echo.

Abstract: Introduction T2 relaxometry has become an important tool in quantitative MRI. Little focus has been put on the effect of the refocusing flip angle upon the offset parameter, which was introduced to account for a signal floor due to noise or to long T2 components. The aim of this study was to show that B1 imperfections contribute significantly to the offset. We further introduce a simple method to reduce the systematic error in T2 by discarding the first echo and using the offset fitting approach. Materials and Methods Signal curves of T2 relaxometry were simulated based on extended phase graph theory and evaluated for 4 different methods (inclusion and exclusion of the first echo, while fitting with and without the offset). We further performed T2 relaxometry in a phantom at 9.4T magnetic resonance imaging scanner and used the same methods for post-processing as in the extended phase graph simulated data. Single spin echo sequences were used to determine the correct T2 time. Results The simulation data showed that the systematic error in T2 and the offset depends on the refocusing pulse, the echo spacing and the echo train length. The systematic error could be reduced by discarding the first echo. Further reduction of the systematic T2 error was reached by using the offset as fitting parameter. The phantom experiments confirmed these findings. Conclusion The fitted offset parameter in T2 relaxometry is influenced by imperfect refocusing pulses. Using the offset as a fitting parameter and discarding the first echo is a fast and easy method to minimize the error in T2, particularly for low to intermediate echo train length.

Trailer backup offset determination

Abstract: A system for calibrating a backup assist system for a trailer attached to a vehicle is provided which includes a hitch sensor continuously measuring a hitch angle for determining an angle rate, a yaw sensor continuously sensing a yaw rate of the vehicle, and a controller configured to determine an offset of the measured hitch angle when vehicle is driving forward and/or rearward.

Reduced-order shape optimization using offset surfaces

Abstract: Given the 2-manifold surface of a 3d object, we propose a novel method for the computation of an offset surface with varying thickness such that the solid volume between the surface and its offset satisfies a set of prescribed constraints and at the same time minimizes a given objective functional. Since the constraints as well as the objective functional can easily be adjusted to specific application requirements, our method provides a flexible and powerful tool for shape optimization. We use manifold harmonics to derive a reduced-order formulation of the optimization problem, which guarantees a smooth offset surface and speeds up the computation independently from the input mesh resolution without affecting the quality of the result. The constrained optimization problem can be solved in a numerically robust manner with commodity solvers. Furthermore, the method allows simultaneously optimizing an inner and an outer offset in order to increase the degrees of freedom. We demonstrate our method in a number of examples where we control the physical mass properties of rigid objects for the purpose of 3d printing.

Offset-Free Model Predictive Control for the Power Control of Three-Phase AC/DC Converters

Abstract: This paper describes an offset-free model predictive control (MPC) algorithm using a disturbance observer (DOB) to control the active/reactive powers of a three-phase ac/dc converter. The strategy of this paper is twofold. One is the use of DOB to remove the offset error, and the other is the proper choice of the weighting matrices of a cost index to provide fast error decay with small overshoot. The DOB is designed to estimate the unknown disturbances of the ac/dc converter following the standard Luenberger observer design procedure. The proposed MPC minimizes a one-step-ahead cost index penalizing the predicted tracking error by performing a simple membership test without any use of numerical methods. A systematic way for choosing the weights of the cost index, which guarantees the global stability of the closed-loop system, is proposed. Use of the DOB eliminates the offset tracking errors in the real implementation. Using a 25-kW ac/dc converter, it is experimentally shown that the proposed MPC enhances the power tracking performance while considerably reducing the mutual interference of the active/reactive powers as well as the output voltage.

Method to Minimize the Low-Frequency Neutral-Point Voltage Oscillations With Time-Offset Injection for Neutral-Point-Clamped Inverters

Abstract: This paper proposes a method to reduce the low-frequency neutral-point voltage oscillations. The neutral-point voltage oscillations are considerably reduced by adding a time offset to the three-phase turn-on times. The proper time offset is simply calculated considering the phase currents and dwell time of small- and medium-voltage vectors. However, if the power factor is lower, there is a limitation to eliminate neutral-point oscillations. In this case, the proposed method can be improved by changing the switching sequence properly. Additionally, a method for neutral-point voltage balancing is also proposed. The change in switching frequency by the proposed method and its effects on the outputs are negligible. Simulation and experimental results verify the validity and feasibility of the proposed strategy.

Clock synchronization for multichannel system

Abstract: An acoustic echo cancellation (AEC) system that detects and compensates for differences in sample rates between the AEC system and a set of wireless speakers based on a search-based trial-and-error technique. The system individually determines a frequency offset for each microphone-speaker pair using an iterative process, determining an echo-return loss enhancement (ERLE) value for each offset that is tried, and selecting the frequency offset associated with the largest ERLE value.

Estimation of offsets in GPS time-series and application to the detection of earthquake deformation in the far-field

Abstract: Extracting geophysical signals from Global Positioning System (GPS) coordinate time-series is a well-established practice that has led to great insights into how the Earth deforms Often small discontinuities are found in such time-series and are traceable to either broad-scale deformation (ie earthquakes) or discontinuities due to equipment changes and/or failures Estimating these offsets accurately enables the identification of coseismic deformation estimates in the former case, and the removal of unwanted signals in the latter case which then allows tectonic rates to be estimated more accurately We develop a method to estimate accurately discontinuities in time series of GPS positions at specified epochs, based on a so-called ‘offset series’ The offset series are obtained by varying the amount of GPS data before and after an event while estimating the offset Two methods, a mean and a weighted mean method, are then investigated to produce the estimated discontinuity from the offset series The mean method estimates coseismic offsets without making assumptions about geophysical processes that may be present in the data (ie tectonic rate, seasonal variations), whereas the weighted mean method includes estimating coseismic offsets with a model of these processes We investigate which approach is the most appropriate given certain lengths of available data and noise within the time-series themselves For the Sumatra–Andaman event, with 45 yr of pre-event data, we show that between 2 and 3 yr of post-event data are required to produce accurate offset estimates with the weighted mean method With less data, the mean method should be used, but the uncertainties of the estimated discontinuity are larger

Measurement and correction of magnetic writer offset error

Abstract: A method, according to one embodiment, includes writing a plurality of shingled tracks using an array of writers, determining first and second positions of an array of readers relative to the shingled tracks, the first and second positions being above and/or beyond track edges of the shingled tracks, repositioning the array of readers to various locations between the first and second positions and reading data from the shingled tracks, determining a read offset point where read performance is about the highest during the reading performed when repositioning the array of readers between the first and second positions, and computing, using the read offset point, data describing a lateral writing position to use during writing such that shingled tracks are written in a location specified by a format Other systems, methods, and computer program products are described in additional embodiments

27.3 A 3-axis open-loop gyroscope with demodulation phase error correction

Abstract: Consumer-electronic (CE) gyroscopes have recently enjoyed broad deployment in high-volume applications, largely due to intuitive user interfaces in smart phones and video game controllers. For their continued expansion into more demanding CE applications, a further reduction of their noise, offset drift, and power dissipation, especially in the emerging always-on category, is mandatory. To be viable, solutions to these conflicting requirements must overcome the challenges of low cost and ever-shrinking package size. This paper describes one such solution with special emphasis on offset drift reduction. The system presented here discards the standard practice of electrically cancelling the quadrature error, and instead combines information derived from continuously monitoring the quadrature error together with a single-point temperature calibration to reduce offset drift. This paper presents the architecture and circuits used to realize a 3-axis open-loop gyroscope with a one-sigma TCO of 0.00657S/K.

Blind Symbol-Rate Estimation and Test Bed Implementation of Linearly Modulated Signals

Abstract: Although several blind symbol-rate estimation methods have been proposed for linearly modulated signals, none of these methods are applicable to offset quadrature phase-shift keying (OQPSK)-modulated signals. The frequently used cyclic correlation (CC) methods are unable to estimate the symbol rate for OQPSK signals as the cyclic peak at the symbol-rate frequency disappears due to the presence of an offset between the in-phase (I) and quadrature (Q) components of OQPSK signals. In this paper, a blind symbol-rate estimation for linearly modulated signals has been proposed. The symbol rate of OQPSK signals has also been estimated with no knowledge of modulation schemes. The offset between I and Q components of the received signals is compensated for by using a set of approximate offsets in obtaining the cyclic peak at the symbol-rate frequency. The proposed estimation has a robust performance in the presence of unknown frequency offset, timing offset, and carrier phase. The algorithm is implemented on a test bed to provide experimental results.

A mapping-based approach to eliminating self-intersection of offset paths on mesh surfaces for CNC machining

Abstract: Geometrically, a tool path can be generated by successively offsetting its adjacent path on the surface with a given path interval, which preferably starts from one of the surface boundaries or a primary curve. The key issues involved in offset path planning are the generation of raw offset paths and the elimination of the self-intersection of raw offset paths. Most researches available in this area are focused on how to generate the raw offset paths, however, the latter, especially how to eliminate the self-intersection of the offset paths on mesh surfaces, has not been sufficiently addressed. In this paper, a mapping-based approach to eliminating the self-intersection of offset paths is proposed for the CNC machining of mesh surfaces. The method first flattens the mesh surface onto a predefined plane by using a mesh mapping technique, and then taking the mapping as a guide, the offset paths are also naturally mapped onto the plane, from which those invalid self-intersection loops can be effectively identified and eliminated. To handle the issue of self-intersection for all types of offset path, a notion of local loop is introduced to detect and eliminate the invalid self-intersection loops. After that the planar paths are inversely mapped into the physical space and the final tool paths used for the machining of mesh surface are obtained. Meanwhile, in order to improve the kinematic and dynamic performance of the machine tool when machining along the generated offset paths, a method for rounding the sharp corners of tool paths, which result from the process of eliminating the self-intersection of raw offset paths, is also preliminarily investigated. Finally, the proposed method is validated by the results of simulations and machining experiments. A method of eliminating self-intersection of offset paths on mesh surfaces is proposed.The new orientation rule based on the local loop is developed and discussed in detail.The method of rounding the sharp corner is preliminarily investigated.Simulation and real machining are performed.

Spatiotemporal Integration of Optical Flow Vectors for Micro-expression Detection

Abstract: Micro-expressions are brief involuntary facial expressions. Detecting micro-expressions consists of finding the occurrence of micro-expressions in video sequences by locating the onset, peak and offset frames. This paper proposes an algorithm to detect micro-expressions by utilizing the motion features to capture direction continuity. It computes the optical flow vector for small local spatial regions and integrates them in local spatiotemporal regions. It uses heuristics to filter non-micro expressions and find the appropriate onset and offset times. Promising results are obtained on a challenging spontaneous micro-expression database. The main contribution of this paper is to find not only the peak but also the onset and offset frames for spotted micro-expressions which has not been explored before.

Learning with Square Loss: Localization through Offset Rademacher Complexity

Abstract: We consider regression with square loss and general classes of functions without the boundedness assumption. We introduce a notion of offset Rademacher complexity that provides a transparent way to study localization both in expectation and in high probability. For any (possibly non-convex) class, the excess loss of a two-step estimator is shown to be upper bounded by this offset complexity through a novel geometric inequality. In the convex case, the estimator reduces to an empirical risk minimizer. The method recovers the results of \citep{RakSriTsy15} for the bounded case while also providing guarantees without the boundedness assumption.

Offset and anteversion reconstruction after cemented and uncemented total hip arthroplasty: an evaluation with the low-dose EOS system comparing two- and three-dimensional imaging

Abstract: Accurate evaluation of femoral offset is difficult with conventional anteroposterior (AP) X-rays. The EOS imaging system is a system that makes the acquisition of simultaneous and orthogonal AP and lateral images of the patient in the standing position possible. These two-dimensional (2D) images are equivalent to standard plane X-rays. Three-dimensional (3D) reconstructions are obtained from these paired images according to a validated protocol. This prospective study explores the value of the EOS imaging system for comparing measurements of femoral offset from these 2D images and the 3D reconstructions. We included 110 patients with unilateral total hip arthroplasty (THA). The 2D offset was measured on the AP view with the same protocol as for standard X-rays. The 3D offset was calculated from the reconstructions based on the orthogonal AP and lateral views. Reproducibility and repeatability studies were conducted for each measurement. We compared the 2D and 3D offset for both hips (with and without THA). For the global series (110 hips with and 110 without THA), 2D offset was 40 mm (SD 7.3; 7–57 mm). The standard deviation was 6.5 mm for repeatability and 7.5 mm for reproducibility. Three-dimensional offset was 43 mm (SD 6.6; 22–62 mm), with a standard deviation of 4.6 for repeatability and 5.5 for reproducibility. Two-dimensional offset for the hips without THA was 40 mm (SD 7.0; 26–56 mm), and 3D offset 43 mm (SD 6.6; 28–62 mm). For THA side, 2D offset was 41 mm (SD 8.2; 7–57 mm) and 3D offset 45 mm (SD 4.8; 22–61 mm). Comparison of the two protocols shows a significant difference between the 2D and 3D measurements, with the 3D offset having higher values. Comparison of the side with and without surgery for each case showed a 5-mm deficit for the offset in 35 % of the patients according to the 2D measurement but in only 26 % according to the 3D calculation. This study points out the limitations of 2D measurements of femoral offset on standard plane X-rays. The reliability of the EOS 3D models has been previously demonstrated with CT scan reconstructions as a reference. The EOS imaging system could be an option for obtaining accurate and reliable offset measurements while significantly limiting the patient’s exposure to radiation.

Around view provision apparatus and vehicle including the same

Abstract: An around view provision apparatus and a vehicle including the same are disclosed. The around view provision apparatus may include a plurality of cameras provided to capture images of different regions around the vehicle. A memory may be provided to store a reference image for each of the cameras. A processor may calculate offset information for at least one of the plurality of cameras based on a difference between the reference image for the camera stored in the memory and an image captured by the camera. Respective images captured through the plurality of cameras may be combined using the offset information so as to generate an around view image

Bandwidth Maximization Using Vehicle Arrival Functions

Abstract: We revisit the offset optimization problem for maximization of two-way progression bands. A new formulation is proposed relying on the concepts of relative offset and vehicle arrival functions. Vehicle arrival functions represent the probability that a vehicle reaches a given intersection at a given time. Relative offsets are the displacement of the arrival functions with respect to a moving coordinate frame. An explicit formula for the bandwidth is derived based on these two quantities. The bandwidth maximization problem is then formulated as an unconstrained nonlinear program. The cases of pulse and Gaussian arrivals are considered in detail. Numerical techniques are proposed for both that return globally optimal solutions with small computational cost.

The role of offset stems in revision knee arthroplasty.

Abstract: Revision total knee arthroplasty (TKA) represents a technically challenging procedure. The use of an offset stem extension can help in addressing some of the difficulties that can be encountered during surgery and, in particular, anatomical mismatch, malalignment, and gap balancing. Different offset stem extensions are available and can be classified according to four parameters: modularity, location of the offset, direction, and size of the displacement. Offset stem extensions can assist with implant alignment on the metaphysis if there is an offset diaphysis, can avoid medial-lateral or anterior-posterior component overhang, can reduce the incidence of coronal or sagittal malalignment, and can help in balancing the flexion and extension spaces by effectively translating the components. The aim of this study is to give an overview of the currently available evidence regarding the use of offset stem extensions in revision TKA as well as some useful surgical tips.

Rapid Calculation of Antenna Noise Temperature in Offset Gregorian Reflector Systems

Abstract: Antenna noise temperature calculations of reflector systems is often a slow process and makes direct optimization of the sensitivity of these systems a difficult and time-consuming task. This paper presents an improvement to a recently proposed method to speed up these calculations by several orders of magnitude for large dish systems. The accuracy of the improved method is tested for several types of offset Gregorian systems, and errors are shown to be in the order of a few percent. Comparisons of several layers of simplification to a standard brightness temperature model are also presented to aid the designer in the choice of model complexity to use.

Latch Offset Cancellation Sense Amplifier for Deep Submicrometer STT-RAM

Abstract: As technology node shrinks, spin-transfer-torque random access memory (STT-RAM) has become a promising memory solution owing to its great scalability. However, the increase in process variation and decrease in the supply voltage result in the degradation of the read yield; thus, achieving the target read yield is an important issue in a deep-submicrometer technology node. In this paper, we propose a latch offset cancellation sense amplifier (LOC-SA) that cancels the latch offset with a compact area by merging the sensing circuit, latch sense amplifier, and write driver. By virtue of the latch offset cancellation characteristic, the voltage developing time can be significantly saved, leading to sensing-speed improvement. The Monte Carlo HSPICE simulation results using industry-compatible 45-nm model parameters show that the LOC-SA satisfies a target read yield of six-sigma (96.74% for 32 Mb) with more than 2 $\times$ faster sensing speed, 1.12 $\times$ lower read energy, and 1.13 $\times$ smaller area when compared with the best value of design parameters of other sense amplifiers.

Learning with Square Loss: Localization through Offset Rademacher Complexity

Abstract: We consider regression with square loss and general classes of functions without the boundedness assumption. We introduce a notion of offset Rademacher complexity that provides a transparent way to study localization both in expectation and in high probability. For any (possibly non-convex) class, the excess loss of a two-step estimator is shown to be upper bounded by this offset complexity through a novel geometric inequality. In the convex case, the estimator reduces to an empirical risk minimizer. The method recovers the results of (Rakhlin et al., 2015) for the bounded case while also providing guarantees without the boundedness assumption.

Adjacent track interference asymmetry mitigation

Abstract: A storage device includes a controller that selects an offset when preparing to write data to a target data track. The offset defines a position for a write head relative to a center of the target track and is selected based on a radial position of a write head at the target data track.

Optimistic Delinearization of Parametrically Sized Arrays

Abstract: A number of legacy codes make use of linearized array references (i.e., references to one-dimensional arrays) to encode accesses to multi-dimensional arrays. This is also true of a number of optimized libraries and the well-known LLVM intermediate representation, which linearize array accesses. In many cases, the only information available is an array base pointer and a single dimensional offset. For problems with parametric array extents, this offset is usually a multivariate polynomial. Compiler analyses such as data dependence analysis are impeded because the standard formulations with integer linear programming (ILP) solvers cannot be used. In this paper, we present an approach to delinearization, i.e., recovering the multi-dimensional nature of accesses to arrays of parametric size. In case of insufficient static information, the developed algorithm produces run-time conditions to validate the recovered multi-dimensional form. The obtained access description enhances the precision of data dependence analysis. Experimental evaluation in the context of the LLVM/Polly system using a number of benchmarks reveals significant performance benefits due to increased precision of dependence analysis and enhanced optimization opportunities that are exploited by the compiler after delinearization.

Signaling signed band offset values for sample adaptive offset (SAO) filtering in video coding

Abstract: A method for signaling sample adaptive offset (SAO) band offset syntax elements in a video encoder is provided that includes receiving a plurality of band offset syntax elements, entropy encoding an absolute value of a magnitude of each band offset syntax element in a compressed video bit stream, and entropy encoding a sign of each non-zero band offset syntax element in the compressed video bit stream following the absolute values of the magnitudes.

Traffic signal control of a road network using MILP in the MPC framework

Abstract: This paper investigates the significance of a traffic signal control scheme that simultaneously adjusts all signal parameters, i.e., cycle time, split time and offset, in a road network. A novel framework of model predictive control (MPC) is designed that overcomes the limitations of other MPC based traffic signal control strategies, which are mostly restricted to control only split or green time in a fixed cycle ignoring signal offset. A simple macroscopic model of traffic tailored to MPC is formulated that describes traffic dynamics in the network at a short sampling interval. The proposed framework is demonstrated using a small road network with dynamically changing traffic flows. The parameters of the proposed model are calibrated by using data obtained from detailed microscopic simulation that yields realistic statistics. The model is transformed into a mixed logical dynamical system that is suitable to a finite horizon, and traffic signals are optimized using mixed integer linear programming (MILP) for a given performance index. The framework makes the signals flexibly turn to red and green by adapting quickly to any changes in traffic conditions. Results are also verified by microscopic traffic simulation and compared with other signal control schemes.

Triangular mesh offset aiming to enhance Fused Deposition Modeling accuracy

Abstract: Fused Deposition Modeling is a worldwide diffused Additive Manufacturing technology able to fabricate prototypes, tooling and end user parts directly from a virtual model. The layer by layer fabrication allows having no limitation of part shape complexity but some weaknesses exist about the obtainable accuracy. The dimensional deviations observed on a physical prototype are of the order of some tenths of millimeter depending upon the local slope of the surface. In order to enhance the accuracy, the idea is to compensate for the deviations by means of a virtual model offset. For the purpose a novel methodology has been developed to offset the triangular mesh: it operates an offset with a variable radius of the vertices without changing their interconnections. In this way the new virtual model is generated in a stable and robust way without modifying the Fused Deposition Modeling process chain. The experimentation carried out both on simple and complex geometries points out a marked improvement of the dimensional accuracy. The assessment has been performed by dimensional measurements and by a preliminary analysis of the errors introduced by the offset method.

Decoding method, memory storage device and memory control circuit unit

Abstract: A decoding method, a memory storage device and a memory control circuit unit are provided. The method includes: determining an offset threshold value and a corresponding check matrix; receiving response data from a rewritable non-volatile memory module and performing an iterative decoding process. The check matrix includes at least one sub-matrix group, each sub-matrix of the sub-matrix group has a default dimension, and the offset threshold value is less than a default dimension value corresponding to the default dimension In the iterative decoding process, several default groups in a data set are shifted, so as to obtain first shift groups, while an offset of each first shift group with respect to a corresponding group among the default groups is not over the default threshold value. Therefore, decoding reference data used in the iterative decoding process may be generated more efficiently.