Abstract: When using plenoptic camera for digital refocusing, angular undersampling can cause severe (angular) aliasing artifacts. Previous approaches have focused on avoiding aliasing by pre-processing the acquired light field via prefiltering, demosaicing, reparameterization, etc. In this paper, we present a different solution that first detects and then removes aliasing at the light field refocusing stage. Different from previous frequency domain aliasing analysis, we carry out a spatial domain analysis to reveal whether the aliasing would occur and uncover where in the image it would occur. The spatial analysis also facilitates easy separation of the aliasing vs. non-aliasing regions and aliasing removal. Experiments on both synthetic scene and real light field camera array data sets demonstrate that our approach has a number of advantages over the classical prefiltering and depth-dependent light field rendering techniques.

Abstract: Spatial aliasing is an undesirable phenomenon that prevents the unique determination of the direction of arrival (DOA) of impinging signals in array signal processing. However, the characteristics of spatial aliasing that generates ambiguous DOAs can be also used to reduce the computational complexity in maximum-likelihood (ML) DOA estimation. This paper proposes a structural method to dramatically reduce the computational complexity of the ML DOA estimation using the spatial aliasing generated by a nested array structure with a doubly scaled aper- ture. An ML full grid search is computationally simplified by the highly compressed searching range and the small number of candidate values to be searched which are derived based on spatial aliasing. Performance analyses based on the theoretical bounds and computational complexity with computer simulations show that the proposed method requires an extremely reduced computational load compared to the conventional ML DOA estimation with a uniform linear array (ULA) while achieving the performance enhancement in the estimation accuracy due to the enlarged array aperture.

Abstract: We investigate the application of a temporal spectral viscosity operator to eliminate aliasing errors associated with the high-dimensional harmonic balance technique, which is an efficient method for modeling nonlinear time-periodic problems. Previous studies have shown that aliasing errors resulting from the discrete Fourier transformation may slow down convergence, trigger a nonlinear instability, or lead to nonphysical solutions. A temporal spectral viscosity operator, similar to that used for pseudospectral methods, is introduced. The temporal spectral viscosity is added to the high-frequency modes of the solution to eliminate aliasing errors so as to ensure the convergence to the physical solution. The implementation of the technique is straightforward and can be incorporated into the high-dimensional harmonic balance solver as a matrix product operator. The accuracy and effectiveness of the modified method is demonstrated for different test cases including a Duffing oscillator and unsteady flow abou...

Abstract: Current temporal gravity field solutions from GRACE suffer from temporal aliasing errors due to undersampling of signal to be recovered (e.g., hydrology), uncertainties in the de-aliasing models (usually atmosphere and ocean), and imperfect ocean tide models. Especially the latter will be one of the most limiting factors in determining high resolution temporal gravity fields from future gravity missions such as GRACE Follow-on and Next-Generation Gravity Missions (NGGM) equipped with improved measurement technology, which cannot be fully exploited due to this dominant systematic error source. In several previous studies it has been shown that temporal aliasing, related to tidal and non-tidal sources, can be significantly reduced by double-pair formations, e.g., in a so-called Bender configuration, and its effects can be migrated to higher frequencies by an optimum orbit choice, especially the orbit altitude (Murböck et al. 2013). Improved processing strategies and extended parameter models should be able to further reduce the problem. Concerning non-tidal aliasing, it could be shown that the parameterization of short-period long-wavelength gravity field signals, the so-called Wiese approach, is a powerful method for aliasing reduction (Wiese et al. 2013), but it does not really work for the very short-period signals of ocean tides with mainly semi-diurnal and diurnal periods (Daras 2015).

Abstract: Visibility may be analytically resolved rather than using point-sampling, thereby entirely avoiding geometric aliasing and the need to store multiple samples per pixel. By relying on existing techniques for shading, i.e., by shading once per fragment and focusing on visibility, visual results may be equivalent to multi-sampled anti-aliasing (MSAA) using an infinite sampling rate in some embodiments.

Abstract: Micro-Doppler is induced by the micro- motion of target and serves as an important characteristic for target recognition once extracted via parameter estimation, but it is generally too significant to result in aliasing in terahertz band. To solve this problem, we analyze the theoretical model and characteristics of aliased micro-Doppler and propose a Doppler aliasing free micro-motion parameter estimation algorithm based on the combination of spliced time-frequency image and the Inverse Radon transform. The basic idea is getting a certain number of aliased time-frequency images spliced, and then make Inverse Radon transform to the spliced image and extract micro-motion parameters. The simulation results show that this method has the advantages of high precision and strong noise suppression and can estimate parameters of aliased micro-Doppler correctly and effectively.

Abstract: 'Hardware aliasing' classically arises when a processor through failure or design has fewer bits than required to address each memory location uniquely, and also - nowadays - in the context of homomorphically encrypted computing. In such contexts, different physical locations may sporadically be accessed by the same address due to factors not directly under the control of the programmer but still deterministic in nature. We check RISC machine and assembly code to ensure that each memory address is calculated in exactly the same way at one write to and the next read from it, which allows programs to work correctly even in a hardware aliasing context.

Abstract: Concert sound reinforcement systems aim at the reproduction of homogeneous sound fields over extended audiences for the whole audio bandwidth. For the last two decades this has been mostly approached by using so called line source arrays for which Wavefront Sculpture Technology (WST) was introduced in the literature. This paper utilizes a signal processing model developed for sound field synthesis in order to analyze and expand WST criteria for straight arrays. Starting with the driving function for an infinite and continuous linear array, spatial truncation and discretization are subsequently taken into account. The role of the involved loudspeakers as a spatial lowpass filter is stressed, which can reduce undesired spatial aliasing contributions. The paper aims to give a better insight on how to interpret the synthesized sound fields.

Abstract: The invention discloses a non-orthogonal joint diagonalization instantaneous blind source separation method based on double iteration. The method comprises the steps that signal data of repeated observation are recorded; a target matrix group based on observation signals is calculated; an observation signal aliasing model is divided into left and right aliasing matrixes; a blind source separation cost function is established; under the condition of equal left and right aliasing matrix nature, the cost function is reconstructed into a symmetric fitting function; a double iteration method is used to estimate left and right aliasing matrix optimal values required by non-orthogonal diagonalization; and an optimal aliasing model is derived to acquire an isolation signal, and instantaneous aliasing blind separation is realized. High demands of the existing non-orthogonal JD method on a target matrix are avoided, and the application scope of the observation signals is expanded. Compared with the prior art, the method provided by the invention has the advantages that the calculation complexity and the iteration number are significantly reduced; the least time is consumed; and when the same SNR is input, the shortest convergence time, the maximum output SINR and the minimum generalized replacement level are realized, and better separation performance and convergence are realized.

Abstract: A side-effect analysis computes for each program phrase a set of memory locations that may be read or written to when executing this phrase. Our analysis expresses abstract objects, points-to and aliasing information, escape information, and side effects all in terms of a single novel abstract domain, generalized access graphs. This abstract domain represents sets of access paths precisely and compactly. It is suitable for intraprocedural analysis as well as for constructing method summaries for interprocedural analysis.

Abstract: Concert sound reinforcement systems aim at the reproduction of homogeneous sound fields over extended audiences for the whole audio bandwidth. For the last two decades this has been mostly approached by using so called line source arrays due to their superior abilities of producing homogeneous sound fields. Design and setup criteria for line source arrays were derived as Wavefront Sculpture Technology in literature. This paper introduces a viewpoint on the problem at hand by utilizing a signal processing model for sound field synthesis. It will be shown that the optimal radiation of a line source array can be considered as a special case of spatial-aliasing-free synthesis of a wave front that propagates perpendicular to the array. For high frequencies the so called waveguide operates as a spatial lowpass filter and therefore attenuates energy that otherwise would lead to spatial aliasing artifacts.

Abstract: One major error source in temporal gravity recovery is temporal aliasing. The satellite mission GRACE suffers from pure along-track observations of its low–low Satellite-to-Satellite Tracking (SST) on a polar orbit. This leads to the typical North-South striped error structures in time-variable gravity fields of GRACE, which are amplified because of the inherent GRACE inverse problem and downward continuation. This study analyzes the possibilities to reduce the non-tidal aliasing effects by formations of future gravity satellite missions. It concentrates on mission options which shall be feasible in the next 10 years. These options contain so-called pendulum formations and double pairs with pairs on orbits with different inclinations. Sharifi et al. Previous studies already analyzed several such mission options and this study on the one hand leads to comparable conclusions for the mission options studied in the cited papers. On the other hand combinations of two low–low SST pairs on polar and sun-synchronous orbits, respectively, which are not studied in the cited papers in detail, and its potential to reduce temporal aliasing are analyzed here. This paper focusses on non-tidal temporal aliasing effects together with typical low–low SST noise characteristics. With semi-analytical simulations it is analyzed that a noise level of \(\mathrm{{10}}^{\mathrm{-11}}\,\mathrm{\mathrm{m}\mathrm{/}\mathrm{{s}}^{\mathrm{2}}}/\sqrt{\mathrm{Hz}}\) of the range acceleration observations is sufficient to get sensitivity for mass variations on the Earth. Comparing the effects of non-tidal aliasing and colored observation noise, closed-loop simulations of ten different future mission options are analyzed. Pure along-track low–low SST observations like GRACE in a so-called in-line formation are highly affected by this temporal aliasing. The double pairs containing an in-line pair on a 63∘ inclined orbit reduce the aliasing effect most. Both the single pendulum pairs, one on a polar and another on a sun-synchronous orbit, and their combination reach the same level of aliasing reduction as the combinations with the 63∘ inclined pair.

Abstract: We present our ongoing effort to implement predicate abstraction in Abstract Pathfinder, which is an extension of Java Pathfinder. Our approach builds upon existing abstraction techniques that have been proposed mainly for low-level programs in C. We support predicates over variables having numerical data types. The main challenges that we have addressed include (1) the design of the predicate language, (2) support for arrays, (3) finding predicates affected by a given statement, (4) aliasing between variables, (5) propagating values of predicates over method call boundaries, and (6) computing weakest preconditions for complex predicates. We describe our solution to these challenges and selected details about the implementation. We also discuss our future plans and research ideas.

Abstract: It is well-known that if a time series is not sampled at a fast enough rate to capture all the high frequencies then aliasing may occur. Aliasing is a distortion of the spectrum of a series which can cause severe problems for time series modelling and forecasting. The situation is more complex and more interesting for nonstationary series as aliasing can be intermittent. Recent work has shown that it is possible to test for the absence of aliasing in nonstationary time series and this article demonstrates that additional benefits can be obtained by modelling a series using a Shannon locally stationary wavelet (LSW) process. We show that for Shannon LSW processes the effects of dyadic-sampling-induced aliasing can be reversed. We illustrate our method by simulation on Shannon LSW processes and also a time-varying autoregressive process where aliasing is detected. We present an analysis of a wind power time series and show that it can be adequately modelled by a Shannon LSW process, the absence of aliasing can not be inferred and present a dealiased estimate of the series.

Abstract: Correlation filters (CFs) are well established and useful tools for a variety of tasks in signal processing and pattern recognition, including automatic target recognition and tracking, biometrics, landmark detection, and human action recognition. Traditionally, CFs have been designed and implemented efficiently in the frequency domain using the discrete Fourier transform (DFT). However, the element-wise multiplication of two DFTs in the frequency domain corresponds to a circular correlation, which results in aliasing (i.e., distortion) in the correlation output. Prior CF research has largely ignored these aliasing effects by making the assumption that linear correlation is approximated by circular correlation. In this work, we investigate in detail the topic of aliasing in CFs. First, we illustrate that the current formulation of CFs in the frequency domain is inherently flawed, as it unintentionally assumes circular correlation during the design phase. This means that existing CFs are not truly optimal. We introduce zero-aliasing correlation filters (ZACFs) which fix this formulation issue by ensuring that each CF formulation problem corresponds to a linear correlation rather than a circular correlation. By adopting the ZACF design modifications, we show that the recognition and localization performance of conventional CF designs can be significantly improved. We demonstrate these benefits using a variety of data sets and present solutions to the computational challenges associated with computing ZACFs. After a CF is designed, it is used for object recognition by correlating it with a test signal. We investigate the use of the well-known overlap-add (OLA) and overlap-save (OLS) algorithms to improve the computation and memory requirements of this correlation operation for high dimensional applications (e.g., video). Through this process, we highlight important tradeoffs between iii these two algorithms that have previously been undocumented. To improve the computation and memory requirements of OLA and OLS, we introduce a new block filtering scheme, denoted partial-aliasing OLA (PAOLA) that intentionally introduces aliasing into the output correlation. This aliasing causes conventional CFs to perform poorly. To remedy this, we introduce partialaliasing correlation filters (PACFs), which are specifically designed to minimize this aliasing. We demonstrate through numerical results that PACFs outperform conventional CFs in the presence of aliasing.

Abstract: The invention relates to a low-density parity check code aliasing and decoding method and a multi-core collaborative aliasing decoder, and belongs to the field of wireless communication. In the aliasing and decoding method, variable node decoding and check node decoding are carried out at the same time to finish low-density parity check code decoding. According to the multi-core collaborative aliasing decoder, the aliasing and decoding method is adopted, a cyclic bus is led in, a variable node arithmetic unit set, a variable node output information storage unit, a check node arithmetic unit set and a check node output information storage unit on the cyclic bus are made to work at the same time, and multi-core collaborative aliasing decoding is achieved. By means of the decoding method and the decoder, the throughput of the decoder and the logic utilization efficiency of hardware are improved; due to lead-in of the cyclic bus in the decoder, multi-core collaborative decoding is achieved, consumption of a hardware logic unit and memory blocks is lowered, and development of a low-density parity check code decoder which is high in speed and low in resource consumption is facilitated.

Abstract: Autocorrelation using in-phase and quadrature (IQ) signals suffers from aliasing when the velocity of rapidly moving tissue, such as the heart wall, is measured. In the present study, a simple method was proposed to expand the aliasing limit. In the proposed method, the velocity difference between two successive frames (corresponding to acceleration) of tissue was also estimated directly from IQ signals. When aliasing occurs in the velocity in the current frame, which was estimated from IQ signals, the velocity in the current frame was corrected by adding the velocity difference to the velocity in the previous frame. Using this procedure, the velocity can be estimated if the difference between velocities in the current and previous frames is less than the aliasing limit. The velocity of the posterior heart wall in the longitudinal-axis view of about 0.08 m/s could be estimated under the aliasing limit of the conventional autocorrelation method of 0.047 m/s. Myocardial velocity over the conventional aliasing limit could be measured by the proposed method.

Abstract: Deadlocks remain one of the biggest threats to concurrent programming. Usually, the best programmers can expect is dynamic deadlock detection, which is only a palliative. Object-oriented programs, with their rich reference structure and the resulting presence of aliasing, raise additional problems. The technique developed in this paper relies on the “alias calculus” to offer a completely static and completely automatic analysis of concurrent object-oriented programs. The discussion illustrates the technique by applying it to two versions of the “dining philosophers” program, of which it proves that the first is deadlock-free and the second deadlock-prone.

Abstract: Generic programming has turned out very useful in the development of reusable software With the Java programming language, genericity is not only meant for reusability, but also for type-safety Java generics constrain a container object (eg, list, hash table) to store objects of a pre-specified data type Nevertheless, safe programming with aliasing (multiple pointers in a program may point to the same object) is still a concern in objectoriented programming language research A pointing object can mutate the state of the aliased object, reflecting the changes to all of the other pointers (aka aliases) thus affecting their behaviour As programs grow larger and more complex, such changes in behaviour can be undesirable and difficult to detect and reason about With respect to container objects, the iterator pattern critically violates encapsulation, allowing aliases to the state (and thereof the components) of its container Object ownership is one of the well-researched paradigms in the area of alias management Ownership types support hierarchical object encapsulation rather than the traditional class-level encapsulation This thesis introduces an extension of Java 6 with support for ownership types as supplementary generic types That is, Java generics are extended with the ability of carrying ownership information This extension provides generic ownership support for all of Java; that is, all major language features are addressed so that programs can safely manage and express their aliasing properties The resulting language is expressive enough to support common programming idioms, with little programming and runtime overhead We evaluated the programmability of the language by refactoring a major (the most essential) portion of the Java Collections Framework We also evaluated the performance impact of our refactoring by conducting a small micro-benchmark study to measure the performance time overhead the refactored collections may impose

Abstract: The invention discloses a time-domain aliasing blind signal separation method based on three-factor iteration joint block diagonalization. The method comprises the steps of firstly rearranging time-domain convolution aliasing signals received from a sensor into observation data vectors; calculating the second order time delay correlation matrix set of the observation data vectors under assigned time delay; calculating a block nature equality matrix of a real block aliasing matrix by using a non-orthogonal joint block diagonalization method based on three-factor iteration; resolving a pseudo-inverse matrix of the block nature equality matrix; calculating an estimation signal of a source signal by using the pseudo-inverse matrix to realize the separation of blind and source signals of the time-domain convolution aliasing signals. According to the method, an object function is built and is used for evaluating a separation effect, further three groups of matrix factors are solved, the separation effect of the blind and source signals of the time-domain convolution aliasing signals is effectively improved, the calculation complexity is reduced, and the defects of easiness in generating a singular integral, sensitivity to noise and the like are overcome; the method is more advantageous in the aspects of application condition, convergence and separation performance, and is a universally suitable and effective method for the separation of the blind and source signals.

Abstract: Direction-of-arrival (DOA) estimation of sound sources by using microphone array is an important technique. Its applications are teleconference system and human-robot communicating system and so on. This paper describes a DOA estimation method using array with arbitrary 3-dimentional configuration. The problem discussed in this study is the case in the presence of spatial aliasing. The proposed method is based on sparseness in time-frequency domain of speech signal. The phase uncertainty caused by spatial aliasing can be solved by selecting reliable time-frequency sells whose propagating vector is mostly close to the unit sphere. Through conducted experiments, the proposed method is proved to estimate more accurately than the conventional methods such as histogram and k-means clustering algorithm. Based on the kernel density algorithm stable accurate estimation of DOA can be realized.

Abstract: One of the well-known problems in response verification is aliasing, ie, the event that a series of responses containing errors results in a signature equal to that of the error-free response sequence In this paper, we propose a scheme to reduce aliasing in accumulator-based response verification The proposed scheme is based on monitoring the value of the carry output of the accumulator Experimental study indicates that the proposed scheme achieves significantly less hardware overhead for the same reduction in the aliasing probability than previously proposed schemes

Abstract: Data-flow testing techniques have long been discussed in the literature, yet to date they are still of little practical relevance. The applicability of data-flow testing is limited by the complexity and the imprecision of the approach: writing a test suite that satisfy a data-flow criterion is challenging due to the presence of many test objectives that include infeasible elements in the coverage domain and exclude feasible ones that depend on aliasing and dynamic constructs. To improve the applicability and effectiveness of data-flow testing we need both to augment the precision of the coverage domain by including data-flow elements dependent on aliasing and to exclude infeasible ones that reduce the total coverage. In my PhD research I plan to address these two problems by designing a new data-flow testing approach that combines automatic test generation and dynamic identification of data-flow elements that can identify precise test targets by monitoring the program executions.

Abstract: Anti-aliasing has recently been employed as a post-processing step to adapt to the deferred shading technique in real-time applications. Some of these existing algorithms store supersampling geometric information as geometric buffer G-buffer to detect and alleviate sub-pixel-level aliasing artifacts. However, the anti-aliasing filter based on sampled sub-pixel geometries only may introduce unfaithful shading information to the sub-pixel color in uniform-geometry regions, and large G-buffer will increase memory storage and fetch overheads. In this paper, we present a new Triangle-based Geometry Anti-Aliasing TGAA algorithm, to address these problems. The coverage triangle of each screen pixel is accessed, and then, the coverage information between the triangle and neighboring sub-pixels is stored in a screen-resolution bitmask, which allows the geometric information to be stored and accessed in an inexpensive manner. Using triangle-based geometry, TGAA can exclude irrelevant neighboring shading samples and achieve faithful anti-aliasing filtering. In addition, a morphological method of estimating the geometric edges in high-frequency geometry is incorporated into the TGAA's anti-aliasing filter to complement the algorithm. The implementation results demonstrate that the algorithm is efficient and scalable for generating high-quality anti-aliased images.

Abstract: The invention belongs to the field of a 3D (three dimensional) video and relates to a processing method for a color aliasing and shadow part in three dimensional video virtual viewpoint synthesis. The method is realized by selectively mapping the color aliasing and shadow part corresponding to the left-right viewpoint depth map boundary part and judging whether the color aliasing and shadow part is remained or not. According to the method, the distortion of the synthesis virtual viewpoint boundary position caused by the color aliasing and shadow part is eliminated and the subjective quality and objective quality of the virtual viewpoints are improved.