Robot path planning using VLSI resistive grids

The resistive grid algorithm for mobile robot path planning is described. A major advantage of the method is that it is capable of a fine-grained parallel analogue VLSI implementation, which offers a fast, low-power solution to the problem of mobile robot navigation. The results from a small-scale test chip are presented, together with their implications for scaling up to a full-sized path-planning chip     

Cyclic wavelet transforms for arbitrary finite data lengths

Multiresolution analysis via decomposition into wavelets has been established as an important transform technique in signal processing. A wealth of results is available on this subject, and particularly, the framework has been extended to treat finite length sequences of size 2ⁿ (for positive integers n) over finite fields. The present paper extends this idea further to provide a framework for dealing with arbitrary finite data lengths. This generalization is largely motivated in part by the need for such transforms for building error correcting codes in the wavelet transform domain. Here we extend the previous two-band formulation of the transform to treat a p-band case in general (i.e. for data length pⁿ), where p is a prime number, and we also give a general result for developing transforms over composite-length sequences. Potential applications and computational complexity issues are discussed as well.     

Density reconstruction using arbitrary ray-sampling schemes

Methods for calculating the distribution of absorption densities in a cross section through an object from density intergrals along rays in the plane of the cross section are well-known, but are restricted to particular geometries of data collection. So-called convolutional-back projection-summation methods, used now for parallelray data, have recently been extended to special cases of the fan-beam reconstruction problem by the addition of pre- and post-multiplication steps. In this paper, a technique for deriving reconstruction algorithms for arbitrary ray-sampling schemes is presented; the resulting algorithms entail the use of a general linear operator, but require little more computation than the convolutional methods, which represent special cases. The key to the derivation is the observation that the contribution of a particular ray sum to a particular point in the reconstruction essentially depends on the negative inverse square of the perpendicular distance from the point to the ray, and that this contribution has to be weighted by the ray-sampling density. The remaining task is the efficient arrangement of this computation, so that the contribution of each ray sum to each point in the reconstruction does not have to be calculated explicitly. The exposition of the new method is informal in order to facilitate the application of this technique to various scanning geometries. The frequency domain is not used, since it is inappropriate for the space-variant operators encountered in the general case. The technique is illustrated by the derivation of an algorithm for parallel-ray sampling with uneven spacing between rays and uneven spacing between projection angles. A reconstruction is shown which attains high spatial resolution in the central region of an object by sampling central rays more finely than those passing through outer portions of the object.     

Time-domain reflectometry using arbitrary incident waveforms

A novel time-domain reflectometry technique is developed for detecting the physical structures of transmission lines by using arbitrary waveforms. By discretizing both incident and reflected waves, we formulate the reflection coefficient of a nonuniform transmission line as a polynomial ratio in the Z-transform, wherein the numerator and denominator represent the reflected and incident waves, respectively. A reconstruction scheme is derived to obtain the characteristic impedance profile of a transmission line. Some examples are presented to illustrate the validity of this new technique.     

Privacy-preserving data aggregation scheme against internal attackers in smart grids

With fast advancements of communication, systems and information technologies, a smart grid (SG) could bring much convenience to users because it could provide a reliable and efficient energy service. The data aggregation (DA) scheme for the SG plays an important role in evaluating information about current energy usage. To achieve the goal of preserving users’ privacy, many DA schemes for the SG have been proposed in last decade. However, how to withstand attacks of internal adversaries is not considered in those schemes. To enhance preservation of privacy, Fan et al. proposed a DA scheme for the SG against internal adversaries. In Fan et al.’s DA scheme, blinding factors are used in evaluating information about current energy usage and the aggregator cannot get the consumption information of any individual user. Fan et al. demonstrated that their scheme was secure against various attacks. However, we find that their scheme suffers from the key leakage problem, i.e., the adversary could extract the user’s private key through the public information. To overcome such serious weakness, this paper proposes an efficient and privacy-preserving DA scheme for the SG against internal attacks. Analysis shows that the proposed DA scheme not only overcome the key leakage problem in Fan et al.’s DA scheme, but also has better performance.     

Minimizing data access latency in data grids by neighborhood‐based data replication and job scheduling

In Data Grid systems, quick data access is a challenging issue due to the high latency. The failure of requests is one of the most common matters in these systems that has an impact on performance and access delay. Job scheduling and data replication are two main techniques in reducing access latency. In this paper, we propose two new neighborhood‐based job scheduling strategies and a novel neighborhood‐based dynamic data replication algorithm (NDDR). The proposed algorithms reduce the access latency by considering a variety of practical parameters for decision making and the access delay by considering the failure probability of a node in job scheduling, replica selection, and replica placement. The proposed neighborhood concept in job scheduling includes all the nodes with low data transmission costs. Therefore, we can select the best computational node and reduce the search time by running a hierarchical and parallel search. NDDR reduces the access latency through selecting the best replica by performing a hierarchical search established based on the access time, storage queue workload, storage speed, and failure probability. NDDR improves the load balancing and data locality by selecting the best replication place considering the workload, temporal locality, geographical locality, and spatial locality. We evaluate our proposed algorithms by using Optorsim Simulator in two scenarios. The simulations confirm that the proposed algorithms improve the results compared with similar existing algorithms by 11%, 15%, 12%, and 10% in terms of mean job time, replication frequency, mean data access latency, and effective network usage, respectively.     

Reversible Resampling of Integer Signals

Except some extremely special cases, signal resampling was generally considered to be irreversible because of strong attenuation of high frequencies after interpolation. In this paper, we prove that signal resampling based on polynomial interpolation can be reversible even for integer signals, i.e., the original signal can be reconstructed losslessly from the resampled data. By using matrix factorization, we also propose a reversible method for uniform shifted resampling and uniform scaled and shifted resampling. The new factorization yields three elementary integer-reversible matrices. The method is actually a new way to compute linear transforms and a lossless integer implementation of linear transforms with the factor matrices. It can be applied to integer signals by in-place integer-reversible computation, which needs no auxiliary memory to keep the original sample data for the transformation during the process or for “undo” recovery after the process. Some examples of low-order resampling solutions are also presented in this paper and our experiments show that the resampling error relative to the original signal is comparable to that of the traditional irreversible resampling.      

Method for replica creation in data grids based on complex networks

In order to reduce makespan and storage consumption in data grids,a node selection model for replica creation is proposed.The model is based on the degree distribution of complex networks.We define two candidate replica nodes: a degree-based candidate pool and a frequency-based candidate pool,through which a degree-based candidate pool is defined m consideration of onsidering the access frequency,a candidate pool-based frequency is also defined.The data replica is copied to the node with the minimum local cost in the two pools.Further,this paper presents and proves a replica creation theorem.A dynamic multi-replicas creation algorithm(DMRC)is also provided.Simulation results show that the proposed method may simultaneously reduce makespan and data used in space storage consumption.     

Distributed wisdom: designing a replication service for large peer-to-peer data grids

We discuss the peer-to-peer middleware architecture for developing grid applications. We present the key issues in building services for large-scale distributed systems. Our approach of developing a replication service using a scalable, reconfigurable shared-object space realized over two-layer P2P architecture appears unique. However, we need to benchmark the platform to test the performance. Also, we must look at key issues in designing the replication service itself, including data redundancy and efficient data placement strategies to minimize computation time and bandwidth.     

防脱片剂APES制备铜网支持膜的新方法

当前电镜制样普遍采用的支持膜为Formvar膜,但Formvar膜制备过程较为复杂,制作要求比较高。制作的支持膜较薄时,容易被电子束击破或样品发生漂移;较厚时降低了样品的分辨率;制膜时如果湿度过大,膜上会出现许多小“白点”而无法使用。在实际工作中,我们把免疫组化技术工作中的防脱片剂APES(3-amtio propyhri ethoxy silane)应用于铜网支持膜的制备,实验结果表明,样品捞在涂有APES的铜网上,镜下观察,样品无漂移,分辨率好。经过两     

Mutual admittance between slots in cylinders of arbitrary shape

A numerical formulation involving the Fourier transform and the combined-field integral equation is presented to calculate the mutual admittance between axial slots or circumferential slots in arbitrarily shaped cylinders. Two cases are considered: coupling between two circumferential slots and coupling between two axial slots. The slots are assumed to be waveguide-fed apertures excited with the TE₁₀ waveguide mode, with no higher-order modes included in the model. The combined field-integral equation (CFIE) formulation was used in conjunction with the magnetic field integral equation (MFIE) to solve the resulting two-dimensional integral equation. Formulations for the axial slot case are discussed. Results concerning the discretization and truncation of the spectrum, as well as the accuracy of the procedure, are presented for both axial and circumferential cases. The accuracy of the procedure is demonstrated by comparison with eigenfunction data for circular cylinders     

Resampling estimates of precision in emission tomography

Methods for estimating the regional variance in emission tomography images which arise from the Poisson nature of the raw data are discussed. The methods are based on the bootstrap and jackknife methods of statistical resampling theory. The bootstrap is implemented in time-of-flight PET (positron emission tomography); the same techniques can be applied to non-time-of-flight PET and SPECT (single-photon-emission computed tomography). The estimates are validated by comparing them to those obtained by repetition of emission scans, using data from a time-of-flight positron emission tomograph. Simple expressions for the accuracy of the estimates are given. The present approach is computationally feasible and can be applied to any reconstruction technique as long as the data are acquired in a raw, uncorrected form.     

New type of microwave power monitoring device using grids of optical-fibre sensors

A new form of power detector for microwave radiation in free space is discussed. Tests are described in which the sensitivity of the detector and the dependence of its response to the direction of arrival and polarisation of the wave are measured.<>     

Accurate DOA estimation using array antenna with arbitrary geometry

The so called universal steering vector (USV) whose locus is equivalent to the array element pattern is applied to the direction of arrival (DOA) estimation by multiple signal classification (MUSIC) algorithm. It is shown that if the USV which includes the effect of the mutual coupling between the array elements is used, the compensation for the received voltage to remove the effect of the mutual coupling is not required any more. The USV for array antennas with arbitrary geometry is derived and evaluated efficiently by using the method of moments (MoM) so that the DOA estimation can be performed accurately by using the array antenna with arbitrary geometry. Numerical examples of the DOA estimation by a dipole array antenna, and an antenna array composed of a monopole antenna and a planar inverted-F antenna (PIFA) mounted on a mobile handset are presented to demonstrate the effectiveness of the proposed method.     

The design of arbitrary FIR digital filters using the eigenfiltermethod

The design of finite impulse response (FIR) digital filters for approximating an arbitrary function (in both magnitude and phase) in the least-square sense is studied. The design method is based on the computation of an eigenvector of an appropriate real, symmetric and positive-definite matrix. The design of the complex-coefficient filter is shown to be an extension of the design of the real-coefficient filter. Several design examples, including the constant-group-delay filters and digital phase all-pass filters, are presented. Comparisons to existing methods are made     

Analysis of closed arbitrary dielectric waveguides using a modifiedRayleigh-Ritz technique

To avoid the meshing difficulties of the finite-element method, the classical Rayleigh-Ritz method is combined with an additional optimization to analyze closed arbitrary dielectric waveguides. The method is easily implemented in compact code and is user-friendly. The method and its rationale are developed, and numerical examples are presented to demonstrate its accuracy in propagation constant and nonperturbational loss calculations. The method is shown to be rapidly convergent and extremely stable     

Pattern synthesis for arbitrary arrays using an adaptive arraymethod

This paper presents a new pattern synthesis algorithm for arbitrary arrays based on adaptive array theory. With this algorithm, the designer can efficiently control both mainlobe shaping and sidelobe levels. The element weights optimize a weighted L₂ norm between desired and achieved patterns. The values of the weighting function in the L₂ norm, interpreted as imaginary jammers as in Olen and Compton's (1990) method, are iterated to minimize exceedance of the desired sidelobe levels and minimize the absolute difference between desired and achieved mainlobe patterns. The sidelobe control can be achieved by iteration only on sidelobe peaks. In comparison to Olen and Compton's method, the new algorithm provides a great improvement in mainlobe shaping control. Example simulations, including both nonuniform linear and planar arrays, are shown to illustrate the effectiveness of this algorithm     

Short distance data transmission method using inaudible high-frequencies between smart devices

Telecommunication Systems - Because wireless communications with inaudible high-frequency signals are used in limited areas due to their low speed, this paper proposes a data communications method...     

几何操作中重采样问题数据并行实现

几何操作是计算机图形和计算机视觉的基本操作之一。如何快速、实时地实现几何操作,是现代媒体应用中的主要问题。重采样操作是图像处理中非常关键的全局操作,一般是通过串行处理方法予以解决。在SIMD处理元阵列上进行数据并行处理几乎是空白,为了满足对图像进行实时处理的需要,提出几何操作中重采样操作的数据并行实现方法,并对结论进行了论证。通过SIMD PE阵列之间的数据并行传送,实现了重采样,从而使实现重采样的复杂度由存储器数据流访问实现方法的Ο（MN）降低到Ο（M＋N）,大大提高了处理速度,能更好地满足图像快速实时处理的需要。