Novel approximations for the Q-function with application in SQNR calculation

In this paper, an upper bound expression for the Q-function approximation is proposed. This expression defines the class of approximations that are upper bounds under the particular condition derived in the paper. The proposed upper bound approximation of the Q-function and the approximations derived from it are applied in signal to quantization noise ratio (SQNR) calculation of variance-matched Gaussian source scalar quantization. The proposed Q-function approximation having a simple analytical form and being a parametric one is optimized in terms of its parameter with respect to relative error (RE) of approximation for the particular problem observed. Specifically, three different optimization methods are proposed, so that different Q-function approximations are provided in the paper. Moreover, the manner for expansion of the obtained results is provided in order to make our proposal applicable for facilitating any mathematical analysis involving Q-function calculation. The results indicate that the proposed Q-function approximations not only outperform the numerous previously reported approximations in terms of accuracy, but also provide the derivation of the reasonably accurate closed-form formula for SQNR of variance-matched scalar quantization for the Gaussian source, which is not achievable with the application of the previously reported Q-function approximations of similar analytical form complexity. The results presented in this paper are applicable to many signal processing and communication problems requiring Q-function calculation.     

GF（3^m）椭圆曲线群快速算术运算研究

详细研究了GF(3m)上椭圆曲线基本算术运算,给出并证明GF(3m)上超奇异和非超奇异椭圆曲线仿射坐标系下点加、倍点、3倍点和3k倍点计算公式.提出高效3k倍点递归算法,在逆乘率较高时,其效率要优于逐次3倍点算法.在此基础上,提出一种新的变长滑动窗口wrNAF标量乘算法,其在保证较少点加法运算优点的同时可有效降低3倍点的计算量.     

关于Br完备的一个注记(英文)

利用滤子理论,给出了一个Ｂｒ完备的等价条件．     

NAF标量乘算法的改进

影响椭圆曲线加密效率的主要因素是椭圆曲线上的动点标量乘法和定点标量乘法,针对定点的标量乘法已经有了很好的算法,然而,动点的标量乘法还有待提高,NAF算法是目前存在的最优的动点标量乘算法。首先对NAF算法进行分析,指出传统NAF算法的不足,再利用m—ary算法和滑动窗口算法的思想,将K的NAF二进制表示变成NAF的2^r进制表示,计算时滑过值为0的位,并将要处理的数划为（2^r）th（h为奇数）。理论和实践证明,已做到能进一步减少椭圆曲线上点加的次数,大大提高椭圆曲线加密的效率。     

Efficient multimedia coprocessor with enhanced SIMD engines for exploiting ILP and DLP

Multimedia applications have become increasingly important in daily computing. These applications are composed of heterogeneous regions of code mixed with data-level parallelism (DLP) and instruction-level parallelism (ILP). A standard solution for a multimedia coprocessor resembles of single-instruction multiple-data (SIMD) engines into architectures exploiting ILP at compile time, such as very long instruction word (VLIW) and transport triggered architecture (TTA). However, the ILP regions fail to scale with the increased vector length to achieve high performance in the DLP regions. Furthermore, the register-to-register nature of SIMD instructions causes current SIMD engines to have limitations in handling memory alignment, data reorganization, and control flow. Many supporting instructions such as data permutations, address generations, and loop branches, are required to aid in the execution of the real SIMD computation instructions. To mitigate these problems, we propose optimized SIMD engines that have the capabilities for combining VLIW or TTA processing with a unified scalar and long vector computations as well as efficient SIMD hardware for real computation. Our new architecture is based on TTA and is called multimedia coprocessor (MCP). This architecture includes following features: (1) a simple coprocessor structure with 8-way TTA, (2) cost-effective SIMD hardware capable of performing floating-point operations, (3) long vector capabilities built upon existing SIMD hardware and a single register file and processor data path for both scalar operands and vector elements, and (4) an optimized SIMD architecture that addresses the SIMD limitations. Our experimental evaluations show that MCP can outperform conventional SIMD techniques by an average of 39% and 12% in performance for multimedia kernels and applications, respectively.     

Simulation of random vectors with given moments

We extend in this article the simulation method of scalar random variables with given moments, which was developed initially by Devroye, to n-dimensional random vectors. Using the conditional distribution approach, we show that the vector simulation problem can be reduced to simulate scalar random variables with given moments, which are solutions of given linear systems.     

A discrete hidden Markov model fault diagnosis strategy based on K-means clustering dedicated to PEM fuel cell systems of tramways

To solve the fault classification problems of fuel cell (FC) various health states for tramways, a discrete hidden Markov model (DHMM) fault diagnosis strategy based on K-means clustering is proposed. In this paper, the K-means clustering algorithm is used to filter the sample points which aren't consistent with the actual class labels. The Lloyd algorithm is employed to quantify the sample vector sets and obtain the discrete code combination of training samples and test samples. The Baum-Welch algorithm and forward-backward algorithm are respectively presented to train and deduce the DHMM. The classification results show that the six concerned faults can be detected and isolated. The targeted fault types include low air pressure, deionized glycol high inlet temperature, deionized humidification pump low pressure, deionized glycol outlet temperature signal voltage overrange, normal state and hydrogen leakage. The fault recognition rates with the novel approach are at best 94.17%.     

Piloted jet flames of CH4/H2/air: Experiments on localized extinction in the near field at high Reynolds numbers

Measurements of temperature and major species concentrations, based on the simultaneous line-imaged Raman/Rayleigh/CO-LIF technique, are reported for piloted jet flames of CH₄/H₂ fuel with varying amounts of partial premixing with air (jet equivalence ratios of ?_j = 3.2, 2.5, 2.1 corresponding to stoichiometric mixture fraction values of ξ_st = 0.35, 0.43, 0.50, respectively) and varying degrees of localized extinction. Each jet flame is operated at a fixed and relatively high exit Reynolds number (60,000 or 67,000), and the probability of localized extinction is increased in several steps by progressively decreasing the flow rate of the pilot flame. Dimensions of the piloted burner, originally developed at Sydney University, are the same as for previous studies. The present measurements complement previous results from piloted CH₄/air jet flames as targets for combustion model calculations by extending to higher Reynolds number, including more steps in the progression of each flame from a fully burning state to a flame with high probability of local extinction, and adding the degree of partial premixing as an experimental parameter. Local extinction in these flames occurs close to the nozzle near a downstream location of four times the jet exit diameter. Consequently, these data provide the additional modeling challenge of accurately representing the initial development of the reacting jet and the near-field mixing processes.     

Scalar energy fluctuations in Large-Eddy Simulation of turbulent flames: Statistical budgets and mesh quality criterion

Large-Eddy Simulation (LES) provides space-filtered quantities to compare with measurements, which usually have been obtained using a different filtering operation; hence, numerical and experimental results can be examined side-by-side in a statistical sense only. Instantaneous, space-filtered and statistically time-averaged signals feature different characteristic length-scales, which can be combined in dimensionless ratios. From two canonical manufactured turbulent solutions, a turbulent flame and a passive scalar turbulent mixing layer, the critical values of these ratios under which measured and computed variances (resolved plus sub-grid scale) can be compared without resorting to additional residual terms are first determined. It is shown that actual Direct Numerical Simulation can hardly accommodate a sufficiently large range of length-scales to perform statistical studies of LES filtered reactive scalar-fields energy budget based on sub-grid scale variances; an estimation of the minimum Reynolds number allowing for such DNS studies is given. From these developments, a reliability mesh criterion emerges for scalar LES and scaling for scalar sub-grid scale energy is discussed.     

A numerical study of the scalar field in turbulent round jet with co-flowing stream

The influence of co-flow on a turbulent binary gas mixing round jet is numerically studied using a first and a second order turbulence closure models. The objective of the study is to obtain a better understanding of the flow structure and mixing process in turbulent variable-density jets. Comparisons between recently published experimental results and mean mixture fraction, the scalar turbulent fluctuation, and the jet spreading rate, feature reasonably good agreements. It is mainly shown that the co-flow reduces the jet spreading rate, but on the otherhand increases the mixing efficiency.An erratum to this article can be found at