一种新型的10G以太网并行循环冗余校验设计

现有10G以太网中的循环冗余校验(CRC)编译码器不能同时兼顾计算速度与资源占用,为此,设计一种新型的10G以太网并行CRC编译码器。编码时,通过编码预处理解决不定长字节带来的CRC编码问题,简化CRC编码电路的设计。译码时,通过译码预处理分离出以太网帧的帧校验序列(FCS)域,恢复编码预处理模块输出的数据,简化CRC校验电路的设计。在实现CRC编码校验时对传统的异或运算电路进行优化,降低运算电路门延时,提高运算速度,并能自动切换CRC编码校验方法以兼容现有以太网。实验结果表明,与其他3种方法相比,该方法占用逻辑资源少,计算速度快,可实现实时性输出,同时满足10G以太网156.25 MHz的时序要求。

TMS320LF2407A与PC多机串行通信的一种典型方法

基于 DSP的两轴高精度稳定平台 ,介绍了一种 TMS32 0 LF2 4 0 7与 PC多机串行通信的软硬件方案 ,并对这种方法的优缺点进行了讨论 ,提出了一种基于奇偶校验的校验数方法 ,实践证明 。

Regular Quasi Cyclic Low Density Parity Check Codes with Girth 8 from Elementary Number Theory

This paper is concerned with (3,n) and (4,n) regular quasi-cyclic Low Density Parity Check (LDPC) code constructions from elementary number theory.Given the column weight,we determine the shift values of the circulant permutation matrices via arithmetic analysis.The proposed constructions of quasi-cyclic LDPC codes achieve the following main advantages simultaneously:1) our methods are constructive in the sense that we avoid any searching process;2) our methods ensure no four or six cycles in the bipartite graphs corresponding to the LDPC codes;3) our methods are direct constructions of quasi-cyclic LDPC codes which do not use any other quasi-cyclic LDPC codes of small length like component codes or any other algorithms/cyclic codes like building block;4)the computations of the parameters involved are based on elementary number theory,thus very simple and fast.Simulation results show that the constructed regular codes of high rates perform almost 1.25 dB above Shannon limit and have no error floor down to the bit-error rate of 10-6.

Evaluation of coal bed methane content using BET adsorption isotherm equation

Coal bed methane is unconventional raw natural gas stored in coal seam with considerable reserves in China.In recent years,as the coal bed methane production,the safety and the use of resources have been paid more attentions.Evaluating coal bed methane content is an urgent problem.A BET adsorption isotherm equation is used to process the experimental data.The various parameters of BET equation under different temperatures are obtained;a theoretical gas content correction factor is proposed,and an evaluation method of actual coal bed methane is established.

Some Properties of Si,Ge,and α-Sn Using Pseudopotential Theory

The pseudopotential theory beyond second order with our well established single parametric model potential is employed to compute total crystal energy, static bulk modulus, energy band gap at the point X on the Jones-zone face and pressure-volume relation （equation of state under pressure） of Si, Ge and α-Sn using Nagy＇s static local field correction function. The results are compared with those obtained using few other local field correction functions. The present results of total energy are in good agreement with the experimental data. Bulk modulus calculated by Nagy＇s screening function is perfectly matching with the experimental results for Ge and α-Sn. Some deviation is found in the value of energy band gap.

Design of Calibration Experiments for Identification of Manipulator Elastostatic Parameters

The paper is devoted to the elastostatic calibration of industrial robots, which is used for precise machining of large-dimensional parts made of composite materials. In this technological process, the interaction between the robot and the workpiece causes essential elastic deflections of the manipulator components that should be compensated by the robot controller using relevant elastostatic model of this mechanism. To estimate parameters of this model, an advanced calibration technique is applied that is based on the non-linear experiment design theory, which is adopted for this particular application. In contrast to previous works, it is proposed a concept of the user-defined test-pose, which is used to evaluate the calibration experiments quality. In the frame of this concept, the related optimization problem is defined and numerical routines are developed, which allow generating optimal set of manipulator configurations and corresponding forces/torques for a given number of the calibration experiments. Some specific kinematic constraints are also taken into account, which insure feasibility of calibration experiments for the obtained configurations and allow avoiding collision between the robotic manipulator and the measurement equipment. The efficiency of the developed technique is illustrated by an application example that deals with elastostatic calibration of the serial manipulator used for robot-based machining.

ELT Professionals＇ Perceptions on Self-Image： A Comparison Between Gender

The study is conducted to examine the differences of gender perception among educators who are teaching in local higher learning institutions in Malaysia, in viewing their roles as the ＇~teacher＂. Several higher learning institutions were randomly targeted. Several researchers were involved in the data collection by means of using questionnaires in the survey over a period of several weeks. The questionnaires were used to fred out about their academic and professional backgrounds, requiring them to list their roles pertinent to their experiences in teaching, ranked them and provided the rationale behind the choices made. Twenty-five samples were collected to scrutinize the data by categorizing the information according to gender and teaching experiences and recording the frequencies of answers. From the study, it is found that regardless of gender and teaching experiences, most participants would consider themselves as ＂Provider of knowledge＂, followed by ＂N^r＂, especially those who are relatively new in teaching. There is also an indication that teacher＇s experiences and gender might affect their perception in mirroring themselves. A larger scale of study is needed in validating the findings of this study for it to be empirical, thus promoting in-depth investigations in viewing whether gender and cultural background may be vital factors that has profound effects towards their professionalism. It is hoped that future studies will shed some light to this rather controversial claims.

Method study and uncertainty analysis of calibration coefficients validation based on the Inner Mongolia test site

Calibration coefficients validation is the foundation for ascertaining the sensor performance and carrying out the quantitative application.Based on the analysis of the differences between the calibration and validation,two calibration coefficients validation methods were introduced in this paper.Taking the HJ-1A satellite CCD1 camera as an example,the uncertainties of calibration coefficients validation were analyzed.The calibration coefficients validation errors were simulated based on the measured data at an Inner Mongolia test site.The result showed that in the large view angle,the ground directional reflectance variation and the atmospheric path variation were the main error sources in calibration coefficients validation.The ground directional reflectance correction and atmospheric observation angle normalization should be carried out to improve the validation accuracy of calibration coefficients.

A Reduced Basis Approach for Some Weakly Stochastic Multiscale Problems

In this paper,a multiscale problem arising in material science is considered.The problem involves a random coefficient which is assumed to be a perturbation of a deterministic coefficient,in a sense made precisely in the body of the text.The homogenized limit is then computed by using a perturbation approach.This computation requires repeatedly solving a corrector-like equation for various configurations of the material.For this purpose,the reduced basis approach is employed and adapted to the specific context.The authors perform numerical tests that demonstrate the efficiency of the approach.

Efficient splitting schemes for magneto-hydrodynamic equations

We present in this paper several efficient numerical schemes for the magneto-hydrodynamic(MHD)equations. These semi-discretized(in time) schemes are based on the standard and rotational pressure-correction schemes for the Navier-Stokes equations and do not involve a projection step for the magnetic field. We show that these schemes are unconditionally energy stable, present an effective algorithm for their fully discrete versions and carry out demonstrative numerical experiments.