裁剪频谱的线性系统DFT反卷积算法

在对传统求冲击响应方法的误差进行分析的基础上,提出了一种新的卷积反演算法。该算法通过提高采样率后对频谱进行裁剪,然后运用zoom运算降低采样率,再通过反卷积求出系统的冲击响应。仿真实验证明,该算法能有效地避免量化误差的放大和迁移所造成的影响,比传统方法和最小二乘法具有更小的误差。     

二阶全展开ETG有限元方法在方腔自然对流模拟中的应用

应用二阶全展开ETG有限元方法离散求解N-S方程和能量方程,并以零初值方腔自然对流问题为例进行了数值模拟。计算了不同瑞利数条件下方腔自然对流的流场和温度场,最终达到的稳态结果与标准数值解符合很好,并且较好地反映了流场和温度场的时间演化过程,特剐是捕捉到了分叉前后流场中涡结构的变化。结果表明二阶全展开ETG有限元方法有较好的稳定性和较高的精度,在计算温度场和流场的时间演化过程方面有一定优点。     

Construction of self‐organizing algorithms for vector quantization

Vector quantization is used for both storage and transmission of speech and image data, and an algorithm that minimizes the distortion error is often required. To obtain the minimum distortion error in neural networks for vector quantization, corrective competitive learning has been introduced. In a large number of algorithms, self‐creating neural networks and self‐deleting neural networks have performed well. In this paper, we improve the self‐deleting neural network and propose a generalized algorithm combining the creating and deleting neural networks. First, a few weight (reference) vectors are prepared, the self‐creating algorithm is applied, and vectors are created automatically. Next, the self‐deleting algorithm is applied, and weight vectors are deleted sequentially to reach a predetermined number. Experimental results show the effectiveness of the proposed algorithm. © 1999 Scripta Technica, Electr Eng Jpn, 127(1): 47–55, 1999     

压力传感器静态校准模型研究

介绍了压力传感器静态校准模型及方法的最新研究.由于传统的模型及方法已不能满足现代科学对数据精度与曲线匹配性高的要求,需要采取一种有效的、低误差的改进校准方案.而且随着传感器特性的深入研究,曲线的匹配程度对传感器非线性特性的依赖性逐渐增强,因此改进以往的线性数据拟合是很必要的.使用虚拟仪器软件LabWindows/CVI与Matlab结合设计的软件易于使用,建议在校准部门推广使用.     

Position computation models for high-speed train based on support vector machine approach

High-accuracy positioning is not only an essential issue for efficient running of high-speed train (HST), but also an important guarantee for the safe operation of high-speed train. Positioning error is zero when the train is passing through a balise. However, positioning error between adjacent balises is going up as the train is moving away from the previous balise. Although average speed method (ASM) is commonly used to compute the position of train in engineering, its positioning error is somewhat large by analyzing the field data. In this paper, we firstly establish a mathematical model for computing position of HST after analyzing wireless message from the train control system. Then, we propose three position computation models based on least square method (LSM), support vector machine (SVM) and least square support vector machine (LSSVM). Finally, the proposed models are trained and tested by the field data collected in Wuhan-Guangzhou high-speed railway. The results show that: (1) compared with ASM, the three models proposed are capable of reducing positioning error; (2) compared with ASM, the percentage error of LSM model is reduced by 50.2% in training and 53.9% in testing; (3) compared with LSM model, the percentage error of SVM model is further reduced by 38.8% in training and 14.3% in testing; (4) although LSSVM model performs almost the same with SVM model, LSSVM model has advantages over SVM model in terms of running time. We also put forward some online learning methods to update the parameters in the three models and better positioning accuracy is obtained. With the three position computation models we proposed, we can improve the positioning accuracy for HST and potentially reduce the number of balises to achieve the same positioning accuracy.     

一种NTC热敏电阻校正方程的试验研究

为了校正NTC热敏电阻的校正方程,提高测温精度。通过对传统的指数方程进行线性变换,得到一种新的NTC热敏电阻温度计R-T特性关系,对此关系进行多阶最小二乘拟合,利用误差评判原理,确定最适合的NTC热敏电阻的校正方程。并且实际验证了此校正方程的测温精度可以满足更高精度要求的需要。     

火花源原子发射光谱法测定铸铁中碳的不确定度评定

对火花源原子发射光谱法测定铸铁中碳含量的不确定度产生原因进行了分析,根据最小二乘法原理拟合工作曲线,确定了二元线性回归拟合引入的标准不确定度,并对一个铸铁样品中碳含量测定结果的不确定度进行了评定。     

成像系统均方根半径及调制传递函数的计算

本文给出了逸出电子在最佳像面上落点的均方根半径值及直观图形表示;以实际管型为例,βeta分布取β_1,8至β_2,1,检验了均方根半径的变化状况,证明了理论分析的正确性;从数据上检验了均方根半径不仅可以表征系统鉴别率特性的好坏,而且和调制传递函数的优劣在像面上是一一对应的;证明了用指数形式表示系统的调制传递函数具有计算速度快、形式简洁、使用方便,并且在低频空间具有足够的精度.     

Revealing the Impact of F4‐TCNQ as Additive on Morphology and Performance of High‐Efficiency Nonfullerene Organic Solar Cells

Fluorinated molecule 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4‐TCNQ) and its derivatives have been used in polymer:fullerene solar cells primarily as a dopant to optimize the electrical properties and device performance. However, the underlying mechanism and generality of how F4‐TCNQ affects device operation and possibly the morphology is poorly understood, particularly for emerging nonfullerene organic solar cells. In this work, the influence of F4‐TCNQ on the blend film morphology and photovoltaic performance of nonfullerene solar cells processed by a single halogen‐free solvent is systematically investigated using a set of morphological and electrical characterizations. In solar cells with a high‐performance polymer:small molecule blend FTAZ:IT‐M, F4‐TCNQ has a negligibly small effect on the molecular packing and surface characteristics, while it clearly affects the electronic properties and mean‐square composition variation of the bulk. In comparison to the control devices with an average power conversion efficiency (PCE) of 11.8%, inclusion of a trace amount of F4‐TCNQ in the active layer has improved device fill factor and current density, which has resulted into a PCE of 12.4%. Further increase in F4‐TCNQ content degrades device performance. This investigation aims at delineating the precise role of F4‐TCNQ in nonfullerene bulk heterojunction films, and thereby establishing a facile approach to fabricate highly optimized nonfullerene solar cells.     

Improved least mean square algorithm based in satellite multi-beamforming

High-throughput satellites use multi-beam technology to achieve polarization isolation and spatial isolation to reuse frequency resources,resulting in increased traffic capacity,but this presents a higher demand for fast adaptive beamforming algorithms.In order to solve the shortcoming that the convergence rate and steady-state error can not be satisfied simultaneously when using the LMS algorithm,an improved least mean square algorithm was proposed,which used the statistical average gradient update to solve the problem of the formation of beam instability caused by the instantaneous gradient,which can speed up at the beginning of the beamforming and maintain a small error value after the convergence has reached a steady state.The use of 61-element hexagonal array phased array antenna to form a 7-point beam in an environment where high-throughput satellites have a strong rainfall attenuation was considered.The results show that the improved algorithm can greatly improve the convergence speed and obtain better steady state performance under the condition of only a small increase in complexity,which can be applied to high-throughput satellite beamforming technology with severe inter-beam co-channel interference in emergency communication scenarios.