材料性质和试样几何形状对应力三维度的影响

为研究应力三维度和塑性应变对金属材料微孔聚合型损伤发展和延性断裂过程的影响,用有限元法计算16Mn钢和两种铝合金材料不同缺口根半径拉伸试样的应力、应变分布. 结果表明:缺口根半径越小,最小横截面上周向和径向应变相差越大且越不均匀,并导致最小横截面上的应力三维度与Bridgman公式预测结果不一样. 材料性质和试样几何形状对应力三维度的影响很大:缺口根半径相同的3种材料试样最小横截面的应力三维度分布形态相似,但应力三维度峰值及其所处位置有所不同;同种材料的试样缺口根半径不同,应力三维度分布形态也不同.     

改进的随机圆检测算法

介绍了一种基于随机圆检测的改进算法。解决了随机圆检测算法随机采样阶段引入的大量无效累积和验证阶段假设圆之外的边缘点所进行的无效计算的问题,首先对边缘图像进行8邻接连通,3个随机采样点在同一个连通曲线内选择,然后利用圆的性质求得圆的参数,再应用证据收集过程来进一步验证圆的真实性,该验证过程中只考虑假设圆的外切正方形和内接正方形之间的边缘点。实验结果表明,该算法计算量小,对比改进前,检测性能有所提高,且鲁棒性也相应提高,同时能够检测圆弧和有相互重叠的多个圆。     

基于圆形约束C-V水平集的肺部CT图像病灶分割

针对肺部CT图像中圆形病灶区域的分割问题,对Chan-Vese水平集图像分割方法进行了分析和改进,提出了基于圆形约束的C-V水平集模型,进而提出了基于圆形约束水平集的肺部图像病灶分割算法,解决了图像中大小不同的多圆检测问题。对合成图像和实际临床肺部CT图像进行了分割实验,结果表明,该方法可以较好地分割出图像中的多个圆形区域,算法具有较好的抗噪性,实现速度较快,有利于实现肺部CT图像肺结节自动检测。     

A variable-precision square root implementation for field programmable gate arrays

Applications requiring variable-precision arithmetic often rely on software implementations because custom hardware is either unavailable or too costly to build. By using the flexibility of the Xilinx XC4010 field programmable gate arrays, we present a hardware implementation of square root that is easily tailored to any desired precision. Our design consists of three types of modules: a control logic module, a data path module to extend the precision in 4-bit increments, and an interface module to span multiple chips. Our data path design avoids the common problem of large fan-out delay in the critical path. Cycle time is independent of precision, and operation latency can be independent of interchip communication delays.Notation S_j square root digit of weight 2^–j - S _j {–1, 0, 1} - S[j] computed square root value as of stepj - S _j ^s sign bit in the representation ofS _j in sign and magnitude form - S _j ^m magnitude bit in the representation ofS _j in sign and magnitude form - w[j] residual at stepj in two's complement carry-save representation - a sum vector in the carry-save representation of 2w[j] - b carry vector in the carry-save representation of 2w[j] - a _i bit of weight 2^–i in the sum vector,a - b_i bit of weight 2^–i in the carry vector,b - T[j]=–S[j – 1]s_j – s _j ² 2^–(j+1) T _i bit of weight 2^–i inT     

用于高能物理实验电子读出芯片的低噪声锁相环芯片设计

基于TSMC 180 nm工艺设计并流片测试了一款用于高能物理实验的电子读出系统的低噪声、低功耗锁相环芯片。该芯片主要由鉴频鉴相器、电荷泵、环路滤波器、压控振荡器和分频器等子模块组成,在锁相环电荷泵模块中,使用共源共栅电流镜结构精准镜像电流以减小电流失配和用运放钳位电压进一步减小相位噪声。测试结果表明,该锁相环芯片在1.8 V电源电压、输入50 MHz参考时钟条件下,可稳定输出200 MHz的差分时钟信号,时钟均方根抖动为2.26 ps(0.45 mUI),相位噪声在1 MHz频偏处为-105.83 dBc/Hz。芯片整体功耗实测为23.4 mW,锁相环核心功耗为2.02 mW。     

基于Conv1d-LSTM模型的能源分配预测

能源分配问题往往与其所在区域环境有关,能源分配的预测可以通过当地环境因素数据来推测之后对该区域的能源分配数值,最大程度上分配好能源. LSTM网络预测短期效果良好,但预测较长时期的数据会导致误差积累,速度慢且准确性差; Informer是近期新提出的能源预测算法模型,速度快但在该任务上预测能力不够.本文提出Conv1d-LSTM模型,预测结果优于上述两个模型,具有更低的平均绝对误差和均方根误差.     

基于集成经验模态分解和最小二乘双支持向量回归机的风速预测算法研究

为有效解决风电大规模并网过程中面临的并网难和弃风等问题,实现可再生能源大规模平滑并网并保证大电网的安全稳定运行,采用集成经验模态分解(ensemble empirical mode decomposition,EEMD)和最小二乘双支持向量回归机(least square twin support vector regression,LSTSVR)算法进行风电场风速预测。分别介绍了LSTSVR、EEMD及自适应变异粒子群算法原理。给出基于EEMD和LSTSVR的风速预测流程,以安徽女儿岭风电场测风声雷达30、70 m处风速采样数据为例,开展基于EEMD和LSTSVR的风速预测算法验证,预测结果误差分析表明:基于EEMD+LSTSVR+自适应变异粒子群算法可以实现风电场风速的高精度预测。     

基于多尺度圆周频率滤波与卷积神经网络的遥感图像飞机目标检测方法研究

针对遥感图像飞机目标检测因目标尺度不一存在漏警、虚警等问题,该文基于遥感图像中飞机目标形状特征和灰度变化特点提出了一种多尺度圆周频率滤波(MSCFF)与卷积神经网络(CNN)相结合的MSCFF+CNN飞机目标自动检测算法.该算法首先采用多尺度圆周频率滤波器滤除遥感图像复杂背景,实现不同尺度飞机目标候选区域提取;然后,通过构建卷积神经网络(CNN)模型实现候选区域有效分类,最终精确确定飞机目标位置.最后,基于获取的真实遥感图像进行目标检测算法实验验证,经统计该算法的飞机目标检测率为94.38%,虚警率为3.76%,实验结果充分验证了该文算法的有效性,该算法可为机场监管、军事侦察等应用提供重要的技术支持.     

Application of ANFIS Model for Thailand’s Electric Vehicle Consumption

Generally, road transport is a major energy-consuming sector. Fuel consumption of each vehicle is an important factor that affects the overall energy consumption, driving behavior and vehicle characteristic are the main factors affecting the change of vehicle fuel consumption. It is difficult to analyze the influence of fuel consumption with multiple and complex factors. The Adaptive Neuro-Fuzzy Inference System (ANFIS) approach was employed to develop a vehicle fuel consumption model based on multivariate input. The ANFIS network was constructed by various experiments based on the ANFIS Parameter setting. The performance of the ANFIS network was validated using Root Mean Square Error (RMSE) and Mean Average Error (MAE) which related to the setting of ANFIS parameters. The experimental results indicated that the training data sample, number, and type of membership functions are the most important factor affecting the performance of the ANFIS network. However, the number of epochs does not necessarily significantly improve the system performance, too many the number of epochs setting may not provide the best results and lead to excessive responding time. The results also demonstrate that three factors, consisted of the engine size, driving speed, and the number of passengers, are important factors that influence the change of vehicle fuel consumption. The selected ANFIS models with minimum error can be properly and efficiently used to predict vehicle fuel consumption for Thailand’s road transport sector.     

圆环式径向换能器声压分布及其指向性

根据圆环式径向换能器的对称性,定性分析了其声压分布性质,提出将辐射面镶在无限幕上并向辐射面的外法线所在的半空间辐射声场的分析模型;根据惠更斯原理,推导了圆环式径向换能器辐射声场远场区的声压分布以及指向性函数;通过MATLAB绘制指向性函数曲线,研究换能器的有效工作段长度、外径以及辐射频率对其指向性的影响。结果表明,当换能器的尺寸一定时,辐射频率增大,指向性增强;当换能器的辐射频率和外径一定时,换能器的有效工作段长度增大,指向性增强;当换能器的辐射频率和有效工作段长度一定时,外径对声场指向性的影响不大。结合有限元分析软件COMSOL Multiphysics,仿真声波在混凝土中的传播,进一步验证了以上结论。