基于MAX114的高速数据采集系统设计

该系统运用简单的MCS-51单片机来实现复杂的数据采集与还原电路.采用89C51单片机作为中心控制单元,由ADC芯片将数字信号转换为模拟信号,经过高速缓存芯片后,由DAC芯片进行数模转换,从而实现数据的高速采集及还原.     

基于RTLinux的开放式数控运动控制器设计

研究了RTLinux在开放式数控运动控制器中的应用.在介绍RTLinux体系结构的基础上,并详细阐述了运动控制器的软、硬件结构.实践证明,将RTLinux应用于开放式数控系统满足了实时控制系统对响应的快速性、时间的精确性和控制的可预测性的要求.     

The gynecologic contribution to intestinal obstruction in females

This study was done to identify the cause of intestinal obstruction with particular emphasis on the gynecologic and perioperative related causes. All medical records from females with the discharge diagnosis "intestinal obstruction" from 1988 to 1991 at Columbia Presbyterian Medical Center were requested. The patient series consisted of the first 100 completed charts received. Forty-eight percent of those patients with intestinal obstruction had experienced a previous gynecologic or obstetric event that could account for the obstruction. Primarily, the gynecologist managed more than 20 percent of all female patients with intestinal obstruction. The most common causative factors contributing to intestinal obstruction were postoperative adhesions (59 percent) and tumor (17 percent). Fifty-six percent of the patients with intestinal obstruction associated with postoperative adhesions had a history of previous gynecologic and obstetric operation. Hysterectomy was the most common previously performed operation. In this series, cesarean section was less likely and myomectomy was more likely to cause subsequent intestinal obstruction than expected. Of 59 female patients with postoperative adhesions associated with intestinal obstruction, 31 had the original operative reports available for analysis. Eleven of these patients were taken to the operating room for management of the obstruction. In the nine patients who had surgical peritoneal closure in the original operation, the adhesions causing the obstruction were always to the site of reperitonealization. In the two patients in whom the peritoneum was left open, the adhesions causing obstruction were remote from the site of spontaneous reperitonealization. In an unselected patient series of intestinal obstruction, a history of previous gynecologic pathology is a significant factor contributing to the total number of instances of intestinal obstruction in females. Also, surgical peritoneal closure may result in an increase in the incidence of intestinal obstruction.     

Mosaic organization of DNA nucleotides

Long-range power-law correlations have been reported recently for DNA sequences containing noncoding regions. We address the question of whether such correlations may be a trivial consequence of the known mosaic structure ("patchiness") of DNA. We analyze two classes of controls consisting of patchy nucleotide sequences generated by different algorithms--one without and one with long-range power-law correlations. Although both types of sequences are highly heterogenous, they are quantitatively distinguishable by an alternative fluctuation analysis method that differentiates local patchiness from long-range correlations. Application of this analysis to selected DNA sequences demonstrates that patchiness is not sufficient to account for long-range correlation properties.     

Long-range correlation properties of coding and noncoding DNA sequences: GenBank analysis

An open question in computational molecular biology is whether long-range correlations are present in both coding and noncoding DNA or only in the latter. To answer this question, we consider all 33301 coding and all 29453 noncoding eukaryotic sequences--each of length larger than 512 base pairs (bp)--in the present release of the GenBank to dtermine whether there is any statistically significant distinction in their long-range correlation properties. Standard fast Fourier transform (FFT) analysis indicates that coding sequences have practically no correlations in the range from 10 bp to 100 bp (spectral exponent beta=0.00 +/- 0.04, where the uncertainty is two standard deviations). In contrast, for noncoding sequences, the average value of the spectral exponent beta is positive (0.16 +/- 0.05) which unambiguously shows the presence of long-range correlations. We also separately analyze the 874 coding and the 1157 noncoding sequences that have more than 4096 bp and find a larger region of power-law behavior. We calculate the probability that these two data sets (coding and noncoding) were drawn from the same distribution and we find that it is less than 10(-10). We obtain independent confirmation of these findings using the method of detrended fluctuation analysis (DFA), which is designed to treat sequences with statistical heterogeneity, such as DNA's known mosaic structure ("patchiness") arising from the nonstationarity of nucleotide concentration. The near-perfect agreement between the two independent analysis methods, FFT and DFA, increases the confidence in the reliability of our conclusion.     

光电平台MEMS陀螺性能及滤波算法的Allan方差评价

光电稳定平台被广泛应用于火控、侦察、制导等武器系统中,具有提供重要的态势感知、监视、瞄准和搜跟能力。随着光电技术的发展,光电稳定平台变得更加精准和轻便小巧。MEMS陀螺具有体积小、重量轻、成本低、可靠性高、测量范围大的优点,使其已经成为小体积、低成本光电稳定平台的首选惯性传感器。但在光电稳定平台设计时,选用MEMS陀螺和陀螺滤波处理就成了首要的问题。本文首先介绍了基于Allan方差评价MEMS陀螺随机漂移误差的方法,描述了4种常用的陀螺滤波算法,然后基于Allan方差详细地分析了这几种滤波器的应用特性和滤波器参数对滤波性能的影响。可以看出,使用Allan方差可以很好地评估MEMS陀螺和滤波器性能,指导陀螺滤波器选型和滤波参数配置,该评估方法可有效地解决光电稳定平台设计阶段的陀螺选型和滤波器选型。     

考虑天气类型和相似日的IWPA-LSSVM光伏发电功率预测

为了提高光伏发电功率预测精度,根据不同天气类型下光伏输出功率特点,确定光伏发电功率预测模型的输入量。针对狼群算法（wolf pack algorithm,WPA）缺陷,对狼群游走位置和奔袭步长进行改进,得到改进狼群算法（improved wolf pack algorithm,IWPA）,并通过IWPA对最小二乘支持向量机（least squares support vector machine,lSSVM）进行优化,建立了考虑天气类型和相似日的IWPA-LSSVM光伏发电功率预测模型。采用不同天气类型下的光伏发电功率数据进行仿真,结果表明：无论是晴天、多云还是阴雨天气,所提方法预测精度更高,回归拟合时的误差波动更小。     

弱电网下直驱风机网侧换流器建模及稳定运行控制策略分析

直驱风机网侧换流器可能因与弱电网动态交互引发系统失稳问题。为探究系统的交互机理,保证系统的稳定运行,首先对直驱风机并网模型进行了合理简化,建立了弱电网下直驱风机网侧换流器与电网交互的单输入单输出传递函数模型,并应用经典频域判据进行稳定性分析,探究电气与控制环节对于系统稳定性的影响。其次在分析锁相环导致系统失稳的原因基础上,提出了一种新型3阶锁相环控制结构设计方案,并对锁相环参数进行了多目标优化设计。结果表明,3阶锁相环具有更好的谐波衰减效果,在短路比为2的极弱电网下仍可以保持稳定运行。最后基于MATLAB/Simulink仿真平台验证了所提设计方案的有效性。     

基于微气泡散射的水下无线光通信复合信道建模

海浪、船舶尾流以及海洋生物游动与呼吸等原因会导致海水中存在大量的气泡,气泡群带来的散射效应对光信号的水下传输具有重要影响,但典型的水下无线光通信信道模型一般不考虑气泡群带来的负面效应。为了进一步完善传统的水下无线光通信信道模型,本文利用Mie散射理论分析海水中的微气泡及微气泡群光散射特性,基于蒙特卡洛法建立包含气泡散射的复合海水信道模型,分析不同海水水质、气泡密度、链路距离等参数条件下接收端的光学特性和信号特性。结果表明:当链路距离为5m时,随着气泡密度的增大,接收端光斑的弥散程度加剧,其面积可增至初始大小的3～5倍,中心能量也显著降低,最多可降至最大值的05;当链路距离为10～40m时,气泡群的存在以及链路距离的增长会导致接收端第一次接收到光子的时间延长约10～200ns,且使脉冲展宽值增大;当链路距离为2～10m时,气泡群密度的增大最多可使归一化接收功率降低至初始值的0004,但随着水质的恶化,其他粒子含量提高,气泡群对接收功率的影响逐渐减小。该研究可以为水下无线光通信系统的设计和理论分析提供参考。     

多尺度特征融合U-Net的遥感影像黑臭水体智能检测

研究采用卫星遥感技术获取高分辨率遥感影像水体样本数据集,基于深度卷积神经网络从高分辨遥感影像中提取水体并进行黑臭水体智能监测,提出了一种改进U-Net的黑臭水体检测网络模型(IWDNet)。基于U-Net结构引入跳跃式多尺度特征融合,结合通道注意力机制、卷积注意力模块、通道与空间注意力机制生成不同多尺度特征融合注意力机制(MFFAM)模块进行对比,并引入空洞卷积扩大网络感受野,最终实现黑臭水体的识别检测。实验证明：基于跳跃式多尺度融合与CBAM注意力机制的黑臭水体检测网络(MFFCBAM-IWNet)模型有效提升了识别精度,在高分辨遥感影像水体样本数据集上表现最佳,总体精度达98.56%,Kappa系数达0.978 4。