Automatic grading of retinal vessel caliber

New clinical studies suggest that narrowing of the retinal blood vessels may be an early indicator of cardiovascular diseases. One measure to quantify the severity of retinal arteriolar narrowing is the arteriolar-to-venular diameter ratio (AVR). The manual computation of AVR is a tedious process involving repeated measurements of the diameters of all arterioles and venules in the retinal images by human graders. Consistency and reproducibility are concerns. To facilitate large-scale clinical use in the general population, it is essential to have a precise, efficient and automatic system to compute this AVR. This paper describes a new approach to obtain AVR. The starting points of vessels are detected using a matched Gaussian filter. The detected vessels are traced with the help of a combined Kalman filter and Gaussian filter. A modified Gaussian model that takes into account the central light reflection of arterioles is proposed to describe the vessel profile. The width of a vessel is obtained by data fitting. Experimental results indicate a 97.1% success rate in the identification of vessel starting points, and a 99.2% success rate in the tracking of retinal vessels. The accuracy of the AVR computation is well within the acceptable range of deviation among the human graders, with a mean relative AVR error of 4.4%. The system has interested clinical research groups worldwide and will be tested in clinical studies.     

Fabrication of hydrophobic structures on coronary stent surface based on direct three-beam laser interference lithography

To solve the problems with coronary stent implantation, coronary artery stent surface was directly modified by three-beam laser interference lithography through imitating the water-repellent surface of lotus leaf, and uniform micro-nano structures with the controllable period were fabricated. The morphological properties and contact angle (CA) of the microstructure were measured by scanning electron microscope (SEM) and CA system. The water repellency of stent was also evaluated by the contact and then separation between the water drop and the stent. The results show that the close-packed concave structure with the period of about 12 μm can be fabricated on the stent surface with special parameters (incident angle of 3°, laser energy density of 2.2 J?cm-2 and exposure time of 80 s) by using the three-beam laser at 1 064 nm, and the structure has good water repellency with CA of 120°.     

Aseismic designs based on artificial simulations

It is commonly believed that the time-varying frequency characteristics are important for the inelastic response of structures. Design code modification means structural cost changes; therefore any change must be based on solid evidence. Although the significance of time-varying frequency characteristics to ground motion has been recognized for a while, much more in-depth research is necessary before any meaningful engineering design conclusions can be reached. We apply joint time-frequency analysis techniques to a fully non-stationary ground motion model, with both intensity and frequency being non-stationary. The chirplet-based signal approximation is used to extract the time-varying frequencies from seismic ground-motion data samples. Based on that information, we compute the frequency-dependent modulating function in the stochastic model of the evolutionary random process. We generate and compare the artificial waves based on stochastic models of a uniform modulating random process and an evolutionary random process, separately. We also investigate the importance of the time-varying frequency characteristics of earthquake ground motion through an oscillator, with a single degree of freedom and elastic-plastic material behavior     

Identification of plasma-induced damage conditions in VLSI designs

Typically, the plasma charging effect is investigated by using antenna test structures that do not replicate well enough conditions occurring in real VLSI integrated circuits (ICs). Consequently, understanding, modeling, and detection of plasma-charging-induced gate oxide damage in real IC's is often inadequate. This paper discusses a new plasma-charging monitoring technique that assesses the extent of the above problem. This technique employs a multiplexed antenna monitoring (MAM) test structure with 400+ antenna configurations to determine the dependency between IC layout and the extent of gate oxide damage. The paper reports the results of application of this technique to a 0.35-μm, 75-Å gate oxide, CMOS technology. The obtained results lead to a new definition of “antenna ratio” that is supposed to capture plasma-charging conditions in real VLSI circuits     

基于GPRS的大口径水表的数据采集系统的设计

本文介绍了基于GPRS技术的大口径水表的数据采集系统的设计与实现。系统利用GPRS的Internet接入功能,通过移动公司的网络来实现远程数据采集与数据服务器之间的无线通信。文章介绍了GPRS无线通信原理、水表数据采集系统的硬件构成、TCP/UDP/IP协议的实现以及水表数据短消息编码协议的设计     

Satellite‐based vessel Automatic Identification System: A feasibility and performance analysis

The Automatic Identification System (AIS) is a VHF communication system that provides identification/location information to vessels and shore stations by exchanging data such as position, identification, course, speed, etc. Recently, the interest in detecting and tracking ships at distances from coastlines larger than what can be accomplished by normal terrestrial VHF communications has grown, driven by requirements of long‐range applications such as better handling of hazardous cargo, improved security and countering illegal operations. This paper presents an extension of AIS to a long‐range positioning reporting through a constellation of LEO satellites. It outlines technical challenges like the high rate of message collisions from ships in the field of view of a satellite. Technical solutions are proposed at system and sub‐system level to address these challenges. A computer‐based system simulator is used to assess the system performance and carry out a high‐level system sizing. Results show that a relatively small constellation of LEO satellites can guarantee good ship position detection probability as well as a reporting time interval of a few hours. System performance aspects to be addressed in future work are the possible impact of terrestrial mobile communications interference as well as variations of the estimated traffic data. Copyright © 2009 John Wiley & Sons, Ltd.     

基于强化特征提取的视网膜血管分割

视网膜血管的分割精确率对眼科疾病和糖尿病早期诊断有着重要影响。面对现有方法在微血管与病变区域分割性能差的问题,本文提出一种强化提取血管特征的分割模型。该模型在编码部位引入多尺度特征提取残差模块(multi-scale feature extraction residual module,MFE-residual) 和多级残差空洞卷积层,用来扩展感受野,学习多层次图像特征,提高模型对血管信息的利用率;下采样和短连接部位分别融入轻量化注意力机制和多通道注意力模块,增加模型对血管的识别度,降低误分割的可能性。本文基于DRIVE和STARE两种公开数据集进行了实验,来验证改 进模型的分割能力。结果表明,两种数据上的准确率分别为0.965 2和0.971 5,灵敏度分别为0.820 5和0.825 6,与其他算法相比,分割性能更有优势。     

基于传感器的压力容器异常信息检测

对压力容器中的异常传感信息准确检测能实现压力容器故障诊断排除。针对压力容器异常传感信息宽平稳性强,检测准确度不高的问题,提出一种基于传感器鉴频特征提取的压力容器异常信息检测方法。首先对压力容器中的异常传感信息进行数据采样,对采样数据进行非线性时间序列信息流建模,采用ARMA模型分析压力容器异常信息的时频特征,结合传感器鉴频特征提取实现信号检测。仿真结果表明,采用该方法进行压力容器传感器信息检测的准确检测概率较高。     

Space-time block codes based on coordinate symmetric orthogonal designs

Space-time block codes based on coordinate symmetric orthogonal designs are proposed. Compared with space-time block codes from complex orthogonal design when the code rate is the same and the transmission rate is fixed, space-time block codes from coordinate symmetric orthogonal design with more transmit antennas can reduce the bit error rate and symbol error rate. Also these new codes have the same low decoding complexity as space-time block codes from complex orthogonal designs.     

基于可分组设计的部分重复码研究

针对最小带宽再生情形下的有效修复问题,提出了一种新型部分重复(FR,fractional repetition)码设计。该设计由外部最大距离可分(MDS,maximum distance separable)码和内部重复码组成,称为GDDBFR(group divisible design based FR)码,可以达到随机访问模式下的系统存储容量,并且能够在很大范围内选择构造参数。理论分析指出,尽管GDDBFR码采用基于表格的修复方式,但通常具有大量的节点修复选择方案。此外,实验结果表明,与传统的RS(Reed-Solomon)码和再生码相比,GDDBFR码可以显著地减少失效修复时间。     

High speed receiver designs based on surface acoustic wave devices

The principles of operation and several types of surface acoustic wave devices are reviewed. One device, the interdigital transducer device, can accomplish matched filtering for complex bandwidth-efficient phase modulations. Data speeds in excess of 120 Mb/s are accomplished with existing thin film lithography. Filters are cheap and small, and show little mismatch to the desired response. A number of receiver designs are proposed that are based on these filters. A bank-of-matched-filters approach seems superior to the Viterbi algorithm at high speeds.     

基于Zigbee的船舶状态监控系统的设计与实现

针对现有的船舶监控系统布线复杂、成本较高、维护困难等问题,并结合Zigbee无线通信特点,提出并设计了一种基于Zigbee技术的船舶状态监控系统。采用CC2530为硬件核心,并基于Z-stack协议栈进行软件开发。阐述了系统的整体构架,设计了节点的硬件组成及软件流程等关键技术问题。实验结果表明,该系统在数据采集传输、功耗等方面的性能达到了系统设计的基本要求,可广泛在船舶监控等方面推广应用。     

基于稀疏表示的船体检测方法研究

为进一步强化航道安全，解决海事CCTV人工值守、非自动化问题，提出了基于稀疏表示的船体检测方法。利用稀疏表示实现对船体的检测时，首先构建样本特征矩阵，然后利用K-SVD算法对样本特征矩阵进行学习，得到冗余字典，最后对测试样本进行重构，根据马氏距离判断测试样本属性。通过与传统方法的试验比较，实验结果表明，该算法实时性好、检测准确率高，可以很好地对CCTV视频监控的船体进行检测与跟踪，解决CCTV人工值守、非自动化问题，节省大量人力资源。     

Construction of low-density parity-check codes based on balanced incomplete block designs

This correspondence presents a method for constructing structured regular low-density parity-check (LDPC) codes based on a special type of combinatoric designs, known as balance incomplete block designs. Codes constructed by this method have girths at least 6 and they perform well with iterative decoding. Furthermore, several classes of these codes are quasi-cyclic and hence their encoding can be implemented with simple feedback shift registers.     

基于加速传感器的船舶振动检测系统设计

船舶振动是船舶与海洋结构物设计中的关键技术之一,船舶架构是一种复杂的组合弹性体,本身的振动非常复杂。不同于传统的机械式船舶振动检测设计,本系统采用嵌入式系统,运用传感器检测、实时数据处理等技术,使产品具有小型、专用、易携带、可靠性高的特点,在船舶振动检测领域有广泛的应用前景。     

Unsupervised PolInSAR classification based on optimal coherence set

Aiming to solve the misclassification problems of unsupervised polarimetric Wishart classification algorithm based on Freeman decomposition, an unsupervised Polarimetric Synthetic Aperture Radar (SAR) Interferomery (PolInSAR) classification algorithm based on optimal coherence set parameters is studied and proposed. This algorithm uses the result of Freeman decomposition to divide the image into three basic categories including surface scattering, volume scattering, and double-bounce. Then, the PolInSAR optimal coherence set parameters are used to finely divide each of the three basic categories into 9 categories, and the whole image is divided into 27 categories. Because both the Freeman decomposition result and optimal coherence set parameters indicate specific scattering characteristics, the whole image is merged into 16 categories based on physical meaning. At last, the Wishart cluster is employed to obtain the final classification result. To preserve the purity of scattering characteristics, pixels with similar scattering characteristics are restricted to be classified with other pixels. The final classification results effectively resolve the misclassification problem, not only the buildings can be effectively distinguished from vegetation in urban areas, but also the road is well distinguished from grass. In this paper, the E-SAR PolInSAR data of German Aerospace Center (DLR), are used to verify the effectiveness of the algorithm.     

基于最优弧的激光光斑中心检测算法

激光光斑中心检测是光学测量中常用的关键技术,广泛应用在光学测量系统、光路自动准直系统、激光通信目标跟踪中。为了提高光斑中心及半径的检测精度和抗干扰性,提出了一种基于最优弧的激光光斑中心检测算法,该算法首先根据圆的对称性排除了受干扰边缘,然后选取对称性好的弧线作为最优弧,最后以最优弧的数据作为拟合数据,利用最小二乘法计算出圆的中心及半径,并与其他算法进行了比较。实验表明,该算法对于中心和半径的定位精度高、计算速度快,并有效地提高了中心检测的抗干扰性,适用于在线实时检测。     

基于Zadoff-Chu矩阵的最优码本构造方法

具有低相关性质的码本在同步码分多址系统(CDMA)、量子信息理论以及压缩感知领域都有重要应用。为扩展码本数量,放宽了变换矩阵的限制条件。基于Zadoff-Chu矩阵,利用差集、几乎差集以及有限域特征和构造了新的码本,得到的码本依照Welch界限或Levenstein界是最优或几乎最优的。通过实验仿真发现,基于该类码本构造的确定性测量矩阵在压缩感知中具有良好的性能。     

分数阶域最优滤波算法

随着社会发展,对于语音信号的增强愈显重要,本文通过对传统傅里叶变换与分数阶傅里叶变换对比研究,充分体现分数阶域的时频分析特性的优越性。并使用一段语音在以均方误差准则下,选取最佳变换阶次,并进行该阶次下的分数阶傅里叶变换。通过MATLAB仿真证明,在关于变换阶次的局部区间内存在着某最佳变换阶次,其增强效果明显优于传统谱减...     

基于模态分析的印制电路板抗振优化设计

在无人机内狭小空间和振动环境下,利用ANSYS有限元软件建立印制电路板模型,在四周固定边界条件下对印制电路板进行模态分析,获得印制电路板的4阶固有频率和振型。基于模态分析结果,对印制电路板进行优化抗振设计。结果表明,优化设计后电路板的一阶固有频率提高了近90 Hz,找到了适合狭小空间下的提高电路板稳定性的方法。