He-Ne激光辐照蚕豆根尖引起细胞染色体变异的研究

采用低功率He-Ne激光辐照蚕豆的根尖,控制辐照剂量.用光学显微摄影系统观察统计细胞有丝分裂活性和染色体变异.发现了受激光辐照样品根尖细胞有丝分裂活性增强,有染色体发生结构变异的现像.分析讨论了He-Ne激光辐照引起染色体变异情况及诱发基因突变的可能性.     

基于Web挖掘的个性化学习系统

随着Internet的深入发展和不断的普及,Web已经成为人们获取信息,进行学习的最重要的手段之一.但是,目前Web系统只为所有用户提供相同的服务,而Web用户的需求却千差万别,用户希望Web系统能够根据他们的不同特性提供个性化的服务.普通的学习系统已经不能适应他们的学习,不能体现他们的个性化.因此,根据他们的不同特性开发个性化的学习系统已变得相当重要.     

分裂孔径发射阵列接收BP算法方位分辨率分析

方位向上的合成孔径可通过接收天线阵列各单元顺序接收来实现,因此研究合理有效的天线配置方式和工作模式具有重要意义.本文基于固定孔径BP成像模型,推导了单发射天线配置和分裂孔径发射配置下方位分辨率的计算公式,从理论上证明了后者比前者的方位分辨率提高了一倍,具有与传统单站SAR相近的方位分辨率.理论计算和仿真结果的一致性验证了所提出的方位分辨率估算方法的正确性,可为天线配置的选择及设计提供理论依据.     

中心局搬迁中SDH传输网的割接组网方案

本文介绍了某中心局搬迁中SDH传输网的割接组网方案.     

新型红外硅微电流光电池的研制

利用ＰＮ结的光生伏特效应,采用集成电路的工艺技术和特殊处理方法,研制成功了短路电流大于１０μＡ,开路电压大于８Ｖ的红外硅微电流光电池。     

指纹图像细化算法的研究

指纹识别是一种重要的生物特征鉴别技术。随着计算机技术的不断发展,自动指纹识别系统得到广泛的应用。因此进一步提高指纹识别的性能具有十分重要的意义,而指纹图像增强在指纹图像预处理过程中非常重要,直接影响指纹识别的识别率和识别速度。对指纹图像的细化算法进行了较深入的研究,分析了OPTA算法并且在OPTA算法的基础上,重新构建了细化模板,提出了一种新的细化算法.经过实验证明,该算法能够很好地满足细化的要求,细化完全彻底,细化以后的指纹骨架在纹线中心线,并保持了纹线原有的拓扑结构和细节特征,而且光滑无毛刺,运算速度也很快。     

Bulk Nanostructured Thermoelectric Materials: Preparation,Structure and Properties

Bulk nanostructured materials have recently emerged as a new paradigm for improving the performance of existing thermoelectric materials. Here, we fabricated two kinds of bulk nanostructured thermoelectric materials by a bottom-up strategy and an in situ precipitation method, respectively. Binary PbTe was fabricated by a combination of chemical synthesis and hot pressing. The grain sizes of the hot pressed bulk samples varied from 200 nm to 400 nm, which significantly contributed to the reduction of thermal conductivity due to the enhanced boundary phonon scattering. The highest figure of merit ZT of the binary PbTe sample reached 0.8 at 580 K. Mg₂(Si,Sn) solid solutions have shown great promise for thermoelectric application, due to good thermoelectric properties, non-toxicity, and abundantly available constituent elements. The nanoscale microstructure observation of the compounds showed the existence of nanophases formed in situ, which is believed to be related to the relatively low lattice thermal conductivity in this material system. The highest ZT of Sb-doped Mg₂(Si,Sn) samples reached 1.1 at 770 K.     

Scalable coding of encrypted images

This paper proposes a novel scheme of scalable coding for encrypted images. In the encryption phase, the original pixel values are masked by a modulo-256 addition with pseudorandom numbers that are derived from a secret key. After decomposing the encrypted data into a downsampled subimage and several data sets with a multiple-resolution construction, an encoder quantizes the subimage and the Hadamard coefficients of each data set to reduce the data amount. Then, the data of quantized subimage and coefficients are regarded as a set of bitstreams. At the receiver side, while a subimage is decrypted to provide the rough information of the original content, the quantized coefficients can be used to reconstruct the detailed content with an iteratively updating procedure. Because of the hierarchical coding mechanism, the principal original content with higher resolution can be reconstructed when more bitstreams are received.     

An Improved Level Set for Liver Segmentation and Perfusion Analysis in MRIs

Determining liver segmentation accurately from MRIs is the primary and crucial step for any automated liver perfusion analysis, which provides important information about the blood supply to the liver. Although implicit contour extraction methods, such as level set methods (LSMs) and active contours, are often used to segment livers, the results are not always satisfactory due to the presence of artifacts and low-gradient response on the liver boundary. In this paper, we propose a multiple-initialization, multiple-step LSM to overcome the leakage and over-segmentation problems. The multiple-initialization curves are first evolved separately using the fast marching methods and LSMs, which are then combined with a convex hull algorithm to obtain a rough liver contour. Finally, the contour is evolved again using global level set smoothing to determine a precise liver boundary. Experimental results on 12 abdominal MRI series showed that the proposed approach obtained better liver segmentation results, so that a refined liver perfusion curve without respiration affection can be obtained by using a modified chamfer matching algorithm and the perfusion curve is evaluated by radiologists.     

Quantitative analysis on the computing performance improvement by parallel optical interconnection

This paper compares the optical and electrical interconnect systems by analyzing the efficiency and evaluating the total processing time, and design an experiment to demonstrate this performance promotion. With the increasing demand on large-scale parallel computing tasks, data transmission instead of data computing has become more and more important, so the rapid development of optical chip-to-chip interconnects techniques has gotten more attention. In this paper, we take fast Fourier transform (FFT) computation as an example to study whether and how the optical interconnection has influence on the computing performance, and three topology models are used to judging the transmission latency, and the relationship between the total processing time and the FFT points is also under investigation. Both results show parallel optical interconnection can bring large advantages in promoting computing performance. It is also found that the larger the transmission scale is, the more saving optical interconnection makes.