蚁群算法在全方向M型心动图检测中的应用与研究

为了解决传统边缘检测算法对全方向M型心动图检测效果差的问题,根据基于蚁群算法边缘检测的思想,提出一种基于改进的蚁群算法的边缘检测算法。根据心动图间接来源于CT图的原理,一幅心动图中包含目标、背景、边界和噪声等内容,因此采用传统的边缘检测算法的效果并不理想。这里在传统蚁群算法边缘检测的基础上,根据心动图的特点,采取改进的转移规则和信息素更新策略,以提高检测精度和适应性。再逐步细化,使用蚂蚁算法进行详细的检测,得到最佳的运动曲线。实验结果表明,该算法可以获得精确的运动曲线,其结果能够比传统的方法获得更丰富更真实的心动图运动细节信息,为医生的诊断提供更多信息。     

上海科研机构向公众开放情况调研分析

随着社会经济的飞速发展,人们的文化素养也得到了很大的提升,人们在社会中参与公共事务的愿望不断增强,对科技知识的要求也越来越高。本调研以2013年科技周期间上海向公众开放的科研机构实验室为调查样本,了解其对公众开放的情况以及开放效果,以期对今后相关工作提供切实可行的建议。调研发现虽然开放机构涉及各个专业,且展示形式多样,但开放期间的观众流量仍然偏低,建议在以后的开放活动中,应加大对活动的宣传力度;开放机构应与周边相关机构联动以扩大影响力;同时要对开放效果好的实验室予以奖励,以提高相关机构对开放活动的积极性。     

A Role Based Privacy-Aware Secure Routing Protocol for Wireless Mesh Networks

Wireless Mesh Networks (WMNs) have drawn much attention for emerging as a promising technology to meet the challenges in next generation networks. Security and privacy protection have been the primary concerns in pushing towards the success of WMNs. There have been a multitude of solutions proposed to ensure the security of the routing protocol and the privacy information in WMNs. However, most of them are based on the assumptions that all nodes cooperate with routing and forwarding packets and the attacks are from outside. In order to defend against the internal attacks and to achieve better security and privacy protection, this paper proposes a role based privacy-aware secure routing protocol (RPASRP), which combines a new dynamic reputation mechanism with the role based multi-level security technology and a hierarchical key management protocol. Simulation results show that RPASRP implements the security and privacy protection against the inside attacks more effectively and efficiently and performs better than the classical hybrid wireless mesh protocol in terms of packet delivery ratio and average route length.     

Two-branch wavelet denoising for accurate spectrum sensing in cognitive radios

In order to detect the unused spectrum bands (the spectrum holes) efficiently in cognitive radios with low signal-to-noise radio (SNR), we propose to adopt two independent branches of wavelet to detect the singularities of the received signals’ power spectrum density (PSD). The sensing structure is flexible such that we can use one or two branches to cope with different SNRs. Under low SNR condition, each branch uses distinct characteristics between noise and signals in the wavelet transform to eliminate the singularities generated by the noise. By using bandpass filter to calculate PSD values of the subbands which are distinguished by the signal’s singularities, the subband with the minimum PSD value among all of the subbands could be found. Then, the results of the two branches are merged and analyzed in order to make the final decision. Finally, we use signal reconstruction to further remove the noise and then accurately detect the spectrum holes. When the SNR is high, only one branch through the denoising procedure is needed to get accurate sensing result. Our simulation results show that the two-branch wavelet method is more accurate than conventional approaches under given SNRs.     

Fully Secure Identity Based Key-Insulated Signcryption in the Standard Model

To achieve unforgeability and confidentiality simultaneously, signcryption has been introduced with better efficiency than the signature-then-encryption approach in terms of computational costs and communication overheads. Taking the key leakage into account, it is desirable to design identity-based key-insulated signcryption (ID-KI-SC) scheme to reduce the damage caused by the secret key leakage. In this paper, we have shown that all of the existing ID-KI-SC scheme can not offer either the unforgeability property or the indistinguishability property. Furthermore, an improved scheme along with the formal security proof in the standard model has been suggested in this paper. In view of computational cost and communication overhead, our scheme is amongst the most efficient IB-SC schemes secure in the standard model.     

单面激光冲击孔壁残余应力与疲劳失效

孔结构往往会造成零件上的应力集中,降低零件的疲劳寿命,激光冲击强化能够有效地缓解这一问题。在试验研究中发现采用高峰值压力对试件进行激光冲击强化后,试件的疲劳寿命反而降低,同时断口上的疲劳源也随之发生内移,这很可能是因为高峰值压力在孔壁内产生较大的残余拉应力而降低了小孔件的疲劳寿命。为此采用ABAQUS软件,针对不同峰值压力、载荷脉宽对7050-T7451小孔件孔壁上应力分布的影响进行研究。研究结果表明:峰值压力的提高在增大压应力层深度的同时也会增大带孔件孔壁上的拉应力,同时残余拉应力所在位置也随之发生内移;当峰值压力不同时,载荷脉宽对孔壁上应力分布的影响也会随之改变。     

有源层溅射温度对非晶铟镓锌氧薄膜晶体管电学特性的影响

The effect of active layer deposition temperature on the electrical performance of amorphous InGaZnO （a-IGZO） thin film transistors （TFTs） is investigated. With increasing annealing temperature, TFT performance is firstly improved and then degraded generally. Here TFTs with best performance defined as ＂optimized-annealed＂ are selected to study the effect of active layer deposition temperature. The field effect mobility reaches maximum at deposition temperature of 150℃ while the room-temperature fabricated device shows the best subthreshold swing and off-current. From Hall measurement results, the carrier concentration is much higher for intentional heated a-IGZO films, which may account for the high off-current in the corresponding TFT devices. XPS characterization results also reveal that deposition temperature affects the atomic ratio and Ols spectra apparently. Importantly, the variation of field effect mobility of a-IGZO TFTs with deposition temperature does not coincide with the tendencies in Hall mobility of a-IGZO thin films, Based on the further analysis of the experimental results on a-IGZO thin films and the corresponding TFT devices, the trap states at front channel interface rather than IGZO bulk layer properties may be mainly responsible for the variations of field effect mobility and subthreshold swing with IGZO deposition temperature.     

角锥棱镜相干合成激光器的自适应驱动方法

针对高功率激光器合成效率低、能量不集中的问题,构建基于角锥棱镜腔的相干合成激光器,分析远场合成效率不高的原因,提出光—电闭环的自适应驱动方法,通过反馈调节,克服因线路、器件以及其他电磁干扰等因素造成的不同步问题,提高相干合成效率。实验结果表明,经过自适应驱动的激光器,能显著提高相干合成效率,避免人工调整参数带来的误差,提高了激光器的稳定性和工作效率。     

一种用于三电平逆变器的SVPWM调制方法研究

本文从二极管箝位型三电平逆变器的基本结构出发，分析其输出状态，推导出六角形空间电压矢量图。然后从一种改进的，可以减小开关损耗，避免高的dv／dt三电平空间矢量PWM调制策略出发，建立了基于Matlab的详细仿真方案，验证了方案的可行性。文章给出了扇区判断的算法流程图，脉冲生成模块的内部结构图，其中的扇区判断的算法和脉冲生成方法对于用DSP实现三电平SVPWM具有重要的参考价值。     

A secure proxy signature scheme based on elliptic curve cryptosystem

Proxy signature is a special digital signature which enables a proxy signer to sign messages on behalf of the original signer. This paper proposes a strongly secure proxy signature scheme and a secure multi-proxy signature scheme based on elliptic curve cryptosystem. Contrast with universal proxy signature schemes, they are secure against key substitute attack even if there is not a certificate authority in the system, and also secure against the original signer＇s forgery attack. Furtherlnore, based on the elliptic curve cryptosystem, they are more efficient and have smaller key size than other system. They can be used in electronics transaction and mobile agent environment.