采用Flat_Cell技术的ROM设计和分析

Flat_Cell ROM具有高密度和高性能的优点。本文介绍了Flat_Cell结构和采用Flat_Cell技术的ROM设计方法。包括Flat_Cell的工艺技术、Flat_Cell基本电路结构和ROM放大器电路。     

无线信道下 Turbo码的信噪比估值新算法

该文基于高阶统计量的分析提出了用于Nakagami-m衰落信道下信噪比估值的新算法,它比已有算法更加简单有效,同时通过进行信噪比估值对Turbo码译码精度的灵敏性仿真测试证明了新算法的有效性。     

转子故障加速度信号的全谱分析

在旋转机械运动中,对于两正交方向的振动信号来说,全谱图相对于传统的谱图包含更多的信息,它包含振动进动方向及轨迹椭圆度.转子在运行过程中的振动加速度变化包含了大量的转子运行状态信号,因此,从分析转子加速度变化的特性来诊断转子故障是必要的.提取和总结出由故障造成的加速度信号突变和对应的加速度全谱级联特征.实验分析结果表明采用加速度信号全谱分析对转子的一些故障进行诊断是有效的.加速度信号全谱图可以丰富旋转机械故障诊断系统知识库中的特征信息,对于更准确地诊断转子中的故障具有重要的意义.     

蓝宝石图形衬底上GaN低温缓冲层的研究

低温下,在蓝宝石图形衬底上使用金属有机化学气相沉积(MOCVD)生长低温GaN(LT-GaN)缓冲层,并对其表面形貌进行了细致的观察,发现了不同于已报道的GaN选择性成核生长现象。基于不同厚度的低温GaN缓冲层生长了n型GaN(n-GaN),发现过厚或者过薄的缓冲层都会对n-GaN晶体质量产生负面影响,并结合初始成核阶段进行了原因分析。制备了基于不同厚度的n-GaN的发光二极管(LED)样品,分析了GaN晶体质量对LED输出功率的影响。同时发现,晶体质量较差的时候,光提取效率可能主导着对LED器件性能的影响。     

一种基于Hash函数的RFID安全认证方法

近年来,射频识别(RFID)技术得到越来越多的应用,随之而来的是各种RFID安全问题。对现有的基于Hash函数的RFID认证协议进行分析,针对现有技术存在的不足,提出了一种基于Hash函数的低成本的RFID双向安全认证方法,该方法只需要进行一次Hash函数计算,且加入了标签ID动态更新机制,通过在后台数据库中存储旧的标签ID解决同步问题,与现有技术相比具有一定的优越性。     

Web Server中静态路由的配置机制及实现

基于Web Server(网页服务器)的Web网管的系统架构和实现过程,以Wind Web Server为平台研究了静态路由的配置机制及实现.阐述了嵌入式网管系统的各个部分,并对前端处理模块和后台处理模块进行了分析与具体的实现,最后对静态路由的功能进行了对比性测试.结果表明,基于Web的网管方式在功能上能够与其他网管方...     

Regularized Pre-image Estimation for Kernel PCA De-noising

The main challenge in de-noising by kernel Principal Component Analysis (PCA) is the mapping of de-noised feature space points back into input space, also referred to as “the pre-image problem”. Since the feature space mapping is typically not bijective, pre-image estimation is inherently illposed. As a consequence the most widely used estimation schemes lack stability. A common way to stabilize such estimates is by augmenting the cost function by a suitable constraint on the solution values. For de-noising applications we here propose Tikhonov input space distance regularization as a stabilizer for pre-image estimation, or sparse reconstruction by Lasso regularization in cases where the main objective is to improve the visual simplicity. We perform extensive experiments on the USPS digit modeling problem to evaluate the stability of three widely used pre-image estimators. We show that the previous methods lack stability in the is non-linear regime, however, by applying our proposed input space distance regularizer the estimates are stabilized with a limited sacrifice in terms of de-noising efficiency. Furthermore, we show how sparse reconstruction can lead to improved visual quality of the estimated pre-image.     

Design and Validation of an Efficient Authentication Scheme with Anonymity for Roaming Service in Global Mobility Networks

Designing a user authentication protocol with anonymity for the global mobility network (GLOMONET) is a difficult task because wireless networks are susceptible to attacks and each mobile user has limited power, processing and storage resources. In this paper, a secure and lightweight user authentication protocol with anonymity for roaming service in the GLOMONET is proposed. Compared with other related approaches, our proposal has many advantages. Firstly, it uses low-cost functions such as one-way hash functions and exclusive-OR operations to achieve security goals. Having this feature, it is more suitable for battery-powered mobile devices. Secondly, it uses nonces instead of timestamps to avoid the clock synchronization problem. Therefore, an additional clock synchronization mechanism is not needed. Thirdly, it only requires four message exchanges between the user, foreign agent and home agent. Further, the security properties of our protocol are formally validated by a model checking tool called AVISPA. We also demonstrate that this protocol enjoys important security attributes including prevention of various attacks, single registration, user anonymity, no password table, and high efficiency in password authentication. Security and performance analyses show that compared with other related authentication schemes, the proposed scheme is more secure and efficient.     

Routing Protocol for Heterogeneous Hierarchical Wireless Multimedia Sensor Networks

Recently, wireless multimedia sensor networks (WMSNs) have emerged as one of the most important technologies, driven by the development of powerful multimedia device such as CMOS. WMSNs require several factors such as resource constraints, specific QoS, high bandwidth and so on. In this paper, we propose a hierarchical heterogeneous network model based routing protocol for WMSNs. In our proposal, proposed network model is classified into monitoring class, delivery class and aggregation class. Also we define two kinds of the routing path in order to ensure bandwidth and QoS. In simulation results, we illustrate the performance of our proposal.     

High Resolution Waveguide Terahertz Time-Domain Spectroscopy

Terahertz time-domain spectroscopy accesses the frequency range between 100 GHz and 5 THz by using the coherent generation and detection based on femtosecond laser sources. On the way to obtain fingerprint absorption spectra of molecular solids, terahertz waveguides have proven to be a valuable tool to extend the results to narrow and high resolution linewidths of crystalline solids. We will discuss the development, properties and applications of terahertz waveguide geometries for spectroscopic applications, in particular high-resolution measurements using parallel-plate waveguides.