深度学习应用技术研究

本文针对深度学习应用技术进行了研究性综述。详细阐述了RBM（Restricted Boltzmann Machine）逐层预训练后再用BP（back-propagation）微调的深度学习贪婪层训练方法,对比分析了BP算法中三种梯度下降的方式,建议在线学习系统,采用随机梯度下降,静态离线学习系统采用随机小批量梯度下降;归纳总结了深度学习深层结构特征,并推荐了目前最受欢迎的5层深度网络结构设计方法。分析了前馈神经网络非线性激活函数的必要性及常用的激活函数优点,并推荐ReLU （rectified linear units）激活函数。最后简要概括了深度CNNs(Convolutional Neural Networks), 深度RNNs(recurrent neural networks), LSTM(long short-termmemory networks)等新型深度网络的特点及应用场景,并归纳总结了当前深度学习可能的发展方向。     

物理层网络编码研究进展

在无线协作环境下,充分利用无线电磁波的广播特性进行物理层网络编码(PLNC)可获得更大的吞吐量和频谱利用率。在物理层网络编码基本思想的基础上,首先着重介绍三类物理层网络编码技术--有限域上的物理层网络编码、模拟网络编码和复数域上的网络编码,给出它们相关理论的研究现状,并对与此相结合的新技术进行了介绍;然后论述目前物理层网络编码应用实现的现状;最后对物理层网络编码相关理论及其应用实现的发展趋势进行了分析与展望。物理层网络编码理论的进一步完善,相关安全性的研究,以及与协作通信理论,如信道编码与调制、中继选择、调度及资源分配等进一步紧密结合等,将是其研究的重要趋势。     

Trusted Directory Services for Secure Internet Connectivity: Transport Layer Security using DNSSEC

The Internet today is a highly dynamic environment which frequently requires secure communication between peers that do not have a direct trust relationship. Current solutions for establishing trust often require static and application-specific Public Key Infrastructures (PKIs). This paper presents trusted directory services as a key infrastructural technology for setting up secure Internet connections, providing an alternative to application-specific PKIs. The directory securely binds public keys to peers through their names in a flexible way that matches the dynamic nature of the Internet. We elaborate on this concept by showing how the Domain Name System (DNS) and its security extensions (DNSSEC) can be leveraged for establishing secure Transport Layer Security (TLS) connections in a dynamic way. A simple enhancement of the TLS protocol, called Extended TLS (E-TLS), required for this purpose, is proposed. We describe our E-TLS implementation and we conclude with an evaluation of our results.     

对象持久层高性能Cache实现技术*

描述了面向对象应用与关系数据库之间的高性能对象持久层的系统结构,重点阐述了其Cache的关键技术。提出了分别针对LOB属性和常用查询的分布式与集中式两层Cache结构,给出了具体的Cache实现,并分析了Cache一致性问题的解决。该Cache实现技术使系统性能得到很大的提高。     

基于语义层行为结构的变换对形式化格局识别技术的再探究*

程序的语义层是程序的词法层和语法层的抽象表达,而蕴涵在软件中的语义层构成了人脑思维与机器思维交互过程的中间变换,从程序的语义层出发,利用行为结构的高层表达进行软件理解,进而抽取设计决策,成为了软件逆向工程理论研究的热门课题,形式化格局识别技术在不同程度上表达了上述思想。基于以上分析,对格局识别技术作进一步探究,并在原有基础上提出了新的改进算法与实施技术。     

测定外延层电阻率的面接触方法研究

评论了美国科学家C.C. Allen等于1966年发表的“测定外延层电阻率的点接触方法”之论文的局限性,从而提出了本方法。本方法从理论上解一维Poisson方程并与C.C。Allen法的公式相比较,获得某些公式。文中导出了面接触方法雪崩击穿电压V_(Ba)~∞(V)及点接触方法雪崩击穿电压V_(Bp)~∞(V)的比值为V_(Ba)~∞=0.456;同时还导出了点接触方法外延层耗尽层宽度为t_(min p)(μm)和面接触方法外延层耗尽层宽度t_(mina(μm)的比值为t_(minp)/t_(mina)=2.565。在实践上,为证实两种模型的功能,利用两种探针进行了对比测试。一种是通常被采用的点接触锇尖探针:另一种是利用φ0.8±0.1mm的银针,在银针顶上吸上φ0.4±0.1mm的汞球,以实现面接触。理论和实验吻合良好。     

An Investigation into Lubrication and Oxide Breakdown During Load-Carrying Capacity Testing

Changes occurring in the friction and wear mechanisms during a load-carrying capacity test, lubricated with cetane containing a carboxylic acid, were investigated. The changes in wear scar/track appearance and oxide coverage/composition were analyzed during every load stage.

The main conclusions were as follows:

• The breakdown in the protective oxide layer formed on the opposing steel surfaces was found to be the prerequisite for initiation of seizure.

• The seizure load achieved during load-carrying capacity testing quantifies the ability of the test fluid to prevent transition to the adhesive wear regime.

• The most severe surface damage was found to occur during the first few seconds after test initiation. Desorption of the adsorbed lubricant film and the subsequent removal of the naturally occurring thin oxide layer results in the initial period of adhesive wear.

• Partial recovery to a state of acceptable friction occurs after the period of initial seizure. During this period, the surface coverage by the adsorption lubricant molecules and the oxide coverage are sufficient to prevent severe adhesive wear from occurring. Wear is primarily a combination of oxidative, abrasive, and fatigue wear (all possible in the regions of mixed friction and boundary lubrication).

• Final lubricant breakdown and eventual seizure are initiated when the oxide removal rate exceeds the oxide formation rate resulting in severe adhesive wear followed by seizure.

     

基于移动信息化的安全接入平台建设

为提高移动信息化接入的安全级别,保障组织内部业务的安全运作,在传统网络安全架构的基础上,使用第二层隧道协议和混合加密技术构建一个安全接入平台。根据平台的功能及其安全性,将移动信息化区域分为5类,并为每一类区域制定安全策略,使原本限制在内网中的业务系统可以安全地在移动终端上使用。实际应用结果表明,该平台可以保证用户身份的匿名性、数据机密性、数据完整性、数据新鲜性及不可抵赖性。