二手设备市场悄然兴起

讨论了二手设备市场的兴起和新动向,中国是二手设备市场的最大买主,并指出购买二手设备应注意的几外问题。     

On the Race of Worms, Alerts, and Patches

We provide an analytical framework for evaluating the performance of automatic patching systems. We use it to quantify the speed of patch or alert dissemination required for worm containment. Motivated by scalability and trust issues, we consider a hierarchical system where network hosts are organized into subnets, each containing a patch server (termed superhost). Patches are disseminated to superhosts through an overlay connecting them and, after verification, to end hosts within subnets. The analytical framework accommodates a variety of overlays through the novel abstraction of a minimum broadcast curve. It also accommodates filtering of scans across subnets. The framework provides quantitative estimates that can guide system designers in dimensioning automatic patching systems. The results are obtained mathematically and verified by simulation.      

Alerts in mobile healthcare applications: requirements and pilot study

Recent advances in mobile technologies have greatly extended traditional communication technologies to mobile devices. At the same time, healthcare environments are by nature "mobile" where doctors and nurses do not have fixed workspaces. Irregular and exceptional events are generated in daily hospital routines, such as operations rescheduling, laboratory/examination results, and adverse drug events. These events may create requests that should be delivered to the appropriate person at the appropriate time. Those requests that are classified as urgent are referred to as alerts. Efficient routing and monitoring of alerts are keys to quality and cost-effective healthcare services. Presently, these are generally handled in an ad hoc manner. In this paper, we propose the use of a healthcare alert management system to handle these alert messages systematically. We develop a model for specifying alerts that are associated with medical tasks and a set of parameters for their routing. We design an alert monitor that matches medical staff and their mobile devices to receive alerts, based on the requirements of these alerts. We also propose a mechanism to handle and reroute, if necessary, an alert message when it has not been acknowledged within a specific deadline.     

入侵告警关联系统及关键技术的研究

入侵检测系统的大部分攻击事件之间都存在某种联系,通过对这些告警的关联分析能够减少告警数量,降低误报率,更好地发现攻击以及动态地监控网络。论文提出了一种告警关联系统,系统包括聚合分析、告警确认、多步攻击关联分析和告警严重度分析等过程。文章还对系统中两种主要方法—步攻击关联进行了描述。     

An Analytical Solution of the Lateral Current Spreading and Diffusion Problem in Narrow Oxide Stripe (GaAl)As/GaAs DH Lasers

An exact solution is presented to the problem of lateral current spreading in the resistive layer of oxide stripe geometry DH lasers. The two-dimensional Laplace equation was solved by conformal mapping using the Schwarz-Christoffel transformation. The diffusion equation containing nonlinear recombination terms was solved numerically. Computed examples demonstrate that the customary one-dimensioned treatment of the resistive layer or the assumption of constant current density under the stripe contact are not always justified, particularly for narrow stripe widths and low specific resistivities. This region of low values of the resistivity and stripe width, however, is of great practical interest in the design of oxide stripe lasers having high thermal stability and kink-free characteristics.     

扩展电阻技术及其应用

本文详细地介绍了包括实验装置、测量程序和数据分析在内的扩展电阻技术.基于这种技术制成了自动两探针扩展电阻测试设备,在离子注入硅片表面得到的测量重复性介于1～3%,在单晶样品上电阻率的测量误差不大于15%.借助扩展电阻技术得到的掺杂分布能与C—V法结合阳极氧化剥层技术得到的分布相一致.基于单层突变结理论,使用计算机计算了修正因子.最后,详细阐述了扩展电阻技术的应用.     

Spreading resistance calculations by the variational method

In this paper the variational principle is applied to the calculations of spreading resistance for both homogeneous and inhomogeneous slabs on a perfectly conducting substrate, using a linear combination of two types of source flux distributions, namely, a uniform flux distribution and the classical form of the distribution for the infinitely thick slab. It is found that, as a rule, a linear combination of these two source distributions yields values of correction factors which agree much more closely with those derived from the exact constant potential approach than any given by previous approximate methods based on either of the source distributions. The variational method is not only accurate but also computationally efficient, being only a factor of three slower than any of the earlier approximate methods.     

基于SEIR的社交网络信息传播模型

结合传染病动力学的SEIR模型,本文建立了适用于社交网络的信息传播模型。该模型基于社交网络用户的行为特征,分析了社交网络的传播机理和网络参数对信息传播过程的影响,得出了动力学演化方程组,刻画了信息传播过程随时间的演化规律。仿真实验的结果表明,本文提出的模型能正确地反映社交网络上的信息传播的趋势,较为准确地描述信息传播过程。     

直觉模糊条件推理与可信度传播

针对直觉模糊逻辑及命题演算,基于直觉指数所表征的中立证据中支持与反对的程度呈均衡状态的假设,提出利用隶属度与犹豫度计算直觉模糊逻辑命题真值的对称合成方法,给出直觉模糊逻辑命题的运算规则。重点研究了基于直觉模糊逻辑的条件推理方法,包括直觉模糊蕴涵式推理、条件式推理、多重式推理、多维式推理及多重多维式推理等;推导了相关的推理合成运算公式。针对带有可信度因子的直觉模糊逻辑推理,包括典型的、加权的及狭义的直觉模糊推理;分析了规则中的可信度因子传播对结论可信度的影响;给出了相关的计算结论真值的公式。     

Convolutional Spreading CDMA and Comparison With the DS-CDMA With RAKE Receiver

For synchronous downlink direct-sequence code-division multiple access (DS-CDMA), we introduce a cyclic-prefix (CP)-based convolutional spreading CDMA (CS-CDMA/CP) scheme employing zero correlation zone (ZCZ) codes, which gives a class of multiuser interference (MUI)-free CDMA schemes, including Suehiro's CDMA and block spreading (BS) CDMA as special cases. We show that CS-CDMA/CP employing appropriately selected binary and ternary ZCZ codes have good user capacity, peak-to-average power ratio (PAPR), and transmission power loss, compared with previously proposed BS-CDMA schemes. By simulation, we show the effect of PAPR to its bit-error rate (BER) performance when nonlinear amplifiers are used, and also compare its BER performance with the conventional DS-CDMA scheme employing a RAKE receiver     

Cooperative Differential Space–Time Spreading for the Asynchronous Relay Aided CDMA Uplink Using Interference Rejection Spreading Code

This letter proposes a differential Space–Time Coding (STC) scheme designed for asynchronous cooperative networks, where neither channel estimation nor symbol-level synchronization is required at the cooperating nodes. More specifically, our system employs differential encoding during the broadcast phase and a Space–Time Spreading (STS)-based amplify-and-forward scheme during the cooperative phase in conjunction with interference rejection direct sequence spreading codes, namely Loosely Synchronized (LS) codes. Our simulation results demonstrate that the proposed Cooperative Differential STS (CDSTS) scheme is capable of combating the effects of asynchronous uplink transmissions without any channel state information.      

Substrate Dissipation Energy Regulates Cell Adhesion and Spreading

Recent evidence has led to the hypothesis that dissipation of energy through the viscoelastic extracellular matrix (ECM) can play a cardinal role in directing cell‐fate decisions, but whether and how it correlates with specific cell response is at present unclear. Here, viscoelastic and plastic 2D chitosan‐based substrates endowed with different dissipative energies are developed and cell behavior studied in terms of adhesion and spreading. While keeping constant stress relaxation and systematically decoupling overall stiffness from linear elongation, an energy dissipation term (J mol^?1) is introduced, that is the molar energy required to deviate from linear stress–strain regime and enter into plastic region. Strikingly, an inverse relationship is unveiled between substrate dissipation energy and cell response, with high adhesion/high spreading and low adhesion/no spreading detected for substrates at low and high dissipation energy, respectively. It is concluded that cells decide how to react depending on the effective energy they can earmark for their functions.     

UWB系统抗干扰扩频编码的研究

将正交频分复用(OFDM)技术和正交扩频交织编码技术相结合,并引入到超宽带(UWB)通信系统中, 通过正交扩频将信息比特扩展到各个子带的子信道中,再进行交织编码,可大大提高系统抗窄带干扰能力。仿真结果表明,这种正交扩频交织编码技术具有明显的抗窄带干扰顽健性,系统信干比提高5dB左右,误比特率改善1-2个数量级。     

AR自编码扩频系统中扩频序列的特性研究

在扩展频谱通信中,扩频序列的性能与系统的抗多址干扰、抗多径衰落的能力,和信号的低截获率概率有密切关系,也关系到捕获与同步系统的实现。扩频序列的特性对扩频系统的性能有重要影响。在自编码扩频通信系统中,自编码扩频序列的特性对于自编码扩频系统的性能同样非常重要。该文详细分析了采用AR滤波方式产生的扩频序列的扩频特性。计算机仿真说明,用AR滤波提取自编码扩频序列完全满足自编码扩频通信的要求。     

Spreading resistance calculations by the use of Gauss-Laguerre quadrature

The Gauss-Laguerre quadrature is proposed as a numerical method for calculating the correction factor integrals that occur in spreading resistance calculations. The method is very efficient in terms of computation time and memory storage, requiring only 33 integrand values for each integral evaluation. The accuracy of the method has been investigated for a variety of graded structures, and found to be better than 5%. As a test of its practical utility, the method has been used in the correction of the spreading resistance profile of a practical buried layer structure, and it has been found that the CPU time taken to correct the entire profile of 57 data points is 1.0 min on an IBM 1130 System with a 16K word (16 bit) memory or 0.4 sec on a UNIVAC 1100/10 Multiprocessor System with a 393K word (36 bit) memory. These times are a factor of 6 to 8 less than those required by using the previously proposed adaptive Simpson's rule to compute the correction factor integrals.