Analyzing and enhancing the resilience of structured peer-to-peer systems

In this paper, we propose an approach to analyze the resilience of structured peer-to-peer (P2P) systems under failures. The approach is Markov-chain based, and can be applied to systems with relatively stable size and uniform distribution of nodes. We apply our approach to several well-known structured P2P systems. We find that different system features (types of neighbors of nodes) in P2P systems have different impacts on their resilience against failures. Following this observation, we propose to add some extra neighbor(s) to CAN using small-world model principles to form a so-called CAN-SW system. We then apply the proposed approach to analyze its resilience. We find that the performance is improved significantly, particularly, in terms of the average path length.     

Evaluation of the DPC-based inclusive payment system in Japan for cataract operations by a new model

We propose a new model for analyzing the length of hospital stay when variances are heterogeneous. This model is an alternative to the conventional models such as Cox's proportional hazard model and can be used to address various problems of survival analysis. The model is a heteroskedastic version of the Box–Cox transformation model and is estimated by the tobit maximum likelihood method, and its estimation can be easily done using a standard statistical package program. Using the proposed model, we analyze the effects of the diagnosis procedure combination/per diem payment system (DPC/PDPS) on the length of hospital stay following cataract operations in Japan. Data collected from six general hospitals before and after the introduction of the system are analyzed. The number of patients is 2677.     

Analysis of the variable length nonzero window method for exponentiation

The variable length nonzero window method is a way of computing exponentiation and modular exponentiation. This method has been analyzed, but there is a substantial difference between the analysis and experimental results. The difference results from some logical errors in the analysis. We analyze the variable length nonzero window method by modeling it as a Markov chain. We consider all details and our analysis predicts the behavior of the variable length nonzero window method exactly.     

A study of controllable motion of a mobile vibration system moving with breakaway from the surface

We consider a model of a two-mass mechanical system consisting of an external body (box) and an internal body (unbalance), which moves on a rough rigid surface with a breakaway from it. We derive differential equations describing the system motion in the phase of flight and determine the conditions of location on the reference surface. The control parameter is proposed to be the angular velocity of unbalance rotation. To find the dependence of hopping height and length on the control frequency of unbalance rotation, we analyze the equations. An algorithm of numerical integration of the system of differential equations of motion was developed. The numerical solution confirms the theoretical conclusions on the dependence of hopping height and length on rotation frequency. At the same time, the form of trajectory of body mass center was found to depend on the value of the control parameter. Also, we reveal the dependence of the direction of robot motion on hopping height and length, and unbalance (on the ratio of system mass).     

CCSDS高级在轨系统协议吞吐量性能分析

简要介绍了CCSDS高级在轨系统（AOS）协议的信源特点，分析了影响AOS协议包业务吞吐量性能的因素，给出传输集中数据时的包业务吞吐量计算公式，讨论了吞吐量-包长、吞吐量-帧长关系曲线，并针对传输集中数据情况下以吞吐量为指标实现优化AOS协议配置给出了指导性建议，为CCSDS AOS协议的应用提供了参考。     

带长度约束的k端网络可靠性分析

在网络视频和实时通信应用中需要研究带长度约束的k端网络可靠性分析问题,即任意两端点之间在给定时间延迟D约束内的k端网络可靠性。对带长度约束的k端网络可靠性问题进行了研究,主要是在传统不带路径约束的双端和k端网络可靠性研究基础上,提出了基于截断的路径约束方法;并根据该方法构造二元决策图BDD模型进行带约束的k端网络可靠性分析。该算法针对k端点对点信息流在一定时间延迟下完成传输问题,具有较强的实际意义。实例分析结果验证了本方法的可行性和有效性。     

基于噪声信道的ARQ系统时延性能及最小滑动窗口控制研究

基于噪声干扰信道（包括正向链路和反馈链路）,并考虑到达信息包的随机拆分、滑动窗口长度、分组长度以及数据链路上的传播时延等影响因素,建立了传输分组批到达情况下链路层上退回N步ARQ系统（GBN-ARQ）和选择重发式ARQ系统（SR-ARQ）的MX/G/1排队时延模型．求得了两系统时延以及归一化的最大吞吐量的表达式．进而获得了在既定系统传输条件下确定最小滑动窗口长度、实施窗口控制的模型和方法．仿真表明,通过自适应地改变滑动窗口长度可以降低GBN-ARQ系统的时延,提高其传输效率,因而在一定条件下可以用GBN-ARQ代替SR-ARQ而避免后者较高的系统实现复杂度．     

On the effects of ring oscillator length and hardware Trojan size on an FPGA-based implementation of AES

The recent trend in a wide range of application domains, from the Internet of Things to space communications, is to deploy computing systems on FPGA devices. Modern FPGA technology encompasses billions of gates integrated in a single chip. In this setting, it is easier for an attacker to inject or introduce additional, malicious logic or to modify an existing one in order to cause abnormal behavior. As a result, new security requirements arise from the design process perspective. A Ring Oscillator (RO) is an established technique to realize a digital sensor in FPGA designs to detect additional or modified malicious circuit, i.e., a hardware Trojan horse or simply a Trojan. Variable-length Ring Oscillators (VLROs) were proposed in the literature as an advanced detection mechanism for run-time configuration of RO length to avoid bypassing. Here, we expand VLROs effectiveness studies in two families of Trojans (combinational and sequential) and Trojans of varying size. We analyze the effect of the Trojan size and the length of the RO on the ability to detect malicious logic injected in a reference FPGA implementation of the AES cryptographic algorithm.     

On the Numerical Approximation of the Length of (Implicit) Level Curves

The evaluation of the length of a curve, represented in an Eulerian way as the zero level set of an implicit function, depends mainly on the representation of the curve. In this paper, we propose a parameter to measure the complexity of the curve, and therefore the accuracy of the evaluation, based on the evolution of the representation in different scales. We will analyze this parameter, its properties and its relations with the regularity of the curve.     

Analysis and design of mobile Wireless Social Model

Delay Tolerant Networks (DTNs) are characterized by very long delay paths and frequent network partitions. Most existing protocols are based on simplistic models which differ from real scenarios or real traces which do not allow for sensitivity analysis. In this paper, we analyze the differences between the Social Network (SN) and the Wireless Social Network (W-SN) in terms of the clustering coefficient, characteristic path length, community size, and membership number. We observe that the clustering coefficient, community size and membership number in the W-SN are bigger than those in the SN, while the character path length in W-SN becomes smaller. And then we propose a new Wireless Social Model (WSM) based on community character. Node in WSM is driven by the α-Model and has an equal probability to move to one of his adjacent vertices. We evaluate our model via real traces supplied by Dartmouth College, which shows that our wireless social mobile model offers a good approximation of real movements.     

Asymptotic study of the solution for pinched cylindrical shells

We consider the displacement problem of a cylindrical roof under a pointwise Dirac load acting in the normal direction, and recognize two classes of possible responses in dependence of the boundary conditions: the bending dominated and the “intermediate” case. We theoretically analyze the local form of the solution around the load application point in both cases; the latter (which is equivalent to the classical pinched cylinder benchmark) shows a layer of characteristic length t^1/4 in the angular direction, while the first one shows a smoother solution. Finally we exploit the results obtained in order to derive some good numerical strategies for the problem. In the last section, we show the perfect correspondence between the theoretical results and the solution obtained through numerical means.     

Average Profile of the Lempel-Ziv Parsing Scheme for a Markovian Source

For a Markovian source, we analyze the Lempel—Ziv parsing scheme that partitions sequences into phrases such that a new phrase is the shortest phrase not seen in the past. We consider three models: In the Markov Independent model, several sequences are generated independently by Markovian sources, and the ith phrase is the shortest prefix of the ith sequence that was not seen before as a phrase (i.e., a prefix of previous (i-1) sequences). In the other two models, only a single sequence is generated by a Markovian source. In the second model, called the Gilbert—Kadota model, a fixed number of phrases is generated according to the Lempel—Ziv algorithm, thus producing a sequence of a variable (random) length. In the last model, known also as the Lempel—Ziv model, a string of fixed length is partitioned into a variable (random) number of phrases. These three models can be efficiently represented and analyzed by digital search trees that are of interest to other algorithms such as sorting, searching, and pattern matching. In this paper we concentrate on analyzing the average profile (i.e., the average number of phrases of a given length), the typical phrase length, and the length of the last phrase. We obtain asymptotic expansions for the mean and the variance of the phrase length, and we prove that appropriately normalized phrase length in all three models tends to the standard normal distribution, which leads to bounds on the average redundancy of the Lempel—Ziv code. For the Markov Independent model, this finding is established by analytic methods (i.e., generating functions, Mellin transform, and depoissonization), while for the other two models we use a combination of analytic and probabilistic analyses. Received June 6, 2000; revised January 14, 2001.     

A Stylometric Analysis of Yaşar Kemal’s İ<Emphasis Type="Italic">nce Memed</Emphasis> Tetralogy

We analyze four ?nce Memed novels of Ya?ar Kemal using six style markers: “most frequent words,” “syllable counts,” “word type – or part of speech – information,” “sentence length in terms of words,” “word length in text,” and “word length in vocabulary.” For analysis we divide each novel into five thousand word text blocks and count the frequencies of each style marker in these blocks. The style markers showing the best separation are “most frequent words” and “sentence lengths.” We use stepwise discriminant analysis to determine the best discriminators of each style marker. We then use these markers in cross validation based discriminant analysis. Further investigation based on multiple analysis of variance (MANOVA) reveals how the attributes of each style marker group distinguish among the volumes.     

Use of a Neural Network as a Predictive Instrument for Length of Stay in the Intensive Care Unit Following Cardiac Surgery

A patient's intensive care unit (ICU) length of stay following cardiac surgery is an important issue in Canada, where cardiovascular intensive care resources are limited and waiting lists for cardiac surgery exist. We trained a neural network with a database of 713 patients and 15 input variables to predict patients who would have a prolonged ICU length of slay, defined as a stay greater than 2 days. In an independent test set of 696 patients, the network was able to stratify patients into three risk groups for prolonged stay (low, intermediate, and high), corresponding to frequencies or prolonged stay of 16.3, 35.3, and 60.86%, respectively. The trained network could potentially be used as a predictive instrument for optimizing the scheduling of cardiac surgery patients in times of limited ICU resources. Neural networks are a new method for developing predictive instruments that offer both advantages and disadvantages when compared to other more widely used statistical techniques.     

宽带电磁散射分析中的ZT-FDTD算法

讨论ZT-FDTD算法,针对其中的不足,提出使用基于Z变换的(FD)2TD算法计算色散半空间上三维有限长介质柱的宽带电磁散射特性.针对在不同极化及入射角情况下的宽带散射,运用(FD)2TD算法进行分析,将频域方程变换到Z域,再返回到时域进行差分计算,并给出仿真结果.     

On the complexity of deciding avoidability of sets of partial words

Blanchet-Sadri et al. have shown that Avoidability, or the problem of deciding the avoidability of a finite set of partial words over an alphabet of size k≥2, is NP-hard [F. Blanchet-Sadri, R. Jungers, J. Palumbo, Testing avoidability on sets of partial words is hard, Theoret. Comput. Sci. 410 (2009) 968-972]. Building on their work, we analyze in this paper the complexity of natural variations on the problem. While some of them are NP-hard, others are shown to be efficiently decidable. Using some combinatorial properties of de Bruijn graphs, we establish a correspondence between lengths of cycles in such graphs and periods of avoiding words, resulting in a tight bound for periods of avoiding words. We also prove that Avoidability can be solved in polynomial space, and reduces in polynomial time to the problem of deciding the avoidability of a finite set of partial words of equal length over the binary alphabet. We give a polynomial bound on the period of an infinite avoiding word, in the case of sets of full words, in terms of two parameters: the length and the number of words in the set. We give a polynomial space algorithm to decide if a finite set of partial words is avoided by a non-ultimately periodic infinite word. The same algorithm also decides if the number of words of length n avoiding a given finite set of partial words grows polynomially or exponentially with n.     

The correlation structure for a class of scene-based video modelsand its impact on the dimensioning of video buffers

We analyze the autocorrelation structure for a class of scene-based MPEG video models at the groups-of-pictures (GOP) (course grain) and frame (fine grain) levels assuming an arbitrary scene-length distribution. At the GOP level, we establish the relationship between the scene-length statistics and the short-range/long-range dependence (SRD/LRD) of the underlying model. We formally show that when the intrascene dynamics exhibit SRD, the overall model exhibits LRD if and only if the second moment of the scene length is infinite. Our results provide the theoretical foundation for several empirically derived scene-based models. We then study the impact of traffic correlations on the packet loss performance at a video buffer. Two popular families of scene-length distributions are investigated: Pareto and Weibull. In the case of Pareto distributed scene lengths, it is observed that the performance is rather insensitive to changes in the buffer size even as the video model enters the SRD regime. For Weibull distributed scene lengths, we observe that for small buffers the loss performance under a frame-level model can be larger than its GOP-level counterpart by orders of magnitude. In this case, the reliance on GOP-level models will result in very optimistic results     

On the computational complexity of binary and analog symmetric hopfield nets

We investigate the computational properties of finite binary- and analog-state discrete-time symmetric Hopfield nets. For binary networks, we obtain a simulation of convergent asymmetric networks by symmetric networks with only a linear increase in network size and computation time. Then we analyze the convergence time of Hopfield nets in terms of the length of their bit representations. Here we construct an analog symmetric network whose convergence time exceeds the convergence time of any binary Hopfield net with the same representation length. Further, we prove that the MIN ENERGY problem for analog Hopfield nets is NP-hard and provide a polynomial time approximation algorithm for this problem in the case of binary nets. Finally, we show that symmetric analog nets with an external clock are computationally Turing universal.     

Analysis of the unique gait mechanism of locusts focusing on the difference in leg length

The various types of gaits shown by insects are very interesting, and many studies have been conducted to investigate the mechanism of these gaits. In nature, there are many insects with apparent differences in the length of each leg, and it seems that the difference in leg length may affect the resultant gait of insects. However, there has not been much discussion about the influence of these differences in leg length on the gait. In this research, in order to investigate the influence of the difference in leg length on gait, we focus on locusts, whose hind legs are considerably longer than the other legs and shows a unique gait not seen in other insects. First, we measure the kinematics of gait of some insects, including locusts, and analyze the unique gait specific to locusts. Next, we reproduce this unique gait via numerical dynamical simulation. By conducting some simulations while changing the length of the legs, we investigate the mechanism of the unique gait of locusts and the influence of difference in leg length on walking. As a result, it is confirmed that the unique gait of locusts can be reproduced with a combination of long hind legs (compared to the front and middle legs) and the adjustment of the stroke and period of the hind leg based on horizontal ground reaction force.