大规模分簇超宽带传感网的生存期渐近界

本文考虑了n个传感节点和一个Sink组成的跳时脉冲无线电超宽带(TH-IR UWB)传感网,其中n个传感节点按照Poisson点过程分布在正方形上.推导结果表明密集分簇TH-IR UWB传感网的生存期界随着节点数的增加而增加;而扩展网络的生存期界随着节点数的增加而减小.研究也表明分簇网络的生存期界远大于非分簇网络的生存...     

Bounds on Reliability of a Coherent System with Positively Correlated Components

An upper bound on the reliability of a coherent system of positively correlated components is obtained via an improved Bonferroni inequality. An example is given. The bound is sharper if the joint survival probability is known for each pair of components.     

荧光寿命观测系统的设计

本文介绍了一种测量荧光寿命的新方法:利用荧光衰减曲线和RC电路衰减曲线合成李萨如图形来测量固体荧光材料的荧光寿命.文中阐述了荧光寿命的测试原理,对激励光源、供电的脉冲电源和光电转换器进行了分析,用所设计的荧光寿命观测系统对Nd:YAG晶体的荧光寿命进行了测量,得到的数值为230 m,与理论值相等.     

存储器数据保持寿命预测方法研究

研究存储器数据保持时间的温度加速效应,建立数据保持时间寿命预测方法和温度加速模型,实现应用温度数据保持时间的准确预测.通过研究和分析存储器在不同温度下的阈值电压随时间加速衰减测试数据,采用阿列纽斯模型即温度倒数(1/T)模型和温度(T)模型,推导出了温度加速参数,分别进行了应用温度下数据保持时间预测外推,并和应用温度下...     

Bounds on information combining

When the same data sequence is transmitted over two independent channels, or when a data sequence is transmitted twice but independently over the same channel, the independent observations can be combined at the receiver side. From an information-theory point of view, the overall mutual information between the data sequence and the received sequences represents a combination of the mutual information of the two channels. This concept is termed information combining. A lower bound and an upper bound on the combined information is presented, and it is proved that these bounds are tight. Furthermore, this principle is extended to the computation of extrinsic information on single code bits for a repetition code and for a single parity-check code of length three, respectively. For illustration of the concept and the bounds on information combining, two applications are considered. First, bounds on the information processing characteristic (IPC) of a parallel concatenated code are derived from its extrinsic information transfer (EXIT) chart. Second, bounds on the EXIT chart for an outer repetition code and for an outer single parity-check code of a serially concatenated coding scheme are computed.     

Bounds on Reliability of a Noncoherent System Using its Length & Width

A new kind of bounds on the reliability of s-noncoherent systems increases the variety of methods for probabilistic analysis of s-noncoherent systems. To compute the bounds, only a) the length and width of the system, and b) component reliabilities must be known. The weak and strong points of the bounds are illustrated by examples. The first example demonstrates the manifold applicability of s-noncoherent systems and compares the new bounds with those of Chu & Apostolakis.     

关于BCH码的广义Hamming重量上,下限

一个线性码的第ｒ广义Ｈａｍｍｉｎｇ重量是它任意ｒ维子码的最小支集大小。本文给出了一般（本原、狭义）ＢＣＨ码的广义Ｈａｍｍｉｎｇ重量下限和一类ＢＣＨ码的广义Ｈａｍｍｉｎｇ重量上限     

Bounds on the entropy series

Upper bounds on the entropy of a countable integer-valued random variable are furnished in terms of the expectation of the logarithm function. In particular, an upper bound is derived that is sharper than that of P. Elias (ibid., vol.IT-21, no.2, p.194-203, 1975), for all values of E_p(log). Bounds that are better only for large values of E_p than the previous known upper bounds are also provided     

Bounds on pseudoexhaustive test lengths

Pseudoexhaustive testing involves applying all possible input patterns to the individual output cones of a combinational circuit. Based on our new algebraic results, we have derived both generic (cone-independent) and circuit-specific (cone-dependent) bounds on the minimal length of a test required so that each cone in a circuit is exhaustively tested. For any circuit with five or fewer outputs, and where each output has k or fewer inputs, we show that the circuit can always be pseudoexhaustively tested with just 2^k patterns. We derive a tight upper bound on pseudoexhaustive test length for a given circuit by utilizing the knowledge of the structure of the circuit output cones. Since our circuit-specific bound is sensitive to the ordering of the circuit inputs, we show how the bound can be improved by permuting these inputs     

Bounds on two-element-kind impedance functions

Four types of two-element-kind networks are considered: R, ±C; R, ±L; ±R, C; and ±R,L networks. Regions in the Zplane are found within which the impedance function Z(j?) must lie.     

Bounds on FSM Switching Activity

This paper obtains lower and upper bounds for the switching activity on the state lines of a finite state machine (FSM) that is driven by typical input sequences. More specifically, the paper provides bounds on the average Hamming distance which is in turn proportional to the switching activity and the overall power dissipation in the system. By introducing the concepts of a distance matrix and a weight matrix, and by exploiting the symmetry of the distance matrix, we are able to obtain bounds that are provably tighter than existing bounds and, as demonstrated by our experimental results, they can offer significant improvements in many cases of interest. Since our bounds are independent of the state assignment and the actual implementation, they can be used at an early stage of the FSM design to indicate the largest/smallest possible power consumption.

Bounds for Queue Lengths in a Contention Packet Broadcast System

A finite number of users communicating through a broadcast channel is considered. Each user has a buffer of infinite capacity, and a user randomly accesses the channel (ALOHA-type protocol). Moreover, only one packet per user might be sent in an access time. Both symmetric and asymmetric models are considered; that is, we assume either indistinguishable or distinguishable users. An exact analysis of the queue lengths in that type of system is not now available, and therefore, based on some algebraic studies, we shall present some lower and some upper bounds for the average queue lengths. These bounds are quite tight for a small number of users and acceptable for a wide range of input parameters in the symmetric case. In the asymmetric case the bounds are acceptable only for light input traffic and a small number of users.     

利用基于扫描相机的荧光寿命成像显微技术研究细胞周期

利用基于扫描相机的荧光寿命成像显微系统,以细胞周期为模型,研究转染绿色荧光蛋白的HeLa细胞的荧光寿命。结果表明,处于周期内不同进程的细胞的荧光寿命为2.50~3.00 ns。处于分裂期的细胞的荧光寿命在1 h内从2.86 ns下降到2.82 ns;在DNA合成前期的8 h内,荧光寿命从2.82 ns下降到2.78 ns。荧光寿命的差异反映了细胞周期中核浆内大分子浓度的变化,对了解细胞周期的分子机制有一定的意义。     

FS-MWPCD少子寿命测量系统的信号处理设计

基于微波移频方法的硅材料少子寿命测量系统,使用采样电路与脉冲计数器结合的方式测量反射微波衰减信号,避免了用示波器观测衰减曲线时易受背景噪声的影响,并使测量装置的结构更加紧凑与轻便。分析了各个状态下反射微波的波形,设计了对反射微波进行信号采样比较及时钟计时的电路。实验结果表明:实验结果与示波器观测衰减曲线的结果吻合,改进方法具有可行性。     

基于BP神经网络的电子元器件寿命预测

电子元器件的寿命预测对于制订寿命试验的规划,确定所需的试验时间及试验经费,都有十分重要的指导作用.基于BP神经网络提出了一种电子元器件寿命预测的方法,该方法可对当前样本的未来观测值或未来样本的观测值进行预测.对MOS电容的加速寿命试验数据进行了仿真试验,结果表明该方法可较好地预测MOS电容在相应的应力条件下的失效时间,且精度较高.     

Sharp Bounds on Generalized EXIT Functions

We consider communication over binary-input memoryless symmetric channels with low-density parity-check (LDPC) codes. The relationship between maximum a posteriori and belief propagation decoding is investigated using a set of correlation inequalities that first appeared in statistical mechanics of Gaussian spin glasses. We prove bounds on generalized extrinsic information transfer (EXIT) functions, that are believed to be tight, and discuss their relationship with the ones obtained by the interpolation method.     

Complexity Bounds on General Hard-Core Predicates

A Boolean function b is a hard-core predicate for a one-way function f if b is polynomial-time computable but b(x) is difficult to predict from f(x) . A general family of hard-core predicates is a family of functions containing a hard-core predicate for any one-way function. A seminal result of Goldreich and Levin asserts that the family of parity functions is a general family of hard-core predicates. We show that no general family of hard-core predicates can consist of functions with O(n ^1-ε ) average sensitivity, for any ε > 0 . As a result, such families cannot consist of • functions in AC ⁰ , • monotone functions, • functions computed by generalized threshold gates, or • symmetric d -threshold functions, for d = O(n ^{1/2 - ε} ) and ε > 0 . Received April 2000 and revised September 2000 Online publication 9 April 2001     

Bounds on the Reliability of Networks

This paper presents criteria for acceptable schemes to approximate system reliability and Investigates such schemes for a special clas of network reliability problems. In this framework, we are able to use powerful combinatorial theory to obtain strong bounds for network reliability which can be computed by efficient algorithms. We demonstrate these bounds on a small example, and give some computational experience.     

Bounds on partial correlations of sequences

Two approaches to bounding the partial auto- and crosscorrelations of binary sequences are considered. The first approach uses the discrete Fourier transform and bounds for character sums to obtain bounds on partial autocorrelations of m-sequences and on the partial auto- and crosscorrelations for the small Kasami sets and dual-BCH families of sequences. The second approach applies to binary sequences obtained by interleaving m-sequences. A bound on the peak partial correlation of such sequences is derived in terms of the peak partial autocorrelation of the underlying m-sequences. The bound is applied to GMW, No (1987), and other families of sequences for particular parameters. A comparison of the two approaches shows that the elementary method gives generally weaker results but is more widely applicable. On the other hand, both methods show that well-known sequence families can have favorable partial correlation characteristics, making them useful in certain spread-spectrum applications     

Bounds on the minimum support weights

The minimum support weight, d_r(C), of a linear code C over GF(q) is the minimal size of the support of an r-dimensional subcode of C. A number of bounds on d_r(C) are derived, generalizing the Plotkin bound and the Griesmer bound, as well as giving two new existential bounds. As the main result, it is shown that there exist codes of any given rate R whose ratio d_r/d₁ is lower bounded by a number ranging from (q^r-1)/(q^r -q^r-1) to r, depending on R