带冗余串联系统可靠性设计的一种高效优化技术

本文对带冗余串联系统的可靠性设计提出了一种新的优化技术。通过控制系统可靠度的取值变化来获得串联系统各阶段的冗余单元数,而系统可靠度的最优值则采用区间对分法来寻求。实例说明,这种方法计算简便,快速和有效。     

一类迭代学习控制的自适应参数优化

针对一类迭代学习控制提出了一种基于二次性能指标函数的自适应参数优化方法。如果原离散系统是正定的，那么这种具有可调参数的学习算法可以保证误差按几何单调收敛于0，如果系统非正定的，提出了一种反馈调节方法使系统正定。数值仿真表明了所提出算法和条件的有效性。     

相邻k/n(F)系统可靠度的一个简单下界

本文应用布尔概率不等式推出了相邻ｋ／ｎ（Ｆ）系统可靠度的一个简单下界，该下界具有计算简便、实用的特点，在某些特定情形下较Ｄ．Ｃｈａｉｎｇ和Ｎｉｕ［１］提出的下限（部件可靠度相等）及Ｄｅｒｍａｎ和Ｌｉｅｂｅｒｍａｎ［２］提出的下限（部件可靠度不相等）更接近系统的真实可靠度，在处理具有统计相依事件的软件可靠性［４］中具有较大的应用前景。     

探索曲面结构的小生境遗传算法

提出了具有适应值曲面结构自学习能力的多区域并行局部搜索算子PLS和约束交叉算子GC，定性地分析了它们的作用机制，给出了基子仿真实验数据的遗传算法收敛速度和全局收敛可靠性的定量计算方法。仿真实验数据表明，PLS能有效地提高搜索速度并维持足够的种群基因多样度，GC可有效地微调解的质量，使改进的遗传算法的全局收敛速度和收敛可靠性均显著地优于标准遗传算法，并具有良好的鲁棒性和稳定性．     

N：K系统可靠度及备件量的仿真计算方法

采用基于排队网络的仿真模型来描述n:k(m)交叉储备系统，并给出了系统可靠度及备件最优储备量的仿真计算方法。本文的方法能适用于具有多个维修台的非马尔科夫型n:k(m)交叉储备系统。各种算例检验了本文方法的适用性。文末用解析的方法和本文的方法计算了马尔科夫型n:k(m)系统的可靠度及备件最优储备量，二者符合的很好。     

可靠性参数的M-Bayes可信限

提出了可靠性参数的一个新估计方法--M-Bayes可信限估计法,对寿命服从指数分布的产品,在无失效数据情形,给出了失效率的M-Bayes可信限的定义、估计及其性质.结合某型发动机的实际问题进行了计算,计算结果表明失效率的M-Bayes可信上限"优于"经典置信上限,可靠度的M-Bayes可信下限"优于"经典置信下限.通过例子可以看出提出的方法便于应用.     

改进微粒群算法及其在生料浆调配多目标优化中的应用

微粒群算法是一种简单易行、收敛快速的演化计算方法，但也存在早熟收敛的缺陷。鉴于惯性权值对控制算法收敛所起的作用，本文提出一种改进的微粒群算法，让惯性权值按类S型曲线形式随迭代次数非线性变化，并根据微粒当前的搜索状态自适应调节该曲线的曲率，有效保证算法收敛速度和全局寻优能力。改进的微粒群算法用于求解氧化铝生料浆调配过程0-1组合优化问题，与传统微粒群算法及遗传算法比较的结果表明，改进的微粒群算法具有较强的全局搜索能力且能有效避免早熟收敛问题。     

基于最大熵原理的多失效模式下煤巷锚杆支护结构体系可靠度模型

煤巷锚杆支护结构中包含多个相关的失效模式,传统的煤巷锚杆支护结构可靠度分析方法没有考虑多个失效模式之间的相关性,使得煤巷锚杆支护结构的可靠度被低估.为此,提出多失效模式下的煤巷锚杆支护结构分析方法,建立考虑多失效模式相关的煤巷锚杆支护结构体系可靠度分析模型.同时,采用最大熵原理推断煤巷锚杆支护结构参数的统计特征,利用对数正态分布描述岩石和煤体的粘聚力和内摩擦角.并采用Monte Carlo模拟法进行多失效模式下结构体系可靠度计算.研究结果表明:采用最大熵原理能有效推断煤巷锚杆支护结构基本变量统计特征;多失效模式相关的结构可靠度模型所得到的可靠度值比传统单一不相关模式下所计算的结果更加科学、准确;在MATIAB环境下采用Monte Carlo模拟法编程计算煤巷锚杆支护结构体系可靠度,无需将功能函数线性化,随机变量正态化,不需要求解近似联合密度函数,不需要进行复杂变换,编程过程简单,精度高.     

基于最大熵原理的多失效模式下煤巷锚杆支护结构体系可靠度模型

煤巷锚杆支护结构中包含多个相关的失效模式,传统的煤巷锚杆支护结构可靠度分析方法没有考虑多个失效模式之间的相关性,使得煤巷锚杆支护结构的可靠度被低估.为此,提出多失效模式下的煤巷锚杆支护结构分析方法,建立考虑多失效模式相关的煤巷锚杆支护结构体系可靠度分析模型.同时,采用最大熵原理推断煤巷锚杆支护结构参数的统计特征,利用对数正态分布描述岩石和煤体的粘聚力和内摩擦角.并采用Monte Carlo模拟法进行多失效模式下结构体系可靠度计算. 研究结果表明：采用最大熵原理能有效推断煤巷锚杆支护结构基本变量统计特征;多失效模式相关的结构可靠度模型所得到的可靠度值 比传统单一不相关模式下所计算的结果更加科学、准确;在MATLAB环境下采用Monte Carlo模拟法编程计算煤巷锚杆支护结构体系可靠度,无需将功能函数线性化,随机变量正态化,不需要求解近似联合密度函数,不需要进行复杂变换,编程过程简单,精度高.     

基于PoF模型的电子产品可靠性参数计算方法

现有的基于失效物理(physics of failure, PoF)模型的可靠性预计只能计算电子产品在寿命周期内经历单一典型任务剖面的失效时间。本文提出了一种基于失效物理模型,并利用蒙特卡罗仿真定量分析电子产品在寿命周期内实际经历多任务剖面的可靠性水平的新方法。将该方法应用于某机载电子设备的平均失效前时间(mean time to failure, MTTF)的计算,建立失效率和可靠度的时间函数,与目前国内工程实践中常用的失效率经验模型法以及设备可靠性强化试验的结果进行了对比分析。结果表明,该方法不仅可以计算可靠性参数,而且通过分析与计算过程可发现设计薄弱环节与可靠性参数的定量关系,有效指导设计改进。     

一种预计系统可靠性参数MTBF的方法

一种预计系统可靠性参数ＭＴＢＦ的方法施军（南京航空航天大学，２１００１６）.     

Efficiently counting affine roots of mixed trigonometric polynomial systems

Estimating the number of isolated roots of a polynomial system is not only a fundamental study theme in algebraic geometry but also an important subproblem of homotopy methods for solving polynomial systems. For the mixed trigonometric polynomial systems, which are more general than polynomial systems and rather frequently occur in many applications, the classical B′ezout number and the multihomogeneous B′ezout number are the best known upper bounds on the number of isolated roots. However, for the deficient mixed trigonometric polynomial systems, these two upper bounds are far greater than the actual number of isolated roots. The BKK bound is known as the most accurate upper bound on the number of isolated roots of a polynomial system. However, the extension of the definition of the BKK bound allowing it to treat mixed trigonometric polynomial systems is very difficult due to the existence of sine and cosine functions. In this paper, two new upper bounds on the number of isolated roots of a mixed trigonometric polynomial system are defined and the corresponding efficient algorithms for calculating them are presented. Numerical tests are also given to show the accuracy of these two definitions, and numerically prove they can provide tighter upper bounds on the number of isolated roots of a mixed trigonometric polynomial system than the existing upper bounds, and also the authors compare the computational time for calculating these two upper bounds.     

Estimated and exact system reliabilities of a maintainable computer network

This paper presents an algorithm to evaluate estimated and exact system reliabilities for a computer network in the cloud computing environment. From the quality of service (QOS) viewpoint, the computer network should be maintained when falling to a specific state such that it cannot afford enough capacity to satisfy demand. Moreover, the transmission time should be concerned as well. Thus, the data can be sent through several disjoint minimal paths simultaneously to shorten the transmission time. Under the maintenance budget B and time constraint T, we evaluate the system reliability that d units of data can be sent from the cloud to the client through multiple paths. Two procedures are integrated in the proposed algorithm-an estimation procedure for estimated system reliability and an adjusting procedure utilizing the branch-and-bound approach for exact system reliability. Subsequently, the estimated system reliability with lower bound and upper bound, and exact system reliability are computed by applying the recursive sum of disjoint products (RSDP) algorithm.     

Time-optimal interpolation for CNC machining along curved tool pathes with confined chord error

In this paper, two new interpolation algorithms lot CNC machining along curve~l tom pathes are proposed： a time-optimal interpolation algorithm under chord error, feedrate, and tangential acceleration bounds, and a greedy interpolation algorithm under the chord error and tangential jerk bounds. The key idea is to reduce the chord error bound to a centripetal acceleration bound which leads to a velocity limit curve, called the chord error velocity limit curve. Then, the velocity planning is to find the proper velocity curve governed by the acceleration or jerk bounds ＇~under＂ the chord error velocity limit curve. For two types of simple tool pathes, explicit formulas for the velocity curve are given and the methods are implemented in commercial CNC controllers.     

Bounding the inefficiency of the C-logit stochastic user equilibrium assignment

Compared with standard logit-based stochastic user equilibrium assignment model, the C-logit model describes route choice behavior in a more realistic way by considering the overlapping effect between routes. This paper investigates the inefficiency upper bounds of this model against the deterministic system optimum and the C-logit stochastic system optimum in terms of the total network travel time. It is found that the commonality factor of overlapping routes significantly affects the inefficiency bound, besides link congestion degree, total demand and the number of feasible routes. If the commonality factor is not considered, the efficiency loss resulting from selfishly stochastic travel behavior will be to large extent underestimated.     

A Fast Approximation Method for Partially Observable Markov Decision Processes

This paper develops a new lower bound method for POMDPs that approximates the update of a belief by the update of its non-zero states. It uses the underlying MDP to explore the optimal reachable state space from initial belief and select actions during value iterations, which significantly accelerates the convergence speed. Also, an algorithm which collects and prunes belief points based on the upper and lower bounds is presented, and experimental results show that it outperforms some of the state-of-art point-based algorithms.     

Upper and lower bounds on PMEPR in OFDM systems and application

Upper and lower bounds on peak-to-mean envelope power ratio (PMEPR) in OFDM systems are derived in this paper. The derivation results show that the upper bound on PMEPR only depends on the aperiodic autocorrelation functions of the data sequences and is quite useful for rapid elimination of sequences that have PMEPR exceeding a given threshold. According to the lower bound on PMEPR,it has a great change as N (number of subcarriers) varies only for a very small N. For a 16-subcarrier BPSK-OFDM system, a selective mapping (SLM) way to reduce PMEPR is investigated with the upper bound on PMEPR and the distribution of PMEPR for all possible message sequences is given. The analytic results show that the maximal PMEPR is about 6.5 dB which is 5.5 dB less than that in worst situation.     

Logcf: An Efficient Tool for Real Root Isolation

Computing upper bounds of the positive real roots of some polynomials is a key step of those real root isolation algorithms based on continued fraction expansion and Vincent's theorem.The authors give a new algorithm for computing an upper bound of positive roots in this paper. The complexity of the algorithm is O(n log(u+1)) additions and multiplications where u is the optimal upper bound satisfying Theorem 3.1 of this paper and n is the degree of the polynomial. The method together with some tricks have been implemented as a software package logcf using C language. Experiments on many benchmarks show that logcf is competitive with RootIntervals of Mathematica and the function realroot of Maple averagely and it is much faster than existing open source real root solvers in many test cases.     

ATIS作用下的混合交通行为网络与效率损失上界

考虑一个被路径诱导系统支持的交通网络,装有ATIS的出行者接受交通中心的指挥、按照系统最优的原则选择路径,没有该装置的出行者根据个人成本最小的原则择路,建立了刻画这种混合交通行为的变分不等式模型,推导了混合交通行为网络的效率损失上界,并以多项式路段成本函数为例给出了一些上界的特殊值.研究表明,效率损失上界与具体被研究的网络结构和交通需求水平有关,只有在特殊情况下,才可以得到与网络需求和网络结构无关的上界值.     

任意分布的冷备表决系统可靠度求解

k/n: M(G)冷备表决系统包含n个工作部件, M个冷储备件, 至少有k个部件工作时系统工作。然而, 现有对于k/n: M(G)冷备表决系统的研究集中在同型指数分布的情况, 缺乏针对其工作部件非同型且服从任意分布的情况的研究。本文研究了k/n: M(G)冷备表决系统的可靠度, 系统部件服从任意分布, 冷备件服从同一分布。对k=n的情况, 给出了M取任意值时部件同型和非同型情况下的系统可靠度解析式。对于k＜n的情况, 考虑了两种不同的冷备件替换策略, 给出了部件同型情况和非同型M取特定值情况下的系统可靠度解析式。蒙特卡罗仿真实验证明了所提方法的准确性。