Relationship Between System Failure Rate and Component Failure Rates

A simple sufficient condition is given for a system to have an increasing failure rate when the identical components comprising it have an increasing failure rate. Systems which function if and only if at least k of the n components function (“k out of n” systems) satisfy this condition. For systems of non-identical components, upper and lower bounds on failure rate are obtained in terms of component failure rates. These bounds are increasing functions of time for “k out of n” structures having components with increasing failure rates.     

Improved dynamic analysis of structures with mechanical uncertainties under deterministic input

This paper addresses the dynamic analysis of linear systems with uncertain parameters subjected to deterministic excitation. The conventional methods dealing with stochastic structures are based on series expansion of stochastic quantities with respect to uncertain parameters, by means of either Taylor expansion, perturbation technique or Neumann expansion and evaluate the first- and second-order moments of the response by solving deterministic equations. Unfortunately, these methods lead to significant error when the coefficients of variation of uncertainties are relatively large. Herein, an improved first-order perturbation approach is proposed, which considers the stochastic quantities as the sum of their mean and deviation. Comparisons with conventional second-order perturbation approach and Monte Carlo simulations illustrate the efficiency of the proposed method. Applications are discussed in order to investigate the influence of mass, damping and stiffness uncertainty on the dynamic response of the system.     

Improved predictor-corrector method for solving fuzzy initial value problems

In this paper, an improved predictor-corrector (IPC) method is proposed to solve the “fuzzy initial value problem”. The IPC method is generated by combining an explicit three-step method and an implicit two-step method. The methods are compared with the methods discussed in [T. Allahviranloo, N. Ahmady, E. Ahmady, Numerical solution of fuzzy differential equations by predictor-corrector method, Information Sciences 177(7) (2007) 1633-1647], and are shown to be more accurate. The convergence and stability of the proposed methods are also presented in detail. These methods are illustrated by solving some examples.     

UODV: improved algorithm and generalized theory

Uncorrelated optimal discrimination vectors (UODV) is an effective linear discrimination approach. However, this approach has the disadvantages in both the algorithm and the theory. In light of this, we propose an improved UODV algorithm based on the typical principal component analysis (TPCA), which can satisfy the statistical uncorrelation and utilize the total scatter information of the training samples. Then, a new and generalized theorem on UODV is presented. This generalized theorem reveals the essential relationship between UODV and the well-known Fisherface method, and proves that our improved UODV algorithm is theoretically superior to the Fisherface method. Experimental results on both 1-D and 2-D data prove that our algorithm outperforms the original UODV approach and the Fisherface method.     

A solar air heater with variable flow passage width

Different designs of solar air heaters with variable width of the flow channels are investigated.

Four possible geometries for the flow passage are considered with the aim to improve the efficienc of the system by maintaining a constant temperature of the absorber plate.

Efficiencies and plate temperatures are calculated for various designs, among them the most efficient is the one with decreasing duct width.     

A new approach to improve the high-voltage cyclic performance of Li-rich layered cathode material by electrochemical pre-treatment

Lithium-rich nickel–manganese–cobalt oxide, Li[Ni_0.17Li_0.2Co_0.07Mn_0.56]O₂, was prepared by a co-precipitation method, and its cyclic behavior at a high potential was investigated. The as-prepared material shows a rapid capacity fading in its initial several cycles when it was operated above 4.5 V, which could be significantly improved through a pre-cycling treatment. Its reversible capacity in the range of 4.8–2 V could be increased from 200 to 250 mAh g⁻¹ after 50 cycle through a stepped pre-cycling treatment.     

川东三岔坪潜伏构造石炭系储层特征及有利区预测

通过对川东三岔坪潜伏构造石炭系储层特征的研究,发现储集空间以溶孔及晶间孔为主;储集类型属裂缝-孔隙型;纵向上以Ⅲ类储层为主,Ⅱ类储层呈局部分布(具有2个相对的高孔带);储层的主要控制因素为溶蚀及构造作用。采用改进曲率及地震方法对石炭系储层进行了综合预测后指出,早期认为的石炭系储层缺失区并不存在,有利储层分布区呈局部的点团状或条带状分布并且是该区下步勘探及井位部署的重点区域。     

装配式高架桥立柱自适应安装测量技术

装配式高架桥立柱安装常需要施工人员进行高空作业,风险较大且测量手段较为复杂。为了解决这一问题,本文提出了一种装配式高架桥立柱自适应安装测量方法并介绍其基本原理和技术特点。基于该方法,设计并加工了一X型导向架,该导向架能够在地面获取立柱的实际位置。同时针对自适应安装测量技术开发了一款施工辅助程序用以辅助计算、缩小系统误差、判断立柱安装是否满足施工精度要求并获取调整结果。最后,以实际工程为例,验证该测量方法和测量装置的有效性。     

A novel method of Coriolis flowmeter phase difference measurement based on improved correlation analysis method

The shortcomings traditional phase difference extraction algorithms have such as being susceptible to noise interference, requiring full cycle conditions, leads to a decrease in phase difference extraction accuracy. To improve the accuracy of the phase difference extraction, two improved correlation analysis methods are proposed in this paper, one of which is based on the relationship between the extreme value of the cross-correlation function and the time difference, the other of which combines correlation analysis method with Hilbert transform. A simulation and experiment were set up to explore the influence of sequence length and signal-to-noise ratio on the extraction accuracy, as well as the influence of Kalman filtering. An experiment is set to compare the extraction mean error and variance of different algorithms under different phase differences. Experimental result shows that the improved algorithms have higher accuracy and stability. The feasibility of the two improved algorithms is verified.     

一种改进型DCSK保密通信系统性能分析

差分混沌键控(DCSK)的输出信号具有固有的抗噪声以及宽频特性,由于其采用非相干解调技术,不必在收发两端建立同步,相比传统通信系统有很多优势。但其传输速率较低、保密性差。针对上述问题,提出一种改进型DCSK保密通信系统。该系统将信息分散于两个正交信道中传输,不仅保证了传输速率而且提高了安全性。理论分析和仿真结果证明,改进型DCSK保密通信系统较原系统性能有极大的提高。