用改进的强隐式方法求解三维不可压粘性流动问题

提出了一种用改进的强隐式方法求解三维不可压缩粘性流动的交错网格有限体积法．该方法在ＳＩＭＰＥＲ算法的基础上，对Ｎ－Ｓ方程的对流项采用ＱＵＩＣＫ格式离散，利用ＭＳＩ方法求解代数方程．数值计算表明本方法具有计算稳定、收敛速度快等特点．     

计算机求解一阶导函数的设计与实现

计算机自动求解导函数实现，在科学计算、公式推导、定理证明、ＣＡＩ软件设计等方面有很重要的意义。文中提出一种计算机求解一阶导函数的设计与实现方法，对函数的表示、分解、类型判断和求导算法进行了详细的介绍，同时给出了求解算法Ｃ语言描述     

Block censoring scheme with two-parameter exponential distribution

This paper deals with a new censoring scheme, called ‘Block Censoring’ which reduces considerably the total time on test in the life testing experiments with respect to the common used experimental tests such as rightly censored data. This new scheme is analysed when the lifetimes of products follow the two-parameter exponential distribution. Specially, it is proved that the respective spacings are independently distributed exponential. The problem of estimating parameters is investigated in details.A Monte Carlo simulation is conducted for obtaining the optimal block censoring scheme in the sense of the shortest expected test time. Finally, a real data set on times to breakdown of an insulating fluid between electrodes from Nelson [Applied life data analysis. New York: Wiley; 1982. p.105] is analysed.     

Stochastic approximation results for variational inequality problem using random-type iterative schemes

Real world problems are embedded with uncertainties. Therefore, to tackle these problems, one must consider probabilistic nature of the problems both in modeling and solution. In this work, concepts of convergence of the solution of variational inequality in classical functional analysis are extended to a stochastic domain for a random Mann-type iterative and Ishikawa-type iterative schemes in a Banach space. A mean square convergence result is proved for this extension.     

A New Fully Polynomial Time Approximation Scheme for the Knapsack Problem

A fully polynomial time approximation scheme (FPTAS) is presented for the classical 0-1 knapsack problem. The new approach considerably improves the necessary space requirements. The two best previously known approaches need O(n + 1/³) and O(n · 1/) space, respectively. Our new approximation scheme requires only O(n + 1/²) space while also reducing the running time.     

农村卫生室收入情况调查与实证分析--以湖北省松滋市为例

村卫生室是农村三级医疗预防保健网的网底,承担着为农村居民提供基本公共卫生服务与疾病初级诊治的职责。村卫生室的收入情况直接影响到农村医生的收入水平与工作积极性。而村卫生室的收入受到村卫生室门诊人数、经营面积、村医人数等因素的影响。通过对湖北省松滋市259所村卫生室年收入情况进行实地调查,运用计量分析方法分析了影响村卫生室年收入的主要因素。     

Pricing and Operational Performance in Discretionary Services

In many services, for example, website or landscape design, the value or quality derived by a customer depends upon the service time, and this valuation differs across customers. Customers procure the service based on the expected value to be delivered, prices charged, and the timeliness of service. We investigate the performance of the optimal pricing scheme as well as two commonly used pricing schemes (fixed fee and time‐based pricing) for such services on important dimensions such as revenue, demand served, and utilization. We propose a novel model that captures the above features and wherein both service rate and demand are endogenous and functions of the pricing scheme. In particular, service time is an outcome of the pricing scheme adopted and the heterogeneous valuations of customers, unlike in the queueing‐based pricing literature. We find that the service system may benefit from a greater variance in consumer valuations, and the performance of pricing schemes is impacted by the shape of the distribution of customers' valuation of service time and the responsiveness desired by customers. Both the fixed fee and time‐based schemes do well relative to the optimal pricing scheme in terms of revenue in many plausible scenarios, but there are substantial differences between the pricing schemes in some important operational metrics. For instance, the fixed fee scheme serves more customers and has higher utilization than the time‐based scheme. We also explore variants of the fixed and time‐based schemes that have better revenue performance and show that the two‐part tariff which is a combination of fixed and time‐based pricing can do as well as the optimal scheme in terms of revenue.     

三维各向同性谐振子的对称守恒张量与欧勒角

三维各向同性谐振子有一对称的守恒张量，由守桓张量可直接求得振子的特征能量和轨道长短轴的长度，确定轨道长短轴方向及轨道平面法线方向的三欧勒角，可由守桓张量的分量及机械能、角动量决定．     

How to Design Rating Schemes of Risk Matrices: A Sequential Updating Approach

Risk matrices have been widely used as a risk evaluation tool in many fields due to their simplicity and intuitive nature. Designing a rating scheme, i.e., determining the number of ratings used in a risk matrix and assigning different ratings to different cells, is an essential part of risk matrix construction. However, most of the related literature has focused on applying a risk matrix to various fields, instead of researching how to design risk matrices. Based on the analysis of several current rules, we propose a new approach, namely, the sequential updating approach (SUA), to design the rating scheme of a risk matrix in a reliable way. In this article, we propose three principles and a rating algorithm based on these principles. The three principles, namely, adjusted weak consistency, consistent internality, and continuous screening, characterize a good rating scheme. The resulting rating scheme has been proven to be unique. A global rating algorithm is then proposed to create the design that satisfies the three principles. We then explore the performance of the SUA. An illustrative application is first given to explain the feasibility of our approach. The sensitivity analysis shows that our method captures a resolution‐reliability tradeoff for decisionmakers in choosing an appropriate rating scheme for a risk matrix. Finally, we compare the designs based on the SUA and Cox's axioms, highlighting the advantages of the SUA.     

多媒体辅助下的大学英语听力课堂的实践研究

随着高等学校英语课堂教学改革的深入[1-5],多媒体辅助教学也日益盛行,但大多数是运用在大学英语精读课堂上。作者从多媒体辅助下的大学英语听力课堂实践研究出发,指出了运用多媒体辅助大学英语听力课堂教学的重要意义,并提出了用多媒体去辅助大学英语听力课教学的方法[6~9]。作者指出,多媒体辅助下的大学英语听力课堂是基于传统听力课堂上的重要教学改革成果,它有利于提高学生学习英语的兴趣和英语听力的水平,也能够进一步提高学生运用英语的综合能力。