Optimal inventory policies when stockouts result from defective products

An implicit assumption underlying most inventory systems is that the lot ordered will not contain any defective, i.e., unsaleable items when delivered and so there will be no ‘shortages’ in the delivery in the sense that every unit of the product in the accepted lot is of perfect quality and therefore fully acceptable to the customers. Such an assumption is not always tenable in view of the extensive use of acceptance sampling by business and industry in the quality control process. The presence of defective items in the traditional inventory models which foresee no such possibility would certainly disrupt the systems in use, and consequently entail higher operating cost on the inventory management. With an aim to broaden the base of applications, and to demonstrate the impacts of the possible presence of defective products upon the structure and the cost of certain inventory systems, this paper extends two inventory models to the case where the proportion of defective units in the accepted lot is a random variable with known probability distributions. Optimal solutions to the modified systems are developed and comparisons with the traditional models are also presented via numerical examples.     

The interpretation of indexing of high Σ CSL grain boundaries from ceramics

Electron backscatter diffraction (EBSD) is a useful technique for measuring the orientation of individual grains and for determining grain boundary misorientations in polycrystals. However, its application to ceramics is more difficult than to metals, because the surface quality that can be achieved often makes the Kikuchi patterns blurred. As a consequence, it can be difficult, even for automated systems, to differentiate between different grain orientations, which have similar patterns. In this paper, we carry out EBSD analyses of SrTiO₃ polycrystalline material prepared with different polishing methods, and we consider the effect of different criteria in interpreting the EBSD patterns from them. In particular, we investigate the CSL statistics using both the Palumbo and Aust and the Brandon criteria in this situation.     

Optimal control of deterministic systems described by integrodifferential equations

The synthesis of an optimal control function for deterministic systems described by integrodifferential equations is investigated. By using the elegant operational properties of shifted Chebyshev polynomials, a direct computational algorithm for evaluating the optimal control and trajectory of deterministic systems is developed. An example is given to illustrate the utility of this method, and other orthogonal functions are also shown for comparison.     

公路隧道火灾紧急应变及救援策略模式之研究

公路隧道因其密闭、空间局限等特性,使其在发生火灾事故时,常具温度高、疏散困难、救灾急迫、抢救不易之特性,除阻碍初期应变、救灾外,更可能因隧道之封闭整修,造成经济及国家形象之重大损失.以雪山隧道为例,探讨公路隧道大规模火灾紧急应变及救援策略模式与消防安全设计趋势.将综览美国、澳洲、欧盟、日本等国隧道消防安全设施及策略及研究计划成果,并以FDS模拟雪山隧道发生大客车火灾事故时固定式水系统灭火设备之动作效能.另假设雪山隧道若发生堵车延烧及大客车事故,探讨其于应变、避难、救援等方面可能衍生之问题,以进一步检视长公路隧道之潜在危机.     

内燃机車駕駛自动化

文内介绍了采用复合控制原理和根据机车所处客观条件自动切换系统结构的内燃机车程序控制方案.介绍了按此方案制成的(自动司机)总体线路及其性能.介绍了利用这台控制机进行内燃机车自动驾驶的全面试验结果.文中着重讨论了自动切换系统结构的逻辑装置的设计计算.给出了综合这类系统参数的计算公式.此外,对系统的控制质量进行了详细讨论.     

Yield and Textural Properties of Soft Tofu as Affected by Coagulation Method

Soft tofu was made using two coagulants (calcium sulfate and modified nigari), three stirring speeds (137, 207, and 285 rpm), and six stirring times (5, 10, 15, 20, 25, and 30 sec). The lowest stirring speed, 137 rpm, did not coagulate the soymilk. Tofu made by the highest stirring speed (285 rpm) had a lower yield, but higher brittleness force, hardness and elasticity than tofu made at 207 rpm. Tofu made from modified nigari had lower textural parameter values than those made from calcium sulfate. Yield of tofu made from both coagulants stirred at 207 or 285 rpm decreased as stirring time increased to 30 sec. Textural properties were related to stirring time. Stirring time < 25 sec was appropriate for soft tofu making.     

Application of digital image correlation method for analysing crack variation of reinforced concrete beams

The Digital Image Correlation (DIC) method is a fast-growing emerging technology that provides a low-cost method for measuring the strain of an object. In this study, the feasibility of using this method to observe cracks developed in reinforced concrete beams will be explored so that a practical application can be proposed. The DIC method has been applied for analysing the field of surface displacement and strain; it is not applicable for measuring non-continuous field of displacement. However, if a singular point (i.e., crack points) can be considered as the area of concentrated strain by imitating the treatment of micro-cracks using the finite element method, the region of concentrated strain field based on analyses of digital images can be applied for determining the locations of cracks. Laboratory results show that cracks developed in reinforced cement beams can be observed with a good precision using the von Mises strain field, and that smaller grids lead to clearer crack images. In addition to identifying visible cracks, the DIC image analysis will enable researchers to identify minute cracks that are not visible to naked eyes. Additionally, the DIC method has more accuracy and precision than visual observation for analysing crack loadings so that earlier warnings can be realized before cracks develop in the specimen.     

Parameter estimation of time-varying systems via Chebyshev polynomials of the second kind

A new method for the parameter estimation of linear time-varying systems using Chebyshev polynomials of the second kind is presented. The systems are characterized by linear differential equations with time-varying coefficients that are in the form of polynomials in the time variable. The operational matrices of integration and time-variable multiplication of Chebyshev polynomials of the second kind play key roles in the derivation of the algorithm. Least-squares estimation of overdetermined linear algebraic equations obtained from polynomial approximations of the systems is used to estimate the unknown parameters. Illustrative examples give satisfactory results