Supplier quality assessment to identify depth technical knowledge of component reliability

As a result of global competition, international companies that manufacture photocopiers, printers or car navigation systems have to purchase low-cost electronic components such as semiconductors and hard disk drives by outsourcing production. However, it is often difficult for these companies to evaluate the quality of their suppliers through interviews and technical documentations. This article proposes new measures for supplier assessment and a systematic approach to select suppliers that have in-depth knowledge of component reliability and technology. The measures for selection not only include the physical quality of components but also information disclosures provided by suppliers, which consist of failure analysis, reliability data and details of the design-manufacturing process. The proposed measures are applied to real data of photocopier manufacturing enterprises. Experiments conducted show that a systematic assessment will enable selecting appropriate suppliers with a lower failure rate.     

Why doLuehdorfia butterflies lay eggs in clusters?

Summary Luehdorfia butterflies lay eggs in clusters. Clones of their host plants (Asiasarum andHeterotropa) are distributed pacthily among the understory of deciduous forests. Groups ofLuehdorfia larvae often exhaust the clones and may wander over the forest floor seeking new clones. The highest mortality observed is during this wandering period. To elucidate whyLuehdorfia butterflies lay eggs in clusters, a simulation experiment was made for hypothetical populations which lay eggs in clusters or singly. Field data on larval mortality, consumption, density of host clones and leaf weight forLuehdorfia japonica were incorporated into the model. The predictions of the simulation were: (1) When the egg density is low, the single egg type could leave many more pupae than the egg clustering type, but when the egg density is high, the former might leave smaller number of pupae than the latter; and (2) There are optimal sizes of egg clusters for different egg densities and the optimal size becomes larger as the egg density increased. This work was supported in part by Grant-in-Aid No. 439017 and No. 56480039 from the Ministry of Education, Science and Culture, Japan.     

试论朝鲜李朝时期“孝”观念与儒教和佛教的关系

李朝时期的"孝"思想是由于性理学的兴起,而成为当时社会的重要价值的。尽管如此,它与性理学的"孝"观念仍存在着非常明显的差异。被性理学看作是异端的佛教"孝"思想因素在李朝时期的"孝"意识中占据着重要的地位。这正是"孝"思想传入朝鲜以后发生的重大变异,是朝鲜独特的"孝"意识结构。     

Genetic risk of domestication in artificial fish stocking and its possible reduction

Genetic hazards associated with the stocking of fish juveniles produced in hatcheries were studied with simple mathematical models. Domestication is the process of acquiring a genetic characteristics that are advantageous in a hatchery environment but that are disadvantageous in a natural environment due to the selection pressure in the hatchery differing from that in the natural environment. Conditions for the propagation of mutants enhancing domestication were obtained for a variety of stocking strategies specified by parameters related to hatchery productivity and kind of brood stock used. By using this, the possibility of reducing the risk of domestication was studied. As a means of reducing the risk, selective use of wild-born individuals for brood stock was considered. The effectiveness of this was analyzed for both the cases where all brood stock is collected from the wild, and the male brood stock is collected from the wild and the female brood stock is born and reared in a hatchery. We also estimate how much hatchery release can be increased without increasing the risk by employing these means. It is concluded that the use of only male brood stock from the wild is not very effective in reducing the risk of domestication. Further, it is concluded that selective use of the wild-born individuals of both sexes for brood stock is highly desirable if the contribution of released individuals to the natural reproduction is high. In other words, substantial increase of hatchery release may be possible while keeping risk at a level comparable to that under moderate hatchery release, if it is accompanied by the selective use of wild-born individuals for brood stock.     

DECOMPOSITION ALGORITHM FOR PERFORMANCE EVALUATION OF AGV SYSTEMS

This paper proposes a realistic queueing model of automated guided vehicle (agv) systems in just-in-time production systems. The model takes into consideration return paths, Erlang distributed service times, and pull-type dispatching rule, assuming finite buffer capacities. Since it has no product-form solution and natural decomposability due to complex nontree fork-cum-join architecture and dynamic dispatching rules, we propose a machine-based decomposition algorithm for the performance evaluation of the model. Each decomposed module consists of the processing machine and its dispatching station. Three flow probabilities, derived from flow conservation analysis, relate the modules, which are updated iteratively until the parameters converge. The numerical results from a real-life Agv system application show that the algorithm is reasonably accurate.