Dependent Dirichlet Process Rating Model (DDP-RM)

Typical IRT rating-scale models assume that the rating category threshold parameters are the same over examinees. However, it can be argued that many rating data sets violate this assumption. To address this practical psychometric problem, we introduce a novel, Bayesian nonparametric IRT model for rating scale items. The model is an infinite-mixture of Rasch partial credit models, based on a localized Dependent Dirichlet process (DDP). The model treats the rating thresholds as the random parameters that are subject to the mixture, and has (stick-breaking) mixture weights that are covariate-dependent. Thus, the novel model allows the rating category thresholds to vary flexibly across items and examinees, and allows the distribution of the category thresholds to vary flexibly as a function of covariates. We illustrate the new model through the analysis of a simulated data set, and through the analysis of a real rating data set that is well-known in the psychometric literature. The model is shown to have better predictive-fit performance, compared to other commonly used IRT rating models.Comment: 2 tables and 5 figure

"Automobiles: Strategy-based Lean Production System"

The present situations and future prospects of the Japanese automobile industry are discussed. Selected topics in this paper include the following: analyses of the basic product-industry characteristics of the automobile (e.g., product architecture); the mature of the dynamic competition in the world auto industry; competitive performance (e.g., productivity) of the Japanese auto makers; organizational capabilities of better Japanese firms in production, development and procurement; overall environments in the 1990s; the concept of "balanced lean" system and its adaptation to environmental changes; new flexible production systems that cope with volume fluctuation; architectural strategies of the auto firms; modularization of parts; M&A and alliance; future of the automobile technologies and architectures; future of the capability-building competition.

Modularization in the Auto Industry: Interlinked Multiple Hierarchies of Product, Production, and Supplier Systems

This paper analyzes the modularization in the world auto industry. The modularization in the industry has involved architectural changes in product, production, and supplier systems with each region (Japan, Europe and the U.S.A.) emphasizing different purposes and aspects. As an attempt to understand such multi-faceted, complex processes coherently, this paper proposes a conceptual framework that sees development / production activities as interlinked, multiple hierarchies of products, processes, and inter-firm boundaries. With this framework, drawing on case studies and questionnaire survey data, the paper examines the on-going processes of modularization in the industry. It is argued that tensions exist among the three hierarchies, and such tensions may lead to further changes in product, production and supplier-system architectures in the auto industry, in a dynamic and path-dependent manner.Automotive industry, modularization, product architecture, production system, supplier system, hierarchies

Evaporation experiments of metallic iron in vacuum

Evaporation experiments were carried out to examine evaporation kinetics of metallic iron, one of the important materials forming terrestrial planets and meteorites. Platelets of pure metallic iron were heated at temperatures ranging from 1075 to 1312℃ under vacuum (10^ to 10^ Torr) for 0.5 to 96 hrs. The evaporation proceeds by forming evaporation steps, although small wustite crystals were formed on the surfaces by partial oxidation of iron under vacuum. Amounts of evaporated iron estimated from mass loss of experimental charges increased with time at constant temperatures, showing a linear rate law. The evaporation rates, j, can be represented by ln j=22.21±2.29[mol m^s^]-390.6±29.2[kJ mol^]/RT. The evaporation coefficients, α_v, were obtained by comparing the experimental results with calculated rates using the Hertz-Knudsen equation. The value of α_v is close to unity if effects of partial oxidation are taken into consideration. The present results give basic information for discussing chemical evolution of the primordial solar nebula

Automobiles:Strategy-based Lean Production System

The present situations and future prospects of the Japanese automobile industry are discussed. Selected topics in this paper include the following: analyses of the basic product-industry characteristics of the automobile (e.g., product architecture); the mature of the dynamic competition in the world auto industry; competitive performance (e.g., productivity) of the Japanese auto makers; organizational capabilities of better Japanese firms in production, development and procurement; overall environments in the 1990s; the concept of ?balanced lean? system and its adaptation to environmental changes; new flexible production systems that cope with volume fluctuation; architectural strategies of the auto firms; modularization of parts; M&A and alliance; future of the automobile technologies and architectures; future of the capability-building competition

Triangle Cylinder Wake Analysis Based on Wavelet and POD Techniques

AbstractThe turbulent structure behind a two-dimensional symmetric triangle cylinder is measured by PIV experiment at Reynolds number of 14440. To reveal the possibly existed flow phenomena that buried in the mean flow, one dimensional orthogonal wavelet and POD analyses are employed to decompose the fluctuating velocity field into different wavelet components and modes. The features of reconstructed flow fields are analyzed in terms of fluctuating energy, time frequency distribution and length scale. It is found that the first two wavelet components and POD modes can give representations to the most energetic large scale structures, contributing about 77% and 73% to the total fluctuating energy respectively. Comparing with the first two wavelet components, the first two POD modes are more appropriate to represent the Karman like vortical structures. The time-frequency and length scale characteristics of wavelet components suggest that frequency behavior can reflect the spatial related length scale and the wavelet analysis can be used to extract turbulent structures of different scales