825 research outputs found
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
Correlation among Solidification Process, Microstructure, Microsegregation and Solidification Cracking Susceptibility in Stainless Steel Weld Metals(Materials, Metallurgy & Weldability)
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
Inter-granular cracking of a splat of zirconia coating fabricated by plasma spraying technique
EFFICACY AND SAFETY OF EARLY ADMINISTRATION OF HEPARIN IN PATIENTS WITH ACUTE MYOCARDIAL INFARCTION
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