Monotonicity in Optimal Policy of a Flexible Manufacturing Cell Feeding Several Production Lines

This paper deals with an optimal part selection problem tominimize the expected cost, in an automated manufacturing system in which a flexible manufacturing cell produces different parts for several production lines. The optimal control problem is formulated as an undiscounted semi-Markov decision process. Properties of the optimal policy are analyzed. Moreover, sufficiency conditions are derived for the optimal policy to be of control iimit type.     

Self-tuning control based on generalized minimum variance criterion for auto-regressive models

Theoretical problems on self-tuning control include stability, performance and convergence of the recursive algorithm involved. In this paper, the problem of controlling minimum or non-minimum phase auto-regressive models with constant but unknown parameters is considered. The stability of an algorithm obtained by combining a recursive estimator for the controller parameters and a generalized minimum variance criterion is proved. The main result is the theorem which assures the overall stability for the closed-loop system in presence of white noise in the input-output relation, where the estimated parameters do not necessarily converge to the true values. The algorithm is proved by the Lyapunov theory.     

Stochastic analysis of a U-shaped production line with multiple workers

In a conveyor system for mass production as in the Ford system, each station processes just one item in one cycle time, where the cycle time is the time-interval between two successive outputs. In a Just-In-Time production system, a single-unit production and conveyance system is applied to a part production line without conveyors, and multi-function workers and a U-shaped layout of machines have been introduced. The multi-function worker takes charge of multiple machines. In this paper, we consider a U-shaped line with multiple multi-function workers, each of which is responsible for several machines. We formulate it into a marked Petri net, which has a convex property of a generalized semi-Markov process. This shows that the cycle times of two different systems are comparable in the sense of an increasing convex order. We also show the reversibility of the system, that is, the expected cycle time of the reversed system where each worker operates items and walks in the reversed order of stations is the same as that of the original system.     

Quantification of SOFC anode microstructure based on dual beam FIB-SEM technique

The three-dimensional microstructure of an SOFC anode is quantified using a dual beam focused ion beam scanning electron microscopy (FIB-SEM) system equipped with an energy dispersive X-ray spectroscopy (EDX) unit. The microstructure of the Ni-YSZ anode is virtually reconstructed in a computational field using a series of acquired two-dimensional SEM images. The three-phase boundary (TPB) density and tortuosity factors are carefully evaluated by applying two different evaluation methods to each parameter. The TPB density is estimated by a volume expansion method and a centroid method, while the tortuosity factors are evaluated by a random walk calculation and a lattice Boltzmann method (LBM). Estimates of each parameter obtained by the two methods are in good agreement with each other, thereby validating the reliability of the analysis methods proposed in this study.     

Characterization of Deformability of Spheroidal Cementite by Residual Stress Measurement

This article deals with the characterization of the mechanical behaviors of spheroidized carbon steels, which contain ferrite and spheroidal cementite. The aim of the study is to identify the deformation behaviors of cementite particles by x-ray diffraction and to correlate them to the residual stress state evolution. The stress state evolutions for both phases during an in situ 4-point bending test and after a uniaxial tensile test that have been well followed by x-ray diffraction. After each tensile loading, optical observation is made to correlate the determined residual stress state with the microstructure. The coupling of techniques helps us to characterize the deformation evolution of spheroidal cementite in the carbon steel: at the initial state, the cementite shows the same elastic behavior as the ferrite; at the next state, the ferrite begins to deform plastically but the cementite deforms elastically; then, plastic relaxation occurs in the ferrite while the cementite still deforms elastically until finally breaking.     

Electrochemical properties of boron-carbon-nitride films formed by magnetron sputtering

The electrochemical behavior of B_1.0C_2.4N_1.0 thin film was investigated in acidic, neutral and alkaline solutions. The anodic polarization curve of the film in 1 M NaOH showed the anodic dissolution of the film. The curve of the film in 1 M HCl showed no anodic dissolution. The cathodic polarization curve in 1 M NaCl showed shift to a negative potential side, but the anodic polarization curve was the same as that of Pt. The anodic dissolution in 1 M NaOH depended on potentials, that is, no anodic dissolution was recognized in a potential range of −0.2 to 0.1 V but the dissolution rate increased with increasing potential in a range of 0.1-0.6 V. The anodic current density of the film is directly proportional to the dissolution rate at potentials higher than 0.1 V. The dissolution rate of the film was increased with increasing solution pH.     

Suppression of interleukin-2 receptor expression on mouse CD4+ T cells by bovine kappa-caseinoglycopeptide

Bovine kappa-caseinoglycopeptide (residues 106-169, CGP) completely inhibited the PHA-induced proliferation of mouse splenocytes when CGP was added simultaneously with PHA. The inhibitory effect, however, was reduced to about one-half when CGP was added after 24 h of cultivating the splenocytes with PHA or when anti-IL-1ra antibody was added simultaneously with PHA and CGP. On the other hand, CGP bound to mouse CD4+ T cells but not to CD8+ T cells. CGP suppressed IL-2 receptor expression of the PHA-stimulated mouse CD4+ T cells.     

Sodium hyaluronate eyedrops enhance tear film stability

Coeliac disease, also known as gluten-sensitive enteropathy or non-tropical sprue, is a relatively uncommon condition. The dietary presence of gliadin, an alcohol-soluble subfraction of gluten, in immunologically susceptible hosts will lead to small intestinal mucosal inflammation and subsequent mucosal villous atrophy which results in nutrient and vitamin malabsorption. The symptomatic presentations of patients with coeliac disease are related to this malabsorption process which can be reversed in the vast majority of patients with a gluten-free diet.     

Numerical Computation of a New Vortex (A Cooled Vortex Street) and its Generation Mechanism in a Cooled Circular Cylinder Wake at Low Reynolds Number

A strongly cooled, circular cylinder wake with an upward main stream of air at low Reynolds number Re, i.e., 15 ≦ Re ≦ 44, is analyzed numerically, and is elucidated as follows. (1) A new vortex street, i.e., a “cooled vortex street,” is discovered, develops in the range of computed Re, i.e., 15 ≦ Re ≦ 44, has strong asymmetry, and is extremely different from the Karman vortex. (2) The vortex street occurring in the cooled wake is either the Karman vortex street or the cooled vortex street. No vortex street except these vortex streets ever occurs in a wake. (3) The critical Reynolds number Re_c, i.e., the minimum Re occurring in the Karman vortex street by cooling a cylinder, is nearly 24. When the isothermal wake is cooled weakly, the Karman vortex street certainly develops at Re > 24, but never occurs at any cooling rate at Re < 24.

The generation mechanism of the cooled vortex street is elucidated by employing the computed vorticity and temperature distributions as follows. (1) With an extreme increase in the cooling rate, the wake vorticity is generated strongly by the temperature gradient, the absolute value of vorticity in shear layers becomes extremely large, and the shear layers are elongated remarkably. The angle between shear layers and the wake width increase remarkably. (2) As a result, shear layers roll up considerably, and their tips reach the midplane alternately. Extremely large-scale vorticity-concentrated tips are generated, and move to the downstream. Thus a stable wake, i.e., the cooled vortex street, is generated. That is, the stable rolling of shear layers is realized only in the Karman and the cooled vortex streets.