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.     

Magnetization dynamics and related phenomena in semiconductors with ferromagnetism

We review ferromagnetic resonance (FMR) and related phenomena in the ferromagnetic semiconductor (Ga,Mn)As and single crystalline Fe/GaAs (001) hybrid structures. In both systems, spin-orbit interaction is the key ingredient for various intriguing phenomena.     

Kinetics of removal of bismuth and lead from molten copper alloys in vacuum induction melting

An investigation was made of the rates of removal of bismuth and lead from molten copper alloys stirred differently under vacuum at 1403 K. The heating conditions, which corresponded to highest, intermediate, and lowest stirring, were referred to as HC-A, HC-B, and HC-C, respectively. The rates of removal were described by a first-order rate equation involving the final concentration of the impurity. The overall mass-transfer coefficient for bismuth or lead (i),K _i, was determined, and it was found that K_i(HC-A) > K_i(HC-B) but K_i(HC-B) < K_i(HC-C) in Cu-Bi, Cu-Pb, and Cu-Bi-Pb alloys. In general, it was found that K_i(Cu-Bi-Pb) > K_i(Cu-Bi) or K_i(Cu-Pb). Oxygen reducedK _i more than sulfur. The reducing effect of oxygen and sulfur was weakened when stirring rate increased. In vacuum melting of Cu-Bi-Pb-O and Cu-Bi-Pb-S alloys under HC-C,K _i tended to decrease with increasing oxygen and sulfur concentrations. The loss of copper indicated that the rates were determined by liquid-phase mass-transfer and evaporation. The liquid-phase mass-transfer coefficient,K _L, was calculated, and it was found thatK _L(UC- A) > K_L(HC-B) but K_L(HC-B) < K_L(HC-C). The last relation was contrary to current theoretical prediction. A new model was assumed to account for this fact. The observed relative volatility coefficients of bismuth and lead were much smaller than their respective theoretical coefficients. Oxygen and sulfur adsorbed on the surface of the melt were considered to be close to equilibrium with their respective bulk concentrations, and their effects on the evaporation mass-transfer coefficients for bismuth and lead were estimated to be fairly small. This result means that the observed reduction ofK _i is due mostly to the decrease inK _L and made possible the calculation ofK _L. Oxygen decreasedK _L more than sulfur. In vacuum melting of Cu-Bi-Pb-O and Cu-Bi-Pb-S alloys under HC-C,K _L decreased linearly with increasing oxygen or sulfur concentration. The final concentrations of bismuth and lead in these alloys under HC-C tended to increase with increasing oxygen and sulfur concentrations and tended to decrease with increasingK _i andK _L.     

A 400 K-transistor CMOS sea-of-gates array with continuous track allocation

A 0.8- mu m CMOS sea-of-gates (SOG) array with first-level wiring channels perpendicular to transistor rows and 40 0K transistors is integrated on a 6*7-mm/sup 2/ chip. Implementation of a 64-bit multiplier shows 60-percent gate utilization and density of 1410 G/mm/sup 2/. The wiring length of the multiplier is 70 percent of that in a conventional SOG.<>     

Gate-controlled modulation of electronic states and conductance in coupled quantum wells having an in-plane periodic potential

We investigated theoretically a unique way to control the dispersion relation of electrons by using a novel double quantum well (DQW) structure, in which an in-plane periodic potential is introduced to one of the channels. It is demonstrated that the effective mass in this system can be abruptly changed by the gate-controlled resonant coupling, resulting in a switching of the channel current. We discuss also a few feasible schemes to achieve the effective mass modulation and their possible applications to the velocity modulation transistor.     

Analysis of vinylidene chloride and 1-chlorobutane in foods packaged with polyvinylidene chloride casing films by headspace gas chromatography/mass spectrometry (GC/MS)

A headspace gas chromatography/mass spectrometry method was developed for the simultaneous determination of vinylidene chloride and 1-chlorobutane in foods packaged with polyvinylidene chloride casing films. The solid foodstuff was homogenized with an equal mass of distilled water. The homogenate was incubated for 1 h at 90°C in a sealed headspace vial, and the headspace gas was then analysed by gas chromatography/mass spectrometry in selected ion-monitoring mode using a bonded porous polymer-coated capillary column. The recovery rates of vinylidene chloride and 1-chlorobutane in foodstuffs were 94.5-103.9 and 85.8-120.3%, respectively. Among 13 samples tested, vinylidene chloride was detected at 0.001-0.020 µg g^-1 in 11 foodstuffs, and 1-chlorobutane was detected at 0.004-0.040 µg g^-1 in all 13 foodstuffs. Furthermore, vinylidene chloride was detected at 0.04 µg g^-1 in one casing film, and 1-chlorobutane was detected in all casing films. The results indicate that these compounds migrated from the casing films into the foodstuffs.     

Experiment and numerical simulation of double-layered RC plates under impact loadings

This paper is to investigate and to propose a method to improve the impact resistance of reinforced concrete (RC) plates against projectile impact, and the damage of double-layered RC plates is examined experimentally and simulated analytically. In tests, a projectile launching apparatus, which is a 40 mm smooth-bore airgun, was used. Based on experimental results, numerical simulations with the DYNA-3D code, which takes account of the dynamic constitutive law of concrete, were done to find the applicability of the present computer code to the analysis of double-layered RC plates under high-speed impact loadings. In this study, the impact resistance of concrete plate is defined as the degree of local damage. In both experiments and numerical simulations, the effect of double-layering on the impact resistance is discussed.     

Increases in hematopoietic responses caused by beta-glucans in mice

The effects of various (1-->3)-beta-D-glucans on hematopoietic responses of mice were investigated by measuring colony stimulating activity in sera and ascites of the mice administered glucan. We have demonstrated that the hematopoietic response was increased by various structures of (1-->3)-beta-D-glucans, i.e. soluble glucans (linear, branched, single helix, triple helix) and particulate glucans. From the viewpoint of structure and activity relationships, we found several characteristic features: i) hematopoietic response induced by the particulate glucan disappeared faster than that by the soluble glucans, ii) conformation of the glucans, single vs. triple helix, are relatively independent of the response, iii) linear glucan had a weaker response, and iv) there is a strong strain-dependency of the response. These results corresponded well with the fact that branched (1-->3)-beta-D-glucans, but not linear and not particulate, are often used as biological response modifiers for cancer patients.