Parallel processing of network calculations in order to speed up transient stability analysis

Power systems have become very large, and in addition the forthcoming open electricity market will make power system operation more complex. Therefore, power system operation must become more efficient and flexible. Very fast power system simulation is a means of achieving more sophisticated power system on‐line monitoring and control, and parallel computing is a key technology for very fast power system simulation. This paper proposes an efficient and fast parallel network calculation algorithm that will contribute to the development of fast power system simulation programs. Numerical examples show that the proposed method using six processors is about 4.0 times as fast as the usual serial algorithm when applied to a large‐scale radial power system and about 3.2 times as fast when applied to a large‐scale loop power system. © 2001 Scripta Technica, Electr Eng Jpn, 135(3): 26–36, 2001     

Large-Scale Shake Table Experiment and Numerical Simulation on the Nonlinear Behavior of Pile-Groups Subjected to Large-Scale Earthquakes

This paper describes the results of large-scale shake-table experiments involving a 3×3 pile-group. The pile-group was embedded in dry sand and subjected to sinusoidal waves and an earthquake motion recorded from the 1995 Hyogo-ken Nanbu (Kobe) earthquake. The load transfer between soil and pile was derived and the group effect was captured. Numerical simulations were also performed using a Beam-on-Nonlinear-Winkler-Foundation approach with a new hysteretic p-y curve. A comparison of the experimental and numerical results revealed that the numerical simulation is capable of accounting for the soil-pile interaction observed in the experiment.     

A 250-Mb/s/pin, 1-Gb double-data-rate SDRAM with a bidirectionaldelay and an interbank shared redundancy scheme

This paper describes three circuit technologies indispensable for high-bandwidth multibank DRAM's. (1) A clock generator based on a bidirectional delay (BDD) eliminates the output skew. The BDD measures the cycle time as the quantity charged or discharged of an analog quantity, and replicates it in the next cycle. This achieves a 0.18-mm ², two-cycle-lock clock generator operating from 25 to 167 MHz with a 30-ps resolution. (2) A quad-coupled receiver eliminates the internal skew caused by the difference between a rise input and a fall input by 40%. (3) An interbank shared redundancy scheme (ISR) with a variable unit redundancy (VUR) efficiently increases yield in multibank DRAM's. The ISR allows redundancy match circuits to be shared with two or more banks. The VUR allows the number of units replaced to be variable. These circuit technologies achieved a 250-Mb/s/pin, 8-bank, 1-Gb double-data-rate synchronous DRAM     

Osteogenic activity of human periosteal sheets cultured on salmon collagen-coated ePTFE meshes

Our animal implantation studies have demonstrated that, after osteogenic processing, cultured human periosteal sheets form osteoid tissue ectopically without the aid of conventional scaffolding materials. To improve the osteogenic activity of these periosteal sheets, we have tested the effects of including a scaffold made of salmon collagen-coated ePTFE mesh. Periosteal sheets were produced with minimal manipulation without enzymatic digestion. Outgrown cells penetrated into the coated mesh fiber networks to form complex multicellular layers and increased expression of alkaline phosphatase activity in response to the osteoinduction. In vitro mineralization was notably enhanced in the original tissue segment regions, but numerous micro-mineral deposits were also formed on the coated-fiber networks. When implanted subcutaneously into nude mice, periosteal sheets efficiently form osteoid around the mineral deposits. These findings suggest that the intricate three-dimensional mesh composed of collagen-coated fibers substantially augmented the osteogenic activity of human periosteal sheets both in vitro and in vivo.     

GaAs/AlGaAs directional coupler switch with submillimetre device length

A GaAs/AlGaAs directional coupler switch, for the first time with a device length shorter than 1 mm, has been fabricated by utilising the good controllability of molecular beam epitaxy and reactive ion beam etching. The switching voltage is as low as 5V. The extinction ratio is 17dB for a crossover state and 14dB for a straight-through state.     

Velocity and absorption coefficient of ultrasonic waves in molten and glassy silicates and borates

The velocity and absorption coefficient of longitudinal ultrasonic waves with 5 and 10 MHz in molten and glassy silicates and borates have been measured by means of the pulse-echo method in 300 to 1600 K. The silicate and borate were Na₂O−SiO₂, K₂O−SiO₂, PbO−SiO₂, Na₂O−B₂O₃, and PbO−B₂O₃. The velocity of sound decreased with increasing temperature and decreased rapidly near the transition temperature of glasses. The product of the one-third power of velocity of sound and the molar volume of the oxide melt was constant and independent of temperature. The absorption coefficient of ultrasonic waves in the oxide melts increased with an increase in viscosity. The absorption mechanisms of ultrasonic waves and the mean free path of phonons in the oxide melts were discussed.     

Synthesis temperature of Ba4CuPt2O9 compounds and the influence of their addition on the orientation of the c-axes of fluorine-doped YBCO superconductors

An experimental study has been carried out to investigate the synergistic effect of Ba₄CuPt₂O₉ compounds on the critical current density of fluorine-doped YBCO superconductors. The Ba₄CuPt₂O₉ compounds were synthesized by a solid state reaction. It was found that the synthesis temperature of the Ba₄CuPt₂O₉ compounds was over 800°C, which was higher than that ever reported previously. In addition, the influence of Ba₄CuPt₂O₉ compounds on the critical current density of YBCO superconductors has been investigated using two types of Ba₄CuPt₂O₉ compounds: one is not heat-treated, i.e. source materials; and the other is heat-treated at 950°C. It was found that the former affected the orientation of the c-axes, but the latter did not have an influence on the orientation of the c-axes, but adversely affected the superconductivity of samples quenched at temperatures above 850°C.     

Effects of compressive strain on the evolution of interfacial strength of steel/nickel solid-state bonding at low temperature

Solid-state bonding between ultralow-carbon steel and pure nickel was conducted by hot pressing with various compressive strain ranging from 5 to 15% and subsequent isothermal holding at 923?K. It was found that the interfacial strength of contact area is accounted for by the evolution of the intrinsic strength of the interface and the amount of plastic energy dissipation at the crack tip during interface fracture. The compression induces severe deformation around the interface and consequently inhibits the plastic energy dissipation during interface fracture. In the first stage of isothermal holding, the residual strain around the interface on the steel side is reduced by recovery process, which concurrently decreases in the yield stress of the area adjacent to the interface. This promotes plastic energy dissipation of the area, leading to a significant increase in interfacial strength in the first stage.