A new technology for the production of aluminum matrix composites by the plasma synthesis method

Aluminum matrix composites were produced via the plasma injection of reinforcing particulates into aluminum melts stirred electromagnetically. In this process, a metallic wire supplied to the active zone of plasma torch disintegrated into fine metallic particles. In the plasma arc, the particles are heated above the melting point and accelerated to close to sonic speed, which helps with the incorporation of the particles into the melt. In this study, the possibility of producing aluminum matrix composites reinforced by intermetallic compound particles via plasma synthesis is demonstrated.     

Comparison of enteral nutrition with combined enteral and parenteral nutrition in post-pancreaticoduodenectomy patients: a pilot study

Background  

Many clinical studies have demonstrated that early postoperative enteral nutrition (EN) improved the postroperative course. Post-pancreaticoduodenectomy (PD), patients tend to suffer from postoperative nausea, abdominal distention, and diarrhoea, causing difficulty in the introduction of EN. In this pilot study, we investigated the appropriate nutritional mode post-pancreatic surgery.     

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     

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.     

Crystallization behaviours around the glass transition temperature in an amorphous Fe–Nb–B alloy

Crystallization behaviours around the glass transition temperature in an amorphous Fe₇₀Nb₁₀B₂₀ alloy were investigated by means of transmission electron microscopy. Dense bcc-Fe nanocrystals initially appeared as the primary phase, followed by the dense formation of the (Fe,Nb)₂₃B₆ nanocrystalline phase. The bcc-Fe nanocrystals were formed even by annealing at a temperature that is 38 K lower than the glass transition temperature. A difference of the low temperature behaviours between the present conventional amorphous alloy and a bulk metallic glass was discussed.     

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.     

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.     

Numerical Modeling of an Earthquake-Induced Landslide Considering the Strain-Softening Characteristics at the Bedding Plane

The damage caused by an earthquake-induced landslide can generally be classified as either a limited deformation or a catastrophic failure. From an engineering point of view, the latter can be much more dangerous because the sliding mass may continue moving until it collides with another object. If a catastrophic failure occurs near a river, the debris may block the river, causing serious damage to the adjacent area. Therefore, examination of the mechanism of such catastrophic slope failures is important with respect to the mitigation of earthquake disasters in mountainous districts, although numerical modeling of such phenomena is rather difficult. In the present study, a new numerical model is developed to simulate an earthquake-induced catastrophic landslide that occured at a typical dip slope, namely, the Yokowatashi Landslide in Japan. In this case, the upper part of the bedrock on the planer tectonic dip surface slid more than 70 m. Only shear-strength degradation at the bedding plane could cause such a long-distance traveling failure. To investigate the strain-softening characteristics of the materials that filled the bedding plane, a series of laboratory tests involving undisturbed block samples was performed. The measured stress-displacement relationships under cyclic loading were numerically modeled as a newly proposed elasto-plastic constitutive model to be used in numerical simulations of landslide, based on the dynamic finite element method. The observed phenomena were appropriately simulated by the proposed method. The mechanism of catastrophic failure is discussed in detail in this paper in order to clarify the relationships between the strain-softening characteristics and the global slope stability. Our newly proposed method to evaluate the possibility of a catastrophic failure was applied to the landslide, and the moment when the slope becomes unstable was able to be predicted. The results confirm that the proposed method can predict the catastrophic failure of a slope.