Electron Spin Dynamics in (DMe-DCNQI)2M (M = Li1-x Cu x (x < 0.14), Ag)

The quarter-filled π band systems, (DMe-DCNQI)_2M(M=Li_1-x Cu _x (x ≤ 0.14), Ag) were systematically studied with electron paramagnetic resonance (EPR). The intercolumn spin hopping rate in Li_1-x Cu _x -salt was obtained from the EPR linewidth. The temperature dependence of can be understood with the hole soliton model which also explains the DC conductivity. The π−d mixing of the Cu-salt enhances both and by 10³ times more than the Li-salt, which is consistent with the fact that the only Cu-salt has three-dimensional Fermi surface, but that Ag-salt is one-dimensional in spite of the mixing enhancement of by 10 times more than the Li-salt.     

Visual analysis of cavity filling and packing process in injection molding of thermoset phenolic resin by the gate‐magnetization method

The Gate‐Magnetization method developed by Yokoi and coworkers for thermoplastics was used to investigate the flow behavior of glass‐fiber reinforced phenolic resin compound inside a mold cavity. Plug flow builds up in the cavity with a decrease of the local viscosity along the cavity wall due to the heat transfer from the wall and shear heating. Simultaneously, a high viscosity layer builds up from the crosslinking reaction along the cavity wall. The thickness of the high viscosity layer increased as the injection rate decreased. An unstable flow boundary formed between the reacted high viscosity layer along the wall and the low viscosity layer just under the layer.     

Film formation from cationic electropaint systems containing resins with different glass transition temperature

Some phenomena in the deposition process of electropainting have not been well elucidated till now. In this paper, to investigate an influence of glass transition temperature (T_g) on film formation, the deposited film was observed with an atomic force microscope and the electrochemistry was investigated, using two kinds of cationic acrylate resin with different T_g (methyl methacrylate system (MMAs): T_g=70°C, and methyl acrylate system (MAs): T_g=5°C). Electrodeposition was performed under constant voltage or current condition.

At constant voltage, the deposition behavior in the two resin systems differed extremely. The MMAs, the resin with high T_g, produced a high resistance film. The MAs, the resin with low T_g, was deposited forming a film at a voltage lower than 20 V. At constant current, the film formation did not result in a rise in voltage. It behaved like a conductive film. When the resin with high T_g was used, particulate deposits were observed by AFM even in the induction period. The resin with low T_g formed flat deposits. These results suggest that paint deposition is initiated once electrolysis of water starts. In addition, there are two types of film formation on the cationic electropainting: high resistance film formation for the resin with high T_g, and ion-permeable film formation for the resin with low T_g. In both cases, film growth occurs at the film/bulk solution interface.     

A 5‐MHz AT‐cut quartz crystal oscillating circuit functioning in 350 nA

An oscillating circuit functioning at ultra low power (350 nA) for a 5‐MHz AT‐cut quartz crystal oscillator was investigated. This circuit has a resistance between the power terminal of the CMOS‐IC and the power supply, and another between the earth terminal of the CMOS‐IC and the ground (GND). These resistances discourage an inrush of current, and set a gain (g_m) necessary for oscillating the circuit at minimum. The developed circuit is quite simple, but enables driving at once‐unthinkable, low power (below 1 µA). © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Sintering Characteristics in BaTiO3–Nb2O5–Co3O4 Ternary System: I, Electrical Properties and Microstructure

The influences of the Nb/Co ratio on electrical properties, densification behavior, and microstructural evolution were investigated on ceramics in the ternary system BaTiO₃-Nb₂O₅-Co₃O₄. Temperature-stable dielectrics were obtained using either a large amount of Nb + Co or a large Nb/Co ratio. The sintering characteristics and electrical properties were studied for the niobium-rich composition (Nb/Co = 3.00; Comp.N) and the cobalt-rich composition (Nb/Co = 1.67; Comp.C) with the same Nb + Co amount of 2 at.%. The temperature characteristic of the dielectric constant was flat, irrespective of the firing temperature, for Comp.N, whereas it was dependent largely on the firing temperature for Comp.C. The grains did not grow in Comp.N but grew in Comp.C. The reaction of Nb₂O₅ and Co₃O₄ with BaTiO₃ yielded secondary phases: Ba₆Ti₁₇O₄₀ phase for Comp.N, and a barium-poor, titanium-rich, and cobalt-rich phase for Comp.C. These secondary phases formed a liquid phase during firing. Comp.N contained a larger amount of the secondary phase than Comp.C. It was concluded that the liquid phase contributed little to densification and microstructural evolution in the system BaTiO₃-Nb₂O₅-Co₃O₄.     

Current status of seismic and borehole measurements for HDR/HWR development

Seismic and borehole measurements provide significant information about HDR/HWR reservoirs that is useful for reservoir development, reservoir characterization, and performance evaluation. Both techniques have been widely used during all HDR/HWR development projects. Seismic measurements have advanced from making passive surface measurements during hydraulic fracturing to making passive observations from multiple boreholes during all phases of HDR/HWR development, as well as active seismic measurements to probe regions of the reservoir deemed to be of interest. Seismic data provide information about reservoir extent, locations and orientations of significant fractures, and areas of thermal drawdown. Recent advances include the ability to examine structures within the seismically active zone using statistics-based techniques and methods such as seismic tomography. Seismic method is the only means to obtain direct information about reservoir characteristics away from boreholes. Borehole measurements provide high-resolution information about reservoir characteristics in the vicinity of the borehole. The ability to make borehole measurements has grown during the course of HDR/HWR development as high temperature tools have been developed. Temperature logging, televiewer logs, and electrical property measurements have been made and shown to provide useful information about locations of fractures intersecting wellbores, and regions where water leaves and enters injection and production wellbores, respectively.     

Numerical analysis of fragmentation mechanisms in vapor explosions

Fragmentation of molten metal is the key process in vapor explosions. However, this process is so rapid that the mechanisms have not yet been clarified in experimental studies. In addition, numerical simulation is difficult because we have to analyze water, steam and molten metal simultaneously with boiling and fragmentation. The authors have been developing a new numerical method, the moving particle semi-implicit (MPS) method, based on moving particles and their interactions. Grids are not necessary. Incompressible flows with fragmentation on free surfaces have been calculated successfully using the MPS method. In the present study, numerical simulation of the fragmentation processes using the MPS method is carried out to investigate the mechanisms. A numerical model to calculate boiling from water to steam is developed. In this model, new particles are generated on water–steam interfaces. A two-step pressure calculation algorithm is also developed. Pressure fields are separately calculated in both heavy and light fluids to maintain numerical stability with the water and steam system. The new model and algorithm are added to the MPS code. Water jet impingement on a molten tin pool is calculated using the MPS code as a simulation of collapse of a vapor film around a melt drop. Penetration of the water jet, which is assumed in Kim–Corradini’s model, is not observed. If the jet fluid density is hypothetically larger, the penetration appears. Next, impingement of two water jets is calculated. A filament of the molten metal is observed between the two water jets as assumed in Ciccarelli–Frost’s model. If the water density is hypothetically larger, the filament does not appear. The critical value of the density ratio of the jet fluid over the pool fluid is ρ_jet/ρ_pool=0.7 in this study. The density ratios of tin–water and UO₂–water are in the region of filament generation, Ciccarelli–Frost’s model. The effect of boiling is also investigated. Growth of the filament is not accelerated when the normal boiling is considered. This is because normal boiling requires more time than that of the jet impingement, although the filament growth is governed by an instant of the jet impingement. Next, rapid boiling based on spontaneous nucleation is considered. The filament growth is markedly accelerated. This result is consistent with the experimental fact that the spontaneous nucleation temperature is a necessary condition of vapor explosions.     

Voltage distribution in multi-cascaded transformer

The voltage distribution for lightning surges in multicascaded transformers that will be used for converter transformers in self-excited dc transmission was studied using model transformers. There was good agreement between measured data and calculated results. It was shown that our calculation program has sufficient accuracy for estimating voltage distribution. Maximum voltages in high-voltage windings for lightning surges were below 120% and transfer voltages to the converting circuit were below about 5%. Therefore, there were no serious problems in cascaded transformers for lightning surges. However, their voltage distribution was not satisfactory when the same transformers were connected in cascade. We determined by a simulation that the distribution could be improved by modifying transformer structures according to their position in the cascade connection. © 1998 Scripta Technica. Electr Eng Jpn, 122(1): 17–24, 1998     

Sediment penetration performance of a portable underwater robot for core sampling

As described in this paper, we investigate the sediment penetration performance of a portable underwater robot with a helical screw pipe using marine thrusters with limited force. First, we derive a mathematical model based on an empirical and simple method using the undrained shear strength of cohesive soil to provide a rough estimate of maximum penetration depths. Then, we perform numerical analysis for estimating the maximum depth of sediment penetration and for designing a sampling pipe. Additionally, we use experimentation to investigate the relation between the penetration depth of the helical screw pipe and the force of marine thrusters mounted on the portable underwater robot. After testing the penetration performance in a water tank, we conduct a field experiment at Lake Biwa and obtain results of the penetration depths. The maximum penetration into the lake sediment is at least 0.30 m. The results demonstrated the possibility of using the derived mathematical model to make a rough estimation of the maximum penetration depth for clay sediments. Additionally, we can use non-powerful thrusters equipped with small autonomous underwater vehicles (AUVs) and remotely operated vehicles (ROVs) for sediment sampling. The proposed method is also applicable for the installation of underwater sensors using small AUVs and ROVs.