Short channel characteristics of quasi-single-drain MOSFETs

It is clearly demonstrated that source/drain (S/D) elevation is remarkably effective in suppressing the short channel effect against the shrinkage of gate sidewall spacers in MOSFETs. Even if the gate sidewall width is reduced to as very thin as 15 nm, the short channel effect is effectively suppressed by means of the highly elevated S/D regions (80 nm in the present case), though the characteristics of conventional MOSFETs are drastically degraded. This result is explained in terms of the fact that the serious influence due to the deep S/D implantation is suppressed by the formation of a quasi-single-drain configuration. Furthermore, the parasitic S/D resistance decrease, which will bring about drivability enhancement, was observed for reduction in the sidewall width. These favorable experimental results may indicate the definite necessity of elevated S/D engineering for future ultrashort MOSFETs     

Evaluation of cost reduction potential for 1 kW class SOFC stack production: Implications for SOFC technology scenario

Recently, a commercial version of a residential solid oxide fuel cell (SOFC) system with a flat tubular cell has been developed. However, the system cost still remains very high, which is a barrier to its widespread use. In this study, the potential for cost reductions in SOFC stack production was investigated in order to contribute to the viability of the widespread use of such residential SOFC systems in future. A cost analysis of 700 W SOFC stack production based on a process integration modeling was conducted. The present bottom–up approach enabled us to perform a sensitivity analysis with a variety of parameters in terms of cell design, the production process and cell performance. This allowed us to investigate the effects of these factors on the production cost, thereby revealing the quantitative impact of each technological improvement on the cost reduction potential. The present analysis also revealed innovation pathways which could result in technology scenarios where residential SOFC systems could reach a break-even point in comparison with the baseload electricity cost. The analysis of the cost reduction potential presented here provides a useful viewpoint for developing a research strategy for state-of-the-art SOFC technology.     

A novel sphingophosphonolipid head group 1-hydroxy-2-aminoethyl phosphonate in Bdellovibrio stolpii

Members of the bacterial genus Bdellovibrio include strains that are free-living whereas others are known to invade and parasitize larger Gram-negative bacteria. The bacterium can synthesize several sphingophospholipid compounds including those with phosphoryl bonds as well as phosphonyl bonds. In the present study, the dominant sphingophosphonolipid component was isolated by column chromatography, and the long-chain bases, fatty acids, and polar head groups were identified by thin-layer and gas-liquid chromatographic procedures. The definitive structural identity of the sphingolipid was established by nuclear magnetic resonance and mass spectrometry of hydrolysis products and the intact compound. The compound was identified as N-2′-hydroxypentadecanoyl-2-amino-3,4-dihydroxyheptadecan-1-phosphono-(1-hydroxy-2-aminoethane).     

Fluid circulation and heat extraction from engineered geothermal reservoirs

A large amount of fluid circulation and heat extraction (i.e., thermal power production) research and testing has been conducted on engineered geothermal reservoirs in the past 15 years. In confined reservoirs, which best represent the original Hot Dry Rock concept, the flow distribution at any given time is primarily determined by three parameters: (1) the nature of the interconnected network of pressure-stimulated joints and open fractures within the flow-accessible reservoir region, (2) the mean pressure in the reservoir, and (3) the cumulative amount of fluid circulation—and therefore reservoir cooling—that has occurred. For an initial reservoir rock temperature distribution and mean fluid outlet temperature, the rate of heat extraction (i.e., thermal power) is at first only a function of the production flow rate, since the production temperature can be expected to remain essentially constant for some time (months, or even years). However, as reservoir circulation proceeds, the production temperature will eventually start to decline, as determined by the mean effective joint spacing and the total flow-accessible (i.e., heat-transfer) volume of the reservoir. The rate of heat extraction, which depends on the production flow rate, can also vary with time as a result of continuing changes in the flow distribution arising from reservoir cooling.The thermal power of engineered reservoirs can most readily be increased by increasing the production flow rate, as long as this does not lead to premature cooldown, the development of short-circuit flow paths, or excessive water losses. Generally, an increase in flow rate can be accomplished by increasing the injection pressure within limits. This strategy increases the driving pressure drop across the reservoir and the mean reservoir pressure, which in turn reduces the reservoir flow impedance by increasing the amount of joint dilation. However, the usefulness of this strategy is limited to reservoir operating pressures below the fracture extension pressure, and may lead to excessive water losses, particularly in less-confined reservoirs. Under such conditions, a downhole production-well pump may be employed to increase productivity by recovering more of the injected fluid at lower mean reservoir operating pressures.     

Characteristics of ions impacting grid surfaces in an ion engine

Numerical evaluations of grid erosions in ion engines are required to estimate the lifetimes of long-term space missions. In this study, to investigate the characteristics of ions colliding with neutrals and impacting the accel grid surface, including ions that collide with neutrals more than once, three-dimensional particle analyses using a full-PIC (Particle in Cell) code were performed. The distributions of erosion by charge-exchanged ions show periodic patterns. The multiple-collided ion constitutes 7 and 8% of the accel grid current to the inner and downstream surfaces, respectively. The energy of the multiple-collided ion impacting the downstream surface has a broader distribution than that of the charge-exchanged ion. These results suggest the importance of investigating multiple-collided ions in high-accuracy quantitative evaluations of grid erosion.     

Albumin stabilizes (–)‐epigallocatechin gallate in human serum: Binding capacity and antioxidant property

(–)‐Epigallocatechin gallate (EGCg) is the major component of green tea and is known to show strong biological activity, although it can be easily oxidized under physiological conditions. In this study, we indicate that EGCg is stable in human serum and that human serum albumin (HSA) stabilizes EGCg under aerobic condition. Although EGCg is usually decomposed within 1 h in aqueous solution at neutral pH, EGCg in serum and phosphate buffer (pH 7.4) containing HSA was stable over 1 h, even at neutral and slightly alkaline pH. Under these conditions, EGCg binds to HSA non‐covalently. The sulfhydryl group acts as an antioxidant for EGCg oxidation. Incubation of EGCg with HSA is accompanied by the oxidation of a free sulfhydryl group in HSA. These results suggest that the antioxidant property and the binding capacity of HSA contribute to the stabilization of EGCg in human serum.     

Growth of emerald crystals from PbO · V2O5 flux

The flux growth of emerald crystals by slow cooling in the PbO · V₂O₅ flux is reported. The crystals exhibited the typical emerald-green colour, were up to 1.8 mm in size and transparent. Their form was a regular hexagonal rod bounded by the well-developed {0001} and {10ˉ10} faces. The solubility of emerald in PbO · V₂O₅ was also investigated; about 9.0 g emerald was dissolved in 100 g PbO · V₂O₅ at 1200 °C. The solubility decreased gradually with decreasing temperature. Taking the solubility data into account, the presence of undissolved particles in the solution was found to be a necessary condition for the growth of large emerald crystals. Unsaturated solution at a soak temperature produced good and relatively small emerald crystals in a subsequent cooling experiment. Advantages of the PbO · V₂O₅ flux are also mentioned. Emerald crystals showing various kinds of imperfections, and even good crystals, were also present.     

Effects of winding connections on characteristics of a five‐phase stepping motor

A method for calculating the single‐step response of five‐phase hybrid stepping motors is obtained. The effects of winding connecting methods—(1) star‐bipolar SB, (2) pentagon PD, and (3) new pentagon NP—on the single‐step response are investigated. By application of the above calculation method, the continuous rotating characteristics are studied. It is found that the maximum slewing pulse rate of NP is higher than that of SB and PD connections, and that the variation of the rotor speed at high speed with the SB and PD connections is larger than that with the NP connection. The effects of the current waveform on the oscillation characteristics and relations between the current waveform and the winding connections are investigated. © 2001 Scripta Technica, Electr Eng Jpn, 136(1): 47–56, 2001