Design Guideline of Multi-Gate MOSFETs With Substrate-Bias Control

A device design guideline of multi-gate MOSFETs with both short-channel effect immunity and a large body factor gamma is developed considering threshold-voltage control by a substrate bias. A sufficiently large gamma, at least 0.04-0.05, is essential for suppressing a subthreshold leakage current and die-to-die characteristic variation by a substrate bias. It is experimentally evaluated that gamma decreases with decreasing channel width. Channel thickness and width design space is explored by means of three-dimensional device simulations, and a thin and wide channel structure is found to be the best design for a threshold-voltage control. Thin buried oxide is advantageous for obtaining a large gamma. When the channel doping concentration is high, channel-structure design window shifts to a thinner and wider region compared to the undoped channel due to the modulation of carrier distribution in the channel. However, due to within-die random variations, highly doped design is not practical, and undoped channel design is only the solution. Required accuracy of structural parameters is also discussed. The thin and wide channel design is also advantageous in the viewpoint of the process variation     

A batchSPP/G/1 queue with multiple vacations and exhaustive service discipline

This paper considers a batch-arrival single-server queueing system with multiple vacations and exhaustive service discipline. Customers arrive to the system in accordance with a batch switched Poisson process (batchSPP). Using the supplementary variable technique, we analyze the stationary queue length distribution and derive various formulas for queue lengths and waiting times. In particular, we analytically show the decomposition property for the waiting time distributions. Therefore, the waiting time formulas developed in this paper can also be applied to a batchSPP/G/1 queue without vacations.     

Spatial configurations,competition and welfare

Studies into the shapes of market areas abound and emphasize the hexagon as the optimal configuration. This paper demonstrates that a triangular or a square market area can be superior to a hexagonal one under certain behavioural conditions. Spatial configurations are evaluated on the basis of (1) the number of firms required to fill a given market area and (2) the level of welfare per unit area that these firms generate under alternative competitive conditions.     

Tuned-pendulum mass damper installed in crystal tower

A new damper to reduce the lateral vibration of buildings has been developed and installed in a 37-story office building: Crystal Tower, Osaka. The tower has a slender proportion of height—width ratio 6. The damper can decrease wind-induced motion by 50%. Crystal Tower is the first high-rise building with this damper in Japan, and the damper weight, 540 tons (1190 kips), is large compared with others in use elsewhere in the world. The damper is a pendulum-type tuned-mass damper and the ice thermal storage tanks for air conditioning are used as the moving mass of the damper. The TMD of Crystal Tower, therefore, needs no additional mass weight nor space for installing. This paper presents some intrinsic features of the damper and demonstrates how simple and practical the damper is. Special considerations are given both to the connecting joints between the tank and the building and also to the sloshing behavior of the liquid contents. Typhoon and earthquake records observed in Crystal Tower have proved that the damper works as well as expected.     

Selective decomposition of the siloxane bond constituting the crosslinking element of silane-crosslinked polyethylene by supercritical alcohol

Material recycling of silane-crosslinked polyethylene (silane-XLPE) was investigated to make thermoplastic polyethylene (PE). To make thermoplastic PE from silane-XLPE, a crosslinking element that consists of a siloxane bond must selectively be decomposed. Supercritical alcohol and water were adopted in this study. An autoclave was applied to expose silane-XLPE to the supercritical fluid. The structure of the products was analyzed with ²⁹Si-NMR, Fourier transform infrared, gel fraction, and molecular weight measurements. The results showed that the siloxane bond was successfully decomposed selectively by supercritical alcohol. It was expected that the structure of the recycled PE would be close to that of the silane-grafted PE. To confirm this expectation, the recycled PE was cured in saturated water vapor to investigate the crosslinking ability. The recycled PE, silane-grafted PE, and silane-grafted PE with a catalyst for condensation were compared. The kinetics and activation energy were calculated from the data of the temperature dependence of the increment of the gel fraction. The results showed that the recycled PE still had the ability to undergo a crosslinking reaction. The kinetics and activation energy of the recycled PE were closer to those of silane-grafted PE than to those of silane-grafted PE with a catalyst. The activity of the catalyst must have been lost by supercritical alcohol. These data support the expectation of the structure of the recycled PE. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Homoepitaxial diamond p–n+ junction with low specific on-resistance and ideal built-in potential

We have realized low specific on-resistance and ideal built-in potential simultaneously for a (111)-oriented homoepitaxial diamond p–n⁺ junction. As the p–n⁺ junction, the heavily phosphorus doped n⁺-type layer, which shows variable range hopping conduction, was formed on the (111)-oriented boron doped p-type one. By using this hopping conduction, the resistivity of the n⁺-type layer becomes lower by three orders of magnitude than that of a lightly P-doped layer. Current density–voltage characteristics showed a rectification ratio of 10⁶ at ± 15 V at room temperature. The current density and the specific on-resistance at forward bias voltage of 15 V at room temperature are over 100 A/cm² and 8 × 10^− 2 Ωcm², respectively. This low specific on-resistance corresponds to the lower resistivity of the n⁺-type layer by three orders of magnitude than that of conventional lightly P-doped n-type layer. The existence of the space-charge layer at the vicinity of the p–n⁺ junction was confirmed from capacitance–voltage (C–V) characteristics. From C⁻²–V characteristics at 200 °C, the built-in potential was estimated as approximately 4.4 eV, which is identical to that of conventional diamond p–n junction.     

Assessment of global warming impacts on water resources and ecology of a river basin in Japan

Global warming may cause serious problems in the world. However, the influence of water-related factors, such as water resources and basin ecology, due to global warming has not been comprehensively investigated. In this study, a distributed hydrological and environmental model is applied to assess the impacts of global warming on water resources and ecology of the Nagara River in Japan. With GCM outputs for the two periods, 1979 to 2000 and 2079 to 2100, the model simulation mainly reveals four aspects of the influences of global warming: (i) precipitation and streamflow discharge increase in summer; (ii) air temperature and water temperature rise; (iii) fish habitats are improved, except in summer; and (iv) the boundaries of the crop and vegetation move to higher elevations.