Evaluating uncertainty in accident rate estimation at hydrogen refueling station using time correlation model

Hydrogen, as a future energy carrier, is receiving a significant amount of attention in Japan. From the viewpoint of safety, risk evaluation is required in order to increase the number of hydrogen refueling stations (HRSs) implemented in Japan. Collecting data about accidents in the past will provide a hint to understand the trend in the possibility of accidents occurrence by identifying its operation time However, in new technology; accident rate estimation can have a high degree of uncertainty due to absence of major accident direct data in the late operational period. The uncertainty in the estimation is proportional to the data unavailability, which increases over long operation period due to decrease in number of stations. In this paper, a suitable time correlation model is adopted in the estimation to reflect lack (due to the limited operation period of HRS) or abundance of accident data, which is not well supported by conventional approaches. The model adopted in this paper shows that the uncertainty in the estimation increases when the operation time is long owing to the decreasing data.     

Autonomous frequency regulation by controllable loads to increase acceptable wind power generation

Output power fluctuation of high penetration of wind power causes demand and supply imbalance in electric power systems and results in frequency deviation if the fluctuation is not fully compensated by other regulable power plants. In Japan, some electric utilities have started to accept only the wind farms which disconnect and give up generating power during light‐load periods with less adjustable reserve. Otherwise, wind farms are required to employ battery energy storage systems (BESSs) to charge the generated power during the light‐load periods. Instead of these uneconomical solutions, this paper proposes autonomous frequency regulation by controllable loads such as electric water heaters (EWHs). In the paper, the acceptable increase of wind power generation by the proposed load control has been evaluated quantitatively in the power system of the Hokkaido Island in Japan. The result indicates that the acceptable increase of wind power generation goes from 250 to 675 MW by applying the proposed autonomous frequency regulation on all EWHs, and the total cost to implement the autonomous frequency regulation on the EWHs is around 1/26 compared with a solution using BESSs. Copyright © 2009 John Wiley & Sons, Ltd.     

Development of an evaluation methodology for the natural circulation decay heat removal system in a sodium cooled fast reactor

A natural circulation evaluation methodology has been developed to ensure the safety of a sodium-cooled fast reactor (SFR) of 1500 MW adopting the natural circulation decay heat removal system (NC-DHRS). The methodology consists of a one-dimensional safety analysis which can evaluate the core hot spot temperature taking into account the temperature flattening effect in the core, a three-dimensional fluid flow analysis which can evaluate the thermal-hydraulics for local convections and thermal stratifications in the primary system and DHRS, and a statistical safety evaluation method for the hot spot temperature in the core. The safety analysis method and the three-dimensional analysis method have been validated using results of a 1/10 scaled water test simulating the primary system of the SFR and a sodium test simulating a part of the primary system and the DHRS with about a 1/7 scale, and the applicability of the safety analysis for the SFR has been confirmed by comparing with the three-dimensional analysis adopting the turbulence model. Finally, a statistical safety evaluation has been performed for the SFR using the safety analysis method.     

Thermotropic cholesteric mesophases in copoly(γ-n-alkyl l-glutamate)s

Summary Thermotropic cholesteric mesophases were found for three types of -helical copoly(-n-alkyl L-glutamate)s; the combination of the n-alkyl groups was methyl-hexyl, methyl-octyl, and propyl-octyl. Cholesteric colors due to the selective reflection were observed in the temperature range from 110 to 190°C for the films with copolymer compositions of about 50/50 in mol%. These thermotropically mesomorphic copolymers had disordered structures in the molecular packing as inferred from the x-ray diffraction patterns. The cholesteric sense was right-handed, since the negative circular dichroism associated with the cholesteric pitch was observed for all the mesomorphic films. The temperature dependence of the pitch was discussed in comparison with that of lyotropic liquid crystals of these polymers.     

Agent技术在中国智能电网建设中的应用

在分析智能电网与Agent技术特点的基础上,针对两者之间的共性,综述了Agent技术在中国智能电网建设中的应用。详细分析了Agent技术在电力市场、继电保护、电力系统无功优化及电网故障诊断中的应用。针对微电网技术的缺陷,提出Agent技术在微电网发展中的应用前景。     

Phase relations in the VxW1−xO2 system (0.2 ≤ x ≤ 0.75)

The phase relations in the V_xW_1?xO₂ system were studied by vacuum seal technique at 900°C. A new phase was found around composition of x=0.5. It has a slightly distorted rutile-type structure with doubling of the $\text{a}$ and $\text{c}$ parameters of rutile. Phase transition from this phase to rutile-type phase was examined by DTA. Transition temperature increased with decreasing x-value. Enthalpy change for the transition and the variation of monoclinic angle of the phase seemed to have maximum values at composition of x=0.5.     

一种具有部分高介电常数介质调制效应的IGBT

提出了一种具有高介电常数介质填充沟槽的绝缘栅双极晶体管(IGBT).分析了高介电常数介质调制效应.结果表明,与普通场阻型IGBT相比,该器件的击穿电压提高了 8％,通态压降减小了 8％,关断损耗降低了 11％;在相同通态压降下,该器件的关断损耗降低了 35％.在栅极与原HK介质之间增加介电常数更高的介质,进一步提升了该...