Novel view of the origin of thermal and intrinsic breakdowns

A novel view is presented on the origin of thermal and intrinsic breakdowns from the analysis of published data for pynax glass and several polymers. For the former, the Origin is not due to failure of thermal balance between joule heating and its dissipation, but to charge injection from the anode, by which the current surge to the cathode is afforded and, when the cathode cannot accommodate the neutralized charge carriers, those neutralized species would pile up and advance the cathode-front back to the anode and, finally, a filamentary conductive path is constructed between the electrodes. It is suggested that the occurrence of intrinsic breakdown is determined by the number of electrons which are injected from the cathode by tunnelling because an individual electron gives rise to a certain amount of damage on its passage through the insulator by momentum transfer. From the analysis of time delay before the onset of breakdown, we can estimate the electron affinity of an insulator.     

Study of rationalized safety design based on the seismic PSA for an LMFBR

Seismic PSA was carried out for a typical liquid metal cooled fast breeder reactor (LMFBR) in order to study the rationalized seismic design, maintaining and/or improving safety during seismic event. The seismic sequence quantification identifies the dominant structures, systems and components (SSCs) to the seismic core damage frequency (CDF). The sensitivity analyses by reducing or increasing the seismic capacity for SSCs are used to examine the optimized seismic design in view of safety and economical aspects. The LMFBR-specific risk-significant SSCs are reactor coolant boundary, decay heat removal coolant path and reactor control rod, which are different from those of light water reactors (LWRs). The electrical power supply system has a minor contribution to the seismic CDF. The sensitivity study shows that passive safety features of LMFBRs are important to maintain and/or enhance seismic capacity. The passive safety includes the decay heat removal capability via natural circulation and safety measures without depending on the support systems such as alternating current (AC) electrical power, for example. On the course of seismic sequence quantification, a methodology to evaluate the probability of seismic-induced multiple failure has been developed and applied to the decay heat removal function. The results suggest the multiplicity of the triply redundant system is to be considered for the significant components such as the decay heat removal path when one considers the difference in the seismic response.     

Coal liquefaction induced by hydrogen atoms

Reactions between coals and hydrogen atoms were studied using a discharge flow apparatus at temperatures ranging from 403 to 523 K under 133 Pa pressure. Australian brown coal (Yallourn) and Japanese subbituminous coal (Taiheiyo) both yielded liquid hydrocarbons of similar composition. In contrast to conventional coal liquefaction, the present system led to the formation of exhaustively hydrogenated products composed mainly of monocyclic alkanes.     

H∞ preview tracking in output feedback setting

The performance of preview control is investigated in terms of H^∞‐criterion. In the output feedback setting, an H^∞ preview control problem is discussed and the analytic solution is characterized by introducing matrix Riccati equations. The strength and the limitation of the H^∞ preview performance are illustrated with numerical examples. Copyright © 2004 John Wiley & Sons, Ltd.     

Basic Study of Performance-Based Design in Civil Engineering

Although performance-based design, procurement, and construction management are now spreading rapidly in the building construction field, full-fledged study of the method for public works has barely begun. At this time, therefore, the concept expressed by the term “performance-based design” (which in this article, for simplicity, will include procurement and construction management) varies from person to person. This article is a basic study of the concepts of performance-based standards, performance-based standardization, and performance-based ordering, which are all necessary to introduce the performance-based design approach into the civil engineering field. It is proposed that performance-based design be defined in terms of two conditions: attainment level of objective of use, and degree of freedom. The article introduces the bottom-up and top-down methods as basic performance standardization methodologies.     

Integral Type Position-Sensitive Proportional Chamber with Multiplexer Readout System

A new position-sensitive detector with a multiplexer readout system for synchrotron radiation measurements is described. The detector consists of many proportional chamber cells with capacitors for charge accumulation. Charges delivered from a detector cell are accumulated in an associated capacitor during a measuring time. The accumulated charges are transferred to a charge-sensitive amplifier through a multiplexer channel which is addressed by binary coded signals. This process corresponds to the integral type radiation measurement which has no dead time in the pulse measurement. Each cell is regarded as a memory cell containing information about X-ray photons. Experiments carried out with a direct X-ray beam show that the detecting system is applicable to a wide range of photon rates from 103 cps to 108 cps per cell.     

The Influence of Iron on Ammonium Ion Generation from Nitrate Ion in Liquid Phase

Flue gas cleaning in discharge plasma process has been Studied intensively and we have tried to remove the NOx and S02 using the wet-type plasma reactor. In this system, NO is oxidized to NO2 and absorbed as NO3^-, and SO2 is absorbed as SO3^2- and oxidized in the liquid to SO4^2-. But the concentration of NO3^- was saturated and the absorption of NOx and SO2 was inhibited. Then, the reduction of NO3^- in the liquid is required. We examined the reductive reaction of NO3^- to NH4^ using discharge above the liquid surface then the pH value of the liquid was changed to alkaline slightly. When the Fe plate was used as a ground electrode in the liquid, NH4^ was generated. Then, the relation between the generation of NH4^ and Fe ions (Fe^2 and Fe^3 ) was studied. When Fe^2 was presented in the liquid, NH4^ was generated and Fe^2 was oxidized to Fe^3 . Fe^2 is required to generate NH4^ from NO3^-. When NH4^ was generated from NO3^-, both the calculated pH value from NH4^ concentration and the measured pH value indicated a similar value. From these results, the discharge above the liquid surface was effective to convert NO3^- to NH4^ and the reductive reaction leads to more absorption of NO3^-. These results showed that the wet-type plasma reactor is effective for NOx and SO2 removal system.