Polarity Effect and Electromagnetic Radiation of Partial Discharge Accompanying Growth of Electrical Tree

We have investigated the characteristics of radiated electromagnetic (EM) waves from positive and negative partial discharges (PD) in epoxy resin and cross‐linked polyethylene. We found that there is a correlation among the EM level from PD, the positive PD current, and electrical trees. Therefore, the growth of an electrical tree produces a lot of positive PD. We have also investigated the characteristics of the frequency region of EM waves from PD in air, insulating oil, and liquid epoxy in addition to the above insulators. EM waves were detected in the frequency region of 40 MHz to 300 MHz from positive and negative PD in epoxy resin and cross‐linked polyethylene. EM waves were also detected in the frequency region of 40 MHz to 150 MHz from positive and negative PD in air. In the case of insulating oil and liquid epoxy, EM waves were detected in the frequency regions of 40 MHz to 150 MHz from positive PD, and 40 MHz to 250 MHz from negative PD. The frequency region differed depending on the material and the discharge polarity. Our investigation indicates that the cause is differences in electric field strength at the time of PD occurrence.     

Recovery of fluorocarbons in Japan as a measure for abating global warming

The objective of this study is to evaluate the potential for recovering fluorocarbons as measures for the abatement of global warming. In this study, we focused on the three different kinds of fluorocarbons: CFCs, HCFCs and HFCs, and targeted refrigerant use because of the availability of relevant data. We first estimated future fluorocarbon emissions from the targeted appliances; we next compared those emissions in the units of CO₂ equivalent to the level of CO₂ emissions in 1990 from a quantitative point of view. As the result of this study, it was found that fluorocarbon emissions in 1999 and 2010 would be equal to approximately 7 and 3% of the level of CO₂ emissions in 1990 respectively. Moreover, if we implement a 100% recovery rate in every recovery route, we can reduce a large amount of emissions which correspond to approximately 2–5% of the level of CO₂ emissions in 1990, even if we take into account the energy-related CO₂ emissions by the transportation and decomposition of fluorocarbons.     

Measurement of the density and surface tension of Ni-based superalloys in the liquid and mushy states

The densities of three Ni-based superalloys have been measured in both liquid and mushy states by both a modified sessile drop method (MSDM) and a modified pycnometric method (MPM) for alloys CMSX-4 and CM186LC, and for CMSX-10 alloy by MSDM only. The surface tensions of liquid CMSX-4, CM186LC, and CMSX-10 superalloys were measured using the sessile drop method. All measurements were carried out in a highly purified argon atmosphere with the oxygen partial pressure of less than 10⁻¹⁹ MPa in the gas outlet. The densities of all superalloys in both liquid and mushy states were found to decrease with increasing temperature. The volume thermal expansion of each superalloy in the mushy state was found to be higher than that in the liquid state. The densities determined by different methods have been critically assessed and recommended values in both liquid and mushy states are given as a linear function of temperature for the three Ni-based superalloys. The surface tension of liquid CMSX-4 superalloy was found to decrease with increasing temperature, while that of liquid CMSX-10 superalloy increases with increasing temperature. The wetting behavior of liquid CM186LC on the alumina substrate was found (1) to differ significantly from that of CMSX-4 and CMSX-10 and (2) to vary with time. A HfO₂-rich layer was found in the contact area of CM186LC with the alumina substrate, which could lead to some uncertainty in the value obtained for the surface tension determined for CM186LC.     

Temporal Specificity of Extinction in Autoshaping.

Three experiments investigated the effects of varying the conditioned stimulus (CS) duration between training and extinction. Ring doves (Streptopelia risoria) were autoshaped on a fixed CS-unconditioned stimulus (US) interval and extinguished with CS presentations that were longer, shorter, or the same as the training duration. During a subsequent test session, the training CS duration was reintroduced. Results suggest that the cessation of responding during an extinction session is controlled by generalization of excitation between the training and extinction CSs and by the number of nonreinforced CS presentations. Transfer of extinction to the training CS is controlled by the similarity between the extinction and training CSs. Extinction learning is temporally specific. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Density Measurement of Liquid Ni-Ta Alloys by a Modified Sessile Drop Method

The density of liquid Ni- Ta alloys was measured by using a modified sessile drop method. It is found that the density of the liquid Ni- Ta alloys decreases with the increasing temperature, but increases with the increase of tantalum concentration in the alloys. The molar volume of liquid Ni- Ta binary alloys increases with the increase of temperature ancl tantalum concentration.     

Bolted tension flanges joining square hollow section members

Tests and theoretical analysis on the maximum strength of high strength bolted tension flanges joining square hollow section members have been carried out. Yield line theory has been applied in a similar way to that presented in a previous paper. Correlation between test results and theoretical predictions is quite satisfactory. Based on this study, a simple design formula has been proposed.     

Survey of switching techniques in high-speed networks and their performance

One of the most promising approaches for high speed networks for integrated service applications is fast packet switching, or ATM (asynchronous transfer mode). ATM can be characterized by very high speed transmission links and simple, hard-wired protocols within a network. To match the transmission speed of the network links, and to minimize the overhead due to the processing of network protocols, the switching of cells is done in hardware switching fabrics in ATM networks. A number of designs have been proposed for implementing ATM switches. Although many differences exist among the proposals, the vast majority of them are based on self-routeing multistage interconnection networks. This is because of the desirable features of multi-stage interconnection networks such as self-routeing capability and suitability for VLSI implementation. Existing ATM switch architectures can be classified into two major classes: blocking switches, where blockings of cells may occur within a switch when more than one cell contends for the same internal link, and non-blocking switches, where no internal blocking occurs. A large number of techniques have also been proposed to improve the performance of blocking and non-blocking switches. In this paper, we present an extensive survey of the existing proposals for ATM switch architectures, focusing on their performance issues.     

A 286 mm2 256 Mb DRAM with ×32 both-ends DQ

This paper describes a 256 Mb DRAM chip architecture which provides up to ×32 wide organization. In order to minimize the die size, three new techniques: an exchangeable hierarchical data line structure, an irregular sense amp layout, and a split address bus with local redrive scheme in the both-ends DQ were introduced. A chip has been developed based on the architecture with 0.25 μm CMOS technology. The chip measures 13.25 mm×21.55 mm, which is the smallest 256 Mb DRAM ever reported. A row address strobe (RAS) access time of 26 ns was obtained under 2.8 V power supply and 85°C. In addition, a 100 MHz×32 page mode operation, namely 400 M byte/s data rate, in the standard extended data output (EDO) cycle has been successfully demonstrated     

Strength and ductility under dynamic loading in fine- grained IN905XL aluminum alloy

Three IN905XL aluminum alloys with fine grain (1 μm), intermediate grain (3 μm), and coarse grain (5 μm) have been developed by a combination of mechanical alloying (MA) and conventional extrusion in order to investigate their mechanical properties at dynamic strain rates of 1 × 10³ and 2 × 10³ s⁻¹ and a quasi-static strain rate of 10^-3 s⁻¹. Flow stresses are found to increase with decreasing grain size for all the strain rates tested. Negative strain-rate sensitivity of flow stress is observed up to 1 × 10³ s⁻¹ in both intermediate- and coarse-grained IN905XL. At the highest strain rate of 2 × 10³ s⁻¹ however, all samples showed a positive strain-rate sensitivity of strength. Total elongation at high strain rates is generally larger than that at low strain rates. Total elongation also decreases with grain size for all the strain rates. This decrease in elongation results from an initiation of microcracks at interfaces between the matrix and particles finely dispersed near grain boundary regions, introduced during MA processing; then, this initiation leads elongation of alloys to small limited values. Formerly with the Department of Mechanical Systems Engineering, University of Osaka Prefecture. This article is based on a presentation made in the symposium “Dynamic Behavior of Materials,” presented at the 1994 Fall Meeting of TMS/ASM in Rosemont, Illinois, October 3-5, 1994, under the auspices of the TMS-SMD Mechanical Metallurgy Committee and the ASM-MSD Flow and Fracture Committee.