Development of New Diagnostic Method for Hot-Line XLPE Cables with Water Trees

A new insulation diagnostic method for XLPE cables containing water trees is presented. A dc component in the ac charging current of these cables was found to be a significant sign of the existence of water trees. The dc component has good correlations with such insulation characteristics of aged XLPE cables as ac breakdown voltage and dc leakage current. Criteria for insulation diagnosis of 6.6kV XLPE cables have been established. An automatic insulation diagnostic device has been developed. It is now being applied to hot-line XLPF cables in distribution systems of TEPCO (The Tokyo Electric Power Co., Inc.).     

The hydrolytic polymerization kinetics of ϵ-caprolactam

The three major kinetics of the polymerization of caprolactam, ring opening, condensation and addition, has already been investigated.In this paper, data and rate constants for the other two important reactions, termination and cyclic oligomer formation are given. The both reactions are catalysed by the carboxyl end groups and the termination reaction with a very small quantity of organic acid is also affected by the viscosity of the solution.The effects of operating conditions on the rates and products of the polymerization have been studied through process simulation. It is shown that, to realize the cyclic oligomer content low as possible, simple optimizing criterion as obtaining given degree of polymerization in the shortest possible reaction time gives quite unfavourable conditions to the oligomer content.     

Characteristics of T cell lines established from skin lesions of Beh?et''s disease

There are no available biochemical analyses that will reliably identify malnourished cats or enable monitoring them during supportive alimentation. Studies in people indicate that creatine kinase (CK) activity is high in malnourished patients and may decrease in response to nutritional intervention. The purpose of this study was to determine the value of quantifying serum CK activities in anorectic cats and to assess the usefulness of this test in monitoring nutritional support in these patients. Serum CK activity was evaluated in nonanorectic cats (Group 1, n = 25), and in hospitalized, anorectic cats that received nutritional support through a nasoesophageal tube (Group 2, n = 25). Anorectic cats had a significantly higher serum CK activity (median = 2,529 U/ L, range 88 to 153,000 U/L) than the control group (median = 175 U/L, range 81 to 363 U/L, P < .001). There were significant positive correlations between serum CK and both aspartate transaminase (AST) (P < .05; r = .59) and lactate dehydrogenase (LDH) (P < .05; r = .41) activities. Serum CK activity was significantly lower in anorectic cats after 48 hours of nutritional support than at time 0 (P < .001) and eventually returned to normal with continued support. Serum CK activity may serve as a useful marker in assessing and monitoring nutritional status in cats.     

A method of designing ac/dc thyristor converter current control systems by using discrete time MRAC with deterministic disturbances

Two design methods of ac/dc thyristor converter current control systems with MRAC (Model Reference Adaptive Control) have been designed. To linearize the input/output relation of the systems, the constant term of the model is considered in different ways. In the first method, a linear transformation of the control input is made while in the second method, the constant term and compensated modeling error are neglected by integral adaptation. Computer simulations and experiments have shown that the control performances of the MRAC systems are much better than that of PI controllers. However, in the first method, since the variable vector is not persistently spanning, the convergence rate of estimated parameters is not as high as expected. The second method has better dynamic characteristics but its stability has not been proved in theory. This paper suggests a new design method in which the constant term is considered as a deterministic disturbance. The feature of this method is that by introducing an equality equation which makes the term of disturbances apparently unobservable, the effect of disturbances can be eliminated and the existing adaptive control scheme without disturbances whose stability has been proved theoretically can be used. Computer simulations and experiments show that the new method can obtain better responses than the old ones.     

Measurement and correlation of mutual diffusion coefficients for polybutadiene-hydrocarbon systems

The mutual diffusion coefficients for polybutadiene-ethylbenzene and polybutadiene-n-nonane systems were measured by using a sorption apparatus with a quartz spring in the temperature region from 80 to 130°C and for mass fraction of hydrocarbon ranging from 0 to 0.27. The mutual diffusion coefficients were correlated with good agreement by the free-volume theory.     

Miniature Loop Heat Pipe With Flat Evaporator for Cooling Computer CPU

This paper presents an experimental investigation on a copper miniature loop heat pipe (mLHP) with a flat disk shaped evaporator, 30mm in diameter and 10-mm thick, designed for thermal control of computer microprocessors. Tests were conducted with water as the heat transfer fluid. The device was capable of transferring a heat load of 70W through a distance up to 150mm using 2-mm diameter transport lines. For a range of power applied to the evaporator, the system demonstrated very reliable startup and was able to achieve steady state without any symptoms of wick dry-out. Unlike cylindrical evaporators, flat evaporators are easy to attach to the heat source without need of any cylinder-to-plane reducer material at the interface and thus offer very low thermal resistance to the heat acquisition process. In the horizontal configuration, under air cooling, the minimum value for the mLHP thermal resistance is 0.17degC/W with the corresponding evaporator thermal resistance of 0.06degC/W. It is concluded from the outcomes of the current study that a mLHP with flat evaporator geometry can be effectively used for the thermal control of electronic equipment including notebooks with limited space and high heat flux chipsets. The results also confirm the superior heat transfer characteristics of the copper-water configuration in mLHPs     

Polarisation mode dispersion measurements in long single mode fibres

A new method to measure polarisation mode dispersion is described, in which the accuracy is more than 0.1 ps. 0.17 ps polarisation mode dispersion was obtained for about 1 km length of fibre. The result is compared with the retardation obtained for a short length of the fibre.     

Evaluation Method for Flow Accelerated Corrosion of Components by Corrosion Analysis Coupled with Flow Dynamics Analysis

The troubles of major components and structural materials in nuclear power plants have often been caused by flow-induced vibration, corrosion, and their overlapping effects. In order to establish safe and reliable plant operation, it is required to forecast future troubles based on combined analyses of flow dynamics and corrosion and prevent them at very early stages. Corrosion analysis models have been combined with three-dimensional flow dynamics and heat transfer analysis models to evaluate corrosion damage (e.g., stress corrosion cracking [SCC] and flow-accelerated corrosion [FAC]) of major components and structural materials.

The models are divided into the following two parts. First is a prediction model of future trouble on materials. The distribution of oxidant concentrations along the flow path are obtained by solving water radiolysis reactions in the boiling water reactor primary cooling water and hydrazine and oxygen reactions in pressurized water reactor secondary cooling water. Then, the distribution of electrochemical corrosion potential (ECP) along the flow path is obtained by oxidant concentration based on a mixed potential model. Higher ECP enhances the possibility of SCC, while lower ECP accelerates FAC. Second is an evaluation model of wall thinning caused by FAC. At the location with a higher possibility for FAC occurrence, a trend of wall thinning is evaluated, and the lifetime is estimated for preventive maintenance.