Diagnosis Criterion of Abnormality of Transformer Winding by Frequency Response Analysis (FRA)

Frequency response analysis (FRA) is a powerful technique to detect internal abnormalities within power transformers. However, diagnosis criteria of power transformers by FRA have not been fully established yet. In this paper, a new evaluation method of degree of identification between two transfer functions is proposed. In the proposed method, a frequency window is employed and cross‐correlation factor is calculated with moving the window. Furthermore, the proposed method is applied to transfer functions of real transformers with or without some abnormalities. Based on this discussion, objective criteria for diagnosis of abnormalities of transformer windings by FRA are proposed. The proposed criteria are based on a few data of transformers with some abnormalities. Therefore, the proposed criteria are tentative and they would be improved by accumulation of further data.     

Day‐Ahead Global Solar Radiation Forecasting Using Binary Trees and Factor Analysis

A method is proposed for forecasting global solar radiation. The method is based on weather information using binary trees and factor analysis. The feature of this method is that it is possible to use a simple linear forecasting equation. The method has been tested on meteorological and global solar radiation data obtained at several observation sites, and the results show that it is a promising means of maintaining the balance between demand and supply of electric power in power systems of the near future with a large number of photovoltaic systems installed.     

Optimum dynamic design for beam shapes subjected to a moving concentrated load

We are concerned with an optimum dynamic design of beams subjected to a moving concentrated load with constant speed. The influence of the dynamic behaviour of the beams is considered in a proposed optimum design problem. The optimum shapes of beams are determined by the minimization of two kinds of performance indices. The optimization procedure is performed by non-linear programming on the basis of the exterior penalty function and BFGS methods. Optimization is calculated by the modal coordinates transformation and the numerical integration method     

A comparative study on heat dissipation, morphological and magnetic properties of hyperthermia suitable nanoparticles prepared by co-precipitation and hydrothermal methods

Magnetite (Fe₃O₄) nanoparticles were prepared by co-precipitation and hydrothermal methods and their phase transfer was done successfully to compare their performances in different aspects. Synthesized nanoparticles were characterized for XRD, FE–SEM, TEM, UV-Vis absorption (reflectance) spectra, magnetic hysteresis loops and a.c. magnetic field induced hyperthermia. The magnetic nanoparticles prepared by the co-precipitation method show superior performances in respect of heat dissipation capability, saturation of magnetization values and particle size when compared to those prepared by the hydrothermal method.     

Isolated Operation of Power System in Complex Housing Supplied by Battery Energy Storage System and Fuel Cells

Fuel cells, as components of cogeneration systems and battery energy storage systems, can be used as power sources in an isolated power system in complex housing at times of blackout. This paper reports study results on such isolated power systems. Simulation models are developed and the results are compared with measured values of active power, reactive power, and voltage. Good agreement is obtained. In this analysis, it is found that there is a stability limit in such inverter power source operation. The stability limit is expressed by a short circuit power ratio that is similar to the one in conventional ac systems. Nonlinear load switching is also studied to demonstrate stable operation.     

A Power Control Method to Save Energy for Wayside Energy Storage Systems in dc‐Electrified Railway System

The introduction of wayside energy storage systems is effective for the recovery of regenerative brake energy in dc‐electrified railways. However, considering the cost of their deployment, it is preferable to maximize the energy saving effect with a minimum capacity of the energy storage devices (ESDs). In this paper, we propose a power control method that can improve the energy saving effect while managing the energy of the ESDs. The proposed method is implemented by controlling the filter capacitor voltage of the line side of the power converter for the ESDs depending on their energy and the line voltage of the overhead contact line to which they are connected. Next, the proposed method is verified by numerical simulations and experimental tests with a 1 kW class downsized model.     

Biochemical Characterization of Collagen in Myocommata and Endomysium Fractions of Carp and Spotted Mackerel Muscle

Myocommata and endomysium fractions were prepared from the different parts of body muscle of carp and spotted mackerel. Both type I and V collagens were detected in the myocommata and endomysium fractions of both fish. The relative concentration of type V collagen to type I collagen was higher in the endomysium fraction than in the myocommata fraction. Both type I and V collagens were less soluble in the endomysium fraction than in the myocommata fraction. These results indicated that the biochemical property of the collagen in the pericellular connective tissue was different from that of the collagen in the interstitial connective tissue of fish.     

DEPENDENCE STRUCTURE— DEPENDENCE AS A BINARY RELATION

In systems theory, we often use the concept of dependence. There are several research to construct a unified framework for dependence. Mainly, the concept of dependence is defined with a dais of subsets, where the concept of algebraic closure systems is often used.

In this paper, we define dependence as a binary relation, which we call dependence structure, and develop a similar argument as for the dependence with a class of subsets. And we will clarify a relationship between dependence structure and the usual concept of dependence.

We also show what conditions assure the existence of a basis for a dependence structure.

The concept of functional dependence in database theory can be represented as a dependence structure and we will show that a key for a relational scheme is a basis for the dependence structure.     

Meaning of state-space representation and its relation to canonical form Part 2. Controllability and constructibility

State space is one of the key concepts of systems theory. In the previous paper (Nakano et al. 1987) a system-theoretic framework about the choice of a state space was developed and the canonical forms of linear control theory were interpreted. Four realizations of a single-input and single-output discrete basic linear system were constructed. The isomorphism between the realizations and the universal state space representation shows systemic meanings of the state space. In this paper, using the same approach, two other realizations—a controllability realization and a constructibility realization—are constructed. By the matrix representations of these realizations the meanings of the controllability and constructibility canonical forms are shown in relation to the universal state-space representation.