Development of Reference Shunt for Short‐Time Alternating High Current Tests and Study of Measuring System

Short‐circuit tests for power circuit breakers and others require alternative short‐time current measurement, from a few kA to over several tens kA. However, the reference measurement system as a national standard or a specified secondary standard instrument to directly perform comparative test as a complete calibration test in high current class has not yet been established globally. The Japan Short‐Circuit Testing Committee (hereinafter referred to as “JSTC”) has therefore developed a shunt resistor that can be used as a standard instrument for high current measurement. Reference system using this shunt resistor is also considered by JSTC. The performance of the newly developed shunt resistor has been checked through several methods, such as resistance measurement, high power current test, high frequency current test, temperature rise test, and interference test. The results of the tests proved satisfactory performance. Resistance of the shunt resistor before and after the tests was invariant and stable. This makes the shunt resistor adequate for a reference in practical use. In addition, evaluation of uncertainty of the whole reference system including this shunt resistor satisfactorily fulfills the requirements of IEC 62475 edition 1.0, 2010.     

Solution to the inverse regulator problem for discrete-time systems

A complete solution is given for the inverse problem of LQ optimal regulators for the discrete-time multi-input case. The Kalman equation for discrete-time systems is derived to characterize the optimal regulators. It is then shown that this equation holds for some quadratic weighting if and only if the feedback satisfies a condition corresponding to the circle criterion for continuous-time systems. The optimality criterion given here consists of this condition and an additional condition to ensure detectability. An example is given to illustrate the results.     

Feedback realizations in linear multivariable systems: model-following with stability and disturbance rejection

This paper deals with the problems of constructing a compensator for linear multi-variable systems that simultaneously ensures: (I) model-following with stability and (ii) disturbance rejection. Necessary and sufficient conditions for the solvability of the problems are given by using a geometric approach. The solvability conditions are explicit and the constructive procedure for finding a solution does not require any additional conditions for the plant.     

Novel active-R synthesis of a driving-point impedance

A novel active-R synthesis baaed on the single-pole rolloff characteristics of operational amplifiers is described. Various types of driving-point impedance, such as an inductance, frequency-dependent negative-resistance and frequency-dependent negative-inductance are systematically derived by the suitable choice of the amplifier transfer function. It is shown by experiments that the inductance simulator presents reliable high frequency performance.     

ELASTIC–PLASTIC ANALYSIS OF THE FATIGUE LIMIT FOR A MATERIAL WITH SMALL FLAWS

Abstract Fatigue tests were carried out on mild steel with small cracks for which linear fracture mechanics is not effective. A fatigue limit criterion, based on the cyclic plastic zone size at a crack tip being a material constant at the fatigue limit, can effectively evaluate the effects of crack length and stress ratio. Regarding flaws as cracks, the theory gives fatigue limit values close to those obtained in experiments on specimens with natural defects, such as surface roughness, micro-shrinkage cavities, inclusions etc. The effect of water corrosion was also investigated.     

LOW CYCLE FATIGUE CRACK PROPAGATION AT A NOTCH UNDER PULSATING LOAD

Abstract Fatigue crack propagation tests were carried out under pulsating stress, partly alternating stress and alternating plastic fatigue for Cr- Mo-V steel and mild steel. Although stress and strain intensity factors do not effectively correlate the fatigue crack growth rate over a wide range of stress and strain conditions, a normalized fatigue crack growth rate [(d a /d N )/ a ] is related to the strain range. The fatigue crack propagation behavior at a notch under pulsating load is analyzed with the above relation by considering the cyclic elastic- plastic condition at the notch.     

Growth characteristics of Bacillus subtilis (natto) in milk

In this paper, Bacillus subtilis (natto) was incubated to develop a possible functional ingredient in ice cream. A lab‐scale culture revealed that incubation in the sterilised milk without dilution and concentration at 37°C for 28 h could obtain ideal growth characteristics of Bacillus subtilis (natto), especially with continuous aeration. Following freezing operation of the cultured milk, survival content of Bacillus subtilis (natto) was at 49–92%, while nattokinase activity was conserved at 62–98% comparing with the initial contents, which indicating a potential for application of natto functional ingredient in frozen milk products.     

Invar36合金搅拌摩擦焊焊缝的低温韧性

为了研究Invar36合金搅拌摩擦焊焊缝的低温韧性,采用小冲杆试验方法（small punch test）对焊接速度2mm／s,搅拌头旋转频率200一1000r／min的Invar36合金焊缝进行低温（77K）和室温（298K）韧性测试．298K下,所有焊接工艺的焊缝小冲杆试验能均高于母材,焊缝韧性随搅拌头旋转频率的提...