The impedance of the fresh-cut lettuce over a frequency range of 10 Hz-1 MHz were analyzed in order to obtain the fundamental knowledge for the application of electrical impedance spectroscopy (EIS) to the evaluation of freshness of vegetables. The measured impedance characteristics were analyzed with two equivalent circuit models: the Hayden model that represents a cell structure and the model modified with constant phase element (CPE). As a result of comparison of goodness of the equivalent circuit model fitting, the modified model showed significantly higher accuracy of fitting than the Hayden model. The mass ratio and CO₂ and O₂ concentrations in the film package containing the samples greatly changed during storage at the temperature of 20°C, indicating the loss of freshness. Also, the extracellular resistance R_e and the intracellular resistance R_i that are the parameters in the modified model decreased with decreasing freshness during storage at 20°C, while R_e and R_i did not change during the storage at 5°C and 10°C. The decreases of R_e and R_i are attributed to the decline in osmoregulatory function of cell membranes and the increase in concentration of electrolyte of cell fluid due to the physiological changes during storage. Therefore, the present results suggested that the EIS has the potential use in evaluation of freshness of vegetables.

Electrical design is usually made with the concepts based on the electric circuit theory. Nowadays it needs to consider the electromagnetic (EM) fields generated in devices, components, and equipment to achieve their expected performances and satisfy the electromagnetic compatibility (EMC) regulations as well. In such kind of design, it is required to pursue a solution which satisfies simultaneously multi-objective performances sometimes including conflicting requirements. In this paper, the application of a multi-objective satisfactory design method to electrical design is discussed. The method, named preference set-based design (PSD), is developed as a concurrent design method in the field of mechanical engineering. As a first application to electric and electronic fields, the method is applied to filter designs and its validity is discussed. Applied filter is an ordinary five-order low-pass filter composed of plural element parameters and objectives or performances of attenuation characteristics. In practical cases, some design uncertainties should be taken into account, for example an unnecessary magnetic fields coupling between inductors. Design solution expressed in terms of point value cannot easily and effectively handle the design uncertainties since there is no theoretical guarantee that the solution converges in such case. Such an uncertainty problem is treated in this study. By using the resultant parameter sets, the attenuation characteristics are analyzed and confirmed whether the required performances are satisfied.

The radiation field from the spark discharge on faulty insulators of distribution lines often influences broadcasting services of radio and television, and communication services. The spark discharge occurs due to loose connection in a metal-fittings connection of strain insulators. The rust of metal-fittings and the low-tension of wire are causes of loose connection. In this paper, the generation conditions of spark discharge were clarified by the basic experiment. And the radiation field which includes frequency component of several GHz due to the spark discharge was measured using a 6.6kV full-scale distribution line, and the amplitude probability distribution (APD) of electric field was analyzed.

Reference junction is one of the most important instruments for thermocouple measurement. On a factory floor of the industrial world, such as heat treat furnace and production line, the reference junction compensation is most commonly used in thermocouple measurement.

In recent years, temperature measurement is required at the level of high precision. There are, however, some disadvantages to using reference junction compensations - notably its lack of accuracy. Therefore, when implementing the high level of sensitivity and accuracy during temperature measurement, the reference junction such as “crushed ice and cold water” (ice point) are effectively used.

For the purpose of an improved reliability in temperature measurement with thermocouples, we evaluated the reliability of the reference junction compensation and the reference junction (in terms of ice point, automatically-operated ice point device and high precision water bath), and compared with both results. The results of the evaluation were different from the utility of each instrument. When working with thermocouples, it was possible to achieve further reliability improvement in the temperature measurement.

In this paper, we describe a grouping and implementations of project studies in the area of natural science in secondary schools, in contrast with “a framework for K-12 science education”. The conventional project studies can be classified into three types. All types are unacceptable for either secondary schools or universities. Two implementations based on the conventional education system and “a framework for K-12 science education” were executed for the subject of crystal structures. As the results, it was confirmed that the latter way was superior to the former one because of inducing new cross cutting concept by using mathematical thinking. The results imply that learning methods based on K-12 science education is useful for the secondary education system. It is also acceptable for the university education.

Electrostatic discharge (ESD) generators must be calibrated for contact discharges with the current waveform specified in IEC61000-4-2; however, there are no requirements in current waveforms due to their bad reproducibility for air discharges in the IEC standard. Nevertheless, the air-discharge immunity testing is under obligation in the present standard. This implies that different ESD generators are likely to provide significantly different test results for air discharge testing. In this study, two types of different ESD generators were used to measure discharge currents both for contact and air discharges with respect to charge voltages from 2 kV to 8 kV under the same conditions of experimental environment. As a result, we confirmed that the measured waveforms were almost identical for contact discharges regardless of charge voltages, while we found that they are quite different for air discharges with the same approaching speed when the charge voltages are increased. The latter result is because the generator has different impedance characteristics deriving from its structure, and because the spark lengths from the generators with the same charge voltage are different. A formula for calculating the discharge current from an ESD generator through an ideal switch in lieu of a spark, which was previously derived by us, was also employed to obtain the current waveform peculiar to the generator, in order to reveal that the formula provides the different upper limit of air discharge current peaks according to the generator.

This paper examines the effect of active learning for students who are first-year and second-year undergraduates majoring in electronic information engineering. Generally, graduation research and job hunting for third year students after belonging to each seminar can be regarded as kinds of very efficient active learnings. On the other hand, the lectures dealing with basic theory for junior students tend to be passive for them. Now we are trying to improve these lectures by using the way of active leanings. We report on some practical examples and its effects for students.