Flashover voltage characteristics of contaminated station insulators under temporary ac overvoltages in the ac system connected with a frequency converter station

According to the recent analysis results of temporary ac overvoltage in the ac system connected with a frequency converter station, large-magnitude over-voltages were confirmed to occur under some special system conditions. Most of the station insulators currently used cannot withstand such overvoltages according to an evaluation based on the data obtained earlier. The necessity of tests to be done to evaluate such performance more accurately was recognized. Both power frequency and switching impulse overvoltage flashover tests were made on contaminated insulators by the method well simulating the natural wetting condition. Switching impulse flashover voltage with the waveshape having a long wavefront time of 2 ms can be well correlated with the flashover voltage characteristics of temporary ac overvoltage. Higher flashover voltage characteristics were obtained by a clean fog test method compared with those obtained by equivalent fog test method.     

Delay time compensation based on coefficient of restitution for collision hybrid motion simulator

A hybrid motion simulator embeds a hardware experiment in a numerical simulation loop. However, it is often subjected to the inherent problem of an energy increase in the collision of two pieces of hardware in a loop because of the delay time. This paper proposes a delay time compensation method based on contact dynamics model for a collision hybrid motion simulator under delay time and establishes a compensation method for coupled translational and rotational motion. The model developed in this paper describes linear uniform motion of a floating object during the period of the delay time until the force and torque are observed and non-linear motion according to environmental stiffness after the initial delay time period in contact. By using the above model, compensation parameters are designed based on desired coefficient of restitution with iterative calculation. The proposed method achieves accurate delay time compensation and simultaneously realizes a variable desired coefficient of restitution over a wide range of frequencies. Furthermore, the compensation method for multi-dimensional motion is established under the assumption that the friction effect is very small. The efficiency of the proposed method is verified through collision experiments for the coupled motion in two dimensions.     

Low‐Energy Electron Beam Induced Charging and Secondary Electron Emission Properties of FEP Film Used on Satellite Surfaces

Many kinds of insulating materials are used outside a spacecraft. They include FEP films, polyimide films, and so on, and are used as thermal control materials. These materials are exposed to a charged‐particle environment around the spacecraft. Thus then become charged due to charged particles, especially electrons. It has been pointed out that charging of these materials is likely to cause discharges on the surfaces. From this viewpoint, we investigated the charging potential characteristics of 127‐μm‐thick FEP film, a typical thermal control material, by exposing it to electron irradiation at various energies below 20 keV. In the dependence of the charging potential on the electron energy, we found that the electron energy at which no charge‐up occurs is about 2.7 keV. This appears to be the energy at the which secondary electron emission yield becomes unity. This indicates that electron irradiation of FEP film with energies lower than 2.7 keV induces positive charging. From the charge decay characteristics after electron irradiation, the volume resistivity of the film was also obtained as a function of the electric fields in the bulk of the FEP film.     

The Ameliorative Effect of Dexamethasone on the Development of Autoimmune Lung Injury and Mediastinal Fat-Associated Lymphoid Clusters in an Autoimmune Disease Mouse Model

In our previous study, we revealed the ameliorative therapeutic effect of dexamethasone (Dex) for Lupus nephritis lesions in the MRL/MpJ-Fas ^lpr/lpr (Lpr) mouse model. The female Lpr mice developed a greater number of mediastinal fat-associated lymphoid clusters (MFALCs) and inflammatory lung lesions compared to the male mice. However, the effect of Dex, an immunosuppressive drug, on both lung lesions and the development of MFALCs in Lpr mice has not been identified yet. Therefore, in this study, we compared the development of lung lesions and MFALCs in female Lpr mice that received either saline (saline group “SG”) or dexamethasone (dexamethasone group “DG”) in drinking water as a daily dose along with weekly intraperitoneal injections for 10 weeks. Compared to the SG group, the DG group showed a significant reduction in the levels of serum anti-dsDNA antibodies, the size of MFALCs, the degree of lung injury, the area of high endothelial venules (HEVs), and the number of proliferating and immune cells in both MFALCs and the lungs. A significant positive correlation was observed between the size of MFALCs and the cellular aggregation in the lungs of Lpr mice. Therefore, this study confirmed the ameliorative effect of Dex on the development of lung injury and MFALCs via their regressive effect on both immune cells’ proliferative activity and the development of HEVs. Furthermore, the reprogramming of MFALCs by targeting immune cells and HEVs may provide a therapeutic strategy for autoimmune-disease-associated lung injury.     

Evaluating a behavioral demand response trial in Japan: evidence from the summer of 2013

This paper presents results from a behavioral demand response trial targeted to both grid and residential peak hours, in which weekly feedback via paper-based reports, real-time feedback via an in-home display, 30-minute tiered rate, and email prompts are adopted to almost 230 residential customers of a condominium in Funabashi, a city located in Greater Tokyo. Through a randomized experiment, we find that the peak saving impact during grid peak hours (1–4 pm, weekdays only) was 11.6 %, given that all the four interventions provided all at once. In addition, the results show that the variation in peak saving effects by household characteristics exists, and the variation differs among packages of peak saving interventions. Furthermore, we analyzed how much informational elements in weekly reports are considered as useful by residential customers. These results suggest that feedback-based approaches for peak saving can promote households’ energy conservation behavior.     

Fabrication of optics by use of plasma chemical vaporization machining with a pipe electrode

We figure optical surfaces by plasma chemical vaporization machining (CVM) with a pipe electrode, in which an rf plasma generated at the electrode tip under approximately atmospheric pressure moves over the surfaces. We propose a shaping method in which the movement of plasma on the surfaces can be determined. Flat and aspheric surfaces are successfully figured with the desired peak-to-valley shape accuracy of 0.1 microm. The root-mean-square roughness of the resultant surfaces is at the subnanometer level. These results confirm that the plasma CVM and the shaping method have the capability to fabricate optics with high accuracy.     

Evaluation of 4-nonylphenols and 4-tert-octylphenol contamination of fish in rivers by laboratory accumulation and excretion experiments

Laboratory accumulation and excretion experiments of 4-nonylphenols (NP) and 4-tert-octylphenol (OP) were performed for killifish (Oryzias latipes). The bioconcentration factors (BCF, wet weight) in the whole fish were mean +/- SD of 167 +/- 23 (n = 4) for NP and 261 +/- 62 (n = 4) for OP. The biological half-lives in the whole fish were 9.9 h for NP and 7.7 h for OP. Parallel to the laboratory experiments, field survey on the chemicals contamination for water and ayu fish (Plecoglossus altivelis) from rivers flowing into Lake Biwa was performed. The contamination was not so high in agreement with the laboratory experimental data and the field BCF values (wet weight) in the ayu fish were 21 +/- 15 (n = 8) for NP and 297 +/- 194 (n = 3) for OP.     

Thermal conductivity of non-stoichiometric americium oxide: A molecular dynamics study

The aim of this paper is to investigate the influence of multi-valency of americium in its oxide for the lowering of the thermal conductivity and the uncertainty in measurement. In the present study, thermal conductivity of non-stoichiometric americium oxide was evaluated up to 2000 K by the non-equilibrium molecular dynamics calculations using the Born-Mayer-Huggins interatomic potential with the partially ionic model. The oxygen-to-americium ratio (O/Am) was varied from 1.6 to 1.9, which corresponded to the variation of the ratio of Am³⁺/Am⁴⁺. So, we prepared potential parameters for both Am³⁺ and Am⁴⁺. The calculated thermal conductivity of non-stoichiometric americium oxide decreased with an increase of temperature, and the degree of the temperature dependence became smaller with a decrease of the O/Am ratio. This was mainly caused by the phonon-scattering due to oxygen vacancies induced with Am³⁺ ions. Comparing two supercells in which (1) short-range ordered Am³⁺ clusters were contained and (2) Am³⁺ ions were randomly distributed, the thermal conductivity of the former seemed to be somewhat larger than that of the latter.     

A METHOD FOR THE PREPARATION OF RAW POWDER FOR THE TANTALUM CAPACITOR: INFLUENCE OF PARTICLE SIZE AND BINDER CONTENT

Raw powder for use in the tantalum solid electrolytic capacitor was prepared by different processes, that is, the wet method (currently used conversion method) and the dry method (the proposed method). The properties of prepared powder from the dry method were compared with those of the wet method. The present report has focused on the relationship between the conditions of binder preparation and the properties of the prepared powder, such as the particle size distribution, angle of repose, and the tap density, respectively. Furthermore, the utility of the dry method was investigated.

Based on the results, it has been clarified that the properties of powder prepared by the dry method differ from those of the wet method. In the case of the dry method, it is suggested that the mechanism of preparation of the fine binder (PMMA powder) differs from that of the coarse binder. Furthermore, based on the experimental results, it has been suggested that the dry method could be used as the preparation method of the raw powder used in the tantalum solid electrolytic capacitor.