Robust fixed-lag smoother for linear systems including outliers in the system and observation noises

We develop a robust fixed-lag smoother for linear discrete-time systems having outliers both in the process and the observation noises. By modifying the system equation to a linear regression model, a robust Kalman filter and a robust fixed-lag smoother are derived using an M-estimate. Then the robust smoother is constructed using a robust Kalman filter and two robust sub-smoothers; the outliers in the observation noise are detected by filtering, and those in the system noise are detected by smoothing. Monte Carlo simulations are also presented to show the effectiveness of the proposed algorithms.     

Pilot-Plant Study of a New Wastewater Treatment System

Because of severe space limitations for the reconstruction of its sewage-treatment system, the city of Nagoya has evaluated a space-saving wastewater treatment system comprising a solid-liquid separator (SLS) and biological aerated filter (BAF). The SLS is filled with plastic media forming a 2 m thick layer, and influent suspended solids are removed through the media packed zone. The BAF plant has a 2 m thick layer packed with porous ceramic media and air is diffused from the bottom of the tank.
The paper outlines the new treatment system and the ongoing study of the demonstration plant since 1992. It discusses the respective SS and BOD removal rates and concludes by showing that the new system can reduce retention period and plant area compared with the conventional activated-sludge process.     

Preparation of Cerium-Activated Silica Glasses: Phosphorus and Aluminum Codoping Effects on Absorption and Fluorescence Properties

Cerium-activated silica (SiO₂) glasses were prepared by plasma torch chemical vapor deposition (CVD). In Ce-doped SiO₂ glasses, most Ce exists as Ce⁴⁺ ions; the remaining small amount of Ce³⁺ ions exhibits a broad fluorescence spectrum with a large Stokes shift, ∼9600 cm^-1, from the excitation spectrum peak of 324 nm. Aluminum and phosphorus codoping considerably increases the Ce³⁺ ratio and shifts the peaks of both spectra to shorter wavelengths. P codoping is the more effective way to achieve this result and in some cases produces an absorption spectrum similar to that of a Ce-doped phosphate glass. These findings are consistent with the solvatiorn shell model for codoping, as previously proposed. To codope P, a soot remelting method was devised to deal with the highly volatile P₂O₅.     

基于共晶键合与对准切割的压电材料微细加工

高硬度陶瓷材料的微加工一直是微细加工的难题。为了解决此难题,采用金膜为中间层的硅-锆钛酸铅(Si-PZT)共晶键合工艺和带进刀标记的PZT压电陶瓷的切割加工,制备出块状PZT微结构。实验结果表明,当金膜厚为1μm时,Si-PZT的共晶键合强度可达20 MPa以上。这个强度可为PZT材料的切割加工和应用提供有力保障。Si-PZT共晶键合与PZT的对准切割加工结合的方法可在微细领域加工PZT等超硬材料,为加工PZT微结构阵列提供一种新途径。     

Voltage Regulation Utilizing Electric Vehicle Rapid Chargers in a Distribution System

From growing interests in the environment issues, promotion of photovoltaic power generation (PV) is accelerated in the world. Meanwhile, rapid chargers (RCs) for popularized electric vehicles are being installed in urban areas. These two trends in distribution system might cause severer voltage fluctuation problems. On the other hand, a RC can provide the reactive power support, which is capable of voltage regulation. Based on this viewpoint, this paper proposes a new framework of voltage regulation, in which the reactive power compensation by RCs is actively utilized. The proposed voltage regulation method combines two different control functions with consideration for over‐compensation avoidance. This paper ascertains the validity of proposed voltage regulation method through numerical simulations.     

Impact of Postfault Active Power Recovery of Photovoltaic Power Generation on Transient Stability

Currently, Japanese grid codes require photovoltaic (PV) power generation systems to continue supplying power to the grid as soon as possible even if the systems temporarily stop their operation. Although the fault ride‐through capability was originally proposed for preventing a cascading frequency drop in the power system, the capability has the impact on other instability phenomena such as transient stability. In this study, we focus on the postfault active power recovery of the PV systems. The impact of the recovery speed on the transient stability is investigated under different load conditions, in particular static/dynamic load condition. Numerical examples are carried out for the one‐machine one‐load infinite‐bus system, and the effects of the recovery speed are evaluated by equal area criterion and critical clearing time. As a result, we have found both desirable and undesirable effects on the transient stability depending on the load condition.     

Properties of Space Charge Distributions and Conduction Current in XLPE and LDPE under DC High Electric Field

Space charge behavior and conduction current in polyethylene under dc stress were investigated. One of the reasons for the different breakdown property in cross‐linked polyethylene (XLPE) from that in low‐density polyethylene (LDPE) may be based on the existence of cross‐linking by‐products in XLPE. Furthermore, a thermal history in cross‐linking process for XLPE may also cause of the difference. It is generally accepted that the existence of the cross‐linking by‐products increase the conduction current in XLPE under dc stress. It is also said that an anneal treatment in air atmosphere may affect to the electrical properties under dc stress. Therefore, we investigated the effect of the cross‐linking by‐products and the anneal treatment on space charge behavior and conduction current in polyethylene under dc stress. In our research, it is thought that the increasing dissipation power in XLPE is the cause of the breakdown in it under dc stress. Therefore, to calculate the dissipation power in the bulk of test sample, we measured the space charge distribution and the external circuit current simultaneously. Based on the results, we discussed the reason of the difference of the space charge properties in XLPE and LDPE focusing on the cross‐linking by‐products and the oxidation of the test samples.     

端铣中工具进给速度的最佳化

This paper deals with the tool feed rate optimization for smoothening of cutting force in end milling of workpiece with corner and straight parts. There is a difference between the cutting force in a corner part cutting and that in a straight part cutting. The cause of this is due to the difference in the instantaneous depths of cut in both cuttings. The scheme of this study is to prevent the generation of excessive cutting force in the corner part machining by comparison with the straight part machining. By dividing the NC (Numerical Control) cutting path of the corner part and changing the tool feed rate in each division, the cutting force in the corner part has been controlled. Furthermore, the possibility of realization of a shortening in machining time has been examined.     

An approach to the design of production systems giving a high quality of working life and production efficiency

People's social and economic desires are gradually becoming more versatile and fragmented. Industries should be developed in such a way that these versatile human desires are brought into harmony with the organizational needs of production engineering.

In this paper we report on the state of the desires and motivations of Japanese workers in 1974 and 1977 resulting from investigation and analysis using application methods of multivariate analysis and give an example of new production systems in which workers are in harmony with organizational needs.