Formation and microwave dielectric properties of Sr(Ga0.5Ta0.5)O3-based complex perovskites

The Sr(Ga0.5Ta0.5)O3-based perovskites with O2- and/or Sr2+ vacancies were formed by changing the A-site and/or B-site cation ratios. The Sr-deficient perovskites with a limited composition of Sr0.86(Ga0.36Ta0.64)O3 could be obtained, whereas oxygen vacancies were hardly created. The B′-site Ga3+ cation could be replaced with large Sc3+, In3+, Y3+, Nd3+ and La3+. The crystal symmetry of the complex perovskites changed from cubic (B′=Ga3+, Sc3+, In3+) to tetragonal (B′=La3+) through rhombohedral (B′=Y3+, Nd3+). The dielectric permittivities of these ceramics indicated no distinct dependence on the B′-site cation species. The temperature coefficient of permittivity might be associated with the symmetry change of the perovskite phases. Higher microwave Qf values, >Qf=38 000 GHz, were obtained for our complex perovskite ceramics, except with B′=La3+. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Influence Analysis that a Phase Characteristic of the High‐Level Earthquake Gives to Vibration Response Characteristic of the 550‐kV Disconnectors

We developed the 550‐kV disconnectors that strengthened earthquake proofing by the addition of the damper unit and weight reduction of conductive part based on the damage of the 550‐kV disconnectors by the Great East Japan earthquake (March 11, 2011) and inspected the earthquake proofing performance by shake table test. In shake table test, we performed the test by the artificial seismic wave that varied in phase characteristic in addition to the test by resonance method. And, in a high‐level earthquake area, we analyzed it about the influence that a phase characteristic of the artificial seismic wave gave to stress to occur in disconnectors. As a result, it is thought that the stress to occur in disconnectors is decided by a primary natural frequency basically because a bending strain to occur to the disconnectors in the time when the resonance frequency ingredient becomes the big acceleration response value grows big. But, on a particular phase condition, it was confirmed that the bending strain to occur in disconnectors might grow big conspicuously. As for this, the possibility is thought about by influence of higher natural frequency doing superposition.     

Energy‐Efficient Train Speed Profile Generator Combining Partial Energy‐Oriented Driving Approaches

One way of reducing the energy consumption of trains is to drive them in an energy‐efficient manner. There can be various driving patterns between two adjacent stops, or various speed profiles, because there is a gap called the running time supplement between the planned running time set in a timetable and the shortest possible running time of the train. Previous studies have proposed using up the supplement by changing the driving operation from powering to coasting at optimal points in terms of energy consumption. Others have shown that full use of regenerative braking helps save energy. In this study, we developed an energy‐efficient speed profile generator by combining these partial energy‐oriented driving approaches when the planned running time is given. We added this generator to existing shortest running time calculation software, so that it works for various vehicle and train route data. Numerical experiments showed that our profile provided superior performance compared to manually created ones for artificial and real data.     

新型混凝土增强纤维基本性能特征分析

针对日本生产的棒状X型聚丙烯纤维,对其抗拉强度、耐碱、耐热性能和结构特征等进行了研究分析.结果表明,X型聚丙烯纤维拉伸强度高、耐碱和耐热性好;纤维截面独特、呈X型,与混凝土的咬合力好;相同纤维掺量下,每立方混凝土中含纤维的根数多,且分散性好.     

Study on Lightning Protection Measures for Distribution Lines and Customer Equipment against Back Flow Lightning Current from Radio Communication Station

Recently, with the expansion of communication network areas, the number of radio communication stations built in the neighborhood of customer houses has increased. If lightning strikes a communication radio tower, part of the lightning current flows into the distribution line and into customer houses. This may cause the failure of distribution lines or customer equipment. To protect distribution lines and customer equipment from lightning faults, it is necessary to analyze the surge phenomena in distribution lines and customer equipment and take appropriate protection measures. In this study, we examined the effect of lightning protection measures for distribution lines and customer equipment against lightning strikes to a communication tower. First, using an actual‐scale test distribution line, we measured the lightning current flowing into distribution lines and customer equipment. Second, we quantitatively examined the effect of lightning protection measures by lighting surge analysis while changing each parameter. From the experimental and analytical results, we show that the proposed protection measures can reduce the lightning current flowing into distribution lines and customer equipment.     

用微波等离子体改性氟树脂表面

我们发现了用微波炉产生的微波来很简单地进行等离子体处理的新方法。用这种方法处理了聚四氟乙烯(PTFE)和四氯乙烯-六氟丙烯共聚物(FEP)。为了评价等离子体处理了的高分子的润湿特性。用了苯二甲酸二烷酯(DAP)作接触角测定的标准液体。由DAP在聚丙烯上的接触角(θ)根据Fowkes方程求出了DAP的表面张力的色散力成分(γ_L~d)及极性成分(γ)。等离子体处理后,标准液体在 FEP和 PTFE上的cosθ增大,而且γ_L(1+cosθ)/(γ_L~d)~(1/2)与(γ_L~P)~(1/2)/(γ_L~d)~(1/2)之间成直线关系。等离子体处理后的FEP和PTFE的γ_3,γ_5~d,γ_s~P都有所增加。ESCA分析结果显示,经等离子体处理后,有相当量的氧导入了高分子表面。粘合到等离子体处理了的FEP和PTFF上的压敏胶带的剥离强度增加到未处理时的约2～3倍。     

Performance of Dead‐Time Compensation Methods in Three‐Phase Grid‐Connection Converters

This paper discusses the performance of compensation methods for dead‐time voltage error in voltage‐source grid‐connection pulse‐width modulation converters. The theoretical analysis in this paper reveals the relationship between the voltage error and the current ripples through the converter. The analytical results imply that the voltage error is strongly affected by the amplitude of the current ripples as well as the source power factor. This paper proposes a new compensation method which makes it possible to use two lookup tables to reduce the calculation time in the controller. The compensation characteristics are compared by using a 200‐V 5‐kW three‐phase grid‐connection converter. As a result, conventional approximation‐based compensation methods exhibit an acceptable performance in a restricted power‐factor operation range. In contrast, the turn‐off transition‐based compensation method and the proposed method have a good compensation performance all over the power factor.     

A New Control Method of Suppressing the DC‐Capacitor Voltage Ripple Caused by Third‐Order Harmonic Compensation in Three‐Phase Active Power Filters

This paper proposes a new control method suitable for active power filters, which can reduce the dc capacitor voltage ripple associated with the third‐order harmonic current compensation. The proposed method superimposes a negative‐sequence fundamental current on the compensating current to cancel out the active power ripple caused by the third‐order harmonic current. As a result, the proposed method has the capability to eliminate the dc capacitor voltage ripple oscillating at double the source frequency. Experimental results obtained by a 10‐kW three‐phase diode rectifier load verify the validity of the proposed method. The proposed method exhibits a small dc capacitor voltage ripple reduced to 43% of that using the conventional method.     

Plasma Fluid Flow Behavior and Power Generation Characteristics in a High‐Temperature Inert Gas Plasma Faraday MHD Generator

The plasma fluid flow behavior and power generation characteristics in a Faraday magnetohydrodynamic (MHD) generator using a high‐temperature inert gas (argon) plasma have been examined in a time‐dependent two‐dimensional numerical simulation. The inhomogeneous and unstable plasma at an inlet total temperature of 7000 K results in reductions and fluctuations in the output power. The plasma becomes homogeneous and stable as the inlet total temperature increases to 9000 K. One of the reasons for the suppression of ionization instability may be weakness of the dependency of the electrical conductivity on the electron number density, because the Coulomb collision of electrons becomes dominant during deviation from Saha equilibrium.     

Development of Semicircular Tubular Coreless Linear Motor and Its Motion Control

This paper proposes a semicircular tubular linear synchronous motor called a “circular shaft motor” (CSM). A CSM can realize direct‐drive motion along the circumference of a circle. The design of the CSM is described. A magnetic field analysis was performed for the CSM model. The thrust characteristics of the prototype CSM system were measured in experiments. Angle control and force control were performed to demonstrate the utility of the developed CSM.