Transient analysis of converter-fed adjustable-speed generator-motor for the pumped storage power plant

A converter-fed adjustable-speed generator-motor for a pumped storage power plant has been developed in order to contribute to the automatic frequency control on an electric power system during pumping operations, as well as to improve the efficiency of turbines during generating operations together with stability. This system consists of a reversible pump turbine, a generator motor, cycloconverter and control units. The rotor of the generator motor, which is coupled directly with the turbine runner, normally is operated at a rotating speed which is equal to the difference between the frequency of the electric power system and that of the rotor current. In the state that a fault has occurred in the primary circuit of the generator motor, the adjustable-speed generator-motor fault current differs from that of a conventional synchronous generator motor. This paper describes the fault current analysis results for the condition when a sudden short-circuit is made on the primary side of the generator motor, and collates the results with the field test and EMTP simulation results.     

Computer vision based on a hypothesization and verification scheme by parallel relaxation

Shape recovery from a monocular image is addressed. It is often said that the information conveyed by an image is insufficient to reconstruct 3D shapes of objects in the image. This implies that shape recovery from an image necessitates the use of additional plausible constraints on typical structures and features of the objects in an ordinary scene. We propose a hypothesization and verification method for 3D shape recovery based on geometrical constraints peculiar to man-made objects. The objective is to increase the robustness of computer vision systems. One difficulty with this method lies in the mutual dependency between proper assignment of constraints to the regions in a given image and recovery of a consistent 3D shape. A concurrent mechanism has been implemented which is based on energy minimization using a parallel network for relaxation. This mechanism is capable of maintaining consistency between constraint assignment and shape recovery.     

On a system of understanding assembly illustrations in an assembly manual

This paper presents an assembly illustration understanding system. The system is eventually expected to be applied to a robot which specializes in automated mechanical assembly. Assembly illustrations in an assembly manual usually have two features: 1) In addition to the figures corresponding to mechanical parts, several special line-drawings referred to as auxiliary lines in this paper are often employed for the visualization of the assembly relations among mechanical parts; 2) The assembly illustrations in an assembly manual are disposed sequentially so that the subgoal of an assembly illustration will definitely appear in its succeeding illustrations as an assemblage. Both features are important clues to the analysis and understanding of assembly illustrations. By extracting the auxiliary lines, the system recognizes assembly relations among mechanical parts, and the 3D shape of the mechanical parts as well. Moreover, based on the assembly relations, it conjectures the structural details of mechanical parts such as insertion holes which are usually invisible. After that, it characterizes the appearance of the completed assemblage described by the current illustration. The system finally verifies the result by matching with the figures in a succeeding illustration in which the completed assemblage is given as a subpart.     

Enhanced conduction-corrected modified effective temperature as the outdoor thermal environment evaluation index upon the human body

This paper aims to clarify the handling technique of the solar radiation in an element of the thermal environment evaluation indices and to add expansions and improvements to conduction-corrected modified effective temperature ETF (Kurazumi et al., 2009) that can quantify the comprehensive effect on sensational and physiological sense and the effect of individual meteorological elements on the same evaluation axis applicable to an outdoor environment. Mean radiant temperature and radiant heat transfer coefficient of the outdoor space was defined. Enhanced conduction-corrected modified effective temperature ETFe that is ETF including short-wave solar radiation in outdoor space was defined. This sensational and physiological climatic environment index can make temperature convert each effect of difference in posture; air velocity; long-wave radiation in the outdoor space; short-wave solar radiation; contact surface temperature and humidity into individual meteorological elements. The addition of each temperature-converted factor is possible and quantifying the composite effect on sensational and physiological sense in the outdoor spaces as well as the discrete effect of each meteorological element is possible on the same evaluation axis. Consequently, it is possible to make the climate modification effects due to tree shade and areas of water that improve the urban thermal environment quantitatively explicit.     

CONTRIBUTION TO THE SEPARATION OF ACIDIC COMPONENTS FROM COAL LIQUEFACTION OIL

ABSTRACT

The naphtha fractions of coal hydrogenation products (IBP-130^°C) were separated by successive extraction with potassium hydroxide solution. Basic oil was also separated from the residue. The extracted fractions were analyzed by H-NMR and FI mass spectroscopy. It is concluded that the consecutive extraction with dilute potassium hydroxide solution should be capable of fractional separation of acidic oil from coal oil and further separation of individual component may be done by increasing the consecutive extraction steps.     

Effect of process-induced voids on isothermal fatigue resistance of CSP lead-free solder joints

With the progressive miniaturization of electronic devices, process-induced voids in lead-free solder joints affect the assessment of thermal fatigue resistance. Voids appear randomly in a solder joint, making quantitative evaluation of fatigue life difficult. This study examined the effect of process-induced voids on the thermal fatigue resistance of CSP solder joints. CSP specimens were subjected to isothermal mechanical fatigue tests; specifically, the accelerated thermal cycle test. When a void is small, it has no apparent effect on fatigue life. However, when voids having diameters of at least 30% of solder diameter are located along the crack propagation route, fatigue life is shortened. FEA and Miner’s law for estimation of fatigue life suggest that voids affect not only the crack initiation but also crack propagation. Estimated numbers of cycles to failure agree quantitatively with the experimental results. The effects of the size, location, and number of voids can be extracted by FEA. As voids along the crack path become larger, fatigue life decreases. Moreover, when two voids are located near the corner of a solder joint on the crack path, a 30% decrease in life appears. This result agrees with experimental results reported in several literatures.     

Analysis of carrier modulation in channel of ferroelectric-gate transistors having polar semiconductor

We have been fabricated and characterized a ferroelectric-gate thin-film transistors (TFTs) using ZnO as a channel polar semiconductor and YMnO₃ as a ferroelectric gate. A typical n-channel transistor property showing clear drain current saturation in I_D-V_D (drain current - drain voltage) characteristics was recognized. When the 3 V of the gate voltage is applied under the 4 V of drain voltage, the large drain current of about 1.1 mA is obtained. These controlled-polarization-type ferroelectric-gate TFTs using ZnO-channel TFTs operate in the accumulation-depletion mode and the ON/OFF state of the ferroelectric-gate TFTs strongly depends on the polarization switching of P_SFe. In this paper, therefore, the polarization switching of P_SFe in the TFT is carefully examined and the relationship between the polarization switching and the carrier accumulation (depletion) state is discussed using impedance spectroscopy and Capacitance-Voltage (C-V) measurements at applied the gate voltage.     

Metal-free phthalocyanine (H2Pc) molecule adsorbed on the Au(111) surface: formation of a wide domain along a single lattice direction

Using low-temperature scanning tunneling microscopy (STM), we observed the bonding configuration of the metal-free phthalocyanine (H₂Pc) molecule adsorbed on the Au(111) surface. A local lattice formation started from a quasi-square lattice aligned to the close-packed directions of the Au(111) surface. Although we expected the lattice alignment to be equally distributed along the three crystallographically equivalent directions, the domain aligned normal to the ridge of the herringbone structure was missing in the STM images. We attribute this effect to the uniaxial contraction of the reconstructed Au(111) surface that can account for the formation of a large lattice domain along a single crystallographical direction.     

A 0.2 W CW laser with buried twin-ridge substrate structure

An extremely high output power has been obtained with a new structure laser named the buried twin-ridge substrate (BTRS) laser. The very thin active layer formed on a ridged substrate permitted high power output increasing the catastrophic damage level. The buried stripe formed with a blocking layer remarkably improved the current confinement lowering the threshold current. A multilayer coating technique was applied to both facets to increase the front facet output. Fundamental transverse mode is achieved at more than 100 mW in CW with an uncoated laser while the maximum output power attained is as high as 200 mW in CW operation with a multicoated laser.     

Synthesis of Fullerenes by Ablation Using Pulsed and cw-Nd:YAG Lasers

Macroscopic quantities of fullerenes were synthesized by ablation of a graphite rod heated with a cw-Nd:YAG laser in Ar gas flow. The ablation was carried out by irradiation of fundamental, second, and third harmonic light emitted from a pulsed-Nd:YAG laser. It was necessary to heat the graphite rod up to a higher temperature than 700 °C for producing macroscopic quantities of fullerenes. The amount of ablation, the fullerene yield and the relative fullerene yield increased with increasing temperature of graphite. The fullerpne yields depended on the pressure of Ar buffer gas as well, in which the j ablation plume was formed, and an optimum pressure range was found to be 53-80 kPa. Relatively high yield of C₇₀ was obtained by ablation method under these conditions.