The relation between the static and dynamic properties and homogenization aspect of added elements (Ni, Mo) in the sinter-forged 95-100% dense steels contained 0.2-0.5%C was investigated.The results obtained are as follows;1) Mechanical properties of full dense materials made from the alloyed powder are the most excellent, while in the case of the material made from the admixed powder, mechanical properties are inferior because Mo does not sufficiently diffuse into the matrix, and brittle intermetallic compounds are formed near the interface of the matrix and Mo particles.2) In the material which contains the ferro-molybdenum powder instead of the metallic molybdenum pow-der, static properties are improved but dynamic ones show no sign of improvement at all owing to brittle intermetallic compounds scattered in the matrix.3) In the case of the materials with residual pores, however, the difference of the dynamic properties between the materials made from the alloyed and the admixed powder extremely decreases, and at 97% density ratio there is little difference in both static and dynamic properties.
In order to mitigate secondary effects caused by high reflection waves from a curtain-walled breakwater, a new type of curtain-walled breakwater was proposed. It consists of two vertical walls with different draft depths. The distance between the two walls is comparatively narrow, e. g., having a similar size to the width of its super structure. The mechanism of effective dissipation of wave energy is to enhance the generation of vortex flows from the curtain walls, especially from the front curtain wall placed on the offshore side, which consists of an array of inclined plates with the same gap. By using the wave resonance of Helmholtz mode between the two walls, enhancement of the vortex flow is realized. In the experimental and theoretical examinations, changing the water depth and the distance between the two walls, important hydraulic properties of a double curtain-walled breakwater, such as reflection and transmission coefficients, wave energy dissipation rates and so on, are clarified.
To reduce implementation, operation, and maintenance costs of large-scale photovoltaic (PV) power plants, we improved upon our previously developed fault-diagnosis architecture that does not require additional sensors. The key technique in this architecture is that, instead of using the irradiation and module temperature measured using pyranometers and thermometers, it uses their theoretical values calculated from the PV-module characteristics and measured dc voltage and current of a PV inverter. Failure and degradation under both maximum power point tracking and clipping of output power are presumed with this technique. This improved architecture is applied to monitoring systems of large-scale PVpower plants. Itis experimentally demonstrated that this architecture can determine the number of fault modules even for a failure rate of only less than 0.2%. It was also demonstrated that this architecture can classify failure and degradation modes, namely, "series-resistance increase," "shunt-resistance decrease," and "bypass diode on," even for a loss of less than 5%-6%.
Rapidly solidified AI-TM-Ln base alloy has excellent mechanical properties such as high specific strength or specific modulus. In this study, Al92Ni4.5Ti1.5CulZr0.8Ce0.2 (at%) alloy powders were directly forged using a double action forging press without preparing a compact preform that is difficult to consolidate because of the spherical shape and hardness of the powder. The tensile strength of above test pieces preheated at 723K for 3600s shows 670MPa and 2% elongation, which is comparable with the test pieces prepared by extrusion from the same powder. This process gives near net shape parts with excellent mechanical properties using the rapidly solidified Al-TM-Ln base alloy.
It was known in the first fundamental study that in the light load and very high speed revolution region (2-6 kg/cm2, above 20, 000 rpm), sintered bearings could be driven under hydrodynamic lubrication after achieving sufficiently good conformity. In the actual applications, however, the state of the lubrication at the start-up becomes a severe boundary owing to insufficient conformity, consequently a large amount of wear occurs or the bearings may seize.On the basis of the above-mentioned study, a new Cu-Sn-P-MoS2 type bearing has been developed, which showed excellent performance under both boundary and hydrodynamic conditions. The distinctive features of the bearing are as follows; the thin layer of the reaction product (phosphorus compound) formed around the MoS2 particles in the sintered structure acted as a kind of binder between the matrix and the MoS2 particles, thus preventing the solid lubricant (MoS2) from mixing into the lubricant oil, which causes the increase in the apparent viscosity of the oil and consequently the coefficient of friction and the bearing temperature under the hydrodynamic conditions.
This paper proposes a robust DC microgrid (MG) operation scheme for intentional power routing (PR) within the MG or between the MG and the utility grid (UG). The MG consists of a photovoltaic (PV) system, a battery energy storage system (BESS), and AC loads connected to the UG via a DC/AC power conditioning system. The operation is achieved by controlling the UG converter and the converter of the BESS in the slack mode with the same or different terminal voltages. In this way, the bus voltage is regulated in a variable range while the magnitude and direction of power exchange between the UG and the MG are realized at the primary voltage control level. The procedure to select the voltage references of the terminals and the control schemes are presented. The system has been implemented in PSIM environment and simulation results proves the reliability and stability of the design.
In order to mitigate secondary effects caused by high reflection waves from a conventionalcurtain-walled breakwater, a new type of breakwater consisting of two different walls was proposed. One wall is animpermeable curtain wall and located on the shore side of the breakwater. The other is consisted of an array of inclinedplates with the same gap and located on the offshore side. By using the Helmholtz mode wave resonance between the twowalls, enhancement of the vortex flow is realized. In this paaper, characteristics of wave forces on the front andrear walls as well as uplift forces on the superstructure were examined by both the phisical model tests and thethoreticalcomputations. The damping wave theory was used for the theoretical examinations. Especially, applicability ofthe theory to the estimation of the wave forces infuemced by the strong vortex formations was extensively examined.
