With the increment of installation density, the PV power generation system may encounter the external interference contributed by unpredictable variation of irradiance. Especially, the partial shadow, as one of main factors that lead to the problem of low conversion efficiency ought to be taken into consideration. This paper presents a novel maximum power point tracking method proposed in order to make sufficient utilization of solar energy, on the occasion when the photovoltaic modules are partially shaded. The novel method is based on Perturbation and Observation (P&O) method, with which the scan method is combined periodically. By using this method, the maximum power point can be checked out within transient period. For the purpose of verifying practicality of this novel method, simulation, as well as experiment have been carried out under the same circumstances, respectively. The consequences intuitively indicate that the conversion efficiency operated by proposed method is substantially improved under partial shadow.
To improve the thermoelectric performance of bismuth telluride (Bi2Te3) thin film using electrodeposition, we investigated the effect of electrolyte temperature ranging from 10°C to 70°C. The thermoelectric properties including electrical conductivity, Seebeck coefficient and power factor were measured at room temperature in the in-plane direction. The structural properties were examined by scanning electron microscope and X-ray diffraction analysis. The maximum power factor of 1.3 μW/(K2･cm) was exhibited at a electrolyte temperate of 20°C. For further increasing the electrolyte temperature, the power factor linearly decreased because both the electrical conductivity and Seebeck coefficient decreased. The surface structure of the Bi2Te3 thin films greatly changed when the electrolyte temperature was changed. The Bi2Te3 thin films at lower electrolyte temperature (T < 30°C) exhibited dense structure while the thin films at higher electrolyte temperature (T > 50°C) exhibited dendrite structure and many deep apertures which caused a decrease in the thermoelectric performance.
We investigated the structual and thermoelectric properties of electrodeposited Bi2Te3 thin films using a two-step process which combined an homogeneous electron beam irradiation with a thermal annealing. The Bi2Te3 thin films were formed on stainless steel substrates by the potentiostatic electrodeposition. We first performed only the thermal annealing to the thin films to determine the optimal annealing temperarure. As a result, we found that the Bi2Te3 thin films at the annealing temperautre of 300°C exhibited the highest thermoelectric performance, which was 4.5 times higher than that of the as-deposited thin films. Thus, in the two-step process, the electron beam irradiation dose was changed from 0.36 to 1.08 MGy while the annealing temperature was set at 300°C. As a result, the Bi2Te3 thin films at the EB irradiation dose of 0.36 MGy exhibited highest thermoelectric properties [power factor = 6.1 μW/(cm·K2)] which was approximately 20% higher than that of the optimized thin films with only the annealing treatment. Therefore, we conclude that two-step process is beneficial to improve the thermoelectric properties of electrodeposited Bi2Te3 thin films.
It is assembled by a plurality of parts, and an easy screw end method is mainstream, and the resolution after at the time of assembling and the assembling is used for an electric appliance and a car, an airplane, a train, the machine tool in that by the various joining method. However, because external force such as vibration and the repetition load acts on the join of the screw, the screw loses a conclusion power, and the slack occurs. This phenomenon causes a serious accident to give material and human damage. In contrast, it is dealt by the slack laboratory procedure of various screws, but lower unevenness and reliability of the measured value, the inspection that let you maintain proofreading and a conclusion state of the screw head again have a problem that it is difficult, and there is not the laboratory procedure that is simple and easy and highly precise in the present conditions. Therefore, in this study, I report it because I studied the slack of the screw which occurs because a spindle is lost by external force for the purpose of the detection of the slack and a thing judging more easily than the method and exactly in before.
We prepared bismuth telluride (Bi2Te3) thin film using radio-frequency magnetron sputtering with different H2-Ar gas mixing ratios, and investigated the structural properties of the Bi2Te3 thin films. The deposition rate of the thin films decreased as the mixing ratio was increased because tellurium atoms were lost from the films via the chemical reaction between the tellurium and hydrogen atoms. This phenomenon was supported with the results of the other analyses such as scanning electron microscopy (SEM), electron probe microanalyzer (EPMA), and X-ray diffraction method (XRD). The highest crystallinity was obtained at the H2-Ar gas mixing ratio of 5%. When the H2 gas was introduced, the oxygen concentration near film surface decreased. Therefore, we conclude that the crystallinity and dense structure of Bi2Te3 thin films improved by introducing an optimal amount of hydrogen gas in the sputtering deposition. It can be expected that the electrical conductivity of the thin films improves owing to the enhancement of electron transport.
Up-conversion phosphors emit light by excitation of light of which wavelength is longer than that of emission. This phenomena is caused by multi-photon excitation and energy transfer in f orbital of rare earth elements. In this study, BaGd2ZnO5 doped with different amount of Tm and Yb were prepared, and their up-conversion emissions were measured. Main phase of the prepared samples were identified as BaGd2ZnO5 by X-ray diffraction. Up-conversion emissions were measured using multi-channel photo detector and 980 nm diode laser, and the optimum amount of Tm and Yb were 0.3% and 7% respectively for the up-conversion emission. The optimized sample showed blue, red, and near infrared emissions. Excitation power intensity dependence of each emission was investigated by changing the excitation laser power. Blue emission intensity was proportional to the 2.5th power of the excitation, and near infrared emission was proportional to the 1.8th power of the excitation. These results indicate blue up-conversion emission is 3 photon excitation process and near infrared emission is 2 photon excitation process. Quantum efficiency was measured using fluorescence spectrometer equipped with integral sphere. Absorption rate of 980 nm was 22.68%. Internal quantum efficiency of blue emission was 0.02%, and of near infrared was 2.38%.
The decolorization of tar dye aqueous solution by the irradiation of an atmospheric-pressure plasma jet was examined by absorbance spectrum measurement and nuclear magnetic resonance (NMR) and mass spectrometry (MS) analyses. An atmospheric-pressure argon (Ar) plasma jet was generated at a frequency of 10 kHz with an applied voltage of 10 kV and an Ar gas flow rate of 10 L/min. When 10 mL of 100 mg/L tartrazine aqueous solution was irradiated with this plasma jet, the yellow solution gradually became lighter with increasing irradiation time and was almost completely decolorized after 50 min of irradiation. In addition, the results of MS analysis revealed that tartrazine molecules with a mass-to-charge ratio (m/z) of 579 were decomposed mainly into unidentified substances with m/z = 271. This result indicated that the decolorization was caused by the destruction of the azo bond in the tartrazine molecules.
In the design of rehabilitation assist suits, safety consideration for patients is one of the most important issues. We have proposed the basic structure of an ankle joint assist suit with a velocity-based safety device. The velocity-based safety device is intended to stop the assist suit if it detects an unexpected high joint angular velocity. This safety device is designed to work even when the computer breaks down, because it consists of only passive mechanical components without actuators, controllers, and/or batteries. In this paper, we introduce the detailed design of the important parts (motor, gear, torsion spring, encoder, and velocity-based safety device) in the assist suit. First, the design specification of the assist suit is described. Next, the structure of the assist suit is explained. Finally, the detailed design is presented.
We are investing effective utilization of the food wastes for agriculture and focusing on coffee grounds which is disposed of in a large quantity and difficult to reuse. There are obstacles in using coffee grounds for agricultural materials, because coffee grounds are high carbon to nitrogen (C/N) ratio and may contain a kind of plant growth inhibitor, therefore here we used water extract from coffee grounds. Growth of Japanese mustard spinach (Brassica rapa var. prviridis) was enhanced by applying the water extract from coffee grounds, and the growth ratio was almost the same as plants applied commercial liquid fertilizer. The water extract from coffee grounds showed higher values in nitrogen, phosphoric acid, potassium, and minerals than the commercial liquid fertilizer, the plants, however, might not use these nutrients enough. Chlorophyll content in the plants applied the water extract from coffee grounds was higher than plants applied the liquid fertilizer, but there was no correlation between chlorophyll content and growth of plants.
This paper describes the influence of the observer’s position to the subject during a calculation task. Pulse waves from subject’s earlobe were measured during the calculation task and converted into the heartbeat interval to obtain the Lorenz Plot and the LF/HF for evaluating the subject’s stress. From results, when the observer was sat face to face with the subject, the subject’s stress became lower compared with other observer's positions. However, results of questionnaire investigation indicated that the subject felt the stress when the observer sat at the same position. Further studies need to investigate the difference.