The electronic products such as laptop PC, cellular phone, robots and etc. need the DC power source. Recently, the secondary battery is frequently used as the portable DC power source and it needs forming process. In this paper, we proposed the bidirectional converter that the battery can be charged with high power factor and the discharged energy is regenerated into AC power source. In the charging mode, the converter acts as the boost rectifier. And the AC input current is controlled in phase with the AC input voltage. As a result, the power factor is improved nearly to unity. In the discharging mode, the DC power of battery wasted in resistor is regenerated to the AC bus line. Finally, the validity of the proposed bidirectional converter is verified by computer simulations and experimentation.
A diagnostic fluoroscopy X-ray system uses a 32kW or greater X-ray generator for obtaining real-time moving images and high-resolution images. Fluoroscopy X-ray systems have to use a high-capacity AC power source to perform long-time low-power fluoroscopy and short-time high-power spot exposure. In this paper, we propose a hybrid type X-ray generator for fluoroscopy X-ray system which can perform fluoroscopy and spot exposure with a low-capacity AC power source and an energy storage device. The characteristics of energy storage devices are compared and each energy storage device is modelled to equivalent circuit. And the characteristics of available energy are analyzed as a function of output voltage and power. A 32kW class hybrid X-ray generator with EDLC as an energy storage device for fluoroscopy X-ray system was constructed, and its validity was verified by means of simulations and experiments.
A direct acting relief valve, of which the override is one of the important issues, is major hydraulic element for controlling pressure and flow in hydraulic actuating systems. Therefore, the research of reducing override of the valve has always been an important topic for decades. Among many design factors of the direct acting relief valve, the shape of the valve poppet is the one that can directly affect the performance the most. Based on previous studies of poppet valve, an actual model is considered as equivalent to the simplified model. The steady flow force acting on the poppet is calculated by momentum theorem applied to the control volume. This paper represents some simulation methods to investigate the flow force effects depending on the shape of the poppet with sharp-edged seat. The result shows that the flow force on poppet is highly affected by inlet/outlet opening areas, poppet tip angle, and poppet plate angle.
This study applied the Bayesian method for the quantification of the parameter uncertainty of spatial linear mixed model in the estimation of the spatial distribution of probability rainfall. In the application of Bayesian method, the prior sensitivity analysis was implemented by using the priors normally selected in the existing studies which applied the Bayesian method for the puppose of assessing the influence which the selection of the priors of model parameters had on posteriors. As a result, the posteriors of parameters were differently estimated which priors were selected, and then in the case of the prior combination, F-S-E, the sizes of uncertainty intervals were minimum and the modes, means and medians of the posteriors were similar to the estimates using the existing classical methods. From the comparitive analysis between Bayesian and plug-in spatial predictions, we could find that the uncertainty of plug-in prediction could be slightly underestimated than that of Bayesian prediction.
This paper proposes a cascaded boost type inverter system to compensate the voltage sag. If the voltage sag has appeared in input voltage, a cascaded boost converter would be operated to compensate voltage sag. The output voltage is kept constant by a direct-quadrature frame controller in the single-phase PWM inverter. The validity of proposed system is verified by simulation on the 300W cascaded boost type inverter system.
Hazardous chemicals emitted from building materials and furniture have led to social problems such as sick house syndrome. Test methods for the evaluation of pollutant emissions from furniture-like products have been applied using various national and international standards and classifications, but they are not currently unified. This research has been done to organize the various standards and certification methods and to make new classification systems. Proper test methods have been proposed, tested, and analyzed through this research.
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