• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.524-529
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• 2013

Recently, researchers have become interested in natural ester fluids, as they are an environmentally friendly alternative to mineral oils. Natural ester fluids are a natural resource made from plants; they have higher biodegradability, flash, and fire points, and a greater permittivity compared to conventional mineral oils. However, natural ester fluids also have a higher pour point, viscosity, and water content. These characteristics can hamper circulation and impair the electrical properties of an oil-filled transformer. A large amount of data has been accumulated over the years in regards to mineral insulating oil involving dielectric breakdown voltage and lightning impulse tests. However, natural ester fluids have not had their electrical properties sufficiently characterized. In this paper, we present an investigation into the characteristics of the electrical discharge development in natural ester fluids and in an oil-filled transformer near the pour points. The experiment results show that the electrical properties decreased according to a decrease in the ambient temperature and freezing time. It was found that the pour point and water content of natural ester fluids have a significant effect on the electrical properties.

• Journal of Yeungnam Medical Science
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• v.21 no.1
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• pp.108-113
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• 2004

A 23 years old single nulligravida woman underwent laparoscopic removal of a huge cystic adnexal mass that occupied her entire abdomen, giving the appearance of a full term pregnancy. After anesthesia, a vertical infra-umbilical incision, 1 cm long, was made and a telescope was introduced through the port to determine the status of the intra-abdomen and the surface contour of the mass. A needle tipped with a laparoscopic suction apparatus was inserted into the cyst through the infra-umbilical port, directly under the mass. Subsequently, 3,200 ml of cystic fluid was aspirated without spillage. A huge cyst, reaching to the level of the xyphoid process was effectively excised through the operative laparoscopy after prelaparoscopic drainage. Operation time was 140 minutes and hospital stay was 2 days. There were no complications during hospital stay and after discharge. It seems the size of the cyst is not a criteria for the contraindication of laparoscopic surgery.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.8
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• pp.975-982
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• 2007

The single-phase switched reluctance motor(SRM) drive requires DC source which is generally supplied through a rectifier connected with a commercial source. The rectifier is consist of a diode full bridge and a filter circuit. Usually the filter circuit uses capacitor with large value capacitance to reduce ripple component of DC power. Although the peak torque ripple of SRM is small, the short charge and discharge current of the filter capacitor draws the low power factor and system efficiency. A modified single phase SRM drive system is presented in this paper, which includes drive circuit realizing reduction of torque ripple and improvement of power factor. In the proposed drive circuit, one switching part and diode which can separate the output of AC/DC rectifier from the filter capacitor is added. Also, a upper switch of drive circuit is exchanged a diode in order to reduce power switching device. Therefore the number of power switch device is not changed, two diodes are only added in the SRM drive. To verify the proposed system, some simulation and experimental results are presented.

• Fire Science and Engineering
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• v.22 no.1
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• pp.93-98
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• 2008

Full-scale fire extinguishment tests were conducted to develop loaded stream fire extinguishing systems for protecting underground transmission cables. The dimension of test mock-up was 5.5m height${\times}3m$ width ${\times}6m$ length, and six 154kV OF cables were piled up. Gasoline was used to ignite cates. Linear heat detection cables were installed on top of 154 kV OF cable and discharge nozzles were installed on the top and sidewalls, respectively. As a result, both surface fires and deap-seated fires were extinguished successfully within the specified 3 minutes by discharging loaded stream agent.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.2
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• pp.1-6
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• 2005

This paper studies the OF-LED(Optical Fiber-LED) illuminated display board system for energy saving. The OF-LED illuminated display board system has PV module, batteries, charge 8t discharge system and dynamic full color display controller. Both maximum power point tracker (MPPT) and constant current & constant voltage controls (CCVC) are used to govern the charging system. This system. improves the charging efficiency of battery. The system is compact and operates only by PV except the rainy days when the sun is unfavorable. in the system display control and charging-discharging control by on-chip microprocessor are simultaneously carried out. To verify the unposed system, me simulation and experiment results show the operating characteristics with a laboratory prototype.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.10
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• pp.587-594
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• 2002

A low frequency square wave electronic ballast for the high intensity discharge(HID) lamps using fuzzy logic controller is developed. This electronic ballast consists a buck converter, a low frequency square wave full bridge inverter, a high voltage pulse generator for the HID lamp ignition, an over current protection circuit and an 8-bit microcontroller. The ballast system is operated on the constant current mode during the HID lamp start-up process and the system is operated on the constant power mode during steady state. Experimental results show that the fuzzy logic control operation is carried out successfully by the 8-bit microcontroller PIC16F877 In this electronic ballast system, in spite of the limited control bandwidth caused by low operating speed of the microcontroller, the good performance in the constant lamp current characteristic is obtained. Acoustic resonance of the HID lamps can be effectively avoided because the instantaneous In lamp power is fully constant due to the low frequency square wave drive.

• International Journal of Fluid Machinery and Systems
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• v.3 no.4
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• pp.352-359
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• 2010

In recent years, the market has shown increasing interest in pump-turbines. The prompt availability of pumped storage plants and the benefits to the power system achieved by peak lopping, providing reserve capacity, and rapid response in frequency control are providing a growing advantage. In this context, there is a need to develop pumpturbines that can reliably withstand dynamic operation modes, fast changes of discharge rate by adjusting the variable diffuser vanes, as well as fast changes from pumping to turbine operation. In the first part of the present study, various flow patterns linked to operation of a pump-turbine system are discussed. In this context, pump and turbine modes are presented separately and different load cases are shown in each operating mode. In order to create modern, competitive pump-turbine designs, this study further explains what design challenges should be considered in defining the geometry of a pump-turbine impeller. The second part of the paper describes an innovative, staggered approach to impeller development, applied to a low head pump-turbine project. The first level of the process consists of optimization strategies based on evolutionary algorithms together with 3D in-viscid flow analysis. In the next stage, the hydraulic behavior of both pump mode and turbine mode is evaluated by solving the full 3D Navier-Stokes equations in combination with a robust turbulence model. Finally, the progress in hydraulic design is demonstrated by model test results that show a significant improvement in hydraulic performance compared to an existing reference design.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.273-276
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• 2005

This paper presents an electronic ballast using a step down converter, a low frequency inverter for high pressure discharge lamp. The proposed ballast is composed of a full-wave rectifier, a step down converter operated as a current source with power regulation and a low frequency inverter with ignition circuit. The ignition circuit generates high voltage pulse of 1${\sim}$2[kV] peak, 130[Hz]. Moreover, it is able to reignite at regular intervals by protective circuit. As experimental results on the test, lamp voltage, current and consumption power are measured 132.5[V], 7.6[A] and 1,005[W], respectively. It was confirmed that the designed ballast operate the lamp with a constant power.

• Neonatal Medicine
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• v.28 no.2
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• pp.77-82
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• 2021

We present the case of a healthy 28-day-old female full-term neonate who was admitted to the neonatal intensive care unit for severe metabolic acidosis, hypoglycemia, and an initial sinus rhythm. The first diagnostic hypothesis was hypovolemic shock, and fluid resuscitation was started immediately. During fluid therapy, cardiovascular collapse occurred with supraventricular tachycardia. The latter was successfully treated with adenosine and beta-blockers. After 8 days, electrocardiography showed ventricular pre-excitation, and Wolff-Parkinson-White syndrome was diagnosed. A novel variant of the MYL2 gene that is related to hypertrophic cardiomyopathy and conduction defect was found after discharge. Cardiogenic shock should be considered, despite being a rare cause of shock in neonates.

• Nuclear Engineering and Technology
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• v.54 no.2
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• pp.554-564
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• 2022

The natural circulation phenomena occurring in fully integrated nuclear reactors are associated with a unique formation mechanism. The phenomenon results from a structural feature of these reactors involving upward flow from the core, located in the central-bottom region of a single vessel, and downward flow to the steam generator in the annulus region. In this study, to understand the natural circulation in a single vessel involving a multi-layered flow path, single-phase and two-phase natural circulation tests were performed using the SMART-ITL facility, and validation analysis of the TASS/SMR-S code was performed by comparing the corresponding test results. Three single-phase natural circulation tests were sequentially conducted at 15%, 10%, and 5% of full-scaled core-power without RCP operation, following which a two-phase natural circulation test was successively conducted with an artificial discharge of coolant inventory. The simulation capability of the TASS/SMR-S code with respect to the natural circulation phenomena was validated against the test results, and somewhat conservative but reasonably comparative results in terms of overall thermalhydraulic behavior were shown.