• Journal of Power Electronics
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• v.19 no.5
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• pp.1099-1107
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• 2019

A soft switching converter with wide voltage range operation is investigated in this paper. A series resonant converter is implemented to achieve a high circuit efficiency with soft switching characteristics on power switches and rectifier diodes. To improve the weakness of the narrow voltage range in LLC converters, an alternating current (ac) power switch is used on the primary side to select a half-bridge or full-bridge resonant circuit to implement 4:1 voltage range operation. On the secondary-side, another ac power switch is adopted to select a full-wave rectifier or voltage-doubler rectifier to achiever an additional 2:1 output voltage range. Therefore, the proposed resonant converter has the capacity for 8:1 (320V~40V) wide output voltage operation. A single-stage hybrid resonant converter is employed in the study circuit instead of a two-stage dc converter to achiever wide voltage range operation. As a result, the study converter has better converter efficiency. The theoretical analysis and circuit characteristics are verified by experiments with a prototype circuit.

• Journal of Korean Port Research
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• v.13 no.2
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• pp.323-332
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• 1999

The bus should supply an equal service to the whole community as feeder trip. However the existing bus route can not supply an effective feeder service in spite of the changes in the latent demand by the variety of regional structural change. This study aimed to establish the concept which frames the bus operation and management to cope with the latent demand to the bus. This study tackled this evidence by analyzing the transportation problems in terms of the urban growth emphasizing the following issues ; First, the strategy to improve the bus operation Second the land use control appropriate for the public transportation network Third economical range to justify the bus operation Second, the land use control appropriate for the public transportation network Third, economical range to justify the bus operation Fourth, the allowance for the private transportation mode On the latter part, the difference on the bus operation was compared to determine the range within which the bus operation could be justified. This study would provide some implications to improve the management for bus operation and fundamental information to develop the bus operation system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.8
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• pp.54-61
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• 2014

This paper proposes a boost/flux-weakening controller (BFWC) for wide speed operation range having engine and interior permanent magnet synchronous generator (IPMSG) for special equipment vehicle. The proposed BFWC exploits direct torque/flux control (DTFC) scheme based on space vector modulation method to control the constant DC voltage output within the entire speed operation range of engine. And, to improve the response characteristics of maximum torque per ampere (MTPA) operation and flux-weakening operation, the MTPA and flux-weakening feed-forward controllers are applied. To estimate feasibility and usefulness of the proposed controller, the simulation and experimental results are compared.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.1047-1051
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• 2004

Charge amplifier systems benefit from the very wide dynamic range of PE accelerometers by offering flexibility in adjusting the electrical output characteristics such as sensitivity and range. They are well suited for operation at high temperatures. Modern charge systems feature improved low noise operation, simplified digital controls, and dual mode operation for operation with charge or IEPE voltage mode sensors. high impedance circuitry is not well suited for operation in adverse field or factory environments. The resolution of a PE accelerometer may not be specified or known since noise is a system consideration determined by cable length and amplifier gain. IEPE accelerometrs operate from a constant current power source, provide a high-voltage, low-impedance, fixed mV/g output. They operate through long, ordinary, coaxial cable in adverse environments without degradation of signal quality. They have limited high temperature range. IEPE sensors are simple to operate. Both resolution and operating range are defined specifications. Cost perchannel is lower compared to PE systems since low-noise cable and charge amplifiers are not required.

• Journal of Chest Surgery
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• v.22 no.4
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• pp.562-572
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• 1989

The changes of serum glutamic oxaloacetic transaminase [SGOT], serum glutamic pyruvic transaminase [SGPT], serum lactic dehydrogenase [LDH] and serum creatine phosphokinase [CPK] were examined during and after the open heart surgery. In the total of 52 patients with heart diseases including 40 cases of congenital heart anomalies and 12 cases of acquired valvular heart diseases who undergone open heart surgery under cardiopulmonary bypass. The results obtained are as follows: 1. The average value of SGOT before surgery was 30.27 [ 18:86 units. The enzyme was reached to the maximum of 139.88 [ 89.43 units on the 1st day after the operation [p< 0.05], the enzyme activity was gradually decreased from the 3rd day after the operation, returned to the normal range on the 7th day after the operation. 2. The average value of SGPT before surgery was 14.36 [ 7.45 units. The enzyme was reached to the maximum of 34.67 [ 27.64 units on the 2nd day after the operation, but it was valueless statistically, the enzyme activity was gradually decreased from the 3rd day after the operation, returned to the normal range on the 5th day after the operation. 3. The average value of LDH before surgery was 263.07 * 86.66 units. The enzyme was reached to the maximum of 662.29 * 303.60 units on the 2nd day after the operation [p < 0.05], the enzyme activity was gradually decreased from the 5th day after the operation, returned to the normal range on the 7th day after the operation. 4. The average value of CPK before surgery was 141.35 * 43.44 units. The enzyme was reached to the maximum of 377.42 [ 222.02 units on the 1st day after the operation [p < 0.05], the enzyme activity was gradually decreased from the 5th day after the operation, returned to the normal range on the 7th day after the operation. 5. In the relationships of the serum enzymes and duration of the extracorporeal circulation, the values on the group over 90 minute of the extracorporeal circulation were increased than on the group below 90 minute of the extracorporeal circulation, but it was valueless statistically.

• Journal of Chest Surgery
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• v.15 no.1
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• pp.46-52
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• 1982

Activities of serum glutamic pyruvic transaminase [SGPT], serum glutamic oxaloacetic transaminase [SGOT] and serum lactic dehydrogenase [LDH] were determined during and after surgery In a total of 18 patients with heart diseases Including 8 cases of congenital heart anomaly and 10 cases of acquired valvular diseases who undergone open heart surgery under cardiopulmonary bypass. The results obtained are as follows: 1]The average value of the activity of SGPT before the surgery was $27.94{\pm}12.24$ units. The value was increased following the operation and reached to the maximum value of $43.83{\pm}37.02$ units 2 days after the operation, which was slightly deviated from the normal range. The enzyme activity returned to the normal range of $32.82{\pm}23.61$ units 4 days after the operation. 2]The average value of the activity of SGOT before the surgery was observed to be $30.5{\pm}11.29$ units. The value increased during the operation and reached to the maximum value of $95.56{\pm}43.38$ units. 2 days after the operation, the enzyme activity was gradually decreased thereafter and returned to the normal range 6 days after the operation. 3]The average value of the activity of serum LDH before the surgery was found to be $258.0{\pm}88.96$ units. The value was increased during the operation and reached to the maximum value of $930.55{\pm} 258.23$ units 2 days after the operation. The enzyme activity was gradually decreased thereafter and returned to normal range 7 days after the operation. 4]It was observed that the longer the time required for the extracorporeal circulation in the open heart surgery became, the greater the changed in activity of SGOT, SGPT and serum LDH were found.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.6
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• pp.573-579
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• 2013

Hydrogen engine with homogeneous charged compression ignition can achieve high efficiency by high compression ratio and rapid chemical reaction rates spatially. However, it needs to expansion of the operation range with over-all load conditions which is very narrow due to extremely high pressure rise rate. The adoption of the lean boosting in a HCCI $H_2$ engine is expected to be effective in expansion of operation range since minimum compression ratio for spontaneous ignition is decreased by low temperature combustion and increased surround in-cylinder pressure. In order to grasp its possibility by using lean boosting in the HCCI $H_2$ engine, compression ratio required for spontaneous ignition, expansion degree of the operation range and over-all engine performance are experimentally analyzed with the boosting pressure and supply energy. As the results, it is found that minimum compression ratio for spontaneous ignition is down to the compression ratio(${\varepsilon}$=19) of conventional diesel engine due to decreased self-ignition temperature, and operation range is extended to 170% in term of the equivalence ratio and 12 times in term of the supply energy than that of naturally aspirated type. Though indicated thermal efficiency is decreased by reduced compression ratio, it is over at least 46%.

• Journal of IKEEE
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• v.23 no.2
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• pp.675-680
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• 2019

The coal-fired power plant is operated by a combined operation method, which is operated by sliding pressure operation under low load and by fixed pressure operation under high load for improved efficiency. The combined operation is divided into two and three valve open modes. Each plant is operated by selecting the turbine control valve mode in accordance with the manufacturer's recommendation, but is not really operating at the optimal sliding pressure operation according to load range, also Load range of each plant is configured differently. The internal efficiency of the high-pressure turbines is reduced due to loss of the turbine valves and the plant efficiency is reduced. To solve these problems, In this paper, the optimum load range is selected through the analysis method of thermal performance by each load in order to improve the optimum variable pressure operation load range by turbine control valve mode.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.177-180
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• 2006

It is essential for engine design and establishment of test program to assign an appropriate performance range of liquid propellant rocket engine(LRE). The present study surveys the operation and qualification test range of LRE developed in Japan, United States, Europe and Russia.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1999.10a
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• pp.123-130
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• 1999

The bus as a feeder trip should supply equality service to the whole community. But in spite of the change of latent demand to the bus by the variety of regional structural change, the existing bus route can not supply effective feeder service. For cope with the latent demand to the bus, this study establish a concept that frame of the bus operation and management. This study tackled to evidence this fact by analyzing the bus transport problems in terms of the urban growth, and following issues were discussed: 1) the strategy for improvement of bus operation, 2) the land use control which is appropriate for the public transport network, 3) the economical range to justify the bus operation, 4) the allowance for the private transport mode. On the second part of this study, the difference on the bus operation was compared to determine the range within which the bus operation can be justified. This would provide the direction to improve the management for bus operation and fundamental information to develop the bus operation system.