• Journal of Drive and Control
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• v.14 no.3
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• pp.1-7
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• 2017

Energy consumption of conventional hydraulic excavators controlled by MCV is considerable when negative load is applied because the meter orifice and meter-out orifice are machined in one spool. Therefore, IMV is introduced to save energy use of hydraulic excavators, but existing hydraulic excavators have various advantages so it is difficult to make a clear comparison. In this study, we compare the use of an existing MCV excavator that has many advantages such as negative control, and IMV for boom up and down operation, and if IMV is used to save energy, we will examine the cause. If possible, for comparability under the same conditions, both systems use pressure balance valves to minimize power consumption when not using power in the actuator. The orifice area at each notch of each valve is calculated, and energy saving is verified by comparing the two systems through simulation.

• Journal of Power Electronics
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• v.16 no.3
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• pp.925-935
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• 2016

This paper proposes a new interleaved double-input three-level Boost (DITLB) converter, which is composed of two boost converters indirectly in series. Thus, a high voltage gain, together with a low component stress and a small input current ripple due to the interleaved control scheme, is achieved. The operating principle of the DITLB converter under the individual supplying power (ISP) and simultaneous supplying power (SSP) mode is analyzed. In addition, closed-loop control strategies composed of a voltage-current loop and a voltage-balance loop, have been researched to make the converter operate steadily and to alleviate the neutral-point imbalance issue. Experimental results verify correctness and feasibility of the proposed topology and control strategies.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.9
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• pp.406-410
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• 2001

This paper develops an efficient evolutionary programming based algorithm for solving the environmentally constrained economic dispatch problem in thermal power system. The proposed algorithm can deal with the power balance constraints and the emission constraints which are equality and inequality constraints, respectively. Numerical results show that the proposed algorithm can provide superior solutions within reasonable time through its application to a test system.

• Journal of Power Electronics
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• v.10 no.4
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• pp.351-356
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• 2010

A new current-balancing multi-channel LED driver is proposed in this paper. The conventional LED driver system consists of three cascaded power conversion stages and its driver stage has the same number of expensive boost converters as those of the LED channels. On the other hand, the proposed LED driver system consists of two cascaded power stages and its driver stage requires only passive devices instead of expensive boost converters. Nevertheless, all of the currents through multi-channel LEDs can be well balanced. Therefore, it features a smaller system size, improved efficiency, and lower cost. To confirm the validity of the proposed driver, its operation and performance are verified on a prototype for a 46" LCD TV.

• Journal of Power Electronics
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• v.19 no.1
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• pp.58-67
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• 2019

This study presents a new portable eight-output light emitting diode (LED) driver. The eight output-channels are divided into two equal groups, and their output powers can be controlled individually by three active switches. In addition, a simple capacitor-based passive current balancing circuit (CBC) is employed in each port to guarantee that the currents of the four LEDs are the same. When compared with the conventionally used separate two-output isolated converters, the proposed one uses one less active switch. Moreover, zero-voltage-switching (ZVS) is achieved, which improves the power efficiency of the driver. Finally, a highly compact prototype is built, which can reach an efficiency of 94.6%.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.9
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• pp.424-430
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• 2001

A multi-level optimal power flow(OPF) algorithm has been evolved from a simple two stage optimal Power flow algorithm for constrained power economic dispatch control. In the proposed algorithm, we consider various constraints such as ower balance, generation capacity, transmission line capacity, transmission losses, security equality, and security inequality constraints. The proposed algorithm consists of four stages. At the first stage, we solve the aggregated problem that is the crude classical economic dispatch problem without considering transmission losses. An initial solution is obtained by the aggregation concept in which the solution satisfies the power balance equations and generation capacity constraints. Then, after load flow analysis, the transmission losses of an initial generation setting are matched by the slack bus generator that produces power with the cheapest cost. At the second stage we consider transmission losses. Formulation of the second stage becomes classical economic dispatch problem involving the transmission losses, which are distributed to all generators. Once a feasible solution is obtained from the second stage, transmission capacity and other violations are checked and corrected locally and quickly at the third stage. The fourth stage fine tunes the solution of the third stage to reach a real minimum. The proposed approach speeds up the two stage optimization method to an average gain of 2.99 for IEEE 30, 57, and 118 bus systems and EPRI Scenario systems A through D testings.

• International Journal of Contents
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• v.9 no.1
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• pp.60-64
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• 2013

This study was performed for two of specific reasons, one is for exercise development for improving stroke patient's muscle power, balance and gait and, after verifying the effect of the exercise, the other is for showing that the appling this exercise was more effective on hemi-plegic stroke patients into the clinical trial. The subjects of this study were hemi-plegic patients by stroke, 51 patients were picked up, who were agreed with this research. Close kinetic chain leg exercise using mirrors was applied to study group I, Close kinetic chain leg exercise without mirrors was applied to study group II and general physical therapy was applied to comparison group. The results of this study are as follows. The difference of the groups, study group I showed more effective than study group II on checking rectus femoris, vastus lateralis, biceps femoris, Korean version of Berg Balance Scale, Center of pressure, Functional gait assessment. In this study, Close kinetic chain leg exercise showed more effective and significant on improving for muscle power, balance and gait on stroke patients. Especially, doing exercise using mirrors is considered as more effective method than without mirrors.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.10 no.3
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• pp.399-407
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• 2003

Purpose: This study was done to identify levels of physical fitness in student nurses and to ascertain the relationship among the different aspects of physical fitness of strength, power, muscle endurance, agility, balance and flexibility. Method: The participants were 266 students selected from one college of nursing. From May 1 to July 31 in 2003, physical constitution, muscle strength (grip strength, back strength), power (standing long jump), muscle endurance (sit-ups), agility (whole body reaction time-light, sound), balance (close-eyes foot-balance), and flexibility (sitting trunk flexion) were measured. Result: The mean(standard deviation) for grip strength was 22.59(3.93) kg., for back strength, 48.52(12.85) kg., for standing long jump, 135.29(20.54) m., for sit-up's, 23.66(9.35) per minute, whole body reaction time (light), 0.43(0.11) sec, whole body reaction time (sound), 0.50(0.16) sec, close-eyes foot-balance, 33.35(38.67) sec, and sitting trunk flexion 34.72(9.37) cm. Conclusion: This study showed that the physical fitness of student nurses is very low compared to the results in a report from the Korea Sports Science Institute. It is necessary to include exercise programs for student nurses in order to improve their physical fitness.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.9 no.2
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• pp.35-41
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• 2010

The balance coefficients between telecommunication lines are specified in the technical standard and the power induction computation method varies in the order of 100 times in magnitude according to the amount of impedance. The results of actual balance measurements, differing from time to time with the measurement circuit or increasing proportionally as the induction voltage increases, appeared as a measurement error because of not using the standard measurement circuit. This article investigates such errors and proposes the use of a standard balance measurement circuit and a measurement device impedance under the domestic notification standard and the ITU-T international standard.

• Journal of Family Resource Management and Policy Review
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• v.19 no.2
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• pp.101-125
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• 2015

Dual-income family is becoming more common in today's society. This study will look at how dual-income households balance between work and life. Specifically, it will study how the families allocate time for work, where they use labor power, and for domestic work and leisure, where they recharge labor power. The data source for this study was the 2009 Korean Time Use Survey. The main results of this research are as follow: The study confirmed that many husbands and wives they still spend much time working. There are differences to spend in restoring labor power; many husbands spend leisure time and many wives spend household labor. Generally in a typical dual-income household, the husband works and enjoys leisure and the wife focuses on working. It was found that the husband and wife in a dual-income family feel time deficient is due to long working hours.