• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.399-404
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• 2005

In this paper, a hybrid photovoltaic fuel-cell generation system employing an electrolyzer for hydrogen generation and battery for storage purpose is designed and simulated. The system is applicable for remote areas or isolated DC loads. Control strategy has been considered to achieve permanent power supply to the load via the photovoltaic/battery or the fuel cell based on the power available from the sun. MATLAB and SIMULINK have been used for the simulation work. A sensitivity analysis is conducted for various load level based on availability of solar radiation.

• Journal of Korean Neurosurgical Society
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• v.54 no.3
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• pp.232-235
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• 2013

Objective : Major complaints of carpal tunnel syndrome (CTS) are sensory components. However, motor deficit also impedes functional status of hand. Contrary to evaluation of sensory function, the objective, quantitative evaluation of median nerve motor function is not easy. The motor function of median was evaluated quantitatively using load cell and its correlation with findings of electrodiagnostic study (EDS) was evaluated. Methods : Objective motor function of median nerve was evaluated by load cell and personal computer-based measurement system. All of the measurement was done in patients diagnosed as having idiopathic CTS by clinical features and EDS findings. The strength of thumb abduction and index finger flexion was measured in each hand three times, and the average value was used to calculate thumb index ratio (TIR). The correlation of TIR with clinical, EDS, and ultrasonographic findings were evaluated. Results : The TIR was evaluated in 67 patients (119 hands). There were 14 males and 53 females, mean age were 57.6 years (range 28 to 81). The higher preoperative nerve conductive studies grade of the patients, the lower TIR was observed [p<0.001, analysis of variance (ANOVA)]. TIR of cases with thenar atrophy were significantly lower than those without (p<0.001, t-test). TIR were significantly lower in patients with severe median nerve swelling in ultrasonography (p=0.042, ANOVA). Conclusion : Measurements of median nerve motor function using load cell is a valuable evaluation tool in CTS. It might be helpful in detecting subclinical motor dysfunction before muscle atrophy develops.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.288-294
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• 2009

Various polymer electrolyte membrane fuel cell (PEMFC) startup procedures were tested to explore possible techniques for reducing performance decay and improving durability during repeated startup-shutdown cycles. The effects of applying a dummy load, which prevents cell reversal by consuming the air at the cathode, on the degradation of a membrane electrode assembly (MEA) were investigated via single cell experiments. The electrochemical results showed that application of a dummy load during the startup procedure significantly reduced the performance decay, the decrease in the electrochemically active surface area (EAS), and the increase in the charge transfer resistance ($R_{ct}$), which resulted in a dramatic improvement in durability. After 1200 startup-shutdown cycles, post-mortem analyses were carried out to investigate the degradation mechanisms via various physicochemical methods including FESEM, an on-line $CO_2$ analysis, EPMA, XRD, FETEM, SAED, FTIR. After 1200 startup-shutdown cycles, severe Pt particle sintering/agglomeration/dissolution and carbon corrosion were observed at the cathode catalyst layer when starting up a PEMFC without a dummy load, which significantly contributed to a loss of Pt surface area, and thus to cell performance degradation. However, applying a dummy load during the startup procedure remarkably mitigated such severe degradations, and should be used to increase the durability of MEAs in PEMFCs. Our results suggest that starting up PEMFCs while applying a dummy load is an effective method for mitigating performance degradation caused by reverse current under a repetition of unprotected startup cycles.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.4
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• pp.97-103
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• 2018

Force is a crucial element to be measured in various industries, especially the machine tool industry. Mega units of force are required in fields such as the heavy and ship industries. Micro/nano units of force are required for microparticles. The detection of force generates a physical transformation due to the force imposed from the outside, atlrnd electrical voltage signals are obtained from the system. For the detection of force, an octagonal ring load cell based on circular ring theory is designed and produced. To design the octagonal strain ring, theoretical values with data from the ANSYS program are compared to determine the size of the octagonal strain ring. An octagonal strain ring of the chosen size is made with the SCM415 material. The strain gauges are attached to the octagonal strain ring, designed to construct a full Wheatstone bridge. The LabVIEW program is used to measure the data, and strain values are found. With the octagonal ring load cell completed in this way, experiments are conducted by imposing forces on the tangential axis and radial axis. Experiments are performed to verify if the octagonal ring load cell conducts measurements properly, and theoretical values are analyzed to find any differences. The data will later be used in further research to develop a machine-tool dynamometer.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.11
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• pp.2230-2237
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• 2015

Inspired by the synchronization phenomena observed in the Nature, we propose an autonomous load balancing method for a wireless network. We model the load balancing problem of cells providing wireless access services as a synchronization problem in the Nature and design an algorithm for each cell to distribute loads in a self-determining way based on the load differences among its neighbor cells. Through simulations, we verify the feasibility of the proposed method in that cell loads can be balanced efficiently eve if cells make decision autonomously using their local information.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1088-1093
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• 2010

The Smart bi-directional pile load test with variable end plate overcomes the shortcoming of the Osterberg cell test. It is possible that the ultimate bearing capacity of piles can be known by using two different end plates. The first step is to measure end bearing capacity with smaller end plate and the second step is similar to the conventional O-cell test. In this study, model test was performed to evaluate the smart bi-directional pile load test in sand. Vertical displacement of the model pile were messured at the axial loading condition.

• Journal of Electrical Engineering and information Science
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• v.2 no.5
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• pp.33-39
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• 1997

In this paper we proposed a new traffic load shedding scheme which maximizes the throughput of traffic control by decreasing the load of the hot-spot cell using minimum load cell selection (MLCS) algorithm and deployed control flow of calls to define characteristic for hadoff region. we compared the performance of the random shedding approach with that of the proposed algorithm. The results of simulation show that MLCS algorithm minimizes the cal blocking rate under a high-density traffic compared to the random shedding scheme.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.520-529
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• 2006

그 동안 몇 차례 오스터버그 셀$(O-cell^{\circledR})$을 이용한 양방향 말뚝 재하시험기법이 국내에 성공적으로 소개/적용된 바 있다. 이 방법은 상대적으로 새롭고 독특한 방법으로서 시험비용과 기존 재래적인 시험방법이 적용상 제한을 받는 경우나 대규모 시험에서 발생할 수 있는 문제점들을 극복할 수 있다. 국내에서는 설계목적을 위한 시험말뚝 뿐 아니라 설계하중이 큰 실제말뚝에 대한 시험이 증가하는 추세에 있다. 이 논문에서 소개하는 양방향 재하시험 방법을 적용하면 기존의 소규모 재하시험 방법에서 발생될 수 있는 주면 마찰력과 선단지지력의 분리측정이나 각각의 지지력에 대한 극한상태를 확인하지 못하는 한계를 극복할 수 있고 시험하중이 270MN을 초과하는 경우까지 적용할 수 있는 장점을 갖고 있다. 본 논문에서는 오스터버그 셀을 이용한 정적 재하시험 방법에 대하여 말뚝종류별로 상세히 기술하였으며 이 시험방법의 장점과 국내현장에 적용되었던 사례를 소개하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.3 s.246
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• pp.193-200
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• 2006

The purpose of this study is to compare the part-load performance of a SOFC/GT hybrid power system with three different kinds of load-following operation modes. The primary mode for the part load operation of a hybrid power system is the reduction of supplied fuel (e.g., fuel control mode) to the hybrid system. The other two options, i.e., variable speed and VIGV controls, are related to the reduction of supplied air simultaneously with the reduction of supplied fuel to the system. With the performance analysis of a SOFC/GT hybrid power system, it is concluded that the variable speed con佐ol mode Provides the best performance for the part-load operations. It is also found that the VIGV control mode, with its better performance behavior than the fuel control mode, can be used as an important option for the part-load operation especially in case that the variable speed control mode can not be adopted.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.1
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• pp.59-68
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• 2009

Fuel cell generators as the distributed generation system with a few hundred watt$\sim$a few hundred kilowatt capacity, can supply the high quality electric power to user as compared with conventional large scale power plants. In this paper, PEMFC(polymer electrolyte membrane fuel cell) generator as micro-source is modelled by using PSIM simulation software and DSP based fuel cell hardware simulator based on the PSIM simulation model is implemented. The relation of fuel cell voltage and current(V-I curve) is linearized by first order function on the ohmic area in voltage-current curve of fuel cell. The implemented system is composed of a PEMFC hardware simulator, an isolated full bridge dc boost converter, and a 60[Hz] voltage source PWM inverter. The voltage-current-power(V-I-P) characteristics of the implemented fuel cell hardware simulator are verified in load variation and transient state and the 60[Hz] output voltage sinusoidal waveform of the PWM inverter is investigated under the resistance load and nonlinear diode load.