• Annals of Clinical Neurophysiology
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• 제15권2호
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• pp.48-52
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• 2013

Background: Meralgia paresthetica (MP) is a mononeuropathy affecting the lateral femoral cutaneous nerve. The disease is often diagnosed clinically, but electrophysiological tests play an important role. The aim of this study is to clarify clinical characteristics of MP as well as the role of sensory nerve conduction study (NCS) in the diagnosis of MP. Methods: Sixty-five consecutive patients with clinical diagnosis of MP between March 2001 and June 2012 were retrospectively reviewed at a single tertiary center. General demographics, clinical characteristics and sensory NCS findings were investigated. Measurements of sensory NCS included the baseline-to-peak amplitude, side-to-side amplitude ratio and the conduction velocity. To compare between the normal and abnormal NCS groups, independent t-tests and chisquare test were performed. Results: Sixty-five patients had male predominance (56.9%) with mean age of $48.4{\pm}13.4$ years (range: 16-75). Seven patients (13.5%) had undergone operation or procedure before the symptom onset. The sensory nerve action potentials were obtainable in 52 (80%) of 65 clinically diagnosed MP patients. Sensory NCS revealed abnormalities in 38 patients (73.1%), and others (n=14, 26.9%) showed normal findings. Between the normal and abnormal NCS groups, there is no statistically significant difference on demographics or clinical features. Conclusions: We clarify the clinical features and sensory NCS findings of MP patients. Due to several limitations of sensory NCS, the diagnosis of MP could be accomplished both clinically and electrophysiologically.

• Advances in pediatric surgery
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• 제13권2호
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• pp.119-126
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• 2007

Trauma is one of the leading causes of death in children. Abdominal trauma is about 10 % of all pediatric trauma. This study describes the sex and age distribution, injury mechanism, site of intraabdominal injury, management and mortality of children aged 16 years or less who suffered abdominal trauma. The hospital records of 63 patients treated for abdominal injury between March 1997 and February 2007 at the department of surgery, Inje University Pusan Paik Hospital, were analyzed retrospectively. The peak age of incidence was between 2 and 10 years (78%) and this report showed male predominance(2.7:1). The most common mechanism of blunt abdominal trauma was pedestrian traffic accident (49%). The most common injured organ was liver. More than Grade IV injury of liver and spleen comprised of 4(12%) and 5(24%), respectively. Fourteen cases (22%) had multiple organ injuries. Forty nine cases (78%) were managed nonoperatively. Three patients (4.8%) died, who had Grade IV liver injury, Grade IV spleen injury, and liver and spleen injury with combined inferior vena cava injury, respectively. All of the three mortality cases had operative management. In conclusion, the liver or spleen injury which was more than Grade 4 might lead to mortality in spite of operation, although many cases could be improved by nonoperative management.

• 대한기계학회논문집B
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• 제22권9호
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• pp.1317-1324
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• 1998

In general, DI gasoline engine has the advantages of higher power output, higher thermal efficiency, higher EGR tolerance and lower emissions due to the operation characteristics of increased volumetric efficiency, compression ratio and ultra-lean combustion scheme. In order to apply the concept of stratified charge into direct injection gasoline engine, some kinds of methodologies have been adapted in various papers. In this study, a reflector was adapted around the injector nozzle to apply the concept of stratified charge combustion which leads the air-fuel mixture to be rich near spark plug. Therefore, the mixture near the spark plug is locally rich to ignite while the lean mixture is wholly introduced into the combustion chamber. The characteristics of combustion is analyzed with the variations of fuel injection pressure and load in a stratified -charge direct injection single cylinder gasoline engine. The obtained results are summarized as follows ; 1. The MBT spark timing approached to TDC with the increase of load on account of the increase of evaporation energy, but has little relation with fuel injection pressure. 2. The stratification effects are apparent with the increase of injection pressure. It is considered by the development of secondary diffusive combustion and the increase of heat release of same region, but proceed rapidly than diesel engine. Especially, in the case of high pressure injection (l70bar) and high load (3.0kgf m), the diffusive combustion parts are developed excessively and results in the decrease of peak pressure than in the case of middle load. 3. The index of engine stability, COVimep value, is drastically decreased with the increase of load. 4. To get better performance of DI gasoline engine development, staged optimizaion must be needed such as injection pressure, reflector, intake swirl, injection timing, chamber shape, ignition system and so on. In this study, the I50bar injection pressure is appeared as the optimum.

• 대한기계학회논문집 C: 기술과 교육
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• 제3권1호
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• pp.15-21
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• 2015

가스 엔진 히트 펌프는 가스 엔진의 축동력으로 압축기를 구동하는 시스템으로 전력을 거의 사용하지 않고, 엔진 폐열을 활용하기 때문에 하절기와 동절기에 전력 Peak 를 억제하는 공조기로 주목을 받고 있는 제품이다. 제품 개발 시 시스템 성능 예측이 중요하므로 이를 위해 초기 설정한 운전점에서 열교환기 및 압축기의 특성을 반영하여 반복 계산을 수행하면 최종적인 운전점을 도출할 수 있고, 가스 엔진의 성능 데이터를 활용하면 가스 엔진 히트 펌프의 정확한 효율을 예측할 수 있다. 난방 성능을 예측할 때에는 엔진 폐열이 시스템에 공급되기 때문에 외부 열을 흡입하는 구간과 엔진 폐열을 흡입하는 구간을 동시에 고려해야 예측의 정확도를 높일 수 있다. 25 마력 가스 엔진 히트 펌프의 성능을 예측한 값은 실제 측정한 값과 비교하였을 경우 5% 정도의 오차가 발생하며 향후 성능 예측 모델을 구성되는 부품 특성을 반영하면 오차의 폭이 감소될 것으로 예상된다.

• 디지털융복합연구
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• 제15권7호
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• pp.41-53
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• 2017

본 연구에서는 2011년 3월 발생한 동일본대지진 이후 스마트그리드에 대한 관심이 높아지고 있는 가운데 일본의 스마트그리드 정책 추진현황 및 문제점에 초점을 맞춰 살펴보았다. 분석 결과, 일본에서는 2011년 동일본대지진으로 인한 전력수급 문제를 계기로 신재생에너지의 고정가격매수제도가 도입되고, 나아가 신재생에너지로 생산된 전력을 거래하는 분산형 그린 전력매매 시장을 설립하는 등 에너지 위기와 환경문제를 동시 해결하는 하나의 솔루션으로서 스마트그리드 관련 프로젝트가 본격적으로 실행되었다. 그 결과 피크전력 억제 및 CO2 삭감효과, 신재생에너지원을 이용한 에너지 수급의 안정적 확보 등 가시적인 성과를 거두었다. 한편, 현행 일본의 스마트그리드 정책 운영상의 개선과제로는 전력계통 안정화 장치의 도입(송배전망의 광역적 운용이나 대형 축전지 도입 등), 스마트그리드 관련 자국기술의 국제표준, 추진 스마트 그리드의 보안성 강화 지원 등을 제시하였다.

• 한국전자파학회논문지
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• 제18권5호
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• pp.503-510
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• 2007

본 논문은 GSM900, DCS1800, PCS1900 대역을 동시에 만족시킬 수 있는 삼중 대역 안테나 설계에 관한 연구이다. 제안된 구조는 소형화와 견고성을 위해 유전체 위에 2개의 금속 가지를 접어서 만든 형태이다. 금속 가지의 길이를 조정하여 반사 손실을 합성시켜서 광대역을 구현하였다. 안테나의 반사 손실은 모의 실험을 통해 구하였으며, 이를 측정값과 비교하였다. 모의 실험은 상용 툴인 Ansoft사의 HFSS 9를 사용하였고, 수치 비교 결과, 원하는 주파수 대역에서 -10 [dB] 이하의 반사 손실을 얻었다. 또한, 안테나의 이득과 복사 패턴을 원거리장 측정 시스템을 사용하여 전파 무반사실에서 측정하였다. 측정 결과 최대 이득은 3.0 [dBi], 평균 이득은 -1.0 [dBi] 이상의 양호한 특성을 보였으며, 대역 내 2개의 주파수의 복사 패턴은 서로 유사하였다.

• 전기학회논문지
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• 제63권5호
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• pp.713-718
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• 2014

DC urban railway power system consists of DC power network and AC power network. The DC power network supplies electric power to railway vehicles and the AC power network supplies electric power to station electric equipment. Recently, because of power consumption reduction and peak load shaving, intelligent measurement of regenerative energy and renewable energy adapted on DC urban railway is required. For this reason, DC smart metering system for DC power network shall be developed. Therefore, in this paper, DC voltage sensor, current sensor, and DC smart meter were developed and evaluated by performance test. DC voltage sensor was developed for measuring standard voltage range of DC urban railway, and DC current sensor was developed as hall effect split core type in order to install in existing system. DC smart meter possesses function of general intelligent electric power meter, such as measuring electricity and wireless communication etc. And, DC voltage sensor showed average 0.17% of measuring error for 2,000V/50mA, and current sensor showed average 0.21% of measuring error for ${\pm}2,000V/{\pm}4V$ in performance test. Also DC smart meter showed maximum 0.92% of measuring error for output of voltage sensor and current sensor. In similar environment for real DC power network, measuring error rate was under 0.5%. In conclusion, accuracy of DC smart metering system was confirmed by performance test, and more detailed performance will be verified by further real operation DC urban railway line test.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.143-151
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• 2018

In this paper, a novel hybrid configuration combining a phase-shift full-bridge (PSFB) and a half-bridge resonant LLC converter is proposed for the On-Board Charger of Electric Vehicles (EVs). In the proposed converter, the PSFB converter shares the lagging-leg switches with half-bridge resonant converter to achieve the wide ZVS range for the switches and to improve the efficiency. The output voltage is modulated by the effective-duty-cycle of the PSFB converter. The proposed converter employs an active reset circuit composed of an active switch and a diode for the transformer which makes it possible to achieve zero circulating current and the soft switching characteristic of the primary switches and rectifier diodes regardless of the load, thereby making the converter highly efficient and eliminating the reverse recovery problem of the diodes. In addition an optimal power sharing strategy is proposed to meet the specification of the charger and to optimize the efficiency of the converter. The operation principle the proposed converter and design considerations for high efficiency are presented. A 6.6 kW prototype converter is fabricated and tested to evaluate its performance at different conditions. The peak efficiency achieved with the proposed converter is 97.7%.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권12호
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• pp.562-567
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• 2003

Lightning arresters are deteriorated by repetition of protective operation against overvoltages or impulse currents in environments of its use. If a deteriorated arrester is left in power lines, it can lead to an accident such as a line to ground fault even in a normal system. Therefore, it is necessary to eliminate the deteriorated arrester in advance by checking the soundness of arresters on a regular basis, and to ensure the reliability of power systems by preventing accidents. Various deterioration diagnostic techniques and devices are suggested, and most of which measure leakage current components as an indicator of arrester ageing. However, the techniques based on the magnitude of leakage current measure simply RMS or peak value of leakage current components and do not provide detailed information needed in the diagnosis. In this study, we found that the wave height distributions of the total leakage currents are remarkably changed or a new wave height are produced with the progress of arrester deterioration. To propose a new technique for the diagnosis, we designed a leakage current detection unit and an analysis program which can measure leakage current magnitudes and analyze wave height distributions. From the experimental results, we confirmed that the proposed technique by analyzing the wave height distribution can simply diagnose the mode of defects such as a partial damage and an existence of punctures in arresters as well as deterioration of arresters.

• 한국구조물진단유지관리공학회 논문집
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• 제15권1호
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• pp.148-158
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• 2011

교량구조물은 사회물류흐름에 필요한 중요한 역할을 하는 사회간접시설물로 공용수명이 다하거나 지진, 폭풍 등의 자연재해에 따라 구조물의 손상이 발생할 경우 기존 교량을 철거하고 재가설 하여야 한다. 공용중인 교량을 재가설할 경우, 차량의 우회, 교통체증에 따른 사용자비용과 공사기간동안의 소음, 분진 등에 따른 사회비용이 발생하게 된다. 하지만 교량의 재가설에 따른 사용자비용과 사회비용은 교량건설시 고려되지 않고, 이를 평가하는 방법 또한 모호하므로 이를 적용한 교량형식이 선정되지 못하고 있다. 따라서 본 연구에서는 교량의 재가설시 발생되는 사회적 간접비용, 즉 사용자의 사회적, 경제적 가치를 파악하여 교량 재가설에 따른 사용자비용의 평가방법을 제안하고 이를 평가하였다. 사용자비용의 평가 시 교량의 일교통량, 첨두시간, 우회거리, 우회시간 등을 포함한 교통정보와 사회적 물동량이 고려되었으며, 차량운행비용과 교량 재가설에 따른 시간지연비용 또한 고려되었다.