• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.317.1-317
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• 2002

In this paper, static analysis of eddy current brake′s frame, which is one of key structural components of brake system for high speed train, was performed in order to evaluate the design by computer simulation. Calculation was carried out in general for the driving modes "braking" and "frame in upper position(brakes inactive)". Several yield stress load cases and fatigue load cases were analysed fur each of the driving modes. (omitted)

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.1774-1781
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• 2007

In this study, Matsuda's formula, which has been used to evaluate the acting load on the concrete pillar in 2-Arch tunnels, is investigated and a load reduction factor $({\alpha})$, which has been estimated from numerical parametric studies, is proposed for a better design of 2-Arch tunnels in the future. Numerical parametric studies show that the concrete pillar is subjected to a stress concentration on the excavation side during the first tunnel driving and when tunnel excavation is completed, the induced stress on the pillar in a poor quality of ground condition is 1.5 to 1.8 times the stress developed during the first tunnel driving. In addition, the numerical studies indicate that the acting load on the pillar is in the range of $14{\sim}83%$ of the load estimated by Matsuda's formula. From these results, a load reduction factor $({\alpha})$ is determined and it would make 2-Arch tunnel design more economically.

• 한국가스학회지
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• 제15권3호
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• pp.58-66
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• 2011

본 연구에서는 건설 현장에 매설된 삼중관이 항타 진동에 노출되었을 경우에 발생하는 동적 거동을 분석하였다. 항타 에너지는 7tonf의 램이 1.2m에서 낙하하였을 경우로 선정하였으며 이격 거리는 5∼30m로 변화하여 연구를 진행 하였다. 관의 길이 방향 중심에서의 진동 속도와 응력을 확인 하였고, 감쇠비를 고려하여 삼중관의 거동을 분석하였다. 매설 심도가 동일한 경우의 진동 속도에 대한 감쇠율은 이격 거리가 증가함에 따라 감소하는 추세를 보이며 내관에서 역시 이격 거리가 증가함에 따라 감소하는 추세를 보인다. 상하부에서 최대 응력값을 보이는 내관과 달리 외관은 불규칙한 응력 분포를 나타내는 것을 확인하였다.

• Journal of Biosystems Engineering
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• 제36권3호
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• pp.163-170
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• 2011

Analysis of load on major parts of the tractor power drive line is critical for efficient and optimum design of a tractor. The purpose of this study was to evaluate severeness of the tractor PTO driving axle during rotary tillage operation. First, S-N (stress vs. number of cycle) curve of a PTO driving gear was obtained through the fatigue life test using a PTO dynamometer. Second, PTO severeness was evaluated during rotary tillage operation. Torque measurement system was constructed with strain-gauge sensors to measure torque of a PTO axle, an I/O interface to acquire the sensor signals, and an embedded system to calculate severeness. The severeness of PTO was analyzed using measured torque data during rotary tillage. In the PTO gear life fatigue test, breakage time and bending stress of the gear were measured by tooth widths and torque change during the fatigue life test. The S-N curve showed a good linear relationship between bending stress and number of cycle (life) with a coefficient of determination of 0.97. For PTO severenss evaluation, rotary tillage operations were conducted at two PTO rotational speeds (level-1, level-2) under different paddy and upland field sites with different soil conditions. Results of averaged relative severeness for PTO level-1 and PTO level-2 were 1.96 and 3.34, respectively, at paddy field sites, and they were 1.36 and 2.51, respectively, at upland field sites. The results showed that the PTO driving axle experienced more severe load during rotary tillage at paddy fields than at upland sites, and relative severeness was greater at the higher PTO rotational speed under all of the soil conditions.

• 가정간호학회지
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• 제10권1호
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• pp.34-40
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• 2003

Purpose: The purpose of this study was to investigate the job stress in home care nurses. Method: The subjects were 139 home care nurses of hospital in an urban cities. The data were collected from 26 Man to 27 June by self report adherence questionnaire. Job stress was measured using CHN-PWRSQ(Community Health Nurses Perceptions of Work-Related Stressors Questionnaire). Result: The average score of job stress was 60.8. There were significantly high levels of job stress in those who have less than 10 years office period, those who have less than 2000000 won monthly salary than in their counterparts. With regard to the level of job stress by item, 'driving long distance and traffic jam', 'risk of traffic accident', 'bad weather condition', 'uncooperative family members', and 'uncooperative client/patient' were higher than other items. The age and office period were negatively correlated with job stress. Conclusion: The average score of job stress was 60.8. 'driving long distance and traffic jam', 'risk of traffic accident', 'bad weather condition', 'uncooperative family members', and 'uncooperative client/patient' were higher than other items. The age and office period were negatively correlated with job stress.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.168.2-168.2
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• 2005

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.325-328
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• 2005

EEFLs are mostly driven by sinusoidal wave driving method although EEFLs (External Electrode Fluorescent Lamps) are driven by both sinusoidal wave and square wave. The sinusoidal driving method reduces the cost and allows more power efficiency since this driving method can reduce the voltage stress of EEFL inverter switches and achieve the soft switching of the switches. And a transformer should be used in the inverter since the high voltage should be applied to the both ends of EEFL to turn on the lamp. However, the power loss mainly occurs at the transformer in the sinusoidal wave driving method. In order to remove the transformer which makes the power loss, a new method is presented. In this paper, the square wave is applied directly to the both ends of EEFL by a proposed two-stage inverter. Moreover, the luminance and power efficiency will be compared between the common sinusoidal wave driving method and square wave driving method.

• 농업과학연구
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• 제47권4호
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• pp.1147-1158
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• 2020

The purpose of this study was to measure the engine torque and rotational speed of a 67 kW class agricultural tractor according to tire type during plow tillage and to analyze the gear strength of the driving shift for the tractor. A field test was performed under the condition with a single tire (Test A) and dual tires (Test B) to increase the ground width of the rear tires. A load monitoring system was developed, and the engine torque and rotational speed were measured using controller area network (CAN) communication. The engine torque and rotational speed during plow tillage were calculated as the equivalent torque and speed using Palmgren Miner's rule. As a result, the equivalent torque and speed in Test A and Test B were 181.0 Nm and 1,913 rpm and 206.1 Nm and 2,130 rpm, respectively. As the ground width of the rear tire was increased, the bending stress in Test B was about 9.9 to 10.5% higher than that of the Test A, and the contact stress was about 4.6 to 4.9% higher than that of the Test A. Under all conditions, the safety factor for the bending and contact stress was 1 or more. Thus, the driving shift gears for the dual tire type are considered safe.

• 한국지반공학회논문집
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• 제39권1호
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• pp.27-38
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• 2023

본 연구에서는 3D 프린팅 기술을 활용하여 타입말뚝 선단의 모양에 따른 관입성 분석을 현장 축소모형시험을 통해 관찰하고, 대변형 수치해석을 통해 타입 중 말뚝 선단에 집중되는 최대응력의 변화를 확인하였다. 3D 프린터를 통하여 다양한 직경, 각도 그리고 모양의 말뚝 선단 모형을 제작하였고, 이를 현장 축소모형시험에 활용하였다. 이를 통해, 말뚝 선단 조건에 따른 말뚝의 침하량의 변화를 관찰하였다. 더 나아가, 대변형 수치해석 기법을 적용하여 다양한 말뚝 선단 조건에 따른 타입 중 말뚝 선단부의 최대응력의 변화와 최대응력 작용 위치 또한 확인하였다. 현장 축소모형시험과 대변형 수치해석의 결과 분석을 토대로 말뚝 선단 조건의 변화를 통해 타입말뚝의 관입성을 향상 시킬 수 있으며 선단부에 집중되는 최대응력 또한 완화 시켜 말뚝 시공 중 말뚝 손상을 방지할 수 있을 것으로 결론지을 수 있었다.

• Journal of Power Electronics
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• 제19권2호
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• pp.403-412
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• 2019

Aiming at the problems of large dv/dt and di/dt in traditional single-ended converters and high electromagnetic interference (EMI) noise levels, a single-ended isolated converter using the secondary resonance technique is proposed in this paper. In the proposed converter, the voltage stress of the main power switch can be reduced and the voltage across the output diode is clamped to the output voltage when compared to the conventional flyback converter. In addition, the peak current stress through the main power switch can be decreased and zero current switching (ZCS) of the output diode can be achieved through the resonance technique. Moreover, the EMI noise coupling path and an equivalent model of the proposed converter topology are presented through the operational principle of the proposed converter. Analysis results indicate that the common mode (CM) EMI noise and the differential mode (DM) EMI noise of such a converter are deduced since the frequency spectra of the equivalent controlled voltage sources and controlled current source are decreased when compared with the traditional flyback converter. Furthermore, appropriate parameter selection of the resonant circuit network can increase the equivalent impedance in the EMI coupling path in the low frequency range, which further reduces the common mode interference. Finally, a simulation model and a 60W experimental prototype of the proposed converter are built and tested. Experimental results verify the theoretical analysis.