• 한국운동역학회지
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• 제29권4호
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• pp.255-261
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• 2019

Objective: The purpose of this study was to investigate differences of shock attenuation strategies between double-leg and single-leg landing on sagittal plane using statistical parametric mapping. Method: Nine healthy female professional soccer players (age: 24.0±2.5 yrs, height: 164.9±3.3 cm, weight: 55.7±6.6 kg, career: 11.2±1.4 yrs) were participated in this study. The subjects performed 10 times of double-leg and single-leg landing from the box of 30 cm height onto force plates respectively. The ground reaction force, angle, moment, angular velocity, and power of the ankle, knee, and hip joint on sagittal plane was calculated from initial contact to maximum knee flexion during landing phase. Statistical parametric mapping was used to compare the biomechanical variables of double-leg and single-leg landing of the dominant leg throughout the landing phase. Each mean difference of variables was analyzed using a paired t-test and alpha level was set to 0.05. Results: For the biomechanical variables, significantly increased vertical ground reaction force, plantarflexion moment of the ankle joint, negative ankle joint power and extension moment of the hip joint were found in single-leg landing compared to double-leg landing (p<.05). In addition, the flexion angle and angular velocity of the knee and hip joint in double-leg landing were observed significantly greater than single-leg landing, respectively (p<.05). Conclusion: These findings suggested that negative joint power and plantarflexion moment of the ankle joint can contribute to shock absorption during single-leg landing and may be the factors for preventing the musculoskeletal injuries of the lower extremity by an external force.

• 한국자기학회지
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• 제20권4호
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• pp.143-148
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• 2010

92.6%Fe-6.5%Si-0.9%Cr(wt%) 연자성 합금 박편을 폴리머 중에 분산시킨 준마이크로파 대역의 전자파 노이즈 흡수용 복합시트를 제조할 때, 시트 두께에 따른 전자파 전력손실(전송손실) 및 전자기적 특성과 내부 미세구조의 변화를 조사하였다. 시트두께 0.3~0.5 mm의 범위에서, 시트가 두꺼울수록 1~5 GHz의 주파수 대역에서 투과 파라미터 $S_{21}$의 값이 현저하게 낮아지면서 전력손실의 크기가 매우 증가하였다. 이 때 복소 투자율 및 자기 손실계수는 시트 두께가 변하여도 거의 비슷한 값을 가져 전력손실의 변화에 별 기여를 하지 못한 것으로 관찰되었다. 한편 복소 유전율은 시트의 두께에 따라 상당한 변화를 보여 1~5 GHz 대역에서 시트 두께가 두꺼우면 유전율 허수부의 크기가 증가하였는바, 내부 미세구조의 변화에 기인하는 것으로 추정되는 이러한 복소 유전율의 변화가 두꺼운 복합 시트의 큰 전력손실 즉 우수한 전자파 흡수 특성의 주된 원인인 것으로 판단되었다.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XII)
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• pp.343-347
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• 2003

황토볼을 이용하여 폐수처리를 한 결과 다음과 같은 결과를 보였다. 흐름도 A에서는 T-P 0.5ppm이하, T-N 1.0 ppm이하, COD 10ppm 이하였으며, 흐름도 B에서는 T-P 0.3ppm이하, T-N 5.0 ppm이하, COD 15 ppm 이하의 결과를 보여 주었다. 흐름도 C에서는 T-P 0.6ppm이하, T-N 10 ppm이하, COD 15 ppm 이하였으며, 흐름도 D에서는 T-P 1 ppm, T-N 8 ppm이하, COD 20ppm 이하의 결과를 보여 주었다. BOD는 각 흐름도 A, B, C, D에서 COD보다 높은 경우에는 6 ppm, 낮은 경우에는 3 ppm 정도의 차이를 보였다. SS는 각 공정에 따라 그다지 큰 차이를 보이고 있지 않으며, 1.0 처리 용량 Ton/day으로 계산 할 경우에 5 - 20 g/day 정도를 보이고 있다. 이러한 결과치는 하수종말처리장(특별대책지역 및 잠실수중보권지역)의 2 ppm 및 폐수처리시설(농공단지, 오${\cdot}$폐수처리시설 포함)의 T-P 8 ppm, T-N 질소성분 60 ppm이내의 탄소원 COD 40 ppm 이내의 기준에 해당하는 수치의 좋은 결과로 황토볼을 이용한 폐수처리 시스템의 가능성을 보여주고 있다.

• 한국분말재료학회지
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• 제16권4호
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• pp.291-295
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• 2009

The electromagnetic wave absorption sheets were fabricated by mixing of $Fe_{73}Si_{16}B_7Nb_3Cu_1$ nanocrystalline soft magnetic powder, charcoal powder and polymer based binder. The complex permittivity, complex permeability, and scattering parameter have been measured using a network analyzer in the frequency range of 10 MHz$\sim$10 GHz. The results showed that complex permittivity of sheets was largely dependent on the frequency and the amount of charcoal powder : The permittivity was improved up to 100 MHz, however the value was decreased above 1 GHz. The power loss of electromagnetic wave absorption data showed almost the same tendency as the results of complex permittivity. However, the complex permeability was not largely affected by the frequency, and the values were decreased with the addition of charcoal powder. Based on the results, it can be summarized that the addition of charcoal powder was very effective to improve the EM wave absorption in the frequency range of 10 MHz$\sim$1 GHz.

• 농업생명과학연구
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• 제46권2호
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• pp.43-48
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• 2012

거대억새 자원의 활용도 제고방안의 일환으로 거대억새 파티클을 이용하여 보드를 제조하고 수지첨가량, 수지타입 및 밀도에 따른 물성을 검토하였다. 흡수율은 보드의 밀도 및 수지첨가량이 증가할수록 감소하였으며, 휨강도와 박리강도는 밀도 및 수지 첨가량이 증가할수록 파티클간 결합력이 강해져 증가하였다. 두께 팽창률은 보드의 밀도가 증가함에 따라 증가하였고 수지 첨가량이 많을수록 감소하였다. 수지타입에 따라 두께 팽창률과 흡수율은 액상 페놀수지로 제조한 보드가 더 나은 치수안정성을 보였고, 보드밀도 $0.4g/cm^3$ 로 제조한 경우 수지 첨가율 11~13% 일 때 휨강도는 분말상 및 액상 페놀수지 간에 차이가 없었으며, 박리강도는 액상의 페놀수지로 제조한 보드가 더 좋은 값을 나타내었다.

• 한국지진공학회논문집
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• 제27권1호
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• pp.69-75
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• 2023

In Korea, most nuclear power plants were designed based on the design response spectrum of Regulatory Guide 1.60 of the NRC. However, in the case of earthquakes occurring in the country, the characteristics of seismic motions in Korea and the design response spectrum differed. The seismic motion in Korea had a higher spectral acceleration in the high-frequency range compared to the design response spectrum. The seismic capacity may be reduced when evaluating the seismic performance of the equipment with high-frequency earthquakes compared with what is evaluated by the design response spectrum for the equipment with a high natural frequency. Therefore, EPRI proposed the inelastic energy absorption factor for the equipment anchorage. In this study, the seismic performance of welding anchorage was evaluated by considering domestic seismic characteristics and EPRI's inelastic energy absorption factor. In order to reflect the characteristics of domestic earthquakes, the uniform hazard response spectrum (UHRS) of Uljin was used. Moreover, the seismic performance of the equipment was evaluated with a design response spectrum of R.G.1.60 and a uniform hazard response spectrum (UHRS) as seismic inputs. As a result, it was confirmed that the seismic performance of the weld anchorage could be increased when the inelastic energy absorption factor is used. Also, a comparative analysis was performed on the seismic capacity of the anchorage of equipment by the welding and the extended bolt.

• 동력기계공학회지
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• 제4권1호
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• pp.45-50
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• 2000

Circuit breakers have traditionally employed mechanical methods to interrupt excessive currents. According to power semiconductor technology advances in power electronic device, some mechanical breakers are replaced with solid state equivalents. Advantages of the contactors using semiconductor devices include faster fault interrupting, fault current limiting, no arc to contain or extinguish and intelligent power control, and high reliability. This paper describes the design of a static $100{\pm}10%V$ and 0 to 50A DC self-protected contactor with 85A "magnetic tripping" and 100A interruption current at $2.2A/{\mu}s$ short circuit of load condition using a new power device the HARRIS MCT (600V-75A). The self-protection circuit of this system is designed by the classical ZnO varistor for energy absorption and turn-off snubber circuit ("C" or "RCD") of the MCT.

• 설비공학논문집
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• 제22권8호
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• pp.545-552
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• 2010

Research and development efforts to reduce $CO_2$ emission are in progress to cope with global warming. $CO_2$ emission from fossil fuel fired power plants is a major greenhouse gas source and the post-combustion $CO_2$ capture is considered as a short or medium term option to reduce $CO_2$ emissions. In this study, the application of the post-combustion $CO_2$ capture system, which is based on chemical absorption and stripping processes, to typical fossil fuel fired power plants was investigated. A coal fired plant and a natural gas fired combined cycle plant were selected. Performance of the MEA-based $CO_2$ capture system combined with power plants was analyzed and overall plant performance including the energy consumption of the $CO_2$ capture process was investigated.

• 전자공학회논문지A
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• 제32A권11호
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• pp.29-34
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• 1995

Mirror coating is applied to laser facets to improve properties of edge emitting laser diodes. In this experiment, InGaAsP/GaAs high power laser diodes were studied with respect to different degrees of anti-reflective coating. Sputterred $Al_{2}$O$_{3}$ was used as the coating material and the HR coating was kept constant at 90%. Threshold current density, differential quantum efficiency, emission wavelength and the operating current at 500mW were measured for a range of AR coating and compared with theoretically calculated values; that showed good agreements. Precise wavelength control is important for laser diodes for solid state pumping because of small absorption bandwidth. In addition, since these lasers operate under CW condition, a lowest possible operating current for a given power is desired in order to minimize the heat produced. From the results of this experiment, we were able to obtain a optimum range of AR coatings for minimum operating current. The wavelength can be varied up to 4nm within this range.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.190-193
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• 2001

ZnO varistors have been widely used to protect power system and electronic system against overvoltages based on their excellent nonlinearity. In order to increase their protection capability, the fracture and protection technologies of arresters have to study according to their applications, namely ImA DC voltage, leakage currents, impulse residual voltages, withstanding capability to impulse surge, and energy absorption capability. ZnO varistors which have nonlinear current-voltage characteristic name a number of failure mechanism when ZnO elements absorb surge energies. Failure mode by thermal stress and Pin hole are among the most common failure mechanism at the high current surge current. In this study, the fracture mechaism of power arresters are introduced and protection technologies are researched. In particular the effect of thermal stress by surge currents to ZnO elements and methods against arc surge energy through withstand structure design of arrester are discussed.