• 디지털콘텐츠학회 논문지
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• 제19권4호
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• pp.815-819
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• 2018

본 논문에서는 Foot Placement Estimator (FPE)를 사용하여 point foot을 갖는 이족 로봇의 3차원 시뮬레이션을 진행하고 이족로봇의 균형유지를 연구하였다. FPE 방법은 에너지 보존에 근거한 제어 방법으로서 보행 중인 로봇의 모든 에너지가 위치 에너지로 변환되는 지점에 로봇이 발을 디뎌 몸체가 넘어지지 않고 균형을 유지하며 이동하도록 하는 제어방법이다. 본 연구에서는 로봇이 이동하지는 않고 제자리에서 균형을 유지하며 서 있는 시뮬레이션을 진행하였다. 이를 위해 point foot을 갖는 6자유도 이족 로봇을 모델링하였으며 바닥과의 접촉 및 마찰 환경을 구현하였다. 로봇의 무게는 1kg이며 지면과 무게 중심점과의 거리는 1m로, 무게중심점은 로봇 몸체의 정 중앙에 위치하도록 설계하였다. 다음으로 로봇 몸체의 각속도와 직선속도 그리고 무게 중심점의 높이로 부터 FPE 지점을 계산하고 로봇이 해당 지점을 디뎌 균형을 유지하게 끔 하였다. 몸체의 초기 각도를 $5^{\circ}$, $-5^{\circ}$로 변화시키며 시뮬레이션 한 결과, 모든 초기 조건에서 로봇이 쓰러지지 않고 자세의 균형을 유지하며 서 있는 것을 확인할 수 있었다.

• 한국운동역학회지
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• 제17권2호
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• pp.157-166
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• 2007

This study was to compare the major kinematic factors between the success and failure group on performing the back somersault motion in floor exercise. Three gymnasts(height : $167.3{\pm}2.88cm$, age : $22.0{\pm}1.0years$, body weight : $64.4{\pm}2.3kg$) were participated in this study. The kinematic data was recorded at 60Hz with four digital video camera. Two successful motions and failure motions for each subject were selected for three dimensional analysis. 1. Success Trail It was appear that success trail was larger than failure group in projection velocity, but success trail was smaller than failure trail in projection angle. Also it was appear that success trail was longer than failure group in the time required. Hand segment velocity and maximum velocity in success trail were larger than those in failure trail, and this result was increasing the projection velocity and finally increasing the vertical height of center of mass. At the take-off(event 2), flection amount of hip and knee joint angle was contributed to the optimal condition for the take-off and at the peak point, hip and knee joint angle was maximum flexed for reducing the moment of inertia. Also in this point, upper extremities of success trail extended more than those of failure trail. in this base, success trail in upward phase(p3) 2. Failure Trail It was appear that failure trail was smaller than success trail in projection velocity, but failure trail was larger than success trail in projection angle. Also it was appear that failure trail was more short than success trail in the time required. Hand segment velocity and maximum velocity in failure trail were smaller than those in success trail, and this result was reducing the projection velocity and finally reducing the vertical high of center of mass. At the take-off(event 2), flection amount of hip and knee joint angle wasn't contributed to the optimal condition for the take-off and at the peak point, hip and knee joint angle wasn't maximum flexed for reducing the moment of inertia. Also in this point, upper extremities of failure trail didn't extended more than those of success trail.

• 상하수도학회지
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• 제21권2호
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• pp.235-242
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• 2007

Road runoff water includes various heavy metals (zinc, Zn; lead, Pb; copper, Cu; chrome, Cr; cadmium, Cd; etc.) and pathogens (E-coli and coliform). Since these pollutants are significantly harmful to human beings and have negative impact on water streams, numerous studies have been conducted to determine the characterization of these non-point pollutants from road runoff water. However, since these non-point pollutant concentrations vary depending on road traffic, road construction, and road maintenance, measurement of pollutant loadings in different site is necessary to estimate the effect of road runoff water on drinking water source. The objective of this study was to examine the quality of road runoff water from a city bridge in Seoul, Korea. This study was conducted for two years to assess annual discharge pollution loads. In this study, five key heavy metals (Zn, Pb, Cu, Cr, and Cd) and two pathogens (E-coli and coliform) were measured at 18 different events. The pollutant load mass transported was always higher than the corresponding runoff volume for Zn, Cu, and Cd, while Pb and Cr showed similar values between the load mass transported and the corresponding runoff volume. The event mean concentrations were Zn (0.908 mg/L), Pb (0.092 mg/L), Cu (0.141 mg/L), Cr (0.023 mg/L), and Cd (0.006 mg/L). Like Zn, Cu, and Cd, E-coli and coliform values (relatively high in Summer and Fall) are higher at the beginning of each event and decrease afterwards.

• Journal of Advanced Marine Engineering and Technology
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• 제32권5호
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• pp.707-716
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• 2008

The objective of this study was to analyze the effect of mixed fuel composition and mass fraction on spray inner structure in evaporating transient spray under the variant ambient conditions. Spray structure and spatial distribution of liquid phase concentration were investigated using a thin laser sheet illumination technique on the three component mixed fuels. A pulsed Nd:YAG laser was used as a light source. The experiments were conducted in a constant volume vessel with optical access. Fuel was injected into the vessel with electronically controlled common rail injector. Used fuel contains i-octane($C_8H_{18}$), n-dodecane($C_{12}H_{26}$) and n-hexadecane($C_{16}H_{34}$) that were selected as low-, middle- and high-boiling point fuel, respectively. Experimental conditions are 42 MPa, 72 MPa and 112 MPa in injection pressure, $5\;kg/m^3$, $15kg/m^3$ and $30kg/m^3$ in ambient gas density, 300 K, 500 K, 600 K and 700 K in ambient gas temperature, 300 K and 368 K in fuel temperature and different fuel mass fraction. Experimental results indicated that the multi-component fuels made two phase region mixed vapor and liquid so that it would are helpful to improve combustion, for the fuels of high boiling point component could accelerate evaporation very much according as low boiling point fuel was added to high boiling point fuel.

• 설비공학논문집
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• 제3권1호
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• pp.51-60
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• 1991

The aim of this study is to investigate the heat transfer characteristics in the transient cooling process of a high temperature wall. The slow transient cooling experiment was carried out with a copper block of high thermal capacity. The results of these experiments are as follows. 1. Temperature histories measured by the thermocouple, which is 0.99, 2.00, 2.99mm from the heat transfer surface showed monotonous during the cooling process. These variation are the curves of typical temperature histories in film-boiling, transition-boiling, and nucleate-boiling regions. 2. The temperature histories were measured by thermocouple installed in the copper block. The variations of the surface heat fluxes and surface temperature were computed from the numerical solution method TDMA from the measured temperature histories for radial position one dimensional heat transfer inverse problem. The boiling curves were found by the computed temperature histories. 3. The rewetting point which starts to change from film boiling to nucleate boiling is not connected with the mass velocity and it were found that the temperature of rewetting point indicated about $100^{\circ}C$. 4. The heat flux of rewetting point was about $10^5Kcal/m^2h$, at that time, the heat transfer coeficient indicated about $1000Kcal/m^2h^{\circ}C$ irrelevent to mass velocity. 5. The wall superheat decreases as the pressure increases. But I found that rewetting point appeared under higher condition in the wall temperature.

• 한국가스학회지
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• 제11권2호통권35호
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• pp.10-14
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• 2007

인화점은 가연성 액체의 화재 위험성을 평가하기 위해 사용되는 중요한 특성치 중의 하나이다. 가연성 액체의 상대적인 화재 위험성을 나타낼 수 있는 특성치로서는 열방출속도(HRR), 최대열방출속도(PHRR), 발화지연시간(TTI),질량 감소율, CO및 $CO_2$발생량 등이 있다. 본 연구에서는 가연성 액체의 가연성 액체의 인화점과 화재 특성치와의 관계에 대해서 검토하였다. 이를 위하여 질량 감소율과 TTI를 측정하여 화재 특성치를 계산하였다. 그 결과, 가연성 액체의 인화점과 TTI와 관련된 화재 특성치가 상관성이 매우 높은 것으로 나타났다. 이 결과로부터 가연성 액체 화재의 상대적인 위험성을 평가할 수 있는 파라미터로 사용할 수 있었다.

• Current Optics and Photonics
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• 제8권1호
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• pp.38-44
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• 2024

Under the influence of atmospheric turbulence, a star's point image will shake back and forth erratically, and after exposure the originally small star point will spread into a huge spot, which will affect the ground calibration of the star sensor. To analyze the impact of atmospheric turbulence on the positioning accuracy of the star's center of mass, this paper simulates the atmospheric turbulence phase screen using a method based on a sparse spectrum. It is added to the static-star-simulation device to study the transmission characteristics of atmospheric turbulence in star-point simulation, and to analyze the changes in star points under different atmospheric refractive-index structural constants. The simulation results show that the structure function of the atmospheric turbulence phase screen simulated by the sparse spectral method has an average error of 6.8% compared to the theoretical value, while the classical Fourier-transform method can have an error of up to 23% at low frequencies. By including a simulation in which the phase screen would cause errors in the center-of-mass position of the star point, 100 consecutive images are selected and the average drift variance is obtained for each turbulence scenario; The stronger the turbulence, the larger the drift variance. This study can provide a basis for subsequent improvement of the ground-calibration accuracy of a star sensitizer, and for analyzing and evaluating the effect of atmospheric turbulence on the beam.

• 분석과학
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• 제5권4호
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• pp.373-379
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• 1992

피난의 열 이성화반응 생성물에 관한 연구를 위하여 열분해 조건을 가스크로마토그래피와 질량분석기에 장치된 전기로형 및 curie-point 열분해기를 이용하여 실험을 행하였다. 그 결과, 최적 조건하에서 전기로형보다는 curie-point 열분해기에 의해서 피난으로부터 주 이성화 생성물인 citronellen (70%)을 얻었다. 본 연구에서 열분해 최적 조건은 $590^{\circ}C$, 4 Sec이고, 확인된 열분해 주 생성물은 citronellene, m-Menth-6-ene, m-Menth-1-ene, 1-Methyl-4(1-methyl-ethylidene) cyclohexane이었다.

• 한국언론정보학보
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• 제47권
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• pp.23-49
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• 2009

본 연구의 목적은 매스미디어의 위기 타개 및 개혁을 위한 규범이론의 내용과 범위를 제안하는 것이다. 이를 위하여, 허친스 보고서와 함께 허친스 보고서를 사상적 토대로 한 기존의 사회적 책임이론 관련 논의를 검토하여 한계점 및 시사점을 살펴보았다. 허친스 보고서는 매스미디어의 책임과 어카운터빌리티를 도덕적 법적 의무로 제시하였으며 미디어와 시민의 상호 협력관계 속에서 적극적 자유 이행이 가능하다고 보았다. 하지만, 사회적 책임이론에서 미디어의 책임은 어카운터빌리티에 관한 논의가 결여된 채, '기능', '자율적 윤리', '자율규제'를 중심으로 논의되어 소극적 자유로서의 한계를 노출해왔다. 따라서 자율규제나 기능주의적 접근에 의한 미디어의 사회적 책임 논의를 미디어 어카운터빌리티를 기반으로 한 적극적 자유 개념으로 확장할 필요가 있다. 그리고 사회적 토론과 합의를 거쳐 사회적 책임의 내용과 범위를 도출해 내야 한다. 허친스 보고서가 권고한 미디어카운터빌리티는 매스미디어가 시민사회와의 상호 커뮤니케이션을 통해서 '사회적 자율규제'를 실천하기 위한 민주적 방안으로서, 그리고 사회적 책임이론에 내재되어 있는 한계 극복을 위해 유용하다. 따라서 다원적 미디어 시스템 하에서 미디어 환경 개선과 신뢰 회복을 도모하기 위해서는 각각의 미디어 특성에 걸맞은 사회적 책임 그리고 어카운터빌리티의 내용 및 범위를 명확히 하기 위해 논의를 확장해야 한다.

• 소음진동
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• 제7권6호
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• pp.953-958
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• 1997

Corrugation of railway track can be caused by the various dynamic behaviors of traveling wheels and track. In this paper, the coupled vibrations of traveling wheel and railway track are analyzed as the cause of corrugations. To analyze the coupled vibration, the track supported by the sleepers and the traveling wheels are identified to the elastically supported infinite beam and the spring-mass system which runs at constant speed. The Hertzian contact spring is considered between the infinite beam and spring-mass system are calculated. The cause and development of rail corrugation are discussed in the view point of contact force fluctuation affected by the elastic supports and the corrugated surface profile on the track. By the obtained results, the possibilities of resonance are checked between the excitation by the corrugated surface profile and the natural frequency of contact spring-mass system. It may be thought to a development of railway corrugation.