• 대한토목학회논문집
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• 제31권1B호
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• pp.57-62
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• 2011

하천에 설치되는 수공구조물은 유수흐름, 소류력 등에 변화를 주어 하천재해의 원인이 된다. 따라서 본 연구에서는 홍수통제 등의 목적으로 설치되는 횡월류위어에 의한 에너지변화와 소류력변화를 수리실험을 통하여 분석하였다. 실험수로는 사다리꼴 형태, 수로경사는 0.1%-1.0% 범위, 유량은 25 l/sec의 조건으로 횡월류위어 설치 전 후에 대한 실험을 수행하였다. 실험결과, 경사가 커질수록 비에너지비가 증가하였고, 경사가 1.0%에서는 비에너지비가 1보다 큰 지점이 나타났다. 소류력비는 경사가 커질수록 작아지지만, 소류력비가 1보다 큰 구간은 하류방향으로 더 넓게 분포하는 것으로 나타났고, 계산된 소류력비는 약 1.3이다.

• 한국태양에너지학회 논문집
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• 제33권3호
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• pp.82-90
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• 2013

Concentration errors critically affect the performance of solar concentrator, so their evaluation is important to the concentrated solar power technology. However, the evaluation is very challenging because error sources are various and not easy to measure individually. Therefore, the integrated effect of concentration errors is often more interesting and useful for large-scale applications. In the present work, we analytically investigate and classify various concentration error sources and then explain that the effect of various concentration errors can be represented in terms of a root mean square value of reflector surface slope error. We present an indirect approach to assessing the reflector surface slope error by comparing solar flux measurement data with modeling calculations. We apply the approach for solar furnaces with different thermal capacity and investigate its advantages and disadvantages.

• 한국지열·수열에너지학회논문집
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• 제4권1호
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• pp.11-19
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• 2008

Groundwater flow in confined aquifer and heat transport in underground geologic media are using same governing equation(line source) like well fuction. Therefore the conventional slope method using only later data obtained from in-situ thermal response test to determine the thermal conductivity of vertical geothermal heat exchanger(GHEX) is basically identical with one of Theis straight line method of aquifer test under artesian condition. In case that the pumping rate(Q, $m^3$/d) and drawdown(s,m) which are used for input data of existing hydrogeologic computer programs for aquifer test are replaced and converted to supplying heat energy per unit length of bore hole(Q/L,w/m or Kcal/h.m) and temperatures (T,$^{\circ}C$)measured at in and out-let of GHEX as in put data respectively, thermal conductivity around geothermal heat exchanger can be easily estimated without any special modification of the existing hydrogeologic computer program. Two numbers of time series temperature variation data obtained from in situ geothermal response test are analized using Theismethods(standard curve and straight line method) by using existing aquifer test program and conventional Slope method proposed by ASHRAE. The results show that thermal conductivity values estimated by two straight methods are identical and the difference of estimated values between standard curve methods and Slope method are also within acceptable ranges. In general,the thermal conductivity estimated from Theis straight linemethod gives more accurate value than the one of Slope method due to that Slope method uses only visual matching otherwise Theis method uses automatic curve matching estimation with reducing RSS.

• Nuclear Engineering and Technology
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• 제48권3호
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• pp.673-683
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• 2016

This paper analyzes the accuracy of the methods used in calibrating the thermal power of Nigeria Research Reactor-1 (NIRR-1), a low-power miniature neutron source reactor located at the Centre for Energy Research and Training, Ahmadu Bello University, Zaria, Nigeria. The calibration was performed at three different power levels: low power (3.6 kW), half power (15 kW), and full power (30 kW). Two methods were used in the calibration, namely, slope and heat balance methods. The thermal power obtained by the heat balance method at low power, half power, and full power was $3.7{\pm}0.2kW$, $15.2{\pm}1.2kW$, and $30.7{\pm}2.5kW$, respectively. The thermal power obtained by the slope method at half power and full power was $15.8{\pm}0.7kW$ and $30.2{\pm}1.5kW$, respectively. It was observed that the slope method is more accurate with deviations of 4% and 5% for calibrations at half and full power, respectively, although the linear fit (slope method) on average temperature-rising rates during the thermal power calibration procedure at low power (3.6 kW) is not fitting. As such, the slope method of power calibration is not suitable at lower power for NIRR-1.

• 대한전기학회논문지:시스템및제어부문D
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• 제55권7호
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• pp.319-326
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• 2006

This paper proposes a novel fault-tolerant gait for Quadruped robots using energy stability margins. The previously developed fault-tolerant gaits for quadruped robots have a drawback of having marginal stability margin, which may lead to tumbling. In the process of tumbling, the potential energy of the center of gravity goes through a maximum. The larger the difference between the potential energy of the center of gravity of the initial position and that of this maximum, the less the robot tumbles. Hence this difference of potential energy, dubbed as Energy Stability Margin (ESM), can be regarded as the stability margin. In this paper, a novel fault-tolerant gait is presented which gives positive ESM to a quadruped robot suffering from a locked joint failure. Positive ESM is obtained by adjusting foot positions between leg swing sequences. The advantage of the proposed fault-tolerant gait is demonstrated in a case study where a quadruped robot with a failed leg walks on a even slope.

• 한국전산구조공학회논문집
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• 제33권1호
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• pp.25-33
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• 2020

본 논문에서는 Coupled Eulerian-Lagrangian(CEL) 기법을 이용하여 인공섬 형식의 방호공을 구성하는 수중사면에 선박이 충돌하는 경우 발생하는 선박의 선수와 지반의 거동에 대한 매개변수 해석을 수행하였다. 고려된 매개변수는 선수의 경우 선수각, 스템각, 충돌위치 그리고 충돌속도이며, 지반의 조건으로 사면의 기울기, 지반과 선박의 마찰계수 그리고 지반의 강도이다. 선수의 거동으로부터 소산된 충돌력과 운동에너지를 각 매개변수에 대해 산정하고, 이를 지반의 변형과 연계하여 에너지 소산기구의 거동을 파악하였다. 충돌력을 변위의 지수함수로 가정하고 매개변수의 영향을 검토하였다. 그 결과 지수함수의 계수는 사면의 경사와 선박과의 마찰계수에만 영향을 받는 결과를 얻었다. 이 관계로부터 소산되는 충돌에너지를 타당하게 산정할 수 있었다. 충돌 시 선수에 의해 밀려난 원지반의 부피와 소산된 충돌에너지는 비례하는 관계로 나타낼 수 있다는 것을 보였고, 이 관계는 선박의 형상보다는 선박과 사면의 마찰계수와 지반의 강도에 영향을 받는 것으로 나타났다.

• Geomechanics and Engineering
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• 제23권4호
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• pp.313-325
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• 2020

Slope displacement and factor of safety (FOS) of a slope are two aspects that reflect the stability of a slope. However, the traditional limit equilibrium (LE) methods only give the result of the slope FOS and cannot be used to solve for the slope displacement. Therefore, developing a LE method to obtain the results of the slope FOS and slope displacement has significance for engineering applications. Based on a force-displacement coupled mode, this work expands the LE Morgenstern-Price (M-P) method. Except for the mechanical equilibrium conditions of a sliding body adopted in the traditional M-P method, the present method introduces a nonlinear model of the shear stress and shear displacement. Moreover, the energy equation satisfied by a sliding body under a small slope displacement is also applied. Therefore, the double solutions of the slope FOS and horizontal slope displacement are established. Furthermore, the flow chart for the expanded LE M-P method is given. By comparisons and analyses of slope examples, the present method has close results with previous research and numerical simulation methods, thus verifying the feasibility of the present method. Thereafter, from the parametric analysis, the following conclusions are obtained: (1) the shear displacement parameters of the soil affect the horizontal slope displacement but have little effect on the slope FOS; and (2) the curves of the horizontal slope displacement vs. the minimum slope FOS could be fitted by a hyperbolic model, which would be beneficial to obtain the horizontal slope displacement for the slope in the critical state.

• 한국전문물리치료학회지
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• 제6권2호
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• pp.67-76
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• 1999

Going up and down the stairs is a repeated task in the activities of daily living. These activities are needed during the recovery process with impaired lower limbs. This paper presents the difference of EEI (energy expenditure index) through the slope of stairs. Twenty-one normal young adults took a part in this study (11 males, 10 females). They stepped up and down the stairs which had two different slopes for 5 minutes. Resting heart rate, walking heart rate, and moving distance were recorded. EEI was calculated from the heart rate and moving speed which was calculated by the distance of movement. Data were analyzed by repeated two-way ANOVA with SAS program and the difference of EEI through the slope of stairs was not statistically significant (p=0.9971). The results show that EEI was not affected by the slope of stairs in normal people. But distance of movement (p=0.0067) and speed (p=0.0064) had a significant difference.

• 한국지반환경공학회 논문집
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• 제12권3호
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• pp.47-54
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• 2011

절토비탈면에서 발생되는 낙석에 대한 안정성을 확보하기 위해 설치되는 낙석방지 울타리는 기본적으로 12.5m 높이에서 400kg인 암괴가 낙하될 때 발생되는 50kJ의 충격에너지를 가정하여 설계되고 있다. 그러나 암괴의 크기가 커지거나 높이가 높은 곳에서 낙하하는 경우에는 기존의 낙석방지울타리로는 안정성 확보가 어려운 실정이다. 본 논문은 낙석해석프로그램을 이용하여 암괴중량에 따른 비탈면 높이, 울타리와의 이격거리, 경사각 등의 변화를 주어 낙석에 대한 안정성 분석을 실시하여 보았다. 해석결과 기존의 2.5m 높이의 낙석방지울타리는 설계하중 조건인 400kg 암괴가 낙석 될 때, 비탈면 높이가 20m 이내의 일부를 제외하고 대부분 낙석에 대해 안정성이 확보될 수 있으나, 20m 이상인 경우 낙석의 튀는 높이가 낙석방지울타리를 넘는 경우가 빈번하고 낙석의 충격에너지도 설계충격에너지 이상인 경우가 발생되는 결과를 얻을 수 있었다. 그러므로 낙석방지울타리의 설계 시 표준도에 준하여 설계하는 방식보다 지반조건에 따른 낙석의 안정성 검토를 실시한 후에 낙석 도약높이 및 충격에너지를 평가하여 낙석방지울타리를 설계하는 것이 적절할 것으로 판단된다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.852-857
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• 2007

For electric traction using a large power converter, harmonic problem in the p-ower quality and regenerating energy in side of efficiency are important. Recently, by advance in power electronics technology, some countries are considering regenerative inverter from the points of view. when the electric tractions are stopped or driven through the falling slope way, it is very useful to supply surplus energy to the power source by regenerating system in the efficient side of energy and it is very economical. these regenerating energy are supported electrical equipment through DC line. In this research, the purposes are suppressing extra DC-line voltage and saving energy generated while electric traction is been driving on the falling slope way or reducing speed for railway using a 1500V DC-voltage. Besides, the accompanied defects of current distortion, low power factor and the voltage unbalance will be solved by developing the algorism of inverter having ability to compensate current harmonic.