• 한국자동차공학회논문집
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• 제1권3호
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• pp.22-33
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• 1993

A theoretical analysis of predicting the detailed motion of a piston-crank mechanism within piston-guide clearance is presented, and the analysis is applied to the piston motion in a gasoline engine. A piston movement program is developed to calculate the piston attitude relative to the bore, the piston to bore impact velocity and kinetic energy loss and the net transverse force acting on the piston. This paper presents the formulation of a set of differential equations governing the transverse and rotational motion of a piston. These equations of motion were solved by well established Runge-Kutta method. As a result of this study, it is possible to predict the effects of piston geometry and piston pin offset on a piston motion and kinetic energy loss.

• 한국군사과학기술학회지
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• 제18권1호
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• pp.31-36
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• 2015

To describe turbulent wake behind a submarine, it is very important to know turbulent kinetic energy distributions in the wake. To get the distribution is to solve the turbulent kinetic energy equation, and to solve the equation, it is needed both information of ${\lambda}$ and ${\sigma}$ which define physical characteristics of the wake. This paper gives analytical solution of the equation, which is driven from $8^{th}$ order polynomial fitting, as a function of given ${\lambda}$, even though there is no information of ${\sigma}$. In comparison between numerical solution(i.e. exact solution) and analytical solution, the relative errors between them are less than to 5% in the range of 0 < ${\xi}$ < 0.95 in most given ${\lambda}$.

• 한국운동역학회지
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• 제21권2호
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• pp.253-258
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• 2011

The purpose of this study was to compare metabolic energy expenditure with the computed kinetic energy for different speeds of walking and running over the treadmill and to find the relevance for individual and group equation by performing a statistical analysis, Bland-Altman plot. Seven male subjects participated, and they were required to walk and run on the treadmill with the gas analyzer and triaxial accelerometer. Walking speeds were 3.0, 4.0, 5.0 and 6.0 km/h and running speeds were 7.0, 8.0 and 9.0 km/h respectively. Kinetic energy was calculated by the integration of acceleration data and compared with the metabolic energy measured by a gas analyzer. Correlation coefficients showed relatively good between the measured metabolic energy and the calculated kinetic energy. In addition, a dramatic increase in kinetic energy was also observed at the transition speed of walking and running, and two standard deviations in Bland-Altman plot, derived from the difference between measured and predicted values, were 1.14, 2.53, 2.93, 1.80, 2.80, 0.60 and 2.48 respectively. It was showed that there is no difference for methods of how to predict the kinetic energy expenditure for individual and group even though people had each different physical characteristic.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2008년도 학술발표회 논문집
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• pp.234-238
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• 2008

The energy conservation theory is introduced for investigating processes of runoff and soil erosion on the hillslope system changed vegetation condition by wildfire The rainfall energy, input energy consisted of kinetic and potential energy, is influenced by vegetation coverage and height. Output energy at the outlet of hillslope is decided as the kinetic energy of runoff and erosion soil, and mechanical work according to moving water and soil is influenced dominantly by the work rather than the kinetic energy. Relationship between output and input energy is possible to calculate the energy loss in the runoff and erosion process. The absolute value of the energy loss is controlled by the input energy size of rainfall because energy losses of runoff increase as many rainfall pass through the hillslope system. The energy coefficient which is dimensionless is defined as the ratio of input energy of rainfall to output energy of runoff water and erosion soil such as runoff coefficient. The energy coefficient and runoff coefficient showed the highest correlation coefficient with the vegetation coverage. Maximum energy coefficient is about 0.5 in the hillslope system. The energy theory for output energy of runoff and soil erosion is presented by the energy coefficient theory associated with vegetation factor. Also runoff and erosion soil resulting output energy have the relation of power function and the rates of these increase with rainfall.

• 대한토목학회논문집
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• 제40권1호
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• pp.111-118
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• 2020

한국은 강우로 인해 발생되는 토양침식량을 정량적으로 예측하기 위해서 미국에서 유도된 강우운동에너지식을 지난 40년 동안 사용해왔다. 강우의 특성은 기후, 지역 및 시간에 의존하기 때문에 연구 지역에서 측정된 호우사상으로부터, 토양 침식을 일으키는 강우운동에너지의 특성을 분석해서 연구에 활용하는 것이 필요하다. 본 연구의 목적은 서울 지역의 강우운동에너지의 특성을 분석하기 위한 것으로서 서울에서 3년 동안 측정 한 파시벨 강우자료를 사용하였다. 본 연구는 파시벨로 측정한 자료 중 강우강도에 따른 강우운동에너지의 관계를 규명하는데 중점을 두었으며, 새로운 강우운동에너지식을 제안하였다. 또한, 기존에 국내 및 국외에서 개발된 강우운동에너지식과 본 연구에서 도출한 서울 지점에서의 강우운동에너지의 특성을 비교 분석하였다.

• 한국지형학회지
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• 제23권3호
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• pp.105-122
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• 2016

To evaluate the changes in the physical characteristics of open rainfall related to canopy effects and rainfall intensity in Korea, the terminal velocity of raindrops and drop size distributions(DSD) were continuously measured by an optical-laser disdrometer in an open site(Op) and in two forest stands(Th1: Larix leptolepis, Th2: Pinus koraiensis) during five rainfall events in 2008. The terminal velocity, DSD and two forms of kinetic energy(KE, $Jm^{-2}$ $mm^{-1}$; KER, $Jm^{-2}$ $h^{-1}$) of open rainfall drops were determined and were compared with those of throughfall drops under two different canopy heights. The effects of the canopy and rainfall intensity, together with wind speed, on the changes in drop size and kinetic energy of throughfall were evaluated. Throughfall drops were larger than open rainfall drops. The distribution of terminal velocities for the drop sizes measured at Th2 was lower than that at Op; however, at Th1 the distribution was similar to that at Op. The total kinetic energy of throughfall at Th1 and Th2 was higher than the total kinetic energy of open rainfall, and the kinetic energy distribution for the drop sizes wassimilar to the drop size distribution. The observed throughfall-KER at Th1 was lower than an estimate previously produced using a model. The overestimation from the modeled value at Th1 was likely to be due to overestimated values of a square root transformation of fall height and its coefficient in the model because the distributions of terminal velocity for the drop size measured at Th1 were similar to those of open rainfall.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.991-992
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• 2010

• Journal of the Optical Society of Korea
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• 제13권1호
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• pp.42-47
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• 2009

The propagation of an intense laser pulse through an upward density-gradient plasma in a self-modulated laser wakefield acceleration (SM-LWFA) is investigated by using particle-in-cell (PIC) simulations. In the fully relativistic and kinetic PIC simulations, the relativistic and kinetic effects including Landau damping enhance the electron dephasing. This electron dephasing is the most important factor for limiting the energy of accelerated electrons. However, the electron dephasing, which is enhanced by relativistic and kinetic effects in the homogeneous plasma, can be forestalled through the detuning process arising from the longitudinal density gradient. Simulation results show that the detuning process can effectively maintain the coherence of the laser wake wave in the spatiotemporal wakefield pattern, hence considerable energy enhancement is achievable. The spatiotemporal profiles are analyzed for the detailed study on the relativistic and kinetic effects. In this paper, the optimum slope of the density gradient for increasing electron energy is presented for various laser intensities.

• Geomechanics and Engineering
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• 제30권4호
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• pp.345-352
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• 2022

When rock burst occurs, the damaged coal, rock and other fragments can be ejected to the roadway at a speed of up to 10 m/s. It is extremely harmful to personnel and mining equipment, and seriously affects the mining activities. In order to study the energy evolution characteristics, especially kinetic energy, in the process of rock mass failure, this paper first analyzes the energy changes of the rock in different stages under uniaxial compression. The formula of the kinetic energy of rock sample considering the energy from the indenter of the testing machine is obtained. Then, the uniaxial compression tests with different stiffness ratios of the indenter and rock sample are simulated by numerical simulation. The kinetic energy U_d, elastic strain energy U_e, friction energy U_f, total input energy U and surface energy U_θ of crack cracking are analyzed. The results show that: The stiffness ratio has influence on the peak strength, peak strain, U_d, U_e, U_θ, U_f and U of rock samples. The variation trends of strength, strain and energy with stiffness are different. And when the stiffness ratio increases to a certain value, if the stiffness of the indenter continues to increase, it will have no longer effect on the rock sample.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1993년도 추계학술발표회 초록집
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• pp.31-36
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• 1993

Three different methods were employed to measure the degree of aerial oxidation in coal and the resulting oxidation/weathering indices were applied to obtain kinetic parameters of aerial oxidation processes, The index (i.e., slurry pH, Free Swelling Index, weight gain) values were subjected to kinetic analysis based on power-law Arrhenius type reaction model. The results show that activation energy of the aerial oxidation in 20-29$0^{\circ}C$ is in the range of 12-16 ㎉/㏖ and the agreement among three techniques is remarkable. The first order kinetic model is suitable in describing low temperature aerial oxidation process, except in the FSI case where the zero order expression is the best one.