• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.983-983
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• 2012

EFDC의 수질모형인 HEM3D는 국내 해양수질모델링에는 적용된 사례가 많지만 담수에 적용된 사례는 거의 없으며, 우리나라 환경부 수질측정항목과 수질 INPUT 자료가 달라서 모델의 적용이 힘들었다. 그러나 HEM3D는 EFDC 수리모델을 연계하는 WASP에 비해 자체 3차원 수리동역학 모델이 있어 셀 개수의 제한이 없고 계산속도 또한 WASP 보다 2~3배 빠른 것으로 알려져 있다. 그러나 현재 우리나라의 수질측정항목은 HEM3D의 수질모의항목과 다소 차이가 있다. 특히 Carbon계열에서 실측수질항목은 BOD, COD인 반면 HEM3D의 모의가능항목은 RPOC, LPOC, DOC, COD로 바로 적용을 하기는 어렵다고 판단하였다. 따라서 환경부 수질자료를 HEM3D에 적용하기위해 문헌자료를 참고한 수질항목간의 분율을 사용하여 필요한 자료를 산출하였고, 환경부 수질자료의 HEM3D적용 결과를 알아보고 현재 자료 사용 시의 문제점과 향후 개선방안을 알아보고자 하였다. HEM3D의 모의 결과 TN, TP 보정에는 큰 문제가 없었으나 $BOD_5$와 세부수질항목의 영향을 많이 받는 조류 등의 항목 보정결과는 성공적이지 못했다. 이것은 분율을 적용해 각 유입지천의 세부항목별 수질 자료를 산출할 때 낙동강 전체 평균을 사용했기 때문에 조류성장에 직접적으로 영향을 받는 세부 항목별 영양염에 대한 실제 값과 산출된 농도 값 사이의 오차가 가장 큰 원인으로 판단된다. 한편 전체 대상지역중 일부구간에 대하여 동일한 수질입력자료를 이용하여 HEM3D와 WASP을 동시 적용하였다. 자료의 변환과정에서의 오차와 입력형태 및 각 모델 변수형태의 차이 등의 한계로 결과값에 차이가 있는 것으로 나타났으며, 본 연구결과 현재 확보된 수질측정망의 수질자료를 이용하여 HEM3D를 구축하는 것은 Carbon 계열과 조류(부영양화)모의에서 문제가 발생할 것으로 판단되며 추가 자료 확보가 필요할 것으로 보인다. 또한 필요한 입력자료가 충분히 확보가 된다면 추가연구결과에서 볼 수 있듯이 미국공변단과 미국 환경부수질모델 모두 동시적용이 가능하다고 판단되며 목적과 편의에 따라 선택적 모의가 가능하다고 판단된다.

• Composites Research
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• v.30 no.5
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• pp.323-330
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• 2017

In this study, multiscale analysis in which the information obtained from molecular dynamics simulation is applied to the continuum mechanics level is conducted to investigate the effects of clustering of silicon carbide nanoparticles reinforced into polypropylene matrix on mechanical behavior of nanocomposites. The elastic behavior of polymer nanocomposites is observed for various states of nanoparticulate agglomeration according to the model reflecting the degradation of interphase properties. In addition, factors which mainly affect the mechanical behavior of the nanocomposites are identified, and new index 'clustering density' is defined. The correlation between the clustering density and the elastic modulus of nanocomposites is understood. As the clustering density increases, the interfacial effect decreased and finally the improvement of mechanical properties is suppressed. By considering the random distribution of the nanoparticles, the range of elastic modulus of nanocomposites for same value of clustering density can be investigated. The correlation can be expressed in the form of exponential function, and the mechanical behavior of the polymer nanocomposites can be effectively predicted by using the nanoparticulate clustering density.

• Transactions of the KSME C: Technology and Education
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• v.3 no.2
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• pp.131-140
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• 2015

The mono-ski for the paraplegia designed to skiing is formed as seat bucket on the sled. The impact force transferred by snow surface during skiing is absorbed by the leg joints of normal human, but it is transferred to the human body on the seat when using mono-ski. Most of commercially available mono-ski have absorbing device and link mechanism between seat and ski mount in order to complement it. In this study we developed the comfort evaluation model that could provide skiing simulation of mono-ski with hydraulic damper and analyzed vibrational acceleration occurred during skiing uneven surface. The evaluation method used in this study is the international standard BS6841. We evaluated comfort performance of mono-ski in accordance with nozzle adjustment of hydraulic damper.

• Journal of Korea Water Resources Association
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• v.42 no.6
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• pp.433-443
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• 2009

For the better understanding of the temporal characteristics of soil water, this study is to suggest a stochastic soil water model and to apply it for impact assessment of climate change. The loss function is divided into 3 stages for more specified comprehension of the probabilistic behavior of soil water, and especially, the soil water model considering the stochastic characteristics of precipitation is developed in order to consider the variation of climatic factors. The simulation result of soil water model confirms that the proposed soil water model can re-generate the observation properly, and it also proves that the soil water behaves with consistent cycle based on the precipitation pattern. Moreover, with the simulation results with a climate change scenario, it can be predicted that the future soil water will have higher variations than present soil water.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.6-11
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• 2009

최근 경제발전과 산업화를 통한 도시화로 인하여 많은 자연하천이 심하게 훼손되고 있으며 도시하천의 경우 치수의 효율성을 강조한 하천정비를 실시함으로써 하천의 외경은 깨끗하게 바꾸어 놓았지만 그로 인한 하천생태계의 파괴가 문제점으로 대두되고 있다. 이에 따라 생태적으로 훼손된 하천의 생태복원이 최근 들어 활발히 추진되고 있으며 하천변의 식물 및 어류 등 다양한 생물에 대한 서식공간의 마련이 주요 이슈로 연구되어지고 있다. 본 연구에서는 2차원 수리서식모형인 River2D를 대표적인 도시하천인 대전천에 적용하여 대전천의 멸종위기에 처해 있는 감돌고기 및 우점종인 피라미를 대상으로 대상 어류의 서식처 제공을 위한 수리학적 분석을 시도하였다. 또한 자연친화적 서식처 개선 공법으로서 거석을 하도 내에 배치함에 따른 가중가용면적의 변화를 비교 검토하였으며 감돌고기를 위한 최적의 서식처 개선 방안을 제시하였다. 현재 상태의 대상하천에 대한 어류서식처를 모의분석한 결과, 현재 직선화되고 단조로운 하천흐름은 피라미의 서식환경에 적합한 것으로 나타났으며 가중가용면적의 경우 감돌기에 비하여 피라미가 약 20배정도 크게 나타났다. 어류서식처 조성공법의 WUA를 산정한 결과 V형 여울공법이 감돌고기의 서식환경을 360%, 징검다리 거석공법이 60%, 외톨이 거석공법이 8%이상 상승시키는 것으로 나타났다. 반면, 거석(Boulder)을 적절히 배치하여 서식처를 개선하는 방법의 경우에도 거석간 간격을 3.5m로 하여 배치하는 경우가 가장 효율적인 것으로 나타났으며 거석을 이용한 여러 가지의 배치형태 중에서 수류를 중앙으로 집중시켰을 때 감돌고기의 서식처가 급격하게 상승하는 것으로 나타났다. 따라서 하도 내 거석의 배치시 하도 및 대상어종의 특성을 고려하여 적절한 배치간격 및 배치방법을 연구하여 시행되어야 할 것이다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.1
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• pp.47-52
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• 2008

As the packing density of IC devices gets ever higher, the thickness of the gate $SiO_2$ layer of the MOS devices is now required to be reduced down to 1 nm. For such a thin $SiO_2$ layer, the MOS device cannot operate properly because of tunneling current and threshold voltage shift. Hence there has been much effort to develop new dielectric materials which have higher dielectric constants than $SiO_2$ and is free from such undesirable effects. In this work, the physical and electrical characteristics of ALD $ZrO_2$ film have been studied. After deposition of a thin ALD $ZrO_2$ film, it went through thermal treatment in the presence of argon gas at $800^{\circ}C$ for 1 hr. The characteristics of morphology, crystallization kinetics, and interfacial layer of $Pt/ZrO_2/Si$ samples have been investigated by using the analyzing instruments like XRD, TEM and C-V plots. It has been found that the characteristics of the $Pt/ZrO_2/Si$ device was enhanced by the thermal treatment.

• Journal of the Korea Computer Industry Society
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• v.2 no.6
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• pp.853-858
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• 2001

When an absolute elastic collision occurs between a motion body and the another body inside a closed space, according to the current physical law and thus a computer graphical expression, it is defined that the center of mass of the closed space is not moved. This paper defines a physical law which includes a minor facts of the center of mass of a closed space moves during an absolute elastic collision occurs between a motion body and another body inside a closed space. The law defined in this paper has been verified using approximate lab equipments, and using this, graphical expression models and mathematical expressions for an absolute elastic collision between two bodies inside a closed space are del ed. When the minor effects of the center of mass moves is applied to the multi-body dynamic simulation program or haptic program, more accurate motion could be expressed. This definition can also be applied to an animation movie or other graphical motion expression for more realistic expression.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.1-8
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• 2017

This paper presents the development of an adaptive cruise control (ACC) system, which is one of the typical advanced driver assist systems, for 4-wheel drive hybrid in-wheel electric vehicles. The front wheels of the vehicle are driven by a combustion engine, while its rear wheels are driven by in-wheel motors. This paper proposes an adaptive cruise control system which takes advantage of the unique driveline configuration presented herein, while the proposed power distribution algorithm guarantees its tracking performance and fuel efficiency at the same time. With the proposed algorithm, the vehicle is driven only by the engine in normal situations, while the in-wheel motors are used to distribute the power to the rear wheels if the tracking performance decreases. This paper also presents the modeling of the in-wheel motors, hybrid in-wheel driveline, and integrated ACC control system based on a commercial high-precision vehicle dynamics model. The simulation results obtained with the model are presented to confirm the performance of the proposed algorithm.

• Journal of the Korean Electrochemical Society
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• v.14 no.3
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• pp.145-151
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• 2011

ZnSe, as a II-VI compound semiconductor which has a wide band gap in the visible region is applicable to the various fields such as laser diode, display and solar cell. By using the electrochemical deposition method, ZnSe thin film was synthesized on the ITO glass substrate. The synthesis of ZnSe grains and their structure having zinc blende shape were verified through the analysis of XRD and SEM. UV spectrophotometric method determined the band gap as the value of 2.76 eV. Applying the DFT (Density Functional Theory) in the molecular dynamics, the band structure of ZnSe grains was analyzed. For ZnSe grains with zinc blende structure, the band structure and its density of state were simulated using LDA (Local Density Approximation), PBE (Perdew Burke Ernzerhof), and B3LYP (Becke, 3-parameter, Lee-Yang-Parr) functionals. Among the calculations of energy band gap upon each functional, the simulated one of 2.65 eV based on the B3LYP functional was mostly near by the experimental measurement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.379-385
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• 2013

The tires, suspension type, and steering system can all cause pulling during braking. Among these, a drag link steering system and leaf-type suspension system are significant causes of vehicle pulling. In this study, the pulling problem is analyzed using the vehicle analysis program "ADAMS/CAR." The drag link and leaf spring behavior is analyzed to find the key reason for pulling. After this, the optimization program "Visual DOC" is used with "ADAMS/CAR" to find a steering link connection point to reduce pulling. After conducting this simulation, K&C (kinematic & compliance) test simulation with a modified connection point is conducted to determine whether the vehicle performance improves. Through a full braking simulation, it is verified that the pulling distance is reduced at braking.