• KSBB Journal
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• 제16권1호
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• pp.66-70
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• 2001

순수한 초임계 이산화탄소를 이용하여 camptothecin(CPT)와 10-hydroxy camptothecin(HCPT) 추출 시험을 결과, 이들은 각각 유기용매 메탄올 추출에 비교하여 3%와 2% 밖에 추출되지 않았다. 보조용매로 메탄올과 에탄올을 이용하여 CPT와 HCPT를 추출하면 추출 효율이 상승됨을 확인할 수 있었다. 특히 에탄올 보다 메탄올이 효율이 좋았다. 따라서 보조용매 적용에 관련된 여러 조건들을 최적화 하였다. 메탄올을 보조용매로 사용하는 경우에 보조용매의 농도가 증가할수록 추출 효율도 증가하였고 16% 이상에서는 추출 효율이 완만하게 증가하였다. 또한 추출은 온도에 따라 크게 영향을 받지 않아으나 온도에 따라 약간 증가하는 경향을 보였다. 초임계 추출에서 압력의 영향을 살펴본 결과 250 bar까지 압력이 증가할수록 추출 효율은 증가하였다. Acetate ion을 공급하여 추출 실험을 수행하였으나 CPT나 HCPT 모두 ion pairing agent의 영향은 없었다. 본 시스템과 같은 solid/fluid 추출 시스템에서 추출 효율에 영향을 크게 미치는 3가지 요소 (용해도, 확산, 및 matrix)중 확산의 영향을 살펴보았다. 여러 기하학적 모델 중 matrix가 구형인 hot-ball model로 확산게수를 계산하였다. 본 시스템에서 보조용매를 포함한 초임계 유체의 $D/r^2$ 값은 0.0072 $min^{-1}$로서 순수한 메탄올 유기용매 추출보다 큰 값을 보였다.

• 대한기계학회논문집A
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• 제38권3호
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• pp.309-314
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• 2014

기계나 토목 구조물의 형상은 일반적으로 전통적인 방법들을 이용하여 얻었다. 예를 들면 전력송전탑이나 해상풍력 하부구조물 이외의 다른 구조물들도 조직적으로 만든다. 한편 컴퓨터 그래픽의 급속한 성장으로 인해, 진화된 구조해석 및 최적설계기법들을 이용하고 있다. 본 논문에서는 해상 풍력 터빈을 위한 자켓 구조물의 구조형상을 위상최적화 기법을 통하여 연구하였다. 이번 연구는 실제작동하중상태로 시뮬레이션을 위하여 다 하중으로 종속시켰으며, 최적화 목적 함수는 주어진 경계조건아래 컴플라이언스로 정의하였다. 최적화는 고유진동수와 체적을 구속함수로 사용하였으며, 1 단계 모델의 결과는 2 단계 구조를 위한 외형을 빠르게 볼 수 있도록 한다. 그 결과로 사각뿔대의 3D 모델은 위상최적화를 통하여 개발하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.396-401
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• 2008

The disc-pad brake system is an important part of automobile safety system. During braking, the kinetic energy and potential energies of a moving vehicle are converted into the thermal energy through frictional heat between the brake disc and the pads. Most of the thermal energy dissipated through the brake disc. The temperature could be exceed the critical value for a given material, which leads to undesirable effects, such as the brake fade, premature wear, brake fluid vaporization, bearing failure, thermal cracks, and thermallyexcited vibration. The object of the present study is to investigate temperature field and temperature variation of brake disc and pad during single brake. The brake disc is decelerated at the initial speed with constant acceleration, until the disc comes to stop. The pad-disc brake assembly is built by 3D model with the appropriate boundary condition. In the simulation process, the mechanical loads are applied to the thermomechanical coupling analysis in order to simulate the process of heat produced by friction.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2005년도 가을 학술발표논문집 Vol.32 No.2 (1)
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• pp.709-711
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• 2005

이 논문에서는 CATIA, PRO-E 등의 CAD에서 3D 모델을 생성할 때 사용하는 파라메트릭 솔리드 모델링 기법에서 일반적으로 사용하는 방법보다 모델링 데이터의 용량을 크게 줄일 수 있는 방법에 대하여 고찰한다. 3D 파라메트릭 솔리드 모델링 기법은 기본적인 상세 솔리드들을 생성하여 부울(Boolean) 연산으로 이들을 조합하여 복잡한 형상(geometric object)을 만드는데 이 과정에서 많은 부울 연산이 수행된다. 그런데 각각의 상세 솔리드들의 크기가 필요 이상으로 크게 만들어 짐으로써 생성된 모델의 데이터 용량이 방대하게 되고 생성시간에도 영향을 미친다. 여기에서는 실무 경험을 바탕으로 처음에 생성된 상세 솔리드의 불필요한 부분을 제거하여 부울 연산에 알맞은 크기로 변경하여 모델링 데이터의 용량을 줄이는 방법을 제안한다.

• Advances in aircraft and spacecraft science
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• 제10권2호
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• pp.179-202
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• 2023

This article presents a numerical analysis to investigate the natural frequencies and harmonic response of a perforated cantilever beam attached to two layers of piezoelectric materials by using the finite element method for the first time. The bimorph piezoelectric is composed of 3 layers; two of them at the outer are piezoelectric, and the inner isotropic material. A higher order 3-D 20-node solid element that exhibits quadratic displacement behavior is exploited to discretize the isotropic layer, and coupled piezoelectric 3D element with twenty nodes is used to mesh the top and bottom layers. CIRCU94 element is added to act as a resistor part of the model. The proposed model is validated with previous works. The numerical parametric studies are presented to illustrate the effects of perforation geometry, the number of rows, the resistance on the natural frequencies, frequency response, and power. It is found that the thickness has a positive relationship with the natural frequency. Perforations help in producing higher voltage, and the best shape is rectangular perforations, and to produce higher voltage, two rows of rectangular perforations should be applied.

• 한국정밀공학회지
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• 제29권2호
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• pp.185-192
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• 2012

The paper presents the development of a cooling circuit design system that automatically creates 3D cooling circuit on a given section plane conforming to design specifications, generates 3D solid model of cooling line segments defined on a 2D sketch plane, and verifies interference of 3D cooling channel with the molding die surface. The system was developed mainly for designing plastic injection molding die of vehicular lamp, which helps the mold designer to rapidly construct cooling circuits but also reduce designer's unintended mistakes by conforming to the dimensional design specifications. It is used by an injection molding die manufacturing company in Korea, and reported approximately 20% reduction of cooling channel design time.

• 대한기계학회논문집
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• 제18권7호
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• pp.1866-1872
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• 1994

Turbulent flow in a channel with a square rib periodically mounted on one wall is studied by large-eddy simulation(LES). An efficient 3D Navier-Stokes solver has been written for this geometry using a fractional step method and a multi-grid technique. The Reynolds number considered is 82, 000 based on the mean velocity above the obstacle height. Near-wall turbulence is approximated by a wall-layer model based on the turbulence intensity at the grid point nearest a solid wall. The results show a good qualitative agreement with experiments currently available for a single rib, indicating that LES can be a useful tool in simulating complex turbulent flows.

• Geomechanics and Engineering
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• 제13권6호
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• pp.1011-1025
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• 2017

The geological conditions surrounding the Jijiapo Tunnel of the Three Gorges Fanba Highway project in Hubei Province are very complex. In this paper, a 3-D physical model was carried out to study the evolution process of filling-type fracture water inrush and mud gush based on the conditions of the section located between 16.040 km and 16.042 km of the Jijiapo Tunnel. The 3-D physical model was conducted to clarify the effect of the self-weight of the groundwater level and tunnel excavation during water inrush and mud gush. The results of the displacement, stress and seepage pressure of fracture and surrounding rock in the physical model were analyzed. In the physical model the results of the model test show that the rock displacement suddenly jumped after sustainable growth, rock stress and rock seepage suddenly decreased after continuous growth before water inrushing. Once water inrush occured, internal displacement of filler increased successively from bottom up, stress and seepage pressure of filler droped successively from bottom up, which presented as water inrush and mud gush of filling-type fracture was a evolving process from bottom up. The numerical study was compared with the model test to demonstrate the effectiveness and accuracy of the results of the model test.

• Advances in nano research
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• 제16권3호
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• pp.313-324
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• 2024

The main aims of this study are to develop a new nonlocal quasi-3D theory for the free vibration behaviors of the functionally graded sandwich nanobeams. The sandwich beams consist of a ceramic core and two functionally graded material layers resting on elastic foundations. The two layers, linear spring stiffness and shear layer, are used to model the effects of the elastic foundations. The size-effect is considered using nonlocal elasticity theory. The governing equations of the motion of the functionally graded sandwich nanobeams are obtained via Hamilton's principle in combination with nonlocal elasticity theory. Then the Navier's solution technique is used to solve the governing equations of the motion to achieve the nonlocal free vibration behaviors of the nanobeams. A deep parametric study is also provided to demonstrate the effects of some parameters, such as length-to-height ratio, power-law index, nonlocal parameter, and two parameters of the elastic foundation, on the free vibration behaviors of the functionally graded sandwich nanobeams.

• 한국환경과학회지
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• 제23권11호
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• pp.1843-1850
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• 2014

PS-D2EHPA beads were prepared by immobilizing di-2-ethylhexyl-phosphoric acid (D2EHPA) with polysulfone (PSf). The removal experiments of Cu(II) and Pb(II) by the prepared PS-D2EHPA beads were conducted batchwise. The removal efficiency of Cu(II) and Pb(II) by PS-D2EHPA beads was increased with increasing pH of solution. The removal rate of Cu(II) and Pb(II) was well described by the pseudo-second-order kinetic model. The maximum removal capacity of Cu(II) and Pb(II) obtained from Langmuir isotherm were 2.58 mg/g and 12.63 mg/g, respectively. External mass transfer coefficients for the removal of Cu(II) and Pb(II) by PS-D2EHPA beads were obtained $0.61{\times}10^{-2}{\sim}5.87{\times}10^{-2}/min$ and $1.55{\times}10^{-2}{\sim}8.53{\times}10^{-2}/min$, respectively and diffusion coefficients were obtained $1.32{\times}10^{-4}{\sim}3.98{\times}10^{-4}cm^2/min$ and $1.80{\times}10^{-4}{\sim}2.28{\times}10^{-4}cm^2/min$, respectively.