• 한국지반환경공학회 논문집
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• 제25권4호
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• pp.21-28
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• 2024

본 연구에서는 SPH 해석을 위한 다면체영역분할 기법이 소개된다. SPH 기법은 유체 유동 모사를 위한 수치해석기법으로 무요소기법(meshless method) 중 하나이다. 유동성 지반 또는 고체-유체 상호작용 해석 등에 유용하게 쓰일 수 있다. SPH는 입자기반 해석이기 때문에 입자가 많을수록 결과의 정확도는 높아지지만 수치적 효율성은 떨어진다. 일반적으로 해석의 효율성을 높이기 위해 병렬 프로세싱 알고리즘과 함께 쓰이는데 직교좌표계 기반의 영역분할 기법이 대표적이다. 그러나 복잡한 기하학적 형태나 동적 경계조건에서 유동 모사 등을 병렬 해석하기 위해서는 직교좌표계 영역분할 방법이 적합하지 않다. 소개하는 다면체영역분할 기법은 이와 같은 문제에서 병렬효율성을 높일 수 있는 장점을 갖는다. 다양한 형태의 3차원 다면체 요소로 분할하여 문제에 적합하게 모델링할 수 있다. SPH 입자들의 물리적 값들은 smoothing 길이 이내의 주위 입자들 정보를 이용하여 계산된다. 영역분할 시 물리적으로 분리될 수 있는 입자정보들을 코어간 공유할 수 있는 방법과 병렬효율성이 떨어질 수 있는 cross-point에서의 정보공유 방법이 소개된다. 수치해석 예제를 통하여 제안된 방법의 병렬효율성은 12코어까지 95%에 근접하였다. 이후 코어가 증가할수록 코어간 공유되는 정보량이 많아져 병렬효율성이 떨어지는 문제가 발생되기도 하였다.

• 한국전기전자재료학회논문지
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• 제15권6호
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• pp.543-550
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• 2002

In this paper, the $CF_4$ decomposition rate and by-product were investigated for two simulated plasma reactors which are metal particle reactor and spiral wire reactors as a function of mixed gases. The $CF_4$ decomposition rate by plasma reactor with metal particle electrode had a gain of 20~25% over that by plasma reactor with spiral wire electrode. The $CF_4$ decomposition efficiency increases with increasing applied voltage up to the critical voltage for spark formation. The $CF_4$ decomposition efficiency of metal particle reactor was about 80% at AC 24kV. The $CF_4$ decomposition rate used Ar-$N_2$ as base gas was the highest among three base gases of $N_2$, $Ar-N_2$, air. The by-products of the $N_2$, $N_2Ar$ base as were similar, but in case of air base they were different.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.912-916
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• 2002

In this paper, the $CF_4$ decomposition rate and by-product were investigated for a simulated two plasma reactors which are metal particle reactor and spiral wire reactor as function of mixed gases. The $CF_4$ decomposition rate by plasma reactor with metal particle electrode had a gain of 20~25[%] over that by plasma reactor with spiral wire electrode. The $CF_4$ decomposition efficiency increases with increasing applied voltage up to the critical voltage for spark formation. The $CF_4$ decomposition efficiency of metal particle reactor was about 80[%] at AC 24[kV]. The $CF_4$ decomposition rate used $Ar-N_2$ as base gas was the highest among three base gases of $N_2$, $Ar-N_2$, air. The by-products of the $N_2$, $Ar-N_2$ base as were similar, but in case of air base they were different.

• 한국기후변화학회지
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• 제8권1호
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• pp.63-71
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• 2017

It is recognized that tetrafluoromethane ($CF_4$) has a great influence on global warming. The $CF_4$ is known to have a large impact on climate change due to its large global warming index. In this study, a waterjet plasma scrubber (WPS) was designed and manufactured for the $CF_4$ decomposition. The WPS is a novel technology which is combined a gliding arc plasma and water injection at the center of the plasma discharge. This can give an innovative way for $CF_4$ decomposition by achieving larger plasma columnand generating OH radicals. A performance analysis was achieved for the design factors such as waterjet flow rate, total gas flow rate, consumption electric power, and electrode gap. The highest $CF_4$ decomposition and energy efficiencies were 64.8% and 6.43 g/kWh, respectively; Optimal operating conditions were 20 mL/min of waterjet flow rate, 200 L/min total gas flow rate, 5.3 kW consumption electric power, and 4.4 mm electrode gap. As for the 2 stage reactor of the WPS, the $CF_4$ decomposition efficiency improved as the 85.3% while the energy efficiency decreased as the 5.57 g/kWh.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2013년 추계학술대회
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• pp.547-560
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• 2013

In this study, the air pollutant removal such as sulfur oxides was studied. A combination of the plasma discharge in the reactor by the reaction surface discharge reactor Calcium hydroxides catalytic reactor and air pollutants, hazardous gas SOx, changes in gas concentration, change in frequency, the thickness of the electrode, kinds of electrodes and the addition of simulated composite catalyst composed of a variety of gases, including decomposition experiments were performed by varying the process parameters. The experimental results showed the removal efficiency of 98% in the decomposition of sulfur oxides removal experiment when Calcium hydroxides catalysts and the tungsten(W) electrodes were used. It was increased 3% more than if you do not have the catalytic. If added to methane gas was added the removal efficiency increased decomposition.

• 소성∙가공
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• 제7권5호
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• pp.474-480
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• 1998

In the present study a domain decomposition scheme using the substructuring method is developed for the computational efficiency of the finite element analysis of metal forming processes. in order to avoid calculation of an inverse matrix during the substructuring procedure, the modified Cholesky decomposition method is implemented. As obtaining the data independence by the substructuring method the program is easily paralleized using the Parallel Virtual machine(PVM) library on a work-station cluster connected on networks. A numerical example for a simple upsetting is calculated and the speed-up ratio with respect to various number of subdomains and number of processors. The efficiency of the parallel computation is discussed by comparing the results.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.471-474
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• 2007

A domain/boundary decomposition technique is applied to carry out efficient finite element analyses of 3-D contact problems. Appropriate penalty functions are selected for connecting an interface and contact interfaces with neighboring subdomains that satisfy continuity constraints. As a consequence, all the effective stiffness matrices have positive definiteness, and computational efficiency can be improved to a considerable degree. If necessary, any complex-shaped 3-D domain can be divided into several simple-shaped subdomains without considering the conformity of meshes along the interface. With a set of numerical examples, the basic characteristics of computational efficiency are investigated carefully.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제18권1호
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• pp.17-26
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• 2014

This paper presents development of an improved domain decomposition method for large scale structural problem that aims to provide high computational efficiency. In the previous researches, we developed the domain decomposition algorithm based on augmented Lagrangian formulation and proved numerical efficiency under both serial and parallel computing environment. In this paper, new computational analysis by the proposed domain decomposition method is performed. For this purpose, reduction in computational time achieved by the proposed algorithm is compared with that obtained by the dual-primal FETI method under serial computing condition. It is found that the proposed methods significantly accelerate the computational speed for a linear structural problem.

• 상하수도학회지
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• 제18권3호
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• pp.392-400
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• 2004

This research uses the $TiO_2$/UV process to verify the most suitable condition and possibility to dispose dyeing wastewater that contains pigment and a large amount of pollutants. For this, this research has enforced experiments that compare photo adsorption, photolysis, and photo catalyst oxidation reaction, and also evaluated and analyzed the change of pH and $TiO_2$ dosage, irradiation rates of ultraviolet rays and the dosage change and injection method of $H_2O_2$. According to the results of the dyeing wastewater experiment of storehouse catalyst that uses the new form of $TiO_2$, the photo catalyst oxidation reaction proved to be more effective than photo adsorption and photolysis; 35%, 21% in the case of $TCOD_{cr}$ and 39%, 28% in the case of chromaticity. Taking into consideration the reaction time, amount of photo catalyst reaction and irradiation amount of ultraviolet rays, the decomposition efficiency of pH change proved to be most effective at pH 4. On the whole, the acidity area proved to be effective in dyeing water exclusion than neutral and alkalinity areas. Having evaluated the influence of $TiO_2$ dosage, not only does the decomposition efficiency continuously improve as the $TiO_2$ dosage increases but the shielding effect does not occur also when the $TiO_2$ is at a fixed state. The influence of ultraviolet irradiation amount concluded in the result that as the ultraviolet irradiation amount increases the decomposition efficiency continually increased, but in the case of chromaticity when the irradiation amount was higher than 37.8mW/cm2 the removal efficiency is slowed remarkably. The influence of $H_2O_2$ dosage evaluation reached the results that although the decomposition efficiency increases with the increase of $H_2O_2$ dosage, when above 150mg (total dosage: 1200mg) $H_2O_2$ consumes OH radical itself and reduces the decomposition efficiency. Also in the case of the $H_2O_2$ injection method rather than injecting in the whole amount of $H_2O_2$ (1200mg) needed at the beginning all at once, injecting divided quantities of $H_2O_2$ whenever the electric current density falls below 10mgfl reduces the wases of OH radical due to an excess of $H_2O_2$ and in tum heightens the decomposition efficiency.

• 한국가스학회지
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• 제4권2호
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• pp.1-6
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• 2000

가스중에 포함되어 있는 NOx를 안전하게 처리하기 위하여 침상전극을 취부한 플라즈마 반응기를 제작하여 장치의 특성을 실험적으로 조사하여 유효성을 검정하였다. 반응가스는 $NO/N_2$ 혼합가스와 $N_2/O_2$ 혼합가스를 이용하여 초기 NO농도를 설정하고, 유속을 2${\iota}$/min으로 공급하였다. NOx의 반응특성은 방전주입전력이 높을때는 NO의 농도가 감소하였으며, 산소의 농도 증가시에 NO의 분해가 용이하고 NO의 분해에너지 효율이 높았다. 또한 NO의 농도가 증가할 수록 NO의 분해에너지 효율은 높으나 분해율은 낮았다. 오존의 특성은 방전주입전력이 높을수록 오존의 생성이 증가하고, $NO/N_2$의 농도가 증가할 수록 오존의 생성량이 감소하였다.