• 한국실내디자인학회논문집
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• 제17호
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• pp.60-64
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• 1998

The results of simulation on greenery ratio using CG are as follows: arrangement type of optimal condition and greenery ratio were summarized as below as dispersion type and 5% ratio greenery for 20 pairs of assessment items and these assessment items were classified into 5 factors as a result of factor analysis,. These factors were Harmony Animation Atmosphere texture Peculiarity. Verification results of factors differences according to each condition can be. there was no apparent difference among factors in accordance with gender, In case of arrangement type dispersion type was higher than concentration type in all factors. Based on the above results dispersion type was assessed higher than concentration type the most suitable condition of Harmony Factor was 5% dispersion type Animation Factor was 5% dispersion type Animation Factor was 7% dispersion type Atmosphere Factor was 10% dispersion type Texture Factor was 5% concentration type and $\ulcorner$Peculiarity Factor$\lrcorner$was 7% concentration type.

• 한국항행학회논문지
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• 제12권3호
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• pp.201-207
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• 2008

대용량 WDM 전송 시스템의 구현을 위해 중간에 광 위상 공액기 (optical phase conjugator)를 갖는 광섬유에서 축적된 분산량을 precompensation과 postcompensation으로 조절하는 분산 제어 (DM; dispersion management) 전송 링크의 설계 기준을 제시하였다. 본 논문에서 살펴본 DM 구조는 precompensation과 postcompensation가 이루어지는 위치에 따라 bi-end 형태와 concentration 형태의 두 가지이다. 전송 링크 설계 파라미터인 송신기부터 OPC까지의 구간과 OPC부터 수신기까지의 유효 잉여 분산 범위는 OPC에 대해서만 대칭되어 있으면 precompensation과 postcompensation을 수행하는 분산 보상 광섬유(DCF; dispersion compensating fiber)의 위치에 크게 의존하지 않는다는 것을 확인하였다.

• 대한기계학회논문집B
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• 제30권8호
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• pp.796-805
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• 2006

In this study, the problem of using the mixing index as a measure of the mixing performance for a certain flow field has been discussed. The flow model subjected to this study is the two-dimensional unsteady lid-driven cavity flow. The transport equation for the concentration within the cavity was solved by using the finite volume method where the convective terms are discretized with the central difference scheme. It was shown that both the concentration dispersion and the mixing index depend highly on the initial distribution of the concentration, and therefore the mixing index obtained from the concentration dispersion equation loses its universal applicability.

• 설비공학논문집
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• 제17권11호
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• pp.1050-1059
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• 2005

Heat and $SF_6$ gas dispersions over a complex terrain were investigated using wind tunnel. The wind speed, temperature and concentration profiles were measured for the 1/1000 scale complicated terrain model in an Eiffel type boundary layer wind tunnel with test section of 2.5m in height and 4.5m in width. The scale model was mounted on the top of a plate which can rotate with respect to the approaching wind. Dispersion processes from a continuous emission source driven by various wind direction were investigated, including plume climbing over the steep up-slope of the mountain and down-spreading toward the lower level of the valley. Extensive dispersion experiment data (wind speeds and concentration profiles) were provided for verification and validation of dispersion models. Under the identical flow and emission conditions, the independently measured profiles of the temperature and $SF_6$ concentration showed an excellent agreement which ensured the credibility of the results.

• 한국대기환경학회지
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• 제15권6호
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• pp.757-765
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• 1999

Lagrangian particle dispersion model(LPDM) is an effective tool to calculate the dispersion from a point source since it dose not induce numerical diffusion errors in solving the pollutant dispersion equation. Fictitious particles are released to the atmosphere from the emission source and they are then transported by the mean velocity and diffused by the turbulent eddy motion in the LPDM. The concentration distribution from the dispersed particles in the calculation domain are finally estimated by applying a particle count method or a Gaussian kernel method. The two methods for calculating concentration profiles were compared each other and tested against the analytic solution and the tracer experiment to find the strength and weakness of each method and to choose computationally time saving method for the LPDM. The calculated concentrations from the particle count method was heavily dependent on the number of the particles released at the emission source. It requires lots fo particle emission to reach the converged concentration field. And resulting concentrations were also dependent on the size of numerical grid. The concentration field by the Gaussian kernel method, however, converged with a low particle emission rate at the source and was in good agreement with the analytic solution and the tracer experiment. The results showed that Gaussian kernel method was more effective method to calculate the concentrations in the LPDM.

• Journal of Mechanical Science and Technology
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• 제17권7호
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• pp.1054-1062
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• 2003

The numerical simulations of flow and pollutant particle dispersion are described for two-dimensional bell shaped hills with various aspect ratios. The Reynolds-averaged incompressible Navier-Stokes equations with low Reynolds number $\kappa$-$\varepsilon$ turbulent model are used to simulate the flowfield. The gradient diffusion equation is used to solve the pollutant dispersion field. The code was validated by comparison of velocity, turbulent kinetic energy, Reynolds shear stress, speed-up ratio, and ground level concentration with experimental and numerical data. Good agreement has been achieved and it has been found that the pollutant dispersion pattern and ground level concentration have been strongly influenced by the hill shape and aspect ratio, as well as the location and height of the source.

• 한국수자원학회논문집
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• 제34권4호
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• pp.289-301
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• 2001

비보존성 오염물질의 종확산에 관한 단계분리 유한차분 모형을 낙동강에 적용하여, 1991년에 발생한 페놀누출 사고에 따른 종확산 모의계산을 수행하였다. Preissmann의 4점 음해법에 근거한 부정류 계산모형으로부터 산정된 계산결과를 종확산 모형의 입력자료로 사용하였다. 종확산계수의 산정을 위한 경험식 및 1차 반응의 감쇠계수에 따른 종확산 계산결과의 민감도를 분석하였다. 하류 지점에서의 첨두농도 발생 시각은 사용된 종확산계수 식에 따라 상당히 달라짐을 알 수 있었다. 또한 농도 분포형은 감쇠계수에 따라 변하지 않는 반면, 농도값은 감쇠계수에 상당히 좌우되는 것으로 나타났다. 최적화 기법을 사용하여 흐름 모형 및 종확산 모형을 보정하였으며, 낙동강에 위치한 주요 취수지점들에 대한 첨두농도 발생시각을 모의하여 제시하였다.

• Safety and Health at Work
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• 제1권1호
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• pp.98-101
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• 2010

This study explored the health hazard of those exposed to methylene chloride by assessing its atmospheric concentration when a tear gas mixture was aerially dispersed. The concentration of methylene chloride ranged from 311.1-980.3 ppm (geometric mean, 555.8 ppm), 30 seconds after the dispersion started. However, the concentration fell rapidly to below 10 ppm after dispersion was completed. The concentration during the dispersion did not surpass the National Institute for Occupational Safety and Health 'immediately dangerous to life or health' value of 2,300 ppm, but did exceed the American Conference of Governmental Industrial Hygienists excursion limit of 250 ppm. Since methylene chloride is highly volatile (vapor pressure, 349 mmHg at $20^{\circ}C$), the post-dispersion atmospheric concentration can rise instantaneously. Moreover, the o-chlorobenzylidenemalononitrile formulation of tear gas (CS gas) is an acute upper respiratory tract irritant. Therefore, tear gas mixtures should be handled with delicate care.

• 한국대기환경학회지
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• 제13권5호
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• pp.383-396
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• 1997

Numerical prediction of the pollutant dispersion over a two-dimensional hilly terrain is presented. The dispersion model used in the present work is based on the gradient diffusion theory and the finite-volume method on a non-orthogonal boundary-fitted grid system. The numerical model is validated by comparing the results with the available experimental data for the flat-floor dispersion within a turbulent boundary-layer. The numerical error analysis is performed based on the guideline of Kasibhatla et al.(1988) for the elevated-source dispersion in the flat-floor boundary layer having a power-law velocity and linear eddy-diffusivity profile. The influences of the two-dimensional hilly terrain on the dispersion from a continuously released source are numerically investigated by changing the emission locations and heights. It is found that the distributions of ground-level concentration are strongly influenced by the source location and the emission height. Hence, the terrain amplification factor is greatly enhanced when the pollutant source is located within a flow separation region. Dispersion from a source of short duration is also simulated and the duration time of the pollutant is compared at several downstream locations on a hilly terrain. The results of the numerical prediction are applied to the evaluation of environmental impacts due to the automobile exhausts at the seashore highway with a parallel mountain range.

• 전기학회논문지
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• 제57권9호
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• pp.1572-1578
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• 2008

The effect of the organoclay_10A nanoparticles on the DSC and Structural and Dielectrics Properties(1Hz-1MHz) for epoxy/Organoclay_10A Nanocomposites has been studied. Dielectric properties of epoxy-Organoclay nanocomposites were investigated at 1, 3, 5, 7, 9 filler concentration by weight. Epoxy nanocomposites samples were prepared with good dispersion of layered silicate using power ultrasonic method in the particles. As structural analysis, the interlayer spacing have decreased with filled nanoparticles contents increase using power ultrasonic dispersion. The maximum increase interlayered spacing was observed to decease for above 5wt% clay loading. The other hand, as decrease with concentration filler of the layered silicate were increased dispersion degree of nanoparticles in the matrix. The interesting dielectric properties for epoxy based nanocomposites systems are attributed to the large volume fraction of interfacesin the bulk of the material and the ensuring interactions between the charged nanoparticle surface and the epoxy chains.