• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.368-375
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• 2010

To alleviate NOx emission, a variety of approaches has been applied. In marine diesels, the application of SCR systems has been considered an effective exhaust aftertreatment method for NOx emission control. Most current SCR systems use a various catalyst for the reaction of ammonia with NOx to form nitrogen and water. In theory, it is possible to achieve 100% NOx if the NH3-to-NOx ratio is 1:1. However, the reaction has a limited non-uniformity of the exhaust gas flow and ammonia concentration distribution. Therefore it is necessary to investigate the optimum flow conditions. In order to achieve uniform flow at monolith front face, we are equipped with a various mixed device. In this paper, it is presented that the mixed devices play an important role improvement of flow patterns and particle distributions of NH3 by numerical simulation.

• 한국전산유체공학회지
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• 제15권4호
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• pp.9-16
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• 2010

To alleviate NOx emission, a variety of approaches has been applied. In marine diesels, the application of SCR systems has been considered an effective exhaust aftertreatment method for NOx emission control. Most current SCR systems use a various catalyst for the reaction of ammonia with NOx to form nitrogen and water. In theory, it is possible to achieve 100% NOx if the $NH_3$-to-NOx ratio is 1:1. However, the reaction has a limited non-uniformity of the exhaust gas flow and ammonia concentration distribution. Therefore, it is necessary to investigate the optimum flow conditions. In order to achieve uniform flow at monolith front face, we are equipped with a various mixed devices. In this paper, it is presented that the mixed devices play an important role improvement of flow patterns and particle distributions of $NH_3$ by numerical simulation.

• 한국표면공학회지
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• 제41권6호
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• pp.279-286
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• 2008

Numerical analysis is done to investigate which would be the most influencing process parameter in determining the uniformity of deposition thickness in TiN ICP-CVD(inductively coupled plasma chemical vapor deposition). Two configurations of ICP antenna are modeled; side and top planar. Side and top gas inlets are considered with each ICP antenna geometries. Precursor for TiN deposition was TDMAT(Tetrakis Diethyl Methyl Amido Titanium). Two step volume dissociation of TDMAT is used and absorption, desorption and deposition surface reactions are included. Most influencing factors are H and N concentration dissociated by electron impact collisions in plasma volume which depends on the relative positions of gas inlet and ICP antenna generated hot plasma region. Low surface recombination of N shows hollow type concentration, but H gives a bell type distribution. Film thickness at substrate edges is sensitive to gas flow rate and at high pressures getting more dependent on flow characteristics.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.61-63
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• 2015

In the low pressure selective catalytic reduction (LP SCR) system, the uniformity of both ammonia concentration and exhaust gas flow at the SCR catalyst layer are important design factor for the efficient SCR-deNOx performance. According to the shape of the guide vane and static mixer, numerical simulations were conducted to analyze flow patterns and finally to find out the appropriate alternative for uniform flow at the front of catalyst in the real scale LP SCR reactor. The variations of gas velocity and ammonia concentration were quantitatively evaluated. Based on the present results, the shape was devised to satisfy the design criteria.

• 한국결정성장학회지
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• 제10권2호
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• pp.91-95
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• 2000

8인치 쵸크랄스키 실리콘 단결성 성장에 있어서, 계면에서의 온도기울기, 산소, 농도 및, 반경방향의 산소농도 분포에 미치는 아르곤 가스 유동의 영향을 조사하였다. 아르곤의 유입량을 증가시킴에 따라 계면 근처 결정내 온도기울기가 증가하였으며. 결정내 산소농도는 감소하였다. 한편, 반경방향의 산소농도 균일성은 악화됨이 관찰되었다. 실험 결과를 종합하여 볼 때, 아르곤 유동이 산소 농도 및 균일 분포성 등의 결정 특성에 중요한 영향을 미치는 성장 공정변수임을 확인할 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1296-1301
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• 2003

The chemical mechanical polishing(CMP) is necessarily applied to manufacturing the dielectric layer and metal line in the semiconductor device. The conditioning of polishing pad in CMP process additionally operates for maintaining the removal rate, within wafer non-uniformity, and wafer to wafer non-uniformity. But the fixed abrasive pad(FAP) using the hydrophilic polymer with abrasive that has the swelling characteristic by water owns the self-conditioning advantage as compared with the general CMP. FAP also takes advantage of planarity, resulting from decreasing pattern selectivity and defects such as dishing due to the reduction of abrasive concentration. This paper introduces the manufacturing technique of FAP. And the tungsten CMP using FAP achieved the good conclusion in point of the removal rate, non-uniformity, surface roughness, material selectivity, micro-scratch free contemporary with the pad life-time.

• 한국자동차공학회논문집
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• 제18권5호
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• pp.31-36
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• 2010

SAI(Secondary Air Injection) system has been studied widely as one of the promising countermeasure for reducing HC emission at cold start. In this paper, in order to find out the optimal position of SAI, computational thermal fluid analysis on exhaust system adapted SAI system is performed using commercial 3-D CFD code, CFX. The present results showed that SAI position strongly affected the uniformity of air distribution in front of catalyst. And also through the decision process of optimal position of SAI, new index, uniformity of air distribution($U_{\phi}$) is proposed to define it quantitively. Because $U_{\phi}$ is very simple equation and similar with flow uniformity, it is very easy to figure out the physical meaning and to apply it to practices. Finally, we applied the index $U_{\phi}$ to the decision process of the optimal position of SAI, so that we could get the clear comparison results.

• 한국전기전자재료학회논문지
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• 제18권1호
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• pp.12-16
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• 2005

Chemical mechanical polishing (CMP) process is one of the most useful methods for improving the surface roughness of films. The effects of CMP on the surface morphology of WO$_3$ films prepared by RF sputtering system were investigated in this paper. A removal rate of films increased, and the uniformity performance of surface decreased with the addition of an oxidizer to the tungsten slurry. Non-uniformity performance of surface was superior as its value was below 5 % when oxidizers of 5.0 vol% and 2.5 vol%, respectively, were added to the tungsten slurry. The optimized oxidizer concentration, reflected both the improved roughness values and hillock-free surface with the good uniformity performance, was 5.0 vol% as an atomic force microscopy(AFM) analysis of thin film topographies. Our CMP results will be a useful reference for advanced technology of thin films for gas sensor applications in the near future.

• 한국표면공학회지
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• 제56권1호
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• pp.94-103
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• 2023

The effects of carburizing pressure and gas ratio on vacuum carburizing properties (uniformity and surface characteristics) have been studied through the analyses of carbon concentration, hardness, surface color, surface roughness and type of carbon bonding. AISI 4115 steel specimens were carburized with various pressures (1, 5, and 10 Torr) at different locations (P₁, P₂, P₃, P₄, P₅, and P₆) inside a furnace held at 950 ℃. Since the carburizing pressure represents the density of the carburizing gas, it plays an important role in improving the carburizing uniformity according to locations in the furnace. As the carburizing pressure increased, the carburizing uniformity according to the sample location was improved, but the surface of the carburized specimen was discolored due to the residual acetylene gas, which does not contribute to the carburizing reaction. Therefore, the carburizing uniformity and surface discoloration have been improved by injecting acetylene gas (carburizing gas) and nitrogen gas (non-reactive gas) in a specific ratio.

• 대한원격탐사학회지
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• 제28권6호
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• pp.635-651
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• 2012

To produce a level-3 monthly composite image from daily level-2 Sea-viewing Wide Field-of-view Sensor (SeaWiFS) chlorophyll-a concentration data set in the East Sea, we applied four average methods such as the simple average method, the geometric mean method, the maximum likelihood average method, and the weighted averaging method. Prior to performing each averaging method, we classified all pixels into normal pixels and abnormal speckles with anomalously high chlorophyll-a concentrations to eliminate speckles from the following procedure for composite methods. As a result, all composite maps did not contain the erratic effect of speckles. The geometric mean method tended to underestimate chlorophyll-a concentration values all the time as compared with other methods. The weighted averaging method was quite similar to the simple average method, however, it had a tendency to be overestimated at high-value range of chlorophyll-a concentration. Maximum likelihood method was almost similar to the simple average method by demonstrating small variance and high correlation (r=0.9962) of the differences between the two. However, it still had the disadvantage that it was very sensitive in the presence of speckles within a bin. The geometric mean was most significantly deviated from the remaining methods regardless of the magnitude of chlorophyll-a concentration values. Its bias error tended to be large when the standard deviation within a bin increased with less uniformity. It was more biased when data uniformity became small. All the methods exhibited large errors as chlorophyll-a concentration values dominantly scatter in terms of time and space. This study emphasizes the importance of the speckle removal process and proper selection of average methods to reduce composite errors for diverse scientific applications of satellite-derived chlorophyll-a concentration data.