• 한국정밀공학회지
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• 제27권6호
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• pp.55-63
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• 2010

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle inside feedwater heater installed downstream of the turbine extraction stream line. At that point, the extract steam from the turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows to reverse direction after impinging the impingement baffle, the shell wall of feedwater heaters may be affected by flow-accelerated corrosion. In this paper, to compare degree of shell wall thinning mitigation rate to squared type with mitigation rate of other type baffle plate, three different types of impingement baffle plate-squared, curved and mitigating type-applied inside the shell. With these comparison data, this paper describes operation of experiments and numerical analysis which is composed similar condition with real feed water heater. And flow visualization is operated for verification of experiments and numerical analysis. In conclusion, this study shows that mitigating type baffle plate is more effective than other baffle plate about prevention of pressure concentration and pressure value decrease.

• 한국조경학회지
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• 제25권2호
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• pp.54-61
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• 1997

This study has conducted to analyze the crelationship among soil properties and to investigate how they affect soil physical characteristics and plant growth. The experiment of woody plant growth was conducted as follows : Type I was the original soil. Type II, the soil particles smaller than 20${\mu}{\textrm}{m}$ was removed from the original soil. Type III, the soil particles is smaller than 75${\mu}{\textrm}{m}$ was removed from original soil. Wisteria floribunda A.P.DC and Celtis sinensisi Pers. were used for plant growth measurement. 1. Soil type II. the closest to Fuller's curved line, showed high dry bulk density and low in soil pores and saturated hydraulic conductivities. This created poor soil aeration and limited space for the root to growth. When the root did not have sufficient space to grow, there was a lot of physical stress, which hindered the root growth. 2. Soil typeIII was high saturated hydraulic conductivity and a lot of soil pores larger than 10 ${\mu}{\textrm}{m}$. As a result, there were more available spaces for root to spread. It was considered that there was less physical stress for root growth. Therefore, soil typeIII showed significantly greater root growth. 3. Because soil type III has less small particles and saturated hydraulic conductivity was high, and water infiltrates rapidly into the underground when there was rainfall or irrigation. The soil typeIII becomes much stronger soil mechanically due to the less small particles. Therefore, soil typeIII was a suitable material for applying on planting sites where soil compaction is expected.

• 패션비즈니스
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• 제11권4호
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• pp.135-151
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• 2007

This study is human body measurement of 200 adult males in their 20s by both direct and indirect methods in order to reveal the representative male upper body types. Composition factors of body types were classified while the combination of direct-indirect measurement values was chosen. The following are the findings: 1) The analysis of direct-indirect measurement statistics showed the following results: 173.80cm (height), 69.87kg (weight), 95.58cm (chest girth), $24.67^{\circ}$ (right shoulder angle), and $9.34^{\circ}$ (shoulder width angle). 2) The factor analysis of the body types by direct measurement produced 5 factors: 1 (front length of upper body), 2 (front length of upper body), 3 (back length of upper body), 4 (circumference of upper body), and 5 (shoulders length). These factors accounted for 90.08%. Also, the cluster analysis of factor scores led to 3 types: 1 (33%, short, comparatively wide shoulders and full in the hips), 2 (25.1%, well-developed upper body in tall, inversed triangle), 3 (41%, average height, short upper body). 3) The body-type factor analysis by indirect measurement resulted in 6 factors with the explanation of 83.24%: 1 (rear upper bady thickness), 2 (front upper body width), 3 (front chest thickness), 4 (left-right shoulder angle), 5 (front width of protrusion distance in chest and shoulders), and 6 (neck's front-rear side angle).In addition, the cluster analysis of factor scores brought about 4 types: 1 (15%, well-developed front chest, beardless waist), 2 (23.5%, flat chest, with shoulder, drooping shoulders, strait neck), 3 (39%, with shoulder, curved back), and 4 (22.5%, narrow and thin, curved waist). 4) Among the 118 subjects (75%), 58 subjects commonly appearing in indirect measurement values group and direct measurement values group were chosen the representative body type group according to asterisk indexes. They had the highest frequency in direct type 3 and indirect type 3, whose combination represented the physical characteristics of the representative body types.

• Bulletin of the Korean Chemical Society
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• 제29권8호
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• pp.1459-1463
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• 2008

Second-order rate constants (kN) have been measured spectrophotometrically for reactions of 3,4-dinitrophenyl 2-thiophenecarboxylate (2) with a series of alicyclic secondary amines in 80 mol % $H_2O$/20 mol % dimethyl sulfoxide at 25.0 ${^{\circ}C}$. The Brønsted-type plot exhibits a downward curvature for the aminolysis of 2. The curved Brønsted-type plot is similar to that reported for the corresponding reactions of 2,4-dinitrophenyl 2- thiophenecarboxylate (1). The reactions of 1 and 2 have been suggested to proceed through the same mechanism, i.e., through a zwitterionic tetrahedral intermediate ($T^{\pm}$) with a change in the rate-determining step. Substrate 2 is less reactive than 1 toward weakly basic amines (e.g., $pK_a$ < 10.4) but becomes more reactive as the basicity of amines increases further. Dissection of kN into the microscopic rate constants has revealed that the reaction of 2 results in a smaller $k_2/k_{-1}$ ratio but larger $k_1$ than the corresponding reaction of 1. Steric hindrance exerted by the ortho-nitro group has been suggested to be responsible for the smaller $k_1$ value found for the reactions of 1.

• 한국주조공학회지
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• 제35권2호
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• pp.29-35
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• 2015

In this study, potential defects of ring-type cast products during the mold-filling stage of the casting process were investigated using computer simulation. The main focus was on the effects of runner extension and ingates. During the mold filling the molten metal flowed from the bottom to the top of the mold in two curved paths along the ring-type cavity. The fluid fronts in the two paths did not show the identical velocity during the mold filling stage. This difference in the filling speeds may cause defects such as voids and local contractions. The present model contained virtual fluid detectors at various positions inside the mold. When the molten metal passed those points, the volume of fluid jumped up from zero to one. The moments were measured to compare the speeds of the fluid fronts. We attempted various combinations of runner extensions and ingates to stabilize the flow and then to optimize the casting mold design.

• 대한전자공학회논문지SD
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• 제48권1호
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• pp.1-6
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• 2011

본 논문에서는 미세피치 프로브 카드 제작을 위한 S 모양의 일체형 외팔보 프로브 형성방법에 대하여 기술하였다. 마세 피치 프로브를 위하여 Deep RIE etching을 이용하여 실리콘 트렌치 안에 일체형 프로브 빔과 탑을 형성하는 방법을 사용하였고, 피라미드 팁의 형성을 위하여 KOH 및 TMAH 습식식각을 이용하였으며, 습식식각시 방향성을 가지는 실리콘 웨이퍼에서도 휘어진 형태의 프로브 빔을 형성할 수 있는 건식 식각 및 습식식각 방법을 제시하였다. 따라서 제작된 외팔보 형태의 프로브는 디렘(DRAM), 플레시 메모리 (Flash memory) 용 프로브 카드 제작에 사용될 뿐만 아니라 RF 소자용 프로브 카드, 아이씨 테스트 소켓 (IC test socket)용 프로브 탐침에도 사용 될 것이다.

• 전기학회논문지
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• 제62권5호
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• pp.723-729
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• 2013

This paper presents an parallel type Linear Induction Motor with ununiform airgap for a shallow-depth underground train with 100‰ grade and 15 m curvature. This parallel type LIM has enough gradability but has inherently ununiform airgap between center and end parts. Consequently, performance when the train passes curved section should be considered with transient analysis. Moreover, general parallel operation, 1C2M which is usually used for train operation, deteriorates LIM performance because of different line velocity between inner and outer LIMs. Transient analysis has many problems such as huge model, lots of meshes, very long calculation time, truncation error and so on. This paper has presented a novel technique using equivalent linear rotating model in order to solve these problems and has analyzed parallel type LIM by using the proposed technique. Finally, LIM performance according to independent operating control has been investigated.

• 대한조선학회논문집
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• 제47권4호
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• pp.543-552
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• 2010

The Coanda effect is noticeable when a jet stream is applied tangential to a curved surface since then the jet stream remains attached to the surface beyond the point where flow separates otherwise and results in augmentation of circulation and lift. Numerous experimental and numerical studies have been performed in various fields of aerodynamics to exploit the Coanda effect and many of them found to be useful. It can be speculated that the Coanda effect may have practical application to the field of marine hydrodynamics as well since various control surfaces are being used to control behaviors of ships and offshore structures. In the present study, the Coanda effect has been applied to a horn type rudder and a series of numerical computations and model experiments are performed to find the practical applicability. The results indicate that the Coanda jet increases the lift coefficient of the rudder as much as 52% at the momentum coefficient $C_j$ = 0.1 and the rudder angle ${\alpha}=10^{\circ}$.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.475-480
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• 2010

The safety step has been developed to ensure the passengers' safety including the disabled and the weak by eliminating gap between vehicle and platform. The type of safety step is divided according to the position that the safety step is installed. The type of safety step attached platform is the rubber type that is previously attached to a platform. The installed rubber can reduces the gap between vehicle and platform by a fixed distance. If the safety step is installed on the vehicle, it is possible to respond to the various platform typed such as straight or curved form. It is also flexible to the height of riding depends on number of passenger and platform conditions and does not require crew's additional operation. We have been developed vehicle attached safety step for advanced electric multiple unit. We hope to increase the use of safety step for the disabled and the weak to expand the convenience use of railway transportation system.

• Bulletin of the Korean Chemical Society
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• 제29권3호
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• pp.580-584
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• 2008

Second-order rate constants (kN) have been measured spectrophotometrically for reactions of Y-substituted phenyl benzoates (1a-h) with azide ion (N3) in 80 mol % H2O/20 mol % DMSO at 25.0 0.1 oC. The Brnsted-type plot for the azidolysis exhibits a downward curvature, i.e., the slope (b lg) changes from 0.97 to 0.20 as the basicity of the leaving group decreases. The pKao (defined as the pKa at the center of the Brnsted curvature) is 4.8, which is practically identical to the pKa of the conjugate acid of N3 ion (4.73). Hammett plots correlated with s o and s constants exhibit highly scattered points for the azidolysis. On the contrary, the corresponding Yukawa-Tsuno plot results in an excellent linear correlation with r = 2.45 and r = 0.40, indicating that the leaving group departs in the rate-determining step. The curved Brnsted-type plot has been interpreted as a change in the rate-determining step in a stepwise mechanism. The microscopic rate constants (k1 and k2/k1 ratio) have been calculated for the azidolysis and found to be consistent with the proposed mechanism.