• 대한기계학회논문집
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• 제15권1호
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• pp.262-273
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• 1991

본 연구에서는 벽면에서의 압력은 압력측정 정치를 제작하여 측정하였으며 평 균유동 및 난류량들은 열선 유속계(hot wire system)을 사용하여 측정하였다.

• 대한조선학회지
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• 제17권3호
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• pp.5-17
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• 1980

A basic procedure to design marine propellers by a curved lifting line theory was shown. By adapting discrete singularity method, it became possible to take into account of skew, rake and the contraction of slip stream in the early stage of preliminary design procedure. It is also shown that lifting line theory based on the discrete singularity method converges to a common solution obtained by induction factor method with a relatively small number of discrete elements. Lifting the blade geometry more accurately on the basis of hydrodynamic principles. A number of numerical results from lifting line calculation are presented for the purpose of comparison with the previous method, and with these results two sample designs are carried out, which are wake-adapted optimum and wake-adapted non-optimum propellers.

• 한국수자원학회논문집
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• 제30권1호
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• pp.15-22
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• 1997

하천형성의 중요한 요인이 되는 사행하천의 흐름은 막곡호안에 많은 영향을 준다. 특정한 하천에 대해 하도개량을 적용시키기 위한 일반적인 기준을 기술하기는 어려우나 토목 설계자에게 어떤 원칙과 지침을 제공하는 것은 대단히 중요하다. 본 고정상 실험연구의 목적은 평균유속과 유로만곡부에서의 곡률변경으로 최대 유속의 크기를 구하여 매번의 수리모형실험을 실시하지 않고도 중소하천의 개수에 이용할 수 있는 자료를 제공함에 있다.

• Ecology and Resilient Infrastructure
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• 제4권1호
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• pp.24-33
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• 2017

본 연구에서 내성천 만곡부에서 유량의 변화에 의한 흐름 및 하도 변화를 2차원 수치모형인 Nays2DH를 이용하여 분석하였다. 만곡부를 통과 된 후에 하폭이 좁은 구간에서 만곡부 외측으로 수심이 깊게 형성되었다. 하폭이 넓은 구간에서는 점사주가 형성된 만곡부 내측에서는 수심이 얕게 형성되었다. 흐름이 집중되는 만곡부 외측에서는 수심이 깊게 형성되었다. 직선이 형성된 하류 구간에서 흐름은 하도 중앙에 집중되었다. 연속적으로 사행이 형성되면서 번갈아 가며 수심이 깊은 곳과 얕은 곳이 형성되었다. 이러한 특성은 사행하천에서 강한 2차류의 영향을 받아 형성된 것이다. 무차원소류력도 유속이 집중된 부분에 크게 나타났다. 그러나 하폭이 감소하고 급만곡부가 형성된 곳에서는 유속과 무차원소류력의 변화에 대한 하상고 변화가 일치되지 않았다.

• 설비공학논문집
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• 제1권4호
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• pp.265-275
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• 1989

An experimental study of decaying swirl air flow has been obtained by tangential inlet in a straight tube with Reynolds number range 20,000~40,000. The friction factor, swirl angle, velocity profiles and turbulent intensity are measured by using micro-manometer and hot-wire anemometer. It is found that the swirl flow behaviors depend on the swirl intensity along the test tube.

• 한국분무공학회지
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• 제15권2호
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• pp.83-93
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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, four different types of impingement baffle plate-squared, curved, mitigating type and multi-hole 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 and multi-hole type baffle plate are more effective than other baffle plate about prevention of pressure concentration and pressure value decrease.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2664-2669
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• 2008

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damange, 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-installed downstream of the high pressure turbine extraction stream line- inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes operation of experience and numerical analysis composed similar condition with real high pressure feedwater heater. This study applied squared, curved and new type impingement baffle plates to feedwater heater same as previous study. In addition, it shows difference of pressure distribution and value between single phase and two phase based on experience and numerical analysis.

• 설비공학논문집
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• 제21권9호
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• pp.483-495
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• 2009

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damange, 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-installed downstream of the high pressure turbine extraction stream line-inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes operation of experience and numerical analysis composed similar condition with real high pressure feedwater heater. This study applied squared, curved and new type impingement baffle plates to feedwater heater same as previous study. In addition, it shows difference of pressure distribution and value between single phase and two phase based on experience and numerical analysis.

• Applied Microscopy
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• 제26권1호
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• pp.33-45
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• 1996

The spermatogenesis of Korean slug, Incilaria fruhstorferi are observed by electron microscope. The results are as follows: The spermatogenesis of Korean slug, Incilaria fruhstorferi, is processed through the five stages; Spermatogonia, primary spermatocyte, secondary spematocyte, spermatid and spermatozoon. The spermiogenesis, the differentiation of the spermatid, is also processed through the five stages. In stage 1, the numerous and round mitochomdria in the cytoplasm are moved around the nucleus of spermatid. In stage 2, the nucleus of spermatid transformed into the oval shape, and the oval nucleus is surrounded by many rough endoplasmic reticulum. In stage 3, the oval nucleus of spermatid is changed to be curved as an arrow, and then two centrioles appeared behind nucleus. The centriole is sucked into the cytoplasm. and almost all the chromatins are changed into heterochromatins. In stage 4, the nucleus of spermatid are transformed into the oval shape, when the lamella plate chromatin of spermatid form in the nucleoplasm. In stage 5, the oval nucleus is then transformed into the stream-line shape when the lamella plate chromatin of spematid gradually concentrated in the nucleus, and long axoneme ($65{\mu}m$ in length) form from the distal centriole. Two long mitochondria in the middle piece and the main piece of spermatozoon array spirally along a long axoneme, and the mitochondria matrix is gradually filled with electron-dense glycogen particles ($0.1{\mu}m$ in size). The axoneme of spermatozoon consists of typical 9+2 microtubular pattern.

• 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.