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RISS 인기검색어
- 검색키워드
- 저자 : 정희찬(Heechan Jeong) (검색결과 18 건)
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표면거칠기 변화에 따른 천이경계층 특성 변화에 대한 연구
정희찬(Heechan Jeong),이승우(Seungwoo Lee),송성진(Seung Jin Song) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
Experiments have been conducted to investigate surface roughness effects on transitional boundary layer characteristics. Transitional boundary layers on flat-plates with zero pressure gradient have been measured with hot-wire anemometer. All of experiments have been conducted with fixed Reynolds number 2,500,000. Two different roughness magnitude, ks values of 1.94㎛ and 10.21 ㎛ have been tested. In non-dimensional terms, both roughness magnitudes are in aerodynamic smooth regime (k⁺ < 5). Experiment results indicated that as the surface roughness increases, earlier transition induced and shorten the length of the transition even both roughness magnitudes are within aerodynamic smooth regime. Skin-friction coefficient within transition region also increases as the surface roughness increases. And also, as the surface roughness increases, disturbance energy within transitional boundary layers are increases as well.
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압축기 캐스케이드에서 표면 거칠기가 박리 유동 프로파일 손실에 미치는 영향
정희찬(HeeChan Jeong),송성진(Seung Jin Song) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
Experiment have been conducted to investigate the effect of surface roughness on separated flow profile loss in a compressor cascade. Tests have been conducted in a low-speed linear compressor cascade in SNU. Static pressure distribution in the blade surface and upstream velocity have been measured with pressure taps and Pitot probe. Blade surface boundary layers have been measured with boundary layer type hot-wire at 70% of chord-wise location on the blade suction side. In order to measure the total pressure loss, total and static pressure have been measured by 5-holes probe at the 30% chord-length downstream of the trailing edge. All of the measurements have been conducted at the mid-span. Three different roughness magnitudes, k<SUB>r</SUB> values of 12 ㎛ (smooth), 58 ㎛ (rough1) and 82 ㎛ (rough2), have been tested. In non-dimensional terms, these value could represent compressor blade roughness measured in real gas turbines. Roughness covered 100% of suction side except leading edge and trailing edge. All of the experiment cases have been conducted with fixed Reynolds number 400,000. As the surface roughness increases, turbulent boundary layer separation onset point moves to the upstream and it results to the significant profile loss increases.
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정희찬(Heechan Jeong),송성진(Seung Jin Song) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
Experiments have been conducted on a flat-plate in an open type wind-tunnel at Seoul National University to investigate effect of surface roughness on transitional boundary layers under zero pressure gradient. Two different magnitude of surface roughness have been tested; one it aerodynamically smooth (k+=0.07~0.19) and the other is transitionally rough (k+=2.71~7.05) regime. By using hot-wire anemometry mounted on 3-axis traverses, mean velocity and streamwise turbulence intensity have been measured. Results indicated that surface roughness increases the streamwise turbulence intensity at outer layer (y/δ~0.4). For this region, mean velocity defect also occurred and that increases a significant enhancement of mean flow momentum deficit.
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정희찬(Heechan Jeong),최성무(Sungmu Choi),서정민(Jungmin Seo),주기형(Kihyeong Joo) 한국자동차공학회 2015 한국자동차공학회 부문종합 학술대회 Vol.2015 No.5
White smoke from the diesel vehicles with DPF using high sulfur fuel (> 50 ppm) are not being selling up to now. The emerging markets like BRIC’s are using quite stringent emission regulations like EU4 and EU5. But their fuel qualities are not higher than their emission regulation. Their poor fuel qualities are preventing car makers from using DPF system to reduce particulate matter. To prevent emitting white smoke and meet EU4 and EU5 emission regulation with DPF in these countries that have poor fuel quality, DOC+DPF system that suppresses white smoke was newly developed. Based on this development, DOC+DPF system that meets Chinese emission regulation like KUK 4 and KUK 5 or India emission regulation like BS4 and BS5 were developed and the mechanism of white smoke was also investigated. By applying this white smoke suppression system, diesel vehicle with DPF can be sold in BRIC’s market. Therefore it is expected that this DOC+DPF that suppresses white smoke can contribute to increasing sales of diesel vehicles in BRIC’s market a lot.
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정희찬(Heechan Jeong) 한국법학원 2012 저스티스 Vol.- No.133
인도는 세계인구의 5분의 1 가량의 인구를 갖고 있는 최대의 민주주의 국가이면서 제국주의 지배를 통해 서구법을 계수하여 현재까지 무리없이 시장경제를 운용하여 오고 있는, 한국과 유사한 처지의 나라로서 인도법은 이러한 관점에서 비교법적으로 흥미로운 연구대상이다. 인도기업법은 외국인이 인도에 대하여 직접투자를 함에 있어서 인도외환관리법과 함께 주로 살펴야할 제도이며 이는 다시 회사법과 조합법으로 나뉜다. 인도의 회사법은 일정 규모를 초과하는 조합에 대하여 법적 규제의 틀을 제공함으로써 법적 안정성을 도모하고자 하는 입법취지를 갖고 있다. 인도회사법은 회사를 구성원의 수와 주식의 양도성에 대한 제한 등을 기준으로 사적 회사와 공적 회사로 분류하고 있고 이는 각각 한국 회사법의 유한회사와 주식회사가 행하는 역할을 수행하고 있다. 사적 회사에는 주식회사 이외에도 무한책임회사나 보증책임회사 등의 유형도 포함되지만 공적 회사는 주식회사이며 주식과 사채의 공모가 가능한 반면 각종 공적 제한을 받고 있다. 특히 국립회사법재판소라는 행정심판위원회는 회사법의 규율에서 강력한 권한을 행사하고 있다. 한편, 인도조합법상 조합의 법인격은 판례와 학설상 부분적으로 긍정되고 있으며 한국의 조합과 마찬가지로 그 재산관계는 합유관계에 의하여 규율되고 있으므로 조합원이 조합재산에 대하여 직접적인 권리는 인정받고 있지 못하고 있다. 조합은 원칙적으로 소송당사자능력이 있으나 등록하지 않으면 계약상 권리에 관하여 원고능력을 부정당하는 제약을 두어 정책적으로 조합도 그 등록이 권장되고 있다. 한편 등록을 강제하면서 다른 한편 유한책임을 인정하는 새로운 형태의 조합제도가 최근 도입되었는데 이는 유한책임조합이라고 불리는 것이다. 외국인은 그간 인도 내에서 조합을 설립할 수 없었으나 이 유한책임조합의 경우에는 허가를 득한 경우에는 설립이 허용되고 있어 특히 회계나 법무 분야의 전문가들이 인도에 진출하는 경우 그 새로운 방법이 될 수 있다. India is the largest democracy in the world and has about one fifth of the entire population of the globe. India had adopted the western legal tradition under the British Empire and, on the foundation of this system, have shown us a kind of successful history of market economy since the Independence, which is similar to the modern history of the Republic of Korea. In this regard, we could say that indian legal system is an interesting subject of comparative legal study in our perspective. There are two main legal systems in India with respect to foreign direct investment. One is foreign exchange management law and the other is indian business law. Furthermore, two core departments of the indian business law are indian company law and indian partnership law. The historical purport of indian company law has been to regulate large partnerships in uniform and clear manner. Therefore, members of a partnership which has more than 20 partners will be even fined criminally for the present. Indian companies can be categorized at large into private companies and public companies. A private company can have its article of association which restricts the right to transfer its share and its number of members are limited up to fifty whereas there is no such restriction in case of a public company. In Korea, a form of limited company(“유한회사”) plays a role similar to one played by a form of private company in India. National Company Law Tribunal is one of the most salient features of indian company law and it operates as a sort of guardian seeking public interest in company-related legal matters in India. On the other hand, indian courts and scholars recognize legal personality of indian partnership only partially. Like korean law, any member of partnership cannot dispose of any part of partnership assets directly. A member of partnership has only a bundle of rights and duties or, in other words, ‘interest’ in regard to all the partnership assets. Therefore, we can say that partnership assets are owned solely by the partnership itself. This implication could lead to the recognition of legal personality of partnership in general. Moreover, in India, a partnership can be a party in civil litigations in principle. The only exception to this is that an unregistered partnership cannot be a plaintiff in a civil litigation with claims based on a contract or agreement between the partnership and the defendant. Recently, the system of limited liability partnership(“LLP”) has been introduced in India. In this case, registering is compulsory but members of LLP enjoy limited liability. Under this regime, foreigners can establish LLPs with a prior approval of the indian government whereas they are still not allowed to make any indian partnership. Professionals in legal and accounting areas who traditionally tend to prefer partnership forms for their enterprises, are lately keen to employ this LLP system for their FDI in India.
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