딤플이 적용된 Blunt-Fin의 항력 감소 영향성 및 충격파 위치에 관한 연구

유경식,이승진,박진용 한국항공우주학회 2024 韓國航空宇宙學會誌 Vol.52 No.1

유도탄에는 체결류 자리와 같이 딤플 또는 Cavity로 표현이 가능한 다양한 표면 형상들이 존재한다. 본 연구에서는 Blunt-Fin에 딤플을 적용하여 항력과 충격파에 미치는 영향에 대하여 확인하였다. 3차원 형상과 실물 풍동시험을 수행하기에 앞서 2차원 모델의 전산해석을 수행하였다. 전산해석에 적용된 난류 모델은 SST 모델을 사용하였고 Mach number 0.3 ~ 0.8 영역에서 수치해석을 수행하였다. 딤플의 형상변수 중 깊이와 위치를 변화시켜가며 항력계수와 충격파 양상을 비교하였다. 본 연구에서는 아음속 영역에서 딤플이 항력과 충격파에 미치는 유의미한 항력감소 및 충격파 위치 변화결과를 확인하지 못하였으나 천음속 영역대에 해당하는 M=0.8 모델에서 딤플에 따른 충격파 위치 변화가 존재하는 것을 확인하였다. In guided missiles, various surface configurations that can be represented as dimples or cavities, exist. This study investigates the impact of dimples applied to a blunt-fin configuration on drag and shock wave characteristics. Prior to conducting three-dimensional physical wind tunnel experiments, numerical analysis was performed on a two-dimensional model. The turbulence model employed for the numerical analysis was the SST model, and numerical simulations were conducted in the Mach number range of 0.3 to 0.8. Dimple parameters, specifically depth and location, were systematically varied to compare drag coefficients and shock wave patterns. In this study, no significant drag reduction or changes in shock wave positioning due to dimples were observed in the subsonic regime. However, it was confirmed that dimples caused variations in shock wave positioning in the transonic regime, corresponding to Mach 0.8.

Ureaplasma urealyticum과 Staphylococcus aureus에 감작된 마우스 복강 대식세포의 탐식능의 변화

유경식,장명웅 고신대학교(의대) 고신대학교 의과대학 학술지 1990 고신대학교 의과대학 학술지 Vol.6 No.1

Several investigators have reported that mycoplasmas might activate macrophages, but some other investigators do not agree with this view. Furthermore, the interaction between ureaplasmas and macrophages has not been studied previously. The phagocytic activies of mice peritoneal macrophages activated with Ureaplasma urealyticum(U. urealyticum) or Staphylococcus aureus(S. aureus) have been compared by calculating Candida albicans(C. albicans) uptake. At same time, hematological changes of peripheral white blood cells in U. urealyticum or S. aureus infected mice were examined. The results are : 1. The phagocytic activities of peritoneal macrophages infected 1 - 4 times with U. urealyticum or S. aureus were augumented for 72 hours. But, after 96 hours, the phagocytic activities of U. urealyticum activated macrophages were decreased, and the phagocytic activities of S. aureus activated macrophages were increased. 2. The number of peritoneal cells infected 1 - 4 times with U. urealyticum or S. aureus were increased after 24 hours, but continuously decreased during 48 - 96 hours. 3. The phagocytic activities of peritoneal macrophages, against C. albicans, activated by U. urealyticum or S. aureus showed the highest activity ini 2 - 3 hours. 4. The number of polymorphonuclear leukocytes in peripheral blood of U. urealyticum or S. aureus infected mice were increased durinig 24 - 72 hours or 24 - 96 hours, respectively. 5. The number of white blood cells in peripheral blood infected by U. urealyticum were variable during 24 - 96 hours. However, the number of white blood cells in peripheral blood by S. aureus were continuously increased during 24 - 96 hours.

다파장 ODCMA 네트워크에서의 2차원 코드 설계 ( 2 Dimensional Code Design in Multi-Wavelength Optical Code Division Multiple Access Networks )

유경식,박남규 한국통신학회 1998 한국통신학회 기타 간행물 Vol.- No.-

A rare case of Enterococcus hirae sepsis in human species

유경식,좌혜영 대한내과학회 2022 대한내과학회 추계학술대회 Vol.2022 No.2

다파장 OCDMA 네트웍에서의 새로운 2차원 코드의 설계

유경식,박남규 한국통신학회 2000 韓國通信學會論文誌 Vol.25 No.1

본 논문에서는 광 코드 분할 다중화방식 (OCDMA)에서 사용할 수 있는 ‘파장’과 ‘시간’영역에서는 준 직교 성질을 가지는 다파장 2 차원 코드의 구성 방법을 새로이 제안하였다. ‘파장’과‘시간’영역에서 직교 특성을 가지는 다파장 OCDMA 방삭은 동시 사용자의 수나 오류 확률 등의 여러 측면에서 기존이 다중 사용자 접속 방식에 비해 우수한 성능을 보인다. 특히, 새로 제안된 코드는 브래그 격자를 이용한 광학적 신호 처리 기법으로 생성, 해독 될 수 있어 전기적 신호 처리로 인한 병목 현상을 줄일 수 있는 장점을 가지고 있다. It has been known that the optical code division multiple access (OCDMA) is a prominent future technology to support many simultaneous users and to increase transmission capacity of optical fiber. In this paper, we proposed the new construction of 2 dimensional code, which can be used as a codeword in temporal/wavelength OCDMA networks. New code family is obtained by extending the concept of Hamming correlation. All optical encoder and decoder for newly proposed code were also developed. In considering bit error ratio, we verified that new coding scheme outperforms conventional coding scheme by simulation. This system is applicable to asynchronous fast local area network, which needs a high security level and a flexible network configuration.

버섯 균사체로 제조한 키토산 모노필라멘트의 특성

유경식,정용현,임호성,어주경,신현재 한국생물공학회 2024 KSBB Journal Vol.39 No.1

Synthetic and natural fibers pose a significant threat to the environment due to their production, usage, and disposal, releasing high levels of toxic substances and microplastics that have detrimental effects on ecosystems. Research is being actively conducted on mushroom-based materials as substitutes for many industrial materials, as they are cost-effective, have simple production processes, and possess eco-friendly properties. However, studies on mushroom fibers are limited. In this study, the mycelium of Ganoderma lucidum, Pleurotus ostreatus, and Schizophyllum commune were utilized to create environmentally sustainable mushroom fibers. Chitosan was extracted from each mushroom mycelium and subsequently formed into monofilament through wet spinning. The characteristic of this chitosan was confirmed through FT-IR and XRD analyses. Comparison with commercial chitosan showed that mushroom mycelium chitosan displayed greater deacetylation (82.8-84.8%), lower molecular weight (21.3-48.3 kDa), and crystallinity. It was confirmed that the surface and tensile strength of the monofilament improved with the addition of mushroom mycelium chitosan.

교통행정의 새로운 계획이 필요 : 관광시설개선으로 관광수입올려야

유경식 대한지방행정공제회 1970 도시문제 Vol.5 No.10

Quenching and Self-Tempering (QST) 공정 제조 H형강의 위치별 미세조직 분석 및 기계적 물성평가

유경식,안민규,박진우,김상은,신찬선 대한용접·접합학회 2023 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2023 No.5

Ureaplasma urealyticum과 Staphylococcus aureus에 감작된 마우스 복강 대식세포의 탐식능의 변화

유경식,장명웅 고신대학교 의학부 1990 高神大學校 醫學部 論文集 Vol.6 No.1

Several investigators have reported that mycoplasmas might activate macrophages, but some other investigators do not agree with this view. Furthermore, the interaction between ureaplasmas and macrophages has not been studied previously. The phagocytic activities of mice peritoneal macrophages activated with Ureaplasma urealyticum (U. urealyticum) or Staphylococcus aureus(S. aureus) have been compared by calculating Candide albicans(C. alvicans) uptake. At same time, hematological changes of peripheral white blood cells in U.urealyticum or S. aureus infected mice were examined. The results are : 1. The phagocytic activities of peritoneal macrophages infected 1-4 times with U. urealyticum or S. aureus were augumented for 72 hours. But, after 96 hours, the phagocytic activihes of U. urealyticum activated macrophages were decreased, and the phagocytic activated of S. aureus activated macrophages were increased. 2. The number of peritoneal cells infected 1-4 times with U.urealyticum or S. aureus were increased after 24 hours, but continuously decreased during 48-96 hours. 3. The phagocytic activities of peritoneal macrophages, against C. albicans, activated by U. urealyticum or S. aureus showed the highest activity in 2-3 hours. 4. The number of polymorphonuclear leukocytes in peripheral blood of U. urealyticum or S. aureus infected mice were increased during 24-72 hours or 24-96 hours, respectively. 5. The number of white blood cells in peripheral blood infected by U. urealyticum were variable during 24-96 hours. However, the number of white blood cells in peripheral blood by S. aureus were continuously increased during 24-96 hours.

소비자의 혁신제품수용에 대한 신제품개발 실패 사례 연구

유경식,강흥식,김인수,김태근 산업진흥원 2024 산업진흥연구 Vol.9 No.1

본 연구는 로저스(1995)의 혁신확산이론 중에서 소비자의 설득 과정에서 중요한 요소인 혁신의 특성에 관한 여러 요인 중 상대적 이익에 대한 신제품의 실패 사례를 분석하였다. 상대적 이익은 여러 혁신 제품의 특성 중에서 구매자의 채택 의도에 가장 큰 영향을 끼치고 있는 요인이기 때문이다(Holak and Lenmann, 1990). 6개 기업의 신제품 실패 사례 분석 결과 이들 제품은 공통적으로 기존 제품에 대하여 상대적 이익이 부족하였다. 상대적이익이란 경제적 의미에서 측정되거나 사회적 우위 요소, 편리도, 만족도 등으로 측정되는 요인이며 적합성, 복잡성, 관찰가능성, 시용가능성 등 다른 요인들에 비해 가장 중요한 요소이기 때문이다. 결국 신제품을 소비자들에게 설득하기 위해서는 기존 제품들에 비해 상대적 이익이 중요한 성공 요인임을 알 수 있었다. This study analyzed the failure cases of new products for relative benefits among various factors related to the characteristics of innovation, which is an important factor in the consumer persuasion process among Rogers (1995)'s innovation diffusion theory. This is because relative profits are the most influential factor in consumers' intention to adopt among the characteristics of various innovative products (Holak and Lenmann, 1990). As a result of analyzing the failure cases of new products of six companies, these products lacked relative profits for existing products in common. Relative profits are factors that are measured in the economic sense or are measured by social advantages, convenience, and satisfaction, and are the most important factors compared to other factors such as suitability, complexity, observability, and applicability. In the end, it was found that relative profits compared to existing products are an important success factor in persuading consumers of new products.