• 폴리머
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• 제34권5호
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• pp.474-479
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• 2010

조직공학에 이용되는 고분자인 poly(lactic-co-glycolic acid)(PLGA)는 높은 생체적합성 및 생분해성의 장점을 지니지만, 생체활성물질의 결여와 소수성으로 인해 세포의 부착에 어려움을 가진다. 또한 PLGA의 가수분해 과정 중 생성되는 산 분해물이 조직주변의 pH를 감소시켜 염증을 유발하는 단점을 가지고 있다. 따라서 이러한 단점을 보완하기 위한 방법으로 천연고분자인 케라틴을 첨가한 PLGA필름을 제작하였으며 조직공학적 디스크재생에 응용하기 위하여 케라틴/PLGA 복합체필름의 원통형 지지체를 제작하였다. 이 원통형 지지체의 내부는 케라틴/PLGA 필름을 말아서 사용하였으며 외부는 PLGA 다공성 지지체 링을 제작하여 사용하였다. 본 연구에서는 이 지지체에 섬유륜세포를 파종하여 PLGA 필름과 케라틴/PLGA 필름을 이용한 원통형 지지체에서의 세포의 부착 및 생존율을 비교하고 케라틴을 첨가한 지지체의 우수성을 확인하였으며 강도의 우수성 또한 확인하였다. 이 결과는 디스크재생을 위한 지지체의 연구에 유용한 정보를 제공할 것이다.

• 한국추진공학회지
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• 제22권2호
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• pp.66-73
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• 2018

밀폐용기 내 Zirconium/Potassium Perchlorate의 연소를 수치적 모델링을 통해 전산해석을 수행하였다. 5차 WENO 공간차분법과 improved delayed detached eddy (IDDES) 난류모델을 사용하여 충격파가 동반되는 내부 유동구조를 모사하였고, 라그랑지안 연소모델을 통해 화약 입자를 계산하였다. 옆면 중앙에 센서가 설치된 원통형 밀폐용기 내부 유동분석을 통해 압력 진동이 발생하는 원인을 규명하였다. 또한 센서 다이어프램 깊이 변화에 따라 측정되는 압력 데이터를 실험값과 비교분석 하였다. 그 결과 센서 탭의 깊이가 약 2.36 mm 이상으로 커지면 유동속도가 아음속으로 감쇠하고 복잡한 eddy가 발생하여 측정값에 큰 불규칙성을 야기하는 현상을 관측하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1991년도 춘계학술대회논문집; 한국해사기술연구소, 대전; 1 Jun. 1991
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• pp.127-132
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• 1991

충격에 민감한 용기나 기계들은 운반이나 보관중에 받을 수 있는 진동충격 을 완화시키기 위해 충격 마운트를 이용하게 되며, 충격마운트는 용기나 기 계들이 허용하는 최대가속도와 이들이 취급되는 환경에 의해 적절히 선정되 어야 한다. 그러므로 내충격 설계는 최대 허용 가속도나 취급환경에 대한 사 양과 이 사양에 의한 충격 마운트의 선정, 그리고 선정된 내충격 시스템의 충격시험에 의한 오일 탬퍼의 결합용이 사용되기도 하지만 구조가 복잡하고 가격이 비싸서 대용량이 경우에만 국한되어 사용되고 있으며, 가장 경제적인 것은 방진고무를 사용한 것이다. 내충격 시스템은 일반적으로 큰 변형량을 요구하고 있으며, 방진고무의 경우 큰 변형에서는 hardening 스프링의 비선 형성을 가지고, 형상계수와 고무배합율에 따라 정적 스프링상수와 동적 스프 링상수가 큰 차이를 보이는 등, 설계상의 여러 제한이 있다. 그러나 방진고 무는 형상변화가 자유로우며 제작이 용이하기 때문에 이러한 장점을 이용하 면 저렴하고 다양한 용도의 충격마운트 제작에 효과적으로 사용될 수 있다. 본 논문에서는 원통형 콘테이너의 내충격 설계를 위해 충격사양에 의한 충 격마운트의 설계, 설계된 내충격 시스템의 충격시험에 의한 검증을 순차적으 로 실시하여, 방진고무를 이용한 충격마운트 설계기술을 제시함으로써, 이후 방진고무제품의 설계를 위한 자료 및 과정의 제정에 도움을 주고자 한다.

• 한국해양공학회지
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• 제33권3호
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• pp.272-279
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• 2019

In order to perform a pressure chamber experiment with a circular cylindrical pressure vessel, the dimensions of the cylinder need to be determined in the range of the maximum externally applied pressure of the chamber to create the collapse process. In this study, the collapse load values from published chamber test results, finite element analysis and the theory of thick cylinders were thoroughly compared in a aluminum cylinder. In order to investigate the effect of collapse load according to the ovality during manufacturing, nonlinear buckling analysis was performed and the collapse load according to ovality was compared. Based on the results, the dimensions of the steel cylinder were determined for the future chamber collapse test.

• 소성∙가공
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• 제7권3호
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• pp.225-232
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• 1998

This article is aimed primarily at establishing a process planning method for complex circular shells. For the deep drawing of complex shaped shell, the optimum process design is required to reduce the trial cost improve the quality, increase the productivity and shorten the delivery. The present approach which is related to the optimum process planning is based on the empirical knowledge through trial and error in the industrial field. In order to check the validity and the effectiveness of proposed work a sample process design has been applied to the multi-stepped deep drawing of com-plex shell considering the process variables such as drawing rate radius and blank development. In particular the difference between the limiting drawing rate and to optimum drawing rate has been discussed and the usefulness of present suggestion has been shown.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 춘계 학술대회논문집
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• pp.35-41
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• 2004

A numerical investigation has been made for flows in an axisymmetric circular cylinder with a rotating cone located at the bottom of the container. The axisymmetric container is completely filled with a viscous fluid. Major parameter for the present research is the vertex angle of the cone, otherwise Reynolds number of fluid and aspect ratio of the vessel is fixed. Main interest is in vortex breakdown of meridional circulation by rotation of the cone with respect to the longitudinal axis of the cylinder. The method to this problem is numerically to integrate momentum and continuity equations on a generalized body fitted grid system. The pattern of vortex breakdown is quite different from that in a right circular cylinder with flat end wall disks. Flow visualization photographs of a preceeding work are compared with the present numerical results.

• 대한기계학회논문집
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• 제3권4호
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• pp.173-180
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• 1979

Temperature distriburion in a hollow chlinder has been analyzed mathematically. Unsteady condition considered assumed a constant heat flux input from the inside. The results are compared with experimental results of surface temperature rise of a gun barrel during continuous firing. Their agreements are acceptable. Effects of various dimensionless parameters on the surface temperature rise are discussed. For small Biot numbers, the external survface temperature approaches more rapidly to the steady temperature. Temperature difference between internal and external surfaces becomes greater for small Biot number. Steady solution assumed that the gas temperature inside the cylinder varies periodically. Relative amplitude and phase angles between the gas temperature and the internal or external surface temperature are obtained. Phase angles become smaller for large radiancy of gas temperature variation, small external Biot number, or large internal biot number. Relative amplitudes become samller as radiancy of gas temperature variation and internal Biot number become smaller. or external Biot number becomes larger. The solution obtained in this paper can be applied to gun barrels, heat pipes used in heat excangers, and reciprocation engines.

• 소성∙가공
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• 제7권4호
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• pp.393-399
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• 1998

For minimizing wall thickness thinning of circular shells, a new stamping technology, the deep draw-ing process combined with ironing is approached and investigated. The design requirements for the deep drawing shells are to keep the optimum wall thickness with max. 10 percent thickness thinning of the initial blank thickness, to make uniform thickness strain distribution for the wall of circular shell and to improve the shape accuracy for the roundness and concentricity. In order to check the validity and effectiveness of proposed work, a sample process design is applied to a circular shell needed for a 4multi-stepped deep drawing. Through experiments, the variations of the thickness strain distribution in each drawing process are observed. Also a series of experiments are performed to investigate optimum process variables such as the geometry of tooling, radius and drawing rate. In particular, the advantage of current approach with ironing is shown in contrast to the conventional deep drawing process. From the results of proposed method, the optimum value of process variables are obtained, which contribute more uniform thickness strain distribution and better quality in the drawn product.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.160-167
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• 1998

This article is aimed primarily at establishing a process planning method for complex circular shells. For the deep drawing of complex shaped shell, the optimum process design is required to reduce the trial cost, improve the quality, increase the productivity and shorten the delivery. The present approach which is related to the optimum process planning is based on the empirical knowledge through trial and error in the industrial field. In order to check the validity and the effectiveness of proposed work, a sample process design has been applied to the multi-stepped deep drawing of complex shell considering the process variables such as drawing rate, radius and blank development. In particular, the difference between the limiting drawing rate and the optimum drawing rate has been discussed and has been shown the usefulness of present suggestion.

• 한국전산유체공학회지
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• 제3권2호
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• pp.27-38
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• 1998

Rotating flow of a stratified fluid contained in a circular cylinder with unstable temperature gradient imposed on the side wall of it has been numerically studied. The temperatures at the endwall disks are constant. The top disk of the container is coider than that of the bottob disk, as much as the temperature difference n${\Delta}$T, (0${\leq}$n${\leq}$3). Flows in the vessel are driven by an impulsive rotation of the hot bottom disk with respect to the central axis of the cylinder. Flow details have been acquired. For this flow, the principal balance in the interior core is characterized by a relationship between the radial temperature gradient and the vertical shear in the azimuthal velocity. As the buoyancy effect becomes appreciable, larger portions of the meridional fluid transport are long-circuit from the bottom disk to the interior region via the side wall.