Effects of corner cuts and angles of attack on the Strouhal number of rectangular cylinders

Choi, Chang-Koon,Kwon, Dae-Kun Techno-Press 2003 Wind and Structures, An International Journal (WAS Vol.6 No.2

An investigation into the effect of corner cuts on the Strouhal number of rectangular cylinders with various dimensional ratios and various angles of attack is described. The Strouhal number given as a function of corner cut size is obtained directly from the aerodynamic behavior of the body in a uniform flow through a series of wind-induced vibration tests. For a quick verification of the validity of the Strouhal numbers obtained in this way, they are compared with the approximated the Strouhal numbers based on Shiraishi's early research. The test results show that the Strouhal number of the model with various corner cuts has a fluctuating trend as the angle of attack changes. For each cutting ratio as the angle of attack increases at each cutting ratio above $15^{\circ}$, the Strouhal number decreases gradually, and these trends are more evident for larger corner cut sizes. However, a certain corner cut size which is effective in reducing the wind-induced vibration can be identified by larger Strouhal numbers than those of other corner cut sizes. Three distinct characteristics of Strouhal number variation can be identified in three regions which are termed as Region I, II, and III based on the general trend of the test results. It is also found that the corner cut is effective in one region (Region-II) and less effective in another one (Region-III) when only the vortex-induced vibration occurs.

원문 : 12주간의 고강도 저항성 운동훈련이 건강한 남성의 혈중 Irisin 농도 및 근기능에 미치는 효과

윤재군 ( Jae Koon Yoon ),김창근 ( Chang Keun Kim ) 한국운동생리학회(구 한국운동과학회) 2014 운동과학 Vol.23 No.4

본 연구의 목적은 12주간의 저항성 운동이 건강한 남성의 irisin 수준과 근기능 및 건강에 미치는 영향을 규명하는 것이다. 이 연구를 위하여 건강한 젊은 남성 8명이 12주 동안 웨이트 트레이닝을 실행하였다(1일 90분, 주 6회). Irisin과 testosterone의 수준은 ELISA kits를 이용하여 측정하였다. 체성분 분석은 Inbody 4.0을 이용하였고, 등속성 근기능 측정은 Humac Norm을 이용하여 대퇴부위의 각속도 60 °/s에서 peak torque를 180 °/s와 240 °/s에서 total work done을 측정하였다. 12주간의 운동전에 비하여 운동 후에 irisin의 레벨은 유의하게 증가하였지만( p=.042, 32%) 운동 후에 testosterone의 수준은 변하지 않았다. 운동전에 비하여 운동 후에 골격근은 유의하게 증가되었지만( p=.039, 3%) 체지방량은 변화하지 않았다. 대퇴부 근기능의 peak torque는 신전에서 28%, 굴곡에서 52%로 유의하게 증가하였으며 180 °/s의 총 일량은 신전과 굴곡이 각각 44%, 64%로 유의하게 증가하였고, 240 °/s의 총 일량 또한 신전과 굴곡이 각각 37%, 47%로 유의한 증가를 보였다( p=.001). 결론적으로 고강도의 저항성 운동은 혈중irisin의 수준을 증가시켰고 또한 근력 및 근육량도 함께 증가하였지만 지방량은 변하지 않았다. The purpose of the present study was to examine the effects of 12-week resistance training on blood irisin level and muscular function in healthy males. For this study, 8 healthy males participated in and performed weight training for 12 weeks (90 min/day, 6 times/week). The levels of irisin and testosterone in blood were analyzed using commercial ELISA kits. Inbody 4.0 was used for measuring body composition. Isokinetic muscular function at 60 °/s, 180 °/s and 240 °/s was measured by Humac Norm. The level of irisin was significantly increased, ( p=.042, 32%) however the level of testosterone was not changed after training. Skeletal muscle mass was significantly increased ( p=.039, 3%) but body fat was not changed. The peak torque at 60 °/s was significantly increased in the leg extensor (28%) and flexor (52%) ( p=.001). The total work done at 180 °/s was significantly increased in the leg extensor (44%) and flexor (64%), also 240 °/s was significantly increased in the leg extensor (37%) and flexor (47%) after training ( p=.001). In conclusion, 12-week high-intensity resistance training increases the level of irisin and improves muscle strength and mass, however fat mass was not changed.

Bleomycin이 Mouse 간장의 Alkaline Phosphatase 활성에 미치는 영향

이규식,정호삼,이군자,김종우 한양대학교 의과대학 1987 한양의대 학술지 Vol.7 No.2

Bleomycin hydrochloride isolated from the Streptomyces veticillus has been widely used as an anticancer drug. In exhibits specific antineoplastic activity against squamous epithelial carcinomas of the skin. Bleomycin causes inhibition of DNA and protein synthesis by incorporating bithiazole group of the drug into DNA. The author undertook the present study to investigate the effect of bleomycin on the alkaline phosphatase activity in the mouse liver. The experimental animals were sacrificed at 6, 12, 24, and 48 hours after administration of 150 mg/kg of bleomycin. The activity of lkaline phosphatase was observed by Gomori's method for histochemical study. The results were as follows. The activity of alkaline phosphatase was decreased in the entire hepatic lobule of the 12 hours belomycin treated group and recovered in the 24 hours bleomycin treated group. Consequently, it is suggested that bleomycin has the cytotoxic effect on the hepatocytes.

프로스타글란딘 유도체의 합성과 그의 생물학적 활성에 관한 연구 2. 위궤양과 위산분비에 대한 프로스타글란딘 유도체의 효과

조태순(Tai Soon Cho),이선미(Sun Mee Lee),함원훈(Won Hun Ham),이병무(Byung Mu Lee),김경례(Kyoung Rae Kim),지상철(Sang Cheol Chi),고준일(Jun Ill Ko),박인(In Park),오창영(Chang Young Oh),박호군(Ho Koon Park),김형자(Hyoung Ja Kim),이향우(H 한국응용약물학회 1995 Biomolecules & Therapeutics(구 응용약물학회지) Vol.3 No.1

The antiulcer effects of newly synthesized prostaglandin derivatives were investigated in various experimental ulcer models and on gastric secretion in rats. HK-3 and HK-4, PGE₂ derivatives, prevented the formation of acute gastric ulcer induced by ethanol or aspirin in pylorus-ligated rats. The ulcer formation was moderately inhibited by HK-1 and HK-2, PGF_(2α) derivatives, and aggravated by SK-1, SK-2 and SK-3, PGF_(2α) derivatives. HK-3 and HK-4 reduced the volume, acid output and pepsin output of gastric juice in pylorus-ligated rats. The gastric perfusion with physiologic saline(pH 6.0) showed relatively constant acid secretion and indomethacin increased the acid secretion. The acid secretion was markedly decreased by PGE₂ but PGF_(2α) caused little change. Prostaglandin derivatives, especially HK-3 and HK-4, significantly inhibited the acid secretion induced by indomethacin. The results show that, PGE₂ derivatives, HK-3 and HK-4, inhibit acid secretion and also have protective effects on gastric ulceration induced by ethanol or aspirin.

Non-conforming modes for improvement of finiteelement performance

Chang-Koon Choi,Tae-YeolLee 국제구조공학회 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.14 No.6

전문가 시스템에 의한 I-BUILDS 의 입력데이타 파얼 작성

Choi Chang- Koon,Kim E- Doo 한국전산구조공학회 1988 한국전산구조공학회논문집 Vol.1 No.1

I - BUILDS는 기존의 CAD 프로그랩인 BUILDS와 지식베이스룹 일판된 시스템으로 통합한 컨쓸설계용 전문가 시스댐이다. 본 시스템올 구축하기 위한 노력의 일환으로 본 논문에서논 추론에 의해 발생된 데이 타 뜰 을다양한계산능력을가지 변서 특별한 업부 도 수행할 수 있게 설계된 건붙의 일팔구조셜계 시스댐인 BUILDS 의 부시스템 (BUILDS - A ) 에 이용되도록 입력파일화하기 위한 기본적인 개념을 기술한다. 1-BUlLDS is, the building design expert system conceptually m여eled for synthesizing the conventional CAD programs (BUILDS: an integrated BUILding Design System) and the knowledge base into an unified system. As a part of the efforts to build this system. this paper presents the conceptual model by which the data items generated by inference are transformed into a formatted input file to be used for several BUTLDS subsystems, each of which is assign어 to have various computational capabilities and to perform specialized task.

Elasto-plastic nonconforming solid element with variable nodes

Choi, Chang-Koon,Chung, Gi-Taek Techno-Press 1995 Structural Engineering and Mechanics, An Int'l Jou Vol.3 No.4

The iterative procedure to use the nonconforming elements in elasto-plastic problems is established and applied to the variable node transition solid element developed for the automated three-dimensional local mesh refinement. Through numerical tests, the validity and performance of the element are examined. As the nonlinear iterative procedure presented in this paper is accomplished for the general three-dimensional case, it can also be easily applied to the two-dimensional elements such as membranes, plates and shells.

Transition membrane elements with drilling freedom for local mesh refinements

Choi, Chang-Koon,Lee, Wan-Hoon Techno-Press 1995 Structural Engineering and Mechanics, An Int'l Jou Vol.3 No.1

A transition membrane element designated as CLM which has variable mid-side nodes with drilling freedoms has been presented in this paper. The functional for the linear problem, in which the drilling rotations are introduced as independent variables, has been formulated. The transition elements with variable side nodes can be efficiently used in the local mesh refinement for the in-plane structures, which have stress concentrations. A modified Gaussian quadrature is needed to be adopted to evaluate the stiffness matrices of these transition elements mainly due to the slope discontinuity of displacement within the elements. Detailed numerical studies show the excellent performance of the new transition elements developed in this study.

Wind tunnel blockage effects on aerodynamic behavior of bluff body

Choi, Chang-Koon,Kwon, Dae-Kun Techno-Press 1998 Wind and Structures, An International Journal (WAS Vol.1 No.4

In wind tunnel experiments, the blockage effect is a very important factor which affects the test results significantly. A number of investigations into this problem, especially on the blockage correction of drag coefficient, have been carried out in the past. However, only a limited number of works have been reported on the wind tunnel blockage effect on wind-induced vibration although it is considered to be fairly important. This paper discusses the aerodynamic characteristics of the square model and square model with corner cut based on a series of the wind tunnel tests with various blockage ratios and angles of attack. From the test results, the aerodynamic behavior of square models with up to 10% blockage ratio are almost the same and square models with up to 10% blockage ratio can be tested as a group which behaves similarly.

Adaptive finite element wind analysis with mesh refinement and recovery

Choi, Chang-Koon,Yu, Won-Jin Techno-Press 1998 Wind and Structures, An International Journal (WAS Vol.1 No.1

This paper deals with the development of variable-node element and its application to the adaptive h-version mesh refinement-recovery for the incompressible viscous flow analysis. The element which has variable mid-side nodes can be used in generating the transition zone between the refined and unrefined element and efficiently used for the construction of a refined mesh without generating distorted elements. A modified Guassian quadrature is needed to evaluate the element matrices due to the discontinuity of derivatives of the shape functions used for the element. The penalty function method which can reduce the number of the independent variables is adopted for the purpose of computational efficiency and the selective reduced integration is carried out for the convection and pressure terms to preserve the stability of solution. For the economical analysis of transient problems in which the locations to be refined are changed in accordance with the dynamic distribution of velocity gradient, not only the mesh refinement but also the mesh recovery is needed. The numerical examples show that the optimal mesh for the finite element analysis of a wind around the structures can be obtained automatically by the proposed scheme.