• Wind and Structures
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• 제15권6호
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• pp.509-529
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• 2012

Traditionally, a quasi steady response concerning the aerodynamic force and moment coefficients acting on a flat plate while 'flying' through the air has been assumed. Such an assumption has enabled the flight paths of windborne debris to be predicted and an indication of its potential damage to be inferred. In order to investigate this assumption in detail, a series of physical and numerical simulations relating to flat plates subject to autorotation has been undertaken. The physical experiments have been carried out using a novel pressure acquisition technique which provides a description of the pressure distribution on a square plate which was allowed to auto-rotate at different speeds by modifying the velocity of the incoming flow. The current work has for the first time, enabled characteristic pressure signals on the surface of an auto-rotating flat plate to be attributed to vortex shedding.

• The Korean Journal of Physiology and Pharmacology
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• 제8권6호
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• pp.329-333
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• 2004

In this study, we investigated whether TNF-alpha, IL-1beta, CTMA (carboxymethyl trimethylammonium) and LPD (Lup-20[29]-ene-3beta,28-diol) affect mucin release from airway goblet cells and compared the activities of these agents with the inhibitory action of PLL and the stimulatory action of ATP on mucin release. Confluent primary hamster tracheal surface epithelial (HTSE) cells were metabolically radiolabeled with $^3H-glucosamine$ for 24 h and chased for 30 min in the presence of varying concentrations of each agent to assess the effects on $^3H-mucin$ release. The results were as follows: TNF-alpha, CTMA and LPD increased mucin release at the highest concentration, but IL-1beta did not. We conclude that CTMA and LPD can stimulate mucin release by directly acting on airway mucin-secreting cells, and suggest that these agents should be further investigated for the possible use as mild expectorants during the treatment of chronic airway diseases.

• 소성∙가공
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• 제27권5호
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• pp.289-295
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• 2018

The profile ring rolling process can realize various ring shapes unlike conventional rectangular cross-sectional ring products. In this paper, the defective groove in the bottom surface of L-shaped ring products was analyzed. Grooves are generated by non-uniform external forces due to profile main roll and initial blank shape. Process parameters such as the motion of dies and working temperature were determined. Mechanism of groove formation was analyzed by FE simulation on the basis of local external forces acting on the blank. Analysis results were similar to the groove actually occurring in the production line. Based on results of the analysis, two solutions were proposed for the groove. The position of the base plate supporting the blank was adjusted and edge length of the main roll was extended to suppress growth of grooves. It has been verified that groove was improved by applying two proposed methods in the shop-floor.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2006년도 전기학술대회논문집
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• pp.271-272
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• 2006

Zinc confers high corrosion resistance by acting as a sacrificial anode, and a zinc coating improves the appearance of steel. Chromate conversion coating (CCC) films are still one of the most efficient surface treatments for steel. Although such films can self-repair via the dissolution of Cr(VI), dissolved Cr(VI) have adverse effects on humans, and the environment. Therefore, we examined the corrosion protection property and morphology of colloidal silica conversion films as an alternative to CCC films. The corrosion behavior was investigated in 3% NaCl solution using electrochemical techniques, including electrochemical impedance spectroscopy, open circuit potential, and the salt spray test(SST). Corrosion was implied by the appearance of red rust on the specimen surface. In corrosion resistance at 3% NaCl solution, red rust appeared at 15-20, 55-70, and 83-98 days on Zn-electroplated steel, colloidal silica conversion-coated specimens, and CCC-coated specimens, respectively. In the salt spray test, the colloidal silica film provided better corrosion protection than CCC films, i.e., red rust appeared at 96 hours on the Zn-electroplated steel sheet, at 432 hours with the CCC films, and at 888 hours with silica conversion coating.

• 대한기계학회논문집
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• 제16권4호
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• pp.658-666
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• 1992

본 연구에서는 고속, 연속장업으로 이루어지고 있는 스템핑 공정에서 금형과 강판간의 접촉-슬립에 따른 마찰 및 윤활특성의 성능을 평가할 수 있도록 한 원형단면 형상의 드로오비드 마찰실험장치를 활용하여 가압력, 윤활유 특성, 드로잉 속도와 강 판의 표면특성 등에 따른 자동차용 냉연강판과 도금강판의 마찰계수와 드로오비드 저 항력에 대한 테이터 베이스를 구축하고자 한다.

• Wind and Structures
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• 제22권3호
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• pp.307-328
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• 2016

This paper describes an investigation of the net wind loads on solar panels and wind loads on the underlying roof surface for panels mounted parallel to pitched roofs of domestic buildings. Typical solar panel array configurations were studied in a wind tunnel and the aerodynamic shape factors on the panels were put in a form appropriate for the Australian/New Zealand Wind Actions Standard AS/NZS 1170.2:2011. The results can also be used to obtain more refined design data on individual panels within an array. They also suggest values for the aerodynamic shape factors on the roof surface under the panels, based on a gust wind speed at roof height, of ${\pm}0.5$ for wind blowing parallel to the ridge, and ${\pm}0.6$ for wind blowing perpendicular to the ridge. The net loads on solar arrays in the middle portion of the roof are larger than those on the same portion of the roof without any solar panels, thus resulting in increased loads on the underlying roof structure.

• 한국인터넷방송통신학회논문지
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• 제13권2호
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• pp.25-32
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• 2013

차량이 곡선도로를 선회함에 있어 차량 내부적 요소인 차량의 진입속도, 차량에 작용하는 횡가속도, 전복과 관련된 롤 각, 그리고 외부적 요소인 노면과 타이어와의 마찰 및 도로의 구조는 중요한 요소이다. 본 연구에서는 교통사고 재현을 위한 PC-Crash프로그램을 이용하여 차량의 진입속도와 도로의 편경사, 노면상태에 따른 마찰계수를 변수로 두어 선회 시 차량의 상태변화를 분석하였다. 그 결과로, 곡선도로 선회시 한계속도 설정에 관해 도로구조와 노면상태에 따른 마찰계수가 중요한 요소가 된다는 것을 확인하였다.

• 한국정밀공학회지
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• 제13권11호
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• pp.106-113
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• 1996

Using stainless steel as the cold forged parts especially the outer parts of automobile is gradually increasing because it can bear up against the erosion and the wear. During cold forging of the stainless steel the working pressure acting on die surface are very high therefore the wear on die surface can be greatly increased. In cold forging processes, die failure must be considered before die design. One of the main reasons of die failure in industrial application of metal forming technologies is wear. The die wear affects the tolerances of forged parts, metal flow and costs of processes etc. The only way to to control these failures is to develop methods which allow prediction of the die wear and which are suited to be used in the desing stage in order to optimize the process. In this paper, the rigid-plastic finite element method was combined with the wear prediction routine and then the forward extrusion process using stainless steel was analysed simultaneously. To minimize the die wear the FPS algorithm was applied and the optimal conditions of die configuration are suggested.

• Structural Engineering and Mechanics
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• 제30권2호
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• pp.165-176
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• 2008

In this paper, a new iterative method for solving vehicle-bridge interaction problems is proposed. Iterative methods have advantages over the non-iterative methods in that it is not necessary to update the system matrix for a given wheel location, and the method can be applied for a new type of car or bridge with few or no modifications. In the proposed method, the necessity of system matrices update is eliminated using the equivalent interaction force acting on the bridge, which is obtained iteratively. Ballast stiffness is included in the interaction forces and the geometric compatibility at the contact points are used as convergence criteria. The bridge is considered as an elastic Bernoulli-Euler beam with surface irregularity and ballast stiffness. The moving vehicle is modeled as a multi-axle mass-spring-damper system having many degrees of freedom depending on the number of axles. The pitching effect, which is the interaction effect between the rear and front wheels when a vehicle begins to enter or leave the bridge, is also considered in the formulation including extended ground boundaries having surface irregularity and ballast stiffness. The applicability of the proposed method is illustrated in the numerical studies.

• 한국실내디자인학회논문집
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• 제22권5호
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• pp.367-375
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• 2013

Using the 'New material' concept has recently been introduced into the natural characteristics. In the course of such a, Janine M. Benyus has proposed to mimic the characteristics of natural ecosystems to mention the concept of Biomimicry. Process made engineered using technical elements for representing the material properties of Biomimicry such will be acting importantly, This study intends to analyze how new materials applied to 'Biomimicry' characteristics are processed in space. The results were as follows : 1) Processing methods of new materials resulted as 'Forming', 'Surface treatment', 'Bonding', 'Inserting'. These four were divided and analyzed into 'Form', 'System', 'Adaptation'. As a result of this analysis, such significances were shown as 'Forming/Surface treatment/Bonding' in 'Form', 'Bonding' in 'System' and 'Adaptation'. 2) 'Bonding' applied to 'System' of new material can be recycled to be combined with other materials through the existing adhesive material, and present as a solution of 'Sustainable development'. 3) 'Bonding' applied to 'Adaptation' of new material is to impart the ability to react to the environment through the joint, but is characteristic, at this time, using digital and other field technology. It appeared primarily that it can be known to meet the social trends and convergence between fields. Thus, as the finish that are friendly to the environment from the interior design, the results of the study are expected to be utilized in the study of new materials guidelines.