• 한국안전학회지
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• 제20권4호
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• pp.54-62
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• 2005

This Study is to find out how RC beam mixed with sawdust acts comparing with normal beam without sawdust mixture, and how they can be applied to the actual structural frame, despite a Int that they are mixed with waste material : saying sawdust. ED3H1, ED3H2, ED5H1, ED5H2, ED3H1UB, ED5H1UB, ED3H2L, ED5H2L and Normal without sawdust mixture are main factor to be tested here in order to apply them to the actual case. D and H means diameter 3cm or 5cm, and holes one and two respectively. And all variables are tested with each two for one variables. Test results are compared using crack diagrams and strain & loads. There are eleven(11)% capacity decrease between ED 3H1 and ED5H1 in rebar, strain. Left and right side crack shapes are much similar in variable ED3H2L having maximum capacity 14.5 tone. ED5H2L having maximum capacity thirteen(13)tone, in case of normal 19.6 tone. Two holes in beam rather on the longitudinal direction than on the forcing direction can be more effective to keep the original capacity of the beam because this case can distribute load more uniformly. There is 33% capacity decreased in case of diameter five(5)cm, compared to diameter three(3)cm. Two holes give thirty nine(39) percent capacity decrease than one of diameter three(3)cm.

• 설비공학논문집
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• 제16권6호
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• pp.589-598
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• 2004

Flow condensation heat transfer coefficients (HTCs) of R22 and R134a were measured on a horizontal 9 hole aluminum multi-channel tube. The main test section in the refrigerant loop was made of a flat multi-channel aluminum tube of 1.4 mm hydraulic diameter and 0.53 m length. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in the vapor qualities of 0.1∼0.9 at mass flux of 200∼400 kg/$m^2$s and heat flux of 7.3∼7.7 ㎾/$m^2$ at the saturation temperature of 4$0^{\circ}C$. All popular correlations in single-phase subcooled liquid and flow condensation originally developed for large single tubes predicted the present data of the flat tube within 20% deviation when effective heat transfer area is used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Thermal insulation for the outer tube section surrounding the test tube for the transport of heat transfer fluid is very important in fluid heat-ing or cooling type heat transfer experimental apparatus.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.621-626
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• 1998

An experimental investigation on the reinforcing bar corrosion and relationshid of reinforcing bar and concrete bond strength has been conducted to establish the allowable limit of rust in the construction field. The reinforcing bars used in this study were rusted before embedding in concrete. The first component of this experiment is to make rust of reinforcing bar rust artificially based on Faraday's theory at certain rates such as 2, 4, 6, 8 and 10% of reinforcing bar weight. For estimation of the amount of rust by weight, Clarke's solution and Shot blasting were adopted and compared. Parameters include 240 and 450kg/㎠ of compressive strengths and diameter of reinforcing bar (16, 19 and 25mm) corresponding development length for pull-ort test. And, pull-out tests were carried. out according to KSF 2441 and ASTMC 234 to investigate the effect of the corrosion rate on reinforcing bar-concrete bond behavior. It is found from the test results that the test techniques for corrosion of bar used in this study is relatively effective and correct test method. Results shows that up to 2% of rust increases the bond strength regardless of concrete strength and diameter of reinforcing bar like the existing data. It might be because of the roughness from rust. As expected, the bond strength increases as compressive strength of concrete increases and the diameter of bar decreases.

• 한국자동차공학회논문집
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• 제6권5호
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• pp.174-181
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• 1998

Experimental and analytical studies are presented to characterize the break-up mechanism and atomization processes of the intermittent- impinging-type nozzle. Gasoline jets passing through the circular nozzle with the outlet diameter of 0.4mm and the injection duration of 10ms are impinged on each other. The impingement of fuel jets forms a thin liquid sheet, and the break-up of the liquid sheet produces liquid ligaments and droplets subsequently. The shape of liquid sheets was visualized at various impinging velocities and angles using the planer laser induced fluorescence (PLIF) technique. Based on the Kelvin-Helmholtz wave instability theory, the break-up length of liquid sheets and the droplet diameter are obtained by the theoretical analysis of the sheet disintegration. The mean diameter of droplet is also estimated analytically using the liquid sheet thickness at the edge and the wavelength of the fastest growing wave. The present results indicate that the theoretical results are favorably agreed with the experimental results. The size of droplets decreases after the impingement as the impinging angle or the injection pressure increase. The increment of the injection pressure is more effective than the increment of the impinging angle to reduce the size of droplets.

• Journal of Chest Surgery
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• 제32권11호
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• pp.1042-1045
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• 1999

Background: Recently, open heart surgerys using homograft are progressively increasing in complex cardiac anomalies, and even though the use of homograft tissues harvested from hearts of transplant recipients and brain-death patients are allowed and their use is increasing, the supply of homograft tissue is very limited. Material and Method: The large diameter homografts are difficult to apply directly for RVOT reconstruction of small neonatal and infant hearts due to the size mismatching. Therefore, were surgically down-sized the large diameter tricuspid homograft into bicuspid conduits by means of a longitudinal incision of the oversized homograft, excision of one cusp, and oversewing of the“Bicuspid homograft”wrapped around a Hega dilator of the appropriate size. Result: 3 patients(Male 1, Female 2: tetralogy of Fallot with pulmonary atresia), ranging in age from 5 months to 4 years and ranging in weight from 5.5Kg to 12.95Kg underwent reconstruction of the RVOT with bicuspid conduits obtained by appropriate tailoring from large-diameter homografts. The mean follow-up period was 4.3 months(range, 2 to 6 months). There were no complications related to the homograft tissues. Conclusion: In the short term follow-up, the bicuspid homografts provided good competence and excellent hemodynamics although a long term follow-up is needed to assess the functions of the bicuspid homografts in RVOT. We believe this technique may be a more effective alternative than the use of synthetic conduits when the use of an appropriate-sized homograft is not possible.

• 한국안전학회지
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• 제29권5호
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• pp.67-73
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• 2014

Construction equipment such as tower crane should be installed in a field without appropriate anchorage to cause a collapse of crane. The anchorage capacity can be varied with Anchor length, concrete strength, anchor diameter, hooked or non hooked these variables will be made and tested in the study. It is shown what anchorage capacity will be more effective case by case. Hooked and non-hooked rebar anchor concrete weight with dia 22mm rebar are shown with initial displacement at 170~220KN of hooked case and 200~210KN of non-hooked one which are linearly increased, without any ductility behavior with almost brittleness. Three(3) same test pieces are almost similarly behaviored without relation to hooked or non-hooked cases. It is found out that the bigger diameter of rebar becomes, the more resistant capacity could be made, but conversely ductility against sudden collapse similar to brittleness becomes the more insufficient. It is also found out that dia 16mm rebar could be more effectively applied to heavy support weight at construction sites.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 총회 및 춘계학술발표회
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• pp.172-181
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• 2001

Upflow anaerobic sludge blanket (UASB) system employs granular sludge to treat various wastewaters including landfill leachate. CH$_4$ production of the granules determines overall performance of a UASB reactor. Sludge granules are developed by self-granulation of microorganisms and dynamic balance between granule growth and decay results in coexistence of granules with different sizes in the reactor. In this study, granules taken from a laboratory-scale UASB reactor were classified into 4 groups based on their diameters and their Physicochemical characteristics we were investigated. Each group was analyzed for settling ability, specific methanogenic activity (SMA), and elemental content. Settling ability was proportional to granule diameter. suggesting effective detainment of larger granules in the reactor. When acetate or glucose was used as a substrate, all groups showed relatively slight difference in SMA. However SMA with a volatile fatty acid mixture showed significant increase with granule diameter, suggesting better establishment of syntrophic relationship in larger granules. Larger granules showed higher value of SMA upon environmental changes (i.e., PH, temperature, or toxicant concentration). Comparative analysis of elemental contents showed that content (dry weight %) of most tested elements (iron, calcium, phosphorus, zinc, nickel. and manganese) deceased with granule diameter, suggesting importance of these elements for initial granulation. Taken together, this study verified experimentally that Physicochemical Properties of granules are related to granule size distributions. Overall results of physicochemical characterization supports that larger.

• 소성∙가공
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• 제21권5호
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• pp.312-318
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• 2012

With an increasing trend toward miniaturization, electrical discharge machining(EDM) has been receiving a lot of attention as a suitable production technology for micro-parts, since it enables the machining of hard conductive materials with a high degree of repeatability and without alteration to the material. When a micro-hole is fabricated by EDM, however, the diameter of the inlet hole is larger than that of the outlet region due to the additional discharge effect caused by the eroded particles. In this paper, a shot blasting surface treatment, in which an abrasive material is accelerated through a pressurized nozzle and directed at the surface of a part, is suggested as an effective method to reduce the tapered shape of EDM micro-hole. In addition, the influence of process parameters such as spark-on time and electrode diameter on the machining performance was investigated. It is shown quantitatively that the difference in diameter between the inlet and outlet holes decreases with the shot blasting treatment and with decreasing spark-on time.

• 대한조선학회논문집
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• 제41권5호
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• pp.21-27
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• 2004

A waterjet propulsion system has many advantages compared with a conventional screw propeller especially for amphibious military vehicles because of a good maneuverability at low speed, good operating ability at shallow water, high thrust at low speed to aid maneuverability and exit from water, etc. Especially, compact design is important for the tracked-vehicle because of buoyancy in water and available space inside the tracked vehicle. The experiment is parametrically performed for various impeller diameters for more compact design. The experimental results are analyzed according to the ITTC 1996 standard analysis method as well as the conventional propulsive factor analysis method. The full-scale effective and delivered power of the tracked-vehicle are evaluated according to the variation of impeller diameter. This paper emphasized the effect of impeller diameter on the performance of waterjet system.

• 상하수도학회지
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• 제22권6호
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• pp.619-625
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• 2008

Urban sewer systems are designed to operate in open-channel flow regime and energy loss at square manholes is usually not significant. However, the energy loss at surcharged manholes is considered as one of the major causes of inundation in urban area. Therefore, it is necessary to analyze the head loss associated with manholes, especially in surcharged flow. Hydraulic experimental apparatus which can change the manhole inner profile(CASE I, II, III, and IV) and the invert types(CASE A, B, C) were installed for this study. The experimental discharge was $16{\ell}/sec$. As the ratio of b/D(manhole width/inflow pipe diameter) increases, head loss coefficient increases due to strong horizontal swirl motion. The head loss coefficients for CASE I, II, III, and IV were 0.46, 0.38, 0.28 and 0.37, respectively. Side covers increase considerably drainage capacity at surcharged square manhole when the ratio of d/D(side cover diameter/inflow pipe diameter) was 1.0. The head loss coefficients for CASE A, B, and C were 0.45, 0.37, and 0.30, respectively. Accordingly, U-invert is the most effective for energy loss reduction at surcharged square manhole. This head loss coefficients could be available to evaluate the urban sewer system with surcharged flow.