• International Journal of Korean Welding Society
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• 제1권2호
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• pp.30-35
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• 2001

Nowadays, repair welding on in-service natural gas pipeline is a matter of primary concern of gas company. The main purpose of this study is to investigate the effects of welding conditions on the allowable heat input for crack-free welds and welds without burn-through onto in-service natural gas pipeline. First of all, single pass weld bead on plates of the various thickness was deposited to evaluate the penetration of weld metal, the depth of heat affected zone and the hardness of repair weld under various welding conditions. Also, finite element analysis has been conducted to validate experimental results of bead-on plate welds and to develop appropriate model for repair welding. The welding experiments of bead-on-plate weld confirmed the influence of plate thickness, heat input and welding process on safety. And, the finite element model was demonstrated by comparing experimental results. The agreement between the computed and measured values was shown to be generally good. Therefore, It is possible to predict the safety of repair welding under various welding conditions with experimental results and finite element analysis model.

• Journal of Advanced Research in Ocean Engineering
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• 제1권2호
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• pp.106-114
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• 2015

In the fabrication of offshore oil and gas facilities, the significance of dimension control is growing continuously. But, it is difficult to determine the deformation of the structure during fabrication by simple lab tests due to the large size and the complicated shape. Strain-boundary method (a kind of shrinkage method) based on the shell element was proposed to predict the welding distortion of a structure effectively. Modeling of weld geometry in shell element is still a difficult task. In this paper, a concept of imaginary temperature pair is introduced to handle the effect of geometric factors such as groove shape, plate thickness and pass number, etc. Single pass imaginary temperature pair formula is derived from the relation between the groove area and the FE mesh size. By considering the contribution of each weld layer to the whole weldment, multi-pass imaginary temperature is also derived. Since the temperature difference represents the distortion increment, cumulative distortion curve can be drawn by integrating the temperature difference. This curve will be a useful solution when engineers meet some problems occurred in the shipyard. A typical example is shown about utilization of this curve. Several verifications are conducted to examine the validity of the proposed methodology. The applicability of the model is also demonstrated by applying it to the fabrication process of the heavy ship block. It is expected that the imaginary temperature model can effectively solve the modeling problem in shell element. It is also expected that the cumulative distortion curve derived from the imaginary temperature can offer useful qualitative information about angular distortion without FE analysis.

• 한국ITS학회 논문지
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• 제9권3호
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• pp.59-66
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• 2010

일반적으로 고속도로 영업소에서는 요금정산을 위해 차량이 감속, 정지, 가속행위를 행해야 하므로, 차량의 멈춤 없이 요금을 징수하는 자동요금징수체계(ETCS)의 일종인 하이패스차로 이용시보다 추가적인 연료소모가 발생하게 된다. 본 연구는 이를 증명하기 위해 현장 실험구간을 선정하고 연료소모량을 측정할 수 있는 실험용 차량을 제작하여 고속도로 영업소 이용방식에 따른 연료소모량을 비교하였다. 실험 결과, 일반차로를 이용하는 차량이 하이패스차로를 이용하는 차량보다 36.7%이상의 추가적인 연료소모가 발생하는 것으로 나타났다. 이에 근거하여 고속도로 상에서 2009년 1월부터 5월까지 실험차량과 동일한 차량들의 하이패스차로 이용에 의한 연료절감 효과를 추정해 본 결과 약 53.4억원의 연료소모비 절감효과가 나타났다. 실제 차량을 이용한 이러한 실험 방법과 분석결과는 하이패스 시스템의 효율성을 증명하는데 유용하게 활용될 것으로 기대된다.

• 여성건강간호학회지
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• 제16권4호
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• pp.409-418
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• 2010

Purpose: The purpose of this study was to identify the effects of a pre-operation video assisted education program on residual urine, gas passing and state anxiety in women undergoing hysterectomy. Methods: Nonequivalent control group non-synchronized design was used for the study. In the research, video assisted education program was applied to the experimental group while a similar conventional education was done to the control group. The pre-operation state anxiety and post-operation residual urine and gas discharge of both the groups were measured. The data were analyzed using SPSS. Results: The experimental group was significantly higher than control group on gas passing (t=3.04, p=.00). However the residual urine (t=0.34, p=.73) and state anxiety (t=0.81, p=.82) did not make significant differences. Conclusion: This study is very meaningful in that it developed and provided a nursing intervention can positively affect hysterectomy patients. The pre-operation video assisted education program may be an effective nursing intervention that is clinically practical and useful to reduce time of the gas passing of hysterectomy patients after the operation.

• Journal of Welding and Joining
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• 제25권4호
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• pp.42-48
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• 2007

An inert gas atomized NiTiZrSiSn bulk metallic glass feedstock was sprayed onto the copper plate using vacuum plasma spraying process. In order to change the in-flight particle energy, that is, thermal energy, the hydrogen gas flow rate in plasma gas mixture was increased at the constant flow rate of argon gas. Coating and single pass spraying bead were produced with the least feeding rate. Regardless of the plasma gas composition, fully melted through unmelted particle could be observed on the overlay coating. However, the frequency of the unmelted particle number density was increased with the decrease of the hydrogen gas flow rate. The amorphous phase fraction within coating was also affected by the number density of the unmelted particle.

• 동력기계공학회지
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• 제9권4호
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• pp.51-57
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• 2005

In order to prevent the environmental pollution, the dryers are commonly used to treat sludge that one of sewages is polluting the quality of water. Generally, the drying method is various as to the property of material and use. Rotary dryer is a good apparatus to treat them. The rotary dryer is the way that is to make substance transmission and heating using hot air between sludge particles and heated gas. In this paper, we performed a numerical analysis of the inner air flow of the 3-pass rotary dryer through the changing rotational speed from 3rpm to 10rpm. In this result, we found that 3rpm is effective to dry material in terms of heat transfer because large scale velocity fluctuation is occurred inside the first and second drum. Also we confirmed that 5rpm and 8rpm showed up uniform flow at the center area of the first drum.

• 수산해양기술연구
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• 제54권1호
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• pp.73-80
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• 2018

Intermittent duty of emergency generator has problems emitting large quantities of PM and NOx in exhaust gas. The aim of this study is to propose DPF system which can be applied to medium-large emergency generators. The system is composed of soot dust collector, silencer and filter trap, which is designed to reduce PM emissions at the emergency generator start-up. The pneumatic system controls a flow direction of exhaust gas to pass through the soot collector and filter trap until the engine reaches complete combustion condition. An experiment is performed to measure PM content and concentration to analyze the performance and characteristics of the proposed system.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.207-210
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• 2005

In this paper, a two-dimensional cross-channel model was applied to investigate influence of the gas diffusion layer(GDL) property and flow field geometry in the anode side for proton exchange membrane fuel cell(PEMFC). The GDL is made of a porous material such as carbon cloth, carbon paper, or metal wire mesh. To the simplicity, the GDL is represented as a block of material containing numerous pathways through which gaseous reactants and liquid water can pass. The purpose of present work was to study the effect of the GDL thickness and the porosity, and flow field geometry by computational fluid dynamics(CFD)

• 한국연소학회:학술대회논문집
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• 한국연소학회 2001년도 제22회 KOSCI SYMPOSIUM 논문집
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• pp.75-81
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• 2001

MCVD(modified chemical vapor deposition) used in making optical-fiber currently utilizes the hydrogen-oxygen burner as a energy supply source. To improve the productivity and to reduce the manufacturing cost of optical-fiber, a natural gas-oxygen burner has been developed. The manufacturing processes of optical-fiber consist of vapor deposition, collapse and drawing processes. Among these processes, the vapor deposition and the collapse processes are important in terms of improving the productivity and saving the production cost. The vapor deposition and collapse processes are performed by combustion heat and flame force supplied by a burner. So the flame force of the burner used in these processes is required to have an optimal and consistent value in order to allow uniform heating and collapse of quartz tube. In this regard, the momentum ratio of natural gas and oxygen has been optimally determined by modification of a burner and the inlet flow pass also has been modified.

• Journal of Welding and Joining
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• 제31권6호
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• pp.71-76
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• 2013

Gas nitriding is a surface hardening process where nitrogen is introduced into the surface of a ferrous alloy. During fusion welding of nitrided carbon steel, the nitride inside weld metal is dissolved and generates nitrogen gas, which causes porosities - blow holes and pits. In this study, several laser welding processes such as weaving welding, two-pass welding, dual beam welding and laser-arc hybrid welding were investigated to elongate the weld pool to enhance nitrogen gas evacuation. The surface pits were successfully eliminated with elongated weld pool. However blowholes inside the weld metal were effective reduced but not fully disappeared.