• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1997년도 제8회 학술강연회논문집
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• pp.235-244
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• 1997

The empirical factor and reaction force based on published data were involved to investigate compressible flows through sudden enlargement and sudden contraction passages. Analytical solutions of engineering interest were obtained from one-dimensional steady compressible gas dynamic equations. The effects of compressibility, cross-sectional area ratio, and inlet Mach number on the air flows were discussed with regards to the total pressure loss and flow choking. The present results provide available information necessary ta design the compressible pipe flow systems.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 봄 학술발표회 논문집
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• pp.25-29
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• 1994

A series of 6 reinforced concrete beams was tested to verify the effects of EBSP strengthened on cracked beams and to identify the various parameters affecting structure strengthening design(SSD). The parameters were the cross-sectional area of steel plates, the thickness of steel plates, and bond length of steel plates. In addition to these parameters, the effect of existing cracks on the strengthening was investigated. Test results show that EBSP is very effective and predictable for strengthening damaged structures. The results also show that the bond length of steel plates is the most important factor to develop ultimate load carrying capacities of strengthened beams. However, considerations in SSD should be given to assure the ductile failure at ultimate load such as the low ratio of thickness to the width of plates.

• 한국산업융합학회 논문집
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• 제8권4호
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• pp.205-212
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• 2005

This paper presents the application of system identification approaches for the load carrying capacity evaluation of composite PCI girder bridges based on the result of field test. For these problems, the moment of inertia of cross-sectional area and the natural frequency of bridge were used as structural parameters, the SAP2000 program for the structural analysis and the SLP method for the minimum error. As a result, it is found that the proposed algorithm for this study appears applicable to real structures with reasonable complexity. It is shown that the introduction of approximate quadratic equations is more realistic and timesaving than the common methods.

• 한국암반공학회:학술대회논문집
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• 한국암반공학회 2011년도 추계 총회 및 창립 30주년 기념 심포지엄
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• pp.3-21
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• 2011

Laboratory experiments and numerical simulations using Particle Flow Code (PFC2D) were performed to study the effects of joint separation and joint overlapping on the full failure behavior of rock bridges under direct shear loading. Through numerical direct shear tests, the failure process is visually observed and the failure patterns are achieved with reasonable conformity with the experimental results. The simulation results clearly showed that cracks developed during the test were predominantly tension cracks. It was deduced that the failure pattern was mostly influenced by both of the joint separation and joint overlapping while the shear strength is closely related to the failure pattern and its failure mechanism. The studies revealed that shear strength of rock bridges are increased with increasing in the joint separation. Also, it was observed that for a fixed cross sectional area of rock bridges, shear strength of overlapped joints are less than the shear strength of non-overlapped joints.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1992년도 춘계학술대회 논문집 92
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• pp.27-46
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• 1992

In this study a new simplified three-dimensional numerical method and the associated computer program have been developed to simulate the non-axisymmetric extrusion processes. The two-dimensional rigid-plastic finite element method under the generalized plane-strain condition, is combined with the slab method. To define the die geometry for non-axisymmetric extrusion, area mapping technique was used. Streamlined die surface was used to miniminze the total extrusion pressure. Extrusion of square, hexagonal and "T" section from round billet have been simulated and experimented with a model material. The computed results were in good agreement with the experiments in cross-sectional grid distortion. Computational results will be valuable for designing tool geometries and corresponding processes.

• 한국정밀공학회지
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• 제23권6호
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• pp.143-150
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• 2006

Recently, in proportion to increased demand on environmentally-friendly heat source, efficient management of district heating(DH) system becomes one of important issue. The objectives of this paper are to systematize data processing of transition temperature, investigate the effect of temperature variations on thermal fatigue and find out a way to improve design fractures of Korean DH pipes. For this purpose, reliable fatigue lift evaluation procedures are examined and applied to quantify thermal fatigue lives. Also, as a prototypal optimization analysis results, mean value of original cross sectional area of selected pipes was reduced 18.6% sustaining their sufficient margins against fatigue failure. So, it is anticipated that the output of this research can be used as useful information of optimal design and operation in the future.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
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• pp.293-298
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• 1995

The strength of shear connectors embedded in lightweight concrete slab with deck plate is influenced by various factors of deck plate, shear conncetor and concrete. Generally, it is reported that the strength of shear connector in lightweight concrete decreases in comparison with that in normal concrete. So this paper is to use compressive strength of lilghtweight concrete, width-height ratio of deck plate, and cross sectional area of shear conncetor as variables, to evaluate the strength of shear conncetors in composite beam of steel and lilghtweight concrete slabs with deck plate, and then to suggest the reasonable strength equation by comparing the push-out test results with establixhed strength formula. As the result of 24 specimens test, in case of lightweight concrete slab with deck plate, it has showed that in the same strength, the strength of shear connector decreased about 10~20% in comparison with that in normal concrete. In spite of lightweight concrete, the test results were closely approached the established strength formula of shear connector using Fisher's reduction coefficient.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.221-226
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• 2002

This paper deals with the estimation of the bond stress based on experimental data that were tensed by axial force on both sides. It is certificated that the concrete stress condition clearly affects the bond-slip relationship. The proposed method utilizes the conventional bond-slip theories as well as the characteristics of deformed reinforcement and concrete cross-sectional area. An analytical equation for the estimation of the bond stress is formulated as the function of non-dimensional factors (e.g. bond stress, relative slip, etc.). The validity, accuracy and efficiency of the proposed method are established by comparing the analytical results with the experimental data of Ikki (1996, 1999) and the representative bond stress equations of Shima (1987). The analytical results presented in this paper indicate that the proposed method can be effectively estimated the bond stress-relative slip relationship.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.968-973
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• 2007

This paper presents an electromagnetic design for the magneto-rheological fluid valve. The MR valve can control high-level fluid power without moving parts, due to the apparent viscosity controllability of the MR fluid in magnetic fields. In order to improve the static characteristic of the MR valve, the length of the flux path is decreased by removing the unnecessary bulk of the yoke. Then, in order to improve the dynamic and hysteretic characteristics, the magnetic reluctance of the ferromagnetic material is increased by minimizing the cross sectional area through which the flux passes. Two MR valves, one is a conventional type valve and the other is the proposed one, were fabricated and performance evaluation is experimentally achieved through the comparison study using by-pass damper system.

• 분석과학
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• 제11권4호
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• pp.316-320
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• 1998

An image analysis was used for the interpretation of microstructures of ferrous metal artifacts. For the purposes, various microstructural features such as average grain size, phase area, shape factor, and composition of the inclusions, were parameterized for the information about manufacturing techniques such as casting, heating and tempering. The carbon content was determined through the evaluation of the amount of pearlite phase. As the amount of pearlite phase increased the shape factor also increased. Grain size was relatively smaller in trans-section than in cross-section. The manufacturing direction was trans-sectional because the orientation of inclusions was elongated lengthwise. All inclusions was of silicate groups and the manufacturing temperature was estimated up to $1450^{\circ}C$.