• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.85-87
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• 2012

We present a numerical investigation on gaseous (ethylene-air mixture) detonation in the elastoplastical metal tubes to understand the wall effects associated with the developing detonation instability. The acoustic disturbances originating from the rapidly expanding tube walls reach the detonating flame surface, thereby causing flame distortions and total energy losses. The compressible Navier-Stokes equations with equation of state for gas and elasto-plastic deformation field equations for inert tubes are solved simultaneously to understand the complex multi-material interaction in the rapidly expanding gas pipe. In order to track governing variables across the material interface, we use the hybrid particle level-set and ghost fluid methods to precisely estimate the interfacial quantities. Features observed from the deforming (thin) tube show substantially different behavior when a detonation propagates in the rigid (thick) tube with no acoustically responding wall conditions.

• Journal of Korean Society of Transportation
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• v.4 no.2
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• pp.15-35
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• 1986

As the population of persons and automobiles rapidly grows, parking problems also grow in large cities of Korea. The purpose of this paper is to first grasp the status of parking facilities and characteristics in large cities of Korea; and introduce new directions of CBD parking policies in north America cities: and finally recommend the adequate parking management strategies and tactics for improving parking problems in Korea. For this purpose, field survey for parking inventories, patrol survey for parking usage as observed demand and drive interview survey for parking behavior were conducted. Compared with the parking characteristics and polices of foreign cities, many differences of characteristics were found, and existing parking management policies, which should be improved, were identified. Five categories of parking management strategies were set on; a) Reasonable control of CBD parking demand, b) securing of the public parking facilities c) Promotion of privately operated parking facilities d) expansion of financial resources for parking facilities construction and e) Improvement of existing parking management system. And actural seventeen tactics to attain the above strategies were recommended.

• Journal of Information Technology Applications and Management
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• v.22 no.2
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• pp.123-148
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• 2015

Today the mobile devices including smart phones have influenced on the users' daily activities in the mobile internet society, and the expansion of social media has also affected on the purchasing behavior of consumers. This study examines whether the quality of corporate twitter, a typical social network service for call centers influences on the customer satisfaction, and brand loyalty. In order to achieve the research goal, the quality of twitter has been divided into four variables; information quality, service quality, system quality, and social quality. The results of our empirical analysis show that the three variables except service quality have significantly influenced on the customer satisfaction and the customer satisfaction also significantly has a casual effect on the brand loyalty. The empirical results are expected as a guideline to contribute on the practical improvement of customer service, satisfaction, and brand loyalty through corporate social network services such as corporate twitters in the future.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.988-990
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• 2005

A 5.0-inch plastic TFT-LCD with the resolution of $400{\times}3{\times}300$ lines (120ppi) was developed. The device is a transmissive type with the transparent PES plastic substrates. The PES films with one side barrier coating were used for the device. In order to produce the high resolution display device, the alignments between all the layers for the TFT and CF are essential. The fundamental shrinkage effect and the thermal expansion behavior of the plastic substrates with and without the barrier coatings were studied. The proper annealing processes followed by immediate second bar-rier coating processes provide the optimal alignment between all the layers of the TFT and CF..

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.178-182
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• 1995

Strain localization is important phenomenon since it governs the total behavior or ultimate loads in various kinds of engineering problems. Establishment of an analysis method for strain localization phenomena is also of great concern for expansion of fracture mechanics of concrete. Inside zone of localization, a decrese in stress is accompanied by an increse in strain; outside the strain decreses. All deformation localization phenomenon cannot be predicted by both the classical stress-strain formulation and the linear elastic fracture mechanics. In this paper, a simple one dimensional model including localized deformation zone is studied under compressive and tensile loading. When the model is loaded. localization is assumed to occur uniformly in a finite region and material outside the localization zone is modelled as elastic unloading occurs. Size effects of effective elastic moduli under compression and tension in localization zone are examined.

• International Journal of Concrete Structures and Materials
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• v.9 no.4
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• pp.463-473
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• 2015

Three full-scale instrumented test slabs were constructed and tested using a heavy vehicle simulator (HVS) to evaluate the structural behavior of internally cured concrete (ICC) for use in pavements under Florida condition. Three mix designs selected from a previous laboratory testing program include the standard mixture with 0.40 water-cement ratio, the ICC with 0.32 water-cement ratio, and the ICC mixture with 0.40 water-cement ratio. Concrete samples were prepared and laboratory tests were performed to measure strength, elastic modulus, coefficient of thermal expansion and shrinkage properties. The environmental responses were measured using strain gages, thermocouples, and linear variable differential transformers instrumented in full-scale concrete slabs. A 3-D finite element model was developed and calibrated using strain data measured from the full-scale tests using the HVS. The results indicate that the ICC slabs were less susceptible to the change of environmental conditions and appear to have better potential performance based on the critical stress analysis.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.423-426
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• 2006

An analysis is made of flow and rocket motion during a supersonic separation stage of air-launching rocket(ALR) from the mother plane. Three-dimensional compressible Navier-Stokes equations is numerically solved to analyze the steady/unsteady flow field around the rocket which is being separated from the mother plane configuration(F-4E Phantom). The simulation results clearly demonstrate the effect of shock-expansion wave interaction between the rocket and the mother plane. To predict the behavior of the ALR according to the change of the C.G., three cases of numerical analysis are performed. As a result, a design-guideline of supersonic air-launching rocket for the safe separation is proposed.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.37-42
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• 2003

The problem of an orthotropic material with a central crack is studied. The material is subjected to uniform biaxial loading along its boundary. The normal stress ratio theory is applied to predict fracture strength behavior in cracked orthotropic material. The dependence of the critical stress with respect to the biaxial loading and the crack orientation is discussed. Our analysis shows significant effects of biaxial loading on the critical stress. The additional tenn in the asymptotic expansion of the crack tip stress field appears to provide more accurate critical stress prediction.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.43-48
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• 2003

The problem of welding stresses and fatigue behavior is the main concerns of welding research fields. The residual stresses and distortion of structures by welding is exert negative effect on the safety of mechanical structures. That is, expansion of material by high temperature and distortion by cooling during welding process is caused of tensile and compressive residual stresses on welding material, and this residual stresses reduce fracture and fatigue strength of welding structures. The accurate prediction of residual stress and relaxation due to loading and post weld heat treatment of weld zone is very important to improve the quality of weldment. In this study, a finite element modeling technique is developed to simulate the relaxation of residual stresses due to loading and post weld heat treatment of weld zone. The accuracy of finite element models is evaluated based on experimental results and the results of the analytical solution.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.4
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• pp.380-387
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• 2009

The reliability concerns of solder interconnections in flip chip PBGA packages are produced mainly by the mismatch of coefficient of thermal expansion(CTE) between the module and PCB. Finite element analysis has been employed extensively to simulate thermal loading for solder joint reliability and deformation of packages in electronic packages. The objective of this paper is to study the thermo-mechanical behavior of FC-PBGA package assemblies subjected to temperature change, with an emphasis on the effect of the finite element model, material models and temperature conditions. Numerical results are compared with the experimental results by using $moir{\acute{e}}$ interferometry. Result shows that the bending displacements of the chip calculated by the finite element analysis with viscoplastic material model is in good agreement with those by $moir{\acute{e}}$ inteferometry.