• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.173-176
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• 2004

Nowadays, mobile devices are very common equipments such as mobile phone, PDA, etc. These equipments need information storage devices. Optical storage devices have more advantages than other storage devices, but it is not free from shock situation like dropping by user's mistakes. A complete model of a Small Form Factor Optical(SFFO) disk drive subject to shock loads is developed to investigate the response of the pickup/disk interface. With this model, we can simulate the drop test and consider the matters of shock simulation using commercial software(Ansys/LS-Dyna).

• Journal of Welding and Joining
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• v.22 no.2
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• pp.69-77
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• 2004

The Gaussian heat source has been widely used to simulate the heat flux of the welding we, and applied to calculating the temperature distribution of a workpiece. The conventional two-dimensional Gaussian heat source for the GMAW is modified in this work by decomposing the arc heat into heats of the cathode and metal transfer. The efficiency and effective arc radius of each heat source are determined analytically for the free-flight mode such as the globular and spray modes. The temperature distribution and weld geometry are calculated using the finite element method, and distribution of the drop heat is found to have significant effects on the penetration. The predicted results show good agreements with the available experimental results, especially with the penetration.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.469-476
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• 2001

The Ν-value in the standard penetration test(SPT) is affected by the magnitude of the rod penetration energy transmitted from the falling hammer as well as the geotechnical characteristics of the ground. Understanding of the striking energy efficiency in the SPT equipment is getting important for that reason. The energy efficiencies of the doughnut hammer with the hydraulic lift system and the automatic trip hammer system were investigated through field tests using the instrumented rod and wave-signal acquisition systems including the pile driving analyzer(PDA) . The rod energy ratio, ΕR$\_$r/ was defined as the ratio of the energy delivered to the drilling rod to the potential free-fall energy of the hammer. It appears that the type of the hammer and lift/drop system had a strong influence on the energy transfer mechanism and ΕR$\_$r/ also varies according to the energy instrumentation system and the analysis methods.

• Ocean Systems Engineering
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• v.10 no.3
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• pp.267-287
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• 2020

The dropped objects are identified as one of the top ten causes of fatalities and serious injuries in the oil and gas industry. It is of importance to understand dynamics of dropped objects under water to accurately predict the motion of dropped objects and protect the underwater structures and facilities from being damaged. In this paper, we study non-dimensionalization of two-dimensional (2D) theory for dropped cylindrical objects. Non-dimensionalization helps to reduce the number of free parameters, identify the relative size of effects of force and moments, and gain a deeper insight of the essential nature of dynamics of dropped cylindrical objects under water. The resulting simulations of dimensionless trajectory confirms that drop angle, trailing edge and drag coefficient have the significant effects on dynamics of trajectories and landing location of dropped cylindrical objects under water.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.119-122
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• 2005

In this paper a method for analysing aerodynamic characteristics of a rotating parachute in steady descending motion is presented. Because of a complex geometric configuration of the parachute associated with side vents and discontinuous skirts, special procedure was adopted th handle the geometry in the analysis. A panel method was successfully applied to the present problem and yielded good results using above procedure. A CFD code using the full Navier-Stokes equations was also applied and provided good results. Parachute free drop and wind tunnel tests were performed to determine the fully developed canopy configuration and aerodynamic characteristics. The method can be used for optimizing the parachute size and side vent configurations in the design period.

• Journal of computational fluids engineering
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• v.11 no.1 s.32
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• pp.52-56
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• 2006

In this paper a method for analysing aerodynamic characteristics of a rotating parachute in steady descending motion is presented Because of a complex geometric configuration of the parachute associated with side vents and discontinuous skirts, special procedure was adopted to handle the geometry in the analysis. A panel method was successfully applied to the present problem and yielded good results using above procedure. A CFD code using the full Navier-Stokes equations was also applied and produced good results. Parachute free drop and wind tunnel tests were performed to determine the fully developed canopy configuration and aerodynamic characteristics. The method can be used for optimizing the parachute size and side vent configurations.

• 전기의세계
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• v.24 no.5
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• pp.97-102
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• 1975

This paper describes the result of a Study for the Optimum Operating method with Spinning reserve in case of outage of large generator unit to improve the system stability and prevent the system frequency drop. This is usually done by governor free operation, so we focused our attention to the operating Char acteristics of spinning reserve. Nexy, a study was made to mesure the upper limit of Spinning reserve and when this upper limit cannot match the required power, a relationship between the amount of spinning reserve and that of the load shedding requirement was searched with regard to several system operating conditions to use it in our future system operation. By this study, the optimum system operating method was recommended for reliable operation of power system.

• Nuclear Engineering and Technology
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• v.30 no.5
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• pp.462-469
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• 1998

A package to transport high-level radioactive materials is required to withstand normal transport and hypothetical accident conditions pursuant to the IAEA and domestic regulations. The package should maintain the structural safety not to release radioactive material in any condition. The structural safety of the package has been evaluated by tests using proto-type or scaled-down models, however, the method by analysis is gradually utilized due to recent advancement of computers and computer codes. In this paper, to evaluate the structural safety of a radioisotope package of the KAERI, the three dimensional impact analyses under 9m free drop and 1m puncture were performed with an explicit finite-element code, the LS-DYNA3D code. The maximum stress intensity on each part was calculated and the structural safety of the package was evaluated in accordance with the regulations.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.4
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• pp.1064-1081
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• 2014

This paper presents a numerical analysis of slamming and whipping using a fully coupled hydroelastic model. The coupled model uses a 3-D Rankine panel method, a 1-D or 3-D finite element method, and a 2-D Generalized Wagner Model (GWM), which are strongly coupled in time domain. First, the GWM is validated against results of a free drop test of wedges. Second, the fully coupled method is validated against model test results for a 10,000 twenty-foot equivalent unit (TEU) containership. Slamming pressures and whipping responses to regular waves are compared. A spatial distribution of local slamming forces is measured using 14 force sensors in the model test, and it is compared with the integration of the pressure distribution by the computation. Furthermore, the pressure is decomposed into the added mass, impact, and hydrostatic components, in the computational results. The validity and characteristics of the numerical model are discussed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3305-3314
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• 1994

In this study, the influence of a frost formed on the vertical plate for different operating conditions(the temperature of the air, the humidity of the air, the velocity of the air, and the temperature of the cooling plate) is investigated. The performance of the heat exchanger is examined by introducing a parameter such as the energy transfer resistance. Correlations which relate frost density, frost thickness and energy transfer resistance to Reynolds number, air temperature and humidity, and cooling plate temperature are developed. Static pressure drop and air flow rate are expressed as a function of free flow area of air.