• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.6
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• pp.265-271
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• 2013

Czochralski (CZ) growth process is one of the most important techniques for growing high quality sapphire single crystal for LED application. In this study, the inductively-heated CZ growth processes for the sapphire crystal of 300 mm length have been analyzed numerically using finite element method. The hot zone structures were modified with the crucible geometry change and the additional insulation layer installed above the crucible. The results show that the solid-liquid interface height decreased from about 80 mm at initial stage to 40 mm after mid-stage due to achieve the growth speed balance. Also the optimal input power of the modified system was similar with the original one due to the compensation effects of the crucible geometry and additional insulation. The crystal temperature grown by the modified CZ grower was increased about 10 K than the original one. Therefore the sapphire crystal of 300 mm height was grown successfully.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.1
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• pp.179-192
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• 1993

Three-dimensional cohesive sediment transport model, COSETM-3, is develpoed using a finite difference method. The model results are compared with the physical experimental results for the relative concentration with time at the mid-depth of the recirculating flume and are found to be in good agreement. This model is applied to Suyoung Bay in Pusan of Korea to verify the field applicability of the model and to investigate on the SS (suspended solids) diffusion phenomena at the bay. Behaviors of discharging SS from Suyoung River at normal river flow and flood river flow are predicted. The numerical results appear to be reasonable and qualitative agreement with field data. The influence of settling velocity on the concentration distribution of SS is also investigated. In case of not considering settling velocity, SS concentration at surface layer is higher than that at lower layer, but in case of considering settling velocity, SS concentration at lower layer is higher than that at surface layer. The fluctuation of SS concentration at surface layer is large due to the strong mixing, but the fluctuation of the concentration at lower layer is small due to the weak mixing. SS diffusion patterns at flood river flow are similar to those at normal river flow, while the concentration at that flow is so much higher than that at this flow. SS concentration increases with time until the peak discharge occurs, but the concentration decreases with time with decreasing river flow after the peak discharge.

• Journal of the Korean Institute of Gas
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• v.14 no.2
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• pp.1-6
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• 2010

The strength safety of high pressure gas cylinder has been analyzed by using a finite element method. In this study, the internal gas pressures of a steel bombe include a service charging pressure of $9kg/cm^2$, high limit charging pressure of $18.6kg/cm^2$, high limit of safety valve operation pressure $24.5kg/cm^2$, and hydraulic testing pressure of $34.5kg/cm^2$. The computed FEM results indicate that the strength safety for a service charging pressure of $9kg/cm^2$ and high limit charging pressure of $18.6kg/cm^2$ is safe because the stress of a gas cylinder is within yield strength of steel. But the stress for a hydraulic testing pressure of $34.5kg/cm^2$ sufficiently exceeds the yield strength and remains under the tensile strength. If the hydraulic testing pressures frequently apply to the gas cylinder, the bombe may be fractured because a fatigue residual stress is accumulated on the lower round end plate due to a plastic deformation. The computed results show that the concentrated force in which is applied on a skirt zone does not affect to the lower round end plate, and the most weak zone of a bombe is a middle part of a lower round end plate between a bombe body and a skirt for a gas pressure. Thus, the FEM results show that the profile of a lower round end plate is an important design parameter of a high pressure gas cylinder.

• Journal of Biomedical Engineering Research
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• v.19 no.5
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• pp.503-511
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• 1998

In this study, the stress distribution for different tibial components was observed In order to Investigate the load transfer and potential failure mechanism of the tibial components subjected to dynamic impact loading and also to evacuate the effect of bone-implant bonding conditions on the implant system. The 3-dimensional finite element models included an intact tibia, cemented metal-backed tibial component, uncemented metal-blocked tibial component, cemented all-polyethylene tibial component, and metal-backed component with a debonded bone/stem interface. The results showed that the cemented metal-hocked component Induced slightly higher peak stress at stem tip than the uncemented component. The peak stress of the all-polyethylene tibia1 component at stem trip showed about half thats of metal-backed tibial components. The all-polyethylene component showed a similar dynamic response to intact tibia. In case of debonded bone/stem interface, the peak stress below the metal tray was three times Higher than that of the fully bonded interface and unstable stress distribution at the stem tip was observed with time, which causes another adverse bone apposition and implant loosening. Thus, the all-polyethylene tibial component bonded fully to the surrounding bone might be most desirable system under an impact loading.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.2
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• pp.67-75
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• 1986

This paper introduces the nonlinear Stream Function Wave Theory for design waves efficiently to compute the wave energy and energy transport quantities and to analyze the effects of nonlinearities on them. The Stream Function Wave Theory was developed by Dean for case of the observed waves with assymmetric wave profiles and of the design waves with symmetric theoretical wave profiles. Dalrymple later improved the computational procedure by adding two Lagrangian constraints so that more efficient convergence of the iterative numerical method to a specified wave height and to a zero mean free surface displacement resulted. And the Stream Function coefficients are computed numerically by the improved Marquardt algorithm developed for this study. As the result of this study the effects of nonlinearities on the wave quantities of the average potential energy density, the average kinetic energy density result in overestimation by linear wave theory compared to the Stream Function Wave Theory and increase monotonically with decreasing $L^*/L_O$ and with increasing $H/H_B$. The effects of nonlinearities on the group velocity and the wavelength quantities result in underestimation by linear wave theory and increase monotonically with increasing $H/H_B$. Finally the effect of nonlinearity on the average total energy flux results in overestimation for shallow water waves and underestimation for deep water waves by linear wave theory.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.1
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• pp.94-105
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• 2013

Recently, the construction industry has been changed in such a way that the cost for bridge construction should be optimized or reduced. Therefore, bridges are required be cost-effective in terms of initial construction as well as in the maintenance during service stage. In order to reduce the cost for bridge construction, the Rahmen typed structure, in which the bridge components from superstructure to substructure are integral, has many advantages to reduce the size of structural members including girders, since the loadings from superstructure may be transferred to substructure through the connecting rebars such as stud, etc. This paper studied on the continuous Up and Down Prestressed Concrete (UD PSC) girder bridge in which the reinforced concrete pier cap is integral with the part of girders in superstructure. In previous studies, it is known that the structural behavior of continuous UD PSC girder bridge is quite different compared to the one of the bridges with conventional bearings or shoes to support the loading from girders. Nevertheless, it has hardly been studied about the structural behavior of bridge with UD PSC girder. Therefore, in this study, various dynamic behaviors of continuous UD PSC girder bridge with integral pier cap have been analyzed using numerical method. Furthermore, an equation to evaluate the impact factor is suggested for the UD PSC girder bridge which has two to three continuous spans.

• Journal of the Korean Geotechnical Society
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• v.28 no.4
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• pp.101-113
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• 2012

The degradation of a tunnel drainage system leads to increases in pore water pressure around the tunnel and the lining stress, which results in affecting the tunnel stability. In the present study of the Namsan 3th tunnel, more than 30 year old tunnel, the effects of the drainage performance reduction due to drain hole clogging on the tunnel lining stability were investigated by examining pore water pressure distribution around the tunnel and the lining stresses through numerical analysis. Groundwater flow modeling on the Mt. Namsan region was done first and 3D seepage and coupled stress-pore water pressure finite element analysis were performed on the tunnel using the results of the groundwater flow modeling. The pore water pressure distribution and the tunnel lining stresses could be predicted using a drain hole outflow data measured in the tunnel site. This analysis method may be used to evaluate the current stability of old tunnels for which in most cases field investigations and related information are not readily available.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.4
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• pp.305-317
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• 2003

Underwater shape and hook depth in tuna longline gear are important factors to decide fishing performance. It also should be considered that management and analysis of hooked rate data from hooked fish species and sizes, and each fishing would be used as a reference data in the future fishing. In this research, after analyzing underwater shape of tuna longline gear by current direction and speed using simulation, experiments were executed in flume tank to verify accuracy of the analysis. Also using the depth of each hook from the simulation, a database system was setup to process the data of bait and hooked fish species. The results were as follows；1. When the attack angle and the shortening rate are fixed, a decrease of the hook depth is proportion to an increase of current speed. 2. When the shortening rate and current speed are fixed, a decrease of hook depth is proportion to an increase of attack angle. 3. When the attack angle and velocity of flow are fixed, a decrease of hook depth is proportion to an increase of shortening rate 4. As a result of comparison between the underwater shape by simulation and that by model gear, the result of the simulation was very close to that of model gear within $$ {\pm}3%$$ 3% error range. 5. In this research, hooked rate database system using hook depth of simulation can analyze the species and size of fish by the parameter; bait. hook depth, so It could be helpful to manage and analyze the hooked data on the field.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.10
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• pp.1008-1016
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• 2013

SAR measurement which was applied only to the mobile phone has been expanded in the Korean radio regulation law to the portable wireless communication equipments within 20 cm from the human body since Jan. 2012. The two-way radio operating at 150 MHz frequency band was newly included following the revised radio regulation in the target equipment of measurement. SAR measurement system at 150 MHz satisfying this regulation is necessary accordingly for SAR conformity assessment. The international SAR measurement standard(IEC 62209-2) includes the evaluation method on frequencies above 300 MHz, and the commercial SAR measurement system can measure SAR above 300 MHz only. The size of the reference dipole antenna(760 mm, return loss: -27.57 dB) and flat phantom ($1,300 mm(L){\times}900 mm(W){\times}200 mm(H)$), targeted SAR values for numerical analysis(1 g: 1.08 W/kg, 10 g: 0.77 W/kg) for SAR validation evaluation at 150 MHz frequency are proposed in this paper. The suggested dipole antenna and flat phantom are assembled and used to verify the conformity assessment of commercial SAR measurement system. The measured SAR values of 1 g and 10 g were obtained respectively to be 1.13 W/kg, 0.81 W/kg, and they satisfied the effective range(within ${\pm}10$ %) of IEC international standard. The standards based on this study are expected to be used for the domestic SAR measurement standard and IEC(International Electrotechnical Commission) international standard.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.9
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• pp.479-490
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• 2001

In this paper, we consider the method of partitioning a sphere into faces with a set of spherical convex polygons $\Gamma$=$｛P_1...P_n｝$ for determining the maximum of minimum intersection. This problem is commonly related with five geometric problems that fin the densest hemisphere containing the maximum subset of $\Gamma$, a great circle separating $\Gamma$, a great circle bisecting $\Gamma$ and a great circle intersecting the minimum or maximum subset of $\Gamma$. In order to efficiently compute the minimum or maximum intersection of spherical polygons. we take the approach of edge-based partition, in which the ownerships of edges rather than faces are manipulated as the sphere is incrementally partitioned by each of the polygons. Finally, by gathering the unordered split edges with the maximum number of ownerships. we approximately obtain the centroids of the solution faces without constructing their boundaries. Our algorithm for finding the maximum intersection is analyzed to have an efficient time complexity O(nv) where n and v respectively, are the numbers of polygons and all vertices. Furthermore, it is practical from the view of implementation, since it computes numerical values. robustly and deals with all the degenerate cases, Using the similar approach, the boundary of a general intersection can be constructed in O(nv+LlogL) time, where : is the output-senstive number of solution edges.