• Journal of the Korean Vacuum Society
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• v.15 no.3
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• pp.325-330
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• 2006

In order to verify the integrity of the first wall (FW) of the International Thermonuclear Experimental Reactor (ITER), the fabricated Cu/SS mock-up is tested in the JAEA Electron Beam Irradiation Test Stand (JEBIS). To fabricate the Cu/SS mock-up, CuCrZr and 316L authentic stainless steel (SS316L) are used for Cu alloy and steel, respectively The hot isostatic pressing (HIP) is used as a manufacturing method with a $1050^{\circ}C$ and 150 MPa. The high heat flux (HHF) test is performed using an electron beam with a heat flux of $5MW/m^2$ and a cycle of 15-sec on time and 30-sec off time. The temperature measurement in the HHF test shows good agreement with the results obtained from ANSYS code analysis, which is used for determining the HHF test conditions.

• Journal of The Korean Astronomical Society
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• v.41 no.6
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• pp.157-161
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• 2008

We have estimated the fractal dimension of the molecular clouds associated with the Hii region Sh 156 in the Outer Galaxy. We selected the $^{12}CO$ cube data from the FCRAO CO Survey of the Outer Galaxy. Using a developed code within IRAF, we identified slice-clouds (2-dimensional clouds in velocity-channel maps) with two threshold temperatures to estimate the fractal dimension. With the threshold temperatures of 1.8 K, and 3 K, we identified 317 slice-clouds and 217 slice-clouds, respectively. There seems to be a turn-over location in fractional dimension slope around NP (area; number of pixel) = 40. The fractal dimensions was estimated to be D = $1.5\;{\sim}\;1.53$ for $NP\;{\geq}\;40$, where $P\;{\propto}\;A^{D/2}$ (P is perimeter and A is area), which is slightly larger than other results. The sampling rate (spatial resolution) of observed data must be an important parameter when estimating fractal dimension. Fractal dimension is apparently invariant when varying the threshold temperatures applied to slice-clouds identification.

• Journal of the Korean Institute of Navigation
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• v.23 no.2
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• pp.29-42
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• 1999

An accurate method of estimating ship maneuverability needs to be developed to evaluate precisely and improve the maneuverability of ships according to the water depth. In order to estimate maneuverability by a mathematical model. The hydrodynamic forces acting on a ship hull and the flow field around the ship in maneuvering motion need to be estimated. The ship speed new the berth is very low and the fluid flow around a ship hull is unsteady. So, the transient fluid motion should be considered to estimate the drag force acting on the ship hull. In the low speed and short time lateral motion, the vorticity is created by the body and grow up in the acceleration stage and the velocity induced by the vorticity affect to the body in deceleration stage. For this kind of problem, CFD is considered as a goof tool to understand the phenomena. In this paper, the 2D CFD code is used for basic consideration of the phenomena to solve the flow in the cross section of the ship considering the ship is slender and the water depth is large enough. The flow fields Added and hydrodynamic forces for the some prescribed motions are computed and compared with the preliminary experiment results. The comparison of the force with measurement is shown a fairly good agreement in tendency. The 3D Potential Calculation based on the Hess & Smith Theory is employed to predict the surge, sway added mass and yaw added moment of inertia of hydrodynamic coefficients for M/V ESSO OSAKA according to the water depth. The results are also compared with experimental data. Finally, the sway added mass of hydrodynamic coefficients for T/S HANNARA is suggested in each water depth.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.8 s.239
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• pp.911-920
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• 2005

The present study investigates heat/mass transfer and flow characteristics in a ribbed rotating passage with turning region. The duct has an aspect ratio (W/H) of 0.5 and a hydraulic diameter ($D_h$) of 26.67 mm. Rib turbulators are attached in the parallel arrangement on the leading and trailing surfaces of the passage. The ribs have a rectangular cross section of 2 m (e) $\times$ 3 m (w) and an attack angle of $70^{\circ}$. The pitch-to-rib height ratio (p/e) is 7.5, and the rib height-to-hydraulic diameter ratio (e/$D_h$) is 0.075. The rotation number ranges from 0.0 to 0.20 while the Reynolds number is constant at 10,000. To verify the heat/mass transfer augmentation, internal flow structures are calculated for the same conditions using a commercial code FLUENT 6.1. The results show that a pair of vortex cells are generated due to the symmetric geometry of the rib arrangement, and heat/mass transfer is augmented up to $Sh/Sh_0=2.9$ averagely, which is higher than that of the cross-ribbed case presented in the previous study for the stationary case. With the passage rotation, the main flow in the first-pass deflects toward the trailing surface and the heat transfer is enhanced on the trailing surface. In the second-pass, the flow enlarges the vortex cell close to the leading surface, and the small vortex cell on the trailing surface side contracts to disappear as the passage rotates faster. At the highest rotation number ($R_O=0.20$), the turn-induced single vortex cell becomes identical regardless of the rib configuration so that similar local heat/mass transfer distributions are observed in the fuming region for the cross- and parallel-ribbed case.

• Journal of Biosystems Engineering
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• v.28 no.4
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• pp.305-314
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• 2003

The ROPS of an agricultural tractor is designed to protect its driver when the tractor overturns. Although the current OECD tests to determine whether the ROPS meets the requirements of the OECD regulation are desirable, they need long time to test. We experimental time and effort by using CAE. We conducted a finite element analysis for the ROPS design of a Dae-Dong tractor cabin in an attempt to reduce the design and manufacturing time. This study shows the interpretative skill using MARC(v.2000) for designing ROPS and difference between the results of testing and FEA. Design process is generally divided into two phases: a concept and a detail design. The concept design uses simple analysis to predict structural behavior, whereas the detail design involves a finite element analysis performed by the results of the concept design. This study focused on the detail design and used Patran(v.2000r2) and MARC(v.2000) of the MSC software corporation. The model consisted of 4812 elements and 4582 nodes. Four tests. specified in the OECD standards, were performed: (1) longitudinal loading test (2) rear crushing test (3) side loading test (4), and front crushing test. Independent analyses were also performed for each test, along with a sequential analysis. When compared, the results of the independent and sequential analyses were found to be similar to the test results.

• Journal of the Korean Society for Railway
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• v.13 no.3
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• pp.271-277
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• 2010

In this paper, a numerical model for a Kevlar/Epoxy and Carbon-Kevlar/Epoxy tube used as an energy absorbing component has been developed and then results have been verified through experiment. The 2D shell element and Chang-Chang failure criterion of LS-DYNA that is commercial explicit FE code was used. Mechanical material properties for the model were obtained by material testing in advance. The numerical results were compared with quasi-static test results under axial compressive loading at 10mm/min. From the results, in the case of the Kevlar/Epoxy tube, load-crushed displacement curves were very close to the experiments and SEA (specific energy absorption) shows a good agreement with experimental one within less than 6%. However, the Carbon-Kevlar/Epoxy tube shows some differences with the experimental results.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.11
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• pp.751-760
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• 2007

Baffles enhance heat transfer by disturbing boundary layer and bulk flow, creating impingement, and increasing heat transfer surface area. This study was performed to determine how the two inclined baffles (${\alpha}=5^{\circ}$ perforated models) placed at a rectangular channel affect heat transfer and associated friction characteristics. The parametric effects of perforated baffles (3, 6 and 12 holes) and flow Reynolds number ranging from 28,900 to 61,800 on the heated target surface are explored. Comparisons of the experimental data with the numerical results by commercial code CFX 10.0 are presented. As for the investigation of heat transfer behaviors on local Nusselt number with two baffles placed at $x/D_h=0.8$ and $x/D_h=8.0$ of the edge of baffles, it is evident that the inclined perforated baffles augment overall heat transfer significantly by both jet impingement and boundary layer separation. There exists an optimum perforation density to maximize heat transfer coefficients; i.e., the average Nusselt number increases with increasing number of holes, but the friction factor decreases with an increase in the hole number placed at baffles.

• Journal of Broadcast Engineering
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• v.10 no.3
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• pp.340-347
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• 2005

This paper presents a polyphase down sampling based multiple description coding applied to H.264 video coding standard. For a given macroblock, a residual macroblock is calculated by motion estimation, and before applying DCT, quantization and entrophy coding of the H.264 coding process, the polyphase down sampling is applied to the residual macroblock to code in four separate descriptions. Experiments were performed for all the 9 test sequences of JVT SVC standardization in various packet loss patterns. Experimental results show that the proposed one gives 0.5 to 5 dB enhancement over an error-concealment based on the slice group map technolgoy.

• Steel and Composite Structures
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• v.13 no.6
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• pp.501-519
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• 2012

As an alternative to current conventional force-based assessment methods, the energy-based seismic performance of a code-designed 20-storey high-rise steel building is evaluated in this paper. Using 3D nonlinear dynamic time-history method with consideration of additional material damping effect, the influences of different restoring force models and P-${\Delta}/{\delta}$ effects on energy components are investigated. By combining equivalent viscous damping and hysteretic damping ratios of the structure subjected to strong ground motions, a new damping model, which is amplitude-dependent, is discussed in detail. According to the analytical results, all energy components are affected to various extents by P-${\Delta}/{\delta}$ effects and a difference of less than 10% is observed; the energy values of the structure without consideration of P-${\Delta}/{\delta}$ effects are larger, while the restoring force models have a minor effect on seismic input energy with a difference of less than 5%, but they have a certain effect on both viscous damping energy and hysteretic energy with a difference of about 5~15%. The paper shows that the use of the hysteretic energy at its ultimate state as a seismic design parameter has more advantages than seismic input energy since it presents a more stable value. The total damping ratio of a structure consists of viscous damping ratio and hysteretic damping ratio and it is found that the equivalent viscous damping ratio is a constant for the structure, while the equivalent hysteretic damping ratio approximately increases linearly with structural response in elasto-plastic stage.

• Nuclear Engineering and Technology
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• v.25 no.2
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• pp.193-203
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• 1993

A new heuristic method for loading pattern search has been developed to overcome short-comings of the algorithmic approach. To reduce the size of vast solution space, general shuffling rules, a regionwise shuffling method, and a pattern grouping method were introduced. The entropy theory was applied to classify possible loading patterns into groups with similarity between them. The pattern search program was implemented with use of the PROLOG language. A two-group nodal code MEDIUM-2D was used for analysis of power distribution in the core. The above mentioned methodology has been tested to show effectiveness in reducing of solution space down to a few hundred pattern groups. Burnable poison rods were then arranged in each pattern group in accordance with burnable poison distribution rules, which led to further reduction of the solution space to several scores of acceptable pattern groups. The method of maximizing cycle length(MCL) and minimizing power-peaking factor(MPF) were applied to search for specific useful loading patterns from the acceptable pattern groups. Thus, several specific loading patterns that have low power-peaking factor and large cycle length were successfully searched from the selected pattern groups.