• Journal of Radiation Protection and Research
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• v.30 no.1
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• pp.39-44
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• 2005

A new developing reactor isn't fixed the structure and the materials of reactor components. To perform the shielding analysis for a reactor vessel by $R-\theta$ geometry, it takes much effort and time to modeling of source term according to the change of reactor components every time. Therefore, we developed the shielding analysis system for the reactor vessel by $R-{\theta}$ geometry, which wasn't affected by the reactor core geometry. By using the developed shielding analysis system, we performed the shielding analysis for the reactor vessel of an integral reactor which has the hexagonal geometry of nuclear fuel assemblies in reactor core. We compared the results obtained from the developed system with those obtained from MCNP analysis. Because the results of developed shielding analysis system were more conservative than those of MCNP calculation, it is useful for shielding analysis. As we had developed the new shielding analysis system for a reactor vessel by $R-{\theta}$ geometry, we reduced error of model for reactor core which was formerly designed by hand and saved the time and the effort to design source term model of reactor core.

• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.1073-1082
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• 2003

Many researchers have investigated the blood flow characteristics through bileaflet mechanical heart valves using computational fluid dynamics (CFD) models. Their numerical approach methods can be classified into three types; steady flow analysis, pulsatile flow analysis with fixed leaflets, and pulsatile flow analysis with moving leaflets. The first and second methods have been generally employed for two-dimensional and three-dimensional calculations. The pulsatile flow analysis interacted with moving leaflets has been recently introduced and tried only in two-dimensional analysis because this approach method has difficulty in considering simultaneously two physics of blood flow and leaflet behavior interacted with blood flow. In this publication, numerical calculation for pulsatile flow with moving leaflets using a fluid-structure interaction method has been performed in a three-dimensional geometry. Also, pulsatile flow with fixed leaflets has been analyzed for comparison with the case with moving leaflets. The calculated results using the fluid-structure interaction model have shown good agreements with results visualized by previous experiments. In peak systole. calculations with the two approach methods have predicted similar flow fields. However, the model with fixed leaflets has not been able to predict the flow fields during opening and closing phases. Therefore, the model with moving leaflets is rigorously required for advanced analysis of flow fields.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.391-394
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• 2005

In this paper, we present an approach that is able to reconstruct 3 dimensional metric models from un-calibrated images acquired by a freely moved camera system. If nothing is known of the calibration of either camera, nor the arrangement of one camera which respect to the other, then the projective reconstruction will have projective distortion which expressed by an arbitrary projective transformation. The distortion on the reconstruction is removed from projection to metric through self-calibration. The self-calibration requires no information about the camera matrices, or information about the scene geometry. Self-calibration is the process of determining internal camera parameters directly from multiply un-calibrated images. Self-calibration avoids the onerous task of calibrating cameras which needs to use special calibration objects. The root of the method is setting a uniquely fixed conic(absolute quadric) in 3D space. And it can make possible to figure out some way from the images. Once absolute quadric is identified, the metric geometry can be computed. We compared reconstruction image from calibrated images with the result by self-calibration method.

• Journal of KIBIM
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• v.5 no.2
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• pp.46-54
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• 2015

Vision-based tracking has been proposed as a means to efficiently track a large number of construction resources operating in a congested site. In order to obtain 3D coordinates of an object, it is necessary to employ stereo-vision theories. Detecting and tracking of multiple objects require an entity matching process that finds corresponding pairs of detected entities across the two camera views. This paper proposes an efficient way of entity matching for tracking of construction workers. The proposed method basically uses epipolar geometry which represents the relationship between the two fixed cameras. Each pixel coordinate in a camera view is projected onto the other camera view as an epipolar line. The proposed method finds the matching pair of a worker entity by comparing the proximity of the all detected entities in the other view to the epipolar line. Experimental results demonstrate its suitability for automated entity matching for 3D vision-based tracking of construction workers.

• ETRI Journal
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• v.42 no.5
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• pp.712-720
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• 2020

Recently, to make the best use of limited and precious spectrum resources, spectrum sharing between satellite and cellular networks has received much interest. In this study, we mathematically analyze the success probability of a fixed (satellite) earth station (FES) based on a stochastic geometry framework. Both the FES and base stations (BSs) are assumed to be equipped with a directional antenna, and the location and the number of BSs are modeled based on the Poisson point process. Furthermore, an exclusion zone is considered, in which the BSs are prohibited from locating in a circular zone with a certain radius around the FES to protect it from severe interference from the cellular BSs. We validate the analytical results on the success probability of the cognitive satellite-terrestrial network with directional antennas by comparing it using extensive computer simulations and show the effect of the exclusion zone on the success probability at the FES. It is shown that the exclusion zone-based interference mitigation technique significantly improves the success probability as the exclusion zone increases.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.1
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• pp.78-87
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• 2014

Recently the offshore wind turbine development is requested to be installed off south-west coast and Jeju island in Korea. Reliable and robust support structures are required to meet the demand on the offshore wind turbine in harsh and rapidly varying environmental conditions. Monopile is the most preferred substructure in shallow water with long term experiences from the offshore gas and oil industries. This paper presents an optimum design of a monopile connection with grouted transition piece (TP) for the reliable and cost-effective design purposes. First, design loads are simulated for a 5 MW offshore wind turbine in site conditions off the southwest coast of Korea. Second, sensitivity analysis is performed to investigate the design sensitivity of geometry and material parameters of monopile connection based on the ultimate and fatigue capacities according to DNV standards. Next, optimization is conducted to minimize the total mass and resulted in 30% weight reduction and the optimum geometry and material properties of the monopile substructure of the fixed offshore wind turbine.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.6
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• pp.2838-2858
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• 2019

Traditional channel models for vehicle-to-vehicle (V2V) communication usually assume fixed velocity in static scattering environment. In the realistic scenarios, however, time-variant velocity for V2V results in non-stationary statistical properties of wireless channels. Dynamic scatterers with random velocities and directions have been always utilized to depict the non-stationary statistical properties of the channel. In this paper, a non-stationary geometry-based cooperative scattering channel model is proposed for multiple-input multiple-output (MIMO) V2V communication systems, where a birth-death process is used to capture the appearance and disappearance dynamic properties of moving scatterers that reflect the time-variant time correlation and Doppler spectrum characteristics. Moreover, our model has more straight and concise to study the impact of the vehicular traffic density on channel characteristics and thus avoid complicated procedure in deriving the analytical expressions of the channel parameters and functions. The numerical results validate our analysis and demonstrate that setting important parameters of our model can appropriately build up more purposeful measurement campaigns in the future.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.5
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• pp.448-454
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• 2019

This paper presents a high-efficiency design technique for developing the serialized models of a single-channel pump based on the diameter, flow rate and head as the main performance parameters. The variation in pump performance by changing of the single-channel pump geometry was predicted based on computational fluid dynamics (CFD). Numerical analysis was conducted by solving three-dimensional steady Reynolds-averaged Navier-Stokes equations with the shear stress transport (SST) turbulence model. The tendencies of the hydraulic performance depending on the pump geometry scale were analyzed with the fixed rotational speed. These performances were expressed and evaluated as the functionalization for designing the serialized models of a single-channel pump in this work.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.397-401
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• 2008

Knowledge of dynamic characteristics of structural elements often can make difference between success and failure in the design of structure due to resonance effect. In this paper an analytical model of a cantilever beam having midpoint load is considered for structural optimization. This involves creating the geometry which allows parametric study of all design variables. For that purpose optimization of cantilever beam is elaborated in order to find the optimum geometry which minimizes its volume eventually for minimum weight using ANSYS. But such geometry could be obtained by different combinations of width and height, so that it may have the same cross sectional area yet different dynamic behavior. So for optimum safe design, besides minimum volume it should have minimum vibration as well. In order to predict vibration different dynamic analyses are performed simultaneously to solve the eigenvalues problem assuming no damping initially through MATLAB simulations using state space form for modal analysis, which identifies the resonant frequencies and mode shapes belonging to the lowest three modes of vibration. And next by introducing damping effects tip displacement, bending stress and the vertical reaction force at the fixed end is evaluated under some dynamic load of varying frequency, and finally it is discussed how resonance can be avoided for particular design. Investigation of results clearly shows that only structural analysis is not enough to predict the optimum values of dimension for safe design. Potentially this technique will meet maintenance and cost goals of many organizations particularly for the application where dynamic loading is invertible and helps a lot ensuring that the proposed design will be safe for both static and dynamic conditions.

• Fire Science and Engineering
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• v.27 no.3
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• pp.20-29
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• 2013

To investigate numerically the effects of geometry and location of vertical opening on the thermal and chemical fire characteristics in full-scale under-ventilated compartment fires, the ventilation factor ($A\sqrt{h}$) to estimate a theoretical maximum inflow of ambient air and the mass loss rate in a heptane pool fire were fixed for all cases. It was shown that variations in door geometry affected significantly the change in thermal and chemical characteristics inside the compartment. Variations in window location resulted in the complex change in additional fire characteristics including the fire duration time and recirculating flow structure. These results were analyzed in details by the multi-dimensional flow and fire characteristics including the vent flow and fuel/air mixing phenomena.