• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.2
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• pp.171-178
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• 2015

This research is the first research on developing the speed limit select model and also it is the result of the research on the importance of each element and consideration factors when selecting the speed limit. For the consideration factor discrimination and calculation of the importance, the delphi method and AHP method was used. The delphi survey was processed through third round survey, 5 high consideration factor(Level 1) and 23 low consideration factor(Level 2) was discriminated. During the process of the third delphi survey, when the CVR cost was in the range between 0.4~1.0 it was treated as the consideration factor when selecting the speed limit and less than 0.4 cost was eliminated. In the process of the second delphi survey, 33 consideration factors were discriminated but was reordered into 23 categories through the third survey. Based on the 23 categories earned through the third delphi analysis, the AHP survey was processed. The result of the AHP survey was that out of the importance of the 5 high consideration factor(Level 1), the traffic condition was evaluated as the number one factor and the vessel condition, waterway condition, environment condition, supporting condition and etc. conditions were evaluated following the traffic condition. Out of the 23 low consideration factor(Level 2) consideration, the visibility was evaluated to be the first important and the performance of the vessel steering, objective factors within the harbor, amount of traffic and density, distance between the passing vessel, speed of the steering capacity and tidal current were the following evaluated factors.

• The KIPS Transactions:PartB
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• v.10B no.4
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• pp.373-380
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• 2003

Most of low cost digital cameras reveal relatively high lens distortion. The purpose of this research is to compensate the degradation of image quality due to the geometrical distortion of a lens system. The proposed method consists of two stages : calculation of a lens distortion coefficient by a simplified version of Tsai´s camera calibration and subsequent image warping of the original distorted image to remove geometrical distortion based on the calculated lens distortion coefficient. In the lens distortion coefficient calculation stage, a practical method for handling scale factor ratio and image center is proposed, after which its feasibility is shown by measuring the performance of distortion correction using a quantitative image quality measure. On the other hand, in order to apply image warping via inverse spatial mapping using the result of the lens distortion coefficient calculation stage, a cubic polynomial derived from an adopted radial distortion lens model must be solved. In this paper, for the purpose of real-time operation, which is essential for embedding into an information device, an approximated solution to the cubic polynomial is proposed in the form of a solution to a quadratic equation. In the experiment, potential for real-time implementation and equivalence in performance as compared with that from cubic polynomial solution are shown.

• Journal of Korean Society of Transportation
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• v.17 no.4
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• pp.47-58
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• 1999

The Purpose of this Paper is to develop a multi-period bus scheduling model, in which a decomposition technique is applied. In general a bus scheduling requires a vast amount of calculation. Thus, a bus scheduling is a very complicated problem even with a single depot and is almost unable to obtain the optimal solution theoretically with many depots. In this paper in order to simplify the problem, the whole operating hours of a day are partitioned into several time periods. In one period, the same headways are maintained. For one period, the bus scheduling is simple and the solution applying the FIFO(First-In, First-Out) Principle is the optimal. However, connection between Periods remains as another scheduling Problem with a reduced problem size. This paper suggests how to connect bus schedules of consecutive periods efficiently, minimizing the operating cost. Through case studies for multiple routes with a single depot, this decomposition technique is proved to be effective practically.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1062-1073
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• 2007

Acoustic Target Strength (TS) is a major parameter of the active sonar equation, which indicates the ratio of the radiated intensity from the source to the re-radiated intensity by a target. In developing a TS equation, it is assumed that the radiated pressure is known and the re-radiated intensity is unknown. This research provides a TS equation for polygonal plates, which is applicable to near field acoustics. In this research, Helmholtz-Kirchhoff formula is used as the primary equation for solving the re-radiated pressure field; the primary equation contains a surface (double) integral representation. The double integral representation can be reduced to a closed form, which involves only a line (single) integral representation of the boundary of the surface area by applying Stoke's theorem. Use of such line integral representations can reduce the cost of numerical calculation. Also Kirchhoff approximation is used to solve the surface values such as pressure and particle velocity. Finally, a generalized definition of Sonar Cross Section (SCS) that is applicable to near field is suggested. The TS equation for polygonal plates in near field is developed using the three prescribed statements; the redection to line integral representation, Kirchhoff approximation and a generalized definition of SCS. The equation developed in this research is applicable to near field, and therefore, no approximations are allowed except the Kirchhoff approximation. However, examinations with various types of models for reliability show that the equation has good performance in its applications. To analyze a general shape of model, a submarine type model was selected and successfully analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11C
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• pp.1077-1084
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• 2006

This paper proposed a fast algorithm to reduce the amount of calculation for inter prediction which takes a great deal of the operational time in H.264/AVC. This algorithm decides a search range according to the direction of predicted motion vector, and then performs an adaptive spiral search for the candidates with JM(Joint Model) FME(Fast Motion Estimation) which employs the rate-distortion optimization(RDO) method. Simultaneously, it decides a threshold cost value for each of the variable block sizes and performs the motion estimation for the variable search ranges with the threshold. These activities reduce the great amount of the complexity in inter prediction encoding. Experimental results by applying the proposed method .to various video sequences showed that the process time was decreased up to 80% comparing to the previous prediction methods. The degradation of video quality was only from 0.05dB to 0.19dB and the compression ratio decreased as small as 0.58% in average. Therefore, we are sure that the proposed method is an efficient method for the fast inter prediction.

• Journal of Korean Society for Geospatial Information Science
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• v.19 no.4
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• pp.71-80
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• 2011

A simple and an improved methods for the assessment of flood damage were used in previous studies, and the Multi-Dimensional Flood Damage Assessment (MD-FDA) has been applied since 2004 in Korea. This study evaluated flood damage of dam downstream using considering MD-FDA method based on GIS data. Firstly, flood water level with FLDWAV (Flood Wave routing) model was input into cross section layer based on enforcement drainage algorithm, water depth grid data were created through spatial calculation with DEM data. The value of asset of building and agricultural land according to local government was evaluated using building layer from digital map and agricultural land map from landcover map. Also, itemized flood damage was calculated by unit price to building shape, evaluated value of housewares to urban type, unit cost to crop, tangible and inventory asset of company connected with building, agricultural land, flooding depth layer. Flood damage in rainfall frequency of 200 year showed 1.19, 1.30 and 1.96 times to flood damage in rainfall frequency of 100 year, 50 year and 10 year respectively by flood damage analysis.

• Journal of Biomedical Engineering Research
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• v.41 no.3
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• pp.128-137
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• 2020

Cardiac electrophysiology studies often use simulation to predict how cardiac will behave under various conditions. To observe the cardiac tissue movement, it needs to use the high--resolution heart mesh with a sophisticated and large number of nodes. The higher resolution mesh is, the more computation time is needed. To improve computation speed and performance, parallel processing using multi-core processes and network computing resources is performed. In this study, we compared the computational speeds of CPU parallelization and GPU parallelization in virtual heart simulation for efficiently calculating a series of ordinary differential equations (ODE) and partial differential equations (PDE) and determined the optimal CPU and GPU parallelization architecture. We used 2D tissue model and 3D ventricular model to compared the computation performance. Then, we measured the time required to the calculation of ODEs and PDEs, respectively. In conclusion, for the most efficient computation, using GPU parallelization rather than CPU parallelization can improve performance by 4.3 times and 2.3 times in calculations of ODEs and PDE, respectively. In CPU parallelization, it is best to use the number of processors just before the communication cost between each processor is incurred.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.352-359
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• 2001

We propose the row method that is able to consider the SAR compliance test from the very beginning step of developing the mobile phone. The reason this new method is plausible is that we adopt the certified FDTD for the reliability of calculation, utilizing 1 mm high resolution model that is to model the phantom and the mobile phone almost identically to the reality. In this paper we introduce the process that will apply the proposed method in order to reduce the SAR of the mobile phone that has been problematic in satisfying the SAR compliance test. It results in dropping in the SAR that we keep the mobile phone or its antenna while we use it. Therefore here we make a claim as fellows. When we develop the new mobile phone, we should use the computer simulation combining the CAD design and radiation pattern rather than make a prototype and then use the trial and error method. Moreover the former way leads us to boost up the developing efficiency and reduce the cost.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.2
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• pp.169-173
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• 2010

Because of power consumption increase, global warming, and limitation of installation, not only high reliability and interruption capability but also compact and light power apparatuses are needed. In this paper, E field calculation and experiment were processed to identify the influence of the shape of end shield and gap distance. It is expected that the results of FEM simulation and experiments could be the basic data to develop VI. the results of FEM simulation and experiments are as following. Firstly, maximum E fields were compared by means of finite element method as a function of the shape of end shield. 3 types of models were used to analyze maximum E field of each model and the influence of shape of shield could be identified. As a result, proposed L type shield could reduce the maximum E field by 20%. Secondly, the influence of the gap distance between end shields on E field was analyzed. As the gap distance become short the gap distance between inner walls of ceramic also become short. And the maximum E field concentrated on inner wall of ceramic finally increased. Thirdly, the experiment was conducted by fabricating each prototype. As a result, no creepage occurred in shieldless model. In other words, creepage occurred in the shield-installed models. And creepage inception voltages were different from each other because of the difference of maximum E field. Fourthly, The equation that shows relation between calculated E field and measured creepage inception voltage was proposed as a result of FEM analysis and experiment. It is concluded that when designing VI this equation could be important data to reduce time and cost by identifying indirectly the optimal gap distance and the shape of shield required to prevent creepage.

• Journal of Internet Computing and Services
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• v.15 no.2
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• pp.41-47
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• 2014

In this paper, we implemented a CUDA Fortran parallel program to run the CFD_NIMR model on GP-GPU's, which simulates air diffusion on urban terrains. A GP-GPU is graphic processing unit in the form of a PCI card, and a general calculation accelerator to perform a large amount of high speed calculations with low cost and electric power. The GP-GPU gives performance enhancement of speed by 15 times to compare the Nvidia Tesla C1060 GPU with Intel XEON 2.0 GHz CPU. In addition, the program on a GP-GPU shows efficient performance compared to an MPI parallel program on multiple CPU's. It is expected that a proposed programming method on the GP-GPU parallel program can be used for numerical models with a similar structure.