• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.4
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• pp.489-494
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• 2013

In analysis of power transformer loss using calculation of magnetic field, Finite element method is commonly used. When using this method, calculation of magnetic field needs the very large number of elements and the performance of common work station is not sufficient to calculate the magnetic fields. In addition, the definition of boundary conditions may arise. However, When using Integral equation method, only ferromagnetic materials need to be modeled, since the domain is infinite. All the space in which the primary and secondary sources exist is regarded as free(${\mu}={\mu}_0$).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.11
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• pp.1089-1096
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• 2010

The relation between the vibration induced from machinery and the radiated sound is complicated. Acoustic intensity method is widely used to obtain the accuracy of noise measurement and noise identification. In this study, as groundwork, the complex acoustic intensity method is performed to identify noise source and transmission path on different free space point source fields. As an industrial application, the complex acoustic intensity method is applied to HVAC to identify sound radiation characteristics in the near field. Experimental complex acoustic intensity method was applied to HVAC, it is possible to identify noise sources in complicated sound field characteristics which noise sources are related with each other, and certificate the validity of complex acoustic intensity. Especially, it can be seen that complex acoustic intensity method using both of active and reactive intensity is vital in devising a strategy for identification of noise. Also, the vector flow of acoustic intensity was investigated to identify sound intensity distributions and energy flow in the near field of HVAC.

• Journal of KIISE:Computing Practices and Letters
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• v.6 no.4
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• pp.411-420
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• 2000

The performance of soft handoffs of CDMA mobile communication systems is potentially determined by several factors such as handoff-related system parameters (T_ADD, T_DROP, T_COMP, T_TDROP), mobile stations' mobility, service areas, capacity of base stations. Due to the importance of handoffs in mobile communications, several methods have been proposed and tested through computer simulations to prove the efficiency of proposed methods. Different assumptions on the above mentioned factors often produce different simulation results. Therefore, the credibility of a simulation result is directly determined by the objectivity of the assumptions made by the simulation. This paper proposes a new soft handoff method that controls handoff delay time based on a mobile station's speed, and compares it with the current method of CDMA systems. The simulation results showed that the new method is much more efficient for mobile stations that are free in their moving direction and space than for those restricted in their moving direction and space. In addition, the results showed that even the same handoff method may produces different simulation results depending on whether a service area is modeled as two-dimensional space or three-dimensional space. These results indicate the importance of suitable models of user mobility, especially the movement types and space allowed for mobile stations, which have been neglected in simulation studies of mobile communications.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.142-145
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• 2005

Since the successful launch of FORMOSAT -2 satellite by National Space Organization of Taiwan in May 2004, the Remote Sensing Instrument (RSI) on- board the FORMOSAT -2 has continuously acquired images at one panchromatic and four multi-spectral bands (http://www.nspo.org.tw). In general, the RSI performs well and receives high quality images which proved to be very useful for various applications. However, some RSI panchromatic products exhibit obvious trembling artifact that must be removed. Preliminary study reveals that the trembling artifact is caused by the instability of the spacecraft attitude. Though the magnitude of this artifact is actually less than half of a pixel, it affects the applicability of panchromatic products. A procedure removing this artifact is therefore needed for providing image products of consistent quality. Due to the nature of trembling artifact, it is impossible to describe the trembling amount by employing an analytic model. Relied only on image itself, an algorithm determining trembling amount and removing accordingly the trembling artifact is proposed. The algorithm consists of 3 stages. First, a cross-correlation based scheme is used to measure the relative shift between adjacent scan lines. Follows, the trembling amount is estimated from the measured value. For this purpose, the Fourier transform is utilized to characterize random shifts in frequency domain. An adaptive estimation method is then applied to deduce the approximate trembling amount. In the subsequent stage, image re-sampling operation is applied to restore the trembling-free product. Experimental results show that by applying the proposed algorithm, the unpleasant trembling artifact is no longer evident.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.728-731
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• 2007

Though the Hough transform is a well-known method for detecting analytical shape represented by a number of free parameters, the basic property of the Hough transform, the one-to-many mapping from an image space to a Hough space, causes the innate problem, the sensitivity to noise. To remedy this problem, Edge Strength Hough Transform (ESHT) was proposed and proved to reduce the noise sensitivity. However the performance of ESHT depends on the size of a Hough space and image and some other parameters, which play an important role in ESHT and should be decided experimentally. In this paper, we derived a formula to decide decreasing parameter. Using the derived formulae, the decreasing parameter value can be decided only with the pre-determined values, the size of a Hough space and an image, which make it possible to decide them automatically.

• Journal of KIISE
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• v.43 no.9
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• pp.1026-1033
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• 2016

Path-finding on a grid map is a problem generally addressed in the fields of robotics, intelligent agents, and computer games. As technology advances, virtual game worlds tend to be represented more accurately and more realistically, resulting in an excessive increase in the number of grid tiles and in path-search time. In this study, we propose a path-finding algorithm that allows a prompt response to real-time queries by constructing a reduced state space and by precomputing all possible paths in an offline preprocessing stage. In the preprocessing stage, we vertically decompose free space on the grid map, construct a connectivity graph where nodes are the decomposed regions, and store paths between all pairs of nodes in matrix form. In the real-time query stage, we first find the nodes containing the query points and then retrieve the corresponding stored path. The proposed method is simulated for a set of maps that has been used as a benchmark for grid-based path finding. The simulation results show that the state space and the search time decrease significantly.

• Journal of Chest Surgery
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• v.18 no.4
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• pp.822-834
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• 1985

Reexpansion of the lung is the most desirable method of filling the pleural space whether it`s contents may be, and closed thoracotomy connected to a water-seal drainage remains the basic therapeutic modality in the treatment of the problems of the pleural space. We usually used rubber mushroom tubes, size No. from 16 to 34 Fr., and performed closed thoracotomy after preliminary thoracentesis to determine the exact depending position. Author reviewed 576 cases of closed thoracotomy which were performed in the Department of Thoracic and Cardiovascular Surgery, Pusan National University Hospital, since Jan., 1980 to June, 1984. The results were as follows: 1. The age distribution was 10 days to 76 years old and mean age of the patients was 36.6 year, and the most prevalent age group was twenties, and sex predisposition was male dominant, 86.9%. 2. The most common etiologic disease group was pneumothorax and the most common etiologic disease was traumatic hemothorax. 3. Sites of tubing were predominantly at posterior axillary line, 7th intercostal space and midclavicular line, 2nd intercostal space even though frequent presence of free pleural space. The two sides, right and left difference of occurrence rate was more frequent at right side, 51.2%. 4. Usually the durations of tubing was less than 10 days, 52.6%, and the number of tubes used to the same patient concomitantly was one, 73.9%, and the time of tubing to the same patient was 1st, 83.6%. 5. The common symptom and sign were dyspnea, 50.0%, chest pain, 30.7%, cough, 10.7%, fever, 6.5%. Especially, fever and cough was the most common symptom and sign in pyogenic empyema, 59.3%. 6. The common etiologic lesions of pneumothorax were blebs and bullae, 73.3%, and of pyogenic empyema was pneumonia, 69.0%. 7. The complication rate of closed thoracotomy was 26.0%. Among these complications, infection was 44.7%, and intercostal neuralgia was 25.3%. 8. 70.9% of all patients recovered with only closed thoracotomy and the rest of patient needed additional some necessary managements such as open thoracotomy [Blebectomy, Resection, Pleurodesis, Decortication, Bleeding control], open drainage, thoracoplasty and so on to have successful results.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.5
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• pp.575-581
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• 2007

Though the Hough transform is a well-known method for detecting analytical shape represented by a number of free parameters, the basic property of the Hough transform, the one-to-many mapping from an image space to a Hough space, causes the innate problem, the sensitivity to noise. To remedy this problem, Edge Strength Hough Transform (ESHT) was proposed and proved to reduce the noise sensitivity. However the performance of ESHT depends on the size of a Hough space and image and some other parameters which should be decided experimentally. In this paper, we derived formulae to decide 2 parameter values; decreasing parameter and broadening parameter, which play an important role in ESHT. Using the derived formulae, 2 parameter values can be decided only with the pre-determined values, the size of a Hough space and an image, which make it possible to decide them automatically. The experiments with different parameter values also support the result.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.906-915
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• 2009

To study the plume effects in the vacuum area, the Direct Simulation Monte Carlo(DSMC) method is usually adopted because the plume field usually contains the entire range of flow regime from the near-continuum in the vicinity of nozzle exit through transitional state to free molecular at far field region from the nozzle. The objective of this study is to investigate the behaviors of a small monopropellant thruster plume in the vacuum area numerically using DSMC method. To deduce accurate results efficiently, the preconditioned scheme is introduced to calculate continuum flow fields inside thruster to predict nozzle exit properties used for inlet conditions of DSMC method. By combining these two methods, the vacuum flow characteristics of plume such as strong nonequilibrium near nozzle exit, large back flow area, etc, can be investigated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.3
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• pp.177-182
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• 2007

The effects of three fuselage head shapes and nonplanar ground surface on the aerodynamic characteristics of FAST fuselages are investigated using a boundary element method. Wind tunnel test is also performed to validate the present method and to identify the wall effect on the frictional drag which cannot be analyzed using the present method. It is found that the channel has an effect of increasing the lift of those investigated fuselages. The optimal head shape depends on the design conditions of the FAST and its guideway channel. Comparing the calculated induced drag with the measured total drag, it can be concluded that the profile drag is independent of the ground height. Thus, the present numerical method can be applied to the conceptual design of the high-speed ground transporters if only the profile drag of the vehicle in free flight is assumed to be known.