• Journal of Ocean Engineering and Technology
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• 제15권2호
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• pp.11-21
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• 2001

The focus of this paper is on the numerical investigation of obliquely incident wav interactions with a system composed of fully submerged and floating dual buoy/vertical-flexible-membrane breakwaters placed in parallel with spacing between two systems. The fully submerged two systems allow surface and bottom gaps to enable wave transmission over and under the system. The problem is formulated based on the two-dimensional multi-domain hydro-elastic linear wave-body interaction theory. The hydrodynamic interaction of oblique incident waves with the combination of the rigid and flexible bodies was solved by the distribution of the simple sources (modified Bessel function of the second kind) that satisfy the Helmholz governing equation in fluid domains. A boundary element program for three fluid domains based on a discrete membrane dynamic model and simple source distribution method is developed. Using this developed computer program, the performance of various dual systems varying buoy radiuses and drafts, membrane lengths, gaps, spacing, mooring-lines stiffness, mooring types, water depth, and wave characteristics is thoroughly examined. It is found that the fully submerged and floating dual buoy/membrane breakwaters can, if it is properly tuned to the coming waves, have good performances in reflecting the obliquely incident waves over a wide range of wave frequency and headings.

• The Korean Journal of Rehabilitation Nursing
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• 제8권2호
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• pp.149-156
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• 2005

Purpose: The purpose of this study was to analyze functional independence and need for home nursing care in stroke patients. Method: This was a descriptive study. The subjects comprised 117 stroke patients who were supposed to discharge in less than a week. The instruments used for this study were the functional independence measure(FIM) and the need assessment for home nursing care of stroke patients. The data were analyzed using frequency, mean, t-test, ANOVA, and Pearson correlation coefficient. Results: Pearson correlation analysis revealed that there were negative correlations between subcategories of the FIM and the need for home nursing care in stroke patients. Especially, in case of the subjects who recorded lower scores at self-care they showed higher needs for home nursing care in the domain of physical problem and rehabilitation. Conclusion: For the operation of the home nursing care, the protocol for home nursing care is needed to the stroke patients living at home. The FIM instrument is recommended as a useful scale in order to assess the disability for the stroke patients and the need for home nursing care because this one has correlation with the scale of need for home nursing care.

• The Bulletin of The Korean Astronomical Society
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• 제39권1호
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• pp.37.2-37.2
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• 2014

Gas in disk galaxies interacts nonlinearly with a underlying stellar spiral potential to form galactic spiral shocks. Numerical simulations typically show that these shocks are unstable to the wiggle instability, forming non-axisymmetric structures with high vorticity. While previous studies suggested that the wiggle instability may arise from the Kelvin-Helmholtz instability or orbit crowding of gas elements near the shock, its physical nature remains uncertain. It was even argued that the wiggle instability is of numerical origin, caused by the inability of a numerical code to resolve a shock that is inclined to numerical grids. In this work, we perform a normal-mode linear stability analysis of galactic spiral shocks as a boundary-value problem. We find that the wiggle instability originates physically from the potential vorticity generation at a distorted shock front. As the gas follows galaxy rotation, it periodically passes through multiple shocks, successively increasing its potential vorticity. This sets up a normal-mode that grows exponentially, with a growth rate comparable to the orbital angular frequency. We show that the results of our linear stability analysis are in good agreement with the those of local hydrodynamic simulations of the wiggle instability.

• Journal of the Korean housing association
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• 제4권2호
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• pp.33-43
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• 1993

The purpose of this study is to support satisfaction for reasonable management method to elevate the enhancement of management attitude and the satisfaction of management state for Multi-family Housing. This study was intended to find out variables which influence on the satifaction and attitude of resident to the management of Apartment, and to investigate variables influencing on the satisfaction and attitude of resident to the management of Apartment. In this study, survey research method is employed. The sample is taken from 336 APT. resident's living in Seoul, from 13th of Sep. to 20th of Sep, in 1993. Used statistica] method are Frequency, Percentage, 1-test, One-way Anova, Duncan-test, Multip]e Regression. The major finding were as follows: 1) The work of management of Multi-family Housing was classified into three type ; a)administration management b) maintenance management c) community-life control. 2) The management attitude of Apartment inhabitant is very high, especially .the attitude of maintenance management is the higest. But they disagree with the raise of management cost necessary to maintenance management. 3) The satisfaction of administration management, maintenance management, community-life control management is all low in the management condition of Apartment.'1'he management method of present Apartment shows a little problem.

• Journal of the Korean Society of Safety
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• 제7권2호
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• pp.71-79
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• 1992

This paper presents a least-square algorithms of lattice structures and their use for adaptive prediction of time series generated from the dynamic system. As the view point of adaptive prediction, a new method of Identification of dynamic characteristics by means of estimating the parameters of linear auto regressive model is proposed. The fast convergence of adaptive lattice algorithms is seen to be due to the orthogonalization and decoupling properties of the lattice. The superiority of the least-square lattice is verified by computer simulation, then predictor coefficients are computed from the linear sequential time data. For the application to the dynamic characteristic analysis of unknown system, the transfer function of ideal system represented in frquency domain and the estimated one obtained by predicted coefficients are compared. Using the proposed method, the damping ratio and the natural frequency of a dynamic structure subjected to random excitations can be estimated. It is expected that this method will be widely applicable to other technical dynamic problem in which estimation of damping ratio and fundamental vibration modes are required.

• Journal of the Korean Society of Safety
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• 제29권3호
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• pp.56-63
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• 2014

This study proposes a new control approach for efficient vibration suppression of two identical adjacent structures. The conventional control approach of two adjacent structures is to interconnect the two structures with passive, semi-active or active control devices. However, when the two adjacent structures are identical to each other, their dynamical behaviors such as frequency and damping properties are also the same. In this case, the interconnected control devices cannot exhibit the dissipative control forces on the both structures as expected since the relative displacements and velocities of the devices become close to zero. In other words, the interconnection method does not work for the twin structures as enough as expected. In order to solve this problem, we propose several new control approaches to effectively and efficiently reduce the identically-fluctuating responses of the adjacent structures with minimum control efforts. In order to demonstrate the proposed control systems, the proposed several control systems are optimally designed and their control performances are compared with that of the conventional optimal control system where each TMD(tuned mass damper) is installed in each structure for independent control purpose. The simulated results show that one of the proposed control systems(System 04) is able to guarantee enhanced control performance compared with the conventional system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 한국정보통신학회 2015년도 추계학술대회
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• pp.77-78
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• 2015

Image Binarization is essential process in the digital image processing for the read out of a one-dimensional barcode. Local threshold method is suitable for binarization of a bar code. However, It has problem that processing time is slower than other binarization algorithm. Also, It's results not appropriate If the image has a noise. In this paper, we propose the modification method for solve these problems. Proposed algorithm help to improve the speed of local thresholding method using average image. Also, we proposed a high frequency filter to one-dimensional barcode for improvement quality of binary image.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제62권6호
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• pp.762-766
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• 2013

Interest in Wireless Power Transmission (WPT) technology has been increasing worldwide recently. This trend is proved by commercialized products such as electric toothbrush, wireless razor, and wireless charger for mobile phone battery. Studies for enhancing the applicability of the technology have been continuously conducted. Currently the WPT technology is based on the technologies using microwave, inductively coupling, and magnetic resonance. In the meantime, development of the microwave-based WPT faces difficulty due to health hazards involved in the technology, and application of the WPT technology using inductively coupling is restricted by area due to the problem of transmission length. In comparison, the WPT technology using magnetic resonance draws attention in terms of efficiency and transmission length. In this study, the sending coil based on the WPT technology using magnetic resonance system was replaced with an HTS coil to enhance transmission efficiency. Since the HTS coil has a zero resistance, power transmission loss can be minimized. At the same time, size of the current density could be increased to 100 times or more than typical coils. In addition, through impedance matching of LC device, maximal resonance properties were induced and consequently, frequency selection quality characteristics or Q was enhanced. As a result, the WPT type using the HTS coil showed a longer transmission length and better transmission efficiency compared with the WPT type using typical coils.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• 제7권1호
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• pp.1-9
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• 2014

Fireworks are used in our country, most of U.S. equipment and software systems are old and outdated technology. If the Fireworks receives a signal, then the start of the pre-placed as the signal proceeds to the middle of a problem with the site manager directly turn off the power and turn on again. Manager, where it should be handled directly. So, in this paper, we researched a domestically developed technology to escape the reality that relies on foreign technology. Our technology should be suited the convenience, reliability and lower cost. This technology can generate revenue from overseas.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.752-760
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• 2018

In this paper, interior permanent magnet synchronous motor (IPMSM) design for sensorless drive, considering magnetic neutral point shift according to magnetic saturation, has been proposed. Sensorless control was divided into a method based on inductance and a method based on back induced voltage. Because induced voltage is very small at zero or low speed, error in rotor initial position estimation may occur. Using the ratio of saliency addresses this problem. When using high-frequency injections at low speed, the rotor's initial position is estimated at the smallest portion of the inductance. IPMSM has the minimum inductance at the d-axis. However, if magnetic saturation leads to magnetic neutral point variation, following the load current change, there is a change in the minimum point of inductance. In this case, it can lead to failure of initial rotor position estimation. As a result, it is essential that the blocking design has an inductance minimum point shift. As such, in this study, an IPMSM design method, by blocking magnetic neutral point change, has been proposed. After determining the inductance profile based on the finite element analysis (FEA), the results of proposed method were verified.