• Journal of the Korea Convergence Society
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• v.8 no.5
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• pp.179-184
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• 2017

The cage of a tapered roller bearing keeps the gap between the rollers, which prevents friction, wear and suppresses heating. The material of the cage is changing from metal to plastic for lightening the weight. If the cage is severely deformed due to resonance, the roller may not be able to roll and even get off the cage. In this paper, the dynamic characteristics of the cage is analyzed according to the cage material. Under the assumption that a train runs at the highest speed, frequency harmonics of that speed is calculated, and the comparative analysis is carried out in order to select the optimum thickness of the cage, which is easy to change among the cage design variables for avoiding the resonance.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.1
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• pp.41-49
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• 1999

This paper describes to analyze the underwater ambient noise and biological noise of cultivating fishes in the fish farm cages at the seawater Tongyong-kun, KyongNam and lake of Chungju, Chech'on, ChungBuk from 10 to 19 Oct. 1997, in order to find out the characteristics of these noises. The results obtained were as follows; (1) The ambient noise around the fish farm cages at lake of Chungju was 10~200Hz frequency range, 70~105dB spectrum level. The central frequency was 50~70Hz, changing of ambient noise was getting bigger than 10~200Hz in 200Hz~2kKz frequency by wind, water current. (2) The frequency of noise source around the fish farm cage at the seawater of Tongyong-kun was 20~200Hz, spectrum level was 80~100dB while feed factory was working around the fish farm cage. When feed factory did not work, noise source was 10~600Hz frequency range, 70~90dB spectrum level. It was 10dB less than that of while feed factory was working, and then the central frequency was 70Hz. (3) The vessel noise of excursion ship had changed largely at 100dB spectrum level in 10~500Hz frequency band, and the fishing boat had 20Hz~2kHz frequency range. (4) The biological noise in the fish farm cage at lake of Chungju, which was feeding of Cyprinus carpio, 2was 10~30Hz frequency, 70~104dB spectrum level. The central frequency was 75Hz. The biological noises in the fish farm cage at the seawater of Tongyong-kun, which were feeding and swimming noise, had very different spectrum pattern by species, and the frequency band was 10~800Hz.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.464-469
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• 2019

Tapered roller bearings are used widely in vans, trucks, and trains because they can support the vehicle in a stable manner even under a heavy load. The cage of a tapered roller bearing maintains the gap between the rollers, which prevents friction wear and suppresses heating. If the cage is severely deformed due to resonance, the roller may not be able to roll smoothly and even leave the cage. Consequently, it is very important to analyze the dynamic characteristics of the cage for reliable performance of a bearing. The cage essentially has geometrical tolerance in the manufacturing process. In this paper, the effects of those geometrical imperfections on the dynamic characteristics of the cage were investigated. As a result, natural frequency separation occurred near the natural frequency of the ideal cage due to geometrical imperfections. In addition, the interval was proportional to the magnitude of the geometric error, and the interval increased with increasing mode number.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.241-247
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• 2014

This paper propose a variable parameter estimations of five-phase squirrel-cage induction motor(IM) for speed control system. In order to high performance control of AC motor using a field oriented control(FOC) and direct torque control(DTC) algorithm, there are required precise motor parameters for slip calculation, flux observer, controller gain, rotor position, speed estimation, and so on. We are suggest a analyzed estimation results of the motor parameters that developing five-phase squirrel-cage IM have a stator of concentrated winding for experimental of variable input power frequency. There are results of stator winding test, no-load test, locked-rotor test, variable actual load test, and estimated parameters of equivalent circuits using manufactured experimental apparatus by IEEE Standard Test Procedure for Polyphase Induction Motors and Generators 112-2004.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.44 no.1
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• pp.46-56
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• 2008

A numerical model analysis was performed to analyze the motion and mooring tension response of submersible fish cage systems in irregular waves and currents. Two systems were examined: a submersible cage mooring with a single, high tension mooring and the same system, but with an additional three point mooring. Using a Morison equation type model, simulations of the systems were conducted with the cage at the surface and submerged. Irregular waves(JONSWAP spectrum) with and without a co-linear current with a magnitude of 0.5m/s were simulated into the model as input parameters. Surge, heave and pitch dynamic calculations were made, along with tension responses in the mooring lines. Results were analyzed in both the time and frequency domains and linear transfer functions were calculated.

• Journal of Korea Multimedia Society
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• v.20 no.7
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• pp.1024-1029
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• 2017

A novel analytic solution has been derived for the bird-cage receiver coil of a magnetic resonance imaging (MRI) system, which is widely used in 3-dimensional medical imaging, by transforming the coil into an equivalent circuit model by using a transmission matrix-based circuit analysis. The bird-cage coil composed of N legs is divided into a cell for which input impedance is to be analyzed and the remaining N-1 cells, and then a transmission matrix corresponding to the N-1 cells is converted into a circuit to transform the 3-dimensional bird-cage coil into the 2-dimensional equivalent circuit model, which is suitable to derive the analytic solution for the input impedance. The proposed method derives directly the analytic solution for the input impedance at an arbitrary point of the coil unlike the conventional analytic solution of a bird-cage coil, so that it can be used not only for resonance frequency calculations but also for various coil characteristics analyses. Since the analytic solution agreed well with the results of computational simulations, it can be useful for the impedance matching of a coil and the analysis and the design of a multi-tune bird-cage coil.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.3
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• pp.330-335
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• 2012

Brushless doubly-fed machine (BDFM) doesn't use brush and slip ring, and has advantages such as high system reliability, small capacity of its frequency converter, low system cost, adjustable power factor and speed, etc. At the same time, it has good applicable potentials on the variable frequency motors and the variable speed constant frequency generators. However, due to the complicacy and particularity of BDFM in the structure and operating mechanism, the effect of magnetic field modulation directly influences the operating efficiency of BDFM. To study the effect of different cage rotor structures on the magnetic field modulation of BDFM, the rotor magnetomotive force (MMF) of BDFM with cage rotor is studied by the analytical method. The components and features of rotor harmonic MMFs are discussed. At the same time, the method to weaken the higher harmonics is analyzed by the theoretic formulae. Furthermore, the magnetic field modulation mechanism is expounded on in detail and the relationship between the magnetic field modulation effect and the operating efficiency of BDFM is established. And then, a new method for estimating the magnetic field modulation effect is proposed. At last, the magnetic field modulation effects of four BDFM prototypes with different cage rotor structures are compared by the MMF analysis and the efficiency data of electromagnetic design. The results verify the effectiveness of the new method for estimating the magnetic field modulation effect of BDFM with cage rotor.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.1
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• pp.43-50
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• 2001

In order to analyze the dynamic motions of fish cage systems made of a frame and a netting under the conditions of waves and current, the hydraulic model experiment at towing tank and the numerical computation using boundary integral element method based on linear potential theory were carried out on a square and a circular type of fish cage, The computed and measured results for the dynamic motions of model fish cage systems showed that the heave and pitch motions were almost unaffected by the inclusion of nets, while the surge motions were very reduced by drag force acting on them. In addition, irregular wave-induced motions of fish cages included non-negligible 2nd order harmonic components at high frequency nearly twice the wave frequency. The reason why these motions were considered was due to resonance or structural components of frames being overflown and out of water during a wave cycle. It was found that circular type was more desirable structure in the open sea than square one only in the respect of dynamic motions due to waves and current. Further verifications were needed considering hydrodynamic forces, fatigue life, and structure analysis based on long term stochastic waves including frequency and time domain for the purpose of analyzing and designing fish cage systems.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.3
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• pp.190-196
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• 2002

In order to analyze the hydrodynamic forces on fish cage systems, made of frames and nettings, under waves and current, hydraulic model experiments for square type and circular type of fish cage system were carried out in a towing tank. Both cage systems consist of net cages supported by floating frames made of two concentric pipes and four weights hanging from the bottom corners of the nets. There was little difference in the hydrodynamic force on the square type of fish cage system by wave heading under regular waves and the peak frequency of the force on each cage system was in a good agreement with that of induced irregular wave. In addition, it was also observed that the circular type of cage system was more stable to the action of waves and current than the square type.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.5 s.120
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• pp.563-568
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• 2007

In this paper, the proposed package antenna, which is meander line structure with short pin, is miniaturized to realize RF-SoP at 900 MHz RFID band. The RFID BGA(Ball Grid Array) chip is put in a cavity of LTCC Layers. The coupling and cross talk, which are happen between BGA chip and proposed package antenna, are reduced by faraday cage, which consists of ground and via fences, is realized to enhance the isolation between BGA chip and antenna. The proposed antenna structure is focused on the package level antenna realization at low frequency band. The novel proposed package antenna size is $13mm{\times}9mm{\times}3.51mm$. The measured resonance frequency is 0.893 GHz. The impedance bandwidth is 9 MHz. The maximum gain of radiation pattern is -2.36 dBi.