• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.3
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• pp.234-239
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• 2013

There are many types of speed reducer for industrial uses. However the cycloid speed reducer is widely used in manipulators based on excellent performance of low backlash, high reduction ratio and compact size. It is essential to use precision speed reducer for accuracy of position controls on robot systems and electric vehicles. The cycloid speed reducer has a eccentric rotating motion and offset to avoid some problem of assembly, so it has a disadvantage for vibration. In this paper, a multi-body dynamic model is developed for a cycloid speed reducer and the dynamic behaviors of the reducer are investigated. The cycloid speed reducer consists of cycloidal plate gears, housing gear, input shaft, output pin and shaft, and eccentric bearings. Using a CAD program, each component of cycloid reducer is modeled based on the offset and eccentric. Multi-body simulations using Recurdyn and test using a rig tester are performed. As a result, the pin reaction force and the amplitude of housing displacement are increased by the larger offset and smaller eccentric value of cycloid reducer.

• Economic and Environmental Geology
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• v.44 no.3
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• pp.229-238
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• 2011

S-wave, which provides lithology and pore fluid information, plays a key role in estimating gas-hydrate saturation. In general, P- and S-wave velocities increase in the presence of gas-hydrate and the P-wave velocity decreases in the presence of free gas under the gas-hydrate layer. Whereas there are very small changes, even slightly increases, in the S-wave velocity in the free gas layer because S-wave is not affected by the pore fluid when propagating in the free gas layer. To verify those velocity properties of the BSR (bottom-simulating reflector) depth in the gas-hydrate prospect area in the Ulleung Basin, P- and S-wave velocity profiles were derived from multi-component ocean-bottom seismic data which were acquired by Korea Institute of Geoscience and Mineral Resources (KIGAM) in May 2009. OBS (ocean-bottom seismometer) hydrophone component data were modeled and inverted first through the traveltime inversion method to derive P-wave velocity and depth model of survey area. 2-D multichannel stacked data were incorporated as an initial model. Two horizontal geophone component data, then, were polarization filtered and rotated to make radial component section. Traveltimes of main S-wave events were picked and used for forward modeling incorporating Poisson's ratio. This modeling provides S-wave profiles and Poisson's ratio profiles at every OBS site. The results shows that P-wave velocities in most OBS sites decrease beneath the BSR, whereas S-wave velocities slightly increase. Consequently, Poisson's ratio decreased strongly beneath the BSR indicating the presence of a free gas layer under the BSR.

• Biotechnology and Bioprocess Engineering:BBE
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• v.5 no.5
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• pp.355-361
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• 2000

A recycling reactor system operated under sequential anoxic and oxic conditions for the treatment of swine wastewater has been developed, in which piggery slurry is fermentatively and aerobically treated and then part of the effluent is recycled to the pigsty. This system significantly removes offensive smells (at both the pigsty and the treatment plant), BOD and others, and may be cost effective for small-scale farms. The most dominant heterotrophic were, in order, Alcaligenes faecalis, Brevundimonas diminuta and Streptococcus sp., while lactic acid bacteria were dominantly observed in the anoxic tank. We propose a novel monitoring system for a recycling piggery slurry treatment system through the use of neural networks. In this study, we tried to model the treatment process for each tank in the system (influent, fermentation, aeration, first sedimentation and fourth sedimentation tanks) based upon the population densities of the heterotrophic and lactic acid bacteria. Principal component analysis(PCA) was first applied to identify a relationship between input and output. The input would be microbial densities and the treatment parameters, such as population densities of heterotrophic and lactic acid bacteria, suspended solids(SS), COD, NH$_4$(sup)+-N, ortho-phosphorus (o-P), and total-phosphorus (T-P). then multi-layer neural networks were employed to model the treatment process for each tank. PCA filtration of the input data as microbial densities was found to facilitate the modeling procedure for the system monitoring even with a relatively lower number of imput. Neural network independently trained for each treatment tank and their subsequent combined data analysis allowed a successful prediction of the treatment system for at least two days.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.1113-1116
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• 2005

Using COMSAT which provides multi-beam switching function, the optimal transmission channel environment which provides the high data rate communication are proposed in this paper. Also the link budget for communication transponder of COMSAT is designed. Based on the channel modeling for group delay, non-linear and gain flatness characteristics, the system performances which provide various data rate services were analyzed in Ka-band satellite channel. As the transmission data rate is increased, the degradation due to these channel characteristics is severely increased. The linear component of group delay and the AM-AM component of non-linear characteristics severely affect the system performance. To efficiently provide the various service via the same transmission system it is necessary to equalize the primary impairment factors. The optimum operating points of HDR satellite transmission system are implemented and operated by considering the analyzed results on channel characteristics.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.1
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• pp.78-82
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• 2014

Power Transformers with more than one secondary winding are not uncommon in industrial applications. But new classes of applications where very large number of independent secondaries are used are becoming popular in controlled converters for medium and high voltage applications. Cascade H-bridge medium voltage drives and Pulse Step Modulation (PSM) based high voltage power supplies are such applications. Regulated high voltage power supplies (Fig. 1) with 35-100 kV, 5-10 MW output range with very fast dynamics (${\mu}S$ order) uses such transformers. Such power supplies are widely used in fusion research. Here series connection of isolated voltage sources with conventional switching semiconductor devices is achieved by large number of separate transformers or by single unit of multi-secondary transformer. Naturally, a transformer having numbers of secondary windings (~40) on single core is the preferred solution due to space and cost considerations. For design and simulation analysis of such a power supply, the model of a multi-secondary transformer poses special problem to any circuit analysis software as many simulation softwares provide transformer models with limited number (3-6) of secondary windings. Multi-Secondary transformer models with 3 different schemes are available. A comparison of test results from a practical Multi-secondary transformer with a simulation model using magnetic component is found to describe the behavior closer to observed test results. Earlier models assumed magnetising inductance in a linear loss less core model although in actual it is saturable core made-up of CRGO steel laminations. This article discusses a more detailed representation of flux coupled magnetic model with saturable core properties to simulate actual transformers very close to its observed parameters in test and actual usage.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.7
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• pp.376-383
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• 1999

The piezoelectric transformer (PT) is an electro-mechanical device that transfers electrical energy through a mechanical vibration. In this paper, a PT operating in the contour vibration mode is introduced for an application of fluorescent lamp ballast. Utilizing its inherent characteristics of the LC resonator and a high voltage gain to ignite the lamp in light load condition, an investigation of a power piezoelectric transformer as a potential component for a fluorescent lamp ballast is discussed. PT is easy to be produced in mass and reduces the cost of the ballast. The modified equivalent circuit model of the PT considering the operating current level is derived to design the fluorescent lamp ballast. This model describes the voltage gain of the PT in wide load variations and various input current levels. The experimental and simulation results are provided to verify theoretical analysis. The power capacity of the currently developed PT is relatively low (15W), but it can be increased by adopting a multi-layer structure and is currently under investigation. It is also possible to parallel the PT for higher power processing.

• The Journal of Korean Institute for Practical Engineering Education
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• v.4 no.2
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• pp.129-135
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• 2012

There are many ways in which electric vehicles are mathematically modeled and simulated. The components have different physical background and models, but have to fit into one mathematical model. A multiphysics model structure is required. Depending on the goal of the simulation, there are various levels on which the simulation can be performed. This is called multilevel, consisting of a conceptual system level, a circuit level and a more detailed component level. This paper discusses which multiphysics models and multilevel simulations are required for the various components in an electric vehicle. Also, this simulation approach could improve the effectiveness of learning in engineering education.

• Journal of Korea Soil Environment Society
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• v.3 no.3
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• pp.11-20
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• 1998

The effects of soil venting on the leaching potential of residual gasoline were characterized by applying a simple multi-component volatilization/dissolution model based on Raoult's law. The validity of Raoult's law in describing dissolution of gasoline was evaluated separately using both pure gasoline and gasoline contaminated soil. The aqueous concentrations of gasoline components equilibrated with pure gasoline could be described by Raoult's law within one order of magnitude, regardless of the composition of the gasoline. The leaching concentrations from contaminated soil could be well predicted at a relatively high gasoline concentration in soil. However, after 93.5% removal of gasoline by venting, the calculated values were higher than the experimental values by 50∼100%. A model involving multi-component evaporation and dissolution was applied and the results were compared with the experimental values. Possible causes of the discrepancy between the predicted values and experimental values were given.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.135-137
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• 2002

In the favor of adjusting microwave signal, Hairpin type Filter, which delay microwave signal enough to several nanosecond, is a key component. One of the main advantage in using Hairpin type Filter is a conveniency for equipping with Delay Module, and because of having a wide bandwidth, Hairpin type Filter can be designed to satisfy the most applications. In this work, we attempted to estimate the delay time in a superconductive hairpin type filter A software to synthesize even and odd order equiripple hairpin type filter has been developed. This software arbitrarily locate its transfer zeros making symmetric of asymmetric amplitude response and equalizing group delay. Borland C++ compiler has been used. The program was designed to run under MS-DOS, Window 98, Window 2000. The program optimizes the position of the transfer function zeros in order to fulfill the group delay specification masks. We designed and fabricated a hairpin type HTS 2-pole microstrip bandpass filter to operate at 5.8Ghz. The fabrication method was pulsed laser deposition and YBCO films were deposited on sapphire substrates with a Ce$O_{2}$ thin layer as a buffer layer. We also developed a new style hairpin type filter by using interdigitide inner-pole. Compared to the same size regular hairpin type filters, our filters had a lower center frequency.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.11
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• pp.1057-1063
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• 2012

A cycloid speed reducer is a type of the speed reducers. The cycloid speed reducer has a eccentric rotating motion and offset to avoid some problem of assembly, so it has a disadvantage for vibration. In this paper, a multi-body dynamic model is developed for a cycloid speed reducer and the dynamic behaviors of the reducer are investigated. The cycloid speed reducer consists of cycloidal plate gears, housing gear, input shaft, output pin and shaft, and eccentric bearings. Using a CAD program, each component of cycloid reducer is modeled based on the offset and multi-body simulations are performed using Recurdyn. As a result, the pin reaction force and the amplitude of bearing displacement are increased by the offset.