• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.379-387
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• 2015

A custom power device provides an integrated solution to the present problems that are faced by the utilities and power distribution. In this paper, a new controller is designed which is connected to a multiconverter unified power quality conditioner (MC-UPQC) for improving the power quality issues adopted modified synchronous reference frame (MSRF) theory with Fuzzy logic control (FLC) technique. This newly designed controller is connected to a source in order to compensate voltage and current in two feeders. The expanded concept of UPQC is multi converter-UPQC; this system has a two-series voltage source inverter and one shunt voltage source inverter connected back to back. This configuration will helps mitigate any type of voltage / current fluctuations and power factor correction in power distribution network to improve power quality issues. In the proposed system the power can be conveyed from one feeder to another in order to mitigate the voltage sag, swell, interruption and transient response of the system. The control strategies of multi converter- UPQC are designed based on the modified synchronous reference frame theory with fuzzy logic controller. The fast dynamics response of dc link capacitor is achieved with the help of Fuzzy logic controller. Different types of fault conditions are taken and simulated for the analysis and the results are compared with the conventional method. The relevant simulation and compensation performance analysis of the proposed multi converter-UPQC with fuzzy logic controller is performed.

• Journal of the Korean Chemical Society
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• v.60 no.2
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• pp.131-136
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• 2016

Copper ion induced photoluminescence (PL) quenching dynamics and recovery of the PL by zinc ions were investigated for CdSe based nanocrystals. When copper ions were added, CdSe quantum dots showed fast and dramatically PL quenching whereas PL of CdSe nanorod gradually decreased. In the presence of zinc ions, the PL of CdSe/CdS (core/shell) nanocrystals that have quenched by copper ions was efficiently recovered. It showed that the PL intensity of nanocrystals increased by 50% in a solution containing 1 μM zinc ions. The PL intensity was increasing with increasing zinc ions, and could be described by Langmuir binding isotherm model. We showcase that the CdSe based nanocrystals can be used as fluorescence turn-on sensor.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.2
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• pp.39-47
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• 1998

It has been known that variable structure control(VSC) has theoretically powerful control technique of providing fast response, no overshoot, and very robust control with respect to system parameter variations and disturbances. However, the technique has not become more widely extended in the industrial circles because chattering phenomenon which may excite high-frequency unmodelled plant dynamics and damage to system components exists. In this paper, a modified variable structure control(MVSC) is developed to alleviate these problems which are applied to the position control of induction motor. While the conventional VSC makes the structure of the system change with high-frequency switching on the center of the one switching surface, in the MVSC two switching surface are used to establish a sliding sector. The structure of the system will be changed with low-frequency switching. Therefore, the proposed algorithm has the properties of reducing chattering, retaining the benefits achieved in the conventional VSC, and working even under the influences of parameter variations. Experimental results show the effectiveness of the control strategy proposed here for the position control of induction motor.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2008.04a
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• pp.101-108
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• 2008

Polymer electrolyte membrane (PEM) fuel cells are promising power generation devices which are ideal for residential and automobile applications, thanks to their fast transient characteristics. However, liquid water produced in PEM fuel cells should be properly managed to enhance the performances and durabilities of the cells. In this study, a visualization experiment was conducted to investigate the flow behavior of water droplets in cathode channels. The visualization experiment was done with four different model flow channels which were made by varying the material (Acrylic and Teflon) and the channel width (1 mm and 2 mm). Acrylic is hydrophilic (contact angle is about $80^{\circ}$) while Teflon is hydrophobic (contact angle is about $120^{\circ}$). A computational fluid dynamics (CFD) analysis was also performed to compare the observed and the simulated two-phase water/air flow characteristics in cathode channels. The computational models were made to be consistent with the geometries and surface properties of the model flow channels. Both the experimental and numerical results showed that the Teflon cathode channel with 1 mm width has the best water management performance among four model flow channels considered. A close correlation was found between the experimental visualization results and the numerical CFD simulation results.

• Asian-Australasian Journal of Animal Sciences
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• v.20 no.6
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• pp.925-932
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• 2007

This study was designed to measure the effect of regrowth age of Digitaria decumbens (D. decumbens) on the intake and dynamics of digesta in the rumen of rams. Six Black-belly rams (mean liveweight: 51.6 (s.d. 0.68) kg) fitted with rumen cannulae were fed twice daily a 14-, 28-, 42- and 56-day old fresh D. decumbens successively for 4 experimental periods. The daily dry matter intake decreased curvilineary from 75.2 to 48.5 (s.e. 2.0) g/kg $BW^{0.75}$ as the age of the D. decumbens grass increased from 14 to 56 days. Dry matter intake for the first 3 h after the morning meal was 863.6, 598.3, 576.4 and 401.5 (s.e. 55.6) g for the 14-, 28-, 42- and 56-day old grasses respectively. The pool of NDF in the rumen at the end of the 3-h feeding period did not vary significantly among the four diets. Twelve hours after the beginning of the morning meal, the pool of NDF increased with the forage regrowth age. Within the total pool of NDF, the pool of large particles tended to increase with the regrowth age. It was concluded that high intake was associated with fast evacuation of NDF from the rumen. Moreover, digestion (cellulolysis) rate and degree of particle reduction by rumination are highly correlated, though speed of physical degradation of forage seems to be the driving force behind intake.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2008.10a
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• pp.24-36
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• 2008

Architecture-based competition has become a very important issue in many industries. As companies seek lower cost, fast development, and more customizability at the same time, modular architecture of products and processes seem to be an inevitable choice. Existing literature, however, has only focused on the basic contents of architecture-based competition. Different competitive environments and technological competencies of incumbent companies influence the evolutionary dynamics of dominant architecture of industries. In this paper we suggest a new theoretical framework to deal with the complex co-adaptation process of architecture-based competition. We first explore the emerging modular architecture in Chinese commercial vehicle industry, and then compare it with the architecture strategies of Korean companies. Based on the explorative case study, we propose new hypotheses relating the market demand, technological competencies of major players and dominant architecture in an indus-try.

• Wind and Structures
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• v.18 no.6
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• pp.693-715
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• 2014

Stochastic processes are used to represent phenomena in many diverse fields. Numerical simulation method is widely applied for the solution to stochastic problems of complex structures when alternative analytical methods are not applicable. In some practical applications the stochastic processes show non-Gaussian properties. When the stochastic processes deviate significantly from Gaussian, techniques for their accurate simulation must be available. The various existing simulation methods of non-Gaussian stochastic processes generally can only simulate super-Gaussian stochastic processes with the high-peak characteristics. And these methodologies are usually complicated and time consuming, not sufficiently intuitive. By revealing the inherent coupling effect of the phase and amplitude part of discrete Fourier representation of random time series on the non-Gaussian features (such as skewness and kurtosis) through theoretical analysis and simulation experiments, this paper presents a novel approach for the simulation of non-Gaussian stochastic processes with the prescribed amplitude probability density function (PDF) and power spectral density (PSD) by amplitude modulation and phase reconstruction. As compared to previous spectral representation method using phase modulation to obtain a non-Gaussian amplitude distribution, this non-Gaussian phase reconstruction strategy is more straightforward and efficient, capable of simulating both super-Gaussian and sub-Gaussian stochastic processes. Another attractive feature of the method is that the whole process can be implemented efficiently using the Fast Fourier Transform. Cases studies demonstrate the efficiency and accuracy of the proposed algorithm.

• Journal of Navigation and Port Research
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• v.29 no.8 s.104
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• pp.747-753
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• 2005

In this paper, as an anti-sway control strategy of container cranes, we investigate a variable structure control in which the moving load follows a given trajectory, whereas both the trolley and hoist controllers achieve their positioning problems. It is crucial, in an automated container terminal, that collisions should be avoided during the transference of containers from one place to another. It is also necessary, in the case of a quay crane, to select suitable loading and unloading trajectories of containers, so that possible collisions with surrounding obstacles are avoided. After a brief introduction of the mathematical model, a robust control scheme (i.e., a second-order sliding mode control that guarantees a fast and precise transference and a suppression of the resulted swing) is presented. Despite model uncertainties and unmodeled actuators dynamics, the swing suppression from the given trajectory is obtained by constraining the system motion on suitable sliding surfaces, which include both the desired path and the swing angle. The proposed controller has been tested with a laboratory-size pilot crane. Experimental results are provided.

• The Journal of the Korea Contents Association
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• v.11 no.9
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• pp.1-8
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• 2011

A fuzzy inference technique for real-time textile animation without integration at textile model based Mass-Spring model is introduced. Until now many techniques have used the Mass-Spring model to describe elastically deformable objects like textile. A textile object is able to represent as a deformable surface composed of spring and masses, the movement of textile surface which is analysed through the numerical integration by the fundamental law of dynamics such as Hooke's law. However, the integration methods have 'instability problems' if the explicit Euler's method is applied or 'large amounts of calculation' if the implicit Euler's method is applied. A simple and fast animation technique for Mass-Spring model of a textile with fuzzy inference is proposed. The stabilized simulation result is obtained the state of each mass-point in real-time for the n of mass-points by a relatively simple calculation.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.1
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• pp.64-71
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• 2006

For SUAV is required to have the capacity of VTOL and fast forward flight, the SUAV development program has decided to adopt the tiltrotor mechanism which includes helicopter and turboprop mechanisms. From the engine point of view, the key engine parameters such as engine operating mechanism, engine control scheme, the dynamics characteristic of power train, engine intake/exhaust concept, and engine installation requirements should fulfill the requirements of the two different mechanisms, helicopter and turboprop. And for the maximum efficiency of the rotor, rotational speed for the two modes are 20% different, the power train shall find a way to make it so. Meeting these specific requirements for the tiltrotor mechanism, this research begins with a conventional OTS(off-the-shelf) turboshaft engine survey and minimizes engine modification to develop an economical propulsion system. The engine technical review has been performed on the basis of those requirements and capabilities.