• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1300-1310
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• 2003

In this paper, the performance of a multicarrier CDMA system using adaptive modulation and adaptive subchannel allocation scheme is analyzed in Rayleigh fading channel. The proposed adaptive modulator consists of modulation schemes using QPSK 16 QAM, 64 QAM and 256 QAM and constellations are pointed by Gray code. In addition, the threshold of the analysis is average E$\_$b//N$\_$o/ when the BER is 1 %. In the multicarrier system with adaptive subchannel allocation scheme, each DS waveform of user is transmitted over the K subchannels with the biggest fading among L subchannels. In case of the proposed system, total 4 subchannels are used and data are transmitted over 2 subchannels with the biggest fading, which results in the threshold of each channels is 5.2 dB, 9 dB, 13.2 dB and 8.4 dB, 12.2 dB, 16.3 dB. In the case of proposed system, the BER of 10$\^$-3/ is satisfied if average E$\_$b//N$\_$o/ is 8.1 dB. This is increased performance of 12.9 dB in comparison with conventional system. The BPS according to average channel is needed average E$\_$b//N$\_$o/ of about 15 dB in 7 bit. In the case of subchannel error, the BER of 10$\^$-3/ is 13.6 dB and is declined about 5.5 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.10
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• pp.876-884
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• 2015

In this paper, a switched beamforming antenna system at 28 GHz frequency band is described for $5^{th}$ generation wireless communication. The butler matrix is used as a beamforming system and it produces linear spaced phase difference at four output ports. Array antenna is designed that can be steered in desired 4 different directions 28 GHz frequency band. Operation of designed butler matrix that composed of couplers and feedline is explained. The antenna system is designed in RO3003 substrate that has a height of 5 mil and dielectric constant of 3. The size of butler matrix is $20.3{\times}13.0mm^2$ and size of array antenna is $21.2{\times}19.9mm^2$. This system can be steered from $-34^{\circ}$ to $33^{\circ}$ and minimum sidelobe level is 12.9 dB.

• Smart Structures and Systems
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• v.26 no.2
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• pp.175-184
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• 2020

Conventional Monte Carlo simulation-based methods for seismic risk assessment of water networks often require excessive computational time costs due to the hydraulic analysis. In this study, an Artificial Neural Network-based surrogate model was proposed to efficiently evaluate the flow-based system reliability of water distribution networks. The surrogate model was constructed with appropriate training parameters through trial-and-error procedures. Furthermore, a deep neural network with hidden layers and neurons was composed for the high-dimensional network. For network training, the input of the neural network was defined as the damage states of the k-dimensional network facilities, and the output was defined as the network system performance. To generate training data, random sampling was performed between earthquake magnitudes of 5.0 and 7.5, and hydraulic analyses were conducted to evaluate network performance. For a hydraulic simulation, EPANET-based MATLAB code was developed, and a pressure-driven analysis approach was adopted to represent an unsteady-state network. To demonstrate the constructed surrogate model, the actual water distribution network of A-city, South Korea, was adopted, and the network map was reconstructed from the geographic information system data. The surrogate model was able to predict network performance within a 3% relative error at trained epicenters in drastically reduced time. In addition, the accuracy of the surrogate model was estimated to within 3% relative error (5% for network performance lower than 0.2) at different epicenters to verify the robustness of the epicenter location. Therefore, it is concluded that ANN-based surrogate model can be utilized as an alternative model for efficient seismic risk assessment to within 5% of relative error.

• Journal of Electrical Engineering and Technology
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• v.7 no.5
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• pp.672-680
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• 2012

This paper proposes the control strategy of the shunt Flexible AC Transmission System (FACTS) devices to improve transient stability in multimachine power system. The multimachine power system has high nonlinear response after severe disturbance. The concept of Lyapunov energy function is applied to derive nonlinear control strategy and it was found that the time derivative of line voltage is not only can apply to control the shunt FACTS devices in multimachine system but also is locally measurable signal. The fuzzy logic control is also applied to overcome the uncertainty of various disturbances in multimachine power system. This paper presents the method of investigating the effect of the shunt FACTS devices on transient stability improvement. The proposed control strategy and the method of simulation are tested on the new England power system. It was found that the shunt FACTS devices based on the proposed nonlinear control strategy can improve transient stability of multimachine power system.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.2099-2104
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• 2015

The paper presents a monitoring system for the cooling of distribution transformers. The suggested system is controlled by a microcontroller scheme. The system is designed to control the oil temperature. It gives a solution to improve the cooling system by adding a number of fans especially for indoor transformers that are placed in badly-ventilated rooms. Also, the paper includes an alarm system with the possibility of tripping the transformer if it is necessary. The monitoring system consists of acquisition temperature sensor, and on-site unit. The hardware and software of the on-site unit are demonstrated with sufficient illustrations. Small prototype is constructed in the laboratory. Some laboratory experiments are carried out for examining the designed circuit by using Proteus Virtual System Modeling as well as for testing the prototype monitoring system. Concerning this research point, a study is carried out to evaluate the economic feasibility. The results are recorded and associated with many recommendations that may be valuable to electrical distribution (utility) companies.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.5
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• pp.622-629
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• 1999

This paper discusses a real time multi-tasking system model and a development environment for an elevator control system. Recently, as the elevator systems become large-scaled and operate with high speed, there are lots of software tasks to be processed with time constraints. Thus, the control systems are designed with distributed control structure and characteristics of typical real time systems. For stuructural design of such real time system, we introduce a multi-tasking model based on a real time operating system model and an software development environment based on virtual protopyping which simulates real system operation in the cross development of a new elevator system with distributed control structure and its system reliability can be verified through numerous field tests.

• Journal of Microbiology and Biotechnology
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• v.23 no.10
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• pp.1445-1453
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• 2013

The scale-up criterion of constant oxygen mass transfer coefficient ($k_La$) was applied for the production of itaconic acid (IA) in a 50 L pilot-scale fermentor by the fungal cells of Aspergillus terreus. Various operating conditions were examined to collect as many $k_La$ data as possible by adjusting the stirring speed and aeration rate in both 5 L and 50 L fermentor systems. In the fermentations performed with the 5 L fermentor, the highest IA production was obtained under the operating conditions of 200 rpm and 1.5 vvm. Accordingly, we intended to find out parallel agitation and aeration rates in the 50 L fermentor system, under which the $k_La$ value measured was almost identical to that ($0.02sec^{-1}$) of the 5 L system. The conditions of 180 rpm and 0.5 vvm in the 50 L system turned out to be optimal for providing almost the same volumetric amount of dissolved oxygen (DO) into the fermentor, without causing shear damage to the producing cells due to excessive agitation. Practically identical fermentation physiologies were observed in both fermentations performed under those respective operating conditions, as demonstrated by nearly the same values of volumetric ($Q_p$) and specific ($q_p$) IA production rates, IA production yield ($Y_{p/s}$), and specific growth rate (${\mu}$). Specifically, the negligible difference of the specific growth rate (${\mu}$) between the two cultures (i.e., $0.029h^{-1}$ vs. $0.031h^{-1}$) was notable, considering the fact that ${\mu}$ normally has a significant influence on $q_p$ in the biosynthesis of secondary metabolites such as itaconic acid.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.996-999
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• 1996

This paper introduces prototype design of 765kV Substation control system based on fiber optics LAN and distributed network protocol. Two major important facts, immunity of any surge which frequently occurs in Ultra High Voltage Substation and the most suitable communication protocol for substation control system, are considered on the system design conception. To meet the first fact, use of fiber optics cable and isolation transformer are considered, and to satisfy the second fact, DNP3.0(Distributed Network Protocol) which is IEC870-5 compatible is adopted.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.2
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• pp.88-95
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• 2014

This paper proposes a novel desktop virtual reality system. Based on the position of the user's face, the proposed system selects the most appropriate image of an object from a set of photographs taken at various angles, and simply "pastes" it onto the display at the appropriate location and scale. Using this system, the users can intuitively feel the presence of the object.

• Journal of Information Display
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• v.5 no.4
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• pp.1-6
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• 2004

In this paper, we investigate on the characteristics of poly-Si TFTs reuired for the implementation of analog circuits to be integrated with System-on-Glass (SoG). Matching requirements in terms of resistor values, threshold voltage and mobility of poly-Si TFTs are derived as a function of the resolution of display system. Effective mobility of poly-Si TFTs required for the realization of source driver is analyzed for various panel sizes.