• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10A
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• pp.823-829
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• 2011

Recently, wireless body area network (WBAN) has received much attention as an application for the ubiquitous healthcare system. In WBAN, each sensor nodes and a personal base station such as PDA have an energy constraint and computation overhead should be minimized due to node's limited computing power and memory constraint. The reliable data transmission also must be guaranteed because it handles vital signals. In this paper, we propose a systematic network coding scheme for WBAN to reduce the network coding overhead as well as total energy consumption for completion the transmission. We model the proposed scheme using Markov chain. To minimize the total energy consumption for completing the data transmission, we made the problem as a minimization problem and find an optimal solution. Our simulation result shows that large amount of energy reduction is achieved by proposed systematic network coding. Also, the proposed scheme reduces the computational overhead of network coding imposed on each node by simplify the decoding process.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.119-122
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• 2005

RFID(Radio Frequency IDentification) is appearing by point technology by Ubiquitous environment of new paradigm and Logistics' application. But, RFID chip of this is high price and short bandwidth, low power and interference etc. can become technological problem. This is getting into obstacle in common use. Reader and tag, Embedded software etc.. that is accomplishing standardization is imported paying most expensive Royalty. This paper is RFID cognition system that use PDA in Ubiquitous environment to apply to Logistics system. RFID cognition system processes input/output of fundamental information attaching tag to Logistics of products. And RFID cognition system supports quick and correct and safe synthetic Logistics managerial system through construction of database. This can prove minimization and customer service of Logistics expense. RFID cognition system is advantage that can widen range of application to area that cognition system of existent fixing style can not do. Also, It can expect economical effect through inexpensive system construction.

• KIEE International Transactions on Power Engineering
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• v.5A no.3
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• pp.269-279
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• 2005

This paper presents an application of the parallel Adaptive Evolutionary Algorithm (AEA) to search an optimal solution of a reconfiguration in distribution systems. The aim of the reconfiguration is to determine the appropriate switch position to be opened for loss minimization in radial distribution systems, which is a discrete optimization problem. This problem has many constraints and it is very difficult to find the optimal switch position because of its numerous local minima. In this investigation, a parallel AEA was developed for the reconfiguration of the distribution system. In parallel AEA, a genetic algorithm (GA) and an evolution strategy (ES) in an adaptive manner are used in order to combine the merits of two different evolutionary algorithms: the global search capability of GA and the local search capability of ES. In the reproduction procedure, proportions of the population by GA and ES are adaptively modulated according to the fitness. After AEA operations, the best solutions of AEA processors are transferred to the neighboring processors. For parallel computing, a PC-cluster system consisting of 8 PCs·was developed. Each PC employs the 2 GHz Pentium IV CPU, and is connected with others through switch based fast Ethernet. The new developed algorithm has been tested and is compared to distribution systems in the reference paper to verify the usefulness of the proposed method. From the simulation results, it is found that the proposed algorithm is efficient and robust for distribution system reconfiguration in terms of the solution quality, speedup, efficiency, and computation time.

• Journal of Korean Society on Water Environment
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• v.37 no.2
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• pp.103-113
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• 2021

In this study, an Excel-based model (ROADMOD) was developed to estimate pollutant loading from the road and evaluate BMPs. ROADMOD employs the Chezy-Manning equation and empirical expression for estimating surface runoff, and power function for pollutant buildup, and exponential function for pollutant washoff in SWMM. The results of model calibration for buildup and washoff using observed data revealed a good match between the simulation results and the observed data. The long-term surface runoff and sediment simulated by ROADMOD demonstrated a good match with those by SWMM with 2 ~ 14% of relative error. The shorter sweeping interval (within 8 days) remarkably decreased sediment loads from the road. It was found that the effect of reducing sediment loads from the road was greatly affected not only by the sweeping interval but also by sweeping on the day before a rainfall event. The 48% of removal efficiency of sediment loads from the road was achieved with 26 times of road sweeping per year when sweeping was performed on the day before the rainfall event. A 4-day sweeping interval showed similar removal efficiency (48%) with 96 times of sweeping per year. It is considered that the road sweeping on the day before a rainfall event could maximize the effect of reducing the non-point source pollution from the road with minimization of the number of road sweeping. So, the road sweeping on the day before a rainfall event can be considered as one of the useful and best management practices (BMPs) on road.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.67-72
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• 2019

This paper evaluates the performance of CCA (Compact Constellation Algorithm) adaptive equalization algorithm by varying the step size for minimization of the distortion effect in the communication channel. The CCA combines the conventional DDA and RCA algorithm, it uses the constant modulus of the transmission signal and the considering the output of decision device by the power of compact slice weighting value in order to improving the initial convergence characteristics and the equalization noise by misadjustment in the steady state. In this process, the compact slice weight values were fixed, and the performance of CCA adaptive equalization algorithm was evaluated by the varing the three values of step size for adaptation. As a result of computer simulation, it shows that the smaller step size gives slow convergence speed, but gives excellent performance after at steady state. Especially in SER performance, the small step size gives more robustness that large values.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.4
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• pp.1042-1058
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• 2024

Terahertz (THz) communication is becoming a key technology for future 6G wireless networks because of its ultra-wide band. However, the implementation of THz communication systems confronts formidable challenges, notably beam splitting effects and high computational complexity associated with them. Our primary objective is to design a hybrid precoder that minimizes the Euclidean distance from the fully digital precoder. The analog precoding part adopts the delay-phase alternating minimization (DP-AltMin) algorithm, which divides the analog precoder into phase shifters and time delayers. This effectively addresses the beam splitting effects within THz communication by incorporating time delays. The traditional digital precoding solution, however, needs matrix inversion in THz massive multiple-input multiple-output (MIMO) communication systems, resulting in significant computational complexity and complicating the design of the analog precoder. To address this issue, we exploit the characteristics of THz massive MIMO communication systems and construct the digital precoder as a product of scale factors and semi-unitary matrices. We utilize Schatten norm and Hölder's inequality to create semi-unitary matrices after initializing the scale factors depending on the power allocation. Finally, the analog precoder and digital precoder are alternately optimized to obtain the ultimate hybrid precoding scheme. Extensive numerical simulations have demonstrated that our proposed algorithm outperforms existing methods in mitigating the beam splitting issue, improving system performance, and exhibiting lower complexity. Furthermore, our approach exhibits a more favorable alignment with practical application requirements, underlying its practicality and efficiency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.2
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• pp.155-161
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• 2013

In this study, a metal-plated polycarbonate was adopted as a material for bipolar plates in a polymer electrolyte membrane fuel cell (PEMFC). The coated layers included 40-${\mu}m$-thick copper, 10-${\mu}m$-thick nickel, and 0.3-${\mu}m$-thick gold that respectively played the roles of current conduction, adhesion between copper and gold, and minimization of surface corrosion. The maximum power of the air-breathing PEMFC with polycarbonate bipolar plates was $120mW/cm^2$, which was similar to that of graphite bipolar plates. Finally, the maximum power of a 12-cell stack of polycarbonate bipolar plates was $132.7mW/cm^2$, and it had an operating time of 12 h. Therefore, this was considered a suitable material for bipolar plates in PEMFCs.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.1
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• pp.97-104
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• 2016

Because of rapid growth of data size, the number of data storage has been increased. When using multiple data storages, a distribute file system is essential to insure the availability of data files. The power consumption is a major problem when using a distributed file system with many data storages. Previous works have aimed at reducing the energy consumption with efficient file block layout by changing some data servers into stand-by mode. The file block migration has not been seriously considered because migration causes large cost. But when we consider addition of a new data server or file, file block migration is needed. This paper formulates the minimization of data block migration as an ILP optimization problem and solves it using branch-and-bound method. Using this technique, we can maximize the number of stand-by data servers with the minimum number of file block movement. However, computation time of branch-and-bound method of an ILP optimization problem increases exponentially as the problem size grows. Therefore this paper also proposes a data block and data server grouping method to solve many small ILP problems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.880-886
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• 2007

We have proposed a new "hybrid" envelope elimination and restoration(EER) transmitter architecture using an efficiency optimized power amplifier(PA) and modified bias modulator. The efficiency of the PA at the average drain voltage is very important for the overall transmitter efficiency because the PA operates mostly at the average power region of the modulation signal. Accordingly, the efficiency of the PA has been optimized at the region. Besides, the bias modulator has been accompanied with the emitter follower for the minimization of memory effect. A saturation amplifier, class $F^{-1}$ is built using a 5-W PEP LDMOSFET for forward-link single-carrier wideband code-division multiple-access(WCDMA) at 1-GHz. For the interlock experiment, the bias modulator has been built with the efficiency of 64.16% and peak output voltage of 31.8 V. The transmitter with the proposed PA and bias modulator has been achieved an efficiency of 44.19%, an improvement of 8.11%. Besides, the output power is enhanced to 32.33 dBm due to the class F operation and the PAE is 38.28% with ACLRs of -35.9 dBc at 5-MHz offset. These results show that the proposed architecture is a very good candidate for the linear and efficient high power transmitter.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.6 s.109
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• pp.562-573
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• 2006

It is required to reduce the peak-to-average power ratio(PAPR) in an orthogonal frequency division multiplexing system or a multicarrier system. And it is needed to eliminate the transmission of the side information in the Partial Transmit Sequences. So, in this paper, a new technique is proposed, where the subcarriers used for the multiple signal representation are only utilized for the reduction of PAPR to eliminate the burden of transmitting the side information. That is, it is proposed by taking the modified minimization criteria of partial transmit sequences scheme instead of using the convex optimization or the fast algorithm of tone reservation(TR) technique As the result of simulation, the PAPR reduction capability of the proposed method is improved by 3.2 dB dB, 3.4 dB, 3.6 dB with M=2, 4, 8(M is the number of partition in the so-called partial transmit reduction sequences(PTRS)), when the iteration number of fast algorithm of TR is 10 and the data rate loss is 5 %. But it is degraded in the capability of PAPR reduction by 3.4 dB, 3.1 dB, 2.2 dB, comparing to the TR when the data rate loss is 20 %. Therefore, the proposed method is outperformed the TR technique with respect to the complexity and PAPR reduction capability when M=2.