• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.4
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• pp.467-478
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• 2016

In this paper, we try to find the optimal locations of NeNB(Nomadic evolved NodeB)s for maximizing the overall throughput of the PS-LTE networks. Since finding optimal locations of all NeNBs in a given area is NP-hard(Non-deterministic Polynomial time-hard) problem, we proposed a PSO-based heuristic approach. In order to evaluate the performance, we conducted two experiments. We compared performance with other schemes such as Exhaustive Search, Random Walk Search, and locating neighboring NeNBs with the same NeNB-to-NeNB distance. The proposed method showed the similar results to the exhaustive search method in terms of locating optimal position and user's data throughput. The proposed method, however, has the fast and consistent convergence time.

• Journal of Korea Water Resources Association
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• v.36 no.5
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• pp.851-861
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• 2003

Snow accumulation and snow melt was simulated and included in the computation of the watershed runoff for Soyanggang Dam and Chungju Dam. A modified Tank Model was used for the simulation, which has three serial tanks and a pulse response function. The model parameters were estimated through the global optimization method of Shuffled Complex Evolution-University of Arizona (SCE-UA). A watershed was divided into four zones of elevation. The temperature decrease of the zones was a rate of -0.6$^{\circ}C$/100m. Almost all precipitation from December to February become accumulated as snow, and then the snow melts and runs off from March to April. The average runoff with snow melt was greater than the average runoff without snow melt during the period from March to April. The improved amount from snow melt simulation was about one fifth of the observed one for Soyanggang Dam. The increased amount for Chungju Dam was about one fourth of the observed average runoff during the same period. Although the watershed runoff was simulated including snow melt, it was less than the observed one for both of the dams.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.5
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• pp.51-57
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• 2014

In this paper, we introduce the adaptive threshold detection scheme based on an evolutionary arithmetic algorithm for the M-ary holographic data storage(HDS) system. The genetic algorithm is a particular class of evolutionary arithmetic based on the process of biological evolution, which is a very promising technique for optimization problem and estimation applications. In this study, to improve the detection performance that is degraded by the HDS channel environment and the pixel misalignment, the threshold value was assumed to be a population set of the evolutionary algorithm. The proposed method can find an appropriate population set of bit threshold, which minimizes bit error rate(BER) as increased generation. For performance evaluation, we consider severe misalignment effect in the 4-ary holographic data storage system. Furthermore, we measure the BER performance and compare the proposed methods with the conventional threshold detection scheme, which verifies the superiority of the proposed scheme.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.1
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• pp.9-21
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• 2018

Survivability of naval vessels is defined as the ability to perform functions and missions in a combat environment. Survivability has close relationship with the spatial layout of naval vessels. In order to maximize survivability, it must be considered from the early stage of design. However the existing concept of survivability was intended to be applied to unit vessels. So it was not suitable for assessment of spatial layout results at the early stage of design. In this paper, a simplified assessment method which can evaluate the spatial layout considering the survivability in the early stage of design has been proposed. For this, assessment layers were defined on survivability components such as susceptibility, vulnerability, and recoverability. Assessment layers of each component were overlapped to deduce a survivability layer of spatial layout alternatives. In addition, the proposed method and optimization algorithm were used to derive optimal spatial layout alternatives considering survivability.

• Journal of Microbiology and Biotechnology
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• v.15 no.1
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• pp.131-135
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• 2005

Under sulfur deprived conditions, PS II and photosynthetic $O_2$ evolution by Chlamydomonas reinhardtii UTEX 90 are inactivated, resulting in shift from aerobic to anaerobic condition. This is followed by hydrogen production catalyzed by hydrogenase. We hypothesized that the photosynthetic capacity and the accumulation of endogenous substrates such as starch for hydrogen production might be different according to cell age. Accordingly, we investigated (a) the relationships between hydrogen production, induction time of sulfur deprivation, increase of chlorophyll after sulfur deprivation, and residual PS II activity, and (b) the effect of initial cell density upon sulfur deprivation. The maximum production volume of hydrogen was 151 ml $H_2$/l with 0.91 g/l of cell density in the late-exponential phase. We suggest that the effects of induction time and initial cell density at sulfur deprivation on hydrogen production, up to an optimal concentration, are due to an increase of chlorophyll under sulfur deprivation.

• Journal of KIISE
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• v.43 no.2
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• pp.204-211
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• 2016

In this paper, we propose an automatic melody composition system that can generate a sophisticated melody by adding non-harmony tone in the given chord progression. An overall procedure consists of two steps, which are the rhythm generation and melody generation parts. In the rhythm generation part, we designed new fitness functions for rhythm that can be controlled by a user setting parameters. In the melody generation part, we designed new fitness functions for melody based on harmony theory. We also designed evolutionary operators that are conducted by considering a musical context to improve computational efficiency. In the experiments, we compared four metaheuristics to optimize the rhythm fitness functions: Simple Genetic Algorithm (SGA), Elitism Genetic Algorithm (EGA), Differential Evolution (DE), and Particle Swarm Optimization (PSO). Furthermore, we compared proposed genetic algorithm for melody with the four algorithms for verifying performance. In addition, composition results are introduced and analyzed with respect to musical correctness.

• Nuclear Engineering and Technology
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• v.45 no.2
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• pp.211-218
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• 2013

Large quantities of irradiated graphite waste from graphite-moderated nuclear reactors exist and are expected to increase in the case of High Temperature Reactor (HTR) deployment [1,2]. This situation indicates the need for a graphite waste management strategy. Of greatest concern for long-term disposal of irradiated graphite is carbon-14 ($^{14}C$), with a half-life of 5730 years. Fachinger et al. [2] have demonstrated that thermal treatment of irradiated graphite removes a significant fraction of the $^{14}C$, which tends to be concentrated on the graphite surface. During thermal treatment, graphite surface carbon atoms interact with naturally adsorbed oxygen complexes to create $CO_x$ gases, i.e. "gasify" graphite. The effectiveness of this process is highly dependent on the availability of adsorbed oxygen compounds. The quantity and form of adsorbed oxygen complexes in pre- and post-irradiated graphite were studied using Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and Xray Photoelectron Spectroscopy (XPS) in an effort to better understand the gasification process and to apply that understanding to process optimization. Adsorbed oxygen fragments were detected on both irradiated and unirradiated graphite; however, carbon-oxygen bonds were identified only on the irradiated material. This difference is likely due to a large number of carbon active sites associated with the higher lattice disorder resulting from irradiation. Results of XPS analysis also indicated the potential bonding structures of the oxygen fragments removed during surface impingement. Ester- and carboxyl-like structures were predominant among the identified oxygen-containing fragments. The indicated structures are consistent with those characterized by Fanning and Vannice [3] and later incorporated into an oxidation kinetics model by El-Genk and Tournier [4]. Based on the predicted desorption mechanisms of carbon oxides from the identified compounds, it is expected that a majority of the graphite should gasify as carbon monoxide (CO) rather than carbon dioxide ($CO_2$). Therefore, to optimize the efficiency of thermal treatment the graphite should be heated to temperatures above the surface decomposition temperature increasing the evolution of CO [4].

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.3
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• pp.386-393
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• 2012

Portfolio selection methods based on stochastic receding horizon approach, which were recently reported in the field of financial engineering, can explicitly consider the dynamic characteristics of wealth evolution and various constraints in the process of performing optimal portfolio selection. In view of the theoretical value, versatility, and effectiveness that receding horizon approach has achieved in many engineering problems, dynamic portfolio selection methods based on stochastic receding horizon optimization technique have the possibility of becoming an important breakthrough. This paper observes through theoretical investigations that the SDP(semi-definite program)-based portfolio selection procedure can be simplified, and has obtained meaningful performance on returns from simulation studies applying the simplified version to Korean financial markets.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.11
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• pp.652-659
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• 2014

In this paper, we propose an access point selection method for mobile users in LTE-femtocell system. In wireless communication system, users want to receive good data service. In LTE-femtocell system, if users move a little, users can experience different data service. The proposed access point selection method help that if users move a little, users obtain the high capacity and that user selects access point that other user have not selected much and so obtains higher data service. We simulated in order to prove performance of the proposed access point selection metod. Simulation results show that in a situation that users are concentrated in order to obtain better data service users are seen scattered look. As a result, we confirm that the proposed access point selection method provides good data service to users.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.3
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• pp.617-636
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• 2017

Many businesses have adopted the standard security management structure such as ISO27001 and K-ISMS for strengthening business's security management structure to protect their core information assets and have acquired partial output from such effort. However, many risk factors such as recent advances in Information Technology and evolution of intrusion methods have increased exponentially requiring the businesses to response even more quickly with better accuracy. For such purpose, a study of 'Real Time Security Management Structure for Business' based on security management process optimization, defining a set of security index for managing core security area and calculation of risk indices for precognition of intrusion risk area has been made. Also, a survey on opinions of an expert panel has been conducted. The effectiveness of studied structure was analyzed using AHP method as well. Using this study, security personnels of a company can improve efficiency of the preemptive responsive and quicker measure from the current security management structure.