• Journal of the Korean Geographical Society
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• v.45 no.4
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• pp.521-539
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• 2010

Recently many local governments have carried out dong merger and abolition process to cope with rapidly changing administrative demand and environment. This administrative effort impacts substantially the locational characteristics of the existing dong offices which directly involve in the quality of local community life. In this paper, we attempt to analyze the location pattern of current dong community service centers (formerly, 'dong office') and suggest the optimal locations maximizing spatial accessibility. As an application, we examine the location pattern of the existing dong community service centers in Mapo-gu, Seoul. Moreover, we compare current spatial configurations with the optimally selected locations such as, a Median maximizing spatial efficiency, a Center maximizing spatial equity, and a Centdian exploring compromising solutions regarding the tradeoff between efficiency and equity. The analytical results present that each of dong community service centers was systematically evaluated in terms of spatial efficiency and equity and in general the community service center locations are not spatially optimized with respect to efficiency and equity, compared with the optimal locations.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.167-174
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• 2007

This study proposes a practical and realistic method to establish an optimal lifetime maintenance strategy for deteriorating bridges by considering the life-cycle performance as well as the life-cycle cost. The proposed method offers a set of optimal tradeoff maintenance scenarios among other conflicting objectives, such as minimizing cost and maximizing performance. A genetic algorithm is used to generate a set of maintenance scenarios that is a multi-objective combinatorial optimization problem related to the and the life-cycle cost and performance as separate objective functions. A computer program, which generates optimal maintenance scenarios, was developed based on the proposed method. The subordinate relation between bridge members has been considered to decide optimal maintenance sequence. The developed program has been used to present a procedure for finding an optimal maintenance scenario for steel-girder bridges on the Korean National Road. Through this bridge maintenance scenario analysis, it is expected that the developed method and program can be effectively used to allow bridge managers an optimal maintenance strategy satisfying various constraints and requirements.

• Journal of IKEEE
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• v.22 no.4
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• pp.886-895
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• 2018

This paper describes a hardware design of the Secure Hash Algorithm-3 (SHA-3) hash functions that are the latest version of the SHA family of standards released by NIST, and an implementation of ARM Cortex-M0 interface for security SoC applications. To achieve an optimized design, the tradeoff between hardware complexity and performance was analyzed for five hardware architectures, and the datapath of round block was determined to be 1600-bit on the basis of the analysis results. In addition, the padder with a 64-bit interface to round block was implemented in hardware. A SoC prototype that integrates the SHA-3 hash processor, Cortex-M0 and AHB interface was implemented in Cyclone-V FPGA device, and the hardware/software co-verification was carried out. The SHA-3 hash processor uses 1,672 slices of Virtex-5 FPGA and has an estimated maximum clock frequency of 289 Mhz, achieving a throughput of 5.04 Gbps.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.21 no.5
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• pp.149-160
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• 2011

Technique based on the notions of anonymity is one of several ways to achieve the goal of privacy and it transforms the original data into the micro data by some group based methods. The first notion of group based method is ${\kappa}$-anonymity, and it is enhanced by the notions of ${\ell}$-diversity and t-closeness. Since there is the natural tradeoff between privacy and data utility, the development of practical anonymization algorithms is not a simple work and there is still no noticeable algorithm which achieves some combined anonymity conditions. In this paper, we provides a comparative analysis of previous anonymity and accuracy measures. Moreover we propose an algorithm to achieve ${\ell}$-diversity by the block merging method from a micro-data achieving ${\kappa}$-anonymity.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.1
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• pp.188-210
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• 2022

As a promising technique to support tremendous numbers of Internet of Things devices and a variety of applications efficiently, mobile edge computing (MEC) has attracted extensive studies recently. In this paper, we consider a MEC-assisted peer-to-peer (P2P) mobile communication system where MEC servers are deployed at access points to accelerate the communication process between mobile terminals. To capture the tradeoff between the time delay and the energy consumption of the system, a cost function is introduced to facilitate the optimization of the computation and communication resources. The formulated optimization problem is non-convex and is tackled by an iterative block coordinate descent algorithm that decouples the original optimization problem into two subproblems and alternately optimizes the computation and communication resources. Moreover, the MEC-assisted P2P communication system is compared with the conventional P2P communication system, then a condition is provided in closed-form expression when the MEC-assisted P2P communication system performs better. Simulation results show that the advantage of this system is enhanced when the computing capability of the receiver increases whereas it is reduced when the computing capability of the transmitter increases. In addition, the performance of this system is significantly improved when the signal-to-noise ratio of hop-1 exceeds that of hop-2.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.2
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• pp.267-277
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• 2022

Due to the increasing proportion of cloud and remote working environments, various information security incidents are occurring. Insider threats have emerged as a major issue, with cases in which corporate insiders attempting to leak confidential data by accessing it remotely. In response, insider threat detection approaches based on machine learning have been developed. However, existing machine learning methods used to detect insider threats do not take biases and variances into account, which leads to limited performance. In this paper, boosting-type ensemble learning algorithms are applied to verify the performance of malicious insider detection, conduct a close analysis, and even consider the imbalance in datasets to determine the final result. Through experiments, we show that using ensemble learning achieves similar or higher accuracy to other existing malicious insider detection approaches while considering bias-variance tradeoff. The experimental results show that ensemble learning using bagging and boosting methods reached an accuracy of over 98%, which improves malicious insider detection performance by 5.62% compared to the average accuracy of single learning models used.

• New & Renewable Energy
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• v.8 no.2
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• pp.33-43
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• 2012

Why solar companies preferred vertical integration of whole value chain? Major solar companies have built internally strong vertical integration of entire PV value chain. We raise a question whether such integration increases the corporate value and whether market situation affects the result. To test these questions, we conducted multi-variant analysis where characteristic factors mainly affect the corporate value measured in terms of Tobin'Q, based on the financial and non-financial data of PV companies listed in US stock market between 2005 and 2010. We hypothesize that since integration increases the overall efficiency but decreases the flexibility to adjust to various market situation, the combined effect of the efficiency gain and the flexibility loss ultimately determines the sign of integration effect on the corporate vale. We infer that the combined effect will be influenced heavily by business cycle, as in boom market (Seller's market) the efficiency gain may be larger than the flexibility loss and vice versa in bust market. We test whether the sign of combined effect changes after the year of 2009 and which factors influence most the sign. Year of 2009 is known as the year when market shifted from Seller's to Buyer's market. We show that 1) integration increases corporate value in general but after 2009 integration significantly decreases the value, 2) the ratios such as Production/Total Cost, Cash turnover period chosen for reversal of the flexibility measure are negatively affect Tobin's Q and especially stronger after 2009. This shows the flexibility improves corporate value and stronger in the recess period (Buyer's market). These results imply that solar company should set up integration strategy considering the tradeoff between efficiency and flexibility and the impact of the business cycle on both factors. Strategy only based on the price competitiveness determined in boom time can bring undesirable outcomes to the company. In addition, Strategic alliances in some value chains as a flexible bondage should be taken in account as complementary choice to the rigid integration.

• The KIPS Transactions:PartC
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• v.14C no.5
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• pp.417-424
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• 2007

Mesh networks using WLAN technology have been paid attention as a key wireless access technology. However, many technical issues still exist for its successful deployment. One of those issues is the routing problem that addresses the path setup through a WLAN mesh network for the data exchanges between a station and a wired network. Since the characteristics of a WLAN mesh network can be very dynamic, the use of single routing protocol would not fit for all environments whether it is reactive or proactive. Therefore, it is required to develop an adaptive routing protocol that modifies itself according to the changes in the network parameters. As a logical first step for the development, an analytical model considering all the dynamic features of a WLAN mesh network is required to evaluate the performance of a reactive and a proactive routing scheme. In this paper, we propose an analytical model that makes us scrutinize the impact of the network and station parameters on the performance of each routing protocol. Our model includes the size of a mesh network, the density of stations, mobility of stations. and the duration of network topology change. We applied our model to the AODV that is a representative reactive routing protocol and DSDV that is a representative proactive routing protocol to analyze the tradeoff between AODV and DSDV in dynamic network environments. Our model is expected to help developing an adaptive routing protocol for a WLAN mesh network.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2021.04a
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• pp.15-15
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• 2021

Seed coat color and seed weight are among the key agronomical traits that determine the nutritional quality of soybean seeds. This study aimed to evaluate the contents of total protein, total oil and five prominent fatty acids in seeds of 49 soybean varieties recently cultivated in Korea, and assess the influences of seed coat color and seed weight on each. Total protein and total oil contents were in the ranges of 36.28-44.19% and 13.45-19.20%, respectively. Likewise, individual fatty acid contents were in the ranges of 9.90-12.55, 2.45-4.00, 14.97-38.74, 43.22-60.26, and 5.37-12.33% for palmitic, stearic, oleic, linoleic, and linolenic acids, respectively. Our results found significant variations of protein, oil and fatty acid contents between the soybean varieties. Moreover, both seed coat color and seed weight significantly affected total oil and fatty acid contents. Total protein content, however, was not significantly affected by any factor. Among colored soybeans, pale-yellow soybeans were characterized by a high level of oleic acid (30.70%) and low levels of stearic (2.72%), linoleic (49.30%) and linolenic (6.44%) acids, each being significantly different from the rest of colored soybeans (p < 0.05). On the other hand, small soybeans were characterized by high levels of all individual fatty acids except oleic acid. The level of oleic acid was significantly high in large seeds. Cluster analysis grouped the soybeans into two classes with notable content differences. Principal component analysis also revealed fatty acids as the prime factors for the variability observed among the soybean varieties. As expected, total oil and total protein contents showed a negative association with each other (r = -0.714, p < 0.0001). Besides, oleic acid and linoleic acid showed a tradeoff relationship (r = -0.936, p < 0.0001) which was reflected with respect to both seed coat color and seed weight. In general, the results of this study shade light on the significance of seed coat color and seed weight to distinguish soybeans in terms of protein, oil and fatty acid contents. Moreover, the soybean varieties with distinct characteristics and nutritional contents identified in this study could be important genetic resources for consumption and cultivar development.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.5_6
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• pp.249-256
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• 2007

GPS(generalized processor sharing) is a fair scheduling scheme that guarantees fair distribution of resources in an instantaneous manner, while virtual clock pursues fairness in the sense of long-term. In this paper, we notice that the degree of memorylessness is the key difference of the two schemes, and propose a unified scheduling model that covers the whole spectrum of history-sensitiveness. In this model, each application's resource right is represented in a value called deposit, which is accumulated at a predefined rate and is consumed for services. The unused deposit, representing non-usage history, gives the application more opportunity to be scheduled, hence relatively enhancing its response time. Decay of the deposit means partial erase of the history and, by adjusting the decaying rate, the degree of history-sensitiveness is controlled. In the spectrum, the memoryless end corresponds GPS and the other end with full history corresponds virtual clock. And there exists a tradeoff between average delay and long-term fairness. We examine the properties of the model by analysis and simulation.