• Journal of the Korean Geotechnical Society
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• v.27 no.11
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• pp.83-92
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• 2011

The random and heterogeneous pore structure is a significant factor that dominates physical and mechanical behaviors of soils such as fluid flow and geomechanical responses driven by loading. The characterization method using non-destructive testing such as micro X-ray CT technique which has a high resolution with micrometer unit allows to observe internal structure of soils. However, the application has been limited to qualitatively observe 2D and 3D CT images and to obtain the void ratio at macro-scale although the CT images contain enormous information of materials of interests. In this study, we constructed the 3D particle and pore structures based on sequentially taken 2D images of glass beads and quantitatively defined complex pore structure with void cell and void channel. This approach was enabled by implementing image processing techniques that include coordinate transformation, binarization, Delaunay Triangulation, and Euclidean Distance Transform. It was confirmed that the suggested algorithm allows to quantitatively evaluate the distribution of void cells and their connectivity of heterogeneous pore structures for glass beads.

• Journal of the Korean Geotechnical Society
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• v.34 no.5
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• pp.37-51
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• 2018

The slope failure due to the rainfall infiltration occurs frequently in Korea, since the depth of the weathered residual soil layer is shallow in mountainous region. Depth of the failure surface is shallow and tends to pass near the interface between impermeable bedrock and soil layer. Soil parameters that have a significant impact on the instability of unsaturated slopes due to rainfall infiltration inevitably include large uncertainties. Therefore, this study proposes a probabilistic analysis procedure by Monte Carlo Simulation which considers the hydraulic characteristics and strength characteristics of soil as random variables in order to predict slope failure due to rainfall infiltration. The Green-Ampt infiltration model was modified to reflect the boundary conditions on the slope surface according to the rainfall intensity and the boundary condition of the shallow impermeable bedrock was introduced to predict the stability of unsaturated soil slope with shallow bedrock under constant rainfall intensity. The results of infiltration analysis were used as inputs of infinite slope analysis to calculate the safety factor. The proposed analysis method can be used to calculate the time-dependent failure probability of soil slope due to rainfall infiltration.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1C
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• pp.28-36
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• 2009

Time-memory trade-off (TMTO) cryptanalysis proposed by Hellman can be applied for the various crypto-systems such as block ciphers, stream ciphers, and hash functions. In this paper, we propose a novel method to reduce memory size for storing TMTO tables. The starting points in a TMTO table can be substituted by the indices of n-bit samples from a sequence in a family of pseudo-random sequences with good cross-correlation, which results in the reduction of memory size for the starting points. By using this method, it is possible to reduce the memory size by the factor of 1/10 at the cost of the slightly increasing of operation time in the online phase. Because the memory is considered as more expensive resource than the time, the TMTO cryptanalysis will be more feasible for many real crypto systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.1
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• pp.45-51
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• 1998

In the realization of a high speed digital transmission over several tens kbps in mobile communications, it follow delay distortion on a count of transmission path variation by multipath interference waves. Therefore it is inevitably necessary to establish the techniques overcoming the frequency selective fading. In this paper, a feedback running RLS algorithm which is improved the RLS algorithm using exponential weighting factor, is proposed for the control algorithm of DFE and by the computer simulation method, and the performance characteristics of DFE is analyzed for the one-ray and two-ray waves model under the random Gaussian noise. The computer simulation results of proposed RLS algorithm for the $\pi$/4QPSK signal with one symbol time delayed interference signal of S/I = 20［dB］, under the S/N = 10［dB］ with $\lambda$= 0.9 showed excellent following characteristics and equalization characteristics.

• Journal of Microbiology and Biotechnology
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• v.17 no.2
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• pp.234-243
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• 2007

Vibrio vulnificus is an opportunistic pathogen that causes septicemia in humans. To identify the genes associated with its pathogenicity, in vivo expression technology (IVET) was used to select genes specifically expressed in a host, yet not significantly in vitro. Random lacZ-fusions in the genome of V vulnificus strain MO6-24/O were constructed using an IVET vector, pSG3, which is a suicide vector containing promoterless-aph and -lacZ as reporter genes. A total of ${\sim}18,000$ resulting library clones were then intraperitoneally injected into BALB/c mice using a colony forming unit (CFU) of $1.6{\times}10^6$. Two hours after infection, kanamycin was administered at $200{mu}g$ per gram of mouse weight. After two selection cycles, 11 genes were eventually isolated, which were expressed only in the host. Among these genes, VV20781 and VV21007 exhibiting a homology to a hemagglutinin gene and tolC, respectively, were selected based on having the highest frequency. When compared to wild-type cells, mutants with lesions in these genes showed no difference in the rate of growth rate, yet a significant decrease in cytotoxicity and the capability to form a biofilm.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.6
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• pp.586-594
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• 2009

This paper is the study on random, sinusoidal and shock vibration responses for the STSAT-3(science and technology satellite-3) proto-model which is the first small size all-composite satellite in Korea. The structure system of the STSAT-3 forms box type structure by joining several hybrid sandwich panels comprised of honeycomb core and carbon fiber reinforced laminated composite skins on both side. Mode shape, stress, displacement and acceleration responses are obtained on both the frequency domain and time domain by means of a commercial FEA software MSC/NASTRAN. From these analysis results, failure, safety factor and design validity are assessed. These results can be successfully applicable as reference data when a new satellite is developed as well as giving out an excellent criteria in satellite vibration treatment design.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.8
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• pp.737-743
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• 2009

Design optimization process and results of Loop Heat Pipe(LHP) using Tabu Search have been presented in this study. An objective of optimization is to reduce a mass of the LHP with satisfying operating temperature of a Lithium Ion battery onboard an aircraft. The battery is assumed to be used as power supply of air borne high energy laser system because of its high specific energy. The analytical models are based on a steady state mathematical model and the design optimization is performed using a Meta Model and Tabu Search. As an optimization results, the Tabu search algorithm guarantees global optimum with small computation time. Due to searching by random numbers, initial value is dominant factor to search global optimum. The optimization process could reduce the mass of the LHP which express the same performance as an published LHP.

• Journal of Electrical Engineering and Technology
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• v.5 no.1
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• pp.116-128
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• 2010

Modeling of the three phase electric arc furnace and its voltage flicker mitigation are the purposes of this paper. For modeling of the electric arc furnace, at first, the arc is modeled by using current-voltage characteristic of a real arc. Then, the arc random characteristic has been taken into account by modulating the ac voltage via a band limited white noise. The electric arc furnace compensation with static VAr compensator, Thyristor Controlled Reactor combined with a Fixed Capacitor bank (TCR/FC), is discussed for closed loop control of the compensator. Instantaneous flicker sensation curves, before and after accomplishing compensation, are measured based on IEC standard. A new method for controlling TCR/FC compensator is proposed. This method is based on applying a predictive approach with closed loop control of the TCR/FC. In this method, by using the previous samples of the load reactive power, the future values of the load reactive power are predicted in order to consider the time delay in the compensator control. Also, in closed loop control, two different approaches are considered. The former is based on voltage regulation at the point of common coupling (PCC) and the later is based on enhancement of power factor at PCC. Finally, in order to show the effectiveness of the proposed methodology, the simulation results are provided.

• The Journal of the Korea Contents Association
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• v.9 no.6
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• pp.399-406
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• 2009

The goal of this research is to examine the influence degree of participant of sports on self-esteem of middle school students. By stratified cluster random sampling method 420, middle school student living in D city joined the survey; it was used to derive the result of this research. Among them, 25 results were excepted by the lack of reliability or un-enough answer rate, so 395 results were used for the research. To analyze collected data, used statistical technique statistical analysis technique frequency, factor analysis, t-test and ANOVA. Through such method of study and formality, this study deduced following result. First, self-esteem of middle school students shows change by the frequency of sports activity. Second, self-esteem of middle school students shows change by the interval of sports activity. Third, self-esteem of middle school students shows change by the intensity of sports activity.

• Steel and Composite Structures
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• v.25 no.6
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• pp.663-670
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• 2017

The problem of layup optimization of the composite laminates involves a very complex multidimensional solution space which is usually non-exhaustively explored using different heuristic computational methods such as genetic algorithms (GA). To ensure the convergence to the global optimum of the applied heuristic during the optimization process it is necessary to evaluate a lot of layup configurations. As a consequence the analysis of an individual layup configuration should be fast enough to maintain the convergence time range to an acceptable level. On the other hand the mechanical behavior analysis of composite laminates for any geometry and boundary condition is very convoluted and is performed by computational expensive numerical tools such as finite element analysis (FEA). In this respect some studies propose very fast FEA models used in layup optimization. However, the lower bound of the execution time of FEA models is determined by the global linear system solving which in some complex applications can be unacceptable. Moreover, in some situation it may be highly preferred to decrease the optimization time with the cost of a small reduction in the analysis accuracy. In this paper we explore some machine learning techniques in order to estimate the failure of a layup configuration. The estimated response can be qualitative (the configuration fails or not) or quantitative (the value of the failure factor). The procedure consists of generating a population of random observations (configurations) spread across solution space and evaluating using a FEA model. The machine learning method is then trained using this population and the trained model is then used to estimate failure in the optimization process. The results obtained are very promising as illustrated with an example where the misclassification rate of the qualitative response is smaller than 2%.