• Geotechnical Engineering
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• v.12 no.3
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• pp.73-82
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• 1996

Limit state design(LSD) principles employing load and resistance factor design(LRFD) are coming into use in geotechnical engineering community around the world. Current working (allowable) stress design principles are expected to be replaced by LRFH method in the near future. North America has recently adopted LRFD principles, and European community has also developed its own code called "Eurocode" based on partial safety factor design which is essentially the same as LRFD. Relevant review and analysis of new global design codes are prerequisites to adopting these codes in the Korean construction industry and in the Korean foundation design prac titre. This paper reviews geotechnical aspects of LRFD and Eurocode, and analyzes the geomaterial resistance factors in LRFD for the design of axially-loaded driven piles.

• Computers and Concrete
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• v.12 no.3
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• pp.261-283
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• 2013

This paper aims to contribute to the three-dimensional generalization of numerical prediction of crack propagation through the formulation of finite elements with embedded discontinuities. The analysis of crack propagation in two-dimensional problems yields lines of discontinuity that can be tracked in a relatively simple way through the sequential construction of straight line segments oriented according to the direction of failure within each finite element in the solid. In three-dimensional analysis, the construction of the discontinuity path is more complex because it requires the creation of plane surfaces within each element, which must be continuous between the elements. In the method proposed by Chaves (2003) the crack is determined by solving a problem analogous to the heat conduction problem, established from local failure orientations, based on the stress state of the mechanical problem. To minimize the computational effort, in this paper a new strategy is proposed whereby the analysis for tracking the discontinuity path is restricted to the domain formed by some elements near the crack surface that develops along the loading process. The proposed methodology is validated by performing three-dimensional analyses of basic problems of experimental fractures and comparing their results with those reported in the literature.

• Journal of the Korean Society of Food Culture
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• v.26 no.6
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• pp.574-582
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• 2011

The aim of this study was to classify Korean consumers based on their food-related lifestyle type, and to investigate the relationship between sushi consumption and food-related lifestyle type. Self-reported questionnaires were completed by 300 Korean adults. The SPSS 18.0 program was used to analyze the samples. Data was analyzed by frequency, descriptive factor, reliability, cluster analysis, ANOVA, and chi-square test. A factor analysis extracted four factors comprising foodrelated lifestyle, which we named Health-seeking (factor 1), Taste-seeking (factor 2), Convenience-seeking (factor 3), and Economy-seeking (factor 4). According to a cluster analysis based on those four factors, consumers were classified into three clusters. Cluster 1 was the Taste and Health-seeking cluster, Cluster 2 was the Convenience-seeking cluster, and Cluster 3 was the Passive Eating Habits cluster. The results also indicated that the selection attributes of each cluster were significantly different in terms of perception, the global state of sushi, sushi preference, frequency, companions, place of sushi consumption, and preference for different sushi sub-ingredients. Based on these results, consumer characteristics in the sushi market are discussed.

• ETRI Journal
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• v.32 no.6
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• pp.854-862
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• 2010

One-way delay variation (OWDV) has become increasingly of interest to researchers as a way to evaluate network state and service quality, especially for real-time and streaming services such as voice-over-Internet-protocol (VoIP) and video. Many schemes for OWDV measurement require clock synchronization through the global-positioning system (GPS) or network time protocol. In clock-synchronized approaches, the accuracy of OWDV measurement depends on the accuracy of the clock synchronization. GPS provides highly accurate clock synchronization. However, the deployment of GPS on legacy network equipment might be slow and costly. This paper proposes a method for measuring OWDV that dispenses with clock synchronization. The clock synchronization problem is mainly caused by clock skew. The proposed approach is based on the measurement of inter-packet delay and accumulated OWDV. This paper shows the performance of the proposed scheme via simulations and through experiments in a VoIP network. The presented simulation and measurement results indicate that clock skew can be efficiently measured and removed and that OWDV can be measured without requiring clock synchronization.

• International Journal of Control, Automation, and Systems
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• v.5 no.6
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• pp.674-680
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• 2007

The probabilistic roadmap (PRM) method, which is a popular path planning scheme, for a manipulator, can find a collision-free path by connecting the start and goal poses through a roadmap constructed by drawing random nodes in the free configuration space. PRM exhibits robust performance for static environments, but its performance is poor for dynamic environments. On the other hand, reinforcement learning, a behavior-based control technique, can deal with uncertainties in the environment. The reinforcement learning agent can establish a policy that maximizes the sum of rewards by selecting the optimal actions in any state through iterative interactions with the environment. In this paper, we propose efficient real-time path planning by combining PRM and reinforcement learning to deal with uncertain dynamic environments and similar environments. A series of experiments demonstrate that the proposed hybrid path planner can generate a collision-free path even for dynamic environments in which objects block the pre-planned global path. It is also shown that the hybrid path planner can adapt to the similar, previously learned environments without significant additional learning.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.359-366
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• 2005

Most engineering optimization are based on numerical linear and nonlinear programming methods that require substantial gradient information and usually seek to improve the solution in the neighborhood of a starting point. These algorithm, however, reveal a limited approach to complicated real-world optimization problems. If there is more than one local optimum in the problem, the result may depend on the selection of an initial point, and the obtained optimal solution may not necessarily be the global optimum. This paper describes a new harmony search(HS) meta-heuristic algorithm-based approach for structural size optimization problems with continuous design variables. This recently developed HS algorithm is conceptualized using the musical process of searching for a perfect state of harmony. It uses a stochastic random search instead of a gradient search so that derivative information is unnecessary. Two classical space truss optimization problems are presented to demonstrate the effectiveness and robustness of the HS algorithm. The results indicate that the proposed approach is a powerful search and optimization technique that may yield better solutions to structural engineering problems than those obtained using current algorithms.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.6
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• pp.3393-3402
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• 2013

The increasing scourge of cancer epidemiology is a global concern. With WHO emphasizing that 40% of all cancer cases are preventable, exposure to known and suspected carcinogens must be discouraged. The battle with communicable diseases and other third world challenges has greatly de-emphasized anti-cancer campaigns in sub-Saharan Africa. The abundant deposit of mineral resources in sub-Saharan Africa has attracted high mining activity with its negative environmental aftermath. Poor regulatory mechanisms have led to environmental contamination by products of mining including heavy metals. In addition to poor urban planning, the springing up of settlements in industrial areas has led to generation and exposure to more hazardous wastes consequent on poor disposal systems. Studies establishing close association between exposure to heavy metals and cancer epidemiology in sub-Saharan Africa are increasing. The current review assesses the level of environmental pollution by heavy metals in sub-Saharan Africa, and brings to the fore available evidence implicating such in the increasing cancer epidemiology in the sub-continent.

• Journal of Astronomy and Space Sciences
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• v.36 no.4
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• pp.249-264
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• 2019

In this study, the precise orbit determination (POD) software is developed for optical observation. To improve the performance of the estimation algorithm, a nonlinear batch filter, based on the unscented transform (UT) that overcomes the disadvantages of the least-squares (LS) batch filter, is utilized. The LS and UT batch filter algorithms are verified through numerical simulation analysis using artificial optical measurements. We use the real optical observation data of a low Earth orbit (LEO) satellite, Cryosat-2, observed from optical wide-field patrol network (OWL-Net), to verify the performance of the POD software developed. The effects of light travel time, annual aberration, and diurnal aberration are considered as error models to correct OWL-Net data. As a result of POD, measurement residual and estimated state vector of the LS batch filter converge to the local minimum when the initial orbit error is large or the initial covariance matrix is smaller than the initial error level. However, UT batch filter converges to the global minimum, irrespective of the initial orbit error and the initial covariance matrix.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1783-1786
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• 2016

The paper investigates the insulation properties of the supercritical $CO_2$ ($SCCO_2$) fluid as an insulating medium for electrical apparatuses. The insulating material is crucial for electrical apparatuses and $SF_6$ gas has been widely used for high power electrical apparatuses. There have been many research efforts to develop substituents for $SF_6$ gas because of high global warming potential. We obtained above 350 kV/mm insulation strength with 12.0 MPa $SCCO_2$. The positive and negative IEC standard pulses are applied between two 10 mm diameter spherical electrodes. The insulation strength of $SCCO_2$ is at least 2.5 times higher than that of $CO_2$ gas at 6.0MPa. The insulation strength of $SCCO_2$ fluid is about 10 times higher than that of $SF_6$ at 0.5MPa which is the ordinary operating pressure of electrical switchgears. Using the result, we expect that the time for switching and dielectric recovery could be reduced using $SCCO_2$ fluid as an insulating medium.

• Journal of Computing Science and Engineering
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• v.11 no.2
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• pp.49-57
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• 2017

This paper proposes a new IPv6 networking paradigm as a counter answer to the rationale for locator/identifier separation. Instead of involving separate number spaces each for node identifiers and locators, the context of the IP address as a node identifier alone is utilized and no additional locators are incorporated. That is, there are only node addresses and no locators, and location information is indirectly derived from neighbor relations between nodes. In order to accomplish this, no subnet IDs are utilized; the ID value is set to zero for all subnets. The paper details how to construct this paradigm through novel choice of operational policies in various IPv6 protocols and some trivial modifications. Especially, inherent provision of intra-domain node- as well as subnet-mobility by use of standard link-state intra-domain routing protocols is discussed. A number of important advantages of this paradigm over the canonical IPv6 networking and various known solutions of locator/identifier separation are discussed. Tailoring for multi-area domains and IPv4 is left for further study.