• Nuclear Engineering and Technology
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• v.54 no.9
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• pp.3448-3451
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• 2022

Biochar is a novel carbon based material derived from waste that shows promising properties for several applications. In this paper we investigate its potential use as a low cost, greener alternative to commonly used aggregates employed to enhance the neutron shielding performance of concrete. Monte Carlo simulations are performed with the PHITS code to estimate the neutron attenuation of blank and biochar-reinforced concrete exposed to high energy neutrons. We find that the shielding performance of concrete with 15% biochar is comparable with commonly used materials such as Boron Carbide at 20% and exceeds that of Basalt fibers with the same concentration, making these composites an interesting greener alternative to current solutions. A combination of biochar and heavier fillers also show extremely promising performance.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1816-1824
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• 2011

Recently, with traffic SOC investment policy changing from road-centered to railway-centered according to environment-friendly and sustainable development, issues regarding overlapping and overinvestment of traffic facility have been raised. Regarding investment of various traffic facilities of which departure and destination are similar to each other, academia, civic organizations, government, etc. are recognizing problems including overlapping investment of budget, environmental destruction, etc., but not suggesting definite solutions. Objective transportation network analysis is required because various positive effects including solutions of delay/congestion may occur due to provision of alternative way and distribution of the amount of traffic when accidents occur, as well as negative effects suggested by some of civic organizations in various transportation facility investment of similar departure and destination. Hereupon, this study tries to suggest a tool that can objectively evaluate interrelations of transportation network by applying multi-criteria analysis including economic feasibility regarding analysis of interconnections between and within means of transportation.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.163-169
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• 2001

The solution of two-dimensional deflection of circular wavy reinforcing fiber elastics was obtained for one end clamped boundary under concentrated load condition. The fiber was regarded as a linear elastic material. Wavy shape was described as a combination of half-circular arc smoothly connected each other with constant curvature of all the same magnitude and alternative sign. Also load direction was taken into account. As a result, the solution was expressed in terms of a series of elliptic integrals. These elliptic integrals had two different transformed parameters involved with load value and initial radius of curvature. While we found the exact solutions and expressed them in terms of elliptic integrals, the recursive ignition formulae about the displacement and arc length at each segment of circular section were obtained. Algorithm of determining unknown parameters was established and the profile curve of deflected beam was shown in comparison with initial shape.

• Journal of applied mathematics & informatics
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• v.15 no.1_2
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• pp.333-341
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• 2004

In the real world there are many linear programming problems where all decision parameters are fuzzy numbers. Several approaches exist which use different ranking functions for solving these problems. Unfortunately when there exist alternative optimal solutions, usually with different fuzzy value of the objective function for these solutions, these methods can not specify a clear approach for choosing a solution. In this paper we propose a method to remove the above shortcoming in solving fuzzy number linear programming problems using the concept of expectation and variance as ranking functions

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.1065-1070
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• 2003

Facility Layout Planning is concerned with how to arrange facilities necessary for production in a given space. Its objective is often to minimize the total sum of all material flows multiplied by the distance among facilities. FLP belongs to NP complete problem; i.e., the number of possible layout solutions increases with the increase of the number of facilities. Thus, meta heuristics such as Genetic Algorithm (GA) and Simulated Annealing have been investigated to solve the FLP problems. However, one of the biggest problems which lie in the existing meta heuristics including GA is hard to find an appropriate combinations of parameters which result in optimal solutions for the specific problem. The Ant System algorithm with elitist and ranking strategies is used to solve the FLP problem as an another good alternative. Experimental results show that the AS algorithm is able to produce the same level of solution quality with less sensitive parameters selection comparing to the ones obtained by applying other existing meta heuristic algorithms.

• Structural Engineering and Mechanics
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• v.50 no.6
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• pp.853-862
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• 2014

In this paper, two approximate analytical methods have been applied to forced nonlinear vibration problems to assess a high accurate analytical solution. Variational Iteration Method (VIM) and Perturbation Method (PM) are proposed and their applications are presented. The main objective of this paper is to introduce an alternative method, which do not require small parameters and avoid linearization and physically unrealistic assumptions. Some patterns are illustrated and compared with numerical solutions to show their accuracy. The results show the proposed methods are very efficient and simple and also very accurate for solving nonlinear vibration equations.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.35 no.2
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• pp.181-188
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• 2012

The fee system on spectrum usage is a usage fee that is charged for using spectrum provided by a wireless tower, and is used for management and promotion of the waves. The current fee system for spectrum usage in South Korea has faced many problems, such as complex calculation for fees, unjustified charges, unfairness in cost sharing among providers, and general inefficiency of operation. This study focuses on comparison of fee systems for spectrum usage of South Korea and other foreign countries, extraction of the root causes and problems by case analyses, and recommendation for better solutions to make a reasonable fee system for spectrum usage. The result of this study can be used as a solution to render spectrum usage more effective.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.7
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• pp.112-120
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• 2020

During the past decades, dramatic technology changes affected the life of billions of people around the globe. Although these changes resulted to economic benefits, mostly for the developed countries, the undiscerning development also resulted to many side effects, such as environment pollution, scarce natural resources, global warming, and an increase of the gap between "those who have" and "those who have not", among others. Also, since these developments were based on high technologies, they were not suitable for 90% of the underdeveloped countries. In this review, the possible ways of increasing the quality of life in underdeveloped countries are described, by providing adaptive solutions using appropriate technologies. Some successful applications of appropriate and intermediate technology are introduced, and the need for a new undergraduate education course of engineering design based on appropriate technology is proposed for Korea.

• Journal of Korea Society of Industrial Information Systems
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• v.13 no.5
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• pp.142-148
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• 2008

Facility Layout Planning is concerned with how to arrange facilities necessary for production in a given space. Its objective is often to minimize the total sum of all material flows multiplied by the distance among facilities. FLP belongs to NP complete problem; i.e., the number of possible layout solutions increases with the increase of the number of facilities. Thus, meta heuristics such as Genetic Algorithm (GA) and Simulated Annealing have been investigated to solve the FLP problems. However, one of the biggest problems which lie in the existing meta heuristics including GA is hard to find an appropriate combinations of parameters which result in optimal solutions for the specific problem. The Ant System algorithm with elitist and ranking strategies is used to solve the FLP problem as an another good alternative. Experimental results show that the AS algorithm is able to produce the same level of solution quality with less sensitive parameters selection comparing to the ones obtained by applying other existing meta heuristic algorithms.

• Journal of Korean Society for Quality Management
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• v.41 no.3
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• pp.371-380
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• 2013

Purpose: This study analyzes the optimal operation scheme of childcare centers in Korea to maximize the quality of childcare service by determining the number of children and number of teachers. Methods: This study employs a mathematical programming methodology called 'nonlinear integer programming (NLIP)' to solve the optimization problems and compare the quality of childcare service of optimal solutions with those of present operation scheme. Results: It is very successful in obtaining the optimal solutions for alternative capacities and they guarantee the substantial improvement in the quality of childcare service. Conclusion: Though more variables should be adapted for defining the quality of childcare service robustly, it is possible to conclude that childcare centers should modify their operation scheme to improve the quality of childcare service.