• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.11 no.4
• /
• pp.815-825
• /
• 2007

The existing web-based self-directed learning systems are in short for the ability of learning skills assessment. Even worse, hey only give test scores as an indicate for test skills, which is also not a good measure for learning skills assessment and makes it difficult to assess learning skills objectively and to present clear assessment criterion. In this paper, we proposed an improved self-directed learning system using fuzzy logic, which can be controlled by learners themselves and helps to evaluate their on learning process. We also implemented the system on the written examination of Engineer Information Processing. The purposed system lust calculates membership functions of learning tine, learning frequency, testing time, and test score. Using them the final membership functions of learning and test skills are calculated and presented in a graphical, i.e. mon understandable, way to user. The purposed system helps learners to assess their achievement and to plan future schedule, and the survey result on the students used the system also supports that.

• Journal of Ocean Engineering and Technology
• /
• v.28 no.5
• /
• pp.404-410
• /
• 2014

The purpose of this study was to find the optimal arrangement of FPSO equipment in a module while considering the economic value and fire risk. We estimated the economic value using the pipe connections and pump installation cost in an HP (high pressure) gas compression module. The equipment risks were also analyzed using fire scenarios based on historical data. To consider the wind effect during a fire accident, fuzzy modeling was applied to improve the accuracy of the analysis. The objective functions consisted of the economic value and fire risk, and the constraints were the equipment maintenance and weight balance of the module. We generated a Pareto-optimal front group using a multi-objective GA (genetic algorithm) and suggested an equipment arrangement method that included the opinions of the designer.

• Earthquakes and Structures
• /
• v.11 no.2
• /
• pp.347-369
• /
• 2016

The main objective of this paper is the robust multi-objective optimization design of semi-active tuned mass damper (STMD) system using genetic algorithms and fuzzy logic. For optimal design of this system, it is required that the uncertainties which may exist in the system be taken into account. This consideration is performed through the robust design optimization (RDO) procedure. To evaluate the optimal values of the design parameters, three non-commensurable objective functions namely: normalized values of the maximum displacement, velocity, and acceleration of each story level are considered to minimize simultaneously. For this purpose, a fast and elitist non-dominated sorting genetic algorithm (NSGA-II) approach is used to find a set of Pareto-optimal solutions. The torsional effects due to irregularities of the building and/or unsymmetrical placements of the dampers are taken into account through the 3-D modeling of the building. Finally, the comparison of the results shows that the probabilistic robust STMD system is capable of providing a reduction of about 52%, 42.5%, and 37.24% on the maximum displacement, velocity, and acceleration of the building top story, respectively.

• The Journal of the Korea Contents Association
• /
• v.11 no.4
• /
• pp.27-32
• /
• 2011

This paper presents a methodology for classifying sleep disturbance using electroencephalogram (EEG) signal at sleep stage 2 and principal component analysis. For extracting initial features, fast Fourier transforms(FFT) were carried out to remove some noise from EEG signal at sleep stage 2. In the second phase, we used principal component analysis to reduction from EEG signal that was removed some noise by FFT to 5 features. In the final phase, 5 features were used as inputs of NEWFM to get performance results. The proposed methodology shows that accuracy rate, specificity rate, and sensitivity were all 100%.

• International Journal of Safety
• /
• v.6 no.2
• /
• pp.27-32
• /
• 2007

For last several decades with the achievement of fast economic development, the electrical fires occupies over 30 percent of total fire incidents almost every year in Korea and not decreased in spite of much times and efforts. Electrical fire cause diagnostics are to confirm a cause for the fire by examination of fire scene. Cause diagnosis methods haven't been systematized yet, because of limits for available information, investigator's biased knowledge, etc. Therefore, in order to assist the investigators and to find out the exact causes of electrical fires, required is research for an electrical fire cause diagnosis system using DB, computer programming and some mathematical tools. The electrical fire cause diagnosis system has two functions of DB and electrical fire cause diagnosis. The cause diagnosis is conducted by a case-based reasoning on a case base and rule-based reasoning on a rule base. For the diagnosis with high reliability, a mixed reasoning approach of a case-based reasoning and fuzzy rule-based reasoning has been adopted. The electrical fire cause diagnosis system proposes the electrical fire causes inferred from the diagnosis processes, and possibility of the causes as well.

• The Journal of Industrial Distribution & Business
• /
• v.9 no.2
• /
• pp.27-38
• /
• 2018

Purpose - This study centers on field surveys aimed at deriving the customer satisfaction factors of customer support centers that are positioned between suppliers and consumers in the supply chain. They consists of manufacturing, sales, distribution, consumption and collection, and that are in charge of core functions for suppliers' customer satisfaction management and consumers' satisfaction with consuming activities. Research design, data, and methodology - The customer satisfaction factors of customer support centers were derived through literature review and expert opinion surveys, and a questionnaire was developed through a process of the refinement of variables using pilot tests and 330 questionnaire sheets were distributed. The questionnaire sheets were collected and opinions in them were analyzed using fuzzy AHP methodology. Results - Three factors, which are turnover intentions, motivation, and job satisfaction, were derived as customer satisfaction factors of customer support centers, and the ranking relationships of these three factors were analyzed. In addition, the ranking relationships among six execution variables of turnover intentions, 10 execution variables of motivation, and 10 execution variables of job satisfaction were analyzed using fuzzy AHP methodology to obtain quite significant results. Based on the results of this study, three implications in the three strategic aspects and an implication in the academic aspects are presented. Conclusions - Motivation and job satisfaction, job satisfaction and turnover intentions, and motivation and turnover intentions are not formed by independent or different factors or environments. They are in the same context with each other (maintaining high correlations) and are in the relationships of virtuous circles in which they complement each other.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.12
• /
• pp.7277-7282
• /
• 2014

In this study, the gradient descent algorithm was used for FLC analysis and the algorithm was used to represent the effects of nonlinear parameters, which alter the antecedent and consequence fuzzy variables of FLC. The controller parameters choose the control variable by iteration for gradient descent algorithm. The FLC consists of 7 membership functions, 49 rules and a two inputs - one output system. The system adopted the Min-Max inference method and triangle type membership function with a 13 quantization level.

• The Transactions of the Korea Information Processing Society
• /
• v.5 no.10
• /
• pp.2584-2590
• /
• 1998

In the existing fuzzy aggregation method, the operators such as t-norm, t conorm, mean operator, Yafer's operator and $\gamma$ operator are used to aggregate the values of membership functions. However, these methods have problems in that they do not reflect the decision situation properlyin the decision process. In order to solve these problems we suggest a situation assessment model(SAM) to reflect the decision situation in the decision proess. In the fuzzy decision environment, we propose a new aggregation method to reflect the decision situation using the result of SAM. We call it the aggregation based on situation assessment (ASA) method. It makes the stepwise aggregation with derection according to the decision situation. Moreover, we compare ASA method with the existing aggregation methods.

• International Journal of Control, Automation, and Systems
• /
• v.5 no.5
• /
• pp.539-546
• /
• 2007

The important field of research in ship operation is related to the high efficiency of transportation, the convenience of maneuvering ships and the safety of navigation. For these purposes, many intelligent technologies for ship automation have been required and studied. In this paper, we propose an intelligent voice instruction-based learning (VIBL) method and discuss the building of a ship's steering control system based on this method. The VIBL system concretely consists of two functions: a text conversion function where an instructor's inputted voice is recognized and converted to text, and a linguistic instruction based learning function where the text instruction is understood through a searching process of given meaning elements. As a study method, the fuzzy theory is adopted to build maneuvering models of steersmen and then the existing LIBL is improved and combined with the voice recognition technology to propose the VIBL. The ship steering control system combined with VIBL is tested in a ship maneuvering simulator and its validity is shown.

• Journal of the Korean Institute of Telematics and Electronics C
• /
• v.34C no.7
• /
• pp.38-50
• /
• 1997

This paper concerns a VHDL design and simulation of an accurate and cost-effective fuzzy logic controller (FLC). The accurcy of the proposed FLC is obtained by using the center of gravity (COG) defuzzifier that considers both membership values and spans of membership functions in calculating a crisp value. The cost-effectiveness of the proposed FLC is obtained by restructuring the conventional FLC in the following ways: Firstly, the MAX-MIN inference is inference is replaced by a read-modify-write operation that can be implemented economically in the structure of register files. Secondly, the division in the COG defuzzifier is avoided by finding the moment equilibrium point. The proposed COG defuzzifier has two disadvantages that it requires additional multipliers and it takes a lot of computation time to find the moment equilibrium point. The first disadvantage is overcome by replacing the mulitpliers with stochastic AND operations and the second disadvantage is alleviated by using a coarse-to-fine searching algorithm. The proposed FLC is described in VHDL structurally and behaviorally and whether it is working well or not is checked on SYNOPSYS VHDL simulator by using the truck backer-upper control problem.