다중모델기법을 이용한 비선형시스템의 퍼지모델링

이철희,하영기,서선학 江原大學校 産業技術硏究所 1997 産業技術硏究 Vol.17 No.-

In this paper, a new approach to modeling of nonlinear systems using fuzzy theory is presented. To express the various and complex behavior of nonlinear system, we combine multiple model method with hierachical prioritized structure, and the mountain clustering technique is used in partitioning of system. TSK rule structure is adopted to form the fuzzy rules, and Back propagation algorithm is used for learning parameters in consequent parts of the rules. Also we soften the paradigm of Mamdani's inference mechanism by using Yager's S-OWA operators. Computer simulations are performed to verify the effectiveness of the proposed method.

洛東江 水質汚染에 따른 淨水處理 改善에 關한 硏究(II)

李哲熙,朴永圭,金水源,具本大 嶺南大學校 環境問題硏究所 1981 環境硏究 Vol.1 No.1

The algae content in the Nackdong river water, which is used as source of water works in Daegu city and carries a pollution load of domestic and industrial wastewater, rises in the warm season to such a level that calls for a improvement process for water treatment. A pilot plant study on the efficiency of the removal of algae by dissolved air flotation was conducted and the results are summarized as follows: 1. Algae concentration in the raw water is the highests in April, May and September below 25 NTU of raw water turbidity. In these dry months, the production of treated water decreases by the conventional water treatment process. 2. The average efficienct of algae removal could be achieved at 96% using coagulants, such as alum or PAC at dissolved air flotation. In the conventional sedimentation process, algae can be removed by only 88% and produces chlorinated organic compounds after breakpoint chlorinatioin. 3. It is required that the ideal flotation area is 7,106㎡ and the detention time is 20 min for treated water of 250,000㎡ /day.

퍼지논리 제어기의 비선형성의 정량적 해석

이철희,서선학 江原大學校 産業技術硏究所 1996 産業技術硏究 Vol.16 No.-

In this paper,the nonlinear I/O characteristic of suzzy logic controller is analyzed by using cell concept. Sources of the conlinearity inafuzzy logic controller include thefuzzification, the fuzzy reasoning and the defuzzification. A closed form expression for the defuzzified output is derived in case of a fuzzy logic controller with two inputs, traingular memberships, MacVicar-Whelan type linguistic rules, and direct fuzzy reasoning. As a result, it is shown that fuzzy logic linguistic rules, an direct fuzzy reasoning. As a result, it is shown that fuzzy logic controller is a nonlinear controller. Also its nonlinearity is analyzed with respect to the conventional PID control and the sliding mode control.

비선형 시스템 제어를 위한 퍼지 PID 제어기의 설계 및 해석

이철희,김성호 강원대학교 산업기술연구소 2000 産業技術硏究 Vol.20 No.B

Although Fuzzy Logic Controller(FLC) adopted three terms as input gives better performance, FLC is in general composed of two-term control because of the difficulty in the construction of fuzzy rule base. In this paper, a three-term FLC which is similar to PID control but acts as a nonlinear controller is proposed. To reduce the complexity of the rule base design and to increase efficiency. a simplified fuzzy PID control is induced from a hybrid velocity/position type PID algorithm by sharing a common rule base for both fuzzy PI and fuzzy PD parts. It is simple in structure, easy in implementation, and fast in calculation. The phase plane technique is applied to obtain the rule base for fuzzy two-term control and the resultant rule base is Macvicar-Whelan type. And the membership function is a Gaussian function. The frequency response information is used in tuning of the membership functions. Also a tuning strategy for the scaling factors is proposed based on the relationship between PID gain and the scaling factors. Simulation results show better performance and the effectiveness of the proposed method.

러프집합과 계층적 구조를 이용한 규칙생성

이철희,김주영 강원대학교 정보통신연구소 2003 정보통신논문지 Vol.7 No.-

This paper deals with the rule generation from data for control system and data mining using rough set which is an effective technique in extracting knowledge from incomplete and inconsistent information. If the cores and reducts are searched for without consideration of the frequency of inconsistent data belonging to the same equivalent class in rough set, unfortunately the necessary attribute may be discarded, or the unnecessary attributes may not be discarded. In consequence, the resultant rules don't fit well the characteristics of the data. To improve this, we handle the inconsistent data with a probability measure defined by support. As a result, the effect of the uncertainty in the knowledge reduction can be reduced to some extent. Also to make effective rule base, we construct the rule base in a hierarchical structure by applying core as the classification criteria at each level. When more than one core exist, the coverage degree is used to select an appropriate one among them to increase the classification rate. The proposed method gives more proper and effective rule base in compatibility and size. For some data mining example, simulations are performed to show the effectiveness of the proposed method.

유연구조 퍼지추론 및 비퍼지화

이철희,서선학,Yager, R. 강원대학교 정보통신연구소 1997 정보통신논문지 Vol.1 No.-

In this paper, we suggest a new approach having the flexibility to the problem of fuzzy inference and defuzzification. For fuzzy inference, we observe the fact that it consists of three parts; the determination of firing level of each rule, the determination of degree of coupling between antecedent and consequent of a rule, and the aggregation of all rules. So we soften the paradigm of Mamdani's fuzzy inference model by using S-OWA operators. Also, for defuzzification, we introduced a combinability function to help to more intelligently guide the difuzzification process. And then, we treat it as a kind of clustering problem and apply the basic idea used in the mountain clustering method. The proposed method includes Mamdani's fuzzy inference model and center of gravity method as a special case, and it has the flexibility.

혈액투석에 의해 유발된 조증 1례

정철호,박영남,이황희,김정범 啓明大學校 醫科大學 1994 계명의대학술지 Vol.13 No.4

Psychiatric complications in patients undergoing hemodialysis include depression, acute psychotic reactions, delirium, and mania. Mania during hemodialysis is not as common as depression, as evidenced by a paucity of such case reports in the foreign literature and by there is no such a report in domestic literature. We experienced the case of 39-year-old man with chronic renal failure secondary to chronic glomerulonephritis who developed mania during hemodialysis for about 2 months. He has been treated with haloperidol, clonazepam, and supportive psychotherapy. With 3 months follow up, has been doing well and has returned to work.

사업장 근로자의 건강위험 평가도구 개발

정규철,이용애,홍윤철,조희숙,박혜숙,임현술,하은희 이화여자대학교 환경문제연구소 1998 이화환경연구 Vol.2 No.-

Health Risk Appraisal(HRA) is usually defined as a process by which we expect of individual's chances of acquiring specific diseases within a defined period of time. The concept of worksite as an area of health maintenance and promotion is newly developing. Our movement for health promotion of employees has been increasingly known in the worksite. The aim of this study is to develop health risk appraisal tools about health promotion at the worksite for employees. We performed this study by two steps: one step was to develop a HRA questionnaire of worksites in Korea, another was to evaluate the reliability of the questionnaire. For developing HRA questionnaire, we reviewed scientific examples at first, and then weighted the score by delphi. To evaluate the reliability of developed questionnaire, we carried out survey by test-retest method. A total of 131 employees completed HRA questionnaire on two times. The results are as follows. The total score of health risk in unhealthy workers was higher than that of healthy workers. The range of test-retest reliability of responses to the questionnaire was 0.57-0.94. Therefore it seems that this questionnaire was very suitable to assess the health behavior of workers. In conclusion, the developed HRA questionnaire can be used as a tool for evaluating health behavior and for providing health counseling materials.

GA와 러프집합을 이용한 퍼지 모델링

이철희,주용석 강원대학교 정보통신연구소 2003 정보통신논문지 Vol.7 No.-

Fuzzy system has in general a drawback that no well-structured and systematic procedure for its design exists. To overcome this difficulty, we suggest a new design method for fuzzy model by combining genetic algorithm(GA) and rough set(RS) theory. Even though the structure and the parameters of fuzzy model may be optimally tuned by GA, it is a time consuming process due the huge serach space. Therefore we introduce rough set theory for rule reduction procedure. As a result, the decrease of learning time and the considerable rate of rule reduction are achieved without loss of useful information. The proposed algorithm is composed of three stages; First stage is quasi-optimization of fuzzy model using GA(coarse tuning). Next the obtained rule base is reduced by rough set concept(rule reduction). Finally only the membership functions of the fixed rules are re-optimized by GA(fine tuning). To check the effectiveness of the suggested algorithm, examples for time series prediction are examined.

오존酸化와 活性炭 濾過에 의한 飮料水의 水質改善에 관하여

李哲熙,金富漢 嶺南大學校 環境問題硏究所 1984 環境硏究 Vol.4 No.2

This research is conducted to find out the effect of ozonization in the removal of hazardous contaminants encountered at Sankyuk Waterworks, and also to modify the conventional treatment plant with ozonization process for producing the sterilized clean water. The ozone treatment rate to maintain 0.4mg/1 of free residual ozone in the gallery infiltered water is 2.1mg/1 for ozone demand flask, 1.8mg/1 for pilot plant. Accordig to increase of iron and manganese in the gallery infiltered water, the turbidity is encreased by ozonization. Through ozonization, sand filtration and activated carbon filtration, the water quality is improved by decreasing above 90% of the organic compounds detergent, algae,E.coli group, iron and manganese, but the ammonia is only removed 51%. As the amount of ammonia containing in the gallery infiltered water is 2.7mg/1, the filtered water through sands is required to aerate with air or to dose more amount of ozone before the activated carbon filtration in order to remove ammonia. When the sand filtration rate is 120m/day, the filter run time after ozonization in the gallery infiltered water is increased to 25% in comparison with the general rapid sand filtration.