• Journal of Chest Surgery
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• v.20 no.2
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• pp.300-308
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• 1987

Clinical and pathologic data were reviewed in 20 patients who had have surgery for isolated aortic valvular heart disease between April 1978 and April, 1987. Hospital mortality was 10%, with no additional late mortality during a mean follow-up period of 24.1 months. Prosthetic valve failure developed in 3 patients and two had reoperation. Niety four percent of the survivors who were in NYHA Funtional class III or IV before operation are now in class I or II. Ninety percent of all patients are still alive at a maximum follow up of 9 years. The clinical histories, gross and histologic examination of valves estabilished the causes for isolated aortic valve disease: 3 rheumatic, 2 congenital bicuspid, 2 hypertention, 2 aortitis and each one case of floppy valve, medial cystic necrosis of aorta, bacterial endocarditis. But etiology was unknown in 8 cases. Sixteen patietns had myxoid degeneration, defined as significant disruption of the valve fibrosa and its replacement by acid mucosaccharides and cystic changes. Myxoid degeneration was also the primary pathologic abnormality in the patients with 2 hypertention, 2 rheumatic, 1 aortitis, 1 bacterial endocarditis, 1 floppy valve, 1 congenital bicuspid. The patients with myxoid degeneration of uncertain origin were 8. Histologic finding of all of them revealed nonspecific patients with myxoid degeneration of uncertain orgin were 8. Histologic finding of all of them revealed nonspecific chronic valvulitis with myxoid degeneration. This finding may indicate that the etiology w uld be infectious.

• The Research Journal of the Costume Culture
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• v.8 no.1
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• pp.30-39
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• 2000

The purpose of this study were to 1) identify types and levels of production environments, 2) classify apparel manufacturers based on production environments and 3) investigate relationship between characteristics of apparel manufacturers and production environment. Apparel manufacturer's characteristics included product line and the number of employees. For this study, the questionnaires were administered to 215 apparel manufacturers in seoul and Kyung-gi region from Feb. to Mar. 1998. Employing a sample of 201, data were analyzed by factor analysis, descriptive statistics, cluster analysis, cluster analysis, discriminant Analysis, and multivariate analysis of variance. The following are the results of this study : 1. The production environment was identified as three types such as complexity of product environment, uncertainty of demand/supply environment and uncertainty of worker environment. 2. Based on three types of the production environment, apparel manufacturers were classified into stable group, uncertain group and complicated group. 3. With respect to product line, men's wear manufacturers were lied the most high complexity of product environment, casual wear and knit wear were lied the most frequently uncertainty of worker environment. With respect to the number employees, apparel manufacturers comprising 50∼99 employees were lied the most high complexity of product environment, while those comprising 100∼299 employees the most high demand/supply environment.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.2
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• pp.235-245
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• 1998

This paper presents the fuzzy optimization model based scheduling methodology for the efficient production control of a FFS(FIexible Flow Shop) under the uncertain production environment. To develop the methodology, a fuzzy optimization technique is introduced in which the uncertain production capacity caused by the random events like the machine breakdowns or the absence of workers is modeled by fuzzy number. Since the problem is NP hard, the goal of this study is to obtain the near optimal but practical schedule in an efficient way. Thus, Lagrangian relaxation method is used to decompose the problem into a set of subproblems which are easier to solve than the original one. Also, to construct the feasible schedule, a heuristic algorithm was proposed. To evaluate the performance of the proposed method, computational experiments, based on the real factory data, are performed. Then, the results are compared with those of the other methods, the deterministic one and the existing one used in the factory, in the various performance indices. The comparison results demonstrate that the proposed method is more effective than the other methods.

• The Journal of Industrial Distribution & Business
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• v.13 no.9
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• pp.11-26
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• 2022

Purpose: Manufacturers rely on interfirm governance mechanisms to reduce the risks inherent in uncertain environments; however, it is unclear which governance mechanisms are developed to manage relationships with suppliers. This study sought to enhance knowledge of how environmental uncertainty affects interfirm governance mechanisms under conditions reflecting varying levels of structural holes. To this end, the study investigated the relationships between manufacturers and major first-tier and sub-suppliers. In particular, the moderating effect of structural holes is examined. Research design, data and methodology: A questionnaire survey was conducted with a major first-tier supplier of a Korean engineering firm. Proposed hypotheses were tested using structural equation modeling. Results: The results show that while the relationship between environmental uncertainty and unilateral governance is positive but statistically insignificant, with bilateral governance is negative and statistically significant. The study also demonstrates that when structural holes are considered, the effects between environmental uncertainty and governance mechanisms are attenuated. Conclusions: This study suggests some theoretical and managerial contributions between exchange partners, especially, the results suggest that structural holes have a critical competitive advantage in uncertain environments. Therefore, manufacturers should carefully consider how they deal with environmental uncertainty when they make a business decision under structural holes situations.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.153-160
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• 1999

It has been recognized that the assessment of concrete lining is very uncertain and subjective depending on the engineers who are in charge. T-FLAS which was based on fuzzy theory was developed in this study for the quantitative and objective assessment of the concrete lining in tunnels. Based on the application of T-FLAS on the evaluated field data, it was shown that the assessment system using fuzzy theory(T-FLAS) can be the effective and objective method for the assessment of concrete lining.

• Transactions on Control, Automation and Systems Engineering
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• v.3 no.2
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• pp.83-88
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• 2001

The robust linear H(sub)$\infty$ FIR filter, which guarantees a prescribed H(sub)$\infty$ performance, is designed for continuous time-varying systems with unknown cone-bounded nonlinearity. The infinite horizon filtering for time-varying systems is systems is investigated in therms of two Riccati equations by the finite moving horizon.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.127-130
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• 1990

The fuzzy logic controller which can be applied to various industrial processes is quite often dependent on the heuristics of the experienced operator. The operator's knowledge is often uncertain. Therefore an incorrect control rule on the basis of the operator's information is a cause of bad performance of the system. This paper proposes a new self-learning fuzzy control method by the fuzzy system identification using the data pairs of input and output and arbitrary initial relation matrix. The position control of a DC servo motor model is simulated to verify the effectiveness of the proposed algorithm.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.264-264
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• 2000

In this paper, we propose a method to automatically extract stable visual landmarks from observed data for a mobile robot with stereo vision system. The robot selects as stable landmarks vertical line segments which are distinct and on planar surfaces, because they are expected to be observed reliably from various view-points. When the robot moves, it uses several, less uncertain landmarks for estimating its motion. Experimental results in real scenes show the validity of the proposed method.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.271-278
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• 2002

Recently, deep excavation for high-rise buildings occurs frequently to accommodate the rapidly increasing population in urban area. The stability of the earth retaining structures for deep excavation becomes more critical. The behavior of the earth retaining structures should be accurately predicted in a design stage, but the predicted behavior is different from the measured data due to uncertain soil properties and problems in construction. In this study the back-analysis using Powell's optimization theory was performed to match the measured deflection and results obtained from back-analysis were presented.

• International Journal of Computer Science & Network Security
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• v.21 no.5
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• pp.52-56
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• 2021

There is no assurance that malware could only cause virtual damage to computer programs and data as its potential is endless. However, legal provisions were earlier developed to cater to either a physical damage caused by a physical action or a virtual damage caused by a virtual action. When crossovers occur, it becomes quite uncertain as to how viable the current laws are in handling this matter. The author seeks to address the issue from the perspective of the laws of Malaysia.