• International Journal of Control, Automation, and Systems
• /
• v.1 no.2
• /
• pp.194-202
• /
• 2003

In this paper, we introduce a category of Multi-FNN (Fuzzy-Neural Networks) models, analyze the underlying architectures and propose a comprehensive identification framework. The proposed Multi-FNNs dwell on a concept of fuzzy rule-based FNNs based on HCM clustering and evolutionary fuzzy granulation, and exploit linear inference being treated as a generic inference mechanism. By this nature, this FNN model is geared toward capturing relationships between information granules known as fuzzy sets. The form of the information granules themselves (in particular their distribution and a type of membership function) becomes an important design feature of the FNN model contributing to its structural as well as parametric optimization. The identification environment uses clustering techniques (Hard C - Means, HCM) and exploits genetic optimization as a vehicle of global optimization. The global optimization is augmented by more refined gradient-based learning mechanisms such as standard back-propagation. The HCM algorithm, whose role is to carry out preprocessing of the process data for system modeling, is utilized to determine the structure of Multi-FNNs. The detailed parameters of the Multi-FNN (such as apexes of membership functions, learning rates and momentum coefficients) are adjusted using genetic algorithms. An aggregate performance index with a weighting factor is proposed in order to achieve a sound balance between approximation and generalization (predictive) abilities of the model. To evaluate the performance of the proposed model, two numeric data sets are experimented with. One is the numerical data coming from a description of a certain nonlinear function and the other is NOx emission process data from a gas turbine power plant.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.28 no.1
• /
• pp.10-20
• /
• 1992

The new course distances of a ship are considered to be the indices to indicate directly her abilities of course altercation. Generally, they have long been calculated by using the maneuvering indices obtained from her Z test. However, at sea actually the maneuvering indices can not sometimes be obtained according to ship's condition or circumstances and the new course distances can not be calculated. To find out other method to calculate the new course distances, in this paper the author analyzed them from a viewpoint of ship motion, and worked out a numerical formula to calculate them easily, using the data of ship's heading test. In order to check whether the presented method is applicable to actual ships or not, the experiment by them were also performed. The results obtained are summarized as follow: 1. The mean difference of the distance between two new course distances by the heading test and the maneuvering indices of the experimental ship was about 0.98% values of the ones by the maneuvering indices, when her heading were 10。, 20。 and 30。, using the rudder angle of 15。. These new course distances were therefore found to be almost same in values of the distance. 2. The mean difference of the distance between two new course distances by the heading test and the observation of experimental ship was about 1.16% values of the ones by the observation, when her headings were 10。, 20。 and 30。, using the rudder angle of 15。. These new course distances were therefore found to be almost same in values of the distance. 3. It is confirmed that the new course distances can be calculated easily by using the method of ship's simple heading test, without the observation or using the maneuvering indices. 4. It is considered to be helpful for the safety of shiphanding to draw curves of new course distances by ship's heading test and utilize them at sea.

• Journal of Korean Academy of Fundamentals of Nursing
• /
• v.6 no.3
• /
• pp.570-582
• /
• 1999

Although computers cannot analyze textual data in the same way as they analyze numerical data. they can nevertheless be of great assistance to qualitative researchers. Thus, the use of computers in analyzing qualitative data has increased since the 1980s. The purpose of this article was to explore advantages and disadvanteges of using computers to analyze textual data and to suggest strategies to prevent problems of using computers. In additon, it illustrated characteristics and functions of softwares designed to analyze qualitative data to help researchers choose the program wisely. It also demonstrated precise functions and procedures of the NUDIST program which was designed to develop a conceptual framework or grounded theory from unstructured data. Major advantage of using computers in qualitative research is the management of huge amount of unstructured data. By managing overloaded data, researcher can keep track of the emerging ideas, arguments and theoretical concepts and can organize these tasks mope efficiently than the traditional method of 'cut-and-paste' technique. Additional advantages are the abilities to increase trustworthiness of research, transparency of research process, and intuitional creativity of the researcher, and to facilitate team and secondary research. On the other hand, disvantages of using computers were identified as worries that the machine could conquer the human understanding and as probability of these problems. it suggested strategies such as 1) deep understanding of orthodoxy in analytical process. To overcome philosophical and theoretical background of qualitative research method, 2) deep understanding of the data as a whole before using software, 3) use of software after familiarity with it, 4) continuous evaluation of software and feedback from them, and 5) continuous awareness of the limitation of the machine, that is computer, in the interpretive analysis.

• Journal of Korean Medicine Rehabilitation
• /
• v.26 no.3
• /
• pp.109-117
• /
• 2016

Objectives The purpose of this study was to investigate the correlation between walking ability of lumbar spinal stenosis patients and the cross-sectional area (CSA) of lumbar paraspinal muscles. Methods This study was carried out on 62 lumbar spinal stenosis patients who had limited walking abilities because of neurogenic claudication (NC). All patients received more than 2 weeks of complex treatment at Mokhuri Neck&Back Hospital. CSA of lumbar paraspinal muscles was measured from axial T2-weighted MRI and divided by CSA of adjacent vertebral body to avoid influence of body statues (RCSA-Relative CSA). Pain Free Walking Distance and Numerical Rating Scale (NRS) was measured before and after treatment. Results The Pain Free Walking Distance had significantly increased in patients who had bigger RCSA of psoas muscle (r=0.313, p<0.05). Conclusions The psoas muscle can be a predictive factor for restoring walking ability of lumbar spinal stenosis patients who have limitations walking.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.18 no.6
• /
• pp.842-848
• /
• 2008

This paper deal with uncertainty problem by using Type-2 fuzzy logic set for nonlinear system modeling. We design Type-2 fuzzy logic system in which the antecedent and the consequent part of rules are given as Type-2 fuzzy set and also analyze the performance of the ensuing nonlinear model with uncertainty. Here, the apexes of the antecedent membership functions of rules are decided by C-means clustering algorithm and the apexes of the consequent membership functions of rules are learned by using back-propagation based on gradient decent method. Also, the parameters related to the fuzzy model are optimized by means of particle swarm optimization. The proposed model is demonstrated with the aid of two representative numerical examples, such as mathematical synthetic data set and Mackey-Glass time series data set and also we discuss the approximation as well as generalization abilities for the model.

• Journal of the Society of Naval Architects of Korea
• /
• v.54 no.2
• /
• pp.161-169
• /
• 2017

Recently, ship owners have been requiring the assessment of the maneuverability of twin-screw ships under mechanical failures. Because this kind of assessment has not yet been conducted, it is necessary to study the types of machinery failures that can significantly affect the maneuverability of a ship, and to construct a procedure to simulate the maneuvering behavior under such failures. In this paper, the sole focus is the steering system failure from among the variety of failure types, and the maneuvering behavior of the ship under the single rudder failure is simulated for an investigation of the unique characteristics. First, the mathematical model for the twin-screw container ship is verified by comparing the simulated results for the $35^{\circ}$ turning test, $10^{\circ}/10^{\circ}$ zigzag test, and $20^{\circ}/20^{\circ}$ zigzag test under the normal operating condition with those obtained from free running model tests. After the IMO maneuvering tests are additionally simulated under the single rudder failure, the results are reviewed to investigate the maneuvering characteristics that are due to the failure. Further, the $35^{\circ}/35^{\circ}$ zigzag test and the $35^{\circ}$ turning test are simulated to additionally investigate the effects of the single rudder failure on the steering and turning abilities.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.2
• /
• pp.357-361
• /
• 2011

The terminal current in voltage driven systems is an essential role for characterizing the pattern of electric discharge such as corona, breakdown, etc. Until now, to evaluate this terminal current, Sato's equation has been widely used in areas of high voltage and plasma discharge. Basically Sato's equation was derived by using the energy balance equation and its final form described physical meaning explicitly. To give more general abilities in Sato's equation, we present a generalized approach by directly using the Poynting's theorem incorporating the finite element method. When the magnetic field effect or the time-dependent voltage source is considered, this generalized energy method can be easily applicable to those problems with any dielectric media such as gas, fluid, and solid. As an alternative approach, the integral Ohm's law resulting in small numerical errors has an ability to be applied to multi-port systems. To test the generalized energy method and integral Ohm's law, first, the results from two prosed methods were compared to those from Sato's approach and an analytic solution in parallel plane electrodes. After verification, the generalized method was applied to the tip-sphere electrodes for evaluating the terminal current with three carriers and the Fowler-Nordheim field emission condition. From these results, we concluded that the generalized energy method can be a consistent technique for evaluating the discharge current with various dielectric materials or large magnetic field.

• Smart Structures and Systems
• /
• v.24 no.1
• /
• pp.83-94
• /
• 2019

Passive negative stiffness dampers (NSDs) that possess superior energy dissipation abilities, have been proved to be more efficient than commonly adopted passive viscous dampers in controlling stay cable vibrations. Recently, inertial mass dampers (IMDs) have attracted extensive attentions since their properties are similar to NSDs. It has been theoretically predicted that superior supplemental damping can be generated for a taut cable with an IMD. This paper aims to theoretically investigate the impact of the cable sag on the efficiency of an IMD in controlling stay cable vibrations, and experimentally validate superior vibration mitigation performance of the IMD. Both the numerical and asymptotic solutions were obtained for an inclined sag cable with an IMD installed close to the cable end. Based on the asymptotic solution, the cable attainable maximum modal damping ratio and the corresponding optimal damping coefficient of the IMD were derived for a given inertial mass. An electromagnetic IMD (EIMD) with adjustable inertial mass was developed to investigate the effects of inertial mass and cable sag on the vibration mitigation performance of two model cables with different sags through series of first modal free vibration tests. The results show that the sag generally reduces the attainable first modal damping ratio of the cable with a passive viscous damper, while tends to increase the cable maximum attainable modal damping ratio provided by the IMD. The cable sag also decreases the optimum damping coefficient of the IMD when the inertial mass is less than its optimal value. The theoretically predicted first modal damping ratio of the cable with an IMD, taking into account the sag generally, agrees well with that identified from experimental results, while it will be significantly overestimated with a taut-cable model, especially for the cable with large sag.

• Journal of Practical Engineering Education
• /
• v.14 no.2
• /
• pp.245-258
• /
• 2022

Computational thinking with programming skills has been widely emphasized for future industrial engineering researchers and practitioners in Industry 4.0. However, industrial engineering students still have limited opportunities to improve their computational thinking abilities during university coursework. In this regard, this research study proposes to use Python programming language for teaching classical Industrial Engineering subjects. For a specific case study, we designed and instructed an Engineering Economy lecture which cultivates the concept and techniques of economic analysis for engineering students. During the class, we introduced the usage of several Python libraries that include numpy-financial for basic financial functions, numpy and scipy for simple numerical computation and analysis, and matplotlib for data visualization. Anonymous class evaluation survey showed the effectiveness of the proposed teaching method in terms of both educational satisfaction and contents delivery. Finally, we found additional needs for providing lectures that adopt the similar teaching style to the proposed method.

• East Asian mathematical journal
• /
• v.40 no.2
• /
• pp.183-207
• /
• 2024

This study is a case study that considered fractional senses and fraction operation abilities for 107 gifted students in elementary school classes. In order to find out the fractional sense, in the first question comparing the sizes of fractions 2/3 and 4/5, the students showed a variety of strategies, but the utilization rate of strategies excluding reduction to a common denominator did not exceed 50%. The second question can be solved by using the first question. It is a problem of finding two fractions by selecting four from six numbers 1, 3, 4, 5, 6, and 7 to create two fractions of which sum does not exceed 1. The percentage of correct answers to this question was about 27% (29 out of 107). Only 5 out of 29 students found answers using the first question, and the rest of the students sought answers through trial and error in various calculations. It shows that the item arrangement method from a deductive perspective has no significant effect on elementary school students. The percentage of correct answers was about 27% in the questions to find out the fraction operation ability-the question of drawing a 4/3 bar using a given 3/8-sized bar and 30.7% (23 out of 75) of the students who had wrong answers showed insufficient splitting operation. In addition, it has been shown that the operation of partitioning and iterating to form numerical senses and fractional concepts related to the fractions of the students has no significant impact.