• International Journal of Aeronautical and Space Sciences
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• v.18 no.2
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• pp.186-196
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• 2017

In order to resolve the trimming difficulty in rotor CFD calculations, a high-efficiency and improved "delta trim method" is established to compute the blade control settings that are necessary to identify the blade motion. In this method, a simplified model which combines the blade element theory and different inflow models is employed to calculate the control settings according to the target aerodynamic forces, then it is coupled into a CFD solver with unsteady Navier-Stokes equations by the delta methodology, which makes the control settings and aerodynamics calculated and updated in the meantime at every trim cycle. Different from the previous work, the current research combines the inflow model based on prescribed wake theory. Using the method established, the control settings and aerodynamic characteristics of Helishape 7A, AH-1G and Caradonna-Tung rotors are calculated. The influence of different inflow models on trimming calculations is analyzed and the computational efficiency of the current "delta trim method" is compared with that of the "CFD-based trim method". Furthermore, for the sake of improving the calculation efficiency, a novel acceleration factor method is introduced to accelerate the trimming process. From the numerical cases, it is demonstrated that the current "delta trim method" has higher computational efficiency than "CFD-based trim method" in both hover and forward flight, and up to 70% of the amount of calculation can be saved by current "delta trim method" which turns out to be satisfactory for engineering applications. In addition, the proposed acceleration factor shows a good ability to accelerate the trim procedure, and the prescribed wake inflow model is always of better stability than other simple inflow models whether the acceleration factor is utilized in trimming calculations.

• 대한공업교육학회지
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• v.30 no.2
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• pp.23-32
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• 2005

The purpose of this study is to investigate and analyze the actual state of teaching and learning methods which are applied to the vocation inquiry section-related subjects of the College Scholastic Ability Test(CSAT) by the teachers who teach specialized subjects of vocational high schools. In order for us to get the background and feature of establishment in the area of vocation inquiry section of the CSAT, previous studies and literature was analyzed and sample survey on the 600 teachers who teach the vocation inquiry section-related subjects was made. The result of this survey is as shown below; First, the teachers who are in charge of vocation inquiry section-related subjects understand that theory and practice is in the ratio 60.76:39.24 and ratio of theory is higher than that of practice. Second, teaching and learning method which is the most relevant to the vocation inquiry section is in the order of lecture(83.9%), experiment & practice(50.4%), computerized learning(41.1%). Third, teaching and learning method which is the most used by the teachers who are in charge of vocation inquiry section-related subjects is in the order of lecture(85.8%), computerized learning(50.1%), experiment and practice(44.4%). Forth, the most desirable teaching and learning method which the teachers who are in charge of vocation inquiry section for this subject believe is in the order of lecture(62.7%) experience & practice(47.7%), computerized learning(44.4%). In light of this result, even though there were not so much difference among the teaching-learning methods which are the most consistent with the contents of the subject in relation to the vocation inquiry section, the most used teaching-learning method by the teachers who teach vocation inquiry section-related subjects and the most desirable teaching-learning method which the teachers who are in charge of vocation inquiry section believe, the most used teaching-learning method by the teachers who are in charge of the vocation inquiry section is lecture. Therefore, it is necessary for us to reinforce the contents in relation to the practice & experiment so that the experience and application can be accumulated and improved through practice which is the specialty of the course of the study in the vocational high school and various teaching and learning method should be developed in consideration of contents of the subject, capability & quality of the learners and status of a classroom.

• Advances in nano research
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• v.16 no.5
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• pp.509-519
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• 2024

In this study, the static analysis of carbon nanotube-reinforced composites (CNTRC) beams resting on a Winkler-Pasternak elastic foundation is presented. The developed theories account for higher-order variation of transverse shear strain through the depth of the beam and satisfy the stress-free boundary conditions on the top and bottom surfaces of the beam. To study the effect of carbon nanotubes distribution in functionally graded (FG-CNT), we introduce in the equation of CNT volume fraction a new exponent equation. The SWCNTs are assumed to be aligned and distributed in the polymeric matrix with different patterns of reinforcement. The rule of mixture is used to describe the material properties of the CNTRC beams. The governing equations were derived by employing Hamilton's principle. The models presented in this work are numerically provided to verify the accuracy of the present theory. The analytical solutions are presented, and the obtained results are compared with the existing solutions to verify the validity of the developed theories. Many parameters are investigated, such as the Pasternak shear modulus parameter, the Winkler modulus parameter, the volume fraction, and the order of the exponent in the volume fraction equation. New results obtained from bending and stresses are presented and discussed in detail. From the obtained results, it became clear the influence of the exponential CNTs distribution and Winkler-Pasternak model improved the mechanical properties of the CNTRC beams.

• Journal of Engineering Education Research
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• v.7 no.4
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• pp.32-37
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• 2004

Well organized design based education is the one of the best way to develop the abilities needed for the engineer such as the recognizing and formulating a problem and then solving it creatively and systematically. In order for this, we prepared a course named 'Introduction to the Engineering Design' for the first-year students, which aims at developing creativity and ability to promote a project. Experiment-design mixed courses and theory-design mixed courses, where students have to solve various design problems, are provided for the higher grade students. In this paper, we are focused on the experiment-design mixed course for the second-year students which has been operating from two years ago. Here we show how the teamwork ability is improved. We also present how to operate the course in detail so that anyone can easily get the way to reach the outcomes needed for the engineers.

• Journal of the Korean Institute of Intelligent Systems
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• v.6 no.2
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• pp.81-89
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• 1996

A design method of fuzzy modeling is presented for the model identification of route choice of traffic problems.The proposed fuzzy modeling implements system structure and parameter identification in the eficient form of""IF..., THEN-.."", using the theories of optimization theory, linguistic fuzzy implication rules. Three kinds ofmethod for fuzzy modeling presented in this paper include simplified inference (type I), linear inference (type 21,and proposed modified-linear inference (type 3). The fuzzy inference method are utilized to develop the routechoice model in terms of accurate estimation and precise description of human travel behavior. In order to identifypremise structure and parameter of fuzzy implication rules, improved complex method is used and the least squaremethod is utilized for the identification of optimum consequence parameters. Data for route choice of trafficproblems are used to evaluate the performance of the proposed fuzzy modeling. The results show that the proposedmethod can produce the fuzzy model with higher accuracy than previous other studies -BL(binary logic) model,B(production system) model, FL(fuzzy logic) model, NN(neura1 network) model, and FNNs (fuzzy-neuralnetworks) model -.fuzzy-neural networks) model -.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.12
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• pp.2313-2327
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• 1994

As the communication environment evolves, there is an increasing need for multiresolution image coding. To meet this need, the entrophy constratined vector quantizer(ECVQ) for coding of image pyramids by spline wavelet transform is introduced in this paper. This paper proposes a new scheme for image compression taking into account psychovisual feature both in the space and frequency domains : this proposed method involves two steps. First we use spline wavelet transform in order to obtain a set of biorthogonal subclasses of images ; the original image is decomposed at different scale using a pyramidal algorithm architecture. The decomposition is along the vertical and horizontal directions and maintains constant the number of pixels required the image. Second, according to Shannon's rate distortion theory, the wavelet coefficients are vectored quantized using a multi-resolution ECVQ(entropy-constrained vector quantizer) codebook. The simulation results showed that the proposed method could achieve higher quality LENA image improved by about 2.0 dB than that of the ECVQ using other wavelet at 0.5 bpp and, by about 0.5 dB at 1.0 bpp, and reduce the block effect and the edge degradation.

• Journal of East-West Nursing Research
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• v.7 no.1
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• pp.18-31
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• 2002

This study, as a basic research to manage a Chinese Medicine Health Promotion Center by way of showing an example, is a before and after experiment research for simple group to verify a difference with cholesterol, health status and perception of health in order to confirm a effectiveness of diet and regimen according to the 4th status of physical constitution. Research object was chosen of 42 persons who operate a physical constitutional dietary regimen among them after selecting professors and clinical nurses (55 persons) majoring in the science of nursing who participated in Chinese Medicine-oriented Nurse Training Course from Aug. of 2001 to Feb. of 2002 all over the country. Diagnostic tools for physical constitution was used of the questionary that is currently consisted of physical constitution grouping test in Eastern & Western Diagnose Center of K Medical Center, and rating of health status was used of the tool that standardized CMI(Cornell Medical Index) to be available for Korean, and perception measurement for health status was used of a visual analogue scale for the health status that each one perceive personally, and physiological status was measured of cholesterol in blood. Analysis for the collected data was carried out by percentage, $X^2$ test, paired t-test according to research object by using SPSS, and the results of this study are as follows. 1) There was no difference with cholesterol before or after the experiment for objects. As a result of estimation about difference with health status by areas before or after the experiment, there are more improved result in eyes, ears, digestive organs, bones and sinews organs, frequency of a disorder, habit, adaptation status, angry, healthy status than before the experiment. As a whole, after the experiment the health was more improved than before the experiment. As the result to inspect a difference of health perception between before and after experiment, after the experiment the health perception level was improved than before, however there was no meaningful differences. 2) As the result to inspect a difference of cholesterol between before and after experiment according to object's physical constitution, in the case of So-yang-in(a person with the minimum male: according to the male and female principles(the sun and the moon)) among the 4th status of physical constitution there was only meaningful difference statistically, however, after the experiment their cholesterol's value was increased. As the result to inspect the difference of health status between before and after the experiment according to physical constitution, all of Ta-um-in(a person with maximum the female), So-yang-in(with the minimum male), So-um-in(with the minimum female) had a meaningful difference before and after the experiment, which means that in all case by physical constitutional groups, after the experiment their health status was more improved than before the experiment. As the result to inspect a difference of health perception between before and after according to physical constitutions, in the case of Tae-um-in and So-um-in, average score after the experiment was risen than before the experiment so that it means that the level of health perception was improved, however, there was no meaning statistically. According to the above results, if continuous diet and regimen by each physical constitutions could be implemented, it is certain that the health could be maintained and promoted. And, what we are healthy is for oneself to feel it subjectively. However, I think that cholesterol score in blood that we can view objectively could be changed distinctly if we can implement a strict diet and regimen. Accordingly, it is necessary for a method and period of experiment to be more strict and longer. According to the above results, I would like to suggest as follows. 1) In order to understand health status by Korean's physical constitutions and to generalize it, these research will be repeated against much more objects that could be selected by proper grouping method to consider a representative. 2) It is necessary for a research to inspect health status by physical constitution by developing a health status measurement tool that has higher confidence and propriety based on physical constitutional theory.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.25 no.1
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• pp.25-38
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• 2022

Urban problems are constantly occurring around the world due to rapid industrialization and population decline. In particular, as the number of vacant houses is gradually increasing as the population decreases, it is necessary to prepare countermeasures. A plan to utilize vacant houses has emerged to restore the natural environment of the urban ecosystem where forest destruction, damage to habitats of wild animals and plants, and disconnection have occurred due to large-scale development. Through connectivity analysis, it is possible to understand the overall ecosystem flow based on the movement of species and predict the effect when vacant houses are converted into green spaces. Therefore, this study analyzed the green area network to confirm the possibility of greening of vacant houses neglected in Jeonju based on circuit theory. Using Circuitscape and Least-cost path, we tried to identify the connectivity of green areas and propose an ecological axis based on the analysis. In order to apply the resistance values required for analysis based on previous studies, the 2020 subdivision land cover data were integrated into the major classification evaluation items. When the eight forests in the target site were analyzed as the standard, the overall connectivity and connectivity between forests in the area were high, so it is judged that the existing green areas can perform various functions, such as species movement and provision of habitats. Based on the results of the connectivity analysis, the importance of vacant houses was calculated and the top 20 vacant houses were identified, and it was confirmed that the higher the ranking, the more positive the degree of landscape connectivity was when converted to green areas. In addition, it was confirmed that the results of analyzing the least-cost path based on the resistance values such as connectivity analysis and the existing conceptual map showed some differences when comparing the ecological axes in the form. As a result of checking the vacant houses corresponding to the relevant axis based on the width standards of the main and sub-green areas, a total of 30 vacant houses were included in the 200m width and 6 vacant houses in the 80m width. It is judged that the conversion of vacant houses to green space can contribute to biodiversity conservation as well as connectivity between habitats of species as it is coupled with improved green space connectivity. In addition, it is expected to help solve the problem of vacant houses in the future by showing the possibility of using vacant houses.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.2
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• pp.63-70
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• 2014

Design sensitivity analysis and topology design optimization for a piezoelectric crystal resonator are developed. The piezoelectric crystal resonator is deformed mechanically when subjected to electric charge on the electrodes, or vice versa. The Mindlin plate theory with higher-order interpolations along thickness direction is employed for analyzing the thickness-shear vibrations of the crystal resonator. Thin electrode plates are masked on the top and bottom layers of the crystal plate in order to enforce to vibrate it or detect electric signals. Although the electrode is very thin, its weight and shape could change the performance of the resonators. Thus, the design variables are the bulk material densities corresponding to the mass of masking electrode plates. An optimization problem is formulated to find the optimal topology of electrodes, maximizing the thickness-shear contribution of strain energy at the desired motion and restricting the allowable volume and area of masking plates. The necessary design gradients for the thickness-shear frequency(eigenvalue) and the corresponding mode shape(eigenvector) are computed very efficiently and accurately using the analytical design sensitivity analysis method using the eigenvector expansion concept. Through some demonstrative numerical examples, the design sensitivity analysis method is verified to be very efficient and accurate by comparing with the finite difference method. It is also observed that the optimal electrode design yields an improved mode shape and thickness-shear energy.

• Journal of Global Scholars of Marketing Science
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• v.20 no.2
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• pp.179-187
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• 2010

Understanding consumers' preferences and use of media types is imperative for marketing and advertising managers, especially in today's fragmented market. A clear understanding assists managers in making more effective selections of appropriate media outlets, yet individuals' choices of type and use of media are based on a variety of characteristics. This paper examines one personality trait, sensation seeking, which has not appeared in the literature examining "new" media preferences and use. Sensation seeking is a personality trait defined as "the need for varied, novel, and complex sensations and experiences and the willingness to take physical and social risks for the sake of such experiences" (Zuckerman 1979). Six hypotheses were developed from a review of the literature. Particular attention was given to the Uses and Gratification theory (Katz 1959), which explains various reasons why people choose media types and their motivations for using the different types of media. Current theory suggests that High Sensation Seekers (HSS), due to their needs for novelty, arousal and unconventional content and imagery, would exhibit higher frequency of use of new media. Specifically, we hypothesize that HSS will use the internet more than broadcast (H1a) or print media (H1b) and more than low (LSS) (H2a) or medium sensation seekers (MSS) (H2b). In addition, HSS have been found to be more social and have higher numbers of friends therefore are expected to use social networking websites such as Facebook/MySpace (H3) and chat rooms (H4) more than LSS (a) and MSS (b). Sensation seekers can manifest into a range of behaviors including disinhibition,. It is expected that alternative social networks such as Facebook/MySpace (H5) and chat rooms (H6) will be used more often for those who have higher levels of disinhibition than low (a) or medium (b) levels. Data were collected using an online survey of participants in extreme sports. In order to reach this group, an improved version of a snowball sampling technique, chain-referral method, was used to select respondents for this study. This method was chosen as it is regarded as being effective to reach otherwise hidden population groups (Heckathorn, 1997). A final usable sample of 1108 respondents, which was mainly young (56.36% under 34), male (86.1%) and middle class (58.7% with household incomes over USD 50,000) was consistent with previous studies on sensation seeking. Sensation seeking was captured using an existing measure, the Brief Sensation Seeking Scale (Hoyle et al., 2002). Media usage was captured by measuring the self reported usage of various media types. Results did not support H1a and b. HSS did not show higher levels of usage of alternative media such as the internet showing in fact lower mean levels of usage than all the other types of media. The highest media type used by HSS was print media, suggesting that there is a revolt against the mainstream. Results support H2a and b that HSS are more frequent users of the internet than LSS or MSS. Further analysis revealed that there are significant differences in the use of print media between HSS and LSS, suggesting that HSS may seek out more specialized print publications in their respective extreme sport activity. Hypothesis 3a and b showed that HSS use Facebook/MySpace more frequently than either LSS or MSS. There were no significant differences in the use of chat rooms between LSS and HSS, so as a consequence no support for H4a, although significant for MSS H4b. Respondents with varying levels of disinhibition were expected to have different levels of use of Facebook/MySpace and chat-rooms. There was support for the higher levels of use of Facebook/MySpace for those with high levels of disinhibition than low or medium levels, supporting H5a and b. Similarly there was support for H6b, Those with high levels of disinhibition use chat-rooms significantly more than those with medium levels but not for low levels (H6a). The findings are counterintuitive and give some interesting insights for managers. First, although HSS use online media more frequently than LSS or MSS, this groups use of online media is less than either print or broadcast media. The advertising executive should not place too much emphasis on online media for this important market segment. Second, social media, such as facebook/Myspace and chatrooms should be examined by managers as potential ways to reach this group. Finally, there is some implication for public policy by the higher levels of use of social media by those who are disinhibited. These individuals are more inclined to engage in more socially risky behavior which may have some dire implications, e.g. by internet predators or future employers. There is a limitation in the study in that only those who engage in extreme sports are included. This is by nature a HSS activity. A broader population is therefore needed to test if these results hold.