• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1893-1899
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• 2010

A foxtail moves forward on a flat surface when pushed by a vertical force. The distance moved by the foxtail depends on the degree of deformation. We experimentally investigated the main parameters that influence the distance moved while varying the pushing force, area, and velocity. We then fabricated a nylon barb that mimics the foxtail barb and performed theoretical and experimental analyses of the displacement according to the acting force and the deflection. In addition, we investigated the relation between the displacement and the angle of a foxtail-like robot's leg by varying the clearance between the robot body and the inner surface of the pipe. To find the design parameters of the barb of the robot for tubular-type digestive organs and blood vessels, we studied the relation between the acting force and the elastic modulus while varying the leg diameter.

• The Journal of the Korea Contents Association
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• v.13 no.12
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• pp.447-454
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• 2013

This research is an empirical study to analyze the relationship among the ethical leadership of supervisor, CSR attitude of subordinate, and supervisor's performance evaluated by subordinate. A survey was conducted for the employees of a large manufacturing company in Korea, and 196 questionnaires were analyzed. Results of multiple regression analyses showed that the relationship between the ethical leadership of supervisor and the CSR attitude of subordinate was positively significant. That is, the supervisor's ethical leadership leads the subordinate's positive CSR attitude. And, supervisor's performance evaluated by subordinate positively moderated the relationship between ethical leadership and CSR attitude. That is, when subordinates assesses the supervisor's performance as high, the positive relationship between supervisor's ethical leadership and subordinate's CSR attitude becomes relatively stronger. Theoretical and managerial implications of these empirical results were discussed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.6
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• pp.31-38
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• 2005

Aerodynamic influence coefficient linearly relates pressure with downwash in panel method for load analysis in which the viscosity of a flow is ignored and the compressibility cannot be taken into account in transonic region. Since the planform of an aerodynamic surface determines the coefficient, the panel method has a limit to the analysis of low Reynolds number flow. The accuracy of the pressure distribution can be improved by a direct correction to the pressure or a correction to the downwash, which is considered the change of camber or thickness, using the aerodynamic coefficients from wind tunnel test as constraints. A premultiplying correction method as well as a postmultiplying correction method is applied to a micro air vehicle to provide more accurate aerodynamic pressure for trim and load analyses. Theoretical aerodynamic pressure is obtained from the panel method. Correction factor matrix and correct pressure coefficient are computed for the conditions with two constraints in addition to single constraint. The postmultiplying correction method gives a better improvement in pressure distribution on micro air vehicle due to the flow characteristics on it.

• Journal of the Korean Society for information Management
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• v.30 no.2
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• pp.61-81
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• 2013

The purpose of this study is to investigate the effect of cultural and demographic factors (age and gender) on the perception of product information. The theoretical frameworks of interest in the current study are two cultural models: Hofstede's individualism (IND) and Hall's context. In examining the research questions, this research discovers that the cultural changes are occurring for the Korean young generation, even though Korean students are still within collectivistic culture. The correlation results suggest that the younger students have the higher individualism values compared to the older students. Using two multiple regression analyses (one set for high-context condition and one set for low-context condition), the study finds that cultural value and age significantly predicts the perception of product information in high-context (visual) condition. However, there is no significant difference in the perception of product information between male and female.

• Journal of Educational Research in Mathematics
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• v.17 no.1
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• pp.1-31
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• 2007

Negative numbers have been one of the most difficult mathematical concepts, and it was only 200 years ago that they were recognized as a real object of mathematics by mathematicians. It was because it took more than 1500 years for human beings to overcome the quantitative notion of numbers and recognize the formality in negative numbers. Understanding negative numbers as formal ones resulted from the Copernican conversion in mathematical way of thinking. we first investigated the historic and the genetic process of the concept of negative numbers. Second, we analyzed the conceptual fields of negative numbers in the aspect of the additive and multiplicative structure. Third, we inquired into the levels of thinking on the concept of negative numbers on the basis of the historical and the psychological analysis in order to understand the formal concept of negative numbers. Fourth, we analyzed Korean mathematics textbooks on the basis of the thinking levels of the concept of negative numbers. Fifth, we investigated and analysed the levels of students' understanding of the concept of negative numbers. Sixth, we analyzed the symbolizing process in the development of mathematical concept. Futhermore, we tried to show a concrete way to teach the formality of the negative numbers concepts on the basis of such theoretical analyses.

• Korean Institute of Interior Design Journal
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• v.21 no.2
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• pp.74-83
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• 2012

This study is an historical consideration about the modern discourse of Japanese spacial tradition driven from cultural background. The purpose of this study is to establish a cartographic map of historical progress, and to shed light on the forming of identity in Japanese traditional space design on the schizo-analytical aspect. It adopts F. Guattari's psychoanalytic theory to the structural analysis of Japanese traditional space design. The process of this study is illustrated as follows: At first, it mentions Guattari's theory of Mechanical Unconscious, Schizo-analysis, Cartography, and Abstract machine as theoretical background. And, it considers the identity of Japanese traditional space constructed by various cultural sign over a long period of time as the statement of apriority. Secondly, it clarifies semiologic generation of Japanese traditional space design based on the analysis of spacial morphemes about each design stemmed from modernization process of Japan. Thirdly, it ascertains semiologic topography the representamens draw, i.e. schizo-analytic cartography from synchronic and diachronic point of view. Fourthly, it analyses traditional discourse structure in terms of generative schizo-analysis and transformational schizo-analysis with four categories- object, style, concept, strategy. Through this process, it studies the reproduction of Japanese tradition in terms of the 'social organization', and explores the way vitalized on the space-time coordinate system by the schizo-analysis of the mechanical unconscious. In conclusion, it clarifies Generative-schizo is accomplished in the level of formulating representamen, and Transformational-Schizo involves experimental mind that induce implantation of the heteromorphic elements and avant-garde experiments of abstract mechanical operation in the schizo-analysis of Japanese traditional space design. The significance of this study is to arrange an opportunity of introspection on Korean-ness seriously from inspecting logic of Japan-ness closely in traditional space design.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.1186-1195
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• 1993

The Japanese type combine harvester has adopted rubber crawlers for the driving mechanism from first production . However, combine harvesters with movable track rollers in the rubber crawler system have been adopted recently for the purpose of stability at the time of climbing over the footpaths between rice fields, as the results of the machines becoming large. However, the dynamic characteristics of movable track rollers have not been clarified. For this reason, the design of movable track rollers depends on trial and errors. It is known that vibration characteristics of the vehicle with movable track rollers are different from the vibration characteristics of the vehicles with fixed track rollers even though the track roller arrangements are the same. Therefore, the theoretical analyses of movable track rollers must be hurried in order to formulate a reasonable track roller arrangement design. the authors have studied the vibration characteristics of the rubber crawler ve icle with fixed track rollers. in this study, the dynamic model of the vehicle with movable track roller sis compared with the dynamic model of the vehicle with fixed track rollers. Next, motions are simulated to analyze the movable track rollers by expanding the motion equation which were constructed for the dynamic model of the fixed track rollers.

• Earthquakes and Structures
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• v.12 no.1
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• pp.119-133
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• 2017

Several theoretical and analytical formulations for the prediction of shear strength in reinforced concrete (RC) beam-to-column joints have been recently developed. Some of these predictive models are included in the most recent seismic codes and currently used in practical design. On the other hand, the influence of the stiffness and strength degradations in RC joints on the seismic performance of RC framed buildings has been only marginally studied, and it is generally neglected in practice-oriented seismic analysis. To investigate such influence, this paper proposes a numerical description for representing the cyclic response of RC exterior joints. This is then used in nonlinear numerical simulations of RC frames subjected to earthquake loading. According to the proposed strategy, RC joints are modelled using nonlinear rotational spring elements with strength and stiffness degradations and limited ductility under cyclic loading. The proposed joint model has been firstly calibrated against the results from experimental tests on 12 RC exterior joints. Subsequently, nonlinear static and dynamic analyses have been carried out on two-, three- and four-storey RC frames, which represent realistic existing structures designed according to old standards. The numerical results confirm that the global seismic response of the analysed RC frames is strongly affected by the hysteretic damage in the beam-to-column joints, which determines the failure mode of the frames. This highlights that neglecting the effects of joints damage may potentially lead to non-conservative seismic assessment of existing RC framed structures.

• The Journal of the Acoustical Society of Korea
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• v.34 no.3
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• pp.210-218
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• 2015

When the driving voltage of an ultrasound transducer is increased to improve the quality of ultrasound images, heat is generated inside the transducer that can cause patient's skin burn and degradation of transducer performance. Hence, in this paper, a method to disperse the heat of the transducer has been studied. The phased array transducer having 3 MHz center frequency and 32 channels was selected for analyses of the thermal dispersion. First, mechanism of the heat generation was investigated in relation to the transducer operation through theoretical analysis, and material damping and sound pressure amplitude were confirmed to be influential on the heat generation. Further, we investigated the effects of the properties of the materials constituting the transducer on the thermal dispersion through finite element analysis. Based on the analysis results, we determined the thermal properties of the constituent materials that could facilitate the thermal dispersion inside the transducer. The determined thermal properties were applied to the finite element model, and the results showed that the maximum temperature at an acoustic lens contacting with a patient was decreased to 51 % of its initial value.

• Journal of the Korean Operations Research and Management Science Society
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• v.39 no.4
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• pp.115-136
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• 2014

The game industry has grown steadily and the online game has become one of the most attractive game segments for its remarkable growth. Customer management in the online game industry, however, has received little attention from the academic field. The purpose of this study is to analyze the drivers of customer defection in the online game setting and suggest not only theoretical but also managerial insights into increasing customer retention rates. Prior to empirical analysis, the authors hypothesized that 3 variables of interests (Learning, Playing, Achievement) would explain the customer defection according to preceeding researches. To demonstrate these hypotheses, the authors obtained data from one of the biggest game publishers in Korea, and the empirical analysis model was developed considering context of research settings. The results of analyses provide the following insights. First, the key behavioral variables of Learning, Playing, and Achievement play substantial roles in explaining the customer defection. Next, the effects of these variables vary between customer types: novice and experienced customers. The defection decisions by novice customers are predicted by all key behavioral variables and Playing serves as the most influential indicator of the defection decisions. However, experienced customers are influenced by Playing and Achievement, while Learning has no impact on the defection decisions. Finally, the authors investigated hypothetical customer retention strategies, using the empirical results. The market outcomes indicate that the customer retention strategies work well with novice customers and it is hard-to-impossible to prevent experienced customers from defection using their behavioral data. These findings together deliver several meaningful insights to management as follow. First, the management should support customers to get involved in Learning activities at the very first stage. Second, customer's Achievement and appropriate compensation for it would work as defection barriers. Last, to optimize the outcomes of firm's marketing investments, it is better to focus on retention of novice users not experienced ones.