• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.4
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• pp.8-15
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• 2011

This paper proposes a real-time navigation algorithm which integrates the artificial potential field (APF) for an unmanned vehicle in the unknown environment. This approach uses repulsive potential function around the obstacles to force the vehicle away and an attractive potential function around the goal to attract the vehicle. In this research, laser range finder is used as range sensor. An obstacle detected by the sensor creates repulsive vector. Differential global positioning system (DGPS) and digital compass are used to measure the current vehicle position and orientation. The measured vehicle position is also used to create attractive vector. This paper proposes a new concept of potential field based navigation which controls unmanned vehicle's speed and steering. The magnitude of repulsive force based on the proposed algorithm is designed not to be over the magnitude of attractive force while the magnitude is increased linearly as being closer to obstacle. Consequently, the vehicle experiences a generalized force toward the negative gradient of the total potential. This force drives the vehicle downhill towards its goal configuration until the vehicle reaches minimum potential and it stops. The effectiveness of the proposed APF for unmanned vehicle is verified through simulation and experiment.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.3
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• pp.343-351
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• 2008

In this paper, a spiral shaped common mode filter(CMF) embedded in a flexible printed circuit board(FPCB) is proposed for a multi-function cable. The CMF embedded in a FPC cable presents a new concept as a multi-function cable by the common mode rejection characteristics without a surface mounted device(SMD) CMF. The embedded CMF has a wideband common mode rejection bandwidth and an enhanced differential mode characteristics compared to conventional CMFs that use a magnetic material such as a ferrite of high loss. The proposed CMF of 3 turn inductors has a common mode rejection bandwidth from 0.4 GHz to 3.12 GHz and has 1.95 dB at 3 GHz, 6.97 dB at 8 GHz improvements of a differential mode insertion loss compared to the commercial LTCC(Low Temperature Co-fire Ceramics) CMFs.

• Structural Engineering and Mechanics
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• v.27 no.6
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• pp.713-739
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• 2007

Nowadays computers can perform symbolic computations in addition to mere number crunching operations for which they were originally designed. Symbolic computation opens up exciting possibilities in Structural Mechanics and engineering. Classical areas have been increasingly neglected due to the advent of computers as well as general purpose finite element software. But now, classical analysis has reemerged as an attractive computer option due to the capabilities of symbolic computation. The repetitive cycles of simultaneous - equation sets required by the finite element technique can be eliminated by solving a single set in symbolic form, thus generating a truly closed-form solution. This consequently saves in data preparation, storage and execution time. The power of Symbolic computation is demonstrated by six examples by applying symbolic computation 1) to solve coupled shear wall 2) to generate beam element matrices 3) to find the natural frequency of a shear frame using transfer matrix method 4) to find the stresses of a plate subjected to in-plane loading using Levy's approach 5) to draw the influence surface for deflection of an isotropic plate simply supported on all sides 6) to get dynamic equilibrium equations from Lagrange equation. This paper also presents yet another computationally efficient and accurate numerical method which is based on the concept of derivative of a function expressed as a weighted linear sum of the function values at all the mesh points. Again this method is applied to solve the problems of 1) coupled shear wall 2) lateral buckling of thin-walled beams due to moment gradient 3) buckling of a column and 4) static and buckling analysis of circular plates of uniform or non-uniform thickness. The numerical results obtained are compared with those available in existing literature in order to verify their accuracy.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.1
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• pp.49-61
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• 2015

Ground Based Augmentation System(GBAS) is a system that offers an aircraft within 23 NM radius from the airport precision positioning service and precision approach service using the concept of Differential Global Positioning System(DGPS). After GBAS ground equipment installing at the airport, functionalities and performances of GBAS should be verified through the GBAS ground and flight testing. This paper describes the methods and results for GBAS flight test using the flight inspection aircraft at Gimpo International Airport. From the test results, we confirmed that the VDB data was received without misleading within the VDB coverage of Gimpo International Airport, and VDB field strength, protection level, and course alignment accuracy met the evaluation's criteria.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.5 no.1
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• pp.3-16
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• 1995

In this paper, we deal with the cryptographic properties of Boolean functions generated by recursively extended methods from the points of balancedness, nonlinearity and correlation properties. First, we propose a new concept 'Strict Uncorrelated Criterion(SUC)' for two Boolean functions as a necessary condition for constructing Boolean functions of S-box which can be guaranteed to be resistant against Differential cryptanalysis, then we show that the recurively extended Boolean functions with particular form preserve the SUC. We also examine the correlation properties of Boolean functions using Walsh-Hadamard transformations and apply them to discuss nonlinearity, correlation properties and SUC of semi-bent function which is defined over odd dimensional vector space. Finally, we compare semi-bent function with Boolean functions which are generated by other similar recursive methods.

• Journal of Educational Research in Mathematics
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• v.27 no.1
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• pp.1-22
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• 2017

This study investigated three $10^{th}$ grade students' concept of rate of change while they perceived changing values of given functions. We have conducted a teaching experiment consisting of 6 teaching episodes on how the students understood and expressed changing values of functions on certain intervals in accordance with the concept of rate of change. The result showed that the students did use the same word of 'rate of change' in their analysis of functions, but their understanding and expression of the word varied, which turned out to have diverse perceptions with regard to average rate of change. To consider these differences as qualitatively different levels might need further research, but we expect that this research will serve as a foundational study for further research in students' learning 'differential calculus' from the perspective of rate of change.

• Herbal Formula Science
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• v.20 no.2
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• pp.187-197
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• 2012

Objectives : The purpose of this study is to find a reasonable solution to a current status of drug classification between the drugs of western conventional (allopathic) medicine and Korean medicine. A clear and distinct concept on the drugs of allopathic medicine and Korean medicine based on reasonable concepts and broad consensus is a pressing issue in Korea, and will facilitate the development of herbal medicinal products and pharmaceutical industry. Methods : Considering the issue of drug classification from domestic and international regulations, we reviewed the current Drug Law of Korea and China, Guidance for Industry, Botanical Drug Products of USA, Directive 2004/24/EC of the European parliament and of the council. Results : In Korea, the drug classification of allopathic medicine and Korean medicine is quite vague even though differential licensure system is enforced for the clinicians of allopathic medicine and Korean medicine field. According to the definition in the Drug Law, the scope of Korean medicine drug is so broad that even a drug made of single-compound material, as well as herbal extract of crude mixture, is regarded as a drug of Korean medicine, as long as the material may be separated from medicinal herbs, animal tissues, or mineral resources. Only new compound not found in natural resources are outside of the scope of Korean medicine drug. In USA and EU, medicinal products manufactured from herbs are approved by separate regulations for the herbs with special waivers. In China, the category of new medicine and the definition of allopathic medicine and traditional chinese medicine are clearly specified and classified. Conclusions : As medicines are validated therapeutic materials for efficacy and toxicity, we suggest that generally the concept of conventional medicines is based on a single compound that has been synthesized and individually validated and that of Korean medicines is based on a compound extracted from natural materials or a complex of compounds that has been validated as a whole in its totality.

• Journal of the Korean Society of Costume
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• v.57 no.4 s.113
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• pp.143-158
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• 2007

This study considers enlargement phenomenon in hair style as one of Costume types and analyzes its artistic characteristics based on the comparison between Hair style in the late Chosun Dynasty and that of the Rococo. First, its formative property, one of the common aesthetic characteristics, breaks the concept of traditional balance in Clothing and emphasizes its transformation, changes, and space beauty. This formative property shows the Enlargement and exaggeration beyond the concept of Space. Its sensuous property reflects women's psychological minds; exaggeration and sensualism. Artistic property doesn't focus on hair style only or clothing style only and considers hair style as renter of beauty as well as its important element. It shows the traditional beauty of nature and creativity in the Chosun Dynasty. Second, its formative property, one of the differential aesthetic characteristics, shows these following differences considering the aesthetic characteristics in the late Chosun Dynasty and that of the Rococo; mutual transformation, independent transformation, focus on distortion, harmony in scale, disharmony between irregularity and exception, extension and separation in space, etc. Sensuous property shows the temperate beauty and metaphorical sense, affected by the Practical Science, in the late Chosun Dynasty while it shows the secular sense and exaggerated beauty, affected by the Enlightenment, in the Rococo. Artistic property shows the harmony with the Clothing style, balanced wearing lines, and natural beauty, as one part of Clothing, in the late Chosun Dynasty. However it shows creativity, as separate part from Clothing, in the Rococo.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.4
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• pp.224-231
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• 2013

The concept of the natural frequency is useful for understanding the characters of oscillating systems. However, when a circular cylinder floating horizontally on the water surface is heaving, due to the hydrodynamic forces, the system is not governed by the equation like that of the harmonic one. In this paper, in order to shed some lights on the more correct use of the concept of the natural frequency, a problem of the heaving circular cylinder is analyzed in the time domain. The equation of motion, an integro-differential equation, was derived following the fashion of Cummins (1962), and its coefficients including the retardation function were obtained using the numerical solution of Lee (2012). The equation was solved numerically, and the experiment was also carried out in the CNU flume. Using our numerical and experimental results, the natural frequency was defined as its average value given by the motion data excluding those of the initial stage. Our results were then compared with those of the existing investigations such as Maskell and Ursell (1970), Ito (1977) and Yeung (1982) as well as the newly obtained results of Lee (2012). Comparison showed that the natural frequency obtained here agrees well with that of Lee (2012), which was found through the frequency domain analysis. It was also shown that the approximation of heaving motion by a damped harmonic oscillation, which was regarded as suitable by most previous investigators, is not physically suitable for the reason that can be clearly shown through comparing the shape of MCFRs(Modulus of Complex Frequency Response). Furthermore, we found that although the previous approximations yield the damping ratio significantly different from our result the magnitude of natural frequency is not much different from our result.

• Korean Institute of Interior Design Journal
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• v.25 no.3
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• pp.121-128
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• 2016

Focusing on the cases applied to korean brand-name apartments In 1960s, economical growth and introduction of western-type cultures led to a boom of apartment construction. After internationalization'in 1980s through Olympic games in 1988, korean culture has attracted attention and individual life quality has been improved. Since 1990s, changes in personal life style has affected the housing culture and the construction companies started moving from quantitative supply to developing their own differential characteristics. Differentiation scheme triggered by construction companies since mid-1990s mainly focused on various ideas for space deployment. Space plans include such things as a private ground, a kitchen in the south, etc. while interior plans include to provide selection of the korean traditional style, natural or casual one. 'korean traditional style' apartment is one of such theme of the brand-named apartment. Interests on 'Tradition' can be broken down into a social trend and media trend. Firstly, the former includes the designation of Bukchon as a reserving area, one of the governmental 'Hanok Survival Program', and traditional building promotion scheme on the basis of construction policy plans. Secondly, the latter covers the interests which attract through the media showing oriental cosmetics, korean culture export via Hallyu, popularity of korean dramas, etc. Thus, it seems worth studying on the apartments with traditional factors. And also, this study aims to setup the concept and trends of korean traditional style apartments through the interior expression on the korean-factor space developed by brand-name apartments so that it could correct such false knowledge out of misunderstood concept of traditional space which results from simple decoration or structure type not accompanying Korean emotion or spirit rendered by some misleading media.