• Steel and Composite Structures
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• 제25권4호
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• pp.497-503
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• 2017

In this paper, nonlinear vibration of multi-degree of freedom systems are studied. It has been tried to develop the mathematical model of systems by second-order nonlinear partial differential equations. The masses are connected with linear and nonlinear springs in series. A great effort has been done to solve the nonlinear governing equations analytically. A new analytical method called Variational Iteration Method (VIM) is proposed and successfully applied to the problem. The linear and nonlinear frequencies are obtained and the results are compared with numerical solutions. The first order of Variational Iteration Method (VIM) leads us to high accurate solution.

• 오토저널
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• 제10권6호
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• pp.54-60
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• 1988

During recent years, a great deal of interest has emerged on the use of adaptive approaches and a posteriori estimates in finite element method. The results are intended to be used to improve the quality of finite element solution by changing the location of the nodes within a fixed number of degrees of freedom-so called r method-, and by increasing the order of polynomial approximation with the new degrees of freedom-p method. This paper deals with error analysis that contains the basic theory and method of deriving error estimates and adaptive processes applied to finite element solutions underlying the rpm method that is the combination of r and p method of finite element. It is shown that we can obtain more accurate solution by applying the method to the 2-dimensional heat transfer problem.

• 한국컴퓨터정보학회논문지
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• 제11권2호
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• pp.169-175
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• 2006

본 논문은 고정된 카메라를 수평 이동(panning)시켜 얻어진 영상으로부터 단순화된 변환식을 이용 실린더 파노라마 영상(cylindrical panorama)을 재구성하는 방법을 제안한다. 일반적인 영상간의 사영 변환식(projective transform)은 3차원 공간의 X, Y, Z축에 대한 카메라의 회전 성분을 모두 고려하지만, 실제 파노라마 영상을 구성하기 위해서는 Y축 중심의 카메라 회전만을 고려한다. 이러한 제약은 기존의 8자유도(degree of freedom)를 갖는 사영 변환식을 4자유도를 갖는 사영 변환식으로 단순화시키고, 그 결과 변환식을 유도하기 위해 필요한 대응점의 개수가 절반으로 줄어들어 전체적인 계산량을 크게 감소시킬 수 있다. 모의실험 결과 제안된 알고리즘은 기존의 알고리즘과 계산량을 감소시키면서 유사한 성능을 보이고 있고, 단순화된 사영 변환식을 이용한 영상을 구성하는 것을 보여주었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1994년도 Proceedings of the Korea Automatic Control Conference, 9th (KACC) ; Taejeon, Korea; 17-20 Oct. 1994
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• pp.289-292
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• 1994

In this paper, the equations of motion are constructed systematically for multibody systems containing closed kinematic loops. For the displacement analysis of the closed loops, we introduce a new mixed coordinates by adding to the reference coordinates, relative coordinates corresponding to the degrees of freedom of the system. The mixed coordinates makes easy derive the explicit closed form solution. The explicit functional relationship expressed in closed form is of great advantages in system dimension reduction and no need of an iterative scheme for the displacement analysis. This forms of equation are built up in the general purpose computer program for the kinematic and dynamic analysis of multiboty systems.

• 정보관리학회지
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• 제24권3호
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• pp.271-297
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• 2007

인터넷의 대중화와 함께, 인터넷의 불법유해정보의 존재는 정부와 인터넷 사용자들에게 큰 근심거리가 된지 오래다. 불법유해정보 문제에 대한 다양한 해법들 중에서, 인터넷 콘텐츠 필터링 기술은 사용자들이 스스로 유해정보 문제에 대처할 수 있도록 개발되어 왔다. 지난 몇 년 사이, 상업 필터링 제품에 대한관심이 높아지고 있다. 부모, 교사, 심지어는 정부 당국도 청소년을 인터넷 유해정보로부터 보호하는 기술적 대안으로써 상업 필터링 제품을 선택하고 있고, 그 시장도 빠르게 성장하고 있다. 하지만 시민단체들을 중심으로 인터넷 콘텐츠 필터링에 대한 비판의 목소리가 높다. 필터링은 기술적 측면에서 태생적인 약점을 가지고 있을 뿐 아니라, 표현의 자유를 위축시키는 결과를 초래할 것이라는 비판이다. 이 논문은 인터넷 콘텐츠 필터링 특히 일세대 필터링과 구분되어 내용등급시스템으로 불리는 PICS/RDF 기반의 라벨 필터링의 기술적 측면을 분석하고 표현의 자유, 사용자 자율성과 관련된 문제들을 살펴봄으로써, 불법유해정보에 대한 기술적 해법의 타당성에 대하여 논하고자 한다.

• Journal of Mechanical Science and Technology
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• 제20권5호
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• pp.658-667
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• 2006

Fractional derivative models, which are used to describe the viscoelastic behavior of material, have received considerable attention. Thus it is necessary to put forward the analysis solutions of dynamic systems containing a fractional derivative. Although previously reported such kind of fractional calculus-based constitutive models, it only handles the particularity of rational number in part, has great limitation by reason of only handling with particular rational number field. Simultaneously, the former study has great unreliability by reason of using the complementary error function which can't ensure uniform real number. In this paper, a new approach is proposed for an analytical scheme for dynamic system of a spring-mass-damper system of single-degree of freedom under general forcing conditions, whose damping is described by a fractional derivative of the order $0<{\alpha}<1$ which can be both irrational number and rational number. The new approach combines the fractional Green's function and Laplace transform of fractional derivative. Analytical examples of dynamic system under general forcing conditions obtained by means of this approach verify the feasibility very well with much higher reliability and universality.

• Journal of Contemporary Eastern Asia
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• 제5권1호
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• pp.1-8
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• 2006

Since its defeat in the Second World War, Japan has been fostering good ties with Western countries, especially the United States. However, some East Asian leaders emboldened by their countries' economic success have proclaimed that the future belongs to Asia and have put forward the "Asian values" argument. It is interesting to note that some elements of the "Asian values" argument resemble ultranationalist discourse that was dominant in Japan before the war. The Japanese Government had a great opportunity to reappraise its role in international politics and take stock of its economic and diplomatic relations with East Asian countries after the end of the Cold War. To meet future challenges, Japan should fully overcome anti-Western sentiment and participate in establishing a truly democratic East Asian regionalism based on the "universal values" of human rights, democracy and freedom. This may prove to be one of the biggest challenges for Japan's East Asia policy in the new century.

• 한국정밀공학회지
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• 제17권4호
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• pp.69-80
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• 2000

Generally, die polishing is a lime consuming process, resulting in 30∼50％ of the whole die manufacturing time. However, die polishing has not been automated yet, since it needs a great deal of experience and skill. This paper describes a new development of automated system for die polishing and focuses on the successful achievements of the element techniques to realize from hand skill to automation, as followings: (1) The 5 axes polishing system by the aid of robot with 2 degrees of freedom, is developed for the application of curved surface die. (2) The CAM system realizes a 5 axes tool path control for polishing and measuring. (3) The conductive elastic tool is able to meet curved surfaces of die and gives a high efficient and quality polishing characteristics. (4) The surface roughness measurement device with noncontact laser is developed and has a high reliability without surface damage.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.814-815
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• 2011

A surfaced permanent magnet spherical motor is capable of operating as three degree of freedom that used for the joints of the robot's arm, leg, and eyes. Ongoing research like new concept is essential part of motor field, it will make a great contribution in the future the overall portion of the motor, is becoming expected. The author analysis torque characteristics in spherical motor with state of rotating and positioning. And future design direction is smaller motors with equivalent or higher output. Solutions as torque and efficiency improvements are selecting the core with special processing type like powder metallurgy materials. Their special characteristic is high permeability and low eddy current losses at high speed, so improved the torque and efficiency.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.19-19
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• 2003

The injection of spins into nonmagnetic semiconductors has recently attracted great interest due to the potential to create new classes of spin-dependent electronic devices. A recent strategy to achieve control over the spin degree of freedom is based on dilute ferromagnetic semiconductors. Ferromagnetism has been reported in various semiconductor groups including II-Ⅵ, III-V, IV and II-IV,-V$_2$, which will be reviewed. On the other hand, to date the low solubility of magnetic ions in non-magnetic semiconductor hosts and/or low Curie temperature have limited the opportunities. Therefore the search for other promising ferromagnetic semiconducting materials, with high magnetic moments and high Curie temperatures (Tc), is of the utmost importance. In this talk, we also introduce new pure ferromagnetic semiconductors, MnGeP$_2$ and MnGeAs$_2$, exhibiting ferromagnetism and a magnetic moment per Mn at 5K larger than 2.40 ${\mu}$B. The calculated electronic structures using the FLAPW method show an indirect energy gap of 0.24 and 0.06 eV, respectively. We have observed spin injection in MnGeP$_2$ and MnGeAs$_2$ magnetic tunnel junctions through semiconducting barriers.