• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1651-1656
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• 2005

This paper describes a natural frequency analysis conducted to find out a suitable working area for a spring-manipulator system generating a large vibrating force with mechanical resonance. Large force generation is one of the functions that we hope for a robot. For example, a weeding robot is required to generate a large force, because some weeds have roots spreading deeply and tightly. The spring-manipulator system has a spring element as an end-effector, so it can be in a state of resonance with the elasticity of the spring element and the inertial characteristics of the manipulator. A force generation method utilizing the mechanical resonance has potential to produce a large force that cannot be realized by a static method. A method for calculating a natural frequency of a spring-manipulator system with the generalized inertia tensor is proposed. Then the suitable working area for the spring-manipulator system is identified based on a natural frequency analysis. If a spring-manipulator system operates in the suitable working area, it can sustain mechanical resonance and generate a large vibrating force. Moreover, it is shown that adding a mass at the tip of the manipulator expands the suitable working area.

• 제어로봇시스템학회논문지
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• 제5권1호
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• pp.105-114
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• 1999

By using the conceptual impedance and the elasticity of a serial chain of spring-damper system, a real-time collision-free trajectory generation algorithm is proposed. The reference points on a trajectory connected by the spring-damper system have a mechanism for self-Position adjustment to avoid a collision by the impedance, and the local adjustment of each reference point is propagated through the elasticity to a real robot at the end of the spring-damper system. As a result, the overall trajectory consisting of the reference points becomes free of collision with environmental obstacles and efficient having the shortest distance as possible. In this process, the reference points connected by the spring-damper system take role of virtual robot as global guidance for a real robot, and a cooperative optimization is carried out by the system of virtual robots. A control algorithm is proposed to implement the impedance for a car-like mobile robot.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.963-968
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• 2004

Free vibration analysis of helical spring with crack was studied. Natural frequency changes due to the crack was analyzed with respect to crack locations. The effect of crack on natural frequency was decreased as crack location is further from the fixed end of a spring. The frequency change was larger in rectangular-shaped spring than that in circular-shaped spring. It was found that experiment may not be appropriate to determine the presence of crack because no significant natural frequency change can be shown by experiment.

• 한국재난정보학회 논문집
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• 제3권2호
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• pp.147-169
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• 2007

This study investigates the reinforcing effects of the Multi-bar Spring nails with respect to the conventional Soil-nails in artificial slopes. Based on wide experience related to design and construction, soil nails have been widely applied to reinforce slope in the world. Multi-bar spring nails are one of the improved soil nailing methods. These method maximizes bending, shearing, pull-out resistance for those multi-nails, not unit nail, that are inserted in the borehole using special spacer at regular intervals. In addition, because cutting plane is confined effect resulting from a pressured plate at the end of the nails with compression spring equipment, slope stability is secured using MS-nailing method. Analyzing bending, pull-out, shearing condition of MS-nail, it was examined throughly elastic region, load transfer capacity, reinforcing effect on cutting plate of MS-nails. In addition, Pilot and laboratory tests, numerical analysis were carried out to verify the superiority of MS-nailing method. In case, MS nailing method is applied to reinforce artificial slope, it was analyzed that bending, pull-out, shearing resistance was increased more than existing nailing method was applied. In this study, it was shown that surface failure was more or less prevented using MS-nailing method, confining effect on cutting plane using spring stuck to flexible equipment.

• 한국심리학회지:학교
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• 제18권2호
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• pp.175-195
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• 2021

친밀한 친구 관계를 맺고 소속감을 느끼는 것은 청소년의 심리·사회적 발달 및 적응에 긍정적인 영향을 미친다. 소속감 지향성은 소속감을 추구하는 동기로, 성장 지향성과 결핍감소 지향성으로 구분된다. 성장 지향성과 결핍감소 지향성은 심리적 적응 및 대인관계 특성에 서로 다른 영향을 주는 것으로 알려져 있다. 본 연구의 목적은 청소년의 소속감 지향성이 심리적 적응과 친구 네트워크에 미치는 효과를 알아보는 것이다. 이를 위해 한 중학교의 2학년 전체 학생을 대상으로 학기 초와 학기 말에 검사를 실시했다. 친구 네트워크는 네트워크 수신 중심성 분석을 통해 측정했다. 다층 회귀모형을 사용한 분석 결과는 첫째, 학기 초의 외로움과 스트레스에 대한 성장 지향성의 효과는 학기 초 친구 네트워크 중심성을 분석 모형에 함께 투입해도 유의했으나, 결핍감소 지향성의 효과는 유의하지 않았다. 둘째, 성장 지향성은 학기 말의 친구 네트워크 중심성을 유의하게 예측했다. 이러한 효과는 학기 초 친구 네트워크 중심성과 학기 말 심리적 적응 수준을 분석 모형에 함께 투입해도 유의했다. 셋째, 학기 말의 심리적 적응에 미치는 학기 말의 친구 네트워크 중심성의 효과는 학기 초 및 학기 말의 심리적 적응을 모형에 함께 투입해도 유의했다. 본 연구는 단기-종단적 설계를 통해 소속감 지향성이 청소년의 학기 초와 학기 말의 심리적 적응과 친구 네트워크 수준에 미치는 효과를 경험적으로 밝혔다는 점에서 의의가 있다. 끝으로, 본 연구의 한계점 및 후속 연구를 위한 제언을 논의했다.

• 영어영문학
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• 제55권1호
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• pp.83-105
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• 2009

Modern poetry begins as criticism of modernity and, by so doing, rejects its idea of time. Modernity emphasizes sequential, linear, and irreversible time and progress. Williams rejects the modern view of time, and attempts to substitute literature for history assuming that literature can take us into the immediacy of time. His poetry asserts the true moment of experience as an immediacy, of words co-existent with things. He suggests that modernity and its idea of time already led to World War I and could clearly lead to an actual, manmade apocalypse with continued technological progress. Already in the 1920s, Williams sensed that he was living in a world where such an end could come all true, which is why Spring and All, his greatest early achievement, begins with a parody of the modern apocalypse. Throughout the work, Williams criticizes "crude symbolism" and expresses his longing to annihilate "strained associations," for he believes that the metaphoric or symbolic association is related to order, the center, and the traditional concept of time itself. The metonymic model of Spring and All substitutes a self-reflexive, open-ended, and indeterminate structure of time for the linear and closed one. Instead of supplying an end, Williams only asserts the rebirth of time and attempts to arrive at immediacy while attacking the mediacy of traditional art. His characteristic use of fragmentation and abrupt juxtapositions disrupts the reader's generic, conceptual, syntactic, and grammatical expectations. His radical poetic experiments, such as the isolation of words and the disruption of syntax, produce a sense of immediacy and force the reader to confront the presence of the poem. His destruction of traditional forms, of the tyrannous designs of history and time, opens up rather than closes the possibility of signification, and takes us into a moment of beginning while disallowing temporal distancing. Spring and All, as a criticism of the modern idea of time, asks us to view Williams's work not as an ahistorical text but as a cultural subversion of modernity.

• 한국지반공학회지:지반
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• 제6권1호
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• pp.7-14
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• 1990

주동단에 반력스프링이 부착된 공진주(spring-top resonant column) 시험기 주동단 불완전 고정의 영향을 연구하기 위해 2자유도 모델을 제안하였다. SYMPHONY스프레드쉿트를 이용하여 무차원주파수, F를 구할 수 있도록 전산화하였으며 이로부터 탄성계수를 구할 수 있다. F에 대한 반력 질량의 영향은 반력질량 및 시료의 질량 및 주파수에 관계되는 계수, T<20인 경우에 는 무시할 수 없음을 밝혔다. 시험기 및 시료의 질량과 주파수에 관계되는 계수, Tci가 증가함에 따라 F의 영향 역시 증가하였으나 T도 20인 경우 그 영향은 적었다. 주동단 고정을 위해서는 T, 이 20이상 되어야 함을 제안하였으며 이 경우 SDOF으로 취급할 수 있다. 시료와 시험기의 감쇠비는 F에 크게 영향을 미치지 않음도 밝혔다.

• Structural Engineering and Mechanics
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• 제16권5호
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• pp.533-556
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• 2003

The flutter and buckling analysis of a beam structure subjected to a static follower force is completely studied in the paper. The beam is fixed in the transverse direction and constrained by a rotational spring at one end, and by a translational spring and a rotational spring at the other end. The co-existence of flutter and buckling in this beam due to the presence of the follower force is an interesting and important phenomenon. The results from this theoretical analysis will be useful for the stability design of structures in engineering applications, such as the potential of flutter control of aircrafts by smart materials. The transition-curve surface for differentiating the two distinct instability regions of the beam is first obtained with respect to the variations of the stiffness of the springs at the two ends. Second, the capacity of the follower force is derived for flutter and buckling of the beam as a function of the stiffness of the springs by observing the variation of the first two frequencies obtained from dynamic analysis of the beam. The research in the paper may be used as a benchmark for the flutter and buckling analysis of beams.

• 대한기계학회논문집A
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• 제20권9호
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• pp.2812-2818
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• 1996

A cantilever beam with a mass and a spring at the end can be use to model a miniature flexible arm. It is necessary to know the natural frequencies and mode shapes to discuss its free vibration, especially when modal analysis is employed. A beam is clamped-free. In this paper we look at the lateral vibration of beams that have step changes in the properties of their cross sections. The frequency equation is derived by Bernoulli-Euler formulation and is sloved by the separation of variable. The parameters of the beam, 'mass and spring stiffness' are defined as nondimensionalized parameters for wide application of the results. According to the change of eigenvalues and mode shape are presented for this beam. The results presented are the eigenvalues and the natural frequencies for the first three modes of vibration. Results show that the parameters have a significant effect on the natural frequency.

• Computers and Concrete
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• 제24권3호
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• pp.237-247
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• 2019

The key issue for the finite element analysis (FEA) of section steel reinforced concrete (SRC) structure is how to consider the bond-slip performance. However, the bond-slip performance is hardly considered in the FEA of SRC structures because it is difficult to achieve in the finite element (FE) model. To this end, the software developed by Python can automatically add spring elements for the FE model in ABAQUS to considering bond-slip performance. The FE models of the push-out test were conducted by the software and calculated by ABAQUS. Comparing the calculated results with the experimental ones showed that: (1) the FE model of SRC structure with the bond-slip performance can be efficiently and accurately conducted by the software. For the specimen with a length of 1140 mm, 3565 spring elements were added to the FE model in just 6.46s. In addition, different bond-slip performance can also be set on the outer side, the inner side of the flange and the web. (2) The results of the FE analysis were verified against the corresponding experimental results in terms of the law of the occurrence and development of concrete cracks, the stress distribution on steel, concrete and steel bar, and the P-S curve of the loading and free end.