• 한국해양공학회지
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• 제25권6호
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• pp.9-16
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• 2011

The feasibility of wave energy extraction from a heaving truncated cylinder and the corresponding response of the linear electric generator (LEG) composed of spring, magnet, and coil has been investigated in the frame of three-dimensional linear potential theory. The heaving motion of a circular cylinder is calculated by means of the matched eigenfunction expansion method. Further, the analytical results are validated by numerical results using the ANSYS AQWA commercial code. By the action of a heaving circular cylinder, the magnet suspended by a spring can slide vertically inside the heaving cylinder. The mechanical power is extracted from the magnet motion relative to the coil/stator which is attached to the cylinder. The coupled ODE of a heaving cylinder and LEG system in waves is derived to obtain the magnet motion relative to a cylinder. To maximize the relative motion of the magnet, both the buoy draft and the LEG system parameters (spring stiffness, damping) should be selected properly for generating the double resonance considering the peak frequency of the target spectrum.

• 한국생활과학회지
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• 제14권1호
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• pp.133-141
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• 2005

This research was designed to investigate the effect of a hand and a sensibility image on the preference to skirt textiles. 131 male and female college students were surveyed and 10 kinds of preferred fabrics were used each as a specimen for all 4 seasons. Factor analysis, t-test, Pearson's correlation, and regression were used for a statistical analysis by SPSS WIN 10.0. The results of this study are as follows: 1. In spring/fall season, 6 factors including 'elasticity/flexibility' were extracted as a hand factor, and 2 factors including 'modern elegance' were extracted as a sensibility factor in skirt textiles. 2. In summer season, 5 factors such as 'unevenness/stiffness' were extracted as a hand factor and 2 factors such as 'modern elegance romantic' as a sensibility image. 3. In winter season, 7 factors including 'elasticity' were extracted as a hand factor and 2 factors including 'modern elegance romantic' as a sensibility image. 4. Significant correlations existed between a hand and a sensibility image in spring/fall, summer, and winter. 5. A sensibility image was one of the important factors in the preference to skirt textiles in spring/fall, summer, and winter.

• 한국철도학회논문집
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• 제11권1호
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• pp.39-44
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• 2008

본 연구에서는 실측 주행시험 결과데이터를 바탕으로 윤축 진동과 설계변수간의 관계를 규명하고자 2 자유도계 모델을 구성하였다. 특히 2차 현가장치인 공기스프링의 점탄성 특성을 반영하기 위해 니시무라 공기스프링 모델을 적용하였다. 수치해석 결과 내부 압력 감소 및 보조 공기탱크 체적 증가 시 객차 가속도응답이 감소하는 것을 확인할 수 있었다. 이에 안정성을 헤치지 않는 범위 내에서 현가장치의 강성을 조정해 볼 필요가 있음을 알았다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.477-482
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• 2001

To realize higher track density of HDD, the servo bandwidth should be higher, however, is limited by the mechanical resonances of the arm, coil of the VCM and ball bearing pivot. The dual-stage actuator systems have been suggested as a possible solution. For the dual-stage actuator systems based on the suspension, the suspension resonance frequencies in the radial access direction are important factors to increase a servo bandwidth, however the improvement of these frequencies may affect the shock resistance performance and spring constant. The slider's flying stability can be deteriorated by the change of a vertical stiffness. In this work, we have investigated a suspension design scheme possessing a milliactuator for dual-stage actuator systems and also achieved higher mechanical characteristics. Design parameters are deduced by finite element analysis with sensitivity function. It is confirmed that the proposed suspension with the milliactuator has the capability of fine tracking motion, due to its hinge structure on the spring region, and achieves higher mechanical resonance frequencies in the radial access direction with a high-shock resistance and a low-spring constant.

• 한국해양공학회지
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• 제10권4호
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• pp.10-16
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• 1996

The vibration due to progressive ocean waves is analyzed for a typical footing-type offshore airport platform. The platform is modelled as a spring-supported Euler beam and buoyancy change due to wave is considered as excitation force, under the assumption that the wave propagates without distortion by the structure. The results show that the natural frequencies of this structure are distributed very closely and are little affected by boundary conditions and that the response charateristics due to ocean waves are quite different according to the wave frequency. In this study, the wave frequencies are divided into three regions; the resonance region at which the response is governed by the resonance between the natural mode at the wave frequency and the corresponding modal component of the wave excitation force, the bending governed region at which the response is governed by the bending stiffness, and the spring (buoyancy) governed region at which the response is governed by the spring constant ahd therefore is same as the incident wave form.

• 대한기계학회논문집A
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• 제35권4호
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• pp.367-374
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• 2011

마찰 스프링은 부하가 가해질 때와 가해지지 않을 때 서로 다른 특성을 가지고 있다. 마찰스프링의 이러한 특성으로 인해 충격 시스템에 주로 사용된다. 본 논문에서는 마찰 스프링을 포함한 발사장치의 주퇴복좌기 설계 연구가 수행되었다. 마찰 스프링의 강성을 결정하기 위해서는 충격량과 운동량 관계를 고려한 단순한 발사장치 모델의 운동방정식이 개발되었다. 발사장치의 동적 거동시뮬레이션 결과에 기초하여, 주퇴복좌 시스템의 마찰 스프링의 지름을 결정하였다.

• 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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.332-339
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• 2006

A leaf spring suspension has been widely used since it can carry big load and simplicity. But one major drawback is the poor ride performance because of the friction in the system and the high stiffness coefficient. To overcome these, air spring suspension can be used. The air spring suspension system can improve the ride of the heavy vehicle significantly and also it can adjust the height to the loading and unloading. A truck with the leaf suspension system is modified with the air suspension system and the performance of the vehicle is compared using the suggested method. The existing leaf suspension can be replaced with the air suspension system to improve the performance.

• 한국전산구조공학회논문집
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• 제19권1호
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• pp.85-92
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• 2006

이 논문은 일단고정 타단스프링으로 지지된 변단면 Beck 기둥의 임계하중에 관한 연구이다. 기둥의 변단면을 중실 직사각형 단면을 갖는 선형 변단면으로 채택하고, Bernoulli-Euler보 이론을 이용하여 경사종동력이 작용하는 소위 Beck 기둥의 자유진동을 지배하는 상미분방정식과 경계조건을 유도하였다. 이 미분방정식을 수치해석하여 하중-고유진동수 곡선을 얻고 이로부터 발산임계하중 및 동요임계하중을 산출하였다. 수치해석의 결과로부터 변단면 형태, 경사변수 및 스프링 강성이 임계하중에 미치는 영향을 고찰하였다

• 한국정밀공학회지
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• 제25권5호
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• pp.140-147
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• 2008

In this study, a carbon nanotube probe (CNT probe) is proposed as a mechanical force transducer for the measurement of pico-Newton (pN) order force in biological applications. In order to measure nantube's displacement in the air or liquid environment, the fabrication of a CNT probe with tip-specific loading of fluorescent dyes is performed using tip- specific functionalization of the nanotube and chemical bonding between dyes and nanotube. Also, we experimentally investigated the mechanical properties of the CNT probe using electrostatic actuation and fluorescence microscope measurement. Using fluorescence measurement of the tip deflection according to the applied voltage, we optimized the bending stiffness of the CNT probe, therefore determined the spring constant of the CNT probe. The results show that the spring constant of CNT probes is as small as 1 pN/nm and CNT probes can be used to measure pN order force.