• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.167-169
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• 2001

In this paper, a controller design for high speed and stiffness linear motor is implemented. The designed controller is mainly composed of speed and current controller, which are carried out by the high-speed digital signal processor(DSP). In addition the PWM inverter is controlled by space voltage PWM method. This system is implemented by using 32-bit DSP(TMS320C31), a high-integrated logic device(EPM7128), and IPM(Intelligent Power Module) for compact and powerful system design. The experimental results show the effective performance of controller for high speed and stiffness linear motor.

• Computers and Concrete
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• 제29권3호
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• pp.127-144
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• 2022

To investigate the flexural stiffness of the steel-composite beam, the contributions of the concrete slab and steel beam to the stiffness were considered separately. The method for flexural stiffness of the composite beam, considering the stiffness of the concrete slab and steel beam, was proposed in this paper. In addition, finite element models of the composite beams were established and validated. Parametric analyses were carried out to study the effects of different parameters on the neutral axis distance reduction factors of the concrete slab and steel beam. Afterward, the neutral axis distance reduction factors were fitted, and the stiffness combination coefficients of the two parts were solved. Based on the stiffness combination coefficients, the flexural stiffness of the composite beam can be obtained. The proposed method was validated by the tested and analyzed results. The method has a simple form and high accuracy in predicting the flexural stiffness of the steel-concrete composite beam, even though the degree of shear connection is less than 0.5.

• 대한토목학회논문집
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• 제30권2A호
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• pp.121-129
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• 2010

본 연구에서는 고감쇠 고무받침 시험체의 다양한 특성실험을 통하여 전단특성 의존성을 파악하였다. 파악하고자 하는 고감쇠 고무받침의 특성은 변위의존성, 면압 의존성, 주파수 의존성, 온도 의존성 등이다. 특성실험결과 고감쇠 고무받침의 특성치는 온도에 가장 큰 영향을 받는 것으로 나타났으며, 주파수가 증가할수록 전단강성과 등가감쇠비 모두 증가하나 반복횟수가 증가 할수록 고무의 온도상승으로 인하여 그 값들은 감소하였다. 그리고 면압이 증가할수록 유효강성은 감소하고 등가감쇠비는 증가하는 것으로 타나났다. 본 실험결과에 의하면 고감쇠 고무받침의 설계의 주요한 변수인 전단강성과 등가감쇠비를 산정함에 있어 설계변위와 가진속도 및 온도의 면밀한 검토가 필요하다고 판단된다.

• 한국소음진동공학회논문집
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• 제13권5호
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• pp.375-383
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• 2003

For a performance analysis of vibration isolation systems, the concept of vibration power flow can be employed preferably when noise radiated from the supporting structure with finite impedances is of interest. The idea is basically simple to understand and formulas for precise estimation of the vibration power are easy to derive. However, It is often required to simplify the process of experimentation under several assumptions due to instrumental limitations. For an example, rotational degree of freedom has not been well treated in bending vibrations of beam or plate-like structures. Yet, several recent studies showed that the moments and rotations play an important role in power transmission and should be taken into consideration carefully as the frequency range of interest goes to audibly high. Therefore, it is readily agreed that reduction of the noise radiation over the high frequency range can be effectively accomplished by adjusting the rotational stiffness of the isolator without changing the vibration isolator efficiency in low frequency range relevant to the translational stiffness of the isolator In this paper, the vibration power flow approach is applied to an AC motor installed on a finite plate in order to illustrate the contribution of the rotational vibration power to the total vibration power transmission. The effects of rotational stiffness of the isolator on the vibration power transmission are investigated by inserting various shapes of Isolators with different rotational stiffness but with $ame translational stiffness between the motor and the plate. The resultant noise radiation from the plate is presented to verify the proposed approach.

• Progress in Superconductivity
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• 제11권1호
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• pp.57-61
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• 2009

A superconductor flywheel energy storage(SFES) system is mainly act an electro-mechanical battery which transfers mechanical energy into electrical form and vice versa. SFES system consists of a pair of non-contacting High Temperature Superconductor (HTS) bearings with a very low frictional loss. But it is essential to design an efficient HTS bearing considering with rotor dynamic properties through correct calculation of stiffness in order to support a huge composite flywheel rotor with high energy storage density. Static properties of HTS bearings provide data to solve problems which may occur easily in a running system. Since stiffness to counter vibration is the main parameter in designing an HTS bearing system, we investigate HTS bearing magnetic force through static properties between the Permanent Magnet(PM) and HTS. We measured axial / radial stiffness and found bearing stiffness can be easily changed by activated vibration direction between PM and HTS bulk. These results are used to determine the optimal design for a 10 kWh SFES.

• 대한기계학회논문집A
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• 제40권5호
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• pp.489-495
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• 2016

기어 맞물림 동적 힘은 축과 베어링을 통해 하우징에 전달되어 소음으로 발생하므로, 베어링 강성은 하우징의 최종 전달자로서 기어 소음을 제어하는데 중요한 역할을 한다. 이 논문은 스퍼기어를 위한 볼 베어링의 강성을 유도하고, 베어링 하중과 반경 방향 틈새를 고려하여 강성을 계산하였다. 그 강성을 이용하여 3 자유도 모델의 스퍼기어계의 운동방정식에 적용하여 모드 특성을 해석하였고, 유한요소법으로 검증하였다. 그 결과 베어링 하중이 클 때보다 작을 때는 틈새에 따라 베어링 강성의 변화가 많았다. 베어링 강성은 저주파 고유 진동수에 영향을 주었고 기어 맞물림 주파수는 고주파 고유진동수에 영향을 주었다.

• Tribology and Lubricants
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• 제30권4호
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• pp.218-223
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• 2014

This paper presents a method of controlling the stiffness of a tungsten probe for an atomic force microscope (AFM) in order to provide high-quality phase contrast images in accordance with sample characteristics. While inducing sufficient deformation on sample surfaces with commercial Si or $Si_3N_4$ probes is difficult because of their low stiffness, a tungsten probe fabricated by electrochemical etching with appropriately high stiffness can generate relatively large elastic deformation without damaging sample surfaces. The fabrication of the tungsten probe involves two separate procedures. The first procedure involves immersing a tungsten wire with both ends bent parallel to the surface of an electrolyte and controlling the stiffness of the tungsten cantilever by decreasing its diameter using electrochemical etching in the direction of the central axis. The second procedure involves immersing the end of the etched tungsten cantilever in the direction perpendicular to the surface of the electrolyte and fabricating a tungsten tip with a tip radius of 20-50 nm via the necking phenomenon. The latter etching process applies pulse waves every 0.25 seconds to the manufactured tip to improve its yield. Finite element analysis (FEA) of the stiffness of the tungsten probe as a function of its diameter showed that the stiffness of the tungsten probes greatly varies from 56 N/m to 3501 N/m according to the cantilever diameters from $30{\mu}m$ to $100{\mu}m$, respectively. Thus, the proposed etching method is effective for producing a tungsten probe having specific stiffness for optimal use with an AFM and certain samples.

• 대한건축학회논문집:구조계
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• 제35권9호
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• pp.183-190
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• 2019

This paper intended to propose the optimal outrigger position in tall building. For this purpose, a schematic structure design of 70 stories building was accomplished by using MIDAS-Gen. In this analysis research, the key variables were the stiffness of outrigger, the stiffness of frame, the stiffness of shear wall, the stiffness of exterior column connected in outrigger and the outrigger location in height. With the intention of looking for the optimum location of outrigger system in high-rise building, we investigated the lateral displacement in top floor. The study proposed the new method to predict the optimal location of outrigger system considering the frame stiffness. And it is verified that the paper results can be helpful in providing the important engineering materials for finding out the optimum outrigger position in tall building.

• 한국기계가공학회지
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• 제8권1호
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• pp.10-17
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• 2009

Spindle design is very important for the improvement of the competitive power in production cost of high quality machine tools. The important factor in spindle design is not only to improve the natural frequency of spindle but also to reduce displacement of spindle end. In this paper, parameters those influence on static and dynamic stiffness of high-speed spindle have selected form preceding studies. And those selected parameters are applied to Taguchi Method. To perform FEM analysis, bearing conditions are selected with optimized condition. To know how to improve static and dynamic stiffness of machine tool spindle, natural frequency and displacement of spindle end are obtained by FEM analysis. The Taguchi Method was used to draw optimized condition of bearing position and it's stiffness. From these results, amplitude of vibration is enough good less than $3{\mu}m$ pk-pk of the spindle of 40,000rpm manufactured in this work by the optimal design.

• Steel and Composite Structures
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• 제33권3호
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• pp.357-373
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• 2019

Steel storage racks are slender structures whose overall behavior and the capacity depend largely on the flexural behavior of the base-plate to upright connections and on the behavior of beam-to-column connections. The base-plate upright connection assembly details, anchor bolt position in particular, associated with the high-rise steel storage racks differ from those of normal height steel storage racks. Since flexural behavior of high-rise rack base connection is hitherto unavailable, this investigation experimentally establishes the flexural behavior of base-plate upright connections of high-rise steel storage racks. This investigation used an enhanced test setup and considered nine groups of three identical tests to investigate the influence of factors such as axial load, base plate thickness, anchor bolt size, bracket length, and upright thickness. The test observations show that the base-plate assembly may significantly influence the overall behavior of such connections. A rigid plate analytical model and an elastic plate analytical model for the overall rotations stiffness of base-plate upright connections with concentric anchor bolts were constructed, and were found to give better predictions of the initial stiffness of such connections. Analytical model based parametric studies highlight and quantify the interplay of components and provide a means for efficient maximization of overall rotational stiffness of concentrically anchor bolted high-rise rack base-plate upright connections.