• 제어로봇시스템학회논문지
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• 제6권1호
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• pp.51-56
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• 2000

This paper presents the characteristics of the dynamic response and calibration technique on a linear variable differential transformer(LVDT). The linear error of the LVDT was proven $\pm$1% in the static calibration and $\pm$0.5% in the dynamic calibration. In this paper, the linearity error generated in the static and dynamic state of the core movement can be eliminated using the correction algorithem of the static and dynamic state derived from the least square linear approximation for the nonlinearity of the curves of direct data fitting and Lagrange polynomials. With the static and dynamic calibration method, the calibration accuracy of the LVDT can be reduced to within $\pm{0.5%.}$.

• Tribology and Lubricants
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• 제10권1호
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• pp.46-55
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• 1994

The static and dynamic analysis of air lubricatied tilting pad journal bearing which considers tilting effect of each pad, preload but which neglects pad inertia effect and deflection are performed. A direct numerical method is used in evaluating the static characteristics such as load carrying capacity, friction force and small peturbation method is used for calculation of dynamic characteristics. Stiffness and damping coefficients are compared with the variation of the preload. And these coefficients are slightly decreased with increased compressibility number under the constant bearing load carrying capacity.

• 한국자동차공학회논문집
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• 제9권5호
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• pp.157-164
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• 2001

This paper performs static and dynamic tests of a multi-leaf spring and a tapered leaf spring to investigate their hysteretic characteristics. In the static test, trapezoidal input load is applied with 0.1Hz excitation frequency and with zero initial loading conditions. In the dynamic test, sinusoidal input load is applied with five excitation amplitudes and three excitation frequencies. In these tests, static and dynamic hysteretic characteristics of the multi-leaf spring and the tapered leaf spring are compared, and, the effects of excitation amplitudes and frequencies on dynamic spring rate are also shown. In this paper, actual vehicle tests are performed to study the effects of hysteretic characteristics of the large-sized truck's handling performance. The multi-leaf spring or the tapered leaf spring is used in the front suspension. The actual vehicle test is performed in a double lane change track with three velocities. Lateral acceleration, yaw rate and roll angle are measured using a gyro-meter located at the mass center of the cab. The test results showed that a large-sized truck with a tapered leaf spring needs to have an additional apparatus such as roll stabilizer bar to increase the roll stabilizer due to hysteretic characteristics.

• 한국자동차공학회논문집
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• 제6권5호
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• pp.119-127
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• 1998

Assuming that the static loaded square tube and the dynamic loaded one have no difference in their characteristics of the crush distance, the theoretical mean dynamic crush load was calculated with respect to the impact speed considering the strain rate sensitivity of the material. The ratio of dynamic to static mean crush load was predicted with previous results. The theoretical analysis was compared with the experimental results of aluminum square tubes axially loaded dynamically.

• 한국소음진동공학회논문집
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• 제16권4호
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• pp.372-379
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• 2006

Little attention has been paid to static-strain-dependence of dynamic complex modulus of viscolelastic materials in computational analysisso far. Current commercial Finite Element Method (FEM) codes do not take such characteristics into consideration in constitutive equations of viscoelastic materials. Recent experimental observations that static-strain-dependence of dynamic complex modulus of viscolelastic materials, especially filled rubbers, are significant, however, require that solutions somehow are necessary. In this study, a simple technique of using a commercial FEM code, ABAQUS, is introduced, which seems to be far more cost/time saving than development of a new software with such capabilities. A static-strain-dependent correction factor is used to reflect the influence of static-strains in Merman model, which is currently the base of the ABAQUS. The proposed technique is applied to viscoelastic components of rather complicated shape to predict the dynamic stiffness under static-strain and the predictions are compared with experimental results.

• KSTLE International Journal
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• 제2권1호
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• pp.46-54
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• 2001

The herringbone groove journal bearing (HGJB) has chevron type grooves on stationary or rotating member of the bearing so that they pump the lubricant inward the grooves when journal rotates. As a result, the pressure is generated around the journal so that the radial stiffness and dynamic stability are improved comparing to the plain journal bearing (PJB) when the bearing operates near the concentric condition. The narrow groove theory, conventionally adopted to simulate the concentric operation of HGJB, is limited to the infinite number of grooves. A numerical study of air-lubricated HGJB is presented for the finite number of grooves. The compressible isothermal Reynolds equation is solved by using Finite Element Method together with the Newton-Raphson iterative procedure and perturbation method. The solutions render the static and dynamic performances of HGJB. Comparison of present results with a PJB validates previously published finite difference solution. The HGJB's geometric parameters influence its static and dynamic characteristics. The optimum geometric parameters are presented for the air-lubricated HGJB in particular conditions.

• 대한기계학회논문집A
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• 제27권2호
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• pp.268-275
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• 2003

Generally, structural optimization is carried out based on external static loads. All forces have dynamic characteristics in the real world. Mathematical optimization with dynamic loads is extremely difficult in a large-scale problem due to the behaviors in the time domain. The dynamic loads are often transformed into static loads by dynamic factors, design codes, and etc. Therefore, the optimization results can give inaccurate solutions. Recently, a systematic transformation has been proposed as an engineering algorithm. Equivalent static loads are made to generate the same displacement field as the one from dynamic loads at each time step of dynamic analysis. Thus, many load cases are used as the multiple leading conditions which are not costly to include in modern structural optimization. In this research, it is mathematically proved that the solution of the algorithm satisfies the Karush-Kuhn-Tucker necessary condition. At first, the solution of the new algorithm is mathematically obtained. Using the termination criteria, it is proved that the solution satisfies the Karush-Kuhn-Tucker necessary condition of the original dynamic response optimization problem. The application of the algorithm is discussed.

• 대한기계학회논문집A
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• 제33권12호
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• pp.1401-1409
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• 2009

All the forces in the real world act dynamically on structures. Design and analysis should be performed based on the dynamic loads for the safety of structures. Dynamic (transient or vibrational) responses have many peaks in the time domain. Topology optimization, which gives an excellent conceptual design, mainly has been performed with static loads. In topology optimization, the number of design variables is quite large and considering the peaks is fairly costly. Topology optimization in the frequency domain has been performed to consider the dynamic effects; however, it is not sufficient to fully include the dynamic characteristics. In this research, linear dynamic response topology optimization is performed in the time domain. First, the necessity of topology optimization to directly consider the dynamic loads is verified by identifying the relationship between the natural frequency of a structure and the excitation frequency. When the natural frequency of a structure is low, the dynamic characteristics (inertia effect) should be considered. The equivalent static loads (ESLs) method is proposed for linear dynamic response topology optimization. ESLs are made to generate the same response field as that from dynamic loads at each time step of dynamic response analysis. The method was originally developed for size and shape optimizations. The original method is expanded to topology optimization under dynamic loads. At each time step of dynamic analysis, ESLs are calculated and ESLs are used as the external loads in static response topology optimization. The results of topology optimization are used to update the design variables (density of finite elements) and the updated design variables are used in dynamic analysis in a cyclic manner until the convergence criteria are satisfied. The updating rules and convergence criteria in the ESLs method are newly proposed for linear dynamic response topology optimization. The proposed updating rules are the artificial material method and the element elimination method. The artificial material method updates the material property for dynamic analysis at the next cycle using the results of topology optimization. The element elimination method is proposed to remove the element which has low density when static topology optimization is finished. These proposed methods are applied to some examples. The results are discussed in comparison with conventional linear static response topology optimization.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 전문대학교육위원
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• pp.126-129
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• 2004

This paper presents the way to analyze the static and dynamic characteristics of the Compound motor and 3 phase slip ring motor using VIS (Virtual Instrument System) and Agilent VEE, GUI(Graphics User Interface) tool. This method is composed of real time measuring of various characteristics, which can't measure using analog meter and analyzer, and presenting and analyzing the static and dynamic characteristics by table, which calculates the measured parameter. Also, this can apply to the various parts.

• 대한전자공학회논문지SP
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• 제42권3호
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• pp.23-30
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• 2005

최근 생체 인식 기술의 하나로, 걸음걸이 인식에 대한 관심이 크게 증가하고 있다. 실루엣기반 걸음걸이 인식은 걸음걸이 인식을 위한 가장 보편적인 방법으로, 본 논문에서는 실루엣 기반 걸음걸이 인식에서 걸음걸이의 특성을 결정하는 정보에 대해 분석한다. 걸음걸이는 크게, 정적인 신체 모양(static body shape)과 동적인 신체 운동(dynamic body motion), 두 가지 단서(cue)에 의해 표현될 수 있다. 최근, 걸음걸이의 특성은 신체 모양과 관련된 정적인 단서에 의해 주로 결정되며 신체 운동과 관련된 동적인 단서는 걸음걸이의 특성에 거의 영향을 주지 않는다는 연구들이 보고되고 있다. 이와 달리, 본 논문에서는 신체운동과 관련된 동적인 단서 역시 걸음걸이의 특성을 결정짓는 중요한 요소라고 판단하여 이를 실험적으로 검증하고자 한다. 이를 위해, 크게 두 개의 걸음걸이 데이터베이스(UBC DB, Southampton Small DB)를 이용하여 실험을 수행하였다. UBC DB는 보편적인 걸음걸이를 저장한 것이고, Southampton DB는 다른 종류의 옷이나 신발, 가방을 착용하거나, 걸음걸이의 속도를 바꾸는 등 보편적인 걸음걸이와 다른 특성을 가지는 걸음걸이를 저장한 것이다. 실험 결과, 인식률은 UBC DB에서 신체 모양을 이용할 경우 $100\%$, 신체 운동을 이용할 경우 $95.2\%$이고, Southampton DB에서는 신체 모양을 이용할 경우 $50.0\%$, 신체 운동을 이용할 경우 $55.8\%$이다. 잘못된 인식을 할 위험도(risk)는 UBC DB에서는 신체 모양을 이용할 경우 0.91, 신체 운동을 이용할 경우 0.97, Southampton DB에서는 신체 모양을 이용할 경우 0.98, 신체 운동을 이용할 경우 0.98이다. 결과적으로, 보편적인 걸음걸이의 특성은 신체 모양과 관련된 정적인 단서에 의해 주로 결정되지만, 옷이나 가방 등에 의해 가장된(disguised) 걸음걸이에서는 신체 운동과 관련된 동적인 단서에 의해 주로 결정된다.