• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.3
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• pp.308-315
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• 2010

This study introduces a new technique to estimate modal parameters of a vibrating string using motion pictures. The approach requires two motion pictures for a vibrating string captured simultaneously by typical potable digital cameras or camcorders. Applying the space intersection theory and the space resection theory in photogrammetry, the steroscopic images for the string are constructed from two flat plane pictures. Then the three dimensional displacement components of the string are extracted by a multiple template matching technique. Finally the modal parameters of the string are estimated from the resulting displacement time histories. The accuracy of the approach has been examined through a small-scale mock-up of a string.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.7
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• pp.98-105
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• 2020

This study deals with the passive control of the dynamic characteristics of a theoretical model which is a string with fixed ends and loaded by two point masses - a main mass (M_o) and a secondary mass (M_s). It has been controlled passively by means of a relocation of a secondary mass. A main mass placed on the string is considered as a vibrating receiver which be forced to vibrate by a vibrating source being positioned on the string. By analyzing the motion of a string, the equation of motion for a string was derived by using a method of variation of parameters. To define the optimal conditions for the vibration reduction, the governing equation, which denotes the dynamic response of a string was derived in the closed form and then evaluated numerically. The possibility of reduction of an amplitude and a power being transmitted to a main mass were found to depend on the location and the magnitude of a secondary mass as well as the range of a forcing frequency.

• The Journal of the Acoustical Society of Korea
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• v.38 no.6
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• pp.710-715
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• 2019

A transmission line based bowed string model is built by analogizing a vibrating string to an electrical transmission line and implementing the calculation for the frictional bow-string force given by a digital bow into a circuit. The performance of the proposed model is demonstrated by showing that the velocity of the string at the bowing point from the proposed model is consistent with that from the finite difference form of the wave equation for a bowed string by the digital bow.

• The Journal of the Acoustical Society of Korea
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• v.32 no.4
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• pp.361-368
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• 2013

As one way to describe the behavior of a vibrating string, analogies to a transmission line have been made based on the fact that they have oppositely travelling waves on each of them. In such analogies, a rigid end to the string has been represented as an open circuit, and the displacement of the string as the current on the transmission line. However it turns out that the rigid end corresponds to a short circuit, the displacement to the voltage by the theory of the transmission line, and it is confirmed by experiments with circuit simulations. Based on these discoveries, a transmission line based plucked string model comprising a transmission line, two piecewise linear current sources, and switches is proposed. The proposed model is validated by showing that the voltage at the arbitrarily chosen location, and the voltage calculated over an infinitesimal portion at the end of the transmission line are consistent with the displacement at the corresponding location and the force on the rigid end of the string from the well known difference form of a wave equation governing the behavior of the string with its fundamental frequency tuned to that for the proposed model, respectively. Moreover, the applicability of the proposed model to modeling string and wind instruments is presented.

• Smart Structures and Systems
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• v.6 no.2
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• pp.167-182
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• 2010

An adaptronic strut for machine tools with parallel kinematics for compensation of the influence of geometric errors is introduced. Implemented within the strut is a piezoelectric sensor-actuator unit separated in function. In the first part of this contribution, the functional principle of the strut is presented. For use of one piezoelectric transducer as both, sensor and actuator as so-called self-sensing actuator, the acquisition of the sensing signal while actuating simultaneously using electrical bridge circuits as well as filter properties are examined. In the second part the control concept developed for the adaptronic strut is presented. A co-simulation model of the strut for simulating the controlled multi-body behavior of the strut is set-up. The control design for the strut as a stand-alone system is tested under various external loads. Finally, the strut is implemented into a model of the complete machine tool and the influence of the controlled strut onto the behavior of the machine tool is examined.

• The Journal of the Acoustical Society of Korea
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• v.26 no.7
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• pp.328-333
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• 2007

In this paper, we describe characteristics of a movable bridge called the Anjok and propose an improved string model which has delay line controller in physical modeling of the Gayageum. Movable bridge, the Anjok determines the length of vibrating string and transmits the vibration of each string to the body of the Gayageum. We analyze the variations in frequency domain and implement the Anjok model as parametric form using the first-order polynomial fitting in logarithmic scale graph, because the length of string changes fundamental frequency. In order to implement the Anjok model, frequency fitting, tension fitting and frequency fitting using leaky integrator are used. The frequency fitting using leaky integrator has the best results among those. Proposed string model with the Anjok model can represent real tuning system of the real Gayageum and the proposed model could synthesize sounds which is similar to original sounds.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.525-530
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• 2000

The vibration shape of the structure with arbitrary boundary condition under excitation is determined by the governing equation and the boundary condition and driving force. In this paper, driving point impedance that is defined by the ratio of the driving force at one point to the velocity of that point is selected as a measure to identify the boundary condition. First, this paper deals with a string with arbitrary boundary condition. It is selected because of its simplicity, but generality of which exhibits the desired physical phenomena. Particularly the relation among the driving point impedance, the boundary condition and the vibration shape is dealt as a primary step to identify the boundary condition by using the driving point impedance.

• Journal of the Korean Society of Costume
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• v.15
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• pp.121-130
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• 1990

This study is focused on the swinging and trembling effect expressed in Korean costume from ancient days to the present. The swinging is a term standing for gentle movements that are created and implied by the long ties, strings, tassels, pendants and hanging ornamentations. These attatched elements of the costume move as the wearer moves. Trembling is a term expressing small vibrating movement which is created by the tiny decorative motifs attatched to Korean costume. This little decorative elements were attatched to the royal crown, earings, necklaces even the sole of the metalic shoes for a change and to draw viewers attention. The Swinging and Trembling have been used mainly to express the decorative desires. The Swinging on shaman costume is a expression of the aesthetics of evil's eye, while the Swinging shown on the costume of a schalor is expressing the beauty of personality and nature. In General during the Choson Period, the Swinging of the tassels, ribbons, string belts is a expression of the beauty of nature. Consequently the Swinging and the Trembling are the typical examples of the "Meot"(멋), Korean traditional aesthetics.

• Korean Journal of Crystallography
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• v.8 no.1
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• pp.38-47
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• 1997

A new weighing sensor for the automatic diameter control system of the crystal growth is developed in this study. This weighing sensor measures the frequency of the vibrating element which is lineally changing with respect to weight. The signal and the power of this system are transmitted without any physical contact, so that this sensor offers high accuracy and resolution. This system consists of a string, a sinusoidal wave generator, an automatic amplification adjusting circuit, signal transformers and a PCB. 4 kinds of programs are developed for checking DAC, weight calibration and controlling growth process. The measurements of the standard deviation and the resolution show $\pm0.10g$(measured at every second) and $5{\times}10^{-5}$, respectively, This weighing sensor is effective under high pres-sure of 200 atm, high temperature and vacuum condition. The weighing system can control the temperature in the accuracy of $\pm0.025^{\circ}C$ with the 'signal divider'. The optical quality single crystals of $(YGd)_3Sc_2Ga_3O_{12},\;Er-Y_3Sc_2Al_3O_{12},\;and\;Bi_{12}GeO_{20}$ have been grown by Czo-chralski method using this auto-diameter control system.