• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.11
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• pp.1121-1127
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• 2012

This paper presents a new small-sized damper featuring magneto-rheological(MR) fluid which can be applied to vibration control system. The proposed MR damper consists of cylinder, piston, a couple of bearings, oil-seals and magnetic circuit which has two coils. In this damper, approximately 5cc of MR fluid is used. The damping force of the MR damper is designed to be followed by linear shear-mode Bingham-plastic model. In order to verify the performance of the MR damper, an experimental apparatus is established. In the experimental test, the damping force of the MR damper is measured with respect to time, displacement and velocity. In addition, the time response of MR damper is measured when 1A of step current is applied. Finally, the proposed small MR damper is applied to vibration control. In this process, a simple 1-DOF system is modeled and controlled using PID controller.

• KSBB Journal
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• v.28 no.2
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• pp.146-150
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• 2013

In this study, we investigated the effects of longterm exposure to ionic liquid (IL) on Shewanella oneidensis MR-1 (MR-1). MR1 was acclimated through repeated exposure to IL. The acclimated strain was named as S. oneidensis SH-1 (SH-1) and compared with MR-1 in various aspects including morphology, cell surface hydrophobicity (CSH), motility, and fatty acid. Compared to the MR-1, SH-1 showed elongated cell shape on scanning electron microscopy. Upon exposure to IL, hydrophobicity of SH-1 (28.2%) was higher that of MR-1 (3.3%). In contrast, motility of SH-1 (7 mm) was lower than that also of MR-1 (22 mm), and branched chain fatty acid of SH-1 was lower than that of MR-1, 27.6% and 41.1%, respectively.

• Journal of Aerospace System Engineering
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• v.15 no.1
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• pp.7-18
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• 2021

A semi-active MR damper landing gear is a damper that generates a fluid damping force and a magnetic field control damping force when the MR fluid passes through annular flow paths. In the case of MR fluid passing through annular flow paths, an incompletely developed flow inevitably occurs, causing an error in calculating damper inner forces including the fluid damping force. This error results in an inaccurate design of damper structural parameters and control gain selection, resulting in deterioration of dynamic characteristics and shock absorption performance of the landing gear. In this paper, we derived a mathematical model of an MR damper landing gear considering additional damping force generated in the entrance region of annular flow paths of the MR damper. If the mathematical modeling derived from this paper is applied to the design and optimization process of an MR damper landing gear, excellent performance of the MR damper landing gear is expected.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1338-1343
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• 2000

This paper deals with an application of Magneto-Rheological (MR) fluid to a small size mount for precision equipment of automobiles. MR fluid is known as a class of functional fluids with controllable apparent viscosity of fluid by the applied magnetic field strength. A typical MR fluid is a suspension where pure iron particles of $1{\sim}20mm$ in diameter are dispersed in a liquid such as mineral oil or silicone oil, at the concentration of $20{\sim}40$ vol%. Electro magnetic coil is installed at the bottom of a variable-damping mount filled with MR fluid, and its performance was investigated experimentally. Furthermore, the properties of the MR Mount on experimental Study were explained analytically by mechanical model of the MR mount.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.6
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• pp.426-431
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• 2015

In this work, a new type of MR damper with additional flow path in piston is proposed and damping force characteristics are numerically evaluated. Flow-mode type MR damper is considered and mathematical model is established based on Bingham rheological model of MR fluid to obtain accurate prediction of damping force characteristics. Damping force of the proposed MR damper are calculated with respect to piston velocity and input current. In addition, investigation on damping force characteristics is carried out according to number of additional flow path and excellence of the proposed MR damper is demonstrated.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.1
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• pp.31-39
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• 2011

This paper presents design and control of a quarter-vehicle magneto-rheological (MR) suspension system for ECS (electronic control suspension). In order to achieve this goal, MR shock absorber is designed and manufactured based on the optimized damping force levels and mechanical dimensions required for a commercial mid-sized passenger vehicle. After experimentally evaluating dynamic characteristics of the manufactured MR shock absorber, the quarter-vehicle MR suspension system consisting of sprung mass, spring, tire and the MR shock absorber is constructed in order to investigate the ride comfort and driving stability. After deriving the equations of the motion for the proposed quarter-vehicle MR suspension system, the skyhook controller is then implemented for the realization of quarter-vehicle MR suspension system. In order to present control performance of MR shock absorber for ECS, ride comfort and driving stability characteristics such as vertical acceleration of sprung mass and tire deflection are experimentally evaluated under various road conditions and presented in both time and frequency domain.

• Structural Engineering and Mechanics
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• v.17 no.3_4
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• pp.493-526
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• 2004

Semiactive control systems have received considerable attention for protecting structures against natural hazards such as strong earthquakes and high winds, because they not only offer the reliability of passive control systems but also maintain the versatility and adaptability of fully active control systems. Among the many semiactive control devices, magnetorheological (MR) fluid dampers comprise one particularly promising class. In the field of civil engineering, much research and development on MR fluid damper-based control systems has been conducted since this unique semiactive device was first introduced to civil engineering applications in mid 1990s. In 2001, MR fluid dampers were applied to the full-scale in-service civil engineering structures for the first time. This state-of-the-art paper includes a detailed literature review of dynamic models of MR fluid dampers for describing their complex dynamic behavior and control algorithms considering the characteristics of MR fluid dampers. This extensive review provides references to semiactive control systems using MR fluid dampers. The MR fluid damper-based semiactive control systems are shown to have the potential for mitigating the responses of full-scale civil engineering structures under natural hazards.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.417-423
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• 2002

Magnetorheological(MR) 댐퍼는 적은 용량의 전력을 사용하고 반응속도가 빠른 장점 때문에 구조물의 내진제어에 적당하여, 근래에 주목받고 있는 새로운 장치이다. MR 댐퍼는 반능동 제어 장치로써, 능동 질량감쇠기와는 다른 특성을 갖는다. 즉 필요한 제어력을 제어신호로 직접 생성해 낼 수 없는 대신에 MR 댐퍼의 입력전원을 제어하여 간접적으로 제어한다. 따라서 MR 댐퍼의 반능동 제어장치로써의 특성을 고려하는 효과적인 제어기법이 요구된다. 그러므로 본 연구에서는 지진에 대한 구조물의 응답을 줄이기 위해서, MR댐퍼를 제어할 수 있는 반능동 제어기법을 Lyapunov 안정성 이론을 바탕으로 제안하고자 한다. 제안방법을 검증하기 위해, 전단형 MR 댐퍼를 1층과 2층에 설치한 수치예제를 수행하였다.

• Earthquakes and Structures
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• v.11 no.6
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• pp.1001-1025
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• 2016

Building structures generally have inherent low damping capability and hence are vulnerable to seismic excitations. Control devices therefore play a useful role in providing safety to building structures subject to seismic events. In recent years semi-active dampers have gained considerable attention as structural control devices in the building construction industry. Magneto-rheological (MR) damper, a type of semi-active damper has proven to be effective in seismic mitigation of building structures. MR dampers contain a controllable MR fluid whose rheological properties vary rapidly with the applied magnetic field. Although some research has been carried out on the use of MR dampers in building structures, optimal design of MR damper and combined use of MR and passive dampers for real scale buildings has hardly been investigated. This paper investigates the use of MR dampers and incorporating MR-passive damper combinations in building structures in order to achieve acceptable levels of seismic performance. In order to do so, it first develops the MR damper model by integrating control algorithms commonly used in MR damper modelling. The developed MR damper is then integrated in to the seismically excited structure as a time domain function. Linear and nonlinear structure models are evaluated in real time scenarios. Analyses are conducted to investigate the influence of location and number of devices on the seismic performance of the building structure. The findings of this paper provide information towards the design and construction of earthquake safe buildings with optimally employed MR dampers and MR-passive damper combinations.

• Journal of the Korean Society of Radiology
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• v.18 no.1
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• pp.37-44
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• 2024

Even though MR can reveal excellent soft-tissue contrast and functional information, CT is also required for electron density information for accurate dose calculation in Radiotherapy. For the fusion of MRI and CT images in RT treatment planning workflow, patients are normally scanned on both MRI and CT imaging modalities. Recently deep-learning-based generations of CT images from MR images became possible owing to machine learning technology. This eliminated CT scanning work. This study implemented a CycleGan deep-learning-based CT image generation from MR images. Three CT generators whose learning is based on T1- , T2- , or T1-&T2-weighted MR images were created, respectively. We found that the T1-weighted MR image-based generator can generate better than other CT generators when T1-weighted MR images are input. In contrast, a T2-weighted MR image-based generator can generate better than other CT generators do when T2-weighted MR images are input. The results say that the CT generator from MR images is just outside the practical clinics and the specific weight MR image-based machine-learning generator can generate better CT images than other sequence MR image-based generators do.