• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.27-33
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• 2004

In this paper, various dynamic model of magnetorheological (MR) damper, is required for describing the hysteresis of MR damper and for their application are investigated to structural control. The dynamic characteristics and control effects of the modeling methods for MR dampers such as Bingham, biviscous, hysteretic biviscous, simple Bouc-Wen, Bouc-Wen with mass element and phenomenological models are studied. Of these models, hysteretic biviscous model which is simple and describes the hysteretic characteristics, is chosen for numerical studies. The capacity of MR damper is determined as a portion of not the building weight but the lateral restoring force.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.323-330
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• 2004

The purpose of this paper is to experimentally identify the finite element (FE) model of a building structure with magnetorheological (MR) fluid damper. Using FE model based system identification (FEBSI) technique, The model of MR damper having nonlinear characteristics is expressed with equivalent linear properties such as mass, stiffness, and damping. Bingham model is used for MR damper modeling. The equivalent stiffness and damping matrices of MR damper are predicted by applying an equivalent linearization technique, and those values are compared with the experimentally obtained ones.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.149-156
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• 2002

This paper examines the ASCE first generation benchmark problem for a seismically excited cable-stayed bridge, and proposes a new semi-active control strategy focusing on inclusion of effects of control- structure interaction. In this study, magnetorheological (MR) fluid dampers, which belong to the class of controllable fluid dampers, are proposed as the supplemental damping devices, and a clipped-optimal control algorithm, shown to perform well in previous studies involving MR fluid dampers, is employed. The dynamic model for MR fluid dampers is considered as a modified Bouc-Wen model, which is obtained from data based on experimental results for large-scale dampers. Numerical results show that the performance of the proposed semi-active control strategy using MR fluid dampers is quite effective.

• Structural Engineering and Mechanics
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• v.41 no.3
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• pp.349-363
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• 2012

Fuzzy logic based control has recently been proposed for regulating the properties of magnetorheological (MR) dampers in an effort to reduce vibrations of structures subjected to seismic excitations. So far, most studies showing the effectiveness of these algorithms have focused on the use of a single MR damper. Because multiple dampers would be needed in practical applications, this study aims to evaluate the effects of multiple individually tuned fuzzy-controlled MR dampers in reducing responses of a multi-degree-of-freedom structure subjected to seismic motions. Two different fuzzy-control algorithms are considered, a traditional controller where all parameters are kept constant, and a gain-scheduling control strategy. Different damper placement configurations are also considered, as are different numbers of MR dampers. To determine the robustness of the fuzzy controllers developed to changes in ground excitation, the structure selected is subjected to different earthquake records. Responses analyzed include peak and root mean square displacements, accelerations, and interstory drifts. Results obtained with the fuzzy-based control schemes are compared to passive control strategies.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3141-3147
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• 2010

The most important cause for shortening LED lighting efficiency and life is the junction temperature rises and, to solve this problem, various studies such as thermally efficient packaging, highly conductive material development, contact resistance improvement or heat sink optimization have been studied. However, most studies so far assumed that the LED lights are in the atmosphere, and thermal performance has not been therefore reported when the LED lights are mounted on the ceiling with ceiling unit. Thus, this study investigates the variation of junction temperature of the MR16 LED light under actual installation conditions and more accurate thermal design for the efficiency and life of LED lights is therefore achieved.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.5 s.39
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• pp.55-64
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• 2004

In this paper, the preliminary design procedure of magnetorheological (MR) dampers is developed for controlling the building response induced by seismic excitation. The dynamic characteristics and control effects of the modeling methods of MR dampers such as Bingham, biviscous, hysteretic biviscous, simple Bouc?Wen, Bouc?Wen with mass element, and phenomenological models are investigated. Of these models, hysteretic biviscous model which is simple and capable describing the hysteretic characteristics, is used for numerical studies. The capacity of MR damper is determined as a portion of not the building weight but the lateral restoring force. A method is proposed for optimal placement and number of MR dampers, and its effectiveness is verified by comparing it with the simplified sequential search algorithm. Numerical results indicate that the capacity, number and the placement can be reasonably determined using the proposed design procedure.

• 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.

• Computational Structural Engineering : An International Journal
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• v.3 no.1
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• pp.61-68
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• 2003

A recently developed semi-active control system employing magneto-rheological (MR) fluid dampers is applied to vibration control of a wind excited tall building. The semi-active control system with MR fluid dampers appears to have the reliability of passive control devices and the adaptability of fully active control systems. The system requires only small power source, which is critical during severe events, when the main power source may fail. Numerical simulation studies are performed to demonstrate the efficiency of the MR dampers on the third ASCE benchmark problem. Multiple MR dampers are assumed to be installed in the 76-story building. Genetic algorithm is applied to determine the optimal locations and capacities of the MR dampers. Clipped optimal controller is designed to control the MR dampers based on the acceleration feedback. To verify the robustness with respect to the variation of the external wind force, several cases with different wind forces are considered in the numerical simulation. Simulation results show that the semi-actively controlled MR dampers can effectively reduce both the peak and RMS responses the tall building under various wind force conditions. The control performance of the MR dampers for wind is found to be fairly similar to the performance of an active tuned mass damper.

• Investigative Magnetic Resonance Imaging
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• v.25 no.3
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• pp.156-163
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• 2021

Recently, neuromelanin and nigrosome imaging techniques have been developed to evaluate the substantia nigra in Parkinson's disease. Previous studies have shown potential benefits of quantitative analysis of neuromelanin and nigrosome images in the substantia nigra, although visual assessments have been performed to evaluate structures in most studies. In this study, we investigate the potential of using deep learning based automatic region segmentation techniques for quantitative analysis of the substantia nigra. The deep convolutional neural network was trained to automatically segment substantia nigra regions on 3D nigrosome and neuromelanin sensitive MR images obtained from 30 subjects. With a 5-fold cross-validation, the mean calculated dice similarity coefficient between manual and deep learning was 0.70 ± 0.11. Although calculated dice similarity coefficients were relatively low due to empirically drawn margins, selected slices were overlapped for more than two slices of all subjects. Our results demonstrate that deep convolutional neural network-based method could provide reliable localization of substantia nigra regions on neuromelanin and nigrosome sensitive MR images.

• Korean Journal of Radiology
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• v.1 no.1
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• pp.43-50
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• 2000

Objective: To evaluate the usefulness of MR imaging for diseases of the small intestine, emphasizing a comparison with CT. Materials and Methods: Thirty-four patients who underwent both CT and MR imaging using FLASH 2D and HASTE sequences were analyzed. All patients had various small bowel diseases with variable association of peritoneal lesions. We compared the detectabilities of CT and MR imaging using different MR pulse sequences. The capability for analyzing the characteristics of small intestinal disease was also compared. Results: MR imaging was nearly equal to CT for detecting intraluminal or peritoneal masses, lesions in the bowel and mesentery, and small bowel obstruction, but was definitely inferior for detecting omental lesions. The most successful MR imaging sequence was HASTE for demonstrating bowel wall thickening, coronal FLASH 2D for mesenteric lesions, and axial FLASH 2D for omental lesions. MR imaging yielded greater information than CT in six of 12 inflammatory bowel diseases, while it was equal to CT in six of seven neoplasms and inferior in five of seven mesenteric ischemia. In determining the primary causes of 15 intestinal obstructions, MR imaging was correct in 11 (73%) and CT in nine (60%) patients. Conclusion: MR imaging can serve as an alternative diagnostic tool for patients with suspected inflammatory bowel disease, small intestinal neoplasm or obstruction.