• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.3
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• pp.243-250
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• 2002

Semi-active control devices have received significant attention in recent Years because they offer the adaptability of active-control devices without requiring the associated large power sources. Magnetorheological(MR) dampers are semiactive control devices that use MR fluids to produce controllable dampers. This paper applies sliding mode control method using target variation rate of Lyapunov function for the control of structures by use of MR dampers. The three-story building model under earthquake excitation is analyzed by installing a MR damper in the first-story. The performance of semi-active controllers designed by clipped-optimal algorithm and modified sliding mode control algorithm is compared to the performance of passive-type MR dampers. The results indicate that semi-active controllers achieve a greater reduction of responses than passive-type system and especially the controller by modified sliding mode control method shows a good applicability in the view of response control and control force.

• Investigative Magnetic Resonance Imaging
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• v.13 no.2
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• pp.190-194
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• 2009

Generalized lymphangiomatosis is a rare congenital malformation of the lymphatics. CT and MR scan have been used to evaluate lymphangiomas, which appear as large multicystic fluid-filled masses. CT and MR Imaging findings are often helpful in distinguishing lymphangiomas from various vascular disorders. We report the findings of CT, MRI and bone scan in a patient with generalized cystic lymphangiomatosis. Whole body 3.0-T MR scan using STIR sequence with a larger FOV could detect the additional lesions that were not seen at other imaging modalities. We believe that whole body 3.0 T MR imaging is a good modality to evaluate the extent of the disease and following up the patients with the generalized cystic lymphangiomatosis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.4
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• pp.1203-1209
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• 2010

LED lights as a newly-growing industry are highly energy-efficient and have drawn lots of attention due to higher illuminance and longer life compared to other light sources. In this study, MR16 lights with one high-power LED were considered for the replacement of the previous halogen lights or LED lamps with many LEDs. Thus, fundamental experiments of LED on a MCPCB, 3-dimensional numerical analysis for heatsink design and performance tests of the prototype lights have been done and the MR16 LED lights have been successfully developed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.3
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• pp.240-249
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• 2008

This paper presents an electromagnetic design method for magneto-rheological (MR) valves. Since the apparent viscosity of MR fluids is adjusted by applying magnetic fields, the MR valves can control high-level fluid power without any mechanical moving parts. In order to improve the performances of the MR valve, it is important that the magnetic field is effectively supplied to the MR fluid. For the purpose, the magnetic circuit composed with the yoke for forming magnetic flux path, the electromagnetic coil and the MR fluid should be well designed. In order to improve the static characteristic of the MR valve, the length of the magnetic flux path is decreased by removing the unnecessary bulk of the yoke. Also, in order to improve its dynamic and hysteretic characteristics, the magnetic reluctance of the magnetic circuit should be increased by minimizing the cross-sectional area of the yoke through which the magnetic flux passes. After two MR valves, one is a conventional type valve and the other is the proposed one, are designed and fabricated, their performances are evaluated experimentally.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.3
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• pp.249-256
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• 2010

This paper presents performance analysis of a quarter-vehicle magneto-rheological(MR) suspension system with respect to different tire pressure. As a first step, MR damper 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 damper, the quarter-vehicle MR suspension system consisting of sprung mass, spring, tire and the MR damper is constructed in order to investigate the ride comfort. After deriving the equations of the motion for the proposed quarter-vehicle MR suspension system, vertical tire stiffness with respect to different tire pressure is experimentally identified. The skyhook controller is then implemented for the realization of quarter-vehicle MR suspension system. Ride comfort characteristics such as vertical acceleration RMS and weighted RMS of sprung mass are evaluated under various road conditions.

• The Journal of Korean Institute of Information Technology
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• v.17 no.1
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• pp.149-156
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• 2019

Mixed reality technology (MR) has become one of the fourth industrial revolution element technologies. MR technology has been widely applied not only as a digital contents industry but also in the fields of architecture, tourism, medical field, and education. In this paper, we propose a collaborative service platform for architectural applications that inter-operate with heterogeneous devices such as MR device, PC and mobile, and develop prototype system and verify it. As a result, the 3D model using the skp extension, which is mainly used in architecture design office, was created by using developed prototype system and generate the MR contents for the hololens, which is the MR device, and the conversion time and normal operation were confirmed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.3
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• pp.234-240
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• 2011

This study deals with progressive collapse of a structure retrofitted with MR dampers. In order to assess their effect of mitigation which prevents progressive collapse, control force ratio is defined by friction force of MR dampers divided by external force. First, simple model of a structure with MR dampers is suggested. Using the model, exact solution with the control force ratio is obtained. When and where the system is stopped is predicted by the derived solution. Through the dissipated energy by MR dampers during collapse event, equivalent damping ratio is derived. Finally, comparison of exact and equivalent solutions is presented.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.8
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• pp.164-170
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• 2004

The skin movement artifacts are referred to as the relative motion of skin with respect to the motion of underlying bones. This is of great importance in joint biomechanics or internal kinematics of human body. This paper describes a novel experiment that measures the skin movement of a hand based on MR(magnetic resonance) images in conjunction with surface modeling techniques. The proposed approach consists of 3 phases: (1) MR scanning of a hand with surface makers, (2) 3D reconstruction from the MR images, and (3) registration of the 3D models. The MR images of the hand are captured by 3 different postures. And the surface makers which are attached to the skin are employed to trace the skin motion. After reconstruction of 3D models from the scanned MR images, the global registration is applied to the 3D models based on the particular bone shape of different postures. The results of registration are then used to trace the skin movement by measuring the positions of the surface markers.

• The Journal of the Convergence on Culture Technology
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• v.3 no.3
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• pp.21-25
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• 2017

In this paper, we review relevant technologies of Mixed Reality(MR) and show important components of perspective that can overcome technical limitations of the current MR. An MR technology combines real and virtual objects in a real environment, and runs interactive in real time, and is regarded as an emerging technology in a large part of the future of Information Technology(IT). We've grouped the major obstacles limiting the wider use of MR technologies into three themes: technological limitations (i,e., tracking, rendering, authoring, and registration), user interface(UI) limitations(i.e., UI metaphor for MR interaction), and social acceptance issues.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.2
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• pp.202-207
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• 2000

The purpose of study was to compare the caries experience between the mentally retarded(MR) and the normal(N) children and adolescents and to survey the dental visit frequency. preventive dental care, and tooth-brushing behavior of the mentally retarded. Two hundred and fifty MR and two hundred and ten N subjects were selected for the study. 1. The number of teeth which had experienced caries was 3.28 in MR and 4.66 in N. The number of decayed teeth was 2.24 in MR and 1.50 in N. The number of filled teeth was 0.71 in MR and 3.06 in N Filled teeth rate was 19.78% in MR and 58.89% in N The differences between MR and N were all significant(P<0.01). 2. Dental visit frequency of MR was 1.15 per year, and the 51.2% of MR did not visit the dental clinic for the last one year. 38.0% of MR had received the preventive dental care. 3. Toothbrushing frequency per day was 2.16 and the toothbrushing time for 78.3% of MR was less than two minutes. 51.2% of MR brushed their teeth by themselves, 13.3% did with the help of the carers, and 35.5% totally depended on the carers. In conclusion, MR experienced less dental caries than N, had more untreated caries than N, and had need for regular preventive dental care.