• Geotechnical Engineering
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• v.11 no.3
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• pp.123-138
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• 1995

To study the grout flow in jointed rock, various nurser characteristics of grout in a single joint plane and two-dperorbed. The joint plane is described as a channel nets properties of grout are considered. To deal with various prob generator and i oint network generator are used. A loss of head due to friction in laminal flow is adopted to between the grout and joint wall. The grout flow is stopped, setting time. To consider this phenomenon, the idea of maxim From the results of numerical simulation on the single jai etration of grout is confirmed. The basic principles for the ation and the selection of the grout are presented. Correlation ant and grouting pressure is defined by analyzing the effects grout flow. Finally, the grout flow around a tunnel is simulate ins grouting operation for jointed rock mass.

• The Korean Journal of Rheology
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• v.11 no.2
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• pp.105-111
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• 1999

Dampers have been used to dissipate energy in mechanical systems. There are several types of dampers such as passive, active, and semi-active damper. Semi-active dampers have higher performance than passive ones and require less power to operate than active ones. Their damping characteristics can be changed properly for varying conditions. In this paper, we investigated the semi-active damper using Magneto-Rheological fluid. Magneto-Rheological fluid, which is one of controllable fluids, changes its damping and rheological characteristics from Newtonian fluid to Bingham fluid as the magnetic field is applied. It has several advantages such as high yield strength, low viscosity, robustness to impurities and wide temperature range of stability. If we designe a semi-active damper by using this material, we can not only design a simply structured damper but also expect rapid response. In this study, we propose several types of semi-active dampers which are designed and manufactured using Magneto-Rheological fluid and some problems encountered during their applications.

• 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.

• Journal of the Korea Convergence Society
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• v.8 no.12
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• pp.291-298
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• 2017

In recent years, the increase of secondary controls within vehicles requires a mechanism to integrate various controls into a single device. This paper presents control performance of an integrated magnetorheological (MR) haptic device which can adjust various in-vehicle comfort instruments. As a first step, the MR fluid-based haptic device capable of both rotary and push motions within a single device is devised as an integrated multi-functional instrument control device. Under consideration of the torque and force model of the proposed device, a magnetic circuit is designed. The proposed MR haptic device is then manufactured and its field-dependent torque and force are experimentally evaluated. Furthermore, an inverse model compensator is synthesized under basis of the Bingham model of the MR fluid and torque/force model of the device. Subsequently, haptic force-feedback maps considering in-vehicle comfort functions are constructed and interacts with the compensator to achieve a desired force-feedback. Control performances such as reflection force are experimentally evaluated for two specific comfort functions.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.2
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• pp.67-72
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• 2004

Electro-Rheological(ER) fluids consist of suspensions of fine polarizable particles In a dielectric oil, which upon application of an external electric field control take on the characteristics of the Bingham solid. In this study, the temperature dependence of the viscosity was Investigated for an ER fluid consisting of 35 weight % of zeolite particles in hydraulic oil 46cSt. Thermal activation analysis was performed by changing the ER fluid's temperature from $-10^{\circ}C$ to $50^{\circ}C$. According to the analysis, the activation energy for flow of the ER fluid was 79.6 kJ/mole without applying electric field. On the other hand, with the electric field of 2kV/mm, the linearity between viscosity and temperature was not existed By changing the temperatures the viscosity (or shear stress) versus shear rates were measured. In this experiment shear rates were increased from 0 to $200s^{-1}$ in 2 minutes. Generally, the hydraulic oil 46cSt will be operated at the temperature of about $40^{\circ}C$, thus, the ER fluid's electric field dependence of viscosity was examined at this temperature. Also, an influence of adding the dispersant(Carbopl 940) on ER effect was discussed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.4
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• pp.346-351
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• 2008

In this paper, the semi-active control of a helicopter landing gear using magneto -rheological(MR) damper is studied. A dynamic model of the MR damper is formulated by incorporating magnetic field-dependent Bingham properties of the MR fluid. The electromagnet of the MR damper is designed and its magnetic field is analyzed using a commercial finite element code. The damping characteristics of MR damper by changing the intensity of the magnetic field are investigated and the dynamic responses of the helicopter landing gear with MR damper are simulated. The semi-active control of the helicopter landing gear is simulated by implementing a sky-kook control algorithm and its performance is evaluated comparing to the passive control.

• Journal of The Korean Society of Grassland and Forage Science
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• v.19 no.4
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• pp.303-308
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• 1999

The conditions for callus formation and plant regeneration were confirmed in birdsfoot trefoil (Lotus corniculatus L.). Among SH (Schenk and Hildebrandt), MS (Murashige and Skoog) and N6 medium (Chu), SH medium was highest degree of efficiencies respectively in callus formation and plant regeneration. In this study, we determined volume of hormones and other compounds appended in media. For callus formation, only $3mg/{\ell}$ of 2,4-D (2,4-dichlorophenoxy acetic acid) was appended in their media. For plant regeneration, we used BOi2Y medium (Bingham et al.). We obtained birdsfoot trefoil plants from callus by regeneration, about sixty days later transfer calli to regeneration media.

• The KSFM Journal of Fluid Machinery
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• v.17 no.6
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• pp.29-37
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• 2014

Non-Newtonian fluid mechanics takes charge of an important role in the oil industries. Especially in the oil well drilling process, the drilling fluid such as mud keeps the drill bit cool and clean during drilling, with suspending drill cuttings and lubricating a drill bit. The purpose of this study is to examine the effect of fluid mud rheological properties to predict different characteristics of non-Newtonian fluid in the mud mixing tank on offshore drilling platforms. In this paper, ANSYS fluent package was used for the simulation to solve the hydrodynamic force and to evaluate mud mixing time. Prediction of the power consumption and the pumping effectiveness has been presented with different operating fluid models as Newtonian and non-Newtonian fluid. The comparison between Newtonain mud model and non-Newtonian mud model is confirmed by the CFD simulation method of drilling mud mixing tank. The results present useful information for the design of the drilling mud mixing tanks and provide some guidance on the use of CFD tool for such non-Newtonian fluid flow.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.5
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• pp.459-467
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• 2012

In this work, the configuration of a haptic gripper featuring magnetorheological(MR) brakes is proposed and an optimal design of the MR brakes for the haptic griper is performed considering the required braking torque, the uncontrollable torque(zero-field friction torque) and mass of the brakes. Several configurations of MR brake is proposed such as disc-type, serpentine-type and hybrid-type. After the configurations of the MR brakes are proposed, braking torque of the brakes is analyzed based on Bingham rheological model of the MR fluid. The zero-field friction torque of the MR brakes is also analyzed. An optimization procedure based on finite element analysis integrated with an optimization toolbox is developed for the MR brakes. The purpose of the optimal design is to find optimal geometric dimensions of the MR brake structure that can produce the required braking torque and minimize the mass of the MR brakes. In addition, the uncontrollable torque of the MR brakes is constrained to be much smaller than the required braking torque. Based on the developed optimization procedure, optimal solution of the proposed MR brakes are achieved and the best MR brake is determined. The working performance of the optimized MR brake is then investigated.

• Korean Journal of Food Science and Technology
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• v.18 no.4
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• pp.278-282
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• 1986

Rheological properties of naked barley (Songhak and Youngsan) starches were compared. The gelatinized starches at $3{\sim}9%$ concentration showed a Bingham pseudoplastic behavior. Songhak starch had higher values of consistency index and yield stress than those of Youngsan starch. The dependence of consistency index on concentration was mere pronounced in Songhak starch. Consistency index of both starches was exponentially dependent on concentration, but the slopes at $3{\sim}5%\;and\;5{\sim}9%$ starch concentration were different. The activation energies of 7% for Songhak and Youngsan starches were 4.10 and 3.71 Kcal/mole, respectively.