• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.6 s.165
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• pp.1055-1064
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• 1999

In this wort ER(electro-rheological) clutch and MR(magneto-rheological) clutch are devised and their performance characteristics such as response time and controllability are compared. As a first step, field-dependent yield stresses of ER and MR fluids are distilled in shear mode. For reasonable comparison between two clutches, a nondimensional design model is established by choosing same design parameters of gap size and number. Following the manufacturing of two clutches, field-dependent torque level, response time to step input, mechanical Power generation to electric power consumption are experimentally measured and compared. In addition, in order to investigate torque controllability of the clutches a sliding mode controller is formulated and experimentally realized. Control bandwidths of two clutches are identified and tracking control responses for desired torque trajectories are presented.

• KCI Concrete Journal
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• v.13 no.1
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• pp.35-41
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• 2001

This paper investigated rheological properties of binder pastes for self-compacting high performance concrete. Six mixtures of self-compacting concrete were initially prepared and tested to estimate self-compacting property. Then, the binder pastes used in self-compacting concrete were tested for rheological properties using a rotary type rheometer. Binder pastes with different water-binder ratios arid flow values were also examined to evaluate their rheological characteristics. The binders were composed of ordinary Portland cement, fly ash, two types of pulverized blast-furnace slag, and limestone powder. The flow curves of binder pastes were obtained by a rotary type rheometer with shear rate control. Slump flow, O-funnel time, box, and L-flow teats were carried out to estimate self-compacting property of concrete. The flow curves of binder pastes for self-compacting concrete had negligible yield stresses and showed an approximately linear behavior at higher shear rates beyond a certain limit. Test results also indicated that the binders incorporating fly ash are more appropriate than the other types of binders in quality control of self-compacting concrete.

• 연구논문집
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• s.30
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• pp.93-99
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• 2000

Electro-Rheological(ER) fluids change their apparent viscosity according to the electric field strength. The electrical and rheological properties of zeolite based the ER fluids were reported. The electric field dependent yield stress are obtained from experimental investigation on the Bingham property of the ER fluid. Using ER fluids, it is possible to directly interface between electric drop and flow rate of the ER fluid was hydraulic control valve measured under application of an electric field. The purpose of the present study is pressure drop measurement of an ER valve by using strain gage. The performance characteristics of the valve system are evalusted in terms of pressrue fixed with respect to the intensity of employed electric fields and flow rates. As a result, it is esperimentally confirmed that pressure control valve using ER fluids applicable to use in hydraulic power systems.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.6
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• pp.1096-1101
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• 1997

Soy curd was prepared using imported soybean(U.S.grade A) and changes in quality were evaluated using different types and mixtures of coagulants(CaCl$_2$, CaSO$_4$, MgCl$_2$, MgSO$_4$, and glucono-$\delta$-lactone). Quality of soy curd was determined by rheological properties, yield, and color. Based upon the characteristics of each coagulant, mixtures of two coagulants were prepared in various ratios. The mixture of CaSO$_4$or MgCl$_2$with glucono-$\delta$-lactone(GDL), and that of CaSO$_4$or MgCl$_2$with MgSO$_4$resulted in soy curd of good quality in terms of rheological properties and yield.

• Advances in concrete construction
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• v.6 no.5
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• pp.465-483
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• 2018

The most crucial factor determining the pumping performance of concrete is the characteristics of the lubricating layer formed between the pipe wall and the inner concrete. Thus, it is important to accurately identify the rheological properties of the lubricating layer to predict the pumping of concrete. In this study, a new method is proposed for measuring the rheological properties of the lubricating layer with improved convenience. To verify the new method, a pumping test was conducted with 337 m-long horizontal piping. The rheological properties of the lubricating layer were assessed by a previously verified method and the new method proposed in this study for a total of four concrete mixtures with design strength ranging from 27 MPa to 60 MPa. The correlation between the existing method and the new method in relation to the viscosity of the lubricating layer was determined, and it was possible to predict the pumping performance with an accuracy of about 88.5% using the viscosity of the lubricating layer obtained from this correlation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.7 s.94
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• pp.1649-1657
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• 1993

This paper reports on a proof-of-concept experimental investigation focused on evaluating the vibration characteristics and control of smart hollow cantilever beams filled with an electro-rheological(ER) fluid. The beams are considered to be of uniform viscoelastic materials and modelled as a viscously-damped harmonic oscillator. Electric field-dependent natural frequencies, loss factors and complex moduli are evaluated and compared among three different beams : two types of different volume fraction of ER fluid and one type of different particle concentration of ER fluid by weight. Modal characteristics of the beams are observed in both the absence and the presence of electric potentials. It is also shown that by constructing active control algorithm the removal of structural resonances and the suppression of tip deflection are obtained. This result provides the feasiblility of ER fluids as an active vibration control element.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.3
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• pp.86-92
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• 2004

This paper describes the properties of temperature-viscosity characteristics of hydrous and anhydrous electro-rheological fluids containing starch and titanium particle in silicone oil ER effects arise from electrostatic forces between the starch particles and titanium particles dispersed to the electrically insulating silicone oil induced when electric field is applied ER fluids under electric field control have been found to provide resonable estimates of ER fluid viscosity variation characteristics. Yield shear stress of the ER fluids were measured the couette cell type rheometer as a function of electrlc fields. The outer cup is connected to positive electrode(+) and bob becomes ground(-). The electrie field is applied by high voltage DC power supply. In this experiment shear rates were increased from 0 to 200 $s^{-1}$ in 2 minutes. The ER fluid's viscosity change is very small and stable at the temperature range of $40^{\circ}C$ to $60^{\circ}C$. Therefore, applications of a new ER fluid to control systems application are suitable.

• Tribology and Lubricants
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• v.26 no.3
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• pp.184-189
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• 2010

In this paper, tactile response characteristics in medical haptic interface are investigated to characterize the feeling of contact between the finger skin and the organic tissue when a finger is dragged over tissue. In order to represent the tactile feeling, a prototype tactile display incorporating Magneto-Rheological (MR) fluid has been developed. Tactile display devices simulate the finger's skin to feel the sensations of contact such as compliance, curvature and friction. Thus, the tactile display provides the surface information of organic tissue to the surgeon using different actuating mechanisms ranging from the conventional mechanical motor to the smart material actuators. In order to investigate the compliance feeling of human finger's touch, vertical force responses of the tactile display under the various magnetic fields have been assessed. Also, frictional resistive force responses of the tactile display are investigated to simulate the action of finger's dragging. From the results, different tactile feelings are observed as the applied magnetic field is varied and arrayed magnetic poles combinations. This research gives a smart technology of tactile displaying.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05a
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• pp.99-101
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• 2011

In order to have pumping technology for high speed construction of tall building, study for quantitative evaluation of flow characteristics and pumpability should be conducted. So, this study evaluate the characteristics among the inner pipe pressure, fresh concrete properties and separated mortar through the continuous pumping test. Then it consider of relations between rheological properties and pumpability. In the result of test, it found that there are high interrelationship between the rheological characteristics which represented plastic viscosity and pressure lose by pipe length.

• Korean journal of food and cookery science
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• v.24 no.6
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• pp.856-860
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• 2008

We prepared Tofu-sulgi by adding tofu and then analyzed the final product in terms of its nutritional quality, rheological characteristics and sensory tests. While the calorie quantity of Sulgi with Tofu was relatively low compared to that of Baeksulgi, it contained the dietary fiber, calcium and iron that were not present in Baeksulgi. Since Baeksulgi holds a large amount of carbohydrates, it shows a higher weight due to its dense fiber. On the other hand, Sulgi with Tofu showed a relatively low level of tofu protein despite the increased amount of tofu protein. This demonstrated the soft characteristics of Sulgi with Tofu. Also, the results of the sensory test showed that Sulgi with Tofu exhibited a higher preference than Baeksulgi in terms of its taste, flavor and fiber content. The preparation method of Sulgi with Tofu in this study used the natural grinding of tofu without removing the moisture. Also the use of both non-glutinous and glutinous rice flour that can be obtained easily in the public market, are convenient due to their characteristics of easy storage and no property change. Therefore, the preparation method of Sulgi with Tofu is quite convenient as compared to that of traditional Dduk (Korean rice cake) including Baeksulgi. From the perspectives of nutritional content, rheological characteristics and taste preference, Sulgi with Tofu fared better than Baeksulgi. Considering the overall quality characteristics of Sulgi with Tofu, we believe that the addition of tofu could contribute positively toward the quality characteristics of Sulgi.