• International Journal of Control, Automation, and Systems
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• v.5 no.3
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• pp.283-294
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• 2007

In this paper, a nonlinear controller based on adaptive sliding-mode method which has a sliding surface vector including new boundizing function is proposed and applied to a two-wheeled welding mobile robot (WMR). This controller makes the welding point of WMR achieve tracking a reference point which is moving on a smooth curved welding path with a desired constant velocity. The mobile robot is considered in view of a kinematic model and a dynamic model in Cartesian coordinates. The proposed controller can overcome uncertainties and external disturbances by adaptive sliding-mode technique. To design the controller, the tracking error vector is defined, and then the sliding surface vector including new boundizing function and the adaptation laws are chosen to guarantee that the error vector converges to zero asymptotically. The stability of the dynamic system is shown through the Lyapunov method. In addition, a simple way of measuring the errors by potentiometers is introduced. The simulations and experimental results are shown to prove the effectiveness of the proposed controller.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.557-560
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• 2005

This paper considers a global asymptotic output tracking problem with a prescribed constant reference signal for a class of single-input and single output-output nonlinear systems. It is shown that under some mild conditions on such a system there is a smooth output feedback achieving global asymptotic output tracking and such a smooth output controller is explicitly constructed by a new design method proposed. The usefulness of our result is illustrated by a numerical example.

• Animal cells and systems
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• v.5 no.3
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• pp.205-209
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• 2001

Mesenchymal cells from the leg buds of stage 24-chick embryos differentiated into chondrocytes when plated at high density. Treatment of high density micromass culture of chick mesenchymal cells with cytochalasin D(CD, 2 $\mu$M for 24 h) resulted in inhibition of chondrogenesis. CD treatment was found to affect the expression of the contractile protein $\alpha$-smooth muscle actin ($\alpha$-SM actin). In control cultures, $\alpha$-SM actin uniformly expressed from culture day 2, but the CD-treated cells induced expression of $\alpha$-SM actin from the first day of culture followed by a continuous increase. Expression of pan-cadherin (P-cadherin) decreased as chondrogenesis proceeded in the control culture, whereas the CD-treated cells showed sustained expression. These results propose a close connection of chondrogenic differentiation with expression of $\alpha$-SM actin and P-cadherin.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.3
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• pp.351-356
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• 1999

The present study was aimed at investigating whether the calcium current in the vascular smooth muscle (VSM) cells is altered in renal hypertension. Two-kidney, one clip (2K1C) and deoxycorticosterone acetate (DOCA)-salt hypertension were made in Sprague-Dawley rats. Rats without clipping the renal artery or implanting DOCA were used as control for 2K1C and DOCA-salt hypertension, respectively. Four weeks after clipping, systolic blood pressure was significantly higher in 2K1C rats than in control $(192{\pm}24\;and\;119{\pm}4$ mmHg, respectively, n=16 each). DOCA-salt rats also showed a higher blood pressure $(180{\pm}15$ mmHg, n=18) compared with control $(121{\pm}6$ mmHg, n=14). VSM cells were enzymatically and mechanically isolated from basilar arteries. Single relaxed VSM cells measured $5{\sim}10\;{\mu}m$ in width and $70{\sim}150\;{\mu}m$ in length were obtained. VSM cells could not be differentiated in size and shape between hypertensive and normotensive rats under light microscopy. High-threshold (L-type) calcium currents were recorded using whole-cell patch clamp technique. The amplitude of the current recorded from VSM cells was larger in 2K1C hypertension than in control. Neither the voltage-dependence of the calcium current nor the cell capacitance was significantly affected by 2K1C hypertension. By contrast, the amplitude of the calcium current was not altered in DOCA-salt hypertension. These results suggest that high-threshold calcium current of the VSM cells is altered in 2K1C hypertension, and that calcium channel may not be involved in calcium recruitment of VSM in DOCA-salt hypertension.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.179-179
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• 2009

For the deposition of the semiconductor nanocrystals or quantum dots, it is required to have the substrates with smooth surface roughness. Slot-die coating method wad adopted and optimized varying the processing parameters like coating speed, gap distance, solution concentration, etc to get the smooth coated films on flexible substrates. The coating speed in slot-die method was varied from 1 m/min to 2.5 m/min focusing especially on its industrial usage. The gap distance between the substrate surface and slot-die lip was changed also to control mainly the thickness of coated films.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.651-655
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• 2000

The objective of present work is to investigate experimentally the characteristics of heat transfer. A fluidized bed combustion has advantages of pollution control, fuel flexibility and excellent heat transfer. The present study investigates fundamental phenomena of bed-to-surface heat transfer in high temperature fluidized beds to improve design of immersed tube surface. The tested operating variables are bed temperature, supeficial velocity, mean size of bed material, and the rake angle of fin. Generally, heat transfer rates between the fluidized bed and immersed finned-tube are much higher than those of a smooth tube. A life time of finned-tube is generally longer than that of smooth tube.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.2
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• pp.260-268
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• 2001

Wake structures behind two circular cylinders with different groove configurations(U and V-shape) have been investigated experimentally. The results were compared with those for the smooth cylinder having the same diameter D. The drag force, mean velocity and turbulent intensity profiles of wake behind the cylinders were measured with varying the Reynolds number in the range of Re(sub)D=8,000∼14,000. As a result, the U-shaped groove was found to reduce the drag up to 18.6%, but the V-shaped groove reduced drag force only 2.5% compared with the smooth cylinder. As the Reynolds number increases, the vortex shedding frequency becomes a little larger than that of the smooth cylinder. The visualized flow using the smoke-wire and particle tracing methods shows the flow structure qualitatively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.918-921
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• 2002

Some investigators who have tried to achieve the highly smooth surface finish using electrochemical processes have reported that high current density produced lustrous surfaces while the opposite conditions produced a passive layer and had a tendency to produce a black surface. However, processing at a low current density may produce a non-lustrous surface but the improvement of dimensional accuracy of the surface is significant. The surface with pulse process was a bit more lustrous than with continuous current but the black passive layer still could be found at grooved surface. There are two ways to achieve highly smooth surface finish. One is brushing it with a brush the other is electrochemical machining (ECM) with high current. The former method is the most common polishing practice, but not only may the surface obtained differ from operator to operator, but precision smooth surface on micro grooves are difficult to obtain. The latter one recently has been used to produce a highly smooth surface after EDM process. However, the material removal rate in ECM with high current is relatively high. Hence the original shape of the micro grooves, which was formed by electrochemical micro-machining (EMM) process, may be destroyed. In this study, an electrochemical polishing process using pulse current is adopted as a possible alternative process when micro grooves formed by EMM process should be polished. Mirror-like micro grooves with lustrous and smooth surface can be produced electrochemically with pulse current because the voltage and current used can be lower than the case of continuous current. This study will discuss the accurate control of physical and electrical conditions so as to achieve mirror-like micro grooves with lustrous and smooth surface without destroying the original shape of micro grooves.

• Journal of Nutrition and Health
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• v.49 no.1
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• pp.59-62
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• 2016

Purpose: Zinc, a biomineral present within and outside cells, manages various cellular mechanisms. In this study, we examined whether zinc was involved in vascular smooth muscle cell (VSMC) calcification via regulation of calcification inhibitor protein, osteopontin (OPN). Methods: Rat aorta cell line (A7r5 cells) and primary vascular smooth muscle cells (pVSMCs) from rat aorta were cultured with phosphate (1-5 mM) and zinc ($0-15{\mu}M$) as appropriate, along with osteoblasts (MC3T3-E1) as control. The cells were then stained for Ca and P deposition for calcification examination as well as osteopontin expression as calcification inhibitor protein was measured. Results: Both Ca and phosphate deposition increased as the addition of phosphate increased. In the same manner, the expression of osteopontin was upregulated as the addition of phosphate increased in both cell types. When zinc was added, Ca and P deposition decreased in VSMCs, while it increased in osteoblasts. Conclusion: The results imply that zinc may prevent VSMC calcification by stimulating calcification inhibitor protein OPN synthesis in VSMCs.

• Korean Journal of Veterinary Service
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• v.18 no.3
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• pp.29-35
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• 1995

The effects of prostaglandin $F_2{\alpha}$ were investigated on the uterine smooth muscle motility in the pig. The results were summarized as follows : 1. Prostaglandin $F_2{\alpha}$ caused the contraction of the porcine uterine smooth muscle and the contractile responses increased between the concentration of prostaglandine $F_2{\alpha}$ $10^{-9}$ M and $5{\times}10^{-8}$ M with a dose-dependent manner. 2. The contractile response induced by prostaglandine $F_2{\alpha}$($10^{-8}$ M) was not blocked by pre-treatment with cholinergic receptor blocker, atropine ($10^{-6}$ M). 3. The contractile response induced by prostaglandine $F_2{\alpha}$(10$^{-8}$ M) was not blocked by pretreament with ${\alpha}$-adrenergic receptor blocker, phentolamine($10^{-6}$ M) and ${\beta}$-adrenergic receptor blocker, propranolol($10^{-6}$ M). From these results, it was concluded that the effects of uterine smooth muscle by prostaglandine $F_2{\alpha}$ were only the contraction mediated by prostaglandine TEX>$F_2{\alpha}$ receptor in pig, and that it may not be related to the cholinergic and adrenergic receptor.