• Journal of the Korean Society for Precision Engineering
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• v.16 no.3 s.96
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• pp.180-188
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• 1999

${\mu}$-synthesis is applied to design a robust controller for a seeker scan loop system which has model uncertainty and is subject to a external disturbance due to abrupt missile maneuver. The issue of modelling a real-valued parametric uncertainty of a physical seeker scan loop system is discussed. The two-degree-of-frame control structure is employed to obtain better performance. It is shown that ${\mu}$-synthesis provides a superior framework for the robust control design of a seeker scan loop system which exhibits robust performance. The proposed robust control system satisfies design requirements, and especially shows good scanning performances for conical and rosette scan patterns despite parametric uncertainty in real system model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.10
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• pp.3186-3198
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• 1996

When a robot is to have contact with its enviornment, such as a medi-care robot, it would be advantageous for the robot to have a high compliance. For this reason, a robot having not only a flexible link but also an actuator with compliance, is desirable. This paper is concerned with the position and vibration control of 1 degree of freedom flexible robot using a pneumatic artificial muscle actuator. The dynamics of the manipulator assumed to be and Euler-Bernoulli beam are derived on the basis of the linear mathematical modle. Although this pneumatic artifical muscle actuator has many merits for the compliance robot, it is difficult to make an effective control scheme of this system because of ths nonlinearity and uncertainty on the dynamics of the actuator. By designing a controller using .mu.-synthesis, robust performance against measurement noise, various modeling uncertainties on the dynamics of the servo valve, actuator and mainpulator, is achieved. The effectiveness of the proposed control method is illustrated through simulations and experiments.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.6
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• pp.41-48
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• 2002

This study is on the structural control experiment for a small scale three-story building structure employing on active mass damper subjected to earthquake loading. $\mu$-synthesis controllers, which belong to robust control strategies, were designed and their performance were experimentally verified. Frequency-dependent weighting functions corresponding to disturbance input and controlled output were defined and combined to produce optimal $\mu$-synthesis controllers. The experiment result shows 60-70% reduction in RMS responses under the band-limited white noise excitation and 30-45% reduction in peak responses under the scaled earthquake excitations. Good agreement was obtained between the simulations based on the identified mathematical model and experimental results. And the simulations for the system with uncertainties show that the designed controllers are robust within a specified range of uncertainties.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.6
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• pp.656-666
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• 1999

In this paper, we design the optimal PD control system which has the robust performance. This PD control system is designed by applying genetic algorithm (GA) to the determination of proportional gain KP and derivative gain KD that are given by PD servo controller, to make the output of plant follow the output of reference model optimally. These proportional and derivatibe gains are simultaneously optimized in the search domain guaranteeing the robust performance of system. And, this PD control system is compared with $\mu$ -synthesis control system for the robust performance. The PD control system designed by the proposed method has not only the robust performance but also the better command tracking performance than that of the $\mu$ -synthesis control system. The effectiveness of this control system is verified by computer simulation.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.27 no.1
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• pp.99-109
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• 2001

Novel glucoconjugates phenolic moiety, 3-(methoxycarbonyl)-4-(hydroxyphenyl)-$\beta$-D-glucopyranoside(4), 3-(methoxyacetyl)-4-(hydroxyphenyl)-$\beta$-D-glucopyranoside(7), 4-(hydroxyphenyl)-$\beta$-D-ribofuranoside(11), were synthesized. In order to investigate their depigmentation effect, inhibitory activity against mushroom tyrosinase and inhibitory activity of melanin synthesis in B16 melanoma cell were evaluated in vitro. Compound 11 showed 92.0$\mu\textrm{g}$/㎖ of tyrosinase inhibitory activity whereas compound 4 and 7 showed very low activity not less than 300$\mu\textrm{g}$/㎖. Inhibitory activities of melanin synthesis in B16 melanoma cell of compound 4, 7, and 11 were 8.7, 15.1, and 36.0%, respectively, at the concentration of 100$\mu\textrm{g}$/㎖. Inhibitory activity of compound 11 was much higher than that of arbutin at the same concentration.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.6
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• pp.729-737
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• 1998

In this paper, using $\mu$ synthesis algorithm with structured uncertainty, we design controller and apply it for the Two-Inertia resonance(TMS: Two Mass Spring) system. The TMS system is one of the simplest models which generate a torsional vibration. In this system, it is required to design a controller achieving the control performance while suppressing the torsional vibration. Furthermore, when vibration frequency for the system is varying by reason of parameter variations, we should consider parameter variations in controller design. Then, we design two other controller schemes of the PI controller and the standard $H_{\infty}$ controller and compare these controllers with the controller designed by the $\mu$ synthesis robust control method by using simulations and experiments.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.321.1-321.1
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• 2002

To indentify inhibitors of melanogenesis. we compared the effect of some natural products on mushroom tyrosinase. human melanocytic tyrosinase activity and melanin content. The cytotoxicity of the component were also tested on cultured mouse melanoma cells, Each extract significantly inhibited tyrosinase activity and melanin synthesis in vitro and B 16 melanoma cell lines. In B 16 cell lines, watermelon's inner shell extract inhibited tyrosinase activity as strong as kojic acid at 150${\um}g$/${\mu}\ell$ concentration. And morning glory'seed extract inhibited melanin synthesis more than kojic acid at 150${\um}g$/${\mu}\ell$ concentration. Each extract were strong inhibitors of tyrosinase activity and total melanin synthesis in B 16 mouse melanoma cell lines at less than 100${\um}g$/${\mu}\ell$ concetration. These result show that extract of watermelon's inner shell. lettuce. morning glory's seed and licorice root could be developed as skin whitening component of cosmetics.

• Asian-Australasian Journal of Animal Sciences
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• v.6 no.4
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• pp.483-489
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• 1993

Bovine fibroblasts were cultured in Dulbecco's Modified Eagle's Medium and then treated with control, insulin (I, $1{\mu}g/ml$), cholera toxin (CT, 0.1-100 ng/ml) or CT (0.1-100 ng/ml) + I ($1{\mu}g/ml$). Cholera toxin, an activator of adenylate cyclase, significantly decreased insulin induced DNA synthesis (p<0.05). The modulation of DNA synthesis apparently involves events occurring in early stage of cell growth, at least between the first 4 and 8 hour of CT treatment. Insulin induced collagen as well as noncollagen synthesis in cell layer, however, these syntheses were reduced by addition of cholera toxin (p<0.05) but were not completely reduced. It is not clear whether the reduction of insulin-induced cell layer collagen or noncollagen proteins by CT is involved in the inhibitory effect on insulin-induced DNA synthesis. However, we could rule out the hypothesis that insulin-induced DNA synthesis is reduced by CT-induced cellular differentiation.

• The Journal of Korean Medicine
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• v.23 no.4
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• pp.45-54
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• 2002

Objectives: In order to investigate the relationship of Radix Trichosanthis components and the melanin synthesis, the author has analyzed the cell viability and tyrosinase activity, melanin content and morphologic changes in n-hexane, EtOAc, n-BuOH, and H2O fraction. Methods: At first, in order to determine the concentration of the Radix Trichosanthis component, the author investigated the viability of B16 melanoma cell. To measure the effects of Trichosanthes kirilowii extracts (n-BuOH, n-Hexane, EtOAc, H2O fractions) on the viability of A549 cells, A549 cells were treated with various concentrations (from 0.5 to $25{\;}\mu\textrm{g}/ml$) of components of Trichosanthes kirilowii. After 24hrs, the cell viability was measured by MTT assay. The EtOAc components of Trichosanthes kirilowii decreased the viability of A549 cells in a dose-dependent manner. H2O and n-BuOH components had no cell toxicity till $25{\;}\mu\textrm{g}/ml$, the n-hexane component showed minor cell toxicity at $25{\;}\mu\textrm{g}/ml$ and the EtOAc component cell toxicity was revealed at $5{\;}\mu\textrm{g}/ml$ concentration. Results: 1. The results of tyrosinase activity and the Radix Trichosanthis component; n-hexane and EtOAc components controlled it effectively; the n-BuOH components were less effective. 2. The results of melanin content analysis showed that the n-hexane and EtOAc components effectively inhibited, the n-BuOH fraction inhibited less, and H2O component didn't inhibit the terminal melanin formation. 3. In the n-BuOH and H2O component there were no changes, but in the n-hexane component the melanin content was effectively inhibited. 4. In the EtOAc fraction, although the melanin content was inhibited, the cell count was evidently suppressed, Of all of the Radix Trichosanthis components, the n-Hexane and EtOAc fractions inhibited the melanin synthesis best, but owing to its toxicity, the EtOAc components inhibited the cell count. Conclusion: The above results demonstrated that Radix Trichosanthis n-hexane fraction efficiently inhibited the tyrosinase activity and melanin synthesis.

• Microbiology and Biotechnology Letters
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• v.18 no.3
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• pp.239-243
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• 1990

In this study the authors investigated the distribution of cadmium accumulated in cadmium-iun tolerant Hansenula anomala B-7 cells and also the effect of cadmium on protein synthesis. 84.9% of the cadmium accumulated was distributed in the soluble fraction (cytosol, etc.). The intracellular protein content was decreased by cadmium (1,000 $\mu g$/ml), but the content of soluble protein preeipitated by ammonium sulfate (30-75% saturation) was increased compared with the content of it obtained from the cells grown without cadmium. Furthermore, in the cells grown with 1,000 $\mu g$/ml of cadmium t h higher molecular weight soluble protein was increased compared with the cells grown without caa, mium, but the lower molecular weight soluble protein was decreased. These results suggested that the protein synthesis was inhibited by cadmium, but synthesis of higher molecular weight soluble protein was remarkably stimulated by cadmium.