• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.163-169
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• 2019

The robust controller synthesis and analysis of the water level process in the U-tube system generator (UTSG) is addressed in this paper. The parameter uncertainties of the steam generator (SG) are modeled as multiplicative perturbations which are normalized by designing suitable weighting functions. The relative errors of the nominal SG model with respect to the other operating power level models are employed to specify the weighting functions for normalizing the plant uncertainties. Then, a robust controller is designed based on ${\mu}$-synthesis and D-K iteration, and its stability robustness is verified over the whole range of power operations. A gain-scheduled controller with $H_{\infty}$-synthesis is also designed to compare its robustness with the proposed controller. The stability analysis is accomplished and compared with the previous QFT design. The ${\mu}$-analysis of the system shows that the proposed controller has a favorable stability robustness for the whole range of operating power conditions. The proposed controller response is simulated against the power level deviation in start-up and shutdown stages and compared with the other concerning controllers.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.275-278
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• 2001

Research on the forced vibration control of a flexible GFR composite beam using $\mu$-synthesis is performed on this paper. Modal analysis method and modal coordinates are introduced to obtain the state equations of the structural system. Using these equations, Robust control algorithm using $\mu$-synthesis is adopted to suppress the forced vibration of a flexible beam since the designed controller can considered plant uncertainty and external disturbance. Constant disturbance which is generated by shaking the flexible beam as I's natural frequency is effectively rejected by a PZT actuator. Simulations and experiments are carried out with the designed controller and effectiveness of forced vibration suppression strategy is verified by results.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.157-160
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• 1998

We argue that the combination of optimal control synthesis and QFT tuning enables design of controllers with levels of performance that surpasses what can be achieved using only a single technique. Using a constructive example, we demonstrate how the strength of each technique is utilized to arrive at a particularly desired controller in terms of tradeoffs between performance and controller complexity.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.849-859
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• 2006

This paper presents an extensive robust analysis of a ${\mu}$-controller in the hybrid system for various uncertainties using the benchmark cable-stayed bridge. The overall system robustness may be deteriorated by introducing active devices and the active controller may cause instability due to small margins. Therefore, a ${\mu}$-synthesis method that simultaneously guarantees the performance and stability of the closed-loop system (robust performance) with uncertainties is used for active devices to enhance the robustness in company with the inherent reliability of passive devices. The robustness of the ${\mu}$-synthesis method is investigated with respect to the additional mass on the deck, structural stiffness matrix perturbation, time delay of actuator, and combinations thereof. Numerical simulation results show that the proposed control system has the good robustness without loss of control performances with respect to various uncertainties under earthquakes considered in this study. Furthermore, the control system robustness is more affected by the perturbation of structural stiffness matrix than others considered in this study. Therefore, the hybrid system controlled by a ${\mu}$-synthesis method could be proposed as an improved control strategy for a seismically excited cable-stayed bridge containing many uncertainties.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.574-577
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• 2004

This paper presents a hybrid system combining lead rubber bearings and hydraulic actuators controlled by a $\mu-synthesis$ method for seismic response control of a cable-stayed bridge. A hybrid system could alleviate some of restrictions and limitations that exist when each system is acting alone because multiple control devices are operating. Therefore, the overall control performance of a hybrid system may be improved compared to each system, however the overall system robustness may be negatively impacted by active device in the hybrid system or active controller may cause instability due to small margins. Therefore, a $\mu-synthesis$ method that guarantees the robust performance is considered to enhance the possibility of real applications of the control system. The performances of the proposed control system are compared with those of passive, active, semiactive control systems and hybrid system controlled by a LQG algorithm. Furthermore, an extensive robust analysis with respect to stiffness and mass matrices perturbation and time delay of actuator is performed. Numerical simulation results show that the performances of the proposed control system are superior to those of passive system and slightly better than those of active and semiactive systems and two hybrid systems show similar control performances. Furthermore, the hybrid system controlled by a f-synthesis method shows the good robustness without loss of control performances. Therefore, the proposed control system could effectively be used to seismically excited cable-stayed bridge which contains many uncertainties.

• 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.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.476-483
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• 2004

This paper presents a hybrid system combining lead rubber bearings and hydraulic actuators controlled by a μ-synthesis method for seismic response control of a cable-stayed bridge. A hybrid system could alleviate some of restrictions and limitations that exist when each system is acting alone because multiple control devices are operating. Therefore, the overall control performance of a hybrid system may be improved compared to each system, however the overall system robustness may be negatively impacted by active device in the hybrid system or active controller may cause instability due to small margins. Therefore, a f-synthesis method that guarantees the robust performance is considered to enhance the possibility of real applications of the control system. The control performances of the proposed control system are compared with those of passive, active, semiactive control systems and hybrid system controlled by LQG algorithm and an extensive robust analysis with respect to stiffness and mass matrices perturbation and time delay of actuator is performed. Numerical simulation results show that the control performance of the proposed control system is superior to that of the passive system and slightly better than that of the active and semiactive systems and two hybrid systems show similar control performances. Furthermore, the hybrid system controlled by a μ-synthesis method shows the good robustness without loss of control performances. Therefore, the proposed control system could effectively be used to seismically excited cable-stayed bridge which contains many uncertainties.

• Journal of Acupuncture Research
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• v.23 no.2
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• pp.91-102
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• 2006

Objectives : Ulmus davidiana Planch (UD) has long been known to have anti-inflammatory and protective effects on damaged tissue, inflammation and bone among other functions. Methods : This study was undertaken to address whether the water extract of the bark of UD could modulate proliferation of mouse osteoclasts in vitro and to investigate its effect on cyclooxygenase-2 (COX-2), which converts arachidonic acid to prostaglandin E2 (PGE2) and is highly expressed in osteoclasts. Mouse osteoclasts were tested in vitro for growth inhibition, proliferation cell nuclear antigen expression, and COX-2 activity and expression after treatment with UD extract. Results : Its effects were compared with those of indomethacin (a nonselective COX inhibitor) and celecoxib (a selective COX-2 inhibitor) by Cell viability assay, Cell cycle analysis, Immunohistochemical analysis of PCNA expression, Western blot analysis and PGE2 Enzyme immunoassay (EIA). UD demonstrated a strong growth inhibitory action in both tested osteoclasts cells. The IC50s were $10\;{\mu}g/ml$ for UD, $6\;{\mu}M$ for celecoxib and $42\;{\mu}M$ for indomethacin. UD, as well as celecoxib and indomethacin, suppressed proliferation cell nuclear antigen expression and PGE2 synthesis in osteoclasts. UD inhibited COX-2 expression, whereas celecoxib inhibited COX-2 activity directly. Conclusion : UD selectively and effectively inhibits osteoclasts cell growth in vitro. Inhibitory action of PGE2 synthesis via suppression of COX-2 expression may be responsible for its anti-inflammatory activity.

• Journal of Life Science
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• v.28 no.8
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• pp.908-916
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• 2018

Hair loses melanin with aging, which leads to hair graying. The change in hair color is caused by a reduction in tyrosinase activity and an accumulation of hydrogen peroxide ($H_2O_2$) in hair follicles. The purpose of this study was to investigate the effect of ethanolic extract of Oryza sativa (OREE) on melanin production and antioxidative activity in B16F1 cells. In this study, OREE showed low DPPH radical scavenging activity and reducing power. However, it displayed a strong antioxidative effect against intracellular $H_2O_2$ in live cells. OREE did not inhibit DOPA oxidation activity in vitro, but it increased tyrosinase activity at a concentration of $64{\mu}g/ml$. OREE at a concentration higher than $32{\mu}g/ml$ showed cell toxicity in B16F1 cells. However, OREE at a concentration higher than $8{\mu}g/ml$ not only increased melanin synthesis in a dose-dependent manner in B16F1 cells but also increased melanin synthesis in cells treated with $H_2O_2$ inhibiting melanin synthesis. To confirm the effect of OREE on melanin production, Western blot analysis was performed. The results revealed that OREE increased the expression levels of tyrosine hydroxylase and tyrosinase-related protein-2 (TRP-2) involved in melanin production in the $H_2O_2$-treated cells in which melanin production was inhibited. The findings suggest that OREE could improve melanin synthesis and be available for development of hair cosmetics aimed at improving melanin production.

• Korean Journal of Animal Reproduction
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• v.21 no.4
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• pp.325-333
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• 1997

Recent evidence indicates that growth factors modulate response of mammary epithelial cells to environmental stress. The objective of this study was to examine the cellular and biochemical responses of mammary tissue to environmental stress caused by artificial mastitis. For experimental a, pp.oach, toxins of most mastitis causing organisms(Staph. aureus or Strep. agalactiae) and heat stress(42$^{\circ}C$) were artificially exposed to mammary tissue. Effects of these environmental stresses on cell growth, cell death and heat shock protein synthesis were examined. Lactating mammary tissure were cultured under basal medium(DMEM) su, pp.emented with insulin(10$\mu\textrm{g}$/ml) and aldosterone(1$\mu\textrm{g}$/ml). All treatment groups in heat stress at 42$^{\circ}C$ incubation significantly decreased DNA synthesis rates in comparison with those at 39$^{\circ}C$(P<0.05), however, these decreased DNAa synthesis rates were recovered by addition of adenosine(10$\mu$M) and IGFI(10ng/ml). Similar results were obtained when tissue growth rates were measured by DNA content/tissue. Strep. agalactiae toxin did not significantly decreased DNA content/tissue in comparison with no treatment of bacterial toxin with or without heat stress, however, tended to decrease DNA contents/tissue without heat stress. In the fluorography analysis, heat stress(42$^{\circ}C$ incubation) slightly increased 35S-methoionine labelled 70kd protein synthesis. These results indicate that environmental stress caused by artificial mastitis slightly decreased mammary growth or mammary size, however, these results could be recovered by addition of adenosine and IGF-I.