• Journal of the Korean Society for Precision Engineering
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• v.24 no.11
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• pp.59-65
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• 2007

A new optimal state feedback and disturbance feedforward control design in the sense of minimizing $L_2$-gain from disturbance to control output is proposed for disturbance attenuation of systems with bounded control input and measurable disturbance. The controller is derived in the framework of linear matrix inequality(LMI) optimization. A gain scheduled state feedback and disturbance feedforward control design is also suggested to improve disturbance attenuation performance. The control gains are scheduled according to the proximity to the origin of the state of the plant and the magnitude of disturbance. This procedure yields a stable linear time varying control structure that allows higher gain and hence higher performance controller as the state and the disturbance move closer to the origin. The main results give sufficient conditions for the satisfaction of a parameter-dependent performance measure, without violating the bounded control input condition.

• Kyungpook Mathematical Journal
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• v.55 no.4
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• pp.909-931
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• 2015

This paper presents some new paranormed sequence spaces $X(r,s,t,p;{\Delta})$ where $X{\in}\{l_{\infty}(p),c(p),c_0(p),l(p)\}$ defined by using generalized means and difference operator. It is shown that these are complete linear metric spaces under suitable paranorms. Furthermore, the ${\alpha}$-, ${\beta}$-, ${\gamma}$-duals of these sequence spaces are computed and also obtained necessary and sufficient conditions for some matrix transformations from $X(r,s,t,p;{\Delta})$ to X. Finally, it is proved that the sequence space $l(r,s,t,p;{\Delta})$ is rotund when $p_n$ > 1 for all n and has the Kadec-Klee property.

• Advanced Composite Materials
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• v.16 no.4
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• pp.259-267
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• 2007

Mechanical reinforcement of an all-sustainable composite, composed of papyrus stem-milled particles as reinforcement and poly-L-lactic acid (PLLA) resin as matrix, was investigated. The papyrus particles (average diameter of $70{\mu}m$) could be well dispersed in PLLA resin up to 50 wt% without any surface modification. Young's modulus of the composite was 4.2 GPa at 50 wt% of the papyrus content. This is a two-fold increment in modulus as compared to that of the PLLA matrix. The tensile strength of the composite was almost constant around 48 MPa irrespective of the papyrus content. Temperature dependence of the storage modulus demonstrated that the incorporation of papyrus restricts the large drop in the modulus above the glass transition of PLLA.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.192.2-192.2
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• 2003

Apigenin-7-O-${\beta}$-D-glucoside, chrysoeriol, and luteolin were isolated from the aqueous ethanolic extract of Zostera marina L. leaves as the scavengers of reactive oxygen species (ROS) with the SC$\_$50/ values of 0.18 mM, 0.68 mM, and 0.18 mM against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 0.04 mM, 0.03 mM, and 0.01 mM against superoxide radicals in the xanthine/xanthine oxidase system, respectively. The luteolin suppressed the expression of matrix metalloproteinase-1 (MMP-1) up to 44% at 4.0 ${\mu}$M. (omitted)

• Honam Mathematical Journal
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• v.30 no.2
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• pp.399-409
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• 2008

We consider the most generalized quadratic matrix equation, Q(X) = $A_7XA_6XA_5+A_4XA_3+A_2XA_1+A_0=0$, where X is m ${\times}$ n, $A_7$, $A_4$ and $A_2$ are p ${\times}$ m, $A_6$ is n ${\times}$ m, $A_5$, $A_3$ and $A_l$ are n ${\times}$ q and $A_0$ is p ${\times}$ q matrices with complex elements. The convergence of Newton's method for solving some different types of quadratic matrix equations are considered and we show that the elementwise minimal positive solvents can be found by Newton's method with the zero starting matrices. We finally give numerical results.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.1
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• pp.77-82
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• 2013

By using simulation, compensating characteristics of a voltage sag compensator utilizing single-phase matrix converter is examined. System configuration is described and mathematical model of single-phase matrix converter is derived by using the state space averaging method. In addition, the single-phase matrix converter is stabilized by phase-lead compensation. Finally, compensating characteristics of the compensator is investigated for 500 W R-L load and it is demonstrated that the compensator can operate correctly for loads for the range of power factor 0.6 (lagging) - 0.8 (leading) and for up to 50% voltage sag.

• Kyungpook Mathematical Journal
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• v.58 no.2
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• pp.271-289
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• 2018

Let 0 < q < ${\infty}$. In this study, we introduce the spaces ${\mathcal{BV}}_q$ and ${\mathcal{LS}}_q$ of q-bounded variation double sequences and q-summable double series as the domain of four-dimensional backward difference matrix ${\Delta}$ and summation matrix S in the space ${\mathcal{L}}_q$ of absolutely q-summable double sequences, respectively. Also, we determine their ${\alpha}$- and ${\beta}-duals$ and give the characterizations of some classes of four-dimensional matrix transformations in the case 0 < q ${\leq}$ 1.

• Structural Engineering and Mechanics
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• v.33 no.3
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• pp.307-323
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• 2009

This article presents the differential system that governs the mechanical behaviour of a curved-beam element, with varying cross-section area, subjected to generalized load. This system is solved by an exact procedure or by the application of a new numerical recurrence scheme relating the internal forces and displacements at the two end-points of an increase in its centroid-line. This solution has a transfer matrix structure. Both the stiffness matrix and the equivalent load vector are obtained arranging the transfer matrix. New structural matrices have been defined, which permit to determine directly the unknown values of internal forces and displacements at the two supported ends of the curved-beam element. Examples are included for verification.

• Analytical Science and Technology
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• v.18 no.3
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• pp.188-193
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• 2005

Three different oriental natural plants (Angelicae Dahuricae Radix, Sanguisorba Officinalis L, Euonymus alatus) were extracted with 70% methanol under refluxing for 4 hr in order to investigate their inhibitory effect on Matrix Metalloproteinase-9 (MMP-9) by a modified gelatin zymography, where only euonymus alatus showed the inhibitory effect on the activity of Matrix MMP-9. The fraction was collected by using the mixture of ethyl acetate and hexane on silica gel column. Seven portions were obtained and three fractions of them (first, third and forth) showed inhibitory effect on the zymography. To verify the effect of these substances on cells, human hepatoma, Hep3B cells as a cancer model, and Chang liver cells as a normal model were selected. In order to examine the cell viability, $1{\mu}g/mL$ of each extract was treated on cells. Most of the methanol soluble fractions showed negligible toxicity on human liver cell line.

• Preventive Nutrition and Food Science
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• v.11 no.3
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• pp.191-197
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• 2006

Matrix metalloproteinase-2 (MMP-2) is a key enzyme involved in tumor invasiveness. The plant of Magnolia officinalis Rehd. et Wils. is often included as an ingredient in various herbal remedies recommended for cancer theraphies in Korea. Various extracts prepared from stems of M. officinalis were tested for cytotoxic activity on human hepatocellular carcinoma cell line, SK-Hep cells using the XTT assay method. Then, the inhibitory effect was examined on MMP-2 activity using gelatin zymography. Methanol (MeOH) extract of M. officinalis caused the strongest inhibition of the MMP-2 activity, as measured by gelatin zymography method for enzyme activity. $IC_{50}$ values of fractions on MMP-2 activity were in a range of $4.9{\sim}11.3\;{\mu}g/mL$. Among each fraction, butanol and ethylacetate (EtOAc) fractions showed the strong inhibitory activities ($IC_{50}=10.7\;and\;4.9\;{\mu}g/mL$, respectively). When the M. officinalis's constituents such as magnolol, honokiol, (-)-epigallocatechin gallate (EGCG) and ovovatol were examined for inhibitory effects on MMP-2 activity, EGCG showed strong inhibitory activity. However, MeOH extract of M. officinalis was dose-dependently inhibited to MMP-2 activity. The MeOH extract, hexane and EtOAc fractions $(IC_{50}\;of\;>200\;{\mu}g/mL)$ exhibited weak cytotoxicity activity, while butanol $(IC_{50}=80\;{\mu}g/mL)$ and chloroform fractions $(IC_{50}=90\;{\mu}g/mL)$ exhibited relatively strong cytotoxic activity. From these results, M. officinalis could be suitable for cancer treatment and chemopreventive drugs.