• Journal of Institute of Control, Robotics and Systems
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• v.4 no.2
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• pp.170-177
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• 1998

In this paper, a unified solution of Hankel norm approximation problem is proposed by $\delta$-operator. To derive the main result, all-pass property is derived from the inner and co-inner property in the $\delta$-domain. The solution of all-pass becomes an optimal Hankel norm approximation problem in .delta.-domain through LLFT(Low Linear Fractional Transformation) inserting feedback term $\phi(\gamma)$, which is a free design parameter, to hold the error bound desired against the variance between the original model and the solution of Hankel norm approximation problem. The proposed solution does not only cover continuous and discrete ones depending on sampling interval but also plays a key role in robust control and model reduction problem. The verification of the proposed solution is exemplified via simulation for the zero-order Hankel norm approximation problem and the model reduction problem applied to a 16th order MIMO system.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1999.04a
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• pp.62-63
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• 1999

Reduction 2,4,6-Trinitrotoluene by zero valent iron was studied in a batch reactor under anoxic conditions. Results showed that the removal of TNT was a pseudo-first order and the rate was dependent on the available metal surface area. Final product, presumably triaminotoluene, accumulated in the solution as well as on the metal surface. However, little amounts of aminodinitrotoluenes were detected. Therefore, it is postulated that the reduction of nitro group occurs simultaneously in all three position.

• YAKHAK HOEJI
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• v.28 no.6
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• pp.299-303
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• 1984

In order to eluciate the effect of humidity and organic solvent on the decomposition of carbamide peroxide, the kinetic study was carried out. The carbamide peroxide was prepared from urea and 30%-hydrogen peroxide. The accelerated stability analysis for carbamide peroxide crystal in various relative humidity, and for 10%-carbamide peroxide solution of organic solvents were investigated. Both humidity and temperature were important factors influencing the decomposition rate of carbamide peroxide crystal. The higher the humidity and temperature, the greater was the reaction rate. The breakdown rate of crystal was observed as an apparent zero-order, and was faster than the rate of decomposition in dilute propylene glycol, glycerine or sorbitol solutioos which were measured as an apparent first-order reaction. The more dilute to 10% the organic solvents of 10%-carbamide peroxide, the slower was breakdown rate. It is, therefore, useful in the aspects of stability and economics to substitute solvent of carbamide peroxide topical solution (USP XXI) with 10%-propylene glycol or glycerine instead of anhydrous glycerine.

• Honam Mathematical Journal
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• v.41 no.1
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• pp.51-65
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• 2019

In this paper, we give sufficient conditions to guarantee the asymptotic stability of the zero solution to a kind of nonlinear fractional dynamic equations of order ${\alpha}$ (1 < ${\alpha}$ < 2). By using the Krasnoselskii's fixed point theorem in a weighted Banach space, we establish new results on the asymptotic stability of the zero solution provided f (t, 0) = 0, which include and improve some related results in the literature.

• Journal of Pharmaceutical Investigation
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• v.21 no.1
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• pp.1-10
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• 1991

Hydrogels containing ketoprofen were prepared by adding NaOH or $Ca(OH)_2$ solution to Eudragit L, S and Eudispert hv at various concentration. And xerogels were prepared by drying hydrogels. On the other hand, organogels containing ketoprofen were prepared by mixing Eudragit L or S and propylene glycol. Effects of polymer content and base on drug release were investigated using KP V dissolution method. The release rate of ketoprofen from Eudragit L & S hydrogel decreased with increasing in polymer content. And the drug release rate from cal. hydroxide based gels were more decreased than that from sod. hydroxide based gels. At pH 7.2 dissolution medium, e release of ketoprofen from Edispert hv hydrogel followed apparent zero order kinetics. The release of ketoprofen from xerogel involved in simultaneous absorption of water and desorption of ketoprofen via a pH-dependant swelling controlled mechanism. The release of ketoprofen from Eudragit S organogels followed apparent zero order kinetics, providing strong evidence for a surface erosion mechanism.

• Bulletin of the Korean Mathematical Society
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• v.40 no.3
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• pp.489-501
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• 2003

In this paper we shall consider the nonlinear delay difference equation $\Delta({p_n}{\Deltax_N})\;+\;q_nf(x_{n-\sigma})\;=\;0,\;n\;=\;0,\;1,\;2,\;...$ when (equation omitted). We will establish some sufficient conditions which guarantee that every solution is oscillatory or converges to zero.

• Structural Engineering and Mechanics
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• v.44 no.1
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• pp.15-34
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• 2012

In the present paper, an improved high-order theory is used for bending analysis of soft-core sandwich plates. Third-order plate assumptions are used for face sheets and quadratic and cubic functions are assumed for transverse and in-plane displacements of the orthotropic soft core. Continuity conditions for transverse shear stresses at the interfaces as well as the conditions of zero transverse shear stresses on the upper and lower surfaces of the plate are satisfied. Also, transverse flexibility and transverse normal strain and stress of the orthotropic core are considered. The equations of motion and boundary conditions are derived by principle of minimum potential energy. Analytical solution for bending analysis of simply supported sandwich plates under various transverse loads are presented using Navier's solution. Comparison of the present results with those of the three-dimensional theory of elasticity and some plate theories in the literature confirms the accuracy of the proposed theory.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7C
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• pp.451-458
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• 2011

Maximally flat (MAXFLAT) FIR filter design provides the advantage of giving a closed-form solution, but there still remains a problem of exactly and efficiently choosing the order of flatness for the accurate design of filters. This paper provides, through the modeling and analysis of a frequency-domain error function in the closed-form solution, how to determine the order of flatness. A proposed method, based on the frequency-domain error function, is accomplished by computing a minimum distance between its peak frequency and specified cutoff frequency. It is also shown that the proposed scheme is computationally efficient and accurate than the empirical formula given by Herrmann.

• Geomechanics and Engineering
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• v.38 no.4
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• pp.381-395
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• 2024

With the wide application of urban subway tunnels, the foundation pits of new stations and existing subway tunnels are becoming increasingly close, and even zero-distance close-fitting construction has taken place. To optimize the construction support scheme, the existing tunnel's vertical displacement is theoretically analyzed using the two-stage analysis method to understand the action mechanism of the construction of zero-distance deep large foundation pits on both sides of the existing stations; a three-dimensional numerical calculation is also performed for further analysis. First, the additional stress field on the existing tunnel caused by the unloading of zero-distance foundation pits on both sides of the tunnel is derived based on the Mindlin stress solution of a semi-infinite elastic body under internal load. Then, considering the existing subway tunnel's joints, shear stiffness, and shear soil deformation effect, the tunnel is regarded as a Timoshenko beam placed on the Kerr foundation; a sixth-order differential control equation of the tunnel under the action of additional stress is subsequently established for solving the vertical displacement of the tunnel. These theoretical calculation results are then compared with the numerical simulation results and monitoring data. Finally, an optimized foundation pit support scheme is obtained considering the pit corner effect and external corner failure mode. The research shows a high consistency between the monitoring data,analytical and numerical solution, and the closer the tunnel is to the foundation pit, the more uplift deformation will occur. The internal corner of the foundation pit can restrain the deformation of the tunnel and the retaining structure, while the external corner can cause local stress concentration on the diaphragm wall. The proposed optimization scheme can effectively reduce construction costs while meeting the safety requirements of foundation pit support structures.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.261-265
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• 1997

Driving the electrodeless fluorescent lamp, the high ac voltage with high frequency is required. The linear power amplifier has been widely used as a driving circuit of electrodeless fluorescent lamp. However, the low efficiency of the power amplifier causes th driving circuit to be replaced by a PWM switching inverter. In order to use a PWM switching inverter as the driving circuit of an electrodeless fluorescent lamp, the high switching frequency is required. But due to the switching loss at switches of the inverter, the limitation of high switching frequency appears in the inverter. One solution to this limitation is to reduce the switching loss by using the zero voltage switching technique. In this paper, zero voltage switching resonant inverter for driving an electrodeless fluorescent lamp is discussed. The results of analysis about the inverter are presented and the equations for design are established. And the validity of the analyzed results are verified through the experiment.