• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.12
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• pp.1586-1594
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• 1997

Performance characteristics of a small propeller fan are numerically investigated solving the continuity and Reynolds-averaged Navier-Stokes equations. The Reynolds stresses for turbulent transport are modelled using a k-.epsilon. turbulence model. The present numerical procedure is constructed using the Finite Volume Method with the SIMPLE algorithms. The performance parameters obtained from the calculations are compared with the measured values for the various flow rates. A performance test of the fan shows different characteristics between a radial type at small flow rates and an axial type at large flow rates. Comparisons between the predictions and the measurements show that the predicted results are in good agreement with the measured values and reasonably reproduce the sharp variations of the power and head coefficient around a flow coefficient .PHI.=0.3. These comparisons indicate that the present numerical method is capable of resolving the performance characteristics with reasonable accuracy. At low flow rates, it is found that the flow enters the fan in an axial direction and is discharged radially outward at the tip which happens in the centrifugal fan. The centrifugal effect makes a significant difference in the characteristics of a fan at the low and high values of flow coefficient.

• Journal of Electrical Engineering and Technology
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• v.5 no.3
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• pp.468-476
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• 2010

This paper presents a direct single-stage power converter using single-phase isolated full-bridge converter modules, with inherent power factor correction (PFC) for a 12 kW switched mode power supply (SMPS). The advantages of the proposed converter are its simple control strategy, reduction in number of conversion stage, low input line current harmonics, and improvement in power factor. Analysis of the single-stage converter is carried out in continuous conduction mode of operation. Steady-state analysis of the proposed converter is conducted to obtain converter parameters. A systematic design procedure is also presented for a 12k W converter with a design example. The effect of load variation on SMPS is also studied in order to demonstrate the effectiveness of the proposed converter for the complete range of load conditions. A set of power quality indices on input ac mains for an SMPS fed from a single-stage converter is also presented for easy comparison of their performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.1
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• pp.37-47
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• 2005

This Paper proposes a practical design and implementation methodology for a disturbance rejection controller. In a 2 Degree-Of-Freedom (DOF) structure, disturbance rejection performance can be improved without a high gain in forward-loop controller which might cause unwanted side-effects in conventional controller. But, since design methodology of 2 DOF controller is originally derived from the 2 DOF theory, it is not easy to utilize fer various industrial applications. Disturbance observer is a simple, but very effective 2 DOF controller. In this paper, practical issues are discussed from basic idea of DOB to technical procedure for design and implementation. Additionally, a methods and their examples of experimental modeling are explained. The proposed method is demonstrated by two examples of linear-type motor systems.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.4 no.2
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• pp.129-134
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• 2004

XML is the new universal format for structured documents and data on the World Wide Web. As the Web becomes a major means of disseminating and sharing information and as the amount of XML data increases substantially, there are increased needs to manage and design such XML document in a novel yet efficient way. Moreover a demand of XML Schema(W3C XML Schema Spec.) that verifies XML document becomes increasing recently. However, XML Schema has a weak point for design because of its complication despite of various data and abundant expressiveness. Thus, it is difficult to design a complex document reflecting the usability, global and local facility and ability of expansion. This paper shows a simple way of modeling for XML document using a fundamental means for database design, the Entity-Relationship model. The design from the Entity-Relationship model to XML Schema can not be directly on account of discordance between the two models. So we present some algorithms to generate XML Schema from the Entity-Relationship model. The algorithms produce XML Schema codes using a hierarchical view representation. An important objective of this modeling is to preserve XML Schema's object-oriented concepts such as reusability, global and local ability. In addition to, implementation procedure and evaluation of the proposed design method are described.

• Journal of Pharmaceutical Investigation
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• v.22 no.1
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• pp.63-68
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• 1992

An HPLC procedure with UV detection has been developed for the quantitation of flurbiprofen released into isopropyl myristate used as the receptor phase in an in vitro membraneless drug diffusion cell. The drug and the internal standard (oxaprozin) were extracted from isopropyl myristate with a mixture of dimethylsulfoxide:methanol:water (2:1:1) and quantitated using a reverse phase $C_{18}$ column. The chromatograms were completely free from interfering peaks, and the relative retention times of flurbiprofen and the internal standard were 4.9 and 6.8 min, respectively. Calibration plots were linear over the concentration range of $1-200\;{\mu}g/ml$ of flurbiprofen with correlation coefficients, all higher than 0.99. The mean intra-day precision and accuracy among three replicate sets of the assay in a day were 4.26 and 4.52%, respectively, whereas the mean inter-day precision and accuracy were 3.35 and 3.64%, respectively. The mean recovery of the drug was 92.5% over the calibration range. The method was simple, reliable and accurate for the quantitation of flurbiprofen in unpurified isopropyl myristate.

• The Korean Journal of Applied Statistics
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• v.22 no.3
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• pp.499-513
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• 2009

An economic signal in the real world usually reflects complex phenomena. One may have difficulty both extracting and interpreting information embedded in such a signal. A natural way to reduce complexity is to decompose the original signal into several simple components, and then analyze each component. Spectral analysis (Priestley, 1981) provides a tool to analyze such signals under the assumption that the time series is stationary. However when the signal is subject to non-stationary and nonlinear characteristics such as amplitude and frequency modulation along time scale, spectral analysis is not suitable. Huang et al. (1998b, 1999) proposed a data-adaptive decomposition method called empirical mode decomposition and then applied Hilbert spectral analysis to decomposed signals called intrinsic mode function. Huang et al. (1998b, 1999) named this two step procedure the Hilbert-Huang transform(HHT). Because of its robustness in the presence of nonlinearity and non-stationarity, HHT has been used in various fields. In this paper, we discuss the applications of the HHT and demonstrate its promising potential for non-stationary financial time series data provided through a Korean stock price index.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.79-82
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• 2004

In this study, a new refinement technique for 3-dimensional hexahedral element mesh is proposed, which is aimed at the control of mesh density. With the proposed scheme the mesh is refined adaptively to the elemental error which is estimated by 'a posteriori' error estimator based on the energy norm. A desired accuracy of an analysis i.e. a limit of error defines the new desired mesh density map on the current mesh. To obtain the desired mesh density, the refinement procedure is repeated iteratively until no more elements to be refined exist. In the algorithm, at first the regions of mesh to be refined are defined and, then, the zero-thickness element layers are inserted into the interfaces between the regions. All the meshes in the regions, in which the zero-thickness layers are inserted, are to be regularized in order to improve the shape of the slender elements on the interfaces. This algorithm is tested on a simple shape of 2-d quadrilateral element mesh and 3-d hexahedral element mesh. A numerical example of elastic deformation of a plate with a hole shows the effectiveness of the proposed refinement scheme.

• Journal of Chest Surgery
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• v.26 no.11
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• pp.827-832
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• 1993

From Jan 1982 through Dec.1991, thirty-three DeVega`s tricuspid annuloplasties were performed in association with mitral and combined mitral and aortic valve disease. Preoperatively,all of the patients were in NYHA functional class III or IV.There were one early death and 4 patients died during follow up period of 18 to 138 months [ mean follow up : 67.3 months ]. Nine patients required reoperation because of biological mitral valve failure at 4.7 to 11 years after tricuspid annuloplasty[TAP]. Among these patients,2 cases needed for reoperation of TAP due to loosening of suture material. Twenty four [86%] of the survivors were in NYHA functional class I or II after TAP.The actuarial survival rate for the TAP was 74% at 138 months. Rt atrial pressure of 9 reoperation cases were significantly decreased [P<0.05] compared with initial Rt.atrial pressure [ Mean period; 93.6 months].Doppler echocardiographic studies for tricuspid regurgitation were performed in 15 cases after TAP [Mean period: 42.3 months].These results showed significantly reduced [P<0.01] tricuspid annulus diameter and tricuspid regurgitation distance [ P<0.05 ].Our surgical experience that the DeVega`s TAP is a simple,safe,effective procedure and resulted in good hemodynamic improvement with moderate to severe functional tricuspid regurgitation.

• Korean Journal of Veterinary Research
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• v.41 no.1
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• pp.13-19
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• 2001

A simple and rapid analytical method for the determination of tylosin in chicken, pork and muscle was established by High-Performance Liquid Chromatography(HPLC). Chicken, pork and beef muscle(5 g) were fortified by adding the $0.2{\mu}g/ml$ of standard tylosin and the drug was extracted from meats with 70% acetonitrile(ACN) and followed by liquid-liquid partition for clean-up procedure. Then $20{\mu}l$ portion of ACN elution was directly analyzed by HPLC with spectra 100 variable wavelength detector, and unfortified blank control were treated similarly. The average recovery rate of tylosin added to chicken, pork and beef muscle were $83{\pm}2.3$, $96{\pm}3.3$ and $92{\pm}1.6$(%) at the level 0.2 ppm, respectively. No tylosin residues in marketing meats. These results suggested that HPLC methodology could be acceptable for the extraction, determination and screening of tylosin residues in edible meats.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.6
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• pp.929-936
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• 1986

Free vibration characteristics of laminated orthotropic circular cylindrical shells with clamped free boundary condition are investigated. The solution is obtained through a direct solution procedure with axial mode displacements represented as simple Fourier series expressions. On the basis of the thin shell theories of Sanders, Love, Loo, Morley and Donnell, the 4*$ frequency determinant is derived and is expressed in a unified form. Various numerical examples determining the natural frequencies of circular cylindrical shells with isotropic material and also with layers of orthotropic elastic material arbitraily laminated either symmetrically or anti-symmetrically about the shell middle surface. The results obtained compared very well with some available experimental and numerical results.