• Bulletin of the Korean Chemical Society
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• 제28권4호
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• pp.662-666
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• 2007

Poly(vinyl butyral) (PVB) with different wt% water was studied gravimetrically as well as with 1H magic angle spinning (MAS) nuclear magnetic resonance (NMR). The composition of PVB samples changes during MAS NMR because of the centrifugal force. As MAS time progresses, initially free water was removed fast but bound water also was gradually depleted. More water was diminished at faster spinning speeds, longer spinning time, higher temperatures, and higher initial water contents. As water in PVB was reduced, the chemical shifts and line widths of different types of water and also those of PVB changed. Our results demonstrate that 1H MAS NMR carried out at 10 kHz in less than about 5 minutes is a convenient and sensitive technique to measure: (a) the content variations of different types of water in polymers, (b) the degree of the interaction of water and polymer, and (c) the molecular dynamics of the polymer. Our study can be extended to different soft polymers with other small molecules than water in them.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 B
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• pp.413-416
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• 1998

We investigate the Hurwitz stability condition using the coefficient diagram. The coefficient diagram consists of a plot of logarithmic values of the coefficients of the characteristic polynomial versus the degree of the coresponding coefficients. The logarithmic value of the coefficient of the characteristic polynomials are plotted in the descending order. Using the Bhattacharyya, Chapellat and Keel's algorithm, the sufficient and necessary condition for Hurwitz stability are reconstructed using the coefficient diagram. With the coefficient diagram we also present some necessary or sufficient conditions for Hurwitz stability of polynomials. In addition we obtain a lower bound for the Manabe parameter $\tau$.

• Structural Engineering and Mechanics
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• 제55권1호
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• pp.29-46
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• 2015

A three-dimensional (3-D) method of analysis is presented for determining the natural frequencies of a truncated shallow and deep conical shell with linearly varying thickness along the meridional direction free at its top edge and clamped at its bottom edge. Unlike conventional shell theories, which are mathematically two-dimensional (2-D), the present method is based upon the 3-D dynamic equations of elasticity. Displacement components $u_r$, $u_{\theta}$, and $u_z$ in the radial, circumferential, and axial directions, respectively, are taken to be periodic in ${\theta}$ and in time, and algebraic polynomials in the r and z directions. Strain and kinetic energies of the truncated conical shell with variable thickness are formulated, and the Ritz method is used to solve the eigenvalue problem, thus yielding upper bound values of the frequencies by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four-digit exactitude is demonstrated. The frequencies from the present 3-D method are compared with those from other 3-D finite element method and 2-D shell theories.

• 대한전기학회논문지
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• 제45권2호
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• pp.273-282
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• 1996

This work is conceded with the estimation of output derivatives and their use for the design of robust controller for linear systems with system uncertainties due to modeling errors and disturbances. It is assumed that a nominal transfer function model and quantitative bounds for system uncertainties and known. The developed control schemes are shown to achieve regulation of the system output and ensures boundedness of the system states without imposing any structural conditions on system uncertainties and disturbances. Output derivative estimation is first conducted through restructuring of the plant in a specific parameterization. They are utilized for constructing robust nonlinear high-gain feedback controller of a SMC(Sliding Mode Control)type. The performances of the developed controller are evaluated and shown to be effective and useful through simulation study.

• Journal of Pharmaceutical Investigation
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• 제19권3호
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• pp.117-121
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• 1989

A metal complex, copper (II) L-proline was chemically bound to ethylene glycol dimethacrylate and divinylbenzene crosslinked chloromethylated polystyrene and they were used as chiral chelate resin matrix for column chromatography to resolve enantiomers of DL-amino acids. The L-enantiomers eluted first and the degree of resolution on the polymer crosslinked with ethylene glycol dimethacrylate was superior to the polymer crosslinked with divinylbenzene.

• 한국정밀공학회지
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• 제8권2호
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• pp.106-113
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• 1991

A diamond grinding wheel is generally used to grind hard and brittle materials, such as advanced ceramics. It is, however, quite difficult to dress a diamond grinding wheel efficiently because of its high degree of hardness. In this study, some investigations are carried out to increase dressing efficiecy of resinoid bonded diamond grinding wheel. Dressing forces are measured over a wide range of dressing conditions, and SEM observation of a grinding wheel is carried out. Special attention is paid to comparison between stick method and rotary brake method. Results obtained in this study provide useful information determining reguired dressing time, and for choosing efficient dressing condition for diamond grinding wheel.

• Nuclear Engineering and Technology
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• 제36권5호
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• pp.460-474
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• 2004

Effects of liquid subcooling on pool boiling heat transfer in an annulus with an open bottom have been investigated experimentally. A tube of 19.1mm diameter and the water at atmospheric pressure have been used for the fest. Up to $50^{\circ}C$ of liquid subcooling has been tested and experimental data of the annulus have been compared with the data of a single unrestricted tube. Temperatures on the heated tube surface fluctuate only slightly regardless of the heat flux in the annulus, whereas high variation is observed on the surface of the single tube. An increase in the degree of subcooling decreases heat transfer coefficients greatly both for the single tube and the annulus. Heat transfer coefficients increase suddenly at ${\Delta}T_{sub}\;{\le}\;10^{\circ}C$ and much greater change in heat transfer coefficients is observed at the annulus. To obtain effects of subcooling on heat transfer quantitatively, two new empirical equations have been suggested, and the correlations predict the empirical data within ${\pm}30\%$ error bound excluding some data at lower heat transfer coefficients.

• 한국축산식품학회지
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• 제37권5호
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• pp.743-751
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• 2017

During slaughtering, animal blood is typically discarded, resulting in water pollution. However, this discarded blood has valuable components, such as immunoglobulin (Ig). Although several studies have been conducted to develop methods for effective recycling of slaughterhouse blood, they have not been commercially utilized in Korea. Here, we extracted an Ig-rich fraction from porcine blood that was then subjected to various in vitro tests, including pathogen growth inhibition, antigenic cross-reactivity, and anti-toxin activity. The porcine immunoglobulin concentrate (PIC) was effectively purified by eliminating other components, such as albumin, and consisted of approximately $63.2{\pm}2.9%$ IgG and $7.2{\pm}0.4%$ IgM on a protein basis. The results showed that it significantly suppressed the growth of pathogenic bacteria, and bound to all tested pathogens, including both gram-positive and gram-negative species, although the degree of activity differed according to strain. The PIC bound to two types of lipopolysaccharide (LPS) obtained from Escherichia coli O111:B4 and Salmonella enterica serotype typhimurium in a concentration-dependent manner. In addition, the PIC restored the proliferation activity of the lymphoblast K-562 cells when co-incubated with pathogenic LPS. These results confirm that the PIC prepared in this study is a potentially valuable functional food material or diet supplement as an alternative to antibiotics that can protect animals from pathogenic bacteria.

• 한국정보과학회논문지:정보통신
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• 제28권3호
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• pp.447-453
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• 2001

본 논문에서는 방향성 커플러를 이용하여 구성한 광 베니언-형 교환 망에 있어 교환소자를 달리하는 멀티캐스팅의 스케줄링을 고려한다. 임의의 주어진 시각에 최대한 하나의 접속만이 각각의 교환소자를 점유하기 때문에 블록킹은 물론 누화가 발생하지 않도록 보장된다. 이러한 멀티캐스팅에서는 대개 수차례 걸친 라우팅이 수반되므로 라우팅 횟수를 최소한으로 하는 것이 바람직하다. 먼저 일-대-다 접속 능력을 제공하는 광 베니언-형 망에서 접속들이 동일한 교환소자를 경유하기 위한 필요충분 조건을 제시한다. 멀티캐스트 접속을 일정한 부분접속들로 분할 하는 규칙을 정의하고 부분접속들간의 누화 관계를 그래프로 표현한다. 최악의 경우의 누화를 분석하기 위해 그래프차수의 상한을 제시한다. 후속 논문(제2부)[14]에서는 스케줄링 알고리즘과 스케줄링 길이의 상한을 고찰하고 관련 연구결과와의 상세한 비교를 다룬다.

• Structural Engineering and Mechanics
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• 제14권2호
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• pp.171-190
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• 2002

Two cases of design are performed for the hyperbolic paraboloid saddle shell (Lin-Scordelis saddle shell) and the hyperbolic cooling tower (Grand Gulf cooling tower) to check the design strength against a consistent design load, therefore to verify the adequacy of the design algorithm. An iterative numerical computational algorithm is developed for combined membrane and flexural forces, which is based on equilibrium consideration for the limit state of reinforcement and cracked concrete. The design algorithm is implemented in a finite element analysis computer program developed by Mahmoud and Gupta. The amount of reinforcement is then determined at the center of each element by an elastic finite element analysis with the design ultimate load. Based on ultimate nonlinear analyses performed with designed saddle shell, the analytically calculated ultimate load exceeded the design ultimate load from 7% to 34% for analyses with various magnitude of tension stiffening. For the cooling tower problem the calculated ultimate load exceeded the design ultimate load from 26% to 63% with similar types of analyses. Since the effective tension stiffening would vary over the life of the shells due to environmental factors, a degree of uncertainty seems inevitable in calculating the actual failure load by means of numerical analysis. Even though the ultimate loads are strongly dependent on the tensile properties of concrete, the calculated ultimate loads are higher than the design ultimate loads for both design cases. For the cases designed, the design algorithm gives a lower bound on the design ultimate load with respect to the lower bound theorem. This shows the adequacy of the design algorithm developed, at least for the shells studied. The presented design algorithm for the combined membrane and flexural forces can be evolved as a general design method for reinforced concrete plates and shells through further studies involving the performance of multiple designs and the analyses of differing shell configurations.