• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.1
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• pp.25-32
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• 1999

In the present paper, we theoretically analyze the flow of magnetic fluids in a circular pipe with a vertical magnetic field and investigate the magnetic response by the external magnetic field. Theoretical study through the governing equation derived by Siliomis is carried out with numerical analysis by the Gauss Elimination Method. Using polar and magnetic effect parameters, theoretical equations and distributions for the velocity, vorticity, internal angular momentum and induced magnetization as the magnetic response are shown. Especially, in the region of strong magnetic field the specific property is appeared by finding a critical magnetic effect parameter for a polar effect parameter.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.2
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• pp.38-44
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• 2008

In the present paper, we theoretically analyze the flow of magnetic fluids in a circular pipe with a vertical magnetic field and investigate the magnetic response by the external magnetic field. Theoretical study through the governing equation derived by Siliomis is carried out with numerical analysis by the Gauss Elimination Method. Using polar and magnetic effect parameters, theoretical equations and distributions for the velocity, apparent viscosity as the magnetic response are shown. Especially, in the region of strong magnetic field the specific property is appeared by finding a critical magnetic effect parameter for a polar effect parameter.

• Applied Chemistry for Engineering
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• v.20 no.3
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• pp.346-350
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• 2009

Natural state materials contain a lot of available nutrient components. Among them, natural nutrient substances are utilized not only as the ingredient of functional foods but also as the excipients of functional cosmetics and pharmaceutic. Of these nutrient substances, solubility parameters of each components were calculated to choose the most suitable solvents for solutions. The solubility parameters for each components were composed of the dispersion contribution of the molecular attractive function, the polar contribution of the molecular attractive function and the contribution of the hydrogen bonding force. The chi parameters ($\chi_{12}$) were calculated with the information of the solubility parameter for the solute and solvent and were used as the criteria for the optimal solute-solvent pair. The optimal solvents were suggested with the numerical values of chi parameters for some amino acids.

• Journal of the Korean Magnetics Society
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• v.10 no.1
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• pp.42-47
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• 2000

In the present work, we analyze theoretically the flow of magnetic fluids in a circular pipe with longitudinal magnetic field. We used governing equations induced Shliomis and Polar theory of Eringen. Using theoretical equations and distributions for the velocity, vorticity and angular velocity as the magnetic response, it is shown that magnetic fluid flow is non-Newtonian fluid. We investigate dynamic characteristic of magnetic fluid by comparing longitudinal magnetic field with transverse magnetic field. And, the limits, influence magnetic fluid, of the intensity of the magnetic field with polar, size and magnetic effect parameters are shown.

• Journal of the Korean Chemical Society
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• v.29 no.1
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• pp.45-51
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• 1985

Rate constants and activation parameters for the methanolysis of t-butyl halide (t-BuCl, t-BuBr, t-BuI) in various MeOH-DMSO mixtures were measured by conductometric method. Taft's solvatochromic parameters, such as polarity-polarizability(SPP's), ${\pi}^{\ast}$, hydrogen bond donor (HBD) acidity, ${\alpha}$, and hydrogen bond acceptor (HBA) basicity, ${\beta}$ of the solvents, were determined by the so called solvatochromic method using five indicators. The variation of methanolysis rate with the solvent composition was discussed on the basis of the activation parameters and the correlation of the rates with the solvatochromic parameters. It is concluded that the polarity-polarizability, HBD acidity and HBA basicity of the mixtures had an effect on the ionization of t-butyl halide cooperatively, also that the specific interaction between the leaving groups and the solvents, such as ion-dipole and hydrogen bond acceptor-donor interaction, is the most important factor of solvent effects on the stabilization of transition states.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.197-199
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• 2009

본 논문에서는 매입형 영구자석 동기기 (Interior Permanent Magent Synchronous Motor)를 이용한 풍력발전 시스템에서의 효과적인 단위 전류 당 최대 토크 (Maximum Torque Per Amper) 제어를 위해 필요한 파라미터인 영구자석 회전자의 초기위치 및 동기 인덕턴스를 측정하는 방법을 보인다. IPMSM을 이용한 풍력 발전 시스템의 경우 기동 토크를 제대로 발생 시키고, 돌극성으로 나타나는 릴럭턴스 토크를 효과적으로 이용하기 위해서는 정확한 회전자의 초기위치 및 인덕턴스 값이 반드시 필요하다. 제안하는 고주파 입력 시험은 역기전력 성분이 발생하지 않아서 이때의 고정자 전류를 해석하여 모터의 회전 없이 현재의 회전자의 위치 및 인덕턴스 값을 측정할 수 있다. 실험 결과를 바탕으로 제안하는 방법의 타당성을 보인다.

• Journal of the Korean Chemical Society
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• v.33 no.5
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• pp.538-544
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• 1989

The increase of B-type hydrogen bonding character between the hydrogen atom($H{\gamma}$) of methylene group in 1-(phenoxymethyl)benzotriazole (1) and 1-(thiophenoxymetyl)benzotriazole (2) derivatives, and solvents was caused by some factors such as;electron withdrawing strength (${\rho} > 0$) of X-substituent; local diamagnetic effect by Y atom (Y = O(1) > S(2)) with adjacent methylene group; and solvent polarity parameter ($E_T$ = Kcal/mol; acetone; 42.2 > chloroform; 39.0). From the basis on the findings, linear free energy relationship (LFER) components on the substituent chemical shift of methylene group ($CH_2-SCS$) in (1) exhibited a tendency that resonance(R)-effect was much larger than field(F) (or inductive(I))-effect in acetone and that the electrical effects were depend upon the solvent.

• Journal of the Korean Chemical Society
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• v.33 no.3
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• pp.287-294
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• 1989

The optimum condition for the separation of priority pollutant phenols using isocratic elution has been determined. The elution behavior of eleven phenols has been also studied to interpret the retention. The reversed phase liquid chromatographic methods were performed on a ${\mu}$-Bondapak $C_{18}$ column with methanol-water, acetonitrile-water, and THF water mixtures as mobile phases. The COF method, where Snyder's solvent triangle concept was combined with a mixture-design statistical technique, was used to optimize the strength and selectivity of solvents for the separation of phenols. The optimum solvent composition, which gives a complete separation of eleven phenols, was found to be $MeOH:ACN:H_2O$ = 7:40:53. The plots of ln k' vs. -${\Delta}H^{\circ}$ and ${\Sigma}{\pi}$ of phenols showed relatively good linearities. Effect of van der Waals volume, pi-energy and hydrogen bonding on the retention of phenols were investigated. The following equation with the correlation coefficient of 0.9927 for ACN-water solvent system was obtained; $log^{k'}=2.515{\times}10^{-2}VWV-1.301{\times}10^{-1}E-3.674{\times}10^{-1}$

• Journal of the Korean Chemical Society
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• v.33 no.2
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• pp.149-155
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• 1989

1H-nmr chemical shifts and lineshapes of amino-protons of thioacetamide in n-alcohols were determined. The chemical shifts are discussed by the Reichardt's solvent polarity parameter, $E_T(30)$. The following relationship between ${delta}_{obs}\;and\;E_T(30)$ was obtained, ${\delta}_{obs}=a{\cdot}E_T(30)＋b{\cdot}(E_T(30))_2$ where a is a characteristic constant for the protons of thioacetamide in n-alcohol solutions and b is a constant for the solute(TA)-solvent (n-alcohols) interactions. The barrier of the hindered rotation about the N-C(S) bond in TA was obtained by analysis of the lineshape of the amino-protons in TA. The behavior of the hindered rotation as well as chemical shifts of the amino-protons in TA has been found to be closely related to the $E_T(30)$ of n-alcohols.

• Journal of the Korean Chemical Society
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• v.34 no.6
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• pp.509-516
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• 1990

1H-nmr chemical shifts and lineshapes of amino-protons of acetamide (AA) in n-alcohols were determined. The chemical shifts are discussed by the Reichardt's solvent polarity parameter, E$_{T}$(30). The following relationship between $\delta$obs and E$_{T}$(30) was obtained. ${\delta}_{obs}$ = ${\delta}_{o}$ ＋ aE$_{T}$ (30) ＋ b[E$_{T}$(30)]$^2$ where ${\delta}_{o}$ is the chemical shift of the solute in gaseous state or at $E_{T}$(30) = 0, a is a characteristic constant for the protons of AA in n-alcohol solutions and b is a constant for the solute (AA)-solvent (n-alcohols) interaction. The barrier of the hindered rotation about the N-C(O) bond in AA was obtained by analysis of the lineshapes of the amino-protons in AA. The behavior of the internal rotation as well as chemical shifts of the amino-protons in AA has been found to be closely related to the $E_{T}$(30) of n-alcohols.