• 한국표면공학회지
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• 제30권5호
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• pp.347-354
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• 1997

Composite plating is a method of co-depositing fine particles of metallic, non-metallic compound or polymers in the plated layer to improve material properties such as were-resistance, lubrication, or corrosion resistance. Graded Ni-Sic composite coating were produced in this research. Prior to produce Graded Ni-SiC composite coatings, effects of particle size, particle content, pH of electrolyte, temperature, current density, stirring rate on the amount of SiC deposited in the Ni layer were investigated. By manipulating current density and plating time properties of these coating were evaluated by micro-indentation hardness test.

• Journal of Pharmaceutical Investigation
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• 제12권3호
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• pp.55-63
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• 1982

The dissolution kinetics for polymorphs of sulpiride, the effect of polyethylene glycol 4000 on the dissolution kinetics of sulpiride polymorphs and the dissolution rate difference between the tablets of polymorph form I and form II were investigated. The results could be summerized as followings: 1. The dissolution rates of two polymorphs of sulpiride were significantly different and the thermodynamic parameters calculated from dissolution kinetics were as follows; transition temperature $98^{\circ}C$, enthalpy change, -2.108 kcal/mole, free energy change, -783 cal/mole $(31.0^{\circ}C)$. 2. The dissolution rates of the two polymorphs of sulpiride containing polyethylene glycol 4000 were significantly diefferent in 0.01N HCl but the effect of polyethylene glycol on the dissolution rates of two polymorphs was not significant at low concentration of polyethylene glycol 4000. The study on the effect by stirring speed showed that at lower stirring speed the promotion rate of dissolution of polymorph form I is greater than that of form II. 3. In the case of tablets the dissolution rates of polymorph form I of sulpiride was two fold as compared with the results obtained from form II.

• 한국주조공학회지
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• 제10권4호
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• pp.316-323
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• 1990

To improve free-cutting property, fine Pb, Bi particles is necessary to be distributed evenly in Al-Cu alloy. The control of added element size and distribution are very difficult because of the insolubility and gravity segregation of Pb, Bi in the matrix. Therefore, in this study, mechanical stirring of the melt, inert gasbubbling, the addition of degasser are used for the fine distribution of Pb, Bi particles. The best distribution are obtained by stirring with 500 rpm for 10min., Ar gas bubbling with 600cc/min for 5min. and degassing with 0.8wt% degasser. As increasing cooling rate, fine grain size and finely dispersed particles were observed. The optimum pouring temperature was $650^{\circ}C$.

• 한국주조공학회지
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• 제13권3호
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• pp.248-258
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• 1993

A semi-solid alloy in which solid and liquid phase are co-existing is obtained by stirring of A17075 molten metal. A semi-solid alloy is dependent on the corresponding temperature within the solid-liquid range, and the process parameters should be controlled accurately to obtain the homogeneous semisolid alloy. The fabrication possibility of fiber-reinforced aluminum alloy containing $Al_2O_3$ short fibers with vigorous agitation of short fibers were obtained by control of stirring time, solid fraction and impeller speed in extrusion billet fabrication processes. The microstructure to extrusion billet fabricated by low pressure casting was investigated for fiber dispersion state. The relationship between the extrustion force and velocity at hot extrustion, the flow strain and extrusion ratio were theoretically described. The surface defects with lubricants and without lubricant after hot extrusion were investigated. The composites materials after hot extrusion were measured by vickers hardness with extrusion ratio. It has become clear that the secondary working such as hot extrusion was very useful to obtained improved the mechanical properties of metal matrix composites.

• 한국축산식품학회지
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• 제37권6호
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• pp.813-822
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• 2017

The aim of this study was to prepare diacylglycerol (DAG) by enzymatic glycerolysis of lard. The effects of reaction parameters such as lipase type, reaction temperature, enzyme amount, substrate molar ratio (lard/glycerol), reaction time, and magnetic stirring speed were investigated. Lipozyme RMIM was found to be a more active biocatalyst than Novozym 435, and the optimal reaction conditions were 14:100 (W/W) of enzyme to lard substrate ratio, 1:1 of lard to glycerol molar ratio, and 500 rpm magnetic stirring speed. The reaction mixture was first incubated at $65^{\circ}C$ for 2 h and then transferred to $45^{\circ}C$ for 8 h. At the optimum reaction conditions, the conversion rate of triacylglycerol (TAG) and the content of DAG in the reaction mixture reached 76.26% and 61.76%, respectively, and the DAG content in purified glycerolized lard was 82.03% by molecular distillation. The distribution of fatty acids and Fourier transform infrared spectra in glycerolized lard samples were similar to those in lard samples. The results revealed that enzymatic glycerolysis and molecular distillation can be used to prepare more highly purified DAG from lard.

• 펄프종이기술
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• 제39권2호
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• pp.1-8
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• 2007

To examine the feasibility of dry forming technology for papermaking, a dry forming mold (DFM) was developed and evaluated. Main fanning section of DFM was a cylindrical tube, and at the top of the mold a stirring equipment was placed to disperse dry fibers. These fibers were screened using a hole type screen plate placed just under the stirring equipment and dropped freely on the fanning wire located 0.9 m below of the screen plate to form a dry fiber pad. The vertical and horizontal velocity of air flow in the forming cylinder were evaluated and analyzed to find the most effective method of air flow control in the cylinder. Humidification and pressing conditions to obtain a decent dry fanned papers were examined. Results showed dry fanned papers can be prepared with this dry forming mold. And this mold can be used to examine the effect of the papermaking process factors including pressing pressure, drying temperature, humidification on sheet quality of dry formed papers.

• 설비공학논문집
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• 제14권10호
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• pp.863-870
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• 2002

Fossil fuels have been depleted gradually and new energy resource which can solve this shortage is needed now. Methane hydrate, non-polluting new energy resource, satisfies this requirement and considered the precious resource prevent the global warming. Fortunately, there are abundant resources of methane hydrate distribute in the earth widely, so developing the techniques that can use these gases effectively is fully valuable. the work presented here is to develop the skill which can transport and store methane hydrate. As a first step, the equilibrium point experiment has been carried out by increasing temperatures in the cell at fixed pressures. The influence of gas consumption rates under variable degree of subcooling, stirring and water injection has been investigated formation to find out kinetic characteristics of the hydrate. The results of present investigation show that the enhancements of the hydrate formation in terms of the gas/water ratio are closely related to operational pressure, temperature, degrees of subcooling, stirring rate, and water injection.

• 약학회지
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• 제41권1호
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• pp.30-37
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• 1997

In order to formulate a controlled release system for oral drug delivery, the microcapsules were prepared in w/o emulsion containing cefaclor as a water-soluble model drug by th e method of interfacial polycondensation. Gelatin wis selected as a suitable polymer for interfacial polycondensation. Gelatin solution containing drug was emulsified in an organic phase under mechanical stirring. After emulsification, terephthaloyl chloride was added as cross linking agent, followed by mechanical stirring, washing and drying. Physical characteristics of microcapsules were investigated by optical microscopy, scanning electron microscopy and particle size analysis. Mean particle sizes of gelatin microcapsules were, in the range, of about 20~50 ${\mu}$m. The microcapsules were in good apperance with spherical shapes before washing, but were destroyed partially after washing and drying, even though some microcapsules were still maintained in their shapes. Contents of cefaclor in the microcapsules were calculated by UV spectrophotometry after 3 days extraction with pH 4 carbonate buffer solution. The effects of cross linking time. pH. concentration of cross-linking agent, and temperature on drug release kinetics have been discussed extensively.

• Composites Research
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• 제13권4호
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• pp.19-32
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• 2000

본 논문은 강화입자가 균일하게 분산된 금속 복합재료의 제조와 반용융 성형을 위한 재가열에 관한 연구결과이다. 강화재 크기의 종류에 따른 금속복합재료를 제조하기 위하여 전자기식 교반과 기계식 교반을 동시에 이용한 복합 교반법을 사용하였다. 복합 교반법에 의하여 제조된 금속복합재료의 분산 상태를 조사하였다. 복합재료를 제조하기 위한 전자기식 교반법과 기계식 교반법을 겸용으로 한 공정이 소개되었다. 금속복합재료의 반용융성형을 위해서, 금속복합재료의 빌렛과 코일표면사이의 길이, 코일의 지름과 빌렛사이의 길이로 구성된 함수로 최적의 코일을 설계하여 빌렛을 재가열하였다. 복합재료의 반용융 성형시에 필요한 재가열 공정 인자인 가열시간과 온도변화의 관계를 조사하였다. 재가열중 강화재의 분산상태가 온도변화에 미치는 영향에 대하여 검토하였다.

• 한국주조공학회지
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• 제28권3호
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• pp.129-135
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• 2008

The reheating stage of electromagnetically stirred Al billet is a critical factor in the thixoforming process. When reheated to the solid-liquid state, the microstructure evolves to a more globular and more homogeneous structure by a coarsening mechanism, the kinetics depending on the initial microstructure. Microstructural evolution has been characterized by conventional parameters (mean size of particle and shape factor) as a function of holding time in the solid-liquid state. The aim of this study is to report experimental results concerning microstructural evolution in the solid-liquid state of electromagnetically stirred Al billet. The material was elaborated in the form of continuously cast bars solidified with electromagnetic stirring to degenerate the dendritic structure. The choice of the reheating conditions is determined by a dendritic ripening and coalescence mechanism, involving variations of both the shape and size of the particles. The reheating time has to be long enough to allow a minimum degree of spheroidizing, but has to be limited as much as possible in order to avoid excessive ripening. The optimum microstructure was obtained at the reheating temperature of near $584^{\circ}C$ and the holding time of 5 min. The only means of combining high productivity with good casting quality was to use feedstock billets whose microstructure showed rapid transformation characteristics.