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다구찌의 2단계 최적화 모델의 필요충분조건에 관한 연구
송서일,배홍석 동아대학교 공과대학부설 생산기술연구소 1996 生産技術硏究所硏究論文集 Vol.1 No.-
Taguchi gave no justification for the use of SN ratios and no explanation of why the two-step procedure that minimize average quadratic loss. But Leon et. al suggested the connection method between SN ratios and average quadratic loss by using Performance Measure Indepentent od Adjustment (PerMIA). In this study the possibility of Taguchi's two-step optimization is defined and it shows that the expected loss function is minimized when Taguchi's two-step optimization is possible. Futhermore, one necessary and sufficient condition for the possibility of Taguchi's two-step optimization suggested. From this result, the constraints for underlying methods of Leon seems to be weaken.
오스템퍼 처리한 구상흑연주철의 드릴가공 특성과 공구수명에 관한 연구
조규재,이승수,전언찬,박흥식 동아대학교 공과대학부설 생산기술연구소 1996 生産技術硏究所硏究論文集 Vol.1 No.2
Drilling tests were carried out austempered ductile cast iron(ADI) to clarify the factors influencing the drilling chracteristics of ADI material. The machinability of material was evaluated using high speed steel drill and cobalt contained drill of 6mm diameter. The spherodal graphite cast iron materials were austenized at 900℃ for in hour and then wear was kept at 375℃ for 2 hours. Austempered ductile cast iron contains a great deal of retained austenite which contributes to an improvement of impact strength. In this paper, machinability of ADI was investigated by drilling experimentation. The results obtained are as follows: a) Flank wear increases logarithmically with the increases of cutting time. b) Relation of flank wear and cutting force can be applied to FZ = 925VB + 820 for the cutting suggested condition. c) Drilling hole number of about 2 times can be reduced more step feed than ordinary feed due to the high hardness of ADI material and hardness increasing ascribed to the martensite of retained austenite.
송성암,김동균,배석태,김시범 동아대학교 공과대학부설 생산기술연구소 1996 生産技術硏究所硏究論文集 Vol.1 No.2
A study on the natural convection inside an L-shaped enclosure of which left wall is maintained at T_C and right wall and part of the bottom are T-H has been performed numeriacally for aspect ratio A=1, geometrically different five cases and for Ra=1×10³∼1×10^5. As the L-shape of the enclosure goes thinner vertically and horizontally like case 5, the mean Nusselt number at the left cold wall becomes smaller for same Ra, and there is little influence of the increase of Ra on mean Nusselt number.
서진기,정상훈,박동원 동아대학교 공과대학부설 생산기술연구소 1996 生産技術硏究所硏究論文集 Vol.1 No.2
The experimental binodal curves and tie lines were determined for solvent-5% KF salt solution-1 propanol systems at 25℃, and those tie line data were used to test thermodynamic consistency. From experimental data of tie line, the parameter estimated using NRTL and the caculated values fo tie line were predicted. The effect of KF salt on liquid-liquid equilibria was also studied.
고탄소 마르텐사이트-베이나이트 2상 혼합조직강의 베이나이트 변태특성 및 기계적 성질
안진환,김순호,성장현 동아대학교 공과대학부설 생산기술연구소 1996 生産技術硏究所硏究論文集 Vol.1 No.-
This study carried out to investigate into the influence of silicon addition on charpy impact values, transformation kinetics and morphology of lower bainite in high carbon steel with a mixed structure of martensite and lower bainite. The width of lower bainite plate was decreased and the transformation kinetics appeared to be fast with the addition fo silicon. The transformation cirves of lower bainite showed to be a sigmoid shape representing the typical nucleation and growth mechanism. Charpy impact values showed linearly increasing tendency with increasing the volume fraction of bainite and tempering temperature for the mixed structure of martensite and bainite. The chaning range of impact value with the variation of the volume fraction of bainite or appeared to be remarkable, except at the 600℃ tempering, with the addition of silicon. The improvement effect of impact value on tempering was depressed with the addition of silicon. This phenomenon was considered to have an retardation effect on carbide precipitation by silicon.
α-셀룰로오즈의 열분해에 관한 연구(Ⅰ) : 산촉매 NaCl의 영향
설수덕,나상도 동아대학교 공과대학부설 생산기술연구소 1996 生産技術硏究所硏究論文集 Vol.1 No.-
The Thermal decomposition of the α-Cellulose and NaCl was a thermal analysis technique in the steam of nitrogen gas with 30ml/min at various heating eates from 4 to 20℃/min. The Derivative and Integral method were used to obtained values of activation energy of decomposition reaction. 1. The values of activation energy evaluated by Derivative and Integral method were consistent with each other very well. 2. The maximum value of heat of decomposition evaluated by DSC method was α-Cellulose/NaCl=90/10. 3. The thermogravimetric trace curve agreed with the theoretical equation.
서해원,서이수,권순석 동아대학교 공과대학부설 생산기술연구소 1996 生産技術硏究所硏究論文集 Vol.1 No.-
The theoretical study addresses the nature of motions and heat transfer in confined rectangular enclosure heated from below and colled on the top simultaneously subject to themal wall conditions that the side walls are insulated or cooled alternately. Also the flow dynamics and the characteristics of convective performance are argued in the numerical scheme by using Grashof no. and Reynolds no. as variable parameters according to the moving conditions in which the natural convections are discussed for fixed condition and the forced and mixed convection also discussed for moving wall at constant speed. It is envisaged that follows below The circulation velocity caused by the buoyant effects exhibits the tendency toward increasing at low Reynolds no., especially this trend is obvious near Re=100. As Re no. is increased, the vortexflow produced at the corners in the low part is inclined to develop thus reduce heat transfer, especially this phenomenon turns to be clear by the advancement of multi-cell at Gr=10^5 and Re=400∼500. The vortex also occurs in the corner under the natural convection, however the effects of the eddy on the heat transfer seems to be more insignificant than in the forced and mixed case. It is also shown that the point at which heat transports best tends to shift from right to left as Re no. is increased, and the reduction of heat transfer neighbouring the wall side is remarkable inproportion to Grashof number.
김영일,진도원,박동원 동아대학교 공과대학부설 생산기술연구소 1996 生産技術硏究所硏究論文集 Vol.1 No.-
Separations by hollow fiber modules are fast compared with conventional extraction equipment because of the large surface area per volume. In these modules, the reactants can be contacted at high speed and two flows are completely independent, so there are no problems with loading and channeling. Generally the mass transfer coefficients in hollow fibers will be maximized when the resistance of the membrane is minimized. This membrane resistance will be minimized if the hollow fiber is wet by the solvent that flow the outside of the fiber. In this paper, for the extraction of Pb(Ⅱ) from wastewater, the extractants were TOA and DP-8R. To determine the rate controlling step in hollow fibers, we examined the effect of inside and outside flow rates of the fibers. From these experiments, we identified for the extraction of system with high partition coefficient in hydrophobic hollow fibers, mass transfer in the inside aqueous feed dominated the overall mass transfer.
키틴질을 이용한 Chitinase/Chitobiase의 생성 특성 연구
이천우,이상만,이은영,최종정,이상록,김광 동아대학교 공과대학부설 생산기술연구소 1996 生産技術硏究所硏究論文集 Vol.1 No.2
This study was carried out to investigate the characteristics of two hydrolases : chitinase and chitobiase. To investigate for the effect on partcle size of chitin, and corelation between activity of hydrolases and effect producing chitinase in 1.5% chitin on N-acetyl-β-D-glucosamine (NAG) by cell density of Serratia marcesdens QM B1466. To examine the effect of substrate concentrations and different preparations of substrate, and also have been obtained chitinase/chitobiase ensemble ratio for the highest NAG production.
장상목,김종민,이현우,정재헌 동아대학교 공과대학부설 생산기술연구소 1996 生産技術硏究所硏究論文集 Vol.1 No.2
This paper shows that an AT-cut quartz crystal analyzer(Q.C.A) can be applied to the investigation of the microheological change of the polymer blend solution during solvent evaporation process casting blend on the surface of quartz crystal. he blend is made from various compositions of poly(methyl methacrylate) (PMMA) and poly(vinyl acetate)(PVAc), and ethyl acetate as slovent. The resonant frequency and resonant admittance of the blend casting Q.C.A are measured simultaneously and the microheological behavior of the blend is analyzed during ethyl acetate evaporation. The PMMA/PVAc blend solution behaves several informative changes of resonant frequency and resonant admittance during ethyl acetate evaporation, depending on the evaporation time and the blend ratio. The PMMA/PVAc blend solution in ethyl acetate exhibited critical changes of resonant frequency and resonant admittance depending on the evaporation time and blend ratio. From this study, it is known that the quartz crystal analyzer can be successfully applicable to analyze viscoelastic changes on the microrheology and phase separation at the initial stage of the blends of PMMA and PVAc during the solvent, ethyl acetate evaporation process by maesuring the resonant freaquency and the resonant resistance in situ.