• 산업기술연구
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• 제24권B호
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• pp.171-176
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• 2004

The effects of agitation and aeration for exopolysaccharide(EPS) production through batch cultivation of an Enterobacter sp. isolated from the composter were investigated. During the EPS fermentation under conditions of constant agitation speed from 200 to 900 rpm and constant aeration rate of 0.5-2.5 vvm, the low yields of EPS(4.8-5.2g/L) was observed as the viscosity increase of culture broth. With the stepwise increases in agitation speed and aeration rate, the EPS production and the viscosity of EPS were increased 1.3~1.4 times and 2.3~3.6 times higher than those of the fixed conditions, respectively. Therefore, these stepwise increases were considered as the key operating parameters for enhancing EPS production. The max. EPS(6.8g/L) and viscosity(14,000cp) were obtained when the agitation speed was increased from 300 to 900 rpm for 54hrs at 1.5 vvm.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.II
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• pp.413-422
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• 2000

Samples of banana were dried in a two-stage heat pump dryer capable of producing stepwise control of the inlet drying air temperature while keeping absolute humidity constant. Two stepwise air temperature profiles were tested. The incremental temperature step change in temperature of the drying air about the mean air temperature of 30 $^{\circ}C$ was 5 $^{\circ}C$. The total drying time for each temperature-time profile was about 300 minutes. The drying kinetics and color change of the products dried under these stepwise variation of the inlet air temperature were measured and compared with constant air temperature drying. The stepwise air temperature variation was found to yield better quality product in terms of color of the dried product. Further, it was found that by employing a step-down temperature profile, it was possible to reduce the drying time to reach the desired moisture content.

• 한국수소및신에너지학회논문집
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• 제21권1호
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• pp.50-57
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• 2010

Stepwise production of syn-gas and hydrogen from methane on ferrite based media added with yttria-stabilized zirconia (YSZ) was carried out using a fixed bed infrared reactor. In this study, all M-ferrite (M=Co, Cu, Mn and Ni) media were prepared by co-precipitation method, and there the YSZ was added as a binder to improve thermal stability, reactivity, and resistance against carbon deposition. Most of the ferrite media containing YSZ showed the good redox property for temperature programmed reduction/oxidation (TPR/O) tests. Notably, the Cu-substituted ferrite medium with YSZ showed the great resistance against carbon deposition as well as the good reactivity for the stepwise production of syngas and hydrogen. Furthermore, it also showed the good durability without significant deactivation during five repeated cyclic tests.

• KSBB Journal
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• 제14권6호
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• pp.639-642
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• 1999

키토산 올리고당을 보다 효율적으로 생산하고자 효소와 기질간의 특성을 조사한 다음, 이를 바탕으로 기질을 단계별로 첨가하여 생산 효율을 높일 수 있었다. 본 실험에 사용된 효소의 안정성을 조사한 결과 pH 5.0에서 6일 후에도 약 90% 이상의 효소활성을 유지하였다. 기질이 초기 농도에 따른 겉보기 수율은 0.5~2% 키토산 용액은 약 90% 이상이었으며, 그이상의 농도일 경우 감소하였다. 그래서, 수율을 증가시키기 위해 초기 반응 속도 및 겉보기 수율이 높은 기실 농도에 기질을 단계 별로 첨가한 결과, 분해 반응에 있어 겉보기 수율은 64.6%에서 83.2%로 증가하였고, 이에 따라 키토산 올리고당의 생산량은 10.52 mg/mL에서 12.26 mg/mL로 증가하였다. TLC분석 결과 Batch type과 기질을 단계별로 첨가하였을 경우의 올리고당 조성은 주로 3-5당이었다. 키토산 올리고당 생산을 위한 최적의 반응 조건은 pH 5.0, 40$^{\circ}C$에서 초기 반응 속도 및 수율이 높은 기질 농도인 2% 키토산 용액에 기질을 3시간마다 첨가할 때였다. 반응 시간에 따른 기질의 양과 효소를 보다 더 최적화하여 키토산 올리고당의 최종 농도와 겉보기 수율을 증가시킬 수 있었다.

• 한국경영과학회지
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• 제39권3호
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• pp.51-61
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• 2014

In this paper, we deal with developing a cost estimation relationships (CER) for Korean maneuverable weapons systems using historical production cost. To develop the CER, we collected the historical data of the production cost of four tanks and five armored vehicles. We also analyzed the Required Operational Capability (ROC) of the weapons systems and chose cost drivers that can compare operational capabilities of the weapons systems We used Forward selection, Backward selection, Stepwise Regression and $R^2$ selection as the cost drivers which have the greatest influence with the dependent variables. And we used Principle Component Regression, Robust Regression and Weighted Regression to deal with multicollinearity and outlier among the data to develop a more appropriate CER. As a result, we were able to develop a production cost CER for Korean maneuverable weapons systems that have the lowest cost errors. Thus, this research is meaningful in terms of developing a CER based on Korean original cost data without foreign data and these methods will contribute to developing a Korean cost analysis program in the future.

• 한국작물학회지
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• 제50권4호
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• pp.268-275
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• 2005

Early predictions of crop yields call provide information to producers to take advantages of opportunities into market places, to assess national food security, and to provide early food shortage warning. The objectives of this study were to identify the most useful parameters for estimating yields and to compare two model selection methods for finding the 'best' model developed by multiple linear regression. This research was conducted in two 65ha corn/soybean rotation fields located in east central South Dakota. Data used to develop models were small temporal variability information (STVI: elevation, apparent electrical conductivity $(EC_a)$, slope), large temporal variability information (LTVI : inorganic N, Olsen P, soil moisture), and remote sensing information (green, red, and NIR bands and normalized difference vegetation index (NDVI), green normalized difference vegetation index (GDVI)). Second order Akaike's Information Criterion (AICc) and Stepwise multiple regression were used to develop the best-fitting equations in each system (information groups). The models with $\Delta_i\leq2$ were selected and 22 and 37 models were selected at Moody and Brookings, respectively. Based on the results, the most useful variables to estimate corn yield were different in each field. Elevation and $EC_a$ were consistently the most useful variables in both fields and most of the systems. Model selection was different in each field. Different number of variables were selected in different fields. These results might be contributed to different landscapes and management histories of the study fields. The most common variables selected by AICc and Stepwise were different. In validation, Stepwise was slightly better than AICc at Moody and at Brookings AICc was slightly better than Stepwise. Results suggest that the Alec approach can be used to identify the most useful information and select the 'best' yield models for production fields.

• Korean Journal of Chemical Engineering
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• 제35권11호
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• pp.2145-2149
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• 2018

The formation of methanol directly from methane and steam was observed over Cu ion-exchanged mordenite. Furthermore, the continuous production of methanol was achieved by co-feeding methane and steam over Cumordenite. The methanol production rate was comparable to that reported in the stepwise process in which activation, methane reaction, and extraction of methanol were carried out separately.

• 수산경영론집
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• 제44권3호
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• pp.77-84
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• 2013

While some steps in laver aquaculture production can be controlled artificially to a certain extent, the culturing process is largely affected by natural factors, such as the characteristics of seawater, climatic and oceanographic conditions, etc. This study aims to find a direct relationship between climatic and oceanographic factors (water temperature, air temperature, salinity, rainfall, sunshine duration and wind speed) and laver aquaculture production in Wando region, the biggest aquaculture production area of laver, located in the southwest coast of Korea using a multiple regression analysis. Despite the small sample size of a dependent variable, the goodness of model fit appeared acceptable. In addition, the R-squared value was 0.951, which means that the variables were very explanatory. Model results indicated that duration of sunshine, temperature, and rainfall during the farming period from the end of September to the end of April would be important factors affecting significantly to the laver aquaculture production.

• 한국약용작물학회지
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• 제21권3호
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• pp.204-212
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• 2013

In general, stepwise hot steaming process is known to be effective in improving its biological activities; however, not much employed in processing Codonopsis lanceolata due to its hardness. The complex processed C. lanceolata showed highest free radical scavenging acitivity as 45.21%. Total phenol and flavonoid content were of complex processed C. lanceolata higher than conventional extract and alone steaming process. It was showed the lower melanogenesis rate on melanin production test by B16F10 cells as 27.46%. High inhibitory of tyrosinase was also measured as 28.61% by adding steamed Codonopsis lanceolata extracts by high pressure extraction of 1.0 $mg/m{\ell}$. And anti-wrinkle activity were 39.08%. In comparing phenolic acids profiles in the extract, in general higher amounts of polyphenol were obtained possibly by easy release of active components during thermal processing, which results in better antioxidant activities than that of general extract. This findings can also be supported by result that the extract by steaming process showed better activities than the general extraction extract.

• Management Science and Financial Engineering
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• 제11권2호
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• pp.45-60
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• 2005

This paper investigates the application of the computer method COMSOAL (Computer Method of Sequencing Operations for Assembly Lines) to the process routing (PR) problem with multiple objectives. In any computer aided process planning (CAPP) system, one of the most critical activities for manufacturing a part could be to generate the sequence that optimizes production time, production cost, machine utilization or with multiple these criteria. The COMSOAL has been adopted to find the optimum sequence of operations that optimizes two major conflicting criteria : production cost and production quality. The COMSOAL is here slightly modified to simultaneously generate and evaluate a set of possible solutions (called as population) instead of processing a solution stepwise in each iteration. The significant features of the COMSOAL include : no parameters settings needed, and a guarantee of feasible solutions. Experimental results show that COMSOAL is a simple but powerful method to quickly generate multiple feasible solutions which are as good as the ones obtained from several other well-known process routing algorithms.