• Steel and Composite Structures
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• 제48권6호
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• pp.625-639
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• 2023

In this paper, a Taguchi-based finite element method (FEM) has been proposed and implemented to assess optimal design parameters for minimum static deflection in laminated composite plate. An orthodox mathematical model (based on higher-order shear deformation plate theory and Green-Lagrange geometrical nonlinearity) has been used to compute the nonlinear central deflection values of laminated composite plates according to Taguchi design of experiment via a self-developed MATLAB computer code. The lay-up scheme, aspect ratio, thickness ratio and the support conditions of the laminated composite plate structure were designated as the governable design parameters. Analysis of variance (ANOVA) is used to investigate the effect of diverse control factors on the nonlinear static responses. Moreover, regression model is developed for predicting the desired responses. The ANOVA revealed that the lay-up scheme alongside the support condition plays vital role in minimizing the central deflection values of laminated composite plate under uniformly distributed load. The conformity test results of Taguchi analysis are also in good agreement with the numerical experimentation results.

• 대한미생물학회지
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• 제17권1호
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• pp.35-41
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• 1982

Enterotoxigenk E. coli is one of the major causative agents of the infantile diarrhea and traveler's diarrhea. The heat-labile enterotoxin is thought to be a virulence factor in the pathogenesis of the diarrhea and to be a marker for identification of the enterotoxigenic E. coli from non pathogenic E. coli. Therefore knowledge about the heat-labile enterotoxin is essential not only for understanding the pathogenesis but also for the diagnosis of the diarrhea. However the in-vitro heat-labile enterotoxin production is reported to be greatly affected by the cultural condition. In this regards, this study was designed to know the optimal conditions for the production of the heat-labile enterotoxin by assaying the permeability factor in the 18 hours culture supernatant of E. coli 08K25(B2) H9 and of E. coli 015 H11. Results obtained were summerized as follows: 1. Amounts of heat-labile enterotoxin produced were greater at initial pH 8.5 than at 7.0 of CYES-2 broth culture. However, the bacterial growth itself was more abundant at 7.0 than at 8.5. 2. Heat-labile enterotoxin per unit volume of culture supernatant was greater at shaking culture than at standing culture condition, but ratio of the enterotoxin produced over the unit mass of E. coli calculated was greater at standing culture than shaking culture condition, indicating that the greater yields of the toxin produced at shaking culture was due to increase in E. coli cell mass compared to the standing culture condition: 3. The enterotoxin produced in the lincomycin(128 microgram/ml) supplemented media was 5 or 11 times greater on the basis of enterotoxin per unit mass of E. coli, compared to the lincomycin-non-supplemented media, indicating that lincomycin itself increases the enterotoxin production. 4. Treatment of 18 hours culture of E. coli with polymyxin B(0.2 mg/ml) for 1 hour increased the yields of enterotoxin amounting to 2 or 5 times of the non-treated control cultures.

• Environmental Engineering Research
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• 제10권5호
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• pp.213-226
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• 2005

To treat wastewater efficiently by a one-step process of nitrogen removal, a new bacterial strain producing $N_2$ gas from ${NH_4}^+$ under an aerobic condition was isolated and identified. The cell was motile and a Gram-negative rod, and usually occurred in pairs. By 16S-rDNA analysis, the isolated strain was identified as Enterobacter asburiae with 96% similarity. The isolate showed that the capacity of $N_2$ production under an oxic condition was approximately three times higher than that under an anoxic condition. Thus, the consumption of ${NH_4}^+$ by the isolate was significantly different in the metabolism of $N_2$ production under the two different environmental conditions. The optimal conditions of the immobilized isolate for $N_2$ production were found to be pH 7.0, $30^{\circ}C$ and C/N ratio 5, respectively. Under all the optimum reaction conditions, $N_2$ production by the immobilized isolate resulted in reduction of ORP with both the consumption of DO and the drop of pH. The removal efficiencies of $COD_{Cr}$, and TN were 56.1 and 60.9%, respectively. The removal rates of $COD_{Cr}$, and TN were the highest for the first 2.5 hrs with the removal $COD_{Cr}/TN$ ratios of 32.1, and afterwards the rates decreased as reaction proceeded. For application of the immobilized isolate to a practical process of ammonium removal, a continuous operation was executed with a synthetic medium of a low C/N ratio. The continuous bioreactor system exhibited a satisfactory performance at 12.1 hrs of HRT, in which the effluent concentrations of ${NH_4}^+$-N was measured to be 15.4 mg/L with its removal efficiency of 56.0%. The maximum removal rate of ${NH_4}^+$-N reached 1.6 mg ${NH_4}^+$-N/L/hr at 12.1 hrs of HRT(with N loading rate of $0.08\;Kg-N/m^3$-carrier/d). As a result, the application of the immobilized isolate appears a viable alternative to the nitrification-denitrification processes.

• Food Science and Biotechnology
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• 제17권3호
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• pp.587-593
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• 2008

Microbial exopolysaccharide (EPS) is a biothickener that can be added to a wide variety of food products, where it serves as a viscosifying, stabilizing, emulsifying, and gelling agent. The objective of this study was to investigate the optimum conditions of pH, incubation temperature, and whey protein concentration (WPC) for EPS production by Lactobacillus rhamnosus ATCC 9595. We found that maximal EPS production was achieved at a pH of 5.5 and temperature of $37^{\circ}C$. At the same fermentation conditions, EPS production was affected by the addition of L. rhamnosus GG (a weak-EPS producer). After growth for 24 hr, total EPS production was $583{\pm}15.4mg/L$ in the single culture system, and $865{\pm}22.6\;mg/L$ in the co-culture system with L. rhamnosus GG. Based on the presence of WPC, EPS production dramatically increased from $583{\pm}15.4$ (under no WPC supplementation) to $1,011{\pm}14.7\;mg/L$ (under supplementation with 1.0% WPC). These results suggest that WPC supplementation and the co-culture systems coupled with small portions of weak-EPS producing strain can play an important role in the enhancement of EPS production.

• Journal of Microbiology and Biotechnology
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• 제15권1호
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• pp.131-135
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• 2005

Under sulfur deprived conditions, PS II and photosynthetic $O_2$ evolution by Chlamydomonas reinhardtii UTEX 90 are inactivated, resulting in shift from aerobic to anaerobic condition. This is followed by hydrogen production catalyzed by hydrogenase. We hypothesized that the photosynthetic capacity and the accumulation of endogenous substrates such as starch for hydrogen production might be different according to cell age. Accordingly, we investigated (a) the relationships between hydrogen production, induction time of sulfur deprivation, increase of chlorophyll after sulfur deprivation, and residual PS II activity, and (b) the effect of initial cell density upon sulfur deprivation. The maximum production volume of hydrogen was 151 ml $H_2$/l with 0.91 g/l of cell density in the late-exponential phase. We suggest that the effects of induction time and initial cell density at sulfur deprivation on hydrogen production, up to an optimal concentration, are due to an increase of chlorophyll under sulfur deprivation.

• 산업경영시스템학회지
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• 제40권1호
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• pp.35-40
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• 2017

A most important progress in civilization was the introduction of mass production. One of main methods for mass production is die-casting molds. Due to the high velocity of the liquid metal, aluminum die-casting is so complex where flow momentum is critical matter in the mold filling process. Actually in complex parts, it is almost impossible to calculate the exact mold filling performance with using experimental knowledge. To manufacture the lightweight automobile bodies, aluminum die-castings play a definitive role in the automotive part industry. Due to this condition in the design procedure, the simulation is becoming more important. Simulation can make a casting system optimal and also elevate the casting quality with less experiment. The most advantage of using simulation programs is the time and cost saving of the casting layout design. For a die casting mold, generally, the casting layout design should be considered based on the relation among injection system, casting condition, gate system, and cooling system. Also, the extent or the location of product defects was differentiated according to the various relations of the above conditions. In this research, in order to optimize the casting layout design of an automotive Oil Pan_BR2E, Computer Aided Engineering (CAE) simulation was performed with three layout designs by using the simulation software (AnyCasting). The simulation results were analyzed and compared carefully in order to apply them into the production die-casting mold. During the filling process with three models, internal porosities caused by air entrapments were predicted and also compared with the modification of the gate system and overflows. With the solidification analysis, internal porosities occurring during the solidification process were predicted and also compared with the modified gate system.

• Korean Chemical Engineering Research
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• 제52권3호
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• pp.302-306
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• 2014

목질계 분해효소 활성 증대를 위해 밀짚을 이용한 고체발효에서 주요 발효인자의 최적화를 수행하였다. Trichoderma reesei와 Aspergillus niger를 이용한 혼합배양에서 고체발효에 주요한 영향을 미친다고 알려진 배양온도, pH, 수분함량과 고체기질 크기를 순차적 최적화를 진행하였다. 실험에 적용 된 인자 모두 목질계 분해효소 활성에 유의한 효과를 주었으며, 발효온도 $40^{\circ}C$, pH 7, 수분함량 75%와 고체기질 크기 0.25~0.5 mm가 목질계 분해효소 생산을 위한 최적 조건임을 알 수 있었다. 최적조건 하에서 밀짚을 이용한 고체발효를 수행하였을 때, 효소활성 기준 cellulase 10.3 IU, endoglucanase 100.3 IU, ${\beta}$-glucosidase 22.9 IU와 xylanase 2261.7 IU/g dry material을 배양 96시간에 확인할 수 있었다. 본 결과는 기존 효소활성 대비 각각 72.6, 48.7, 55.2와 51.9% 증가한 수치로 혼합배양과 순차적 최적화를 적용하여 효과적인 목질계 분해효소 활성 증대가 가능함을 확인하였다.

• Korean Chemical Engineering Research
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• 제52권3호
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• pp.402-406
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• 2014

본 실험에서는 농부산물인 밀짚을 고체배지로 사용하여 Aspergillus niger NRRL 567에서 구연산 생산 시, 발효조건과 첨가제가 구연산 생산에 미치는 영향을 단일변수(one-factor-at-a-time) 최적화를 이용하여 주요 인자의 순차적 최적화를 수행하였다. 발효 72시간에서 온도, 수분함량, 입자크기, pH와 첨가제 농도를 최적화했을 때, 각각 $30^{\circ}C$, 70%, 0.5~1.0 mm, pH 5.5와 4% 메탄올 첨가조건에서 최대 구연산 생산인 206.0 g/kg 건조중량 (DM)을 확인할 수 있었다. 이는 최적화 이전 구연산 최고 생산인 74.5 g/kg DM 대비 177% 증가한 결과이다. 최적화 실험에서 도출된 조건을 밀짚, 옥수수대와 피트모스(peat moss)에 적용하여 고체발효를 수행하였을 때, 발효 120시간에서 각각 231.8, 213.8, 240.2 g/kg DM 구연산 생산을 확보하였다. 본 실험 결과는 밀짚과 옥수수대 등의 목질계 농부산물을 이용한 구연산 생산 시, 고체발효법이 기존의 액체발효법의 대체가 가능함을 시사하였다.

• Asian-Australasian Journal of Animal Sciences
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• 제8권6호
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• pp.641-645
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• 1995

This study was conducted to develop a method for production of nuclear transplant bovine embryos using in vitro-matured (IVM) oocytes and to examine the effect of different conditions of electrofusion on fusion rate and developmental capacity of donor nucleus transplanted to enucleated oocytes. Eight- to sixteen-cell embryos derived from oocytes matured and fertilized in vitro used as donor blastomeres and IVM oocytes were used as recipient oocytes. Oocytes were enucleated immediately after 23-24 h IVM and then reconstituted with a donor blastomere in two different micromanipulation media. Fusion rate and subsequent development of the reconstituted oocytes was compared under the different electric stimuli and recipient oocyte ages. Success rate of enucleation was significantly higher in TCM-199 medium containing FCS than in DPBS. The high fusion rate(75-94%) and development (6.4-14.8%) to morulae and blastocyst (M + B) were obtained from 0.6-0.75 kV/cm DC voltage, although total cleavage was not different among the electric pulses. Most optimal condition of electric stimulation for fusion and development was 1 DC voltage of 0.75 kV/cm, in which 80.5% of oocytes were fused, 80.0% and 31.7% of which was cleaved and developed to M + B, respectively. No M + B was obtained from 1.2 kV/cm DC voltage regardless of pulse frequency. Recipint oocyte age at electrofusion greatly affected the cleavage and subsequent development to M + B, showing high rate at 40-41 h oocyte maturation. These results suggest that a suitable condition of electrofusion for donor nuclei derived from IVF may be 1-2 DC pulses of 0.7 kV/cm for $70{\mu}sec$ and that processing of a transplanted nucleus in IVM oocytes may be affected by maturation age of recipient oocytes.

• 한국버섯학회지
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• 제6권1호
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• pp.27-31
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• 2008

현재까지 연구로는 흰목이 균사체에서 EPS 생산과 균사생장에 대한 적정 정치배양 조건이 연구되었다. 본 연구로부터 탄소원과 질소원의 처음 농도, 균사 형태와 발효조의 타입의 선택은 흰목이 균사체 EPS 생산에 가장 영향을 미친다는 것을 알게 되었다. 이들 결과는 공기주입식 반응기에서 EPS 생산성은 진탕탱크 반응기 보다 더 높았다는 점을 증명하였다. 또한 흰목이 균사의 정치배양의 생리적 생장에 대한 지식은 아직도 제한적이다.