• Journal of Microbiology and Biotechnology
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• v.34 no.3
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• pp.525-537
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• 2024

Pilins are protein subunits of pili. The pilins of type IV pili (T4P) in pathogenic bacteria are well characterized, but anything is known about the T4P proteins in acidophilic chemolithoautotrophic microorganisms such as the genus Acidithiobacillus. The interest in T4P of A. thiooxidans is because of their possible role in cell recruitment and bacterial aggregation on the surface of minerals during biooxidation of sulfide minerals. In this study we present a successful ad hoc methodology for the heterologous expression and purification of extracellular proteins such as the minor pilin PilV of the T4P of A. thiooxidans, a pilin exposed to extreme conditions of acidity and high oxidation-reduction potentials, and that interact with metal sulfides in an environment rich in dissolved minerals. Once obtained, the model structure of A. thiooxidans PilV revealed the core basic architecture of T4P pilins. Because of the acidophilic condition, we carried out in silico characterization of the protonation status of acidic and basic residues of PilV in order to calculate the ionization state at specific pH values and evaluated their pH stability. Further biophysical characterization was done using UV-visible and fluorescence spectroscopy and the results showed that PilV remains soluble and stable even after exposure to significant changes of pH. PilV has a unique amino acid composition that exhibits acid stability, with significant biotechnology implications such as biooxidation of sulfide minerals. The biophysics profiles of PilV open new paradigms about resilient proteins and stimulate the study of other pilins from extremophiles.

• Elastomers and Composites
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• v.59 no.2
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• pp.51-63
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• 2024

Polypropylene (PP) is a commodity plastic that is widely used owing to its cost-effectiveness, lightweight nature, easy processability, and outstanding chemical and thermomechanical characteristics. However, the imperative to address energy and environmental crises has spurred global initiatives toward a circular economy, necessitating sustainable alternatives to traditional fossil-fuel-derived plastics. In this study, we conducted a series of comparative investigations of bio-based polypropylene (bio-PP) blends with current PP of the same and different grades. An extrusion-based processing methodology was employed for the bio-PP composites. Talc was used as an active filler for the preparation of the composites. A comparative analysis with the current petroleum-based PP indicated that the thermal properties and tensile characteristics of the bio-PP blends and composites remained largely unaltered, signifying the feasibility of bio-PP as a potential substitute for the current PP. To achieve a higher Young's modulus, elongation at break (EAB), and melt flow index (MFI), we prepared different composites of PP of different grades and bio-PP with varying talc contents. Interestingly, at higher biomass contents, the composites exhibited higher MFI and EAB values with comparable Young's moduli. Notably, the impact strengths of the composites with various biomass and talc contents remained unaltered. In-depth investigations through surface analysis confirmed the uniform dispersion of talc within the composite matrix. Furthermore, the moldability of the bio-PP composites was substantiated by comprehensive rheological property assessments encompassing shear rate and shear viscosity. Thus, from these outcomes, the fabricated bio-PP-based composites could be an alternative to petroleum-based PP composites for sustainable automobile applications.

• Applied Chemistry for Engineering
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• v.35 no.4
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• pp.329-334
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• 2024

To improve the UV absorbance and emulsion stability of sunscreen creams prepared using refined seabuckton oil, experimental conditions were designed utilizing the central composite design model-response surface methodology (CCD-RSM). The amount of surfactant, emulsification time, and thickener amount were chosen as independent variables, and the experiment was carried out after the reaction values of ESI, MDS, and UV absorbance at 290 nm were determined. The main effect and interaction effect, which have the most influence on the response value, were analyzed through the F-value and P-value of the regression equation coefficient calculated through RSM, and the statistical significance of the coefficient was evaluated through the P-value. The optimal emulsification conditions using RSM were calculated as follows: amount of surfactant (4.39 wt%), emulsification time (25.42 min), and amount of thickener (1.24 wt%). At these conditions, the reaction value was calculated as ESI (98.5%), MDS (32.9 nm), and UV absorbance (2.73). As a result of conducting an actual experiment under the calculated optimal conditions, the average error rate was measured as ± 2.7%

• Journal of Electrochemical Science and Technology
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• v.15 no.3
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• pp.388-404
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• 2024

In the present work, the operating parameters were optimized using Box Behnken Design (BBD) in response surface methodology (RSM) to maximize the hydrogen production rate (R₁) and hydrogen production rate per unit watt consumed (R₂) of a proton exchange membrane electrolysis cell (PEMEC), a third response (R₃) which was the sum of the scaled values of R₁ and R₂ were selected to be maximized so that both hydrogen production rate and hydrogen production rate per unit watt consumed could be maximized. The major parameters which were influencing the experiment for enhancing the output responses were oxygen electrode/anode electrocatalyst loading (A), current supplied (B) and water inlet temperature (C). The commercial proton exchange membrane Nafion^® was used as the electrolyte. The acetylene black carbon (C_AB) supported IrO₂ was used as the electrocatalyst for preparing oxygen electrode/anode whereas commercial Pt (40 wt%)/C_HSA was used as the H₂ electrode/cathode electrocatalyst. The quadratic model was developed to predict the output/ responses and their proximity to the experimental output values. The developed model was found to be significant as the P values for both the responses were < 0.0001 and F values were greater than 1. The optimum condition for both the responses were O₂ electrode/anode electrocatalyst loading of 1.78 mg/cm², supplied current of 0.33 A and water inlet temperature of 54℃. The predicted values for hydrogen production rate (R₁) and hydrogen production rate per unit watt consumed (R₂) were 2.921 mL/min and 2.562 mL/(min·W), respectively obtained from the quadratic model. The error % between the predicted response values and experimental values were 1.47% and 3.08% for R₁ and R₂, respectively. This model predicted the optimum conditions reasonably in good agreement with the experimental conditions for the enhancement of the output responses of the developed PEM based electrolyser.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.439-444
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• 2003

The major factors related in enzymatic hydrolysis of food waste using cellulolytic enzymes of Trichoderma harzianum FJ1 were optimized by response surface analysis. The factors largely affecting to the reducing sugar concentration and enzymatic saccharification rate of food waste such as substrate concentration ($X_1$, %), enzyme concentration ($X_2$, U/ml), and reaction time ($X_3$, hr) were employed. A quadratic polynominal expressing the reducing sugar (RS) concentration relating with the above factors was as follows : RS (g/l) = -17.80 + $5.04X_1$ + $51.37X_2$ + $1.21X_3$ - $0.11X_1\;^2$ - $38.86X_2\;^2$ - $0.03X_3\;^2$ + $1.64X_1X_2$ + $0.04X_1X_3$ - $0.70X_2X_3$ ($R^2$=0.9939). The maximum value of the reducing sugar concentration and saccharification rate were obtained in the conditions of substrate concentration of 18.2%, enzyme concentration of 0.78 U/ml, and reaction time of 19 hr, respectively. The predicated reducing sugar concentration and saccharification rate by the response surface methodology were 95.13 g/l and 47.27%, respectively.

• Korean journal of food and cookery science
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• v.26 no.5
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• pp.627-635
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• 2010

This study was performed to determine the optimal manufacturing conditions of cookies prepared with Hizikia fusiformis. The variables in Hizikia fusiformis cookies production were the amounts of Hizikia fusiformis powder, butter, and sugar. Six sensory characteristics were used for sensory evaluations, including color, appearance, taste, brittleness, hardness, and overall acceptability. The optimal amounts of the three variables were found to be 6.00 g for Hizikia fusiformis powder, 100.00 g for butter, and 70.00 g for sugar against flour powder 200 g, which satisfies a target sensory score (7.0/9.0) according to the response surface method. Cookies with these optimal amounts of Hizikia fusiformis powder, butter, and sugar were tasted by 114 consumers and showed a high acceptability score (7.21). Females preferred the flavor of Hizikia fusiformis significantly more than males did (p<0.05). Older consumers (${\geq}30$ years old) scored significantly higher than younger consumers (${\leq}29$ years old) in texture (p<0.05). Spread ratio and hardness scores of Hizikia fusiformis cookies were lower than those of control cookies. Color analysis results of Hizikia fusiformis cookies were significantly lower in brightness and redness, and higher in yellowness than control cookies (p<0.01).

• Korean Journal of Remote Sensing
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• v.34 no.5
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• pp.787-799
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• 2018

Accurate and effective mapping is critical step to monitor the spatial distribution and change of flood inundated area in large scale flood event. In this study, we try to suggest methods to use low spatial resolution satellite optical imagery for flood mapping, which has high temporal resolution to cover wide geographical area several times per a day. We selected the Sebou watershed flood in Morocco that was occurred in early 2010, in which several hundred $km^2$ area of the Gharb lowland plain was inundated. MODIS daily surface reflectance product was used to detect the flooded area. The study area showed several distinct spectral patterns within the flooded area, which included pure turbid water and turbid water with vegetation. The flooded area was extracted by thresholding on selected band reflectance and water-related spectral indices. Accuracy of these flooding detection methods were assessed by the reference map obtained from Landsat-5 TM image and qualitative interpretation of the flood map derived. Over 90% of accuracies were obtained for three methods except for the NDWI threshold. Two spectral bands of SWIR and red were essential to detect the flooded area and the simple thresholding on these bands was effective to detect the flooded area. NIR band did not play important role to detect the flooded area while it was useful to separate the water-vegetation mixed flooded classes from the purely water surface.

• Steel and Composite Structures
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• v.34 no.5
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• pp.681-698
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• 2020

The paper addresses contribution to the modeling and optimization of major machinability parameters (cutting force, surface roughness, and tool wear) in finish dry hard turning (FDHT) for machinability evaluation of hardened AISI grade die steel D₃ with PVD-TiN coated (Al₂O₃-TiCN) mixed ceramic tool insert. The turning trials are performed based on Taguchi's L₁₈ orthogonal array design of experiments for the development of regression model as well as adequate model prediction by considering tool approach angle, nose radius, cutting speed, feed rate, and depth of cut as major machining parameters. The models or correlations are developed by employing multiple regression analysis (MRA). In addition, statistical technique (response surface methodology) followed by computational approaches (genetic algorithm and particle swarm optimization) have been employed for multiple response optimization. Thereafter, the effectiveness of proposed three (RSM, GA, PSO) optimization techniques are evaluated by confirmation test and subsequently the best optimization results have been used for estimation of energy consumption which includes savings of carbon footprint towards green machining and for tool life estimation followed by cost analysis to justify the economic feasibility of PVD-TiN coated Al₂O₃+TiCN mixed ceramic tool in FDHT operation. Finally, estimation of energy savings, economic analysis, and sustainability assessment are performed by employing carbon footprint analysis, Gilbert approach, and Pugh matrix, respectively. Novelty aspects, the present work: (i) contributes to practical industrial application of finish hard turning for the shaft and die makers to select the optimum cutting conditions in a range of hardness of 45-60 HRC, (ii) demonstrates the replacement of expensive, time-consuming conventional cylindrical grinding process and proposes the alternative of costlier CBN tool by utilizing ceramic tool in hard turning processes considering technological, economical and ecological aspects, which are helpful and efficient from industrial point of view, (iii) provides environment friendliness, cleaner production for machining of hardened steels, (iv) helps to improve the desirable machinability characteristics, and (v) serves as a knowledge for the development of a common language for sustainable manufacturing in both research field and industrial practice.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.6
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• pp.427-434
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• 2008

Processing of collagen from yellowfin tuna (Thunnus albacares) abdominal skins was optimized by response surface methodology and central composite design. The values of independent variables at optimal conditions were NaOH concentration: 0.5 N, NaOH treatment time: 36.2 hr, pepsin concentration: 1:4.9 ratio (0.245%, w/v), and digestion time: 48.1 hr, respectively. The collagen content estimated under optimal conditions was 33.1%, and the actual experimental collagen content was 32.3%. Physicochemical properties of collagen from yellowfin tuna abdominal skin were investigated by amino acids analysis, SDS-PAGE, FT-IR, viscosity and denaturation temperature. Amino acids content of the collagen was 21.0%. SDS-PAGE pattern of the collagen showed two different $\alpha$-chain (${\alpha}_1$- and ${\alpha}_2$- chain), $\beta$-component and $\gamma$-component. The spectrum of FT-IR of the collagen showed wavenumber at 3,434, 1,650, 1,542 and $1,235\;cm^{-1}$ representing the regions of amide A, I, II and III, respectively. Relative viscosity of the collagen decreased continuously on heating up to $32^{\circ}C$, and the rate of decrease was retarded in the temperature range of $35-50^{\circ}C$. Denaturation temperature (Td) of the collagen solution (0.06%, w/v) was $31^{\circ}C$ and was lower than calf skin collagen ($35^{\circ}C$).

• Food Science and Preservation
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• v.17 no.1
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• pp.66-71
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• 2010

In the Joseon Dynasty, various fruit teas were popularized to promote health, with spread of Donguibogam and Hyangyag gugeupbang. As interest in fruit tea has recently increased, studies on its manufacture have become necessary. We used response surface analysis for rediscovery and commercialization of grape tea. Major materials of traditional grape tea are grape juice, pear juice, ginger juice, and honey, and the sugar contents of these materials were 12.3, 14.1, 3.3 and 75 $^{\circ}Brix$, respectively. When sensory examinations were conducted with subjects aged 40-60 years, the difference between dilution ratios of 100% and 150% was not significant, but tea diluted by 150% showed somewhat higher scores than did tea diluted by 100%. Ginger taste and sweetness were found to have the greatest effect on overall acceptance. Regression analysis on color, flavor, taste, and overall acceptance values, with reference to ginger juice and honey as independent variables, revealed that the $R^2$ values were 0.8411, 0.6717, 0.9499, and 0.9015, respectively. Contour maps were superimposed to obtain an optimal combination of ingredients for traditional grape tea, and the indicated levels of ginger juice and honey were 0.46-0.69% and 3.85-5.20%, in combination with grape juice, pear juice, and water concentrations of 28%, 9% and 60% (all w/w), respectively. Thus, it is now possible to prepare traditional grape tea.