• 한국과학교육학회지
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• 제30권7호
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• pp.920-932
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• 2010

Many topics in science, especially, abstract concepts, relationships, properties, entities in invisible ranges, are described in mathematical representations such as formula, numbers, symbols, and graphs. Although the mathematical representation is an essential tool to better understand scientific phenomena, the mathematical element is pointed out as a reason for learning difficulty and losing interests in science. In order to further investigate the relationship between mathematics knowledge and science understanding, the current study examined 793 high school students' understanding of the pH value. As a measure of the molar concentration of hydrogen ions in the solution, the pH value is an appropriate example to explore what a student mathematical structure of logarithm is and how they interpret the proportional relationship of numbers for scientific explanation. To the end, students were asked to write their responses on a questionnaire that is composed of nine content domain questions and four affective domain questions. Data analysis of this study provides information for the relationship between student understanding of the pH value and related mathematics knowledge.

• International Journal of Industrial Entomology and Biomaterials
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• 제35권2호
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• pp.111-117
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• 2017

Mulberry leaves containing 1-deoxynojirimycin (DNJ) known to be a strong inhibitory effect for ${\alpha}-glucosidase$. Thus, DNJ has been recognized as a potentially important source for prevent or treat hyperglycemia. More effective method for the DNJ high-production is needed because DNJ content of natural mulberry leaf are as low as 0.1%. Many researchers have studied for the DNJ high-production in mulberry leaves such as the harvest season, fermentation using microorganisms, optimal culture conditions, and optimal extraction conditions. In order to provide for useful data that is anticipated at the level of industrial scale, we investigated ${\alpha}-glucosidase$ inhibitory activity, pH value and DNJ content in large-scale based on the optimal culture conditions for mulberry leaf fermentation of small-scale in our previous study. The ${\alpha}-glucosidase$ inhibitory activity, pH value, and DNJ content in this study were measured from the mulberry leaf fermentation broth for 7 days. During mulberry leaf fermentation, the ${\alpha}-glucosidase$ inhibitory activity and DNJ content was increased until 2 to 4 days, but after 4 day was decreased. The pH value showed a decreasing trend up to 2 day, and little changes in 2 to 4 days. However, the pH was started to increase after 4 days.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.33.1-33.1
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• 2018

pH is expressed mathematically as $pH=-{\log}[H^+]$, is a measure of the hydrogen ion concentration, [$H^+$] to specify the acidity or basicity of an aqueous solution. The pH scale usually ranges from 0 to 14. Every aqueous solution can be measured to determine its pH value. The pH values below 7.0 express the acidity, above 7.0 are alkalinity and pH 7.0 is a neutral solution. The solution pH can be determined by indicator or by measurement using pH sensor, which measuring the voltage generated between a glass electrode and a reference electrode according to the Nernst Equation. The pH value of solutions depends on the temperature and the activity of contained ions. In nickel electroless plating process, the controlled pH value in some limited ranges are extremely important to achieve optimal deposition rate, phosphorus content as well as solution stability. Basically, nickel electroless plating solution contains of $Ni^{2+}ions$, reducing agent, buffer and complexing agents. The plating processes are normally carried out at $82-92^{\circ}C$. However, the change of its pH values with temperatures does not follow any rule. Thus, the purpose of study is to understand the relationship between pH and temperature of some based solutions and electroless nickel plating solutions. The change of pH with changing temperatures is explained by view of the thermal dynamic and the practical measurements.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1989년도 한국자동제어학술회의논문집; Seoul, Korea; 27-28 Oct. 1989
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• pp.337-342
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• 1989

The control of a pH value in radwaste treatment process is difficult due to the nonlinearity of the titration curve and its strong sensivity to disturbances. This paper describes an adaptive control strategy which is model-based and allows for direct use of available measurements. This algorithm forces the nonlinear process to follow a desired linear system trajectory, and were applied to the control of a simulated pilot-scale pH process. The simulation study showed that it has the potential advantage over the transformation methods that control effort saturation can be accomodated readily.

• Journal of Animal Science and Technology
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• 제45권5호
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• pp.835-840
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• 2003

NPPC 육색기준에 의한 PSE육과 정상육의 pH$_1$ 및 pH$_{u}$ 특성은 기준 전구간에서 유의한 차이가(p〈0.05)가 있었으며 중증 PSE, 경증 PSE, 정상육 및 경증 DFD 순으로 낮게 나타났으나, pH$_3$와 pH$_6$는 중증 PSE에서 정상육의 구간에서는 유의한 차이가 없었고 경중 DFD에서만 유의차(p〈0.05)가 있었다. 따라서 NPPC 육색기준에 의한 pH특성은 pH 측정시간에 따라 달라지는 것으로 사료되었다. CIE L$^{*}$은 중증 PSE에서 경증 DFD로 변화함에 따라 낮아지는 경향을 나타내었으며 측정부위에 관계없이 NPPC기준 전구간에서 유의차(p〈0.05)가 있었다. CIE a$^{*}$값은 제4~5늑골 직상부의 LD 근육절단면에서는 중증, 경증 PSE, 정상육과 경증 DFD간에는 유의한 차이(p<0.05)가 있으나 마지막 요추부위 절단면에서는 전구간에서 차이가 없었다. CIE b$^{*}$값은 제4~5늑골 직상부에서는 중증, 경증 PSE, 정상육과 경증 DFD 간에 유의한(p〈0.05) 결과를 나타내었다. 마지막 요추에서는 중증 PSE와 정상육 및 경증 DFD에서 유의차(p〈0.05)가 있어 측정위치에 따라 색차값의 특징이 달랐다. 보수성 및 가열감량은 NPPC 기준 전 구간에서 유의차(p〈0.05)가 있었다. 관능특성 중 다즙성은 중.경증 PSE와 정상육, 경증 DFD에서 유의한(p〈0.05) 차이가 있었고 연도와 향미에서는 차이가 없었다. NPPC 육색기준과 CIE L$^{*}$, 보수성, Cu 및 pH$^{u}$와의 단순회귀 상관계수(R$^2$)는 각각 0.77, 0.66, 0.59 및 0.54였다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권6호
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• pp.371-374
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• 2002

Production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)［P(3HB/V)］, by fed-batch culture of recombinant Escherichia coli harboring a plasmid containing the Alcaligenes latus polyhy-droxyalkanoate (PHA) biosynthesis genes, was examined in two pilot-scale fermentors with air supply only, In a 30 L fermentor having a XLa value of 0.11 S­$^1$, the final P(3HB/V) concentration and the P(3HB/V) content obtained were 29.6 g/L and 70.1 wt%, respectively giving a productivity of 1.37 g P(3HB/V)/L-h. In a 300 L fermentor having a XLa of 0.03 S­$^1$, the P(3HB/V) concentration and the P(3HB/V) content were 20.4 g/L and 69 wt%, respectively giving a productivity of 1.06g P(3HB/V)/L-h. These results suggest that economical production of P(3HB/V) is possible by fed-batch culture of recombinant E. coli in a large-scale fermentor having low KLa value.

• 멤브레인
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• 제2권2호
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• pp.122-128
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• 1992

여러 크기의 이중실관 생물 반응기에서의 Aspergillus niger(KCTC 1232)를 이용한 구연산 생산 실험을 수행하였다. 초종 세포농도는 세포 성장구간 기준으로 300g/l에 달하였다. 공기와 산소의 공급 조건하에서의 단위 용적당의 생산성은 각각 0.63, 0.02g/l.h였고 이는 회분식 발효에 대해 10, 16배 증가한 결과이다. 공급배지의 초기 pH는 구연산의 생산에 중요한 요소이며 pH가 낮을수록 높은 구연산 생산수율을 얻을 수 있었다. Scale-up의 가능성을 알아보기 위해 반응기 unit와 배지의 공급속도를 변화시킨 결과 반응기 unit와 배지 공급속도의 증가는 기질의 높은 소비속도로 인해 생산성의 증가를 가져왔다.

• Advances in environmental research
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• 제5권3호
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• pp.189-200
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• 2016

This study aimed at advanced oxidation of hetero tri-functional reactive dye Acid orange 7 using photo-Fenton conditions in a lab-scale experiment. Decolourisation of Acid Orange 7 dye by Fenton's process was dependent on concentration of Hydrogen peroxide, Ferrous sulphate, pH, and contact time. A $2^3$ factorial design was used to evaluate the effects of these key factors: pH, Fe(II), and $H_2O_2$ concentration, for a dye concentration of 50 mg/L with COD of 340 mg/L at pH 3.0. The response function was removal of colour under optimised conditions; pH 3.0, [Fe(II)] 40.83 mg/L, [$H_2O_2$] 4.97 mmol/L; 13.6 min. of treatment resulting in 100% colour removal. The final COD of treated wastewater was nil suggesting that AOP is a potentially useful process of color removal and dye degradation/mineralisation of effluent having AO7. Minimum contact time for complete decolourisation was at 5 mmol/l $H_2O_2$ concentration. Increase in $FeSO_4$ (mg/l) concentration resulted in decrease of time for complete decolourisation. Box-Behnken Design was used to optimize the process variables. Maximum and minimum levels of pH (3-5), $H_2O_2$ (4-6 mmol/l), $FeSO_4$ (30-46 mg/l) and contact time (5-15 minutes) were used. The statistical analysis revealed a value of 0.88 for coefficient of regression ($R^2$) indicating a good fit of model. Calculated F-value was found higher than the tabulated value confirming to significance of the model. Based on student's t-test, Ferrous sulphate, pH, and contact time have a positive effect on the percent decolourisation of Acid Orange 7.

• Membrane and Water Treatment
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• 제6권1호
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• pp.43-52
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• 2015

A small-scale electro-dialysis system was constructed for domestic use. It is composed of six compartments in which five special polystyrene ionic membranes are housed. A series of experiments on the transport of sodium and chloride ions through polystyrene membranes was performed and the effects of electric current and voltage on the pH of water were investigated. This electrodialyser could reduce the NaCl content to an acceptable level (5307 mg/L) when water containing 9945 mg/L of sodium chloride is fed to the electrodialyser. The reduction was by the action of direct current 60 mA/100 mA when a 15 V / 20 V potential is maintained across the membrane. The results showed that the pH of the treated water attained a value in the range of 7-8, with the chloride concentration of 5307 mg/L when the voltage was in the range of 20 volts. This was achieved when two of the small-scale electro-dialysers were placed in series and the solutions from the respective compartments were mixed. This is considered useful because this complies to the requirement of drinking water standard both in terms of chloride and pH. Therefore, this type electrodialyserhas the potential for domestic uses in isolated houses where potable water supply is not available.

• KSBB Journal
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• 제7권1호
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• pp.79-83
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• 1992

Erwinia rhapontici를 Ca-alginate에 고정화시켜 고정화 세포의 반응특성을 고찰하고, STR, PBR을 이용하여 Palatinose의 생산을 검토하였다. Free cell과 고정화 세포의 반응최적 pH는 5.5-6.0, 반응 최적온도는$30-35^{\circ}C$로 동일하였으나 고정화에 의해 pH 및 온도 범위가 보다 넓어졌고, 이때 Free cell및 고정화 세포의 겉보기 Km갑슨 각각 0.13, 0.28M이었다. STR을 이용한 Palatonose 생산시 고정화 세포의 반감기는 약 380 시간으로 낮았으나, PBR을 통해 30일까지 안정운전이 가능하였다. PBR 운전시의 운전온도 30, $33^{\circ}C$에서 Palatinose수율 및 고정화 세포의 안정성은 거의 동일한 결과를 나타내었으며 이때 PBR생산성은 약 120g/l$\cdot$h이었고, Pilot scale인 50L 까지 성공적으로 Scale up 되었다.