• 대한화학회지
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• 제42권4호
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• pp.432-442
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• 1998

$pH=-loga_H$ 정의에서 pH는 단일 이온의 활동도항을 포함하므로 단지 측정의 방법만으로는 결정되어질 수 없고 근사법을 필요로 한다. 근사법에 의한 pH 측정은 수소전극과 은/염화은 전극을 사용한 액간 접촉이 없는 cell의 기전력 측정으로부터 이루어지는 방법이며, 이 과정을 통해 pH 값이 인증된 pH의 일차 표준 물질을 얻을 수 있다. 일반적인 pH 미터와 전극을 검정하는 데에는 인증된 pH 값을 가지는 표준 완충용액을 사용하므로 표준 완충용액의 pH 값 정혹도는 실제 측정된 pH 값의 실효성을 제한할 수 있다. 본 연구에서는 정확한 pH의 측정을 위해서 pH 값을 인증할 수 있는 시스템을 구축하기 위한 제반의 연구를 수행하였으며, 이를 토대로 pH 1.6∼12.5의 범위에 해당하는 완충용액의 pH를 0.005 pH 단위 이내의 불확도로 인증하였다.

• Preventive Nutrition and Food Science
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• 제21권1호
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• pp.73-77
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• 2016

Flow and dynamic rheological properties of thickened waters prepared with commercial food thickeners were investigated at different pH levels (3, 4, 5, 6, and 7). The commercial xanthan gum (XG)-based thickener (thickener A) and starch-based thickener (thickener B), which have been commonly used in a domestic hospital and nursing home for patients with swallowing difficulty (dysphagia) in Korea, were selected in this study. Thickened samples with both thickeners at different pH levels showed high shear-thinning flow behaviors (n=0.08~0.22). Thickened samples at pH 3 showed higher n values and lower consistency index (K) values when compared to those at other pH levels. The K values of thickener A increased with an increase in pH level, while the n values decreased, showing that the flow properties greatly depended on pH. There were no noticeable changes in the K values of thickener B between pH 4 and 7. At pH 3, the thickened water with thickener A showed a higher storage modulus (G') value, while that with thickener B showed a lower G'. These rheological parameters exhibited differences in rheological behaviors between XG-based and starch-based thickeners, indicating that the rheological properties of thickened waters appear to be greatly influenced by the acidic condition and the type of food thickener. Appropriately selecting a commercial food thickener seems to be greatly important for the preparation of thickened acidic fluids with desirable rheological properties for safe swallowing.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1988년도 한국자동제어학술회의논문집(국내학술편); 한국전력공사연수원, 서울; 21-22 Oct. 1988
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• pp.476-481
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• 1988

In this paper a pH process of a weak acid with a strong base is modeled into a bilinear form, and a self-tuning pH control algorithm which is robust against initial values of solution and disturbances is presented. The control algorithm employs the recursive least square method for the parameter estimation and the generalised minimum variance criterion as the objective function. The computer simulation shows that the tracking of desired pH values is obtained in satisfactory manner regardless of the initial values chosen for the process.

• Asian-Australasian Journal of Animal Sciences
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• 제19권4호
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• pp.605-610
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• 2006

The objective of the present experiment was to determine the effects of slaughtering at different ages and the use of a commercial probiotic (115-Biogallinox) in broiler diets on the color properties of carcasses, during the first 24 h following slaughter. Ross 308 male broiler chickens obtained from a commercial hatchery were raised to either 35 or 42 days of age. Chickens were fed with different levels of probiotic ($P_0$: 0.0%, $P_1$: 0.1% and $P_2$: 0.2%) containing Saccharomyces cerevisiae during the experimental period. At the end of the trial all birds were slaughtered and then stored at $3^{\circ}C$ for 24 h. The pH and skin colour of carcasses were determined 1, 3, 7, 10, 13, 17 and 24 h after slaughter. Although the use of probiotic and post-mortem ageing time affected the pH (p<0.01), it was not affected by slaughter age (35 and 42 days) (p>0.05). The highest pH values occurred in carcasses of broilers fed 0.2% probiotic. The pH values of carcasses decreased with post-mortem ageing time (p<0.01). Main factors (treatment, slaughter age and post-mortem ageing time) had an effect on colour ($L^*$, $a^*$ and $b^*$) values (p<0.01). $L^*$ values of 42d-old slaughter and $P_2$ group were lower than those of 35d-old slaughter and other probiotic groups. The $a^*$ and $b^*$ values of 35d-old slaughter were lower than those of 42d-old slauhgter. The $a^*$ and $b^*$ values increased during post-mortem ageing (p<0.01). It was determined that changing of the colour traits of broiler carcasses was correlated with probiotic, pH and post-mortem ageing time. Also, it was observed that darkness of carcass colour increased as time progressed.

• 한국세라믹학회지
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• 제26권2호
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• pp.157-166
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• 1989

The effect of pH variation in starting solution on the characteristics of hydroxyapatite precipitates and powder prepared by the wet method was investigated. Hydroxyapatite precipitates was agglomerated, the average agglomerated particle size was decreased in the range from 2 to 6${\mu}{\textrm}{m}$ with increasing pH values in starting solution. The aspect ratio of rod-shaped hydroxyapatite particle was rapidly increased at pH 11 and 11.5. The maximum specific surface area, 91.1$m^2$/g, was at pH 10.5. Dried powder prepared at high pH values contained more minutes CO2 than that prepared at low pH values. The poor crystallinity was maintained up to $600^{\circ}C$ regardless of the pH values in starting solutions. However, the second phase or high crsytalline hydroxypatite phase appeared above 80$0^{\circ}C$. In pH 9.5 and pH 10, $\beta$-whitlockite transformed to $\alpha$-whitlockite at 120$0^{\circ}C$, while in pH 10.5-11.5, hydroxyapatite phase was maintained up to 120$0^{\circ}C$.

• 대한화학회지
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• 제11권4호
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• pp.179-184
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• 1967

pH 6.0~12.6 範圍에서 0.15M 타르타르酸鹽支持溶液 속에서의 Cd(II)플라로그람을 20$^{\circ}C 및 25$^{\circ}C에서 調査한 結果 pH 7.8 部分까지는 限界電流값 및 半波電位값이 一定하지만 같은 이온强度의 窒酸鹽支持溶液을 사용하였을 때에 비하여 半波電位값이 0.05 volt 負쪽으로 移行하고 있으며 限界電流값은 28% 감소되었다. pH 8.2 部分以上부터는 限界電流값이 急激하게 감소하다가 pH11.2~11.4 부근 以上부터 다시 急激히 증가하는 現象을 보여 주었다. 한편 pH 8.2 部分以上부터는 半波電位값은 pH증가에 따라 계속 負 쪽으로 移行하여 pH 12.6에서는 -0.78volt로 되었다. 可能한 電極反應機構를 假定하고 pH 9.4에 이르기 까지의 還元波變動의 原因을 檢討하였다.

• 한국해양학회지
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• 제1권1_2호
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• pp.1-6
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• 1966

A latitudinal, differential pH distribution is observed in the Northeastern Pacific Ocean with a pH range of 8.15 at high latitude (42 N) to 8.29 at low latitude (23 N). These pH values are generally greater than the calculated equilibrium pH with respect to atmospheric carbon dioxide. If we assume that the calculated equilibrium pH values ae valid, then the surface waters are undersaturated with respect to the atmospheric carbon dioxide during April to June 1966. A high surface pH value of about 8.26 was observed immediately south of the SubarcticBoundary zone near 170 W. This value differs from the equilibration pH by as much as 0.1 unit.

• 한국산림과학회지
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• 제86권1호
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• pp.56-68
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• 1997

본 연구는 산지 물순환 과정별 수질변화를 추적하여 계류수질의 형성 과정 및 산림의 환경적 정화기능을 평가하고자 실시하였다. 팔공, 용성 및 대동의 3개 조사지에서 한 단위강우에 대한 임외우, 수관통과우, 수간류, 낙엽층류 및 계류수, 그리고 장기 계류수를 대상으로 하여 각각의 유출수량과 pH, 전기전도도, 용존산소량 및 용존원소의 농도변화를 분석한 결과는 다음과 같다. 1. 계류수의 pH, 용존산소량은 유출수량의 증가에 따라 값이 상승하였으나, 전기전도도는 값이 낮아지는 것으로 나타났다. 2. 수간류 및 수관통과우의 pH는 임외우에 비해 경시적으로 낮은 값을 나타내며, EC는 강우초기에 높은 값, 그 이후는 강우시간의 경과와 함께 값이 낮아지는 경시적 변화를 보였다. 낙엽층류의 pH는 임외우에 비해 낮은 값, EC는 높은 값을 나타냈다. 계류수에 있어서 pH 동태는 강우초기에 높은 값을 나타내고 강우시간이 경과함에 따라 큰 폭으로 떨어지다가 강우종료 및 그 이후에는 초기 수준 또는 그 이상의 값으로 회복하였으나, EC는 거의 반대의 경향이 있었다. 낙엽층류 및 계류수의 DO는 강우시간의 경과에 따라 값이 점차 낮아졌으나, 임외우, 수간류 및 수관통과우에서는 경시적으로 뚜렷한 경향이 없었다. 3. 수간류 및 수관통과우에 있어서 pH는 소나무에 비해 상수리나무가 높았으나, EC는 낮은 값을 나타내었다. 양이온 총량은 상수리나무에 비해 소나무의 수간류에서 높은 값을 나타냈다. 4. 물순환의 각 과정에 있어서 pH는 낙엽층류<임내우(수간류+수관통과우)<임외우<계류수의 순으로, DO는 낙엽층류<임내우<임외강우<계류수, 그리고 EC는 임외우<계류수<임내우<낙엽층류의 크기 순으로 나타났다. 양이온 총량은 임외우<임내우<낙엽층<계류수의 크기 순으로 나타났다. 5. EC는 팔공조사지에 비해 용성조사지에서 전체적으로 높은 값을 나타내어 팔공계류수가 수질이 더 깨끗한 것으로 나타났다. 그리고 장기 계류수에 있어서 pH, DO, EC 및 양이온 총량은 월별로 각각 독특한 경시적 변화를 보였다.

• 한국농공학회지
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• 제44권6호
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• pp.99-105
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• 2002

A series of physical properties and rigid wall permeability tests were performed on two clays to investigate changes in permeability characteristics of clays with various pH values. Results of the study are as follows. As pH values were increased, coefficients of permeability of S-clay(clay fraction 18%) and J-clay(clay fraction 30%) were decreased in 3 and 4 times, respectively. Variation of coefficient of permeability of J-clay was considerably related to clay fraction. It can be said that coefficient of permeability of clays tested was increased, as pH values were decreased. This was because of increase in effective voids caused by decrease in thickness of diffused double layer, that is, change in soil structures and effective grain sizes.

• Bulletin of the Korean Chemical Society
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• 제17권10호
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• pp.925-929
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• 1996

Uranyl hydrolysis precipitates were obtained by increasing pH value of aqueous uranyl solution in the range of neutral to alkaline pH value and their phase transformation during the solubility experiment under various conditions has been examined. The precipitates formed in the hydrolysis reaction of uranyl ion had a layered structure such as a meta-schoepite phase, a schoepite structure, or a mixed phase of meta-schoepite and schoepite. Phase transformation between them was strongly dependent on the pH value at which the precipitate was formed. The distance between the layers in meta-schoepite or schoepite phase was ∼7.35 Å, and it was increased with the pH value at which the precipitate was synthesized as well as the pH values of the aqueous solution. The phase transformation from a meta-schoepite to schoepite was fast for the precipitates formed at low pH values, however, it was not the case for the precipitates formed at high pH values. A small difference of pH value in aqueous solution gave a great change on its solubilities near pH 9.7, because a layered structure of the precipitates became amorphous above that pH value. Greater solubility for the precipitate formed at higher pH value can be explained from the fact that the precipitates formed at low pH value had a better crystallinity and also that the precipitates formed at higher pH value has a slower rate of crystallization.