• 대한화학회지
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• 제6권2호
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• pp.113-116
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• 1962

In this study we have measured the activity coefficients of NaCl in solution by E.M.F. method, depending upon MacInnes' equation at 25 dog. The cell (electrodes) is same as MacInnes' except the cock which was designed by ourselves as figure 1.Additionally, we have calculated the hydration number of NaCl from the activity coefficients using Robinson's equation and ionic hydration number according to our new formula $\frac{n_M{^+}+0.8}{n_A{^-}-0.1}=n_{MA}$, which was mentioned our former thesis.We also have calculated the hydration number of some salts from the ionic hydration number using upper formula and have got reasonable series match with other's value.As the results of our studying, we conclude it as follow;1) Liquid junction potential depend only on the bulk concentration of the both solution.2) The formula $\frac{n_M{^+}+0.8}{{n_A{^-}}-0.1}=n_{MA}$ is reasonable one in deducing to ionic hydration number.3) From upper relation, we can calculate the hydration number of unknown salts from it's ionic hydration numbers.

• 대한화학회지
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• 제14권2호
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• pp.185-192
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• 1970

The extension of the theory of the electrolyte solution to the calculation of the hydration number and the mean activity coefficient of some 1:1 electrolytes in the concentrated solutions has been made. In this derivation, the hydration number has been calculated from the equation of the dielectric constant proposed by Hobbs, Jhon, and Eyring, and the mean activity coefficient from the theoretical formula developed by Jhon and Eyring. The agreement between theory and experiment over a.wide concentration range is quite satisfactory.

• Journal of Advanced Marine Engineering and Technology
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• 제31권1호
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• pp.51-57
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• 2007

In process of reinforced concrete (RC) box structure. the heat of hydration may cause serious thermal cracking. In order to eliminate hydration heat of mass concrete. this paper reports results of hydration heat control in mass concrete structure using the pulsating heat pipe. There were three RC box molds($1.2{\times}l.8{\times}2.4m^3$) which shows a difference as compared with each other. One was not equipped with pulsating heat pipe. The others were equipped with pulsating heat pipe. All of them were cooled with natural air convection. The pulsating heat pipe was composed of serpentine type copper pipe with 10 turns (outer diameter: 4mm. inner diameter: 2.8mm). The working fluid was R-22 and its charging ratio was 40% by volume. The conditions such as the number of turns. the length and the pitch of the pulsating heat pipe and the size of concrete structure were changed. Based on these experiments, it was confirmed that this construction method using pulsating heat pipe was effective to remove hydration heat of mass concrete structure and thus it was possible to prevent harmful thermal crack and construction Period and costs of concrete structure would be cut down.

• Computers and Concrete
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• 제8권6호
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• pp.647-675
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• 2011

Our ability to predict hydration behavior is becoming increasingly relevant to the concrete community as modelers begin to link material performance to the dynamics of material properties and chemistry. At early ages, the properties of concrete are changing rapidly due to chemical transformations that affect mechanical, thermal and transport responses of the composite. At later ages, the resulting, nano-, micro-, meso- and macroscopic structure generated by hydration will control the life-cycle performance of the material in the field. Ultimately, creep, shrinkage, chemical and physical durability, and all manner of mechanical response are linked to hydration. As a way to enable the modeling community to better understand hydration, a review of hydration models is presented offering insights into their mathematical origins and relationships one-to-the-other. The quest for a universal model begins in the 1920's and continues to the present, and is marked by a number of critical milestones. Unfortunately, the origins and physical interpretation of many of the most commonly used models have been lost in their overuse and the trail of citations that vaguely lead to the original manuscripts. To help restore some organization, models were sorted into four categories based primarily on their mathematical and theoretical basis: (1) mass continuity-based, (2) nucleation-based, (3) particle ensembles, and (4) complex multi-physical and simulation environments. This review provides a concise catalogue of models and in most cases enough detail to derive their mathematical form. Furthermore, classes of models are unified by linking them to their theoretical origins, thereby making their derivations and physical interpretations more transparent. Models are also used to fit experimental data so that their characteristics and ability to predict hydration calorimetry curves can be compared. A sort of evolutionary tree showing the progression of models is given along with some insights into the nature of future work yet needed to develop the next generation of cement hydration models.

• 대한화학회지
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• 제36권6호
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• pp.791-795
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• 1992

압력하에서 전해질을 구성하는 이온의 한계당량전도도를 구하는데 TATB법을 적용하였다. TATB법을 적용하여 구한 이온의 한계당량전도도와 물의 점성도로부터 고전적인 hydrodynamics에 기초를 둔 이온의 Stokes 반지름을 구하였다. Stokes 반지름으로부터 수화된 이온의 반지름을 구하기 위하여 Nightingale법을 사용하였으며, 이온의 보정된 반지름과 이온의 결정반지름으로부터 수화수를 구하였다. 압력이 증가함에 따라 이온의 수화수는 아주 작은량의 감소경향을 보이고 있으며 이러한 경향은 Horne의 pressure-induced dehydration으로 설명되었다. 본 연구의 결과를 Nakahara 등의 결과와 비교하여 보면, 본 연구에서 계산된 $K^+$와 $Cl^-$ 이온의 수화수는 Nakahara 등의 같은 이온들에 대한 수화수의 두배에 가까왔다. 그리고 Kollman 등의 결과와도 비교하여 보아 고압하에서 이온의 수화수를 구하는데 TATB법과 Nightingale법을 적용하여 비교적 좋은 결과를 얻을 수 있음을 알았다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2006년도 춘계학술논문 발표대회 제6권1호
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• pp.15-18
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• 2006

The test result of mat concrete applying both hydration heat difference and insulation curing method on new construction of Cheongju university educational building are summarized as following. Both fresh concrete and compressive strength properties were satisfied In aimed value. Setting time of concrete incorporating 15% of fly ash(FA) retarded 1.2 hour than control concrete. Temperature history of mali concrete indicated that the highest temperature of center was exhibited at $126^{\circ}C$ after 51 hours while the highest temperature of upper section was $10.6^{\circ}C$ after 46 hours. Temperature Difference between center and surface was managed at less than $6^{\circ}C$ during whole curing period. In addition the temperature of upper section secured more than $3.3^{\circ}C$ while the temperature of outside was indicated at less than $-10^{\circ}C$. Maturity by parts of construction secured more than $30^{\circ}C$ DD higher than outside at 3 days. The more number of times, applying insulation curing method by double bubble sheets, increased, the higher economic effect was secured. Overall it was clear that applying both double bubble sheets and hydration heat difference method on this new construction can resist hydration heat crack, early frost demage and strength decrease. It also significantly contributed quality improvement of cold weather concreting

• 한국수소및신에너지학회논문집
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• 제33권3호
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• pp.219-225
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• 2022

In this study, as one part of the studies on the mechanical properties of the polymer electrolyte membrane, a study was conducted on the change in the mechanical properties due to hydration before and after aging of the polymer electrolyte membrane. The mechanical properties of the polymer electrolyte membrane changes due to hydration were confirmed through tensile tests of hydrated and non-hydrated Nafion 117. As results of this study, non-hydrated membrane showed higher mechanical properties than hydrated thing in the elastic region and some plastic regions. But, it was confirmed that hydrated membrane exhibited higher mechanical properties than non-hydrated thing in the large plastic region. Hydrated membrane has a lower glass transition temperature than non-hydrated thing due to the role of water as a plasticizer. In addition, the number of ion aggregates decreases, but the size increases, and the hydrated Nafion 117 is thought to have different mechanical properties from that of the non-hydrated thing due to the characteristic that the internal attraction is strengthened.

• Structural Engineering and Mechanics
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• 제74권6호
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• pp.747-756
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• 2020

High-strength concrete (HSC) generally is made with high amount of cement which may release large amount of hydration heat at early age. The hydration heat will increase the internal temperature of slab and may cause potential cracking. In this study, slab specimens with a dimension of 600 × 600 × 100 mm were cast with concrete incorporating silica fume for test. The thermistors were embedded in the slabs therein to investigate the interior temperature development. The test variables include water-to-binder ratio (0.25, 0.35, 0.40), the cement replacement ratio of silica fume (RSF; 5 %, 10 %, 15 %) and fly ash (RFA; 10 %, 20 %, 30 %). Test results show that reducing the W/B ratio of HSC will enhance the temperature of first heat peak by hydration. The increase of W/B decrease the appearance time of second heat peak, but increase the corresponding maximum temperature. Increase the RSF or decrease the RFA may decrease the appearance time of second heat peak and increase the maximum central temperature of slab. HSC slab with the range of W/B ratio of 0.25 to 0.40 may occur cracking within 4 hours after casting. Reducing W/B may lead to intensive cracking damage, such as more crack number, and larger crack width and length.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.537-540
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• 2006

Over the past few decades, a considerable number of studies on the durability of concrete have been carried out extensively. A lot of improvements have been achieved especially in modeling of ionic flows. However, the majority of these researches have not dealt with the chloride binding isotherm based on the mechanism, although chloride binding capacity can significantly impact on the total service life of concrete under marine environment. The purpose of this study is to develop the model of chloride binding isotherm based on the individual mechanism. It is well known that chlorides ions in concrete can be present; free chlorides dissolved in the pore solution, chemical bound chlorides reacted with the hydration compounds of cement, and physical bound attracted to the surface of C-S-H grains. First, sub-model for water soluble chloride content is suggested as a function of pore solution and degree of saturation. Second, chemical model is suggested separately to estimate the response of binding capacity due to C-S-H and Friedel's salt. Finally, physical bound chloride content is estimated to consider a surface area of C-S-H nano-grains and the distance limited by the Van der Waals force. The new model of chloride binding isotherm suggested in this study is based on their intrinsic binding mechanisms and hydration reaction of concrete. Accordingly, it is possible to characterize chloride binding isotherm at the arbitrary stage of hydration time and arbitrary location from the surface of concrete. Comparative study with experimental data of published literature is accomplished to validity this model.

• 한국산학기술학회논문지
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• 제11권11호
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• pp.4455-4459
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• 2010

호호바오일 마사지가 건조피부에 미치는 효과를 알아보고자, 건조피부로 평가된 10명을 대상으로, 한쪽 팔에는 호호바오일 마사지를, 다른 쪽 팔에 아무것도 적용하지 않았다. 호호바오일 마사지 그룹은 호호바오일을 이용, 10분간의 팔 마사지를 주 2회로 총 8회 실시하였다. 실험 결과 호호바오일 마사지를 한 그룹은 유분과 수분의 함유량이 증가하였다. 특히, 마사지의 횟수가 증가 될수록 피부에서의 유 수분은 증가하는 것을 알 수 있었다(유분 : t=-7.470, p<0.001(팔안쪽)/t=-4.666, p<0.01(팔바깥쪽), 수분 :t=-3.966, p<0.01(팔안쪽)/t=-6.847, p<0.001(팔바깥쪽). 따라서 호호바오일 마사지는 건조피부를 개선시키는 효과가 있는 것으로 확인되었다.