• Journal of the Korean Chemical Society
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• v.25 no.4
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• pp.214-218
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• 1981

Kinetic studies were carried out on urethane polymerization reaction of hydroxyl-terminated polybutadiene with isophorone diisocyanate under presence of Hexogen as solid additive. The rate was found to increase with the amount of Hexogen added. However the rate acceleration was not a catalytic effect but solely due to an increase of activation entropy. The reaction was a good 2nd order process with nearly constant activation energy of 8.4 kcal/mole.

• Journal of the Korean Chemical Society
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• v.15 no.6
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• pp.352-358
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• 1971

The interaction between dimethylsulfoxide molecules and some organic molecules, i.e.nitrobenzene, m-dinitrobenzene, o-dinitrobenzene, 1,3,5-trinitrobenzene, m-xylene, mesitylene, bibenzyl, biphenyl, o-phenanthrene, naphthalene, has been studied. The organic molecules exhibit negative deviation from Raoult's law due to the formation of the charge transfer complexes with dimethylsulfoxide. The stability constants of the complexes were determined spectrophotometrically, and also some thermodynamic functions were calculated. The binding energies of the complexes appear in the range of -1 ∼ -4 kcal/mole. The stability depends on the polarity and basicity of the solvent used.

• Journal of the Korean Chemical Society
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• v.29 no.1
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• pp.3-8
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• 1985

Molecular electronegativity (EN) values are calculated employing the density functional definition of EN: the negative of the chemical potential in the density functional theory. Calculations are limited to the use of valence electrons (valence electron approximation). Our formula for the EN is given in terms of Hartree-Fock(HF) orbital energies. Resulting EN values for molecules as well as atoms exhibit a remarkable correlation with other existing scales. For molecules, we have achieved electronegativity equalization principle (Sanderson's principle).

• Journal of the Korean Chemical Society
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• v.54 no.3
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• pp.338-349
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• 2010

This study compared the instruction effectiveness between experiments of precipitation and a ball & stick model related to the 'Law of Definite Proportions' of 9th grade science in this study. The subjects were 250 students in the 9th grade. They were divided into two groups, an experimental group and a model group. The results showed that the ratio of thought in which the elements were divided in the solutions and the ratio of thought in which a new compound was created when the two solutions were mixed were higher in the precipitation experiment group than in the model group. The two groups were not different in terms of the ratio of thought related to the reason for the creation of the precipitate. The ratio of thought pertaining to incorrect answers was high, implying that the two strategies were not effective in correcting students' thoughts. However, the ratio of finding patterns from the measuring data in the model group was higher than in the experimental group. However, the ratios of 'definite proportions' inference in the bonding of the reactants were similar in the two groups. From these data, we concluded that the inference of the 'Law of definite proportion' from experiments or models was not suitable for middle school students.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.116.2-116.2
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• 2013

최근 그래핀, hexagonal boron nitride (h-BN) 및 $MoS_2$ (molybdenum disulfide)와 같은 2차원 결정 물질들은 무어의 법칙 (Moore's Law)를 뛰어넘어 계속적인 소자의 소형화를 가능케 하고 또한 대면적, 저비용 소자 개발을 가능케 하는 우수한 특성을 가진 차세대 반도체 트랜지스터 소재로 각광받고 있다. $MoS_2$는 bulk 상태일 때는 1.2 eV의 indirect 밴드갭을 가지지만 단층형태일 때는 1.8 eV의 direct 밴드갭을 가지며 dielectric screening 기법 등을 통해 mobility를 향상시킬 수 있는 것으로 연구된 바 있다. 본 연구에서는 화학기상증착(chemical vapor deposition, CVD)법을 이용하여 $MoS_2$박막을 형성하기 위한 기초연구인 Mo전구체의 특성 평가 및 적합한 공정조건 개발 연구를 수행하였다. 사용한 전구체는 $Mo(CO)^6$ (Molybdenum hexacarbonyl)이고, 온도 및 압력, 반응기체($H_2S$, Hydrogen sulfide) 유량 등의 공정 조건 변화에 따른 거동을 Fourier transform infrared spectroscopy (FT-IR) 시스템을 사용하여 측정하였다. 또한 $Mo(CO)^6$의 분자구조를 상용 프로그램인 Gaussian으로 시뮬레이션 하여 실제 FT-IR 측정 결과값과 비교 분석하였다. 화학기상증착법을 이용한 $MoS_2$ 증착조건 최적화를 위하여 다양한 온도, 유량, 압력, 및 기판 종류에 대하여 증착 실험을 수행하였으며, 증착된 샘플은 scanning electron microscope (SEM), Raman spectroscopy를 이용하여 분석하였다.

• Journal of The Korean Association For Science Education
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• v.18 no.3
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• pp.337-345
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• 1998

This study examined the influences of computer-assisted instruction(CAl) upon high school students' conceptual understanding, algorithmic problem solving ability, learning motivation, and attitudes toward chemistry instruction. CAl programs were designed to supply animated molecular motions for emphasizing the particulate dynamic nature of matter and immediate feedbacks according to students' response types at each stage of four stage problem-solving strategy(understanding, planning, solving, and reviewing). The CAl and control groups (2 classes) were selected from a girls high school in Seoul, and taught about gas law for four class hours. Data analysis indicated that the students at the CAl group scored significantly higher than those at the control group in the tests on conceptual understanding and algorithmic problem solving ability. In addition, the students at the CAl group performed significantly better in the tests on the learning motivation and attitudes toward chemistry instruction.

• Clean Technology
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• v.26 no.3
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• pp.161-167
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• 2020

For the design of the prevention and mitigation measures in process industries involving flammable substances, reliable safety data are required. An important property used to estimate the risk of fire and explosion for a flammable liquid is the flash point. Flammability is an important factor to consider when developing safe methods for storing and handling solids and liquids. In this study, the flash point data were measured for the binary systems {2-butanol + 2,2,4-trimethylpentane}, {2-butanol + methylcyclohexane} and {2-butanol + toluene} at 101.3 kPa. Experiments were performed according to the standard test method (ASTM D 3278) using a Stanhope-Seta closed cup flash point tester. A minimum flash point behavior was observed in the binary systems as in the many cases for the hydrocarbon and alcohol mixture that were observed. The measured flash points were compared with the predicted values calculated via the following activity coefficient (GE) models: Wilson, Non-Random Two-Liquid (NRTL), and UNIversal QUAsiChemical (UNIQUAC) models. The predicted data were only adequate for the data determined by the closed-cup test method and may not be appropriate for the data obtained from the open-cup test method because of its deviation from the vapor liquid equilibrium. The predicted results of this work can be used to design safe petrochemical processes, such as the identification of safe storage conditions for non-ideal solutions containing flammable components.

• Journal of the Korean Chemical Society
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• v.50 no.6
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• pp.477-485
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• 2006

study investigated the influences of the forms of verbal external representations and students' verbal learning style in learning chemical concepts with drawing as a method to assist students in connecting and integrating multiple external representations. Seventh graders (N=133) at a coed middle school were assigned to formal drawing (FD) and personalized drawing (PD) groups. Students in the PD group were provided words at personalized style as verbal external representations for drawing, while those in the FD group were provided words at formal style. All students were taught about Boyles Law and Charless Law for two class hours. Results revealed that the scores of a conception test for the PD group were significantly higher than those for the FD group. In a situational interest test, students with strong verbal learning style preference scored significantly higher than students with weak verbal learning style preference in the two groups. Most PD group students were found to prefer to read verbal external representations at personalized style for drawing rather than at formal style, and perceived their activities positively upon cognitive, affective and motivational aspects. Students with strong verbal learning style preference had more positive perceptions about their activities than students with weak verbal learning style preference especially upon affective and motivational aspects.

• Communications of Mathematical Education
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• v.25 no.3
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• pp.497-524
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• 2011

This study was to understand students' learning about the function of math combined with molecular motions of science using the block scheduling. It was based on the revised Class Structure Model of Lee et al.(2010) where MBL as a tool was used to increase students' participation and understanding in the integrated concepts. The researcher provided the 6th grade students who lived in Sung Nam-Si, Kyung Gi-Do with 8 unit lessons, consisting of 5 stages of CSM. As a result of the study, the integrated education of Mathematics and Science showed synergic effect in studying both subjects and brought a positive result in gradual mathematization. It may be hard to combine all the contents of mathematics and science together. However, learning the relation between volume and pressure, and between volume and temperature of gas used as an example of function shown in our daily life was appropriate through Fogarty's integrated education model because it supported the objective of both subjects. Also, it was a good idea to develop CSM because it was composed of the contents from both subjects held in the same period of a year. Through the five stages, students were able to establish and generalize the definitions and the concepts of function.

• Journal of the Korean Chemical Society
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• v.67 no.5
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• pp.378-392
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• 2023

The purpose of this study is to analyze the pre-service chemistry teachers' cognition of the nature of model in process of designing and developing models using technology. For this purpose, 19 pre-service chemistry teachers' in the 3rd grade of a education college located in the central region observe experimental phenomena related to Boyle's law presented in the 7th grade science textbook and researchers required the design and development of a model related to the observed experimental results using technology. Based on previous studies, the nature of model were classified into two aspect: 'Representational aspect' and 'Explanatory aspect'. The 'Representational aspect' was classified into 'Representation', 'Abstraction', and 'Simplification', and the 'Explanatory aspect' was classified into 'Analysis', 'Interpretation', 'Reasoning', 'Explanation', and 'Quantification'. The pre-service chemistry teachers' cognition were analyzed by the classification. As a result of the study, the 'Representation' of the 'expressive aspect' was uniformized in the form of space that changes in volume, and the pressure was expressed as the Brightness inside the cylinder or frequency of color change of particles for 'Abstraction'. In the case of 'Simplification', the particle collision was expressed as a perfectly elastic collision, but there was a group that could not simply indicate the type of particle. In the 'Explanatory aspect', in the case of 'Analysis', volume was classified as a manipulated variable, and in the case of 'Interpretation', most groups analyzed the change in pressure through the collision of gas particles. However, the cognition involved in 'Reasoning' was not observed much. In the case of 'Explanation', there were groups that did not succeed in explanation because the area where the particles collided was not set or incorrectly set, and in the case of 'Quantification', there was a group that formulated the number of collisions per unit time, and on the contrary, there was a group that could not quantify the number of collisions because they could not be expressed in numbers.