• Title/Summary/Keyword: base reactions

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Effects of infill walls on RC buildings under time history loading using genetic programming and neuro-fuzzy

  • Kose, M. Metin;Kayadelen, Cafer
    • Structural Engineering and Mechanics
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    • v.47 no.3
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    • pp.401-419
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    • 2013
  • In this study, the efficiency of adaptive neuro-fuzzy inference system (ANFIS) and genetic expression programming (GEP) in predicting the effects of infill walls on base reactions and roof drift of reinforced concrete frames were investigated. Current standards generally consider weight and fundamental period of structures in predicting base reactions and roof drift of structures by neglecting numbers of floors, bays, shear walls and infilled bays. Number of stories, number of bays in x and y directions, ratio of shear wall areas to the floor area, ratio of bays with infilled walls to total number bays and existence of open story were selected as parameters in GEP and ANFIS modeling. GEP and ANFIS have been widely used as alternative approaches to model complex systems. The effects of these parameters on base reactions and roof drift of RC frames were studied using 3D finite element method on 216 building models. Results obtained from 3D FEM models were used to in training and testing ANFIS and GEP models. In ANFIS and GEP models, number of floors, number of bays, ratio of shear walls and ratio of infilled bays were selected as input parameters, and base reactions and roof drifts were selected as output parameters. Results showed that the ANFIS and GEP models are capable of accurately predicting the base reactions and roof drifts of RC frames used in the training and testing phase of the study. The GEP model results better prediction compared to ANFIS model.

Lack of Sub-microscopic Representation Ability of 12th Grade Science Students in Various Acid and Base Problem Solving Processes (다양한 산·염기 문제해결과정에서 드러난 고등학교 3학년 이과 학생들의 준미시적 표상화 능력의 결여)

  • Park, Chul-Yong;Won, Jeong-Ae;Kim, Sungki;Choi, Hee;Paik, Seoung-Hey
    • Journal of the Korean Chemical Society
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    • v.64 no.1
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    • pp.30-37
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    • 2020
  • The purpose of this study was to identify the problems faced by students in sub-microscopic representation of acid-base reactions. Herein, we selected 30 students of 12th grade science classes, who had studied various acid-base models. In order to investigate the sub-microscopic representation ability of the students, we developed nine items related to various contexts, such as one type of solute and solvent, two types of solutes and solvent, cases with water as solvent or with nonaqueous solvents. For all items, we consistently observed lack of concept of chemical change. In context of aqueous and nonaqueous solutions, the frequency of lack of concept of chemical bonding was high if ammonia was the solute or solvent. Moreover, the frequency of lack of concept related to the degree of electrolytic dissociation was high. Therefore, chemistry teachers should understand that students' ability to sub-microscopic representation of acid-base reactions can be enhanced by analyzing the difficulties faced by the students in solving diverse acid-base problems.

Tailoring Molecular Precursors for Multicomponent Oxides

  • Hubert-Pfalzgraf, Liliane G.
    • The Korean Journal of Ceramics
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    • v.6 no.4
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    • pp.370-379
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    • 2000
  • Simple ways to build up mixed-metal molecules which can act as potential single-source precursors to multimetallic oxides are reviewed. Emphasis is given to Lewis acid-base reactions between metal alkoxides M(OR)/sub n/, and between metal alkoxides and more accessible oxide precursors, carboxylates M(O₂CR)/sub n/ and β-diketonates M(β-dik)/sub n/. Characterization of the precursors is achieved in the solid state (single crystal X-ray diffraction, FT-IR) and by multinuclear NMR in solution. The reactions proceed toward the formation of aggregates in which the different metals display their usual coordinations numbers, often six for transition metals, as shown. Strategies for fixing the stoichiometry between the metals are developed. The reactivity of the MM species (dissociation, effects of chemical modifiers, of other metallic species, hydrolytic or non-hydrolytic condensation, etc.) will be indicated. Transformations into oxides are illustrated on precursors for titanates or niobates.

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Synthesis and Fluorescence Properties of New Rhodamine 6G Derivarives Containing Hydroxy Coumarin Moiety (새로운 로다민 6G 하이드록시 쿠마린 유도체의 합성과 형광특성)

  • Park, Seong Ho;Chang, Seung Hyun
    • Journal of Environmental Science International
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    • v.25 no.9
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    • pp.1283-1288
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    • 2016
  • In this study, we synthesized fluorescent sensors from rhodamine 6G derivatives and hydroxy coumarin. The synthetic routes to the rhodamine 6G derivatives containing hydroxy coumarin are shown in Fig. 1. Two derivatives were synthesized through Schiff base reactions. The structures of the new compounds were confirmed by melting point, $^1H$-NMR, and GC-MS analyses. The compounds were found to selectively bind to tin ($Sn^{2+}$) ion by fluorescence titration using various metal cations. Longer carbon chains gave more sensitivity. $Sn^{2+}$ ions exhibited the strongest fluorescence among the nime ions. The binding analysis using Job plots suggested that compounds form 1:1 complexes with the $Sn^{2+}$ ions.

Acid-base Reaction (산-염기 반응)

  • Lee, Man-Seung
    • Resources Recycling
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    • v.27 no.5
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    • pp.3-8
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    • 2018
  • Acid-base reaction together with oxidation-reduction reaction is an important reaction occurring in the aqueous phase. The definition by Lewis on the acid and base is more comprehensive than several definitions. HSAB theory has been introduced to consider the difference in the reactivity among the acids/bases. In this paper, several acid-base reactions were analyzed by applying the definition of acid and base. Moreover, the background of the introduction of HSAB and its application was explained.

Intercalation of Primary Diamines in the Layered Perovskite Oxides, $HSr_2Nb_3o_{10}$

  • 홍영식;김시중
    • Bulletin of the Korean Chemical Society
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    • v.17 no.8
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    • pp.730-735
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    • 1996
  • The layered perovskite oxide, KSr2Nb3O10, was synthesized. The interlayer potassium cations were readily exchanged by protons in hydrochloric acid solution to give the protonation compound, HSr2Nb3O10·0.5H2O. The intercalation compounds, [NH3(CH2)nNH3]xSr2Nb3O10, were also obtained by acid-base reactions between the protonation compound and organic bases, 1,n-alkyldiamines. The interlayer distances in the intercalation compounds were linearly increased with the increase of the number of carbon (Δc/Δn=1.05 Å) in 1,n-alkyldiamines. The intercalated alkyldiammonium ions formed a paraffin-like monolayer with average tilting angle (θ) of ca. 56°. The intercalation reactions occurred stoichiometrically. The thermal decomposition process of the intercalation compounds showed distinct three steps due to the desorption of hydrated water, the decomposition of organic moiety, and the decomposition of Sr-related compounds.

Natural time period equations for moment resisting reinforced concrete structures comprising hollow sections

  • Prajapati, Satya Sundar;Far, Harry;Aghayarzadeh, Mehdi
    • Computers and Concrete
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    • v.26 no.4
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    • pp.317-325
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    • 2020
  • A precise estimation of the natural time period of buildings improves design quality, causes a significant reduction of the buildings' weight, and eventually leads to a cost-effective design. In this study, in order to optimise the reinforced concrete frames design, some symmetrical and unsymmetrical buildings composed of solid and hollow members have been simulated using finite element software SAP 2000. In numerical models, different parameters such as overturning moment, story drift, deflection, base reactions, and stiffness of the buildings were investigated and the results have been compared with strength and serviceability limit criteria proposed by Australian Standard (AS 3600 2018). Comparing the results of the numerical modelling with existing standards and performing a cost analysis proved the merits of hollow box sections compared to solid sections. Finally, based on numerical simulation results, two equations for natural time period of moment resisting reinforced concrete buildings have been presented. Both derived equations reflected higher degree of correlation and reliability with different complexities of building when compared with existing standards and relationships provided by other scholars. Therefore, these equations will assist practicing engineers to predict elastic behaivour of structures more precisely.

Analysis of Curriculum and Textbooks of Chemistry I and Survey of Chemistry Education Major Teachers' Conceptions Related to Electron Movement Model and Oxidation Number Change Model (전자 이동 모델과 산화수 변화 모델에 대한 화학 I 교육과정과 교과서 분석 및 화학교육전공 교사들의 인식 조사)

  • Kim, Kihyang;Paik, Seoung-Hey
    • Journal of the Korean Chemical Society
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    • v.61 no.4
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    • pp.204-210
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    • 2017
  • In this study, we analyzed the descriptions of the electron movement model and the oxidation number change model presented in the 2009 revised curriculum and textbooks. We also investigated chemistry education major teachers' conceptions of limitations of each model. The electron movement model and oxidation number change model were presented in the curriculum and the textbooks. However, hybrid model was also presented which fail to grasp the limitation of each model. The hybrid model explains redox reactions of covalent bond compounds by electron movement model or even if it explains redox reactions by oxidation number change model, this explanations have the problem of confusing the virtual electron movement with the actual electron movement. A questionnaire and interviews were conducted to investigate chemistry education major teachers' perceptions of redox reactions. As results, many teachers did not recognize the limitations of each model and had difficulties to distinguish redox reactions from acid-base reactions because of the hybrid model.

Analysis of Chemistry Teachers' Cognitive level related to Two Types of Acid-Base Models based on Epistemological and Ontological viewpoint (인식론 및 존재론적 관점에서 두 유형의 산·염기 모델에 대한 화학 교사들의 인지 수준 분석)

  • Lyu, Eun-Ju;Paik, Seoung-Hey
    • Journal of the Korean Chemical Society
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    • v.64 no.5
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    • pp.267-276
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    • 2020
  • This study analyzed the level of chemistry teachers' cognition related to two types of acid-base models taught in secondary schools. For the purpose, a questionnaire was developed to identify teachers' cognitions based on previous studies that analyzed the 'Ignorance' of each model. The questionnaire consisted of two items, one related to acid and base reactions and one related to acid and base dissociation, which suggested inconsistencies between the two models. The subjects were 15 chemistry teachers, and as a result, teachers' cognitions were analyzed at four levels. The four levels are: if they don't know the two models, if they only understand one model, if they understand the two models, and perceived the 'Ignorance' of one model, and if they understand the two models and perceived the 'Ignorance' of the two models. The largest proportion of teachers understood the two models and perceived the 'Ignorance' of one model. However, the proportion of understanding the two models and perceiving the 'Ignorance' of the two models was very small. Through this, we argued that efforts to increase the level of chemistry teachers' cognition of the model and 'Ignorance' were necessary.

Injectable hydrogels delivering therapeutic agents for disease treatment and tissue engineering

  • Lee, Jin Hyun
    • Biomaterials Research
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    • v.22 no.4
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    • pp.235-248
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    • 2018
  • Background: Injectable hydrogels have been extensively researched for the use as scaffolds or as carriers of therapeutic agents such as drugs, cells, proteins, and bioactive molecules in the treatment of diseases and cancers and the repair and regeneration of tissues. It is because they have the injectability with minimal invasiveness and usability for irregularly shaped sites, in addition to typical advantages of conventional hydrogels such as biocompatibility, permeability to oxygen and nutrient, properties similar to the characteristics of the native extracellular matrix, and porous structure allowing therapeutic agents to be loaded. Main body: In this article, recent studies of injectable hydrogel systems applicable for therapeutic agent delivery, disease/cancer therapy, and tissue engineering have reviewed in terms of the various factors physically and chemically contributing to sol-gel transition via which gels have been formed. The various factors are as follows: several different non-covalent interactions resulting in physical crosslinking (the electrostatic interactions (e.g., the ionic and hydrogen bonds), hydrophobic interactions, ${\pi}$-interactions, and van der Waals forces), in-situ chemical reactions inducing chemical crosslinking (the Diels Alder click reactions, Michael reactions, Schiff base reactions, or enzyme-or photo-mediated reactions), and external stimuli (temperatures, pHs, lights, electric/magnetic fields, ultrasounds, or biomolecular species (e.g., enzyme)). Finally, their applications with accompanying therapeutic agents and notable properties used were reviewed as well. Conclusion: Injectable hydrogels, of which network morphology and properties could be tuned, have shown to control the load and release of therapeutic agents, consequently producing significant therapeutic efficacy. Accordingly, they are believed to be successful and promising biomaterials as scaffolds and carriers of therapeutic agents for disease and cancer therapy and tissue engineering.