• Title/Summary/Keyword: Chemical structure analysis

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Using DQ method for vibration analysis of a laminated trapezoidal structure with functionally graded faces and damaged core

  • Vanessa Valverde;Patrik Viktor;Sherzod Abdullaev;Nasrin Bohlooli
    • Steel and Composite Structures
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    • v.51 no.1
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    • pp.73-91
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    • 2024
  • This paper has focused on presenting vibration analysis of trapezoidal sandwich plates with a damaged core and FG wavy CNT-reinforced face sheets. A damage model is introduced to provide an analytical description of an irreversible rheological process that causes the decay of the mechanical properties, in terms of engineering constants. An isotropic damage is considered for the core of the sandwich structure. The classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. The First-order shear deformation theory of plate is utilized to establish governing partial differential equations and boundary conditions for the trapezoidal plate. The governing equations together with related boundary conditions are discretized using a mapping-generalized differential quadrature (GDQ) method in spatial domain. Then natural frequencies of the trapezoidal sandwich plates are obtained using GDQ method. Validity of the current study is evaluated by comparing its numerical results with those available in the literature. After demonstrating the convergence and accuracy of the method, different parametric studies for laminated trapezoidal structure including carbon nanotubes waviness (0≤w≤1), CNT aspect ratio (0≤AR≤4000), face sheet to core thickness ratio (0.1 ≤ ${\frac{h_f}{h_c}}$ ≤ 0.5), trapezoidal side angles (30° ≤ α, β ≤ 90°) and damaged parameter (0 ≤ D < 1) are carried out. It is explicated that the damaged core and weight fraction, carbon nanotubes (CNTs) waviness and CNT aspect ratio can significantly affect the vibrational behavior of the sandwich structure. Results show that by increasing the values of waviness index (w), normalized natural frequency of the structure decreases, and the straight CNT (w=0) gives the highest frequency. For an overall comprehension on vibration of laminated trapezoidal plates, some selected vibration mode shapes were graphically represented in this study.

Structural and Thermal Analysis and Membrane Characteristics of Phosphoric Acid-doped Polybenzimidazole/Strontium Titanate Composite Membranes for HT-PEMFC Applications

  • Selvakumar, Kanakaraj;Kim, Ae Rhan;Prabhu, Manimuthu Ramesh;Yoo, Dong Jin
    • Composites Research
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    • v.34 no.6
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    • pp.373-379
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    • 2021
  • A series of novel PBI/SrTiO3 nanocomposite membranes composed of polybenzimidazole (PBI) and strontium titanate (SrTiO3) with a perovskite structure were fabricated with various concentrations of SrTiO3 through a solution casting method. Various characterization techniques such as proton nuclear magnetic resonance, thermogravimetric analysis, atomic force microscopy (AFM) and AC impedance spectroscopy were used to investigate the chemical structure, thermal, phosphate absorption and morphological properties, and proton conductivity of the fabricated nanocomposite membranes. The optimized PBI/SrTiO3-8 polymer nanocomposite membrane containing 8wt% of SrTiO3 showed a higher proton conductivity of 7.95 × 10-2 S/cm at 160℃ compared to other nanocomposite membranes. The PBI/SrTiO3-8 composite membrane also showed higher thermal stability compared to pristine PBI. In addition, the roughness change of the polymer composite membrane was also investigated by AFM. Based on these results, nanocomposite membranes based on perovskite structures are expected to be considered as potential candidates for high-temperature PEM fuel cell applications.

Synthesis, Crystal Structure and Theoretical Calculation of a Novel Nickel(II) Complex with Dibromotyrosine and 1,10-Phenanthroline

  • Huang, Guimei;Zhang, Xia;Fan, Yuhua;Bi, Caifeng;Yan, Xingchen;Zhang, Zhongyu;Zhang, Nan
    • Bulletin of the Korean Chemical Society
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    • v.34 no.10
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    • pp.2889-2894
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    • 2013
  • A new complex [$Ni(phen)(C_9H_8Br_2NO_3)_2{\cdot}2CH_3OH{\cdot}2H_2O$] [phen: 1,10-phenanthroline $C_9H_8Br_2NO_3$: 3,5-dibromo-L-tyrosine] was synthesized and characterized by IR, elemental analysis and single crystal X-ray diffraction. X-ray crystallography shows that Ni(II) ion is six-coordinated. The Ni(II) ion coordinates with four nitrogen atoms and two oxygen atoms from three ligands, forming a mononuclear Ni(II) complex. The crystal crystallizes in the Orthorhombic system, space group $P2_12_12$ with a = 12.9546 ${\AA}$, b = 14.9822 ${\AA}$, c = 9.9705 ${\AA}$, V = 1935.2 ${\AA}$, Z = 1, F(000) = 1008, S = 0.969, ${\rho}_{calcd}=1.742g{\cdot}cm^{-3}$, ${\mu}=4.688mm^{-1}$, $R_1$ = 0.0529 and $wR_2$ = 0.0738 for 3424 observed reflections (I > $2{\sigma}(I)$). Theoretical study of the title complex was carried out by density functional theory (DFT) method and the B3LYP method employing the $6-3l+G^*$ basis set. The energy gap between HOMO and LUMO indicates that this complex is prone to interact with DNA. CCDC: 908041.

Strength Method Using Pre-flexed Members for the Corner of Underground Box Structures under Additional Surface Load (추가 상재하중을 받는 지중박스구조물의 우각부에 대한 프리플렉스 부재를 이용한 보강공법)

  • Chung, Jee Seung;Lee, Jin Hyuk;Kim, Ki Am
    • Journal of the Korean Society of Safety
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    • v.31 no.5
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    • pp.102-108
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    • 2016
  • This paper presents a new strength method of underground box structures under additional surface load. An L-bracing using pre-flexed steel member threads called the "Pre-flex strength method" is used to improve capacity of the RC box structure under earth pressure due to additional surface load. The pre-flexed steel member is fixed the top and bottom of the structure after chemical anchor was installed by drilling hole on the box structure. The structural performance was evaluated analytically. 3 types of underground RC box structure were used; $2.0m{\times}2.0m$, $3.0m{\times}3.0m$ and $4.0m{\times}4.0m$. For the performance evaluation, structure analysis were performed on moment and shear resisting structures with and without pre-flex strength method. Numerical results confirmed that the proposed strength member system installed on underground RC box structures enhanced the strength capacity. The feasible region of the proposed pre-flex strength method in accordance with the earth pressure due to additional surface depth was evaluated.

Influence of Heating Rate and Temperature on Carbon Structure and Porosity of Activated Carbon Spheres from Resole-type Phenolic Beads

  • Singh, Arjun;Lal, Darshan
    • Carbon letters
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    • v.10 no.3
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    • pp.181-189
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    • 2009
  • Activated carbon spheres (ACS) were prepared at different heating rates by carbonization of the resole-type phenolic beads (PB) at $950^{\circ}C$ in $N_2$ atmosphere followed by activation of the resultant char at different temperatures for 5 h in $CO_2$ atmosphere. Influence of heating rate on porosity and temperature on carbon structure and porosity of ACS were investigated. Effect of heating rate and temperature on porosity of ACS was also studied from adsorption isotherms of nitrogen at 77 K using BET method. The results revealed that ACS have exhibited a BET surface area and pore volume greater than $2260\;m^2/g$ and $1.63\;cm^3/g$ respectively. The structural characteristics variation of ACS with different temperature was studied using Raman spectroscopy. The results exhibited that amount of disorganized carbon affects both the pore structure and adsorption properties of ACS. ACS were also evaluated for structural information using Fourier Transform Infrared (FTIR) Spectroscopy. ACS were evaluated for chemical composition using CHNS analysis. The ACS prepared different temperatures became more carbonaceous material compared to carbonized material. ACS have possessed well-developed pores structure which were verified by Scanning Electron Microscopy (SEM). SEM micrographs also exhibited that ACS have possessed well-developed micro- and meso-pores structure and the pore size of ACS increased with increasing activation temperature.

Lanthanide Complexes of Some High Energetic Compounds (II), Crystal Structures and Thermal Properties of Picrate Complexes

  • Yun, Sock-Sung;Kang, Sung-Kwon;Suh, Hong-Ryol;Suh, Hyung-Sock;Lee, Eun-Kwang;Kim, Jae-Kyung;Kim, Chong-Hyeak
    • Bulletin of the Korean Chemical Society
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    • v.26 no.8
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    • pp.1197-1202
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    • 2005
  • The Ln(III) complexes with picrate ligand, $[Sm(Pic)_2(H_2O)_6]Pic{\cdot}6H_2O$, 1, and $[Ho(Pic)(H_2O)_7](Pic)_2{\cdot}3H_2O$, 2, have been synthesized and their crystal structures are analyzed by X-ray diffraction methods. Complex 1, crystallizes in the monoclinic $P2_1/n$ space group and complex 2 in the triclinic P-1 space group. In complex 1, two picrate ligands coordinate to the Sm(III) ion, one of them in the bidentate fashion. There are one picrate anion and six water molecules in the crystal lattice. The nine-coordinated Sm(III) ion forms a slightly distorted tricapped trigonal prism. In complex 2, only one picrate ligand coordinates to the metal ion as a monodentate. There are two picrate anions and three water molecules in the crystal lattice. The eight-coordinated Ho(III) ion forms a distorted bicapped trigonal prism. Based on the results of the TG-DTG and DSC thermal analysis, it was analyzed that the lanthanide picrate complexes 1 and 2 are thermally decomposed in three distinctive stages, the dehydration, the picrate decomposition, and the formation of the metal oxide.

Real-Time XRD Analysis of Polystyrene/Clay Nanocomposites by In-Situ Polymerization (In-situ 중합법에 의한 폴리스티렌/점토 나노복합재료의 실시간 X선 분석)

  • Kim, Jang-Yup;Hwang, Seok-Ho;Hong, Yoo-Seok;Huh, Wan-Soo;Lee, Sang-Won
    • Polymer(Korea)
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    • v.29 no.1
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    • pp.87-90
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    • 2005
  • In this study, we have examined the exfoliation behavior of layered clay during in-situ polymeriztion with styrene by using real-time XRD analysis. The 4C1 beam line at the Pohang Accelerator Laboratory (PAL) was used for this study. Different exfoliation behaviors have been shown to depend on the cation exchange capacity (CEC) of clay and the chemical structure of organic modifiers. For 10A-MMT and 15A-MMT having high CEC, no peak shifts were observed on real-time XRD analysis during polymerization. However, 2$\theta$ for 25A-MMT and VDAC-MMT, each having low CEC’s as well as aromatic benzene moieties and vinyl groups, respectively, decreased as polymerization time increased.

Chemo-Mechanical Analysis of Bifunctional linear DGEBF/Aromatic Amino Resin Casting Systems (DGEBF/방향족아민 경화계의 벤젠링 사이에 위치한 Methyl기와 Sulfone기가 유발하는 물성변화에 대한 연구)

  • Lee Jae-Rock;Myung In-Ho
    • Composites Research
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    • v.18 no.4
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    • pp.14-20
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    • 2005
  • To determine the effect of chemical structure of aromatic amino curing agents on thermal and mechanical properties, standard epoxy resin DGEBF (diglycidylether of bisphenol F) was cured with diaminodiphenyl methane (DDM) and diaminodiphenyl sulphone (DDS) in a stoichiometrically equivalent ratio. From this work the effect of aromatic amino curing agents on the thermal and mechanical properties is significantly influenced by the chemical structure of curing agents. In contrast, the results show that the DGEBF/DDS system having the sulfone structure between the benzene rings had higher values in the thermal stability, density, shrinkage ($\%$), thermal expansion coefficient, tensile modulus and strength, flexural modulus and strength than the DGEBF/DDM system having methylene structure between the benzene rings, whereas the DGEBF/DDS system presented low values in maximum exothermic temperature, conversion of epoxide, and grass transition temperature. These results are caused by the relative effects of sulfone group having strong electronegativity and methylene group having (+) repulsive property. The result of fractography shows that the grain distribution of DGEBF/DDS system is more irregular than that of the DGEBF/DDM system.

Existing test data for the Act on Registration & Evaluation, etc. of Chemical Substances

  • Choi, Bong-In;Ryu, Byung-Taek;Na, Suk-Hyun;Chung, Seon-Yong
    • Environmental Analysis Health and Toxicology
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    • v.30
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    • pp.17.1-17.6
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    • 2015
  • Objectives In this study, the possibility of using existing test data provided in Korea and elsewhere for the registration of chemical substances was examined. Data on 510 chemical substances that are among the first subject to registration under the "Act on the Registration and Evaluation, etc. of Chemical Substances (K-REACH)" were analyzed. Methods The possibility of using existing data from 16 reference databases was examined for 510 chemical substances notified in July 2015 as being subject to registration. Results Test data with the reliability required for the registration of chemical substances under the K-REACH constituted 48.4% of the required physicochemical characteristics, 6.5% of the required health hazards, and 9.4% of the required environmental hazards. Conclusions Some existing test data were not within the scope of this research, including data used for registration in the European Union (EU). Thus, considering that 350 of these 510 species are registered in EU Registration, Evaluation, Authorisation & Restriction of Chemicals, more test data may exist that can be utilized in addition to the data identified in this study. Furthermore, the K-REACH states that non-testing data (test results predicted through Read Across, Quantitative Structure-Activity Relationships) and the weight of evidence (test results predicted based on test data with low reliability) can also be utilized for registration data. Therefore, if methods for using such data were actively reviewed, it would be possible to reduce the cost of securing test data required for the registration of chemical substances.

3D-QSAR Studies on Chemical Features of 3-(benzo[d]oxazol-2-yl)pyridine-2-amines in the External Region of c-Met Active Site

  • Lee, Joo Yun;Lee, Kwangho;Kim, Hyoung Rae;Chae, Chong Hak
    • Bulletin of the Korean Chemical Society
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    • v.34 no.12
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    • pp.3553-3558
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    • 2013
  • The three dimensional-quantitative structure activity relationship (3D-QSAR) studies on chemical features of pyridine-2-amines in the external region of c-Met active site (ER chemical features of pyridine-2-amines) were conducted by docking, comparative molecular field analysis (CoMFA), and topomer CoMFA methods. The CoMFA model obtained the partial least-squares (PLS) statistical results, cross-validated correlation coefficient ($q^2$) of 0.703, non cross-validated correlation coefficient ($r^2$) of 0.947 with standard error of estimate (SEE) of 0.23 and the topomer CoMFA obtained $q^2$ of 0.803, $r^2$ of 0.940, and SEE of 0.24. Further, the test set was applied to validate predictive abilities of models, where the predictive $r^2$ ($r{^2}_{pred}$) for CoMFA and topomer CoMFA models were 0.746 and 0.608, respectively. Each contribution of ER chemical features of pyridine-2-amines to the inhibitory potency showed correlation coefficients, $r^2$ of 0.670 and 0.913 for two core parts, 3-(benzo[d]oxazol-2-yl)pyridine-2-amine and 3-(1-(2,6-dichloro-3-fluorophenyl)ethoxy) pyridine-2-amine, respectively, with corresponding experimental $pIC_{50}$.