Dynamic and buckling analysis of polymer hybrid composite beam with variable thickness

This work deals with a study of the dynamic and buckling analysis of polymer hybrid composite(PHC) beam. The beam has variable thickness and is reinforced by carbon nanotubes(CNTs) and nanoclay(NC) simultaneously. The governing equations are derived based on the first shear deformation theory(FSDT). A three-phase HalpinTsai approach is used to predict the mechanical properties of the PHC. We focus our attention on the effect of the simultaneous addition of NC and CNT on the vibration and buckling analysis of the PHC beam with variable thickness. Also a comparison study is done on the sensation of three impressive parameters including CNT, NC weight fractions, and the shape factor of fillers on the mechanical properties of PHC beams,as well as fundamental frequencies of free vibrations and critical buckling load. The results show that the increase of shape factor value, NC, and CNT weight fractions leads to considerable reinforcement in mechanical properties as well as increase of the dimensionless fundamental frequency and buckling load. The variation of CNT weight fraction on elastic modulus is more sensitive rather than shear modulus but the effect of NC weight fraction on elastic and shear moduli is fairly the same. The shape factor values more than the medium level do not affect the mechanical properties.     

核电结构土-结相互作用分析分区混合计算方法

土-结构相互作用分析是核电结构进行抗震设计和安全评估的重要环节.在核电结构的土-结相互作用分析中,阻尼和非线性是影响结构反应的重要因素. 若采用频域分析,可以方便考虑阻尼,但需通过等效线性化来考虑非线性,不适合于强震作用下的土体非线性.若采用时域分析的逐步积分方法,适合于考虑非线性,但材料阻尼一般采用瑞利阻尼模型,除了紧靠指定阻尼比的少数几个振型外,其他振型的反应将受到瑞利阻尼模型所确定的大阻尼所抑制,造成地震反应与真实情形有较大差异.若采用时域分析的模态叠加法,可合理计入阻尼效应,但模态叠加法不能考虑非线性.因此,如何合理考虑阻尼和非线性是核电结构土-结相互作用分析需要关注的问题.基于此,本文提出一种模态叠加和时步积分结合的土-结相互作用分区算法.其中,出于安全性考虑,地震作用下核电主体结构一般不允许进入非线性,因此结构可采用模态叠加方法,以便合理考虑结构阻尼;土体和基础采用显式时步积分法,可考虑土体非线性;通过人工边界条件考虑无限域的影响 (辐射阻尼).通过简单算例对该方法进行了验证,并用于CAP1400核电结构的土-结相互作用分析中,对比分析了采用模态阻尼和瑞利阻尼时核电结构和场地反应的差异,结果表明结构阻尼模型对场地的反应影响不大,但对结构反应影响明显,在实际工程中应合理选取阻尼模型.      

Autonomously Propelled Motors for Value‐Added Product Synthesis and Purification

A proof‐of‐concept design for autonomous, self‐propelling motors towards value‐added product synthesis and separation is presented. The hybrid motor design consists of two distinct functional blocks. The first, a sodium borohydride (NaBH₄) granule, serves both as a reaction prerequisite for the reduction of vanillin and also as a localized solid‐state fuel in the reaction mixture. The second capping functional block consisting of a graphene–polymer composite serves as a hydrophobic matrix to attract the reaction product vanillyl alcohol (VA), resulting in facile separation of this edible value‐added product. These autonomously propelled motors were fabricated at a length scale down to 400 μm, and once introduced in the reaction environment showed rapid bubble‐propulsion followed by high‐purity separation of the reaction product (VA) by the virtue of the graphene–polymer cap acting as a mesoporous sponge. The concept has excellent potential towards the synthesis/isolation of industrially important compounds, affinity‐based product separation, pollutant remediation (such as heavy metal chelation/adsorption), as well as localized fuel‐gradients as an alternative to external fuel dependency.     

Formation and Reactivity of Organo‐Functionalized Tin Selenide Clusters

Reactions of R¹SnCl₃ (R¹=CMe₂CH₂C(O)Me) with (SiMe₃)₂Se yield a series of organo‐functionalized tin selenide clusters, [(SnR¹)₂SeCl₄] ( 1 ), [(SnR¹)₂Se₂Cl₂] ( 2 ), [(SnR¹)₃Se₄Cl] ( 3 ), and [(SnR¹)₄Se₆] ( 4 ), depending on the solvent and ratio of the reactants used. NMR experiments clearly suggest a stepwise formation of 1 through 4 by subsequent condensation steps with the concomitant release of Me₃SiCl. Furthermore, addition of hydrazines to the keto‐functionalized clusters leads to the formation of hydrazone derivatives, [(Sn₂(μ‐R³)(μ‐Se)Cl₄] ( 5 , R³=[CMe₂CH₂CMe(NH)]₂), [(SnR²)₃Se₄Cl] ( 6 , R²=CMe₂CH₂C(NNH₂)Me), [(SnR⁴)₃Se₄][SnCl₃] ( 7 , R⁴=CMe₂CH₂C(NNHPh)Me), [(SnR²)₄Se₆] ( 8 ), and [(SnR⁴)₄Se₆] ( 9 ). Upon treatment of 4 with [Cu(PPh₃)₃Cl] and excess (SiMe₃)₂Se, the cluster fragments to form [(R¹Sn)₂Se₂(CuPPh₃)₂Se₂] ( 10 ), the first discrete Sn/Se/Cu cluster compound reported in the literature. The derivatization reactions indicate fundamental differences between organotin sulfide and organotin selenide chemistry.     

Attapulgite grafted with polystyrene via a simultaneous reverse and normal initiation atom transfer radical polymerization

The surface grafting of attapulgite (ATP) with polystyrene (PS) was established via a simultaneous reverse and normal initiation atom transfer radical polymerization (SR&NIATRP). 4‐(chloromethyl)phenyltrimethoxysilane (CMPTMS) chemical bounded on the surface of ATP (ATP‐Cl, Cl‐I) was prepared via one‐step self‐assembly. SR&NI ATRP of styrene was conducted using CuCl₂ complex tris(2‐(dimethylamino)ethyl)amine (Me₆‐TREN) as the catalytic system, initiated by 2,2‐azobis(isobutyronitrile) (AIBN) and ATP‐Cl. FT‐IR, XRD, XPS, TGA and TEM data were consistent with the grafting of benzyl chloride groups and PS chains on ATP surface. The controllability of polymerization was investigated by the kinetics behavior under different molar ratio of AIBN and CuCl₂. The obtained polymer possessed a uniform distribution of molecular weights with a lower polydispersity index of 1.2～1.4. The relationship between polymerization on the surface of ATP and in solution was discussed in detail based on TGA data of hybrid particles and GPC trace of free polymer in solution. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1508–1516     

A new class of stereoregular vinylene‐arylene copolymers with double‐decker silsesquioxane in the main chain

A synthesis of a new macromolecular class of vinylene‐arylene copolymers with double‐decker silsesquioxane in the main chain is presented. Two transition‐metal‐catalyzed processes, which is silylative‐coupling copolycondensation (SCC) and ADMET copolymerization of divinyl‐substituted double‐decker silsesquioxanes (DDSQ‐2SiVi) with selected diolefins, are reported to be highly efficient tools for the formation of stereoregular copolymers containing DDSQ‐silylene‐vinylene‐arylene units. The copolymeric products are studied in terms of their structural, thermal, and mechanical properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1044–1055     

Enhancing the Water Stability of Al‐MIL‐101‐NH2 via Postsynthetic Modification

The resistance of metal–organic frameworks towards water is a very critical issue concerning their practical use. Recently, it was shown for microporous MOFs that the water stability could be increased by introducing hydrophobic pendant groups. Here, we demonstrate a remarkable stabilisation of the mesoporous MOF Al‐MIL‐101‐NH₂ by postsynthetic modification with phenyl isocyanate. In this process 86 % of the amino groups were converted into phenylurea units. As a consequence, the long‐term stability of Al‐MIL‐101‐URPh in liquid water could be extended beyond a week. In water saturated atmospheres Al‐MIL‐101‐URPh decomposed at least 12‐times slower than the unfunctionalised analogue. To study the underlying processes both materials were characterised by Ar, N₂ and H₂O sorption measurements, powder X‐ray diffraction, thermogravimetric and chemical analysis as well as solid‐state NMR and IR spectroscopy. Postsynthetic modification decreased the BET equivalent surface area from 3363 to 1555 m² g^?1 for Al‐MIL‐101‐URPh and reduced the mean diameters of the mesopores by 0.6 nm without degrading the structure significantly and reducing thermal stability. In spite of similar water uptake capacities, the relative humidity‐dependent uptake of Al‐MIL‐101‐URPh is slowed and occurs at higher relative humidity values. In combination with ¹H‐²⁷Al D ‐HMQC NMR spectroscopy experiments this favours a shielding mechanism of the Al clusters by the pendant phenyl groups and rules out pore blocking.     

一种饱和Keggin硅钨酸盐过渡金属衍生物[Cu(biim)_2]_4[α-SiW_(12)O_(40)]_2·4H_2O（英文）

在水热环境下,将Na10[α-SiW9O34]爛18H2O和CuCl2爛2H2O在2,2′-联咪唑和4,4′-联吡啶存在下反应合成一种饱和Keggin硅钨酸盐杂化物[Cu(biim)2]4[α-SiW12O40]2爛4H2O(1),并通过红外光谱,X射线光电子能谱和X射线单晶衍射进行了结构表征.化合物1分子包含2个中性的Keggin[Cu(biim)2]2[α-SiW12O40]单元和4个结晶水分子.值得注意的是在[α-SiW12O40]4-单元中,与硅原子相连的每个氧原子无序排列在两个位置,这导致了硅原子呈现立方体的几何构型.中性Keggin型[Cu(biim)2]2[α-SiW12O40]单元具有中心对称性,两个[Cu(biim)2]2+配离子对称连接在[α-SiW12O40]4-的两端.邻近的[Cu(biim)2]2[α-SiW12O40]单元之间通过氢键作用形成三维的超分子结构.     

A novel Ni/Na – Containing inorganic-organic hybrid supramolecule based on polyoxometalate and EDTA with ultraviolet-visible light photochromism

A novel Ni/Na – containing inorganic-organic hybrid supramolecule {(PW₁₂O₄₀)·[Na₂(NiH₂EDTA·H₂O)(H₄EDTA)·2H₂O]·2H₂O·H₃O}_n (short for NiEDTA-PW₁₂) has been successfully synthesized by solution method, and investigated by thermogravimetric-differential thermal analysis (TG-DTA), ultraviolet visible (UV-Vis) spectroscopy, cyclic voltammetry (CV), photoluminescence (PL), ultraviolet visible diffuse reflectance spectrum (UV-vis DRS) and single-crystal X-ray diffraction (XRD). NiEDTA-PW₁₂ exhibits intriguing infinite supramolecular structure with Na⁺ ions as linker. Furthermore, NiEDTA-PW₁₂ displays a fast-responsive reversible photochromism under ultraviolet or visible light. The photochromic property of NiEDTA-PW₁₂ has been investigated by techniques of UV-vis DRS and PL, and the impact of the O₂ on fading of the colored NiEDTA-PW₁₂ has been investigated.     

MHD flow and heat transfer of a hybrid nanofluid past a permeable stretching/shrinking wedge

The steady flow and heat transfer of a hybrid nanofluid past a permeable stretching/shrinking wedge with magnetic field and radiation effects are studied. The governing equations of the hybrid nanofluid are converted to the similarity equations by techniques of the similarity transformation. The bvp4c function that is available in MATLAB software is utilized for solving the similarity equations numerically. The numerical results are obtained for selected different values of parameters. The results discover that two solutions exist, up to a certain value of the stretching/shrinking and suction strengths. The critical value in which the solution is in existence decreases as nanoparticle volume fractions for copper and wedge angle parameter increase. It is also found that the hybrid nanofluid enhances the heat transfer rate compared with the regular nanofluid. The reduction of the heat transfer rate is observed with the increase in radiation parameter. The temporal stability analysis is performed to analyze the stability of the dual solutions, and it is revealed that only one of them is stable and physically reliable.