Aeroelastic analysis of wind turbines using a tightly coupled CFD–CSD method

This paper presents aeroelastic analyses of wind turbines, using the compressible flow Helicopter Multi-Block (HMB2) solver of Liverpool University, coupled with a Computational Structural Dynamics method. For this study, the MEXICO and NREL Phase VI wind turbines were employed. A static aeroelastic method was first employed for the analysis of the MEXICO blade and the effect of the torsional stiffness was studied at 10, 15 and 24 m/s axial wind speeds. The torsional deformations showed strong dependency on this parameter and the blade region from mid-span to the tip was the most susceptible to aeroelastic effects. The work progressed by studying both the static and dynamic response on the NREL wind turbine, where the nacelle and the tower were considered. Mean deflections between the static and dynamic methods showed consistency and, due to the structural properties of this blade, flapping modes were dominant. The dynamic aeroelastic method enabled an assessment of the effect of flapping on the blade loads, in conjunction with the effect of tower. Aeroelastic effects were found to be secondary for the MEXICO blade, but had a stronger effect on the larger NREL Phase VI blade.     

Purine 3′:5′‐cyclic nucleotides with the nucleobase in a syn orientation: cAMP,cGMP and cIMP

Purine 3′:5′‐cyclic nucleotides are very well known for their role as the secondary messengers in hormone action and cellular signal transduction. Nonetheless, their solid‐state conformational details still require investigation. Five crystals containing purine 3′:5′‐cyclic nucleotides have been obtained and structurally characterized, namely adenosine 3′:5′‐cyclic phosphate dihydrate, C₁₀H₁₂N₅O₆P·2H₂O or cAMP·2H₂O, (I), adenosine 3′:5′‐cyclic phosphate 0.3‐hydrate, C₁₀H₁₂N₅O₆P·0.3H₂O or cAMP·0.3H₂O, (II), guanosine 3′:5′‐cyclic phosphate pentahydrate, C₁₀H₁₂N₅O₇P·5H₂O or cGMP·5H₂O, (III), sodium guanosine 3′:5′‐cyclic phosphate tetrahydrate, Na⁺·C₁₀H₁₁N₅O₇P⁻·4H₂O or Na(cGMP)·4H₂O, (IV), and sodium inosine 3′:5′‐cyclic phosphate tetrahydrate, Na⁺·C₁₀H₁₀N₄O₇P⁻·4H₂O or Na(cIMP)·4H₂O, (V). Most of the cyclic nucleotide zwitterions/anions [two from four cAMP present in total in (I) and (II), cGMP in (III), cGMP⁻ in (IV) and cIMP⁻ in (V)] are syn conformers about the N‐glycosidic bond, and this nucleobase arrangement is accompanied by C_rib—H…N_pur hydrogen bonds (rib = ribose and pur = purine). The base orientation is tuned by the ribose pucker. An analysis of data obtained from the Cambridge Structural Database made in the context of syn–anti conformational preferences has revealed that among the syn conformers of various purine nucleotides, cyclic nucleotides and dinucleotides predominate significantly. The interactions stabilizing the syn conformation have been indicated. The inter‐nucleotide contacts in (I)–(V) have been systematized in terms of the chemical groups involved. All five structures display three‐dimensional hydrogen‐bonded networks.     

Crystallization Temperature Limit of (Ba,Sr)TiO<Subscript>3</Subscript> Thin Films Prepared by a Non Oxocarbonate Phase Forming CSD Route

A new chemical solution deposition (CSD) route for the fabrication of Ba_0.7Sr_0.3TiO₃ (BST) thin films has been developed which completely prevents the formation of an intermediate oxo-carbonate phase. The latter has been reported previously by several authors to be responsible for increased crystallization temperatures. Barium and strontium diaminoethoxides were synthesized starting from pure barium and strontium metal and aminoethanol. These alkoxides were found to be readily soluble in a wide range of solvents and thus were excellent candidates for the CSD process. To prepare a stable precursor solution the aminoalkoxides were dissolved in 2-butoxyethanol and then used for the deposition of BST thin films. We conclude that the minimum crystallization temperature of 600C to be independent of the formation of the oxo-carbonate phase. DTA-TGA were performed on the precursors and their solutions to study their decomposition behaviour. All films annealed at different temperatures were physically characterized by XRD, IR, and SEM. The films prepared by this route at 650C were found to have high dielectric constant and the leakage currents were comparable to BST films prepared by normal carboxylate based routes at 750C.     

Theoretical ab Initio Study on Cooperativity Effects between Nitro π-hole and Halogen Bonding Interactions

This article analyzes the interplay between nitro's π-hole and halogen–bonding (XB) interactions in nitroarenes. Remarkable cooperativity effects are observed when π–hole and XB interactions coexist in the same complex. The nitroarene presents two π-holes, one approximately over the N atom of the nitro group and the other over the aromatic ring, being the former more positive. The interplay between both interactions has been analyzed in terms of energetic and geometric features of the complexes, which are computed at the RI-MP2/def2-TZVPD level of theory. Molecular electrostatic potential (MEP) surface calculations have been used to explore the variation of the MEP values at the π-hole upon the formation of halogen bonding interactions between the nitroarene and CF₃X (X=Cl, Br and I) molecules. In addition, the Bader's theory of atoms in molecules” (AIM) is used to characterize the interactions by means of the distribution of bond critical points and bond paths and to analyze their strengthening or weakening depending upon the variation of charge density at critical points. The aforementioned computational methods are adequate to examine how these interactions mutually influence each other. Natural bond orbital (NBO) and noncovalent interaction plot (NCIPlot) computational tools have been also used in some representative complexes to further analyze cooperativity effects. Finally, the Cambridge Structural Database (CSD) is used to provide some experimental evidence.     

Comparative Solution Synthesis of Mn Doped (Na,K)NbO3 Thin Films

(K_0.5Na_0.5)NbO₃ (KNN) is a promising lead-free alternative for ferroelectric thin films such as Pb(Zr,Ti)O₃. One main drawback is its high leakage current density at high electric fields, which has been previously linked to alkali non-stoichiometry. This paper compares three acetate-based chemical solution synthesis and deposition methods for 0.5 mol % Mn-doped KNN film fabrication, using lower crystallization temperature processes in comparison to the sintering temperatures necessary for fabrication of KNN ceramics. This paper shows the crucial role of the A site homogenization step during solution synthesis in preserving alkali chemical homogeneity of Mn doped KNN films. Chemically homogeneous films show a uniform grain size of 80 nm and a leakage current density under 2.8×10⁻⁸ A cm⁻² up to electric fields as high as 600 kV cm⁻¹, which is the highest breakdown strength reported for KNN thin films. Solution synthesis involving two-step pyrolysis resulted in films with dense, columnar microstructures, which are interesting for orientation control and enhancement of piezoelectric properties. This study reports detailed solution synthesis and deposition processes with good dielectric, ferroelectric and breakdown field properties. An optimized fabrication method that should couple low leakage current density with dense and oriented microstructures is proposed.     

Some more space‐group corrections

A survey of approximately 100 000 entries in recent releases of the Cambridge Structural Database (CSD) has uncovered 156 crystal structures that were apparently described in inappropriate space groups. We have revised these space groups and prepared CIFs containing the new coordinates and brief comments describing the revisions.     

Structural conversion of an oxazolidine ligand upon treatment with copper(I) and (II) halides; structural,spectral, theoretical and docking studies

Abstract

In this work, the 2-(2-(pyridin-2-yl)oxazolidin-3-yl)ethanol (AEPC) ligand was prepared under solvent free conditions using ultrasonic irradiation, before reaction with a Cu(NO₃)₂/KSCN mixture, CuCl₂ and CuI, the products of which were characterized by elemental analysis, UV-Vis, FT-IR spectroscopy and single-crystal X-ray diffraction. The X-ray analyses results revealed that AEPC, after reactions with the three copper(I/II) halides, gave structures ([Cu(DEA)Cl₂] (2), DEA?=?diethanolamine, [Cu(BHEG)₂] (3), BHEG?=?bis(2-hydroxyethyl)glycinato); however, it retains its structure on treatment with Cu(NO₃)₂/KSCN mixture ([Cu(AEPC)(NCS)₂] (1)). The geometrical parameters for the complexes were compared with the Cambridge Structural Database (CSD) and coordination modes for thiocyanate ion were extracted. In the crystal structure of 1, the copper ion has a distorted square-pyramidal geometry and a CuN^pyN₂^NCSN^tertO^alc environment in which the AEPC acts as NN'O-donor in a facial coordination mode. In the crystal structure of 2, the copper ion has a Cu(N^sec)(O^alc)₂Cl₂ environment and distorted square-pyramidal geometry in which the DEA ligand is coordinated as a mer-NO₂-donor. The copper ion in 3 has a CuN₂O₄ environment and distorted octahedral geometry. The ability of these compounds to interact with the nine biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS and Top II) was investigated by Docking calculations and compared with that of doxorubicin. The thermodynamic stability of 1 and its isomer and also charge distribution patterns were studied by DFT and NBO analysis, respectively.     

一种几何大变形下的非线性气动弹性求解方法

非线性气动弹性的时域求解中, 涉及到非线性的流体动力学(CFD)和非线性的结构动力学(CSD)耦合问题. 基于Co-rotational理论, 推导了三维壳单元几何非线性下的切线刚阵和内力公式, 针对推进过程中的能量守恒, 引入预估-校正推进格式, 发展了一种近似能量守恒的非线性动态响应算法; 基于1/2时间步的交错耦合格式, 结合带有几何守恒律的双时间推进求解雷诺平均N-S方程的求解器, 发展了非线性气动弹性求解的高精度耦合格式. 通过结构几何大变形下的静力和动力分析验证了所发展的结构非线性求解器, 并通过AGARD445.6机翼的非线性气动弹性响应分析, 说明了所发展耦合求解方法的实用性.