Theoretical study of the CH3 + NS and related reactions: mechanism of HCN formation

More than thirty equilibrium and transition structures on the [CH₃NS] potential energy surface have been located using the B3LYP/6-311 + + G(d,p) method. Thioformaldoxime (3) turns out to be the most stable isomer followed by thionitrone (2), a three-membered ring, thionitrosyl methane (1) and thiazyl methane. These isomers are connected to each other by 1,2H and 1,3H shifts and ring—chain rearrangement, but the associated energy barriers are rather high, making most of them stable with respect to unimolecular transformations. Starting from CH₃ + NS, a possible initial atmospheric reaction, HCN formation appears to be the most favoured process through a cascade involvement of 1, 2 and 3. The standard heats of formation, ΔH ⁰ _f,298 are calculated to be: 3, 149kJmol^?1; and 1, 218kJmol^?1; using the CCSD(T)/6-311+ +G(3df,2p) method, with an error of ±10kJ mol^?1.     

Free vibration characteristics of sectioned unidirectional/bidirectional functionally graded material cantilever beams based on finite element analysis

Advancements in manufacturing technology, including the rapid development of additive manufacturing (AM), allow the fabrication of complex functionally graded material (FGM) sectioned beams. Portions of these beams may be made from different materials with possibly different gradients of material properties. The present work proposes models to investigate the free vibration of FGM sectioned beams based on onedimensional (1D) finite element analysis. For this purpose, a sample beam is divided into discrete elements, and the total energy stored in each element during vibration is computed by considering either the Timoshenko or Euler-Bernoulli beam theory. Then, Hamilton's principle is used to derive the equations of motion for the beam. The effects of material properties and dimensions of FGM sections on the beam's natural frequencies and their corresponding mode shapes are then investigated based on a dynamic Timoshenko model (TM). The presented model is validated by comparison with three-dimensional (3D) finite element simulations of the first three mode shapes of the beam.     

A Unified Approach to Construct a Class of Daubechies Orthogonal Scaling Functions

We use Lorentz polynomials to give an efficient way to prove Daubechies’ results on the existence of spline type orthogonal scaling functions and to evaluate a class of Daubechies scaling functions in a unified approach.     

沸石咪唑酯骨架结构材料ZIF-8催化Friedel-Crafts酰基化反应(英文)

A zeolite imidazolate framework,ZIF-8,was synthesized and characterized by dynamic laser light scattering,X-ray powder diffraction,scanning electron microscopy,transmission electron microscopy,thermogr...     

Molecular and electronic structure of zwitterionic diamino-meta-quinonoid molecules

Quantum chemical calculations using molecular orbital (HF, CASSCF) and density functional theory (B3LYP) methods, in conjunction with the 6–311 + + G(d,p) basis set, have been applied to investigate the molecular and electronic structure of two diamino-meta-quinonoid molecules 1a and 2a, each containing a six-membered ring coupled with two exocyclic C = O bonds situated in a meta position, along with two amino substituents (NH₂ and NH-CH₃). It is confirmed that these substituted meta-quinone systems exhibit a zwitterionic structure in which the positively charged N-C-C(H)-C-N subunit, containing the two amino-groups, forms two chemical bonds with the negatively charged O-C-C(H)-C-O subunit. The negative charge amounts to about half of an electron. The charge separation has been approached in terms of geometries, vibrational frequencies, and electronic distribution. The ionization energy for molecule 1a is about 7.8±0.3eV. The quinonoid systems are essentially non-aromatic characterized by the NICS(+1) values of around 1.2 ppm.     

CONVERGENCE RESULTS FOR NON-OVERLAP SCHWARZ WAVEFORM RELAXATION ALGORITHM WITH CHANGING TRANSMISSION CONDITIONS

In this paper,we establish a new algorithm to the non-overlapping Schwarz domain decomposition methods with changing transmission conditions for solving one dimensional advection reaction diffusion problem.More precisely,we first describe the new algorithm and prove the convergence results under several natural assumptions on the sequences of parameters which determine the transmission conditions.Then we give a simple method to estimate the new value of parameters in each iteration.The interesti...     

EXISTENCE AND CONVERGENCE RESULTS FOR AN ELASTIC FRICTIONAL CONTACT PROBLEM WITH NONMONOTONE SUBDIFFERENTIAL BOUNDARY CONDITIONS

The goal of this paper is to study a mathematical model of a nonlinear static frictional contact problem in elasticity with the mixed boundary conditions descri...     

Elliptical diffusion of dye in hexagonal columnar polycatenar mesophases

We have studied polycatenar compounds which exhibit hexagonal columnar mesophases. In the planar orientation of these mesophases, the elliptical diffusion of the dissolved dyes is visualized by taking several pictures of the sample. The diffusion ratio D// /D is deduced for these columnar mesophases. Furthermore, using a classical optical absorption technique, we present measurements of dye diffusion in the same mesophases. The diffusion constants are measured in two geometries, along and perpendicular to the columns. The diffusion anisotropy ratios are in agreement with those deduced from the ellipse axes. The structure of these new columnar mesophases exhibited by rod-like mesogens is compared with that of disk-like mesogens.     

Experimental and theoretical study of dicyanocarbene C(CN)2

Dicyanocarbene C(CN)₂ and its radical cation (m/z 64) were generated by dissociative ionization of tetracyanoethene, dicyanofuroxan and dicyanofurazan and characterized by collisional activation (CA) and neutralization-reionization (NR) mass spectrometries and tandem MS³ experiments performed in a ‘hybrid’ tandem mass spectrometer having a sector-quadrupole-sector configuration. In both neutral and ionized forms, dicyanocarbene is found to be a stable and detectable species. Existence of the peaks at m/z 52, 24 and 12 in the CA/NR spectra suggests however some possible post-collisional rearrangements. The carbene was further studied by ab initio calculations using B3LYP/6-311+G(3df) for geometries and CASPT2(14,12) and MR-SDCI with the cc-pVTZ and aug-cc-pVTZ basis sets for relative energies. The dicyano form NC-C-CN is consistently more stable than its isocyano isomers CN-C-CN and CN-C-NC, irrespective of the electronic state. Each neutral carbene exhibits a triplet ground state lying up to 2.6 eV below the singlets. All the triplet, singlet and ionized states of dicyanocarbene have a linear shape. The other states have either linear or bent shape but small barriers to linearity. Adiabatic ionization energies (IE_a) were estimated as follows: NC-C-CN: 11.3 eV with linear ²Π_u cation; NC-C-NC: 10.4 eV with linear ²Π cation, and CN-C-NC: 9.9 eV with bent ²A₁ cation.     

石榴石型偏振调节器温度效应研究

采用磁控溅射法制备了石榴石型偏振调节器并研究了温度对其的影响.利用斯托克斯偏振仪和CCD,研究激光透过石榴石及石榴石型偏振调节器的偏振极化性质和光斑变化.实验结果表明:在25～75℃温度范围内,激光穿过不同材料时,斯托克斯参量变化趋势不同;但是因方位角不改变,激光的偏振度、线偏振度、圆偏振度基本不变.