Quantum chemical calculations using gradient-corrected DFT at the BP86/TZ2P+ level were carried out for the metal-dioxime complexes [M{RC(NOH)C(NO)R}2]with M = Ni, Pd, Pt, R = CH3, H, F, Cl, Br, Ph, CF3. The nature of the metal-ligand bond was investigated with an energy decomposition analysis (EDA). The complexes with electron donating substituents R = H, CH3 have the strongest metal-ligand interaction energies ΔEint, as well as the largest bond dissociation energies. The analysis of the bonding situation revealed that the metal ← ligand σ donation is much stronger than the metal → ligand π backdonation. The breakdown of the orbital interactions into the contributions of orbitals with different symmetry indicates that the donation from the in-plane lone-pair donor-orbitals of nitrogen into the dxy AO of the metal provides about one half of the stabilization which comes from ΔEorb. Inspection of the EDA data indicates that the electrostatic term ΔEelstat is more important for the trend of the metal-oxime interactions in [M{RC(NOH)C(NO)R}2] than the orbital term ΔEorb. 相似文献
The main aim of this research was to study the electrochemical behavior of novel optically active poly(amide-imide)s (PAIs). Polycondensation reactions of a 3,5-diamino-N-(4-hydroxyphenyl)benzamide with different synthetic diacid chlorides derivatives based on natural amino acids resulted in preparation of five different aromatic–aliphatic PAIs. These polymers were characterized by Fourier transform infrared, proton nuclear magnetic resonance, and elemental analyses. Also, we used electrochemical impedance spectroscopy for the evaluation of these novel optically active PAIs for the first time. Presence of p-substituted phenol groups in the structure of these polymers has been used for electrochemical investigation. Results showed that the oxidation currents in five diverse polymers were affected by their structures. In addition, the influence of carbon nanotubes on the oxidation of phenolic groups was studied using carbon paste matrix in an aqueous buffer solution (pH 7.0).
This paper addresses a method for predicting the participating constants in equation of state (EOS) for compressed polymeric
fluids using two scaling constants, the surface tension γg and the molar density ρg, both at the glass transition point. The theoretical EOS undertaken is the one attributed to Tao and Mason. The second virial
coefficients are calculated from a two-parameter corresponding states correlation, which is constructed with two constants
as scaling parameters, i.e., the surface tension γg and the molar density ρg. This new correlation has been applied to the Tao–Mason (TM) EOS to predict the volumetric behavior of several polymer melts.
The operating temperature range is from 291.25 to 603.4 K and pressures of up to 202.5 MPa. A collection of 516 data points
has been examined for the aforementioned polymers. The average absolute deviation between the calculated densities and the
experimental ones is of the order of 0.44%. 相似文献
In this paper, a simple method for detection of multiple edge cracks in Euler–Bernoulli beams having two different types of cracks is presented based on energy equations. Each crack is modeled as a massless rotational spring using Linear Elastic Fracture Mechanics (LEFM) theory, and a relationship among natural frequencies, crack locations and stiffness of equivalent springs is demonstrated. In the procedure, for detection of m cracks in a beam, 3m equations and natural frequencies of healthy and cracked beam in two different directions are needed as input to the algorithm. 相似文献
Polystyrene nanocomposites, being a combination of nanoclay-attached and free polystyrene chains were prepared using in situ atom transfer radical polymerization. Subsequently, they were electrospun to form fibers with diameter varying from 450?C700 nm according to scanning electron microscopy data; in addition, the transmission electron microscopy and x-ray diffraction analysis revealed that nanoclay layers were oriented along the nanofiber axis during the electrospinning process. Molecular weight of the extracted free polymer chains from the nanocomposites is higher than the attached chains. However, Anchored chains are characterized by higher polydispersity index in comparison with the free ones. Polydispersity index of polymer chains increases by the addition of nanoclay. Thermogravimetric analysis results shows that increasing clay content leads to a decrease in the quantity of polymer chains attached to the clay surface. 相似文献
This paper focuses on the uncertainty bound parameter (UBP) to design the robust control of electrical manipulators. The UBP
is commonly obtained by considering the worst case of uncertainties in bounding functions. However, too high estimation of
UBP may cause saturation of input, higher frequency of chattering in the switching control laws, and thus a bad behavior of
the whole system, while too low estimation of UBP may cause a higher tracking error. A proper UBP is preferred to improve
the performance of robust control system. A simple, less dependent and proper UBP is proposed based on the nominal model of
electrical manipulator and feedbacks of joint accelerations. This work is motivated by recent experimental results in measuring
acceleration by optical encoder. Modeling of an electrical manipulator with presence of uncertainties is presented for control
purposes. The proposed robust control is justified by stability analysis. 相似文献
In this paper, we derive distributions of order statistics and a linear combination of order statistics arising from a bivariate selection normal distribution. We show that they are mixtures of univariate selection normal distributions. We then illustrate the usefulness of these results with a real-life data relating to visual acuity analysis. Finally, some concluding remarks are made. 相似文献
A convenient and efficient procedure for the regioselective ring opening of epoxides in the presence of Dowex (strongly acidic cationic exchange resin), as reusable eco‐friendly catalyst under solvent free conditions is described. Thus, several β‐hydroxy thiocyanates, useful intermediates toward pharmaceutical and biologically active molecules, are easily obtained in high isolated yields. 相似文献