关键词： 中国航天科工集团   机械测试   内蒙   固体火箭发动机   试验基地   研究院  

摘要： 中国航天科工集团第六研究院六0一所（又名内蒙航天动力机械测试所）创建于1965年，是我国第一座大型固体火箭发动机地面试验基地。

关键词： 课程教学   热能动力机械测控技术   MATLAB软件  

摘要： 文章主要是针对我校热能与动力工程专业学生学习测控技术课程过程中遇到的问题进行了探讨。结合MATLAB软件数值计算和图形处理功能,不断改进教学方法和手段。将MATLAB软件应用于热能动力机械测控技术课程理论与实践教学,不仅提高了学生学习主动性和积极性,而且培养了学生的创新能力,逻辑思维能力,以及工程应用能力。

关键词： Lipids   Interfaces   QM/MM   Molecules   Membranes  

摘要： Biomolecular dynamics studies using a QM/MM approach have been largely used especially to study enzymatic reactions. However, to the best of our knowledge, the very same approach has not been used to study the water/membrane interface using a quantum mechanical treatment for the lipids. Since a plethora of biochemical processes take place in this region, we believe that it is of primary importance to understand, at the level of molecular orbitals, the behavior of a drug in such an odd environment. In this work, we take advantage of an integration of the CPMD and the GROMACS code, using the Car- Parrinello method, to treat the benzocaine local anesthetic as well as two of the membrane lipids and the GROMOS force field to treat the remaining lipids and the water molecules.

关键词： Aluminium alloys   Amorphous   Crystallization kinetics   Mechanical properties  

摘要： The crystallization kinetics and mechanical properties of Al86Ni6Y4.5Co2La1.5 metallic glass powder have been investigated using differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM) and nanoindentation. The first crystallization stage of the Al86Ni6Y4.5Co2La1.5 glass powder is identified to be a surface nucleation and one-dimensional growth process while the second and third crystallization stages are characterized by volume nucleation but followed by one-dimensional growth and two-dimensional growth, respectively. The hardness and elastic modulus show opposite trends on crystallization;they are both sensitive to the precipitation of fcc-Al, growth of fcc-Al and precipitation of complex intermetallic phases. The changes of hardness and elastic modulus of the Al86Ni6Y4.5Co2La1.5 metallic glass powder with crystallization are discussed. (C) 2012 Elsevier B.V. All rights reserved.

关键词： Molecular dynamics  

摘要： In recent years, polymer/carbon nanotube composites have attracted a lot of attention because the polymer properties are significantly improved. In this work, the mechanical properties, namely Young's modulus, bulk modulus, shear modulus and compressibility of single-walled carbon nanotube (SWCNT) reinforced polyethylene (PE) composite had been investigated by molecular dynamics (MD) simulation. The results showed that SWCNT can significantly improve the elastic property of SWCNT reinforced PE composite, especially in the longitudinal direction of the nanotube. The Young's modulus found by MD simulations is compared with values obtained using macroscopic rule-of-mixture. The results are in disagreement revealing the fact that rule-of-mixture in not an excellent approximate in estimating the overall response of the composite system since it assumes perfect bonding between fibre and matrix. The simulation results are also compared with existing experimental results. The simulation result gives a close agreement to calculate the elastic modulus of nanocomposite since it shows good agreement with experimental results. © 2012 Inderscience Enterprises Ltd.

关键词： IAPP   Aggregation   Sequence analysis   Molecular dynamics   Fibril   Type II diabetes  

摘要： A collective approach of sequence analysis, phylogenetic tree and in silico prediction of amyloidogenecity using bioinformatics tools have been used to correlate the observed species-specific variations in IAPP sequences with the amyloid forming propensity. Observed substitution patterns indicate that probable changes in local hydrophobicity are instrumental in altering the aggregation propensity of the peptide. In particular, residues at 17th, 22nd and 23rd positions of the IAPP peptide are found to be crucial for amyloid formation. Proline25 primarily dictates the observed non-amyloidogenecity in rodents. Furthermore, extensive molecular dynamics simulation of 0.24 mu s have been carried out with human IAPP (hIAPP) fragment 19-27, the portion showing maximum sequence variation across different species, to understand the native folding characteristic of this region. Principal component analysis in combination with free energy landscape analysis illustrates a four residue turn spanning from residue 22 to 25. The results provide a structural insight into the intramolecular beta-sheet structure of amylin which probably is the template for nucleation of fibril formation and growth, a pathogenic feature of type II diabetes. (c) 2012 Elsevier B.V. All rights reserved.

关键词： hydroformylation   propene   rhodium   cyclohexyl diphenylphosphine   kinetic modeling  

摘要： Hydroformylation of propene to isobutyraldehyde and n-butyraldehyde was studied in the kinetic regime in a semibatch stainless steel reactor at 85-115 degrees C and 115 bar pressure in 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate solvent with rhodium catalyst cyclohexyl diphenylphosphine as a ligand, which showed lower normal/isometric aldehyde ratio (n/i) than previously studied triphenylphosphine. The rate was pressure and Rh concentration dependent. The regioselectivity was conversion independent;however, dependent on the ligand concentration, as higher ligand concentration promoted isobutyraldehyde formation. The influence of ligand concentration on regioselectivity was investigated. A kinetic model was proposed based on the mechanism of alkene hydroformylation and compared with experimental observations. Numerical data fitting was performed showing good agreement of reaction rates and regioselectivity with experimental data. (C) 2011 American Institute of Chemical Engineers AIChE J, 2012

关键词： Bangham's equation   Endothermic   Film diffusion   Pseudo second-order model  

摘要： Biosorption potential of Cedrus deodara sawdust (CDS) in terms of sorption of Zn(II) ion across liquid phase has been evaluated in the present investigation. The surface of the CDS biomass before the sorption of Zn(II) ions seemed to be more porous, non-crystalline and heterogeneous. The maximum uptake capacity of CDS was 97.39?mg?g-1. Sorption of Zn(II) ion on the surface of CDS sawdust was maximum at pH 5, temperature 45 degrees C, initial concentration of Zn(II) ion 100?mg?L-1, biomass dose 1?g?L-1, contact time 150?min, and agitation rate 160?rpm. Pseudo second-order kinetics with the highest linear regression coefficient (R2?=?0.99), and lowest values of error functions, i.e., chi (?2) and sum of square errors (SSE) against pseudo first-order rate kinetics showed that the sorption of Zn(II) ion on the surface of CDS was mediated by chemosoprtive forces of attraction rather than physical adsorption. Mechanistically, relatively higher proportion of sorption of Zn(II) ion in early phase of contact time was profoundly explained by Bangham's equation and film diffusivity (Df). Intraparticle or pore diffusion (Dp) of Zn(II) ion inside the pores of CDS was rate limiting step at the later stage of contact time. Furthermore, the thermodynamic study on sorption of metal ion delineated the fact that the Zn(II) sorption on the surface of CDS was spontaneous, endothermic together with increased entropy at solid liquid interface.

关键词： proton transport   quanta   Fragments   Molecular Dynamics  

摘要： We show that the hybrid quantum mechanical/effective fragment potential (QM/EFP) can be a very effective and practical quantum mechanical molecular dynamics method, when it is properly combined with well-developed traditional molecular dynamics (MD) techniques. QM/EFP-MD simulations on intra-molecular proton transfer of glycine with 290 EFP waters yielded accurate free energy change and reaction barrier of the zwitterion -> neutral form conversion. Water rearrangements turned out to be the main driving force of the proton transfer. (C) 2012 Elsevier B. V. All rights reserved.

关键词： Microscopy, Atomic Force   Models, Molecular   Molecular Dynamics Simulation   Protein Conformation   Protein Folding   Proteins/chemistry  

摘要： Protein structure is highly diverse when considering a wide range of protein types, helping to give rise to the multitude of functions that proteins perform. In particular, certain proteins are known to adopt a knotted or slipknotted fold. How such proteins undergo mechanical unfolding was investigated utilizing a combination of single molecule atomic force microscopy (AFM), protein engineering, and steered molecular dynamics (SMD) simulations to show the mechanical unfolding mechanism of the slipknotted protein AFV3-109. Our results reveal that the mechanical unfolding of AFV3-109 can proceed via multiple parallel unfolding pathways that all cause the protein slipknot to untie and the polypeptide chain to completely extend. These distinct unfolding pathways proceed via either a two- or three-state unfolding process involving the formation of a well-defined, stable intermediate state. SMD simulations predict the same contour length increments for different unfolding pathways as single molecule AFM results, thus providing a plausible molecular mechanism for the mechanical unfolding of AFV3-109. These SMD simulations also reveal that two-state unfolding is initiated from both the N- and C-termini, while three-state unfolding is initiated only from the C-terminus. In both pathways, the protein slipknot was untied during unfolding, and no tightened slipknot conformation was observed. Detailed analysis revealed that interactions between key structural elements lock the knotting loop in place, preventing it from shrinking and the formation of a tightened slipknot conformation. Our results demonstrate the bifurcation of the mechanical unfolding pathway of AFV3-109 and point to the generality of a kinetic partitioning mechanism for protein folding/unfolding.