Structural investigation of high‐transmittance aluminum oxynitride films deposited by ion beam sputtering

Aluminum oxynitride films were deposited by ion beam sputtering technique at room temperature. The optical properties and morphologies of the aluminum oxynitride films were studied and reported previously. It was found that the optical properties are closely related to the O contents in the films. In this study, the structures of the films were investigated by X‐ray diffractometer and XPS. Three oxidation states of N_1s in oxynitride films, N⁺, N²⁺ and N³⁺, were clearly deduced from N_1s spectra in the amorphous films fabricated under various oxygen partial pressures (P_O2). To our knowledge, three oxidation states of N_1s have not been simultaneously observed and reported in the aluminum oxynitride films previously. Corresponding bonding variations in Al_2p and O_1s spectra indicated more oxygen in oxynitride in the film as P_O2 increases. Three aluminum oxynitride networks, AlO₂N, AlO_2.5N and AlO₃N were deduced. Optical properties of aluminum oxynitride films resemble those of AlN and Al₂O₃ films when P_O2 is low and high during the deposition. The refractive indices and extinction coefficients of the aluminum oxynitride films can be adjusted by using proper P_O2 during the film depositions. Copyright © 2010 John Wiley & Sons, Ltd.     

热红联用研究催化剂对PDADN-RDX改性双基推进剂热分解的影响

利用PDSC、TG和DSC -FTIR联用技术和加热裂解原位池红外技术研究了两种燃速催化剂对PDADN -RDX - CMDB推进剂热分解的影响,结果表明,推进剂的热行为有很大改变:分解温度降低、分解热增大、分解放热速率提高,主要组分的标志性官能团提前消失,主要气体产物提前出现,具有负生成热的气体放出量明显增加.初步阐...     

管件无模拉伸成形力能参数数学模型研究

对不锈钢管件无模拉伸变形速度场及力能参数进行了理论及实验研究.分析了不锈钢管件无模拉伸的变形模型、速度场以及力能参数的影响因素及影响规律,采用上限法确定了不锈钢管件无模拉伸速度场及力能参数物理模型,填补了国内外关于不锈钢管件无模拉伸变形及力能参数物理模型研究的空白.为不锈钢管件无模拉伸工艺工业化应用奠定基础.     

Correlated n1,3S states for coulomb three‐body systems

n^1,3S (n = 1 ? 4) states for atomic three‐body systems are studied with the Angular Correlated Configuration Interaction method. A recently proposed angularly correlated basis set is used to construct, simultaneously and with a single diagonalization, ground and excited states wave functions which: (i) satisfy exactly Kato cusp conditions at the two‐body coalescence points; (ii) involve only linear parameters; (iii) show a fast convergency rate for the energy; and (iv) form an orthogonal set. The efficiency of the method is illustrated by the study a variety of three‐body atomic systems [m m m] with two negatively charged light particles, with diverse masses m and m, and a heavy positively charged nucleus m. The calculated ground 1¹S and excited n^1,3S (n = 2 ? 4) state energies are compared with those given in the literature, when available. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Ab initio calculations of surface electronic states in indium oxide

A slab approach in the framework of ab initio calculations was applied to study surface electronic states in In₂O₃ crystal. Density functional theory (DFT) calculations were carried out employing the WIEN 2k code and using the full potential method with Augmented Plane Waves + local orbitals (APW+lo) formalism. Total and partial DOS (Density of States) were calculated for In and O atoms in two upper (110) surface layers. Comparison of total and partial DOS allowed determining a contribution of electronic states of different In and O surface atoms into formation of surface electronic spectra and corresponding chemical bonds. A dominant ionic character of chemical bonds in In₂O₃ is found. Calculations were performed for three slab models with different geometry parameters. It was shown that an optimal ratio between the whole vertical size of a supercell and the vertical size of atomic cluster has to be chosen. The size of vacuum region in the slab model influences significantly on the reliability of calculated characteristics of the surface electronic structure. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Mechanistic Photodissociation of Glycolaldehyde: Insights from Ab Initio and RRKM Calculations

Herein we report a theoretical study on mechanistic photodissociation of glycolaldehyde, HOCH₂CHO. Equilibrium structures, transition states, and intersection structures for the α‐C? C and ‐C? H bond fissions and the β‐C? O bond fission in the excited states are determined by the complete active space self‐consistent field (CASSCF) method. Based on the CASSCF optimized structures, the potential energy profiles for the dissociations are refined by performing single‐point calculations using the multi‐state multi‐reference CASSCF second order perturbation (MS‐MR‐CASPT2) method. With a low excitation energy of 280–340 nm, the T₁ α‐C? C and β‐C? O bond fissions following intersystem crossing from the S₁ state are the predominant and comparable channels, whereas the α‐C? H bond fissions both in the S₁ and in the T₁ states are nearly prohibited due to the relevant high barriers. The rate constants for the T₁ α‐C? C and β‐C? O bond fissions are also calculated by RRKM theory. Furthermore, the S₀ reactions can occur as a consequence of intersystem crossing via T₁/S₀ intersection points resulting from the T₁ C? C and C? O bond cleavages. This photodissociation mechanism is consistent with recent experimental studies.     

A Simple Model for Barrier Frequencies for Enzymatic Reactions

We present a simple model to rationalize the effects of environment on the reaction barrier frequencies derived from free energy profiles. These frequencies are relevant in deviations of a rate constant from its transition state theory value and in determining which environmental dynamics participate in the reaction. In particular, this simple model can be used to understand the changes in the reaction barrier frequencies of an enzymatic catalyzed reaction and the corresponding uncatalyzed process in aqueous solution, a change which has implications for dynamical environmental effects on the enzymatic reaction. Two possible cases are analyzed, in which the polarity (charge separation/localization) of the reacting system increases or decreases as the reaction advances. A simple modeling of the environment′s effects allows the explanation of an unusual “inverse” effect on the reaction frequencies, that is, a free energy barrier lowering accompanied by an increase of the reaction frequency, a behavior observed in some enzymes. The model predictions are successfully compared with results from full simulations for four different enzyme reactions.     

Supporting disciplinary and interdisciplinary knowledge development and design thinking in an informal,pre‐engineering program: A Workplace Simulation Project

In this paper, we examined students’ engagement in an implementation of a Workplace Simulation Project (WSP). The WSP was designed to actively engage students in learning disciplinary content by inviting engineers from industry to have a physical presence within the school building to collaborate with teachers and students to complete projects which simulate the tasks authentic to their work. We focus on the first year implementation of the program that partnered a high school in the rural Midwest with an engineering unit of a government organization. Using a multiple methods study design, we analyzed disciplinary and interdisciplinary pre and posts test along with students’ interviews to determine learning gains as well as students’ interpretations of creative and critical thinking as experienced in the project and their knowledge of the engineering design process. Effect sizes showed that students in the WSP group had notable gains over the control group participants. Additionally, students’ knowledge of core elements of the design process were identified in inductive analyses of the interviews. Findings from this study will provide usable knowledge about effective ways to support systems and design thinking and ways to support expert‐novice collaboration to ensure success.