关键词： CL-20/TNTcocrystal explosive   Molecular dynamics   Mechanical properties Sensitivity   Binding energy   Detonation performance  

摘要： To investigate and compare the differences of structures and properties of CL-20/TNT cocrystal and composite explosives, the CL-20/TNT cocrystal and composite models were established. Molecular dynamics simulations were performed to investigate the structures, mechanical properties, sensitivity, stabilities and detonation performance of cocrystal and composite models with COMPASS force field in NPT ensemble. The lattice parameters, mechanical properties, binding energies, interaction energy of trigger bond, cohesive energy density and detonation parameters were determined and compared. The results show that, compared with pure CL-20, the rigidity and stiffness of cocrystal and composite models decreased, while plastic properties and ductility increased, so mechanical properties can be effectively improved by adding TNT into CL-20 and the cocrystal model has better mechanical properties. The interaction energy of the trigger bond and the cohesive energy density is in the order of CL-20/ TNT cocrystal > CL-20/TNT composite > pure CL-20, i.e., cocrystal model is less sensitive than CL-20 and the composite model, and has the best safety parameters. Binding energies show that the cocrystal model has higher intermolecular interaction energy values than the composite model, thus illustrating the better stability of the cocrystal model. Detonation parameters vary as CL-20 > cocrystal > composite, namely, the energy density and power of cocrystal and composite model are weakened;however, the CL-20/TNT cocrystal explosive still has desirable energy density and detonation performance. This results presented in this paper help offer some helpful guidance to better understand the mechanism of CL-20/TNT cocrystal explosives and provide some theoretical assistance for cocrystal explosive design.

关键词： Advanced oxidation processes   Congo red   Langmuir-Hinshelwood   N-TiO2   Photocatalysis  

摘要： In this study, the photocatalytic degradation of Congo red has been investigated in N-doped TiO2 (N-TiO2) aqueous suspensions under visible light irradiation. Visible light-active N-TiO2 was successfully prepared at three different weight contents (2.5, 5, and 7%) employing sol-gel method. It was able to harvest the visible irradiation with wavelength suitable for activation. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometer, diffused reflectance UV-Vis spectroscopy, nitrogen adsorption Brunauer-Emmert-Teller, Raman spectroscopy, photoluminescence and X-ray photoelectron spectrometer were used to characterize the doped catalyst. The samples had a relatively large specific Brunauer-Emmert-Teller surface areas of about 42 m(2) g(-1) with average X-ray diffraction crystalline size of 52 nm and showed visible light photocatalytic activity at about 408 nm. The impacts of several operating parameters on the Congo red photodegradation process were examined. Langmuir-Hinshelwood model exhibited pseudo-first-order degradation kinetics. N-TiO2-assisted plausible photodegradation mechanism has been suggested based on the qualitatively detected intermediate compounds.

关键词： Arsenic   Biosorption   Kinetic   Mechanistic   Thermodynamic   Modelling  

摘要： In the present study, TW/MnFe2O4 composite (MTW) was synthesized and estimated as an effective biosorbent for removing As (III) and As(V) from wastewater. Physicochemical analysis of composite was performed through SEM-EDX. 86.615 and 83.478% removal efficiency were obtained by composite dosage of 2 g/L at contact time 120 min at temperature 30 degrees C and pH 7.0 and 4.0 for As(III) and As(V), respectively. Kinetic results study showed that Brouers-Weron-Sotolongo and Ritchie second-order for As(III) and Brouers-Weron-Sotolongo model for As(V) were capable to describe an accurate explanation of adsorption kinetic. Applicability of mechanistic models in the current study exposed that the rate-controlling step in the biosorption of both As(III) and As(V) on the surface of composite was film diffusion rather than intraparticle diffusion. The estimated thermodynamic parameters Delta G degrees, Delta H degrees and Delta S degrees revealed that the biosorption of both As(III) and As(V) on the composite was feasible, spontaneous and exothermic.

关键词： Foot   Mechanical energetics   Kinetics   Multi-segment foot model   Walking  

摘要： Introduction/aim: Foot structure has been implicated as a risk factor of numerous overuse injuries, however, the mechanism linking foot structure and the development of soft-tissue overuse injuries are not well understood. The aim of this study was to identify factors that could predict foot function during walking. Methods: A total of eleven variables (including measures of foot structure, anthropometry and spatiotemporal gait characteristics) were investigated for their predictive ability on identifying kinematic, kinetic and energetic components of the foot. Three-dimensional motion capture and force data were collected at preferred walking speed on an instrumented treadmill. Mechanical measures were subsequently assessed using a custom multi-segment foot model in Opensim. Factors with significant univariate associations were entered into multiple linear regression models to identify a group of factors independently associated with the mechanical measures. Results: Although no model could be created for any of the kinematic measures analysed, approximately 46% and 37% of the variance in the kinetic and energetic measures were associated with three or two factors respectively. Arch-height ratio, foot length and step width were associated with peak subtalar joint (STJ) moment, while greater STJ negative work was correlated to a low arch-height ratio and greater foot mobility. Conclusion: The models presented in this study suggest that the soft-tissue structures of a flat-arched, mobile foot are at a greater risk of injury as they have greater requirements to absorb energy and generate larger forces. However, as these associations are only moderate, other measures may also have an influence.

关键词： Density functional theory   rhodium borides   mechanical properties   phonon   thermodynamic properties   electronic structure  

摘要： The structural, electronic, vibrational, mechanical and thermodynamic properties of Rh5B4 have been investigated within the framework of the density functional theory (DFT) and the direct method using first-principles calculations. The calculated lattice parameters are in good agreement with the available experimental data. The electronic structure suggests that Rh5B4 should exhibit the metallic behavior and hybridizations exist between Rh-d and B-s, B-p orbitals, which illuminates that the bonding between them has certain covalent character. Mechanical properties including elastic constants, bulk modulus, shear modulus, Young's modulus, and Poisson's ratio v are calculated. Phonon dispersions and phonon density of states (DOS) are obtained, respectively. Our results indicate that Rh5B4 is dynamically and mechanically stable with better ductility (B/G = 3.28) at ambient pressure. In addition, the phonon frequencies at the center (Gamma point) of the first Brillouin zone are predicted and Raman-active and infrared-active modes are also assigned. Finally, the phonon contribution to the Helmholtz free energy F, the phonon contribution to the internal energy E, the constant volume specific heat Cv and vibrational entropy S are studied over the range 0 similar to 1000 K.

摘要： This study reports the synthesis of nanocrystalline undoped and europium doped BaWO4:Eu3+ nanophosphors by a mechanical activation process using high energy ball mill (HEBM) technique. The prepared nanophosphors were characterized systematically by Rietveld analysis of the X-ray powder diffraction (XRD) data, Raman spectroscopy, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The synthesized nanophosphors were found to possess spherical morphology and small particle sizes similar to 25 nm. To explore this material for application in luminescence, detailed time resolved photoluminescence studies were carried out. It was observed that it is a rare breed of phosphor material that exhibits exceptional luminescence properties such as the capability to give high emission output till 5.0 mol% without undergoing quenching and unique property to get excited by mid ultraviolet (MUV) light, near ultraviolet (NUV) light, as well as by visible light such as blue and green. It was also observed that energy transfer primarily takes place from tungstate group of host to Eu3+. In fact energy transfer from the host to Eu3+ becomes more and more efficient with the increasing concentration of Eu3+ ions. Two lifetime values are observed for all europium ion (Eu3+) concentrations, one of the order of 465-650 mu s (T-S, short lifetime) and the other of the order of 1050-1320 ms (T-L, longer lifetime). This reflects the fact that Eu3+ ions occupy two sites;regular symmetric Ba2+ site (S-1) and asymmetric site (S-2), which will be closer to charge compensating defects. Calculation of Judd-Ofelt parameter illustrated that at all europium concentrations, the local surrounding around it lacked inversion symmetry (asymmetric environment), and the exact point group symmetry around europium ion was found to be C-6v. The red purity (intense D-5(0)-F-7(2)) and high quantum efficiency (78%) of BaWO4:Eu3+ projects it as a new red ph

关键词： 机械产品   动力设计   转动  

摘要： 随着新材料、新工艺、新方法的逐渐引入,机械产品除要求能实现预期的功能外,还应使设计出的机械系统满足运行可靠、对环境污染小等一系列要求。设计质量的实验是产品设计的重要组成部分,通过设计实验能对机械产品的主要功能、辅助功能、结构性能、工作性和工艺性能进行检验。本文说明了机械产品的动力与传动设计原则,并针对机械产品设计质量检验的总体结构和功能结构设计进行了具体阐述。

关键词： 驱动桥   机械式双动力输入   履带式   大功率   原地差速转向  

摘要： 随着我国农业基础地位的强化,农业产业化和规模经营的推进以及大型履带式拖拉机独有的特性(高效、节能、适应性强),现代农业的发展对大型履带式拖拉机的需求越来越大。双动力输入驱动桥是一款先进的机械传动驱动桥,传递功率大,传动效率比液力传动驱动桥高10%以上,制造成本低。此款驱动桥还解决了我国传统履带拖拉机驱动桥滑移转向的缺点(如,破坏路面、降低功率、转向阻力大、下坡时逆转向造成不安全事故等),实现了差速转向、零转弯半径,是一种先进的更适合我国大型履带拖拉机快速发展的驱动桥。

关键词： 机械工业   2017年   经济运行  

摘要： 2017年8月8日,2017年上半年机械工业运行情况发布会在中国机械工业联合会举行。中国机械工业联合会执行副会长陈斌、中国汽车工业协会常务副会长董扬、中国机械工业联合会统计工作部副主任田淑坤出席,会议由中国机械工业联合会执行副会长兼秘书长赵驰主持。陈会长指出,考虑到去年下半年基数较高的因素,预计全年机械工业增加值增长8%左右,主营业务收入和利润总额增长8%左右,对外贸易出口有望结束连续两年的颓势,同比增速由负转正。