关键词： 检测   机械   运动学  

摘要： 目前工业中的机械臂在工程应用中,经常有工人在复杂的环境中进行多点示教,这就要求机械臂在工作的过程中还要保证工人的安全。机械臂在感知到与外部环境碰撞时可以及时检测到碰撞,这在工程应用中是非常重要的安全性能。现在市场上对于小负载的机械臂UR构型的比较常见,UR结构的机械臂包揽轻量级,快速,易于编程,灵活且安全的有点,并且具有6个自由度。它在控制上凭借着开放的控制结构和具有高控制带宽的编程途径吸引了许多科研以和工程人员。本文对于UR机器人的运动学和动力学提出了一整套的研究方法,同时本文借助碰撞检测的实例应用进行了验证。

关键词： Geopolymer   Aluminosilicate powder   SiO2/Al2O3 ratio   Molecular dynamics simulation   Structural properties   Mechanical properties  

摘要： In this study, the impacts of different SiO2/Al2O3 ratio on the molecular structural and mechanical properties of geopolymer were investigated by molecular dynamics and experiment. Complex composition of raw materials may affect the analysis of geopolymer gels. Therefore, pure aluminosilicate powder with different SiO2/Al2O3 ratio were synthesized by sol-gel method firstly. Then the prepared powder mixed with the activating agent of NaOH and sodium silicate to prepare geopolymer. After 28d curing age, chemical composition and crystalline phase of geopolymer were characterized by X-ray fluorescence (XRF) and X-ray Diffraction (XRD) respectively. Based on the above characterization results of geopolymer gel, different SiO2/Al2O3 ratio of molecular models were built. Finally, molecular dynamics were performed on the molecular models to study energy and temperature, simulated XRD, radial distribution function (RDF), distribution of bond length and bond angle and elastic modulus. Results showed that with the increases of SiO2/Al2O3 ratio, both stability of molecular structure and mechanical properties of geopolymer were decreased. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Carbon dioxide  

摘要： In this work, the first investigation of the structural, dynamical and thermodynamical properties of solvated CO2 in liquid ammonia using a recently developed Quantum Mechanical/Molecular Mechanical Molecular Dynamics Thermodynamic Integration (QM/MM MD TI) approach has been carried out. The correlated resolution-of-identity Moller-Plesset Perturbation Theory (RI-MP2) ab initio level of theory has been applied to treat CO2 and its entire first solvation shell. In contrast to aqueous CO2, a negative value for the absolute solvation free energy of -25.9 +/- 1.5 kJ/mol was found. This latter value reflects that the solute-solvent interaction is more favorable in liquid ammonia solution. In order to obtain a detailed structural characterisation of solvated CO2, the evaluation of radial distribution functions was performed in conically restricted regions with respect to the main axis of the CO2 molecule. The presented data provides detailed information on the solvation properties of CO2 in pure liquid ammonia. Since knowledge about the latter is a key prerequisite to understand CO2-capture in ammonia solutions, the simulation results can be expected to act as a valuable reference. In addition, the detailed analysis of the individual QM/MM energy contributions showed that the overall potential energy is not affected by artificial contributions, which might influence the determination of solvation free energy. (C) 2020 Published by Elsevier B.V.

关键词： Adsorption   MOFs   PBA/GO   Ciprofloxacin   Kinetics and thermodynamic studies  

摘要： Water as a universal solvent has well-documented for its ability to dissolve various substances leading to water pollution. Metal organic frameworks (MOFs) have been proved to have interesting properties for the adsorptive removal of pollutants from water. In this work, Mn-PBA (Mn[Fe(CN)(6)]) and Mn-PBA/GO composite have been developed using simple and facile method for the adsorption of ciprofloxacin (CIP). The adsorption kinetic performance of as-synthesized composite for CIP is justified by applying pseudo-second order (R-2 = 0.99638) and liquid-film diffusion model (R-2 = 0.91603), whereas for the Mn-PBA, pseudo-second order (R-2 = 0.99951) and intra-particle model (R-2 = 0.80577) is well-fitted. The adsorption isotherm data of Mn-PBA/GO composite for CIP is fitted using Langmuir model (R-2 = 0.99994) and adsorption capacity (1826.64 mg/g) is observed higher than previous reports. The relative correlation coefficient value is calculated by using Tampkin model (R-2 = 0.62798), which indicated electrostatic relationship between Mn-PBA/GO and ciprofloxacin (CIP). Adsorption of CIP on the Mn-PBA/GO takes place according to endothermic and spontaneous processes (Delta H = +16.94 kj/mol, Delta G = -9.25 kj/mol). The composite has well retained its reusability and the removal efficiency is reduced only 5% after several cycles. Further, the influence of various factors (pH, contact time, adsorbent dose, adsorbate quantity, temperature and ionic strength) on adsorptive removal of CIP is also discussed.

关键词： Thermomechanical properties   BxCyNz heteronanotubes   NiTMTAA   Adsorption   Molecular dynamics simulation  

摘要： In this study, the adsorption characteristics together with the modified thermomechanical properties of stable BxCyNz heteronanotubes, i.e. BC2N, BC3, and NC3, in ambient conditions have been explored under the adsorption of NiTMTAA molecules (NiTMTAA/heteronanotube). Employing molecular dynamics study, it is observed that pi-pi stacking interaction plays a major role in the adsorption of NiTMTAA. The radius of gyration and circumferential distribution along the axis of NTs demonstrate the higher agglomeration of molecules near the wall of CNT and BC3 than that of other NTs. Moreover, it is observed that CNT and BNNT possess the highest Young's modulus and thermal conductivity than those of heteronanotubes. According to the results, the adsorption of NiTMTAA molecules reduces thermal conductivity. Unlikely, Young's modulus of NiTMTAA/heteronanotubes for small weight percentage of NiTMTAA molecules (< similar to 20%) is slightly higher than pure heteronanotubes. Furthermore, it is shown that for more than 20%, the thermomechanical properties are approximately converged to the slightly lower value than that of pure heteronanotubes. Finally, it is demonstrated that the presence of both boron (B) and nitrogen (N) atoms in heteronanotubes, i.e. BC2N, results in higher thermomechanical properties than the individual presence of B and N.

关键词： Molecular dynamics   Diamond   Nanotribology   Sliding   Rolling   Oscillating  

摘要： Molecular dynamics simulation is employed to analyze the effect of sliding, rolling and oscillating movements on nanotribology properties of a diamond abrasive on a silicon substrate. The abrasive oscillating mechanism is achieved by simulating megasonic vibration-assisted on the planarization process. In this paper, the effects of abrasive size, sliding velocity, depths of polishing, rolling velocity, rolling direction, oscillating amplitude and oscillating frequency on material removal are considered. The results showed that the rolling mechanism reaches the highest number of atoms removed while the suitable oscillating mechanism gains the lowest height of asperity. The oscillating movement has remarkable results in wiping out the asperity atoms, although at a high amplitude and a low frequency causing some atoms from the flat substrate stuck to the abrasive and left some surface defects. Moreover, a multi-asperities model is set up to simulate the global-scale ability of sliding, oscillating and rolling mechanisms on polishing. This model indicates the saturated behavior of the rolling mechanism, while the lowest value of the surface roughness attained by the sliding mechanism. Combining three types of removing mechanisms could create a smooth surface with a high effective removal rate on both local and global-scales.

关键词： Hydrogen storage   TiFe alloy   Metal hydride   Ball milling   Cold rolling  

摘要： In this paper, effect of air exposure on first hydrogenation kinetics of TiFe +4 wt% Zr + 2 wt % Mn alloy was studied. After 7 days of air exposure, the first hydrogenation kinetics of the alloy was slow with a long incubation time. An air exposure of 30 days made the alloy totally inert to hydrogen. In an attempt to recover the hydrogen absorption ability of the alloy, it was mechanically treated using cold rolling and ball milling processes. It was found that the air exposed alloy could be successfully hydrogenated after ball milling and after cold rolling with some loss in hydrogen storage capacity. The loss in storage capacity was more important after ball milling than after cold rolling. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Graphene   nanocomposites   molecular dynamics (MD) simulation   Halpin_Tsai semi-empirical micromechanical model   mechanical properties  

摘要： In this study, the mechanical properties of graphene-epoxy nanocomposites were investigated using experimental tests, molecular dynamics (MD) simulation and Halpin_Tsai semi-empirical micromechanical model. To fabricate graphene/epoxy nanocomposite, specimens containing 0, 0.3, 0.5 and 0.7 weight percent (wt.%) of graphene nanoparticle (GNP), high power dispersion sonicating method and high-speed shearing were employed. Then, tensile and flexural modulus of manufactured nanocomposites were obtained, and the results illustrated that the elastic and flexural modulus of GNP/epoxy nanocomposites increased significantly until GNP was added up to 0.5 wt.% and after that, the trend of increasing elastic modulus declined which could be due to local GNP agglomerations within the nanocomposites with higher contents of filler. Furthermore, graphene, epoxy and graphene-epoxy nanocomposites were simulated by MD, and the mechanical properties of simulated graphene-epoxy nanocomposites were calculated. However, the effect of temperature and strain rate on tensile properties of graphene-epoxy nanocomposites was studied, which showed that increasing temperature decreased the strength of graphene-epoxy nanocomposites, and also increasing the strain rates led to an increase in the elastic modulus. Finally, experimental results and the Halpin_Tsai model were compared in which a good agreement between experimental and analytical results was observed.

关键词： assisted circulation   catheterization   hemodynamics   shock   cardiogenic  

摘要： The recent widespread availability and use of mechanical circulatory support is transforming the management and outcomes of cardiogenic shock (CS). Clinical decision-making regarding the optimization of therapies for patients with CS can be guided effectively by hemodynamic monitoring with a pulmonary artery catheter (PAC). Because several studies regarding the benefit of PACs are ambiguous, the use of PACs is variable among clinicians treating patients with CS. More notable is that PAC use has not been studied as part of a randomized, controlled trial in patients with CS with or without mechanical circulatory support. Standardized approaches to hemodynamic monitoring in these patients can improve decision-making and outcomes. In this review, we summarize the hemodynamics of CS and mechanical circulatory support with PAC-derived measurements, and provide a compelling rationale for the use of PAC monitoring in patients with CS receiving mechanical circulatory support.

关键词： Bowen病   手部   机械磨削术   氨基酮戊酸   光动力疗法  

摘要： 目的:探讨机械磨削术联合氨基酮戊酸光动力疗法(ALA-PDT)治疗手部Bowen病疗效。方法:10例经病理确诊的手部Bowen病患者,均行机械磨削术联合ALA-PDT治疗。磨削时从外向里进行磨削,磨至弥漫性出血为止。后将氨基酮戊酸配成20%溶液涂于皮损及外周0.5cm,3~4h后行635nm红光照射,能量密度为80~100J/cm2,时间20min,每周照射1次,共3次。6个月后观察肿瘤有无复发,患者满意度及瘢痕形成等情况。结果:10例患者行机械磨削联合ALA-PDT治疗后,至少随访6个月,均未见肿瘤复发;10例患者均非常满意,治疗后无明显瘢痕增生。结论:机械磨削术联合ALA-PDT治疗手部Bowen病安全高效,痛苦小,创伤轻,患者满意度高,无明显瘢痕形成,值得临床推广。