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。

关键词： 多转子轴系   动力学响应   加重影响系数   无试重   虚拟动平衡  

摘要： 为解决透平机械多转子轴系动平衡需频繁多次启停机的问题,提出一种基于动力学响应分析的多转子轴系无试重虚拟动平衡方法。通过仿真构建与轴系结构尺寸和运行参数相符的有限元模型,分别在各转子平衡配重位置处施加虚拟不平衡激励,进行动力学稳态不平衡响应分析,得到轴系平衡转速下各振动测点处的振动响应值,从而避免需多次启机试重来获取轴系转子配重位置处的加重影响系数,结合实测的轴系不平衡振动基频值,通过矢量计算获得轴系各转子所需的平衡配重。采用搭建的四跨五支承透平机械轴系转子模拟试验台,应用该方法开展1 200 r/min低平衡转速下无试重虚拟动平衡试验,结果表明一次配重平均降幅高达55%,不仅减少了启停机次数,而且可降低因试重不当、测试误差所导致平衡失败概率;该方法还可推广应用到柔性转子轴系的现场动平衡。

关键词： 华中科技大学   控制工程   流体动力   工程学院   机械科学   基础零部件   学习   中国制造  

摘要： 国务院颁布《中国制造2025》，这是我国全面推进实现制造强国三步走战略第一个十年的行动纲领。《中国制造2025》已把强化基础零部件（元器件）能力列为战略任务重点，并明确提出2020年40%核心基础零部件、2025年70%核心基础零部件实现自主保障目标。《液压气动与密封》杂志作为行业媒体，与行业全心全意践行装备制造业的“主机与配套同步发展战略”，执行“尽快扭转重要配套件依赖进口局面”的艰巨任务。坚持“面向企业、面向生产、面向应用、理论与实践相结合”的办刊方针，坚持贴近实际、贴近生活、贴近群众的原则，同心协力搭建产学研用平台，推广新技术、新工艺和创新成果，注重产业化应用，为实现企业、政府、社团同步联动，发挥着行业旗舰媒体的积极作用，为创新服务理念，开展务实有效工作发出行业媒体的正能量……。