关键词： Hydrogels  

摘要： Understanding the three-dimensional (3D) mechanical and chemical properties of distinctly different, adjacent biological tissues is crucial to mimicking their complex properties with materials. 3D printing is a technique often employed to spatially control the distribution of the biomaterials, such as hydrogels, of interest, but it is difficult to print both mechanically robust (high modulus and toughness) and biocompatible (low modulus) hydrogels in a single structure. Moreover, due to the fast diffusion of mobile species during printing and nonequilibrium swelling conditions of low-solids-content hydrogels, it is challenging to form the high-fidelity structures required to mimic tissues. Here a predictive transport and swelling model is presented to model these effects and then is used to compensate for these effects during printing. This model is validated experimentally by photopatterning spatially distinct hydrogel elastic moduli using a single photo-tunable poly(ethylene glycol) (PEG) pre-polymer solution by sequentially patterning and in-diffusing fresh pre-polymer for further polymerization.

关键词： Hydrogen   Desorption   Solutions   Composites   Indium  

摘要： Improving desorption kinetics and achieving thermodynamic destabilization of MgH2 is of great importance for its practical applications. In the present study, a MgH2-In composite was synthesized through high-energy ball milling of MgH2 and In, and microstructures;hydrogen ab/desorption properties of the composite were carefully investigated with respect to the identically processed pure MgH2. The thermodynamic destabilization of MgH2 was achieved through reversible phase transformation of Mg(In) solid solution due to the partial solubility of In in Mg lattice (11 atom %), which resulted in lower enthalpy values and reduced desorption temperatures. X-ray diffraction peak analysis revealed the presence of internal stress/strain fields caused by the lattice mismatch between Mg and indium, which could play an important role in improving the desorption properties of the composite. Hydrogen evolution of the MgH2-In composite was directly observed via an in situ highresolution transmission electron microscope (TEM), which shows the "hydrogen pump" effect of a Mg3In phase which is stable only under a hydrogen environment. The formation mechanism of the Mg3In phase and its role as "hydrogen pump" in the improvements of desorption kinetics are thoroughly discussed based on the TEM observations and density functional theory (DFT) calculations.

关键词： energy transfer   luminescence   luminescence decay dynamics   phosphor   rare earths  

摘要： In this work, a latent energy-transfer process in traditional Eu3+,Tb3+-doped phosphors is proposed and a new class of Eu3+,Tb3+-doped Na4CaSi3O9 (NCSO) phosphors is presented which is enabled by luminescence decay dynamics that optimize the electron-transfer energy process. Relative to other Eu3+,Tb3+-doped phosphors, the as-synthesized Eu3+,Tb3+-doped NCSO phosphors show improved large-scale tunable emission color from green to red upon UV excitation, controlled by the Tb3+/Eu3+ doping ratio. Detailed spectroscopic measurements in the vacuum ultraviolet (VUV)/UV/Vis region were used to determine the Eu3+-O2- charge-transfer energy, 4f-5d transition energies, and the energies of 4f excited multiplets of Eu3+ and Tb3+ with different 4f(N) electronic configurations. The Tb3+-> Eu3+ energy-transfer pathway in the co-doped sample was systematically investigated, by employing luminescence decay dynamics analysis to elucidate the relevant energy-transfer mechanism in combination with the appropriate model simulation. To demonstrate their application potential, a prototype white-light-emitting diode (WLED) device was successfully fabricated by using the yellow luminescence NCSO:0.03Tb(3+), 0.05Eu(3+) phosphor with high thermal stability and a BaMgAl10O17:Eu2+ phosphor in combination with a near-UV chip. These findings open up a new avenue to realize and develop multifunctional high-performance phosphors by manipulating the energy-transfer process for practical applications.

关键词： 运动力学   机械结构   设计   应用  

摘要： 随着我国经济水平的提升,机械制造行业正处于快速发展阶段。当前机械制造业,是我国工业领域以及制造业发展的基石。为应对社会经济结构的改变,机械领域相关企业或单位应该重视机械制造技术的创新以及升级。结合运动学力学原理,提升机械产品的科技感。本文主要介绍运动力学相关原理在机械结构设计中的应用,以期为相关工作人员提供有价值的参考内容。

关键词： Metallic glasses   Molecular dynamics   Mechanical behavior   Atomic structure   Hydrogen  

摘要： Comparative studies on Zr35Cu65and Zr65Cu35amorphous systems were performed using molecular dynamic simulations to explore whether their hydrogenated mechanical behavior depends on the content of hydride-forming *** both of them present an increased strength and ductility after hydrogen microalloying,we observe the improved mechanical behavior for Zr35Cu65is more pronounced than that for *** these two samples,the distribution of configurational potential energy and flexibility volume respectively follows a similar H-induced variation tendency;all of the hydrogenated alloys not just have more stable atoms with smaller flexibility volume,but possess a larger fraction of readily activated ***,the atomic-scale details,based on the local"gradient atomic packing structure"model,indicate minor additions of hydrogen can promote more"soft spots"along with more strengthened"backbones"in the low-Zr alloy than that in the high-Zr sample,which endows the former with much higher strength and deformability after hydrogen *** regard this finding as a further step forward to distilling the tell-tale metrics of the H-dependent mechanical behavior observed in Zr-based metallic glasses.

关键词： 运动力学   机械结构   设计  

摘要： 在当下制造业发展迅速,基础设施建设发展火热的状况下,对于机械结构设计的研究变得尤为重要.本文就针对运动力学在机械结构设计之中的应用进行了一定的探讨,供有关部门进行参考.

关键词： 纳米机械加工   晶体铜   表层形成机理  

摘要： 晶体铜纳米机械加工技术前的发展受到机械加工理论及实际加工工艺、质量测量等诸多方面的制约,对加工表面形成机理及损伤的控制、测量等方面均有待理论和实践多方面的提高。表层形成机理是机械加工机理的重要一环,制约着纳米机械技术的提高。为此,文章基于分子动力学可信有用的模拟原理,从晶体铜纳米机械加工原理、表层损伤的检测控制等方面对晶体铜纳米机械加工技术的表层形成机理进行了分析。

关键词： 机械臂   非线性摩擦模型   动力学建模   Newton-Euler法   正-反向动力学   机械臂运动学   运动轨迹  

摘要： 现有研究大多采用分段线性组合而成的拟非线性摩擦模型来描述机械臂各关节摩擦力矩大小及其分布,忽略了低速区关节摩擦的实际非线性变化,而该非线性变化恰恰是影响机械臂轨迹精度及稳定性的关键因素之一。基于此,着重研究机械臂关节非线性摩擦模型及其对机械臂末端轨迹的影响。对多关节机械臂进行几何机构建模,对任意设定的机械臂理想运动轨迹,通过机构运动学分析得到各关节的角位移、角速度和角加速度。考虑非线性摩擦,建立高可靠性的关节非线性摩擦的一般模型。对给定的理想运动轨迹下的角位移、角速度和角加速度进行Newton-Euler反向动力学分析,从而得到各关节的非线性驱动力矩。基于一般非线性摩擦模型,将得到的驱动力矩代入正向动力学模型中得到机械臂末端实际的运动轨迹。通过上述分析步骤,深入研究各关节在不同类型驱动力矩组合条件下对机械臂末端运动轨迹、及各关节角位移的影响。研究结果表明机械臂各关节的不同摩擦形式对末端运行轨迹影响显著,各关节驱动力矩的变化对其相邻关节的角位移也有明显影响。

关键词： 机械式枣去核设备   动力主轴   工作原理   性能指标   计算分析  

摘要： 文章对机械式枣去核设备的设计、工艺及工作方式进行了介绍,同时开展了动力主轴的计算分析,并与现有技术进行了对比。经鉴定检验,该设备能够满足预期控制要求且运行良好,对今后枣去核设备的设计思路有一定的指导作用。

关键词： 重症肺炎   呼吸衰竭   俯卧位机械通气   血气分析指标   血流动力学  

摘要： 目的:探讨俯卧位机械通气对重症肺炎并呼吸衰竭患者血气分析指标、血流动力学的影响。方法:选取2017年12月~2019年12月收治的重症肺炎并呼吸衰竭患者64例为研究对象,采用随机数字表法分为研究组和对照组,各32例。两组均给予常规治疗,对照组予以仰卧位机械通气治疗,研究组予以俯卧位机械通气治疗,对比两组患者不同体位机械通气治疗前和治疗后1 h、6 h、7 d后血气分析指标、血流动力学指标,对比两组患者治疗前及治疗7 d后急性生理与慢性健康状况评分。结果:给予不同体位机械通气治疗后,两组血氧饱和度、氧合指数均有改善,与同组治疗前比较,差异有统计学意义(P<0.05);研究组氧合指数在治疗6 h、7 d后较对照组显著提升,差异有统计学意义(P<0.05);治疗前及治疗后两组血流动力学指标比较无显著性差异(P>0.05);治疗7 d后两组患者急性生理与慢性健康状况评分较治疗前均有下降,且研究组较对照组下降更明显,差异有统计学意义(P<0.05)。结论:俯卧位机械通气对重症肺炎并呼吸衰竭患者血气分析指标均有改善,对血流动力学无不良影响,能有效改善重症肺炎并呼吸衰竭患者的氧合及病情。