关键词： 呼吸衰竭   机械通气   胃肠动力药   胃肠功能障碍   效果  

摘要： 目的探讨机械通气治疗的呼吸衰竭患者胃肠动力药的应用研究。方法50例重症加强护理病房(ICU)行机械通气治疗的呼吸衰竭患者,随机分为对照组和观察组,每组25例。两组均给予常规治疗,对照组采用常规运动及按摩治疗,观察组在对照组基础上采用用胃肠动力药西沙必利片治疗。比较两组胃肠功能障碍症状发生率,治疗后急性胃肠损伤(AGI)分级,治疗前后急性生理学与慢性健康状况评分系统Ⅱ(APACHEⅡ)评分及腹内压,治疗前后肺功能指标[氧合指数(PaO_(2)/FiO_(2))、静态顺应性(Cst)、动态顺应性(Cdyn)]。结果观察组患者的胃肠功能障碍症状发生率12.00%明显低于对照组的60.00%,差异具有统计学意义(P<0.05)。观察组治疗后AGI分级明显优于对照组,差异具有统计学意义(P<0.05)。治疗前,两组患者的APACHEⅡ评分及腹内压比较差异无统计学意义(P>0.05);治疗后,观察组患者的APACHEⅡ评分(10.54±2.97)分、腹内压(7.47±2.36)mm Hg(1 mm Hg=0.133 kPa)均明显低于对照组的(16.41±3.68)分、(15.72±3.08)mm Hg,差异具有统计学意义(P<0.05)。治疗前,两组患者的Cdyn、Cst、PaO_(2)/FiO_(2)比较差异无统计学意义(P>0.05);治疗后7 d,观察组患者的Cdyn、Cst、PaO_(2)/FiO_(2)均明显高于对照组,差异具有统计学意义(P<0.05)。结论机械通气治疗的呼吸衰竭患者应用胃肠动力药能有效降低胃肠功能障碍发生率,改善胃肠功能,抑制胃肠损伤,并有助于呼吸力学的改善,提高整体治疗效果。

关键词： 日光性角化病   面部   光动力   机械磨削   疗效   护理  

摘要： 目的:探讨机械磨削术联合光动力疗法治疗面部日光性角化病的疗效及护理要点。方法:选择2015年1月-2019年5月笔者医院收治的124例面部日光性角化病患者为研究对象,均采用机械磨削术联合光动力疗法治疗,观察其临床疗效,观察临床护理对疗效的影响。结果:124例患者,经4~6次治疗后,12个月后随访,120例患者痊愈,4例患者部分复发。结论:机械磨削术联合光动力疗法治疗面部日光性角化病,具有创伤小、复发率低等优点,在治疗过程中做好相应的护理工作,对于保证治疗顺利进行和良好疗效具有重要作用。

关键词： 书本内容   摩擦学设计   专业书籍   机械装备   现代机械   知识逻辑   西南交通大学   摩擦动力学  

摘要： 在2019年的8月1日《机械装备摩擦学设计及典型失效案例》一书在西南交通大学出版社出版,书籍采用了传统的16开,大小适中便于学生翻阅学习,在书本内容上则做到了具体详实,理论知识逻辑清晰,案例分析具体明确,是一本可供本专业学生学习和行业从业者参考的专业书籍。《机械装备摩擦学设计及典型失效案例分析》为了便于阅读理解,在语言措辞上言简意赅,核心意思突出。

关键词： Solubility  

摘要： As known, the poor toughness of Polylactic acid (PLA) limits its further application, especially as a bone implant withstanding complex loadings. Blending PLA with Poly (epsilon-caprolactone) (PCL) under the action of compatibilizers is a proven method to improve the toughness of PLA, while the excess compatibilizers is hard to remove and easy to contaminate the matrix material. This study employed a molecular dynamics simulation combining experimental testing method to investigate the miscibility, mechanical properties and printability of PLA/PCL blends at different compositions without adding any compatibilizers, so as to obtain an ideal PLA/PCL filament for FDM printing bone scaffolds. Results of binding energy distribution and intermolecular interaction show that the miscibility of PLA and PCL is not very good, only the blend of 9PLA/1PCL is miscible. The calculated static mechanical properties and tensile testing results indicate the stiffness or hardness of blends decrease with the addition of PCL, while the toughness firstly increases and then decreases with the introduction of PCL, and the blend of 9PLA/1PCL possesses the best ductility and toughness. Moreover, the results of surface morphology confirm the miscible of 9PLA/1PCL blend and explain why the tensile properties of 9PLA/1PCL is the best, a better miscibility indicating better mechanical properties. Finally, the results of printability indicates that, due to the fluidity of PCL, the printability of blend becomes worse with the increase of PCL content, and the blend of 9PLA/1PCL possesses a relatively good printability. This work provides a practical guidance to the design of PLA/PCL blend filament for FDM printing bone scaffolds. [GRAPHICS] .

关键词： Molecular dynamic simulation   Cross-linking   SWCNT   Polymeric nano-composite   Thermo-mechanical properties  

摘要： In this study, the mechanical and thermal properties of carbon nanotube-reinforced polymeric nano-composite have been predicted by simulating molecular dynamics (MD). The polymer matrix is of epoxy polymer type with EPON828 resin along with EpiCure Curing Agent-3234 hardener which is reinforced with a single-walled carbon nanotube (SWCNT). Mechanical and thermal properties such as density, elastic modulus, Poisson's ratio, and coefficient of thermal expansion (CTE) for various states, including the cross-linking degree of resin and hardener molecules 10-65%, carbon nanotubes (CNTs) with different diameters, and weight fraction of carbon nanotubes of 0.5, 1 and 2% have been estimated. The cell's stiffness matrix in all cases was extracted, and thermo-mechanical properties were obtained using it. The placement of carbon nanotubes in a representative cell is completely random which has a random orientation, and the cell is dynamically analyzed separately under constant temperature and constant pressure conditions at the specified time, and after equilibration, its properties are extracted. The results show an obvious increase in the elastic modulus by increasing cross-linking degrees and an increase in the elastic modulus, and a significant decrease in the nano-composite CTE when the weight fraction of CNTs has increased. The experimental studies and simulation of other researchers were examined to validate the simulation that, the results are in good agreement with each other.

关键词： Manganite nanopowder   Grain growth   Cation segregation   X-ray diffraction   Magnetism  

摘要： The nanograin polycrystalline Nd1-xCaxMnO3 +/-delta (x = 0;0.15;0.25) with orthorhombic structure were obtained by mechanical activation. X-ray diffraction analysis and transmission electron micrographs showed that the average crystallite size is in the range of 10-30 nm. Grain growth kinetics was studied using three different models using data from high temperature X-ray diffraction analysis. Two models - normal grain growth and grain growth in a two-phase system - were compatible with experimental data up to higher temperatures. Grain growth was found to be kinetically hindered in Ca-doped compositions despite the lower activation energy. That was accounted for by the surface modification involving formation of oxide phases trapping grain boundaries and limiting their mobility. It was found that the Neel temperature in NdMnO3+delta monotonically decreased with decreasing grain size, while the Curie temperature in Nd0.85Ca0.15MnO3-delta varied nonmonotonically. The spin-reorientation transition was found as strongly manifested in NdMnO3+delta and completely suppressed in Nd0.85Ca0.15MnO3-delta. The magnitude of the spin-reorientation effect decreased with decreasing grain size. The peculiarities of the magnetic behaviour were accounted for by the reduction of Jahn-Teller distortion with decreasing grain size, the emergence and increase of local structural and magnetic inhomogeneities, competing d-d superexchange, double-exchange and f-d exchange. (C) 2021 Published by Elsevier B.V.

关键词： Nanocantilevers  

摘要： We present coherent phonon-mediated dynamics for addressable motion transfer in a scalable mechanical transducer consisting of three nearest-neighboring coupled micro-cantilevers. To connect two distant cantilevers without direct interaction, two parametric pumps are applied to couple the cantilevers to an intermediate mechanical mode simultaneously. We demonstrate that the distant cantilevers can be coherently coupled even when the intermediate mode is effectively decoupled as a result of two-pump on-resonance coupling. The phonon-mediated coupling is controlled for long-range transferring of both iterating and intra-mode motions while avoid unwanted exciting of the intermediate mode.

关键词： Si anodes   Li-ion batteries   fracture   structural relaxation   atomistic simulation  

摘要： This is the first study that employs large-scale atomistic simulations to examine the stress generation and deformation mechanisms of various Si nanopillars (SiNPs) during Li-ion insertion. First, a new robust and effective minimization approach is proposed to relax a lithiated amorphous SiNP (a-SiNP), which outperforms the known methods. Using this new method, our simulations are able to successfully capture the experimental morphological changes and volume expansions that SiNPs, hollow a-SiNPs, and solid crystalline SiNPs (c-SiNPs) experience upon maximum lithiation. These simulations enable us to selectively track the displacement of Si atoms and their atomic shear strain in the Li3.75Si alloy region, allowing us to observe the plastic flow and illustrate the atomistic mechanism of lithiation-induced deformation for various SiNPs for the first time. Based on the simulation results, a simple fracture mechanistic model is used to determine the fracture resistance of SiNPs, showing that the hollow a-SiNP is the optimal form of Si as an anode because it has the highest fracture resistance. The crack propagation simulation suggests that the preexisting dislocations in pristine c-Si can contribute toward the fracture of c-SiNPs during lithiation. These findings can guide the design of new Si-based anode geometries for the next-generation Li-ion batteries.

关键词： Mechanical property   Dislocation   Superalloys   Re effect   Molecular dynamics  

摘要： Re is one of the newly added key elements of single crystal Ni-based superalloys for advanced aero-engine turbine blades. The mechanisms that how Re influences the mechanical behavior of single crystal Ni-based superalloys are still debatable. In the present work, we trace back to some Re associated fundamental aspects affecting mechanical behavior by experiments, first-principle and molecular dynamics methods. The distribution of Re, the effect of Re on lattice parameter, stacking fault energy, elastic and plastic deformations at different temperatures are systematically analyzed. The results not only quantitatively reveal some significant mechanisms behind the Re effect, but also bring inputs for larger scale simulation methods. Based on the simulation results, the influence of Re on long-term deformation property of single crystal Ni-based superalloys is reasonably discussed in the viewpoint of thermodynamic and dislocation dynamics. (C) 2021 Elsevier B.V. All rights reserved.

关键词： morphology   polyurea coatings   theory and modeling  

摘要： Today, polyurea is known as one of the most famous and widely used protective coatings in the world. The unique properties of polyurea are at such a high level that it is possible to use this coating in a wide range of applications. Although polyurea is generally made from the reaction between two types of precursors (diisocyanate and diamine), it is challenging to choose the right precursor pair for producing a coating with a specific application due to the great variety of introduced diisocyanate and diamine precursors. On the other hand, the experimental synthesis of the formulations and the study of their performance is also very costly and time-consuming. In this study and by examining a series of commercially available precursors for polyurea coatings synthesis, well-known materials have been introduced and classified. Then, a representative of each formulation family is simulated by a molecular dynamics and mechanical approach using a three-step method on atomic, meso, and continuum scales, and the mechanical properties of the formulations are extracted. Then, by examining the response of each formulation to the three types of dynamic load (earthquake, projectile impact, and air blast), the protective capabilities of these formulations have been compared, and the optimal formulation for each application has been introduced.