关键词： 动力机械   维护   保养   检查  

摘要： 我国的动力机械在不断的进步,不仅提高了生产效率,同样也适应了社会经济发展的趋势。但是有一些实际操作者缺乏对动力机械的维护和保养意识,在使用过程中出现大量的违规操作,大大减少了动力的使用寿命。本文重点对动力机械如何进行合理使用时应注意的事项进行了分析,并提出了对动力机械维护以及保养方面的几点体会。

关键词： 吸入性肺炎   急性呼吸窘迫综合征   机械通气   俯卧位通气   血流动力学   气道引流  

摘要： 目的探讨俯卧位机械通气对重症吸入性肺炎合并急性呼吸窘迫综合征(ARDS)患者氧合、血流动力学及气道痰液引流的影响。方法纳入2010年1月至2012年6月宿迁市钟吾医院ICU收治的28例严重吸入性肺炎合并ARDS患者,镇静、肌松、持续俯卧位通气状态下监测初始仰卧位、俯卧位1 h、俯卧位2 h、恢复仰卧位2 h各时间点的平均动脉压(MAP)、心率(HR)、中心静脉压(CVP)、脉搏血氧饱度(SpO2)、动脉血氧分压(PaO2)、二氧化碳分压(PaCO2),氧合指数(PaO2/FiO2)、痰液引流量等指标。结果与初始仰卧位比较,患者俯卧位1 h、俯卧位2 h时PaO2[(85±12)mm Hg和(97±10)mm Hg比(65±11)mm Hg]、PaO2/FiO2[(150±37)mm Hg和(158±50)mm Hg比(130±28)mm Hg]明显升高(P<0.05),且恢复仰卧位2 h时持续存在[PaO2(87±11)mm Hg,PaO2/FiO2(150±52)mm Hg,P<0.05],MAP、HR、CVP、SpO2差异无统计学意义(P>0.05)。俯卧位2 h时气道痰液引流量较初始仰卧位明显增加[(15.3±2.0)mL比(8.1±1.1)mL,P<0.05],而俯卧位1 h、恢复仰卧位2 h痰液引流量与初始仰卧位时比较差异无统计学意义[(9.1±1.0)mL和(8.3±1.2)mL比(8.1±1.1)mL,P>0.05]。结论俯卧位通气可改善严重吸入性肺炎合并ARDS患者的氧合,且恢复仰卧位后氧合改善持续存在;可改善气道痰液引流,但恢复仰卧位后改善引流作用消失;俯卧位通气对血流动力学无明显影响。俯卧位通气可用于严重吸入性肺炎并ARDS的辅助治疗,需气道充分引流的患者可适当延长俯卧位通气时间。

关键词： Mechanical alloying   Glassy powder   Crystallization   Thermal stability  

摘要： Al76Ni8Ti8Zr4Y4 glassy powder was produced by mechanical alloying process. The phase structure and the crystallization kinetics as well as the thermal stability were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential scanning calorimeter (DSC) in non-isothermal mode. The glassy alloy powder shows a distinct one-stage crystallization process with a wide supercooled liquid region. Crystallization occurs by the precipitation and growth of FCC-Al, with intermetallic compound AlTi, AlTi3, Al2Y and Al3Zr. The non-isothermal crystallization kinetics is analyzed by the modified Johnson-Mehl-Avrami (JMA) equation. The values of the Avrami exponent imply that the dominating crystallization mechanism of the present glassy powder is two- or three-dimensional nucleation and growth controlled by diffusion of atoms. The present glass powder has a large supercooled liquid region (SLR) Delta T-x value (86 K) and the apparent activation energy for crystallization is as high as 316 kJ/mol. The thermal stability was also evaluated by continuous transformation diagram (CHT) obtained by the extended Kissinger equation. To convince the thermal stability for a very long period of time, a quick annealing of the glassy powder at 700 K for 24 h was conducted and the related result was discussed. (C) 2013 Elsevier B.V. All rights reserved.

关键词： 农业机械总动力   预测   时间序列   ARIMA  

摘要： 运用黑龙江省1980-2011年的统计数据,建立了黑龙江省农业机械总动力的ARIMA模型,并进行了预测分析。结果表明:黑龙江省农业机械总动力是非平稳的时间序列,ARIMA模型的拟合效果良好;应用ARIMA(0,2,1)模型进行预测,1980-2011年预测值与实际值之间的平均相对误差为2.87%,可用于今后黑龙江省农业机械总动力的预测与分析。

关键词： 人工心脏瓣膜-患者不匹配   心脏瓣膜   心瓣膜置换术   血流动力学  

摘要： 目的探讨应用不同品牌19 mm机械瓣行单纯主动脉瓣置换术后早期血流动力学变化情况。方法回顾性分析2007年1月至2012年1月北京安贞医院116例单纯主动脉瓣狭窄患者行主动脉瓣置换术后血流动力学变化,其中男61例、女55例,年龄(52±13)岁。根据使用的瓣膜品牌将患者分为3组:***瓣膜组,38例(33%),男20例、女18例,平均年龄(52±15)岁;Carbomedics瓣膜组,40例(34%),男21例、女19例,平均年龄(51±17)岁。On-X瓣膜组,38例(33%),男20例、女18例,平均年龄(55±16)岁。比较患者术前和术后左心室收缩期末内径、左心室舒张期末内径、射血分数(EF)值、室间隔厚度、左心室壁厚度、主动脉瓣瓣上流速、跨瓣压差以及术后有效瓣口面积指数(EOAI)。结果三组患者术前及术后的左心室收缩期末内径、左心室舒张期末内径、EF值、室间隔厚度、左心室壁厚度差异均无统计学意义(P>0.05)。主动脉瓣瓣上流速和跨瓣压差术前、术后有差异有统计学意义。***瓣膜组和Carbomedics瓣膜组患者较On-X瓣膜组患者的术后主动脉瓣瓣上流速[(244.30±33.67)cm/s vs.(249.69±79.13)cm/s vs.(294.83±52.05)cm/s]和跨瓣压差[(27.77±3.33)mm Hg vs.(33.58±18.90)mm Hg vs.(38.56±13.21)mm Hg]明显偏小,其差异有统计学意义。结论运用19 mm机械瓣进行主动脉瓣置换术,***和Carbomedics瓣膜较On-X瓣膜有更好的血流动力学效果。

关键词： Micro-mechanics   Apple   Enzyme degradation   Kinetics   Diffusion  

摘要： The enzymatic texture loss during apple maceration was studied by two micro-mechanical techniques. The first technique consisted of a 5% strain compression cycles at a strain rate of 4.5 x 10(-4) s(-1). The second technique consisted on micro-puncture of the apple parenchyma with a small needle. The first technique led to the peripheral tissues degradation modelling with a first order kinetic reaction or a more pertinent Weibull function. The second technique evidenced that the jagged part of the load vs penetration curve corresponded to an interaction between the needle tip and the turgescent apple texture and the fractal dimension of this jagged part was chosen as the texture parameter. Modelling the enzyme diffusion phenomenon with the second Fick's law and taking into account the model previously established on peripheral tissues allowed the estimation of an equivalent enzyme diffusivity through the apple parenchyma varying between 3.5 x 10(-11) and 5.5 x 10(-11) m(2) s(-1). (c) 2013 Published by Elsevier Ltd.

关键词： mechanical properties   molecular dynamics   nanowires   SiGe   vibrational properties  

摘要： In this work, we examine the vibrational and mechanical properties of clamped-clamped rectangular SixGe1-x and Si/SixGe1-x nanowires (NWs) using molecular dynamics simulations. A virtual atomic force microscope nanotip is used to drive the vibration. The frequency response, the beat vibration phenomenon and the calculation of mechanical properties such as quality factor Q and Young's modulus E are thoroughly analyzed. The influence of added mass and hydrogen passivation on the NW resonator performance is also demonstrated. The decreasing frequency trend with increasing Ge concentration was different for binary alloys and alloy superlattices, while it remained unaffected by the superlattice period. The beat vibration phenomenon driven by a single excitation was observed at elevated temperatures for all studied configurations. The resonance frequency decreases linearly with increasing temperature whereas the Q-factor follows a power law decrease. The Young's modulus E obtained through stress-strain computational experiments is found to be overestimated compared to the classical beam theory. Frequency decreases linearly as more atoms are added to the resonator. For low temperatures, the quality factor of composite Si/Ge resonators increased from 10(4) to 10(5) at T=23K, after performing hydrogen passivation on the NW free surfaces. The frequency shift due to the change in stoichiometry in a Si NW, alongside with representative snapshots of the vibrational behavior.

关键词： POLYAMIDES   NANOCOMPOSITE materials   RESEARCH   TITANIUM dioxide   POLYMERIC nanocomposites   NANOPARTICLE research   DIFFERENTIAL scanning calorimetry   NUCLEATION   CRYSTALLIZATION  

摘要： Titanium dioxide (TiO2) nanoparticles were pretreated with excessive toluene-2,4-diisocyanate (TDI) to synthesize TDI-functionalized TiO2 (TiO2-NCO), and then polymeric nanocomposites consisting of polyamide 6 (PA6) and functionalized-TiO2 nanoparticles were prepared via a melt compounding method. The interfacial interaction between TiO2 nanoparticles and polymeric matrix has been greatly improved due to the isocyanate (NCO) groups at the surface of the functionalized-TiO2 nanoparticles reacted with amino groups (NH2) or carboxyl (COOH) groups of PA6 during the melt compounding and resulted in higher tensile and impact strength than that of pure PA6. The nonisothermal crystallization kinetics of PA6/functionalized TiO2 nanocomposites was investigated by differential scanning calorimetry (DSC). The nonisothermal crystallization DSC data were analyzed by the modified-Avrami (Jeziorny) methods. The results showed that the functionalized-TiO2 nanoparticles in the PA6 matrix acted as effective nucleation agents. The crystallization rate of the nanocomposites obtained was faster than that of the pure PA6. Thus, the presence of functionalized-TiO2 nanoparticles influenced the mechanism of nucleation and accelerated the growth of PA6 crystallites. POLYM. COMPOS., 35:294-300, 2014. (c) 2013 Society of Plastics Engineers

关键词： Polyoxymethylene   recycled carbon fibre   composites   reinforcement   mechanical properties   crystallization kinetics  

摘要： Recycled carbon fibre was employed as a reinforcing material to prepare polyoxymethylene?based composites through a simple melting extrusion. An effective approach was developed to clean and modify the surface of as-received recycled carbon fibre with nitric acid and then with a silane-coupling agent. The mechanical evaluation demonstrated that a significant reinforcement was achieved for polyoxymethylene/recycled carbon fibre composites due to the improved interfacial adhesion between fibres and the matrix. The thermal stabilities of the composites were also improved in the presence of recycled carbon fibre. The morphological observation of impact fracture surfaces indicated a good interfacial boding between fibres and matrix. The studies on nonisothermal and isothermal crystallization behaviors showed that recycled carbon fibre acted as a nucleation agent for the crystallization of polyoxymethylene domain in composites; therefore, the crystallization rate and nucleation density increased remarkably due to the heterogeneous nucleating effect of recycled carbon fibre. These crystallization features may be advantageous for the enhancement of mechanical performance and processability of polyoxymethylene?based composites. Derived from a combination of polyoxymethylene and recycled carbon fibre, this study may provide a development guide for sustainable engineering materials with a great potential as well as a low cost for industrial and civil applications.

关键词： Spatial ecology   Patchy landscape   Model reduction   Reaction-diffusion equation   Patch model  

摘要： Reaction-diffusion models for the dynamics of a biological population in a fragmented landscape can incorporate detailed descriptions of movement and behavior, but are difficult to analyze and hard to parameterize. Patch models, on the other hand, are fairly easy to analyze and can be parameterized reasonably well, but miss many details of the movement process within and between patches. We develop a framework to scale up from a reaction-diffusion process to a patch model and, in particular, to determine movement rates between patches based on behavioral rules for individuals. Our approach is based on the mean occupancy time, the mean time that an individuals spends in a certain area of the landscape before it exits that area or dies. We illustrate our approach using several different landscape configurations. We demonstrate that the resulting patch model most closely captures persistence conditions and steady state densities as compared with the reaction-diffusion model.