关键词： 呼吸窘迫综合征   血流动力学变化   肺容积   高频机械通气   早产儿   重症加强治疗病房   二氧化碳分压   体积描记法  

摘要： 近期澳大利亚学者在意大利一个新生儿重症加强治疗病房（ICU）进行了一项前瞻性单中心非随机的观察性临床研究，旨在评价存在呼吸窘迫早产儿高频通气过程中呼气末肺容积和血流动力学的变化。研究假设持续高膨胀压力阻碍了肺的血流量，并减少了肺容积。氧合变化、通气和外周灌注作为该研究的次要评价指标。在复张的过程中，同时记录在每个气道压时的呼气末肺容积（通过呼吸感应体积描记法测量）、氧饱和度、灌注指数、脑和肾组织氧合、心率、经皮二氧化碳分压（PtCO2）和潮气量。

关键词： 装载机   燃油箱   柴油机系统   进排气系统   散热系统  

摘要： 由于欧日和北美地区2010年10月1日开始执行非道路工程机械柴油机排放IIIB阶段标准,2013年10月1日开始执行非道路工程机械柴油机排放Ⅳ阶段标准,为满足欧日和北美地区非道路工程机械柴油机排IIIB阶段要求,开发设计一种轮式装载机,在原满足非道路工程机械柴油机排放IIIA阶段机型基础上进行动力系统升级。

关键词： 流体动力学理论   接触力模型   “Coulomb”摩擦力模型   间隙   润滑  

摘要： 在考虑关节间隙与润滑的条件下,对机械系统的动力学性能进行了分析。认为关节在只考虑间隙的情况下其接触为干接触,并基于Lankarani-Nikravesh接触力模型建立了间隙关节元素之间的法向接触力;利用修正的"Coulomb"摩擦力模型计算了其摩擦力。而对于考虑关节润滑的情况,利用流体动力学理论(基于雷诺方程)计算了其流体压力,进而通过多体系统动力学方程建立了考虑关节润滑的机械系统动力学模型;以平面曲柄滑块机构为例,通过数值计算比较了间隙关节是否存在润滑时该机构的动态特性。数值结果证明,考虑关节润滑时该机构的动力学性能更加接近理想状态。

关键词： Density functional theory   Gas phase   Decomposition   Reaction mechanism   Precursor  

摘要： The reaction mechanism of the gas phase decomposition of Pb[(Pr-i)(2)PSSe](2) single-source precursor has been investigated theoretically by means of the density functional theory (DFT). The geometries of all the stationary points and the selected points along the potential energy surfaces were optimized at the M06/LACVP* level of theory. The harmonic vibrational frequencies of all the stationary points were calculated at the above same level of theory. Ten possible reaction pathways including seventeen reaction pathways on both the singlet and doublet potential energy profiles were explored. The results indicate that the steps that lead to PbS formation on both the singlet and the doublet potential energy surfaces are favored kinetically over those that lead to PbSe and ternary PbSexS1-x formation. However, thermodynamically, the steps that lead to ternary PbSexS1-x formation are more favorable than those that lead to PbSe and PbS formation on the doublet PESs. Moreover, the energetics also suggests the proposed scheme involving the dissociation of PbSe to be the most stable species on the singlet PES. Density functional theory calculations of the gas phase decomposition of the complex indicate that the deposition of ternary PbSexS1-x in chemical vapor deposition may involve more than one steps but the steps that lead to the its formation are consistent with a dominant role for thermodynamic factors, than kinetic. (C) 2015 Elsevier B.V. All rights reserved.

关键词： 企业经济效益   江苏大学   机械系   主任   生产企业   CGT   市场营销   品牌效应  

摘要： 目前国内的尿素生产企业水平参差不齐,所以规范化很重要。获得CGT标识标志使用授权的企业,必须严格按照要求去做。CGT标识标志有3年的有效期,协会会定期抽查,不达标的企业将会被淘汰,企业在市场营销方面就会受到影响,所以企业必须要认真对待。同时,产品的后续推广也很重要。让用户了解和使用有CGT标识标志的企业的产品,这样品牌效应就更好,也可以使生产尿素的企业经济效益提高。

关键词： 教育部重点实验室   流体动力传输   重型机械   控制   工程技术研究中心   工程研究中心   燕山大学   材料科学  

摘要： 燕山大学重型机械流体动力传输与控制实验室的前身为东北重型机械学院液压教研室，始建于1977年。2005年实验室成为河北，2007年成为机械工业流体动力传输技术重点实验室。实验室是燕山大学国家冷轧板带装备及工艺工程技术研究中心、国家地方联合工程研究中心、极端条件下机械结构和材料科学国防重点学科实验室、先进锻压成形技术与科学教育部重点实验室的重要组成部分。

关键词： 电-机械转换器   空气动力学   高速   动网格  

摘要： 针对高频高速工况下电-机械转换器动圈组件的空气阻尼问题,基于开孔对平板空气阻尼特性影响的理论分析,对电-机械转换器的绕线筒进行结构优化,并采用动网格技术对其运动空气阻尼特性进行CFD计算。结果表明,随着运动频率和速度的增大,动圈组件受到的空气阻尼几乎与速度的平方成正比。对绕线筒的端部开孔,可大大提高空气流通能力,改善其周围流场的速度和压力分布。相对于结构一,结构二和结构三的空气阻尼分别减小64.3%和97.1%,效果显著。高频高速工况下作用于电-机械转换器的空气阻尼,能够通过优化其内部结构而得到减小。

关键词： 脑小血管病   环壁张力   急性腔隙性脑梗死   神经影像  

摘要： 目的探讨急性腔隙性脑梗死患者脑小血管病（cSVD）负荷与颈总动脉机械动力学指标环壁张力（WT）的相关性。方法前瞻性连续入组芜湖市第一人民医院神经内科自2010年9月至2012年12月收治的首发急性腔隙性脑梗死患者227例。对所有患者行常规MRI序列和磁敏感加权成像扫描，依据患者MRI上无症状腔隙性脑梗死、脑白质病变、脑微出血以及扩大的血管周围间隙的出现和程度评测患者cSVD负荷。同时超声测量患者颈动脉内径并计算WT。使用Logistic回归分析患者颈动脉WT与cSVD负荷的相关性。结果6例患者cVSD负荷评分0分，37例患者cVSD负荷评分1分，103例患者cVSD负荷评分2分，61例患者cVSD负荷评分3分，20例患者cVSD负荷评分4分。将患者按照上述cSVD负荷评分成5组（0-4分组），每组的收缩期WT依次为：（5．79±0．24）×10^4 dyne／cm^2、（5．70±0．49）×10^4 dyne／cm^2、（5．89±0．71）×10^4 dyne／cm^2、（7．12±1．19）×10^4dyne／cm^2、（6．63±0．76）×10^4dyne／cm^2、舒张期WT依次为：（3．37±0．31）×10^4dyne／cm^2、（3．29±0．26）×10^4dyne／cm^2、（3．50±0．43）×10^4dyne／cm^2、（3．99±0．49）×10^4dyne／cm^2．（4．30±0．85）×10^4dyne／cm^2。单因素分析结果显示，年龄、高血压病史、糖尿病病史、颈总动脉收缩期和舒张期末内径、收缩期WT以及舒张期WT在5组患者间分布差异有统计学意义（P〈0．05）。回归分析结果显示，收缩期WT[优势比（OR）：1．555，95％可信区间（CI）：1．203-2．479，P=-0．038]及舒张期WT（OR：5．287，95％CI：2．713～10．302，P=0．001）与cVSD负荷有显著关联。结论急性腔隙性脑梗死患者WT是影响cSVD负荷的独立危险因素。

关键词： Bulk fill   Giomers   Resin based composite   Hardness   Modulus of elasticity   Polymerisation kinetics  

摘要： Objectives: The study aims to characterise a low and high viscosity giomer bulk fill resin restorative with established low and high viscosity resin-based composite (RBC) restoratives at simulated clinical relevant specimen depths. Methods: The irradiance of a light curing unit (Bluephase 20i) was measured on a laboratory-grade spectrometer at distances up to 10 mm from the light tip (in 1 mm increments). Polymerization kinetics (real-time decrease of C=C double bond and degree of cure, DC) and micro-mechanical properties (Vickers hardness/HV;Depth of cure/DOC;Indentation modulus/E) were assessed at varying specimen depths (0.1-6 mm in 100 mm steps for E, DOC and HV and 0.1, 2, 4 and 6 mm for DC) for a 20 s irradiation. Results: One and two-way ANOVA (alpha = 0.05) were performed. The parameter material has a significant (p < 0.001) effect on DC (eta(2)(P) = 0.839), HV (eta(2)(P) = 0.683), and E (eta(2)(P) = 0.536), whereas the specimen depth influenced only DC (eta(2)(P) = 0.584) but not HV (p = 0.093) or E (p = 0.133). The polymerisation kinetic could be described by an exponential sum function, distinguishing between the gel and the glass phase. The hardness drop out was lower than 20%, indicated a depth of cure of 6 mm for all materials. Conclusions: The low and high viscosity giomer bulk-fill restoratives fulfil the requirements of bulk-fill placement, since under the analysed irradiation conditions an adequate depth of cure of >4 mm was identified. Variation of DC with specimen depth was low, with little variation at specimen depths of <4 mm. The micro-mechanical properties of the giomer materials were higher compared with the conventional RBC materials. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Electrohydraulic systems   electrohydraulics   pressure feedback   proportional valve   counterbalance valve  

摘要： The goal of this article is to formulate and validate a model for the prediction of the mechanical dynamics of hydraulic actuators controlled by means of proportional directional valves (PDVs). The model inputs are the pressure at the PDVs ports and the current to the solenoids: no further input is required even when additional elements are installed in the line between PDV and actuator. The model finds application in closed-loop control of mobile electrohydraulic machines for load handling, construction and agriculture. These machines are typically based on open-loop control of the actuator speed. Nevertheless, these machines are often characterized by non-cyclical operation, large disturbances (e.g. drive on uneven ground) and time-varying parameters (e.g. load mass). Due to these features, closed-loop control has potential to improve the machine dynamics with consequent benefits in terms of productivity and operation safety. However, because of the harsh working conditions, the installation of feedback sensors in proximity of the hydraulic actuator is impractical and rarely exploited. The proposed model offers a solution to implement closed-loop control using pressure sensors in a compact and reliable arrangement, next to PDVs ports. The case study is a hydraulic crane using PDVs in combination with counterbalance valves (CBVs) to control the mechanical arms. The experiments were performed without altering the basic hydraulic circuit of the commercial crane and using an electronic hardware with performance comparable to standard controllers for mobile hydraulics. The results show the accuracy of the model for all operating conditions, including the assistive load condition.