关键词： Bainite   Kinetics   Tensile properties  

摘要： The present investigation concerns high performance mechanical components such as crankshafts, injection rails, or many other parts which are manufactured using specially designed steel grades. These steel grades are such that they produce a mostly bainitic microstructure when cooled from a hot-forming process and without the need for heat-treatment. The relationship between cooling conditions (i.e. product dimensions), mechanical properties and bainite transformation kinetics is investigated on laboratory and industrial materials. It is shown that fast transformation kinetics are best to ensure insensitivity to cooling conditions. Material design based on this principles allowed the manufacture of a steel grade that exhibited a constant UTS of approximately 1200 MPa for bars as small as 16 mm up to over 160 mm. (C) 2013 Elsevier B.V. All rights reserved.

关键词： Cardiopulmonary bypass   Catheter ablation   Impella   Left ventricular assist device   Mechanical circulatory support   Unstable ventricular tachycardia  

摘要： Background: Catheter ablation of hemodynamically unstable ventricular tachycardia (VT) is possible with mechanical circulatory support (MCS), little is known regarding the relative safety and efficacy of different supporting devices for such procedures. Methods and results: Sixteen consecutive patients (aged 63 +/- 11 years with left ventricular ejection fraction of 20 +/- 9%) who underwent ablation of hemodynamically unstable VT were included in this study. Hemodynamic support included percutaneous (Impella(R) 2.5, n = 5) and implantable left ventricular assist devices (LVADs, n = 6) and peripheral cardiopulmonary bypass (CPB, n = 5). Except for 2 Impella cases, hemodynamic support was adequate (with consistent mean arterial pressure of >60 mmHg) to permit sufficient activation mapping for ablation. In the Impella and CPB groups, mean time under hemodynamic support was 185 +/- 86 min, and time in VT was 78 +/- 36 min. Clinical VT could be terminated at least once by ablation in all patients except 1 case with Impella due to hemodynamic instability. Peri-procedural complications included hemolysis in 1 patient with Impella and surgical intervention for percutaneous Impella placement problems in another 2. The median number of appropriately delivered defibrillator therapies was significantly decreased from 6 in the month before VT ablation to 0 in the month following ablation (p = 0.001). Conclusions: Our data suggest that peripheral CPB and implantable LVAD provide adequate hemodynamic support for successful ablation of unstable VT. Impella(R) 2.5, on the other hand, was associated with increased risk of complications, and may not provide sufficient hemodynamic support in some cases. (C) 2013 The Authors. Published by Elsevier Ireland Ltd. All rights reserved.

关键词： POLYVINYL acetate   DIELECTRICS   ARRHENIUS equation   GLASS transition temperature   GLASS transitions   SUPERPOSITION principle (Physics)   CHEMICAL relaxation  

摘要： R. Richert has made a comment to a paper of ours in which dielectric measures on poly(vinyl acetate) suggest that there is a change in temperature dependence of the temperature shift factors from Vogel-Fulcher-Tammann (VFT) to Arrhenius near to the glass transition temperature. He notes that we made an error in the description of his data and further notes that the data we did not use show a VFT behavior to well below the glass transition. Here we respond to the comment and add additional analysis that suggest that the differences in results are related to the differences between time temperature superposition (TTS) of data and fitting the data with a Kohlrausch, Williams, and Watts function. When TTS is used on the data from Wagner and Richert [Polymer38, 255 (1997)] the change in behavior to Arrhenius-like below Tg is recovered.

关键词： POLYVINYL acetate   DIELECTRICS   GLASS transition temperature   CALORIMETRY   GLASS transitions   CHEMICAL equilibrium   DIELECTRIC relaxation   ELECTRIC fields  

摘要： The temperature dependence of polymer dynamics below the standard glass transition is of considerable interest. Glassy relaxation dictates the process of physical aging, and understanding these slow dynamics helps in assessing a possible divergence at a finite temperature. In a recent paper, Zhao and McKenna have measured the equilibrium dynamics of poly(vinyl acetate) in the range from T g ? 15 K to T g + 30 K using Struiks protocol [J. Zhao and G. B. McKenna, J. Chem. Phys.136, 154901 (2012)]. In a figure that is meant to compare their results with dielectric relaxation data from Wagner and Richert [Polymer38, 255 (1997)], dielectric retardation data from that work is shown instead. The corrected figure shows a considerable difference in the two measurements below T g ? 10 K, Arrhenius versus Vogel-Fulcher-Tammann behavior, and a possible source of the difference is discussed.

关键词： 混合动力公交客车   自动机械变速器   换档决策   动态规划  

摘要： 混合动力汽车与传统车有很大区别,目前的混合动力AMT多采用传统的单参数或双参数换档规律,难以充分发挥混合动力的优势。基于简化后混合动力系统模型,建立了混合动力客车燃油经济性、排放性最优和换档频率较低的目标泛函,并设计了基于动态规划的新型求解算法。最后得出了在中国典型城市公交循环工况下的最优换档决策序列。在中国典型城市公交工况下分别使用传统双参数和基于动态规划的换档决策进行仿真和实车试验,结果表明混合动力公交客车应用最优换档决策序列后,其燃油经济性有了明显提高,换档次数明显减少。

关键词： 变压力   研究所   创新   精神   信心   机械   领导班子   经济发展  

摘要： 本刊讯10月22日，机械研究所召开坚定信心、创新发展动员大会。传达贯彻局领导班子对该所经济发展问题专题研究精神。会议号召全所干部职工振奋精神，坚定信心,变压力为动力，积极走创新发展之路,再创新的辉煌。会上,党委书记黄欣向大家通报了所领导班子成员参加局领导班子为本所经济发展问题“会诊”情况。他指出，局领导班子对我所发展高度重视，召开专题会议进行研究，我们必须变压力为动力，静下心，多思考，出实招，认真做。

关键词： 高原肺水肿   急性呼吸窘迫综合征   机械通气   血流动力学   氧动力学  

摘要： 目的探讨早期机械通气治疗对急性高原肺水肿（HAPE）继发急性呼吸窘迫综合征（ARDS）患者氧合及血流动力学的影响。方法以2001年5月至2006年12月格尔木市人民医院收治的8例HAPE继发ARDS患者为研究对象，在肺水肿发生24h内接受有创机械通气治疗，监测治疗前及治疗96h后血流动力学和心排血量、动脉和混合静脉血气及氧代谢指标。结果治疗前患者右房压（RAP）、平均肺动脉压（mPAP）、肺循环阻力指数（PVRI）、肺内分流（Qs／Qt）均高于正常，氧输送（DO2）、氧摄取率（02ER）及氧合指数（PaO2／FiO2）均低于正常。机械通气治疗后，患者动脉血氧分压（PaO2）、Pa02／FiO2、动脉血氧饱和度（SaO2）、混合静脉血氧分压（Pv02）、混合静脉血氧饱和度（Sv-02）均较治疗前明显增加[Pa02（mmHg，1mmHg=0．133kPa）：70.3±2．9比49．9±3．5，t=15．292，P=0．001；PaO2／FiO2（mmHg）：201．6±4．8比134．5±5．2，t=19．618，P=0．004；Sa02：0．929±0．021比0．780±0．073，t=6．226，P=0．002；PvO2（mmHg）：54．8±2．9比44．9±2．6，t=6．767，P=0．002；SvO2：0．726±0．017比0．663±0．053，t=3．262，P=0．008]，心率（HR）、RAP、mPAP、肺动脉楔压（PAWP）、PVRI、有心室作功指数（RVSWI）、Qs／Qt较治疗前明显降低[HR（次／min）：73±2比102±13，t=6．228，P=0．000；RAP（mmHg）：6．9±1．0比13．9±1．5，t=3．609，P=0．008；mPAP（mmHg）：18．5±2．9比41．6±3．0，t=4．773，P=0．000；PAWP（mmHg）：6．9±2．2比14．0±4．2，t=2．747，P=0．030；PVRI（kPa·S·L^-1）：26．3±1．7比49．6±10．0，t=9．861，P=0．000；RVSWI（g·cm^-1·min·m^2）：11．0±1．9比22．0±1．5,t=12．704，P=0．000；Qs／Qt：（26±18）％比（35±15）％，t=7．603，P=0．000]，同时心排血指数（CI）、DO2、氧消耗（VO2）、O2ER亦较治疗前明显增加[CI（mL·s^-1·m^-2）：71．68±6．67比70．01±6．67，t=2．832，P=0．036；DO2（L·min^-1·m^-2）：460．9±14．0比410．0±3．1．t=9．268．P=0．000：VO2（L·min^-1·m^-2）：158．5±9．2比129．9±5．3，t=2．818，P=0．004；02ER：（20±1）％比（18±1）％，t=7．652，P=0．000]。经治疗8例患者全部存活。结论HAPE继发ARDS在导致呼吸衰竭的同时出现明显肺循环血流动力学及全身氧代谢紊乱，以早期机械通气为核心的综合治疗可明显改善患者的氧合，纠正肺动脉高压，提高患者心排血量及氧输送。

关键词： 机械通气   恒定送气流速模式   自动变流模式  

摘要： 目的 探讨不同机械通气模式对老年腹部手术患者围术期呼吸力学及血流动力学的影响.方法 选择2012年1～10月深圳市第二人民医院择期行腹部手术全麻机械通气的老年患者（年龄＞65岁）48例,随机分为4组,每组各12例,A0组：容量控制通气（VCV）＋自动变流（auto flow）模式;C0组：VCV＋恒定送气流速（const flow）模式;A8组：VCV＋呼气末正压（PEEP）8 mm Hg＋auto flow模式;C8组：VCV＋PEEP 8 mm Hg＋const flow模式.监测每分钟通气量（MV）、气道吸气峰压（APIP）、气道阻力（Raw）、胸肺顺应性（C）、平均动脉压（MAP）、心率（HR）、动脉血氧分压（PaO2）等呼吸力学及血流动力学指标并进行统计学分析比较.结果 ①各组患者在应用VCV＋const flow模式通气60 min时,APIP、Raw、C、MAP、HR及PaO2比较差异均无统计学意义（P＞0.05）.②各组患者在应用各自通气模式4h后,A0组与C0组比较或A8组与C8组比较,APIP和Raw显著降低,C有显著增加,差异均有统计学意义（P＜ 0.05）;A8组Raw低于其他3组,差异有统计学意义（P＜0.05）;而MAP、HR各组差异无统计学意义（P＞0.05）.A8组与A0、C0组比较,或C8组与A0、C0组比较,PaO2显著增加,差异有统计学意义（P＜0.05）.结论 老年腹部手术患者全身麻醉应用VCV＋const flow＋ PEEP 8 mm Hg通气模式,可以降低气道峰压和气道阻力,改善胸肺顺应性,同时提高动脉血氧分压有利于组织供氧,可能有助于预防机械通气所致的肺损伤.

关键词： 优化   内燃机   泵   机械-液压双元动力发动机   锥形阀   容积效率  

摘要： 机械-液压双元动力输出发动机(MHPE)将传统的内燃机和柱塞泵融为一体,可同时或单独输出机械、液压2种动力。MHPE采用锥形阀配流系统,其容积效率高低直接影响MHPE的整机性能。该文以容积效率为目标函数,以锥形阀的工作条件和结构尺寸为约束条件,以MHPE锥形阀的结构参数为优化变量,建立了优化模型,并基于iSIGHT软件进行优化设计。优化结果表明,优化后系统的容积效率提高5.71%,改善程度较大。

关键词： 机械密封   摩擦副   油膜流场   动力特性   数值模拟  

摘要： 为了研究高参数机械密封摩擦副油膜流场动力特性以提高密封系统的稳定性,建立了摩擦副油膜流场的三维有限元模型,运用计算流体力学分析软件对油膜流场的压力、转速、摩擦扭矩、承载力和泄露量等进行了数值模拟,分析了机械密封的工作转速、压力与摩擦副油膜流场的压力场、承载能力、摩擦扭矩及泄漏量间的关系及其影响规律.