ISBN: (纸本)9787030702937

ISBN: (纸本)9787111701712

关键词： 液压机械   无级变速器   行星排   换段   动力学  

摘要： 课题组使用AMESim和Adams两个软件进行联合仿真,研究了拖拉机液压机械无级变速器换段过程行星排不同换段时序的动力学特性。仿真结果表明:换段时序不同,行星排齿轮啮合力也不同;随着换段重叠时序的增加齿轮啮合力增大,加剧轮齿间磨损,使得行星排振动加剧;在保证变速器换段的平顺性和效率的情况下,降低换段重叠时序有助于达到减振、降噪和延长齿轮使用寿命的效果。

关键词： 呼气末正压   机械通气   下腔静脉变异度   血流动力学  

摘要： 目的 探讨呼气末正压 (PEEP) 对机械通气患者下腔静脉变异度 (dIVC) 及血流动力学的影响。方法 48 例因呼吸衰竭进行机械通气并需使用脉波指示剂连续心排血量 (PICCO) 进行血流动力学监测的患者,均给予深镇静镇痛状态下定容型持续指令通气 (V-CMV) 模式正压通气。比较不同 PEEP 下血流动力学指标[心脏指数 (CI)、心输出量 (CO)、体循环阻力 (SVR)]、下腔静脉变异度(dIVC) 及心脏前负荷相关指标[每搏量变异 (SVV)、脉压变异 (PPV)、全心舒张末期容积指数 (GEDVI)]。结果 与呼吸支持前比较,CI、CO 在 0~5 cm H_(2)O PEEP 下逐渐增加,SVR 逐渐降低,比较差异均有统计学意义 (P<0.05);7~15 cm H_(2)O PEEP 下,CI、CO 逐渐降低,SVR 逐渐增加,比较差异均有统计学意义(P<0.05)。不同 PEEP 下 dIVC 变化幅度较小,比较差异无统计学意义 (P>0.05)。在 15 cm H_(2)O PEEP 下SVV 显著高于呼吸支持前,GEDVI 低于呼吸支持前,差异均有统计学意义 (P<0.05);在 15 cm H_(2)O PEEP下 PPV 与呼吸支持前对比,差异无统计学意义 (P>0.05)。GEDVI 随着 PEEP 升高降低,与 PEEP 呈负相关。结论 患者 dIVC 可准确反映血容量,不同 PEEP 会对患者动态容量指标产生影响。7~10 cm H_(2)O PEEP 可有效减少对血流动力学的影响,最大程度减少对心脏功能的损伤,有效提高危重患者抢救成功率。

关键词： 水下机械手   水动力学模型   动力学模型   RBF神经网络   自适应鲁棒控制  

摘要： 水下机械手可以代替人类在水下的极端环境中完成各种复杂作业,目前已得到广泛应用,针对水下机械手控制方法的研究已成为水下机械手领域研究的热点,但目前的研究多局限于静水环境,忽略自然水体中存在的定向流,造成研究环境与实际工况存在较大差异。本研究考虑水体中定向流的影响,建立基于水动力学模型的水下机械手动力学模型,提出基于定向流影响的RBF神经网络进行模型整体逼近的非线性鲁棒自适应控制方法,并进行稳定性分析。通过分析不同速度定向流的轨迹跟踪仿真结果,证明该控制方法在控制误差、稳定性及自适应性方面相比常见的计算力矩法存在明显优势。

关键词： 出风口过滤器   改造设计   试验对比  

摘要： 通过对原FXD3-J型动车组动力车机械间出风口过滤器使用情况分析,找出缺陷不足的原因,并进行两次设计改进,介绍设计改进的原理与结构。针对原始设计、第一次改进设计和第二次改进设计,分别在过滤器试验台上进行试验,寻求最优方案,得到FXD3-J型动车组动力车机械间出风口过滤器第二次改造的形式为最优方案的结论。

关键词： curing kinetics   cyanate ester   hyperbranched benzoxazine   mechanical properties  

摘要： In the current study, three different curing kinetics models were used to analyze the curing kinetics of hyperbranched benzoxazine (HB-PED230) and monofunctional benzoxazine (P-a) modified cyanate ester (CE) resin by non-isothermal differential scanning calorimeter. Moreover, the effects of two benzoxazines on the copolymerization behavior, thermal stability, and mechanical properties of CE resin were studied. Compared with the P-a modified CE resin, HB-PED230 greatly reduces the curing temperature of the copolymer, while improving the bending strength and impact strength. The curing temperature of HB-PED230 modified CE resin was 79 degrees C lower than neat CE resin, while the CE/P-a blended resin only reduce 48 degrees C. As the amount of HB-PED230 increased, the flexural strength and flexural modulus of the copolymers were improved. Surprisingly, when 7 wt% of HB-PED230 was added, the impact strength of the copolymer was increased by 177.6%, implying that the toughness of CE resin had been greatly improved. Moreover, the fracture morphology of the copolymers was observed by scanning electron microscope. In summary, a small amount of HB-PED230 blending can effectively improve the overall performance of CE resin.

关键词： carbon dioxide   carbon steel   electrochemical studies   formic acid   hydrogen sulfide  

摘要： Anodic dissolution of carbon steel in solution mixtures of simulated CO2-H2S in the presence of formic acid (0-500 ppm) was investigated using electrochemical methods such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results show that the corrosion rate increases with an increase in the concentration of formic acid. Potentiodynamic polarization data revealed that the increase in cathodic current density plays a significant role in the increase of carbon steel corrosion rate. A combination of equivalent circuits was employed to model the impedance spectra of the carbon steel electrode acquired at open circuit potential and different overpotentials. The EIS data obtained at various overpotentials were further analyzed by reaction mechanism analysis (RMA) approach to interpret the dissolution mechanism. A multi-step reaction model including two dissolution paths and ferrous intermediate adsorbed species determined the dissolution behaviour of carbon steel. The best fit RMA kinetic parameters were retrieved using an optimization technique and the surface coverage of adsorbed species was estimated. Surface morphology of corroded steel surfaces was also examined with field emission scanning electron microscope demonstrating aggressive uniform corrosion of carbon steel in the presence of formic acid.

关键词： Cavity quantum electrodynamics   Optomechanics   Squeezing of quantum noise   Nanoparticles  

摘要： We theoretically show that strong mechanical quantum squeezing in a linear optomechanical system can be rapidly generated through the dynamical instability reached in the far red-detuned and ultrastrong coupling regime. We show that this mechanism, which harnesses unstable multimode quantum dynamics, is particularly suited to levitated optomechanics, and we argue for its feasibility for the case of a levitated nanoparticle coupled to a microcavity via coherent scattering. We predict that for submillimeter-sized cavities the particle motion, initially thermal and well above its ground state, becomes mechanically squeezed by tens of decibels on a microsecond timescale. Our results bring forth optical microcavities in the unresolved sideband regime as powerful mechanical squeezers for levitated nanoparticles, and hence as key tools for quantum-enhanced inertial and force sensing.

关键词： 铁水脱硫   KR机械搅拌法   反应动力学  

摘要： KR铁水脱硫工艺(又称机械搅拌法)因其较优的反应动力学条件,及脱硫效率高、脱硫效果稳定和脱硫成本低等优点,广泛应用于国内外各大钢铁企业,逐渐成为铁水预处理脱硫的首选工艺。综述了近年来提高KR机械搅拌法铁水脱硫动力学条件方面的研究成果,通过了解国内外脱硫反应动力学条件的发展动态,为KR动力学条件的改进或优化提供参考。