关键词： 工程机械   换挡过程   动力学模型  

摘要： 分析了换挡过程中各传动部件的工作原理,建立了发动机-变矩器联合动力学模型、整车行驶模型和变速器换挡模型,进而建立了应用于换挡过程分析的工程机械液力机械传动系统动力学模型.推导出工程机械换挡过程的运动方程.仿真分析了典型装载机在换挡过程中的动力学行为.

关键词： 农业机械   燃油喷射系统   单体泵   泵喷嘴   共轨   专利分析  

摘要： 针对柴油机目前广泛应用的3种燃油喷射系统(电控单体泵系统、电控泵喷嘴系统、共轨燃油喷射系统)进行分析,从专利申请趋势、技术发展趋势、区域分布、主要竞争机构以及在农用发动机中的应用等角度探讨其竞争态势。结果表明,电控单体泵、电控泵喷嘴系统整体技术已趋于稳定,目前技术发明主要布局在系统零部件或新材料研发等外围专利上,共轨燃油喷射系统技术已趋于成熟,德国和日本在相关技术领域处于绝对领先地位,我国在该领域的研究与开发尚处于起步阶段。

关键词： 电动汽车   电磁制动   耦合制动   制动力分配   制动能回收  

摘要： 针对现行电动汽车再生制动的不足,提出一种新型电磁机械耦合再生制动系统(electromagnetic-mechanical coupled regenerative braking system,EMCB),并对其进行动力学分析和耦合机理研究;基于EMCB系统和理想制动力分配曲线提出一种制动力分配策略,构建EMCB系统模型和控制策略仿真系统,应用Car Sim&Simulink联合仿真平台,以有、无滑移率控制的紧急制动工况为例,对制动能回收、制动稳定性和制动舒适性等进行对比研究和验证分析。研究结果表明,所提出的制动力分配策略不仅实现中低制动强度下实际制动力分配曲线与理想I曲线高度吻合,还满足高制动强度下制动效能的需求,即保证了制动稳定性和制动舒适性,又提高了能量回收效率,有效增加了电动汽车的续驶里程,为进一步获得良好的防抱死制动系统(ABS)、电子制动力分配系统(EBD)、电子稳定系统(ESP)等控制性能奠定了基础。

关键词： 机械通气模式   新生儿胎粪吸入综合征   血流动力学   影响  

摘要： 目的探究不同机械通气模式对新生儿胎粪吸入综合征血流动力学的影响。方法选取2014年1月~2016年7月我院新生儿胎粪吸入综合征104例为研究对象,采用随机数字表法分为常规通气组和高频通气组,每组52例。常规通气组采用常频机械通气治疗方法 ,高频通气组采用高频振荡机械通气治疗方法。比较两组患儿治疗总有效率、呼吸机应用时间、住院时间;比较两组患儿治疗前后氧分压、二氧化碳分压、每搏量、搏动指数。结果高频通气组患儿新生儿胎粪吸入综合征治疗总有效率高于常规通气组(P<0.05);高频通气组呼吸机应用时间、住院时间均短于常规通气组(P<0.01);治疗前两组患儿氧分压、二氧化碳分压、每搏量、搏动指数相似(P>0.05);治疗后高频通气组氧分压、二氧化碳分压显著优于常规通气组(P<0.05)。治疗后两组每搏量、搏动指数与治疗前比较,差异无统计学意义(P>0.05)。结论高频机械通气模式对新生儿胎粪吸入综合征血流动力学有改善作用,可更好地改善血气分析结果 ,缩短呼吸机治疗时间和住院时间,改善患儿预后。

关键词： 吉林石化公司   汽机   密封环   车间   王志  

摘要： 王志久是吉林石化公司动力二厂汽机车间一名机械师,1.8米的个头,身材微胖,黑黝黝的国字脸上,总是挂着和蔼的笑容,大家都亲切地叫他'老王'。屈指算来,再有个6月,老王就要退休了。精打细算过日子是他那个年代人的特点,老王就是车间里最'抠'的那个人。腊月里,车间检修滤水器时拆卸下18对螺栓。

关键词： Algal growth dynamics   Mechanistic model   Photobioreactor   Nutrient uptake   Algal excretions  

摘要： A comprehensive mechanistic model for describing algal growth dynamics in a photobioreactor was developed in this work with state of the art understanding and realistic assumptions for major associated processes. The model included 27 state variables related to various algal processes. This model was validated with extensive experimental data obtained from independent growth experiments in batch reactors, and was able to simulate system performance reasonably well. The comprehensive nature of the formulation also highlights the complex inter-relationship between all processes, and provides a tool for gaining more systematic insights into algal behavior in photobioreactors and other such systems. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Gaussian Processes   Mechanistic emulation   Model order reduction   Hydrology   Principal components   Nonnegative matrix factorization  

摘要： System identification, sensitivity analysis, optimization and control, require a large number of model evaluations. Accurate simulators are too slow for these applications. Fast emulators provide a solution to this efficiency demand, sacrificing unneeded accuracy for speed. There are many strategies for developing emulators but selecting one remains subjective. Herein we compare the performance of two kinds of emulators: mechanistic emulators that use knowledge of the simulator's equations, and purely data-driven emulators using matrix factorization. We borrow simulators from urban water management, because more stringent performance criteria on water utilities have made emulation a crucial tool within this field. Results suggest that naive data-driven emulation outperforms mechanistic emulation. We discuss scenarios in which mechanistic emulation seems favorable for extrapolation in time and dealing with sparse and unevenly sampled data. We also point to advances in Machine Learning that have not permeated yet into the environmental science community. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Indoor dispersion   CFD   Mixing   Pollutant   Safety   Automation  

摘要： Understanding mixing times for transient pollutants in mechanically ventilated rooms is important for resilience and safety planning for accidental releases of toxic material. There is a lack of information on the ability of simple models available to predict these times for ventilated spaces with different geometries and ventilation configurations. Three analytical mixing time models, including a novel jet transit based approach, have been selected for comparison with computational fluid dynamics (CFD) predictions for a wide range of cuboidal rooms with ceiling ventilation. A modelling tool has been developed, using open source and open source based software, to automatically build and run a large number of Reynolds averaged Navier-Stokes CFD models. The tool has been used to study the dependence of the chosen mixing metrics on room geometry and ventilation parameters, such as the air change rate, for a transient pollutant entering the room via the ventilation system. The room volume, shape, air change rate and vent layout were varied for each room using a Sobol sequence experimental design. The CFD tool has been used to assess the validity of the analytical mixing time models and to derive parameters for the scenarios of interest. Crown Copyright (C) 2017 Published by Elsevier Ltd.

关键词： Molecular dynamics  

摘要： In this article, we present two principal stimuli that affect the deformation response: additional covalent crosslinking and external deformation. Additional crosslinking leads to hybrid gels which show improved toughness in comparison to the physical gels. The article considers also the change of response of the model as a consequence of external mechanical loading. In this case, the structural changes driven by deformation induce permanent structural changes owing to extensive stretching analogous to filament drawing in spider silk or collagen. Almost identical atomistic configurations are transformed into various materials, depending on the stimulus and the conditions. The intensity of stimuli can be regulated also in real materials. The degree of covalent crosslinking can be regulated for example by ultraviolet irradiation. The permanent changes are observed only when the stretching ratio is sufficiently large and stretching is quick. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

关键词： Anelastic deformation   Cell adhesion   Cell mechanics   Viscoelasticity  

摘要： Cell adhesion is an essential biological process. However, previous theoretical and experimental studies ignore a key variable, the changes of cellular volume and pressure, during the dynamic adhesion process. Here, we treat cells as open systems and propose a theoretical framework to investigate how the exchange of water and ions with the environment affects the shape and dynamics of cells adhered between two adhesive surfaces. We show that adherent cells can be either stable (convex or concave) or unstable (spontaneous rupture or collapse) depending on the adhesion energy density, the cell size, the separation of two adhesive surfaces, and the stiffness of the flexible surface. Strikingly, we find that the unstable states vanish when cellular volume and pressure are constant. We further show that the detachments of convex and concave cells are very different. The mechanical response of adherent cells is mainly determined by the competition between the loading rate and the regulation of the cellular volume and pressure. Finally, we show that as an open system the detachment of adherent cells is also significantly influenced by the loading history. Thus, our findings reveal a major difference between living cells and nonliving materials.