关键词： 血流动力学   心房间传导阻滞   左心房功能  

摘要： 目的探讨心房间传导延迟对小型猪的左心房血流动力学及机械运动功能的影响。方法8只巴马猪在三维电解剖标测系统指引下,在右心房内膜面尝试进行经导管射频消融Bachmann传导束,建立心房间传导延迟模型(消融建模不成功设立为对照组)。通过超声心动图记录左心房机械功能参数,使用Swan-Ganz导管测定血流动力学参数,对比消融建模后即刻(急性期)以及消融后3个月(慢性期)与消融前左心房最大容积、左心房扩大指数、肺毛细血管楔压及心排出量等参数的变化。结果5只猪心房间传导延迟模型建模成功(延迟组),P波宽度从消融术前(69.4±2.9)ms延长至术后(113.4±4.5)ms及术后3个月(115.8±3.9)ms(P<0.001);另外3只猪P波未见明显改变(P=0.47)。延迟组肺毛细血管楔压在消融术后慢性期较消融前明显增加[(18.0±1.8)mmHg(1mmHg=0.133kPa)对(11.2±1.3)mmHg;P<0.001],对照组肺毛细血管楔压则未发生显著变化[(12.3±0.5)mmHg对(12.0±1.0)mmHg;P=0.79]。两组左心房机械运动功能参数改变差异无统计学意义(P均>0.05)。结论心房间传导延迟可导致肺毛细血管楔压显著升高,此可能是射血分数保留心力衰竭的发病原因之一。

关键词： 工程机械市场   济宁   常柴公司   城镇化建设   产品配套   农用机械   新品开发   市场对接  

摘要： 常柴柴油机在山东济宁小型工程机械配套领域发展迅速,已经连续三年实现较大增长,其中在压路机和挖掘机领域配套常柴风冷机的销量逐年上升,年均增长在50%以上,发展态势向好。近年来,常柴公司审时度势,对非农用机械产品配套布局进行了细分规划,紧紧抓住国家加快城镇化建设的发展机遇,在压路机、挖掘机等小型工程机械市场充分发力,加快新品开发,加强市场对接,狠抓产品质量。据悉,常柴公司在济宁小型工程机械配套领域已取得了突破性进展,配套商由最初的4、5家发展到了现在的20多家,市场配套份额已超过50%。

关键词： 大气粉尘   工程机械发动机   磨损   动力性   影响  

摘要： 首先介绍了大气粉尘对工程机械发动机的磨损和动力性的影响,随后分析大气粉尘的形成的原因和具体情况及发动机动力不足的原因,从而有效掌握工程机械发动机防止出现大气粉尘影响的策略,明确工程机械发动机保养的方法,使得大气粉尘对工程机械发动机的磨损情况得到控制,提升发动机的动力性程度。

关键词： IKB alpha   Kusabira-Orange 2   Ubiquitin-proteasomal degradation   PEST domain   Ankyrin repeats  

摘要： In resting cells, the nuclear factor kappa B (NF-kappa B) family of transcription factors is stabilized by complexation with the cytoplasmic inhibitor of kappa B alpha (I kappa B alpha). Extracellular stimuli, such as tumor necrosis factor alpha (TNF alpha) or bacterial lipopolysaccharide activate NF-kappa B through I kappa B alpha phosphorylation and ubiquitin-proteasomal degradation. Herein, we developed a novel biosensor, by fusing the monomeric fluorescent protein Kusabira-Orange 2 to I kappa B alpha (mKO2-I kappa B alpha), to study the dynamics and structure-activity relationship of I kappa B alpha degradation. Site-specific deletion studies on the I kappa B alpha sequence revealed that the C-terminal PEST domain is required in signal-induced proteasomal degradation of I kappa B alpha and functions independently from ankyrin repeats. Using deletion mutants, we show that I kappa B alpha ankyrin repeats do not affect I kappa B alpha degradability but affect its degradation rate. We demonstrate, by both real-time confocal microscopy and western blot analysis, that the half-life of mKO2-I kappa B alpha in response to TNF alpha is approximately 35 min, which is similar to the half-life of endogenous I kappa B alpha. Using this biosensor we also show that selective proteasome inhibitors, such as lactacystin and MG132, inhibit degradation and affect the kinetics of I kappa B alpha in a dose-dependent manner. The techniques described here can have a range of possible applications, such as facilitating studies associated with I kappa B alpha dynamics and biochemical characteristics, as well as the screening of potential proteasome inhibitors.

关键词： Titanium alloy   Phase transformation kinetics   Precipitation   Microstructure   Mechanical properties  

摘要： The influences of up-quenching aging (UQA) and step-quenching aging (SQA) on the microstructure development and mechanical properties of near beta-Ti alloy Ti-5Al-3Mo-3V-2Cr-2Zr-1Nb-1Fe have been comparatively studied. The results showed that a large number of fine alpha precipitates were uniformly formed in UQA sample via omega-assisted nucleation, resulting in a higher aging hardening effect. Whereas under SQA treatment, the alpha precipitates had lower number density and became coarser in addition to inhomogeneous size distribution, in which plenty of alpha precipitates with large aspect ratio (> 50) could be observed. With increasing the aging temperature from 480 degrees C to 650 degrees C, the number density of alpha precipitates with large aspect ratio was gradually reduced, and the hardness interval between UQA and SQA samples was decreased from 90 HV to 20 HV. When aged at high temperature (600 degrees C), a large number of ultrafine a precipitates were obtained in the UQA sample within 30 min, the number density, thickness and length of alpha precipitates were similar to 20 ppt/mu m(2), 40 nm and 180 nm, respectively, resulting in very high peak hardness (473 HV), but a rapid over-aging occurred due to the ripeness of alpha precipitates. The SQA treatment showed no evident over-aging tendency, and could yield a good combination of ultimate tensile strength (1284 MPa) and elongation (8%) with the existence of multiscale a precipitates.

关键词： Particle-fluid flow   Parallel plates   CFD-DEM   JRC   Hydrodynamic and mechanical retardation  

摘要： A coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) approach is used to investigate the hydrodynamic and mechanical behavior of multi-particle, which settle and horizontally transport between two parallel plates. The particle-fluid interaction is two-way coupled, while inter-particle and particles-walls interactions are calculated based on the soft-sphere model. The Joint Roughness Coefficient (JRC) is used to represent the roughness of planar walls, and its effect on particle transport is quantitatively studied. When particles transport between two parallel smooth plates, the planar walls exert extra hydrodynamic retardation, which causes particle transport velocity to decrease with the decrease in the aperture between two plates. In contrast, when particles transport between two parallel rough plates, due to frequent interaction between particles, the mechanical interaction-induced retardation starts to work and further decreases particle transport velocity. Particle longitudinal migration is frequent because of inter-particle interaction, which hinders its transverse transport and even causes particle agglomeration in a duct during horizontal transport. In addition, the mechanical retardation is significantly dependent of particle transport regimes, and its effect gradually increases and changes to be dominant at high particle Reynold number regime. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

关键词： Melting point  

摘要： In the present work, molecular dynamics simulation has been performed to characterize the thermal and mechanical behavior of graphene sheet. For this purpose, graphene sheet is subjected to dynamic heating process and its melting point has been predicted. Structural and thermal properties have been analyzed using radial distribution function and energy per atom. To analyze factors affecting melting temperature, four graphene sheets with different dimensions have been chosen for the dynamic heating process. The melting temperature of graphene decreases with increase in the sheet dimension, hence graphene sheet having smaller dimensions show relatively better thermal stability. To analyze the mechanical behavior, graphene sheet has been subjected to uniaxial tensile loading along zigzag and armchair directions respectively. It is observed that zigzag-oriented graphene sheet shows high fracture strength and stability as compared to armchair direction. Multilayer graphene sheets have been selected to investigate the effect of multilayers on the mechanical strength. It can be revealed from results that fracture strength decreases with increase in layers, however, brittleness of the sample relatively decreases with increase in a number of graphene layers.

关键词： Bubble dynamic behavior   Welding speed   Mechanical constraint   Underwater wet welding   FCAW   Process stability  

摘要： Dynamic behavior of the bubble was investigated by high-speed camera and using the dysprosium lamp method for welding speed ranging from 1.0 mm/s to 6.0 mm/s during conventional underwater wet welding and mechanical constraint-assisted underwater wet welding. Process stability analysis was conducted by welding electric signal to predict the evolution of bubble features. For conventional underwater wet welding, the variation in bubble geometry over time is visually observed and its track morphology changes from a vertically upward track to a deflected track with increasing welding speed. The stable and sustained bubble with its structural integrity benefits from mechanical constraint for all welding speeds. Mechanical constraint can compensate for the insufficient bubble protection and successfully prevent further bubble-induced perturbation on welding arc. In comparison to onshore welding and underwater wet welding with mechanical constraint, conventional underwater wet welding indicates the most variation of welding electric signal. The variation coefficient exhibits similar result with welding speed for the exertion of mechanical constraint, whereas the difference in variation coefficient exists for conventional underwater wet welding. The direct observation over weld morphology is also demonstrated to show the feasibility of bubble control using the developed process. Discernible difference in weld penetration appears, displaying higher value with mechanical constraint than without mechanical constraint.

关键词： Molecular dynamics   ReaxFF   CMP   Diamond   Mechanochemistry  

摘要： Diamond CMP mechanisms have been widely investigated using the CMP experimental methods. However, the experiment could not observe the details of the removal process, it could not explain the mechanism of removal. The atom removal mechanism of chemical mechanical polishing (CMP) process on the diamond surface polished with a silica abrasive in aqueous H2O2/pure H2O was elucidated using ReaxFF molecular dynamics (MD) simulations. The research shows that the oxidation of diamond surface plays a dual role in the removal of C atoms. First, the diamond surface absorbs -OH, O or H to form C-O, C-OH or C-H bonds. Then, the C atoms on the oxidized diamond surface are removed under the mechanical action of abrasive in aqueous H2O2. Three types of C atom removal pathway are detected in the CMP process: it can be removed in the form of CO, CO2 or C chain and C atom removal occurs on the first layer. However, no C atoms are removed in pure H2O. The friction in pure H2O is less than that in aqueous H2O2 due to the lubrication of pure H2O. In addition, comparing the different pressures applied to the abrasive, it is found that the greater the pressure applied, the more -OH adsorbed on the diamond surface so that the more C atoms are removed. This work shows that the removal of C atoms is the result of the combination of chemical and mechanical effects, which helps understand the removal process of C atoms at the atomic scale in the CMP process and provide an effective method to choose the CMP slurry.

关键词： Off-highway vehicles   continuously variable transmission   zero-speed-ratio   design optimization   Pareto optimal solutions  

摘要： The power-cycling hydrodynamic mechanical transmissions have the advantages of continuously adjustable speed ratio and high efficiency compared with the traditional automatic transmissions, so they may be a good substitute for the prior art. For off-highway vehicles which frequently work in low speed and confront great resistance, the zero-speed-ratio torque ratio (TR) of the power-cycling hydrodynamic mechanical transmissions represents the power performance of the vehicles. Furthermore, the complexity of the transmissions is an indispensable consideration for industrial designers. The radial and axial dimensions of the power-cycling hydrodynamic mechanical transmissions are determined by the effective diameter of the torque converter's circuit and the number of transmissions gears, respectively. In order to optimize the zero-speed-ratio TR and the complexity of the power-cycling hydrodynamic mechanical transmissions, a design methodology is proposed. Considering that there is no explicit mathematical relationship between the design variables and the multi-objective functions, the parametric design and numerical simulation for the torque converter are carried out. The intrinsic mapping between the design variables and the multi-objective functions is fitted by the radial basis function neural network. On this basis, the fast and elitist non-dominated sorting genetic algorithm (NSGA-Iota Iota) is used to solve the multi-objective optimization problem. The numerical simulation for one group of solution selected from the Pareto optimal solutions is conducted. The simulation results indicate that the design methodology proposed in this study is effective. The optimal results show that the zero-speed-ratio TR of the power-cycling hydrodynamic mechanical transmissions is heavily influenced by the radial and axial space of such transmissions. The design optimization helps to find the optimal solutions for the power-cycling HMTs, which are superior to the traditional autom