变温环境对橡胶力学性能的影响

文中分析研究了天然橡胶在-50~100℃温度范围内的各项力学性能和交联密度等参数的对应关系,并给出了数学模型,分析了橡胶在变温环境中的力学性能和交联密度的变化原因。结果表明,橡胶的各项力学性能指标与交联密度之间存在较强的相互关系,同时各项力学性能之间也有较强的相关性。在实际测量条件有限的情况下,可以将硬度参数用于橡胶材料力学性能的简单估算。通过建立的数学模型,还有助于橡胶零件根据性能要求设计改进配方,为橡胶产品设计使用和维修全过程提供良好的数据分析手段。文中目前以天然橡胶为实验对象,对后续其他橡胶材料的分析建模具有指导意义。

Incoherent pulse Doppler lidar as the velocimeter system

This note reports a new type of incoherent pulse laser Doppler lidar velocimeter with iodine molecular filter as a frequency discriminator. Its transmitter subsystem applies a Nd:YAG pulse laser which is injected with a single longitudinal-mode diode pumped continuous seeder laser. The field experiment proved that this velocimeter measurement results are consistent with those measured by photoelectric velocimeter. Measurements of eight different velocities show that the standard deviation is 0.56m/s, the range resolution is 3.75m.

Structural characterizations of protonated homodimers of amino acids:Revealed by infrared multiple photon dissociation(IRMPD) spectroscopy and theoretical calculations

Infrared multiple photon dissociation （IRMPD） spectroscopic and theoretical studies of protonated homodimers of amino acids generated by electrospray ionization in the gas phase have been reviewed. Results show that proton affinity （PA） may be applied as a probe to predict their structural type： salt- bridged or charge-solvated. Proline can be viewed as a reference. For an amino acid with a PA value higher than that of proline, the most stable conformation of its protonated homodimer tends to prefer salt- bridged conformation; otherwise, charge-solvated conformation is expected to be the most stable. However, side chain effects may cause the inaccuracy in structural determination due to the strong interactions with the charge, which makes the charge-solvated structure more stable even for species with high PA values. Temperature effect on distribution of different isomers is also very important. In lots of cases, the coexistence of multiple isomers is general, which makes the explanation of an overall IRMPD spectrum difficult. So a statistical view on the distribution of optimized isomers is very helpful.

Ion current rectification: from nanoscale to microscale

Ion current rectification(ICR)is an electrodynamic phenomenon in electrolyte solution which is defined as the asymmetric potential-dependent ion flux through a confined environment,giving rise to asymmetric electrical current-voltage characteristics induced by the influence of an asymmetric electrical double layer structure.Since the discovery of the ICR phenomenon,the observation and application of ICR at nanoscale and microscale have been widely investigated experimentally and theoretically.Here,the recent progress of ICR from nanoscale to microscale is systematically reviewed.Nano/micropore structures of different materials,shapes and pore sizes are first discussed.Then,the factors influencing ICRs by thermodynamically or kinetically regulating the electrical double layer structure are introduced.Moreover,theoretical models are presented to explain the mechanism of ICRs.Based on the understanding of this phenomenon,the applications,especially in biosensors,are discussed.Finally,future developments of this area are briefly presented.This review covers the representative related literature published since 2010 and is intended to give a systematic introduction to this area.

Real-time and in-situ intracellular ATP assay with polyimidazolium brush-modified nanopipette

The level and dynamics of adenosine 5’-triphosphate(ATP) in single living cells are closely related to many kinds of important physiological and pathological processes. Herein, we report a nanosensor based on polyimidazolium brush(PimB)-modified nanopipette for intracellular ATP assay, which shows good selectivity, high spatiotemporal resolution and excellent stability.Both the specific supramolecular interaction between polyimidazolium and ATP, and the rationally tunable property of the ion transport at a confined nanopipette enable the selective assay of ATP even in complex intracellular environment. Moreover, the tiny tip(ca.300 nm) and the low polarized current(e.g., 1 nA) essentially make the as-prepared nanosensor safe to the living cells. The nanosensor is demonstrated to be useful for in-situ monitoring the basal ATP levels of chromaffin cells from wild-type mice and DJ-1 knockout mice, and for real-time monitoring the metabolism process of intracellular ATP.

Influence of vibration on the lubrication effect of a splash-lubricated gearbox

In this study,we investigate the effect of rail vibrations on the lubrication and efficiency of a splash-lubricated gearbox;specifically,the gearbox of a rail-transit vehicle.A high-fidelity 3D numerical model of the gearbox in a moving reference system is described,as well as computational fluid dynamics(CFD)simulations of the gearbox with different vibration directions.The effects of rotational speed,oil-immersion depth,and different oil-injection volume rates on lubrication and efficiency are discussed.We propose a method of evaluating the internal lubrication condition of a splash-lubricated gearbox and quantitatively compare the effects of different operating parameters on lubrication and efficiency.Finally,our experiment to verify the feasibility of the simulation method is described.The results show that with vibration,the churning loss and oil supply for the bearings are significantly higher than those under static conditions.In addition,among different vibrational directions,lateral vibration has the greatest influence on the lubrication condition and efficiency of the gearbox.For the studied railway-vehicle gearbox,the best lubrication condition is achieved at a rotational speed of 1600 r/min and an oil-immersion depth of two times the tooth height(2.Oh).Rotational speed is the operating parameter that has the most significant effect on the lubrication and efficiencyofthegearbox.