汽车多楔带摩擦噪声机理分析与试验研究

针对汽车多楔带传动时噪声的特性与变化规律，通过分析多楔带噪声产生的机理，建立了摩擦振动的理论模型，推导出多楔带传动系统的不稳定条件，并在设计的振动和噪声测试试验台上进行了多楔带传动振动和噪声试验研究。结果表明，带段张力的波动导致了多楔带的低频振动噪声，带与带轮间的黏滑摩擦引起了高频摩擦噪声

基于小波分解的同步带传动噪声特性研究

同步带传动噪声可以分为啮合冲击噪声、横向振动噪声、空气流动噪声和摩擦噪声，每种噪声所处的具体频段不同。为了研究汽车同步带噪声信号的频率分布特性，首先，理论分析了同步带传动各种噪声的频域分布情况；然后，针对ZA型汽车同步带进行变转速变张紧力试验；最后，基于小波分解的分析方法，得出同步带传动噪声信号的频段分布特性。结果表明，随着转速的增加，啮合冲击噪声增加，同步带传动噪声源中啮合冲击噪声能量比重增加，啮合冲击噪声主要集中在高频段，横向振动噪声主要集中在低频段。研究为汽车发动机的减振降噪提供了依据

在Ni沉积的石墨表面氧吸附和还原的反应机理第一性密度泛函理论研究

Nitrogen doped graphene （N-graphene）has been reproted possessing significant oxygen reduction reaction （ORP）activity in recent years. However, how the activity depended on the distribution condiguration of nitrogen and doping concentration are still ambigugous, and the ORP mechanism on N-graphene and the rate-determaing steps are figured out. The adsorption energy of Oads species on the surface in contrast with that on Pt can be used to approximately describe the ORP activity.Using density functional calculationas (VASP),We find that on N-graphene with 9%~20% doping concentration the dissociation adsorption energy of dioxygen is comparable with that on Pt. The change atom and the adsorption energy in variation with N concentration is dominated by the electrostatic force between the oxygen atom and the adsorption-site carbon atom. Too low (20%)nitrogen concentration will depress the electrostatic force of C-O adsorption bond and weaken the adsorption because the oxygen atom will withdraw fewer electrons from the surface

Graphene and N-doped graphene for electrocatalysis

Unique structural and electronic properties of graphene have evoked huge interest in its potential applications in a wide range of fields, e.g. nanoelectronic devices, sensors and catalysis. However, realization of these applications will rely on the availability of high quality graphene on a large scale. We developed here a non-liquid phase method for production of free-standing graphene nanosheets via one step thermal splitting of commercial polycrystalline silicon carbide granules. These graphene sheets contain few defects and exhibit a good stability against oxidation. This novel synthetic approach is expected to enable mass production of high quality graphene, which could promote further development of graphene-based technologies, in particular fuel cell electrocatalysts and other industrial catalysts. On the other hand, theoretical studies predicted that doping graphene with nitrogen can tailor its electronic properties and chemical reactivity. However, experimental investigations are still limited due to the lack of synthesis techniques that can deliver a reasonable quantity. We report here a novel bottom up approach for N-doped graphene based on a simple reaction of tetrachloromethane and lithium nitride under mild conditions. A gram scale N-graphene can be easily obtained in laboratory with varying nitrogen contents. The electronic structure perturbation in the graphene network due to the incorporation of nitrogen has been observed experimentally using STM, which is corroborated by density functional theory simulations. This method could enable a larger scale production since the one-pass yield only depends on the capacity of the autoclave. The obtained N-doped grapheme showed an enhanced activity as a catalyst for fuel cell cathode oxygen reduction reaction with respect to pure graphene and commercial carbon black XC-72