方向导数的计算公式的注记

方向导数本质上也是函数的一种变化率.利用向量的Schmidt正交化方法进行坐标变换,将方向导数转换为对新变量的偏导数,再结合多元复合函数的求导法则,给出方向导数计算公式的一种新的证明.     

振动噪声等高图的电驱动桥噪声预测及优化*

在项目开发前期通过优化电驱动桥扭矩特性的设计,可以规避噪声大问题。根据电驱动桥台架在对应扭矩下的振动噪声特性,提出了一套稳定高效的测试流程和分析方法。首先设计了一套完整的试验流程,制定了精准的数据分析方法。然后绘制出能够全面反映电驱动桥振动噪声特性的等高图。最后利用电驱动桥台架的振动噪声等高图,准确评估电驱动桥加速工况下振动噪声风险,为主机厂和电驱动桥零部件企业提供电驱动桥扭矩特性设计前期指导。利用该方法成功识别到某电驱动桥匀速及加速工况下电机及齿轮的啸叫问题。通过优化电驱动桥扭矩特性设计,电机48阶噪声峰值降低了8.5dB(A),确认该方法准确可靠,具备推广应用价值。     

Nanosized multilayer films with concurrent photochromism and electrochromism based on Dawson-type polyoxometalate

An inorganic-organic composite multilayer film constructed of poly(vinyl alcohol) (PVA) with Dawson-type phosphotungstate anion [P₂W₁₈O₆₂]⁶⁻ (P₂W₁₈) and poly(allylamine hydrochloride) (PAH) were fabricated on quartz, ITO, silicon and CaF₂ substrates by a layer-by-layer self-assembly method. The film was provided with concurrent photochromism and electrochromism. IR spectra showed that the structure of the PVA was fully maintained in the multilayer film. And their photochromic and electrochromic properties were investigated by UV-vis spectra, cyclic voltammetry (CV), chronoamperometry (CA) measurement and X-ray photoelectron spectra (XPS). Atomic force microscopy (AFM) was used to investigate the surface topography. This study provides a new route to explore the possibility of application to polyoxometalate-based hybrid inorganic-organic materials.     

povel isomers of hexasulfur: Prediction of a stable prism isomer and implications for the thermal reactivity of elemental sulfur

High-level ab initio molecular orbital calculations were employed to explore the potential energy hypersurface of hexasulfur, S(6). Twelve isomeric structures of S(6) have been identified: two unbranched rings (chair and boat), one trigonal prism of D(3h) symmetry, two singly branched rings (S(5)double bondS), three triplet chains, one singlet chain, and three doubly branched rings (Sdouble bondS(4)double bondS). The prism structure is essentially a cluster of three S(2) molecules connected via a six-center pi(*)-pi(*)-pi(*) interaction. It is by 51 kJ mol(-1) less stable than the lowest-energy chair form. The reactions to generate the boat, the prism, and the singly branched isomers from the chair form are predicted to have lower barriers than the ring opening reaction of cyclo-S(6), which requires an activation energy of 149 kJ mol(-1). The prism and singly branched isomers are found to be more reactive species than the chair form and they are potential sources of S(2) in chemical reactions involving elemental sulfur.     

Three-dimensional nitrogen-doped graphene hydrogel supported Co-CeOx nanoclusters as efficient catalysts for hydrogen generation from hydrolysis of ammonia borane

Benefit from the strong synergistic electronic effect between Co and CeO_x, as well as the strong metalsupport interaction between Co-CeO_x and 3D NGH, the as-synthesized Co-(CeO_x)_0.91/NGH catalyst exhibits excellent catalytic activity toward hydrolysis of ammonia borane, with the turnover frequency (TOF) value of 79.5 min^-1.     

Synthesis and Application of Some Dianilinosilanes,Bis (Trimethylsilyl) Phenylenediamines and Dialkyl Benzo-1,3,2-Diazasilolines as Antioxidants

Negative hyperconjugation of the type n_N→σ* is responsible for the planar or almost planar geometry at nitrogen in certain S–N compounds.     

Malonyl peroxides in organic synthesis (microreview)

Chemistry of Heterocyclic Compounds - A summary of the most recent applications of malonyl peroxides as reagents in organic synthesis is discussed. The microreview covers the latest selected...