Phase‐Junction Electrocatalysts towards Enhanced Hydrogen Evolution Reaction in Alkaline Media

To ensure sustainable hydrogen production by water electrolysis, robust, earth‐abundant, and high‐efficient electrocatalysts are required. Constructing a hybrid system could lead to further improvement in electrocatalytic activity. Interface engineering in composite catalysts is thus critical to determine the performance, and the phase‐junction interface should improve the catalytic activity. Here, we show that nickel diphosphide phase junction (c‐NiP₂/m‐NiP₂) is an effective electrocatalyst for hydrogen production in alkaline media. The overpotential (at 10 mA cm^?2) for NiP₂‐650 (c/m) in alkaline media could be significantly reduced by 26 % and 96 % compared with c‐NiP₂ and m‐NiP₂, respectively. The enhancement of catalytic activity should be attributed to the strong water dissociation ability and the rearrangement of electrons around the phase junction, which markedly improved the Volmer step and benefited the reduction process of adsorbed protons.     

生物质气化技术的研究进展

生物质能是一种可再生能源,它来源于生物体(如植物、动物、微生物等)通过光合作用将太阳能转化为化学能,并以有机物的形式储存。生物质能可以在适当的条件下被转化为热能、电能、生物燃料等,是一种重要的替代传统化石能源的可持续能源。生物质气化作为生物质的开发路径之一,是利用生物质生产合成气的有效方式。本文综述了生物质气化技术的研究,包括传统气化技术、共气化技术、化学链气化技术以及超临界气化技术等。介绍了每个气化技术的实验研究,阐述了各个气化技术的特点;详细介绍了化学链气化中载氧体与共气化中掺杂剂的使用。本文旨在探索使生物质气化效率达到最优的方案,并列举了目前存在的局限性,为进一步发展生物质气化技术以及生物质气化研究提供有益参考。     

Hyperchaos,quasi-period and coexisting behaviors in second-order-memristor-based jerk circuit

The European Physical Journal Special Topics - This paper generalizes a second-order-memristor-based jerk circuit, which is achieved by substituting the first-order memristor contained diode-bridge...     

溶剂热法合成六方氮化硼纳米晶的影响因素研究

以Li_3N和BBr3为原料,采用溶剂热法在220 ℃合成了h-BN纳米晶,研究了反应时间、表面活性剂和诱导晶粒对产物的影响.研究结果表明:反应产物主要为h-BN,同时含有少量c-BN,随着反应时间从12 h延长至36 h,晶粒尺寸从20 nm增大至80 nm;十二烷基苯磺酸钠的引入可以控制产物颗粒尺寸在10 nm左右,并且使球形度得到提高;以h-AlN为诱导晶粒时,产物中六方相含量增加,并且出现了h-BN纳米棒.     

On Precision Measurement of the Frequency of the 1<Superscript>1</Superscript><Emphasis Type="Italic">S</Emphasis>–2<Superscript>3</Superscript><Emphasis Type="Italic">S</Emphasis> Forbidden Transition of a Helium Atom

The possibility is demonstrated of a precision frequency measurement for the 1¹S₀?2³S₁ forbidden transition (at 62.6 nm) of a helium atom using the stimulated Raman scattering method. The 1¹S₀ singlet state is the ground state of ⁴He, while the metastable 2³S₁ state has the lowest energy in the triplet part of the spectrum (⁴He*). The transition has a very small natural width, which allows us to consider it as a possible reference for creation of a frequency standard in the vacuum ultraviolet region.     

Preference of sensory neural coding for 1/f signals

We investigated the influences of different types of temporal correlations in the input signal on the functions and coding properties of neurons in the primary visual cortex (V1). We found that the temporal transfer functions of V1 neurons exhibit higher gain, and the spike responses exhibit higher coding efficiency and information transmission rates, for the 1/f (natural long-term correlation) signals than for 1/f(0) (no correlation) and 1/f(2) (stronger long-term correlation) signals. These results suggest that the intermediate long-term correlation ubiquitous to natural signals may play an important role in shaping and optimizing the machinery of neurons in their adaptation to the natural environment.     

Absolute mean square exponential stability of Lur’e stochastic distributed parameter control systems

In this work the absolute mean square exponential stability of Lur’e stochastic distributed parameter control systems has been addressed. Delay-dependent sufficient conditions for the stochastic stability in Hilbert spaces are established in terms of linear operator inequalities (LOIs). Finally, the stochastic wave equation illustrates our result.     

Method for studying boundary value problems with nonlinear boundary conditions

A constructive approach to the determination of an approximate solution of a boundary value problem with nonlinear boundary conditions g[z (0), z (T)]=0 is proposed. Existence of the exact solution is proved, and error estimates for the constructed approximate solution are provided.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 42, No. 7, pp. 951–957, July, 1990.     

On the convergence of hybrid polynomial approximation to higher derivatives of rational curves

In this paper, we derive the bounds on the magnitude of l  th (l=2,3)$(l=2,3)$ order derivatives of rational Bézier curves, estimate the error, in the _L∞$L_{\infty }$ norm sense, for the hybrid polynomial approximation of the l  th (l=1,2,3)$(l=1,2,3)$ order derivatives of rational Bézier curves. We then prove that when the hybrid polynomial approximation converges to a given rational Bézier curve, the l  th (l=1,2,3)$(l=1,2,3)$ derivatives of the hybrid polynomial approximation curve also uniformly converge to the corresponding derivatives of the rational curve. These results are useful for designing simpler algorithms for computing tangent vector, curvature vector and torsion vector of rational Bézier curves.     

Effects of substituent and solvent on the structure and spectral properties of maleimide derivatives

The maximum absorption wavelength , emission wavelength (λ_em) and the related oscillator strength (f) of the maleimides in the ground and first excited states were calculated by using the DFT, CIS and the time-dependent density functional theory (TD-DFT) methods, where the molecular structures were optimized by DFT/B3LYP/6-31G^* calculation. Solvent effects on the maleimides were examined using the PCM simulation at DFT/B3LYP level with the 6-31G^* basis set. For N-substituted maleimide, the substituent gives only a slight influence on the maleimide chromophore, while planar conformation of PhMLH leads to the improvement in π-delocalization from substituent to maleimide unit. For 3,4-substituted maleimide, the steric repulsion between substituent and maleimide chromophore influences the extent of π-delocalization and the molecular conformation. The calculated and λ_em of maleimides are in good agreement with the experimental data. In the gas phase, both absorption and emission peaks are red-shift as compared to the non-substituted maleimide. Under solvent environment, the more planar conformation of PhMLH shows a blue-shift in the calculated and λ_em as compared with other N-substituted maleimides. For 3,4-substituted maleimides, the effect of substitution produces the most significant spectral red-shift as compared to other maleimides.