DECAYING SOLUTIONS OF NEUTRAL DIFFERENCE EQUATIONS WITH DELAYS

ＤＥＣＡＹＩＮＧＳＯＬＵＴＩＯＮＳＯＦＮＥＵＴＲＡＬＤＩＦＦＥＲＥＮＣＥＥＱＵＡＴＩＯＮＳ　ＷＩＴＨＤＥＬＡＹＳＸｉｅＳｈｅｎｇｌｉ（谢胜利）（ＪｉｎｚｈｏｕＴｅａｃｈｅｒ＇ｓＣｏｌｌｅｇｅ，湖北荆州师专，邮编：４３４１００）＆ＳｕｉＳｕｎＣｈｅｎｇ...     

含间断项的非线性积分、微分方程极解的存在性

在不涉及紧型条件和耗散型条件的情形下，证明了Ｂａｎａｃｈ空间中含间断项的非线性积分、微分方程极解的存在性，推广了文［１］、［２］和［３］中的结果．     

边界元素法中有关积分的计算方法(Ⅱ)柱状边界条件下对曲面积分及椭圆积分的计算

在柱状边界条件下将对柱侧面的曲面积分表示成一维积分，同时还给出了椭圆积分的计算方法，由对空间立体角积分的算例可知，其计算的速度有了显著的提高．     

A new coordinate condition in general relativity

In this paper, a new coordinate condition in general relativity is proposed. This coordinate condition is just Euler's equations of the harmonic map theory. It is shown that in case of rectangular coordinates our coordinate condition reduces to Fock's harmonic coordinate condition. Using this new coordinate condition the different spherical symmetric solutions of the Einstein equations are discussed. The axisymmetric case is also investigated.     

变厚度圆柱型正交各向异性圆形薄板的非线性非对称弯曲问题

本文首先导出变厚度圆柱型正交各向异性圆形薄板的非线性非对称弯曲的基本方程，利用“两变量法”，引进四个小参数，对厚度线性变化的圆柱型正交各向异性圆形薄板的非线性非对称弯曲问题进行研究，得到了挠度函数W（r，θ）和应力函数F（r，θ）对ε1为N阶及对ε2为M阶的一致有效渐近解．     

Size effect on pull-in behavior of electrostatically actuated microbeams based on a modified couple stress theory

A variety of micro-scale experiments have demonstrated that the mechanical property of some metals and polymers on the order of micron scale are size dependence. Taking into account the size effect on the mechanical property of materials and the inherent nonlinear property of electrostatic force, the static pull-in behavior of an electrostatically actuated Bernoulli–Euler microbeam is analyzed on the basis of a modified couple stress theory. The approximate analytical solutions to the pull-in voltage and pull-in displacement of the microbeam are derived by using the Rayleigh–Ritz method. The results show that the normalized pull-in voltage of the microbeam increases by a factor of 3.1 as the microbeam thickness equals to the material length scale parameter and exhibits size effect remarkably. However, the size effect on the pull-in voltage is almost diminishing as the microbeam thickness is far greater than the material length scale parameter. The normalized pull-in displacement of the microbeam exhibits size independence and equals to 0.448 and 0.398 for the cantilever beam and clamped–clamped beam, respectively.     

Boosting Hydrogen Oxidation Activity of Ni in Alkaline Media through Oxygen‐Vacancy‐Rich CeO2/Ni Heterostructures

The search for highly efficient platinum group metal (PGM)‐free electrocatalysts for the hydrogen oxidation reaction (HOR) in alkaline electrolytes remains a great challenge in the development of alkaline exchange membrane fuel cells (AEMFCs). Here we report the synthesis of an oxygen‐vacancy‐rich CeO₂/Ni heterostructure and its remarkable HOR performance in alkaline media. Experimental results and density functional theory (DFT) calculations indicate the electron transfer between CeO₂ and Ni could lead to thermoneutral adsorption free energies of H* (ΔG_H*). This, together with the promoted OH* adsorption strength derived from the abundance of oxygen vacancies in the CeO₂ species, contributes to the excellent HOR performance with the exchange current density and mass activity of 0.038 mA cm_Ni^?2 and 12.28 mA mg_Ni^?1, respectively. This presents a new benchmark for PGM‐free alkaline HOR and opens a new avenue toward the rational design of high‐performance PGM‐free electrocatalysts for alkaline HOR.     

Light-driven circular plasmon current in a silver nanoring

A circular plasmon current in a silver nanoring is demonstrated and investigated with electrodynamics theory. The circular current is driven by the incident plane electromagnetic wave. For a silver ring with a thickness of 50 nm and inner and outer diameters of 200 and 300 nm, the circular current can be obtained when the incident wavelength is at 650 nm, which is about twice the diameter of the ring. The circular current can be observed only when the incident wave and the polarization directions are both parallel to the ring plane. The resonance wavelength shifts to red with the expansion of the ring diameter and the drop in the ring thickness. The discovery holds promise for the design of artificial materials with negative refractive index in the visible wavelengths and might stimulate new ideas for the development of nanoelectronic devices.     

Chitosan hydrogel,as a biological macromolecule-based drug delivery system for exosomes and microvesicles in regenerative medicine: a mini review

Cellulose - Extracellular vesicles are membrane-packed entities that are involved in various physiological and pathological processes. Recently, the role of exosomes and microvesicles in...