Skyrmion transport driven by pure voltage generated strain gradient

The magnetic skyrmion transport driven by pure voltage-induced strain gradient is proposed and studied via micromagnetic simulation. Through combining the skyrmion with multiferroic heterojunction, a voltage-induced uniaxial strain gradient is adjusted to move skyrmions. In the system, a pair of short-circuited trapezoidal top electrodes can generate the symmetric strain. Due to the symmetry of strain, the magnetic skyrmion can be driven with a linear motion in the middle of the nanostrip without deviation. We calculate the strain distribution generated by the trapezoidal top electrodes pair, and further investigate the influence of the strain intensity as well as the strain gradient on the skyrmion velocity. Our findings provide a stable and low-energy regulation method for skyrmion transport.     

一类新的多功能构筑基块-多吡唑化合物的设计合成

The design and synthesis of novel polypyrazolyl aromatic bridging ligands 1,3,5-tris（3,5-dimethyl-1-pyrazol-4-yl）benzene and 2,4,6-tris（4-（3,5-dimethyl-^1H-pyrazol-4-yl）phenyl）-1,3,5-triazine from simple starting materials mesitylene and p-tolunitrile were reported.     

排序集抽样下Inverse Rayleigh分布的Fisher信息量及其在参数估计中的应用

文章分别在简单随机抽样和排序集抽样下研究了Inverse Rayleigh分布中对应样本所含刻度参数θ的Fisher信息量.数值结果表示,同等样本容量的排序集样本比简单随机样本提供更多关于θ的信息.接着分别基于简单随机样本和排序集样本构造了θ的一些优良估计,并对估计结果进行了数值比较.     

导数振荡与应变能极小的平面分段三次参数Hermite插值

由于分段三次参数Hermite插值的切矢往往被作为变量,故可对其进行优化以使得构造的插值曲线满足特定的要求.为了构造兼具保形性与光顺性的平面分段三次参数Hermite插值曲线,给出了一种通过同时极小化导数振荡和应变能来确定切矢的方法.首先以导数振荡函数和应变能函数为双目标建立了切矢满足的方程系统;然后证明了方程系统存在唯一解,并给出了解的具体表达式;最后给出了误差分析,并通过数值算例表明方法的有效性.结果表明,相对于导数振荡极小化方法和应变能极小化方法,所提出的导数振荡和应变能极小化方法同时兼顾了平面分段三次参数Hermite插值曲线的保形性和光顺性.     

高色纯度高热稳定性红色荧光粉Sr3La2Ge3O12:Sm^3+的合成及其性能

通过高温固相法合成了一系列Sr3La2-xGe3O12:xSm^3+(0≤x≤0.04)红色荧光粉,并对样品的形貌、元素组成、晶体结构、发光性能及热稳定性进行了探究。结果表明:样品Sr3La2Ge3O12:xSm^3+为较宽尺寸分布的颗粒,且结构中仅含有Sr、La、Ge、O、Sm等元素。样品Sr3La1.97Ge3O12:0.03Sm^3+的Rietveld结构精修图与实测XRD图完全吻合,具有六方晶系结构。漫反射测试结果显示基质Sr3La2Ge3O12的带宽为5.54 eV,属于宽带隙材料。在404 nm激发下,样品Sr3La2-xGe3O12:xSm^3+(0≤x≤0.04)的最大发射峰位于601nm处,属于Sm^3+的6H5/2→4L13/2能级跃迁。此外,样品Sr3La1.97Ge3O12:0.03Sm^3+的发光性能最佳,其CIE色坐标为(0.5321,0.4601),色纯度高达94.2%,在298-473 K范围内具有较好的热稳定性,测试温度达到423 K时发射强度仍为室温时的81.6%。     

Damage resistance of carbon fibre reinforced epoxy laminates subjected to low velocity impact: Effects of laminate thickness and ply-stacking sequence

A major concern affecting the efficient use of composite laminates is the effect of low velocity impact damage on the structural integrity [1–3]. The aim of this study is to characterize and assess the effect of laminate thickness, ply-stacking sequence and scaling technique on the damage resistance of CFRP laminates subjected to low velocity impact. Drop-weight impact tests are carried out to determine impact response. Ultrasonic C-scanning and cross-sectional micrographs are examined to assess failure mechanisms of the different configurations.It is observed that damage resistance decreases as impact energy increases. In addition, thicker laminates show lower absorbed energy but, conversely, a more extensive delamination due to higher bending stiffness. Thinner laminates show higher failure depth. Furthermore, quasi-isotropic laminates show better performance in terms of damage resistance. Finally, the results obtained demonstrate that introducing ply clustering had a negative effect on the damage resistance and on the delamination area.     

Preparation and characterization of carbon aerogel microspheres by an inverse emulsion polymerization

Carbon aerogel (CA) microspheres have been successfully synthesized by an inverse emulsion polymerization and characterized by scanning electron microscopy (SEM), N₂ sorption isotherm and X-ray diffraction (XRD). The results show that the size and pore characteristics of carbon microsphere obviously depend on stirring speed and concentration of surfactant in the emulsion polymerization process. The resultant CA microspheres are amorphous carbon structure with the size ranging from about 2 to 50 μm by changing the stirring speed. CA microspheres with S_BET of 414-603 m² g^− 1 and V_meso of 0.028-0.432 cm³ g^− 1 are synthesized using different SPAN80 concentrations. The results of cyclic voltammetry indicate that the CA microspheres prepared at a stirring speed of 480 rpm and at V_s/V_h = 0.01 have ideal supercapacitive behavior in 6 M KOH electrolyte, the maximum specific capacitance of the electrode reaches 180 F g^− 1.     

SPME and SPE comparative study for coupling with microwave-assisted micellar extraction in the analysis of organochlorine pesticides residues in seaweed samples

Solid-phase microextraction (SPME) and solid-phase extraction (SPE) procedures were coupling with microwave-assisted micellar extraction for organochlorine pesticides residues determination in seaweed samples. They were optimized, compared and discussed.Preliminary experiments were performed in order to study experimental conditions for the extraction of pesticides from spiked seaweed samples with microwave-assisted micellar extraction (MAME) using a non-ionic surfactant (Polyoxyethylene 10 Lauryl Ether). After that, SPME and SPE were used to clean-up and preconcentrate MAME extract prior the analysis by liquid chromatography with photodiode array (PDA) detection.Excellent results were obtained for both procedures. Average pesticide recoveries between 80.5 and 104.3% for MAME-SPME and between 73.9 and 111.5% for MAME-SPE were obtained. Relative standard deviations (RSDs) were lower than 10.3% and 5.3% respectively for all recoveries tested, and LOD between 138–348 ng g^− 1 for MAME-SPME and 2–38 ng g^− 1 for MAME-SPE were obtained. The method was validated using Soxhlet extraction procedure.Both methods were applied to analyse target organochlorine pesticides in several seaweed samples and results were compared. These results show the great possibilities of combining MAME-SPE-HPLC-UV for the analysis of seaweed samples, improving the selectivity and sensitivity in the determination of organochlorine pesticides analysis for this kind of samples.     

Feedback control of combustion oscillations in combustion chambers

Model-based algorithms are generally employed in active control of combustion oscillations. Since practical combustion processes consist of complex thermal and acoustic couplings, their accurate models and parameters may not be obtained in advance economically, a model free controller is necessary for the control of thermoacoustic instabilities. Active compensation based control algorithm is applied in the suppression of combustion instabilities. Tuning the controller parameters on line, the amplitudes of the acoustic waves can be modulated to desired values. Simulations performed on a control oriented, typical longitudinal oscillations combustor model illustrate the controllers’ capability to attenuate combustion oscillations.     

0-1非线性混合整数规划的罚函数解法

本文中我们对一类0-1非线性混合整数规划的解法进行了探讨,通过罚函数把有约束问题化为相应的无约束问题,我们证明了可通过求解一个无约束非线性规划问题得到原问题的ε近似极小解,数值试验表明算法是有效的.