Synthesis and Characterization of a Manganese(Ⅱ) Coordination Compound with Two-dimensional Layer Structure: {[Mn_2(IP)_2(1,4-bdc)_2]·H_2O}n

A new complex {[Mn2(IP)2(1,4-bdc)2]·H2O}n(1)(IP = 1H-imidazo[4,5-f][1,10]-phenanthroline, 1,4-H2 bdc = 1,4-benzendicarboxylic acid), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. It crystallizes in monoclinic, space group Cc with a = 20.326(2), b = 24.249(2), c = 7.621(1), β = 108.546(6), V = 3561.2(7)3, Z = 4, Dc = 1.672 g/cm3, μ = 0.785 mm-1, F(000) = 1824, S = 1.067, the final R = 0.0299 and wR = 0.0752. Compound 1 possesses a 2D structural motif, in which two crystallographically independent 1,4-bdc dianions adopt the alternative mode of mixed bis(bidentate) and monodentate-bidentate coordination modes to bridge neighboring Mn(II) centers. And the 2D layers are linked up by hydrogen bonding and π···π stacking interactions to form a 3D network. The title compound has good thermal stability and exhibits photoluminescent emission maximum at 518 nm.     

LOCAL REGULARITY RESULT IN OBSTACLE PROBLEMS

We obtain a local regularity result for solutions to Kψ,θ-obstacle problem of A-harmonic equation divA(x,u(x),▽u(x))=0,where A:Ω× R×Rn → Rn is a Carath'eodory function satisfying some coercivity and growth conditions with the natural exponent 1pn,the obstacle function ψ≥0,and the boundary data θ∈W1,p(?).     

高压下的铁基超导体:现象与物理

始于2008年的铁基超导体研究续写了高温超导发展史的新篇章.回顾过去十年对铁基超导体的研究,在理论、实验及应用方面都取得了辉煌的成绩,丰富了人们对高温超导电性的认识,为突破高温超导机理研究、最终实现超导材料的人工设计与更广泛的应用奠定了坚实的基础.本文主要介绍了通过高压实验研究手段在铁基超导体的研究中取得的一些重要进展及呈现出的新现象和新物理,例如压致超导现象、压力导致的超导再进入现象、压力对超导转变温度的提升效应、压力研究对铁基超导体超导转变温度的预测、相分离结构对超导电性的影响及反铁磁-超导双临界点的发现等.希望这些高压研究结果与本文报道的其他各类实验与理论研究成果一起,为全面、深入地理解铁基超导体勾画出一幅较为完整的物理图像.     

微陀螺滑模控制器中的积分算法设计（英文）北大核心CSCD

为了去除不定积分环节产生的直流偏置项,提出了一种基于"一次移动平均法"的改进积分算法。利用一个整数周期的积分信号值构成一个集合,计算出集合的算术平均值作为瞬时直流偏置,将原积分信号减去该直流偏置,最终可得到无直流偏置项的积分信号。为实时更新直流偏置,在每个时钟上升沿将一个积分信号的新采样值加入集合尾部,并去除集合首部的数值点,从而确保集合长度维持固定值并能实时反映出最新的直流偏置。以FPGA为信号处理平台,采用Modelsim仿真和实验测试相结合的方法验证了该算法的可行性。该方法已成功用于电磁式微陀螺仪的滑模控制器之中。同已有方法相比,该积分算法复杂度低、实时性好、易于实现。     

三元添加剂水溶液体系制备CaCO3空心球

利用原位聚合方法, 通过加入一定量的引发剂使甲基丙烯酸原位聚合, 在三嵌段共聚物(P123)、聚甲基丙烯酸(PMAA)和十二烷基硫酸钠(SDS)的三元添加剂混合溶液体系中成功地制备了CaCO3空心球. 采用扫描电子显微镜(SEM)和X射线粉末衍射(XRD)对合成样品的形貌、结构进行了表征. 结果显示, 方解石CaCO3空心球直径约0.5-2 μm. 空心球壁由直径约25-35 nm的圆形粒子组成, 壁厚约100-300 nm. 利用核鄄壳机理解释了空心球结构的形成过程.     

Carrier envelope phase effect on the spatial distribution of high-order harmonic generation in asymmetric molecule

The spatial distribution in high-order harmonic generation(HHG) from the asymmetric diatomic molecule He H~(2+) is investigated by numerically solving the non-Born–Oppenheimer time-dependent Schr?dinger equation(TDSE). The spatial distribution of the HHG spectra shows that there is little contribution in HHG around the geometric center of two nuclei(z = 1.17 a.u.) and the equilibrium internuclear position of the H nucleus(z = 3.11 a.u.). We demonstrate the carrier envelope phase(CEP) effect on the spatial distribution of HHG in a few-cycle laser pulse. The HHG process is investigated by the time evolution of the electronic density distribution. The time–frequency analysis of HHG from two nuclei in HeH~(2+) is presented to further explain the underlying physical mechanism.     

双色激光场中一维氢分子的经典动力学性质研究

应用经典理论方法,采用辛算法,数值求解双色激光场作用下的一维共线氢分子的哈密顿正则方程,得到氢分子在激光场作用下的经典轨迹,并计算H₂⁺,H₂²⁺,H,H⁺等产物的产生概率随时间的演化,分析了双色场的光强、倍频、相位的变化对氢分子动力学性质的影响并给出相关的物理解释.     

高速列车制动盘温度场的建模及分析

高速列车在制动过程中,制动盘在制动块的摩擦力作用下温度急剧升高,从而产生了热应力。过高的热应力往往会引起制动盘的疲劳破损,因此在设计制动盘时考虑温度场的影响非常重要。对速度为300km/h的列车在紧急制动工况下的制动盘,建立了含有局部内热源的数学模型和瞬态热传导方程。采用微分求积法,对热传导方程中的温度函数进行关于空间坐标的离散,得到了离散节点上仅含时间自变量的温度函数表示的一阶常微分方程组,然后采用龙格-库塔法求解。最后,对Mechanite Cast Iron G.C.40、AISI301、Chromium Copper Casting三种材料制造的制动盘进行分析和计算,得到了制动过程中温度随时间和沿轮轴半径的变化情况。结果表明:导热好的材料的温度沿径向分布的均匀程度好;制动过程中有动压力作用时,导热好的材料在有效摩擦区域沿径向的温度场与热流的分布规律基本一致,并逐渐趋向于稳态值。     

Robust Magnetism Against Pressure in Non-Superconducting Samples Prepared from Lutetium Foil and H2/N2 Gas Mixture

We report the observation of a magnetic transition at the temperature about 56 K, through the high-pressure heat capacity and magnetic susceptibility measurements on the samples that have been claimed to be a nearroom-temperature superconductor [Dasenbrock-Gammon et al. Nature 615, 244(2023)]. Our results show that this magnetic phase is robust against pressure up to 4.3 GPa, which covers the critical pressure of boosting the claimed superconductivity.     

Exploration of strong-field double ionization of C_3H_6 with the structures of propene and cyclopropane in intense laser fields

By using classical ensemble method, we investigate the double ionization of C_3H_6 molecule with different structures(propene and cyclopropane) in intense laser fields. The numerical results show that the non-sequential double ionization occurs in propene molecule rather than cyclopropane molecule in 1200 nm laser field. To further explain this interesting phenomenon, the momentum distribution of double ionized electrons is presented and the result presents the "finger-like" structure at about 30 TW/cm~2 of propene molecule, and this structure is more obvious than that in cyclopropane molecule.The above phenomena are also demonstrated by analysing the energy distributions of double-ionized electrons versus time. Moreover, we also investigated the angular distribution at the end of pulse, which is different between propene and cyclopropane.