Synthesis and Characterization of a New Metal-organic Framework with Nou Topology

A new compound, [H2N(CH3)2]2[Zn(btec)].H2O(1, H4 btec = 1,2,4,5-benzenetetracarboxylic acid) has been solvothermally synthesized and structurally characterized by singlecrystal X-ray diffraction. The crystal structure is of monoclinic, space group P21/c with a = 9.5741(3), b = 14.5044(4), c = 13.7329(5) , β = 100.582(4)°, V = 1874.61(10) 3, C14H20N2O9 Zn, Mr = 425.7, Z = 4, Dc = 1.387 g/cm3, μ = 1.349 mm-1, F(000) = 776, R = 0.0560 and w R = 0.1684 for 2834 observed reflections(I 2σ(I)). Compound 1 based on μ4-btec and tetrahedral building unit features a three-dimensional(3D) anionic framework with mixed connected nou topology. The luminescent property and thermogravimetric analysis of compound 1 are investigated.     

Micro/Nanoengineered α-Fe2O3 Nanoaggregate Conformably Enclosed by Ultrathin N-Doped Carbon Shell for Ultrastable Lithium Storage and Insight into Phase Evolution Mechanism

The Fe-based transition metal oxides are promising anode candidates for lithium storage considering their high specific capacity, low cost, and environmental compatibility. However, the poor electron/ion conductivity and significant volume stress limit their cycle and rate performances. Furthermore, the phenomena of capacity rise and sudden decay for α-Fe₂O₃ have appeared in most reports. Here, a uniform micro/nano α-Fe₂O₃ nanoaggregate conformably enclosed in an ultrathin N-doped carbon network (denoted as M/N-α-Fe₂O₃@NC) is designed. The M/N porous balls combine the merits of secondary nanoparticles to shorten the Li⁺ transportation pathways as well as alleviating volume expansion, and primary microballs to stabilize the electrode/electrolyte interface. Furthermore, the ultrathin carbon shell favors fast electron transfer and protects the electrode from electrolyte corrosion. Therefore, the M/N-α-Fe₂O₃@NC electrode delivers an excellent reversible capacity of 901 mA h g⁻¹ with capacity retention up to 94.0 % after 200 cycles at 0.2 A g⁻¹. Notably, the capacity rise does not happen during cycling. Moreover, the lithium storage mechanism is elucidated by ex situ XRD and HRTEM experiments. It is verified that the reversible phase transformation of α↔γ occurs during the first cycle, whereas only the α-Fe₂O₃ phase is reversibly transformed during subsequent cycles. This study offers a simple and scalable strategy for the practical application of high-performance Fe₂O₃ electrodes.     

Rational design of thermoelastic damping in microresonators with phase-lagging heat conduction law

The design of thermoelastic damping (TED) affected by the phase-lagging non-Fourier heat conduction effects becomes significant but challenging for enlarging the quality factor of widely-used microresonators operating in extreme situations, including ultra-high excitation frequency and ultra-low working temperature. However, there does not exist a rational method for designing the TED in the framework of non-Fourier heat conduction law. This work, therefore, proposes a design framework to achieve low thermoelastic dissipation of microresonators governed by the phase-lagging heat conduction law. The equation of motion and the heat conduction equation for phase-lagging TED microresonators are derived first, and then the non-Fourier TED design problem is proposed. A topology optimization-based rational design method is used to resolve the design problem. What is more, a two-dimensional (2D) plain-strain-based finite element method (FEM) is developed as a solver for the topology optimization process. Based on the suggested rational design technique, numerical instances with various phase lags are investigated. The results show that the proposed design method can remarkably reduce the dissipation of microresonators by tailoring their substructures.     

Experimental study on synchrotron radiation photoionization of secondary organic aerosol derived from styrene ozonolysis

Secondary organic aerosol (SOA) produced by ozonolysis of styrene and other alkene compounds is a major part of fine particles in urban atmospheres. The atmospheric ozonolysis process of styrene is simulated in a smog chamber, and the formed SOA particles are detected on-line by a synchronous radiation vacuum ultraviolet photoionization mass spectrometer (VUV-PIMS) in this study. Through molecular ion peaks in the photonionization mass spectra of SOA and the corresponding photoionization efficiency curve, combined with off-line measurement verification of ultraviolet visible and infrared absorption spectra, it is determined that formaldehyde, formic acid, benzene, phenol, benzaldehyde, and benzoic acid are the main constituents of styrene SOA. These provide new information for studying the atmospheric ozonolysis oxidation mechanism of styrene. VUV-PIMS can get over complicated sample preparation procedures, secondary pollution, and other shortcomings of the off-line method and is a useful instrument to measure constituents and unveil the formation process of SOA particles.     

黄光类水滑石的制备、表面改性及应用

采用共沉淀法合成了荧光类水滑石材料,该材料在470 nm蓝光激发下可发出黄色荧光(557 nm),采用硅烷偶联剂对其进行表面改性,探讨了表面改性对黄光类水滑石的发光性能、结构及热稳定性的影响。将改性黄光类水滑石与GaN基蓝光芯片封装后制得了白光LED。研究结果表明,改性的黄光类水滑石是制作白光LED可供选用的黄色发光材料。本文成功地将低温一步法制备得到的金属有机配合物/无机纳米杂化材料应用于LED,拓展了LED用荧光粉的选用范围。     

硫酸肼比浊法测定微量硒

依据硒(Ⅳ)在以甘油为稳定剂,盐酸为反应介质的条件下,被过量硫酸肼还原,使体系形成稳定悬浊液的原理,建立了比浊法测定硒的方法。探讨了盐酸用量、甘油用量、反应温度和反应时间以及硫酸肼用量等5个关键因素的影响,确定了最佳测定条件。实验结果表明:大量的共存物质不干扰测定。在选定的实验条件下,线性方程为:ΔA750nm=12.725ρ+0.0076,在2.0×10-4~3.2×10-2mg·m L-1范围内线性关系良好,相关系数(R2)=0.9911,方法的检出限为1.2×10-4mg·m L-1。方法用于测定强化营养盐中总硒,回收率在97.0~103.5%之间,RSD为1.8%。     

用指数型整函数的最佳限制逼近

我们研究了由仅有实零点的代数多项式导出的微分算子确定的广义Sobolev类利用指数型整函数作为逼近工具的最佳限制逼近问题.利用Fourier变换和周期化等方法,得到在L_2(R)范数下的广义Sobolev光滑函数类的相对平均宽度和最佳限制逼近的精确常数,以及当0是这个代数多项式的一个至多2重的零点时,得到最佳限制逼近在L_1(R)范数和一致范数下的广义Sobolev类的精确到阶的结果.     

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In this paper, the empirical Bayes (EB) two-sided test for parameter of Cox models is investigated under square loss functions. At first by using recursive kernel estimation of probability function the empirical Bayes two-sided test rule is constructed. It proves that the proposed empirical Bayes test rule is asymptotic optimal and convergence rates are obtained under suitable conditions. Finally an example of satisfying theorem conditions is given.     

一种新型黄色荧光类水滑石材料的制备及表征

用适量的Zn(Ⅱ)取代镁铝水滑石中的Mg(Ⅱ),同时将一定量的2-对联苯基-8-羟基喹啉分散到类水滑石层间的亲油性阴离子中,使其与层板表面上的Zn(Ⅱ)配位,用一步法合成、组装得到一类新型黄色荧光类水滑石复合物(Zn-(HQ-4-biPh)-HTlc)。采用荧光光谱、红外光谱、X射线衍射、扫描电子显微镜和热分析等对其进行了表征。研究结果表明,Zn-(HQ-4-biPh)-HTlc在蓝光(481 nm)激发下可发出黄色荧光(554 nm),与其相应的含锌配合物(Zn[2-(p-biph)-8-Q-O]2)相比,不仅可节省配体用量,而且具有更高的发光强度和更好的热稳定性,有望在白光LED等光电领域得到应用。