9-(4-溴丁基)-9H-咔唑的相转移催化合成、表征及室温磷光性能研究——推荐一个大学化学综合实验

推荐了一个大学化学综合实验"9-(4-溴丁基)-9H-咔唑的相转移催化合成、表征及室温磷光性能研究"。实验利用相转移催化合成9-(4-溴丁基)-9H-咔唑分子,采用核磁共振、高分辨质谱和红外光谱对其分子结构进行表征,并利用紫外-可见吸收光谱、稳态/瞬态荧光光谱和密度泛函(DFT)理论计算对其室温磷光性能进行研究。本综合实验涵盖了有机化学、分析化学、物理化学、仪器分析以及理论化学的知识点,建议纳入化学专业高年级综合实验课程。     

Tensor method for optimal control problems constrained by fractional three-dimensional elliptic operator with variable coefficients

We introduce the tensor numerical method for solving optimal control problems that are constrained by fractional two- (2D) and three-dimensional (3D) elliptic operators with variable coefficients. We solve the governing equation for the control function which includes a sum of the fractional operator and its inverse, both discretized over large 3D $n\times n\times n$ spacial grids. Using the diagonalization of the arising matrix-valued functions in the eigenbasis of the one-dimensional Sturm–Liouville operators, we construct the rank-structured tensor approximation with controllable precision for the discretized fractional elliptic operators and the respective preconditioner. The right-hand side in the constraining equation (the optimal design function) is supposed to be represented in a form of a low-rank canonical tensor. Then the equation for the control function is solved in a tensor structured format by using preconditioned CG iteration with the adaptive rank truncation procedure that also ensures the accuracy of calculations, given an $\epsilon$-threshold. This method reduces the numerical cost for solving the control problem to $O(n\log n)$ (plus the quadratic term $O(n^2)$ with a small weight), which outperforms traditional approaches with $O(n^3\log n)$ complexity in the 3D case. The storage for the representation of all 3D nonlocal operators and functions involved is also estimated by $O(n\log n)$. This essentially outperforms the traditional methods operating with fully populated $n^3\times n^3$ matrices and vectors in ${?}^{n^3}$. Numerical tests for 2D/3D control problems indicate the almost linear complexity scaling of the rank truncated preconditioned conjugate gradient iteration in the univariate grid size n.     

Experimental and numerical simulation of effects of CO2/N2 concentration and initial temperature on combustion characteristics of biomass syngas

Biomass syngas is a form of renewable energy with very broad application prospects, and it has different combustion characteristics according to the fuel composition and processing technology of biomass syngas. The influence of combustion composition, diluent and temperature variation on combustion characteristics were studied in this paper. The FFCM-1 mechanism was used to investigate the combustion characteristics of CO/CH₄/H₂ under varied diluents CO₂/N₂ and temperature by using spherical expansion flame method and ANSYS CHEMKIN-PRO. The experimental laminar burning velocity was compared with the simulation results of FFCM-1 mechanism. The results reveal that the experimental data are in good agreement with the simulation results, which are somewhat different under the condition of rich fuel. The laminar burning velocity decreases significantly with the increase of diluent CO₂/N₂, with the effect of diluent CO₂ being more significant. The laminar burning velocity increase dramatically with the increase of initial temperature, and the adiabatic flame temperature also decreases with the increase of diluent. The reduction caused by diluent CO₂ is much larger than that caused by diluent N₂. The change of initial temperature also affects the adiabatic flame temperature, but the range of variation is not as pronounced as that of diluent. Not only was the interaction between the combustion characteristics of CO/CH₄/H₂ under different diluents and temperature changes explored in this paper, but the influence mechanism was also revealed in depth.     

田字形地震超材料甚低频宽带隙机理

在地球中传播的地震波主要有体波和表面波,而表面波中Rayleigh波对建筑物造成的破坏最为强烈。针对Rayleigh波的振动控制,提出一种田字形超材料结构。相比于传统的地震超材料,这种超材料屏障是由外部口字形框体内部嵌套十字形柱体组成,形成4个可填充区域,其外部框体采用部分埋入的方式,具有高强度、强稳定性、填充方式灵活的特点。应用有限元法计算了田字形超材料的能带结构和传输特性,并通过分析带隙边界处模态振型可知,带隙的打开是由于柱体的局域共振。结合带隙机理可知,柱体结构中土壤填充量不同可改变柱体的质量,形成不同的谐振频率,产生甚低频带隙。为进一步拓宽带隙,设计研究了正、负梯度的质量填充方式,均可得到3.3~13.1 Hz甚低频宽带隙,在谐振频率范围内两者的隔震方式分别为Rayleigh波彩虹捕获和Rayleigh波到体波的转化。最后,采用EI-Centro地震波对填充屏障进行了时程验证,加速度最大幅值衰减超过80%,为地震超材料在减震隔震方面应用提供了新的设计思路和方法。     

基于不确定控制理论的最优策略研究

本文在不确定理论的框架下,研究一类带背景状态变量的最优控制模型.在乐观值准则下,利用不确定动态规划的方法,证明了不确定最优性原则,得到最优性方程.作为应用,求解一个固定缴费(DC)型养老金的最优投资策略问题,在乐观值准则下,以工资变量为背景状态变量,建立养老金模型.通过求解不确定最优性方程得到最优投资策略和最优支付率.     

Site Occupancies,Electron–Vibration Interaction and Energy Transfer of CaMgSi2O6: Eu2+, Mn2+ Phosphors for Potential Temperature-Sensing and Anti-counterfeiting Applications

Eu²⁺-, Mn²⁺- and Eu²⁺−Mn²⁺-doped CaMgSi₂O₆ phosphors have been prepared by a high-temperature solid-state reaction. Systematic investigation of the concentration- and temperature-dependent luminescence of Mn²⁺ showed that Mn²⁺ ions occupy two distinct sites in CaMgSi₂O₆. Electron–vibration interaction (EVI) analyses of Mn²⁺ ions revealed Huang–Rhys factors of 4.73 and 2.82 as well as effective phonon energies of 313 and 383 cm⁻¹ for the two sites. Eu²⁺−Mn²⁺ energy transfer is also discussed, and its efficiency is estimated by lifetime and luminescence spectra. The different thermal quenching behaviours of Eu²⁺ and Mn²⁺, the distinct emission colours of Eu²⁺ (blue, band peak at ∼451 nm) and Mn²⁺ (yellow–red range, band peaks at ∼583 and 693 nm) endow the co-doped samples with potential applications in luminescence thermometry and temperature-/excitation wavelength-responsive dual anti-counterfeiting.     

Effect of pressure on the low-temperature reaction of ethylene with N2O4

Calorimetric monitoring of the autoclave reaction N₂O₄ + C₂H₄ at –85 to +10 °C under argon pressure 10–30 bar revealed that the exothermic chemical reaction started at temperatures above –52 °C at 10 bar, whereas an intensive exothermic reaction started at –85 °C and pressure of 30 bar. IR study showed that oligo/polynitroethylene was formed at 30 bar, while carbonyl and hydroxy compound as well as nitrate R–ONO₂ formation occurred upon processing at 10 bar.     

新型BT-BMT-xBNT无铅高储能密度陶瓷研究

本文采用传统固相反应法,成功制备了新型无铅弛豫铁电陶瓷(1-x)[0.9BaTiO₃-0.1Bi(Mg_0.25Ta_0.5)O₃]-xBi_0.5Na_0.5TiO₃。结果表明,较高居里温度的Bi_0.5Na_0.5TiO₃的引入,使得材料体系中建立了更多的以Bi—O耦合为主的极性纳米区域,弥补了因Bi(Mg_0.25Ta_0.5)O₃的加入导致的宏观极化强度的减少,提高了材料的饱和极化强度,实现了较高储能密度的同时具有更好的温度稳定性。在245 kV/cm电场强度下,x=0.2样品的储能密度约为4.01 J/cm³,储能效率约为84.86%,同时该组分在20~170 ℃储能密度的变化率小于5%,储能效率的变化率小于6%,表现出优异的温度稳定性。     

Influence of staff number and internal constellation on surgical site infection in an operating room

Prediction of bacteria-carrying particle （BCP） dispersion and particle distribution released from staffmem- bers in an operating room （OR） is very important for creating and sustaining a safe indoor environment. Postoperative wound infections cause significant morbidity and mortality, and contribute to increased hospitalization time. Increasing the number of personnel within the OR disrupts the ventilation airflow pattern and causes enhanced contamination risk in the area of an open wound. Whether the amount of staffwithin the OR influences the BCP distribution in the surgical zone has rarely been investigated. This study was conducted to explore the influence of the number of personnel in the OR on the airflow field and the BCP distribution. This was performed by applying a numerical calculation to map the airflow field and Lagrangian particle tracking （LPT） for the BCP phase. The results are reported both for active sampling and passive monitoring approaches. Not surprisingly, a growing trend in the BCP concentration （cfu/ms） was observed as the amount of staff in the OR increased. Passive sampling shows unpredictable results due to the sedimentation rate, especially for small particles （5-10 i~m）. Risk factors for surgical site infections （SSls） must be well understood to develop more effective prevention programs.     

Shape‐directed platinum nanoparticle synthesis: nanoscale design of novel catalysts

Platinum‐based catalytic materials have received significant attention, particularly in the shape and size control of faceted materials for catalysis. More recently, there has been a rapid increase in the number of reports of successful preparations in this field; however, a fundamental understanding of controlled growth towards catalytic material design is essential for future implementation and broad application. In this review, we provide an overview of the recent findings reported since 2009, focusing on methods for shape control as well as the effects of exposed surface facets on select catalytic reactions. Copyright © 2013 John Wiley & Sons, Ltd.