微观结构对Eu:Ti纳米材料光学性能的影响

以TiO_2∶Eu纳米颗粒为原材料,采取水热和高温(700 ℃)退火的方法合成了铕掺杂钛纳米棒(简写成Eu∶Ti 纳米棒).其结构和光学性能用场发射扫描电镜,显微共聚焦激光拉曼光谱,稳态荧光以及寿命谱进行表征.场发射扫描电镜图片显示纳米棒的直径大约为30 nm,长度大约为300~600 nm.显微共聚焦激光拉曼光谱测试结果表明纳米棒中含有部分锐钛矿结构.稳态荧光光谱显示纳米棒的发光强度明显比纳米颗粒的强度强,而且发光谱线也不同.检测Eu~(3+)的~5D_0→~7F_2跃迁(发光峰位在612 nm)的发光强度,采用394 nm激发,发现纳米棒的寿命比纳米颗粒的长120 μs.     

A New Approach to Optimization Under Monotonic Constraint

A new efficient branch and bound method is proposed for solving convex programs with an additional monotonic nonconvex constraint. Computational experiments demonstrated that this method is quite practical for solving rank k reverse convex programs with much higher values of k than previously considered in the literature and can be applied to a wider class of nonconvex problems.     

青蟹养殖池沉积物无机氮释放通量及其影响因素

探讨了青蟹养殖池塘沉积物-水界面无机氮的通量及环境因子对沉积物无机氮释放的影响．计算了养殖池沉积物-水界面NO2-、NO3-、NH4＋的交换通量分别为238．779（μmol·m^-2）·d^-1、-1322．948（μmol·m^-2）·d^-1和199．422（μmol·m^-2）．d^-1．试验表明：35℃时沉积物NH44＋-N的释放量是15℃时的1．348倍,NO2--N和NO3--N随着温度升高释放量增加;pH=9．0时,沉积物释放NH4＋-N和NO2--N量最大,pH=7．0时最小：不充气时氨氮释放量是充气时的1．877倍,而充气时NO2--N释放量大于不充气．表明青蟹养殖中期池塘沉积物是水柱中无机氮的汇,能对水质起调节作用．     

煤油超燃冲压发动机三维大规模并行数值模拟

在我国巨型计算机上,采用1024个CPU对煤油燃料超燃冲压发动机燃烧流场进行三维大规模并行数值模拟.计算软件采用自主研发的并行软件AHL3D,控制方程采用雷诺平均的N-S方程,无粘项计算采用Steger-Warning矢通量分裂格式,湍流模型采用k-ω双方程模型,煤油分子式采用正癸烷代替.计算给出的发动机壁面压强分布与试验测量结果有较好的一致性.结果表明,凹槽是发动机主要的着火区和火焰稳定区,同时,由于燃料的喷注形成的回流区也起到一定的稳焰作用.计算结果验证了AHL3D程序和采用的理论模型可以用于模拟煤油燃料超燃冲压发动机内部的复杂流动.     

COLLOCATION METHOD FOR CONVECTIVE FLOW INDUCED BY DIRECTIONAL SOLIDIFICATION IN A CYLINDER

The paper presents a Chebyshev–Fourier collocation method for solving the unsteady 3D Navier–Stokes equations in a cylindrical domain. The numerical scheme uses primitive variables and the incompressibility constraint is satisfied by applying iteratively a correction to the pressure field. The method, due to Cahouët and Chabard (Int. j. numer. methods fluids, 8 , 869–895 (1988)) and originally developed in the framework of finite elements, is checked with respect to the present high-order approach. Several tests are carried out in Cartesian geometries, successively 2D and 3D, then a comparison is performed in a cylindrical domain with two different sets of radial collocation nodes: Gauss-Lobatto nodes and Gauss-Radau points. Although quite acceptable results are obtained with the latter chain, a general decrease in efficiency is noticeable in the collocation method. This is interpreted as the consequence of two factors: the collocation formulation is not symmetric and the Fourier analysis, used as heuristic guide by CahouMt and Chabard, loses its efficiency in a non-equidistant grid, especially in a cylindrical geometry. We present an application to the study of thermosolutal convection induced by unidirectional solidification of a binary alloy. The latter grows from a Pb–30%Tl liquid phase in a cylindrical crucible corresponding to the vertical Bridgman upward configuration. We study the influence of the flow patterns on the crystal composition.     

水泥池养殖条件下虎斑乌贼的生长特性

以体重、胴长、墨囊重和壳重4个指标变化情况,研究了水泥池养殖条件下虎斑乌贼(Sepia pharaonis)的生长特性.结果表明:体重呈指数增长,日均增重量(0.09~2.78 g)不断增加,瞬时增重率(11.86%~1.03%)呈下降趋势;胴长呈直线增长,日均增长量(0.03~0.13cm)不断波动,瞬时增长率(4.99%~0.35%)呈下降趋势;墨囊重呈指数增长,日均增重量(0.01~0.09g)呈上升趋势,瞬时增重率(11.95%~1.68%)呈下降趋势,墨囊指数3.06%~4.25%;壳重呈指数增长,日均增重量(0.01~0.13 g)呈上升趋势,瞬时增重率(10.73%~1.02%)呈下降趋势,壳指数为5.06%~7.65%.成活率在日龄0~45d(90.69%~95.25%)和60~150d(95.73%~98.89%)时平稳上升,而在日龄45~60d(饵料转变过程中)下降至最低(50.01%).体重和胴长、墨囊重、壳重之间均具有显著相关性.     

陶瓷料浆喷雾干燥三维DPM数值模拟

针对现有陶瓷料浆喷雾干燥二维数学模型简化了干燥过程中干燥塔内复杂气固两相运动,造成计算结果与实际存在较大偏差等问题,基于CFD方法,采用DPM模型描述干燥塔中陶瓷料浆颗粒相运动轨迹,进行陶瓷料浆喷雾干燥过程三维数学模型构建及数值求解.在数学模型经实验验证有效的基础上,模拟了不同料浆流量、入口热空气温度的陶瓷料浆喷雾干燥过程,对比分析了干燥塔中颗粒粒径分布、空气湿度场、颗粒温度变化情况,获得了陶瓷料浆喷雾干燥的最佳操作参数.对于此小型喷雾干燥装置,当陶瓷料浆初始湿含量为60;、入口热空气速度为0.3m·s-1时,最佳的陶瓷料浆流量和入口热空气温度参数值分别为0.01 kg·s-1和413 K.     

"三个和尚没水喝"问题的心结与新解

针对"三个和尚没水喝"这一有趣的问题,运用结构力学的知识,分析其中所包含的有趣力学问题。对此问题进行简化抽象,将问题中公平性的基本依据简化为三个和尚需承受相同的载荷。文中采用从组成结构体系的各个主要部分进行修改的思路,以获得新的结构方案,之后根据各个改造后的结构方案分析结果,探讨达到三个和尚抬水喝时公平性所需采取的理论措施。     

冲击作用下易碎式密封盖数值仿真及实验分析

确定了易碎式密封盖的材料和结构,运用有限元法进行了火箭弹和燃气流冲击的数值仿真计算,通过冲破实验进行了间接验证,从而掌握了密封盖的破碎效果和性能。结果表明,密封盖能沿预置沟槽方向破裂,能满足引信体的安全性和可靠性,不影响火箭弹的正常飞行;燃气流冲击力对密封盖影响不大,不会对密封盖造成破坏。     

CLASSIFICATION OF SOLUTIONS TO HIGHER FRACTIONAL ORDER SYSTEMS

Let 0 ＜ α,β ＜ n and f,g ∈ C([0,∞) ×[0,∞)) be two nonnegative functions.We study nonnegative classical solutions of the system{(-Δ)α/2u=f(u,v) in Rn,(-Δ)β/2 v =g...