A new constitutive equation for solid propellant with the effects of aging and viscoelastic Poisson’s ratio

A new constitutive equation for solid propellant with the effects of aging and viscoelastic Poisson’s ratio is proposed. Effects of thermo-oxidative aging and viscoelastic Poisson’s ratio are considered in this comprehensive constitutive equation with two sets of reduced time system coping with the time and temperature dependence. In order to simulate the single and combined effects of aging and viscoelastic Poisson’s ratio, constitutive equation is rewritten into an incremental form and implemented in the user subroutine UMAT at the platform of finite element code ABAQUS. Detailed procedure for acquiring the parameters in constitutive equation is introduced and conducted for the subsequent applied analysis. Two typical loading cases during the service life of solid rocket motor and four sets of combined constitutive models are simulated. Von Mises strain and stress distribution and their changes versus time are utilized as the main analysis index. The results show that the effects of aging and viscoelastic Poisson’s ratio or their combinations will improve or decrease the level and change the distribution of Von Mises strain and stress in varying degrees.     

Supercritical Elliptic Equation in Hyperbolic Space

In this paper, we study the following semi-linear elliptic equation $$-Δ_H^nu=|u|^{p-2}u,\qquad\qquad (0.1)$$ in the whole Hyperbolic space $\mathbb{H}^n$,where n ≥ 3, p › 2n/(n-2). We obtain some regularity results for the radial singular solutions of problem (0.1). We show that the singular solution $u^∗$ with $lim_{t → 0}(sinht)^{\frac{2}{p-2}}⋅u(t)=±(\frac{2}{p-2}(n-2-\frac{2}{p-2})^{\frac{1}{p-2}}$ belongs to the closure (in the natural topology given by $H¹_{loc}(\mathbb{H}^N)∩L^p_{loc}(H^N))$ of the set of smooth classical solutions to the Eq. (0.1). In contrast, we also prove that any oscillating radial solutions of (0.1) on $\mathbb{H}^N$\{0} fails to be in the space $H¹_{loc}(\mathbb{H}^N)∩L^p_{loc}(H^N)$.     

气相色谱-单光子电离飞行时间质谱的联用及在柴油组分表征中的应用

建立了一种气相色谱(GC)与单光子电离-飞行时间质谱(SPI-TOF MS)联用(GC/SPI-TOF MS)的分析方法。首先,设计了一种双层套管的传输管用于连接GC与SPI-TOF MS,实现了GC与单光子电离离子源的无缝连接。在此基础上,以n-十五烷标准品和苯/甲苯/二甲苯的标准气为对象,对电离源的重要电压参数进行了优化,得到了纯净的分子离子峰,实现了对各类有机物的快速和准确定性。最后,将该方法用于分析柴油中的挥发性与半挥发性有机物,获得了柴油组分的二维GC×SPI-TOF MS谱图。不需要复杂的谱图解析和数据处理,根据谱图中离子的质荷比(m/z)归纳了柴油的主要成分,包括脂肪烃、芳香烃和含量很低的苯并吡咯等含氮化合物;根据色谱的保留时间将柴油中的同分异构体区分开来。结果表明GC/SPI-TOF MS法是一种简单、有效的分析方法,非常适于柴油及复杂环境样品等的分析表征。     

咔咯及其金属配合物与DNA的作用和抗肿瘤活性

咔咯及其金属配合物与DNA相互作用和它们的抗肿瘤活性研究已成为咔咯大环化学前沿课题之一。本文综述了咔咯及其金属配合物与DNA相互作用和关于这类化合物在抗肿瘤方面的研究进展,系统介绍了咔咯及其金属配合物与DNA结合模式、在氧化剂存在或光照条件下的核酸酶活性、与G-四链体DNA相互作用以及这类化合物抗肿瘤活性。     

地球静止轨道光综合孔径相机的能耗与(u,v)覆盖研究

围绕高分辨率对地观测实时成像需求,研究了地球静止轨道分布式卫星光综合孔径相机的能耗情况和空间频谱(u,v)覆盖情况.从静止轨道卫星动力学特性出发,分析了在天底对地观测和斜向对地观测两种情况下,维持分布式卫星编队飞行组成的光综合孔径阵列的收集器卫星的能耗情况,并给出仿真计算结果;从高质量成像需求出发,研究了实时成像情况下,对地面天底观测和对地面纬度为20°情况下的斜向观测两种情况下,不同时刻的(u,v)覆盖变化情况.研究方法和研究成果也可以扩展应用到其他天基轨道(如低轨道、深空探测轨道)的不同波段(如毫米波、微波)的综合孔径成像情况,对于发展中国空间对地观测高分辨率成像遥感等,具有重要的参考价值.     

Aqueous germanate solution,alternative sol–gel precursor for preparation of Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript> diluted magnetic semiconductors

The solids content and gelation time of aqueous germanate solution were examined in this work. Samples of 5, 10 and 20 mol% Mn doped Ge were prepared by using the aqueous germanate solution as a liquid Ge precursor. No second phase such as Mn₅Ge₃ was detected in the 5 and 10 mol% Mn doped samples, implying that Mn ions were uniformly diluted into the Ge host matrix. The 5 and 10 mol% Mn-doped Ge samples exhibit room-temperature ferromagnetic behaviors that are likely originated from the RKKY (Ruderman–Kittel–Kasuya–Yosida)-like interaction between the localized Mn ions in the Ge matrix. Therefore, the aqueous germanate solution can be an alternative sol–gel precursor for preparation of the Mn _x Ge_1−x diluted magnetic semiconductors (DMSs).     

Excluded volume effect on confined polymer translocation through a short nanochannel

We simulated the translocation process of a polymer chain from a source container to a drain container through a short nanochannel. We utilized the bond fluctuation model coupled with Monte Carlo dynamics in our simulations. The calculation results show that the excluded volume effect significantly affects the polymer's translocation time tau. This time depends nonmonotonically on the polymer length N. For a fixed nanochannel length, tau decreases when the polymer length increases. tau, however, increases when the polymer length exceeds a certain threshold. This observation differs from those predicated for a Gaussian chain. In this paper, we will further present our findings to explain this phenomenon. The knowledge we gain from this research can enhance the understanding of complex transport processes in many biological systems.     

Determination of four nitroimidazoles in poultry and swine muscle and eggs by liquid chromatography/tandem mass spectrometry

A rapid method is presented for the determination of 4 nitroimidazoles in poultry and swine muscle and eggs by liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS). Samples were extracted with acetonitrile, then evaporated the organic phase. After filtration, the extract was directly injected into the LC/ESI-MS/MS system. The LC separation was made on a C8 column by applying a gradient composed of water and acetonitrile. Overall average recoveries ranged from 50-86% for egg, 66-115% for poultry muscle, and 79-111% for swine muscle. The decision limits ranged from 0.05-0.25 microg/kg for egg, 0.07-0.27 microg/kg for poultry muscle, and 0.07-0.26 microg/kg for swine muscle; and detection capabilities ranged from 0.51-0.68 microg/kg for egg, 0.41-0.75 microg/kg for poultry muscle, and 0.53-0.78 microg/kg for swine muscle.     

大霍尔系数下电离气体与磁场相互作用规律数值研究

通过洛伦兹力与焦耳热耦合流场N-S方程和电势场泊松方程, 实现对低磁雷诺数磁流体流场的数值模拟, 并考虑霍尔效应和外电路对计算结果的影响. 采用无虚拟时间步的LUSGS预处理BI-CGSTAB算法解决了大霍尔系数下泊松方程病态矩阵求解问题. 对霍尔系数10$^2$的量级的高超声速磁流体圆管绕流和进气道隔离段能量沉积两种现象的数值模拟表明, 外电路、电极冷却措施、等离子体均匀度对电磁力作用效果影响很大.      

A high-efficiency spin polarizer based on edge and surface disordered silicene nanoribbons

Using the tight-binding formalism, we explore the effect of weak disorder upon the conductance of zigzag edge silicene nanoribbons (SiNRs), in the limit of phase-coherent transport. We find that the fashion of the conductance varies with disorder, and depends strongly on the type of disorder. Conductance dips are observed at the Van Hove singularities, owing to quasilocalized states existing in surface disordered SiNRs. A conductance gap is observed around the Fermi energy for both edge and surface disordered SiNRs, because edge states are localized. The average conductance of the disordered SiNRs decreases exponentially with the increase of disorder, and finally tends to disappear. The near-perfect spin polarization can be realized in SiNRs with a weak edge or surface disorder, and also can be attained by both the local electric field and the exchange field.