惰气熔融-红外光谱法测定镨钕镝中的氧

研究了惰性气体-红外光谱法测定镨钕镝合金中的氧,采用石墨套坩埚和高纯镍篮,在4500W的分析功率下,对0.1g实际样品进行分析,取得了满意的效果。实验结果表明,样品释放完全,测定结果相对标准偏差(RSD,n=5)为1.9%,以GSBH40104—1996标准样品(ω(O)/%=0.00943)进行加标回收实验,回收率测量结果为95%～108%。     

Graphene oxide doped poly(vinylidene fluoride-co-hexafluoropropylene) gel electrolyte for lithium ion battery

Gel poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymer electrolytes doped with graphene oxide (GO) (GO/PVDF-HFP) were designed and fabricated through a phrase inversion method and followed by LiPF₆ solution uptake. It was demonstrated that the as-prepared GO/PVDF-HFP polymer electrolytes have uniform porous morphologies, and their crystalline state, thermal stability, interfacial resistance, and electrolyte uptake and retention capabilities can be tuned by varying the GO contents. Further, it was found that the GO can prominently enhance the ionic conductivity of the GO/PVDF-HFP polymer electrolyte. The electrochemical property measurements show that the lithium ion batteries using as-prepared GO/PVDF-HFP polymer electrolytes afford admirable charge/discharge rate and cycle stability.     

幂强化材料和超弹性材料组合球体中孔穴的动态生成

在简单加载条件下,研究幂强化材料和超弹性材料组合球体中的动态孔穴生成和增长问题,首先在有限变形动力学的框架下建立了相应的非线性数学模型,得到了应力的表达式,利用变量变换的方法求得了外加载荷和孔穴半径之间的一个精确的微分关系式,证明了当突加载荷超过其临界值时,球体内部有孔穴的突然生成,并随时间呈现非线性的周期振动．通过数值计算,分析了材料参数和球体的半径比对孔穴生成和增长的影响,并与相应的静态结果进行了比较．结果发现,惯性力的影响降低孔穴生成的临界载荷,而且材料的塑性对孔穴生成和增长有明显的影响．     

应用不对称一维光子晶体结构制备窄光谱LED

对周期性的GaAlAs／AlAs模块堆积组成的有缺陷的一维光子晶体的光波传输模式进行了理论与实验研究。由于堆积结构的周期性受到破坏,导致了光子晶体中模密度发生变化,光波的传播也发生了变化。对模密度和光的传播模式分别用流行的光子能态理论和光学传输矩阵进行了计算和模拟。计算发现采用不对称结构的一维光子晶体结构在实际应用中有更大的灵活性。用金属有机物化学汽相沉积方法实现一维光子晶体,并用于裁剪普通的发光二极管电致发光谱,在20mA的激发电流下,半峰全宽为2．8mm,单色性优 于共振腔发光二极管。在较大的激发电流下,带边发射的增强现象也被观测到。     

生长对超弹性球壳变形和稳定性的影响

应用连续介质力学有限变形理论建立受内压作用不可压超弹性球壳大变形问题的力学模型, 且运用基于变形梯度张量极分解的弹性体积生长理论分析生长对不可压超弹性球壳变形和稳定性的影响. 通过对球壳变形与内压关系式的数值计算得到不同生长条件下球壳的变形曲线和应力分布曲线及由生长引起的残余变形和残余应力分布. 计算结果表明生长对球壳变形特性有明显的影响, 生长影响球壳可产生不稳定变形的临界壁厚和临界内压, 且在某些情况下可改变球壳的稳定性. 生长在球壳中可产生一定的残余变形和残余应力, 对球壳中的应力分布有一定的影响. 另外当生长的程度足够大时, 即便没有外力作用,球壳仅在生长引起的残余应力作用下也可产生不稳定变形.      

具有初始构型的MEMS驱动器的跳跃和吸合现象研究

在曲梁变形后以弧长为参数的自然坐标系中,利用曲梁大变形分析理论,建立了具有任意初始构型的微电驱动器大变形电动力学分析的数学模型,并采用微分求积法(DQM)进行空间离散,得到了一组具有强非线性的微分-代数系统方程,运用Petzold-Gear BDF方法进行时间域内的求解。研究了MEMS驱动器在电场力作用下的瞬态动力学特性,包括跳跃(snap-through)和吸合(pull-in)现象,并与已有实验结果进行了比较。     

不同形貌纳米FeNi合金的制备

纳米FeNi合金因其独特的电磁及催化性能在磁记录、催化剂、吸波材料及生物医学等领域存在广阔的应用前景。由于材料的形貌对其性能有着重要的影响,本文重点介绍了不同形貌(球形、一维形貌、纳米点阵、纳米环、纳米片、纳米花、树枝状及无特定形貌)纳米FeNi合金的制备方法,叙述了各方法制备纳米FeNi合金的基本原理及调控规律,并对各方法的优缺点作出了简要评价。同时,对材料形貌与尺寸对其性能影响的机理及规律作出了简要说明,阐述了其形貌及结构特征对材料性质的影响,指出了不同形貌纳米FeNi合金的优势应用领域。最后,对该领域未来的研究方向作出了展望。     

Pulsation of black holes

The Hawking–Penrose singularity theorem states that a singularity forms inside a black hole in general relativity. To remove this singularity one must resort to a more fundamental theory. Using a corrected dynamical equation arising in loop quantum cosmology and braneworld models, we study the gravitational collapse of a perfect fluid sphere with a rather general equation of state. In the frame of an observer comoving with this fluid, the sphere pulsates between a maximum and a minimum size, avoiding the singularity. The exterior geometry is also constructed. There are usually an outer and an inner apparent horizon, resembling the Reissner–Nordström situation. For a distant observer the horizon crossing occurs in an infinite time and the pulsations of the black hole quantum “beating heart” are completely unobservable. However, it may be observable if the black hole is not spherical symmetric and radiates gravitational wave due to the quadrupole moment, if any.     

Magnetic irreversibility of the Fe antidot arrays film by depositing on the porous alumina templates

An Fe layer was sputter-deposited onto porous alumina templates and Kapton respectively. Fe layer on the porous alumina templates formed an antidot arrays nanostructure, while Fe layer on the Kapton substrate formed a continuous film. Scanning electron microscopy and grazing incidence X-ray diffraction were employed to characterize the morphology and crystal structure of the Fe antidot arrays and continuous film, respectively. The temperature dependence of magnetic properties was shown in the temperature range 2-300 K. The irreversibility of the magnetization of Fe antidot arrays film, as measured in zero-field cooling (ZFC) and field cooling (FC) states, was attributed to the pinning effect of the holes.     

弹性或弹塑性土体中桩基的大变形分析

采用弧坐标,首先建立了位于弹性地基或弹塑性地基上并具有初始位移的桩基大变形行为的非线性微分方程组,并采用Winkeler模型来模拟地基对桩基的抗力;其次,应用微分求积方法离散非线性微分方程组,得到一组离散化的非线性代数方程,并给出了利用Newn-Raphson方法求解非线性代数方程的步骤;作为应用给出了数值算例,得到了桩顶受组合载荷作用时,变形后桩基的构形、弯矩和剪力,考察了土的弹性和弹塑性性质、桩基初始位移、荷载等参数对桩基力学行为的影响.最后将模型进行简化,得到了小变形理论的解析解,并比较了由大变形理论与小变形理论所得结果的差别.