基于ANSYS混凝土重力坝流固耦合动力特性分析

以某混凝土重力坝非溢流坝段动力特性为背景,探讨流固耦合效应对结构自振特性的影响,运用大型有限元软件对结构自振特性进行分析计算,得出了流体对结构自振特性影响以及结构的固有频率,避免在运行过程中发生共振,造成对结构的破坏。     

Experimental Study on Phase Transformation Between MgB2 and MgB4

Using X-ray diffraction (XRD), scanning electron microscope (SEM), and differential scanning calorimetry (DSC), we have investigated the reaction between MgB₄ and Mg in its solid, liquid, and gas physical states. The XRD results indicate that the reaction of MgB₄+Mg=2MgB₂ always occurs independently of the different states of Mg. DSC measurements show that the solid–solid reaction MgB₄( s )+Mg( s )=2MgB₂( s ), the Mg melting Mg( s )→Mg( l ), and the Mg volatilization occur in turn with increasing temperature for mixed (MgB₄+Mg) powder with a nominal stoichiometry of MgB₂. SEM observations indicate that the resulting synthesized MgB₂ samples, obtained from the MgB₄+Mg mixtures, have a denser microstructure than those obtained directly from Mg+B mixtures. On the basis of XRD, DSC, and SEM results, a kinetic model for the reaction between MgB₄ and Mg is proposed.     

Multidimensional ARKN methods for general oscillatory second-order initial value problems

Based on B-series theory, the order conditions of the multidimensional ARKN methods are presented for the general multi-frequency and multidimensional oscillatory second-order initial value problems by Wu et al. (2009). These multidimensional ARKN methods exactly integrate the multi-frequency and multidimensional unperturbed oscillators. In this paper, we pay attention to the analysis of the concrete multidimensional ARKN methods for the general multi-frequency oscillatory second-order initial value problems whose right-hand side functions depend on both  y$y$and  y^′$y^{\prime }$ (the class of physical problems which fall within its scope is broader). Numerical experiments are carried out to show that the new multidimensional ARKN methods are more efficient compared with some well-known methods for dealing with the oscillatory problems in the scientific literature.     

A novel microneedle array for the treatment of hydrocephalus

We present a microfabricated 10 by 10 array of microneedles for the treatment of a neurological disease called communicating hydrocephalus. Together with the previously reported microvalve array, the current implantable microneedle array completes the microfabricated arachnoid granulations (MAGs) that mimic the function of normal arachnoid granulations. The microneedle array was designed to enable the fixation of the MAGs through dura mater membrane in the brain and thus provide a conduit for the flow of cerebrospinal fluid. Cone-shaped microneedles with hollow channels were fabricated using a series of microfabrication techniques: SU-8 photolithography for tapered geometry, reactive ion etching for sharpening the microneedles, 248 nm deep UV excimer laser machining for creating through-hole inside the microneedles, and metal sputtering for improved rigidity. Puncture tests were conducted using porcine dura mater and the results showed that the fabricated microneedle array is strong enough to pierce the dura mater. The in vitro biocompatibility test result showed that none of the 100 outlets of the microneedles exposed to the bloodstream were clogged significantly by blood cells. We believe that these test results demonstrate the potential use of the microneedle array as a new treatment of hydrocephalus.     

高岭土在碳热还原氮化过程中的相变

系统研究了苏州高岭土碳热还原氮化合成SiAlON过程在不同温度下的相变。对试样的XRD、SEM以及EDXA分析结果表明 ,1 30 0℃之前 ,试样中没有氮化物生成 ,物相为莫来石、石英和方石英 ;1 30 0℃时 ,高岭土开始发生氮化反应 ,生成过渡型SiAlON和β SiAlON。此时 ,石英和方石英相基本消失 ;1 4 0 0℃时 ,过渡型SiAlON、β SiAlON和X SiAlON三相共存 ,β SiAlON有所增多并有少量刚玉相生成 ;从 1 4 50℃到 1 550℃ ,Z值为 3的β SiAlON成为惟一的氮化产物 ,与少量SiC和刚玉相并存。莫来石在 1 50 0℃时完全消失     

糠醛生产与热电联合处理糠醛废渣模式探讨

糠醛废渣问题是制约我国糠醛行业发展的瓶颈。本文运用工业协作的基本原理,对糠醛生产和热电联合处理糠醛废渣模式进行了分析探讨,对于有效解决糠醛废渣问题及糠醛行业和其它行业实践生态工业具有积极的意义。     

边坡可靠性分析的非线性有限元正交设计算法

非线性有限元正交设计算法，是借助于回归分析，用正交多项式拟合各岩石力学特性参数与各单元滑移面及岩体整体滑动安全余量间的函数关系，以评判边坡工程的可靠性。该法较蒙特卡罗法精度高，能满足工程计算的精度要求，且方法简单、计算时间少，不需改变有限元法的有关方程和计算程序，易为人们接受。     

用于虚拟现实的360度视频编码技术新进展*

随着虚拟现实技术不断发展,360度视频编码开始成为研究热点。应用于虚拟现实的360度视频与传统的视频相比分辨率更高,编码数据量更大,在实际应用中面临传输带宽有限的瓶颈,编码效率问题有待解决。归纳分析了国际标准组织联合视频研究组（joint video exploration team, JVET）正在制定的360度视频编码投影变换技术及其编码优化方法,综合对比了各变换技术的编码性能。根据当前最新研究成果,对下一步研究需要解决的问题进行了探讨总结,给出未来的研究方向和思路。     

新型液晶PVDF合金的研究

本文系统地研究了液晶聚合物(LCP)与PVDF合金共混体系的组成及加工工艺条件对共混物制件性能的影响。并用SEM观察了合金的形态结构。结果表明:在液晶含量10%左右时,加工温度为210℃,合金的拉伸强度最高,磨耗量最低,体系分散均匀并形成了较多的微纤结构。     

Synthesis and thermal properties of block copolyetheresters with poly(pentamethylene p,p′-bibenzoate) segments

The block copolyetheresters with hard segments of poly(pentamethylene p,p-bibenzoate) and soft segments of poly (tetramethylene ether) were prepared by melt polycondensation of dimethyl-p,p-bibenzoate, 1,5-pentanediol and poly (tetramethyene ether) glycol (PTMEG) with molecular weights of 650, 1000 and 2000. The results by NMR indicate that the polymer composition is determined by the charge molar ratio (x) of PTMEG to dimethyl-p,p-bibenzoate. The thermal transitions of the block copolyetheresters were investigated by DSC in combination with X-ray diffraction and polarized microscopy. Some block copolyetheresters exhibit a monotropic smectic phase due to the presence of the poly (pentamethylene p,p-bibenzoate) segments. As the molar content of PTMEG increases, the average sequence length of the polyester segments decreases, the isotropic-smectic transition temperature and the smectic order decrease accordingly. When x is as high as 0.3, the block copolyetheresters exhibit no liquid crystallinity.