A short proof that hyperspaces of Peano continua are absolute retracts

We give a short proof of Wojdyslawski's famous theorem.

     

关于伪投射模的若干讨论

给出了伪投射模的另外一种等价定义,并对伪投射模的自同态环的Jacobson根做了讨论,还对伪投射盖做了某些探讨.     

高效液相色谱法快速测定冰淇淋中的糖精钠

用高效液相色谱法快速测定了冰淇淋中的糖精钠。使用反相径向加压柱,紫外检测定量。样品用硫酸铜及氢氧化钠处理后,滤液不用萃取即可上机检测。方法的最低检测限为0．38mg／kg,变异系数为1．72％,回收率为96．25％。     

海冰动力学中本构模型研究的若干进展

从20世纪70年代, 人们在不同尺度下建立了一系列的海冰动力学本构模型用于海冰数值模拟和预测. 将目前应用的海冰动力学本构模型分为弹塑性、黏塑性、各向异性和颗粒流体动力学中的黏弹塑性模型4类,并分别讨论了各类模型的特点和适用范围. 尤其对在极区及副极区大、中尺度下广泛应用的黏塑性及其改进的本构模型进行了深入地分析. 最后得出: 在大、中尺度下建立海冰动力学的黏弹塑性本构模型是提高海冰动力学计算精度的有效途径; 将小尺度下采用黏弹塑性本构模型的海冰颗粒流体动力学的计算时效进一步改进后, 可在大、中尺度下对海冰的重叠、堆积特性进行模拟; 进一步开展海冰动力学的尺度效应研究, 进行海冰本构模型的实验验证, 并建立不同尺度模型间的相互联系也应是海冰动力学本构模型研究的重要内容.      

冰雪路面汽车轮胎摩擦特性研究进展

简要总结了中、高模量材料同冰雪之间的摩擦机理及相关理论，系统分析了影响冰雪路面上橡胶块和轮胎摩擦行为的因素；指出在一定工作条件下，轮胎性能和设计参数，包括胎面胶的低温模量、轮胎结构和胎面花纹等是影响轮胎摩擦牵引力的重要因素，其影响程度取决于运行条件；并就轮胎摩擦特性、全天候轮胎研制及轮胎力主动控制等方面的研究方向和热点提出了建议．     

基于巴西盘试验的海冰拉伸强度研究

海冰拉伸强度是其基本力学性能之一, 同时也是冰区船舶与海洋工程结构设计所需的重要参数. 对于脆性材料的拉伸强度测试, 巴西盘劈裂试验相比单轴拉伸试验在试样制备与加载上具有明显的优势. 为研究海冰的拉伸强度特征, 对渤海辽东湾沿岸的粒状冰开展了系统的巴西盘劈裂试验研究. 在加载过程中与试样破坏后, 分别对加载横梁的位移与加载力以及试样最终破坏模式进行了记录. 同时, 对试样的冰晶结构、盐度、温度以及密度进行了测量. 通过改变加载速率、试样厚度与试样温度以研究不同参数对试验结果的影响. 针对传统试验中试样的刚体假设, 考虑了试样变形对应力状态的影响并将其引入了理论模型. 试验过程中所有海冰试样均以劈裂模式破坏. 试验结果表明, 加载速率与试样厚度对拉伸强度的影响并不显著, 但孔隙率的影响较为明显. 当孔隙率由75‰降低至10‰时,拉伸强度由1.0 MPa升高至2.8 MPa. 与单轴拉伸试验所测得数据对比, 巴西盘劈裂试验所得到的拉伸强度随孔隙率的变化趋势相一致. 但该方法所得到的粒状冰拉伸强度要高于预期结果. 试验表明巴西盘劈裂试验中海冰试样的破坏模式与试验结果均较为合理, 可成为海冰拉伸强度的有效测试方法.      

The coupling between ocean waves and rectangular ice sheets

This paper describes a semi-analytic approach to problems involving rectangular elastic plates of shallow draft floating on water. Specifically, two problems are considered: the scattering of plane monochromatic incident waves by a single elastic plate and the propagation/attenuation of waves through a periodic rectangular arrangement of plates. The approach combines Fourier methods with Rayleigh–Ritz methods for free modes of rectangular plates which reduces each problem to an algebraic system of equations which are numerically accurate and efficient to compute. A selection of results are given to illustrate the work. The approach can be applied to many problems in hydroelasticity including the seakeeping of large flat-bottomed marine vessels, deflections in very large floating structures such as offshore airports and wave propagation through areas of broken sea ice.     

In situ Raman and optical microscopy of the relaxation behavior of amorphous ices under pressure

The transformation of low‐density amorphous (LDA) ice produced from high‐density amorphous (HDA) ice was studied up to 400 MPa as a function of temperature by in situ Raman spectroscopy and optical microscopy. Changes in these amorphous states of H₂O were directly tracked without using emulsions to just above the crystallization temperature T_x. The spectra show significant changes occurring above ∼125 K. The results are compared with data reported for the relaxation behavior of HDA, to form what we call relaxed HDA, or rHDA. We find a close connection with expanded HDA (eHDA), which is reported to exist as another metastable form in this P–T region. The observation of this temperature‐induced LDA transition under pressure complements the previously observed pressure‐induced reversible transition between LDA and HDA at 120–140 K. Copyright © 2009 John Wiley & Sons, Ltd.     

Toric rings arising from vertex cover ideals

We extend the sortability concept to monomial ideals which are not necessarily generated in one degree and as an application we obtain normal Cohen-Macaulay toric rings attached to vertex cover ideals of graphs. Moreover, we consider a construction on a graph called a clique multi-whiskering which always produces vertex cover ideals with componentwise linear powers.     

On the Galois covers of degenerations of surfaces of minimal degree

We investigate the topological structures of Galois covers of surfaces of minimal degree (i.e., degree n) in ${\mathbb{CP}}^{n+1}$. We prove that for $n\ge 5$, the Galois covers of any surfaces of minimal degree are simply-connected surfaces of general type.