Material Properties of Basalt-Fiber-Reinforced Gypsum-Based Composites Made with Metakaolin and Silica Sand

Mechanics of Composite Materials - The effects of metakaolin (MK) and basalt fiber (BF) on the performance of gypsum-based composites were investigated. BFs 6 and 12 mm long were used in...     

Palm pairs and the general mass-transport principle

We consider a lcsc group G acting on a Borel space S and on an underlying ??-finite measure space. Our first main result is a transport formula connecting the Palm pairs of jointly stationary random measures on S. A key (and new) technical result is a measurable disintegration of the Haar measure on G along the orbits. The second main result is an intrinsic characterization of the Palm pairs of a G-invariant random measure. We then proceed with deriving a general version of the mass-transport principle for possibly non-transitive and non-unimodular group operations first in a deterministic and then in its full probabilistic form.     

我国棕榈油期货市场效率研究——基于VAR及其扩展模型的实证分析

利用2007年10月至2012年3月国内棕榈油期货市场、国际棕榈油产区以及国内棕榈油、豆油、菜籽油现货市场的交易日价格,运用VAR及其扩展模型验证了关于期货市场效率的两个假说.研究结果表明:棕榈油国际产区市场对来自期货市场的冲击有一定程度的反映,但不是主要作用,且期货市场对国际产区市场还没有预测力;棕榈油期货市场价格对现货市场发现功能不强,但对棕榈油、菜籽油、豆油现货价格具有较强的预测力,长期均衡关系对现货市场的调整力小.     

Delamination of Composites along the Interface as Buckling Failure of the Stressed Layer

A refined model for free vibrations of a Griffith crack in layered composites is investigated. The delamination of the composites along an interface is studied in the context of growth of instability of the stressed layer. This is analogous to the bending of a beam on an elastic foundation. The second-order gradient terms are taken into account in the power-series expansion of deflections. These terms are responsible for nonlinear phenomena in the interaction zone. The zero-order frequency of free vibrations of the crack along the interface and the time of instability growth are determined.     

Absolute continuity and singularity of Palm measures of the Ginibre point process

We prove a dichotomy between absolute continuity and singularity of the Ginibre point process \(\mathsf {G}\) and its reduced Palm measures \(\{\mathsf {G}_{\mathbf {x}}, \mathbf {x} \in \mathbb {C}^{\ell }, \ell = 0,1,2\ldots \}\), namely, reduced Palm measures \(\mathsf {G}_{\mathbf {x}}\) and \(\mathsf {G}_{\mathbf {y}}\) for \(\mathbf {x} \in \mathbb {C}^{\ell }\) and \(\mathbf {y} \in \mathbb {C}^{n}\) are mutually absolutely continuous if and only if \(\ell = n\); they are singular each other if and only if \(\ell \not = n\). Furthermore, we give an explicit expression of the Radon–Nikodym density \(d\mathsf {G}_{\mathbf {x}}/d \mathsf {G}_{\mathbf {y}}\) for \(\mathbf {x}, \mathbf {y} \in \mathbb {C}^{\ell }\).     

Structurally and Surface-Modified Alumina Particles as a Reinforcement in Polyester-Based Composites with an Improved Toughness

Mechanics of Composite Materials - Commercial γ ? Al2O3 particles, Al2O3 n, and synthesized Al2O3 doped with iron oxide (Al2O3 Fe) were used as reinforcements to enhance the toughness of...     

Description of the Structure of the Polymer Matrix of Particulate-Filled Polymer Composites as a Thermal Cluster: the Critical Indices

The adequacy of the model of a thermal cluster for describing the structure of the polymer matrix of particulate-filled composites is shown. The equality of the critical indices _T = of thermal and percolation clusters is realized in the composites at a nonzero molecular mobility, which is characterized by the fractal dimension D of the chain fragment between entanglements. The variation interval of D for the polymer matrix of a composite is smaller than for the initial polymer because of the influence of the filler on its structure.     

Stochastic Models for Oil Prices and the Pricing of Futures on Oil

Abstract

In this article, we investigate and compare the performance of various one-factor diffusion models in their ability to capture the behaviour of Brent crude oil prices. New proposed models, which have a three-quarters power in the diffusion term, are found to outperform all other popular models tested. Analytic solutions for futures prices under the new models are found and used to calibrate market prices. Results from the calibration show that one of the new three-quarters models with a mean-reverting property outperforms other popular models in fitting and forecasting futures prices.     

国际原油价格波动与原油进口对GDP的影响研究

基于国际原油价格的历史数据,应用统计学的方法证明国际原油价格的波动具有马尔科夫性。视我国原油进口的价格为马尔科夫链,计算其状态转移概率。在总结我国原油进口策略的基础上,估算了在各种进口价格状态下每种策略对我国GDP造成的损失,继而建立了最优策略的线性规划模型。结果显示,即使在最优策略的情况下,国际原油价格的波动仍会每月对我国的GDP造成470.78亿元的损失。     

A connectionist model using probability data as weights and parameters

Based on the concept of virtual lateral inhibition [1,2], a two layered connectionist model is developed, and its properties explored. This model is called LIBRA/RX. The flow of acitivation in this model is described by a set of 3N ordinary nonlinear differential equations, where N is the number of nodes on the nets' upper level. The mathematical properties of the equations are explored, and in particular, the dynamics of the net is demonstrated to be convergent in nearly all cases. The model has thus far been employed in the task of pattern recognition, and more recently in control tasks [3]. In the task of pattern recognition, the lower level or input nodes represent the possible features, and the upper level or output nodes represent the possible classes of patterns. This model uses the probabilities of the pattern classes given the features, and the features given the pattern classes as weights. The prior probabilities of the features and pattern classes also appear as parameters—thus, no learning need be involved. Examples of the nets use in classifying patterns are presented and discussed.     

Bounds and Self-Consistent Estimates for the Overall Properties of Nonlinear Composites

Variational ‘self-consistent’ estimates for nonlinearproblems are formulated, building on a variational formulationpreviously developed by the authors. The formulation employsa linear ‘comparison medium’ for whose propertiessome ‘self-consistent’ choice is made. In contrastto linear problems, three possible self-consistent choices presentthemselves. The results that they give are analysed for twoparticular systems (a nonlinear dielectric and a nonlinear lossycomposite) for which bounds are already available. Estimatesbased on self-consistent embedding of a single inclusion ina homogeneous matrix composed of ‘comparison material’are also developed.     

Studies in the separation and determination of zirconium using vanillin as an analytical reagent

Vanillin, quantitatively precipitates zirconium between pH 5·0–6·5, as insoluble complex. This complex on ignition gives ZrO₂ which can be weighed. Zirconium can be readily separated and determined in the presence of varying quantities of chromium (III), cobalt (II), copper (II), manganese (II), molybdenum (VI), nickel (II), titanium (IV), tungsten (VI), uranium (VI), vanadium (V), zinc (II) and trivalent rare earths.     

Oil Exploration and the Environment: the Mutual Effects

The interactions of the environment with operations involved in offshore oil and gas exploration and production are briefly reviewed with respect to possible effects of operations on the environment and, conversely, consideration of effects of the environment on installations and operations.     

三维四向编织复合材料刚度和强度的理论预测

以单胞模型为基础,将三维四向编织复合材料中相同走向的纤维束视为单向复合材料,利用桥联模型确定了单向复合材料的柔度矩阵,再将具有不同材料主向的单向复合材料的刚度矩阵通过体积平均,得到了三维四向编织复合材料的总体刚度矩阵,从而得到其工程弹性常数．然后,以单向复合材料为基础,基于等应变假设和桥联模型,确定出材料内各组分（纤维束和基体）的细观应力分布,且对纤维束采用Hoffman失效准则,对基体采用Mises失效准则,预报了三维四向编织复合材料的拉伸强度．     

Modeling the Nonlinear Deformation and Damage of Carbon-Aramid Fabric Composites in Tension

Mechanics of Composite Materials - To model the deformation of fabric polymer composite materials highly nonlinear in tension along the warp/weft threads, an analytical approach is proposed. Based...     

Modeling and simulation of keyhole-based welding as multi-domain problem using the extended finite element method

In this article, we demonstrate the flexibility of a multi-domain approach combined with the extended finite element method by addressing the modeling and simulation of keyhole-based welding. The welding process is modeled by the heat equation where the keyhole geometry and the interface separating molten and solid area are represented by two independent level set functions, separating the domain into three time-dependent subdomains. The keyhole shape is computed by an analytical approach based on the energy balance at the keyhole wall and its shape is assumed to be fixed. The solid-liquid interface is considered as free boundary whose evolution is described by the two-phase Stefan problem. The coupled problem including the two discontinuities is solved using a multi-domain XFEM implementation. The simulated results are shown together with experimental data on different welded materials.     

铜基复合材料组织形态分形特征的统计分析与研究

通过对铜基复合材料显微组织结构相图的分析和研究,根据分形理论,计算了不同实验条件下铜基复合材料横截面和平行压制力面的显微组织结构相图的分形维数,同时结合统计方法分析了铜基复合材料分形维数的一些统计特性,结果表明,分形维数反映了石墨在样品中的分布规律,分形维数越大,组织结构相图越复杂,石墨分布越不规则,故石墨分布的不规则性可用分形维数来刻画,分形维数可作为材料组织形态分析的一个表征参数,通过统计分析可知,铜基复合材料横截面和平行压制力面的组织结构相图的分形维数服从正态分布,且横截面和平行压制力面的分形维数随石墨含量变化的情况互不影响。