节理岩体表征单元体的分形几何研究

节理岩体的尺寸效应是其内在结构复杂性的体现,应归因于岩体内裂隙网络系统的存在。提出在岩体结构宏观分区的基础上研究表征单元体,应用分形几何的观点进行研究。结果表明,分区内岩体结构具有统计自相似性。进一步的计算表明,用于描述岩体结构特征的分形维数随岩石试样尺寸的增加而减小;但当尺寸增加到某特定值时,分形维数趋于稳定,将此特定值称为结构表征单元体,即尺寸大于结构表征单元体的样本其结构具有代表性。根据表征单元体的定义,尺寸大于表征单元体的岩体试样,其力学性质具有代表性;而结构相似是性质相似的前提,由此可以推知,结构表征单元体为表征单元体取值的下限。     

微量元素在某些青瓷判别中的应用

选择适当的多元统计分析，整理和分析了我国某些青瓷胎的微量元素组成，揭示出不同产地以及不同年代相同窑口瓷胎中微量元素组成的变化规律．确定了一批具有判别能力的特征元素，并建立了相应的判别函数．判别效果显著，表明了利用微量元素进行古陶瓷断源的科学性和便捷性．     

Probability distribution characteristics and estimation method of prestress of concrete structures based on Gaussian mixture model

为解决预应力混凝土框架结构预应力筋数量众多、有效应力不确定性强且分布不均匀、抽样检测评估无法准确表征结构有效应力整体特征等结构评价难题，引入高斯混合模型研究结构有效应力概率分布特征，并据此提出了一种概率估计方法。该方法通过MonteCarlo模拟建立预应力筋集有效应力的高斯混合模型；通过中心化、去除离散点等方式修正模型以增强其高斯特性；基于模型高斯显著性检验准则确定正态分布近似估计范围，并以此为总体样本进行抽样检测，进而估计预应力筋集实时有效应力的概率分布；以某无黏结预应力混凝土框架结构为工程实例验证了该方法有效性。研究结果表明：既有结构预应力筋集有效应力概率分布由多个均值与方差相近的子分布组成，可采用近似正态的高斯混合模型统一表征；由设计差异导致的有效应力分布不均匀性可采用中心化的数学方法进行消除，进而提升模型近似估计的准确性；既有结构施工阶段以张拉工艺为主的建造误差上限可通过模型计算结合实测值统计分析综合推定。     

灰元、灰代数及广义概率空间

把灰数结构理论推广到一般被认识对象,得到了灰元、灰事件及灰代数,在认知结构上建立了允许概率动态变化的广义概率空间;分析了A·H·Kолмогоров概率空间的局限性,讨论了广义概率空间的可能应用前景。     

Fragility analysis for ballistic design

Effective structural design to resist ballistic effects such as small arms or fragmenting weapons has been a goal since weapons were developed. Approaches currently in use for ballistic design are predominantly deterministic and allow designers to decide what wall thickness should be used to stop a prescribed projectile impacting at a predefined velocity. The research presented in this paper provides a framework for conducting reliability analysis of structures subjected to bullet and fragment demands. Thus, pseudo-fragility curves are developed for the limit states related to spall and perforation of wall panels, residual velocities of bullets and fragments, and injury to personnel. The pseudo-fragility analysis provides engineers and owners with a tool to quickly assess the reliability of a wall system subjected to high velocity, low mass projectiles. In particular, the proposed analysis method allows designers and owners to determine the probability of spall and perforation, residual velocity, and injury as a function of wall thickness or threat standoff distance.

Abbreviations: Cumulative distribution function (CDF): Gives the probability that a stochastic variable ‘X’, with a proper probability density function, is equal to or less than a value (x). Coefficient of variation (COV): The quotient of the standard deviation and the mean     

Estimation of torsional-flutter probability in flexible bridges considering randomness in flutter derivatives

Torsional-flutter instability is an aeroelastic phenomenon of interest to the bridge engineer, corresponding to a torsionally unstable vibration regime of the deck driven by wind excitation and appearing beyond a certain critical wind velocity. In this study a method for the derivation of the flutter probability for long-span bridges with bluff decks is proposed.In the first part of this study the deterministic problem is addressed. In contrast with the classical solution method in the frequency domain based on a numerical procedure for assessing the critical wind velocity, a single-mode “closed-form” algorithm for the derivation of the critical velocity was investigated. A polynomial representation of the aeroelastic-loading coefficients (flutter derivatives), necessary for torsional-flutter analysis, was utilized.In the second part an algorithm for estimating the torsional-flutter probability was developed, considering randomness in bridge properties, and flutter derivatives in particular due to their preeminent role in torsional-flutter velocity estimation.Experimental errors in the extraction of flutter derivatives from wind tunnel tests were analyzed. The “closed-form” algorithm, developed in the first part, allowed for a direct numerical solution of the flutter probability in a simple way.The torsional-flutter probability for three simulated bridge models with rectangular closed-box and truss-type girder deck was numerically determined. A set of experimental data, available from the literature, was employed. The simulations enabled the validation of the proposed algorithm.     

Design Water Levels in Tidal River Systems under the Influence of Typhoons

Water levels in tidal rivers are subject to the influence of both fluvial and tidal factors. The interaction between these factors is rendered more complex in regions affected by typhoons, which typically result in the combined occurrence of heavy rainfall and high sea levels.
Previous studies have outlined an analytical approach for calculating design water levels based on dividing the fluvial and tidal series into a typhoon and a non-typhoon component. This paper illustrates the steps involved in the analytical approach and describes its application to drainage basins in Hong Kong.
The approach provides a practical means for calculating design water levels, and is recommended for final design purposes. The results of using the full analysis may be approximated by using a sub-set of analytical results, and should prove satisfactory for the purposes of outline design.     

论组合数行列式

组合数是基础数的概念,被普遍的使用.由组合数构成的行列式具有特色.本文研究了组合数行列式的独特、奇妙的性质,并给出了严密的证明。     

桩基超声检测分析的逆概率法

本文论述了应用概率论的逆概率法分离超声波测桩曲线中缺陷信息与干扰的原理和计算方法，并通过实例将邀概率法与常用的概率统计法和PSD判别法作了比较，逆概率法的应用效果最好     

改进的微分等价递归算法

微分等价递归算法计算简单,在体系可靠度计算中有着广泛的应用。但是传统的微分等价递归算法精度低,并且利用数值差分来求解等价失效模式,计算量大。本文推出了等价线性失效模式的解析表达式,提高了等价模式的精度,并大大降低了计算量;在此基础上,分析了传统微分等价递归算法利用等价线性失效模式代替两个失效模式交集产生误差的原因,提出了改进的微分等价递归算法,从而大幅度地提高了计算精度,为微分等价递归算法在实际工程中的应用奠定了良好基础。