单轴压缩条件下石灰岩的声发射试验及工程应用研究

运用TAW-2000B微机控制电液伺服岩石三轴试验机和SDAES数字声发射检测仪系统,在单轴压缩条件下,对石灰岩在应力-应变曲线全过程中不同阶段的声发射特征进行分析,通过试验研究对岩石应力-应变曲线不同阶段的声发射特征进行系统分析,在原岩开挖后,立即进行初喷混凝土等柔性支护,可以使围岩能够尽可能的变形,使其达到弹性变形的极限,开始出现塑性变形支护效果最好,能充分发挥围岩自身的稳定性,这对何时进行支护才能最大程度的发挥围岩自身的稳定性奠定理论基础。     

基于声发射的不同粒径花岗岩细观破裂机理研究

为了研究粒径对岩石细观破裂机制的影响,本文开展了直剪条件下不同粒径花岗岩的声发射试验,结合矩张量反演理论分析岩石微破裂机制。研究结果表明：(1)在相同应力水平下,随着粒径的增加,微破裂的扩展范围及贯通程度均有增加趋势;(2)不同粒径花岗岩的微观破裂机制均以剪切型为主比,随着粒径的增大,剪切型占比逐渐升高。以上研究成果有利于增进人们对岩石微观破裂机制及其影响因素的认识,可应用于预测及解释岩石宏观断裂过程及模式。     

酸性溶蚀作用下灰岩弱化力学效应的试验研究

通过自制的自平衡岩石真三轴压缩仪(SRT)对灰岩岩样在溶蚀作用下真三轴、常规三轴的压缩试验,探讨了试样在不同的应变条件下溶蚀作用对于轴向的抗压强度的溶蚀效应;真三轴实验σ2的初始应力高于常规三轴的围压但是其σ3未施加应力约束使得灰岩岩样的抗压峰值强度任低于常规三轴的抗压峰值;溶蚀作用对于灰岩力学性质发生改变机理在于溶蚀作用使得裂隙临界应力强度因子降低,其灰岩宏观力学特性不断弱化,但灰岩力学破坏机理并没有本质上的改变。从而对岩溶地区岩体工程的长期稳定性提供了科学依据。     

基于AE全波形信号的钢筋混凝土动态破坏监测研究

全波形声发射信号分析是钢筋混凝土结构检测的一种有效方法。分析了动态弯曲破坏下,钢筋混凝土梁不同破坏阶段全波形声发射信号的频谱特性。结果表明,在钢筋混凝土梁破坏的各个阶段,全波形声发射信号的频谱特性呈现规律性变化。随着破坏严重,钢筋混凝土的破坏机理呈现多样化,声发射信号功率谱密度的峰值频率也显著增加。     

Q235钢箱型梁弯曲试验的声发射检测

对带有外部缺陷的Q235钢箱型梁弯曲试验过程中的声发射特征进行监测,研究试验过程中裂纹扩展的声发射参数特征和定位特征。弹性变形阶段的声发射密集程度和能量比屈服变形后的阶段弱,弹性阶段的声发射信号最高幅度为64d B。在弹性阶段期间,当箱型梁承受的最大载荷比带有缺陷的试件承受的最大载荷小时,缺陷很难被检测到。结果表明:在三点弯曲试验中,当裂纹发生扩展时,直线定位方法可以有效地对声发射源进行定位。     

氢致开裂试验及分析

文章研究了石油液化气钢瓶氢致开裂的声发射试验,采用德国Vallen公司生产的AMSY-5型声发射仪,将液化气钢瓶打压,内为饱和H2S溶液,用声发射仪24小时连续不断的监测液化气钢瓶在湿硫化氢环境下氢致裂纹从萌芽到破裂的全过程。     

室内配制混凝土单轴试验全应力-应变曲线试验研究

本文采用TAW-2000微机控制岩石伺服三轴压力试验机,对室内配制普通混凝土圆柱体试件(高径比约2:1)进行单轴受压实验。测定了普通混凝土全应力-应变曲线。通过对试验的研究,循环加载条件下,确实形成了一个封闭的塑性滞回环,且峰后塑性滞回环随循环的次数的增加而变小变窄;加载应力和加载段变形模量呈一定的线性关系;峰后卸载点的应力和峰值应力差越大,峰后曲线的变化越明显,变得越平缓,重新加载曲线的趋近线斜率与初始变形曲线的趋近线斜率相差越大。     

刘家畈铁矿采空区地压监测及安全对策

文章通过对刘家畈铁矿采空区地压现状的分析,采用岩体声发射监测、地面沉降监测、矿柱应力监测、采空区顶板位移监测等综合监测手段对其地压进行监测。对各测点的监测结果进行分析研究发现,有几处矿柱声发射现象较活跃,某些矿柱应力一直处于正压状态,进而提出了一些针对性的安全对策,对指导矿山安全生产,预防矿山安全事故的发生具有一定的实际意义。     

简支梁受力过程中变形和声发射参数的关系探究

利用声发射技术和常规检测技术对简支梁破坏过程进行了试验检测,并探究了变形和声发射参数的关系,并给出了同级荷载下,声发射能量和振铃计数随着变形的增大,先增大后减小,不同荷载下,声发射能量、振铃计数和幅度随变形的增大而增大的结论。     

声发射技术在海上压力容器检测中的应用

压力容器在海上作为重要的生产设备大量存在,由于海上工作环境的特殊性,同时随着其使用时间的增长,一些压力容器难免出现问题,从而影响生产,容器的安全及检测评价成为了使用者及管理者所关心的问题。本文首先介绍了声发射检测技术的检测原理,然后简述了声发射在压力容器检测中的实际应用,其中包括检测设备,加压程序,最后介绍了声发射检测结果的评价方法。     

Incumplimiento del salario mínimo en Europa central y oriental

En este estudio se analiza el incumplimiento del salario mínimo durante el periodo 2003–2012 en diez países de Europa central y oriental con salario mínimo obligatorio nacional. A partir de los datos de EU‐SILC y la metodología propuesta por Bhorat, Kanbur y Mayet (2013), se cuantifica la incidencia y magnitud del incumplimiento. Se realizan análisis de regresión sobre determinantes individuales, laborales y macroeconómicos. Aunque la incidencia permanece relativamente baja, los trabajadores a los que se dirigen las políticas de salario mínimo parecen los más expuestos a su incumplimiento. Con el tiempo, una mayor incidencia se asocia a una razón más alta entre salario mínimo y salario medio.     

Cultural Economy Planning in Creative Cities: Discourse and Practice

While a growing body of research analyses the functional mechanisms of the cultural or creative economy, there has been little attention devoted to understanding how local governments translate this work into policy. Moreover, research in this vein focuses predominately on Richard Florida's creative class thesis rather than considering the wider body of work that may influence policy. This article seeks to develop a deeper understanding of how municipalities conceptualize and plan for the cultural economy through the lens of two cities held up as model ‘creative cities’ — Austin, Texas and Toronto, Ontario. The work pays particular attention to how the cities adopt and adapt leading theories, strategies and discourses of the cultural economy. While policy documents indicate that the cities embrace the creative city model, in practice agencies tend to adapt conventional economic development strategies for cultural economy activity and appropriate the language of the creative city for multiple purposes.     

Input/output ranges and performance: an examination of US machine tool producers

Despite the establishment of high-tech multinational enterprises (MNEs) in Ireland since the late 1950s, the country did not succeed in closing the technological gap with most of its EU counterparts. The weak National System of Innovation (NSI), and in particular low business and government R&D levels, combined with a lack of research and technology linkages between MNEs and indigenous firms, explain these poor results. However, the Shannon region in the West of the country presents some specific institutional characteristics that could theoretically make the region a strong technological enclave. The various actors in the region - i.e. the administrative, financial, political and research institutions, as well as the business organizations - have indeed infused a new type of economic development. After a brief review of the available concepts and models articulated around these actors and their interrelationships, the paper analyses whether the Shannon region, taken as an illustrative example, mirrors a specific economic and technological localized setting. The study is based on a survey of indigenous and foreign firms.     

Sixty years of discrimination and diversity research in human resource management: A review with suggestions for future research directions

This article reviews discrimination and diversity research published in Human Resource Management (HRM) over the past 60 years. While discrimination and diversity are very different constructs, it is often informative to study them together, because when people recognize each other's diversity, this can result in bias, stereotyping, and discrimination. We conducted bibliographic searches for terms related to discrimination and diversity as well as a manual search through every title and abstract published in HRM over the last 60 years to assess article relevance. The search resulted in 135 research articles with 136 unique studies (i.e., samples) which are reviewed in this article. Sex and race are the demographics that have been examined the most in HRM, while religion has been examined the least. Moreover, the number of studies examining lesbian, gay, bisexual, transgender, and queer (LGBTQ) employees in the workplace in HRM has grown quickly within the past 10 years, culminating in a recent meta‐analysis. Our review looks at some of the earliest research published, the most recent research published, and the overall trends we identified in the research over the years for both discrimination and diversity articles. We then make future research suggestions and recommendations to advance the study of discrimination and diversity in the coming years.     

The Early History of the Cumulants and the Gram-Charlier Series

The early history of the Gram-Charlier series is discussed from three points of view: (1) a generalization of Laplace's central limit theorem, (2) a least squares approximation to a continuous function by means of Chebyshev-Hermite polynomials, (3) a generalization of Gauss's normal distribution to a system of skew distributions. Thiele defined the cumulants in terms of the moments, first by a recursion formula and later by an expansion of the logarithm of the moment generating function. He devised a differential operator which adjusts any cumulant to a desired value. His little known 1899 paper in Danish on the properties of the cumulants is translated into English in the Appendix.     

Capturing the Implications of Services Trade Liberalization

This paper evaluates the impact of service sector trade liberalization on the world economy by a ten-region, eleven-sector CGE model with import embodied technology transfer from developed countries to developing countries. Simulation results show that service sector trade liberalization not only directly affects world service production and trade, but also has significant implications for other sectors in the economy. The major channel of the impact is through inter-industry input-output relations and TFP growth induced from services imported by developing countries from developed countries, which may be embodied with new information and advanced technology.     

City Children and Genderfied Neighbourhoods: The New Generation as Urban Regeneration Strategy

Former industrial cities in the West are employing gentrification as urban policy. In these policies, women and families currently play an important role as gentrification pioneers. In my analysis of Rotterdam in the Netherlands, I propose the term genderfication to understand the gender dimensions of this process. Genderfication refers to the production of space for different gender relations. I analyse Rotterdam's urban planning program for becoming a ‘child‐friendly city’, which entails replacing existing urban dwellings with new, larger and more expensive ‘family‐friendly homes’ as a strategy for urban re‐generation. Urban re‐generation supplements regeneration in the form of material and economic restructuring, and refers to the replacement of part of the current population by a new and better suited generation. The ‘child‐friendly city program’ is considered in tandem with punitive ‘youth policies’.     

Hierarchical Models in Environmental Science

Environmental systems are complicated. They include very intricate spatio-temporal processes, interacting on a wide variety of scales. There is increasingly vast amounts of data for such processes from geographical information systems, remote sensing platforms, monitoring networks, and computer models. In addition, often there is a great variety of scientific knowledge available for such systems, from partial differential equations based on first principles to panel surveys. It is argued that it is not generally adequate to consider such processes from a joint perspective. Instead, the processes often must be considered as a coherently linked system of conditional models. This paper provides a brief overview of hierarchical approaches applied to environmental processes. The key elements of such models can be considered in three general stages, the data stage, process stage, and parameter stage. In each stage, complicated dependence structure is mitigated by conditioning. For example, the data stage can incorporate measurement errors as well as multiple datasets with varying supports. The process and parameter stages can allow spatial and spatio-temporal processes as well as the direct inclusion of scientific knowledge. The paper concludes with a discussion of some outstanding problems in hierarchical modelling of environmental systems, including the need for new collaboration approaches.     

Multinomial distributions applied to random sampling of particulate materials

When sampling a batch consisting of particulate material, the distribution of a sample estimator can be characterized using knowledge about the sample drawing process. With Bernoulli sampling, the number of particles in the sample is binomially distributed. Because this is rarely realized in practice, we propose a sampling design in which the possible samples have a nearly equal mass. Expected values and variances of the sample estimator are calculated. It is shown that the sample estimator becomes identical to the Horvitz–Thompson estimator in the case of a large batch-to-sample mass ratio and a large sample mass. Simulations and experiments were performed to test the theory. Simulations confirm that the round-off error due to the discrete nature of particles is negligible for large sample sizes. Sampling experiments were carried out with a mixture of PolyPropylene (PP) and PolyTetraFluorEthylene (PTFE) spheres suspended in a viscous medium. The measured and theoretical variations are in good agreement.