适用于堆石料的分数阶下加载面模型

堆石料的应力-应变曲线具有应变硬化和软化的特性,并且体积变形会伴随着剪缩和剪胀现象的发生;此外,应力水平、应力路径和密度等因素均会对堆石料的力学特性产生显著的影响。基于临界状态土力学的理论框架,建立了适用于堆石料的分数阶下加载面模型,该模型为典型的双屈服模型。在平均主应力p-剪应力q平面,剪切过程中堆石料当前应力状态点和参考应力点分别位于下加载面和参考屈服面上,两者之间的相对位置与孔隙比之差ρ相关。相比于状态参量Ψ,ρ能够额外考虑应力路径对堆石料剪胀特性的影响。新模型的另一个显著特点在于能够考虑堆石料塑性流动方向与加载方向之间的差异性。在不引入塑性势函数的情况下,新模型对屈服函数进行Caputo微分并得到分数阶塑性流动法则,进而统一描述相关联和非相关联的塑性流动法则。新模型具有形式简单且参数较少等优点,所包含的7个材料参数均具有明确的物理意义,并且可以采用常规的室内试验结果进行标定。通过将模型计算结果与Tacheng堆石料在不同初始孔隙比和围压条件下的三轴压缩排水试验结果进行对比分析,结果表明新模型能够准确地描述堆石料的应力-应变曲线和体积变形特点;同时,新模型也能够合理地描述初始孔隙比对堆石料在e-lnp平面(e为孔隙比)临界状态线的影响。     

Availability of offloading from an LNG barge

Long-term data sets are discussed for three locations – a southern North Sea location, where sea states are typically dominated by wind-sea conditions, a Northwest Shelf of Australia location, where sea states are often a mix of wind-sea and swell conditions, and a Guinea Gulf location offshore Nigeria, where sea states are dominated by swell. Various types of sea state statistics that have application to availability studies are presented; but databases of these type that also include wind and current data can also be used to estimate response parameters, which can give a more direct assessment of availability, and some example statistics of these are also given. Finally, the availability of offloading an FLNG barge to carrier is evaluated for each of the data sets, for specific operability criteria. Two types of operability criteria are used in the availability evaluations, and the results compared.     

2020年河北唐山5.1级地震前震源参数变化

利用谱分析方法对河北省测震台网2016年1月—2020年7月唐山老震区(117.5°～119.5°E,39°～41°N)85次M_L≥2.5地震进行震源参数分析,发现该时段唐山老震区应力降范围在0.1～10.3MPa,主要集中在0.1～1.0MPa,其中应力降小于2MPa的地震占81%。当2.5≤M_L≤3.5时,应力降、拐角频率与震级之间无明显的对应关系;ML≥4.0地震较少,但应力降有随震级增大而增大的趋势,拐角频率有随震级增大而减小的趋势。2019年12月5日河北丰南M4.5地震和2020年7月12日唐山M5.1地震之间发生了 7次M_L≥2.5地震,震级范围为2.5≤M_L≤2.8,提取该震级范围的震源参数进行时空分析,发现唐山M5.1地震前有2次明显的高应力降事件,2次高应力降事件呈现出应力降数值高、拐角频率高、震源尺度小的特点,表明单位体积所释放能量较多。2次高应力降事件均发生在唐山M5.1地震震中17km范围内,可能是唐山M5.1地震前震源区构造应力较高的一个标志。     

The Estuarine Quality Paradox, Environmental Homeostasis and the difficulty of detecting anthropogenic stress in naturally stressed areas

Estuaries have long been regarded as environmentally naturally stressed areas because of the high degree of variability in their physico-chemical characteristics, for example oxygen, temperature and salinity in the water column and bed sediment dynamics. However, their biota is well-adapted to cope with that stress and so the areas may be regarded as resilient because of that inherent variability; their ability to absorb stress without adverse effects is regarded here as Environmental Homeostasis. Hence these areas may only be regarded as stressful for marine or freshwater-adapted organisms and that for estuarine organisms this environmental stress is regarded as a subsidy whereby they successfully capitalise on the stressful conditions. In addition, using examples of the estuarine fauna and flora, this article indicates that the characteristics of natural stress in estuaries are similar to those for anthropogenic stress. An over-reliance on ecosystem structural features, such as diversity, in quality indicators therefore makes the detection of the anthropogenic stress more difficult. This difficulty is termed the Estuarine Quality Paradox. Because of these difficulties, the article argues that functional characteristics either as well as or rather than structural ones should be used in detecting environmental perturbations in estuaries.     

Equation of state constraints from neutron stars

Recent measurements of thermal radiation from neutron stars have suggested a rather broad range of radiation radii ( ). Sources in M13 and Omega Cen imply R _∞∼12–14 km, but X7 in 47 Tuc implies R _∞∼16–20 km and RX J1856-3754 R _∞>17 km. If these measurements are all correct, only a limited selection of EOS’s could be consistent with them, but a broad range of neutron star masses (up to 2 M_⊙) would also be necessary. The surviving equations of state are incompatible with significant softening above nuclear saturation densities, such as would occur with Boson condensates, a low-density quark-hadron transition, or hyperons. Other potential constraints, such as from QPO’s, radio pulsar mass and moment of inertia measurements, and neutron star cooling, are compared. US DOE Grant DE-FG02-87ER-40317.     

基态修正的GIS数据库增量更新建模

为了对GIS数据库增量更新中的增量信息、版本数据库进行组织和管理,本文采用基态修正模型,将版本数据作为基态、版本数据对应的增量信息作为修正,分别设计了其存储的数据结构,并给出了基于该模型的增量更新流程。以1∶2000地形图数据的增量更新为例,开发了空间数据库增量更新原型系统,实现了多个增量信息文件的组织存储、快速集成到历史数据中,能够满足GIS数据库增量更新的需求。     

城市道路交通状态信息服务系统设计与实现

通过对交通信息服务系统的现状分析,本文提出了基于浮动车数据的城市道路交通状态信息服务系统设计方案,阐述了系统的交通工程理论和系统技术基本原理,结合需求分析设计了系统的功能结构,重点研究了一种高效的数据存储管理设计方法,最后结合目前流行的富客户端技术研究了系统实现问题,提出了未来的发展趋势。     

Restructuring and socially managed flexibility in the Norwegian hotel industry

The article explores processes of restructuring firms in the Norwegian hotel industry in the light of constant negotiations between neoliberalisation and countermeasures in the social-democratic welfare state, and the effects of this restructuring on labour. Inspired by scholarship on neoliberal restructuring, the article examines how competitive strategies in the hotel industry are shaped by intensified competition, by the interface of industry regulations, labour market regulations, and social security, and by the labour movement. Social-democratic welfare states are not insulated from neoliberal currents in either accumulation or regulation, and the concept of socially managed flexibility proves helpful in examining regulatory resistance to neoliberalisation. As in other advanced economies, the Norwegian hotel industry faces increased competition through intensification of labour efforts and strategies to increase flexibility, especially numerical flexibility aimed at cutting costs. Norwegian labour market regulations to some extent curb numerical flexibility for cost-cutting purposes, and the centralised labour movement plays an important role in this regard. Nonetheless, the hotel industry has found room to manoeuvre. The article reveals the state's difficulties in managing flexibility in a way that permits numerical flexibility, yet prevents cost-cutting that leads to intensified labour efforts at the lower end of the service sector.     

The local impact of increased numbers of state employees on start-ups in Norway

ABSTRACT

The purpose of the article is to assess the impact of concentrations of state employees on local growth and development. Local multiplier effect theory suggests that the increased local demand for state employees, especially highly skilled employees, would stimulate the local supply of goods and services, and hence local development. However, other theories of regional development have shown that factors such as having a university or city size may also explain why some municipalities with a high percentage of state employees grow faster than others. Following a multilevel panel data analysis of Norwegian municipalities, the author found that the percentage of state employees did not have any effect on local development, measured in terms of the relative number of start-up firms or population growth. While there was a small positive effect of state employees in the bivariate model, state employees did not have a significant effect on local development when controlling for relevant factors such as municipality size or the presence of universities. The author concludes that the relocation of state employees may be a rather limited tool for stimulating local and regional growth and, if applied, policymakers should consider how the relocation could stimulate place-sensitive development in individual municipalities.