Characteristics and potential impacts of under-ice river plumes in the seasonally ice-covered Bothnian Bay (Baltic Sea)

The northernmost basin of the Baltic Sea, the Bothnian Bay, is ice-covered for about half the year. During this time, distinct under-ice river plumes develop, even seaward of the smallest rivers, that are substantially thicker and larger in extent than during the summer months. Wind mixing is negligible, and during late spring in April or May, the highest annual discharge occur while the sea is ice covered, thus providing conditions for the formation of extensive under-ice plumes. These plumes are characterised by high levels of trace elements (e.g., Al, Fe and Zn), organic matter (TOC and dissolved organic carbon [DOC]), nutrients and also optically active substances (colored dissolved organic matter, CDOM). The under-ice plumes provide an important pathway for undiluted transport of land-derived substances to the pelagic waters of the basin, affecting the salinity, chemistry and optical properties of coastal waters. Freshwater ice growth on the underside of an existing sea ice sheet also restricts the buildup of sea ice and under-ice algal communities, potentially in large areas along the coasts. Plume water influences the optical characteristics of coastal waters for a period of time after ice break-up, potentially affecting primary production in these areas. Furthermore, the formation of under-ice plumes potentially has a positive feedback on the ice season length due to freshening of the coastal waters (earlier freeze-up) and restricted oceanic heat flux (slower melting).     

基于熵权的TOPSIS钢桥面防水黏结材料组合体系优选分析

为合理选择钢桥-沥青混凝土铺装结构防水黏结材料，首先，制作含不同防水黏结材料组合体系的钢板-沥青混凝土复合试件，并在低温（0℃）、常温（25℃）和高温（70℃）环境下分别测试复合试件的拉拔强度（Direct Tensile Strength，DTS）、直剪强度（Direct Shear Strength，DSS）和45°斜剪强度（Skew Shear Strength，SSS）。同时，利用UTM万能试验机测试常温（25℃）状态下复合试件的疲劳寿命。构建包括拉拔强度（DTS）、直剪强度（DSS）、45°斜剪强度（SSS）、疲劳寿命（Fatigue Life，FL）和材料成本（Materials Cost，MC）在内的钢桥面防水黏结材料评价指标体系。利用"信息熵"理论对评价指标的权重进行求解，结合逼近理想解排序（TOPSIS）方法，比较不同防水黏结材料组合体系的综合性能，建立基于熵权-TOPSIS钢桥面防水黏结材料组合体系优选模型，并获取优选结论。最后，通过图像二值化验证优选结论。结果表明：图像二值化分析结果与基于熵权-TOPSIS防水黏结材料组合体系优选模型得出的优选结论一致，验证了熵权-TOPSIS方法在钢桥面防水黏结材料优选设计中的有效性。该模型排除了人为主观因素影响，可为钢桥面防水黏结材料选择提供一种客观有效的方法。     

Ship ballast water as a main vector of marine introductions in the Mediterranean Sea

Marine invasive species are currently recognized as one of the most significant threats to global biodiversity. Marine bioinvasions are more likely in the Mediterranean Sea because of its wide temperature range, degraded habitats, historical and high volume of shipping traffic, and high occurrence of aquaculture. One of the main vectors of marine introductions globally and Mediterranean-wide is commercial shipping. Of the 3,000–4,000 species transferred around the world via commercial vessels, approximately 30% of these species may have been redistributed in the Mediterranean. Ships and marine invasive species arriving in the Mediterranean are mainly from temperate to cold-water regions. Standardized research and management approaches between countries are required to address the threat of ballast water borne marine invasives on a global scale. Regionally, a Mediterranean program involving the different states is currently needed to develop a common line of research and management operations.     

Resolving the impact of short-term variations in physical processes impacting on the spawning environment of eastern Baltic cod: application of a 3-D hydrodynamic model

Variations in oxygen conditions below the permanent halocline influence the ecosystem of the Baltic Sea through a number of mechanisms. In this study, we examine the effects of physical forcing on variations in the volume of deep oxygenated water suitable for reproductive success of central Baltic cod. Recent research has identified the importance of inflows of saline and oxygenated North Sea water into the Baltic Sea for the recruitment of Baltic cod. However, other processes have been suggested to modify this reproduction volume including variations in timing and volume of terrestrial runoff, variability of the solubility of oxygen due to variations in sea surface temperature as well as the influence of variations in wind stress. In order to examine the latter three mechanisms, we have performed simulations utilizing the Kiel Baltic Sea model for a period of a weak to moderate inflow of North Sea water into the Baltic, modifying wind stress, freshwater runoff and thermal inputs. The model is started from three-dimensional fields of temperature, salinity and oxygen obtained from a previous model run and forced by realistic atmospheric conditions. Results of this realistic reference run were compared to runs with modified meteorological forcing conditions and river runoff.From these simulations, it is apparent that processes other than major Baltic inflows have the potential to alter the reproduction volume of Baltic cod. Low near-surface air temperatures in the North Sea, the Skagerrak/Kattegat area and in the western Baltic influence the water mass properties (high oxygen solubility). Eastward oriented transports of these well-oxygenated highly saline water masses may have a significant positive impact on the Baltic cod reproduction volume in the Bornholm Basin.Finally, we analysed how large scale and local atmospheric forcing conditions are related to the identified major processes affecting the reproduction volume.     

Direct Computation of the Performance Index for an Optimally Controlled Active Suspension with Preview Applied to a Half-Car Model

A quadratic integral performance index is defined for a linear active preview-type suspension and a series of matrix expressions derived for its evaluation by means of MATLAB or some similar computer program in the case of a unit step input to the system. The computation, which is both fast and accurate compared to simulation, requires the solution of Lyapunov- and Riccati-type equations. Some examples of numerical computation are given and these show excellent agreement with published results. The conclusion features a useful computer program.     

Macroscopic location models revisited

Recent developments in residential location choice models have considered the individual as the basic unit of analysis and have attempted to model the actual choice process used by individuals in selecting residential location sites. This paper demonstrates that the choice model derived from these studies is a more general form of many macroscopic models of location used in the past. The prime difference between the two classes of model is seen to be the much wider range of factors and geographic settings which can be accounted for in disaggregate behavioural models of residential location choice.     

) and annual payments (a) is a follows:

Modern management techniques are slowly but surely being introduced aslo in shipping management. Large sections of the industry practises strategic management at various levels in the firm. This paper outlines a method for deciding chartering strategies in the international bulk shipping industry. A well known risk/return model is tailored to transportation contracts in the shipping industry. The model delineates a set of optimally defined transportation contracts that may serve as a basis for the shipowner's strategic decisions. The strategies and elements of strategies suggested by the model have historically been practised by a number of successful shipowners. An important conclusion of the paper is that no second best problems exists and hence movement towarts the optimal solution is advocated even if such a solution cannot or will not be reached. Additionally, the paper provides an organized way of crafting, analysing and applying chartering strategies where the outcomes can be clearly defined and analysed based on well known statistical concepts and theories.     

Dense network traffic models,travel time reliability and traffic management. Ii: Application to network reliability

This paper is the second of a pair of papers discussing two main themes concerning dense network modelling. These themes are: (1) the changing nature of traffic management technology and the underlying objectives behind traffic management practice, and (2) the use of measures of network reliability in models, especially as an element of the evaluation of alternative network configurations. This paper develops and applies the second theme, the use of network reliability concepts in the evaluation of traffic networks, through consideration of variations in travel times, distinction between local street and arterial road networks, and the definition and application of a set of reliability indices that may be used to study different trip movements in a network. It indicates how these indices may be used in appraising different traffic management plans for a dense network of local streets and arterial roads, using a case study application.     

Public transport policy in Canada and the United States: Developing political commitment from the federal government

The United States federal government has been involved in public transport funding for over 40 years, whereas in Canada the federal government has little history of urban public transport policy. In that context, over the past 10 years, Canada has made significant progress in developing new federal commitments for public transport. Critical as these developments have been, however, they do not represent a true National Transit Strategy, which needs to be permanent, predictable and comprehensive. This claim is supported by economic analysis which suggests that Canadian government investment in transit is significantly below the optimal level.     

基础设计中的可靠度评估

阐述基于可靠度理论的基础设计的评估。首先总结具有结构抗力和荷载效应2个基础变量的结构可靠度基本理论。结构抗力的不确定性可以由统计学上的平均值和变异系数（cov或）Ω来描述。变异系数指变量的标准差和平均值的比值。敏感度分析的结果显示结构抗力的变异系数（ΩR）在其应用范围之内时,在分析结构可靠度方面扮演着相当重要的角色。基于这些阐述,在预先指定的风险水平（pf）上ΩR一定有其上限。当结构抗力呈正态分布的时候,这个极限ΩR独立于荷载效应随机性,和安全指数β成反比。安全指数可以定义为在标准正态分布区间极限状态到原点之间的最小距离。在这个极限ΩR之下,结构可以在预定风险水平之下安全工作。中心安全系数（FS）可以由结构抗力和荷载效应的变异系数根据平方关系求得。然而,一些情况下结构抗力为非正态分布的情况并不少见。因此,等效正态分布的概念可以用来得到非正态分布结构抗力的ΩR极限。地质方面的随机变量可能是正态分布,也可能是非正态分布,结构抗力中基本变量之间的关系可能是线性也可能是非线性,或者非常复杂以致于结构抗力只能通过有限元分析才能得到。在此情况下,随机数可以通过蒙特卡洛模拟技术获得。拟合的结构抗力的分布可以在随机试验的基础上通过配合度检验确定。现实中,土壤的力学特性不是各向同性的,同样也不能认为是单一材料的,它们的不确定性是不可以被忽略的。简便的设计方式认为不确定参数是常数,并且通过使用定值的安全系数来确定结构截面,设计原则没有将土壤参数对安全系数的影响考虑进去。参考计算出来的失效概率表明,确定值的安全系数法无法保证足够的安全。因此,在某种情况下,安全系数大于等于3,对于结构容许承受能力,并不能认为太保守。