沥青混合料级配曲线研究进展

级配曲线是由富勒模型中最大粒径和形状系数两个参数来确定的,富勒模型能够很好地拟合使用性能良好的级配.级配曲线图是由形状系数和最大粒径组成的直角坐标系,它可以表示出级配范围、砂石比和相关的性能参数.该文分析了Superpave沥青混合料力学和水稳性能的试验结果,提出了根据级配曲线推荐的集料设计出满足路面各项性能的自由设计理念.     

不同加载幅值下考虑层间界面条件和侧向剪力作用的柔性铺面响应

该文进行了一个三维有限元参数量化的粘弹性路面响应研究,由于不同的轮胎配置:双轮和宽基轮胎在3种温度(5、25和40℃)和两种速度(8、72 km/h);还有影响路面响应的3种因素:移动车轮荷载幅值(连续,梯形),层间界面条件(简单的摩擦和粘弹性模型)和横向力共同对路面响应的影响进行了研究.研究发现连续加载幅值,不但可以模拟路面对运动轮荷载的响应,并且是一种比目前使用的梯形荷载幅值更准确的研究模型.粘弹性模型极大地提高了双轮胎对预测路面的响应,而简单的摩擦模型更接近宽基轮胎的实地测量.侧向剪力是积极改善预测轮底的表面磨损和底部热拌沥青(沥青)基层的较小程度上的应变.研究表明:使用连续加载幅值和非均匀压力分布模拟移动轮,侧向剪切力和适当的界面摩擦可显著改善有限元模型对车辆加载路面响应的预测能力.     

Overview of past, present and future marine power plants

In efforts to overcome an foreseeable energy crisis predicated on limited oil and gas supplies, reserves; economic variations facing the world, and of course the environmental side effects of fossil fuels, an urgent need for energy sources that provide sustainable, safe and economic supplies for the world is imperative. The current fossil fuel energy system must be improved to ensure a better and cleaner transportation future for the world. Despite the fact that the marine transportation sector consumes only 5% of global petroleum production; it is responsible for 15% of the world NO _x and SO _x emissions. These figures must be the engine that powers the scientific research worldwide to develop new solutions for a very old energy problem. In this paper, the most effective types of marine power plants were discussed. The history of the development of each type was presented first and the technical aspects were discussed second. Also, the fuel cells as a new type of power plants used in marine sector were briefed to give a complete overview of the past, present and future of the marine power plants development. Based on the increased worldwide concerns regarding harmful emissions, many researchers have introduced solutions to this problem, including the adoption of new cleaner fuels. This paper was guided using the same trend and by implementing the hydrogen as fuel for marine internal combustion engine, gas turbines, and fuel cells.     

矩形槽道采用不同冷却介质的传热与阻力特性分析(英文)

Several industrial applications such as electronic devices,heat exchangers,gas turbine blades,etc.need cooling processes.The internal cooling technique is proper for some applications.In the present work,computational simulations were made using ANSYS CFX to predict the improvements of internal heat transfer in the rectangular ribbed channel using different coolants.Several coolants such as air,steam,air/mist and steam/mist were investigated.The shear stress transport model(SST)is selected by comparing the standard k-ωand Omega Reynolds Stress(ωRS)turbulence models with experimental results.The results indicate that the heat transfer coefficients are enhanced in the ribbed channel while injecting small amounts of mist.The heat transfer coefficients of air/mist,steam and steam/mist increase by 12.5%,49.5%and 107%over that of air,respectively.Furthermore,in comparison to air,the air/mist heat transfer coefficient enhances by about 1.05 to 1.14 times when the mist mass fraction increases from 2%to 8%,respectively.The steam/mist heat transfer coefficient increases by about 1.12 to 1.27 times higher than that of steam over the considered range of mist mass fraction.     

Dynamic interaction of parallel moving ships in close proximity

Nowadays,there are many studies conducted in the field of marine hydrodynamics which focus on two vessels traveling and floating in sufficiently close proximity to experience significant interactions.The hydrodynamic behavior of parallel moving ships in waves is an interesting and important topic of late.A numerical investigation has been carried out for the prediction of wave exciting forces and motion responses of parallel moving ships in regular waves.The numerical solution was based on 3D distribution technique and using the linear wave theory to determine the exciting forces and ship＇s motion.The speed effects have been considered in the Green function for more realistic results.The numerical computations of wave exciting forces and motion responses were carried out for a Mariner and Series 60 for the purpose of discovering different Froude numbers and different separation distances in head sea conditions.Based on the numerical computations,it was revealed that the sway,roll and yaw have a significant effect due to hydrodynamic interaction.     

Maritime logistics as an emerging discipline

The evolution of maritime logistics as an emerging discipline has resulted, to a large extent, from the increasing and varied demands of shippers and customers and the rapidly changing role of ports in the context of supply and logistics chains. Scholars are becoming increasingly aware of the need to integrate logistics and supply chain management concepts in the maritime transportation chain and operations. This article aims to provide a review and foundation for understanding the domain of maritime logistics and to assess its potential as an emerging discipline. To do so, a framework for understanding the various aspects of maritime logistics strategy and implementation is developed. A synthesis of the existing knowledge on maritime logistics is done by integrating diverse explorations forming the basis of this framework. We draw upon the literature on maritime transport and ports and primarily theliterature that analyses concepts by adopting an economic or management perspective.     

Use of GIS-Based Models for Integrating and Developing Marine Fish Cages within the Tourism Industry in Tenerife (Canary Islands)

Site selection is a key factor in any aquaculture operation, affecting both success and sustainability. Moreover, it can solve conflicts between different coastal activities, making a rational use of the coastal space. Geographical information systems (GIS) have become of increased significance for environmental planning and assessment mainly because of the need to compare a great number of spatially related data, and because it can be used to couple these spatial data with their attributes and overlay them. This study used GIS and related technology to build a spatial database using those criteria which were considered to have any influence in integrating marine fish-cage culture within the tourism industry in Tenerife. Criteria were grouped in three submodels (distance to beaches, nautical sports, and viewshed), which were combined to generate a final output showing the most suitable areas for cage culture development in coexistence with tourism. Most areas of the coastline of Tenerife were identified as being suitable (56%) or very suitable (46%), suggesting that marine cage aquaculture could be developed on the island in coexistence with the well-established tourism industry.     

Synergies between Adjacent Beach-Nourishing Communities in a Morpho-Economic Coupled Coastline Model

Beach “nourishment” consists of placing sand on an eroding beach. The widened beach provides increased storm protection to adjacent structures and improved recreational benefits, but is most often transient, requiring on-going, repeated nourishment episodes. Numerical models of beach nourishment typically address such questions as how long a widened beach will last; economic models compare the benefits and costs of preserving a stretch of beach without regard to its geomorphic evolution. Neither have addressed the physical nor economic interactions between adjacent nourishing communities. Here, we couple a numerical model of coastline evolution and a cost-benefit model of beach nourishment, allowing adjacent communities to make dynamic nourishment decisions. Beach nourishment benefits adjacent communities both “updrift” and “downdrift.” The total amount of money spent on nourishment activities can decrease by as much as 25% when adjacent communities both conduct on-going nourishment projects, as opposed to the case where each community nourishes in isolation.     

Collaborative Management of Natural Resources in San Diego Bay

This article presents the results of a three-year effort at applying information technology to the problem of collaborative natural resource management in San Diego Bay. As such, it represents an approach to integrated coastal zone management (ICZM). This effort resulted from a collaboration between the San Diego Supercomputer Center at the University of California, San Diego and the San Diego Bay Interagency Water Quality Panel for the purpose of (1) developing an environmental data repository to facilitate the acquisition and sharing of data and (2) the development of a visual model of the bay in support of the development of a comprehensive, coordinated management plan for San Diego Bay. It was determined from this study that information technology is an important and key component to ICZM but that sociopolitical factors may override the benefits of decision-support systems and should be considered at the outset of any project of this kind.     

Mumbai lunch box delivery system: A transferable benchmark in urban logistics?

This paper presents findings of a freight transport study carried out for Mumbai city (India). Based on the case study of lunch box delivery system organized by the Mumbai dabbawalas, demonstrated that an informal sector was capable of developing an urban logistics system that was precise, reliable and affordable to the middle class society in Mumbai. These facts suggest an approach based on adapting logistics solutions harmoniously to the urban landscape, public policy, infrastructure and skill sets of the company’s employees in order to be attractive to the end customer, offering a good match between supply and demand i.e., consumer and producer satisfaction. At the same time logistics solutions should evolve continuously in order to be attractive to the core customer base and should be customer driven. These basic management principles can be applied in the management of other urban logistics companies in the world over.