大堆积密度骨料配制的混凝土的性能(英文)

当今世界对可持续发展的关注促进了低水泥用量混凝土建筑工程的产生。增加混凝土中骨料体系的堆积密度是降低水泥用量的一个策略。增加骨料体系的堆积密度可以降低填充骨料颗粒间隙所需要的水泥浆体的量。研究了大堆积密度骨料配制的混凝土。这些混凝土比普通的结构混凝土低15%～25%的水泥用量,当骨料体系级配合理时混凝土工作性好。水泥浆体体积的降低在明显改进混凝土干缩与徐变性能的同时,也会对其工作性产生不利影响。骨料含量不会显著影响不同配比混凝土的抗压强度和劈裂强度。     

What do we do next;To survive,grow and be distinguished

In a new world era,where financial systems are being restructured,manufacturing insight reconsidered and ways of doing business is changing,the foundry industry has to adapt herself to the winds of change by placing all her inputs onto the table and reevaluate them to fit into this new era.The inherent strengths of the foundry industry alone would not be enough to fit in this change process,where careful and intelligent operation of the back office and the front office of the foundry should come into the picture.The recent global crisis and previous ones have had positive effects on the improvement of foundry competitiveness by opening opportunities to change and "clean the house".The survival strategies,as well as what actions to be taken for growth and maintaining a strong foot print in this complicated atmosphere,is discussed in several headlines.In the long run,survival of individual foundries depends on well managed orchestration by the "decision makers" of each individual component of the foundry.Sustainability of the whole is the sum of survival capabilities of its components and the management of their harmonization.     

A bi‐criterion optimization approach for the design and planning of hydrogen supply chains for vehicle use

In this article, we address the design of hydrogen supply chains for vehicle use with economic and environmental concerns. Given a set of available technologies to produce, store, and deliver hydrogen, the problem consists of determining the optimal design of the production‐distribution network capable of satisfying a predefined hydrogen demand. The design task is formulated as a bi‐criterion mixed‐integer linear programming (MILP) problem, which simultaneously accounts for the minimization of cost and environmental impact. The environmental impact is measured through the contribution to climate change made by the hydrogen network operation. The emissions considered in the analysis are those associated with the entire life cycle of the process, and are quantified according to the principles of Life Cycle Assessment (LCA). To expedite the search of the Pareto solutions of the problem, we introduce a bi‐level algorithm that exploits its specific structure. A case study that addresses the optimal design of the hydrogen infrastructure needed to fulfill the expected hydrogen demand in Great Britain is introduced to illustrate the capabilities of the proposed approach. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Blends of Bio-Based Poly(Limonene Carbonate) with Commodity Polymers

In this study, blends of the bio-based poly(limonene carbonate) (PLimC) with different commodity polymers are investigated in order to explore the potential of PLimC toward generating more sustainable polymer materials by reducing the amount of petro- or food-based polymers. PLimC is employed as minority component in the blends. Next to the morphology and thermal properties of the blends the impact of PLimC on the mechanical properties of the matrix polymers is studied. The interplay of incompatibility and zero-shear melt viscosity contrast determines the blend morphology, leading for all blends to a dispersed droplet morphology for PLimC. Blends with polymers of similar structure to PLimC (i.e., aliphatic/aromatic polyester) show the best performance with respect to mechanical properties, whereas blends with polystyrene or poly(methyl methacrylate) are too brittle and polyamide 12 blends show very low elongations at break. In blends with Ecoflex (poly(butylene adipate-co-terephthalate)) and Arnitel EM400 (copoly(ether ester)) with poly(butylene terephthalate) hard and polytetrahydrofuran soft segments) a threefold increase in E-modulus can be achieved, while keeping the elongation at break at reasonable high values of ≈200%, making these blends highly interesting for applications.     

Designing biomass supply chains within planetary boundaries

The design of sustainable supply chains, which recently emerged as an active area of research in process systems engineering, is vital to ensure sustainable development. Despite past and ongoing efforts, the available methods often overlook impacts beyond climate change or incorporate them via standard life cycle assessment metrics that are hard to interpret from an absolute sustainability viewpoint. We here address the design of biomass supply chains considering critical ecological limits of the Earth—planetary boundaries—which should never be surpassed by anthropogenic activities. Our method relies on a mixed-integer linear program that incorporates a planetary boundaries-based damage model to quantify absolute sustainability precisely. We apply this approach to the sugarcane-to-ethanol industry in Argentina, identifying the optimal combination of technologies and network layout that minimize the impact on these ecological boundaries. Our framework can find applications in a wide range of supply chain problems related to chemicals and fuels production, energy systems, and agriculture planning.     

Up-pulling force analysis for ESC hollow cylindrical casting

Electroslag casting(ESC)is an important method to produce high quality castings.In this study,the ESC up-pulling inner mold method(EUPIM)was used to produce hollow cylindrical castings with the multiple consumable electrodes.The radial deformation,the axial and radial internal stress of the inner mold,and the axial internal stress of the slag shell were analyzed using the finite element method(FEM)with the aid of ANSYS software.The ProCAST software was used to calculate the specific heat,heat conductivity and density curve of Cu.Simulation results show that the radial deformation,the axial and radial internal stress of the inner mold,and the axial internal stress of the slag shell near the slag-metal interface of hollow cylndrical casting gradually increase from 0 s to 360 s after the ESC starting(slagging)process but before applying the up-pulling force.The suitable initial up-pulling moment of the inner mold is at around 180-198 s after the starting process.     

Fire safe,sustainable loose furnishing

The aim of this exploratory study has been to investigate the fire properties and environmental aspects of different upholstery material combinations, mainly for domestic applications. An analysis of the sustainability and circularity of selected textiles, along with lifecycle assessment, is used to qualitatively evaluate materials from an environmental perspective. The cone calorimeter was the primary tool used to screen 20 different material combinations from a fire performance perspective. It was found that textile covers of conventional fibres such as wool, cotton and polyester, can be improved by blending them with fire resistant speciality fibres. A new three‐dimensional web structure has been examined as an alternative padding material, showing preliminary promising fire properties with regard to ignition time, heat release rates and smoke production.     

分布式光伏储能系统的设计方法及运行特性

针对典型的户用光伏储能系统,建立了各个部件的数学模型,研究了系统的运行特性,考虑最大光伏自给率基础策略与加入谷时电网和蓄电池交互的改进策略,探究了经济性指标净现值、技术性指标光伏自给率及用户自用率与蓄电池容量的关系,绘制了经济性指标与技术性指标关系曲线,提出一种分布式光伏储能系统的容量设计方法,基于MATLAB进行全年能量流动与全生命周期经济结果分析,并针对上海市地区典型日晴天系统运行特性进行了模拟研究。结果表明,技术性指标与经济性指标随蓄电池容量变化呈现相反的变化趋势,在基础与改进策略下,蓄电池容量分别超过10.5和6.5 kW·h后,降低净现值以提升光伏自给率与用户自用率的效果逐渐减弱,因此基于蓄电容量为5 kW·h（基础策略）和6.5 kW·h（改进策略）的拐点前的曲线,依据实际需要确定系统蓄电池的容量。模拟结果表明,对于案例中的3.06 kW（峰值）的光伏系统和4.8 kW·h的蓄电池,系统较单独的光伏系统有明显的削峰填谷效果。考虑谷时蓄电池与电网交互的改进策略比基础策略有更好的技术性与经济性表现,但是系统对市电电网的传输负担会有所加重。     

Sustaining a Community Computing Infrastructure for Online Teacher Professional Development: A Case Study of Designing Tapped In

Community computing has recently grown to become a major research area in human–computer interaction. One of the objectives of community computing is to support computer supported cooperative work among distributed collaborators working toward shared professional goals in online communities of practice. A core issue in designing and developing community computing infrastructures – the underlying socio-technical layer that supports communitarian activities – is sustainability. Many community computing initiatives fail because the underlying infrastructure does not meet end user requirements; the community is unable to maintain a critical mass of users consistently over time; it generates insufficient social capital to support significant contributions by members of the community; or, as typically happens with funded initiatives, financial and human capital resource become unavailable to further maintain the infrastructure. Based on more than nine years of design experience with Tapped In – an online community of practice for education professionals – we present a case study that discusses four design interventions that have sustained the Tapped In infrastructure and its community to date. These interventions represent broader design strategies for developing online environments for professional communities of practice.     

Water services industry reforms in Malaysia

Concerted efforts to reform and transform the water industry in Malaysia began in 2006. It was a visionary effort by the federal government to ensure an adequate supply of clean water to the public and industry. A policy and institutional framework was created to re-invent and transform the water services industry into an efficient and sustainable sector that will play a pivotal role as one of the major components of economic growth. Though minor adjustments may be needed during its implementation, the overall policy direction is pragmatic and viable and has started to produce tangible outcomes.