Reducing energy-related CO2 emissions using accelerated weathering of limestone

The use and impacts of accelerated weathering of limestone (AWL; reaction: CO₂+H₂O+CaCO₃→Ca²⁺+2(HCO₃⁻) is explored as a CO₂ capture and sequestration method. It is shown that significant limestone resources are relatively close to a majority of CO₂-emitting power plants along the coastal US, a favored siting location for AWL. Waste fines, representing more than 20% of current US crushed limestone production (>10⁹ tonnes/yr), could provide an inexpensive or free source of AWL carbonate. With limestone transportation then as the dominant cost variable, CO₂ mitigation costs of $3-$4/tonne appear to be possible in certain locations. Perhaps 10–20% of US point–source CO₂ emissions could be mitigated in this fashion. It is experimentally shown that CO₂ sequestration rates of 10⁻⁶ to 10⁻⁵ moles/sec per m² of limestone surface area are achievable, with reaction densities on the order of 10⁻² tonnes CO₂ m⁻³day⁻¹, highly dependent on limestone particle size, solution turbulence and flow, and CO₂ concentration. Modeling shows that AWL would allow carbon storage in the ocean with significantly reduced impacts to seawater pH relative to direct CO₂ disposal into the atmosphere or sea. The addition of AWL-derived alkalinity to the ocean may itself be beneficial for marine biota.     

Stochastic analysis of file-swarming systems

File swarming (or file sharing) is one of the most important applications in P2P networks. In this paper, we propose a stochastic framework to analyze a file-swarming system under realistic setting: constraints in upload/download capacity, collaboration among peers and incentive for chunk exchange. We first extend the results in the coupon system [L. Massoulie, M. Vojnovic, Coupon replication systems, in: Proc. ACM SIGMETRICS, Banff, Alberta, Canada, 2005] by providing a tighter performance bound. Then we generalize the coupon system by considering peers with limited upload and download capacity. We illustrate the last-piece problem and show the effectiveness of using forward error-correction (FEC) code and/or multiple requests to improve the performance. Lastly, we propose a framework to analyze an incentive-based file-swarming system. The stochastic framework we propose can serve as a basis for other researchers to analyze and design more advanced features of file-swarming systems.     

激光光束质量因子的研究进展

本文详细分析了各种光场下光束质量M2因子。在不同的场中,A.E.Siegman当初所定义的M2因子,已经有了很大的变化,因而M2因子的特性也与当初不同,不仅M2因子可以大于等于1,而且可以小于1,甚至小于0。其反映的物理意义,也从经典场中的衍射极限倍数,变化为非经典场中的准直性量度以及对空间相干性的某些反映。此外还列举并分析了几种特殊的光束质量因子,最后讨论了M2因子应用的问题并指出了其局限性。     

氯化钙改善羊毛织物抗皱性能的研究

用氯化钙、水、乙醇(1:8:2摩尔比)的二元体系溶液对精纺毛织物进行抗皱整理,在三种处理温度(50℃、60℃、70℃)和两档时间(20min、40min)的条件下,分别测定整理后毛织物的折皱恢复角和断裂强度。结果表明,毛织物的折皱性能都有不同程度的改善,而且温度越高越不利,时间越长越不好,温度影响尤为显著,但断裂强度都略有下降。在本次实验条件下,处理温度50℃,时间20min最为有利;同时,通过对毛纤维的进一步处理也验证了这一点。     

Determining actual LNAPL plume thickness: review and case study in a fractured aquifer

Determining the thickness of a LNAPL (light non-aqueous phase liquid) hydrocarbon plume in the fractured rock surrounding a borehole is a very important aspect in determining the quantity and degree of contamination of the groundwater and soil, as well as deciding on applicable remediation measures. This review aims to compare some of the field and empirical methods to eventually propose a method of confirming the plausibility of the determined thickness. General insight is supplied relating to the occurrence of groundwater in the Earth’s crust, the basic principles of multiphase flow and the properties of the three fluids of importance, being water, Jet A-1 fuel and air. From the methods applied, the field bail-down method of Hughes et al. and the mathematical approach according to CONCAWE supplied reasonable results, with the Zillox and Muntzer equation providing no rational outcome due to changing water levels from regular bailing of the LNAPL. Furthermore, practically none of these methods have been developed for deep, fractured aquifers. By plotting regular depths to water and fuel on the abscissa axis with free product thickness on the ordinate, the depth to water and depth to fuel linear plots will intersect where the free product thickness equals zero. This indicates the static water level (i.e., the ground water level prior to hydrocarbon contamination) and by subtracting this from the free product depth, a maximum product thickness is obtained.      

微波辐射下无溶剂合成苯并咪唑-2-酮

以多聚磷酸(PPA)为催化剂,邻苯二胺和脲为原料,在微波辐射下无溶剂合成了苯并咪唑-2-酮,反应时间由2～3 h缩短到6～10 min,产率为62．81％;正交实验所得影响因素顺序为:微波功率>照射时间>原料配比>催化剂用量。最优化合成工艺条件为:n(邻苯二胺):n(脲)为1:2;微波功率为126 W;反应时间为7 min;数字熔点仪、红外光谱(IR)与核磁共振谱(1H NMR)等测试结果表明产物为苯并咪唑-2-酮。     

Effect of Y2O3 Content on Microstructure of Gradient Bioceramic Composite Coating Produced by Wide-Band Laser Cladding

Hydroxyapatite (HA) ,a kind of bioactive materi-al , has wide application prospect in hard tissue re-placemen and repairment due to its si milar chemicalcomposition and crystallographic structure to that ofbone mineral[1 ,2]. Since HA has lowstrength (50 …     

Service life planning and performance requirements

Service life planning comprises a model for the determination of a reasonable expected service life for buildings and components, and it establishes a routine for the assessment of design alternatives. A design option is considered reasonable when it meets or exceeds performance requirements over time that have been drawn up specifically for the specific project. Due to this assessment reference, there is a very evident link to the concept of performance-based building. Any stakeholder involved in the value chain or in the design process of the building, as well as regulators and building users, can express performance requirements. Identified requirements, both in relevance and in quality, will vary with the stakeholder and his/her perspective of interest. As building sector manufacturers develop most products with reference to standards rather than with reference to specific requirements, there is no direct link from user requirements to the product design. Instead, the building designer has the responsibility to ensure performance requirements are met by the performance of products integrated into the design. As these design decisions also have to be made at the material and component level, a performance-based building would benefit from an established rationale that enables the communication of performance requirements across the relevant system levels in the relevant design processes. A path for the connection of the established concepts of service life planning and performance-based building is presented. The aim is to identify key elements that need to be developed for the successful linkage of performance-based building with service life planning.     

计算机支持的技术支援:概念与网络体系结构

首次提出了计算机支持的技术支援（CSTA）概念。计算机支持的技术支援是信息社会中技术支援的主要形式。分析了技术支援的过程、CSTA的技术特点和优点．总结了CSTA的基本研究内容和常用形式。针对技术支援的新需求、介绍了基于P2P的CSTA网络体系结构。