单个大气超细颗粒物源特征的同步辐射光源X射线探针初步研究

研究了单个大气超细颗粒分析靶样的制备方法, 在美国阿贡国家实验室APS同步光源的13-ID-C试验站, 用束斑为2 μm的X射线探针分析了不同污染源超细颗粒物, 得到了单个超细颗粒物的特征X射线谱. 实验结果表明, 来自不同污染源的超细单颗粒具有不同的特征X射线能谱. 这为单颗粒分析方法识别大气超细颗粒物来源提供了依据. 超细含铅颗粒物的分析暗示, 大气颗粒物中的铅污染是多源的, 除燃烧加铅汽油外, 燃煤和钢铁工业也是大气铅污染的排放源. 来自燃煤排放的超细颗粒分析提示, 燃煤超细颗粒物对人体健康具有更大的潜在危害.     

An analysis of patient register data in the Longitudinal Study - what does it tell us about the quality of the data?

This article uses data for members of the ONS Longitudinal Study (LS) from both Census 2001 enumeration and patient registrations "frozen" on census day 2001 from the National Health Service Central Register (NHSCR) to examine potential sources of difference in area of usual residence.Overall 95.7 per cent of ONS LS members enumerated at census resided in the same area as recorded on the NHSCR data. Where areas differed, or the ONS LS member was not on the NHSCR on census day, subsequent NHSCR records were examined. Records flagged on the NHSCR as ONS LS members in England and Wales on census day but with no census record were also investigated.     

混合式可重构数字多核并行处理器平台

一种高性能、RISC-VLIW融合的多核、可重构数字媒体处理器已经从专利发明顺利形成了一个先进的数据处理器设计平台(Digital Multi-processor Platform)。研发的结果体现若干先进处理器技术的融合。(1)应用:低功耗并行运算处理覆盖数字信号处理(DSP)、数字媒体处理(DMP)和超级并行处理器(SPP)的应用扩展领域;(2)体系结构:精简指令(RISC)和超常指令字(VLIW)处理器融合于同一个可配置的平台;(3)运算能力:处理器群调用异构的通用处理器核,使用两类处理器核实例:通用处理器核(包括ALU等的通用运算)和专用处理器核(包括DDCU的用户自定义运算核);(4)可配置和可重构:硅编译器、SoC集成工具、用户自定义运算单元、多核间的和槽内的流水线、包括运算单元的现场编程;(5)设计自动化平台:专用工具用于设计、分析与验证;与商业电子自动化设计(EDA)流程接口;(6)产品模式:硅知识产权(Silicon IP)、通用处理器芯片系列(IC Series)、定制单片系统(SoC)。命名为Fusion的融合式数字多核处理器平台把数个先进处理器技术集成到一个统一的体系结构和设计环境之中...     

Jovian-like aurorae on Saturn

Planetary aurorae are formed by energetic charged particles streaming along the planet's magnetic field lines into the upper atmosphere from the surrounding space environment. Earth's main auroral oval is formed through interactions with the solar wind, whereas that at Jupiter is formed through interactions with plasma from the moon Io inside its magnetic field (although other processes form aurorae at both planets). At Saturn, only the main auroral oval has previously been observed and there remains much debate over its origin. Here we report the discovery of a secondary oval at Saturn that is approximately 25 per cent as bright as the main oval, and we show this to be caused by interaction with the middle magnetosphere around the planet. This is a weak equivalent of Jupiter's main oval, its relative dimness being due to the lack of as large a source of ions as Jupiter's volcanic moon Io. This result suggests that differences seen in the auroral emissions from Saturn and Jupiter are due to scaling differences in the conditions at each of these two planets, whereas the underlying formation processes are the same.     

锚杆锚固结构中导波传播的数值模拟

用理论分析、数值模拟和实验测试的方法研究了自由锚杆和锚固锚杆中的波传播特性.研究结果显示在测试激发波的频率范围内(10～100 kHz),锚杆中传播的波是一个和边界条件相关的导波,不同频率的波在锚杆中传播的速度不同.同时分析了采用有限元模拟锚杆中传播的导波时网格密度对模拟结果精度的影响.模拟体波时一般要求在波传播方向上的N值(一个波长内的单元数)大于20,但模拟杆状结构中的导波传播时N值要大于30,并且径向(垂直波传播方向)的N要求比轴向(波传播方向)N值更大.而且模拟不同频散特性的波需要用不同的N值,也就是说对于同一频率的波,频散越大,所需要的N值亦越大.实验室对自由锚杆和锚固锚杆的测试结果与数值模拟的结果取得了很好的一致性.     

亭南煤矿综放开采矿山压力数值模拟

为了分析综放工作面顶板断裂、垮落形式,以及工作面支承压力分布及影响区域范围,对亭南煤矿101综放面,分别应用UDEC与FLAC3D软件进行了数值模拟对比分析.结果表明随工作面的推进,直接项出现离层、破断,并在采空区前后煤壁上方基岩出现拉裂缝.当工作面推进到60m左右,老顶出现初次破断,形成初次来压,之后工作面每推进30 m,老项出现周期来压.模拟结果再现了顶板冒落、离层、破断,综放面初次、周期来压及围岩应力集中、重新分布等现象,这些结果与现场矿山压力观测结果基本吻合,为矿压观测提供了直观、准确的数值分析方法.     

Persistence of soil organic matter as an ecosystem property

Globally, soil organic matter (SOM) contains more than three times as much carbon as either the atmosphere or terrestrial vegetation. Yet it remains largely unknown why some SOM persists for millennia whereas other SOM decomposes readily--and this limits our ability to predict how soils will respond to climate change. Recent analytical and experimental advances have demonstrated that molecular structure alone does not control SOM stability: in fact, environmental and biological controls predominate. Here we propose ways to include this understanding in a new generation of experiments and soil carbon models, thereby improving predictions of the SOM response to global warming.