沙尘分析及等离子空气清洁系统沙尘去除效果的评价

本研究对在中国和韩国采集的沙尘的粒径分布及质量浓度进行了测定,使用黄沙标准物质对基于静电沉降原理的等离子空气清洁系统的去除沙尘效率进行了评价。本研究所使用的黄沙采集于北京和汉城,其粒径中值在7.0~80μm之间,浓度范围为300~1462μg·m^-3。在单通道测试中,沙尘去除效果随粒径增大和流速降低而增加。系统速度为1.0m·s^-1时,去除率大于80%。在27m2的房间中,进行多通道测试时,浓度为300μg·m^-3的大气颗粒物仅用10min即可降至150μg·m^-3。因此,等离子空气清洁系统能够有效地去除沙尘及保持室内空气质量。     

Oxygen isotope anomalies of the Sun and the original environment of the solar system

Abstract— We present results from a model of oxygen isotopic anomaly production through selective photodissociation of CO within the collapsing proto‐solar cloud. Our model produces a proto‐Sun with a wide range of Δ¹⁷O values depending on the intensity of the ultraviolet radiation field. Dramatically different results from two recent solar wind oxygen isotope measurements indicate that a variety of compositions remain possible for the solar oxygen isotope composition. However, constrained by other measurements from comets and meteorites, our models imply the birth of the Sun in a stellar cluster with an enhanced radiation field and are therefore consistent with a supernova source for ⁶⁰Fe in meteorites.     

海洋环境立体监测系统的设计方法

“九五”和“十五”期间,在国家海洋863计划的支持下,我国分别在上海和台湾海峡及毗邻海域建立了两个区域性海洋环境立体监测示范系统。在这两个示范系统的技术研究成果的基础上,通过分析国际海洋立体监测系统的设计模型,提出了区域性海洋环境立体监测系统的设计原则和设计方法,包括:系统结构、数据与信息服务通信网络、数据处理中心、数据流程以及系统功能等方面的设计方法。     

GPS PERFORMANCE IN YUKON'S ARCTIC COAST

This study analyses GPS performance in Yukon's Arctic coast to inform future research that uses this technology in the region. To test this, Telonics GPS collars were placed on stakes during the summers of 2009 and 2010 throughout the region for varying lengths of time. The fix records produced by these collars were then collected and cleaned, leaving 30 samples. Using these records combined with a digital elevation model, eight variables were extracted and analysed in an attempt to find relationships, such that a fix rate could be predicted throughout the landscape. The results indicated that very few strong relationships existed. Densiometer values proved to be the only relationship between an environmental variable and fix rate. Available sky and aspect data produced results that were contrary to those expected. Overall, Telonics Generation 3 collars had extremely high fix rates, high accuracy, and low positional dilution of precision. Moreover, there was little variation in these results. This means that future GPS studies in the region would likely require minimal correction for fix rate bias. However, if corrections were to be made, more data would have to be gathered to ensure the results were statistically sound. The analysis suffered from the limitations of small sample size and low sample variance, among several others. Therefore, future studies should increase the number and diversity of sites tested.     

龙门山泥盆纪腕足化石锶同位素组成特征及其古环境意义

生物成因的海相碳酸盐岩中Sr同位素组成与演化是目前研究古海平面变化、造山运动以及古气候变化的主要工具,在海相地层定年及全球等时对比研究中发挥着重要作用。对四川龙门山泥盆纪剖面腕足化石Sr同位素组成进行了研究。保存鉴定结果显示：腕足化石壳体结构保存完整;阴极射线照射下壳体不发光或部分壳体呈微弱橙黄色;大多数壳体微量元素Mn〈250μg／g、Sr〉400μg／g。表明腕足化石保存完好,后期成岩作用影响微弱。锶同位素结果显示：龙门山泥盆纪sr同位素演化同全球泥盆纪Sr同位素演化基本一致,表明龙门山泥盆纪Sr同位素演化受全球性变化影响。早泥盆世较高Sr同位素比值（甘溪组0．708437）可能是受加里东造山运动的影响,大量古陆的出露,风化作用的加强所致。其后的缓慢下降可能受海平面上升古陆面积缩小的影响。中泥盆世Sr同位素组成低值平台显示着幔源Sr和陆源Sr（风化作用较弱）输入量之间的平衡。随后的Sr同位素组成的上升可能是受中泥盆世开始温度上升的影响,致使风化作用的加强所致。     

Composition and genesis of glacial hummocks, western Wisconsin, USA

Glacial hummocks associated with the Superior Lobe in western Wisconsin are stagnant-ice features composed of melt-out till, meltwater-stream sediment, and flow till. The greater proportion of melt-out till in these hummocks than in hummocks described elsewhere suggests that a model of extensive, supraglacial reworking of supraglacially released debris does not apply to the western Wisconsin hummocks. Interpretation of melt-out till in hummock exposures is based on its strong fabric oriented parallel to regional ice-flow direction. Other features of this melt-out till include poorly developed stratification (color banding and discontinuous thin sandy lenses), and minor faulting, both of which support a melt-out origin. We suggest that as stagnant, debris-rich ice began to melt, supraglacially released debris was deposited as flow till and meltwater-stream sediment (with some debris-flow sediment and lake sediment), but as the thickness of supraglacial debris increased, debris melting out at depth was stabilized, allowing features characteristic of melt-out till to be retained. Because the supraglacial debris was sandy and the stagnant ice was likely at the pressure-melting point, the supraglacial debris was well drained and did not readily fail and flow. Debris volume in the glacier generally was greater at the glacier margin, but lateral and longitudinal variations within this zone were caused by thrusting, freezing-on, or ice-margin fluctuations, which in turn resulted in variations in hummock relief. Ice-walled-lake plains are commonly associated with the hummocks and developed where debris volume was small.     

INTERPRETATION OF VLF-EM IN-PHASE DATA USING CURRENT DENSITY PSEUDOSECTIONS1

The interpretation of VLF-EM surveys in terms of buried conductors can be assisted by the application of a linear filter to the observed in-phase component of the vertical magnetic field. One such scheme is examined critically by using the calculated response from a variety of synthetic models to compute theoretical current density pseudosections. The results confirm that this filter technique provides a useful complementary tool for studying the third (i.e. depth) dimension. For single, steeply dipping plates (> 45°) diagnostic information may be derived concerning the depth, size, lateral location, and direction of dip, since the current density maxima seems always to occur within the conductor or at least within one data interval. However, there are some limitations which do not appear to be widely recognized. For single plates the angle of dip cannot be resolved by the current density transformation. Pattern distortions can occur where targets are in close proximity, where the cross-sectional form of the conductor is complex or where the dip is shallow (< 45°). In these latter cases the current density maxima may not occur within the conductive structure and therefore cannot be used to infer depth of burial and/or conductor shape with the same degree of confidence.     

Anomalous luminescence of subglacial sediment at Haut Glacier d'Arolla,Switzerland – a consequence of resetting at the glacier bed?

Swift, D. A., Sanderson, D. C. W., Nienow, P. W., Bingham, R. G. & Cochrane, I. C. 2010: Anomalous luminescence of subglacial sediment at Haut Glacier d'Arolla, Switzerland – a consequence of resetting at the glacier bed? Boreas, Vol. 40, pp. 446–458. 10.1111/j.1502‐3885.2010.00196.x. ISSN 0300‐9483. Luminescence has the potential to elucidate glacial geomorphic processes because primary glacial sediment sources and transport pathways are associated with contrasting degrees of exposure to light. Most notably, sediment entrained from extraglacial sources should be at least partially reset, whereas sediment produced by glacial erosion of subglacial bedrock should retain substantial luminescence commensurate with a geological irradiation history. We set out to test the validity of this assumption at Haut Glacier d'Arolla, Switzerland using sediment sampled extraglacially and from the glacier bed. Contrary to our expectations, the subglacial samples exhibited natural signals that were substantially lower than those of other sample groups, and further (albeit limited) analyses have indicated no obvious differences in sample‐group luminescence characteristics or behaviour that could account for this observation. For glaciological reasons, we can eliminate the possibilities that the subglacial sediment has been extraglacially reset or exposed in situ to heat or light. We therefore advocate investigation of possible resetting processes related to subglacial crushing and grinding, and speculate that such processes, if more generally present, may enable the dating of subglacially deposited tills using luminescence‐based techniques.     

边坡开挖破坏过程的离心模型试验研究

边坡开挖是工程中经常遇到的问题。在清华大学土工离心机上,开发了一种离心机运转过程中的边坡开挖模拟技术。进行了土坡开挖的离心模型试验,测量了开挖过程中边坡的位移场变化。结果表明,边坡的破坏过程是从坡体下部开始的剪切带逐渐向上发展贯通的过程,并经历了滑裂面贯通前的平缓变形和贯通后变形迅速增大两个阶段。坡顶裂缝最初均是由受拉引起的,但随着剪切带的不断向上发展,裂缝的扩展是由拉伸和剪切两种作用综合引起的。