The coupled rotation of the inner core

The rotation of the inner core (IC) is influenced by the rest of the Earth through a number of coupling mechanisms. Among four possible coupling mechanisms, gravitational, pressure, viscous and electromagnetic, the first two torques are dominant. Numerous existing IC gravitational torque estimates have been shown to agree very well with one another Xu & Szeto 1996 ). It is shown in this paper that different estimates of the IC pressure torque are also in good agreement.
The coupled rotation of the IC has been investigated in the frequency domain by several research groups (Mathews et al. 1991a,b; De Vries & Wahr 1991 ; Dehant et al. 1993; Jiang 1993 ). Not all of these efforts obtained two IC-related rotational modes, the inner-core wobble (ICW) and the free-inner-core nutation (FICN). We investigate this problem in the time domain and confirm the existence of the two modes. The periods of ICW and FICN are in good agreement with those obtained by other researchers. In studying the effects of coupling torques on the IC rotational modes we have found that depending on whether the IC net torque is 'restoring' or otherwise, an increased torque magnitude will respectively shorten or lengthen the ICW period. We have also found that the sense of FICN is determined by the orientation of the net coupling torque on the IC.     

用反射波法振幅比判定单桩相对承载力的尝试

利用动测桩中的桩底反射信号研究了应力波在桩体和土体中的衰减情况。结果表明,应力波在桩体中的衰减比在土中小的多,在考虑了桩周土与反射系数的关系后,尝试给出应用桩底反射信号与桩头人射信号振幅之比判定单桩承载力相对大小的基本理论和初步研究结果。     

不同底质对方斑东风螺生长及存活的影响

比较了自然沙、棕色陶粒、白色陶粒、70%棕色陶粒+30%贝壳砂、贝壳砂等5种底质材料及空白对照组(无底质),对体质量为0.193 g±0.03 g的方斑东风螺生长、存活、摄食以及培育过程中水质的影响。结果表明,白色陶粒组的存活率为80%,显著低于其他各组(P0.05);棕色陶粒组的体质量特定生长率最高(4.31%/d),且显著优于白色陶粒组和对照组(P0.05);棕色陶粒处理组方斑东风螺的饵料转化效率显著高于白色陶粒组和空白对照组;水质中总氨氮、亚硝酸氮和COD均呈上升趋势,各组之间差异不显著。     

海底观测网技术进展与发展趋势

海底观测网络由于其特有的能源供给与信息传输优势,受到了广泛关注与重视。文中简要回顾了国内外海底观测网技术的发展现状,并就海底观测网技术发展趋势进行了探讨。     

不同截止高度角下BDS-3SPP精度分析

针对卫星可见数与历元可用率较低情况下的BDS-3定位性能,本文基于MEGX跟踪站BDS-3与GPS实测数据,分析了不同高度角（10°、20°、30°、40°）下BDS-3卫星B1I、B1C、B2a、B3I,以及GPS系统L1频率的单点定位（SPP）精度。研究发现,BDS-3平均卫星可见数与卫星空间几何构型优于GPS,且随着高度角的增加呈线性变化。BDS-3的4个频率的SPP精度随着高度角的增加呈先增加后降低的趋势,高度角为20°时,定位精度最高,高度角达到40°时,定位精度最低,且历元可用率也最低;但B1I和B3I历元可用率仍大于90%,而B1C和B2a历元可用率大于70%;不论是SPP定位精度还是历元可用率,均优于GPS系统L1频率。     

Ocean/ice shelf interaction in the southern Weddell Sea: results of a regional numerical helium/neon simulation

Ocean/ice interaction at the base of deep-drafted Antarctic ice shelves modifies the physical properties of inflowing shelf waters to become Ice Shelf Water (ISW). In contrast to the conditions at the atmosphere/ocean interface, the increased hydrostatic pressure at the glacial base causes gases embedded in the ice to dissolve completely after being released by melting. Helium and neon, with an extremely low solubility, are saturated in glacial meltwater by more than 1000%. At the continental slope in front of the large Antarctic caverns, ISW mixes with ambient waters to form different precursors of Antarctic Bottom Water. A regional ocean circulation model, which uses an explicit formulation of the ocean/ice shelf interaction to describe for the first time the input of noble gases to the Southern Ocean, is presented. The results reveal a long-term variability of the basal mass loss solely controlled by the interaction between waters of the continental shelf and the ice shelf cavern. Modeled helium and neon supersaturations from the Filchner–Ronne Ice Shelf front show a “low-pass” filtering of the inflowing signal due to cavern processes. On circumpolar scales, the simulated helium and neon distributions allow us to quantify the ISW contribution to bottom water, which spreads with the coastal current connecting the major formation sites in Ross and Weddell Seas.

南海北部似海底反射层速度结构全波形反演

似海底反射层的速度异常是识别天然气水合物的重要标志,这里提出了一种针对天然气水合物似海底反射层的全波形反演方法。这种方法分为全局搜索与局部搜索二部份:首先使用遗传算法进行旅行时,反演得到背景速度模型;然后用其作为初始模型,使用共轭梯度算法进行全波形反演。通过对含噪数据的数值试验,算法表现出了较高的稳定性,并确定了进行全波形反演的遗传算子。将这种波形反演方法应用于我国南海北部海域的天然气水合物研究,反演得到了分辨率高于常规速度分析的似海底反射层速度结构,并识别出似海底反射层的速度异常。利用纵波速度反演的结果,计算出沉积物中游离气的含量,认为BSR下方的低速层可以解释为含至少1%游离气的薄层。并分析了研究区内甲烷气的来源,认为该区域游离气兼有生物气和热解气。     

漓江水系汞的分布和污染研究

对漓江水系干流、支流、连体湖泊、较大的孤立湖塘和近岸水井设置40个采样点。水样采样周期为2个水文年,分枯水季和丰水季两次采样,现场测定水温、电导率、pH值等理化参数。系统采集水样112件、底泥样40件、水草样40件、近岸土壤样40件。底泥样用逐步浸提法进行不同形态汞分析。研究结果显示,干流河水、底泥和水草中汞的平均含量分别为0．12μg／L、0．20μg／g和0．032μg／g;主要支流河水、底泥和水草中汞的平均含量高于干流,分别为0．15—0．23μg／L、0．38～1．7μg／g和0．028—0．044μg／g。底泥中汞含量均高于近岸土壤汞含量。无论是干流还是支流,河水汞含量与底泥、水草汞含量有明显的相关关系。由上游至下游,漓江水系干流、主要支流河水样汞含量均不断增高,可高出源头河水汞含量的1．5—5倍。相应地指示重金属离子污染的参考指标——电导率值不断增高,河水的pH值亦逐渐增高。丰水期（5月至6月）河水中的汞含量（0．12—0．28μg／L）明显高于枯水期（9月至11月）河水中的汞含量（0．091—0．28μg／L）。不同断面河水汞含量均高于相应近岸井水汞含量。不同水体底泥中汞的形态分布一般顺序为：残渣态〉难氧化降解有机质结合态〉腐殖酸结合态〉碳酸盐和铁锰氧化物吸附态〉交换态〉易氧化降解有机质结合态〉水溶态。综合各项资料分析,认为漓江干流是桂林城市汞污染最大的汇。根据地表水环境质量标准（GB3838--2002）,仅汞而言,漓江水系均达到Ⅳ类水质标准（河水中汞含量≤1μg／L）。漓江支流汞污染高于干流,对干流存在较大的污染风险。     

积雪底部温度(BTS)方法在冻土分布调查和模型研究中的应用:研究进展

多年冻土的调查方法很多,如坑探、物探、遥感等,但相对于积雪底部温度(BTS)测量方法来说,这些方法都比较费时、费力、费钱.目前,BTS已经被成功应用于阿尔卑斯山等地多年冻土的调查研究,不过在国内的应用却是个空白.引入BTS方法,希望能为我国多年冻土的研究开辟一条新路.     

西霞口龙眼港-4.5m码头加固扩建施工新方法

以山东西霞口集团龙眼港—4.5m码头的改扩建工程为例,阐述了采用三管法旋喷桩托底置换、加劲旋喷桩配合锚拉支护方法在码头改造施工中的可行性及其施工工艺和施工方法,为同类工程施工积累了经验。