双频载波相位求差法在周跳探测与修复中的应用

载波相位测量中小周跳的探测与修复一直是高精度GPS定位研究中的热点领域。分析了L1和L2载波相位观测值的关系,通过相邻历元的相位观测值求差来探测周跳,并结合伪距差分约束条件来确定及修复周跳。结合实例分析,证明该方法可以有效地探测并修复周跳,并通过Matlab编程实现了算法的程序化。     

冷却剂参数对铣槽喷管低周疲劳寿命的影响

采用有限体积流固耦合计算方法、非线性有限元热结构耦合分析方法和局部应变法研究大面积比铣槽喷管三维再生冷却槽道在循环工作条件下的热结构变形与低周疲劳寿命,并对比分析了冷却剂质量流量与入口温度对铣槽喷管疲劳使用寿命的影响。计算结果表明,铣槽喷管热结构响应呈现复杂的三维效应,应变较大位置主要分布在与肋连接的内衬区域,喷管中部的残余应变量最大;冷却槽道低周疲劳寿命分布和热结构响应基本一致,最小寿命位于喷管中部与肋相连的内衬区域燃气侧;随冷却剂质量流量增加,铣槽喷管低周疲劳寿命不断提高;随冷却剂入口温度增加喷管尾部低周疲劳寿命值不断降低,而喷管中前部的低周疲劳寿命值却不断提高,当冷却剂入口温度为280K左右时,本文的铣槽喷管总体使用寿命达到最大。      

干湿循环条件下固化污泥的物理稳定性研究

针对采用水泥和膨润土为固化材料处理的污水厂污泥为研究对象,采用干湿循环试验测量了在水分强烈变化下固化体的质量、体积、含水率及强度等参数的变化情况,进而评价固化污泥的干湿耐久性。结果表明,水泥的掺入是提高固化体干湿耐久性的主要因素,但要达到一定的掺入量才能发挥作用。膨润土对固化体的干湿耐久性影响呈现两面性,适当地掺入膨润土有利于干湿耐久性的形成,而过多地掺入膨润土反而不利于干湿耐久性的形成。在水泥掺入质量比小于或等于0.4时,干湿循环后固化体相对控制样强度明显提高,但体积显著减小,而水泥掺入质量比大于0.4时,干湿循环后固化体相对控制样强度有所下降而体积基本不变。     

Selective organic carbon losses from soils by sheet erosion and main controls

Although the impact of sheet erosion on the selective transportation of mineral soil particles has been widely investigated, little is yet known about the specific mechanisms of organic carbon (OC) erosion, which constitutes an important link in the global carbon cycle. The present study was conducted to quantify the impact of sheet erosion on OC losses from soils. Erosion plots with the lengths of 1‐ and 5‐m were installed at different topographic positions along a hillslope in a mountainous South African region. A total of 32 rainfall events from a three years period (November 2010 up to February 2013), were studied and evaluated for runoff (R), particulate and dissolved organic carbon (POC_L and DOC_L). In comparison to the 0–0·05 m bulk soil, the sediments from the 1‐m plots were enriched in OC by a factor 2·6 and those from the 5‐m long plots by a factor of 2·2, respectively. These findings suggest a preferential erosion of OC. In addition, total organic carbon losses (TOC_L) were incurred mainly in particulate form (~94%) and the increase in TOC_L from 14·09 ± 0·68 g C m^?1 yr^?1 on 1‐m plots to 50·03 ± 2·89 g C m^?1 yr^?1 on 5‐m plots illustrated an increase in sheet erosion efficiency with increasing slope length. Both TOC_L and sediment enrichment in OC correspondingly increased with a decrease in soil basal grass cover. The characteristics of rainstorms had no significant impact on the selectivity of OC erosion. The results accrued in this study investigating the links between sheet erosion and OC losses, are expected to be of future value in the generation of carbon specific erosion models, which can further help to inform and improve climate change mitigation measures. Copyright © 2016 John Wiley & Sons, Ltd.     

太阳绕太阳系质心运动22年周期及其与太阳活动的联系

对于太阳活动22年周期的成因机制长期存在着争论.本文借助于行星会合指数以及开普勒第三定律,对太阳绕太阳系质心运动周期进行了分析计算.结果发现,太阳绕太阳系质心运动存在22.1826年显著周期,这与太阳磁场变化的22.20年周期相吻合.并从太阳系角动量守恒的角度解释了两者之间的成因联系:在太阳绕太阳系质心运动的准22年周期中,太阳系质心与太阳质心逐步接近而后逐步分离.当两个质心之间的距离接近零的时候,太阳轨道角动量与自转角动量叠加,会导致太阳自转角速度的加快;当两个质心之间的距离逐渐远离的时候,则导致太阳自转角速度的减慢.这可能是引发太阳活动和太阳磁场变化的原因.这一新认识为太阳活动准22年周期成因机制的解释提供了新的线索和依据.     

考虑轴力弯矩耦合的截面随动强化恢复力模型

截面层次的恢复力模型能兼顾计算精度与计算效率,为此在梁-柱单元中得到了广泛的应用。但目前给定＂轴力-弯矩-曲率＂的截面恢复力模型无法灵活考虑轴力与弯矩的耦合作用;采用屈服面的截面恢复力模型尚未考虑截面强化效应。提出了基于屈服面的截面随动强化恢复力模型及其积分方法,首先依据截面屈服面建立了截面随动强化恢复力模型,然后依托塑性理论,进行截面状态确定和本构关系积分。最后利用所提出的恢复力模型进行了悬臂柱的静力往复分析。结果表明：（1）所选用的截面恢复力模型能很好考虑轴力存在对弯矩的影响;（2）该模型具有随动强化的特性;（3）在精度上接近纤维截面所用的单轴材料随动强化模型。     

Geochemistry of rare earth elements in the mid-late Quaternary sediments of the western Philippine Sea and their paleoenvironmental significance

Based on a δ18O chronology,rare earth elements(REE) and other typical elements in sediments from core MD06-3047 in the western Philippine Sea were analyzed to constrain the provenances of the sediments and investigate quantitative changes in the Asian eolian input to the study area over the last 700 ka.Among the competing processes that might affect REE compositions,sediment provenance is the most important one.Provenance analysis suggests that the study sediments have two provenance end-members;local volcanic sources are dominant,and eolian dust from the Asian continent has a smaller contribution.During glacial periods,eolian input to the western Philippine Sea was enhanced.In contrast,material supply from local volcanics increased during interglacial periods.Changes in eolian input to the study area were probably related to the strength of the East Asian winter monsoon(EAWM) as well as aridity in the Asian continent on an orbital time scale,and were partly influenced by local control factors on shorter time scales.Therefore,we propose that the present study expands the application of the REE-based method for quantitatively estimating the eolian component from the mid-latitude northern Pacific to the low-latitude western Pacific.Additionally,the study preliminarily confirms the influence of EAWM-transported eolian material on sedimentation in the western Philippine Sea since 700 ka.     

天然饱水-失水对三峡库岸边坡土体的影响研究

三峡水库运行后水位周期性涨落,导致边坡土体在天然条件下长期处于被库水饱和-失水-再饱和的交替过程。分析2005－2009年库区水位变化,以及边坡土体在库水涨落被饱水-失水的次数与时间长度,分时段采集三峡库区库岸石榴树包滑坡堆积土样,分析其化学和矿物成分,观察土体微观结构,探索天然饱水-失水过程中水-岩相互作用对库岸边坡土体的影响和力学效应作用规律。研究结果表明,天然饱水-失水过程对库岸不同高程土体的化学组成和物理结构影响显著,其中172 m高程比168 m高程处受饱水-失水过程的影响较大。饱水-失水作用后,土体中SiO2、Al2O3、Na2O成分的含量上升,CaO、烧失量含量下降,土体的结构由致密的斑块状结构逐渐变成散乱的絮凝状结构,对库岸土体的力学效应产生了巨大的影响。     

冻融作用下冻结黄土黏聚力长期强度变化规律

以陕西富平重塑黄土为研究对象,使土样在封闭系统下经历不同次数的冻融循环作用,分析不同次数的冻融循环作用下土体黏聚力的变化规律。试验利用球形模板压入试验测定冻结黄土的相对瞬时强度和长期强度,结果表明,第4次冻融循环后冻结黄土的相对瞬时强度最大,之后在第6次大幅度降低,第8次又大幅度增加,但小于第4次,第10次之后逐渐趋于稳定。冻结黄土的长期强度在冻融循环第8次时最大,第6次和10次强度相近,处于中间水平,第4、50、100次时强度最低。相对瞬时强度的变化和其孔隙比、密度的变化整体上是相互对应的,这种变化规律与冻融过程中的水分迁移有着密切的关系。长期强度与物理性质的关系并不明显,它是土样内部结构、矿物成分以及物理性质的综合反映。     

IAP第四代大气环流模式的耦合气候系统模式模拟性能评估

本文首先扼要介绍了基于中国科学院大气物理研究所(简称IAP)第四代大气环流模式的新气候系统模式-CAS-ESM-C(中国科学院地球系统模式气候系统模式分量)的发展和结构,之后主要对该模式在模拟大气、海洋、陆面和海冰的气候平均态、季节循环以及主要的年际变率等方面的能力做一个初步的评估.结果表明:模式没有明显的气候漂移,各...