病态线性方程组的简单迭代解法

针对地球物理反问题中经常碰到的病态线性方程组的求解问题。本文提出了一种简单迭代（ＳＩ）算法,从理论上证明了解序列收敛且收敛到方程组的真解,然后给出了几个算例,将计算结果与对付病态问题能力很强的ＣＧ类算法的结果进行了对比,结果表明：ＳＩ算法具有极强的抗病态能力,计算精度明显高于ＣＧ类算法,但计算速度稍低于后者     

Processes and mechanisms of multi-collapse of loess roads in seasonally frozen ground regions: A review

Usually, the collapsible loess widely distributed across the world can serve as a type of foundation soil that meets its strength requirement after dense compaction and elimination of collapsibility. However, many problems such as cracks and differential settlement still occur in loess roads in the seasonally frozen ground regions after several years of operation. Many studies have demonstrated that these secondary or multiple collapses primarily result from the repeatedfreezing-thawing, wetting-drying, and salinization-desalinization cycles. Therefore, we conducted a research program to (1) monitor the in-situ ground temperatures and water content in certain loess roads to understand their changes, (2) study the effects of freezing-thawing, wetting-drying, and salinization-desalinization cycles on geotechnical properties and micro-fabrics of compacted loess in the laboratory, and (3) develop mitigative measures and examine their engineered effectiveness, i.e., their thermal insulating and water-proofing effects in field and laboratory tests. Our results and advances are reviewed and some further research needs are proposed. These findings more clearly explain the processes and mechanisms of secondary and multiple collapse of loess roads. We also offer references for furtherstudy of the weakening mechanisms of similar structural soils.     

极端干旱地区绿洲小气候特征及其生态意义

1 Introduction Microclimate is one of the most important environmental factors for plant growth and development. Different plant communities create different microclimatic environments and different microclimatic environments support different biotic comm…     

六盘山森林资源动态遥感与GIS监测及其马尔可夫链预估

应用两个时期遥感图像解译制图,在GIS支持下,建立空间数据库,获得六盘山地区森林资源变化转移矩阵,并利用马尔可夫链模型对未来森林资源演变趋势进行预估。     

成矿后构造破坏对矿床勘查类型的影响及勘查类型系数优化

现行勘查规范中,主要依据五个地质因素划分勘查类型,其中构造复杂程度因素对划分勘查类型的影响权重约10%。通过对多个矿床勘查类型的分析以及勘查工作经验的总结,研究构造复杂程度对矿床勘查类型的影响,发现成矿后构造破坏程度对矿床勘查类型划分的影响可能被低估。本文以湘潭锰矿为例,该矿床具有成矿后构造复杂、对矿体的破坏大等特点,勘探时将其划分为第Ⅱ勘查类型,以相应的勘查工程网度进行勘查,未能有效控制矿体;如果充分认识成矿后构造复杂、对矿体破坏大的实际情况,提高构造破坏程度对矿床勘探类型划分的影响权重,湘潭锰矿就会被确定为第Ⅲ勘查类型,方可有效控制矿体,也更符合地质实际。本文尝试将构造复杂程度对划分勘查类型的影响权重增大至25%,其勘查类型系数由0.1~0.3调整为0.1~0.9,即第I、第Ⅱ、第Ⅲ勘查类型的五个地质因素类型系数之和分别由2.5~3.0、1.8~2.4、1.0~1.7调整为3.0~3.6、2.2~2.9、1.0~2。在更充分认识成矿后构造破坏程度对勘查类型的影响后,可进一步优化矿床勘查类型系数,更合理地确定矿床勘查类型,进而改进对矿床的控制程度和勘查程度的评价。     

基于马尔可夫模型预测长汀县土地利用动态变化

以福建省长汀县为研究对象,利用1995年、2005年的遥感图像,运用RS和GIS技术分析了用动态变化过程以及土地利用各类型之间的相互转化情况。在此基础上,求得研究区土地利用的转移矩阵,据此分析了长汀县1995年-2005年间土地利用动态变化的空间过程。同时运用马尔可夫模型对2015和2025年的土地利用动态变化及演变趋势预测进行了分析,得出长汀县内土地利用变化情况。     

Bedload hysteresis in a glacier‐fed mountain river

Sediment transport during flood events often reveals hysteretic patterns because flow discharge can peak before (counterclockwise hysteresis) or after (clockwise hysteresis) the peak of bedload. Hysteresis in sediment transport has been used in the literature to infer the degree of sediment availability. Counterclockwise and clockwise hysteresis have been in fact interpreted as limited and unlimited sediment supply conditions, respectively. Hysteresis has been mainly explored for the case of suspended sediment transport, but it was rarely reported for bedload transport in mountain streams. This work focuses on the temporal variability of bedload transport in an alpine catchment (Saldur basin, 18.6 km², Italian Alps) where bedload transport was monitored by means of an acoustic pipe sensor which detects the acoustic vibrations induced by particles hitting a 0.5m‐long steel pipe. Runoff dynamics are dominated by snowmelt in late spring/early summer, mostly by glacier melt in late summer/early autumn, and by a combination of the snow and glacier melt in mid‐summer. The results indicate that hysteretic patterns during daily discharge fluctuations are predominantly clockwise during the snowmelt period, likely due to the ready availability of unpacked sediments within the channel or through bank erosion in the lower part of the basin. On the contrary, counterclockwise hysteresis tend to be more frequent during late glacier melting period, possibly due to the time lag needed for sediment provided by the glacial and peri‐glacial area to be transported to the monitoring section. However, intense rainfall events occurring during the glacier melt period generated predominantly clockwise hysteresis, thus indicating the activation of different sediment sources. These results indicate that runoff generation processes play a crucial role on sediment supply and temporal availability in mountain streams. Copyright © 2014 John Wiley & Sons, Ltd.     

太湖水面蒸发量预报模型及其应用

介绍了几种太湖水面蒸发量的数学模型和预报模型,并用其预测伏旱和夏涝期间旬、月的湖面蒸发量。最后提出应用湖面蒸发量进行太湖水位预报的方法。     

西北干旱区城市土地利用变化及其区域生态环境效应--以甘肃河西地区为例

基于高分辨率土地利用/土地覆盖数据,本文对1985～2000年期间河西地区城市土地利用变化的区域生态环境效应进行了定量分析,结果表明:1)1985～2000年期间河西地区总体生态环境质量在一定程度上维持着相对稳定,但生态环境质量改善和恶化的两种趋势并存,并在县级行政单元上表现出明显的区域分异特征,城市用地变化对区域生态环境的影响总体而言不显著;2)整个河西地区城市用地增长缓慢,表明其城市化进程缓慢.与城市用地变化有关的土地利用类型也多分布在金昌、嘉峪关、张掖、武威和酒泉5个地级市所在地区,表明这些区域的城市化过程相对活跃;3)城市用地变化对生态环境影响的空间规律表现为:使生态环境原本较差的地区生态环境质量有所增加,而使生态环境质量较好的地区生态环境质量降低;4)城镇用地与工矿用地对区域生态环境的影响表现出与城市用地总体基本一致的规律,但农村居民点则对生态环境正、负两方面影响都较为显著;5)城市用地扩展对区域生态环境的影响也体现出与城市用地总体类似的区域分异特征;而城市用地收缩的影响则与此趋势相反.     

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