基于RS和GIS的黄土丘陵沟壑区浅沟侵蚀地形特征研究

为了解黄土高原浅沟侵蚀地形特征,基于Qucickbird高分辨率遥感影像和数字高程模型,提取了坡面浅沟及其地形参数,并对浅沟侵蚀的地形特征参数和分布规律进行了统计分析,结果表明：黄土丘陵沟壑区,坡面坡度、长度、坡向以及上坡长度是影响坡面浅沟数量的主要地形要素,而浅沟侵蚀地形特征主要由坡面坡度、坡面长度、上坡长度和汇流面积共同决定;坡面长度与浅沟平均长度呈显著线性关系,坡面坡度与浅沟频度、浅沟坡度与其上坡长度间则均满足二次曲线;发生浅沟侵蚀的上限与下限临界坡度分别介于26～27°和15～20°,临界坡长介于50～80 m;由浅沟坡度的正弦值与汇流面积确定出浅沟分布的临界曲线;阳向坡面的平均浅沟长度小于阴向坡面。基于RS和GIS技术能有效确定浅沟侵蚀地形特征,为黄土区坡面水土流失治理提供了技术支撑。     

地形效应下的区域蒸散遥感估算

在地表起伏地区,由于受到坡度、坡向等的影响,地表能量通量表现出与水平地表不一样的特征,为了定量表征起伏地表条件下的蒸散格局,以位于陕甘宁交界区的华池县、庆城县、镇原县、西峰区和合水县为研究区,从能量平衡原理入手,对各能量通量进行了量化计算,并着重考虑了蒸散的能量来源即地表净辐射的地形效应;同时,针对研究区地表特征,确定了土壤热通量的计算方案和感热通量的参数化方案,如零平面位移、动量粗糙长度、热量粗糙长度、动量和热量的稳定度校正项等算法;在此基础上,计算了研究区的瞬时蒸散,计算结果表明采用的蒸散遥感估算方案     

Modeling Tree Loss Versus Tree Recruitment Processes in SW Iberian Rangelands as Influenced by Topography and Land use and Management

The sustainability of Iberian open wooded rangelands is threatened by recent land use changes and lack of tree recruitment. As trees are key elements of these systems, the characterization of their spatiotemporal trend is essential for the system's management. Our objective is to develop spatial models reflecting the temporal dynamic of trees in terms of recent tree loss and tree gain processes in farms, evaluating the influence on the models of topography and land use and management. Aerial photographs of 1956 and 2009 were compared, analyzing lost and new trees in five dehesas of Extremadura (Spain). Multivariate adaptive regression splines was used to produce the spatial models that characterize the proneness of an area to undergo tree loss or recruitment. Models showed good performances. Although land use and management intensively influenced on tree dynamics, because it depends on topography, models built by considering just the topographic variables showed only slightly lower fitness. Tree recruitment mostly happened in the marginal places with steep slopes, while tree loss occurred in elevated, gently undulated and more intensively used places of the farms. A spatial polarization of both processes has been observed that leads to the lack of replacement of lost trees. The work provides some clues on the design of tree management procedures for dehesas and montados. The implementation of measures to address the degradation processes in dehesas should take into account the spatial arrangement of the areas where tree loss or gain is actually happening or it is likely to occur. Copyright © 2017 John Wiley & Sons, Ltd.     

五角前吻吸虫成虫体表超微结构研究

用扫描电镜对寄生于斑Ｈｕ肠道中的五角前吻吸虫成虫体表超微结构进行了观察。成虫的前吸器具有伸缩性，当完全伸展时，前吸器呈喇叭状，中央凹陷，７个角状突起呈放射状排列；当前吸器完全收缩时，７个突起缩入体内，此时，前吸器呈钝锥状，中央部位凸于身体最前端。成虫体棘也具有伸缩性，当完全伸出时，体棘呈刷状，当体棘完全收缩时，体表仅剩下一个一个的长方形棘囊。成虫表皮凸凹不平，似由鹅卵石状突起紧密排列而成。成虫的体     

滑动轴颈轴承表面形貌的摩擦学研究

用摩擦学理论综合分析滑动轴颈轴承摩擦系统 ,针对现行施工与验收存在的问题结合有关理论进行分析探讨 ,总结出轴瓦刮研的最佳表面形貌主控参数为表面方向参数和波纹度参数。并对现行施工工艺进行理论分析 ,从工程实际应用方面进行了改进。     

滑动轴承表面形貌的摩擦学研究

用摩擦学理论综合分析滑动轴颈轴承摩擦系统,针对现行施工与验收存在的问题结合有关理论进行分析探讨,总结出轴瓦刮研的最佳表面形貌主控参数为表面方向参数和波纹度参数。并对现行施工工艺进行理论分析,从工程实际应用方面进行了改进。     

Synergistic induction of wheat stem rust appressoria by chemical and topographical signals

The leaf alcohols cis -3-hexen-1-ol and trans -2-hexen-1-ol have been previously shown to induce the wheat stem rust (Puccinia graminis f. sp. tritici) to differentiate appressoria in a complex axenic culture medium. In this paper, the possible role of these chemicals in appressorium induction during infection has been analysed further. The inductive potential of ethylene and three cutin monomers were also tested because they have been found to induce appressoria in other fungi. Both hexenols were found to be inductive in aqueous solution in the absence of media constituents. 0.5–1 m trans -2-hexen-1-ol was the most inductive resulting in a maximum of 51% appressorium differentiation. trans -2-hexen-1-ol was also shown to be inductive in vapour form. In aqueous solution, trans -2-hexen-1-ol acted synergistically with topographical signals by increasing the rate of appressorium induction. Combining the two signals also increased the total number of appressoria differentiated (88%). The other chemicals tested were non-inductive although a biochemical domain rich in exposed cutin was localized around stomatal apertures of wheat leaves. The characteristic bipolar morphology of appressoria formed over stomata was found to be determined by topographical signals. Overall, our data support a role for both chemical signals (hexenols or their analogues) and topographical signals being involved in appressorium induction by wheat stem rust.     

连云港花果山森林景区高分辨率火险区划

利用10cm高空间分辨率航空遥感影像,在森林资源二类调查的基础上,获取研究区的可燃物类型及其特征信息;利用1∶10 000地形图获取地形因子信息。在此基础之上,通过加权叠置法计算火险指数,并将研究区划分为Ⅰ级(没有危险)、Ⅱ级(低度危险)、Ⅲ级(中度危险)、Ⅳ级(高度危险)、Ⅴ级(极度危险)等5个火险区划。结果表明:Ⅰ级火险区面积最小,占研究区总面积3.98%;Ⅱ级火险区面积最大,占32.25%;Ⅲ级火险区面积占21.05%;Ⅳ级和Ⅴ级火险区面积分别占22.14%和20.58%,两者之和较大,占研究区总面积的42.72%,研究区防火任务艰巨。研究区内可燃物类型对火险等级划分起重要作用,其中麻栎和茶树在森林防火工作中发挥重要作用;松树、竹林和荒草地是防火的重点。     

永安市巨尾桉人工林生长的区位效应初步研究

依据调查样地资料,分别对永安市巨尾桉人工林在不同小地形、不同坡位和不同坡向上的生长进行了研究,结果表明:山脊和山坡的林分生长量相差不大;山洼林分生长最好,其次为山脊和山坡,山顶林分生长最差;不同年龄、不同坡向的林分中,不同坡位的生长差异不大;巨尾桉在阳坡上生长明显优于半阴半阳坡的林分。     

Topmodel模型在黑河金盆水库流域的应用研究

【目的】预测黑河金盆水库的入库流量过程,为水库汛期的安全运行提供理论依据。【方法】根据陕西省黑河金盆水库流域水文、气象资料,采用Topmodel模型模拟流域的降雨径流过程,以流域内2003-2007年雨量站及水文站的实测数据进行模型率定,以2009年的实测资料对模型进行检验。【结果】Topmodel模型模拟结果显示,模拟期Nash系数平均值为0.78,洪峰预报误差的平均值为-10.3%,峰现时间平均值为-1 h;检验期Nash系数平均值为0.875,洪峰预报误差平均值为11.2%,峰现时间平均值为-1 h。Topmodel模型在黑河金盆水库流域的预报水平为乙等水平。【结论】模型在该流域具有较强的适用性,可以用于金盆水库汛期的入库流量预报,可为水库的安全运行和科学管理提供数据支持。