任意三角形毛细管中水力传导率与形状因子关系研究     

陶军  姚军  李爱芬  赵秀才 《岩土力学》2007,28(8):1729-1732

孔隙级网络模型可以用简单几何体来代表真实的孔隙孔喉,以分析流体在这些简单几何体中的流动,具有重要的意义。利用有限元法对任意三角形截面管中的单相和油水两相流动的速度场进行了求解,后由速度场进一步计算出了水力传导率。研究了水力传导率与形状因子之间的关系,结果表明,单相流水力传导率与形状因子近似呈直线关系,而油水两相流时,水力传导率除与形状因子有关外,还随着角落半角和油水接触角的变化而变化。  相似文献   

球状星团NGC4147基于依巴谷系统的自行和空间运动     

王家骥  武振宇 《天文学报》1999,40(3):335-336

王家骥等［１］曾得到球状星团ＮＧＣ４１４７的绝对自行为（－２．８２±０．４９,２．３７±０．４３）ｍａｓ／ｙｒ．但是,其中所用的参考星表是Ｂｒｏｓｃｈｅ等［２］１９８５年发表的结果,含有ＡＧＫ３星表的系统误差．在Ｄａｕｐｈｏｌｅ等［３］给出的２６个球状星团轨道远银心距（ａｐｏｇａｌａｃｔｉｃｄｉｓｔａｎｃｅ）与金属度［Ｆｅ／Ｈ］的关系图上,ＮＧＣ４１４７处于一个特殊的位置,即按照它的远银距（５２ｋｐｃ）,它的金属度［Ｆｅ／Ｈ］应该大于－２．０,但实际上只有－１．８３［４］．类似的问题在文［１］的…  相似文献   

不同季节黄柳气孔导度和水分状况的变化特征     

周海燕  赵爱芬 《中国沙漠》1999,19(Z1):69-71

干旱季节上下表皮日间气孔开启程度不同,下表皮气孔受环境因子的影响较大;湿润季节则相同。不同季节气孔导度值不同,下表皮气孔对季节变化反应灵敏。不同季节黄柳体内水分状况参数值不同,在5、6月份抗旱性最强;沙丘不部位各参数值亦不相同,在沙丘中部和丘脚抗旱性最强,而在丘顶水分状况最好。湿润的7月黄柳一日内各时刻的膨压值均大于0,说明虽然此期间水势随环境条件和气孔调节有所升降,但未影响植株的正常生长。  相似文献   

氮素添加对草原不同冠层植物光合作用的影响   总被引：1，自引：0，他引：1  

徐翀  庾强  左小安  张春萍  牛得草 《中国沙漠》2019,39(1):135-141

氮沉降对植物的生理生态特征具有重要影响，草原不同冠层植物光合特性对氮沉降的响应不同。通过向内蒙古典型草原人工施加氮肥模拟氮沉降，测定上层代表性植物羊草（Leymus chinensis）及下层代表性植物黄囊苔草（Carex korshinskyi）的光合速率（P_n）、水分利用效率（WUE）、蒸腾速率（Tr）和气孔导度（G_s）等光合特性指标及生物量，分析氮沉降对草原不同冠层植物的影响。结果表明：羊草净光合速率随着氮添加量增加呈先上升后下降趋势，而黄囊苔草净光合速率随着氮添加量增加呈上升趋势。氮添加增加了羊草的水分利用效率、生物量和相对生物量，但是对黄囊苔草的水分利用效率、生物量和相对生物量没有影响。在施氮量高于0.8 mol·m^-2后，黄囊苔草的气孔导度和蒸腾速率极显著高于羊草（P<0.01）；整体上看，随着氮添加梯度黄囊苔草蒸腾速率呈现增加的趋势，而羊草的气孔导度和蒸腾速率的变化没有明显的规律。典型草原区不同冠层植物的光合特性对氮添加具有不同的响应，上层植物对下层植物光合作用的限制较小。  相似文献   

全波形时间域航空电磁探测分辨率   总被引：6，自引：0，他引：6  

嵇艳鞠  栾卉  李肃义  万玲  王远  许洋钺  李丽  林君 《吉林大学学报(地球科学版)》2011,41(3):885-891

时间域航空电磁系统的传统记录方式存在不能探测高导异常等不足。以导电薄板为模型,研究了梯形波激励、全波形记录方式下的探测分辨率。采用等效涡流环近似方法,在计算了任意位置两线圈互感的基础上,实现了薄板电流关断期间和断开期间感应电动势的数值计算。数值计算表明:当存在覆盖层时,如果测量系统最小分辨率为5 nV/m2,在电流断开期间可检测目标体电导为1~400 S,在电流关断期间可检测目标体电导为0.1~1 000 S。时间域航空电磁系统采用全波形测量,可以拓宽电磁系统检测异常电导的分辨率孔径。  相似文献   

Relationship between canopy height and the reference value of surface conductance for closed coniferous stands     

Hikaru Komatsu 《水文研究》2003,17(12):2503-2512

When estimating the dry‐canopy evaporation rate of coniferous stands using the Penman–Monteith equation, it is crucial to determine the reference value of surface conductance G_s. This paper examines the relationship between canopy height and the reference value of G_s based on the maximum value of G_s with a vapour pressure deficit ≥ 1·0 kPa, ?_{s max}. There is a clear correlation between canopy height and ?_{s max} when the projected leaf area index ≥3·0. This suggests that using this relationship will enable more accurate determination of the reference value of G_s for closed stands. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Geothermal solute flux monitoring and the source and fate of solutes in the Snake River,Yellowstone National Park,WY     

《Applied Geochemistry》2016

The combined geothermal discharge from over 10,000 features in Yellowstone National Park (YNP) can be can be estimated from the Cl flux in the Madison, Yellowstone, Falls, and Snake Rivers. Over the last 30 years, the Cl flux in YNP Rivers has been calculated using discharge measurements and Cl concentrations determined in discrete water samples and it has been determined that approximately 12% of the Cl flux exiting YNP is from the Snake River. The relationship between electrical conductivity and concentrations of Cl and other geothermal solutes was quantified at a monitoring site located downstream from the thermal inputs in the Snake River. Beginning in 2012, continuous (15 min) electrical conductivity measurements have been made at the monitoring site. Combining continuous electrical conductivity and discharge data, the Cl and other geothermal solute fluxes were determined. The 2013–2015 Cl fluxes (5.3–5.8 kt/yr) determined using electrical conductivity are comparable to historical data. In addition, synoptic water samples and discharge data were obtained from sites along the Snake River under low-flow conditions of September 2014. The synoptic water study extended 17 km upstream from the monitoring site. Surface inflows were sampled to identify sources and to quantify solute loading. The Lewis River was the primary source of Cl, Na, K, Cl, SiO₂, Rb, and As loads (50–80%) in the Snake River. The largest source of SO₄ was from the upper Snake River (50%). Most of the Ca and Mg (50–55%) originate from the Snake Hot Springs. Chloride, Ca, Mg, Na, K, SiO₂, F, HCO₃, SO₄, B, Li, Rb, and As behave conservatively in the Snake River, and therefore correlate well with conductivity (R² ≥ 0.97).  相似文献   

Transpiration of a Linze jujube orchard in an arid region of China     

W. Zhao  X. Chang  Z. Zhang 《水文研究》2009,23(10):1461-1470

As an important source of income in the region's economy, the jujube plantations are very common in arid north‐western China, and their planted areas continue to expand. In the central Heihe River Basin of arid north‐western China, Linze jujube (Zizyphus jujuba Mill. var. inermis (Bunge) Rehd.) plantations cover more than 10,000 ha, too. Water use by this species is expected to change or modify catchment hydrological process. To our knowledge, there is no information on the transpiration and canopy conductance of the jujube plantations in arid north‐western China. Therefore, Transpiration and canopy conductance were monitored in a 14‐year‐old Linze jujube orchard. The experiment was carried out in the central Heihe River Basin, near Pingchuan Town (Linze County, Gansu Province, China) during growing season of 2006, from May to the first ten days of October. Eight trees were used to measure sap flow using the heat‐pulse‐velocity method. The orchard was irrigated adequately during the study. Transpiration was estimated from the sap flow measurements. During the experiment, the transpiration rate of the orchard ranged from 0·32 to 1·40 mm per day. Canopy conductance was obtained from estimated daily transpiration and climatic variables measured on a half‐hour basis, and canopy conductance for water vapour transfer was between 1·20 to 82·57 mm s^?1, with a mean of 11·86 ± 6·84 mm s^?1 during the observation period. Air temperature and vapour‐pressure deficit exhibited a linear relationship with sap flow velocity and the relationship between these factors and canopy conductance could be represented by an exponential decay function. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Disorder-induced enhancement of conductance in doped nanowires     

徐宁  王保林  孙厚谦  孔凡杰 《海洋学报(英文版)》2010,29(11)

A new mechanism is proposed to explain the enhancement of conductance in doped nanowires. It is shown that the anomalous enhancement of conductance is due to surface doping. The conductance in doped nanowires increases with dopant concentration, which is qualitatively consistent with the existing experimental results. In addition, the I-V curves are linear and thus suggest that the metal electrodes make ohmic contacts to the shell-doped nanowires. The electric current increases with wire diameter (D) and decreases exponentially with wire length (L). Therefore, the doped nanowires have potential application in nanoscale electronic and optoelectronic devices.  相似文献   

淮北棉区花铃期冠层不同高度叶片光合特性的差异     

周晓冬  李永秀  张雪松  申双和 《南京气象学院学报》2009,32(5):673-676

基于多层二叶模型,在自然群体条件下,将棉花冠层分为上、中、下三层,研究淮北棉花花铃期冠层上、中、下层,阴叶（无直射光照射）与阳叶（有直射光照射）的光合特性的差异。结果表明,同一高度阳叶的光量子通量密度与光合速率显著大于阴叶;不同高度叶片光量子通量密度与光合速率均表现为上层阳叶〉中层阳叶〉下层阳叶,上层阴叶〉中层阴叶〉下层阴叶;上层阳叶气孔导度大于阴叶,中、下层阴、阳叶的气孔导度无显著差异;上部叶片气孔导度〉中部叶片〉下部叶片;同一高度阳叶胞间二氧化碳浓度显著小于阴叶,随着冠层深度（形态学自上而下）的增加,两者差异增大;不同高度叶片胞间二氧化碳浓度随着冠层深度的增加,呈增加趋势,阳叶差异不显著,阴叶差异显著。  相似文献