Effects of changes in canopy interception on stream runoff response and recovery following clear-cutting of a Japanese coniferous forest in Fukuroyamasawa Experimental Watershed in Japan     

Tomoki Oda  Tomohiro Egusa  Nobuhito Ohte  Norifumi Hotta  Nobuaki Tanaka  Mark B. Green  Masakazu Suzuki 《水文研究》2021,35(5):e14177

Understanding changes in evapotranspiration during forest regrowth is essential to predict changes of stream runoff and recovery after forest cutting. Canopy interception (Ic) is an important component of evapotranspiration, however Ic changes and the impact on stream runoff during regrowth after cutting remains unclear due to limited observations. The objective of this study was to examine the effects of Ic changes on long-term stream runoff in a regrowth Japanese cedar and Japanese cypress forest following clear-cutting. This study was conducted in two 1-ha paired headwater catchments at Fukuroyamasawa Experimental Watershed in Japan. The catchments were 100% covered by Japanese coniferous plantation forest, one of which was 100% clear-cut in 1999 when the forest was 70 years old. In the treated catchment, annual runoff increased by 301 mm/year (14% of precipitation) the year following clear-cutting, and remained 185 mm/year (7.9% of precipitation) higher in the young regrowth forest for 12–14 years compared to the estimated runoff assuming no clear-cutting. The Ic change was −358 mm/year (17% of precipitation) after cutting and was −168 mm/year (6.7% of precipitation) in the 12–14 years old regrowth forest compared to the observed Ic during the pre-cutting period. Stream runoff increased in all seasons, and the Ic change was the main fraction of evapotranspiration change in all seasons throughout the observation period. These results suggest that the change in Ic accounted for most of the runoff response following forest cutting and the subsequent runoff recovery in this coniferous forest.  相似文献   

脐带缆螺旋滑移分析及力学性能研究   总被引：1，自引：0，他引：1  

李英  吴潘  冯雅萍  曹静萱 《海洋工程》2018,36(6):58-68

针对脐带缆内部螺旋层,应用Darboux标架建立螺旋结构空间坐标系,推导弯曲载荷下螺旋结构的局部变形和滑移。考虑螺旋构件间的接触和摩擦作用,建立螺旋结构的受力平衡偏微分方程,并研究螺旋角和摩擦系数对螺旋结构滑移的影响。基于同层螺旋结构本构关系相同假设,将所有螺旋结构力学性能线性叠加,拟合脐带缆整体弯曲刚度。运用建立的理论解析方法,对某双层铠装脐带缆的力学性能进行研究,并与数值模拟结果进行对比验证。对比结果表明,理论解析得到的螺旋滑移结果与数值模拟结果一致,理论解析得到的脐带缆弯曲刚度与数值模拟结果在全滑动阶段比较接近。  相似文献   

Evolutionary Processes in Low-Mass Binary Systems     

Peter P. Eggleton  Ludmila Kisseleva-Eggleton 《Astrophysics and Space Science》2005,296(1-4):327-336

We consider the evolution of certain low-mass binaries, incorporating models of (a) internal evolution, (b) tidal friction, (c) dynamo activity driven by an elementary α,Ω dynamo, (d) stellar wind driven by the activity, and (e) magnetic braking as a consequence of wind and poloidal dynamo-generated magnetic field. In some circumstances the stellar wind is found to remove mass on a nuclear timescale, as is necessary to explain some observed systems. We can hope that various uncertainties in the model may be clarified by a careful comparison of the models with such observed quantities as rotation periods. These are modified by processes (a), (b) and (e). Assuming that stellar evolution is slow, rotation rate should in some circumstances represent a balance between magnetic braking trying to slow the star down and tidal friction trying to spin it up. Preliminary attempts are promising, but indicate that some fine tuning is necessary. When there is a third body present, in an orbit which is inclined but not necessarily of short period, the eccentricity of a close binary can be strongly modified by ‘Kozai cycles’. We show that this may complicate attempts to account for spin rates of stars in close binaries.  相似文献   

西安地区单桩桩土相互作用数值模拟分析   总被引：1，自引：0，他引：1  

魏静  王建华  李永林 《地球科学与环境学报》2003,25(3):63-66

随着计算机技术和数值方法的不断发展和完善,使有限元法得到越来越多的应用。根据西安地区原型摩擦桩的地层特点和土性条件,运用有限元基础理论,利用相应的边界条件与假设条件,建立单桩数学模型。通过模型研究了单桩的沉降特性与土共同作用的影响因素,对西安地区单桩桩土相互作用机理进行了探讨。  相似文献   

Magnetic Reconnection, Turbulence, and Collisionless Shock     

Hantao Ji  Russell Kulsrud  Masaaki Yamada 《Astrophysics and Space Science》2005,298(1-2):219-226

A short summary of recent progress in measuring and understanding turbulence during magnetic reconnection in laboratory plasmas is given. Magnetic reconnection is considered as a primary process to dissipate magnetic energy in laboratory and astrophysical plasmas. A central question concerns why the observed reconnection rates are much faster than predictions made by classical theories, such as the Sweet–Parker model based on MHD with classical Spitzer resistivity. Often, the local resistivity is conjectured to be enhanced by turbulence to accelerate reconnection rates either in the context of the Sweet–Parker model or by facilitating setup of the Pestchek model. Measurements at a dedicated laboratory experiment, called MRX or Magnetic Reconnection Experiment, have indicated existence of strong electromagnetic turbulence in current sheets undergoing fast reconnection. The origin of the turbulence has been identified as right-hand polarized whistler waves, propagating obliquely to the reconnecting field, with a phase velocity comparable to the relative drift velocity. These waves are consistent with an obliquely propagating electromagnetic lower-hybrid drift instability driven by drift speeds large compared to the Alfven speed in high-beta plasmas. Interestingly, this instability may explain electromagnetic turbulence also observed in collisionless shocks, which are common in energetic astrophysical phenomena.  相似文献   

滇西动态重力网的分形特征及空间分辨力   总被引：1，自引：1，他引：0  

贾民育 《大地测量与地球动力学》1996,(4)

介绍了用分形学描述地球物理观测网非均匀分布和联合应用分形特征与Ｓｈａｎｎｏｎ定理确定最佳网格距的方法。研究了滇西动态重力网的分形特征，它的分形维Ｄｆ＝１．２７，最佳网格距ｒ０＝２８ｋｍ。讨论了１９８６年至１９９４年间网区发生的８次Ｍｓ＞５．０级地震前重力场变化的可信性，指出这些变化的波长均大于１００ｋｍ，至少２倍于网的最小空间分辨力，因而是可信的  相似文献   

基于STC单片机的实验开发平台的设计     

杨明欣  张杰  郑郁正 《成都信息工程学院学报》2006,21(3):410-413

介绍了基于STC89C516RD＋单片机的实验开发平台的硬件电路设计、ISP编程、软件开发实例及系统的抗干扰措施.为帮助学生学习单片机技术,同时也为有经验者开发和调试产品打下基础.  相似文献   

Electromagnetic signals associated with stick–slip of quartz-free rocks     

Akito Tsutsumi  Nobumasa Shirai 《Tectonophysics》2008,450(1-4):79-84

We recorded clear transients in the electric and magnetic fields upon sudden slip in stick–slip experiments on dry, cylindrically shaped, quartz-free rock specimens of basalt and peridotite with a 30° saw-cut (representing a fault) at confining pressures of up to 120 MPa. The amplitudes of the measured electric field signals were always higher at the electrode pair oriented parallel to the strike of the fault than at the pair oriented perpendicular. This anisotropy suggests a preferred electric polarization normal to the slip surface. The transients in the electric and magnetic fields were observed only when the fault slip occurred by stick–slip mode, not by a stable mode of the sliding, and the amplitudes of the electric field signals increased with increasing stress drop. It is suggested that the generation process of the electromagnetic signals is closely related to the characteristic behavior of the fault at the time of the initiation of slip during stick–slip events, probably with respect to the intensity of the signals. We propose that one or both of the following two processes characteristic of the fault at the time of the initiation of slip during stick–slip events are essential for the generation of detectable electromagnetic signals: rapid slip along the simulated fault and separation of the rock masses across the fault.  相似文献   

煤岩对压裂裂缝长期导流能力影响的实验研究   总被引：7，自引：0，他引：7  

张士诚  牟善波  张劲  王雷 《地质学报》2008,82(10):1444-1449

煤层中一般都伴有煤层气,通过压裂可以将煤层气释放出来,一方面能够获得清洁能源,另一方面可以提高煤田的安全开采。煤岩层自身特点决定了其在压裂中应用的实验评价方法及结论应具有特殊性,本文主要针对煤层气井的煤岩层压裂裂缝长期导流能力进行实验评价研究。实验表明,与砂岩地层不同,煤岩的硬度较小,压裂中支撑剂嵌入情况较严重;煤岩易破碎,碎屑颗粒充填到支撑剂中;同时支撑剂存在破碎及吸附伤害等,多种作用导致支撑裂缝的导流能力降低。实验中,以煤岩层闭合压力为一个重要的参数,实验对比分析了在不同闭合压力下,铺砂浓度、支撑剂粒径、支撑剂种类及组合的选择、支撑剂颗粒的破碎与嵌入、压裂液残渣等因素对煤岩层导流能力的影响。本文的实验结论为,嵌入对煤岩层支撑裂缝的导流能力伤害很大,加大铺砂浓度、采用低破碎率支撑剂、降低压裂液伤害能在一定程度上提高煤层裂缝的导流能力,但影响程度随闭合压力的增加而逐渐降低。本文所得出的结论对今后煤层气的开发及设计施工具有一定的指导意义。  相似文献   

Experimental constraints on the effects of pressure and H2O on the fractional crystallization of high-Mg island arc basalt     

Morihisa Hamada  Toshitsugu Fujii 《Contributions to Mineralogy and Petrology》2008,155(6):767-790

H₂O-undersaturated melting experiments of synthesized basalt (SiO₂ = 50.7 wt.%, MgO = 8.3 wt.%, Mg# = 60) were conducted at fO₂ corresponding to NNO+1 and NNO−1 to clarify the effects of pressure (2–7 kbar) and H₂O on fractional crystallization in island arcs. H₂O content was ranged from nominally anhydrous to 4.4 wt.%. Differentiation trends, namely the liquid lines of descent, change sensitively according to pressure-H₂O relations. Tholeiitic differentiation trends are reproduced with H₂O ≤ ∼2 wt.% in primary magma. With such quantities of H₂O, fractional crystallization is controlled by olivine + plagioclase at 2 kbar. Increasing the pressure from 2 to ≥4 kbar induces early crystallization of orthopyroxene instead of olivine and therefore SiO₂ enrichment in the residual melts is suppressed. Increasing H₂O (≥ ∼2 wt.% in primary magma) stabilizes clinopyroxene relative to orthopyroxene and/or magnetite. Although the phase relations and proportions strongly depend on fO₂ and H₂O content, differentiation trends are always calc-alkaline.  相似文献