Successful vegetative propagation by stem cuttings of Tetraena mongolica Maxim.     

ZhiGang Zhou  GuoHou Liu  Fang Luo 《寒旱区科学》2009,1(5):0423-0431

Techniques have been developed for the vegetative propagation of Tetraena mongolica,a rare and endangered species endemic to the western Ordos Plateau in the northcentral portion of China.The purpose of the study was to investigate the rooting characteris-tics of the plant species from the aspects of length and ages of cuttings,external hormone concentration,leaf retention,cutting orientations,and cutting positions.The results obtained from the experiments indicated that the rooting ratio of 2-year or 3-year old cuttings was larger than more than of 4-year old cuttings.The influence of external hormone concentration on rooting was ob-vious;the rooting ratio of cuttings was increased by external hormone treatment,especially when treated by ABT1(ABT No.1 Rooting Powder) 50 mg/L for 3 hours,in which case,the rooting ratio reached 91 percent.Leaf retention influenced rooting sig-nificantly;the rooting rate of cuttings became greater as the leaf retention increased.There was no significant difference in rooting capability between south and north orientations of the ortets.The rooting ratio of the cuttings obtained from the distal portions of shoots was significantly larger than those obtained from the middle and the basal portions of the shoots.On day three after treat-ment,calluses started appearing at the incisions of some cuttings dipped in 500 mg/L IAA(indole acetic acid).Most cuttings were healed or swelled,and 6 percent of cuttings rooted on day 6 after treatment.Higher rooting period occurred 7-10 days after the experiment was set up.  相似文献   

The tropical intraseasonal oscillation in SAMIL coupled and uncoupled general circulation models   总被引：4，自引：1，他引：3  

杨静  包庆  王晓聪  周天军 《大气科学进展》2012,29(3):529-543

Simulations of tropical intraseasonal oscillation(TISO) in SAMIL,the Spectral Atmospheric Model from the Institute of Atmospheric Physics(IAP) State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG) coupled and uncoupled general circulation models were comprehensively evaluated in this study.Compared to the uncoupled model,the atmosphere-ocean coupled model improved the TISO simulation in the following aspects:(1) the spectral intensity for the 30-80-day peak eastward periods was more realistic;(2) the eastward propagation signals over western Pacific were stronger;and(3) the variance distribution and stronger signals of Kelvin waves and mixed Rossby gravity waves were more realistic.Better performance in the coupled run was assumed to be associated with a better mean state and a more realistic relationship between precipitation and SST.In both the coupled and uncoupled runs,the unrealistic simulation of the eastward propagation over the equatorial Indian Ocean might have been associated with the biases of the precipitation mean state over the Indian Ocean,and the unrealistic split of maximum TISO precipitation variance over the Pacific might have corresponded to the exaggeration of the double Intertropical Convergence Zone(ITCZ) structure in precipitation mean state.However,whether a better mean state leads to better TISO activity remains questionable.Notably,the northward propagation over the Indian Ocean during summer was not improved in the mean lead-lag correlation analysis,but case studies have shown some strong cases to yield remarkably realistic northward propagation in coupled runs.  相似文献   

北京721特大暴雨极端性分析及思考（二）极端性降水成因初探及思考   总被引：22，自引：10，他引：12  

孙军  谌芸  杨舒楠  代刊  陈涛  姚蓉  徐珺 《气象》2012,38(10):1267-1277

本文是“北京7.21特大暴雨极端性分析及思考”的第二部分,第一部分“观测分析及思考”对此次过程的降水特点、水汽特点、中尺度对流系统（MCS）的环境场条件和发生发展过程进行了分析,指出这是一次极端降水过程。本文进一步从影响降水的因子：降水效率、水汽、上升运动、持续时间等方面进一步探讨极端性降水的成因,所用资料为业务中常用的模式分析和各种观测资料。分析表明,本次过程为典型华北暴雨环流形势,其中高层气流辐散区与低层低涡切变线的耦合是直接诱因;较高的环境相对湿度和湿层较厚,较低的抬升凝结高度和自由对流高度以及热带降水性质提高了本次过程的降水效率;异常大的水汽含量（可降水量达60－80mm）及与其相关的物理量异常,可作为判断极端降水的重要因子;环境大气具有中下层条件性不稳定,上层湿中性层结特性,CAPE值中等,同时上层干侵入增加了对流不稳定,有利于上升运动发展;低涡切变线及华北地形共同触发了MCS的在暖区生成发展;低涡北跳、MCS后向传播特性使暖区MCS东移速度慢,形成“列车效应”,造成降雨持续时间长。本文最后探讨了极端降水的预报思路。  相似文献   

On different types of adjustment usable to calculate the parameters of the stream power law     

Alain Demoulin  Arnaud BeckersBenoît Bovy 《Geomorphology》2012,138(1):203-208

Model parameterization through adjustment to field data is a crucial step in the modeling and the understanding of the drainage network response to tectonic or climatic perturbations. Using as a test case a data set of 18 knickpoints that materialize the migration of a 0.7-Ma-old erosion wave in the Ourthe catchment of northern Ardennes (western Europe), we explore the impact of various data fitting on the calibration of the stream power model of river incision, from which a simple knickpoint celerity equation is derived. Our results show that statistical least squares adjustments (or misfit functions) based either on the stream-wise distances between observed and modeled knickpoint positions at time t or on differences between observed and modeled time at the actual knickpoint locations yield significantly different values for the m and K parameters of the model. As there is no physical reason to prefer one of these approaches, an intermediate least-rectangles adjustment might at first glance appear as the best compromise. However, the statistics of the analysis of 200 sets of synthetic knickpoints generated in the Ourthe catchment indicate that the time-based adjustment is the most capable of getting close to the true parameter values. Moreover, this fitting method leads in all cases to an m value lower than that obtained from the classical distance adjustment (for example, 0.75 against 0.86 for the real case of the Ourthe catchment), corresponding to an increase in the non-linear character of the dependence of knickpoint celerity on discharge.  相似文献   

西藏地区强降雪过程的波包分布及传播特征     

李晓婧  林莉  肖天贵  唐毅  何建军 《高原山地气象研究》2012,32(1):29-34

利用NCEP/NCAR高度场的再分析资料,通过波包传播诊断方法(WPD),对2005年10月19～23日西藏地区中东部及南部边缘地区一次大范围强降雪天气过程进行波包分布与波能传播特征分析。结果表明:500hPa高度场的波包分布和传播特征很好地反映此次过程;强降雪天气发生在波包大值区域内而且反映了过程的爆发和消亡;波包的分布特征与强对流天气的发生状况是一致的;波包的移动路径很好地反映了扰动能量的传播。此次过程是"积累-释放"的三次循环。  相似文献   

Sources of SEP Acceleration during a Flare – CME Event     

N. J. Lehtinen  S. Pohjolainen  K. Huttunen-Heikinmaa  R. Vainio  E. Valtonen  A. E. Hillaris 《Solar physics》2008,247(1):151-169

A high-speed, halo-type coronal mass ejection (CME), associated with a GOES M4.6 soft X-ray flare in NOAA AR 0180 at S12W29 and an EIT wave and dimming, occurred on 9 November 2002. A complex radio event was observed during the same period. It included narrow-band fluctuations and frequency-drifting features in the metric wavelength range, type III burst groups at metric – hectometric wavelengths, and an interplanetary type II radio burst, which was visible in the dynamic radio spectrum below 14 MHz. To study the association of the recorded solar energetic particle (SEP) populations with the propagating CME and flaring, we perform a multi-wavelength analysis using radio spectral and imaging observations combined with white-light, EUV, hard X-ray, and magnetogram data. Velocity dispersion analysis of the particle distributions (SOHO and Wind in situ observations) provides estimates for the release times of electrons and protons. Our analysis indicates that proton acceleration was delayed compared to the electrons. The dynamics of the interplanetary type II burst identify the burst source as a bow shock created by the fast CME. The type III burst groups, with start times close to the estimated electron-release times, trace electron beams travelling along open field lines into the interplanetary space. The type III bursts seem to encounter a steep density gradient as they overtake the type II shock front, resulting in an abrupt change in the frequency drift rate of the type III burst emission. Our study presents evidence in support of a scenario in which electrons are accelerated low in the corona behind the CME shock front, while protons are accelerated later, possibly at the CME bow shock high in the corona.  相似文献   

煤岩水力压裂裂缝扩展形态试验研究     

姜婷婷  张建华  黄刚 《岩土力学》2018,39(10):3677-3684

通过室内水力压裂物理模拟试验系统,对大尺寸原煤进行了水力压裂模拟试验,根据水力裂缝的空间展布形态分析了煤岩储层水力裂缝的延伸规律,揭示了网状裂缝的形成机制。结果表明：水力裂缝易在弱层理处分叉和转向,发育的层理和裂缝系统等结构面为压裂形成裂缝网络提供了前提条件。泵压曲线呈现出的频繁波动是煤岩内产生网状裂缝的一个显著特征。水力裂缝的起裂与延伸有4种基本模式,裂缝网络的形成多为这4种基本模式的组合。地应力差异系数和泵注排量对煤层水力裂缝形态有较大影响。较小的地应力差异系数更利于网状裂缝的形成;较高的压裂液排量易形成相对简单的裂缝形态,导致压裂改造效果较差。该试验方法和试验结果可为现场水力压裂参数设计和优化提供参考和依据。  相似文献   

基于解耦传播的波场分解方法在VTI介质弹性波逆时偏移中的应用     

周进举  王德利  李博文  李强  王睿 《吉林大学学报(地球科学版)》2018,48(3):909-921

由于弹性波逆时偏移更符合实际情况,而且转换波的成像结果有更高的分辨率,因此弹性波逆时偏移越来越受到重视。然而,弹性波逆时偏移需要多波多分量数据,为了减少成像结果中的串扰假象,在逆时偏移过程中进行P波和S波分解就变得非常必要。结合基于向量的激发振幅成像条件,我们把基于解耦传播的波场分解方法应用到弹性波逆时偏移中,并对比了其在各向同性介质和横向各向同性（VTI）介质中的应用效果。结果说明,该方法可以在各向同性介质中完全分解P波和S波,并保留波场的向量信息。虽然在VTI介质中有较小的分解残余,但是该分解残余不会在逆时偏移结果中产生明显的串扰;因此,这种波场分解方法可以应用于各向同性介质和VTI介质弹性波逆时偏移。该方法是在时间空间域实现的,可以在波场传播过程中直接对P波和S波进行分离,应用方便,计算效率高。与利用Helmholtz分解的弹性波逆时偏移相比,该方法避免了在PS波成像结果中的极性反转问题。在复杂Hess VTI模型的逆时偏移结果中,高速岩体和断层的成像清晰,甚至是两个低速薄夹层也能较好成像;这说明该方法对复杂介质具有较好的适应性。PS波成像结果中的各向异性体成像清晰,说明各向异性介质弹性波逆时偏移可以对传统逆时偏移不能很好成像的构造进行成像。  相似文献   

基于离散元方法对走滑拉分盆地演化及次级断裂扩展过程研究     

刘源  KONIETZKY Heinz 《地质力学学报》2019,25(5):840-852

拉分盆地是一种与走滑断裂带密切相关的特殊拉张构造,因其重要的构造意义,及其与火山活动、中小地震群集、特殊的成矿作用间的伴生关系而受到研究者的高度重视。关于拉分盆地的形成演化过程,已有较多的研究成果,但是由于研究手段的限制,缺少对盆地演化中次级断裂扩展过程的研究。基于离散元的数值计算方法是研究断裂扩展方式的理想方法。本文采用基于离散元的颗粒流方法,揭示纯走滑拉分盆地发育过程中的断裂扩展和连接过程,为拉分盆地演化机理和断裂扩展提供新的研究方法。同时,根据主走滑断层与块体运动方向的夹角不同,建立不同的张扭性拉分盆地模型,系统研究张扭性盆地的断裂扩展和演化机理。将上述理论研究结果与死海盆地等经典拉分盆地实例相结合,探讨了死海盆地、土耳其Cinarcik盆地、哥伦比亚El Paraiso盆地等的形成演化机理和断裂扩展方式。   相似文献   

后撤式逆冲推覆断层成因机制及物理模拟——以准噶尔盆地西北缘克-百断裂带为例     

熊连桥  于福生  姚根顺  倪超  安原  李震 《大地构造与成矿学》2017,41(6):1011-1021

位于准噶尔盆地西北缘中段的克-百断裂带,晚二叠世以来发育了一系列后撤式逆冲断层。长期以来,关于克-百断裂带高角度逆冲断层的成因机制一直处于争论当中,后撤式逆冲断层的物理模拟在国内尚未见文献报道。论文通过地震解释研究了克-百断裂带的构造变形特征及其演化阶段;应用断层"活动性系数"理论,半定量地描述了挤压条件下断层"活动性系数"、摩擦系数与断层倾角之间的关系,证明了挤压条件下也能形成高角度逆断层;结合"造山楔"理论解释了后撤式逆冲断层的成因机制。研究认为,克-百断裂带后撤式逆冲断层是印支期、燕山期持续挤压和扎伊尔山隆升效应综合作用的产物:挤压过程中发生"泊松效应",随着断层倾角增大,断层面上的正压力迅速增大、"活动性系数"降低,当倾角增大到一个临界值后断层停止活动,形成高角度的逆断层;同时扎伊尔山隆升造成挤压应力上移,为断层的后撤奠定了基础。最后利用砂箱物理实验模拟了克-百断裂带后撤式逆冲断层的形成过程。  相似文献