26 resultados para Musschenbroek (P. v. van). album lui ayant appartenu

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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In this paper, we propose the dynamic P-V curve for modulator and P-I curve for laser diode, and present a simple approach to deriving the curves from the small-signal frequency responses measured using a microwave network analyzer. The linear response range, modulation efficiency, optimal driving conditions at different frequency can, therefore, be determined. It is demonstrated that the large-signal performance of electro-absorption (EA) modulator and the directly modulated semiconductor lasers can be predicted from the dynamic curved surface. Experiments show a good agreement between the evaluated characteristics and the measured large-signal performance.

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多线程并发是提高系统性能的常用手段,文章提出了一种用信号量的不对称P/V操作来设计多线程并发算法的新思路,这种思路适合于设计多线程同步程序以解决某些具有复杂同步语义要求的问题,而这些问题用传统的方法很难得到简洁高效的求解。为了演示这种新思路的特点和优点,笔者对几个常见问题(读写锁、排队锁和记录锁)给出了新的算法设计以及实现。实验数据表明,采用这种思路设计的算法在算法复杂度,读写速度和资源使用方面相对于传统的算法存在较大优势。

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通过对策勒绿洲的 4种杨树 (新疆杨、箭杆杨、胡杨和灰胡杨 )的P -V线和持水力的测定分析 ,得出了初步结论 :人工栽培种新疆杨和箭杆杨的抗旱性能低于乡土树种胡杨和灰胡杨

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A new compound [H(2)en](2)[H3O](6)[Co(H2O)(2)(VO)(8)(OH)(4)(PO4)(8)] has been hydrothermally synthesized. Single crystal X-ray analysis indicates that this compound crystallizes in a monoclinic system, space group P2(1)/n with a=1.438 5(3) nm, b=1.012 2(2) nm, c=1.832 5(4) nm, beta=90.21degrees, V=2.668 2 (9) nm(3), Z = 2, D-c = 2.112 g/cm(3), R = 0.055, wR = 0.149 7, S = 1.037. The structure of [H(2)en](2)[H3O](6)[Co(H2O)(2)(VO)(8)(OH)(4)(PO4)(8)] is characterized by P-V-O layers constructed by [(VO)4 (OH)(2)(PO4)(4)](6-) non-symmetric units. The P-V-O layers are pillared by [Co(H2O)(2)](2+) group, resulting in the channels within which the protonated diaminoethane and H3O+ are located.

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系统地综述了压力 -温度 -体积 ( p- V- T)性质在高聚物及其共混物中的应用 ,展示了 p- V- T在研究高聚物实际应用中的重要作用

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Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide. Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.

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This paper presents the electromagnetic wave propagation characteristics in plasma and the attenuation coefficients of the microwave in terms of the parameters n(e), v, w, L, w(b). The phi800 mm high temperature shock tube has been used to produce a uniform plasma. In order to get the attenuation of the electromagnetic wave through the plasma behind a shock wave, the microwave transmission has been used to measure the relative change of the wave power. The working frequency is f = (2 similar to 35) GHz (w = 2pif, wave length lambda = 15 cm similar to 8 mm). The electron density in the plasma is n(e) = (3 x 10(10) similar to 1 x 10(14)) cm(-3). The collision frequency v = (1 x 10(8) similar to 6 x 10(10)) Hz. The thickness of the plasma layer L = (2 similar to 80) cm. The electron circular frequency w(b) = eB(0)/m(e), magnetic flux density B-0 = (0 similar to 0.84) T. The experimental results show that when the plasma layer is thick (such as L/lambda greater than or equal to 10), the correlation between the attenuation coefficients of the electromagnetic waves and the parameters n(e), v, w, L determined from the measurements are in good agreement with the theoretical predictions of electromagnetic wave propagations in the uniform infinite plasma. When the plasma layer is thin (such as when both L and lambda are of the same order), the theoretical results are only in a qualitative agreement with the experimental observations in the present parameter range, but the formula of the electromagnetic wave propagation theory in an uniform infinite plasma can not be used for quantitative computations of the correlation between the attenuation coefficients and the parameters n(e), v, w, L. In fact, if w < w(p), v(2) much less than w(2), the power attenuations K of the electromagnetic waves obtained from the measurements in the thin-layer plasma are much smaller than those of the theoretical predictions. On the other hand, if w > w(p), v(2) much less than w(2) (just v approximate to f), the measurements are much larger than the theoretical results. Also, we have measured the electromagnetic wave power attenuation value under the magnetic field and without a magnetic field. The result indicates that the value measured under the magnetic field shows a distinct improvement.

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在用大口径、长焦距平行光管模拟激光远场特性时,其光组透镜在重力作用下的变形不能忽略,为了分析对出射光束质量的影响,采用有限元分析软件“ANSYS”建立了平行光管光组中声400mm平凸透镜的有限元模型,给出一种分析透镜轴向变形引起的波像差的方法,在不同工况下,计算了平凸透镜在重力作用下轴向变形的峰谷值和均方根值,对轴向变形量均方根值最小工况画出了透镜表面变形的等值线图,计算了声350mm通光口径内的波像差峰谷值和均方根值,对平行光管光组的波像差做出估计,验证了设计的合理性。

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在星间激光通信中,涉及对大口径衍射极限激光波面的检测,为保证测量精度,必须严格控制波面十涉仪镜子的自重和温度变形。采用有限元方法对大型干涉仪镜子在不同支承方式下的表面变形进行了分析,结果表明,接触角为180°的钢带支承是较好的支承方式,反射镜表面变形峰-谷(P-V)值仅为1.35nm,均方根(RMS)值为0.363nm根据这一结论,设计了一个同定支承点与浮动支承相结合的超静定钢带支承结构。在该结构下,分析了镜子轴向、径向、周向的温度梯度效应,分析数据表明,镜子的热弹性变形远大于自重变形,建议采取一定的温控

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The paper comprehensively analyzes the distortions of a circular wedge prism with 400 mm diameter in a scanner by method of optical-mechanical-thermal integrating analysis. The structure and intensity of the prism assembly is verified and checked, and the surface deformations of the prism under gravity load, as well as the thermo-elastic distortions of the prism, are analyzed in detail and evaluated, which is finally contrasted with the measured values of Zygo Mark interferometer. The results show: the maximal distortion of the prism assembly is 10 nm magnitude and the maximal stress is 0.441 Mpa, which has much tolerance to the precision requirement of structure and the admissible stress of material; the influence of heat effect on the surface deformations of prism is proved to be far greater than the influence of gravity load, so some strict temperature-controlled measures are to be considered when the scanner is used. (c) 2006 Elsevier GmbH. All rights reserved.

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等离子体平板显示(PDP)是目前高清晰度、大屏幕平板显示中的佼佼者,使挂壁彩电成为现实,但其关键部分之一-PDP荧光粉的发展却存在着相当滞后的问题,因此急需开发出性能更好的PDP荧光粉或对现有荧光粉的性能进行改善。改善PDP荧光粉性能的重要手段之一是选择合适的合成路径,因此本文探索了软化学合成方法-水热法在合成 PDP荧光粉合成中的应用,同时也采用高温固相法、共沉淀法对PDP荧光粉进行了合成,通过对比分析探索合成方法对PDP荧光粉光谱性质的影响。分别采用水热法、高温固相法、共沉淀法对掺杂稀土发光离子的稀土正硼酸盐(Y,Gd)BO_3、正磷酸盐(La,Gd)PO4、矾酸盐(Y,Gd)VO4、矾磷酸盐Y(PVO_4和硼硅酸盐LoBSIOS进行了合成,并用XRD、IR、SEM、XPSTG-DTA等手段对其结构进行了表征,对上述PDP荧光粉的真空紫外(VUV)光谱、紫外可见光谱及发射光谱性质进行了研究,得到了一些新的、有意义的结果。(1)首次采用水热法以稀土氧化物、氢氧化物或硝酸盐与硼酸为原料合成了(Y,Gd)BO_3:RE~(3+)(RE=Eu,Th)系列荧光粉,并对其VUV光谱特性进行了研究。sEM分析发现水热法以氢氧化物、硝酸盐合成的荧光粉粒度在100-200nm之间。XPS示不同基质中带结构具有一定的差异。光谱分析发现(Y,Gd)BO_3:RE~(3+)的VUV光谱中110-175nm范围内存在着基质硼酸根(B3场)的吸收带,该吸收带随基质中G矛"浓度的增大而增强并发生了红移,认为红移是由于基质中B-O反键轨道能量的变化引起的。对能量传递过程进行分析认为G矛十起到能量传递中间体的作用,使基质对激活剂的敏化效率随G矛十浓度的增大而提高。(Y,Gd)BO3:RE3+中基质敏化效率的提高也可能是由于基质敏化带的红移使Gd3十或RE3+更容易从基质中获得能量。我们认为作为PDP荧光粉Eu3+或Th3+在GdB03基质中的发光性能更好。对水热合成的(Y,Gd)BO3:Eu~(3+)荧光粉进行热处理发现,荧光粉的亮度随热处理温度的提高而明显增强,说明一定温度下热处理有利于提高荧光粉的发光性能,这可能是由于热处理后荧光粉的结晶度提高,内部缺陷减少。比较水热法、高温固相法和共沉淀法对荧光粉性质的影响时发现三种方法制备的荧光粉光谱特性基本一致,但高温固相法和共沉淀法制备的荧光粉粒度较大,形貌不规则。(2)采用水热法制备了不同G矛十浓度的PDP荧光粉(L a,Gd)Po4:RE3+(RE=Eu,Tb),发现以稀土硝酸盐溶液和伽玩)2HPO4为原料,在pH为5·240oC下反应3天可以合成出结晶度较高的纯相。从SEM照片中观察到水热法制备的荧光粉为晶化很好的棒状晶体。对水热法制备的LaP04:Eu3+和GdPO4:Eu3+进行热处理后发现热处理后晶体的尺寸变小,但形貌没有发生明显的变化,发光性能效果稍有提高。首次对共沉淀法合成的不同Gd3+浓度的(La,Gd)PO4:KE3+(RE=Eu,Tb)荧光粉的VUV光谱进行了分析,并研究了Gd3+在能量传递过程中的作用,发现随基质中Gd3十浓度的增大,基质对发光离子的敏化效率提高,认为Gd3+起着能量传递中间体的作用。同时观察到(La,Gd)PO4:Eu3+中电荷迁移带随着Gd3+浓度的增大而发生红移,这也可能会导致基质对Eu3+敏化效率的提高。首次利于xPs析了LaPO4和GdP04的价带结构,发现LaP04的价带由O2的2P级构成,而GdPo4的价带则是由O2-的2p级和Gd3+的4f能级共同构成,这种价带结构的差异可能对(La,Gd)PO4:RE3+在VUV区的吸收产生影响。(3)首次对水热法合成的(Y,Gd)VO4:Eu3+的VUV光谱进行了研究,观察到120-170nm范围内存在着vO43一离子团的弱吸收带,200nm处存在着来自2PO)→4f(Y)或5d(均跃迁的激发带,20onm以后的激发宽带是由Eu3+的电荷迁移带与VO43-的吸收带重叠而成的。对不同Gd3+浓度的(Y,Gd)VO4:E矿"的vLJ'v谱进行研究发现,在一定G矛+浓度范围内Gd3+的加入使基质vo43+对Eu3+的敏化效率提高。对(Y,Gd)VO4:Eu3+中的能量传递过程进行分析认为,(Y,Gd)vo4:Eus+中可能存在着VO_4~(3-)→Eu~(3+)和VO_4~(3-)(vuv)→Gd~(3+)→VO_4~(3-)(UV→Eu~(3+)等几种能量传递方式,Gd3+起着能量传递中间体的作用。(4)首次采用水热法合成了Y(PvO4:Eu3"红色荧光粉,发现初始体系pH12.5、在240℃下反应6天可以得到Y(PVo4:Eu3+纯相。结合XRD和SEM分析发现Y(PVO4:Eu3+荧光粉的粒径随VO3-4浓度的增大而增大,YPO4:Eu3+的粒径为100-150nm,而YVO4:Eu3+的粒径则为400-450nm。对水热法合成的Y(P VO4:Eu3+的VUV光谱进行研究发现基质对Eu3+的敏化效率随VO3-4户含量的增多而提高。通过比较发射光谱中~5D_0→~7F_2与~5D_0→~7F_1跃迁的强度发现二者强度之比随VO_4~(3-_浓度的增大而增大,说明荧光粉的色纯度随VO4含量的增多而更好。比较水热法和高温固相法合成的Y(PVO4:Eus"的VUV光谱发现水热法制备的荧光粉在真空紫外区的吸收较弱,说明水热法制备的荧光粉虽然粒度较小,形貌规则,但发光性能不如高温固相法制备的Y(P,V)O4:Eu3+荧光粉。(5)分别采用水热法和高温固相法制备了单掺稀土发光离子的LaBSIOS,并对它们的光谱性质进行了研究。通过比较产物的SEM照片发现水热法可以制备出粒度为2-3μm,形状近似于球形的产物,而高温固相法制备的样品形貌不规则,粒度分布范围广。对水热法制备的LaBSiO_5:Eu~(3+)进行红外光谱分析发现1300-400cm~(-1)范围内为BO_4基团和SiO_4基团的振动峰。首次对高温固相法制备的LaBSiO_5:Re~(3+)(RE=Eu,Sm,Th)的vuv光谱性质进行了分析,认为其VUV光谱中125-200nm范围内存在着BO_4基团的吸收带(125-165nm)和SiO4四面体的吸收带(165-183nm)。比较两种方法制备的荧光粉的光谱性质和亮度发现两种方法制备的荧光粉光谱性质基本一致,而水热法制备的LaBSiO_5:RE~(3+)(RE=Eu,Sm,Tb)在254nm紫外光激发下亮度相对较低。

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本论文由六部分组成第一部分文献综述,对近年来碱性染料-元素杂多酸显色反应的研究及其应用的进展情况作了介绍。第二部分研究了乙基罗丹明B与硅钼杂多酸 PVA存在下的显色条件,缔合物的最大吸收波长为584nm,在测量波长586nm处,ε_(586) = 3.4 * 10~5lmol·cm~(-1), 缔合物至少可稳定1小时,0~1.3μg Si(IV)/25ml Beer定律,只有P(V)、A(s)、Ge(IV)离子干扰严重,可采用酒石酸掩蔽之。从而提出了测定硅的高灵敏光度法。本法可不经分离直接用于水样及NaOH、NH_4G、NH_4NO_3等试剂分析,检测下限分别为10ppb(水样,5ml) 1 * 10~(-5)%(试剂,1g)。第三部分研究了乙基罗丹明B-磷钼杂多酸-PVA新的显色体系的光度测定条件,缔合物的最大吸收波长为584nm,在工作波长586nm下,ε_(586) = 3.2 * 10~5l·mol~(-1)·cm~(-1),配合物至少可稳定1小时,0~1.5μgP(V)/25ml服从Beer定律。藉提高酸度和还原剂以消除Si(IV)As(V)离子的干扰。本法可不经分离直接用于钢样及硫酸钠、硫酸镁试剂中痕量磷的测定,检测下限达1 * 10~(-5)%(试剂1g)。第四部分研究了乙基罗丹明B-锗钼杂多酸在PVA存在下的显色条件,缔合物最大吸收波长为584nm,在测量波长588nm下,缔合物的表观摩尔吸光系数ε_(588) = 3.8 * 10~5l·mol~(-1)·cm~(-1),0~1.5μg Ge(IV)/25ml服从Beer定律,缔合物至少可稳定2小时,仅P(V)、As(V) Si(IV)离子严重干扰。第五部分研究了缔合物的形成机理。我们用摩尔比法,等摩尔连续变化法及摩尔吸光系数对比法分别研究呈溶液或结晶状的缔合物组成比,所得结果一致,即Si(或 PGe):ERB=1:4。由红外光谱的研究证明,染料ERB~+的结构未受缔合物形成的影响。ERB~+阳离子与杂多酸阴离子是藉离子链力结合成离子对缔合物,并讨论了本类显色反应的历程。第六部分是罗丹明类碱性染料中取代基对缔合的稳定性及萃取率的影响的研究。对用苯萃取罗丹明类碱性染料-高氯酸缔合物体系,进行了吸收光谱、酸度影响、表现摩尔吸光系数、萃取率和萃取平衡常数的测定实验,各种缔合物的最大吸收波长分别为:BRB, 567nm; ERB, 567nm; R6G, 536nm; RB, 563nm。表观摩尔吸光系数分别为(l·mol~(-1)·cm~(-1):BRB, 9.86 * 10~4; ERB, 8.82*10~4;R6G, 4·0.3 * 10~4。萃取率分别为:BRB, 91.9%, ERB, 79.2%; R6G, 45.7%。萃取平衡常数分别为:BRB, 1.32 * 10~4; ERB, 1.14 * 10~3; R6G, 6.06 * 10~2。并用平衡移动法测定缔合物组成均为1:1。根据上述实验结果,从离子体积、憎水和亲水基、取代基的酸碱性及染料阳离子的正电性等四个方面对染料分子上不同取代基对缔合物稳定性、可萃性和溶解度影响进行了讨论,得到了一些规律性的认识:随着取代基体积增大、憎水基的引入和加重、碱性减弱、染料阳离子正电性的增加,均能使形成缔合物的稳定性和可萃性增加,其增加顺序为BRB > ERB > R6G > RB。

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蛇毒C一型凝集素样蛋白一般是由两个相似亚基组成的异构二聚体或由多个异构二聚体组成的多聚体。烙铁头蛇毒血小板活化素TMVA一个高分子量的C一型凝集素样蛋白。本文研究了烙铁头蛇毒C一型凝聚素样蛋白的生物活性及其作用机制。同时还从烙铁头蛇毒中分离到一个抗凝蛋白(mucroqucetin)。TMVA量效关系地诱导P和洗涤血小板聚集,提示其活化血小板并不调节v下或不依赖于vWF。抗人血小板糖蛋白(GPIb单克隆抗体HIPI剂量依赖性特异性抑制TMVA导的血小板聚集。抗人GPllb单克隆抗体PZ抑制血小板聚集。单克隆抗体和流式细胞术分析显示,FITC一TMVA异性地、剂量依赖性地结合到福尔马林固定的人血小板上,在FIIC-TMVA4O砚浓度时达到饱和性结合状态,这种结合被HIPI异性地抑制,并呈剂量依赖性。TMVA结合血小板GPIX、GPllb、GPllla、GPIa、GPlla和GPIV。Mocarhagin仅能部分阻断TMVA导的血小板聚集,然而TMVA能诱导mocarhagin阻断的血小板聚集。以上结果显示TMVAGPIbQ上的主要受体位于富含亮氨酸第二次重复区氨基酸残基59一81,除此之外,TMVA能还有其他结合位点。小鼠体内首次给予TMVA,在短时间内(15min-30min)引起循环血小板数及网织血小板百分率暂时性减低、血小板膜表面P-seleetin的表达暂时性增加,但循环血液中血小板一白细胞复合物未增加;抗鼠血小板单克隆抗体Pselectin、GPllb、GPlll。免疫组化染色显示脾和肺的组织巨噬细胞呈阴性反应,提示TMVA致循环血小板减少不是巨噬细胞系统对血小板的清除所致。可能是由于TMVA通过GPIb活化血小板后使P-selectin暴露于胞浆膜表面,这些脱颗粒的血小板在补体的参与下自身溶破,而导致快速的暂时性血小板减少。给予TMVA后组织病理学显示,肝、脾、肺、肾、胰、大肠及小肠血管未血栓形成;TMVA影响内源性和外源性凝血系统;TMVA剂量依赖性延长小鼠的出血时间,但在TMvA25pg时小鼠的出血时间未延长、仍小于5分钟,是一个安全的剂量。以上结果充分证明TMVA有体内抗血栓作用,血小板自身溶破导致血小板减少在体内抗血栓中可能也起到重要的作用。体内外实验显示TMVA动物体内外都具有抗补体活性作用。TMVA调血小板上DAF和CD59的表达,不同程度地上调白细胞上D胚和CDS夕的表达。TMVA补体系统中的作用可能与其在异种器宫移植中抗IIAR的发生相关。Mucroqucetin是一个由Q链和p组成的异二聚体蛋白质,其分子量为25KD。。N一末端氨基酸序列与其它该类蛇毒C一型凝集素样蛋白有很高的同源性。Mucroqucetin呈量效关系延长部分凝血活酶时间(APTT),几乎不影响凝血酶原时间(PT。因子IX和X的抑制试验显示,该纯化蛋白呈量效关系抑制工X因子的凝血活性,不影响X因子,提示mucroqucetin的抗凝活性主要通过结合FIX而实现,是一个血液凝固IX因子结合蛋白。

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Neutron irradiated high resistivity (4-6 kOMEGA-cm) silicon detectors in the neutron fluence (PHI(n)) range of 5 X 10(11) n/cm2 to 1 X 10(14) n/cm2 have been studied using a laser deep level transient spectroscopy (L-DLTS). It has been found that the A-center (oxygen-vacancy, E(c) = 0.17 eV) concentration increases with neutron fluence, reaching a maximum at PHI(n) almost-equal-to 5 X 10(12) n/cm2 before decreasing with PHI(n). A broad peak has been found between 200 K and 300 K, which is the result of the overlap of three single levels: the V-V- (E(c) = 0.38 eV), the E-center (P-V, E(c) = 0.44 eV), and a level at E(c) = 0.56 eV that is probably V-V0. At low neutron fluences (PHI(n) < 5 X 10(12) n/cm2), this broad peak is dominated by V-V- and the E-centers. However, as the fluence increases (PHI(n) greater-than-or-equal-to 5 X 10(12) n/cm2), the peak becomes dominated by the level of E(c) = 0.56 eV.

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植被破坏是造成塔克拉玛干沙漠南缘地区沙漠化严重发生的原因之一。研究植物的水分生理特性将为其恢复重建提供科学依据。本文在对塔克拉玛干沙漠南缘的四种荒漠植物(胡杨Popul us euphratica Oliv. 怪柳 Tamarixramosissima Ledeb.沙拐枣Calligonum caput medusae Schrenk.和骆驼刺Alhagi sparsifolia Shap.的生态生理学特性(清晨水势、水势日变化、PV线、茎流量、蒸腾速率、光合速率及水分利用效率)进行系统野外试验研究的基础上,经分析归纳,得出如下结论:(1)四种植物的清晨水势排序为:骆驼刺>沙拐枣>胡杨>怪柳。四种植物的水势日变化同其清晨水势有基本一致的趋势(2)四种植物平均光合速率的排序为:怪柳>胡杨>沙拐枣>骆驼刺;平均水分利用效率的排序为:沙拐枣>胡杨>怪柳>骆驼刺;(3)四种植物在低水势下保持膨压能力大小的排序为:怪柳>胡杨>骆驼刺>沙拐枣。其应对水分胁迫的共同反应是在细胞出现质壁分离时,保持高的体内含水量;(4)胡杨和怪柳的水分状况与水分的传输距离呈负相关关系。在对地下水传输距离的适应方面怪柳比胡杨表现出更强的适应性。(5)灌溉对怪柳幼苗的生长有利,而过量灌溉对于沙拐枣幼苗的生长不利。(6)在植被生长期内,四种植物没有受到严重的水分胁迫。植物的根系达到地下水位处并利用地下水。维持地下水位的基本稳定,是保证植被恢复重建的重要前提。本研究以欧盟合作项目和中国科学院策勒沙漠研究站为依托,结合当地实际,符合国家需求,在研究的系统性和区域水平性上属于首次。