Relationship Between Dynamic and Static Value of Elastic Modulus in Rock

Taking the deposited-layer rock and compacted-layer rock as study target,by elastic wave experiment and uniaxial compression experiment,the physics mechanics parameters and acoustics parameters of these rock are worked out; Based on it, by the correlativity is established between dynamic and static value of elastic modulus in rock of different lithology taking nonlinear fitting,it offers reference for the study of the drill and measuring well in the exploitation of oil. Influenced by the integrality and weathering breakage degree of rock,the biggish different is existed between dynamic elastic modulus gained by dynamical method and static elastic modulus obtained by static method,and the relationship between dynamic and static value of elastic modulus is approximatively expressed as a relationship of quadratic polynomial function.     

基于微钻阻力的落叶松弹性模量快速检测

以落叶松(Larix gmelinii)新鲜材、古建筑旧材为试验材料,运用微钻阻力仪对其内部的微钻阻力进行了快速检测,分析微钻阻力与两种落叶松材弹性模量之间的相关性及利用微钻阻力快速评估木材弹性模量的可行性.结果表明,对于新鲜落叶松材料,其微钻阻力检测值与弹性模量呈显著线性相关,可以利用微钻阻力较好地评估其弹性模量,且二者相关系数为0.831 9;对于古建筑的落叶松材料,利用微钻阻力快速检测弹性模量的精度则相对较差,二者相关系数为0.341 5,需结合其他检测指标综合进行判断.     

林木根系单根的生物力学特性

以黄土高原半干旱区17年生的刺槐(Robinia pseudoacacia)人工林和17年生的侧柏(Platycladus orientalis)人工林为对象,通过单根拉伸试验研究了根系的抗拉强度和杨氏模量.结果表明,刺槐根与侧柏根的生物力学特性表现出显著的尺度效应.根系的抗拉强度与杨氏模量都随直径的增大而减小,且刺槐根的强度约是侧柏根的2倍.     

Sensitivity Analysis of Cantilever Box Beam Temperature Effects Based on the Prestressed Concrete Parameter Changes

On the construction of large-span prestressed box beam Cantilever, the parameter frequent changes in concrete modulus E, coefficient of thermal expansion α.In a certain temperature case, the change of concrete parameters will cause the changes on internal stress and strain of the bridge and the difference of the changes will affect the bridge safety. Accordingly,based on a bridge cross-section of a temperature field and combined with the actual bridge construction, give concrete Cantilever bridge parameters change, calculated and analyzed the sphere of influence of parameters on the stress and strain fields of bridge, asked the law of sensitivity on stress changes. Summarize the sensitivity factors of temperature stress which is used to improve bridge safety.     

Response to drought and salt stress of lemon ‘Fino 49’ under field conditions: Water relations,osmotic adjustment and gas exchange

Drought and salinity are two of the most important factors limiting the lemon yield in south-eastern Spain. The effects of drought and salt stress, applied independently, on water relations, osmotic adjustment and gas exchange in the highest evapotranspiration period were studied to compare the tolerance and adaptive mechanisms of 13-year-old ‘Fino 49’ lemon trees, in immature and mature leaves. The study was carried out in an experimental orchard located in Torre Pacheco (Murcia). Three treatments were applied: Control, well-irrigated; drought-stress (DS), non-irrigated from 15th May to 7th July and salinity, irrigated with 30 mM NaCl from 1st March to 7th July. At the end of the experiment, only DS trees showed a decreased leaf stem water potential (Ψ_md). Under DS conditions, both types of leaf lost turgor and did not show any osmotic or elastic mechanism to maintain leaf turgor. Osmotic adjustment was the main tolerance mechanism for maintenance of turgor under salt stress, and was achieved by the uptake of Cl⁻ ions. Gas-exchange parameters were reduced by DS but not by salinity, stomatal closure being the main adaptive mechanism for avoidance of water loss and maintenance of leaf turgor. Salinity gave rise to greater Cl⁻ accumulation in mature than in immature leaves. The increase of proline in immature leaves due to DS indicates greater damage than in mature leaves.     

场地土动剪模量的试验对比研究

由于土动力参数的不同，土动力计算分析的结果将有一定差异，为更合理的取得地基一基础一上部结构相互作用体系动力特性研究的野外大比例模型试验的场地土的动力特性，在100kPa，200kPa，300kPa3种固结压力下，分别进行了原状土样的循环单剪试验、扰动土样的动三轴试验，得到了2种试验在3种固结压力下的最大动剪模量Gdmax和G／Gdmax-γ，曲线，并进行了对比分析．结果表明，循环单剪试验得到的原状土的Gd一比相同固结压力下的扰动土的动三轴试验值稍低；100kPa和200kPa固结压力下原状土的循环单剪试验得到的动剪模量比G／Gdmax大于相应的扰动土的动三轴试验值，而300kPa固结压力下原状土的循环单剪试验得到的G／Gdmax却小于相应的扰动土的动三轴试验值。     

Influence of trypsin on the dynamic mechanical properties of intact RBC membrane

AIM: To study the influence of trypsin on the membrane dynamic mechanical properties and the surface charge density of single living intact red blood cell (RBC). METHODS: Young and old RBCs were separated from health adult human blood using the density gradient centrifugation. Then RBCs at different ages were incubated with trypsin at different concentration at 37 ℃ for 60 min. The surface negative charge density of RBCs was determined using ZetaPLUS potential analyzer. The size and membrane bending elastic modulus (Kc) and shear elastic modulus (μc) were determined by fast micro-image analyzing technology. RESULTS: (1) The surface negative charge density of normal and trypsin-treated old RBCs was significantly lower than those of normal and trypsin-treated young RBCs respectively (P<0.01). (2) The contact area of normal old RBCs was significantly smaller than that of normal young RBCs(P<0.05), but there was no difference in shape between normal young RBCs and normal old ones. Trypsin reduced the size of RBCs but did not affect the shape and size of both young and old RBCs. (3) The Kc and μc of normal old RBCs membrane were markedly larger than those of normal young RBCs respectively (P<0.05). The Kc and μc of young and old RBCs membrane were both increased at different concentration of trypsin. CONCLUSION: The surface negative charge density of young and old RBCs decreases, and the membrane elastic modulus of young and old RBCs membrane increases after treatment with trypsin. Therefore, the mechanical deformability of RBCs membrane is reduced.     

早园竹的力学性能特点及测试方法研究

通过该项研究结果表明,采用3点弯曲方法与顺纹压剪方法测定的竹材弦面剪切强度所得结果有着良好的拟合性;早园竹的力学性能在三度竹时达到最高峰,四度竹的弹性模量显著下降,抗弯强度和弹性模量略有下降;采用3种方法测试(沿竹青方竹黄和弦向加压)结果表明,3种测试数值结果具有良好的相关性。对早园竹采用不同测试方法所得的力学结果表明,对小径级竹材可以参照单向纤维增强材料的方法测定其力学性能,为小径竹材力学性能测试以及相关标准的制定提供可以借鉴的方法。     

黄土高原水蚀风蚀交错区不同下垫面土壤水蚀特征实验研究

以位于黄土高原水蚀风蚀交错区的神东矿区为研究基地,以黄土、沙黄土、风沙坡、基岩风化坡地、人为弃矿渣为物质基础,采用野外人工模拟降雨的方法,重点分析不同组成物质和同一物质不同固结程度斜坡地的土壤水蚀特征。对系列实验数据,应用SPSS和DPS数据处理系统进行分析。结果表明:①在条件相近的情况下,场降雨侵蚀模数的排序为:黄土>沙黄土>沙坡>弃矿渣>风化壳;②在相同的雨强和坡度条件下,黄土坡面产流快,易形成细沟、浅沟,使坡地变得起伏不平;沙黄土坡面则产流慢,形成沟谷的时间较迟,但演化快。③多石块的粗骨性风化壳侵蚀量随降雨强度的增加而增加,但产沙过程却以产流初期最大,之后趋于减少并稳定;④同一物质不同堆积年限的坡地,在没有人为破坏的情况下,随着堆积年限的增加而固结程度提高,侵蚀模数由16 379 t/（km²·a）下降到1 227 t/（km²·a）。⑤弃矿渣坡地的侵蚀容易出现滑塌和滑坡,产沙过程波动明显,有短暂的高含沙量的泥石流过程。     

竹材梯度结构对弯曲力学性能的影响

竹材梯度结构对力学性能影响显著，尤其是在弯曲应力下，更呈现明显的非对称行为。文章对竹材梯度结构进行详细解析，提取了维管束形状、纤维鞘面积、维管束梯度变化规律等多个梯度因子，然后对其弯曲力学性能进行测试，解析竹材梯度结构因子与弯曲力学性能之间的关系，阐明梯度结构对弯曲力学的影响机制。结果发现，毛竹维管束沿径向梯度分布的曲线属于下凹型曲线，梯度分布指数n=2.28；从竹青到竹黄，维管束长径比呈现明显下降的趋势，靠近竹青侧的维管束长径比较大，靠近竹黄侧的维管束长径比较小，形状更趋近于圆形；对比了竹黄侧加载和竹青侧加载2种模式下的竹材弯曲力学性能，当竹青侧受压、竹黄侧受拉的情况下，竹材的弯曲韧性最好；当竹青侧受拉、竹黄侧受压的情况下，竹材的弯曲模量最大。