共查询到20条相似文献，搜索用时 187 毫秒
1.
The effect of fiber in asphalt mixtures has attracted general concern. For study of this problem, four kinds of fibers are chosen in this test. Asphalt and modified asphalt are adopted in asphalt mixtures AC-16I. The road performance influenced by additional fiber was analyzed impersonally,i, e. the stability of asphalt concrete under high temperature condition, anti-crack ability under low temperature condition, the water resistance and fatigue performance. It was shown through the research that the optimum asphalt content, air void rate, clearance rate of the mineral powder, saturation degree, and the flow value were increased and the density was decreased after adding the fiber. The road performance, such as the stability of asphalt concrete under high temperature condition, anti-crack ability under low temperature condition, water resistance and fatigue performance, was obviously improved,and the high temperature stability and fatigue performance improved most evidently. The fiber asphalt mixture performance reached and even exceeded the modified asphalt mixture performance. The modified asphalt performance after adding fiber would be improved more greatly. 相似文献
2.
Liu Boquan 《保鲜与加工》1996,(2):92-99
For the sake of setting up more rational damage criteria for RC structures based on the relationship between displacement amplitude after yielding and low-cyclic fatigue life, this paper Presents six RC columns test results focusing on development of cumulative damage and low-cyclic fatigue life varying with displacement amplitude and positive/ negative displacement ratio. On this basis, expression is provided to describe the relation between low-cyclic fatigue life and positive/negative displacements amplitude ratio under different displacement levels. 相似文献
3.
Zhao Kangjie Liu Bo 《保鲜与加工》1988,(2)
It is known that cylinder heads, exhaust manifoids, ingot molds, etc. are often failed resulting from thermal fatigue. For this reason, the influence of RE on the thermal fatigue behavior of cast iron was studied by measn of a thermal fatigue test unit with completely constrained strain developed by ourselves. The test results shown that RE can improve the thermal fatigue resistance of cast iron greatly when residual RE contents surpass a critical value. This value is 0.04-0.045% for light Rare-Earth, and 0.045-0.05%; for heavy Rare-Earth. Further more, the relationship between RE and the thermophysical and mechanical properties of cast iron which have influence on thermal fatigue resisteance was also discussed. 相似文献
4.
Aanandini Ganesalingam Alison B. Smith Cameron P. Beeck Wallace A. Cowling Robin Thompson Brian R. Cullis 《Euphytica》2013,190(3):371-383
Disease resistance is often measured as plant survival, which involves taking multiple counts of plants before and after disease incidence. Often, survival data are analyzed by forming a single derived variable, namely final counts expressed as a percentage of initial counts. In this study we propose a bivariate linear mixed model approach in which the two variables are the initial and final counts. This approach is demonstrated using data from nine blackleg disease nurseries in the 2009 growing season in Australia. Replicated experiments were grown at each nursery with a mixture of commercial Australian canola cultivars and breeding lines (collectively called ‘entries’) being tested. Plant survival was determined by counting all the seedlings at emergence and then recounting the number surviving at maturity in each plot. The counts were considered as two ‘traits’, which were log transformed prior to a bivariate linear mixed model analysis. Each trait had different error variances, spatial components (both local and global) and outliers. The variance of entry effects was non-zero for both traits at all locations. The correlation of entry effects between the traits ranged from 0.218 to 0.935 across locations. Best Linear Unbiased Predictors (BLUPs) of entry effects at both sampling times provided three possible indices for selection: (log) counts at emergence, (log) counts at maturity and the difference between these two which could be exponentiated to provide percentage survival values. Thus the bivariate mixed model approach for the analysis of plant survival data provided a more detailed picture of the impact of disease resistance compared with the univariate analysis of percentage survival data. Additionally the predicted entry effects for survival were more accurate in the bivariate analysis. 相似文献
5.
YANG Xi wu 《保鲜与加工》2008,(4):136-140
To prevent asphalt pavement from cracking under low temperatures and prolong its fatigue life, we tested the properties of a new type of steel fiber asphalt pavement. The tests evaluated Marshall stability, dynamic ruts, and cleavage strength under both low and normal temperature conditions. We also analyzed the anti-corrosion property of steel fiber and the factors affecting the properties of the steel fiber asphalt mixture. The steel fiber asphalt pavement was installed on a highway in Chongqing, P. R. China to investigate the construction art of the steel fiber asphalt mixture and examine its effect in field use. The test results and concrete use in the field show that the cleavage strength and flexibility of steel fiber asphalt concrete increase due to the action of steel fiber. We conclude that the anti-cracking capacity of asphalt pavement under low temperature conditions can be improved by steel fiber. The construction art of steel fiber asphalt pavement is the same as common asphalt pavement without the necessity of anti-corrosion processing for steel fiber. The research results are useful for pavement material selection in low temperature regions and heavy traffic road pavement designs. 相似文献
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High strain and low cycle fatigue(HSLCF)life of anti-seismic behaviors of rebars was investigaoted. Reliable theoretical basis was provided for data analysis on high strain and low cycle fatigue life of anti-seismic behaviors of rebars. The low cycle fatigue life of the HRB400 anti-seismic behaviors of rebars by quenching and self tempering (QST) process was tested. Because the low cycle fatigue life data was disperse, some kinds of mathematical statistics methods, such as Weibull double parameters probability function, normal distribution, lognormal distribution function and t-distribution function were used to statistically analyze the low cycle fatigue life data. The results indicate that in all of the probability functions, the low cycle fatigue life has the highest reliability by the t-distribution function method; the low cycle fatigue life has the lowest reliability by the normal distribution method; and the low cycle fatigue life has the highest safety by Weibull maximum likelihood method. 相似文献
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枯萎病是危害海岛棉生产的重要因素之一, 研究枯萎病抗性分子机制将为培育抗病海岛棉品种、解决枯萎病对海岛棉的危害问题提供坚实的基础。本研究在前期转录组测序的基础上, 对海岛棉枯萎病抗性差异表达基因进行分析(DEG, Differentially Expressed Gene); 以7个抗病性表现不同的海岛棉品种为材料, 利用qRT-PCR的方法研究抗病差异表达基因在不同接菌时间点的表达量差异, 并分析基因表达量与病情指数的相关性。结果表明, DEG分析得出类黄酮代谢通路相关基因与海岛棉枯萎病抗性有关。qRT-PCR分析显示抗病材料中类黄酮代谢通路关键基因的表达量显著高于感病材料。在接菌后多个时间点, 类黄酮代谢通路中的关键基因TT7、CHI和DFR在抗病材料中的表达量显著或极显著高于感病材料, 其中CHI和DFR基因的表达量与病情指数呈显著负相关。综上所述, 类黄酮代谢通路相关基因对海岛棉枯萎病抗性均有影响, 且CHI、TT7和DFR基因是关键基因。 相似文献
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根据框架结构耗散塑性变形能与存储弹性变形能能力的损失界定结构的整体损伤,根据塑性铰耗散塑性变形能能力的损失来界定局部损伤,并以拟力法为基础推导了局部损伤与整体损伤的解析表达式,进而讨论框架结构局部损伤与整体损伤的相关性。研究表明,控制框架结构整体损伤的手段有：减小局部损伤区域的强度衰减、提高局部损伤区域的极限转动能力和减小局部损伤区域的残余变形。其机理是通过提高局部损伤区域的耗能能力与约束能力来提高整个结构耗散与存储地震能量的能力;框架结构整体损伤与局部损伤的加权值较为接近,可以采用框架局部损伤的加权值来近似估计结构的整体损伤值。 相似文献
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利用相似材料模拟高速铁路隧道基底软岩,采用荷载控制和非对称正弦波循环加载方式对软岩试件进行动三轴疲劳与损伤检测综合试验。通过试验结果分析,建立了软岩3参数多项式疲劳寿命计算模型和4参数多项式累积损伤参量计算模型,获得了软岩疲劳损伤特性,即：软岩疲劳破坏表现为端部拉-剪复合破坏和中部压-剪复合破坏两种模式;疲劳破坏全过程表现为初始微孔隙压密、裂纹发生与稳定扩展以及损伤裂纹加速发展3个发展阶段;软岩疲劳寿命主要取决于本身强度和动应力水平,强度愈高、动力应力水平愈低,其疲劳寿命就越长;当动应力水平相同时,软岩疲劳寿命与其弹性模量呈线性增长关系。 相似文献
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为了解山东地区不同类型牛奶中金黄色葡萄球菌流行情况和耐药特征,对37个牧场的乳房炎和非乳房炎奶样进行细菌分离鉴定及MIC测定试验。采用常规方法与PCR技术进行金黄色葡萄球菌的分离鉴定,微量肉汤稀释法进行MIC测定,卡方检验进行数据差异显著性分析。①共分离到150株金黄色葡萄球菌,检出率为11.26%(150/1332),且乳房炎奶样显著高于非乳房炎(P=0.009);②12种药物的MIC与EUCAST分布趋势大致相同;③分离菌株对青霉素(91.38%)耐药最严重,且乳房炎/非乳房炎奶样差异显著(P=0.047);④116株分离菌株中多重耐药(≥3)菌株为34(29.31%)株,乳房炎/非乳房炎奶样差异不显著(P=0.611);⑤威海对6种药物的耐药率在60%以上,其他地区仅对1~2种药物的耐药率在50%以上。乳房炎奶样的金黄色葡萄球菌检出率显著高于非乳房炎;分离菌株对青霉素严重耐药且乳房炎奶样多重耐药问题突出;不同地区均呈现不同程度的耐药。 相似文献
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为了解低磷胁迫下不同磷利用效率玉米叶片在光能的吸收、分配和过剩激发能的耗散方面的差异,以利用细胞工程技术获得的不同磷利用效率玉米齐319 和Qi319-96 为材料,采取水培的方法,研究了低磷(KH2PO4 5 μmol/L,-P)和正常供磷(KH2PO4 1000 μmol/L,+P) 2 个供磷水平对玉米叶片的光合作用及叶绿素荧光参数的影响。结果表明：低磷胁迫下突变体齐319-96 叶片的光能转换和电子传递效率高于玉米自交系齐319;突变体齐319-96 叶片吸收的光能用于光化学反应部分显著高于齐319;通过天线热耗散部分的能量低于齐319;二者通过其他途径耗散过剩光能的部分差异不显著。叶片通过活性氧清除系统对过剩光能耗散作用在自交系齐319 和突变体齐319-96 间差异不显著。低磷胁迫下与齐319 相比,突变体齐319-96 叶片中的无机磷含量显著提高。与自交系齐319 相比低磷下自交系齐319-96具有更高的光能利用效率和碳同化速率,推测不同磷效率玉米自交系之间光合特性差异与叶片中无机磷含量的差异有关。 相似文献
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Under seismic action, the damage of critical regions in ductile reinforced concrete structures can be regarded as combined results of cumulative damage caused by positive/ negative displacements with different displacement levels after yielding. On the basis of symmetric low-cyclic fatigue experiments on eight half-scale RC columns under different displacement levels, the development of cumulative damage and relationships between low-cyclic fatigue life and symmetric displacement amplitude are investigated. It is hoped that on this ground, more rational damage criteria for RC structures can be put forward. 相似文献
14.
By four-point bending test and fatigue test,the authors studied the flexural toughness and fatigue property of semi-rigid base course of cement-stabilized macadam with and without polypropylene(PP) fiber.Some significant data about these two kinds of material have been obtained,such as the load-deflection curves,toughness index according to the standard methods of JCI and ASTM C1018-97,the fatigue lifetime under different stress levels and the fatigue lifetime regression equation.The results show that the reinforcing effect of the PP fiber is remarkable;the bending strength,ultimate deformability,JCI toughness index,ASTM C1018-97 toughness index and fatigue life of cement-stabilized macadam with PP fiber are increased by about 10%,150%,67.7%,36.1%~79.8%,and 126%~352%,respectively,when the volume fraction of PP fiber is only 0.077%.At the same time,the authors revealed the toughness improving mechanism and the anti-fatigue mechanism of the fiber in such material based on the fracture mechanics theory. 相似文献
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Pearlitic steel is composed of numerous pearlitic colonies with randomly distributed orientations,and each colony is composed of many alternatively arranged parallel lamellas of ferrite and cementite.The pearlitic steel with fine interlamellar spacing possesses excellent mechanical properties,such as high strength,good resistance against wear,and high fatigue life,etc. Based on the inconsistency of the deformation between the two phases,a strain_equivalent and non_local constitutive model is proposed. Using this model,the effect of the interlamellar spacing of peailitic steel,a fundamental parmeter of the microstructure of pearlitic material, on its macroscopic mechanical behavior can be described without changing the local material parameters for each phase of the material.The asymmetrical cyclic plasticity of both the hot_rolled and the off_line full_length quenched pearlitic steel PD3 is analyzed.The comparison between the computational and the experimental results shows satisfactory agreement. 相似文献
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针对平面应变条件下各向异性砂土剪切带角度的试验规律,采用传统的3种理论和分叉理论进行对比分析。将平面应变条件下剪切带角度的试验结果按照传统3种理论整理发现,尽管传统3种理论可以估算同种砂剪切带角度的极小、中间和极大值,但无法解释其各向异性规律。砂土在平面应变条件下破坏时会产生明显的剪切带,当剪切带方向和砂土沉积面方向接近时,会较早诱发剪切带的产生,使材料强度降低,造成了平面应变条件下各向异性强度规律明显不同于常规三轴条件下的试验规律,采用分叉理论结合各向异性模型则可以有效解释这个规律。随砂土沉积面角度的变化,模型可以从细观角度解释常规三轴条件下剪切带角度的单调变化的试验规律,结合分叉理论可以描述平面应变条件下其先减小然后增大的规律。通过几种理论对比分析表明,模型结合分叉理论不但能够描述多种应力状态下的平面应变和常规三轴应力条件下剪切带角度表现的不同规律,而且能够从细观角度解释其各向异性成因。 相似文献
17.
The inheritance of resistance to head blight caused by Fusarium culmorum in winter wheat 总被引：8，自引：0，他引：8
C.H.A. Snijders 《Euphytica》1990,50(1):11-18
Summary Crosses were made among ten winter wheat genotypes representing different levels of resistance to Fusarium head blight to obtain F1 and F2 generations. Parents, F1 and F2 were inoculated with one strain of Fusarium culmorum. Data on incidence of head blight 21 days after first inoculation were analyzed. Broad-sense heritabilities averaged 0.39 and ranged from 0.05 to 0.89 in the individual F2 families. The joint-scaling test indicated that the inheritance of Fusarium head blight resistance was adequately described by the additive-dominance model, with additive gene action being the most important factor of resistance. With respect to the non-additive effects, dominance of resistance predominated over recessiveness. The number of segregating genes governing resistance in the studied populations was estimated to vary between one and six. It was demonstrated that resistance genes differed between parents and affected resistance differently. 相似文献
18.
干旱胁迫对假俭草气体交换和叶绿素荧光特性的影响 总被引：2，自引：1，他引：1
以假俭草为实验材料,研究干旱胁迫对假俭草气体交换、叶绿素荧光的影响。结果表明,干旱胁迫使假俭草净光合速率（Pn）和气孔导度（Gs）明显下降,胞间CO2浓度（Ci）也略有下降,说明Pn的下降是气孔因素和非气孔因素共同作用的结果。干旱胁迫使得PSⅡ反应中心捕获激发能效率（F′v/F′m）和光化学猝灭（qP）降低,从而引起电子传递速率（ETR）的降低。干旱胁迫后,假俭草非光化学猝灭（NPQ）和反应中心过剩激发能（Ex）明显上升,说明假俭草天线色素尽管可以耗散部分能量,但不能及时地有效地耗散过剩激发能,从而使假俭草发生明显的光抑制。 相似文献
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根据吊索镀锌钢丝腐蚀疲劳破坏特点,把镀锌钢丝腐蚀疲劳纹形成和扩展过程分解成镀锌层腐蚀失效、蚀坑萌生、蚀坑形成、短裂纹扩展、长裂纹扩展和断裂破坏等阶段,建立各阶段时间表达式,得到镀锌钢丝疲劳寿命表达式,提出基于断裂力学的吊索钢丝腐蚀疲劳寿命评估研究结果方法。通过算例分析复杂运营条件下腐蚀环境和应力幅等因素对吊索钢丝腐蚀疲劳寿命的影响,研究结果表明：吊索钢丝腐蚀疲劳寿命主要由钢丝镀锌层腐蚀、蚀坑发展和短裂纹扩展等3个阶段组成,为了准确地评估吊索腐蚀疲劳寿命,需要掌握大桥的运营环境和交通荷载。 相似文献