多轴应力状态下脆性材料统计断裂判据的研究

应用统计断裂理论,用分币裂纹模型模拟材料中的缺陷,通过用裂纹面的法向矢量反映材料中裂纹面的随机取向,用等效应力代替实际应力状态的破坏效应,提出了多轴应力状态下脆性材料统计断裂的判据。判据反映了结构的破坏强度与其所受的应力状态、破坏概率及材料的性能参数之间的联系关系。通过判据可得出对当前研究成果的一些合理解释,最后用判据的预测与实验数据进行比较,结果较吻合。     

工程控制理论在规则断裂中的应用

从裂纹技术的需要出发 ,根据工程控制理论和断裂力学的基本原理 ,对控制规则断裂过程做了初步的理论分析 .建立了数学模型和基本分析模型 ,讨论了规则断裂过程的稳定性 ,并用能量法建立裂纹扩展的稳定性判据     

广义塑性区尺寸因子断裂判据

本文从广义Mises屈服准则出发,建立了一个新的复合型断裂判据—广义塑性区尺寸因子判据。通过选择判据中的参变数α,可望得到与工程实际更加相符的断裂判据。该判据还可用来求解三维裂纹问题。     

结构非概率可靠性模型在断裂力学分析中的应用研究

工程实际中的构件或材料由于不可避免地存在缺陷或裂纹,其强度大大低于理想模型的强度.考虑含裂纹结构的性能参数、几何参数及作用载荷、缺陷特征等的不确定性的可靠性分析具有重要的工程实际意义.针对大型、贵重构件或材料样本数据少、统计信息缺乏的情况,提出了含缺陷结构断裂失效的非概率可靠性分析方法.对非概率可靠性度量方法进行了分析、比较,由于以断裂判据建立的功能函数往往为多维非线性方程,针对非概率集合可靠性模型的计算困难,提出用Monte-Carlo模拟方法计算非概率可靠度具有易实现、精度高的特点.本文方法克服了概率断裂力学(PFM)方法需要大量统计数据的局限性,具有重要的工程应用价值.实例分析对本文方法的可行性和有效性进行了验证.     

压剪复合应力强度因子和混凝土压剪断裂判据

含裂纹构件在压剪荷载作用下,裂纹面将闭合.本文在对裂纹前缘应力场的奇异性分析后,得出裂纹尖端只存在K_Ⅱ的结论.试验研究表明,混凝土在压剪情况下的破坏仍符合库仑-莫尔准则.因此,本文对压剪断裂提出了考虑裂纹面闭合和材料内摩擦双重影响的判据:在起裂时,是纯Ⅱ型扩展;其后是沿裂纹扩展方向剪断;并给出两个判据式.经8组单边裂纹压剪试样的试验验证,结果是令人满意的.     

运动裂纹止裂判据的一种新提法

从断裂动力学问题的非线性性质和能量观点出发，讨论了运动裂纹止裂判据的正确提法；指出了目前广泛使用的运动裂纹止裂判据的不适当性；提出了一种新的运动裂纹的止裂判据．研究表明，裂纹失稳扩展时存在一个极小的速度值     

热成形韧性断裂判据的建立及应用

针对大锻件设备或配件在热成形过程中产生的裂纹缺陷，采用热力学实验方法，研究了以50＃钢为代表的热裂行为.结果显示：临界断裂应变与变形温度和应变速率呈函数关系.基于热裂行为分析和损伤力学理论，提出了预测裂纹发生的韧性断裂判据.将判据应用于不同变形条件下的镦粗试验，能够较好地预测裂纹发生时所对应的压下量及裂纹产生的位置，并通过嵌入不同判据预测镦粗过程中的开裂.结果表明：所建立判据对于大锻件高温热成形过程的开裂现象具有更高的预测精度.     

平面复合型疲劳裂纹扩展问题

本文要解决的是平面复合型疲劳裂纹扩展方向以及疲劳寿命的预测问题。主要内容如下: 1.提出“等双剪应力线上δθmax平面复合型裂纹开裂判据”。与其它判据相比较;本判据所预测的裂纹开裂方向更接近于疲劳裂纹扩展试验的结果。2.文中指出:是Z形裂纹的分支方向,而不是其主裂纹方向,在Z形裂纹的KⅠ,KⅡ值中起着支配性的作用。接着提出二个计算Z形裂纹应力强度因子的近似方法。3.为预测复合型疲劳裂纹扩展的寿命,文中提出了一个新的裂纹扩展速率表达式,即折合张应力强度因子指数公式。此式所预测的寿命较接近于实验值。最后,还讨论了应用主应力强度因子K*,应变能释放率G,应变能密度因子S,预测复合型疲劳裂纹扩展的寿命问题。     

运动裂纹止裂判据的一种新提法

从断裂动力学问题的非线性性质和能量观点出发讨论了运动裂纹止裂判据的正确提法，指出了目前广泛使用的运动裂纹止裂判据的不适当性，提出了一种新的运动裂纹的止裂判据。研究表明，裂纹失稳扩展时存在一个极小的速度值。     

脆性材料复合裂纹断裂判据研究

研究了混凝土等拉压强度不等的脆性材料在平面应力和平面应变情况下裂纹附近的塑性区的范围，并给出了相应的表达式；运用在一定外力作用下物体内等效应力作为断裂判据，推测含复合裂纹的脆性材料的裂纹扩展时的临界条件相扩展方向，计算了试件在6个不同裂纹角时断裂角的大小，其结果与最大周向正应力理论判据、最小应变能密度理论判据及实验结果比较，说明用最小等效应力作为含复合裂纹的脆性材料的裂纹断裂判据是可行的．     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

Quality traits in wheat （Triticum aestirum L.） were studied by quantitative trait locus （QTL） analysis in a recombinant inbred line （RIL） population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross （ChSh）. Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.