一种长时延网络中移动节点间的时间同步算法

长时延网络的同步对于提升网络传输效率,增加网络吞吐量具有重要意义。现有用于长时延网络典型时间同步协议有TSHL,Tri-Message等,这些同步协议都是针对传播时延保持稳定或者保持短时稳定的长时延网络,但在实际情况中,有时传播时延会发生变化,如节点间相对位移的变化,如何在这样的长时延网络中进行时间同步也是一个值得研究的问题,文中提出了一种运用于长时延网络中移动节点间的时间同步算法,利用节点间多次的信息交互计算出传播时延变化的速率,然后对时延变化进行估算来进行时间偏移的补偿以达到时间同步。     

基于eXpress平台地层破裂压力预测参数的改进

利用eXpress平台处理Xmac测井资料对地层破裂压力进行预测的过程中,发现计算岩石力学参数程序中比奥特压缩系数常出现奇异值或断点.在实际应用中,比奥特压缩系数对其他力学参数、泥浆参数的求取和破裂压力的预测起着很关键的作用.经过多次试验发现通过增加1组泥岩参数值的方法可以得到新的比奥特压缩系数,利用改进后连续的比奥特压缩系数曲线就可以在很大程度上解决这个问题.根据改进后的岩石力学参数进行地层破裂压力的预测,并与实际施工数据进行了结果对比, 取得了较好的效果.     

地质断裂面分形性研究

通过现场勘察发现，地质断裂面的几何形态表现为粗糙起伏的不规则性质，这种性质可以用分形几何学描述。以阜新矿区刘家沟Ｆ１号地质断裂露头为窗口，研究断裂面的分形性质，研究表明，断裂面具有各向异性分形特征。     

岩石爆破损伤断裂中的逾渗行为

爆破载荷作用下岩石损伤演化具有明显的逾渗效应，采用逾渗模型来描述岩石爆破损伤断裂之一过程是可行的，提出了进一步可能的研究途径。     

Using a strain based failure assessment diagram for creep–brittle materials

Recently, there has been considerable interest in studying creep crack growth in creep–brittle materials. For example, the methodologies for assessing creep ductile materials, using fracture mechanics parameters like C^* and C_t, have been extended to include creep–brittle materials [1]. This paper begins by examining these recent developments and outlines the difficulties in adopting these developments. An alternative approach is then proposed. This new approach leads from recent work proposed by the authors [2], where a strain based failure assessment diagram (SB-FAD) is used. Experimental results from a series of tests on a simulated heat affected zone of a low alloy steel are explored. The application of the methodology for assessing the initiation and growth of a defect in a creep–brittle material is also demonstrated.     

Fracture behavior dependence on load-bearing capacity of filler in nano- and microcomposites of polypropylene containing calcium carbonate

The fracture toughness and deformation mechanism of PP/CaCO₃ (15 wt.%) composites were studied and related to load-bearing capacity of the particles. To alter the load-bearing capacity of the particles, different particle sizes (0.07–7 μm) with or without stearic acid coating were incorporated. The fracture toughness of the composites was determined using J-Integral method and the deformation mechanism was studied by transmission optical microscopy of the crack tip damage zone. It was observed that the load-bearing capacity of the particles decreased by reduction of particle size and application of coating. A linear relationship between normalized fracture toughness and inverse of load-bearing capacity of particles was found. The crack tip damage zone in composites, which consists in massive crazing, further grows by reduction in load-bearing capacity.     

Physically Based Failure Criterion for Dimensioning of Thick-Walled Laminates

The extreme lightweight potential of modern composites for the application in highly strained and thick walled components can only be sucessfully utilized with the help of adapted design procedures. Therefore, the stress and strain analysis of fibre reinforced components has experienced a tremendous improvement in recent years. The derived mechanical methods and the existing computing facilities are now capable of calculating complex and three-dimensional states of stress for single layers within laminated structures. The adequate development of appropriate failure criteria for the evaluation of such stress states has unfortunately not been promoted in the desired manner. In 1980, Hashin proposed a new generation of physically based failure analysis which could only be realized by a considerably increased numerical effort. Recently, Puck made a new attempt based on Hashin's concept using fundamental elements of the failure criterion by Mohr and Coulomb. Applying this model, the three-dimensional state of stress is evaluated in a realistic manner. It is assumed that besides the occurence of fibre failure only tensile stresses and shear stresses in loading planes tangential to the fibre direction induce the inter-fibre failure of the unidirectionally reinforced composite, whereas compressive stresses in these planes obstruct failure.     

Acoustic Harmonic Generation Due to Thermal Embrittlement of Inconel 718

This paper describes an attempt to characterize the deterioration of a structural material's mechanical properties by nonlinear acoustics. In this particular case, the damage was caused by “thermal embrittlement” during which the material, here the nickel-based alloy Inconel 718, loses a significant fraction of its fracture toughness. Harmonic generation was the experimental method used to characterize the microstructural changes in the material as a function of exposure time at elevated temperatures. Tests were performed on two heats of Inconel 718 with slightly different chemistries, with one heat showing particular sensitivity of the fracture toughness to the elevated temperature exposure with corresponding higher changes in the nonlinearity parameter. As a mechanical measure of the fracture toughness deterioration, a small specimen punch test was used in which the ductility of a thin slice of material is determined. A clear difference between the two heats was noted in the metallographic examination, which is reflected in the harmonic generation as well as the punch test data. An explanation for the changes of the harmonic generation during the embrittlement process is speculative at the present time.     

焊接用盘条拉拔断裂原因分析

对在拉拔过程中出现断裂的焊接用盘条进行化学成分和金相组织检测。原料表面裂纹、表面组织不均、贝氏体组织、成分偏析、夹杂物严重是引起焊接用盘条拉拔断裂的主要原因。轧制时采用1000℃加热温度,开轧温度在1050～1000℃,吐丝温度小于950℃,保持炉温均匀,控制辊道速度小于0.05m/s,吐丝后的冷却速度约为0.37℃/s可得到符合要求的盘条。     

棉型中空纱强度与PVA含量关系的研究

采用水溶性维纶纱线作纱芯,棉作外包纤维,在传统的环锭纺纱机上纺制棉包芯纱,溶去芯纱,制得棉型中空纱。并对棉型中空纱的强力与PVA含量的关系进行了试验、分析与讨论。其结果对中空纱的纺制有指导意义。