基于全U网络的混凝土路面裂缝检测算法

针对现有的混凝土裂缝检测算法在各种复杂环境中检测精度不够、鲁棒性不强的问题,根据深度学习理论和U-net模型,提出一种全U型网络的裂缝检测算法。首先,依照原U-net模型路线构建网络;然后,在每个池化层后都进行一次上采样,恢复其在池化层之前的特征图规格,并将其与池化之前的卷积层进行融合,将融合之后的特征图作为新的融合层与原U-net网络上采样之后的网络层进行融合;最后,为了验证算法的有效性,在测试集中进行实验。结果表明,所提算法的平均精确率可达到83.48%,召回率为85.08%,F1为84.11%,相较于原U-net分别提升了1.48%,4.68%和3.29%,在复杂环境中也能提取完整裂缝,保证了裂缝检测的鲁棒性。     

Constructing developable surfaces by wrapping cones and cylinders

We model developable surfaces by wrapping a planar figure around cones and cylinders. Complicated developables can be constructed by successive mappings using cones and cylinders of different sizes and shapes. We also propose an intuitive control mechanism, which allows a user to select an arbitrary point on the planar figure and move it to a new position. Numerical techniques are then used to find a cone or cylinder that produces the required mapping. Several examples demonstrate the effectiveness of our technique.     

Thermal Bending Analysis of Doubly Curved Composite Laminated Shell Panels with General Boundary Conditions and Laminations

Thermal bending analysis of doubly curved laminated shell panels with general boundary conditions and laminations is presented. The equations of equilibrium are derived in the form of two coupled sets of ordinary differential equations based on a general shell theory and solved through the state-space approach in a repeated manner. It is depicted that the results of the present method are in great agreement with analytical solutions. Cylindrical shell panels with general boundary conditions and laminations, where no analytical solution is available, are solved. It is found that the present method exhibits a high convergence rate as well as presenting accurate results in all cases.     

Bulging in incremental sheet forming of cold bonded multi-layered Cu clad sheet: Influence of forming conditions and bending

Bulge is a defect that causes geometrical inaccuracy and premature failure in the innovative incremental sheet forming (ISF) process. This study has two-fold objectives: (1) knowing the bulging behavior of a Cu clad tri-layered steel sheet as a function of forming conditions, and (2) analyzing the bending effect on bulging in an attempt to identify the associated mechanism. A series of ISF tests and bending analysis are performed to realize these objectives. From the cause-effect analysis, it is found that bulge formation in the layered sheet is sensitive to forming conditions in a way that bulging can be minimized utilizing annealed material and performing ISF with larger tool diameter and step size. The bending under tension analysis reveals that the formation of bulge is an outgrowth of bending moment that the forming tool applies on the sheet during ISF. Furthermore, the magnitude of bending moment depending upon the forming conditions varies from 0.046 to 10.24 N·m/m and causes a corresponding change in the mean bulge height from 0.07 to 0.91 mm. The bending moment governs bulging in layered sheet through a linear law. These findings lead to a conclusion that the bulge defect can be overcome by controlling the bending moment and the formula proposed can be helpful in this regards.     

一种弯曲抽油杆打捞工具

为安全、快速、有效地解决顶部极度弯曲、径向变形尺寸很大的落井抽油杆打捞难题,研制了一种在套管内打捞弯曲抽油杆的工具。该工具把以往从落物顶端引入打捞改为从落物侧面引入打捞,使复杂的井下故障处理简单化,从而缩短修井周期,减少修井费用,及时恢复油井生产。该项技术先后在江苏油田6口油井上应用,成功率100%,验证了工具的独特性和可靠性。     

径向水平井弯曲转向机构影响因素仿真研究

针对径向水平井钻进中钻杆弯曲转向前进运动困难的问题,通过建立弯曲转向机构仿真有限元模型,对其主要影响因素:滑道轨迹曲率、间隙、工作压力、滚轮形状与位置和钻杆壁厚等用ANSYS软件进行仿真研究。研究表明:影响截面变形的主要因素是滑道曲率的改变和滑道摩擦因数,钻井失败时钻杆所受阻力的增大不是因为升高工作压力导致截面变形过大与滑道干涉所致,钻杆经校直段,钻头中轴线与校直中心线存在一定的角度,即钻杆的前进轨迹就会偏离理论值,或与地层干涉,或可能再次发生弯曲变形;另一主要原因是转向器滑道工作恶化。增加钻杆壁厚,降低工作压力和滑道摩擦因数,设计合理弯曲转向机构是解决问题的关键。     

两种基于弯曲损耗的光纤测试仪器原理及应用

光纤通信技术的飞速发展带动了光纤测试仪器的发展。主要对两种利用弯曲损耗对光纤进行检测的仪器——光纤识别仪、光纤对线器的原理、结构及其在光纤通信工程中的应用进行了阐述，两种仪器可以在不中断光纤通信的情况下对光纤进行检测，极大地降低了对光纤通信系统的影响，对光纤通信系统具有重要意义。     

具有初始弯曲转子振动峰值的控制方法

本文从理论上研究了控制初始弯曲引起的转子振动幅值的一种新方法。通过在与转轴初始弯曲方向成较大夹角的方向添加不平衡质量的方法 ,使转子新的不平衡方向与初始弯曲方向夹角接近 180° ,则可以减小转子在临界转速附近的振幅。无论新的不平衡参数大于或小于初始弯曲参数 ,只要新的不平衡参数不至于太大 ,则临界转速附近的振幅响应肯定会得到改善。特别是当新的不平衡参数近似等于初始弯曲参数时 ,无论转速高低 ,振幅都会大幅下降。当重力参数、外阻尼系数和内阻尼系数改变后仍有同样结论。本文援引文献 [2 ]中的实例对这种方法进行了验证 ,并给出了解决类似故障的步骤。本文的方法可用于处理生产实际中转轴初弯引起的振动问题     

Homogeneity characterisation of sintered (U,Gd)O2 pellets by X-ray diffraction

(U,Gd)O₂ sintered pellets are fabricated by different methods. The homogeneity characterisation of the Gd content seems to be necessary for a production control to qualify the process and the final product obtained. In this paper, we propose an analysis of the X-ray diffraction powder patterns through the Rietveld method, in which the differences between the experimental and the calculated data proposed from a crystalline structure model are evaluated. This result allows us to determine the cell parameters, that can be correlated with the Gd concentration, and the existence of other phases with different Gd contents.     

Determination of the uranium enrichment with the NaIGEM code

The traditional method used to non-destructively determine the uranium enrichment with an NaI detector is based on the “enrichment meter principle” (Progress report LA-4605-MS, Los Alamos National Laboratory, NNM, 1970, p. 19), which involves measuring the intensity of the 186 keV line of ²³⁵U by selecting two regions of interest for the peak and the background. This type of method suffers from several limitations, the most limiting of which are the impossibility to make wall thickness correction or to take the inference of foreign radioisotopes into account. The NaIGEM software (A guide for using NaIGEM code, version 1.5 for DOS and Windows, 2001; Nucl. Instr. and Meth. A 458 (2001) 196) was developed to overcome these limitations by calculating the 186 keV line intensity with a fitting procedure. The code was tested in different measurement conditions on the wide variety of certified samples, in particular, on reprocessed uranium and on depleted material with thick steel filters interposed between the source and the detector. The results are presented to illustrate the performance and limitations of the tested version (A guide for using NaIGEM code, version 1.5 for DOS and Windows, 2001). The general performance is good except in the case of low-enriched uranium in thick containers.