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1.
具有一定曲率外形的铝合金整体壁板属于典型的多筋零部件,传统弯曲成形工艺成形困难,容易产生多种缺陷。提出了离散填料辅助滚弯成形整体2A12T4铝合金壁板滚弯工艺,并通过实验与整体填料滚变成形进行了对比,同时采用有限元模拟技术,探究了离散填料辅助整体壁板滚弯成形中的影响因素。研究结果表明:填料数量、上下垫板厚度等因素对成形性能影响较大,填料在3~6块时成形稳定,可以有效地避免筋条屈曲与失稳;随垫板厚度增加,壁板表面圆弧更加光滑、连续,但是回弹性增强;上下垫板分别在10~20 mm厚度时,综合性能较好。通过离散填料辅助滚弯技术可以成形出质量较高的整体壁板。 相似文献
2.
The Caputo and Caputo–Fabrizio derivative are applied to study a second‐grade nanofluid over a vertical plate. A comparative analysis is presented to study the unsteady free convection of a second‐grade nanofluid with a new time–space fractional heat conduction. The governing equations with mixed time–space fractional derivatives are non‐dimensionalized and solved numerically, and a comparison between the Caputo and the Caputo–Fabrizio models is made. It is found that the temperature is higher for the Caputo–Fabrizio fractional model than the Caputo model, but the higher velocity only exists near the vertical plate for the Caputo–Fabrizio model than the Caputo model. Moreover, the velocity for the Caputo model will exceed the Caputo–Fabrizio model as y evolves. 相似文献
3.
Shoji Nakamura Yuji Shibahara Atsushi Kimura Osamu Iwamoto Akihiro Uehara Toshiyuki Fujii 《Journal of Nuclear Science and Technology》2020,57(4):388-400
ABSTRACTThe thermal-neutron capture cross-section (σ0) and resonance integral (I0) were measured for the 135Cs(n,γ)136Cs reaction by an activation method and mass spectrometry. Because of difficulty in the preparation of pure 135Cs samples, we used 135Cs contained as an impurity in a normally available 137Cs standard solution. An isotope ratio of 135Cs and 137Cs in a standard 137Cs solution was measured by mass spectrometry to quantify 135Cs. Cesium-135 impurity along with the 137Cs standard solution was irradiated at the hydraulic conveyer of the research reactor in the Institute for Integral Radiation and Nuclear Science, Kyoto University. Wires of Co/Al and Au/Al alloys were used as neutron monitors to measure thermal-neutron fluxes and epi-thermal Westcott’s indices at an irradiation position. A gadolinium filter was used to measure the σ0, and a value of 0.133 eV was taken as the cut-off energy. Gamma-ray spectroscopy was used to measure induced activities of 137Cs, 136Cs and monitor wires. On the basis of Westcott’s convention, the σ0 and I0 values were derived as 8.57 ± 0.25 barn, and 45.3 ± 3.2 barn, respectively. The value of σ0 obtained in the present study agreed within the limits of uncertainties with the past-reported value of 8.3 ± 0.3 barn. 相似文献
4.
Hongjun Yu 《先进材料力学与结构力学》2019,26(7):631-638
This paper develops a domain-independent interaction integral (DII-integral) for extracting mixed-mode stress intensity factors (SIFs) for orthotropic materials with complex interfaces. The DII-integral does not require material property gradients, and moreover its validity is not affected by material interfaces. Combined with the extended finite element method (XFEM), the DII-integral is employed to investigate a straight crack in an orthotropic functionally graded plate and a curved crack in orthotropic particulate composites. 相似文献
5.
6.
陈超 《计算机工程与应用》2019,55(12):124-131
鉴于高斯混合模型对背景变化快时无法精确检测出目标和目标跟踪的适应性差等瑕疵,提出了基于加权似然跟踪器来改进高斯混合模型实现运动目标跟踪算法。主要引入了自适应高斯混合模型来实时检测运动目标,然后空间加权似然来进行视频中的目标定位,引入加权似然期望值来改进高斯混合模型处理视频中的多尺度、多角度变化的目标跟踪不精准问题。通过VOT 2014 dataset对比实验结果表明提出的基于加权似然跟踪(Weighted Likelihood Tracking,WLT)和改进高斯混合模型(Improved Gaussian Mixture Model,IGMM)的目标跟踪算法较传统高斯混合模型跟踪算法在跟踪的精度有较大提高。在应对多尺度、多角度变化的目标跟踪表现出了较大的优势。 相似文献
7.
针对赵固二矿煤层透气性低、钻孔有效影响半径小,实施定向长钻孔代替底板岩巷进行区域瓦斯治理期间钻孔工程量大、瓦斯抽采效果不理想的问题。结合煤层赋存特征及钻孔施工情况,采用定向长钻孔整体水力压裂增透技术,理论分析了合理坐封位置、压裂参数,完成200 m煤巷条带一次整体压裂,最大泵注压力24.3 MPa、累计注水量1 613 m3。并基于煤层全水分变化,考察确定了单个钻孔压裂影响范围达到巷道两帮30 m,有效改善了煤体储层特性,提高了煤层瓦斯抽采效率。在实现定向钻孔对预抽煤巷条带可靠控制的同时,最大程度降低了钻孔工程量、缩短了瓦斯治理周期,为实现矿区“以孔代巷”及高效安全开采提供了技术支撑。 相似文献
8.
Rashid Jan Hassan Khan Poom Kumam Fairouz Tchier Rasool Shah Haifa Bin Jebreen 《计算机、材料和连续体(英文)》2021,68(3):3185-3201
It is eminent that partial differential equations are extensively meaningful in physics, mathematics and engineering. Natural phenomena are formulated with partial differential equations and are solved analytically or numerically to interrogate the system’s dynamical behavior. In the present research, mathematical modeling is extended and the modeling solutions Helmholtz equations are discussed in the fractional view of derivatives. First, the Helmholtz equations are presented in Caputo’s fractional derivative. Then Natural transformation, along with the decomposition method, is used to attain the series form solutions of the suggested problems. For justification of the proposed technique, it is applied to several numerical examples. The graphical representation of the solutions shows that the suggested technique is an accurate and effective technique with a high convergence rate than other methods. The less calculation and higher rate of convergence have confirmed the present technique’s reliability and applicability to solve partial differential equations and their systems in a fractional framework. 相似文献
9.
Toxicity of smoke generated in a fire is difficult to measure accurately. That is because gas sensors for measuring rapidly varying concentrations of toxic gases are not yet developed. Simple expressions are searched for quick measurement in assessing smoke toxicity practically. Four equations on calculating fractional effective dose (FED) related to toxic effluents were reported in the literature, each based on different assumptions. FED value was proposed to be calculated based on peak carbon monoxide concentration and peak carbon dioxide concentration, and transient carbon monoxide, carbon dioxide, and oxygen concentrations. The four values were compared in this article using literature data on toxic gases from different materials measured by (i) cone calorimeter; (ii) full-scale burning tests; and (iii) tunnel full-scale tests. Measured carbon monoxide, carbon dioxide, and oxygen concentrations by standard equipment of oxygen consumption calorimeters were used to calculate the four FED values. It is found that the values of FED based on peak carbon monoxide and carbon dioxide concentrations (denoted as FED2) are similar to the average values of FED calculated from the updated equation in the literature using the oxygen consumption calorimeters. Putting the values of FED2 in fire safety design guides is then recommended. 相似文献
10.
Javier A. Gallegos Norelys Aguila-Camacho Manuel A. Duarte-Mermoud 《International Journal of Adaptive Control and Signal Processing》2020,34(11):1572-1589
In this article, we develop proportional, fractional-integral, and derivative () controllers for the regulation and tracking problems of nonlinear systems. The analytic results are obtained by extending the passivity-based approach to include fractional operators. Robustness under parametric uncertainty is dealt with by a combination with an adaptive scheme. It is also shown their robustness under additive noise and their robustness under uncertainty in the derivation order. The advantages in the controlled system performance and in the control energy consumption in comparison to classic PI and proportional integral derivative controllers are illustrated for the quadratic boost converter and a benchmark system in the literature. 相似文献