Sandwich structures with tapered tubes as core:A quasi-static investigation

In this article,the experimental and finite element analysis is utilized to investigate the quasi-static compression features of sandwich constructions built with tapered tubes.3D printing technology was utilized to create the hollow centers of the tapering tubes,with and without corrugations.The results demonstrate that the energy absorption(EA)and specific energy absorption(SEA)of the single corrugated tapered tube sandwich are 51.6% and 19.8% higher,respectively,than those of the conical tube sandwich.Furthermore,the results demonstrate that energy absorbers can benefit from corrugation in order to increase their efficiency.Additionally,the tapered corrugated tubes'resistance to oblique impacts was studied.Compared to a straight tube,the tapered tube is more resistant to oblique loads and has a lower initial peak crushing force(PCF),according to numerical simulations.After conducting a parametric study,it was discovered that the energy absorption performance of the sandwich construction is significantly affected by the amplitude,number of corrugations,and wall thickness.EA and SEA of DTS with corrugation number of 8 increased by 17.4%and 29.6%,respectively,while PCF decreased by 9.2% compared to DTS with corrugation number of 10.

Evolution mechanism of crystallographic orientation in grain continuator bars of a Ni-based single-crystal superalloy prepared by Bridgman technology during directional solidification

Single-crystal rods with different diameters and deviation angles with respect to the solidification direction were produced by Bridgman rapid solidification method at withdrawal rates of 3 and 6 mm·min^(-1) and used as grain continuators.The crystallographic orientation of the rods,which cross-sections were perpendicular to the solidification direction at different solidification heights,was measured by electron backscattered diffraction,while the corresponding microstructures were observed by optical microscopy.The mushy zone morphology and the distribution of the temperature gradient were simulated by the finite element analysis software ProCAST.The experimental results indicate that the crystallographic orientation of the single-crystal rods corresponds to the statistical average value of all the dendrite orientations in cross-section.The crystallographic orientation of the primary and secondary dendrites of each single-crystal rod at different cross-sections fluctuates irregularly within a small range(less than 4°).The crystallographic orientation of the dendrite in each single-crystal rod is not exactly consistent with each other and is affected by their branching mode of dendrites in the solidification space.In addition,the simulation results show that the mushy zone shapes and the temperature gradient of single-crystal rods change with the increase of solidification height during the solidification process.Finally,the evolution mechanism of the crystallographic orientations and the corresponding influence factors were analyzed and discussed.

Diagnostic value of18F-FDG PET/CT in cervical lymph node metastasis of oral cancer: Meta-analysis

Objective:To evaluate the value of18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in the diagnosis of cervical lymph node metastasis of oral carcinoma.Methods:China national knowledge infrastructure, Wanfang, Chinese sci-tech journal database, PubMed, EMbase, the Cochrane Library and Web of Science were searched for18F-FDG PET/CT in cervical lymph node metastasis oral cancer. Literature screening, data extraction and literature quality evaluation were carried out independently by two researchers according to the unified classification criteria. Stata13.0 software and Meta-Disc1.4 software were used for meta-analysis.Results: A total of 14 studies with 849 cases of patients with cervical metastasis of oral cancer were included, among which 9 studies were conducted on patients, with a total of 299 patients, and 5 studies were conducted on lymph nodes, with 1965 patients with cervical lymph node proved pathologically. The results of meta analysis showed that18F-FDG PET/CT had good sensitivity and specificity in the diagnosis of cervical lymph node metastasis of oral cancer. The results showed that sensitivity = 0.81 (95% CI: 0.73-0.87), specificity = 0. 90 (95% CI: 0.83-0.94), combined likelihood ratio = 7. 9 (95% CI: 4.9-12.7), negative likelihood ratio = 0. 21 (95% CI: 0.15-0.30), diagnostic odds ratio=37 (95% CI: 20-67), and receiver operating characteristic curve =0.91 (95% CI: 0.89-0.94). Conclusions:18F-FDG PET/CT has high sensitivity and specificity in the diagnosis of cervical lymph node metastasis, and can be used as an important preoperative evaluation method for oral cancer.

Improving EGT sensing data anomaly detection of aircraft auxiliary power unit

The reliability of the on-wing aircraft Auxiliary Power Unit(APU)decides the cost and the comfort of flight to a large degree.The most important function of APU is to help start main engines by providing compressed air.Especially on the condition of sudden shutdown in the air,APU can offer additional thrust for landing.Therefore,its condition monitoring has drawn much attention from the academic and industrial field.Among the on-wing sensing data which can reflect its condition,Exhaust Gas Temperature(EGT)is one of the most important parameters.To ensure the reliability of EGT,one kind of data-driven anomaly detection framework for EGT sensing data is proposed based on the Gaussian Process Regression and Kernel Principal Component Analysis.The situations of one-dimensional and two-dimensional input data for EGT anomaly detection are considered,respectively.The cross-validation experiments are carried out by utilizing the real condition data of APU,which are provided by China Southern Airlines Company Limited Shenyang Maintenance Base.The anomalous stuck condition of EGT sensing data is also detected.Experimental results show that the proposed EGT sensing data anomaly detection method can achieve better performance of false positive ratio,false negative ratio and accuracy.