Ultrasonic Vibration Assisted Cutting of Nomex Honeycomb Core Materials

Dao‑Hui Xiang,Bang‑Fu Wu,Yun‑Long Yao,Bo Zhao,Jin‑Yuan Tang 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.1

Nomex honeycomb core materials have been widely used in the aviation industry due to their special structure and performance. Conventional high-speed machining have resulted in the poor machinability of the honeycomb core so that the ultrasonic machining technology was applied. The kinematic characteristics in the ultrasonic vibration assisted cutting process were analyzed according to the movement of the sharp tool. Based on slide effect, a cutting force model was proposed to study the relationship between cutting parameters and cutting force. Ultrasonic vibration assisted cutting and ordinary cutting tests of Nomex honeycomb core material were conducted by considering feed rate, the inclined angle and the deflected angle. Besides, the effects of cutting parameters on machined surface quality of honeycomb core wall were studied. The test results show that slide effect caused by ultrasonic vibrations can reduce cutting resistance compared with ordinary cutting. The developed cutting force model can be applied to evaluated the cutting force in the ultrasonic vibration assisted cutting of Nomex honeycomb core material. The inclined angle has a great influence on the cutting force during ultrasonic vibration assisted cutting. High-speed reciprocating sliding action can effectively cut aramid fibers so that burrs and tearing defects of the incision have been greatly improved under condition of ultrasonic vibration assisted cutting.

Effect of Ultrasonic Vibration Tensile on the Mechanical Properties of High-Volume Fraction SiCp/Al Composite

Dao-Hui Xiang,Zhi-Meng Zhang,Bang-Fu Wu,Hao-Ren Feng,Zhan-Li Shi,Bo Zhao 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.11

Silicon carbide particle-reinforced aluminum matrix composite has been widely used in the military and aerospace industry due to its special performance; however, there remain many problems in processing. The present paper introduces an ultrasonic vibration tensile device with a view to investigating an ultrasonic vibration tensile specimen. The results show that there are three major stages in the change in stress of the material under ultrasonic vibration: the ultrasonic stress superposition effect, softening effect, and Hall–Petch strengthening effect, these three effects occupy different proportions in different tensile stages. In addition, increasing the frequency of ultrasonic vibration increased the degree of stress reduction. Increasing the ultrasonic vibration amplitude reduced the fracture strength of the material. Comparison of the fracture morphology shows that the conventional condition was mainly interfacial peeling of SiC particles, and cleavage of the fracture occurred under ultrasonic vibration conditions.

Association Between the GSTP1 Codon 105 Polymorphism and Gastric Cancer Risk: an Updated Meta-analysis

Bao, Li-Dao,Niu, Jian-Xiang,Song, Hui,Wang, Yi,Ma, Rui-Lian,Ren, Xian-Hua,Wu, Xin-Lin Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.8

Objective: The current meta-analysis was performed to address a more accurate estimation of the association between glutathione S-transferase P1 (GSTP1) codon 105 polymorphism and risk of gastric cancer (GC), which has been widely reported with conflicting results. Methods: A comprehensive literature search was conducted to identify all the relevant studies. Fixed or random effect models were selected based on the heterogeneity test. Publication bias was estimated using Begg's funnel plots and Egger's regression test. Results: A total of 20 studies containing 2,821 GC cases and 6,240 controls were finally included in the analyses. Overall, no significant association between GSTP1 polymorphism and GC risk was observed in worldwide populations. However, subgroup analysis stratified by ethnicity showed that GSTP1 polymorphism was significantly associated with increased risk of GC in Asians (G vs. A, OR = 1.273, 95%CI=1.011-1.605; GG vs. AA, OR=2.103, 95%CI=1.197-3.387; GG vs. AA+AG, OR =2.103, 95%CI=1.186-3.414). In contrast, no significant association was found in Caucasians in any genetic models, except for with AG vs. AA (OR=0.791, 95%CI=0.669-0.936). Furthermore, the GSTP1 polymorphism was found to be significantly associated with GC in patients with H. pylori infection and in those with a cardiac GC. Subgroup analysis stratified by Lauren's classification and smoking status showed no significant association with any genetic model. No studies were found to significantly influence the pooled effects in each genetic mode, and no potential publication bias was detected. Conclusion: This meta-analysis suggested that the GSTP1 polymorphism might be associated with increased risk of GC in Asians, while GSTP1 heterozygote genotype seemed to be associated with reduced risk of GC. Since potential confounders could not be ruled out completely, further studies are needed to confirm these results.

The diversity, recombination and horizontal transmission of Wolbachia in spiders in China

Yang Xiao-Hui,Gong Yu-Hui,Xu Xiang,Yin Hai-Qiang,Zhu Dao-Hong 한국응용곤충학회 2021 Journal of Asia-Pacific Entomology Vol.24 No.3

Wolbachia are maternally inherited endosymbiotic bacteria. These intracellular bacteria are common in ar thropods and could manipulate host reproduction in diverse ways, such as feminization, parthenogenesis, male killing and cytoplasmic incompatibility. In spiders, infection by Wolbachia has been found in a total of 99 species belonging to 62 genera and 17 families. Furthermore, recent studies analyzed the phylogeny of Wolbachia in Hylyphantes graminicola, 2 cave spiders and Agelenopsis species using multilocus sequence typing (MLST) approach. However, the diversity of Wolbachia strains determined by MLST in spiders from China is still largely unknown. In this study, we collected 1153 spider individuals from Mangshan in China and screened for Wolbachia in 975 individuals representing 68 spider species belonging to 45 genera of 16 families. We analyzed the phylogenetic relationship between Wolbachia and their host spiders by MLST approach. We found novel infections of Wol bachia in 1 family, 9 genera and 20 species of spiders. We found 13 new Wolbachia strains and suggest that group A is more common than group B in Wolbachia that infect spiders. Our results revealed three recombination events of the concatenated multilocus sequences in Wolbachia that infect spiders. Furthermore, our results demonstrated the phylogenetic incongruence between Wolbachia and spiders, suggesting the horizontal transmission of Wol bachia in spiders. We suggest that recombination and horizontal transmission may play an important role in the diversity and evolution of Wolbachia in spiders.

Finite Element and Experimental Analysis of Ultrasonic Vibration Milling of High-Volume Fraction SiCp/Al Composites

Zhan-Li Shi,Dao-Hui Xiang,Hao-Ren Feng,Bang-Fu Wu,Zhi-Meng Zhang,Guo-Fu Gao,Bo Zhao 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.10

SiCp/Al composites have been widely used in many fields due to their excellent mechanical properties. However, the addition of reinforced phase SiC particles makes the overall properties of the composites hard and brittle, which brings great challenges to milling. Ultrasonic vibration-assisted processing technology has great advantages in processing hard and brittle materials. However, the process of rupture of SiC particles cannot be effectively observed during the test processing, and a large number of tests increase the cost of the test. The combination of finite element analysis and experiment was used to study the machining performance of High-volume fraction SiCp/Al composites in longitudinal-torsional ultrasonicassisted milling (LTUAM), and its feasibility was evaluated by comparing with conventional Milling (CM). By analyzing the trajectories of cutting edges in ultrasonic-assisted milling, It was found that ultrasonic frequency determines the time of periodic contact-separation between chisel edge and workpiece, and ultrasonic amplitude determines the maximum distance of contact-separation. Using ABAQUS finite element software, a polygon SiC particles model with a high-volume fraction was established to investigate the SiC particles crushing process under different ultrasonic-assisted milling conditions. The results showed that high-frequency ultrasonic-assisted milling could soften SiCp/Al composites, and the structural integrity of silicon carbide particles could be better maintained under appropriate ultrasonic amplitudes, reducing the probability of fragmentation. The removal mode was mainly plastic removal or crushing into small particles. The surface roughness value and milling force were reduced, improving the surface quality of the processed composite material. The conclusions of the milling test were basically consistent with the simulation results, which prove the correctness and feasibility of the simulation results