Microstructure of Gear Steels Treated by Shot Peening by X-Ray Line Profile Analysis Method

Pengfei Zhu,Hongzhi Yan,Jibo Zhou,Youliang Zhou,Yin Zhang,Zhi Chen 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.10

Shot peening is a common surface strengthening process of gears. It can induce compressive residual stress, refine grain size and increase dislocation density. However, there are limited reports on the quantitative analysis of dislocation substructures (type, fraction and arrangement), crystallite size and micro-strain in different crystal planes. To further reveal the microstructure strengthening mechanism of gears during shot peening, X-ray diffraction line profile analysis (XRDLPA) method is applied to study the effect of coverage on the microstructure of the gear steels. The results show that with increasing coverage, the dislocation density is increased from 2.62 × 1016 to 3.37 × 1016 m−2 in the form of screw-edge-mixed type as determined from the dislocation characteristic parameter q. The fraction of edge dislocation increases, whereas the fraction of screw dislocation decreases. The dislocation arrangement parameter M is decreased from 7.1 to 5.6, indicating that the formation of dislocation dipoles or dislocation cells in the surface layer can be further enhanced by increasing coverage. Due to the different degrees of atomic slip, the (200) crystallographic plane exhibits the smallest crystallite size and highest micro-strain, whereas the (222) plane shows the smallest micro-strain and the largest crystallite size. In addition, during shot peening, the enhancement of surface hardness of the gear steels is attributed to the phase transformation strengthening, grain-boundary hardening and dislocation hardening. The surface compressive stress of the gear steels induced by shot peening is affected not only by phase transformation, but also by Bauschinger effect, surface topography, grain refinement and so on.

Lactate potentiates angiogenesis and neurogenesis in experimental intracerebral hemorrhage

Jing Zhou,Tao Liu,Hao Guo,Hanjin Cui,Pengfei Li,Dandan Feng,En Hu,Qing Huang,Ali Yang,Jun Zhou,Jiekun Luo,Tao Tang,Yang Wang 생화학분자생물학회 2018 Experimental and molecular medicine Vol.50 No.-

Lactate accumulation has been observed in the brain with intracerebral hemorrhage (ICH). However, the outcome of lactate accumulation has not been well characterized. Here, we report that lactate accumulation contributes to angiogenesis and neurogenesis in ICH. In the first set of the experiment, a rat model of ICH was induced by injecting collagenase into the brain. The effects of lactate accumulation on the neurological function, apoptosis, and numbers of newborn endothelial cells and neurons, as well as the proliferation-associated signaling pathway, were evaluated in the rat brain. In the second set, exogenous L-lactate was infused into intact rat brains so that its effects could be further assessed. Following ICH, lactate accumulated around the hematoma; the numbers of PCNA+/vWF+ nuclei and PCNA+/DCX+ cells were significantly increased compared with the numbers in the Sham group. Moreover, ICH induced translocation of nuclear factor-kappa B (NF-κB) p65 into the nucleus, resulting in a notable upregulation of VEGF and bFGF mRNAs and proteins compared with the levels in the Sham controls. Administration of a lactate dehydrogenase inhibitor dramatically inhibited these effects, decreased the vascular density, and aggravated neurological severity scores and apoptosis after ICH. After exogenous L-lactate infusion, the numbers of PCNA+/vWF+ nuclei and PCNA+/DCX+ cells were strikingly increased compared with the numbers in the Sham controls. In addition, lactate facilitated NF-κB translocation to induce increased transcription of VEGF and bFGF. Co-infusion with an NF-κB inhibitor significantly inhibited these effects. These data suggest that lactate potentiates angiogenesis and neurogenesis by activating the NF-κB signaling pathway following ICH.

Stress-Release Law and Deformation Characteristics of Large-Span Tunnel Excavated with Semi Central Diaphragm Method

Shen Zhou,Liping Li,Zhimin An,Hongliang Liu,Guangyu Yang,Pengfei Zhou 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.6

The proportion of large-span tunnels in newly-built highway tunnels is getting higher and higher, revealing the stress release law and deformation characteristics of the tunnel at different excavation steps has important guiding significance for the rational design of the supporting structure parameters. In this paper, a typical section of the Laohushan Tunnel was selected to analyze the stress and deformation response of the large-span tunnel excavated with the semi central diaphragm method (SCDM), with the numerical simulation and field monitoring method. The study found that during the excavation of the large-span tunnel with the SCDM, the stress and deformation response characteristics are different from those ordinary tunnels. Influenced by the settlement of the vault, there was a significant outward expansion tendency, and a high degree of stress concentration in the sidewall. In particular, the supporting structure at the sidewall has a deformation characteristic of expanding outward and then converging inward. In this paper, the in-depth analysis of the stress release law and deformation characteristics of the excavation process of large-span tunnels can provide reference for the excavation and support parameter design of similar projects.

Effect of post-heat treatment on the microstructure and mechanical properties of laser metal deposition Inconel 718

Pengfei Li,Jianzhong Zhou,Yadong Gong,Xiankai Meng,Jinzhong Lu 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.7

The microstructure, hardness, and fracture strength of Inconel 718 fabricated with laser metal deposition are investigated. The solution treatment plus aging (STA) (including 980 °C, 720 °C, and 620 °C for 1, 8, and 8 h, respectively) and low-temperature stress-relief annealing (LTSLA) (including 650 °C for 1 h) are compared, which can respectively improve the hardness and tensile properties. Results show that the as-deposited sample mainly contained γ matrix, coarse Laves phase, granular carbides, and nitrides. STA and LTSLA post-heat treatments could respectively improve the hardness and tensile properties, while the elongation slightly decreased. The solution treatment promoted almost Laves phase to dissolve into γ matrix and homogenized the matrix, and the aging treatment promoted the precipitation of γ′ and γ′′ phases, which significantly improved the mechanical properties.

Characterization and functional study of juvenile hormone diol kinase gene in Nilaparvata lugens (Stål) (Hemiptera: Delphacidae)

Pengfei Xie,Zhenghui Li,Xu Ding,Yaodong Zhou,Jing-Lan Liu 한국응용곤충학회 2018 Journal of Asia-Pacific Entomology Vol.21 No.4

The brown planthopper, Nilaparvata lugens (Stål) is an important pest in rice. It has been widely recognized that the juvenile hormone (JH) is regulated by its hydrolase, which includes juvenile hormone esterase (JHE), juvenile hormone epoxide hydrolase (JHEH) and juvenile hormone diol kinase (JHDK). In this paper, we cloned the gene of Jhdk and the gene expression at different stages of N. lugens was analysed, and the relationship with Jhe and Jheh was studied after silencing the jhdk gene of N. lugens (Nljhdk) through double-stranded RNA (dsRNA) feeding. We also explored the expression of the three JH hydrolase after indoxacarb treatments. RT-PCR was used to amplify the full length Jhdk cDNA, and the Nljhdk gene was expressed throughout all the development periods tested and showed the lowest level at the 4th instar and the highest in the 5th instar. The expression level of Nljhdk in male adults was higher than that of female adults. Through feeding, dsRNA against Nljhdk successfully knocked down the target gene, which had no significant effect on the expression of the jhe gene of N. lugens (Nljhe), while the expression of Nljheh was upregulated. Indoxacarb could inhibit N. lugens reproduction, and the expression level of Nljhe and Nljhdk increased with the increasing of indoxacarb concentration, but the expression of the jheh gene of N. lugens (Nljheh) was reduced. These studies provide a line of experimental evidence in N. lugens to support that Nljhdk encodes the functional protein involved in JH degradation and further showed the relationship of the three hydrolases and the mechanism of indoxacarb inhibition of the fecundity of N. lugens.

Numerical studies on cavitation behavior in impeller of centrifugal pump with different blade profiles

Pengfei Song,Yongxue Zhang,Cong Xu,Xin Zhou,Jinya Zhang 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.2

To investigate the influence of blade profiles on cavitation behavior in impeller of centrifugal pump, a centrifugal pump with five different blade profiles impellers are studied numerically. The impellers with five different blade profiles (single arc, double arcs, triple arcs, logarithmic spiral and linear -variable angle spiral) were designed by the in-house hydraulic design code using geometric parameters of IS 150-125-125 centrifugal pump. The experiments of the centrifugal pump have been conducted to verify numerical simulation model. The numerical results show that the blade profile lines has a weak effect on cavitation inception near blade inlet edge position, however it has the key effect on the development of sheet cavitation in impeller, and also influences the distribution of sheet cavitation in impeller channels. A slight changing of blade setting angle will induce significant difference of cavitation in impeller. The sharp changing of impeller blade setting angle causes obvious cavitation region separation near the impeller inlet close to blade suction surface and much more flow loss. The centrifugal pump with blade profile of setting angle gently changing (logarithmic spiral) has the super cavitation performance, which means smaller critical cavitation number and lower vapor cavity volume fraction at the same conditions.

Numerical studies on cavitation behavior in impeller of centrifugal pump with different blade profiles

Song, Pengfei,Zhang, Yongxue,Xu, Cong,Zhou, Xin,Zhang, Jinya Korean Society for Fluid machinery 2015 International journal of fluid machinery and syste Vol.8 No.2

To investigate the influence of blade profiles on cavitation behavior in impeller of centrifugal pump, a centrifugal pump with five different blade profiles impellers are studied numerically. The impellers with five different blade profiles (single arc, double arcs, triple arcs, logarithmic spiral and linear-variable angle spiral) were designed by the in-house hydraulic design code using geometric parameters of IS 150-125-125 centrifugal pump. The experiments of the centrifugal pump have been conducted to verify numerical simulation model. The numerical results show that the blade profile lines has a weak effect on cavitation inception near blade inlet edge position, however it has the key effect on the development of sheet cavitation in impeller, and also influences the distribution of sheet cavitation in impeller channels. A slight changing of blade setting angle will induce significant difference of cavitation in impeller. The sharp changing of impeller blade setting angle causes obvious cavitation region separation near the impeller inlet close to blade suction surface and much more flow loss. The centrifugal pump with blade profile of setting angle gently changing (logarithmic spiral) has the super cavitation performance, which means smaller critical cavitation number and lower vapor cavity volume fraction at the same conditions.

Experimental Study on Fire Resistance Performance of Concrete-Filled Steel Plate Composite Walls

Ting Zhou,Xueshan Liu,Hongbo Liu,Yixuan Li,Pengfei Zhang,Huazhou Chen,Zhi-Hua Chen 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.2

Concrete-filled steel plate composite walls are increasingly used in high-rise buildings; their mechanical properties at room temperature have produced fruitful results. However, research on their mechanical properties in fire and at high temperatures is scarce. Moreover, published studies on the fire resistance of concrete-filled steel plate composite walls have not considered the impact of fire protection measures. Based on previous fire resistance research, a fire resistance test was designed in this study for four walls under the combined action of axial compression and a single-sided fire under the ISO-834 standard heating curve. Apart from that, the existing fire protections have the disadvantages of too thick, easy falling off and cracking or difficult to install. In order to eliminate the disadvantages of existing fire prevention measures, new composite fireproof structure using a rock wool board and a thin fire-retardant coating is proposed. The effects of no fireproof structures, autoclaved lightweight concrete plate fireproof structures, thick-coated fire-retardant structures, and new composite fireproof structures on the fire resistance of concrete-filled steel plate composite walls were studied experimentally. The results show that the fire resistance of the four test specimens meets the 3 h fire resistance limit of the primary load-bearing component in the specification. Based on the experimental results, reasonable fire protection methods are suggested for concrete-filled steel plate composite walls in actual projects, and an experimental basis is provided for further numerical simulation.

A key ABA hydrolase gene, OsABA8ox3 is involved in rice resistance to Nilaparvata lugens by affecting callose deposition

Yaodong Zhou,Litong Sun,Shuang Wang,Pengfei Xie,Jing-Lan Liu 한국응용곤충학회 2019 Journal of Asia-Pacific Entomology Vol.22 No.2

Abscisic acid (ABA) is an important plant hormone in regulating abiotic and biotic stresses. OsABA8ox3 is the key gene in ABA hydrolase genes, and plays an important role in controlling ABA level, but little is known in rice resistance to insects. We used rice osaba8ox3 T-DNA insertion mutant (knocking down the OsABA8ox3 gene) to elucidate rice resistance to the insect. There were obvious phenotype differences between the osaba8ox3 T-DNA insertion mutant and wild-type (WT), and the relative expression of synthetase genes in the osaba8ox3 mutant was higher, while the relative expression of hydrolase genes was lower than that of WT, respectively. The electrical penetration graph (EPG) recording indicated that the osaba8ox3 mutant had the less sucking phloem sap duration compared with WT, which indicated a significant increase in rice resistance to brown planthopper (Nilaparvata lugens; BPH). The callose deposition in the osaba8ox3 mutant increased by 60.39%, 52.2%, 26.6% and 31.7% than that of WT after BPH feeding for 0, 24, 48, and 72 h, respectively. These results showed OsABA8ox3 gene played an important role in rice resistance to BPH, and also provided new insights into the mechanism of callose deposition regulation in response to the piercing-sucking pest.

The Monocot-Specific Receptor-like Kinase SDS2 Controls Cell Death and Immunity in Rice

Fan, Jiangbo,Bai, Pengfei,Ning, Yuese,Wang, Jiyang,Shi, Xuetao,Xiong, Yehui,Zhang, Kai,He, Feng,Zhang, Chongyang,Wang, Ruyi,Meng, Xiangzong,Zhou, Jinggeng,Wang, Mo,Shirsekar, Gautam,Park, Chan Ho,Bell Elsevier 2018 Cell host & microbe Vol.23 No.4

<P><B>Summary</B></P> <P>Programmed cell death (PCD) plays critical roles in plant immunity but must be regulated to prevent excessive damage. The E3 ubiquitin ligase SPL11 negatively regulates PCD and immunity in plants. We show that <I>S</I>PL11 cell-<I>d</I>eath <I>s</I>uppressor <I>2</I> (SDS2), an S-domain receptor-like kinase, positively regulates PCD and immunity in rice by engaging and regulating SPL11 and related kinases controlling defense responses. An <I>sds2</I> mutant shows reduced immune responses and enhanced susceptibility to the blast fungus <I>Magnaporthe oryzae</I>. Conversely, <I>SDS2</I> over-expression induces constitutive PCD accompanied by elevated immune responses and enhanced resistance to <I>M. oryzae</I>. SDS2 interacts with and phosphorylates SPL11, which in turn ubiquitinates SDS2, leading to its degradation. In addition, SDS2 interacts with related receptor-like cytoplasmic kinases, OsRLCK118/176, that positively regulate immunity by phosphorylating the NADPH oxidase OsRbohB to stimulate ROS production. Thus, a plasma membrane-resident protein complex consisting of SDS2, SPL11, and OsRLCK118/176 controls PCD and immunity in rice.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The RLK SDS2 positively regulates plant cell death and immunity in rice </LI> <LI> SDS2 phosphorylates E3 ligase SPL11, which in turn ubiquitinates SDS2 for degradation </LI> <LI> SDS2 phosphorylates receptor-like cytoplasmic kinases RLCK118 </LI> <LI> RLCK118 interacts with and phosphorylates the NADPH oxidase OsRbohB </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>