Numerical investigation on the dynamic behaviors of turbine valve disc–seat impact at low velocity

Jianfeng Mao,Wei Zhe Wang,Junhui Zhang,Ying Zheng Liu 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.2

In this study, the dynamic behaviors on a valve seat subjected to the impact of the valve disc at low velocities were investigated by usingnumerical analysis with finite element method. The impact damage of the valve disc against seat was evaluated through a threedimensionaldynamic explicit calculation. The parameters considered in the simulations were impact velocity, disc obliquity, aspect ratio,and contact area ratio. The model for impact calculation was implemented in the code ABAQUS, which is based on the constitutiveequation and fracture strain equation of Johnson and Cook, as well as on continuum damage mechanics. The distribution of damagecaused by the impact was computed and discussed. The impact damage of the valve disc was minimized when the disc obliquity wasapproximately 40°. The effects of variation of selected design parameters on dynamic behaviors were discussed. The best design parameterswere proposed, which served as a guide for future valve design.

Experimental and theoretical investigation on the sealing performance of the combined seals for reciprocating rod

Jianfeng Mao,Weizhe Wang,Yingzheng Liu 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.6

Sealing performance of the combined seals at supply oil pressure of 40MPa was experimentally and theoretically investigated. An experimental setup of combined seals for reciprocating piston rods was established in Shanghai Jiao Tong University. Two combined seals were chosen for studies, e.g. C-shape and T-shape (Fig. 1). A theoretical model based on one-dimensional Reynolds equation was made for obtaining the oil film distribution between the rod and the combined seals. Finite element method was used to calculate the contact pressure between the rod and the combined seals. The sealing performance of combined seals was analyzed in terms of the contact pressure,the back-pumping ability, the fluid transport and the net leakage under the conditions of varying the inlet pressure, the frequency of the pressure and the velocity of the rod. The experimental results demonstrated that the velocity of the rod significantly influences the sealing performance of the combined seals. Furthermore, the theoretical analysis on the influence of the rod velocity on the fluid transport was in good agreement to the experimental measurements.

Effect of strain amplitude and temperature on creep-fatigue behaviors of 9-12 % Cr steel

Jianfeng Mao,Jian Zhu,Xiangyang Li,Dasheng Wang,Fengping Zhong,Jichang Chen 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.5

The creep-fatigue behaviors of P92 steel under strain range of 0.3 %-0.5 % and test temperature of 600-650 °C was studied carefully in this paper. With the increase of temperature, the creep-fatigue life is significantly reduced, and more vulnerable to temperature than strain amplitude. In addition, the dislocation density decreases with increasing creep fatigue, and the martensite laths become coarser. Furthermore, the increase of strain amplitude leads to more significant secondary cracks and fatigue striation. The higher temperature causes much deeper and larger dimples. During the test, the growth and accumulation of precipitates inevitably lead to stress concentration, resulting in material fracture and destruction. Finally, the linear cumulative damage (LCD), the modified ductility exhaustion (MDE) and the frequency separation life (FSL) model are used to predict the creep-fatigue life of P92 steel, and it is found that the frequency separation life model had the highest prediction accuracy among the threes.

Mesenchymal glioma stem cells are maintained by activated glycolytic metabolism involving aldehyde dehydrogenase 1A3

Mao, Ping,Joshi, Kaushal,Li, Jianfeng,Kim, Sung-Hak,Li, Peipei,Santana-Santos, Lucas,Luthra, Soumya,Chandran, Uma R.,Benos, Panayiotis V.,Smith, Luke,Wang, Maode,Hu, Bo,Cheng, Shi-Yuan,Sobol, Robert W National Academy of Sciences 2013 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.110 No.21

<P>Tumor heterogeneity of high-grade glioma (HGG) is recognized by four clinically relevant subtypes based on core gene signatures. However, molecular signaling in glioma stem cells (GSCs) in individual HGG subtypes is poorly characterized. Here we identified and characterized two mutually exclusive GSC subtypes with distinct dysregulated signaling pathways. Analysis of mRNA profiles distinguished proneural (PN) from mesenchymal (Mes) GSCs and revealed a pronounced correlation with the corresponding PN or Mes HGGs. Mes GSCs displayed more aggressive phenotypes in vitro and as intracranial xenografts in mice. Further, Mes GSCs were markedly resistant to radiation compared with PN GSCs. The glycolytic pathway, comprising aldehyde dehydrogenase (ALDH) family genes and in particular ALDH1A3, were enriched in Mes GSCs. Glycolytic activity and ALDH activity were significantly elevated in Mes GSCs but not in PN GSCs. Expression of ALDH1A3 was also increased in clinical HGG compared with low-grade glioma or normal brain tissue. Moreover, inhibition of ALDH1A3 attenuated the growth of Mes but not PN GSCs. Last, radiation treatment of PN GSCs up-regulated Mes-associated markers and down-regulated PN-associated markers, whereas inhibition of ALDH1A3 attenuated an irradiation-induced gain of Mes identity in PN GSCs. Taken together, our data suggest that two subtypes of GSCs, harboring distinct metabolic signaling pathways, represent intertumoral glioma heterogeneity and highlight previously unidentified roles of ALDH1A3-associated signaling that promotes aberrant proliferation of Mes HGGs and GSCs. Inhibition of ALDH1A3-mediated pathways therefore might provide a promising therapeutic approach for a subset of HGGs with the Mes signature.</P>

Cloning of the Correct Full Length cDNA of NF-kB-repressing Factor

Yumin Mao,Dai Jianfeng,Jin Feng,Ji Chaoneng,Zheng Zhongshou,Gu Shaohua,Wu Qihan,Wang Liu,Yin Gang,Xie Yi 한국분자세포생물학회 2003 Molecules and cells Vol.16 No.3

Antifungal bio-coating of endotracheal tube built by overexpressing MCP1 gene of Saccharomyces boulardii and employing hydrogel as a “house” antagonize Candida albicans

Yunyun Wei,Jianfeng Qiu,Ziqiang Han,Xuanyi Wang,Hui Zhang,Xinya Hou,Xiangwei Lv,Xiaolong Mao 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Background For some ICU patients, an artificial airway must be established with an endotracheal tube, but Candida albicans can easily adhere to the tube surface and form a biofilm, leading to potentially life threatening fungal infections. Therefore, it is urgent to prevent and reduce C. albicans infections introduced by the endotracheal tube. However, there are few antifungal drugs effective against C. albicans, and each of these drugs may have adverse effects on human cells. Saccharomyces boulardii is regarded as an alternative strategy to inhibit the adhesion of C. albicans, but it is affected by environmental stress. We hypothesized that it is feasible to strengthen the antagonistic ability of S. boulardii via encapsulating and genetically modification. Methods In this study, a bioactive material carrying the overexpressed MCP1 gene of Saccharomyces boulardii was constructed based on one-step photo-crosslinking. This material achieved spatial growth control of S. boulardii by encapsulating each S. boulardii cell within a hydrogel pore. The bioactive material was coated on an endotracheal tube and tested for its ability to inhibit the adhesion of C. albicans. Additionally, the material’s antagonistic activity towards C. albicans was evaluated by detecting intracellular Adenosine-triphosphate content, reactive oxygen species level and the activity of antioxidative enzymes. Tissue invasion experiment was executed to further evaluate the antiadhesion ability of S. boulardii bio-coating. Results Encapsulating the overexpression of MCP1 by S. boulardii in hydrogel pores enhanced the viability of probiotics in the presence of high salt and oxidation stress. When used as the coating of an endotracheal tube, the S. boulardii bioactive material efficiently inhibited the adhesion of C. albicans by impairing the activities of superoxide dismutase and catalase and disturbing mitochondrial functions. In vivo, the S. boulardii bioactive material coating displayed good biocompatibility and reduced the host tissue invasion and virulence of C. albicans. Conclusions The integration of genetic modification and immobilization model breaks the bottleneck of previous application of microorganisms, and provides a new way to prevent fungal infections introduced by endotracheal tubes.

Comparison of Hybridization Behavior between Double and Single Strand of Targets and the Application of Asymmetric PCR Targets in cDNA Microarray

Wei, Qing,Liu, Sanzhen,Huang, Jianfeng,Mao, Xueying,Chu, Xiaohui,Wang, Yu,Qiu, Minyan,Mao, Yumin,Xie, Yi,Li, Yao Korean Society for Biochemistry and Molecular Biol 2004 Journal of biochemistry and molecular biology Vol.37 No.4

Double stranded targets on the cDNA microarray contain representatives of both the coding and noncoding strands, which will introduce hybridization competition with probes. Here, the effect of double and single strands of targets on the signal intensity and the ratios of Cy5/Cy3 within the same slide were compared. The results show that single stranded targets can increase the hybridization efficiency without changing the Cy5/Cy3 ratio. Based on these results, a new strategy was established by generating cDNA targets with asymmetric PCR, instead of conventional PCR, to increase the sensitivity of the cDNA microarray. Furthermore, the feasibility of this approach was validated. The results indicate that the cDNA microarray system based on asymmetric PCR is more sensitive, with no decrease in the reliability and reproducibility as compared with that based on conventional symmetric PCR.