Effect of Temperature and Strain Rate on the Hot Deformation Behaviour of Ferritic Stainless Steel

Guoqing Zu,Yukuan Lu,Yi Yan,Xiaoming Zhang,Jingwei Zhao,Wei Du,Xu Ran,Zhengyi Jiang 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.2

The fow behaviour and microstructure characteristics of a ferritic stainless steel were investigated using plain strain compression test on a Gleeble 3500 thermo-mechanical test simulator with a hydrawedge system in the temperature range of850–1100 °C and strain rate range of 0.1–50 s−1. The phenomenological constitutive model and the relationship betweenthe Zener–Hollomon (Z) parameter and fow stress were established. The results reveal that the fow softening phenomenonoccurs at high strain rate, which is caused by the coupling efect of the adiabatic heating and dynamic recrystallisation (DRX). New grains nucleate preferentially at the original grain boundaries by strain-induced grain boundary migration. With anincrease of temperature or strain rate, a part of new grains form in the interior of deformed grains. The DRX grain size andfraction increase with the increase of temperature, however, exhibit a non-linear relationship with strain rate.

Multivariable Integrated Model Predictive Control of Nuclear Power Plant

Guoqing Xia,Jie Su,Wei Zhang 보안공학연구지원센터 2008 International Journal of Control and Automation Vol.1 No.1

Characterization of the brittleness of hard rock at different temperatures using uniaxial compression tests

Chen, Guoqing,Li, Tianbin,Wang, Wei,Guo, Fan,Yin, Hongyu Techno-Press 2017 Geomechanics & engineering Vol.13 No.1

The failure mechanism of a deep hard rock tunnel under high geostress and high geothermalactivity is extremely complex. Uniaxial compression tests of granite at different temperatures were conducted. The complete stress-strain curves, mechanical parameters and macroscopic failure types of the rock were analyzed in detail. The brittleness index, which represents the possibility of a severe brittleness hazard, is proposed in this paperby comparing the peak stress and the expansion stress. The results show that the temperature range from 20 to $60^{\circ}C$ is able to aggravate the brittle failure of hard rock based on the brittleness index. The closure of internal micro cracks by thermal stress can improve the strength of hard rock and the storage capacity of elastic strain energy. The failure mode ofthe samples changes from shear failure to tensile failure as the temperature increases. In conclusion, the brittle failure mechanism of hard rock under the action of thermal coupling is revealed, and the analysis result offers significant guidance for deep buried tunnels at high temperatures and under high geostress.

Natural fracture prediction in Keshen 2 ultra-deep tight gas reservoir based on R/S analysis, Kuqa Depression, Tarim Basin

Hui Zhang,Wei Ju,Guoqing Yin,Xinyu Liu,Zhimin Wang,Sijia Liu,Ke Wang,Hui Yang,Ke Xu,Wenbo Luan 한국지질과학협의회 2021 Geosciences Journal Vol.25 No.4

Within ultra-deep tight sandstone gas reservoirs, natural fractures indicate significant effects on reservoir performance because they can serve as storage spaces for hydrocarbons and improve the permeability. Accurate prediction of natural fractures in ultra-deep reservoirs is critical to the exploration and development of tight gas in Keshen 2 Block of Kuqa Depression. In this study, several conventional logs are selected and the R/S analysis method is introduced to predict the development and distribution of natural fractures in ultra-deep tight sandstone reservoirs. Fracture development coefficient Q is calculated based on the second derivatives of lg(R/S) function and corresponding weight of each log parameter, which matches well with linear fracture density measured from image logs. There is a positive correlation between parameter Q and fracture density, higher Q values usually indicate larger fracture density. Factors causing mismatches between calculated parameter Q and fracture density are also analyzed. Fracture dip angle, fracture filling condition, vertical resolution of logs, multiple interpretations of conventional logs, and lateral detection difference between image and conventional logs may contribute to generate those false appearances. The results in this study are expected to provide new geological references for the exploration and development of ultra-deep tight gas in Keshen 2 Block of Kuqa Depression.

An Innovative Rotor Position Detection at Stand-Still and Low Speed with Carrier Phase-Shifted PWM Method

Kewang Qu,Guoqing Xu,차석원,Yanhui Zhang,Wei Feng,Junci Cao,Weili Li,Yihuang Zhang,Zhigang Wu 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.9

An innovative permanent magnet synchronous motor rotor position detection method using d-q reference-frames derived from PWM inverter switching is presented based on carrier phase-shift PWM method. It also gives the development the polarity identification at standstill for permanent magnet synchronies motor in the rotary frame with position detected of the neutral voltage. The new technique detects the motor position from simple measurements of the neutral point voltage of the motor influenced by the variation of inductances with respect to rotor position. The transfer is derived with constant element and 2nd harmonic element of selfinductance and mutual-inductance between three phase inductances and the inductance of d-axis and q-axis. Theoretical studies are carried out and verified using experiment results with variation rotor position over one electrical cycle at standstill. Rotor position estimation from stator inductance variation with rotor position is effective in zero speed and low speed.

Occurrence and Molecular Identification of Giardia duodenalis from Stray Cats in Guangzhou, Southern China

Guochao Zheng,Wei Hu,Yuanjia Liu,Qin Luo,Liping Tan,Guoqing Li 대한기생충학열대의학회 2015 The Korean Journal of Parasitology Vol.53 No.1

The objective of this study was to genetically characterize isolates of Giardia duodenalis and to determine if zoonotic potential of G. duodenalis could be found in stray cats from urban and suburban environments in Guangzhou, China. Among 102 fresh fecal samples of stray cats, 30 samples were collected in Baiyun district (urban) and 72 in Conghua district (suburban). G. duodenalis specimens were examined using light microscopy, then the positive specimens were subjected to PCR amplification and subsequent sequencing at 4 loci such as glutamate dehydrogenase (gdh), triose phosphate isomerase (tpi), β-giardin (bg), and small subunit ribosomal RNA (18S rRNA) genes. The phylogenetic trees were constructed using obtained sequences by MEGA5.2 software. Results show that 9.8% (10/102) feline fecal samples were found to be positive by microscopy, 10% (3/30) in Baiyun district and 9.7% (7/72) in Conghua district. Among the 10 positive samples, 9 were single infection (8 isolates, assemblage A; 1 isolate, assemblage F) and 1 sample was mixed infection with assemblages A and C. Based on tpi, gdh, and bg genes, all sequences of assemblage A showed complete homology with AI except for 1 isolate (CHC83). These findings not only confirmed the occurrence of G. duodenalis in stray cats, but also showed that zoonotic assemblage A was found for the first time in stray cats living in urban and suburban environments in China.

Flow Behaviour and Constitutive Modelling of a Ferritic Stainless Steel at Elevated Temperatures

Jingwei Zhao,Zhengyi Jiang,Guoqing Zu,Wei Du,Xin Zhang,Laizhu Jiang 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.3

The flow behaviour of a ferritic stainless steel (FSS) was investigated by a Gleeble 3500 thermal-mechanical test simulator over the temperature range of 900-1100 °C and strain rate range of 1-50 s -1 . Empirical and phenomenological constitutive models were established, and a comparative study was made on the predictability of them. The results indicate that the flow stress decreases with increasing the temperature and decreasing the strain rate. High strain rate may cause a drop in flow stress after a peak value due to the adiabatic heating. The Zener-Hollomon parameter depends linearly on the flow stress, and decreases with raising the temperature and reducing the strain rate. Significant deviations occur in the prediction of flow stress by the Johnson-Cook (JC) model, indicating that the JC model cannot accurately track the flow behaviour of the FSS during hot deformation. Both the multiple-linear and the Arrhenius-type models can track the flow behaviour very well under the whole hot working conditions, and have much higher accuracy in predicting the flow behaviour than that of the JC model. The multiple-linear model is recommended in the current work due to its simpler structure and less time needed for solving the equations relative to the Arrhenius-type model.

Preparation and thermo-mechanical properties of heat-resistant epoxy/silica hybrid materials

Yang, Peng,Wang, Guoqing,Xia, Xue,Takezawa, Yoshitaka,Wang, Haitao,Yamada, Shinji,Du, Qiangguo,Zhong, Wei Wiley Subscription Services, Inc., A Wiley Company 2008 Polymer engineering and science Vol.48 No.6

<P>Diglycidyl ether of bisphenol-A (DGEBA) based epoxy/silica hybrid materials filled with various amounts of 3-glycidoxypropyltrimethoxysilane (GPTMS) and silica nanoparticles were prepared, using 4,4′-diaminodiphenyl sulfone (DDS) as curing agent. The obtained hybrid materials were analyzed by means of Fourier-transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The results indicated that the introduction of GPTMS and silica nanoparticles had synergistic effect. The addition of GPTMS not only ameliorated the compatibility between silica and the epoxy matrix but also increased the crosslinking density of the epoxy system; meanwhile the nano-silica further reinforced the inorganic network of the hybrid system. Consequently, the hybrid materials showed much improved heat-resistant properties. The storage modulus of the hybrid systems showed no obvious decrement in the glass transition region and kept at a high value even in the temperature region up to 300°C. The integral thermal stability of the resulting hybrid materials was also improved compared with the corresponding pure epoxy resin. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.</P>

Immunomodulatory biomaterials for implant-associated infections: from conventional to advanced therapeutic strategies

Dong Jiale,Wang Wenzhi,Zhou Wei,Zhang Siming,Li Meng,Li Ning,Pan Guoqing,Zhang Xianzuo,Bai Jiaxiang,Zhu Chen 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Implant-associated infection (IAI) is increasingly emerging as a serious threat with the massive application of biomaterials. Bacteria attached to the surface of implants are often difficult to remove and exhibit high resistance to bactericides. In the quest for novel antimicrobial strategies, conventional antimicrobial materials often fail to exert their function because they tend to focus on direct bactericidal activity while neglecting the modulation of immune systems. The inflammatory response induced by host immune cells was thought to be a detrimental force impeding wound healing. However, the immune system has recently received increasing attention as a vital player in the host’s defense against infection. Anti-infective strategies based on the modulation of host immune defenses are emerging as a field of interest. This review explains the importance of the immune system in combating infections and describes current advanced immune-enhanced anti-infection strategies. First, the characteristics of traditional/conventional implant biomaterials and the reasons for the difficulty of bacterial clearance in IAI were reviewed. Second, the importance of immune cells in the battle against bacteria is elucidated. Then, we discuss how to design biomaterials that activate the defense function of immune cells to enhance the antimicrobial potential. Based on the key premise of restoring proper host-protective immunity, varying advanced immune-enhanced antimicrobial strategies were discussed. Finally, current issues and perspectives in this field were offered. This review will provide scientific guidance to enhance the development of advanced anti-infective biomaterials.

Di-2-ethylhexyl phthalate induced oxidative damage involving FasL-associated apoptotic pathway in mouse spermatogenic GC-2spd cells

Xiao Tang,Kun Tong,Lishan Zhu,Guoqing Fu,Wei Chang,Ting Zhou,Zhibing Zhang,Ling Tong,Ling Zhang,Yuqin Shi,Ling Zhang,Yuqin Shi 대한독성 유전단백체 학회 2016 Molecular & cellular toxicology Vol.12 No.4

Di-2-ethylhexyl phthalate (DEHP) which belongs to phthalatic-acid esters, is a kind of harmful, global environmental pollutants. It is a known endocrine disrupting chemical and male reproductive toxicant. However, the mechanism by which DEHP exposure result in male reproductive toxicity is still unclear. To elucidate the productive toxicity mechanism of DEHP, we attemptted to investigate oxidative stress, apoptotic effects, mRNA and protein expression of apoptosis-associated genes including FasL, caspase-3, and caspase-8 in GC-2spd (mouse spermatogenic cells). The results showed that, with the increase of DEHP concentration, cell apoptosis rate increased; the activities of relation index of oxidative stress such as malondialdehyde (MDA), superoxide dismutase (SOD) and glutatione peroxidase (GSH-PX) changed significantly; the mRNA and protein expression levels of FasL, caspase-3, -8, altered obviously. These results suggested that DEHP could induce apoptosis of GC-2spd cells through oxidative stress and FasL-dependent pathway.