Irradiation-Induced Hardening and Softening of CLAM Steel Under Fe Ion Irradiation

Qingshan Li,Yinzhong Shen,Xi Huang,Zhiqiang Xu,Jun Zhu 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.6

The irradiation-induced hardening and softening of CLAM steel irradiated with 3.5 MeV Fe13+ions at temperaturesof 300 °C and 550 °C were investigated by nanoindentation tests in combination with microstructures. Irradiation-induced hardening occurred in the steel irradiated at 300 °C to doses of 0.46 dpa, 0.94 dpa, and 2.79 dpa. The hardening occurred at 300 °C is mainly attributed to the formation of irradiation-produced dislocation loopsand a network of tangled dislocations in the irradiated steel samples. Significant hardening was found in the steelirradiated at 550 °C to 0.38 dpa. On the contrary, irradiation-induced softening occurred in the steel irradiated at550 °C to both 0.76 dpa and 2.75 dpa. Irradiation-produced dislocation loops are not dominant effect on the irradiationhardening of the steel samples irradiated at 550 °C. The hardening and softening of the irradiated steel wereexplained in terms of the irradiation-produced defects and recovery process occurred during the irradiation.

Optoelectronic Characteristics of UV Photodetector Based on GaN/ZnO Nanorods p-i-n Heterostructures

Qingshan Li,Lichun Zhang,Fengzhou Zhao,Caifeng Wang,Feifei Wang,Ruizhi Huang 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.4

We demonstrate an efficient ultraviolet (UV) photodetector operating at room temperature based on n-ZnO nanorods/i-ZnO/p-GaN heterojunctions. We employ x-ray diffraction and field-emission scanning electron microscopy to confirm the high quality of the ZnO nanorods using an undoped ZnO film as the interlayer. Then, we investigate the photoelectric properties of the fabricated photodetector with UV light illumination under a different reverse bias. Based on the current-voltage curve, the photocurrent to dark current ratio is approximately 73.3 at −4 V. At zerobias voltage, the peak responsivity was 138.9 mA/W at 362 nm under front-illumination conditions. Time-varying measurements indicate the reproducibility and stability of the heterojunction photodetector.

Effect of irradiation temperature on the nanoindentation behavior of P92 steel with thermomechanical treatment

Huang Xi,Shen Yinzhong,Li Qingshan,Li Xiaoyan,Zhan Zixiong,Li Guang,Li Zhenhe 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.7

The nanoindentation behavior of P92 steel with thermomechanical treatment under 3.5 MeV Fe13þ ion irradiation at room temperature, 400 and 700 C was investigated. Pop-in behavior is observed for all the samples with and without irradiation at room temperature, while the temperature dependence of pop-in behavior is only observed in irradiated samples. The average load and penetration depth at the onset of pop-in increase as the irradiation temperature increases, in line with the results of the maximum shear stress. Irradiation induced hardening is exhibited for all irradiated samples, but there is a significant reduction in the hardness of sample irradiated at 700 C in comparison to the samples irradiated at room temperature and 400 C. The ratio of hardness to elastic modulus for all samples decreases with increasing penetration depth except for samples at 700 C. With the increasing of irradiation temperature, the ratio of the irreversible work to the total work gradually decreases. In contrast, it increases for samples without irradiation

Expression Profile of Neuro-Endocrine-Immune Network in Rats with Vascular Endothelial Dysfunction

Li, Lujin,Jia, Zhenghua,Xu, Ling,Wu, Yiling,Zheng, Qingshan The Korean Society of Pharmacology 2014 The Korean Journal of Physiology & Pharmacology Vol.18 No.2

This study was to determine the correlation between endothelial function and neuro-endocrine-immune (NEI) network through observing the changes of NEI network under the different endothelial dysfunction models. Three endothelial dysfunction models were established in male Wistar rats after exposure to homocysteine (Hcy), high fat diet (HFD) and Hcy+HFD. The results showed that there was endothelial dysfunction in all three models with varying degrees. However, the expression of NEI network was totally different. Interestingly, treatment with simvastatin was able to improve vascular endothelial function and restored the imbalance of the NEI network, observed in the Hcy+HFD group. The results indicated that NEI network may have a strong association with endothelial function, and this relationship can be used to distinguish different risk factors and evaluate drug effects.

Cross-coupling control method of the two-axis linear motor based on second-order terminal sliding mode

Zheng Li,Qingshan Zhang,Jinfeng An,Huixian Liu,Hexu Sun 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.3

When the dual-axis linear motor is processing components, its accuracy will be affected by the uncertainty and nonlinearity of the system, and the complexity of the processing curve trajectory. The goal is to improve the machining accuracy and response speed of the XY dual-axis permanent magnet synchronous linear motor two-dimensional platform, improve the anti-interference ability, and reduce the contour error. This paper proposes a coupled control method based on dual closed-loop single-axis high-order terminal sliding mode position control (TSMC). First, an improved mathematical model of equivalent contour error is established. Combine the coordinated controller to get the coupling link. Then, to accelerate error convergence and suppress chattering, a high-order terminal sliding mode controller is designed. The single-axis current controller is designed using high-order sliding mode algorithms. Simulations and experiments show the effectiveness and feasibility of the proposed method.

Expression Profile of Neuro-Endocrine-Immune Network in Rats with Vascular Endothelial Dysfunction

Lujin Li,Yiling Wu,Qingshan Zheng,Zhenghua Jia,Ling Xu 대한약리학회 2014 The Korean Journal of Physiology & Pharmacology Vol.18 No.2

This study was to determine the correlation between endothelial function and neuro-endocrineimmune(NEI) network through observing the changes of NEI network under the different endothelialdysfunction models. Three endothelial dysfunction models were established in male Wistar rats afterexposure to homocysteine (Hcy), high fat diet (HFD) and Hcy+HFD. The results showed that therewas endothelial dysfunction in all three models with varying degrees. However, the expression of NEInetwork was totally different. Interestingly, treatment with simvastatin was able to improve vascularendothelial function and restored the imbalance of the NEI network, observed in the Hcy+HFD group. The results indicated that NEI network may have a strong association with endothelial function, andthis relationship can be used to distinguish different risk factors and evaluate drug effects.

Room Temperature Electroluminescence from n-ZnO:Ga/i-ZnO/p-GaN:Mg Heterojunction Device Grown by PLD

Lichun Zhang,Qingshan Li,Feifei Wang,Chong Qu,Fengzhou Zhao 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.3

The n-ZnO:Ga/p-GaN:Mg and n-ZnO:Ga/i-ZnO/p-GaN:Mg heterojunction light emitting diodes (LEDs) were fabricated by the pulsed laser deposition (PLD) technique. The blue electroluminescence (EL) of the n-ZnO:Ga/ p-GaN:Mg heterojunction LEDs is emitted mainly from the p-GaN layer instead of the n-ZnO:Ga layer, for the reason that the electron injection from n-ZnO:Ga prevailed over the hole injection from p-GaN:Mg due to the higher carrier concentration and carrier mobility in n-ZnO:Ga. On the other hand, the n-ZnO:Ga/i-ZnO/p- GaN:Mg heterojunction LEDs exhibited dominant ultraviolet-blue emission. The reason for this difference is attributed to the inserted undoped i-ZnO layer between n-ZnO:Ga and p-GaN:Mg, in which the holes from p- GaN:Mg and the electrons from n-ZnO:Ga are recombined.

Developments and applications of a modified wall function for boundary layer flow simulations

Jian Zhang,Qingshan Yang,Q.S. Li 한국풍공학회 2013 한국풍공학회지 Vol.17 No.4

Wall functions have been widely used in computational fluid dynamics (CFD) simulations and can save significant computational costs compared to other near-wall flow treatment strategies. However, most of the existing wall functions were based on the asymptotic characteristics of near-wall flow quantities, which are inapplicable in complex and non-equilibrium flows. A modified wall function is thus derived in this study based on flow over a plate at zero-pressure gradient, instead of on the basis of asymptotic formulations. Turbulent kinetic energy generation (GP), dissipation rate () and shear stress () are composed together as the near-wall expressions. Performances of the modified wall function combined with the nonlinear realizable k - turbulence model are investigated in homogeneous equilibrium atmosphere boundary layer (ABL) and flow around a 6 m cube. The computational results and associated comparisons to available full-scale measurements show a clear improvement over the standard wall function, especially in reproducing the boundary layer flow. It is demonstrated through the two case studies that the modified wall function is indeed adaptive and can yield accurate prediction results, in spite of its simplicity.

Non-stationary and non-Gaussian characteristics of wind speeds

Hui, Yi,Li, Bo,Kawai, Hiromasa,Yang, Qingshan Techno-Press 2017 Wind and Structures, An International Journal (WAS Vol.24 No.1

Non-stationarity and non-Gaussian property are two of the most important characteristics of wind. These two features are studied in this study based on wind speed records measured at different heights from a 325 m high meteorological tower during the synoptic wind storms. By using the time-frequency analysis tools, it is found that after removing the low frequency trend of the longitudinal wind, the retained fluctuating wind speeds remain to be asymmetrically non-Gaussian distributed. Results show that such non-Gaussianity is due to the weak-stationarity of the detrended fluctuating wind speed. The low frequency components of the fluctuating wind speeds mainly contribute to the non-zero skewness, while distribution of the high frequency component is found to have high kurtosis values. By further studying the decomposed wind speed, the mechanisms of the non-Gaussian distribution are examined from the phase, turbulence energy point of view.

An alternative method for estimation of annual extreme wind speeds

Yi Hui,Qingshan Yang,Zhengnong Li 한국풍공학회 2014 Wind and Structures, An International Journal (WAS Vol.19 No.2

This paper presents a method of estimation of extreme wind. Assuming the extreme wind follows the Gumbel distribution, it is modeled through fitting an exponential function to the numbers of storms over different thresholds. The comparison between the estimated results with the Improved Method of Independent Storms (IMIS) shows that the proposed method gives reliable estimation of extreme wind. The proposed method also shows its advantage on the insensitiveness of estimated results to the precision of the data. The volume of extreme storms used in the estimation leads to more than 5% differences in the estimated wind speed with 50-year return period. The annual rate of independent storms is not a significant factor to the estimation.