Experimental study and analysis of design parameters for analysis of fluidelastic instability for steam generator tubing

Guangming Xiong,Yong Zhu,Teng Long,Wei Tan 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.1

In this paper, the evaluation method of fluidelastic instability (FEI) of newly designed steam generator tubing in pressurized water reactor (PWR) nuclear power plants is discussed. To obtain the parameters for prediction of the critical velocity of FEI for steam generator tubes, experimental research is carried out, and the design parameters are determined. Using CFD numerical simulation, the tube array scale of the model experiment is determined, and the experimental device is designed. In this paper, 7 groups of experiments with void fractions of 0% (water), 10%, 20%, 50%, 75%, 85% and 95% were carried out. The critical damping ration, fundamental frequency and critical velocity of FEI of tubes in flowing water were measured. Through calculation, the total mass and instability constant of the immersed tube are obtained. The critical damping ration measured in the experiment mainly included two-phase damping and viscous damping, which changed with the change in void fraction from 1.56% to 4.34%. This value can be used in the steam generator design described in this paper and is conservative. By introducing the multiplier of frequency and square root of total mass per unit length, it is found that the difference between the experimental results and the calculated results is less than 1%, which proves the rationality and feasibility of the calculation method of frequency and total mass per unit length in engineering design. Through calculation, the instability constant is greater than 4 when the void fraction is less than 75%, less than 4 when the void fraction exceeds 75% and only 3.04 when the void fraction is 95%.

Differences in the starvation-induced autophagy response in MDA-MB-231 and MCF-7 breast cancer cells

Wanyun Zhu,Hong-Jiang Wei,Hong-Ye Zhao,Hao Qu,Kaixiang Xu,Baoyu Jia,Haifeng Li,Yimin Du,Guangming Liu 한국통합생물학회 2017 Animal cells and systems Vol.21 No.3

Breast cancer is a heterogeneous disease with distinct subtypes that have made targeted therapy of breast cancer challenging. Previous studies have demonstrated that an altered autophagy capacity can influence the development of breast cancer. However, the molecular differences in starvationinduced autophagic responses in MDA-MB-231 and MCF-7 cells have not been fully elucidated. In this study, we found that an increase of LC3B-II protein expression level and a decrease of the p62 protein expression level in both cells treated by Earle’s balanced salt solution. Meanwhile, we observed an increase of autophagosome using transmission electron microscopy and an enhancement in the green fluorescence intensity of LC3B protein by confocal microscopy. Furthermore, we detected the expression of 13 autophagy-related (ATG) genes and 11 autophagy signaling pathway-related genes using qPCR. Among 13 ATG genes, we found that 6 genes were up-regulated in treated MDA-MB-231 cells, while 4 genes were up-regulated and 1 gene was down-regulated in treated MCF-7 cells. In addition, among 11 autophagy signaling pathway-related genes, 7 genes were up-regulated in treated MDA-MB-231 cells, while 5 genes were up-regulated and 1 gene was down-regulated in treated MCF-7 cells. These findings suggest that the autophagic response to starvation was different in the two treated cell lines, which will contribute to further study on the molecular mechanism of starvation-induced autophagy and improve the targeted therapy of breast cancer.

Implementation of the Adaptive CSMA-CA Algorithm Based on Traffic Load

Lin Zhu,Guangming Li,Wei Liu 보안공학연구지원센터 2014 International Journal of Future Generation Communi Vol.7 No.4

Preparation and Characterization of Polyimide/Alumina Composite Films as Improved Solid Dielectrics

Xiaoping Cui,Guangming Zhu,Wenyuan Liu 한국고분자학회 2016 폴리머 Vol.40 No.4

Polyimide/alumina (PI/Al₂O₃) nanocomposite films were prepared by incorporating different nano-sized Al₂O₃ contents into PI which derived from pyromellitic dianhydride (PMDA) and a flexible diamine 4,4-bis(3-aminophenoxy) biphenyl (4,3-BAPOBP). The micromorphology, chemical structure, dielectric, mechanical properties and glass transition temperatures (Tg) of prepared films were investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), LCR metry, electronic tensile testing and differential scanning calorimetry (DSC). SEM images show uniform distribution of Al₂O₃ nanoparticles in matrix. FTIR spectra indicate that Al₂O₃ nanoparticles are functionalized with γ-aminopropyl triethoxysilane (γ-APS) and the imidization was complete. XRD patterns reveal the peaks of PI/Al₂O₃ composite films were similar to those of Al₂O₃, indicating that the crystal structure of Al₂O₃ remains unchanged and stable after being doped into PI matrix. Meanwhile, the effects of additives on the dielectric and mechanical properties of composite films were also studied. The results show the dielectric constant and dielectric loss of hybrid materials increase with the addition of Al₂O₃ nanoparticles. The electrical breakdown strength and tensile strength of PI/Al₂O₃ can be markedly improved by the addition of appropriate amounts of Al₂O₃ to the PI matrix.

Tuning of BixOyCl formation with sonication time during ultrasound-hydrothermal preparation

Zeqing Long,Guangming Zhang,Ting Wei,Lijun Niu,Jia Zhu,Jinwei Li 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.84 No.-

Developing novel and visible-light drive photocatalysts is a hot topic, and bismuth oxychloride is one ofthe popular photocatalysts. In this paper, a series of bismuth oxychloride were synthesized by ultrasonic-hydrothermal method with different ultrasonic time. By simply changing the ultrasonic time, we cancontrol the morphology, structure, stoichiometry and photoelectric performance of bismuth oxychloride. The possible mechanism for the formation of BixOyCl photocatalysts involved the ultrasonic destructionof chemical bonds and increase of oxygen vacancy concentration, and the influence of ultrasonic on thepH during preparation. The sample of ultrasonic 30 min (U-30) showed the best photocatalytic activitydue to the suitable morphology, structure, photoelectric performance, the formation of theheterostructure, and the presence of oxygen vacancies. For the removal of Rhodamine B (/Ciprofloxacin),the reaction rate constant for U-30 was 10.4 (/3.6), 4.9 (/1.6), 6.9 (/4.8), and 9.3 (/2.3) times that of the U-0,U-10, U-20, and U-40, respectively. Photoluminescence spectra showed that the photogeneratedelectron-hole recombination rate decreased gradually with the ultrasonic time. Further, the possiblemechanism of photocatalytic process was investigated. This research provides a green, economical andsimple method to modify bismuth oxychloride.

Improving Interfacial Interactions of CF/PEEK Composites with Sulfonated Polyether Sulfone

Tianning Ren,Guangming Zhu,Xiaoming Ren,Renjie Tian,Ben Li 한국섬유공학회 2021 Fibers and polymers Vol.22 No.1

Due to the limitation of surface inertness and wettability of carbon fibers (CF), the adhesion between Poly(etherether-ketone) (PEEK) resin matrix and CF is poor, which reduces the mechanical properties of CF/PEEK composites. Inorder to improve the interfacial performance between PEEK matrix and carbon fiber fabric, sulfonated-polyether-sulfone (s-PSF) was coated as a sizing agent on the surface of the carbon fiber to construct CF/PEEK composite interface. On one hand,the formation of hydrogen bonds between s-PSF and activated CF increases the adhesion between s-PSF and fibers. On theother hand, Good compatibility between S-PSF and PEEK, which improves the interface performance between PEEK andCF. The results showed that the mechanical properties and interface properties of CF/PEEK composite prepared by modifiedCF were improved to some extent. The flexural strength, flexural modulus, impact strength and interlaminar shear strength ofthe materials were increased by 57.5 %, 16.7 %, 44.2 % and 39.7 %, respectively. By introducing s-PSF as sizing agent intoCF/PEEK composite interface, the comprehensive properties of the material were effectively improved.

Research on metal flow law of micro-riblets based on multi-pass rolling

Xujie Gao,Huihang Wang,Guangming Zhu,Zheng Chang,Nana Guo,Zongshen Wang,Lihua Zhu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.5

Micro-riblets (grooves) can reduce surface friction in turbulent flow by up to 10 %. Furthermore, roll forming is an effective method for manufacturing large-area groove structures. In this study, the fluidity of metal during the multi-pass rolling of microgrooves was studied, and the reason for the accumulation of materials at the end of rolling was explained. A comparative analysis was conducted between single-pass rolling and multi-pass rolling. Then, according to the distribution of stress field and strain field, the force and flow tendency of the metal during rolling were studied. The gradually changing streamlined roller tooth profile promoted the flow of metal to both sides of the gear hob. Given the same reduction, the forming height of micro-grains during multi-pass rolling was 64.2 % higher than that during single-pass rolling.

Self-bending extrusion molding of distorted channels

Fanlei Min,Huiping Liu,Guangming Zhu,Zheng Chang,Xujie Gao,Bowen Yue,Nana Guo,Xiaoqing Zhai 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.5

Using an integrated profile extrusion and bending forming process with a streamlined extrusion die, a new self-bending extrusion molding technology is proposed with an axis-distorted variable channel. By designing the streamlined extrusion die structure of the distorted central axis, the metal was made to flow non-uniformly in the die cavity, thereby directly extruding a bent profile. The central axis of the streamlined extrusion die is described by a trigonometric function and a Gaussian function. A numerical simulation was applied to analyze the metal flow pattern, equivalent strain, and strain-rate distribution during the self-bending extrusion process. The influences of the extrusion velocity and the addition of a bearing on the self-bending deformation profiles were investigated. During the extrusion process, the streamline at the center of the billet could describe the overall flow of the metal in the die cavity, and the distance between the point on the end face of the die outlet and the center of the die outlet directly determined the degree of extrusion and bending. The greater the distance was, the larger was the degree of bending. The metal strain on the convex edge of the die was greater than that on the concave edge of the die, with the extruded profile always bending toward the concave edge. The strain rate of the metal changed the fastest near the most convex point of the die. As the extrusion velocity increased or more bearings were added, the radius of curvature of the extruded profile increased nonlinearly.