HVOF Spray Performance Optimization Analysis and Experimental Research of WC–12Co Coating on Ti Alloy

Xinxue Chen,Chang Li,Siyu Li,Xing Han,Haisheng Jiang,Xiaoyu Zhao 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.12

TC18 titanium alloy, with low density, high strength and corrosion resistance, is a significant material for the main loadbearingcomponents of aircraft landing gear and other aviation structures. However, its corrosion resistance and wear resistanceare insufficient when it is serviced in the extreme corrosion environments such as sea salt spray and hygrothermal,which greatly affects its wide application. It is significant to design and develop high-quality anti-corrosion and wear resistantcoatings for TC18 titanium alloy. High Velocity Oxygen Fuel (HVOF) spraying WC–12Co is an ideal strengthening methodto replace surface chromium plating. Quantitatively evaluating the influence of spraying process parameters on the coatingquality is the key to prepare high-quality coatings. In this study, a numerical model of HVOF spraying WC–12Co wasestablished with JP5000 spray gun. The spray combustion reaction model and discrete phase model were solved to reveal theevolution characteristics of combustion flame flow and particle flight behavior in the spraying process. Based on the responsesurface method, the optimum spraying process parameters were determined, and the WC–12Co coatings were prepared. Onthis basis, the coating was tested by the SEM, XRD, hardness, friction and wear, salt spray corrosion and seawater corrosion. The corrosion resistance and wear resistance of the WC–12Co coating were comprehensively evaluated. The experimentshows that the WC–12Co coating prepared by HVOF spraying has great performance, which can effectively improve theprotective performance of TC18 substrate.

Study on Multi-Field Coupled Evolution Mechanism of Laser Irradiated 40Cr Steel Quenching Process Based on Phase Change Induced Plasticity

Chang Li,Hexin Gao,Xinxue Chen,Zhaotai Liu,Xing Han 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8

40Cr is essential to steel for the manufacture of hardened gears, and optimizing its laser quenching process will be of greatsignificance for gear wear and life extension. However, the complete reliance on the experimental trial-and-error approachdoes not effectively reveal the mechanism of the evolution of the laser quenching process in disk laser. Numerical simulationprovides an effective way to obtain the transient evolution of the laser quenching process. In this paper, the temperaturechanges physical parameters of the quenched material are calculated based on the CALPHAD method. Establish a thermoelastic–plastic multi-field coupling model for the laser hardening process of the disk laser 40Cr gear steel. Perform thenumerical calculations on the transient temperature, martensite phase fraction, and the transformation-induced plasticitystress evolution of the 40Cr laser hardening process. Focus on the mechanism of the mutual coupling between phase changebehavior and plastic strain. Calculations show that there is heat accumulation during quenching, with a peak temperatureof 1448 K. Plastic stress has a “hump” distribution, with a peak value of 834 MPa, which is 1.25 mm from the center ofthe focal point. The experimental analyses of the 40Cr gear steel quenching microstructure and hardness distribution stateby the Axioskop2 scanning electron microscope, the KEYENCE VH-Z100R super depth of field 3D microscope, and theQ10M microhardness tester reveal the mechanical behavior of the material and the phase hardening law during the quenchingprocess. That provided an essential theoretical basis for effective prediction on quenching residual stress and optimizingindustrial production parameters.

Testicular fat deposition attenuates reproductive performance via decreased follicle-stimulating hormone level and sperm meiosis and testosterone synthesis in mouse

Miao Du,Shikun Chen,Yang Chen,Xinxu Yuan,Huansheng Dong Asian Australasian Association of Animal Productio 2024 Animal Bioscience Vol.37 No.1

Objective: Testicular fat deposition has been reported to affect animal reproduction. However, the underlying mechanism remains poorly understood. The present study explored whether sperm meiosis and testosterone synthesis contribute to mouse testicular fat deposition-induced reproductive performance. Methods: High fat diet (HFD)-induced obesity CD1 mice (DIO) were used as a testicular fat deposition model. The serum hormone test was performed by agent kit. The quality of sperm was assessed using a Sperm Class Analyzer. Testicular tissue morphology was analyzed by histochemical methods. The expression of spermatocyte marker molecules was monitored by an immuno-fluorescence microscope during meiosis. Analysis of the synthesis of testosterone was performed by real-time polymerase chain reaction and reagent kit. Results: It was found that there was a significant increase in body weight among DIO mice, however, the food intake showed no difference compared to control mice fed a normal diet (CTR). The number of offspring in DIO mice decreased, but there was no significant difference from the CTR group. The levels of follicle-stimulating hormone were lower in DIO mice and their luteinizing hormone levels were similar. The results showed a remarkable decrease in sperm density and motility among DIO mice. We also found that fat accumulation affected the meiosis process, mainly reflected in the cross-exchange of homologous chromosomes. In addition, overweight increased fat deposition in the testis and reduced the expression of testosterone synthesis-related enzymes, thereby affecting the synthesis and secretion of testosterone by testicular Leydig cells. Conclusion: Fat accumulation in the testes causes testicular cell dysfunction, which affects testosterone hormone synthesis and ultimately affects sperm formation.

Appraisal of Guidelines for the Management of Blood Pressure in Patients with Diabetes Mellitus: The Consensuses, Controversies and Gaps

Menghui Liu,Shaozhao Zhang,Xiaohong Chen,Yue Guo,Xiangbin Zhong,Zhenyu Xiong,Yifen Lin,Huimin Zhou,Yiquan Huang,Zhengzhipeng Zhang,Lichun Wang,Xiaodong Zhuang,Xinxue Liao 대한당뇨병학회 2021 Diabetes and Metabolism Journal Vol.45 No.5

Background: Currently available guidelines contain conflicting recommendations on the management of blood pressure (BP) in patients with diabetes mellitus (DM). Therefore, it is necessary to appraise the guidelines and summarize the agreements and differences among recommendations.Methods: Four databases and the websites of guideline organizations were searched for guidelines regarding BP targets and thresholds for pharmacologic therapy in DM patients, and the included guidelines were appraised with the Appraisal of Guidelines for Research and Evaluation (AGREE) II instrument.Results: In 6,498 records identified, 20 guidelines met our inclusion criteria with 64.0% AGREE II scores (interquartile range, 48.5% to 72.0%). The scores of the European and American guidelines were superior to those of the Asian guidelines (both adjusted P<0.001). Most of the guidelines advocated systolic BP targets <130 mm Hg (12 guidelines, 60%) and diastolic BP targets <80 mm Hg (14 guidelines, 70%) in DM patients. Approximately half of the guidelines supported systolic BP thresholds >140 mm Hg (10 guidelines, 50%) and diastolic BP thresholds >90 mm Hg (nine guidelines, 45%). The tiny minority of the guidelines provided the relevant recommendations regarding the lower limit of official BP targets and the ambulatory BP monitoring (ABPM)/home BP monitoring (HBPM) targets and thresholds in DM patients.Conclusion: The lower official BP targets (<130/80 mm Hg) in patients with DM are advocated by most of the guidelines, but they contain conflicting recommendations on the official BP thresholds. Moreover, the gaps regarding the lower limit of official BP targets and the ABPM/HBPM targets and thresholds need to be considered by future study.

Study of flow instability in a centrifugal fan based on energy gradient theory

Meina Xiao,Qing Xiao,Hua-Shu Dou,Xiaoyang Ma,Yongning Chen,Haijiang He,Xinxue Ye 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.2

Flow instability in a centrifugal fan was studied using energy gradient theory. Numerical simulation was performed for the threedimensional turbulent flow field in a centrifugal fan. The flow is governed by the three-dimensional incompressible Navier-Stokes equations coupled with the RNG k-ε turbulent model. The finite volume method was used to discretize the governing equations and the Semiimplicit method for pressure linked equation (SIMPLE) algorithm is employed to iterate the system of the equations. The interior flow field in the centrifugal fan and the distribution of the energy gradient function K are obtained at different flow rates. According to the energy gradient method, the area with larger value of K is the place where the flow loses stability easier. The results show that instability is easier to generate in the regions of impeller outlet and volute tongue. The air flow near the hub is more stable than that near the shroud. That is due to the influences of variations of the velocity and the inlet angle along the axial direction. With the decrease of the flow rate, instability zone in a blade channel moves to the impeller inlet from the outlet and the unstable regions in different channels develop in opposite direction to the rotation of impeller.

Maternal betaine supplementation ameliorates fatty liver disease in offspring mice by inhibiting hepatic NLRP3 inflammasome activation

Li Lun,Sun Liuqiao,Liang Xiaoping,Ou Qian,Tan Xuying,Li Fangyuan,Lai Zhiwei,Ding Chenghe,Chen Hangjun,Yu Xinxue,Wu Qiongmei,Wei Jun,Wu Feng,Wang Lijun 한국영양학회 2023 Nutrition Research and Practice Vol.17 No.6

BACKGROUND/OBJECTIVES: Previous research has shown maternal betaine supplementation alleviates fetal-derived hepatic steatosis. Therefore, this study examined the anti-inflammatory effect of maternal betaine intake in offspring mice and its mechanism. MATERIALS/METHODS: Female C57BL/6J mice and their offspring were randomly divided into 3 groups according to the treatment received during gestation and lactation: control diet (CD), fatty liver disease (FLD), and fatty liver disease + 1% betaine (FLD-BET). The FLD group was given a high-fat diet and streptozotocin (HFD + STZ), and the FLD-BET group was treated with HFD + STZ + 1% betaine. After weaning, the offspring mice were given a normal diet for 5 weeks and then dissected to measure the relevant indexes. RESULTS: Compared to the CD group, the offspring mice in the FLD group revealed obvious hepatic steatosis and increased serum levels of alanine aminotransferase, interleukin (IL)-6, and tumor necrosis factor (TNF)-α; maternal betaine supplementation reversed these changes. The hepatic mRNA expression levels of IL-6, IL-18, and Caspase-1 were significantly higher in the FLD group than in the CD group. Maternal betaine supplementation reduced the expression of IL-1β, IL-6, IL-18, and apoptosis-associated speck-like protein containing C-terminal caspase recruitment domain (ASC). Maternal betaine supplementation also reversed the increasing protein expressions of nitric oxide dioxygenase-like receptor family pyrin domain containing 3 (NLRP3), ASC, Caspase-1, IL-1β, and IL-18 in offspring mice exposed to HFD + STZ. Maternal betaine supplementation decreased the homocysteine (Hcy) and s-adenosine homocysteine (SAH) levels significantly in the livers. Furthermore, the hepatic Hcy concentrations showed significant inverse relationships with the mRNA expression of TNF-α, NLRP3, ASC, and IL-18. The hepatic SAH concentration was inversely associated with the IL-1β mRNA expression. CONCLUSIONS: The lipotropic and anti-inflammatory effect of maternal betaine supplementation may be associated with the inhibition of NLRP3 inflammasome in the livers of the offspring mice.