TATB造型颗粒温等静压成型X射线微层析成像

与传统钢模成型相比,温等静压成型是一种获得致密、均匀高聚物粘结炸药的更优方法,为温等静压成型高聚物粘结炸药精密物理性能研究提供细观结构基础,利用X射线微层析成像技术研究了三氨基三硝基苯(TATB)造型颗粒经温等静压成型圆柱样品的三维细观结构。结果显示,TATB造型颗粒经过温压后仍保留完整,典型形态呈多边体,压实颗粒间有高密度薄层、颗粒接触数最大达到12。CT图像分析表明,压实颗粒尺寸轴向分布保持不变,径向存在沿轴心方向的密度降和压力降;层面密度离散性高于1.15%,但体密度趋向均匀;分析内部力链分布情况,发现了温等静压成型过程TATB造型颗粒呈现等向压缩特征;基于细观颗粒接触角统计了颗粒接触数,证实了压实颗粒构形态及其排列趋向各向同性,但局部颗粒仍存在剪切压缩状态。

An interface shear damage model of chromium coating/steel substrate under thermal erosion load

The Cr-plated coating inside a gun barrel can effectively improve the barrel’s erosion resistance and thus increase the service life.However,due to the cyclic thermal load caused by high-temperature gunpowder,micro-element damage tends to occur within the Cr coating/steel substrate interface,leading to a gradual deterioration in macro-mechanical properties for the material in the related region.In order to mimic this cyclic thermal load and,thereby,study the thermal erosion behavior of the Cr coating on the barrel’s inner wall,a laser emitter is utilized in the current study.With the help of in-situ tensile test and finite element simulation results,a shear stress distribution law of the Cr coating/steel substrate and a change law of the interface ultimate shear strength are identified.Studies have shown that the Cr coating/steel substrate interface’s ultimate shear strength has a significant weakening effect due to increasing temperature.In this study,the interfacial ultimate shear strength decreases from 2.57 GPa(no erosion)to 1.02 GPa(laser power is 160 W).The data from this experiment is employed to establish a Cr coating/steel substrate interface shear damage model.And this model is used to predict the flaking process of Cr coating by finite element method.The simulation results show that the increase of coating crack spacing and coating thickness will increase the service life of gun barrel.

A review on ignition mechanisms and characteristics of magnesium alloys

Magnesium alloys have become more attractive because of their low density and electromagnetic shielding effectiveness in the aerospace industry.However,some unpredictable situation may lead to the ignition of magnesium alloys.In this review,the thermodynamic conditions and transfer processes of magnesium alloys ignition are analyzed from the point of mechanisms.The criteria of ignition are emphasized.In addition,ignitability and flammability test systems are compared.And a more suitable method to assess the potential ignition and flammability risks of magnesium alloys in extreme environments is recommended.Furthermore,the ignition characteristics of magnesium alloys are discussed in detail.It was found that the ignition of magnesium alloys is a complex process determined by internal properties such as thermo-physical properties,oxide film properties,chemical compositions and geometrical parameters,as well as the external environment such as gas species,oxygen concentration and oxygen pressure.Ignition temperature is not physical constants of materials.It is not simply assumed that ignition may occur when the temperature of Mg alloys reaches a certain ignition point.Finally,the unsolved issues in the ignition of magnesium alloys are pointed out and the future investigation are suggested for improving the safety and reliability of magnesium alloys in the aerospace applications.

Effect of homogenization annealing on internal residual stress distribution and texture in ME21 magnesium alloy extruded plates

The distribution of residual stresses through thickness of 5 mm-thick ME21 magnesium alloy extruded plates was analyzed non-destructively using short-wavelength X-ray diffraction(SWXRD),and the effect of homogenization annealing before extrusion on the residual stress was discussed.The classic d 0 method with an annealed stress-free reference specimen was employed to determine the residual stress of the extruded plates.The residual stress results showed that the gradient of residual stress in the transverse direction was larger than that of the extrusion direction.The homogenization process prior to extrusion weaken the formed sample’s texture.The maximum residual stress of the as-extruded plate was reduced,and the residual stress distribution was homogenized.

Research progress of residual stress determination in magnesium alloys

With the research development of the magnesium alloys,the deformation or stress corrosion induced by residual stress(RS)attracted extensive interests in industry and research efforts extensive.However,there are relatively few studies on the RS of magnesium alloys in the world.The generation cause of RS in magnesium alloys was analyzed at first.Several methods of determinate the RS,including destructive methods(drilling hole,crack compliance,layer exfoliation etc.)and non-destructive methods(X-ray Diffraction,Neutron Diffraction,Short Wavelength X-ray Diffraction)were summarized.The factors that influence the measuring accuracy of XRD method were emphasized.The research trends of RS in magnesium alloys were put forward.

槲皮素对脂多糖诱导的小胶质细胞增殖、迁移作用的作用

目的基于磷脂酰肌醇3-激酶(PI3K)/丝苏氨酸蛋白激酶(AKT)通路探究槲皮素对脂多糖(LPS)诱导的人小胶质细胞(HMC3)增殖、迁移和M1型极化的影响。方法将HMC3细胞分为对照组(正常培养)、模型组(炎症模型)、槲皮素组(造模后加入10.0μmol·L^(-1)槲皮素)、胰岛素样生长因子-Ⅰ(IGF-I)组(造模后再加入50.0 mg·mL^(-1)IGF-Ⅰ)、激动药组(造模后再加入10.0μmol·L^(-1)槲皮素+50.0 mg·mL^(-1)IGF-Ⅰ)和抑制药组(造模后再加入10.0μmol·L^(-1)槲皮素+10.0μmol·L^(-1)LY294002)。用细胞计数试剂盒-8(CCK-8)检测细胞活力;用酶联免疫吸附试验(ELISA)检测白细胞介素(IL)-10、肿瘤坏死因子(TNF-α)水平;用蛋白质印迹法检测精氨酸酶1(Arg1)和PI3K/AKT通路相关蛋白水平。结果对照组、模型组、槲皮素组、IGF-I组、激动药组和抑制药组的增殖率分别为(42.46±3.37)%、(15.21±1.37)%、(26.86±0.21)%、(25.31±1.91)%、(35.63±1.55)%和(15.79±1.18)%,迁移细胞数分别为68.67±3.51、155.33±6.51、109.33±2.08、95.33±4.62、75.67±6.66和147.33±4.73,IL^(-1)0水平分别为(44.26±1.30)、(17.84±0.82)、(26.26±1.00)、(28.74±0.87)、(37.00±1.24)和(21.56±0.94)ng·L^(-1),TNF-α水平分别为(2.81±0.57)、(18.91±1.01)、(12.04±0.57)、(11.52±0.77)、(5.81±0.50)和(16.56±1.29)pg·mL^(-1),Arg1蛋白表达水平分别为0.95±0.01、0.68±0.01、0.95±0.01、0.90±0.01、1.18±0.03和0.79±0.01,p-PI3K蛋白表达水平分别为0.63±0.02、0.13±0.01、0.37±0.02、0.33±0.02、0.47±0.01和0.19±0.02,p-AKT蛋白表达水平分别为0.69±0.02、0.16±0.01、0.41±0.01、0.42±0.01、0.52±0.01和0.21±0.01。模型组的上述指标与对照组比较,差异均有统计学意义(均P<0.05);槲皮素组的上述指标和IGF-I组与模型组比较,差异均有统计学意义(均P<0.05);激动药组的上述指标和抑制药组与槲皮素组比较,差异均有统计学意义(均P<0.05)。结论槲皮素促进PI3K/AKT信号通路活化提升LPS诱导的HMC3细胞的增殖能力,抑制HMC3细胞的迁移和M1型极化。

Hydrophobicity and tribological properties of Al_(2)O_(3)/PTFE composite coating

Al_(2)O_(3)/polytetrafluoroethylene(PTFE)composite coating was prepared on titanium alloy by cathode plasma electrolytic deposition(CPED)and impregnation method,to improve the hydrophobicity and tribological properties.Scanning electron microscopy(SEM)and energy-dispersive spectroscopy(EDS)analysis of the coating indicate that PTFE penetrates into the interior of the coating and is well bonded to titanium alloy substrate by cross-linking with Al_(2)O_(3) ceramic coating.The contact angles were measured by contact angle measurement,and the tribological properties of the composite coating were evaluated by sliding wear test.The surface of the composite coating is found to possess good hydrophobicity with a water contact angle of 140°.The results also indicate an improved tribological properties of Al_(2)O_(3)/PTFE composite coating at room temperature with a steady friction coefficient as low as 0.05.The self-lubricating anti-wear composite coating is expected to solve fouling problems and poor wear resistance of titanium alloys.

Acid Phosphatase Activity May Affect the Tuber Swelling by Partially Regulating Sucrose-mediated Sugar Resorption in Potato

APase activity is involved in regulating many physiological and developmental events by affecting the resorption process. In this study, we investigate the role of APase activity in tuber development in potato. APase activities were mainly localized in cytoplasm, gaps among cells and stroma of amyloplasts of parenchyma cells at the stage of tuber swelling. AP1, encoding a putative APase, was also highly expressed in swelling tubers and a low level of expression was observed in elongated stolons and matured tubers. Inhibition of APase activity by applying Brefeldin A, an inhibitor of APase production and secretion, significantly suppressed the tuber swelling and moderately affected the stolon elongation and the tuberization frequency. During tuber development, sucrose serves as the main soluble sugar for long-distance transportation and resorption. Moreover, inhibition of APase activity by Brefeldin A markedly reduced the sucrose content in tubers and further decreased the starch accumulation, suggesting that the function of APase in regulating the tuber swelling might be at least partially mediated by the sugar resorption. Exogenous sucrose treatments further indicate the important role of sucrose-mediated sugar resorption in tuber swelling. These results suggest that the APase activity might affect the tuber swelling by partially regulating the sucrose-mediated sugar resorption.

Energy-efficient digital and wireless IC design for wireless smart sensing

Wireless smart sensing is now widely used in various applications such as health monitoring and structural monitoring.In conventional wireless sensor nodes,significant power is consumed in wirelessly transmitting the raw data.Smart sensing adds local intelligence to the sensor node and reduces the amount of wireless data transmission via on-node digital signal processing.While the total power consumption is reduced compared to conventional wireless sensing,the power consumption of the digital processing becomes as dominant as wireless data transmission.This paper reviews the state-of-the-art energy-efficient digital and wireless IC design techniques for reducing the power consumption of the wireless smart sensor node to prolong battery life and enable self-powered applications.

Influence of Micro/Nano-Ti Particles on the Corrosion Behavior of AZ31-Ti Composites

Adding Ti particles to magnesium alloy simultaneously enhances its strength and ductility.However,how these particles influence on Mg alloy’s corrosion performance is seldom reported.The corrosion behavior of AZ31-Ti composites containing titanium nanoparticles(1.5 and 5 wt%)and micron particles(10 wt%)prepared by powder metallurgical in 3.5 wt%NaCl solution was investigated.The results indicate that Ti particles serve as the primary location for the cathodic hydrogen reduction reaction,resulting in intense galvanic corrosion between the Ti and Mg matrix.Ti nanoparticles distributed at the interface of the original AZ31 powder were in a discontinuous mesh structure,thus failing to act as a barrier against corrosion.The corrosion products with the existence of numerous cracks gradually peel off during the corrosion process and cannot protect the matrix.The average corrosion rate P_(w) of AZ31,AZ31-1.5%Ti,AZ31-5%Ti,and AZ31-10%Ti after 7 days of immersion is 27.55,105.65,283.67,and 99.35 mm/y,respectively.Therefore,AZ31-Ti composites can be considered as potential candidates for degradable fracturing tools.Otherwise,it is recommended to improve their corrosion resistance through surface treatment.