Wrapping effect of secondary phases on the grains: increased corrosion resistance of Mg–Al alloys

The discrete secondary phases usually cause severe galvanic corrosion, thereby resulting in rapid degradation for Mg–Al alloys in orthopaedics application. In this study, CaO was introduced into Mg–Al–Zn (AZ61) alloy via selective laser melting (SLM) to ameliorate the characterisations of the secondary phases, with an aim to improve its corrosion behaviour. Results revealed that CaO reacted with Mg and Al in Mg–Al alloys during SLM, suppressing the formation of coarse Mg₁₇Al₁₂ phase and promoting the formation of (Mg, Al)₂Ca phase. Meanwhile, the rapid solidification during SLM promoted the homogeneous precipitation of the second phase. As a result, inert (Mg, Al)₂Ca phase homogeneously wrapped the Mg grains, which effectively protected them from the invasion of corrosion solution. Thus, the degradation rate was remarkably reduced from 0.073 to 0.031?mg?cm^–2?h^–1. Furthermore, AZ61-9CaO exhibited good cytocompatibility. This work suggested that AZ61-9CaO was promising candidates for orthopaedics implants.     

基于PXI总线的24通道高精度铂热电阻模拟板设计

针对市场上现有模拟铂热电阻的不足,使用数字电位器和精密电阻设计了一款基于PXI总线的24通道高精度铂热电阻模拟板——PXI5440;依据误差传递原理对设计进行了误差分析,结果表明:更换精密电阻可调整铂热电阻输出范围,但不影响其输出精度;输出电阻越大,数字电位器步长对输出电阻精度的影响将减小,输出电阻的绝对误差将减小;同时,给出了软件驱动函数算法,实际测量结果,证明了设计思路的正确性,理论的正确性;本产品同市场上现有产品相比,其具有价格低、通道个数多及精度高等优点。     

不同预冷温度对甜樱桃果实保鲜效果的影响

目的 探究不同预冷温度对采后甜樱桃果实生理品质的影响,找出最适宜的预冷温度,进而推动甜樱桃产业化发展。方法 本实验分别将采后甜樱桃分别预冷至15、12、9、6、3、0℃后回温至室温,以不进行预冷处理为对照组,比较6种处理方式果实预冷和回温过程中的温度变化,并分别测定回温前后果实的色差、呼吸强度及乙烯释放量、硬度、可溶性固形物(TSS)、风味、感官评价,总酚、类黄酮、花色苷、维生素C(Vc)、可溶性蛋白、丙二醛(MDA)含量以及超氧阴离子产生速率(O₂^-)。结果不同预冷温度均可较好地保持果实外观及风味,能够降低甜樱桃果实呼吸强度与乙烯释放量,抑制果实TSS、MDA含量和O₂^-产生速率的上升,延缓甜樱桃果实硬度的下降,从而保持甜樱桃果实的外观品质,且有利于维持甜樱桃果实中的Vc、可溶性蛋白和花色苷含量,以0℃预冷效果最佳,感官评分最高。结论 预冷能够有效维持甜樱桃果实采后的品质,达到增加甜樱桃果实经济价值的作用。     

大豆蛋白胶黏剂及其胶合板防霉研究进展

目的 改进大豆蛋白胶易霉变、储存时间短,将其作为胶黏剂使用制备的板材性能低等缺点,提高胶合板的使用寿命,使板材的适用范围和领域得以拓宽。方法 通过综述大豆蛋白胶和胶合板易发霉原因,以及近年来国内外在针对大豆蛋白胶和胶合板防霉性能方面的研究进展,分析其改性原理以及仍存在的问题,介绍原子转移自由基聚合（ATRP）法目前在豆胶改性中的应用。结论 采用ATRP法对大豆蛋白胶黏剂进行防霉接枝改性,可在保证胶合强度的同时延长胶合板使用时间,为今后制备具有优良防霉性能的大豆蛋白胶合板以及工业化推广提供新思路。     

基于 ResU-Net 的三维断层识别方法及应用

断层刻画了地层的边界位置,地震成像数据中反射层的不连续性可作为断层解释的主要依据。深度神经网络的强非线性性质可作为地震数据中断层不连续特征表达的有力工具,断层识别问题可视作一个像素级别的二分类问题,并使用深度学习方法对此问题进行建模求解。据此可给出一种端到端的基于深度学习网络的三维断层自动识别方法。首先利用地震子波与反射系数卷积合成多组三维地震数据,建立用于深度网络学习断层特征的样本数据,随后搭建网络进行训练,网络训练完成后应用于实际地震数据。鉴于残差模块可很好地提升网络泛化性能,所提出的将残差网络中的残差块结构引入U-Net中的方法,可用于提升通过合成数据样本训练得到的网络模型在训练数据之外,即实际地震数据上的断层识别性能。所建立网络用于断层解释时,输入为叠后三维地震数据,输出为相同维度的三维数据体,其中每一输出值代表输入三维地震数据相同位置处断层的概率。实际算例对比测试表明,此方法可对三维地震数据中的断层进行有效识别,在合成数据集上训练精度相差不大的前提下,引入残差模块的ResU-Net在实际地震数据上的断层识别泛化性能得到提升。     

Effects of Fe/Ni Ratio on Microstructure and Properties of FeNiCrAlNb High-Entropy Alloys

Herein, the effects of Fe/Ni ratio on the microstructure, mechanical properties, and corrosion resistance in a 3.5 wt% NaCl solution of Fe_xNi_65−xCr₂₀Al₁₀Nb₅ are investigated systematically. It is found that the phases shifted from the FCC-dominated to the BCC-dominated with the molar ratio of the Fe/Ni increased. The strength of Fe_xNi_65−xCr₂₀Al₁₀Nb₅ increases with the molar ratio of Fe/Ni further increased, while the plasticity decreases. The yield strength reaches 1,653 MPa at x = 45. The alloy exhibits the best corrosion resistance when x = 35 which is attributed to the dominant FCC phases in the dendritic region.     

Characterization of Cementitious Materials Exposed to Freezing and Thawing in Combination with Deicing Salts Using 3D Scans

Surface deterioration of concrete subjected to freezing and thawing in combination with deicing salts is one of the most important factors determining the durability of concrete infrastructure in cold climates. The freeze–thaw deicing salt (FTDS) resistance of cementitious materials can be determined by the capillary suction of de-icing chemicals and freeze–thaw (CDF) test. Specimens are subjected to repeated freeze–thaw cycles with simultaneous addition of deicing salt and the amount of material scaled off near the surface is determined. For concretes with adequate FTDS resistance, this test method works very well. However, specimens with unknown performance often experience increased edge scaling. This leads to a falsification of results and consequently to an underestimation of the actual freeze–thaw resistance. In materials research, however, concretes with high levels of surface deterioration are studied in order to investigate various factors of influence on the freeze–thaw resistance of concretes in a targeted manner. This article presents a novel methodology that delivers new information regarding surface deterioration of CDF samples using high-resolution 3D scan data. Change of volume is used to support deterioration results of the standard CDF methodology. Increase of surface area is used to estimate change in roughness of samples.     

Effect of Mn-Bearing Dispersoids on Tensile Properties and Recrystallization Resistance of Al-3Mg-0.8Mn Rolled Alloy

Herein, the precipitation behavior of Mn-bearing dispersoids in Al-3Mg-0.8Mn (AA5454) alloy subjected to different heat treatments is investigated. The effects of Mn-bearing dispersoids on the tensile properties and recrystallization resistance of the abovementioned alloy during hot/cold rolling and postrolling annealing are evaluated. The results show that a low-temperature three-step heat treatment (275 °C/12 h + 375 °C/48 h + 425 °C/12 h) generates a higher number density of Mn-bearing dispersoids with finer sizes compared with the typical high-temperature heat treatment (430 °C/2 h + 480 °C/2 h + 525 °C/2 h), thus resulting in significantly improved tensile strengths of hot/cold-rolled sheets. After annealing at 300 °C, the yield strength (YS) of the alloy reached 196 MPa after hot rolling and 237 MPa after cold rolling, showing an improvement of 30%–32% over samples subjected to high-temperature heat treatment. In addition, the low-temperature heat treatment provides a higher recrystallization resistance after hot and cold rolling owing to the higher number density of Mn-bearing dispersoids and the lower fraction of dispersoid-free zones. The YS contributions of various strengthening components after hot and cold rolling are discussed based on constitutive models. The predicted yield strengths agree well with the experimental values.     

电阻电路割集矩阵电压法

以树支电压为求解变量建立割集矩阵电压方程,通过矩阵运算,求出树支电压,再求各支路电压和电流。     

厂校合作,搞好炼铁专业技能考核工作

为了达到对学生进行工程师的训练的培养目标,把炼铁专业的专业技能训练的岗位起点确定为高炉值班工长,按高炉值班工长的基本要求进行专业技能培训。实行厂校合作,严格训练,严格考核,实施以后效果明显。