A Degeneration Gradient of Poplar Trees Contributes to the Taxonomic,Functional, and Resistome Diversity of Bacterial Communities in Rhizosphere Soils

Bacterial communities associated with roots influence the health and nutrition of the host plant. However, the microbiome discrepancy are not well understood under different healthy conditions. Here, we tested the hypothesis that rhizosphere soil microbial diversity and function varies along a degeneration gradient of poplar, with a focus on plant growth promoting bacteria (PGPB) and antibiotic resistance genes. Comprehensive metagenomic analysis including taxonomic investigation, functional detection, and ARG (antibiotics resistance genes) annotation revealed that available potassium (AK) was correlated with microbial diversity and function. We proposed several microbes, Bradyrhizobium, Sphingomonas, Mesorhizobium, Nocardioides, Variovorax, Gemmatimonadetes, Rhizobacter, Pedosphaera, Candidatus Solibacter, Acidobacterium, and Phenylobacterium, as candidates to reflect the soil fertility and the plant health. The highest abundance of multidrug resistance genes and the four mainly microbial resistance mechanisms (antibiotic efflux, antibiotic target protection, antibiotic target alteration, and antibiotic target replacement) in healthy poplar rhizosphere, corroborated the relationship between soil fertility and microbial activity. This result suggested that healthy rhizosphere soil harbored microbes with a higher capacity and had more complex microbial interaction network to promote plant growing and reduce intracellular levels of antibiotics. Our findings suggested a correlation between the plant degeneration gradient and bacterial communities, and provided insight into the role of high-turnover microbial communities as well as potential PGPB as real-time indicators of forestry soil quality, and demonstrated the inner interaction contributed by the bacterial communities.     

稳流仓进料调节装置和出料稳流装置的设计与应用

稳流仓广泛应用于水泥生产行业,仓内布料情况直接关系到辊压机运行的稳定性,直接影响系统的台时产量、工序电耗等经济指标。为了使稳流仓内物料均匀分布,生产现场通常采用打散板、打散格等方式,但由于仓位变化、结皮等因素导致物料离析,最终影响辊压机运行。     

锈蚀钢筋混凝土梁的力学性能研究

对24根直径不同的钢筋和8根钢筋混凝土梁进行电化学加速腐蚀模拟后,研究了24根受损钢筋的伸长率、屈服强度和极限强度的变化规律,以及8根不同腐蚀程度钢筋混凝土梁的应力-应变、荷载-挠度曲线和强度的变化规律.结果表明:伸长率的降低是导致锈蚀梁失去安全性能的主要因素;梁的极限承载能力和延性首先呈上升趋势,然后成反比例下降,最后出现陡降,形成不统一的单体,最终发生脆性破坏.     

D152树脂对镝的吸附及机制

对D152树脂吸附镝(Ⅲ)的过程及镝在D152树脂上的吸附行为进行了研究。研究了介质pH、温度、吸附时间、树脂量等因素对吸附过程的影响。实验结果表明:D152树脂对镝(Ⅲ)的吸附在pH=5.93的HAc-NaAc的缓冲溶液中为最佳。25℃时静态饱和吸附量为314.6mg.g-1(干树脂)。用1.0 mol.L-1的HCl溶液作为解吸剂,解吸率为96.2%;D152树脂对镝(Ⅲ)的表观吸附活化能Ea=18.28 kJ.mol-1,表观吸附速率常数k298=2.54×10-5s-1,k308=2.93×10-5s-1,k318=4.05×10-5s-1,测得热力学参数分别为ΔH=18.19 kJ.mol-1,ΔG=-0.88 kJ.mol-1,ΔS=63.99 J.mol-1.K-1,等温吸附服从Freundlich经验式。并用化学和红外光谱的方法探求树脂对镝(Ⅲ)的吸附机制。     

α-Al_2O_3:C单晶的β辐射热释光与光释光性能研究

以高纯碳粉作为碳源直接加入原料,采用导模法(EFG)生长了α-Al2O3:C单晶。研究了晶体经过低剂量β射线辐照后的热释光与光释光特性,α-Al2O3:C单晶的热释光发光曲线在350 K、540 K和689 K附近有3个热释光峰,540 K附近为主要热释光峰,689 K附近为新的热释光峰,发现晶体的陷阱能级深度发生变化并产生了新深度的陷阱能级;随着β吸收剂量的增加,发光强度也随之增强,但是3个热释光峰温位置大致保持不变。在多次连续同剂量辐照过程中,随着辐照次数的增加,主热释光峰强度增强,峰温向高温方向偏移。α-Al2O3:C单晶的光释光衰减曲线呈指数变化,其由前期快衰减部分和后期慢衰减部分组成,快衰减部分衰减速率随着吸收剂量的增加变化很小,而慢衰减部分衰减速率则有较为明显的减慢。在低剂量范围内(低于10Gy),热释光和光释光过程灵敏度不随吸收剂量而变化,剂量响应曲线呈线性的特点。     

Predicting the dynamic behavior of asphalt concrete using three-dimensional discrete element method

A user-defined three-dimensional(3D)discrete element model was presented to predict the dynamic modulus and phase angle of asphalt concrete(AC).The 3D discrete element method(DEM)model of AC was constructed employing a user-defined computer program developed using the "Fish" language in PFC3D.Important microstructural features of AC were modeled,including aggregate gradation,air voids and mastic.The irregular shape of aggregate particle was modeled using a clump of spheres.The developed model was validated through comparing with experimental measurements and then used to simulate the cyclic uniaxial compression test,based on which the dynamic modulus and phase angle were calculated from the output stress-strain relationship.The effects of air void content,aggregate stiffness and volumetric fraction on AC modulus were further investigated.The experimental results show that the 3D DEM model is able to accurately predict both dynamic modulus and phase angle of AC across a range of temperature and loading frequencies.The user-defined 3D model also demonstrated significant improvement over the general existing two-dimensional models.     

类金刚石膜对铝合金疏水结构耐久性能影响

为提高2024铝合金疏水及耐蚀性能,利用电化学刻蚀结合等离子体增强化学气相沉积(PECVD)技术,在其表面制备微纳米浮凸疏水结构及类金刚石(DLC)薄膜。利用接触角测量仪、电化学工作站及冲刷试验装置,对不同处理工艺下2024铝合金的疏水、耐蚀及疏水耐久性能进行了研究,并讨论了相应的作用机制。结果表明,电化学刻蚀后2024铝合金与水的静态接触角可达到130o以上,疏水性能显著提高。阻抗结果表明,刻蚀后阻抗模值提高了约8倍,腐蚀电流密度降低了两个数量级,耐蚀性能显著提高。刻蚀后镀非晶态惰性DLC膜的铝合金,其阻抗模值可达1.016×10⁷Ω·cm^-2,可有效阻碍腐蚀过程的电荷转移和离子传输电荷的传递,显著延长疏水结构的耐久性能。     

Thermodynamic Evaluation of the Co-Al-C System by Coupling Ab Initio Calculations and CALPHAD Approach

The ternary Co-Al-C system was thermodynamically assessed using the CALPHAD method based on the critical review of all experimental information in the system. The κ-carbide was described with a three-sublattice model (Al,Co)₃(Al,Co)₁(C,Va)₁. To support the assessment, the enthalpies of formation of all end-members of the κ-carbide were studied by ab initio calculations. The solubility ranges of the carbon in the κ-carbide, the αCo and the AlCo (B2) phases were well reproduced. The equilibria involving the liquid phase were reasonably described using the present set of thermodynamic parameters.     

基于深度学习的机器阅读理解研究综述

机器阅读理解任务在近年来备受关注,它赋予计算机从文本数据中获取知识和回答问题的能力。如何让机器理解自然语言是人工智能领域长期存在的挑战之一,近年来大规模高质量数据集的发布和深度学习技术的运用,使得机器阅读理解取得了快速发展。基于神经网络的端到端的模型结构,基于预训练语言模型以及推理技术的应用,其性能在大规模评测数据集上有很大提升,但距离真正的理解语言还有较大差距。本文对机器阅读理解任务的研究现状与发展趋势进行了综述,主要包括任务划分、机器阅读理解模型与相关技术的分析,特别是基于知识推理的机器阅读理解技术,总结并讨论了该领域的发展趋势。     

基于图像分析的节理岩体单轴压缩损伤演化研究

 为定量地研究节理岩体的损伤演化规律,对岩体石膏模型试件单轴压缩试验过程中拍摄的表面数字图像进行处理分析。编制Matlab程序,实现单个裂纹的识别、裂纹长度和方位角、总裂纹面积分数和总裂纹分形维数的计算。对节理倾角和节理连通率这2个参数组合变化下的试件表面裂纹图像的分析结果为：(1) 试件表面总裂纹面积分数和总裂纹分形维数变化规律基本相似,在各节理连通率和各节理倾角下,2个参量都随轴向应变的增加而增大;(2) 可将试件分为两大组,节理倾角为0°,15°,75°,90°试件(劈裂破坏为主)和节理倾角为30°,45°,60°的试件(剪切破坏为主),第1组试件表面的总裂纹面积分数和总裂纹分形维数值都高于第2组试件;(3) 具有相同节理连通率的试件,在试验开始点不同节理倾角的总裂纹面积分数基本相同,在峰值荷载点和试验结束点的总裂纹面积分数随节理倾角的变化曲线基本呈V型(最小值在节理倾角为45°处,最大值在节理倾角为0°处);(4) 表面裂纹在试验开始时和加载过程中的各向异性分布特征,可以用裂纹面积分数沿裂纹方位角的分布图来表征。研究结果表明,表面裂纹图像分析可以有效地定量研究节理岩体试件的各向异性损伤演化特征。