胶结充填体在动荷载作用下的响应特征

为掌握大红山铜矿井下在用的胶结充填材料对爆破荷载的响应特征,对质量浓度为72%、水泥含量为180 kg/m³的胶结充填材料开展了不同加载应变率下的常规单轴冲击试验。试验结果表明:CTB_(180)试件对入射冲击波的透射能力微弱,在较低的冲击应变率作用下即发生破裂;当■_s≥42.3 s3的胶结充填材料开展了不同加载应变率下的常规单轴冲击试验。试验结果表明:CTB_(180)试件对入射冲击波的透射能力微弱,在较低的冲击应变率作用下即发生破裂;当■_s≥42.3 s^(-1)时,试件韧性增加,试件瞬间被压密,增幅较■_s=30.3 s(-1)时,试件韧性增加,试件瞬间被压密,增幅较■_s=30.3 s^(-1)时明显提升,破坏应变量发生了突增;随着■_s的增加,反射能占比先减后增,透射能占比先增后减,但耗散能占比呈递增趋势;破坏形态上,当■_s≤20.7 s(-1)时明显提升,破坏应变量发生了突增;随着■_s的增加,反射能占比先减后增,透射能占比先增后减,但耗散能占比呈递增趋势;破坏形态上,当■_s≤20.7 s^(-1)时,试件仍保持其整体性,但当■_s≥42.3 s(-1)时,试件仍保持其整体性,但当■_s≥42.3 s^(-1)时,将整体失稳破坏。研究结果可以指导充填材料配比选型以及矿柱回采爆破参数优化。     

Research on mine dust suppression by spraying: Development of an air-assisted PM10 control device based on CFD technology

In order to solve the serious pollution problem of PM10 in a fully mechanized mining face, focusing on the drum cutting process which produces the most dust, a new type of shearer sprayer is developed in the paper. At present, it is difficult for a single spray device to meet the dust control demands of a mine. Therefore, in combination with the airflow-carrying-droplet mechanism, a fan is added to the shearer’s spray device to develop an air-assisted PM10 control device. A No. III nozzle is optimally chosen following the spray experiments, and CFD software is used for a numerical simulation of the 4307 fully mechanized mining face of the Bailu Coal Mine. According to the airflow and spraying field distribution, it is observed that when the spray device’s pressure is 8 MPa, the spraying field’s microscopic parameters are more conducive to the settling of PM10 by the mist droplets. The PM10 data measured at 1^#-3^# measuring points of the 4307 fully mechanized mining face of the Bailu Coal Mine have shown that the best PM10 settling effect is at a spraying pressure of 8 MPa. The PM10 concentrations at 1#-3# measure points were reduced to 0.987 mg/m³, 0.405 mg/m³ and 0.262 mg/m³ respectively, with the dust control rate being above 90%. Thus the serious PM10 pollution problem in a fully mechanized mining face has been solved effectively.     

MXenes Antibacterial Properties and Applications: A Review and Perspective

The mutations of bacteria due to the excessive use of antibiotics, and generation of antibiotic-resistant bacteria have made the development of new antibacterial compounds a necessity. MXenes have emerged as biocompatible transition metal carbide structures with extensive biomedical applications. This is related to the MXenes’ unique combination of properties, including multifarious elemental compositions, 2D-layered structure, large surface area, abundant surface terminations, and excellent photothermal and photoelectronic properties. The focus of this review is the antibacterial application of MXenes, which has attracted the attention of researchers since 2016. A quick overview of the synthesis strategies of MXenes is provided and then summarizes the effect of various factors (including structural properties, optical properties, surface charges, flake size, and dispersibility) on the biocidal activity of MXenes. The main mechanisms for deactivating bacteria by MXenes are discussed in detail including rupturing of the bacterial membrane by sharp edges of MXenes nanoflakes, generating the reactive oxygen species (ROS), and photothermal deactivating of bacteria. Hybridization of MXenes with other organic and inorganic materials can result in materials with improved biocidal activities for different applications such as wound dressings and water purification. Finally, the challenges and perspectives of MXene nanomaterials as biocidal agents are presented.     

AlSi10Mg(Cu)铸铝合金的热疲劳裂纹萌生及早期扩展行为

微观观察AlSi10Mg(Cu)铸铝合金在热疲劳裂纹的萌生和早期扩展过程,重点研究共晶硅粒子对热疲劳裂纹行为的影响。结果表明:热疲劳裂纹萌生于脱粘共晶硅粒子与铝基体间的开裂界面,原因是共晶硅粒子与铝基体的热膨胀系数不同,引起热循环过程中两相热应变不协调,从而在两相界面处产生循环应力而引起疲劳破坏。热疲劳裂纹的扩展在长度和宽度上同时进行,具有良好塑性的铝枝晶对疲劳裂纹的扩展起阻碍作用。对热疲劳过程中共晶硅粒子周围应力场的模拟分析进一步解释了实验现象。     

440MPa级10MnNiCrMoV钢板裂纹分析

采用金相显微镜、扫描电镜及能谱仪等分析设备,研究了440MPa级10MnNiCrMoV钢板裂纹产生的原因.结果表明,裂纹附近钢板组织、硬度与基体相同,而裂纹表面存在大量氧化物,可断定该缺陷来源于连铸坯端部的某种缺陷,通过轧制经延展形成.     

Web应用的漏洞分析与研究

本文基于OWASP(开放式Web应用程序安全项目)TOP10 2021的十大漏洞进行分析和研究,逐步形成安全漏洞的定义、威胁、成因、修复及预防分析框架。Web应用的安全防御始终是一个动态的过程,需要共同防御,才能最大限度的降低Web安全漏洞带来的危害。     

基于脉冲神经网络的迁移学习算法与软件框架

使用脉冲序列进行数据处理的脉冲神经网络具有优异的低功耗特性,但由于学习算法不成熟,多层网络训练存在收敛困难的问题。利用反向传播网络具有学习算法成熟和训练速度快的特点,设计一种迁移学习算法。基于反向传播网络完成训练过程,并通过脉冲编码规则和自适应的权值映射关系,将训练结果迁移至脉冲神经网络。实验结果表明,在多层脉冲神经网络中,迁移学习算法能够有效解决训练过程中收敛困难的问题,在MNIST数据集和CIFAR-10数据集上的识别准确率分别达到98.56%和56.00%,且具有微瓦级别的低功耗特性。     

Quantum transport simulation of the two-dimensional GaSb transistors

Owing to the high carrier mobility,two-dimensional (2D) gallium antimonite (GaSb) is a promising channel material for field-effect transistors (FETs) in the post-silicon era.We investigated the ballistic performance of the 2D GaSb metal-oxide-semiconductor FETs with a 10 nm-gate-length by the ab initio quantum transport simulation.Because of the wider bandgap and better gate-control ability,the performance of the 10-nm monolayer (ML) GaSb FETs is generally superior to the bilayer counterparts,including the three-to-four orders of magnitude larger on-current.Via hydrogenation,the delay-time and power consumption can be further enhanced with magnitude up to 35％ and 57％,respectively,thanks to the expan-ded bandgap.The 10-nm ML GaSb FETs can almost meet the International Technology Roadmap for Semiconductors (ITRS) for high-performance demands in terms of the on-state current,intrinsic delay time,and power-delay product.     

严寒区胶凝砂砾石坝施工期冻融温度与应力仿真

在严寒地区修筑胶凝砂砾石坝时,其冻胀抗裂性能往往是工程关注的重点。在前人研究的基础上,以守口堡胶凝砂砾石坝为研究对象,通过分析胶凝砂砾石的特点,利用编制的胶凝砂砾石三维非稳定冻融温度场与应力场有限元计算程序,对施工期的冻融与温度应力进行数值模拟。研究结果表明,即使不采取温控措施,坝体产生的温度应力也很小,不会产生温度裂缝;在冬季低温季节,严寒地区胶凝砂砾石坝施工期长间歇仓面易发生冻胀开裂,应予以重视。     

基于强度参数演化的胶凝砂砾石材料本构关系研究

胶凝砂砾石材料应力-应变关系具有明显的弹塑性和应变软化特性,当前其本构关系推导较为复杂。针对这一问题,本文借鉴岩石材料峰后强度参数演化行为,基于摩尔-库伦强度准则,采用最大主应变ε₁作为应变软化参数,将凝聚力c、内摩擦角φ看作ε₁的分段线性函数,较为简便的推导胶凝砂砾石材料的本构关系。由本构关系式拟合得到不同围压时胶凝砂砾石材料应力-应变关系曲线变化趋势与三轴试验数据吻合良好,说明该方法得到的本构关系可以反映胶凝砂砾石材料的应力-应变特征。