High-temperature stability of Mg(Al,Cr)2O4 spinel co-existing with calcium aluminates in air

Cr₂O₃ is a well-known corrosion resistant oxide used in refractory applications. However, it can oxidize into toxic and water-soluble Cr(VI) compounds upon reaction with calcium aluminate cement phases in the presence of oxygen, which subsequently causes disposal problems after use. This study describes the extent to which chromium in the spinel Mg(Al,Cr)₂O₄ phase can be oxidized to Cr(VI) when it reacts with the calcium aluminate cement phases C₁₂A₇, CA, CA₂ and free CaO at 1300 °C in air, using XRD, XPS and leaching tests (TRGS 613 standard) as analytical tools. On reaction with CaO, the Mg(Al,Cr^III)₂O₄ spinel mainly transformed into hauyne (Ca₄Al₆Cr^VIO₁₆) and Ca₅Cr₃O₁₂ which contains both Cr(IV) and Cr(VI). The reaction of C₁₂A₇ and CA with the spinel phase also resulted in the formation of Ca₄Al₆CrO₁₆. Conversely, the reaction of Mg(Al,Cr^III)₂O₄ spinel with CA₂ resulted in the formation of only a trace amount of Cr(VI). Water-soluble Cr(VI) leached in large quantities (>100 mg/L) from samples where the Mg(Al,Cr^III)₂O₄ reacted with either C₁₂A₇ or CA. Almost no Cr(VI) leached from the sample when Mg(Al,Cr^III)₂O₄ reacted with CaO, using the standard TRGS 613 leach test, but a significant amount of Cr(VI) was released into solution when leached with a HCl solution for 12 h. Both Cr(IV) and Cr(VI) present in the Ca₅Cr₃O₁₂ dissolved into acidic solution. Only a small amount of Cr(VI) leached from the sample that resulted when spinel was reacted with CA₂, even after a prolonged HCl leach. Cr(III) in spinel Mg(Al,Cr)₂O₄ is very stable and does not leach in either distilled water or acidic solution.     

一种新型竹材生态护岸型式及其稳定性模拟分析

本文以济南创新谷小刘河山区河流段为研究区域,提出一种竹材式柔性锚固框架生态护岸结构,并对该结构进行稳定性模拟分析,旨在确定新型竹材生态护岸所能发挥最佳锚固作用的合适工况。研究通过ABAQUS有限元软件进行强度折减计算,将竹筋模拟为"锚固杆"的部件作用于边坡,模拟不同的坡角、土质类型对于边坡模型稳定性的影响。数值模拟计算结果表明:新型竹材护岸锚固框架结构可有效地对粉质黏土边坡和黄棕壤土边坡进行锚固。随着坡度的增加,竹筋深层锚固作用效果愈加明显,安全稳定性能得到了稳定的提升。其中60°边坡锚固后效果最佳,两种土质边坡的塑性应变与位移均减小近100%。     

砂土中支盘桩抗压性能试验研究

支盘桩轴向受压过程是桩与周围土体相互作用的过程,研究支盘桩桩周土体的变形破坏机理对支盘桩竖向承载力的预测具有重要的意义。通过利用粒子图像测速技术进行了一系列的室内双支盘桩模型试验,对轴向荷载作用下支盘桩桩周土体变形特性进行非介入式测量。试验结果表明,不同相对密度下的荷载－位移曲线存在明显差异,相对密度增大可以大幅度提高双支盘桩竖向承载力并有效减小桩基沉降,密砂中双支盘桩的极限承载力是松砂的两倍以上。试验中发现支盘间距对支盘桩的竖向承载力有显著影响,随着盘间距的增加,支盘桩承载力增大但承载力增长率呈现出逐渐减小的趋势。针对地基土为密实砂土时,双支盘桩的支盘间距宜取盘径的３倍。     

基于AHP和熵权法组合权重的京津冀地区水循环健康模糊综合评价

在阐明健康水循环内涵的基础上,构建涵盖水资源、水环境、水生态、水效用和水灾害等5个准则层,包括降水量、人均水资源量、亩均水资源量、地下水供水占比等18个指标的水循环健康评价指标体系,采用层次分析法与熵权法组合赋权,运用模糊综合评价法评价了京津冀地区2009-2018年水循环健康状况。评价结果显示:近10年京津冀地区水循环健康状况总体呈逐步向好趋势,北京、天津和河北水循环健康等级分别为亚健康、一般和亚病态;中水供水率、平原地下水埋深下降量、河湖调蓄能力、万元工业增加值用水量等是影响京津冀地区健康水循环的主要指标,但各指标间发展不平衡,仍有较大提升空间。     

基于单片机的家庭报警系统设计

本文设计了一种基于AT89C2051芯片为CPU的家用报警系统,以烟雾探测器、门磁报警器、燃气体探测器等传感器为节点,当收集到异常信息后,由无线网络节点送至报警主机,通过主机报告给预留电话,从而完成了家庭报警系统的硬件组成、软件设计、数据采集与通信策略以及主程序设计,实现对家庭的非法入侵、火灾、燃气泄漏等事故的报警保护。     

扫描速度对硼铸铁气缸套表面钨极氩弧硬化效果的影响

研究了钨极氩弧扫描速度对硼铸铁表面硬化效果的影响规律。结果表明：扫描速度增加,硬化层宽度、深度减小,而硬度提高,裂纹率增大；硬化层硬度沿层深的分布是从表及里由高而低,在过渡区下降缓慢；沿层宽的分布是层中心最高,向两侧逐渐降低,直至硼铸铁基体达到最低值；在保证不出现裂纹的条件下,硬化层表面的最高硬度值可达61．4HRC,硬化层最高显微硬度值可达1156．4HV0．1；硼铸铁材料采用氩弧热源淬火时,淬硬层与基体之间过渡区明显,硬化区组织为莱氏体,过渡区为马氏体、残余奥氏体和少量石墨。     

Discriminative Hough context model for object detection

This paper presents a novel Hough context model for detecting and localizing instances of a certain object class. In particular, our approach detects the object in parameter space by applying Hough voting in context. First, in Hough context, the features around object center or a point in parameter space are sampled and organized in context sense respectively for both training images and test images. Then a parametric discriminant function is constructed based on the Hough context. Such function scores the existence likelihood of object centers in parameter space. Finally, we formulate the training process of this discriminative model as a structure learning problem, which has already been well solved. Compared with the ISM-related methods that the voting is performed by the features independently, the core contribution of our method is that the voting based on context information is available. The experiments on several popular and challenging object datasets (i.e., ETHZ Shape, UIUC Cars, and PASCAL VOC 2007) demonstrate that the detection accuracy can be improved and the voting speed are impressively accelerated via using Hough context.     

一种数控机床学习机的设计

介绍了一种数控机床学习机的功能和特点,详细阐述了设计方案.该机采用了真实、分层、可视、人机一体化等独特的设计理念,集数控手工编程与操作学习、零部件造型和自动编程学习、数控PMC编程与调试学习、数控结构与原理学习、数控连接与调试学习、数控电气控制学习等多种功能于一身,具有真实再现、功能丰富、可视清晰、人机合理、操作方便、安全可靠等特点,有利于学习者快速掌握数控技术.     

基于DSP的智能饮水机纸杯水位检测方法

为了提高传统饮水机的智能化水平,采用DSP芯片TMS320C6416作为处理核心设计了智能饮水机纸杯水位线自动检测系统,系统由摄像头、编码、处理器、阀门开关和显示模块组成.通过对放在出水口处纸杯的原始图像进行灰度化处理、边缘检测、连通域提取和噪声去除算法,分割出杯口内边缘和水位线,并根据像素点的个数计算纸杯内边缘线与水位线的距离.实验结果表明,该智能饮水机具有良好的鲁棒性,平均测量误差为0.88％,也为灌装饮料和食品的满度检测提供了思路和方法.     

基于模态分解和云粒子网络的大坝基岩地震动输入研究

在大坝抗震安全评价中基岩地震动输入多采用实测数据或人工生成等方式,而当坝址仪器损坏或历史震害资料不足时,确定基岩地震动就变得尤为困难。本文提出对大坝基岩地震动进行反演的研究思路,并开发了基于经验模态分解和云粒子网络的分解—训练—反演混合模型,在不依赖场地历史震害资料的情况下,仅用少量周边测站数据即可确定大坝的基岩地震动。首先,选取坝址周边地表及基岩的地震动实测记录,采用经验模态分解法将地震加速度序列分解;其次,通过粒子群算法建立与神经网络连接权值的映射,采用云理论优化粒子群算法的全局寻优能力,建立反演模型,将分解后的加速度序列作为训练集进行反演训练;然后,选取与大坝处于相似地质情况的地表实测地震动信息,结合反演模型对大坝基岩输入地震动进行反演;最后,以紫坪铺大坝为研究实例,通过对比传统输入方法,验证该模型的适用性。结果表明：本文所提的混合模型综合性能稳定,能较好地反演地震加速度序列,模型决定系数均大于0.9,平均绝对百分比误差均在11%左右;采用本文反演得到的基岩地震动进行计算,较已有研究成果计算误差降低0.79%~17.28%,与工程实际动力响应更为吻合。本文方法可为解决大坝基岩输入地震动的获取提供一条新途径。