爆炸塔内悬置裸露药包爆炸地表振动试验研究

为研究爆炸塔内裸露药包爆炸地表振动衰减规律,进行了不同药量和悬置高度裸露药包爆炸振动测试试验。结果表明,爆炸塔内悬置裸露药包爆炸地表振速表现为垂向径向切向,地表振速受药量影响大于药包悬置高度影响。振动频率在爆源近区高频衰减速度大于爆源远区低频衰减速度。对地表振速进行回归分析发现,悬置裸露爆破衰减系数明显小于经验值,存在一个与悬置药包有关的爆炸折减系数K′,K′取值为0.26~0.56。     

一种增大尾矿库回水量的方法

在分析尾矿库回水量组成的基础上,以内蒙古锡林郭勒盟地区某湿排尾矿库为例,提出了一种采用悬浮球增大回水量的方法。理论分析和对比试验验证表明,该方法能够大大减少蒸发量,增大尾矿库回水量,操作简单,可在缺水地区的尾矿库运行管理中推广应用。     

基于小波脊线的OFDM与单载波信号识别

正交频分复用(OFDM,Orthogonal Frequency Division Multiplexing)与单载波信号广泛应用于短波通信领域。针对低信噪比和多径环境下OFDM与单载波信号识别效率低的问题,本文提出了基于小波脊线的信号识别算法。本文推导了常用信号对应的小波脊线幅度和脊点位置,并分析了小波脊线幅度和脊点形态。通过理论推导和仿真测试证明了OFDM与单载波信号对应小波脊线具有不同特征,对小波脊线差分、中值滤波、并利用其熵作为特征值能够有效的进行OFDM信号与单载波信号的识别。仿真结果证明该算法对输入信号点数要求低,在低信噪比和短波中等信道下识别效果具有稳健性和有效性。      

基于最小误码率准则的多载波CDMA系统多用户检测算法

本文介绍了一种将正交频分复用(OFDM)技术和码分多址(CDMA)技术相结合的多载波CDMA (MC-CDMA)系统,分析了MC-CDMA系统的发射端和接收端的结构,建立了MC-CDMA系统的信号模型,详细分析了MC-CDMA中的多址干扰形式,以及针对MC-CDMA系统的多用户检测原理,提出了一种基于最小误码率准则的多用户检测算法。理想的基于最小误码率准则的多用户检测算法在实际中难于实现,本文采用估计概率密度函数的方法,推导出了一种自适应实现的最小误码率多用户检测算法。仿真结果表明,该算法能够有效抑制多址干扰,降低误码率,同时,该算法还具有比基于最小均方误差准则的多用户检测器更低的误码率的优点。      

Transformation of methane into synthesis gas using the redox property of Ce-Fe mixed oxides: Effect of calcination temperature

Ce-Fe mixed oxides prepared by co-precipitation were used as oxygen carriers for converting methane into synthesis gas through gas-solid reactions. The structural evolution and reducibility of Ce-Fe oxygen carriers with calcination temperatures from 600 to 900 °C were investigated by XRD, BET, Raman, XPS and TPR techniques and correlated to their activity for methane selective oxidation. The Ce-Fe mixed oxides calcined at low temperatures (e.g., 600 °C) show abundant oxygen vacancies and high specific surface areas, which enhances the concentration of surface adsorbed oxygen and favors the complete oxidation of methane by means of gas-solid reactions. On the other hand, a calcination temperature of 900 °C results in serious sintering and militates against the formation of Ce-Fe solid solution, which brings about catalytic methane decomposition because of the low lattice oxygen mobility. A compromise calcination temperature at 800 °C favors the interaction between iron and cerium oxides, which could improve the lattice oxygen mobility of Ce-Fe oxygen carrier, leading to a high reactivity for methane selective oxidation. More importantly, the lattice oxygen mobility of the oxygen carrier is enhanced by the generation of oxygen vacancies after a repetitive redox treatment (methane reduction/air re-oxidation), which allows the Ce-Fe oxygen carrier to maintain a high activity and stability during the successive production of synthesis gas through a redox process.     

Photoelectrical and charge transfer properties of hydrogen-evolving TiO2 nanotube arrays electrodes annealed in different gases

TiO₂ nanotube arrays were fabricated by sonoelectrochemical anodic oxidation and calcined in nitrogen, air, or 5% hydrogen/nitrogen which was denoted as TNT-A, TNT-N, and TNT-H, respectively. All annealed TiO₂ nanotube arrays samples exhibited similar surface morphology. With UV illumination (365 ± 15 nm), the photocurrent density of the TNT-A, TNT-N and TNT-H was about 0.27 mA/cm², 0.45 mA/cm² and 0.60 mA/cm², respectively. The trapped electron at the Ti⁴⁺ center of TiO₂ nanotube arrays shows absorption at around 500-700 nm. From the XPS measurement, it was found that annealing in 5% hydrogen/nitrogen helped the sample obtain a greater defect density. Because of the reduction of Ti⁴⁺ and the formation of oxygen vacancies, the charge transfer resistance appeared in this order: TNT-A > TNT-N > TNT-H. Thus TNT-H harvested the greatest charge carrier density of 9.86 × 10²⁰ cm⁻³, TNT-N and TNT-A obtained a charge carrier density of 1.38 × 10²⁰ cm⁻³ and 1.06 × 10²⁰ cm⁻³, respectively. Accordingly, the hydrogen production rate by water splitting over TNT-A, TNT-N and TNT-H (320-780 nm irradiation, 3 h) was about 120 μL/h cm², 159 μL/h cm² and 231 μL/h cm², respectively.     

主持人服装语言的承载功能研究

主持人的服装语言是一种显性的文化符号,是主持人外部形象的重要组成部分。准确而恰当地运用主持人服装语言,是主持人个人形象塑造的重要手段,也是体现节目风格与定位的重要元素。重视主持人服装语言所承载的功能,也要注重其所形成的审美导向,让正确的创作方向把握住主持人服装语言这种公众关注的媒体元素。     

纳米活性炭对中药或植物活性成分的吸附与缓释研究进展

文章综述药物缓释制剂的作用和种类,评述纳米活性炭作为活性成分缓释载体的理化特性,归纳近年来国内外对纳米活性炭作为中药或植物活性成分缓释制剂载体的研究进展,指出纳米活性炭的制备以及纳米活性炭作为活性成分缓释制剂遇到的技术瓶颈和今后的研究方向。     

基于循环灰热载体煤热解的固-固颗粒冷态混合特性

以开发循环流化床（CFB）燃烧/煤热解分级转化工艺为应用背景,为在移动床混合段内利用有限高度空间达到理想的灰/煤混合效果,建立了内置锥面形挡板结构的固-固冷态混合实验装置,并对颗粒的混合特性进行了研究。分别以石英砂和硅胶模拟CFB循环灰和煤,采用挡板重力混合的方法,探究了挡板角度、层数、放置方式（对向和旋转放置）以及物料混合比等因素对混合效果的影响,并与机械混合实验进行了对比。结果表明,在混合过程中颗粒的混合和分散是并存的,旋转放置30°的挡板层数越多,硅胶和石英砂颗粒混合越均匀,混合物料中石英砂比例越高,混合效果越好。通过优化挡板结构及设置方式强化对流混合和剪切混合可明显改善固-固混合效果。虽然与机械混合相比,挡板混合效果略差,但在一定操作范围内仍可满足灰/煤混合热解工艺的要求。     

基于铁矿石载氧体的生物质化学链气化机理研究

在单批次进料小型流化床上,以稻壳为生物质燃料,研究了床料、气化温度、水蒸气体积分数以及载氧体载氧量与生物质含碳量的摩尔比(O/C)对生物质化学链气化反应特性的影响,并考察了铁矿石的长期交替氧化还原过程中的反应特性,分析了在小型流化床,水蒸气气氛气化条件下,铁矿石载氧体在反应过程中主要的反应以及反应后的铁矿石的床料变化。研究表明:在载氧体条件下,生物质的碳转化率显著增大,随着反应温度的升高,合成气中的H_2和CO的体积分数也相应升高。在温度不变情况下,随着水蒸气比例的升高,CO_2和H_2的体积分数显著上升。伴随着O/C摩尔比的升高,CO和H_2均显著下降。因此,在不同的反应条件下,铁矿石在生物质化学链气化过程中对反应速度、合成气比例等均有明显的作用,对研究生物质的综合利用具有一定的意义。