动态改变惯性权重的新模式粒子群算法

针对标准粒子群算法在求解复杂优化问题时易陷入局部最优、收敛精度不高和收敛成功率低的不足,提出了一种改进的粒子群算法.通过算法所处的迭代阶段和粒子的分布情况动态改变惯性权重的值,并根据每个粒子的更新情况调整其飞行的起点.最后4个测试函数仿真结果表明,在求解复杂优化问题时,改进后算法的收敛精度和收敛成功率均有明显提高.     

一种CDMA2000 1xEV-DO终端物理层软件验证方法

提出了一种可以在计算机上验证CDMA2000 1x EV-DO(EVDO)终端物理层软件的仿真系统.该系统可以模拟实际硬件电路板各个软硬件模块的行为,以及模拟和终端物理层软件相关网络侧的行为,基于此对EVDO终端物理层软件进行仿真验证,提高了新项目的开发效率.     

一种构造“点模式”的转换方法及其铀成矿分析应用

为进一步挖掘构造及铀成矿之间的关系,基于ARCGIS9.3软件设计了提取构造交点及构造走向的技术,将构造的“线数据”转换成“点数据”,以服务于点类型分析.此外,构造交点与铀矿床(点)之间,全部构造、14个典型矿床的控矿、容矿构造走向-数量分布之间,呈现出一定的吻合性.     

应用于无线通信基站的Doherty功率放大器

采用Doherty技术设计并实现了一款应用于无线通信基站的S波段高效率功率放大器,通过非对称功率输入的方式使得整个功放在更宽的功率范围内获得高效率。设计中采用了安捷伦公司的先进设计系统软件(advanced design system,ADS),选取恩智浦公司型号为MRF7S21080H与MRF8S21100H的横向扩散金属氧化物半导体(laterally diffused metal oxide semiconductor,LDMOS)功放晶体管,两款晶体管的工作频率均为2.14~2.17 GHz。经过电路仿真与实物调试,最终设计并实现了功率回退达到7 dB的功率放大器,其增益为13.5 dB,并且在7 dB功率回退点上效率达到35%,峰值功率效率达到42%。相比其他功率放大器,该放大器具有较大的功率回退范围与更高的效率。结果证明,通过不对称输入方式所设计的Doherty功率放大器可以获得更宽的功率回退范围。     

Seasonal Variation and Land-Use/Land-Cover Type Impacts on the Correlation of Urban Heat Island Intensity and Difference Vegetation Index with Satellite Data in Xi’an,China

Green coverage has pronounced influences on urban heat island (UHI) effect, while the impacts of seasonal variation and Land-Use/Land-Cover (LULC) types on this effect has not been implemented. This paper investigated the spatio-seasonal characteristics of urban thermal environment and the vegetation-soil mixed area, and then explored the effects of vegetation status on UHI intensity from the perspectives of seasons and regions in Xi’an using four Landsat 8 images. UHI intensity index was implemented to extract UHI intensity based on thermal infrared imagery, and difference vegetation index (DVI) was used to represent vegetation-soil mixed area. Results indicated that DVI has impacts on UHI intensity, and their relations vary with season and region. In the whole Xi’an, if UHI intensity is smaller than -0.1, DVI increases with the increase of UHI intensity; whereas for UHI intensity is greater than -0.1, DVI decreases with increases of the UHI intensity from early spring to autumn. The highest correlation level was discovered in the autumn map (R²=0.713). Results of correlation analysis further displayed that DVI positively correlated with UHI intensity at impervious surface, and that the main urban area possessed the best correlation with R²=0.564 5.     

大数据背景下电子商务信息流优化研究

信息流作为电子商务中的一大构成要素,对电子商务的发展起着至关重要的作用。随着电子商务的不断发展,数据信息量也呈几何级增长,在大数据背景下如何更好地管理和利用信息流已成为电子商务中的一个突出问题。文章以电子商务信息流的优化为选题,分析了其存在的形式,描述了信息流对电子商务活动的影响,并结合其现有的特点,从企业内部和外部两个不同的角度来提出优化思路,以期为提高电子商务活动的效率及促进电子商务的健康发展提供参考。     

中间相沥青基介孔炭的表征及其用作锂离子电池负极材料的电化学性能

以中间相沥青为碳源、CaCO_3为模板,制备中间相沥青基介孔炭(MPMC)。采用XRD、SEM、TEM等手段表征所制介孔炭的结构和形貌,并将其用作锂离子电池的负极材料,测试电化学性能。结果表明,所制MPMC具有丰富的介孔结构和较大的比表面积及孔体积,随着CaCO_3质量分数的增加,MPMC的比表面积和孔体积先增加后减小,当CaCO_3的质量分数为70%时,所制MPMC的比表面积和孔体积最大;MPMC用作锂离子电池负极材料具有良好的电化学性能,能有效提高锂离子电池的可逆比容量,具有良好的循环稳定性和倍率性能。     

Alkaline digestion behavior and alumina extraction from sodium aluminosilicate generated in pyrometallurgical process

In pyrometallurgical process, Al-and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na₂O constituents, which alters the leaching behaviors of Al₂O₃ and SiO₂. It was confirmed that sodium aluminosilicates with different phase compositions synthesized at various roasting conditions were effectively digested in the alkaline digestion process. Under the optimum conditions at temperature of 100-120℃, liquid-to-solid ratio (L/S) of 10:2 mL/g, caustic ratio of 4, and Na₂O concentration of 240 g/L, the actual and relative digestion ratio of Al₂O₃ from the synthesized sodium aluminosilicates reached maximums of about 65% and 95%, respectively, while SiO₂ was barely leached out. To validate the superior digestion property of sodium aluminosilicate generated via an actual process, the Bayer digestion of an Al₂O₃-rich material derived from reductive roasting of bauxite and comprising Na_1.75Al_1.75Si_0.25O₄ was conducted; the relative digestion ratio of Al₂O₃ attained 90% at 200℃.     

人工智能政策解析及建议

 人工智能已成为推动新一轮科技革命和产业变革的驱动力,世界发达国家纷纷把发展人工智能提升至国家战略高度,争相出台相关政策。通过解析美国、英国、法国、德国、欧盟、日本和中国的人工智能政策,借鉴发达国家的人工智能政策和相关措施,提出了发展中国人工智能的政策建议。     

Experimental investigation and thermodynamic assessment of the yttriumhydrogen binary system

A coupled experimental investigation and thermodynamic study of the yttrium-hydrogen(Y-H) binary system were carried out to provide more comprehensive and quantitative insights into the key thermodynamic properties of this system. Y-H system in the full range of H/Y = 0–3.0 was investigated by accurate pressure composition isotherm(PCI) measurement to provide credible phase equilibria information and thermodynamic data.The phase boundaries obtained were in agreement with previous experimental data but with improved accuracy.With the guide of the crystal structures, all the solid phases were modelled using the three sublattice model. The Y-H phase diagram and thermodynamic parameters were calculated and assessed with the CALPHAD technique.The obtained results are in very good agreement with our experimental data and the published data reported in literature. The obtained thermodynamic database of Y-H system can be used to predict the hydrogenation behavior and decomposition temperatures of hydrides.