Diversified recommendation method combining topic model and random walk

As one of the most widely used algorithms in recommendation field, collaborative filtering (CF) predicts the unknown rating of items based on similar neighbors. Although many CF-based recommendation methods have been proposed, there still be room for improvement. Firstly, the data sparsity problem still remains a big challenge for CF algorithms to find similar neighbors. Secondly, there are many redundant similar items in the recommendation list generated by traditional CF algorithms, which cannot meet the user wide interest. Therefore, we propose a diversified recommendation method combining topic model and random walk. A weighted random walk model is presented to find all direct and indirect similar neighbors on the sparse data, improving the accuracy of rating prediction. By taking both users’ behavior data and items’ lags into account, we give a diversity measurement method based on the topic distribution of items discovered by Linked-LDA model. Furthermore, a diversified ranking algorithm is developed to balance the accuracy and diversity of recommendation results. We compare our method with six other recommendation methods on a real-world dataset. Experimental results show that our method outperforms the other methods and achieves the best personalized recommendation effect.     

红外成像系统中激光耀斑成因机理

在使用CO2激光干扰红外热像仪时发现了大面积同心圆环状激光耀斑.针对激光耀斑的形状,综合考虑等厚干涉的形成条件、等厚干涉条纹的形状、热像仪光学系统的结构、热像仪的光阑结构、光学元件在出现损伤后生成的衍射条纹形状、圆孔衍射的光斑形状、CO2激光的热效应等因素,对其成因从干涉、衍射和热像仪光阑二次成像等角度进行了分析,对部...     

基于模糊神经网络的液体火箭发动机振动检测

液体火箭发动机振动检测涉及部件振动数据的收集、振动特征的抽取与度量以及度量结果的决策。基于模糊神经网络提出了一种发动机振动故障检测的基本系统。这种技术的吸引力在于：神经网络采用可变模糊集代表发动机工作模式，自然地提供了反映故障程度的有用信息；神经网络的离线学习算法可以从训练样本中提取振动知识；神经网络的监测算法不仅能正确预报故障，同时也能对新的振动信息进行在线学习。实验研究结果表明：模糊神经网络可以成功地用于泵压式液体火箭发动机热试车的振动故障检测。     

电感耦合等离子体原子发射光谱法测定钢丝帘线三相合金镀层的钴含量

研究电感耦合等离子体原子发射光谱法测定钢丝帘线三相合金镀层的钴含量。确定仪器分析参数为：分析谱线波长　238.892 nm,高频发生器发射功率　1.2 kW,等离子气体流量　15.0 L·min-1。试验结果表明,钴含量测定标准曲线的线性相关因数为0.999 975,检出限为0.001 86 μg·mL-1,相对标准偏差小于1%,回收率为100.59%～101.66%。该方法结果准确,重复性好。     

课程思政视域下大学生网络文明培养体系研究

基于课程思政,将德育内涵与元素融入课程教学目标与课堂教学内容中,分别从从"六个方面"、"四个课堂"、"四个层面"三维度展开,全面构建了具备针对性、实效性、立体化的"644"大学生网络文明培养体系。通过对大学生网络文明培养体系的研究,为各个专业和课程融入网络文明这一元素提供重要借鉴,并着力规范大学生网络行为,促进高校大学生网络文明素养的提高。     

对山西省轴计量式汽车衡现状的评估

我省公路运输以煤为主要货物。６０年代以前煤炭价格低廉,汽车运煤基本上按体积估算或凭经验估计,后来逐渐采用机械衡进行计量。随着科学进步,电子衡器又将取代机械衡器,目前应用的电子汽车衡有２种类型：整车计量的静态汽车衡和轴计量的动态汽车行。整车计量的准确度高,可达到０．１％,但造价高;轴计量的价格便宜,但准确度稍差,为０．５％。根据所运物料价值的不同,计量允差是不同的。我国对此尚无明确条文规定,但参照铁路运输煤炭计量以０．５％准确度的轨道衡为财务结算依据,因此使用０．５％准确度的汽车衡也是可以接受的。…     

古法榨油类非物质文化遗产的 技艺特点及生产性保护

古法榨油工艺是我国传统技艺类非物质文化遗产的一个重要组成部分,其制油方法、技艺特点凝结着中国古代科技精神。回顾了我国古代的制油方法,总结了其技艺特点,阐明了古法榨油产品的营养性和安全性;在此基础上,挖掘出古法榨油类非物质文化遗产的文化内涵,提出通过树立"非遗"品牌意识、建立古法工艺与现代技术的关联等措施实现其生产性保护的建议,旨在促进古法榨油类非物质文化遗产从文化资源到经济资源的转化。     

基于Hatlab／Simulink的永磁同步电机的直接转矩控制系统的研究

在定子坐标系下分析了永磁同步电机（PMSM）的数学模型,建立了针对永磁同步电机直接转矩控制（DTC）系统的模型,采用了具有零矢量作用的电压空间矢量脉宽调制（SVM）进行仿真。在Matlab／Simulink环境下的仿真结果表明,此方法有效地减小了转矩和电流的脉动,改善了电机的动静态性能。     

Heterogeneous AgxCdyS-AgCd Nanoparticles with Chiral Bias for Enhanced Photocatalytic Efficiency

Stereoselective catalysis is common in living systems mediated by natural nanoenzymes. However, few artificial nanomaterials are developed for enantioselective and stereoselective catalysis. In this study, Ag_xCd_yS-AgCd nanoparticles (NPs) with specific heterojunctions, strong chiral optical activities, and excellent enantioselective catalytic ability are constructed. Similar to photosensitive enzymes, Ag_xCd_yS-AgCd NPs stabilized with l -/d -penicillamine (l -/d -Ag_xCd_yS-AgCd NPs) can serve as photocatalysts, which show the highest catalytic efficiency toward the photodegradation of methyl blue compared with that of Ag₂S and CdS NPs and lead to 50% enhancement of photoconversion efficiency of Cr⁶⁺ to Cr³⁺ as well. Moreover, attributed to the higher chiral preference between l -Ag_xCd_yS-AgCd NPs and l -Tartaric acid (l -TA), d -Ag_xCd_yS-AgCd NPs and d -Tartaric acid (d -TA), the photoreduction efficiency of Cr⁶⁺ to Cr³⁺ mediated by l -Ag_xCd_yS-AgCd NPs with l -TA, and d -Ag_xCd_yS-AgCd NPs with d -TA samples is enhanced as high as 30% compared with the samples of l -Ag_xCd_yS-AgCd NPs with d -TA, and d -Ag_xCd_yS-AgCd NPs with L-TA. This study establishes a versatile way to construct enantioselective inorganic catalysts for biocatalysis, biomedicine, and other applications.