Item2vec与改进DDPG相融合的推荐算法

传统的推荐算法能够有效解决信息过载问题,但在冷启动和数据稀疏的情况下,传统方法仍有其局限性。针对以上问题本文提出一种基于深度强化学习理论的推荐算法,该算法使用深度确定性策略梯度(DDPG,deep deterministic policy gradient,DDPG)算法来解决推荐问题,使用Item2vec将离散的动作空间转换为连续的表示,同时提出了一种余弦距离和欧氏距离相结合的奖励函数,能够保障神经网络不会过早的收敛于局部最优。应用该算法进行电影的推荐,实验结果表明本文提出的算法能够产生较好的推荐并能缓解冷启动所带来的影响。     

理论力学"四堂融合"混合式教学和考核模式改革的实践

探讨了一种在新兴教育技术下传统课堂、在线课堂、雨课堂和翻转课堂"四堂融合"的混合式理论力学教学方法,并进行基于此模式的考核模式改革,显著提高了学生的学习成绩,提高了课堂教学成效,取得了良好的教学效果。这种教学和考核模式改革给当代理论力学课堂教学改革提供了一种思路。     

High accuracy amplitude and phase measurements based on a double heterodyne architecture

In the digital low level RF (LLRF) system of a circular (particle) accelerator, the RF field signal is usually down converted to a fixed intermediate frequency (IF). The ratio of IF and sampling frequency determines the processing required, and differs in various LLRF systems. It is generally desirable to design a universally compatible architecture for different IFs with no change to the sampling frequency and algorithm. A new RF detection method based on a double heterodyne architecture for wide IF range has been developed, which achieves the high accuracy requirement of modern LLRF. In this paper, the relation of IF and phase error is systematically analyzed for the first time and verified by experiments. The effects of temperature drift for 16 h IF detection are inhibited by the amplitude and phase calibrations.     

基于灰色聚类分析的风险评价方法研究——以江苏民间资本进入金融领域风险评价为例

运用灰色系统理论,结合AHP方法,建立灰色聚类分析模型,对风险进行评价,并以江苏民间资本进入金融领域风险评价为例进行研究.结果表明,民间资本进入金融领域的风险属于高风险范畴,其中进入风险中的产业风险和社会风险属于高风险,信用风险属于较高风险,政治风险属于中等风险.并针对上述风险的等级,提出了相应的政策建议.模型具有一定的实用价值,它对于正确认识民间资本进入金融领域的风险和有针对性地制定相应的政策措施具有一定的理论和现实意义.     

手性胺膦配体在不对称催化中的应用

利用邻二苯基膦苯甲醛分别与多种手性二胺的缩合反应,设计合成了一系列新型手性四齿胺膦配体.这类多齿胺膦配体含有两个软的磷原子和两个硬的氮原子,具有丰富的配位化学性能和优秀的不对称诱导能力.本文综述了手性胺膦金属络合物催化剂在不对称转移氢化反应、氧化动力学拆分反应、烯烃的不对称环氧化反应和不对称环丙烷化反应、不对称D-A反应中的应用.     

钴-席夫碱-壳聚糖/凹凸棒土对苯乙烯环氧化的催化性能

以NaOH固化法制备的壳聚糖/凹凸棒土(CS/ATP)复合树脂为载体,以水杨醛和天冬氨酸合成的席夫碱为配体,分别合成Co、Mn、Cu、Fe和Ni的席夫碱金属配合物及其负载型席夫碱金属配合物,并通过FT-IR对其进行结构表征,且以苯乙烯为底物,分子氧为氧源,分别考察了各种催化剂对苯乙烯的环氧化性能。实验结果表明,在小分子席夫碱金属配体中,Co-Schiff碱催化性能较好。将Co-Schiff碱负载到CS/ATP复合树脂中,综合考察了Co-Schiff碱-CS/ATP的用量、温度、时间对苯乙烯催化环氧化性能的影响,结果表明,反应温度为80℃,反应时间为8 h,苯乙烯的转化率达93.1%。     

二阶积分微分方程的广义拟线性化方法

运用广义拟线性化方法研究了正规锥上的二阶积分微分方程初值问题,获得了逼近解序列一致且平方收敛的结果.     

尿素/己内酞胺/氢氧化钠/水溶剂体系对纤维素的溶解和再生性能

探讨了尿素/己内酞胺/氢氧化钠/水溶剂体系对纤维素的溶解和再生情况.利用正交试验确定了该体系各组分的最佳组成(质量分数):尿素10%,己内酞胺4%,氢氧化钠8%.采用红外光谱(MR)、热重失重(TGA)分析和X射线衍射(XRD)等手段对再生前后的纤维素进行了表征.结果表明,该溶剂体系对纤维素具有良好的溶解性能,并且是纤...     

Determination of 12 additives in beverages by evaporation-assisted dispersive liquid-liquid microextraction based on the solidification of floating organic droplets combined with liquid chromatographyEI北大核心CSCD

An analytical method for the simultaneous determination of 12 additives in beverages was developed using evaporation-assisted dispersive liquid-liquid microextraction based on the solidification of floating organic droplets EVA-DLLME-SFOcombined with high performance liquid chromatography HPLC. The samples were extracted twice with 70%V/Vmethanol aqueous solution and extracted by EVA-DLLME-SFO method after the combination of the extractsand finally determined by HPLC. Extraction parameterssuch as types and amounts of extractantevaporant and heating agentthe concentration of saltand the extraction time were optimized. Under the optimized conditionsthere were good relationships in the ange of 0.25-50 μµg/mL with the limits of detection of 1.5 to 13.6 mg/kg and limits of quantification of 5.2 to 45.3 mg/kg. The recoveries at three spiked levels1025 and 50 mg/kgwere 76.8% to 101.2% with the relative standard deviations of 0.11% to 4.7%. The method can be used for rapid detection of 12 additives in beverages. © 2022, Youke Publishing Co.,Ltd. All rights reserved.