Synthesis of aromatic polyethers by Scholl reaction

This paper describes the synthesis and cation-radical polymerization of 1,5-bis(1-naphthoxy)-3-oxapentane. This monomer contains a flexible diethylene oxide unit between two 1-naphthalene rings. The FT-IR analysis of the resulted polymer indicates that it contains 1,4-disubstituted naphthalene structural units, i.e. 4,4-disubstituted-1,1-binaphthalene units. The polymer is crystalline with a melting point of 236 °C.Part IX: V. Percec and J. H. Wang: J. Mater. Chem., in press     

多源异构数据融合驱动的股票指数预测研究

现代信息技术的广泛应用使得资本市场投资者能够获得更及时、更有价值的信息,也更容易受到金融论坛、专业投资网站的影响。融合资本市场的多源异构数据对股票指数进行预测成为该领域的研究热点。提出了一种基于多源异构数据的长短期神经网络（Long Short-Term Memory,LSTM）模型,通过对融合资本市场交易数据、技术指标数据、投资者情绪三种源数据的量化来预测股票指数的走势。提出了一种可以提取深度情感特征的卷积神经网络（Convolutional Neural Networks,CNN）情感分析模型,构建了投资者情绪特征模型。利用“上证50指数”数据进行实验,结果显示：LSTM模型的预测准确率比传统模型更为优秀,数据源的增加也对模型准确率的提升有较大贡献,验证了该方法的可行性和有效性。     

基于LoRa自组网无线传输技术实现用电信息采集系统设计

针对传统通信技术存在经济需求高、易被外界干扰、功率损耗高等问题,设计了一套非常适用的解决方案,该方案基于LoRa自组网无线传输技术,与A/D用电信息采集系统结合,组成一套很好的方案;通过LoRa扩频技术和低功耗技术来解决远距离无线通信易受到干扰和功率损耗高的问题,利用A/D用电信息采集系统解决大数据环境下传统采集方法准确率低的问题;经过仿真实验结果表明,该方案LoRa无线传输技术的远距离通信和低功耗能够实现,在大数据环境下A/D用电信息采集系统的准确率比WEB自动采集程序高达3%。     

基于Pro/E的机械零部件三维动态序列装配技术研究

三维动态序列装配技术在机械产品和工程设计行业的设计、制造、检测、展示、学习、资金节约、功效提高等方面具有非常重要的意义,其制作具有一定的技术复杂性和技巧性,目前许多三维CAD软件有此功能,但很少有此方面的具体介绍,为了给机械及工程技术人员提供一些有益的借鉴,以某高楼外墙清洗机吸盘部件三维动态序列装配动画的制作为例,针对Pro/E三维机械设计软件的动态序列装配技术进行了详细介绍,给出了整个制作流程.     

Simultaneously achieved high-energy storage density and efficiency in (K,Na)NbO3-based lead-free ferroelectric films

With the development of advanced electrical and electronic devices and the requirement of environmental protection, lead-free dielectric capacitors with excellent energy storage performance have aroused great attention. However, it is a great challenge to achieve both large energy storage density and high efficiency simultaneously in dielectric capacitors. This work investigates the energy storage performance of sol-gel-processed (K,Na)NbO₃-based lead-free ferroelectric films on silicon substrates with compositions of 0.95(K_0.49Na_0.49Li_0.02)(Nb_0.8Ta_0.2)O₃-0.05CaZrO₃-x mol% Mn (KNN-LT-CZ5-x mol% Mn). The appropriate amount of Mn-doping facilitates the coexistence of orthorhombic and tetragonal phases, suppresses the leakage current, and considerably enhances the breakdown strengths of KNN-LT-CZ5 films. Consequently, large recoverable energy storage density up to 64.6 J cm⁻³ with a high efficiency of 84.6% under an electric field of 3080 kV cm⁻¹ are achieved in KNN-LT-CZ5-5 mol% Mn film. This, to the best of our knowledge, is superior to the majority of both the lead-based and lead-free films on silicon substrates and thus demonstrates great potentials of (K,Na)NbO₃-based lead-free films as dielectric energy storage materials.     

一种虚拟景象合成系统技术研究

本文探讨了一种照片合成工作方式,利用电子技术获得拍摄场景中灯光以及照相机位置、焦距等信息并通过计算机接口输入,参考这些数据修改3DS文件,再利用三维软件进行真实的照片级渲染,最终合成照片作品.     

Pre-Buried ETL with Bottom-Up Strategy Toward Flexible Perovskite Solar Cells with Efficiency Over 23%

With rapid development of photovoltaic technology, flexible perovskite solar cells (f-PSCs) have attracted much attention for their light weight, high flexibility and portability. However, the power conversion efficiency (PCE) achieved so far is not yet comparable to that of rigid devices. This is mainly due to the great challenge of depositing homogeneous and high-quality perovskite films on flexible substrate. In this study, the pre-buried 3-aminopropionic acid hydroiodide (3AAH) additives into the electron transport layer (ETL) and modified the ETL/perovskite (PVK) interface by a bottom-up strategy. 3AAH treatment induced a templated perovskite grain growth and improved the quality of the ETL. By this, the residual stresses generated in PVK during the annealing-cooling process are released and converted into micro-compressive stresses. As a result, the defect density of f-PSCs with pre-buried 3AAH is reduced and the photovoltaic performance is greatly improved, reaching an exceptional PCE of 23.36%. This strategy provides a new idea to bridge the gap between flexible and rigid devices.     

Energy Transfer Induced by TADF Polymer Enables the Recycling of Excitons in Perovskite Solar Cells

Formamidinium lead triiodide (FAPbI₃) has been demonstrated as the most efficient perovskite system to date, due to its excellent thermal stability and an ideal bandgap approaching the Shockley-Queisser limit. Whereas, there are intrinsic quantum confinement effects in FAPbI₃, which lead to unwanted non-radiative recombination. Additionally, the black α-phase of FAPbI₃ is unstable under room temperature due to the significant residual tensile stress in the film. To simultaneously address the above issues, a thermally-activated delayed fluorescence polymer P1 is designed in the study to modify the FAPbI₃ film. Owing to the spectral overlap between the photoluminescence of P1 and absorption of the above-bandgap quantum wells of FAPbI₃, the Förster energy transfer occurs at the P1/FAPbI₃ interface, which further triggers the Dexter energy transfer within FAPbI₃. The exciton “recycling” can thus be realized, which reduces the non-radiative recombination losses in perovskite solar cells (PSCs). Moreover, P1 is found to introduce compressive stress into FAPbI₃, which relieves the tensile stress in perovskite. Consequently, the PSCs with P1 treatment achieve an outstanding power conversion efficiency (PCE) of 23.51%. Moreover, with the alleviation of stress in the perovskite film, flexible PSCs (f-PSCs) also deliver a high PCE of 21.40%.     

国外电子任务飞机现状与发展趋势

机载电子任务系统以其高灵活性和强适应能力成为世界各军事强国装备体系的重要组成部分,在历次局部战争中展现出越来越重要的价值,发挥了重要的作用。近年来,随着人工智能技术的不断发展和成熟,无人化装备迅速发展,但在一定时期内依然是有人、无人并存,各有侧重,共同组成完整的航空装备体系。分析了世界军事强国典型任务电子飞机的发展现状、作战运用方式,并总结了当今任务电子飞机发展的几个重要趋势。     

Facial Expression Recognition Based on Spatial and Channel Attention Mechanisms

Wireless Personal Communications - Microarray-based gene expression profiling is an emerging method to predict, classify, diagnose and to treat cancer efficiently. The characteristics of this...