Designing polymeric hydrogen-bonded networks using 4,4-dipyridyl and aromatic carboxylic acids containing N–H substituents

Three adduct structures of 4,4-dipyridyl (4,4-DP) have been prepared and studied using single-crystal X-ray techniques. These are indole-2-carboxylic acid [(4,4-DP)(ICA)₂] 1, 3-aminobenzoic acid [(4,4-DP)(3-ABA)] 2, and 4-aminobenzoic acid [(4,4-DP)(4-ABA)] 3. The structures have an increasing degree of complexity in the overall hydrogen-bonding network. The structure of 1 comprises polymeric hydrogen-bonded chains of associated 4,4-DP and ICA molecules which propagate through a complementary site on the ICA molecules. The structure of 2 consists of two parallel polymeric hydrogen-bonded chains, each involving associated 4,4-DP and 3-ABA molecules, which cross-link through complementary 3-ABA sites. The structure of 3 is an extensive 3-dimensional hydrogen-bonded network involving all hydrogen-bond donor and acceptor sites on the constituent molecules. In each case the positions and directions of the N–H groups are important in determining the eventual lattice network.     

大数据相似性连接查询技术研究进展

为了深入理解和全面把握大数据相似性连接查询技术的研究进展,更好地促进其在图片聚类、实体解析、相似文档检测、相似轨迹检索等领域的广泛应用,对大数据相似性连接查询技术相关研究工作进行了深入调研和分析。首先对相似性连接查询的基本概念进行了介绍,然后分别对集合、向量、空间数据、概率数据、字符串等不同类型大数据的相似性连接查询相关研究工作进行了深入研究,对其优缺点进行了分析和总结。最后,指出了大数据相似性连接查询面临的若干挑战性问题及未来的研究重点。     

不含双线性对的高效无证书聚合签密方案

现有的聚合签密方案主要是基于复杂的双线性对构造,计算效率较低,不能很好地适用于计算资源和通信带宽受限的应用环境。为了提高聚合签密的效率,提出一种不含双线性对映射的无证书聚合签密方案。基于计算Diffie-Hellman问题（CDHP）和离散对数问题（DLP）的困难性,在随机预言模型下证明了方案满足机密性和不可伪造性。该方案不含双线性对运算和指数运算,在单签密阶段仅需要2个点乘运算,与已有的典型聚合签密方案相比具有更高的计算效率且密文长度更短;而且方案的聚合签密验证阶段无需任何用户的秘密信息,方案具有可公开验证性;此外,方案在部分私钥生成阶段不需要安全信道,降低了通信复杂度。     

Asymptotical Stability of Riemann–Liouville Fractional-Order Neutral-Type Delayed Projective Neural Networks

Neural Processing Letters - In this paper, a new class of Riemann–Liouville fractional-order neutral-type delayed projective neural networks are introduced and studied. By utilizing the...     

Fabrication of ball-milled MgO–Mg(OH)2-hydromagnesite composites and evaluation as an air-stable hydrogen storage material

A phase stability map of metallic magnesium powder, exposed to environmental conditions for 12 months (Mg-12M) and subjected to different high-energy ball-milling speeds and milling times, was constructed. Mg-12M−160 [½MgO-⅓Mg(OH)₂-⅙hydromagnesite] and Mg-12M−640 [¼MgO-⅝Mg(OH)₂-⅛hydromagnesite] composites were obtained changing the milling conditions. The correlation among the accumulated energy (ΔE_accum), the impact energy (ΔE_hit), and the phase stability under different high-energy ball-milling conditions were generated. The Mg-12M−160 composite had a hydrogen storage capacity of 0.63 wt% at −196 °C and 8.3 bar, although further hydrogen adsorption at higher pressures is expected. Structural defects play a significant role in the adsorption capacity. A representation of the possible absorption mechanism is proposed.     

基于GIS的地理教学辅助软件设计及应用研究

GIS是一种现代信息地理系统,在课堂教学中展现了巨大的优势。文中开发了一种具有三维GIS功能的教学软件,实现了地理知识的直观展示和深入分析。该软件不仅丰富了地理教学内容,还提升了学生的实践能力和学习兴趣,为高校地理教学提供了有效的工具。研究表明,GIS辅助软件的应用显著提高了地理教学效果,有助于培养高素质的复合型人才。     

周期离散时间系统的预见控制器设计

对于一类线性周期离散时间系统,提出一种新的周期预见控制器的设计方法.首先,利用二维模型方法及系数矩阵的周期性特点,将系统状态与其稳态值之差代替通常的状态差分,成功地构造出原系统的二维(2D)扩大误差系统;然后,针对导出的扩大误差系统,结合Lyapunov稳定性理论和LMI方法,给出闭环系统渐近稳定的条件及预见控制器的设计方法;最后,通过数值仿真说明该方法的有效性.