2,2,2-三硝基乙基-N-硝基甲胺的热安全性

为评价2,2,2-三硝基乙基-N-硝基甲胺(TNMA)的热安全性, 得到计算TNMA热安全性参数用的基本数据, 用经验式估算了TNMA的比热容(C_p)和热导率(λ). 用键能贡献于生成热Q_f的加和法, 估算了TNMA的标准生成焓Δ_cH_m^θ(TNMA, s, 298.15 K). 用热力学公式计算了TNMA的标准燃烧焓ΔU_m^θ(TNMA, s, 298.15 K)和标准燃烧能Δ_cH_m^θ(TNMA, s, 298.15 K). 用Kamlet-Jacobs 公式估算了爆速、爆压和爆热. 用经验式估算了分解热(Q_d). 通过差示扫描量热(DSC)曲线和高灵敏度布鲁顿玻璃薄膜压力计测得的逸出气体标准体积(V_H)-时间(t)曲线, 得到了TNMA放热分解反应的动力学参数. 用上述基本数据得到了评价TNMA的热安全性参数: 自加速分解温度(T_SADT), 热爆炸临界温度(T_be0和T_bp0), 绝热至爆时间(t_TIad), 撞击感度50%落高(H₅₀), 热点起爆临界温度(T_cr), 被300 K环境包围的半厚和半径为1 m的无限大平板、无限长圆柱和球形TNMA的热感度概率密度函数S(T), 相应于S(T)-T关系曲线最大值的峰温(T_S(T)max), 安全度(SD), 临界热爆炸环境温度(T_acr)和热爆炸概率(P_TE). 结果表明: (1) TNMA有较好的热安全性和对热抵抗能力, 与环三亚甲基三硝胺(RDX)相比, TNMA易从热分解过渡到热爆炸; (2) 不同形状大药量TNMA 热安全性降低的次序为: 球>无限长圆柱>无限大平板; (3)TNMA有高的燃烧能、高的爆轰化学能(爆热)和接近环四亚甲基四硝胺(HMX)的爆炸性能, 其对冲击敏感, 冲击感度与季戊四醇四硝酸酯(PETN)和特屈尔接近, 可用作混合炸药主组分.     

内嵌镧金属富勒烯的高产率合成及异构体比例调控

采用电弧放电法制备内嵌镧金属富勒烯的原灰,通过改变氦气压力及电流强度来提高内嵌镧金属富勒烯产率。原灰由1,2,4-三氯苯提取并回溶入甲苯后,利用分析型高相液相色谱（HPLC）对提取液中各富勒烯组分进行分析。通过分别衡量3种常见含镧金属富勒烯La@C_2v-C₈₂、La@C_s-C₈₂和La₂@C₈₀与C₈₄的相对峰面积比,探讨了氦气压力和电流强度等对3种金属富勒烯产率的影响。实验结果表明,氦气压力与电流强度共同决定了金属富勒烯的产率,在（1）低电流高氦气压、（2）中等电流中等氦气压、（3）高电流低氦气压的条件下都可以高产率地获得含镧金属富勒烯。此外,调整电流强度和氦气压力可以改变La@C_2v-C₈₂和La@C_s-C₈₂的相对比例。例如,在电流为100、120 A或氦气压为20、35 kPa时,此前认为的"minor"异构体La@C_s-C₈₂的含量甚至高于"major"异构体La@C_2v-C₈₂。我们还发现,降低电流强度或减小氦气压力可促进La₂@C₈₀的生成,这表明La₂@C₈₀与La@C₈₂的形成过程可能是不同的。     

基于主动式时间反转镜的声呐目标强度测量研究

为提高目标强度测量过程中的抗噪声、混响以及浅海多途干扰性能,从军标文件中的目标强度测量方法以及主动式时间反转镜的基本原理出发,经过研究和推演,发现可将基于单阵元的主动式时间反转镜与相关器结合应用于目标强度测量过程,提出了一种新的目标强度测量方法。该方法利用了主动式时间反转镜的抗多途特性,使得测量具有抗多途的性能;利用噪声与信号的不相关特性,算法结合相关器起到了很好的抗随机噪声效果;混响中的体积混响是随机的,算法具有抗体积混响的性能。论文分别从理论仿真和水池实验验证了算法的有效性和正确性。     

不同结构驱油聚合物的界面剪切流变性质

利用双锥法研究了油田现场用超高分子量部分水解聚丙烯酰胺(PHPAM)和疏水改性聚丙烯酰胺(HMPAM)溶液与航空煤油间的界面剪切流变性质,考察了时间、应变幅度和剪切频率对不同浓度PHPAM和HMPAM溶液界面剪切流变参数的影响.结果表明,只有在适宜的剪切频率条件下,流变数据才能反映界面膜的结构信息.HMPAM分子具有界面活性,能吸附在界面上,其界面膜的强度随时间变化逐渐增强,且在高浓度时以黏性为主;PHPAM分子不具有界面活性,其剪切流变参数没有时间依赖性,界面层以弹性为主.HMPAM能通过疏水作用形成界面网络结构,界面膜的剪切复合模量明显高于PHPAM界面层.HMPAM界面层中网络结构在剪切形变作用下的破坏与重组这一慢弛豫过程是其强度较高的原因.     

Research Progress of Regulation of Driving Forces in Short Peptide Supramolecular Self-Assembly北大核心CSCD

Some short peptides can spontaneously self-assemble into various nanostructures via the synergistic driving forces of non-covalent interactions. These non-covalent interactions,including electrostatic interaction,hydrogen bonding,aromatic interactions and other non-covalent interactions,are usually highly coupled together. Through rational sequence design and proper modification of short peptide molecules,the driving forces could be regulated purposively,and the nanostructures and morphologies of the self-assemblies could be controlled accordingly,and thus so as to achieve the fabrication of peptide-based supramolecular biomaterials and develop their functions. In this paper,the effects of hydrogen bonding,π-π stacking, electrostatic interaction,hydrophobic interaction,metal ion coordination and chiral center on the self-assembly behavior of peptide self-assembly have been reviewed. The driving force regulation strategies, including sequence design,pH and concentration adjustment and metal ion coordination,and the resulted nanostructures have also been discussed. We also make the outlooks on the development of peptide-based supramolecular biomaterials with specific functions in biomedicines and biocatalysis. © 2022, Science Press (China). All rights reserved.     

Preparation and Properties of Poly（ether ether ketone）/Carbon Nanotube Modified Polypropylene Janus Composite Separator北大核心CSCD

Lithium-ion batteries （LIBs）have attracted wide attention because of their broad prospects in electric vehicles. However,the safety problems and low multiplier performance of the commercial polyolefin separator limit their further development,due to the poor dimensional thermal stability and low electrolyte absorption rate. Poly（ether ether ketone）（PEEK）and carbon nanotube（CNT）are compounded to coat on polypropylene （PP） to prepare Janus composite separator （PP@C） through the phase inversion method. PP@C composite separator does not deform at 180 ℃ for 0. 5 h（only slight deformation）,illustrating excellent thermal stability. The electrolyte absorption rate of PP@C2 is 193. 8%. The electrolyte uptake rate of the PP@C2 composite membrane was 193. 8%,which was 64. 5% higher than the PP membrane,showing a superduper electrolyte permeability. As a result,the specific discharge capacity of LIBs assembled with PP@C2 composite separator is 157. 6 mA·h/g at 0. 2 C and 129. 8 mA·h/g at 2 C,showing good rate performance with the capacity recovery rate of more than 99%. This might be attributed to the ultra-high thermal stability of PEEK,the good affinity of the electrolyte,the high conductivity of CNT,as well as the uniform dispersion of Li+ ,so that the separator can have excellent electrochemical performance while improving safety. © 2022, Science Press (China). All rights reserved.     

一种计算液接电势的新方法*

依据液接电势达稳态时通过边界层的净电荷为零这一思想,提出了一种计算液接电势的新方法。对于3类液接电势的计算,特别是Lewis-Sargent公式与Henderson方程的推导,思路清晰易懂,避免了过往液接电势计算方法存在的一些问题。本文所提出的方法能够为液接电势相关内容的教学提供借鉴。     

X射线光栅微分相衬成像视场分析

X射线光栅微分相衬成像对由轻元素构成的物质的内部探测具有传统吸收成像无法比拟的优势, 尤其在癌症的早期诊断和轻元素材料及器件的无损检测等领域应用潜力巨大. 大视场成像是影响该技术从实验室走向实际应用的重要因素. 针对大视场成像的客观需求, 基于菲涅耳衍射原理和光栅结构特征, 建立了量化物理模型用于分析影响成像视场的因素, 提出了实现大成像视场的有效途径, 为未来大视场光栅微分相衬成像方法的设计和应用提供理论依据.     

金属卤化物钙钛矿光电材料和器件

2009年ABX₃钙钛矿晶型的甲胺铅卤CH₃NH₃PbX₃(X=I、Br、Cl)钙钛矿材料首次应用于太阳能电池,但初始报道效率低、稳定性差。2012年后,可溶液法制备的钙钛矿太阳能电池凭借其吸光系数高、激子结合能低等优点,迅速表现出低成本和高效率的突出优势,并在光电器件等交叉领域具有很强的应用潜力。因此,钙钛矿太阳能电池被Science杂志评为2013年度国际十大科技进展,是化学和材料领域特别是光伏领域新兴的变革性技术之一。钙钛矿太阳能电池材料与器件的发展一直面临大面积、高效率、稳定性和环境友好性等挑战,对应的是钙钛矿晶体可控生长、缺陷钝化、器件优化材料稳定性和铅毒性等科学问题。     

Design and performance of the LLRF system for CSNS/RCS

The rapid cycling synchrotron(RCS) is part of the China Spallation Neutron Source(CSNS). The RCS provides 1.6 Ge V protons with a repetition rate of 25 Hz. The RF system in RCS is mainly composed of a ferrite loaded RF cavity, a high power tetrode amplifier, a bias supply of 3300 A and a digital low level RF(LLRF) system based on FPGA. The major challenge of the LLRF system is to solve problems caused by rapid frequency sweeping and the heavy beam loading effect. A total of eight control loops are applied to ensure the normal operation. An effective feedforward scheme is widely used to improve the dynamic performance of the system. The design of the LLRF system and high power integration test results with the prototype RF system are presented.