控制异丁烯阳离子聚合终止方式的新方法—活性中心转化法

控制异丁烯阳离子聚合终止方式的新方法──活性中心转化法曹宪一，王强，武冠英（北京化工大学高分子材料研究所，北京，１０００２９）关键词异丁烯，阳离子聚合，活性中心转化自八十年代中期Ｈｉｇａｓｈｉｍｕｒａ及Ｋｅｎｎｅｄｙ等人陆续发现乙烯基醚类单体及异丁烯...     

Tetrachlorosilane Consumption in Radio Frequency Glow Discharge

Time-resolved mass spectrometry was used for analysis of the plasma reactions in radio frequency (RF) SiCl ₄ and SiCl ₄ –O ₂ discharges as functions of starting partial pressure and electrical power. Molecular concentrations of the reactants and products from SiCl ₄ alone and with O ₂ were obtained from the mass spectra and used for plotting the kinetic curves. The SiCl ₄ and O ₂ consumption rates were calculated from the kinetic curves and compared with results of theoretical simulation of the reaction. Direct electron impact decomposition was found to be the main pathway for pure SiCl ₄ conversion. On the contrary, the consumption of SiCl ₄ in the SiCl ₄ +O ₂ mixtures was largely chemical. The experimental macrokinetics are in agreement with a model in which oxidation is caused by the atomic oxygen.     

恒电流库仑法测定基准试剂三氧化二砷的含量

用恒电流库仑法测定基准试剂三氧化二砷的含量，以恒电流通过含有碘化钾，基准试剂三氧化二砷试样的弱碱性水溶液，利用工作电极铂阳极上电生滴定剂I2与亚砷酸盐定量反应，以死停终点法确定滴定终点，测量出电解电流和电解时间，根据法拉第电解定律并利用EXCEL计算出基准试剂三氧化二砷的含量。方法的回收率为100％。     

Cationic polymerization of hydrocarbon monomers induced by complexes of acyl halides with Lewis acids 5. Polymerization of isobutylene in the presence of the complexes of benzoyl chloride with aluminum bromide

Polymerization of isobutylene inn-hexane at -78 °C in the presence of the complex of benzoyl chloride with AIBr₃ (1 : 2) was investigated. The results were compared to those obtained previously for the polymerization of this monomer induced by the complex of acetyl bromide with AlBr₃. Both complexes initiate the polymerization only by acyl cations. The number average molecular weight (M _n ) of the polymer linearly increases as the degree of isobutylene conversion increases. The polymerization restarts after repeated addition of the monomer, andM _n continues to increase linearly. The efficiency of the initiaton by the benzoyl chloride complex does not exceed 6.2 %; the reaction has the second order with respect to the initiator in the case of PhCOCI · A1₂Br₆; and the chain-propagation rate constant is 13.9 L mol^–1 s t. The use of PhCOCI Al₂Br₆ as the initator of the polymerization of isobutylene allows one to prepare macromolecules with very low contents of the terminal C=C double bonds and with narrow molecular weight distributions. Unlike the MeCOBr·AlBr₃ complex, PhCOCl · AlBr₃ does not initiate polymerization of isobutylene.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1175–1179, May, 1996.     

基于残差神经网络的无人机射频信号识别

针对民用小型无人机对低空领域安全造成威胁及无人机视觉上识别难的问题,提出了一种无人机射频信号识别的方法,使用深度学习技术学习无人机与控制器之间的射频信号特征来识别无人机。首先将射频信号数据集中的无人机信号进行预处理操作,接着使用残差神经网络进行模型训练,最后使用训练好的网络模型对无人机信号进行识别验证。实验结果表明,该方法识别无人机是否存在的准确率达到99.8%,识别无人机型号的准确率达到91.1%,识别无人机运行模式的准确率达到70.3%,且该方法具备较强的鲁棒性和环境抗干扰能力,性能明显优于基准方法。     

采用射频直采技术的超宽带软件无线电平台

针对现代无线电系统对超宽带、可重构、多功能等需求日益增长的问题,基于射频直接采样技术,构建了一套符合PXI(PCI extensions for Instrumentation)标准的通用化超宽带软件无线电平台,硬件上以数模转换芯片AD9173和模数转换芯片ADC083000为核心,直接采样率高达3 Gsample/s;采用20 nm工艺制程的UltraScale Kintex FPGA,以IP(Intellectual Property)化开发理念设计FPGA固件,实现用户可编程。该平台能够满足0.1~1.4 GHz超宽带软件无线电应用需求,瞬时带宽高达1.3 GHz。     

面向电子战射频光传输的宽带射频信号杂散产生机理及优化方法

针对电子战系统的宽带射频信号波分复用传输,通过理论分析给出了微波光子链路中各关键参量对杂散信号的影响规律,提出了非均匀信道间隔分配的除杂优化方法。该方法通过微调各通道的波长,使四波混频产生的杂散频率超过电子战接收机带宽,从而降低杂散对系统的影响。该方案实现简单,且无需改变现有电子战系统架构,具有较好的工程实现性。实验结果表明:与等波长间隔相比,5通道非均匀波分复用信号传输1 km时,在接收机带宽内四波混频引起的杂散得到了显著优化,动态范围提升了26 dB以上。     

多功能射频综合系统中的电磁协同北大核心CSCD

限定时空条件下,射频综合系统有效发挥多功能效应的实质是实现系统多功能协同高效运行,而制约其协同高效运行的瓶颈是特定时空条件下可用的电磁资源。电磁资源的高效利用依赖电磁协同,是按照任务要求及限定条件,在时间、频率、空间、能量多个维度寻求构建电磁协同自组织结构的最优解,并确定具体任务时空下有序运行自组织结构的驱动方式,按照求解出的电磁资源动态分配结果,执行任务,使系统电磁效应在任务牵引下受控。电磁协同服务于多功能射频综合系统融合,可以有效利用、管理战场电磁环境,高效提升多功能射频综合系统的运行效率。本文从多功能射频综合系统融合运行之瓶颈、电磁协同概念和电磁协同方法三个方面论述电磁协同的核心要点,期望为实现多功能射频综合系统融合运行提供可行的技术途径。     

Penetration of plasma surface modification. I. Cf4 and C2F4 glow discharge plasmas

Plasma treatment of a polymeric surface could involve at least three major mechanisms: (1) direct interaction of reactive species in the low-temperature plasma state with the surface (line of sight irradiation effect), and (2) chemical reactions of plasma-induced reactive species with the surface, and (3) reactions among reactive species and the surface (plasma polymerization). The first and the third effects are considered to be limited to the surfaces which directly contact with plasma (glow). The second effect is not limited to the surfaces that contact with plasma state but can penetrate beyond the plasma zone by diffusion. Using an assembly of fibers, of which only the top layer contacts with plasma (glow), the penetration of chemical changes caused by plasma exposure was investigated. Results indicate that the fluorination effect (incorporation of fluorine-containing moieties on the surface of polymeric substrate) penetrates through a considerable thickness of the assembly of fibers, depending on the porosity (gas permeability) of the system. Chemical reactions of plasma-induced (chemically) reactive but nonpolymerizing species with the substrate fibers seems to predominate. The direct interactions of energetic species, such as ions, electrons, and electronically excited species, with polymeric surfaces seems to play relatively minor roles in the plasma treatment investigated. The major role of plasma, in this case, seems to be creating such chemically reactive species. © 1994 John Wiley & Sons, Inc.     

Description of the turbidity measurements near the phase transition temperature of poly(N-isopropyl acrylamide) copolymers: the effect of pH, concentration, hydrophilic and hydrophobic content on the turbidity

Absorbance values between 300 and 800 nm of aqueous solutions of poly(N-isopropyl acrylamide-co-itaconic acid-9.80), poly(N-isopropyl acrylamide-co-itaconic acid-52.05) and poly(N-isopropyl acrylamide)s containing Tegomer H-Si 2111 end groups and/or blocks were measured using a Shimadzu 160-A UV-visible spectrometer. Turbidities obtained from these absorbance values were used to interpret the macromolecular phase transition from a hydrophilic to a hydrophobic structure of the polymers. The effects of comonomer type and content, concentration of the solutions, pH and temperature on the coil-globule transition were discussed in terms of turbidity form factor, β related to size and shapes of particles and calculated by using the simplified form of Debye equation.The results presented in this work show that the presence of Tegomer H-Si 2111 (Si containing end groups and/or blocks) or high amount of itaconic acid (IA) in the chains prevent a collapse transition from hydrated extended coils to hydrophobic globules, which aggregate and form a separate phase (β<2). Furthermore, it was observed that in the case of concentrated solutions intermolecular hydrophobic interactions between isopropyl groups overcame the repulsive forces resulting from the ionized carboxylic acid groups of IA or surface active nature of Si containing hydrophobic groups (β>2). This stage of the transition corresponds to macroscopic phase separation after an intramolecular process.