Distribution of Platinum and Palladium between Dissolved,Nanoparticulate, and Microparticulate Fractions of Road Dust

Ageing processes of vehicle catalytic converters inevitably lead to the release of Pt and Pd into the environment, road dust being the main sink. Though Pt and Pd are contained in catalytic converters in nanoparticulate metallic form, under environmental conditions, they can be transformed into toxic dissolved species. In the present work, the distribution of Pt and Pd between dissolved, nanoparticulate, and microparticulate fractions of Moscow road dust is assessed. The total concentrations of Pt and Pd in dust vary in the ranges 9–142 ng (mean 35) and 155–456 (mean 235) ng g⁻¹, respectively. The nanoparticulate and dissolved species of Pt and Pd in dust were studied using single particle inductively coupled plasma mass spectrometry. The median sizes of nanoparticulate Pt and Pd were 7 and 13 nm, respectively. The nanoparticulate fraction of Pt and Pd in Moscow dust is only about 1.6–1.8%. The average contents of dissolved fraction of Pt and Pd are 10.4% and 4.1%, respectively. The major fractions of Pt and Pd (88–94%) in road dust are associated with microparticles. Although the microparticulate fractions of Pt and Pd are relatively stable, they may become dissolved under changing environmental conditions and, hence, transformed into toxic species.     

A Collection of Molecular Fingerprints of Single Aerosol Particles in Air for Potential Identification and Detection Using Optical Trapping-Raman Spectroscopy

Characterization, identification, and detection of aerosol particles in their native atmospheric states remain a challenge. Recently, optical trapping-Raman spectroscopy (OT-RS) has been developed and demonstrated for characterization of single, airborne particles. Such particles in different chemical groups have been characterized by OT-RS in recent years and many more are being studied. In this work, we collected single-particle Raman spectra measured using the OT-RS technique and began construction of a library of OT-RS fingerprints that may be used as a reference for potential detection and identification of aerosol particles in the atmosphere. We collected OT-RS fingerprints of aerosol particles from eight different categories including carbons, bioaerosols (pollens, fungi, vitamins, spores), dusts, biological warfare agent surrogates, etc. Among the eight categories, spectral fingerprints of six groups of aerosol particles have been published previously and two other groups are new. We also discussed challenges, limitations, and advantages of using single-particle optical trapping-Raman spectroscopy for aerosol-particle characterization, identification, and detection.     

Field-Induced Slow Magnetic Relaxation in CoII Cyclopropane-1,1-dicarboxylates

New Co^II substituted malonate field-induced molecular magnets {[Rb₆Co₃(cpdc)₆(H₂O)₁₂]∙6H₂O}_n (1) and [Cs₂Co(cpdc)₂(H₂O)₆]_n (2) (where cpdc²⁻ stands for cyclopropane-1,1-dicarboxylic acid dianions) were synthesized. Both compounds contain mononuclear bischelate fragments {Co^II(cpdc)₂(H₂O)₂}²⁻ where the quasi-octahedral cobalt environment (CoO₆) is complemented by water molecules in apical positions. The alkali metal atoms play the role of connectors between the bischelate fragments to form 3D and 2D polymeric structures for 1 and 2, respectively. Analysis of dc magnetic data using the parametric Griffith Hamiltonian for high-spin Co^II supported by ab initio calculations revealed that both compounds have an easy axis of magnetic anisotropy. Compounds 1 and 2 exhibit slow magnetic relaxation under an external magnetic field (H_DC = 1000 and 1500 Oe, respectively).     

ADS注入器Ⅰ高频四极场功率源系统研制

ADS注入器Ⅰ高频四极场(RFQ)功率源系统将为325 MHz RFQ提供连续波功率,使束流离开RFQ时,其能量达到几MeV。功率源系统除了补偿RFQ腔耗外,还必须提供足够的功率以保证RFQ中的加速电场。ADS注入器Ⅰ RFQ功率源系统主要包括600 kW连续波速调管、80 kV/18 A基于脉冲步进调制技术的PSM电源、环流器以及相应的波导传输系统等。根据ADS总体指标和RFQ的相关技术参数,提出了功率源的总体布局、技术指标以及设计要求等,在此基础上完成系统安装与调试,并通过专家组测试与验收。     

用于原子氧地面模拟设备精密压控恒流源

针对原子氧地面模拟设备需要通过电流源形成磁镜效应对其发射度进行约束,以及用于原子氧参数测试仪器校准,研制了一款基于运算放大器的精密压控恒流源。为了防止恒流源的供电电源纹波对电路性能的影响,又配套研制一款开关电源滤波器。最后测试表明：开关电源滤波器能有效减少电源噪声,+15 V电源的纹波系数降到万分之一,恒流源输出电流10 pA～1 A,精度500 fA,其稳定和负载稳定性优异。     

基于X光微点源的半影成像技术

基于X光微点源装置,从实验角度验证了半影成像的原理。利用针孔成像,直接测量了微点源源区图像;给出了半影孔成像、半影锥成像和环孔成像原理,以及在微点源的半影成像结果和维纳滤波重建结果。从实验结果可知：半影锥成像具有与半影孔成像相同的诊断能力,两种方法的重建图像尺寸与源尺寸一致;环孔成像的诊断能力更好,重建图像的尺寸和形状更接近源图像。     

低约束试件断裂韧性测试方法研究进展 1)

低约束试件断裂韧性测试对油气管道安全运营具有重要意义。本文回顾了低约束试件断裂韧性测试方法及发展过程,介绍了裂纹尖端张开位 移(crack tip opening displacement, CTOD)和J积分等常用断裂韧性表征参数,并对断裂韧性测试中应力强度因子、J积分塑性因子、J积分与CTOD转换因子、裂纹尺寸测量方法、数 字图像相关方法等关键问题进行对比分析,总结需要深入研究的问题,为低约束试件断裂韧性测试发展提供一定依据。     

典型卫星轨道辐射环境及在轨软错误率预计模型分析

使用最新版本的Space Radiation 7.0软件对典型卫星轨道（包括地球同步轨道、中地轨道和低地轨道）的空间辐射环境进行提取和计算,分析不同空间天气和屏蔽条件下的轨道离子通量-能量谱和通量-线性能量沉积（LET）谱特点。以一款SOI SRAM为例,结合地面加速器重离子试验获得的单粒子翻转截面-LET值关系曲线,预计该器件的在轨软错误率（SER）,并分析关键参数对预计结果的影响规律和内在机理。结果表明,使用Space Radiation软件的四种输入模式获得的预计结果可相差5倍左右;灵敏区厚度的增大导致在轨SER降低数个数量级,原因为灵敏区厚度的设置与灵敏区平均投影面积和符合条件的空间离子通量的大小直接相关;漏斗长度的大小对预计结果有一定的影响。最后,对SER预计模型的适用性和发展趋势进行了讨论。     

1.2 kW C波段固态高效率GaN微波源研制

针对传统大功率Si,GaAs固态微波源效率低和高温度性能差的不足,采用导热系数优良的宽禁带GaN单元功放模块集成、低损耗同轴波导径向空间功率合成方法,研制出一种1.2 kW全固态C波段高效率宽禁带GaN微波源。实验结果表明：该方法实现了大功率固态微波源高效率及连续长时间高温风冷散热运行,系统安全可靠。单路功放模块集成6位移相器,移相精度5.6,增益35 dB,输出功率大于31 W。系统连续波输出功率1.2 kW ,总效率30%,谐波抑制-54.8 dBc;杂散-63.69 dBc,相位噪声-94.03 dBc/Hz@1kHz。     

神光-Ⅲ主机装置MJ级能源系统研制现状

介绍了神光-Ⅲ主机装置能源系统的功能要求、组成结构和设计方法,以及关键单元器件的功能要求和设计方法。该系统是片状放大器系统的重要组成部分,由6个束组共108套最大储能为1.2 MJ的能源模块组成,总储能达到110 MJ（最大130 MJ）。每套模块产生一个脉宽610 s(10 %峰值)的电流脉冲,驱动10组、共20支氙灯,为片状放大器提供泵浦能量,峰值电流为0.25 MA。目前投入试运行的36套能源模块的各项电气性能指标满足设计要求,能确保片状放大器小信号增益系数达到5.0%/cm,为片状放大器提供足够的泵浦能量,满足激光器的能量需求。