流动注射一超声雾化器一电感耦合等离子体-原子发射光谱(FI-UN-ICP-AES)同时测定头发中多种元素条件的优化

建立了FI－UN－ICP－AES联用技术，用所发展技术进行了头发中多种微量元素的同时测定，对载流流速、积分时间、进样体积等进行了优化。多次注射测定的再现性（RSD）在0.6％一5．0％范围内，标准加入回收率为90％一101％。     

Spin-glass behavior and magnetic splitting in molecular magnetic materials {[N(n-C4H9)4][MIIFeIII(C2O4)3]}n (M = Co, Mn)

The mixed valence character and the antiferromagnetic coupling in the molecular magnetic materials {[N(n-C₄H₉)₄][M^IIFe^III(C₂O₄)₃]}_n (M = Co, Mn) were investigated by Mössbauer spectroscopy and magnetic measurements. In the material {[N(n-C₄H₉)₄][CoFe(C₂O₄)₃]}_n, the appearence of the spin-glass phase transition temperature and the magnetic phase transition under zero-field-cooled AC magnetic measurements were studied in the temperature range 5–100 K. In the Mössbauer spectra of {[N(n-C₄H₉)₄][MnFe(C₂O₄)₃]} a magnetic splitting was observed below 30 K. The appearance of the magnetic splitting indicates the occurrence of magnetic ordering in this complex. The hyperfine parameters show that the electronic state of iron is high-spin Fe³⁺.     

Efficient CS Cross‐Coupling of Thiols with Aryl Iodides Catalyzed by Cu(OAc)2·H2O and 2,2′‐Biimidazole

The classical Ullmann C? S cross coupling reaction of aryl iodides with aromatic/alkyl thiols under catalysis of 15 mol% Cu(OAc)₂·H₂O and 15 mol% 2,2′‐biimidazole works at 80°C in DMSO for 3 h to provide a variety of aryl sulfides in good to excellent yields.     

掺氢可燃气体燃爆特性研究进展

随着全球新能源产业的快速发展,氢能因其高效、无污染、可持续的特点而备受关注,但由于氢气的固有特性很难保持其安全性,因此安全问题一直是氢能利用的重中之重。本文以氢气的安全利用为背景对掺氢可燃气体燃爆特性的研究进展进行了系统总结,首先介绍了掺氢可燃气体的燃爆机理,然后讨论其最小点火能、燃爆极限及其火焰行为特性,最后强调了掺氢可燃气体在能源利用中的重要意义及未来的发展方向。

     

空孔与运动裂纹相互作用的动焦散线实验研究

为研究预制裂纹不同偏移距离时运动裂纹与空孔的相互作用规律,采用动态焦散线实验系统,将预制裂纹的偏移距离设定为唯一变量,对含空孔的有机玻璃(PMMA)试件进行冲击三点弯实验。研究表明,存在两个临界距离：（6 mm (2 R )、9 mm (3 R )）,在该偏移距离下,裂纹扩展轨迹、动态断裂特性发生显著改变：(1) 预制裂纹偏移距离不大于3 mm时,裂纹贯穿空孔,发生二次起裂,且二次起裂的速度与应力强度因子显著大于一次起裂,无偏移时裂纹轨迹的分形维数为最小值;(2) 偏移距离增大至6 mm时,裂纹不再贯穿空孔,空孔对裂纹先吸引后排斥,裂纹速度与应力强度因子先减小后增大,裂纹轨迹的分形维数达到最大值;(3) 偏移距离大于6 mm时,空孔对裂纹的吸引作用逐渐减小,大于9 mm后,空孔对裂纹的吸引不再显著,裂纹起裂后即向落锤加载方向扩展直至贯穿试件。

     

气冷微型堆可燃毒物研究北大核心CSCD

为分析气冷微型堆可燃毒物布置策略,分别建立长寿期(15 MW-20 a)、短寿期(5 MW-1 a)、较长寿期(5 MW-3~10 a)不换料堆芯模型,利用通用蒙卡程序,研究气冷堆中常用可燃毒物核素种类、可燃毒物布置方案对堆芯反应性、寿期等特性的影响。研究结果表明:长寿期堆芯中,整体型Er2O3可以有效控制堆芯剩余反应性,但在寿期末会造成一定的反应性惩罚;整体型B4C可以较好地控制堆芯剩余反应性,并在寿期末几乎不会造成反应性惩罚,通过分区布置还可以优化功率分布;分离型B4C可以使燃耗特性曲线在寿期初和寿期中变化很平坦。短寿期堆芯中,分离型Gd2O3毒物棒可以很好地控制剩余反应性且不会缩短堆芯寿期;常见的B4C布置方式并不合适,但B4C弥散在堆芯石墨内可以起到较好的毒物效果。较长寿期堆芯中,分离型Gd2O3毒物棒不仅可以有效控制剩余反应性,还可以保证堆芯具备仅依靠温度负反馈实现自动停堆的固有安全性。研究结果将为后续气冷微堆型号研发提供指导。     

SERS study on surface chain geometry of atactic poly (methyl methacrylate) film and nanosphere

The surface chain geometry of atactic poly (methyl methacrylate) (a‐PMMA) film and nanosphere (NS) was revealed by surface‐enhanced Raman scattering (SERS) spectra. The Ag nanoparticles and nanoplates were prepared by electrochemical deposition and chemical synthesis for SERS substrates. The experimental results suggested that the molecular chain axis of a‐PMMA film adopted a trans‐conformation on bonding to Ag surface ascribed to the short‐range chemical (CHEM) effect according to the SERS selection rules. However, for the well‐coated monolayer of a‐PMMA NSs, the α‐CH₃ in polymer chains stood vertically to the Ag surface due to the giant local electromagnetic effect, then the chain conformation presented in the interface between a‐PMMA NSs and Ag metal was adopted the opposite orientation compared with a‐PMMA film. The Raman enhancement of the Ag nanoparticles was more prominent than that of the Ag nanoplates due to the free energies of face‐centered cubic crystal faces in nanoparticles, but the single crystals with (111) plane of Ag nanoplates could improve the stability of SERS signals when the annealed temperature was above T_g of a‐PMMA NSs. The present work can provide some useful information of surface chain geometry and conformation of NSs for designing various materials with well‐defined structure via a‐PMMA NSs template. Copyright © 2013 John Wiley & Sons, Ltd.     

Complexity Evaluation of an Environmental Control and Life-Support System Based on Directed and Undirected Structural Entropy Methods

During manned space missions, an environmental control and life-support system (ECLSS) is employed to meet the life-supporting requirements of astronauts. The ECLSS is a type of hierarchical system, with subsystem—component—single machines, forming a complex structure. Therefore, system-level conceptual designing and performance evaluation of the ECLSS must be conducted. This study reports the top-level scheme of ECLSS, including the subsystems of atmosphere revitalization, water management, and waste management. We propose two schemes based on the design criteria of improving closure and reducing power consumption. In this study, we use the structural entropy method (SEM) to calculate the system order degree to quantitatively evaluate the ECLSS complexity at the top level. The complexity of the system evaluated by directed SEM and undirected SEM presents different rules. The results show that the change in the system structure caused by the replacement of some single technologies will not have great impact on the overall system complexity. The top-level scheme design and complexity evaluation presented in this study may provide technical support for the development of ECLSS in future manned spaceflights.     

Solution-Processable Pure-Red Multiple Resonance-induced Thermally Activated Delayed Fluorescence Emitter for Organic Light-Emitting Diode with External Quantum Efficiency over 20 %

Developing solution-processable red organic light-emitting diodes (OLEDs) with high color purity and efficiency based on multiple resonance thermally activated delayed fluorescence (MR-TADF) is a formidable challenge. Herein, by introducing auxiliary electron donor and acceptor moieties into the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) distributed positions of multiple resonance skeleton simultaneously, an effective strategy to obtain red MR-TADF emitters was represented. The proof-of-the-concept molecule BN-R exhibits a narrowband pure-red emission at 624 nm, with a high luminous efficiency of 94 % and a narrow bandwidth of 46 nm. Notably, the fabricated solution-processable pure-red OLED based on BN-R exhibits a state-of-the-art external quantum efficiency over 20 % with the Commission Internationale de I’Éclairage coordinates of (0.663, 0.337) and a long operational lifetime (LT₅₀) of 1088 hours at an initial luminance of 1000 cd m⁻².