Spatial-dependent probe transmission based high-precision two-dimensional atomic localization

Herein, we propose a scheme for the realization of two-dimensional atomic localization in aλ-type three-level atomic medium such that the atom interacts with the two orthogonal standing-wave fields and a probe field. Because of the spatially dependent atom-field interaction, the information about the position of the atom can be obtained by monitoring the probe transmission spectra of the weak probe field for the first time. A single and double sharp localized peaks are observed in the one-wavelength domain. We have theoretically archived high-resolution and high-precision atomic localization within a region smaller thanλ/25×λ/25. The results may have potential applications in the field of nano-lithography and advance laser cooling technology.     

Controlled Oligomerization of Lewis Acid/Base‐Stabilized Phosphanylalanes

PAls should stick together : The cyclo‐trimer 2 is obtained by H₂ elimination of Lewis acid/base‐stabilized parent compound of the phosphanylalanes 1 . The elimination is controlled by fine tuning the temperature and solvent conditions. A subsequent H₂ elimination produces the ladder compound 3 . Compounds 2 and 3 are the first of a new class of Group 13/15 compounds which show no additionally donor–acceptor bonds within the framework.

     

声发射特性与材料断裂韧性相关性研究

以高强度铝合金的断裂过程为研究对象，利用先进的声发射试验系统，考察了拉伸试样和带有预制疲劳裂纹的DCB试样在断裂时的声发射事件特性，揭示了材料断裂韧性和声发射特性 间的关系.试验结果表明，材料稳态裂纹扩展起始于K_1C并发射出许多幅值超过 阈值35 dB的信号，材料裂纹失稳扩展时爆发出强烈的声发射信号，材料断裂的累积声发射能与宏 观断裂能呈线性关系. 关键词： 声发射 断裂韧性 铝合金     

Aluminum hypophosphite in combination with expandable graphite as a novel flame retardant system for rigid polyurethane foams

The main aim of this work was to investigate the synergistic effect of expandable graphite (EG) and aluminum hypophosphite (AHP) on the flame retardancy of rigid polyurethane foams (RPUFs). A series of flame retardant RPUF containing EG and AHP were prepared by one‐shot and free‐rise method. The flame retardant, thermal degradation, and combustion properties of RPUF hybrids were characterized through limiting oxygen index (LOI) test, vertical burning (UL‐94) test, thermogravimetric analysis and microscale combustion calorimeter. The LOI and UL‐94 results showed that the RPUF sample with 10 wt% EG and 5 wt% AHP passed UL‐94 V‐0 rating and reached a relatively high LOI value of 28.5%, which is superior over other EG/AHP ratios in RPUF at the equivalent filler loading. Microscale combustion calorimeter results revealed that the incorporation of EG and AHP into RPUF reduced the peak heat release rate and total heat release, thus decrease the fire risk of RPUF significantly. Incorporation of EG and AHP improved the thermal stability of RPUF as observed from the thermogravimetric analysis results and also enhanced the thermal resistance of char layer at high temperature from scanning electron microscopy and Raman spectroscopy. Moreover, it could be seen from thermogravimetric analysis/infrared spectrometry spectra that the addition of EG and AHP significantly decreased the combustible gaseous products such as hydrocarbons and ethers. Finally, the synergistic mechanism in flame retardancy was discussed and speculated. Copyright © 2014 John Wiley & Sons, Ltd.     

5-（烯丙氧）甲基-8-羟基喹啉铝配合物的合成和性能研究

以8-羟基喹啉为原料,合成了5-（烯丙氧）甲基-8-羟基喹啉配体及其铝配合物,并通过红外光谱对配体和配合物进行了表征,通过荧光光谱研究了配合物的光致发光性能。     

含8-羟基喹啉侧基聚酯及其锌和铝配合物的合成与荧光性质

经多步反应合成3种含8-羟基喹啉侧基聚酯(P7~P9),进一步与无水醋酸锌和六水氯化铝反应,得到6种聚酯锌、铝配合物(P7-Zn~P9-Zn,P7-Al~P9-Al)。 采用元素分析、红外光谱、紫外可见光谱、核磁共振氢谱、凝胶渗透色谱、热重分析仪、差示扫描量热和荧光光谱等技术手段对其结构和性能进行表征。 P7~P9易溶于N,N-二甲基甲酰胺(DMF)、N,N-二甲基乙酰胺(DMAC)、二甲基亚砜(DMSO)和N-甲基吡咯烷酮(NMP),P7-Zn~P9-Zn和P7-Al~P9-Al部分溶于DMF、DMAC、DMSO和NMP。 P7~P9的质均相对分子质量(M_w)为1.79×10⁴、2.14×10⁴和2.52×10⁴ g/mol,相对分子质量分布指数PDI为1.54、1.64和1.72。 P7~P9的5%失重温度分别为291.6、291.3和284.9 ℃,P7-Zn~P9-Zn、P7-Al~P9-Al的5%失重温度分别为348.7、339.2、334.6、316.1、316.7和316.0 ℃。 P7~P9的玻璃化转变温度(T_g)分别为121.8、106.2和86.4 ℃,聚酯锌、铝配合物的T_g均高于180 ℃。 P7~P9的DMF溶液(5×10^-5 mol/L)在413~418 nm处发紫色荧光,P7-Zn~P9-Zn、P7-Al~P9-Al的DMF溶液(5×10^-5 mol/L)分别在509~513和485~487 nm处发强绿色荧光,固体分别在516~519和492~497 nm处发强绿色荧光。 P7~P9、P7-Zn~P9-Zn和P7-Al~P9-Al的荧光量子产率分别为5.5%~8.4%、21%~28%和23%~29%。     

Induced Super‐Halogen Behavior of Metal Moieties in Halogen‐Doped Clusters: LinI(‐) and AlnI(‐), n = 13, 1, 2, 3.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

Natural convection of non-Newtonian power-law fluid over axisymmetric and two-dimensional bodies of arbitrary shape in fluid-saturated porous media

Numerical analysis of the free convection coupled heat and mass transfer is presented for non-Newtonian power-law fluids with the yield stress flowing over a two-dimensional or axisymmetric body of an arbitrary shape in a fluid-saturated porous medium. The governing boundary layer equations and boundary conditions are cast into a dimensionless form by the similarity transformation. The resulting system of equations is solved by a finite difference method. The parameters studied are the rheological constants, the buoyancy ratio, and the Lewis number. Representative velocity, temperature, and concentration profiles are presented and discussed. It is found that the results depend strongly on the values of the yield stress parameter and the power-law index of the non-Newtonian fluid.     

Selective Dimerization of Lewis‐Acid/Base‐Stabilized Phosphanylalanes

The reaction of [{(CO)₅W}PRH₂] (R=H, Ph) with H₃Al ? NR₃ (R=Et, Me) leads to the formation of four‐membered heterocyclic compounds [({(CO)₅W}P(H)AlH ? NEt₃)₂] and [({(CO)₅W}PhPAlH ? NMe₃)₂]. Upon dissolving the solid compounds, fast equilibria between the isomers are observed on the NMR timescale. Further insight into the stability and reactivity of the isomers was gained by applying theoretical methods. DFT calculations predict that hydrogen elimination in the case of [({(CO)₅W}PhPAlH ? NMe₃)₂] may be reversible.     

面层混凝土对跑道内爆毁伤影响的仿真研究

 采用考虑混凝土拉伸破坏的TCK失效模型,运用AUTODYN软件对跑道内爆毁伤进行了数值模拟。研究了炸点置于面层混凝土底部时,不同装药量和不同面层混凝土厚度对爆破漏斗坑参数的影响规律。结果表明：数值模拟结果较好地反映了混凝土因拉伸损伤引起的破裂和抛掷漏斗现象。基于数值模拟得到的漏斗坑参数值,建立了漏斗坑半径、空腔半径与面层厚度的无量纲表达式,计算得到的漏斗坑参数值得到了实验验证。