Laser-jamming analysis of combined fiber lasers to imaging CCD

To complete a successful laser jamming to imaging charge coupled device (CCD) based on combined fiber lasers, the interactions between CCD and combined fiber lasers were analyzed in detail. The saturation and crosstalk thresholds of CCD were achieved, which are lower than 10 mW/cm². Through theoretical analysis and numerical simulations, the thermal processes under single pulse, multi-pulses and continuous laser irradiations were developed. The simulation results have proved the possibility of hard damage caused by multi-pulses and continuous laser irradiations. The combined fiber lasers is suitable to deploy optical saturation jamming at present. The further applications of combined fiber lasers need a more powerful laser source and a more accurate tracking and pointing system.     

Synthesis and swelling behavior of amphiphilic comb‐like branched polymer (AA‐co‐CMS)‐g‐PMMA

Copolymerization of acrylic acid and p‐chloromethylstyrene (p‐CMS) in dioxane initiated with α,α′‐azobisisobutyronitrile was carried out to produce macroinitiator P(AA‐co‐CMS) containing PhCH₂Cl group at 65°C. Then methyl methacrylate was grafted onto P(AA‐co‐CMS) backbone using PhCH₂Cl group as an initiation site and FeCl₂/triphenyl phosphine complex as a catalyst. The resulted copolymer (AA‐co‐CMS)‐g‐PMMA with a comb‐like branched structure has a hydrophilic backbone (PAA) and hydrophobic side chains (PMMA). Compositions and structures of macroinitiator and the grafted product of P(AA‐co‐CMS)‐g‐PMMA were determined by ¹H‐NMR, infrared (IR), and gel permeation chromatography (GPC). The average graft number, the average length of branch chains, the graft ratio, and the graft efficiency were investigated. The swelling behavior of the comb‐like branched polymer was also investigated. The gradual increase of swelling ratios was accompanied by an increase of pH and temperature. The kinetic exponents indicated that the swelling transport mechanisms transformed from Fickian diffusion to non‐Fickian transport as the decreasing pH. Copyright © 2009 John Wiley & Sons, Ltd.     

Pubescone,a Novel 11(7→6)Abeo‐14‐norcarabrane Sesquiterpenoid from Siegesbeckia pubescens

The phytochemical investigation of the aerial parts of Siegesbeckia pubescens L. yielded 16 sesquiterpenoids, including a novel 11(7→6)abeo‐14‐norcarabrane sesquiterpenoid, pubescone ( 1 ), and a new germacrane sesquiterpene, 5 . The molecular structures of the isolated compounds were elucidated on the basis of extensive spectroscopic analysis, including 1D‐ and 2D‐NMR.     

Axially chiral C2-symmetric N-heterocyclic carbene (NHC) palladium complexes-catalyzed asymmetric arylation of aldehydes with arylboronic acids

Chiral C₂-symmetric N-heterocyclic carbene (NHC) palladium diaquo complexes 5a–c and the chiral C₂-symmetric NHC-palladium complexes 5d and 5e prepared from (R)-BINAM or H₈-(R)-BINAM could be used as the catalysts for the enantioselective arylation of arylaldehydes with arylboronic acids in which NHC-Pd complex 5a was found to be fairly effective in this reaction to give the corresponding adducts in moderate enantioselectivities along with moderate to good yields.     

Dicarboxylic imide‐substituted poly(p‐phenylene vinylenes) with high electron affinity

Synthesis of n‐type organic semiconductors with high electron mobilities, good environmental stability, and good processability is an urgent task in current organic electronics. This is because most of π‐conjugated materials are p‐type and prefer to transport positive hole carriers. In this article, a series of new dicarboxylic imide‐substituted poly(p‐phenylene vinylenes) (DI‐PPVs) were first synthesized. They exhibited a high electron affinity of 3.60 eV and thus are able to transport electrons. The polymers showed tunable solubility in common organic solvents and high chemical and thermal stability. They remain rigidity of the PPV backbone, and strong interchain π‐stacking was observed in thin films by X‐ray diffraction measurement. All these suggested that these polymers could serve as good candidates as n‐type semiconductors in organic electronic devices such as n‐channel field‐effect transistors and all polymer‐based solar cells. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 186–194, 2010     

In-site observation of the crystallization of nylon-6 mediated by the interfacial hydrogen bonds

Hydrogen bonds exist in many polymer systems and play a large role in the physical and chemical properties. In this study, nylon-6, which consists of repeated amide groups and contains large number of hydrogen bonds, is chosen as an example. Meanwhile, the oxidized unzipped MWCNTs (μCNTs) with oxygenated species such as carboxyl and hydroxyl groups are used as mediator to regulate the crystallization process of nylon-6 thin films. In-site experimental techniques, including Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, and polarized optical microscopy were utilized to get more direct insights on the crystallization mechanism of nylon-6 and μCNTs systems.     

极限热环境下大功率PCB散热改进研究

通过改进太阳罩结构、改变PCB安装形式、设置隔热等方式,对大功率PCB在大空间极限热环境下的散热方式进行了优化和数值模拟。研究结果表明,根据不同发热电子元件的功率及其在PCB上的安装位置及与PCB的连接形式,采用上述措施,可以显著改善散热效果。