Two-stage γ ray emission via ultrahigh intensity laser pulse interaction with a laser wakefield accelerated electron beam

In this study, we investigate the generation of twin γ ray beams in the collision of an ultrahigh intensity laser pulse with a laser wakefield accelerated electron beam using a particle-in-cell simulation. We consider the composed target of a homogeneous underdense preplasma in front of an ultrathin solid foil. The electrons in the preplasma are trapped and accelerated by the wakefield. When the laser pulse is reflected by the thin solid foil, the wakefield accelerated electrons continue to move forward and pass through the foil almost without influence from the reflected laser pulse or foil. Consequently, two groups of γ ray flashes, with tunable time delay and energy, are generated by the wakefield accelerated electron beam interacting with the reflected laser pulse from the foil as well as another counter-propagating petawatt laser pulse behind the foil. Additionally, we study the dependence of the γ photon emission on the preplasma densities, driving laser polarization, and solid foil.     

漏极散射机制对弹道和非弹道沟道应变硅二极管中电子输运特性的影响

在漏极区域，多重散射对于沟道区域有无散射的应变硅二极管中电子传输性能的影响进行了数值研究。使用应变和散射模型，对于非弹道（有散射）沟道硅二极管的性能与弹道（无散射）沟道的硅二极管的性能进行了比较研究。研究结果表明应变模型中的电子速度和电流的值比无应变模型的相应值更高，弹道沟道模型中的电子速度和电流的值比非弹道沟道模型中的相应值更高。使用应变和散射模型，漏极区域中的每个散射机制对于硅二极管性能的影响进行了分析。对于弹道沟道模型，结果表明谷间光学声子散射会提高器件的性能，而谷内声学声子散射会降低器件的性能。对于应变模型，结果表明较大应变硅能带分裂可以抑制谷间声子散射率。总而言之，为了提高纳米级弹道器件性能，对于漏极区域应变和散射机制模型的研究是很有必要的。     

A novel signal diagnosis technique using pseudo complex-valued autoregressive technique

In this paper, a new method of biomedical signal classification using complex- valued pseudo autoregressive (CAR) modeling approach has been proposed. The CAR coefficients were computed from the synaptic weights and coefficients of a split weight and activation function of a feedforward multilayer complex valued neural network. The performance of the proposed technique has been evaluated using PIMA Indian diabetes dataset with different complex-valued data normalization techniques and four different values of learning rate. An accuracy value of 81.28% has been obtained using this proposed technique.     

Magnetic M–H loops family characteristics in the microstructure evolution of BaFe12O19

A polycrystalline magnetic materials series produced from the same batch of high-reactivity powder by multi-sample sintering in a range of increasing temperatures can supposedly reveal its property and microstructural evolution through magnetic property measurement and clear morphological changes. Hence, in our work, we attempt to find out the variation of magnetic properties of BaFe₁₂O₁₉ against its evolving microstructure. Hexagonal BaFe₁₂O₁₉ nanometer-sized powder with the M-type structure was synthesized by the mechanical alloying method. The crystal structure, grain size and magnetic properties were studied by means of XRD, field emission scanning electron microscopy and a vibrating sample magnetometer. The ferrite materials were obtained from a mixture of barium carbonate and iron oxide by mixing them using conventional ball milling (12 h) and then assisted by high energy ball milling for 6 h. The comminuted powder was divided into several batches, moulded in pellet shape and sintered at different temperatures ranging from 400 to 1400 °C for a constant sintering time of 10 h in a static air atmosphere. Effects of sintering temperature on the formation, crystallite size, morphology and magnetic properties were systematically studied. In the sintering temperature range from 800 to 1200 °C, the coercivity (Hc) gradually increased due to the effect of rapid grain growth. This is because the fine starting powder was so reactive that rapid grain growth easily occurred. In the grains, strong interaction of magnetic moments within domains due to exchange forces led to strong anisotropy. It was also observed that three M–H-loop groups each belonging to a particular range of grain sizes exhibited different strengths of magnetism. It is believe of similar results have never been reported before and should be useful to the permanent-magnet industry.     

Unsteady MHD mixed convection flow of a micropolar fluid along an inclined stretching plate

In this research, the unsteady magnetohydrodynamic mixed convection flow of a micropolar fluid over an inclined plate has been investigated. The problem is reduced to a system of non‐dimensional partial differential equations, which are solved numerically using the implicit finite‐difference scheme. Velocity profiles, temperature profiles, concentration profiles, the skin friction coefficient, the rate of heat transfer, and the rate of mass transfer are computed numerically for various values of different physical parameters. In this study, we consider both assisting and opposing flow. It is found that in the assisting flow case, a solution could be obtained for all positive values of the buoyancy parameter λ, while in the opposing flow case the solution terminated at $\lambda = {\lambda _c}(\lambda < 0)$ . © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21034     

丁基磺酸纤维素醚减水剂的合成及应用

纤维素棉桨粕经酸水解得到具有确定聚合度的微晶纤维素(MCC)后,以其为原料,在氢氧化钠活化下,与1,4-丁烷磺内酯(BS)反应.得到了具有良好水溶性的丁基磺酸纤维素醚(SBC)减水剂.采用红外光谱(FTIR)、核磁共振谱、扫描电镜(SEM)、X-衍射(XPD)等分析手段对产品结构进行了表征,考察了MCC聚合度、原料配合...     

磺化纤维素开发用作新型减水剂及其分散机理研究

以纤维素棉桨粕为基材,氯磺酸为磺酸试剂,二氯甲烷为分散剂,一步法合成了磺化纤维素(SC).采用红外光谱(FTIR)、核磁共振碳谱(<'13>CNMR)、扫描电镜(SEM)、X-衍射(XRD)等分析手段对产品结构进行了表征,并考察了纤维素聚合度、原料配合比、反应温度、反应时间等合成工艺参数对CS减水剂分散性能的影响.从C...     

丁基磺酸纤维素醚减水剂的合成及表征

以纤维素棉桨粕经酸水解得到具有确定聚合度的微晶纤维素(MCC)为原料,在氢氧化钠活化下,与1,4-丁烷磺内酯(BS)反应,得到了具有良好水溶性的丁基磺酸纤维素醚(SBC)减水剂.采用红外光谱(FT-IR)、核磁共振谱(NMR)、扫描电镜(SEM)、X射线衍射(XRD)等分析方法对产品结构进行了表征,并考察了MCC聚合度、原料配比、反应温度、反应时间、悬浮剂种类等合成工艺条件对产品减水性能的影响.结果表明:当原料MCC聚合度为45,反应物物质的量比为:AGU(纤维素葡萄糖苷单元):n(NaOH):n(BS)=1.0:2.1:2.2,悬浮剂为异丙醇,原料室温活化时间为2h,产物合成时间为5h,温度为80℃时,所得产品丁磺酸基取代度最高,产品减水性能最优.