石墨烯纳米带电极区N掺杂电子输运性质研究

运用密度泛函理论和非平衡格林函数结合的方法,研究电极区N掺杂对扶手椅型石墨烯纳米带电子输运特性的影响.结果表明,与本征扶手椅型石墨烯纳米带电流-电压曲线相比,宽度为7的石墨烯纳米带电流-电压曲线表现出明显的不对称性,其中心N掺杂表现强烈的整流特性,整流系数达到102数量级,且将N原子从电极区中心位置移动到边缘,整流特性减弱.研究结果表明宽度为7的扶手椅型石墨烯纳米带出现强整流现象的原因主要是负向偏压下能量窗内没有透射峰引起的,该研究结果对将来石墨烯整流器件的设计具有重要的意义.     

空间调制型全Stokes参量偏振成像系统原理及仿真

空间调制型全Stokes参量偏振成像是针对同一目标不同偏振分量的同时探测技术,以双折射晶体作为调制元件,将Stokes参量S0~S3调制在同一幅图像中,只一次采集便可获得包含4个Stokes参量的调制信息。分析空间调制型全Stokes偏振成像系统的探测原理和数学模型。阐明重构偏振图像S0~S3的理论依据,并分析了系统参数的选择对图像重构效果的影响。根据实际系统参数,进行数值仿真模拟成像过程,获取调制图像,使用一种简单的频域解调算法,重构出S0~S3的4幅偏振图像,得到比较满意的重构效果,不仅验证了方案的可行性,同时为仪器设计或器件选型提供参考。     

A Maximal Correlation Framework for Fair Machine Learning

As machine learning algorithms grow in popularity and diversify to many industries, ethical and legal concerns regarding their fairness have become increasingly relevant. We explore the problem of algorithmic fairness, taking an information–theoretic view. The maximal correlation framework is introduced for expressing fairness constraints and is shown to be capable of being used to derive regularizers that enforce independence and separation-based fairness criteria, which admit optimization algorithms for both discrete and continuous variables that are more computationally efficient than existing algorithms. We show that these algorithms provide smooth performance–fairness tradeoff curves and perform competitively with state-of-the-art methods on both discrete datasets (COMPAS, Adult) and continuous datasets (Communities and Crimes).     

100～500 GPa 4.2Ni2.45Fe0.35CoW合金的冲击压缩性和物态方程

 用二级轻气炮驱动飞片技术及对称碰撞技术，测量了两相合金4.2Ni2.45Fe0.35CoW（以下简称93W）的雨贡纽线。其压力范围为100~500 GPa。实测的冲击波速度D和粒子速度u可用直线关系式D=4.008+1.277u (km/s)描述。实验结果与用混合物雨贡纽线叠加原理的计算结果符合甚好。文中还给出了由实验数据计算得到的物态方程数据。     

Generalized composition operators from F(p, q, s) spaces to Bloch-type spaces

Let H(B) denote the space of all holomorphic functions on the unit ball B of Cⁿ. Let φ be a holomorphic self-map of B and g ∈ H(B) such that g(0) = 0. In this paper, we investigate the boundedness and compactness of the generalized composition operator

     

Ionization of hydrogen and deuterium atoms in thermal energy collisions with state-selected Ne(3s 3 P 2,3 P 0) metastable atoms

High resolution energy spectra of electrons and ions resulting from thermal energy collisions of hydrogen and deuterium atoms with state-selected metastable Ne(Ne(3s ³ P ₂,³ P ₀) atoms are reported. The electron spectra for Ne(³ P ₂)+H(D) are very broad: The high energy part due to formation of NeH⁺ (NeD⁺) bound states (associative ionization), amounts to about 30% of the ionizing events, whereas the dominant part of the spectrum including a prominent low-energy peak is due to Penning ionization out of a strongly-attractive entrance potential curve. Comparison of the spectra with quantum mechanical fit calculations yields fairly accurate information on this potential, in particular its well depthD _e [Ne(³ P ₂)?H,D]= 2.0(1) eV. The spectra for Ne(³ P ₀)+H, D are comparatively narrow with much lower cross sections than the one for the Ne(³ P ₂) state. The corresponding entrance channel is a weakly bound van der Waals molecule with a well depth below 0.1 eV. A perturbation calculation of the Ne(3s)+H(1s) potential energy curves at large distances explains the observed difference between the Ne(³ P ₂)+H(D) and Ne(³ P ₀)+H(D) systems. Symmetry arguments are given that the major contribution to the Ne(³ P ₂)+H(D) spectra is due to the² Σ potential.     

Current-induced colossal electroresistance in La0.8Ba0.2MnO3 films fabricated by sol–gel method

Transport properties of La_0.8Ba_0.2MnO₃ thin films deposited by the sol–gel method were investigated. It has been found that resistivity plateaus occurred in the ρ–T curves after application of a dc bias current over a critical value. A current of 200 μA could induce a huge resistance variation ∼1200% in these La_0.8Ba_0.2MnO₃ films near room temperature, demonstrating a colossal electroresistance effect. Such strange transport behavior suggests the formation of conductive filaments and that the multi-phase coexistence is sensitive to external stimuli. This phenomenon may find applications in sensing and logic devices.     

XPS and ionic conductivity studies on Li1.3Al0.15Y0.15Ti1.7(PO4)3 ceramics

Li_1.3Al_0.15Y_0.15Ti_1.7(PO₄)₃ compound was synthesized by solid-state reaction, and ceramics were sintered. The surfaces of the ceramics were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. Li_1.3Al_0.15Y_0.15Ti_1.7(PO₄)₃ samples were tested in solid galvanic cells Ag|O₂+CO₂|Li₂CO₃|Li_1.3Al_0.15Y_0.15Ti_1.7(PO₄)₃|LiMnO₂+Mn₂O₃|O₂|Ag. The electromotive force measurements of this cell indicated that investigated samples are practically pure Li-ion conductors. Impedance spectroscopy studies have been performed in the frequency range 10^?2–3·10⁹ Hz and temperatures from ?57 °C to 334 °C. Three dispersion regions related to Li⁺ ionic transport in bulk, grain boundaries of the ceramics and to polarization of electrodes have been found. Total conductivity changes according to Arrhenius law in the studied temperature range, but an anomalous behavior was observed for the bulk conductivity of the ceramics.     

基于频域相位共轭技术的交叉相位调制所致失真的复原

理论分析和讨论了基于频域相位共轭技术的交叉相位调制所致信号失真的复原和补偿机理，数值模拟了在交叉相位调制作用下，高斯脉冲在中距相位共轭光纤系统中的传输演化过程.结果表明，频域相位共轭技术能够抑制交叉相位调制对光纤系统中传输信号的损害，复原其所导致的信号失真，并能够同步补偿群速度色散和自相位调制非线性效应所导致的信号失真.合适的初始脉冲时延和初始脉冲啁啾有利于频域相位共轭技术对交叉相位调制所致信号失真的抑制. 关键词： 频域相位共轭 交叉相位调制 色散 自相位调制     

{Well-posedness of degenerate differential equations with infinite delay in Holder continuous function spaces

Using operator-valued $\dot{C}^\alpha$-Fourier multiplier results on vector- valued H\"older continuous function spaces, we give a characterization for the $C^\alpha$-well-posedness of the first order degenerate differential equations with infinite delay $(Mu)"(t) = Au(t) + \int_{-\infty}^t a(t-s)Au(s)ds + f(t)$ ($t\in\R$), where $A, M$ are closed operators on a Banach space $X$ such that $D(A)\cap D(M)\neq \{0\}$, $a\in L^1_{\rm{loc}}(\R_+)\cap L^1(\mathbb{R}_+; t^\alpha dt)$.