电子俘获材料的红外最小可激发阈值

A study is made of the steady-state populations of a three-level ladder atom in a squeezed vacuum, driven by a superposition of a monochromatic laser wave with incoherent population pumping. Using the density matrix equations for the system, the steady-state populations are calculated numerically and shown graphically as functions of two-photon detuning for various cases of the squeezed vacuum and different incoherent pump rates. It is shown that the incoherent population pumping tends to greatly decrease the two-photon absorption from the squeezed vacuum.     

Population Risk Improvement with Model Compression: An Information-Theoretic Approach

It has been reported in many recent works on deep model compression that the population risk of a compressed model can be even better than that of the original model. In this paper, an information-theoretic explanation for this population risk improvement phenomenon is provided by jointly studying the decrease in the generalization error and the increase in the empirical risk that results from model compression. It is first shown that model compression reduces an information-theoretic bound on the generalization error, which suggests that model compression can be interpreted as a regularization technique to avoid overfitting. The increase in empirical risk caused by model compression is then characterized using rate distortion theory. These results imply that the overall population risk could be improved by model compression if the decrease in generalization error exceeds the increase in empirical risk. A linear regression example is presented to demonstrate that such a decrease in population risk due to model compression is indeed possible. Our theoretical results further suggest a way to improve a widely used model compression algorithm, i.e., Hessian-weighted K-means clustering, by regularizing the distance between the clustering centers. Experiments with neural networks are provided to validate our theoretical assertions.     

Comparison Study of Mixing Effect on Batch Cooling Crystallization of 3‐Nitro‐1,2,4‐triazol‐5‐one (NTO) Using Mechanical Stirrer and Ultrasound Irradiation

The insensitive explosive 3‐Nitro‐1,2,4‐triazol‐5‐one (NTO) has been recrystallized from water in an effort to prepare crystals with smaller size and narrower distribution in a batch cooling crystallizer. Two mixing devices, i.e., a mechanically stirred system with and without ultrasound in aqueous media were employed to compare the mixing effect on the crystallization. Under ultrasound irradiation, the metastable zone width was significantly reduced by more than 2 fold and the crystal size was shifted from 140∼160 μm to 50∼70 μm with a narrower CSD compared to the mechanically stirred system. However in the mechanical stirrer, the mixing effect on NTO crystallization was negligible if the impeller speed was sufficient to suspend all crystals in the crystallizer. It was found that the crystal growth was not influenced by mixing. We suggest that the NTO crystals were formed by primary heterogeneous nucleation that is common in batch cooling system. Finally, the population balance model (PBM), with the empirical nucleation and growth kinetic expressions, was solved numerically to predict the crystal size and the CSD with batch time, and the results were in good agreement with the experimental data.     

双活动星系核寄主星系的光谱合成分析

星系并合会产生不同尺度距离的星系对甚至双活动星系核,同时在过程中会触发星暴以及超大质量黑洞的活动。在光谱上,当两个星系并合到kpc尺度时,其两个核的相互绕转在总光谱上会表现出窄线双峰谱线轮廓。以这个观测特性为起点,从郭守敬望远镜巡天的第四次释放数据(LAMOST DR4)中系统的搜寻带有窄发射线双峰特征的双AGN候选体。AGN的发射线光谱轮廓由发射线的若干种不同的动力学成分构成,主要可以分为三类,窄线成分(Hβ,[OⅢ], Hαand [NⅡ]),[OⅢ]的线翼、以及宽的Balmer发射线。基于LAMOST DR4河外光谱数据,应用了一套搜寻流程,在初始筛选(涉及到发射线的信噪比、等值宽度和红移)及目视检查挑选之后,通过建立的多高斯拟合模型挑选出在发射线的流量、半高全宽、窄线双峰之间速度分离程度等一系列参数上符合我们限制要求的样本,并借助于Baldwin-Phillips-Terlevich (BPT)图来鉴别每个成分的来源,确定出了28个双AGN候选体。为了获取更准确的星族成分并发现这类双AGN候选体样本的共有特性,对28个双AGN候选体的光谱流量用一个低阶多项式重新进行了修正并采用传统的统一插值和中值方法对其进行合并得到一条高信噪比光谱,并以目前已有的来源于LAMOST星系光谱数据的Ⅱ型AGN(单AGN)的复合光谱作为对照样本,采用STARLIGHT软件分别拟合了合并的双AGN和对照的单AGN的光学光谱中的吸收线和连续谱。通过研究它们的星族特性及两者间的异同,发现与单AGN复合谱相比,双AGN候选体样本的合并谱具有更多中等年龄及老年星族的贡献,反映出更剧烈的中心黑洞。在金属丰度方面,单AGN的主导星族为太阳金属丰度的星族Z_⊙,而双AGN候选体合并谱中贡献较多的星族为亚太阳金属丰度星族0.2 Z_⊙和富金属丰度星族2.5 Z_⊙,表现出了差异性特征,也预示着这类样本中恒星形成历史更加复杂,呈现出了多样化。在幂律谱成分贡献方面在单、双AGN中老年星族都贡献了其大部分质量,但单AGN复合谱中幂律成分占比为8.2%,明显高于双AGN候选体合并谱中幂律成分的贡献。     

多个偏正态总体共同位置参数的Bootstrap置信区间

该文基于Bootstrap 方法研究多个偏正态总体共同位置参数的区间估计和假设检验问题.首先,分别给出未知参数的矩估计和极大似然估计.其次,将徐礼文[1]对多个正态总体共同均值的探讨推广到多个偏正态总体,进而构造共同位置参数的Bootstrap 置信区间和Bootstrap检验统计量.Monte Carlo模拟结果表明...     

掺铒玻璃波导放大器中抽运光信号光重叠因子分析

通过分析掺铒(Er3 )玻璃波导放大器(EDWA)的放大增益机理,提出抽运光与信号光光模场分布之间的归一化重叠积分因子(Γ),并引入到掺铒波导放大器增益模拟计算中,使理论模型更切合实际。以Ag -Na 二次离子交换工艺制作的具有埋入型渐变折射率分布的掺铒波导放大器为例,采用数值方法模拟了条形波导截面上的二维折射率分布及抽运光、信号光的光模场分布。计算了不同工艺参量设置下的Γ大小,讨论Γ对放大器增益的影响。结果显示,在二次离子交换制作过程中设置适当工艺参量优化折射率分布,能有效改善波导中抽运光与信号光光模场分布之间的重叠因子,提高掺铒波导放大器的增益。计算结果显示,在一定条件下,Γ从0.5增至0.8,每厘米长度掺铒波导放大器的放大增益可提高近1.5 dB。     

Molecular electronegativity in density functional theory(Ⅷ)——Charge polarization modes in a closed system

Based on the density functional theory and the atom-bond electronegativity equalization model (ABEEM), a method is proposed to construct the softness matrix and to obtain the electron population normal modes (PNMs) for a closed system. Using this method the information about the bond charge polarization in a molecule can be obtained easily. The test calculation shows that the PNM obtained by this method includes all the modes about the bond charge polarization explicitly. And the bond charge polarization mode characterized by the biggest eigenvalue, which is the softest one of all modes related with chemical bonds, can describe the charge polarization process in a molecule as exquisitely as the corresponding ab initio method.     

The survival analysis for gallopin' s system in a polluted environment

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｐｅｒｓｉｓｔｅｎｃｅｐｒｏｂｌｅｍｏｆａＬｏｇｉｓｔｉｃｐｏｐｕｌａｔｉｏｎｉｎａｐｏｌｌｕｔｅｄｅｎｖｉｒｏｎｍｅｎｔｗａｓｓｔｕｄｉｅｄｉｎｐａｐｅｒ [1 ] .Ｂｕｔｏｎｌｙｏｎｅｓｐｅｃｉｅｓｗａｓｕｎｄｅｒｔｈｅｃｏｎｓｉｄｅｒａｔｉｏｎｉｎｔｈｅｐａｐｅｒ.Ｉｎｆａｃｔ,ａｎｙｐｏｐｕｌａｔｉｏｎｉｎａｃｔｕａｌｂｉｏｌｏｇｉｃａｌｓｉｔｕａｔｉｏｎｓｍｕｓｔｂｅｌｉｖｉｎｇｏｎｏｔｈｅｒｐｏｐｕｌａｔｉｏｎｓ .ＡｓｉｍｐｌｅＧａｌｌｏｐｉｎ’ｓｒｅｓｏｕｒ…     

草酰胺衍生物桥联双核镍配合物从头算研究

采用LanL2DZ基组 ,对N,N′ 双(2 苯甲酸根)草酰胺桥联双核镍配合物Ni(obbz)Ni(H2O)4 进行从头计算研究 ,探讨该配合物单、三重态的电子组态的稳定性、电子结构特征及电子自旋布居规律等。计算结果表明 ,该配合物分子的三重态比单重态稳定 ,因此 ,该配合物择型于三重态的电子组态。电子自旋主要布居于八面体环境的Ni(1)中心上 ,而处于四方配位环境的Ni(2)中心则没有发现电子自旋布居。同时 ,Ni(2)中心主要参与的分子轨道都处于低能区 ,表明Ni(2)中心的配位是相当稳定的 ,这与实验规律相符。     

Reynolds Number Dependence of Energy Spectra in the Overlap Region of Isotropic Turbulence

A Near-Asymptotics analysis of the turbulence energy spectrum is presented that accounts for the effects of finite Reynolds number recently reported by Mydlarski and Warhaft [21]. From dimensional and physical considerations (following Kolmogorov and von Karman), proper scalings are defined for both low and high wavenumbers, but with functions describing the entire range of the spectrum. The scaling for low wavenumbers uses the kinetic energy and the integral scale, L, based on the integral of the correlation function. The fact that the two scaled profiles describe the entire spectrum for finite values of Reynolds number, but reduce to different profiles in the limit, is used to determine their functional forms in the “overlap” region that both retain in the limit. The spectra in the overlap follow a power law, E(k) =Ck _{−5/3 + μ}, where μ and C are Reynolds number dependent. In the limit of infinite Reynolds number, μ → 0 and C → constant, so the Kolmogorov/Obukhov theory is recovered in the limit. Explicit expressions for μ and the other parameters are obtained, and these are compared to the Mydlarski/Warhaft data. To get a better estimate of the exponent from the experimental data, existing models for low and high wavenumbers are modified to account for the Reynolds number dependence. They are then used to build a spectral model covering all the range of wavenumbers at every Reynolds number. Experimental data from grid-generated turbulence are examined and found to be in good agreement with the theory and the model. Finally, from the theory and data, an explicit form for the Reynolds number dependence of φ = ɛL/u ₃ is obtained. This revised version was published online in July 2006 with corrections to the Cover Date.