Structural,Magnetic and Optical Properties of Rh2☎ Centres in NaCl Lattices: An Explanation

A method for exploring Jahn—Teller systems in the framework of Density Functional Theory is described in the present work. Using such a method the properties of the Rh^2? centre in NaCl with remote charge compensation are studied. The calculations support the existence of a strong Jahn—Teller effect and account reasonably for the main features of EPR and optical spectra. The onset of charge transfer excitations is calculated to be at about 3.7 eV a fact which concurs with available experimental data. The elongated geometry is found to be about 200cm^?1 more stable than the compressed one in agreement with experiments.     

具有模糊需求的闭环供应链网络均衡

利用模糊事件的可信性测度理论、变分不等式理论建立了具有模糊需求的闭环供应链网络均衡模型,其中闭环供应链网络中的制造/再制造工厂存在产能约束,消费市场存在商品限制性价格上限.设计了求解闭环供应链网络均衡解的投影收缩算法,结合数值算例分析了产能约束与限制性价格上限对闭环供应链网络均衡解的影响.结果表明:消费市场中的商品会发生短缺,如果政府对竞争市场实行限制性价格上限,尤其当存在产能约束时商品短缺会更为严重.     

Co-B非晶态合金中电子转移问题的量子化学研究

根据Co -B非晶态结构的短程有序、Co和B之间是较强的化学作用以及化学键理论 ,设计了ComB2 (m=1～ 4)原子簇模型 ,用DFT方法对其进行高水平的量子化学计算 ,结果表明 ,模型体系ComB2 (m =1～ 4)中 ,B原子供给Co原子电子 ,这与非晶态合金的实验结果一致 ,同时存在B -B直接相连 ,为了比较 ,也选择了ConB (n =1～ 4)模型 ,计算结果与实验不符 ,说明ComB2 (m =1～ 4)原子簇模型更能反映非晶态的结构特点 .     

基于GARCH族模型的沪深300股指VaR度量

本文在修正了沪深300股票指数收益率序列的非平稳性和自身相关性之后,把ARMA模型与GARCH模型、GJR模型、IGARCH模型、FIGARCH模型、FIEGARCH模型、FIAPARCH模型、HYGARCH模型相结合,然后依次假设残差分布服从正态分布、t分布和偏t分布,来描述沪深300股票指数日对数收益率序列的尖峰厚尾性、杠杆效应和长记忆特性,利用上述模型分别计算沪深300股票指数的VaR值.在空头和多头投资者情况下,不同的波动性模型和不同残差分布的VaR预测有效性差距很大.比较得知,在不同的置信水平下,沪深300股票指数收益率序列空头和多头的VaR预测成功概率比较高的模型有HYGARCH和FIEGARCH这两类具有长记忆性的模型.     

Identification of nonlinear system using extreme learning machine based Hammerstein model

In this paper, a new method for nonlinear system identification via extreme learning machine neural network based Hammerstein model (ELM-Hammerstein) is proposed. The ELM-Hammerstein model consists of static ELM neural network followed by a linear dynamic subsystem. The identification of nonlinear system is achieved by determining the structure of ELM-Hammerstein model and estimating its parameters. Lipschitz quotient criterion is adopted to determine the structure of ELM-Hammerstein model from input–output data. A generalized ELM algorithm is proposed to estimate the parameters of ELM-Hammerstein model, where the parameters of linear dynamic part and the output weights of ELM neural network are estimated simultaneously. The proposed method can obtain more accurate identification results with less computation complexity. Three simulation examples demonstrate its effectiveness.     

RECURSIVE FORMULA FOR CALCULATING THE CHROMATIC POLYNOMIAL OF A GRAPH BY VERTEX DELETION

A new recursive vertex-deleting formula for the computation of the chromatic polynomial of a graph is obtained in this paper. This algorithm is not only a good tool for further studying chromatic polynomials but also the fastest among all the algorithms for the computation of chromatic polynomials.     

Properties of Ahlfors constant in Ahlfors covering surface theory

This paper is a subsequent work of [Invent. Math., 2013, 191: 197-253]. The second fundamental theorem in Ahlfors covering surface theory is that, for each set E_q of q (≥3) distinct points in the extended complex plane \overline{ℂ}; there is a minimal positive constant H₀ (E_q) (called Ahlfors constant with respect to E_q), such that the inequality(q-2)A(\sum )-4\pi ♯(f^{-1}(E_q)\cap U)\le H_0(E_q)L(\partial \sum )holds for any simply-connected surface{\displaystyle \sum \mathrm{=}（f,\bar{U}）} ; where A(\sum) is the area of\sum; L(\partial \sum) is the perimeter of\sum; and # denotes the cardinality. It is difficult to compute H₀ (E_q) explicitly for general set E_q; and only a few properties of H₀(E_q) are known. The goals of this paper are to prove the continuity and differentiability of H₀ (E_q); to estimate H₀ (E_q); and to discuss the minimum of H₀ (E_q) for fiixed q.     

基于光谱技术的双孢蘑菇新鲜度量化检测技术研究

双孢蘑菇质地柔嫩、营养丰富,具有很好的降血压、降血脂、消炎护肝等多种保健价值,其新鲜度是反映内外部品质的重要指标之一。目前双孢蘑菇新鲜度鉴别大多依据其外观品质变化（褐变）,缺乏精准的量化评价指标与方法,因此提出了以贮藏天数为新鲜度检测的量化指标,并利用近红外光谱技术对双孢蘑菇新鲜度进行检测分析。依据存储天数不同,将双孢蘑菇样本分为1~5组,每组40个样本,依次采集每组双孢蘑菇的近红外光谱数据。针对采集的原始光谱数据,首先选用卷积平滑滤波（SG）与多元散射校正（MSC）消除原始光谱噪声、基线平移以及光散射的影响,并选取399.81~999.81 nm的光谱波段作为数据处理范围;然后分别使用主成分分析（PCA）和连续投影算法（SPA）进行光谱降维和特征波长选择,继而建立极限学习机（ELM）分类模型;同时考虑到ELM模型中初始值对分类准确率影响较大,分别选用粒子群优化算法（PSO）、海鸥优化算法（SOA）对ELM中初始权值及阈值进行寻优,形成PSO-ELM,SOA-ELM优化组合分类模型;最后分别将全光谱、提取主成分以及所选的特征波长｛556.87,445.51,481.15,885.10,802.25,720.90,861.34,909.79,924.44,873.17 nm｝输入到分类模型中,建立不同输入、不同分类模型的双孢菇新鲜度检测模型。最终试验结果表明,当ELM为分类模型,以全光谱、主成分以及特征波长为输入时的预测精度分别为75%,95%,88%;以SPA优选特征波长作为输入的PSO-ELM、SOA-ELM分类模型训练集精度为96.25%,93.25%,预测集精度为92.5%,94%。可知,SPA波长选择算法可以有效降低光谱信息中存在的冗余信息,加快建模效率,同时海鸥优化算法能较好的优化ELM分类模型的初始参数,分类精度较ELM模型提高了6.8%,同时不产生过拟合现象。因此,利用光谱特征可以快速、准确无损的识别双孢蘑菇的新鲜度,研究结果为便携式双孢蘑菇新鲜度快速无损检测设备的开发提供了理论依据。     

EAST快速极紫外光谱仪波长的原位标定及其应用

介绍了东方超环(experimental advanced supereonducting tokamak, EAST)托卡马克上的两套快速极紫外（EUV）光谱仪系统波长的原位标定方法、结果及其应用。这两套谱仪均为掠入射平场谱仪，时间分辨均为5 ms·frame-1。两套谱仪分别工作在20～500和10～130 Å的波段范围，由步进电机控制探测器在焦平面上移动实现整个观测波段上的波长扫描。利用这两套谱仪系统观测极紫外波段光谱，计算EAST中低-高Z杂质离子特征线辐射强度随时间的演化，监测和研究等离子体中杂质的行为。高Z杂质尤其是钨、钼等金属元素，发出的EUV波段光谱的构成非常复杂，准确识谱对谱仪精确的波长测量能力以及谱分辨能力要求很高，因此精确的波长标定是识别钨、钼等高Z杂质谱线以及研究它们行为的最关键的技术之一。利用EAST等离子体中类氢到类铍的低、中Z杂质的特征谱线以及它们的二阶甚至三阶谱线，结合谱仪系统的色散能力，对这两套快速极紫外光谱仪的波长进行了精确的原位标定。用于波长标定的杂质谱线有O Ⅷ 18.97 Å，O Ⅶ 21.60 Å，C Ⅵ 33.73 Å，Li Ⅲ 113.9 Å，Li Ⅲ 135.0 Å，Li Ⅱ 199.28 Å，Ar ⅩⅤ 221.15 Å，He Ⅱ 256.317 Å，He Ⅱ 303.78 Å，Ar ⅩⅥ 353.853 Å及C Ⅳ 384.174 Å等。利用波长标定的结果对观测到的EUV光谱进行谱线识别，两套谱仪观测到的绝大多数谱线波长与美国技术标准局(National Institute of Standards and Technology, NIST)数据库的标准波长相差分别小于0.08和0.03 Å。开发了谱仪波长原位标定程序模块，将这个模块内嵌到谱仪数据实时上传的交互式软件中，实现了全谱数据以及特征谱线强度随时间演化数据的实时处理和上传。同时利用开发的全谱分析交互式软件以及EAST上的数据查看软件，最终实现了快速EUV谱仪自采数据的准实时分析、读取和查看。