Theoretical study of the structural,elastic and thermodynamic properties of chalcopyrite ZnGeP2

The structural, elastic, and thermodynamic properties of ZnGeP₂ with chalcopyrite structure are investigated using the pseudo-potentials plane wave method based on the density functional theory with the generalized gradient approximation. The lattice parameters (a, c and u) are directly calculated and agree well with previous experimental and theoretical results. The obtained negative formation enthalpy shows that ZnGeP₂ crystal has strong structural stability. We have also calculated the bulk modulus B and the elastic parameters (C₁₁, C₁₂, C₁₃, C₃₃, C₄₄, and C₆₆) which have not been measured yet. The accuracy and reliability of the calculated elastic constants of ZnGeP₂ crystal are discussed. In addition, the pressure and temperature dependencies of the lattice parameters, bulk modulus, Debye temperature, Grüneisen parameter, entropy, volume thermal expansion coefficient, and specific heat capacity are obtained in the ranges of 0–20 GPa and 0–1200 K using the quasi-harmonic Debye model. To our knowledge this is the first quantitative theoretical prediction of the thermodynamic properties for ZnGeP₂ compound and still awaits experimental confirmations.     

Coexistence of three ferroelectric phases and enhanced piezoelectric properties in BaTiO3–CaHfO3 lead-free ceramics

Perovskite ferroelectrics possess the fascinating piezoelectric properties near a morphotropic phase boundary, attributing to a low energy barrier that the results in structural instability and easy polarization rotation. In this work, a new lead-free system of (1-x)BaTiO₃-xCaHfO₃ was designed, and characterized by a coexistence of ferroelectric rhombohedral-orthorhombic-tetragonal (R-O-T) phases. With the increase amount of CaHfO₃ (x), a stable coexistence region of three ferroelectric phases (R-O-T) exists at 0.06 ≤ x ≤ 0.08. Both large piezoelectric coefficient (d₃₃～400 pC/N), inverse piezoelectric coefficient (d₃₃^*～547 pm/V) and planar electromechanical coupling factor (k_p～58.2%) can be achieved for the composition with x = 0.08 near the coexistence of three ferroelectric phases. Our results show that the materials with the composition located at a region where the three ferroelectric R-O-T phases coexist would have the lowest energy barrier and thus greatly promote the polarization rotation, resulting in a strong piezoelectric response.     

邻域等价关系诱导的改进ID3决策树算法

经典ID3决策树算法适用于离散型数据分类,但用于连续处理时需要数据离散化容易导致信息损失。提出邻域等价关系从而诱导邻域ID3(NID3)决策树算法,NID3算法改进了ID3决策树算法,能够直接实施连续预测并获取更好的分类效果。在邻域决策系统中,挖掘一种邻域等价关系;基于邻域等价粒化,构建邻域信息度量;基于邻域信息增益,设计NID3决策树算法。实例分析与数据实验均表明,NID3算法具有连续数据分类预测有效性,在分类机器学习中优于ID3算法。     

支持向量机及其在径流预测中的应用

给出了支持向量机方法(SVM)的思路、特点及关键之处,探讨了SVM在径流预测中的可能性,并与基于遗传算法的门限回归模型(TR) 进行了对比分析。径流预测实例分析表明,在拟合阶段,SVM模型要好于TR模型;在预留检验阶段,SVM模型与TR模型接近。同时SVM模型适合于小样本情况且能达到全局最优。SVM模型用于径流预测是可行的、优越的。     

Three schemes of remote information concentration based on ancilla-free phase-covariant telecloning

In this paper, remote information concentration is investigated which is the reverse process of the $1\rightarrow 3$ optimal asymmetric economical phase-covariant telecloning (OAEPCT). The OAEPCT is different from the reverse process of optimal universal telecloning. It is shown that the quantum information via $1\rightarrow 3$ OAEPCT procedure can be remotely concentrated back to a single qubit with a certain probability via several quantum channels. In these schemes, we adopt Bell measurement to measure the joint systems and use projected measurement and positive operator-valued measure to recover the original quantum state. The results shows non-maximally entangled quantum resource can be applied to information concentration.     

Transformation of hardening to softening behaviors induced by Sb substitution in CuO-doped KNN-based piezoceramics

Pb-free piezoceramics of K_0.5Na_0.5Nb_1-xSb_xO₃ + 1 mol% CuO are synthesized via a solid-state reaction. Furthermore, the transformation of hardening to softening behaviors induced by Sb substitution is exhibited and the corresponding microscopic mechanism is proposed. The CuO-doped K_0.5Na_0.5NbO₃ ceramic without adding Sb exhibits extremely hardening characteristics (i.e., ultrahigh Q_m of ∼2426, low tanδ of 0.32%, and pinched ferroelectric hysteresis loop) due to the formation of defect combinations (${({\text{Cu}}_{\text{Nb}}^{\text{'''}}-{\text{V}}_{\text{o}}^{••})}^{\text{'}}$ and ${({\text{V}}_{\text{o}}^{••}-{\text{Cu}}_{\text{Nb}}^{\text{'''}}-{\text{V}}_{\text{o}}^{••})}^{•}$). Whereas, the addition of Sb dramatically reduces the levels of defect combinations, leading to obviously softening properties (d₃₃ > 210 pC N⁻¹, k_p > 40%, low Q_m, and normal single P-E hysteresis loop). Our results indicate that the decrease of defect combinations with Sb addition should be responsible for the hardening-softening transformation of piezoelectricity and ferroelectricity in CuO-doped K_0.5Na_0.5Nb_1-xSb_xO₃ piezoceramics.     

基于知识情感等级BDI主体的决策行为模型研究

为了将知识、信念、愿望和意图以及害怕、焦虑和自信对决策行为的影响的强烈程度进行形式化,把无穷值的卢卡斯维茨逻辑的真值取值范围从[0,1]扩展到[-1,1]。知识情感等级BDI主体的决策行为通过添加了具体条件的不同背景的不同测度来决定;知识情感等级BDI主体模型清晰地表示了主体的知识状态、心智状态和情感状态的不确定性;此模型可以轻易地向其他类型的主体进行推广。在给出了知识情感等级BDI模型的语言、语义以及此模型的不同背景之间的相互关系之后,对知识情感等级BDI主体的军事决策行为进行了实例分析。此研究旨在为分布式人工智能和军事仿真提供形式支持。     

热挤压铋黄铜的显微组织及性能研究

采用工频感应炉熔炼,半连续铸造＋热挤压的方法生产铋黄铜棒,并分析了其显微组织,测定了力学性能和切削加工性.研究结果表明,采用半连续铸造＋热挤压的方法生产出的铋黄铜棒显微组织由α相、β相和少量单质铋相组成,其力学性能和切削加工性能与HPb59-1黄铜相当,完全可以代替HPb59-1黄铜,从而有利于环境保护.     

Decomposition of realizable fuzzy relations

This paper deals with the decomposition problem of realizable fuzzy relations. First, given a realizable fuzzy relation $A$ , a method to construct a fuzzy relation $B$ such that $A=B\odot B^T$ (where $\odot $ is the max–min composition, $B^T$ denotes the transpose of $B$ ) is proposed. Then it is proved that the content of a realizable fuzzy relation is equal to the chromatic number of a simple graph generated by the realizable fuzzy relation. Therefore, many existing algorithms (including exact and heuristic algorithms) developed to find the chromatic number or to get an upper bound on chromatic number of a graph can be applied to solve the calculating problem of the content of a realizable fuzzy relation.     

Global dynamics for non-autonomous reaction-diffusion neural networks with time-varying delays

In this paper, a class of non-autonomous reaction-diffusion neural networks with time-varying delays is considered. Novel methods to study the global dynamical behavior of these systems are proposed. Employing the properties of diffusion operator and the method of delayed inequalities analysis, we investigate global exponential stability, positive invariant sets and global attracting sets of the neural networks under consideration. Furthermore, conditions sufficient for the existence and uniqueness of periodic attractors for periodic neural networks are derived and the existence range of the attractors is estimated. Finally two examples are given to demonstrate the effectiveness of these results.