Strong Pauli paramagnetic effect in the upper critical field of KCa2Fe4As4F2

Recently, 12442 system of Fe-based superconductors has attracted considerable attention owing to its unique double-Fe As-layer structure. A steep increase in the in-plane upper critical field with cooling has been observed near the superconducting transition temperature, Tc, in KCa2Fe4As4F2 single crystals. Herein, we report a high-field investigation on upper critical field of this material over a wide temperature range, and both out-of-plane(H∥c, Hc2c) and in-plane(H∥ab, Hc2ab ) directions have been measured.A sublinear temperature-dependent behavior is observed for the out-of-plane Hc2c , whereas strong convex curvature with cooling is observed for the in-plane Hc2ab . Such behaviors could not be described by the conventional Werthamer-Helfand-Hohenberg(WHH) model. The data analysis based on the WHH model by considering the spin aspects reveals a large Maki parameter α=9,indicating that the in-plane upper critical field is affected by a very strong Pauli paramagnetic effect.     

Route to hyperchaos and chimera states in a network of modified Hindmarsh-Rose neuron model with electromagnetic flux and external excitation

Analyzing the chaos and bursting phenomenon of neurons has been of interest in the past decade. In this paper, we discuss an extended Hindmarsh-Rose neuron model by taking into consideration the slowly interacting cell phenomenon due to the calcium ions. In the extended model, we consider the effect of an external forcing current, and the electromagnetic coupling between the magnetic flux and the membrane potential of the neuron. We analyze the modified neuron model in the presence of periodic and quasi-periodic excitations. A more complex chaotic behavior (hyperchaos) is identified in the neuron model. The results also demonstrate the multistable nature, which was not explored earlier. To discuss the dynamical behavior of the modified neuron in a network, we construct a ring network of neurons and capture the spatiotemporal patterns of the neuron in the network, in the presence of different excitations.

     

Investigation of the Solution Status of TGS and ATGSP Crystals

This paper reports on the solubility curves of TGS and ATGSP crystals with different pH's. The relationship of (010) growth rate in solutions with different pH varied with the supersaturation, has been studied. The influence of pH on the metastable region of solution have been measured. The experimential results are discussed with respect to the structure and viscosity of solution and the solubility of the crystals. Finally the optimum conditions for the rapid growth of TGS and ATGSP crystals is given.     

Visual Recognition of Traffic Signs in Natural Scenes Based on Improved RetinaNet

Aiming at recognizing small proportion, blurred and complex traffic sign in natural scenes, a traffic sign detection method based on RetinaNet-NeXt is proposed. First, to ensure the quality of dataset, the data were cleaned and enhanced to denoise. Secondly, a novel backbone network ResNeXt was employed to improve the detection accuracy and effection of RetinaNet. Finally, transfer learning and group normalization were adopted to accelerate our network training. Experimental results show that the precision, recall and mAP of our method, compared with the original RetinaNet, are improved by 9.08%, 9.09% and 7.32%, respectively. Our method can be effectively applied to traffic sign detection.     

Multi-Objective Optimization of Braun-Type Exothermic Reactor for Ammonia Synthesis

The exothermic reactor for ammonia synthesis is a primary device determining the performance of the energy storage system. The Braun-type ammonia synthesis reactor is used as the exothermic reactor to improve the heat release rate. Due to the entirely different usage scenarios and design objectives, its parameters need to be redesigned and optimized. Based on finite-time thermodynamics, a one-dimensional model is established to analyze the effects of inlet gas molar flow rate, hydrogen–nitrogen ratio, reactor length and inlet temperature on the total entropy generation rate and the total exothermic rate of the reactor. It’s found that the total exothermic rate mainly depends on the inlet molar flow rate. Furthermore, considering the minimum total entropy generation rate and maximum total exothermic rate, the NSGA-II algorithm is applied to optimize seven reactor parameters including the inlet molar flow rate, lengths and temperatures of the three reactors. Lastly, the optimized reactor is obtained from the Pareto front using three fuzzy decision methods and deviation index. Compared with the reference reactor, the total exothermic rate of the optimized reactor is improved by 12.6% while the total entropy generation rate is reduced by 3.4%. The results in this paper can provide some guidance for the optimal design and application of exothermic reactors in practical engineering.     

A Mechanism of High-Tc Superconductivity Relating to Perovskite Crystal Structure

A mechanism of high-T_c superconductivity related to the perovskite crystal structure is proposed by a “phonon attenuation model”, which means that in the perovskite-like crystal structure, a number of “ordering” vacancies or holes occur due to the non-stoichiometric structure features. Such a reticular “spongly-like” structure facilitates lattice thermovibration attenuation perovskite (phonon attenuation) during temperature reduction. This leads to an abrupt drop of the resistivity, owing to the conduction electrons transmitted through the media without collision with irregularities in the lattice due to the lattice thermovibration. This probably is the main reason for high-T_c superconductivity of the perovskite cuprates.     

大脑血液动力学现象中的能量编码

神经信息的编码与解码是神经科学中的核心研究内容,同时又极具挑战性.传统的编码理论都具有各自的局限性,很难从脑的全局运行方式上给出有效的理论.而由于能量是一个标量具有可叠加性,因此能量编码理论可以从神经元活动的能量特征出发来研究脑功能的全局神经编码问题,取得了一系列的研究成果.本研究以王-张神经元能量计算模型为基础,构建了一个多层次结构的神经网络,通过计算机数值模拟得到了神经网络的能量消耗和血液中葡萄糖供能的变化情况.计算结果显示,和网络的神经活动达到峰值的时间相比,血液中葡萄糖的供能达到峰值的时间延迟了约5.6s.从定量的角度再现了功能性核磁共振(fMRI)中的血液动力学现象:大脑某个脑区的神经元集群被激活以后经过5~7 s的延迟,脑血流的变化才会大幅增加.模拟结果表明先前发表的由王-张神经元模型所揭示的负能量机制在控制大脑的血液动力学现象中起着核心的作用,预测了刺激条件下大脑的能量代谢与血流之间变化的本质是由神经元在发放动作电位过程中正、负能量之间的非平衡、不匹配性质所决定的.本文的研究结果为今后进一步探究血液动力学现象的生理学机制提供了新的研究方向,在神经网络的建模与计算方面给出了一个新的视角和研究方法.      

功能梯度球形水凝胶的化学力学耦合分析

作为一种新型智能材料,水凝胶具有特殊的化学力学耦合性能.采用功能梯度形式可使得水凝胶具有更好的适应性和可调控性.本研究中假设交联密度沿径向按幂函数规律变化,并基于水凝胶的大变形多场耦合一般理论,采用Flory-Huggins自由能函数,建立了功能梯度球形水凝胶在球对称情形的控制方程,并开展了功能梯度球形水凝胶在给定内压和化学势情行的非均匀大变形溶胀行为的理论研究.计算结果表明,不同梯度指数的球形水凝胶的内压、内孔半径曲线和内压、内表面径向伸长率曲线均呈现出一段稳定区间和另一段不稳定区间,说明内压超出某临界值会发生失稳并导致水凝胶的最终破坏.内压的临界值随梯度指数的增大而增大.研究表明,功能梯度球形水凝胶的材料参数(梯度指数、亲疏水特性、交联密度和溶剂分子的体积)和环境化学势对水凝胶溶胀行为具有重要的影响.在给定内表面压力的情况下,功能梯度球形水凝胶内表面的径向位移随梯度指数的改变接近为线性变化,而随其他参数的影响都呈现出明显的非线性.本研究有助于实现水凝胶智能结构和器件在复杂条件下的精准调控.}      

Syntheses,crystal structures and properties of Cd(II) and Ag(I) complexes based on 2-p-methylphenyl-5-(2-pyridyl)-1,3,4-thiadiazole

Abstract

Complexes of [CdL₂(NO₃)₂]·1.5H₂O and [Ag₂(μ-L)₂(NO₃)₂] were synthesized by the reactions of 2-p-methylphenyl-5-(2-pyridyl)-1,3,4-thiadiazole (L) with Cd(NO₃)₂·4H₂O and AgNO₃, respectively. Their structures were determined by single crystal X-ray diffraction. The photophysical property and thermal stability were characterized by FT???IR, UV???Vis absorption, fluorescence, and thermogravimetric analysis (TGA). Both complexes belong to the triclinic system with space group p???1. The central metal of [CdL₂(NO₃)₂]·1.5H₂O has a distorted octahedral geometry [CdN₄O₂], while two central Ag(I) atoms of [Ag₂(μ-L)₂(NO₃)₂] exhibit distorted tetrahedral geometries [AgN₃O].