Photoluminescence studies of Eu2+-Yb3+ co-doped BaMgAl10O17 phosphor synthesized by the combustion method

BaMgAl10O17:Eu2+,Yb3+ was investigated as a possible quantum cutting system to enhance solar cells efficiency. Phosphors were synthesized by combustion method and composed of nanorods. Photoluminescence spectra showed that Eu in the sample was reduced to bi-valence while Yb remained trivalence. Through a cooperative energy transfer process, the obtained powders exhibited both blue emission of Eu2+ (around 450 nm) and near infrared emission of Yb3+ (around 1020 nm) under broad band excitation (250-410 nm) originating from 4f→5d transition of Eu2+. Energy transfer phenomenon between the sensitizer Eu2+ and the activator Yb3+ was investigated via the lumines-cent spectra and the decay curves of Eu2+ with different Yb3+ concentrations. Results indicated that energy transfer efficiency from Eu2+ to Yb3+ was not high. The poor efficiency can be explained by the long distance between rare earth ions.     

传感技术在农业机械自动化系统中的应用

本文以传感器的发展作为切入点,详细分析了农业机械化中传感器自动化技术类型,探究了农业机械自动化系统中传感器技术的具体应用,进一步验证了农业机械自动化中传感技术的重要性,对农业领域传感技术的推广与创新具有借鉴意义。     

Strong dependence of upconversion luminescence on doping concentration in holmium and ytterbium co-doped Y2O3 phosphor

Under the excitation of 980 nm diode laser, intense green emission (5F4+5S2-5I8) of Ho3+ was observed in Ho3+ and Yb3+ co-doped cubic Y2O3. The doping concentration and laser power dependence of the upconverted emission were studied. The decay curves of 5F4+5S2 emission of Ho3+ under the excitation of 355 nm pulse laser were measured to investigate the energy transfer process between Ho3+ and Yb3+. The results indicated that two-photon process was responsible for the upconversion (UC) emission. The Ho3+ con...     

二级行星轮系第二级太阳轮ADAMS几种仿真研究

为了得到某掘进机截割部二级行星减速器的第二级太阳轮精准的运动和受力情况,利用UG软件建立二级行星轮系模型,选择不同的ADAMS积分格式对机构进行动力学仿真,得出第二级太阳轮的运动曲线图,同时将仿真所得的各个载荷谱导入ANSYS中对模型进行瞬态动力学分析,得出第二级太阳轮的应力云图。将第二级太阳轮由刚性体生成柔性体再进行上述联合仿真,得出的结果与前者进行比较。     

香甜爽口“欢喜团”

“欢喜团”又名“麻元宵”或“麻鸡蛋”.这种点心色泽金黄,浑圆膨松,外皮焦酥,内里韧软,芝麻粘裹均匀,吃来甜香爽口.欢喜团分包馅与不包馅两种,包馅的,习惯上多称为“麻鸡蛋”.为什么叫“欢喜团”?原来,这种小吃的出现与一家的团圆喜庆有关.清末荆州城内有陶姓一家,在战     

对中小企业人才流失问题的分析和思考

在激烈的商业竞争中,人才是企业最重要的战略资源。对中小企业而言,严重的人才流失是其面临的最大困境,本文就中小企业人才流失现状和原因进行分析,并对留住人才的策略进行简要探讨。     

大图采样方法综述EI北大核心CSCD

大图采样是常用的网络图简化方法,可显著降低大图数据的规模.文中从随机图采样、特征驱动的大图采样方法、大图采样的评估指标和大图采样方法的应用4个角度进行综述.首先介绍随机点、随机边和随机游走的随机图采样方法;然后论述拓扑结构、社区结构、动态网络关联和语义关联特征驱动的大图采样方法;再介绍拓扑结构、视觉感知和特征驱动的大图采样指标;最后介绍了大图采样方法在社交网络、地理交通、生物医学和深度学习等领域的应用,并展望了该方法的发展前景.     

智能制造背景下纺织机械设计制造及自动化技术的发展趋势浅析

目前,随着各行业都进入了智能制造阶段,我国机械设计制造水平及自动化技术得到不断提高与发展。机械设计制造和自动化是现代工业中最重要的组成部分之一,它能够有效推动机械制造业向智能化方向前进。我国机械设计制造及自动化技术的发展受益于已有智能制造技术的支撑,因此,为了促进我国机械制造业的长远发展,必须重视机械设计制造和自动化技术产业。要想在机器制造领域中发挥优势,需以智能制造为切入点,找到二者的关联,由此发现优化策略,推动机械设计制造及自动化技术的深入发展与优化。随着社会经济的快速发展,科学技术也随之得到了很大程度上的进步,这就给机械设计制造和自动化带来了新的挑战。文章在此基础上研究了智能制造环境下机械设计制造及自动化技术的发展趋势,以供参考。     

Broadband downconversion in YVO4：Tm3＋,Yb3＋ phosphors

An efficient near-infrared (NIR) downconversion (DC) by converting broadband ultraviolet (UV) into NIR was demonstrated in YVO4:Tm3+,Yb3+ phosphors. The phosphors were extensively characterized using various methods such as X-ray diffraction, photoluminescence excitation, photoluminescence spectra and decay lifetime to provide supporting evidence for DC process. Upon UV light varying from 260 to 350 nm or blue light (473 nm) excitation, an intense NIR emission of Yb3+ corresponding to transition of 2F5/2→2F7/2 peaking at 985 nm was generated. The visible emission, the NIR mission and the decay lifetime of the phosphors of various Yb3+ concentrations were investigated. Experimental results showed that the energy transfer from vanadate group to Yb3+ via Tm3+ was very efficient. Application of the broadband DC YVO4:Tm3+,Yb3+ phosphors might greatly enhance response of siliconbased solar cells.     

GPS三维联合平差

文中论述了GPS网与地面网测量数据的三维联合平差的函数模型和随机模型 ,讨论了平差中数据处理的某些技术 ,最后还介绍了根据这一模型研制的平差软件。