微波场作用下Y2O2S：Tb绿色荧光粉的快速合成及其发光特性

采用微波法快速合成了Y2O2S：Tb绿色荧光粉。用X射线衍射（XRD）仪、扫描电镜（SEM）、荧光分光光度计等对合成产物的相结构、形貌、以及发光特性进行了研究。结果表明：材料的晶体结构为六方晶系，与Y2O2S相同。颗粒的形貌为类球形，分散性很好，平均晶粒尺寸在300nm左右。发射光谱由384，418，439，460，475，498，547，590，624nm等一系列窄带发射峰组成，归属于Tb^3＋从^5D3，^5D4到^7FJ（J=0～6）的跃迁。研究发现Tb的掺杂浓度对样品的发射光谱有着很重要的影响，当其浓度为0．5％（摩尔分数，下同）时，^5D3→^7FJ的蓝光发射发生猝灭，当其浓度为9％时，^5D4→^7FJ的绿光发射发生猝灭。     

用微信点赞,教餐饮企业免费做广告拉生意

<正>微信目前已经成为广大手机用户必定会安装的手机APP,上至花白老人,下至学龄儿童,都会用微信去跟朋友语音,在朋友圈发图片。拒不完全统计,目前至少有5亿甚至跟多的微信用户。然而,微信的功能已经远远不只是朋友交际、嘘寒问暖,它更是商家用于广告宣传的免费平台,更是方便快捷的手机交易终端。各位餐饮行业的老板们,如果你们还不会在微信上营销;     

Oscillation propagation features of the atmosphere around the Qinghai-Xizang Plateau during the spring season of typical strong and weak monsoon years

The interaction between the low-frequency atmospheric oscillation(Madden-Julian Oscillation,MJO) and the diabatic heating over the Qinghai-Xizang Plateau(QXP) from March to June is analyzed.The results show that there are respectively two and one wave trains around the QXP during the onset of the South China Sea monsoon in strong and weak monsoon years.The locations and strength of the wave train propagation differ between the strong and weak monsoon years.Because diabatic heating of the QXP prevents the lo...     

激光制导弹药半实物仿真目标模拟技术

对激光半主动制导武器半实物仿真系统中的激光目标模拟技术进行了研究。提出了激光制导弹药半实物仿真对目标模拟的技术要求。根据该要求,设计了激光目标模拟器及其分系统方案。该目标模拟器可实现激光光斑能量、尺寸以及弹目视线相对运动特性的模拟。     

摩擦摆中的摩擦激励特性研究

介绍一种摩擦摆实验装置,建立摩擦摆稳定摆动状态下系统的运动微分方程,计算并讨论摩擦副间相对角速度和相对角加速度对摩擦摆自激振动稳定性的影响。结果表明:与相对加速度有关的交变摩擦力是系统自激振动的主要原因,因此有效控制工程实践中各种摩擦自激振动的途径在于,力求使摩擦副间摩擦力既不随相对速度变化,更不随相对加速度波动。     

输送垃圾和稀泥浆等用耐磨损UOE焊管的开发

管道输送垃圾和稀泥浆用管要求有较好的耐磨性，铁素体－马氏体双相结构的耐磨ＵＯＥ管已经被开关，这种ＵＯＥ管合金元素含量较低；如Ｃ，Ｍｎ等元素含量比普通耐磨钢管低，因此有较好的焊接性能和成型性能，该ＵＯＥ管适合用普通圆周焊接方法进行圆周焊接，并且可用感应加热弯曲法制作弯管。     

Criteria for obtaining and interpreting breast thermagrams

The thermal and graphic criteria which should be used to evaluate breast thermograms are outlined. Thermograms are then categorized as normal, suspicious, or abnormal on the basis of the criteria outlined. It is hoped that these criteria can be used widely to standardize breast thermographic evaluation.     

Influences of Friction Stir Welding and Post‐Weld Heat Treatment on Al–Cu–Li Alloy

In this paper, the influences of friction stir welding (FSW) and post‐weld heat treatment (PWHT) on the microstructures and tensile properties of Al–Cu–Li alloy are investigated. After FSW, strengthen loss occurred in the welding area. Remarkable softening occurs in the thermo‐mechanically affected zone (TMAZ) resulting from dissolution of Al₃Li (δ′) phases. Recrystallization and precipitation of ultra‐fine δ′ phases take place in the nugget zone (NZ) that lightens the softening degree of this zone. A noteworthy enhancement in the hardness and tensile strength of the joint is achieved after T8 re­aging treatment (3% ? pre‐deformation, 30 h at 152 °C). However, re‐solution treatment coupled with re‐aging treatment leads to ductility deterioration in the joint because coplanar slip of coarse Al₃Li phases induces severe stress concentration during plastic deformation.

     

Piezoelectric-based crack detection techniques of concrete structures: Experimental study

Feasibility of a wave propagation-based active crack detection technique for nondestructive evaluations(NDE)of concrete structures with surface bonded and embedded piezoelectric-ceramic(PZT)patches was studied.At first,the wave propagation mechanisms in concrete were analyzed.Then,an active sensing system with integrated actuators/sensors was constructed.One PZT patch was used as an actuator to generate high frequency waves,and the other PZT patches were used as sensors to detect the propagating wave.Scattered wave signals from the damage can be obtained by subtracting the baseline signal of the intact structure from the recorded signal of the damaged structure.In the experimental study,progressive cracked damage inflicted artificially on the plain concrete beam is assessed by using both lateral and thickness modes of the PZT patches.The results indicate that with the increasing number and severity of cracks,the magnitude of the sensor output decreases for the surface bonded PZT patches,and increases for the embedded PZT patches.