Activated-TIG Welding of Different Steels: Influence of Various Flux and Shielding Gas

In tungsten inert gas (TIG) welding, a low depth of penetration (DOP) is achieved during single pass. To achieve the required DOP, the speed of welding should be reduced; thus productivity reduces significantly. In this work, influence of 14 different oxide-, chloride-, and fluoride-based fluxes are evaluated on DOP and width-to-penetration ratio during flux-activated TIG (ATIG) welding of low alloy steel (AISI 4340), austenitic (AISI 304 and AISI 316) and duplex (Duplex 2205) stainless steels. The effect of welding current and three different shielding gas compositions is also studied during ATIG for these workpieces. Arc and weld metal pool behaviors are captured in order to study the physical behavior of the process. Results revealed that oxide-based fluxes like SiO₂, MoO₃, MoS₂, CrO₃, and TiO₂ increases DOP significantly and in many cases through penetration (penetration reaches beyond plate thickness) is achieved. There is a noteworthy enhancement in penetration because of the addition of H₂ in shielding gas. Addition of helium also helps to increase DOP. Arc behavior reveals the constriction of arc column during activated TIG welding, and positive surface tension-induced flow in centripetal (inward) direction is observed.     

通信设备的电磁兼容性设计

本文介绍了通信产品的电磁兼容性要求、国内外标准、电磁兼容设计。     

屏蔽泵常见故障分析及解决方案

轻质油装置屏蔽泵在运行中发生泵体内有杂音、振动超标、轴承磨损的故障。通过对屏蔽泵结构和故障现象的分析,找到了故障产生的原因。含气态组分的介质进入屏蔽泵冷却腔体和润滑轴承的循环管路,使得轴承容易磨损;泵体结构的流向设计得不合理,造成介质在泵腔内汽化,形成汽蚀,并造成轴承磨损;介质流量不平稳造成轴向力不平衡。实施了相应的解决方案,降低了设备故障率和检修率,确保了装置安全平稳运行。     

基于空间场屏蔽效能测试方法研究

基于空间电磁场屏蔽效能测试中,目前存在着各种测试标准,虽然每种方法都能获得实验数据,但是不同测试方法下的实验数据差异性很大,不具有可比性。针对以上问题,该文对各种方法的选用、原理以及优缺点展开详细的研究和分析,并对基于空间电磁场屏蔽效能测试方法标准的统一性和规范化做了相应的建议和尝试,来优化和控制屏蔽部件、屏蔽材料和屏蔽实体的屏蔽效能测试,使测试标准更加符合实际测试和生产实践。     

Highly efficient white light with sharp red–green–blue emissions from iridium complexes doped carbazole-grafted poly(para-phenylene)

We demonstrated a high-efficiency white polymer light-emitting diode (WPLED) based on carbazole-grafted poly(para-phenylene) (CzPPP) doped with green- and red-emitting Ir complexes as the emitting layer. The device exhibits pure white light yet with stable sharp blue (430 nm), green (512 nm), and red (613 nm) emissions and has the maximum current and external quantum efficiencies of 16.8 cd/A and 8.65%, respectively. The overall performance is resulted from the excellent shielding effect of CzPPP host to prevent back transfer of triplet energy especially from the green phosphor.     

MSF-电感耦合等离子体发射光谱法测定钼铁中磷的研究

在用电感耦合等离子体发射光谱法测定钢中磷时，已有的研究报告中大多采用P178．221nm作分析谱线。但因其发射强度低而使测定精密度和检出限不理想。本文在采用多重谱线拟合（MsF）法扣除光谱干扰的基础上进行屏蔽，测定了存在严重光谱干扰的P214．914nm、P213．617nm谱线，同时也测定了没有光谱干扰的P178．221nm、P177．434nm谱线，结果表明，P213nm谱线的测定精密度和检出限最好，比常用P178nm谱线的精密度高，RSD达到小，检出限也比常用P178nm谱线的低。     

论高频屏蔽体的波阻抗及屏蔽效能

介绍了屏蔽体波阻抗及涡流系数与材料的主要特性参数的关系,并对当前德、俄与美、英等国所用的屏蔽效能计算公式进行了比较，最后介绍如何合理选择屏蔽结构以提高屏蔽体的屏蔽效果。     

助剂和工艺条件对导电性复合材料性能的影响及其分析

本文以低密度聚乙烯－镍粉为基础成分，引入各种助剂和改变工艺条件，研究了导电性复合材料的导电性和力学强度的变化规律，并考察了其作用机制。结果表明，导电性增加，伸长率和冲击强度就下降，这是由于填料的分散状态及其与聚合物基体的相互作用发生变化造成的。在实际使用中，必须良好地也能够适当地调节这两种性能。     

重离子核反应中的中子辐射屏蔽计算

在分析重离子核反应中中子的产生和有关保健物理数据的基础上,确定了用于屏蔽计算的核反应系统和计算参数,计算了单核能为100MeV、束流强度为3.9×10~(11)离子/s的~(12)C离子轰击Cu靶时距靶5m和10m处达到不同中子剂量当量率时需要设置的混凝土(ρ=2.3g/cm~3)屏蔽厚度。     

金属导电短纤维提高Ni涂层导电性能研究

探索了金属导电短纤维提高电磁波屏蔽用Ｎｉ涂层导电性能的机制。结果表明，金属导电短纤维能大幅度地提高Ｎｉ涂层的导电性能，经分析是由于增大涂层中导电网络的密度所致。还对复合型涂层的屏蔽效能进行了理论预测。