RAPTAP: a socio-inspired approach to resource allocation and interference management in dense small cells

Wireless Networks - Femto Cells offer higher data rates to users within closed spaces. Dense deployment of small cells is a characteristic of pre-5G/LTE-Advanced Pro (LTE-A Pro) networks and is a...     

Effects of laser polishing on surface quality and mechanical properties of PLA parts built by fused deposition modeling

Fused deposition modeling (FDM) produces parts through layer by layer on the top of each other, making it almost impossible to obtain smooth printed parts. Hence, there is a huge demand for the postprocessing of the FDM-printed parts. Laser polishing is a novel technique that can be used to polish products to obtain a smoother surface. The aim of this work was to explore the feasibility of surface-finishing FDM-printed polylactic acid (PLA) parts by laser polishing. The surface roughness, surface morphology, dynamic mechanical analysis (DMA), and tensile properties were investigated. The results indicated that the lower laser power and the bigger laser beam diameter within a certain range could facilitate the formation of smoother surface. With optimized parameters, the surface roughness was reduced by 90.4%. DMA showed that the storage modulus (E’) and glass transition temperature of PLA specimens were significantly improved due to the decrease of molecular mobility of denser structures. Moreover, the tensile strength and Young's modulus of the PLA specimen were also significantly increased after laser polishing. The fracture morphologies were observed, and the possible strengthening mechanism was also discussed. These results indicated that laser polishing could be an efficient method for surface polishing of FDM parts. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48288.     

间歇精馏分离杂醇溶液的实验研究

通过间歇精馏分离杂醇溶液,得到浓度≥99%的异丁醇和正丁醇产品,并对分离过程中塔顶浓度随时间的变化趋势,塔顶、塔釜温度随时间的变化趋势进行了实验研究及数据分析。结果表明:随着精馏过程的进行,塔顶产品浓度、塔顶温度、塔釜温度呈现逐渐上升的趋势,但在合格产品采出阶段,塔顶产品浓度、塔釜温度、塔顶温度比较稳定,为工业生产回收异丁醇和正丁醇提供了有效的操作依据。     

净水功能型粉煤灰透水混凝土性能研究

通过向透水混凝土中引入净化材料(粉煤灰、硫酸改性粉煤灰),制备了具有净水功能的透水混凝土,研究了净化材料掺量对透水混凝土力学性能、孔隙率、透水性能及吸附水中Zn²⁺性能的影响.结果表明：硫酸改性粉煤灰能够促进水化硅酸钙凝胶的生成,改善透水混凝土的孔隙结构,提高其力学性能和对Zn²⁺的吸附效果;当硫酸改性粉煤灰掺量为20%时,透水混凝土试件的抗压强度达到峰值,孔隙率与透水系数降到最低值;随着净化材料掺量的增加,透水混凝土对Zn²⁺的吸附效果逐渐明显.     

基于故障树的采煤机液压盘式制动器故障研究

通过逻辑分析构建了采煤机液压盘式制动器故障与基本事件的故障树模型;采用二元决策图分析故障树模型,得到了导致制动器故障发生的最小割集,并通过状态枚举法计算了基本事件的结构重要度。结果表明,所列举的任一基本事件的失效均会导致制动器故障。为采煤机液压盘式制动器的故障诊断提供了理论依据。     

Invariance problem in structural non-probabilistic reliability index

Journal of Mechanical Science and Technology - The non-probabilistic reliability index has been extensively used to evaluate the safety degree of structures with limited experiment data. By dealing...     

R290应用在大容积卧式冷柜上的性能实验研究

R290(丙烷)制冷工质具有优良的环保性和热力学特性,是替代R134a应用在BC/BD-625卧式大容积冷柜(商用冷柜)上的潜在工质之一。采用R290对目前R134a系统进行充注式替代,R134a压缩机换成R290工质的压缩机。测试并优化毛细管的参数及R290最佳蒸发温度的确定。实验结果表明:系统充注R290后冷冻能力略高于R134a系统(110%),性能系数(COP)提高了24.7%。     

符合IEC61850标准的行波电流选线装置研制

基于故障行波理论和IEC61850标准,研制了中性点非有效接地系统数字化变电站中的单相接地故障行波选线装置.介绍了单相接地故障行波选线原理.故障线路电流初始行波幅值最大,极性与非故障线路相反.建立了符合IEC61850标准的数字化变电站中通用选线装置模型,一个包括3个逻辑节点的逻辑设备.设计了基于故障电流初始行波的选线...     

极化电流行波方向继电器

电容式电压互感器不能有效传变宽频带的电压故障行波信号,使得传统利用电压故障行波构成行波方向继电器的保护算法不能应用于实际电力系统保护中,为此提出了一种极化电流行波方向继电器。该方向继电器以电压故障行波中工频分量初始极性与电流故障初始行波的波头极性相比较判定故障方向,解决了传统行波方向继电器因不能有效获取宽频带电压故障行...     

基于AMESim有机肥-化肥开沟施肥机仿真分析

为提高果园有机肥和化肥混合施肥机施肥的精准性,结合新疆果园的施肥作业要求,设计出一种有机肥-化肥开沟施肥一体机,对整机的结构与工作原理进行阐述,并对其液压系统进行理论与仿真分析。结果表明,当施肥机在满载工作时,有机肥输肥马达的扭矩为363.21 N·m,与理论计算结果364.2 N·m的误差为0.27%,液压缸的运动速度平均值为30.59 mm/s,满足工作需求且验证了理论计算的准确性,此外有机肥施肥马达在理论计算参数下可进行稳定工作,验证AMESim仿真模型参数设置的合理性。