多用户多服务无线网络中感知用户体验的比例公平调度

The effective radio resource allocation algorithms, which satisfy diversiform requirements of mobile multimedia services in wireless cellular networks, have recently attracted more and more attention. This paper proposes a service-aware scheduling algorithm, in which the Mean Opinion Score (MOS) is chosen as the unified metric of the Quality of Experience (QoE). As the network needs to provide satisfactory services to all the users, the fairness of QoE should be considered. The Proportional Fair (PF) principle is adopted to achieve the trade-off between the network performance and user fairness. Then, an integer programming problem is formed and the QoE-aware PF scheduling principle is derived by solving the relaxed problem. Simulation results show that the proposed scheduling principle can perform better in terms of user fairness than the previous principle maximizing the sum of MOS. It also outperforms the max-min scheduling principle in terms of average MOS.     

基于概率的增强型区分服务算法

相对区分服务中成比例延迟区分(PDD)服务模型算法的公平性不高。为此,提出一种基于概率的增强型区分服务算法WPPLQ。该算法对等待时间的计算进行优化,利用数据包大小确定服务响应时间,适用于移动定位服务平台。在NS-2模拟器上的仿真结果表明,PLQ和WPPLQ均符合PDD区分服务模型的性能要求,在高带宽情况下,WPPLQ具有更高的公平性。     

协作干扰技术的提出、现状和未来展望

在物理层安全技术的研究中,协作干扰技术是较为特殊的一类,通过引入人为的干扰信号,降低窃听节点的接收性能,进而提升系统的保密容量。本文回顾了协作干扰技术的提出背景,总结了其研究现状,并对未来的发展前景和潜在研究点进行了展望。目前协作干扰技术的研究可以根据干扰信号的不同分为4类,也可根据窃听系统的不同分为简单和复杂场景下的自干扰和外协作干扰技术的研究。     

电极形状对铝-钢点焊接头组织及力学性能的影响*

研究6061-T6铝合金-SUS301L不锈钢异种金属电阻点焊接头的微观组织特点及电极形状的影响规律。结果表明,铝-钢点焊接头具有熔-钎焊特征,铝合金熔核由α-Al胞状晶、胞状树枝晶和树枝晶组成,铝/钢界面层具有双层结构,靠近铝熔核侧主要为细针状Fe₄Al₁₃,靠近不锈钢侧主要为Fe₂Al₅金属间化合物,接头主要为界面断裂模式,铝/钢界面是点焊接头最薄弱的区域。电极形状对铝合金-不锈钢点焊接头具有明显的影响。获得的优化电极形状为：不锈钢侧为圆形平面电极,电极端面直径为10 mm;铝合金侧为球面电极,球面半径为35 mm。在优化电极条件下,铝合金-不锈钢点焊接头的熔核直径、拉剪力及压痕率分别为7.5 mm、4.7 kN和13.5%。与采用F型电极相比,其熔核直径和拉剪力分别提高53.1%和56.7%,压痕率降低47.3%。因此,采用优化电极更有利于改善铝合金-不锈钢电阻点焊接头的力学性能及表面质量。     

时变非整数非均匀码书

研究了空间相关信道下的预编码码书设计,提出了接近工程实现的自适应码书设计,即时变非整数非均匀码书,同时提供了等效码书大小和预编码性能之间的多种折中方案,统一了自适应非均匀码书和固定均匀码书. 提出了码书周期的概念,并指出在码书周期较短时,即使空间相关系数估计不正确,选中的码书仍包括当前最优的预编码矩阵,时变码书近似等效为1个较大的固定码书. 当信道的空间相关特征变化较快时,应使用较小的码书周期以保证时变码书的跟踪特性.     

Effects of nugget alloying on microstructures and properties of resistance spot welded joints of aluminum and steel

The resistance spot welding of 6063-716 aluminum alloy and l6 Mn steel was studied by nugget alloying.The results indicated that the Al-steel joint had characteristics of welding-brazing.The nugget zone consisted mainly of α-Al solid solution with dislocations and fine Mg_2Si particles.The interface zone had a double-layer structure:Fe_2Al_5 layer at steel side and Fe_4Al_(13) layer at Al nugget side.The nugget alloying has a significant effect on the joint properties by changing phase composition and refinement of grains.When alloy elements Cu,Zn,Ti and Ni were added,the tensile shear load of Al-steel joints reached 2 780 N,2 910 N,2 915 N and 2 929 N respectively,which increased by 24.1%,29.9%,30.1%and30.7%respectively compared with that(2 241 N) of joint without nugget alloying.Therefore,it is an effective way for improving mechanical properties of resistance spot welded Al-steel joints.     

Effect of electrode morphology on steel/aluminum alloy joint

Microstructure characteristics of dissimilar-metal resistance spot welded joints of SUS301 L austenitic stainless steel and 6063-T6 aluminum alloy, and effects of electrode morphology were studied. Results indicated that welded joints of dissimilar materials between austenitic stainless steel and aluminum alloy had characteristics of welding-brazing. The aluminum nugget consisted mainly of the cellular crystal, cellular dendrites and dendrites. The interface between austenitic stainless steel and aluminum alloy had a two-layered structures:a flat front surface θ-Fe_2Al_5 on the steel side and a serrated morphology θ-FeAl_3 on the aluminium alloy side, and it was the weakest zone of the joints. The electrode morphology had great effects on spot welded joints of stainless steel and aluminum alloy. The custom electrodes were a planar circular tip electrode with tip diameter of 10 mm on the stainless steel side and a spherical tip electrode with spherical radius of 35 mm on the aluminum alloy side. When the custom electrodes were used, the nugget diameter, tensile shear load and indentation ratio of spot welded joint were 7.22 mm, 3 606 N and 10.71%, respectively. The nugget diameter and joint tensile shear load increased by 34% and 102% respectively, and the indentation ratio decreased by 65% compared with the F-type electrodes(nugget diameter: 5.384 mm, tensile-shear load 1 783 N, indentation rate 30.94%). Therefore, it was more favorable to use the custom electrodes for improving the mechanical properties and appearance quality of resistance spot welded joints of stainless steel and aluminum alloy.     

浅析无线网络的用户体验质量建模及性能优化

随着移动互联网业务的蓬勃发展,用户需求日益多样化,不断涌现各种无线新业务。如何提供良好的用户体验质量(QoE),是无线新业务是否获得成功的关键,同时也是衡量用户对业务认可程度的重要方式。文章首先对无线业务用户体验质量的影响因素和评价方法进行了介绍,然后分析了各种方法的特点和缺陷,并进一步总结了基于用户体验质量的性能优化领域的研究现状,最后展望了未来的研究前景。     

面向用户体验的异构网络资源分配

针对异构网络环境下的资源分配问题,提出了面向用户体验质量(QoE)的静态资源分配方案,即最大化用户体验(MaxQoE)分配方案. 该方案可应用于异构网络环境下多业务的场景中,为具有不同QoE需求的用户提供适度服务,并分配适量的无线资源. 仿真结果表明,与最大吞吐量分配方案和资源平均分配方案相比,采用MaxQoE方案能有效增强异构网络中的用户QoE指标,提高用户满意度.     

BIM技术与3D打印技术于建筑建造应用性研究

为研究BIM技术与3D打印技术在建筑建造中的辅助作用，本研究依托某学校基建项目，结合BIM、3D打印技术，系统性分析了BIM技术与3D打印技术在实际工程中的优劣。首先通过分析BIM技术在消防设计、管道设计、建筑规划设计、装修改造的优势，最后分析了3D打印技术与BIM技术结合后在实际工程中的应用。研究结果表明，本项目利用BIM集成管线碰撞检查技术，可有效减少返工次数，并将提高施工效率7.5%，节约成本约50万元；可视化检查分析有效提升了建筑物的美观性与实用性，以期为类似工程提供借鉴。