Unmanned aerial vehicles in collaboration with fog computing network for improving quality of service

In this paper, we study a UAV-based fog or edge computing network in which UAVs and fog/edge nodes work together intelligently to provide numerous benefits in reduced latency, data offloading, storage, coverage, high throughput, fast computation, and rapid responses. In an existing UAV-based computing network, the users send continuous requests to offload their data from the ground users to UAV–fog nodes and vice versa, which causes high congestion in the whole network. However, the UAV-based networks for real-time applications require low-latency networks during the offloading of large volumes of data. Thus, the QoS is compromised in such networks when communicating in real-time emergencies. To handle this problem, we aim to minimize the latency during offloading large amounts of data, take less computing time, and provide better throughput. First, this paper proposed the four-tier architecture of the UAVs–fog collaborative network in which local UAVs and UAV–fog nodes do smart task offloading with low latency. In this network, the UAVs act as a fog server to compute data with the collaboration of local UAVs and offload their data efficiently to the ground devices. Next, we considered the Q-learning Markov decision process (QLMDP) based on the optimal path to handle the massive data requests from ground devices and optimize the overall delay in the UAV-based fog computing network. The simulation results show that this proposed collaborative network achieves high throughput, reduces average latency up to 0.2, and takes less computing time compared with UAV-based networks and UAV-based MEC networks; thus, it can achieve high QoS.     

Time-scale separation and robust controller design for uncertain nonlinear singularly perturbed systems under perfect state measurements

We study time-scale separation and robust controller design for a class of singularly perturbed nonlinear systems under perfect state measurements. The system dynamics are taken to be jointly linear in the fast state variables, control and disturbance inputs, but nonlinear in the slow state variables. Since global timescale separation may not always be possible for nonlinear singularly perturbed systems, we restrict our attention here to some closed subset of the state space, on which a timescale separation holds for sufficiently small values of the singular perturbation parameter. We construct a slow controller and a composite controller based on the solutions of particular slow and fast games obtained using time-scale separation. For the class of systems for which the slow controller can be selected to be robust with respect to small regular structural perturbations on the slow subsystem, we show under some growth conditions that the composite controller can achieve any desired level of performance that is larger than the maximum of the performance levels for the slow and fast subsystems,. A slow controller, however, is not generally as robust as the composite controller; but, still under some conditions which are delineated in the paper, the fast dynamics can be totally ignored. The paper also presents a numerical example to illustrate the theoretical results.     

基于超声波衰减法浆体质量浓度检测系统的设计

研究基于超声波衰减原理的浆体质量浓度检测技术,利用超声波幅值的衰减与浆体质量浓度之间的关系对浆体质量浓度实现在线测量。设计了实验装置,模拟工业现场进行了纸浆质量浓度的测量。实验结果表明,利用设计的浆体质量浓度检测系统所测得的纸浆质量浓度值与实际值是基本相符的,验证了系统的可行性。     

Gamma and neutron shielding characterizations of the Ag2O–V2O5–MoO3–TeO2 quaternary tellurite glass system with the Geant4 simulation toolkit and Phy-X software

Gamma and neutron shielding potential of the newly developed xAg₂O-(35-x)[0.5V₂O₅-0.5MoO₃]-65TeO₂ (x = 0, 5, 10, 15, 20 and 25 mol%) quaternary tellurite glass system were investigated computationally by means of Geant4 Monte Carlo simulations and Phy-X software. Gamma ray shielding capabilities were studied via the mass attenuation coefficient (μ_m), transmission fractions (T), effective atomic number (Z_eff), half value layer (HVL) and mean free path (MFP) parameters and for the photon energies of 0.284, 0.356, 0.511, 0.662, 1.173 and 1.330 MeV. Fast neutron removal cross-section (∑_R) parameter of the glasses was calculated to assess the neutron shielding capabilities. The results of this study revealed that tellurite glass containing 25% moles of Ag₂O has highest μ_m and Z_eff and lowest T, HVL and MFP values due to the high atomic number of Ag. In this study it was also seen that the ∑_R of the investigated glass system increases with the increase of Ag₂O fraction and ∑_R values of the studied glasses are higher than barite added concrete and close to the ∑_R of the PbO added borate glasses.     

基于最大衰减因子模型的服装热防护性能预测

为解决全尺度燃烧假人实验测试成本高、实验效率低,以及尚未与织物小样测试统一联合表征等难题,利用新型的热防护性能评估模型:二级烧伤最大衰减因子模型,对热防护服装的织物试样测试与燃烧假人实验进行同步研究,并建立基于织物试样测试的服装整体热防护性能预测模型。结果表明:防护织物的热防护性能与其服装整体的热防护性能具有显著相关性;将织物热防护性能值、服装平均衣下空气层厚度以及服装热暴露时间作为预测模型输入参数,可以实现服装热防护性能值以及人体皮肤烧伤百分比的预测;经模型验证发现,服装实测热防护性能值与其预测值间的相对误差仅为5.1%。     

饱和砂岩中衰减、模量和速度的流体效应

饱和砂岩中孔隙液体的粘滞系数对饱和砂岩的衰减,模量和速度色散的影响在较低频段是明显的。通过对３种不同粘滞系数的液体和砂岩的低频共振实验结果表明,随液体的粘滞九的增大,衰减显著增大,模量增大,存在明显的和速度色散,随液体粘性增强,模量与速度色散也有增强的趋势。     

衰减与频散的补偿方法

大地滤波作用不仅引起高频成分的迅速衰减,而且造成子波相位特征的畸变。要进行高分辨率地震资料的处理;必须对上述衰减和频散进行补偿。本文采用李氏经验公式计算的衰减因子Q值,提出一种具有空变和时变特性的Q值补偿方法。补偿处理是在单道上进行的,可以是动较正后的叠前道,也可以是叠后道,使用非常方便。     

液固两相介质多频超声粒径分布测量

液固两相流动广泛存在于工业过程中,其粒径分布信息在线测量对生产优化与控制十分重要。超声法作为无扰动式多相流动参数测量方法,其衰减特性与固相颗粒粒径、体积分数等密切相关,可用于实现粒径分布在线测量。本文搭建液固两相介质超声衰减实验装置,装置采用石英砂作为固相颗粒,自来水为液相,利用线性调频超声信号激励研究液固两相介质的超声衰减特性。实验结果表明,随着激励频率和固相体积分数的升高,超声衰减系数逐渐增加,采用Twomey及遗传算法等对液固两相介质粒径分布进行反演,测试结果与马尔文激光粒度分析仪的粒径分布结果相比,相关系数为0.918。     

紧缩型EMC暗室的NSA理论值分析

本文首先介绍了紧缩型电磁兼容(EMC)暗室归一化场地衰减(NSA)的测试方法和理论值的计算模型.然后定量的分析了采用3米法测量,计算结果与CI SPR和ANSI中给出的标准值之差不大干±4dB;最后用NSA理论值计算模型,计算收发天线间距离为5米时的NSA值并与标准值比较,分析误差,结果满足测试精度要求.     

测试消光比的衰减系统研究

基于偏振干涉原理,设计了一种用于测量偏光镜消光比的连续可调智能化衰减系统。该系统由3个标准偏光镜、1个632.8 nm的1/4波片、1个步进电机和微机共同组成,其中1个偏光镜的主透射方向和波片快慢轴的夹角为45°并组成标准圆偏器,利用计算机控制步进角为0.25°的步进电机旋转圆偏器,从而达到连续衰减光强目的。其衰减范围可在0~60 dB间扩展,插入损耗小于1.2 dB。用该系统测量时,可得到优于10-7量级的消光比值。对衰减系统的调节机理进行了分析,并给出圆偏器旋转不同角度下系统的透射曲线。