在车载自组织网络(vehicular ad hoc network,VANET)(也称车联网)中,基于地理位置的路由协议能够较好地适应网络拓扑的动态性变化和链路质量的不稳定性.由于位置信息需要在邻居节点间采用信标分组进行交互,信标分组间隔内的转发决策可...
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在车载自组织网络(vehicular ad hoc network,VANET)(也称车联网)中,基于地理位置的路由协议能够较好地适应网络拓扑的动态性变化和链路质量的不稳定性.由于位置信息需要在邻居节点间采用信标分组进行交互,信标分组间隔内的转发决策可能因车辆节点位置的移动而不准确,需要进行位置预测来修正车辆节点的位置.已有的位置预测算法存在普适性差或预测误差大的问题.针对上述问题,提出了一种新的预测算法,首次通过测量得到车辆加速度服从正态分布的结论,利用线性回归进行预测,并采用反馈机制进行结果修正.利用真实车辆轨迹进行测试,新的预测算法的预测精度大为提高.然后,提出了一种新的基于位置的即时路由协议.在该协议中,发送节点利用邻居节点位置和目的节点位置计算出转发下一跳.将新的位置预测算法加入到即时路由协议中,实时预测和更新车辆的位置.利用SUMO软件生成了基于真实地图道路轨迹的车辆运动模型,结合NS3网络仿真平台进行了仿真实验.实验结果表明:采用新的预测算法后,相比传统的GPSR协议和不带预测的即时路由协议,新方法的收包率提高、延迟下降,并且协议开销显著降低.
作者：
Lan, chuwenli, BoZhou, JiTsinghua Univ
Sch Mat Sci & Engn State Key Lab New Ceram & Fine Proc Beijing 100084 Peoples R China Tsinghua Univ
Shenzhen Grad Sch Adv Mat Inst Shenzhen 518057 Peoples R China
In recent years, considerable attention has been focused on transformation optics and metamaterial due to their fascinating properties and wide range of promising applications. Concentrator, one of the most well-known...
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In recent years, considerable attention has been focused on transformation optics and metamaterial due to their fascinating properties and wide range of promising applications. Concentrator, one of the most well-known applications of transformation optics and metamaterial, is now limited only to a single physical domain. Here we propose and give the experimental demonstration of a bifunctional concentrator that can concentrate both electric and thermal fields to a given region simultaneously while keeping the external fields undistorted. Fan-shaped structure composed of alternating wedges made of two kinds of natural materials is proposed to achieve this goal. Numerical simulation and experimental results show good agreement, indicating the soundness and feasibility of our scheme. (C) 2015 Optical Society of America
In this study, a simple and delicate approach to realizing manipulation of multi-physics field simultaneously through combination of passive and active schemes is proposed. In the design, one physical field is manipul...
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In this study, a simple and delicate approach to realizing manipulation of multi-physics field simultaneously through combination of passive and active schemes is proposed. In the design, one physical field is manipulated with passive scheme while the other with active scheme. As a proof of this concept, a bifunctional device is designed and fabricated to behave as electric and thermal invisibility cloak simultaneously. It is found that the experimental results are consistent with the simulated ones well, confirming the feasibility of our method. Furthermore, the proposed method could also be extended to other multi-physics fields, which might lead to potential applications in thermal, electric, and acoustic areas. (C) 2016 Author(s).
A pre-mixed abrasive and water jet united cutting tooth type roller of a coal mining machine comprises a cutting shaft (1), a barrel (2), a high-pressure hose (7), cutting teeth (5), a spray head assembly (4), and a c...
标准号:
WO2017020519(A1)
A pre-mixed abrasive and water jet united cutting tooth type roller of a coal mining machine comprises a cutting shaft (1), a barrel (2), a high-pressure hose (7), cutting teeth (5), a spray head assembly (4), and a core sleeve (3). The barrel (2) sleeves the periphery of the core sleeve (3), and the cutting shaft (1) sleeves a matched inner cavity in the core sleeve （3）to drive a cutting head to move. Two ends of the high-pressure hose (7) are threaded to the core sleeve (3) and the barrel (2) separately. A nozzle base flow channel (4-5), a sleeve (4-3), and a nozzle (4-4) are disposed in the spray head assembly (4). The cutting shaft (1) is provided with a water inlet hole (1-1), a main flow channel (1-2), and a water outlet hole (1-3). One end of the water inlet hole (1-1) is connected to a high-pressure water source, and the other end of the water inlet hole (1-1) is in communication with the main flow channel (1-2). One end of the water outlet hole (1-3) is connected to the main flow channel (1-2), and the other end of the water outlet hole (1-3) is in communication with a core sleeve flow channel (3-1). The barrel (2) is provided with a barrel flow channel (2-1). A mixture of water and abrasive enters the main flow channel (1-2) via the water inlet hole (1-1), passes through the core sleeve flow channel (3-1) via the water outlet hole (1-3), further flows into the barrel flow channel (2-1) via the high-pressure hose (7), then flows into the spray head assembly (4), successively passes through the nozzle base flow channel (4-5) and the sleeve (4-3) in the spray head assembly (4) to enter the nozzle (4-4), and forms a high-pressure abrasive and water jet. The roller can effectively improve the efficiency of mining a thin coal seam, and reduce cutter wear.
We numerically and experimentally demonstrated a polarization insensitive dual-band metamaterial perfect absorber working in wide incident angles based on the two magnetic Mie resonances of a single dielectric "a...
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We numerically and experimentally demonstrated a polarization insensitive dual-band metamaterial perfect absorber working in wide incident angles based on the two magnetic Mie resonances of a single dielectric "atom" with simple structure. Two absorption bands with simulated absorptivity of 99% and 96%, experimental absorptivity of 97% and 94% at 8.45 and 11.97 GHz were achieved due to the simultaneous magnetic and electric resonances in dielectric "atom" and copper plate. Mie resonances of dielectric "atom" provide a simple way to design metamaterial perfect absorbers with high symmetry. Published by AIP Publishing.
Dual band metamaterial perfect absorbers with two absorption bands are highly desirable because of their potential application areas such as detectors, transceiver system, and spectroscopic imagers. However, most of t...
Dual band metamaterial perfect absorbers with two absorption bands are highly desirable because of their potential application areas such as detectors, transceiver system, and spectroscopic imagers. However, most of these dual band metamaterial absorbers proposed were based on resonances of metal patterns. Here, we numerically and experimentally demonstrate a dual band metamaterial perfect absorber composed of artificial dielectric "molecules" with high symmetry. The artificial dielectric "molecule" consists of four "atoms" of two different sizes corresponding to two absorption bands with near unity absorptivity. Numerical and experimental absorptivity verify that the dual-band metamaterial absorber is polarization insensitive and can operate in wide-angle incidence.
A slurry abrasive jet system, consisting of a closed-loop hydraulic oil system and an open-loop slurry jet system. The closed-loop hydraulic oil system comprises: a hydraulic oil tank, an oil filter (1), a high-pressu...
标准号:
WO2018/103284(A1)
A slurry abrasive jet system, consisting of a closed-loop hydraulic oil system and an open-loop slurry jet system. The closed-loop hydraulic oil system comprises: a hydraulic oil tank, an oil filter (1), a high-pressure oil pump (2), an electromagnetic directional valve (4, 7, 10), a one-way check valve (5), a high-pressure oil chamber, and a double acting piston (8). The open-loop slurry jet system comprises: a one-way check valve, a slurry pressurizing chamber, a double-acting piston, and an electromagnetic directional valve. The relatively independent slurry chamber and the high-pressure oil chamber effectively prevent a slurry abrasive from mixing with another substance during a pressurization process. The adoption of the double-acting piston effectively solves the problem of intermittent feeding of a slurry jet, thus achieving continuous operation of the slurry jet system.
The essential oils obtained by hydrodistillation of flowers,young leaves and epicormic branches of Cinnamomum camphora *** were comparatively studied by gas chromatography with flame ionization detector(GC/FID) and GC...
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The essential oils obtained by hydrodistillation of flowers,young leaves and epicormic branches of Cinnamomum camphora *** were comparatively studied by gas chromatography with flame ionization detector(GC/FID) and GC/mass spectrometry(GC/MS).Among the verified constituents,oxy-terpene accounted for the most abundant constituent in all volatile oils(flowers 50.83%,leaves 70.75%,branches 78.22%).d-Borneol,the characteris- tic oxy-terpene of the volatile oils of *** ***,was the highest-content compound among all the three parts(flowers 12.13±.67 g/kg,leaves 17.22±.85 g/kg and branches 4.47±.79 g/kg),while camphor was absent in flowers,low in leaves(0.05±.01 g/kg) but rich in branches(1.09±.44 g/kg).These findings suggested that volatile oils from the leaves and flowers of *** *** would serve as a better resource for d-bomeol prepara- tion,and there might be an a-pinene-borneol-camphor bioconversion during the growth time extension of *** ***(flower < leaf < branch)
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