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排序方式: 共有887条查询结果,搜索用时 15 毫秒
1.
针对移动群智感知任务中区域全覆盖感知成本过高问题,提出基于压缩感知的移动群智感知任务分发(CS-TD)机制。首先提出了感知任务整体成本模型,该模型综合考虑了参与感知任务的节点个数、节点的感知次数与数据上传次数;然后基于成本模型,分析感知节点的日常移动轨迹,结合压缩感知数据采集技术,提出了一种基于感知节点轨迹的压缩感知采样方法;其次通过区域全覆盖最少节点(RCLN)算法,选出最佳节点集合,对节点进行任务分配,利用压缩感知技术恢复节点数据;最后在多次感知任务的迭代中对感知节点的可信程度进行评定,保证任务方案的最优性。对CS-TD分发模型进行多次实验验证,与已有的CrowdTasker算法相比,CS-TD算法平均成本降低了30%以上。CS-TD模型能有效降低感知节点的消耗,能在全覆盖感知任务中降低整体感知成本。 相似文献
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Background/purposeMeasurements of strains in critical components are often required in addition to finite element calculations when evaluating a structure.MethodsThis paper describes how standard optical fibers, bonded to the surface or embedded in a laminate, can measure strain fields along the entire length of the fiber, using the optical backscatter reflectometer.ResultsA strain field measurement can be much better compared to simulations than the more common single point measurements with strain gauges or Bragg Gratings. Changes of the strain field can be related to damage development and can be used for structural health monitoring. Practical aspects of using the fibers are also discussed.ConclusionDistributed Fiber-Optic Sensing was successfully embedded and bonded to a composite joint. Adhesive damage was identified and the strain field agreed well with FE-Analysis. 相似文献
3.
《Journal of the European Ceramic Society》2020,40(4):1376-1385
This work proposed pyrochlore doped-Pr2Sn2O7 ceramics with electronic transport and NO2 sensitivity through molecular insights into sensing mechanism by DFT. NO2 adsorbed on the p-type semiconductor metal oxide NiO(100) can be decomposed into three stable adsorbed states NO2, NO and O that will obtain electrons from the NiO valence band to form N2 (or N2O) and O2−, resulting in an increase of the holes concentration. The results suggest that the response current value of the sensor based on Pr2Sn2O7 doped by Ca2+ at A site is 53.5 times higher than that of commercial YSZ, indicating high sensitivity with 420 nA/ ppm at mild temperature 550 °C. Besides the creation of oxygen-defect sites, the electronic transport is responsible for the improved sensing properties. The electrons on doped Pr2Sn2O7 ceramics can complement the hole-accumulation layer and make NO2, NO, O accept electrons quickly to accelerate the rate of the electrochemical cyclic reaction. 相似文献
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Crowd counting with density estimation has been an active research community due to its significant applications in the fields of public security, video surveillance, traffic monitoring. However, Crowd counting for congested scenes often suffers from some obstacles including severe occlusions, large scale variations, noise interference, etc. In this paper, using the first ten layers of a modified VGG16 and dilated convolution layers as the framework, we have proposed a CNN based crowd counting and density estimation model improved by the attention aware modules with residual connections. To tackle the problem of noise interference, convolutional block attention modules have been introduced into the deep network to segment the foreground and background to focus on interest information, refining deeper features of the input image. To improve information transmission and reuse, residual connections are utilized to link 3 attention blocks. Meanwhile, dilated convolution layers keep larger reception fields and obtain high-resolution density maps. The proposed method has been evaluated on three public benchmarks, i.e. Shanghai Tech A & B, UCF-QNRF and MALL, achieving the mean absolute errors of 64.6 & 8.3, 113.8 and 1.68, respectively. The results outperform some existing excellent approaches. This indicates that the proposed model has high accuracy and better robustness, which is suitable for crowd counting and density estimation in various congested scenes. 相似文献
5.
《International Journal of Hydrogen Energy》2021,46(56):28823-28837
In this study, an excellent hydrogen gas sensor based on the WO3–CoO nanohybrids (WCNHs) heterojunction structure has been successfully fabricated. The WCNHs device showed superior sensitivity, admirable selectivity as well as excellent long-term stability for target gas. In particular, the considerable gas sensing response of WCNHs (5:4) towards 100 ppm hydrogen gas (H2) concentration was reached 39, which is superior to that of the outstanding candidates. Especially, the detection limit capability was as low as 311 ppb. The remarkable response of WCNHs (5:4) can mainly be ascribed to appropriate morphology characteristics and the promising p-n heterojunction architecture, resulting in efficient absorbing behavior and beneficial charge carrier transportation. As a Result, the aims of improving Ra (intrinsic resistance) and decreasing Rg (test resistance) have been simultaneously achieved ultimately leading to an impressive response value of WCNHs sensing materials. The present results verified that WCNHs heterojunction structure was an outstanding design to enhance the H2 sensing performance for WO3-based gas sensors. 相似文献
6.
GIS支持下的矿区土壤含水量遥感反演及变化规律 总被引:2,自引:1,他引:2
遥感方法可以开展大范围土壤含水率的连续监测,其技术关键是建立土壤含水率的遥感信息模型.针对矿区采动影响特征,提出了应用归一化植被指数NDVI=0.3作为判别高、低植被覆盖条件的阈值;裸地或低植被覆盖条件(NDVI≤0.3)采用基于热惯量理论的表现热惯量法(ATI)、高植被覆盖条件(NDVI>0.3)采用作物供水指数法(VSWI)来反演土壤含水量.并根据采后"三带"高度和植被覆盖情况,将矿区分为6种不同的研究区域,提出应用MODIS数据和TM/ETM 数据定量反演矿区土壤含水量,进一步提出了在GIS支持下,由非采煤区推算采煤区采矿前的土壤含水量以及分析采矿前后土壤含水量变化规律的理论和方法. 相似文献
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煤田火灾问题存在由来已久,利用遥感技术进行煤火监测正引起广泛关注。为更加精确地圈定乌达煤火的燃烧范围,本文以乌达2000年、2006年和2010年三时期的Landsat TM和ETM 热红外及多光谱遥感影像作为基本信息源,采用温度反演、最优密度分割和地质条件分析,提取各年的煤田热异常信息,再通过ArcGIS空间叠加分析和逻辑分析,研究煤田火灾随时间的动态变化过程。结果圈定了煤田火区的燃烧范围和2000-2010年来煤火变化面积及速率,对于发展煤火理论和乌达煤火的治理皆有一定的理论与实践意义。 相似文献
10.
A new europium complex Eu(tta)3Li(la)based on 1,10-phenanthroline derivative(Li=(2-(3,5-dimethoxyphenyl)-1 H-imidazo[4,5-f][1,10]phenanthroline),tta=2-thenoyItrifluoroacetone)was designed and synthesized.Its structure was characterized by1H and13C NMR,elemental analysis,UV-vis,fluorescence spectra and single crystal X-ray diffraction.The crystal of the complex la belongs to monoclinic system with the space group P21/n.The europium complex la in the solid and in the solution displays the typical emission of Eu(III)ion centered at 612 nm as a result of the electric dipole transition(5D0-?7F2).It exhibits high quantum yield(20.42%),long lifetime(0.29 ms)and good CIE color coordinate(0.67,0.33)in solid.In addition,the complex shows high sensitivity and selectivity towards Al3+and Zn2+in methanol solution which can be attributed to the Al3+/Zn2+cation instead of Eu3+in the complex la.The LODs for Al3+and Zn2+were calculated to be 5.880×10-7and 7.678×10-8mol/L,respectively.Besides,the additions of Al3+and Zn2+express remarkable color changes from red to bright blue and ivory that can be clearly observed by the naked eye respectively. 相似文献