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文章速递Analysis of the Resolution of Crime Using Predictive Modeling 认领
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作者 Keshab R. Dahal Jiba N. Dahal +1 位作者 Kenneth R. Goward Oluremi Abayami 《统计学期刊(英文)》 2020年第3期600-610,共11页
There has been evidence of crime in the US since colonization. In this article, we analyze the crime statistics of San Francisco and its resolution of crime recorded from January to September of the year 2018. We defi... There has been evidence of crime in the US since colonization. In this article, we analyze the crime statistics of San Francisco and its resolution of crime recorded from January to September of the year 2018. We define resolution of crime as a target variable and study its relationship with other variables. We make several classification models to predict resolution of crime using several data mining techniques and suggest the best model for predicting resolution. 展开更多
关键词 Machine Learning Classification Model Comparison Predictive Modeling Resolution of Crime
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文章速递Analytical Case Study on a Dedicated Pigment in Recycling Processes of Polyethylene 认领
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作者 Petra Krystek 《化学工程与科学期刊(英文)》 2020年第3期181-189,共9页
The ability to track & trace materials is a key feature in the entire chain, and it ensures circularity principles. Examples from plastic recycling show the enormous added value that analytical technology can have... The ability to track & trace materials is a key feature in the entire chain, and it ensures circularity principles. Examples from plastic recycling show the enormous added value that analytical technology can have for the circular economy. During polymer production and recycling processes, pigments can be added for different purposes;e.g. as colouring agent of the polymeric product but also as tracer for tracking process development and control in the final recycle products versus possible by-products. An analytical method for tracking the pigment Solvent Blue 15 in input materials, in intermediates as well as in recyclates was developed by tracing and quantifying an indicator metal which is copper (Cu). Therefore, suitable digestion procedures and a quantification method by high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) were developed and used for measuring the polymeric digests. The method was tested on relevant samples from chemical recycling processes. The background concentrations in base/raw material are in the range of 0.05 - 0.1 mg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>kg<span style="font-family:'Verdana, Helvetica, Arial';"><span style="background-color:#FFFFFF;"><sup>-1<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"></span></sup></span></span> Cu. The processing concentrations are in the range of 4.2 to 28 mg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>kg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><sup>-1</sup></span><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"></span></span> Cu, while the pigment starting material (polyethylene, PE) has a concentration of around 50 mg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>kg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><sup>-1</sup></span><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"></span></span> Cu. 展开更多
关键词 Cupper Pigment Solvent Blue Recycled Polyethylene Track & Trace High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICPMS)
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文章速递Study of CdZnTeSe Gamma-Ray Detector under Various Bias Voltages 认领
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作者 Mebougna L. Drabo Stephen U. Egarievwe +4 位作者 Utpal N. Roy Benicia A. Harrison Carmella A. Goree Emmanuel K. Savage Ralph B. James 《材料科学与应用期刊(英文)》 2020年第8期553-559,共7页
Cadmium zinc telluride selenide (CdZnTeSe) is a new semiconductor material for gamma-ray detection and spectroscopy applications at room temperature. It has very high crystal quality compared to similar materials such... Cadmium zinc telluride selenide (CdZnTeSe) is a new semiconductor material for gamma-ray detection and spectroscopy applications at room temperature. It has very high crystal quality compared to similar materials such as cadmium telluride and cadmium zinc telluride. The consistency of peak position in radiation detection devices is important to practical applications. In this paper, we have characterized a CdZnTeSe planar detector for bias voltages in the range of -20 V to -200 V and amplifier shaping time of 2, 3 and 6 μs. The peak position of the 59.6-keV gamma line of <sup>241</sup>Am becomes more stable as the absolute value of the applied voltage increases. The best energy resolution of 8.5% was obtained for the 59.6-keV gamma peak at -160 V bias voltage and 3-μs shaping time. The energy resolution was relatively stable in the -120 V to -200 V range for a 6-μs shaping time. Future work will be focused on the study of the peak position and energy resolution over time. 展开更多
关键词 CdZnTeSe Energy Resolution Energy-Peak Stability Gamma-Ray Spectroscopy Nuclear Detectors
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文章速递Steady-State Analysis of the Distributed Queueing Algorithm in a Single-Channel M2M Network 认领
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作者 Romeo Nibitanga Elijah Mwangi Edward Ndung’u 《电脑和通信(英文)》 2020年第9期28-40,共13页
The Distributed Queuing (DQ) algorithm is predicted as one of the solutions to the issues currently found in IoT networks over the use of Aloha based algorithms. Since recently, the algorithm has been of interest to m... The Distributed Queuing (DQ) algorithm is predicted as one of the solutions to the issues currently found in IoT networks over the use of Aloha based algorithms. Since recently, the algorithm has been of interest to many IoT researchers as a replacement of those Aloha variants for channel access. However, previous works analyzed and evaluated the DQ algorithm without any consideration of the stability of its queues, assuming it is stable for any given number of nodes in the network. In this paper, we define the DQ stability condition in a single-channel M2M environment considering a traffic model of periodic and urgent frames from each node in the network. Besides, a steady-state evaluation of the algorithm’s performance metrics is also presented. In general, the DQ algorithm, when it is stable, was observed not to efficiently use the contention slots for the collision resolution. In a single-channel environment, the DQ algorithm is found to outperform the Aloha based algorithms only in an idle-to-saturation scenario. 展开更多
关键词 Aloha Collision Resolution Distributed Queueing IoT Networks M2M Communications Stability Condition
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基于垂直带谱的南北过渡带1:5万植被类型图遥感制图研究——以太白山为例 认领
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作者 姚永慧 索南东主 张俊瑶 《地理学报:英文版》 SCIE CSCD 2020年第2期267-280,共14页
The compilation of 1:250,000 vegetation type map in the North-South transitional zone and 1:50,000 vegetation type maps in typical mountainous areas is one of the main tasks of Integrated Scientific Investigation of t... The compilation of 1:250,000 vegetation type map in the North-South transitional zone and 1:50,000 vegetation type maps in typical mountainous areas is one of the main tasks of Integrated Scientific Investigation of the North-South Transitional Zone of China.In the past,vegetation type maps were compiled by a large number of ground field surveys.Although the field survey method is accurate,it is not only time-consuming,but also only covers a small area due to the limitations of physical environment conditions.Remote sensing data can make up for the limitation of field survey because of its full coverage.However,there are still some difficulties and bottlenecks in the extraction of remote sensing information of vegetation types,especially in the automatic extraction.As an example of the compilation of 1:50,000 vegetation type map,this paper explores and studies the remote sensing extraction and mapping methods of vegetation type with medium and large scales based on mountain altitudinal belts of Taibai Mountain,using multi-temporal high resolution remote sensing data,ground survey data,previous vegetation type map and forest survey data.The results show that:1)mountain altitudinal belts can effectively support remote sensing classification and mapping of 1:50,000 vegetation type map in mountain areas.Terrain constraint factors with mountain altitudinal belt information can be generated by mountain altitudinal belts and 1:10,000 Digital Surface Model(DSM)data of Taibai Mountain.Combining the terrain constraint factors with multi-temporal and high-resolution remote sensing data,ground survey data and previous small-scale vegetation type map data,the vegetation types at all levels can be extracted effectively.2)The basic remote sensing interpretation and mapping process for typical mountains is interpretation of vegetation type-groups→interpretation of vegetation formation groups,formations and subformations→interpretation and classification of vegetation types&subtypes,which is a combination method of top-down m 展开更多
关键词 vegetation type map high resolution REMOTE SENSING data MOUNTAIN altitudinal BELTS REMOTE SENSING interpretation Taibai MOUNTAIN
WRF Simulations of Extreme Rainfall over Uganda’s Lake Victoria Basin: Sensitivity to Parameterization, Model Resolution and Domain Size 认领
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作者 Ronald Opio Geoffrey Sabiiti +2 位作者 Alex Nimusiima Isaac Mugume Julianne Sansa-Otim 《地球科学和环境保护期刊(英文)》 2020年第4期18-31,共14页
Rainfall extremes have strong connotations to socio-economic activities and human well-being in Uganda’s Lake Victoria Basin (LVB). Reliable prediction and dissemination of extreme rainfall events are therefore of pa... Rainfall extremes have strong connotations to socio-economic activities and human well-being in Uganda’s Lake Victoria Basin (LVB). Reliable prediction and dissemination of extreme rainfall events are therefore of paramount importance to the region’s development agenda. The main objective of this study was to contribute to the prediction of rainfall extremes over this region using a numerical modelling approach. The Weather Research and Forecasting (WRF) model was used to simulate a 20-day period of extremely heavy rainfall that was observed in the March to May season of 2008. The underlying interest was to investigate the performance of different combinations of cumulus and microphysical parameterization along with the model grid resolution and domain size. The model output was validated against rainfall observations from the Tropical Rainfall Measuring Mission (TRMM) using 5 metrics;the rainfall distribution, root mean square error, mean error, probability of detection and false alarm ratio. The results showed that the model was able to simulate extreme rainfall and the most satisfactory skill was obtained with a model setup using the Grell 3D cumulus scheme combined with the SBU_YLin microphysical scheme. This study concludes that the WRF model can be used for simulating extreme rainfall over western LVB. In the other 2 regions, central and eastern LVB, its performance is limited by failure to simulate nocturnal rainfall. Furthermore, increasing the model grid resolution showed good potential for improving the model simulation especially when a large domain is used. 展开更多
关键词 EXTREME RAINFALL WRF PARAMETERIZATION Model RESOLUTION DOMAIN Size
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浅谈CR检测中的分辨力与分辨率 认领
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作者 陈小明 石爱玲 +2 位作者 张军辉 吴志波 谭云华 《无损检测》 2020年第2期17-20,31共5页
现行CR检测标准中涉及多个有关分辨力和分辨率的术语,如分辨力、分辨率、图像分辨率、系统分辨率和扫描分辨率等,容易混淆。通过理论分析、试验和实际应用几个方面入手,阐明其间的内在联系和区别,以为从业人员学习与应用CR检测技术提供... 现行CR检测标准中涉及多个有关分辨力和分辨率的术语,如分辨力、分辨率、图像分辨率、系统分辨率和扫描分辨率等,容易混淆。通过理论分析、试验和实际应用几个方面入手,阐明其间的内在联系和区别,以为从业人员学习与应用CR检测技术提供帮助。 展开更多
关键词 CR检测 数字图像 分辨力 分辨率
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Utilization of Extrinsic Fabry-Perot Interferometers with Spectral Interferometric Interrogation for Microdisplacement Measurement 认领
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作者 Leonid Liokumovich Aleksandr Markvart Nikolai Ushakov 《电子科技学刊:英文版》 CAS CSCD 2020年第1期59-75,共17页
The paper presents a number of signal processing approaches for the spectral interferometric interrogation of extrinsic Fabry-Perot interferometers(EFPIs). The analysis of attainable microdisplacement resolution is pe... The paper presents a number of signal processing approaches for the spectral interferometric interrogation of extrinsic Fabry-Perot interferometers(EFPIs). The analysis of attainable microdisplacement resolution is performed and the analytical equations describing the dependence of resolution on parameters of the interrogation setup are derived. The efficiency of the proposed signal processing approaches and the validity of analytical derivations are supported by experiments. The proposed approaches allow the interrogation of up to four multiplexed sensors with attained resolution between 30 pm and 80 pm, up to three times improvement of microdisplacement resolution of a single sensor by means of using the reference interferometer and noisecompensating approach, and ability to register signals with frequencies up to 1 kHz in the case of 1 Hz spectrum acquisition rate. The proposed approaches can be used for various applications, including biomedical, industrial inspection, and others, amongst the microdisplacement measurement. 展开更多
关键词 Absolute MEASUREMENT dynamic MEASUREMENT Fabry-Perot interferometer LEAST-SQUARES methods optical fiber sensors RESOLUTION analysis RESOLUTION enhancement sensor multiplexing SPECTRAL interferometry
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Thermal behavior of materials in laser-assisted extreme manufacturing:Raman-based novel characterization 认领
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作者 Ridong Wang Shen Xu +1 位作者 Yanan Yue Xinwei Wang 《极端制造(英文)》 2020年第3期86-102,共17页
Laser-assisted manufacturing(LAM)is a technique that performs machining of materials using a laser heating process.During the process,temperatures can rise above over 2000°C.As a result,it is crucial to explore t... Laser-assisted manufacturing(LAM)is a technique that performs machining of materials using a laser heating process.During the process,temperatures can rise above over 2000°C.As a result,it is crucial to explore the thermal behavior of materials under such high temperatures to understand the physics behind LAM and provide feedback for manufacturing optimization.Raman spectroscopy,which is widely used for structure characterization,can provide a novel way to measure temperature during LAM.In this review,we discuss the mechanism of Raman-based temperature probing,its calibration,and sources of uncertainty/error,and how to control them.We critically review the Raman-based temperature measurement considering the spatial resolution under near-field optical heating and surface structure-induced asymmetries.As another critical aspect of Raman-based temperature measurement,temporal resolution is also reviewed to cover various ways of realizing ultrafast thermal probing.We conclude with a detailed outlook on Raman-based temperature probing in LAM and issues that need special attention. 展开更多
关键词 Raman spectroscopy temperature response spatial resolution temporal resolution ultrafast characterization
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文章速递Diffraction-Limited Imaging with a Graphene Metalens 认领
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作者 李雪岩 林瀚 +1 位作者 赵跃进 贾宝华 《中国物理快报:英文版》 SCIE CAS CSCD 2020年第10期54-60,共7页
Planar graphene metalens has demonstrated advantages of ultrathin thickness(200 nm),high focusing resolution(343 nm)and efficiency(>32%)and robust mechanical strength and flexibility.However,diffraction-limited ima... Planar graphene metalens has demonstrated advantages of ultrathin thickness(200 nm),high focusing resolution(343 nm)and efficiency(>32%)and robust mechanical strength and flexibility.However,diffraction-limited imaging with such a graphene metalens has not been realized,which holds the key to designing practical integrated imaging systems.In this work,the imaging rule for graphene metalenses is first derived and theoretically verified by using the Rayleigh-Sommerfeld diffraction theory to simulate the imaging performance of the 200 nm ultrathin graphene metalens.The imaging rule is applicable to graphene metalenses in different immersion media,including water or oil.Based on the theoretical prediction,high-resolution imaging using the graphene metalens with diffraction-limited resolution(500 nm)is demonstrated for the first time.This work opens the possibility for graphene metalenses to be applied in particle tracking,microfluidic chips and biomedical devices. 展开更多
关键词 resolution holds rule
文章速递土壤污染监测卫星遥感应用需求与载荷配置初探 认领
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作者 赵少华 朱军 +7 位作者 白志杰 屈然 刘思含 王玉 熊文成 尹欢 孟庆岩 田金雨 《环境与可持续发展》 2020年第5期114-117,共4页
本文针对国家土壤污染防治工作的严峻形势和迫切需要,总结分析国内外土壤污染遥感监测的研究进展,分析土壤重金属污染的敏感波段,梳理我国土壤污染遥感监测工作任务需求,设计土壤污染遥感监测应用的技术指标和土壤污染监测卫星载荷配置... 本文针对国家土壤污染防治工作的严峻形势和迫切需要,总结分析国内外土壤污染遥感监测的研究进展,分析土壤重金属污染的敏感波段,梳理我国土壤污染遥感监测工作任务需求,设计土壤污染遥感监测应用的技术指标和土壤污染监测卫星载荷配置需求,提出加紧开展土壤污染定量化遥感监测技术研究、研发土壤污染监测卫星等建议,以支撑土壤污染防治行动计划目标的实现,为早日打赢净土保卫战提供支撑。 展开更多
关键词 重金属 高光谱 分辨率
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文章速递增强重建单帧字符图像分辨率的方法研究 认领
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作者 徐秀妮 胡紫微 《延边大学学报:自然科学版》 CAS 2020年第3期221-225,共5页
针对传统单帧字符图像重建方法存在分辨率较低的问题,提出了一种增强重建单帧字符图像分辨率的方法.首先,构建单帧字符图像重建的三维轮廓特征检测模型;其次,采用边缘轮廓分割法提取单帧字符图像的三维细节特征,并结合小波多尺度分解法... 针对传统单帧字符图像重建方法存在分辨率较低的问题,提出了一种增强重建单帧字符图像分辨率的方法.首先,构建单帧字符图像重建的三维轮廓特征检测模型;其次,采用边缘轮廓分割法提取单帧字符图像的三维细节特征,并结合小波多尺度分解法实现尺度特征分离;然后,采用小波阈值去噪法对图像进行滤波降噪,并使用非负邻域嵌入的方法增强小波阈值辨识度,以此构建增强重建单帧字符图像分辨率的模型,完成单帧字符图像的高分辨率重建.最后,以Matlab 2013软件为实验平台进行仿真测试显示,采用本文方法得到的重建图像的清晰度明显优于文献[2-4]方法,且平均峰值信噪比(26 dB)也显著优于文献[2](15 dB)、文献[3](10 dB)、文献[4](16 dB)的方法.因此,本文方法在车牌号码识别、基于内容的图像检索、文档图像分析等领域中具有较好的应用价值. 展开更多
关键词 单帧字符图像 三维轮廓 边缘轮廓 分辨率
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冲击回波声频法用于铁路隧道衬砌质量检测 认领
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作者 姜勇 吴佳晔 +1 位作者 马永强 邓立 《铁道建筑》 北大核心 2020年第5期6-10,共5页
研究开发了冲击回波声频法这一新型无损检测方法,通过非接触式拾取冲击弹性波信号和高分辨力频谱分析,大大提高了对衬砌厚度、缺陷等的识别能力.百余座铁路隧道检测的实际应用及与地质雷达法等的对比验证结果表明,冲击回波声频法具有测... 研究开发了冲击回波声频法这一新型无损检测方法,通过非接触式拾取冲击弹性波信号和高分辨力频谱分析,大大提高了对衬砌厚度、缺陷等的识别能力.百余座铁路隧道检测的实际应用及与地质雷达法等的对比验证结果表明,冲击回波声频法具有测试精度高、分辨力强、测试效率较高等特点,非常适合于铁路隧道衬砌质量的检测. 展开更多
关键词 冲击回波声频法 隧道衬砌 无损检测 衬砌厚度 衬砌缺陷 分辨力
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Guided filter-based multi-scale super-resolution reconstruction 认领
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作者 Xiaomei Feng Jinjiang Li Zhen Hua 《智能技术学报》 2020年第2期128-140,共13页
The learning-based super-resolution reconstruction method inputs a low-resolution image into a network,and learns a non-linear mapping relationship between low-resolution and high-resolution through the network.In thi... The learning-based super-resolution reconstruction method inputs a low-resolution image into a network,and learns a non-linear mapping relationship between low-resolution and high-resolution through the network.In this study,the multi-scale super-resolution reconstruction network is used to fuse the effective features of different scale images,and the non-linear mapping between low resolution and high resolution is studied from coarse to fine to realise the end-to-end super-resolution reconstruction task.The loss of some features of the low-resolution image will negatively affect the quality of the reconstructed image.To solve the problem of incomplete image features in low-resolution,this study adopts the multi-scale super-resolution reconstruction method based on guided image filtering.The high-resolution image reconstructed by the multi-scale super-resolution network and the real high-resolution image are merged by the guide image filter to generate a new image,and the newly generated image is used for secondary training of the multi-scale super-resolution reconstruction network.The newly generated image effectively compensates for the details and texture information lost in the low-resolution image,thereby improving the effect of the super-resolution reconstructed image.Compared with the existing super-resolution reconstruction scheme,the accuracy and speed of super-resolution reconstruction are improved. 展开更多
关键词 RESOLUTION IMAGE NETWORK
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IMPACT OF VERTICAL RESOLUTION, MODEL TOP AND DATA ASSIMILATION ON WEATHER FORECASTING——A CASE STUDY 认领
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作者 邵旻 张宇 徐建军 《热带气象学报:英文版》 SCIE 2020年第1期71-81,共11页
The impacts of stratospheric initial conditions and vertical resolution on the stratosphere by raising the model top,refining the vertical resolution,and the assimilation of operationally available observations,includ... The impacts of stratospheric initial conditions and vertical resolution on the stratosphere by raising the model top,refining the vertical resolution,and the assimilation of operationally available observations,including conventional and satellite observations,on continental U.S.winter short-range weather forecasting,were investigated in this study.The initial and predicted wind and temperature profiles were analyzed against conventional observations.Generally,the initial wind and temperature bias profiles were better adjusted when a higher model top and refined vertical resolution were used.Negative impacts were also observed in both the initial wind and temperature profiles,over the lower troposphere.Different from the results by only raising the model top,the assimilation of operationally available observations led to significant improvements in both the troposphere and stratosphere initial conditions when a higher top was used.Predictions made with the adjusted stratospheric initial conditions and refined vertical resolutions showed generally better forecasting skill.The major improvements caused by raising the model top with refined vertical resolution,as well as those caused by data assimilation,were in both cases located in the tropopause and lower stratosphere.Negative impacts were also observed in the predicted near surface wind and lower-tropospheric temperature.These negative impacts were related to the uncertainties caused by more stratospheric information,as well as to some physical processes.A case study shows that when we raise the model top,put more vertical layers in stratosphere and apply data assimilation,the precipitation scores can be slightly improved.However,more analysis is needed due to uncertainties brought by data assimilation. 展开更多
关键词 WRF model vertical resolution model top data assimilation weather forecast
Cross-cumulant enhanced radiality nanoscopy for multicolor superresolution subcellular imaging 认领
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作者 ZHIPING ZENG JING MA CANHUA Xu 《光子学研究:英文版》 SCIE EI CSCD 2020年第6期893-898,共6页
Fluorescence fuctuation-based superresolution techniques can achieve fast superresolution imaging on a cost-effective wide-field platform at a low light level with reduced phototoxicity.However,the current methods exh... Fluorescence fuctuation-based superresolution techniques can achieve fast superresolution imaging on a cost-effective wide-field platform at a low light level with reduced phototoxicity.However,the current methods exhibit certain imaging deficiencies that misinterpret nanoscale features reconstructed from fluctuating image scquences,thus degrading the superresolution imaging quality and performance.Here we propose Cross-cumulant enhanced radiality nanoscopy(CERN),which employs cross cumulant analysis in tandem with radiality processing.We demonstrated that CERN can significantly improve the spatial resolution at a low light level while eliminating the misinterpretations of nanoscale features of the existing fluctuation-based superresolution methods.In the experiment,we further verified the superior performance of CERN over the current methods through performing multicolor superresolution imaging of subcellular microtubule networks and clathrin-coated pits as well as the high-precision reconstruction of densely packed RNA transcripts. 展开更多
关键词 RADIAL RESOLUTION packed
基于损失函数的采样策略研究 认领
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作者 纪文昕 赵雷 张晓林 《信息通信》 2020年第5期5-9,共5页
使用ADC芯片进行数据转换时,可在过采样条件下用算术平均滤波法降噪,但该算法在噪声RMS值可变系统中难以兼顾效率和降噪效果。基于损失函数对算术平均滤波法做出了改进,将平均次数与噪声RMS和分辨率(信噪比)相对应,再根据分辨率(信噪比... 使用ADC芯片进行数据转换时,可在过采样条件下用算术平均滤波法降噪,但该算法在噪声RMS值可变系统中难以兼顾效率和降噪效果。基于损失函数对算术平均滤波法做出了改进,将平均次数与噪声RMS和分辨率(信噪比)相对应,再根据分辨率(信噪比)要求,对不同的噪声RMS值(信噪比)使用不同的过采样次数。理论分析和实测结果表明,该方法可在更大噪声RMS值变化范围内获得更好的降噪结果和更高的采样效率。 展开更多
关键词 损失函数 采样策略 分辨率
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VHF波段星载SAR系统电离层效应仿真研究 认领
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作者 姚佰栋 时晶晶 +2 位作者 盛磊 赵宁 葛家龙 《空军预警学院学报》 2020年第2期84-87,共4页
为研究VHF波段星载合成孔径雷达(SAR)系统,分析了雷达中心频率、信号带宽、电离层总电子含量(TEC)以及闪烁强度等因素对于VHF波段星载SAR成像的影响,并进行了仿真研究.仿真结果表明,在空间电离层中传播时,VHF波段星载SAR的距离向分辨率... 为研究VHF波段星载合成孔径雷达(SAR)系统,分析了雷达中心频率、信号带宽、电离层总电子含量(TEC)以及闪烁强度等因素对于VHF波段星载SAR成像的影响,并进行了仿真研究.仿真结果表明,在空间电离层中传播时,VHF波段星载SAR的距离向分辨率与雷达中心频率、信号带宽以及传播路径上的电离层TEC大小密切相关,同时由于时延的影响,还会导致SAR距离向图像发生移位,造成定位精度下降;方位向分辨率受闪烁效应影响严重,当处于弱闪烁或中等闪烁时,旁瓣抬升明显,且产生微小的移位,当处于强闪烁时,方位向分辨率明显降低,甚至无法成像. 展开更多
关键词 电离层 VHF波段 星载合成孔径雷达 分辨率 电离层总电子含量
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Improved spatial filtering velocimetry and its application in granular flow measurement 认领
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作者 孔平 王必得 +2 位作者 王蓬 Zivkovic V 张建青 《中国物理B:英文版》 SCIE EI CAS CSCD 2020年第7期300-307,共8页
Spatial filtering velocimetry(SFV)has the advantages of simple structure,good stability,and wide applications.However,the traditional linear CCD-based SFV method requires an accurate angle between the direction of lin... Spatial filtering velocimetry(SFV)has the advantages of simple structure,good stability,and wide applications.However,the traditional linear CCD-based SFV method requires an accurate angle between the direction of linear CCD and the direction of moving object,so it is not suitable for measuring a complex flow field or two-dimensional speed in a granular media.In this paper,a new extension of spatial filtering method(SFM)based on high speed array CCD camera is proposed as simple and effective technique for measuring two-dimensional speed field of granular media.In particular,we analyzed the resolution and range of array CCD-based SFV so that the reader can clarify the application scene of this method.This method has a particular advantage for using orthogonal measurement to avoid the angle measurement,which were problematic when using linear CCD to measure the movement.Finally,the end-wall effects of the granular flow in rotating drum is studied with different experimental conditions by using this improved technique. 展开更多
关键词 spatial filtering velocimetry array CCD end-wall effects RESOLUTION
全球250 m反照率产品算法及验证 认领
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作者 陆彦蓉 刘强 +4 位作者 李霞 李秀红 刘璐 肖洒 孙美莹 《地球信息科学学报》 CSCD 北大核心 2020年第2期328-335,共8页
反照率是反映地表能量平衡的重要参数之一,也被运用于全球变化与天气预测研究中。为了更好地获取反照率产品,学者们在不断地更新反照率产品和提出新算法。本文主要是在1 km分辨率的全球陆表特征参量(GLASS)反照率产品基础上进一步开发25... 反照率是反映地表能量平衡的重要参数之一,也被运用于全球变化与天气预测研究中。为了更好地获取反照率产品,学者们在不断地更新反照率产品和提出新算法。本文主要是在1 km分辨率的全球陆表特征参量(GLASS)反照率产品基础上进一步开发250 m反照率产品。算法思路是利用中分辨率成像光谱仪(MODIS)传感器的250 m分辨率波段提供纹理信息,利用成熟的GLASS 1 km反照率产品提供均值信息,进行数据融合,实现GLASS 1 km反照率产品的降尺度。相比于GLASS 1km反照率产品,250 m产品首先展现出更为丰富的空间细节信息,并且在与地面站点观测数据(北美地区站点数据)直接对比中显示出稍高的验证精度,GLASS 1 km产品的验证精度为0.0257,而250 m产品验证精度0.0235。最后,以北京市为例,基于2003-2013年的产品分析了北京市周边反照率及其变化趋势的空间分布,可以看到250 m反照率产品视觉效果更好,相比于1 km产品能够揭示反照率变化趋势的更多空间细节信息。分析表明,在北京城市化进程中,由于加大了城市绿化,主城区反照率总体呈降低趋势。 展开更多
关键词 地表反照率 GLASS MODIS 算法 验证 分辨率 空间细节
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