Accurate estimation of the double-bounce scattering fd and surface scattering fs coefficients with Freeman-Durden decomposition is still difficult. This difficulty arises because overestimation of the volume scatterin...Accurate estimation of the double-bounce scattering fd and surface scattering fs coefficients with Freeman-Durden decomposition is still difficult. This difficulty arises because overestimation of the volume scattering energy contribution Pv leads to negative values for fd and fs. A generalized residual model is introduced to estimate fd and fs. The relationship between Pv and the residual model is analyzed. Eigenvalues computed from the residual model must be positive to explain physical scattering mechanisms. The authors employ a new volumetric scattering model to minimize Pv as calculated by several decomposition methods. It is concluded that decreasing Pv can help reduce negative energy. This conclusion is validated using actual polarimetric SAR data.展开更多
Severe acute respiratory syndrome coronavirus-2 (SARS CoV-2) has been a global threat spreading in Sierra Leone, and many studies are being conducted using various Statistical models to predict the probable evolution ...Severe acute respiratory syndrome coronavirus-2 (SARS CoV-2) has been a global threat spreading in Sierra Leone, and many studies are being conducted using various Statistical models to predict the probable evolution of this pandemic. In this paper, we use the autoregressive integrated moving average (ARIMA) model with the aim of forecasting the cumulative confirmed cases of SARS CoV-2 in Sierra Leone. The Akaike Information Criterion (AIC) was applied to the training data as a criterion method to select the best model. In addition, the statistical measure RMSE and MAPE were utilized for testing this data, and the model with the minimum RMSE and MAPE was selected for future forecasting. ARIMA (3, 2, 1) was confirmed to be the optimal model based on the lowest AIC value. This model was then applied to study the trend of SARS CoV-2 from 1st February 2022 to 30th February 2022. The result shows that incidence of SARS CoV-2 from 1st February 2022 to 30th February 2022, increasing growth steep in Sierra Leone (7718.629, 95% confidence limit of 6785.985 - 8651.274).展开更多
针对长江中游城市群洪涝灾害应急转移人口预测中存在的精度瓶颈问题,提出了广义线性模型(generalized linear model,GLM)-空间滞后模型(spatial autoregressive model,SAR)联合预测框架,通过log-link函数与负二项分布解决灾害数据的右...针对长江中游城市群洪涝灾害应急转移人口预测中存在的精度瓶颈问题,提出了广义线性模型(generalized linear model,GLM)-空间滞后模型(spatial autoregressive model,SAR)联合预测框架,通过log-link函数与负二项分布解决灾害数据的右偏分布与过离散问题,构建了以水位超警幅度为核心解释变量的单维度预测模型,并引入空间滞后模型(SAR)量化流域内应急响应的协同效应。基于长江中游三省2019—2023年面板数据的实证结果表明:该模型在跨区域预测中的误差率≤9.2%,较传统线性回归模型降低了8.2个百分点,极端事件的预测误差率压缩至6.7%;揭示了地理异质性对参数的驱动规律,并通过参数迁移模型实现了跨区域适配;通过单维度设计,基层响应效率得到了显著提升,决策链条缩短了4.5 h。研究的创新性体现在“分布修正-空间耦合-动态适配”三重机制,为高波动右偏态灾害数据建模提供了兼具解释力与稳健性的新范式,并为长江中游差异化防灾策略提供了科学支撑。展开更多
We estimate tree heights using polarimetric interferometric synthetic aperture radar(PolInSAR)data constructed by the dual-polarization(dual-pol)SAR data and random volume over the ground(RVoG)model.Considering the Se...We estimate tree heights using polarimetric interferometric synthetic aperture radar(PolInSAR)data constructed by the dual-polarization(dual-pol)SAR data and random volume over the ground(RVoG)model.Considering the Sentinel-1 SAR dual-pol(SVV,vertically transmitted and vertically received and SVH,vertically transmitted and horizontally received)configuration,one notes that S_(HH),the horizontally transmitted and horizontally received scattering element,is unavailable.The S_(HH)data were constructed using the SVH data,and polarimetric SAR(PolSAR)data were obtained.The proposed approach was first verified in simulation with satisfactory results.It was next applied to construct PolInSAR data by a pair of dual-pol Sentinel-1A data at Duke Forest,North Carolina,USA.According to local observations and forest descriptions,the range of estimated tree heights was overall reasonable.Comparing the heights with the ICESat-2 tree heights at 23 sampling locations,relative errors of 5 points were within±30%.Errors of 8 points ranged from 30%to 40%,but errors of the remaining 10 points were>40%.The results should be encouraged as error reduction is possible.For instance,the construction of PolSAR data should not be limited to using SVH,and a combination of SVH and SVV should be explored.Also,an ensemble of tree heights derived from multiple PolInSAR data can be considered since tree heights do not vary much with time frame in months or one season.展开更多
A Z curve-based coordination model of genome sequences for the interaction of the SARS coronavirus (SARS-CoV) with its receptor, angiotensin-converting enzyme 2 (ACE2) is proposed. The model provides a novel, intuitiv...A Z curve-based coordination model of genome sequences for the interaction of the SARS coronavirus (SARS-CoV) with its receptor, angiotensin-converting enzyme 2 (ACE2) is proposed. The model provides a novel, intuitive tool for visualizing and analyzing DNA sequences of SARS. It will be useful to the analysis of SARS-CoV in lab detection. Also, it can be used as a solution to other studies in bioinformatics field.展开更多
由于合成孔径雷达独特的成像机制,现有的深度学习检测算法,难以在精度和速度之间找到良好的平衡。因此针对边缘端应用需求,结合剪枝方法设计了一种更轻量的SAR图像飞机目标检测网络SAERFDnet。其以YOLOv8n模型为基线,主干使用重参数化...由于合成孔径雷达独特的成像机制,现有的深度学习检测算法,难以在精度和速度之间找到良好的平衡。因此针对边缘端应用需求,结合剪枝方法设计了一种更轻量的SAR图像飞机目标检测网络SAERFDnet。其以YOLOv8n模型为基线,主干使用重参数化大核卷积进行特征提取,颈部使用自适应多尺度离散特征融合模块,以较浅的网络深度获得更大的有效感受野。其次,改进网络在检测头分类分支引入可变形卷积,使得网络更关注不同类别目标的几何特征差异,在回归分支引入频率自适应扩张卷积,加强对图像高频区域的目标定位能力。最后,使用了模型剪枝技术获得了更轻量高效的模型。采用3个公开的实测数据集进行实验,在SAR-AIRcraft-1.0数据集上的结果表明,该方法以0.5 M参数量和2 G FLOPS的参数量和计算量达到了96.3%mAP50和72.5%mAP50-95,相比YOLOv8n模型参数量降低83.3%,计算量降低75.3%,同时提高了0.7%mAP50和2.2%mAP50-95的检测精度,对比其他模型检测结果,该方法能在保证检测精度的条件下,有效提升SAR图像飞机目标检测的检测效率。此外,在SADD数据集和高分三号飞机目标数据集上进行了迁移实验,结果均表明该方法具有良好的泛化性和鲁棒性。展开更多
文摘Accurate estimation of the double-bounce scattering fd and surface scattering fs coefficients with Freeman-Durden decomposition is still difficult. This difficulty arises because overestimation of the volume scattering energy contribution Pv leads to negative values for fd and fs. A generalized residual model is introduced to estimate fd and fs. The relationship between Pv and the residual model is analyzed. Eigenvalues computed from the residual model must be positive to explain physical scattering mechanisms. The authors employ a new volumetric scattering model to minimize Pv as calculated by several decomposition methods. It is concluded that decreasing Pv can help reduce negative energy. This conclusion is validated using actual polarimetric SAR data.
文摘Severe acute respiratory syndrome coronavirus-2 (SARS CoV-2) has been a global threat spreading in Sierra Leone, and many studies are being conducted using various Statistical models to predict the probable evolution of this pandemic. In this paper, we use the autoregressive integrated moving average (ARIMA) model with the aim of forecasting the cumulative confirmed cases of SARS CoV-2 in Sierra Leone. The Akaike Information Criterion (AIC) was applied to the training data as a criterion method to select the best model. In addition, the statistical measure RMSE and MAPE were utilized for testing this data, and the model with the minimum RMSE and MAPE was selected for future forecasting. ARIMA (3, 2, 1) was confirmed to be the optimal model based on the lowest AIC value. This model was then applied to study the trend of SARS CoV-2 from 1st February 2022 to 30th February 2022. The result shows that incidence of SARS CoV-2 from 1st February 2022 to 30th February 2022, increasing growth steep in Sierra Leone (7718.629, 95% confidence limit of 6785.985 - 8651.274).
文摘We estimate tree heights using polarimetric interferometric synthetic aperture radar(PolInSAR)data constructed by the dual-polarization(dual-pol)SAR data and random volume over the ground(RVoG)model.Considering the Sentinel-1 SAR dual-pol(SVV,vertically transmitted and vertically received and SVH,vertically transmitted and horizontally received)configuration,one notes that S_(HH),the horizontally transmitted and horizontally received scattering element,is unavailable.The S_(HH)data were constructed using the SVH data,and polarimetric SAR(PolSAR)data were obtained.The proposed approach was first verified in simulation with satisfactory results.It was next applied to construct PolInSAR data by a pair of dual-pol Sentinel-1A data at Duke Forest,North Carolina,USA.According to local observations and forest descriptions,the range of estimated tree heights was overall reasonable.Comparing the heights with the ICESat-2 tree heights at 23 sampling locations,relative errors of 5 points were within±30%.Errors of 8 points ranged from 30%to 40%,but errors of the remaining 10 points were>40%.The results should be encouraged as error reduction is possible.For instance,the construction of PolSAR data should not be limited to using SVH,and a combination of SVH and SVV should be explored.Also,an ensemble of tree heights derived from multiple PolInSAR data can be considered since tree heights do not vary much with time frame in months or one season.
基金The research was supported in part by Doctoral Foundation from National Education Committee.(20030255009),P.R.China.
文摘A Z curve-based coordination model of genome sequences for the interaction of the SARS coronavirus (SARS-CoV) with its receptor, angiotensin-converting enzyme 2 (ACE2) is proposed. The model provides a novel, intuitive tool for visualizing and analyzing DNA sequences of SARS. It will be useful to the analysis of SARS-CoV in lab detection. Also, it can be used as a solution to other studies in bioinformatics field.
文摘由于合成孔径雷达独特的成像机制,现有的深度学习检测算法,难以在精度和速度之间找到良好的平衡。因此针对边缘端应用需求,结合剪枝方法设计了一种更轻量的SAR图像飞机目标检测网络SAERFDnet。其以YOLOv8n模型为基线,主干使用重参数化大核卷积进行特征提取,颈部使用自适应多尺度离散特征融合模块,以较浅的网络深度获得更大的有效感受野。其次,改进网络在检测头分类分支引入可变形卷积,使得网络更关注不同类别目标的几何特征差异,在回归分支引入频率自适应扩张卷积,加强对图像高频区域的目标定位能力。最后,使用了模型剪枝技术获得了更轻量高效的模型。采用3个公开的实测数据集进行实验,在SAR-AIRcraft-1.0数据集上的结果表明,该方法以0.5 M参数量和2 G FLOPS的参数量和计算量达到了96.3%mAP50和72.5%mAP50-95,相比YOLOv8n模型参数量降低83.3%,计算量降低75.3%,同时提高了0.7%mAP50和2.2%mAP50-95的检测精度,对比其他模型检测结果,该方法能在保证检测精度的条件下,有效提升SAR图像飞机目标检测的检测效率。此外,在SADD数据集和高分三号飞机目标数据集上进行了迁移实验,结果均表明该方法具有良好的泛化性和鲁棒性。
