简介:摘 要:通过主动遥感的SAR雷达数据与被动遥感的多光谱遥感数据进行水体信息提取已成为重要的研究热点之一。本文将借助Sentinel-1和Sentinel-2的雷达数据与多光谱数据进行影像融合,并利用随机森林机器学习方法进行渭河段水体信息的提取。
简介:摘要:本文基于Sentinel-2数据,选取中国桂林市灵川县潭下镇为研究区,通过比较NDVI和RENDVI指数,发现RENDVI在地物识别上更有效。研究还涵盖了多种分类方法,包括支持向量机和神经网络,发现这两者在分类精度上较高,但支持向量机因其理论基础和泛化能力,在小样本情况下更为适用。本研究成果为桂林柑橘种植提供了科学的精准估产依据。
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简介:摘要:Sentinel影像的高分辨率和海量数据为应用提供了广阔的空间。然而,由于大气散射和吸收对遥感图像质量的影响,遥感图像在实际应用中经常受到大气干扰。基于此,该文提出了一种基于Python的Sentinel影像大气校正方法。首先,采用6S模型对大气参数进行反演,然后对影像进行辐射校正。校正后影像光谱曲线与地面实测光谱曲线的变化趋势一致,具有较高的拟合度。模型大气校正的结果具有较强的相关性和较高的精度。实验结果表明,该方法能够有效地降低Sentinel影像的大气干扰,提高遥感图像的质量和信度。
简介:AbstractBackground:Methylene blue is the most commonly used tracer for sentinel lymph node (SLN) biopsy (SLNB) in China. This study aimed to investigate the feasibility of clinical application of SLNB using methylene blue dye (MBD) for early breast cancer and the prognosis of patients with different SLN and non-SLN statuses.Methods:We retrospectively analyzed the clinicopathological data of patients with early breast cancer treated at the Peking University First Hospital between 2013 and 2018. We calculated the SLN identification rate (IR) in SLNB with MBD and the false-negative rate (FNR), and analyzed the prognosis of patients with different SLN and non-SLN statuses using Kaplan-Meier curves.Results:Between January 2013 and December 2018, 1603 patients with early breast cancer underwent SLNB with MBD. The SLN IR was 95.8% (1536/1603). Two SLNs (median) were detected per patient. There were significant differences in FNR between patients with SLN micrometastasis and macrometastasis (19.0% vs. 4.5%, χ2 = 12.771, P < 0.001). Chi-square test showed that there were significant differences in SLN successful detection rates among patients with different vascular tumor embolism status (96.3% vs. 90.8%, χ2 = 9.013, P = 0.003) and tumor (T) stages (96.6% vs. 94.1%, χ2 = 5.189, P = 0.023). Multivariate analysis showed that vascular tumor embolism was the only independent factor for SLN successful detection (odds ratio: 0.440, 95% confidence interval: 0.224-0.862, P = 0.017). Survival analysis showed a significant difference in disease-free survival (DFS) between patients with non-SLN metastasis and patients without non-SLN metastasis (P = 0.006).Conclusion:Our single-center data show that, as a commonly used tracer in SLNB in China, MBD has an acceptable SLN IR and a low FNR in frozen sections. This finding is consistent with reports of dual tracer-guided SLNB. Positive SLNs with non-SLN metastasis are associated with DFS.
简介:摘要: 基于北京地区29景2018年1月3日至2018年12月29日的Sentinel-1数据,利用SARScape软件采用PS-InSAR技术获取地表沉降信息,获取的沉降成果精度可以达到毫米级别。对实验结果分析得出 :(1)北京市三环内区域内沉降差异性特征明显,而且形状大小不一;(2)西城区沉降部分地区出现小面积的沉降,沉降区域多为高层建筑与地下设施密集;(3)东、西城区地层都比较稳定,均未出现大面积沉降,其最大沉降速率为-5.863mm/y。
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简介:Objective:Thisrandomizedstudyaimedtocomparetheclinicalefficacybetweenthenoveldualtracercomposedofindocyaninegreen(ICG)andbluedye(BD)andtheconventionaldualtracercomposedofradioisotopeandBDforsentinellymphnode(SLN)mappinginpatientswithbreastcancer.Methods:Thisstudyenrolled471clinicallylymphnode-negativepatientswithprimarybreastcancer.Allpatientsunderwentmastectomy,andthoseundergoingsentinellymphnodebiopsy(SLNB)wererandomizedtoreceivebluedyeplusradioisotope(RBgroup)orBDplusICG(IBgroup).ThedetectionperformancesonSLNidentificationrate,positiveSLNcounts,detectionsensitivity,andfalse-negativeratewerecomparedbetweenthetwogroups.Results:IntheIBgroup,97%(194/200)ofthepatientswhounderwenttheICGandBDdualtracerinjectionshowedfluorescentpositivelymphaticvesselswithin2–5min.TheidentificationrateofSLNswascomparablebetweentheIBgroup(99.0%,198/200)andtheRBgroup(99.6%,270/271)(P=0.79).NosignificantdifferenceswereobservedintheidentificationrateofmetastaticSLNs(22.5%vs.22.9%,P>0.05,RBgroupvs.IBgroup,thesamebelow),positiveSLNcounts(3.72±2.28vs.3.91±2.13,P>0.05),positivemetastaticSLNcounts(0.38±0.84vs.0.34±0.78,P>0.05),SLNBdetectionsensitivity(94.4%vs.92.5%,P>0.05),orfalse-negativerate(5.6%vs.7.5%,P>0.05)betweenthetwogroups.Conclusions:ICGcanbeusedasapromisingalternativetracerforradioisotopeinSLNmapping,andwhenitiscombinedwithBDinlymphangiography,itofferscomparabledetectionsensitivitycomparedtotheconventionallymphaticmappingstrategiesthatarewidelyusedinclinicalpractice.
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简介:【摘要】:集体备课活动是现代教学中不可或缺的重要内容,说课是集体备课中的重要环节,通过有效措施提高教师说课水平,达到提升集体备课效果的目的,从而整体提高课堂教学质量。
简介:二次根式(a~2)~(1|2)和((a~2)~(1|2))有什么区别吗?主要表现在下面三个方面:1.读法不同.(a~2)~(1|2)读作根号a的平方,而((a~2)~(1|2))读作括号根号a括号的平方.2.表示的意义不同.(a~2)~(1|2)是求a~2。的算术平方根.((a~2)~(1|2))求的是a的算术平方根的平方.一个表示求一