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纳米氧化镁/环氧树脂复合电介质高温介电响应特性的研究
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作者 肖异瑶 周求宽 +4 位作者 晏年平 王子悦 武康宁 李欢 李建英 《绝缘材料》 CAS 北大核心 2017年第4期36-41,共6页
针对纳米氧化镁/环氧树脂复合电介质的高温介电响应特性展开研究,测试了其热失重曲线和在120~200℃的宽频介电谱。实验结果表明:复合介质的最大热失重速率随着纳米氧化镁掺杂量的增加先上升后下降,并在掺杂量为2%时达到最大值;复合介质... 针对纳米氧化镁/环氧树脂复合电介质的高温介电响应特性展开研究,测试了其热失重曲线和在120~200℃的宽频介电谱。实验结果表明:复合介质的最大热失重速率随着纳米氧化镁掺杂量的增加先上升后下降,并在掺杂量为2%时达到最大值;复合介质工频下的相对介电常数随掺杂量的变化规律与最大热失重速率类似,并在不同的温度区间出现了两个松弛过程,分别对应热离子极化导致的δ松弛和偶极子转向极化导致的α松弛。通过模量谱计算发现,掺杂0.1%的纳米氧化镁导致载流子跃迁的平均势垒升高,随着掺杂量的进一步增加,平均势垒开始降低;而转向极化的活化能则在掺杂量为2%时达到最低。纳米粒子和环氧树脂基体之间形成的交互区是影响高温介电性能的主要原因。 展开更多
关键词 纳米氧化镁 环氧树脂 热失重特性 高温介电响应 复合电介质
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Constructing an Extensible Building Damage Dataset via Semi-supervised Fine-Tuning across 12 Natural Disasters
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作者 Zeyu Wang Chuyi Wu +1 位作者 Feng Zhang Junshi Xia 《Journal of Remote Sensing》 2025年第1期377-396,共20页
Post-disaster building damage assessment(BDA)is vital for emergency response.Deep learning(DL)models are increasingly being applied to achieve quick and automatic BDA on disaster remote sensing imagery,and their perfo... Post-disaster building damage assessment(BDA)is vital for emergency response.Deep learning(DL)models are increasingly being applied to achieve quick and automatic BDA on disaster remote sensing imagery,and their performance largely relies on the knowledge base offered by the dataset.However,constructing a BDA dataset requires intensive expert labeling work and a massive time,leading to a substantial lag in dataset enrichment and model development in the current research field.To address this,this paper introduces a new multidisaster BDA benchmark,the extensible building damage(EBD)dataset,which includes over 18,000 pre-and post-disaster image pairs from 12 recent disaster events,covering over 175,000 building annotations with 4-level damage labels.Unlike previous BDA datasets,EBD follows a semiautomatic labeling workflow and has reduced construction time by 80% compared to full manual labeling.In this process,the DL model served as the machine expert to perform automatic labeling.It was pretrained on the xView2 building damage dataset and then transferred to each new disaster scenario via semi-supervised fine-tuning(SS-FT).SS-FT not only leverages a few labeled samples for supervised fine-tuning but also incorporates both labeled and unlabeled samples into pixel-level contrastive learning.Results demonstrate that the DL model has considerably improved annotation performance under SS-FT.A series of analyses have proven EBD’s building damage feature diversity,practical value in emergency mapping,and knowledge enrichment to the existing benchmark.EBD advances data renewal for natural disaster scenarios and supports the application of artificial intelligence in emergency response efforts. 展开更多
关键词 knowledge base expert labeling emergency responsedeep extensible building damage dataset dataset enrichment disaster remote sensing imageryand semi supervised fine tuning model development
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