本文针对长基线(long baseline,LBL)声学定位系统中声信标几何构型优化问题,系统分析了克拉默-拉奥下界(Cramer-Rao lower bound,CRLB)、Fisher信息矩阵(Fisher information matrix,FIM)和几何精度因子(geometric dilution of precision...本文针对长基线(long baseline,LBL)声学定位系统中声信标几何构型优化问题,系统分析了克拉默-拉奥下界(Cramer-Rao lower bound,CRLB)、Fisher信息矩阵(Fisher information matrix,FIM)和几何精度因子(geometric dilution of precision,GDOP)三种评价因子的性能特征及应用场景.与雷达/卫星定位不同,水声定位受复杂海洋环境影响显著,本文重点研究了三种评价因子在300 m×300 m监测区域内的应用差异及其在水声环境中的特殊性.结果表明:水声定位受声信标几何构型的影响,导致定位误差模型更为复杂,而CRLB能够更敏感地反映该因素对理论误差下界的影响.FIM在水下定位应用中需结合系统构型分析信息量分布,避免几何构型缺陷导致的信息不均衡问题.几何精度因子(geometric dilution of precision,GDOP)的无量纲特性可直观体现声信标空间分布对定位误差的几何放大效应.本文以此提出多指标联合评估策略:优先采用GDOP进行构型筛选,结合CRLB验证理论极限精度,辅以FIM分析信息量分布特性.弥补了单一指标在水声复杂场景下的局限性.展开更多
Drug-eluting magnesium(Mg)alloy stents have a slower degradation rate and lower restenosis rate compared with uncoated stents,demonstrating good clinical efficacy.However,the release of anti-hyperplasia drugs from coa...Drug-eluting magnesium(Mg)alloy stents have a slower degradation rate and lower restenosis rate compared with uncoated stents,demonstrating good clinical efficacy.However,the release of anti-hyperplasia drugs from coatings delays endothelial tissue repair,thus leading to late stent thrombosis.To address these issues,a dual self-healed coating with various biological properties was fabricated on magnesium fluoride/polydopamine(MgF_(2)/PDA)-treated Mg alloys by spraying-assisted layer-by-layer(LBL)self-assembly of chitosan(CS),gallic acid(GA),and 3-aminobenzeneboronic acid-modified hyaluronic acid(HA-ABBA).The LBL coating,approximately 1.50μm thick,exhibited a uniform morphology with good adhesion strength(~1065 mN).The annual corrosion rate(Pi)of LBL samples was~1400 times slower than that of the Mg substrate,due to the physical barrier function provided by MgF_(2)/PDA layers and the dual self-healed ability of LBL layers.The rapid self-healing ability(with a healing period of~4 h under dynamic/static conditions)resulted from the synergistic interplay between the recombination of diverse chemical bonds within the LBL coating and the coordination of LBL-released GA with Mg2+,as corroborated by computer simulations.Compared with the drug-eluting coatings,the LBL sample demonstrated substantial advantages in anti-oxidation,anti-denaturation of fibrinogen,anti-platelet adhesion,anti-inflammation,anti-hyperplasia,and promoted-endothelialization.These benefits effectively address the limitations associated with drug-eluting coatings.展开更多
文摘本文针对长基线(long baseline,LBL)声学定位系统中声信标几何构型优化问题,系统分析了克拉默-拉奥下界(Cramer-Rao lower bound,CRLB)、Fisher信息矩阵(Fisher information matrix,FIM)和几何精度因子(geometric dilution of precision,GDOP)三种评价因子的性能特征及应用场景.与雷达/卫星定位不同,水声定位受复杂海洋环境影响显著,本文重点研究了三种评价因子在300 m×300 m监测区域内的应用差异及其在水声环境中的特殊性.结果表明:水声定位受声信标几何构型的影响,导致定位误差模型更为复杂,而CRLB能够更敏感地反映该因素对理论误差下界的影响.FIM在水下定位应用中需结合系统构型分析信息量分布,避免几何构型缺陷导致的信息不均衡问题.几何精度因子(geometric dilution of precision,GDOP)的无量纲特性可直观体现声信标空间分布对定位误差的几何放大效应.本文以此提出多指标联合评估策略:优先采用GDOP进行构型筛选,结合CRLB验证理论极限精度,辅以FIM分析信息量分布特性.弥补了单一指标在水声复杂场景下的局限性.
基金supported by the National Key Research and Development Program of China(No.2021YFC2400703)the Key Scientific and Technological Research Projects in Henan Province(Nos.232102311155 and 232102230106)Zhengzhou University Major Project Cultivation Special Project(No.125-32214076).
文摘Drug-eluting magnesium(Mg)alloy stents have a slower degradation rate and lower restenosis rate compared with uncoated stents,demonstrating good clinical efficacy.However,the release of anti-hyperplasia drugs from coatings delays endothelial tissue repair,thus leading to late stent thrombosis.To address these issues,a dual self-healed coating with various biological properties was fabricated on magnesium fluoride/polydopamine(MgF_(2)/PDA)-treated Mg alloys by spraying-assisted layer-by-layer(LBL)self-assembly of chitosan(CS),gallic acid(GA),and 3-aminobenzeneboronic acid-modified hyaluronic acid(HA-ABBA).The LBL coating,approximately 1.50μm thick,exhibited a uniform morphology with good adhesion strength(~1065 mN).The annual corrosion rate(Pi)of LBL samples was~1400 times slower than that of the Mg substrate,due to the physical barrier function provided by MgF_(2)/PDA layers and the dual self-healed ability of LBL layers.The rapid self-healing ability(with a healing period of~4 h under dynamic/static conditions)resulted from the synergistic interplay between the recombination of diverse chemical bonds within the LBL coating and the coordination of LBL-released GA with Mg2+,as corroborated by computer simulations.Compared with the drug-eluting coatings,the LBL sample demonstrated substantial advantages in anti-oxidation,anti-denaturation of fibrinogen,anti-platelet adhesion,anti-inflammation,anti-hyperplasia,and promoted-endothelialization.These benefits effectively address the limitations associated with drug-eluting coatings.
