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Solving Traveltime Tomography with Deep Learning

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Communications in Mathematics and Statistics 2023年第1期11卷 3-19页

作者： yuwei fan Lexing Ying Department of Mathematics Stanford UniversityStanfordCA 94305USA

This paper introduces a neural network approach for solving two-dimensional traveltime tomography(TT)problems based on the eikonal *** mathematical problem of TT is to recover the slowness field of a medium based on the boundary measurement of the traveltimes of waves going through the *** inverse map is high-dimensional and *** the circular tomography geometry,a perturbative analysis shows that the forward map can be approximated by a vectorized convolution operator in the angular *** by this and filtered backprojection,we propose an effective neural network architecture for the inverse map using the recently proposed BCR-Net,with weights learned from training *** results demonstrate the efficiency of the proposed neural networks.

关键词： Traveltime tomography Eikonal equation Inverse problem Neural networks Convolutional neural network

Superfluid density of two-dimensional weakly interacting boson system at zero temperature

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Chinese Science Bulletin 2011年第12期56卷 1230-1233页

作者： HE PeiSong fan yuwei School of Physics Peking University Beijing 100871 China Yuanpei College Peking University Beijing 100871 China

We compute the superfluid density of a two-dimensional boson system with weak two-body repulsive interactions at zero temperature using one-loop perturbation theory in the weak coupling region. The boson fields are taken to be in continuum form in real space, and the interactions are approximated by a δ function of the distance between the bosons. We find that the one-loop fluctuations slightly decrease the superfluid density of a classical level. The superfluid density is approximated by the condensate density multiplied by the mass of the boson particle.

关键词：玻色子系统弱相互作用流密度温度二维摄动理论现实空间函数近似

Dimension-Reduced Hyperbolic Moment Method for the Boltzmann Equation with BGK-Type Collision

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Communications in Computational Physics 2014年第5期15卷 1368-1406页

作者： Zhenning Cai yuwei fan Ruo Li Zhonghua Qiao School of Mathematical Sciences Peking UniversityBeijing 100871China CAPT LMAM&School of Mathematical SciencesPeking UniversityBeijing 100871China Department of Applied Mathematics The Hong Kong Polytechnic UniversityHung HomHong Kong.

We develop the dimension-reduced hyperbolic moment method for the Boltzmann equation,to improve solution efficiency using a numerical regularized moment method for problems with low-dimensional macroscopic variables and highdimensional microscopic *** the present work,we deduce the globally hyperbolic moment equations for the dimension-reduced Boltzmann equation based on the Hermite expansion and a globally hyperbolic *** numbers of Maxwell boundary condition required for well-posedness are *** numerical scheme is then developed and an improved projection algorithm between two different Hermite expansion spaces is *** solving several benchmark problems,we validate the method developed and demonstrate the significant efficiency improvement by dimension-reduction.

关键词： Dimension-reduction moment system NRxx global hyperbolicity boundary condition microflow

Machine Learning Analysis of Impact of Western US Fires on Central US Hailstorms

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Advances in Atmospheric Sciences 2024年第7期41卷 1450-1462页

作者： Xinming LIN Jiwen fan yuwei ZHANG ZJason HOU Pacific Northwest National Laboratory RichlandWA 99354USA Argonne National Laboratory LemontIL 60439USA

Fires,including wildfires,harm air quality and essential public services like transportation,communication,and *** fires can also influence atmospheric conditions,including temperature and aerosols,potentially affecting severe convective ***,we investigate the remote impacts of fires in the western United States(WUS)on the occurrence of large hail(size:≥2.54 cm)in the central US(CUS)over the 20-year period of 2001–20 using the machine learning(ML),Random Forest(RF),and Extreme Gradient Boosting(XGB)*** developed RF and XGB models demonstrate high accuracy(>90%)and F1 scores of up to 0.78 in predicting large hail occurrences when WUS fires and CUS hailstorms coincide,particularly in four states(Wyoming,South Dakota,Nebraska,and Kansas).The key contributing variables identified from both ML models include the meteorological variables in the fire region(temperature and moisture),the westerly wind over the plume transport path,and the fire features(i.e.,the maximum fire power and burned area).The results confirm a linkage between WUS fires and severe weather in the CUS,corroborating the findings of our previous modeling study conducted on case simulations with a detailed physics model.

关键词： wildfire severe convective storm hailstorm machine learning

Estimating blue marlin(Makaira nigricans)sustainable yield in the Indian Ocean using a data-poor approach

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Aquaculture and Fisheries 2019年第3期4卷 122-127页

作者： yuwei fan Zhe Geng Jiangfeng Zhu Xiaojie Dai Kindong Richard College of Marine Sciences Shanghai Ocean UniversityShanghai201306China Key Laboratory of Oceanic Fisheries Exploration Shanghai Ocean UniversityMinistry of AgricultureShanghai201306China National Engineering Research Center for Oceanic Fisheries Shanghai201306China Scientific Observing and Experimental Station of Oceanic Fisheries Resources and Environment Ministry of AgricultureShanghai201306China

Blue marlin(Makaira nigricans)is a common bycatch species in the global tuna longline *** this study,we applied a common data-poor approach,i.e.,depletion-corrected average catch(DCAC)to assess stock status of the Indian Ocean blue *** yield(Ysust),one reference point in this case,was estimated,and its uncertainty was integrated by using Monte Carlo *** results revealed the estimate of Ysust by DCAC was lower than MSY of 11,926 t by BSP-SS and is also lower than the provisional reference point of 11,704 t by the management *** is reliable for blue marlin in driving precautionary management quantity based on the CPUE of Japan(1980–2015).This study also implies that DCAC could be applied to other billfish stocks and uncertainty be estimated for sustainable ***,data-poor methods could be adjusted with precautionary approaches.

关键词： Blue marlin Data-poor approach Stock assessment Indian Ocean

超早产儿生后不同日龄发生中/重度支气管肺发育不良的预测模型构建

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新医学 2024年第7期55卷 549-556页

作者：古健樊雨薇龙欢夏昌顺范斯潆李苑钟怡钟鑫琪广州医科大学附属第三医院新生儿科广东省产科重大疾病重点实验室广东省妇产疾病临床医学研究中心粤港澳母胎医学高校联合实验室广东广州510150

目的构建超早产儿生后不同日龄发生中/重度支气管肺发育不良(BPD)的预测模型。方法回顾性选取2017年9月至2019年12月期间在广州医科大学附属第三医院出生、胎龄<28周且诊断为BPD的超早产儿为研究对象,分为轻度BPD和中/重度BPD 2组,将单... 详细信息

目的构建超早产儿生后不同日龄发生中/重度支气管肺发育不良(BPD)的预测模型。方法回顾性选取2017年9月至2019年12月期间在广州医科大学附属第三医院出生、胎龄<28周且诊断为BPD的超早产儿为研究对象,分为轻度BPD和中/重度BPD 2组,将单因素分析中P<0.05变量纳入多因素Logistic回归进行风险评估分析,建立早期预测模型,进行验证并评估预测效能。结果共纳入研究对象90例,其中轻度BPD组和中/重度BPD组分别为58例(64.4%)和32例(35.6%)。多因素Logistic回归分析结果显示,超早产儿生后7日龄影响中/重度BPD发生的因素有出生体质量、孕母孕前BMI≥25 kg/m^(2)、出生后1分钟Apgar评分≤7分和肺炎。14日龄危险因素有子痫前期、孕母孕前BMI≥25 kg/m^(2)、肺炎和具有血流动力学意义动脉导管未闭(hsPDA)。28日龄危险因素有子痫前期、孕母孕前BMI≥25 kg/m^(2)、有创机械通气时间和hsPDA。生后7、14和28日龄预测模型的ROC曲线下AUC值分别为0.864(95%CI 0.776~0.952)、0.860(95%CI 0.774~0.946)和0.863(95%CI 0.783~0.944)。基于高危因素构建列线图模型,校准后曲线接近参考线,预测值与实际值接近,模型具有较好的校准度。结论超早产儿生后第7、14、28日龄时发生中/重度BPD的危险因素略有差别,主要集中在出生体质量、孕母孕前BMI≥25 kg/m^(2)、生后1分钟Apgar评分≤7分、肺炎、子痫前期、hsPDA和有创机械通气天数等指标,根据不同因素所构建的不同时间点的预测模型均具有较好的预测价值,可以为临床提供指导。

关键词：超早产儿支气管肺发育不良危险因素预测模型

Compact intense electron-beam accelerators based on high energy density liquid pulse forming lines

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Matter and Radiation at Extremes 2018年第6期3卷 278-292页

作者： Jianhua Yang Zicheng Zhang Hanwu Yang Jun Zhang Jinliang Liu Yi Yin Tao Xun Xinbing Cheng yuwei fan Zhenxing Jin Jinchuan Ju College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha 410073People's Republic of China State Key Laboratory of Pulsed Power Laser Technology National University of Defense TechnologyChangsha 410073People's Republic of China

This paper provides a review of the compact intense electron-beam accelerators (IEBAs) based on liquid pulse forming lines (PFLs) that havebeen developed at the National University of Defense Technology (NUDT) in China. The history and roadmap of the compact IEBAs used todrive high-power microwave (HPM) devices at NUDT are reviewed. The properties of both de-ionized water and glycerin as energy storagemedia are presented. Research into the breakdown properties of liquid dielectrics and the desire to maximize energy storage have resulted in theinvention of several coaxial PFLs with different electromagnetic structures, which are detailed in this paper. These high energy density liquidPFLs have been used to increase the performance of IEBA subsystems, based on which the SPARK (Single Pulse Accelerator with spark gaps)and HEART (High Energy-density Accelerator with Repetitive Transformer) series of IEBAs were constructed. This paper also discusses howthese compact IEBAs have been used to drive typical HPM devices and concludes by summarizing the associated achievements and theconclusions that can be drawn from the results.

关键词： High-power microwave(HPM) Intense electron-beam accelerator(IEBA) Pulsed power technology(PPT) Pulse forming line(PFL) Fluid of high energy density De-ionized water Glycerin

基于广义Hermite展开的全局双曲矩方程组

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中国科学：数学 2015年第10期45卷 1635-1676页

作者：樊玉伟李若北京大学数学科学学院北京100871

在最近的研究中,Cai等人(2014)使用本征热通量代替通常使用的沿坐标轴方向的热通量作为变量获得了一个改进的13矩方程组.该方程组比使用坐标轴方向的热通量获得的Grad 13矩方程组具有更好的性质,例如,局部平衡态是双曲区域的内点.该改进... 详细信息

在最近的研究中,Cai等人(2014)使用本征热通量代替通常使用的沿坐标轴方向的热通量作为变量获得了一个改进的13矩方程组.该方程组比使用坐标轴方向的热通量获得的Grad 13矩方程组具有更好的性质,例如,局部平衡态是双曲区域的内点.该改进的13矩方程组是通过对分布函数使用广义的各向异性Hermite展开获得,其中该各向异性展开是指,使用完全的温度张量代替局部平衡态的温度.本文将该方法推广到高阶广义Hermite展开从而获得任意阶的新的矩方程组,并类似Cai等人(2014)的方法提出了一个正则化方案,使得所得方程组全局双曲,从而保证所得方程组的局部适定性.此外,本文还深入研究该方程组的系数矩阵的特征结构,并剖析了方程组的所有特征波.该矩系统提供了一套系统的可看成是Euler方程组的推广的动力学模型,并可通过提高展开阶来逼近Boltzmann方程本身.

关键词：动力学模型矩方法全局双曲性正则化 NRxx

水溶液中阴极电沉积半导体 CdTe 薄膜性能的研究

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太阳能学报 1998年第4期19卷 425-428页

作者：樊玉薇李永祥吴冲若东南大学电子工程系

研究了半导体ＣｄＴｅ薄膜不同阴极电沉积条件（搅拌、加温）下，沉积电位与电流密度、沉积速率的关系。着重研究了沉积电位对ＣｄＴｅ膜层成份及导电类型的影响，通过控制沉积电位制备了不同导电类型的半导体ＣｄＴｅ薄膜。对沉积膜形... 详细信息

研究了半导体ＣｄＴｅ薄膜不同阴极电沉积条件（搅拌、加温）下，沉积电位与电流密度、沉积速率的关系。着重研究了沉积电位对ＣｄＴｅ膜层成份及导电类型的影响，通过控制沉积电位制备了不同导电类型的半导体ＣｄＴｅ薄膜。对沉积膜形貌和结构分析表明，室温搅拌条件下沉积的ＣｄＴｅ薄膜，整体均匀性好，呈非晶结构，氮气氛中高温退火后，ＣｄＴｅ膜沿一定方向有较明显取向。

关键词：半导体薄膜沉积电位太阳能