以Mamba为代表的状态空间模型(state space models,SSM)凭借其出色的长程依赖建模能力与较低的线性计算复杂度,在医学图像分割领域展现出广阔的应用前景。但该类方法对图像逐像素展平的处理方式会破坏图像空间结构,导致局部细节提取不足...以Mamba为代表的状态空间模型(state space models,SSM)凭借其出色的长程依赖建模能力与较低的线性计算复杂度,在医学图像分割领域展现出广阔的应用前景。但该类方法对图像逐像素展平的处理方式会破坏图像空间结构,导致局部细节提取不足,且缺乏对器官与病灶的聚焦机制,在复杂背景下易引入冗余背景信息。为解决上述问题,本文提出了一种融合谱域动态特征与注意力机制的医学图像分割网络——频域动态注意力U型Mamba(spectral dynamic attention U-Mamba,SDA U-Mamba)。该网络采用分层U型结构设计,分别从空间连续性建模和区域聚焦能力两方面对Mamba进行优化。在网络浅层设计Mamba空频注意力模块,通过融合空域卷积、频域变换和金字塔自注意力结构以提升模型的局部信息感知能力与多尺度上下文建模效果;在网络深层引入双极路由注意力模块,通过动态路由选择与稀疏激活机制增强模型对医学图像器官或病灶的表征。实验结果表明,SDA U-Mamba在BUSI、CVCClinicDB与CHAOS-Liver这3个公开医学数据集上的分割性能显著优于当前主流方法,平均交并比(intersection over union,IoU)提升2.61%。本文所提算法可用于临床医学图像分割。展开更多
Contemporary methods for visualizing phenotypic evolution,such as phylomorphospaces,often reveal patter ns which depart strongly from a naive expectation of con siste ntly divergent branchi ng and expansion.Instead,br...Contemporary methods for visualizing phenotypic evolution,such as phylomorphospaces,often reveal patter ns which depart strongly from a naive expectation of con siste ntly divergent branchi ng and expansion.Instead,branches regularly crisscross as convergence,reversals,or other forms of homoplasy occur,forming patterns described as"birds'nests","flies in vials",or less elegantly,"a mess".In other words,the phenotypic tree of life often appears highly tangled.Various explanations are given for this,such as differential degrees of developmental constraint,adaptation,or lack of adaptation.However,null expectations for the magnitude of disorder or"tangling"have never been established,so it is unclear which or even whether various evolutionary factors are required to explain messy patter ns of evolution.I simulated evolution along phyloge nies under a number of varying parameters(number of taxa and number of traits)and models(Brownian motion,Ornstein-Uhlenbeck(OU)-based,early burst,and character displacement(CD) and quantified disorder using 2 measures.All models produce substantial amounts of disorder.Disorder increases with tree size and the number of phenotypic traits.OU models produced the largest amounts of disorder-adaptive peaks influence lineages to evolve within restricted areas,with concomitant in creases in crossing of branches and density of evolution.Large early cha nges in trait values can be important in minimizing disorder.CD consistently produced trees with low(but not absent)disorder.Overall,neither constraints nor a lack of adaptation is required to explain messy phylomorphospaces-both stochastic and deterministic processes can act to produce the tantalizingly tangled phenotypic tree of life.展开更多
U型中深层地埋管换热器(U-bend Deep Borehole Heat Exchanger,UDBHE)具有广阔的应用前景。文章基于无限柱热源(Infinite Cylindrical Source,ICS)和无限线热源(Infinite Line Source,ILS)模型的G函数,建立了4种UDBHE传热模型,采用ICS或...U型中深层地埋管换热器(U-bend Deep Borehole Heat Exchanger,UDBHE)具有广阔的应用前景。文章基于无限柱热源(Infinite Cylindrical Source,ICS)和无限线热源(Infinite Line Source,ILS)模型的G函数,建立了4种UDBHE传热模型,采用ICS或ILS模型的G函数,考虑或忽略钻孔壁热流随时间变化,分别简称为ICS-q,ILS-q,ICS-c,ILS-c模型。通过与较为准确的二维数值模型及实验数据在2种边界条件下的对比,分析了这4种模型的准确性。结果表明:ILS-q模型在整体上最为准确,而ICS-q模型在分析UDBHE长期性能时最为准确;4种模型在前期均存在较大误差,但在足够长时间后,除了ILS-c和ICS-c模型在入口温度边界下仍有较大误差外,其他模型的误差均较小。研究结果可为UDBHE传热模型研究提供参考。展开更多
The geometric characteristics of fractures within a rock mass can be inferred by the data sampling from boreholes or exposed surfaces.Recently,the universal elliptical disc(UED)model was developed to represent natural...The geometric characteristics of fractures within a rock mass can be inferred by the data sampling from boreholes or exposed surfaces.Recently,the universal elliptical disc(UED)model was developed to represent natural fractures,where the fracture is assumed to be an elliptical disc and the fracture orientation,rotation angle,length of the long axis and ratio of short-long axis lengths are considered as variables.This paper aims to estimate the fracture size-and azimuth-related parameters in the UED model based on the trace information from sampling windows.The stereological relationship between the trace length,size-and azimuth-related parameters of the UED model was established,and the formulae of the mean value and standard deviation of trace length were proposed.The proposed formulae were validated via the Monte Carlo simulations with less than 5%of error rate between the calculated and true values.With respect to the estimation of the size-and azimuth-related parameters using the trace length,an optimization method was developed based on the pre-assumed size and azimuth distribution forms.A hypothetical case study was designed to illustrate and verify the parameter estimation method,where three combinations of the sampling windows were used to estimate the parameters,and the results showed that the estimated values could agree well with the true values.Furthermore,a hypothetical three-dimensional(3D)elliptical fracture network was constructed,and the circular disc,non-UED and UED models were used to represent it.The simulated trace information from different models was compared,and the results clearly illustrated the superiority of the proposed UED model over the existing circular disc and non-UED models。展开更多
This paper proposes a case study in the control of a heavy oil pyrolysis/cracking furnace with a newly extended U-model based pole placement controller(U-PPC). The major work of the paper includes: 1) establishing a c...This paper proposes a case study in the control of a heavy oil pyrolysis/cracking furnace with a newly extended U-model based pole placement controller(U-PPC). The major work of the paper includes: 1) establishing a control oriented nonlinear dynamic model with Naphtha cracking and thermal dynamics; 2) analysing a U-model(i.e., control oriented prototype) representation of various popular process model sets; 3)designing the new U-PPC to enhance the control performance in pole placement and stabilisation; 4) taking computational bench tests to demonstrate the control system design and performance with a user-friendly step by step procedure.展开更多
文摘以Mamba为代表的状态空间模型(state space models,SSM)凭借其出色的长程依赖建模能力与较低的线性计算复杂度,在医学图像分割领域展现出广阔的应用前景。但该类方法对图像逐像素展平的处理方式会破坏图像空间结构,导致局部细节提取不足,且缺乏对器官与病灶的聚焦机制,在复杂背景下易引入冗余背景信息。为解决上述问题,本文提出了一种融合谱域动态特征与注意力机制的医学图像分割网络——频域动态注意力U型Mamba(spectral dynamic attention U-Mamba,SDA U-Mamba)。该网络采用分层U型结构设计,分别从空间连续性建模和区域聚焦能力两方面对Mamba进行优化。在网络浅层设计Mamba空频注意力模块,通过融合空域卷积、频域变换和金字塔自注意力结构以提升模型的局部信息感知能力与多尺度上下文建模效果;在网络深层引入双极路由注意力模块,通过动态路由选择与稀疏激活机制增强模型对医学图像器官或病灶的表征。实验结果表明,SDA U-Mamba在BUSI、CVCClinicDB与CHAOS-Liver这3个公开医学数据集上的分割性能显著优于当前主流方法,平均交并比(intersection over union,IoU)提升2.61%。本文所提算法可用于临床医学图像分割。
基金Dr Martha Muiioz and the editorial staff at Current Zoology were exceptionally accommodating when the original deadline for submission was complicated by COVID-19I thank them for their patience and understanding through the submission process.I also thank the executive and handling editors,and D.Adams,B.Sidlauskas,and an anonymous reviewer for helpful comments and extensive efforts on behalf of this manuscript。
文摘Contemporary methods for visualizing phenotypic evolution,such as phylomorphospaces,often reveal patter ns which depart strongly from a naive expectation of con siste ntly divergent branchi ng and expansion.Instead,branches regularly crisscross as convergence,reversals,or other forms of homoplasy occur,forming patterns described as"birds'nests","flies in vials",or less elegantly,"a mess".In other words,the phenotypic tree of life often appears highly tangled.Various explanations are given for this,such as differential degrees of developmental constraint,adaptation,or lack of adaptation.However,null expectations for the magnitude of disorder or"tangling"have never been established,so it is unclear which or even whether various evolutionary factors are required to explain messy patter ns of evolution.I simulated evolution along phyloge nies under a number of varying parameters(number of taxa and number of traits)and models(Brownian motion,Ornstein-Uhlenbeck(OU)-based,early burst,and character displacement(CD) and quantified disorder using 2 measures.All models produce substantial amounts of disorder.Disorder increases with tree size and the number of phenotypic traits.OU models produced the largest amounts of disorder-adaptive peaks influence lineages to evolve within restricted areas,with concomitant in creases in crossing of branches and density of evolution.Large early cha nges in trait values can be important in minimizing disorder.CD consistently produced trees with low(but not absent)disorder.Overall,neither constraints nor a lack of adaptation is required to explain messy phylomorphospaces-both stochastic and deterministic processes can act to produce the tantalizingly tangled phenotypic tree of life.
文摘U型中深层地埋管换热器(U-bend Deep Borehole Heat Exchanger,UDBHE)具有广阔的应用前景。文章基于无限柱热源(Infinite Cylindrical Source,ICS)和无限线热源(Infinite Line Source,ILS)模型的G函数,建立了4种UDBHE传热模型,采用ICS或ILS模型的G函数,考虑或忽略钻孔壁热流随时间变化,分别简称为ICS-q,ILS-q,ICS-c,ILS-c模型。通过与较为准确的二维数值模型及实验数据在2种边界条件下的对比,分析了这4种模型的准确性。结果表明:ILS-q模型在整体上最为准确,而ICS-q模型在分析UDBHE长期性能时最为准确;4种模型在前期均存在较大误差,但在足够长时间后,除了ILS-c和ICS-c模型在入口温度边界下仍有较大误差外,其他模型的误差均较小。研究结果可为UDBHE传热模型研究提供参考。
基金funded by National Natural Science Foundation of China(Grant No.41972264)Zhejiang Provincial Natural Science Foundation of China(Grant No.LR22E080002)the Observation and Research Station of Geohazards in Zhejiang,Ministry of Natural Resources,China(Grant No.ZJDZGCZ-2021).
文摘The geometric characteristics of fractures within a rock mass can be inferred by the data sampling from boreholes or exposed surfaces.Recently,the universal elliptical disc(UED)model was developed to represent natural fractures,where the fracture is assumed to be an elliptical disc and the fracture orientation,rotation angle,length of the long axis and ratio of short-long axis lengths are considered as variables.This paper aims to estimate the fracture size-and azimuth-related parameters in the UED model based on the trace information from sampling windows.The stereological relationship between the trace length,size-and azimuth-related parameters of the UED model was established,and the formulae of the mean value and standard deviation of trace length were proposed.The proposed formulae were validated via the Monte Carlo simulations with less than 5%of error rate between the calculated and true values.With respect to the estimation of the size-and azimuth-related parameters using the trace length,an optimization method was developed based on the pre-assumed size and azimuth distribution forms.A hypothetical case study was designed to illustrate and verify the parameter estimation method,where three combinations of the sampling windows were used to estimate the parameters,and the results showed that the estimated values could agree well with the true values.Furthermore,a hypothetical three-dimensional(3D)elliptical fracture network was constructed,and the circular disc,non-UED and UED models were used to represent it.The simulated trace information from different models was compared,and the results clearly illustrated the superiority of the proposed UED model over the existing circular disc and non-UED models。
基金partially supported by the National Natural Science Foundation of China(61273188,61473312)Taishan Scholar Construction Engineering Special Funding of Shandong
文摘This paper proposes a case study in the control of a heavy oil pyrolysis/cracking furnace with a newly extended U-model based pole placement controller(U-PPC). The major work of the paper includes: 1) establishing a control oriented nonlinear dynamic model with Naphtha cracking and thermal dynamics; 2) analysing a U-model(i.e., control oriented prototype) representation of various popular process model sets; 3)designing the new U-PPC to enhance the control performance in pole placement and stabilisation; 4) taking computational bench tests to demonstrate the control system design and performance with a user-friendly step by step procedure.
