Smoothly stitching multiple surfaces mainly represented by B-spline or NURBS together is an extremely important issue in complex surfaces modeling and reverse engineering.In recent years,a lot of progress has been mad...Smoothly stitching multiple surfaces mainly represented by B-spline or NURBS together is an extremely important issue in complex surfaces modeling and reverse engineering.In recent years,a lot of progress has been made in smooth join of non-trimmed surface patches,while there has been seldom research on smoothly stitching trimmed surface patches together.This paper studies the problem of global continuity adjustment,damaged hole repair and local shape optimization for complex trimmed surface model,and presents a uniform scheme to deal with continuity adjustment of trimmed surfaces and geometric repair of local broken region.Constrained B-spline surface refitting technique and trim calculation are first utilized to achieve global G^1 continuity,and then local shape optimization functional is adopted to reduce fitting error and improve local quality of refitted surface patch.The proposed approach is applied to a discontinuity ship hull surface model with an irregular hole,and the result demonstrates the validation of our method.Furthermore,on the premise of global continuity,the proposed locally repairing damaged surface model provides a better foundation for following research work,such as topology recovery technique for complex surface model after geometric repair.展开更多
Compared with the pair-wise registration of point clouds,multi-view point cloud registration is much less studied.In this dissertation,a disordered multi-view point cloud registration method based on the soft trimmed ...Compared with the pair-wise registration of point clouds,multi-view point cloud registration is much less studied.In this dissertation,a disordered multi-view point cloud registration method based on the soft trimmed deep network is proposed.In this method,firstly,the expression ability of feature extraction module is improved and the registration accuracy is increased by enhancing feature extraction network with the point pair feature.Secondly,neighborhood and angle similarities are used to measure the consistency of candidate points to surrounding neighborhoods.By combining distance consistency and high dimensional feature consistency,our network introduces the confidence estimation module of registration,so the point cloud trimmed problem can be converted to candidate for the degree of confidence estimation problem,achieving the pair-wise registration of partially overlapping point clouds.Thirdly,the results from pair-wise registration are fed into the model fusion to achieve the rough registration of multi-view point clouds.Finally,the hierarchical clustering is used to iteratively optimize the clustering center model by gradually increasing the number of clustering categories and performing clustering and registration alternately.This method achieves rough point cloud registration quickly in the early stage,improves the accuracy of multi-view point cloud registration in the later stage,and makes full use of global information to achieve robust and accurate multi-view registration without initial value.展开更多
An algorithm of trimmed surface triangulation is put forward by using the isoparametric curves of aircraft surfaces to evenly allocate the mesh nodes. Further refinements are made to deal with the trimming loops and e...An algorithm of trimmed surface triangulation is put forward by using the isoparametric curves of aircraft surfaces to evenly allocate the mesh nodes. Further refinements are made to deal with the trimming loops and ensure the mesh consistency.展开更多
This work presents some numerical aspects of isogeometric boundary element methods(IGABEM).The behavior of hyper-singular and nearly-singular integration is first explored on the distorted NURBS surface.Several numeri...This work presents some numerical aspects of isogeometric boundary element methods(IGABEM).The behavior of hyper-singular and nearly-singular integration is first explored on the distorted NURBS surface.Several numerical treatments are proposed to enhance the quadrature in the framework of isogeometric analysis.Then a numerical implementation of IGABEM on the trimmed NURBS is detailed.Based on this idea,the surface crack problem is modeled incorporation with the phantom element method.The proposed method allows the crack to intersect with the boundary of the body while preserving the original parametrization of the NURBS-based CAD geometry.展开更多
An improved algorithm of Delaunay triangulation is proposed by expanding the scope from a convex polygon to an arbitrary polygon area in which holes can be contained in the subdivision procedure. The data structure of...An improved algorithm of Delaunay triangulation is proposed by expanding the scope from a convex polygon to an arbitrary polygon area in which holes can be contained in the subdivision procedure. The data structure of generated triangles and the exuviationslike method play a key role, and a single connectivity domain (SCD) without holes is constructed as the initial part of the algorithm. Meanwhile, some examples show that the method can be applied to the triangulation of the trimmed NURBS surface. The result of surface tessellation can be used in many applications such as NC machining, finite element analysis, rendering and mechanism interference detection.展开更多
Proceeded from trimmed Hill estimators and distributed inference, a new distributed version of trimmed Hill estimator for heavy tail index is proposed. Considering the case where the number of observations involved in...Proceeded from trimmed Hill estimators and distributed inference, a new distributed version of trimmed Hill estimator for heavy tail index is proposed. Considering the case where the number of observations involved in each machine can be either the same or different and either fixed or varying to the total sample size, its consistency and asymptotic normality are discussed. Simulation studies are particularized to show the new estimator performs almost in line with the trimmed Hill estimator.展开更多
The paper presents a new approach for triangulating trimmed NURBS surface. The basic strategy is to perform the triangulation precisely in parametric space according to given tolerance. The domain of the trimmed surfa...The paper presents a new approach for triangulating trimmed NURBS surface. The basic strategy is to perform the triangulation precisely in parametric space according to given tolerance. The domain of the trimmed surface is first mapped into parameter space as trimmed region, then triangulate the trimmed region by extended Delaunay algorithm, testing the precision of the generating triangle in Euclidean space and then subdivided it according to given tolerance. This approach makes the triangulation more reliable and faster, and avoids complex recursive calculation. Thus the algorithm is particularly suitable for the precise triangulation model for many engineering applications, for example, NC machining.展开更多
辽河口湿地是东亚-澳大利西亚候鸟迁飞通道上重要的水鸟栖息地,已有的研究主要集中在区域水鸟分布、栖息地面积和质量的时空变化上,对于关键种的识别、季节分布及种群长期变化特征鲜有报道。利用2010—2023年辽河口湿地水鸟监测数据,通...辽河口湿地是东亚-澳大利西亚候鸟迁飞通道上重要的水鸟栖息地,已有的研究主要集中在区域水鸟分布、栖息地面积和质量的时空变化上,对于关键种的识别、季节分布及种群长期变化特征鲜有报道。利用2010—2023年辽河口湿地水鸟监测数据,通过国际重要意义湿地标准和监测数据的趋势与指数模型(Trends and Indices for Monitoring data,TRIM),识别了区域分布的关键水鸟物种、季节性分布的重要地点,分析了关键种的种群长期变化特征。结果显示,辽河口湿地共记录到133种水鸟,隶属于9目18科,其中鸻形目水鸟种类最多。在满足国际重要意义湿地标准的区域,共发现54种关键水鸟物种,分布在188个重要地点。不同种类水鸟的栖息地分布和出现频次存在显著的季节性差异,辽河口湿地南小河、三角洲水库、酒壶嘴、二界沟桥、三道沟和滩海站是多数水鸟重要的春秋停歇地,部分鸥类水鸟的夏季繁殖地和部分鹤鹳类、雁类水鸟的越冬地。2010—2023年,满足国际重要意义湿地标准的水鸟栖息地数量呈显著上升趋势。不同类别的水鸟数量总体呈上升趋势,部分物种如白额雁(Anser albifrons)、白鹤(Leucogeranus leucogeranus)、丹顶鹤(Grus japonensis)和灰斑鸻(Pluvialis squatarola)等种群数量呈下降趋势。研究结果显示,在保护区面积不变的前提下,水鸟数量不断增加可能导致未来辽河口湿地资源承载力不足。展开更多
【目的】探究猪德尔塔冠状病毒(Porcine deltacoronavirus,PDCoV)感染对先天性免疫的影响及免疫信号传导的干扰机制,重点解析信号传导转录激活因子1(signal transducer and activator of transcription 1,STAT1)与三方基序蛋白21(tripar...【目的】探究猪德尔塔冠状病毒(Porcine deltacoronavirus,PDCoV)感染对先天性免疫的影响及免疫信号传导的干扰机制,重点解析信号传导转录激活因子1(signal transducer and activator of transcription 1,STAT1)与三方基序蛋白21(tripartite-motif protein 21,TRIM21)在此过程中的作用。【方法】通过倒置显微镜观察感染复数(multiplicity of infection,MOI)为1的PDCoV感染IPEC-J2细胞1、12、24、48 h后细胞形态学变化,采用实时荧光定量PCR和Western blotting分别检测PDCoV-N基因及蛋白的表达水平,以此筛选PDCoV感染IPEC-J2细胞模型的最佳条件。在PDCoV感染峰值时,通过实时荧光定量PCR和Western blotting检测STAT1、TRIM21及干扰素刺激基因(interferon-stimulated genes,ISGs)的mRNA和蛋白表达水平;通过双荧光素酶报告基因系统检测过表达或抑制STAT1对PDCoV复制及干扰素激活反应元件(interferon-stimulated response element,ISRE)启动子活性的影响;将TRIM21与STAT1真核表达载体共转染至IPEC-J2细胞,结合激光共聚焦显微镜、免疫共沉淀技术(coimmunoprecipitation,Co-IP)和Western blotting验证二者的相互作用及TRIM21对STAT1的调控效应。【结果】PDCoV在感染IPEC-J2细胞24 h达复制高峰,同时试验组细胞中STAT1、TRIM21蛋白表达及ISGs转录水平均极显著高于对照组(P<0.01)。与对照组相比,过表达STAT1后ISRE启动子活性极显著增强,PDCoV-N基因及其蛋白表达量极显著降低(P<0.01),而氟达拉滨抑制STAT1后则极显著促进病毒复制(P<0.01)。激光共聚焦显微镜观察与Co-IP结果显示,STAT1与TRIM21存在共定位及相互作用,且与对照组相比,过表达TRIM21后STAT1蛋白表达量极显著降低(P<0.01)。【结论】本研究解析了PDCoV与宿主IPEC-J2细胞先天性免疫的相互作用机制,STAT1作为关键抗病毒因子通过ISRE通路增强先天性免疫来抑制病毒复制,TRIM21则靶向STAT1并下调其表达从而帮助病毒免疫逃逸。研究结果不仅为深入理解PDCoV的致病分子机制提供了新见解,也为制定PDCoV防控策略奠定了基础。展开更多
Let θ∈^d be a unit vector and let X, X1, X2,…… be a sequence of i.i.d. Xd-valued random vectors attracted to operator semi-stable laws. For each integer n ≥1, let X1,≤……≤ Xn,n denote the order statistics of X...Let θ∈^d be a unit vector and let X, X1, X2,…… be a sequence of i.i.d. Xd-valued random vectors attracted to operator semi-stable laws. For each integer n ≥1, let X1,≤……≤ Xn,n denote the order statistics of X1, X2,..., Xn according to priority of index, namely ｜（X1,nθ）｜≥…≥ [（Xn,n,θ）1, where （., .） is an inner product on Rd. For all integers r ≥ 0, define by （r）Sn =∑n-r i=1Xi,n the trimmed sum. In this paper we investigate a law of the iterated logarithm and limit distributions for trimmed sums （r）Sn. Our results give information about the maximal growth rate of sample paths for partial sums of X when r extreme terms are excluded. A stochastically compactness of （r）Sn is obtained.展开更多
基金supported by National Natural Science Foundation of China(Grant No.50575098)
文摘Smoothly stitching multiple surfaces mainly represented by B-spline or NURBS together is an extremely important issue in complex surfaces modeling and reverse engineering.In recent years,a lot of progress has been made in smooth join of non-trimmed surface patches,while there has been seldom research on smoothly stitching trimmed surface patches together.This paper studies the problem of global continuity adjustment,damaged hole repair and local shape optimization for complex trimmed surface model,and presents a uniform scheme to deal with continuity adjustment of trimmed surfaces and geometric repair of local broken region.Constrained B-spline surface refitting technique and trim calculation are first utilized to achieve global G^1 continuity,and then local shape optimization functional is adopted to reduce fitting error and improve local quality of refitted surface patch.The proposed approach is applied to a discontinuity ship hull surface model with an irregular hole,and the result demonstrates the validation of our method.Furthermore,on the premise of global continuity,the proposed locally repairing damaged surface model provides a better foundation for following research work,such as topology recovery technique for complex surface model after geometric repair.
文摘Compared with the pair-wise registration of point clouds,multi-view point cloud registration is much less studied.In this dissertation,a disordered multi-view point cloud registration method based on the soft trimmed deep network is proposed.In this method,firstly,the expression ability of feature extraction module is improved and the registration accuracy is increased by enhancing feature extraction network with the point pair feature.Secondly,neighborhood and angle similarities are used to measure the consistency of candidate points to surrounding neighborhoods.By combining distance consistency and high dimensional feature consistency,our network introduces the confidence estimation module of registration,so the point cloud trimmed problem can be converted to candidate for the degree of confidence estimation problem,achieving the pair-wise registration of partially overlapping point clouds.Thirdly,the results from pair-wise registration are fed into the model fusion to achieve the rough registration of multi-view point clouds.Finally,the hierarchical clustering is used to iteratively optimize the clustering center model by gradually increasing the number of clustering categories and performing clustering and registration alternately.This method achieves rough point cloud registration quickly in the early stage,improves the accuracy of multi-view point cloud registration in the later stage,and makes full use of global information to achieve robust and accurate multi-view registration without initial value.
文摘An algorithm of trimmed surface triangulation is put forward by using the isoparametric curves of aircraft surfaces to evenly allocate the mesh nodes. Further refinements are made to deal with the trimming loops and ensure the mesh consistency.
基金National Natural Science Foundation of China(NSFC)under Grant(No.51904202).
文摘This work presents some numerical aspects of isogeometric boundary element methods(IGABEM).The behavior of hyper-singular and nearly-singular integration is first explored on the distorted NURBS surface.Several numerical treatments are proposed to enhance the quadrature in the framework of isogeometric analysis.Then a numerical implementation of IGABEM on the trimmed NURBS is detailed.Based on this idea,the surface crack problem is modeled incorporation with the phantom element method.The proposed method allows the crack to intersect with the boundary of the body while preserving the original parametrization of the NURBS-based CAD geometry.
文摘An improved algorithm of Delaunay triangulation is proposed by expanding the scope from a convex polygon to an arbitrary polygon area in which holes can be contained in the subdivision procedure. The data structure of generated triangles and the exuviationslike method play a key role, and a single connectivity domain (SCD) without holes is constructed as the initial part of the algorithm. Meanwhile, some examples show that the method can be applied to the triangulation of the trimmed NURBS surface. The result of surface tessellation can be used in many applications such as NC machining, finite element analysis, rendering and mechanism interference detection.
文摘Proceeded from trimmed Hill estimators and distributed inference, a new distributed version of trimmed Hill estimator for heavy tail index is proposed. Considering the case where the number of observations involved in each machine can be either the same or different and either fixed or varying to the total sample size, its consistency and asymptotic normality are discussed. Simulation studies are particularized to show the new estimator performs almost in line with the trimmed Hill estimator.
文摘The paper presents a new approach for triangulating trimmed NURBS surface. The basic strategy is to perform the triangulation precisely in parametric space according to given tolerance. The domain of the trimmed surface is first mapped into parameter space as trimmed region, then triangulate the trimmed region by extended Delaunay algorithm, testing the precision of the generating triangle in Euclidean space and then subdivided it according to given tolerance. This approach makes the triangulation more reliable and faster, and avoids complex recursive calculation. Thus the algorithm is particularly suitable for the precise triangulation model for many engineering applications, for example, NC machining.
文摘辽河口湿地是东亚-澳大利西亚候鸟迁飞通道上重要的水鸟栖息地,已有的研究主要集中在区域水鸟分布、栖息地面积和质量的时空变化上,对于关键种的识别、季节分布及种群长期变化特征鲜有报道。利用2010—2023年辽河口湿地水鸟监测数据,通过国际重要意义湿地标准和监测数据的趋势与指数模型(Trends and Indices for Monitoring data,TRIM),识别了区域分布的关键水鸟物种、季节性分布的重要地点,分析了关键种的种群长期变化特征。结果显示,辽河口湿地共记录到133种水鸟,隶属于9目18科,其中鸻形目水鸟种类最多。在满足国际重要意义湿地标准的区域,共发现54种关键水鸟物种,分布在188个重要地点。不同种类水鸟的栖息地分布和出现频次存在显著的季节性差异,辽河口湿地南小河、三角洲水库、酒壶嘴、二界沟桥、三道沟和滩海站是多数水鸟重要的春秋停歇地,部分鸥类水鸟的夏季繁殖地和部分鹤鹳类、雁类水鸟的越冬地。2010—2023年,满足国际重要意义湿地标准的水鸟栖息地数量呈显著上升趋势。不同类别的水鸟数量总体呈上升趋势,部分物种如白额雁(Anser albifrons)、白鹤(Leucogeranus leucogeranus)、丹顶鹤(Grus japonensis)和灰斑鸻(Pluvialis squatarola)等种群数量呈下降趋势。研究结果显示,在保护区面积不变的前提下,水鸟数量不断增加可能导致未来辽河口湿地资源承载力不足。
文摘【目的】探究猪德尔塔冠状病毒(Porcine deltacoronavirus,PDCoV)感染对先天性免疫的影响及免疫信号传导的干扰机制,重点解析信号传导转录激活因子1(signal transducer and activator of transcription 1,STAT1)与三方基序蛋白21(tripartite-motif protein 21,TRIM21)在此过程中的作用。【方法】通过倒置显微镜观察感染复数(multiplicity of infection,MOI)为1的PDCoV感染IPEC-J2细胞1、12、24、48 h后细胞形态学变化,采用实时荧光定量PCR和Western blotting分别检测PDCoV-N基因及蛋白的表达水平,以此筛选PDCoV感染IPEC-J2细胞模型的最佳条件。在PDCoV感染峰值时,通过实时荧光定量PCR和Western blotting检测STAT1、TRIM21及干扰素刺激基因(interferon-stimulated genes,ISGs)的mRNA和蛋白表达水平;通过双荧光素酶报告基因系统检测过表达或抑制STAT1对PDCoV复制及干扰素激活反应元件(interferon-stimulated response element,ISRE)启动子活性的影响;将TRIM21与STAT1真核表达载体共转染至IPEC-J2细胞,结合激光共聚焦显微镜、免疫共沉淀技术(coimmunoprecipitation,Co-IP)和Western blotting验证二者的相互作用及TRIM21对STAT1的调控效应。【结果】PDCoV在感染IPEC-J2细胞24 h达复制高峰,同时试验组细胞中STAT1、TRIM21蛋白表达及ISGs转录水平均极显著高于对照组(P<0.01)。与对照组相比,过表达STAT1后ISRE启动子活性极显著增强,PDCoV-N基因及其蛋白表达量极显著降低(P<0.01),而氟达拉滨抑制STAT1后则极显著促进病毒复制(P<0.01)。激光共聚焦显微镜观察与Co-IP结果显示,STAT1与TRIM21存在共定位及相互作用,且与对照组相比,过表达TRIM21后STAT1蛋白表达量极显著降低(P<0.01)。【结论】本研究解析了PDCoV与宿主IPEC-J2细胞先天性免疫的相互作用机制,STAT1作为关键抗病毒因子通过ISRE通路增强先天性免疫来抑制病毒复制,TRIM21则靶向STAT1并下调其表达从而帮助病毒免疫逃逸。研究结果不仅为深入理解PDCoV的致病分子机制提供了新见解,也为制定PDCoV防控策略奠定了基础。
基金Supported by National Natural Science Foundation of China(Grant No.11071076)NSF of Zhejiang Province(Grant No.LY14A010025)
文摘Let θ∈^d be a unit vector and let X, X1, X2,…… be a sequence of i.i.d. Xd-valued random vectors attracted to operator semi-stable laws. For each integer n ≥1, let X1,≤……≤ Xn,n denote the order statistics of X1, X2,..., Xn according to priority of index, namely ｜（X1,nθ）｜≥…≥ [（Xn,n,θ）1, where （., .） is an inner product on Rd. For all integers r ≥ 0, define by （r）Sn =∑n-r i=1Xi,n the trimmed sum. In this paper we investigate a law of the iterated logarithm and limit distributions for trimmed sums （r）Sn. Our results give information about the maximal growth rate of sample paths for partial sums of X when r extreme terms are excluded. A stochastically compactness of （r）Sn is obtained.
