摘要：为了提高无监督深度点云降噪算法的性能,提出密度先验引导的无监督深度点云降噪算法.基于现有的网络框架,首先设计了密度先验,通过噪声点云的整体分布计算每点位于真实底层曲面的概率;然后利用深度网络,通过上采、下采等策略克服大噪声点的影响,得到降噪点云;最后利用密度先验优化干净点的条件概率分布,设计无监督损失函数对网络进行优化,得到最终算法.此外,基于密度先验还提出低噪声点筛选方法和滤波算法.所提算法在PyTorch上实现,以基于ModelNet-40构造的仿真数据库及真实扫描数据PERL为例,以倒角距离及点到曲面的距离为评价指标.与DMR等算法相比,倒角距离平均降低0.35~1.34,点到曲面的距离平均降低0.68~1.94.实验结果表明,所提算法降噪结果优于现有算法,且具有较强的鲁棒性、普适性和泛化能力.

摘要：为研究桥梁抗风型调谐质量阻尼器(tuned mass damper, TMD)对车辆荷载引起结构振动的减振效果,并揭示车载作用下的TMD激振机理,提出了基于模态动能演化的多自由度结构TMD控制方法,确定了安装TMD的最优设计参数和布设位置;考虑桥梁有限元模型动力求解的通用性,基于桥梁三维动力分析系统BDANS软件建立了车-桥-TMD动力耦合分析系统;以经典单自由度移动弹簧质量过简支梁模型为研究对象,分析了车-桥-TMD系统振动特性,结合某深水区非通航桥梁抗风型TMD工程实例分析了TMD对车致振动的减振效果和机理。研究结果表明:TMD行程幅值与减振效果呈现正相关特点,即行程幅值越大对车-桥动力效应引起的振动减振效果越好;安装TMD可以显著提高结构的等效阻尼比,满足等效阻尼比>1%的工程需求,提高桥梁结构振动的稳定性;TMD在一定条件下可以减小车辆通过时引发桥梁竖向位移冲击效应,最大可减少3%左右;TMD对车-桥2个子系统的加速度瞬态峰值均起到了一定的抑制效果,尤其对桥梁结构竖向振动加速度作用效果明显,安装TMD后的桥梁跨中竖向振动加速度RMS值减少约20%;对大跨钢箱桥梁而言,相比较小的车辆荷载冲击效应,一阶竖弯呈邻跨反对称特性的桥梁结构在车辆通行过程中更容易激起TMD,使桥梁结构获得更佳的减振效果。

摘要：针对清梳棉流程中产出棉含杂高、质量差的问题,结合改进高斯混合模型(Gaussian mixed model, GMM)与帧差法,提出一种局部运动棉杂率控制优化方法。首先针对清棉机除杂原理及棉杂特性进行分析;其次通过提取视频关键帧并改进GMM与帧差法对图像序列“与”运算实现目标的精确提取,进而通过设计GMM分类器获得棉杂率并进行分析;最后与传统的检测算法作对比验证。实验表明,改进后的算法在有效性以及实用性方面优于传统算法。同时,通过引入闭环控制能满足工业高精度、实时性的需求。

摘要：A lot of 3D shape descriptors for 3D shape retrieval have been presented so far. This paper proposes a new mechanism, which employs several existing global and local 3D shape descriptors as input. With the sparse theory, some descriptors which play the most important role in measuring similarity between query model and the model in the dataset are selected automatically and an affinity matrix is constructed. Spectral clustering method can be implemented to this affinity matrix. Spectral embedding of this affinity matrix can be applied to retrieval, which integrating almost all the advantages of selected descriptors. In order to verify the performance of our approach, we perform experimental comparisons on Princeton Shape Benchmark database. Test results show that our method is a pose-oblivious, efficient and robustness method for either complete or incomplete models.

摘要：Circular objects detection in digital images, a vital and recurring problem in image processing and computer vision, has many applications especially aiding vectorization of line drawing images, pupil and iris detection, circular traffic sign detection, and so on. In this paper, we lever Midpoint Circle Algorithm to speed up circle validation with sub-pixel precision. At the same time, we combine the least square method to improve the accuracy of circle detection. Experimental results from tests on synthetic and natural images validate that the proposed technique is efficiency regarding accuracy, speed and robustness.

摘要：This paper presents an efficient technique for processing of 3D meshed surfaces via spherical wavelets. More specifically, an input 3D mesh is firstly transformed into a spherical vector signal by a fast low distortion spherical parameterization approach based on symmetry analysis of 3D meshes. This signal is then sampled on the sphere with the help of an adaptive sampling scheme. Finally, the sampled signal is transformed into the wavelet domain according to spherical wavelet transform where many 3D mesh processing operations can be implemented such as smoothing, enhancement, compression, and so on. Our main contribution lies in incorporating a fast low distortion spherical parameterization approach and an adaptive sampling scheme into the frame for pro- cessing 3D meshed surfaces by spherical wavelets, which can handle surfaces with complex shapes. A number of experimental ex- amples demonstrate that our algorithm is robust and efficient.

摘要：Meshed surfaces are ubiquitous in digital geometry processing and computer graphics. The set of attributes associated with each vertex such as the vertex locations, curvature, temperature, pressure or saliency, can be recognized as data living on mani- fold surfaces. So interpolation and approximation for these data are of general interest. This paper presents two approaches for mani- fold data interpolation and approximation through the properties of Laplace-Beltrami operator （Laplace operator defined on a mani- fold surface）. The first one is to use Laplace operator minimizing the membrane energy of a scalar function defined on a manifold. The second one is to use bi-Laplace operator minimizing the thin plate energy of a scalar function defined on a manifold. These two approaches can process data living on high genus meshed surfaces. The approach based on Laplace operator is more suitable for manifold data approximation and can be applied manifold data smoothing, while the one based on bi-Laplace operator is more suit- able for manifold data interpolation and can be applied image extremal envelope computation. All the application examples demon- strate that our procedures are robust and efficient.

摘要：目的研究下斜肌肌腹转位术治疗合并代偿头位的小角度先天性上斜肌麻痹的临床效果。设计回顾性病例系列。研究对象2019年4月至2022年12月在北京儿童医院保定医院眼科就诊的合并代偿头位的单眼小角度先天性上斜肌麻痹患者18例(18眼)。方法对18例患者均行下斜肌肌腹转位术,即将距离下斜肌止端约10~11 mm处肌腹固定于下直肌颞侧止端后5 mm处。术前与术后6个月用三棱镜测量第一眼位患眼垂直斜视度,根据Hunter分级法评价患眼下斜肌亢进程度,观察代偿头位变化,采用Photoshop 7.0软件测量患者眼底照片黄斑中心凹-视盘中心夹角度数(FDA)。主要指标垂直斜视度、下斜肌亢进程度、代偿头位、FDA。结果术后6个月第一眼位平均垂直斜视度为(0.51±0.60)棱镜度(PD),较术前的(5.03±0.84)PD显著降低(t=14.241,P<0.001)。18眼中术前10眼下斜肌功能亢进程度为2+,术后6眼消失、4眼为1+;术前8眼下斜肌功能亢进程度为1+,术后均消失。术前18例患儿代偿头位均表现为头向健眼侧倾斜,术后12例消失,6例患儿歪头症状明显改善,且未出现反向歪头。术后FDA(4.81±2.53)°较术前的(9.82±5.17)°减少(3.02±0.91)°。术后随访6个月,所有患者均未出现并发症。结论下斜肌肌腹转位术治疗小角度先天性上斜肌麻痹,尤其是合并代偿头位的患者是安全有效的。(眼科,2024,33:61-65)

摘要：将复杂几何体网格转换为参数曲面是CAD几何引擎设计中的关键问题.针对赋予四边形粗剖分结构的三角网格模型,提出一种基于Powell-Sabin细分的参数曲面重建方法.首先利用均值参数化方法建立每个粗四边形结构MT到参数域D的映射,同时得到D的三角剖分△;然后对△进行一次Powell-Sabin细分得到加细三角剖分△^(S),并且利用MT的几何信息构造二元一次样条函数空间S(△^(S))中的插值函数S;对D均匀采样之后,利用插值函数S得到规则型值点作为参数曲面表面点的近似;最后建立具有光顺性质的能量函数,求解出双三次B样条曲面的控制点网格,完成曲面重建.实验给出了柱面、鞍面等基础曲面和人头模型等自由曲面的重建结果.数值结果表明,与自适应算法相比,所提方法能够捕获由给定三角网格呈现的几何细节,重建复杂模型的点距均方误差减小38%.

摘要：探索现代化道路,“既要遵循现代化一般规律,更要符合本国实际,具有本国特色”,在此基础上选择好实现方式,从而实现现代化实现方式的“现代化”。西方传统的现代化显现着财富与进步,也充斥着窘困、矛盾等“现代性危机”。因此,需要重新反思实现现代化的“资本主义”方式。中国探索现代化的历程几经波折,当今又面临着诸多难题。“中国式现代化”具有一系列科学的目标设计、价值考量,蕴含着领导方式和推进方式的现代化、社会系统管理和整合方式的现代化、发展和创新模式的现代化。“中国式现代化”作为现代化的新型实现方式,超越了以往的现代化,具有重要的世界历史意义。