In recent years,the concept of digital human has attracted widespread attention from all walks of life,and the modelling of high-fidelity human bodies,heads,and hands has been intensively studied.This paper focuses on...In recent years,the concept of digital human has attracted widespread attention from all walks of life,and the modelling of high-fidelity human bodies,heads,and hands has been intensively studied.This paper focuses on head modelling and proposes a generic head parametric model based on neural radiance fields.Specifically,we first use face recognition networks and 3D facial expression database FaceWarehouse to parameterize identity and expression semantics,respectively,and use both as conditional inputs to build a neural radiance field for the human head,thereby improving the head model’s representation ability while ensuring editing capabilities for the identity and expression of the rendered results;then,through a combination of volume rendering and neural rendering,the 3D representation of the head is rapidly rendered into the 2D plane,producing a high-fidelity image of the human head.Thanks to the well-designed loss functions and good implicit representation of the neural radiance field,our model can not only edit the identity and expression independently,but also freely modify the virtual camera position of the rendering results.It has excellent multi-view consistency,and has many applications in novel view synthesis,pose driving and more.展开更多
We introduce the artificial fish swarm algorithm for heading motion model identification and control parameter optimization problems for the“Ocean Rambler”unmanned wave glider(UWG).First,under certain assumptions,th...We introduce the artificial fish swarm algorithm for heading motion model identification and control parameter optimization problems for the“Ocean Rambler”unmanned wave glider(UWG).First,under certain assumptions,the rigid-flexible multi-body system of the UWG was simplified as a rigid system composed of“thruster+float body”,based on which a planar motion model of the UWG was established.Second,we obtained the model parameters using an empirical method combined with parameter identification,which means that some parameters were estimated by the empirical method.In view of the specificity and importance of the heading control,heading model parameters were identified through the artificial fish swarm algorithm based on tank test data,so that we could take full advantage of the limited trial data to factually describe the dynamic characteristics of the system.Based on the established heading motion model,parameters of the heading S-surface controller were optimized using the artificial fish swarm algorithm.Heading motion comparison and maritime control experiments of the“Ocean Rambler”UWG were completed.Tank test results show high precision of heading motion prediction including heading angle and yawing angular velocity.The UWG shows good control performance in tank tests and sea trials.The efficiency of the proposed method is verified.展开更多
The globalization and the intensive competition of th e automotive market require shortening the product development cycle, improving the quality and reducing the cost. Optimizing the product development process, b ui...The globalization and the intensive competition of th e automotive market require shortening the product development cycle, improving the quality and reducing the cost. Optimizing the product development process, b uilding product’s consistent defining model for life cycle, and realizing the in tegration of CAD/CAM/CAE and Concurrent Engineering (CE) become the means to acc ept the challenge. A new product modeling technology, Multi Model Technology (MM T), is provided in this paper to meet the needs of the challenge for automotive powertrain product development. First, the paper introduces the concept of Multi Model Technology. MMT introduce s Object-oriented Technology (OT) into product modeling process and combine OT with feature-based modeling technology. With the help of OT, MMT builds product object model to support system level management in product development. The obj ect model of the product is a Multi Model Structure. The MMS consists of finish part model level (assembly model level), rough part model level (part model leve l), function model level and basic model level. Every models in the MMS is creat ed by feature-based technology in design process. In this case, models in the M MS of product can be shared by casting mould, sand core and sand core mould. The refore, CAD engineers, CAE engineers and CAM engineers can work concurrently and the integration of CAD/CAM/CAE can be realized. Second, MMT is applied in cylinder head development. The multi model structures of cylinder head, its casting mould, sand core and sand core mould are built, an d the process-oriented feature models of every objects in the multi model struc tures are modeled, the application of different model objects in development pro cess is analyzed. The integrated modeling technology of cylinder head, its casti ng mould, sand core and sand core mould under MMT is studied. And the concurrent engineering oriented integration method of CAD/CAE and the method to realize th e integration of CAD/CAE under MMT are also discussed. Based on above, the integ ration of CAD/CAM/CAE of cylinder head is realized in automotive powertrain prod uct. The practice results shows that the modeling technology in this paper can optimi ze the development process, realize the data sharing and concurrent engineering in the product development process.展开更多
为清晰阐明钝性弹道冲击下人体头部的受损机理,基于THUMS(Total Human Model for Safety)模型,通过材料参数优化、比例缩放及流固耦合方法,构建符合中国50百分位成年男性头部特征的有限元模型。以LS-DYNA(Livermore Software Technology...为清晰阐明钝性弹道冲击下人体头部的受损机理,基于THUMS(Total Human Model for Safety)模型,通过材料参数优化、比例缩放及流固耦合方法,构建符合中国50百分位成年男性头部特征的有限元模型。以LS-DYNA(Livermore Software Technology Corporation's Dynamic Analyzer)软件为仿真平台,采用任意拉格朗日-欧拉算法定义脑脊液流体特性,优化颅骨与脑组织的弹塑性材料参数,并通过网格变形技术实现头部尺寸与解剖结构的本土化适配。选取前额、顶壁、枕部及后窝等典型易损区,对比Nahum尸体实验及THUMS模型数据,验证模型的生物力学响应。研究结果表明:改进模型在易损区域的颅内压峰值分别为150 kPa、75 kPa、53 kPa及69 kPa,与实验数据误差为4%~10%,且动态响应曲线形态一致;脑组织最大von Mises应力(29.5 kPa)与颅骨主应力(18.7 kPa)均接近Marjoux和Yoganandan仿真实验阈值,证实模型可有效预测颅脑损伤风险。结合北约AEP-103标准评估表明,典型冲击下前额颅内压峰值达511.1 kPa,远超颅骨骨折阈值(150 kPa),凸显现有防护装备的优化需求。该模型应用性强,可为钝性弹道冲击下的头部损伤评估与安全防护提供方法参照和理论支撑。展开更多
个性化三维(three-dimensional,3D)头部模型在头相关传输函数(head-related transfer function,HRTF)和虚拟听觉重放中有着重要应用。光学扫描是获取3D头部模型的常用方法,但不同光学扫描方式的误差及其对HRTF的影响尚不明确。文章以自...个性化三维(three-dimensional,3D)头部模型在头相关传输函数(head-related transfer function,HRTF)和虚拟听觉重放中有着重要应用。光学扫描是获取3D头部模型的常用方法,但不同光学扫描方式的误差及其对HRTF的影响尚不明确。文章以自主设计的3D头部模型为参照模型MO(基准),并将3D打印制作的模型作为扫描对象。选取三款代表性光学扫描设备(手持式红色激光扫描仪HandySCAN 300、手持式白光发光二极管扫描仪Reeyee Pro 2X、红外激光iPhone12手机)扫描得到对应的模型M_(H),M_(R)和M_(I)。为评价新采集模型曲面精度,对比了模型间图形偏差的色阶图和偏差距离均方根(root mean square,RMS),进一步分析模型精度对HRTF数据的影响,对比了模型间的HRTF谱误差。结果表明,图形偏差主要集中在耳廓局部细节,HRTF谱误差主要出现在高频。相较而言,模型M_(H)与M_(O)最为接近,曲面误差基本在±0.40 mm以内,超过3.0 dB的HRTF谱误差仅出现在8 kHz以上的频段,且这种误差只在少数空间方向中观察到。模型M_(R)和M_(I)相比于M_(O)的曲面误差分别达到约−0.90~1.90 mm和−1.20~3.20 mm,8 kHz以上HRTF谱误差在大多数方向均超过3.0 dB。相关研究为3D头部扫描方式选用提供了参考依据。展开更多
创伤性脑损伤(traumatic brain injury,TBI)是发病率、患病率最高的神经系统疾病,为全社会带来了巨大的公共卫生负担。深入研究TBI的生物力学原理有助于提升头部防护效果,发展快速评估技术并采取及时干预,从而降低伤情恶化的风险。人类...创伤性脑损伤(traumatic brain injury,TBI)是发病率、患病率最高的神经系统疾病,为全社会带来了巨大的公共卫生负担。深入研究TBI的生物力学原理有助于提升头部防护效果,发展快速评估技术并采取及时干预,从而降低伤情恶化的风险。人类头部有限元模型(finite element head model,FEHM)作为一种数值分析工具,能够模拟头部在受到冲击时的动态响应,包括脑组织的应力应变时空分布、颅内压的变化等,为理解创伤性脑损伤的力学机制提供了重要依据。本文详细总结了国内外主流的人类头部有限元模型的现状与发展,追溯了模型的发展历程,总结了模型的特点并介绍了基于有限元模型的TBI机制研究进展。对相关研究的总结和梳理将有助于开发新型FEHM,并为创伤性脑损伤的风险评估及防护装备的设计提供理论指导和技术支撑。展开更多
文摘In recent years,the concept of digital human has attracted widespread attention from all walks of life,and the modelling of high-fidelity human bodies,heads,and hands has been intensively studied.This paper focuses on head modelling and proposes a generic head parametric model based on neural radiance fields.Specifically,we first use face recognition networks and 3D facial expression database FaceWarehouse to parameterize identity and expression semantics,respectively,and use both as conditional inputs to build a neural radiance field for the human head,thereby improving the head model’s representation ability while ensuring editing capabilities for the identity and expression of the rendered results;then,through a combination of volume rendering and neural rendering,the 3D representation of the head is rapidly rendered into the 2D plane,producing a high-fidelity image of the human head.Thanks to the well-designed loss functions and good implicit representation of the neural radiance field,our model can not only edit the identity and expression independently,but also freely modify the virtual camera position of the rendering results.It has excellent multi-view consistency,and has many applications in novel view synthesis,pose driving and more.
基金Project(51779052)supported by the National Natural Science Foundation of ChinaProject(QC2016062)supported by the Natural Science Foundation of Heilongjiang Province,China+2 种基金Project(614221503091701)supported by the Research Fund from Science and Technology on Underwater Vehicle Laboratory,ChinaProject(LBH-Q17046)supported by the Heilongjiang Postdoctoral Funds for Scientific Research Initiation,ChinaProject(HEUCFP201741)supported by the Fundamental Research Funds for the Central Universities,China
文摘We introduce the artificial fish swarm algorithm for heading motion model identification and control parameter optimization problems for the“Ocean Rambler”unmanned wave glider(UWG).First,under certain assumptions,the rigid-flexible multi-body system of the UWG was simplified as a rigid system composed of“thruster+float body”,based on which a planar motion model of the UWG was established.Second,we obtained the model parameters using an empirical method combined with parameter identification,which means that some parameters were estimated by the empirical method.In view of the specificity and importance of the heading control,heading model parameters were identified through the artificial fish swarm algorithm based on tank test data,so that we could take full advantage of the limited trial data to factually describe the dynamic characteristics of the system.Based on the established heading motion model,parameters of the heading S-surface controller were optimized using the artificial fish swarm algorithm.Heading motion comparison and maritime control experiments of the“Ocean Rambler”UWG were completed.Tank test results show high precision of heading motion prediction including heading angle and yawing angular velocity.The UWG shows good control performance in tank tests and sea trials.The efficiency of the proposed method is verified.
文摘The globalization and the intensive competition of th e automotive market require shortening the product development cycle, improving the quality and reducing the cost. Optimizing the product development process, b uilding product’s consistent defining model for life cycle, and realizing the in tegration of CAD/CAM/CAE and Concurrent Engineering (CE) become the means to acc ept the challenge. A new product modeling technology, Multi Model Technology (MM T), is provided in this paper to meet the needs of the challenge for automotive powertrain product development. First, the paper introduces the concept of Multi Model Technology. MMT introduce s Object-oriented Technology (OT) into product modeling process and combine OT with feature-based modeling technology. With the help of OT, MMT builds product object model to support system level management in product development. The obj ect model of the product is a Multi Model Structure. The MMS consists of finish part model level (assembly model level), rough part model level (part model leve l), function model level and basic model level. Every models in the MMS is creat ed by feature-based technology in design process. In this case, models in the M MS of product can be shared by casting mould, sand core and sand core mould. The refore, CAD engineers, CAE engineers and CAM engineers can work concurrently and the integration of CAD/CAM/CAE can be realized. Second, MMT is applied in cylinder head development. The multi model structures of cylinder head, its casting mould, sand core and sand core mould are built, an d the process-oriented feature models of every objects in the multi model struc tures are modeled, the application of different model objects in development pro cess is analyzed. The integrated modeling technology of cylinder head, its casti ng mould, sand core and sand core mould under MMT is studied. And the concurrent engineering oriented integration method of CAD/CAE and the method to realize th e integration of CAD/CAE under MMT are also discussed. Based on above, the integ ration of CAD/CAM/CAE of cylinder head is realized in automotive powertrain prod uct. The practice results shows that the modeling technology in this paper can optimi ze the development process, realize the data sharing and concurrent engineering in the product development process.
文摘个性化三维(three-dimensional,3D)头部模型在头相关传输函数(head-related transfer function,HRTF)和虚拟听觉重放中有着重要应用。光学扫描是获取3D头部模型的常用方法,但不同光学扫描方式的误差及其对HRTF的影响尚不明确。文章以自主设计的3D头部模型为参照模型MO(基准),并将3D打印制作的模型作为扫描对象。选取三款代表性光学扫描设备(手持式红色激光扫描仪HandySCAN 300、手持式白光发光二极管扫描仪Reeyee Pro 2X、红外激光iPhone12手机)扫描得到对应的模型M_(H),M_(R)和M_(I)。为评价新采集模型曲面精度,对比了模型间图形偏差的色阶图和偏差距离均方根(root mean square,RMS),进一步分析模型精度对HRTF数据的影响,对比了模型间的HRTF谱误差。结果表明,图形偏差主要集中在耳廓局部细节,HRTF谱误差主要出现在高频。相较而言,模型M_(H)与M_(O)最为接近,曲面误差基本在±0.40 mm以内,超过3.0 dB的HRTF谱误差仅出现在8 kHz以上的频段,且这种误差只在少数空间方向中观察到。模型M_(R)和M_(I)相比于M_(O)的曲面误差分别达到约−0.90~1.90 mm和−1.20~3.20 mm,8 kHz以上HRTF谱误差在大多数方向均超过3.0 dB。相关研究为3D头部扫描方式选用提供了参考依据。
文摘创伤性脑损伤(traumatic brain injury,TBI)是发病率、患病率最高的神经系统疾病,为全社会带来了巨大的公共卫生负担。深入研究TBI的生物力学原理有助于提升头部防护效果,发展快速评估技术并采取及时干预,从而降低伤情恶化的风险。人类头部有限元模型(finite element head model,FEHM)作为一种数值分析工具,能够模拟头部在受到冲击时的动态响应,包括脑组织的应力应变时空分布、颅内压的变化等,为理解创伤性脑损伤的力学机制提供了重要依据。本文详细总结了国内外主流的人类头部有限元模型的现状与发展,追溯了模型的发展历程,总结了模型的特点并介绍了基于有限元模型的TBI机制研究进展。对相关研究的总结和梳理将有助于开发新型FEHM,并为创伤性脑损伤的风险评估及防护装备的设计提供理论指导和技术支撑。
