基于计算机视觉和粒子系统的三维云模拟

云是很常见的一种自然现象，真实感云的模拟是计算机图形学领域具有挑战性的研究课题。文章提出了一种基于计算机视觉和粒子系统的三维云建模方法。首先利用计算机视觉技术从现有的二维云图像中提取云的三维信息，然后利用粒子系统填充该三维空间，最后通过纹理映射和Billboard技术实现三维云的绘制。与以往云建模方法相比，该方法简单、实用，适用于模拟不同种类的云，如层云、积云、卷云等。     

基于隐式限制四叉树的大规模动态地形建模与仿真方法

大规模动态地形场景的建模与仿真是计算机图形学与虚拟显示领域的重要课题之一。本文提出了一种基于隐式限制四叉树的地形建模方法,用四叉树标记数组代替四叉树节点结构与指针操作,不但节省了大规模地形数据集所占的存储空间,而且提高了节点的索引效率。另外,提出了基于高程值的地形纹理图像合成方法,根据地形采样点的高程值实时合成匹配地形特征的纹理图像。本文还给出了弹坑与车辙的建模方法。仿真结果表明,本文描述的方法可以实时获得逼真的大规模动态地形仿真效果。     

实景树木参数化建模方法研究

受限于航空倾斜摄影图像的拍摄角度，三维重建场景中的树木模型存在大量失真、变形和空洞。而更为精细的树木建模方法，如基于近景图像、激光点云的树木建模方法效率低且成本较高。因此，提出一种具有真实感的实景树木参数化建模方法，对真实场景中的航空倾斜摄影图像和树木三维点云进行特征提取，归纳各类树木的几何外形、拓扑结构和纹理材质，设计一套适用于各类树木的生长规则，最终实现实景树木多细节层次建模。实验结果表明，该方法能够保证模型整体的完整性和细节的真实性，同时满足场景渲染要求，为三维场景重建、数字林业和智慧城市等应用提供有效的技术支撑。     

网络中心战通信仿真模型结构与逻辑研究

网络通信效能的建模仿真是网络中心战（network centric warfare,NCW）信息增值链条仿真研究的重要组成部分。在HLA（high level architecture）分布式虚拟战场环境中进行NCW信息网络的建模仿真,有＂分散式＂和＂集中式＂两种实现途径。本文通过对网络中信息传递过程的分析,分别给出了两种仿真途径的通信模型组成和仿真实现逻辑。对于＂分散式＂通信仿真,引入了多个功能函数对消息的各个处理流程及通信链路性能进行功能性建模;借助网络仿真工具构建NCW跨层的网络通信协议栈模型,从而实现NCW虚拟战场＂集中式＂通信仿真。这两种仿真途径的逻辑实现方法为在HLA分布式虚拟战场中进行NCW通信仿真研究提供了一种解决思路,对NCW网络化信息增值的效果研究具有实际意义。     

2015全国环境建模与仿真技术学术交流会征文通知

7月上旬连云港由中国体视学学会虚拟现实与仿真技术分会、中国系统仿真学会环境建模与仿真专业委员会联合主办的2015年全国环境建模与仿真技术学术交流会将于7月上旬在海滨城市连云港召开,促进建模仿真理论与方法、虚拟现实技术、环境仿真方法与技术、仿真应用技术学术成果的交流,促进仿真科学与技术在理论、方法及应用领域的创新。欢迎中国体视学学会、中国系统仿真学会的广大会员、科技工作者、技术人员以及在     

2013全国环境建模与仿真技术学术交流会征文通知

由中国系统仿真学会环境建模仿真专业委员会、中国体视学学会仿真与虚拟现实分会联合主办的2013年全国环境建模与仿真技术学术交流会将于7月下旬在海滨城市秦皇岛召开。会议宗旨为促进建模仿真理论与方法、虚拟现实技术环境应用学成果的交流，科在及领域创新欢迎中国体视系统广大员工作者人以校生踊跃投稿积极参活动。     

2010年“虚拟技术与环境仿真学术年会”会议纪要

2010年8月21日至23日，由中国体视学学会仿真与虚拟现实分会以及中国系统仿真学会环境仿真专业委员会（筹）联合发起、北京航空航天大学自动化学院承办的2010年“虚拟技术与环境仿真学术年会”在湖南吉首市今朝宾馆召开。会议旨在促进建模仿真理论与方法、虚拟现实技术、环境仿真方法与技术、仿真应用技术学术成果的交流，促进仿真科学与技术在理论、方法及应用领域的创新。     

2015全国环境建模与仿真技术学术交流会征文通知

由中国体视学学会虚拟现实与仿真技术分会、中国系统仿真学会环境建模与仿真专业委员会联合主办的2015年全国环境建模与仿真技术学术交流会将于7月上旬在海滨城市连云港召开,促进建模仿真理论与方法、虚拟现实技术、环境仿真方法与技术、仿真应用技术学术成果的交流,促进仿真科学与技术在理论、方法及应用领域的创新。欢迎中国体视学学会、中国系统仿真学会的广大会员、科技工作者、技术人员以及在校学生踊跃投稿,积极参与学术交流活动。     

形态定量技术在食管癌病理学研究中的应用及其历史回顾

文章在简述形态定量技术基本原理和检测意义的基础上，对该技术在食管细胞涂片检测、组织纹理分析、分形及分形维数等定量指标在食管癌病理学研究中的应用进行了复习及回顾。     

分形纹理分析及其在雷达目标识别中的应用

作为一种自然景物的模型,分形几何越来越多地受到了人们的关注。分形纹理分析是分形在图像处理中的应用研究的一个主要内容。注意到仅用分形维数特征不足以描述和区分不同的图像纹理,本文采用不同尺度下的方向性分维的变化曲线作为纹理图像的特征,对不同纹理的图像进行识别。实验表明这一方法是有效的。最后,本文讨论了该方法在雷达目标情况识别技术中的应用。     

Automated model-based organ delineation for radiotherapy planning in prostatic region

PURPOSE: Organ delineation is one of the most tedious and time-consuming parts of radiotherapy planning. It is usually performed by manual contouring in two-dimensional slices using simple drawing tools, and it may take several hours to delineate all structures of interest in a three-dimensional (3D) data set used for planning. In this paper, a 3D model-based approach to automated organ delineation is introduced that allows for a significant reduction of the time required for contouring. METHODS AND MATERIALS: The presented method is based on an adaptation of 3D deformable surface models to the boundaries of the anatomic structures of interest. The adaptation is based on a tradeoff between deformations of the model induced by its attraction to certain image features and the shape integrity of the model. To make the concept clinically feasible, interactive tools are introduced that allow quick correction in problematic areas in which the automated model adaptation may fail. A feasibility study with 40 clinical data sets was done for the male pelvic area, in which the risk organs (bladder, rectum, and femoral heads) were segmented by automatically adapting the corresponding organ models. RESULTS: In several cases of the validation study, minor user interaction was required. Nevertheless, a statistically significant reduction in the time required compared with manual organ contouring was achieved. The results of the validation study showed that the presented model-based approach is accurate (1.0-1.7 mm mean error) for the tested anatomic structures. CONCLUSION: A framework for organ delineation in radiotherapy planning is presented, including automated 3D model-based segmentation, as well as tools for interactive corrections. We demonstrated that the proposed approach is significantly more efficient than manual contouring in two-dimensional slices.     

Computational feasibility of deformable mirror microwave hyperthermia technique for localized breast tumors.

PURPOSE: Computational feasibility of a new non-invasive microwave hyperthermia technique that employs dual deformable mirror is investigated using simplified computational tools and anatomically realistic breast models. MATERIALS AND METHODS: The proposed technique employs two pairs of electromagnetic sources and continuously deformable mirrors to focus the electromagnetic radiation at the target site for hyperthermia. The mirror functions like a continuum of radiating elements that offer effective scan coverage inside the breast with efficient field focusing at the target location. The electric field focusing and temperature mapping in the two-dimensional numerical simulations are investigated using wave propagation and bio-heat transfer models respectively. The method of moments, a popular numerical simulation tool, is used to model the electric field maintained by the deformable mirrors for continuous wave excitation. The electromagnetic (EM) energy deposited by the mirrors is used in the steady state bio-heat transfer equation to quantify the temperature distribution inside two-dimensional anatomically realistic breast models. RESULTS: Feasibility of the proposed technique is evaluated using numerical breast models derived from magnetic resonance images of patients with variation in breast density, age and pathology. CONCLUSIONS: The computational study indicates preferential EM energy deposition and temperature elevation inside tumor tissue with minimum collateral damage to the neighboring normal tissues. Simulation results obtained for the magnetic resonance (MR) breast data appear promising and indicate the merit in pursuing the investigation using 3D computational models.     

Stereoscopic presentation of computed tomography and magnetic resonance images

This technical note describes a direct and simple method of stereoscopically presenting three-dimensional (3-D) CT and MRI volumetric models. This method has negligible cost both in monetary terms and in extra processing time, is extremely accessible, easy to learn and apply and can be effectively used in the absence of any sophisticated equipment. It has the potential to greatly boost the communications value of many complex studies where 3-D models are already normally generated.     

Cancer systems biology: signal processing for cancer research

In this editorial we introduce the research paradigms of signal processing in the era of systems biology.Signal processing is a field of science traditionally focused on modeling electronic and communications systems,but recently it has turned to biological applications with astounding results.The essence of signal processing is to describe the natural world by mathematical models and then,based on these models,develop efficient computational tools for solving engineering problems.Here,we underline,with exa...     

Simulation studies promote technological development of radiofrequency phased array hyperthermia

A treatment planning program package for radiofrequency hyperthermia has been developed. It consists of software modules for processing three-dimensional computerized tomography (CT) data sets, manual segmentation, generation of tetrahedral grids, numerical calculation and optimisation of three-dimensional E field distributions using a volume surface integral equation algorithm as well as temperature distributions using an adaptive multilevel finite-elements code, and graphical tools for simultaneous representation of CT data and simulation results. Heat treatments are limited by hot spots in healthy tissues caused by E field maxima at electrical interfaces (bone/muscle). In order to reduce or avoid hot spots suitable objective functions are derived from power deposition patterns and temperature distributions, and are utilised to optimise antenna parameters (phases, amplitudes). The simulation and optimisation tools have been applied to estimate the improvements that could be reached by upgrades of the clinically used SIGMA-60 applicator (consisting of a single ring of four antenna pairs). The investigated upgrades are increased number of antennas and channels (triple-ring of 3 × 8 antennas and variation of antenna inclination. Significant improvement of index temperatures (1–2°C) is achieved by upgrading the single ring to a triple ring with free phase selection for every antenna or antenna pair. Antenna amplitudes and inclinations proved as less important parameters.     

Three-dimensional treatment planning for lung cancer

The experience of four institutions involved in a three-dimensional treatment planning contract (NCI) for lung cancer is described. It was found that three-dimensional treatment planning has a significant potential for optimization of treatment plans for radiotherapy of lung cancer both for tumor coverage and sparing of critical normal tissues within the complex anatomy of the human thorax. Evaluation tools, such as dose-volume histograms, and three-dimensional isodose displays, such as multiple plane views, surface dose displays, etc., were found to be extremely valuable in evaluation and comparison of these complex plans. It is anticipated that with further developments in three-dimensional simulation and treatment delivery systems, major progress towards uncomplicated local regional control of lung cancer may be forthcoming.     

Simulation studies promote technological development of radiofrequency phased array hyperthermia

A treatment planning program package for radiofrequency hyperthermia has been developed. It consists of software modules for processing three-dimensional computerized tomography (CT) data sets, manual segmentation, generation of tetrahedral grids, numerical calculation and optimisation of three-dimensional Ε field distributions using a volume surface integral equation algorithm as well as temperature distributions using an adaptive multilevel finite-elements code, and graphical tools for simultaneous representation of CT data and simulation results. Heat treatments are limited by hot spots in healthy tissues caused by Ε field maxima at electrical interfaces (bone/muscle). In order to reduce or avoid hot spots suitable objective functions are derived from power deposition patterns and temperature distributions, and are utilised to optimise antenna parameters (phases, amplitudes). The simulation and optimisation tools have been applied to estimate the improvements that could be reached by upgrades of the clinically used SIGMA-60 applicator (consisting of a single ring of four antenna pairs). The investigated upgrades are increased number of antennas and channels (triple-ring of 3 × 8 antennas and variation of antenna inclination. Significant improvement of index temperatures (1–2°C) is achieved by upgrading the single ring to a triple ring with free phase selection for every antenna or antenna pair. Antenna amplitudes and inclinations proved as less important parameters.     

Multivariable modeling of radiotherapy outcomes, including dose-volume and clinical factors

PURPOSE: The probability of a specific radiotherapy outcome is typically a complex, unknown function of dosimetric and clinical factors. Current models are usually oversimplified. We describe alternative methods for building multivariable dose-response models. METHODS: Representative data sets of esophagitis and xerostomia are used. We use a logistic regression framework to approximate the treatment-response function. Bootstrap replications are performed to explore variable selection stability. To guard against under/overfitting, we compare several analytical and data-driven methods for model-order estimation. Spearman's coefficient is used to evaluate performance robustness. Novel graphical displays of variable cross correlations and bootstrap selection are demonstrated. RESULTS: Bootstrap variable selection techniques improve model building by reducing sample size effects and unveiling variable cross correlations. Inference by resampling and Bayesian approaches produced generally consistent guidance for model order estimation. The optimal esophagitis model consisted of 5 dosimetric/clinical variables. Although the xerostomia model could be improved by combining clinical and dose-volume factors, the improvement would be small. CONCLUSIONS: Prediction of treatment response can be improved by mixing clinical and dose-volume factors. Graphical tools can mitigate the inherent complexity of multivariable modeling. Bootstrap-based variable selection analysis increases the reliability of reported models. Statistical inference methods combined with Spearman's coefficient provide an efficient approach to estimating optimal model order.     

Computational feasibility of deformable mirror microwave hyperthermia technique for localized breast tumors

Purpose: Computational feasibility of a new non-invasive microwave hyperthermia technique that employs dual deformable mirror is investigated using simplified computational tools and anatomically realistic breast models.

Materials and methods: The proposed technique employs two pairs of electromagnetic sources and continuously deformable mirrors to focus the electromagnetic radiation at the target site for hyperthermia. The mirror functions like a continuum of radiating elements that offer effective scan coverage inside the breast with efficient field focusing at the target location. The electric field focusing and temperature mapping in the two-dimensional numerical simulations are investigated using wave propagation and bio-heat transfer models respectively. The method of moments, a popular numerical simulation tool, is used to model the electric field maintained by the deformable mirrors for continuous wave excitation. The electromagnetic (EM) energy deposited by the mirrors is used in the steady state bio-heat transfer equation to quantify the temperature distribution inside two-dimensional anatomically realistic breast models.

Results: Feasibility of the proposed technique is evaluated using numerical breast models derived from magnetic resonance images of patients with variation in breast density, age and pathology.

Conclusions: The computational study indicates preferential EM energy deposition and temperature elevation inside tumor tissue with minimum collateral damage to the neighboring normal tissues. Simulation results obtained for the magnetic resonance (MR) breast data appear promising and indicate the merit in pursuing the investigation using 3D computational models.