Impact of Urban 3D Morphology on Particulate Matter 2.5(PM2.5) Concentrations:Case Study of Beijing, China

Urban particulate matter 2.5(PM2.5)pollution and public health are closely related,and concerns regarding PM2.5 are widespread.Of the underlying factors,the urban morphology is the most manageable.Therefore,investigations of the impact of urban three-dimensional(3D)morphology on PM2.5 concentration have important scientific significance.In this paper,39 PM2.5 monitoring sites of Beijing in China were selected with PM2.5 automatic monitoring data that were collected in 2013.This data set was used to analyze the impacts of the meteorological condition and public transportation on PM2.5 concentrations.Based on the elimination of the meteorological conditions and public transportation factors,the relationships between urban 3D morphology and PM2.5 concentrations are highlighted.Ten urban 3D morphology indices were established to explore the spatial-temporal correlations between the indices and PM2.5 concentrations and analyze the impact of urban 3D morphology on the PM2.5 concentrations.Results demonstrated that road length density(RLD),road area density(RAD),construction area density(CAD),construction height density(CHD),construction volume density(CVD),construction otherness(CO),and vegetation area density(VAD)have positive impacts on the PM2.5 concentrations,whereas water area density(WAD),water fragmentation(WF),and vegetation fragmentation(VF)(except for the 500 m buffer)have negative impacts on the PM2.5 concentrations.Moreover,the correlations between the morphology indices and PM2.5 concentrations varied with the buffer scale.The findings could lay a foundation for the high-precision spatial-temporal modelling of PM2.5 concentrations and the scientific planning of urban 3D spaces by authorities responsible for controlling PM2.5 concentrations.

When a tree model meets texture baking:an approach for quality-preserving lightweight visualization in virtual 3D scene construction

Three-dimensional(3D)high-fidelity surface models play an important role in urban scene construction.However,the data quantity of such models is large and places a tremendous burden on rendering.Many applications must balance the visual quality of the models with the rendering efficiency.The study provides a practical texture baking processing pipeline for generating 3D models to reduce the model complexity and preserve the visually pleasing details.Concretely,we apply a mesh simplification to the original model and use texture baking to create three types of baked textures,namely,a diffuse map,normal map and displacement map.The simplified model with the baked textures has a pleasing visualization effect in a rendering engine.Furthermore,we discuss the influence of various factors in the process on the results,as well as the functional principles and characteristics of the baking textures.The proposed approach is very useful for real-time rendering with limited rendering hardware as no additional memory or computing capacity is required for properly preserving the relief details of the model.Each step in the pipeline is described in detail to facilitate the realization.

A real 3D scene rendering optimization method based on region of interest and viewing frustum prediction in virtual reality

As an important technology of digital construction,real 3D models can improve the immersion and realism of virtual reality(VR)scenes.The large amount of data for real 3D scenes requires more effective rendering methods,but the current rendering optimization methods have some defects and cannot render real 3D scenes in virtual reality.In this study,the location of the viewing frustum is predicted by a Kalman filter,and eye-tracking equipment is used to recognize the region of interest(ROI)in the scene.Finally,the real 3D model of interest in the predicted frustum is rendered first.The experimental results show that the method of this study can predict the frustrum location approximately 200 ms in advance,the prediction accuracy is approximately 87%,the scene rendering efficiency is improved by 8.3%,and the motion sickness is reduced by approximately 54.5%.These studies help promote the use of real 3D models in virtual reality and ROI recognition methods.In future work,we will further improve the prediction accuracy of viewing frustums in virtual reality and the application of eye tracking in virtual geographic scenes.

Propagations of Fresnel diffraction accelerating beam in Schrodinger equation with nonlocal nonlinearity

Accelerating beams have been the subject of extensive research in the last few decades because of their selfacceleration and diffraction-free propagation over several Rayleigh lengths.Here,we investigate the propagation dynamics of a Fresnel diffraction beam using the nonlocal nonlinear Schrodinger equation(NNLSE).When a nonlocal nonlinearity is introduced into the linear Schrodinger equation without invoking an external potential,the evolution behaviors of incident Fresnel diffraction beams are modulated regularly,and certain novel phenomena are observed.We show through numerical calculations,under varying degrees of nonlocality,that nonlocality significantly affects the evolution of Fresnel diffraction beams.Further,we briefly discuss the two-dimensional case as the equivalent of the product of two one-dimensional cases.At a critical point,the Airy-like intensity profile oscillates between the first and third quadrants,and the process repeats during propagation to yield an unusual oscillation.Our results are expected to contribute to the understanding of NNLSE and nonlinear optics.

凸轮轴虚拟磨削加工三维实景的建立

凸轮轴磨削工艺系统三维实景是本研究中凸轮轴虚拟磨削加工系统的基础功能单元。本文详细探讨了凸轮轴磨削工艺系统三维实景建立的技术方法。首先对虚拟磨床信息进行数据抽象以便于数据处理,再对虚拟加工工艺系统进行结构组织和再现,按照工艺系统各组成部分的运动关系来组织其数据关系,并据此建立了一个完整的三维实景平台系统,能用于凸轮轴磨削加工动态过程的虚拟再现,并实现了能增强用户真实感体验和提高用户操作效率的交互功能。

进藏公路三维实景技术军事应用研究

为提高进藏部队道路勘察效果,改善当前军用电子地图信息不全、代入感不强等弊端,以三维实景技术应用为切入点,分析了当前国内外研究现状,介绍了军事应用实现的关键技术及主要功能,提出了使用进藏公路三维实景地图来推动进藏部队摩托化机动训练和完成处置的方法,确保部队能够根据实时道路环境制订和开展有针对性的摩托化机动训练方案和相关处置预案,对提高训练效果有显著作用。

New Version of the CMA-GFS Dynamical Core Based on the Predictor–Corrector Time Integration Scheme

The operational numerical weather prediction system established by the China Meteorological Administration(CMA),based on the Global/Regional Assimilation and Prediction System(GRAPES)model,adopts the classical semi-implicit semi-Lagrangian(SISL)time integration algorithm.This paper describes a major upgrade to the dynamical core of the CMA global forecast system(CMA-GFS),which was successfully incorporated into operation in 2020.In the upgrade,the classical SISL is further developed into a predictor–corrector scheme,a three-dimensional(3D)reference profile instead of the original isothermal reference profile is applied when implementing the semi-implicit algorithm,and a hybrid terrain-following vertical coordinate system is also applied.The new version of the dynamical core greatly improves the model performance,the time integration reaches second-order accuracy,the time step can be extended by 50%,and the efficiency is greatly improved(by approximately 30%).Atmospheric circulation simulation is systematically improved,and deviations in temperature,wind,and humidity are reduced.The new version of the dynamical core provides a solid foundation for further development of the entire operational system of the CMA.