Transformation of a thin-walled solid model into a surface model via solid deflation

A simplified geometric model with lower dimensionality, such as a mid-surface model, is often preferred over a detailed solid model for the analysis process, if the analysis results are not seriously impacted. In order to derive a mid-surface model from a thin-walled solid model, in this paper, we propose a novel approach called the solid deflation method. In this method, a solid model is assumed to be created by using air to inflate a shell that comprises the surface of the solid model. First, the model is simplified by the removal of any detailed features whose absence would not alter its overall shape. Next, the solid model itself can be converted into a degenerate solid model with zero thickness. Finally, a surface model is generated by splitting large faces paired in the thinned solid model, selecting one face per pair for creating a sheet model, and sewing the selected faces. Using this method, a more practical and usable mid-surface model can be very efficiently generated from a solid model because it can circumvent not only the tedious trimming and extension processes of the medial axis transformation method but also the time-consuming patch joining process of the mid-surface abstraction approach.     

Atmospheric correction of optical imagery from MODIS and Reanalysis atmospheric products

In this paper we analyze the differences obtained in the atmospheric correction of optical imagery covering bands located in the Visible and Near Infra-Red (VNIR), Short-Wave Infra-Red (SWIR) and Themal-Infrared (TIR) spectral regions when atmospheric profiles extracted from different sources are used. In particular, three sensors were used, Compact High Resolution Imaging Spectrometer (CHRIS), Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER) and Landsat5 Thematic Mapper (TM), whereas four atmospheric profiles sources were considered: i) local soundings launched near the sensor overpass time, ii) Moderate Resolution Radiometer (MODIS) atmospheric profiles product (MOD07), iii) Atmospheric Correction Parameter Calculator (ACPC) generated by the National Center for Environmental Prediction (NCEP) and iv) Modified Atmospheric Profiles from Reanalysis Information (MAPRI), which includes data from NCEP and National Center of Atmospheric Research (NCAR) Reanalysis project but interpolated to 34 atmospheric levels and resampled to 0.5° × 0.5°. MODIS aerosol product (MOD04) was also used to extract Aerosol Optical Thickness (AOT) values at 550 nm. Analysis was performed for three test dates (12th July 2003, 18th July 2004 and 13th July 2005) over an agricultural area in Spain. Results showed that air temperature vertical profiles were similar for the four sources, whereas dew point temperature profiles showed significant differences at some particular levels. Atmospheric profiles were used as input to MODTRAN4 radiative transfer code in order to compute atmospheric parameters involved in atmospheric correction, with the aim of retrieving surface reflectances in the case of VNIR and SWIR regions, and Land Surface Temperature (LST) in the case of the TIR region. For the VNIR and SWIR region, significant differences depending on the atmospheric profile used were not found, particularly in the Visible region in which the AOT content is the main parameter involved in the atmospheric correction. In the case of TIR, differences depending on the atmospheric profile used were appreciable, since in this case the main parameter involved in the atmospheric correction is the water vapor content, which depends on the vertical profile. In terms of LST retrieval from ASTER data (2004 test case), all profiles provided satisfactory results compared to the ones obtained when using a local sounding, with errors of 0.3 K for ACPC and MAPRI cases and 0.7 K for MOD07. When retrieving LST from TM data (2005 test case), errors for MOD07 and MAPRI were 0.6 and 0.9 K respectively, whereas ACPC provided an error of 2 K. The results presented in this paper show that the different atmospheric profile sources are useful for accurate atmospheric correction when local soundings are not available. In particular, MOD07 product provides atmospheric information at the highest spatial resolution, 5 km, although its use is limited from 2000 to present, whereas MAPRI provides historical information from 1970 to present, but at lower spatial resolution.     

Numerical simulation of steady planar die swell for a Newtonian fluid using the spectral element method

This paper is concerned with two dimensional numerical simulations of plane extrusion of a Newtonian fluid. The problem is discretized using the spectral element method and the free surface is evolved according to an ALE treatment. Numerical simulations are performed over a wide range of Reynolds and Weber numbers to highlight the effects of inertia and surface tension, respectively. Convergence of the numerical approximations with respect to polynomial order is demonstrated for the sensitive measures of free surface location and downstream relaxation distance. The higher the inertia the further downstream the relaxation occurs. Numerical results show good qualitative and quantitative agreement with predictions of other numerical schemes and experiments.     

Hybrid LES/RANS modelling of free surface flow through vegetation

Vegetated channels are environmentally friendly and frequently used to convey water for drainage and recreational purposes. The design and assessment of these channels often requires the use of numerical models which are based on the Reynolds Averaged Navier-Stokes (RANS) approach or Large Eddy Simulations (LES). It is well accepted that both approaches have their advantages and disadvantages. To overcome these disadvantages a hybrid model combining the RANS and LES methodologies is proposed in this work. The major task for the model development is to couple the RANS and the LES models effectively. Various methods have been investigated and the results are as follows. At the inflow boundary of the computational domain, a semi-analytical velocity profile for submerged vegetation is used as the RANS inflow condition to shorten the unrealistic flow transition region. At the interface of the upstream RANS region and the downstream LES region, turbulence fluctuations are artificially generated using a spectral line processor, with the mean velocity determined by using the frozen cloud assumption. At the interface of the upstream LES region and the downstream RANS region, a virtual momentum sink is imposed to dissipate the sub-grid scale fluctuations and to shorten the transition region. The final model has been verified against experiments of flow through submerged and emergent vegetation, as well as a partly vegetated channel.     

昆仑山口西8.1级大地震震后库赛湖地区多时相InSAR地表形变遥感探测

利用2003年~2007年间14景欧空局ENVISAT ASAR卫星数据,结合SRTM DEM数据,采用多时相SAR协同配准方法进行二路干涉处理,对2001年11月昆仑山口西8.1级大地震宏观震中—库赛湖地区的地表形变场进行了多时相探测。结果表明:①多时相InSAR技术能够对位于高海拔山区的东昆仑断裂带库赛湖段的地表形变实施连续监测;②震后发震断裂带的调整活动经历了一个动态变化的过程,2003年~2004年、2005年9月至2006年2月相对活跃,调整幅度较大,2004年11月至2005年9月间调整较小;③2006年~2007年发震断裂带地区活动逐渐减弱。     

A portable stereo vision system for whole body surface imaging

This paper presents a whole body surface imaging system based on stereo vision technology. We have adopted a compact and economical configuration which involves only four stereo units to image the frontal and rear sides of the body. The success of the system depends on a stereo matching process that can effectively segment the body from the background in addition to recovering sufficient geometric details. For this purpose, we have developed a novel sub-pixel, dense stereo matching algorithm which includes two major phases. In the first phase, the foreground is accurately segmented with the help of a predefined virtual interface in the disparity space image, and a coarse disparity map is generated with block matching. In the second phase, local least squares matching is performed in combination with global optimization within a regularization framework, so as to ensure both accuracy and reliability. Our experimental results show that the system can realistically capture smooth and complete whole body shapes with high accuracy.     

我国古代造园手法在现代城市园林规划设计中的应用

中国造园有着悠久的历史和高深的造诣,在世界造园史上,它独树一帜,并对东、西方造园业产生了一定的影响。随着我国城市化进程的加快,如今的人们越来越渴望自然、亲近自然。如果我们敢于求教于先人,能够将这些先人们的造园法则运用于现代城市园林规划设计中的话,必将会为我国现代城市园林规划设计带来极大的帮助。     

城市地铁车站环境艺术设计要点探讨

城市地铁在世界各地得到大力发展。地铁车站环境艺术设计对提升城市居民出行效率和质量,展现城市地域文化和特色都具有重要作用。地铁车站环境艺术设计应注意光线、空气和自然等三个重要问题,并应把握安全性、方便性、人性化、协调性、地域性和艺术性六个原则。     

基于城市文化的城市礼品设计研究

2010上海世博会首次将"城市"作为主题,为城市未来的发展提供多种新的思考方式。城市文化是城市主题中的一个核心要素,各个城市都在为如何审视自己城市文化的内涵特征、呈现方式及传播方式进行探讨。在此背景下,城市礼品作为城市文化载体,越来越受到人们的关注。文章通过对城市礼品设计相关的理论学习和对设计实务的调查分析,利用设计管理思维技术的框架,开发出一件基于城市文化进行城市礼品设计的应用型设计工具,以期提升城市礼品设计的功能和价值。     

Adaptive neural dynamic surface control for servo systems with unknown dead-zone

An adaptive neural controller is proposed for nonlinear systems with a nonlinear dead-zone and multiple time-delays. The often used inverse model compensation approach is avoided by representing the dead-zone as a time-varying system. The “explosion of complexity” in the backstepping synthesis is eliminated in terms of the dynamic surface control (DSC) technique. A novel high-order neural network (HONN) with only a scalar weight parameter is developed to account for unknown nonlinearities. The control singularity and some restrictive requirements on the system are circumvented. Simulations and experiments for a turntable servo system with permanent-magnet synchronous motor (PMSM) are provided to verify the reliability and effectiveness.