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21.
3D GIS最重要的特征之一就是虚拟现实表现,其本质是可视化技术与GIS数据库的整合,以满足各种应用如生态农业、灾害预测等方面的需求。以GIS数据库的环境数据和气象数据为基础,通过对雨雪的效果模拟,将GIS气象数据以实时的可视化形式逼真地表现出来。实验方法采用粒子系统,对单个点元赋予利用Photoshop制作的大面积纹理,这样采用的粒子数减少到普通粒子系统的十分之一,渲染速度为普通粒子系统的十倍以上,以较小的系统资源消耗达到了更加实时逼真的效果,对雪的动态堆积和雨水地面效果采用GPU加速3维渲染,原型系统同时能接受用户对实验环境如粒子纹理、雨雪量的设置。提出根据气象数据进行天气模拟的自适应策略,从而更加适应实际应用需要。 相似文献
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23.
S. S. Andreiko 《Journal of Mining Science》2003,39(4):354-363
An analysis and estimate are performed for possible schemes of spatial distribution of gas-dynamic phenomena in potash deposits by the methods of mathematical statistics. The problem stated is solved by comparing the numerical characteristics of the events observed and those obtained on the basis of the theoretical model developed. 相似文献
24.
Synchronization of a self-excited dust density wave has been experimentally investigated in a strongly coupled dusty plasma. A dust density wave of frequency ~78 Hz is spontaneously generated from the dust void boundary due to the ion streaming instability. The electric field in the dust void region is measured, and the electric field force and ion drag force on the dust particles at the void boundary are estimated to explain the mechanism of spontaneous dust density wave excitation. Synchronization occurring through the suppression mechanism is observed by modulating the ion streaming by applying an external sinusoidal signal to the dust void. At sufficiently high modulation amplitude, the onset of period-doubling bifurcation is observed. Fast Fourier transform spectral analysis is done using time-series data obtained from high-speed video imaging. The van der Pol equation with a force term is used to correlate the observed suppression phenomena. 相似文献
25.
According to the investigations of Cameron and his coworkers1–5 into the chain-matching phenomena between normal paraffin as a solvent and straight-chain fatty acid as an additive, the optimum condition in boundary lubrication is attained when the chain lengths of the additive and solvent are equal. A series of experiments has been conducted over the past ten years on the role of the chain-matching effect, not only on boundary lubrication but also widely on relevant interfacial phenomena. The results of the investigations are discussed. 相似文献
26.
沙维 《稀有金属(英文版)》1993,(4)
Worldwide researches on Ni-P alloys have been briefly reviewed,including their corrosion resistance,crystallisation behaviour,amorphisation by ion implantation,and usage as underlayer for thin film magnet-ic media. 相似文献
27.
PMSM无位置传感器控制中数字滑模观测器抖振现象分析与抑制 总被引:2,自引:0,他引:2
通过对永磁同步电机(PMSM)反电动势滑模观测器观测结果进行加窗快速傅里叶变换(FFT)频谱分析,发现抖振信号频谱范围较宽、幅值较大,观测结果无法直接使用,低通滤波器使得观测信号发生变化,难以精确补偿。本文提出了一种以电流和磁链为观测对象的扩展滑模观测器,磁链观测结果由磁链实际值和经过滤波后的抖振信号组成。根据磁链观测结果的频谱分析,抖振现象的影响可以忽略不计,转子角度可以由磁链观测结果直接计算,不需要低通滤波,避免了相位滞后。着重分析了速度估计误差对观测结果和转子角度计算的影响,并以此为基础进行反馈矩阵计算。仿真和实验结果表明该方法能够准确计算出电机的位置和速度,使系统具有良好的稳态精度和动态性能。 相似文献
28.
Mohsen Lashgari 《Electrochimica acta》2011,(9):3322
Using quantum electrochemical/thermodynamical approaches based on coupled cluster/polarized continuum models and density functional theory (CM/PCM–DFT), we investigated the corrosion inhibition mechanism of Al/NaOH system in the presence of some p-phenol derivatives. The influencing parameters on inhibitory action, i.e. charges on oxygen and hydrogen atoms of hydroxyl group, charge transfer, interaction energy, molecular activity and softness, electric dipole moment and de-solvation free energy, were determined for both neutral and deprotonated species at metal|solution interface. A good correlation was observed between these parameters and inhibition efficiency data reported in the literature. By introducing an appropriate thermodynamic procedure, we also determined the proton-loss tendency of the molecules nearby interface. The results were amazing and revealed a complicated protonation/deprotonation cycle for inhibitor species inside electrical double layer; the corrosive agents in the vicinity of metal surface become locally neutralized and pushed away. 相似文献
29.
Henry C. W. Chu Stephen Garoff Robert D. Tilton Aditya S. Khair 《American Institute of Chemical Engineers》2020,66(2):e16831
A multiple-scale perturbation is conducted to derive an averaged equation for predicting the longtime solute transport in an eccentric annulus in which the uniaxial flow may oscillate periodically in time. A proof for the positiveness of the dispersivity is presented, implying that over a cycle of oscillation a solute cloud always broadens. For a steady flow driven by a fixed pressure gradient, increasing the eccentricity and annulus size gives rise to stronger dispersion. This relationship holds when the flow becomes unsteady. In the limit of slow oscillation, dispersion due to an oscillatory flow asymptotes to one-half of that by a steady flow. Increasing the oscillation frequency leads to a two-step decay of the dispersivity. The maximum dispersion in an oscillatory flow can be achieved in the limit of slow oscillation and large eccentricity, where dispersion can be O(103) times larger than that in an otherwise concentric annulus. 相似文献
30.
以镍渣、高炉渣为主要原料,研究了这类富铁冶金渣玻璃陶瓷的组成及结晶变化规律.结果表明:镍渣-高炉渣玻璃陶瓷的抗折强度与高炉渣镍渣质量比及样品中SiO2含量有关.样品抗折强度随着质量比和SiO2含量的增大呈现出先增大后减小的变化趋势.试验确定的最佳组成参数为:高炉渣与镍渣的质量比为3.5/1,样品中SiO2的含量在42%.同时,试验利用XRD、SEM分析方法对这类富铁冶金渣玻璃陶瓷结晶过程进行了分析,最后得出镍渣-高炉渣玻璃陶瓷结晶过程是从非结晶态向结晶态逐渐转变的过程,结晶过程中伴有热量的释放和亮度的变化等现象. 相似文献