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81.
82.
We present a detailed analysis and comparison of two time series models, i.e., ARIMA and ARIMA-GARCH, to simulate the discharge of a karst spring (Niangziguan Springs (NS) complex) in the northern China. Statistical tests for the residuals are applied to examine the reasonability of the models. Statistically, both models are reasonably good to simulate the mean value of the discharge of the NS complex. The statistical test shows that the residual discharge data have conditional time-varying variance and volatility clustering, known as heteroscedasticity of the data. Calibration test shows that the ARIMA-GARCH model gives a varying confidence interval, which can more effectively capture the heteroscedasticity of the data, comparing with a constant confidence interval in the ARIMA model. In the validation and application process, we applied two approaches to simulate the discharge data: (1) fixed models, and (2) evolving models. The confidence interval width monotonically increases in both fixed models, and the fixed ARIMA-GARCH model has faster increasing confidence interval width than the fixed ARIMA model. This suggests that the fixed time series models are only suitable for short-term prediction. However, we found that this drawback can be compensated by updating the model once new data become available. Our evolving models show more reasonable confidence interval width for both models. In addition, the application shows that the ARIMA-GARCH model is very sensitive to the data fluctuation. We also found the evolving ARIMA-GARCH model was able to return to the narrow confidence interval width once the fluctuation diminished. Hence, we conclude that the ARIMA-GARCH model is more suitable for the sequences with strong heteroscedasticity. 相似文献
83.
PEN/PTT共混聚酯的熔融行为 总被引:1,自引:0,他引:1
利用差示扫描量热仪对不同配比的聚萘二甲酸乙二醇酯/聚对苯二甲酸丙二醇酯(PEN/PTT)共混体系的熔融行为进行了分析,发现在共混体系中两组分形成各自的晶体,PEN和PTT的熔点均随另一组分含量的增加而下降。根据Nishi-Wang方程,按300℃计算,由PEN/PTT共混体系中PEN熔点下降计算所得到的相互作用能密度为-0.214 2 J/cm~3,相互作用参数为-0.006 8,表明PEN/PTY共混体系在熔融态是热力学性质稳定的相容体系。 相似文献
84.
Zhan Yu Xuan Yu Christopher Thorpe Scott Grauer-Gray Feng Li Jingyi Yu 《The Visual computer》2014,30(1):45-58
The ability to produce dynamic Depth of Field effects in live video streams was until recently a quality unique to movie cameras. In this paper, we present a computational camera solution coupled with real-time GPU processing to produce runtime dynamic Depth of Field effects. We first construct a hybrid-resolution stereo camera with a high-res/low-res camera pair. We recover a low-res disparity map of the scene using GPU-based Belief Propagation, and subsequently upsample it via fast Cross/Joint Bilateral Upsampling. With the recovered high-resolution disparity map, we warp the high-resolution video stream to nearby viewpoints to synthesize a light field toward the scene. We exploit parallel processing and atomic operations on the GPU to resolve visibility when multiple pixels warp to the same image location. Finally, we generate racking focus and tracking focus effects from the synthesized light field rendering. All processing stages are mapped onto NVIDIA’s CUDA architecture. Our system can produce racking and tracking focus effects for the resolution of 640×480 at 15 fps. 相似文献
85.
86.
青花红绿彩作为加彩器的一种,比传统的观点早一个朝代,根据明中青花红绿彩盖罐结合最新的窑址考古成果,得出元代的窑炉设计和釉面配方的缺陷,使元代青花红绿彩的生产和存世极少,明官窑中由于斗彩的出现,青花红绿彩在民间一直沿烧。与元代风格相近,只是到了后期风格才大变。 相似文献
87.
88.
Two-dimensional locality preserving projections (2DLPP) was recently proposed to extract features directly from image matrices based on locality preserving criterion. A significant drawback of 2DLPP is that it only works on one direction (left or right) to reduce the dimensionality of the image matrices and thus too many coefficients are needed for image representation in low-dimensional subspace. In this paper, we propose a novel method called two-dimensional bilinear preserving projections (2DBPP) for image feature extraction. We generalized the image-based (2D-based) feature extraction techniques into bilinear cases, in which 2DLPP is a special case of our proposed method. In order to obtain the bilinear projections, we proposed an iteration method by solving the corresponding generalized eigen-equations. Moreover, analyses show that 2DBPP has stronger locality preserving abilities than 2DLPP. By using the label information and defining different local neighborhood graphs, the proposed framework is further extended to supervised case. Experiments on three databases show that 2DBPP and its supervised extension are superior to some other image-based state-of-the-art techniques. 相似文献
89.
高分子铁盐絮凝剂制备及其应用研究 总被引:5,自引:0,他引:5
研究了以废铁屑和工业硫酸亚铁为原料,在常压和加热条件下,用氯酸钾作为氧化剂制取聚合硫酸铁(PFS)的工艺条件,并在PFS制备的基础上,合成了聚磷硫酸铁(PPFS)和聚氯硫酸铁(PFCS)。将所制备的聚铁用于污水处理实验,结果表明:用该方法制备的聚铁絮凝剂对实际水样具有较好的混凝处理效果,且制备工艺简单、速度快,从根本上消除了用NaNO_2催化氧化法制备聚铁对环境造成的二次污染。 相似文献
90.
准确有效地提取肝脏CT序列的轮廓线是腹部软组织三维模型重建与可视化的关键问题之一。针对肝脏轮廓线提取准确性不高的问题, 提出了一种基于先验知识的肝脏轮廓线提取算法。首先利用拉普拉斯算法进行CT图像增强, 再利用基于边缘先验知识的套索模型对感兴趣区域进行半自动的初始化, 最后通过改进的Snake算法准确地提取肝脏CT图像的边缘。针对序列CT肝脏的边缘提取, 提出根据CT图像序列之间的相关性, 将上一幅图像的轮廓线提取结果作为下一幅CT图像边缘提取的初始化点, 接着批处理地提取CT序列的肝脏边缘。实验结果表明:该算法大大减少了手动初始化结果对目标边缘轮廓准确提取的依赖性, 并有效地解决了肝脏轮廓线的提取问题。 相似文献