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71.
A posteriori error analysis for nonconforming approximations of an anisotropic elliptic problem
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Boujemâa Achchab Abdellatif Agouzal Adil Majdoubi Driss Meskine Ali Souissi 《Numerical Methods for Partial Differential Equations》2015,31(3):950-976
We develop in this article an a posteriori error estimator for the P1‐nonconforming finite element approximation, for a diffusion‐reaction equation. We adopt the error in a constitutive law approach in two and three dimensional space, for not necessary piecewise constant data of problems. The efficiency and the reliability of our estimators are proved, neither Helmholtz decomposition of the error nor saturation assumption. The constants are explicitly given, which prove the robustness of these estimators. © 2014 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 31: 950–976, 2015 相似文献
72.
Fast parallel algorithm for three-dimensional distance-driven model in iterative computed tomography reconstruction
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The projection matrix model is used to describe the physical relationship between reconstructed object and projection.Such a model has a strong influence on projection and backprojection,two vital operations in iterative computed tomographic reconstruction.The distance-driven model(DDM) is a state-of-the-art technology that simulates forward and back projections.This model has a low computational complexity and a relatively high spatial resolution;however,it includes only a few methods in a parallel operation with a matched model scheme.This study introduces a fast and parallelizable algorithm to improve the traditional DDM for computing the parallel projection and backprojection operations.Our proposed model has been implemented on a GPU(graphic processing unit) platform and has achieved satisfactory computational efficiency with no approximation.The runtime for the projection and backprojection operations with our model is approximately 4.5 s and 10.5 s per loop,respectively,with an image size of 256×256×256 and 360 projections with a size of 512×512.We compare several general algorithms that have been proposed for maximizing GPU efficiency by using the unmatched projection/backprojection models in a parallel computation.The imaging resolution is not sacrificed and remains accurate during computed tomographic reconstruction. 相似文献
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Dongxu Yan Jing Chen Hongpeng Jia 《Angewandte Chemie (International ed. in English)》2020,59(32):13562-13567
Single‐atom noble metals on a catalyst support tend to migrate and agglomerate into nanoparticles owing to high surface free energy at elevated temperatures. Temperature‐induced structure reconstruction of a support can firmly anchor single‐atom Pt species to adapt to a high‐temperature environment. We used Mn3O4 as a restructurable support to load single‐atom Pt and further turned into single‐atom Pt‐on‐Mn2O3 catalyst via high‐temperature treatment, which is extremely stable under calcination conditions of 800 °C for 5 days in humid air. High‐valence Pt4+ with more covalent bonds on Mn2O3 are essential for anchoring isolated Pt atoms by strong interaction. An optimized catalyst formed by moderate H2O2 etching exhibits the best performance and excellent thermal stability of single‐atom Pt in high‐temperature CH4 oxidation on account of more exposed Pt atoms and strong Pt‐Mn2O3 interaction. 相似文献
75.
Wei Shengqun Wu Qihui Wang Jinlong Wang Fan 《电子科学学刊(英文版)》2007,24(1):32-38
In this paper, an efficient Cyclic Prefix (CP) reconstruction scheme is proposed for Single-Carrier systems with Frequency-Domain Equalization (SC-FDE) that employ insufficient length of CP at the transmitter. By utilizing a decision feedback filter to cancel the residual InterSymbol Interference (ISI) in the equalized signal, the proposed scheme can effectively lower the low bound of performance for the CP reconstruction schemes and can greatly improve the Bit Error P~te (BER) performance of SC-FDE systems. In addition, the existing methods and the proposed scheme are also optimized. It is shown in the simulation results that, when the Signal-to-Noise Ratio (SNR) exceeds a certain threshold, the proposed scheme can achieve the low bound of performance for the existing methods. Moreover, by increasing the number of iteration or through optimization, the low bound can be outperformed. 相似文献
76.
Bin Tian Robert J. Sclabassi Jennting T. Hsu Qiang Liu Ching Chung Li Mingui Sun 《电子科学学刊(英文版)》2007,24(5):642-648
Research interest in multi-frame Superresolution has risen substantially in recent years.This paper presents a modified Projection Onto Convex Set (POCS) superresolution method based on wavelet transform.The method analyzes the image formation model from wavelet multiresolution analysis point of view and defines an closed convex set and its corresponding projection based on wavelet transform.An iterative procedure is utilized to reduce the estimated errors of the result image,and this guarantees the estimated image to lay in the intersection of different convex sets,thus produces a high resolution image with a reduced error.The effectiveness of the algorithm is demonstrated by experimental results. 相似文献
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In this paper, we considered the representation power of local overlapping histograms for discrete binary signals. We give an algorithm that is linear in signal size and factorial in window size for producing the set of signals, which share a sequence of densely overlapping histograms, and we state the values for the sizes of the number of unique signals for a given set of histograms, as well as give bounds on the number of metameric classes, where a metameric class is a set of signals larger than one, which has the same set of densely overlapping histograms. 相似文献
80.
为了把量热法应用于远场激光强度时空分布测量,研究了基于热像仪靶面温度测量反演入射激光强度时空分布的重构理论。针对背光面两种不同边界条件(对流-辐射热流边界和恒定温度边界)推导出了由靶面温度分布反演激光束时空分布的重构表达式。获得的分析表达式对广泛的材料具有适用性。通过引入广义参量F0=α/L2,分别就F0》1和F0《1情况给出了重构近似表达式,并对满足F0》1条件的回推算法进行了数值模拟验证。数值结果表明,两种背光面边界条件下回推得到的激光束时空分布与原始激光束达到了很好的一致,但存在一与靶材傅里叶数相关的最小起始回推时间τ0。成果可用于强激光远场参量测量设备的研制。 相似文献