Papers by Keyword: Compression

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Authors: Abel Cherouat, Shi Jie Zhu, Houman Borouchaki, Xiao Lu Gong
Abstract: The compression characteristics of open-cell aluminum foams were experimentally and numerically investigated. It is found that the mechanical parameters, such as collapse stress and absorbed energy, are dependent on the porosity of aluminum foams material. During simulation of metal foam compression, the finite elements distort severely at the local regions with high gradient of physical field. The procedure integrates Explicit solver of Abaqus FEA, 3D Optiformmesher and Python script program transfer to execute step by step the incremental deformation of deformable body.
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Authors: Shi Jie Zhu, Abel Cherouat, Houman Borouchaki, Xiao Lu Gong
Abstract: The compression characteristics of open-cell aluminum foams were experimentally and numerically investigated. It is found that the mechanical parameters, such as collapse stress and absorbed energy, are dependent on the porosity of aluminum foams. Three macroscopic models were chose to predict the compression behavior of open-cell foams. During simulation of metal foam compression, the finite elements distort severely at the local regions with high gradient of physical field such as stress, strain due to these problems. The procedure integrates Explicit solver of ABAQUS, OPTIFORM mesher and python script program transfer to execute step by step the incremental deformation process. At each step, the meshes are refined and coarsened automatically based on geometrical and physical error estimations; the physical fields are transferred from old to the new one using advanced algorithm.
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Authors: Xue Fei Gao, Guo Yang, Jing Wang, Xiang Xie, Jing Ming Kuang
Abstract: This paper proposes a backward-compatible multichannel audio codec based on downmix and upmix operation. The codec represents a multichannel audio input signal with downmixed mono signal and spatial parametric data. The encoding method consists of three parts: spatial temporal analysis of audio signal, compressing multi-channel audio into mono audio and encoding mono signals. The proposed codec combines high audio quality and low parameter coding rate and the method is simpler and more effective than the conventional methods. With this method, its possible to transmit or store multi-channel audio signals as mono audio signals.
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Authors: Hua Qian Yang, Chang Jiu Pu, Fei Hu, Tao Peng
Abstract: In the paper, a novel combined image encryption and compression scheme is proposed. It performs encryption before compression. Making use of the properties of discrete wavelet transform (DWT) and Set Partitioning in Hierarchical Trees (SPIHT) coding, confusion is restricted to the interior of single subband image itself and so image details are retained. The proposed algorithm possesses a good visual quality of the reconstructed image and a high encryption speed.
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Authors: I. Aleixo, A.C. Vale, M. Lúcio, P.M. Amaral, L.G. Rosa, J. Caetano-Lopes, A. Rodrigues, H. Canhão, J.E. Fonseca, M. Fatima Vaz
Abstract: We addressed the importance of defining a mechanical testing methodology for the compression of human trabecular bone specimens. In fact, currently there are several protocols to test trabecular bone, but a single, standard and validate method has not been accepted yet. In our work, human femoral epiphyses collected from patients with osteoporosis (fragility fractures) and hip osteoarthritis, submitted to total hip replacement surgery, were used. The aims of our work were to develop a mechanical testing methodology for the compression of trabecular bone specimens taking into account the optimization of bone extrinsic and intrinsic variables, in order to establish a patient bone sample database with clinical, structural and mechanical information. Extrinsic variables, such as the effect of specimen preparation, with particular focus on the dimensions of test specimens, and others associated with the compression test, such as the method employed to determine specimen deformation, and hence strain, were evaluated. Also, a new device used to withhold the specimens was developed and tested by the present authors. Although each specimen showed a unique behaviour, even when comparing compression curves between patients from the same disease group, implicating additional complexity and difficulty in the data analysis, the authors managed to assemble the results in two groups related with a possible difference in the deformation mechanisms occurring after yielding.
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Authors: Li Juan Duan, Chun Xia Ke, Chun Peng Wu, Zhen Yang, Jun Miao
Abstract: In this paper, a natural image compression method is proposed based on independent component analysis (ICA) and visual saliency detection. The proposed compression method learns basis functions trained from data using ICA to transform the image at first; and then sets percentage of the zero coefficient number in the total transforming coefficients. After that, transforming coefficients are sparser which indicates further improving of compression ratio. Next, the compression method performance is compared with the discrete cosine transform (DCT). Evaluation through both the usual PSNR and Structural Similarity Index (SSIM) measurements showed that proposed compression method is more robust to DCT. And finally, we proposed a visual saliency detection method to detect automatically the important region of image which is not or low compressed while the other regions are highly compressed. Experiment shows that the method can guarantee the quality of important region effectively.
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Authors: G.R. Gnana King, C. Christopher Seldev, N. Albert Singh
Abstract: Compound image is a combination of natural images, text, and graphics.This paper presents a compression technique for improving coding efficiency. The algorithm first decomposes the compound images by using 3 level biorthogonal wavelet transform and then the transformed image was further compressed by Parallel dictionary based LZW algorithm called PDLZW.In PDLZW algorithm instead of using a unique fixed word width dictionary a hierarchical variable word width dictionary set containing several dictionaries of small address space and increases the word widths used for compression and decompression algorithms. The experimental results show that the PSNR value is increased and the Mean Square error value was improved.
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Authors: Qiao Chen, Li Jie Wang, Stephen Westland
Abstract: Spectral images contain a large volume of data and the development of multispectral imaging systems places considerable demands on computer hardware and software compared with standard three-component or trichromatic image storage and processing. This study is concerned with lossy compression techniques for spectral images since many color images are intended for display for human perception and it is well established that images contain redundancies (in terms of their color, spatial and temporal properties) that can be removed without any loss in image quality. The lossy compression technique that is considered in this work is a low-dimensional linear model of spectral reflectance, with which the basis function are derived from color matching functions that are correlated with human visual system.
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Authors: Jiang Tao Ruan, Shi Bin Wang, Jing Wei Tong, Min Shen, Francesco Aymerich, Pierluigi Priolo
Abstract: The results on a numerical and experimental study of graphite/epoxy composite plates [03/903]S are presented. Each specimen was firstly impacted by the low velocity with different energy level. Compression experiment based on carrier electronic speckle pattern interferometry (carrier-ESPI) is made for the post-impact composite plate. The finite element method (FEM) is used to gain further understanding of the deformation behavior of impacted specimens. The compressive deformation of various delaminated composite plates are analyzed with software ANSYS to see that the impact parameters and delamination damage data, such as impact energy, maximum impact force and delamination area, affect the deformation fields. In addition, the comparisons between the finite element results and experimental measurements are considered under different compression loads.
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