Search results for " Compression"
showing 10 items of 400 documents
Optimized adiabatic passage with dephasing
2008
We study adiabatic population transfer with dephasing in two-level models driven by a chirped driving field. We show that the population transfer is maximized when the dynamics follows specific ellipses as trajectories in the parameter space. We determine the optimal parameters and estimate the losses in a closed form. These estimates show a similar robustness as for the standard lossless adiabatic processes with respect to variations of the parameters.
Efficient image compression using directionlets
2007
Directionlets are built as basis functions of critically sampled perfect-reconstruction transforms with directional vanishing moments imposed along different directions. We combine the directionlets with the space-frequency quantization (SFQ) image compression method, originally based on the standard two-dimensional wavelet transform. We show that our new compression method outperforms the standard SFQ as well as the state-of-the-art image compression methods, such as SPIHT and JPEG-2000, in terms of the quality of compressed images, especially in a low-rate compression regime. We also show that the order of computational complexity remains the same, as compared to the complexity of the sta…
Image compression based on a multi-directional map-dependent algorithm
2007
Abstract This work is devoted to the construction of a new multi-directional edge-adapted compression algorithm for images. It is based on a multi-scale transform that is performed in two steps: a detection step producing a map of edges and a prediction/multi-resolution step which takes into account the information given by the map. A short analysis of the multi-scale transform is performed and an estimate of the error associated to the largest coefficients for a piecewise regular function with Lipschitz edges is provided. Comparisons between this map-dependent algorithm and different classical algorithms are given.
Performance and Implementation Modeling of Gated Linear Networks on FPGA for Lossless Image Compression
2020
Over recent years, imaging systems have seen explosive increase in resolution. These trends present a challenge for resource-constrained embedded imaging devices. Efficient image compression is essential to reduce bandwidth consumption and to increase the capability of on-board storage. Especially, for imaging systems where information loss is not allowed, for example, in medical, military and remote sensing imaging systems. This paper explores the use of Gated Linear Networks (GLNs) for development of embedded lossless compression systems. GLNs have proved themselves via PAQ archiver series, that have been ranked among the top across several lossless compression benchmarks. We propose an a…
A robust and efficient method for obtaining the complex modes in inhomogeneously filled waveguides
2003
In this paper, we present a computational simulation of the complex wave propagation in inhomogeneously filled waveguides with lossless and lossy dielectrics. We use a biorthonormal-basis method as a numerical technique. The behavior of complex modes in different waveguides whose characterization with other methods involves some difficulties is analyzed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 218–222, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10875
Performance evaluation of different techniques to estimate subjective quality in live video streaming applications over LTE-Advance mobile networks
2018
Abstract Current mobile service providers are offering Gigabit Internet access over LTE-Advanced networks. Traditional services, such as live video streaming, over wired networks are feasible on these networks. However different aspects should be taken into account due to the fast changing network conditions as well as the constrained resources of the mobile phones, in order to provide a good subjective video quality in terms of Mean Opinion Score (MOS). Our goal is to estimate and predict this subjective metric without information or reference from the original video, known as Non Reference approach. This approach is important for the Service Provider from a practical point of view, becaus…
Bone marrow fat quantification of osteoporotic vertebral compression fractures: comparison of multi-voxel proton MR spectroscopy and chemical-shift g…
2011
Background Only a few studies have used in/opposed phase method for a quantitative evaluation of fat fraction in the spine. Purpose To compare multivoxel proton MR spectroscopy and chemical-shift gradient-echo MR imaging for bone marrow fat quantification in vertebral compression fractures (VCF). Material and Methods Vertebral marrow fat quantification in fifteen patients was measured at 3.0-T. Multi-voxel proton spectroscopy (MRS) and in/opposed-phase MR imaging using a fat map build with a triple-echo gradient-echo sequence was used. All the patients had benign vertebral collapse. Bone marrow fat content was evaluated by both techniques in compressed (acute or chronic) and in non-compress…
Acute effects of wearing compression knee-length socks on ankle joint position sense in community-dwelling older adults
2021
Functional proprioceptive information is required to allow an individual to interact with the environment effectively for everyday activities such as locomotion and object manipulation. Specifically, research suggests that application of compression garments could improve proprioceptive regulation of action by enhancing sensorimotor system noise in individuals of different ages and capacities. However, limited research has been conducted with samples of elderly people thus far. This study aimed to examine acute effects of wearing knee-length socks (KLS) of various compression levels on ankle joint position sense in community-dwelling, older adults. A total of 26 participants (12 male and 14…
Erythropoietin and erythropoietin receptor expression after experimental spinal cord injury encourages therapy by exogenous erythropoietin
2005
OBJECTIVE: Erythropoietin (EPO) is a pleiotropic cytokine originally identified for its role in erythropoiesis. Recent studies have demonstrated that EPO and its receptor (EPO-R) are expressed in the central nervous system, where EPO exerts neuroprotective functions. Because the expression of the EPO and EPO-R network is poorly investigated in the central nervous system, the aim of the present study was to investigate whether the resident EPO and EPO-R network is activated in the injured nervous system. METHODS: A well-standardized model of compressive spinal cord injury in rats was used. EPO and EPO-R expression was determined by immunohistochemical analysis at 8 hours and at 2, 8, and 14 …
Subcortical somatosensory evoked potentials after median nerve and posterior tibial nerve stimulation in high cervical cord compression of achondropl…
2008
Abstract Children with achondroplasia may have high cervical myelopathy from stenosis of the cranio-cervical junction resulting in neurological disability and an increased rate of sudden death. To detect myelopathy we recorded somatosensory evoked potentials after median nerve (MN) and posterior tibial nerve (PTN) stimulation in 77 patients with achondroplasia aged 0.3–17.8 years (mean 2.7 years). In addition to the conventional technique of recording the cortical components and the central conduction time (CCT) we employed non-cephalic and mastoid reference electrodes to record the subcortical waveforms N13b and P13 (MN-SEP) as well as P30 (PTN-SEP), respectively, which are generated near …