Compressed video bitstreams are intended for real-time transmission over communication networks. Because video coding standards eliminate the temporal, spatial, and statistical redundancies, the coded video bitstreams...
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Compressed video bitstreams are intended for real-time transmission over communication networks. Because video coding standards eliminate the temporal, spatial, and statistical redundancies, the coded video bitstreams are very sensitive to transmission errors. Many error resilience coding schemes are available to get high video quality over noisy channels. We propose an error resilient coding technique to limit the effect of error propagation in low bit-rate video coding. The success of error resilient coding techniques relies on how accurately the transmission errors can be detected. Therefore, we propose a very simple error detection technique using data hiding. After error detection, we conceal the corrupted MB data using intra MB refresh and motion compensation with the estimated motion vector. This method will be useful in video communication in error prone environment such as WCDMA networks.
In VOD systems, allocating more bandwidths to broadcast hotter videos, the minimal average client waiting time will be achieved. But the hot degree of videos is fluctuating dynamically, and it requires the algorithm t...
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In VOD systems, allocating more bandwidths to broadcast hotter videos, the minimal average client waiting time will be achieved. But the hot degree of videos is fluctuating dynamically, and it requires the algorithm to be scalable. According to the research of broadcasting algorithms for CBR encoded video, most of the bandwidth-effective algorithms (such as greedy equal bandwidth broadcasting (GEBB) and poly-harmonic broadcasting (PHB) etc.) use narrower channel bandwidth than the video's actual playing rate and greedy downloading method. Based on this theory, some derived high-performance algorithms for VBR encoded videos were proposed, such as FSEB, BSEB-PC, VBHB and SVBR etc. But there is no one that has the capability of changing the bandwidth dynamically at running time (which was also called channel transition). This paper presents the first algorithm named bandwidth-scalable broadcasting for VBR encoded videos (SB-VBR) which is able to dynamically shift bandwidth at running time. To get the high performance, this algorithm places the possible longest segments from the last channel to previous channels by utilizing the best bandwidth-effective algorithm model. A new method of Byte_Align for B frame is put forward in this paper in order to enhance the performance. With adoption of additional channels, the process of channel transition is transparent to clients and easier to be realized. Furthermore, this paper presents a simple method to compute the limitation of performance. Using data from real videos, we compare the total bandwidth needed by our algorithm with the theoretical minimum bandwidth and other algorithms for VBR encoded videos. The experimental results demonstrated that the algorithm is high-performance and practical.
A study of the one‐dimensional isentropic compression experiment (ICE), performed with High Explosive Pulsed Power (HEPP), has demonstrated that accurate, high stress, isentropic Equations of State (EOS) data may be ...
A study of the one‐dimensional isentropic compression experiment (ICE), performed with High Explosive Pulsed Power (HEPP), has demonstrated that accurate, high stress, isentropic Equations of State (EOS) data may be obtained with this technique. The physics and accuracy of electromagnetic loading in the ICE technique are presented. It is shown that the HEPP‐ICE load configuration is capable of producing magnetic stresses that are uniform to 1 part in 1000 over the central 87% of the sample faces, and that HEPP‐ICE provides exact matching of the stresses between opposing samples. This magnetic uniformity, the exact matching, and the large sample sizes possible with HEPP‐ICE, are necessary for the highest accuracy isentropic EOS data. The results for tungsten and copper demonstrate the inaccuracy of the technique, which may be as low as 0.2% in stress.
Complementary gas‐gun and electromagnetic pulse tests conducted in Sandia's Dynamic Integrated compression Experimental (DICE) Facility have, respectively, probed the behavior of electronic‐grade Kovar® sam...
Complementary gas‐gun and electromagnetic pulse tests conducted in Sandia's Dynamic Integrated compression Experimental (DICE) Facility have, respectively, probed the behavior of electronic‐grade Kovar® samples under controlled impact and intermediate‐strain‐rate ICE (Isentropic compression Experiment) loading. In all experiments, velocity interferometer (VISAR) diagnostics provided time‐resolved measurements of sample response for conditions involving one‐dimensional (i.e., uniaxial strain) compression and release. Wave‐profile data from the gas‐gun impact experiments have been analyzed to assess the Hugoniot Elastic Limit (HEL), Hugoniot equation of state, spall strength, and high‐pressure yield strength of shocked Kovar®. The ICE wave‐profile data have been interpreted to determine the locus of isentropic stress‐strain states generated in Kovar® for deformation rates substantially lower than those associated with a shock process. The impact and ICE results have been compared to examine the influence of loading rate on high‐pressure yield strength.
Currently there are three platforms that offer quasi‐isentropic compression or ramp‐wave compression (RWC): light‐gas gun, magnetic flux (Z‐pinch), and laser. We focus here on the light‐gas gun technique and on s...
Currently there are three platforms that offer quasi‐isentropic compression or ramp‐wave compression (RWC): light‐gas gun, magnetic flux (Z‐pinch), and laser. We focus here on the light‐gas gun technique and on some current theoretical insights from experimental data. An impedance gradient through the length of the impactor provides the pressure pulse upon impact to the subject material. Applications and results are given concerning high‐pressure strength and the liquid‐to‐solid, phase transition of water giving its first associated phase fraction history. We also introduce the Korteweg‐deVries‐Burgers equation as a means to understand the evolution of these RWC waves as they propagate through the thickness of the subject material. This model equation has the necessary competition between non‐linear, dispersion, and dissipation processes, which is shown through observed structures that are manifested in the experimental particle velocity histories. Such methodology points towards a possibility of quantifying dissipation, through which RWC experiments may be analyzed.
The compact capacitor bank CQ‐1.5 is a pulsed power generator developed at the Institute of Fluid Physics, and capable to deliver a current of peak 1.5 MA within rise time 500–575 ns into a 2–3 nH inductive load. I...
The compact capacitor bank CQ‐1.5 is a pulsed power generator developed at the Institute of Fluid Physics, and capable to deliver a current of peak 1.5 MA within rise time 500–575 ns into a 2–3 nH inductive load. It is motivated to do isentropic compression experiments (ICE) on metals up to 0–50 GPa and to launch flyer plates at velocities over 8 km/s. The measured free surface velocities of two ICE specimens of different thickness were treated by backward integration to acquire the compression isentrope of copper up to 35 GPa. Meanwhile theoretical isentropes and an energy conservation based model to predict magnetically driven flyers' final velocity are proposed here, and compared with the experimental data.
The presence of suprathermal tails of solar wind and pickup ions in interplanetary space has been widely observed, even during quiet times with no simultaneous observation of solar energetic particles. One of the pers...
The presence of suprathermal tails of solar wind and pickup ions in interplanetary space has been widely observed, even during quiet times with no simultaneous observation of solar energetic particles. One of the persistent characteristics of these tails have been power law spectra of the velocity distribution function with a v −5 dependence in the solar wind reference frame and exponential fall-off at higher energies, but variations in the spectra including those of other species have also been observed. Several attempts to explain the formation of suprathermal tails during quiet times have been made, among them continuing acceleration by compressive fluctuations of the solar wind and the stochastic superposition of exponential, Gaussian, and variable power law spectra from diffusive shock, stochastic, and other acceleration processes. We find here that acceleration is effective within compression regions with and without shocks. In the context of a superposed epoch analysis of the evolution of He+ pickup ion distributions across compression regions, we report on a related study of He+ tails, using STEREO PLASTIC data from 2007 through 2014. Quiet times have been selected based on limiting energetic He fluxes above the tail energies and based on the tail fluxes themselves. We find that the suprathermal tail flux is dependent on the compression strength and varies substantially across the compression region. The strongest tails with spectra somewhat steeper than v −5 occur in the compressed fast solar wind, and they decrease rapidly with distance from the preceding and following compression into the rarefaction region, when using an unbiased data sample and applying a quiet time criterion based on higher energy ions. This may be consistent with the compressions being a potential source of the tails. When applying a quiet time criterion based on the observed tail fluxes, the temporal evolution disappears, possibly implicating a selection of the lower end of a Poisson
The goals, technical approach and first results of a new-type Laser-Plasma experiment AMEX for the simulation of over-compression effect of the Earth' magnetosphere by Giant Coronal Mass Ejections are described. P...
The goals, technical approach and first results of a new-type Laser-Plasma experiment AMEX for the simulation of over-compression effect of the Earth' magnetosphere by Giant Coronal Mass Ejections are described. Parameters of large-scale KI-1 facility of ILP with kJ-laser provide such values of dimensionless criteria which are in the range of very rare and enormous Solar flares that could cause a shift of magnetopause from the usual distance of 10RE down to ~ (2-3)RE. These extreme 'Artificial Magnetosphere' states with highly compressed dipole field could result in world-wide damage phenomena in various networks and its physics could be explored in laboratory only by using of compact dipoles with a large moment. In a series of experiments with a variable magnetic moment and plasma blobs of effective energy up to 500 J an important role of plasma instabilities at magnetopause was revealed. The data on the magnetopause shape and stand-off size show a good correspondence both to general magnetospheric models and to expected scaling of 'Artificial Magnetosphere'.
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