977 research outputs found

    Multi-frame Packet Reservation Multiple Access Using Oscillation-scaled Histogram-based Markov Modelling of Video Codecs

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    A model is proposed for replacing the video codec in networking studies, which is tested for sources with a mean bitrate in the range of 10Kb/s to 10Mb/s. The standard frame sizes investigated are the International Telecommunications Union's (ITU) 352 x 288-pixel Common Intermediate Format (CIF), 176 x 144-pixel Quarter CIF (QCIF), 704 x 576-pixel 4CIF and 128 x 96-pixel Sub-QCIF (SQCIF). The proposed 20-state 'oscillation-scaled’ Markov model was found to represent the relevant video codec characteristics adequately. The performance of this model is then tested in the context of a novel Multi-frame Packet Reservation Multiple Access or MF-PRMA scheme, which is shown in Figure 17 to outperform conventional PRMA in terms of both its delay and packet dropping performance, reaching throughput values as high as 79%

    Examining Seasonal Trends of the Martian Polar Warming with the NASA Ames Mars Global Climate Model

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    The presented work focuses on polar warming as a diagnostic of the mean circulation to increase our understanding of processes that control the mean meridional circulation and transport in the Mars middle atmosphere. The NASA Ames Mars Global Climate Model is utilized to isolate physical processes to determine their impact on polar warming and its seasonal trends

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    Upper Boundary Extension of the NASA Ames Mars General Circulation Model

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    Extending the NASA Ames Mars General Circulation Model (MGCM) upper boundary will expand our understanding of the connection between the lower and upper atmosphere of Mars through the middle atmosphere. The extension's main requirements is incorporation of Non-local thermodynamic equilibrium (NLTE) heating (visible) and cooling (infrared). NLTE occurs when energy is exchanged more rapidly with the radiation field (or other energy sources) rather than collisions with other molecules. Without NLTE above approximately 80km/approximately 60km in Mars' atmosphere the IR/visible heating rates are overestimated. Currently NLTE has been applied successfully into the 1D RT code and is in progress for the 3D application

    Cortical fosGFP expression reveals broad receptive field excitatory neurons targeted by POm

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    Neighboring cortical excitatory neurons show considerable heterogeneity in their responses to sensory stimulation. We hypothesized that a subset of layer 2 excitatory neurons in the juvenile (P18 to 27) mouse whisker somatosensory cortex, distinguished by expression of the activity-dependent fosGFP reporter gene, would be preferentially activated by whisker stimulation. In fact, two-photon targeted, dual whole-cell recordings showed that principal whisker stimulation elicits similar amplitude synaptic responses in fosGFP-expressing and fosGFP(-) neurons. FosGFP(+) neurons instead displayed shorter latency and larger amplitude subthreshold responses to surround whisker stimulation. Using optogenetic stimulation, we determined that these neurons are targeted by axons from the posteromedial nucleus (POm), a paralemniscal thalamic nucleus associated with broad receptive fields and widespread cortical projections. We conclude that fosGFP expression discriminates between single- and multi-whisker receptive field layer 2 pyramidal neurons
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