Quantifying motion in video recordings of neonatal seizures by robust motion trackers based on block motion models

This paper introduces a methodology for the development of robust motion trackers for video based on block motion models. According to this methodology, the motion of a site between two successive frames is estimated by minimizing an error function defined in terms of the intensities at these frames. The proposed methodology is used to develop robust motion trackers that rely on fractional block motion models. The motion trackers developed in this paper are utilized to extract motor activity signals from video recordings of neonatal seizures. The experimental results reveal that the proposed motion trackers are more accurate and reliable than existing motion tracking methods relying on pure translation and affine block motion models.     

Improving the accuracy and reliability of motion tracking methods used for extracting temporal motor activity signals from video recordings of neonatal seizures

This paper presents an approach for improving the accuracy and reliability of motion tracking methods developed for video based on block motion models. This approach estimates the displacement of a block of pixels between two successive frames by minimizing an error function defined in terms of the pixel intensities at these frames. The minimization problem is made analytically tractable by approximating the error function using a second-order Taylor expansion. The improved reliability of the proposed method is illustrated by its application in the extraction of temporal motor activity signals from video recordings of neonatal seizures.     

A function for generating nearly balanced binary search trees from sets of non-random keys

A function for generating nearly balanced binary search trees from sets of non-random keys is described. This function can be used in hashing organization where collisions are resolved by construction of binary trees. In particular it can be used as the secondary function in the relatively new technique of dynamic hashing.     

Wind velocity directional fluctuation prediction model

A two-dimensional analytical model of wind directional fluctuation exceedence rates is presented. The model assumes that wind directional fluctuations are binormally distributed. The model correctly predicts the trends but tends to underestimate the exceedence rates. Improvements by making the model three-dimensional are outlined.     

Triaxial Vector Accelerometry: A Method for Quantifying Tremor and Ataxia

A triaxial vector accelerometry system for quantitatively assessing tremor and ataxia is described. Since movement at a specific anatomical site can be three dimensional, previously reported single-and dual-axis methods are not satisfactory for quantitative analysis. The accelerometer contains three identical piezoelectric transducers, and it easily attaches to the wrist, hand, ankle, foot, etc., while the subject performs controlled repetitive movement of a particular anatomical site. Signals from the accelerometer are processed by associated electronic circuitry which provides a graphic write-out of selected parameters. Equations from which these parameters were derived are discussed, as is their integration into performance indexes. A brief report is given on testing of normal volunteers and patients presenting abnormal neuromuscular function.     

Fragmentation mechanisms based on single drop steam explosion experiments using flash X-ray radiography

Flash X-ray and high-speed regular photography were used to investigate the fragmentation processes during the vapor explosion of single drops of molten metal immersed in water. For relatively low ambient flow velocities (< 5 m/s), a comparison of the breakup of hot and cold drops shows that whereas cold drops breakup due to the stripping of fragments by the relative flow, the fragmentation of a hot drop is dominated by the growth and collapse of a vapor bubble. X-ray radiographs show during the growth of the bubble, that fine filaments of metal protrude from the drop and the drop surface becomes highly convoluted. Using a simple model for the bubble dynamics, an estimate of the energy budget shows that the majority (about 80%) of the thermal energy transfer occurs during bubble collapse. For hot drops at higher flow velocities (> 45 m/s), vapor bubble growth is diminished and high-speed motion of vapor within the bubble leads to an enhanced fragmentation rate.     

Limiting Densities for Dense Random Packing of Spheres

Theoretical packing densities are derived for dense random packing of hard spheres for single-valued and for multivalued particle diameters. The optimum particle-size distribution for maximum density is calculated. The results are compared with packing densities for close-packed arrangements. The results may be useful in estimating inhomogeneities in density of green-powder compacts. They may also be useful in understanding the role of particle rearrangement during sintering.     

Describing Network Traffic Using the Index of Variability

Commonly used measures of traffic burstiness do not capture the fluctuation of traffic variability over the entire range of time-scales. In this paper, we present a measure of variability, called the Index of Variability (Hv(tau)), that depicts the degree of variability (burstiness) of a typical network traffic process at each time-scale and is analytically tractable for many traffic models. As an illustration, we derive the closed-form expressions of Hv(tau) for two traditional traffic models and generate a variety of two-dimensional (2D) and three-dimensional (3D) Index-of-Variability curves. These curves demonstrate that the Index of Variability can help in determining the complexities of the network traffic variability over the network performance relevant time-scales. We then introduce a practical method for estimating the Index-of-Variability curve from a given traffic trace. Using this method, we estimate the Index-of-Variability curves for 12 long NLANR network traffic traces. The results indicate that the variability of real network traffic varies with time-scales and that the Index of Variability has the ability to discern qualitative differences between traffic traces obtained from different networks. Thus, the Index of Variability offers the potential to gain insights into the dynamics of network traffic that existing tools do not offer.