Privacy region protection for H.264/AVC with enhanced scrambling effect and a low bitrate overhead

While video surveillance systems have become ubiquitous in our daily lives, they have introduced concerns over privacy invasion. Recent research to address these privacy issues includes a focus on privacy region protection, whereby existing video scrambling techniques are applied to specific regions of interest (ROI) in a video while the background is left unchanged. Most previous work in this area has only focussed on encrypting the sign bits of nonzero coefficients in the privacy region, which produces a relatively weak scrambling effect. In this paper, to enhance the scrambling effect for privacy protection, it is proposed to encrypt the intra prediction modes (IPM) in addition to the sign bits of nonzero coefficients (SNC) within the privacy region. A major issue with utilising encryption of IPM is that drift error is introduced outside the region of interest. Therefore, a re-encoding method, which is integrated with the encryption of IPM, is also proposed to remove drift error. Compared with a previous technique that uses encryption of IPM, the proposed re-encoding method offers savings in the bitrate overhead while completely removing the drift error. Experimental results and analysis based on H.264/AVC were carried out to verify the effectiveness of the proposed methods. In addition, a spiral binary mask mechanism is proposed that can reduce the bitrate overhead incurred by flagging the position of the privacy region. A definition of the syntax structure for the spiral binary mask is given. As a result of the proposed techniques, the privacy regions in a video sequence can be effectively protected by the enhanced scrambling effect with no drift error and a lower bitrate overhead.N/

Experimental validation study of 3D direct simple shear DEM simulations

Simple shear element tests can be used to examine numerous geotechnical problems; however, the cylindrical sample (NGI-type) direct simple shear (DSS) devices have been criticized for an inability to apply uniform stresses and strains, as well as the inability to fully define the stress state of the soil during shearing. Discrete element method (DEM) simulations offer researchers a means to explore the fundamental mechanisms driving the overall behavior of granular soil in simple shear, as well as improve understanding of the DSS device itself. Here three-dimensional DEM simulations of laminar NGI-type direct simple shear element tests and equivalent physical tests are compared to validate the numerical model. This study examines the sensitivity of the DEM simulation results to sample size, contact model and stiffness inputs, and ring wall boundary effects. Sample inhomogeneities are also considered by examining radial and vertical void ratio distributions throughout the sample. Both the physical experiments and the DEM simulations presented indicate that the observed material response is highly sensitive to the particle size relative to the sample dimensions. The results show that samples with a small number of relatively large particles are very sensitive to small changes in packing, and thus an exact match with the DEM simulation data cannot be expected. While increasing the number of particles greatly improved the agreement of the volumetric and stress-strain responses, the dense DEM samples are still initially much stiffer than the experimental results. This is most likely due to the fact that the inter-particle friction was artificially lowered during sample preparation for the DEM simulations to increase the sample density.This material is based upon work supported by the National Science Foundation under Grant No. 0449021 and the Graduate Research Fellowship Program. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. The authors would like to thank Ignazio Cavarretta for his contribution to this research in conducting the interparticle friction tests. The authors also wish to acknowledge the support provided by the Zachry Department of Civil Engineering.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.sandf.2016.04.00

The employment consequences of private equity acquisitions: The case of institutional buy outs

There is a growing controversy as to the impact of private equity acquisitions, especially in terms of their impact on employment and subsequent organizational performance. It has been suggested that closer owner supervision and the injection of a new management team revitalize the acquired organization and unlock dormant capabilities and value. However, both politicians and trade unionists suggest that private equity acquirers may significantly reallocate value away from employees to short term investors, typically through layoffs and reduced wages, which may undermine future organizational sustainability. This article investigates this in the context of a sample of institutional buy outs (IBOs) undertaken in the UK between 1997 and 2006. Specifically we examine the impact of IBOs on both employment and remuneration against two control groups of non-acquired firms. In designing our study we follow the empirical approach taken by Conyon et al. (2001, 2002) in investigating the employment consequences of regular takeovers. Our main finding is a significant loss in employment in firms subject to an IBO in the year immediately following the acquisition as well as lower wage rates, when compared to either of the two control groups. Furthermore, we find no evidence of a subsequent improvement either in productivity or profitability in the acquired businesses. © 2014 Elsevier B.V

Effects of fire-fighting on a fully developed compartment fire: temperatures and emissions

This study evaluates the effects and consequences of fire-fighting operations on the main characteristics of a fully-developed compartment fire. It also presents data and evaluation of the conditions to which fire-fighters are exposed. A typical room enclosure was used with ventilation through a corridor to the front access door. The fire load was wooden pallets. Flashover was reached and the fire became fully developed before the involvement of the fire-fighting team. The progression of the fire-fighters through the corridor and the main-room suppression attack - in particular the effect of short, medium and long water pulses on either the hot gas layer or the fire seat - was charted against the compartment temperatures, heat release rates, oxygen levels and toxic species concentrations. The fire fighting team was exposed to extreme conditions, heat fluxes in excess of 35 kW/m2 and temperatures of the order of 250 oC even at crouching level. The fire equivalence ratio showed rich burning with high toxic emissions in particular of CO and unburnt hydrocarbons very early in the fire history and a stabilisation of the equivalence ratio at about 1.8. The fire fighting operations made the combustion temporarily richer and the emissions even higher

Experimental validation study of 3D direct simple shear DEM simulations

Simple shear element tests can be used to examine numerous geotechnical problems; however, the cylindrical sample (NGI-type) direct simple shear (DSS) device has been criticized for its inability to apply uniform stresses and strains, as well as for its inability to fully define the stress state of the soil during shearing. Discrete element method (DEM) simulations offer researchers a means to explore the fundamental mechanisms driving the overall behavior of granular soil in simple shear and to improve the understanding of the DSS device itself. Here, three-dimensional DEM simulations of laminar NGI-type direct simple shear element tests and equivalent physical tests are compared to validate the numerical model. This study examines the sensitivity of the DEM simulation results to sample size, contact model and stiffness inputs, and ring wall boundary effects. Sample inhomogeneities are also considered by examining the radial and vertical void ratio distributions throughout the samples. Both the physical experiments and the DEM simulations presented herein indicate that the observed material response is highly sensitive to the particle size relative to the sample dimensions. The results show that samples with a small number of relatively large particles are very sensitive to small changes in packing; and thus, an exact match with the DEM simulation data cannot be expected. While increasing the number of particles greatly improved the agreement of the volumetric and stress–strain responses, the dense DEM samples were still initially much stiffer than the experimental results. This is most likely due to the fact that the inter-particle friction was artificially lowered, during the sample preparation for the DEM simulations, in order to increase the sample density