6,598 research outputs found

    Indoor radon survey in university buildings: a case study of Sapienza - University of Rome

    Get PDF
    The indoor radon concentration in underground workplaces pertaining to Sapienza – University of Rome have been monitored since the 90’s according to prescription of Italian Legislative Decree 230/95. In the last years, the recommendations contained in the Council Directive 2013/59/Euratom have shifted the focus to all indoor exposure situations by promoting actions to identify workplaces and dwellings with radon concentrations exceeding the reference level of 300 Bq/m3. In response to the upcoming transposition into national legislation, Sapienza has promoted the first Italian survey addressing workplaces in university buildings, regardless of the position with respect to the ground floor. The survey has interested more than three hundred workplaces, i.e. administration and professors’ offices, research and educational laboratories, conference rooms and classrooms, distributed in fifteen different buildings. Places monitored are strongly heterogeneous in terms of users’ habit, occupancy pattern and building characteristics. The influence of these parameters into seasonal variation have been addressed by organizing the survey in four quarters. The indoor radon concentration is measured by solid state nuclear track detectors, CR39. The aim of the paper is to present features, methods and intermediate results of the survey. The work, relying on the analysis of previous measurements interesting underground workplaces, focuses on methodology followed during all the preliminary and preparatory phases: active measurements by ionization chamber radon continuous monitor, radon progeny equilibrium factor estimations by radon daughters monitor, strategies for occupants’ awareness, positioning protocol and provisions to maximize representativity of results

    Video Coding with Motion Estimation at the Decoder

    Get PDF
    Predictive video coding is based on motion estimation. In such systems, the temporal correlation is exploited at the encoder, whereas at the decoder, the correlation between the previously decoded frames and the current frame is never exploited. In this chapter, we propose a method for motion estimation at the decoder. Based on the prediction residue and on the already decoded frames, the decoder is able to partially reconstruct the motion field, which therefore can be skipped in the encoded stream. The proposed approach is based on Least Square Estimation (LSE) prediction, and is suitable for low bit-rate video coding, in which the transmission of the motion field has a significant impact on the overall bit-rate. The same technique could also be useful in case of high definition video coding, where a detailed and accurate motion field is required. Preliminary results seem to be very promising

    Coherent video reconstruction with motion estimation at the decoder

    Get PDF
    In traditional predictive video coding the block matching is performed at the encoder. The obtained motion field is then transmitted to the decoder, together with the prediction residue. Nevertheless, if the motion field is not provided it can be reconstructed, as long as the decoder manages to exploit some correlated information. This paper presents an algorithm for the motion estimation at the decoder side, given the prediction residue only. The main novelty of this algorithm relies on the contextual reconstruction of a frame region composed of several blocks. Simulation results show that taking into account a whole row can improve significantly the results obtained with an algorithm that reconstructs each block separately

    Performance of a Distributed Video Codec Behaviours in Presence of Transmission Errors

    Get PDF
    Distributed Video Coding (DVC) is one of the most important and active research fields in video coding. The basic idea underlying DVC is to exploit the temporal correlation among frames directly in the decoding phase. The main properties of a distributed video coding system is that the computational load could in principle be shifted towards the decoder, with respect to a traditional video coding system. Anyway, the distributed coding approach has other interesting properties. In particular, one of the most promising benefits derived by the use of DVC is its natural error resilience to channel errors. Nevertheless, very few results on the actual error resilience properties of distributed video coding systems have been presented in literature. In this contribution we present a detailed analysis of the error resilience properties of a video coding system based on Stanford architecture. We analyze the behavior of such codec in presence of channel error, first focusing on the effect of such errors on the different parts of the encoded stream, and then making a preliminary comparison with H264

    Error Resilience Performance Evaluation of a Distributed Video Codec

    Get PDF
    Distributed Video Coding (DVC), one of the most active research field in the video coding community, is based on the combination of Slepian-Wolf coding techniques with the idea of performing the prediction at the decoder side rather than at the encoder side. Besides its main property, which is flexible allocation of computational complexity between encoder and decoder, the distributed approach has other interesting properties. One of the most promising DVC characteristics is its intrinsic robustness to transmission errors. In this work we have evaluated the error resilience performance of a video codec based on the DVC scheme proposed by Stanford, and we have carried out a preliminary comparison with traditional H.264 encoding, showing that at high error probabilities and high bitrates the distributed approach can also outperform the traditional one

    Influence of calcium and phosphorus feeding on markers of bone metabolism in transition cows

    Get PDF
    A study was carried out to verify the effect of Ca and P levels on production, digestibility, and serum bone metabolism biomarkers in dairy cows. Fifty-two nonlactating multiparous cows (≥3 lactations) were confined in a free-stall barn approximately 20 d before calving. A standard close-up diet was fed to cows once daily until d 2 postpartum. Cows were randomly assigned to 1 of 4 dietary treatments arranged in a 2 × 2 factorial approach averaging 0.64% Ca for high Ca (HCa), 0.46% Ca for low Ca (LCa), 0.47% P for high P (HP), and 0.38% P for low P (LP) on a dry matter basis. Experimental diets were fed twice daily from 3 d in milk (DIM) until 31 DIM. Intake and milk yield were recorded daily. Milk samples were collected on d 28, 29, and 30 postpartum for components analyses. Blood samples were drawn 10 d before expected calving, at calving, and at 15 and 30 DIM for serum analyses of osteocalcin, a biomarker of bone accretion, and pyridinoline, a biomarker of bone resorption. Total fecal collection was conducted when cows in a block averaged 20 DIM. Intake and production traits were not significantly affected by any of the dietary treatments. Cows averaged nearly 21 kg/d dry matter intake and 44 kg/d milk yield from 6 to 31 DIM. There were no significant differences across treatments in body weight or body condition score loss. Phosphorus intake, P fecal output, P digestibility, and P apparent absorption were affected by dietary P content. Calcium intake was higher with HCa, but Ca fecal output, digestibility, and apparent absorption showed an interaction between dietary Ca and dietary P. Calcium fecal output was 100.6 g/d for cows fed HCaHP, intermediate for cows on the HCaLP diet (89 g/d), and similar among cows fed the 2 LCa diets (70 g/d with LCaHP and 75 with LCaLP). There was no significant effect of Ca or P on osteocalcin measurements. Pyridinoline concentrations were affected by dietary Ca levels and tended to have a significant dietary Ca × dietary P interaction. Phosphorus apparent digestibility occurred independently of dietary Ca levels. Results of this study suggest that more bone was mobilized in cows fed LCa diets, but excess dietary P caused greater and prolonged bone mobilization regardless of dietary Ca content. © American Dairy Science Association, 2009

    Non-minimality of corners in subriemannian geometry

    Get PDF
    We give a short solution to one of the main open problems in subriemannian geometry. Namely, we prove that length minimizers do not have corner-type singularities. With this result we solve Problem II of Agrachev's list, and provide the first general result toward the 30-year-old open problem of regularity of subriemannian geodesics.Comment: 11 pages, final versio

    Report of CE on Semantic DS

    Get PDF
    The Semantic DS allows describing the world depicted by the AV content and interpreting that world, i.e., the “about” of the AV content or depicted narrative reality, which sometimes is imaginary. This document reports on the core experiment on the Semantic DS [6]. The CE originally started at the Maui meeting in December 1999 [3]. Progress reports of the CE were provided at the Geneva meeting [1] and at the Beijing meeting [2]. In Beijing, some components of the Semantic DS were promoted to the XM: Semantic DS, Object DS, PersonObject DS, Event DS, State DS, MediaOccurrence DS, SemanticTime DS, SemanticLocation DS, UsageLabel D, and some semantic relations. The main tasks of this core experiment have been the following: 1) To refine the specification of the Semantic DS by solving identified issues; 2) To define the Conceptual DSs; 3) To recommend the standardization of more semantic relations; 4) To investigate the use of membership functions to describe the strength of relations; 5) To generate simple and complex semantic descriptions of multimedia material; 6) To implement a retrieval and browsing application/s that uses the generated descriptions and that shows the functionality of the UsageLabel D, the Conceptual DSs, the State DS, and membership functions for relations, especially; 7) To recommend changes and additions to the Semantic DS based on the results of the experiment. The retrieval application that the CE has accomplished two objectives: (1) to show the utility of the components of the Semantic DS in a retrieval scenario, and (2) to be the software for the MPEG-7 XM platform
    corecore