Adaptive Streaming in P2P Live Video Systems: A Distributed Rate Control Approach

Dynamic Adaptive Streaming over HTTP (DASH) is a recently proposed standard that offers different versions of the same media content to adapt the delivery process over the Internet to dynamic bandwidth fluctuations and different user device capabilities. The peer-to-peer (P2P) paradigm for video streaming allows to leverage the cooperation among peers, guaranteeing to serve every video request with increased scalability and reduced cost. We propose to combine these two approaches in a P2P-DASH architecture, exploiting the potentiality of both. The new platform is made of several swarms, and a different DASH representation is streamed within each of them; unlike client-server DASH architectures, where each client autonomously selects which version to download according to current network conditions and to its device resources, we put forth a new rate control strategy implemented at peer site to maintain a good viewing quality to the local user and to simultaneously guarantee the successful operation of the P2P swarms. The effectiveness of the solution is demonstrated through simulation and it indicates that the P2P-DASH platform is able to warrant its users a very good performance, much more satisfying than in a conventional P2P environment where DASH is not employed. Through a comparison with a reference DASH system modeled via the Integer Linear Programming (ILP) approach, the new system is shown to outperform such reference architecture. To further validate the proposal, both in terms of robustness and scalability, system behavior is investigated in the critical condition of a flash crowd, showing that the strong upsurge of new users can be successfully revealed and gradually accommodated.Comment: 12 pages, 17 figures, this work has been submitted to the IEEE journal on selected Area in Communication

Proposal for a methodology based on XRD and SEM-EDS to monitor effects of lime-treatment on clayey soils

The aim of this paper is to present the results of X-ray diffraction (XRD) tests and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analyses on a natural and lime-treated clay, in order to determine the percentage of lime able to stabilize soil. For this reason, XRD test analyses have been conducted on natural soil (TQ0) and on two different mixtures (TQ3 and TQ5): The former with 3% and the latter with 5% by mass of quicklime. These mixtures have been analyzed at different curing times: At the addition of lime (0 d), and after a mellowing period of 7 and 28 d. The obtained results show that 3% of CaO is the percentage of quicklime able to modify the material (initial consumption of lime (ICL) and 5% of CaO is the percentage able to stabilize it (lime stabilization optimum (LSO). Finally, SEM images allowed for the monitoring of the process of reactions between the soil and lime during the mellowing period, while EDS analyses validated the XRD results in terms of chemical composition of the examined soil. For the examined natural clay, statistical analysis of the obtained EDS results identified a linear regression curve between the added quicklime and the after-treatment Ca content. The proposed approach could be adopted to calculate the content of calcium after the treatment and verify the in situ-added CaO during roadworks or at the end of them

High Entropy Cantor Alloys (HEAs) modification induced by tungsten alligation, heat treatment and deep cold plastic deformation

High Entropy Alloys (HEAs) is a unique class of materials that combine particular properties in a large-scale of temperatures, able to guarantee new unexplored materials and alloys with several potentially engineering applications (i.e. space and aerospace industries). As promising structural materials, HEAs consist of five or more principal elements. As a consequence of the monophasic microstructure which usually characterizes HEAs, these alloys offer an excellent combination of strength, strain hardening ability, good plasticity, ductility and fracture toughness especially at cryogenic temperatures better than the existing conventional metals and alloys. For the above reasons, the present work deals with Classic Cantor alloy, a well-known CoCrFeMnNi HEA, where mechanical properties were improved using low cost casting techniques and a combination of different metallurgical methodologies (heat treatment, cold working and adding alloying elements). A promising alloy element, tungsten, was used in the experimentation where mechanical and microstructural characterization were performed using different technique

damage micromechanisms in a hot dip galvanized steel

Abstract: Hot-dip galvanizing is one of the most used methods to apply zinc-based coatings on steels in order to provide sacrificial protection against corrosion over all the steel surface. The aim of this work is the analysis of the hot dip zinc coated steel plates mechanical properties by means of a non-standardized bending test performed minimizing both the bending moment differences along the bending axis and the interactions between the clamping system and the specimen coating. Bending tests are performed both on non-coated and on hot dip zinc coated plates, correlating the measured variables (applied load and crosshead displacement) with the bending moment and the specimen bending angle. Tests are characterised by a good repeatability. Results show that the main damaging mechanisms depend on the different mechanical behaviour of the intermetallic phases and on their thickness. For all the investigated coating conditions, radial cracks are observed. They initiate corresponding to the Γ phase and propagate up to the ζ-η interface. The coating thickness increase implies both an increase of the importance of the cracks in δ and ζ phases and the presence of cracks at ζ-η interfaces

sn and ti influence on damage of bent hot dip galvanizing phases

Abstract: Hot dip galvanizing is the most used technique in the metallic protection field. The coating formation is mainly due to interdiffusion phenomena between iron and zinc atoms. In the last years, the introduction of different elements allows to obtain baths optimized by different characteristics. For example, the presence of Sn in the bath fluidifies the bath and it allows the formation of coatings characterized by an improved homogeneity of thickness. Presence of Ti, allows to obtain different colors of coatings due to different oxidation of Ti in the coatings. In this work a comparison between coatings obtained by the presence of 3%Sn and 0.5%Ti in the baths has been investigated at five different dipping time. In order to analyse the kinetics of coatings formation and the intermetallic phases, longitudinal sections of the bended specimens have been metallographically prepared and observed by means of an optical microscope (LOM). Finally, the mechanical behaviour of all coatings has been investigated using bending tests carried out on specimens

Analysis of the winter and semiannual ionospheric anomalies in 1999-2009 based on GPS global International GNSS Service maps

Our work is focused on the analysis of seasonal and semiannual ionospheric anomalies using vertical total electron content (VTEC) measurements obtained by the International GNSS Service (IGS). For this study we use principal component analysis (PCA) and wavelet transform (WT) because both numerical tools allow us to isolate principal components of the VTEC variability as much spatially as temporally. The IGS VTEC maps are reorganized, and from each daily global data set, two maps were constructed: one at 12:00 LT and the other at 22:00 LT. From these two series of VTEC maps covering the period 1999-2009 for each local time, we found that the semiannual anomaly is globally recorded at noon, especially at mid and low geomagnetic latitudes, and its amplitude has a close relationship with the solar activity, and at night this anomaly is recorded during high solar activity and the larger values are located in the South American region. The values of VTEC at the March equinox exceed that of the September equinox, especially during high solar activity; the winter anomaly is recorded at noon near the geomagnetic poles region, and the effect is more important during high solar activity. At night this anomaly is present during the ascending and descending phases and minimum of the solar cycle. Thus, the night winter anomaly effect is clearly evidenced from our results.Facultad de Ciencias Astronómicas y Geofísica

Analysis of the winter and semiannual ionospheric anomalies in 1999-2009 based on GPS global International GNSS Service maps

Our work is focused on the analysis of seasonal and semiannual ionospheric anomalies using vertical total electron content (VTEC) measurements obtained by the International GNSS Service (IGS). For this study we use principal component analysis (PCA) and wavelet transform (WT) because both numerical tools allow us to isolate principal components of the VTEC variability as much spatially as temporally. The IGS VTEC maps are reorganized, and from each daily global data set, two maps were constructed: one at 12:00 LT and the other at 22:00 LT. From these two series of VTEC maps covering the period 1999-2009 for each local time, we found that the semiannual anomaly is globally recorded at noon, especially at mid and low geomagnetic latitudes, and its amplitude has a close relationship with the solar activity, and at night this anomaly is recorded during high solar activity and the larger values are located in the South American region. The values of VTEC at the March equinox exceed that of the September equinox, especially during high solar activity; the winter anomaly is recorded at noon near the geomagnetic poles region, and the effect is more important during high solar activity. At night this anomaly is present during the ascending and descending phases and minimum of the solar cycle. Thus, the night winter anomaly effect is clearly evidenced from our results.Facultad de Ciencias Astronómicas y Geofísica

La hora del juego libre en los sectores en el desarrollo de la autonomía en los niños de 4 años en la institución educativa inicial Walter Peñaloza Ramella distrito de Mariano Melgar, Arequipa - 2019

El presente trabajo de investigación denominado “La hora del juego libre en los sectores en el desarrollo de la autonomía en los niños de 4 años en la institución educativa Inicial Walter Peñaloza Ramella distrito de Mariano Melgar, Arequipa - 2019”. El estudio de investigación está fundamentado teóricamente en el proceso de desarrollo de la Autonomía basándose en la teoría de Piaget, en la que considera que los niños y niñas dentro de un contexto autónomo desarrollan su autonomía y la teoría de María Montessori quien sustenta que el niño para que pueda aprender de una manera más dinámica y esencial para su edad necesita el juego, estímulos y estrategias que le propicien nuevos aprendizajes. El tipo de investigación que se ha utilizado en el presente estudio es experimental con un diseño pre - experimental y como nivel de investigación es aplicada, debido a que se empleó un taller de juego libre en sectores: para obtener resultados y dar una conclusión más precisa a la problemática. Se trabajó con una población y muestra conformada por 13 niños del sexo masculino y femenino, de 4 años. A la muestra de estudio se le aplicó como instrumento una Lista de Chequeos de Logros Pedagógicos que tuvo validez y confiabilidad para evaluar el nivel de Autonomía en niños de 4 años. Luego se aplicó sesiones de aprendizaje basadas en el juego libre en sectores para promover su Autonomía en los niños y niñas de 4 años de la muestra en estudio. Finalmente, después de hacer la prueba de hipótesis prevista, se puede concluir que “la hora del juego libre en los sectores”, como estrategias, influyó significativamente en el desarrollo de la Autonomía en los niños

Endothelin-1 decreases gap junctional intercellular communication by inducing phosphorylation of connexin 43 in human ovarian carcinoma cells

Endothelin-1 (ET-1) is overexpressed in ovarian carcinoma and acts as an autocrine factor selectively through the ETA receptor (ETAR) to promote tumor cell proliferation, survival, neovascularization, and invasiveness. Loss of gap junctional intercellular communication (GJIC) is critical for tumor progression by allowing the cells to escape growth control. Exposure of HEY and OVCA 433 ovarian carcinoma cell lines to ET-1 led to a 50–75% inhibition in intercellular communication and to a decrease in the connexin 43 (Cx43)-based gap junction plaques. To investigate the phosphorylation state of Cx43, ovarian carcinoma cell lysates were immunoprecipitated and transient tyrosine phosphorylation of Cx43 was detected in ET-1-treated cells. BQ 123, a selective ETAR antagonist, blocked the ET-1-induced Cx43 phosphorylation and cellular uncoupling. Gap junction closure was prevented by tyrphostin 25 and by the selective c-Src inhibitor, PP2. Furthermore, the increased Cx43 tyrosine phosphorylation was correlated with ET-1-induced increase of c-Src activity, and PP2 suppressed the ET-1-induced Cx43 tyrosine phosphorylation, indicating that inhibition of Cx43-based GJIC is mainly mediated by the Src tyrosine kinase pathway. In vivo, the inhibition of human ovarian tumor growth in nude mice induced by the potent ETAR antagonist, ABT-627, was associated with a reduction of Cx43 phosphorylation. These findings indicate that the signaling mechanisms involved in GJIC disruption on ovarian carcinoma cells depend on ETAR activation, which leads to the Cx43 tyrosine phosphorylation mediated by c-Src, suggesting that ETAR blockade may contribute to the control of ovarian carcinoma growth and progression also by preventing the loss of GJIC