Performance analysis of 802.11ac with frame aggregation using NS3

802.11ac is an interesting standard of IEEE bringing multiple advantages than its predecessor 802.11n. 802.11ac is faster and more scalable version of 802.11n offering the capabilities of wireless Gigabit Ethernet. 802.11ac will enable access points (AP) to support more STAs with a better experience for clients and more channel bonding increasing from a maximum of 40 MHz with 802.11n up to 80 or 160 MHz with 802.11ac standard. In this paper, we analyze and evaluate the 802.11ac performance using NS3 simulator (v3.26) relying on several features like channel bonding, modulation and coding schemes, guard interval and frame aggregation. Then, we present the effect of the variation of distance between STAs and AP on the network performance in term of throughput. Finally, we capture the most relevant simulations outcomes and we indicate some research challenges for the future work

Selective Fetal Growth Restriction in Dichorionic Twin Pregnancies: Diagnosis, Natural History, and Perinatal Outcome.

This study aims to evaluate the natural history, disease progression, and outcomes in dichorionic twins with selective fetal growth restriction (sFGR) according to different diagnostic criteria and time of onset. Dichorionic twins seen from the first trimester were included. sFGR was classified according to the Delphi consensus, and was compared to the outcomes of those classified by the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) diagnostic criteria. Early sFGR occurred before 32-weeks, and late sFGR after 32-weeks. Disease progression, neonatal outcomes such as gestation at delivery, birthweight, neonatal unit (NNU) admission, and morbidities were compared. One-hundred twenty-three of 1053 dichorionic twins had sFGR, where 8.4% were classified as early sFGR, and 3.3% were late sFGR. Disease progression was seen in 36%, with a longer progression time (5 vs. 1 week) and higher progression rate (40% vs. 26%) in early sFGR. Perinatal death was significantly higher in the sFGR than the non-sFGR group (24 vs. 16 per 1000 births, p = 0.018), and those with early sFGR had more NNU admissions than late sFGR (p = 0.005). The ISUOG diagnostic criteria yielded a higher number of sFGR than the Delphi criteria, but similar outcomes. sFGR have worse perinatal outcomes, with early onset being more prevalent. Use of the Delphi diagnostic criteria can reduce over-diagnosis of sFGR and avoid unnecessary intervention

Low scale B-L extension of the Standard Model at the LHC

The fact that neutrinos are massive indicates that the Standard Model (SM) requires extension. We propose a low energy (<TeV) B-L extension of the SM, which is based on the gauge group SU(3)_C x SU(2)_L x U(1)_Y x U(1)_{B-L}. We show that this model provides a natural explanation for the presence of three right-handed neutrinos in addition to an extra gauge boson and a new scalar Higgs. Therefore, it can lead to very interesting phenomenological implications different from the SM results which can be tested at the LHC. Also we analyze the muon anomalous magnetic moment in this class of models. We show that one-loop with exchange Z' may give dominant new contribution ~ few x 10^{-11}.Comment: 12 page

Influence of laser power on tensile properties and material characteristics of laser-sintered UHMWPE

Ultra High Molecular Weight Polyethylene (UHMWPE) has excellent properties, such as high mechanical performance, low friction, high wear and chemical resistance but so far there has been limited use in additive manufacturing (AM). Laser sintering of polymers is one of the most promising AM technologies due to its ability to produce complex geometries with accurate dimensions and good mechanical properties. Consequently, this study investigates the influence of laser power on physical and mechanical properties of UHMWPE parts produced by laser sintering. In particular mechanical properties, such as Ultimate Tensile Strength (UTS), Young’s Modulus and elongation at break were evaluated alongside relative density, dilation and shrinkage. Finally, the fracture surface of the tensile test specimens was examined by electron microscopy. Results show that within a laser power range of 6–12 W there appears to be an optimum where tensile strength and relative density reach a maximum, dilation is minimised and where elongation increases with laser power. UTS up to 2.42 MPa, modulus up to 72.6 MPa and elongation at break up to 51.4% were observed. Relative density and part dimensions are also influenced by laser power

New Study Of Electrical Conductivity In Ni-Doped Non -Stoichiometric Lithium Tantalite

Electrical conductivity in Ni-doped nonstoichiometric lithium tantalite was described by a new theoretical approach. From the experience, we have proposed the new vacancy models which are able to describe substitutional mechanism in Ni-doped lithium tantalite. A combinaison of phase transition theory and generalised vacancy models allows us to establish a new expression of electrical conductivity which takes into account the defect structure of Ni-doped lithium tantalate. Calculations of the conductivity in Ni-doped nonstoichiometric lithium tantalate reveal good correspondence with experimental results.Electrical conductivity in Ni-doped nonstoichiometric lithium tantalite was described by a new theoretical approach. From the experience, we have proposed the new vacancy models which are able to describe substitutional mechanism in Ni-doped lithium tantalite. A combinaison of phase transition theory and generalised vacancy models allows us to establish a new expression of electrical conductivity which takes into account the defect structure of Ni-doped lithium tantalate. Calculations of the conductivity in Ni-doped nonstoichiometric lithium tantalate reveal good correspondence with experimental results

Some Theoretical Results of Ferroelectric Transition In The Doped Crystal LiMO3 (M= Nb, Ta)

This work behaves like an extension of the Safaryan theory. A new analytical description has been proposed based on the vibrations of crystal planes. LiMO3 is formed by a succession of the plans in the following sequence: Li, M, O3, etc.  In the N doped LiMO3 crystal, we supposed that the LiNMO3 system is formed by a succession of the plans of the sequence: Li, N, M, O, ect. These four crystalline plans vibrate in the direction of trigonal c-axis where each plan consists the ions Li+, Nx+, M5+ or O2-. The dynamic solution of the vibrations of these planes shows that one of two optical branches describes the soft mode at the ferroelectric transition in LiNMO3. From dispersion equation, we have show the bond between the soft mode frequency, the Curie temperature, the charges, the masses of ions and the distance between these ions. The substitution mechanism of the doped compositions N in LiMO3 crystal is discussed. So, the mechanism of phase transition due to thermal expansion of crystal is described.This work behaves like an extension of the Safaryan theory. A new analytical description has been proposed based on the vibrations of crystal planes. LiMO3 is formed by a succession of the plans in the following sequence: Li, M, O3, etc.  In the N doped LiMO3 crystal, we supposed that the LiNMO3 system is formed by a succession of the plans of the sequence: Li, N, M, O, ect. These four crystalline plans vibrate in the direction of trigonal c-axis where each plan consists the ions Li+, Nx+, M5+ or O2-. The dynamic solution of the vibrations of these planes shows that one of two optical branches describes the soft mode at the ferroelectric transition in LiNMO3. From dispersion equation, we have show the bond between the soft mode frequency, the Curie temperature, the charges, the masses of ions and the distance between these ions. The substitution mechanism of the doped compositions N in LiMO3 crystal is discussed. So, the mechanism of phase transition due to thermal expansion of crystal is described

New Approach To Study The Influence Of The Defect Structure On The Refractive Indices Of Mg-Doped Lithium Niobate

We proposed a new approach to calculate the refractive indices of Mg-doped lithium niobate using generalized vacancy models combined with a ferroelectric phase transition theory. We have obtained a generalised Sellmeier equation which takes into account the defect structure and Mg-doped lithium niobate. A comparison between the calculated values from this approach and the experimental data of the temperature and refractive indices is detailed.We proposed a new approach to calculate the refractive indices of Mg-doped lithium niobate using generalized vacancy models combined with a ferroelectric phase transition theory. We have obtained a generalised Sellmeier equation which takes into account the defect structure and Mg-doped lithium niobate. A comparison between the calculated values from this approach and the experimental data of the temperature and refractive indices is detailed

An Approach To The Defect Structure Analysis Of Niobate And Tantalate Lithium Ilmenite Type Structure

We present in this work a comparative study between normal LiNbO3 (LiTaO3) and ilmenite structural LiNbO3 (LiTaO3). Namely, the normal cation stacking sequence is replaced by ilmenite ordering …Nb (Ta) Li vacancy Li Nb (Ta) vacancy Nb (Ta) Li vacancy Li Nb (Ta) vacancy… From Safaryan’s approach which combines a ferroelectric phase transition theory and vacancy models we calculated the Curie temperature in ilmenite LiNbO3 (LiTaO3). Comparatively, we showed that the ilmenite structural LiNbO3 (LiTaO3) is in an excellent agreement with experiment result than normal LiNbO3 (LiTaO3).We present in this work a comparative study between normal LiNbO3 (LiTaO3) and ilmenite structural LiNbO3 (LiTaO3). Namely, the normal cation stacking sequence is replaced by ilmenite ordering …Nb (Ta) Li vacancy Li Nb (Ta) vacancy Nb (Ta) Li vacancy Li Nb (Ta) vacancy… From Safaryan’s approach which combines a ferroelectric phase transition theory and vacancy models we calculated the Curie temperature in ilmenite LiNbO3 (LiTaO3). Comparatively, we showed that the ilmenite structural LiNbO3 (LiTaO3) is in an excellent agreement with experiment result than normal LiNbO3 (LiTaO3)

Properties of Carbon Black From Jatropha Seed Shell as a Potential Source of Filler Enhancement in Biocomposites

The use of biomass as filler in biocomposites are becoming widespread in the present decade because its variety of advantages. Jatropha (jatropha curcas L) seed shell after separated from kernel can be used to produce carbon black because of its higher carbon content, and have the potentiality to use as reinforcement in composites. In this study, carbon black was produced from jatropha seed shell by carbonization in furnace method for 1 hour at 600oC. Thermo gravimetric analysis to analyze seed shell of jatropha as raw material. The morphological properties of the carbon black were analyzed by elemental analysis by X-ray (EDX), SEM, TEM, XRD, SEM, and TEM. It was found that the yield of carbon black was 40% which included 4 different sizes ranging from 70 – 300 mesh in distribution of particle size analysis. Carbon black suggested that it could be a good filler or reinforcement in biocomposite