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Transmit Antenna Subset Selection in Generalized Spatial Modulation Systems
No full textThe existing literature on transmit antenna selection (TAS) aided spatial modulation (SM) systems extensively deals with the Euclidean distance (ED) based TAS owing to its high transmit diversity gain. In this paper, we consider the ED-TAS aided generalized spatial modulation (GSM) system that transmits multiple symbols in each channel use and characterize its attainable diversity gain. Second, we show that the minimum ED of the received constellation does not grow beyond a certain point when the size of the signal set is sufficiently large, which facilitates low-complexity implementations of the ED-TAS aided SM system. Our numerical studies revealed that a signal-to-noise gain of about 8 dB is achievable by employing ED-TAS in the GSM system compared to its counterpart dispensing with ED-TAS
On the relationship of daily rainfall extremes and local mean temperature
No full textExtreme rainfall is the most common cause of flooding and likelihood of such events is found to increase in recent studies. Large scale natural variability, human induced global warming and local atmospheric warming are important drivers of extreme rainfall. Understanding the association of these drivers with extreme rainfall and finding out the most significant physical driver will provide a foundation for risk assessment. This study presents a methodology to investigate the association of extreme rainfall events with physical drivers and to model their dependence structure. The methodology is demonstrated with application to Mahanadi River basin, India. Non-stationary extreme value models with multivariate ENSO index, global average temperature anomalies and local mean temperature anomalies as covariates are fitted at non-stationary rainfall grids of the basin. Statistical modelling confirms localized temperature to be the main driver influencing rainfall extremes. Clausius-Clapeyron (CC) scaling curves relating daily rainfall extremes and local mean temperature are developed at all the grids to obtain insights into warming induced changes in rainfall extremes. Significant deviations from the expected CC scaling behaviour are observed. Daily rainfall extremes show peaks at low (25 °C) to medium (30 °C) range of temperature, but exhibit a decrease at high temperatures for most of the grids. No change in this pattern of relationship is observed when the extreme rainfall is lagged by 1�9 days with temperature. This time lag is selected based on the concept of residence time of water in the atmosphere. The Copula theory is applied to capture the dependence of annual maximum daily rainfall and temperature extremes. Conditional probabilities of extreme rainfall are estimated by conditioning on local mean temperature values of strongest extreme rainfall events. Comparison of conditional probabilities suggests that stronger rainfall events are occurring at 30 °C. This study emphasizes the necessity of understanding the dependence structure of extreme rainfall and local mean temperature. © 2019 Elsevier B.V
Search for new physics in final states with a single photon and missing transverse momentum in proton-proton collisions at <mml:msqrt>s</mml:msqrt>=13 TeV
No full textA search is conducted for new physics in final states containing a photon and missing transverse momentum in proton-proton collisions at <mml:msqrt>s</mml:msqrt>=13 TeV, using the data collected in 2016 by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9 fb(-1). No deviations from the predictions of the standard model are observed. The results are interpreted in the context of dark matter production and models containing extra spatial dimensions, and limits on new physics parameters are calculated at 95% confidence level. For the two simplified dark matter production models considered, the observed (expected) lower limits on the mediator masses are both 950 (1150) GeV for 1 GeV dark matter mass. For an effective electroweak-dark matter contact interaction, the observed (expected) lower limit on the suppression parameter is 850 (950) GeV. Values of the effective Planck scale up to 2.85-2.90 TeV are excluded for between 3 and 6 extra spatial dimensions
Phase diagram of the system Ce-Rh-O
No full textAlthough important for catalytic applications, a phase diagram for the ternary system Ce-Rh-O is not found in the literature. Phase diagrams of most Ln-Rh-O systems show LnRhO 3 with orthorhombic perovskite structure as the lone stable ternary oxide. Based on systematic trends in experimentally determined thermodynamic properties of eleven LnRhO 3 compounds, the Gibbs energy of formation of CeRhO 3 is evaluated as a function of temperature. For the reaction, 1/2 Ce 2 O 3 (A-rare earth) + 1/2 Rh 2 O 3 (ortho) � CeRhO 3 , �G°/J mol �1 = �69,336 + 5.26(T / K). The estimated data for CeRhO 3 along with evaluated data for the binary Ce-Rh and data for binary oxides from the literature are used to compute the phase diagram for the system Ce-Rh-O at high temperature. Because of the significantly higher stability of CeO 2-x compared to Ce 2 O 3 , the compound CeRhO 3 is found to be unstable. A section of the phase diagram and an oxygen potential � composition diagram for the system Ce-Rh-O at 1200 K are computed from thermodynamic data. © 2019 Elsevier Lt
Shape factor of the turbulent boundary layer on a flat plate and the Reynolds shear stress in the outer region
No full textIt has recently been shown by Wei and Klewicki Phys. Rev. Fluids 1, 082401 (2016)2469-990X10.1103/PhysRevFluids.1.082401 that in a zero-pressure-gradient turbulent boundary layer flow, the product of the nondimensional free-stream velocities in the streamwise (U�+) and wall-normal (V�+) directions is the flow shape parameter (H): U�+V�+=H. It is suggested here that this result is a consequence of the variation of the Reynolds shear stress with U�V in the outer region of the boundary layer. © 2019 American Physical Society
Enhanced microwave absorption properties of PMMA modified MnFe 2 O 4 -polyaniline nanocomposites
No full textA manganese based spinel ferrite, chemically modified with polymethyl methacrylate (PMMA) and polyaniline (PANI) are synthesized and their composites are used as electromagnetic interference (EMI) shielding materials. X-ray diffraction studies show that the as-prepared manganese ferrite crystallizes in a cubic spinel structure. The particles are highly agglomerated and nanocrystalline as indicated by transmission electron microscopy. Manganese exists in +2 and +4 oxidation states and Fe in +2 and +3 oxidation states. Modified manganese ferrite and polyaniline composites in different weight ratios are evaluated for their EMI shielding properties. It is observed that composites containing the PMMA modified ferrite show enhanced total shielding effectiveness (SE T ) compared to those containing the unmodified ferrite in the X band frequency range (8-12 GHz). The optimized ratio of the PMMA modified ferrite and PANI demonstrates SE T values as high as �44 dB in the X band frequency range. © the Owner Societies
Crystal Engineering: An Outlook for the Future
No full textCrystal Engineering has traditionally dealt with molecular crystals. It is the understanding of intermolecular interactions in the context of crystal packing and in the utilization of such understanding in the design of new solids with desired physical and chemical properties. We outline here five areas which come under the umbrella of Crystal Engineering and where we feel that a proper planning of research efforts could lead to higher dividends for science together with greater returns for humankind. We touch on themes and domains where science funding and translation efforts could be directed in the current climate of a society that increasingly expects applications and utility products from science and technology. The five topics are: 1) pharmaceutical solids; 2) industrial solid state reactions; 3) mechanical properties with practical applications; 4) MOFs and COFs framework solids; 5) new materials for solar energy harvesting and advanced polymers. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei
Multi-layered stack consisting of PVDF nanocomposites with flow-induced oriented MWCNT structure can supress electromagnetic radiation
No full textPolymeric nanocomposites have emerged as a potential material in the electronic world owing to its numerous advantages like ease of processing, design flexibility, light-weight, ease of embedding and integrating with the existing production line. Given the surge in electronic components, electromagnetic interference, which severely impairs the reliability of precise electronic devices, has emerged as a new challenge. Hence, technologically, viable design is the need of the day. However, the high concentration of fillers required to achieve the desired properties still remains a challenge with respect to the design of functional polymeric nanocomposites. In this context herein, we report as to how flow induced distribution of multi-walled carbon nanotubes (MWCNT) in poly-vinylidene (PVDF) matrix during mechanical rolling influence the texture, polymorphism and electromagnetic shielding properties. We demonstrate the flow induced orientation of MWCNT, polymorphism in PVDF and composites shielding performance by TEM, crystallographic texture and shielding effectiveness measurements, respectively. Further, mechanical and thermal properties of as pressed and mechanically rolled samples were investigated by DMA and DSC. TEM analysis revealed that MWCNT form small aggregate, however were aligned along the rolling direction. This observation is in sharp contrast to the random distribution for as pressed samples. Quantitatively, a strong texture was observed for rolled samples as compared to as pressed samples. Absorption of EM waves is the major shielding mechanism which is mechanistically discussed here through associated dielectric loss parameters. Interactions, alignment of MWCNTs, and polymorphism influence the shielding efficiency in these composites. In addition, stacking of such nanocomposite layers further enhances the overall shielding efficiency by absorption (up to 72) due to the polarization, multiple internal reflections and interlayer charge storing capacity. A Bluetooth module was employed to successfully demonstrate the efficacy of this approach in supressing unwanted EM interference. This study comprehensively guides researchers as to how processing or flow-induced changes alter the distribution of MWCNTs in polymer composites and how this influences the overall shielding behaviour. © 2019 Elsevier Lt
Enhanced structural, optical, thermal, mechanical and electrical properties by a noval approach (nanoparticle doping) on ferroelectric triglycine sulphate single crystal
No full textThe pristine and AgNP-doped TGS crystals are studied using powder X-ray diffraction, density measurements, solubility studies, UV�Vis analysis, photoluminescence spectroscopic analysis, thermal gravimetric analysis, differential thermal analysis, differential scanning calorimetry, Vicker�s hardness measurements, I�V and impedance measurements. From the XRD studies, TGS crystal formation is confirmed and by further analyzing X-ray diffraction data it is noticed that the incorporation of nanoparticles induce stress in the lattice of TGS crystal, which, in turn, lead to shift in peak positions. Crystal solubility and density values are increased after doping process. From the emission spectrum it is evident that emission intensity increases as the doping concentration increased. The melting point and mechanical hardness of the crystals also showed improvement after AgNP doping. Band gap calculated by Tauc�s relation is found to decrease with increase in doping concentration. Further, electrical studies demonstrated that crystal conductivity is improved as the doping concentration increases. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature
Consistency limits and compaction characteristics of clay soils containing rubber waste
No full textThe aim of the study reported in this paper was to develop practical correlative models capable of predicting the compaction characteristics of clay soils blended with rubber from waste vehicle tyres. Four different clay soils, ranging from intermediate to high plasticity, were adopted for the test programme and each was blended with four different percentages of ground rubber waste. The test programme consisted of cone penetration (consistency limits) and standard Proctor compaction tests. As a result of ground rubber inclusion, the consistency limits and compaction characteristics all exhibited a linear decreasing trend with increase in rubber content. The rate of decrease, however, was greater for the high-plasticity clays. Simple correlative models, linking the compaction characteristics to the consistency limits, were suggested and validated by statistical techniques. The proposed models provide a practical procedure towards predicting the compaction characteristics of ground rubber-clay blends without the hurdles of conducting laboratory compaction tests, and thus can be implemented in practice for preliminary assessments