Uplink coverage probability and spectral efficiency for downlink uplink decoupled dense heterogeneous cellular network using multi-slope path loss model

Telecommunication Systems - Low powered node densification leading to dense and ultra dense heterogeneous networks is a feature of 5th generation cellular networks. With this densification, the...     

Development of high performance amine functionalized zeolitic imidazolate framework (ZIF-8)/cellulose triacetate mixed matrix membranes for CO2/CH4 separation

High cost and complex fabrication process of inorganic membranes and lower position of pristine polymeric membranes in the Robeson upper bound curve urged the researchers to develop mixed matrix membranes (MMMs). Cellulose acetate being most commercially used polymer, dominates the market of CO₂ separation mainly because of low cost and environmental friendly resource. In the present study, MMMs consists of amine functionalized zeolitic imidazolate framework (NH₂-ZIF-8) and cellulose triacetate were fabricated for the first time. NH₂-ZIF-8 was used as a filler because the pore size of ZIF-8 is between the kinetic diameter of separating gases (CO₂ and CH₄). Moreover,  NH₂ group attached on the surface of ZIF-8 has affinity with condensable gases like CO₂. Morphology, crystallinity, tensile strength and functional groups of fabricated membranes were investigated using different analytical techniques. Results revealed that the increase of feed pressure has increased CO₂ permeability and decreased permselectivity. However, improvements in gas separation performance were observed with the addition of nanofiller. Best position in Robeson's upper bound curve at 4 bar was obtained with 10 wt% loading with CO₂ permeability and CO₂/CH₄ permselectivity of 218 barrer and 13.84, respectively. The improvement in the gas separation performance with loading is attributed to the increased diffusion coefficients as well as solubility coefficients, which was increased to 33% and 3.8%, respectively.     

Heat transfer analysis for particle–fluid suspension thermomagnetohydrodynamic peristaltic flow with Darcy–Forchheimer medium

This theoretical analysis explores the effect of heat and mass transfer on particle–fluid suspension for the Rabinowitsch fluid model with the stiffness and dynamic damping effects through Darcy–Brinkman–Forchheimer porous medium. In this study, we also incorporate slip and transverse magnetic field effects. Using low Reynolds number, to neglect inertial forces and to keep the pressure constant during the flow, channel height is used largely as compared with the ratio of length of the wave. A numerical technique is used to solve flow governing system of differential equations. Particular attention is paid to viscous damping force parameter, stiffness parameter, and rigidity parameter; also, the numerical data for thermal profile, momentum, and concentration distribution are presented graphically. Outcomes are deliberated in detail for different fluid models (thinning, thickening, and viscous models). It is found that velocity profile increases for greater values of viscous damping effect and stiffness and rigidity parameter for shear thinning, but conflicting comportment is showed for thickening nature model. Viscous dissipation effects increases the thermal profile for all cases of fluid models. The scope of the present article is valuable in explaining the blood transport dynamics in small vessels while considering the important wall features with chemical reaction characteristics. The current analysis has extensive applications in biomedical engineering field, that is, peristaltic pumps.     

Carbon nanotubes/nanofibers (CNTs/CNFs): a review on state of the art synthesis methods

Microsystem Technologies - This research article discusses the state of the art synthesis methods for the formation of carbon nanotubes and nanofibers (CNTs/CNFs). Carbon nanotubes have a number of...     

Social media in conflicts and crises

ABSTRACT

The growing importance of social media in conflicts and crises is accompanied by an ever-increasing research interest in the crisis informatics field in order to identify potential benefits and develop measures against the technology’s abuse. This special issue sets out to give an overview of current research on the use of social media in conflicts and crises. In doing so, it focuses on both good and malicious aspects of social media and includes a variety of papers of conceptual, theoretical and empirical nature. In six sections, the special issue presents an overview of the field, analytical methods, technical challenges, current advancements and the accepted papers before concluding. Specific topics range from cyber deception over information trustworthiness to mining and near-real-time processing of social media data.     

Root Cause Failure Analysis of a Domestic Pressure Cooker Through Metallurgical Characterization and Computational Simulation

Pressure cooker is a closed domestic pressure cooking vessel for use with external heat source and capable of maintaining nominal cooking pressure up to 1.0 kgf/cm² (100 kN/m² approximately) gauge nominal. In pressure cookers, despite the development of electronic controllers, the basic edition of such vessels are still equipped with fewer advanced safety functions due to economic constraints. Although the provision of pressure relief valves (PRV) is considered as one of the major protective features, however, pressure cooker failure accidents have been reported frequently. This paper describes the analysis of pressure cooker failure that failed prematurely after 1 year of service considering the design life of > 5 years. It was hypothesized that the root cause of pipe failure was either material degradation from exposure to an aggressive environment or an inherent defect in the pressure cooker. To test this hypothesis, a thorough visual examination of the exhumed failed section and the fracture surface was undertaken, followed by liquid penetrant testing, material identification, hardness testing, and metallographic analysis. Computational models of static and transient loading were also used to determine the stress distribution along the actual geometry of the failed cooker and to understand the main causes of recurrent failures. Visual and macroscale examination revealed significant body deformation at the lower dish-ended shell showing distorted locking grooves. It was also noticed that dirt and food particle, from the earlier cooking, were stuck in the pressure valves orifice. In addition, no evidence of metallurgical defect was observed. The inspection indicated that the cause of failure is primarily due to the choking of pressure relief value (PRV) and overpressure safety valves. Consequently, the pressure release occurred from the sealing side of the top lid, which resulted in its ejection.     

Microwave assisted synthesis and antimicrobial activity of Fe3O4-doped ZrO2 nanoparticles

Composites play important role in dental filling by controlling shrinkage along with correction in teeth's shape and position. Rehabilitation of severely worn dentition can be achieved using mechanically strong composites. This study aims to synthesize zirconia-based composites to be used as dental fillers. Effect of microwave powers (100–900?W) along with Fe₃O₄ doping are studied on the structural, mechanical and magnetic properties of stabilized zirconia. SEM and TEM reveal formation of spherical nanoparticles with diameter of ～30?nm. XRD results shows phase pure tetragonal zirconia (t-ZrO₂) at microwave power of 500?W without any post heat treatment. Crystallite size calculated from XRD data (～23?nm) matches well with the previously reported value for stabilization of t-ZrO₂. Microwave energy dissipation results in stresses causing volume shrinkage leading to monoclinic to tetragonal phase transformation with higher X-ray density and hardness of ～1347HV. VSM results show ferromagnetic response with low coercivity (600Oe) value and saturation magnetization (～2emu/g). It is worth mentioning here that this is one of its kind study reporting synthesis of room temperature stabilized Fe₃O₄ doped zirconia composites at microwave power of 500?W. Antibacterial studies reveal inhibition zone of ～32?mm against bacillus bacteria suggesting their potential use as dental filler.     

Numerical solution of 2D and 3D elliptic-type interface models with regular interfaces

Engineering with Computers - In the current paper, two numerical methods are proposed for the numerical solution of two- and three-dimensional elliptic partial differential equations (PDEs) with...     

Analysis of the decoupled uplink downlink technique for varying path loss exponent in multi-tier HetNet

In this paper, the impact of varying path loss exponent (PLE) on user association probability, decoupled uplink coverage probability as well as decoupled uplink average spectral efficiency in downlink uplink decoupled (DUDe) multi-tier heterogeneous networks, is investigated. We investigate the effect of the difference in path loss exponents in both macro and small cell environments over uplink network performance. It is assumed that the mobile user connected to the macro base station experience different path loss exponent as compared to when connected to small base station. It is observed that the difference of path loss exponents in both cases has significant effect on the user association probability, decoupled uplink coverage probability as well as decoupled uplink average spectral efficiency. Moreover, in order to further support key findings and make sound comparison between coupled and DUDe performance in varying PLE environment, generalized analytical expressions for coupled association probabilities, along with coupled uplink coverage probability and coupled uplink average spectral efficiency have been derived. The analytical results evaluated in this paper are compared with the computer simulation and found in good agreement. Our analysis shows that decoupling technique performs suboptimal for cases where the environments around macro and small base stations are different with respect to each other. The work explained in this paper highlights the limitation of applying DUDe technique in realistic conditions where the PLEs of cellular tiers are not exactly equal to one another.