Scanning Electron Microscopic Studies of Microwave Sintered Al-SiC Nanocomposites and Their Properties

Al-metal matrix composites (AMMCs) reinforced with diverse volume fraction of SiC nanoparticles were synthesized using microwave sintering process. The effects of the reinforcing SiC particles on physical, microstructure, mechanical, and electrical properties were studied. The phase, microstructural, and surface analyses of the composites were systematically conducted using X-ray diffraction (XRD), scanning electron microscope (SEM), and surface profilometer techniques, respectively. The microstructural examination revealed the homogeneous distribution of SiC particles in the Al matrix. Microhardness and compressive strength of nanocomposites were found to be increasing with the increasing volume fraction of SiC particles. Electrical conductivity of the nanocomposites decreases with increasing the SiC content. ? 2018 M. A. Himyan et al.This publication was made possible by NPRP Grant 7159-2-076 from Qatar National Research Fund (a member of the Qatar Foundation).Scopu

Evidence for magnetic clusters in Ni1−x_{1-x}Vx_{x} close to the quantum critical concentration

The d-metal alloy Ni$_{1-x}$V$_{x}$ undergoes a quantum phase transition from a ferromagnetic ground state to a paramagnetic ground state as the vanadium concentration $x$ is increased. We present magnetization, ac-susceptibility and muon-spin relaxation data at several vanadium concentrations near the critical concentration $x_c \approx11.6$ at which the onset of ferromagnetic order is suppressed to zero temperature. Below $x_c$, the muon data reveal a broad magnetic field distribution indicative of long-range ordered ferromagnetic state with spatial disorder. We show evidence of magnetic clusters in the ferromagnetic phase and close to the phase boundary in this disordered itinerant system as an important generic ingredient of a disordered quantum phase transition. In contrast, the temperature dependence of the magnetic susceptibility above $x_c$ is best described in terms of a magnetic quantum Griffiths phase with a power-law distribution of fluctuation rates of dynamic magnetic clusters. At the lowest temperatures, the onset of a short-range ordered cluster-glass phase is recognized by an increase in the muon depolarization in transverse fields and maxima in ac-susceptibility.Comment: 6 pages, 5 figures, submitted to Proceedings of SCES 201

Container shipment demand forecasting in the Australian shipping industry: A case study of asia–oceania trade lane

Demand forecasting has a pivotal role in making informed business decisions by predicting future sales using historical data. Traditionally, demand forecasting has been widely used in the management of production, staffing and warehousing for sales and marketing data. However, the use of demand forecasting has little been studied in the container shipping industry. Improved visibility into the demand for container shipments has been a long-held objective of industry stakeholders. This paper addresses the shortcomings of both short-term and long-term shipment demand forecasting for the Australian container shipping industry. In this study, we compare three forecasting models, namely, the seasonal auto-regressive integrated moving average (SARIMA), Holt–Winters’ seasonal method and Facebook’s Prophet, to find the best fitting model for short-term and long-term import demand forecasting in the Australian shipping industry. Demand data from three years, i.e., 2016–2018, is used for the Asia–Oceania trade lane. The mean absolute percentage error (MAPE), root mean squared error (RMSE) and 2-fold walk-forward cross-validation are used for the model evalua-tion. The experiment results observed from the selected metrics suggest that Prophet outperforms the other models in its comparison for container shipment demand forecasting

Development and properties of polymeric nanocomposite coatings

Polymeric-based nanocomposite coatings were synthesized by reinforcing epoxy matrix with titanium nanotubes (TNTs) loaded with dodecylamine (DOC). The performance of the developed nanocomposite coatings was investigated in corrosive environments to evaluate their anti-corrosion properties. The SEM/TEM, TGA, and FTIR analysis confirm the loading of the DOC into the TNTs. The UV-Vis spectroscopic analysis confirms the self-release of the inhibitor (DOC) in response to the pH change. The electrochemical impedance spectroscopic (EIS) analysis indicates that the synthesized nanocomposite coatings demonstrate superior anticorrosion properties at pH 2 as compared to pH 5. The improved anticorrosion properties of nanocomposite coatings at pH 2 can be attributed to the more effective release of the DOC from the nanocontainers. The superior performance makes polymeric nanocomposite coatings suitable for many industrial applications.Qatar University, University of Auckland, Qatar FoundationScopu

Synthesis and properties of polyelectrolyte multilayered microcapsules reinforced smart coatings

The present research work focuses on the synthesis, characterization and properties of novel polyelectrolyte multilayered microcapsules used as smart additives in organic coatings for corrosion protection of steel parts. Urea formaldehyde microcapsules encapsulated with linalyl acetate (UFMCs), sensitive to mechanical stimulus, were synthesized by in situ emulsion polymerization technique. In the next step, dodecylamine, working as a pH stimulus corrosion inhibitor, was loaded into layers of polyelectrolyte molecules, polyethylenimine (PEI) and sulfonated polyether ether ketone (SPEEK). These were applied layer-by-layer over the microcapsules to form inhibitor containing multilayered urea formaldehyde microcapsules (MLUFMCs). In the next step, MLUFMCs (5.0 wt%) and UFMCs (5.0 wt%) were thoroughly dispersed into the epoxy resin and coated on cleaned steel. A comparison of the structural, thermal and anticorrosive properties indicates that coatings modified with multilayered capsules (PMLSCs) demonstrate good thermal stability, improved self-healing characteristics and higher corrosion resistance compared to the coating modified with urea formaldehyde microcapsules. The improved properties of PMLSCs can be attributed to efficient release of the encapsulated self-healing agent and corrosion inhibitor from the MLUFMCs. Therefore, epoxy coatings modified with the novel multilayered capsules may be attractive for corrosion protection of steel parts used in oil and gas and related industries. - 2019, The Author(s).Open Access funding provided by the Qatar National Library. This publication was made possible by NPRP Grant 9–080-2-039 from Qatar National Research Fund (a member of the Qatar Foundation). Statements made herein are solely the responsibility of the authors. R. A. Shakoor would like to acknowledge the financial support of QU internal grant-QUCG-CAM-2018/2019-3 and the Core Labs, QEERI for their SEM and TEM imaging. M.F. Mon-temor thanks Fundac¸ão para a Ciência e a Tecnologia (FCT, Portugal) for financial support under the projects PEst-OE/QUI/UI0100/2013.Scopu

Evidence for Magnetic Clusters in Ni₁₋ₓVₓ Close to the Quantum Critical Concentration

The d-metal alloy Ni1-xVx undergoes a quantum phase transition from a ferromagnetic ground state to a paramagnetic ground state as the vanadium concentration x is increased. We present magnetization, ac-susceptibility and muon-spin relaxation data at several vanadium concentrations near the critical concentration xc ~ 11.6 % at which the onset of ferromagnetic order is suppressed to zero temperature. Below xc, the muon data reveal a broad magnetic field distribution indicative of a long-range ordered ferromagnetic state with spatial disorder. We show evidence of magnetic clusters in the ferromagnetic phase and close to the phase boundary in this disordered itinerant system as an important generic ingredient of a disordered quantum phase transition. In contrast, the temperature dependence of the magnetic susceptibility above xc is best described in terms of a magnetic quantum Griffiths phase with a power-law distribution of fluctuation rates of dynamic magnetic clusters. At the lowest temperatures, the onset of a short-range ordered cluster-glass phase is recognized by an increase in the muon depolarization in transverse fields and maxima in ac-susceptibility

Quantum Griffiths effects and smeared phase transitions in metals: theory and experiment

In this paper, we review theoretical and experimental research on rare region effects at quantum phase transitions in disordered itinerant electron systems. After summarizing a few basic concepts about phase transitions in the presence of quenched randomness, we introduce the idea of rare regions and discuss their importance. We then analyze in detail the different phenomena that can arise at magnetic quantum phase transitions in disordered metals, including quantum Griffiths singularities, smeared phase transitions, and cluster-glass formation. For each scenario, we discuss the resulting phase diagram and summarize the behavior of various observables. We then review several recent experiments that provide examples of these rare region phenomena. We conclude by discussing limitations of current approaches and open questions.Comment: 31 pages, 7 eps figures included, v2: discussion of the dissipative Ising chain fixed, references added, v3: final version as publishe

Serum ferritin levels, socio-demographic factors and desferrioxamine therapy in multi-transfused thalassemia major patients at a government tertiary care hospital of Karachi, Pakistan

<p>Abstract</p> <p>Background</p> <p>Beta thalassemia is the most frequent genetic disorder of haemoglobin synthesis in Pakistan. Recurrent transfusions lead to iron-overload manifested by increased serum Ferritin levels, for which chelation therapy is required.</p> <p>Findings</p> <p>The study was conducted in the Pediatric Emergency unit of Civil Hospital Karachi after ethical approval by the Institutional Review Board of Dow University of Health Sciences. Seventy nine cases of beta thalassemia major were included after a written consent. The care takers were interviewed for the socio-demographic variables and the use of Desferrioxamine therapy, after which a blood sample was drawn to assess the serum Ferritin level. SPSS 15.0 was employed for data entry and analysis.</p> <p>Of the seventy-nine patients included in the study, 46 (58.2%) were males while 33 (41.8%) were females. The mean age was 10.8 (± 4.5) years with the dominant age group (46.2%) being 10 to 14 years. In 62 (78.8%) cases, the care taker education was below the tenth grade. The mean serum Ferritin level in our study were 4236.5 ng/ml and showed a directly proportional relationship with age. Desferrioxamine was used by patients in 46 (58.2%) cases with monthly house hold income significant factor to the use of therapy.</p> <p>Conclusions</p> <p>The mean serum Ferritin levels are approximately ten times higher than the normal recommended levels for normal individuals, with two-fifths of the patients not receiving iron chelation therapy at all. Use of iron chelation therapy and titrating the dose according to the need can significantly lower the iron load reducing the risk of iron-overload related complications leading to a better quality of life and improving survival in Pakistani beta thalassemia major patients.</p> <p>Conflicts of Interest: None</p

A Comprehensive Survey of Security Threats and their Mitigation Techniques for next-generation SDN Controllers

Software Dened Network (SDN) and Network Virtualization (NV) are emerged paradigms that simplied the control and management of the next generation networks, most importantly, Internet of Things (IoT), Cloud Computing, and Cyber-Physical Systems. The Internet of Things (IoT) includes a diverse range of a vast collection of heterogeneous devices that require interoperable communication, scalable platforms and security provisioning. Security provisioning to an SDN based IoT network pose a real security challenge leading to various serious security threats due to the connection of various heterogeneous devices having a wide range of access protocols . Furthermore, the logical centralized controlled intelligence of the SDN architecture represents a plethora of security challenges due to its single point of failure. it may throw the en tire network into chaos and thus expose it to various known and unknown security threats and attacks. security of SDN controlled IoT environment is still in infancy and thus remains the prime research agenda for both the industry and academia. This paper comprehensively reviews the current state-of-the-art security threats, vulnerabilities and issues at the control plane. Moreover, this paper contributes by presenting a detailed classfication of various security attacks on the control layer. A comprehensive state-of-the-art review of the latest mitigation techniques for various security breaches is also presented. Finally, the paper presents future research directions and challenges for further investigation down the line