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Nanoceramic-reinforced aluminum composites have been utilized in most engineering applications such as the automotive and aerospace components due to their mechanical strength efficiency, and tribological performances. In this research, efforts were made to develop AA8011 composite with varying weight fraction of nano-Si3N4 up to 20% in a step of 5 through a two-step stir casting process. Scanning electron and the optical microscope were employed to investigate the microstructural evolution and modification of the developed composite, which reveals even dispersion of Si3N4 particulates. The X-ray diffraction analysis was conducted to check the phases present, and the broad peak shows mainly the presence of Si3N4. Likewise, the mechanical properties, viz, ultimate tensile strength, yield strength propagation, and hardness, were examined to determine the strengthening mechanism of the developed composite. The results show that the reinforced composite possesses better mechanical properties compared with the unreinforced AA8011 and the composite with 20% Si3N4 inclusion had the best properties. Moreover, the wear behavior and the friction coefficient of the developed composite results depicted an enhanced wear resistance and decrease in the coefficient of friction by increasing the Si3N4 particulate, though the wear rate increases with an increase in the applied load from 20 to 40 N. [ABSTRACT FROM AUTHOR]

One of the identified shortcomings militating against the widespread application of Ti6Al4V alloy in the aerospace sector of the economy includes its unsatisfactory hardness and proneness to high-temperature oxidation which in turn adversely impact its abrasion resistance properties in certain service conditions. The work reported in this paper forms an important aspect of the effort put together in addressing these composite issues. Precisely, the effects of the nano-reinforcements of aluminum nitride (AlN) and hexagonal boron nitride (h-BN) on the microstructure, phase contents, hardness, and oxidation resistance of Ti6Al4V-based composites were considered. The prepared powders were sintered by spark plasma sintering (SPS), an innovative sintering method which enables the implementation of fast heating and cooling rates. Thereafter, scanning electron microscopy, optical microscopy, and X-ray diffractometry were employed to observe and study the microstructure and phase contents, Archimedes' principle was applied to evaluate the densification, Vickers' microhardness test was used to measure the hardness values, and thermogravimetric analysis technique was used to study the oxidation resistance of the sintered composites. A homogeneous blend of the nano-reinforcements of 1.5 wt% each of AlN and h-BN gave the highest relative densification value of 99.77% while the hardness value (656.01 HV) was less than that of Ti6Al4V-3h-BN (716.80 HV) which gave more credence to the phase contents in the microstructure as the most influencing factor determining the hardness property of the composites than ordinary relative densification. Meanwhile, Ti6Al4V-1.5AlN-1.5h-BN with the minimum positive weight change (0.36 mg/cm2) exhibited the greatest thermal oxidation resistance in air. [ABSTRACT FROM AUTHOR]

Polymeric materials have become useful in advancing technology due to their distinct properties. One of the useful applications of polymeric materials is in optical conditions such as fibre core, cladding and jacketing of optical fibre. However, polymers suffer from poor thermal properties, which limit their applications in high-temperature environments. Polymers show different properties at various temperatures with respect to time or duration of exposure. In most cases, they show high deterioration of properties at elevated temperature. This often limits the use of polymer in optical application at some certain elevated temperature. Notwithstanding, there has been an advancement on improving thermal stability of polymers as optical fibre materials. Therefore, discussion in this review focused on polymers as cladding and coating materials for high-temperature applications. This review summarized polymeric cladding materials, behaviours and properties of polymeric cladding materials under high temperature. It was concluded with advancements, challenges and recommendations for high-temperature polymeric cladding materials. It is believed that this review will give insight into advancement and selection of high-temperature polymeric materials for cladding, jacketing and coating applications. It will also give a platform for further research. [ABSTRACT FROM AUTHOR]

Monolithic aluminium 1000 alloy is used in overhead transmission conductors because of its light weight, high electrical conductivity and high passivation property. But its low strength is a very big challenge to this application. However, the strength can be improved by proper reinforcement in a way that will not compromise other properties. So, this work was focused on improving the strength and corrosion properties of Al alloy with carbon nanotubes (CNTs) using spark plasma sintering (SPS). The start-up powders were blended with tubular mixer and sintered with SPS technique. The densities, microhardness and corrosion characteristics of the sintered samples were determined accordingly. Results obtained showed that there was a homogeneous dispersion of CNTs in the Al matrix of all the samples except Al-8CNTs. Al-4CNTs gave the highest microhardness of 482.60 ± 12 MPa which represented 27% improvement in relation to monolithic Al alloy. Again, Al-4CNTs gave the least corrosion rate of 0.26723 mm/year in NaCl medium and 0.24188 mm/year in H2SO4 medium (46% and 47% improvements, respectively). These results indicate that Al-CNTs composite is a robust material for high transmission conductors. [ABSTRACT FROM AUTHOR]

Cable manufacturing in a developing country like Nigeria today is faced with the problem of thermoplastic extrusion processes due to the complex nature of the parameters that are involved in the process. These process parameters that include melt temperature, pressure, and screw speed generally impact the quality of the electrical insulation product. The main consequence of the problems is the low and variable output rate from extruder causing non-uniform diameter along the cable length which often increases the production cost. Different researches have been done to improve extrusion output quality in developed countries. However, there are still some problems in achieving consistent product quality as most of the developing countries still use the trial and error techniques to determine cable insulation thickness. This paper presents a method of predicting electrical cable insulation thickness during the process of any type of thermoplastic (i.e. PVC, PE or XLPE) extrusion using an artificial neural network. A three-layered feedforward artificial neural network with back propagation algorithm was developed using MATLAB to predict the insulation thickness in thermoplastic extrusion. The neural network model developed was able to accurately predict the insulation thickness based on process parameters such as the melt temperature, pressure and line speed that have been determined in production. The possibilities of adopting neural network controllers in the thermoplastic extrusion process were also discussed. [ABSTRACT FROM AUTHOR]

Studies show that monolithic Al lacks requisite properties required for industrial applications. However, these properties can be enhanced by the addition of high-performing reinforcement such as carbon nanotubes (CNTs). Here, Al is reinforced with CNTs and consolidated via spark plasma sintering, with the aims of improving its tribology, thermal and electrical properties. The tribological test was conducted on a ball-on-disc tribometer. The thermal test was done with the thermogravimetric analyzer and laser flasher apparatus; the electrical conductivity test was carried out with four-point probe meter. Results obtained showed that 4 wt% of CNTs improved the COF of Al alloy by 52% and wear volume by 23%. It also improved the thermal conductivity by 35%. The electrical result showed a marginal improvement of 2% with Al-8CNTs. Therefore, the improvements in tribology and thermal properties without compromising electrical conductivity show that Al-CNTs are a robust material for industrial application especially in high-transmission conductor. [ABSTRACT FROM AUTHOR]

This study focused on rheological and mechanical properties of poly(vinylidene fluoride) nanocomposites incorporated with functionalized graphene nanoplatelets and hydroxylated titanium dioxide. Mechanical properties of the ternary composites were improved with a slight reduction in damping coefficient compared to the pure polymer and graphene binary composites. The storage modulus of the ternary composites significantly increased from about 67.5 Pa for the pure polymer to 3.24 × 105 Pa and 3.49 × 105 Pa at 0.1 rad/s for 6.67 wt% graphene composites containing 10 wt% and 20 wt% titania respectively. All ternary composites showed higher tensile strength and Young modulus compared to the pure polymer. Strong bonding between the polymer and co-fillers with a reduction in interfacial slipping in the ternary composites resulted in their lower damping factor and higher strength compared to their counterparts. The composite samples were prepared by solution and melt mixing methods. The scanning electron microscope was used to examine the samples' morphology and dispersion of the co-fillers in the matrix. Such composites can find applications in automobile and aerospace industries where materials with good strength and noise or vibration absorption capability are required. [ABSTRACT FROM AUTHOR]

An experimental study of the microstructure, electrical conductivity, corrosion characteristics and mechanical strength of Al-Nb nanocomposite consolidated via spark plasma sintering was the focus of this work. The start-up powders as well as the sintered samples were characterised with X-ray diffractometer, transmission electron microscopy and field-emission scanning electron microscope equipped with energy dispersive X-ray spectroscopy. The microhardness of the sintered samples was tested with Vickers hardness tester. The polarisation test was carried out with Potentiostat Autolab. The electrical conductivity was tested with four-point probe meter. The microstructural results showed homogenous dispersion of Nb reinforcement in the matrix, no grain growth and absence of voids. Good corrosion characteristics were achieved with Al-1Nb and Al-4Nb composites while the highest microhardness of 420 MPa and tensile strength of 138 MPa were obtained with Al-4Nb. The electrical conductivity increased from 38.9 to 40.1% IACS with Al-8Nb. The improved properties were as a result of the optimal sintering parameters, good fabrication attributes of SPS and the synergistic effects of Al and Nb. [ABSTRACT FROM AUTHOR]

Optimisation of process parameters is usually undertaken to achieve more efficient and cost-effective process conditions. This work deals with the optimisation of spark plasma sintering process parameters which include sintering temperature, pressure, dwell time and heating rate for the development of Al-CNTs-Nb nano-composite. Taguchi Design of Experiment (DOE) was used to design the sintering operation, while analysis of variance (ANOVA) was used to investigate the contribution of the factor variables to the response variables of density and micro-hardness. The admixed powders were consolidated as designed with SPS machine, while the sintered compacts were characterised using optical microscope, Vickers hardness tester and Archimedes-based density tester. The results obtained were a maximum density of 2.68 g cm−3 (99.3% relative density) and maximum micro-hardness of 38.57 HV (0.37 GPa), while the optimal SPS parameters were sintering temperature of 630 °C, pressure of 30 MPa, dwell time of 10 min and heating rate of 200 °C/min. This work has achieved a 20% improvement in micro-hardness which is good for so many engineering applications. [ABSTRACT FROM AUTHOR]

Graphene nanoplatelets (GNPs) were mechanically insulated with titanium dioxide (TD) nanopowder to address challenges of high dielectric loss and low breakdown strength associated with polymer/graphene nanocomposites. GNPs were functionalized (fGNPs) and TD was hydroxylated (TD-OH) to ensure wettability of the co-particles and well dispersion in polymer matrix. The composite samples were developed by solution blending and melting compounding processes. Successful modification of the co-particles and insulation of fGNPs were examined using Fourier transform infrared (FTIR), X-ray diffractometer (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). Energy storage capacity, dielectric and electrical properties of the composites were investigated. Insulated fGNPs composites showed significant improvement in energy storage capacity and reduction in dielectric loss with addition of 10 wt % TD-OH compared to bared fGNPs composites. About 92.6% reduction in dielectric loss and 77% increase in energy storage density were recorded for 6.67 wt % fGNPs/10 wt % TD-OH composite compared to 6.67 wt % fGNPs composite at 100Hz. This was due to excellent insulating property of TD-OH on fGNPs. Although dielectric loss was further reduced on addition of 20 wt % TD-OH into fGNPs composites, their dielectric constant and energy storage density were slightly reduced compared to composites containing 10 wt % TD-OH. This study revealed that mechanical insulation of graphene with ceramic nanopowder can suppress energy dissipation associated with polymer/graphene nanocomposites with improve energy storage capacity. [ABSTRACT FROM AUTHOR]

Abstract Background Refugees as “People Living in Highly Stressful Situation” are particularly vulnerable to mental ill-health as a result of the trauma experienced pre- and post-migration. The lack of information on the mental health disparities of refugees and non-refugees in West Africa is what this study aimed to bridge. A cross-sectional study design was employed using a cluster sampling technique. Interviewer-administered structured questionnaires consisting of the Mini-International Neuropsychiatric Interview (MINI), WHO quality of life (WHOQOL-BREF) and the Community Quality of Life (CQoL) were used for data collection. Data were analyzed with SPSS version 17. Logistic regression analysis was used to determine the predictors of mental health status and QoL. Results Respondents consisted of 444(45.7%) refugees and 527(54.3%) non-refugees. Two-thirds 292 (66%) of the refugees were Liberians. Mean age: refugees - 34.8 ± 12.8 years versus non-refugees - 33.3 ± 8.1 years (p Conclusions QoL and occupational status were the major threats to the mental health of the refugees. Results of this study point to the need for continued attention to not only the healthcare needs but the welfare, housing, employment and overall QoL to support the long-term mental health of refugees and non-refugee populations alike.

Abstract Background The emergence of Anopheles populations capable of withstanding lethal doses of insecticides has weakened the efficacy of most insecticide based strategies of vector control and, has highlighted the need for further studies on the mechanisms of insecticide resistance and the various factors selecting resistant populations of mosquitoes. This research targeted the analysis of breeding sites and the oviposition behaviour of susceptible and resistant populations of Anopheles in localities of spilled petroleum products. The aim was to establish the possible contribution of oil spillage in the selection of pyrethroid resistance in malaria vectors. Methods Anopheles breeding sites were identified and the insecticide susceptibility of the Anopheles gambiae populations mapped in 15 localities of South Western Nigeria. The presence of oil particles as well as the turbidity, the dissolved oxygen and the pH of each identified breeding site was recorded. Data were cross-analysed to correlate the habitat types and the insecticide susceptibility status of emerging mosquitoes. The second phase of this study was basically a laboratory model to provide more information on the implication of the spillage of petroleum on the selection of pyrethroid resistance in An. gambiae. Results Moderate levels of resistance following exposure to permethrin-impregnated papers were recorded with the majority of An. gambiae samples collected in the South Western Nigeria. Data from this study established a link between the constituency of the breeding sites and the resistance status of the emerging Anopheles. Conclusion This study has revealed the segregational occupation of breeding habitats by pyrethroid resistant and susceptible strains of An. gambiae in south-western Nigeria. Compiled results from field and laboratory research point out clear relationships between oil spillage and pyrethroid resistance in malaria vectors. The identification of this factor of resistance could serve as strong information in the management of insecticide resistance in some West African settings.

Thermomagnetic properties, and its effects on Fisher information entropy with Schioberg plus Manning-Rosen potential are studied using NUFA and SUSYQM methods in the presence of the Greene-Aldrich approximation scheme to the centrifugal term. The wave function obtained was used to study Fisher information both in position and momentum spaces for different quantum states by the gamma function and digamma polynomials. The energy equation obtained in a closed form was used to deduce numerical energy spectra, partition function, and other thermomagnetic properties. The results show that with an application of AB and magnetic fields, the numerical energy eigenvalues for different magnetic quantum spins decrease as the quantum state increases and completely removes the degeneracy of the energy spectra. Also, the numerical computation of Fisher information satisfies Fisher information inequality products, indicating that the particles are more localized in the presence of external fields than in their absence, and the trend shows complete localization of quantum mechanical particles in all quantum states. Our potential reduces to Schioberg and Manning-Rosen potentials as special cases. Our potential reduces to Schioberg and Manning-Rosen potentials as special cases. The energy equations obtained from the NUFA and SUSYQM were the same, demonstrating a high level of mathematical precision. [ABSTRACT FROM AUTHOR]

The study assessed the contamination status of a fish pond with the view of offering insight on the accumulative features of polycyclic aromatic hydrocarbons (PAHs) in the sediments and fish parts. The PAHs were extracted and cleaned up on activated alumina adsorbent. A gas chromatograph coupled with flame ionization detector (FID) was used to quantify the compounds. In general, the sediments were more concentrated in the analyzed PAHs than the water samples. Low (3.51–24.7%) spatial distribution existed in the PAHs level as revealed in the calculated CV%. Fluoranthene, pyrene and anthracene were most concentrated compounds in the fish. The PAHs percentage load ratio of 34.9:34.2:30.9 were observed in the muscle, head and liver, respectively. Acenaphtylene, acenaphthene, indeno(1,2,3-cd)pyrene and dibenzo(a,h)anthracene were highly accumulated in the sediments as compared to other samples, while fluorene and benzo(k)fluoranthene showed the least and highest accumulated PAHs respectively in all the fish parts. [ABSTRACT FROM AUTHOR]

Though the trilateral cycle (TLC) is a promising heat recovery-to-power cycle, its application has not been widely accepted or commercialised due to some thermodynamic feasibility concerns. This study examined the performance analysis and sensitivity of the system parameters on the thermodynamic performance of the TLC power generator systems for waste heat recovery-to-power generation. Thermodynamic models of the simple, recuperative, reheat and regenerative TLCs were established. Performance analysis and sensitivity of the system parameters on the cycles' performance were conducted at the expander inlet temperature of 453 to 473 K, expander pressure of 2 to 3 MPa and expander isentropic efficiency of 50% to 100%. The expander inlet temperatures, pressures, and its isentropic efficiencies have significant effects on the thermodynamic efficiencies and net work output of the cycles. At 473 K cycle high temperature, the thermal efficiencies of the cycles increase from 20.13% to 21.97%, 23.29% to 23.91%, 20.62% to 22.07% and 20.66% to 22.9% for the simple, recuperative, reheat and regenerative TLCs, respectively. Their corresponding net power outputs varied from 131.6 to 134.1 kW, 145.9 to 152.2 kW, 113.8 to 124.1 kW and 124.9 to 130.5 kW, respectively. The cycles' thermodynamic performance increased with an increase in expander inlet temperature, expander pressure and expander isentropic efficiencies. [ABSTRACT FROM AUTHOR]

The vibrational resonance (VR) phenomenon has received a great deal of research attention over the two decades since its introduction. The wide range of theoretical and experimental results obtained has, however, been confined to VR in systems with constant mass. We now extend the VR formalism to encompass systems with position-dependent mass (PDM). We consider a generalized classical counterpart of the quantum mechanical nonlinear oscillator with PDM. By developing a theoretical framework for determining the response amplitude of PDM systems, we examine and analyse their VR phenomenona, obtain conditions for the occurrence of resonances, show that the role played by PDM can be both inductive and contributory, and suggest that PDM effects could usefully be explored to maximize the efficiency of devices being operated in VR modes. Our analysis suggests new directions for the investigation of VR in a general class of PDM systems. This article is part of the theme issue 'Vibrational and stochastic resonance in driven nonlinear systems (part 1)'. [ABSTRACT FROM AUTHOR]

Automated person identification and authentication systems are useful for national security, integrity of electoral processes, prevention of cybercrimes and many access control applications. This is a critical component of information and communication technology which is central to national development. The use of biometrics systems in identification is fast replacing traditional methods such as use of names, personal identification numbers codes, password, etc., since nature bestow individuals with distinct personal imprints and signatures. Different measures have been put in place for person identification, ranging from face, to fingerprint and so on. This paper highlights the key approaches and schemes developed in the last five decades for voice-based person identification systems. Voice-base recognition system has gained interest due to its non-intrusive technique of data acquisition and its increasing method of continually studying and adapting to the person’s changes. Information on the benefits and challenges of various biometric systems are also presented in this paper. The present and prominent voice-based recognition methods are discussed. It was observed that these systems application areas have covered intelligent monitoring, surveillance, population management, election forensics, immigration and border control.