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Studies have shown that managing household solid waste from low-cost housing in urban and sub-urban communities is challenging, especially in developing countries and COVID-19 era. Previous research proved that the fourth industrial revolution (4IR) technologies could be engaged to improve urban public services such as household solid waste. Thus, the study investigated 4IR role in improving low-cost housing solid waste management (LCHSWM) in the COVID-19 era across Malaysia's cities.

The researchers selected four Malaysian cities (Pulau Pinang, Kuala Lumpur, Kuching and Putrajaya) to achieve the study's objectives via a qualitative research design. The study engaged forty experts through semi-structured virtual interviews. A thematic approach was used to analyse the collected data.

Findings identified initial high implementation and maintenance costs, unwillingness to accept change, inadequate knowledge and skilled personnel to manage the operation, amongst others, as the perceived challenges facing 4IR technologies in managing low-cost housing solid waste across Malaysian cities in the COVID-19 era. Also, the study proffered measures to improve 4IR technologies usage.

This paper is limited to the perceived contributory challenges and proffered measures to improve 4IR technologies usage in managing LCHSW across Malaysian cities in the COVID-19 era.

Proffered measures will stir policymakers and the political class (city councils) to start thinking of an all-inclusive approach to addressing the issue of LCHSW in the 21st century. As part of the practical implications, the possible outcome might enhance collaboration between the public and private sectors to better service delivery to mitigate environmental degradation.

As revealed in the review, there is a paucity of literature regarding digital technology's roles in mitigating LCHSW across Malaysian cities in the COVID-19 era.

This paper aims to the transportation of high concentration slurry through pipelines that will require thorough understanding of physical and rheological properties of slurry, as well as its hydraulic flow behavior. In spite of several contributions by the previous researchers, there is still a need to enrich the current understanding of hydraulic conveying through pipeline at various flow parameters. The pilot plant loop tests, particularly at high concentrations, are tedious, time-consuming and complex in nature. Therefore, in the current research the prediction methodology for slurry pipeline design based on rheological model of the slurry is used for calculation of pressure drop and other design parameters.

It has been established that slurry rheology plays important role in the prediction of pressure drop for laminar and turbulent flow of commercial slurries through pipeline. In the current research fly ash slurry at high concentration is chosen for rheological analysis. The effect of particle size and solid concentration is experimentally tested over the rheological behavior of slurry and based on the rheological data a correlation is developed for calculation of pressure drop in slurry pipeline.

The present study strongly supports the analytical approach of pressure drop prediction based on the rheological parameters obtained from the bench scale tests. The rheological properties are strongly influenced by particle size distribution (PSD), shear rate and solid mass concentration of the slurry samples. Pressure drop along the pipeline is highly influenced by flow velocity and solid concentration. The presence of coarser particles in the slurry samples also leads to high pressure drop along the pipeline. As the concentration of solid increase the shear stress and shear viscosity increase cause higher pressure drop.

The transportation of slurry in the pipeline is very complex as there are lot of factors that affect the flow behavior of slurry in pipelines. From the vast study of literature it is found that flow behavior of slurry changes with the change in parameters such as solids concentration, flow velocity, PSD, chemical additives and so on. Therefore, the accurate prediction of hydraulic parameter is very difficult. Different slurry samples behave differently depending upon their physical and rheological characteristics. So it is required to study each slurry samples individually that is time-consuming and costly.

Nowadays in the world, long distance slurry pipelines are used for the transportation of highly concentration slurries. Many researchers have carried out an experiment in the design aspects of hydraulic transportation system. Rheological characteristics of slurry also play crucial role in determining important parameters of hydraulic conveying such as head loss in commercial slurry pipeline. The current research is useful for the prediction of pressure drop based on rheological behavior of fly ash slurry at various solid concentrations. The current research is helpful for finding the effect of solid concentration and flow velocity on the flow behavior of slurry.

Slurry pipeline transportation has advantages over rail and road transportation because of low energy consumption, economical, less maintenance and eco-friendly nature. Presently majority of the thermal power plants in India and other parts of the world dispose of coal ash at low concentration (20 per cent by weight) to ash ponds using the slurry pipeline. Transporting solids in slurry pipelines at higher concentrations will require a thorough knowledge of pressure drop. In the current research a rheological model is proposed for prediction of pressure drop in the slurry pipeline, which is useful for optimization of flow parameters.

All the experimental work is done on fly ash slurry samples collect from the Jharli thermal power plant from Haryana State of India. Bench scale tests are performed in the water resource laboratory of IIT Delhi for physical and rheological analysis of slurry. It has been shown in the results that up to solid concentration of 50 per cent by mass all the samples behave as non-Newtonian and follows a Herschel–Bulkley model with shear thickening behavior. In the present research all the result outcomes are unique and original and does not copied from anywhere.

The purpose of this paper is to propose two linear solid-shell finite elements, a six-node prismatic element denoted SHB6-EXP and an eight-node hexahedral element denoted SHB8PS-EXP, for the three-dimensional modeling of thin structures in the context of explicit dynamic analysis.

These two linear solid-shell elements are formulated based on a purely three-dimensional (3D) approach, with displacements as the only degrees of freedom. To prevent various locking phenomena, a reduced-integration scheme is used along with the assumed-strain method. The resulting formulations are computationally efficient, as only a single layer of elements with an arbitrary number of through-thickness integration points is required to model 3D thin structures.

Via the VUEL user-element subroutines, the performance of these elements is assessed through a set of selective and representative dynamic elastoplastic benchmark tests, impact-type problems and deep drawing processes involving complex non-linear loading paths, anisotropic plasticity and double-sided contact. The obtained numerical results demonstrate good performance of the SHB-EXP elements in the modeling of 3D thin structures, with only a single element layer and few integration points in the thickness direction.

The extension of the SHB-EXP solid-shell formulations to large-strain anisotropic plasticity enlarges their application range to a wide variety of dynamic elastoplastic problems and sheet metal forming simulations. All simulation results reveal that the numerical strategy adopted in this paper can efficiently prevent the various locking phenomena that commonly occur in the 3D modeling of thin structural problems.

To provide an overview of how the solid‐to‐solid contact force equation in MSC.ADAMS can be used to reduce contact model development, minimize the probability of introducing an error and reduce simulation run time by citing the example of the International Space Station (ISS).Design/methodology/approach – In early 2000, a redesign of the ISS required a more thorough representation of the contacting geometry. The MSC.ADAMS solid to solid contact force statement became available in time to solve this problem. This allowed simulation of the segment to segment attachment, including various combinations of contact feature misalignment.Findings – A structural failure of a “Zip” nut during qualification testing resulted in a NASA request for a force balance on the nut housing, internal nut segments and bolt. Using MSC.ADAMS solid to solid contact simulation, the desired force balance was obtained. The analysis showed the coarse guide to fine guide handoff did not bind and fine guide seating engaged, allowing the four motorized bolts to connect the segment‐to‐segment interface.Originality/value – MSC.ADAMS solid to solid contact algorithms decreased simulation time, allowing this very complicated contact problem to be completed in less than 30 min. Using CAD model solid geometry greatly reduced model development time. Solid to solid contact simulation eliminated the need for tedious derivation vector algebra contact equations and greatly advanced the level of geometric complexity that could be modeled as contacting interfaces. This also minimizes the probably of errors.

This paper aims to obtain high mechanical and good tribological properties of epoxy resin-based coatings under dry friction conditions.

Bonded solid lubricant coatings containing Kevlar fibres were prepared by a spraying method. The friction and wear properties of the coatings were experimentally investigated with a face-to-face tribometre under dry friction conditions. Scanning electron microscopy, energy dispersive X-ray spectroscopy and 3D laser scanning technologies were used to characterise the tribological properties. The action mechanism of the Kevlar fibres on a solid lubricant transfer film was also analysed.

Adding Kevlar fibres can significantly improve the wear resistance of the coatings. When the Kevlar fibre content increases, the tribological properties of the coatings improve and then worsen. Superior properties are obtained with 0.03 g of Kevlar fibres. Appropriately increasing the load or speed is beneficial to the removal of the outer epoxy resin and the formation of a lubricant film. During friction, the solid lubricants wrapped in the epoxy resin accumulate on the surface to form a transfer film that shows a good self-lubricating performance. In the later friction stage, fatigue cracks occur on the solid lubricant film but cannot connect to one another because of the high wear resistance and the entanglement of the rod-like Kevlar fibres. Thus, no large-area film falls from the matrix, thereby ensuring the long-term functioning of solid lubricant coatings.

Epoxy resin-based solid lubricant coatings modified by Kevlar fibres were prepared, and their friction and wear properties were investigated. Their tribological mechanisms were also proposed. This work provided a basis for the analysis of the tribological properties and design of bonded solid lubricant coatings containing Kevlar fibres.

The purpose of this paper is to study the operation performance of the high-speed ramjet kinetic energy projectile using solid fuel ramjet as power plant that is a new short-range and small caliber projectile.

The numerical investigation on combustion characteristic of polyethylene in high-speed ramjet kinetic energy projectile is carried out in this paper. The flow characteristics’ differences are analyzed when ramjet works or do not work, and both the combustion characteristics and propulsive performance are analyzed when ramjet works.

The results show that with the increase of the abscissa x, the flame front is close to solid fuel surface at first and then keeps away from solid fuel surface. With the increase of the abscissa x, the temperature of solid fuel surface and regression rate of solid fuel continues to increase before re-attachment point and then decreases, which a maximum locate at the re-attachment point. Both the average temperature and the regression rate on the surface of the solid fuel tend to rise as the increase of inflow Mach number. As the inflow of Mach number increases, the mass flow rate of gaseous fuel increases.

The research results can provide useful database for the subsequent research on high-speed ramjet kinetic energy projectile.

This paper studies the operation characteristics of the ramjet projectile, especially the effect of the change of the flight velocity on the performance of high-speed ramjet projectile.

The purpose of this paper is to present a three‐dimensional CFD model that simulates the pyrolysis, combustion and heat transfer phenomena in a refuse‐derived fuel (RDF) gasifier. Correlations between different operation conditions and the waste stack morphology are also investigated. Parametric studies are conducted to optimize operating conditions to achieve an even stack surface minimal the local oxidation in the waste stack.

This paper proposes a Lagrangian pyrolysis submodel which can be applied to determine the local pyrolysis rate and porosity field by introducing the local characteristic diameter of the waste solid sphere. The flow field is described by a single‐phase porous flow model using the SIMPLE algorithm with momentum extrapolation. A one‐step global reaction was adapted for the chemical reactions inside the gasifier.

Computational results produced three‐dimensional distribution of the flow field, temperature, species concentration, porosity and the morphology of the waste stack under different operation conditions. Some parametric studies were conducted to assess the effects of the inlet temperature and the feeding rate on the waste stack shape. The results demonstrated that the model can properly capture the essential physical and chemical processes in the gasifier and thus can be used as a predictive simulation tool.

Due to the lack of accurate reaction rate information, the computational results have not been directly compared against experimental data. Additional refinement and subsequent validation against prototype gasifier experiment will be reported in future work.

A full three‐dimensional computational model is developed for the complex two‐phase flow based on porous medium representation of the solid stack. A Lagrangian pyrolysis model based on the characteristic diameter of the solid waste material was proposed to describe the pyrolysis rate history. The developed model reproduces correct physical and chemical behavior inside gasifier with adequate computational efficiency and accuracy.

This study aims to investigate the controlling mechanisms of ambient oxygen and pressure on piloted ignition of solid combustibles under external radiant heating.

The numerical simulation method was used to model the influence of ambient oxygen concentration on the piloted ignition of a thermally irradiated solid sample in reduced pressure atmospheres. The solid phase decomposition and gas phase kinetics were solved simultaneously.

It was determined that the elevated oxygen atmospheres resulted in a higher flame temperature and a thicker temperature profile over the solid surface. Also, increasing oxygen and reducing pressure had a similar effect in the decrease of the ignition delay time. The shorter ignition time in reduced pressure was mainly because of the decreasing of convective heat losses from the heated solid. As oxygen was reduced, however, ignition occurred later and with a greater mass loss rate because more volatiles of solid fuel at transient ignition were required to sustain a complete reaction under an oxygen-poor condition.

The results need to be verified with experiments.

The results could be applied for design and assessment of fire-fighting and fire prevention strategies in reduced pressure atmosphere.

This paper shows the effect mechanism of ambient oxygen and pressure on piloted ignition of solid combustibles.

The purpose of this paper is to study the influence of magnetic field on natural convection inside the enclosures partially filled with conducting square solid obstacles. Also, the effect of thermal conductivity ratio between the solid and fluid materials is investigated for different number of solid blocks.

The dimensionless governing equations are transformed into sets of algebraic equations using finite volume method and momentum equations are solved by the SIMPLE algorithm with the hybrid scheme. The validation of the numerical code was conducted by comparing the results of average Nusselt number with previously published works.

The results indicate that both the magnetic field and solid blocks can significantly affect the flow and temperature fields. It is shown that for a given Rayleigh number, variation of Nusselt number might be increasing or decreasing with change in solid-to-fluid thermal conductivity ratio depending on magnetic field strength and number of solid blocks.

No work has been reported previously on the effect of magnetic field on natural convection flow in a cavity partially filled with square solid blocks. The numerical analysis of conductivity ratio between the solid and fluid materials under the effect of magnetic field have been carried out for the first time.

This paper aims to find out the tribological performance and self-lubricating mechanism of the laser-textured surface filled with solid lubricant in rolling friction pair.

The textures on the surfaces of GCr15 bearing steel were produced by acousto-optic Q diode-pumped yttrium aluminum garnet laser with the technology of “single pulse one time, repeating at intervals” and filled with composite solid lubricant. The tribology tests were conducted on the MMW-1A universal friction and wear testing machine.

It was found that the solid-lubricated micro-textured surface can reduce the friction coefficient effectively. The MoS2/PI composite solid lubricant works better than the single MoS2 solid lubricant, and the ratio of PI/MoS2 + PI at 20 per cent is the best recipe. The friction coefficient of the sample surfaces decreases first and then increases with the increase in texture densities, and a texture density of 19.6 per cent has the best effect on friction reduction. The friction coefficient of the textured surfaces gradually decreases with the increase in both rational speed and load. For the same texture density, the friction coefficient of textured surfaces decreases slightly with the increase in diameter. Furthermore, the mechanism of “rolling-extrusion-accumulation” occurred on the textured surface can collect the solid lubricant, thereby, improve the effect of lubricating and anti-friction.

The results of the experimental studies demonstrated the application prospect of laser surfaces texturing combined with solid lubricant in rolling friction pair.