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To investigate numerically the settling of small solid particles in a suspension of motile gyrotactic micro‐organisms in order to evaluate the possibility of using bioconvection to slow down settling and enhance mixing between particles.

Numerical computations are performed at the North Carolina Supercomputing Center utilizing an Origin 2400 workstation. A conservative finite‐difference scheme is used to discretize the governing equations. A staggered uniform grid with the stream function and vorticity stored in one set of nodes and the number densities of micro‐organisms and solid particles stored in another set of nodes is utilized. CPU time required to investigate plume development until it attains steady‐state for 36 × 36 uniform mesh is about 50 h.

It is established that small solid particles that are heavier than water slow down bioconvection. Extremely small particles (nanoparticles) that have negligible settling velocity do not have any noticeable impact on bioconvection, very large particles (that have negligible diffusivity), or very heavy particles (that have very large settling velocity) also do not have any impact on bioconvection because they simply settle at the bottom. However, if the particles are of the optimal size and density (gravitational settling must compete with Brownian diffusion to create an exponential number density distribution of solid particles with the maximum at the bottom of the chamber), these particles can effectively slow down bioconvection.

The question how solid particles may affect the wavelengths of bioconvection patterns requires further investigation.

The finding that solid particles slow down bioconvection may be important in using bioconvection to enhance mixing in fluid microvolumes.

The paper provides a model and numerical data about the effect of bioconvection on mixing of small solid particles. These data are valuable for researches working in fundamental fluid mechanics, multiphase flow, and applications of bioconvection.

The quality of the surface being machined and tool life are greatly affected by heat generated during machining. Abundant use of cutting fluid leads to higher production rates and a threat for environment and worker’s health. Hence, the need is to identify eco-friendly lubricants. The purpose of the current work is to investigate the effects of solid lubricants (boric acid and molybdenum disulphide) mixed with oil during turning of EN-31 using cemented carbide tools. The concentration of solid lubricants in oil is varied to analyze output parameters such as surface roughness, process temperature, power consumption and tool wear.

EN 31 steel material is machined at various cutting speeds and constant feed and depth of cut to determine the effects of dry, wet and solid lubricant assisted machining.

Experimental study revealed that the solid lubricants performed better while machining and therefore it may be considered as environment friendly and cost effective way of lubrication as compared to flood cooling.

The work can be extended to identify the effects of solid lubricants on micro hardness and cutting force.

From the findings of the work, solid lubricants may be considered as suitable choice as compared to fluid cooling because it improves process performance without much affecting the environment and worker’s health.

So far the use of solid lubricants in machining is limited. The results of the work will be useful to explore various efficient way to apply solid lubricants.

The problem of transient heat transfer and growth of solid in the inviscid stagnation flow when phase change from liquid to solid occurs is considered. A fast and accurate numerical scheme is developed to determine the instantaneous temperature distribution in both solid and liquid phases and the growth rate of solid directly, without iterative calculation. The solution of the dimensionless governing equations is dependent on the three dimensionless parameters. The characteristics of the transient heat transfer and solidification process for all the parameters are elucidated.

This paper aims to examine the thermal transmission and entropy generation of hybrid nanofluid filled containers with solid body inside. The solid body is seen as being both isothermal and capable of producing heat. A time-dependent non-linear partial differential equation is used to represent the transfer of heat through a solid body. The current study’s objective is to investigate the key properties of nanoparticles, external forces and particular attention paid to the impact of hybrid nanoparticles on entropy formation. This investigation is useful for researchers studying in the area of cavity flows to know features of the flow structures and nature of hybrid nanofluid characteristics. In addition, a detailed entropy generation analysis has been performed to highlight possible regimes with minimal entropy generation rates. Hybrid nanofluid has been proven to have useful qualities, making it an attractive coolant for an electrical device. The findings would help scientists and engineers better understand how to analyse convective heat transmission and how to forecast better heat transfer rates in cutting-edge technological systems used in industries such as heat transportation, power generation, chemical production and passive cooling systems for electronic devices.

Thermal transmission and entropy generation of hybrid nanofluid are analysed within the enclosure. The domain of interest is a square chamber of size L, including a square solid block. The solid body is considered to be isothermal and generating heat. The flow driven by temperature gradient in the cavity is two-dimensional. The governing equations, formulated in dimensionless primitive variables with corresponding initial and boundary conditions, are worked out by using the finite volume technique with the SIMPLE algorithm on a uniformly staggered mesh. QUICK and central difference schemes were used to handle convective and diffusive elements. In-house code is developed using FORTRAN programming to visualize the isotherms, streamlines, heatlines and entropy contours, which are handled by Tecplot software. The influence of nanoparticles volume fraction, heat generation factor, external magnetic forces and an irreversibility ratio on energy transport and flow patterns is examined.

The results show that the hybrid nanoparticles concentration augments the thermal transmission and the entropy production increases also while the augmentation of temperature difference results in a diminution of entropy production. Finally, magnetic force has the significant impact on heat transfer, isotherms, streamlines and entropy. It has been observed that the external magnetic force plays a good role in thermal regulations.

Hybrid nanofluid is a desirable coolant for an electrical device. Various nanoparticles and their combinations can be analysed. Ferro-copper hybrid nanofluid considered with the help of prevailing literature review. The research would benefit scientists and engineers by improving their comprehension of how to analyses convective heat transmission and forecast more accurate heat transfer rates in various fields.

Due to its helpful characteristics, ferrous-copper hybrid nanofluid is a desirable coolant for an electrical device. The research would benefit scientists and engineers by improving their comprehension of how to analyse convective heat transmission and forecast more accurate heat transfer rates in cutting-edge technological systems used in sectors like thermal transportation, cooling systems for electronic devices, etc.

Entropy generation is used for an evaluation of the system’s performance, which is an indicator of optimal design. Hence, in recent times, it does a good engineering sense to draw attention to irreversibility under magnetic force, and it has an indispensable impact on investigation of electronic devices.

An efficient numerical technique has been developed to solve this problem. The originality of this work is to analyse convective energy transport and entropy generation in a chamber with internal block, which is capable of maintaining heat and producing heat. Effects of irreversibility ratio are scrutinized for the first time. Analysis of convective heat transfer and entropy production in an enclosure with internal isothermal/heat generating blocks gives the way to predict enhanced heat transfer rate and avoid the failure of advanced technical systems in industrial sectors.

This study evaluates the quantity and composition of solid waste produce in secondary schools and assesses level of environmental consciousness and management activities. This is aimed for the present and future planning of high schools' environment as well as integrating the system into urban waste management.

This research used primary and secondary data to realize its purpose. Primary data was obtained through measurement of actual waste generation and questionnaire administration. Secondary data was the official information obtained on the schools selected. The primary data collected was analysed with descriptive statistical method such as percentage, mean cross measures of central tendency, frequency distribution and cross tabulation.

The study established that a total of 375.6 kg of solid waste is generated in the selected schools and daily per capita waste generation is 0.56 kg. Paper material is the waste component with the highest quantity and 88.5% of waste produced is recyclable. Thus, solid waste generated in secondary schools if carefully managed with suitable management options has potential for promoting circular economy and sustainable development. The paper recommends environmental education for stakeholders in secondary schools and waste segregation culture should be enforced in every secondary school.

The paper builds on the reasons for poor environmental quality in secondary schools in developing countries and revealed unscientific means by which resources are wasted and the environment is mismanaged through low understanding of solid waste.

This study aims to form composite solid lubricant coatings on the surface of bearing steel, which can significantly improve the tribological properties of thrust cylindrical roller bearings (TCRBs). Phosphating films possess microscopic porosity that typically needs to be sealed with oil, grease or wax. Due to its unique crystal structure, the phosphating film itself also exhibits a certain degree of lubricity. In this study, solid lubricants are used to fill the pores of the phosphating film. By combining the phosphating film with solid lubricants, lubrication and wear reduction can be achieved.

In this study, the surfaces of the shaft washer (WS) and seat washer (GS) were treated with zinc-phosphating. Subsequently, a solid lubricant solution (polytetrafluoroethylene [PTFE], MoS₂ and graphite) was sprayed onto the phosphated samples at concentrations of 1 , 2  and 3 g/L. The porous and adsorptive nature of the phosphating film was used to embed the solid lubricant particles into the film, thus forming a composite lubrication layer containing solid lubricants on the surface of the bearing steel.

The addition of solid lubricant materials has shown significant potential in reducing wear losses compared with phosphated samples without such additives. Increasing the amount of solid lubricant added can facilitate the formation of a transfer film, which further enhances the protective properties. However, it is important to note that excessive amounts of solid lubricant material can contribute to seizure, leading to increased wear losses of the cage and a higher average coefficient of friction (ACOF).By spraying a PTFE solution with a concentration of 2 g/L, the lowest ACOF and cage wear loss were achieved, resulting in reductions of 60.5% for the ACOF and 89.4% for the cage wear loss. Similarly, when spraying a graphite solution with a concentration of 3 g/L, the lowest wear losses for GS and WS were observed, with reductions of 51.7% for GS wear loss and 38.9% for WS wear loss.

The combination of the phosphating film and solid lubricants aims to achieve lubrication and wear reduction, providing a new approach to wear-resistant technology for TCRBs.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2023-0231/

The purpose of this paper is to formulate frameworks for the drivers and barriers of integrated sustainable solid waste management (ISSWM) with reference to conditions prevailing in India.

A multi-phased approach was adopted in this paper to come up with the conceptual framework of the drivers and barriers of ISSWM. In the first phase, drivers and barriers of ISSWM were identified based on a systematic literature review process. In the second phase, 25 experts having 15 plus years of experience in the field of sustainable development and environmental management were consulted to get their opinion. Validation and understanding of the interrelationship among the selected drivers and barriers were done based on the insights from expert interviews. And in the final phase, structural self-interaction matrix and transitive links are defined based on the expert opinion to come up with the theoretical frameworks of drivers and barriers of ISSWM.

Findings reveal the importance to have a system view point approach by giving equal importance to social, environmental and economic pillars of sustainability along with the technology component to effectively and sustainably manage the solid waste disposal. Institutional effectiveness and the robust policy and frameworks are the two variables found to have the highest driving power. Poor social values and ethics, huge population and illiteracy are the three most critical barriers faced by developing nations in achieving the sustainability practices in the solid waste management. The proposed frameworks of drivers and barriers of ISSWM will definitely help policy makers to effectively manage the sustainable waste management practices for developing economies by focusing on the key variables listed out.

One of the limitations is in the use of very limited sample size in the study. Another limitation is that total interpretive structural modeling fails to come up with the relative weightings of drivers and barriers used in the study. These limitations can be overcome by extending the research by using a semi-structured questionnaire survey with higher sample size for the empirical validation of the model.

This research will help to clearly understand the framework of drivers and barriers of variables and their hierarchical level based on the driving power and dependence. Since such articles focusing on the conceptual frameworks of drivers and barriers of ISSWM are found to be very scant, this paper will equally help academicians and waste management professionals to understand the concepts deeply, by getting answers to the fundamental questions of “what,” “why” and “how.” Developed framework of drivers explicitly shows the need to attain financial stability through the commercialization of the waste management initiatives, which will help to reduce burden on various governmental institutions. Commercialization opportunities will also help to have more successful start-up ventures in solid waste management domain that can provide improved employment opportunities and hygiene environment in the developing nations like India.

Based on the authors’ best knowledge, there is hardly any article that explicitly explains the conceptual frameworks of the drivers and barriers of ISSWM by considering the conditions prevailing in developing countries like India. And thus, this can be considered as one of the unique research attempts to build a clear conceptual framework of ISSWM. The study contributes significantly to the existing literature body by clearly interpreting the interrelationships and the driving power and dependence of variables of ISSWM.

This paper examined the current status of municipal solid waste management across Nigeria. The core aspects covered are generation, characterization, collection, scavenging, open dumping, disposal and environmental implications of poor solid waste management. The purpose of this paper is to present a comprehensive overview of the current state of municipal solid waste management in Nigeria.

This study was executed by a combination of an extensive literature search and field study. Solid waste generation rates for 31 Nigerian cities were obtained from literature. In addition, characteristics of municipal solid waste from 26 Nigerian cities were also obtained from literature. Other aspects such as characterization of solid waste obtained from final dumpsite and heavy metals accumulation in solid waste dumpsites were undertaken first hand.

Solid waste generation rate was found to vary from 0.13 kg/capita/day in Ogbomosho to 0.71 kg/capita/day in Ado-Ekiti. Factors affecting solid waste generation rates were identified. Typically, food waste was found to constitute close to 50 percent of overall municipal solid waste in Nigerian cities. This study shows that the rate of generation of plastics, water proof materials and diapers has assumed an upward trend. Due to the dysfunctional state of many municipal waste management authorities, many cities have been overrun by open dumps. For instance, more than 50 percent of residents of Maiduguri in northern Nigeria and Ughelli in southern Nigeria dispose of their waste in open dumps. Indiscriminate disposal of waste has also resulted in the preponderance of toxic heavy metals in agricultural soils and consequent bioaccumulation in plants as well as groundwater contamination.

The main limitation of this research is municipal waste management authorities do not have relevant data. Hence, there was heavy reliance on published materials. The status of waste management in Nigeria is very deplorable and therefore poses serious threats to public and environmental health. There is urgent need for both government and individuals to adopt holistic and sustainable waste management strategies in order to safeguard public/environmental health.

Findings from this paper can form a veritable resource for the formulation and implementation of sustainable municipal solid waste management framework and strategies in Nigeria.

While most studies on municipal solid waste management in Nigeria are focussed on selected cities of interest, this particular study cuts across most cities of Nigeria in order to present a broader and holistic view of municipal solid waste management in Nigeria. The paper has also unraveled core municipal solid waste management challenges facing Nigerian cities.

The purpose of the paper is to assess the influence of the volume fraction solid lubricants like talc lead and graphite in oil separately and in combination towards controlling the sliding wear behaviour of a grey cast iron and understand the factors controlling the response of the material in a given set of experimental conditions.

The composition of the lubricating medium (oil) has been changed by dispersing 5 per cent graphite, talc and lead particles separately and in combination. Sliding wear tests were conducted on grey cast iron samples over a range of applied pressures. Parameters determined were wear rate and frictional heating. The wear behaviour of the samples was further substantiated through the features of wear surfaces, subsurface regions and debris particles. Material removal mechanisms and factors responsible for a specific response of the samples have also been analysed.

The wear rate increased with increasing applied pressure. Addition of graphite and lead to the oil separately or in combination brought about a reduction in the wear rate of the samples; talc and talc + lead produced a reverse trend. Temperature near the specimen surface increased with test duration and applied pressure. The test environment influenced the frictional heating in a manner similar to that of the wear rate. Adhesion and abrasion were observed to be the operating material removal mechanisms. Smearing of the solid lubricating phase and delamination resulting from cracking tendency also controlled the wear response.

Oil is a very popular lubricant used in engineering applications involving friction and wear. Solid lubricants are used along with the oil. The nature, characteristics and content of the solid lubricants very much control the performance. Limited information is available pertaining to assessing the influence of the type and fraction of solid lubricants in the oil towards controlling the wear behaviour of cast irons (popularly known tribomaterials). The present study enables to understand the effectiveness of talc, lead and graphite in oil towards governing the wear characteristics of cast iron and analyse wear mechanisms and controlling parameters.

Graphite and talc are available in nature in abundance. Graphite is a popularly known solid lubricant, while talc is less explored. Lead is also well-known as a solid lubricant but poses health hazard in practice due to its toxic nature. The present study explores the lubricating capability of talc when mixed with oil separately or in combination with lead and graphite towards controlling the wear response of a grey cast iron. It enables to understand the factors responsible for the specific response of talc.

Assessment of the lubricating potential of talc as a possible substitute to lead is important in view of the toxic nature of the latter. If successful, the exercise could enable to replace lead with talc.

The present manuscript is an original piece of the author's research work.

Environmental engineering is primarily concerned with the application of technology to the urgent tasks of cleaning up our environment. Its practitioners generally attempt to cope with the problems of streams and waterways polluted by sewage and industrial waste, oceans damaged by oil spills and sewage sludge dumpings, air polluted with noxious fumes and land abused by solid waste disposal. But that is not all that they do. The recent energy crisis has sharply brought into focus the need for alternate energy strategies, including energy extraction from solid waste. Under current estimates, the United States will produce approximately 340 million tons of solid waste by 1980. This is equivalent to one ton of solid waste per person per year. The most widely used methods of waste disposal right now are dumping, incineration and sanitary landfill. They are expensive and they cause pollution. Instead, solid waste can be burned to produce steam which can be used for heating or to generate electricity. It can also be converted to pyrolysis gas or oil, which can be stored or transported. It is from this standpoint that environmental engineering assumes considerable importance. A report which presents an overview of the state of the art in this area is the Resource Recovery from Municipal Solid Waste. Other pertinent guides include Energy from Solid Waste, Conversion of Refuse to Energy, Recycling and Reclaiming of Municipal Solid Wastes, Resource Recovery and Recycling Handbook of Industrial Wastes, and Wasteheat Management Guidebook. No project of this nature can be undertaken without government assistance. A description of the activities of the Federal Solid Waste Management Program is available from EPA's Solid Waste Recycling Projects: A National Directory.