Search results

The purpose of the study is to indicate a three-dimensional convective heat transfer properties evaluation of magnetohydrodynamics nanofluid flow, comprising motile oxytactic microorganisms and nanoparticles, passing through a rotating cone.

The imposed technique for solving the governing equations is the Runge–Kutta fifth-order method. The main point of this survey is to diagnosis the influence of diverse factors on velocity, temperature distributions and concentration profile. Furthermore, appending the magnetic field, thermal radiation and viscous dissipation in calculations; also, simultaneous involvement of heat absorption and excretion has been represented as novelties.

The results elucidate that by changing the Peclet number from 1 to 2, the dimensionless concentration of the microorganisms has been diminished by about 34.37%. In addition, variation of the magnetic parameter from 0 to 1 has been resulted in reducing the temperature distribution by about 3.11%.

Recently, attention has been absorbed to adding the motile microorganisms to nanofluid for enhancement of heat transfer and avoiding aggregation of particles. In this regard, the hydrothermal flow of microorganisms has been investigated in this study.

The purpose of this paper is to investigate natural convection in a porous wavy-walled enclosure that is including a cylinder cavity in the middle of it and filled with a hybrid nanofluid contains 1-Butanol as the base fluid and MoS₂–Fe₃O₄ hybrid nanoparticles.

The domain of interest is bounded by constant temperature horizontal corrugated surfaces and isothermal vertical flat surfaces. The numerical outputs are explained in the type of isotherms, streamline and average Nusselt number with variations of the Rayleigh number, Hartmann number, nanoparticle shape factor and porosity of the porous medium. For solving the governing equations, the finite element method has been used.

The results show that Nuave is proportional to Rayleigh and nanoparticle shape factor directly as well as it has an inverse relation with Hartmann and porosity. The obtained results reveal that the shape factor parameter has a significant effect on the heat transfer performance, which shows a 55.44% contribution on the average Nusselt number.

As a novelty, to maximize the heat transfer performance in a corrugated walls enclosure, the optimal parameters have intended by using the response surface and Taguchi methods. Additionally, an accurate correlation for the average Nusselt number is developed with sensibly great precision.

The purpose of this paper is to investigate micropolar magnetohydrodynamics (MHD) fluid flow passing over a vertical plate. Three different base fluids have been used that include water, ethylene glycol and ethylene glycol/water (50%–50%). Also, a nanoparticle was used in all of the base fluids. The effects of natural convection heat transfer and magnetic field have been taken into account.

The main purpose of solving the governing equations is to scrutinize the effects of the magnetic parameter, the nanoparticle volume fraction, micropolar parameter and nanoparticles shape factor on velocity, temperature and microrotation profiles, the skin friction coefficient and the Nusselt number. These surveys have been considered for three base fluids simultaneously.

The results indicate that for water-based fluids, the temperature profile of lamina-shaped nanoparticles is 38.09% higher than brick-shaped nanoparticles.

This paper provides micropolar MHD fluid flow analysis considering natural convection heat transfer and magnetic field in three different base fluids. The aim of assessments is the diagnosis of some parameter effects, such as magnetic parameter and nanoparticle volume fraction, on velocity, temperature and microrotation profiles and components. Also, the use of mixed base fluids presented as a novelty in this paper.

The purpose of this study is, mixed convection on magnetohydrodynamic (MHD) flow of Eyring–Powell nanofluid over a stretching cylindrical surface in the presence of thermal radiation, chemical reaction, heat generation and Joule heating effect is investigated and analyzed. The Brownian motion and thermophoresis phenomenon are used to model nanoparticles (Buongiorno’s model).

The numerical method is applied to solve the governing equations. Obtained results from the effects of different parameters changes on velocity, temperature and concentration profiles are reported as diagrams.

As a result, velocity profile has been reduced by increasing the Hartman number (magnetic field parameter) because of the existence of Lorentz force and increasing Eyring–Powell fluid parameter. In addition, the nanoparticle concentration profile has been reduced because of increase in chemical reaction parameter. At the end, the effects of different parameters on skin friction coefficient and local Nusselt number are investigated.

Eyring–Powell nanofluid and MHD have significant influence on flow profile.

Public debt forecasts represent a key policy issue. Many methodologies have been employed to predict debt sustainability, including dynamic stochastic general equilibrium models, the stock flow consistent method, the structural vector autoregressive model and, more recently, the neuro-fuzzy method. Despite their widespread application in the empirical literature, all of these approaches exhibit shortcomings that limit their utility. The present research adopts a different approach to public debt forecasts, that is, the random forest, an ensemble of machine learning.

Using quarterly observations over the period 2000–2021, the present research tests the reliability of the random forest technique for forecasting the Italian public debt.

The results show the large predictive power of this method to forecast debt-to-GDP fluctuations, with no need to model the underlying structure of the economy.

Compared to other methodologies, the random forest method has a predictive capacity that is granted by the algorithm itself. The use of repeated learning, training and validation stages provides well-defined parameters that are not conditional to strong theoretical restrictions This allows to overcome the shortcomings arising from the traditional techniques which are generally adopted in the empirical literature to forecast public debt.

This study forecasts the government expenditure components in Nigeria, including recurrent and capital expenditures for 2021 and 2022, based on data from 1981 to 2020.

The study employs statistical/econometric problems using the Feasible Quasi Generalized Least Squares approach. Expenditure forecasts involve three simulation scenarios: (1) do nothing where the economy follows its natural path; (2) an optimistic scenario, where the economy grows by specific percentages and (3) a pessimistic scenario that defines specific economic contractions.

The estimation model is informed by Wagner's law specifying a positive link between economic activities and public spending. Model estimation affirms the expected positive relationship and is relevant for generating forecasts. The out-of-sample results show that a higher proportion of the total government expenditure (7.6% in 2021 and 15.6% in 2022) is required to achieve a predefined growth target (5%).

This study offers empirical evidence that specifically requires Nigeria to invest a ratio of 3 to 1 or more in capital expenditure to recurrent expenditure for the economy to be guided on growth.

In this paper, the authors analyse a 2010 legal reform in the Czech Republic, which allowed retirees to simultaneously receive regular pension benefits and to work on a permanent contract for a period longer than one year. Previously, concurrence of employment and receipt of retirement benefits were only allowed in conjunction with a temporary work contract with a maximum duration of one year.

The authors employ the difference-in-differences method. The authors include only males in the analysis because it is not possible to identify the legal retirement age for women from available data. Men in the workforce 1–3 years prior to the statutory retirement age are in a control group, while men 1–3 years older are in a treatment group.

The authors show that the reform significantly increased the share of permanent contracts held by retirees (by 22.5–27.6 percentage points), though we do not find any aggregate short-term change in employment of retirees. Heterogeneity analysis shows a significant increase in the employment of retirees with only elementary school education (by 17.9 percentage points) and a significant decrease in the number of hours worked by retirees (by 2.5 h weekly for low-educated workers).

The policy conclusion is that the regulation of employment contract does not affect aggregate employment, but may improve employment of low skilled workers.

To the authors’ best knowledge, there are no studies directly analysing motivation of retirees by types of employment contracts. The authors, thus, add to the literature that studies dealing with the general fixed-term versus permanent contracts (Engellandt and Riphahn, 2003) and motivation to work.

The purpose of the paper is to study a new type of lubrication additive with Nano‐Tin, and to analyze the tribological performance of the friction coatings that are formed by the lubricants.

The Tin‐base additives were prepared and activated, friction testing was performed on an improved type MS‐800 four‐ball tester, and the nanometer additives with different contents of Tin were used as lubricants in steel‐copper tribo‐pair. The surface elements of friction coatings were investigated with Auger electron spectrum, and the thickness and element distribution of the coating were measured with scanning electron microscope.

The ultra‐thick friction coating (10‐20 μm) with abundant Tin was carried out and combined well with the surface of the copper sample when lubricated with oil containing this additive. The coating exhibited excellent anti‐wear and friction‐reducing capacities.

The anticorrosion properties have not been estimated.

A useful Nano‐Tin base lubricating oil additive is prepared and the activate method is explored. It may provide the potential lubricating oil additive for steel‐copper tribo‐pair, such as steel worm‐copper worm wheel transmission.

This paper provides a Nano‐Tin base‐activated additive which, when used in lubricating oil, can form an ultra‐thick friction coating. It has the same self‐repairing properties as a steel‐copper tribo‐pair.

Presents the comparative surface roughness measurement data from a paper on the wear of filled PTFE lip seals in contact with a variety of different surfaces, as reported in a paper from the University of Stuttgart Institute of Machine Elements.

This paper aims to provide details of commercially available domestic robots and recent product developments and consider whether a significant boost in the robot population is imminent.

Following a short introduction, this paper first provides a brief overview of existing domestic robots and identifies recent product trends. It then discusses some newer product developments which extend the capabilities of domestic robots. This is followed by a consideration of the many recently launched companion robots, and the paper concludes with a discussion of the likely impact on the domestic robot market.

This paper shows that domestic robots have benefited from developments in artificial intelligence, sensor technology and connectivity, which have led to greater versatility and enhanced ease of use. Several new product developments are extending the range of functions conducted by domestic robots. Many small, mobile companion/social robots have recently been developed which interact with humans by speech and vision and conduct functions such as entertainment, the control of household appliances and security.

This paper provides an insight into the wide range of domestic robots which are available or under development and considers their commercial prospects.