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A two-dimensional (2D) numerical simulation is performed to simulate the laminar forced convection of a nanofluid in a ribbed channel with apart heating (cooling) sources using lattice Boltzmann method (LBM). The multi-walled carbon nanotubes–iron oxide nanoparticles/water hybrid nanofluid (MWCNT–Fe 3 O 4 /water hybrid nanofluid) is used in this simulation. The velocity field, temperature distribution and heat transfer rate are numerically analyzed with the streamlines and isotherm patterns employing of a house code. In addition, the effect of Reynolds number ( Re  = 25, 50, 75 and 100), nanoparticle solid volume fraction ( ϕ  = 0, 0.001, 0.003) and ratio of the blocks height ( A  = 0.2, 0.3, 0.4) are measured. The results are validated against the results reported in the literature, and a good agreement is reported. The obtained results show a maximum value of 16.49% increase in the average heat transfer coefficient for all the considered cases relative to the base fluid. Moreover, the local Nusselt number proves that the use of blocks on the channel walls can increase the amount of heat transfer. Finally, the average Nusselt number shows a linear dependence on the increasing ratio of blocks height for constant solid volume fraction. The results of this study apply to the industrial equipment heating and cooling applications.

Radiative heat transfer in two-dimensional irregular geometries is analyzed using a direct-forcing immersed boundary-lattice Boltzmann method (IB-LBM) in participating media. In this paper, the radiative transfer equation (RTE) is discretized by the lattice Boltzmann method, which Yi et al. (Phys Rev E 94(2):023312, 2016) have recently presented. The D2Q9 scheme is used to solve the lattice Boltzmann equation (LBE) and the quadrature scheme SN to discrete the angular space. The irregular geometries’ boundaries are simulated by Immersed Boundary Method (IBM). The effect of boundaries that do not match the computational nodes is determined by adding a radiation density term to the LBE. Radiative heat flux distribution for different extinction coefficients are compared with the results obtained from the blocked-off domain method (BOM), embedded boundary method (EBM), and body-fitted grid method (BFM). Compared to the BFM, the proposed method has perfect accuracy, and for all considered problems, the average percent relative error in the estimation of radiative heat flux is between 0.4 and 9.8%. The results show that IBM can solve the difficulties of simulating curved boundaries efficiently. It is found that IB-LBM has been able to solve the problem of thermal radiation in irregular geometries for media with any optical depth.

The rapid growth of the electronics industry and the increase in processor power levels requires new techniques to improve the heat transfer rate in their cooling systems. In this study, ultrasonic vibration technology was introduced as an active method to enhance the thermal performance of water-cooling systems. The effects of ultrasonic vibrations at power levels of 30, 60, and 120 watts for different cooling airflow rates were investigated experimentally. The results were validated with available empirical correlations to ensure the accuracy of the measurement systems. The findings indicated that the ultrasonic vibrations enhanced the heat transfer in the liquid-cooling heat exchangers. In addition, the thermal performance of the ultrasonic vibrations was improved by reducing the airflow rate and increasing the ultrasonic power. In addition to the feature of heat transfer improvement, ultrasonic waves are widely used for the cleaning of different types of heat exchangers. Regarding the anti-fouling and anti-accumulation effects of the ultrasonic vibrations, the introduced technology could provide a practical way for developing high-performance nanofluids-based computer cooling systems.

This study aimed at presenting a steady-state analytical solution for the two-dimensional heat conduction in a cylindrical segment made of functionally graded materials. It is acquired by taking advantage of the Fourier transform and separation of variables rather than numerical methods. Sturm–Liouville theory is employed to find the proper and adequate Fourier transformation. Continuous variations along the radial and circumferential directions based on the power-law function are taken into account, and non-homogeneous boundary conditions are applied to the problem. The obtained formulation is verified by the available solutions. Through solving an illustrative example, the temperature distribution is deliberated for a combination of boundary conditions. It is to be emphasized that mathematical robustness and generality of the solution are its primary advantage which is not often seen in the previously published literature.

Background Socioeconomic status (SES) is associated with stroke incidence and mortality. Distribution of stroke risk factors is changing worldwide; evidence on these trends is crucial to the allocation of resources for prevention strategies to tackle major modifiable risk factors with the highest impact on stroke burden. Methods We extracted data from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2017. We analysed trends in global and SES-specific age-standardised stroke incidence, prevalence, mortality, and disability-adjusted life years (DALYs) lost from 1990 to 2017. We also estimated the age-standardised attributable risk of stroke mortality associated with common risk factors in low-, low-middle-, upper-middle-, and high-income countries. Further, we explored the effect of age and sex on associations of risk factors with stroke mortality from 1990 to 2017. Results Despite a growth in crude number of stroke events from 1990 to 2017, there has been an 11.3% decrease in age-standardised stroke incidence rate worldwide (150.5, 95% uncertainty interval [UI] 140.3–161.8 per 100,000 in 2017). This has been accompanied by an overall 3.1% increase in age-standardised stroke prevalence rate (1300.6, UI 1229.0–1374.7 per 100,000 in 2017) and a 33.4% decrease in age-standardised stroke mortality rate (80.5, UI 78.9–82.6 per 100,000 in 2017) over the same time period. The rising trends in age-standardised stroke prevalence have been observed only in middle-income countries, despite declining trends in age-standardised stroke incidence and mortality in all income categories since 2005. Further, there has been almost a 34% reduction in stroke death rate (67.8, UI 64.1–71.1 per 100,000 in 2017) attributable to modifiable risk factors, more prominently in wealthier countries. Conclusions Almost half of stroke-related deaths are attributable to poor management of modifiable risk factors, and thus potentially preventable. We should appreciate societal barriers in lower-SES groups to design tailored preventive strategies. Despite improvements in general health knowledge, access to healthcare, and preventative strategies, SES is still strongly associated with modifiable risk factors and stroke burden; thus, screening of people from low SES at higher stroke risk is crucial.

Utilizing ultrasonic excitation as an active method for studying the rate of heat transfer has gained considerable attention recently. The present study investigated the effects of ultrasonic excitation on the heat transfer rate in a fin-and-flat tube heat exchanger experimentally. The performance of the heat exchanger was investigated with and without the presence of ultrasonic excitation. A comprehensive parameter study was attempted, so several parameters, including ambient temperature, flow rate, air passing velocity, Reynolds number, and Nusselt number, were studied in a relatively wide range. An adequate uncertainty test, as well as a validation assessment, is provided to certify the credibility of the obtained results and the hired facility. The results revealed that reducing the flow rate, ambient temperature, and air passing velocity on the heat exchanger increased the ultrasonic excitation’s effects. The highest heat transfer enhancement in the present experiment was 70.11%, measured at the lowest air passing velocity and ambient temperature with a Reynolds number 2166. The data presented in this paper will be useful for the optimal design of ultrasonic vibrating fin-and-tube heat exchangers.

Purpose The purpose of this study is to investigate heat transfer and electrokinetic non-Newtonian flow in a rectangular microchannel in the developed and transient states. Design/methodology/approach The Carreau–Yasuda model was considered to capture the non-Newtonian behavior of the fluid. The dimensionless forms of governing equations, including the continuity equation for the Carreau–Yasuda fluid, are numerically solved by considering the volumetric force term of electric current (DC). Findings The impact of pertinent parameters such as electrokinetic diameter (R), Brinkman number and Peclet number is examined graphically. It is observed that for increasing R, the bulk velocity decreases. The velocity of the bulk fluid reaches from the minimum to the maximum state across the microchannel over time. At the electrokinetic diameter of 400, the maximum velocity was obtained. Temperature graphs are plotted with changes in the various Brinkman number (0.1 < Br < 0.7) at different times, and local Nusselt are compared against changes in the Peclet number (0.1 < ℘e < 0.5). The results of this study show that by increasing the Brinkman number from 0.25 to 0.7, the temperature along the microchannel doubles. It was observed that increasing the Peclet number from 0.3 to 0.5 leads to 200% increment of the Nusselt number along the microchannel in some areas along the microchannel. The maximum temperature occurs at Brinkman number of 0.7 and the maximum value of the local Nusselt number is related to Peclet number 0.5. Over time in the transient mode, the Nusselt number also decreases along the microchannel. By the increasing of time, the temperature increases at given value of Brinkman, which is insignificant at Brinkman number of 0.1. The simulation results have been verified by Newtonian and non-Newtonian flows with adequate accuracy. Originality/value This study contributes to discovering the effects of transient flow of electroosmotic flow for non-Newtonian Carreau–Yasuda fluid and transient heat transfer through rectangular microchannel. To the authors’ knowledge, the said investigation is yet not available in existing literature.

In this paper, the fabrication and optimization of a spiral-tube heat exchanger (STHE) were considered for improving the heat transfer rate and efficiency of traditional instantaneous water heaters. The large number of instantaneous water heaters exported from the customers of the “Garman Gas Toos” company, which was mainly due to corrosion and leakage, imposed a lot of cost and credit reduction for this company. The high energy consumption was the second reason that justified working on a new STHE. The main innovation of this research is the design and construction of a new heat exchanger with a smaller size and higher efficiency with the help of identifying the factors affecting its efficiency and heat transfer rate. In order to optimize the responses, three variables were considered, including fin number (per unit area), exhaust outlet diameter, and water flow rate. Implementing face-centered central composite design (CCD), the proposed levels of factors and the corresponding response variables were measured in the “Garman Gas Toos” laboratory. Using the design of experiments (DoE), the effects of the three factors and their mutual interaction effects were evaluated. Response surface methodology (RSM) was devised to build a prediction model and obtain the values of the factors for which the responses were optimal. Based on the results, optimum conditions for the STHE were found to be an exhaust diameter of 4 cm and a water flow rate of 6 L/min coupled with six fins. At this optimal point, the values of efficiency and heat transfer rate, as response variables, were obtained as 85% and 8480 W, respectively.

Rocking foundations offer potential benefits, such as energy dissipation and reduced superstructure ductility demand during severe earthquake loadings. However, it can result in residual deformations at the soil-foundation interface, and uncertainties regarding its performance still remain, particularly for pile-supported structures. For the foundation of structures like tall bridges supported by pile groups, the system’s behavior during rocking motions can be influenced by various factors, such as static vertical safety factor, pile-to-cap connection, and pile length. The present study explores influences of pile-to-cap connections on the rocking behavior of the system for different pile group lengths and static safety factors. A physical single-degree-of-freedom (SDOF) structural model with a novel semi-fixed pile-to-cap connection was developed for this study. Results indicate that unrestricted rocking on unattached connections lead to significantly lower residual settlements than those for fixed connections. Also, semi-fixed connections reduce settlements for long pile groups, with a slight decrease in resistance moment capacity. Moreover, unattached connections demonstrate a superior energy dissipation ratio of the system compared to that for fixed ones, in long pile groups with low bearing safety factors. The current study would expand our insight into the performance of different pile-to-cap connections under various conditions during rocking motions.

This study uses advanced time-series forecasting and causal modelling techniques to examine long-term patterns in Australian road traffic fatalities. Four statistical approaches were assessed: Holt-Winters, Theta, TBATS, and Vector Autoregression, with each offering strengths across different forecasting horizons. TBATS provided the most reliable short-term predictions, while Vector Autoregression performed best for medium- and long-term projections. A causal analysis using a random-effects panel model identified several key contributors to fatal crash risk, including older age groups, remote and outer-regional settings, nighttime periods, and high-speed environments. In contrast, younger adults and single-vehicle crashes were associated with lower fatality likelihood. Overall, the results demonstrate the value of flexible time-series techniques and panel data methods for guiding evidence-based road safety policy, targeted interventions, and infrastructure planning.