Search Results (1,937)

Background: Although computational models are advancing air quality prediction, achieving the desired performance or accuracy of prediction remains a gap, which impacts the implementation of machine learning (ML) air quality prediction models. Several models have been employed and some hybridized to enhance air quality and air quality index predictions. The objective of this paper is to systematically review machine and deep learning techniques for spatiotemporal air prediction challenges. Methods: In this review, a methodological framework based on PRISMA flow was utilized in which the initial search terms were defined to guide the literature search strategy in online data sources (Scopus and Google Scholar). The inclusion criteria are articles published in the English language, document type (articles and conference papers), and source type (journal and conference proceedings). The exclusion criteria are book series and books. The authors’ search strategy was complemented with ChatGPT-generated keywords to reduce the risk of bias. Report synthesis was achieved by keyword grouping using Microsoft Excel, leading to keyword sorting in ascending order for easy identification of similar and dissimilar keywords. Three independent researchers were used in this research to avoid bias in data collection and synthesis. Articles were retrieved on 27 July 2024. Results: Out of 374 articles, 80 were selected as they were in line with the scope of the study. The review identified the combination of a machine learning technique and deep learning techniques for data limitations and processing of the nonlinear characteristics of air pollutants. ML models, such as random forest, and decision tree classifier were among the commonly used models for air quality index and air quality predictions, with promising performance results. Deep learning models are promising due to the hyper-parameter components, which consist of activation functions suitable for nonlinear spatiotemporal data. The emergence of low-cost devices for data limitations is highlighted, in addition to the use of transfer learning and federated learning models. Again, it is highlighted that military activities and fires impact the O₃ concentration, and the best-performing models highlighted in this review could be helpful in developing predictive models for air quality prediction in areas with heavy military activities. Limitation: This review acknowledges methodological challenges in terms of data collection sources, as there are equally relevant materials on other online data sources. Again, the choice and use of keywords for the initial search and the creation of subsequent filter keywords limit the collection of other relevant research articles. Full article

Global climate change and rapid urbanization have brought unprecedented environmental challenges, especially in rapidly expanding cities like Xi’an, posing potential challenges to sustainable development if not accompanied by adequate greenery, thoughtful layouts, and pollution control measures. The increasing frequency and intensity of urban air pollution (e.g., PM_2.5, PM₁₀, O₃) and extreme climate events (e.g., heatwaves) have heightened health risks for residents. Existing studies mostly focus on single pollution or climate factors, neglecting the compounded effects of these factors. To fill this research gap, this study presents a health risk assessment model, specifically by analyzing the compounded effects of heatwaves and air pollution. By integrating hazard, exposure, and vulnerability factors using the entropy weight–TOPSIS method, the results reveal significant spatial differences in health risks across various regions of Xi’an. The findings provide valuable guidance for urban planners and policymakers to better address environmental hazards, reduce health risks, and promote sustainable urban development. Full article

Demand is high for small, lightweight, and power-dense machines. However, as power increases and size decreases, rejecting losses becomes more difficult. Many novel cooling systems have been developed, which have allowed machines to be made smaller while increasing power. This paper proposes a cooling system making use of soft magnetic composite (SMC) cores to improve cooling specifically in a high-speed axial-flux machine via the use of an integrated cooling channel in the SMC core. A series of experiments on a prototype machine are performed and the experimental data are used to determine a set of parameters for the FEA thermal model. Using the thermal FEA model, a comparison is completed with a traditional closed cooling system using laminated steels and an attached cooling plate.The SMC machine is then simulated at speeds up to 160 krpm and currents up to 8 A. To achieve the same coil temperature between the two designs, the laminated steel model required 4 MPa contact pressure at 10 krpm and 5 MPa contact pressure at 20 krpm. At the same time, the novel design removed approximately 20% more heat per shear air gap surface area and approximately 15% more heat per total machine surface area than the version with the attached cooling plate. Extending the operating range of the model to 160 krpm demonstrated that the maximum temperature rise remained below 180 °C. Full article

In 2019, more than 16% of the globe’s total production of electricity was provided by hydroelectric power plants. The core of a typical hydroelectric power plant is the turbine. Turbines are subjected to high levels of pressure, vibration, high temperatures, and air gaps as water passes through them. Turbine blades weighing several tons break due to this surge, a tragic accident because of the massive damage they cause. This research aims to develop predictive models to accurately predict the status of hydroelectric power plants based on real stored data for all factors affecting the status of these plants. The importance of having a typical predictive model for the future status of these plants lies in avoiding turbine blade breakage and catastrophic accidents in power plants and the resulting damages, increasing the life of these plants, avoiding sudden shutdowns, and ensuring stability in the generation of electrical energy. In this study, artificial neural network algorithms (RNN and LSTM) are used to predict the condition of the hydropower station, identify the fault before it occurs, and avoid it. After testing, the LSTM algorithm achieved the greatest results with regard to the highest accuracy and least error. According to the findings, the LSTM model attained an accuracy of 99.55%, a mean square error (MSE) of 0.0072, and a mean absolute error (MAE) of 0.0053. Full article

Background/Objectives: An air–bone gap (ABG) on audiometry is usually secondary to a conductive hearing loss. However, persistent and repeatable ABGs on audiometry in the absence of external or middle ear pathology is thought to arise from inner ear disorders including Meniere’s Disease (MD). In this paper, we aim to showcase this interesting finding occurring in MD with an associated literature review. Methods: Using retrospective review and analysis of case notes, we describe eight cases of persistent ABG on audiometry in MD. All other causes for the ABG were explored and excluded with the aid of objective audiological testing. Results: ABG can occur in a small sub-set of the MD population. In our case series, the ABG was typically found to affect the low frequencies. Higher frequencies appear to be spared. However, a detailed history, examination and battery of objective tests are required to ensure that all other causes of the ABG are reliably considered and excluded prior to attributing it to the inner ear. The finding of an ABG in MD may be dependent on the stage of the disease. Further research is required to determine the underlying cause of the ABG and its potential applications to help guide treatment. Full article

Dynamic wireless power transfer (DWPT) systems with segmented transmitters suffer from output pulsations during the moving process. Although numerous coil structures have been developed to mitigate this fluctuation, the parameter design process is complicated and restricted by specific working conditions (e.g., air gaps). To solve these problems, a novel reverse-bent modular transmitter structure is proposed for DWPT in industrial automatic application scenarios such as linear transport systems. Considering the heterogeneous current density distribution in the adjacent region between two coils which causes a drop in magnetic field, the proposed coil structure attempts to eliminate the effects of the adjacent region by bending the terminal parts of each coil reversely to the ferrite layer for shielding. Compared to traditional planar couplers, this structure array can generate a uniform magnetic field over various air gaps. A 100 W laboratory prototype was built to verify the feasibility of the proposed system. The experimental results show that the proposed system achieved a constant output voltage, and the output pulsation was within ±2.3% in the dynamic powering process. The average efficiency was about 88.29%, with a 200 mm transfer distance. When the air gap varied from 20 mm to 30 mm, the system could still retain constant voltage output characteristics. Full article

The rationale for this work arose from the urgency of improving the energy efficiency of buildings at the design stage, given the changing requirements of energy efficiency standards such as the Polish Technical Conditions (WT 2014 and WT 2020). This research is novel as there is currently limited information available on the improvement of the thermal performance of ventilated stone facade systems, although they are now widely used due to their practical and aesthetic advantages. The first objective of this work is to evaluate the thermal performance of the ventilated facades of the Praski Student House (Akademik Praski) and to assess how certain design variations can help achieve a lower level of energy consumption. Using a comprehensive case study approach, this study provides accurate thermal calculations of the facade to assess its global thermal insulation coefficient (Rt) and thermal transmittance (Uc). The improvement in the actual U-value from the original design is as follows: the U-value is reduced from 0.33 originally to 0.228 for WT 2014 and to 0.198 for WT 2020, showing a reduction of about 30.9% and 13.2%, respectively. These results indicate the energy efficiency of increased insulation thickness and optimally oriented air gap dimensions. The practical contributions of this research are valuable for architects, engineers, and contractors involved in the design and construction process of buildings aiming to achieve near-zero energy buildings (nZEBs), including concrete suggestions on how to improve current construction practices as well as material recommendations. There is a need for durability studies, for example to assess the performance of such facades under different climatic conditions, as part of future work to support these findings. Full article

Microplastics, defined as plastic particles less than 5 mm in size, have become a pervasive environmental contaminant detected across a wide range of ecosystems. While the presence of microplastics in marine life and humans has been extensively documented, there remains a significant gap in understanding their full health impacts. Moreover, the effects of microplastics on animals, particularly those in close proximity to human activities, remain underexplored, representing a key area for future research. In this study, we found high levels of microplastic accumulation in animal tissues, particularly in the lungs, intestines, and reproductive organs. Our results also indicate that ingestion of microplastics occurs through multiple environmental sources, including contaminated food, water, and air, reflecting their widespread distribution. Evidence of microplastics crossing biological barriers and accumulating in critical organ systems suggests potential long-term health risks for animals that may also have implications for humans through environmental and food-chain exposure. Given the interconnectedness of ecosystems and the potential for these contaminants to enter the food chain, the presence of microplastics in animals raises serious concerns for broader ecological and human health. The findings underscore the urgent need for further research to clarify the long-term effects and to develop effective strategies for mitigating this emerging global threat. Full article

Water scarcity is a global issue, and desalination is an alternative to providing fresh water. Renewable energies could be used in thermal desalination to produce freshwater from high saline concentration solutions. In this paper, the experimental performance of an air-injection-Air Gap Membrane Distillation (AGMD) module is presented. The effect of the operation parameters (saline solution temperature, air flow, and salt concentration) on the distilled water rate was evaluated. The air injection enhanced the distilled water rate by 22% at the highest air flow and a solution flow rate of 80 °C, compared to the conventional condition (without air injection) at a salt concentration of 100,000 ppm. Under the same operating conditions, the increase was 17% at a salt concentration of 70,000 ppm. The maximum distilled water rate was 14.10 L/m²·h at 80 °C and an airflow of 1.5 L/min with the highest salt concentration, while it was also 14.10 L/m²·h at the lower salt concentration was 14.10 L/m²·h. The distilled water quality also improved as the air flow increased, since a conductivity reduction of 66% was observed. With the described mathematical model, 94% of the calculated values fell within ±10% of the experimental data for both salt concentration conditions. Full article

This study experimentally analyzed the impact of air gaps between a magnetic sheet and a test board with a microstrip line, which is used to measure the near-field magnetic shielding effectiveness (NSE) of magnetic sheets made of metallic powder. To conduct the measurements, a material fixture equipped with a microstrip line to generate the near magnetic field, a rectangular loop probe, and an automatic probe positioning system capable of moving the loop probe along three axes were designed and fabricated. In addition, to systematically vary the thickness of the gaps, three paper spacers with a thickness of 0.11 mm per paper were used, and a 1.0 mm thick acrylic sheet, along with a specially designed material fixture, was used to press down the magnetic sheets during measurement. The magnetic shielding properties were measured and compared under various air gap conditions using a near-field magnetic loop probe. The effect of the gaps on the shielding performance of the magnetic sheets was quantitatively evaluated for three different magnetic sheets. The experimental results showed that as the gap thickness increased, NSE tended to improve up to a frequency around 1 GHz, while in the higher frequency range of a few GHz, NSE tended to decrease. The physical background of this phenomenon was explained using an equivalent magnetic circuit represented by reluctances for the structure, where the magnetic sheet is placed above the microstrip line with an air gap. This model helps to elucidate how the presence of the air gap affects the near-field magnetic shielding performance. Full article

There is limited information regarding the grain sorghum production trends from early in the millennium towards the 2020s. The main objective of this study was to quantify the grain sorghum production area, economic value, productivity, annual production variation, relationship with changing weather patterns, and yield gap and to identify future areas of intervention and research. The results indicated that the grain sorghum production area in Kansas has increased in the most recent decade (2010–2022) at an average rate of 8 thousand ha year⁻¹. With the current 1.2 million ha harvest area, Kansas continues to allocate more land area for sorghum than any other state in the USA. The average current annual economic value of sorghum in Kansas is USD 0.5 billion. The average sorghum grain productivity for recent years (2000–2022) was 4.3 Mg ha⁻¹ in Kansas. The year-to-year yield variation in the grain sorghum average for Kansas in the years 1929–1956 was ±0.5 Mg ha⁻¹ but increased to ±2 Mg ha⁻¹ for the years 1957–2022. The results also showed a 66 to 96% yield gap between the actual yield (USDA data) and potential non-irrigated yield (Kansas State Grain Sorghum Hybrid Performance Trial data). There was a significant positive correlation between the July–August precipitation and a significant negative correlation between air temperatures and sorghum yield. We conclude that there was an increasing sorghum harvest area trend in Kansas for the years 2010 to 2022. Further research that identifies more unique and important agronomic and economic advantages of sorghum, increasing productivity per unit area across different environments, communicating existing benefits, and developing crop production management best practices are essential to sustain gains in the production area. Full article

Atmospheric air, being also a moist gas, is present as a working medium in various areas of technology, including the areas of airframe aerodynamics and turbomachinery. Issues related to the condensation of water vapor contained in atmospheric air have been intensively studied analytically, experimentally and numerically since the 1950s. An effort is made in this paper to present new, unique and complementary results of the experimental testing of moist air expansion in the de Laval nozzle. The results of the measurements, apart from the static pressure distribution on the nozzle wall and the images obtained using the Schlieren technique, additionally contain information regarding the quantity and quality of the condensate formed due to spontaneous condensation at the transition from the subsonic to the supersonic flow in the nozzle. The liquid phase was identified using the light extinction method (LEM). The experiments were performed for three geometries of convergent–divergent nozzles with different expansion rates of 3000, 2500 and 2000 s⁻¹. It is shown that as the expansion rate increases, the phenomenon of water vapor spontaneous condensation appears closer to the critical cross-section of the nozzle. A study was performed of the impact of the air relative humidity and pollution on the process of condensation of the water vapor contained in the air. As indicated by the results, both these parameters have a significant effect on the flow field and the pressure distribution in the nozzle. The results of the experimental analyses show that in the case of the atmospheric air flow, in addition to the pressure, temperature and velocity, other parameters must also be taken into account as boundary parameters for possible numerical analyses. Omitting information about the air humidity and pollution can lead to incorrect results in numerical simulations of transonic flows of atmospheric air. The presented results of the measurements of the moist air transonic flow field are original and fill the research gap in the field of experimental studies on the phenomenon of water vapor spontaneous condensation. Full article

Permanent magnet eddy current heating as a new type of wind energy utilization method, which is energy-saving, is zero-emission, and involves no pollution and a high utilization of wind energy, has attracted more and more attention. This paper deals with the simulation and optimal design of a permanent magnet eddy current heater (PMECH) driven by wind. Solid steel, closed-slot, and open-slot PMECH are proposed, and corresponding 2D finite element method (FEM) models are established. Using the skin depth concept, numerical analyses are conducted on the influence of the number, size, and position of copper strips on the thermal power of closed-slot and open-slot PMECHs, and the thermal power growth compared to solid steel PMECH. The results showed that there is an optimal value for stator wall thickness. When the air-gap length is 0.5 mm and the rotation speed is 200 and 1000 rpm, the optimal stator wall thickness is 16 and 9 mm, respectively. Compared to the influence of conductivity on thermal power, the influence of permeability is more significant. Compared with solid steel PMECH, both closed-slot and open-slot PMECH in a low-speed region can effectively improve thermal power, and the open slot has more obvious advantages. The maximum values of the thermal power growth (TPG) and thermal power growth rate (TPGR) of the closed-slot PMECH are 1.57 kW and 120.15%, respectively. The maximums of TPG and TPGR of the open-slot PMECH are 2.58 kW and 175.08%, respectively. The experimental results prove the validity of the analytical calculation. Full article

This article uses numerical simulation methods to study the comprehensive influences of the stator structure and materials on the thermal power of an interior permanent magnet eddy current heater (IPMECH). By analyzing the air-gap magnetic flux density (MFD), stator MFD, thermal power, and torque at different rotational speeds, the mechanism of thermal power enhancement has been revealed in depth. The results indicate that the armature magnetic field (MF) generated by the eddy current produces a magnetization effect on the side of its rotation direction, but the MF in the stator will be weakened in general, and this effect becomes more significant with the increase in the rotational speed. The stator material of the IPMECH has higher permeability, which has higher thermal power and torque, and a lower proportion of high-order harmonics, which is beneficial for reducing the radial vibration of the IPMECH. A permanent magnet with high remanence can increase the thermal power and torque of the IPMECH. Reducing the length of the air gap is beneficial for improving the thermal power, but it also increases the harmonic MFD. The rotational speed is 200 rpm, the air gap is 0.1 mm and 2 mm, and the thermal power is 1.12 kW and 0.35 kW, respectively. The fundamental amplitudes of the 0.1 mm and 2 mm air-gap lengths are 0.94 T and 0.64 T, respectively, and the 3rd harmonic $B_i^{*}$ values are 0.24 and 0.18, respectively. At rotational speeds of 200 rpm, 800 rpm, and 1600 rpm, the ${\delta }_{P_{\max }}$ values are 17 mm, 11 mm, and 8 mm, respectively. When designing a heater, the higher the rotational speed, the smaller the stator wall thickness should be. Full article

This study proposes a positive pressure re-acceleration assisted seeding mechanism and analyzes the motion mechanism of corn seeds during the seeding process. By employing the CFD-EDEM gas-solid coupling simulation analysis method, the fluid characteristics, initial ejection velocity of seeds, seed dropping time difference, and sowing position difference in the seeding mechanism under different structural parameters of the air pressure valve body were investigated. The optimal structural parameters of the air pressure valve body were determined (nozzle gap c = 0.6 mm, throat constriction diameter d = 16 mm, and throat constriction length l = 44 mm). A multi-factor experimental method was used to explore the effects of airflow pressure, forward speed during sowing, and sowing distance on sowing performance, aiming to identify the optimal working parameters for the positive pressure re-acceleration seeding mechanism. High-speed camera technology was used to record and analyze the seed movement process. The results indicate that an increase in positive pressure within the seed guide tube shortens the sowing time of corn seeds, reduces the coefficient of variation of seed dropping time difference, and effectively improves the consistency of sowing distance. The optimal parameters are a forward speed of 8 km/h, sowing distance of 20 cm, airflow pressure of 10 kPa, with a sowing distance coefficient of variation of 7.56%, and a seed dropping time difference coefficient of variation of 5.35%. Full article