Search Results (157)

Steel is an important product in many engineering sectors; however, steelmaking remains one of the largest ${\mathrm{CO}}_2$ emitters. Therefore, new governmental policies drive the steelmaking industry toward a cleaner and more sustainable operation such as the gas-based direct reduction–electric arc furnace process. To become carbon neutral, utilizing more scrap is one of the feasible solutions to achieve this goal. Addressing knowledge gaps regarding scrap heterogeneity (size, shape, and composition) is essential to evaluate the effects of increased scrap ratios in basic oxygen furnace (BOF) operations. This review systematically examines heat and mass transfer correlations relevant to scrap melting in BOF steelmaking, with a focus on low Prandtl number fluids (thick thermal boundary layer) and dense particulate systems. Notably, a majority of these correlations are designed for fluids with high Prandtl numbers. Even for the ones tailored for low Prandtl, they lack the introduction of the porosity effect which alters the melting behavior in such high temperature systems. The review is divided into two parts. First, it surveys heat transfer correlations for single elements (rods, spheres, and prisms) under natural and forced convection, emphasizing their role in predicting melting rates and estimating maximum shell size. Second, it introduces three numerical modeling approaches, highlighting that the computational fluid dynamics–discrete element method (CFD–DEM) offers flexibility in modeling diverse scrap geometries and contact interactions while being computationally less demanding than particle-resolved direct numerical simulation (PR-DNS). Nevertheless, the review identifies a critical gap: no current CFD–DEM framework simultaneously captures shell formation (particle growth) and non-isotropic scrap melting (particle shrinkage), underscoring the need for improved multiphase models to enhance BOF operation. Full article

Compression–ignition engines emit particulate matter (PM) (soot), prompting the widespread use of diesel particulate filters (DPFs) in the automotive sector. An alternative method for PM reduction involves the use of ultrasonic waves to disperse and modify the structure of exhaust particles. This article presents experimental results of the effects of ultrasonic emitter parameters, including the number, arrangement, and power, along with the engine speed, on the exhaust smoke density. Tests were conducted on a laboratory prototype equipped with six ultrasonic emitters spaced 0.17 m apart. The exhaust source was a diesel engine from a construction excavator, based on the MTZ-80 tractor design, delivering 80 HP and a displacement of 4750 cm³. A regression model was developed to describe the relationship between the engine speed, emitter power and spacing, and smoke density. The optimal configuration was found to involve an emitter power of 319.35 W and a spacing of 1.361 m for a given engine speed. Under the most effective conditions—an engine speed of 1500 rpm, six active emitters, and a total power of 600 W—smoke emissions were reduced by 18%. These findings support the feasibility of using ultrasonic methods as complementary or alternative exhaust gas filtration techniques for non-road diesel engines. Full article

Carbon Capture and Storage (CCS) is a key technology for reducing anthropogenic greenhouse gas emissions, in which pipelines play a vital role in transporting CO₂ captured from industrial emitters to geological storage sites. To aid the efficient and safe operation of the CO₂ transport infrastructure, robust, accurate, and reliable solutions for monitoring pipelines transporting industrial CO₂ streams are urgently needed. This literature review study summarizes the monitoring objectives and identifies the problems and relevant mathematical algorithms developed for optimization of monitoring systems for pipeline transportation of water, oil, and natural gas, which can be relevant to the future CO₂ pipelines and pipeline networks for CCS. The impacts of the physical properties of CO₂ and complex designs and operation scenarios of CO₂ transport on the pipeline monitoring systems design are discussed. It is shown that the most relevant to liquid- and dense-phase CO₂ transport are the sensor placement optimization methods developed in the context of detecting leaks and flow anomalies for water distribution systems and pipelines transporting oil and petroleum liquids. The monitoring solutions relevant to flow assurance and monitoring impurities in CO₂ pipelines are also identified. Optimizing the CO₂ pipeline monitoring systems against several objectives, including the accuracy of measurements, the number and type of sensors, and the safety and environmental risks, is discussed. Full article

Air pollution is one of the most serious environmental threats, with particulate matter PM₁₀ and PM_2.5 representing its most harmful components, significantly affecting public health. These particles are primarily generated by transport, industry, residential heating, and agriculture, and are associated with increased incidence of respiratory and cardiovascular diseases, asthma attacks, and heart attacks, as well as chronic illnesses and premature mortality. The most vulnerable groups include children, the elderly, and individuals with pre-existing health conditions. This study focuses on the analysis of health risks associated with PM₁₀ and PM_2.5 air pollution in the city of Zvolen, which serves as a representative case due to its urban structure, traffic load, and industrial activity. The aim is to assess the current state of air quality, identify the main sources of pollution, and evaluate the health impacts of particulate matter on the local population. The results will be compared with selected Slovak cities—Banská Bystrica and Ružomberok—to understand regional differences in exposure and its health consequences. The results revealed consistently elevated concentrations of particulate matter (PM) across all analyzed cities, frequently exceeding the guideline values recommended by the World Health Organization (WHO), although remaining below the thresholds set by current national legislation. The lowest average concentrations were recorded in the city of Zvolen (PM₁₀: 20 μg/m³; PM_2.5: 15 μg/m³). These lower values may be attributed to the location of the reference monitoring station operated by the Slovak Hydrometeorological Institute (SHMÚ), situated on J. Alexy Street in the southern part of the city—south of Zvolen’s primary industrial emitter, Kronospan. Due to predominantly southerly wind patterns, PM particles are transported northward, potentially leading to higher pollution loads in the northern areas of the city, which are currently not being monitored. We analyzed trends in PM₁₀ and PM_2.5 concentrations and their relationship with hospitalization data for respiratory diseases. The results indicate a clear correlation between the concentration of suspended particulate matter and the number of hospital admissions due to respiratory illnesses. Our findings thus confirm the significant adverse effects of particulate air pollution on population health and highlight the urgent need for systematic monitoring and effective measures to reduce emissions, particularly in urban areas. Full article

Heating, Ventilation and Air Conditioning (HVAC) systems are significant carbon emitters in buildings, and precise regulation is crucial for achieving carbon neutrality. Computer vision-based occupant behavior prediction provides vital data for demand-driven control strategies. Real-time multi-person pose estimation faces challenges in balancing speed and accuracy, especially in complex environments. Traditional top-down methods become computationally expensive as the number of people increases, while bottom-up methods struggle with key point mismatches in dense crowds. This paper introduces the Efficient-RTMO model, which leverages the Parameter Inverted Image Pyramid (PIIP) with hierarchical multi-scale symmetry for lightweight processing of high-resolution images and a deeper network for low-resolution images. This approach reduces computational complexity, particularly in dense crowd scenarios, and incorporates a dynamic sparse connectivity mechanism via the star-shaped dynamic feed-forward network (StarFFN). By optimizing the symmetry structure, it improves inference efficiency and ensures effective feature fusion. Experimental results on the COCO dataset show that Efficient-RTMO outperforms the baseline RTMO model, achieving more than 2× speed improvement and a 0.3 AP increase. Ablation studies confirm that PIIP and StarFFN enhance robustness against occlusions and scale variations, demonstrating their synergistic effectiveness. Full article

The context of this study is the geolocation of signal emitters on the Earth’s surface through satellite platforms able to perform Angle of Arrival (AOA) measurements. This paper provides the theoretical framework to solve the optimization problem for the orbital deployment of the satellites minimizing the variance on the position error estimation with constraints on the line of sight (LOS). The problem is theoretically formulated for an arbitrary number of satellites in Low Earth Orbit (LEO) and target pointing attitude, focusing on minimizing the Position Dilution of Precision (PDOP) metric, providing a methodology for translating mission design requirements into problem formulation. An exemplary numerical application is presented for the operative case of the placement of a second satellite after a first one is launched. Simulation results are on angles of true anomaly, right ascension of the ascending node, and spacing angle, while accounting for orbital radius and emitter latitude. New insights on trends, parameter dependencies, and properties of symmetry and anti-symmetry are presented. The topic is of interest for new technological demonstrators based on CubeSats with AOA payload. Civil applications of interest are on interceptions of non-cooperative signals in activities of spectrum monitoring or search and rescue. Full article

This article discusses the superionic glassy GeS₂-Sb₂S₃-AgI system with mobile silver ions as a material for creating new energy-efficient solid-state ion emitters. The effect of replacing silver iodide with germanium sulfide on the structure of the electrolyte, activation energy of diffusion, and specific ionic conductivity was studied. Electrolytes (2.5 + x)GeS₂-27.5Sb₂S₃-(70 − x)AgI, x = 0, 5, 10, 15 were synthesized using the melt-quenching technique in evacuated quartz ampoules. The temperature dependence of conductivity and glass stability parameters (Hruby’s, Weinberg’s and Lu–Liu’s) were determined for them, and the mechanism for increasing glass-forming ability was clarified. It was shown that the presence of iodine in a germanium structural unit is more preferable than in an antimony structural unit; germanium structural units compete for iodine, reducing the number of SbI₃ crystallization centers and chain terminations, resulting in additional structural connectivity and stability. It was shown that when silver iodide was replaced by germanium sulfide, the decrease in conductivity due to the reduction in charge carriers was less than expected due to the expansion of the conduction channels. Full article

Against the backdrop of global climate change and rapid urbanisation, carbon-neutral urban governance and sustainable urban development have become core issues of concern to the international community. As the world’s largest carbon emitter, Chinese cities shoulder the significant responsibility of achieving the “dual-carbon” goal. This study utilised a unique panel dataset of 300 cities in China from 2015 to 2022 and proposed a multi-dimensional analytical framework from the perspective of environmental sociology. This paper empirically examines the impact mechanism of carbon-neutral governance on urban sustainable development and its regional heterogeneity by using this framework. The research findings are as follows: First, carbon-neutral governance has a significant promoting effect on the sustainable development of cities. Secondly, technological input (the number of scientific researchers) plays a significant mediating role between carbon-neutral governance and sustainable development, indicating that technology diffusion is an important way for the transmission of policy effects. Thirdly, the analysis of regional heterogeneity indicates that due to policy inclination and resource concentration, western cities contribute the most to sustainable development, followed by eastern cities, and central cities contribute the least to sustainable development. The eastern region was identified as the second weakest and the central region as the weakest. This research provides theoretical and empirical basis for differentiated formulation of carbon neutrality policies, strengthening scientific and technological support, and optimising regional collaborative governance. Full article

Bifacial solar cells are the leading technology, and the number of steps in the manufacturing process influences the processing time and production cost. The goal of this paper is to optimize the boron back surface field (B-BSF) produced with reduced thermal steps and to analyze its influence on the electrical parameters and bifaciality coefficients of p-type bifacial PERT solar cells. The boron diffusion and a silicon oxide layer grown as a phosphorus diffusion barrier were carried out in a single thermal step, according to the patent granted BR102012030606-9. The sheet resistance of the emitter and B-BSF were not affected by the reduced thermal steps, demonstrating the effectiveness of the silicon oxide layer as a barrier to phosphorus diffusion in the boron-doped side. The short-circuit current density with incident irradiance on the boron-doped side was impacted by the B-BSF sheet resistance, affecting the efficiency and the maximum power bifaciality coefficient. The high recombination in the pp⁺ region limited the maximum power bifaciality coefficient to approximately 0.7, which is typical in p-type solar cells. Considering the achieved results, the boron and phosphorus diffusion performed with reduced thermal steps produces bifacial p-PERT solar cells with typical bifaciality, avoiding two thermal steps for silicon oxide growth and chemical etching and cleaning. Full article

As the global ecological environment faces serious challenges and extreme climate change threatens the survival of humankind, the promotion of green development has become the focus for all countries in the world. As one of the world’s major greenhouse gas emitters, China has put forward the “twin goals” of achieving carbon peaking and carbon neutrality and is committed to promoting the green and low-carbon transformation of its cities. As the core of economic and social development, cities are the main source of carbon emissions. In response to the dual challenges of carbon emission control and traffic growth, it is particularly important to promote the development of green transportation. With the acceleration of urbanization, urban traffic pollution is becoming more and more serious. As a zero-emission transportation mode, electric vehicles have become a key way to achieve the carbon peak and carbon neutrality targets. In order to deeply analyze the research status of electric vehicles in the field of the green and low-carbon transformation of urban transportation in China and to explore the research hot spots, evolution trends, and their roles and strategies in the construction of green transportation networks, this paper uses the CiteSpace, VOSviewer, and Tableau analysis tools to review and analyze the 2460 articles and reviews in the Web of Science Core Collection (WOS) and 2650 articles and reviews in the China National Knowledge Infrastructure (CNKI), including the “publication volume and publication trend”, “subject citation path”, “countries cooperation and geographical distribution”, “author cooperation and institution cooperation”, “keyword co-occurrence and keywords clusters”, and the “evolution trend of research hot spots in timeline”. The results show that: (1) Since 2010, the research focus on electric vehicles has gradually increased, and especially in the past three years, the number of such publications has increased significantly. (2) China holds the lead in research output regarding electric vehicles and related fields, but its international cooperation needs to be strengthened. (3) In recent years, the research has focused on “energy transformation”, “energy-saving technology”, “carbon emissions”, “battery recycling”, and other relevant topics. The promotion and development of electric vehicles will continue to usher in new opportunities concerning technological innovation, policy support, and market expansion. Finally, based on the research hot spots and evolution trends of electric vehicles in the field of urban green transportation and low-carbon transportation in China, this paper discusses the key paths and strategies for electric vehicles to promote the transformation of urban transportation in China to green and low-carbon types and looks forward to future research directions. The research in this paper can provide theoretical support and practical guidance for China to promote electric vehicles, build low-carbon cities, and realize green transportation. It is expected to act as a useful reference for relevant policy formulation and academic research. Full article

This paper focuses on the modeling challenges of a multi-cell heterojunction bipolar transistor (HBT) used in radio frequency (RF) power amplifiers and proposes an innovative linear small-signal modeling method. Based on devices with an emitter size of 3 μm × 40 μm × 2–6 (emitter width × emitter length × emitter index-cell number), an equivalent circuit model including peripheral parasitic parameters is constructed by analyzing device layout characteristics in response to additional parasitic effects introduced by the multi-cell structure. A step-by-step parameter extraction method is used, with particular attention paid to the correction of saturated current parameters, temperature coefficients, thermal resistance correction, and the optimization of junction capacitance parameters based on the capacitance ratio relationship. After the extraction of parasitic parameters, the input and output reflection coefficient errors of the model under zero-bias conditions are below 1.66% in the 0.7–25 GHz frequency band. The accuracy of this model is significantly improved compared to the directly parallel single-cell model. The power simulation results match the measured results very well at frequencies of 2.6 GHz and 3.5 GHz. This modeling method significantly improves the model accuracy of multi-cell HBT devices in RF circuit design and provides an effective tool for high-power amplifier optimization. Full article

The localization of radio emitters is a fundamental task in reconnaissance systems, and it has become increasingly important with the evolution of mobile networks. The signal Doppler frequency (SDF) method, developed for dual-use applications, leverages Doppler frequency shifts (DFSs) in received signals to estimate the positions of radio transmitters. This paper proposes enhancements to the SDF method through advanced signal processing techniques, including dedicated filtering and a novel two-level overlapping approach, which significantly improve localization accuracy. The overlapping technique increases the number of DFS estimations per time unit by analyzing overlapping segments at both the signal sample level and within the DFS vector. Simulation studies using various filter types and overlapping parameters were conducted to evaluate the effectiveness of these enhancements in a dynamic scenario involving multiple stationary transmitters and a single moving receiver. The results demonstrate that the proposed approach minimizes localization errors. The application of low-pass filtering at the DFS vector level improves localization accuracy. In the study, three types of filters for different cutoff frequencies are considered. Each of the analyzed filters with an appropriately selected cutoff frequency provides a comparable reduction in localization error at the level of about 30%. The use of overlapping at the signal sample level with a factor of 10% allows for more than a twofold decrease in localization errors, while overlapping at the DFS vector provides an increase in the refresh rate of the position of localized objects. Comparative analysis with direct position determination techniques additionally showed high effectiveness of the SDF method, especially using data filtration and overlapping. The simulation studies carried out are of significant importance for the selection of the operating parameters of real localization sensors in unmanned aerial vehicle (UAV) equipment. Full article

This study presents a parametric analysis of the factors impacting particle distribution within a bus environment using computational fluid dynamics (CFD) simulations, with a primary focus on the relative concentration (RC) of particles. The Novel Relative Concentration (RC) metric, which measures the deviation from a return concentration, was used to assess the effects of ventilation rates, the number and spatial arrangement of particle emitters, and thermal conditions. Our investigation reveals that increasing air changes per hour (ACHs) from 5.74 h⁻¹ to 28.66 h⁻¹ reduces the overall particle concentration by approximately 45%, but localized high concentration zones persist, with maximum RC values observed at 1.57. Scenarios with evenly distributed emitters achieved near-uniform particle distribution, with RC values averaging around 0.95, while clustered emitters resulted in localized high concentrations, with RC values exceeding 2.0. Thermal conditions were found to have a minimal effect on RC, with average values of 1.664 for cooling and 1.588 for heating, showing only a 4.68% difference. The RC metric provided clear insights into the non-uniformity of particle distribution, highlighting areas prone to higher concentrations, with some zones reaching RC values of 2.5, indicating concentrations 2.5 times higher than the well-mixed average. These findings underscore the importance of optimizing ventilation systems for both overall air exchange and uniform air distribution, offering practical implications for improving air quality and reducing the risk of airborne pathogen transmission in public transportation systems. Future research should explore real-time ventilation adjustments based on passenger load, the effects of different particle types, and the development of models incorporating human behavior and movement patterns. Full article

Targeted Auger emitters are being considered as a cancer treatment owing to the high linear energy transfer of Auger electrons. When targeted to cancers, this allows for a highly efficient treatment with a low risk of damage to surrounding healthy tissue. The purpose of this study was to determine the most DNA-damaging Auger emitters from a range of radionuclides, some of which are clinically utilised. A Monte Carlo method-based software (Geant4-DNA version 10.7) was used to determine the energy deposition and number of DNA double-strand breaks from Auger (and internal conversion) electrons imposed on a tetranucleosome. The Auger emitters, ¹¹⁹Sb and ¹⁰³Pd, have similar or slightly greater damaging properties compared to ¹²³I, ¹¹¹In, and ⁸⁹Zr. ^193mPt demonstrated the greatest therapeutic potency. Whilst ¹²⁵I was highly damaging, its relatively long half-life (60 days) makes it less desirable for clinical use. Geant4-DNA modelling identified the radionuclide ^193mPt as being highly favourable for use in radiotherapy. Full article

We report the results of a zinc oxide (ZnO) low-power microsensor for sub-ppm detection of NO₂ and H₂S in air at 200 °C. NO₂ emission is predominantly produced by the combustion processes of fossil fuels, while coal-fired power plants are the main emitter of H₂S. Fossil fuels (oil, natural gas, and coal) combined contained 74% of USA energy production in 2023. It is foreseeable that the energy industry will utilize fossil-based fuels more in the ensuing decades despite the severe climate crises. Precise NO₂ and H₂S sensors will contribute to reducing the detrimental effect of the hazardous emission gases, in addition to the optimization of the combustion processes for higher output. The fossil fuel industry and solid-oxide fuel cells (SOFCs) are exceptional examples of energy conversion–production technologies that will profit from advances in H₂S and NO₂ sensors. Porosity and surface activity of metal oxide semiconductor (MOS)-based sensors are both vital for sensing at low temperatures. Oxygen vacancies (${\mathbf{V}}_{\mathbf{O}}^{••}$) act as surface active sites for target gases, while porosity enables target gases to come in contact with a larger MOS area for sensing. We were able to create an open porosity network throughout the ZnO microstructure and simultaneously achieve an abundance of oxygen vacancies by using a heat treatment procedure. Surface chemistry and oxygen vacancy content in ZnO were examined using XPS and AES. SEM was used to understand the morphology of the unique characteristics of distinctive grain growth during heat treatment. Electrical resistivity measurements were completed. The valance band was examined by UPS. The Engineered Porosity approach allowed the entire ZnO to act as an open surface together with the creation of abundant oxygen vacancies (${\mathbf{V}}_{\mathbf{O}}^{••}$). NO₂ detection is challenging since both oxygen (O₂) and NO₂ are oxidizing gases, and they coexist in combustion environments. Engineered porosity ZnO microsensor detected sub-ppm NO₂ under O₂ interference, which affects mimicking realistic sensor operation conditions. Engineered porosity ZnO performed better than the previous literature findings for H₂S and NO₂ detection. The exceptionally high sensor response is attributed to the high number of oxygen vacancies (${\mathit{V}}_{\mathit{O}}^{••}$) and porosity extending through the thickness of the ZnO with a high degree of tortuosity. These features enhance gas adsorption and diffusion via porosity, leading to high sensor response. Full article