Mobile Sources Research Articles

TOA based mobile source localization with unknown start transmission time and sensor position uncertainty in asynchronous networks

ABSTRACT This letter addresses the issue of mobile source localization using time of arrival (TOA) measurements in scenarios where the source and sensors are not synchronized, and the start transmission time is unknown. We propose a non-convex weighted least squares (WLS) minimization problem for estimating the source position, velocity and start transmission time from the distance measurement equation, without the need for Taylor approximation commonly used in traditional processing approaches. To effectively solve the non-convex WLS optimization problem, we use the semi-positive definite relaxation (SDR) technique to transform the original problem into a convex semi-positive definite programming (SDP) problem. Additionally, we further extend the proposed method to scenarios where the positions of sensors are uncertain. Computer simulation results demonstrate that the proposed method surpasses the existing methods, whether the positions of sensors are known or uncertain.

Real-time correction of light dilution effect for ship emission monitoring of SO2

With the rapid development of the shipping industry, ship emissions have become a focal point in environmental protection. SO2, as a major component of ship emissions, is crucial to monitor to ensure environmental compliance. SO2-sensitive ultraviolet (UV) cameras represent an advanced emerging technology for remote sensing monitoring of ship emissions. However, as monitoring distance increases, errors in the monitoring results due to the light dilution (LD) effect rise significantly. The aim of this study is to address the LD effect in SO2 monitoring for mobile pollution sources and propose a real-time correction method. Based on the atmospheric radiative transfer model and developed data processing algorithms, the method corrects the LD effect in real-time, enhancing the accuracy and reliability of SO2 UV camera monitoring. Experimental data collected from ship emissions at Yantai port are used to validate the accuracy of the correction method. Results show that the LD effect can lead to a 60% underestimation in the monitoring results at a distance of 4 km. The proposed method effectively corrects the LD effect, improves the accuracy of the monitoring results, lays the foundation for the engineering application of UV cameras in ship exhaust monitoring, and therefore promotes the wide application of UV cameras in air quality monitoring and environmental protection.

Sulfur-resistant catalytic NO oxidation over surface-disproportionated CaMnO3 perovskites

A highly active CaMnO3 perovskite catalyst (CMO-H) was fabricated for NO oxidation, a key reaction in the control of NOx emissions from mobile and stationary sources, by tuning the average oxidation state of Mn on the surface via acid-initiated Mn disproportionation. In-depth structure-performance investigations suggest that an increased abundance of surface Mn4+ on CMO-H is responsible for its high activity. Doping with a tiny amount of Pd promoted the formation of reactive oxygen species on the CMO-H surface, leading to a further increase of NO oxidation activity which was largely sustained even in the presence of CO and hydrocarbons. Strikingly, an increased SO2-resistance was achieved over the Pd-doped CMO-H, due to an alleviation of surface sulfate formation by Pd. Our study sheds new lights on the rational fabrication of active, poisoning-resistant and cost-effective oxide catalysts for NO oxidation, which is an important reaction in various environmental and industrial applications.

Selenium-modulated Pt/Al2O3 electronic structure induces deactivation during catalytic CO oxidation

Industrial sources, such as steel and power activities continue to emit substantial amounts of CO, but have not received the same level of attention as mobile sources due to a lack of relevant regulations. This work reports that a commercial Pt/Al2O3 catalyst used in vehicle CO catalytic converters may face severe selenium (Se) poisoning deactivation from industrial sources. The turnover frequency (TOF) of the Pt/Al2O3 catalyst (250 °C) decreased from 2.18 s−1 to 0.12 s−1 with only 0.49 wt% (ICP) Se deposition. Se deposition causes the Pt 5d orbital shift to a higher energy state, raising the oxidation state of platinum. As a result, the back-donation from the 5d electrons of Pt to the 2π* antibonding orbital of the adsorbed CO molecule is inhibited, weakening the bonding between Pt/Al2O3 and the CO antibonding orbital, thereby significantly reducing CO activation ability. DRIFTS results, combined with apparent and microscopic kinetics, indicate that the surface of Se deposited Pt/Al2O3 catalyst remains O* available (500 K, θO* = 0.16), and the rate-controlling step changes from O2 + 2* → 2O* to CO + * → CO*. The work suggests that the application of CO catalytic oxidation technology for industrial source should fully consider the toxic effect of Se, but is often neglected.

Multicity accountability and uncertainty assessment of the impacts of regulations on air quality in Atlanta, New York City, and Southern California

Multiple regulations have been promulgated to improve air quality, and previous studies have used an accountability chain to evaluate the effects of these regulations on emission levels, air quality, and human health. However, quantifying these impacts through the accountability chain is complex due to interactions between multiple factors that can influence the efficacy of control policies and introduce uncertainties at each step. We evaluated and quantified the impact of emission controls on electricity generating units (EGU) and motor vehicle sources on emissions and air quality via Generalized Additive Models. These GAMs have minimal bias (around 10−5 to 10−2 μg/m3 or ppbV) and r2 values for daily concentrations ranging from 0.4 to 0.7 Counterfactual air pollutant concentrations, in the absence of EGU and mobile source regulations, were calculated using estimated counterfactual emissions for the period 2005 to 2019 in Atlanta, New York City, and California's South Coast Air Basin. Counterfactual air pollutant concentrations indicated that the effects of regulations on air pollutants varied depending on the season and location. Predicted counterfactual air pollutant concentrations were generally 2–12 times higher than the measured concentrations at these sites, except for ozone. The impact of regulations on ozone concentrations typically resulted in reduced peak ozone values in the summer, but increased concentrations in the winter. Monte Carlo modeling found small to modest uncertainties, depending on the pollutant, location and regulations assessed. Counterfactual concentrations predicted in this project will be used in the assessment of the trends of toxicity in PM2.5.

Sources and their contributions of ambient PM2.5 concentrations in an industrial area of Atlanta from 1998 to 2016

The SouthEastern Aerosol Research CHaracterization (SEARCH) program examined air quality at 6 sites across the southeastern United States. The Jefferson Street site in Atlanta operated from 1998 to 2016 with the collection and chemical characterization of PM2.5 that provide data suitable for source identification and apportionment with a sufficiently long time series to permit effective trend analyses. Although there have been analyses of parts of these data, there is no prior comprehensive analysis relating the changes in source-specific PM2.5 with policy implementations and economic drivers. The major sources were secondary sulfate, traffic sources (spark- and compression-ignition vehicles), and secondary nitrate. Several local industrial sources were identified primarily assigned as metal working, but likely including a nearby bus maintenance garage. A combined biomass burning and pyrolyzed organic carbon factor was resolved that reflected the extensive prescribed burning that occurred in the southeastern United States to control larger wildfires and that increased in recent years. The major trends were reductions in concentrations of sulfate and nitrate likely as a result of policies to reduce emissions from coal-fired power plants and mobile sources. Gasoline vehicle contributions uniformly declined, but there was a period of increase diesel concentrations in the middle of the study period for which the cause is unknown.

Indoor and ambient influences on PM2.5 exposure and well-being for a rail impacted community and implications for personal protections

Abstract Background
Higher air pollution concentrations can be observed near rail networks, local and highway automobile corridors, and shipyards. Communities adjacent to such sources are disproportionately exposed to air pollution from these stationary and mobile sources. One such community is West San Bernardino in California, where households are feet away from the Burlington Northern Santa Fe intermodal facility and are impacted by activities that are estimated to continuously emit air pollutants due to 24/7 operation.
Objective
This study aimed to (1) quantify the impact of personal mobility and housing characteristics on daily PM2.5 exposures and well-being for West San Bernardino community members, and (2) develop individualized resilience plans for community collaborators to support future PM2.5 exposure reduction. 
Methods
Personal PM2.5 exposures were measured for community collaborators for seven consecutive days during three deployment periods: October 2021, January 2022, and March 2022. Indoor and ambient PM2.5 levels were also continuously measured for five households over six months using PurpleAir Classic monitors. Demographic and well-being data were collected upon recruitment and after each week of engagement, respectively. 
Results
Personal exposures in home microenvironments were highest near the railyard and lower farthest away from the railyard. Home exposures were 40% higher on average compared to non-home microenvironments. Household PM2.5 had a higher-than-expected average infiltration factor of 0.55, and indoor 98th percentiles across the households far exceeded a healthy level at an average of 165 μg/m3. Resilience plans featured summaries of personal data and recommendations for mitigating exposures. 
Significance
Results suggest that surrounding land use and residential building characteristics compound to worsen air pollution exposures beyond what is expected for exposures in non-industrialized areas. Findings prompt a call for stronger regulation, not only for emissions, but also for indoor air quality and zoning standards that specifically protect disproportionately impacted communities.

Empowering microgrids for sustainable transportation electrification: A comprehensive methodology for resource adequacy and grid resilience

Transportation electrification has emerged as a pivotal solution to mitigate carbon emissions from the transportation sector. However, this shift towards electric vehicles (EVs) presents significant challenges for municipalities and utilities, particularly in ensuring the electrical grid's capacity to meet the increased demand. In this sense, this work introduces a novel methodology to address these challenges by 1) quantifying the impact of EVs on the hosting capacity (HC) of residential microgrids (MGs), and 2) proposing a novel control strategy to meet grid resource adequacy requirements under high levels of transportation electrification. For this, first, a simplified approach to quantify the overall demand in residential MGs, accounting for the influence of EVs and typical demand profiles based on real-world data from municipalities and utility systems is developed. Second, a new frequency controller is introduced, utilizing Distributed Phasor Measurement Units (D-PMU) and mobile energy sources (MES) to ensure compliance with resource adequacy requirements under high levels of EVs penetration. The proposed controller takes advantage of the low latency and high-resolution capabilities of D-PMU technology to enable the harnessing of MES, preventing critical frequency nadir events, and improving the overall system resource adequacy performance under both transient and steady-state analysis. Real-world data from Seattle, WA, USA, is used in the developed case studies, and comparative analysis between traditional SCADA, state-of-the-art D-PMU-based controller, and the proposed controller is presented. The obtained results indicate that significant improvements are achieved by the proposed controller, empowering utilities to ensure reliable operations amidst transportation electrification challenges imposed on resource adequacy.

Labour process theory: in and beyond the core: continuities, challenges, and choices

Since the publication of Braverman’s seminal Labor and Monopoly Capital (1974), labour process theory (LPT) has become a successful theory-building project driven by empirical expansion and conceptual innovation, operating as the equivalent of a normal science, with a distinctive scope and specific empirical focus on workplace regimes in the context of capitalist political economy. It’s toolkit or conceptual architecture combines underpinning and ordering principles with contingent and flexible operational categories concerning labour power and control. Though LPT has built stronger conceptual connections between workplace and accumulation regimes, changes in the global order have brought new theoretical and empirical challenges that are requiring it to adjust some of its core concepts and boundaries to consider development such as new sources of labour power, migration, and mobility.

Resilience enhancement of cyber–physical distribution systems via mobile power sources and unmanned aerial vehicles

Mobile power sources (MPS) and unmanned aerial vehicles (UAV) are critical and flexible resources to enhance the resilience of cyber–physical distribution systems. However, they are usually independently planned and dispatched. In this paper, considering the cyber–physical interdependence, topology reconfiguration and planned distribution generator islanding, an allocation and dispatch strategy of MPSs and UAVs is proposed. Before an event, a two-stage stochastic optimization based allocation model is built to pre-position MPSs and UAVs considering the uncertainty of events. After the event, a dispatch model is proposed to identify routings of MPSs and UAVs to restore electricity services. Note that both the models are mixed-integer nonlinear three-dimensional (3D) problems. As the optimal service radius and height of a UAV are independent with other variables, these two models are decomposed into two parts, i.e., one part to calculate the optimal service radius and height, and the other to identify resilience enhancement strategy. Then the two models are transformed into a mixed-integer convex programming solved by Progressive Hedging algorithm and a mixed-integer second-order cone programming, respectively. The effectiveness is verified on the modified IEEE 33-node and 123-node test systems. Numerical results highlight the necessity of co-optimizing MPSs and UAVs on cyber–physical distribution systems.

Bi-Directional Charging with V2L Integration for Optimal Energy Management in Electric Vehicles

Electric vehicles (EVs) are becoming increasingly popular as an efficient transportation solution but they also present unique challenges for energy management. Bi-directional charging (BDC) is a solution that allows EVs to not only consume energy from the grid but also supply energy back to the grid. This facilitates vehicle-to-load (V2L) integration, where EVs can act as mobile power sources for homes, buildings, and the grid. V2L enables better energy management by utilizing EVs as a flexible resource to balance grid demand and supply in the proposed system. This is achieved through intelligent coordination between the EVs, charging stations, and the grid, using smart meters and communication networks. Integration of BDC and V2L also enables EVs to provide backup power during grid outages, reduce the need for costly grid infrastructure, and support renewable energy integration. BDC with V2L integration is a promising approach for optimal energy management in EVs and can play a significant role in the future of sustainable transportation and energy systems. The proposed model reached 95.13% charging efficiency, 95.03% energy management, 95.69% power rating, 96.28% voltage support and 87.99% temperature management.

Research on the process of heat transfer between mobile variable temperature heat source and thermoacoustic plate

The purpose of this paper is to analyze the effects of several easy-to-operate parameters (operating frequency, plate stack length, plate stack position, and amplitude) on the refrigeration performance, to explore the optimization path of thermoacoustic refrigerator, and to provide a design basis for further cost reductions. The heat transfer process between the air mass and the plate was investigated as an object, and the physical and mathematical models of the heat transfer process were established. The gas microcluster moving heat and plate stack temperature difference were taken as the response. Operating frequency, plate position, plate length and gas vibration displacement amplitude were the design factors. The change relationship of the system response under the interaction of factors was analyzed by using the central composite experimental design and the response surface method, and experimental verification was carried out. The results show that the deviation of the predicted model from the experimental data is less than 5.9 % when the operating frequency is in the range of 0 Hz–12 Hz, and that the location of the plate stack is 0.45 from the pressure belly point of the sound field, where the heat of the air mass transfer is the largest.

Pollutant Dispersion of Aircraft Exhaust Gas during the Landing and Takeoff Cycle with Improved Gaussian Diffusion Model

Evaluating aviation emissions and examining the dispersion properties of contaminants are crucial for understanding atmospheric pollution. To assess the pollutant emissions and dispersion of aircraft during the landing and takeoff (LTO) cycle, and address air pollution surrounding the airport resulting from flight operations, this study evaluated emissions throughout the LTO phase based on Quick Access Recorder (QAR) data in conjunction with the first-order approximation method. An improved Gaussian diffusion model for mobile point sources was employed to examine the diffusion characteristics of contaminants. Additionally, CFD calculation outcomes for various exhaust velocities and wind speeds were utilized to validate the trustworthiness of the improved Gaussian model. The discussion also encompasses the influence of diffusion time, wind direction, wind speed, temperature gradient, and particle deposition on the concentration distribution of contaminants. The findings indicated that the Gaussian diffusion model aligned with the results of the CFD calculations. The diffusion distribution of contaminants around airports varies over time and is significantly influenced by atmospheric environmental factors, including wind direction, wind speed, and atmospheric stability. Specifically, a change in wind direction from 0° to 45° caused a shift of approximately 1000 m in the contaminant’s center. An increase in wind speed from 3 m/s to 5 m/s led to a decrease in concentration by about 15%. Furthermore, a transition in atmospheric stability from category ‘a’ (very unstable) to ‘f’ (very stable) resulted in a two-order-of-magnitude increase in contaminant concentrations.

Pinpointing sources of pollution using citizen science and hyperlocal low-cost mobile source apportionment

Currently, methodologies for the identification and apportionment of air pollution sources are not widely applied due to their high cost. We present a new approach, combining mobile measurements from multiple sensors collected from the daily walks of citizen scientists, in a high population density area of Birmingham, UK. The methodology successfully pinpoints the different sources affecting the local air quality in the area using only a handful of measurements. It was found that regional sources of pollution were mostly responsible for the PM2.5 and PM1 concentrations. In contrast, PM10 was mostly associated with local sources. The total particle number and the lung deposited surface area of PM were almost solely associated with traffic, while black carbon was associated with both the sources from the urban background and local traffic. Our analysis showed that while the effect of the hyperlocal sources, such as emissions from construction works or traffic, do not exceed the distance of a couple of hundred meters, they can influence the health of thousands of people in densely populated areas. Thus, using this novel approach we illustrate the limitations of the present measurement network paradigm and offer an alternative and versatile approach to understanding the hyperlocal factors that affect urban air quality. Mobile monitoring by citizen scientists is shown to have huge potential to enhance spatiotemporal resolution of air quality data without the need of extensive and expensive campaigns.

Catalytic hydrolysis of HCN on the coupled sites of Lewis acid and surface hydroxyl of Fe-BEA catalyst leading to the presence of HCHO positively affects NH3-SCR activity

Formaldehyde (HCHO) in the exhaust gas of diesel or natural gas engines is usually considered to be a serious hindrance to the NH3-SCR process. However, the promotion effects of HCHO on the NH3-SCR activity and its temperature dependence were discovered in this work for the first time. For the Fe-BEA catalysts, below 300 °C, a notable decrease in activity observed, up to 40 % at 300 °C, and HCN selectivity reached 35 %. However, with the increase in temperature, a significant promotion effect was produced. Not only for the increase of NOx conversion, but also the diminish of the by-product HCN. The disparity in the number and activity of Lewis acid sites (Fe3+) and surface hydroxyls was the primary reason why Fe-BEA catalysts with varying Fe contents exhibited different influence. The presence of HCHO resulted in a modification of the oxidation pathway of NH3 at high temperatures. Surface hydroxyls facilitated the hydrolysis reaction of the as-formed HCN to produce NH3, with NH3 on Lewis acid sites subsequently re-participating in the SCR process. This enhanced the NOx conversion and the selectivity of carbon-containing products. Furthermore, it was demonstrated that HCHO completely converted to hexamethylenetetramine (HMTA) by reacting with NH3 prior to passing through the SCR catalyst. The thermal decomposition of HMTA on the catalyst was identified as a crucial step for the subsequent generation of HCN, and the detailed mechanism of how to effectively inhibit the decrease of de-NOx activity and the formation of HCN in the HCHO-containing NH3-SCR conditions was elucidated. This study paves the way for the development of effective SCR catalysts for the synergistic control of HCN from mobile and stationary sources.

High-resolution observations of shallow-water acoustic propagation with distributed acoustic sensing.

Distributed acoustic sensing (DAS), converting fiber-optic cables into dense acoustic sensors, is a promising technology that offers a cost-effective and scalable solution for long-term, high-resolution studies in ocean acoustics. In this paper, the telecommunication cable of Martha's Vineyard Coastal Observatory (MVCO) is used to explore the feasibility of cable localization and shallow-water sound propagation with a mobile acoustic source. The MVCO DAS array records coherent, high-quality acoustic signals in the frequency band of 105-160 Hz, and a two-step inversion method is used to improve the location accuracy of DAS channels, reducing the location uncertainty to ∼2 m. The DAS array with refined channel positions enables the high-resolution observation of acoustic modal interference. Numerical simulations that reproduce the observed interference pattern suggest a compressional speed of 1750 m/s in the sediment, which is consistent with previous in situ geoacoustic measurements. These findings demonstrate the long-term potential of DAS for high-resolution ocean acoustic studies.

Comparison of aerosol number size distribution and new particle formation in summer at alpine and urban regions in the Guanzhong Plain, Northwest China

Ultrafine particles play a crucial role in understanding climate change, mitigating adverse health effects, and developing strategies for air pollution control. However, the factors influencing the occurrence and development of new particle formation (NPF) events, as well as the underlying chemical mechanisms, remain inadequately explained. This study compared number concentrations and size distributions of atmospheric ultrafine particles at Xi'an (urban area) and the summit of Mt. Hua (alpine region) in summer to investigate the NPF mechanism and particle growth in both clean and polluted areas of the Guanzhong Plain. The average particle number concentration in Xi'an was significantly higher than that at Mt. Hua. The diurnal variation of total particle number concentration differed between Xi'an and Mt. Hua indicating a divergence in influencing factors. The size distributions in Xi'an varied across different timescales and weather conditions, whereas Mt. Hua exhibited little variation. This stability at Mt. Hua is attributed to its cleaner background atmosphere and the steady influx of aging particles with larger diameters transported from the free atmosphere. In both areas, geometric mean diameters (GMDs) were inversely proportional to particle number concentrations suggesting that increase in particle numbers were primarily due to the generation of smaller particles. The potential governing factors for NPF events differed somewhat between the urban and mountainous stations. In the urban area, intense local stationary and mobile emission sources promoted the growth of newly formed nanoparticles, with ozone-oxidized condensable vapors serving as key precursors. In contrast, at the mountainous station, NPF process were significantly influenced by anthropogenic precursors from long-range transport and locally emitted biogenic organics. The rapid increase in ultrafine particle concentrations primarily poses serious health risks and degrades air quality in urban areas, while also contributing to climate-related effects in alpine regions.

Selective Catalytic Reduction of Nitrogen Oxides with Hydrogen (H2‐SCR‐DeNOx) over Platinum‐Based Catalysts

AbstractSelective catalytic reduction of NOx with hydrogen (H2‐SCR‐DeNOx) is applied among other techniques (i. e., SCR‐DeNOx by applying NH3 or hydrocarbons as reducing agents) to control nitrogen oxides from mobile and stationary sources. As a zero carbon technology, which efficiently reduces NOx below 200 °C, H2‐SCR‐DeNOx has gained attention in installations and plants with H2 availability. The catalytic properties of platinum‐based catalysts with the main focus on the applied supports (i. e., inorganic oxides and zeolites) are given in detail. Another focus concerns on how the feed composition affects catalytic properties, specifically the levels of oxygen, water vapor, sulfur, and carbon oxides present in the exhausts. The major challenges are presented in enhancing the N2 selectivity and stability of catalysts at low temperatures without affecting their activity. Promising research prospects in this area include the development of catalysts with improved dispersion and distribution of Pt particles. In addition, the proposed bi‐functional (dual‐function) reaction mechanism over Pt‐containing catalysts, together with the adsorption/dissociation mechanism and NO oxidation/reduction mechanism, is described and critically reviewed. Also, Pd‐based catalysts are briefly discussed. It is expected that the review will provide broad insights into the design and optimization of catalysts in the H2‐SCR‐DeNOx.

Optimization of Ionomer for High‐Performance Self‐Humidifying Air‐Breathing Proton‐Exchange Membrane Fuel Cells in Portable Device Power Systems

This study investigates the impact of ionomer types and content in the catalyst layer on the performance of proton exchange membrane fuel cells (PEMFCs) under room temperature and atmospheric pressure. Four commercially available ionomers with varying equivalent weights (EWs) and side‐chain lengths are evaluated as catalyst layer binders in membrane‐electrode assemblies (MEAs). The assessments are conducted at room temperature and ambient pressure without additional humidification, focusing on understanding the distinctive characteristics of each ionomer. In addition, this study investigates the prospective application of an air‐breathing passive‐type cell, dependent exclusively on natural convection for air supply. The notable performance of the passive‐type cell shown in this study indicates its suitability as a compact mobile power source, especially for drone applications. Furthermore, the stability of various ionomer binders is also compared to establish a correlation between EW and side‐chain length of ionomer binder stability. Overall, the findings will serve as a valuable reference for optimizing ionomer selection and composition in specialized applications for powering portable devices.

Recent Progress on Low-Temperature Selective Catalytic Reduction of NOx with Ammonia.

Selective catalytic reduction of nitrogen oxides (NOx) with ammonia (NH3-SCR) has been implemented in response to the regulation of NOx emissions from stationary and mobile sources above 300 °C. However, the development of NH3-SCR catalysts active at low temperatures below 200 °C is still needed to improve the energy efficiency and to cope with various fuels. In this review article, recent reports on low-temperature NH3-SCR catalysts are systematically summarized. The redox property as well as the surface acidity are two main factors that affect the catalytic activity. The strong redox property is beneficial for the low-temperature NH3-SCR activity but is responsible for N2O formation. The multiple electron transfer system is more plausible for controlling redox properties. H2O and SOx, which are often found with NOx in flue gas, have a detrimental effect on NH3-SCR activity, especially at low temperatures. The competitive adsorption of H2O can be minimized by enhancing the hydrophobic property of the catalyst. Various strategies to improve the resistance to SOx poisoning are also discussed.