Stationary Air Research Articles

Adequacy of stationary measurements as proxies for residential personal exposure to gaseous and particle air pollutants

People are exposed to myriad of airborne pollutants in their homes. Owing to diverse potential sources of air pollution and human activity patterns, accurate assessment of residential exposures is complex. In this study, we explored the relationship between personal and stationary air pollutant measurements in residences of 37 participants working from home during the heating season. Stationary environmental monitors (SEMs) were located in the bedroom, living room or home office and personal exposure monitors (PEMs) were worn by the participants. SEMs and PEMs included both real-time sensors and passive samplers. During three consecutive weekdays, continuous data were obtained for particle number concentration (size range 0.3–10 μm), carbon dioxide (CO2), and total volatile organic compounds (TVOC), while passive samplers collected integrated measures of 36 volatile organic compounds (VOCs) and semi volatile organic compounds (SVOCs). The personal cloud effect was detected in >80% of the participants for CO2 and >50% participants for PM10. Multiple linear regression analysis showed that a single CO2 monitor placed in the bedroom efficiently represented personal exposure to CO2 (R2 = 0.90) and moderately so for PM10 (R2 = 0.55). Adding a second or third sensor in a residence did not lead to improved exposure estimates for CO2, with only 6–9% improvement for particles. Selecting data from SEMs when participants were in the same room improved personal exposure estimates by 33% for CO2 and 5% for particles. Out of 36 detected VOCs and SVOCs, 13 had at least 50% higher concentrations in personal versus stationary samples. Findings from this study aid improved understanding of the complex dynamics of gaseous and particle pollutants and their sources in residences, and could support the development of refined procedures for residential air quality monitoring and inhalation exposure assessment.

Derivation of the Penman–Monteith Equation with the Thermodynamic Approach. I: A Review and Theoretical Development

A review of the derivation of the Penman–Monteith equation, with the thermodynamic approach of Monteith, is presented. Evapotranspiration (henceforth referred to simply as evaporation) is described as a process consisting of a pair of formal thermodynamic subprocesses (adiabatic cooling and diabatic heating) that leads to changes in the energy states of the ambient air in ways that are readily quantifiable. The Penman–Monteith equation is derived in two steps. As an initial approximation, first a form of the equation that models evaporation into a quiescent ambient air, from a wet source/sink surface, is developed based on thermodynamic equations of state applied to a suitably defined system. In a subsequent step, resistance parameters are introduced into the basic equations, accounting for the dynamic effects of wind-surface interactions and those of (bulk) canopy system effects on evaporation, leading to the Penman–Monteith equation. Although less compact than the conventional approach, the thermodynamic approach to the derivation of the Penman–Monteith equation exhibits a benefit of revealing key assumptions and concepts that are not explicit in the conventional approach. The initial step of the thermodynamic formulation accentuates the notion that the Penman–Monteith equation is fundamentally a description of the process of vapor and heat transfer between a wet source/sink surface and a stationary ambient air. The subsequent step, on the other hand, emphasizes the fact that wind and crop effects on evaporation are taken into account in an approximate sense. The thermodynamic approach also shows that evaporation is essentially a process driven by energy supply and as such, each term of the Penman–Monteith equation represents a separate heat source for evaporation. Furthermore, the approach reveals some useful mathematical/physical attributes of the key parameters of the Penman–Monteith equation. The derivation here emphasizes basic assumptions and mathematical/physical interpretations of results and fills conceptual gaps left from the original discussion. The resultant equations for latent heat flux, sensible heat flux, and the final air temperature represent a coupled set. Thus, numerical solutions to this system of equations are presented and evaluated in a companion manuscript.

A high sensitivity and multi-axis fringing electric field based capacitive tactile force sensor for robot assisted surgery

This paper presents a design of multi-axis tactile force sensor using the fringe effect of an electric field between stationary patterned electrodes. The unique configuration of the electrodes consisting of four separate square-shaped sensing electrodes, with each encircled by excitation electrodes, allows to achieve enhanced fringe field effect and hence sensitivity. The proposed sensor can decouple the normal, shear and angular shear applied forces. The sensor is fabricated using low-cost rapid prototyping techniques with flexible Ecoflex 00–30 and silicone rubber RTV-528 as the elastomers for contact with the environment. An analytical model is developed that correlates the nominal capacitance of the sensor with that of the geometric dimensions of the stationary electrodes and air cavity height between the electrodes and elastomer. The force measurement ranges in the normal, shear, and angular axis are 5 N, 1.5 N, and 1 N respectively. The sensor shows a perfectly linear response, repeatability, and a low hysteresis error, thermal stability and robustness to the environmental interferences that makes it suitable to be used for force feedback in minimally invasive robotic surgery.

Numerical Simulation for Nonlinear Interaction between an Attached Air Bubble and Nearby Oscillating Bubble

The numerical simulations of a non-spherical evolution of pulsating bubble interacting with a stationary air bubble attached to a fixed structure were performed by using the three-dimensional boundary integral method which is based on the mirror image method to simplify the processing of the numerical model. Validation of the code is presented by comparison of numerical predictions with laboratory experimental data obtained by our previous research. Complex phenomena are observed such as three kinds of bubble jet forms: upward bubble jet, bubble splitting phenomenon, and downward bubble jet. The present simulations provide insight into the interesting bubble jetting phenomena in detail, including bubble splitting, jet away from the plate, and bubble shedding.

Assessing the Spatial Distribution of NO2 and Influencing Factors in Urban Areas—Passive Sampling in a Citizen Science Project in Berlin, Germany

Nitrogen dioxide (NO2) is a major air pollutant with diverse impacts on human health and the environment. In urban areas, road traffic is the main emission source for NO2. In Berlin, Germany, a network of measurement stations is operated by the state, fulfilling the monitoring requirements set by the European Union. To get a more detailed overview of the spatial distribution of NO2 concentrations in Berlin, a citizen science project allowed for collection of additional data and an increase in the number of sampling sites. Passive samplers (modified Palmes tubes) were distributed to participants to collect NO2 at a site of their choice. When returned, the samplers were analyzed based on the Griess–Ilosvay reaction and spectrophotometric detection. The results confirmed a seasonal trend of higher NO2 concentrations in winter and lower concentrations during the summer period. Furthermore, the spatially and monthly averaged NO2 concentrations observed in the study period from March 2019 to October 2020 were in good agreement with the average urban background concentration. At small spatial scales, a tendency of decreasing NO2 concentrations with increasing distance from roads was observed. Overall, this study shows the added benefit of extensive low-cost measurements of NO2 concentrations across urban environments in a citizen science project to complement stationary air pollution monitoring networks.

Development of functionally graded anode supports for microtubular solid oxide fuel cells by tape casting and isostatic pressing

This paper suggests an alternative method to manufacture functionally graded anode supports for microtubular solid oxide fuel cells by employing tape casting and isostatic pressing for the first time in the literature. In this regard, six different anode support strips with various pore former contents are produced by tape casting. Besides the anode supports made from uniform tapes, three-layered anode supports composed of various combination of these tapes are also fabricated by wrapping the corresponding tape(s) of the same total length on a metallic rod followed by isostatic pressing. Microtubular cells are then built on these anode supports by dip coating the other layers and evaluated by microstructural investigations and electrochemical performance tests performed under the same conditions. Porosity measurements of the homogeneous anode supports are also carried out. Microstructural examinations reveal that not only the homogeneous anode supports but porosity graded anode supports can be also successfully manufactured by the suggested method. Electrochemical tests indicate that the performance of the cells with a uniform anode support tends to increase with the anode support porosity up to ∼26% porosity then shows a decreasing trend. The highest maximum performance of 0.645 Wcm−2 at 800 °C under 0.3 NLmin−1 hydrogen and stationary air, on the other hand, is obtained from the cell with a porosity graded anode support.

Air contamination, syringe contamination, and cross-contamination when using an automatic compounding device for sensitizing drugs

Abstract Objectives To measure cross-contamination between batches of different sensitizing drugs, contamination on the outside of compounded syringes, and drug concentrations in environmental air when using an automated compounding device. Methods One batch of piperacillin/tazobactam syringes followed by one batch of meropenem syringes were compounded daily for three consecutive days by one operator. For each batch two hundred syringes were filled. During each batch, three stationary air samples (two inside and one outside the compounding device), and one personal air sample were collected. At the end of the compounding process, the outside of 40 syringes was tested for drug contamination by wipe sampling. The drug compounded was checked for cross-contamination with the other drug compounded in the previous batch. Liquid chromatography tandem mass spectrometry was used for the analysis of piperacillin and meropenem. Results Piperacillin was measured in environmental air inside the device (8.1–335 ng/m3), outside the device (5.2–21 ng/m3), and in the personal air samples of the operator (15 and 155 ng/m3) during two batches. Meropenem was not detected during meropenem compounding. Piperacillin was found in the air samples of the operator during two batches (12 and 15 ng/m3). Meropenem was not detected in any of the air samples. The drug compounded was found on the outside of the syringes for all batches (piperacillin: 1.35–30 ng/cm2; meropenem: 0.07–0.65 ng/cm2). Piperacillin was detected on the syringes in all meropenen batches (0.56–11 ng/cm2), and meropenen in two piperacillin batches (0.07 and 0.46 ng/cm2). The drug solutions show no cross-contamination with the other drug for any of the batches. Conclusions Cross-contamination was not found and the drug concentrations in environmental air were below the Occupational Exposure Limit of 0.1 mg/m3. The automatic compounding device meets the criteria for a safe compounding of sensitizing drugs for patient and operator.

Portable air quality monitor based on low-cost sensors

National systems of automatic air quality monitoring are based on automatic measuring instruments that are installed in stationary air quality monitoring stations. Substantial financial resources are required for the procurement, installation, calibration, and maintenance of such measuring devices. For this reason, existing national and local air quality monitoring networks are not able to provide a high temporal and spatial resolution of measurement results. In the last decade, as a possible alternative to the conventional approach to air quality monitoring, real-time monitoring systems using low cost sensors and sensor platforms have begun to be applied. This paper describes the basic characteristics of a portable air quality monitor PAQMAN 2020 based on low-cost sensors. Part of the results of comparative measurements of this device with the reference instruments is presented in the paper.

МОДЕРНИЗАЦИЯ ВПУСКНОГО ТРАКТА ПУТЕМ ПРИМЕНЕНИЯ КВАДРАТНЫХ И ТРЕУГОЛЬНЫХ КАНАЛОВ ПРИМЕНИТЕЛЬНО К АВТОМОБИЛЬНОМУ ДВИГАТЕЛЮ РАЗМЕРНОСТИ 8,2/7,1

The article is devoted to the gas-dynamic improvement of processes in the cylinder of an internal combustion engine by using profiled channels in the intake tract. Based on experimental studies of the gas dynamics of stationary air flows, thermograms of distribution of the gas flow inside the cylinder for the intake tract with channels having cross sections in the form of a circle, square and triangle for various initial velocities were obtained. The flow structure inside the cylinder was studied using the method of thermal survey, the average air flow velocity was determined using the method of thermal anemometry. It is established that the use of profiled channels in the intake tract leads to a significant change in the flow structure inside the cylinder, improving uniformity of distribution of the velocity field and reducing stagnant zones, and in the future it will increase the specific power of the internal combustion engine, reduce specific fuel consumption and the amount of harmful substances in the exhaust gases.

Association between Air Pollution Exposure and Daily Outpatient Visits for Dry Eye Disease: A Time-Series Study in Urumqi, China

The potential effects of air pollution on the ocular surface environment have not been fully evaluated, and even fewer studies have been conducted on the lagged effects of air pollution on dry eye disease (DED). The data of 9970 DED outpatients between 1 January 2013 and 31 December 2020, and data for six air pollutants, including PM10, PM2.5, carbon monoxide (CO), sulfur dioxide (SO2), nitrogen dioxide (NO2), and ozone (O3), were obtained from 11 standard urban background stationary air quality monitors in Urumqi, Xinjiang, China. Time series analysis design and quasi-Poisson generalized linear regression models combined with distributed lagged nonlinear models (DLNM) were used. Single- and multi-pollutant model results suggest that each additional per 10 μg/m3 of PM10, NO2, and SO2 is associated with an increased risk of outpatient DED on lag day 0 and PM2.5, NO2, and SO2 with other cumulative lag days; R software version 4.0.4 (15 February 2021) was used for the analysis. We conducted first time series analysis with a large sample size in northwest China (Xinjiang) and confirmed, for the first time, the impact of air pollution including particulate pollutants (PM10, PM2.5) and acidic gasses (SO2, NO2) on DED risk in the Urumqi region, and suggested the potential lagged effects of PM2.5, SO2, and NO2.

Proxy methods for detection of inhalation exposure in simulated office environments

BackgroundModern health concerns related to air pollutant exposure in buildings have been exacerbated owing to several factors. Methods for assessing inhalation exposures indoors have been restricted to stationary air pollution measurements, typically assuming steady-state conditions.ObjectiveWe aimed to examine the feasibility of several proxy methods for estimating inhalation exposure to CO2, PM2.5, and PM10 in simulated office environments.MethodsIn a controlled climate chamber mimicking four different office setups, human participants performed a set of scripted sitting and standing office activities. Three proxy sensing techniques were examined: stationary indoor air quality (IAQ) monitoring, individual monitoring of physiological status by wearable wristband, human presence detection by Passive Infrared (PIR) sensors. A ground-truth of occupancy was obtained from video recordings of network cameras. The results were compared with the concurrent IAQ measurements in the breathing zone of a reference participant by means of multiple linear regression (MLR) analysis with a combination of different input parameters.ResultsSegregating data onto sitting and standing activities could lead to improved accuracy of exposure estimation model for CO2 and PM by 9–60% during sitting activities, relative to combined activities. Stationary PM2.5 and PM10 monitors positioned at the ceiling-mounted ventilation exhaust in vicinity of the seated reference participant accurately estimated inhalation exposure (adjusted R² = 0.91 and R² = 0.87). Measurement at the front edge of the desk near abdomen showed a moderate accuracy (adjusted R² = 0.58) in estimating exposure to CO2. Combining different sensing techniques improved the CO2 exposure detection by twofold, whereas the improvement for PM exposure detection was small (~10%).SignificanceThis study contributes to broadening the knowledge of proxy methods for personal exposure estimation under dynamic occupancy profiles. The study recommendations on optimal monitor combination and placement could help stakeholders better understand spatial air pollutant gradients indoors which can ultimately improve control of IAQ.

Measuring TrafficRelated Air Pollution Using Smart Sensors In Sri Lanka: Before And During A New Traffic Plan

Motor vehicle emissions are the primary air pollution source in cities worldwide. Changes in traffic flow in a city can drastically change overall levels of air pollution. The level of air pollution may vary significantly in some street segments compared to others, and a small number of stationary ambient air pollution monitors may not capture this variation. This study aimed to evaluate air pollution before and during a new traffic plan established in March 2019 in the city of Kandy, Sri Lanka, using smart sensor technology. Street level air pollution data (PM2.5 and NO2 ) was acquired using a mobile air quality sensor unit before and during the implementation of the new traffic plan. The sensor unit was mounted on a police traffic motorcycle that travelled through the city four times per day. Air pollution in selected road segments was compared before and during the new traffic plan, and the trends at different times of the day were compared using data from a stationary smart sensor. Both PM2.5 and NO2 levels were well above the World Health Organization (WHO) 24-hour guidelines during the monitoring period, regardless of the traffic plan period. Most of the road segments had comparatively higher air pollution levels during compared to before the new traffic plan. For any given time (morning, midday, afternoon, evening), day of the week, and period (before or during the new traffic plan), the highest PM2.5 and NO2 concentrations were observed at the road segment from Girls High School to Kandy Railway Station. The mobile air pollution monitoring data provided evidence that the mean concentration of PM2.5 during the new traffic plan (116.7 µg m-3) was significantly higher than before the new traffic plan (92.3 µg m-3) (p < 0.007). Increasing spatial coverage can provide much better information on human exposure to air pollutants, which is essential to control traffic related air pollution. Before implementing a new traffic plan, careful planning and improvement of road network infrastructure could reduce air pollution in urban areas.

Stationary Gas Dynamics and Heat Transfer of Turbulent Flows in Straight Pipes at Different Turbulence Intensity

The gas-dynamic and heat-exchange behaviours of air flows in gas-dynamic systems have a significant impact on the efficiency and environmental performance of most technical equipment (heat engines, power plants, heat exchangers, etc.). Therefore, it is a relevant task to obtain reliable experimental data and physical laws on the influence of cross-sectional shape and initial turbulence intensity on gas dynamics and the level of heat transfer. In this study, data were experimentally obtained on the instantaneous values of the local velocity and local heat transfer coefficients of stationary air flows in straight pipes with circular, square, and triangular cross-sections at different initial values of the turbulence intensity. The measurements were carried out with a constant temperature hot-wire anemometer, thermocouples, and pressure sensors. Based on the research results, data on the turbulence intensity and averaged local heat transfer along the length of pipes with different cross-sections were summarised. It has been established that turbulence intensity in a square pipe is up to 40% higher than in a round channel; in a triangular channel, on the contrary, it is up to 28% lower. After the air flow’s initial turbulence, the relaxation of the flow in square and triangular pipes occurs faster than in a round channel. It is found that the initial intensity of turbulence leads to an increase in the averaged local heat transfer, which is typical of all investigated pipe configurations and initial conditions.

Natural and human factors influencing urban particulate matter concentrations in central heating areas with long-term wearable monitoring devices

In northern China, central heating, as an important source of urban particulate matter (UPM), causes more than half of the air pollution during the heating season and has significant spatial-temporal heterogeneity. Owing to the limitations of stationary air monitoring networks, few studies distinguish between heating/non-heating seasons and few have been conducted in urban areas. However, fixed monitoring cannot accurately capture the dynamic exposure of residents to UPM, and there is a lack of comprehensive evaluation of the factors affecting UPM. Therefore, this study used wearable Sniffer 4D equipment to monitor the concentrations of UPM (PM1, PM2.5, and PM10) in selected typical areas of Shenyang City from March 2019 to February 2020. A random forest model was combined with land use and point-of-interest data to analyze the contributions and marginal effects of multiple influences on UPM, in both heating and non-heating seasons. The results showed that in the eastern part of the study area, UPM showed completely opposite spatial distribution characteristics during the two seasons. The concentrations of UPM were higher during the heating season than during the non-heating season. The results indicated that temperature and humidity were important factors in diffusing UPM. The production and operation of boilers were important for the production of UPM. In two-dimensional landscape pattern indices, the percentage of forest and Shannon diversity index were the first and second most important factors, respectively. The three-dimensional pattern of buildings had important effects on the transport and diffusion of UPM (landscape height range >100, floor area ratio >1.3, and landscape volume density >5). Wearable devices could monitor the real situation of residents’ exposure to UPM and quantify the factors influencing the spatial-temporal distribution of UPM in an ecological sense. These results provide a scientific basis for urban planning and for health risk reduction for residents.

A robust scheme for numerical simulation of heat transfer in two-fluid flows with high volumetric heat capacity contrasts

PurposeThis paper aims to propose a new method for robust simulations of passive heat transfer in two-fluid flows with high volumetric heat capacity contrasts.Design/methodology/approachThis paper implements a prediction–correction scheme to evolve the volumetric heat capacity. In the prediction substep, the volumetric heat capacity is evolved together with the temperature. The bounded downwind version of compressive interface capturing scheme for arbitrary meshes and central difference scheme are used for the spatial discretization of the advection and diffusion terms of the heat transfer equation, respectively. In the correction substep, the volumetric heat capacity is updated in accordance with the interface captured by using a coupled level-set and volume-of-fluid method to capture the interface dynamics precisely.FindingsThe proposed method is verified by simulating the advection of a hot droplet with high volumetric heat capacity, a stationary air–water tank with temperature variation between top and bottom walls and heat transfer during wave plunging at . The test results show that the proposed method is practical and accurate for simulating two-fluid heat transfer problems, especially for those feature high volumetric heat capacity contrasts.Originality/valueTo ensure the numerical stability, this paper solves an additional conservative form of volumetric heat capacity equation along with the conservative form of temperature equation by using consistent spatial-discretization and temporal-integration schemes.

Polybenzoxazine/Silica Hybrid Aerogels for Thermally Insulating Ablation

Lightweight microablation thermal protection materials are one of the crucial factors contributing to the rapid development of next-generation aircrafts. However, the maintenance of a high mass residual and long-term antioxidant capacity of the matrix after bearing high-temperature aerobic environments remains a major challenge. Herein, we put forward a strategy for constructing polybenzoxazine/silica hybrid aerogels depending on the introduction into silica inorganic phases by different technologic preparation routes, possessing excellent thermal insulation, superior self-extinguishing properties, and outstanding thermal stability. In detail, the mass residual rate of polybenzoxazine/silica aerogels (PSAs) as-prepared could reach up to 40.19%, mainly due to the reinforced networking structure by the introduction of silica that would be preserved well due to the inorganic phase nature in the high-temperature oxidizing environment. The pore size of polybenzoxazine/silica/chitosan aerogels (PSCAs) is mainly distributed within 5–35 nm, which contributes to obtaining a low thermal conductivity (0.037 W m–1 K–1) due to the pore size being smaller than the mean free path of stationary air at normal temperature and pressure. PSAs and PSCAs both exhibit excellent self-extinguishing properties, attributed to the presence of a large number of aromatic ring structures and the introduction of the silica inorganic phase in polybenzoxazine itself. The microscopic morphology, crystalline shape, and Si-related chemical bonding of PSAs did not significantly change after muffle thermal treatment, including the three-dimensional network structure composed of polybenzoxazine and silica. This study provides a kind of approach for designing a thermal protection material matrix with high mass residual and excellent thermal insulation performance in the aerospace field.

Wildfire Impact on Indoor and Outdoor PAH Air Quality.

Air quality impacts from wildfires are poorly understood, particularly indoors. As frequencies increase, it is important to optimize methodologies to understand and reduce chemical exposures from wildfires. Public health recommendations use air quality estimates from outdoor stationary air monitors, discounting indoor air conditions, and do not consider chemicals in the vapor phase, known to elicit adverse effects. We investigated vapor-phase polycyclic aromatic hydrocarbons (PAHs) in indoor and outdoor air before, during, and after wildfires using a community-engaged research approach. Paired passive air samplers were deployed at 15 locations across four states. Twelve unique PAHs were detected only in outdoor air during wildfires, highlighting a PAH exposure mixture for future study. Heavy-molecular-weight (HMW) outdoor PAH concentrations and average Air Quality Index (AQI) values were positively correlated (p < 0.001). Indoor PAH concentrations were higher in 77% of samples across all sampling events. Even during wildfires, 58% of sampled locations still had higher indoor PAH air concentrations. When AQI values exceeded 140 (unhealthy for sensitive groups), outdoor PAH concentrations became similar to or higher than indoors. Cancer and noncancer inhalation risk estimates from vapor-phase PAHs were higher indoors than outdoors, regardless of the wildfire impact. Consideration of indoor air quality and vapor-phase PAHs could inform public health recommendations regarding wildfires.

Sixteen-Year Monitoring of Particulate Matter Exposure in the Parisian Subway: Data Inventory and Compilation in a Database

The regularly reported associations between particulate matter (PM) exposure, and morbidity and mortality due to respiratory, cardiovascular, cancer, and metabolic diseases have led to the reduction in recommended outdoor PM10 and PM2.5 exposure limits. However, indoor PM10 and PM2.5 concentrations in subway systems in many cities are often higher than outdoor concentrations. The effects of these exposures on subway workers and passengers are not well known, mainly because of the challenges in exposure assessment and the lack of longitudinal studies combining comprehensive exposure and health surveillance. To fulfill this gap, we made an inventory of the PM measurement campaigns conducted in the Parisian subway since 2004. We identified 5856 PM2.5 and 18,148 PM10 results from both personal and stationary air sample measurements that we centralized in a database along with contextual information of each measurement. This database has extensive coverage of the subway network and will enable descriptive and analytical studies of indoor PM exposure in the Parisian subway and its potential effects on human health.

Characterization of the terminal area of standard arrival routes using the queueing system

The article solves the problem of determining the probabilistic characteristics of the STARs legs which specify a sequencing technique of “point merge” and “trombone”-type considering the intensity of the air traffic flow and the formation of a queue. This task is closely related to the airspace efficiency, as well as to the limit values of flight safety performance. An application of the queueing system makes it possible to optimize the elements of the airspace structure on an objective basis, and in the event of considering the inverse problem to establish limit values for the air traffic flow characteristics. The characteristics of the “point merge” and “trombone”-type schemes become of prime importance in the air hub, where several airfields function of each other in a relatively small volume of airspace – as it happens in the Moscow air hub, so it is the given hub that is taken as a practical example. In this problem the basic model is the queueing system with limited-size queues where the optimal number of service channels in a stationary air traffic flow is determined in a probabilistic way. The stated model encapsulates the essence of the “trombone” or “point merge”-type scheme, where the number of service channels corresponds to the number of flight levels on the arc of the “point merge” or on the horizontal flight segment of the “trombone”. Now, the number of such flight levels, as a rule, corresponds to the number of standard arrival routes involved in the formation of a “trombone” (“point merge”), which, from a practical point of view, is excessive. The task of using the mathematical apparatus of the queueing system is to determine the optimal number of flight levels – service channels of the model while establishing the required probability of its failure. As a mathematical model of the queueing system, the “trombone”-type scheme is used, and in the mentioned above example, the structure of the airspace is presented using the “point merge”-type scheme as a regulator of the aircraft sequence for landing. All the computations are performed for the certain intensity of air traffic flow for a specified airfield, considering the full-scale application of continuous descent operations and continuous climb operations (CDO, CCO). As a result of solving the problem, the value for the optimal number of flight levels on the “trombone” or “point merge”-type scheme was obtained, and the dependence of the number of service channels (flight levels on the “trombone” or “point merge”) on the value of the given probability of the queueing system failure was shown. The proposed approach to the airspace structure formation has prospects for implementation.

Scenarios for future Indian HFC demand compared to the Kigali Amendment

Demand for hydrofluorocarbon (HFC) refrigerants used as substitutes for ozone-depleting substances is growing in India and is estimated to continue growing at a high rate through the middle of this century. HFCs, although not directly ozone-depleting, are highly potent greenhouse gases subject to a global phasedown under the 2016 Kigali Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer. As of 20 January 2022, 130 Parties have ratified the Kigali Amendment, including India. This analysis evaluates scenarios for India’s HFC demand trajectory compared to likely control obligations under the Kigali Amendment. It is based on current and projected markets for HFC-using equipment and types of refrigerants utilized now and likely to be used in the future. Sectors considered in this work include mobile air conditioning, stationary air conditioning, refrigeration, and foam blowing agents. Results suggest that India’s annual HFC demand under current market trends could reach 76 MMT CO2-equivalent (CO2e) in 2030 and 197 MMT CO2e in 2050, from 23 MMT CO2e in 2020, making no changes to the current mix of HFCs in use. The Kigali Amendment requires for compliance that India freeze its HFC consumption in 2028 at a projected level of 59–65 MMT CO2e and phase down progressively over the following 29 years; in that case, annual Indian HFC demand would peak in 2030 at a projected 57 MMT CO2e and fall to 8 MMT CO2e by 2050. This trajectory would avoid cumulative HFC use of 2.2 GT CO2e through 2050 versus the current market trends. If actions are taken to accelerate the refrigerant transition in stationary air conditioning by five years, India could peak its annual HFC demand by 2028 at 40 MMT CO2e and avoid additional cumulative HFC demand of 337 MMT CO2e between 2025 and 2050, exceeding its obligations under the Kigali Amendment.