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Formaldehyde (HCHO) is a widespread air pollutant in the indoor environment. Previous studies have shown that some bacteria have potential application to remove indoor HCHO. The purpose of this study is to evaluate the effectiveness of Methylobacterium sp. strain R1 (S-R1) in removing formaldehyde (HCHO) from indoor air using biofilters. Three experiments confirmed S-R1's ability to degrade HCHO in the air, with 13C-NMR analysis revealing its involvement in the metabolic process. Optimal biofilter parameters, including 35 sponge layers, 30% humidity, and 9.50 m3/min air flow, resulted in a removal efficiency of up to 90% and an elimination capability of 24111-27000 μg/(m3 ∗ h) during a 60-minute test period. Long-term (31-day) operation of the biofilter with the optimal parameters effectively reduced HCHO levels from 1.60 mg/m3 to 0.02-0.03 mg/m3, below China's national standard, and maintained this level. Fluorescence microscope observation and downstream gas detection revealed stable S-R1 cell numbers and no bacterial leakage, respectively. Two conclusions can be drawn: (1) S-R1 is effective in removing HCHO in polluted air and (2) with optimum parameters, the S-R1 biofilter is engineering effective in purifying the indoor air environment. [ABSTRACT FROM AUTHOR]

With the development of civil aviation in China, airspace congestion has become more and more serious and has gradually spread from airport terminal areas to en route networks. Traditionally, most prediction methods that obtain traffic flow data are based on the number of aircraft passing through an en route sector and require flight data to meet strict assumptions and conditions. While these methods are normally used in the actual operation of air traffic flow management departments in China, the results are not satisfactory due to the nonlinearity of traffic demand along en route sectors and the change in high-frequency noise. In order to refine aircraft control in airspace, it is necessary to predict traffic flow accurately. Thus, this paper proposes the quantile regression neural network and kernel density estimation method to obtain some quantiles of continuous traffic demand data in the future, which combines the strong nonlinear adaptive ability of neural networks with the ability of quantile regression to describe explanatory variables. By using these continuous conditional quantiles, we obtain the probability density function and probability density curve of the continuous traffic demand in the future using the kernel density estimation method. In this way, we can obtain not only a specific point prediction value and its change interval but also the probability of each value in the prediction change interval of traffic demand in the en route sector as well as a more accurate point prediction value for a specific day. [ABSTRACT FROM AUTHOR]

Air Traffic Flow Management (ATFM) delay can quantitatively reflect the congestion caused by the imbalance between capacity and demand in an airspace network. Furthermore, it is an important parameter for the ex-post analysis of airspace congestion and the effectiveness of ATFM strategy implementation. If ATFM delays can be predicted in advance, the predictability and effectiveness of ATFM strategies can be improved. In this paper, a short-term ATFM delay regression prediction method is proposed for the characteristics of the multiple sources, high dimension, and complexity of ATFM delay prediction data. The method firstly constructs an ATFM delay prediction network model, specifies the prediction object, and proposes an ATFM delay prediction index system by integrating common flow control information. Secondly, an ATFM delay prediction method based on feature extraction modules (including CNN, TCN, and attention modules), a heuristic optimization algorithm (sparrow search algorithm (SSA)), and a prediction model (LSTM) are proposed. The method constructs a CNN-LSTM-ATT model based on SSA optimization and a TCN-LSTM-ATT model based on SSA optimization. Finally, four busy airports and their major waypoints in East China are selected as the ATFM delay prediction network nodes for example validation. The experimental results show that the MAEs of the two models proposed in this paper for ATFM delay regression prediction are 4.25 min and 4.38 min, respectively. Compared with the CNN-LSTM model, the errors are reduced by 2.71 min and 2.59 min, respectively. Compared with the TCN-LSTM model, the times are 3.68 min and 3.55 min, respectively. In this paper, two improved LSTM models are constructed to improve the prediction accuracy of ATFM delay duration so as to provide support for the establishment of an ATFM delay early warning mechanism, further improve ATFM delay management, and enhance resource allocation efficiency. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic has emphasized the crucial role of ventilation systems in mitigating cross-infections, especially in infectious-disease hospitals. This study introduces a dual-design operation ventilation system that can operate under two sets of ventilation conditions for normal and epidemic times. A challenge is optimizing duct diameters for required airflow while maintaining hydraulic balance. We designed an improved genetic algorithm with an adaptive penalty factor and velocity constraint, as well as the improved crossover probability and mutation probability. The improved genetic algorithm is suitable for ventilation system networks, which can find a better combination of air duct diameters to improve the hydraulic balance rate and reduce the usage of air valves, resulting in efficient hydraulic balancing commissioning. A supply air ventilation system of an actual hospital in China was selected as a case study, and the number of imbalanced air ducts was reduced from 14 to 4. Compared with the traditional genetic algorithm, it has a faster search speed and a better global search ability, which is effective for the optimal design of ventilation system networks. [ABSTRACT FROM AUTHOR]

The tropical cyclones (TCs) often cause intense rain and destructive winds. While these catastrophic weather conditions capture our attention, the less-known impact of TCs remains overlooked. This study reveals that TCs have a notable suppressive effect on monsoonal rainfall in southern China when they traverse the South China Sea. This phenomenon can be attributed to the influence of these mesoscale disturbances on the quasi-stationary, large-scale monsoonal circulation, which alters the moisture pathway. Furthermore, the case-by-case analysis indicates that ~76% of TCs correspond to rainfall reduction, whereas the other 24% correspond to rainfall increase. The latter is due to the concurrent occurrence of another independent influencing factor: extratropical cyclonic anomalies that promote enhanced rainfall through favoring lower-tropospheric moisture convergence. This study suggests that TCs, as mesoscale disturbances, can change the moisture channel that is usually controlled by quasi-stationary and large-scale monsoonal airflows, and suppress the adjacent land rainfall over China. [ABSTRACT FROM AUTHOR]

Plant protection drones are fast and efficient application machines that are characterised by high application efficiency and no damage to crops. They are particularly suitable for small areas of farmland and mountainous terrain in regions such as Asia and are currently the dominant insecticide application technology in China. The presence of wind is a prerequisite for the spread and dissemination of airborne diseases and it can directly influence the distance and height of ascent of pathogenic spores. This paper investigates the effect of downwash airflow generated by the flight altitude of a plant protection drone on the horizontal distribution, vertical distribution and ground distribution of powdery mildew spores in wheat. Monitoring the changing dynamics of airborne powdery mildew conidia using spore traps. The test results show that: the number of powdery mildew pathogenic spores is related to various factors such as weather, relative humidity and wind speed; the release of spores is greatly influenced by airflow disturbances but has little effect at the early stages of sporulation; the disease is caused by the accumulation process of pathogenic spores and in the control of powdery mildew in wheat, preventive spraying should be carried out within 2–3 days of the germination of pathogenic spores. The study lays the foundation for further in-depth research on the spread of powdery mildew spores and improved pest control, and provides a basis for scientific and rational spraying and control by agricultural drones. [ABSTRACT FROM AUTHOR]

The opposed wall-fired boiler has been widely employed in power plants in China due to its adaptability. However, the airflow in the same layer burners from the large air box is uneven, affecting the combustion characteristics of pulverized coal and causing the corrosion and slagging of the water-cooled wall. In this study, the numerical simulation is performed on a 600 MW wall-fired boiler to investigate the air distribution and flow characteristics of each burner and the secondary air duct under variable boiler loads (100%, 75%, 50%, and 30%), which would provide the basis for optimization of the secondary air box. The effectiveness of the modified burner, over-fire air (OFA) nozzle, and secondary air duct is demonstrated through the numerical simulation. The results indicate that the burner and OFA nozzle exhibit distinct flow deviation characteristics within the original air box. Specifically, the burner demonstrates a flow deviation ranging from 2% to 4%, whereas the OFA nozzle exhibits a flow deviation ranging from 10% to 35%. Integrating poly air rings into the burners and OFA nozzles on the sidewall separately addresses the issue of non-uniform flow distribution of the OFA nozzle while concurrently improving the air flow rate on both sides of the burners and OFA nozzles. The main air duct could be divided into three smaller air ducts by installing two deflectors at the corner of the secondary air duct. This scheme effectively decreases the pressure drops at the corner interface from 337.4 to 254.3 Pa. The findings of this study could have the potential to offer scientific insights into and recommendations for the optimal functioning of the boiler system. [ABSTRACT FROM AUTHOR]

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With the steady increase of air traffic column, an auxiliary decision tool is required to compensate the operation redundancy deficiency of more sectors of air traffic control. To solve the problem of nonconflict high-density departure and arrival traffic flow, this method is expected to rapidly establish and maintain safe separation with more flexible changing strategies for aircraft heading and speed. This paper proposes an improved reinforcement learning framework to achieve conflict detection and resolution. The proposed framework includes the first development of an air traffic flow model based on a multiagent Markov decision process. The goal reward function was then maximized by improved Monte-Carlo tree search combined with an upper confidence bound tree. Three simulation scenarios were designed for illustrating the improvements of the proposed algorithm, with the results indicating that the algorithm could establish and maintain safe separation between 20 agents in the simplified hexagon-shaped airspace of Huadong, China. Furthermore, the proposed method was demonstrated to reduce the number of conflicts between aircraft agents by up to 26.32% compared to previous research. [ABSTRACT FROM AUTHOR]

Rainstorms always occur in the southeast and northeast quadrants of the Northeast China Cold Vortex (NCCV), resulting in significant flooding. This study investigated water vapor and trigger mechanisms for rainstorms within these two regions of an NCCV event during 11–14 June 2022 in terms of Lagrangian backward tracking, stratification stability, and upward motion using the ERA5 reanalysis. In the mid-troposphere, a quasi-stationary "ridge-NCCV-ridge" pattern resided over northeastern China, with an "anticyclonic-cyclonic-anticyclonic" airflow in the lower troposphere. As a result, water vapor originated from the Yellow Sea and was transported in an "L" shape toward both two regions. The southeast region was influenced by southwesterly and northwesterly airflows, resulting in the convergence of moist air from the Yangtze River and Lake Baikal and significant vertical shear of positive vorticity advection. This dynamic created deep and pronounced upward currents in the southeast of the NCCV, leading to the development of intensive and extensive rainstorms in situ. In contrast, the northeast region of the NCCV was dominated by southerly airflow. The moist air converged against the lee side of the Great Khingan Mountains and generated shallow, unstable stratification. The upward motion in this area was relatively weaker and thus induced regional rainstorms. [ABSTRACT FROM AUTHOR]

A multilayer network approach to model and analyze air traffic networks is proposed. These networks are viewed as complex systems with interactions between airports, airspaces, procedures, and air traffic flows (ATFs). A topology-based airport-airspace network and a flight trajectory network are developed to represent critical physical and operational characteristics. A multilayer traffic flow network and an interrelated traffic congestion propagation network are also formulated to represent the ATF connection and congestion propagation dynamics, respectively. Furthermore, a set of analytical metrics, including those of airport surface (AS), terminal controlled airspace (TCA), and area-controlled airspace (ACA), is introduced and applied to a case study in central and south-eastern China. The empirical results show the existence of a fundamental diagram of the airport, terminal, and intersections of air routes. Moreover, the dynamics and underlying mechanisms of congestion propagation through the AS-TCA-ACA network are revealed and interpreted using the classical susceptible-infectious-removed model in a hierarchical network. Finally, a high propagation probability among adjacent terminals and a high recovery probability are identified at the network system level. This study provides analytical tools for comprehending the complex interactions among air traffic systems and identifies future developments and automation of layered coupled air traffic management systems. [ABSTRACT FROM AUTHOR]

The spring sensible heating (SSH) over the Tibetan Plateau (TP), which can significantly affect the precipitation in China, has experienced three different stages of change, showing significant increasing (1961–1979, Stage I), decreasing (1980–2002, Stage II), and increasing (2003–2014, Stage III) trends. In this study, the impact of these different trends in TP SSH on spring precipitation (SPR) in China and their possible mechanisms are investigated, based on observations and the reanalysis product. In Stage I, the SPR represents a contrasting north-south pattern associated with the increasing TP SSH, showing increasing trends over southern China and decreasing trends over central and northern China. Further, the spatial distribution of SPR trends shows a contrasting east-west pattern in Stage II. That is, persistent weakening TP SSH plays a more crucial role in increasing and decreasing SPR over southwestern and southern China, respectively. However, compared with the significant trend in SPR in Stage III, the regulation of TP SSH on SPR weakens significantly. Dynamically, the increasing TP SSH in Stage I can strengthen the subtropical westerly jet in the upper layer, simultaneously configured with an anomalous cyclone in northeastern China, which deepens the East Asian trough. Thus, anomalous convergence in the upper layer occurs over central and northern China, favoring the downdraft. It then causes more cold and dry air to move southward in the lower troposphere, which then encounters the warm and wet southwest airflows, boosting the updraft over southern China. In Stage II, regression analysis shows that if the TP SSH increases, an anomalous cyclone in the middle and upper troposphere occurs over the western TP, causing the downdraft and less precipitation over southwestern China, while a cyclone in the lower troposphere occurs over the western North Pacific and extends to southern China, promoting the ascending motions and more precipitation in southern China. However, in this stage, TP SSH actually weakens, thus contributing to more precipitation over southwestern China and less precipitation over southern China. [ABSTRACT FROM AUTHOR]

This study identifies causal links between a high-PM2.5 episode in Korea and air pollutants originating from China during a high-PM2.5 episode that occurred in Korea between February 23 and March 12, 2019. Datasets on ground-based PM2.5 levels in Korea and China, airflows from the back-trajectory models, and satellite images were investigated, and long-range transboundary transport (LRTT) effects were statistically analyzed using spatial panel-data models. The findings are: 1) visual presentations of the observed PM2.5 concentration in China and Korea, back-trajectory air flows, and satellite images from the Moderate Resolution Imaging Spectroradiometer Aerosol Optical Depth and the Copernicus Atmosphere Monitoring Service clearly show that transboundary air pollutants from China affect PM2.5 concentration in Korea; 2) the effect of LRTT from China is likely to intensify under certain meteorological conditions, such as westerly winds from China to Korea, the formation of high pressure in China and low pressure in Korea, relatively high temperature, and stagnant air flow in Korea; 3) the results from the spatial panel-data models provide statistical evidence of the positive effect of LRTT from China on increasing local PM2.5 concentration in Korea. The nationwide average LRTT contributions to PM2.5 concentration in Korea are 38.4%, while regional contributions are 41.3% for the Seoul Metropolitan Area, 38.6% for the northwest region, and 27.5% for the southeast regions in Korea, indicating the greatest impact on the Seoul Metropolitan Area. [ABSTRACT FROM AUTHOR]

Stable isotopes (18O/16O and 2H/1H) are fingerprints of water molecules and thus can be used to gain insight on water circulation. Especially, the factors controlling the isotopic composition of precipitation should be identified because they act as baseline determinants of the isotopic variations of surface water and groundwater. Here, using the HYSPLIT model, we attribute observed isotope variations to different moisture sources and characterize the isotopic composition of meteoric precipitation in Northwest China. Results show that the westerlies play a dominant role across the region throughout the year, while other moisture sources only affect some parts of the region during a specific season, i.e., Arctic airflow only affects the Altay Mountains as far as the Middle Tianshan Mountains; the East Asia Monsoon only affects the region east of 100° E longitude during the summer; and summer rainfall of local origin may contribute to the precipitation budget of basin areas. Given the different moisture sources across Northwest China, a local meteoric water line (NWMWL) of δ2H = 6.8δ18O − 1.6 is observed. Our findings not only can provide valuable insights into the mechanism of precipitation isotope fractionation in Northwest China but also can contribute to a better understanding of regional climate and hydrological studies. [ABSTRACT FROM AUTHOR]

The air traffic control (ATC) network's airspace sector is a crucial component of air traffic management. The increasing demand for air transportation services has made limited airspace a significant challenge to sustainable and efficient air transport operations. To address the issue of traffic congestion and flight delays, improving the operational efficiency of ATC has been identified as a key strategy. A clear understanding of the characteristics of airspace sectors, which are the building blocks of ATC, is essential for optimizing air traffic management. In this research, a novel approach using complex network theory was applied to examine the features and invulnerability of the airspace sector network. We developed a model of the airspace sector network by treating air traffic control sectors as network nodes and the flow of air traffic between these sectors as edges. Network characteristics were analyzed using several metrics including degree, intensity, average path length, betweenness centrality, and clustering coefficient. The static invulnerability of the airspace sector network was evaluated through simulation, and the network efficiency and the size of the connected component were used to assess its invulnerability. A study was conducted in North China based on the ATC sector network. The findings of the study revealed that the sector network did not exhibit the traits of a small-world network model, characterized by short average path lengths and high clustering coefficients. The evaluation of network invulnerability showed that the network's invulnerability varied depending on the attack strategy used. It was discovered that attacking sectors with high betweenness resulted in the most significant harm to network invulnerability, and betweenness centrality was considered to be a useful indicator for identifying critical sectors that require optimization. [ABSTRACT FROM AUTHOR]

Through a field experiment on a sandy beach at Pingtan, China, we propose the first model to characterize the variability of apparent von Kármán parameter κa ${\kappa }_{a}$ in the thermally and sedimentologically stratified air flows. The model shows that κa ${\kappa }_{a}$ is negatively correlated to flux Richardson number as well as sediment transport rate. The atmospheric stability can be either from thermal stratification or sedimentological stratification, neglecting either of them can lead to substantial errors in predicting shear velocity and sediment transport rate. Plain Language Summary: In natural conditions, atmospheric boundary layer flows are often non‐neutral due to thermal stratification. However, recent studies indicate sedimentological stratification may also have a similar effect while almost no research was conducted to examine their combined effect on the flows. We present the first model to characterize the apparent von Kármán parameter κa ${\kappa }_{a}$, a parameter representing the scale of flow eddy size, as a function of thermal and sedimentological stabilities. This work provides a feasible means to correct the potentially substantial errors when estimating shear velocity and predicting sediment transport rate for sedimentologically and thermally stratified air flows. Key Points: Apparent von Kármán parameter for thermally and sedimentologically stratified air flows was obtainedApparent von Kármán parameter has a negative, linear relationship with flux Richardson number and sediment transport rateNeglecting thermal and sedimentological stratifications can lead to substantial errors in shear velocity and transport rate estimations [ABSTRACT FROM AUTHOR]

At present, China's high-speed rail is in a period of rapid development. Most of the refrigerants used in Chinese motor train units at this stage are still R134a and R407c, which have an impact on the environment. In response to the environmental protection concept of green travel, it is of great significance to study the air conditioning system of motor train units using CO2 refrigerant. Using CFD simulation analysis technology, the heat transfer performance of the air side of the CO2 finned tube evaporator used in the air conditioning system of the motor train unit is studied. We select the air outlet temperature, pressure drop, heat transfer factor, and resistance factor as the objective function, in addition, monitoring points are set up in the air flow channel to monitor the turbulent flow field and pipe wall pressure. Our research shows that the cooling capacity of the CO2 evaporator can reach up to 29.76 kW, which can meet the heat exchange required in the air conditioning system of the motor train unit. In order to obtain a better structure and the conditions of the heat transfer effect, structural optimization was conducted. The simulation results demonstrate several trends: (i) With the augment of the air inlet velocity, the cooling capacity of the evaporator increases and the heat exchange effect improves; when the air inlet ve > 2.2 m/s, the effect of continuing to augment ve on heat exchange is weak. (ii) Following appropriate reduction of the diameter of the heat exchange tube, the wind resistance is reduced and the cooling capacity of the evaporator is improved. (iii) With the enlargement of the fin spacing, the turbulent motion in the flow channel can be fully developed, there is a peak in the change in the heat exchange tube area optimization factor, and the optimal fin spacing is between 1.6 mm and 1.7 mm; at this time, the average turbulent kinetic energy of the air side is larger and the turbulent dissipation rate is smaller. These results provide a reference for the practical application of CO2 refrigerant in the motor train unit. [ABSTRACT FROM AUTHOR]

The wind environment in residential areas can exert a direct or indirect influence on the spread of epidemics, with some scholars paying particular attention to the epidemic prevention and control of residential areas from the perspective of wind environments. As a result, it is urgent to re-examine the epidemic prevention response of residential spaces. Taking high-rise residential areas in Xi'an as an example, the article defines the air flow field area based on on-site wind environment measurements, crowd behavior annotation, and CFD simulation. Using the double-effect superposition of crowd behavior and risk space, the paper undertook a multiple identification strategy of epidemic prevention space. The identification methods and management and control strategies of epidemic prevention in high-rise residential areas are proposed. Additionally, the living environment of residential areas is optimized, and a healthy residential space is created. The transformation from concept and calls for action to space implementation is made to provide a reference for improving the space management and control capabilities in high-rise residential areas in China. The results of this study can be used as a guideline for future residential planning and design from the perspective of preventing airborne diseases. [ABSTRACT FROM AUTHOR]

In order to find potential low-frequency signals and provide new ideas for extended-range forecasting, the intraseasonal oscillation (ISO) characteristics of persistent high temperature events (PHTEs) in the extended summer in Jiangnan area are explored by using daily maximum air temperature (Tmax) data from the China Meteorological Data Network and daily reanalysis data provided by NCEP/DOE. The results show that the low-frequency PHTEs can be classified into three types according to the position variation of the Western Pacific subtropical high (WPSH). For the first two types of PHTEs, a southwestward migrating mid-latitude wave train from the North American coast to the central and eastern China can be clearly seen in the whole troposphere. Whereas the two types of PHTEs show different features in the low-latitude. It is found that a significantly westward extension of the WPSH during the first type of PHTEs, with the low-frequency anticyclone moving westward in the mid-lower troposphere. For the second type of PHTEs, the WPSH is mainly located in the southeastern China with slightly movement. Analysis of the low-frequency vertical circulation and the thermodynamic equation further reveal that the increase of temperature in Jiangnan region is primarily attributed to the descending airflow. [ABSTRACT FROM AUTHOR]

Air-assisted sprayers are the mainstream orchard plant protection machinery in China. During the usage of sprayers, the pesticide droplets carried by strong air jets from sprayers enter into the target canopy. Therefore, the distribution of airflow field in the canopy has significant influence on the spatial movement of the droplets and the adhesion and penetration of the droplets inside the canopy. To enhance the working performance of sprayers, it is imperative to study their use in tree canopies. Based on computational fluid dynamics (CFD), the k-ε turbulence model, and the SIMPLE algorithm, a 3D simulated model of the spatial distribution of the airflow field in and around the tree canopy was established based on the porous model in this paper. The model was used to simulate and calculate the air field distribution of an air-assisted orchard sprayer under different operating parameters. The results showed that the optimal operation effect was achieved when the driving speed and the air speed of the fan outlet were 1 m/s and 20 m/s, respectively, while the air speed in the canopy was not less than 2 m/s. The 36 points measured in the canopy were compared with the simulated results through field experiments. It showed that average relative error between the measured and simulated values was 13.85%, and the overall goodness-of-fit was 0.97656. The model accurately simulated the airflow distribution in the canopy and provided a basis for optimizing the operating parameters of the air-assisted sprayers in orchards. [ABSTRACT FROM AUTHOR]

The built-in refrigerator has been popular in China in recent years due to users' high requirements for the integration of home appliances and furnishings. However, the built-in configuration will cause a significant performance deterioration, which has been less quantitively studied. The condenser and its refrigerator performance are compared experimentally and numerically between built-in and free-standing configurations. By contrast with the free-standing condition, the built-in condenser has poor performance attributed to two reasons: 28.6% lower condenser air flowrate and 10.72 °C higher condenser inlet air temperature caused by the hot short-circuited airflow. This heat dissipation deterioration increases the condensing temperature and discharge temperature, resulting in a refrigerator cooling capacity loss. Correspondingly, the compressor increases the rotating speed and power to compensate for the loss. The compressor ON-time ratio reduces by 8% but the average power during the compressor-on period increases by 56.9%, finally increasing the energy consumption by 43.4%. This study also provides some guidance for further heat dissipation and airflow field optimization of built-in refrigerators. [ABSTRACT FROM AUTHOR]

The study of particle nucleation and growth within clouds forms the fundamental microphysical component of cloud precipitation physics. Thus, we can establish cloud and fog precipitation development theories, providing a foundation for understanding weather, climate, and environmental changes. This case study, we observed ice cloud particles and meteorological elements using aircraft instruments over the North China Plain region on February 18, 2019. Focusing on aerosol–cloud interactions, we categorized clouds using altitude, vertical airflow, and cloud droplet concentration. The average number concentrations of cloud droplets (Nc), ice (Ni), and aerosols (Na) were 1.06 cm−3, 5.30 L−1, and 1.63 × 10 3 cm−3, respectively. The ice water content (IWC) in clouds was two orders of magnitude higher than the liquid water content (LWC). The differences in Nc at different heights were primarily caused by the presence of small droplets (smaller than 15 μm). Droplet concentrations were higher at 1–2 km and at the top of the clouds (5–6 km). Ice formation and growth was nonuniform in all zones, concentrated in the smallest and largest particle size ranges, with peaks at 125 and 1500 μm. Updraft significantly impacted cloud droplets, promoting their development and growth through water vapor condensation. Vertical airflow exerted a minor impact on aerosols. The Wegener–Bergeron–Findeisen process, driven by ice supersaturation and cloud liquid water subsaturation, led to a decrease in cloud droplet concentration and an increase in ice crystal concentration within the updraft region. In regions with different cloud droplet enrichment levels, the distribution of particles varied within the clouds. Zone with no vertical movement exhibited higher Nc than zone with downdraft airflow. The dense cloud droplet zone with downdraft airflow indicated narrower spectrum. Nc ranged from 2.5 to 19 μm, Ni ranged from 125 to 1350 μm, and Na ranged from 0.1 to 1 μm (no particles between 0.4 and 1 μm were observed). Ice formation and growth varied in each zone, possibly due to ice fragmentation. [Display omitted] • The sizes of ice cloud particles are predominantly found at 125 and 1500 μm. • Cloud drops in the updraft region were prone to form ice through the WBF process. • Formation and growth of ice were non-uniform due to ice fragmentation. • The dense cloud droplets zone with downdraft airflow had a narrower spectrum. [ABSTRACT FROM AUTHOR]

The existing knowledge illustrated the role of surrounding mountains in the transportation of dust into a basin, including the blocking of low-layer dust and the allowance of elevated dust intrusion. Taking the Sichuan Basin in southwestern China as an example, we found the impact of clouds on the transportation process of dust in the basin area. If there were low-level clouds on the basin edges, the dust particles could not penetrate the cloud layers, but settled down from upper air into the basin in the cloudless regions. They could be transported beneath clouds in the basin. Considering that the upslope airflow accompanied by dust transportation was conducive to the low-level clouds on the basin edge, this mechanism further reduced the dust intrusion besides the shelter of the surrounding mountains. [ABSTRACT FROM AUTHOR]

On the basis of the Prandtl boundary layer theory and an improved perturbation method, the process of laminar flow bifurcating into the Southwest China vortex (SWV) in the Hengduan Mountains is studied. The results show that the formation of SWV is mainly determined by the speed of incoming airflow in the direction of the main axis of the Hengduan Mountains. The vortex is generated in the leeward area of the Hengduan Mountains when the speed of incoming airflow is greater than the critical velocity. Moreover, it means that the laminar flow bifurcates into a vortex. The formation position of the SWV is mainly determined by the relative position of the incoming airflow in the windward area of the Hengduan Mountains and the main axis of the Hengduan Mountains. The seasonal distribution of SWVs is determined by both the velocity of the incoming airflow and the relative position of the incoming airflow to the main axis of the Hengduan Mountains. These findings are consistent with the SWV observation facts, which not only adequately explain the physical formation mechanisms and processes of SWVs, but also present the formation location and seasonal distribution of SWVs. Meanwhile, a solution from laminar to vortex in circumflow motion is also presented. [ABSTRACT FROM AUTHOR]

Extreme torrential rainfall events are low‐probability events. A "China‐Record Extremely Heavy Rainfall" (CREHR) event with rain rate of 201.9 mm/hr occurred on 20 July in Zhengzhou in North China. Using high‐density meteorological observations, ERA5 reanalysis data, remote sensing data from China's FY‐4A satellite, and numerical simulation, we revealed that sufficient warm–humid airflows were continuously transported to the Zhengzhou area via multiple pathways that were mainly modulated by the large‐scale western Pacific subtropical high to the north along with the anomalies of the westerly belt and a meso‐scale binary typhoon system. At the local scale, under the combined action of the vertical circulation that caused low‐level convergence and high‐level divergence, and the rapid uplift of water vapor related to the blocking by mountainous terrain, this CREHR event was eventually triggered. Particularly, our present work shows the roles of both typhoon Cempaka and meso‐scale convective systems to south of Henan province can not be ignored, producing a strong super‐thick water vapor transport layer. The existence of the binary typhoon raises the level of uncertainty involved in the water vapor transport of this CREHR event. Plain Language Summary: Extreme torrential rainfall events are low‐probability events. The rainfall from 16:00 to 17:00 Beijing time on 20 July in Zhengzhou in North China reached 201.9 mm, which was a record in mainland China—a so‐called "China‐Record Extremely Heavy Rainfall" (CREHR) event. By using high‐density meteorological observations, ERA5 reanalysis data, remote sensing data from China's FY‐4A satellite, and numerical simulation, we found that sufficient warm–humid airflows were continuously transported to the Zhengzhou area via multiple pathways that were mainly modulated by the large‐scale western Pacific subtropical high to the north along with the anomalies of the westerly belt and a meso‐scale binary typhoon system. At the local scale, under the combined action of the vertical circulation that caused low‐level convergence and high‐level divergence, and the rapid uplift of water vapor related to the blocking by mountainous terrain, this CREHR event was eventually triggered over northern mainland China. Our findings reveal that the existence of the binary typhoon circulation raises the level of uncertainty involved in the water vapor transport of this CREHR event, which has implications for improving our ability to predict and provide early warnings for severe rainstorms and related disasters in cities with such a complex context. Key Points: Sufficient warm‐humid airflows were continuously transported to the Zhengzhou area via multiple water vapor pathwaysMultiple pathways were mainly modulated by the large‐scale western Pacific subtropical high, the westerly belt and mesoscale binary typhoonsNorthward movement of multiple meso‐scale convective systems caused a strong super‐thick water vapor transport layer [ABSTRACT FROM AUTHOR]

The Huaihe River basin (HRB) is an important economically developed and grain production region in China, which is severely affected by rainfall anomalies, especially extreme rainfall events (EREs). It is crucial to the features of interdecadal change in EREs and the contribution of EREs to summer-mean total rainfall amount (TRA) over the HRB. Using the observational 24-h ac-cumulated rainfall and the reanalysis products from the European Center for Medium-Range Weather Forecast (ECMWF), as well as the methods of composite analysis and Mann–Kendal and running t tests, we revealed that the EREs experienced a significant interdecadal increase from the period 1990–1999 to the period 2000–2009. The EREs, particularly long persistent extreme rainfall events (LPEREs), occurred more frequently over the HRB during the latter period and dominated the interdecadal increase in the summer mean TRA. An anomalous high-pressure ridge and associated anomalous anticyclone appeared around Lake Baikal during the latter period, which led to anomalous northeasterlies along the eastern flank of the anomalous anticyclone, inducing the southward intrusion of cold air flow from higher latitudes and associated anomalous ascent and more active convection over the HRB. As such, more EREs and LPEREs occurred during the latter period. The higher pseudo-equivalent temperatures also support more active convective ascent and relevant more EREs. The results may shed light on further understanding the effect of large-scale atmospheric circulation on the interdecadal variability of EREs over the HRB, helping mitigate the disastrous impacts of EREs on local ecosystems, agriculture, soil erosion, and societies. [ABSTRACT FROM AUTHOR]

The highest concentration of PM2.5 in cold rural dwellings of Northeast China is often generated by using mini stoves for cooking and heating, which can directly influence human health. As of yet, little is known about the impact of different daily life behavior on PM2.5 diffusion and residents' exposure in rural dwellings. In this study, the characteristics of indoor PM2.5 variation and diffusion in rural dwellings was described by measuring some rural dwellings and establishing a multi-zone network model. The calculated results indicated that the relative errors between theoretical calculated results and experimental measured results are within 10%. PM2.5 diffusion in a rural dwelling can be predicted. Furthermore, the impacts of daily life behavior on PM2.5 diffusion and exposure assessment can be analyzed. Through discussion, heating behavior is the most important factor causing high concentrations of PM2.5 in each room, followed by cooking, smoking, and cleaning. Door opening time can lead to different interzonal airflows and PM2.5 diffusion rates. By reducing the inner door opening time to less than 1 min, PM2.5 could decrease to 300 μg/m3. Door closing behavior could decrease risk that PM2.5 diffuses to bedrooms by more than 50%, and exposure of residents in bedrooms could reduce to 100 (μg·h)/m3 effectively. [ABSTRACT FROM AUTHOR]

With the increase in orchard areas and the transfer of rural labor, various air-assisted sprayers have been widely used in China. However, the problem of off-target drift still exists, which has caused pesticide waste and environmental pollution. In order to improve the droplet deposition in the canopy of fruit trees, a V-shaped anti-drift spray device with multi-airflow synergy was designed in this paper. A droplet spatial motion model was constructed, and the anti-drift mechanism of multi-airflow synergy was clarified based on particle dynamics analysis. The influences of spray pressure and V-shaped wind speed on droplet movement were investigated by Matlab, and the experimental results showed that the machine's anti-drift effect was better when the V-shaped wind speed ranged from 15 m/s to 25 m/s. According to modern orchards with low root stock in a high-density planting, a simulation model of the flow field between the spray device and the fruit trees canopy was established by the method of computational fluid mechanics (CFD). By considering crosswind speed, V-shaped wind speed, and spray pressure, three-level simulation experiments of droplet deposition were designed for each factor using a partial multivariate orthogonal regression method. The influence of V-shaped wind speed on the droplets' spatial distribution was analyzed, and the prediction model of the drift distance of the droplets' deposition center was established. The simulation results showed that the three factors had a significant influence on the droplets' deposition characteristics, and the degree from big to small was V-shaped wind speed, crosswind speed, and spray pressure. The fitting degree of the prediction model was high, and the correlation coefficient was 0.998. The anti-drift experiments of the machine were carried out, and the results showed that when the crosswind speed, the spray pressure, and V-shaped wind speed were 2.2 m/s, 0.52 MPa, and 20.8 m/s, respectively, the droplet drift rate was 29.2% lower than that of single-airflow. The drift distance of the droplets deposition center was 5.0 cm, which was consistent with the prediction model. The research can provide a basis for the design and parameters optimization of the similar sprayers used in modern orchards with low root stock in a high-density planting. [ABSTRACT FROM AUTHOR]

Large-scale open burning of straw residues causes seasonal and severe atmospheric pollution in Northeast China. Previous studies focused on the causes or assessment of atmospheric pollution in a single city. However, studies conducted on the interaction range, degree and policy control of pollutant transport on a large scale are still to be performed. In this study, we propose combined control of straw burning by dividing region the straw burning in Northeast China in recent 20 years, determining the transport routes between main cities, and analyzing the interaction characteristics of straw burning under different scenarios. The fire point data suggest that the most intense straw burning years in Northeast China in the past 20 years occurred in the range from 2014 to 2017, mainly after the autumn harvest (October–November) and before spring cultivation (March–April). The burning areas were concentrated in the belt of Shenyang-Changchun-Harbin, the border of the three provinces and Eastern-Inner Mongolia, and the surrounding area of Hegang and Jiamusi City. The lower number of fire points before 2013 indicates that high-intensity burning has not always been the case, while the sharp decline after 2018 is mainly due to scientific control of straw burning and increased comprehensive utilization of straw. Compared with S2, the PM2.5 concentrations increased by 6.2% in S3 and 18.7% in S4, indicating that burning in three or four provinces at the same time will significantly increase air pollution and exert a regional transmission effect. Straw burning in Northeast China is divided into six main regions based on correlation analysis and satellite fire monitoring. Under typical S3, the case analysis results indicate that there is regional transmission interaction between different cities and provinces, focusing on multi-province border cities, and it is affected by Northwest long airflow, and Southeast and Northeast short airflow. These results provide scientific and technological support for implementing the joint prevention and control plan for straw incineration in Northeast China. [ABSTRACT FROM AUTHOR]

Among food crops, rice has the largest planting area, the highest yield per unit area and the largest total yield in China. However, cleaning performance is reduced by the high moisture content of rice during the harvesting process. In order to decrease the adhesion among wet rice threshed mixtures and improve the cleaning performance, the method of hot airflow cleaning was proposed. Firstly, the fluidization characteristics of wet sticky rice under the action of hot air were compared with those of dry particles. In this work, the minimum suspension velocity and the fastest suspension time were used and quantified to characterize the fluidization characteristics. It was found that the minimum suspension velocity and the fastest suspension time of the wet rice threshed mixture are both higher than those of dry particles due to the liquid bridge force. Moreover, the dispersion degree of the wet rice threshed mixture can be improved by the hot airflow due to the decrease in the surface water content of impurities. Secondly, the influence of the temperature and vibration frequency in the air-and-screen cleaning device on the dispersion characteristics of the wet rice threshed mixture were investigated. The accumulation mass was measured to quantify the dispersion degree. It was found that the increase in vibration frequency has little effect on the dispersion of the wet rice threshed mixture. The accumulation mass on the front of the sieve decreases slightly with the increase in the gas temperature range from ambient temperature to 30 °C. Then, the dispersion degree increases rapidly when the temperature exceeds 40 °C. The dispersion effect is the best when the temperature is 50 °C and the vibration frequency is 5 Hz. These results provide a basis for the cleaning of the wet rice threshed mixture in a combine harvester. [ABSTRACT FROM AUTHOR]

Extremely persistent heavy rainfall (EPHR) events frequently occur in southern China. The mechanisms underlying their generation and development are not well understood, and this leads to difficulties in accurately forecasting these events. In this paper, hourly precipitation grid data and ERA‐5 reanalysis data are used to examine the relationships between precipitation, ageostrophic winds, and low‐level jets (LLJ). The results suggest that ageostrophic winds in the boundary layer mainly exhibit confrontational and asymptotic convergence, with the former being accompanied by double LLJ, which transport more vapor and provide favorable uplift conditions, thus producing stronger precipitation and wider rainbands. The different cooperated relationships between LLJ and ageostrophic winds play an important role in the development of EPHR events, and greater account needs to be taken of these relationships when forecasting. Plain Language Summary: Coastal extremely persistent heavy rainfall (EPHR), long‐duration heavy rainfall in local coastal area, occurs frequently in Southern China, and this kind of rainfall is usually accompanied by southwesterly in the lower atmosphere, which we call as the southwest low‐level jet. Generally, the occurrence and development of rainfall is accompanied by the convergence of the lower air flow. Since the divergence of the geostrophic wind component of the wind field is zero, the convergence situation is characterized by the ageostrophic wind component, which doesn't satisfy the geostrophic balance. In this type of coastal EPHR accompanied by the Southwest Jet, the ageostrophic wind is mainly manifested in two different convergence situations. One is that the ageostrophic wind presents several opposite branches of directions presenting a confrontational pattern around the rainfall area, and the other is an asymptotic convergence in which two similar wind directions, such as northeasterly and southeasterly, gradually converge to the rain area. The former has stronger lower‐level uplift, greater precipitation and wider rain bands, while the latter is relatively weak. This is an interesting phenomenon, of which the specific mechanisms need to be further studied. Key Points: About 74% of extremely persistent heavy rainfall cases along the coast of southern China are accompanied by southwest jets in the marine boundary layerAgeostrophic winds mainly exhibit confrontational and asymptotic convergence, and the former is accompanied by double low‐level jetsCases of ageostrophic winds with confrontational convergence have stronger precipitation and wider rainband [ABSTRACT FROM AUTHOR]

Over the past decades, China has suffered from negative environmental impacts from distempered dust-laden airflow-purification activities. After a decade of effort, dust-laden airflow purification and powder particle recycling have been realized in specialized companies in China, and law enforcement for illegal activities of dust-laden airflow discharge has also been made increasingly strict. Thus, up to now, dust-laden airflow purification in China should be developed toward being more in-depth and refined to promote industrial applications of dust-laden airflow purification. This article reviews the status of existing technologies for dust-laden airflow purification. A novel and environmentally friendly technology for purifying the dust-laden airflow is proposed which uses a metal bag filter to collect dust particles. The bottlenecks in the dust-laden airflow-purification system are analyzed. Some preliminary experiments of pinch technologies are also conducted. Finally, in order to provide directional guidance for the future development of metal bag filters, some key points regarding the metal bag filter purification system are proposed to point towards a future trend in dust-laden airflow purification. [ABSTRACT FROM AUTHOR]

Actual airborne time (AAT) is the time between actual wheels-off and actual wheels-on of a flight. Given the ever-growing demand for air travel and growing flight delays, understanding the behavior of AAT is increasingly important for on time performance and delay propagation. Of particular interest is the comparison on AAT in different countries with varying air route structures, air traffic management systems, weather, and geography. This paper performs the first comparative empirical analysis of AAT behavior, focusing on the U.S. and China. The focus is on how AAT is affected by origin-destination (OD) distance, the possible pressure to reduce AAT from other parts of flight operations, hub status of departure/arrival airports, enroute and terminal traffic conditions, and convective weather. Econometric models are developed to quantify the impacts of factors on AAT behavior in China and the U.S., separately. The estimation results show that in both countries AAT is highly correlated with OD distance. Flight time in China is longer than that in the U.S. given the same OD distance which indicates a low effective speed may be the result of a low aircraft speed, or due to the flight experiencing metering, rerouting, holding or vectoring in Chinese airspace. In addition, we find that a flight has limited capability to make up for pre-departure delay. Sensitivity analysis of AAT to flight length and aircraft utilization is further conducted. Given the more abundant civil airspace, flexible routing networks, and efficient air traffic flow management (ATFM) procedures, we performed a counterfactual analysis to investigate how Chinese AATs would change if they were governed by the U.S. model. We find that this would result in significant efficiency gains for the Chinese air traffic system. On average, 13 min of AAT per flight would be saved. Systemwide fuel saving would amount to 326 million gallons with CO 2 emission reduction of 2.7 million tons and direct airline operating cost saving of over $1.3 billion in 2016. • Perform empirical analysis of flight Actual Airborne Time (AAT) in the US and China. • AAT is found highly correlated with OD distance. • Flight time in the US is shorter than in China given the same OD distance. • Flight has limited capability to make up for pre-departure delay. • Efficiency gains could be achieved if applying the US model to the Chinese system. [ABSTRACT FROM AUTHOR]

The flow-field characteristics of high-temperature airflow and particle distributions generated from the running furnace during smelting process in foundry shop were studied by on-site measurements and theoretical analysis in this work. A theoretical model was proposed to describe the dispersion characteristics of the high-temperature buoyant jet flow and plume induced by the furnace with two typical opening modes. The coupling effects of the heat source features and environmental factors were emphatically discussed by comparing the trajectory, cross-section diameter, velocity and temperature decay, and volumetric flow rate during the dispersion process. Results show that in the large foundry shop with natural ventilation, there is a vertical temperature gradient of 0.1–0.4 °C/m, which can make the pollutant locked in the workshop and weaken the entrainment of the thermal flow. The crossflow is a non-negligible factor, which causes the dispersion trajectory of the pollutant flatter and induces a long travelling distance along the horizontal direction. The indoor particle concentration when the furnace opens concentration seriously exceeds the limits in the existing indoor air quality standard of China. This work is expected to give suggestions on ventilation designs and arrangements of the exhaust port or device in industrial environments. [ABSTRACT FROM AUTHOR]

Passages of strong cold airflow can quickly purge air pollutants over source region, e.g. North China Plain (NCP), while regional transport of air pollutants from source region would exacerbate air quality in the receptor region of Twain-Hu Basin (THB), due to the cold airflows modulated by atmospheric circulations over China. In this study, nine heavy pollution events (HPEs) in THB, Central China during the winters of 2015–2019 were identified for investigating the regional transport patterns of air pollutants from Central and Eastern China (CEC) to THB driven by strong cold airflows. Once regional transport of air pollutants from the CEC source regions was triggered by strong northerlies, PM 2.5 pollution parcels then converged in the downwind THB receptor region through a dominant dynamic mechanism for most HPEs (66.7%) with downward airflow, which generally resulted in long durations of high PM 2.5 concentrations and the impacted areas were modulated by synoptic patterns over the CEC. Non-dominant transport patterns were also observed with a cyclonic circulation of high wind speeds or a local stagnation of cold air over the THB, contributing to the highest and shortest PM 2.5 peak or small impacted areas limited to the northern THB, respectively. It was estimated that the regional transport of PM 2.5 from non-local regions accounted for 51.0%–85.7% of PM 2.5 concentrations during the HPEs at Wuhan, revealing the dominance of regional transport of air pollutants from CEC to the THB with the meteorological drivers. • Nine heavy pollution (HPEs) in the Twain-Hu Basin were driven by strong cold airflows. • A dominant dynamic mechanism was identified for the HPE formation. • Regional pollutant transport from the north contributed significantly to the HPEs. [ABSTRACT FROM AUTHOR]

• Three control methods for water pumps in district heating using ASHPs are proposed. • A new bypass branch is proposed to reduce the energy loss at small heating load. • Power input of water pumps can be decreased by 0–31.84%. • An average decrease rate of 13.40% in power input of ASHP system is obtained. In recent years, the application of air source heat pumps (ASHPs) in centralized heating has grown rapidly in North China. However, there is still lack of theoretical investigation on the control methods of water pump. To decrease the system power consumption, a mathematical model of variable-frequency ASHP used for supplying heating for ten users was established in this work. Meanwhile, three control methods of water pumps were proposed. The heating performance of ASHP system under the three control methods was investigated. Besides, the appropriate control methods of heating terminals under the three control methods were analyzed. Results showed that the minimum relative water flow rate is 30%. Among the three proposed control methods, the power input of water pump is the minimum in the pressure differential control method of the most unfavorable terminal, and its difference with the highest value is 0–31.84%. For the power input of ASHP system, it is always the maximum in constant flow control method, while the minimum in the pressure differential control method of the most unfavorable terminal. Compared with the values in the former control method, the power input of ASHP system in the latter control method decreases by an average of 13.40%. [ABSTRACT FROM AUTHOR]

Simple Summary: Airflow is very important for the long-distance migration of O. decorus asiaticus, and wind shear, in particular, is the main factor related to forced landing. Analyzing the weather records, we found that the northwest wind prevailed when the population invaded. Specifically, from July to August, a large number of emerging adults appeared in the source areas of Mongolia, and the large-scale northwest wind was the decisive condition for the successful long-distance migration of O. decorus asiaticus. The species has a strong migratory ability, flying along the airflow for several nights. If the northwest air current meets the southwest warm current going north, a large number of O. decorus asiaticus will drop due to wind shear, and then a major outbreak will occur. Analysis of the source of the insects shows that the O. decorus asiaticus break outs in China may have originated from Mongolia. They were brought into China by the southerly airflow at night, and they likely made a forced landing in Beijing due to wind shear, sinking airflow, rainfall and other reasons. In summary, through analysis of the insect's prevalence and the meteorological conditions in Mongolia, we can provide a basis for predicting the occurrence of O. decorus asiaticus in China. Oedaleus decorus asiaticus (Bey-Bienko) is a destructive pest in grasslands and adjacent farmland in northern China, Mongolia, and other countries in Asia. It has been supposed that this insect pest can migrate a long distance and then induce huge damages, however, the migration mechanism is still unrevealed. The current study uses insect light trap data from Yanqing (Beijing), together with regional meteorological data to determine how air flow contributes to the long-distance migration of O. decorus asiaticus. Our results indicate that sinking airflow is the main factor leading to the insects' forced landing, and the prevailing northwest wind was associated with O. decorus asiaticus taking off in the northwest and moving southward with the airflow from July to September. Meanwhile, the insects have a strong migratory ability, flying along the airflow for several nights. Thus, when the airflow from the northwest met the northward-moving warm current from the southwest, a large number of insects were dropped due to sinking airflow, resulting in a large outbreak. Our simulations suggest that the source of the grasshoppers involved in these outbreaks during early 2000s in northern China probably is in Mongolia, and all evidence indicates that there are two important immigrant routes for O. decorus asiaticus migration from Mongolia to Beijing. These findings improves our understanding of the factors guiding O. decorus asiaticus migration, providing valuable information to reduce outbreaks in China that have origins from outside the country. [ABSTRACT FROM AUTHOR]

In rice–wheat rotation areas of China, traditional wheat seeders have severe blockage, low working efficiency and poor seeding quality. In this study, a pneumatic shooting technology was designed, consisting mainly of a nozzle, shell and acceleration tube. To improve the sowing depth of the pneumatic shooting device, the response-surface methodology of structure parameters and CFD simulation technology was adopted in this work. The effects of working pressure, acceleration-tube diameter and throat distance on the steady airflow length (SAL) and steady airflow velocity (SAV) were studied by airflow field analysis, and the response-surface method was introduced to obtain the optimal parameter combination of the pneumatic shooting device for wheat. The optimal parameter combination was working pressure 686 kPa, acceleration tube diameter 8 mm and throat distance 20 mm. The simulation result showed that the optimized device of pneumatic shooting performs faster and has more stable airflow field characteristics in comparison to the initial device. The field test demonstrated that the optimized device has about 68% higher seeding depth than the initial device. The average field-seeding depth of the optimized device was 19.95 mm, which is about 68% higher than the initial device. The emergence rate for the optimized device was about 88.7% without obvious reduction. CFD and response-surface methods positively affect the optimization of pneumatic wheat-shooting devices, and the significance was also confirmed. [ABSTRACT FROM AUTHOR]

The development of energy-saving technologies for buildings is an important means of achieving carbon neutrality. The respiration-type double-layer glass curtain wall (RDGCW) is a kind of enclosure structure with natural air circulation and a shading function. The RDGCW provides energy saving, and it is being widely promoted and used in China. However, there is still a lack of relevant research on the energy-saving effects and operating strategies of the RDGCW throughout the year. In response, this paper describes experimental evaluation and numerical simulation. First, the energy-saving effects in an office building using an RDGCW in Tianjin during the winter were studied experimentally, and the real-time temperature changes in the RDGCW and the room were measured with high accuracy under different operating strategies. Second, because the temperature distribution and energy consumption in a room is affected by the air flow in the RDGCW and by outdoor meteorological parameters in a complex manner, this investigation developed a coupled model on the basis of TRNSYS and CONTAM. The simulation results were in good agreement with the experimental results. Third, the verified model was used to evaluate the annual energy-saving effects of the RDGCW under dynamic outdoor meteorological conditions in Tianjin. When the optimal operating strategy was adopted, the energy-saving effect of the RDGCW in comparison with single skin façade (SSF) reached 32.8% under summer conditions and 38.3% under winter conditions. Finally, the RDGCW system in typical cities (Changchun, Shanghai, Guangzhou, Kunming and Tianjin) in five climate zones in China was simulated for the whole year. Under the optimal strategy, the RDGCW achieved good energy-saving effects. The energy saving was 27.7–49.2% in summer and 25.6–46% in winter, in comparison with SSF. [ABSTRACT FROM AUTHOR]

Air traffic trajectory optimization is a complex, multidimensional and non-linear optimization problem and requires a firm focus on the essential criteria. The criteria cover operational, economical, environmental, political, and social factors and differ from continent to continent. Since air traffic is a transcontinental transport system, the criteria may also change during a single flight. Historic flight track data allow observation and assess real flights, to extract essential criteria and to derive optimization strategies to increase air traffic efficiency. Real flight track data from the Chinese and European air traffic show significant differences in the routing structure in both regions. For that reason, reference trajectories of historic ADS-B 24-h air traffic data in China and Europe have been extracted and analyzed regarding horizontal flight efficiency and the most restrictive criteria of trajectory optimization. We found that prohibited areas might be the most powerful reason to describe deviations from the great circle distance in the Chinese air traffic system. Atmospheric conditions, network requirements, aircraft types and flight planning procedures are similar in China and Europe and only have a minor impact on flight efficiency during the cruise phase. In a multi-criteria trajectory optimization of the extracted reference trajectories considering the weather, operational constraints and prohibited areas, we found that flown ground distances could be reduced by 255 km in the Chinese airspace and 2.3 km in the European airspace. The resultant reference trajectories can be used for further analysis to increase the efficiency of continental air traffic flows. [ABSTRACT FROM AUTHOR]

Pollination success is essential for hybrid oilseed rape (OSR, Brassica napus) seed production, but traditional pollination methods are not efficient. The unmanned agricultural aerial system (UAAS) has developed rapidly and has been widely used in China. When flying, the wind field generated by the rotors overcomes the UAAS gravity, and it blows and disturbs the crops below, which helps the pollen spread. In order to investigate the distribution law of the three-dimensional (direction x, y, z) airflow field, experiments involving three levels of flight speed (FS) at 4.0, 5.0, and 6.0 m/s, and three levels of flight height (FH) at 1.5, 2.0, and 2.5 m were conducted in the OSR field by using an electric four-rotor UAAS P20. The effects of FS and FH on airflow velocities ( v x , v y , v z ) were analyzed. High-speed dynamic camera (HSDC) technology was used to capture the swings of OSR plants under airflow field disturbance. OSR pollen samples were collected during the experiments. The results showed that the airflow field in the direction x was mainly concentrated on the center of the flight path (S3), and the maximum wind velocity of direction x was 8.01 m/s (T1, S3). The direction x airflow field width was distributed almost symmetrically, but the center position shifted easily, due to crosswind. The airflow field in the direction y was distributed on both sides of the center flight path, and the velocity was generally larger, with the maximum at 7.91 m/s (T1, S2). The airflow field in the direction z was distributed irregularly, and the velocity was small. The FH had highly significant impacts on   v x (p < 0.01), and the interaction of FS and FH had significant impacts on   v x (0.01 < p < 0.05), while the FS had no significant impact on v x (p = 0.70804 > 0.05). The FS, FH, and interaction of FS and FH all had highly significant impacts on v y (p < 0.01). The swings of the OSR plant captured by the HSDC proved that the UAAS airflow field could effectively blow the OSR plant. The swing amplitude changes showed a positive correlation with airflow velocities ( v x ) in general. Although the observed OSR plant swung forward and backward repeatedly, there was a law of first forward, and then backward, and forward again at the beginning of each swing. The pollen collected on the sampler verified that the UAAS airflow field could help with pollen spread. The research results provide technical support for UAAS application on supplementary pollination for hybrid OSR seed production. [ABSTRACT FROM AUTHOR]