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Label assignment is a crucial process in object detection, which significantly influences the detection performance by determining positive or negative samples during training process. However, existing label assignment strategies barely consider the characteristics of targets in remote sensing images (RSIs) thoroughly, e.g., large variations in scales and aspect ratios, leading to insufficient and imbalanced sampling and introducing more low-quality samples, thereby limiting detection performance. To solve the above problems, an elliptical distribution aided adaptive rotation label assignment (EARL) is proposed to select high-quality positive samples adaptively in anchor-free detectors. Specifically, an adaptive scale sampling (ADS) strategy is presented to select samples adaptively among multilevel feature maps according to the scales of targets, which achieves sufficient sampling with more balanced scale-level sample distribution. In addition, a dynamic elliptical distribution (DED) aided sampling strategy is proposed to make the sample distribution more flexible to fit the shapes and orientations of targets and filter out low-quality samples. Furthermore, a spatial distance weighting (SDW) module is introduced to integrate the adaptive distance weighting into loss function, which makes the detector more focused on the high-quality samples. Extensive experiments on several popular datasets demonstrate the effectiveness and superiority of our proposed EARL, where without bells and whistles it can be easily applied to different detectors and achieve state-of-the-art performance. The source code will be available at: https://github.com/Justlovesmile/EARL.

Ammonia control has received increasing attention as a measure to decrease particulate concentrations. Modeling analysis of observation data from central China over the period of September 2015 to August 2016 shows clear asymmetric responses of particulate pH and mass to ammonia emissions. With a change of ±80% of NHx(NH3+ NH4+), the corresponding ΔpH are +0.5 and −3.0, respectively, and the corresponding particulate NH4+changes are +2.62% and −61.8%, respectively. This asymmetry implies that there is a Critical Total Ammonia Concentration, above which particulate pH and mass are insensitive to ammonia control. Analysis of the observation data suggests that the Critical Total Ammonia Concentration is −25%. The estimated cost for an NHxreduction of 25% is $140 – 320 million for Hubei province, which is the initial cost barrier before ammonia control can effectively affect particulate pH and mass in central China. This cost barrier will increase as NOxand SO2emissions decrease. Only after NHxreduction exceeds 25% can ammonia control effectively reduce the inorganic aerosol massMore NHx reduction will be required to reach the critical point of effective ammonia control as NOxand SO2emissions decreaseA large enough NHxreduction (60%–80%) renders concurrent reduction of NOxemissions ineffective and even the effect of SO2emission control is reduced

Secondary organic aerosol (SOA) can affect the atmospheric radiation balance through absorbing light at shorter visible and UV wavelengths. However, the composition and optical properties of light-absorbing SOA is poorly understood. In this work, SOA filter samples were collected during individual chamber experiments conducted with three biogenic and eight aromatic volatile organic compound (VOC) precursors in the presence of NOXand H2O2. Compared with the SOA generated using the aromatic precursors, biogenic SOA generally exhibits negligible light absorption above 350 nm; the aromatic SOA generated in the presence of NOXshows stronger light absorption than that generated with H2O2. Fifteen nitroaromatic compound (NAC) chemical formulas were identified and quantified in SOA samples. Their contributions to the light absorption of sample extracts were also estimated. On average, the m-cresol/NOXSOA sample has the highest mass contribution from NACs (10.4 ± 6.74%, w/w), followed by naphthalene/NOX(6.41 ± 2.08%) and benzene/NOX(5.81 ± 3.82%) SOA. The average contributions of NACs to total light absorption were at least two times greater than their average mass contributions at 365 and 400 nm, revealing the potential use of chromophoric NACs as brown carbon (BrC) tracers in source apportionment and air quality modeling studies.

To understand diurnal variations in PM2.5composition and aerosol extract absorption, PM2.5samples were collected at intervals of 2 hr from 8:00 to 20:00 and 6 hr from 20:00 to 8:00 (the next day) in northern Nanjing, China, during the winter and summer of 2019–2020 and analyzed for bulk components, organic tracers, and light absorption of water and methanol extracts—a proxy measure of brown carbon (BrC). Diurnal patterns of measured species reflected the influences of primary emissions and atmospheric processes. Light absorption coefficients of water (Abs365,w) and methanol extracts (Abs365,m) at 365 nm shared a similar diurnal profile peaking at 18:00–20:00, generally following changes in biomass burning tracers. However, Abs365,w, Abs365,m, and their normalizations to organic aerosols increased at 14:00–16:00, earlier than that of levoglucosan in the late afternoon, which was attributed to secondarily formed BrC. The methanol extracts showed a less drastic decrease in light absorption at night than the water extracts and elevated absorption efficiency during 2:00–8:00. This is due to the fact that the water‐insoluble OC has a longer lifetime and stronger light absorption than the water‐soluble OC. According to the source apportionment results solved by positive matrix factorization (PMF), biomass burning and secondary formation were the major BrC sources in northern Nanjing, with an average total relative contribution of about 90%. Compared to previous studies, diurnal source cycles were added to the PMF simulations in this work by using time‐resolved speciation data, which avoided misclassification of BrC sources. Light‐absorbing organic carbon (OC), also known as “brown carbon”, plays an important role in influencing the Earth's radiative balance. Filter samples of particulate matter with an aerodynamic diameter of less than 2.5 μm (PM2.5) were collected at a resolution of 2 hr from 8:00 to 20:00 and a resolution of 6 hr from 20:00 to 8:00 (the next day) in northern Nanjing, China, during the winter and summer of 2019 and 2020. To understand the diurnal variations of BrC and its sources, each sample was analyzed for bulk components (OC, elemental carbon, and water‐soluble ions), organic molecular markers, and light absorption by BrC, and a receptor model was used to identify potential BrC sources based on PM2.5composition data. We found that diurnal variations of BrC generally followed changes in concentrations of levoglucosan‐a tracer of biomass burning; the increase in BrC absorption in the early afternoon was caused by secondary formation of BrC chromophores; biomass burning and secondary formation were the main sources of BrC. Time‐resolved measurements of PM2.5components were rarely used to investigate the diurnal variations of BrC and its sources, which is very important for modeling the climate impact of BrC. Diurnal variations in PM2.5bulk components and organic tracers reflect diurnal cycles of sourcesLight absorption of water and methanol extracts of PM2.5exhibited a similar diurnal profile that followed changes in levoglucosanShort‐term and high time‐resolved data of organic tracers should be used for source apportionment to avoid misclassification Diurnal variations in PM2.5bulk components and organic tracers reflect diurnal cycles of sources Light absorption of water and methanol extracts of PM2.5exhibited a similar diurnal profile that followed changes in levoglucosan Short‐term and high time‐resolved data of organic tracers should be used for source apportionment to avoid misclassification

By developing a nontarget tandem mass spectrometry experiment workflow, we identified the most probable structures of 100 brown carbon (BrC) chromophores in five types of atmospherically relevant samples including ambient aerosols, biomass burning aerosols, road tunnel aerosols, toluene secondary organic aerosol and rainwater. These chromophores were classified into nine groups, that is, 31 nitrophenols, 12 benzoic acids, 11 oxygenated polycyclic aromatic hydrocarbons, 10 phenols, 10 aryl amides/amines, 9 phenylpropene derivatives, 9 coumarins and flavonoids, 5 pyridines, and 3 nitrobenzoic acids. Among them, aryl amides/amine chromophores, which were mostly found in rainwater, were reported for the first time. The identified chromophores accounted for 20.9%–83.5% of total light absorption over 300–400 nm wavelength or total ion intensity in the 5 types of samples. We identified the characteristic chromophore groups in each sample type and identical chromophores among different sample types, especially between the source samples and ambient aerosols. Gas‐particle distribution and diurnal variation of 13 BrC compounds in the atmosphere were measured by an online high‐resolution chemical ionization mass spectrometer equipped with a Filter Inlet for Gases and Aerosols. It was found that gas‐particle distribution of BrC compounds was dictated by their functional group, oxygen and carbon atom numbers. The BrC compounds containing nitro‐group had higher nighttime concentrations, while those without nitro‐group had higher daytime concentrations. Brown carbon chromophores absorb near‐ultraviolet and visible light and thus influence atmospheric radiation and atmospheric chemistry. By developing a nontarget tandem mass spectrometry experiment workflow, we identified the most probable structures of a large diversity of brown carbon (BrC) chromophores in atmospherically relevant samples like ambient aerosols, biomass burning aerosols, road tunnel aerosols, secondary organic aerosol and rainwater. The similarity and difference of BrC chromophores in these samples were investigated, with a focus on exploring the source of the chromophores in ambient aerosols. For the first time, an online high‐resolution chemical ionization mass spectrometer was applied to measure gas‐particle distribution and diurnal variation of BrC chromophores in the atmosphere. We developed a nontarget tandem mass spectrometry experiment workflow to identify the most probable structures of brown carbon (BrC) chromophoresWe identified 100 BrC chromophores in five types of atmospheric samples, among which 33 chromophores was reported for the first timeFilter Inlet for Gases and Aerosols‐chemical ionization mass spectrometer was applied to measure gas‐particle distribution and diurnal variation of BrC chromophores in the atmosphere We developed a nontarget tandem mass spectrometry experiment workflow to identify the most probable structures of brown carbon (BrC) chromophores We identified 100 BrC chromophores in five types of atmospheric samples, among which 33 chromophores was reported for the first time Filter Inlet for Gases and Aerosols‐chemical ionization mass spectrometer was applied to measure gas‐particle distribution and diurnal variation of BrC chromophores in the atmosphere

This work focuses on the mass content of plasticizers in children’s backpacks and toys, and their mass transfer from product surfaces to cotton wipes. The mass content of plasticizers in six backpacks and seven toys was measured by extracting them in tetrahydrofuran. Bis(2-ethylhexyl) terephthalate (DEHT) was the most common plasticizer, dominating the composition of plasticizers in four backpacks (average mass content in product polyvinyl chloride, 5.38±1.98%–25.5±3.54%) and six plastic toys (8.17±1.85%–21.2±1.11%). The surface of each product was wiped with three dry and three wet (by isopropanol) cotton wipes, so as to evaluate the mass transfer of plasticizers to clothing and human skin, respectively. DEHT was the most common plasticizer detected on wipe samples. There were strong correlations (backpacks r=0.90; plastic toys r=0.96) between average mass transfer of DEHT to wet wipes and its average mass content in the product. The mass transfers of the five dominant plasticizers in one backpack to both dry and wet wipes were also correlated (both r=1.00) with their mass contents. These results suggest that the mass transfer of plasticizers from products to clothing or human skin is strongly associated with their mass content.

In this study, collocated filter samples of particulate matter with aerodynamic diameter less than 2.5 μm (PM2.5) from northern Nanjing were extracted using water and methanol, followed by analysis of light absorption. A backup quartz filter was used to correct sampling artifacts caused by adsorption of gaseous organics. The collocated precision of light‐absorbing properties of water‐soluble organic carbon (WSOC) and methanol‐extractable organic carbon (MEOC) were parameterized using correlation coefficient (r), coefficient of divergence (COD), and average relative percent difference (ARPD, %). In general, the light absorption of WSOC and MEOC showed good agreement (r> 0.80, COD < 0.20) between collocated samples. Performing artifact correction is necessary and will increase the heterogeneity between collocated measurements. The duplicate‐derived ARPD values of MEOC absorption were more than 60% higher than those of WSOC absorption. Then, it would be inappropriate to assume a uniform uncertainty fraction (e.g., ∼10%) for WSOC and MEOC absorption in future studies on their climate effects and source apportionment. To apportion artifact‐corrected absorption of aerosol extracts to specific emission sources or formation pathways, positive matrix factorization was performed by using concentration data of selected bulk species and organic molecular markers. Among the nine identified factor/sources, the biomass burning factor had the highest average contributions to the absorption of both WSOC (31.6%) and MEOC (48.0%), followed by dust resuspension and coal combustion factors. Unlike combustion‐related primary emissions, the factors containing influences from atmospheric processing (e.g., secondary nitrate) contributed more fractions of WSOC absorption than MEOC absorption. Collocated measurements provide an approach to estimate uncertainties in light‐absorbing properties of solvent‐extractable organic carbonIgnoring the adsorption of gaseous organics onto filter medium will lead to significant overestimation of brown carbon absorptionAerosol sources influenced by aging processes contributed more fractions of aqueous extracts absorption than methanol extracts absorption Collocated measurements provide an approach to estimate uncertainties in light‐absorbing properties of solvent‐extractable organic carbon Ignoring the adsorption of gaseous organics onto filter medium will lead to significant overestimation of brown carbon absorption Aerosol sources influenced by aging processes contributed more fractions of aqueous extracts absorption than methanol extracts absorption

In this paper, the time series analysis method CLEANest is employed to search for characteristic periodicities in the radio light curves of the blazar NRAO 530 at 4.8, 8.0 and 14.5 GHz over a time baseline of three decades. Two prominent periodicities on time scales of ∼6.3 and ∼9.5 a are identified at all three frequencies, in agreement with previous results derived from different numerical techniques, confirming the multiplicity of the periodicities in NRAO 530. In addition to these two significant periods, there is also evidence of shorter-timescale periodicities of ∼5.0, ∼4.2, ∼3.4 and ∼2.8 a showing lower amplitude in the periodograms. The physical mechanisms responsible for the radio quasi-periodic oscillations and the multiplicity of the periods are discussed.

This study seeks to understand the ambient levels, gas/particle partitioning, and sources of nonpolar organic molecular makers (OMMs) at a suburban site in Nanjing, China. Particle‐ and gas‐phase OMMs were collected using a medium volume sampler equipped with two quartz filters in series and a polyurethane foam (PUF)/XAD‐4/PUF (PXP) adsorbent sandwich. More than 100 pairs of filter and PXP samples were collected diurnally from September 2018 to September 2019. The concentration profiles of total n‐alkanes and polycyclic aromatic hydrocarbons were peaking at n‐C12–n‐C17 homologs (9.98 ± 5.43–38.4 ± 17.7 ng m−3) and naphthalene (92.5 ± 56.7 ng m−3), respectively, followed by decreasing concentrations with further increases in molecular weight. Three artifact correction methods with different pre‐assumptions on relative contributions of evaporation loss to backup filter measurements were used to separate particle‐ and gas‐phase OMMs. The resulting particle‐phase fractions showed significant differences for OMMs with vapor pressure <10−9atm at 298.15 K. Absorptive gas/particle partitioning coefficients of OMMs were empirically calculated based on measurements and theoretically predicted for comparison. The results obtained under the three artifact correction methods suggested growing importance of evaporation loss with decreased vapor pressure. Positive matrix factorization (PMF) was performed for source apportionment using total (PMFtotal) and particle‐phase (PMFparticle) OMMs data, respectively. Besides eliminating the influence of gas/particle partitioning, the involvements of more volatile species and gaseous OMMs data improved the identification of specific emission sources, supporting the usage of total OMMs data over a wide vapor pressure range for PMF source apportionment. The particulate fractions of organic molecular markers attained their minima in summer, when the total concentrations increasedEvaporation loss might be the main sampling artifact of particulate organics when the vapor pressure is lower than 10−10atmTotal concentrations of organic molecular markers over a wide vapor pressure range should be used for positive matrix factorization analysis The particulate fractions of organic molecular markers attained their minima in summer, when the total concentrations increased Evaporation loss might be the main sampling artifact of particulate organics when the vapor pressure is lower than 10−10atm Total concentrations of organic molecular markers over a wide vapor pressure range should be used for positive matrix factorization analysis

The mechanism of bubble removal in a narrow viscous fluid by using ultrasonic vibration is analyzed in this study. Experimental studies were performed on the adhesive bonding between a carbon fiber reinforced plastic (CFRP) laminate and an aluminum plate. After applying ultrasonic vibration on the CFRP laminate, it was found that the high-frequency vibration could induce an oscillating flow of the adhesive in the narrow bonding layer. Such a flow caused the entrapped bubbles to move and break until all of them were eliminated from the viscous adhesive. A fluid-solid coupling simulation and fluid tracer analysis were performed to analyze the underlying principle of bubble motion. The results reveal that because of the internal pressure of the bubble and the asymmetric characteristic of the fluid resistance around the bubble, the oscillating fluid induced by ultrasonic vibration drove the bubble to move in the direction closest to the edge. The reduction of the gas volume fraction in the adhesive resulted in an improved bonding between the CFRP laminate and aluminum plate.

Many software tools have been developed for the automated identification of peptides from tandem mass spectra. The accuracy and sensitivity of the identification software via database search are critical for successful proteomics experiments. A new database search tool, PEAKS DB, has been developed by incorporating the de novo sequencing results into the database search. PEAKS DB achieves significantly improved accuracy and sensitivity over two other commonly used software packages. Additionally, a new result validation method, decoy fusion, has been introduced to solve the issue of overconfidence that exists in the conventional target decoy method for certain types of peptide identification software.

Many software tools have been developed for the automated identification of peptides from tandem mass spectra. The accuracy and sensitivity of the identification software via database search are critical for successful proteomics experiments. A new database search tool, PEAKS DB, has been developed by incorporating the de novosequencing results into the database search. PEAKS DB achieves significantly improved accuracy and sensitivity over two other commonly used software packages. Additionally, a new result validation method, decoy fusion, has been introduced to solve the issue of overconfidence that exists in the conventional target decoy method for certain types of peptide identification software.