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The reactions of sulfur dioxide (SO2) with surface-bound compounds on atmospheric aerosols lead to the formation of organic sulfur (OS) compounds, thereby affecting the air quality and climate. Here, we show that the heterogeneous reaction of SO2 with authentic urban grime under near-ultraviolet sunlight irradiation leads to a large suite of various organic compounds including OS released in the gas phase. Calculations indicate that at the core area of Guangzhou, building surface uptake of SO2 is 15 times larger than uptake of SO2 on aerosol surfaces, yielding ~20 ng m-3 of OS that represents an important fraction of the observed OS compounds (60 to 200 ng m-3) in ambient aerosols of Chinese megacities. This chemical pathway occurring during daytime can contribute to the observed fraction of OS compounds in aerosols and improve the understanding of haze formation and urban air pollution.

BACKGROUND Hexabromocyclododecanes (HBCDs) have been identified as organic pollutants with the properties of persistence, long-distance migration, bioaccumulation, and biological toxicity. HBCDs have been detected in all kinds of biological and abiotic samples around the world, and have adverse effects on the environment and human body. As a non-invasive biological sample, human milk is a good medium for evaluating the exposure of HBCDs in the human body, and is widely used in the study of the exposure level of HBCDs in various countries, especially in nursing infants and young children. According to the survey, the production and use of HBCDs in Beijing has continued to rise since the use and production restriction of HBCDs in 2016, and the total use of HBCDs in 2019 increased by 60.8% compared with 2018. Therefore, in recent years in Beijing, especially before and after the use and production restriction of HBCDs, the residual characteristics and change trend of HBCDs in breast milk have attracted much attention. OBJECTIVES To investigate the residual characteristics and trends of HBCDs in breast milk in Beijing from 2010 to 2018, evaluate the health risks for infants to intake HBCDs via breastfeeding, and provide basic data support for the scientific use, management, control, and human exposure risk assessment of HBCDs. METHODS Breast milk samples (n=233) were obtained from 85 volunteer donors living in Beijing from 2010 to 2018. All volunteers have been living in Beijing for more than 5 years, are healthy, and do not directly engage in HBCDs production, processing, and other related occupations. Each sample was about 30mL, which was manually collected by volunteers into a 30mL clean glass bottle with a Teflon lined screw cap, and then transferred to a laboratory refrigerator for cryopreservation at -20℃. All volunteers were informed of the objective of this study. Pretreatment was conducted by liquid-liquid extraction and ammonia, ethanol, ether and n-hexane were added in turn. After liquid-liquid extraction, concentrated sulfuric acid sulfonation was combined with solid phase extraction (SPE) to purify the samples. Finally, 200μL methanol was added for constant volume. After centrifugation, the upper layer solution was transferred to a brown sample bottle (including lined tube) for storage. The qualitative and quantitative analysis of HBCDs was performed by Waters UPLC CLASS ultra-high performance liquid phase tandem API 4000 triple quadrupole mass spectrometry(LC-MS/MS). The isotope internal standard method was used for quantitative analysis to reduce the matrix effect. RESULTS The detection rate of HBCDs in breast milk was 100%, indicating that HBCDs have been widespread in the human body. The concentration range of HBCDs was 0.46-93.5ng/g lw (lipid weight), with the average and median values of 7.27ng/g lw and 5.77ng/g lw, respectively. The 95th percentile of high-end exposure was 15.6ng/g lw. There were individual differences in the milk samples. The detection rates of α, β and γ-HBCD in all breast milk samples were 100%, 35.6% and 70.8%, respectively. α-HBCD had the most abundant diastereomers in breast milk samples, accounting for 80.1%, followed by γ-HBCD and β-HBCD in order. There were also a small number of breast milk samples that were dominated by γ-HBCD, accounting for 52.2%-83.5%. Even samples taken by the same volunteer in different months had different major diastereomers. The median EDI of HBCDs via human milk for infant was 20.5ng/kg bw/day, and the 95th percentile value was 71.4ng/kg bw/day, which was comparable to the previous research in Beijing, but higher than Japan, Ghana and other cities in China. CONCLUSIONS Compared with the HBCDs in breast milk from other regions at home and abroad, the level of HBCDs in breast milk in this study is close to the previous research data in Beijing, but higher than that of Shanghai, Shenzhen and other cities in China, as well as higher than the results of recent studies in Japan, the United Kingdom, the United States, Canada, India, the Philippines and some African countries, which may be related to the continuous use of HBCDs in China and the large amount of use. In human breast milk, α-HBCD is the main diastereomers, while in a small number of samples, γ-HBCD is the main diastereomers. The differences in the distribution characteristics of these diastereomers may be due to the differences in the absorption, metabolism and excretion mechanisms among individuals, and the transformation of HBCDs among different isomers in vivo, and the differences in the main external exposure pathways. The level of HBCDs showed an obvious upward trend from 2010 to 2013, reached the highest value of 6.84ng/g lw in 2013, and then decreased slightly and remained constant, which may be related to the production, use and prohibition of HBCDs globally and domestically. The time trend of α-HBCD and HBCDs is basically the same, while the content of β-HBCD and γ-HBCD in breast milk is low, and the change trend is stable with time. The concentration of HBCDs in breast milk changed slowly from 2014 to 2018 but did not show a significant downward trend after the initial ban of HBCDs in China in 2016, which may indicate that there are still a large number of HBCDs in production and use on the market, and human intake of HBCDs through air, dust, diet and other ways does not decrease. The risk assessment results indicate that the Hazard Quotient (HQ) of 99% breast milk samples is less than 1, which indicates that the intake of HBCDs through breast-feeding during lactation would not bring significant health risk to infants, but the HQ value of 1% breast milk samples is greater than 1, which suggests that breastfeeding may bring health risks to infants. More research is needed to further investigate the major sources of exposure and the effect of each potential factor.

We obtain a characterization of bijective maps preserving the trace of products on the set of tensor products of rank‐1 idempotents, which may be considered as a generalization of Molnár's Wigner‐type theorem in multipartite systems. The proof is based on the studies in linear preserver problems on tensor products. Moreover, a corresponding result on the finite‐dimensional case is presented. [ABSTRACT FROM AUTHOR]

Monitoring the health of lithium batteries is a crucial undertaking in ensuring the safe and dependable functioning of electric vehicles. Data‐driven methods have been proved to be an effective method for identifying the complex degradation process of batteries. To augment the precision of predicting the remaining useful life (RUL), this paper introduces a pioneering architecture for a denoising autoencoder (DAE). This architecture integrates a stacked convolutional neural network with subsequent layers of bidirectional gated recurrent units within an encoder–decoder framework. The utilization of the DAE network is employed as a means to effectively capture and represent the intricate and nonlinear knowledge associated with degradation data acquired from measured sources. Simultaneously, the reconstruction loss is incorporated into the total loss to improve the accuracy and generalization of the prediction model. The efficacy of the proposed approach is substantiated through the utilization of data sets sourced from the NASA Ames Prognostics Data Repository. The comparative findings suggest that the proposed approach demonstrates an exceptional ability to achieve precise and robust estimation in predicting the RUL, surpassing other advanced methodologies. [ABSTRACT FROM AUTHOR]

Aiming at the two-phase flow characteristics of the automotive gear, based on the PLIC-VOF algorithm, the three-dimensional churning process model of the gear is numerically calculated by Matlab software. The influence of different rotational speed and immersion depth as well as viscosity on churning power loss of the gear is discussed. Then the three-dimensional churning model of the gear is simulated by Fluent. The power loss experimental and the visual experiment are conducted. The results show that the PLIC-VOF algorithm is suitable for calculating churning loss of the gear. The turbulence of oil distribution increased with the rotational speed. The churning power loss increased with rotational speed and immersion depth as well as viscosity, among which the rotational speed has the greatest influence.

Humic‐like substances (HULIS) are a ubiquitous reactive component of atmospheric aerosol. They participate in the formation of secondary organic aerosols via chemical reactions with atmospheric oxidants. Here, we assess the influence of transition metal ions (namely ferric iron, Fe(III)), and nitrate ions (NO3− ${{\text{NO}}_{3}}^{-}$) on the heterogeneous reaction of gaseous NO2 with an aqueous film containing gallic acid (GA) or tannic acid (TA) as proxies for HULIS. Using a vertical wetted wall flow tube technique, the uptake coefficients of gaseous NO2 on GA and TA increased nonlinearly with increasing [Fe(III)], in dark and under light irradiation. However, the combined effect of both ions, Fe(III) and NO3− ${{\text{NO}}_{3}}^{-}$, led to a substantial decrease in NO2 uptake in the dark and under simulated near‐UV sunlight irradiation (300 < λ < 400 nm). The lifetime of GA in dilute aqueous phase, which corresponds to cloud water, due to reaction with NO2 would be 6 hr during both nighttime and daytime. However, the lifetime of GA in aerosol particles which contain both ions, that is, Fe(III) and NO3− ${{\text{NO}}_{3}}^{-}$, would increase to 27 hr during nighttime and 11 days and 6 hr due to light‐induced reaction with NO2. Also, we observed, using Fourier transform ion cyclotron resonance mass spectrometry, the formation of nitrocatechols compounds (e.g., methyl‐nitrocatechol), which contribute to brown carbon. Compounds with reduced functional groups such as amines were also observed in the presence of iron and nitrate ions in the dark and under irradiation, indicating that Fe(III) and NO3− ${{\text{NO}}_{3}}^{-}$, can influence the kinetics and product distribution in deliquescent aerosol particles. Plain Language Summary: Biomass burning is one of the main sources of humic‐like substances (HULIS) in the aerosol particles covering a large fraction of the water‐soluble organic carbon. Here we assessed the impact of nitrate and iron ions on the uptake coefficients of NO2 on gallic acid (GA) and tannic acid (TA) as HULIS proxies. The uptake coefficients and consequently the atmospheric lifetimes were dramatically impacted by the presence of nitrate and iron ions. The analysis of the formed product compounds in the condensed phase by Fourier transform ion cyclotron resonance mass spectrometry indicates that the presence of nitrate and iron ions largely impact the observed nitrogen‐containing organic compounds formed during the reaction of NO2 with GA. Majority of the formed compounds contain reduced nitrogen‐functional groups such as amines, amides, and imines. We identified the formation of nitroaromatics with at least one nitro functional group attached directly to a benzene ring, like 5‐Nitroguaiacol, 4‐methyl‐5‐nitrocatechol. These compounds, can cause positive radiative forcing of aerosols due to their light‐absorbing properties. Key Points: Uptake coefficients of gas phase NO2 on humic‐like substances proxies in aerosol particles are largely impacted by nitrate and iron ionsFormation of nitrogen containing product compounds in aerosols are impacted by nitrate and iron ions compared to that in cloud waterFormation of nitrocatechols like methyl‐nitrocatechol, which contribute to brown carbon is observed upon influence of nitrate and iron ions [ABSTRACT FROM AUTHOR]

This paper introduces diffusion into an immunosuppressive infection model with virus stimulation delay and Beddington-DeAngelis functional response. First, we study the stability of positive constant steady state solution and show that the Hopf bifurcation will exist under certain conditions. Second, we derive the normal form of the Hopf bifurcation for the model reduced on the center manifold by using the multiple time scales (MTS) method. Moreover, the direction and stability of the bifurcating periodic solution are investigated. Finally, we present numerical simulations to verify the results of theoretical analysis and provide corresponding biological explanations. [ABSTRACT FROM AUTHOR]

For the severe vibration and scream noise of a mini car main reducer in high- speed neutral coasting condition,the pressure angle of the main reducer hypoid gears is taken as the study object. A torsional vibration dynamics model of gears system is established,after changing the pressure angle on both sides of gear tooth in the UG model and importing into the ADMAS,the dynamics characteristics of the gear system with different pressure angle under the same coasting condition are studied and compared. It is concluded that the meshing vibration performance of main reducer gears system could be improved when the convex surface pressure angle of the passive gear tooth decreased 1° at the same time the concave surface pressure angle of the passive gear tooth increased 1°. The correctness of the simulation analysis is verified by experiments at last,and the research result could be applied to the design and manufacture of the main reducer gear.

The purpose of this paper is to investigate working performance for a four-stroke piston type compressed air engine (CAE) via experimental research. A conventional internal combustion engine(IC engine) is modified to a four-stroke CAE and a mathematical model is set up. Working performances are investigated by output torque, power, air consumption, exhaust pressure, exhaust temperature and cylinder pressure on a test bench. The CAE is installed on a vehicle for the road test. The experiment and analysis show several meaningful results. The increase of the supply pressure will result in the increase of the rotational speed, and it can effectively improve the output torque and power. However, it can lead to an increase in air consumption. The success of this application demonstrates compressed air cars are likely to be industrialized duo to their zero pollution and zero emissions.

In the operating process, it is found the vibration of main reducer reaches a maximum value when certain types of vehicles are running at a speed around 4000 RPM. However, how the rotation speed of engine affects the vibration responses to automobile transmission system has not been investigated theoretically in details. To investigate this problem, the transmission system of automobile is simplified to a drive-final shaft system in this research, and a coupled vibration model of drive-final shaft system is developed. This model is used to simulate the vibration response to transmission system at different rotation speeds. Simulation results show that the torsional vibration responses reach the maximum when the rotation speeds are 3800 RPM and 4200 RPM and the vibration responses of pinion reach the maximum value when the rotation speeds are 4000 RPM and 4200 RPM. Moreover, finite element analysis is conducted to investigate the reason for this phenomenon. It is found that the torsional vibration responses reach the maximum value when the excitation frequency of engine is close to the resonance frequency of drive shafts. This research provides an effective method to analyse the vibration characteristics of automobile transmission system.

The bearing stiffness has a considerable influence on the nonlinear coupling vibration characteristics of the shaft-final drive system. A 14-DOF nonlinear coupled vibration model was established by employing the lumped mass method so as to identify the coupling effects of the bearing stiffness to the vibration response of the shaft-final drive system. The engine’s torque ripple, the alternating load from the universal joint (U-joint), and the time-varying mesh parameters of hypoid gear of the shaft-final drive system were also considered for accurate quantitative analysis. The numerical analysis of the vibration response of the coupled system was performed and the experimental measurements were carried out for the validation test. Results show that, at the given driving speed, improving the bearing stiffness can reduce the vibration response of the given coupled system; however, when the bearing stiffness increases to a critical value, the effects of bearing stiffness on the vibration reduction become insignificant; when the driving speed changes, the resonance regions of the coupled system vary with the bearing stiffness. The results are helpful to determine the proper bearing stiffness and the optimum control strategy for the shaft-final drive system. It is hoped that the optimal shaft-final drive system can provide good vibration characteristics to achieve the energy saving and noise reduction for the vehicle application.