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To perform realistic high-resolution air quality modeling in a polluted urban area, the Weather Research and Forecasting (WRF) model is used with an embedded large-eddy simulation (LES) module and online chemistry. As an illustration, a numerical experiment is conducted in the megacity of Hong Kong, which is characterized by multi-type inhomogeneous pollution sources and complex topography. The results from the multi-resolution simulations at mesoscale and LES scales are evaluated by comparing them with ozone sounding profiles and surface observations. The comparisons show that both mesoscale and LES simulations reproduce the mean concentrations of the chemical species and their diurnal variations at the background stations well. However, the mesoscale simulations largely underestimate the NOx concentrations and overestimate O3 at the roadside stations due to the coarse representation of the traffic emissions. The LES simulations improve the agreement with the measurements near the road traffic, and the LES with the highest spatial resolution (33.3 m) provides the best results. The large-eddy simulations show more detailed structures in the spatial distributions of chemical species than the mesoscale simulations, highlighting the capability of LES to resolve high-resolution photochemical transformations in urban areas. Compared to the mesoscale model results, the LES simulations show similar evolutions in the profiles of the chemical species as a function of the boundary layer development over a diurnal cycle.

To perform realistic high-resolution air quality modeling in a polluted urban area, the WRF (Weather Research and Forecasting) model was used with an embedded large-eddy simulation (LES) module and with online chemistry. As an illustration, the numerical experiment was conducted in the polluted megacity of Hong Kong, which is characterized by multi-type pollution sources as well as complex topography. The multi-resolution simulations from mesoscale to LES scales were evaluated by comparing the calculated fields with ozone sounding profiles and with the observations at surface monitoring stations. The comparison shows that both mesoscale and LES simulations reproduced well the mean concentrations of the chemical species and their diurnal variations at the background sites; however, the mesoscale simulations largely underestimated the NOXconcentrations and overestimated O3 near roadside stations due to the coarse representation of the traffic emissions. The LES simulations improved the agreements with the measurements near the road traffic, and the LES with highest spatial resolution (33 m) provided the best results. The LES simulations showed more detailed structures of the spatial distributions of chemical species than the mesoscale simulations, indicating the capability of LES of resolving high-resolution photochemical transformations in urban areas like Hong Kong. The LES simulations showed similar trends with the mesoscale model in the evolution of the profiles of the chemical species with the development of the boundary layer over a diurnal cycle. The vertical fluxes of the chemical species are stronger in the 33 m LES than the 100 m LES, because the high-resolution LES can better resolve the turbulent eddies.

Different entrainment-mixing processes of turbulence are crucial to processes related to clouds; however, only a few qualitative studies have been concentrated on the vertical distributions of entrainment-mixing mechanisms with low vertical resolutions. To quantitatively study vertical profiles of entrainment-mixing mechanisms with a high resolution, the stratiform clouds observed in the Physics of Stratocumulus Top (POST) project are examined. The unique sawtooth flight pattern allows for an examination of the vertical distributions of entrainment-mixing mechanisms with a 5 m vertical resolution. Relative standard deviation of volume mean radius divided by relative standard deviation of liquid water content is introduced to be a new estimation of microphysical homogeneous mixing degree, to overcome difficulties of determining the adiabatic microphysical properties required in existing measures. The vertical profile of this new measure indicates that entrainment-mixing mechanisms become more homogeneous with decreasing altitudes and are consistent with the dynamical measures of Damköhler number and transition scale number. Further analysis shows that the vertical variation of entrainment-mixing mechanisms with decreasing altitudes is due to the increases of turbulent dissipation rate in cloud and relative humidity in droplet-free air and the decrease of size of droplet-free air. The results offer insights into the theoretical understanding and parameterizations of vertical variation of entrainment-mixing mechanisms.

The Copernicus Atmosphere Monitoring Service (CAMS) operated by the European Centre for Medium-Range Weather Forecasts (ECMWF) has produced a global reanalysis of aerosol and reactive gases (called CAMSRA) for the period 2003–2016. Space observations of ozone, carbon monoxide, NO2 and aerosol optical depth are assimilated by a 4D-Var method in the 60-layer ECMWF global atmospheric model, which for the reanalysis is operated at a horizontal resolution of about 80 km. As a contribution to the evaluation of the reanalysis, we compare atmospheric concentrations of different reactive species provided by the CAMS reanalysis with independent observational data gathered by airborne instrumentation during the field campaigns INTEX-A, INTEX-B, NEAQS-ITCT, ITOP, AMMA, ARCTAS, VOCALS, YAK-AEROSIB, HIPPO and KORUS-AQ. We show that the reanalysis rather successfully reproduces the observed concentrations of chemical species that are assimilated in the system, including O3 and CO with biases generally less than 20 %, but generally underestimates the concentrations of the primary hydrocarbons and secondary organic species. In some cases, large discrepancies also exist for fast-reacting radicals such as OH and HO2.

Aims: This research aimed to test the relationship among Happiness Orientations and four aspects of social competence: initiation, supportiveness, self-disclosure and assertive, and reveal whether grit is a mediating variable between happiness orientations and social competence. Methods: This study used correlational design. Participants are 380 college students from China, aged 18 to 25. Data was collected by 3 self-report questionnaires: happiness orientations (Peterson et al., 2005), social competence (Peter, 2008) and grit (Duckworth et al., 2007). Results: (1) The dimensions of happiness orientation, the dimensions of social competence and the dimensions of grit are significantly related; (2) Happiness orientation can positive predictive influence to social competence; (3)Grit have a positive predictive influence to social competence; (4) Grit play a fully intermediary role between the happiness orientation and the social competence.

Global and regional chemical transport models of the atmosphere are based on the assumption that chemical species are completely mixed within each model grid box. However, in reality, these species are often segregated due to localized sources and the influence of the topography. In order to investigate the degree to which the rates of chemical reactions between two reactive species are reduced due to the possible segregation of species within the convective boundary layer, we perform large-eddy simulations (LES) in the mountainous region of the Hong Kong island. We adopt a simple chemical scheme with 15 primary and secondary chemical species including ozone and its precursors. We calculate the segregation intensity due to inhomogeneity in the surface emissions of primary pollutants and due to turbulent motions related to topography. We show that the inhomogeneity in the emissions increases the segregation intensity by a factor 2–5 relative to a case in which the emissions are assumed to be uniformly distributed. Topography has an important effect on the segregation locally, but this influence is relatively limited when considering the spatial domain as a whole.

Recently, the COVID-19 virus pandemic has led to many studies on the airborne transmission of expiratory droplets. While limited experiments and on-site measurements offer qualitative indication of potential virus spread rates and the level of transmission risk, the quantitative understanding and mechanistic insights also indispensably come from careful theoretical modeling and numerical simulation efforts around which a surge of research papers has emerged. However, due to the highly interdisciplinary nature of the topic, numerical simulations of the airborne spread of expiratory droplets face serious challenges. It is essential to examine the assumptions and simplifications made in the existing modeling and simulations, which will be reviewed carefully here to better advance the fidelity of numerical results when compared to the reality. So far, existing review papers have focused on discussing the simulation results without questioning or comparing the model assumptions. This review paper focuses instead on the details of the model simplifications used in the numerical methods and how to properly incorporate important processes associated with respiratory droplet transmission. Specifically, the critical issues reviewed here include modeling of the respiratory droplet evaporation, droplet size distribution, and time-dependent velocity profile of air exhaled from coughing and sneezing. According to the literature review, another problem in numerical simulations is that the virus decay rate and suspended viable viral dose are often not incorporated; therefore here, empirical relationships for the bioactivity of coronavirus are presented. It is hoped that this paper can assist researchers to significantly improve their model fidelity when simulating respiratory droplet transmission.

The authors have analyzed the scaling behavior of marine boundary layer (MBL) clouds using high-resolution temperature (T) and liquid water content (LWC) fluctuations from aircraft measurements collected over the Pacific Ocean during the Physics of Stratocumulus Top (POST) research campaign in summer of 2008. As an extension of the past studies for scale-invariant properties of MBL clouds, the authors studied the variability of scaling exponents with height. The results showed that both LWC and T have two distinct scaling regimes: the first one displays scale invariance over a range from about 1–5 m to at least 7 km, and the second one goes from about 0.1–1 to 1–5 m. For the large-scale regime (r > 1–5 m), turbulence in MBL clouds is multifractal, while scale break and scaling exponents vary with height, most significantly in the cloud-top region. For example, LWC spectral exponent β increases from 1.42 at cloud base to 1.58 at cloud top, while scale break decreases from ~5 m at cloud base to 0.8 m at cloud top. The bifractal parameters (H1, C1) for LWC increase from (0.14, 0.02) at cloud base to (0.33, 0.1) at cloud top while maintaining a statistically significant linear relationship C1 ≈ 0.4H1 − 0.04 in MBL clouds. From near surface to cloud top, (H1, C1) for T also increase with height, but above cloud top H1 increases and C1 decreases with height. The results suggest the existence of three turbulence regimes: near the surface, in the middle of the boundary layer, and in the cloud-top region, which need to be distinguished.

Turbulence observed during the Physics of Stratocumulus Top (POST) research campaign is analyzed. Using in-flight measurements of dynamic and thermodynamic variables at the interface between the stratocumulus cloud top and free troposphere, the cloud top region is classified into sublayers, and the thicknesses of these sublayers are estimated. The data are used to calculate turbulence characteristics, including the bulk Richardson number, mean-square velocity fluctuations, turbulence kinetic energy (TKE), TKE dissipation rate, and Corrsin, Ozmidov and Kolmogorov scales. A comparison of these properties among different sublayers indicates that the entrainment interfacial layer consists of two significantly different sublayers: the turbulent inversion sublayer (TISL) and the moist, yet hydrostatically stable, cloud top mixing sublayer (CTMSL). Both sublayers are marginally turbulent, i.e., the bulk Richardson number across the layers is critical. This means that turbulence is produced by shear and damped by buoyancy such that the sublayer thicknesses adapt to temperature and wind variations across them. Turbulence in both sublayers is anisotropic, with Corrsin and Ozmidov scales as small as ∼ 0.3 and ∼ 3 m in the TISL and CTMSL, respectively. These values are ∼ 60 and ∼ 15 times smaller than typical layer depths, indicating flattened large eddies and suggesting no direct mixing of cloud top and free-tropospheric air. Also, small scales of turbulence are different in sublayers as indicated by the corresponding values of Kolmogorov scales and buoyant and shear Reynolds numbers.

A comprehensive literature review on the estimation of the dissipation rate of turbulent kinetic energy is presented to assess the current state of knowledge available in this area. Experimental techniques (hot wires, LDV, PIV and PTV) reported on the measurements of turbulent dissipation rate have been critically analyzed with respect to the velocity processing methods. Traditional hot wires and LDV are both a point-based measurement technique with high temporal resolution and Taylor’s frozen hypothesis is generally required to transfer temporal velocity fluctuations into spatial velocity fluctuations in turbulent flows. Multi probes of hot wires and multi points LDV could be used to measure velocity spatial gradients for a direct calculation of turbulent dissipation rate from its definition. Nevertheless, only PIV and PTV could provide simultaneous measurements of the distribution of turbulent dissipation rate in a turbulent field. These methods all suffer from the deficiency of spatial resolution as velocity measurements are required to resolve down to Kolmogorov scales for a strictly direct calculation of turbulent dissipation rate from fluctuating velocity gradients. To eliminate the necessity of resolving down to Kolmogorov scales, a large eddy simulation analogy and Smagorinsky model could be used for estimating the unresolved small scales, but Smagorinsky constant acts as an adjustment parameter at this stage. Different velocity processing methods are compared in the estimation of turbulent dissipation rate. The estimation of turbulent dissipation rate using structure function, energy spectrum and dimensional analysis methods could reduce the effects of low resolution, but it only provides temporal or spatial mean turbulent dissipation rate. Nevertheless, the field of turbulent dissipation rate, which is not distributed homogeneously, has intermittent spatio-temporal nature. The aim of this paper is to review the developments and limitations of the existing experimental techniques and different calculating methods and identify the future directions in successfully estimating turbulent dissipation rate in turbulent multiphase flows.

Anisotropy of turbulence near the top of the stratocumulus‐topped boundary layer (STBL) is studied using large‐eddy simulation (LES) and measurements from the POST and DYCOMS‐II field campaigns. Focusing on turbulence ∼100 m below the cloud top, we see remarkable similarity between daytime and nocturnal flight data covering different inversion strengths and free‐tropospheric conditions. With λ denoting wavelength and zt cloud‐top height, we find that turbulence at λ/zt≃0.01 is weakly dominated by horizontal fluctuations, while turbulence at λ/zt>1 becomes strongly dominated by horizontal fluctuations. Between are scales at which vertical fluctuations dominate. Typical‐resolution LES of the STBL (based on POST flight 13 and DYCOMS‐II flight 1) captures observed characteristics of below‐cloud‐top turbulence reasonably well. However, using a fixed vertical grid spacing of 5 m, decreasing the horizontal grid spacing and increasing the subgrid‐scale mixing length leads to increased dominance of vertical fluctuations, increased entrainment velocity, and decreased liquid water path. Our analysis supports the notion that entrainment parameterizations (e.g., in climate models) could potentially be improved by accounting more accurately for anisotropic deformation of turbulence in the cloud‐top region. While LES has the potential to facilitate improved understanding of anisotropic cloud‐top turbulence, sensitivity to grid spacing, grid‐box aspect ratio, and subgrid‐scale model needs to be addressed.

In this paper we propose two approaches to estimating the kinetic energy dissipation rate, based on the zero-crossing method by Sreenivasan et al. [J. Fluid Mech., 137, 1983]. The original formulation requires a good accuracy of the measured signal (down to the smallest dissipative scales). However, due to finite sampling frequency, as well as measurement errors, velocity time series obtained from airborne experiments are characterized by the presence of effective spectral cut-offs. In contrast to the original formulation the new approaches are suitable for use with signals originating from such experiments. The fittingness of the new approaches is tested using measurement data obtained during the Physics of Stratocumulus Top (POST) airborne research campaign.

This research discussed the rational mixing moisture content (MMC) in foamed asphalt (FA) mix design. Sieve analysis was firstly used to study the bitumen dispersion and bitumen-aggregate coating and bonding action in FA mixes with three levels of MMC. Then, through variance analysis, the impacts of MMC, bitumen content and their interaction effect on the mechanical properties of FA mixes were studied. Indirect tensile strength test and dry density determination were carried out on FA mixes consisting of different gradings and material types to explore the rational MMC. On base of that, monotonic triaxial test was performed on two types FA mixes with various filler contents to further investigate the rational MMC for FA mix. The research results indicated that improper MMC led to bitumen clots and affected cohesion of FA mix. MMC and bitumen content had important impacts on mechanical properties of FA mix, while their interaction effect could be ignored in mix design. Optimal MMC increased to a certain extent with the increase of fine aggregates content, especially filler content in the grading. 70–80% of the optimum moisture content (OMC) was recommended as rational range of MMC for FA mix with 5–15% filler content and 75–85% of OMC for mix with 15–20% filler content, which offered a reference for easy and simplified MMC design for FA mix.

Aero2k and SAGE model havebeen developed in the contemporary society when emissions attract extensive attention, especially on aviation emissions. In this paper, origin and functions of SAGE model are introduced simply, while its calculation model is analyzed in detail. Based on SAGE model, process analysis of calculating aviation emissions has been made and Calculation procedure has been designed, then software about calculation of aviation emissions has been developed according to the procedure. There is no much deviation between true values and results based on the software, which is a good proof of feasibility of the software.

Seasonal variation of temperature, pressure, snow accumulation, winds, and their harmonic analysis are presented by using the data from Zhongshan Station and three Automatic Weather Stations deployed between the East Antarctic coast and the summit of the ice sheet at Dome A for the period 2005–07. Results show that: 1) temperature, snow accumulation and specific humidity decrease with increasing elevation and distance from the coast, with snow accumulation decreasing from 199 mm water equivalent (w.e.) yr-1 at LGB69 (180 km from the coast) to 31 mm w.e. yr-1 at Dome A, 2) Dome A experiences an extremely low minimum temperature of -82.5°C with the monthly mean temperature below -50°C for eight months in contrast to Zhongshan Station which does not show any monthly mean temperatures below -20°C, 3) mean surface wind speed increases from the coast to the escarpment region, and then reduces rapidly towards the interior plateau with the strongest winds occurring at katabatic sites with the greatest surface slopes, 4) temperature and pressure all shows a distinct biannual oscillation with a main minimum in spring and a secondary minimum in autumn, differing slightly from station to station, and 5) winter temperature corelessness increases as a function of elevation and distance from the coast, from 0.260 at the coastal Zhongshan Station to 0.433 at Dome A.

Magnetic-electrochemical compound polishing is applied in difficult-to-process materials little by little. The influence of the magnetic field to electrochemical process is very complicated. In the paper, using Coulomb laws and Lorentz force, the two kinds of math model of the movement of the charged particles are established according to the different magnetic field whose direction is vertical or parallel to the electrical field. The velocity equations and loci equations of three typical particles are concluded in two kinds of magnetic field’s directions. To be compared and analyzed carefully, the influence of the magnetic field’s direction to polishing is concluded. This study can guide how to determine the magnetic field’s direction in magnetic-electrochemical compound polishing, and build the theoretical basis to study the mechanism of magnetic-electrochemical compound polishing.

Provincial highway safety is one of the most important issues in transportation. To evaluate or assess the safety performance of provincial highway, traffic crash analysis or traffic conflict analysis has been used for a long history. However, it is very difficult and time-consuming to obtain historical crash data or traffic conflict data. This study analyzes the provincial highways' accident data during 2006–2010, and the characteristics of provincial highway have been investigated; in addition the influencing elements are identified. A comprehensive approach is introduced to evaluate provincial highway safety performance and corresponding models are developed considering the accidents, geometrics, facilities, and traffic environment. The approach will also result in a safety index to indicate the safety performance level of the provincial highway. In this paper, the approach (called safety evaluation approach) is practically applied to evaluate the safety performance of some provincial highways in Hebei Province. Results from the real application indicate that the approach has good applicability and can be used by field safety engineers.

In this paper,a predator-prey systems with time delays and simplified Holling type-IV functional response is investigated, the predator's numerical response has Leslie form.Proved that the solutions with positive initial values are positive and bounded. Give the existence conditions of the positive equilibrium point and prove the equilibrium point is uniqued. Given the conditions of local asymptotic stability by Routh-Hurwiitz theroy.The impact of the time delay on the stability of the model is considered by choosing the delay time 1 as a bifurcation parameter, the existence of Hopf bifurcation is also found by bifurcation theory.

In this paper, Global dynamics of an SIQR epidemic model with quarantine strategy and delay was studied. On the basis of the SIQR epidemic model which completely determines the global dynamics and results of disease was given in [1], considering the latency of the disease and introducing discrete time-delay, we established the new dynamic model with time delays describing epidemic. The basic reproduction number R0 which completely determines the global dynamics and results of disease was solved in this paper. We give a qualitative analysis of this model and reveal the inherent rule of infectious diseases.

To study the effects of ketamine anesthesia and surgery on cognition and synaptic structure in hippocampus of senile rats.Fifty-six rats aged 18 months were randomly divided into 3 groups: Groups C (control group), A (ketamine 40 mg/kg, i.p.) and O (ketamine anesthesiasplenectomy). Morris water maze test was used to observe cognition at Days 1, 37 after ketamine anesthesia or operation respectively. Accordingly Groups A and O were divided into 3 subgroup, i.e. A1, A3, A7 and O1, O3, O7. The time of Morris water maze test was recorded and the synaptic structure was measured in the polymorphic layer of the rat hippocampal field CA3.Compared to Group C, the latency period and swimming distance significantly increased in Groups A1, O1 and O3 (P0.05), and the numbers passing the original platform decreased significantly in Groups O1 and O3 (P0.01). The latency period was significantly longer in Group O1 than that in Group A1 (P0.05) while the swimming distance was unchanged. Compared to Group C, the width of synaptic cleft (P0.01) increased, the length and area of postsynaptic densities (P0.05 or P0.01) as well as synaptic curvature (P0.01) decreased in Groups O1 and O3. The percentage of perforated synapses also decreased in Groups O1 and O3.Surgical injury can impair cognition of senile rats and the synaptic plasticity might be involved in postoperative cognitive dysfunction.

This paper addresses the problem of fast computation of the ambiguity function using a new method based on pre-weighted zoom FFT algorithm, which employs zoom FFT technique and performs the weighting process previously and thus gets ride of the extra computation. The computational complexity of the presented algorithm is compared with other methods and the simulation results are given. Both the theory and the simulations show that, pro weighted zoom FFT method has lower computational complexity, less memory need and negligible error, and can meet the need of real-time processing.

Seasonal variation in surface ozone and the relationship between the background ozone concentration and wind were evaluated at Zhongshan Station, Antarctica using 2008 data. The wind frequency from the station area was only 2%, while the prevailing wind frequency was much larger (79.2%). This indicates that the surface ozone observations were not affected by the human activities at the station, and therefore could be counted as background concentrations of surface ozone along Antarctic coast. The concentration of surface ozone shows a distinct annual variation with the yearly mean of 25.0 nmol mol−1 and the maximum in winter, the minimum in summer. The surface ozone concentration had a strong negative correlation with ultraviolet radiation, and the mean values during polar night were one to two times higher than those in summer. These results imply that photochemical destruction of ozone dominates over Antarctica. The ozone depletion events at Zhongshan Station were obviously related to lower temperatures and higher BrO concentrations. Backward trajectory analysis reveals that the ozone depletion events are predominately caused by the high BrO concentrations.