Numerous steady Reynolds-averaged Navier-Stokes (SRANS) two-equation turbulence models have been applied to modeling urban airflow and pollutant dispersion. Their low accuracy has been attributed to SRANS ill-conditioning, the linear eddy viscosity hypothesis, and uncertainty contributed by empirical formulations and coefficients. Many studies have attempted to modify the two-equation models specifically for urban problems by correcting the model formulations and calibrating the coefficients. However, the models are not universally applicable to a variety of urban problems. To improve the generalizability of the models, this study introduced multiple correctors to the empirical formulations and coefficients of the k-ε model. The inherent shortcoming of SRANS ill-conditioning was managed by increasing the model’s flexibility in accommodating the model's flaws and prioritizing critical parameters. In particular, the transferability and robustness of the corrected model were considered by retaining the linear eddy viscosity closure and employing symbolic formulations. This investigation designed an integrated multiple expression programming framework to support simultaneous symbolic regression and coefficient calibration for corrector training. The generalizability of the corrected model was evaluated for airflow and dispersion around a single building, a building array, and a group of complex buildings. The corrected model performed consistently for the three flow types and exhibited generalizability.
Enhanced soiling on the surfaces around air supply nozzles due to particle deposition is frequently observed in commercial airliners. The problem is worsened by severe outdoor air pollution and flight delays in China. The particles in an aircraft cabin originate from both outdoor and in-cabin sources. This study conducted measurements on multiple commercial flights to obtain particle emission rates from in-cabin sources. Additional experiments on a retired MD-82 airplane provided justification of the in-flight measurements. The in-cabin sources emitted more particles during boarding/deplaning than during meal servicing and sitting. The average PM2.5 emission rates were 7.2, 2.6, 1.9, and 1.8 (μg/min per person), respectively, during the boarding/deplaning, sitting on the ground, sitting in the air, and meal servicing. The corresponding PM10 emission rates were 15.4, 6.1, 5.3, and 5.4 (μg/min per person), respectively, for these four periods. The average particle emission rate from in-cabin sources varied seasonally and was the highest in winter. With the measured data, this investigation used a CFD model to predict the accumulation of particles deposited around the nozzles of an airplane, taking into account the flight routes and the outdoor particle concentrations at the airports where the airplanes were parked. For the most polluted airplane in China, the dirty spots/areas around the nozzles inside the airplane became visible after 6 months. The method proposed in this study can be used for any commercial airplane to predict the accumulation of particles deposited around the air supply nozzles.
Benthic nitrogen cycling, including nitrification, N-loss, and other nitrogen transformations, plays a crucial role in the marine nitrogen budget. However, studies on benthic nitrogen cycling mainly focus on marginal seas, while attention to the deep ocean, which occupies the largest area of the seafloor, is severely lacking. In this study, we investigate the benthic nitrogen cycling in the Kuroshio Extension region (KE) of the northwest Pacific Ocean at water depths greater than 5,000 m through 15 N enrichment slurry incubation and pore-water dissolved oxygen and inorganic nitrogen profiles. The slurry incubation indicates nitrification is the predominant process in benthic nitrogen cycling. The potential nitrification rates are nearly an order of magnitude higher than dissimilatory nitrate reduction. Nitrification and total N-loss flux estimated from pore-water nitrate and ammonium profiles are 6–42 and 5–30 μmol N m −2 d −1 , respectively. Generally, anammox is the predominant N-loss process in KE sediment. The temperature gradient experiment indicates that the optimum temperature for anammox and denitrification is 13 and 41°C, respectively, partially explaining anammox as the dominant process for deep-ocean benthic N-loss. Both the low concentration of ammonium in pore-water and the discrepant results between anoxic incubation amended with 15 NO 3 − and 15 NH 4 + + 14 NO 3 − suggest that ammonium is another limiting factor for benthic anammox. N-loss activity gradually declines with the distance from the Oyashio–Kuroshio transition zone. However, nitrification has the opposite trend roughly. This reveals that the sediment in KE transfers from nitrate sink to source from north to south. This trend is mainly caused by the variation of primary production and the supplement of active organic matter, which is the energy source for microbes and the potential source for ammonium through remineralization. Overall, our results highlight temperature and ammonium as two limiting factors for deep-ocean benthic N-loss and also exhibit a tight coupling relationship between pelagic primary production and the benthic nitrogen cycle in KE.
Pulmonary fibrosis is a severe disease that contributes to the morbidity and mortality of a number of lung diseases. However, the molecular and cellular mechanisms leading to lung fibrosis are poorly understood. This study investigated the roles of epithelial-mesenchymal transition (EMT) and the associated molecular mechanisms in bleomycin-induced lung fibrosis. The bleomycin-induced fibrosis animal model was established by intratracheal injection of a single dose of bleomycin. Protein expression was measured by Western blot, immunohistochemistry, and immunofluorescence. Typical lesions of lung fibrosis were observed 1 week after bleomycin injection. A progressive increase in MMP-2, S100A4, α -SMA, HIF-1 α , ZEB1, CD44, phospho-p44/42 (p-p44/42), and phospho-p38 MAPK (p-p38) protein levels as well as activation of EMT was observed in the lung tissues of bleomycin mice. Hypoxia increased HIF-1 α and ZEB1 expression and activated EMT in H358 cells. Also, continuous incubation of cells under mild hypoxic conditions increased CD44, p-p44/42, and p-p38 protein levels in H358 cells, which correlated with the increase in S100A4 expression. In conclusion, bleomycin induces progressive lung fibrosis, which may be associated with activation of EMT. The fibrosis-induced hypoxia may further activate EMT in distal alveoli through a hypoxia-HIF-1 α -ZEB1 pathway and promote the differentiation of lung epithelial cells into fibroblasts through phosphorylation of p38 MAPK and Erk1/2 proteins.
Net community production (NCP) corresponds to the difference between photosynthesis and respiration and can be estimated based on the dissolved oxygen to argon ratio (O2/Ar) in the mixed layer. NCP is also an important proxy for the biological pump in the ocean. In order to figure out the influencing factors on NCP in the northern slope region of the South China Sea (SCS), we conducted high-resolution underway measurements of O2/Ar and hydrographic parameters using membrane inlet mass spectrometry (MIMS) and multi-parameter water quality logger (RBR Maestro) in the northern slope region of the SCS in October 2014 and June 2015, assisted by nutrients measurements. NCP in the mixed layer was estimated using the biological supersaturation of O2/Ar, Δ (O2/Ar), and gas transfer velocity (k). All the underway data were compiled into the 5-min interval. Surface water samples for the nutrients analysis were collected from Niskin bottles mounted on the conductivity–temperature–depth (CTD) rosette at sampling stations, the nutrients were then photometrically determined by an auto-analyzer. The mixed layer depth (MLD) and the euphotic depth (Zeu) were calculated at stations where CTD casts were made based on potential density and chlorophyll fluorescence profile, respectively.
Net community production (NCP) corresponds to the difference between photosynthesis and respiration and can be estimated based on the dissolved oxygen to argon ratio (O2/Ar) in the mixed layer. NCP is also an important proxy for the biological pump in the ocean. In order to figure out the influencing factors on NCP in the northern slope region of the South China Sea (SCS), we conducted high-resolution underway measurements of O2/Ar and hydrographic parameters using membrane inlet mass spectrometry (MIMS) and multi-parameter water quality logger (RBR Maestro) in the northern slope region of the SCS in October 2014 and June 2015, assisted by nutrients measurements. NCP in the mixed layer was estimated using the biological supersaturation of O2/Ar, Δ (O2/Ar), and gas transfer velocity (k). All the underway data were compiled into the 5-min interval. Surface water samples for the nutrients analysis were collected from Niskin bottles mounted on the conductivity–temperature–depth (CTD) rosette at sampling stations, the nutrients were then photometrically determined by an auto-analyzer. The mixed layer depth (MLD) and the euphotic depth (Zeu) were calculated at stations where CTD casts were made based on potential density and chlorophyll fluorescence profile, respectively.
Cost-Volume-Profit Analysis is a economic and effective method,is conducive to scientific management of enterprises,and can promote the development of social science research and economic and social development to a large extent.This article researched this method,to promote socio-economic development by further understanding.
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