Investigation on the Dispersal Characteristics of Liquid Breakup in Vacuum

This work presents an experimental study on the dispersal characteristics of a liquid jet ejecting into vacuum. The liquid breaking experiments of several kinds of liquid under different pressure and temperature conditions are carried out in a flash chamber. The stability of the jet and the sizes of the droplets or the icing particles formed during liquid flashing dispersing are analyzed. The influences of the superheat degree, spray velocity, and the mass of the volatile liquid mixing in the nonvolatile liquid on these characteristics are discussed. Moreover, the applicability of the two definitions of superheat degree is discussed. The results show that the superheat degree is an important parameter influencing the pattern of the breaking liquid, and the jet velocity has a large influence on the distribution of particle sizes. In addition, mixing some volatile liquid with nonvolatile liquid can enhance the dispersion of the latter

Large-Eddy Simulation of Flow and Pollutant Transport in Urban Street Canyons with Ground Heating

Our study employed large-eddy simulation (LES) based on a one-equation subgrid-scale model to investigate the flow field and pollutant dispersion characteristics inside urban street canyons. Unstable thermal stratification was produced by heating the ground of the street canyon. Using the Boussinesq approximation, thermal buoyancy forces were taken into account in both the Navier–Stokes equations and the transport equation for subgrid-scale turbulent kinetic energy (TKE). The LESs were validated against experimental data obtained in wind-tunnel studies before the model was applied to study the detailed turbulence, temperature, and pollutant dispersion characteristics in the street canyon of aspect ratio 1. The effects of different Richardson numbers (Ri) were investigated. The ground heating significantly enhanced mean flow, turbulence, and pollutant flux inside the street canyon, but weakened the shear at the roof level. The mean flow was observed to be no longer isolated from the free stream and fresh air could be entrained into the street canyon at the roof-level leeward corner. Weighed against higher temperature, the ground heating facilitated pollutant removal from the street canyon.Singapore-MIT Alliance for Research and Technology. Center for Environmental Sensing and Monitorin

Perceived cost potential field cellular automata model with an aggregated force field for pedestrian dynamics

postprin

Large-eddy simulatoin of flow field and pollutant dispession in urban street canyons under unstable atmospheric

Thermal stratification plays an important role in the air flow and pollutant dispersion processes. This study employed a large-eddy simulation (LES) code based on a one-equation subgrid-scale (SGS) model to investigate the flow field and pollutant dispersion characteristics inside urban street canyons. The unstable thermal stratification was simulated by heating the ground level of the street canyons. The thermal buoyancy forces were, using the Boussinesq assumption, taken into account in both the Navier-Stokes equations and the transport equation for SGS turbulent kinetic energy (TKE). The LES had been validated against experimental data obtained in wind tunnel studies before it was applied to study the detailed turbulence and pollutant dispersion characteristics in urban street canyons. The effects of different bulk Richardson number (Rb) were investigated. Several typical temperature differences between the street bottom and ambient air were configured to simulate the scenarios occurring at different times during the day.postprintThe 7th International Conference of Urban Climate (ICUC-7), Yokohama, Japan, 29 June-3 July 2009

Contributions of residential coal combustion to the air qualityin Beijing–Tianjin–Hebei (BTH), China: a case study

In the present study, the WRF-Chem model is used to assess contributions of residential coal combustion (RCC) emissions to the air quality in Beijing-Tianjin-Hebei (BTH) during a persistent air pollution episode from 9 to 25 January 2014. In general, the predicted temporal variations and spatial distributions of the mass concentrations of air pollutants are in good agreement with observations at monitoring sites in BTH. The WRF-Chem model also reasonably reproduces the temporal variations in aerosol species when compared with the aerosol mass spectrometer measurements in Beijing. The RCC emissions play an important role in the haze formation in BTH, contributing about 23.1% of PM2.5 (fine particulate matter) and 42.6% of SO2 during the simulation period on average. Organic aerosols dominate the PM2.5 from the RCC emissions in BTH, with a contribution of 42.8 %, followed by sulfate (17.1 %). The air quality in Beijing is remarkably improved when the RCC emissions in BTH and the surrounding areas are excluded in model simulations, with a 30% decrease in PM2.5 mass concentrations. However, if only the RCC emissions in Beijing are excluded, the local PM2.5 mass concentration is decreased by 18.0% on average. Our results suggest that the implementation of the residential coal replacement by clean energy sources in Beijing is beneficial to the local air quality. Should residential coal replacement be carried out in BTH and its surrounding areas, the air quality in Beijing would be improved remarkably. Further studies would need to consider uncertainties in the emission inventory and meteorological fields

Cyanobacterial bloom mitigation using proteins with high isoelectric point and chitosan-modified soil

A new environmental friendly method was developed for cyanobacterial blooms mitigation using local lake shore soil modified by protein with high isoelectric point (pI) and chitosan jointly. Results suggested that 5 mg/L lysozyme (pI ≈ 11) and 100 mg/L bromelain (pI ≈ 9.5) modified 10 mg/L soil can both reduce the surface charge of microcystis aeruginosa, the dominant species forming cyanobacterial blooms, from -26 mv to -10 mv and remove 73% and 60% of algal cells in 30 min, respectively. The limited improvement of removal efficiency was due to the small flocs (< 60 μm) formed by charge neutralization, which need more than 90 min to settle in static condition. However, when the small flocs were linked and bridged by the other modifier, chitosan with long polymer chain, large flocs of about 800 μm and 300 μm were fomed and more than 80% of algal cells were removed in 5 min and 30 min by lysozyme-chitosan modified soil and bromelain-chitosan modified soil, respectively. The lower removal ability of bromelain-modified soil was due to the lower charge density leading to less powerful in destabilization of algal cells. Depending on the bi-component modification mechanism including charge neutralization of proteins with high pI and netting and bridging function of chitosan with long polymer chain, it is possible to flocculate cyanobacterial blooms in natural waters effectively using locally available materials

Balancing hydrogen adsorption/desorption by orbital modulation for efficient hydrogen evolution catalysis

Hydrogen adsorption/desorption behavior plays a key role in hydrogen evolution reaction (HER) catalysis. The HER reaction rate is a trade-off between hydrogen adsorption and desorption on the catalyst surface. Herein, we report the rational balancing of hydrogen adsorption/desorption by orbital modulation using introduced environmental electronegative carbon/nitrogen (C/N) atoms. Theoretical calculations reveal that the empty d orbitals of iridium (Ir) sites can be reduced by interactions between the environmental electronegative C/N and Ir atoms. This balances the hydrogen adsorption/ desorption around the Ir sites, accelerating the related HER process. Remarkably, by anchoring a small amount of Ir nanoparticles (7.16 wt%) in nitrogenated carbon matrixes, the resulting catalyst exhibits significantly enhanced HER performance. This includs the smallest reported overpotential at 10 mA cm(-2) (4.5 mV), the highest mass activity at 10 mV (1.12 A mg(Ir)(-1)) and turnover frequency at 25 mV (4.21 H2 s(-1)) by far, outperforming Ir nanoparticles and commercial Pt/C

Observation of a ppb mass threshoud enhancement in \psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p}) decay

The decay channel $\psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p})$ is studied using a sample of $1.06\times 10^8$ $\psi^\prime$ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the $p\bar{p}$ invariant mass spectrum. The enhancement can be fit with an $S$-wave Breit-Wigner resonance function with a resulting peak mass of $M=1861^{+6}_{-13} {\rm (stat)}^{+7}_{-26} {\rm (syst)} {\rm MeV/}c^2$ and a narrow width that is $\Gamma<38 {\rm MeV/}c^2$ at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with those of any known meson resonance.Comment: 5 pages, 3 figures, submitted to Chinese Physics

Disparities and risks of sexually transmissible infections among men who have sex with men in China: a meta-analysis and data synthesis.

BACKGROUND: Sexually transmitted infections (STIs), including Hepatitis B and C virus, are emerging public health risks in China, especially among men who have sex with men (MSM). This study aims to assess the magnitude and risks of STIs among Chinese MSM. METHODS: Chinese and English peer-reviewed articles were searched in five electronic databases from January 2000 to February 2013. Pooled prevalence estimates for each STI infection were calculated using meta-analysis. Infection risks of STIs in MSM, HIV-positive MSM and male sex workers (MSW) were obtained. This review followed the PRISMA guidelines and was registered in PROSPERO. RESULTS: Eighty-eight articles (11 in English and 77 in Chinese) investigating 35,203 MSM in 28 provinces were included in this review. The prevalence levels of STIs among MSM were 6.3% (95% CI: 3.5-11.0%) for chlamydia, 1.5% (0.7-2.9%) for genital wart, 1.9% (1.3-2.7%) for gonorrhoea, 8.9% (7.8-10.2%) for hepatitis B (HBV), 1.2% (1.0-1.6%) for hepatitis C (HCV), 66.3% (57.4-74.1%) for human papillomavirus (HPV), 10.6% (6.2-17.6%) for herpes simplex virus (HSV-2) and 4.3% (3.2-5.8%) for Ureaplasma urealyticum. HIV-positive MSM have consistently higher odds of all these infections than the broader MSM population. As a subgroup of MSM, MSW were 2.5 (1.4-4.7), 5.7 (2.7-12.3), and 2.2 (1.4-3.7) times more likely to be infected with chlamydia, gonorrhoea and HCV than the broader MSM population, respectively. CONCLUSION: Prevalence levels of STIs among MSW were significantly higher than the broader MSM population. Co-infection of HIV and STIs were prevalent among Chinese MSM. Integration of HIV and STIs healthcare and surveillance systems is essential in providing effective HIV/STIs preventive measures and treatments. TRIAL REGISTRATION: PROSPERO NO: CRD42013003721

Observation of CR Anisotropy with ARGO-YBJ

The measurement of the anisotropies of cosmic ray arrival direction provides important informations on the propagation mechanisms and on the identification of their sources. In this paper we report the observation of anisotropy regions at different angular scales. In particular, the observation of a possible anisotropy on scales between $\sim$ 10 $^{\circ}$ and $\sim$ 30 $^{\circ}$ suggests the presence of unknown features of the magnetic fields the charged cosmic rays propagate through, as well as potential contributions of nearby sources to the total flux of cosmic rays. Evidence of new weaker few-degree excesses throughout the sky region $195^{\circ}\leq$ R.A. $\leq 315^{\circ}$ is reported for the first time.Comment: Talk given at 12th TAUP Conference 2011, 5-9 September 2011, Munich, German