Experimental study and numerical simulation of the kinetic energy recovery of the mine's exhaust gas.

In mines, the exhaust gas is mainly discharged from main ventilators in free dissipation state. The effective recovery of its kinetic energy is lucrative from economical and technical standpoints. This study is focused on recovering the kinetic energy of the exhaust gas without deteriorating the main ventilator's safe operation or increasing power dissipation. The related experiments and numerical simulations were performed for the conical diffusers with diffusing angles of 16° and inlet diameters of 220 and 320 mm, respectively. By examining the start-up and operation states of the wind turbines using inlet collectors with conical, circular arc, and cone-arc shapes, it was found that the wind speed at the inlet of the drainage tube exceeded 4 and 20 m/s at the minimal and maximal distances from the wind turbine, respectively. The wind speed at the overflow tube outlet was no less than 1.8 m/s, proving a certain recovery of kinetic energy by the wind turbine. Thus, the critical distance between the diffuser and the inlet collector should be at least four times the diffuser's inlet diameter. Finally, the velocity, pressure, and flow fields in the vortex core regions of the kinetic recovery system with different types of inlet collectors were simulated with the FLUENT commercial software package. The simulation results revealed that the circular-arc collector outperformed other three tested configurations in kinetic energy recovery.Implications: This study is focused on recovering the kinetic energy of the exhaust gas without deteriorating the main ventilator's safe operation or increasing power dissipation. China is a country with coal as its main energy source, which releases over ten billion cubic meters of the exhaust gas annually. In addition to low-concentration methane, there is also the exhaust gas released at a velocity of about 20 m/s, which kinetic energy recovery would be very lucrative.The significance of this study is that the mine's main ventilator outlet was simplified as two conical diffusers with parameters α=16°/n=2 and α=16°/n=2.5, and the optimal critical distance between the diffuser and the collector was determined as 4Di, where Di was the diffuser's inlet diameter. Under that optimal condition, the system can achieve the maximum power without affecting the ventilator's normal operation. It is instructive to make full use of and manage the exhaust gas in mine that fits the journal on the purpose of air waste management.Finally, we provide a statement serious that the article is original and unpublished and is not being considered for publication elsewhere.

Broadband near-infrared TiO2 dielectric metamaterial absorbers.

Metamaterial absorbers (MAs) have drawn increasing attention due to their prospects in many fields such as sensing, thermal emission, solar energy harvesting, etc. However, it remains challenging to realize broadband MAs with a simple structure. Here, we propose a broadband, polarization-insensitive, and omnidirectional MA working in the near-infrared range with simple structure, which is composed of titanium dioxide (TiO2) cylinder nano-antenna arrays on the top of a vanadium (V) film deposited on a silicon substrate. This device demonstrates broadband absorption spectra from 820 to 1440 nm with the absorption above 90%, with high absorption up to the incident angle of ∼50°. The broadband absorption of the designed MA is mainly attributed to the interaction both of dielectric cavity resonance and electric dipole resonance. The electric and magnetic field intensity distribution of the MA are analyzed to better understand its absorption mechanism. In addition, the effects of the geometrical parameters on absorption are discussed. The demonstrated MA is relatively easy to fabricate and can be realized with other proper materials to work in other wavelength bands. The design is useful for applications such as solar energy harvesting, sensing, and camouflage.

Wide-angle, polarization-insensitive, and broadband metamaterial absorber based on multilayered metal-dielectric structures.

A wide-angle, polarization-insensitive, and broadband metamaterial absorber (MA) based on multilayered metal-dielectric structures was designed and investigated using the finite-difference time-domain solution. The device exhibited polarization-insensitive absorption in the 475-592 nm range, with the absorption higher than 95%. At the same time, the broadband absorption was nearly unaffected for incident angles below 50°. To understand this absorption mechanism of this broadband MA, we investigated the magnetic field distributions at the resonance wavelength. Different metallic layers yielded different resonant wavelengths, leading to the observed high absorption in the broadband spectrum. For broadband MAs, the absorption spectrum can be expanded by adjusting structural parameters.

Single particle aerosol mass spectrometry of coal combustion particles associated with high lung cancer rates in Xuanwei and Fuyuan, China.

Coal combustion particles (CCPs) are linked to the high incidence of lung cancer in Xuanwei and in Fuyuan, China, but studies on the chemical composition of the CCPs are still limited. Single particle aerosol mass spectrometry (SPAMS) was recently developed to measure the chemical composition and size of single particles in real-time. In this study, SPAMS was used to measure individual combustion particles emitted from Xuanwei and Fuyuan coal samples and the results were compared with those by ICP-MS and transmission electron microscopy (TEM). The total of 38,372 particles mass-analyzed by SPAMS can be divided into 9 groups based on their chemical composition and their number percentages: carbonaceous, Na-rich, K-rich, Al-rich, Fe-rich, Si-rich, Ca-rich, heavy metal-bearing, and PAH-bearing particles. The carbonaceous and PAH-bearing particles are enriched in the size range below 0.56 µm, Fe-bearing particles range from 0.56 to 1.0 µm in size, and heavy metals such as Ti, V, Cr, Cu, Zn, and Pb have diameters below 1 µm. The TEM results show that the particles from Xuanwei and Fuyuan coal combustion can be classified into soot aggregates, Fe-rich particles, heavy metal containing particles, and mineral particles. Non-volatile particles detected by SPAMS could also be observed with TEM. The number percentages by SPAMS also correlate with the mass concentrations measured by ICP-MS. Our results could provide valuable insight for understanding high lung cancer incidence in the area.

[Distribution Characteristics of Heavy Metals in the Street Dusts in Xuanwei and Their Health Risk Assessment].

Relationship between high lung cancer incidence in Xuanwei residents and environmental pollution has been a hot topic in the field of environmental sciences. Street dusts in Xuanwei power plant area as well as its upwind area (Banqiao town) and downwind area (Laibin town, Tangtang town) were collected. Chemical elements in the street dust samples were investigated using ICP-MS. Health risk assessment of heavy metals in the street dusts was carried out using the US EPA Health Risk Assessment Model. Our results showed that the mass level of Al, V, Ni, Co, Zn and Cd in street dusts followed the order of Xuanwei power plant > Laibin town > Tangtang town. The mean concentrations of V, Cd, Cr, Cu, Mn, Co, Ni, Pb, As and Zn were all higher than the background values in Yunnan soil, indicating that the street dusts of Xuanwei city have been heavily polluted by those metals. The health risk assessment results showed that the non-cancer hazard risks induced by the 10 heavy metals were higher to children compared to adults. The heavy metals in street dust were mainly ingested by human bodies through hand-mouth ingestion. The 5 carcinogenic metals, including Cd, Cr, Ni, Cr and As, had a potential risk of carcinogenicity in human after exposed to the dusts. Cr was the major toxic element to the local children's health.

Comparison of cellular toxicity caused by ambient ultrafine particles and engineered metal oxide nanoparticles.

OBJECTIVE: The development of nanotechnology has spurred concerns about the health effects of exposure to nanoparticles (NPs) and ultrafine particles (UFPs). Toxicological data on NPs and UFPs may provide evidence to support the development of regulations to reduce the risk of particle exposure. We tried to provide fundamental data to determine differences in cytotoxicity induced by ambient UFPs and engineered metal oxide NPs (ZnO, NiO, and CeO2). METHODS: UFPs were sampled by using of a nano micro-orifice uniform deposit impactor. Physicochemical characterization of the UFPs and nano metal oxide particles were studied by scanning electron microscopy and transmission electron microscopy. Cellular toxicity induced by the different particles was assessed by using of comprehensive approaches and compared after A549 cells were exposured to the particles. RESULTS: All of the measured particles could damage A549 cells at concentrations ranging from 25 to 200 µg/mL. The lowest survival ratio and the highest lactate dehydrogenase level were caused by nano-ZnO particles, but the highest levels of intracellular reactive oxygen species (ROS) and percentages of apoptosis were observed in cells treated with the soluble fraction of ambient fine particles (PM1.8) at 200 µg/mL. Relatively high concentrations of anthropogenic metals, including Zn, Ni, Fe, and Cu, may be responsible for the higher toxicity of fine ambient particles compared with the ambient coarse particles and UFPs. The selected heavy metals (Zn, Ni, Fe, and Cu) were found to be located in the perinuclear and cytoplasmic areas of A549 cells. The distribution pattern of metals from ambient particles showed that distributions of the metals in A549 cells were not uniform and followed the pattern Cu>Zn>Fe>Ni, suggesting that Cu was absorbed by A549 cells more easily than the other metals. CONCLUSIONS: Metal nanoparticles oxides and UFPs at low concentration could damage to cells, but the manufactured metal oxide nanoparticles are not highly toxic to lung cells compared to environmental particles. The local concentration effect of heavy metals in A549 cells, as well as the induction of oxidative stress by the particles, may be responsible for the damage observed to the cells.