Increasing Particle Concentration Research Articles

Household solid waste combustion with wood increases particulate trace metal and lung deposited surface area emissions

In households, municipal solid waste (MSW) is often burned along with wood to get rid of waste, to help in ignition or simply to reduce fuel costs. The aim of this study was to characterize the influence of household waste combustion, along with wood, on the physical and chemical properties of particulate emissions in a flue gas of a masonry heater.The MSW burning alongside wood increased average particulate matter (PM) mass (65%), lung deposited surface areas (LDSA, 15%), black carbon (BC, 65%) concentrations and the average particle size in the flue gas. The influence of MSW was smaller during ignition and burning phases, but especially during fuel additions, the mass, number, and LDSA concentrations increased significantly and their size distributions moved towards larger particles. For wood burning the trace metal emissions were relatively low, but significant increase (3.3–179 -fold increase over cycle) was seen when MSW was burned along the wood. High ratios were observed especially during fuel addition phases but, depending on compounds, also during ignition and burning end phases. The highest ratios were observed for chloride compounds (HCl, KCl, NaCl). The observed increase in light-absorbing particle, trace metal and BC concentrations in flue gas when adding wood with MSW are likely to have negative impacts on air quality, visibility, human health and climate. Furthermore, metals may also affect the condition and lifetime of the burning device due to corrosion.

Effects of TiC nanoparticle additions on microstructure and mechanical properties of FeCrAl alloys prepared by directed energy deposition

• Near fully dense TiC particles strengthened FeCrAl alloys have been fabricated by directed energy deposition. • TiC additions significantly refine the grain sizes and prompt columnar to equiaxed grain transition. • TiC particles strengthened FeCrAl alloys have good mechanical properties both at room temperature and high temperature of 650 ℃. Directed energy deposition (DED) additive manufacturing process has been attractive to the fabrications of FeCrAl alloys due to the advantage of near net shaping of complex shaped components. In order to improve the strength, TiC particles strengthened FeCrAl alloys have been fabricated by DED using blended FeCrAl powder and TiC nanoparticles. The results show that the TiC particles in the DED alloys have submicron sizes, and polygonal or dendritic shapes. Most TiC particles are distributed along the dendritic/grain boundaries. The additions of TiC particles effectively refine the grain sizes, and at the same time prompt a columnar to equiaxed transition of grains. The grain sizes are reduced from 1377 μm to 47 μm, 21 μm and 22 μm when the TiC particle contents in the DED alloys increase from 0 wt% to 0.7 wt%, 2.4 wt% and 3.5 wt%, respectively. The room temperature strength of the FeCrAl alloys increase with the increase of TiC particle content. With 3.5 wt% TiC particle content, the FeCrAl alloy has good mechanical properties with yield strength of 437 MPa, ultimate tensile strength of 688 MPa, and an elongation of 19 %. The 650 ℃ high temperature strength of the FeCrAl alloys first decrease and then increase with the increase of TiC particle content. With 3.5 wt% TiC particle content, the FeCrAl alloy has excellent mechanical properties with yield strength of 208 MPa, ultimate tensile strength of 223 MPa, and an elongation of 53 %. The present study provides an important basis for fabricating high strength particle-strengthened FeCrAl alloys using the DED process.

Enhancement of gas-liquid mass transfer by nanofluids in a microchannel under Taylor flow regime

The gas-liquid two-phase flow and the enhancement of mass transfer by nanoparticles for the process of CO2 absorbed by SiO2 nanofluids were investigated in a microchannel under Taylor flow regime. The influences of the dispersed and continuous phase flow rates and particle concentration in slurry on liquid side volumetric mass transfer coefficient (KLa), mass transfer enhancement factor (E), CO2 absorption efficiency, and pressure drop were studied systematically. The results show that the presence of nanoparticles can effectively enhance the gas-liquid mass transfer. Both KLa and pressure drop increase, while the CO2 absorption efficiency decreases with increasing the gas-liquid flow rate ratio. Differently, KLa, CO2 absorption efficiency and pressure drop increase with the increase of particle concentration in slurry. Considering the energy consumption and mass transfer enhancement effect, the effective mass transfer enhancement efficiency is in the range of 1.2 ~ 2.4, which shows the excellent enhancement performance of nanoparticles on gas-liquid mass transfer.

Simulation of Aerosol Evolution within Background Pollution for Nucleated Vehicle Exhaust via TEMOM

This work is intended to study the effect of background particles on vehicle emissions in representative realistic atmospheric environments. The coupling of Reynolds-Averaged Navier–Stokes equation (RANS) and Taylor-series Expansion Method Of Moments (TEMOM) is performed to track the emissions of the vehicle and simulating the evolution of the matters. The transport equation of mass, momentum, heat, and the first three orders of moments are taken into account with the effect of binary homogeneous nucleation, Brownian coagulation, condensation, and thermophoresis. The parameterization model is utilized for nucleation. The measured data for Beijing’s particle size distribution under both polluted and nonpolluted conditions are utilized as background particles. The relationship between the macroscopic measurement results and the microscopic dynamic process is analyzed by comparing the variation trend of several physical quantities in the process of aerosol evolution. It is found with an increase of background particle concentration, the nucleation is inhibited, which is consistent with the existing studies.

Characteristics of Particulate Emissions from Co-Firing in An Industrial Boiler

Characteristics of Particulate Emissions from Co-Firing in An Industrial Boiler. PT. X is a textile industry that consumes a massive amount of coal for its boiler operation. It requires substantial costs to obtain coal from Sumatra and Kalimantan. An alternative solid biofuel (briquette) was developed to combine bottom ash and biomass made from municipal solid waste called Biomass Coal Fuel (BCF) briquette. The purpose of this study is to measure the total concentration of particulate matter and emission factor (PM) emitted from two burning experiments: only coal (100%) and mixed coal fuel with 10% of BCF (co-firing). Mixed coal and BCF burning are carried out in the fire-tube boiler where the PM emission is released through the stack. The Center for Pulp and Paper measured particulate emission with methodology referring to SNI 7117.17-2009. Particulate matter concentration emitted from only coal-burning was 12,1 mg/Nm3,but when mixed BCF and coal were used, the higher concentration was emitted 70,9 mg/Nm3. The addition of BCF briquettes affects the particulate matter emission, even though the emission does not exceed the regulated quality standard. The increase of particulate concentration is due to the BCF briquette characteristics, which have a low heating value and high ash content. The boiler has already been equipped with cyclone and wet scrubber; therefore, PM emissions presented here are treated emissions. The controlled PM emission factor of BCF was 4,46 g/kg, which is higher than only coal which was 0,51 g/kg. BCF briquette can still be used as co-fuel for the boiler, but further effort is still required to reduce the ash content of the BCF and increase the calorific value of the BCF.

Antibacterial and cytotoxic activity of polymer-metal hybrid nanoparticle

Recently, there is a growing demand for the polymer-nanoparticle hybrid system due to their long-term stability against aggregation and enhanced functionality for different applications in both material science and biology. In the current study, we have prepared a novel stimuli-responsive biocompatible polymer-silver nanoparticle hybrid using polymeric microgel particles as a micro-reactor in an in-situ treatment, and these hybrid particles are characterized using UV-Vis, dynamic light scattering, and transmission electron microscope with respect to their size distribution and optical properties. Next, these hybrid particles were tested for antibacterial and cytotoxic activities against Salmonella typhimurium bacteria and HeLa cancer cells, respectively using bulk-diffusion, agar diffusion assay, and MTT assay. Both bulk and agar diffusion assays confirm the antibacterial properties of the hybrid microgel-silver nanoparticles against Salmonella typhimurium. Agar diffusion assay shows a systematic trend in the increase of the width of inhibition zone as a function of increasing particle concentration and thus relating the linear relationship between hybrid nanoparticle concentration and concentration of inhibited bacteria. Similarly, linear behavior is also observed with MTT assay, where cell viability decreases linearly with an increase in hybrid particle concentration. Thus, we believe that our polymer-nanoparticle hybrid system may have a wide range of industrial applications as an antibacterial agent and in cancer therapy applications.

Characteristics of Particulate Emissions from Co-Firing in An Industrial Boiler

Characteristics of Particulate Emissions from Co-Firing in An Industrial Boiler. PT. X is a textile industry that consumes a massive amount of coal for its boiler operation. It requires substantial costs to obtain coal from Sumatra and Kalimantan. An alternative solid biofuel (briquette) was developed to combine bottom ash and biomass made from municipal solid waste called Biomass Coal Fuel (BCF) briquette. The purpose of this study is to measure the total concentration of particulate matter and emission factor (PM) emitted from two burning experiments: only coal (100%) and mixed coal fuel with 10% of BCF (co-firing). Mixed coal and BCF burning are carried out in the fire-tube boiler where the PM emission is released through the stack. The Center for Pulp and Paper measured particulate emission with methodology referring to SNI 7117.17-2009. Particulate matter concentration emitted from only coal-burning was 12,1 mg/Nm3,but when mixed BCF and coal were used, the higher concentration was emitted 70,9 mg/Nm3. The addition of BCF briquettes affects the particulate matter emission, even though the emission does not exceed the regulated quality standard. The increase of particulate concentration is due to the BCF briquette characteristics, which have a low heating value and high ash content. The boiler has already been equipped with cyclone and wet scrubber; therefore, PM emissions presented here are treated emissions. The controlled PM emission factor of BCF was 4,46 g/kg, which is higher than only coal which was 0,51 g/kg. BCF briquette can still be used as co-fuel for the boiler, but further effort is still required to reduce the ash content of the BCF and increase the calorific value of the BCF.

Issledovaniye vzveshennykh mikrochastits v atmosfere beregovoy zony Chernogo morya po naturnym i sputnikovym dannym

Purpose. One of the most pressing problems of large cities is air pollution resulting from presence of various large and fine particles in the air. These micro-particles can be transported by the air currents over considerable distances, as well as coagulate various substances also present in the atmosphere. The purpose of the work is to study the content of particulate matter of 2.5 and 10 microns (PM2.5 and PM10) in the atmosphere of Sevastopol, as well as the processes affecting their concentration. Methods and Results. During the period from February to June, 2020, the scientists of Marine Hydrophysical Institute (MHI), RAS measured mass concentration of PM2.5 and PM10 in Sevastopol using the “Atmas” dust analyzer. A total of 180 measurements of the micro-particle concentrations in the air of Sevastopol were done, and 60 values of the PM2.5 and PM10 daily average concentrations were obtained. To analyze the preferred aerosol type for the dates with high content of suspended particles in the air, the CALIPSO satellite data were used. It is shown that the smoke recorded in the Sevastopol atmosphere on 19.02.2020 could lead to increase of the PM10 particles concentration. A day before the increased concentrations of suspended particles were revealed in the Sevastopol atmospheric air, the CALYPSO satellite data on aerosol typing over the Black Sea had shown predominance of the smoke aerosol in the atmosphere over the region under study. Conclusions. The results of the investigation show that in the atmosphere of Sevastopol, the cases when the PM2.5 and PM10 particles contents exceeded the maximum permissible daily average concentration by up to 3.4 times were detected. It was found that the main cause of air pollution with micro-particles in Sevastopol was the transfer both of the air masses from the deserts in the African continent and Asia, and the burning biomass aerosol (smoke). Air pollution with the PM10 particles caused by the local source, namely soil exсavation in immediate proximity to the air sampling point, was less significant.

Welding Fume Exposure and Health Risk Assessment in a Cohort of Apprentice Welders.

Welding fumes vary in composition depending on the materials and processes used, and while health outcomes in full-time welders have been widely studied, limited research on apprentices exists. Besides, few data are available for metals such as vanadium and antimony. This study aimed to look at individual metals present in welding fumes in the learning environment of apprentice welders. Forty-three welders and 41 controls were chosen from trade programmes at the Northern Alberta Institute of Technology. Ambient and personal air samples were collected at days 0, 1, 7, and 50 of their training and analysed for mass and metal concentrations using Inductively Coupled Plasma Mass Spectrometry. Results showed increases in particle and metal concentrations as apprentices progressed throughout their education and that concentrations at day 50 were similar to levels found in the literature for professional welders. Variable concentrations indicate that some individuals may not properly use the local exhaust ventilation system. Other possible explanation for variations are the position of the sampler on the shoulder, the time spent welding and in each welding position, and the skills of the welders. Strong relationships were observed between particle and metal concentrations, suggesting that these relationships could be used to estimate metal exposure in welders from particle exposure. Welding processes were the most important determinant of exposure in apprentice welders, with Metal Core Arc Welding producing the largest particle concentrations followed by oxyacetylene cutting, and Gas Metal Arc Welding. Health risk assessment showed that welder apprentices are at risk for overexposure to manganese, which suggests that professional welders should be monitored for manganese as they are exposed more than apprentices. Training in proper positioning of local exhaust ventilation system and proper use of respirators are recommended in training facilities.

Photocurable magnetic materials with tailored functional properties

Magnetic materials are among the most commonly required for a wide variety of applications. Further, their fabrication and implementation by means of additive manufacturing technologies are also getting increasing attention. In this context, photocurable magnetic materials based on polyurethane acrylated (PUA) polymer and different magnetic particles including magnetite (Fe3O4), cobalt ferrite oxide (CFO) and neodymium iron boron alloy (NdFeB) have been developed. The influence of filler type and content on the photopolymerization process, sample morphology, Young modulus, electric conductivity and magnetic properties has been investigated. It is observed that increasing particle content diminishes the conversion degree, independently of the filler type. The largest effect on the conversion degree is observed for magnetite (20% degree of conversion for 6.3 wt.% filler content) and the lowest for NdFeB (99% for 6.5 wt.% sample). Fe3O4 and CFO particles form small agglomerates within the sample, which increase with filler content, whereas NdFeB shows a good degree of dispersion. Regarding the mechanical properties, a remarkable decrease on the Young modulus of the films prepared with iron oxide-based fillers is observed, while the inclusion of NdFeB shows an increase in the Young modulus. Finally, magnetic properties are characterized by an increase in the saturation magnetization and remanence with increased filler content, while the coercivity remained constant for all filler types. A maximum magnetization of 3.70, 3.50 and 49.64 emu/g is obtained for Fe3O4, CFO and NdFeB based composites. This demonstrates the possibility of easily developing materials with tailored magnetic response by means of additive manufacturing technologies.

Impacts of vegetation on particle concentrations in roadside environments

In roadside environments, commuters are exposed to a high level of traffic-related pollution. Despite vegetation is often used to mitigate air pollution in road environments, its air quality impacts are complex and could be both positive or negative depending on specific conditions. This study conducted field measurements to assess the air quality impacts of roadside vegetation. Three common street vegetation configurations (dense vegetation, porous vegetation, and clearing) were selected and the concentrations of size-resolved particles and black carbon were measured. Results show that dense vegetation formed an accumulation area of particle pollutants on the sidewalk and bikeway, which was attributable to the increased deposition of pollutants. Compared with porous vegetation, the increase in particle concentrations before dense vegetation was 0–35% on the sidewalk (closer to vegetation) and 0–6% on the bikeway. Due to high homogeneity, fine particles (0.3–1 μm) showed low variability among different sample points, while coarse particles (>1 μm) showed high variability and presented a significant increase in concentration before dense vegetation. Porous vegetation showed weak interception effects on pollutants, and the particle concentrations before porous vegetation were close to those in the clearing. The horizontal decay of particle concentrations in porous and dense vegetation showed that particle pollutants were difficult to penetrate dense vegetation, which concentrations of particles presented a pronounced increase in the front part (0–5 m) of dense vegetation but also showed a large drop across it. These results suggest that vegetation serves as a good filter to clean the air and could improve the air quality away from the vegetation but could also worsen the air quality close to the vegetation. This study provides an insight into the environmental impacts of roadside vegetation, which could have practical implications in air pollution abatement.

Computational study of enhanced oil recovery from a porous medium using nanosuspension

The paper presents the results of direct numerical simulations of the process of oil displacement by nanosuspension with SiO2 particles from two-dimensional micromodels of a porous medium with different values of permeability. In the calculations, the experimentally measured values of the interfacial tension coefficient and the contact angle of wetting were used. The calculations were performed for pure water and a suspension of silicon oxide nanoparticles with a mass concentration of 1%. The computational study was performed using the VOF method. The influence of the displacement fluid flow rate, nanoparticle concentration and core permeability on the efficiency of oil displacement by nanosuspension was studied. As a result of the work, it was shown that the use of nanosuspensions makes it possible to increase the oil recovery factor. It is shown that with an increase in the mass concentration of particles, the value of the oil recovery factor increases.

Nanoparticle tracking analysis as a process analytical tool for characterising magnetosome preparations

Nanoparticle Tracking Analysis (NTA) has been employed to measure the particle concentration and size distribution of magnetosomes extracted and purified from Magnetospirillum gryphiswaldense MSR-1, and then exposed to probe ultrasonication for various times, or 1% (w/v) sodium dodecyl sulphate (SDS) for 1 h. Particle concentration increased 3.7-fold over the first 15 min of ultrasonication (from 2 × 108 to >7.3 × 108 particles mL−1), but fell steeply to ∼3.6 × 108 particles mL−1 after 20 min. NTA of untreated magnetosome preparation confirmed a wide particle distribution dominated by larger species (D[1,0] = 312 nm; Dn50 = 261 nm; mode = 243 nm) with no particles in the size range of isolated single magnetosomes. After 5 min of ultrasonication the whole particle size distribution shifted to smaller size (D[1,0] = 133 nm; Dn50 = 99 nm; mode = 36 nm, corresponding to individual magnetosomes), but longer treatment times (15 and 20 min) reversed the previous transition; all characteristic numbers of the particle size distributions increased and very few small particles were detected. Side-by-side comparison of NTA and TEM sizing data revealed remarkable similarity at low ultrasonication times, with both showing single magnetosomes accounted for ∼30% population after 5 min. Exposure of magnetosomes to SDS resulted in a ∼3-fold increase in particle concentration to 5.8 × 108 particles mL−1, narrowing of the size distribution and gross elimination of particles below 60 nm. We conclude that NTA is a rapid cost-effective technique for measuring particle concentration, size distribution and aggregation state of magnetosomes in solution.

Viscoelastic Particle Train Formation in Microfluidic Flows Using a Xanthan Gum Aqueous Solution.

Viscoelastic polymer solutions have been widely employed as suspending liquids for a myriad of microfluidic applications including particle and cell focusing, sorting, and encapsulation. It has been recently shown that viscoelastic solutions can drive the formation of equally spaced particles called "particle trains" as a result of the viscoelasticity-mediated hydrodynamic interactions between adjacent particles. Despite their potential impact on applications such as droplet encapsulation and flow cytometry, only limited experimental studies on viscoelastic ordering are currently available. In this work, we demonstrate that a viscoelastic shear-thinning aqueous xanthan gum solution drives the self-assembly of particle trains on the centerline of a serpentine microfluidic device with a nearly circular cross section. After focusing, the flowing particles change their mutual distance and organize in aligned structures characterized by a preferential spacing, quantified in terms of distributions of the interparticle distance. We observe the occurrence of multi-particle strings, mainly doublets and triplets, that interrupt the continuity of the particle train. To account for the fluctuations in the number of flowing particles in the experimental window, we introduce the concept of local particle concentration, observing that an increase of the local particle concentration leads to an increase of doublets and triplets. We also demonstrate that using only a single tube to connect the sample to the microfluidic device results in a drastic reduction of doublets/triplets, thus leading to a more uniform particle train. Our findings establish the foundation for optimized applications such as deterministic droplet encapsulation in viscoelastic liquids and optimized flow cytometry.

Improving the sectional Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) aerosols of the Weather Research and Forecasting-Chemistry (WRF-Chem) model with the revised Gridpoint Statistical Interpolation system and multi-wavelength aerosol optical measurements: the dust aerosol observation campaign at Kashi, near the Taklimakan Desert, northwestern China

Abstract. The Gridpoint Statistical Interpolation data assimilation (DA) system was developed for the four size bin sectional Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) aerosol mechanism in the Weather Research and Forecasting-Chemistry (WRF-Chem) model. The forward and tangent linear operators for the aerosol optical depth (AOD) analysis were derived from WRF-Chem aerosol optical code. We applied three-dimensional variational DA to assimilate the multi-wavelength AOD, ambient aerosol scattering coefficient, and aerosol absorption coefficient, measured by the sun–sky photometer, nephelometer, and aethalometer, respectively. These measurements were undertaken during a dust observation field campaign at Kashi in northwestern China in April 2019. The results showed that the DA analyses decreased the model aerosols' low biases; however, it had some deficiencies. Assimilating the surface particle concentration increased the coarse particles in the dust episodes, but AOD and the coefficients for aerosol scattering and absorption were still lower than those observed. Assimilating aerosol scattering coefficient separately from AOD improved the two optical quantities. However, it caused an overestimation of the particle concentrations at the surface. Assimilating the aerosol absorption coefficient yielded the highest positive bias in the surface particle concentration, aerosol scattering coefficient, and AOD. The positive biases in the DA analysis were caused by the forward operator underestimating aerosol mass scattering and absorption efficiency. As compensation, the DA system increased particle concentrations excessively to fit the observed optical values. The best overall improvements were obtained from the simultaneous assimilation of the surface particle concentration and AOD. The assimilation did not substantially change the aerosol chemical fractions. After DA, the clear-sky aerosol radiative forcing at Kashi was −10.4 W m−2 at the top of the atmosphere, which was 55 % higher than the radiative forcing value before DA.

Fabrication of high permeability SiC ceramic membrane with gradient pore structure by one-step freeze-casting process

A highly permeable porous SiC ceramic membrane with multilayered unidirectional gradient pore microstructure was prepared by one-step freeze-casting process. The multilayer microstructures, mechanical properties and filtering performances of freeze-casting SiC ceramic membranes were controlled by optimizing the preparation process. It was found that with the increase of solid content from 30 vol% to 40 vol%, the directional pore channels gradually narrowed by about 50% and the mechanical properties increased from 0.47 MPa to 5.44 MPa. In addition, the increase of coarse particle content not only thickened the separation layer and the transition layer, but also widened the directional pore channel, which is beneficial to improve the permeability efficiency. When the coarse particle content of SiC ceramic membranes was 90%, the average pore size of separation layer, transition layer and lamellar structure was 5.52 μm, 7.63 μm and 36.09 μm, respectively. The maximum water permeability of S35C90 ceramic membrane reached up to 5.67 × 105 L/m2 h bar, and the rejection rate for ground calcium carbonate was 96.1%, confirming the superior perviousness and separation efficiency of freeze-casting ceramic membranes in the field of filtration.

Investigate on the phase interfaces and performance evaluation of TiB2p/Al–Si–Cu–Zn (T6) composites

In this paper, the microstructures, mechanical properties, and corrosion behavior of xTiB2/Al–9Si–3Cu-0.8Zn composites after T6 heat treatment were invested in detail through the combination of different technologies, including optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile testing, corrosion testing, etc. The research results showed that the average size of the α-Al grains gradually decreased with the increase of TiB2 particles (TiB2p) content. In addition, there was a semi-coherent relationship between TiB2p and the α-Al matrix, and the nanoscale precipitates were identified as θ and θʹ phases by virtue of their crystal orientation relationship. Tensile testing results revealed that an increase in TiB2 content caused the elastic modulus, yield strength and tensile strength of the composites to increase and then decrease. And with a TiB2p content of 4 wt%, they reached 85.7 GPa, 360 MPa and 398 MPa, reflecting increases of 26.2%, 60.0%, and 30.9%, respectively. The contributions of thermal mismatch, grain boundary and Orowan strengthening mechanisms to the overall yield strength of the 4%TiB2/Al–9Si–3Cu–0.8Zn composite were 72.1, 3.8, and 35.6 MPa, respectively. Unfortunately, the corrosion resistance of xTiB2/Al–9Si–3Cu–0.8Zn composites gradually decreased with increasing TiB2p content. The corrosion morphology analysis indicated that the agglomeration of TiB2p and Si weakened the protection afforded by the oxide film, evolving into a point of nucleation for the subsequent corrosion reaction. Moreover, point–pair correlation was observed between the TiB2p and Al matrix, exacerbating the corrosion. The results implied that extra factors be considered in industrial application of TiB2 ceramic particles in a metallic system.

Effect of TiC and TiB2 Content on Properties of TiAl Based Alloys

In this paper, we added different content of TiC and TiB2 particles powder into TiAl based alloy as particle reinforcement, and prepared different components of TiAl based composite. We also studied the influence of the content of TiC and TiB2 particles on the physical and mechanical properties of TiAl based composite. The results show that in a certain range, the physical properties of TiAl based alloy increase with the increase of TiC and TiB2 particle content, and the mechanical properties first increase and then decrease with the increase of TiC and TiB2 particle content. It is proved that the physical and mechanical properties of TiAl alloy can be effectively improved by adding the proper amount of TiC and TiB2 particles.

Analysis of the Air Pollution Index and Meteorological Factors and Risk Assessment for Tibet

An analysis and statistical evaluation of the environmental air quality, meteorological conditions, and human health effects were carried out for major cities and towns in Tibet. The study selected PM10, SO2, NO2, PM2.5, O3, and CO atmospheric pollutant monitoring data, a pollutant index, and the air quality index for seven cities and towns in Tibet in the year 2017 and for the Lhasa urban area in the period from June 2000 to December 2017. The data were combined with meteorological elements, namely precipitation, temperature, wind, and total solar radiation, for the same period. Results show that the air quality index is highest in Nag Qu, among of the seven cities and towns, followed by Shigatse, which roughly reflects the characteristics of pollution emissions dominated by biomass fuels in agricultural and pastoral areas of Tibet, a lack of vegetation, strong winds and less rain, and increased particle concentration. These factors affects human health. The six pollutants had higher concentrations in the winter half of the year (November to April) and lower concentrations in the summer half of the year (May to October); i.e., the concentration of pollutants was 38% higher in the winter half of the year. The change trend of the six pollutants has changed over the years; the concentrations of NO2 and PM2.5 have increased, the concentration of PM10 has decreased, and the concentrations of O3 and SO2 have not changed appreciably. According to national air quality standards, the percentage number of days with excellent air quality was 22.7%, the percentage number of days with good air quality was 62.7%, the percentage number of days with light pollution was 11.3%, and the percentage number of days with moderate or heavy pollution was 0.6%. Meteorological factors such as precipitation, wind speed, visibility, and total solar radiation affect air pollution.

Effect of strong electric field on heat transfer enhancement in a mini channel containing Al2O3/oil nanofluid

The present work aims to investigate the heat transfer and pressure drop of Alumina/oil nanofluid flow in a miniaturized square channel in the presence of strong DC electric fields. The high voltage was applied using a thin wire on top of the channel. The bottom of the channel was used as both a ground electrode and a heated surface. Results showed that increasing particle concentration caused heat transfer augmentation for all Reynolds numbers. Applying a strong electric potential of 15.51 kV resulted in considerable heat transfer enhancement of 52% for the nanofluid with 0.3% volume fraction, at the Reynolds number of 7. This considerable enhancement can be attributed to the formation of the ion injection-based secondary flows and motion of the particles. The generated secondary flow disrupts the boundary layer and increases the heat absorption from the heated surface. The experiments were confined to the volume fraction of 0.3% since the rapid agglomeration of particles occurred on electrode and walls at the volume fraction of 0.5%.