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Slurry shields rely on the formation of a compact filter cake to maintain excavation face stability and ensure construction safety. In strata with high permeability, significant slurry loss occurs, making filter cake formation and air tightness maintenance challenging. In this study, light organic walnut shell was selected as an additive coarse particle material for slurry. Slurries incorporating two types of coarse particles, sand and walnut shell, were prepared, and tests on slurry permeation and air tightness of the filter cake were conducted in three different strata. The results indicate that the addition of coarse particles effectively improves filter cake formation and air tightness in high-permeability strata. It is essential to use graded particles in highly permeable strata, with controlled maximum and minimum particle sizes. As the content of coarse particles increases, the air tightness of the filter cake initially increases and then decreases. Notably, the air tightness of filter cakes containing walnut shell is superior to those containing sand. Replacing sand with walnut shell as a slurry plugging material enhances filter cake quality in high-permeability strata. For highly permeable strata with a permeability coefficient greater than 1.0 × 10−3 m/s, an addition of 30 g/L to 40 g/L is recommended. [ABSTRACT FROM AUTHOR]

QCM or quartz crystal microbalance is a non static crystal that can be used as a mass sensor. As a piezoelectric crystal, a QCM generates an electrical signal with a specific frequency. The frequency change can be utilized as a frequency counter in a mass measurement system. This study aims to develop a coarse particle sensor system using a QCM and an oscillator circuit. In line with this, this study uses an oscillator circuit and a QCM for a sensor development. Thus, the frequency measurement of the QCM contains an oscillator and a signal conditioner connected to a microcontroller. For this purpose, an Arduino Nano was used as the signal processing, while a QCM was used as a coarse particle sensor and compared to a digital dust sensor (Winsen ZH03). The sensor system was evaluated using a fixed-type crystal connected to an oscillator: 2.5 MHz - 7.2 MHz. Arduino Nano processed the frequency signal generated by the developed oscillator. The results show that the sensor system has a stable output signal compared to the comparator. There is a linear correlation between the frequency measured by the system and the oscilloscope (99.73%). It can be concluded that the sensor system can measure coarse particle concentrations from 32-620 ug/cm3 (frequencies from 2 MHz to 7.2 MHz) with a response time of 1 second. The system has an accuracy of 99% and a resolution of 1 Hz.

The 3D reconstruction and quantitative characterization of drainage channels and coarse tailings particles in a bed were conducted in this study. The influence of variations in the azimuthal angle (θ) and polar angle (φ) of coarse particles on drainage channel structure was analyzed, and the drainage mechanism of the bed was studied. Results showed that water discharge in the bed reduced the size of pores and throat channels, increasing slurry concentration. The throat channel structure was a key component of the drainage process. The φ and θ of particles changed predominantly along the length direction. The changes in φ had a cumulative plugging effect on the drainage channel and increased the difficulty of water discharge. The rake and rod formed a shear ring in the tailings bed with shear, and the θ distribution of particles changed from disorderly to orderly during the rotation process. The drainage channel was squeezed during the shearing process with the change in θ, which broke the channel structure, encouraged water discharge in the bed, and facilitated a further increase in slurry concentration. The findings of this work are expected to offer theoretical guidance for preparing high-concentration underflow in the tailings thickening process. [ABSTRACT FROM AUTHOR]

In order to explore inter-particle contact mechanical properties of geotechnical coarse particles after wetting, the contact form between coarse particles is simplified into point-surface contact. The normal and tangential contact tests of coarse particles with different wetting degrees are carried out using modified rock biaxial rheometer. The mechanical properties of wetting contact between coarse particles are studied, and the empirical model of coarse particles wetting contact is deduced. Aiming at coarse-grained soil with different wetting degrees, the large-scale shear tests are carried out. Using the wetting contact model, the shear tests are simulated by distinct element method (DEM). The reliability of wetting contact model is verified by data comparison. The results show that the wetting level has significant influence on the failure pattern of point-surface contact between coarse particles. The normal and tangential contact stiffness of coarse particles in surface wetting state decreases slightly. But the contact stiffness in soaking state decreases significantly. The particle contact stiffness curves after wetting can be fitted into empirical model by power function. This model can be used for numerical simulation of large-scale shear tests with a calculation error not exceeding 5%. This research can provide reference for DEM numerical calculation of coarsegrained soil engineering. [ABSTRACT FROM AUTHOR]

Since the grinding and chemical reagents required for flotation are expensive, coarse particle flotation reduces grinding costs and makes the subsequent process more accessible and cheaper. Recent studies suggest that the flotation of coarse particles using microbubbles has some advantages. However, a thorough analysis of the effectiveness of various flotation parameters and the impact of their interactions on the recovery of coarse particles in the presence and absence of microbubbles has yet to be fully understood. In the current study, the two-level factorial and Box-Behnken experimental designs were performed to characterize, assess, and optimize the implications of seven numerical (sodium oleate, collector; calcium oxide, activator; MIBC, frother; impeller speed; froth depth; pulp concentration; fine particles) and one categorical (microbubbles) independent parameters on the coarse quartz particles. Characterization revealed that froth depth did not significantly affect the flotation recovery of coarse particles in the mechanical laboratory cell. The effects of the variables in the presence of microbubbles revealed that sodium oleate and impeller speed significantly impacted recovery, followed by calcium oxide and fine particles, both of which had a medium influence, and MIBC and pulp concentration, which had a minimal impact. The recovery of coarse particles increased by 92.714% when microbubbles were used, compared to the estimated maximum recovery under ideal conditions of 62.258% without them. From this, it can be concluded that a high coarse particle flotation recovery is possible by optimizing the hydrodynamic conditions and the chemical environment using microbubbles. [ABSTRACT FROM AUTHOR]

• NO 3 –, SO 4 2–, and WSON in coarse particles indicate heterogeneous conversion. • Excessive biomass burning led to an increase in coarse fractions of WSOC in PM 10. • Light absorption of aerosol extracts in water depends on aerosol size. • Coarse PM is a mixture of combustion particles and surface reactions with dust. To understand the differences in the composition and sources of PM 2.5 and PM 10 caused by coarse particles, integrated PM 2.5 and PM 10 samples were synchronously collected in Nanjing, East China, in summer 2020 and winter 2020/2021. Bulk and molecular speciation and light absorption measurements of aerosol extracts were performed, followed by positive matrix factorization (PMF) based on the PM 2.5 and PM 10 data sets, respectively. The difference in average concentrations of total bulk species between PM 2.5 and PM 10 was mainly caused by the distribution of considerable NO 3 –, SO 4 2–, Ca2+, and organic carbon (OC) in coarse particles. Coarse PM influenced by abrasion products from tire wear and leaves contributed about half of the low-volatility n- alkanes in summer. The contribution of coarse PM to biomass burning tracers and water-soluble OC increased in winter when biomass combustion was excessively active. More than 70% of sugar polyols were attributable to coarse PM in summer, and biomass burning could be an important source in winter. The light-absorbing organic chromophores were almost entirely associated with PM 2.5 , but water-soluble organic carbon (WSOC) exhibited stronger light absorption in PM 10 extracts than in PM 2.5 extracts possibly due to the influence of coarse PM on pH. PMF analysis indicated that biomass burning, aqueous-phase reactions, and processed dust were the main contributors of organic matter and its light absorption in winter. Biogenic primary and secondary sources made discernable contributions only in summer. The differences between PM 2.5 and PM 10 were likely attributed to mixing of crustal dust, combustion particles, and surface reactions. [Display omitted] [ABSTRACT FROM AUTHOR]

Coarse particles in Cu-0.39Cr-0.24Zr-0.12Ni-0.027Si alloy were studied with scanning electron microscopy and transmission electron microscopy. Three types of coarse particles were determined: a needle-like Cu5Zr intermetallic phase, a nearly spherical Cr9.1Si0.9 intermetallic phase and (Cu, Cr, Zr, Ni, Si)-rich lath complex particles. The crystallographic orientation relationships of the needle-like and nearly spherical coarse particles were also determined. The reasons for formation and the role of the coarse phases in Cu-Cr-Zr alloys are discussed, and some suggestions are proposed to control the coarse phases in the alloys. [ABSTRACT FROM AUTHOR]

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In this study, the revolution of individual plug constituent particles, the relation between plug length and pressure drop, and the relation between plug velocity and pressure drop were experimentally examined, for a single plug in a negative pressure system, using high-speed video cameras. The horizontal pipeline consists of an 8.8 m long, 30 mm i.d. transparent acrylic tube. The particles used are three kinds of uniform spherical ABS resin particles of 6.0 mm diameter and different densities, and the non-spherical polyethylene pellet of 3.27 mm spherical equivalent diameter. By observing the plug-constituent particles, it was found that more than 65% of spherical particles revolve and about 33–39% of them are forward revolving. Some plug-constituent particles revolve in reverse due to the frictional force between the particles. For non-spherical particles, more than half revolve, although the revolution axis frequently changes and most revolutions are intermittent. Furthermore, a plug begins to be conveyed spontaneously as soon as it is generated, and plug length increases up to a definite length depending on the pressure drop across the plug. [ABSTRACT FROM AUTHOR]

Physical enrichment technologies can be used worldwide in various coal washing plants to enrich up to 500 μm particle size. Conversely, coals smaller than this are discarded as waste, causing storage and environmental issues. In this regard, studies on coal below 500 μm in Turkey have recently acquired attraction. The Jameson flotation cell and flotation column, which have many uses worldwide but are not used throughout the plant in Turkey, were used to investigate the separation possibilities of coals below 500 μm. In the study, the flotation column and Jameson cell performances for three different particle sizes (-500+300, -300+212 and -212+106 μm) were compared. For the first time, both machines operated in a negative bias condition. In addition, the flotation kinetics of the machines were modelled with some critical operating parameters. Models illustrating the main and multiple effects of the parameters were developed using the data derived from the experimental results, and the models were statistically significant at the 95% confidence level. In the experiments performed with both flotation machines, the flotation rate increases with the decrease in particle size in general. According to the results, the velocity increase in the Jameson cell was 0.0050-0.0075 min-1 compared to the flotation column in the experiments performed in the size range of -500+300 μm, and the flotation rate constant increased approximately twice. In the size range of -212+106 μm, the difference became larger, and the flotation rate of the Jameson cell increased up to six times with a difference of 0.0450-0.0500 min-1. [ABSTRACT FROM AUTHOR]

With the development of coal mining, the use of elbows has diversified the forms of underground backfill pipelines, which has inevitably complicated the transportation characteristics of filling slurry in the pipeline, thus affecting the entire backfilling system. The objective of this study is to numerically investigate the running state of cemented paste backfilling (CPB) slurry and coarse particles at different velocities by transporting in bend pipes. To better understand the transportation state of CPB slurry in pipeline, a computational fluid dynamics (CFD) model—mixture model was developed to study the transportation of CPB slurry. The volume distribution of coarse particles in slurry under different pipe types and different flow rates, as well as the velocity profiles of slurry at different positions, were simulated and analyzed, and the pressure losses under different pipe types were compared. The results show that the distribution of coarse particles varies with the tube type, and the effect of coarse particles on the position of tube wall changes with the increase in velocity. The high-speed zone of CPB slurry will move toward the outer wall of the elbow with the increase in velocity. The pressure loss of CPB slurry in the vertical–horizontal pipeline is larger than that in the horizontal–vertical pipeline, and the difference is larger in the bend section. This study provides a theoretical and meaningful reference for CPB slurry backfilling operations in different bends. [ABSTRACT FROM AUTHOR]

Damage induced by coarse particle erosion is the main cause of premature failure of transport structures used in deep-sea mining. In this study, a free fall coarse particle stress-erosion (i.e., the erosion of a highly stresses target material) test method is proposed as an alternative to the traditional impinge jet test. The erosion behavior of stainless steel SS304 under different loads and impact angles was experimentally studied. The related mass loss was quantified, the microscopic wear morphology was observed and the erosion mechanism was revealed. This study indicates that the erosion damage caused by coarse gravels is much severer than that caused by fine sands, while the stress-acceleration effect (generally, the erosion damage will be enhanced when the target material is suffering from high tensile stress) of SS304 is relatively marginal. Finally, the validity of some widely used erosion equation was examined by the test data. [ABSTRACT FROM AUTHOR]

Exposure to airborne particulate matter (PM) is related to the increased risk of several diseases, including chronic and allergic rhinitis. We have previously shown that atmospheric endotoxin level was positively associated with the number of emergency department visits for asthma even after adjusting for meteorological factors, suggestive of the significant association between atmospheric endotoxin level and asthma exacerbation. Whether atmospheric endotoxin level is related to inflammatory response induction is, however, unclear. Here, we established stable cell lines to determine the promoter activity of the genes encoding pro-inflammatory cytokines such as tumor necrosis factor alpha, interleukin 6 (IL6), and IL33 by transfection of each reporter plasmid into rat tracheal epithelial EGV-4 T cells. These cells could measure the inflammatory response induced by endotoxin treatment more easily, rapidly, and sensitively than the conventional system using immunodetection assays. Furthermore, we revealed a relationship between atmospheric endotoxin level and inflammatory response induction. Thus, the system established herein may serve as a promising tool to monitor inflammatory response induced upon PM exposure.

Coarse particles in Cu-0.39Cr-0.24Zr-0.12Ni-0.027Si alloy were studied with scanning electron microscopy and transmission electron microscopy. Three types of coarse particles were determined: a needle-like Cu5Zr intermetallic phase, a nearly spherical Cr9.1Si0.9 intermetallic phase and (Cu, Cr, Zr, Ni, Si)-rich lath complex particles. The crystallographic orientation relationships of the needle-like and nearly spherical coarse particles were also determined. The reasons for formation and the role of the coarse phases in Cu-Cr-Zr alloys are discussed, and some suggestions are proposed to control the coarse phases in the alloys.

The hydrolysis of Ti(IV)-bearing acid solution to prepare titanic acid particles is a crucial step for the production of TiO 2 material. The hydrolysis which takes place in HCl medium was investigated particularly with the purpose of preparing coarse particles with narrow size distributions for applications such as Ti metal powder production. The key factors that affect the hydrolysis ratio and rate, the morphology, and the size of the titanic acid particles were investigated. The results illustrated that temperature, initial free acid and equivalent TiO 2 concentrations cross-influence the above-mentioned key attributes of the product particles. Near spherical rutile particles with a D50 of around 30 μm were obtained under the optimal parameters. Four stages, including incubation, acceleration, near steady-state reaction, and deceleration, were observed during the progress of the hydrolysis reaction, while the precipitate morphology evolved from irregular to smooth, and to round as a result of the nucleus agglomeration. [Display omitted] • Micron-sized and near spherical TiO 2 powder is prepared via hydrolysis. • Initial free acid and equivalent TiO 2 concentrations cross-influence the size and morphology. • A sigmoid shape of yield vs. time illustrates the progression of hydrolysis with four stages. [ABSTRACT FROM AUTHOR]

The slug characteristics of dense phase pneumatic conveying of coarse particles were numerically studied on the basis of experimental verification. A light medium mixed flow pneumatic conveying was introduced to improve the slug formation. The slug conveying process, the slug and particles motion during slug formation, and the slug shape characteristics were evaluated. Three points are worth highlighting: (1) Slugs are continuously updated and rolled forward accompanied by exchange of particles exchanging. (2) Slug velocity increases with the slug conveying process, and the gap between particle velocity and slug velocity gradually declines. (3) The rear angle shows obvious segregated distribution for formed slug and collapsed slug, with the mean values of 37.0°degree and 74.6°, respectively. [Display omitted] • Coarse particles slug flow pneumatic conveying process were simulated. • A light medium mixed flow pneumatic conveying for coarse particles was introduced. • Slugs continuously update and roll forward accompanying particles exchanging. • Rear angle could be used as an indicator to identify whether slug formation. [ABSTRACT FROM AUTHOR]

Background: From around 2012, the use of automated equipment for fine particulate matter (PM2.5) measurement with equivalence to a reference method has become popular nationwide in Japan. This enabled us to perform a national health effect assessment employing PM2.5 concentrations based on the standardized measurement method. We evaluated the association between non-accidental mortality and short-term exposure to PM2.5 and coarse particulate matter (PM), with the latter estimated as the difference between suspended particulate matter and PM2.5, for the fiscal years 2012–2014. Methods: This was a time-stratified case-crossover study in 100 highly-populated Japanese cities. Mortality data was obtained from the Ministry of Health, Labour and Welfare. City-specific estimates of PM-mortality association were calculated by applying a conditional logistic regression analysis, and combined with a random-effects meta-analysis. Results: The respective averages of daily mean concentration were 14.6 µg/m3 for PM2.5 and 6.4 µg/m3 for coarse PM. A 10 µg/m3 increase in PM2.5 concentrations for the average of the day of death and the previous day was associated with an increase of 1.3% (95% confidence interval (CI), 0.9–1.6%) in total non-accidental mortality. For cause-specific mortality, PM2.5 was positively associated with cardiovascular and respiratory mortality. After adjustment for PM2.5, we observed a 1.4% (95% CI, 0.2–2.6%) increase in total mortality with a 10 µg/m3 increase in coarse PM. Conclusion: The study revealed that short-term exposure to PM2.5 had adverse effects on total non-accidental, cardiovascular, and respiratory mortality in Japan. Coarse PM exposure also increased the risk of total mortality.

The objective of this study was to evaluate various physical and mechanical properties of experimental particleboard panels made from Asian giant bamboo (Dendrocalamus asper). Single layer panels having a density level of 0.75 g/cm3 from coarse and fine particles were used within the scope of this study. Thickness swelling, water absorption, surface roughness, and wettability characteristics of the samples were tested as physical properties while bending, internal bond strength, and screw withdrawal strength of the panels were considered for their mechanical properties. Resistance of the panels against termite and fungus were also determined. Based on the findings in the work both physical and mechanical properties of the panels made from coarse particles resulted in higher values than those made from fine particles with the exception of their internal bond strength. It appears that using fine particles in the panels enhanced their overall surface quality as well as wettability. Regarding biological deterioration of the samples, those made with coarse particles had better resistance. It seems that giant bamboo as a non-wood lignocellulosic species would have potential to be used as raw material to the manufacture value added particleboard with accepted characteristics. [ABSTRACT FROM AUTHOR]

Abstract Background The health effects of biological aerosols on the respiratory system are unclear. The purpose of this study was to clarify the association of airborne particle, protein, and endotoxin with emergency department visits for asthma in Kyoto City, Japan. Methods We collected data on emergency department visits at a hospital in Kyoto from September 2014 to May 2016. Fine (aerodynamic diameter ≤ 2.5 μm) and coarse (≥ 2.5 μm) particles were collected in Kyoto, and protein and endotoxin levels were analyzed. The association of the levels of particles, protein, endotoxin, and meteorological factors (temperature, relative humidity, wind speed, and air pressure) with emergency department visits for asthma was estimated. Results There were 1 to 15 emergency department visits for asthma per week, and the numbers of visits increased in the autumn and spring, namely many weeks in September, October, and April. Weekly concentration of protein in fine particles was markedly higher than that in coarse particles, and protein concentration in fine particles was high in spring months. Weekly endotoxin concentrations in fine and coarse particles were high in autumn months, including September 2014 and 2015. Even after adjusting for meteorological factors, the concentrations of coarse particles and endotoxin in both particles were significant factors on emergency department visits for asthma. Conclusions Our results suggest that atmospheric coarse particles and endotoxin are significantly associated with an increased risk of asthma exacerbation.

The low separation efficiency of traditional mechanical flotation cells for galena flotation primarily was caused by the low collision probability between bubbles and fine particles and high detachment probability of coarse particles. A flotation device named Aerated Jet Flotation Cell (AJFC) was adopted to improve the separation efficiency of galena flotation. Reducing bubble size and optimizing turbulence distribution were respectively confirmed as effective ways to improve fine galena-bubble collision efficiency and decrease detachment probability of coarse galena. In AJFC, micro-bubbles in diameter of 0.1-0.3 mm were generated by forcing compressed air to pass through porous high-density polyethylene tube, and high shear rate and appropriate turbulence were provided by installing a sparger with holes at the end of downcomer. The key parameters, including sparger hole number, turbulent kinetic energy (TKE), air-slurry ratio and superficial gas velocity (Jg) were optimized to achieve a desired separation performance of galena flotation. Separation efficiency of 62.54 % at a residence time of 2.25 min was achieved by AJFC, while separation efficiency of 59.12 % at a residence time of 7.5 min was achieved by mechanical flotation cell. Besides, AJFC had less loss of Pb in tailings than mechanical flotation cell in the whole particle size range, especially for fine (-25 µm) and coarse (+74 µm) size fractions. [ABSTRACT FROM AUTHOR]

This study investigates the influence of bubble size distribution and operational parameters on the flotation behavior of quartz coarse particles. The parameters evaluated during this study include the different bubble size distribution, air flow rate and impeller speed. Experiments were conducted at three different bubble sizes: 110, 171 and 293 nm as db(32). Then, the results were compared with common air bubbles of the conventional flotation process. The bubble size distribution was measured using a laser particle size analyzer (LPSA). Results showed that the recovery of − 4 2 5 + 1 0 6 μ m particles increased in presence of nano bubbles (NBs) up to 25% compared to the conventional flotation. The maximum recovery of 95.59% was obtained using NBs size of 171 nm at the impeller speed of 900 rpm and air flow rate of 30 l/h. It was also indicated that NBs caused an increasing in flotation recovery for all the samples in any size ranges in comparison with the conventional method. [ABSTRACT FROM AUTHOR]

PM10 and PM2.5 were collected at the Gosan Site on Jeju Island from 2013 to 2015, and their ionic and elemental species were analyzed to examine the variations in their chemical compositional characteristics related to different meteorological conditions. Concentrations of nss-SO42- and NH4+ were respectively 6.5 and 4.7 times higher in the fine particle mode (PM2.5) compared to the coarse particle mode (PM10-2.5), however NO3- concentrations were 2.4 times higher in the coarse mode compared to the fine particle mode. During Asian dust days, the concentrations of nss-Ca2+ and NO3- increased to 8.2 and 5.0 times higher in PM10, and 3.5 and 6.0 times higher in PM2.5, respectively. During haze days, the concentrations of secondary pollutants increased by 3.1-4.7 and 3.2-7.9 in PM10 and PM2.5, respectively, and they were, respectively, 1.2-2.1 and 0.9-2.1 times higher on mist days. The aerosols were acidified largely by sulfuric and nitric acids, and neutralized mainly by ammonia in the fine particle mode during the haze days, but neutralized by calcium carbonate in coarse particle mode during the Asian dust days. Clustered back trajectory analysis showed that concentrations of nss-SO42-, NO3-, and NH4+ were relatively high when air masses travelled from China.

The objective of this study was to evaluate various physical and mechanical properties of experimental particleboard panels made from Asian giant bamboo (Dendrocalamus asper). Single layer panels having a density level of 0.75 g/cm3 from coarse and fine particles were used within the scope of this study. Thickness swelling, water absorption, surface roughness, and wettability characteristics of the samples were tested as physical properties while bending, internal bond strength, and screw withdrawal strength of the panels were considered for their mechanical properties. Resistance of the panels against termite and fungus were also determined. Based on the findings in the work both physical and mechanical properties of the panels made from coarse particles resulted in higher values than those made from fine particles with the exception of their internal bond strength. It appears that using fine particles in the panels enhanced their overall surface quality as well as wettability. Regarding biological deterioration of the samples, those made with coarse particles had better resistance. It seems that giant bamboo as a non-wood lignocellulosic species would have potential to be used as raw material to the manufacture value added particleboard with accepted characteristics.

Velocity distribution of vertical pipes with large particle slurry plays an important role in pipeline transportation of minerals in hydraulic coal mining and ocean mining industry. The experiments of particle fluidization and particle vertical lift are conducted and the fluidization data of three kinds of large particles are analyzed. The results show that the vortex resistance prevents particles from moving as the coarse particles move in vertical pipes. An additional coefficient method is proposed to study the vortex resistance by increasing the coefficient of vortex resistance before interference. Mathematical model is established to describe the drag coefficient of the vortex by analyzing the influence factors of the experimental data and the drag coefficient of the vortex. In addition, calculation model of the velocity distribution of large particles in vertical pipe is proposed by analyzing the force, the fluid, and the solid momentum. Moreover, the experimental data of particle transport in vertical pipes are utilized to verify and analyze the proposed model. [ABSTRACT FROM AUTHOR]

Jameson cell is a flotation device that has unique characteristics for fine grained particles, and thus, it has more than three hundred applications in worldwide. On the contrary, the flotation performance of the cell decreases by coarser feeding, which limits the application of the Jameson cell. It has been figured out that the main reason for the performance decrease for coarse particle is turbulence which occurs at the outlet of the downcomer in the Jameson cell. Therefore, the aim of this study was to prevent the performance decrease in the Jameson cell by modifying the downcomer which was implemented by taking into account the fluid mechanics law and mathematical modelling. The modified downcomer, which can be called as diffuser, can provide better aggregate stability and less turbulence at the end of the downcomer. Thus, theoretically the better performance was obtained by the use of the new form of downcomer. In addition, a series of experiments were carried out to verify the success of the modified downcomer. According to the results, velocity gradient (G) decreased to 640 s−1 from 671 s−1 by using the modified downcomer, and the maximum floatable particle size increased to 255 µm from 225 µm. [ABSTRACT FROM AUTHOR]

To protect the population from respiratory diseases and to prevent the damages due to air pollution, the main cause of air pollution should be identified. This research assessed the relationship between the airborne particulate concentrations (PM10) and the urban expansion in Daegu City in South Korea from 2007 to 2017 using multi-temporal spatial datasets (Landsat images, measured PM10 data) and the machine learning technique in the following steps. First, the expanded urban areas were detected from the multiple Landsat images using support vector machine (SVM), a widely used machine learning technique. Next, the annual PM10 concentrations were calculated using the long-term measured PM10 data. Finally, the degrees of increase of the expanded urban areas and of the PM10 concentrations in Daegu from 2007 to 2017 were calculated by counting the pixels representing the expanded urban areas and computing variation of the annual PM10 concentrations, respectively. The experiment results showed that there is a minimal or even no relationship at all between the urban expansion and the PM10 concentrations because the urban areas expanded by 55.27 km2 but the annual PM10 concentrations decreased by 17.37 μg/m³ in Daegu from 2007 to 2017. [ABSTRACT FROM AUTHOR]

This study measured both PM10 and surface dust concentrations at roadside in the Central Business District of Baguio City. A total of 66 PM10 filters and 25 surface dust samples were analyzed for 14 metals (Na, Mg, Al, Ca, Cr, Mn, Co, Ni, Cu, Zn, As, Sr, Cd and Pb) using inductively coupled plasma mass spectrometer ICP-MS to characterize sources of airborne particulate matter (APM). Calculation of enrichment factors indicated elements Zn, Cd, Pb and As to be enriched in both PM10 and surface dust samples. The compositional signature of local surface dust was found to be strongly correlated with that of PM10 particles. Enrichment Factor, Conditional Probability Function (CPF), Correlation Analysis and Principal component analysis were applied to determine sources affecting the Baguio CBD area, and results indicate three APM contributing sources (1) soil sources and (2) soil-road dust resuspension and vehicular emissions (3) vehicular emissions. The NE and SW wind sectors were dominant for most of the identified sources. [ABSTRACT FROM AUTHOR]

• The matching mechanism for bubble and particle sizes in fluidized-bed flotation was investigated. • Stable bubble and particle adhesion did not necessarily result in particle separation. • Only the stable bubble adhesion that effectively decreased particle density led to the separation. • Fluidized-bed flotation was a consequence of matched bubble and particle size affected by mineral exposure pattern. Fluidized-bed flotation is a novel process with combined features of flotation and density separation. The application of fluidized-bed flotation in grinding circuit to reject coarse gangues for sulfide ores has been increasingly attracting attentions. Previous studies have focused on the effect of mineral liberation on coarse particle separation. Little work has yet been conducted to simultaneously investigate the effect of mineral liberation, particle and bubble sizes on the fluidized-bed flotation efficiency. The lack of this work has hindered the process optimization to some extent. In this study, three sizes of bubbles (498 μm, 1200 μm, 1952 μm) were generated to separate molybdenite ores under three particle size fractions (150–450 μm, 450–700 μm and 700–1000 μm) in a fluidized-bed flotation column (80 mm in diameter). For the 150–450 μm and 450–700 μm particles, small bubbles of 498 μm could achieve separation by effectively reducing the particle density. For the 700–1000 μm particles with greater mass, intermediate bubble of 1200 μm was required to reduce the particle density for separation. No separation was observed for the three particle size classes with the oversized bubbles of 1952 μm due to high bubble detachment probability. It was concluded that fluidized-bed flotation is a consequence of matched bubble and particle sizes affected by the exposure rate of hydrophobic mineral and its distributing discreteness, the underlying mechanism for which was discussed. It is believed that the outcomes of this work could facilitate the optimization of fluidized-bed flotation in coarse gangue rejecting for sulfide ores. [ABSTRACT FROM AUTHOR]

Former studies show that the coarse particle plays a very important role in the determination of the yield stress of fluid-solid mixtures such as debris flows. The characteristics of the coarse particle in these mixtures include particle size, gradation, shape, and type of material. To assess the influence of these coarse particles on the yield stress the concept of equivalent volumetric solid concentration C is introduced. The equivalent concentration can be derived from the volumetric solid concentration by considering the particle size, gradation, shape, and type of material. Laboratory experiments to determine the yield stress of various mixtures were conducted to calibrate the coefficients of these coarse particle characteristics. A yield stress phenomenological expression is proposed using the refined volumetric solid concentration (equivalent concentration), which could be calibrated by the experiments in this study. The validation of this phenomenological expression with data from literature shows good agreements, especially for higher volumetric concentrations of the sediments.

The short-term mortality effects of ambient fine particulate matter air pollution have been widely investigated in China. However, the associations between day-to-day variation in ambient coarse particles pollution (PM c ) and mortality, as well as the corresponding mortality burden, remain understudied. We estimated the short-term PM c -mortality association in three Chinese cities of the Pearl River Delta (PRD) region during the period of 2013–16. The city-specific association was first estimated using generalized additive models and then combined to obtain the overall effect estimates. We further estimated PM c related attributable fraction and attributable mortality. Our study found a significant association between PM c and mortality. Each 10 μg/m 3 increase of a current day's PM c was associated with a 1.37% (95% CI: 0.55%, 2.22%) increase in total mortality, a 1.63% increase (95% CI: 0.31%, 2.98%) in cardiovascular mortality, and a 0.97% increase (95% CI: −0.17%, 2.13%) in respiratory mortality in the three cities. We estimated that 0.37% (95% CI: 0.14%, 0.61%) and 2.72% (95% CI: 1.03%, 4.50%) of total mortalities were attributable to PM c by using China's standards and WHO's air quality guidelines as references—corresponding to 1394 (95% CI: 528, 2291) and 10,305 (95% CI: 3884, 17,000) attributable premature mortalities in the three cities, respectively. This study suggests that ambient coarse particulate pollution might be one important risk factor of total, cardiovascular, and respiratory mortality, as well as account for substantial mortality burdens in the three Chinese cities of the PRD. [ABSTRACT FROM AUTHOR]

In this paper, the effect of powder processing conditions on the fracture strength of advanced ceramics is discussed. Manufacturing processes of silicon nitride ceramics and alumina ceramics are utilized to explain the relationship between powder processing conditions and major fracture origin in the ceramics. The preparation conditions of powder slurry are found affecting the structure and strength of powder granules, which can influence the properties of green compact and thus the quality of sintered ceramics. These phenomena can be investigated by using new characterization tools such as the liquid immersion method and the observation technique using thinned ceramics specimen under the transmission mode. Also, very small amount of coarse particles contained in the powder slurry is found starting the fracture in ceramics by using wet sieve analysis and the observation technique with thinned ceramic specimen. As a result, it is found that the major ceramics fracture is originated from the large pores and coarse particles in powder granules, green compact and sintered ceramics. They can be unintentionally introduced in the manufacturing steps of ceramics, such as powder slurry preparation, spray drying, and forming process of green compact. By making use of these characterization tools, effective processing conditions to eliminate the large pores and coarse particles can be identified for producing high quality advanced ceramics.

To protect the population from respiratory diseases and to prevent the damages due to air pollution, the main cause of air pollution should be identified. This research assessed the relationship between the airborne particulate concentrations (PM10) and the urban expansion in Daegu City in South Korea from 2007 to 2017 using multi-temporal spatial datasets (Landsat images, measured PM10 data) and the machine learning technique in the following steps. First, the expanded urban areas were detected from the multiple Landsat images using support vector machine (SVM), a widely used machine learning technique. Next, the annual PM10 concentrations were calculated using the long-term measured PM10 data. Finally, the degrees of increase of the expanded urban areas and of the PM10 concentrations in Daegu from 2007 to 2017 were calculated by counting the pixels representing the expanded urban areas and computing variation of the annual PM10 concentrations, respectively. The experiment results showed that there is a minimal or even no relationship at all between the urban expansion and the PM10 concentrations because the urban areas expanded by 55.27 km2 but the annual PM10 concentrations decreased by 17.37 μg/m³ in Daegu from 2007 to 2017.

PM10 and PM2.5 were collected at the Gosan Site on Jeju Island from 2013 to 2015, and their ionic and elemental species were analyzed to examine the variations in their chemical compositional characteristics related to different meteorological conditions. Concentrations of nss-SO4 2- and NH4 + were respectively 6.5 and 4.7 times higher in the fine particle mode (PM2.5) compared to the coarse particle mode (PM10-2.5), however NO3 - concentrations were 2.4 times higher in the coarse mode compared to the fine particle mode. During Asian dust days, the concentrations of nss-Ca2+ and NO3 - increased to 8.2 and 5.0 times higher in PM10, and 3.5 and 6.0 times higher in PM2.5, respectively. During haze days, the concentrations of secondary pollutants increased by 3.1-4.7 and 3.2-2.1 and 0.9-2.1 times higher on mist days. The aerosols were acidified largely by sulfuric and nitric acids, and neutralized mainly by ammonia in the fine particle mode during the haze days, but neutralized by calcium carbonate in coarse particle mode during the Asian dust days. Clustered back trajectory analysis showed that concentrations of nss-SO2.5, respectively, and they were, respectively, 1.2-2.1 and 0.9-2.1 times higher on mist days. The aerosols were acidified largely by sulfuric and nitric acids, and neutralized mainly by ammonia in the fine particle mode during the haze days, but neutralized by calcium carbonate in coarse particle mode during the Asian dust days. Clustered back trajectory analysis showed that concentrations of nss-SO42-, NO3 -, and NH4 + were relatively high when air masses travelled from China. [ABSTRACT FROM AUTHOR]