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The dust generated during tunnel construction poses serious health risks to workers, as it not only causes respiratory obstruction but also leads to pneumoconiosis and respiratory failure after prolonged exposure. However, most existing studies focus on specific construction stages or particular particle sizes and often assume an ideal airflow, neglecting the complex flow fields, vortex effects, and dust composition variations at different stages in tunnel and mine construction. This study systematically analyzes the spatiotemporal distribution characteristics of dust at various stages of tunnel construction and proposes targeted prevention and control strategies. On the basis of measured data from three construction stages—the working face, initial support, and secondary lining stages—and SPSS 27 statistical analysis, a dynamic analysis was conducted on the concentration and distribution patterns of total suspended particulates (TSPs) and particulate matter of different sizes (PM10, PM4, PM2.5, and PM1). The results show that coarse particles dominate during the working face stage, whereas fine particles gradually accumulate during the initial support and secondary lining stages. Finally, this work establishes a dust concentration–excavation time/tunnel depth equation and proposes targeted dust control measures. These findings offer important practical value for enhancing construction safety and air quality. [ABSTRACT FROM AUTHOR]

The large size shearer drum in the large mining height working face generates more obvious turbulent wind in cutting the coal body, which causes the local wind speed of the working face to change, and the horizontal diffusion of dust particles to the sidewalk area. In order to clarify the influence mechanism of cutting turbulent wind on the dust mass concentration distribution along the working face with large mining height, a coupled mathematical model of airflow and dust was constructed by numerical simulation method for 85219 working face, and the airflow distribution, dust migration and dust mass concentration distribution at the height of the breathing zone were studied. The results show that, compared with the flow field under system ventilation only, the partial velocity of negative drift increases significantly at the front and back of the drum and at the moving frame, and a “wind drift zone” with negative drift wind velocity value of -1.06 m/s is generated near the drum. Under the disturbance of cutting turbulent wind, dust masses with a mass concentration of more than 151.85 mg /m3 at the front and back rollers have transverse dispersion to the sidewalk area. In the state of downwind coal cutting, the ability of cutting turbulent wind at the front rollers to induce transverse dispersion of cutting coal dust is higher than that at the back rollers. The dust mass concentration in the breathing zone of the sidewalk near the front roller was increased by 64.77% compared with the condition of system ventilation only. The comparison between the simulated data and the field-measured data shows that the relative error is less than 12.57%, and the simulated data is relatively accurate. Based on this, a dust-bearing air flow dust control device shearer is proposed, which is applied in the field and its dust control effect is tested. The dust removal efficiency in the working area of the working face is more than 78.31%, and the total dust removal efficiency is more than 89.93%.

The dust generated during tunnel construction poses serious health risks to workers, as it not only causes respiratory obstruction but also leads to pneumoconiosis and respiratory failure after prolonged exposure. However, most existing studies focus on specific construction stages or particular particle sizes and often assume an ideal airflow, neglecting the complex flow fields, vortex effects, and dust composition variations at different stages in tunnel and mine construction. This study systematically analyzes the spatiotemporal distribution characteristics of dust at various stages of tunnel construction and proposes targeted prevention and control strategies. On the basis of measured data from three construction stages—the working face, initial support, and secondary lining stages—and SPSS 27 statistical analysis, a dynamic analysis was conducted on the concentration and distribution patterns of total suspended particulates (TSPs) and particulate matter of different sizes (PM10, PM4, PM2.5, and PM1). The results show that coarse particles dominate during the working face stage, whereas fine particles gradually accumulate during the initial support and secondary lining stages. Finally, this work establishes a dust concentration–excavation time/tunnel depth equation and proposes targeted dust control measures. These findings offer important practical value for enhancing construction safety and air quality.

In order to obtain the dust distribution law in the fully mechanized coal face, the distribution of shearer cutting dust and the dust along the working face was studied by numerical simulation and field measurement respectively. The results show that when the shearer cuts coal downwind, along the direction of the air flow from the rear drum to the front drum area, the dust concentration keeps rising, and the diffusion caused by the air flow has an obvious effect on the increase of dust concentration. When the shearer cuts coal upwind, the dust concentration along the road shows an increasing trend, and the dust concentration in the dust source area changes rapidly. The dust produced by the drum plays a leading role in the dust pollution of the working face. The change trend of dust concentration in the groove of scraper conveying machine is basically the same as that in the support walkway, but the latter lags behind relatively, and the dust concentration is relatively low. Therefore, when taking measures to prevent dust, downwind coal cutting should focus on the influence of air flow, while upwind coal cutting is mainly aimed at the dust production of the drum itself, but under any conditions, cutting dust production is the main source of dust on the working face.

The special linear shape of spiral tunnel changes the air flow structure during tunnel construction and changes the diffuse and distribution of blasting dust. Mastering the blasting dust distribution and diffuse mechanisms can provide theoretical basis for ventilation layout and dust removal measures during spiral tunnel construction. To study the influence of spiral shape on dust diffusion and concentration distribution after tunnel blasting, a similar scale model of 1:20 and full-scale numerical model of spiral tunnel during construction were established. The similarity criterion and the similarity ratio of each physical quantity are derived from the dust motion equation. The dust distribution and diffuse characteristics in the spiral tunnel under different dust release quantity and release velocity were studied by model experiment. The dust distribution and diffuse characteristics in spiral tunnel with different curvature radius were studied by numerical simulation. The dust distribution model is refined based on the research results. The dust distribution model divides the tunnel into heavily polluted area and slightly polluted area, and the influence characteristics of the curvature radius on the dust export area are found. The layout of ventilation systems can be optimized according to the volume of heavily polluted areas. The heavily polluted area should be as small as possible; the dust in the heavily polluted area should be discharged to the slightly polluted area in an orderly manner to avoid the accumulation of dust. Dust removal measures can also be arranged according to the dust export location to improve dust removal efficiency. [ABSTRACT FROM AUTHOR]

Dust comprises particles usually present in the atmosphere. The deposition of dust on the surface of the solar panel seriously affects the light transmittance, resulting in lower pow-er generation efficiency and shortening the service life of the solar panel. Therefore, it is important to understand the dust distribution on the surface of solar panels and discuss the influence of dust on the power generation efficiency of solar panels for the efficient prevention of dust deposition on the panel. In this study, to analyze the dust distribution on the surface of the solar panel, the discrete element method was used to establish the contact mechanics model between dust particles and the solar panel. The number of dust particles on the surface of solar panels was calculated at different solar panel inclination angles, wind speeds, and wind directions. The wind speed of 1 and 3 m/s did not affect the dust deposition significantly but the speed over 5 m/s reduced the dust particles from the surface of the solar panel. The inclination angle of 23° influenced dust deposition on the surface of the solar panel. Wind direction did not show a significant effect on dust deposition. The longer the deposition time, the more particles remained on the surface due to the increased force between the particles and the surface of the solar panel. The results from calculation and measurement from transmittance were similar with a different rate of 3.41%. Thus, the result of the proposed calculation in this study provides a basis for de-signing the solar power generation plant and decision-making on the maintenance of the solar panel. [ABSTRACT FROM AUTHOR]

Turbulence generated by rotation of shearer has a great impact on the distribution of dust. The MRF method of multiple reference frame was employed to simulate airflow and dust distribution during mining process. The distribution of cutting dust under different airflow velocities, cutting speeds, and cutting direction (against or follow the direction of airflow) were compared and analyzed. Results show that the generated cutting dust using MRF method tends to move horizontally and vertically. As the speed of airflow increases, vertical characteristics diminish. Simultaneously, horizontal dissipation rises with the deviation of airflow speed. The increase of rotational speed augments the distance covered by cutting airflow, including vertical offset and windward motion. Moreover, the elevated drum speed amplifies airflow speed in the sidewalk and the primary influence range is approximately 80 m. When cutting in the downwind direction, the airflow exhibits a pronounced vertical and horizontal offset behind the drum. Conversely, when cutting in the upwind direction, these characteristics are less evident, resulting in a more uniform spatial distribution of cutting dust in the downwind direction. The majority of dust generated when cutting against the airflow tends to move in the low-altitude area, contributing to a more disordered pattern. [Display omitted] • A more refined model of the shearer drum has been established. • A numerical simulation study was conducted on the fully mechanized mining face under drum rotation using the MRF method. • Analyzed the airflow motion state under different ventilation speeds and cutting speeds. • Explored the movement law of airflow dust under coal cutting with forward and backward wind. [ABSTRACT FROM AUTHOR]

In this paper, we present solution of Einstein field equations which admit dust distribution and negative energy massless scalar field as a source with cosmological term (Λ) in the frame work of Bianchi type II space-time. The models satisfy conservation equation and creation field increases with time satisfying the result as investigated by Hoyle and Narlikar [A new theory of gravitation, Proc. Roy. Soc. A 282 (1964) 191]. The deceleration parameter (q) for the model (22) shows a transition from decelerating to accelerating regime with creation. A comparison with other cosmological models shows a transition from decelerating to accelerating regime with and without creation is mentioned. The present model is free from singularity, particle horizon and provides a natural explanation for inflationary scenario and isotropization. These features make the creation field cosmological models theoretically superior to the Big Bang models. Creation field and Einstein field equation are derived using principle of least action and the Lagrangian formulation of variable cosmological term is derived as mentioned by Moffat [Lagrangian formulation of a solution to the cosmological constant problem (1996), arXiv:astro-ph/9608202v1]. The current creation rate with other physical consequences is also discussed. For illustrative purposes, evolutionary behaviors of some cosmological parameters are shown graphically. In the figures, the cosmic time t is given in gravitational units assuming the velocity of light c = 1. This t = c T and T = t c . Therefore, by multiplying cosmic time t by (light years)−1, we obtain the coordinate time in years. [ABSTRACT FROM AUTHOR]

• Dust effects of space/time factors on trough solar system are studied in alpine areas. • Dust distribution characteristics are described by multiple variables. • Experimental platform was built to test optical and thermal performance concurrently. • The relative reflectivity fell by 20.58% for dust density 0–2.46 g/m2. • Collecting/exergy efficiency fell by 48.30%/55.08% for dust density 0–2.46 g/m2. Based on the dust accumulation and distribution characteristics of concentrator surfaces in alpine regions, a comparative experimental platform for measuring the energy flux density of the focal plane and thermal performance was developed in this study. By combining theory and experimentation, the influence of time (dust deposition density) and space (concentrator tilt angle) on the dust distribution characteristics and photothermal performance of a trough solar system was studied. The optical loss caused by concentrator dust was evaluated based on the intercept factor, while the thermodynamic loss caused by dust was evaluated based on the collecting efficiency and exergy efficiency. The results demonstrate that concentrator dust at a tilt angle of 60° will lead to a maximum center shift of 1.66 mm of the focal plane. Importantly, the inconsistency between thermal performance and dust deposition density indicates that the dust distribution characteristics caused by tilt angle have a significant influence on the thermal performance of the system. Comparatively, an increase in dust deposition density from 0 to 2.46 g/m2 leads to a 20.58% relative reflectivity loss, together with 48.30% and 55.08% reductions in the collecting efficiency and exergy efficiency, respectively. This study revealed the influence of space–time factors on dust distribution characteristics and photothermal performance, which can provide design ideas regarding dust removal for the application of trough solar systems in alpine areas. [ABSTRACT FROM AUTHOR]

To obtain the adaptability range of the single-filter cartridge dust collector, a numerical analysis of the key component (filter cartridge) that affects the filter performance of the dust collector is carried out. The study found that the filtration air velocity gradually decreases from the top A to the bottom C of the filter cartridge surface. During the filtration process, along the surface of the filter cartridge from C to A, the pressure first drops and then rises. At C, the negative pressure is the largest, with an average of about 525 Pa. The ineffective filtration area of section A of the upper part of the filter cartridge accounts for 2/5 of the filtration area, and the concentration of the first layer of dust is y = (0.01 ± a) + 0.02 × (0.08 ± b)x exponentially decreasing. The critical particle size range that the filter cartridge can filter dust is M≥1.87 μm, and the best dust removal range of the dust collector is N≥4.625 μm. An agreement between experiment and simulating results proves the validity of simulation model and reliability of the experimental data. Enterprises can choose a reasonable dust removal method based on the research results to optimize the adaptability of the working environment and the dust collector. It also provides a theoretical basis for researchers to solve the problems in the filtration and cleaning process. [ABSTRACT FROM AUTHOR]

Residents in arid regions of northwest China, where dust storms are more common, are continually exposed to air pollution particularly fine particles of PM2.5 and PM10, causing health hazards to residents. Urban greening species have a strong dust retention capacity which is also available in arid conditions and should be chosen to reduce the impact of air pollution on people and the urban environment. In this paper, three common tree species in four different functional areas: Transportation area (TA), Residential area (RA), Industrial area (IA), and Clean area (CA) of Aksu City were selected to measure their foliar dust to select the matching trees for appropriate sites. The dust particle size distribution for PM2.5 and PM10 was analyzed to explore the particle size difference between foliar dust and natural landing dust. The largest particle size was recorded in IA (168.56 µm), while the smallest was found in CA (43.25 µm). Furthermore, Salix babylonica (S. babylonica) absorbed the highest PM2.5 and PM10, 0.15% and 1.39% respectively; while Ulmus densa (U. densa) absorbed the least PM2.5 and PM10, 0.08% and 0.37%. Platanus acerifolia (P. acerifolia) foliar dust particle density was the highest, and has stable dust retention capacity, while, S. babylonica foliar dust particulate density is the lowest under the same conditions (height/location, pollution exposition, weather). Our findings concluded that the average values of dust diameters in the four areas differed significantly. It is concluded that P. acerifolia is the best performer in removing dust in different functional urban areas and S. babylonica was more suitable for CA because of having the capacity to remove fine particle matter. [ABSTRACT FROM AUTHOR]

In the present work, the dust pollutants from a fully mechanized mining face under different situation were investigated for a typical coal roadway. The Euler-Lagrange model was adopted for dust movement process. After the validation, the varieties of the air curtain, the spatial and temporal distribution of dust pollutants under various conditions were analyzed. The present study revealed that the air curtain jet flow develops with time and space and significantly influences the surrounding flow field. The dust concentration was controlled for the front part of the roadway. The higher initial supply air velocities (<15 m/s) and the smaller inclined angle (< 30°) of the air curtain can really cut down the mere concentration of PM2.5 at the sit of the driver. The relative fitting functions are provided to determine the initial velocity and angle of the air curtain properly, which can provide a cleaner working environment around the driver. [Display omitted] • Dust distribution was investigated systematically with the air curtain. • The development and variation of the air curtain was presented. • The air curtain can be determined according to the present regularities. • The gained results provide predictions for PM2.5 around the driver. [ABSTRACT FROM AUTHOR]

In order to obtain the dust distribution of PM5 and PM10 in large mining height fully-mechanized face, the dust concentration around the shearer drum and along the downwind side of the shearer are measured under the conditions of the following wind and upwind respectively. The results show that when coal is cut in following wind, the initial concentration of PM5 and PM10 dust around the rear drum is high, then gradually decreases and becomes stable. The concentration of the front drum is low at first, and rises sharply after 70 to 80 s. When coal is cut in upwind, the initial concentration of the front drum fluctuates greatly, and the concentration of the rear drum rises about 10 s earlier than that in following wind. When coal is cut in following wind, the PM5, PM10 and total coal dust concentration reach the highest at the downwind of shearer around 10 m, then gradually reduce and tend to be stable at 40 m. The PM5 proportion is higher at first, and falls to the lowest at about 15 m, then rises again under the effect of wind. The PM10 proportion is on the decline overall. When coal is cut in upwind, the dust concentration reaches the highest at the downwind of shearer 6 m or so, and is stable about 20 m. PM5 accounts for 60% to 80%, while PM10 accounts for 65% to 95% under both conditions.

The turbulent airflow generated by the shearer's rotation has a significant impact on the spread of cutting dust. In this study, the actual shearer drum was used as a physical model, and the MRF method was applied to simulate coal cutting operations with consideration of rotating fluid, accurately reproducing the turbulent airflow generated during cutting. By comparing the different simulation results, it is found that: the wind flow under systematic ventilation is gentle and even, while the cut-off wind flow generated by "inlet" has a great impact on the coal mining area in terms of scope and degree, and the horizontal and vertical dispersion is very strong, with a large amount of wind flow shifting in the range of 17 m < x < 36 m, and the dust mass concentration increasing rapidly; When the MRF method is adopted, the wind flow disperses more gently, and the dust is shifted to the pavement within the ranges of 19 m < x < 25 m and 27 m < x < 36 m, which makes the dust distribution more uniform and continuous in space, and forms a dust belt with high concentration of about 10 m in length on the downwind side of the front drum, which is more in line with the production reality. • First application of MRF method in fully mechanized mining face. • Studied the dynamic drum cutting law of fully mechanized mining face. • Constructed a 1:1 drum model according to the actual production. • Obtained the motion characteristics of dust under dynamic simulation. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyze the dust load in St. Petersburg based on the measurements of dust levels in different areas of the city using a CEM DT-9880 portable dust particle counter. A uniform one-character bottom up zoning was performed to determine the parameters, and the dependencies of dust distribution on various factors were identified using the "Ecolog" software package. The zoning was based on more than 2.5 thousand measurements of dust levels. An effective and rational solution to the problem of increased aerotechnogenic load in different areas of the city through the use of modern te chnologies of hydro-dedusting of city roads with a dust-binding solution based on surfactants was proposed for increasing the adhesion ability of the solution to the standard roadbed. [ABSTRACT FROM AUTHOR]

To study the distribution pattern of drug dust in the antibiotic raw material drug powder screening workshop and improve the working environment, we used COMSOL Multiphysics 6.0 software to simulate and study the airflow distribution and dust transport law in the powder screening workshop. The results indicated that the dust in the powder screening workshop diffused rapidly with the airflow and reached a stable state at the 100th second. After the dust migrated to a stable state, the area with excessive dust concentration (dust concentration>6 mg/m(3)) widely distributed, mainly distributed in the middle and lower parts of the wall opposite the air inlet from the rotary vibrating screen. The distribution of dust showed a characteristic of local aggregation, and dust transport was related to airflow movement, which was prone to aggregation in areas with low airflow velocity and eddy currents. On the plane of the human respiratory belt height (h=1.5 m), the concentration near the dust producing surface was high, with local concentrations exceeding 32 mg/m(3). It was the key area for dust prevention and control. And the working environment can be improved by changing the air flow distribution in the workshop or other dust reduction methods.

Dust pollution is one of the most serious problems in underground coal mines. To effectively control dust, it is necessary to investigate the dust distribution in the coal roadways. In this study, the dust distribution under the isolation effect of an air curtain was investigated in a coal roadway. First, the coal roadway was presented with a vault, a hybrid ventilation system, and an air curtain system installed on the digging machine. Second, the dust movement was simulated via the Euler-Lagrange method. Meanwhile, dust was treated as a discrete phase under a Lagrangian frame, and the air flow was modelled as the continuous phase. Then the spatiotemporal distribution of dust in the coal roadway was studied with and without the air curtain system. The results show that the spatiotemporal concentration of dust clearly reduces after the air curtain when compared with that of the system without the air curtain and the conventional hybrid ventilation system (FSNE), particularly for the working area. The isolation action of the air curtain is obvious for total dust. It is also found that the air curtain system can obviously reduce the dust concentration on the side of the operator, and provide a cleaner environment for the miners. Moreover, selected results show agreement with the relevant experimental and simulation ones. The air curtain is useful for resolving the problem of dust-isolation in the coal roadway, and can be used to improve the working environment in underground coal mines. It also has a practical background with several extensive applications. [ABSTRACT FROM AUTHOR]

At present, the fact that the airflow of the air duct outlet in fully mechanized heading face cannot be adjusted and cannot meet the practical requirement of ventilation dust suppression may lead to the steep rise of safety hazard and pollution risk. While by adjusting the angle, caliber, and the distance from the air duct outlet to the heading face, the dust distribution can be optimized and the dust suppression efficiency can be effectively improved. The acquisition method of regulation rules under different sizes of the roadways, the angles, calibers, and distance from the air duct outlet to the heading face is investigated by using the rough set theory, finite element flow field numerical simulation and underground test verification. Then, the decision information system, the discernibility matrix algorithm for attribute reduction and the heuristic value reduction algorithm for rule acquisition are established, and the regulation rules of the outlet parameters are obtained and expressed. The dust concentration analysis after adjusting shows that the area of the dust concentration is significantly reduced and the dust reduction rate at drivers can be increased by 48% compared with the original field, which provides theoretical basis for the optimal dust distribution and dust sup pression. [ABSTRACT FROM AUTHOR]

[Display omitted] • A highway tunnel model more suitable for practical engineering. • Space-time evolution law of dust and inhalable particles. • Consider the effect of air velocity of duct. • Use VB program for data statistics. • Predict the time it takes for dust to escape from the tunnel exit. Dust problem is serious in a highway tunnel during the full-face excavation, particularly after blasting of tunnel face. In order to solve the problem of dust pollution after blasting effectively, this study investigated the space–time evolution law of dust and inhalable particles within 100 s after blasting under blowing ventilation. First, the Euler-Lagrange method is used to simulate the coupled motion of air and dust. Then, the influences of air velocity on the distribution of dust and inhalable particles are considered, and the simulation results are verified by field measured data. The present study indicated that the heavier particles in the dust produced by blasting of tunnel face are deposited at the bottom of wind-return side in front of duct. The inhalable particles which particle size less than or equal to 10 μm are more uniformly dispersed in the whole tunnel space, and the higher the air velocity, the shorter the time required for the process. In addition, by analyzing and fitting the particle moving distance along the length of tunnel, the approximate time required for dust to migrate to a certain location can be predicted. The prediction of space–time evolution law of dust and inhalable particles in this study can provide some guidance for practical engineering cleaner production. [ABSTRACT FROM AUTHOR]

Dust contamination to ventilation systems is a common issue for mine operators during underground coal mining. In the present study, dust dispersion driven by a hybrid ventilation system in an underground mine has been investigated via a computational fluid dynamics (CFD) model. Specifically, the numerical model was developed based on the Euler-Lagrange method where the trajectory of dispersed dusts was solved individually. Dust dispersion induced by turbulence was considered by a stochastic tracking model. Effects of key parameters (e.g., gas velocity and exhaust duct length) on dust dispersion characteristics throughout the coal roadway have been examined. The results showed that the distribution of dusts exhibited extreme non-uniformity with a significantly higher concentration present near the mining face, particularly on the exhaust side. The cross-sectional average dust concentration substantially decreased along the axial direction in the front part of the coal roadway. Intense circumfluence and secondary sedimentation of dusts were found to be the main mechanisms that drove the non-uniform distribution of dusts. The model is shown to be capable of reproducing the dust dispersion process captured in the experiments and the prediction results agree well with the experimental data. [ABSTRACT FROM AUTHOR]

The coal roadway heading using a blasting method is very common in China. However, the coal dust produced by blasting is the most serious problem in a roadway of coal mine. The gas–solid two-phase flow regularity for blasting heading face is the key scientific issue for dust control. In this paper, a real blasting heading face in China was taken as the physical model and a method coupling a direct simulation Monte Carlo (DSMC) scheme with a CFD software was adopted to study the properties of dust particles (0.1–100 μm in diameter) in the flow field of a roadway after blasting. The results show that dust group produced from the heading face is jetted into the roadway under the shock wave after blasting, and is diluted from its back-end to the front-end by the airflow from the pressing pipe arranged around the heading face, then dust concentration shows an overall gradual decrease, and finally the respirable dust particles exhibit an alternant thin dense phase distribution in the roadway, whereas other dust particles (>5 μm in diameter) spread at the bottom of the roadway and form dust retention. The dust concentration in the front-end of the roadway around the heading face is always higher than that in other zones due to the existence of vortex region. The respirable dust concentration is slightly greater than the standard of air quality in the beginning, and quickly reaches the standard. But the total dust concentration always does not meet the standard of air quality in general. The simulation results are also verified by the field data. The research results are helpful for providing more suitable guidance for the dust control. [ABSTRACT FROM AUTHOR]

During loss of vacuum accident (LOVA), the dust in the divertor may be resuspended with the air ingression, to threaten the safety of the fusion device. There is the need for further study of the dust distribution characteristics to evaluate the possibility of the risk of dust explosion. The three-dimensional numerical model of ITER is built by computational fluid dynamics (CFD) method, which is validated by comparison with the results calculated by the code MELCOR in Accident Analysis Report (AAR). The migration process of dust composed of beryllium particles during LOVA is reproduced, in which the dust distributions at different heights and moments are investigated, showing that the average volume fraction of dust particles decreases in the early stage and then remains approximatively constant with the height increasing and that the maximum volume fraction of dust particles decreases as a whole with the height increasing. The effects of the dust mass and the crevasse location on the dust distribution have been discussed, which shows that the dust distribution in the space will not change noticeably with the assumed initial dust mass increasing, and also shows that the condition of different crevasses has an impact on the distribution of dust. This research can provide a reference for the safe operation of the ITER device. [ABSTRACT FROM AUTHOR]

Coal mines face a significant situation with regard to dust control. Numerical simulation was used in this paper to study the distribution of dust of different particle sizes in a specific case, as well as the influence of changing the supply airflow velocity on the dust distribution. The findings demonstrate that the airflow primarily migrates from the return air side to the air inlet side and the exit, with the intensity of the airflow decreasing as the distance increases. The amount of dust is high in the area with a strong airflow and low in other areas, and dust of different particle sizes is separated gradually. Increasing the supply air velocity has a greater effect on large dust particles than on small dust particles under the conditions and air speed range studied in this paper. Reasonable reduction of the supply air velocity can effectively reduce the amount of suspended dust. [Display omitted] • Dust of different particle sizes will be separated in the airflow. • The airflow intensity on the return side is higher than that on the inlet side. • Proper reduction in the airspeed is conducive to dedust. [ABSTRACT FROM AUTHOR]

Due to the similarity theory and the gas-solid two-phase flow equation motion, taking 11/96 belt conveyer inclined shaft in Xishimen Iron Ore as the research background, author educed the similarity index and designed a parallel model device for the specific situation in the belt convey roadway. Meanwhile, the dust distribution was experimentally studied. The results indicate that dust concentration along the first rises gradually to a maximum value in the roadway model,then gradually slowed down. Airflow direction,the average velocity of wind,the operating speed of the belt, ore moisture, feeding rate and feeding height are main influencing factors of dust distribution in the belt conveyer roadway. When the belt run along the wind direction in a low speed,the higher the velocity of wind,the smaller dust concentration will be. In the same way,the higher ore moisture,the lower the dust concentration. In addition,when ore moisture reaches the value of 3.09%,the dust concentration no longer reduces; What is more, the faster the feeding rate and the higher the feeding height,the greater dust concentration will be. [ABSTRACT FROM AUTHOR]

Field equations in a modified theory of gravitation proposed by Harko et al. (Phys. Rev. D 84: 024020, ) are obtained with the aid of a spatially homogeneous and anisotropic LRS Bianchi type-II metric. Cosmological models corresponding to stiff fluid, disordered radiation, dust and false vacuum are obtained. Some physical and kinematical properties of each of the models are also studied. [ABSTRACT FROM AUTHOR]

Former studies, the methods for estimating the ventilation time are all empirical in construction schedule simulation. However, in many real cases of construction schedule, the many factors have impact on the ventilation time. Therefore, in this paper the 3D unsteady quasi-single phase models are proposed to optimize the ventilation time with different tunneling lengths. The effect of buoyancy is considered in the momentum equation of the CO transport model, while the effects of inter-phase drag, lift force, and virtual mass force are taken into account in the momentum source of the dust transport model. The prediction by the present model for airflow in a diversion tunnel is confirmed by the experimental values reported by Nakayama [Nakayama, In-situ measurement and simulation by CFD of methane gas distribution at a heading faces, Shigen-to-Sozai 114 (11) (1998) 769–775]. The construction ventilation of the diversion tunnel of XinTangfang power station in China is used as a case. The distributions of airflow, CO and dust in the diversion tunnel are analyzed. A theory method for GIS-based dynamic visual simulation for the construction processes of underground structure groups is presented that combines cyclic operation network simulation, system simulation, network plan optimization, and GIS-based construction processes’ 3D visualization. Based on the ventilation time the construction schedule of the diversion tunnel is simulated by the above theory method. [Copyright &y& Elsevier]

Axially symmetric cosmological models are obtained in a scalar tensor theory proposed by Sen (Z. Phys. 149:311, ) based on Lyra manifold with time dependent β in the presence of string source, perfect fluid distribution, dust distribution and thick domain walls. Some physical and geometrical properties of these models are discussed. [ABSTRACT FROM AUTHOR]

Abstract: We present a comparative study of the inner comae of comets 1P/Halley and 19P/Borrelly using data from the Halley Multicolour Camera (HMC) onboard Giotto and the Miniature Integrated Camera and Spectrometer onboard Deep Space 1 (DS1). We show that the dust brightness dependence as a function of radial distance is different for both comets. We suggest that optical depth or fragmentation effects dominate the brightness distribution at comet 1P/Halley whereas acceleration or non-point source geometry effects dominate at comet 19P/Borrelly. The nightside profiles of comet 19P/Borrelly suggest a continuing non-radial outflow from the nucleus out to several tens of kilometres. This modifies the observed dayside to nightside brightness ratio with distance and offers a further constraint on dust emission models. By setting up a linear system of equations to fit the dust intensity distribution, better fits could be obtained by incorporating acceleration into the equation of free-radial outflow. Finally, we estimate the dust production rate of 19P/Borrelly at the time of DS1 encounter as no higher than 324kg/s based on comparisons with HMC intensity measurements. [Copyright &y& Elsevier]

[Display omitted] • The new moving granular bed can adjust the particle layer thickness, with a filtration efficiency exceeds 96%. • For 1–5 μm fine dust, the filtration efficiency is higher than 94%, and the bed pressure drop is small. • The flue gas flow rate and filter moving speed influence the filtration performance of granular bed. • Dust distribution is related to the structure of the device and the flow rate of the filter. The effects of important parameters, such as moving speed, wind speed, particle layer thickness and dust particle size, on bed pressure drop and filtration efficiency of new moving granular bed filter were studied experimentally in this work, and the distribution law of collected dust was elucidated. The new granular bed filter, which adopts the moving bed continuous filtration method, has two inclined surfaces that can increase a flue gas particle contact surface and a baffle that can adjust the thickness of the filter material; thus, a high-efficiency filtration of fine dust and high performance for different environments is achieved, and the filtration characteristics of existing particulate filtration devices are improved. Experimental results show that the new moving granular bed filter demonstrates better dust removal performance than other granular layer dust collectors, thereby possibly achieving low bed resistance and high filtration efficiency and has wide adaptability. The selection of an appropriate filter medium and speed for the fine dust of 1–5 μm can maintain the filtration efficiency of the granular bed at 0.94 or more and the bed pressure drop at approximately 100 pa. The particle area with the most dust collection is on the windward side of the lower part of the granular bed, and several of the particles are replaced whilst the filter particles move. Furthermore, the dust collected by the particles in the dead zone cannot be replaced. [ABSTRACT FROM AUTHOR]