Zone Dust Research Articles

Study on temporal and spatial evolution law for dust pollution in double roadway ventilation system of short wall continuous mining face.

To explore the laws of variations in the evolution of dust pollution within a double tunnel ventilation system at a short wall continuous mining face, a numerical simulation of air flow movement was conducted in this study. Results showed that after the wind flowing in the supporting and heading tunnels reached the head, the wind sides returned at speeds of 6.5 and 10.3m/s, respectively. Affected by the air volume and pressure differences between the two tunnels, part of the air flow entered the connecting tunnel at an average speed of 0.8m/s and moved to the heading tunnel. Affected by the turbulence at the driving face, a high dust concentration zone with a maximum dust concentration of 1700mg/m3 was formed in the tunnels at a distance of 15m from the heading. Dust blocked by the shuttle car accumulated and settled near it and formed a dust zone with an approximate average concentration of 750mg/m3 at a distance of 19-23m from the heading. The dust produced by the bolt machine formed a dust mass with an average concentration of 900mg/m3 at a distance of 0.5-4.5m from the head. Quantitative analyses of the changes in dust concentration with time at the position of a driver of the continuous mining machine, shuttle car, and anchor bolt machine were conducted, and functional formulae for the quadratic distribution were obtained. Suggestions for dust control were then proposed.

Evaluation of experimental research on black cotton soil stabilization using stone powder

A test is apportioned to verify Stone dust’s effect on BC Soil’s architecture and quality properties. The properties of stable soil such as compaction consistency, triaxial compressive quality and proportion of California bearing were evaluated and their varieties with stone dust zone unit substance were assessed. The extension of either Optimum extent of stone dust or Optimum extent of its mixture to black cotton soil has improved sub-review efficiency attributes.

Slices reconstructing algorithm for single image dedusting

For solving the image degradation in the non-uniform dusting environment with multiple scattering lights, the slices reconstructing algorithm for single image was proposed for dust elimination in the paper. Firstly, the slices along the depth orientation were produced based on McCartney model in dust environment. Secondly, the union algorithm of dust detection was used to detect dust patches in the slices where non-dust areas were reserved while the dust zones were marked as the candidate detecting areas of the next slice image. Then, the image was reconstructed by combining these non-dust areas of each slice and the dust zone of the last slice. Finally, the faster guided filter was applied to the reconstructed area. The experimental results had proved that the reconstruction algorithm could get rid of dust in object image not only effectively but also fast. The paper's work had laid the foundation for object detection and recognition work had based on computer vision in dust's environment.

Research on Dust Suppression Technology of Shotcrete Based on New Spray Equipment and Process Optimization

In order to reduce the dust hazard of shotcrete, the paper analyzed the mechanism of dust production from the perspective of various dust sources and developed the plunger‐type wet spraying machinery and wet mixer which can be applied in the small‐section tunnel for reducing dust on the root cause. The dust concentration between dry‐mix shotcrete and wet‐mix shotcrete was compared and analyzed. The results showed that the average total dust concentration and respirable dust concentration in the process of dry spraying were 99.4 mg/m3 and 52 mg/m3, respectively, while 9.8 mg/m3 and 4.08 mg/m3 in the wet‐mix shotcrete process, and the average dust concentration decreased by more than 90% after applying new wet‐mix shotcrete outfits. The clean zone of dust was divided according to the dust distribution. Finally, the dust suppression technology was optimized by using an accelerator and adjusting wind pressure and spraying angle. Results indicated that the application of the accelerator reduced the dust production efficiently; moreover, when the wind pressure was 0.2 MPa with 1 m spraying distance and 90° angle of spraying, the dust concentration and rebound reached the minimum.

The Process of Formation of a Single Star System for Gravitational Compression of a Gas-dust Cloud in Outer Space

In this paper it is shown that in the process of formation of a single star system favorable conditions are created for the appearance of the planetary system due to the collision of the oppositely moving condensed dust zones from the newly born star and falling onto it from the periphery. A hypothetical version of the possible structure of the core of a single star born in a rarefied gas-dust cloud, explaining the cause of the mismatch of the axis of rotation of the star and the dipole magnetic field, is proposed. An assumption is made about the causes of the appearance of a directed orbital motion of planets that are not related to external perturbations of the initial gas-dust cloud.

Diffusion and pollution of multi-source dusts in a fully mechanized coal face

Abstract In order to provide theoretical guidance for dust prevention and treatment, as well as environmental protection for mines, we investigated the diffusion and pollution of multiple sources in a fully mechanized coal face using CFD-DPM based airflow-dust coupling method, and analyzed the distributions of dust particle diameter at different positions. Results show that, the air was mainly leaked from three positions in the mining area, 6 m away from the air inlet on the leeward side, the position where the hydraulic prop was moved and the middle part of the shearer. A high-velocity airflow zone was formed around the shearer’s front roller, with airflow velocity up to 2.2 m/s. The dusts produced by the advancing support were superposed with the dusts from the roller’s coal cutting, and a high-concentration dust zone with a length of approximately 2 m was formed at the front roller, with dust concentration as high as 3000 mg/m3. Within 40 m from the air outlet, a great number of dusts larger than 70 μm settled. Finally, the field measured results of airflow and dust concentration verified the accuracy of the simulation of dust diffusion and pollution behaviors in the fully mechanized coal face.

THE IMPACT OF ANTHROPOGENIC ALLUVIAL ARRAYS ON AREAS SETTLEMENTS DEPENDING ON THE PARTICLE SIZE DISTRIBUTION OF STORED TAILLINGS

Developing devices for dust suppression one should consider important factors, such as the size distribution of transferred dust, duration of exposure in residential areas. Often the total amount of dust emissions may exceed the estimated figure for maximum permissible emissions, but their share transferred in sanitary protection zone of dust is negligible. Tailing dump of Kovdor MPE is one of the largest in Russia. The construction of dust dispersion halos was performed using a universal program calculation of air pollution “Ecolog” (Russia). Based on a comparison of dispersed compositions tails similar in composition tailing dumps in Russia, it can be concluded that in the beach area of the Kovdor dump share of dust tranfered to the territory of settlements has ranged from 10 to 40%. It was found that the maximum diameter of the particles carried by the territory of the city under consideration is 50 microns. We can conclude that under the conditions of the object the development of special devices for dust suppression is required.

Effect of magnetic field on dust charging and corresponding probe measurement

The effect of external magnetic field on the Langmuir probe measurement and dust charging are studied in low-pressure hydrogen plasma. The experiment is performed in a dusty plasma device where plasma is created by the hot cathode filament discharge technique. A strong Strontium ferrite magnet is used inside the plasma, near the dust zone. The plasma parameters are measured at different distances from the magnet with the help of Langmuir probe system. It is observed that even at “low magnetic field case,” where rLe≥rP, rLi〉〉rP; the electron collection by the probe deviates strongly from the actual value, until rLe≥10rP. The observations of electron energy probability function show that at higher magnetic field, the Langmuir probe collects only the higher energy electrons compared to the low energy electrons. Both Quasi-neutrality condition and capacitance model are used separately to calculate the charge accumulated on the dust grain. Introducing the reduction factor on quasi-neutrality condition, it is observed that the influence of magnetic field on dust charge is almost negligible for “low magnetic field” case. The dust charge calculated from quasi-neutrality condition matches well with the experimentally observed dust current results, within the experimental error range. However, capacitance model deviates from the experimental results at higher magnetic field.

Economic Modeling of the Regional Polices to Combat Dust Phenomenon by Using Game Theory

In recent years, dust phenomenon as an environmental externality has affected Iran and other Middle East countries. The major parts of dust which has polluted Iran's atmosphere, mainly comes from Iraq. This dust phenomenon has also had a lot of economic and social damages for these two countries. The main aim of this study is to analyse the advantages of cooperation between Iran and Iraq against this phenomenon. The significant damage of this phenomenon has been estimated on health and hygiene, transportation and agriculture sections. The expenditure in contrast with this problem has also been calculated in the crucial zone of creation dust. According to the estimation of this study, total damages of dust for Iran and Iraq are 1043.5 and 1404 million dollars, respectively. While the cost of solving this problem is about 2425.7 million dollars. By applying cooperative games theory, the cooperation between Iran and Iraq to combat dust phenomenon has been analysed. Net benefits of these two countries has been calculated in two cooperation games and their characteristic functions has been derived. Then by using Shapley solution, outcome benefits have been distributed between these two countries. The results suggest that the net benefits of two countries will increase if they associate with each other. In the meantime, based on the results of coalition, a fairly allocation has also been used for costs which has been utilized against dust phenomenon between Iran and Iraq. So these two countries should spend 1442.6 and 1082.1 million dollars to conquer this phenomenon, respectively. The managers of Iranian environmental protection organization should have more effective cooperation with Iraq to resolve dust problem by using diplomatic means and provide parts of its cost by side payments.

INFRARED SPECTROSCOPY OF SYMBIOTIC STARS. IX. D-TYPE SYMBIOTIC NOVAE

Time-series spectra of the near-infrared 1.6 {mu}m region have been obtained for five of the six known D-type symbiotic novae. The spectra map the pulsation kinematics of the Mira component in the Mira-white dwarf binary system and provide the center-of-mass velocity for the Mira. No orbital motion is detected in agreement with previous estimates of orbital periods {approx}>100 yr and semimajor axes {approx}50 AU. The 1-5 {mu}m spectra of the Miras show line weakening during dust obscuration events. This results from scattering and continuum emission by 1000 K dust. In the heavily obscured HM Sge system the 4.6 {mu}m CO spectrum formed in 1000 K gas is seen in emission against an optically thick dust continuum. Spectral features that are typically produced in either the cool molecular region or the expanding circumstellar region of late-type stars cannot be detected in the D-symbiotic novae. This is in accord with the colliding wind model for interaction between the white dwarf and Mira. Arguments are presented that the 1000 K gas and dust are not Mira circumstellar material but are in the wind interaction region of the colliding winds. CO is the first molecule detected in this region. We suggest that dust condensingmore » in the intershock region is the origin of the dust obscuration. This model explains variations in the obscuration. Toward the highly obscured Mira in HM Sge the dust zone is estimated to be {approx}0.1 AU thick. The intershock wind interaction zone appears thinnest in the most active systems. Drawing on multiple arguments masses are estimated for the system components. The Miras in most D-symbiotic novae have descended from intermediate mass progenitors. The large amount of mass lost from the Mira combined with the massive white dwarf companion suggests that these systems are supernova candidates. However, timescales and the number of objects make these rare events.« less

Cantor dust zone plates

In this paper we use the Cantor Dust to design zone plates based on a two-dimensional fractal for the first time. The pupil function that defines the coined Cantor Dust Zone Plates (CDZPs) can be written as a combination of rectangle functions. Thus CDZPs can be considered as photon sieves with rectangular holes. The axial irradiances produced by CDZPs of different fractal orders are obtained analitically and experimentally, analyzing the influence of the fractality. The transverse irradiance patterns generated by this kind of zone plates has been also investigated.

Impact of the flotation tailing dumps on the living environment of Bor and protective measures

In the southeastern Serbia, in the area of the municipality Bor, there are three flotation tailing dumps: FTD Bor, FTD RTH (the ore body H) and FTD Veliki Krivelj. The Flotation Tailing Dump Bor is abandoned, partly reclamated. The other two are active flotation tailing dumps. All three flotation tailing dumps are serious polluters of air, water and soil. The affected zones by dust from these tailing dumps threat large areas in a direction of dominant wind from the northwest direction. The affected areas by the impact zone of dust from: the Bor Flotation Tailing Dump amount to 18,361,074 m2, flotation tailing dump of the ore body H, 3,713,408 m2 and Flotation Tailings Dump Veliki Krivelj, 16,077,805 m2. The most effective measure against dust rising from dry areas by the wind is the use of reclamation with the phases of technical, agrotechnical and biological reclamation.

Sahel dust zone and synoptic background

Present weather reports from synoptic station data from 1983 to 2008 are analyzed to establish the climatological existence of a zone of frequent dust events and high dust concentration over the Sahel. This zone, to be referred to as the “Sahel dust zone” (SDZ), is situated between 10°N and 16°N, and is most prevalent during the period between December and April, stretching almost over the entire North African continent from west to east. SDZ corresponds well to the convergence zone located to the north of the African monsoon trough, and the dust is primarily transported from the Sahara. Using the ERA‐Interim Reanalysis data, we examine the synoptic patterns in February and March, which generate dust emission from the Sahara and subsequently transport the dust to the Sahel. Three synoptic patterns are found to be mainly responsible for the formation of SDZ.

THE DEBRIS DISK AROUND HR 8799

We have obtained a full suite of Spitzer observations to characterize the debris disk around HR 8799 and to explore how its properties are related to the recently discovered set of three massive planets orbiting the star. We distinguish three components to the debris system: (1) warm dust (T ~150 K) orbiting within the innermost planet; (2) a broad zone of cold dust (T ~45 K) with a sharp inner edge, orbiting just outside the outermost planet and presumably sculpted by it; and (3) a dramatic halo of small grains originating in the cold dust component. The high level of dynamical activity implied by this halo may arise due to enhanced gravitational stirring by the massive planets. The relatively young age of HR 8799 places it in an important early stage of development and may provide some help in understanding the interaction of planets and planetary debris, an important process in the evolution of our own solar system.

Exposures to Refractory Ceramic Fibers in Manufacturing and Related Operations: A 10-Year Update

Refractory ceramic fiber (RCF) is a man-made vitreous fiber used for its insulating properties. Since 1987, the work environment of approximately 800 persons employed in fiber manufacture or production operations directly related to manufacturing has been monitored to evaluate exposure levels. Samples were collected quarterly from the breathing zones of randomly selected workers. The measurements from those working in areas of similar activities and exposure controls (dust zones or homogeneous exposure groups) were used to calculate a mean exposure during identified time periods. Persons who spent all of their work time in one zone/group were assigned this mean exposure; those with responsibilities in more than one area were assigned an exposure based on a time-weighted formula. A total of 3213 measurements were used to estimate exposure for 130 job titles; because of the mobile jobs, many samples contribute to the estimates of exposure for multiple job titles. The majority of exposure estimates (53%) have remained stable over the operational history of the plant reported here. For 32 job titles (25%) exposures have decreased, and for 28 job titles (22%) exposures have increased. Of the 122 job titles active in 2001, 97 (79%) exposures were estimated to be at 0.25 f/cc or lower; 8 (7%) had an exposure exceeding 0.5 f/cc (range 0.51–0.80) and 17 (14%) of these exposure estimates were in the range of > 0.25 f/cc to 0.5 f/cc. The continuing program to measure exposure supports a respiratory health surveillance program in these facilities.

Detection of a subarcsecond dust shell around the Wolf-Rayet star WR 112

A lunar occultation event of the Wolf-Rayet star WR 112 (type WC9) has been observed simultaneously from two independent telescopes at λ = 2.2 μm, allowing us to investigate this source with an angular resolution of ≈ 0.003 arcsec. We have detected a circumstellar dust envelope the brightness distribution of which can be approximately fitted by a Gaussian with a FWHM of ≈0.06 arcsec (≈ 1015> cm). We present and discuss the reconstructed brightness profile, which shows an asymmetry in the radial dust distribution. The derived dust grain temperature at the inner dust zone of ≈ 1150 K is consistent with available model calculations. There is no signature of the central star from our observations, providing a direct confirmation that the circumstellar shell emission dominates over the photospheric emission at 2.2 μm as predicted by fits to the spectral energy distribution. Further lunar occultation observations at different position angles are essential to reconstruct the two-dimensional image of the dust shell around WR 112. The current series of lunar occultations of WR 112 will continue to the end of 1999, and will be visible for all equatorial and southern latitude observatories.

A COMPARISON OF EXPOSURES TO REFRACTORY CERAMIC FIBRES OVER MULTIPLE WORK SHIFTS

As part of an ongoing, industry-wide study in the manufacture of refractory ceramic fibres (RCF), time weighted average (TWA) exposures have been collected at five facilities according to a standardised protocol. Work activities were grouped into dust zones (DZs). Persons to be sampled were randomly selected according to a protocol designed to assure that at least one sample was collected annually from each DZ; each work shift is also sampled at least annually. TWA exposures calculated over a sampling period of at least 360 min were included in the data set. DZs were combined into one of three groups (DZGs): fibre production; vacuum processes; other. The data were analysed to identify any differences by DZG between airborne fibre exposures, by the shift worked at each facility, and across all facilities. There were no statistically significant shift-related differences detected between airborne fibre exposures across the five RCF facilities when analysed as a group. Within four of the facilities, no shift-related differences were detected between airborne fibre exposures; however, at one facility, first and third shift exposures were statistically different. No documentation related to job activities was found to account for the observation. The data generally support the use of a single exposure estimate for each DZG in each of these facilities, regardless of shift worked. Researchers reconstructing exposure and not able to determine the shift worked by study subjects may find these results useful, but are cautioned that substantial differences in exposure across shifts may exist in other types of manufacturing. © 1997 Published by Elsevier Science Ltd.

A comparison of exposures to refractory ceramic fibres over multiple work shifts

As part of an ongoing, industry-wide study in the manufacture of refractory ceramic fibres (RCF), time weighted average (TWA) exposures have been collected at five facilities according to a standardised protocol. Work activities were grouped into dust zones (DZs). Persons to be sampled were randomly selected according to a protocol designed to assure that at least one sample was collected annually from each DZ; each work shift is also sampled at least annually. TWA exposures calculated over a sampling period of at least 360 min were included in the data set. DZs were combined into one of three groups (DZGs): fibre production; vacuum processes; other. The data were analysed to identify any differences by DZG between airborne fibre exposures, by the shift worked at each facility, and across all facilities. There were no statistically significant shift-related differences detected between airborne fibre exposures across the five RCF facilities when analysed as a group. Within four of the facilities, no shift-related differences were detected between airborne fibre exposures; however, at one facility, first and third shift exposures were statistically different. No documentation related to job activities was found to account for the observation. The data generally support the use of a single exposure estimate for each DZG in each of these facilities, regardless of shift worked. Researchers reconstructing exposure and not able to determine the shift worked by study subjects may find these results useful, but are cautioned that substantial differences in exposure across shifts may exist in other types of manufacturing.

Estimation of Historical and Current Employee Exposure to Refractory Ceramic Fibers during Manufacturing and Related Operations

Abstract Refractory ceramic fibers (RCFs) have been produced in the United States since the early 1950s for use as a high temperature insulation material, or in the production of specialty products for insulation. Environmental data collected through 1991 have been assembled and used to reconstruct exposures at jobs in RCF manufacture or related operations. The algorithm incorporated consideration of the statistical distribution of the data, dates of implementation of engineering or process modifications potentially associated with a change in airborne fiber concentration, and the area in the facility (dust zone) where the sample was collected. Analysis of variance was used to test if differences between time periods within a dust zone were statistically significant. Time period was considered a fixed effect; the days of sample collection within a time period were considered a random, nested effect. Exposure estimates were constructed for 81 job tides in seven facilities for specified time periods. Overal...

The infrared spectrum of M8 E - Evidence for circumstellar CO

High-resolution spectroscopic observations of the compact infrared source M8 E are reported in the region from 3 to 5 microns. Very prominent CO absorption lines are observed in the v = 1-0 band at 4.7 microns. The velocity width and rotational temperature suggest that this CO absorption occurs in a highly excited region. The high background continuum flux level and the prominent appearance of the CO features suggest that the CO line-forming region must be in front of the dust emission region. A blister model for M8 E, which places most of the dust continuum emission behind the source, satisfies this requirement. According to this picture, the observed circumstellar CO spectrum shows a high rotational temperature and a large velocity dispersion because of the combined effects of the strong stellar wind and possible shock heating near the dust zone as the wind encounters the ambient molecular cloud.