Evaluation of the influence of aerodynamic aging of production on aerological risks on coal mines

2020 ◽  
pp. 74-83 ◽  
Author(s):  
O. V. Skopintseva ◽  
S. V. Balovtsev
Keyword(s):  
Rock Pressure ◽  
Average Rate ◽  
Coal Mines ◽  
Entire Period ◽  
Risk Indicator ◽  
Average Value ◽  
Rate Of Increase ◽  
Mine Workings ◽  
Aging Factor

The results of a study of the aerodynamic aging of mine workings are presented. It is established that the local workings located in the zone of active manifestation of rock pressure are most deformed. The average rate of increase in their resistance reaches 0.0112 N×s2 / m9×yr, and the degree of increase in their resistivities over 4-9 years of existence reaches 7-8 times. The rate of aging of the mine workings is much lower than that of the local workings, averaging 0.0014 N×s2/m9×year for the inclined workings on average over the entire period of their existence, and 0.0009 N×s2/m9×year for horizontal ones. The degree of increase in the resistivity of capital workings for 12-25 years of their existence reaches 3 times. The workings were ranked by relative aerological risk indicator Rac by aerodynamic aging factor. The calculations showed that the average value of the relative aerological risk indicator for the aerodynamic aging factor of the Rac mine workings for the local haul drifts was 0.541; for precinct ventilation drifts - 0.842; for capital inclined workings - 0.172; for capital horizontal workings - 0.101. When assessing the risk of gassing of workings, it is necessary to take into account data on the aerodynamic aging of mine workings.

scholarly journals Production and dissipation of vorticity in a turbulent fluid

1938 ◽  
Vol 164 (916) ◽  
pp. 15-23 ◽  
Keyword(s):  
Short Distance ◽  
Vortex Line ◽  
Average Rate ◽  
Turbulent Motion ◽  
Vortex Filaments ◽  
Diffusive Motion ◽  
Turbulent Fluid ◽  
Average Value ◽  
Subsequent Time ◽  
Rate Of Increase

In some recent publications (Taylor 1937; Taylor and Green 1937) the author has put forward the view that the high average vorticity which is known to exist in turbulent motion is caused by the extension of vortex filaments in an eddying fluid. Let A and B be two particles a short distance, d 0 , apart on a vortex line where the vorticity is ω 0 . At a subsequent time when the distance between A and B has changed from d 0 to d and the vorticity from ω 0 to ω then, neglecting the effects of viscosity, the equation representing the conservation of circulation is ω / ω 0 = d / d 0 . (1) Turbulent motion is found to be diffusive, so that particles which were originally neighbours move apart as the motion proceeds. In a diffusive motion the average value of d 2 / d 2 0 continually increases. It will be seen therefore from (1) that the average value of ω 2 / ω 2 0 continually increases. An equation for the average rate of increase in ω 2 has been given by v. Karman (1937) which contains the term ω 2 ∂ u 3 /∂ x 3 , where the bar shows that the average value has been taken and ∂ u 3 /∂ x 3 represents the rate of stretching of vortex filaments.

scholarly journals Development of a methodology for assessing the expediency of mine workings decommissioning based on the geomechanical factor

2021 ◽  
pp. 10-16
Author(s):  
I.A. Salieiev ◽  
V.I Bondarenko ◽  
H.A Symanovych ◽  
I.A Kovalevska
Keyword(s):  
Rock Pressure ◽  
Mine Working ◽  
Negative Influence ◽  
Dispersion Analysis ◽  
The State ◽  
Entire Period ◽  
Synthesis Methods ◽  
Mine Closure ◽  
Geological Conditions ◽  
Mine Workings

Purpose. Substantiation of the methodology for predicting the state of mine workings based on the study on geomechanical processes when assessing the consequences of mine closure taking into account the entire period of their existence, during which the development of displacement with various intensity occurs in the surrounding coal-bearing mass. Methodology. The study is based on methods of analysis and synthesis, methods of comparison, abstraction, analogy, calculation and construction. The methods of mine tool observations of the manifestations of rock pressure and their processing by methods of correlation and dispersion analysis for establishing the relationship of displacements of the mine working contour with geomechanical factors were used. Findings. A possibility of stage-by-stage decommissioning of mine workings when grouping mining-and-geological conditions is substantiated. An example of calculating the displacements in a mine working during its decommissioning is presented. The given calculation expressions make it possible to assess the mine working state, taking into consideration the patterns of the geomechanical factor influence on making a technical decision on the expediency of its further operation. Originality. The patterns of the rock pressure manifestation development in sequentially abandoned mine workings have been determined. Based on the methods of correlation-dispersion analysis, the dependence of the mine working contour displacements on geomechanical factors have been revealed throughout the entire period of its existence. Practical value. A methodology for assessing the state of mine workings at the time of their decommissioning has been developed, which is an integral part of the recommendations to limit the negative influence of mine closure. The peculiarity of the methodology is in taking into account the entire period of mine workings existence, which leads to a well-grounded technical decision on the possibility of dismantling the metal structures with the complete exclusion of emergency situations.

Variation during growth of twin cattle

1967 ◽  
Vol 9 (1) ◽  
pp. 35-60 ◽  
Author(s):  
C. S. Taylor ◽  
Jean Craig
Keyword(s):  
Genetic Variation ◽  
Body Part ◽  
Body Measurements ◽  
Body Parts ◽  
Genetic Variances ◽  
Average Value ◽  
Coefficients Of Variation ◽  
Rate Of Increase ◽  
Early Maturing ◽  
Degree Of Maturity

Phenotypic variances within pairs of monozygotic and dizygotic twin heifers and also genetic variances and heritabilities were calculated for 12 linear body measurements at a sequence of eight ages up to two years old. The 60 pairs of fraternal and 60 pairs of identical twins used were reared as part of a larger uniformity trial in which feeding was effectively ad libitum throughout.Size differences between members of DZ twin pairs were found to be approximately normally distributed with about the same variance for all breeds and crosses. The variance within DZ pairs increased strongly with age, with a marked increase between 9 and 12 months of age and with most body measurements showing a broadly similar trend. On a logarithmic scale DZ variances increased roughly linearly with degree of maturity and at about the same rate in each body measurement. Coefficients of variation within DZ pairs corrected for measuring error had an average value of 2%. They did not change greatly with age, and were roughly the same for most body measurements although width measurements tended to be more variable than average.Coefficients of variation within MZ pairs had a corresponding overall average of 1·4%; they declined rapidly with age from 2·0% to 1·1%, were roughly the same for all body measurements, but at early ages tended to be greater in late than in early maturing body parts. However, they showed no association with the earliness of maturing of a body part provided variation was measured at the same degree of maturity for each body part.Genetic variation increased rapidly with age in all body measurements. The rate of increase with age was greater for late than for early maturing parts. The rate of increase with degree of maturity, however, was about the same for all body measurements. Coefficients of genetic variation increased slowly with age; they had an average value of 1·6%.Estimates of heritability are given at a sequence of eight ages for each of 12 body measurements. They increased strongly with age from 0·14 on average at three months of age to 0·67 on average at two years of age. At any fixed age, early maturing body parts tended to have higher heritabilities than later maturing body parts. However, if heritability was measured at the same degree of maturity in each body part, early and late maturing parts had about equal heritabilities.The present results are compared with those obtained from twin cattle studies in New Zealand, Sweden and Wisconsin, U.S.A.Inferences from twins about genetic variances and heritabilities for unrelated animals are discussed.

The physical sustainability of the coastal zone of the Ganges-Brahmaputra-Meghna delta under climatic and anthropogenic stresses

2021 ◽  
Author(s):  
Stephen Darby ◽  
Md. Munsur Rahman ◽  
Anisul Haque ◽  
Robert Nicholls ◽  
Frances Dunn
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Average Rate ◽  
River Management ◽  
Tidal River ◽  
Natural Conditions ◽  
Fluvial Sediment ◽  
Average Value ◽  
Delta Plain ◽  
The Ganges

<p>The Ganges-Brahmaputra-Meghna (GBM) delta is one of the world’s largest deltas, and consists of large areas of low flat lands formed by the deposition of sediment from the GBM rivers. However, recent estimates have projected between 200~1000 mm of climate-driven sea-level rise by the end of the 21st century, at an average rate of ~6 mm/yr. Eustatic sea-level rise is further compounded by  subsidence of the delta, which in the coastal fringes varies from 0.2 to 7.5 mm/yr, at an average value of ~2.0 mm/yr. Therefore, the combined effect of sea-level rise and subsidence (termed relative sea-level rise, RSLR) is around 8.0 mm/yr. Such high values of RSLR raise the question of whether sediment deposition on the surface of the delta is sufficient to maintain the delta surface above sea level. Moreover, as the total fluvial sediment influx to the GBM delta system is known to be decreasing, the retained portion of fluvial sediment on the delta surface is also likely decreasing, reducing the potential to offset RSLR. Within this context, the potential of various interventions geared at promoting greater retention of sediment on the delta surface is explored using numerical experiments under different flow-sediment regime and anthropogenic interventions.  We find that for the existing, highly managed, conditions, the retained portion of fluvial sediment on the delta surface varies between 22% and 50% during average (when about 20% of the total floodplain in the country is inundated) and extreme (> 60% of the total floodplain in the country is inundated) flood years, respectively. However, the degree to which sediment has the potential to be deposited on the delta surface increases by up to 10% when existing anthropogenic interventions such as polders that act as barriers to delta-plain sedimentation are removed. While dismantling existing interventions is not a politically realistic proposition, more quasi-natural conditions can be reestablished through local- sediment management using tidal river management, cross dams, dredging, bandal-like structures and/or combinations of the above measures.</p>

Ecological characteristics of Thaumetopoea pityocampa Denis & Schiffermüller, 1775 (Lepidoptera: Notodontidae) in egg stage in Thasos Island, Greece

2020 ◽  
Vol 32 ◽  
pp. 1-9
Author(s):  
Margarita Georgieva ◽  
Maria Matova ◽  
Gergana Zaemdzhikova ◽  
Ivailo Markoff ◽  
Plamen Mirchev ◽  
...  
Keyword(s):  
Pinus Halepensis ◽  
Average Rate ◽  
Aleppo Pine ◽  
Thaumetopoea Pityocampa ◽  
Egg Masses ◽  
Ecological Characteristics ◽  
Average Value

In September 2017, 96 egg batches of Thaumetopoea pityocampa were collected from Aleppo pine (Pinus halepensis) trees at four sites of Thasos Island in Greece. In the different localities, the average number of eggs in batches varied from 196.5 to 223.9 (212.4 for the Thasos Island). The length of P. halepensis needles with egg batches differed in size - between 84 to 210 mm. Approximately 75% of batches were laid close to the middle of needles, between 121 and 180 mm. The egg masses were formed mainly on two needles (84.4%) and the rest - on one, three or four needles (13.6%) or on fine shoots (2%). In most cases (88.3%), the female moths started to lay eggs from the tip of the needle. The distance from the base of the needle to the beginning of the egg batches was established between 0 and 180 mm, as most of them (62.7%) were clustered around the average value (87.3 mm) in the diapason of 60-120 mm. The average rate of T. pityocampa survival in egg stage was 48%. The parasitized eggs were 43.8%, and the rest included unhatched eggs, predominately undeveloped eggs with dried-up yolk. No correlation was found between the percentage of parasitized eggs and the distance of the egg batches from the base of needles.

scholarly journals Nitrogen Utilization from Ammonium Nitrate and Urea Fertilizer by Irrigated Sugarcane in Brazilian Cerrado Oxisol

Agriculture ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 323
Author(s):  
Nelmício Furtado da Silva ◽  
Edson Cabral da Silva ◽  
Takashi Muraoka ◽  
Marconi Batista Teixeira ◽  
Frederico Antonio Loureiro Soares ◽  
...  
Keyword(s):  
Ammonium Nitrate ◽  
Crop Residues ◽  
Average Rate ◽  
Block Design ◽  
Residual Effect ◽  
N Fertilization ◽  
Isotopic Dilution ◽  
Average Value ◽  
Randomized Block Design ◽  
N Utilization

Sugarcane is the most promising among renewable biofuel-producing crops. An adequate availability of water and nutrients, especially nitrogen (N), is of utmost importance. From the hypothesis that the source and the rate of N fertilization influence the N use efficiency of an irrigated soil–sugarcane system, this study aimed to evaluate the stalk and crop residues (pointer and leaves) yield, as well as the N utilization, from different rates of ammonium nitrate and urea by irrigated sugarcane in the cane plant cycle, using an 15N isotopic dilution technique. The soil used for the experiment was an Oxisol (Rhodic Haplustox) Cerrado (savannah) phase. The experiment was carried out at a farm of the Raízen Mill, which was located in the municipality of Jataí, Goias State, Brazil. The sugarcane variety IACSP95–5000 was used in a randomized block design, with three replicates, four N rates (30, 60, 120, and 180 kg ha−1), and two fertilizer sources labeled with 15N isotopes (urea and ammonium nitrate). The average value for N utilization was 60.17% for the ammonium nitrate source and 44.95% for urea. The responses in the percentage and quantity of N in the sugarcane from the fertilizer increase with the increasing N rate. The soil was the main N source for sugarcane. The higher stalk and pointer yield was recorded at the average rate of 143.61 kg N ha−1. Further studies are needed to evaluate the residual effect of N in the next cycles.

Mechanism for cardiac stimulation during hypoxia

1965 ◽  
Vol 208 (6) ◽  
pp. 1237-1242 ◽  
Author(s):  
Mario Penna ◽  
Francisco Linares ◽  
Laura Cáceres
Keyword(s):  
Average Rate ◽  
Contractile Force ◽  
Isometric Tension ◽  
Isometric Contractions ◽  
Papillary Muscles ◽  
Stimulant Effect ◽  
Cat Papillary Muscle ◽  
Cardiac Stimulation ◽  
Average Value ◽  
Guinea Pig Atria

In isolated guinea pig atria, hypoxia was induced by bubbling nitrogen through Tyrode solution. A significant increase in both the amplitude and frequency of the contractions occurred, followed by a decrease. Average rate in 11 control atria was 138 ± 9.2 contractions/min and increased during hypoxia by an average value of 12.7 ± 2.3 contractions/min ( P < 0.001). Amplitude of shortening increased by an average of 10.5 ± 2.12% ( P <0.001). In 19 preparations pretreatment with reserpine blocked the transient stimulant effect of hypoxia on both amplitude and frequency of contractions. Isometric contractions were recorded from 30 isolated cat papillary muscles. The developed isometric tension increased during hypoxia by an average of 17.3 ± 2.8% ( P < 0.001). Later, a decrease in contractile force was observed. Pretreatment of the animals with guanethidine and chronic cardiac sympathectomy blocked and pretreatment with reserpine decreased the stimulant effect of hypoxia on the cat papillary muscle. The transient stimulant effect of hypoxia was compared to the staircase phenomenon. Both chronic cardiac sympathectomy and pretreatment with reserpine blocked the increase in force induced by a change in rate from 60 to 120.

scholarly journals Classification of Theories about Rock Pressure

2018 ◽  
Vol 277 ◽  
pp. 157-167 ◽  
Author(s):  
Oleh Khomenko ◽  
Maksym Kononenko ◽  
Janchiv Bilegsaikhan
Keyword(s):  
Physical Properties ◽  
Rock Pressure ◽  
Mine Working ◽  
Physical Processes ◽  
Classification Feature ◽  
The World ◽  
Underground Mine Working ◽  
Mine Workings ◽  
Energy Theory

The first classificationsw of physical properties of rocks and hypotheses of rock pressure in the world practice are analysed. The analysis of internationally widely known theories about rock pressure and physical processes around mine workings is executed. Classification of theories about rock pressure on classification feature “condition of investigated massif” is constructed. The energy theory that describing capsulation by the massif of underground mine working is offered.

scholarly journals Predicting Hidden Danger Quantity in Coal Mines Based on Gray Neural Network

Symmetry ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 622
Author(s):  
Hongze Zhao ◽  
Qiao He ◽  
Zhao Wei ◽  
Lilin Zhou
Keyword(s):  
Neural Network ◽  
Coal Mine ◽  
Large Scale ◽  
Safety Management ◽  
Coal Mines ◽  
Development Trend ◽  
Good Prediction ◽  
Average Value ◽  
Normal Distribution Curve ◽  
Safety Production

The hidden danger is the direct cause of coal mine accidents, and the number of hidden dangers in a certain area not only reflects the current safety situation, but also determines the development trend of safety production in this area to a large extent. By analyzing the formation and development law of the hidden dangers and hidden danger accident-induced mechanism in coal mines, it is concluded that there are some objective laws in the process of occurrence, development, weakening, and even stabilization of hidden dangers in a certain area. The development of the number of hidden dangers for a coal mine generally presents the law of similar normal distribution curve, with a certain degree of partial symmetry. Many years of hidden danger elimination in coal mines will accumulate large-scale hidden danger data. In this paper, by using the average value of hidden danger quantity in consecutive months to weaken the oscillation of hidden danger quantity sequence, and combining with gray model (1,1) and the neural network of extreme learning machine, and employing big data of hidden dangers available, a hidden danger quantity prediction model based on the gray neural network was established, and the experimental analysis and verification carried out. The results show that the model can achieve good prediction effect on the number of hidden dangers in a coal mine, which not only reflects the complex gray system behavior of hidden dangers of a coal mine, but also can predict dynamically. The safety management efficiency and emergency capacity of the coal mine enterprise will be greatly improved.

INFLUENCE OF PARAMETERS OF THE ROUGHLY DISPERSED DUST GAS MIXTURES AT THE TIME OF THEIR BURN-OUT IN MINE WORKINGS OF COAL MINES

Ugol ◽  
2018 ◽  
pp. 44-49 ◽  
Author(s):  
S.V. Cherdantsev ◽  
◽  
Kh.U. Lee ◽  
Yu.M. Filatov ◽  
P.A. Shlapakov ◽  
...  
Keyword(s):  
Coal Mines ◽  
Gas Mixtures ◽  
Burn Out ◽  
Mine Workings
Sign in / Sign up

Export Citation Format

Share Document