Release Zone Research Articles

The Impact of Methane Seepage on the Pore-Water Geochemistry across the East Siberian Arctic Shelf

East Siberian Arctic Shelf, the widest and the shallowest shelf of the World Ocean, covering greater than two million square kilometers, has recently been shown to be a significant modern source of atmospheric methane (CH4). The CH4 emitted to the water column could result from modern methanogenesis processes and/or could originate from seabed deposits (pre-formed CH4 preserved as free gas and/or gas hydrates). This paper focuses primarily on understanding the source and transformation of geofluid in the methane seepage areas using ions/trace elements and element ratios in the sediment pore-water. Six piston cores and totally 42 pore-water samples were collected in the East Siberian Sea and the Laptev Sea at water depths ranging from 22 to 68 m. In the active zones of methane release, concentrations of vanadium, thorium, phosphorus, aluminum are increased, while concentrations of cobalt, iron, manganese, uranium, molybdenum, copper are generally low. The behavior of these elements is determined by biogeochemical processes occurring in the pore-waters at the methane seeps sites (sulfate reduction, anaerobic oxidation of methane, secondary precipitation of carbonates and sulfides). These processes affect the geochemical environment and, consequently, the species of these elements within the pore-waters and the processes of their redistribution in the corresponding water–rock system.

Параметры дегазации высокопроизводительных выемочных участков на неизученных шахтных полях

Conditions of the coal seams bedding at the mines of Kuzbass and Vorkutskoye deposits, their natural methane content and coal grades are studied in the article. Performance of shearers and the natural degassing effect of the second working on the change in the methane content of the massif in the coal mining zone are evaluated. Dependence is established concerning the coefficient of coal seams natural degassing on the thickness of the mined seam. The influence of natural and mining-technical factors on the efficiency of second working and degassing parameters were studied. The relationship is revealed between the natural methane content of coal seams with the yield index of the volatile substances contained in the coals of various grades. The relationship is defined related to the intensity of the initial methane release from the coal mass to the reservoir degassing wells depending on the natural methane content of the reservoir with the outgoing air flow. Comparison of the data obtained during geological exploration works, and the predicted values calculated based on the identified dependencies showed their good convergence. The dependences were revealed concerning the zones of intense methane release in the degassing wells on the thickness of the inter-layer of the unloaded adjacent layers in the roof and soil of the working layer in the process of moving the working face. This information allows to select the optimal mode of wells functioning for extracting methane-air mixtures suitable for utilization in the unexplored mine fields. Recommended coefficients of degassing of the methane emission sources were determined for ensuring the planned productivity of the working face with the view to ensure its safety on the gas factor.

Nonparametric estimation of aggregated Sobol’ indices: Application to a depth averaged snow avalanche model

Avalanche models are increasingly employed for elaborating land-use maps and designing defense structures, but they rely on poorly known parameters. Careful uncertainty assessment is thus required but difficulty arises from the nature of the outputs of these models, which are commonly both functional and scalar. Hence, so far in the avalanche field, few sensitivity analyses have been performed. In this work, we propose to determine the most influential inputs of an avalanche model by estimating aggregated first-order Sobol’ indices. We propose a nonparametric estimation procedure based on the Nadaraya–Watson kernel smoother, which allows to estimate the aggregated Sobol’ indices from a given random sample of small to moderate size. Due to the limited size of the sample, the kernel estimation is biased. Therefore, we propose a bootstrap based bias correction before selecting the bandwidth by cross-validation. To estimate the aggregated Sobol’ indices, we reduce the dimension of the output using principal components analysis. After different test cases showing the efficiency of our approach, it is applied to a real avalanche case. Results show that the friction parameters and the snow depth in the release zone are the most influential parameters determining the avalanche characteristics.

Performance prediction of the tangentially fired pulverised-Coal boiler furnace using a mathematical model and its validation

ABSTRACT A simple thermodynamic model is developed for performance prediction for a tangentially fired pulverized-coal boiler furnace. For this purpose, the furnace is sliced into number of zones of rectangular parallelepiped. These zones are further divided into heat release zones and non-heat release zones. The major sub-routines of the program include framing equations for the definition of the heat release zones, a reasonably approximate flow model to simulate tangential firing, radiation formulation and equations for the calculation of emissivity of CO2 and H2O. A few of the inputs required for this model have been obtained from offline-CFD simulations. The solution for the model’s equations is obtained using the Newton Raphson method. The outputs of the program include the variation of the heat flux along with the height of the boiler furnace and furnace exit gas temperature (FEGT). The influence of operating conditions on the furnace in terms of its performance is also studied. The FEGT predicted using the mathematical model is in fairly good agreement with the site measured data. The model can be used as an effective tool by powerplant operators to optimize the performance of the boiler furnace.

Conventional tagging of sharks in Western Australia: the main commercial species exhibit contrasting movement patterns

Understanding movement patterns underlies effective management and conservation measures. The current study summarises the main findings from a tagging program of Western Australian sharks to provide insights into the movement patterns of the main commercial shark species: dusky (Carcharhinus obscurus), sandbar (C. plumbeus), gummy (Mustelus antarcticus) and whiskery (Furgaleus macki) sharks. Between 1993 and 2020, >12 000 individuals from 52 taxonomic groups were implanted with conventional tags in Western Australia, of which 8.5% were recaptured. Most of the tagged (74.5%) and recaptured (95.8%) individuals belong to the four main commercial shark species. Recaptured individuals of these species, as well as tiger (Galeocerdo cuvier) and bronze whaler (C. brachyurus) sharks showed displacements of >1000 km and rates of movement (ROMs) of >10 km day–1, with the exception of whiskery sharks, which showed much slower ROMs (<3 km day–1). Despite tagged dusky and sandbar sharks being predominately small individuals and gummy and whiskery sharks being large individuals, dusky and sandbar sharks had faster ROMs and a greater proportion of recaptures outside the release zone. Our study provided the information required for estimating movement rates across different fishing zones and therefore defining the spatial scale for managing these shark species.

Numerical Simulation of Emergency Release of Liquid Petroleum Gas on a Car Gas Station

LPG storage tanks may be seriously threatened by a fire coming from nearby fuels or by leakage appearance. The aim of the study was to prepare a three-dimensional model of LPG release on a car gas station under different environmental conditions. CFD simulations of liquid and gas phase release from a tank localized on a car gas station was performed. First, ALOHA software was applied to determine mass flow rate, while Ansys software was used to determine the shape and size of hazardous zone. To reflect real condition atmospheric stability classes were applied. It was observed that for classes A-D the hazardous zone was decreasing. While, for E and F class the range was increased. It was noticed that the location of the leakage affects the extent of the danger zone. For the leaking below the liquid surface analyzed LPG has liquid form. While, for the leaking above the liquid surface analyzed LPG has gas form. Furthermore, for liquid leakage the largest hazard zone of release was observed.

Relationships between Potential Risk of Hazardous Material Releases and Socio-Economic Demographic Characteristics Using Geospatial Analysis

The problem investigated in this research is about the potential risk of technological hazards, which poses a perilous threat to humankind and the environment. Rapid urbanization has been increasing the population density in an area, elevating the risk of exposure to technological disasters. Therefore, it is necessary to detect the areas with higher chemical risk to spread awareness about the potential risk zones and reduce actual damage and casualties resulting from the hazardous substance events. The basic design of the study utilizes geospatial analysis to map the TRI (Toxics Release Inventory) facilities in the communities of Texas to establish a relationship between potential hazardous material release zones and the human population at risk. The study identified the vulnerable counties as well as investigated how those risk areas are related to race/ethnicity, income and education. The research would contribute to the policymakers acting on the hazard situation and keep them better prepared for chemical hazards. In addition, it would help the residents and emergency managers to better understand the circumstance to mitigate the consequences as well as increase their awareness to be ready for the uncertainties in the hotspots involved in high risk of the hazards.

ОЦЕНКА ЭФФЕКТИВНОСТИ ПРОТИВОЛАВИННЫХ МЕРОПРИЯТИЙ НА ГОРНОЛЫЖНОМ КУРОРТЕ «КРАСНАЯ ПОЛЯНА»

For the first time, a qualitative and quantitative evaluation of the effectiveness of anti-avalanche measures was carried out for the territory of the «Krasnaya Polyana» ski resort, located in the Western Caucasus on the Aibga ridge. The following materials were used for this work: the results of field survey in 2019, which made it possible to map the resort's infrastructure exposed to possible snow avalanches and protected by existing preventive (anti-avalanche) measures, experience of similar studies from other regions as well as identification of the avalanche release zones by means of digital elevation model and analysis of remote sensing data, archive data on the snow avalanches regime at the site, and numerical modeling of the snow avalanches with different starting conditions. Modeling of the avalanches was performed in the RAMMS program basing on three scenarios: 1) taking account of the successful operation of existing anti-avalanche measures; 2) with regard for the failures in the work of existing anti-avalanche measures that were recorded earlier during the operation of the resort; 3) without considering any anti-avalanche measures, which corresponded to the conditions at the stage of the territorial planning of the resort. Differences in the impact of simulated avalanches on the resort infrastructure were interpreted as «high», «medium» and «low» effectiveness of existing antiavalanche measures. It was found that the dynamical characteristics of the local avalanches (run-out distance, volume, velocity, and pressure) had different importance for different types of the infrastructure with regard to the effectiveness of anti-avalanche measures. Under existing conditions of the relief, climate and vegetation of the investigated territory the artificial triggering (at the ski resort it is mainly made by the Gazex systems) is the most efficient. Snow-retaining structures often do not perform their functions, while dams and avalanche cutters can be successful only in combination with the properly functioning artificial triggering. It was found that there are areas where the run-out distance of artificially controlled avalanches is smaller than that of possible natural avalanches, and these areas can still be dangerous for the infrastructure of the resort due to the high values of the avalanche speed and pressure.

N-cadherin localization in taste buds of mouse circumvallate papillae.

Taste buds, the receptor organs for taste, contain 50-100 taste bud cells. Although these cells undergo continuous turnover, the structural and functional integrity of taste buds is maintained. The molecular mechanisms by which synaptic connectivity between taste buds and afferent fibers is formed and maintained remain ambiguous. In the present study, we examined the localization of N-cadherin in the taste buds of the mouse circumvallate papillae because N-cadherin, one of the classical cadherins, is important for the formation and maintenance of synapses. At the light microscopic level, N-cadherin was predominantly detected in type II cells and nerve fibers in the connective tissues in and around the vallate papillae. At the ultrastructural level, N-cadherin immunoreactivity appears along the cell membrane and in the intracellular vesicles of type II cells. N-cadherin immunoreactivity also is evident in the membranes of afferent terminals at the contact sites to N-cadherin-positive type II cells. At channel type synapses between type II cells and nerve fibers, N-cadherin is present surrounding, but not within, the presumed neurotransmitter release zone, identified by large mitochondria apposed to the taste cells. The present results suggest that N-cadherin is important for the formation or maintenance of type II cell afferent synapses in taste buds.

Dynamics of laser plasma convective plume in high pressure xenon

This paper presents the results of numerical simulation of convective plume pulsations from a concentrated heat source equivalent to a continuous optical discharge (COD) in high pressure xenon compared to originally obtained experimental results. Simulated dynamic distributions of temperature, density and velocity of the gas around small spheroidal heat release zone are obtained, showing the process of formation of toroidal vortices in the convection zone, leading to the appearance of pulsations. The simulation results are qualitatively and quantitatively consistent with previously obtained experimental data.

Оценка амплитуды давления на преграду продуктов недосжатой уходящей детонационной волны структурированного заряда

The study relies on the concepts of various mechanisms of explosives decomposition at supersonic propagation of the under-compressed detonation reaction zones, and examines the structured charges explosion effect on compressible obstacles. In such charges, artificially or naturally, there can appear rod-like formations highly capable of detonation, penetrating the charge and ensuring the propagation of the complete heat release zone at a speed greater than the normal, and the ideal detonation speed of a monodisperse charge is of the same density. We introduce a simple algebraic model of the explosive process of structured charges, the process proceeding in the form of under-compressed detonation. We obtained algebraic expressions that make it possible to compare the peak pressures at the obstacles depending on the direction of detonation propagation relative to the obstacle and on the mode of detonation, i.e. whether it is normal or “under-compressed”.

Effect of hydrogen enrichment on flame broadening of turbulent premixed flames in thin reaction regime

An experimental study to identify the effect of hydrogen enrichment and differential diffusion on the flame broadening is conducted. Turbulent lean premixed flames in the Broadened Preheat–Thin Reaction (BP-TR) regime are obtained. The flames are stabilized on a Bunsen burner and CH4/H2/air mixtures are adopted with three hydrogen fractions of 0, 30% and 60%. The preheat zone and heat release zone are captured with the multi-species Planar Laser-Induced Fluorescence (PLIF) of OH and CH2O radicals. Flame thicknesses of the preheat and heat release layers are measured. Results show broadened preheat zone and thin heat release layers for the flames, as predicted by the BP-TR regime. The preheat zone thickness can be increased to about 3–6 times compared to the laminar preheat thickness. An apparently decreased preheat zone thickness with hydrogen addition is observed. The differential diffusion is anticipated to locally thicken the heat release zone along the flame front. The mean heat release thickness is nearly not affected by the turbulence or hydrogen addition.

Using spatial genetics to quantify mosquito dispersal for control programs

BackgroundHundreds of millions of people get a mosquito-borne disease every year and nearly one million die. Transmission of these infections is primarily tackled through the control of mosquito vectors. The accurate quantification of mosquito dispersal is critical for the design and optimization of vector control programs, yet the measurement of dispersal using traditional mark-release-recapture (MRR) methods is logistically challenging and often unrepresentative of an insect’s true behavior. Using Aedes aegypti (a major arboviral vector) as a model and two study sites in Singapore, we show how mosquito dispersal can be characterized by the spatial analyses of genetic relatedness among individuals sampled over a short time span without interruption of their natural behaviors.ResultsUsing simple oviposition traps, we captured adult female Ae. aegypti across high-rise apartment blocks and genotyped them using genome-wide SNP markers. We developed a methodology that produces a dispersal kernel for distance which results from one generation of successful breeding (effective dispersal), using the distance separating full siblings and 2nd- and 3rd-degree relatives (close kin). The estimated dispersal distance kernel was exponential (Laplacian), with a mean dispersal distance (and dispersal kernel spread σ) of 45.2 m (95% CI 39.7–51.3 m), and 10% probability of a dispersal > 100 m (95% CI 92–117 m). Our genetically derived estimates matched the parametrized dispersal kernels from previous MRR experiments. If few close kin are captured, a conventional genetic isolation-by-distance analysis can be used, as it can produce σ estimates congruent with the close-kin method if effective population density is accurately estimated. Genetic patch size, estimated by spatial autocorrelation analysis, reflects the spatial extent of the dispersal kernel “tail” that influences, for example, the critical radii of release zones and the speed of Wolbachia spread in mosquito replacement programs.ConclusionsWe demonstrate that spatial genetics can provide a robust characterization of mosquito dispersal. With the decreasing cost of next-generation sequencing, the production of spatial genetic data is increasingly accessible. Given the challenges of conventional MRR methods, and the importance of quantified dispersal in operational vector control decisions, we recommend genetic-based dispersal characterization as the more desirable means of parameterization.

Effects of CO2 dilution on partially premixed CH4-air flames in swirl and bluff body stabilized combustor

The effect of CO2 dilution on the flame characteristics and pollutant emission of a partially premixed CH4-air flame in a confined bluff body and swirl influenced flowfield is investigated using optical and laser diagnostic methods. The non-premixed burner produced a converging-diverging flowfield at the burner exit and a lifted flame is produced at all test cases, with an upstream movement of the flame with decreasing global equivalence ratios (ϕg). Based on variations in ϕg, two flame stabilization modes – bluff body influenced and swirl stabilized – with a transition mode in-between is observed for the cases with (flame FB) and without dilution (flame FM). The characteristics of the heat release zone are influenced by dilution, with the FB flames being longer and also less intense when compared to FM flames. Pollutant measurement at 30 mm downstream from the combustor exit highlighted the ultra-low NOx capability of the IIST-GS2 burner. CO2 dilution leads to a reduction in NOx emission due to both thermal and chemical effects. For ϕg ≥ 0.7 extreme low levels of CO and unburned hydrocarbons (UHC) are observed for both cases. For ϕg ≤ 0.6 the dramatic increase of both CO and UHC maybe due to the lower flame temperatures and shorter flame zone residence times, respectively.

On the Nature of the Synergistic Effect in Flames of Methane and Formaldehyde Mixtures with Air

This paper deals with the nature of the synergistic effect in flames of methane and formaldehyde mixtures with air. Combustion of mixtures of different fuels is of great practical and fundamental interest. It has been found that the addition of formaldehyde to a rich methane/air flame at a constant concentration of methane first reduces the flame speed and then begins to increase it. The synergism mechanism in this case is due to the predominant and complete consumption of formaldehyde due to its higher reactivity and its negative impact on the rate of methane consumption. The predominant combustion of one of the fuels leads to the existence of two spatially separated heat release zones in the flame. In the first zone, heat release is mainly due to the oxidation of formaldehyde and formyl radical, and in the second zone, it is due to the recombination of methyl radicals. An analysis of the flame speed sensitivity has shown that the key reactions affecting the flame speed are the stages of formation of radicals (mainly hydroxyl) or products that lead to their formation. Reactions that make the main contribution to the heat release generally do not affect the flame speed. It has been found that the interaction of two fuels CH4 and CH2O in a mixture with air leads to a marked increase in the superadiabatic temperature effect.

Heat release zones in turbulent, moderately dense spray flames of ethanol and biodiesel

This paper extends the application of laser-induced fluorescence imaging of OH & CH2O (LIF-OH-CH2O) to provide a measure of heat release zones in turbulent, moderately dense spray flames of ethanol and biodiesel fuels. A custom filter is used to remove interference from stimulated Raman scattering arising from the liquid fragments. Mie scattering is measured jointly on a separate camera to co-locate the fluid fragments with respect to the reaction zones. It is found that while the overall spray flame structure is similar to that of a turbulent gaseous diffusion flame, additional complexities arise due to the continuous release of fresh fuel vapor from the evaporating fragments. Structures referred to as burning rings of different sizes are observed, and these are ignited by interfacing with a hot edge before they grow, propagate, and burnout. Statistics on the occurrence of these rings, with and without clouds of liquid fragments within them, are presented. These findings are common to both ethanol and biodiesel, although measurements in the latter were affected by strong fluorescence interference from the excited components in the biodiesel blend.

Structure and propagation of n-heptane/air premixed flame in low temperature ignition regime

This paper presents a large eddy simulation of n-heptane/air turbulent premixed combustion in a reactor assisted turbulent slot (RATS) burner under different preheating conditions. N-heptane/air mixture at an equivalence ratio of 0.6, pressure of 1 atm and temperature of 600, 650 and 700 K is considered to investigate the effect of low temperature chemistry on turbulent burning velocities and flame regimes, including chemically frozen (CF) regime where the fuel/air mixture inside the burner is chemically frozen, low temperature ignition (LTI) regime where the fuel/air mixture inside the burner undergoes LTI reactions, and transition regime from CF to LTI. The results show that the flame in the LTI regime exhibits the highest turbulent burning velocity. Differential diffusion is found to play an important role in the LTI regime whereas it is less important in the CF regime. To investigate the effect of LTI reactions on the flame, a series of two-dimensional laminar flames are simulated, in which the effect of turbulence on the flames is eliminated. The results show that in the LTI regime, the laminar burning velocity is drastically enhanced and the heat release zone is broadened. Budget term analysis shows that the enhanced rate of production and diffusion towards the preheat zone of the flames and the smaller gradient of reactant mass fraction are the main reasons behind the increased laminar burning velocity in the LTI regime.

Spatial structural characteristics of a combustion flow field in an ethylene-fueled supersonic combustor with a rear-wall-expansion cavity

A hybrid large eddy simulation (LES)/assumed subgrid probability density function (PDF) closure model was employed to investigate the structural characteristics of the combustion flow field in an ethylene-fueled supersonic combustor with a rear-wall-expansion cavity. The wall pressure distribution from numerical simulation was compared with experimental data, and the numerical results are in good agreement with the experimental data. The spatial distribution characteristics of combustion heat release in the flow field are obtained from the simulation results. The reaction heat release zone is mainly distributed in the cavity. The cavity shear layer forms a concentrated reaction zone that produces a large amount of chemical heat release, thus further maintaining local stable combustion and forming a flame base. The front part of the cavity shear layer has the highest temperature in the whole flow field. There is still excess fuel reaching the cavity rear wall and producing a certain intensity of reaction. In addition, a dispersed small flame intermittently forms in the downstream near-wall region. The premixed combustion mode dominates the cavity recirculation zone, while the combustion in the downstream region evidently shows a non-premixed mode.

Snow avalanche detection and mapping in multitemporal and multiorbital radar images from TerraSAR-X and Sentinel-1

Abstract. Snow avalanches can endanger people and infrastructure, especially in densely populated mountainous regions. In Switzerland, the public is informed by an avalanche bulletin issued twice a day during winter which is based on weather information and snow and avalanche reports from a network of observers. During bad weather, however, information about avalanches that have occurred can be scarce or even be missing completely. To assess the potential of weather-independent radar satellites, we compared manual and automatic change detection avalanche mapping results from high-resolution TerraSAR-X (TSX) stripmap images and medium-resolution Sentinel-1 (S1) interferometric wide-swath images for a study site in central Switzerland. The TSX results were also compared to available mapping results from high-resolution SPOT-6 optical satellite images. We found that avalanche outlines from TSX and S1 agree well with each other. Cutoff thresholds of mapped avalanche areas were found with 500 m2 for TSX and 2000 m2 for S1. S1 provides a much higher spatial and temporal coverage and allows for mapping of the entire Alps at least every 6 d with freely available acquisitions. With costly SPOT-6 images the Alps can even be covered in a single day at meter resolution, at least for clear-sky conditions. For the SPOT-6 and TSX mapping results, we found a fair agreement, but the temporal information from radar change detection allows for a better separation of overlapping avalanches. Still, the total mapped avalanche area differed by at least a factor of 3 because with radar mainly the avalanche deposition zone was detected, whereas the release zone was very visible already in SPOT-6 data. With automatic avalanche mapping we detected around 70 % of manually mapped new avalanches, at least when the number of old avalanches is low. To further improve the radar mapping capabilities, we combined S1 images from multiple orbits and polarizations and obtained a notable enhancement of resolution and speckle reduction such that the obtained mapping results are almost comparable to the single-orbit TSX change detection results. In a multiorbital S1 mosaic covering all of Switzerland, we manually counted 7361 new avalanches which occurred during an extreme avalanche period around 4 January 2018.

Three-Dimensional Numerical Simulation of a Flow Structure in the Asynchronous Polar CD Ind in the Approximation of an Offset Dipole Magnetic Field of a White Dwarf

The flow structure in the asynchronous polar CD Ind was investigated in the approximation of an offset dipole. Computation results made it possible to identify such system features as the drift of hot spots over the white dwarf surface, the flow structure dependence on the phase of the beat period, and the magnetic pole switching. To study the flow structure, a three-dimensional numerical MHD model based on the approximation of modified magnetic hydrodynamics was used. Numerical calculations were performed for ten phases of the beat period at a constant rate of mass transfer. In addition, for a more detailed study of the poles switching, additional calculation series were carried out in the corresponding phase ranges of the beat period. The energy release zones during the spin-orbit period shift in longitude on average by 20°, which corresponds to 0.05 of the orbital period phase. The magnetic pole switching occurs in a time that does not exceed 0.1 of the beat period. In the middle of this process, accretion occurs on both poles with the same intensity, and the flow resembles an arch. Based on the calculation results, synthetic light curves were constructed for the optical range of the spectrum.