Semi-confined Environment Research Articles

Semi-autonomous sensor fusion-based strategy for unmanned aerial atmospheric surveillance system in open field environments

<p>This paper explores the convergence of semi-autonomous systems and sensor fusion for monitoring hazardous atmospheric substances in open and semi-confined environments such as open-pit mines. As the heart of this system, a universal and flexible device leveraging wireless technologies to collect and analyze large volumes of data, designed by the authors, is proposed. The article outlines the key components of the platform, emphasizing its potential for increasing personnel safety levels as stipulated by the international public exposure guidelines. In modern mines, it becomes crucial to monitor elevated concentrations of nitrogen and carbon oxides, as well as other pollutants after blasting and the toxic gas emissions produced by the heavy transportation equipment such as mining trucks and excavators. In this paper, industrial-grade electrochemical sensors are compared with price-affordable but less precise microelectrochemical ones. The performed experiments for lowering computational requirements show promising results. The integration of an ultrasonic anemometer enhances the system’s capabilities, contributing to a comprehensive understanding of atmospheric conditions. In parallel, the research discusses the role of computer vision in autonomous control systems, with a focus on the architecture and processing pipeline of the state-of-the-art system-on-module Kria by AMD. Advocating the potential of adaptive computing for enhanced efficiency in dynamic environments, the paper underlines the importance of the integrated approach in developing a semi-autonomous atmospheric surveillance system and highlights the impact of adaptive computing in dynamic scenarios. The main part of the measuring equipment and methods has been experimented with in real conditions in open-pit mines in Bulgaria. This is an initial phase of ongoing research aimed at serving as a foundation for future improvements and the elaboration of a fully autonomous prototype for hazardous substances evaluation in the atmosphere of open-pit mines.<strong></strong></p>

Trumpet-shaped diffuse plasma jet in a semi-confined environment

Abstract This paper reports a unique trumpet-shaped diffuse plasma jet (TDPJ) with a caliber exceeding 30 mm in a semi-confined environment, which is larger than the diameter of existing atmospheric pressure plasma jets (APPJs) in an open environment. The morphology of the TDPJ is attributed to the influence of the electric field on the development characteristics of ionization waves in the ambient environment. High-speed ICCD camera images show that the plasma bullets in the TDPJ have a completely different propagation trajectory compared to the APPJ. Different shapes of diffuse plasma jets can also be formed by adjusting the doping gas, which is due to the Penning ionization and consistent with the impact of the electric field. This research reveals the long-neglected effect of the electric field on ionization waves and provides a way to manipulate the morphology of plasma jets efficiently. The generation mechanism of the TDPJ can provide preliminary guidance for the effective medical treatment of plasma jets in semi-confined environments, such as human internal organs.

Experimental and numerical analysis of low-density gas dispersion characteristics in semi-confined environments

Hydrogen, as a clean fuel, offers a practical pathway to achieve net-zero targets. However, due to its physical and chemical characteristics, there are some safety concerns for large-scale hydrogen utilisation, particularly in process safety management. Leakage of gaseous hydrogen, especially in semi-confined spaces such as tunnels, can lead to catastrophic outcomes including uncontrolled fire and explosion. The current paper describes the outcome of an experimental and numerical study that aims to understand the dispersion of leaked light gas in a semi-confined space to support the adoption of hydrogen. A dispersion chamber with dimensions of 4m × 0.3m × 0.3m was constructed to investigate a baseline gas leakage scenario. To reduce the risk of the experiment in the laboratory, helium is utilised as a surrogate for hydrogen. Computational fluid dynamics simulations are conducted using FLACS-CFD to model the dispersion of leaked gas in different scenarios focusing on the impact of the ventilation velocity, leakage rate, and slope. The results from comprehensive numerical simulations show that ventilation is a critical safety management measure that can significantly reduce the growth of flammable clouds and mitigate the fire and explosion risk. Even with the lowest ventilation velocity of 0.25 m/s, an improvement in the gas concentration level of 29.34% can be achieved in the downstream chamber. The current results will help to further enhance the understanding of hydrogen safety aspects.

Biodiversity and conservation correlation in the case of a Roman fresco located in a semi-confined environment

The subterranean heritage includes both natural and built sites with a strong cultural and historical fingerprint, some of each being enriched with painted surfaces. These semi-confined environments shelter specific and fragile biodiversity. This paper is focused on the case of a Roman painting (2nd-3rd century AD) located in an underground archaeological site in Marino Laziale, near Rome, which was opened to the public for the first time in 2021. The painted Mithraic scene is in a good state of conservation. The methodological approach included on site and laboratory investigations aimed to screen the main biological components associated to this hypogeum monument. The observed biodiversity included heterotrophic and chemolithotrophic microorganisms, and a mesofauna composed of eutroglophile and subtroglophile species, characteristic for many subterranean environments. The ecological mechanisms and the conservation state of the work of art were analyzed for planning the best fruition practices. The aesthetic change, the possible mechanical damages induced by various organisms, and the presence of significant amounts of organic matter, represent the main risks for painting conservation. These aspects, beside the new possible risks associated with the presence of visitors, are under a constant and ongoing conservation surveillance program.

Detonation process of high-speed flowing multiphase energetic mixture under high temperature and high pressure

The detonation process of high-speed flowing multiphase energetic cloud in a high-temperature and high-pressure semi-confined environment has extensive engineering backgrounds, and is a common form of energy output. A two-dimensional combustor model is established to numerically study the process and propagation laws of hexogen/air explosion, isopropyl nitrate/air explosion and hexogen/isopropyl nitrate/air explosion under 600 m/s flow. The results show that the high-speed flowing multiphase cloud will be subject to a first and second explosion under high temperature and high pressure. Under different concentrations of hexogen/air, the first explosion pressure of mixture is about 1.32 MPa; the second explosion pressure is 1.68–3.11 MPa and the peak temperature is 2732–4084 K, which first increase and then flatten with the increase of hexogen concentration. Under different concentrations of isopropyl nitrate/air, the first explosion pressure is about 1.28 MPa; the second explosion pressure is 1.59–6.49 MPa and two peak temperatures appear obviously during the explosion process, which increase with the increasing isopropyl nitrate concentration. For the three-phase mixture under hexogen: isopropyl nitrate=1:1, the detonation pressure and temperature increase with the increase of mixture concentration. Compared with hexogen/air, hexogen/isopropyl nitrate/air mixture has better detonation performance at high concentration (>1800 g/m3). The detonation performance of hexogen/isopropyl nitrate/air mixture at hexogen ratio ≤30% is similar to that of pure hexogen/air, and at proportion ≥40% is close to that of pure isopropyl nitrate/air. As the hexogen ratio increases, the explosion pressure and temperature of three-phase cloud present an inverted 'V' shape and reach the maximum when the hexogen ratio accounts for 90% of the multiphase mixture, which indicates that the detonation process of the three-phase hexogen/isopropyl nitrate/air mixture is the mutual coupling of decomposition exothermic reaction of hexogen and oxidation reaction of isopropyl nitrate and oxygen.

Experimental investigation of the confinement effect on a flame impinging a ceiling in an enclosure

This experimental study highlights the confinement effect on a flame impinging a ceiling in confined or semi-confined environment. The enclosure used in this study represents a 1:10 scale model of a student compartment with two possible openings: a door and a window. It is developed based on the conservation of the Froude number in scaling law. The objective of this work is to provide explanations in terms of fire safety on thermal phenomena that can occur during fires in closed environments, for example in a room of a university residence, regarding eight heat rates release of fuel and five confinement levels. A flame oscillation modelling of propane-air flame is proposed and is verified by the experimental results. It is shown both by theoretical modeling and experimental results that the confinement of a compartment has an effect on period time of flame oscillation. Moreover, experimental results show that the confinement level of compartment is a key parameter to characterize vertical temperature evolution both in the center (impinging zone) and near the wall in the enclosure. The correlations for normalized gas temperature rise near the wall are proposed and these temperature evolutions are bounded by the ventilation conditions of the five configurations. Indeed, under condition of equivalence ratio greater than 1, the maximum gas temperature near the wall of a certain heat release rate decreases dramatically with the increasing of configurations' confinement levels, which is associated to the decrease in flame intensity by lack of oxygen with a great criterion of under ventilation.

The nature of flammable cloud volumes in semi-confined environment under the influence of flow of air

In the Explosion Risk Analysis (ERA), ventilation and dispersion calculations using Computational Fluid Dynamics (CFD) are usually used when the level of confinement and congestion cannot be neglected. As far as the dispersion analysis is considered, alternative approaches are sought when a large number of simulations is required. Setting many scenarios and simulate them all is not always suitable within the time-frame of real engineering design. As a result, semi-empirical dispersion models and several procedures based on statistical approaches using CFD have been proposed by other researchers to improve the robustness and the accuracy of prediction of the flammable gas cloud volume. In addition, despite the use of Response Surface Method (RSM) and Frozen Cloud Approach (FCA), it is convenient to address the problem on the basis of the physics underlying the dispersion of a scalar in the chemical process area. In this work we developed a novel mathematical approach for dispersion calculations based on CFD data. We propose a new dimensionless number balancing the transport of the flammable cloud and the accidental leak rate. Numerical experiments have shown that the dimensionless number is related to the angle of the wind direction as the angles in a circle are related to the phase angle in a sine wave Vˆ≈sin(kφπ+β), where Vˆ is the non-dimensional flammable cloud volume and φ the phase angle. The effect of wake wind is investigated and there seems to be no preferable wind direction that leads to the largest cloud volume in the module for the geometry considered in the current research.

Large eddy simulation of explosion deflagrating flames using a dynamic wrinkling formulation

Reliable predictions of flames propagating in a semi-confined environment are vital for safety reasons, once they are representative of accidental explosion configurations. Large eddy simulations of deflagrating flames are carried out using a dynamic flame wrinkling factor model. This model, validated from a posteriori analysis, is able to capture both laminar and turbulent flame regimes. At early stages of the flame development, a laminar flame propagates in a flow essentially at rest and the model parameter is close to zero, corresponding to a unity-wrinkling factor. Transition to turbulence occurs when the flame interacts with the flow motions generated by thermal expansion and obstacles. The model parameter and wrinkling factor take higher values at these stages. Three configurations investigated experimentally by Masri et al. 2012, corresponding to different scenarios of flame acceleration are simulated. The first case (OOBS) is characterized by a long laminar phase. In the second one (BBBS) the flame is the most turbulent and the highest overpressure is observed in the vessel. For the last case (BOOS), the flame front is relaminarized after crossing the first row of obstacles. In all configurations, large eddy simulations (LES) predict the flow dynamics and maximum overpressure with good accuracy.

Palazzi, E.; Currò, F.; Fabiano, B. Accidental Continuous Releases from Coal Processing in Semi-Confined Environment. Energies 2013, 6, 5003–5022

The authors wish to make the following corrections, due to typographical errors, to this paper [1]. [...]

Accidental Continuous Releases from Coal Processing in Semi-Confined Environment

Notwithstanding the enforcement of ATEX EU Directives (94/9/EC of 23 March 1994) and safety management system application, explosions in the coal sector still claim lives and cause huge economic losses. Even a consolidated activity like coke dry distillation allows the opportunity of preventing explosion risk connected to fugitive emissions of coke oven gas. Considering accidental releases under semi-confined conditions, a simplified mathematical approach to the maximum allowed gaseous build-up is developed on the basis of the intrinsic hazards of the released compound. The results will help identifying and assessing low rate release consequences therefore to set-up appropriate prevention and control measures. The developed methodology was tested at the real-scale and validated by numerical computational fluid dynamics (CFD) simulations showing the effectiveness of the methodology to evaluate and mitigate the risk connected to confined hazardous releases.

Microclimate monitoring of Ariadne’s house (Pompeii, Italy) for preventive conservation of fresco paintings

BackgroundAriadne’s house, located at the city center of ancient Pompeii, is of great archaeological value due to the fresco paintings decorating several rooms. In order to assess the risks for long-term conservation affecting the valuable mural paintings, 26 temperature data-loggers and 26 relative humidity data-loggers were located in four rooms of the house for the monitoring of ambient conditions.ResultsData recorded during 372 days were analyzed by means of graphical descriptive methods and analysis of variance (ANOVA). Results revealed an effect of the roof type and number of walls of the room. Excessive temperatures were observed during the summer in rooms covered with transparent roofs, and corrective actions were taken. Moreover, higher humidity values were recorded by sensors on the floor level.ConclusionsThe present work provides guidelines about the type, number, calibration and position of thermohygrometric sensors recommended for the microclimate monitoring of mural paintings in outdoor or semi-confined environments.

Microscopy and Molecular biology techniques for the study biocenosis diversity in semi-confined environments

This study is part of a wider conservation project of artistic and anthropological finds located in the Grotto of the Saints (Licodia Eubea, Alia, Sicily), and represents an opportunity for investigating the micro-and macro biological systems colonizing this particular environment. It is well-known that the bio-receptivity of surfaces is strongly related to its constituent materials and environmental parameters, whose effects promote the establishment of specific biotic communities. This is particularly true for caves, hypogea and semi-confined environments and, in particular for the Grotto of the Saints, where besides the presence of different nutrient sources, there are also high humidity values, percolating water and an aerobiological exchange with the surrounding countryside. Moreover, the weathering of this structure is enhanced by the canyon effect of the wind and the day-night temperature range. The identification and characterization of the biocenosis present in this environment was performed combining microscopy (optical, fluorescent, CLSM) and molecular biology analysis (DNA sequences). The aim was to identify the biological systems able to trigger the degradation processes, in order to plan their growth control and to prevent the colonization of the entire environment.

Microclimate inside a semi-confined environment: Valuation of suitability for the conservation of heritage materials

Abstract The microclimatic analysis of the Petrarca's tomb in Arqua Petrarca, Padua (Italy) was performed to assess the suitability of a closed environment located outdoors respect to the conservation requirements of heritage materials. Results showed that the thermo-hygrometric conditions inside the tomb were not suitable for the conservation of organic materials, like bones and wood. The orientation (north or south) was the main responsible for the different damage features of the two sides of the wooden case housing the human remains inside the tomb. Technical solutions were finally implemented to improve the conservation conditions, thus avoiding further damage.

An integrated approach to assess air pollution threats to cultural heritage in a semi-confined environment: The case study of Michelozzo's Courtyard in Florence (Italy)

An example of an integrated approach to assess air pollution threats to cultural heritage in a semi-confined environment is presented in this work, where the monitoring campaign carried out at the Michelozzo's Courtyard (in Palazzo Vecchio, Florence, Italy) is used as a case study. A wide research project was carried out, with the main aim of obtaining the first quantitative data on air quality and microclimate conditions inside the Courtyard, and, if possible, identifying the main causes of degradation and suggesting appropriate conservation strategies. The investigation adopted a holistic approach involving thermographic measurements on the wall paintings, microclimatic analysis, gaseous pollutant monitoring, atmospheric particles characterisation and dry deposition compositional analysis. Attention was focused on the wall painting depicting the city of Hall because of its anomalous and critical conservation conditions, which are visible at a glance, due to the contrast between a wide darker zone around the central subject of the painting and external lighter areas.

An inter-comparison exercise on CFD model capabilities to simulate hydrogen deflagrations in a tunnel

Abstract In the frame of the European Commission co-funded Network of Excellence HySafe (Hydrogen Safety as an Energy Carrier, www.hysafe.org ), five organizations with significant experience in explosion modelling have performed numerical simulations of explosions of stoichiometric hydrogen–air mixtures in a 78.5 m long tunnel. The five organizations are the Karlsruhe Research Centre, GexCon AS, the Joint Research Centre, the Kurchatov Institute Research Centre and the University of Ulster. Five CFD (Computational Fluid Dynamics) codes with different turbulence and combustion models have been used in this Standard Benchmark Exercise Problem (SBEP). Since tunnels are semi-confined environments, hydrogen explosions in tunnels can potentially be critical accident scenarios from the point of view of the accident consequences and CFD methods are increasingly employed to assess explosions hazards in tunnels. The objective of the validation exercise is to assess the accuracy of the theoretical and numerical models by comparisons of the simulation results with the experimental data. A very good agreement between experiments and simulations was found in terms of maximum overpressures.

Nature mineralogique et origine des glauconies du plateau continental du Gabon et du Congo

RÉSUMÉSur le plateau continental du Congo et du Gabon, on constate la formation de goethite, de berthiérine et de glauconies (smectite et glauconite). La berthiérine caractérise un milieu deltaïque a sedimentation active; les glauconies se forment sur le plateau continental à plus grande profondeur (—50à—300m). Dans un milieu original granulaire (généralement des coprolites) tous les stades d'une succession minéralogique depuis la kaolinite jusqu'à un minéral voisin de la glauconite ont été décelés. Cette formation passe nécessairement par le stade smectite ferrifère. La formation préalable de granules crée un milieu semi‐confiné remarquable qui est, ici, la condition primordiale des évolutions minérales.

Visualization Of Reacting Gas Flows OnNon-structured Grids

A software package TURCOM has been developed to visualize the results of 2-d fluid dynamics modelling on non-structured grids. This software is written in the PV-WAVE command language [1] and runs on most graphic workstations. Calculations are performed of chemically reacting gases within containers of variable geometry [2]. A database is used to store the results together with the grid geometry [3]. This database is accessed by TURCOM via mouse-driven menus and icons. An objective of this work has been to avoid interpolation onto regular grids. Therefore some new algorithms have been developed to present the results of model calculations graphically. Scalar fields can be displayed as iso-contours or as colour shaded iso-plots. Vector fields can be displayed as vector flows with or without a scalar colour index. Visualization of the time evolution of data is also possible. Introduction A research project for the Numerical Simulation of Reactive Gas Flows [4] is in progress at the JRC-lspra. It's primary aim is. to predict the development of explosions in confined or semi-confined environments. This involves simulating shock wave propagation and reflection from container walls. The calculations are performed on a non-structured grid in two dimensions. Complex geometries are defined by a mesh of node points and by triangular finite elements. Two examples of such mesh grids are shown in fig.1. In general a 2-d non-structured grid can be defined as follows: #„,*,;• = 1, a) / (C,c,c.) j = i,N (2) Transactions on Information and Communications Technologies vol 5, © 1993 WIT Press, www.witpress.com, ISSN 1743-3517 406 Visualization and Intelligent Design where: N^ = no. of nodes, x= position vector of node i Ny = no. of triangular elements , C /2// ) = end node indices for j th face in the i th boundary Some further geometric properties of such triangular grids are found to be useful. These are indexed for each node and deduced by a sorting procedure. They are: L} = 0: if node is internal = m: if it forms part of boundary m NP= number of triangles with this node as a vertex { V .. } = triangle index connecting this node ji j = i,MP. ^ ordered anti-clockwise This is illustrated in fig. 2. Transactions on Information and Communications Technologies vol 5, © 1993 WIT Press, www.witpress.com, ISSN 1743-3517 Visualization and Intelligent Design 407 Figure 2 also defines what is known as the control volume for this node. The fluid calculations are discretised within these control volumes. This means that the resultant physical properties for each node point apply for all fluid within the control volume. These control volumes are therefore also important when visualizing the results of calculations. They are defined geometrically as the polygon formed by joining the mid-points of each triangle associated with a given node. The mid-point of each triangle is calculated from the intersection of lines bisecting each angle of the triangle. Many runs of the code REAC are performed. The objective of the work described here has been to organise storage of results and geometry in a database [3] and to develop a sophisticated data visualization system. internal node i