Large Opening Research Articles

Performance of Air Curtain located at the top of entrance opening - Difference among indoor/outdoor/double-sided installation

Large openings of buildings are often used open, which results in heat loss due to intrusion of outdoor airflow and leakage of indoor air through the opening. To reduce air-conditioning load and to improve thermal environment in such a building, installing an air curtain at the opening can be a beneficial technique. The airflow blowing out of the device suppresses the heat exchange by buoyancy-induced convection through the opening. The impact of temperature difference, blowing speed, and installation position of the air curtain on temperature distribution and invasion flow rate of outdoor air was investigated by full-scale experiment under heating operation. Thermocouples were installed to measure vertical temperature distribution. Outdoor air infiltration was measured using tracer-gas method. The amount of outdoor air infiltration was evaluated based on both temperature difference and CO2 concentration. Comparing the results, it was found that the indoor air curtain was able to suppress the airflow through the opening. The indoor-outdoor temperature difference and CO2 concentration were highest when the air velocity was 4 m/s, suggesting that there is an optimal air velocity at which the air curtain can effectively suppress the airflow through the opening.

Efficient Multigram Procedure for the Synthesis of Large Hydrazone-linked Molecular Cages.

Covalently linked molecular cages can provide significant advantages (including, but not limited to enhanced thermal and chemical stability) over metal-linked coordination cages. Yet, while large coordination cages can now be created routinely, it is still challenging to create chemically robust, covalently linked molecular cages with large internal cavities. This fundamental challenge has made it difficult, for example, to introduce endohedral functional groups into covalent cages to enhance their practical utility (e.g., for selective guest recognition or catalysis), since the cavities would have simply been filled up with such endohedral functional groups in most cases. Here we now report the synthesis of some of the largest known covalently linked molecular tetrahedra. Our new covalent cages all contain 12 peripheral functional groups, which keep them soluble. They are formed from a common vertex, which aligns the hydrazide functions required for the hydrazone linkages with atropisomerism. While we previously reported this vertex as a building block for the smallest member of our hydrazone-linked tetrahedra, our original synthesis was not feasible to be carried out on the larger scales required to successfully access the larger tetrahedra. To overcome this synthetic challenge, we now present a greatly improved synthesis of our vertex, which only requires a single chromatographic step (compared to 3 chromatographic purification steps, which were needed for the initial synthesis). Our new synthetic route enabled us to create a whole family of molecular cages with increasing size (all linked with hydrolytically stable hydrazone bonds), with our largest covalent cage featuring p-quarterphenyl linkers and the ability to encapsulate a hypothetical sphere of approximately 3 nm in diameter. These results now open up the possibility to introduce functional groups required for selective recognition and catalysis into chemically robust covalent cages (without blocking the cavities of the covalent cages).

Nonlinear Finite Element Analysis of High-strength Reinforced Concrete Beams with Severely Disturbed Regions

The inclusion of D-regions within a reinforced-concrete member may affect largely the general behavior of the structure. Different techniques and approaches were proposed to control the behaviour of D-regions, such as the shear-friction approach and the STM model. Such proposals may not be applicable for all types of Dregions. The current work presents a nonlinear finite element model using the ANSYS software, that is adopted to study three types of D-regions, which are dapped ends, deep beams with openings and beams with loaded openings. The results revealed that the proposed FE model predicted adequately the effects of the inclusion of D-regions in RC beams. It is found that reducing the hanger or the nib reinforcement of a dapped end by 25% resulted in reducing capacity by 15% and 32%, respectively. Also, the results showed that for these deficiently reinforced dapped ends, reducing a/d ratio from 1.5 to 0.75 improved capacity by 23% and 36%. For the deficiently shearreinforced flanged deep beams, it was found that the inclusion of large openings within the shear span resulted in a capacity drop by (41-49) %. An enhancement of 23% was obtained when using stirrups of 12mm on both sides of the openings. Moreover, it is confirmed that the optimum location of the openings is under the diagonal path. Furthermore, it has been concluded that for loaded openings, the use of T-rolled sections within the bottom chord of the opening yielded an enhancement of 23% relative to the rhombus-shaped configuration. KEYWORDS: Dapped ends, T-deep beams with openings, Loaded openings, Hanger reinforcement.

Divisive Refinement of Metal Fiber at the PM0.1 Classification Stage for PM0.5-0.1 Sampling with Nanosampler

Multi-component analysis of PM0.5-0.1 collected by Nanosampler II metal (Steel Use Stainless: SUS) wool fiber at the PM0.1 classification stage is challenging owing to difficulties in SUS wool fiber separation after collection. A 4-division (4D) cartridge was developed to enable quantitative analysis of multiple components by dividing the SUS wool fibers into four sections. The performance of the 4D cartridge was evaluated using sulfate ion concentrations of actual atmospheric particulate matter (PM). Observations using the 4D cartridge revealed that the relative standard deviation (RSD) of sulfate ions was lower for mesh with a large open area. In the case of the mesh with a large opening area, the partition did not block too much of the cross-sectional area of the SUS wool fiber, thus minimizing its effect on the airflow and possibly suppressing particle adhesion on the stainless-steel mesh. The PM0.1 classification efficiency test was conducted, and a linear analysis of the total filling mass of SUS wool fiber along with classifying efficiency of 100 nm PM was performed. In the 4D cartridge, it was estimated that 8.7 mg of SUS wool fiber was required to achieve a classification efficiency of 100 nm at 50% cutoff diameter because the apparent volume fraction of SUS wool fiber increases with the introduction of the partition. Using optimal mesh and amount of SUS wool fiber, the average RSD of sulfate ions was 5.6%, which was within the acceptable range (± 15%) for reanalysis of the Ministry of the Environment in Japan due to changes in analytical sensitivity of ionic components, confirming that PM was evenly collected from the four pieces of SUS wool fiber. This enabled multi-component analysis of all particle sizes including PM0.5-0.1 through the classified collection of PM using Nanosampler II.

Estimating the air exchange rates in naturally ventilated cattle houses using Bayesian-optimized GBDT

It is challenging to estimate the air exchange rate (AER) dynamically in naturally ventilated livestock buildings such as dairy houses due to the influence of complex and variable outdoor environmental factors, large opening ratios, and the confusion of inflow and outflow at openings. This makes it difficult to efficiently regulate the opening ratio to meet the ventilation requirements in naturally ventilated livestock buildings. In this study, the air exchange rates of naturally ventilated cattle houses (NVCHs) in different seasons and opening ratios were obtained through field measurements and computational fluid dynamics (CFD) simulations. A fast and efficient machine learning framework was proposed and examined to predict AER based on the gradient boosting decision tree (GBDT) combined with Bayesian optimization. Compared with commonly used machine learning models such as multilayer perceptrons (MLPs) and support vector machines (SVMs), the proposed GBDT model has higher prediction accuracy and can avoid falling easily into local optima. Compared with the existing mechanical model based on the Bernoulli equation, the proposed GBDT model showed a slightly higher prediction than the mechanistic model and was much easier to use in AER estimation when inputting easily collected environmental factors in practical applications. Using Bayesian optimization could dramatically reduce the computing time when determining the optimal hyperparameter for establishing the GBDT model, dramatically saving on computing resources. Based on the Bayesian optimized GBDT model, the desirable opening ratio of the side curtain can be determined for automatically regulating the AER of cattle houses in future applications. Keywords: natural ventilation, Bayesian, GBDT, air exchange rate, cattle house DOI: 10.25165/j.ijabe.20231601.7309 Citation: Ding L Y, E L, Lyu Y, Yao C X, Li Q F, Huang S W, et al. Estimating the air exchange rates in naturally ventilated cattle houses using Bayesian-optimized GBDT. Int J Agric & Biol Eng, 2023; 16(1): 73–80.

Driftwood blocking sensitivity on sluice gate flow

Abstract Hydraulic structures such as sluice gates are more sensible of driftwood that is transported by a river; all this debris, like a trunk, deadwood, and rootstocks, can be accumulated upstream hydraulic structures may cause many hydraulic troubles, so studded such as these phenomena more essential to prevent or reduce its effects on these structures. Many studies dealt with the impact of driftwood on scouring around piers and weirs and its hydraulics, but the studded dealt with sluice gate structures are few and still need deep studies. This study dealt with the sensitivity of driftwood blocking flow under a sluice gate. It found that a large gate opening and 50% of the maximum upstream head lead to a decreased probability of trapped index and an increasing likelihood of driftwood passage beneath the sluice gate, which causes scour if driftwood is blocked under a sluice gate, so this case must be avoided. The driftwood trap probability of rootstock is greater than the trunk, and accumulated driftwood causes an increasing upstream water depth by 15%. Increasing its volume increases trapping probability.

Active lateral spreads monitoring system in East-Central Sardinia

ABSTRACT In Italy, landslides are one of the main geological hazards. Sometimes urban areas are affected by deep-seated gravitational slope deformations (DGSDs) that can lead to a potentially catastrophic failure and trigger a secondary collateral landslide. In these cases, monitoring is important for early warning and risk reduction. In this study, we analyzed DGSDs, in particular, lateral spreads, and landslides in the inhabited areas of Ulassai, in eastern-central Sardinia. Starting from high-resolution geostructural and geomorphological surveys of lateral spread, integrated with high-resolution digital elevation models acquired by UAV (Unmanned Aerial Vehicle), we created geological 3D models of the slope deformations. To better understand the kinematics and temporal evolution of unstable slope deformation, a monitoring system, consisting of Space-borne Interferometric Persistent Scatter Synthetic Aperture Radar (PS-InSAR), GNSS antennas, tiltmeters, and extensometers, was performed. PS-InSAR analysis confirmed by GNSS periodic measurement identified downslope movement of up to 10 mm per year in the lateral spread. Continuous acquisition by extensometers and tiltmeter recorder displacement in large block inclinations and opening and closing of fractures since 2021. Integrated data analysis will be essential to define the threshold for a future 24/7 early-warning system.

Computed Tomography Observation and Image-Based Simulation of Fracture Propagation in Compressed Coal

In this study, the fracture propagation characteristics and associated mechanisms of coal are investigated by using computed tomography (CT) observation and image-based simulation. The spatial distribution and the structural morphology of original fractures provide significant influences on the failure behavior of fractured coal. The fractures with small dip angles and large openings result in more-obvious fracture closure and stable propagation stages, while failure pattern is more sensitive to those with large dip angles. The coal tends to experience brittle failure, which transits from a splitting to mixed-splitting faulting mode because of the difference in original fracture distribution. The final failure fracture network originates mainly from the propagation of original fractures, driven by localized tensile stress. Fracture interaction and mineral influence tend to increase the complexity in the failure fracture network. Moreover, image-based numerical models are established on the basis of CT reconstruction, where the spatial distribution and the structural morphology of original fractures are properly considered. Numerical modeling reproduces similar stress–strain responses and failure fracture networks to that observed in the experiment. The predicted distribution of tensile stress shows a similar evolution trend to the failure fracture network, implying that the fracture propagation of coal is dominated by tensile failure. Shear cracks emerge mainly after the large fracture running through the coal sample has been formed.

Floquet Hofstadter butterfly in trilayer graphene with a twisted top layer

The magnetic field generated Hofstadter butterfly in single-twist trilayer graphene (TLG) is investigated using circularly polarized light (CPL) and longitudinal light emanating from a waveguide. We show that single-twist TLG has two distinct chiral limits in the equilibrium state, and the central branch of the butterfly splits into two precisely degenerate components. The Hofstadter butterfly appears to be more discernible. We also discovered that CPL causes a large gap opening at the central branch of the Hofstadter butterfly energy spectrum and between the Landau levels, with a clear asymmetry corresponding to energy E=0. We point out that for right-handed CPL, the central band shifts downward, in stark contrast to left-handed CPL, where the central band shifts upward. Finally, we investigated the effect of longitudinally polarized light, which originates from a waveguide. Interestingly, we observed that the chiral symmetries of the Hofstadter butterfly energy spectrum are broken for small driving strengths and get restored at large ones, contrary to what was observed in twisted bilayer graphene.

1225. The Perfect Storm: A Hardy and Lethal Pathogen and a Unit Filled with Immunocompromised Patients with Large Open Wounds. Troubles with Candida Auris in a Burn Intensive Care Unit

Abstract Background C auris is an emerging often multidrug resistant pathogen capable of causing severe morbidity and mortality. C auris has been increasingly isolated from patients in skilled nursing facilities and hospitals, and has been associated with facility outbreaks. A resilient pathogen, C. auris survives harsh disinfectants, desiccation and readily colonizes the environment posing an especially great risk to immunocompromised patients with large open wounds and long lengths of stay. Methods From 7/1/21 - 8/30/21 we noted a cluster of 4 patients with C auris in clinical cultures from the Burn ICU (BICU). A multidisciplinary team involving infection prevention, nursing/medical directors, health and safety, engineering, environmental services, and hospital leadership investigated the cluster as a potential outbreak. Mitigation measures involved a multi-modal response of C auris admission screening, weekly point prevalence testing of all BICU patients, environmental surface cultures, enhanced room cleaning, staff education, hand hygiene and personal protective equipment usage audits. Results 11 cases of C auris were identified on our BICU from 7/1/21 - 2/28/22. 5 (45.5%) cases from clinical isolates, 1 (9.1%) from a BICU point prevalence screen on 12/15/21, 5 (45.5%) as a part of weekly point prevalence screens started on 1/1/22. 6 (54.5%) patients were admitted for burn related injuries, 2 (18.2%) for Steven Johnson Syndrome, 2 (18.2%) for necrotizing wounds, and 1 (9.1%) for COVID-19 pneumonia. Cases occurred in 6/10 rooms in the Burn ICU. One (9.1%) patient expired during this outbreak (not deemed to be from C auris infection). Conclusion Resilient infections like C auris pose a risk of nosocomial transmission and potential high morbidity and mortality to burn patients with impaired immune defense and large open wounds. A multidisciplinary team using targeted interventions including screening, education, enhanced cleaning eradicated the outbreak in our BICU. As of 5/1/22, we went 13 + weeks without identifying a new case. The last patient with C auris was discharged 3/16/22. To prevent future outbreaks, we created a standardized response plan and instituted a universal screening protocol for C auris targeting all patient admissions from skilled nursing facilities and admissions to all ICUs. Disclosures Jorge Paiva Parada, MD MPH, Shionogi: Honoraria.

A novel strain field reconstruction method for test monitoring

For the static loading test in the aerospace field, conventional strain field reconstruction based on finite element analysis (FE-SFRM) is difficult to meet the accuracy requirements of test monitoring. A novel experiment strain field reconstruction method (EXP-SFRM) is proposed to improve the accuracy and monitoring effect of reconstructed field. Firstly, the coordinates of strain gauges are introduced to build the connections in space between discrete strain gauges and make it possible to check the accuracy of finite element analysis. Next, the real-time strains with high-precision coordinates are employed to reconstruct the strain field by radial basis function. A cantilever plate test and a large opening cylindrical shell (LOCS) test are performed to validate the high accuracy and good monitoring effect of EXP-SFRM. For the LOCS test, a maximum inward and outward bending criterion (MIOBC) is also proposed to determine the buckling regions. The results show that the average errors of EXP-SFRM are 2.8% (cantilever plate) and 17.4% (LOCS), which are 4.8% and 26.4% lower than these of FE-SFRM. Additionally, for LOCS, the risk regions predicted by EXP-SFRM are finally consistent with the real buckling regions, while these predicted by FE-SFRM are not. Compared with conventional FE-SFRM, the EXP-SFRM is proved to have high accuracy and good monitoring effect during test process.

Determination of the Acute and Chronic Toxicity of Sulfate from the Sulfur Autotrophic Denitrification Process to Juvenile Zebrafish (Danio rerio).

Sulfur-based materials are widely used as electron donors for denitrification to enhance nitrogen removal from water. This leads to an increased sulfate concentration in the effluent or sulfate accumulation in recirculating aquaculture systems. This study explored acute and chronic toxicity of sulfate to juvenile zebrafish (Danio rerio) and investigated the histopathological changes in the gills of juvenile zebrafish exposed to sulfate. Results show that zebrafish had a high tolerance to sulfate, with no acute toxicity at sulfate concentrations from 250 to 3200 mg/L. For the chronic toxicity study, it was found that zebrafish mortality decreased with the increase in sulfate concentrations ranging from 250 to 1500 mg/L. In contrast, when the sulfate concentration was 1500-3000 mg/L, zebrafish mortality increased with the increasing sulfate concentration. In addition, in the ion balance test, KCl was added to balance the effects of Na+ from the Na2SO4 used to obtain the desired sulfate concentrations, showing that fish mortality correspondingly increased with increasing KCl addition. Furthermore, when living in an environment with elevated sulfate concentrations for a long period, changes were observed in the morphology, behavior, and gill tissue of the zebrafish, including slow and lateral swimming; bottom settling; and large opening and closing, lamellar fusion, and necrosis of gills. This research reveals the toxicity of sulfate to aquatic organisms, providing a scientific basis for the promotion and application of sulfur or sulfur-based materials in autotrophic reduction processes for wastewater treatment.

A 2E, energy and environment performance of an optimized vernacular house for passive cooling - Case of North-East India

Energy consumption in buildings has been increasing in recent years due to global warming, resulting in the increased use of HVACs, and causing environmental pollution. To fulfill the target of net-zero energy building and less building-generated pollution, vernacular houses can be constructed for their climate-adaptive architectural design, natural ventilation, and low cost. However, such houses suffer from excessive heat gain in summer due to large window openings, infiltration, and occupancy. There is also a lack of understanding of the energy and environment (2E) performance of a vernacular house in passive cooling compared to modern buildings with active cooling features. This paper aims to find optimal energy-efficient and environment-friendly passive cooling features that can be integrated with a 1BHK vernacular house for summer cooling as a case for North-East India. This study employs a simulation-based multi-objective optimization method that combines the architectural modeling tool EnergyPlus with a non-sorting genetic algorithm (NSGA-II) to find the best possible combinations of different passive cooling features. The findings show that conventional vernacular houses can be more energy efficient and eco-friendly by incorporating passive cooling strategies. The most optimal design is obtained with passive cooling elements, such as an external wall bonded with paraffin, cemented ground floor, false roof, double blue 6 mm air glazing, 1.5 m overhang, and the window-to-wall ratio of 32%, and site orientation of 167°. The optimal passive house has resulted in nearly 50.45% of energy savings and 29.40% less operational and embodied carbon emissions than conventional buildings. Thus, this study contributes to the debate over the applicability of different passive cooling strategies in vernacular houses and encourages further exploration.

Control Efficiency of Biochar Loaded with Bacillus subtilis Tpb55 against Tobacco Black Shank

Black shank caused by Phytophthora nicotianae has become a destructive soil-borne disease to different flue-cured tobacco cultivars in Southwest China. The use of biochar amendments for microorganism synergy is a promising effective strategy for P. nicotianae development control. In this study, biochar samples were prepared from tamarisk with different pyrolization temperatures (300–500 °C). The effect of pyrolytic temperatures on the bacteria immobilization efficiency of biochar was investigated. B. subtilis Tpb55 was successfully loaded on different biochars as biocontrol composites. The survival investigation of the inoculum suggested that biochar pyrolized at 300 °C (BC300), with a large pore opening diameter; a greater pore volume exhibited a better Tpb55 immobilization. A pot experiment indicated that Tpb55-loaded BC300 had a more pronounced decrease in the disease severity index of black shank disease and an increase in the soil pH, alkali-hydrolyzable nitrogen, soil-available phosphorus, and available potassium. BC300 inoculated with Tpb55 showed the highest control effect (79.60%) against tobacco black shank in the pot experiments, with the lowest copy number of P. nicotianae DNA. In conclusion, biochar-immobilized Tpb55 may provide a new strategy for preventing and controlling tobacco black shank.

Development and operation of the Hemispherical Blackbody (HSBB) for the calibration of infrared radiometers with a hemispherical acceptance angle.

Longwave downward radiation measurements are fundamental for investigating the surface and atmospheric energy budget of the Earth. Such measurements are performed using broadband infrared radiometers that have a hemispherical acceptance angle. A new hemispherical reference blackbody has been developed to provide a new traceability path of longwave downward radiation measurements to the SI. The Hemispherical Blackbody (HSBB) was specifically designed to meet the large opening angle of radiometers used for measuring longwave downward radiation. The first step was to find a suitable design candidate for the HSBB by simulating the effective emissivity using the Monte Carlo ray-tracing software STEEP. The most promising candidate was then realized in two versions with similar coatings and both versions were taken into operation.

A INFLUÊNCIA DO TREINAMENTO DE FORÇA DO CORE NO CORPO DE JOGADORES DE BASQUETE

ABSTRACT Introduction Modern basketball is very competitive and enjoyable; it combines several factors. Basketball requires specific physical characteristics such as high stature, which raises the position of the center of gravity, making the stability angle smaller. This compromises stability, especially in sudden speed and direction changes, because it requires a large base opening. The core musculature is intimately involved with body balance; however, there is a lack of studies verifying the impact of specific training of this region on balance in basketball athletes. Objective To explore the influence of core strengthening on the physical fitness of college basketball players. Methods 12 college basketball players were selected and randomly divided into a control group and an experimental group. The experimental group performed core strengthening training, while the control group practiced traditional strength training. After six weeks, physical fitness and basic skills were compared between the groups. Data were statistically treated and discussed confronting the literature. Results Basketball players in the experimental group obtained higher fast dribbling passes and shots than before the experiment (P<0.05), there was no statistically significant difference in several indicators in the control group ( P>0.05); Basketball players in the experimental group had higher fast dribbling passes and shots than the control group (P<0.05), there was no statistically significant difference in approach height between the experimental group and the control group (P>0.05). Conclusion Core strengthening training can improve the physical fitness of college basketball players. Evidence level II; Therapeutic Studies - Investigating the results.

Analysis of confined masonry with strengthening around the opening

Analysing confined masonry (CM) with strengthening around the opening (analytical model) was conducted numerically. The opening variations were centric and eccentric opening doors with an opening ratio of 16.93% and 31.75%; centric and eccentric opening windows with opening ratios of 10.16% and 19.05%. This analysis aims to apply the procedure for analysing the CM models by using layered shell elements and also comparing the behaviour and performance of each model. The masonry and frames were modelled using layered shell elements in SAP2000 software and analysis were done by using nonlinear static pushover analysis. This analysis starts by making a validation model based on other experimental work and comparing the behaviour of the structure modelled in the form of CM without openings and CM with openings. The results show that both models have load-displacement diagrams similar to the experimental results. By using the same modelling method applied to the analytical model, it was found that CM with large opening ratios have less strength than small opening ratios, and CM with centric openings was more robust than the eccentric openings.

Thermal destressing: Implications for short-circuiting in enhanced geothermal systems

Viable Enhanced Geothermal Systems (EGS) require (1) access to large reservoir volumes at high temperatures and (2) sufficient permeability for large production flow rates. However, working fluid injection might quickly decrease the recoverable heat energy. Thermal destressing increases fracture transmissivity and reduces the production temperature. Large fracture openings cause the injection fluid to localize in a single fracture, or a few dominant fractures, and leads to thermal short-circuiting within the EGS hydraulic network. This work provides novel numerical simulations of a multi-fracture EGS that models the fracture aperture from initially closed to mechanically open. Fractures are modeled as discontinuities within a three dimensional thermo-poroelastic rock mass. We derived weak-form equations of mass balance, energy balance, and mechanical contact for fractures and wells and coupled those equations to the Comsol Multiphysics base package. The simulations investigate the full reservoir behavior through coupling of fluid flow through wellbores and fractures with the surrounding rock. Results show that large in-situ stresses contribute to a uniform fluid flow distribution in the fracture network because high compressive contact stresses decrease fracture compressibility and prevent large fracture openings. Initial or late large fracture openings cause thermal short-circuiting and are more likely to arise in locations with low initial stress and compliant fractures. Geometrical and operational properties of the EGS hydraulic network can minimize the severity of thermal short-circuiting including wellbore diameter, fracture spacing, injector/producer lateral spacing, EGS doublet orientation, and number of transmissive fractures. Thermo-mechanical interference between fracture stages causes (1) larger fracture opening displacements and (2) thermal short-circuiting earlier in time. Distinct initial fracture geometries and compliance causes the EGS hydraulic network to flow a non-uniform distribution of the injection fluid from the beginning and tends to decrease heat recovery.

An investigation of airflow distributions with booster fan for a large opening mine through field study and CFD modeling

In this study, we conducted a field survey for the large opening mine with the survey data serving as the numerical modeling inputs to investigate the booster fan airflow distribution using a computational fluid dynamics (CFD) model. A CFD model was created with a booster fan inside the model domain, the airflow distribution patterns around the booster fan were then examined to gain insights on the booster fans impact on the air distribution in the dedicated mining section. Based on the modeling results, the booster fan is an effective ventilation control for airflow direction in large opening mine and the booster fan placement can significantly influence the effectiveness of face pollutants’ removal through airflow recirculation. The fan can boost air velocity to create the multi-pillar scale airflow recirculation to dilute the extraction heading pollutants. Furthermore, the typical continuous traverse done by many mine operators, which only covering part of the entire cross section, may be inadequate around booster fans with errors ranging from 35% to 210%. The airflow calculated at the entry adjacent to the booster fan was 25% that of the fan setting with the subsequent entries exchange diminishing by ∼65.2% per entry indicating streamlining of airflow in the booster fan entry. While the geometry of the mine will play a significant role in determining the airflow distributions this study lays the groundwork for future studies on booster fan placement optimization and effectiveness for face ventilation.

Investigation on in-plane structural behavior of steel arches with rectangular web-openings

This study presents an experimental study and a finite element analysis of the in-plane structural properties of steel arches with rectangular web openings under static loading. The failure mode, deflection, section stress distribution, and other mechanical properties of three steel arch specimens with equidistant rectangular web openings are investigated. It is found that the ultimate load capacity, ductility, and stiffness of the steel arch decrease owing to large-scale openings compared with small-scale openings. The ultimate loading capacity and stiffness of the web-opening steel arches can be improved by welding stiffeners on the edge of the opening. In addition, 52 finite element models are established for parametric analysis to investigate the influence of the steel arch and stiffener geometries on the structural performance. The results show that increasing the rise-span ratio and web and flange thickness increase the ultimate loading capacity of the steel arch. A larger opening will cause the ultimate loading capacity and ductility to decrease significantly. The ultimate loading capacity of the steel arch is affected by horizontal stiffeners, whereas ductility is affected by both horizontal and vertical stiffeners. Finally, this study provides design recommendations to serve as engineering design references.