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Recycled Glass as Partial Replacement for Fine Aggregates in Concrete for Marine Structure Application
No full textThe rapid rise in the generation of waste and the increased quantities of waste glass have created several environmental hazards. For effective remediation of the waste generated on a large scale, the prospects of using waste glasses within concrete have been explored. In marine environments, there is a high probability that concrete structures would degenerate. In concrete structures subjected to marine environments, the attack by sulfate and chloride ions causes degradation. To find effective alternatives for concrete components within marine environments, the feasibility of using recycled glasses has been explored. The feasibility and suitability of using waste glasses that have been recycled have been explored to replace the aggregate materials. Four different concrete mixes containing varying percentages of waste glasses that have been crushed have been investigated. The concrete specimens have been subjected to a marine environment for a period of 28 days. In the concrete specimens subjected to marine environments, the tidal wet-dry cycles lead to structural degradation by inducing internal microcracks due to salt crystallization. The main concerns of this study is the assessment for the chemical resistance based on the changes of mass and water absorption and to evaluate the compressive strength. From the experimental findings, it was evident that the increase in the amount of recycled glass resulted in the reduction of the compressive strength of the resulting concrete. On the other hand, the water absorption was found to be reduced with a steady rise in the rate of chemical resistance along with the increase of the recycled glass replacement. From the findings, it was evident that when the proportion of recycled glass was between 20 and 50 wt.%, there were substantial changes with regards to the performance of the resulting concrete. However, with the addition of recycled glass to the mixture, the strength was reduced; nonetheless, the durability was heightened, indicating that there was a balance of durability and strength at 30 wt%. This study illustrates the benefits to the environment with the utilization of recycled glass as partial replacement of fine aggregates in the concrete exposed in the marine environment
Impact of Bentonite Clay on the Structural and Durability properties of concrete
No full textThe study explores the significance of Bentonite Clay (BC) as a partial substitute for cement on the fresh, mechanical, and durability properties of M25 grade concrete. BC, which is naturally available aluminosilicate substance has a pozzolanic property. BC was used as a 5%, 10%, 15% and 20% replacement by weight of cement while a constant water-binder ratio of 0.50 was used for all the mixtures. Workability, compressive (CS), split tensile (STS), flexural strengths (FS), and water absorption (WA) tests were carried out in accordance with IS standards. The results show that generally as the BC content increased workability tended to decrease due to its high potential for water absorption. The best result was for when 10% was used (BC10) with CS (36.4 MPa) synergies, improved STS and FS performances, and lower WA (2.65%) compared with the control mixture. Compressive and durability performance decreased from 10% replacement of BC because of dilution of the cement paste and cement porosity associated with further replacement of BC. This study concluded that using 10% BC could be successfully used as a Sustainable mineral admixture in concrete that allows for better performance of combined 10% BC while reducing the consumption of cement and environmental factors
Evaluating the Effectiveness of IoT-Based Environmental Monitoring Systems in Minimizing Ecological Impact at Eco-Tourism Sites
No full textIn recent years, several empirical investigations have focused on a technological framework that would have increased monitoring accuracy by integrating sensor-based analytics with the operational capacity to detect and manage environmental disturbances. Therefore, the aim of this study is to find out what sustainability outcomes will emerge when IoT-based environmental monitoring is implemented in the eco-tourism context. The analysis of environmental parameters to change their response patterns due to the deployment and the intensity of the amount of this monitoring in the ecosystem are the main benefits of this approach. The empirical data of the analysis are data collected by a sensor-based monitoring network in the eco-tourism sector in Uzbekistan; the comparison group is represented by pre-implementation observations. The results from the empirical estimation indicate that sites with more than one monitoring zone, having a calibrated sensor network, or integration of an adaptive feedback mechanism are more likely to be environmentally responsive. The results obtained in the MIMIC-SEM analysis indicate that there are significant differences with the results of the simple ordinary least squares estimation, not only for ecological sustainability in eco-tourism sites but also for the other latent constructs for several of the environmental indicators used in the model. It is evident that maintaining a higher level of calibration is an effective strategy to increase ecological sustainability across eco-tourism sites. However, adaptive monitoring and digital calibration reduce ecological pressure and improve the overall environmental performance
Urban infrastructure of large city environments in Uzbekistan
No full textSocial and various high concentrations create a number of unconditional advantages. The natural and artificial components of the urban environment are increasingly converging. The process of degradation is approaching a critical point where it may spiral out of control. The biosphere becomes unmanageable. Cities are undergoing rapid transformations. A new, humanistically-oriented model is emerging. Stimulating human society in a co-evolutionary mode (joint evolution) is tied to nature. Urban development continues. Environmental degradation, therefore, transforms into a focus on sustainable urban development and ecological considerations within the concept. These arise as a result of transformations directly related to immediate needs. The role and significance of reconstructing the urban environment lead to changes in the socio-economic conditions, which, in the modern world, shape the material and spatial environment surrounding humans, reflecting its diversity and rapid changes
Thermodynamic geometry of two-dimensional square-well fluids
No full textThermodynamic geometry of two-dimensional fluids has been investigated using a square-well model as a prototype fluid. A comparison with the three-dimensional case is performed in the subcritical and supercritical domains of thermodynamic space. In the subcritical region, it is found that the R-crossing method has a narrower range of validity for two-dimensional fluids compared to three-dimensional ones. On the other hand, in the supercritical region, an analysis of different Widom lines, including the R Widom line, shows that for two-dimensional fluids these lines extend further into the supercritical region than their three-dimensional counterparts. A similar behavior is observed for the validity of the Clausius-Clapeyron equation in two-dimensional fluids
Trip transient analysis on the main feedwater pump of HPR1000
No full textIn PWR, the main feedwater pump is one of the main equipment in the secondary side which has an important impact on the safe and stable operation of the entire power plant, and then directly affecting the output and availability of the unit. Based on the system manual and equipment data of a HPR1000 nuclear power unit, a mathematical model including the deaerator system and main feedwater pump system was established on the APROS platform. Through transient simulation and calculations of the main feedwater pump trip, it was shown that the load reduced to 50% FP quickly when backup pump for the tripping main feedwater pump did not start, and which can avoid reactor shutdown caused by low steam generator water level, whereas the three initial conditions of unit are 90% FP, 80% FP, and 70% FP. The comparison of debugging test data and the simulation data of a feedwater pump tripping under an initial load of 70% FP shows that the data is in good agreement, and the error between the experimental data and the simulation data for initial and final values of the deaerator pressure is within 1.5%. The flowrate error between the debugging test data and the simulation data of the tripping pump is about 8.1%, and the maximum flowrate error between the debugging test data and the simulation data for the normal operation pump overspeed operation is about 2‰, and the flowrate error between the debugging test data and the simulation data after stabilizing at 50% FP is about 10.1%. The mathematical model established in this paper can effectively predict the changes in deaerator pressure and liquid level, feedwater pump flowrate under transient conditions of a single feedwater pump failure and trips. The modeling method for the main feedwater pump, deaerator, and other systems and equipment used in this paper, as well as the boundary condition assumptions for calculating the operating conditions, can provide reference for the design of the subsequent HPR1000 nuclear power unit
The properties of primordially-seeded black holes and their hosts in the first billion years: implications for JWST
No full textAims. James Webb Space Telescope (JWST) observations have opened a tantalising new window onto possible black holes as early as redshifts of z ∼ 10.4. Using local relations for calibration, these systems show a number of puzzling properties including black holes as massive as MBH ≳ 108 M⊙ in place at z ∼ 10, unexpectedly high black hole-to-stellar mass ratios of MBH/M* ≳ 0.1 and, for some of them, extremely low metallicities. These pose a serious challenge for “astrophysical” seeding and growth models that we aim to explain with “cosmological” primordial black holes (PBHs) in this work.
Methods. We present PHANE
Asymmetric torus variability in active galactic nuclei driven by global brightening and dimming
No full textTemporal asymmetry in the flux variability of active galactic nuclei (AGNs) offers key insights into the physical mechanisms driving AGN variability. In this study, we investigated the variability of the torus by analyzing temporal asymmetry in the mid-infrared (MIR) continuum. We compared ensemble structure functions between the brightening and dimming phases for AGNs at 0.15 < z < 0.4, using monitoring data in the optical from the Zwicky Transient Facility and in the MIR from the Near-Earth Object Wide-field Infrared Survey Explorer. We found that AGNs with bluer optical-to-MIR colors exhibit positive temporal asymmetry in the MIR, indicating that their variability amplitude is larger when brightening. Conversely, those with redder colors show negative asymmetry, exhibiting larger variability amplitude when decaying. However, there is no significant temporal asymmetry in the g band variability driven by the accretion disk, suggesting that the temporal asymmetry in the MIR continuum primarily originates from intrinsic processes in the torus instead of the reflection of the ultraviolet-optical variability from the accretion disk. Analysis of the composite light curves revealed that AGNs with bluer optical-to-MIR colors tend to brighten gradually in the MIR, leading to the observed temporal asymmetry. This finding suggests that hot-dust-rich AGNs evolve with a gradual decline in hot dust emission, while hot-dust-poor AGNs are associated with a steady increase
Clumpiness of galaxies revealed in the near-infrared with COSMOS-Web
No full textContext. Clumps in the rest-frame UV emission of galaxies at z ≲ 3 have been observed for decades. Since the launch of the James Webb Space Telescope (JWST), a large population is detected in the rest-frame near-infrared (NIR), raising questions about their formation mechanism.
Aims. We investigate the presence and properties of NIR overdensities (hereafter substructures, including clumps) in star-forming and quiescent galaxies at 1 < z < 4 to understand their link to the evolution of their host galaxy.
Methods. We identified substructures in JWST/NIRCam F277W and F444W residual images at a rest-frame wavelength of 1 μm.
Results. The fraction of galaxies with substructures with M★ > 109 M⊙ has steadily decreased with cosmic time from 40% at z = 4 to 10% at z = 1. NIR clumps, the most common type of small substructure, are much fainter (2% of the total galaxy flux) than similar UV clumps in the literature. Nearly all galaxies at the high-mass end of the main sequence (MS), starburst, and green valley regions have substructures. However, we do not find substructures in low-mass galaxies in the green valley and red sequence. Although massive galaxies on the MS and in the green valley have a 40% probability of hosting multiple clumps, the majority of clumpy galaxies host only a single clump.
Conclusions. The fraction of clumpy galaxies in the rest-frame NIR is determined by the stellar mass and star formation rate (SFR) of the host galaxies. Its evolution with redshift is due to galaxies moving toward lower SFRs at z ≲ 2 and the buildup of low-mass galaxies in the green valley and red sequence. Based on their spatial distribution in edge-on galaxies, we infer that most substructures are produced in situ via disk fragmentation. Galaxy mergers may still play a role at high stellar masses, especially at a low SFR
Ancrage vissé postérieur mandibulaire : technique synthétique
No full textLe recul des dents mandibulaires grâce aux ancrages vissés temporaires est une technique qui trouve de nombreuses indications en orthodontie. Son efficacité largement décrite ne semble pourtant pas être devenue systématique en pratique courante. Après avoir testé cliniquement et évalué la majorité des techniques actuellement décrites nous proposerons une technique dite « synthétique » visant à garder le meilleur de chacune pour permettre une utilisation rationnelle et efficace. L’association d’une microvis enfouie en ancrage et de fil d’ostéosynthèse comme potence de liaison semble répondre au mieux à nos objectifs comme nous l’exposerons dans 3 situations cliniques. Notre taux de succès est actuellement de 100 % sur un premier échantillon (31 ancrages) qui devra être augmenté