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Imperfection Tolerances During the Erection of Steel Plate Girders and Geometrical Nonlinearities
Get PDFThis work aims to prove that the strict initial imperfection tolerance limits proposed by the American AWS D1.1/D1.1M and the European EN 1090-2 codes could be relaxed for the webs of the most encountered steel I-plate girders subjected to local bend-buckling during their erection phase. To achieve this scope, a parametric study was done involving 36 perfect and 612 imperfect web models with varying aspect ratio, slenderness ratio, initial imperfection amplitude, and stress ratio using Abaqus/CAE by Finite Element (FE) linear buckling analyses then FE geometrically and materially nonlinear analyses with imperfections included (GMNIA). After investigating the results, two main research novelties were found. An easily applicable equation to determine the ultimate strength of webs subjected to direct stresses, which is a function of not only the slenderness ratio and stress ratio (as in other research) but also a function of the initial imperfection amplitude, was derived. Secondly, a tolerance limit equation that is a function of not only the slenderness ratio but also the stress ratio, thus considering the symmetry of the section of plate girders, has been derived. The derived tolerance limit equation provides acceptable and inclusive parameter-wise imperfection tolerances for webs of plate girders so as to relax strict and costly tolerance limits. The results obtained show that for monosymmetric I-plate girders during erection, EN 1090-2 and AWS D1.1/D1.1M tolerance limits can be relaxed to around 40% and 80% in less slender webs and close to 60% and 200% in more slender webs, respectively
Evolution of Pumping and Piezometry of the Carboniferous Aquifers, Western Border of Aïr Massif: Case of the Tarat Aquifer in the Arlit Sector
Get PDFThe Tarat aquifer provides drinking water for the population of the city of Arlit and also provides water to industries. The exploitation of this aquifer has considerably increased in recent years. The main objective of this study is to contribute to a better understanding of the functioning of the Tarat aquifer. Thus, a methodological approach focusing mainly on the piezometric study and the analysis of evolution and estimation of the volumes of water pumped, since its development from 1969 to 2012, which has resulted in highlighting not only a general decline in the level of the Tarat aquifer, but also the piezometer level (Arli_182), reacts strongly to the solicitations of the aquifer. On this same piezometer, the water table was lowered by 30 m from 1980 to 2006 (26 years), so a drawdown of 0.86 /year
Second-Law Analysis of a Double-Effect Evaporator with Thermal Vapor Compression
Get PDFIn this paper, we present a steady-state analysis of a double-effect evaporator with thermal vapor compression (MED-TVC) installed in the Tunisian Chemical Group (GCT) factory. A thermodynamic model including mass and energy balances of the system is developed and integrated in a Matlab program. The model resolution yields to the determination of the operating parameters of the plant and the Gain Output Rate (GOR) was found to be roughly equal to 5. In a second step, the simulation results served to conduct a second law analysis of the unit. The performance criterion used in this analysis is the second law efficiency, i.e., the ratio of the least theoretical work of separation to the actual work input to the plant. The second law efficiency was found to be 2.4%. The distribution of the irreversibility between the different components of the plant was, in addition, assessed. As a conclusion, it was established that the most irreversibility occurs in the thermo-compressor which contributes with more than 50% to the global imperfection and which presents an exergy efficiency of less than 77%. The remaining irreversibility comes from the three exchangers (the two evaporators and the condenser) with an average contribution of 16%. As it is very difficult to introduce modifications into an existing unit, we assume that the importance of the results is not limited to the studied unit. They serve, rather, as an aid to the future design of a MED-TVC plant
A Pilot Study of a Hybrid Process Involving In Situ Regenerated Activated Carbon, Membrane Separation and Advanced Oxidation for Water Pollution Abatement
Get PDFThe assessment of a pilot-scale hybrid system coupling powdered activated carbon (PAC) adsorption with membrane ultrafiltration (UF), in respect of activated carbon regeneration and organic micropollutant removal, was investigated in this study. Field tests with two adsorbents (i.e. a commercial PAC and a PAC-Fe(II) composite), conducted in the premises of Thessaloniki Water Treatment Plant, demonstrated the high efficiency of the combined PAC/UF process. Regeneration efficiencies varying between approximately 95% and 110%, complete diclofenac (DCF) degradation and rather moderate mineralization (TOC removal) rates of up to 47%, can be achieved by UVC/H2O2 or photo-Fenton oxidation after 4 hours of treatment; this performance is attributed to the in situ generation of reactive oxidant species by photolysis of H2O2, which seems to enhance the process effectiveness. Among the two adsorbent materials tested, composite PAC-Fe(II) exhibited a higher DCF adsorption capacity than the original PAC, probably due to the improved chemisorption and/or the electrostatic attractive interactions between the negatively charged DCF molecules and the positively charged iron species, at neutral pH. Furthermore, a rather insignificant effect of PAC-Fe(II) loading on the regeneration efficiency was observed. The advantages of totally controlled H2O2 dosages and short operating times render the hybrid PAC/UF system a promising alternative to conventional and advanced drinking water purification methods
Approach for Smart Use of Wastes and Biofuels
Get PDFThe urgent need to reduce greenhouse gas emissions by gradually abandoning fossil fuel sources is required due to climate-changing emergencies. Employing as much as possible renewable energy, in any form and any field, together with a reduction of per capita energy need, can reduce this tendency and contrast the catastrophic consequence of our planet temperature increasing. In this scenario, biofuels production, together with reuse and recycling represent a correct strategy to contrast environmental degradation. Biofuel has been the subject of great interest over the past decade. Their development from the first to the fourth generation has led to significant improvements in the production cycles and extended the interest in new resources. The availability of different choices could permit to use always the best solution to maximize the result.
In this paper, the different biofuel generations are presented with the aim of highlighting strengths and weaknesses to identify a smart approach to energy conversion and land utilization. Even today the first-generation biofuels are the most widespread, while second-generation gives a small contribution, with a low replacement share of fossil fuels. Land use and competition with other human necessities are the most relevant constraints in this evaluation. In general, the production of gaseous fuels requires less energy than liquid for both the first as well as second-generation technologies. When considering gaseous options, biomethane should be preferred for convenient energy balance in the productive process and when biogas cannot be directly employed. Moreover, biomethane gives the possibility to be added to the existing gas network. The new third and fourth-generation technologies could allow a considerable efficiency increase while reducing the problem of the biofuel productive chain
A Holistic Approach for Enhancing the Efficacy of Soil Microbial Inoculants in Agriculture: From Lab to Field Scale
Get PDFMicrobial inoculants can be an efficient tool to manage the soil and plant microbiomes providing direct beneficial effects, and for modulating native soil and plant-associated microbiota. However, the application of soil microbial inoculants as biofertilizers and biopesticides in agriculture is still limited by factors related to their formulation, application method, and the knowledge about the impact and interactions between microbial inoculants and native soil and plant host microbiomes. The review is thus describing and discussing three major aspects related to microbial-based product exploitation, namely: i) the discovery and screening of beneficial microbial strains; ii) the opportunities and challenges associated with strain multifunctional features; iii) the fermentation and formulation strategies also based on the use of wastes as growth substrates and the technical and regulatory challenges faced in their path to field application. All these issues are addressed in activities performed by the EXCALIBUR project (www.excaliburproject.eu), which aims to expand the current concept about microbiomes interactions, acknowledging their interactive network that can impact agricultural practices as well as on all living organisms within an ecosystem
Biofumigation: A Cover Crop Option 12 Months of the Year to Manage Three Soilborne Pathogens Ailing the Australian Vegetable Industry
Get PDFBrassica biofumigant cover crops are being increasingly considered in vegetable crop rotations as part of an integrated disease management strategy and simply as a cover cropping choice. Nine biofumigant varieties were assessed to see if they could be grown year-round in the Lockyer Valley South East Queensland region, for yield, days to incorporation and glucosinolate concentrations, as well as efficacy against 3 soilborne pathogens; Sclerotinia sclerotiorum, Sclerotium rolfsii and Macrophomina phaseolina. The fastest growing brassica biofumigant was BQ Mulch which reached 25% flowering in 36 and 59 days from planting to incorporation with a summer and winter planting respectively. Nemcon and Nemclear took the longest to incorporation when planted in summer, 101 days and failed to flower, while Caliente, Tillage Radish and Biofum reached 25% flowering and incorporation in 98 days when planted in winter. BQ Mulch produced the least amount of biomass, 30.93 t/ha fresh weight and 2.92 t/ha dry weight with a summer planting. Biofum producing the greatest amount of biomass, 185.76 t/ha fresh weight and 17.34 t/ha dry weight with a summer and winter planting respectively. Most varieties produced more total glucosinolates during summer compared to winter. Caliente produced the highest levels of Total GSLs with 53.47 µmol/g DW in summer compared to 23.78 µmol/g DW in winter. This was reflected in their efficacy against the soilborne pathogens. Caliente and Mustclean were more efficacious at controlling Macrophomina and Sclerotinia in summer compared to winter while all varieties were more efficacious at controlling Sclerotinia with a summer planting compared to a winter planting
High Rise Buildings: Design, Analysis, and Safety: An Overview
Get PDFHigh-rise buildings have been rapidly increasing worldwide due to insufficient land availability in populated areas and their primary role as essential buildings in modern cities and capitals. However, high-rise buildings are very complicated due to the huge number of structural components and elements unlike low-rise buildings, as well as these high-rise buildings demand high structural stability for safety and design requirements. This paper aims to provide brief information about high-rise buildings regarding the basic definition, safety features, structural stability, and design challenges. A brief description of existing structural systems that are available in the literature is presented to articulate a technical issue that has been widely reported, named, adopting an effective structural system for resisting lateral loads resulting from wind and seismic activities. Consequently, a general overview is presented that covers the behavior of various structural systems for different heights of high-rise buildings by implementing a number of nonlinear static procedure analyses (pushover) and nonlinear dynamic procedure analyses (for wind and earthquake loading). Finally, a critical review of the available simplified model and seismic energy base design are also presented. This paper is intended to help in the development and application of construction systems for high-rise buildings in the future
The Current Progress of the Titanium Preparation by Electrolysis in the Room-Temperature Ionic Liquid Electrolytes
Get PDFTitanium is a beneficial metallic material due to its excellent properties. However, the large-scale application of titanium is inhibited by the high production cost of the Kroll process. To address this challenge, researchers have proposed many new strategies based on electrochemical technology over the past decades. Those electrochemical methods show potential practical value to replace the Kroll process. Nevertheless, many of them are conducted in high-temperature melts, limiting the rapid development of those methods. Accordingly, room-temperature electrolysis in ionic liquid electrolytes was employed in titanium production. At present, there is no systematic and in-depth summary on room-temperature titanium electrolysis, although many pathways in room-temperature melts have been reported. In this review, we briefly outline the development of the titanium electrolysis methods firstly and summarize the room-temperature titanium electrolysis in ionic liquid electrolytes.
Furthermore, we have discussed the fundamental mechanisms and key challenges occurring in room-temperature titanium electrolysis. Finally, we proposed the opportunities and research direction on room-temperature titanium electrolysis. We hope this review will be a valuable roadmap for room-temperature titanium electrolysis
Review of Wastewater Treatment Technologies in View of their Application in the DR Congo Mining Industry
Get PDFThe world is currently experiencing a water crisis in terms of both quantity and quality due to water ever-growing demand in large-scale consumer sectors such as agriculture, industry and tourism. This crisis results from the increasing pressure on water resources brought about the world population growth, continued urbanization and rapid industrialization as sources of an increased release of contaminated water into watercourses. Faced with this worrying situation, strategies have been developed throughout the world for improving both the availability and access to water. Different technologies, both established and emerging ones, are utilized in view to treat wastewaters, including those of the mining origin. The present work reviews the different uses of water in the mining industry and identifies its different sources of polluted water. It analyses some wastewater treatment techniques and their applicability in the reclamation of wastewater generated by the DR Congo mining industry. The adopted approach, in dealing with the relevant issue of water crisis experienced worldwide in terms of both quantity and quality, is expected to help improving practices in the management of wastewater of mining origin, increasing access to water and its sustainable use