4653 research outputs found
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Tensile strength and durability performances-based evaluation of 3D-printed and mold-cast fibrous geopolymer composites produced at various alkaline activator combinations
No full textThis study aimed to investigate the effects of the sodium silicate-to-sodium hydroxide ratio, SH molarity, and carbon fiber volume fraction on the tensile strength and durability properties of mold-cast and 3D-printed geopolymer composites, including flexural and splitting tensile strengths, ultrasonic pulse velocity, water absorption, sorptivity index, and chloride penetration properties. For that purpose, the ground-granulated blast furnace slag and fly ash were employed as alumino-silicate-rich raw material. In order to activate the alumino-silicate-rich raw material, two sodium silicate/sodium hydroxide ratios of 1 and 2 and three sodium hydroxide molarities of 8M, 10M, and 12M were designated. Furthermore, carbon fiber was incorporated into the geopolymer composites at three volume fractions: 0 %, 0.3 %, and 0.6 %. In total, 18 nonfibrous and fibrous geopolymer composites were manufactured in two different ways: mold-cast and 3D- printed. The findings demonstrated that the strength and durability characteristics of 3D-printed specimens were inferior to those of mold-cast specimens, attributed to the presence of weak interfacial bonds between layers. It has been observed that the incorporation of carbon fiber has the effect of improving tensile strength performance. Nevertheless, the addition of carbon fiber led to a slight decrease in UPV values, and an increase in water absorption and sorptivity index values. Also, it adversely influenced the chloride penetration of geopolymer composites. The findings of the study also indicated that increasing the sodium hydroxide molarity had a positive impact on the strength and durability properties of the composites. Nevertheless, it was observed that increasing the sodium silicate-to-sodium hydroxide ratio led to a decrease in both tensile strength and durability performances. Additionally, the microstructure of the geopolymer composites was analyzed using scanning electron microscope (SEM) images.Construction & Building Technology || Engineering, Civi
Mineralogical and elemental composition of the Middle Miocene coal seams from the Alpu coalfield (Eskis,ehir, Central Türkiye): Insights from syngenetic zeolite formation
No full textThis study focuses on determining mineralogical and elemental compositions of coal seams (to the upwards, D, C, B, A, and S0) within seven coal exploration wells from the Alpu coalfield (Eskis,ehir, Central Turkiye). Furthermore, the special goal of the study is a comparative analysis of the relations between the elements by using agglomerative hierarchical clustering algorithm with different linkage methods as well as different similarity measures. Clay minerals and quartz are commonly detected as abundant to dominant phases, while natural zeolite formations were detected in the studied seams C, B, A, and S0. The SEM-EDX data shows that clinoptilolites in zeolite minerals were observed within the organic matter, while crystalline and non-crystalline analcime minerals along with syngenetic authigenic rhomboid K-feldspars were only detected in the seam A from one studied well. The existence of some micron-sized minerals such as apatite, monazite, and Ti-oxides within the smectite matrix and the measurable amount of Ti in smectite imply that alteration of epiclastic and contemporaneous volcanic inputs was developed under weak acidic to neutral conditions during peat accumulation. The lack of natural zeolite and carbonate minerals in the seam D could be an indicator of weak acidic to neutral conditions and semi-closed hydrogeological conditions. Nevertheless, the alkalinity of mire water, water table, and hydrogeological regime seem to be variable during the accumulation of precursor peats of seams C, B, A, and S0. In turn, alteration of volcanic inputs was observed under neutral to weak alkaline conditions and semi-closed to closed hydrogeological regime. Hence, syngenetic authigenic, micron-sized clinoptilolites were formed. Moreover, the existence of authigenic rhomboid K-feldspars and syngenetic authigenic analcimes in certain exploration well could suggest local increases on dissolved Na+ concentrations, alkalinity, and water table. Except for volcanogenic origin for minerals, accessory micron-sized minerals, like chromite, pentlandite, and allanite grains presumably originated from clastic influxes of ophiolitic rocks in the basement into palaeomires. The variations in mire water chemistry and clastic-influx source area could also control the elemental enrichments in the studied seams. Epiclastic and contemporaneous volcanic inputs into palaeomires seem to control enrichments of Li, B, Sc, and Ti in coal samples, while clastic influx from ophiolitic rocks into palaeomires caused to enrichments of Cr, V and Ni. Furthermore, the liberated Ba, Sr, and As ions from the alteration of epiclastic and contemporaneous volcanic inputs are absorbed by syngenetic zeolite minerals, while anoxic conditions in the palaeomires resulted in precipitation of Sr-barite and As-bearing pyrite grains during peat accumulation and/or early diagenetic stages. Overall, the differences in water chemistry of mire water, epiclastic and contemporaneous volcanic inputs, and clastic influx from the adjacent areas also caused several elemental enrichments and variations in mineralogical compositions of the Middle Miocene coal seams in the Alpu coalfield.Energy & Fuels || Geosciences, Multidisciplinar
Life cycle assessment and life cycle costing approach for building decarbonization by design choices: A case study
No full textDecarbonizing the urban environment has two significant challenges: Increasing electricity demand due to the electrification of space heating and increased renewables share in the electricity supply. The European Commission defines a new grid support mechanism for peak-shaving products in renewed Electricity Market Design. This aims to enable a new market tool to stabilize electric supply and demand. This study examines a grid-integrated thermal storage device's technical feasibility and economic performance to meet net zero building (nZEB) definitions. Alternative scenarios considering current national nZEB targets, present energy market options, and regulations are compared using the life cycle cost and the global warming potentials over the building lifetime. The results show that better building performance is possible even with a low investment increase of 6.7% compared to minimum building standards based on regulations. This enables older building cases to perform similarly with new building targets for Turkish National nZEB. Building electrification using heat pumps and thermal storage systems gives similar economic performances in the long term when a dynamic electricity tariff is available. Adapting the life cycle approach to decision-making in construction contracts can lead to a 50% decrease in building emissions while staying within the same construction budget.Energy & Fuel
Multi-objective turbine allocation on a wind farm site
No full textThe Multi-Objective Turbine Allocation (MOTA) method is introduced as a novel approach for wind farm layout optimization and site selection. By incorporating Geographic Information System (GIS) tools and the Analytical Hierarchy Process (AHP), the MOTA method offers a comprehensive solution to balance energy production, cost factors, and environmental impacts. In this study, the MOTA method is applied to Go center dot kceada, Turkiye, for wind farm development. Results show that the MOTA method effectively proposes the optimum wind farm layout by selecting the best site for each turbine. The sequential turbine allocation approach, integration of multiple objectives, and use of GIS tools and AHP are the key capabilities and novelties of the MOTA method. The method allows for flexible investment decisions, considering technical and economic aspects. The outcomes from the Go center dot kceada case study highlight the effectiveness of the MOTA method in maximizing energy production while considering cost factors and environmental impacts. The results indicate that for the selected objective functions, the optimal net profit is attained with the installation of 155 turbines on Go center dot kceada. The MOTA method presents a practical and efficient solution for wind farm development, contributing to sustainable and efficient renewable energy generation.Energy & Fuels || Engineering, Chemica
A STOCHASTIC MAXIMUM PRINCIPLE FOR GENERAL MEAN-FIELD SYSTEM WITH CONSTRAINTS
No full textIn this paper, we study the optimal control of a general mean-field stochastic differential equation with constraints. We establish a set of necessary conditions for the optimal control, where the coefficients of the controlled system depend, nonlinearly, on both the state process as well as of its probability law. The control domain is not necessarily convex. The proof of our main result is based on the first-order and second-order derivatives with respect to measure in the Wasserstein space of probability measures, and the variational principle. We prove Peng's type necessary optimality conditions for a general mean-field system under state constraints. Our result generalizes the stochastic maximum principle of Buckdahn et al. [2] to the case with constraints.Mathematics, Applie
Migrants as agents in placemaking: A socio-spatial analysis of Basmane area in Izmir, Turkiye
No full textThis article explores the place-making practices of displaced Syrian refugees living in Basmane area of Izmir's historic Konak district. By examining everyday spaces, the spatio-material and socio-relational outcomes of Syrians' placemaking practices, the study positions refugees as active agents of placemaking. Through empirical fieldwork, it underscores the spatio-material consequences and socio-relational wellbeing outcomes of Syrians' placemaking practices, illustrating how these are shaped and constrained by multi-scale configurations of Turkiye's refugee policies and the perceptions of the local population towards migrants.Geography || Public, Environmental & Occupational Healt
Wind farm site selection using GIS-based multicriteria analysis with Life cycle assessment integration
No full textThe sustainability of wind power plants depends on the selection of suitable installation locations, which should consider not only economic and technical factors including manufacturing and raw materials, but also issues pertaining to the environment. In the present study, a novel methodology is proposed to determine the suitable locations for wind turbine farms by analyzing from the environmental perspective. In the methodology, the life cycle assessment (LCA) of wind turbines is incorporated into the decision process. The criteria are ranked using analytical hierarchy process (AHP). The study area is chosen as the western region of Turkiye. The obtained suitability map reveals that wind speed is not the sole criterion for selecting a site for wind turbine farms || other factors, such as bird migration paths, distance from urban areas and land use, are also crucial. The results also reveal that constructing wind power plants in the vicinity of Izmir, canakkale, Istanbul, and Balikesir in Turkiye can lead to a reduction in emissions. Izmir and its surrounding area show the best environmental performance with the lowest CO2 per kilowatt-hour (7.14 g CO2 eq/kWh), to install a wind turbine due to its proximity to the harbor and steel factory across the study area. canakkale and the northwest region of Turkiye, despite having high wind speeds, are less environmentally favorable than Izmir, Balikesir, and Istanbul. The findings of LCA reveal that the nacelle and rotor components of the wind turbine contribute significantly (43-97%) to the environmental impact categories studied, while the tower component (0-36%) also has an impact.Computer Science, Interdisciplinary Applications || Geosciences, Multidisciplinar
A Design Proposal for Improving Daylight Availability of a Deep-Plan Classroom by Using Tubular Daylight Guidance Systems and Movable Shading Devices
No full textThe use of daylight in educational settings has a significant impact on the well-being, attention, and academic achievement of students. However, providing adequate daylighting without glare can be difficult, especially in deep-plan layout classrooms, because daylight is not constant and its strength varies with distance from the facade, necessitating the use of additional solutions frequently. In this study, tubular daylight guidance systems (TDGS) and movable shading devices are proposed to increase daylight availability in the Yasar University Faculty of Architecture Temporary Studio, which has a deep plan layout and receives daylight only from the southeast facade. The objective was to meet the LEED daylight evaluation requirements for each zone, which require sDA to be at least 55% and ASE to be at most 10% in the selected analysis area. To propose TDGS and movable shadings with the most efficient angles and positions || Rhinoceros, Grasshopper, and Climate Studio were used, and simulation results were validated by real -time measurements. The design proposal simulation results achieved a significant increase in daylight availability in the rear part of the room (zone 2-3), while glare was diminished near the facade (zone1). The proposed design strategy improved daylight availability through the room, demonstrating that the systems perform well together.Engineering, Multidisciplinar
New Turkey, social policy, and a daytime talk show as a remedy: Muge Anli as a modern Calikusu
No full text'Muge Anli ile Tatli Sert', which investigates unresolved criminal cases with interactive audience support, is one the most popular daytime television shows in contemporary Turkey. The neoliberal restructuring of the welfare system in New Turkey posits that providing protection and security against social risks is the sole responsibility of individuals and families. In line with this approach, the show individualizes social problems ready to be resolved by 'Muge Abla' (Sister Muge) and her audience. Muge Anli's image, which conforms to the ideal modern and modest Republican woman, allows her to gain authority, trust, respect, and popularity. The show's discourses, structure, and communicative strategies are the product of the New Turkey where 'the sacred family' is the central political unit and the nation is an extended, happy family reproduced through this show.Area Studie
Navigating a net-zero economy future: Antecedents and consequences of net-zero economy-based green innovation
No full textThe pursuit of net-zero economy goals and government emphasis on sustainable performance has compelled numerous firms to focus on sustainable production through the adoption of net-zero economy-based green innovation. The digital transformation of manufacturing systems and supply chains, supported by the utilization of big data and the adoption of net-zero economy-oriented lean practices in the presence of net-zero economy-based green practices, can converge to enhance net-zero economy-based green innovation in manufacturing firms. This convergence leads to an improvement in green competitive advantage and net zero-based green performance. To examine the aforementioned linkages using a framework based on the dynamic capabilities view paradigm, a time-lagged design was employed to collect data from 594 manufacturing firms. The empirical findings indicate that big data analytics capabilities and net-zero economy-oriented lean practices of firms significantly influence net-zero economy-based green innovation. Green organizational identity strengthens the effect of net zero-based green innovation on green competitive advantage and net zero-based green performance.Business || Environmental Studies || Managemen