Yazarlar
- Can, Erol(29)
- Kumbasaroglu, Atila(17)
- Yalciner, Hakan(17)
- Bayata, Halim Ferit(14)
- Ting, Naim Suleyman(14)
- Katipoğlu, Okan Mert(13)
- Bayrak, Osman Ünsal(12)
- Sahin, Yakup(12)
- Turan, Ahmet İhsan(9)
- Baş, Fatih İrfan(8)
- Destek, Mehmet Akif(8)
- Manga, Müge(8)
- Çolak, Muhammed Ali(8)
- Bulut, H. Alperen(6)
- Manga, Muge(6)
- Tastimur, Canan(6)
- Akin, Erhan(5)
- Akoğuz, Harun(5)
- Akın, Fatih(5)
- Balli, Esra(5)
- Dede, Tayfun(5)
- Sarıgöl, Metin(5)
- Sarıçiçek, İnci(5)
- Aka, Salih(4)
- Ayasun, Saffet(4)
- Ayaz, Yaşar(4)
- Celik, Alper(4)
- Demirci, Oğuz Kürşat(4)
- Demirel, Soner(4)
- Kalkan, Orhan(4)
- Keleş, Ömer Faruk(4)
- Tortum, Ahmet(4)
- Tuysuz, Suat(4)
- Yavuz, Selahattin(4)
- Yazici, Ahmet(4)
- Yazıcı, Ahmet(4)
- Yesilyurt, Huseyin(4)
- Yılmaz, Mehmet(4)
- Çabuk, Umut Can(4)
- Özkan, Kemal(4)
Yayınlar
- ArticleAçık Erişim2024Impact of Internet Use on Ecological Footprint: Panel Data Analysis for Fragile Five Countries (Brazil, India, Indonesia, South Africa, and Turkiye); [Wpływ korzystania z Internetu na ślad ekologiczny: analiza danych panelowych dla pięciu krajów niestabilnych (Brazylia, Indie, Indonezja, Republika Południowej Afryki i Turcja)]
Akın, Fatih; Özgün, Fergül
In addition to the views that claim that the development of information and communication technologies will result in less environmental pollution and better environmental quality, there are also views that claim that it will increase environmental pollution. In this study, the relationship between environmental quality and information and communication technologies for the 1995–2021 period for the Fragile Five countries was examined using the panel augmented autoregressive distributed lag (ARDL) bounds test method. Ecological footprint was used to represent environmental quality, and the proportion of individuals using the internet was used to represent developments in information and communication technologies. In addition, economic growth, energy consumption, and financial development are included in the model as explanatory variables. According to the results of this study, internet use reduces the ecological footprint in both the short and long run. While financial development reduces the ecological footprint in the long run, energy consumption increases both in the short and long run. Economic growth, on the other hand, increases the ecological footprint in the short run. In line with these results, expanding internet use in the Fragile Five Countries may increase environmental quality.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024Torques and the speed vibrations reducing and optimization of asynchronous motor with ECCA-PID controlling in power system
CAN, EROL
In renewable energy-sourced power systems, asynchronous motors serve as elements that both produce and consume electricity. The stability and efficiency of the asynchronous motor in renewable energy system should be considered. Although performance optimization studies have been carried out using power circuits that control the asynchronous motor fed with solar energy and control units such as proportional, integral, derivation (PID), and Fuzzy logic; They may be insufficient to eliminate and reduce vibrations in the output values of an induction motor fed with a renewable energy source. Losses occur as the system performance decreases constantly due to oscillations. In this study, an induction motor power system is optimized with the extra control coefficient (ECCA)-PID, which provides semi-linear control for the first time, unlike the power systems controlled by other linear controllers used so far to reduce oscillations, and the vibration losses are eliminated. The speed oscillations, torque oscillations, and oscillation losses of the induction motor in the system are controlled by conventional PID, and Fuzzy logic controllers in order to demonstrate the effectiveness of the proposed method in simulation and experimentation. Then, the results are compared after the proposed method are examined. As a result of the comparisons, while the motor oscillations and losses in the power system continue throughout the control period in traditional control methods, the proposed method reduces the losses to zero in a large part of the control period.
RDL Kalıcı Kaydıİncele - Conference ObjectAçık Erişim2024Analysis of Barrel Electroplating Line with Process Mining and Petri-Net Model
Ozates, Ayse; Akin, Erhan; Bilgic, Aykut; Akca, Emre; Tastimur, Canan
Nowadays, many companies carry out efficiency studies to increase their profitability. The most important step in productivity studies is to objectively analyze the processes and identify the points that can be improved. Process mining shows the actual functioning within the process. It also identifies points of improvement such as bottlenecks, waiting times and deviations in the process. In this article, it is aimed to analyze the production process of the barrel electrolytic coating line with the process mining method. In order to perform the analysis, firstly, the data related to the production process was obtained from the ERP system in. csvformat. Within the scope of process mining, data obtained from the event log were used to analyze and visualize the processes affecting the coating line and to identify areas where improvements can be made. Process mining techniques were applied to the event log of the production identified after the electrolytic coating process. ProM 6.12, a widely used open source tool for process mining, was used to perform our analysis. After examining the in-line processes of the product produced in the electrolytic coating line, the data from the event logs were processed and analyzed with process discovery algorithms. In the literature, there has been no research to date on using a process mining perspective to detect anomalous flows in electrolytic coating production.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024A new high-frequency multilevel inverter effecting cables weight and energy efficiency of aircraft
Can, Erol; Kilic, Ugur
Purpose: Static inverters are very important for the emergency energy distribution system of aircraft and similar machines. At the same time, the electrical energy produced at high frequency for electrical devices is used to reduce the weight of the cables in the aircraft and spacecraft because of the skin effect. In the high-frequency system, a thinner cable cross-section is used, and a great weight reduction occurs in the aircraft. So, fuel economy, less and late wear of the materials (landing gear, etc.) can be obtained with decreasing weight. This paper aims to present the development of a functional multilevel inverter (FMLI) with fractional sinus pulse width modulation (FSPWM) and a reduced number of switches to provide high-frequency and quality electrical energy conversion. Design/methodology/approach: After the production of FSPWM for FMLI with a reduced component, which, to the best of the authors’ knowledge, is presented for the first time in this study, is explained step by step, and eight operating states are given according to different FSPWMs operating the circuit. The designed inverter and modulation technique are compared by testing the conventional modular multilevel inverter on different loads. Findings: According to application results, it is seen that there is a 50% reduction in cross-section from 100 Hz to 400 Hz with the skin effect. At 1000 Hz, there is a 90% cross-section reduction. The decrease can be in cable weights that may occur in aircraft from 10 kg to 100 kg according to different frequencies. It causes less harmonic distortion than conventional converters. This supports the safer operation of the system. Compared to the traditional system, the proposed system provides more amplitude in converting the source to alternating voltage and increases the efficiency. Practical implications: FSPWM is developed for multilevel inverters with reduced components at the high frequency and cascaded switching studies in the power electronics of aircraft. Social implications: Although the proposed system has less current and power loss as mentioned in the previous sections, it contains fewer power elements than conventional inverters that are equivalent for different hardware levels. This not only reduces the cost of the system but also provides ease of maintenance. To reduce the cable load in aircraft and create more efficient working conditions, 400 Hz alternative voltage is used. The proposed system causes less losses and lower harmonic distortions than traditional systems. This will reduce possible malfunctions and contribute to aircraft reliability for passengers and cargo. As technology develops, it is revealed that the proposed inverter system will be more efficient than traditional inverters when devices operating at frequencies higher than 400 Hz are used. With the proposed inverter, safer operation will be ensured, while there will be less energy loss, less fuel consumption and less carbon emissions to the environment. Originality/value: The proposed inverter structure shows that it can provide energy transmission for electrical devices in space and aircraft by using the skin effect. It also contains less power elements than the traditional inverters, which are equivalent for different levels of hardware.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024Retrofitting of squat RC column by using TRM strip under axial load
Mercimek, Ömer; Çelik, Alper; Ghoroubi, Rahim; ANIL, Özgür
This study investigates the retrofitting of reinforced concrete columns with TRM strips. Seventeen test specimens were produced, and one was chosen as a reference test specimen. Damaged by loading up to 50% of their maximum axial load-carrying capacity test specimens were retrofitted with two different carbon textiles. In addition to the textile type, TRM strip width, strip spacing, and the use of anchors were determined as experimental variables. Maximum bearing capacity, displacement at bearing capacity, initial stiffness, displacement ductility ratio, and energy consumption capacity were calculated using the axial load-displacement graphs obtained from the experimental study. Depending on the obtained results, the effects of experimental variables on the behavior of damaged reinforced concrete columns were interpreted and compared. It has been determined that the retrofitting method presents very successful results. It has been observed that the fan-type anchor, which is rarely used in literature studies, significantly increases the maximum bearing capacity and energy consumption capacity values of test specimens. Finally, the experimental results were compared with those obtained from the numerical models created by the ABAQUS finite element software.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Investigating the usability of kevlar and steel fibers as a hybrid in concrete pavements
Mola, Erhan; Bayrak, Osman Ünsal; Baş, Fatih İrfan; Bayata, Halim Ferit
In this study, the hybrid usage of Kevlar and steel fiber in concrete pavements was investigated. For this purpose, the concrete was designed using the water/binder ratio (0.40, 0.45, 0.50), silica fume (instead of cement 0, 5, 10%), Kevlar fiber (0 gr/m3, 500 gr/m3, 1000 gr/m3) and steel fiber (0 gr/m3, 500 gr/m3, 1000 gr/m3). Taguchi method was used as the experimental design, and optimum levels of parameters were determined for 28-days compressive strength, flexural strength, and toughness. According to the experiments and observations, the positive effect of Kevlar fiber upon energy absorption capacity (toughness), compressive and flexural strength of concrete was determined. Using only Kevlar fiber increasing up to 5.1% in compressive strength and up to 14.5% in flexural strength were observed. Considering the obtained results, Kevlar was noticed as a possible recycling material to be introduced into the economy by adding concrete.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024Ac-Dc multi pulse converter for dc power distribution system in aircraft
Can, Erol
The Transformer Rectifier Unit (TRU) in aircraft is DC power supplies. Three-phase AC power supplies are available as long as they work. DC power distribution, on the other hand, provides DC power directly to all DC users, providing input power to the emergency AC distribution system so that the static inverter can generate AC power. To the voltages produced by TRUs to be less oscillating and of higher quality, multi-pulse ones are studied and recommended for aircraft systems. In this study, Zener diode filtered multi-pulse rectifier, which can further reduce the oscillations in the output voltage, is recommended for aircraft. Three-phase half-wave rectifier design and analysis are presented to better demonstrate the effectiveness of Zener diode regulation in multi-pulse TRUs. First, the parts of the power system, which includes the rectifier circuit of a two-engine aircraft and fed by this rectifier, are given. The circuit structure and working order of the rectifier are given with mathematical explanations. In the application phase, low oscillating output voltages and currents are obtained by creating currents and voltages on the load for different Zener voltages. Conventional rectifiers and the proposed rectifier are tested on the same loads, and comparisons are done.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024Unleashing power of financial technologies on mineral productivity in G-20 countries
Cevik, Nuket Kırcı; Cevik, Emrah I.; Destek, Mehmet Akif; Bugan, Mehmet Fatih; Manga, Müge
This study aims to investigate the effects of financial technologies (FinTech) on mineral productivity, used for the first time in an empirical analysis, for G-20 countries. In the process, the impacts of financial technology, population, economic growth, trade openness, human capital, and total factor productivity on mineral productivity are examined using panel regression and panel VAR procedure for the period from 2002 to 2019. Empirical research yielded evidence indicating that increasing factor productivity and finance technology drive an increase in mineral productivity. Nonetheless, there is an inverse relationship between trade openness and mineral productivity. Moreover, there is no statistically significant relationship between economic growth, population growth, human capital accumulation, and mineral productivity. Furthermore, we also utilized with method of moments quantile regression technique to observe the effects of explanatory variables on different quantiles of mineral productivity. The findings demonstrate that although economic growth has a negative effect on mineral productivity across all quantiles, a positive increase in factor productivity has an influence on mineral productivity across all quantiles. However, financial technology and human capital accumulation only benefit mineral productivity at huge quantiles. Additionally, the outcomes of the robustness check techniques used show that financial technologies and mineral productivity have a bidirectional causal link and that, in the former instance of positive shocks in the latter, there are positive and substantial reactions.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Experimental and Analytical Investigation of Moment-Carrying Capacities of Reinforced Concrete Frame Systems Corroded by Accelerated Corrosion Method; [Hızlandırılmış Korozyon Yöntemiyle Paslandırılan Betonarme Çerçeve Sistemlerinin Moment-Taşıma Kapasitelerinin Deneysel ve Analitik İncelenmesi]
Turan, Ahmet İhsan; Ayaz, Yaşar; Yalçıner, Hakan; Kumbasaroğlu, Atila; Çelik, Alper
Technical investigations carried out after the devastating earthquakes in Turkey in the last 25 years show that one of the main causes of damage to reinforced concrete structures is reinforcement bar corrosion. The deterioration caused by reinforcement corrosion in reinforced concrete elements reduces the parameters that define the performance level of the structure, such as ductility, stiffness, bond-slip relationship, load carrying capacity, and energy absorption capacity. Therefore, determining the specified performance levels of reinforced concrete structures exposed to corrosion before any seismic activity occurs is of great importance in preventing loss of life and property. Cross-section behavior in reinforced concrete structures represents the load-bearing element behavior In order to accurately determine the section behavior, the Moment-Curvature relationship must be defined. In this study, the structural behavior of reinforced concrete frames exposed to corrosion was examined experimentally and analytically. For this purpose, 4 of the 5 reinforced concrete frame specimens constructed were corroded at different ratios using the accelerated corrosion method. After the corrosion process was completed, in the experimental part of the study, all specimens were tested under the effect of a 20% constant axial load and reversal-cyclic loading. In the analytical study, as a result of the cross-sectional analyzes carried out by taking into account the material-mechanical properties changing with the effect of corrosion, it was determined that the calculated moment values were in high predicted with the experimentally measured moment values.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Performance Analysis of Modulation Strategies in Single-Phase HBNPC Inverter Across Variable Operating Conditions
Cavli, Nazlican; Ozkop, Emre
This study investigates the performance of a single-phase 5-level H-Bridge Neutral Point Clamped (HBNPC) inverter across various operating conditions. These conditions encompass variations in output power, frequency, modulation index, and modulation techniques. To adapt modulation strategies typically employed in three-phase inverter structures, we apply them to a single-phase HBNPC inverter. The modulation strategies under consideration include level-shifted (LS) based on phase disposition pulse width modulation (PD-PWM), third harmonic injection pulse width modulation (THI-PWM), space vector pulse width modulation (SV-PWM), and modified PWM (MPWM). These strategies are developed using different types of reference signals (RS) and carrier signals (CS). Initially, we analyze the inverter's output voltage and current waveforms across various modulation strategy states. Subsequently, we explore the relationships between efficiency, total harmonic distortion (THD), and variable output power across different modulation strategy states. We uncover distinct patterns between modulation strategy-THD, efficiency, and output voltage for maximum inverter output power. Furthermore, we examine the relationship between the modulation index and THD for each modulation strategy state, considering different switching frequencies. Additionally, we investigate the relationship between switching frequency and THD across different modulation index values, approaching the analysis from multiple perspectives.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024Examination of mechanical, permeability, and durability properties of sustainable lightweight concrete composites with natural perlite aggregate
Bulut, H. Alperen
This article presents the outcomes of a comprehensive study utilizing all-natural perlite in producing lightweight aggregate concrete composites and investigating the mechanical, permeability, and durability properties. With this aim, lightweight concrete composites were produced using 10%, 20%, 30%, 40%, 50%, 75% and 100% of natural perlite aggregate in concrete production. In addition to fresh density, compressive strength, ultrasonic pulse velocity (UPV), dynamic modulus of elasticity, capillary absorption, electrical resistivity, acid and sulfate attack tests were carried out on 28–56–90-day-ϖold concretes. Accordingly, the highest compressive strength value was obtained after 90 days using 10% natural perlite (62.42 MPa for NP10/90). In terms of UPV values, concretes with natural perlite were able to produce good or excellent class concretes. The experimental results indicated that the increase in the dynamic modulus of elasticity of concretes cured for 90 days (35 GPa for NP100/90) can be up to 14% compared to concretes cured for 28 days (30.7 GPa for NP100/28). Capillary absorption coefficients decreased in all concretes at advanced ages. The electrical resistivity value of concrete with 100% natural perlite (139.75 kΩ-m for NP100/90) was 140% higher than the control concrete (58.14 kΩ-m for C/90). It was observed that insulating concrete could be produced with an increase in the use of natural perlite at advanced ages. It was determined that concretes with 75% and 100% natural perlite exhibited high resistance against acid and sulfate attacks. The 30% perlite ratio was the critical ratio against aggressive solutions. In line with the aim of the study, it has been proved that lightweight concretes with a high natural perlite dosage can be produced in terms of permeability and durability properties without compromising mechanical strength. Graphical abstract: (Figure presented.)
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Foreign investments and load capacity factor in BRICS: the moderating role of environmental policy stringency
Yıldırım, Metin; Destek, Mehmet Akif; Manga, Müge
This research examines whether environmental regulations have a moderating effect on the link between foreign direct investment and the environment, as well as the effect of foreign capital investments on environmental quality for BRICS nations. In this approach, using second-generation panel data methodologies for the period 1992–2020, the impacts of foreign direct investments, real national income, consumption of renewable energy, and environmental stringency index on the load capacity factor are explored in the base empirical model. In order to test if there is any evidence of a potential parabolic link between economic growth and environmental quality, the model also includes the square of real national income. In addition, in the robustness model, the moderating role of environmental policy on foreign investment and environmental quality is checked. Empirical results show a U-shaped association between environmental quality and economic development. The usage of renewable energy and the environmental stringency index is also shown to improve environmental quality, although foreign direct investments decrease it. Finally, it is determined that environmental regulations are effective in undoing the negative impacts of foreign capital investments on environmental quality, demonstrating the validity of their moderating function.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Effect of Longitudinal Circular Hollows on the Flexural Strength of Reinforced Concrete Beams
Kumbasaroglu, Atila; Korkmaz, Emre
In this study, the effect of hollows passing through reinforced concrete (RC) beams in the longitudinal direction on flexural strength was examined. 4 RC beams were designed to satisfy the conditions for implementation. One of the beams was fabricated as a reference specimen and 3 of the remaining beams were fabricated with total of 5 pipes in the tension, neutral axis and compression regions. All experimental beam specimens were subjected to 4-point axial flexural tests with the request for constant flexural moments at the limits of loading. Experimental beams with pipes in the compression region, tensile region and neutral axis regions were confronted with the reference beam in terms of initial stiffness, ductility, load-bearing capacity and energy absorption capacity. It was verified that to provide that both the sufficient stiffness and sufficient ductility conditions for the reinforced concrete beams, do not establish any structural discontinuity, the longitudinal orbicular cross-section hollows created by pipes should be passed through the neutral axis region as much as possible. The results of the present study not only align with those of previous research (e.g., the correlative results) but also extend the current state of research (e.g., the revealed differences) and provide starting points for future research. Conclusions are drawn from these results at the end of the paper.
RDL Kalıcı Kaydıİncele - Conference ObjectYalnız künye2024Application of Grey Wolf Algorithm with Archive and Grid Mechanisms for Solving Construction Time–Cost–Quality Problems
Yılmaz, Mehmet; Dede, Tayfun; Venkata Rao, R.; Taler, J.
Multi-objective optimization problems are an important research area widely used to solve complex and competitive problems in various industries. In the construction sector, time, cost, and quality factors hold critical importance for the success of projects. Minimizing time, managing costs, and enhancing quality are essential elements for achieving success in many application areas. grey wolf optimization (GWO) is a natural search algorithm that has been effectively utilized in optimization problems in recent years. GWO offers an optimization approach that mimics the interaction between leader wolves, sub-leader wolves, and hunting wolves. The aim of this study is to enhance the performance of GWO algorithm in solving multi-objective construction time–cost–quality problems by integrating archive and grid mechanisms. The archive serves as a data structure to preserve diversity within the solution population and store better solutions. On the other hand, the grid mechanism aims to improve the search process by dividing the solution space. This study evaluates the performance of the GWO algorithm by addressing multi-objective construction time–cost–quality problems with 7 and 13 activities. The results obtained demonstrate that GWO algorithm outperforms genetic algorithm (NSGA-II). These findings highlight the impact and advantages of the GWO algorithm in solving multi-objective construction time–cost–quality optimization problems.
RDL Kalıcı Kaydıİncele - Conference ObjectYalnız künye2024Routing with Pickup and Delivery via Deep Reinforcement Learning; [Derin Pekiştirmeli Öğrenme ile Al-Bırak Rotalama]
Aslan Yildiz, Özge; Sariçi̇Çek, İnci; Özkan, Kemal; Yazici, Ahmet
Intelligent transportation systems are an important issue within the scope of smart cities. Vehicle routing problems, which are a combinatorial problem, need to be solved in the design of the relevant systems. In this regard, the use of artificial intelligence optimization algorithms such as meta-heuristics has increased significantly in recent years. To the best of our knowledge, there are no papers that address the Dial and Ride problem by using reinforcement learning, one of the learning-based models. In this study, the Dial and Ride problem is solved for a single service vehicle using the transformer-based deep reinforcement learning method. The proposed method is tested on a problem generated in an environment in Eskişehir Büyükdere Neighborhood. As a result of the test problem, it is shown that the proposed method produced a solution to the problem in a reasonable time. The study showed that the Dial and Ride Problems can be solved with reinforcement learning.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Analyzing the load capacity curve hypothesis for the Turkiye: A perspective for the sustainable environment
Caglar, Abdullah Emre; Destek, Mehmet Akif; Manga, Muge
Although it takes time to achieve a sustainable environment, this goal can be possible with the Sustainable Development Goals. The transition from gray energy sources to green in the 21st century is among the important policy goals of global economies. Since this process is long, countries focus on energy efficiency as part of their carbon reduction policies. In this context, this study investigates the impact of clean energy technologies on environmental quality in Turkiye. Using the load capacity curve (LCC) hypothesis, human capital, income, and natural resources are theoretically added to the balance model. The novel Augmented ARDL with Fourier terms approach is used in the empirical analysis. As a result of the analysis, the LCC hypothesis is valid, and income will support environmental quality after a certain level. While human capital increases environmental quality, natural resources bring environmental pollution. Finally, it is determined that clean energy technologies have not yet reached the level that enables carbon reduction. The finding that clean energy technologies are insufficient for Turkiye, as a result of empirical analysis, shows the uniqueness of this study. With our new findings, policymakers can take action for a sustainable environment. Since Turkiye has to ensure energy security due to its regional characteristics, it should increase investments in clean energy technologies. Based on empirical findings, clean energy technologies will gain momentum as policymakers support human capital.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Designing an explainable bio-inspired model for suspended sediment load estimation: eXtreme Gradient Boosting coupled with Marine Predators Algorithm
Moazenzadeh, Roozbeh; Katipoğlu, Okan Mert; Shateri, Ahmadreza; Nasiri, Hamid; Abdallah, Mohammed
This study aimed to develop an accurate and reliable model for predicting suspended sediment load (SL) in river systems, which is crucial for water resource management and environmental protection. While Xtreme Gradient Boosting (XGB), a powerful ensemble machine learning (ML) model, has been employed in previous studies, the novelty of this research lies in the introduction of a hybrid approach that synergistically combines XGB with the bio-inspired Marine Predators Algorithm (XGB-MPA) to estimate SL in the Yeşilirmak River (Turkey). To this end, streamflow (Q) and sediment concentration (SC) values as well as their lag times (1 to 3 month lag times) were fed as input variables–under 9 scenarios–into ML models. A time series of datasets from March 1973 to December 2011 and January 2012 to March 2023 were used for training and testing of ML models, respectively. The superiority of the proposed model (XGB-MPA) compared to two other hybrid models, including XGB-PSO (Particle Swarm Optimization) and XGB-GWO (Grey Wolf Optimization) was also investigated. According to the results, the simultaneous application of Q and SC lag time values as inputs has led to the best SL estimates by XGB-MPA, with XGB-MPA9 (RMSE = 103.7 ton/day; NSE = 0.96) exhibiting the lowest error rates. In addition, XGB-MPA has performed better than XGB in all scenarios, with the lowest and highest reduction in RMSE being 19.3% (scenario 5) and 97.4% (scenario 1), respectively. When comparing the performance of hybrid models, the proposed XGB-MPA model has performed best with MAE, RMSE and NSE of 40.94, 103.7 and 0.96, respectively, in comparison with 816.02, 1063.74 and −2.94 for XGB-PSO and 693.16, 981.68 and −2.37 for XGB-GWO. Further research can include the use of time series of efficient variables extracted from satellite images (e.g. land cover, river morphology, etc.) as model inputs. Highlights: Improvement of SL estimation by coupling MPA with XGB model Using delayed combinations of streamflow and sediment concentration as model inputs Superiority of MPA compare to PSO and GWO in SL estimation Greater variations in SHAP caused by sediment concentration compared to streamflow Further studies required on the effects of hydrological and topographical features.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Mechanical properties of cement-based composites incorporating eco-friendly aggregate of waste rubber
Bulut, H. Alperen; Kandil, Ufuk
The purpose of this study is to evaluate the waste tires that harm the environment as aggregate in concrete and to examine the effect on the mechanical properties of concrete. Three different classes (powder, crumb and chips) of waste rubber with seven different ratios (0%, 4%, 8%, 12%, 16%, 20% and 24%) and two different water to cement ratio (0.4 and 0.5) were used in concrete production. In this regard, this study conducted various experiments consisting of 28 and 90 days of the curing process to determine the properties of unit weight, compressive, flexural, and splitting tensile strength, along with ultrasonic pulse velocity (UPV) and dynamic modulus of elasticity. The waste rubber concrete with the highest compressive strength at the end of 90 days is the concrete that includes 4% waste rubber (0.4WR4) with 58.81 MPa. Concrete containing 8% waste rubber has the highest UPV of 5660 m/s after 90 days. The increase in the water/cement ratio from 0.4 to 0.5 and the waste rubber ratio cause deterioration in the mechanical properties of concrete. Although the use of waste rubbers does not bring an increase in strength, it is feasible to produce high strength concretes with 4% and 8% waste rubber substitution ratios. The water/cement ratio and curing time were highly effective on the mechanical properties of rubberized concrete.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Optimization of Structural Steel Used in Concrete-Encased Steel Composite Columns via Topology Optimization
İnce, Elif Gökçe; Özkal, Fatih Mehmet
Concrete-encased steel composite columns are preferred for their exceptional ductility and strength, particularly in high-rise buildings. This research aims to enhance both the strength and ductility of these composite columns by increasing the height of the steel profile. Typically, hexagonal or circular openings, referred to as castellated elements, are incorporated into the steel profile to achieve this height increase. This study employed a topology optimization method to identify the ideal opening shape for the steel profile in concrete-encased steel composite columns. The analysis revealed a sinusoidal-like opening shape, which was then refined for manufacturing. The optimal opening shape was used to increase the height of the existing steel profile, and nonlinear analyses were conducted to evaluate the effectiveness of this new optimized steel profile in concrete-encased steel composite columns. Two concrete-encased steel composite columns were designed: one with the optimal steel profile and the other with a standard steel I profile. ANSYS APDL 19.0 software was used to simulate an experiment based on an existing concrete-encased steel column to validate the nonlinear analysis. The verification analysis demonstrated a remarkable similarity between the experimental and numerical load–displacement graphs, indicating that the numerical analysis was reliable. In the analysis of the composite columns, both axial and lateral forces were applied in the nonlinear analyses. The axial force was applied at 15% of the column’s capacity, while the lateral force was applied until the composite column reached a state of failure. The results of the nonlinear analyses allowed for a comparison of load–displacement curves and the performance of the composite columns. In comparison to the standard steel I profile, the steel profile with the optimal opening shape increased load-carrying capacity by approximately 19% and energy absorption capacity by approximately 24%.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024High-income developing countries as pollution havens: Can financial development and environmental regulations make a difference?
Destek, Mehmet Akif; Yıldırım, Metin; Manga, Müge
The argument that foreign direct investments inflows in developing countries harm the environmental quality of these countries is evaluated within the scope of Pollution Haven Hypothesis. However, the Pollution Halo Hypothesis, the counterargument, contends that foreign investment has several positive effects on the environmental circumstances in the host nation. Therefore, firstly the unit root properties of variables and cointegration existence among variables are checked with newly developed panel data techniques that both allows cross-sectional dependence and structural breaks. In addition, using recently established CS-ARDL technique for high-income developing nations (BRICS-T), this research examines the effects of foreign direct investment on the environment as well as whether environmental regulations and financial development have changed the potential haven hypothesis into the halo hypothesis for the period from 1995 to 2020. The pollution haven theory holds true for these nations, according to the results of empirical research. On the other side, it is determined that tighter environmental restrictions support the environmental quality, and the usage of renewable energy also improves environmental quality, even if economic growth harms environmental quality. In addition, it is found that both regulations and financial development has a moderating role on reversing the haven to halo.
RDL Kalıcı Kaydıİncele
