Mortality risks of important diseases such as cancer can be estimated using gene profiles which are high-dimensional data obtained from gene expression sequences. However, it is impossible to analyze high-dimensional data with classical techniques due to multicollinearity, time-consuming processing load, and difficulty interpreting the results. For this purpose, extreme learning machine methods, which can solve regression and classification problems, have become one of the most preferred machine learning methods regarding fast data analysis and ease of application. The goal of this study is to compare estimation performance of risk score and short-term survival with survival extreme learning machine methods, L2-penalty Cox regression, and supervised principal components analysis in generated high-dimensional survival data. The survival models have been evaluated by Harrell’s concordance index, integrated Brier score, F1 score, kappa coefficient, the area under the curve, the area under precision-recall, accuracy, and Matthew’s correlation coefficient. All results showed that survival extreme learning machine methods that allow analyzing high-dimensional survival data without the necessity of dimension reduction perform very competitive with the other popular classical methods used in the study.
{"title":"Survival Prediction with Extreme Learning Machine, Supervised Principal Components and Regularized Cox Models in High-Dimensional Survival Data by Simulation","authors":"Fulden CANTAŞ TÜRKİŞ, İ. Kurt Omurlu, M. Türe","doi":"10.35378/gujs.1223015","DOIUrl":"https://doi.org/10.35378/gujs.1223015","url":null,"abstract":"Mortality risks of important diseases such as cancer can be estimated using gene profiles which are high-dimensional data obtained from gene expression sequences. However, it is impossible to analyze high-dimensional data with classical techniques due to multicollinearity, time-consuming processing load, and difficulty interpreting the results. For this purpose, extreme learning machine methods, which can solve regression and classification problems, have become one of the most preferred machine learning methods regarding fast data analysis and ease of application. The goal of this study is to compare estimation performance of risk score and short-term survival with survival extreme learning machine methods, L2-penalty Cox regression, and supervised principal components analysis in generated high-dimensional survival data. The survival models have been evaluated by Harrell’s concordance index, integrated Brier score, F1 score, kappa coefficient, the area under the curve, the area under precision-recall, accuracy, and Matthew’s correlation coefficient. All results showed that survival extreme learning machine methods that allow analyzing high-dimensional survival data without the necessity of dimension reduction perform very competitive with the other popular classical methods used in the study.","PeriodicalId":12615,"journal":{"name":"gazi university journal of science","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46047966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Umut, Hakan Üstünel, Güven Çentik, E. Uçar, L. Öztürk
In this study, it was aimed to find out whether electroencephalographic (EEG) frequency bands can be used to distinguish people with obstructive sleep apnea (OSA) from those who do not have it. 11842 different cases taken from 121 patients suffering from OSA were combined with the case study of 30-person control group without sleep apnea. Apneas were highlighted at the respiration-record channels and EEG records which are concurrent with abnormal respiration cases were extracted from C4-A1 and C3-A2. Following that, they were examined with Fourier and Wavelet Transforms using a new software that was developed by us. The percentage values of Delta (0, 5-4 Hz), Theta (4-8 Hz), Alpha (8-13 Hz) and Beta (13-30 Hz) frequency bands were evaluated with the help of t-test and ROC Analysis to differentiate between apneas. The C3-A2 Beta (%) frequency level gave the highest distinguishing asset (AUC=0.662; p
{"title":"Distinguishing Obstructive Sleep Apnea Using Electroencephalography Records","authors":"I. Umut, Hakan Üstünel, Güven Çentik, E. Uçar, L. Öztürk","doi":"10.35378/gujs.1229166","DOIUrl":"https://doi.org/10.35378/gujs.1229166","url":null,"abstract":"In this study, it was aimed to find out whether electroencephalographic (EEG) frequency bands can be used to distinguish people with obstructive sleep apnea (OSA) from those who do not have it. 11842 different cases taken from 121 patients suffering from OSA were combined with the case study of 30-person control group without sleep apnea. Apneas were highlighted at the respiration-record channels and EEG records which are concurrent with abnormal respiration cases were extracted from C4-A1 and C3-A2. Following that, they were examined with Fourier and Wavelet Transforms using a new software that was developed by us. The percentage values of Delta (0, 5-4 Hz), Theta (4-8 Hz), Alpha (8-13 Hz) and Beta (13-30 Hz) frequency bands were evaluated with the help of t-test and ROC Analysis to differentiate between apneas. The C3-A2 Beta (%) frequency level gave the highest distinguishing asset (AUC=0.662; p","PeriodicalId":12615,"journal":{"name":"gazi university journal of science","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49468964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Determining the minimum dominating set in connected graphs is one of the most difficult problems defined as NP-hard. In this problem, it is aimed to determine the important nodes that can influence all nodes via the minimum number of nodes on the graph. In this study, an efficient near optimal algorithm showing a deterministic approach has been developed different from the approximation algorithms mentioned in literature for discovering dominating set. The algorithm has O(n3) time complexity in determining the Dominating Set (DS). At the same time, the algorithm is a original algorithm whose solution is not random by using fundamental cut-set. The DS algorithm consists of 3 basic phases. In the first phase of the algorithm, the algorithm that constructs the special spanning tree (Karci Max tree) of the graph is developed. In the second phase, the algorithm that finds the fundamental cut sets using the Kmax spanning tree is developed. In the last phase, Karci centrality node values are calculated with fundamental cut set and by using these Karci centrality node values, an algorithm has been developed to identify DS nodes. As a result of these three phases, the dominance values of the nodes on the graph and the DS nodes are calculated. The detected Karci centrality node values give priority to the node selection for determining the DS. All phases of the developed DS and Efficient node algorithms were coded in R programming language and the results were examined by running on sample graphs.
{"title":"Efficient Algorithm for Dominatig Set In Graph Theory Based on Fundamental Cut-Set","authors":"Furkan Öztemiz, A. Karcı","doi":"10.35378/gujs.1243008","DOIUrl":"https://doi.org/10.35378/gujs.1243008","url":null,"abstract":"Determining the minimum dominating set in connected graphs is one of the most difficult problems defined as NP-hard. In this problem, it is aimed to determine the important nodes that can influence all nodes via the minimum number of nodes on the graph. In this study, an efficient near optimal algorithm showing a deterministic approach has been developed different from the approximation algorithms mentioned in literature for discovering dominating set. The algorithm has O(n3) time complexity in determining the Dominating Set (DS). At the same time, the algorithm is a original algorithm whose solution is not random by using fundamental cut-set. The DS algorithm consists of 3 basic phases. In the first phase of the algorithm, the algorithm that constructs the special spanning tree (Karci Max tree) of the graph is developed. In the second phase, the algorithm that finds the fundamental cut sets using the Kmax spanning tree is developed. In the last phase, Karci centrality node values are calculated with fundamental cut set and by using these Karci centrality node values, an algorithm has been developed to identify DS nodes. As a result of these three phases, the dominance values of the nodes on the graph and the DS nodes are calculated. The detected Karci centrality node values give priority to the node selection for determining the DS. All phases of the developed DS and Efficient node algorithms were coded in R programming language and the results were examined by running on sample graphs.","PeriodicalId":12615,"journal":{"name":"gazi university journal of science","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48515752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study examined the corrosion resistance of the metallic paint-coated, uncoated, and damaged paint-coated form of the high-strength 6061 T6 Al alloy inside seawater. Solvent-based paint containing two different metallic pigments produced with an alkyd binder was produced and the coating of Al 6061 T6 alloy was made with this paint. To determine the course of corrosion electrochemical impedance spectroscopy method was used. Ecor and Rp values were calculated from potential and current change values. As a result, it was determined from the Ecor, Rp, SEM -EDX images, and Nyquist curves that the corrosion resistance of impact coatings was lower. The corrosion resistance of gold color paint substantially containing copper pigment was lower than that of silver color paint containing Al pigment was observed.
{"title":"Examining the Corrosion Behavior of The 6061-T6 Al Alloy Inside Seawater With Decorative Gold- And Silver-Color Coating","authors":"J. Erkmen, Benek Hamamci, A. Aydin","doi":"10.35378/gujs.1219180","DOIUrl":"https://doi.org/10.35378/gujs.1219180","url":null,"abstract":"This study examined the corrosion resistance of the metallic paint-coated, uncoated, and damaged paint-coated form of the high-strength 6061 T6 Al alloy inside seawater. Solvent-based paint containing two different metallic pigments produced with an alkyd binder was produced and the coating of Al 6061 T6 alloy was made with this paint. To determine the course of corrosion electrochemical impedance spectroscopy method was used. Ecor and Rp values were calculated from potential and current change values. As a result, it was determined from the Ecor, Rp, SEM -EDX images, and Nyquist curves that the corrosion resistance of impact coatings was lower. The corrosion resistance of gold color paint substantially containing copper pigment was lower than that of silver color paint containing Al pigment was observed.","PeriodicalId":12615,"journal":{"name":"gazi university journal of science","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49536947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The initial risk assessment, especially when using a risk score system, is the main step in a risk assessment process that comes after determining the scope of the risks and assessment. The Fine-Kinney method, a thorough approach to quantitative assessments to help keep risks under control, is commonly used in risk assessment. A risk score (RS) is determined using the standard version of Fine-Kinney by mathematically multiplication of probability (P), exposure (E), and consequence (C) parameters. The Fine-Kinney-based risk evaluation approach has the disadvantage of not accounting for the relationships among the risk parameters' interaction and determining the risk precedence of work-related hazards. Hence, a new hazard evaluation method for occupational health and safety (OHS) is required to lessen the adverse effects of rising dangers. In this paper, a novel approach is proposed for integrating Fine–Kinney-based occupational hazard evaluation and AHP-COPRAS for the energy distribution and investment sector under the Pythagorean fuzzy environment. A lifting equipment case study is used to demonstrate practicality and efficacy of the suggested integrated approach. To verify the novel method to risk assessment, a comparative study and sensitivity analysis are also provided. As a result, using the benefit of Pythagorean fuzzy sets, which more effectively express uncertainty, the integrated approach yields more logical conclusions for assessing work-related hazards in the energy distribution and investment sector.
{"title":"Fine-Kinney-Based Occupational Risk Assessment using Pythagorean Fuzzy AHP-COPRAS for the Lifting Equipment in the Energy Distribution and Investment Sector","authors":"Suleyman Recep Satici, Suleyman Mete","doi":"10.35378/gujs.1227756","DOIUrl":"https://doi.org/10.35378/gujs.1227756","url":null,"abstract":"The initial risk assessment, especially when using a risk score system, is the main step in a risk assessment process that comes after determining the scope of the risks and assessment. The Fine-Kinney method, a thorough approach to quantitative assessments to help keep risks under control, is commonly used in risk assessment. A risk score (RS) is determined using the standard version of Fine-Kinney by mathematically multiplication of probability (P), exposure (E), and consequence (C) parameters. The Fine-Kinney-based risk evaluation approach has the disadvantage of not accounting for the relationships among the risk parameters' interaction and determining the risk precedence of work-related hazards. Hence, a new hazard evaluation method for occupational health and safety (OHS) is required to lessen the adverse effects of rising dangers. In this paper, a novel approach is proposed for integrating Fine–Kinney-based occupational hazard evaluation and AHP-COPRAS for the energy distribution and investment sector under the Pythagorean fuzzy environment. A lifting equipment case study is used to demonstrate practicality and efficacy of the suggested integrated approach. To verify the novel method to risk assessment, a comparative study and sensitivity analysis are also provided. As a result, using the benefit of Pythagorean fuzzy sets, which more effectively express uncertainty, the integrated approach yields more logical conclusions for assessing work-related hazards in the energy distribution and investment sector.","PeriodicalId":12615,"journal":{"name":"gazi university journal of science","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42866825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The development and launch of communication satellite projects pose significant challenges and costs. The expenses can range from several hundred million dollars, contingent on factors such as mission objectives, satellite system size and complexity including the launch vehicle, and ground infrastructure. Satellites must be designed to withstand harsh conditions in space, such as the extreme temperatures, radiation, and other hazards, while delivering reliable communication services to its users. However, once a satellite is launched, physical maintenance interventions become infeasible in the event of technical problems. Thus, reliability is a critical aspect for these expensive systems. This study aims to minimize the cost of a high-tech communication satellite by addressing design considerations that meet customer reliability requirements without exceeding power and redundant equipment limits. To achieve this goal, we propose an integer non-linear programming model in this research. To solve the satellite design problem, we adopt a two-stage solution approach. Conventional industrial practices in satellite design often involve iterative attempts to determine the redundancy level of onboard units based on customer reliability requirements. These processes rely heavily on the experience of design engineers who evaluate a limited number of alternatives to determine the number of redundant units, resulting in sub-optimal outcomes. In contrast, our proposed approach systematically handles the problem and yields optimal results. Our findings demonstrate that the proposed two-phase approach can achieve optimal redundancy levels within seconds.
{"title":"A Two-Phase Approach for Reliability-Redundancy Optimization of a Communication Satellite","authors":"Gazi University, T. Teti̇k, G. Das, B. Birgoren","doi":"10.35378/gujs.1186561","DOIUrl":"https://doi.org/10.35378/gujs.1186561","url":null,"abstract":"The development and launch of communication satellite projects pose significant challenges and costs. The expenses can range from several hundred million dollars, contingent on factors such as mission objectives, satellite system size and complexity including the launch vehicle, and ground infrastructure. Satellites must be designed to withstand harsh conditions in space, such as the extreme temperatures, radiation, and other hazards, while delivering reliable communication services to its users. However, once a satellite is launched, physical maintenance interventions become infeasible in the event of technical problems. Thus, reliability is a critical aspect for these expensive systems.\u0000\u0000This study aims to minimize the cost of a high-tech communication satellite by addressing design considerations that meet customer reliability requirements without exceeding power and redundant equipment limits. To achieve this goal, we propose an integer non-linear programming model in this research. To solve the satellite design problem, we adopt a two-stage solution approach. Conventional industrial practices in satellite design often involve iterative attempts to determine the redundancy level of onboard units based on customer reliability requirements. These processes rely heavily on the experience of design engineers who evaluate a limited number of alternatives to determine the number of redundant units, resulting in sub-optimal outcomes. In contrast, our proposed approach systematically handles the problem and yields optimal results. Our findings demonstrate that the proposed two-phase approach can achieve optimal redundancy levels within seconds.","PeriodicalId":12615,"journal":{"name":"gazi university journal of science","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43719902","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As waste production is becoming more widely recognized as a significant issue, particularly in developing nations, rising food consumption and population growth have caused environmental degradation and health crises. Nigeria's waste collection and disposal problems are commonly associated with environmental pollution and health crises. Consequently, throwing garbage on roads during environmental sanitation, is a typical method of waste disposal, leading to large piles of refuse along the roadside, which hinders the nation's beauty. Therefore, for Nigeria's waste management system to be effective, sustainable smart bins with efficient Internet of Things (IoT) applications must be quickly adopted to create a green, clean atmosphere within cities. Smart bins with integrated IoT can provide a sustainable future for cities' waste management.. This model seeks to develop a low-cost, intelligent waste bin system with IoT technology. Sensors and data sharing over a Wi-Fi network, allow for remote control of the waste bin, leading to improved optimization of the bin's level of waste. The economic benefits of this IoT-based system include remote access for efficient level control, lower labour costs, improved time and energy efficiency, and reduced congestion in waste bins.
{"title":"Smart Bin and IoT: A Sustainable Future for Waste Management System in Nigeria","authors":"A. Okubanjo, B. Odufuwa, A. Okandeji, E. Daniel","doi":"10.35378/gujs.1254271","DOIUrl":"https://doi.org/10.35378/gujs.1254271","url":null,"abstract":"As waste production is becoming more widely recognized as a significant issue, particularly in developing nations, rising food consumption and population growth have caused environmental degradation and health crises. Nigeria's waste collection and disposal problems are commonly associated with environmental pollution and health crises. Consequently, throwing garbage on roads during environmental sanitation, is a typical method of waste disposal, leading to large piles of refuse along the roadside, which hinders the nation's beauty. Therefore, for Nigeria's waste management system to be effective, sustainable smart bins with efficient Internet of Things (IoT) applications must be quickly adopted to create a green, clean atmosphere within cities. Smart bins with integrated IoT can provide a sustainable future for cities' waste management.. This model seeks to develop a low-cost, intelligent waste bin system with IoT technology. Sensors and data sharing over a Wi-Fi network, allow for remote control of the waste bin, leading to improved optimization of the bin's level of waste. The economic benefits of this IoT-based system include remote access for efficient level control, lower labour costs, improved time and energy efficiency, and reduced congestion in waste bins.","PeriodicalId":12615,"journal":{"name":"gazi university journal of science","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49075808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The performance of a tunnel furnace and a tunnel dryer in a brick production was exergoenvironmentally assessed. The real production data of a brick factory in Turkey with a daily production capacity of 392 tons of fired bricks were used in the analysis. The exergoenvironmental factor of the control volume was calculated as 0.87. The specific exergoenvironmental cost of the control volume was determined to be 559.55 €/h, 3.39 €cent/ kg fired brick and 1.94 €cent/MJ. The specific exergoeconomic cost and the environmental damage prevention cost were obtained to be 0.41 € cent/MJ and 1.53 € cent/MJ, respectively. Because the ratio of exergoenvironmental cost to sales price of 2.41 € cent / kg fired brick was 1.41 (above 1), it was concluded that the brick production in Turkey was not sustainable in terms of exergoenvironmental analysis.
{"title":"Theoretical Exergoenvironmental Analysis of a Tunnel Furnace and Drying System in a Brick Production","authors":"Gurhan Tahtali, H. Olgun, M. Günes, A. Hepbasli","doi":"10.35378/gujs.1052416","DOIUrl":"https://doi.org/10.35378/gujs.1052416","url":null,"abstract":"The performance of a tunnel furnace and a tunnel dryer in a brick production was exergoenvironmentally assessed. The real production data of a brick factory in Turkey with a daily production capacity of 392 tons of fired bricks were used in the analysis. The exergoenvironmental factor of the control volume was calculated as 0.87. The specific exergoenvironmental cost of the control volume was determined to be 559.55 €/h, 3.39 €cent/ kg fired brick and 1.94 €cent/MJ. The specific exergoeconomic cost and the environmental damage prevention cost were obtained to be 0.41 € cent/MJ and 1.53 € cent/MJ, respectively. Because the ratio of exergoenvironmental cost to sales price of 2.41 € cent / kg fired brick was 1.41 (above 1), it was concluded that the brick production in Turkey was not sustainable in terms of exergoenvironmental analysis.","PeriodicalId":12615,"journal":{"name":"gazi university journal of science","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49249919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sonya Javadi̇, Ali İhsan Özer, Olcay Keten, Remziye Zeynep Alkan
The COVID-19 pandemic has already crippled normal life all over the world. Its negative effect not only changed the human health system tragically but also disrupted the global economic system. One result of such negative disruption was on the food supply chain. The strict lockdown has suspended the manufacturing and logistic activities and therefore, the consumers experienced unimaginable chose on the grocery markets which has never faced before. Along with this mess, the shopping behavior of the consumers has remarkably changed compared to pre-pandemic. To meet this new demand pattern, many large convenience stores and small retailers tried to adapt to the new normal. While a standard way to manage the grocery supply chain before the pandemic was the offline system, after the pandemic, the online service got tremendous attention from the consumers. In this study, the online grocery supply chain management during the Covid-19 in Istanbul is considered. The purpose is to find out how more efficient online services can be provided during the pandemic. To do so, first, some questions related to online grocery shopping were asked and three major grocery retailers in Istanbul which have provided online services were taken. Then, a survey was conducted to understand the consumer’s experience with respect to online shopping at these stores. Following that, the performances of the companies and their SWOT analyses were discussed. Finally, some strategic recommendations were given to the companies to manage their online services throughout the pandemic and post-pandemic.
{"title":"The Impact of the COVID-19 Pandemic on Online Grocery Supply Chain Management: A Case Study in Istanbul","authors":"Sonya Javadi̇, Ali İhsan Özer, Olcay Keten, Remziye Zeynep Alkan","doi":"10.35378/gujs.1025914","DOIUrl":"https://doi.org/10.35378/gujs.1025914","url":null,"abstract":"The COVID-19 pandemic has already crippled normal life all over the world. Its negative effect not only changed the human health system tragically but also disrupted the global economic system. One result of such negative disruption was on the food supply chain. The strict lockdown has suspended the manufacturing and logistic activities and therefore, the consumers experienced unimaginable chose on the grocery markets which has never faced before. Along with this mess, the shopping behavior of the consumers has remarkably changed compared to pre-pandemic. To meet this new demand pattern, many large convenience stores and small retailers tried to adapt to the new normal. While a standard way to manage the grocery supply chain before the pandemic was the offline system, after the pandemic, the online service got tremendous attention from the consumers. In this study, the online grocery supply chain management during the Covid-19 in Istanbul is considered. The purpose is to find out how more efficient online services can be provided during the pandemic. To do so, first, some questions related to online grocery shopping were asked and three major grocery retailers in Istanbul which have provided online services were taken. Then, a survey was conducted to understand the consumer’s experience with respect to online shopping at these stores. Following that, the performances of the companies and their SWOT analyses were discussed. Finally, some strategic recommendations were given to the companies to manage their online services throughout the pandemic and post-pandemic.","PeriodicalId":12615,"journal":{"name":"gazi university journal of science","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45941430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Coupled shear walls with coupling beams are constructed because of openings such as doors, windows, or other installations that are left behind due to functional reasons in shear walls. The seismic behavior of coupled shear walls with coupling beams depends on the structural performance of the coupling beams. In coupling beams having a ratio of span-to-depth less than two, shear fracture occurs rather than flexural fracture. In order to meet the shear force and the bending moment formed by the coupling beams, diagonal bundles are used in the coupling beams. Diagonal reinforced coupling beams are generally preferred because diagonal reinforced coupling beams exhibit better behavior than conventional reinforced coupling beams. The diagonal reinforcement bundles have to be confined by transverse reinforcements prescribed in the codes. Confined concrete in the diagonal reinforcement bundles has stress-strain characteristics that are distinctly different from those of plain concrete. The effects of longitudinal and transverse reinforcement ratios on the stress-strain behavior of confined concrete inside the diagonal reinforcement bundles were investigated. Fifty-four reinforced concrete coupling beams with different confining parameters of the diagonal reinforcement bundles and different variables were analyzed using the program. It was demonstrated that the strength and the maximum strain of the concrete inside the diagonal reinforcement bundles increase with the reinforcement ratio of the confinement reinforcement. The increase in the diameter of the transverse reinforcement and the decrease in the transverse reinforcement spacing in the diagonal bundles, increase the confining effect in the concrete sections, increasing the ductility and strength, and has a significant effect on the seismic behavior of the coupling beams.
{"title":"Nonlinear Behavior of the Concrete Core of the Diagonally Reinforced Coupling Beams","authors":"Saeid Foroughi, Bahadır Yüksel","doi":"10.35378/gujs.1233545","DOIUrl":"https://doi.org/10.35378/gujs.1233545","url":null,"abstract":"Coupled shear walls with coupling beams are constructed because of openings such as doors, windows, or other installations that are left behind due to functional reasons in shear walls. The seismic behavior of coupled shear walls with coupling beams depends on the structural performance of the coupling beams. In coupling beams having a ratio of span-to-depth less than two, shear fracture occurs rather than flexural fracture. In order to meet the shear force and the bending moment formed by the coupling beams, diagonal bundles are used in the coupling beams. Diagonal reinforced coupling beams are generally preferred because diagonal reinforced coupling beams exhibit better behavior than conventional reinforced coupling beams. The diagonal reinforcement bundles have to be confined by transverse reinforcements prescribed in the codes. Confined concrete in the diagonal reinforcement bundles has stress-strain characteristics that are distinctly different from those of plain concrete. The effects of longitudinal and transverse reinforcement ratios on the stress-strain behavior of confined concrete inside the diagonal reinforcement bundles were investigated. Fifty-four reinforced concrete coupling beams with different confining parameters of the diagonal reinforcement bundles and different variables were analyzed using the program. It was demonstrated that the strength and the maximum strain of the concrete inside the diagonal reinforcement bundles increase with the reinforcement ratio of the confinement reinforcement. The increase in the diameter of the transverse reinforcement and the decrease in the transverse reinforcement spacing in the diagonal bundles, increase the confining effect in the concrete sections, increasing the ductility and strength, and has a significant effect on the seismic behavior of the coupling beams.","PeriodicalId":12615,"journal":{"name":"gazi university journal of science","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2023-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42692027","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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