Publications without Fulltext
Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
Browse
7 results
Search Results
Item Metadata only The effect of ionic liquids incorporation on the self-healing behavior of the bitumen(Springer Heidelberg, 2023) Arca, Serhat; Gurdal, Savas; Caniaz, Ramazan Oguz; Yilmaz, Kadir; Komurcu, Hasan; Cetintas, Refika; Aydemir, Emel Baskent; Yasar, Muzaffer; N/A; Canıaz, Ramazan Oğuz; PhD Student; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and EngineeringIn the asphalt pavements, which are prepared by mixing bitumen and aggregates, fatigue cracking and thermal cracking failure occur due to continuous loading and climate conditions. Extending the life of asphalt pavements is very important from an environmental and economic point of view. In this study, reactions are conducted to investigate the effects of six ionic liquids (IL) with different side-chain lengths on the self-healing properties of bitumen. Thermogravimetric analysis and differential scanning calorimetry analysis are performed for ionic liquid characterization, while for bitumen characterization, Saturates, Aromatics, Resins, Asphaltenes (SARA) fractionation of bitumen and Gel Permeation Chromatography, Nuclear Magnetic Resonance, Elemental Analysis of these sub-fractions were performed. In addition, two new test methods have been developed to measure the self-healing capacity of bitumen. The first method shows the effects of rest times when intermittent loading is applied to the sample at high temperatures, while the other method was developed to demonstrate the self-healing ability of bitumen at low temperatures with long rest periods. Stripping tests, asphalt fatigue tests and zeta potential measurements are done to investigate the effects of ionic liquids on bitumen and aggregate interactions. The results indicated that different ionic liquids have different effects on asphalt self-healing mechanism. IL improved the self-healing performance of asphalt 40% at high temperatures, and 100% at low temperature while stripping properties 25% and asphalt fatigue life 20% improved. Therefore, it can be concluded that different bitumen-IL modification recipes could be used for self-healing of asphalt pavements, depending on climatic conditions and traffic density.Publication Metadata only A framework for evaluating the safety and homogenizing effect of freeway traffic controllers on mixed traffic conditions(Springer Heidelberg, 2023) Silgu, Mehmet Ali; Graduate School of Sciences and EngineeringDue to recent advancements in connected and autonomous vehicles (CAVs), freeway traffic control (FTC) has become a trendy area of research. Combining CAVs and control measures has opened more efficient traffic flow possibilities. However, while there is extensive research on how traffic control and CAVs can enhance traffic flow performance, their safety benefits should be evaluated more comprehensively. It is challenging to distinguish their contributions to traffic flow safety. Studies on the safety of CAVs in traffic flow indicate that traffic flow safety improves with higher market penetration rates (MPR) of CAVs. However, this finding only sometimes aligns with the traffic flow performance effects of CAVs on freeways. This paper introduces a framework for assessing the safety effects of FTC strategies in mixed traffic scenarios involving human-driven vehicles and CAVs. The proposed framework is tested through a microsimulation-based case study in Istanbul, Turkey. The results show that, despite varying MPRs, the safety effects of CAVs and FTC methods do not consistently reduce the number of conflicts in the traffic flow context.Publication Metadata only Insectivorous birds consume an estimated 400-500 million tons of prey annually(Springer, 2018) Nyffeler, Martin; Whelan, Christopher J.; Department of Molecular Biology and Genetics; Department of Molecular Biology and Genetics; Şekercioğlu, Çağan Hakkı; Faculty Member; College of Sciences; 327589In this paper, we present an estimate of the predation impact of the global population of insectivorous birds based on 103 (for the most part) published studies of prey consumption (kg ha(-1) season(-1)) of insectivorous birds in seven biome types. By extrapolation-taking into account the global land cover of the various biomes-an estimate of the annual prey consumption of the world's insectivorous birds was obtained. We estimate the prey biomass consumed by the world's insectivorous birds to be somewhere between 400 and 500 million metric tons year(-1), but most likely at the lower end of this range (corresponding to an energy consumption of ae 2.7 x 10(18) J year(-1) or ae 0.15% of the global terrestrial net primary production). Birds in forests account for > 70% of the global annual prey consumption of insectivorous birds (a 300 million tons year(-1)), whereas birds in other biomes (savannas and grasslands, croplands, deserts, and Arctic tundra) are less significant contributors (a 100 million tons year(-1)). Especially during the breeding season, when adult birds feed their nestlings protein-rich prey, large numbers of herbivorous insects (i.e., primarily in the orders Coleoptera, Diptera, Hemiptera, Hymenoptera, Lepidoptera, and Orthoptera) supplemented by spiders are captured. The estimates presented in this paper emphasize the ecological and economic importance of insectivorous birds in suppressing potentially harmful insect pests on a global scale-especially in forested areas.Publication Metadata only Unidirectional invisibility and non-reciprocal transmission in two and three dimensions(Royal Soc Chemistry, 2016) Loran, Farhang; Department of Mathematics; Department of Mathematics; Mostafazadeh, Ali; Faculty Member; College of Sciences; 4231We explore the phenomenon of unidirectional invisibility in two dimensions, examine its optical realizations and discuss its three-dimensional generalization. In particular, we construct an infinite class of unidirectionally invisible optical potentials that describe the scattering of normally incident transverse electric waves by an infinite planar slab with refractive-index modulations along both the normal directions to the electric field. A by-product of this investigation is a demonstration of non-reciprocal transmission in two dimensions. To elucidate this phenomenon, we state and prove a general reciprocity theorem that applies to quantum scattering theory of real and complex potentials in two and three dimensions.Publication Metadata only The association between Acinetobacter baumannii infections and the COVID-19 pandemic in an intensive care unit(Nature Publishing Group (NPG), 2022) N/A; Boral, Jale; Pınarlık, Fatihan; Can, Füsun; Ekinci, Güz; Kuşkucu, Mert Ahmet; Ergönül, Önder; Genç, Zeliha; İrkören, Pelin; Kapmaz, Mahir; Çakar, Nahit; Şentürk, Evren; Yurdakul, Fatma; Dikenelli, Bilge; Tekin, Süda; PhD Student; PhD Student; Faculty Member; Master Student; Faculty Member; Faculty Member; Nurse; Doctor; Doctor; Faculty Member; Faculty Member; Doctor; Doctor; Faculty Member; Koç Üniversitesi İş Bankası Enfeksiyon Hastalıkları Uygulama ve Araştırma Merkezi (EHAM) / Koç University İşbank Center for Infectious Diseases (KU-IS CID); Graduate School of Health Sciences; Graduate School of Health Sciences; School of Medicine; Graduate School of Health Sciences; School of Medicine; School of Medicine; N/A; N/A; N/A; School of Medicine; School of Medicine; N/A; N/A; School of Medicine; Koç University Hospital; N/A; N/A; 103165; N/A; N/A; 110398; N/A; N/A; N/A; 198906; 48359; N/A; N/A; 42146We aimed to describe the increased rate of Acinetobacter baumannii infections during the COVID-19 pandemic and define its significance within the last five years. This study was performed in a tertiary hospital with 280 beds and included all patients infected with A. baumannii in the intensive care unit between January 1, 2018, and June 30, 2022. A. baumannii-infected patients in the intensive care unit 27 months before the pandemic and 27 months during the pandemic were included. Pulsed-field gel electrophoresis was performed to assess clonal relatedness. The infection control measures were specified based on the findings and targeted elimination. In total, 5718 patients were admitted to the intensive care unit from January 1st, 2018, to June 30th, 2022. A. baumannii infection was detected in 81 patients. Compared to the pre-pandemic era, the rate of A. baumannii infection during the pandemic was 1.90 times higher (OR: 1.90, 95% CI: [1.197, 3.033]). Clonality assessment of multidrug-resistant A. baumannii samples revealed eight clusters with one main cluster comprising 14/27 isolates between 2021 and 2022. The case fatality rate of the pre-pandemic and pandemic era was not different statistically (83.33% vs. 81.48%, p=0.835). Univariate analysis revealed the association of mechanical ventilation (p=0.002) and bacterial growth in tracheal aspirate (p=0.001) with fatality. During the COVID-19 pandemic, potential deficits in infection control measures may lead to persistent nosocomial outbreaks. In this study, the introduction of enhanced and customized infection control measures has resulted in the containment of an A. baumannii outbreak.Publication Metadata only Robustness of transcriptional regulation in yeast-like model boolean networks(World Scientific Publ Co Pte Ltd, 2010) Tugrul, Murat; Department of Physics; Department of Physics; Kabakçıoğlu, Alkan; Faculty Member; College of Sciences; 49854We investigate the dynamical properties of the transcriptional regulation of gene expression in the yeast Saccharomyces Cerevisiae within the framework of a synchronously and deterministically updated Boolean network model. With a dynamically determinant subnetwork, we explore the robustness of transcriptional regulation as a function of the type of Boolean functions used in the model that mimic the influence of regulating agents on the transcription level of a gene. We compare the results obtained for the actual yeast network with those from two different model networks, one with similar in-degree distribution as the yeast and otherwise random, and another due to Balcan et al., where the global topology of the yeast network is reproduced faithfully. We, surprisingly, find that the first set of model networks better reproduce the results found with the actual yeast network, even though the Balcan et al. model networks are structurally more similar to that of yeast.Publication Metadata only Integrated usage of historical geospatial data and modern satellite images reveal long-term land use/cover changes in Bursa/Turkey, 1858-2020(Nature Publishing Group (NPG), 2022) Ettehadi Osgouei, Paria; Sertel, Elif; Department of History; Department of History; Kabadayı, Mustafa Erdem; Faculty Member; College of Social Sciences and Humanities; 33267Land surface of the Earth has been changing as a result of human induced activities and natural processes. Accurate representation of landscape characteristics and precise determination of spatio-temporal changes provide valuable inputs for environmental models, landscape and urban planning, and historical land cover change analysis. This study aims to determine historical land use and land cover (LULC) changes using multi-modal geospatial data, which are the cadastral maps produced in 1858, monochrome aerial photographs obtained in 1955, and multi-spectral WorldView-3 satellite images of 2020. We investigated two pilot regions, Aksu and Kestel towns in Bursa/Turkey, to analyze the long-term LULC changes quantitatively and to understand the driving forces that caused the changes. We propose methods to facilitate the preparation of historical datasets for the LULC change detection and present an object-oriented joint classification scheme for multi-source datasets to accurately map the spatio-temporal changes. Our approach minimized the amount of manual digitizing required for the boundary delineation of LULC classes from historical geospatial data. Also, our quantitative analysis of LULC maps indicates diverging developments for the selected locations in the long period of 162 years. We observed rural depopulation and gradual afforestation in Aksu; whereas, agricultural land abandonment and deforestation in Kestel.