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    PublicationOpen Access
    1899 yılı Osmanlı İmparatorluğu için jeomekansal ve çok modlu bir ulaşım ağı oluşturma denemesi
    (Koç University Research Center for Anatolian Civilizations (ANAMED) / Koç Üniversitesi Anadolu Medeniyetleri Araştırma Merkezi (ANAMED), 2020) Gerrits, Piet; Department of History; Kabadayı, Mustafa Erdem; Özkan, Osman; Koçak, Turgay; Faculty Member; Teaching Faculty; Department of History; College of Social Sciences and Humanities; 33267; N/A; N/A
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    PublicationOpen Access
    A preliminary attempt to construct a geospatial, multimodal Ottoman transport network for 1899
    (Koç University Press (KUP) / Koç Üniversitesi Yayınları (KÜY), 2021) Gerrits, Piet; Department of History; Kabadayı, Mustafa Erdem; Özkan, Osman; Koçak, Turgay; Faculty Member; Teaching Faculty; Department of History; College of Social Sciences and Humanities; 33267; N/A; N/A
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    PublicationOpen Access
    A wearable paper-integrated microfluidic device for sequential analysis of sweat based on capillary action
    (Royal Society of Chemistry (RSC), 2022) Koydemir, Hatice Ceylan; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Beker, Levent; Abbasiasl, Taher; Mirlou, Fariborz; İstif, Emin; Faculty Member; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; 308798; N/A; N/A; N/A
    Soft, skin-mounted microfluidic devices can collect microliter volumes of eccrine sweat and are capable of in situ real-time analysis of different biomarkers to assess physiological state and health. Chrono-analysis of sweat can be implemented to monitor temporal variations of biomarker concentrations over a certain period of interest. Conventional methods used to capture sweat or some of the newly developed microfluidic platforms for sweat collection and analysis are based on absorbent pads. They suffer from evaporation, leading to considerable deviations in the concentration of the biomarkers. Here, a paperintegrated microfluidic device is presented for sequential analysis of sweat that is easy to fabricate and does not include air exits for each reservoir, which reduces undesirable effects of sweat evaporation. Furthermore, the high capillary force of filter paper is leveraged to route the liquid into the chambers in a sequential fashion and allow further chemical analysis. The employed design of the paper-embedded microfluidic device successfully samples and analyzes artificial sweat sequentially for flow rates up to 5 ?L min?1 without showing any leakage. We demonstrated the performance of the device, employing colorimetric assays for chrono-analysis of glucose standard solutions at concentrations in the range of 10– 100 mM and pH of sweat during exercise. The results reveal the presented approach's functionality and potential to analyze the concentration of biomarkers over a certain period sequentially.
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    PublicationOpen Access
    An extensive comparative analysis of two MOF databases: high-throughput screening of computation-ready MOFs for CH4 and H2 adsorption
    (Royal Society of Chemistry (RSC), 2019) Eruçar, İlknur; Department of Chemical and Biological Engineering; Keskin, Seda; Velioğlu, Sadiye; Altıntaş, Çiğdem; Avcı, Gökay; Harman, Hilal Dağlar; Azar, Ayda Nemati Vesali; Researcher; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; 40548; N/A; N/A; N/A; N/A; N/A
    Computation-ready metal–organic framework (MOF) databases (DBs) have tremendous value since they provide directly useable crystal structures for molecular simulations. The currently available two DBs, the CoRE DB (computation-ready, experimental MOF database) and CSDSS DB (Cambridge Structural Database non-disordered MOF subset) have been widely used in high-throughput molecular simulations. These DBs were constructed using different methods for collecting MOFs, removing bound and unbound solvents, treating charge balancing ions, missing hydrogens and disordered atoms of MOFs. As a result of these methodological differences, some MOFs were reported under the same name but with different structural features in the two DBs. In this work, we first identified 3490 common MOFs of CoRE and CSDSS DBs and then performed molecular simulations to compute their CH4 and H2 uptakes. We found that 387 MOFs result in different gas uptakes depending on from which DB their structures were taken and we identified them as ‘problematic’ MOFs. CH4/H2 mixture adsorption simulations showed that adsorbent performances of problematic MOFs, such as selectivity and regenerability, also significantly change depending on the DB used and lead to large variations in the ranking of materials and identification of the top MOFs. Possible reasons of different structure modifications made by the two DBs were investigated in detail for problematic MOFs. We described five main cases to categorize the problematic MOFs and discussed what types of different modifications were performed by the two DBs in terms of removal of unbound and bound solvents, treatment of missing hydrogen atoms, charge balancing ions etc. with several examples in each case. With this categorization, we aimed to direct researchers to computation-ready MOFs that are the most consistent with their experimentally reported structures. We also provided the new computation-ready structures for 54 MOFs for which the correct structures were missing in both DBs. This extensive comparative analysis of the two DBs will clearly show how and why the DBs differently modified the same MOFs and guide the users to choose either of the computation-ready MOFs from the two DBs depending on their purpose of molecular simulations.
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    PublicationOpen Access
    Artificial eye model and holographic display based IOL simulator
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2023) N/A; Department of Electrical and Electronics Engineering; N/A; Şahin, Afsun; Ürey, Hakan; Aygün, Uğur; Kavaklı, Koray; Akyazı, Deniz; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; School of Medicine; College of Engineering; Graduate School of Sciences and Engineering; 171267; 8579; N/A; N/A; N/A
    Cataract is a common ophthalmic disease in which a cloudy area is formed in the lens of the eye and requires surgical removal and replacement of eye lens. Careful selection of the intraocular lens (IOL) is critical for the post-surgery satisfaction of the patient. Although there are various types of IOLs in the market with different properties, it is challenging for the patient to imagine how they will perceive the world after the surgery. We propose a novel holographic vision simulator which utilizes non-cataractous regions on eye lens to allow the cataract patients to experience post-operative visual acuity before surgery. Computer generated holography display technology enables to shape and steer the light beam through the relatively clear areas of the patient’s lens. Another challenge for cataract surgeries is to match the right patient with the right IOL. To evaluate various IOLs, we developed an artificial human eye composed of a scleral lens, a glass retina, an iris, and a replaceable IOL holder. Next, we tested different IOLs (monofocal and multifocal) by capturing real-world scenes to demonstrate visual artifacts. Then, the artificial eye was implemented in the benchtop holographic simulator to evaluate various IOLs using different light sources and holographic contents.
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    PublicationOpen Access
    Çin’in yükselişi ve yeni kapitalizm
    (Sosyoekonomi Society, 2018) Department of Sociology; Yörük, Erdem; Faculty Member; Department of Sociology; College of Social Sciences and Humanities; 28982
    This article presents a theoretical discussion about the new forms of capitalism in the context of the economic and political rise of China. The article raises a discussion on the changes that the rise of China has instigated in both China and the world capitalism. This is considered in the context of mode of production, international trade, state and capital, by analysing China and capitalism from the perspective of long historical periods. In doing this, the article benefits from the work of and polemics between Giovanni Arrighi, Joel Andreas ve Richard Walker, who provided very important contemporary debates on this issue in the field of historical sociology.
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    PublicationOpen Access
    Computational selection of high-performing covalent organic frameworks for adsorption and membrane-based CO2 /H2 separation
    (American Chemical Society (ACS), 2020) Department of Chemical and Biological Engineering; Keskin, Seda; Altıntaş, Çiğdem; Harman, Hilal Dağlar; Aksu, Gökhan Önder; Researcher; Department of Chemical and Biological Engineering; College of Engineering; Graduate School of Sciences and Engineering; 40548; N/A; N/A; N/A
    Covalent organic frameworks (COFs) have high potential in gas separation technologies because of their porous structures, large surface areas, and good stabilities. The number of synthesized COFs already reached several hundreds, but only a handful of materials were tested as adsorbents and/or membranes. We used a high-throughput computational screening approach to uncover adsorption-based and membrane-based CO2/H2 separation potentials of 288 COFs, representing the highest number of experimentally synthesized COFs studied to date for precombustion CO2 capture. Grand canonical Monte Carlo (GCMC) simulations were performed to assess CO2/H2 mixture separation performances of COFs for five different cyclic adsorption processes: pressure swing adsorption, vacuum swing adsorption, temperature swing adsorption (TSA), pressure−temperature swing adsorption (PTSA), and vacuum−temperature swing adsorption (VTSA). The results showed that many COFs outperform traditional zeolites in terms of CO2 selectivities and working capacities and PTSA is the best process leading to the highest adsorbent performance scores. Combining GCMC and molecular dynamics (MD) simulations, CO2 and H2 permeabilities and selectivities of COF membranes were calculated. The majority of COF membranes surpass Robeson’s upper bound because of their higher H2 permeabilities compared to polymers, indicating that the usage of COFs has enormous potential to replace current materials in membrane-based H2/CO2 separation processes. Performance analysis based on the structural properties showed that COFs with narrow pores [the largest cavity diameter (LCD) < 15 Å] and low porosities (ϕ < 0.75) are the top adsorbents for selective separation of CO2 from H2, whereas materials with large pores (LCD > 20 Å) and high porosities (ϕ > 0.85) are generally the best COF membranes for selective separation of H2 from CO2. These results will help to speed up the engineering of new COFs with desired structural properties to achieve high-performance CO2/H2 separations.
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    PublicationOpen Access
    Cross-context news corpus for protest event-related knowledge base construction
    (Massachusetts Institute of Technology (MIT) Press, 2021) Department of Sociology; N/A; Department of Computer Engineering; Yörük, Erdem; Hürriyetoğlu, Ali; Gürel, Burak; Duruşan, Fırat; Yoltar, Çağrı; Mutlu, Osman; Yüret, Deniz; Faculty Member; Teaching Faculty; Faculty Member; Researcher; Researcher; Faculty Member; Department of Sociology; Department of Computer Engineering; College of Social Sciences and Humanities; Graduate School of Sciences and Engineering; College of Engineering; 28982; N/A; 219277; N/A; N/A; N/A; 179996
    We describe a gold standard corpus of protest events that comprise various local and international English language sources from various countries. The corpus contains document-, sentence-, and token-level annotations. This corpus facilitates creating machine learning models that automatically classify news articles and extract protest event-related information, constructing knowledge bases that enable comparative social and political science studies. For each news source, the annotation starts with random samples of news articles and continues with samples drawn using active learning. Each batch of samples is annotated by two social and political scientists, adjudicated by an annotation supervisor, and improved by identifying annotation errors semi-automatically. We found that the corpus possesses the variety and quality that are necessary to develop and benchmark text classification and event extraction systems in a cross-context setting, contributing to the generalizability and robustness of automated text processing systems. This corpus and the reported results will establish a common foundation in automated protest event collection studies, which is currently lacking in the literature.
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    PublicationOpen Access
    Dynamic accommodation measurement using Purkinje reflections and ML algorithms
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2023) Department of Electrical and Electronics Engineering; N/A; Aygün, Uğur; Şahin, Afsun; Ürey, Hakan; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); College of Engineering; School of Medicine; N/A; N/A; N/A; 171267; 8579
    We developed a prototype device for dynamic gaze and accommodation measurements based on 4 Purkinje reflections (PR) suitable for use in AR and ophthalmology applications. PR1&2 and PR3&4 are used for accurate gaze and accommodation measurements, respectively. Our eye-model was developed in Zemax and matches the experiments well. Our model predicts the accommodation from 25cm to infinity (<4 diopters) with better than 0,25D accuracy. We performed repeatability tests and obtained accurate gaze and accommodation estimations using 15 subjects. We are generating a large synthetic data set using physically accurate models and machine learning algorithms.
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    PublicationOpen Access
    Energy and climate security priorities and challenges in the changing global energy order
    (FEUTURE: The Future of EU-Turkey Relations, 2017) Martínez-García, Enrique; Soytaş, Mehmet Ali; Department of International Relations; Yılmaz, Şuhnaz Özbağcı; Faculty Member; Department of International Relations; College of Administrative Sciences and Economics; 46805
    Global energy markets are facing an era of extensive change through a radical process of transformation known as the “energy transition”, which ranges from the unprecedented growth of renewables and the success of the Paris Agreement to the still unpredictable future of gas and oil prices. Europe and Turkey are heavily influenced by these phenomena, and so are their relations. A more climate-friendly position by Turkey would increase chances for cooperation with the EU – still the de facto global climate leader. A greater role for gas would boost the EU and Turkey’s need for diversification, and thus possibly for cooperation. Turkey’s significant focus on coal could, however, move the country instead closer to the anti-climate stance opened up by President Donald Trump’s exit from the Paris Agreement, thus leading to a conflict scenario with the EU. The energy transition could provide a robust framework for the EU’s and Turkey’s future energy and climate relations, and one that might possibly be open to a new role for platforms such as the G20. However, its final impact will be a result of the evolution of its individual components, and the choices that the EU and Turkey will make in regard to these.