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Öğe ALMOST alpha-COSYMPLECTIC f-MANIFOLDS(Univ Al I Cuza, Fac Math, 2014) Öztürk, Hakan; Murathan, Cengizhan; Aktan, Nesip; Vanlı, Aysel TurgutThe purpose of this paper is to study a new class of framed manifolds. Such manifolds are Called almost alpha-cosymplectic f-manifolds. For some special cases of alpha and s, one obtains (almost) alpha-cosymplectic, (almost) C-manifolds, and (almost) Kenmotsu f-manifolds. Moreover, several tensor conditions are studied. We conclude our results with a general example on alpha-cosymplectic f-manifolds.Öğe Atık lastik katkısının kendiliğinden yerleşen betonların mühendislik özelliklerine etkileri(Düzce Üniversitesi, 2016) Öztürk, Hakan; Bideci, AlperDünyada her yıl 10 milyon tondan daha fazla atık lastik oluşmakta ve bu rakam, ülkemiz için 300 bin ton civarına ulaşmaktadır. Atık lastiklerin doğada bozulması oldukça zordur ve bu lastiklerin çevreye verilmesi hem insan sağlığı hem de çevre için ciddi tehlikeler doğurmaktadır. Dolayısıyla, atık lastikler için atık yönetiminin yapılması gereklidir. Atık lastiklerin yeniden kullanımı, beton üretim süreci içerisinde kullanılan geri dönüşüm metotlarından biridir. Bu metot, daha hafif beton malzemeleri, daha yüksek eğilme tokluğu ve atıkların bertaraf edilmesine katkı sağlar. Bu çalışmada, 25, 50 ve 75 mm uzunluğunda mekanik olarak kesilen atık lastikler (LA) kendiliğinden yerleşen beton (KYB) içerisinde iri agrega ile hacimce yer değiştirilerek değerlendirilmiştir. %5, %10 ve %15 oranlarında hacimsel olarak iri agrega ile yer değiştirilerek elde edilen betonlar üzerinde, birim ağırlık, slump yayılma, J-ringi, kolon segregasyon, su emme 28 günlük basınç dayanımı, ultrases geçiş hızı, kırılma enerjisi deneyleri yapılmıştır. Ayrıca numunelerin SEM (Taramalı Elektron Mikroskobu) ve EDS (Enerji Dağılımı Spektroskopisi) analizleri de incelenmiştir. Çalışmada, LA ikamesinin taze betonun birim ağırlığını düşürdüğü, LA boy oranı arttıkça betonun donatı aralığından geçişinin zor hale geldiği, sertleşmiş beton numunelerde kuru birim ağırlığının azaldığı, %10 lif katkısının basınç dayanım değerlerini arttırdığı, ultrases geçiş hızları ölçümü sonrası betonların "iyi" beton sınıfına girdiği belirlenmiştir. Sonuç olarak, kendiliğinden yerleşen betonlara 25mm boyunda %10 atık lastik agrega ikamesinin optimum sonuçlar verebileceği tespit edilmiştir.Öğe Development of a safety protocol for training and using SARS-CoV-2 detection dogs: A pilot study(Elsevier Inc., 2023) Demirbaş, Yasemin Salgırlı; Kısmalı, Görkem; Saral, Begüm; Sareyyüpoğlu, Barış; Habiloğlu, Arif Doğan; Öztürk, Hakan; Baş, BülentMedical detection dogs have potential to be used to screen asymptomatic patients in crowded areas at risk of epidemics such as the SARS-CoV-2 pandemic. However, the fact that SARS-CoV-2 detection dogs are in direct contact with infected people or materials raises important concerns due to the zoonotic potential of the virus. No study has yet recommended a safety protocol to ensure the health of SARS- CoV-2 detection dogs during training and working in public areas. This study sought to identify suitable decontamination methods to obtain nonpathogenic face mask samples while working with SARS-CoV-2 detection dogs and to investigate whether dogs were able to adapt themselves to other decontamination procedures once they were trained for a specific odor. The present study was designed as a four-phase study: (a) Method development, (b) Testing of decon- tamination methods, (c) Testing of training methodology, and (d) Real life scenario. Surgical face masks were used as scent samples. In total, 3 dogs were trained. The practical use of 3 different decontam- ination procedures (storage, heating, and UV-C light) while training SARS-CoV-2 detection dogs were tested. The dog trained for the task alerted to the samples inactivated by the storage method with a sensitivity of100 % and specificity of 98.28 %. In the last phase of this study, one dog of 2 dogs trained, alerted to the samples inactivated by the UV-C light with a sensitivity of 91.30% and specificity of 97.16% while the other dog detected the sample with a sensitivity of 96.00% and specificity of 97.65 %. © 2023 Elsevier Inc.Öğe Fracture energy and mechanical characteristics of self-compacting concretes including waste bladder tyre(Elsevier Sci Ltd, 2017) Bideci, Alper; Öztürk, Hakan; Bideci, Özlem Sallı; Emiroğlu, MehmetManagement of solid wastes is one of the most important environmental problems in the world. Waste tyres are also one of these solid wastes. The growing number of waste tyres that are stocked every year brings problems in respect of human health, environmental pollution, and also causes esthetical problems. The main purpose of this study is to investigate the effect of waste tyre addition on self compacting concretes' mechanical characteristics and fracture properties under bending. In this study, waste bladder tyres (RA) mechanically cut in 25, 50 and 75 mm lengths were used by volumetric replacement of coarse aggregates in self-compacting concretes (SCC). Unit weight, flow, J-ring, column segregation, water absorption, 28 days of compressive strength, ultrasound pulse velocity and fracture energy tests were applied on concretes obtained by replacement of coarse aggregates in 5%, 10% and 15% ratios by volume. Also, Scanning Electronic Microscope (SEM) and Energy Distribution Spectroscopy (EDS) analyses of the samples were examined. In the study, it was determined that RA replacement decreases unit weight of fresh concrete; when RA length ratio increases, it becomes difficult for the concrete to pass through reinforcement openings; in hardened concrete samples dry unit weight decreases; 10% fibre addition increases compressive strength values; after the ultrasonic pulse velocity measurement, the concretes are included in "good" quality concrete classifications. As a conclusion, it was determined that 25 mm long 10% rubber aggregate replacement to self-compacting concretes can give optimum results. (C) 2017 Elsevier Ltd. All rights reserved.Öğe Response of nonconforming RC shear walls with smooth bars under quasi-static cyclic loading(Springer, 2022) Olabi, Muhammed Nadir; Çağlar, Naci; Arslan, Mehmet Emin; Öztürk, Hakan; Demir, Aydın; Dok, Gökhan; Aykanat, BatuhanIn this study, an experimental investigation is conducted to determine the behavior of RC shear walls found in old and existing buildings that do not comply with the design rules in modern earthquake standards. Scaled reinforced concrete shear wall specimens are built with smooth bars and low concrete quality. The dimensions of the shear wall specimens were selected with an aspect ratio bigger than two as 2500, 1050, and 150 mm for the height, length, and thickness, respectively. Four specimens are representative of nonconforming shear walls, and one wall is used as a reference specimen which was designed in accordance with recent building codes using deformed bars. The behavior of the shear walls is determined experimentally by displacement-lateral load relationship under lateral cyclic loading. The study used measurable parameters to investigate the behavior of the test specimens in terms of lateral force capacity, rigidity, ductility, dissipated energy, and displacement components contribution to the total lateral response of the walls. The results showed a substantial loss of stiffness, ductility and energy dissipation capabilities for the tested nonconforming shear walls. Moreover, it is proven in this study that these specimens are governed by the bar slip phenomena which demonstrated more than 80% contribution to the total lateral displacement capacity. In contrast, the reference shear wall exhibited a notable flexural behavior and plastic hinge formation. Additionally, the shear walls built with smooth reinforcement bars lost about 44% of their theoretical potential flexural capacity due to the observed bar slip failure.Öğe Utilizing of waste ceramic powders as filler material in self-consolidating concrete(Elsevier Sci Ltd, 2017) Subaşı, Serkan; Öztürk, Hakan; Emiroğlu, MehmetUsing filler materials finer than 0.125 mm is quite effective on the fresh state properties, strength and durability of self-consolidating concretes. Most common filler materials used in self -consolidating concretes are minerals, blended cements and natural or artificial pozzolans. In this study, usability of granulated waste ceramic powder as filler material in self -consolidating concretes was investigated. Properties of self -consolidating concretes produced with 5501 kg/m(3) dosage and cement was replaced with (WCP) in the amounts of 5%, 10%, 15% and 20% (by weight) were determined in the fresh and hardened phases. As a result, it is determined that use of WCP has some positive effect on viscosity of the mixes. However, a slight decrease was observed on the strength values based on the substitution of cement with ceramic powder. It can be concluded that finely ground WCP5 could be evaluated up to 15% for production of self-consolidating concretes as a filler material if the strength and flowability parameters are evaluated together. (C) 2017 Elsevier Ltd. All rights reserved.