Investigation Of Ageing Effects On Commercial Lifepo4 Cathode Material

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2013Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2013Bu çalışmada, düğme tipi (saat pili) ve üç elektrotlu elektrokimyasal empedans spektroskopi (EIS) ölçümlerine olanak sağlayan Swagelok T tipi LiFePO4/Grafit lityum iyon pilleri kullanılarak farklı cevrim sayılarının ve farklı cevrim parametrelerinin (voltaj, akım ve sıcaklık) kullanıldığı galvanostatik cevrim testleri ile LiFePO4 katot malzemesinin yaslanma davranışı incelenmiştir. Bu cevrim testlerinden sonra pilin ve LiFePO4 katot malzemesinin empedanslarındaki değişimleri incelemek için EIS ölçümlerinden yararlanılmıştır. EIS ölçümlerini takiben LiFePO4 katot malzemesi üzerinde gerçekleştirilen bir dizi karakterizasyon analizi ( Raman, XRD ve SEM) ile yaslanmanın LiFePO4 üzerindeki etkileri incelenmiştir. Yapılan bu çalışımlar sonucu; yüksek şarj ve deşarj akımlarının katot malzemesinin ulaşabildiği kapasite değerlerini ve kapasite düşüş karakteristiğini olumsuz yönde etkilediği anlaşılmış ve kapasite düşüşündeki ana etkenin lityum iyon batarya içerisindeki aktif lityum iyon miktarındaki azalma olduğu belirlenmiştir. Lityum iyon bataryanın toplam empedansındaki en büyük katkının katot malzemesi kaynaklı olduğu fakat çevrimler sonrası meydana gelen empedans artışında katot malzemesinin rolünün diğer bileşenlere göre daha az olduğu anlaşılmıştır. Bir cevrim süresince meydana gelen LiFePO4 ile FePO4 arasındaki çift taraflı faz dönüşümlerinin kristal kafeste değişikliklere yol açtığı fakat artan çevrim sayısının LiFePO4 kristal yapısında fazla bir değişikliğe yol açmadığı buna karşın çok kullanım süresince çok sayıda tekrarlanan bu faz dönüşümlerinin aktif malzemede iç gerilmelere ve yorulmaya yol açabileceği bununda cevrim testlerinden sonra gerçekleştirilen karakteriyaszon analizleri sonucu LiFePO4 partiküllerinde gözlemlenen mikro çatlakların, yüzey bozulmalarının ve katot yüzeyindeki karbon kaplamadaki kalite düşüşünün nedeni olabileceği kanısına varılmıştır. Buna ilaveten sıcaklık artışının katot malzemesinin ulaşabileceği maksimum kapasiteyi artırıcı etkisi olduğu fakat aynı zamanda kapasite düşüşünü ve empedans artışını tetiklediği görülmüştür.In this study, galvanostatic cycle tests having different number of cycles have been carried out using coin cells and Swagelok T cells, which have been used to make three-electrode electrochemical impedance spectroscopy (EIS) measurements, in order to clarify the ageing effects on a commercial LiFePO4 cathode material. Also, cycle tests using different cycling parameter (current, voltage, and ambient temperatures) have been performed to identify the effects of these parameters on capacity fading. After cycle tests, EIS measurements have been conducted to determine impedance changes in the lithium ion battery and on the cathode material. After cycle tests and EIS measurements, a series of qualitative analysis (XRD, Raman, and SEM) have been conducted on the LiFePO4 cathode material. After all these measurements; high charge current was found to affect the reachable capacity and capacity fading characteristic profoundly. Additionally, loss of cyclable lithium was found to be the main reason for capacity fading during ageing, followed by accelerated deformation of the LiFePO4 cathode material and the deformation of carbon coating towards the end of the cycle tests. The LiFePO4 cathode material was found as the main reason for impedance of the lithium ion batteries. On the other hand, Swagelok T cells measurements was indicated an impedance increase of lithium ion batteries after cycle tests is not directly related with the LiFePO4. In addition, temperature rise was observed as activator to increase rechargeable capacity but it leads to an increment of impedance and capacity fading at the same time.Yüksek LisansM.Sc

An efficient framework for visible-infrared cross modality person re-identification

Visible-infrared cross-modality person re-identification (VI-ReId) is an essential task for video surveillance in poorly illuminated or dark environments. Despite many recent studies on person re-identification in the visible domain (ReId), there are few studies dealing specifically with VI-ReId. Besides challenges that are common for both ReId and VI-ReId such as pose/illumination variations, background clutter and occlusion, VI-ReId has additional challenges as color information is not available in infrared images. As a result, the performance of VI-ReId systems is typically lower than that of ReId systems. In this work, we propose a four-stream framework to improve VI-ReId performance. We train a separate deep convolutional neural network in each stream using different representations of input images. We expect that different and complementary features can be learned from each stream. In our framework, grayscale and infrared input images are used to train the ResNet in the first stream. In the second stream, RGB and three-channel infrared images (created by repeating the infrared channel) are used. In the remaining two streams, we use local pattern maps as input images. These maps are generated utilizing local Zernike moments transformation. Local pattern maps are obtained from grayscale and infrared images in the third stream and from RGB and three-channel infrared images in the last stream. We improve the performance of the proposed framework by employing a re-ranking algorithm for post-processing. Our results indicate that the proposed framework outperforms current state-of-the-art with a large margin by improving Rank-1/mAP by 29.79%/30.91% on SYSU-MM01 dataset, and by 9.73%/16.36% on RegDB dataset.WOS:000551127300017Scopus - Affiliation ID: 60105072Science Citation Index ExpandedQ2ArticleUluslararası işbirliği ile yapılmayan - HAYIREylül2020YÖK - 2020-2

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Estimating Steel Fabrication Costs For Modular Shipbuilding Practice

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2016Thesis (M.Sc.) -- İstanbul Technical University, Instıtute of Science and Technology, 2016Herhangi bir iş alanında olduğu gibi, tersaneler de her zaman kârlarını arttırmak için maliyetlerini düşürme konusunda diğer tersaneler ile yarışıyor. Tersaneler için bir proje elde etmenin ilk adımı, inşaat maliyeti ve zamanlamasını içeren bir teklif hazırlamakla başlıyor. Bir gemiyi inşa etmek için gereken malzeme ve insan gücünü tahmin etmek karmaşık bir süreçtir. Geminin boyutu büyüdükçe, bu tahmin süreci de daha karmaşıklaşır. Tersanelerde, bu karmaşık süreci yönetebilecek profesyönel kişiler görev yapmaktadırlar. Eğer bir tersane sürekli aynı türdeki gemileri inşa etmiyorsa, tahmin ve teklif hazırlanırken gerekli sağlam bir temel oluşturacak tarihsel inşa verileri olmaz. Böyle bir durumda, gemi inşa endüstrisi için ortak maliyet tahmin formüllerine başvurulur. Bu yaygın olarak kullanılan formüllerin büyük çoğunluğu gemi ağırlığı ve uzunluğu veya blok katsayısı gibi bir kaç gemi özelliklerini baz alırlar. Gemi özelliklerine ek olarak, bu formüller çok sayıda "tersane verimlilik" katsayılarına sahiptirler. Ağırlık esaslı ortak tahmin yöntemleri ile ilgili temel sorun ise bu yöntemlerin, tasarımın karmaşıklığını veya üretilebilirliğini göz önünde bulundurmamalarıdır. Diğer bir deyişle, yaygınca kullanılan ton çelik başına düşen adam saat miktarının geniş bir tasarım yelpazesine uygun olabileceği beklenmektedir. "Tersane verimlilik" katsayısi ile ilgili esas muamma ise bu rakkamın ağır bir şekilde teklif hazırlayan kişilerin bilgisine bağlı olması ile istenen ve gerçek üretim verimlilikleri arasında büyük bir boşluğun olmasıdır. Bu katsayılar kişisel bakış acısına bağlı olduklarından takip etmek ve geliştirmek çok zordur. Bu tez çalışması dahilindeki tahmin yaklaşımı, geminin ağırlık, uzunluk veya blok katsayısı gibi karakterlerini göz ardı eder ve gemi inşa sürecini, çeşitli atölyeleri kapsayan bir üretim süreci olarak ele alır. Her atölyedeki işi gerçekleştirmek için gereken süre, bu tahmin yaklaşımı için önemli bir girdi değeri olur. Diğer bir önemli girdi değeri ise geminin detaylı tasarım nitelikleridir. Bu özellikler, teklif hazırlanmasi icin tersaneye verilen, fabrikasyon sırası, 3 boyutlu yapısal model ve montaj çizimlerinden elde edilir. Bu tez çalışması dahilindeki tahmin yaklaşımı, atölyenin verimliliğini ve geminin detaylı tasarım yönlerini bilgisayar tabanlı bir şekilde birleştirir ve daha sonra en fazla getiriyi vaat edebilecek bireysel üretim aşamalarının inceleneceği bir çalışmaya yol açabilir Bu tez içeriğindeki tahmin yaklaşımı aynı zamanda boru sistemleri, elektrik sistemleri ve diğer donatım öğeleri için de kullanılabilir ancak, bu tez sadece yapısal tahminlere odaklanır çünkü ilk büyük hakediş, genellikle, yapısal çalışmalarla ilgilidir. Tersanelerde nakit akışını başlatmak ve sürdürmek için, gemi inşa süreci daha küçük “kilometre taşları”na bölünür ve dolayısıyla her kilometre taşı bir ana ödemeyi temsil eder. Bu ödemelere hakediş denir. Genellikle, ilk büyük kilometre taşı omurga döşeme veya birinci plaka kesimi ile ilgilidir ve gemi sahibi tarafından tersaneye yapılan ilk büyük ödemeye karşılık gelir. Bu tez, iki bloğu inceler alır ve her yapı parçasının malzeme ve imalat özelliklerini inceleyerek, her parçaya tersaneye mahsus parça işleme sürelerini atayarak, mevcut ağırlık bazli çelik imalat maliyet tahmini yöntemleri geliştirmeyi amaçlar. Bu tez aşağıdaki gibi yapılandırılmıştır: Birinci bölüm, gemi maliyetinin tahmininde kullanılan farklı yöntemleri belirleyen ve karşılaştıran bir literatür incelemesini içerir. İkinci bölüm, gemi inşa yöntemlerine değinirken, bloklarla üretim yönteminin faydalarını özetlemektedir. Üçüncü bölüm, çelik imalat süreci ve üretiminde önemli olan maliyet öğelerini inceler. Dördüncü bölüm ise 3-boyutlu yapısal model ve tasarım çizimlerinden türetilen ve tahmin yönteminde kullanılacak metrikler hakkında ayrıntılar verir. Beşinci bölüm, algoritmada kullanılan çelik parçalar ve metrik değerleri arasındaki ilişkileri detaylarken, tahmin algoritması hakkında ayrıntılı bilgi sağlar. Altıncı bölüm, algoritmanin üzerinde uygulandığı bir üst yapı bloğunun seçiminin arkasındaki nedenleri açıklar. Aynı zamanda, bloğun yapısal ayrıntıları ve blok sınırları için bilgi verir. Yedinci bölüm, algoritmanın üzerinde uygulandığı diğer üst yapı bloğu hakkındaki bilgileri, altıncı bölümde verilen ayrıntılarla, sunar. Sekizinci bölüm, bu tez kapsamındaki VBA yöntemiyle tahmin edilen adam saat sonuçlarını içerir. Hesaplanan sonuçları karşılaştırır ve VBA yönteminin diğer avantajlarına değinir.As in any business, shipyards are always competing with other shipyards about lowering their costs to increase their profits. The first step in getting a project into the shipyard is preparing a proposal that includes the construction cost and schedule. Estimating the amount of material and man-power that is needed to fabricate a vessel is a complex process. As the vessel size gets larger, this estimating process also gets more complicated. Fortunately, shipyards do have estimating departments with professional estimators to handle such complex process. Unless the shipyard has been in business for constructing the same style vessels and made a name for itself to be the “go-to” yard for such vessels, the shipyard estimators will not have the historical construction data to use a solid foundation for their proposals. In that case, they will try to employ the common cost estimating formulas for the shipbuilding industry. The great majority of these commonly available formulas rely heavily on the vessel weight and a few vessel characteristics, such as the length or block coefficient. In addition to the vessel characteristics, these formulas have numerous “shipyard productivity” coefficients. The main problem with the weight based common estimating methods is that they do not consider the complexity or the producibility of the design. In other words, a set number of man-hours per ton of steel is expected to cover a wide range of vessel design practices. The main puzzle with the “shipyard productivity” coefficients is that they rely, heavily, on the estimator’s knowledge of the capabilities of the fabrication facility with a large gap between the desired and actual production efficiencies. These coefficients are subjective and, therefore, extremely difficult to monitor and improve. The estimating approach in this thesis takes the vessel weight, length or block coefficient out of the equation and treats the shipbuilding as a fabrication process that takes place in many workstations. The time it takes to perform each task at each workstation becomes an important input value for the approach. The other important input value is the detailed design attributes of the vessel structure. These attributes are extracted from the build sequence, 3-dimensional structural model and assembly drawings that are provided to the shipyard for the proposal preparation purposes. The approach, then, combines the capabilities of the fabrication facility and detailed design aspects of the structure in a formulated, computer-based manner that can actually lead to a study of individual production steps that promises the most return when improved. Although this approach can be employed for pipe systems, electrical systems and other outfitting items, this thesis focuses only on the structural estimate because the first major progress payment will, usually, be about the structural work. In order to initiate and maintain cash flow in shipyards, the long and complicated shipbuilding process is broken into smaller milestones and, consequently, each milestone represents a payment. These payments are called progress payments. Usually, the first major milestone is the keel laying or first plate cutting that corresponds to the first major payment to the shipyard by the vessel owner. This thesis will try to improve on the current weight-based steel fabrication cost estimating methods by examining the material and fabrication characteristics of each structural part in two structural blocks, and assigning shipyard specific work times to these parts. This thesis is structured as follows: Chapter 1 is a literature review to identify and compare the different methods in shipbuilding cost estimation. Chapter 2 outlines the shipbuilding methods and summarizes the benefits of shipbuilding in blocks. Chapter 3 examines the steel fabrication sequence and the major cost items in fabrication. Chapter 4 provides details about the metrics that are extracted from the 3-dimensional structural model and design drawings to be used in the estimating method. Chapter 5 provides details about the estimating algorithm, including the relations between the piece parts and metric values that are used in the algorithm. Chapter 6 explains the reason behind selecting a super structure module for testing the algorithm. It also provides structural details and boundary information for the module. Chapter 7 goes over the same details provided in Chapter 6 for the other module that is used to test the algorithm. Chapter 8 shows the results of the VBA method in estimated man-hours. It compares the calculated results and mentions other benefits of the VBA method.Yüksek LisansM.Sc

An efficient multiscale scheme using local zernike moments for face recognition

In this study, we propose a face recognition scheme using local Zernike moments (LZM), which can be used for both identification and verification. In this scheme, local patches around the landmarks are extracted from the complex components obtained by LZM transformation. Then, phase magnitude histograms are constructed within these patches to create descriptors for face images. An image pyramid is utilized to extract features at multiple scales, and the descriptors are constructed for each image in this pyramid. We used three different public datasets to examine the performance of the proposed method:Face Recognition Technology (FERET), Labeled Faces in the Wild (LFW), and Surveillance Cameras Face (SCface). The results revealed that the proposed method is robust against variations such as illumination, facial expression, and pose. Aside from this, it can be used for low-resolution face images acquired in uncontrolled environments or in the infrared spectrum. Experimental results show that our method outperforms state-of-the-art methods on FERET and SCface datasets.WOS:000437326800174Scopus - Affiliation ID: 60105072Science Citation Index ExpandedQ2 - Q3ArticleUluslararası işbirliği ile yapılmayan - HAYIRMayıs2018YÖK - 2017-1

The protective effect of letrozole in a rat ovarian ischemia-reperfusion injury model

INTRODUCTION: Torsion of the ovary is a surgical emergency. Future fertility is an important question for choosing the most appropriate treatment strategy as radical or conservative. Conservative treatment includes detorsion of the twisted ovary and after detorsion, the ischemic injury in ovary increases with reperfusion. During the detorsion process, abundant amounts of reactive oxygen species (ROS) are produced. ROS causes cellular injury by attacking cellular membranes through the peroxidation of polyunsaturated fatty acids and causing cellular death. Letrozole is a nonsteroid aromatase inhibitor that blocks estrogen production in all tissues, increases gonadotropin secretion and induces follicular development. METHODS: In this study, rats are divided into 5 groups including 8 rats in each group; control group, ischemia group, ischemia and letrozole group, ischemia-reperfusion group, ischemia-reperfusion and letrozole group. For each group Malondialdehyde (MDA) levels were measured, degree of ischemia and number of follicles were recorded by histopathological examination. Endometrial thicknesses were also measured. RESULTS: In the ischemia and ischemia-reperfusion groups, MDA levels and grade of ischemia were significantly decreased with letrozole. Ovarian follicle numbers were higher and endometrial thickness was lower in the letrozole used groups. DISCUSSION AND CONCLUSION: Letrozole can be protective on ovarian ischemia-reperfusion injury and this effect will be related to hypoestrogenic environment by inhibition of aromatase activity, antiinflammatory effects and increased blood flow to the ovary by letrozole

Corticosteroid hypersensitivity in allergic rhinitis

Corticosteroid hypersensitivity in allergic rhinitis. Background: intranasal corticosteroid (IC) is the most effective treatment method in allergic rhinitis patients who are unresponsive to antihistamines. The literature reports an approximate 20% treatment failure for instances where IC is used for the treatment allergic rhinitis. Hypersensitivity reaction to corticosteroids may be one of the causes of this treatment failure. Objective: to discover the incidence and confounding factors of corticosteroid hypersensitivity in patients with allergic rhinitis. Methods: after 31 patients were excluded, 150 consecutive patients who were prospectively evaluated in our outpatient clinics with the diagnosis of allergic rhinitis and 50 age- and sex- matched healthy volunteers were included in this study. To diagnose allergic rhinitis, the symptoms of patients and a skin prick test were used. A skin patch test was used to determine corticosteroid hypersensitivity. Total IgE values and total eosinophil count were obtained for all patients. Total symptom scores were calculated for the severity of symptoms and to determine the response to therapy using intranasal corticosteroids. Results: the incidence of corticosteroid hypersensitivity determined via the skin patch test was 14.0% (21 out of 150 patients). A difference was observed for patch test positivity results between the study and control groups (14% vs. 0%, respectively). Serum IgE levels and total eosinophil count were higher among patients who had corticosteroid hypersensitivity (p:0.005 and p:0.004, respectively). Patients unresponsive to intranasal corticosteroids had a higher incidence of corticosteroid hypersensitivity (71.4% vs. 4.4%, p<0.001). Conclusion: our study is the largest to date investigating CH in patients with allergic rhinitis and patients with allergic rhinitis have been found to have a high incidence (14%) of corticosteroid hypersensitivity, which may affect the response of patients to intranasal corticosteroid treatment

The Petroglyphs of Yandaklıdere

Rock Art have been studied by scientists in various research institutions for many years, and studies on this subject, as well as the publishing of papers, have occurred in Türkiye in recent years. The Yandaklıdere petroglyphs that can be found within the borders of Çağa village in the Güdül district of Ankara, constitute the main theme of the study. While the Yandaklıdere petroglyphs have been mentioned in other publications, no scale drawings and individual explanations of the depictions in the petroglyphs are available, and current comparative evaluations of the inscriptions are also limited. This study serves to address that lack with scale drawings of the panels and depictions of the Yandaklıdere petroglyphs. Necessary explanations for identifying the figures are provided by assigning a unique number to each figure. Relevant explanations of the character of the figures are also included in the text. Depictions of similar forms and body shapes are examined under the following categories: Shamans, Riders, Horses, Goats, Deers, Plants/Trees, Nets/Cages/ Traps, Tamgas and Inscriptions. Depictions which are not in these groups are included in the category of Unidentified Depictions. Other examples similar to the Yandaklıdere petroglyphs were first looked for in Central Asia, then in regions where Turkish tribes migrated, and finally in Türkiye. Yandaklıdere petroglyphs, such as the petroglyphs with period names such as Proto-Turk, Saka, Hun, Taştik, Göktürk, Akhun, etc. in the geography of Central Asia, were also examined, and yielded data that indicated that the Turks were very early arrivals in Anatolia. Techniques used in the drawings are presented, as well as their estimated production dates, and the study also examines findings that show that the Turks continued their rock drawing traditions under Shamanism and Tengrism by discussing the meaning of petroglyphs for Turkish tribes separately for each depiction. As a result of these examinations, which contain examples from possibly the Bronze or Iron Age, it can be seen that the petroglyphs were made by using pecking and engraving techniques. It is suggested that the petroglyphs were made in different periods, but mainly in the Middle Ages. These dating suggestions, based on similar examples, are also explained in the study within the chronicles and the illustrated examples included in the depictions

Successful treatment of a case with cervical lymphatic malformation: Repeated bleomycin sclerotherapy

Lymphatic malformations (LM) are benign congenital malformations of the lymphatic system. They are frequently seen in the neck and sometimes can be life-threatening due to compression to the airway. Treatment modalities are widespread including surgical excision, radiotherapy, laser therapy, and application of intralesional sclerosing agents. We report the successful treatment of cervical LM in a 3-year-old boy who presented with a sudden onset of a large cystic mass in the posterior cervical triangle and was treated with repeated injections of intralesional bleomycin