A practical approach to improve optical channel utilization period for hybrid FSO/RF systems

In hybrid FSO/RF systems, mostly a hard switching mechanism is preferred in case of the FSO signal level falls below to the predefined threshold. In this work, a computationally simple approach is proposed to increase the utilization of the FSO channels bandwidth advantage. For the channel, clear air conditions have been supposed with the atmospheric turbulence. In this approach, FSO bit rate is adaptively changed to achieve desired BER performance. An IM/DD modulation, OOK (NRZ format) has been used to show the benefit of the proposed method. Furthermore, to be more realistic with respect to the atmospheric turbulence variations within a day, some experimental observations have been followed up

Early Detection and Multidisciplinary Approach to Oral Cancer Patients

“Oral cancer” is a term usually describing oral cavity and oropharyngeal malign tumors. The most histologic type of carcinoma is squamous cell carcinoma, seen in oral and oropharyngeal region with the incidence of 90%. Prevention or early diagnosis of premalignant and oral cancer requires increased public awareness and educating practitioners to be skillful in identifying oropharyngeal region pathology. To prevent oral cancers, the etiological factors should be known, and measures must be taken according to those factors. Premalignant lesions are leukoplakia, lichen planus in oral and cutaneous form, erythroplakia, stomatitis nicotina, and submucous fibrosis. Premalignant lesions should be treated, if possible, or followed up on carefully. To date, there are many clinical, histopathological, radiological, and optical techniques to diagnose or capture precancerous and oral cancer lesions early. The routine management of oral cancers is firstly surgical resection with or without postoperative adjuncts and other therapies such as the use of postoperative chemoradiation and radiation. Successful treatment of oral cancer patients is a complex issue that requires a multidisciplinary approach, including oral and maxillofacial surgeons, oral and maxillofacial radiologists, ENT specialists, medical and radiological oncologists, prosthodontists, dentists, speech therapists, supportive care experts, and also pathologists or, if possible, oral and maxillofacial pathologists

Silisyum nitrür tozunun AI2O3,MgO,MgF2 sinterleme ilaveleri kullanılarak sinterlenmesi

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Silisyum nitrür(Si3N4) seramikleri sertlik, aşınma drenci, oksidasyon drenci, mükemmel ısıl şok drenci gibi özelliklerinden ve yüksek sıcaklıklarda bu özelliklerini korumalarından dolayı birçok alanda tercih edilen malzemelerdir. Si3N4 güçlü kovalent bağ yapısına sahip olması nedeniyle difüzyon katsayısı düşüktür. Bu nedenden dolayı Si3N4 saf halde sinterlenmesi oldukça zordur. Si3N4 esaslı seramiklerin özellilikleri; sinterleme öncesi izlenen yola, sinterleme ilavelerine ve sinterleme tekniğine bağlı olarak değişmektedir. Si3N4 tozları AI2O3, MgO gibi sinterleme ilâveleri kullanılarak basınçlı sinterleme yöntemi ile tam yoğun malzemeler üretildiği bilinmektedir. Ancak basınçsız sinterleme diğer yöntemlere göre ucuz ve karmaşık şekillerin sinterlenmesine olanak sağlayan bir tekniktir.Bu çalışmada farklı sıcaklıklarda MgO, Al2O3, MgF2 sinterleme ilavesiyle çeşitli kompozisyonlarda azot atmosferinde grafit fırın kullanılarak sinterleme yapılmıştır. Si3N4 tozları MgO, Al2O3, MgF2 katkı maddeleri ile basınçsız olarak sinterlenmiş ve tam yoğunluğa yakın sonuçlar elde edilmiştir. Sonuçta elde edilen Si3N4 seramikleri, arşimet yoğunluk, X-ışınları difraksiyonu(XRD) ve taramalı elektron mikroskobu (SEM) yöntemleri kullanılarak karakterize edilmiştir.Anahtar kelimeler: Silisyum nitrür, Sıvı faz sinterlemesiSilicon nitride based ceramics are of some specific characteristics, that is to say, hardening, abrasion resistance, oxidation resistance, perfect thermal shock resistance and they retain these properties at high temperatures. Thus, they are preferred in some specific areas. Due to the fact that Si3N4 ceramics have strong covalent bonds, their diffusion coefficient is low. Due to this reason, it is difficult to sinter pure silicon nitride. The properties of Si3N4 based ceramics change depending on preparation before sintering, additive, and sintering method. It is known that Si3N4 can be produced in full density using pressureless sintering method with various additives. However, pressureless sintering is both cheaper techniques and provides more complex result product comparing to other methods sintering methods.At this study, Silicon nitride powders were sintered with the addition of MgO, Al2O3, MgF2 at various temperatures and different compositions in nitrogen atmosphere using graphite furnace. Si3N4 powders were sintered with pressureless sintering technique with additives of MgO, Al2O3, MgF2 and nearly full dense results were achieved. The sintered Si3N4 ceramics density measurements were characterized by using archimedes method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies were also carried out.Keywords: Silicon nitride, Liquid phase sintering

DA motor kontrolünde gürültünün sistem performansına olan etkisi

DA motor endüstride ve günlük yaşantıda en çok kullanılan elektrik motorlarındandır. Bu tip motorların hız ve konum kontrolü özellikle hassas üretim, güvenli haraket sağlanması ve verimlilik bakımından önem taşımaktadır. PID, DA motor kontrolünde en sık kullanılan kontrol yöntemlerinden birisidir. Bu çalışmada gerçek DA motor parametreleri üzerinden, Parçacık Sürü Optimizasyonu algoritması ve Ziegler-Nichols yöntemi kullanarak DA motor hız kontrolünde PID kontrolcü katsayıları belirlenmiş ve bu iki yöntemin karşılaştırması yapılmıştır. Çalışmada çıkış sinyaline gürültü eklenmiş, gerçek sistem değerlerine yakın çıkış değerleri elde edilmiştir. Böylelikle test sonuçlarının gerçeğe daha yakın bulunması amaçlanmıştır.DC motor is one of the most used electric motors in industry and daily life. The speed and position control of this type of motor is especially important in terms of precision production, safe movement and efficiency. PID is one of the most commonly used control methods in DC motor control. In this study, PID controller coefficients were determined in DC motor speed control by using Particle Swarm Optimization algorithm and Ziegler-Nichols method over real DC motor parameters and these two methods were compared. In the study, noise was added to the output signal, and output values close to the real system values were obtained. Thus, it was possible to obtain test results that can approximately represent real conditions

Does the Angulation of an Impacted Mandibular third Molar Affect the Prevalence of Preoperative Pathoses?

Statement of the Problem: The removal of a third molar tooth associated with a pathological condition is usually an easy decision. However, it is necessary for clinicians to know about the prevalence of preoperative pathologies associated with impacted mandibular third molars to the identification of the prophylactic approach to be applied to symptom-free impacted third molars. Purpose: The objective was to investigate the effect of the angulation of impacted mandibular third molars on the prevalence of associated pathologies. Materials and Method: In this retrospective study, we examined the panoramic radiographs of 954 patients referred for impacted third molar surgery. A total of 1598 impacted mandibular third molar teeth were included in the study. Pathological conditions included the caries on distal surface of the adjacent second molar, caries on impacted mandibular third molars, bone loss distal to the adjacent second molar, the radiolucent area distal to the impacted mandibular third molar were determined. Results: Caries were observed more in the impacted third molar (18.9%) compared to the adjacent second molar (15.8%). The radiolucent area on distal surface of the impacted mandibular molar was 11%, while the periodontal bone loss distal to the adjacent second molar was 4.9%. Mesioangular-impacted mandibular third molars had high risk of caries development on second and third molar. The prevalence of periodontal tissue damage to the adjacent second molar was higher in horizontal and mesioangular angulation. Vertical and distoangular-impacted mandibular third molars had high risk for bone loss at distal aspect. Conclusion: The prevalence rate of pathological conditions in mesioangular impacted teeth was higher

SERBEST ORTAMDA LAZER İLE OPTİKSEL İLETİŞİM SİSTEMLERİ İÇİN BİLGİSAYAR SİMÜLASYONU

Free-Space Optical Communication (FSOC) systems are practical and effective wireless communication tools, because of their unique advantages: extremely high bandwidth, rapid deployment, low power consumption, weight, and size. However, adverse weather conditions, such as fog and haze degrade the system performance. In this study, a computer simulation model has been developed including semiconductor laser, photodetector and communication channel to evaluate the performance of a FSOC system for the horizontal paths shorter than 1 km.Çok yüksek band genişliği, düşük güç tüketimi, hızlı kurulum, ağırlık ve boyut gibi önemli avantajlar sağlayan Serbest Ortamda Optiksel İletişim (SOOİ) sistemleri, pratik ve etkin bir kablosuz iletişim türüdür. Bununla birlikte sisli ve puslu hava gibi hava koşulları sistemin performansını olumsuz etkiler. Bu çalışmada 1 km’den kısa yatay linkler için bir SOOİ sisteminin performansını değerlendirmek üzere yarıiletken lazer, fotodedektör ve iletişim kanalını içeren bir bilgisayar simülasyon modeli geliştirildi

Restoration of Süleymaniye Mosque and Restoration Decisions Between the Years of 2007-2010

Süleymaniye Camii 2007-2011 yılı restorasyonu Cumhuriyet tarihinin en kapsamlı restorasyonudur. Bu restorasyon İstanbul 4 no.lu Kültür ve Tabiat Varlıklarını Koruma Bölge Kurulu’nun 14.02.2007 tarih ve 1047 sayılı kararına göre yapılmıştır. Restorasyon çalışmaları Koruma Kurulu ve Uzmanlar Kurulu kararlarına bağlı olarak yapılmıştır. Uluslararası koruma kriterlerine bağlı olarak yapı genelindeki muhdesler ve çimento sıvalar kaldırılmıştır. Kubbe ve minarelerde strüktürel sağlamlaştırma, bozulan hatların ve kalemişi bezeme programının konservasyonu vs. gibi restorasyon çalışmaları yapılmıştır

Endovascular treatment of huge saccular abdominal aortic aneurysm in a young Behcet patient: mid-term result

BACKGROUND: Abdominal aortic aneurysm formation is among the arterial complications of Behcet's disease. Weakness and fragility of aortic walls leads to the development of arterial complications like pseudoaneurysms. CASE PRESENTATION: A case of huge saccular abdominal aortic aneurysm in a young Behcet patient who was successfully treated with endovascular stent graft placement is reported, diagnostic and interventional procedures are discussed, and mid-term follow-up results are presented. CONCLUSIONS: Endovascular treatment of abdominal aortic aneurysm complications of young Behcet patients who are not suitable for open surgery and need intervention could be an alternative treatment modality even without performing preprocedural angiography

EFFECT OF ASPECT RATIO ON THE FREEZING-THAWING OF A CH CLAY

Donma-çözülmeye maruz zeminlerin davranışı numune boyutuna (ξ=boy/çap) bağlı olarak nasıl değişeceği tam olarak bilinmemektedir. Bu çalışmada numune boyutunun ince daneli zeminlerde 0, 5, 10 ve 20 donma-çözülme çevrim sonrası serbest basınç mukavemeti ve donma-çözülme dayanımı üzerindeki etkisi araştırılmıştır. Donma-çözülme deneyi donma sıcaklığı -20oC çözülme sıcaklığı +25oC olan otomatik donma-çözülme kabininde, serbest basınç deneyi yükleme hızı 0.8 mm/dk olan serbest basınç deney aletinde yapılmıştır. Bu değerler deney sırasında sabit tutulmuştur. Deneyler standart proktor enerjisinde hazırlanmış farklı ξ (boy/çap) oranlarına sahip silindirik numuneler üzerinde yürütülmüştür. Deney sonuçlarından numunelerin ρ oranı ve donma-çözülme çevrim sayısının artmasıyla serbest basınç mukavemeti ile donma-çözülme dayanıklılığının azaldığı belirlenmiştir

Cleft Palate Repair with Orbicularis Oris Plus Buccal Mucosal Flap: A New Double Layered-Technique

Recurrent oronasal fistula closure is a challenging phenomenon that has been managed with many surgical or flap techniques, such as local, regional, and distant flaps, with various modifications. Despite these options, the ideal method to repair this kind of chronic fistula has not yet been established. It is difficult to repair because recurrent surgical repairs or interventions cause this region to become more fibrotic with less vascular tissue, which considerably reduces the likelihood of closing this kind of fistula. For this reason, surgeons and researchers continue to work to overcome these obstacles by using more regional, vascular, and neighboring tissue. Classic cleft palate repair techniques use double-layered, nasal, and oral side closure and even a three-layered technique (e.g. plus levator veli palatini and tensor veli palatini muscular repair) in the soft palate region. Hence, we used partial orbicularis oris muscle with enough vascular supply to repair the nasal side and cheek mucosal flap to repair the oral side as a double-layered repair technique. Two years later, during routine patient follow-up, no complications were identified, and the patient’s satisfaction with this treatment was acceptable