itüdergisi (E-Journals - İstanbul Teknik Üniversitesi, Istanbul Teknik Uniersity., İTÜ)
itüdergisi (E-Journals - İstanbul Teknik Üniversitesi, Istanbul Teknik Uniersity., İTÜ)Not a member yet
1059 research outputs found
Sort by
İzmit Körfezi ve çevresinin morfotektoniği
Get PDFIn this study, the morphology of area surrounding the Gulf of Izmit located on North Anatolian Fault, one of the most important active tectonic elements of the world, is examined by using quantitative methods, and the role of young tectonics on the morphological evolution of the region is investigated. In recent years a number of new approaches have emerged in the study morphotectonics. These fall into three categories: use of new techniques, search for new types of data (such as digital elevation data), application to geomorphological studies. At the simplest level, landforms can be characterized in terms of their size, elevation (maximum, minimum, or average), and slope. Quantative measurements allow to us objectively to compare different landforms and to calculate less straightforward parameters (geomorphic indices) that may be useful for identifying a particular characteristic of an area. Some geomorphic indices have been developed as basic reconnaissance tools to identify areas experiencing rapid tectonic deformation. This information is used for planning research to obtain detailed information about active tectonics. Geomorphic indices are particularly useful in tectonic studies because they can be used for rapid evaluation of large areas and necessary data often can be obtained easily from topographic maps (especially digital elevation data). The drainage basins are determined from the digital terrain models of the region. Then the morphometrical analysis, hypsometric curve and hypsometric integral, drainage basin asymmetry, mountain-front sinuosity, ratio of valley-floor width to valley height are applied to these basins. Hypsometry has been generally used to infer the stage of geomorphic development. From an analysis of numerous drainage basins, has shown that a convex shaped hypsometric curve characterizes basins in the youth stage, an S-shaped hypsometric curve (concave upwards at high elevations and concave downwards at low elevations) characterizes basins in the stage of maturity, and a concave hypsometric curve characterizes basins in the peneplain stage. Drainage basin asymmetry is the tectonic influences on drainage networks. Tectonic tilting at the scale of drainage basins can be detected from the Asymmetry Factor (AF). For a stable setting, AF = 50. The more that AF departs from 50, the more the influence of tectonic tilting. Mountain-front sinuosity (Smf index) is defined as mountain fronts associated with active tectonics and uplift are relatively straight, with low values of Smf. If the rate of uplift is reduced or ceases, the erosional processes will carve a more irregular mountain front, and Smf will increase. Ratio of valley floor width to valley height (Vf index) differentiates between broad floored canyons, with relatively high values of Vf, and shaped valleys with relatively low values. The study area is formed of different morphological regions. The Gulf of Izmit is east-west trending depression on the northern branch of the young depression placed on the North Anatolian Fault. This depression is delimited by to mountainous belt in the north and south. Drainage basin asymmetry values on the selected drainage basins indicate that the northern belt (Kocaeli Peninsula) is northward tilted as peneplain. Southern part of this peneplain was cut by the North Anatolian Fault. The watershed is very close to the south. On the south-facing slope headward erosion is main morphologic activity. Geomorphic indices indicate that this southern slope is very young and related with the North Anatolian Fault. Southern part of the depression, Samanlı Mountains are higher than the northern part. It is elevated as positive flower structure between the northern and middle branch of the North Anatolian Fault. In the north-facing slope of this area deeply incised valleys and large alluvial fans are the main geomorphic entities. Lithology of the rock forming this area is also affected the morphology. This can be seen hypsometric integrals and other geomorphic indices. In the light of mountain front sinuosity (Smf index) and ratio of valley floor width to valley height (Vf index) values we applied it is clear that the morphology of the region was heavily affected by active faults which have been affecting the southern region rather than northern region. The analysis results indicate that a) rock types, b) the structural features of the rocks, c) the NE and NW trending faults older than the North Anatolian Fault, and d) the active E-W trending North Anatolian Fault controlled the morphological evolution of the region. Keywords: North Anatolian Fault, Gulf of Izmit, morphology, morphometry.Dünyanın önemli aktif tektonik unsurlarından biri olan Kuzey Anadolu Fayı (KAF) üzerinde yer alan İzmit Körfezi çevresinin morfolojisi ölçüye dayalı (kantitatif) yöntemlerle araştırılmış ve genç tektoniğin bölgenin morfolojik evrimindeki rolü anlaşılmaya çalışılmıştır. Bu bağlamda çeşitli veri setleri kullanılarak, karşılaştırma ve tümdengelim yöntemiyle morfometrik analizler yapılabilmektedir. Bunun için, önce bölgenin sayısal yükseklik modelleri üretilerek drenaj havzaları belirlenmiş, daha sonra bu havzalar üzerinde hipsometrik eğri ve integral, drenaj havzası asimetrisi, dağ cephesi eğrilik oranı, vadi tabanı genişliğinin vadi yüksekliğine oranı olarak bilinen morfometrik analizler uygulanmıştır. Bölgede kuzey kuşağı oluşturan peneplen morfolojisinin drenaj havzası asimetrisi değerleri, seçilen drenaj havzalarında kuzeye eğimlenmeyi göstermektedir. Dolayısıyla günümüz su bölümü çizgisi güneye daha yakın ve Körfez’e akan dereler kısa, dar ve derin deşilmiş vadilere sahip bir morfoloji sergilemektedir. Morfolojik indisler, KAF ile ilişkili olarak güneydeki yamaçların daha genç olduğunu göstermektedir. Güney kuşağı oluşturan Samanlı Dağları, kuzey bölümden daha yüksektir. Bu alanda kuzeye bakan yamaçlarda derin deşilmiş vadiler ve kalın alüvyal yelpazeler başlıca morfolojik özelliklerdir. Kayayı şekillendiren litoloji ise morfolojiden etkilenmiştir. Bunlar hipsometrik integral ve diğer morfolojik indislerde açıkça görülmektedir. Dağ cephesi eğriliği değerlerine bakıldığında güneyin dağ cephesi kuzeyin dağ cephesinden daha fazla aktif faylarla kontrol edildiğini göstermektedir. Vadi tabanı genişliğinin, vadi yüksekliğine oranı ile ilgili elde edilen düşük değerlerin KAF’ın güneyindeki vadilerde elde edilmesi, bu dar vadilerde aktif bir yükselmeyi işaret etmektedir. Bu analiz sonuçları bölgenin morfolojik evriminde a) kaya türlerinin b) kayaların yapısal özelliklerinin, c) KAF’dan önce bölgede etkin olan KD ve KB uzanımlı fayların, d) halen aktif olan D-B uzanımlı KAF’ın etkili olduğunu işaret etmektedir. Anahtar Kelimeler: Kuzey Anadolu Fayı, İzmit Körfezi, morfoloji, morfometri
Usage of error matrix in the accuracy assessment of geographic data selection results
Get PDFBilgi sistemlerinin yoğun olarak kullanıldığı günümüzde, Coğrafi Bilgi Sistemlerine (CBS) ve CBS’nin temel bileşenlerinden coğrafi verilere olan ihtiyaç, artarak devam etmektedir. Coğrafi verilerin üretimi, CBS bileşenleri arasında en çok zaman ve maliyet gerektiren işlemi oluşturmaktadır. Dolayısıyla coğrafi veri üreticileri için, üretim süreçlerinin otomasyonu son derece önem taşımaktadır. İstenilen nitelik ve içerikteki coğrafi veriler, daha yüksek mekânsal çözünürlüğe sahip coğrafi verilerin bulunması durumunda bu verilerden türetme yolu ile üretilebilir. Türetilen coğrafi verilerin doğruluğu, CBS içindeki veriyi ve dolayısıyla analiz sonuçlarını doğrudan etkilediğinden, basılı haritalardaki durumlarından daha da önemli hale gelmektedir. Bilgisayar destekli harita üretim tekniklerin kullanımı ile birlikte, genelleştirme işlemleri sonuçlarının değerlendirilmesinde kullanılacak yeni yöntemlere olan gereksinim, kendini belirgin olarak göstermektedir. Hata matrisi, raster verilerle yapılan sınıflandırma işlemlerinin doğruluk analizlerinde yoğun olarak kullanılmaktadır. Bu çalışmada; hata matrisinin, türetme coğrafi veri üretim amaçlı gerçekleştirilen coğrafi veri seçim işlemi sonuçlarının değerlendirmesinde kullanımı irdelenmiştir. Türetme coğrafi verilerin üretiminde gerçekleştirilen coğrafi veri seçimi, aslında bir tür sınıflandırma işlemidir. Coğrafi detaylar, “seçilen” ve “seçilmeyen” şeklinde iki ayrı sınıfa ayrıştırılmaktadır. Hata matrisinin, coğrafi veri otomatik seçim sonuçlarının değerlendirilmesinde kullanımı bir uygulama ile gerçekleştirilmiştir. Hata matrisinin, yapılan seçim işlemi sonucu ve doğruluğu hakkında yansız ve kapsamlı bir değerlendirme sunduğu ve bu amaçla kullanılabileceği görülmüştür. Hata matrisinin, seçim işlemini doğrudan etkileyen en iyi seçim ölçütlerinin belirlenmesinde de kullanılabileceği değerlendirilmektedir. Anahtar Kelimeler: Coğrafi veri, seçme ve eleme, doğruluk, hata matrisi.Nowadays, as being in the information age, the needs for Geographic Information Systems (GIS) and for its main component geographic data are incrementally increasing. Geographic data is the most expensive and time consuming component of GIS (Longley et al., 2001). Therefore construction of automation processes in geographic data production has high importance for data providers. In case of the availability of data having higher spatial resolution, derived geographic data with certain contents and specifications can be produced through generalization. Generalization is important to GIS, not only because of to drive towards automating the process to obtain derived databases, but also because generalization can seriously affect data within a GIS, even more so than within paper maps (Joao, 1998). A fully automated generalization cannot be anticipated at this moment (Spiess et al., 2005). Still lots of efforts are needed to automate the generalization processes (Stoter, 2005). And new automated methods need new quality control methods (Jaakola, 1994; Ruas, 2001). In this study, the usage of error (confusion) matrix is investigated in the accuracy assessment of selection process aiming to obtain derived geographic data. Geographic data selection process constitutes an important step in the production of derived datasets through generalization. The results of the selection process build the main skeleton of the derived data. Selection process and criteria used are highly depended on the intended usage purpose of the generalized data. In the selection process, unwanted features are eliminated and important features are retained. It is the one of the most immediate differences between maps of the same region at different scales (Joao, 1998). Contextual relations among geographic features should be considered in the selection process. Although selection process of geographic features constitutes an important step in the production of derived datasets, it is not only enough by itself. It should be considered together with other generalization operators (Shea and McMaster, 1989) in map or geographic data production line. Error matrix is generally used in the accuracy assessments of supervised and unsupervised classification of raster data (Congalton ve Green, 1999). An error matrix is a square array of numbers set out in rows and columns which expresses the number of sample units assigned to a particular class relative to actual class as verified by some reference data (Figure 3). The selection processes in the production of derived geographic data can be assessed as a kind of classification. Geographic data is classified in two different categories as “selected” or “eliminated”. The usage of error matrix in the accuracy assessment of selection results has been realized with an application. In the application, the automatic selection result of running waters and canals for the production of derived topographic maps has been used. Geographic data covered by Balıkesir J19 topographic map sheet was chosen as a test data. 1:25.000 scale content data was used for the automatic selection of running waters and canals for the production of 1:100.000 scale Balıkesir J19 topographic map sheet. Last edition of 1:100.000 scale Balıkesir J19 map sheet has been used as a reference data that is needed for verifying the selection result and constructing the error matrix. Due to the subjectivity of generalization, extra comments have been made in defining the accuracy of the selection results of individual features, in case of conflicts occurred between the selection results and the reference data. The lengths of geographic features can also be used in constructing error matrix. In this study, two types of error matrixes were constructed, using feature numbers and feature lengths, respectively. Then the accuracies of classification as a whole and as individual categories have been computed by using the error matrixes constructed. As a result, it has been found that error matrix provides objective and thorough information for the accuracy assessment of the selection process results for obtaining derived geographic data. It can be used for this purpose. Selection criteria would directly affect the selection results. Determining optimum criteria that will be used in the production lines constitute a critical issue. The Kappa coefficient of agreement (Cohen, 1960), which takes into account all the elements of the error matrix, yields a robust assessment for the accuracy of whole classification process and can be used in determining the optimum selection criteria. Keywords: Geographic features, selection process, accuracy assessment, error matrix
Vibration control of a laminated com-posite plate subjected to blast loading
Get PDFBu sayısal çalışmada, bir kenarından ankastre olarak mesnetlenmiş konsol bir plağın üzerine etkiyen anlık basınç yükü nedeniyle oluşan titreşimler, plak üzerine yerleştirilmiş piezoelektrik uyarıcılarla kontrol edilerek sönümlenmiştir. Anlık basınç yükü modeli için zamana bağlı olarak üstel bir biçimde azalan Friedlander fonksiyonu kullanılmış ve bu fonksiyondaki parametreler için deneysel çalışmalardan elde edilen değerlerden yararlanılmıştır. Plağın sonlu eleman modelinin oluşturulması için bilinen semiloof kabuk eleman ile piezoelektrik etkilerin eklendiği semiloof kabuk sonlu eleman modeli kullanılmıştır. Sonlu eleman modelinin serbestlik derecesi yüksek olduğundan ve günümüzün modern kontrol yöntemlerinde yaygın olarak kullanılan durum denklemleriyle sistemin ifade edilmesi halinde serbestlik derecesinin ikiye katlanması nedeniyle sonlu eleman modelini indirgemek için mod toplama yöntemi ile indirgeme işlemleri yapılmıştır. Bu işlemler sonucunda elde edilen plak modelinin statik ve dinamik analizleri yapılmıştır. Plak aynı zamanda ANSYS yazılımı ile de modellenerek statik ve dinamik analizlerin sonuçları karşılaştırılmış ve bu sonuçların uyumluluğu gösterilmiştir. İndirgenmiş plak sonlu eleman modelinden sistemin durum denklemleri elde edilmiştir. Kararlılık sınırında bulunan sistemin kararlı olmasını garantilemek için optimum doğrusal regülatör problemi (optimal linear regulator problem, LQR) araştırılmıştır. Duyargalardan ölçülen deplasman değerlerini kullanarak sistemin durumlarını tahmin edecek gözleyicili bir kontrol sistemi ile oluşan yapısal titreşimler başarılı bir şekilde kontrol edilmiş ve sönümlenmiştir.Anahtar Kelimeler: Titreşim kontrolü, durum gözleyici, semiloof kabuk eleman, piezoelektrik, anlık basınç yükü.Plates and shells are the most widely used elements in aeronautics industry and the use of layered composite materials in the manufacturing of these parts is increasing. Layered composite materials, commonly used in aerospace structures, are chosen as plate material. Still, applications of smart structures which involve the use of piezoelectric parts not only in the desired shape changes of command and control surfaces of aeronautics and space structures, but also in vibration suppression, is one of the most popular research subjects. For this reason, static and dynamical analyses of these types of structural parts are very important. In this numerical study, vibrations of a cantilever composite plate subjected to blast loading are controlled and suppressed by the use of piezoelectric actuators. The dynamic responses of structures under blast loading have been investigated in many applications. Blast loading depends on magnitude and orientation of the blast pressure, geometry and size of the surface that the shock wave encounters and on the distance from the detonation source. Commonly, Friedlander exponential decay function can be used for expressing uniform time dependent blast loading which affects object surface through normal direction. Various parameters of the equation can be obtained from some of the experimental studies. Piezoelectric materials also have been investigated in many applications. Piezoelectric elements are used for controlling and suppression as preferred widely in recent years. The development of piezoelectric composite materials offers great potential for use in advanced aerospace structural applications. For a material to exhibit an anisotropic property such as piezoelectricity, its crystal structure must have no centre of symmetry. The piezoelectric effects can be seen as transformations between electrical and mechanical energy. That is linear piezoelectric constitutive equations include electromechanical coupling. Semiloof shell finite element including piezoelectric effects is used for finite element modeling of the plate. Semiloof shell element is one of the most efficient elements for solution of shells having arbitrary geometry and it accounts for both membrane and bending actions. Three displacement degrees of freedom at the corner and mid-side nodes are sufficient for defining the membrane action. The rotations at loof nodes are necessary to impart C1 continuity and account for bending action. Stiffness, mass and damping matrices which express the structural model are obtained from the semiloof shell finite element. In order to reduce the degrees of freedom of the finite element model, mode summation method is used with weighted modal vector including dominant modes in the dynamic behavior. Calculated results of the static and dynamic analyses of the plate are compared with those modeled by using Ansys software. A good agreement is observed. After noticing the good agreement between dynamic and static analysis, state-space equations are obtained from the reduced finite element model. The system of equation must satisfy the controllability condition in order to be taken under control. If this system is also desired to be controlled by using a state observer, it must satisfy the observability condition. Optimal linear quadratic regulator (LQR) problem has been investigated to guarantee the stability of the system on the stability edge due to neglecting structural damping. In this work, both piezoelectric pairs were used as actuators. This change doubled the force used in vibration suppression. In this case the voltages applied to the piezoelectric actuators are determined by employing state observer feedback control system which estimates all states by using displacements of some specific points of the plate. Structural vibrations due to blast loading have been successfully controlled and suppressed by using a state observer feedback control system. This study will provide noteworthy supports for experimental works in this area in the future. Vibration control of plates under different loads such as random or harmonic can be investigated by using different control strategies in experimentally or numerically. The influence of different boundary conditions and addition of stiffeners to the plate on structural vibrations and vibration control can also be investigated. Furthermore, some issues like nonlinear effects on plate deformations and adding structural damping are needed to be explored.Keywords: Vibration control, state observer, semiloof shell element, piezoelectric, blast loading
Dosimetric evaluation of gamma doses using irradiated lead-alkali-silicate glass
Get PDFKurşun-alakali-silika cam örnekleri 1-36 kGy arasında ışınlanarak, gama radyasyonuna maruz bırakılmıştır. Bu çalışmada, gama ışın kaynağı olarak, Co-60 radyoizotop kaynak kullanılmıştır. Gama ışınlarına maruz kalmış kurşun-alkali-silika camların, soğurduğu doz seviyesine bağlı olarak, renklerinin giderek koyulaştığı belirlenmiştir. Kurşun-alkali-silika cam yapının radyasyonla uyartılması sonucu, bu camların, görünür bölgedeki, geçirgenlik, yansıtıcılık ve soğurma değerlerinin değiştiği tespit edilmiştir. Optik özelliklerdeki değişimlerin incelenmesi, elektromanyetik spektrumun, 380-1500 nm dalgaboyu aralığına düşen bölgesinde yapılmıştır. Işınlanmış camlar ile ışınlanmamış camların optik parametrelerinde meydana gelen değişimler karşılaştırılarak, farklı doz seviyelerinde ışınlanan, kurşun-alkali-silika camlarının, dozimetre olarak kullanılabilirliği incelenmiştir. Anahtar kelimeler: Cam dozimetreler, dozimetri, kurşun-alkali-silika cam, soğurulan doz.Dosimetric evaluation is important especially at the high dose levels. Glass dosimeters are used in dosimetry in several high-level exposure applications, employing mainly spectrophotometric or densitometric analysis of colour-center formation. The chemical composition of lead-alkali-silicate glass was determined using a wavelength dispersive X-ray fluorescence spectrometer. The balance between the ionic forms of the glass impurity atoms, which are transition metals, determines the glass colour to the transition elements ferric iron, titanium and nickel, and post transition elements like antimony. The radiation-induced absorption in the visible spectral region in Pb-containing glasses undergoes rapid thermal and optical bleaching, provided the glass does not contain alkali ions. The addition of just a few percent alkali ions stabilises the absorption. Lead-alkali-silicate glass samples were irradiated with 1-36 kGy dose levels using a Co-60 radioisotope source. The colour of the lead-alkali-silicate glass turned to brownish orange with absorbed dose. Radiation-induced changes in the properties of visible light transmittance and absorbance were examined between wavelengths of 380 and 1500 nm using a spectrophotometer. Changes in the optical density were determined and compared with those of unexposed glasses. The optical density was investigated for different dose levels in this study. The optical density curves indicated the strong radiation induced absorption in a band around 700 nm wavelength. Keywords: Absorbed dose, dosimetry, glass dosimeter, lead-alkali-silicate glass
Models inspired by the scalar Gürsey model
Get PDFDoğadaki tüm parçaçıkların yapıtaşının fermiyonlar olduğu düşüncesiyle yazılan teorilerden biri de Gürsey tarafından sunulan klasik konformal değişmez modeldir. Modelin klasik çözümleri Kortel tarafından verilmiştir. Kuantum mekaniksel yapısı ise sonraki yıllarda, Gürsey'in polinom olmayan Lagranjiyenine denk olduğu düşünülen bir eşdeğer Lagranjiyen yazılarak, incelenmiştir. Denk model kuantize edilerek Gürsey modelinin de kuantize edildiği iddia edilmiştir. Bu çalışmada model, pertürbatif ve pertürbatif olmayan yöntemlerle incelenmiştir. Modelde, serbest durumda kütlesiz olan fermiyonların yüksek mertebelerde de kütle kazanmadığı Dyson-Schwinger denklemi çözülerek gösterilmiştir. Alanların etkileşimleri incelendiğinde, Yukawa tipi etkileşmelerin sonlu kaldığı, modelin temel parçacıkları olan fermiyonların fiziksel süreçlerde yer almadığı bulunmuştur. Bethe-Selpeter denklemleri çözülerek sonuçlar yüksek mertebeler için de kontrol edilmiştir. Bu triviyal modelde renormalizasyon gerektiren tek etkileşmenin dört skaler etkileşmesidir. Literatürde triviyal Nambu-Jona-Lasinio modelinin belirli şartlarda ayar model haline getirilmesiyle trivial olmayan sonuç verdiği gösterilmiştir. Eşdeğer modelin de, triviyal olmayan bir model haline gelebilmesi için öncelikle abelyen gerçek vektör alanı yeni bir kuplaj sabiti ile modele eklenmiştir. Önceki modele ait bazı özelliklerin değiştiği görülmüştür. Bunlardan en önemlisi temel parçacıkların fiziksel süreçlerde yer alabilmesidir. Modelin renormalizasyon grubu denklemleri çözüldüğünde, "Landau Kutbu" problemiyle karşılaşılmıştır ve trivial olmayan model elde edilememiştir. Probleminin kaldırılması için abelyan vektör alanı yerine abelyan olmayan vektör alanı modele eklenmiştir. Yeni modelin renormalizasyon grup denklemleri bir çevrime kadar çözülmüş ve detaylıca incelenmiştir. Belirli şartlar altında trivial olmayan bir model elde edilmiştir. Anahtar Kelimeler: Kompozit skaler alanlar, triviyallik, renormalizasyon grup denklemleri, Landau kutbu.To write a field theoretical model which has nonzero values for the coupling constants at zeroes of the beta function of the renormalization group is an endeavor which is still continuing in particle physics. The theory is a "laboratory" where different methods in quantum field theory are first applied. The perturbatively nontrivial in four dimensions was shown to go to a free theory as the cut-off is lifted. During the last twenty years, many papers were written on making sense out of "trivial models", interpreting them as effective theories without taking the cutoff to infinity. One of these models is the Nambu Jona-Lasinio model, hereafter NJL. Although this model is shown to be a trivial one in four dimensions, since the coupling constant goes to zero with a negative power of the logarithm of the ultraviolet cut-off, as an effective model in low energies it gives us important insight to several processes. There were also attempts, by Bardeen et al., to couple the NJL model to a gauge field, the so called gauged NJL model, to be able to get a non-trivial field theory. It was shown that if one has sufficient number of fermion flavors, such a construction is indeed possible. There are other models, made out of only spinors, which were constructed as alternatives of the original Heisenberg model, the first model given as "a theory of everything", using only spinors. The Gürsey model was proposed, before the NJL model, as a substitute for the Heisenberg model. The Classically the Gürsey model had the conformal symmetry. It had classical solutions, given by Kortel, which were interpreted as instantons and merons by Akdeniz, much like the solutions of the Yang-Mills (YM) theories. It had one important defect, though. Its non-polynomial Lagrangian made the use of standard methods in its quantization not feasible. Akdeniz et al. tried to make quantum sense of this model a while ago. They defined an equivalent Lagrangian, inspired by Gross-Nevue, which is polynomial. They quantized the equivalent model by this way the Gürsey model. They concluded that the model was resulted as a "trivial model". In other words the processes involving the constituent spinors resulted freely. Here we want to give a new interpretation of that work. We go to higher orders in our calculation in the new version, beyond the one loop for the scattering processes. It is shown that by using the Dyson-Schwinger and Bethe-Salpeter equations some of the fundamental processes can be better understood. We see that while the non-trivial scattering of the fundamental fields is not allowed, bound states can scatter from each other with non-trivial amplitudes. This phenomena can be understood as an example of treating the bound states, instead of the principal fields, as physical entities, that go through physical processes such as scattering. In our model we need an infinite renormalization in one of the diagrams. Further renormalization is necessary at each higher loop, like any other renormalizable model. The difference between our model and other renormalizable models lies in the fact that, although our model is a renormalizable one using naive dimensional counting arguments, we have only one set of diagrams which is divergent. We need to renormalize only one of the coupling constants by an infinite amount. This set of diagrams, corresponding to the scattering of two bound states to two bound states, have the same type of divergence in the dimensional regularization scheme for all odd number of loops. The contributions from even number of diagrams are finite, hence require no infinite renormalization. Using a new interpretation of the model and taking hints from the work of Bardeen et al., we studied a model, which classically simulates the Gürsey model, by coupling constituent U(1) gauge field to the spinors. We investigated whether this new coupling makes this new model a truly interacting one. We found that we are mimicking a gauge Higgs Yukawa (gHY) system, which had the known problems of the Landau pole, with all of its connotations of triviality. Then we studied our original model, coupled to a SU(N) gauge field, instead. We derived the renormalization group (RG) equations in one loop, and tried to derive the criteria for obtaining nontrivial fixed points for the coupling constants. Finally we showed that the renormalization group equations give indications of a nontrivial field theory when it is gauged with a SU(N) field. Keywords: Composite scalar fields, triviality, renormalization group equations, Landau pole
Existence of solitary wave solutions for long wave-short wave interaction equations
Get PDFSürekli bir ortamda yayılan iki kısa ve bir uzun dalganın rezonans etkileşimi bir boyutlu üç kuple uzun dalga-kısa dalga (LSI) etkileşim denklemleri ile temsil edilmektedir. Kısa dalgaların aynı grup hızına sahip olması ve bu grup hızının uzun dalganın faz hızına eşit olması rezonans durumunu oluşturmaktadır. LSI denklemleri yüzey su dalgalarının etkileşimi, elastik bir ortamda yayılan iç elastik dalgaların rezonans etkileşimi gibi fiziksel olayları tanımlayan denklemler olarak türetilmiştir. Bu çalışmada LSI denklem sisteminin yalnız dalga çözümlerinin varlığı ispat edilmiştir. İspat esas olarak kübik nonlineerliğe sahip tek bileşenli nonlineer Schrödinger (NLS) denklemi için önerilmiş yaklaşımın genişletilmesi üzerine inşa edilmiştir ve kısıtlamasız bir varyasyonel problemin çözümüne dayanmaktadır. Bunun için öncelikle LSI denklemlerinin yalnız dalga çözümlerinin sağlamış olduğu iki-kuple denklem sistemi elde edilmiştir. Daha sonra Euler-Lagrange denklemleri bu iki-kuple denklem sistemini veren bir fonksiyoneli, Gagliardo-Nirenberg eşitsizliği yardımıyla tanımlanmıştır. Böylece, yalnız dalgaların varlığı problemi fonksiyonelinin bir minimumunun varlığının gösterilmesi problemine indirgenmiştir. Fonksiyonelin minimumunun varlığını göstermek için Lieb’in kompaktlık lemması kullanılmıştır. NLS denkleminin yalnız dalga çözümlerinin varlığını göstermek amacıyla literatürde tanımlanmış olan fonksiyoneli uzay boyutu için geçerli iken, şimdiki çalışmada tanımlanmış olan fonksiyonel uzay boyutunda da geçerlidir. Ayrıca, çözümlerin pozitif tanımlılığı gösterilmiş ve fonksiyoneli ile enerji fonksiyoneli arasındaki ilişki de verilmiştir. Anahtar Kelimeler: Uzun dalga-kısa dalga etkileşim denklemleri, yalnız dalgalar.Nonlinear dispersive wave equations arise in many areas of physics, such as solid mechanics, nonlinear optics and plasma. Solitary wave solutions occur as a result of the balance of dispersive and nonlinear effects. This balance makes the localized waves travel without change of form. So there is a wide interest for the behaviour of solitary wave solutions of nonlinear wave equations: existence and uniqueness, continuous dependence to initial data, stability. In the present study we are interested in establishing the existence of solitary wave solutions for a particular nonlinear dispersive wave equation. Short waves propagating in various continuous media are governed by the nonlinear Schrödinger (NLS) equation and its generalizations. In one dimensional case there exists a unique localized solitary wave solution of the NLS equation and can easily be evaluated. The existence problem in the multidimensional case has generally been investigated by using constrained or unconstrained variational methods. The constrained variational methods are based on minimization of energy functionals, which take the infimum value at the ground state solutions, under some constraints. Weinstein proved the existence problem of solitary wave solutions of the NLS equation in the multidimensional case by the help of an unconstrained variational problem. In his study a functional associated with the Gagliardo-Nirenberg inequality is defined. The solution of the Euler-Lagrange equation of is the solitary wave solution of the NLS equation. So the existence of solitary wave solutions was shown by proving the existence of a minimizer of the functional . The resonant interaction among two short wave modes with equal group speeds and one long wave mode whose phase speed is equal to the group speed of short waves is represented by the three coupled long wave-short wave interaction (LSI) equations of the form; where, is the spatial coordinate, is the time; and and are real constants. Here represents the long wave mode; and denote short wave modes. The above three-component system of long wave-short wave interaction equations describes the resonant wave propagation in various continuous media, for instance, the surface of water and a bulk elastic medium. The aim of the present study is to prove the existence of solitary wave solutions for the LSI system by using variational methods. Substitution of solitary wave solutions of the form with into the LSI system yields the coupled system In spite of a wide interest in this system and its generalizations, a few rigorous results on the existence of solutions exist up to present. In recent years there has been a large number of studies devoted to the problem of existence of solutions for various settings of this system. In these studies, the problem of existence of nontrivial solutions has been investigated extensively using variational methods based on minimization of certain energy functionals under some constraints. Here, to prove the existence of positive solutions to the above two-component system, we use a different approach based on adapting the method used by Weinstein for the NLS equation. As the one-variable functional defined by Weinstein is valid for , a new functional associated with the Gagliardo-Nirenberg inequality has been defined for . The new two-variable functional assumes the solutions of two coupled system as the critical points. And the existence of a minimizer for is proved using Lieb's compactness Lemma. The positivity of solutions and the relation between and the energy functional are also investigated. Keywords: Long wave-short wave interaction equations, existence of solitary waves
Agent based distributed event system
Get PDFGeleneksel istemci-sunucu mimarisinin kullanıldığı küçük ölçekli dağıtılmış sistemler uçtan uca ve senkron haberleşmeleri sebebi ile statik uygulamaların geliştirilmesinin ötesine geçmemiştir. Bu haberleşmenin büyük ölçekli sistemlerde kullanılması ise uygulamaların hantal ve kullanışsız olmalarını sağlamıştır. Bu kısıtlamalar, dinamik olan ve bağlantısız uygulamaların çalıştığı bir ortamda, daha esnek haberleşme modellerini kullanan yazılım sistemlerinin geliştirilmesi gerekliliğini ortaya çıkarmıştır. Yapılan çalışmada sistem bileşenleri arasında haberleşme için kullanılan olay kavramının üretim niteliği geliştirilmesi amaçlanmış olup olaylar sadece ham veri üretiminin yanı sıra, eylemlerin de üretildiği ve saklandığı ileri bir düzeye yerleştirilmiştir. Bu düzeydeki bir olay, işlenebilir veriler üretebileceği gibi, kendine özgü bir kontrol akışına sahip olan bir eylemler dizisinin tetikleyicisi de olabilir. Söz konusu eylemler belirli bir amacı gerçeklemeye yönelik işlem dizisine, karar mekanizmalarına ve çoğunlukla birlikte üretildikleri bir veri kümesine sahip olmaktadır. Sistemde olay yapısı, içerdiği eylem dizisinin ve bu eylemleri yerine getirmede kullanacağı veri bloğunun yer aldığı bir “gezgin etmen” yapısıyla temsil edilmektedir. Bu yeni yapıdaki olaylara “agvent-agent event” adı verilmiş olup sistem bir bütün olarak “Etmen Tabanlı Dağıtılmış Olay Sistemi” veya kısaca “ABDES Sistemi” olarak adlandırılmıştır. Geliştirilen sistem, kayıt/yayım haberleşme modelinin asenkron haberleşme, bir uçtan çok uca haberleşme ve zayıf bağlı haberleşme özellikleri ile gezgin-zeki etmenlerin amaca yönelik davranmalarını, sosyal yeteneklerini, tepkisel davranabilmelerini ve otonom olma özelliklerini esnek bir ortamda birleştirmiştir. Anahtar Kelimeler: Dağıtılmış olay sistemi, gezgin etmenler, kayıt/yayım modeli.In recent years, a growing attention has been paid to the publish/subscribe communication paradigm as a means for disseminating information, also called as events, through distributed systems on wide-area networks. As it allows events to be propagated in a way that is completely hidden to the component that has generated them as well as to its receivers, it is particularly interesting when easy reconfiguration and decoupling among components in a distributed system is required. The historical development of publish/subscribe systems has followed a line which has evolved from channel-based systems, to subject-based systems, next content-based systems and finally type (object) based systems. In this study, we propose a new model for agent based distributed event systems, called as ABDES system, which combines the advantages of distributed event systems (like loosely coupled, asynchronous and one to many communication) and the advantages of intelligent mobile agents (like autonomy, reactivity, social ability and goal driven execution) into a flexible and extensible distributed execution environment. The major novelty of the model is that an event is represented by a mobile agent, (called as agvent-agent event), which is treated as a first class citizen of the system and given autonomy features to travel between system components. ABDES system differs from other distributed event systems with its distinct characteristics that are described below. Event Definition: In most event systems, events are defined as low-level messages, which consist of record like structures, list of strings, tuple based structures, etc. In type-based systems, events are defined as objects and viewed as main component of the system. Nevertheless, they are not autonomous. In ABDES system, events are represented as mobile agents that have their own goals, beliefs and behaviors that they acquire at their creation. When an agvent reaches to an agvent server, it examines the routing table of the server and selects its targets autonomously. This approach reduces the load and complexity of agvent servers as well. Subscription Mechanism: In most distributed event systems, subscribers register on a channel, on a specific topic or on a specific content of an event message. In ABDES system, subscribers register on types of agvents. For example, a subscriber can register on an agvent, which is an instance of "Agv_type1" class, specifying certain constraints based on its advertised attributes and behaviors. Information hiding: In previously developed event systems, an event server can, actually has to, access the content of the published event data. If you have a valuable data and you want to keep it secret it is really a hard work. In ABDES system, a published agvent searches the knowledge base of the agvent server, selects the registered subscribers, clones itself and sends clones of agent to each subscriber on the selected list. Therefore, the agvent server has no access to the content of the published event data, which simplifies its role and consequently facilitates the server development process. Information hiding also meets requirements of certain applications where secrecy of event data is essential for them. User defined agvent types: Distributed event systems generally use predefined event types. Therefore, to add a new event type you have to make changes in the dispatch service and also at publisher and subscriber sites. In ABDES system, a publisher can create its own agvent type and declare its properties and behaviors through an advertisement message. Once an agvent type is announced to the system, subscribers can register on agvents of that type. Filtering Mechanism: Distributed event systems use client side filtering. A client defines its profile by a subscription message and system forwards incoming events to this client according to its profile. There is not any possibility for producers to put their dispatching criteria to select the clients. Because of the agvents autonomous and self routing structure we can achieve the producer side filtering also. Faults and failures are inevitable in a distributed system built over a wide area network and they should be tolerated for continuing system transactions. Therefore we also developed a fault tolerance mechanism by dynamically reconfiguring the connections among agvent servers in order to create paths that increase the performance of message routing. We think the new model will serve as an effective choice for large scale distributed computing application, automatic virus updating and several information oriented applications, such as e-commerce and information retrieval.Keywords: Distributed event system, mobile agent, publish/subscribe model
An examination of spectral characteristics of aquatic vegetation
Get PDFSon yıllarda Türkiye’de ve Dünya’da sulak alanların önemi birçok kamu kurum ve kuruluşu tarafından daha iyi anlaşılmış ve korunması öncelikli alanlar arasına dâhil edilmiştir. Bu alanlarda yaşayan bitkiler su kalitesi üzerindeki olumlu etkileri, birçok kuş türü için beslenme ve barınma alanları olmaları ve diğer birçok yönden ekonomik değere sahip olmaları nedeniyle birçok bilim adamı tarafından çeşitli yönleriyle incelenme alanları olarak görülmüşlerdir. Son 30 yıldır bu tür çalışmalarda kullanılan uzaktan algılama teknikleri manuel metotların sahip olduğu dezavantajları ortadan kaldırması nedeniyle sulak alan çalışmalarında da yoğun bir şekilde tercih edilmişlerdir. Özellikle orta çözünürlükteki uydu verileri daha ucuz olmaları, yoğun işgücüne olan ihtiyacı ortadan kaldırmaları, geniş alanlarda bütün ekosistemi içerisine alacak şekilde tekrarlanabilen verileri üretmeleri nedeniyle birçok araştırıcı tarafından kullanılmıştır. Bu araştırmada suda yaşayan bitkilerin spektral özelliklerini tespit etmek amacıyla üzerinde bataklık bitkileri yerleştirilmiş bir panel tank içerisinde çeşitli derinliklere indirilerek farklı zemin ve bulanıklık koşullarında ölçümlere tabi tutulmuştur. Reflektans değerlerini toplamak amacıyla Spectron Engineering SE–500 spektroradyometresi kullanılmıştır. Spektron 368.5–1113.7 nanometre(nm) arasında değişen 252 farklı dalga boyunda veri toplama kapasitesine sahiptir. Laboratuvar ortamında yapılan bu deney, doğal su ortamlarında yaşayan bitkilerin yakın mesafe uzaktan algılama yöntemleri ile incelenmesi sırasında temiz su ve koyu renkli zemin koşullarında daha doğru ve güvenilir sonuçlar verebileceğini ortaya koymuştur. Elektro manyetik spektrumun yakın kızılötesi bölgesinin özellikle 700–730 nm’lik bölümünün sucul bitkilerin özelliklerinin belirlenmesinde önemli dalga boyu aralığı olduğunu deney sonuçları açıkça göstermiştir.Anahtar Kelimeler: Uzaktan algılama, sulak alan, bataklık bitkisi, spektroradyometre, su.In recent decades wetlands have been recognized as important ecosystem areas that should to be protected in Turkey and through out the World. Aquatic plants are an important indication of lake and we-tland health because they help protect water quality and provide habitat for fish and other wildlife animals (Vatla-Hulkkonen vd., 2004). Therefore these valuable areas should be protected and monitored. Monitoring aquatic vegetation helps to protect wetlands and provides useful information about nature of wetlands. Many researches have been done several studies concerning about determination of status of aquatic vegetation in various water bodies by using traditional methods which are time consuming, expensive and labor intensive. In contrast, remote sensing is an economic way to monitor wetland areas, because it can mon-itor large areas in a short time on a repetitive basis. Remote sensing is a reliable tool for the examination of vegetation, both terrestrial and aquatic. Data from remote sensors have been used to determine at least four pertinent issues with regard to vegetation such as presence and absence of vegetation, type, condition of vegetation and production. In this experiment, the lab exercise was aimed at the use of close range remote sensing to examine several ref-lectance properties of submerged aquatic vegetation in different depth. The water tank was used for the experiment has 150 gallons volume, black polyethylene, and around m. depth. The experiment was conducted in a room that has painted black to control illumination and eliminate unwanted reflectance. Light measurements were made with a spectron Engineering, SE-590 spectroradiometer. This spect-ron collects data in 256 discrete channels. To elimi-nate noise effect a smoothing technique was used to calculate results. A white panel was used as a solar calibration standard. The volume reflectivity was calculated by rationing upwelling target radiance and calibrated radiance. Black and white panels were used as surrogate bottom during scanning. This target lowered in a horizontal position. This procedures were repeated the experiment with sediment solution above black bottom. The spectral response of the aquatic vegetation was reported in terms of percentage reflectance in different bottom and depth conditions. Results represent the variation of reflectance values in different wavelengths. The spectral features signifying the presence of aquatic vegetation in the water column consists of low reflectivity in all depth conditions between 400 and 500 nm because of absorption of blue lights. It seems that blue chlorophyll absorption region is more obvious with black background than with white because of white reflectance at shorter wavelength. There is a maximum green reflectivity between 500 and 600 nm following by classic red absorption region around 670 nm in both white and black bottoms and in different depth conditions. Maximum reflectance in the green region of EMS is related to presence of chlorophyll in the plants. Red absorption feature seems more apparent in both white and black bottom conditions. The highest reflectance is located in the NIR region of the EMS with both white and black bottom at the surface. High reflectance in the NIR results primarily from the internal structure of the vegetation. According to figures in the NIR there is another peak around 850 nm due to back scattering. Between these two peaks a small water absorption feature is present. In general, as suspended sediment amounts increa-sed reflectance increased at the visible and NIR region with black bottom. In the case of no vegetation white background has highest reflectance curve than black bottom and turbid water. The amount of reflectance with white bottom reaches around 23 percent. In contrast the volume reflectance with black bottom is too low which is less than 1 percent because water absorbs all lights. In the case of presence of sediment with black bottom, the volume of reflectance increases and is higher than clear water with black background. Our experiment led us to conclude that the ordered patterns of either increasing or decreasing volume of reflectance of aquatic vegetation with different depth and bottom conditions were both logical and consistent. The useful findings from this experiment consisted of the apparent importance of bottom color on vegetation signals. With depth total amount of reflectance decreased both over the white and black background. Presence of suspended sediment in-creases the volume reflectance over black bottom. Keywords: remote sensing, wetland, aquatic vege-tation, spectroradiometer, water.
Dinek (Şarkikaraağaç-Isparta) ve çevresindeki barit cevherleşmeleri
Get PDFIn the study area basement rocks were formed during Cambrian-Ordovician era. These rocks were effected by regional metamorphism. Çaltepe Formation is at the bottom of the basement rocks. This formation contains metamorphosed dolomit, recrystallize and noduler limestone units. Sultandede Formation was seen on the Çaltepe Formation. This formation contains phillite, schists, chalkschists and quartzites, which was exposed to low degree green schist metamorphism. Hacıalabaz Formation overlies Sultandede formation uncomformably. This formation which contains dolomit, dolerite and limestone units was formed on carbonate platform in Jurassic–Cretaseous era. In Neogene, Bağkonak Formation was formed in terrestrial river facies. It overlies Lower Paleozoic and Mesozoic formations unconformably. Barite ores are observed only in lower Paleozoic units. Mineral assemblage in the region IV is pyrite, malachite, azurite, limonite, hematite, manganite, sericite and chlorite. In addition to such minerals, some metal sulphide minerals such as galena with amount of silver, sphalerite, chalcopyrite, pyrite, tetrahedrite are more common in the regions I, II and III. Isotopic data shows that ore fluids have approximately the same character. Some sedimentary features in the region IV such as cross-bedding, ritmicity layering, alternation, geopetal fabrics, brecciation, orientation with schistosity etc. are more common than the other regions. Ba sources were generally related to the connate waters of Sultandede formation and sulphate sources of barites which were enriched with heavy sulphur isotope ratios by the effect of sea water. Keywords: Barite, stratiform, stratabound, seconder, layered.İnceleme alanında temel kayaçlar Kambriyen-Ordovisiyen periyodunda oluşmuş metamorfik sedimanter birimleri içerir. Bu kayaçlar, doleritik seviyeler içeren Jura yaşlı sedimanter birimlerce uyumsuz olarak örtülür. Neojen birimleri Alt Paleozoik temeli ve Mesozoik kayaçları üzerine uyumsuz olarak gelir. Barit cevherleşmeleri sadece Alt Paleozoik kayaçları içinde bulunmaktadır. Barit cevherlerinin kimyasal özellikleri I., II.ve III. bölgelerde bazı farklar içerir. İzotopik veriler cevherleştirici sıvıların bazı farklar içermesinin yanında yaklaşık aynı karakterde olduğunu göstermektedir. Baritler hakim olarak sedimanter kökende oluşmuş ve stratiform-stratabound katmanlı, merceksi ve ikincil damar şekillidir. Anahtar Kelimeler: Barit, stratiform, stratabound, ikincil, katman. 
Türkiye göl su seviyelerinin eğilim ve harmonik analizi
Get PDF Lake levels have been continuously affected by hydrological, meteorological and anthropogenic conditions. Hydroclimatologic variables are important indicators of climatic change. It will be of great use to know the regime and tendency of changes in lake water levels in Turkey for both current and future studies, which are of importance for accurate assumption in future. Therefore, annual Turkish lake levels are analyzed to document some of their variability characteristics in this study. Annual cycles are first computed from monthly means at each individual lake station. The amplitudes and phases of the first harmonics, fitted to monthly lake level means, are displayed in vectorial fashion. Secondly a non-parametric trend test is applied to detect possible linear trends in the lake levels. The Mann-Kendall is known as appropriate tool in detecting linear trends of a hydrological time series. Statistically significant upward trends in lake level were found at the larger scale in the north coastal region. Downward trends in lake level were found at the larger scale the Midwest region. These results are in agreement with those of the precipitation, streamflow and temperature trend studies in Turkey. Harmonically significant maximum water level of spring season were found at large scale in the northwest regions and southwest region while summer season in lake level were found at the east regions. Keywords: Annual cycle, climate change, lake level, trend analysis, the first harmonic. 20. yüzyılın başından beri dünyanın pek çok yerinde göl seviyelerinde ölçümler yapılmaktadır, ölçülen göl su seviyelerinde alçalmalar ve yükselmeler gözlenmektedir. Göl su seviyeleri hidrolojik, meteorolojik ve antropojenik şartlardan etkilenirler. Çalışmada, tüm Türkiye’yi temsil edebilecek 25 göl su seviye verilerinin zamana göre eğilimleri parametrik olmayan Mann-Kendall testi ile incelenirken, göl su seviyelerinin mevsimsel değişkenliği ve bölgesel değişimi de harmonik analizle incelenmiştir. Bulunan sonuçlar Türkiye Yağış Rejimleriyle ilişkilendirilmiştir. Bu araştırmanın sonuçlarının, şimdiki ve ilerideki bölgesel gelişme çalışmalarında yararlı olacağı düşünülmektedir. Bu çalışmada amaç göl su seviyelerinde mevsimsel değişkenliğin coğrafik ölçeğinin saptanması ve Türkiye genelinde göl rejimi hakkında bir fikir sahibi olmaktır.Anahtar Kelimeler: Yıllık döngü, iklim değişimi,göl su seviyesi, eğilim analizi, birinci harmonik
Data sources:
Access Repository Dashboard
Do you manage itüdergisi (E-Journals - İstanbul Teknik Üniversitesi, Istanbul Teknik Uniersity., İTÜ)? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard!