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The aim of this work is the development of a method to operate elementary spin excitations (magnons) in a ferromagnetic metal by means of elementary vibrational excitations of the lattice (phonons). The utilized magnon-phonon coupling was confirmed more than 50 years ago, but only recently the experimental approaches of ultrafast acoustics have made available the excitation and time-resolved detection of coherent phonons in the sub-THz frequency range. The most intriguing regime of the magnon-phonon coupling is the strong coupling regime, which guarantees a conversion of phonons to magnons and vice versa at unity fidelity. This regime is extremely difficult to achieve in ferromagnetic metals due to a typically weak magnon-phonon coupling and fast relaxation processes. In this work, we demonstrate a way to overcome these limitations and to achieve the regime of strong magnon-phonon coupling. We have utilized a lateral nanoscale pattering (nanograting) of a Galfenol nanolayer, in order to introduce two additional localized high-Q phonon modes (~ 10 GHz). By means of an in-plane external magnetic field, we control the frequency detuning between the magnon and phonons modes, while their spatial overlap is determined by the lateral pattern. We observe two bright manifestations of the magnon-phonon coupling, i.e. resonant phonon driving and avoided crossing. The latter one clearly indicates the regime of strong magnon-phonon coupling with formation of a hybridized state known as magnon polaron. Theoretically, the magnon-phonon coupling is considered in the frame of coupled oscillators, whose coupling strength is determined by the spatial overlap of the interacting modes. The presented experimental and theoretical results may aid in the development of energy-efficient transducers between magnonic and phononic systems.

The performance of resultant topological structure of Kohonen Self Organizing Map SOM is highly dependent of the learning rate and neighborhood parameters. In literature there are plenty many different types of approaches to and proposals for those parameters. It has been investigated that in general the learning rate and neighborhood parameters are data independent and predefined before the training period. Here in this paper a novel approach has been proposed to change the learning rate parameter according to the interaction of neurons with data. During training, the worst matching neuron also tracked and used to trace the formation of topological structure of SOM. A slight modification on conventional learning rate with proposed method has a considerable influence on resultant topologies in a positive way. The effects of this approach have been tested with the real world problem and different synthetic data.

The role of air transport in transportation system is increasing every year. However, there can be difficulties to meet this increase. Therefore, efforts to resolve the problems in air transport become important. Delays and congestions are seen in the air transport system are among these problems. Airports are one of the most critical points of air transportation system facing these problems. One of the measures to be taken to resolve this problem is improving the existing system. Istanbul Ataturk Airport, the busiest airport in Turkey, often experiences delay and congestion problems. To propose a solution to these problems and to reduce runway occupancy time in Istanbul Ataturk Airport, additional fast-exit taxiways to the runway 05 were constructed. In this study, the impact of infrastructure changes made in Istanbul Ataturk Airport is examined, and traffic flow and capacity analysis is carried out comparing three different runway configurations. In consequence of the construction of additional fast-exit taxiways to the runway 05, airport capacity has increased 1.9 per cent. It is also shown that the high average delay time reduces airport capacity.

Thiophene belongs to a class of heterocyclic compounds. In this study, three new dimethyl-5-hydroxy isophtalate derived thiophene esters were successfully synthesized and characterized by FT-IR, Elementel Analysis, 1H-NMR, 13C-NMR and HRMass techniques. Synthesized compounds antimicrobial effects were tested on Staphylococcus aureus (ATCC 25923); Enterococcus faecalis (ATCC 29212); Enterococcus faecalis (ATCC 51922); Klebsiella pneumoniae (ATCC 700603); Pseudomonas aeruginosa (ATCC 27853); Escherichia coli (ATCC 35218); Escherichia coli (ATCC 25922) and Candida albicans (ATCC 90028); Candida glabrata (ATCC 90030); Candida krusei (ATCC 6258); Candida parapsilosis (ATCC 22019). Compound C1 showed the highest antimicrobial activity, possessing the same potential as chloramphenicol against, P. aeruginosa ATCC 27853. According to MTT assays, this compound (C1) was identified as non-toxic.

research Thermoluminescence study on nitrogen doped Tl2Ga2S3Se single crystals was achieved by performing the experiments with different stopping temperatures of 10?24 K and various heating rates between 0.4 and 1.2 K/s below room temperature. Thermoluminescence peak with peak maximum temperature of 54 K was detected from the emitted luminescence. Two trap levels were obtained from the observed spectra. Curve fitting and initial rise methods were applied to compute the activation energies and the values of 34 ± 2 and 70 ± 4 meV were found. Thermal cleaning process was applied to separate the overlapping peaks and so true energy region of trapping levels was corroborated. Moreover, variations of shape and position of TL curve were studied by investigating the heating rate behavior of trap levels. The best known behavior which the peak maximum temperature increases while the thermoluminescence intensity decreases with raising heating rate was observed. The effect of the N doping on the existed defects was discussed.

Bu çalışmada Öklidyen 3-uzayındaki Hasimoto yüzeyleriincelenmiştir. İlk olarak, Öklidyen 3-uzayındaki Hasimoto yüzeyleriningeometrik özellikleri incelenmiştir. Özellikle Bishop çatısı ile ilişkilendirilmişbu yüzeylerin eğrilikleri elde edilmiştir. Daha sonrasında bu yüzeylerin Bishopçatısına göre parametre eğrilerinin bazı karakterizasyonları verilmiştir., In this paper, weinvestigate the Hasimoto surfaces in Euclidean 3- space. Firstly, weinvestigate the geometric properties of these surfaces in Euclidean 3-space.Especially, we obtain the curvatures of Hasimoto surface according to Bishopframe. Then we give some characterization of parameter curves obtainedaccording to Bishop frame of Hasimoto surfaces.

Having access to health care services is the most primary of the basic human rights. It is vital that all citizens in a country are able to get these services equally and homogeneously. Despite its importance, providing health services vary from both country to country and between different provinces or states in country. Similarly, it may cause severe disparities and negative effects between individuals in the society. The primary concern of this study is to determine whether there is any difference between Turkey provinces in terms of accessing health care services, or not. Several clustering algorithms including hierarchical clustering, k-means and partitioning around medoids (pam) were applied to the data set including 31 health indicators of all provinces in Turkey. After comparing these algorithms via using some measures for determining the number of clusters and cluster validity, the findings showed that there were four distinct and significant clusters based on k-means clustering algorithm. It seemed that these clustering results were in a a close reciprocal relationship with the economic development and geographical location of provinces. Clustering results were evaluated and interpreted according to these two important findings.

The increase in the frequency of use of the Internet causes the attacks on computer networks to increase. Such phenomena also increase the importance of intrusion detection systems. In this paper, KDD Cup 99 dataset is used for the classification of the network attacks. Four different classification algorithms were used, and the results were compared. These algorithms were multilayer perceptron network, decision trees, fuzzy unordered rule induction algorithm (FURIA) and support vector machines. The most successful algorithm in this dataset found as FURIA. As the second part of this study, the most important feature sets were found by correlation-based feature selection and best first search algorithm. Then, the results of classification algorithms were compared with these new feature sets according to the performance of the algorithms.

The purpose of this research was to evaluation the effects on antioxidant defense system of chondroitin-4-sulphate (C4S) in high glucose treated human erythrocytes. 10-20 ml venous blood samples from ten healthy volunteers ages 20-40, nonsmoker, were accumulated in ethylenediamine tetraacetic acid (EDTA) vials for the preparation of red blood cell (RBC) suspensions. Blood for in vitro treatments was divided into six groups. The activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), acetylcholinesterase (AChE), the levels of glutathione (GSH) and malondialdehyde (MDA) were calculated to determine the effects on antioxidant defense system in all groups. As a result of the statistical evaluations, the significant increases (p, Bu çalışmada, yüksek glukoza maruz kalmış insan eritrositlerinde kondroitin-4-sülfatın (C4S) antioksidan savunma sistemine olan etkisi araştırılmıştır. Eritrosit süspansiyonu hazırlamak için, sigara içmeyen, 20-40 yaş aralığında sağlıklı gönüllülerden 10-20 ml venöz kanı etilendiamin tetraasetik asitli (EDTA) tüplere toplanmıştır. İn vitro uygulamalar için kanlar 6 gruba ayrılmıştır. Tüm gruplarda antioksidan savunma sistemi üzerine olan etkilerin belirlenmesi için süperoksit dismutaz (SOD), katalaz (CAT), glutatyon peroksidaz (GSH-Px), asetilkolinesteraz (AChE) enzim aktiviteleri, glutatyon (GSH) ve MDA düzeyleri ölçülmüştür. İstatistiksel değerlendirmeler sonucunda, C4S uygulanan gruplar ile sadece glukoz uygulanan gruplar karşılaştırıldığında GSH-Px ve AChE enzim aktivitelerinde önemli ölçüde artış (p

A combination of attenuated total reflectance–Fourier transform infrared (ATR–FTIR) spectroscopy and chemometric techniques was used to classify different trademarks of edible oils available on the Turkish markets. A total of 144 spectra of edible oil samples, including extra virgin olive oil (VOO), hazelnut oil (HNO), cottonseed oil (CSO), sunflower oil (SFO) and soybean oil (SBO), was recorded. The feasibility of ATR–FTIR with multivariate data analysis for discrimination of extra VOOs from other edible oils was also evaluated. Classification of edible oils was performed using principal components analysis (PCA), hierarchical cluster analysis (HCA), linear discriminant analysis (LDA) and soft independent modeling of class analogies (SIMCA). The spectra collected from wavelength region of 4000–650 cm-1 and 28 different wavelength ranges selected from full spectra were evaluated for optimal classification models. All multivariate analysis provided excellent discriminations between the edible oil classes with low classification error. LDA models constructed with five predictors, and a total of 100% of edible oil samples from different trademarks were correctly classified. Furthermore, no misclassification was reported for the discriminant analysis in supervised SIMCA models with an accuracy of 95%. Consequently, ATR–FTIR spectroscopy combined with multivariate data analyses provides excellent illustrations of the relative positions of the different brands of commercial edible oils according to their quality and purity.

The extraction of lycopene from dried tomato powder was carried out using ultrasound assisted (UAE) and conventional solvent (COSE) extraction methods with varying liquid/solid ratio (10:1-50:1), extraction time (5-60 min), temperature (20-50 ° C) and ultrasonic power (150-200 W). The response surface methodology was used to optimize the extraction parameters and to determine their individual and interaction effects on the extraction yield. The maximum extraction yields of UAE (722.321 mg lycopene/kg tomato powder) and COSE (975.833 mg lycopene/kg tomato powder) was observed using the following conditions: 166 W for 26 min, and a 56:1 liquid/solid ratio, and 45 ° C for 50 min, and a 56:1 liquid/ solid ratio, respectively. At the same extraction conditions UAE is reaching the same extraction yield faster than the COSE. Even the lycopene contents of the extracts were the same, the antioxidant capacity of the UAE and COSE extracts were 12.48 and 11.08 mg Trolox/g tomato powder, respectively .

Let R be a 2-torsion free semiprime ring, U a noncentral square-closed Lie ideal of R. A map F:R?R is called a generalized derivations if there exists a derivation d:R?R such that F(xy) = F(x)y + xd(y) for all x,y?R. In the present paper, we shall prove that h is commuting map on U if any one of the following holds: i) F(u)u = ±uG(u), ii) [F(u),v] = ±[u,G(v)], iii) F(u)?v = ±u?G(v), iv) [F(u),v] = ±u?G(v), v) F([u,v]) = [F(u),v] + [d(v),u] for all u,v?U, where G:R?R is a generalized derivation associated with the derivation h:R?R., R, 2-torsion free bir yarıasal halka ve U, R halkasının bir merkez tarafından kapsanılmayan kare-kapalı Lie ideali olsun. Eğer her x,y?R için F(xy) = F(x)y + xd(y), koşulunu sağlayan bir d:R?R türevi varsa F dönüşümüne R halkasının d ile belirlenmiş bir genelleştirilmiş türevi denir. Bu çalışmada, aşağıdaki koşullardan biri sağlanırsa d dönüşümünün U üzerinde komüting dönüşüm olduğu gösterilecektir: i) F(u)u = ±uG(u), ii) [F(u),v] = ±[u,G(v)], iii) F(u)?v = ±u?G(v), iv) [F(u),v] = ±u?G(v), v) F([u,v]) = [F(u),v] + [d(v),u]. Burada G:R?R dönüşümü h:R?R türevi ile belirlenmiş bir genelleştirilmiş türevdir.

Rhodium(I) complex of perfluorinated thiophene ligand was synthesized and heterogenized over the modified silica support. SEM, XRF, TGA and BET methods were used for the characterization of the heterogenized catalyst (SiAPTES-RhL). Heterogenization of catalyst and the catalytic activity tests were carried out in scCO 2 as a greener alternative to traditional reaction media. The catalytic activities of complex were investigated in hydrogenation reactions of some alkenes such as styrene, 1-octene and cyclohexene. 100% ethyl benzene conversion was observed at 370 K, 10 bar H 2 and 1900 psi total pressure in styrene hydrogenation. Also, it was found that the catalyst remains active at least throughout ten cycles. Similarly, the activity of the catalyst in the hydrogenation of 1-octene and cyclohexene was investigated. For 1-octene, 100% n-octan selectivity was obtained at 370 K and 10 Bar H 2 . The catalyst was found to be effective at 370 K while the activity was low at 350 and 360 K in cyclohexen hydrogenation. When compared with the homogenous system, the heterogenized catalyst had more activity and selectivity and also reusability without losing its activity

CdS and CdS:Li films were produced by means of ultrasonic spray pyrolysis (USP) method by spraying on glass substrates heated up to 340±5 ?C. LiCl in three different rates was added into the preliminary solution while producing the CdS:Li films. The effect of Li on the structural and optical characteristics of the CdS film was analyzed. XDR spectra showed that the crystallization degree decreases while lithium is 15% and increases when lithium rate increases. The crystallite sizes were calculated to be in the range of 60-85 nm. SEM photographs showed that the contribution of Li changed surface appearances of films and their particle size. All films exhibited the Raman peaks centered 298 and 590 cm-1 and the peak profiles were almost symmetric. The optical band gap and Urbach energy values of these films were determined. The maximum transmittance was found to be almost 80% for the visible region. LiCl which was added to the preliminary solution changed the optical characteristics of CdS film.

Digested water hyacinth with activated sludge as inoculum were obtained after anaerobic digestion at 35 and 45 ° C. High organic content of digested biomass were evaluated through gasification at supercritical conditions of water in the absence and presence of catalysts (KOH, NaOH, LiOH and K 2 CO 3 ) with 10 wt.% of volatile solid in feed. Supercritical water gasification of digested biomass was performed in batch reactor system at temperature and pressure ranges of 500 – 600 ° C and 350 –450 bar, respectively. The highest carbon gasification efficiency, hydrogen and methane yields were reached at 600 ° C (with samples digested at 45 ° C ) in the absence of catalyst as 84.6 ( g C in gaseous/g C in digestate) , 53.0 (mol H 2 %) and 12.5 (mol CH 4 %), respectively. High organic content of digested biomass was converted by supercritical water gasification to hydrogen and methane rich gas, and aqueous products (aliphatic hydrocarbons, phenol, substituted phenols, N-heterocyclic, substituted N-heterocyclics, and substituted benzene) that can be evaluated as platform chemicals.

Refractive index (RI) is one of the optical parameters that is of paramount interest in characterizing liquid solutions and solvents. Increased public awareness and legal requirements for quality standards in different sectors have created a need for reliable, fast, automated, remote and/or portable refractive index sensors with multi-measurement capability. The fiber-based RI sensors are very good candidates in providing attractive solutions in such application areas and have been attracting a growing interest by the scientific community. In this work, a fiber optic refractive index sensor has been investigated. It uses a long-period fiber grating (LPFG) and an Optical Spectrum Analyzer (OSA), as sensor head and interrogator unit, respectively. New measurements of refractive indices of common solvents and solutions at the low-loss telecom wavelength band have been successfully demonstrated by using the proposed sensor. The reported measurement results are in excellent agreement with our simulation results and reference measurements realized by conventional measurement techniques.

SnO2 (tin dioxide) thin film was deposited on commercial glass substrate by spray pyrolysis technique at 420o C. The XRD analyses indicated that the SnO2 thin film is found to tetragonal rutile structure. Optical transmission values (T %) of the film are the range of 80-96 % in the visible region and its highly transparent. The absorption coefficients (?) were defined from transmission spectrum. Refractive indices (n) and film thickness (t) were determined from interferences of the optical transmission curve with envelope method. The refractive indices (n) were altered between 1.83-1.97 in the ultravioletvisible-near-infrared (UV-VIS-NIR) regions. The thickness (t) and optical energy gap (Eg) of the SnO2 thin film were found to be 1.22 ?m and 3.98 eV, respectively. SnO2 (kalay dioksit) ince film ticari cam alttaban üzerinde 420o C’de püskürtme tekniği ile depolanmıştır. XRD analizleri SnO2 ince filmin tetragonal rutil yapıya sahip olduğunu göstermiştir. Filmin optik geçirgenlik değerleri (% T) görünür bölgede % 80- 96 aralığındadır ve son derece şeffaftır. Soğurma katsayıları (?) geçirgenlik spektrumundan hesaplanmıştır. Kırılma indisleri (n) ve film kalınlığı (t) zarf yöntemi kullanılarak optik geçirgenlik eğrisinin girişimlerinden belirlenmiştir. Ultraviyolegörünür-yakın kızılötesi (UV-VIS-NIR) bölgelerinde kırılma indisleri (n) 1.83-1.97 aralığında değişmiştir. SnO2 ince filmin kalınlığı (t) ve optik enerji aralığı, sırasıyla 1.22 ?m ve 3.98 eV olarak bulunmuştur.

Since geodetic and fossil energy that Turkey owns is insufficient and do not meet the demand, evaluation of renewable energy resource is very important for Turkey. For this reason, tending towards hydro-electric power is an applicable option and hydroelectric power is one of the most important energy resource for the country. From the point of view of water resources, evaluation of water potential of large and small streams for the purpose of energy production is vital for the country. Thereby, the existing deficit gap relevant to the energy, is reduceable. Within this paper, Seydisuyu basin has been selected as the research area. Precipitation in the watershed is drained by Seydisuyu stream. Only two dams named as Kunduzlar and Çatören, were constructed and are currently in operation in the study area. These dams were built for the purposes of only irrigation and flood control, in the watershed. Water potential of the basin is very small, due to the slight amount of precipitation within that area. Accordingly, planning of only small-scale hydro-electric energy potential is considerable over these dams, for region/national economic advantage of the country. In this study, the hydro-electric power potential of these two existing dams, were investigated. For this purpose, using 19 years of monthly data obtained from six existing flow gauging stations in the basin, the amount of hydroelectric energy generation of these dams was analyzed individually. As the result of these analysis, the calculation of the annual energy production capacity, the installed power production, and the annual economic contribution for both Çatören and Kunduzlar dams were estimated as 4.14 GWh (2.15 GWh (Çatören) + 1.99 GWh (Kunduzlar)), 0.843 MW (0.273 MW (Çatören) + 0.57 MW (Kunduzlar)), and 495000 USD (257000 USD (Çatören) + 238000 USD (Kunduzlar)), respectively.

If the coefficients of a polynomial depend on uncertainty parameter then a polynomial family is under consideration [1,4]. In many stability problems the investigation of pure imaginary roots for a polynomial family is very important. Given a pure imaginary complex number, the set of all images of uncertainty vectors is called the value set corresponding to this pure imaginary complex number. The question whether these sets contain the origin is very important from robust stability point of view of a polynomial family. Cutoff frequency guarantees the noninclusion of the origin to the value set for large frequencies. In this paper we give a procedure for more strict estimation of cutoff frequency and applications the obtained result to the constant inertia problem of polynomial family., Bir polinomun katsayıları belirsiz parametrelere bağlı olduğunda bir polinom ailesi söz konusu olur [1,4]. Pek çok kararlılık probleminde, polinom ailesinin pür imajiner köklerinin araştırılması oldukça önemlidir. Pür imajiner bir kompleks sayı verildiğinde, belirsizlik vektörlerinin görüntülerinin kümesi bu kompleks sayıya karşılık gelen değer kümesi olarak adlandırılır. Değer kümelerinin orijini kapsayıp kapsamadığı sorusu, polinom ailesinin gürbüz kararlılığı açısından çok önemlidir. Kesme frekansı, daha büyük frekanslar için değer kümesinin orijini içermemesini garanti eder. Bu çalışmada, kesme frekansını daha iyi belirlemek için bir prosedür verilmiştir ve elde edilen sonuçlar polinom ailesinin sabit inerşiya problemine uygulanmıştır.

Im Folgenden werden einige Facetten dieses weiten Feldes [der Synästhesie] herausgegriffen, nämlich das der Farblichtmusik und der Verbindung von Ton und Bild zwischen 1920 und 1930 mittels apparativer Verschaltungen. Hierzu werden zwei technische Anordnungen gegenübergestellt, die eine Ton-Bild-Wandlung auf eine Weise vornahmen, die radikaler als die damals weit verbreiteten Lichtorgeln vorging, indem sie nicht nur metaphorisch mit der gleichschwingenden Kraft von Tönen und Bildern agierten, sondern diese zum Gegenstand medientechnischer Anordnungen machten. Die eine dieser Apparaturen wurde im Kontext der Kunst entwickelt und stammt von Raoul Hausmann, während die andere von dem Fernmeldetechniker Fritz Winckel realisiert wurde. Indem Hausmann und Winckel die Zuordnung von Tönen und Bildern nicht assoziativ realisierten wie die meisten Lichtorgeln dieser Zeit, sondern die Ton- und Bildquellen mit analoger Technik direkt verschalteten, riefen sie umso mehr den Vergleich mit der durch Menschen wahrgenommenen Synästhesie auf, weshalb zu Beginn auf diese etwas breiter eingegangen werden muss. Hier ist zu fragen, was geschieht, wenn Synästhesie zu einem künstlerischen Konzept wird und welche Rhetoriken von Kunstschaffen in den 1920er Jahren daran gebunden waren. Es soll deutlich werden, dass die vom Menschen wahrgenommene Synästhesie in ihrer körperlichen Grundlage sowie in ihrem ästhetischen Empfinden nicht mehr als eine Metapher für ihr medientechnisches Pendant sein konnte. Synästhetische Wahrnehmung und verschaltete Medien bringen jeweils ihre eigenen ästhetischen Reiche hervor. Andererseits boten die unscharfen und vielschichtigen Konzepte der Synästhesie zahlreiche Anregungen für Künstler, schufen Raum für eine Synthese der Künste und waren der Anstoß für neue künstlerische Ausdrucksformen mittels Medientechnik und damit eine frühe Form der Medienkunst.

In this work, 5-(3-methyl-3-phenylcyclobutyl)-N-phenyl-3,6-dihydro-2H-1,3,4-thiadiazin-2-imine (C20H21N3S), MPDT, was prepared and characterized by X – ray single crystal diffraction and IR and 13C-NMR spectroscopic techniques. The molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO) 13C chemical shift values of MPDT in the ground state have been calculated by using the Hartree-Fock (HF) and Density Functional Theory (B3LYP) with 6-31G(d) basis set. The scaled B3LYP/6-31G(d) results shows the best agreement with the experimental values over the other method. B3LYP is applied to explore the Mulliken atomic charges of the title molecule. In addition to frontier molecular orbital (FMO) and molecular electrostatic potential (MEP) of the title molecule have been calculated by using the HF and B3LYP with 6-31G(d) basis set. Bu çalışmada, 5-(3-methyl-3-phenylcyclobutyl)-N-phenyl-3,6-dihydro-2H-1,3,4-thiadiazin-2-imine (C20H21N3S), MPDT, IR ve 13C-NMR spektroskopik teknikleriyle ve X-ışını tek kristal kırınımı ile karakterize edilip hazırlandı. Temel halde molekülün, moleküler geometri, titreşim frekansları, GIAO 13C kimyasal değişim değerleri 6-31G(d) baz seti ile HF ve B3LYP metotları kullanılarak hesaplandı. B3LYP/6-31G(d) de elde edilen sonuçları diğer metoda kıyasla deneysel veriler ile daha uyumlu sonuçlar gösterdi. Bu sebeple molekülün Mulliken yük dağılımları B3LYP ile hesaplandı. Ek olarak molekülün moleküler orbital ve moleküler elektrostatik potensiyeli de HF/6-31G(d) ve B3LYP/6-31G(d) kullanılarak hesaplandı.

Bu çalışmanın esas amacı, Ekici tarafından tanımlanan hemen hemen ??-sürekli fonksiyonların karakterizasyonlarını araştırmak ve bu kavrama ilişkin bazı temel özellikler elde etmektir. Ayrıca hemen hemen ??-süreklilik kavramının sadece bazı temel özellikleri değil aynı zamanda literatürde bulunan diğer birçok fonksiyon tipleri ile aralarındaki ilişkiler incelenmiştir. Dahası bu kavram ile ayırma aksiyomları arasındaki bazı temel özellikler de araştırılmıştır. The main purpose of this study is to investigate the characterizations of almost ??-continuous functions defined by Ekici and to obtain some fundamental properties related to this concept. In addition, we investigate not only some of its fundamental properties but also its relations with other types of already existing topological functions. Moreover, we look into some basic properties between this notion and separation axioms.

4 ? manifoldların yapısını incelemekte kullanılan Seiberg?Witten denklemleri, Dirac denklemi ve Eğrilik denklemi olmak üzere iki denklemden oluşmaktadır. Bu denklemlerin yüksek boyutlarda da self –dualite seçimine bağlı olarak genellemeleri yapılmıştır [1,2,6,9]. Bu çalışmada öncelikle 4-boyutlu Hiperbolik uzay üzerinde klasik Seiberg?Witten denklemleri yazılmış daha sonra [1,2,6,9] de verilen yöntem kullanılarak 8 ? boyutlu Hiperbolik uzay üzerinde genelleştirilmiş Seiberg-Witten denklemleri yazılmıştır., Seiberg?Witten equations, which are used to investigate the structure of 4 ?dimensional manifds, consist of two equations. The first item is Dirac equation and the latter is Curvature equation. According to choosing of the self?duality concept, the generalized of these equations were done in higher dimensions [1, 2,6,9]. In this paper, at first the classical Seiberg?Witten equations are written on 4 ?dimensional Hiperbolic space. Then, the generalized Seiberg?Witten equations are written on 8 ?dimensional Hiperbolic space by using the method given in [1].

Kazalar veya ihmaller sonucunda ham petrol ve rafinasyon ürünleri ile oluşan deniz veya kara ekosistemindeki kirliliklerin biyomarker verileri ile araştırılması, kaynağa ait izlerin takibi ve buna neden olan kaynağın (petrol tankeri, gemi, tekne vb) ortaya çıkartılması son yıllarda sıkça uygulanan bir yöntemdir. Günümüzde detaylı ve gelişmiş aletsel yöntemlerle gittikçe gelişen bir araştırma türü olmuştur. Biyolojik işaretçiler veya biyomarkerler yaşayan organizmalardan itibaren oluşan kompleks moleküllerdir. Bu bileşenler, birincil organizmalardaki orjinal karbon iskeletlerinin tamamını veya büyük kısmını korumaları nedeniyle önemlidir. Tanımlanan yapısal benzerlik faktörü sızıntı petrol veya rafineri ürünlerinin kaynaklarının belirlenmesi için petrolde bulunan diğer bileşen gruplarına göre daha fazla bilgi verir. Bu nedenle, biyomarkerlerin kimyasal parmak izi, sızıntı petrol ve/veya rafineri ürünlerinin kaynağını belirleme, petrolleri ayırt etme ve karşılaştırma ile petrollerin bozunma sürecini ve aşamasını izleme ve değerlendirme açısından çok çeşitli koşullarda çevresel adli araştırmalara çok önemli bilgileri üretir. Bu makalede biyomarkerlerin kimyasal özellikleri kısaca anlatılarak, biyomarker tanımlama ve değerlendirilmesi, dağılımları, bileşimindeki bozunma etkileri, tanımlayıcı oranlar, petrol ve türevlerine ait sızıntı çalışmalarında biyomarker parmak izlerinin kullanımı ve bu kapsamda dünyada yapılan bazı örnek çalışmalar hakkında genel bir değerlendirme yapılmıştır., The investigation of the pollution of marine or land ecosystem resulting from accidents or negligence of crude oil and refinery products by biomarker data, the trace of the source and the find the suspect source (oil tanker, ship, boat etc.) have been frequently applied for the last years by this method. Recently, it has become a advanced research method by detailed and advanced instrumental methods. Biological markers or biomarkers are complex molecules formed from living organisms. These components are important, because they maintain all or most of original carbon skeleton of the primary organism. This identified structural resemblance factor reveals more information about a spilled oil’s or refinery products’s source than do other compound groups present in crude oil. For this reason, chemical fingerprinting of biomarkers generates information of great importance to environmental forensic investigations in terms of identify the source of spilled oil and/or refinery products, differentiating and correlating oils, and monitoring and evaluation the degradation process and weathering state of oils under a wide diversity of conditions. This article briefly reviews biomarker chemistry and characterization and quantification, distributions, weathering effects on biomarker composition, diagnostic ratios, application of biomarker fingerprinting techniques for spill source investigations.

It is known that there exists a family of connection 1-forms depending on two parameters on the standard quaternionic Hopf bundle. This family is constructed by using the canonical connection 1-form. In this work, the self duality and the anti-self duality of these connection 1-forms are investigated. Parameters for which the family of connection 1-forms are self dual and anti-self dual are determined., Standart kuaternionik Hopf demeti üzerinde iki parametreye bağlı bağlantı formlarının bir ailesinin varlığı bilinmektedir. Bu bağlantı formların ailesi kanonik konneksiyon 1-formu kullanılarak inşaa edilmiştir. Bu çalışmada, bu bağlantı 1-formlarının self dual ve anti-self dualliği araştırılmıştır. Bu bağlantı 1-formların hangi parametreler için self dual ya da anti-self dual olduğu belirlenmiştir.

In the present study we have formulated a new Maximum Fuzzy Entropy Problem (Max(F)EntP) for fuzzy membership function and proposed sufficient conditions for existence of its solution. Mentioned problem consists of approximation fuzzy membership function by maximizing Maximum Fuzzy Entropy (Max(F)Ent) measure with respect to membership functions with finite number of the fuzzy values subject to constraints generated by given moment functions. The existence of solution of mentioned problem is proved by virtue of convexity property of Max(F)Ent measure, the implicit function theorem and Lagrange multipliers method. Moreover, by using MATLAB programme one application of suggested method on fuzzy data analysis is given., ÖZET Bu çalışmada, tarafımızdan bulanık üyelik fonksiyonu için yeni bir maksimum bulanık entropi problemi (Max(F)EntP) geliştirilmiş ve bu problemin çözümünün varlığı için yeterli koşullar belirlenmiştir. Söz konusu problem sonlu sayıda bulanık değerlere sahip üyelik fonksiyonunu bulanık entropi ölçümünü verilmiş moment fonksiyonları yardımıyla üretilen moment koşulları altında maksimize etmekle yaklaşık olarak elde etme problemidir. Söz konusu problemin çözümünün varlığı Max(F)Ent ölçümünün konvekslik özelliği, kapalı fonksiyon teoremi ve Lagrange çarpanları yardımıyla ispatlanmıştır. Buna ek olarak, bulanık veri analizi üzerine sunulmuş yöntemin bir uygulaması MATLAB programı kullanılarak verilmiştir.

The “Walled Obelisk” is a 32.77-meter high, 2x2 meter mean square, rough-cut limestone monument that is becoming thinner to the four-sided hill. This monument is in a very sensitive seismic region of the World-Istanbul and remains intact from the time of its construction (approximately tenth century) to the present despite all seismic activity during that time. The current study extracts and investigates a mathematical model of the monument, which reveals that support of the structure incorporates a “natural seismic isolator” that demonstrates behavior similar to current used lead-core rubber-bearings isolator (LRB). The total height of the “natural seismic isolator” is 3.44 m. and consists of three–steps of rough-cut limestone and a massive marble stone that forms four sliding surfaces bonded with Horasan mortar. The components of the “natural seismic isolator” form four sliding surfaces and appear to function similar to LRB’s combined layers of steel plates and hard rubber. The massive marble stone appears to function like the lead cylinder core of the LRB. The “natural seismic isolator” demonstrates fully plastic behavior and differs from the LRB by maintaining the monument’s upper part in equilibrium during earthquake excitation, which also varies near zero equilibrium. During this study’s comparison of the isolator’s use of the expression, “similar” is frequent used in this meaning, and the comparison uses a fixed base model of the monument that cannot reciprocate during recovery from earthquakes over the 1000-year history. The proposed model of “natural seismic isolation” from historical experience (for this monument, 1000 years), suggests that the easily constructed natural isolator requires no special maintenance, and is suitable for modern structures in seismic regions.

Coprime array geometries provide robust performance for direction-of-arrival estimation problem with more sources thansensor elements. In previous works it is shown that K source directions can be resolved using only 2M N -1 sensorelements where K is less than or equal to MN for M and N are integer numbers. In this paper we introduce a new approach toenhance the degrees of freedom (DOF) from MN to 2MN by using the same number of sensor elements. The proposedmethod is based on computing the covariance matrix of the observation data multiple times. Hence more DOF can beobtained. The resulting cross terms corresponding to the coherent sources are modeled as interference in a sparse recoveryalgorithm which is solved effectively by an alternating minimization procedure. The theoretical analysis of the proposedmethod is provided and its superior performance is evaluated through numerical simulations.

The scope of this study is to determine the effectiveness of using rivets in the adhesive joints in order to combine plastic-based composite materials which are often used in today's engineering structures, to the joint strength. For this purpose, double lap joints are prepared in 3 different types of configuration included adhesive, pinned and both adhesive and pinned and also prepared in 3 different overlap lengths as 30, 45 and 60 mm. Stress-strain diagrams were derived by exposing the joints obtained, to the axial tensile test and then the most appropriate joint type was determined by comparing each of the results obtained. The evaluation of the results pointed out that the hybrid joints where adhesive and rivet are used together can carry much more load than the joints where the only adhesive was used or the joints which are combined with a rivet in terms of joint strength.

1 Department of Mathematics, )DFXOW\RI6FLHQFHDQG$UW?Giresun University, Giresun, Turkey 2 Department of Mathematics, )DFXOW\RI6FLHQFH?Anadolu University, Eskişehir, Turkey ABSTRACT An analysis of the distributed moving load along the surface of a coated half space is presented. The formulation of the problem depends on the hyperbolic-elliptic asymptotic model developed earlier by the authors. The integral solution of the longitudinal and transverse displacements along the surface for the sub and super-Rayleigh cases are obtained by using the uniform stationary phase method. Numerical comparisons of the exact and asymptotic solutions of the longitudinal displacement are illustrated for the certain cross-sections of the profile., Kaplamalı elastik bir yarı uzayın yüzeyi boyunca dağılımlı hareketli yükün bir analizi sunulmuştur. Problemin formülasyonu yazarlar tarafından önceden geliştirilmiş hiperbolik-eliptik modele dayanmaktadır. Sub ve süper Rayleigh durumları için yüzey boyunca boyuna ve enine yer değiştirmelerin integral çözümleri düzgün durağan faz metodu kullanılarak elde edilmiştir. Boyuna yer değiştirmenin tam ve asimptotik çözümlerinin nümerik karşılaştırmaları profilin belirli kesitleri için grafikler ile gösterilmiştir.

The main aim of this work, was to lay the foundations for the experimental realisation of a quantum mechanical controlled NOT gate in rare-earth-metal-ion-doped crystals. Small amounts of rare-earth elements, added during the growth of some inorganic crystals, will become substituted into the crystal lattice as trivalent ions. The trivalent rare-earth-metal ions between cerium, with atomic number 58, and ytterbium, with atomic number 70, have a partly filled 4f shell, which does not extend spatially outside the full 5s and 5p shells. The 4f vacancies make electronic inner shell transitions possible between spectroscopic 4f terms. Some of these optical transitions have coherence times of the order of milliseconds, when the crystals are cooled down to ~ 4 K. There are several reasons for these extraordinary coherence times, which are approximately 8 orders of magnitude greater than those typical for electronic transitions in solids. The most important one is the cage-like shield which the outer 5s and 5p shells provide for the 4f electrons. Furthermore, since these ions are naturally trapped inside the crystal lattice there is no Doppler broadening of the line-width. The coherence properties of these optical transitions is one of the features that makes these materials attractive for use as a solid-state platform for quantum computing, using these ions as qubits. Another appealing characteristic is the fact that different ions have different optical resonance frequencies, which means that ions belonging to different qubits, which only have nm separation, can still be addressed separately by using different laser frequencies. Since the inter-ion spacing is so small, it is possible to make two ions interact strongly, although they are well shielded, through a permanent dipole-dipole interaction. This interaction can be turned on and off by switching between two different ways of encoding the qubit, a most useful feature. When the qubit is represented as a superposition between two ground state hyperfine levels, the interaction is turned off. The interaction is turned on selectively by transferring this superposition to the optical transition with a pi-pulse, for the specific ions that are to interact. This thesis describes how peaks of ions, absorbing on a single transition, residing in spectral pits with no other ions, have been isolated. It is shown how these ions can be coherently transferred between hyperfine levels via the optically excited state, how the interaction between such peaks of ions representing qubits can be turned on and off, and how subgroups of ions with strong interaction can be distilled out. All the work described here has been performed using the ensemble approach. The ensemble approach will, however, be difficult to scale up to large numbers of qubits. A method employing a single ion in each qubit, using a specialised ion for readout, has therefore also been proposed. The rare-earth-metal-ion-based quantum computing experiments require a laser with coherence properties which at least match those of the material. To this end a frequency stabilisation system was developed for a dye laser. This system uses a transient spectral hole in a rare-earth-metal-ion-doped crystal, of the same kind that is used in the experiments, as frequency reference, and is to the authors knowledge the first demonstration of locking a dye laser to a spectral hole. This system provides a line-width of 1 kHz on a 10 microseconds timescale and a frequency drift below 1 kHz/s. Kvantdatorer har den unika egenskapen att de kan utföra samma beräkning för många olika startvärden samtidigt. Informationen i en vanlig dator är lagrad i ett minne som består av bitar, som kan ha värdena 1 eller 0. När ett program körs beror slutresultatet av startvärdena hos dessa bitar. Minnet i en kvantdator lagrar istället kvantbitar, som även de kan ha värdena 1 eller 0. Men kvantbitarna kan även befinna sig i ett ``kanske-tillstånd'', en så kallad superposition, där de kanske har värdet 0 och kanske 1. Om några av kvantbitarna i ett kvantdatorminne från början sätts i ett "kanske-tillstånd", utförs alla beräkningar, vilka motsvarar de olika möjliga kombinationerna av "kanske-bitarna", samtidigt när programmet körs. När man sedan ser på resultatet av programmet får man slumpvis ett av de möjliga svaren, vilket kan tyckas vara ineffektivt. Det visar sig, emellertid, att vissa problem som tar orimligt lång tid att beräkna med en vanlig dator, kan lösas effektivt av en kvantdator med specialskrivna program. I detta arbetet har jag jobbat med kvantbitar, som är baserade på joner som hör till gruppen sällsynta jordartsmetaller. Jonerna sitter mycket nära varandra i genomskinliga kristaller. Dessa joner har den ovanliga egenskapen att kunna komma ihåg "kanske-tillståndet" för en kvantbit länge, trots att "kanske-tillstånd" normal sett är mycket kortlivade. Programmen i våra kvantdatorer består av pulser av laserljus, med vilka vi belyser jonerna. Olika joner påverkas av olika frekvenser hos laserljuset, på liknande sätt som en radiomottagare inställd på en kanal bara tar emot den kanalen. Genom att byta frekvens på ljuset kan olika grupper av joner påverkas separat. I arbetet, som denna avhandling beskiver, har en teknik utvecklats för att med hjälp av ljuspulser plocka bort alla joner inom ett frekvensintervall och sedan lyfta tillbaka joner med bara en välbestämmd frekvens, som skall utgöra en kvantbit i vår kvantdator. Denna kvantbit skiftas sedan mellan värde 1 och 0 upprepade gånger, en så kallad en-bitars grind. Om man upprepar denna procedur för två olika frekvensintervaller, så kan man skapa två kvantbitar. För att kunna skapa kvantgrindar med två bitar, så måste en kvantbit kunna påverka en annan. I vårt fall kan en jon, som tillhör en av kvantbitarna, ändra vilken ljusfrekvens som en annan jon annars skulle ha påverkats av. ändringen kan liknas vid att radions kanalinställning ändras lite, varvid man inte längre kan ta emot radiokanalen. I detta arbete har vi visat detta fenomen. Det är endast de joner som råkar sitta nära varandra, som har tillräckligt stor påverkan för att kunna användas som kvantbitar. Vi har experimentellt visat hur endast de joner, som påverkas mycket, kan väljas ut. Ovanstående kvantdatorschema fungerar för två kvantbitar, men skall man ha fler kvantbitar blir det för få joner kvar i ett närliggande område som alla påverkar varandra, för att man skall kunna detektera dem. En metod som gör det möjligt att ha fler kvantbitar beskrivs i denna avhandling. I denna metod har man endast en jon per kvantbit och utläsningen sker med hjälp av en speciell utläsningsjon, som har dåliga kvantbitsegenskaper, men är lätt att detektera. Frekvensen och fasen på de laserpulser som används, till att manipulera jonerna, måste vara mycket stabil. Jag beskriver därför, hur vi har stabiliserat en laser genom att jämföra dess frekvens med frekvensen hos samma typ av joner, som kvantbitarna består av, och sedan korrigera frekvensfelen.

Monitoring of environmental gases is necessary to understand the complex processes governing global warming and the impact of pollutant emissions related to human activity. Diode-laser-based spectroscopic techniques, being robust and affordable, have a great potential to become an industrially well-established technology for environmental sensing. This thesis deals with the further development of these techniques, demonstrated in several applications to atmospheric gas detection and sensing. The accessible spectral range of tunable diode lasers was extended by use of sum-frequency generation. High-resolution ultraviolet spectroscopy of mercury isotopes around 254 nm was performed on low-pressure cells as well as at atmospheric pressure. Ultraviolet radiation around 300 nm, utilized for monitoring of sulfur dioxide and studies of the pressure dependence of the absorption spectrum, was produced using a sum-frequency generation scheme employing a blue and a near-infrared diode laser. Detection sensitivity was improved by several orders of magnitude by employing frequency modulation techniques. This was demonstrated with blue continuous-wave diode lasers in measurements on ground state potassium atoms, and lead atoms in very weakly populated meta-stable states. In the red spectral region, traffic-generated emission of nitrogen dioxide was monitored in situ using long path absorption at a wavelength around 635 nm. A new temporal gas-correlation scheme was developed, which overcomes the intrinsic multimode and mode-jump behaviour of diode lasers. The concentration of a gas under study is determined by temperature tuning the wavelength of a diode laser across an absorption band of the gas, and by simultaneous temporal correlation of the detected signal with the signal from a known reference gas concentration. No knowledge of the exact spectrum is needed. The method was tested in diffusion related measurements. A novel technique for analysis of free gas in scattering media by use of absorption spectroscopy, GASMAS, was introduced. The sharp absorption features of the gas, contrasted to the very slow wavelength dependence of the bulk material, can be picked up by use of modulation techniques. Dispersed molecular oxygen embedded in various natural and man-made porous materials was detected and measured. The gas concentration was determined by combining absorption and time-resolved laser spectroscopy measurements. Investigations were performed to assess the internal gas pressure and gas diffusion characteristics. A new single-aerosol particle detector using a coupled-cavity diode laser was developed. Simultaneous size and shape determination was demonstrated by recording of the optical extinction and a diffraction image in the near-forward scattered light.

In this thesis, aspects of the use of cryogenically cooled rare-earth-ion-doped crystals in the fields of quantum optics and quantum information processing are addressed. The experiments and theoretical considerations referred to in this thesis are based on the coherent transient interaction between light and the ions in the crystals. A photon echo experiment has been performed where faint optical pulses were accumulated in the crystal. In this experiment, the possibility of single photons acting as two of the optical fields in the photon echo process was investigated. Different aspects on the experiment, which can be viewed as delayed self-interference of a single photon, are discussed in this thesis. A scheme for the possible implementation of quantum information processing in rare-earth-ion-doped crystals is presented. A key feature in this scheme is that small groups of ions, which can be optically manipulated and which interact in a controlled way, can be extracted from a collection of randomly positioned ions in the crystal host. Initial experimental investigations of the scheme, indicating the possibility of implementing quantum gates, are also presented in this thesis. In another experiment, the application of magnetic fields of up to 5 T was seen to increase the lifetime of information stored as frequency-dependent modulation of the population of thulium ions doped into a YAG crystal by several orders of magnitude. This mechanism might be useful in data storage and information processing applications. An experiment in which the same type of crystal was used as the active medium in a photon-echo-based pulse compression experiment, where microsecond long pulses were compressed to nanosecond duration using frequency-chirped light pulses, is also reported in this thesis. Ljusets minsta kända beståndsdelar kallas fotoner. Enligt kvantmekaniken har dessa egenskaper som normalt förknippas med vågor och samtidigt sådana egenskaper som normalt förknippas med partiklar. Partikelegenskaperna tar sig uttryck i att den minsta mängd ljus som går att mäta är den mängd som motsvaras av en foton. Vågegenskaperna, å andra sidan, visar sig i interferensexperiment, där en enskild foton verkar kunna ta två olika vägar samtidigt för att sedan kunna interferera med sig själv. Denna dualism mellan våg- och partikelnaturen hos fotoner har studerats flitigt under de senaste hundra åren. I denna avhandling presenteras ett experiment, där enskilda fotoner har fått växelverka med joner indopade i en kristall. Experimentet indikerar att enskilda fotoner kan delas upp i två pulser som absorberas av jonerna i kristallen. Sedan absorptionen av många enskilda fotoner ackumulerats i kristallen är det möjligt att få information om tidsskillnaden mellan de två pulserna. Detta trots att en direkt mätning av pulserna skulle visa att fotonerna befann sig i antingen den ena pulsen eller den andra, men aldrig i båda samtidigt. Vid en sådan mätning skulle det vara omöjligt att få information om tiden mellan pulserna. Experimentet som presenteras i avhandlingen kan tolkas som att de båda pulserna interfererar med varandra i kristallen trots att de aldrig befinner sig där samtidigt. En annan del av avhandlingen behandlar området kvantdatorer. Dagens datorer behandlar information i form av bitar som kan ha antingen värdet ett eller värdet noll. I en kvantdator representeras bitarna, vilka kallas kvantbitar, av kvantmekaniska system. Detta innebär att kvantbitarna kan anta värdena noll och ett, precis som bitarna i en vanlig dator, men att de även kan vara i en superposition av de båda värdena. Detta gör att datorn kan räkna på båda de möjliga värdena parallellt, vilket gör det möjligt att utföra vissa typer av beräkningar snabbare än om en vanlig dator hade använts. Byggandet av kvantdatorer befinner sig fortfarande på experimentstadiet och ett stort antal fysikaliska system, som föreslagits som möjliga för att implementera kvantdatorberäkningar, undersöks för närvarande. Inom ramen för denna avhandling har möjligheten att utföra elementära kvantdatorberäkningar med hjälp av kristaller dopade med joner från de sällsynta jordartsmetallerna undersökts. I avhandlingen presenteras ett förslag på hur detta skulle kunna göras. Förslaget går ut på att låta joner som absorberar ljus med olika våglängd utgöra olika kvantbitar. För att kunna använda kvantbitarna i logiska grindar krävs det att jonerna i de olika kvantbitarna kan växelverka med varandra. Ett tillvägagångssätt för att från en kristall välja ut endast de joner där denna växelverkan är tillräckligt stark har också utvecklats och presenteras i avhandlingen. Vidare har experiment utförts för att undersöka om förslaget går att realisera i praktiken. Slutligen har samma typ av kristaller som de ovan beskrivna använts för att komprimera optiska pulser. Genom att använda en optisk process kallad fotonekon, kunde optiska pulser, ursprungligen mikrosekunder långa, komprimeras till längder i nanosekundsområdet. Samma typ av kristaller har också undersökts då de placerats i ett starkt magnetfält. Detta visade sig ge upphov till en mekanism för långtidslagring av information i kristallen, vilket kan ha tillämpningar inom optisk datalagring och signalbehandling.

This thesis is concerned with the propagation of transient electromagnetic waves in nonlinear media. It consists of a General Introduction and five scientific papers. The General Introduction gives a broad overview of nonlinear electromagnetic phenomena. The emphasis is on the representation of the constitutive functional modeling the material's response to electromagnetic excitation, and the methods employed to analyze the combination of the constitutive functional and the Maxwell equations. Some applications of nonlinear electromagnetics are also discussed. Paper I treats the inverse scattering problem for an isotropic, homogeneous, nonlinear slab, subjected to a normally incident field. It is shown that when both reflected and transmitted fields are measured, we can reconstruct both the nonlinear permittivity and permeability. When one of these functions is known, reflection data is sufficient to obtain the other. Paper II gives a formulation of transient electromagnetic fields, that can be used to analyze wave propagation in homogeneous media. The source free Maxwell equations are treated as an eigenvalue problem, from which we deduce the propagating waves and their wave speeds. The analysis is applied to the case of obliquely incident waves on a semi-infinite, bianisotropic, nonlinear medium. Paper III analyzes the propagation of electromagnetic waves in a waveguide filled with an isotropic, nonlinear material. The equations governing each waveguide mode are derived, and it is shown that the different modes couple to each other. This coupling is quantified, and a growth estimates is given for the induced modes. Paper IV deals with discontinuous electromagnetic waves, shock waves. It is shown that in order for these waves to be stable, they must satisfy a number of conditions, similar to Lax's classical shock conditions. These conditions permit us to classify electromagnetic shock waves as slow, fast or intermediate shock waves. Finally, Paper V investigates the uniqueness and continuous dependence on data for solutions of the quasi-linear Maxwell equations, when we also require them to satisfy an entropy condition. This condition is related to the second law of thermodynamics, that the energy that is not described by our model must be dissipated. Denna avhandling behandlar hur elektromagnetiska vågor utbreder sig i olika material. Vanligtvis antar man i elektromagnetiska problem att materialen är linjära, det vill säga om man vet att man får en viss utsignal från materialet vid en given insignal, så förväntar man sig att få två gånger så stor utsignal om man fördubblar insignalen. I avhandlingen försöker vi klara oss utan denna egenskap, och utvecklar metoder som inte behöver linjäritet för att behandla vågutbredning. Detta kan behövas för att beskriva fenomen där man använder mycket stora energier, och vi ger ett antal olika exempel på sådana situationer i den allmänna inledningen, som föregår de fem vetenskapliga artiklar som utgör huvuddelen av avhandlingen. Olika problem som behandlas i detta verk är hur man kan tolka mätningar utförda på olinjära material, och hur vågutbredningen i materialen kan beskrivas. Vi undersöker dels material som har samma egenskaper i alla riktningar, så kallade isotropa material, som material som har särskilda egenskaper i någon riktning, så kallade anisotropa material. Det visar sig att man vanligtvis har två olika vågutbredningshastigheter i ett olinjärt material. Dessa hastigheter kallas karakteristiska hastigheter, som dessutom visar sig bero på hur starka vågor vi försöker skicka genom materialet. Ett typiskt fenomen som inträffar med vågutbredning i olinjära material är så kallade chockvågor. Detta är vågor som kan börja som lugna och mjuka vågor, men efter en viss ändlig tids utbredning börjar de kantra och blir skarpare och skarpare. Ett typiskt exempel på detta är vattenvågor som kommer in mot en grund strand; då avståndet mellan vattenytan och botten minskar, kommer toppen av vågen att färdas snabbare än resten, varpå vågen till slut bryts och vi får de typiska bränningar som kan iakttas vid en strand. Det visar sig att det finns tre sorters elektromagnetiska chockvågor, som skiljer sig åt beroende på hur snabbt de utbreder sig i förhållande till de två karakteristiska hastigheterna som vi nämnde i förra stycket: de snabba, långsamma eller mellanliggande chockvågorna.

The present thesis is devoted to the theoretical study of two-dimensional electron systems moving in a modulated lateral periodic potential and a competing perpendicular magnetic field. The three introductory chapters offer a brief exposition of the basic issues in this area -- the description of the electron motion in a prependicular magnetic field, the group of magnetic translations and the commensurability phenomena -- at an elementary level. The second part of the thesis is a collection of original papers. A bandstructure calculation scheme based on the ray group of magnetic translation operators is introduced and used to investigate the electronic structure of modulated two-dimensional electron systems. In addition to the expected intricate internal structure of the energy subbands, the results reveal characteristic oscillations of the band-widths as a function of the magnetic field strength. The quantized Hall conductance in periodic systems is extracted from the bandstructure data. Its study predicts a possible rearrangement of the energy bands in superlattices composed of narrow and steep antidots. This rearrangement facilitates an easier access to the energy subgaps characterized by nontrivial, that is, different from 0 or 1, quantum Hall indices. The study of tunneling between two parallel layers of modulated two-dimensional electron systems has lead to the formulation of the methodological approach to the spectroscopic measurement of the electronic structure properties. The optical spectra of the considered systems are addressed both using a microscopic quantum mechanical approach based on the random-phase approximation and simplified semiclassical methods. A number of collective modes are identified and analyzed.

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