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1,27-2,50 GeV/c momentumlu pozitif pionların protonlarla etkileşmeleri
(Thesis (Assoc. Prof.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 1981., 1981.) Arık, Engin.
3 - D optical profilometry at micron scale with modified fiber optic Lloyd's mirror technique
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2017., 2017.) İnanç, Arda.; İnci, Naci.
In this thesis, it is shown that a modiﬁed ﬁber optic Lloyd’s mirror technique is suitable and practical to produce fringe patterns that have easily adjustable frequency. This allows measuring 3D height distribution of test objects at micron scale without using additional elements as part of the optical projection unit. To test the validity of the proposed method, images that contain deformed fringe patterns due to the height distribution of micron scale test objects are recorded by a CCD camera and analysed with one dimensional continuous wavelet transform. After the extraction of phase map using 1D continuous wavelet transform, the height dis tribution of the test objects is obtained by further analyses. Finally, the results are discussed and compared with the expected values.
3+1 formulation in Newton-Cartan gravity
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2022., 2022) Aras, Ulaş.; Bleeken, Dieter Van den.
In this thesis, we will give a review of torsion-free Newton- Cartan theory. We will start by doing a large c expansion of general relativity and we will restrict ourselves to a few leading orders. After obtaining Newton-Cartan theory in this way, we will explore its symmetries. Through a special set of combined symmetries, we will construct a split space and time structure. Lastly, we will work out the field equations and equations of motion for a particle in the 3+1 formulation we have obtained.
3D optical profilometry using fiber optics lloyd's mirror method
(Thesis (Ph.D.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2017., 2017.) Köseoğlu, Gülşen.; İnci, Naci.
A ber optic Lloyd's mirror assembly is investigated to obtain various optical interference patterns for the detection of three-dimensional shapes of rigid bodies. Two types of the ber optic Lloyds systems are used in this work. The rst one consists of a single mode optical ber and a highly re ecting at mirror to produce bright and dark strips. The second one is constructed by locating a single mode optical ber in a v-groove, which is formed by two orthogonal at mirrors to allow the generation of square type interference patterns for the desired applications. The structured light patterns formed by these two ber optic Lloyds techniques are projected onto three-dimensional objects. Fringe patterns are deformed due to the object0s surface topographies, which are captured by a digital CCD camera and are processed with the following signal processing techniques to accomplish their three-dimensional surface topographic maps: Fourier Transform Pro lometry, Phase Stepping Pro lometry, and Continuous Wavelet Transform Pro lometry. The method is developed for extracting 3D height distribution of various objects at the micron scale with a resolution of 5 m by elegantly interrogating the rst ber optic assembly to an optical microscope and a CCD camera. It is demonstrated that the proposed technique is quite suitable and practical to produce a structured light pattern with an adjustable frequency. By increasing the distance between the ber and the mirror with a micrometer stage in the Lloyd0s mirror assembly, the separation between the two bright fringes is lowered down to the micron scale without using any additional elements as part of the optical projection unit. The phase analysis of the acquired image is carried out by One Dimensional Continuous Wavelet Transform.
3D optical profilometry with a double beam - splitter setup
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2019., 2019.) Çetin, İsra Merve.; İnci, Naci.
In this thesis, it is demonstrated that a double beam splitter arrangement is very convenient and more practical to generate square shaped fringe patterns, and fringe distribution can be easily controlled in two dimensions. This enables to extract 3D height distribution of test objects without using any additional component as a projection unit. To approve the validity of the proposed technique, various frequencies of the fringe pattern are obtained by rotating a cubic beam splitter, and images that include deformed fringe patterns due to the height distribution of test objects are captured by a CCD camera. The resultant square fringe pattern is analyzed with two-dimensional continuous wavelet transform method and is separated into two fringe patterns in horizontal and vertical axes with a certain algorithm. The height-related phase map is acquired after analysis process.
A compilation of dualities between 4D N=2 supersymmetric gauge theories and 2D conformal field theories
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2019., 2019.) Kurşun, A. Kerem.; Kozçaz, Can.
In this thesis AGT-W conjecture is reviewed. AGT conjecture is a phenomenon which is shown by Luis F. Alday, Davide Gaiotto and Yuji Tachikawa in their paper published in 2009. It relates the partition functions of both N = 2 supersymmetric U(2), SU(2) gauge theories and Liouville ﬁeld theory which is a type of conformal ﬁeld theory. One month later, Niclas Wyllard extended the conjecture and proved the connection between N = 2 supersymmetric SU(N) gauge theories and AN−1 Toda ﬁeld theories. In addition to AGT-W conjecture, gauge/Liouville Triality, spectral duality and 2D/4D duality through Nekrasov-Shatashvili limit are summarized. N = 2 supersymmetric gauge theories are also studied in type IIA, IIB and topological string theory background.
A hybrid optical tweezers and photoacoustic microscopy system
(Thesis (Ph.D.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2017., 2017.) Kipergil, Esra Aytaç.; Ünlü, Mehmet Burçin.
Photoacoustic microscopy (PAM) is a promising imaging modality that combines optical and ultrasound imaging. It takes advantage of high optical contrast and high ultrasonic spatial resolution. Conventionally, piezoelectric transducers are used to de tect photoacoustic waves. Here, it is aimed to utilize a particle trapped by an optical tweezers (OT) system as a sensor by tracking the change in its displacements caused by the photoacoustic radiation force. By this way, it is possible to put the detector as close as a few microns to the absorber which is not possible with any other currently existing detection mechanisms. An all-ﬁber integrated laser with custom-developed electronics and software is developed speciﬁcally for the hybrid PAM and OT system. The laser is home-built for maximum ﬂexibility in adjustment of its parameters; pulse duration (5-10 ns), energy (up to 10 µJ) and repetition frequency (up to 1 MHz) in dependently from each other. It covers a broad spectral region from 450 to 1100 nm and can also emit wavelengths of 532, 355, and 266 nm. Photoacoustic radiation force caused by the change in the density of time-averaged kinetic and potential energy of the acoustic wave when encountered with a compressible or incompressible sphere is analyzed theoretically. Then, experiments are conducted on several particles and cells to manipulate them inside an absorbing medium. Apart from system development for diagnostics, to turn a hand on the treatment side, proton-induced acoustics is studied which has a potential to get real-time feedback for intratreatment adjustments and to reduce range uncertainty via high spatial resolution in ultrasound. In this regard, an analytic solution for the proton-induced acoustic wave is presented; then it is combined with an analytic approximation of the Bragg curve. The inﬂuence of the beam energy, pulse duration and beam diameter variation on the acoustic waveform are investigated.
A new methodology for climate model selection and application to temperature, heat wave, WBGT and labor productivity analysis
(Thesis (Ph.D.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2018., 2018.) Altınsoy, Hamza.; Kurnaz, M. Levent.
In this thesis, the answers to four main research questions are sought. The ﬁrst eﬀort is about the ﬁnding the most accurate model combinations to project intended climate variables. A new methodology is proposed and testiﬁed to achieve this purpose. CORDEX Project is the main model data source and monthly temperature is the observed climate variable over Europe, Africa, West Asia, Central and South America. The suggested methodology outreaches the favorite EWA (Equally Weighted Average) approach in climate studies. It is found that CSIRO as GCM and CLM as RCM is the best choice to simulate temperature patterns. Besides, another methodology is proposed to select daily data sets of the most successful model combinations. Moreover, a new deﬁnition of “extremely hot day” is proposed. The selected model combinations, new deﬁnition of extremely hot day and TLVs of NIOSH are used to estimate the future heat waves, Wet Bulb Globe Temperature (WBGT) and labor productivity. It is found that adverse eﬀects of climate change over the Northern Europe, the Mediterranean Coastal, the Sub-Saharan and Northern Africa, the southern Arabian Peninsula, Brazil, Iran, Afghanistan, Pakistan and the eastern Turkey will be more devastating than the remaining parts of the World.
A new tracking algorithm for atlas trigger
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2012., 2012.) Sarıkaya, Saime.; Özcan, Veysi Erkcan.
The Large Hadron Collider (LHC) is the world's highest energy accelerator with the highest luminosity, which aims to nd answers to the most fundamental questions of particle physics. It leads us to the discoveries of new particles (e.g discovery of Higgs boson nowadays), as predicted by Standard Model and its extensions like supersymmetry. However, coping up with the data produced by the LHC, and nding the interesting events, is not an easy task. LHC produces 1TB of data per second and approximately only 1 event per million is from interesting physics. At this point, looking for an event in the whole data is like trying to nd a needle in the haystack and to nd the interesting events out of the entire data, trigger systems are used. One of the most important part of trigger is tracking, which one needs to identify the tracks made by particles, and to identify the physics objects in the event. In this thesis, we describe an algorithm, to run at one of the LHC detectors, ATLAS, in order to achieve fast tracking. The algorithm is tested, using very high luminosity simulation data both running on hits obtained from the entire detector and also in certain small regions around interesting signals. The performance is shown to be satisfactory both in terms of tracking e ciency and in terms of timing requirements.
A permanent-magnet microwave discharge ion source at KAHVELab
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2022., 2022) Açıksöz, Sevim.; Özcan, Veysi Erkcan.; Çetinkaya, Hakan.
A new Permanent Magnet Microwave Discharge Ion Source (PM-MDIS) has been designed and constructed at Boğaziçi University Kandilli Detector, Accelerator, and Instrumentation Laboratory (KAHVELab). The PM-MDIS design includes a plasma chamber surrounded by permanent magnets, a hydrogen gas supply to sustain the plasma, the waveguide system used to transfer power to the plasma chamber, a dualelectrode extraction system used to extract ions from the chamber, and a Faraday cup to measure the beam current. The aim is to extract ions from the thermal hydrogen plasma generated using a 2.45 GHz microwave source. In order to extract ions from the plasma medium, a magnetic field exceeding 875G has to be applied over the plasma chamber to ensure Electron Cyclotron Resonance (ECR) condition is satisfied. Since the plasma chamber is to be operated on the high voltage (HV) platform, higher system stability can be achieved by using the permanent magnet configuration shown in this work. Based on the designed magnetic field profile of the constructed system, the dual-electrode extraction system has also been designed using IBSIMU integrated DemirciPro software and produced to transmit proton beams from the plasma chamber to the beamline. The determination of the magnetic field profile, and the vacuum, HV, and beam tests are completed before integration with the rest of the beamline. Finally, how the transmitted proton beams behaved on the existing Low Energy Beam Transport (LEBT) line has been examined, and the LEBT line configuration has been optimized accordingly. In addition, besides the protons, the trajectories of H+ 2 and H+ 3 ions from the PM-MDIS have also been studied to optimize the LEBT beam optics. As a result of this study, the PM-MDIS has been integrated with the proton beamline, and 0.38mA mean beam current has been measured with the Faraday cup in the experiments performed at 20 kV and 0.01 sccm gas flow.
A ramond-nevu schwarz string one end fixed
(Thesis (Ph.D.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2005., 2005.) Arapoğlu, A. Savaş.; Turgut, Osman Teoman.; Saçlıoğlu, Cihan,
We study an open string with one end free and the other fixed on a D0-brane as a qualitative guide to the spectrum of hadrons containing one very heavy quark. We first consider the bosonic degrees of freedom, then introduce the fermionic degrees offreedom through the world sheet supersymmetry. The mixed boundary conditions break half of the world sheet supersymmetry and allow only odd-moded a and even-moded d oscillators in the Ramond sector, while the Neveu-Schwarz oscillators b's become odd-integer moded. Boson-fermion masses can still be matched if space-time is 9 dimensional; thus SO(8) triality still plays a role in the spectrum, although full space-time supersymmetry does not survive. We quantize the system in a temporal-like gauge where X^0 ~ t. Although the gauge choice eliminates negative-norm states at the outset, there are still even-moded Virasoro and even(odd) moded super-Virasoro constraints to be imposed in the NS(R) sectors. The Casimir energy is now positive in both sectors; there are no tachyons. States for a' M^2 b 13/4 are explicitly constructed and found to be organized into SO(8) irreps by (super)constraints, which include a novel ``" operator in the NS and I in the R-sectors. GSO projections are not allowed. The pre-constraint states above the ground state have matching multiplicities, indicating spacetime supersymmetry is broken by the (super)constraints. A distinctive physical feature of the system is a slope twice that of the open RNS string. When both ends are fixed, all leading and subleading trajectories are eliminated, resulting in a spectrum qualitatively similar to the J/ and particles.
A search for vector-like leptons in ATLAS Run 2 data
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2021., 2021.) Örgen, Bora.; Özcan, Veysi Erkcan.; Ünel, N. Gökhan.
The search for pair-produced heavy iso-singlet leptons predicted by Grand Unified Theory (GUT) based on group E6 is detailed in this study. The discovery channel through which the search has been conducted is pp→L_e L ‾_e→ZeWν_e→3l 2j E_T^miss. The data used in the study is the ATLAS Run 2 data which has an integrated luminosity of L=139 fb^(-1) from proton-proton collisions at 13 TeV center of mass-energy. A cut-based event selection has been performed to maximize signal to background yields. Exclusion limits without systematic uncertainties have been obtained, and the results have been found to be promising with the possibility to increase the lower mass limit of the heavy charged lepton to about 250 GeV from the previous limit of 100 GeV.
A study of anomalous events in CMS-HF PMTs
(Thesis (M.S.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2009., 2009.) Halu, Arda.; Gülmez, Erhan.
The Forward Hadronic (HF) calorimeter of the CMS detector will measure the hadronic jets as well as determine the missing transverse energy generally attributed to new physics phenomena. HF is a quartz ber calorimeter in which the Cerenkov light generated by charged particles is collected by conventional photomultiplier tubes (PMT). In the HF test beam of 2004, events with unusually high energies with respect to the incoming beam energy were seen. These abnormal events were later con rmed in the 2007 test beam study. In this thesis, anomalous events are studied in various aspects, with more emphasis on the comparison of their electromagnetic (EM) and hadronic (HAD) channel signals. EM/HAD and HAD/EM energy ratio histograms are plotted for several pion and muon test runs with di erent beam momenta. Incident tower ratio histograms in the typical energy range display a clear peak, justifying the existence of a correlation while histograms of abnormally high energy events for the sum of all other towers do not exhibit such a relation. This observation might help us infer that these anomalous events, which most probably result from particles striking PMT windows directly instead of passing through bers to reach them, are of no experimental signi cance and may be tagged as \unreal" events to be discarded.
A study of non-cool core galaxy clusters and the feedback from their central active galactic nuclei
(Thesis (Ph.D.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2019., 2019.) Tümer, Ayşegül.; Ercan, E. Nihal.
The study of the brightest cluster galaxy (BCG) coronae of non-cool core (NCC) galaxy clusters and their central active galactic nuclei (AGN) is crucial for the under standing of the BCG’s role on galaxy cluster evolution as well as the activation of the cooling and heating mechanism in the central regions of galaxy clusters. In this thesis, the X-ray properties of the intracluster medium (ICM) of a sample of NCC galaxy clusters and their BCG interstellar medium (ISM), along with their central AGN is investigated using archival XMM-Newton observations. For this purpose, a joint spec troscopic and imaging method is proposed and applied to the sample. It is found that, AGN plays an important role on the ICM structure and the heating of the central regions of the clusters, although at smaller spatial scales compared to that of cool core clusters. In addition, BCG coronae seem to preserve their structural integrity and are isothermal, despite the disturbed morphology and merger history of the cluster. Fur thermore, a chemically rich BCG tail structure is discovered that extends up to 40 kpc even though they are assumed to be rare in galaxy populations.
A study on susy search strategies in the CMS, HPD noise spectrum and electron reconstruction efficiency
(Thesis (Ph.D.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2010., 2010.) Deliömeroğlu, Mehmet.; Gülmez, Erhan.
The hybrid photo diodes in the HCAL will play an important role in detection of the jets and missing energy. It is very important to understand and monitor their charge spectrum. The charge spectrum of the HPD detectors in the HB and HE with high statistics and their noise rate have been studied. In this study a method to monitor the HPD charge spectrum was developed. The relation between jets and electron reconstruction efficiency is quite important. The jets in the events may effect the reconstruction efficiency and quality of the electron reconstruction. The analysis showed that for each increase in the number of jets the efficiency of electrons decrease by about 1-7%. SUSY is a symmetry relating the standard model particles to their superpartners. It must be a broken symmetry since no supersymmetric particle has been observed yet. A constrained model of SUSY breaking, mSUGRA predicts experimental signals in the CMS detector for detecting the evidence for SUSY. One of these, dielectron with large missing energy and jets is studied with MC simulation. It is shown that SUSY can be discovered with 1 fb-1 data at ps = 10 TeV. Different clustering algorithms for the jets and missing energy are used and compared for the best result.
A study on the stability of the led gain monitoring system for the CMS-HF PMTs during 2009
(Thesis (M.S.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2010., 2010.) Özbek, Melih.; Gülmez, Erhan.
The Hadronic Forward (HF) calorimeter improves the jet detection and the missing transverse energy resolution of the Compact Muon Solenoid (CMS). In HF, the Photo Multiplier Tubes (PMTs) convert optical signals (i.e., Čerenkov light) to electrical signals. For monitoring the PMT gains, LED signals are extensively used. LED data collected throughout 2009 were thoroughly studied in this thesis. The focus was analyzing the stability of the LED system over time by graphical means. Also, by plotting the average charge versus position, it was possible to identify problematic channels.
Accretion discs around compact objects
(Thesis (M.S.)- Bogazici University. Institute for Graduate Studies in Science and Engineering, 1999., 1999.) Ekşi, K.Yavuz.; Ercan, E. Nihal.
Accretion onto a compact object is the process that is thought to power unexpectedly intense radiation of some astrophysical objects like Active Galactic Nuclei and X-Ray Binaries. A similar process is known to exist in Cataclysmic Variables and Young Stellar Objects. When the accreting matter has enough angular momentum it forms a disc around the compact object (a black hole, neutron star or white dwarf) and this disc is called an accretion disc. In this thesis accretion discs around compact objects are studied both analytically and numerically. Simplifying hydrodynamic equations in their full generality by the assumptions of the standart accretion disc theory, both time-independent and time-dependent equations were solved analytically. Time-dependent solutions are supported by numerical results. In all solutions a viscosity prescription which is a little more generalized than the standart prescription is used. The solution of the time-dependent equations with the generalized viscosity belong to the same family with the earlier ones.
Acoustic radiation enhanced drug delivery
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2015., 2015.) Yılmaz, Defne.; Ünlü, Mehmet Burçin.
Drug development is one of the main concerns in cancer research. In recent years, lots of new drugs have been discovered in order to increase the e ciency of cancer treatment and enhance the quality of patient's life. However, anti-cancer drugs, which are e ective in laboratory experiments, may not give positive results when they are injected to humans. Because of the abnormal vasculature in tumor microenvironment, drug particles face with several physiological barriers preventing the transport of therapeutic agents homogeneously from the region of administration to the cells in solid tumors. Recent studies have revealed that drug response of a tumor cell is determined by its biological characteristics and its microenvironment regulation. The abnormalities in tumor vasculature result in uneven drug distribution and blood ow within solid tumors. Moreover, the leaky, tortuous and highly permeable tumor vessels and the lack of functional lymphatic vessels lead to the elevated interstitial uid pressure (IFP). The use of radiation force is for the enhancement of drug delivery is an emerging method. Experimental studies have shown that radiation force can manipulate delivery vehicles in the vasculature by changing their velocities and positions. In the light of these experiments, a mathematical model which associates the e ect of acoustic radiation force for the convective transport and the drug distribution in tumors is constructed. Governing equations in the model involve the principles for transvascular and interstitial drug transport as well as conservation laws.
Active brownian particles propelled by sound
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2016., 2016.) Kaya, Serhat.; Ünlü, Mehmet Burçin.
Small particles in acoustic elds experience the so-called acoustic radiation forces by which the motion of particles can be manipulated in a contact-less way. Active Brownian particles have the ability to propel themselves by converting ambient energy into kinetic energy. However, because of the lack of study, the behavior of active Brownian particles in vicinity of external elds is not well-understood. The usage of acoustic elds in controlling the motion of these particles was suggested before, but this e ect has not been resolved analytically yet. In the analysis contained herein, the behavior of active particles inside an acoustic eld is investigated by constructing the equation of motion for a single particle. This is the rst time in the literature whereby the analytic form of the acoustic radiation forces is integrated with the dynamic equations of the system. The resulting equation is solved via numerical techniques. Then, with the performed simulations for two di erent active matter models, the collective behavior of active Brownian particles is also exploited.
Adiabatic solutions in general relativity and boundary symmetries
(Thesis (Ph.D.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2020., 2020.) Kutluk, Emine Şeyma.; Bleeken, Dieter Van den.
We investigate adiabatic solutions to general relativity for a spacetime with spatial slices with boundary, by Manton approximation. This approximation tells us for a theory with a Lagrangian in the natural form, a motion that is described as a slow motion on the space of vacua-static solutions that minimize the energy- is a good approximate solution. To apply this to the case of general relativity we rst bring it to the natural form by splitting space and time and choosing Gaussian normal coordinates, where a spacetime is described by the metric on its spatial slices. Then following Manton we propose slow solutions such that each slice is a slowly changing di eomorphism of a reference slice, and thus each solution is described by a vector eld on the spatial slice. These solutions will have the property that the action will become a functional of the vector elds on the boundaries of the spatial slices. Moreover using the Hodge- Morrey-Friedrichs decomposition we will show that the constraints of general relativity will identify a unique solution for a given boundary value. Then we comment on the structure of the space of vacua which we show to be a (pseudo)-Riemannian homogeneous space. We illustrate our procedure for a speci c reference slice we choose: the 3d Euclidean round ball.

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