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Proton conductive polymer/metal organic framework composi·te membranes / Proton iletken polimer/metal organik kafes yapılar içeren
(Abdullah Gül Üniversitesi, 2015) MUSTAFA ERKARTAL; AGÜ, Fen Bilimleri Enstitüsü, Malzeme Bilimi ve Makine Mühendisliği Ana Bilim Dalı; MUSTAFA ERKARTAL
Proton exchange membrane fuel cells (PEMFCs) are one of the most innovative research areas in search of novel power sources, especially because of their no to low greenhouse gas emissions, high efficiency, diverse fuel options and low maintenance costs. Hence, PEMFCs are regarded as one of the potential alternatives for the conventional power generators. Proton exchange membrane (PEM) is the core component of the PEMFC. Still, Nafion® and PBI are the commonly used membrane materials in fuel cell technology. The development of novel PEMs with high proton conductivity, good mechanical and chemical stability and cost-effective manufacturing remain as obstacles for the commercialization of PEMFCs. In this thesis for the first time, we present preparation and characterization of two types of novel composite proton exchange membranes which consist of zeolitic imidazolat framework-8 (ZIF-8). In the first part of this study, consisting of poly(vinyl alcohol) (PVA), poly(2- acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) and zeolitic imidazolat framework-8 (ZIF-8) ternary Nafion-like composite membranes were prepared with different composition to use in the PEMFCs which of their operation temperatures below 100 0C. All of the membranes were structurally characterized and their proton conductivities were measured by electrochemical impedance spectroscopy. The fully hydrated membrane with 55 PVA/40 PAMPS/5 ZIF-8 composition shows the highest proton conductivity with about 0.13 S cm-1 at 80 0C and the result thus obtained is comparable to the proton conductivity value of the Nafion in the literature. The aim of second part of this study is the preparing of membranes for high temperature proton exchange fuel cells (HTPEMFCs), which operate between 100-200 0C, the binary mixed membrane were manufactured incorporation of PBI and ZIF-8. In the membrane PBI ii was used as host polymer whereas ZIF-8 is used as filler material. Among the structurally well-characterized membranes, the membrane with 12.5 ZIF-8/PBI membrane has the highest proton conductivity with about 0.0045 S cm-1 at 160 0C under anhydrous condition.
QOS-AWARE DOWNLINK SCHEDULING ALGORITHM FOR LTE NETWORKS: A CASE STUDY ON EDGE USERS
(Abdullah Gül Üniversitesi, 2016) UYAN, OSMAN GÖKHAN; AGÜ, Mühendislik Fakültesi, Elektrik & Elektronik Mühendisliği Bölümü; UYAN, OSMAN GÖKHAN
4G/LTE (Long Term Evolution) is the state of the art wireless mobile broadband technology. It allows users to take advantage of high internet speeds. It makes use of the OFDM technology to offer high speed, which supplies the system resources both in time and frequency domain. The allocation of these resources is operated by a scheduling algorithm running on the base station. In this thesis, we investigate the performance of existing downlink scheduling algorithms in two ways. First we look at the performance of the algorithms in terms of throughput and fairness metrics. Second, we suggest a new fairness criterion, QoS-aware fairness which accepts that the system is fair if it can supply the users with the packet delays that they demand, and we evaluate the performance of the algorithms according to this metric. We also propose a new algorithm according to these two metrics, which especially increase the throughput gained by the edge users, the QoS-fairness, and classical fairness of the system without causing a big degradation in cell throughput when compared to other schedulers.
Development of novel nanomaterials for display and catalysis applications
(Abdullah Gül Üniversitesi, 2016) TAHAOĞLU, DUYGU; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; TAHAOĞLU, DUYGU
Nanomaterials established a research presence due to their large variety and unique properties for many areas such as biotechnology, energy, fabrics, construction, food etc. Transparent conductors and catalysis applications are also two other important areas in which nanomaterial studies are carried out. For display applications, metal nanowires, especially silver and copper, draw too much attention as transparent conductors as an alternative to indium tin oxide (ITO), which is the most used material in this market, due to their high conductivity, low cost and availability for flexible device applications which are limitations for ITO. In catalysis applications, using nanomaterials are also important to provide two essential parameters: increasing the efficiency of reactions and lowering the cost. In this thesis, on the whole, we present the synthesis of silver and copper nanowires by optimizing some parameters for controlling the length and diameter of nanowires. For the surface passivation of nanowires, we offered some coating methods with noble metals such as gold, platinum and palladium. Also we investigated the catalytic activity of copper nanowires on dye wastewater treatment. In the first part of this study, effects of polyvinylpyrrolidone (PVP) polymer length and PVP:AgNO3 molar ratio on the efficiency of silver nanowire synthesis and nanowire size were investigated for polyol synthesis method. The results showed that reaction yield is highly depended on these parameters. Also, by using different coating methods such as direct addition or biphasic titration, and by using different noble metal precursors, galvanic exchange reactions on silver nanowire surfaces were studied. The results for coating showed that it is possible to replace silver and noble metal atoms through these methods. The next part of the thesis reports the copper nanowire synthesis ii by two different methods: hydrothermal and solution based synthesis. The copper nanowires showed different size properties for these two methods. In addition, the same coating processes were also performed for copper nanowires and the results are promising as silver nanowires. In the last part, catalytic performance of copper nanowires was studied on degradation reactions of three different organic dyes. Great differences between catalyzed and uncatalyzed reaction periods were observed for all dyes.
Sliding mode and PID based tracking control of magnetic levitation plant and hil tests
(Abdullah Gül Üniversitesi, 2016) EROĞLU, YAKUP; AGÜ, Fen Bilimleri Enstitüsü, Elektrik ve Bilgisayar Mühendisliği Ana Bilim Dalı; EROĞLU, YAKUP
Magnetic levitation systems are convenient to provide frictionless, reliable, fast and economical operations in wide-range applications. The effectiveness and applicability of these systems require precise feedback control designs. The position control problem of the magnetic levitation plant can be solved with a cascade control method. In this thesis, sliding mode and PID based cascade controllers are designed to render high position control performance and robustness to the magnetic levitation. Sliding mode control (SMC) based cascade controller is proposed for controlling magnetic levitation. The SMC based controllers for the inner current loop are designed to eliminate the effects of the inductance related uncertainties of the electromagnetic coil of the plant. For the outer position loop, the integral SMC is designed to eliminate disturbances around operating point resulting from the linearization of the mechanical part. Finally, numerical simulation and experimental results for various cascaded controllers are provided and compared in order to validate the efficacy of the approaches.
PERFORMANCE EVALUATIONS OF SINGLE MODE OPTICAL RECEIVER FOR DEGRADED VISUAL FIELD AND PHOTONIC LANTERN BASED COHERENT DETECTION
(Abdullah Gül Üniversitesi, 2016) ORAN, ABDULLAH; AGÜ, Fen Bilimleri Enstitüsü, Elektrik ve Bilgisayar Mühendisliği Ana Bilim Dalı; ORAN, ABDULLAH
Imaging at degraded visual environments is one of the biggest challenges in today’s imaging technologies. Especially military and commercial rotary wing aviation is suffering from impaired visual field in sandy, dusty, marine and snowy environments. For example, during landing the rotor churns up the particles and creates dense clouds of highly scattering medium, which limits the vision of the pilot and may result in an uncontrolled landing. The vision in such environments is limited because of the high ratio of scattered photons over the ballistic photons that have the image information. In this thesis, we propose to use optical spatial filtering (OSF) method in order to eliminate the scattered photons and mainly collect the ballistic photons at the receiver. OSF is widely used in microscopy; to the best of our knowledge this thesis will be the first application of OSF for macroscopic imaging. Our experimental results show that most of the scattered photons are eliminated using the spatial filtering in a highly scattering degraded visual field. The results are compared with a standard broad area photo detector which shows the effectiveness of spatial filtering. Free space optical systems have applications in different areas such as laser ranging, three-dimensional imaging, weather predictions and optical wireless communication. Some applications require very high performance free space optical systems that are not available today. The need of systems with higher performance and lower size, weight and power (SWaP) is the biggest research motivation of free space optical systems. Between various detection techniques, vi coherent optical detection comes forward for applications that require high sensitivity and bandwidth. Coherent detection based LIDAR systems have the potential to provide quantum noise limited performance. However coherent systems suffer from poor free space to fiber collection efficiency due to the single mode detection characteristics and small size of the optical fiber. In order to overcome this problem, photonic lantern is introduced to effectively collect the multimode beam coming from free space and convert it to a number of single mode fibers. The photonic lantern consists of a multimode fiber to a number of single-mode fibers. The collection efficiency enhancement of photonic lanterns have been investigated, however there is no study on the signal to noise ratio –performance- improvement on the photonic lantern based free space coherent systems. In this thesis; the effect of random distribution of the optical power in the 19-port photonic lantern will be investigated mathematically. The photonic lantern based coherent detection system performance will also be simulated by using the MATLAB software. The output of this thesis may open the path to experimental demonstration and maybe even to a prototype.
Photometric modelling for efficient lighting and display technologies
(Abdullah Gül Üniversitesi, 2016) GENÇ, SİNAN; AGÜ, Fen Bilimleri Enstitüsü, Elektrik ve Bilgisayar Mühendisliği Ana Bilim Dalı; GENÇ, SİNAN
Using light emitting diodes (LEDs) as lighting devices has come to the sight as a compulsory step in terms of the energy efficiency. Almost a quarter of total consumed energy that generated whole around the world is used for lighting. Using incandescent bulbs as lighting devices is forbidden in most of Europe and light emitting devices are one of the most important choices in order to compensate that need. Their high performance in terms of both luminance levels and energy efficiency has opened a new research area to increase their performance. White light has different requirements based on an application area. Providing that necessities by engineering on light parameters is one of the main aims of this thesis. In display technology, the development from cathode ray tubes to organic light emitting devices has increased the performance of both display quality and energy efficiency. Enhancement of the color scale that can be perceived by the human eye is the main purpose so that the reference color area increases systematically. The last announced reference, Rec.2020, has two thirds of the colors perceived by human eye. In this thesis, considering the current references such as National Television System Committee (NTSC) color gamut, the broadening of Rec.2020 is also presented as a new important figure of merit. In this thesis, we have studied on the investigation of the parameters of the emitters, i.e., peak emission wavelength, full width at half maximum and peak intensity to achieve the desired quality white light. Although it is possible to get white light in each step, the high quality requirements have been implemented by four colors within the simulation vi range of thesis which possess color rendering index value >90, correlated color temperature <4000K and luminous efficacy of optical radiation 380 lm/Wopt. In addition, in terms of display technology, we have shown that using ultra narrow emitters is an optimal choice for achieving Rec.2020 color triangle. Using ultra-narrow emitters, it is possible to obtain 99,89% of the Rec.2020 that also almost covers the NTSC. As expected, using a fourth color component cyan has increased the reached area to 169,55% of NTSC on color space dramatically
Improving sensitivity biosensors by using micro/nano magnetic particles
(Abdullah Gül Üniversitesi, 2016) OMARY MUSTAFA, MZAVA; AGÜ, Fen Bilimleri Enstitüsü, Elektrik ve Bilgisayar Mühendisliği Ana Bilim Dalı; OMARY MUSTAFA, MZAVA
Currently micro/nanoparticles such as magnetic beads are not only used as labels to acquire signals from biosensors but they are also used to enhance the signals obtained from various biosensors. Magnetic beads or target are linked to other molecular labels such as fluorescence and chemiluminescence labels by biomolecules such as antibody to reach higher sensitivity and provide signal amplification for the measurement. This dependency on biomolecular binding has several disadvantages such as molecular binding is sensitive to environmental conditions such as pH and temperature, labels are costly and molecular binding may require extra time. In this thesis a time and cost efficient signal amplification method that does not need any biomolecular coating but based on magnetic interaction of magnetic micro/nanoparticles is developed. Magnetic particles subjected to external magnetic field are magnetized and form a local field around them, attract each other and accumulate along the magnetic field lines. These controlled accumulations can be used to amplify the pixel area or the contrast of magnetic particles. Accumulation dynamics of magnetic particles under magnetic field are studied and the application of this method to the Escherichia coli 0157:H7 sample is demonstrated. Lastly the integration of this signal amplification method to a flow chamber and a complete biosensing procedure is pursued. Magnetic micro/ nano particles that are immobilized on gold-coated surface under external magnetic field inside a flow chamber attract the iron nanoparticles in a running fluid to form chains of accumulations around them. The accumulations formed under magnetic field are used to improve the Contrast to Noise Ratio (CNR) of the images thus the sensitivity.
Design, synthesis, and characterization of n-type and ambipolar small molecules as air-stable and solution-processable semiconductors in ofets
(Abdullah Gül Üniversitesi, 2016) ÖZDEMİR, RESUL; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; ÖZDEMİR, RESUL
The design and development of novel ambipolar and n-channel semiconductors is very crucial to advance various optoelectronic technologies including organic fieldeffect transistors (OFETs) and complementary (CMOS) integrated circuits. Although numerous ambipolar and n-channel polymers have been realized to date, small molecules have been unable to provide high device performance in combination with ambient-stability and solution-processibility. In the first part of this thesis, two novel small molecules, 2OD-TTIFDK and 2ODTTIFDM, were designed, synthesized and characterized in order to achieve ultralow band-gap (1.21-1.65 eV) semiconductors with sufficiently balanced molecular energetics for ambipolarity. Bottom-gate/top-contact OFETs fabricated via solutionshearing of 2OD-TTIFDM yield perfectly ambient stable ambipolar devices with reasonably balanced electron and hole mobilities of 0.13 cm2 /V·s and 0.01 cm2 /V·s, respectively with Ion/Ioff ratios of ~103 -104 , and 2OD-TTIFDK-based OFETs exhibit ambipolarity under vacuum with highly balanced (µe/µh ~ 2) electron and hole mobilities of 0.02 cm2 /V·s and 0.01 cm2 /V·s, respectively with Ion/Ioff ratios of ~105 -106 . Furthermore, complementary-like inverter circuits were demonstrated with the current ambipolar semiconductors resulting in high voltage gains of up to 80. Our findings clearly indicate that ambient-stability of ambipolar semiconductors is a function of molecular orbital energetics without being directly related to bulk ?-backbone structure. To the best of our knowledge, considering the processing, charge-transport and inverter ii characteristics, the current semiconductors stand out among the best performing ambipolar small molecules in the OFET and CMOS-like circuit literature. Our results provide an efficient approach in designing ultralow band-gap ambipolar small molecules with good solution-processibility and ambient-stability for various optoelectronic technologies including CMOS-like integrated circuits. In the second part of this thesis, a new solution-processable and air-stable liquidcrystalline n-channel organic semiconductor (?,?-2OD-TIFDMT) was designed, synthesized, and characterized. The new semiconductor exhibits a low LUMO energy level (-4.19 eV) and a narrow optical band gap (1.35 eV). Typical pseudo focal-conic fan-shaped texture of a hexagonal columnar liquid crystalline (LC) phase was observed over a wide temperature range from melting point at 139 °C to isotropic transition point at 232 °C. The semiconductor thin-films prepared by spin-coating ?,?-2OD-TIFDMT shows the formation of large (~0.5-1 µm sizes) and highly crystalline plate-like grains with good interconnectivity. The molecules were found to adopt edge-on orientation on the dielectric surface resulting in favorable charge-transporting networks of ?-? stacking along the dielectric-semiconductor interface. Top-contact/bottom-gate organic fieldeffect transistors fabricated by using the spin-coated semiconductor films, which were annealed at a low temperature (Tannealing = 50 °C), have yielded good electron mobilities as high as 0.11 cm2 /V·s and high Ion/Ioff ratios of 107 -108 with excellent ambient stability. This indicates two orders of magnitude (100×) enhancement in OFET mobility when compared with a low-temperature annealed well-known semiconductor, ß-DDTIFDMT. Side-chain engineering in the new semiconductor structure offers great advantage for the D-A-D ?-core co-planarity while maintaining a good solubility in organic solvents, and leads to favorable optoelectronic and physicochemical characteristics for better OFET performance. Thermal annealing at LC phase results in significant deterioration in charge-transport with much lower (10,000×) electron mobility. These remarkable findings demonstrate that this new small molecule is a promising semiconductor material for the development of n-channel OFETs on flexible plastic substrates and LC-state annealing in columnar liquid crystals can be deteriorating for transistor-type charge transport.
Usage of laser induced bubbles for measuring intraocular eye pressure
(Abdullah Gül Üniversitesi, 2017) ALTINDİŞ, FATİH; AGÜ, Fen Bilimleri Enstitüsü, Elektrik ve Bilgisayar Mühendisliği Ana Bilim Dalı; ALTINDİŞ, FATİH
There are different methods of measuring intraocular pressure in clinics, but those methods fail to measure intraocular pressure under certain conditions. Most common problem of these methods are that they are inapplicable to patients who had eye surgery. In this study laser induced bubble characteristics are investigated in order to develop a new method to measure intraocular eye pressure with lasers. For this purpose, first, intraocular environment is imitated to perform laser experiments. Then imaging system is developed to digitally visualize laser induced bubbles that are created in intraocularlike environment. Digital image processing algorithms were developed to detect and measure bubble features. Different fluid pressure levels were configured to investigate the pressure effect on laser induced bubbles. Results showed that volume of laser induced bubbles are higher in lower fluid pressure and bubble volume decrease with the increased fluid pressure. In light of these findings, it can be concluded that the change in volume can be used to estimate fluid pressure. Thus, this study proposes a new technique for measuring intraocular pressure by using volume feature of laser induced bubbles that are created in the anterior chamber of the eye.
QUANTUM DOT BASED BIOSENSING
(Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2017) ÜNLÜ, Miray; AGÜ, Fen Bilimleri Enstitüsü, İleri Malzemeler ve Nanoteknoloji Ana Bilim Dalı
Semiconductor nanocrytals also known as quantum dots (QD) with high photoluminesce quantum yield (PLQY), size tunability and favorable optical characteristics occupy a significant area in display technology, solar energy conversion and bioapplications. Size tuning feature of QDs allows emission wavelength ranging from ultraviolet to infrared spectral region. In literature, QD based studies have been performed in visible spectral range by employing mostly cadmium, being a toxic heavy metal. Recently, the search for less toxic alternatives revealed the cadmium free compounds, particularly InP. Cadmium free semiconductor nanocrytals’ potential to be used as fluorescent probes in biodetection and biolabeling area has been proved over the past decades. Pathogens threaten life particularly via water sources like rivers, reservoirs and groundwater. Increasing demand for managing the ‘contamination of drinkable water by pathogenic bacteria’ problem needs a broad perspective about pathogens and their membrane characteristics which are integral part of microorganism detection platforms. Bacteria are categorized mainly upon their membrane properties which are gram negative and gram positive. Extra wall called as peptidoglycan layer in gram positive bacteria makes them more resistant to external forces. Gram negative bacteria with wavy wall is relatively more prone to their environment. One of the most known pathogenic bacteria, E. Coli, have damaged and destroyed many lives throughout the world. High growth rate enables this microorganism to spread around large areas in short time. Therefore, accurate and definite detection of this bacteria in water is crucial. The main frame of this research depends on QD based biodetection of bacteria. First of all, organic based QDs (50% PLQY) containing triocytlyphosphine-sulfur ligand were synthesized and via successful phase transfer, aqueous QDs with 20% PLQY were achieved. Although surface is damaged during ligand exchange procedure, aqueous QDs with high PLQY were obtained. SiO2 was covered with QDs thanks to the attraction between their NH2 group and carboxylic ends, respectively. In the final step, this hybrid structure was covered with SiO2 and silica coated QDs (SCQD) were formed. In order to utilize SCQDs in bacteria detection, fluorescent agents were embeded in polymeric films which were formed by spin coating. As a result, SCQD facilitates the attachment of negatively charged bacteria onto the surface of the films. Appropriately grown DH5 alpha (E. Coli strain) expressing green fluorescent protein (GFP) was used as pathogen in the detection part. SCQD thin films were treated with water containing E.Coli DH5 alpha. Positively charged SCQD attracted negatively charged bacteria and the conjugation between them was analysed with time resolved spectroscopy and monitored with fluorescence microscope. Thus, usage of QDs as biosensor in pathogen detection could provide an insight in the future studies.
DIMENSIONALITY REDUCTION FOR PROTEIN SECONDARY STRUCTURE PREDICTION
(Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2017) GÖRMEZ, Yasin; AGÜ, Fen Bilimleri Enstitüsü, Elektrik ve Bilgisayar Mühendisliği Ana Bilim Dalı
Proteins are important for our lives and they execute essential metabolic processes. The functions of the proteins can be understood by looking at the three-dimensional structures of the proteins. Because the experimental detection of tertiary structure is costly computational systems that estimate the structure provides a convenient alternative. One of the important steps of protein structure estimation is the identification of secondary structure tags. As new feature extraction methods are developed, the data sets used for this estimation can have high dimensions and some of the attributes can contain noisy data. For this reason, choosing the right number of features and the right attributes is one of the important steps to achieve a good success rate. In this study, size reduction process is applied on two different datasets using a deep autoencoder and various dimension reduction and feature selection techniques such as basic component analysis, chi-square, information gain, gain ratio, correlation-based feature selection (CFS) and the minimum redundancy maximum relevance algorithm as well as search strategies such as best first, genetic search, greedy algorithm. To evaluate the prediction accuracy, a support vector machine classifier is employed.
PARALLEL MACHINE SCHEDULING IN THE FACE OF PROCESSING TIME UNCERTAINTY
(Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2017) BEKLİ, Rahime Şeyma; AGÜ, Fen Bilimleri Enstitüsü, Endüstri Mühendisliği Ana Bilim Dalı
Competition in today’s business and production world leads the companies to generate schedules that increase productivity and decrease manufacturing cost. However, most of the schedules cannot be executed exactly because of the unexpected disruptions such as machine breakdowns, order cancellations and so forth. In order to develop disruption resistant schedules, robust scheduling subject has gained interest among researchers. In this study, we consider a parallel machine environment with processing time uncertainty. The performance measure is taken as the completion time of the last job. The uncertainty is modeled by discrete set of scenarios. An integer programming model that can handle small problems is proposed. We observe that this model cannot manage large problems. To alleviate this difficulty, we propose to decrease number of scenarios selected for model. Next, we apply dual decomposition method in order to solve many smaller problems rather than a large problem. Large problems cannot be handled by this method either. This is why; we alter dual decomposition method by relaxing and develop a new heuristic. Also we propose a hybrid tabu search algorithm to solve the large problems.The results show that, the proposed heuristics; selecting scenario approach and tabu search algorithm perform well for the parallel machine scheduling problems.
Immunomagnetic separation and immobilization of leukemia cells using cell surface markers /
(Abdullah Gül Üniversitesi, 2017) GERÇEK, TAYYİBE; AGÜ, Yaşam ve Doğa Bilimleri Fakültesi, Biyomühendislik Bölümü; GERÇEK, TAYYİBE
Acute Lympoblastic Leukemia, shortly ALL, especially B-precursor Acute Lymphoblastic Leukemia is the most common blood malignancies among childhood cancers. There are different kinds of leukemia treatments but after those therapies, there is likelihood of relapsing the cancer in years because of remained cancer cells in the patient’s body. Nevertheless remained cancer cells in the body after therapy cannot be seen in the routine clinical follow-up tests. Those kind of diseases like leukemia are named as Minimal Residual Disease (MRD). Currently, there are only two ways to detect Minimal Residual Disease. These are flow cytometry and real-time quantified polymerase chain reaction (RQ-PCR). However many different labs have these Flow Cytometry and RQ-PCR, both devices should be calibrated to detect MRD cells. Nowadays there is a consensus about requiring MRD detection but still it is discussed by the authorities about when and how it should be done. The ultimate aim of this project is to produce a chip that can detect MRD cells. With these work we try to capture leukemic cells by using magnetic beads in nano and microsize. These magnetic beads are coated with CD19 and CD45 antibody markers that are in the membrane of leukemia cells. Next step after capturing them with magnetic beads is to immobilize them onto a surface. Golden surfaces are used and functionalized by antibodies. Thus an immunosandwich structure is occured and the cells are immobilized.
DESIGNING RELIABLE MICROARCHITCTRURES ACCORDING TO APPLICATION REQUIREMENTS
(Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2017) Kahira, Albert; AGÜ, Fen Bilimleri Enstitüsü, Elektrik ve Bilgisayar Mühendisliği Ana Bilim Dalı
One of the most important factors to consider when designing a new computer architecture besides cost, energy consumption and performance is reliability. Reliability looks into how often the computer produces the correct results and when it’s expected to fail (Mean time to failure). Reliability heavily affects all the other factors such as cost, area and performance and therefore a careful tradeoff has to be made between reliability and the other factors. One factor that has come into play recently is application requirement. The need for more computing power by applications has been increasing. Because of this, designers have designed much more powerful and sophisticated architectures putting millions of transistors into a single chip and more recently increasing the number of chips. However, this has increased the likelihood of failures occurring. A study of these failures and the reliability of this microarchitectures is therefore required. In this study, we investigate the reliability of current micro architectures for different applications and further propose reliable microarchitectures for those applications or mechanisms to adjust reliability parameters based on the application. We mostly focus on fault tolerance as a reliability parameter.
FABRICATION OF NANOCOMPOSITE MEMBRANES AND THEIR APPLICATIONS IN OILY WASTEWATER TREATMENT
(Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2017) SAKİ, Seda; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü
Industrial oily wastewaters are generated by various industries such as steel, food, textile, leather, petrochemical and metal milling and should be treated before discharging natural environment due to its serious environmental problems. With this view, membrane separation processes have promote a significant development of novel and green technology for oily wastewater treatment due to its clear advantages, for instance, ease in operation, efficient separation, low energy consumption and cost. Specially microfiltration (MF) and ultrafiltration (UF) membranes are playing a more prominent role in the oily wastewater treatments because of many advantages like as stable effluent quality, small area requirement, no chemicals addition, high chemical oxygen demand (COD) removal and low energy need. But the main drawback of membrane processes is the fouling problem. To overcome this problem, many researchers effort fabrication of high performance of membrane with higher hydrophilicity and antifouling properties. In this study, flat-sheet PSF/PEI nanocomposite membranes using Al2O3 and CaCO3 nanoparticles were prepared by phase inversion method. The effect of Al2O3 and CaCO3 nanoparticles were investigated on the structural properties and filtration performance of the nanocomposite membranes. Prepared membranes were characterized with scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR), contact angle, porosity, water flux, thermogravimetric analysis (TGA), atomic force microscope ii (AFM), X-ray diffraction (XRD), BSA rejection, tensile strength, and viscosity measurements. Membrane permeability performance and antifouling properties towards oil water emulsion separation of these new generation nanocomposite membranes were evaluated for synthetic and real industrial oily wastewater. The results showed that there is a great potential to use these nanocomposite membranes for oily water treatment with higher permeability and antifouling capacity. All Al2O3 and CaCO3 nanocomposite membranes reached higher oil rejection ratios over 90%.
OPTIMIZING CLASSIFIERS FOR PROTEIN SECONDARY STRUCTURE PREDICTION
(Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2017) UZUT, Ömmu Gülsüm; AGÜ, Fen Bilimleri Enstitüsü, Elektrik ve Bilgisayar Mühendisliği Ana Bilim Dalı
Protein secondary structure prediction is important for understanding protein structure and function. PSSP can be seen as a bridge between amino acid sequence and 3D structure of a protein. Many methods have been performed to improve prediction accuracy rate and get good achievement. There are multiple situations that will affect the performance of a method. One of these situations is selection of correct parameter. Hyperparameters are parameters that cannot be directly learned from the regular training process. Although the methods have default hyperparameter values, it is possible to improve performance of methods by using those hyperparameters with different values which can be more convenient. Parameter optimization plays an important role at this stage. It applies to methods to find best hyperparameter values to apply methods. In our thesis, computational methods such as Random forest, Support vector machines and deep convolutional neural fields have been used and optimized on CB513 dataset. We have aimed to optimize methods with different values to improve the results and show the importance of parameter optimization in protein structure prediction. We also tried to use some ensemble methods to compare our results with individual classifiers to see the improvement of results.
Flow-based p-hub median interdiction problem
(Abdullah Gül Üniversitesi, 2017) BENLİ, ABDULKERİM; AGÜ, Mühendislik Fakültesi, Endüstri Mühendisliği Bölümü; BENLİ, ABDULKERİM
There are two players in a network interdiction problem: a network user who wishes to operate a system optimally, and an opponent/interdictor who tries to prevent the system from operating optimally. Interdiction problems can be modeled as a bi-level min-max or max-min problem in the Stackelberg Game logic. In this thesis, we handle the interdiction problem within the context of the p-hub median problem. The network user solves the problem of locating p hubs to minimize the cost associated with operating the network. In response to the network user, the interdictor tries to maximize network user’s cost by removing hub characteristics of effective hubs with its limited resources. The p-hub median problem of the network user is modeled on the flow-based networks. The model we develop in this study, unlike the previous literature, does not require the complete network and enables one to find the correct solution in cases that do not provide triangle inequality between nodes. Therefore, this new model provides significant advantages regarding the solution times and modeling capabilities compared to the facility interdiction models offered by the literature.
Investigation of interaction between nanocrystal quantum dot films and escherichia coli
(Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2017) Ünlü, Miray; 0000-0001-8165-6164; AGÜ, Fen Bilimleri Enstitüsü, İleri Malzemeler ve Nanoteknoloji Ana Bilim Dalı
Semiconductor nanocrytals also known as quantum dots (QD) with high photoluminesce quantum yield (PLQY), size tunability and favorable optical characteristics occupy a significant area in display technology, solar energy conversion and biotechnology. Size tuning feature of QDs allows peak emission wavelength ranging from ultraviolet to infrared spectral region. In literature, QD based studies have been performed in visible spectral range by employing mostly cadmium, being a toxic heavy metal. Recently, the search for less toxic alternatives revealed the cadmium free compounds, particularly InP. Cadmium free semiconductor nanocrytals' potential to be used as fluorescent probes in biodetection and biolabeling area has been proved over the past decades. Pathogens threaten life particularly via water sources like rivers, reservoirs and groundwater. Increasing demand for managing the 'contamination of drinkable water by pathogenic bacteria' problem needs a broad perspective about pathogens and their membrane characteristics which are integral part of microorganism detection platforms. Bacteria are categorized mainly upon their membrane properties which are gram negative and gram positive. Extra wall called as peptidoglycan layer in gram positive bacteria makes them more resistant to external forces. Gram negative bacteria with wavy wall is relatively more prone to their environment. One of the most known pathogenic bacteria, E. Coli, have damaged and destroyed many lives throughout the world. High growth rate enables this microorganism to spread around large areas in short time. Therefore, accurate and definite detection of this bacteria in water is crucial. The main frame of this research depends on QD based biodetection of bacteria. First of all, organic based QDs (50% PLQY) containing triocytlyphosphine-sulfur ligand were synthesized and via successful phase transfer, QDs in aqueous solvent with 20% PLQY were achieved. Although surface is damaged during ligand exchange procedure, QDs in aqueous solvent with high PLQY were obtained. SiO2 was covered with QDs thanks to the attraction between their NH2 group and carboxylic ends, respectively. In the final step, this hybrid structure was encapsulated with SiO2 and silica coated QDs (SCQD) were formed. In order to utilize SCQDs in bacteria detection, fluorescent agents were embeded in polymeric films which were formed by spin coating. As a result, SCQD facilitates the attachment of negatively charged bacteria onto the surface of the films. Appropriately grown DH5 alpha (E. Coli strain) expressing green fluorescent protein (GFP) was used as pathogen in the detection part. SCQD thin films were treated with water containing E.Coli DH5 alpha. Positively charged SCQD attracted negatively charged bacteria and the conjugation between them was analysed with time resolved spectroscopy and monitored with fluorescence microscope. Thus, usage of QDs as biosensor in pathogen detection could provide an insight in the future studies. Keywords: biodetection, E.coli, quantum dots, semiconductors, silica coated quantum dots, indium phosphate, InP QD
PERFORMANCE ANALYSIS OF UNDERWATER COMMUNICATION WITH DIFFERENT MODULATION TECHNIQUES
(Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2017) BAHÇEBAŞI, Akif; AGÜ, Fen Bilimleri Enstitüsü, Elektrik ve Bilgisayar Mühendisliği Ana Bilim Dalı
There is an increasing interest in using Underwater Acoustic Sensor Networks (UASNs) for various oceanographic applications, such as pollution monitoring, seismic monitoring, environmental data collection, offshore exploration, and tactical surveillance. As well as underwater sensor nodes, unmanned underwater vehicles are used in some application scenarios of UASNs such as exploration of underwater resources and data gathering in collaboration-requiring missions. UASNs rely on acoustic communications; however, the underwater acoustic channel is highly variable and its link quality depends on environmental factors and the locations of the communicating nodes. Therefore, ensuring reliable communication in UASNs is quite difficult. Moreover, path losses and retransmissions lead to the wastage of energy resources and reduce the network lifetime. In this study, we used well-known underwater modulation schemes to analyse and simulate various underwater scenarios with different depth, distance and BER values in order to make a fair comparison between the modulation schemes and find the optimal transmission power. As proven in our simulation study 32-PSK and 16-QAM techniques achieved the minimum energy consumption rates. Therefore network designers can prolong the underwater network lifetime using 32-PSK and 16-QAM modulation techniques.
Nanoparticle reinforced hybrid composite material production process optimization / Nano-parçacık takviyeli hibrit kompozit üretimi için reçine geçişli kalıplama prosesi optimizasyonu
(Abdullah Gül Üniversitesi, 2017) DOĞUŞ KAÇMAZ, AZER; AGÜ, Fen Bilimleri Enstitüsü, İleri Malzemeler ve Nanoteknoloji Ana Bilim Dalı; DOĞUŞ KAÇMAZ, AZER
Composite materials have increasing application areas in today's industry and daily life due to their low density structure and high mechanical properties. Also, thermalstability and electrical conductivity can be improved by particle inclusion. Composite materials consist of preform, matrix and particles in matrix. Various production methods have been developed to bring these components together. Among these production methods, liquid composite molding methods are the most widely used methods for producing parts having advanced properties. A different method logic has been tried to obtain more homogeneous product than traditional resin Transfer Molding method in order to produce composite parts with superior mechanical properties. Since the Resin Transfer Molding (RTM) method is expensive and time-consuming, simulation is the fastest and economical method for optimization of the process. In this study, COMSOL software was used for numeric analysis. As a result, when production of hybrid composite materials with highly different permeable components performed with Resin Transfer Molding Method, Compression Resin Transfer Molding (CRTM) logic works much more precisely in terms of avoiding voids and providing homogeneity through preform when filling is performed from the top.

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