Hacettepe Üniversitesi Açık Erişim Sistemi (HÜAES)
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Karstik Ortamda İnşa Edilen Bir Viyadük Temelindeki Mühendislik Jeolojisi Sorunlarının Ve Mühendislik Çözümlerinin Araştırılması
(Fen Bilimleri Enstitüsü, 2025) Gültekin, Mehmet; Jeoloji Mühendisliği
In engineering geology applications, karst environments cause problems in the form of
settlement, sudden collapse, water leaks, cracks, sinkhole formations and unexpected
deformations. Such problems have the potential to cause major losses of life and property,
especially in engineering structures such as highways, railways, pipelines. Due to the fact
that Turkey is located both in the active earthquake belt and geographically has a transitional
climate, especially the sinkholes caused by the collapse of underground cavities formed as a
result of karstization are critical in terms of engineering structures. For this reason, accurate
description of the problem and taking the right engineering measures to solve these problems
are of vital importance for the safety of the engineering structure. If a change of location
cannot be made in case of encountering a karst environment, improvement methods are used.
These measures include grouting, bored piling and jet grouting.
The Ankara-Izmir High Speed Railway Project, which is one of the most important
investments of our country, has been designed according to the speed of 250 km/h. In this
design, the lowest slope radius is 3000 m and the longitudinal slope is 0.2%. This situation
almost eliminates the option of relocation for engineering problems encountered during the construction phase. In this case, special engineering solutions are applied for the problems
encountered. Karstic cavities have been encountered in the section of the V16 Viaduct
located in the Banaz-Eşme route of the Ankara-Izmir High-Speed Train Project. Therefore,
the purpose of this thesis is to describe the engineering geology problems in the karst unit
that forms the basis of the viaduct, one of the critical and high-weight art structures of high
speed railway projects, and to reveal the optimal engineering measures for solving these
problems. For this purpose, drilling data, geophysical measurement data, geomechanical
parameters of the rock material and mass, geological cross-section and all data belonging to
the site were evaluated together and the levels formed by karstic voids were determined.
Ground Penetrating Radar and Electrical Resistivity Tomography measurements were made
within the scope of geophysical studies, but since sufficient data could not be obtained from
ground penetrating radar, the number of ERT measurements, which yielded better results,
was increased and the research was detailed.
With the help of drilling data and data obtained from geophysical measurements, it was
decided to carry out grouting work for the identified cavity levels. A total of 748 drillings,
20870 meters of drilling and 1339.018 m³ of grouting were carried out. In order to check
that the injections filled the cavities, vertical borings were made from the sides of the bored
piles. When the cores were examined, it was understood that the injection traces were clearly
observed and the voids were filled. Viaducts apply very high stresses to the ground due to
their structure. These stresses have the potential to cause complete failure if there are voids
or gaps in the units forming the foundation. For this reason, Viaduct V16 is designed as
bored pile foundation. Pile loading tests were carried out in the field to test whether the
bored piles could carry lateral loads and whether they would show settlement behavior
against the tensile load, friction pressure and applied load to which they would be exposed.
It was stated that no sudden settlement or collapse was observed in the test columns and the
deformations occurred within elastic limits.
Yüzdeliğe Dayalı Kontrol Kartları
(Fen Bilimleri Enstitüsü, 2025) Öztürk, Derya; İstatistik
In this thesis study, the process monitoring performance of percentile-based control
charts, which aim to overcome the limitations of classical quality control methods, has
been evaluated on non-normally distributed data. The analyses were conducted using
energy consumption measurements obtained under real production conditions, with the
goal of reducing false alarm risks caused particularly by skewed distribution structures
and improving the balance of signal generation.
Two scenarios were constructed using an energy consumption dataset. In the first
scenario, a combined X ̄–S control scheme was designed using the logic of percentile
based control charts (PBCC) and enhanced with optimization techniques. In this
scenario, both the process mean and variance are monitored simultaneously, and the
goal is for the control chart to reliably generate signals under a specific percentile
condition. As an alternative to the traditional Average Run Length approach, control
limit designs were created at a specific confidence level using the percentile-based control chart methodology. In this study, for the optimal design of the PBCC X ̄–S
control chart, the control limit coefficient was optimized using a deterministic search
method, while the lower and upper limits were optimized using a genetic algorithm.
In the second scenario, the Shewhart median control scheme was examined and
evaluated using a percentile-based approach under different sample sizes and design
scenarios. In this context, run length distributions under both in-control and out-of
control conditions were analyzed; in addition to traditional metrics such as average run
length and median run length, run length percentiles were also considered for
comparison. As a result of the application, it was observed that while the percentile
based approach enabled more sensitive signal generation for small sample sizes, delays
in signal generation occurred for larger sample sizes due to the increasing stability of
the median.
When the results of both scenarios are evaluated together, it is seen that percentile
based approaches offer more flexible systems with a lower likelihood of false alarms
compared to classical control schemes. These findings support the preference for
percentile-based control charts in modern production environments, especially for
datasets with unknown distribution structures or those that do not meet standard
assumptions. The study contributes to academic literature and also provides practical
recommendations for developing more reliable process monitoring techniques in
industrial applications.
İkincil İşlevli Proteinler: Biyoloji Felsefesi Bağlamında İşlev Problemine Bütünlüklü Bir Bakış
(Fen Bilimleri Enstitüsü, 2025) Tümer, Selenay; Biyoloji
This study aims to trace the concept of function and functional explanation in the
history of philosophy, and to put forward the thesis that moonlighting proteins
have changed the paradigm of molecular biological function by addressing the
current problem field in the philosophy of biology. After the basic structure of the
issue is presented in the introductory chapter, some historically important points
of the philosophy of biology, the conceptual framework of the problem of function
and the progress of the thesis are discussed in the general information section.
In the third part, the foundations of the problem are laid through a reflection on
the determination of the concept of function in the philosophies of Aristotle, Kant,
and Hegel, and by considering how the function–teleology debates are
represented with respect to the domain of nature. In the fourth part, information is provided on moonlighting proteins, which challenge the idea of one gene–one
protein–one function and show multifunctionality in biochemical or biophysical
contexts through their structure that performs distinct functions. In order to
comprehend the mechanisms of functional change, their interactions, differences
in cellular and phylogenetic contexts, and functional diversity, 100 moonlighting
proteins are discussed according to prokaryotic and eukaryotic cells, organisms,
cellular localizations, and their primary and moonlighting functions. In the last
part, encompassing the previous two parts, normativity, the etiological, functional
analysis, and organizational views in the philosophy of biology are revealed, and
the limits faced by functional approaches in explaining moonlighting proteins are
critiqued. Ultimately, by showing how the problem of function has been shaped
from its inception to the present day, it is intended that the perspective offered by
moonlighting proteins be introduced into the literature and spark new discussions.
MoC İnce Film Kaplamaların Pem Tipi Yakıt Hücreleri İçin Korozyon Direnç Performansların Araştırılması
(Fen Bilimleri Enstitüsü, 2025) Kesik, Oğuldeha; Nanoteknoloji ve Nanotıp
In this thesis study, the performance of molybdenum carbide (MoC) thin film coating
developed to enhance the corrosion resistance of bipolar plates (BPs), a crucial
component of proton exchange membrane (PEM) fuel cells was examined in detail within
the context of hydrogen technologies, which play a critical role in the search for
sustainable energy solutions in light of the finite nature and environmental impacts of
fossil fuels. PEM fuel cells stand out as environmentally friendly, high efficiency energy
conversion systems, with widespread applications in automotive and portable power
systems. BPs account for 80 % of the stack’s total mass and 45 % of its cost, underscoring
their importance. These plates must exhibit excellent electrical and thermal conductivity,
low gas permeability, and high corrosion resistance. Although BPs are typically made
from graphite, its brittleness and difficulty of machining have led to the adoption of
metallic materials particularly stainless steel (SS). However, metallic BPs are prone to
corrosion in the perfluorosulfonic-acid and electrochemical environment of PEM cells,
which degrades fuel cell performance. To address this issue, protective and conductive
surface coatings are applied to the BPs. In this context, the development of coating
materials that are highly conductive, corrosion resistant, and cost-effective is of great
importance. MoC is recognized as a good corrosion-resistant material due to its low cost,
high melting point, thermal stability, hardness, and high conductivity. Therefore, MoC
emerges as a potential candidate for enhancing the corrosion resistance of bipolar plates
used in PEM fuel cells. In this work, MoC thin films were deposited onto SS, Si, and soda
lime glass (SLG) substrates using two different techniques: a hybrid method combining magnetron sputtering with plasma enhanced chemical vapor deposition (PECVD), and a
magnetron co-sputter method. While films produced by the hybrid method exhibited
structural defects, those prepared by the magnetron co-sputter technique met the U.S.
Department of Energy’s (DOE) standards by improving the corrosion resistance of the
BPs. MoC thin film coated SS plates demonstrated a 50% improvement in ICR compared
to uncoated SS plates. Furthermore, potentiodynamic polarization measurements
revealed a very low corrosion current density of 5.813 × 10⁻⁷ A·cm⁻². This value is
approximately one order of magnitude lower than the target set by the U.S. Department
of Energy (DOE) (<1 × 10⁻⁶ A·cm⁻²), indicating that the DOE target was successfully
achieved. These results demonstrate that MoC thin-film coatings offer innovative
solutions to the corrosion challenges encountered in fuel-cell technologies and introduce
materials-engineering approaches capable of revolutionizing the energy sector.films
produced by the hybrid method, those prepared via the magnetron co-sputter method
significantly enhanced the corrosion resistance of the bipolar plates, surpassing DOE
standards. It was determined that stainless steel (SS) plates coated with MoC thin films
exhibited a 50% improvement in ICR values compared to uncoated SS plates, and
potentiodynamic polarization measurements yielded a very low corrosion current density
of 5.813 × 10⁻⁷ A·cm⁻². These results demonstrate that MoC thin film coatings offer
innovative solutions to the corrosion challenges encountered in fuel cell technologies and
reveal materials engineering approaches that could revolutionize the energy sector.
Context Aware Task Orchestration With Deep Reinforcement Learning In Real Time Fog Computing Simulation Environment
(Fen Bilimleri Enstitüsü, 2025) Hoşsucu, Alp Gökhan; Bilgisayar Mühendisliği
In the ever-evolving landscape of cloud computing, fog and edge computing have become
more prominent because of their natural property of proximity to the demanding parts.
Having all the heterogeneity on the processor side, task generators also have a variety of
requirements in terms of complexity and latency. This dissertation gathered all of these
different dimensions together in a robust ecosystem which can simulate a huge number
of various scenarios that complies with the changing requirements for task orchestration
and serves as a versatile platform for exploring task orchestration strategies. An advanced
multi-layered cloud simulation model is proposed that intricately considers both low-level
edge/fog and cloud environment constraints. At the core of the contribution lies a novel task
orchestration model that transforms the orchestration process into reinforcement learning
training steps. The proposed approach offers substantial advantages in terms of task
succession, energy efficiency, and resource utilization. The system is evaluated with a custom
developed simulation tool under different ambient fog computing conditions in terms of the
edge device and the density of the task. The results of the experiment proved the superiority
of the proposed system over the existing round-robin, heuristic-based, and PGOA algorithms with an overall increase in precision up to 28%. Besides, an efficient action space reduction
technique is introduced to reduce the complexity of the action space, the proposed technique
simplifies the decision-making process, leading to faster convergence and improved training
efficiency.