Hacettepe Üniversitesi Açık Erişim Sistemi (HÜAES)
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Nejat Başeğmezler’in Suite Adlı Eserinin Biçim, Armonik Yapı ve Bestecilik Teknikleri Açısından İncelemesi
(Güzel Sanatlar Enstitüsü, 2026) Vecihe Cansu Yılmaz; Kompozisyon ve Orkestra Şefliği
Nejat Başeğmezler is a composer recognized for his productivity, diverse output, and distinctive musical language, particularly through his works written for viola, chamber ensembles, and orchestra. His sustained compositional activity across both the twentieth and twenty-first centuries, as well as his engagement with the musical transformations that characterized these periods, renders the study of his works particularly significant. Within this context, Suite (1997), composed for string orchestra, constitutes the primary focus of this artistic research report.
The aim of this study is to examine the work in terms of its form, harmonic structure, and compositional techniques, and to clarify the evaluation of the work by elucidating Başeğmezler’s musical perspective through his own statements. Furthermore, the study evaluates, through a descriptive approach, the manner in which Başeğmezler approaches the suite tradition within a contemporary context as reflected in the work itself. Within this framework, the aforementioned work constitutes the scope of the study.
The data collection and analysis process was conducted in three stages. In the first stage, a review of the relevant literature was carried out; sources related to the suite genre were examined, and the work was analyzed in terms of its form, harmonic structure, and compositional techniques through the method of document analysis. In the second stage, a semi-structured interview technique was employed, allowing the composer to articulate his approach to the work in his own words. In the final stage, the findings of the musical analysis and the interview data were considered together, enabling a comprehensive evaluation of the work within a holistic framework.
The findings of this study reveal Nejat Başeğmezler’s approach to the suite tradition in his work, particularly in terms of form, harmonic structure, and compositional techniques.
Horozibiği (Amaranthus Caudatus L.) Çiçeklerinden Betalainler ve Fenolik Bileşiklerin Vakum Mikrodalga-Destekli Ekstraksiyonu ve Enkapsülasyonu
(Fen Bilimleri Enstitüsü, 2025) Akdeniz Sena Nur; Gıda Mühendisliği
Amaranthus caudatus L., with its pink-purple flowers rich in betalains, has gained attention in recent years as a potential natural food colorant due to its high phenolic content and strong antioxidant capacity. However, the limited stability of bioactive compounds of the natural sources limits their applications. Because extraction with traditional methods takes a long time and requires high amounts of solvent, vacuum microwave-assisted technology, which is a new generation green extraction method that
can provide more efficient extraction in shorter times, has been developed. Encapsulation techniques have been introduced to enhance the stability of these natural pigments and health-promoting bioactive compounds. Among these, niosomes are vesicular carriers composed of surfactants that facilitate the delivery of bioactive compounds. According to the literature review and common knowledge, no study has been found that extracts betalains and phenolic compounds from amaranth flowers using vacuum microwave-assisted extraction and subsequently encapsulates them in niosomal vesicular
structures for stability enhancement. Therefore, in this thesis, betalain and phenolic compound extraction from amaranth flowers was performed using both conventional and vacuum microwave-assisted extraction methods, and the results were comparatively analyzed. Subsequently, niosomal encapsulation was applied to improve the stability of the extracted pigments and bioactive compounds. The optimization of process conditions
and formulations for extraction and encapsulation was conducted using the response surface methodology (RSM). Maceration was used as the conventional extraction (CE) method, while vacuum microwave-assisted extraction (VMAE) was selected as the new-generation extraction
technique. A Box-Behnken design was applied with four independent variables at three levels for both methods. The independent variables for CE were extraction time (1, 2, and 3 hours), temperature (30, 40, and 50°C), ethanol concentration (20%, 40%, and 60%), and sample-to-solvent ratio (1:10, 1:20, and 1:30 g/mL). For VMAE, the independent variables were pressure (150, 300, and 450 mmHg), extraction time (3, 9, and 15 min),
ethanol concentration (20%, 40%, and 60%), and sample-to-solvent ratio (1:10, 1:20, and 1:30 g/mL). The total betalain content (TBC), total phenolic content (TPC), and total antioxidant capacity (TACDPPH and TACCUPRAC) were analyzed for all extract samples. The response values obtained from CE experiments ranged between 1554.67–2918.67 mg betalain/kg dry weight for TBC, 9.19–14.81 mg GAE/g dry weight for TPC, 34.08 109.55 mmol TE/kg dry weight for TACDPPH, and 107.53–167.02 mmol TE/kg dry weight
for TACCUPRAC. In the VMAE method, the response values ranged between 993.54 3153.58 mg betalain/kg dry weight for TBC, 5.54–17.04 mg GAE/g dry weight for TPC, 21.86–101.42 mmol TE/kg dry weight for TACDPPH, and 69.42–195.39 mmol TE/kg dry weight for TACCUPRAC. The optimization results revealed the optimal CE conditions as 1hour extraction time, 50°C temperature, 40.99% ethanol concentration, and a 1:10 g/mL sample-to-solvent ratio. For VMAE, the optimal conditions were determined as 450
mmHg pressure, 12-minute extraction time, 30.74% ethanol concentration, and a 1:23.91 g/mL sample-to-solvent ratio. The morphology of extracts obtained under optimal conditions was examined using scanning electron microscopy (SEM), revealing that CE resulted in a more fragmented
and irregular cell structure, whereas VMAE produced smoother and more porous structures. Additionally, betalain composition analysis was performed using Q-TOF LC/MS, and the betalain content of extracts obtained under optimal conditions was calculated as 6393.17 ppm for CE and 9256.50 ppm for VMAE in betanin equivalents. The results demonstrated that VMAE achieved more efficient extraction than CE, reducing the processing time by 80% while using lower ethanol concentrations. The TBM value of untreated amaranth flowers was found to be 38.26% with KE and 44.27% with
VMDE. Therefore, extracts obtained under the optimal VMAE conditions were selected for niosomal encapsulation. The response surface methodology was applied to optimize formulation parameters and ultrasonication time, with the independent variables being the molar ratio of surfactants (Span60:Tween80, mol:mol), extract-to-surfactant ratio (mg extract/100 mg surfactant), cholesterol-to-surfactant ratio (mg cholesterol/100 mg surfactant), and ultrasonication time (s). The experimental design followed a Box-Behnken model, and responses included total betalain content (TBC), total phenolic content (TPC), total antioxidant capacity (TACCUPRAC), and red color intensity measurements. The optimization results identified the optimal conditions as a 1:1 molar ratio of surfactants (Span60:Tween80), 8.109 mg
extract/100 mg surfactant, 0.1 mg cholesterol/100 mg surfactant, and 81.877 sultrasonication time. Additionally, thermal stability, stability after 30 days of storage, TEM, FT-IR, particle size, and zeta potential analyses were conducted for the optimized niosome samples. According to the thermal stability experiments, the KE and VMDE thermal stability rates, which were found to be 67.35% and 65.73%, were increased to 97.974% with the niosome method. In conclusion, this study showed that the extraction of betalains and phenolic compounds from amaranth flowers can be efficiently performed using VMAE, which offers advantages over conventional methods in terms of time efficiency and solvent usage. Furthermore, niosomal encapsulation proved to be an effective strategy for enhancing the stability of betalains and phenolic compounds. In conclusion, VMAE was found to be a more sustainable and efficient technique than conventional extraction for obtaining betalains and phenolics from A. caudatus, with lower ethanol usage and shorter processing time. Moreover, niosomal encapsulation provided an effective strategy to improve the stability of these bioactive compounds, suggesting that the combined use of VMAE and niosomal encapsulation holds strong potential for the development of natural colorants for the food industry.
Makine Öğrenmesi Teknikleri Kullanılarak Heyelan Duyarlılık Haritalarının Üretilmesi: İnegöl (Bursa) Örneği
(Fen Bilimleri Enstitüsü, 2025) Güler Elif; Geomatik Mühendisliği
In this thesis study, a research was conducted to determine landslide susceptibility in the İnegöl district of Bursa province. 13 environmental factors influencing landslide occurrence (slope, aspect, elevation, lithology, soil group, NDVI, land use, precipitation, distance to fault lines, distance to streams, distance to roads, curvature, and topographic wetness index) were analyzed within a Geographic Information System (GIS) environment; each factor was
reclassified into five classes and thematic suitability maps were generated. The dominant class for each factor in the study area was identified to assemble the input dataset for the classification algorithms. Four different machine learning algorithms (Logistic Regression, Support Vector Machines, LightGBM, and Random Forest) were applied in a comparative framework. Model performance was assessed using metrics such as accuracy, precision,
recall, and F1 score. According to the analysis results, the Random Forest algorithm achieved the highest performance with 98% accuracy, 98% precision, 98% recall, and a 98% F1 score. The study demonstrates that Random Forest delivers high performance in spatial data analyses and, when integrated with GIS, provides a reliable approach for landslide risk mapping. The resulting susceptibility map can serve as a decision-support tool for disaster risk reduction and land-use planning.
Esnek Kapasitif Basınç Sensörlerinin Fabrikasyonu ve Elektriksel Karakterizasyonu
(Fen Bilimleri Enstitüsü, 2025) Bebek Turgay; Elektrik –Elektronik Mühendisliği
In today's technological world, the growth of flexible electronic applications and their widespread adoption has significantly increased the importance of human-machine interaction and sensor applications. Flexible sensors that convert a physical or mechanical effect into an electrical signal output, and enable the interpretation of these outputs to serve desired purposes in technological applications such as health, robotics, wearable technology, education, and entertainment, hold an important place in flexible electronic
applications due to factors like high flexibility, stability, high accuracy, ease of
manufacturing, and low cost. Within the scope of this thesis, two different types of materials, namely Polydimethylsiloxane (PDMS) which stands out with its properties such as flexibility, adjustable hardness, heat resistance, biocompatibility, and Polyvinyl alcohol (PVA) and Borax mixture which have similar properties and also self-healing properties and hydrogel structure, were produced with different mixing ratios and different dielectric layer thicknesses without any additional micro and nano particle doping. The effects of both mixing ratio and dielectric layer thickness on sensor performance were investigated, and the two materials were compared. The produced sensors were subjected to electromechanical tests at various pressure values, and the effects of different materials, hardnesses, and thicknesses on sensor sensitivity and linearity in flexible capacitive pressure sensors were investigated. In addition, as a result of these studies, an 8×8 size capacitive sensor array was fabricated for the PVA and Borax mixture with the determined hardness value, and the sensor performance and its mapping
according to the applied force on the sensor array are demonstrated. It has been observed that the parameters characterizing the sensor, such as sensitivity and linearity, of the PDMS-based sensor designs tested in this thesis vary with the mixing of the components that make up the material in different ratios and the use of varying thicknesses of the dielectric material. It was observed that the sensitivity and linearity were low due to the
absence of any micro- and nano-particle doping in the PDMS. PDMS-based sensor designs exhibited sensitivity in the low-pressure range, and it was assessed that these sensor designs could be appropriate for use at low pressures. It has been observed that the parameters characterizing the sensor, such as sensitivity and linearity, of the PVA Boraxbased sensor designs tested within the scope of the thesis vary with the mixing of the components constituting the material in different ratios and the use of various thicknesses
of the dielectric material. Additionally, it was noted that sensor performance was impacted by the weight loss of PVA Borax hydrogel over time. Although weight loss over time led to a decrease in peak capacitance values at the highest pressure in sensors with a PVA Borax dielectric layer, it was found that the material's transformation into a more rigid structure and the establishment of its stability positively influenced sensor performance. Compared to PDMS, it was observed that PVA-Borax hydrogel operates
with higher sensitivity and linearity over a broader pressure range. Moreover, due to the self-healing property of PVA-Borax hydrogel, PVA-Borax sensor designs can be used for a long time. Producing PVA-Borax hydrogel requires less cost, effort, and ease compared to producing PDMS material. With this advantage, it is evident that PVABorax hydrogel possesses superior qualities compared to PDMS elastomer.
Π-Π İstiflenmesinin Mekanistik Etkileri ve Olefin Metatezde Katalitik Uygulamaları
(Fen Bilimleri Enstitüsü, 2025) Güzelaraz Engin; Kimya
π–π stacking phenomenon is one of the topics that has attracted increasing attention from researchers in recent years. However, only a few studies have been published on this subject in literature. Olefin metathesis, on the other hand, has been an efficient synthetic method, and has become a key tool in organic synthesis and polymerizations. In this thesis work, a ligand containing a polyaromatic structure pyrene was synthesized and characterized using 1H-NMR, 13C-NMR, and GC-MS. Its electronic transitions were analyzed using UV-Vis and fluorescence spectroscopy. To examine the effect of varying
degrees of π–π stacking on the electronic and structural properties of coordination compounds, a compound was synthesized using the synthesized ligand and Grubbs First Generation Catalyst. To demonstrate the catalytic applications in olefin metathesis, in-situ catalyst systems were also prepared. These catalyst systems were analyzed using 1H-NMR, 31P{1H}-NMR, and MALDI-MS. The results supported each other and illuminated the structures. In addition, graphene oxide nanoplatelets (GONP) were synthesized from graphene nanoplatelets (GNP), and its structure was characterized using X-ray photoelectron (XPS) spectroscopy and Fourier Transform Infrared (FT-IR) spectroscopy. GNP and GONP were used as heterogeneous support materials to be compared with homogeneous counterparts in catalytic activities, and their stacking properties were examined using UV-Vis spectroscopy to enable the separation of catalyst systems involving π–π stacking from the reaction medium at the end of the reaction. The catalytic activities of the synthesized catalyst systems were evaluated through ringclosing metathesis of diethyl diallylmalonate and ring-opening metathesis polymerization of cyclooctene which have been previously used as testing substrates in olefin metathesis. In these experiments, additional compounds capable of π–π stacking such as graphene nanoplatelets (GNP), graphene oxide nanoplatelets (GONP), and pyrene, as well as the 31P{1H}-NMR’s of the catalyst systems with varying acid ratios which are different from those of literature were used to examine both catalytic performance and mechanistic effects. Due to the results of these experiments, this thesis presents, to the best of our knowledge, for the first time the mechanistic and catalytic impact of π–π stacking to literature.