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An analytical and simulation model for IEEE 802.11af based cognitive radio sensor networks
Get PDFIn this study, a cognitive radio sensor network based on IEEE 802.11af technology is proposed for data with priority classes. In IEEE 802.11af technology, the White Space Device (WSD), Station (STA), and Access Point (AP) communicate opportunistically over the television white spectrum without causing any harmful interference to licensed services. In the proposed network structure; WSDs, STA and AP use the Frequency Division Multiple Access (FDMA) technique to communicate over the white space spectrum determined by the White Space Map (WSM). WSD collects data such as temperature, humidity, pressure from sensors in various environments. The priority class is determined as red, yellow and green depending on the urgency of the data. After the analytical model of the proposed network was obtained, the simulation model was implemented using Riverbed Modeler. The graphical results prove the validity and feasibility of the proposed network in terms of latency (0.17 s) and energy consumption (4.7 mJ/s) without any spectrum cost for monitoring priority-based data
On 2-distance 16-coloring of planar graphs with maximum degree at most five
Get PDFA vertex coloring of a graph G is called a 2-distance coloring if any two vertices at a distance at most 2 from each other receive different colors. Suppose that G is a planar graph with a maximum degree at most 5. We prove that G admits a 2-distance 16-coloring, which improves the result given by Zou et al. (2024) [13]. (c) 2024 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.TUBITAK (The Scientific and Technological Research Council of Turkey) [122F250]This research was supported by TUBITAK (The Scientific and Technological Research Council of Turkey) under the project number 122F250. The author extends thanks to Kengo Aoki, and the anonymous referees for their careful reading and numerous suggestions for improving the presentation. Their feedback revealed several errors in the early version of this paper and significantly contributed to its overall improvement
Factors Affecting the Joy of Life in Old Age: A Scale Development Study
Get PDFThis study aims to introduce a measurement tool into the literature that can reveal the factors affecting the joy of life in older adulthood. Participants included 266 individuals aged 55 and over living in Izmir, Turkey. The process of developing the scale includes the following stages: problem identification, item pool creation, expert opinion, form shaping, pilot application, and finalizing the scale. The exploratory factor analysis revealed that the scale consists of 6 different dimensions, and the variance explained by these dimensions was found to be 65.184%. The acceptable values for the scale's fit indicators are as follows: chi(2)/df0.90, IFI > 0.90, TLI > 0.90, CFI > 0.90, RMSEA < 0.08, and SRMR < 0.08. These values indicate an appropriate fit between the model and the data set. It was determined that the scale of factors affecting the joy of life in older adulthood is valid and reliable. The scale consists of six dimensions and 23 items
Retinal changes in children with Familial Mediterranean Fever: the effect of chronic subclinical inflammation
Get PDFBackground: In Familial Mediterranean Fever (FMF), acute-phase reactants rise during attacks, indicating active inflammation. However, subclinical inflammation-present even during remission-may contribute to organ damage, including ocular involvement. This study aimed to investigate the effects of subclinical chronic inflammation on ocular structures in children with FMF. Methods: The study involved 51 pediatric FMF patients in remission for at least three months and healthy controls. Spectral domain optical coherence tomography (SD-OCT) was used to measure intraocular pressure, axial length, peripapillary retinal nerve fiber layer (RNFL) thickness, central macular thickness, and subfoveal choroidal thickness. Results: Acute-phase reactant levels were significantly elevated in the FMF group (p < 0.001). Inferotemporal RNFL thickness was notably reduced (p = 0.008), along with central macular, subfoveal, nasal, and temporal choroidal thicknesses. A mild positive correlation was observed between proteinuria and axial length (r = 0.282, p = 0.045). Conclusion: Subclinical inflammation in FMF may lead to early structural changes in the eye, potentially progressing over time. These findings highlight the importance of long-term ophthalmologic monitoring in pediatric FMF patients to better understand the cumulative impact of persistent inflammation.Scientific and Technological Research Council of Turkiye (TUEBITAK)Open access funding provided by the Scientific and Technological Research Council of Turkiye (TUEBITAK)
Use of waste vehicle tire powder in polymer matrix composites with glass fiber reinforcement
Get PDFBu tez çalışmasında, atık araç lastiklerinden elde edilen atık lastik tozu, cam elyaf ile güçlendirilerek stiren bazlı epoksi reçine içinde dolgu malzemesi olarak kullanılmıştır. Atık lastik tozu içeren stiren bazlı epoksi reçine, metil etil keton katalizörü kullanılarak ve el yatırma yöntemiyle oda sıcaklığında üretilmiştir. Üretilen kompozit malzemelerin mekanik özellikleri, çekme dayanımı ve üç nokta eğilme dayanımı testleri ile değerlendirilmiş ve ortalama dayanım değerleri belirlenmiştir. Ayrıca, düşük hız darbe testleri yapılarak malzemelerin darbe direnci incelenmiştir. Çekme testi, malzemenin maksimum gerilim altında dayanımını ve elastikiyetini analiz ederek, lastik tozunun kompozitin çekme mukavemetine etkisini ortaya koymuştur. Eğme testi, kompozitin bükülme dayanımını ve rijitliğini inceleyerek, cam elyafın ve lastik tozu katkısının bükülme davranışı üzerindeki etkisini değerlendirmemize olanak sağlamıştır. Darbe testi ise kompozitlerin ani darbelere karşı direncini ve enerji absorpsiyon kapasitesini ölçmek amacıyla yapılmış, malzemenin kırılma tokluğu hakkında bilgi sağlamıştır. Bu testler sonucunda elde edilen veriler, atık lastik tozu oranının kompozit malzemenin dayanıklılığı üzerinde ne derece etkili olduğunu göstererek, geri dönüştürülmüş atıkların endüstriyel kullanımı için önemli bulgular sunmuştur. Sonuç olarak, bu çalışma, geri dönüşümden elde edilen malzemelerin kompozitlerde kullanım potansiyelini değerlendirmekte ve çevresel sürdürülebilirlik hedeflerine katkı sağlamak amacıyla atıkların değerli bir kaynak olarak kullanılabileceğini göstermektedir.In this thesis, waste tire powder obtained from discarded vehicle tires was used as a filler material in a styrene-based epoxy resin, reinforced with fiberglass. The styrene-based epoxy resin containing waste tire powder was produced using methyl ethyl ketone as a catalyst and the hand lay-up method at room temperature. The mechanical properties of the produced composite materials were evaluated through tensile strength and three-point bending strength tests, and the average strength values were determined. Additionally, low-velocity impact tests were conducted to examine the impact resistance of the materials. The tensile test analyzed the material's maximum stress resistance and elasticity, revealing the effect of tire powder on the tensile strength of the composite. The bending test evaluated the flexural strength and stiffness of the composite, allowing an assessment of the impact of fiberglass and tire powder on bending behavior. The impact test measured the resistance of the composites to sudden impacts and their energy absorption capacity, providing insights into the fracture toughness of the material. The data obtained from these tests demonstrated the significant effect of waste tire powder content on the durability of the composite material, offering valuable findings for the industrial application of recycled materials. In conclusion, this study evaluated the potential use of recycled materials in composites and showed that waste materials could be utilized as a valuable resource to contribute to environmental sustainability goals
Determination of both the expression and serum levels of epidermal growth factor and transforming growth factor β1 genes in COVID-19
Get PDFWe aimed to evaluate the effects of both the expression and serum levels of Epidermal growth factor (EGF) and Transforming growth factor-beta 1 (TGF-beta 1) genes in patients with different degrees of cellular damage as mild, moderate, severe, and critical illness that can lead to fibrosis caused by SARS-CoV-2. Totally 45 individuals (male: 21(46.67%); female: 24(53.33%)) with COVID-19 infection were included in this study. Four groups were constituted as mild (n = 16)], moderate (n = 10), severe (n = 10), and critical (n = 9) according to the severity of the disease. Blood samples were drawn from the patients, and all of the hemograms, EGF and TGF beta 1 gene expression, and serum levels were evaluated. The mean age of individuals was 57.311 +/- 18.383 (min: 28, max: 94). Significant differences were found among the groups for PLT (chi(2) = 9.955; p = 0.019), CRP (chi(2) = 7.693; p = 0.053), Ferritin (chi(2) = 22.196; p < 0.001), D-dimer (chi(2) = 21.982; p = 0.000), LDH (chi(2) = 21.807; p < 0.001) and all these parameters (exclude PLT in severe groups) was increased depending on the severity of the disease. Additionally, significant differences were detected for EGF (chi(2) = 29.528; p < 0.001), TGFB1 (chi(2) = 28.981; p < 0.001) expression (that increased depending on the disease severity), and EGF (chi(2) = 7.84; p = 0.049), TGFB1 (chi(2) = 17.451; p = 0.001) serum concentration levels (that decreased depending on the disease severity). This study found statistically significant differences for both EGF 2(-Delta Delta Ct). TGF beta 1 2(-Delta Delta Ct) and EGF, TGF beta 1 serum concentration values among all patient groups. As disease severity increased, EGF 2(-Delta Delta Ct). TGF beta 1 2(-Delta Delta Ct) levels increased, while EGF and TGF beta 1 serum concentration levels decreased. Perhaps this study will be useful in managing COVID-19 infection severity and pulmonary fibrosis cases secondary to COVID-19.Duezce UniversityThe Duezce University coordinatorship of scientific research projects
Teaching Profession in the Written and Oral Proposals Submitted to the TBMM: Problems, Demands and Issues on the Agenda
Get PDFThis study examines the discussions on the teaching profession and the search for solutions through written and oral proposals submitted to the Grand National Assembly of T & uuml;rkiye (TBMM) between 2002 and 2024. In this research, which was carried out using the document analysis model within the qualitative methodology, a total of 3671 proposals were identified from the official archive of the TBMM and these proposals were analyzed by content analysis. These proposals were analyzed through content analysis. The results of the research show that the problems of the teaching profession in the proposals submitted to the Grand National Assembly of T & uuml;rkiye are concentrated in the economic, social and professional dimensions. The proposals focus on issues such as teacher appointments, personal rights, professional development opportunities and teacher shortages in rural areas. However, low response rates and delays in the process prolong the time it takes to find solutions to teachers' problems. It was observed that opposition parties are more likely to raise teachers' issues, while the ruling party makes limited contributions to these issues. The research shows that a comprehensive restructuring of education policy is needed to address the chronic problems of the teaching profession. In addition, improving teachers' personal rights, increasing professional development opportunities and ensuring equal educational opportunities in disadvantaged regions are crucial for the sustainability of the profession
Dielectric Resonator Antenna-Based Sensing Technology for Enhanced Insulation Oil Diagnostics
Get PDFThe insulating oil in transformers plays a critical role both as a coolant supporting the paper insulation and as an element protecting the dielectric properties of the system. Serious failures may result from changes in the oil's dielectric characteristics brought on by the presence of water and other contaminants. This study assesses the insulation condition of transformer oils by designing and simulating three different dielectric resonator antennas (DRA) in the CST Design Environment. An attempt is made to find the best design by analyzing the effect of variations in dielectric constant on various resonator antenna designs. The resonant frequency range of 1.5-3GHz and the RT5880 dielectric substrate are chosen. Simulations are carried out to illustrate situations where the epsilon r value of the oil varies between 1 and 5. In general, it is found that as the dielectric constant of the oil (epsilon r) increases, the resonant frequency (fr) and the S11 parameter decrease. Single DRA-A single SMA port is advised for low-cost and straightforward applications, but Dual DRA can be chosen for investigations needing high sensitivity and double-check. The analysis allows the best approach to be selected based on the requirements of the application by highlighting the advantages and disadvantages of different designs.Dzce University [2025.06.03.1572]M.D. and Y.B. contributed equally to this work. The authors would like to thank Duezce University for financial support, Grant No. 2025.06.03.1572. The authors acknowledge the use of AI-based tools for enhancing the linguistic clarity of the manuscript and assisting in the refinement of figures
The Effect of Heating Time in Induction Hardening Process on the Hardness Profile of a Ball Stud: A Case Study
Get PDFThe induction hardening method is widely used for the surface hardening of industrial products to improve the resistance of the material to various failure modes such as fatigue, wear, etc. Hence, surface hardening of parts that undergo repetitive forces and that work in close contact with other moving components plays a significant role in their service life. In this study, an automotive ball stud part, which is a highly prone part to fatigue and wear failures, has been induction hardened for varying amounts of heating time (2s, 3s, 4s and 5s) under constant power (135 A) and frequency (50 Hz). The hardness, the hardness depth and the microstructure of the parts have been investigated utilizing hardness tests and optical microscopy. Additionally, the effect of different cooling durations (3s, 5s, and 7s) and the resistance of the parts to the bending force has also been examined. The results show that the increase in heating time has an increasing impact on the hardness of parts and the hardness depth. The bending forces have also been shown to be increasing by increasing the heating time. The highest hardness level, hardness depth and bending resistance have been found when induction heating the specimens for 5s. Increasing the cooling time has not led to a considerable variation in the hardness profile of the specimens. © 2025 Elsevier B.V., All rights reserved
Mineral oils modified with CdSeTe QDs for improved stability and dielectric performance in high-voltage applications
Get PDFThis study explored the application of CdSeTe quantum dots (QDs) in mineral oils for high-voltage applications through a comprehensive approach. CdSeTe QDs were synthesized using an organometallic method and added to mineral oil at concentrations of 1 mg/L (C1), 5 mg/L (C2), and 10 mg/L (C3). The samples' stability condition was monitored for a long period, and physicochemical tests were performed. Experimental results show that QD-modified oils have enhanced electrical properties compared to the base oil. The breakdown voltage was in the range of 17 to 23 kV for the base oil, while the breakdown voltage was in the range of 20 to 39 kV for the QD-modified (C2) insulating fluid sample. Throughout the 25-day monitoring period, the QDs were found to be properly dispersed in oil and free of aggregation in all samples. Values such as density and viscosity remained fairly constant due to the relatively low concentration ratio. However, an increase in total acid number was observed with increasing concentration. These results imply that QD-enhanced insulation oils may have applications in high-voltage applications in the future. The main innovation of this study lies in demonstrating that CdSeTe QDs can significantly enhance the dielectric strength of mineral oils while maintaining their essential physicochemical properties, offering a novel approach for improving insulation performance in high-voltage applications.Scientific and Technological Research Council of Turkiye (TUBITAK) [122F434]TUBITAKThe CdSeTe QDs used in this study were obtained within the scope of project number 122F434 carried out by the Scientific and Technological Research Council of Turkiye (TUBITAK). We thank TUBITAK for financial support