Sürdürülebilir Kalkınma Amaçları
Yayınlar
- ArticleAçık Erişim2026The Effect of Fin Parameters on Cooling of Lithium-ion Batteries: Numerical Analysis and Optimization
Kalkan, Orhan; Demir, Fatih
Lithium-ion batteries are frequently preferred for electric vehicles and diverse applications due to their high energy density, high specific energy, and superior efficiency. Despite these advantages, they generate substantial heat during charge and discharge at high C-rates, which can lead to thermal runaway. Thus, an appropriate Battery Thermal Management System is necessary to prolong their lifespan and maintain performance and capacity. This study considers a passive cooling technique for cooling a Lithium-ion battery using fins. The effect of fin geometric parameters on battery thermal management was numerically investigated, and optimal values were determined through multiple optimizations, thereby contributing to the literature. For this purpose, analyses were obtained for varying diameters (20 mm-36 mm), thicknesses (0.5 mm-2 mm), and numbers (3-9) of cylindrical fins placed on a cylindrical battery at a high discharge rate of 5C. In the results, battery surface temperatures, battery temperature difference, and mass were evaluated in detail. Next, the maximum and average battery temperatures, the maximum and minimum temperature differences for homogeneity, and mass were selected as objective functions for multiple optimizations. The I-optimal algorithm based on the Response Surface Method was used to create a Design of Experiment. Optimization parameters and levels were determined by numerical analysis. The mathematical models derived for the selected performance parameters (maximum temperature (Tmax), average temperature (Tavg), maximum and minimum temperature difference (∆T) for homogeneity, and mass were tested using ANOVA, with prediction accuracies of 0.9923%, 0.9866%, 0.9381%, and 0.9314%, respectively. The results indicate that increasing the fin diameter (from 20 to 36 mm) decreases Tmax by 3.4% and Tavg by 3.7%, but increases mass by 12.2% and ∆T by 5 K to 11 K. Moreover, as fin thickness increases from 0.5 mm to 2 mm, Tmax and Tavg decrease by 2.2%, but increases mass by 21% and ∆T by 9.8 K to 10.8 K. Furthermore, as the number of fins increases from 3 to 9, Tmax and ∆T decrease by 6.0% and 36.3%. Increasing the number of fins is more effective at increasing homogeneity than increasing their diameter and thickness. Optimization results show that with a fin diameter of 32.4 mm, a thickness of 1.35 mm, and 9 fins, the battery temperature can be maintained below 349 K under these optimal conditions.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2026Experimental and optimization study of co-axial impinging jet parameters on thermal behavior at impingement plates with and without fins
Demir, Fatih; Turgut, Oguz; Çolak, Andaç Batur; Abdulkarim, Ali Hussein
Impingement jets are one of the promising cooling techniques in thermal management. This study investigates the thermal effects of impinging co-axial jets on different operating parameters. This objective is achieved by experimental and machine learning in the cases of confined and unconfined jets with different nozzle-to-plate distances at constant flow rate ratio and different total flow rates. The study is innovative in that it specifically examines the effect of total flow rate variation of coaxial impinging jet on thermal management at constant flow rate ratio for impingement plates with and without fins, in confined and unconfined jet cases. Experiments and machine learning are conducted for dimensionless nozzle-to-plate distances of H/D = 0.8, 1.6, 2.4, 3.2, a flat impingement plate, and impingement plates with fins of 2 and 6 mm length at Q = 60 and 80 LPM total flow rates and flow rate ratio Q* = 0.5. While the experimental results analyze stagnation, average Nusselt numbers, and heat transfer uniformity, machine learning provides highly accurate predictions and enables thermal performance optimization. The results reveal that while fins and a rise in total flow rate increase heat transfer, they reduce heat transfer uniformity. This is the opposite for H/D≥1.6. Heat transfer on a 2 mm fin-length plate improves by 26% and 22% at 80 and 60 LPM, respectively, compared to a flat plate. On the other hand, the heat transfer deviation on the flat plate is 2.16% and 1.79% for 80 and 60 LPM, while it is 9.05% and 7.33% for a 2 mm fin-length plate. Further, as H/D = 0.8 increases to 3.2, the heat transfer deviation for the flat plate at 60 LPM decreases from 2.62% to 1.79%, while for the 2 mm fin-length plate, it decreases from 9.10% to 7.33%, respectively. Finless plates and low total flow rates are recommended for applications requiring uniform heat transfer, while high heat transfer applications benefit from finned plates and high total flow rates. Finally, machine learning predicts the results with high accuracy.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2026Appendiceal Collision Tumors: An Institutional Case Series and Systematic Review of the Histologic Spectrum, Clinical Outcomes, and Management Strategies
Issin, Gizem; Demir, Fatih; Cagatay, Diren Vuslat; Guvendir, Irem; Simsek, Hasan Aktug; Zemheri, Itir Ebru
Background/Objectives: Appendiceal collision tumors (ACTs), defined by the coexistence of two or more histologically distinct neoplastic components within the appendix, are rare entities. We aimed to characterize their clinicopathologic features, management strategies, and outcomes by integrating an institutional case series with a systematic review of the literature. Methods: We retrospectively identified ACTs diagnosed at our institution and performed a PRISMA 2020-guided search of PubMed, Scopus, and Web of Science databases through May 2025 for case reports and case series. Two reviewers screened studies and extracted data on presentation, histologic composition, treatment, approaches and outcomes. Results: ACTs accounted for 4% of appendiceal tumors in our institution, all combining a neuroendocrine neoplasm (NEN) with a low-grade appendiceal mucinous neoplasm. The literature search identified 69 ACTs from 33 studies; pooled with our cases, 74 patients were evaluated. The most common pairings were NEN–appendiceal mucinous neoplasm (53%) and NEN–adenocarcinoma (26%), while three-component tumors were rare (n = 2). Early-stage tumors (pTis–pT1) were uniformly managed with appendectomy or limited resection, in line with established stage-based management algorithms for appendiceal neoplasms. Advanced-stage tumors (pT3–pT4) were treated according to the biologically dominant component, frequently with colectomy and, in high-risk mucinous disease, cytoreductive approaches. Across stages, outcomes appeared to be driven by the non-neuroendocrine component; a coexisting low-grade NEN did not independently confer worse prognosis. In ACTs with an adenocarcinoma component, goblet cell morphology was common, and outcomes appeared similar to those reported for non-collision appendiceal adenocarcinoma. Conclusions: ACTs represent a heterogeneous group in which prognosis is dictated by the non-neuroendocrine component and tumor stage. Low-grade NEN components appear biologically indolent, whereas adenocarcinoma and high-risk mucinous components have been observed to exhibit behavior similar to their solitary counterparts.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2026Effects of Flow Rate Ratio and Swirl Number on Heat Transfer and Flow Field in Combined Swirl Impinging Jets
Demir, Fatih; Turgut, Oguz
Combined impingement jets are a promising cooling technique for enhancing heat transfer and uniformity. This study focuses on understanding the heat transfer and flow field of a combined impinging jet. It presents a novelty by addressing the compound effects of two important characteristics of a combined impingement jet: the swirl number and the flow rate ratio. To achieve this objective, combined impinging jets with axial and tangential velocities are produced using a combined nozzle that has circular and quadruple helical flow sections. The flow rate ratio is defined to examine the effects of the separate flow rates of the circular and quadruple helical sections of the combined nozzle, keeping the total flow rate constant at 75 L/min. The study is carried out for two different flow rate ratios (0.2 and 0.5) and a dimensionless nozzle-plate distance of 1. On the other hand, depending on the geometry of the combined nozzle, the swirl number is 0.0, 0.3, 0.6, 0.8, and 1.7. All parameters studied are investigated separately for confined and unconfined jet cases. The results demonstrate that the numerical model agrees with the experimental findings. It is observed that increasing the flow rate ratio from 0.2 to 0.5 results in a decrease in the Nusselt number of 28.4%–29.5% in the unconfined jet case and 28.7%–30.4% in the confined jet case, depending on the change in swirl number. Increasing the flow rate ratio improves heat transfer uniformity better than enhancing the swirl number. The swirl number becomes more effective on heat transfer and pressure with an increasing flow rate ratio. The confinement plate used to create the confined case reduces the drag ratio compared to the confined case. Finally, one advantage of the combined nozzle geometry is that the saddle-shaped formation, which negatively affects heat transfer uniformity, is not observed in the local Nusselt number distribution.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2026Comparative study of diverging and converging coaxial jet nozzles for thermal management of H-CPV modules
Demir, Fatih; Kalkan, Orhan
Jet impingement cooling is widely recognized as one of the most effective methods for achieving high heat transfer rates in compact systems, making it particularly suitable for cooling photovoltaic devices. This paper investigates the effects of newly designed coaxial nozzle configurations on the thermal management of a high-concentration photovoltaic system. Four different nozzle geometries, such as square, circular, hexagonal, and triangular, are considered, with constant outer cross-sectional areas, while the inner sections are designed to diverge or converge. Simulations are performed for Reynolds numbers of 2000–4000 and dimensionless coaxial nozzle-heat sink distances of 0.5–3. The results reveal that the coaxial nozzle enhances heat transfer performance compared to conventional nozzles. The diverged triangular coaxial nozzle achieves the best heat transfer at a Reynolds number of 4000, with a 19 % increase in the modified Nusselt number compared to the conventional triangular nozzle. The highest temperature uniformity (6.39 °C) is observed in the converged hexagonal coaxial nozzle, while the lowest maximum and average cell temperatures (46.1 °C and 44 °C) are achieved with the diverged triangular coaxial nozzle. The lowest pressure drop (1297 Pa) is found in a diverged hexagonal coaxial nozzle, corresponding to the lowest net electrical power (17.53 W) and cell efficiency (38.97 %). Despite the pressure drops, the diverged triangular coaxial nozzle achieves the highest electrical efficiency of 39.41 %, as its geometry promotes favorable power generation. The coaxial configuration increases the cell efficiency by up to 1.13 % and improves temperature uniformity by 23.3 %. Total exergy follows the same trend as electrical exergy, with the converged hexagonal coaxial nozzle exhibiting the highest total exergy efficiency of 38.35 %. The findings demonstrate that coaxial nozzles can significantly improve thermal uniformity and system efficiency in high-concentration photovoltaic cooling applications.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2026Parametric study of ternary nanofluid (Al2O3-CuO-SiO2) on thermal performance and entropy generation in impinging jet
Demir, Fatih; Ekiciler, Recep
This study investigates the effects of individual nanoparticle concentrations at a ternary nanofluid on flow and heat transfer characteristics under confined impingement jet conditions. The results shed light on the development of high-performance thermal management applications. The total nanoparticle concentration of the ternary nanofluid in the impingement jet formed by the circular nozzle was kept constant at 3%. Four cases were considered by varying the concentration of Al2O3, CuO, and SiO2 nanoparticles in the total nanoparticle concentration between 0.5 and 2%. The study was carried out for dimensionless nozzle-to-plate distances of 1.1, 2.2, and 3.3, and Reynolds numbers of 9000, 15,000, 21,000, and 27,000. The results show that 0.5% Al2O3- 0.5% CuO-2% SiO2/water ternary nanofluid increases the heat transfer than water and other ternary nanofluids, and it provides a 16.53% enhancement in heat transfer compared to water. It is also noticed that the concentration of nanoparticles and Reynolds numbers are generally more effective on average Nusselt numbers and pumping power than at nozzle-to-plate distances. Nevertheless, the stagnation Nusselt number change depends much more on the dimensionless nozzle-to-plate distance. A 15.24% rise in the stagnation point Nusselt number is noted as the H/D is increased from 1.1 to 3.3 at Re = 27,000. Furthermore, it is seen that after a certain Reynolds number, the entropy production due to friction becomes more dominant than the entropy production due to heat in the total entropy production.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2026Application of a heat spreader plate and metal foam for battery thermal management in different cases
Demir, Fatih
Effective temperature management is crucial to ensuring the safety, performance, and lifespan of lithium-ion batteries, especially as electric vehicles become more prevalent globally as part of sustainable transport efforts. Significant temperature increases during cycling may reduce efficiency, promote irregular aging, and raise safety concerns. This study aims to improve heat transfer for batteries operating under natural convection at reliable operating temperatures, without requiring maintenance or additional costs at high discharge rates of 7C to 10C. First, the numerical models of the lithium-ion battery and the metal foam are validated through experimental studies. After that, an innovative approach is presented that uses a heat spreader plate and heat spreader metal foam, either separately or in a hybrid, for battery thermal management. It investigates the effect of heat spreader plate thickness (0.5–2 mm), heat spreader metal foam thickness (0.5–2 mm), porosity (5–40), pore per inch (0.899–0.958), hybrid structures (1 to 8 cases), and different coolants (air, mineral oil, synthetic, and natural esters) on battery thermal management. The thermocouple measurements and infrared camera images are evaluated in the experimental study. At the same time, the battery surface temperatures, temperature homogeneity, temperature contours, and velocity vectors are discussed in the numerical model. The results show that increasing the thickness of the heat spreader plate from 0.5 to 2 mm leads to 17.5% and 16% decreases in maximum temperatures at 7C and 10C discharge rates, respectively, at 100% discharge depth. The battery temperatures depend on the varying thicknesses rather than the changing positions of the heat spreader plate and heat spreader metal foam that form the hybrid structures. On the battery surface with a heat spreader plate and with a heat spreader foam, mineral oil reduces the maximum battery surface temperature by factors of 1.6 and 1.92, respectively, compared to air. Increasing the pore per inch at a given ε reduces temperature homogeneity on the battery surface.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2026Macroscopic growth patterns and their molecular implications in gastric carcinoma: toward risk stratification via borrmann classification
Issin, Gizem; Demir, Fatih; Cagatay, Diren Vuslat; Bakkaloglu, Irem Guvendir; Gamsizkan, Mehmet; Yildiz, Zeliha; Yilmaz, Ismail; Ozmen, Sevilay; Zemheri, Itir Ebru; Demiriz, Murat
Abstract: Gastric carcinoma (GC) is a heterogeneous disease with diverse histopathological and molecular features. The Borrmann classification, which reflects the macroscopic growth pattern, has potential value in correlating with molecular characteristics and predicting disease extent and prognosis. However, its relationship with GC molecular subtypes remains incompletely defined. In the present study, we attempted to assess the relationship between Borrmann classification and clinical, pathological, and molecular findings in GC, as well as its impact on overall survival. Material and methods: A retrospective analysis was conducted on 255 patients who underwent surgery for GC between January 2012 and 2021. Cases were classified into types I, II, III, and IV, according to the Borrmann classification. Clinical data, tumor characteristics, molecular marker expression status, and survival data were analyzed in relation to the Borrmann classification. Result: The most common macroscopic growth pattern was Borrmann type III (38.8%). Type IV tumors were associated with younger patients, larger size, epithelial-mesenchymal transition–related molecular subtype, diffuse histology, and a higher incidence of peritoneal dissemination. In contrast, type I tumors were more frequently diagnosed at earlier stages and demonstrated well-differentiated morphology, frequent HER2 positivity, and p53 mutant expression. Kaplan–Meier analysis demonstrated clear survival differences among Borrmann types, with type I tumors showing the most favorable outcomes (median 82.2 months) and type IV tumors the poorest (median 34.6 months; log-rank p < 0.001). When adjusted for covariates in the multivariate Cox model, only age, Borrmann type III (compared to type I) and advanced nodal status (pN0 compared to pN2–3) were found to be independent prognostic indicators. Advanced age was consistently associated with reduced survival time, type III tumors resulted in more than a twofold increase in mortality risk, and higher nodal stages were strongly linked to poor outcomes. Conclusion: The Borrmann classification showed associations with molecular and pathological features of GC, and survival varied among types, suggesting potential utility for prognostic assessment prior to surgery.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2026SOX17 and TRPS1 in Müllerian, Breast, and Mesothelial Tumors: Tissue-Based Specificity Profiles and Diagnostic Pitfalls in Malignant Serous Effusions
Issin, Gizem; Demir, Fatih; Yaylı, Esra; Çağatay, Diren Vuslat; Yılmaz, İsmail; Girgin, Rabia Burçin; Gamsızkan, Mehmet; Zemheri, Ebru; Şimşek, Hasan Aktuğ; Sayar, İlyas
Background: Malignant serous effusions may be the first manifestation of an underlying malignancy, and accurate primary-site attribution is essential. However, distinguishing Müllerian carcinoma, breast carcinoma, and mesothelioma in effusion cytology remains a challenge because of overlapping immunophenotypes. We evaluated SOX17 and TRPS1 in this setting. Materials and Methods: A multicenter retrospective cohort including 650 tissue specimens (300 breast carcinomas, 300 Müllerian tumors, and 50 mesothelial lesions) and 150 malignant serous effusion cell blocks was analyzed. SOX17 and TRPS1 expression was assessed by immunohistochemistry and compared with established markers, including PAX8, GATA3, WT1, and calretinin. Sensitivity, specificity, and positive predictive value (PPV) were calculated according to the primary diagnosis. Results: In the tissue cohort, SOX17 showed 87% sensitivity and 100% specificity for Müllerian tumors, with no expression in breast carcinomas or mesothelial lesions, including tumors with PAX8/WT1 co-expression. This specificity was retained in cell blocks, yielding a PPV of 100%. TRPS1 showed 98% sensitivity for breast carcinoma and identified 84% of GATA3-negative breast carcinomas. However, TRPS1 expression was also observed in 48% of tubo-ovarian serous carcinomas, limiting its PPV for breast carcinoma in effusions to 55% despite a negative predictive value of 97%. Conclusion: SOX17 is a highly specific confirmatory marker for Müllerian origin and may help resolve diagnostic pitfalls related to PAX8-positive mesothelial lesions. TRPS1 is a complementary marker for breast carcinoma, including GATA3-negative tumors, but its stand-alone diagnostic value is limited by cross-reactivity in Müllerian serous carcinomas. These findings support a panel-based approach for accurate primary-site attribution in malignant serous effusions.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2026The thermal-hydraulic performance evaluation of a triangular groove duct with L-shaped baffles: Multi-objective optimization and numerical analysis
Ekiciler, Recep; Demir, Fatih; Kalkan, Orhan
Enhancing heat transfer efficiency is crucial for improving performance and reducing the energy consumption of thermal equipment in various industrial sectors. The emergence of passive enhancement methods, such as corrugated grooves, has improved convective heat transfer cost-efficiently. To this end, this study addresses the thermal and hydraulic performance of the baffle duct with numerical analysis and multi-objective optimization methods. The study is innovative in that it places movable L-shaped baffles inside the duct, which have their own internal connections and a connection to the grooved channel. L-shaped baffles have the ability to move at alpha angles (α = 30°, 60°, 90°) with the upper wall of the duct and at beta angles (β = 60°, 90°, 120°, 150°) with their internal connection points, which affect the thermal and hydraulic performance of the duct. Air, water, mono (GO/water), and tetra hybrid (Al2O3-Au-Ag-TiO2/water) nanofluids are used as coolant fluids in the range of Re = 2500 to 3100. The coolant air and a baffle-less triangular grooved duct are used for comparison to evaluate the thermal and hydrodynamic performance in other cases. The results show that at Re = 2500, the baffled duct achieves a 65% higher Nu than the one without baffles. As α = 90° decreases to 30°, Nu increases by 12.85% and 12.11%, respectively. As β = 60° to 120° increases, Nu increases by 21.67%, while f increases by 59% from β = 90° to 120°. The highest performance evaluation criteria (PEC) is achieved at β = 90° and the lowest at β = 150°. The tetra hybrid nanofluid exhibits the highest Nu and f values across all Re ranges, demonstrating the most efficient cooling performance with a PEC value approximately 8% higher than that of water. Multi-objective optimization reveals that the combination of α = 30°, β = 35°, Re = 2500, and water is the most suitable design. Generally, thermal and hydraulic performance can be significantly improved by carefully selecting channel geometry and fluid properties.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2025A Quantitative Analysis on the Differences in Secondary School Students’ Use of Learning Strategies
Demir, Fatih; Bahar, Hüseyın Hüsnü; Malkoç, Musa
Learners use various strategies to acquire new knowledge, skills or attitudes. In this context, it can be said that secondary school students also use various strategies in the learning-teaching process. It is important that the methods, techniques, and practices that teachers will use are appropriate for students' learning strategies in order to realize effective teaching. This study aims to determine the level of secondary education students' use of learning strategies and the level of secondary education students' use of learning strategies in terms of some variables. The population consists of 13762 secondary education students studying in Erzincan province in the 2023-2024 academic year, and the sample consists of 1247 secondary education students studying in secondary education institutions located in Erzincan city centre and a district and selected by a decisional way. Data were collected from the sample through a personal information form and the ACRA-shortened learning strategies scale. Descriptive statistics, factorial ANOVA, correlation and stepwise regression analyses were used to analyse the data. In the study, it was determined that secondary school students mostly used explanation and metacognitive strategies, and that female students benefited from learning strategies more than male students. When the type of school is taken into consideration, it was found that Anatolian High School students used explanation and metacognitive strategies more than Science High School and Fine Arts High School students, and Social Sciences High School students more than Fine Arts High School students. Anatolian High School students used to learn supportive strategies more than Science High School and Fine Arts High School students, Vocational and Technical Anatolian High School students more than Science High School and Fine Arts High School students. Anatolian High School students used repeating and organizing strategies more than Science High School, Social Sciences High School and Vocational and Technical Anatolian High School students, Social Sciences High School students more than Science High School and Fine Arts High School students. In addition, some of the results of the study revealed that secondary school students who frequently use explanation and metacognitive strategies are students with high academic achievement.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2025EZH2 expression in colorectal carcinoma: an evaluation of clinicopathological and prognostic value
Cagatay, Diren Vuslat; Balci, Mecdi Gurhan; Issin, Gizem; Demir, Fatih
Background: Enhancer of zeste homolog 2 (EZH2), the catalytic subunit of Polycomb Repressive Complex 2, catalyzes trimethylation of histone H3 lysine 27 and has been implicated in tumor progression. Aim: Our study aims to assess the relationship between EZH2 expression and clinicopathologic data, and survival in colorectal carcinomas (CRC). Materials and methods: EZH2 immunohistochemistry was performed on tumor blocks from 124 CRC patients. Based on H-scores, cases were stratified into low- and high-expression groups. EZH2 status was correlated with demographic, clinical, and pathologic features, and overall survival was analyzed with the Kaplan–Meier method and log-rank test. Results: A total of 124 cases of CRC; 12 (9.7%) cases were classified as low EZH2 expression, and 112 (90.3%) cases were classified as high EZH2 expression. A significant association was found between EZH2 expression and microsatellite stability. High EZH2 expression was significantly enriched in microsatellite-stable tumors (p = 0.007) and in left-sided lesions (p = 0.049). No significant associations were detected with sex, stage, grade, lymph-node status, or vascular invasion. Kaplan–Meier analysis revealed no difference in overall survival between low- and high-EZH2 groups (log-rank p = 0.47; hazard ratio = 1.13, 95% CI 0.45–2.85). EZH2 staining was uniformly strong in normal mucosa and adenomas, mirroring the high expression observed in most CRCs. Conclusions: EZH2 is highly expressed across the normal-adenoma-carcinoma sequence and, in our cohort, was not linked to overall survival or to most clinicopathologic parameters in CRC. The lower expression observed in a subset of MSI-H tumors warrants further investigation; present evidence remains insufficient to establish EZH2 as an independent prognostic biomarker.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2025Study of heat transfer and flow field of coaxial round and swirl impinging jets on flat and finned plates via experimental and numerical approaches
Demir, Fatih; Turgut, Oguz
Impingement jets are a promising cooling technique for achieving uniform and high heat transfer. This study investigates the heat transfer and flow fields of coaxial round and swirl jets on flat and finned impingement plates, both experimentally and numerically. Experimental and numerical studies are carried out under different parameters and states. Coaxial nozzle geometry, the dimensionless nozzle-to-plate distance (H/D = 0.8–3.2), fin length (0, 2, and 6 mm), flow rate ratio (Q*=0.176–0.823) and restricted and unrestricted jet depending on the presence or absence of blocking plate are taken into consideration as parameters and states. The total flow rate is constant at 85 L/min for all cases. The results show that uniform heat transfer on a flat impingement plate can be achieved for specific parameters. The average Nusselt number (Nu) increases with high Q* and low H/D. Moreover, changes in Nu with respect to variations in H/D are more pronounced at higher flow rate ratios. Although the impingement plates with fins increase the heat transfer, they negatively affect the uniformity of heat transfer on impingement plate. The formation and positioning of recirculation zones in the flow field are affected by the impingement plate geometry, fin length, H/D, and blocking plate. This study is important because it presents an innovation considering the combined effects of coaxial impinging jets and finned impingement plates on heat transfer and flow fields. High and uniform heat transfer is possible for certain parameters and states studied. These results can be guided in electronic device cooling and thermal management systems.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2025Columnar cell variant of papillary thyroid carcinoma in an adolescent: a comprehensive histopathological, immunohistochemical, and molecular analysis
Issin, Gizem; Demir, Fatih; Cagatay, Diren Vuslat; Yilmaz, Ismail
The columnar cell variant (CCV) of papillary thyroid carcinoma (PTC) is a rare histological subtype with distinct morphological and immuno-histochemical (IHC) features, which can present diagnostic challenges. We report a case of a 13-year-old girl diagnosed with CCV of PTC (CCV–PTC) following a total thyroidectomy for a solitary thyroid nodule. Histopathological (HP) examination revealed aggressive features, including vascular invasion and extrathyroidal extension. However, no metastases or recurrences were observed during six years of follow-up. This case report provides a comprehensive analysis of a rare CCV–PTC in an adolescent, focusing on its HP, IHC, and molecular characteristics. It also discusses diagnostic pitfalls and differential diagnoses that should be considered.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024Üniversitelerarası İşbirliği Programlarının Değerlendirilmesi: Yüksek Öğretim Kurulu Anadolu Projesi Örneği
Ilhan, Elif; Demir, Fatih
Üniversiteler arası rekabet hızlanırken ulusal ve uluslararası işbirlikleri de her geçen gün artmaktadır. Ancak önemli olan nicelik artışı değil nitelikli ve sürdürülebilir işbirliklerinin kurulmasıdır. Bu araştırmada üniversiteler arası işbirliği kapsamında Yüksek Öğretim Kurulu (YÖK) Anadolu Projesi-Eğitim-Öğretim ve Araştırmada Destek Programının eğitim öğretim destek boyutunun değerlendirilmesi amaçlanmıştır. Araştırma, nitel araştırmaların bütüncül tek durum desenine uygun olarak tasarlanmıştır. Araştırmanın çalışma grubunu, YÖK Anadolu Projesi kapsamdaki bir genç üniversiteden 45 öğrenci ile bir kıdemli üniversiteden 6 öğretim üyesi oluşturmaktadır. Görüşmeler yoluyla elde edilen veriler, betimsel analiz yöntemi ile analiz edilmiştir. Araştırmanın bazı bulguları şöyledir: Öğrencilerin projeye ilişkin ilk tepkileri çoğunlukla olumlu görüşleri kapsamaktadır. Öğrenciler, kıdemli üniversiteden aldıkları tüm derslerin etkili olduğunu ve derslerin işlenişine, içeriğine, ölçme-değerlendirme sürecine ve öğretim üyelerine odaklanarak derslere ilişkin memnuniyetlerini belirtmişlerdir. Araştırma kapsamında görüşleri alınan öğretim üyeleri ise farklı bir üniversitedeki öğrencilere ders vermekten ve onların gelişimlerine katkıda bulunmaktan memnun olduklarını, ancak proje sürecinde pek çok olumsuzluk ve sorunla mücadele etmek zorunda kaldıklarını belirtmişlerdir. Araştırma sonuçlarına dayalı olarak üniversiteler arası işbirliklerinin sürdürülebilir olmasına katkı sağlayacak nitelikte öneriler ve son olarak araştırmacılara yönelik öneriler sunulmuştur.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024Experimental and numerical study of combined impinging jets at low nozzle-plate distance for confined and unconfined impingement plate
Demir, Fatih; Turgut, Oguz
This study investigates the heat transfer and flow dynamics of combined impinging jets at low nozzle-plate distances. The combined jets comprise (i) circular and quadruple helical jets and (ii) circular and double helical jets. A conventional jet is generated from the only circular part of the combined jet. Experiments are conducted with a constant total flow rate (Qt = 85 LPM) and low nozzle-plate distances (H/D = 0.1, 0.2, 0.3, 0.4) for confined and unconfined jet cases. Flow rate ratios (Q*=0.176, 0.235, 0.352, 0.588, 0.823) are used for different swirl intensities. A numerical study was performed using ANSYS Fluent software. The results show that the numerical analysis is consistent with the experimental research. The combined impingement jet shows a potential to improve the low heat transfer occurring at the stagnation zone at low nozzle-plate distance in the swirl jet, leading to non-uniform heat transfer. The confined jet case at the low nozzle-plate distance reduces the heat transfer at the stagnation point and over the entire plate as regards the unconfined jet case. Increasing the H/D distance in the combined impinging jet improves the heat transfer in the confined jet case but reduces it in the unconfined case. Correlations are given for heat transfer prediction depending on H/D and Q* for unconfined and confined cases of the combined jet. Increasing the flow rate ratio and the nozzle-plate distance increases the heat transfer uniformity for the confined and unconfined jet cases. In contrast, the unconfined jet case is better regarding heat transfer uniformity. The confinement plate creates a negative pressure on the impingement plate in all conditions. In contrast, the unconfined jet case is precisely the opposite.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Evaluating the associate degree curriculum in child development
Demir, Fatih
This case study aims to evaluate the associate degree curriculum in child development. In the curriculum evaluation process, Stufflebeam's CIPP curriculum evaluation model was chosen. In the process of collecting data, interviews were conducted with 64 associate degree students and six instructors working in this programme. The data obtained from the interviews were analyzed by content analysis method. The results suggest that the content of the most effective courses in the program includes important and new information for students’ professional development, and includes the information needed in daily life. In addition, the students prefer to be taught practically and effectively with different methods/techniques in the teaching and learning processes. They also suggest that the program should include formative assesment and extracurricular activities such as visits to institutions, conferences/ seminars, and internships. On the other hand, the instructors stated that the problems arising from the students and the deficiencies related to the physical facilities (infrastructure), such as students' lack of interest/willingness to the course, reduce the effectiveness of the curriculum. Based on the results of the study, 21st-century skills should be included and students' professional, academic and social development should be supported in the program. Different methods/techniques, materials and extracurricular activities should be used to ensure that students engage in the course with interest and enthusiasm, and multiple assessment methods/tools should be used in the assessment and evaluation process.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2023Clinicopathologic Features and Prognostic Significance of Immunohistochemistry and In Situ Hybridization Based Molecular Classification in Gastric Carcinoma
Issin, Gizem; Sayar, İlyas; Demir, Fatih; Bakkaloğlu, İrem Güvendir; Gamsizkan, Mehmet; Yildiz, Zeliha; Yilmaz, İsmail; Özmen, Sevilay Akalp; Çağatay, Diren Vuslat; Zemheri, Itır Ebru
Background/Aim: Gastric carcinoma (GC) is a highly heterogeneous disease with many subtypes that have different morphologic and molecular characteristics. In the current study, we analyzed immunohistochemical (IHC) and in situ hybridization (ISH) features of GCs and evaluated their association with prognosis and clinicopathological features. Materials and Methods: Three hundred cases analyzed by IHC and ISH for microsatellite stability, p53, e-cadherin, HER2, PD-L1 expression, and Epstein-Barr virus (EBV) status. Cases were classified into five subgroups based on expression profile. The relationships between subgroups, clinicopathological features, and survival were determined. Results: Ten (3.3%) cases were classified as EBV-associated, 45 (15%) as microsatellite instable (MSI), 73 (24.3%) as EBV–/microsatellite-stable (MSS)/epithelial−mesenchymal−transformation (EMT)-like, 75 (25%) as EBV–/MSS/non-EMT-like/p53+, and 97 (32.3%) as EBV–/MSS/non-EMT-like/p53–. The MSI subtype had the best overall survival (OS). In contrast, the EBV–/MSS/EMT-like subtype had the poorest OS. The MSI subtype was also related with old age of the patient and antrum-corpus localized tumors, whereas the EBV–/MSS/EMT-like was associated with young age, larger tumor size, and advanced stage presentation. PD-L1 positivity is highly correlated with MSI and EBV-associated subtypes. Conclusion: Our data demonstrated a link between IHC/ISH characteristics of GC and clinical outcomes. IHC/ISH based molecular classification may be helpful in predicting the survival.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2023Retrospective analysis of the appendiceal neoplasms: sampling technique may influence neoplasm detection
Issin, Gizem; Demir, Fatih; Simsek, Hasan Aktug; Cagatay, Diren Vuslat; Tayfur, Mahir; Balci, Mecdi Gurhan
Background and aims: Appendiceal neoplasms are uncommon entities that are usually determined incidentally during the histopathological examination. Different techniques used for the macroscopic sampling of appendectomy material may affect the determinating neoplasms. Materials and methods: H&E-stained slides of 1280 cases who underwent appendectomy between 2013 and 2018 were reviewed retrospectively for histopathological features. Results: Neoplasms were determined in 28 cases (3.09%); 1 lesion was observed in the proximal part of the appendix, 1 covering the entire length from proximal to distal and 26 in the distal part. In the 26 cases that observed in the distal part, the lesion was seen on both sides of the longitudinal section of the distal appendix in 20 cases, while it was seen on only one distal longitudinal section in the remaining 6 cases. Conclusion: The vast majority of appendiceal neoplasms are seen in the distal part of the appendix, and, in some cases, neoplasms might be seen on only one side of the distal section. Sampling only one-half of the distal part of the appendix, where tumours are most often observed, could result in some neoplasms being missed. Therefore, sampling the whole distal part would be more beneficial to determine small diameter tumours that do not create macroscopic findings.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2023Seeds or Parasites? Clinical and Histopathological Features of Seeds and Parasites in the Appendix
Issin, Gizem; Demir, Fatih; Simsek, Hasan Aktug; Cagatay, Diren Vuslat; Tayfur, Mahir; Kandemir, Ali; Balci, Mecdi Gürhan
Objective: Parasites and plant seeds may both be found in appendectomy specimens. Each plant seed has a different appearance and can thus exhibit wide variations under the microscope. Fragmented seeds may histologically mimic parasites. The differential diagnosis between seeds and parasites can be challenging in such cases. This study aimed to determine the incidence of parasites, seeds, and foreign bodies in appendectomy materials and highlight the most characteristic histopathological features associated with these structures. Material and Method: In this study, pathology slides of 9,480 patients, who underwent appendectomy between 2010 and 2021, were reviewed, and cases that contained parasites, seeds, or foreign bodies were identified. We reviewed the literature on seeds and parasites in appendectomy specimens. Results: Parasites were observed in 56 (0.6%) cases. Of these cases, 45 had Enterobius vermicularis (80%), and 11 had Taenia subspecies (20%). Plant seeds were observed in 47 cases (0.5%), and were macroscopically recognizable in 5 of them as olive, lemon, and cherry seeds. Parasites and seeds were usually observed in the lumen of appendix vermiformis, filled with abundant fecal materials. Conclusion: Seeds are seen in approximately 0.5% of the appendectomy specimens. Though rarely seen, the fragmented seed appearance may cause diagnostic difficulties. In this context, the key morphological features of parasites and plant seeds outlined in this study may be helpful in their differential diagnosis.
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