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  • Öğe
    Investigation of inspiratory muscle training efficiency before bronchoscopic lung volume reduction: a randomized controlled trial
    (Sociedad Espanola de Neumologia y Cirugia Toracica (SEPAR), 2025) Pehlivan, Esra; Çetinkaya, Erdoğan; Özcan, Zeynep Betül; Karaahmetoğlu, Fulya Senem; Çörtük, Mustafa; Ataç, Amine; Çınarka, Halit
    Introduction: Pulmonary rehabilitation (PR) is recommended prior to bronchoscopic lung volume reduction (BLVR) procedures to optimize patient outcomes. However, there's a lack of clear guidance on PR content. The aim of our study is to examine the effect of adding inspiratory muscle training (IMT) to standard PR before BLVR on exercise capacity, dyspnea, fatigue level and quality of life. Methods: Sixty-four patients were randomly assigned to either the PR Group (PRGr) or the PR with IMT group (IMTGr). Both groups underwent an 8-week standard PR program, including breathing exercises, muscle strengthening, and walking. Additionally, IMTGr received IMT sessions. Outcome measures comprised six-minute walking distance (6MWD), maximal inspiratory and expiratory pressures (MIP, MEP), peripheral muscle strength, modified Medical Research Council dyspnea score, fatigue symptom scale, spirometric parameters, Saint George Quality of Life Questionnaire (SGRQ), International Physical Activity Questionnaire Short Form (IPAQ-SF), and Hospital Anxiety and Depression Scale. Results: Our study found no significant difference in exercise capacity improvement between IMTGr and PRGr. However, IMTGr showed significant improvement in MIP compared to PRGr. Both groups experienced improvements in dyspnea, fatigue, and depression scores, as well as enhancements in 6MWD, MEP, peripheral muscle strength, IPAQ-SF and SGRQ scores. Conclusion: Adding IMT to PR did not show a significant difference between groups among BLVR-eligible patients. However, improved respiratory muscle strength may have positive clinical implications. Further research is needed to explore short and long-term effects.
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    Relationship between nutritional literacy and healthy life skills of university students
    (John Wiley and Sons Inc, 2025) Karadağ, Gülendam; Bilgiç, Dilek; Öztürk, Nuray; Özdemir, Tuğba
    Health literacy is important for maintaining healthy diets and lifestyles. This study examined the relationship between nutrition literacy and healthy life skills of university students. This study was a descriptive and correlational design. The students' Food and Nutrition Literacy Scale knowledge sub-dimension mean score was found to be 10.30 +/- 2.11, at the limited knowledge level, the attitude sub-dimension mean score was 49.32 +/- 7.26, at the limited attitude level, and the behaviour sub-dimension mean score was 31.04 +/- 5.71, at the limited level. The mean Scale of Healthy Life Skills in University Students score of the university students was 62.96 +/- 9.99, at a moderate level. Multiple regression analysis showed that the mean scores obtained from the attitude and behaviour sub-dimensions, studying in the Faculty of Nursing, being 18 years old, and studying in the first or second year were the main variables influencing the healthy life skills of university students. The food and nutrition literacy of the students was limited and their healthy life skills were at a moderate level. As the food and nutrition literacy of the students increased, their healthy life skills became more positive.
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    Developing a xenophobia scale for healthcare workers in Türkiye
    (Chiang Mai University, 2025) Karagöz, Yalçın; Karaşin, Yusuf; Filiz, Mustafa; Genç, Gülşen
    T his study proposes a psychometric measurement tool to determine the level of xenophobia among healthcare workers. To this end, 312 healthcare workers serving in Istanbul were reached through convenience sampling and data was generated through face-to-face interviews. A preliminary scale comprising 33 items was initially created. Following expert opinions and pilot study phases, six items were removed from the draft scale, leaving 27 items. Exploratory factor analysis was initially applied to the data, resulting in the removal of nine more items from the scale, thus reducing the number of items to a final scale of 18. The final scale was grouped into three factors: "General Xenophobia," "Occupational Xenophobia," and "Cultural Xenophobia." The items obtained following exploratory factor analysis were subjected to confirmatory factor analysis. The analysis demonstrated that the model obtained fits the data perfectly. The Cronbach's alpha value for the developed scale was found to be 0.905. In conclusion, the developed scale was found to be a valid and reliable measurement tool for the measurement of xenophobic attitudes among healthcare workers.
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    Efficacy of ursodeoxycholic acid in reducing the necessity of cholecystectomy due to pre-existing and subsequently formed gallstones in patients who underwent laparoscopic sleeve gastrectomy
    (BMC, 2025) Demirpolat, Muhammed Taha; Çelikkaya, Muhammet Oğuz; Ertekin, Süleyman Çağlar; Başak, Fatih; Şişik, Abdullah
    BackgroundIn this study, we aimed to investigate whether ursodeoxycholic acid (UDCA) would reduce the necessity of cholecystectomy in patients diagnosed with asymptomatic gallstones after laparoscopic sleeve gastrectomy (LSG) and in patients diagnosed with asymptomatic gallstones before LSG.MethodsBetween July 2020 and November 2022, at least 2-year follow-ups of patients who underwent LSG for obesity were retrospectively analyzed. Patients with pre-existing asymptomatic gallstones during preoperative evaluation, those with UDCA treatment (group 1), and observation group (group 2). Patients with newly formed gallstones in postoperative outpatient clinic follow-up, those with UDCA treatment (group A), and those without UDCA treatment (group B).ResultsA total of 425 patients included. At the end of the first year, patients who had newly formed gallstones after LSG had a higher total weight loss percentages (TWL%) (39.8 +/- 6.1) compared to those who did not develop gallstones (37.9 +/- 7.4), which were statistically significant (p = 0.004). Among patients who developed gallstones postoperatively, UDCA treatment was associated with a significantly lower cholecystectomy rate in patients with newly formed gallstones postoperatively (p = 0.025), while no significant difference was shown in patients with preoperative gallstones (p = 0.631).ConclusionUDCA is a promising option for reducing the need for cholecystectomy in patients with post-LSG gallstones, but it appears ineffective for pre-existing gallstones.
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    Search for new physics in the lepton plus missing transverse momentum final state in proton-proton collisions at √s=13 TeV
    (Springer, 2022) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; del Valle, A. Escalante
    A search for physics beyond the standard model (SM) in final states with an electron or muon and missing transverse momentum is presented. The analysis uses data from proton-proton collisions at a centre-of-mass energy of 13 TeV, collected with the CMS detector at the LHC in 2016-2018 and corresponding to an integrated luminosity of 138 fb(-1). No significant deviation from the SM prediction is observed. Model-independent limits are set on the production cross section of W' bosons decaying into lepton-plus-neutrino final states. Within the framework of the sequential standard model, with the combined results from the electron and muon decay channels a W' boson with mass less than 5.7 TeV is excluded at 95% confidence level. Results on a SM precision test, the determination of the oblique electroweak W parameter, are presented using LHC data for the first time. These results together with those from the direct W' resonance search are used to extend existing constraints on composite Higgs scenarios. This is the first experimental exclusion on compositeness parameters using results from LHC data other than Higgs boson measurements.
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    Free volume impact on ionic conductivity of PVdF/GO/PVP solid polymer electrolytes via positron annihilation approach
    (Elsevier Ltd, 2025) Yılmazoğlu, Mesut; Okkay, Hikmet; Abacı, Ufuk; Tekay, Emre; Çoban, Ozan; Veziroğlu, Sümeyye; Yumak Yahşi, Ayşe; Tav, Cumali; Yahşi, Uğur
    This study reports the effects of free volume (FV) profiles on the ionic conductivities of PVdF/GO/PVP ternary polymer electrolytes using positron annihilation lifetime spectroscopy (PALS). The electrolytes were characterized by various tests such as FTIR, XRD, TGA-DTG, SEM, contact angle and DMA. FV profiles were evaluated by o-Ps lifetime (τ₃), intensity (I3) and FV fractions (fυ). PVdF exhibits a proton conductivity of 2.1 × 10⁻5 S/m at 80 °C. However, the introduction of GO leads to a decrease in conductivity, with PVdF/GO showing 1.7 × 10⁻5 S/m at 80 °C. The presence of PVP in PVdF/GO/PVP10 and PVdF/GO/PVP30 creates new FV spaces via hydrogen bonds and intermolecular interactions, expanding hydrophobic areas and increasing I₃ values. PVP's high mobility and positive charge density reduce the τ₃ values. In contrast, I₃ and fυ values decrease in PVdF/GO/PVP50, accompanied by a significant drop in τ₃ values and the proton conductivity and dielectric constant peak at 6.1 × 10⁻2 S/m and 77.38, respectively. High PVP concentration may enhance interactions within the polymer matrix, forming a dense structure that, despite reduced FV, maintains or enhances proton mobility through alternative conduction pathways and increased polarization. This study emphasizes the balance of FV and dielectric behavior for efficient electrochemical processes.
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    Human side of strategic alliances, cooperations and manoeuvrings during recession and crisis
    (Springer, 2017) Uslu, Tuna
    Together with the globalizing economy, it is no more possible for any system to survive by ignoring the market changes and transformations. A change taking place anyhow in any place of the world triggers complex processes and affects everyone by growing in waves. Successful ways of business conduct of today is based on predicting the growth speed of these waves and on the ability to carry out strategic cooperations and manoeuvres accordingly. Sometimes these fluctuations also trigger serious crises. Apart from the shocks created in organizational structures, periods of crisis have complex effects on people. Some people approach to these events in hesitation, while other people or organizations happen to have skills to turn these processes into opportunity. The practical examples show that the organizations that adapt to new condition by getting simpler and getting rid of burdens in the constriction process are able to come out in a better condition before the crisis. This section discusses the way of organizations to become human oriented when acting strategically during strategic alliances, cooperations and manoeuvrings.
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    Geodesic path planning characteristics of the reconfigurable 1-S robot workspaces for hyperbolic, elliptical, and Euclidean geometries
    (Polska Akademia Nauk, 2024) Şahin, Haydar
    The path-planning strategies are implemented by establishing the Riemann curvature tensor and geodesic equations of the 1-S robot workspace. This paper’s originality lies in formulation of the parametric 1-S robot workspace for path planning, which is based on the differential geometry of the geodesic and Riemann curvature equations. The novel results in defining the path plan with diffeomorphic and expandable trajectories with zero and negative sectional curvatures are encouraging, as shown in the research article’s result sections. The constant negative, constant positive, and zero sectional curvatures produce hyperbolic, elliptical, and Euclidean geometries. The workspace equation, derived using Lie algebra, defines the parameters of u12, u3, and u4 to obtain the shortest distances in path planning. The geodesic equations determine the shortest distances in the context of Riemann curvature tensor equations. These parameters from the workspace equation (α1, α2, θ1, r1) are used in the geodesic and Riemann curvature tensor equations. The results show that one needs to choose the most convenient parameters of the mechanism for path-planning capabilities. Both the topology of the mechanism, which is 1-S herein and the parameters of the workspaces should be selected for the pre-defined trajectories of the path planning, as shown in the results. The reconfigurable robots have many mechanism topologies to transform.
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    K0S and Λ((Λ)over-bar) two-particle femtoscopic correlations in PbPb collisions at √sNN=5.02 TeV
    (Elsevier B.V., 2024) Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.; del Valle, A. Escalante
    Two-particle correlations are presented for KS0, [Formula presented], and [Formula presented] strange hadrons as a function of relative momentum in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The dataset corresponds to an integrated luminosity of 0.607nb−1 and was collected using the CMS detector at the CERN LHC. These correlations are sensitive to quantum statistics and to final-state interactions between the particles. The source size extracted from the KS0KS0 correlations is found to decrease from 4.6 to 1.6 fm in going from central to peripheral collisions. Strong interaction scattering parameters (i.e., scattering length and effective range) are determined from the [Formula presented] and [Formula presented] (including their charge conjugates) correlations using the Lednický–Lyuboshitz model and are compared to theoretical and other experimental results.
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    Distinctive delta and theta responses in deductive and probabilistic reasoning
    (Wiley, 2025) Sevim, Emir Faruk; Yıldırım, Yasin; Ünsal, Esra; Dalmızrak, Esra; Güntekin, Bahar
    IntroductionThe neural substrates of reasoning, a cognitive ability we use constantly in daily life, are still unclear. Reasoning can be divided into two types according to how the inference process works and the certainty of the conclusions. In deductive reasoning, certain conclusions are drawn from premises by applying the rules of logic. On the other hand, in probabilistic reasoning, possible conclusions are drawn by interpreting the semantic content of arguments.MethodsWe examined event-related oscillations associated with deductive and probabilistic reasoning. To better represent the natural use of reasoning, we adopted a design that required participants to choose what type of reasoning they would use. Twenty healthy participants judged the truth values of alternative conclusion propositions following two premises while the EEG was being recorded. We then analyzed event-related delta and theta power and phase-locking induced under two different conditions.ResultsWe found that the reaction time was shorter and the accuracy rate was higher in deductive reasoning than in probabilistic reasoning. High delta and theta power in the temporoparietal, parietal, and occipital regions of the brain were observed in deductive reasoning. As for the probabilistic reasoning, prolonged delta response in the right hemisphere and high frontal theta phase-locking were noted.ConclusionOur results suggest that the electrophysiological signatures of the two types of reasoning have distinct characteristics. There are significant differences in the delta and theta responses that are associated with deductive and probabilistic reasoning. Although our findings suggest that deductive and probabilistic reasoning have different neural substrates, consistent with most of the studies in the literature, there is not yet enough evidence to make a comprehensive claim on the subject. There is a need to diversify the growing literature on deductive and probabilistic reasoning with different methods and experimental paradigms.
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    The effectiveness of the 'my hands are clean program' based on the health promotion model conducted with virtual reality method
    (Marmara University, 2024) Yurt, Seher; Özdemir, Tuğba; Gür, Kamer; Çalık Tümerdem, Kevser Burcu
    Objective: Hand hygiene is very important as the hand is the organ that contains the most microorganisms. On the other hand, the school environment is an important environment for raising awareness of hand hygiene and acquiring handwashing behavior. This research was conducted to determine the effectiveness of the 'My Hands are Clean Program', which is carried out with the virtual reality method based on the health promotion model. Methods: This research is a quasi-experimental study with a pre-test and post-test model. The research population is 4th-8th grades in a school. Data were collected by socio-demographic characteristics form, hand hygiene observation form, and decision scale. Measurements were made before the training, after the training, the first follow-up after one month and the second follow-up after two months. Data were analyzed using IBM SPSS 26.0, Kolmogorov-Smirnov, Wilcoxon Test, Fridman Test, Mann Whitney U test, Kruskal Wallis test, and Bonferronicorrected pairwise comparisons in further analysis. The "TREND checklist" was used to report it. Results: The students got the highest score on the hand hygiene observation form at the first follow-up. It was determined that students' post-test, first follow-up and second follow-up mean scores were significantly higher than the pre-test mean scores. In Gpower Post hoc power analysis, the power of the study was determined to be 99%. Conslusion: It can be said that the use of technology-based methods in developing handwashing behavior, which will affect lifelong health, is effective for school-age students.
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    Investigation of residual stress variation in sequential butt welding and pocket material removal machining processes utilizing pre-stress method: a 3D simulation approach
    (Multidisciplinary Digital Publishing Institute (MDPI), 2024) Çetintav, Işık; Can, Yılmaz; Akkuş, Nihat
    This study investigates the residual stresses arising from welding and machining processes, recognizing their adverse implications in manufacturing. Employing experimental analysis and simulation techniques, the research scrutinizes residual stress alterations resulting from sequential butt welding and subsequent machining. Utilizing MSC Marc Mentat software(version 2016), three-dimensional models are developed to simulate these processes. The finite element model from welding simulation seamlessly integrates into cutting simulations via the pre-state option. The experimental procedures involve 100 × 100 × 10 mm AISI 304 steel plates subjected to sequential welding and machining, with residual stresses measured at each stage. A comparative analysis between experimental and simulation results elucidates variations in residual stresses induced by sequential processes. The study focuses on examining the initial stress state post-welding and numerically assessing stress modifications due to milling. The results suggest minimal material removal insignificantly affects stress distribution and magnitude at the weld centerline. However, increased material removal leads to noticeable changes in through-thickness transverse stress within the weld zone, contrasting with marginal alterations in through-thickness longitudinal stress. Regions distanced from the weld seam show substantial increases in through-thickness longitudinal stress compared to marginal changes in through-thickness transverse stress.
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    Chemical and vibrational criteria for identifying early sèvres factory porcelain productions
    (Multidisciplinary Digital Publishing Institute (MDPI), 2024) Colomban, Philippe; Şimşek Franci, Gülsu; Gerken, Mareike; Gironda, Michele; Mesqui, Viviane
    Thirteen porcelains assigned to Sèvres factory productions and a few references to the other contemporary factories (Chantilly, Limoges, and Venice) have been studied on-site with a portable X-ray fluorescence (pXRF) spectrometer in order to control the provenance attribution. Characteristic XRF signals of major elements (Si, Ca, K, Pb) and minor/trace (Au, Bi, As, Ti, Co, Cu, Zn, Ni, Y, Zr, Rb, and Sr) elements are compared for the paste, blue mark, various glazed (colored) areas, and gilding. The comparison of peak intensities clearly distinguishes different types of hard- and soft-paste porcelain, made from either similar or distinct raw materials. The analysis of transition elements associated with cobalt identifies three types of cobalt blue and reveals that du Barry-style decoration on certain artifacts was typical of 19th-century production. On-site comprehensive studies of the two famous Etruscan-style breast bowls from Rambouillet Castle dairy, using pXRF and Raman spectroscopy, confirm the use of soft-paste porcelain for the cup and hard-paste for its support, providing detailed information on the use of gold nanoparticles in the burgundy-colored decoration.
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    Non-enzymatic electrochemical sensor behaviors of polyaniline: silicene nanocomposite-a study on sensitive and selective sensor design against glucose
    (Electrochemical Society Inc., 2024) Baytemir, Gülsen; Akay, Özge; Konuk Ege, Gözde; Taşaltın, Nevin
    This study represents a non-enzymatic electrochemical sensor based on a Polyaniline: Silicene nanocomposite for the detection of glucose. A simple, clean and a low-cost sonication technique was used to prepare silicene nanosheets. XRD, FFT, SAED, HRTEM and FT-IR tecniques were used for characterization and CV for the detection of glucose. Current-voltage measurements were taken at various scanning rates (10-100 mV s-1). The active surface areas of PANI and PANI: Silicene nanocomposite based sensors were determined as 0.122 cm2 and 0.179 cm2, respectively. The nanocomposite material presented large peak currents, indicating that the nanocomposite elicited enhanced electrochemical activity with the presence of silicene for glucose detection in the concentration range of 0.75-12 mM. At a scan rate of 50 mV s-1, PANI-based sensor exhibited a sensitivity of 6.51 mu AmM-1 cm-2 with detection limit of 5.52 mu M, while the PANI: Silicene nanocomposite-based sensor exhibited a sensitivity of 20.93 mu AmM-1 cm-2 with 0.43 mu M detection limit. The selectivity of the sensors to measure glucose was also explored by characterizing their electrochemical performances in the presence of fructose and lactose. Due to these enhanced electrochemical performance, PANI: Silicene nanocomposite could be a promising biosensor material for glucose analysis for biomedical applications. A simple, clean and a low-cost sonication technique was used to prepare silicene nanosheetsPANI: Silicene nanocomposite material was prepared and used to modify the PANI electrode for use in the detection of glucose by cyclic voltammetry.The nanocomposite showed enhanced electrochemical activity with the presence of silicene.The electrochemical sensor made it possible to distinguish the glucose signal in the presence of coexisting substancesPANI: Silicene nanocomposite material validated glucose detection accuracy with a low detection limit, promising material in biomedical applications.
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    Speed of light in vacuum in the case of arbitrarily non-uniform motion of reference frames
    (IEEE, 2021) Yener, Namık
    Reference frames in arbitrary relative motion and with a coordinate transformation law are considered. It is shown that continuity of the time coordinate of one frame in the time coordinate of the other is a necessity for any physical coordinate transformation even if the velocity function for the relative motion of the reference frames is discontinuous in time. Then the differential Lorentz transform is used to infer an infinite speed of light in vacuum c, when the reference frames are in non-uniform relative motion. Based on the continuity of the time coordinate of one frame on the time coordinate of the other and on the integral representation of the differential Lorentz transform, a set of necessary and sufficient conditions is proved for the attainment of an infinite speed of light for reference frames in arbitrary relative motion. Using these conditions, it can be inferred that an initially finite c can be made infinite if and only if i) the reference frames are initially at rest and their motion, be it uniform rectilinear or arbitrarily non-uniform, starts with an initially discontinuous relative speed v'(x) in time or ii) the frames are in arbitrary motion which at t' = 0 undergoes a jump discontinuity in v'(x) with v'(x) not equal 0 at t' = 0+. After the infinite character of c is attained, c remains infinite regardless of whether the change in v'(x) is smooth or not, until the motion comes to a stop not to start again with another initial discontinuous v'(x). On the other hand, the differential Lorentz transform that holds in the immediate neighborhood of a fiducial observer, is only local and is therefore incapable of allowing drawing of global conclusions directly, such as the globally infinite c result of the paper. However, the proof that c is infinite locally can be generalized to hold for all space coordinates and for all future time, if one observes that unless the motion of the frames comes to a stop not to start again with a discontinuous v'(x) the infinite character of c does not change when immediate neighborhoods of particular observers are jointed to constitute the full space and future time.
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    Development of deep learning approaches for drought forecasting: a comparative study in a cold and semi-arid region
    (Springer Science and Business Media Deutschland GmbH, 2025) Gharehbaghi, Amin; Ghasemlounia, Redvan; Vaheddoost, Babak; Ahmadi, Farshad
    Drought is an intricate natural disaster that substantially menace the world. Its exact forecasting has a remarkable impact in several parts such as food production, business, industry, etc. In this study, in order to assess the drought procedure in Mahabad River basin, the temporal meteorological reconnaissance drought index (RDIMRB) in four diverse time scales including 3, 6, 9, and 12-month are computed using 576 monthly climatic datasets recorded from Sep 1974 to Aug 2022. To predict the time series RDIMRB, different standalone deep neural network (DNN) models including LSTM, GRU, Bi-directional LSTM (Bi-LSTM), and Bi-directional GRU (Bi-GRU) with the sequence-to-one regression module of forecasting (seq2one) are developed. For sake of this aim, the first 70% of data (395 months) and the last 30% of data (169 months) chronologically are used in the calibration and validation parts, respectively, to feed in the models development process. So as to achieve the most advantageous models’ structure, a lot of scenarios are adopted by tuning the meant meta-parameters including NHU (number of hidden units), SAF (state activation function), and P-rate (learning dropout rate). According to the performance assessment criteria, total learnable parameters (TLP) criterion, and comparison plots, the Bi-GRU model is verified as the most satisfactory model, and best results are obtained in RDIMRB-12. It under the epitome meant meta-parameters achieved (i.e., NHU = 120, P-rate = 0.5, and softsign as the suitable SAF) results in the RMSE, MBE, NSE, PBIAS, and R2 of 0.17, 0.011, 0.92, -2.02%, and 0.86, respectively, nonetheless for the GRU model are gotten 0.64, 0.071, 0.23, 17.97%, and 0.65, respectively.
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    Comparison of the mechanical properties and drilling performance of the AISI 316 parts produced with casting, LPBF and WAAM
    (Springer Science and Business Media Deutschland GmbH, 2024) Kocaman, Engin; Köklü, Uğur; Morkavuk, Sezer; Coşkun, Mert; Koçar, Oğuz; Dilibal, Savaş; Gürol, Uğur
    AISI 316 stainless steel parts are widely utilized in many industrial fields with a vast scope of applications. These steel parts, which are used in many fields, can be produced using different production methods, but the mechanical properties of the parts produced with different processes may be different, and the machinability characteristics will also be different. In this study, the drilling machinability characteristics of AISI 316 stainless steel parts manufactured via cast, LPBF and WAAM methods were experimentally investigated and compared considering thrust force generation, burr analysis and chip morphology. In order to clarify the differences in machinability behavior among the tested samples, the corresponding microstructure, microhardness and mechanical strength (yield strength, UTS and elongation) were also examined in detail. The experimental results showed the manufacturing method, and particularly cooling rate, significantly affecting the microstructure, mechanical response and further machinability characteristics; besides, due to higher cutting forces generation, the machinability of the parts produced by additive manufacturing methods (LPBF and WAAM) is more difficult compared to the parts produced by conventional manufacturing methods (cast and cast-HT).
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    Mechanical and ballistic performance of high-hardness armor steels welded with ASS-LHF sandwich joint design
    (Elsevier Ltd, 2025) Gürol, Uğur; Çelik, Ceren; Çoban, Ozan; Göçmen, Müesser; Koçak, Mustafa
    Armor steels are widely recognized for their exceptional mechanical and ballistic performance, particularly in the fabrication of armored vehicles. Austenitic stainless steel (ASS) wires are commonly used in their welding processes to mitigate hydrogen-induced cracking. However, joints formed using ASS often suffer from reduced ballistic performance due to the strength mismatch (undermatching) compared to the base material. This study explores the application of butt joints, integrating low hydrogen ferritic (LHF) deposits between softer ASS weld layers, which can be expressed as sandwich layer design, in gas metal arc welded (GMAW) armor steel plates. The mechanical properties were evaluated through hardness, tensile, and Charpy V-notch impact tests. Ballistics test performances were measured using depth of penetration (DoP) and width of penetration (WoP) values. The microstructural analysis utilized stereo, optical, and scanning electron microscopes. The results demonstrated that the sandwich joint configuration met the Charpy-V impact toughness requirements of the base metal, achieving 31.4 J and 65 J at −40 °C for the WM and HAZ regions, respectively, compared to 20 J for the base material. Moreover, this innovative joint design effectively combined the high toughness and ductility of austenitic wire, reaching a low DoP value of 7.2 mm, with the superior strength of ferritic filler metal, which contributes to a low WoP value of 12.5 mm and a joint efficiency of 48 %. By combining these properties, the joint design significantly enhances ballistic performance in welded regions, traditionally considered vulnerable to ballistic threats, without compromising overall mechanical integrity.
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    Effect of post-deposition heat treatments on high-temperature wear and corrosion behavior of Inconel 625
    (Elsevier Ltd, 2025) Kocaman, Engin; Gürol, Uğur; Günen, Ali; Çam, Gürel
    This study uses the arc-directed energy deposition method to fabricate and heat treatment of a Ni-based Inconel 625 wall structure. Heat treatment involved solution treatment at 980°C with and without aging at 720°C, comparing results to the as-built condition. The effects of these heat treatments were analyzed through microstructural investigations, nanoindentation tests, and high-temperature wear and corrosion tests in 0.5 M NaCl and 0.5 M HCl solutions. In the as-built state, the Inconel 625 alloy exhibited a columnar dendritic structure predominantly composed of a gamma matrix along with Laves phase and MC carbides. Solution treatment dissolved the Nb-rich Laves phases and encouraged the formation of needle-like particles in regions with high Nb segregation, while also reducing voids and minimizing corrosion susceptibility along grain boundaries. This resulted in the formation of a uniform oxide layer on the surface, significantly enhancing wear and corrosion resistance. Both heat-treated samples showed improvements in mechanical ratios such as H/E, H³/E², and H²/2E in the WAAM-produced Inconel 625 alloy, resulting in a 67 % enhancement in wear resistance compared to the as-built sample. Corrosion tests also revealed that solution treated samples showed the highest corrosion resistance, followed by aged treatment and as-built samples, respectively. In conclusion, this study provides a thorough understanding of the substantial impact of heat treatments on the microstructure, mechanical properties, and corrosion resistance of Inconel 625, offering valuable insights for advancements in the field.
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    Could DTI unlock the mystery of subjective tinnitus: it's time for parameters that go a little out of the routine
    (Springer, 2024) Yılmaz, Eren; Yıldırım, Düzgün; Tekcan Şanlı, Deniz Esin; Elpen, Pınar; Gösterişli Tüzüner, Filiz; Gökmen İnan, Neslihan; Şirin, Ahmet; Yağımlı, Mustafa; Tozan, Hakan; Şanlı, Ahmet Necati; Kandemirli, Sedat Giray
    In this study, it was aimed to assess the microstructural changes in the main central auditory pathway in cases with subjective tinnitus. In total, 101 subjects (52 cases with bilateral subjective non-pulsatile tinnitus and 49 healthy cases as the control group) were included in the study. Participants underwent pure tone audiogram and Diffusion Tensor Imaging-Magnetic Resonance Imaging (DTI-MRI) examination with a 3 Tesla MRI device. The number of tracts, tract length, volume, and quantitative anisotropy (QA) and normalized quantitative anisotropy' (nQA) values were calculated by plotting cochleocortical pathways from the cochlear nerve to ipsilateral and contralateral Heschl's gyrus (HG). In pure tone audiometry, the control group had lower hearing thresholds than cases with tinnitus. Fibres and nQA values from the right cochlear nerve to the right HG were significantly lower in the tinnitus group than in the control group. Cochlear nuclei voxel counts were significantly decreased in the tinnitus group. Both cochlear nucleus volumes were higher in the tinnitus group than in the control group. nQA values in both cochlear nuclei were decreased in the tinnitus group. This study showed that the most commonly affected part in subjective non-pulsatile tinnitus cases is the cochlear nucleus. Therefore, the cochlear nucleus should be evaluated more carefully in cases presenting with subjective tinnitus.