142 research outputs found
The Diophantine equation revisited
No full textLet k,l >= 2 be fixed integers, and C be an effectively computable constant depending only on k and l. In this paper, we prove that all solutions of the equation (x + 1)(k) + (x + 2)(k) + ... + (lx)(k) = y(n) in integers x, y,n with x, y >= 1, n >= 2, k not equal 3 and l 1 (mod 2) satisfy max{x, y, n} < C. The case when is even has already been completed by the second author (see [24])
Experimental Evaluation and Machine Learning-Based Prediction of Laser Cutting Quality in FFF-Printed ABS Thermoplastics
No full textAdditive manufacturing, particularly Fused Filament Fabrication (FFF), provides notable advantages such as design flexibility and efficient material usage. However, components produced via FFF often exhibit suboptimal surface quality and dimensional inaccuracies. Acrylonitrile Butadiene Styrene (ABS), a widely used thermoplastic in FFF applications, commonly necessitates post-processing to enhance its surface finish and dimensional precision. This study investigates the effects of CO2 laser cutting on FFF-printed ABS plates, focusing on surface roughness, top and bottom kerf width, and bottom heat-affected zone. Forty-five experimental trials were conducted using different combinations of plate thickness, cutting speed, and laser power. Measurements were analysed statistically, and analysis of variance was applied to determine the significance of each parameter. To enhance prediction capabilities, seven machine learning models—comprising traditional (Linear Regression and Support Vector Regression), ensemble (Extreme Gradient Boosting and Random Forest), and deep learning algorithms (Long Short-Term Memory (LSTM), LSTM-Gated Recurrent Unit (LSTM-GRU), LSTM-Extreme Gradient Boosting (LSTM-XGBoost))—were developed and compared. Among these, the LSTM-GRU model achieved the highest predictive performance across all output metrics. Results show that cutting speed is the dominant factor affecting cutting quality, followed by laser power and thickness. The proposed experimental-computational approach enables accurate prediction of laser cutting outcomes, facilitating optimisation of post-processing strategies for 3D-printed ABS parts and contributing to improved precision and efficiency in polymer-based additive manufacturing
The validity and reliability of the Turkish version of the 6-item female sexual function index (FSFI-6) and the relationship between climacturia and female sexual dysfunction
No full text© 2021, The Author(s), under exclusive licence to Springer Nature Limited.This study aims to assess the validity and reliability of the Turkish version of the FSFI-6 questionnaire,an abbreviated version of FSFI-19,a common tool for evaluating female sexual function. The study included 120 female patients aged between 18–65 years who presented to the urology clinic between December 2019 and March 2020. The Turkish version of FSFI-6 was translated from the English version for validation. The abridged FSFI-6 questionnaire consists of questions 2, 4, 7, 11, 16, and 17 of the FSFI-19 form. We recorded the demographic data of the patients. All subjects filled out the FSFI-19 and FSFI-6 questionnaires. The patients were asked to fill out the questionnaires again after two weeks. The mean age of the subjects was 46.58 ± 9.89 years (28–63). The results of the reliability analysis indicated that the intraclass correlation coefficient of the total FSFI-6 score was 0.92 (weighted kappa coefficients of individual items, 0.868–0.975) and the Cronbach’s alpha was 0.862. The validity analysis indicated that the mean total FSFI-6 score was strongly correlated with the mean FSFI-19 score (p < 0.001, r = 0.997). In the test-retest analysis,the kappa coefficient was calculated as 0.891. The FSFI-19 and FSFI-6 scores of the patients with (n = 52) and without climacturia (n = 68) were compared, and it was observed that the scores of the patients with climacturia were significantly lower than those without climacturia (p < 0.001). The abbreviated FSFI-6 questionnaire is a valuable tool for screening women with FSD. It can be used more extensively due to being short and easy to apply. Our results approve the Turkish version of the questionnaire as a valid and reliable tool for evaluating FSD
INVESTIGATION OF THE EFFECTS OF PROCESS PARAMETERS ON MACHINING PERFORMANCE IN LASER CUTTING OF 3D-PRINTED PLA
No full textIn the current research, the influences of process parameters on surface roughness and kerf width in CO₂ laser cutting of PLA plates produced by the fused filament fabrication method were experimentally investigated. Laser cutting was performed using three plate thicknesses (2, 3, and 4 mm), three cutting speeds (3, 6, and 9 mm/s), and three laser power levels (90, 95, and 100 W). Surface roughness was determined with a surface roughness tester, and kerf widths were evaluated using a digital microscope. The findings indicate that higher cutting speeds and lower laser power lead to a reduction in both surface roughness and kerf width. Higher cutting speeds combined with lower laser power decreased the thermal effect during cutting by reducing the interaction between the laser and material, resulting in lower surface roughness and narrower kerf width. The effect of plate thickness on surface roughness and kerf width was complex, varying with cutting speed and laser power. The lowest surface roughness (0.951 µm) and kerf width (0.793 mm) values were achieved with a plate thickness of 3 mm, a cutting speed of 9 mm/s, and a laser power of 90 W. This study provides valuable insights into how laser cutting parameters affect the surface quality and dimensional accuracy of PLA plates, contributing to quality improvements in industrial applications. The results highlight the essential influence of cutting speed and laser power on managing surface roughness and kerf width, thus aiding in optimizing the process
Resilience in Individuals with Gender Dysphoria: Association with Perceived Social Support and Discrimination
No full textObjective: Psychological distress associated with discrimination is proposed to have an indirect effect on the development of mental disorders, through its negative influence on individual's cognitive, affective and social coping strategies. The aim of this study was to investigate the association between resilience, perceived social support, and perceived discrimination in individuals with gender dysphoria. Method: Individuals with gender dysphoria were assessed with Turkish validated forms of Resilience Scale for Adults (RSA), Multidimensional Scale of Perceived Social Support (MSPSS), Perceived Discrimination Scale (PDS), and Beck Depression Inventory (BDI). Diagnoses of mental disorders, history of suicide attempt and non-suicidal self injury were assessed with clinical interviews. Self-report forms were used to obtain demographic information and gender transition related features. Results: Participants' (n = 116, 88 trans men) median age was 25. Significantly low RSA scores, indicating poor resilience, were obtained in participants with lifetime (59.5 %) and present (27.6 %) diagnosis of any mental disorder, history of suicide attempt (23.3 %). There was significant direct correlation between RSA and MSPSS scores, inverse correlation with BDI and personal PDS scores, but not with group PDS. Regression analysis revealed that only friends domain score in MSPSS predicted better resilience, whereas personal perceived discrimination score predicted poor resilience. Conclusion: Findings support the association between poor resilience and vulnerability to mental and behavioral problems in individuals with gender dysphoria. The associations reveal the significance of addressing discrimination and assisting individuals with gender dysphoria in developing strategies to obtain peer support in providing mental health services.WoSScopusTr-Dizi
Multi-objective optimization of process parameters for laser cutting polyethylene using fuzzy AHP-based MCDM methods
No full textThis experimental study examines how cutting parameters influence surface roughness (Ra), kerf width (KW), heat-affected zone (HAZ), and material removal rate (MRR) during CO2 laser cutting of polyethylene (PE) material. The aim is to determine the optimal cutting conditions by integrating fuzzy analytic hierarchy process (AHP) and multi-criteria decision-making (MCDM) methods. Control factors (i.e. focal length, power, and cutting speed) were varied in a full factorial experimental design. Criterion weights for the responses were calculated with the help of the AHP method in fuzzy environment, resulting in weights of 0.442 for Ra, 0.102 for KW, 0.287 for HAZ, and 0.169 for MRR. These weights were integrated into MCDM methods (i.e. combined compromise solution [CoCoSo], technique for order preference by similarity to ideal solution [TOPSIS], and Vlsekriterijumska Optimizacija I Kompromisno Resenje [VIKOR]) to rank the experiments and identify the optimal parameters. The optimal cutting condition was found to be a focal length of 8 mm, power of 90 W, and cutting speed of 12 mm/s. Spearman's rank correlation coefficients were applied for analysis of the consistency among the hybrid approaches, with results indicating a very strong positive relationship between them. This comprehensive approach ensures precise and efficient laser cutting of PE, contributing valuable insights to the field of manufacturing and materials processing
PREDICTION OF SURFACE HARDNESS IN A BURNISHING PROCESS USING TAGUCHI METHOD, FUZZY LOGIC MODEL AND REGRESSION ANALYSIS
No full textThe available work is aimed for comparison and estimation of surface hardness in ball burnishing process of aluminum alloy based upon the Taguchi technique, Fuzzy logic and regression models. The ball burnishing parameters like burnishing speed, force, feed rate and number of passes were designed using Taguchi L-25 orthogonal design matrix. Taguchi's signal to noise ratio was used to optimize the surface hardness. The effect of burnishing parameters on surface hardness was established by analysis of variance. Fuzzy logic was conducted using Matlab Toolbox. Taguchi technique, second order regression model and variance analysis were developed using MINITAB 17. The predicted hardness values of performance parameters were operated to compare the distinct models. The results of predicted models indicated that the consistent predictive model is the fuzzy logic model. With high correlation coefficient (R-2 = 97.52 %), the model was regarded adequately accurate
Laser micro-polishing of stainless steel for antibacterial surface applications
No full textIn this work laser micro polishing (LMP) of cold rolled 0.3 mm thick 304 stainless steel with a pulsed fibre laser is studied, for applications
where antibacterial properties are required. Due to its production method, the initial surface roughness of the tested material was considerably
low (Sa=85.3±2.8 μm), rendering a demanding case for the laser polishing process. Accordingly, process feasibility under three different
atmospheric conditions, namely ambient, Ar and N2 atmosphere, was investigated. A large set of process parameter combinations was tested
and initial analysis was carried out to identify the polishing feasibility by inspection under an optical microscope. Once the feasibility window
was determined, a primary characterization was made on selected surfaces for roughness and waviness. Results show that in some process
conditions belonging to the explored feasibility range, surface roughness could be decreased by 50%
SamenMarkt®, a Proposal for Restoring Trust in the Horticultural Fresh Food Market by Using Multi-agent System Technology
No full textIn the horticultural fresh food supply chain network in the Netherlands, a crisis is emerging. The market is out of balance and many growers are facing bankruptcy, in the period of 2011–2013, 50% of the growers were not able to pay interest and redemption. Trust between participants in the supply chain network has decreased. This chapter presents the currently not established and identiies design requirements for new systems to address this challengeand provide directions for possible improvement. As a result, this chapter introduces the concept of SamenMarkt®, a participatory system in which multi-agent system technology enables distributed price negotiation, distribution and communication between producers, retailers and consumers. A SWOT analysis of the concept of SamenMarkt® is provided together with a research and development plan in which simulation and emulation create the basis for stakeholder- and participant involvement in the design process of a distributeddigital market place. Further research aims to study how SamenMarkt® can provide a solution space for the emerging global food crises. At present, we are using agent-based modelling to simulate the present market and scenarios. The next step will be to build the actual agent-based platform for real-time negotiations and business intelligence
Hand-held spectrophotometer design for textile fabrics
No full textIn this study, a hand-held spectrophotometer was designed by taking advantage of the developments in modern optoelectronic technology. Spectrophotometer devices are used to determine the color information from the optic properties of the materials. As an alternative to a desktop spectrophotometer device we have implemented, it is the first prototype, low cost and portable. The prototype model designed for the textile industry can detect the color tone of any fabric. The prototype model consists of optic sensor, processor, display floors. According to the color applied on the optic sensor, it produces special frequency information on its output at that color value. In Arduino type processor, the frequency information is evaluated by the program we have written and the color tone information between 0-255 ton is decided and displayed on the screen
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