Browsing by Publisher "World Scientific"
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Item Renormalization of the γ-ray strength functions of light nuclei(World Scientific, 2015) Canbula B.; Erşan S.; Babacan H.γ-ray strength function is the key input for the photonuclear reactions, which have a special astrophysical importance, and should be renormalized by using the nuclear level density for calculating the theoretical average radiative capture width, but performing such renormalization is challenging for light nuclei. With this motivation, recently introduced level density parameter formula including collective effects is used to calculate the average radiative capture width of light nuclei, and therefore to renormalize their γ-ray strength functions. Obtained normalization factors are tested in (n, γ) reactions for the necessity of renormalization for light nuclei. © 2015 World Scientific Publishing Company.Item On the kinematic interpretation of timelike ruled surfaces(World Scientific, 2015) Önder M.; Ekinci Z.Timelike ruled surfaces are studied in dual Lorentzian space D-13 by considering E. Study Mapping and Blaschke frame. A reference timelike ruled surface is considered and associated surfaces are defined. First, it is shown that the surface generated by the instantaneous screw axis (ISA) is a Mannheim offset of reference surface. Later, the kinematic interpretations between these surfaces are introduced by means of Blaschke invariants. © 2015 World Scientific Publishing Company.Item A Novel Floating/Grounded Meminductor Emulator(World Scientific, 2020) Sozen H.; Cam U.Meminductor is a nonlinear two-Terminal element with storage energy and memory ability. To date, meminductor element is not available commercially as memristor and memcapacitor are. Therefore, it is of great significance to implement a meminductor emulator for breadboard experiment. In this paper, a flux-controlled floating/grounded meminductor emulator without a memristor is presented. It is built with commercially available off-The-shelf electronic devices. It consists of single operational transconductance amplifier (OTA), single multiplier, two second-generation current conveyors (CCIIs), single current-feedback operational amplifier (CFOA) and single operational amplifier. Using OTA device introduces an additional control parameter besides frequency and amplitude values of applied voltage to control the area of pinched hysteresis loop of meminductor. Mathematical model of proposed emulator circuit is given to describe the behavior of meminductor circuit. The breadboard experiment is performed using CA3080, AD844, AD633J and LM741 for OTA, CCII-CFOA, multiplier and operational amplifier, respectively. Simulation and experimental test results are given to verify the theoretical analyses. Frequency-dependent pinched hysteresis loop is maintained up to 5 kHz. The presented meminductor emulator tends to work as ordinary inductor for higher frequencies. © 2020 World Scientific Publishing Company.Item Evaluation of Screwing Configurations in Conventional Plating of Femoral Shaft Fractures Using Finite Element Analysis(World Scientific, 2021) Öztepe B.; Gök K.; Erdoǧan Y.; Inal S.; Gok A.Several fractures that occur in the human body depend on trauma or as a result of hormonal and bone fatigue. Fracture types that take place out of the neck area of the femoral bone are named femoral shaft fractures. Femoral shaft fractures are frequent conditions in orthopedics. Conventional plating method is a method that necessitates the fixation of the contact surface by contacting the epiphyses used in the treatment of such fractures. This method is known to be efficent in speeding up the healing process by reducing the movement between the epiphyses. In this study, femur models which are plated in various forms with fractures were analyzed with computer-aided finite element software and stresses on bone surfaces and fracture surfaces were determined. It is aimed to determine the best result by examining the relationship between the inputs such as the number of screws used during plating, the fixation area and material selection and the outputs obtained by finding the stresses on the bone surface and stresses on the broken surfaces. © 2021 World Scientific Publishing Company.Item Nonlinear Vibration Movements of the Mid-Supported Micro-Beam(World Scientific, 2022) Akkoca S.; Baǧdatli S.M.; Kara Toǧun N.This study analyzes the vibration movements of multi-support micro beams placed in an electrically smooth area using the modified couple stress theory. It has been assumed that the potential voltage that creates the electrical field strength varies harmonically. Large number of experiments in recent years have indicated that classical continuum theory is unable to predict the mechanical behavior of microstructure with small size. However, nonclassical continuum theory should be used to accurately design and analyze the microstructures. Modified couple stress theory models the micro and nanomechanical systems with higher accuracy because they employ additional material parameters to the equation considering size dependent behavior. The most general nonlinear motion equations for multi-support microbeams have been obtained by considering the material size parameter, the number of support and support positions, damping effect, axial stresses, electrical field strength, and nonlinear effects resulting from elongations. The nonlinear equations of motion are obtained according to the Hamilton method using the modified couple stress theory (MCST). The resulting equations of motion are nondimensionalized. In this way, the mathematical model has been made independent of the type and geometric structure of the material. Approximate solutions of the obtained dimensionless motion equation are obtained by the multi-scale method, which is one of the perturbation methods. As a result, an increase occurs in the first mode frequencies (ω1) and nonlinear correction effect parameters (λ(ω1)) with the progress of the center support position gradually towards η=0.5 and the increase of the microbeam elasticity coefficient (α2). © 2022 World Scientific Publishing Company.Item EXPERIMENTAL ASSESSMENT and TOPSIS OPTIMIZATION of CUTTING FORCE, SURFACE ROUGHNESS, and SOUND INTENSITY in HARD TURNING of AISI 52100 STEEL(World Scientific, 2022) Rafighi M.; Özdemir M.; Şahinoǧlu A.; Kumar R.; Das S.R.In this work, initially, the raw AISI 52100 bearing steel was heat-treated to obtain 40 HRC and 45 HRC workpiece hardness. Further, dry hard turning tests were carried out to study the impact of workpiece hardness (H), cutting speed (v), feed (f), and depth of cut (a) on cutting force (Fy), surface roughness (Ra), and sound intensity (SI). An economically viable PVD-coated carbide turning tool was implemented for the experiments. The Taguchi L18 (2-3 mixed level) design of experiments was employed to establish the experimental plan in order to save the experimental time, energy, and cost of manufacturing. The results disclosed that the feed has the prevailing consequence on surface roughness with a 96.3% contribution, while it also significantly affects the cutting force with a contribution of 13.8%. The contribution of cutting speed and workpiece hardness on the cutting force was reported as 48.3% and 35.1%, respectively. Higher workpiece hardness required more energy for plastic deformation as a result the cutting force increases with leading hardness. The sound intensity was dominantly influenced by depth of cut (53.3%) and cutting speed (40%). Finally, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was performed to determine the optimum machining parameters. According to the TOPSIS, the optimum level of cutting parameters was predicted as 40 HRC hardness (H), 150m/min cutting speed (V), 0.15mm/rev feed (f), and 0.1mm depth of cut (a) while the optimal result of Fy, SI, and Ra were noted as 27.66N, 70.7dB, and 0.86μm individually. © 2022 World Scientific Publishing Company.Item INVESTIGATIONS on the MECHANICAL ALLOYING PROPERTIES of AL 2024 ALLOY by THREE-DIMENSIONAL BALL MILL(World Scientific, 2022) Soy G.; Korucu S.Aluminum-based composite materials are frequently preferred in many new-generation engineering applications due to their high strength, wear and corrosion resistance, improvement of mechanical properties, machinability, and low density. Mechanical alloying has an important place in the production of composites with high properties in powder metallurgy, which is one of the composite material production methods. In this paper, the deformation of Al 2024 alloy powder, which is frequently used in the industry, is investigated by the three-dimensional ball mill. Three different rotation speeds (150, 200 and 250rev/min), three different ball-to-powder ratio (5:1, 10:1 and 20:1) and three different milling times (30, 60 and 90min) were used in the milling processes. Deformations in the powders were evaluated by particle size analysis and powder structure examination. The obtained results were analyzed with analysis of variance and regression method, three-dimensional graphics, and scanning electron microscope images. When the results are examined, the maximum percent areas covered by the deformed particles and maximum particle size among the selected experimental parameters were obtained at 250rev/min, 20:1 ball-to-powder ratio and 60min as 6.849% and 54μm. © 2022 World Scientific Publishing Company.Item COMPARISON OF THE SUCCESS OF META-HEURISTIC ALGORITHMS IN TOOL PATH PLANNING OF COMPUTER NUMERICAL CONTROL MACHINE(World Scientific, 2022) Çaşka S.; Gök K.; Gök A.Carrying out an engineering process with the least cost and within the shortest time is the basic purpose in many fields of industry. In Computer Numerical Control (CNC) machining, performing a process by following a certain order reduces cost and time of the process. In the literature, there are research works involving varying methods that aim to minimize the length of the CNC machine tool path. In this study, the trajectory that the CNC machine tool follows while drilling holes on a plate was discussed within the Travelling Salesman Problem (TSP). Genetic Algorithms (GA), Particle Swarm Optimization (PSO), and Grey Wolf Optimizer (GWO) methods were used to solve TSP. The case that the shortest tool path was obtained was determined by changing population size parameter in GA, PSO, and GWO methods. The results were presented in tables. © 2022 World Scientific Publishing Company.Item New Numerical Iteration Schemes Based on Perturbation Iteration Algorithms(World Scientific, 2024) Pakdemirli M.Perturbation-Iteration algorithms (PIA) have been developed recently to solve differential equations analytically. A continuous solution in terms of closed form functions as an approximation of the original equation can be found using the method. The method has been implemented to algebraic equations, ordinary and partial differential equations successfully. Based on the formalism developed previously, in this work, purely numerical versions of the perturbation-iteration algorithms are proposed for the first time for first-order nonlinear ordinary differential equations. The new algorithms are called as the Numerical Perturbation-Iteration Algorithms (NPIA) to distinguish them from the continuous analytical ones (PIA) and the method in general will be called the Numerical Perturbation-Iteration Method (NPIM). Iteration schemes based on one correction term in the perturbation solution and first-order derivatives in the Taylor series expansions (NPIA(1,1)), and one correction term in the perturbations and second-order derivatives in the series expansions (NPIA(1,2)) are derived. The numerical results are compared with the exact solutions and a very good match is observed. NPIA(1,2) produced slightly better results compared to NPIA(1,1) with total errors being at least O(h2), h being the step size for both methods. An improvement suggestion for NPIA(1,1) is proposed in the last section to eliminate unrealistic blow-up solutions which are encountered for some specific equations. © 2024 World Scientific Publishing Company.Item THE ROLE OF FINANCIAL DEVELOPMENT ON THE SHARE OF RENEWABLE ENERGY IN JAPAN: A COMPREHENSIVE TIME-SERIES ANALYSIS(World Scientific, 2024) Gök A.; Demir C.The purpose of this study is to analyze the effect of financial development (FD) on the share of renewable energy (RE) usage in Japan. The existing theoretical literature and empirical analyses covering different country cases reveal that FD might have positive, negative, or insignificant effect on RE use. Since there is no empirical investigation of the issue for Japan, the study aims to contribute to the literature. To that end, we used several time-series techniques to detect the association between RE usage and FD in Japan over the 1970-2020 period. The results obtained from the ARDL, Hatemi-J, Maki, Tsong et al. and NARDL cointegration tests showed that there is a significant cointegrated relationship between the share of RE use, FD, GDP per capita and trade openness. As for the long-run coefficients obtained from the ARDL, FMOLS, CCR and NARDL estimators revealed that increases in FD and trade openness raise the share of RE usage while increases in GDP per capita reduce it. Briefly, for the Japan case, we may suggest that improving the financial market structure of the country will bear fruit in terms of the share of cleaner and sustainable energy usage. © 2024 World Scientific Publishing Company.Item GJO-MLP: A NOVEL METHOD FOR HYBRID METAHEURISTICS MULTI-LAYER PERCEPTRON AND A NEW APPROACH FOR PREDICTION OF WEAR LOSS OF AZ91D MAGNESIUM ALLOY WORN AT DRY, OIL, AND h-BN NANOADDITIVE OIL(World Scientific, 2024) Altay O.; Gurgenc T.In this study, the AZ91D magnesium alloy was worn at different wear conditions (dry, oil, and h-BN nanoadditive oil), loads (10–60 N), sliding speeds (50–150 mm/s) and sliding distances (100–1000 m). Wear losses increased with the increase of applied load, sliding speed, and sliding distance. Wear losses were decreased in the h-BN nanoadditive oil conditions. For the first time, the wear losses were predicted using the hybrid golden jackal optimizer-multi-layer perceptron (GJO-MLP) method proposed in this study, using the experimentally obtained data. In addition, the performance of the proposed method was compared with the whale optimization-MLP (WOA-MLP), genetic algorithm-MLP (GA-MLP) and ant lion optimization-MLP (ALO-MLP) methods, which are widely used in the literature. The results showed that GJO-MLP outperformed other methods with a performance of 0.9784 in R2 value. © World Scientific Publishing Company.