Mekatronik Mühendisliği Bölümü Yayın Koleksiyonu

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  • Article
    Citation - WoS: 4
    Citation - Scopus: 4
    String Stability Under Actuator Saturation on Straight Level Roads: Sufficient Conditions and Optimal Trajectory Generation
    (Ieee-inst Electrical Electronics Engineers inc, 2022) Bingol, Hilal; Schmidt, Klaus Werner
    The heterogeneity of vehicles is an important factor when realizing cooperative adaptive cruise control (CACC) in practice. Specifically, it has to be considered that platoons generally consist of vehicles with both different dynamic properties and actuator limits on the engine and braking force, which is expected to have a negative impact on important properties such as string stability. Accordingly, the subject of this paper is the preservation of string stability for CACC in heterogeneous vehicle strings with potential actuator saturation. To this end, the paper formulates a velocity-dependent force bound that enables the derivation of sufficient conditions for preserving string stability during velocity changes of heterogeneous platoons. These conditions are then used for the analytical computation of trajectories for time-optimal velocity changes. The formal results of the paper are supported by an illustrative simulation study.
  • Article
    New Model for Liquid-Based Rapid Prototyping With a Scanning Lorentz Beam
    (Elsevier Gmbh, 2021) Arpali, C. Caglar
    In this work, a new model is proposed to examine the effect of scanning Lorentz beam on a liquid based rapid prototyping scheme. The interaction of a Lorentz laser beam with a photocurable resin is analysed for different kinds of processing parameters such as beam power, beam size, scan speed, cure depth, width of the cured region and critical radiant exposure. The penetration depth profile of curing is obtained while the beam propagates inside the resin. It is shown that the proposed laser scanning model can be used to estimate the depth profile of the cured region that is treated for a certain amount of critical exposure. The Lorentzian beam generates fine and narrow hatch structures along the scan direction. This distinct ability facilitates the development of a low resolution process for fabricating complex patterns.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 6
    Multi-Objective Trajectory Planning for Slung-Load Quadrotor System
    (Ieee-inst Electrical Electronics Engineers inc, 2021) Ergezer, Halit
    In this article, multi-objective trajectory planning has been carried out for a quadrotor carrying a slung load. The goal is to obtain non-dominated solutions for path length, mission duration, and dissipated energy cost functions. These costs are optimized by imposing constraints on the slung-load quadrotor system's endpoints, borders, obstacles, and dynamical equations. The dynamic model of a slung-load quadrotor system is used in the Euler-Lagrange formulation. Although the differential flatness feature is mostly used in this system's trajectory planning, a fully dynamic model has been used in our study. A new multi-objective Genetic Algorithm has been developed to solve path planning, aiming to optimize trajectory length, mission time, and energy consumed during the mission. The solution process has a three-phase algorithm: Phase-1 is about randomly generating waypoints, Phase-2 is about constructing the initial non-dominated pool, and the final phase, Phase-3, is obtaining the solution. In addition to conventional genetic operators, simple genetic operators are proposed to improve the trajectories locally. Pareto Fronts have been obtained corresponding to exciting scenarios. The method has been tested, and results have been presented at the end. A comparison of the solutions obtained with MOGA operators and MOPSO over hypervolume values is also presented.
  • Article
    Citation - WoS: 51
    Citation - Scopus: 54
    Functionally Graded Hollow Cylinder Under Pressure and Thermal Loading: Effect of Material Parameters on Stress and Temperature Distributions
    (Pergamon-elsevier Science Ltd, 2018) Gulgec, Mufit; Evci, Celal
    This study presents an analytical solution of stresses and displacements in a long functionally graded (FGM) hollow cylinder subjected to uniform heat generation and internal pressure. Thermo-elastic material properties of FGM cylinder continuously vary in radial direction along the thickness with a power function. The temperature distribution is assumed to vary as a function of the radial coordinate and in steady state. Stress formulation approach is employed using the Airy stress function to derive the analytical solution. In the failure analysis of FGM cylinder, Coulomb-Mohr theory is applied for the ceramic phase whereas Tresca yield criterion is used for the metal phase. The stress analysis reveals that stresses in FGM cylinder decrease considerably, compared to the homogenous one, for a particular interval of material parameters. Radial displacement analysis in FGM cylinder supports the results obtained from stress analysis. (C) 2017 Elsevier Ltd. All rights reserved.
  • Article
    Citation - WoS: 102
    Robust Scheduling and Robustness Measures for the Discrete Time/Cost Trade-Off Problem
    (Elsevier Science Bv, 2010) Hazir, Oencue; Haouari, Mohamed; Erel, Erdal
    Projects are often subject to various sources of uncertainties that have a negative impact on activity durations and costs. Therefore, it is crucial to develop effective approaches to generate robust project schedules that are less vulnerable to disruptions caused by uncontrollable factors. In this paper, we investigate the robust discrete time/cost trade-off problem, which is a multi-mode project scheduling problem with important practical relevance. We introduce surrogate measures that aim at providing an accurate estimate of the schedule robustness. The pertinence of each proposed measure is assessed through computational experiments. Using the insights revealed by the computational study, we propose a two-stage robust scheduling algorithm. Finally, we provide evidence that the proposed approach can be extended to solve a complex robust problem with tardiness penalties and earliness revenues. (C) 2010 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 65
    Citation - Scopus: 67
    Robust Optimization Models for the Discrete Time/Cost Trade-Off Problem
    (Elsevier Science Bv, 2011) Hazir, Oncu; Erel, Erdal; Gunalay, Yavuz
    Developing models and algorithms to generate robust project schedules that are less sensitive to disturbances are essential in today's highly competitive uncertain project environments. This paper addresses robust scheduling in project environments; specifically, we address the discrete time/cost trade-off problem (DTCTP). We formulate the robust DTCTP with three alternative optimization models in which interval uncertainty is assumed for the unknown cost parameters. We develop exact and heuristic algorithms to solve these robust optimization models. Furthermore, we compare the schedules that have been generated with these models on the basis of schedule robustness. (C) 2010 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 8
    Citation - Scopus: 8
    Effects of the Information Presentation Format on Project Control
    (Taylor & Francis Ltd, 2011) Hazir, O.; Shtub, A.; Hazr, Ö.
    In this paper, we investigate the relationship between the information presentation format and project control. Furthermore, the effects of some system conditions, namely the number of projects to be controlled and the level of time pressure, on the quality of the project control decisions are analyzed. Information provided by Earned Value Analysis is used to monitor and control projects, and simulation is applied to replicate and model the uncertain project environments. Software is developed to generate random cost figures, to present the data in different visual forms and to collect users' responses. Having performed the experiments, the statistical significance of the results is tested. Journal of the Operational Research Society (2011) 62, 2157-2161. doi: 10.1057/jors.2011.11 Published online 2 March 2011
  • Article
    Citation - WoS: 32
    Citation - Scopus: 36
    Sers-Based Ultrafast and Sensitive Detection of Luteinizing Hormone in Human Serum Using a Passive Microchip
    (Elsevier Science Sa, 2018) Yildirim, Ender; Eryilmaz, Merve; Selbes, Yesim; Saglam, Necdet; Tamer, Ugur; Gjergjizi, Belma; Cogun, Ferah
    Human luteinizing hormone (LH) is an important analyte for doping control analysis since it increases the athletic performance. However, traditional methods to detect LH have few disadvantages, such as long analysis duration, waste disposal problem and sample matrix effect. Addressing these problems, surface enhanced Raman spectroscopy based LH analysis using a passive microfluidic chip was developed and optimized. Antibody modified magnetic gold nanoparticles captured the LH and then, 4-aminothiophenol (4-ATP) labeled nanoparticles formed the sandwich immunoassay structure. The complex and the other reactions occurred in different chambers of the chip. The SERS signals of 4-ATP were recorded from the chamber and the system was shown to detect 0.036 IU L-1 in serum samples. The performance of the immunoassay was compared to all other methods and the proposed assay was the fastest analysis of LH without any problems associated with the sensitivity. The shorter analysis time was recorded because the chip enables the control of all reactions in one place and there was no requirement of a specialized laboratory. (c) 2018 Elsevier B.V. All rights reserved.
  • Conference Object
    Citation - WoS: 21
    Citation - Scopus: 25
    Effect of Electrical Discharge Machining on Dental Y-Tzp Ceramic-Resin Bonding
    (Elsevier Ireland Ltd, 2017) Kucukturk, Gokhan; Gurun, Hakan; Cogun, Can; Esen, Ziya; Rona, Nergiz; Yenisey, Murat
    Purpose: The study determined (i) the effects of electrical discharge machining (EDM) on the shear-bond strength (SBS) of the bond between luting resin and zirconia ceramic and (ii) zirconia ceramic's flexural strength with the three-point bending (TPB) test. Methods: Sixty 4.8 mm x 4.8 mm x 3.2 mm zirconia specimens were fabricated and divided into four groups (n = 15): SBG: sandblasted + silane, TSCG: tribochemical silica coated + silane, LTG: Er:YAG laser treated + silane, EDMG: EDM + silane. The specimens were then bonded to a composite block with a dual-cure resin cement and thermal cycled (6000 times) prior to SBS testing. The SBS tests were performed in a universal testing machine. The SBS values were statistically analyzed using ANOVA and Tukey's test. To determine flexural strength, sixty zirconia specimens were prepared and assigned to the same groups (n = 15) mentioned earlier. After surface treatment TPB tests were performed in a universal testing machine (ISO 6872). The flexural strength values were statistically analyzed using ANOVA and Tukey's test (a = 0.05). Results: The bond strengths for the four test groups (mean SD; MPa) were as follows: SBG (Control), 12.73 +/- 3.41, TSCG, 14.99 +/- 3.14, LTG, 7.93 +/- 2.07, EDMG, 17.05 +/- 2.71. The bond strength of the EDMG was significantly higher than those of the SBG and LTG (p < 0.01). The average flexural strength values for the groups SBG (Control), TSCG, LTG and EDMG were 809.47, 800.47, 679.19 and 695.71 MPa, respectively (p > 0.05). Conclusions: The EDM process improved the SBS. In addition, there was no significant adverse effect of EDM on the flexural strength of zirconia. (C) 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.
  • Article
    Citation - WoS: 191
    Citation - Scopus: 228
    An Experimental Investigation on the Impact Response of Composite Materials
    (Pergamon-elsevier Science Ltd, 2012) Gulgec, Mufit; Evci, Celal
    Due to the improved impact performance characteristics, composites are widely used in engineering and military applications to absorb the impact energy. Determination of impact response of composite materials provides the engineer and the manufacturer with critical knowledge to understand the failure criteria, initiation of the first failure and damage growth through the laminates. This study covers the investigation of impact damage growth and determination of Hertzian failure and maximum force thresholds in three different types of composites. Unidirectional E-Glass, woven E-Glass and woven Aramid composite samples with dimensions of 100 x 100 mm are subjected to low velocity impact with an instrumented impact test system. Rebound, on-set of perforation and perforation limits of composites are found out. Also, energy profile diagrams of both unidirectional and plain weave E-Glass composites are obtained. According to test results, woven composites are found to be superior to unidirectional composites in the protection limit of low velocity impact. It is also observed that damage growth in woven composites is restricted within a smaller area. Impact tests conclude that strength of the composite materials under dynamic loading increases considerably compared to static loading case as a result of strain rate sensitivity. (C) 2011 Elsevier Ltd. All rights reserved.