Scopus İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395

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Now showing 1 - 10 of 31
  • Conference Object
    Symmetric Electret-Based Vibration Energy Harvesters With Curved-Beam Hinges
    (IEEE, 2023-05-28) Hah, Dooyoung
    Broadband power spectral characteristics are desirable in vibration energy harvesters, and it can be achieved by employing curved-beam hinges, which exhibit force-displacement nonlinearity. Via numerical analysis by using stochastic differential equations and colored-noise inputs, this study shows that a symmetric configuration of the curved-beam hinges in electret-based harvesters can produce higher (up to 8% more) power outputs than an asymmetric one. It also presents that the harvesters with curved-beam hinges can produce higher (up to 4.4 times) power outputs than those with straight hinges when the vibration magnitude is 0.05g.
  • Conference Object
    Structural Integrity Analysis of a Two-Pole Synchronous Reluctance Machine With Non-Circular Shaft
    (IEEE, 2023-06-14) Tekgun, Didem; Tekgun, Burak; Alan, Irfan
    This paper investigates the structural strength of a 6-inch diameter, two-pole, 4 kW line start synchronous reluctance machine (LS-SynRM) designed with a new non-circular shaft structure that serves as a pump motor. Flux paths on the rotor are widened while narrowing down the shaft of the motor on the q- axis to improve the motor efficiency. By using this method, a wider path is created for the flux in the d-axis. As a result, the inductance in the d-axis, the ratio of inductance between the d-axis and q-axis (referred to as saliency ratio), and the difference in inductance between the d-axis and q-axis are all amplified. To evaluate the structural strength of the machine, a series of analyses are conducted, including modal, harmonic, and static examination on the rotor using ANSYS Structural. The findings indicate that to prevent redundant deformations and undesirable vibrations because of resonance, the maximum safe limit for shaft size reduction is determined as 8 mm.
  • Conference Object
    Citation - WoS: 3
    Citation - Scopus: 6
    Single and Double Side Comb-Shaped Patch Antenna Design Evolved From Rectangular Shape for Reduced Sized Antenna Applications
    (IEEE, 2020-11-18) Baydar, Huseyin; Aslan, Melih; Kilic, Veli Tayfun
    This paper reports single and double side comb-shaped patch antennas to be used in reduced-sized antenna applications. The proposed antenna designs are evolved from regular rectangular shape antennas. The designed single and double side comb-shaped antennas were investigated in a complete set of study together with the rectangular shape antenna that resonates at 5 GHz frequency. Reflection coefficient (S-11) parameter of the designed comb-shaped antennas and the rectangular antenna were calculated together with three-dimensional (3D) directivity patterns in simulations for different arm lengths, arm widths, and arm numbers of the comb-shaped antennas. Results show that with the comb-shaped antennas it is possible to shift the resonance frequency of a regular rectangular shape antenna to a frequency lower than its half without enlarging the foot-print area or with the smaller foot-print area. Also, resonance frequency change and peak directivity variations at resonance frequencies of the antennas with geometrical parameters of the antennas were calculated, too. The findings indicate that due to the large number of geometrical parameters that come with the nature of the comb shape, comb-shaped antennas provide more flexibility while constructing an antenna.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 1
    Sensorless Position and Speed Control of IPMSM With Sliding Mode Observer and Voltage Signal Injection
    (IEEE, 2021) Ates, Ertugrul; Tekgun, Burak; Ablay, Gunyaz
    A sensorless control approach based on a sliding mode observer for predicting the rotor position and speed is studied in this work. For predicting the motor speed and position, the sliding mode observer followed by a phase locked loop is formulated by means of the back EMF model. The voltage signal injection method is utilized for accurate estimation in zero or low speed region. Numerical simulation results are provided for an 8-pole IPMSM, which shows that the motor speed and position in zero or low-speed region are accurately estimated with the designed observer and voltage signal injection approach.
  • Conference Object
    Citation - WoS: 11
    Citation - Scopus: 20
    ROI Detection in Mammogram Images Using Wavelet-Based Haralick and Hog Features
    (IEEE, 2018-12) Tasdemir, Sena Busra Yengec; Tasdemir, Kasim; Aydin, Zafer; Yengec Tasdemir, Sena Busra
    Digital mammography is a widespread medical imaging technique that is used for early detection and diagnosis of breast cancer. Detecting the region of interest (ROI) helps to locate the abnormal areas, which may be analyzed further by a radiologist or a CAD system. In this paper, a new classification method is proposed for ROI detection in mammography images. Features are extracted using Wavelet transform, Haralick and HOG descriptors. To reduce the number of dimensions and eliminate irrelevant features, a wrapper-based feature selection method is implemented. Several feature extraction methods and machine learning classifiers are compared by performing a leave-one-image-out cross-validation experiment on a difficult dataset. The proposed feature extraction method provides the best accuracy of 87.5% and the second-best area under curve (AUC) score of 84% when employed in a random forest classifier.
  • Conference Object
    Citation - Scopus: 1
    PCB Component Recognition With Semi-Supervised Image Clustering
    (IEEE, 2021-06-09) Unal, Ahmet Emin; Tasdemir, Kasim; Bahcebasi, Akif
    Classification of surface mounted devices plays an important role on automated inspection systems of printed component board production. Limited number of publicly available datasets which the components are labeled and high intraclass variance in these datasets causes the supervised approches to be inefficient. In this study a deep learning method, enhanced with an unsupervised clustering system, which uses a small set of labeled data is proposed. The method compared with the current studies and the supervised systems. Most optimized setting reached high accuracy results by outrunning current classification methods.
  • Conference Object
    Citation - Scopus: 1
    Optimal Target Capture and Station Keeping Control of Mobile Agents Without Global Position Information
    (IEEE, 2023-06-13) Mostafa, Ahmed Fahim; Fidan, Baris; Guler, Samet
    The target capture problem, i.e., the problem of reaching a target zone, by a mobile robotic agent that cannot sense its own global position requires reactive motion control algorithms based on onboard sensor data. Although the existing solutions to the target capture problem provide robust convergence guarantees, they do not address the mobile agent's path and motion optimality. We address the agent path and motion optimality in target capture control and its extension to station keeping, i.e., steering the agent to a location that is pre-defined with respect to a set of beacons, in global positioning system (GPS)-denied environments. We formulate optimal control problems aiming to minimize the agent-target distance for target capture, and the difference of desired and actual agent-station distances for station keeping. We design and analyze a linear quadratic optimal control scheme involving a Luenberger observer based state estimator, for each of the target capture and station keeping problems. The proposed schemes outperform the previous approaches in numerical simulations in terms of agent path length and smoothness.
  • Conference Object
    Citation - WoS: 5
    Citation - Scopus: 5
    Investigation of the Effects of Multi-Layer Winding Structures in Two Pole Synchronous Reluctance Machines
    (IEEE, 2021-10-05) Tekgun, Didem; Cosdu, Muhammed Muhsin; Tekgun, Burak; Alan, Irfan; Muhsin Cosdu, Muhammed
    In this paper, a comparative study is performed between single, various double, and triple-layer winding structures to investigate the effects of the winding MMF harmonics and end winding length on the two-pole synchronous reluctance machines (SynRM). A two-step design approach is used including winding and geometry optimization using multi-objective differential evolution (MODE) algorithm. In the first stage, a Pareto front is obtained which determines the number of turns for each coil group for all winding configurations. Later in the second stage, three results are selected from the first stage to perform a geometric optimization to distinguish the effects of the THD and end winding length on the synchronous performance of a 4 kW two-pole SynRM. For the same average torque output, efficiency, mass, and the torque ripple of the selected designs are investigated and compared. Based on the analysis, it is concluded that rather than focusing on shortening the end winding length, reducing the MMF harmonics have a more positive effect on the machine performance as reduced harmonics resulted in efficiency improvement up to 2 points and torque ripple is reduced up to 8 points while having similar motor mass.
  • Conference Object
    Integral-Equation Study of Ray Effects and Natural-Mode Resonances in a 2-D Dielectric Prism
    (IEEE, 2015) Sukharevsky, Ilya O.; Altintas, Ayhan
    We analyze the interplay of two different types of electromagnetic behavior demonstrated by a 2-D dielectric prism: Geometrical Optics and resonance. As it is shown, the first is responsible, for instance, for enhanced reflection from an isosceles 90-degree prism of arbitrary epsilon and size, if illuminated from the base. The second is responsible for the peaks in the total scattering and absorption cross-sections (RCS) at the natural-mode frequencies. The numerical model is based on Nystrom discretization of Muller-type integral equations that provides guarantied convergence.
  • Conference Object
    Graph-Based Biomedical Knowledge Discovery
    (IEEE, 2024-05-15) Altuner, Osman; Bakir-Gungor, Burcu; Bakal, Gokhan
    The digitalization process is progressing at a very high speed all over the world. While this situation provides many conveniences in today's life, it also brings along a problem such as analyzing and processing the huge digital data. This also applies to published academic studies. In this sense, the process of evaluating each study to access previously unknown information within the studies requires a very laborious process. For this reason, in this study, the publications obtained for the target diseases were analyzed by text analysis processes and converted into a graph structure that enables the linking of meaningful terms through biomedical relationships. On the dense graph structure obtained, binary biomedical entities with important links such as treats, causes, associated_with were queried. The entity pairs obtained according to the query results were also confirmed by manual search method and proved to be real connections. In this study, retrieval of known biomedical entities with the proposed approach solved the time-consuming manual search problem. There is also the potential to obtain unknown/unexplored possible new relationships (e.g., therapeutic, causal, etc.) with multiple binary linking patterns.