WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7150

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  • Conference Object
    Speckle Intensity Correlation Distribution Analysis Based on Coincidence Detection for Scattering Medium Characterization
    (IEEE, 2025) Yoldas, Cansu; Kisa, Alperen; Atac, Enes; Karatay, Anil; Dinleyici, Mehmet Salih
    Characterizing a scattering medium is essential for understanding and controlling light propagation, enabling accurate imaging, correlation analysis, and material diagnostics in scientific applications. In this study, the scattering medium has been characterized by examining the spatial distribution of the second-order temporal correlation function of varying speckle patterns obtained under faint-light conditions using a charge-coupled device (CCD) camera. In the proposed method, the exposure time has been utilized as a self-coincidence circuit of the CCD. The spatial statistics of second-order temporal autocorrelation values have been analyzed through power spectral density and radial spatial autocorrelation function. The scattering degree of the medium has been determined using our proposed autocorrelation-based metric. The results from three different media have shown that the method is effective and holds potential for applications such as characterization through speckle imaging.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 1
    Çelik Fiber Katkısının Farklı Boyuna Donatı Oranına Sahip Betonarme Döşemelerin Zımbalama Davranışı Üzerinde Etkileri
    (2019) Saatci, Selcuk; Yasayanlar, Suleyman; Yasayanlar, Yonca; Batarlar, Baturay
    Sunulan çalışmada her iki yönde birbirine dik 0,004 (D1 serisi) ve 0,002 (D2 serisi) oranında boyuna donatıiçeren 2150x2150x150 mm boyutlarında iki grup betonarme döşeme, hacimce %0, %0,5, %1 ve %1,5oranında çelik fiber katkısı içeren beton karışımlarıyla dökülmüştür. Üretilen toplam sekiz döşeme ortanoktalarından statik yük altında test edilmişlerdir. Çelik fiber katkısı olmayan numunelerde yüksek boyunadonatı oranına sahip döşeme boyuna donatısında akma gerçekleşmeden gevrek bir şekilde zımbalamagöçmesi oluşurken düşük boyuna donatı oranına sahip döşeme zımbalama gerçekleşmeden önce çok dahasünek bir davranış göstermiştir. Çelik fiber katkısı her iki boyuna donatı oranında da iki kata varan oranlardazımbalama dayanımı artışlarına sebep olmuştur. Ancak D1 serisi döşemelerde çelik fiber katkısı maksimumyer değiştirmeleri önemli ölçüde arttırırken D2 serisinde maksimum yer değiştirmelerde önemli bir farkoluşmamış, bu döşemelerin yer değiştirmesi boyuna donatının akması tarafından kontrol edilmiştir. Çelikfiber katkısı oranının arttırılması D1 serisi döşemelerde dayanımın ve maksimum yer değiştirmelerinartmasına sebep olurken, D2 serisi döşemelerde %1'in üstü çelik fiber katkı oranları davranışta önemli birfark oluşturmamıştır. Yapılan deneyler Kritik Kesme Çatlağı Teorisi kullanılarak analitik olarakmodellenmiş ve bu tip modelleme ile ilgili bazı iyileştirmeler önerilmiştir.
  • Conference Object
    Outage and Intercept Performance in THz LEO-Ground Communication With Satellite Selection
    (IEEE, 2025) Bakirci, Emre Berker; Ahrazoglu, Evla Safahan; Altunbas, Ibrahim; Erdogan, Eylem
    Satellite communication and THz communication systems are some of the methods that aim to meet the demand of increasing data rates. With an importance growing alongside increasing data amounts, data security is on its way to a position that cannot be neglected when building systems. In this study, it has been shown that secure data transmission can be made possible through the use of THz frequencies in a link between LEO satellites and a ground station. Proposed scenarios data transmission performance have been analyzed. It has been shown that selection transmission have improved both data transmission and security performances.
  • Conference Object
    Performance Evaluation of Filter-Based Gene Selection Methods in Cancer Classification
    (IEEE, 2025) Gokalp, Osman
    With the advances in microarray technology, gene expression levels can be measured efficiently, and this data can be used to solve important problems such as cancer classification. However, microarray data suffers from the high-dimensionality problem and requires dimensionality reduction techniques such as feature selection. This study addresses the cancer classification problem using microarray datasets and comparatively evaluates the performance of different filter-based gene (feature) selection methods. To this end, 11 microarray datasets have been evaluated using 6 different filter methods, and experimental results are presented. According to the findings, the gene selection methods used can improve classification performance by 5% to 30%. Using 5-fold cross-validation, the highest accuracy rates were achieved with 32 genes selected by the gain ratio filter for the Breast and Colon datasets, and with 8 genes selected by the information gain filter for the CNS dataset.
  • Conference Object
    Citation - Scopus: 2
    Outage Probability Analysis of Triple-Hybrid Rf/Fso Communication System
    (Ieee, 2024) Bakirci, Emre Berker; Ahrazoglu, Evla Safahan; Altunbas, Ibrahim; Erdogan, Eylem
    Terahertz (THz) and free space optical (FSO) transmission techniques are considered as alternatives for radio frequency (RF) transmission to meet the requirements for the sixth generation and beyond wireless communication systems. However, these transmission techniques may experience high level of deterioration under different weather conditions. In this study, triple-hybrid RF/FSO/THz system is proposed to enhance the system performance. The results have shown that the proposed system has improved outage probability performance under wide range weather conditions compared to only RF, only FSO, and only THz systems as well as dual-hybrid systems (RF/FSO, RF/THz, and FSO/THz). Theoretical results are validated via computer simulations.
  • Conference Object
    Improvements on a Multi-Task Bert Model
    (Ieee, 2024) Agrali, Mahmut; Tekir, Selma
    Pre-trained language models have introduced significant performance boosts in natural language processing. Fine-tuning of these models using downstream tasks' supervised data further improves the acquired results. In the fine-tuning process, combining the learning of tasks is an effective approach. This paper proposes a multi-task learning framework based on BERT. To accomplish the tasks of sentiment analysis, paraphrase detection, and semantic text similarity, we include linear layers, a Siamese network with cosine similarity, and convolutional layers to the appropriate places in the architecture. We conducted an ablation study using Stanford Sentiment Treebank (SST), Quora, and SemEval STS datasets for each task to test the framework and its components' effectiveness. The results demonstrate that the proposed multi-task framework improves the performance of BERT. The best results obtained for sentiment analysis, paraphrase detection, and semantic text similarity are accuracies of 0.534 and 0.697 and a Pearson correlation coefficient of 0.345.
  • Conference Object
    Citation - WoS: 1
    Konteyner Görüntülerini Kullanarak Hasar Tespiti ve Sınıflandırması
    (IEEE, 2020) Imamoglu, Zeynep Ekici; Tuglular, Tugkan; Bastanlar, Yalin
    In the logistics sector, digital transformation is of great importance in terms of competition. In the present case, container warehouse entry / exit operations are carried out manually by the logistics personnel including container damage detection. During container warehouse entry / exit process, the process of detecting damaged containers is carried out by the personnel and several minutes are required to upload to the IT system. The aim of our work is to automate the detection of damaged containers. This way, the mistakes made by the personnel will be eliminated and the process will be accelerated. In this work, we propose to use a convolutional neural network (CNN) that takes the container images and classify them as damaged or undamaged. We modeled the problem as a binary classification and employed different CNN models. The result we obtained shows that there is no single best method for the classification. It is shown how the dataset was created and how the parameters used in the layered structures affect the models employed in this study.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 1
    Görgül kip ayrıştırması kullanılarak optik faz kırınımında hassasiyet iyileştirilmesi
    (IEEE, 2023) Ataç, Enes; Dinleyici, Mehmet Salih
    Phase diffraction is a potent property used in transparent dielectric film characterization. The measured diffraction pattern on the camera is evaluated by matching numerically computed diffraction patterns to determine the optical properties of the ultra-thin films (refractive index, thickness, etc.). However, the obtained diffraction data is not only a nonlinear and non-stationary signal but also exhibits micron-scale variations, thus limiting the measurement accuracy. Therefore, it is challenging to identify shifts in minima and deviations in amplitude on diffraction data to extract information about the optical properties of phase objects. In this study, it is aimed to improve the thickness sensitivity of the system by applying Empirical Mode Decomposition (EMD) to plane wave-based near-field phase diffraction data. Since EMD is very sensitive to abrupt changes in the signal due to the spatial frequency components, the nanoscale variations in the film thickness become more observable and detectable. Experimental outputs and numerical simulations show that the decomposition increases the thickness sensitivity comparing the classical matching technique.
  • Conference Object
    Citation - WoS: 1
    An Origami-Inspired Low-Cost Waveguide Design, Fabrication and Measurements for X-Band Satellite Communication Systems
    (IEEE, 2023) Karatay, Anıl; Ataç, Enes; Yaman, Fatih
    In many applications such as satellite communication, transmission lines are required and waveguides are widely used in these applications. This passive component, which is an indispensable element of microwave systems, is generally not suitable for practical and low-cost applications due to being produced from costly and heavy metals. Therefore, nowadays, the tendency to use low-cost, light and practical components has increased. In this study, origami-inspired waveguide design for X-band satellite communication systems is aimed. This component, which is formed by folding a paper into a three-dimensional structure and covering it with a conductive material, is both practical and fast to produce, portable and adjustable. The obtained simulation results match well with the experimental results, and it has been proven that the paper-based waveguide performs as well as the conventional aluminum waveguide. This makes the proposed method an innovative and cost-effective solution for waveguide fabrication.
  • Conference Object
    Citation - Scopus: 2
    Parkinson hastalığı sınıflandırmasına yönelik ivmeölçer tabanlı zamanlama analizi
    (IEEE, 2023) Karaçalı, Bilge; Onay, Fatih
    Parkinson's disease is a neurodegenerative disorder caused by dopamine deficiency in the basal ganglia, resulting in cognitive and motor impairments. In this study, accelerometer signals were used to estimate the delay time between the command to start pedaling and the actual movement onset in three groups: healthy individuals (n=13), Parkinson's disease patients (n=13), and patients with freezing of gait symptoms (n=13). Features were extracted from the delay time distributions for each participant and subjected to a triple classification. Linear support vector machine achieved a classification accuracy of 69.2% for all participants. Notably, the average time to start pedaling was found to be significantly different among the three groups, and accelerometer-based timing analysis could be used as a diagnostic tool to assist clinical tests.