TOBB ETU GCRIS Database
Not a member yet
9778 research outputs found
Sort by
Aldatma Saldirisi Tespiti ve Aldatmaya Karsi Önlem için Kalman Filtresi Tasarimi
No full textWith the widespread use of global navigation satellite systems (GNSS) measurements in positioning solutions and especially forming the basis of autonomous vehicle navigation, the importance of measurement accuracy from these systems has increased. On the other hand, applications have also started to become widespread in recent years, for spoofing attacks, ensuring that the GNSS receivers obtain incorrect positioning solutions. Therefore, adding detection and countermeasure algorithms, within GNSS receivers, against possible spoofing attacks is critically important. For spoofing detection and countermeasure, there are many different methods developed within GNSS receivers, and these methods are recommended for use in different parts of the receiver structure. Within the scope of this study, in order to detect and prevent the spoofing attack a Kalman filter design is presented for use in a GNSS receiver mounted on an autonomous moving vehicle, which provides a positioning solution by using GPS, Galileo, GLONASS, and BeiDou systems, that are actively providing global positioning services. This proposed filter is designed to be used in the navigation block, just before presenting the final position solution, after generating a positioning solution with the signals received by the GNSS receiver from different positioning systems. The algorithm designed in the first part of the studies detects spoofing, based on the method of comparing the residual calculations of different GNSS measurements, and then continues to produce a positioning solution using non-spoofed system measurements. In addition to this algorithm, in the second part of the studies, generating positioning solutions with an accelerometer to be integrated into the GNSS receiver is modeled. The comparison of the residuals calculated by using these solutions with the GNSS residuals is included in the algorithm. By integrating the accelerometer into the system, the number of possible spoofing scenarios is increased. The performance of the designed filter has been tested with Monte-Carlo simulations. By creating different spoofing trajectories, the performance of the filter is examined in terms of percentage spoofing detection performance and detection time under all possible scenarios in which spoofing attacks can be applied in these trajectories. For the created spoofing trajectories, the relationship between the dominant and recessive GNSS position accuracies and detection times is explained in the applied spoofing scenarios. Finally, by testing the threshold value used by the filter to detect spoofing for different levels, receiver operating characteristics curves were drawn, and the performances of the filter in different spoofing trajectories were given by calculating the areas under these curves.Küresel konumlama sistemleri (KKS) ölçümlerinin konumlama çözümlerinde kullanılmasının yaygınlaşması ve özellikle otonom araç navigasyonunun temelini oluşturmasıyla, bu sistemlerden alınan ölçüm doğruluklarının önemi artmıştır. Öte yandan, aldatma saldırıları ile KKS alıcılarının gerçekten farklı konumlama çözümü elde edip aldanmasının sağlanması üzerine uygulamalar da son yıllarda yaygınlaşmaya başlamıştır. Dolayısıyla, KKS alıcıları içerisinde, olası aldatma saldırılarına karşı tespit ve karşı tedbir algoritmalarının eklenmesi oldukça kritik önem taşımaktadır. Aldatma tespit ve aldatmaya karşı önlem için KKS alıcıları içerisinde geliştirilen pek çok farklı yöntem bulunmakta olup, bu yöntemler alıcı yapısının farklı kısımlarına kullanılmak üzere önerilmektedir. Bu çalışma kapsamında, günümüzde aktif olarak küresel konumlama hizmeti sunan GPS, Galileo, GLONASS, BeiDou sistemleri ile konumlama çözümü üreten, hareketli bir araç üzerindeki KKS alıcısı içerisinde, aldatma tespiti ve aldatmaya karşı tedbir amacıyla kullanılmak üzere Kalman filtresi tasarımı sunulmaktadır. Önerilen bu filtre, KKS alıcısının farklı konumlama sistemlerinden aldığı sinyaller ile konumlama çözümü ürettikten sonra, nihai pozisyon çözümünü sunmadan hemen önceki navigasyon bloğunda kullanılmak üzere tasarlanmıştır. Çalışmaların ilk bölümünde tasarlanan algoritma, farklı KKS ölçümleri artıklık hesaplarının karşılaştırılması yöntemini esas alarak aldatma tespiti yapmakta, ardından aldatma olmayan sistem ölçümlerini kullanarak konumlama çözümü üretmeye devam etmektedir. Bu algoritmaya ek olarak, çalışmaların ikinci bölümünde, KKS alıcısının içerisine entegre edilecek bir ivmeölçer ile konumlama çözümleri üretilmesi modellenmiştir. Bu çözümlerle artıklık hesaplarının da KKS artıklıkları ile karşılaştırılması algoritmaya dahil edilmiştir. İvmeölçerin de sisteme entegre edilmesi ile olası aldatma senaryolarının sayısının arttırılması sağlanmıştır. Tasarlanan filtrenin başarımı Monte-Carlo simülasyonları ile test edilmiştir. Farklı aldatma yörüngeleri oluşturularak, bu yörüngelerde aldatma saldırılarının uygulanabileceği olası tüm senaryolar altında filtrenin performansı yüzde tespit başarımı ve tespit süresi cinsinden incelenmiştir. Oluşturulan aldatma yörüngeleri için, uygulanan aldatma senaryolarındaki baskın ve resesif olan KKS'lerin pozisyon doğrulukları ile tespit süreleri arasındaki ilişki açıklanmıştır. Son olarak, filtrenin aldatma tespiti yapmak için kullandığı eşik değerinin farklı seviyeler için test edilmesi ile alıcı çalışma karakteristiği eğrileri çizdirilmiş, bu eğrilerin altında kalan alanların hesaplanması ile filtrenin farklı aldatma yörüngelerindeki başarımları verilmiştir
Authentication-Enabled Attribute-Based Access Control for Smart Homes
No full textSmart home technologies constantly bring significant convenience to our daily lives. Unfortunately, increased security risks accompany this convenience. There can be severe consequences when unauthorized or malicious users gain access to smart home devices. Therefore, dependable and comprehensive access control models are needed to address the security concerns. To this end, the attribute-based access control (ABAC) model is usually considered the most satisfactory access control model for running IoT applications. However, the uncertainty left with the authentication stage should be carried to the authorization policy specification. In this work, we extend the ABAC model by carrying the assurance level of user authentication obtained from biometric authentication systems for authorization. The extended ABAC model quantifies how far the authentication matching score is from the predefined threshold. This quantification serves as a regular attribute like others to define authorization policies. The novelty in this quantification is that it consults false matching rate and hence can easily normalize across wide range of biometric authentication devices and algorithms. As a result, the resulting access control policies are concise and easy to comprehend. Moreover, our model is fine-grained in that different access policies can be specified for each smart device functionality. This work also shows, through case studies, that the extended ABAC model is feasible and implementable in XACML language
Search for Heavy Resonances Decaying Into a Z or W Boson and a Higgs Boson in Final States with Leptons and b-jets in 139 fb−1 of pp Collisions at √s = 13 TeV with the ATLAS Detector
No full textThis article presents a search for new resonances decaying into a Z or W boson and a 125 GeV Higgs boson h, and it targets the νν¯ bb¯ , ℓ+ℓ−bb¯ , or ℓ±νbb¯ final states, where ℓ = e or μ, in proton-proton collisions at s = 13 TeV. The data used correspond to a total integrated luminosity of 139 fb−1 collected by the ATLAS detector during Run 2 of the LHC at CERN. The search is conducted by examining the reconstructed invariant or transverse mass distributions of Zh or Wh candidates for evidence of a localised excess in the mass range from 220 GeV to 5 TeV. No significant excess is observed and 95% confidence-level upper limits between 1.3 pb and 0.3 fb are placed on the production cross section times branching fraction of neutral and charged spin-1 resonances and CP-odd scalar bosons. These limits are converted into constraints on the parameter space of the Heavy Vector Triplet model and the two-Higgs-doublet model. [Figure not available: see fulltext.]. © 2025 Elsevier B.V., All rights reserved
Does the Sleeper Plate Application for Temporary Epiphysiodesis Make Life Easier or Complicated? Increased Risk of Tethering
No full textBackground: The present study aims to investigate the frequency of recurrence and tethering effect after only metaphyseal screw removal (sleeper plate technique) compared with the conventional complete plate removal in the treatment of lower extremity deformities with guided growth surgery. Methods: Seventy-two patients (107 limbs) treated by an 8-plate hemiepiphysiodesis technique around the knee joint were evaluated. After the desired correction, only metaphyseal screw was removed (sleeper plate group) in 35 limbs (25 patients), whereas both screws and plate were removed (plate removal group) in 72 limbs (47 patients). An increase of 5 degrees or more in joint orientation angles in the direction of the initial deformity was considered as recurrence. The rate of rebound, tethering, and maintenance of correction in groups was analyzed at the latest follow-up (mean of 49 mo). Results: The mean age of the patients was 97 months (range: 80 to 129 mo) at the time of index surgery. After a mean of 49 months (range: 16 to 86), 17 (48.5%) limbs maintained the desired stable correction in the sleeper plate group compared with 59 stable limbs (72.2%) in the plate removal group (P0.001). There was no statistically significant difference regarding recurrence between the sleeper plate group and the plate removal group (34.3% vs. 27.8%, respectively) (P=0.216). Reinsertion of the metaphyseal screw was possible 8/12 limbs, and the remaining 4 limbs underwent further surgeries. There were 6 limbs (17.3%) of tethering in the sleeper plate group, and 4/6 limbs required further corrective surgeries. The remaining 2 limbs with slight tethering did not require further surgeries. Conclusions: Removing only metaphyseal screw increases the risk of tethering. In addition, reinsertion of the screw may not be possible in all cases due to bony growth, and further corrective surgeries may be necessary. Close follow-up is required if the sleeper plate technique is to be applied. Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved
Topology Optimization using Lattice Materials with Isotropy Condition
No full textThe 3rd BEYOND 2023: Computational Science, Mathematical Modeling and Engineering Conference TOBB University of Economics and Technology, Ankara-Turkey, 19-20 October 2023Lattice materials have a lot of advantages such as lightness, stiffness, vibration damping, and heat insulation. Nowadays the use of lattice materials has begun to become widespread in many different areas since the designs which are generated by lattice materials can be manufactured with additive manufacturing technologies. When the design is performed by lattice materials proper densities of lattice cells in a part are determined by doing density mapping with homogenization-based topology optimization. However, the mechanical behaviors of most of the lattice materials which change by direction as with composite materials are not isotropic. For the Solid Isotropic Material with Penalization (SIMP) method, which is used commonly in topology optimization for density mapping in commercial software due to its simplicity, some problems appear in the use of lattice materials, since homogenized properties, which are not isotropic, generate different stress and displacement in different direction. The method of isotropy conditioned density mapping (ICDM) is proposed to solve the problem within the scope of this thesis. Lattice cells, which are modeled by strut elements that ensure isotropy condition of homogenized elastic properties at whole density values, are determined with this proposed model. Since these lattice cells ensure isotropy conditions, the SIMP method can be used in topology optimization. The density range, which can be used in topology optimization, is determined to be produced with additive manufacturing. To show the effectiveness of the proposed method, three-dimensional examples used in the literature have been designed. The results of the optimized design which is generated by the proposed ICDM model are compared with the results in the literature to demonstrate its effectiveness. It was shown that macroscopic distributions of lattice cells can be obtainable with topology optimization with the SIMP method available in commercial software when the lattice configurations, which ensure isotropy condition, are determined with this proposed method
Search for a New Scalar Resonance in Flavour-Changing Neutral-Current Top-Quark Decays T → Qx (q = U, C), With X → B(b)over-Bar, in Proton-Proton Collisions at √s=13 Tev With the Atlas Detector
No full textA search for flavour-changing neutral-current decays of a top quark into an up-type quark (either up or charm) and a light scalar particle X decaying into a bottom anti-bottom quark pair is presented. The search focuses on top-quark pair production where one top quark decays to qX, with X -> b (b) over bar, and the other top quark decays according to the Standard Model, with the W boson decaying leptonically. The final state is thus characterised by an isolated electron or muon and at least four jets. Events are categorised according to the multiplicity of jets and jets tagged as originating from b-quarks, and a neural network is used to discriminate between signal and background processes. The data analysed correspond to 139 fb(-1) of proton-proton collisions at a centre-of-mass energy of 13TeV, recorded with the ATLAS detector at the LHC. The 95% confidence-level upper limits between 0.019% and 0.062% are derived for the branching fraction B(t -> uX) and between 0.018% and 0.078% for the branching fraction B(t -> cX), for masses of the scalar particle X between 20 and 160 GeV.ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW, Austria; FWF, Austria; ANAS, Azerbaijan; CNPq, Brazil; FAPESP, Brazil; NSERC, Canada; CFI, Canada; NSFC, China; MEYS CR, Czech Republic; DNRF, Denmark; DNSRC, Denmark; IN2P3-CNRS, France; CEA-DRF/IRFU, France; BMBF, Germany; MPG, Germany; Hong Kong SAR, China; ISF, Israel; INFN, Italy; MEXT, Japan; JSPS, Japan; CNRST, Morocco; RCN, Norway; MEiN, Poland; FCT, Portugal; MNE/IFA, Romania; MESTD, Serbia; MSSR, Slovakia; ARRS, Slovenia; MIZS, Slovenia; MICINN, Spain; Wallenberg Foundation, Sweden; SERI, Switzerland; MOST, Taiwan; DOE, United States of America; NSF, United States of America; BCKDF, Canada; CANARIE, Canada; Compute Canada, Canada; Czech Republic [PRIMUS 21/SCI/017, UNCE SCI/013]; COST, European Union; ERC, European Union; ERDF, European Union; Horizon 2020, European Union; Marie Skodowska-Curie Actions, European Union; Investissements d'Avenir Labex, France; Investissements d'Avenir Idex , France; ANR, France; DFG , Germany; AvH Foundation, Germany; Herakleitos programme - EU-ESF, Greece; Thales programme - EU-ESF, Greece; Aristeia programme - EU-ESF, Greece; Greek NSRF, Greece; BSF-NSF, Israel; MINERVA, Israel; Norwegian Financial Mechanism 2014-2021, Norway; NCN, Poland; NAWA, Poland; La Caixa Banking Foundation, Spain; CERCA Programme Generalitat de Catalunya, Spain; PROMETEO Programme Generalitat Valenciana, Spain; GenT Programme Generalitat Valenciana, Spain; Goran Gustafssons Stiftelse, Sweden; Royal Society, United Kingdom; Leverhulme Trust, United Kingdom; STFC, United Kingdom; TENMAK, Turkiye; Canton of Geneva, Switzerland; Canton of Bern, Switzerland; SNSF, Switzerland; SRC, Sweden; DSI/NRF, South Africa; NWO, Netherlands; Benoziyo Center, Israel; RGC, China; GSRI, Greece; HGF, Germany; SRNSFG, Georgia; Minciencias, Colombia; MOST, China; CAS, China; ANID, Chile; CERN; NRC, CanadaWe acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; ANID, Chile; CAS, MOST and NSFC, China; Minciencias, Colombia; MEYS CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS and CEA-DRF/IRFU, France; SRNSFG, Georgia; BMBF, HGF and MPG, Germany; GSRI, Greece; RGC and Hong Kong SAR, China; ISF and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; NWO, Netherlands; RCN, Norway; MEiN, Poland; FCT, Portugal; MNE/IFA, Romania; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZS, Slovenia; DSI/NRF, South Africa; MICINN, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TENMAK, Turkiye; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, CANARIE, Compute Canada and CRC, Canada; PRIMUS 21/SCI/017 and UNCE SCI/013, Czech Republic; COST, ERC, ERDF, Horizon 2020 and Marie Skodowska-Curie Actions, European Union; Investissements d'Avenir Labex, Investissements d'Avenir Idex and ANR, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF, Greece; BSF-NSF and MINERVA, Israel; Norwegian Financial Mechanism 2014-2021, Norway; NCN and NAWA, Poland; La Caixa Banking Foundation, CERCA Programme Generalitat de Catalunya and PROMETEO and GenT Programmes Generalitat Valenciana, Spain; Goran Gustafssons Stiftelse, Sweden; The Royal Society and Leverhulme Trust, United Kingdom
Metamaterial-Assisted Power Division: an Inverse Design Study in 1d Grating Waveguides
No full text13th International Conference on Metamaterials, Photonic Crystals and Plasmonics, META 2023 -- 18 July 2023 through 21 July 2023 -- 300609Power dividers are vital components playing a crucial role in facilitating signal merging, routing, and division to ensure the efficient functioning of multi-channel systems in photonic integrated circuits. However, the use of bulky power splitters can occupy a significant amount of space on the chip. Therefore, we propose the utilization of a metamaterial-assisted ultra-low-loss T junction power divider, which integrates an input and two output grating waveguides, with a size of just 2.1 × 2.1 ×m2. © 2023, META Conference. All rights reserved.Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, TÜBİTAK: 119E501, BIDEB 2210
Author Correction: a Detailed Map of Higgs Boson Interactions by the Atlas Experiment Ten Years After the Discovery (nature, (2022), 607, 7917, (52-59), 10.1038/S41586-022-04893-w)
No full textCorrection to: Nature Published online 4 July 2022 In the version of this article initially published, the ATLAS Collaboration author names, affiliations and acknowledgements were omitted and have now been included in the HTML and PDF versions of the article. © 2023, The Author(s)