Research Outputs
Permanent URI for this communityhttps://hdl.handle.net/20.500.14288/2
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Publication Restricted A discrate-continuous optimization approach for the design and operation of synchromodal transportation networks(Koç University, 2016) Reşat, Hamdi Giray; Türkay, Metin; 0000-0003-4769-6714; Koç University Graduate School of Sciences and Engineering; Industrial Engineering; 24956Publication Restricted A method for pickup and delivery and its application to truck route scheduling(Koç University, 2015) Altun, Aysu; Oğuz, Ceyda; 0000-0003-0994-1758; Koç University Graduate School of Sciences and Engineering; Industrial Engineering; 6033Publication Restricted Air Carrier’s Liability under the 1999 Montreal Convention: Death, Bodily Injury and Delay of Passenger(Koç University, 2015) Gölcüklü, İlyas; Özbek, Meltem Deniz Güner; Koç University Graduate School of Social Sciences and Humanities; LawPublication Restricted Carrier's liability in international carriage of goods by air(Koç University, 2016) Turhan, Gökhan; Buğra, Ayşegül; 0000-0003-2578-5660; Koç University Graduate School of Social Sciences and Humanities; Law; 237477Publication Open Access Coordinate interleaved orthogonal design with media-based modulation(Institute of Electrical and Electronics Engineers (IEEE), 2021) Yldırım, İbrahim; Altunbaş, İbrahim; Department of Chemical and Biological Engineering; Başar, Ertuğrul; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; 149116In this work, we propose a new multiple-input multiple-output (MIMO) concept, which is called coordinate interleaved orthogonal design with media-based modulation (CIOD-MBM). The proposed two novel CIOD-MBM schemes provide improved data rates as well as diversity gain while enabling hardware simplicity using a single radio frequency (RF) chain. Moreover, using the equivalent channel model, a reduced complexity can be obtained for maximum likelihood (ML) detection of the proposed system. Using computer simulations, it is shown that CIOD-MBM schemes provide remarkably better performance against the conventional MBM and CIOD systems.Publication Open Access Hub location, routing, and route dimensioning: strategic and tactical intermodal transportation hub network design(The Institute for Operations Research and the Management Sciences (INFORMS), 2021) Yaman Hande; Karaşan Oya Ekin; Department of Industrial Engineering; Yıldız, Barış; Faculty Member; Department of Industrial Engineering; College of Engineering; 258791We propose a novel hub location model that jointly eliminates some of the traditional assumptions on the structure of the network and on the discount as a result of economies of scale in an effort to better reflect real-world logistics and transportation systems. Our model extends the hub literature in various facets: instead of connecting nonhub nodes directly to hub nodes, we consider routes with stopovers; instead of connecting pairs of hubs directly, we design routes that can visit several hub nodes; rather than dimensioning pairwise connections, we dimension routes of vehicles; and rather than working with a homogeneous fleet, we use intermodal transportation. Decisions pertinent to strategic and tactical hub location and transportation network design are concurrently made through the proposed optimization scheme. An effective branch-and-cut algorithm is developed to solve realistically sized problem instances and to provide managerial insights.Publication Open Access Index modulation based coordinate interleaved orthogonal design for secure communications(Institute of Electrical and Electronics Engineers (IEEE), 2021) Yıldırım, İbrahim; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Özpoyraz, Burak; Faculty Member; Master Student; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; 149116; N/AIn this paper, we propose a physical layer security scheme that exploits a novel index modulation (IM) technique for coordinate interleaved orthogonal designs (CIOD). Utilizing the diversity gain of CIOD transmission, the proposed scheme, named CIOD-IM, provides an improved spectral efficiency by means of IM. In order to provide a satisfactory secrecy rate, we design a particular artificial noise matrix, which does not affect the performance of the legitimate receiver, while deteriorating the performance of the eavesdropper. We derive expressions of the ergodic secrecy rate and the theoretical bit error rate upper bound. In addition, we analyze the case of imperfect channel estimation by taking practical concerns into consideration. It is shown via computer simulations that the proposed scheme outperforms the existing IM-based schemes and might be a candidate for future secure communication systems.Publication Restricted Integration of facility location and layout of intermodal transportation system with scheduling(Koç University, 2008) Kaya, Güven; Türkay, Metin; Oğuz, Ceyda; 0000-0003-4769-6714; 0000-0003-0994-1758; Koç University Graduate School of Sciences and Engineering; Industrial Engineering; 24956; 6033Publication Open Access Machine learning based channel modeling for Vehicular Visible Light Communication(Institute of Electrical and Electronics Engineers (IEEE), 2021) Department of Electrical and Electronics Engineering; Ergen, Sinem Çöleri; Turan, Buğra; Faculty Member; Other; PhD Student; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; 7211; N/AVehicular Visible Light Communication (VVLC) is preferred as a vehicle-to-everything (V2X) communications scheme due to its highly secure, low complexity and radio frequency (RF) interference free characteristics, exploiting the line-of-sight (LoS) propagation of visible light and usage of already existing vehicle light emitting diodes (LEDs). Current VVLC channel models based on deterministic and stochastic methods provide limited accuracy for path loss prediction since deterministic methods heavily depend on site-specific geometry and stochastic models average out the model parameters without considering environmental effects. Moreover, there exists no wireless channel model that can be adopted for channel frequency response (CFR) prediction. In this paper, we propose novel framework for the machine learning (ML) based channel modeling of the VVLC with the goal of improving the model accuracy for path loss and building the CFR model through the consideration of multiple input variables related to vehicle mobility and environmental effects. The proposed framework incorporates multiple measurable input variables, e.g., distance, ambient light, receiver inclination angle, and optical turbulence, with the exploitation of feed forward neural network based multilayer perceptron neural network (MLP-NN), radial basis function neural network (RBF-NN) and decision tree based Random Forest learning methods. The framework also includes data pre-processing step, with synthetic minority over-sampling technique (SMOTE) data balancing, and hyper-parameter tuning based on iterative grid search, to further improve the accuracy. The accuracy of the proposed ML based channel modeling is demonstrated on the real-world VVLC vehicle-to-vehicle (V2V) communication channel data. The proposed MLP-NN, RBF-NN, and Random Forest based channel models generate highly accurate path loss predictions with 3.53 dB, 3.81 dB, 3.95 dB root mean square error(RMSE), whereas the best performing stochastic model based on two-term exponential fitting provides prediction accuracy of 7 dB RMSE. Moreover, MLP-NN and RBF-NN models are demonstrated to predict VVLC CFR with 3.78 dB and 3.60 dB RMSE, respectively.Publication Restricted Mathematical models for maritime terminal operations(Koç University, 2019) Ünsal, Celal Özgür; Oğuz, Ceyda; 0000-0003-0994-1758; Koç University Graduate School of Sciences and Engineering; Industrial Engineering; 6033