Uçak ve Uzay Bilimleri Fakültesi

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  • Öge
    10th International Symposium on Atmospheric Sciences : e-proceedings, 18-21 October 2022
    (İTÜ Yayınevi, 2023) Meteoroloji Mühendisliği ; Kahya, Ceyhan ; Öztopal, Ahmet
  • Öge
    11th International Symposium on Atmospheric Sciences : e-proceedings, 23-25 October 2024, Istanbul, Turkey
    (İTÜ Yayınevi, 2025) İklim Bilimi ve Meteoroloji Mühendisliği ; Efe, Bahtiyar ; Demirhan, Deniz ; Yakut Şevik, Sena Ecem
    This 11th Atmospheric Sciences Symposium; ATMOS2024 built upon the series that began at Istanbul Technical University, Department of Climate Science and Meteorological Engineering in 2024. Subsequent meetings have been held in 1991; 2003; 2008; 2011; 2013; 2015; 2017; 2019 and 2022 in Istanbul, Türkiye. And it is not just enough to produce scientific data for people but it is also necessary to process the data and share the results of those data as a source for students and a starting point for all researchers, users and policy makers, it is a treasure for mankind. We are very greatful and thankful to all the valuable researchers, session chairs and all participants who have contributed to ATMOS2024 from all around the world, whose valuable contributions made this event possible. This e-Proceedings present a collection of 86 papers presented at the Symposium
  • Öge
    Adaptive fault-tolerant multiplicative attitude filtering for small satellites
    (Wiley, 2024) Kınataş, Hasan ; Hajiyev, Chingiz ; orcid.org/0000-0003-2089-223X ; orcid.org/0000-0003-4115-341X ; Uzay Mühendisliği
    This study tackles the problem of fault-tolerant attitude estimation for small satellites. A probabilistic adaptive technique is presented for the multiplicative extended Kalman filter (MEKF) algorithm that is used in attitude estimation. The presented method is based on tracking the normalized measurement innovations in the filter and calculating the probability of the normal operation of the estimation system. Using this probability, the filter gain is corrected to maintain the tracking performance of the filter despite faulty measurements. In order to evaluate the performance of this method, several simulations are performed where different types of faults are introduced to the synthetic attitude sensor measurements (magnetometer and sun sensor) at different times. Simulation results are compared not only with a conventional EKF but also with another popular adaptive Kalman filter, an adaptive Kalman filter with multiple scaling factors (MSFs).
  • Öge
    Attitude filtering with uncertain process and measurement noise covariance using SVD-aided adaptive UKF
    (Wiley, 2023) Hajiyev, Chingiz ; Cilden-Guler, Demet ; orcid.org/0000-0003-4115-341X ; orcid.org/0000-0002-3924-5422 ; Uzay Mühendisliği
    It is presented in this article how to simultaneously alter the process and measurement noise covariance matrices for nontraditional attitude filtering technique. The unscented Kalman filter (UKF) and singular value decomposition (SVD) methods are integrated in the nontraditional attitude filtering algorithm to estimate a nanosatellite's attitude with an inherent robustness feature. The SVD approach determines the attitude of the nanosatellite and provides one estimate at a single frame utilizing measurements from the magnetometer and Sun sensor as the initial stage of the algorithm. These attitude terms are subsequently fed into the UKF with their error covariances, which makes the filter robust inherently. The attitude estimations of the satellite are compared between the filters presented. The Q (process noise covariance) adaption approach with multiple scale factors is specifically suggested for differences in between the process channels. Performance of the multiple scale factors-based adaptive SVD-aided UKF is examined in the event of process noise increase, which may result from changes in the environment or satellite dynamics.
  • Öge
    Convection-permitting climate simulations with COSMO-CLM over northwestern Türkiye under the RCP8.5 scenario
    (Wiley, 2023) Yürük Sonuç, Cemre ; Ünal, Yurdanur ; İncecik, Selahattin ; orcid.org/0000-0002-8585-1319 ; orcid.org/0000-0003-2006-1372 ; İklim Bilimi ve Meteoroloji Mühendisliği
    The performance of the climate simulations by the regional climate model COSMO-CLM forced by MPI-ESM-LR, as well as projected future temperature and precipitation conditions over northwestern Türkiye at the convection-permitting resolution, are shown in this study. In terms of mean, maximum and minimum temperatures and daily total precipitation, the model response was examined. Comparisons with observations were made on an annual and seasonal basis. The convection-permitting model (0.0275°) provides a satisfactory representation of annual and seasonal mean temperatures according to bias, MAE and RMSE. Better results were found for precipitation with respect to RE, MAE and RMSE. Finally, we used the RCP8.5 emission scenario to investigate future climate changes in terms of average temperature and precipitation variations for northwestern Türkiye, including Istanbul, over two projection periods (2041–2060 and 2071–2090) compared to the reference period (1991–2005). The model predicts significant warming in northwestern Türkiye, particularly in Istanbul and its environs, by the end of the century, as well as a general decrease in precipitation, especially evident in the spring and summer. The findings of this study can be used to develop climate adaptation policies based on temperature and precipitation variables in and around the study area.
  • Öge
    e-Proceedings of the 9th International Symposium on Atmospheric Sciences
    (İstanbul Teknik Üniversitesi, 2019-10) Department of Meteorology ; Şaylan, Levent ; Koçak, Kasım ; Kaymaz, Zerefşan ; Özgür, Evren ; Eyigüler, Ceren
  • Öge
    Earth, air quality and climate
    (İTÜ Yayınevi, 2024) Meteoroloji Mühendisliği ; Kahya, Ceyhan ; Öztopal, Ahmet
    Istanbul Technical University - Department of Meteorological Engineering has been organizing the International Symposium on Atmospheric Sciences - ATMOS every two years, since 2000. This book consists of scienti􀃶c papers that were presented at the 10th ATMOS event in 2022 and were selected by the scienti􀃶c committee after being refereed again. This book, which consists of papers under the theme of EARTH, AIR QUALITY and CLIMATE, will provide valuable contributions to related research and researchers.
  • Öge
    Effects of climate trends and variability on tree health responses in the Black Sea and Mediterranean forests of Türkiye
    (Springer, 2024) Dogan Ciftci, Nida ; Şahin,, Ahmet Duran ; Yousefpour, Rasoul ; Christen , Andreas ; Meteoroloji Mühendisliği
    To adapt forest ecosystems and forest management to climate change, it is essential to know which forest regions and which tree species are resilient to climate variability and which ones are possibly affected most by past and anticipated future changes. In this contribution, for the main forest regions of Türkiye and six tree species, recent climate variability and trends were quantified and statistically correlated to record tree defoliation and vitality. Climate variables considered are maximum temperature (Tmax), minimum temperature (Tmin), mean temperature (Tmean), and total precipitation (Prcp), which are compared to forest health responses recorded as part of the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) on 277 plots across forests along the Black Sea and Mediterranean regions. In addition, long-term data on satellite measurements of the normalized difference vegetation index (NDVI) were extracted for the same 277 plots for the period 2008–2020. Firstly, 30 years (1991–2020) of reanalysis of climate variables from ECMWF were extracted for all plots; secondly, individual correlations and cross-correlations of climate variables and tree health and vitality were computed for the period 2008–2020 (significance level of 95%) for the four most dominant species from the Black Sea forests (F. orientalis, Q. cerris, P. sylvestris, P. orientalis) and two species from Mediterranean forests (P. brutia and C. libani). Temperature showed a stronger effect on most species than precipitation. Finally, time-lagged correlations were analyzed for seven-time lags (significance level of 95%) to evaluate legacy effect. The analysis revealed that different tree species from the two regions show different responses to climate variables. Species in the Mediterranean region are more resistant to droughts and climatic variations. Legacy effects of defoliation and NDVI have lasted for at least 2 years.
  • Öge
    Future change of humid heat extremes and population exposure in Turkey
    (Wiley, 2024) Dönmez, Berkay ; Dönmez, Kutay ; Yürük Sonuç, Cemre ; Unal, Yurdanur ; orcid.org/0000-0001-5978-3642 ; orcid.org/0000-0003-2344-5822 ; orcid.org/0000-0002-8585-1319 ; orcid.org/0000-0003-2006-1372 ; İklim Bilimi ve Meteoroloji Mühendisliği
    Global climate projections show that humid heat extremes will expand toward the higher latitudes, making the midlatitudes hotspots for these extremes. Therefore, a thorough explanation of their regional characteristics becomes crucial, given that the changes in these extremes can potentially render a large proportion of the global population at risk. Here, we perform the first analysis of historical and projected changes in the intensity and frequency of humid heat extremes and quantify the population exposure to these extremes in Turkey, using long-term simulations from the non-hydrostatic mesoscale model of Consortium for Small-scale Modeling (COSMO-CLM) under the RCP8.5 emission scenario. We portray not only the nationwide changes in the humid heat extremes and population exposure but also their regional aspects by exploiting the K-means clustering algorithm. Our results suggest significant future increases in the intensity and frequency of these extremes over a wide geographical area, which includes the surroundings of Adana, Antalya, Izmir, Sakarya, Ordu and Diyarbakir, most of which are coastal locations. Over most of these regions, severe humid heat stress is expected to last nearly a month every year, with almost 56% of the land area is projected to experience local historical upper tail heat stress conditions for at least an additional 10 consecutive hours. Further, we explicate a significant rise in the number of people exposed to severe humid heat stress, concentrated along most coastal regions, by as much as 1.6 million person-days. More than 20% of Turkey's population may confront severe humid heat stress for at least 1 h, with that percentage falling to 4.15% for at least five consecutive hours, which indicates that people will not only endure more intense humid heat stress but also be exposed to these conditions consecutively over a period of many hours.
  • Öge
    High-velocity impact behavior of nonwoven mats and unidirectional prepreg hemp and flax fibers reinforced hybrid biocomposites
    (Wiley, 2024) Baysal, Ataberk ; Turkmen, Halit Süleyman ; Yayla, Paşa ; orcid.org/0000-0001-5508-7236 ; orcid.org/0000-0002-1787-9475 ; Uçak Mühendisliği
    High specific impact strength and stiffness are demanded in various applications, leading to the widespread utilization of fiber-reinforced polymers. Synthetic fiber-reinforced polymers have been used to meet these engineering requirements. However, the current popularity of biocomposites arises from their environmental friendliness, ease of availability, and affordability, making them a favored alternative to synthetic-based fiber-reinforced polymers. An assessment must be conducted to determine whether biocomposites can replace their synthetic fiber counterparts, necessitating a thorough investigation into their impact behavior. This study aims to unveil the impact performance of hybrid biocomposites made from unidirectional prepregs comprising flax/polypropylene fibers and nonwoven mats composed of hemp/polypropylene fibers. The impact performance of hybrid biocomposites has also been studied concerning the number of layers and stacking sequence. Eight different designs of biocomposite plates are manufactured through compression molding and subsequently subjected to high-velocity impact tests. Additionally, numerical simulation using the FEM is utilized to model and analyze the impact behavior of one specimen. The test results indicate that each design possesses unique characteristics and impact behaviors differ. Highlights Adding prepreg significantly improved mechanical performance in the biocomposites. Performance enhancement varies depending on the stacking sequence. Adding multiple layers of UD prepregs enhances mat impact performance. Numerical simulations validate the Tsai-Wu criterion for impact testing.
  • Öge
    International symposium on remote sensing in meteorology: METEO IRS 2021, 1-3 December 2021, İstanbul/TÜRKİYE
    (ITU Press, 2022-11-28) International symposium on remote sensing in meteorology (2022: İstanbul) ; Meteoroloji Mühendisliği ; Öztopal, Ahmet ; Akın, Melek ; Durmaz, Abdurrahman
    In today's world, remote sensing is an important tool used in many fields. Atmospheric Sciences is the main field in which remote sensing is used 24/7 operationally. This technology makes important contributions to detect, understand and solve meteorological, climatological, hydrological problems and to detect and track ordinary or extreme weather events. In addition, remote sensing has undeniable contributions to forecasters and decision makers in terms of very short-term weather forecasting and early warning. Considering that our country's studies on Meteorological Remote Sensing are not sufficient in number and level, it is aimed to increase the studies on this subject throughout the country with the International Symposium on Remote Sensing in Meteorology - METEO IRS 2021. The interest shown in the first METEO IRS, with a total of 9 invited speakers from the United States, Finland, Italy and Turkey, is encouraging. I would like to express my gratitude to all the participants for their contributions, and I wish to be together again in METEO IRS 2023. Dr. Ahmet Öztopal Chair of METEO IRS 2021
  • Öge
    Investigation of the coupling between the dynamics of vortical structures and flame stability in bluff-body premixed combustion using extended spectral proper orthogonal decomposition
    (ASME, 2025) Khalifehei, Morteza ; Yalçınkaya, Yağız ; Padilla-Montero, Iván ; Güngör, Ayşe Gül ; Rodríguez, Daniel ; Uzay Mühendisliği
    Large eddy simulation data of a bluff-body stabilized flame are analyzed using spectral proper orthogonal decomposition (SPOD) to investigate: (i) the role of flame-vortex interactions in the dominant flow dynamics and (ii) how the proper choice of the cross-spectral density (CSD) defining SPOD can assist in identifying the underlying dynamics. Bluff-body flame holders aim to achieve stable flames under lean premixed conditions to minimize pollutant emissions. The recirculation region induced by the body promotes the mixing of hot combustion products with unburnt gases, preventing the global blowoff. However, the coupling between the shear layers and flame-induced vorticity sources can result in large flow structures that either contribute to increased flame stability or exhibit features typical of the early stages of flame blowout. SPOD is a data-driven technique remarkably powerful in extracting low-dimensional models. For each frequency, it computes a basis of orthogonal modes that maximizes the content of a predefined CSD in the leading modes. By choosing physically relevant variables to construct the CSD, different physics can be explored, which is used here to investigate the coupled dynamics between the flame-induced baroclinic torque, vortical structures, and the temperature field. The results show that the vorticity and temperature fields exhibit low-dimensional dynamics characterized by a narrowband frequency and its harmonics; these dynamics are varicose oscillations of the flame region, governed by the baroclinic torque. Sinuous oscillations typical of wake instability for nonreactive flows are also present, suggesting a competition between them.
  • Öge
    The impact-induced deformation characteristics of polycarbonate panels
    (Wiley, 2024) Mullaoglu, Fehmi ; Usta, Fatih ; Turkmen, Halit Suleyman ; orcid.org/0000-0001-5508-7236 ; Uçak Mühendisliği
    In this study, the investigation of damage caused by a spherical steel projectile on the polycarbonate (PC) panels has been undertaken both numerically and experimentally. The material properties are obtained from both static and dynamic tests. High-velocity impact experiments are performed using a pressure-based projectile launching system. The effect of panel curvatures and impact locations on the deformation are investigated experimentally. The impact locations are selected as both at the plate center and near the edge of the plate. A validation study is performed by analyzing the impact response of a PC plate as previously presented in the literature and subsequently comparing it with the results obtained. An analysis of the impact behavior of PC panels is carried out through numerical simulations using finite element program (LS-DYNA). The effect of boundary conditions on the impact response is also investigated numerically. Plastic strains, von Mises stresses, dent depth, and energy absorption are obtained. It is indicated by the results that the deformation behavior of PC panels exhibits a strain rate dependence. Additionally, the deformation behavior is influenced by panel curvatures and boundary conditions, emphasizing the necessity to consider these factors in the design of structures, such as canopies made of PC panels. Highlights Provides a comprehensive understanding of polycarbonate behavior. Emphasizes the influence of impact locations and panel curvatures. Dent depth and stress rise with panel curvature, crucial for design considerations. Emphasizes the significance of strain rate and boundary condition in design.
  • Öge
    Variables controlling growing season carbon dynamics in desert shrub ecosystem
    (Springer, 2024) Şaylan, Levent ; Kimura, Reiji ; Başakın, Eyyup Ensar ; Kurosaki, Yasunori ; 0000-0003-3233-0277 ; 0000-0001-7700-3566 ; 0000-0002-9045-5302 ; 0000-0002-9595-0484 ; Meteoroloji Mühendisliği
    Arid and semi-arid lands (drylands) are under the influence of extreme environmental conditions and cover large areas on Earth’s land surface. Determining temporal and spatial variations of the greenhouse gas and energy exchange in these ecosystems will provide a better understanding of both, the dynamics between the drylands’s surface and the atmosphere and the importance in climate change. In this study, CO2 exchanges over a shrub steppe ecosystem were determined using the Eddy Covariance method during both dry and wet growing seasons in the Gobi Desert, Mongolia. The net ecosystem exchange (NEE) was modeled using the extreme gradient boosting method (XGBOOST). Variables influencing NEE were estimated employing the SHapley Additive exPlanations algorithm (SHAP). The XGBOOST predictions demonstrated impressive results across all growing seasons, with high performance metrics (R2 = 0.821; NSE = 0.817), particularly notable during the wet season (R2 = 0.932; NSE = 0.929). The total NEE changed between 79.7 and -110.4 gC m−2 throughout the growing seasons. Especially the precipitation before the growing period has a positive impact on carbon sequestration in the shrub ecosystem in the following dry season. A high similarity was found in the patterns of daily NEE of all growing seasons and normalized difference vegetation index (NDVI), albedo, soil water content, temperature, sensible heat flux, the difference between air and soil temperature in desert shrub ecosystem. Although NDVI was the dominant factor during the wet season, there was a weaker relationship between these factors and NEE in the dry season than in the wet season.