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Yayın Cryptanalysis of Fridrich's chaotic image encryption(World Scientific Publishing, 2010-05) Solak, Ercan; Çokal, Cahit; Yıldız, Olcay Taner; Bıyıkoğlu, TürkerWe cryptanalyze Fridrich's chaotic image encryption algorithm. We show that the algebraic weaknesses of the algorithm make it vulnerable against chosen-ciphertext attacks. We propose an attack that reveals the secret permutation that is used to shuffle the pixels of a round input. We demonstrate the effectiveness of our attack with examples and simulation results. We also show that our proposed attack can be generalized to other well-known chaotic image encryption algorithms.Yayın Breaking an orbit-based symmetric cryptosystem(Pergamon-Elsevier Science Ltd, 2011-09) Solak, Ercan; Rhouma, Rhouma; Belghith, Safya MdimeghWe report a break for a recently proposed class of cryptosystems. The cryptosystem uses constant points of a periodic secret orbit to encrypt the plaintext. In order to break the system, it suffices to sort the constant points and find the initial fixed point. We also report breaks for modified versions of the cryptosystem. In addition, we discuss some efficiency issues of the cryptosystem.Yayın Projected changes in temperature and precipitation climatology of Central Asia CORDEX Region 8 by using RegCM4.3.5(Elsevier Ltd, 2017-01-01) Öztürk, Tuğba; Turp, Mustafa Tufan; Türkeş, Murat; Kurnaz, Mehmet LeventThis work investigated projected future changes in seasonal mean air temperature (°C) and precipitation (mm/day) climatology for the three periods of 2011–2040, 2041–2070, and 2071–2100, with respect to the control period of 1971–2000 for the Central Asia domain via regional climate model simulations. In order to investigate the projected changes in near future climate conditions, the Regional Climate Model, RegCM4.3.5 of the International Centre for Theoretical Physics (ICTP) was driven by two different CMIP5 global climate models. The HadGEM2-ES global climate model of the Met Office Hadley Centre and the MPI-ESM-MR global climate model of the Max Planck Institute for Meteorology were downscaled to 50 km for the Coordinated Regional Climate Downscaling Experiment (CORDEX) Region 8. We investigated the seasonal time-scale performance of RegCM4.3.5 in reproducing observed climatology over the domain of the Central Asia by using two different global climate model outputs. For the future climatology of the domain, the regional model projects relatively high warming in the warm season with a decrease in precipitation in almost all parts of the domain. A warming trend is notable, especially for the northern part of the domain during the cold season. The results of our study show that surface air temperatures in the region will increase between 3 °C and about 7 °C on average, according to the emission scenarios for the period of 2071–2100 with respect to past period of 1971–2000. Therefore, the projected warming and decrease in precipitation might adversely affect the ecological and socio-economic systems of this region, which is already a mostly arid and semi-arid environment.Yayın Generating multi-atom entangled W states via light-matter interface based fusion mechanism(Nature Publishing Group, 2015-11-09) Özaydın, Fatih; Zang, Xue-Ping; Yang, Ming; Song, Wei; Cao, Zhuo-LiangW state is a key resource in quantum communication. Fusion technology has been proven to be a good candidate for preparing a large-size W state from two or more small-size W states in linear optical system. It is of great importance to study how to fuse W states via light-matter interface. Here we show that it is possible to prepare large-size W-state networks using a fusion mechanism in cavity QED system. The detuned interaction between three atoms and a vacuum cavity mode constitute the main fusion mechanism, based on which two or three small-size atomic W states can be fused into a larger-size W state. If no excitation is detected from those three atoms, the remaining atoms are still in the product of two or three new W states, which can be re-fused. The complicated Fredkin gate used in the previous fusion schemes is avoided here. W states of size 2 can be fused as well. The feasibility analysis shows that our fusion processes maybe implementable with the current technology. Our results demonstrate how the light-matter interaction based fusion mechanism can be realized, and may become the starting point for the fusion of multipartite entanglement in cavity QED system.Yayın Impacts of climate change on precipitation climatology and variability in Turkey(Springer International Publishing Ag, 2020) Türkeş, Murat; Turp, M. Tufan; An, Nazan; Öztürk, Tuğba; Kurnaz, Mehmet LeventIn this chapter, changes in seasonal precipitation climatology, extreme weather conditions, and aridity conditions of Turkey are evaluated for the period of 2021-2050 with respect to the reference period of 1971-2000 by using regional climate model simulations. Projections of future climate conditions are modeled by forcing Regional Climate Model, RegCM4.4 of the International Centre for Theoretical Physics (ICTP) with MPI-ESM-MR global climate model of the Max Planck Institute for Meteorology. The outputs of MPI-ESM-MR are used to generate 10 km resolution data by the double nesting method under both RCP4.5 and RCP8.5 emission scenarios. The seasonal time-scale performance of RegCM4.4 in reproducing the observed climatology over Turkey is tested by using the output of the global climate model. The projection results show a strong decrease in precipitation for almost all parts of the domain according to the output of the regional model. The intensity of drought conditions is projected to increase. According to the projection results, more arid conditions are expected in the region for the near future. Therefore, drier than present climate conditions are projected to occur more intensely over Turkey.Yayın Impact of climate change on natural snow reliability, snowmaking capacities, and wind conditions of ski Resorts in Northeast Turkey: a dynamical downscaling approach(Mdpi Ag, 2016-04) Demiroğlu, Osman Cenk; Turp, Mustafa Tufan; Öztürk, Tuğba; Kurnaz, Mehmet LeventMany ski resorts worldwide are going through deteriorating snow cover conditions due to anthropogenic warming trends. As the natural and the artificially supported, i.e., technical, snow reliability of ski resorts diminish, the industry approaches a deadlock. For this reason, impact assessment studies have become vital for understanding vulnerability of ski tourism. This study considers three resorts at one of the rapidly emerging ski destinations, Northeast Turkey, for snow reliability analyses. Initially one global circulation model is dynamically downscaled by using the regional climate model RegCM4.4 for 1971-2000 and 2021-2050 periods along the RCP4.5 greenhouse gas concentration pathway. Next, the projected climate outputs are converted into indicators of natural snow reliability, snowmaking capacity, and wind conditions. The results show an overall decline in the frequencies of naturally snow reliable days and snowmaking capacities between the two periods. Despite the decrease, only the lower altitudes of one ski resort would face the risk of losing natural snow reliability and snowmaking could still compensate for forming the base layer before the critical New Year's week. On the other hand, adverse high wind conditions improve as to reduce the number of lift closure days at all resorts. Overall, this particular region seems to be relatively resilient against climate change.Yayın Simulation of temperature and precipitation climatology for the Central Asia CORDEX domain using RegCM 4.0(Inter-Research, 2012) Öztürk, Tuğba; Altınsoy, Hamza; Türkeş, Murat; Kurnaz, Mehmet LeventThe Coordinated Regional Climate Downscaling Experiment (CORDEX) is a framework designed to coordinate international efforts on regional climate simulations. CORDEX domains encompass the majority of land areas of the world. Region 8 of the CORDEX basically covers Central Asia, with the corners of the domain at 54.76 degrees N, 11.05 degrees E; 56.48 degrees N, 139.13 degrees E; 18.34 degrees N, 42.41 degrees E; and 19.39 degrees N, 108.44 degrees E and with a horizontal resolution of 50 km. In the present study, the results of an experiment with the ICTP regional climate RegCM 4.0 model that was run for seasonal mean air temperature and precipitation total series are presented. The experiment consists of one simulation from 1989 to 2010 using ERA-Interim reanalysis data as the boundary condition, another simulation for the period 1970-2000 using the global climate model ECHAM5 A1B scenario data for forcing, and finally a simulation for the period 2070-2100 using the ECHAM5 A1B scenario projection data for forcing. Between these 3 simulations we determined the temperature and precipitation climatology obtained from RegCM 4.0 downscaling for Region 8 of the CORDEX framework. In spite of the diverse topography of the region, the temperature and precipitation climatology obtained by RegCM 4.0 from hindcast data captures the general characteristics of the climate of Central Asia. In winter, the warm temperature bias of the forcing data is slightly decreased by regional downscaling. The influences of the Indian monsoon system are well represented, as this region covers a large area towards the southern boundary of Region 8, even though the focus of this work was to capture the general characteristics of the whole region.Yayın Deterministic generation of large scale atomic W states(Optical Soc Amer, 2016-05-30) Zang, Xue-Ping; Yang, Ming; Özaydın, Fatih; Song, Wei; Cao, Zhuo-LiangWe present a deterministic scheme for generating large-scale atomic W states in a cavity QED system via a simple expansion mechanism, which is realized only by a detuned interaction between two identical atoms and a vacuum cavity mode. With the presented scheme, a W-type Bell pair can be created and an n-atom W state can be expanded to a 2n-atom W state with a unit probability of success in principle. No multi-atom gates, quantum memories or quantum non-demolition measurements are required, greatly simplifying the experimental realization of the scheme. The feasibility analysis shows that our expansion scheme can be implemented with state-of-the-art technologies. Our scheme enables advances not only in quantum information and communication but also in quantum thermodynamics, where atomic W states plays a crucial role.
