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Hücresel kablosuz ağ analizi için bir stokastik geometri yaklaşımı
No full textCellular wireless communications systems transformed the way people communicated by combining communication and mobility. Since the early 1970s, the mobile industry has been driving the development and evolution of cellular technology. The first generation only offered voice communication, whereas the second generation offered both voice and data services. Furthermore, as cellular wireless technology advanced, 3G enabled video conferencing and other services. With rising demand, 4G emerged, ensuring us with ultra-broadband internet access. 5G will be able to provide us with services that we have never had before. Cellular wireless networks are typically modeled by placing base stations on a regular hexagonal grid and mobile users either randomly or deterministically distributed. These models have been widely used, but they have the disadvantage of being both highly idealized and not very tractable, so complex system-level simulations are used to assess coverage probability and rate. Models that are more tractable have long been desired. In this dissertation, we develop novel methods based on stochastic geometry to analyze the coverage and average spectral efficiency of downlink cellular wireless networks. In the first part of the dissertation, we consider to analyze the performance of SISO (Single Input Single Output) transmission scheme. Regarding this analysis, both the positions of base stations (BS) and mobile users are modeled as points of an independent Poisson Point Process' (PPP). We consider to use the max C/I (Carrier to Interference Ratio) scheduling method, to select the user with the best SIR (Signal to Interference Ratio) value among the users that are connected to the same base station. Since the base stations are randomly placed and users are linked to their closest base stations, the C/I ratios of multiple users become conditionally dependent. For such a realistic deployment scenario, we utilize stochastic geometry tools and copula functions to take into account this correlation and analyze the coverage probability and spectral efficiency. Our simulation results demonstrate that the commonly used independence assumption of the user C/I values overestimates both actual coverage probability and spectral efficiency of the system. In the second part, we analyze the coverage performance of multi-user multiple-input multiple-output (MU-MIMO) downlink cellular networks. We model the locations of the base stations and mobile users using Poisson Point Processes and employ maximum ratio transmission precoding at the base station. Our analysis builds upon Prony's method to approximately calculate the coverage probability using the sum of exponentials which facilitates the computation of Laplace transform of both intra-cell and inter-cell interference. We demonstrate the accuracy of derived approximate coverage probability expressions through numerical simulations for different MU-MIMO configurations. In the third part, we analyze the downlink coverage performance of general user, arbitrarily located in the 2-D region, edge user and worst user sit on the boundary between two neighbor cells and vertex where three neighbor cells meet respectively, considering the Coordinated Multipoint (CoMP) transmission scheme by using stochastic geometry approach. In addition, we analyze the performance of two users, in terms of average spectral efficiency in the CoMP transmission scheme where the users are connected to the closest and second closest BS's, by using stochastic geometry approach. The correlation of SIR values of two users are again modeled by using copula functions. The max C/I scheduling method is employed to select the user in this scheme.Hücresel kablosuz iletişim sistemleri, iletişim ve mobiliteyi birleştirerek insanların iletişim kurma şeklini değiştirmiştir. 1970'lerin başından beri, mobil endüstri, hücresel teknolojinin gelişimini ve evrimini yönlendirmektedir. Birinci nesil (1G) kablosuz haberleşme sistemleri sadece sesli iletişim sunarken, ikinci nesil (2G) hem ses hem de veri hizmetleri sunuyordu. Ayrıca, hücresel kablosuz teknoloji geliştikçe, 3G haberleşme sistemleri video konferans ve benzeri diğer hizmetleri etkinleştirmiştir. Artan taleple birlikte 4G kablosuz haberleşme sistemleri geliştirilmiş ve bu sayede ultra geniş bant internet erişimi sağlanmıştır. Halihazırda geliştirilmekte olan 5G ise bize daha önce hiç sahip olmadığımız hizmetleri sunabilecektir. Hücresel kablosuz ağlar, genel olarak, baz istasyonlarının düzenli bir altıgen ızgaraya yerleştirilmesi ve mobil kullanıcıların rastgele veya deterministik olarak dağıtılmasıyla modellenir. Bu modeller yaygın olarak kullanılmaktadır, ancak hem idealize edilmiş olmaları dezavantajına hem de matematiksel olarak çözümlenebilir olmama dezavantajına sahiptirler. Bu nedenle kapsama olasılığını ve kanal kapasitesini hesaplamak için karmaşık, sistem düzeyinde simulasyonlar yapılmaktadır. Sonuç olarak, matematiksel olarak çözümlenebilir modeller uzun zamandır arzu edilmektedir. Bu tezde, indirme yönündeki hücresel kablosuz ağların kapsama alanını ve ortalama spektral verimliliğini analiz etmek için stokastik geometriye dayalı yeni yöntemler geliştirilmiştir. Tezin ilk bölümünde, tek girişli tek çıkışlı (SISO-Single Input Single Output) iletim şemasının performansı analiz edilmiştir. Bu analiz kapsamında, hem baz istasyonlarının (BS) hem de mobil kullanıcıların konumları, bağımsız bir Poisson Noktası Süreci'nin (PPP-Poisson Point Process) noktaları olarak modellenmiştir. Aynı baz istasyonuna bağlı kullanıcılar arasında en iyi SIR (Sinyal-Girişim Oranı) değerine sahip kullanıcıyı seçmek için maksimum C/I (Carrier to Interference Ratio-Taşıyıcı Girişim Oranı) zamanlama yöntemi kullanılmıştır. Baz istasyonları rastgele yerleştirildiğinden ve kullanıcılar en yakın baz istasyonlarına bağlı olduğundan, birden fazla kullanıcının C/I oranları koşullu olarak bağımlı hale gelir. Böyle gerçekçi bir yerleştirme senaryosu için, bu korelasyonu hesaba katmak ve kapsama olasılığı ile spektral verimliliği analiz etmek için stokastik geometri araçları ve kopula fonksiyonları kullanılmıştır. Simülasyon sonuçlarımız, kullanıcı C/I değerleri için yaygın olarak kullanılan bağımsızlık varsayımının, sistemin hem gerçek kapsama olasılığının hem de spektral verimliliğinin olduğundan fazla hesaplanmasına neden olduğunu göstermektedir. İkinci bölümde, çok kullanıcılı çok girişli çok çıkışlı (MU-MIMO-Multiuser Multiple Input Multiple Output) aşağı yönlü hücresel ağların kapsama performansı analiz edilmiştir. Baz istasyonlarının ve mobil kullanıcıların konumları PPP kullanarak modellenmiş ve baz istasyonunda maksimum oranlı iletim (MRT-Maximum Ratio Transmission) ön kodlaması kullanılmıştır. Analizimiz, hem hücre içi hem de hücreler arası girişimin Laplace dönüşümünün hesaplanmasını kolaylaştıran üstellerin toplamını kullanarak kapsama olasılığını yaklaşık olarak hesaplamak için Prony'nin yöntemini temel almaktadır. Farklı MU-MIMO konfigürasyonları için nümerik simülasyonlar yoluyla, analitik olarak türetilmiş yaklaşık kapsama olasılığı ifadelerinin doğruluğu gösterilmiştir. Üçüncü bölümde, 2 boyutlu bölgeye rastgele yerleştirilen genel kullanıcı, iki komşu hücre arasındaki sınırda yer alan uç kullanıcı ve üç komşu hücrenin birleştiği köşe noktasındaki en kötü kullanıcı için, Koordineli Çoklu Nokta (CoMP-Coordinated Multipoint) yöntemiyle iletim yapıldığı göz önünde bulundurularak indirme yönündeki kapsama performansı, stokastik geometri yaklaşımıyla analiz edilmiştir. Ayrıca, kullanıcıların en yakın ve ikinci en yakın BS'lere bağlı olduğu, CoMP yöntemiyle servis verilen iki kullanıcının performansı stokastik geometri yaklaşımı kullanılarak analiz edilmiştir. İki kullanıcının SIR değerlerinin korelasyonu yine kopula fonksiyonları kullanılarak modellenmiştir. Bu CoMP iletim şemasında, kullanıcıyı seçmek için maksimum C/I zamanlama yöntemi kullanılmıştır
Understanding the feeling of missing out: A temporal perspective
No full textResearch to date has explored the feeling (or fear) of missing out phenomenon from different temporal perspectives, as an instant feeling about missing out on current activities and as a retrospective feeling about missing out on past events. Combining the two research streams, we conceptualize and distinguish the two types of feelings of missing out with different temporal orientations based on the circumplex model of affect. We show that both feelings are negative in valence, yet the feeling of missing out related to ongoing activities indicates a higher arousal and a stronger affective state. We also investigate the coping efforts with these feelings of missing out and show that individuals may rely on both emotion-focused and problem-focused coping strategies. Theoretical and well-being implications of the findings are discussed
Covid-19 karantina sürecinde çocukların duygusal durumları: Ebeveynlik stresi ve çocuğun mizacının katkısı
No full textChildren's emotional regulation and dysregulation emerge through the interaction between the child's individual (temperament) and the environmental (e.g., parenting stress) characteristics. The aim of the current study was to investigate the contributions of child temperament and parenting stress to children's emotional states during the COVID-19 outbreak. This study also examined the moderating role of parenting stress on the association between child temperament and children's emotional states. Participants were mothers of 219 (110 girls) Turkish preschool children whose ages ranged from 36 months to 76 months (M = 56.95 months, SD = 11.736 months). Mothers reported on children's emotional states (emotion regulation, emotion dysregulation, child aggression, and child anxiety), child temperament (persistence and reactivity), and parenting stress. Bivariate correlations and hierarchical regression models were run to test the hypotheses. Results indicated that persistence was negatively associated with emotion dysregulation and child aggression, whereas reactivity was negatively associated with emotion regulation and positively associated with emotion dysregulation, aggression, and anxiety. Besides, parenting stress was negatively associated with emotion regulation and positively associated with emotion dysregulation, aggression, and anxiety. Results from the hierarchical regression analyses revealed that parenting stress moderated the association between persistence, and emotion regulation, and child aggression. Simple slopes analyses showed that combinations of high persistence and low parenting stress increased emotion regulation, while combinations of low persistence and high parenting stress increased child aggression. The findings underline the significance of both child temperament and parenting stress for children's emotional states. In the light of previous studies, findings were discussed in the current study, considering limitations, future directions, and implications.Çocukların duygu düzenleme ve düzensizlikleri çevre (ebeveynlik stresi) ve çocuğun bireysel karakteri (mizaç) arasındaki etkileşimle ortaya çıkar. Bu çalışmanın amacı, çocuğun mizacı ve ebeveynlik stresinin, COVID-19 karantina döneminde çocukların duygu durumlarına katkılarını incelemektir. Bu çalışma aynı zamanda ebeveynlik stresinin çocuğun mizacı ile çocukların duygu durumları arasındaki ilişki üzerindeki ılımlı rollerini incelemiştir. Katılımcılar 36 ay ve 76 ay arasında 219 (110 kız) Türk okulöncesi dönemdeki çocuğun anneleridir (ortalama yaş: 56.95 ay, SS: 11.736 ay). Ebeveynler, çocukların duygu durumları (duygu düzenleme, duygu düzensizliği, kızgınlık, anksiyete), çocuğun mizacı (sebatkarlık ve tepkisellik) ve ebeveynlik stresi hakkında rapor verdiler. İki değişkenli korelasyonlar ve hiyerarşik regresyon modelleri, hipotezi test etmek için çalıştırılmıştır. Sonuçlar, sebatkarlığı duygu düzensizliği ve kızgınlıkla negatif ilişkili gösterirken, tepkiselliği duygu düzenleme ile negatif, duygu düzensizliği, kızgınlık ve anksiyete ile pozitif ilişkili olarak göstermiştir. Ayrıca, ebeveynlik stresi duygu düzenleme ile negatif, duygu düzensizliği, kızgınlık ve anksiyete ile pozitif ilişkili bulunmuştur. Hiyerarşik regresyon analizi sonuçları ebeveynlik stresinin sebatkarlık ve, duygu düzenleme ve kızgınlık arasındaki ilişkiyi denetlediğini göstermiştir. Basit eğim analizleri, yüksek düzeyde sebatkarlık ve düşük düzeyde ebeveynlik stresi kombinasyonlarının çocukların duygu düzenlemesine katkı sağladığını gösterirken düşük düzeyde sebatkarlık ve yüksek düzeyde ebeveynlik stresi kombinasyonlarının çocukların kızgınlıklarını arttırdığını göstermiştir. Bulgular hem ebeveynlik stresinin hem de çocuğun mizacının çocukların duygu durumları açısından öneminin altını çizmektedir. Sınırlılıklar ve olası uygulamalar dikkate alınarak, önceki çalışmalar ışığında, sonuçlar tartışılmıştır
Outage performance analysis of vertical underwater VLC links
No full textIn this paper, we investigate the outage performance of vertical stratified underwater optical links in the presence of moderate/strong turbulence conditions. Specifically, we consider the cascaded Gamma-Gamma turbulence channel model and derive a closed-form expression for outage probability. We then use our derived expression to investigate the achievable diversity order (DO) and asymptotic diversity order (ADO). We further confirm our derivations through Monte Carlo simulations
Analysis of offshore wind turbine by considering soil-pile-structure interaction: effects of foundation and sea-wave properties
No full textPrediction of the dynamic performance of an offshore wind turbine (OWT) requires consideration of many different design parameters. Besides the superstructure, the OWT foundation also plays an important role both functionally and financially in the design. In this study, numerical dynamic analyses of an offshore wind turbine with a monopile foundation are performed under wave loading that may lead to soil liquefaction around the pile due to cyclic stresses induced by the pile displacements using the open-source program, OpenSees. Effects of foundation properties such as monopile diameter, pile embedment depth, and sea-wave characteristics such as its period, sea-water depth, duration, and level of the loading on the dynamic performance of the system are investigated. The results in terms of deformations, excess pore water pressure, and inertial forces are presented and discussed. The findings are considered as valuable guidance on the estimation of the dynamic performance and liquefaction susceptibility of the offshore wind turbine foundations under cyclic sea-wave loads
Measurement of the inclusive tt¯ production cross section in proton-proton collisions at s√ = 5.02 TeV
No full textThe top quark pair production cross section is measured in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data were collected in a special LHC low-energy and low-intensity run in 2017, and correspond to an integrated luminosity of 302 pb−1. The measurement is performed using events with one electron and one muon of opposite charge, and at least two jets. The measured cross section is 60.7 ± 5.0 (stat) ± 2.8 (syst) ± 1.1 (lumi) pb. A combination with the result in the single lepton + jets channel, based on data collected in 2015 at the same center-of-mass energy and corresponding to an integrated luminosity of 27.4 pb−1, is then performed. The resulting measured value is 63.0 ± 4.1 (stat) ± 3.0 (syst+lumi) pb, in agreement with the standard model prediction of 66.8−3.1+2.9 pb.BMBWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, FAPERGS, and FAPESP (Brazil); MES and BNSF (Bulgaria); CERN; CAS, MoST, and NSFC (China); MINCIENCIAS (Colombia); MSES and CSF (Croatia); RIF (Cyprus); SENESCYT (Ecuador); MoER, ERC PUT and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRI (Greece); NKFIA (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic of Korea); MES (Latvia); LAS (Lithuania); MOE and UM (Malaysia); BUAP, CINVESTAV, CONACYT, LNS, SEP, and UASLP-FAI (Mexico); MOS (Montenegro); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS, RFBR, and NRC KI (Russia); MESTD (Serbia); MCIN/AEI and PCTI (Spain); MOSTR (Sri Lanka); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR, and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United Kingdom); DOE and NSF (U.S.A.).r Individuals have received support from the Marie-Curie program and the European Research Council and Horizon 2020 Grant, contract Nos. 675440, 724704, 752730, 758316, 765710, 824093, 884104, and COST Action CA16108 (European Union); the Leventis Foundation; the Alfred P. Sloan Foundation; the Alexander von Humboldt Foundation; the Belgian Federal Science Policy Office; the Fonds pour la Formation a la Recherche dans l'Industrie et dans l'Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); the F.R.S.-FNRS and FWO (Belgium) under the "Excellence of Science-EOS"-be.h project n. 30820817; the Beijing Municipal Science & Technology Commission, No. Z191100007219010; the Ministry of Education, Youth and Sports (MEYS) of the Czech Republic; the Deutsche Forschungsgemeinschaft (DFG), under Germany's Excellence Strategy -EXC 2121 "Quantum Universe" -390833306, and under project number 400140256 -GRK2497; the Lendulet ("Momentum") Prog ram and the Janos Bolyai Research Scholarship of the Hungarian Academy of Sciences, the New National Excellence Program UNKP, the NKFIA research grants 123842, 123959, 124845, 124850, 125105, 128713, 128786, and 129058 (Hungary); the Council of Science and Industrial Research, India; the Latvian Council of Science; the Ministry of Science and Higher Education and the National Science Center, contracts Opus 2014/15/B/ST2/03998 and 2015/19/B/ST2/02861 (Poland); the Fundacao para a Ciencia e a Tecnologia, grant CEECIND/01334/2018 (Portugal); the National Priorities Research Program by Qatar National Research Fund; the Ministry of Science and Higher Education, projects no. 14.W03.31.0026 and no. FSWW-2020-0008, and the Russian Foundation for Basic Research, project No. 19-42-703014 (Russia); MCIN/AEI/10.
13039/501100011033, ERDF "a way of making Europe", and the Programa Estatal de Fomento de la Investigacion Cientifica y Tecnica de Excelencia Maria de Maeztu, grant MDM-2017-0765 and Programa Severo Ochoa del Principado de Asturias (Spain); the Stavros Niarchos Foundation (Greece); the Rachadapisek Sompot Fund for Postdoctoral Fellowship, Chulalongkorn University and the Chulalongkorn Academic into Its 2nd Century Project Advancement Project (Thailand); the Kavli Foundation; the Nvidia Corporation; the SuperMicro Corporation; the Welch Foundation, contract C-1845; and the Weston Havens Foundation (U.S.A.).Publisher versio
Search for a heavy resonance decaying into a top quark and a W boson in the lepton+jets final state at s√ = 13 TeV
No full textA search for a heavy resonance decaying into a top quark and a W boson in proton-proton collisions at s = 13 TeV is presented. The data analyzed were recorded with the CMS detector at the LHC and correspond to an integrated luminosity of 138 fb−1. The top quark is reconstructed as a single jet and the W boson, from its decay into an electron or muon and the corresponding neutrino. A top quark tagging technique based on jet clustering with a variable distance parameter and simultaneous jet grooming is used to identify jets from the collimated top quark decay. The results are interpreted in the context of two benchmark models, where the heavy resonance is either an excited bottom quark b∗ or a vector-like quark B. A statistical combination with an earlier search by the CMS Collaboration in the all-hadronic final state is performed to place upper cross section limits on these two models. The new analysis extends the lower range of resonance mass probed from 1.4 down to 0.7 TeV. For left-handed, right-handed, and vector-like couplings, b∗ masses up to 3.0, 3.0, and 3.2 TeV are excluded at 95% confidence level, respectively. The observed upper limits represent the most stringent constraints on the b∗ model to date.BMBWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, FAPERGS, and FAPESP (Brazil); MES and BNSF (Bulgaria); CERN; CAS, MoST, and NSFC (China); MINCIENCIAS (Colombia); MSES and CSF (Croatia); RIF (Cyprus); SENESCYT (Ecuador); MoER, ERC PUT and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRI (Greece); NKFIA (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic of Korea); MES (Latvia); LAS (Lithuania); MOE and UM (Malaysia); BUAP, CINVESTAV, CONACYT, LNS, SEP, and UASLP-FAI (Mexico); MOS (Montenegro); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS, RFBR, and NRC KI (Russia); MESTD (Serbia); SEIDI, CPAN, PCTI, and FEDER (Spain); MOSTR (Sri Lanka); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR, and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United Kingdom); DOE and NSF (U.S.A.).r Individuals have received support from the Marie-Curie program and the European Research Council and Horizon 2020 Grant, contract Nos. 675440, 724704, 752730, 758316, 765710, 824093, 884104, and COST Action CA16108 (European Union); the Leventis Foundation; the Alfred P. Sloan Foundation; the Alexander von Humboldt Foundation; the Belgian Federal Science Policy Office; the Fonds pour la Formation a la Recherche dans l'Industrie et dans l'Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); the F.R.S.-FNRS and FWO (Belgium) under the "Excellence of Science -EOS" -be.h project n. 30820817; the Beijing Municipal Science & Technology Commission, No. Z191100007219010; the Ministry of Education, Youth and Sports (MEYS) of the Czech Republic; the Deutsche Forschungsgemeinschaft (DFG), under Germany's Excellence Strategy -EXC 2121 "Quantum Universe" -390833306, and under project number 400140256 -GRK2497; the Lendulet ("Momentum") Program and the Janos Bolyai Research Scholarship of the Hungarian Academy of Sciences, theNew National Excellence Program UNKP, the NKFIA research grants 123842, 123959, 124845, 124850, 125105, 128713, 128786, and 129058 (Hungary); the Council of Science and Industrial Research, India; the Latvian Council of Science; the Ministry of Science and Higher Education and the National Science Center, contracts Opus 2014/15/B/ST2/03998 and 2015/19/B/ST2/02861 (Poland); the Fundacao para a Ciencia e a Tecnologia, grant CEECIND/01334/2018 (Portugal); the National Priorities Research Program by Qatar National Research Fund; the Ministry of Science and Higher Education, projects no. 14.W03.31.0026 and no. FSWW-2020-0008, and the Russian Foundation for Basic Research, project No.
19-42-703014 (Russia); the Programa Estatal de Fomento de la Investigacion Cientifica y Tecnica de Excelencia Maria de Maeztu, grant MDM-2015-0509 and the Programa Severo Ochoa del Principado de Asturias; the Stavros Niarchos Foundation (Greece); the Rachadapisek Sompot Fund for Postdoctoral Fellowship, Chulalongkorn University and the Chulalongkorn Academic into Its 2nd Century Project Advancement Project (Thailand); the Kavli Foundation; the Nvidia Corporation; the SuperMicro Corporation; the Welch Foundation, contract C-1845; and the Weston Havens Foundation (U.S.A.).Publisher versio
Performance study and analysis of MIMO visible light communication-based V2V systems
No full textVehicular Visible Light Communication (VLC) has recently attracted much interest from researchers and scientists. This technology enables the connectivity between the vehicles and the infrastructures along the road utilizing the Lighting-Emitting-Diodes based vehicle HeadLights (HLs) and TailLights (TLs) as wireless transmitters. This paper investigates the performance of a Vehicle-to-Vehicle VLC system using a Multiple-Input Multiple-Output (MIMO) scheme. Specifically, we establish the MIMO transmission system by using the two HLs of the source vehicle as wireless transmitters and multiple receivers (RXs) installed at the rear of the destination vehicle as wireless receivers. We consider different numbers of RXs, which result in various MIMO configurations, i.e., 2 × 2 , 2 × 3 , and 2 × 4. We conduct a channel modeling study based on the non-sequential ray-tracing capabilities of the OpticStudio software to obtain the optical channel gain, considering the possibility of both horizontal and vertical displacement between vehicles. We then explore the contribution of each RX in the total received power. In addition, we investigate the effect of weather conditions, modulation orders, and artificial light sources on the bit error rate (BER) performance of the considered MIMO configurations. The obtained results demonstrate that deploying the MIMO with higher orders can significantly enhance the system performance, particularly when there is a lateral shift between the two cars. It has been drawn from our results that the required SNR to achieve a BER of 10- 4 reduces by 6 dB when 2 × 4 MIMO configuration is deployed compared to the 2 × 2 MIMO configuration
Stochastic production planning with flexible manufacturing systems and uncertain demand: A column generation-based approach
No full textThe ongoing pandemic, namely COVID-19, has rendered widespread economic disorder. The deficiencies have delayed production at manufacturers in several industries on the supply side. The effects of disruption were more notable for industries with longer supply chains, especially reaching East Asia. Regarding the demand, sectors can be divided into three categories: i) the ones, like e-commerce companies, that experienced augmented demand; ii) the ones with a plunged demand, like what hotels and restaurants experience; iii) the companies experiencing a roller-coaster-ride business. After mitigation efforts, the economy started recovering, resulting in increased demand. However, regardless of their struggles, the companies have not fully returned to their pre-pandemic levels. One of the strategies to gain resilience in its supply chain and manage the disruptions is to employ flexible/hybrid manufacturing systems. This paper considers a flexible/hybrid manufacturing production setting with typically dedicated machinery to satisfy regular demand and a flexible manufacturing system (FMS) to handle surge demand. We model the uncertainty in demand using a scenario-based approach and allow the business to make here-and-now and wait-and-see decisions exploiting the cost-effectiveness of the standard production and responsiveness of the FMS. We propose a column generation-based algorithm as the solution approach. Our computational analysis shows that this hybrid production setting provides highly robust response to the uncertainty in demand, even with high fluctuations
Su altı kanallarında kuantum anahtar dağılımının performans analizi
No full textThe current literature on quantum key distribution (QKD) is mainly limited to the transmissions over ber optic, atmospheric or satellite links and are not directly applicable to underwater environments with di erent channel characteristics. Absorption, scattering, and turbulence experienced in underwater channels severely limit the range of quantum communication links. In the rst part of this thesis, we analyze the quantum bit error rate (QBER) and secret key rate (SKR) performance of the well-known BB84 protocol in underwater channels. As path loss model, we consider a modi ed version of Beer-Lambert formula which takes into account the e ect of scattering. We derive a closed-form expression for the wave structure function to determine the average power transfer over turbulent underwater path and use this to obtain an upper bound on QBER as well as a lower bound on SKR. Based on the derived bounds, we present the performance of BB84 protocol in di erent water types including clear, coastal and turbid water and under di erent atmospheric conditions such as clear, hazy and overcast. We further investigate the e ect of system parameters such as aperture size and detector eld-of-view on QBER and SKR performance metrics. In the second part of this thesis, as a potential solution to overcome range limitations, we investigate a multi-hop underwater QKD where intermediate nodes between the source and destination nodes help the key distribution. We consider the deployment of passive relays which simply redirect the qubits to the next relay node or the receiver without any measurement. Based on the near- eld analysis, we present the performance of relay-assisted QKD scheme in terms of quantum bit error rate and secret key rate in di erent water types and turbulence conditions. We further investigate the e ect of system parameters such as aperture size and detector eld-of-view on the performance. Our results demonstrate under what conditions relay-assisted QKD can be bene cial and what end-to-end transmission distances can be supported with a multi-hop underwater QKD system. In the last part of this thesis, we investigate the fundamental performance limits of decoy BB84 protocol over turbulent underwater channels and provide a comprehensive performance characterization. As path loss model, we consider a modi ed version of Beer-Lambert formula, which takes into account the e ect of scattering. Based on near eld analysis, we utilize the wave structure function to determine the average power transfer over turbulent underwater path and use this to obtain a lower bound on key generation rate. Based on this bound, we present the performance of decoy BB84 protocol in di erent water types (clear and coastal). We further investigate the e ect of transmit aperture size and detector eld of view.Kuantum anahtar da g t m (QKD) hakk ndaki mevcut literatur, esas olarak ber optik, atmosferik veya uydu ba glant lar uzerinden yap lan aktar mlarla s n rl d r ve farkl kanal ozelliklerine sahip su alt ortamlar na do grudan uygulanamaz. Sualt kanallar nda ya sanan absorpsiyon, sa c lma ve turbulans, kuantum ileti sim ba glant lar n n aral g n ciddi sekilde s n rlar. Bu tezin ilk bolumunde, iyi bilinen BB84 protokolunun sualt kanallar nda kuantum bit hata oran (QBER) ve gizli anahtar oran (SKR) performans n analiz ediyoruz. Yol kayb modeli olarak, sa c lma etkisini hesaba katan Beer-Lambert formulunun de gi stirilmi s bir versiyonunu ele al yoruz. Turbulansl su alt yolu uzerindeki ortalama gu c transferini belirlemek i cin dalga yap s fonksiyonu i cin kapal bi cimli bir ifade turetiyoruz ve bunu QBER'de bir ust s n r ve SKR'de bir alt s n r elde etmek i cin kullan yoruz. Elde edilen s n rlara dayanarak, BB84 protokolunun berrak, k y ve bulan k su dahil farkl su turlerinde ve berrak, puslu ve bulutlu gibi farkl atmosferik ko sullar alt nda performans n sunuyoruz. A c kl k boyutu ve dedektor goru s alan gibi sistem parametrelerinin QBER ve SKR performans ol cutleri uzerindeki etkisini ayr ca ara st r yoruz. Bu tezin ikinci bolumunde, menzil s n rlamalar n n ustesinden gelmek i cin potansiyel bir cozum olarak, kaynak ve hedef du gumler aras ndaki ara du gumlerin anahtar da g t m na yard mc oldu gu cok atlamal bir sualt QKD'sini ara st r yoruz. Kubitleri herhangi bir ol cum yapmadan bir sonraki role du gumune veya al c ya yonlendiren pasif rolelerin konu sland r lmas n du sunuyoruz. Yak n alan analizine dayanarak, farkl su turleri ve turbulans ko sullar nda kuantum bit hata oran ve gizli anahtar oran a c s ndan role destekli QKD semas n n performans n sunuyoruz. A c kl k boyutu ve dedektor goru s alan gibi sistem parametrelerinin performans uzerindeki etkisini ayr ca ara st r yoruz. Sonu clar m z, role destekli QKD'nin hangi ko sullar alt nda faydal olabilece gini ve cok sekmeli bir sualt QKD sistemi ile hangi u ctan uca iletim mesafelerinin desteklenebilece gini gostermektedir. Bu tezin son bolumunde, calkant l su alt kanallar uzerinde yem BB84 protokolunun temel performans s n rlar n ara st r yoruz ve kapsaml bir performans karakterizasyonu sa gl yoruz. Yol kayb modeli olarak, sa c lma etkisini hesaba katan Beer-Lambert formulunun de gi stirilmi s bir versiyonunu ele al yoruz. Yak n alan analizine dayanarak, turbulansl su alt yolu uzerindeki ortalama gu c transferini belirlemek i cin dalga yap s fonksiyonunu kullan yoruz ve bunu anahtar uretim h z nda daha du suk bir s n r elde etmek i cin kullan yoruz. Bu s n ra dayanarak, yem BB84 protokolunun farkl su turlerinde (temiz ve k y ) performans n sunuyoruz. _Iletim a c kl g boyutunun ve dedektor goru s alan n n etkisini daha da ara st r yoruz