Interference-free Spectrum Sharing In Cognitive Radio Based On Space Time Coding

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2016Thesis (M.Sc.) -- İstanbul Technical University, Instıtute of Science and Technology, 2016Yeni nesil telsiz iletişim sistemleri ve gezgin sistemler daha yüksek veri hızlarının yanında, maksimum bant genişliği kullanımına da gereksinim duyarlar. Son yıllarda, literatürde bazı teknikler telsiz sistemlerin yüksek veri hızlarını destekleyeceği çeşitli şekillerde ortaya konulmuştur. Ancak, yüksek veri hızlarını destekleme gereksinimini karşılamada, spektrumun çoğunun lisanslı kullanıcılara ait olduğu spektrum tahsis tablosunda olduğu gibi spektrum yetersizliği problemiyle karşılaşılır. Bununla birlikte, spektrum ölçümleri frekansa, coğrafi konuma ve zamana bağlı olarak spektrumun büyük bir kısmının sürekli olarak kullanılmadığını göstermektedir. Sonuç olarak, yüksek veri hızlarını desteklemek için spektrum dağılımını kabul edilebilir servis kalitesine göre yöneterek kaynakların verimli bir şekilde kullanılması gerekmektedir. Bu nedenle, telsiz iletişimde mevcut spektrumu paylaşarak spektrum yetersizliği problemini ortadan kaldırmak için pek çok yaklaşım ortaya atılmıştır. İki farklı telsiz sistemin önceliklerine göre aynı frekans bandında çalıştığı bilişsel radio (CR) spektrum kullanımını arttırmak ve spektrum yetersizliğini çözmek için potansiyel bir yol olarak kabul edilmiştir. CR ilerideki yeni nesil kablosuz sistemler için yenilikçi bir teknik ve gelişen bir araştırma alanıdır. CR’da lisanslı bandlara erişmek için ikincil kullanıcılar (SU) tarafından araya yerleştirme, altına serme ve üstüne serme teknikleri kullanılabilir. Araya yerleştirme tekniğinde, SU’lar birincil kullanıcılara (PU) girişim yaratmadan spektrum boşluklarını kullanmak için PU’ların varlığını ya da yokluğunu sezerler. Altına serme tekniğinde, eğer PU’lardaki girişim önceden belirlenmiş bir girişim seviyesinin altındaysa, SU’lara lisanslı spektrumu kullanma hakkı verilir. Üstüne serme tekniğinde ise, lisanssız kullanıcılar genellikle lisanslı spektrumu paylaşmak için spektrum sahiplerinin yararına işbirliği yaparak bir bedel öderler. Literatürde karma ve toplamsal kodlama teknikleri gibi farklı spektrum paylaşım türleri önerilmiştir. Toplamsal kodlamada SU, PU’nun ve kendi işaretini birleştirir, sonra birincil alıcıya (PR) ve ikincil alıcıya (SR) yayın yapar. Ancak bu teknik her iki kullanıcının alıcılarında önemli girişime neden olur. Sistemin, spektrumdan yarar sağlamak ve PU ile işbirliği yapmak için farklı teknikleri bir araya getirdiği karma yöntemlerden de yaralanılabilir. İletilen işarete kanalların sönümleme etkisini azaltabilen, modülasyon çeşitlemesi olarak da bilinen bir çeşitleme tekniği işaret uzayı çeşitlemesidir (SSD). SSD fazladan band genişliği ya da güç kullanmadan sönümlemeli kanallarda başarımı artırır. SSD işleminde veri iletiminin öncesinde modülasyonlu işaret kümeleri belli bir açı ile döndürülür ve döndürülen işaretler arasındaki minimum çarpımsal uzaklık maksimize edilir. Döndürülmüş işaret kümesine koordinat serpiştirmeli dik tasarım (CIOD) uygulandıktan sonra düzensiz bir modülasyonlu işaret kümesi elde edilir. Normalde işbirlikli haberleşmede verinin alıcıya iletilmesi birden fazla zaman aralığı aldığı için tüm sistemin band verimliliği düşer. Ancak, SSD ve CIOD tekniklerini sistem yapısında kullanmak sistemin karmaşıklığını artırmadan işbirlikli sistemlerde band verimliliğini kolaylıkla artırabilir. Bu tezde, üstüne serme yöntemiyle çalışan bilişsel radyo için iki farklı spektrum paylaşım protokolü önerilmiştir. İlk protokolde, birincil sistem her biri bir antenle donatılmış bir birincil verici (PT) ve bir birincil alıcı (PR) ile ikincil sistem ise her biri bir antenle donatılmış bir ikincil verici (ST) ve bir ikincil alıcı (SR) dan oluşmaktadır. Birincil sistem ile işbirliği çerçevesinde, SU’nun PU ya ait spektrum bandını kullanmasına izin verilmektedir. Bu çalışmada hem spektral verimliliği ve çeşitlemeyi artırmak hem de iki kullanıcının karşılıklı girişimini ortadan kaldırmak amacıyla üç zaman aralığında iki kullanıcının iletimini sağlayan CIOD uzay zaman kodlaması kullanan bir iletim protokolu önerilmektedir. İlk zaman aralığında, PT kendi işaretini PR ve ST’ye iletir ve ST iletilen işareti çözmeye çalışır. ST, PU nun işaretini doğru çözerse, serpiştirilmiş birincil işaret koordinat çiftini PR’ye ikinci zaman aralığında iletilmektir ve PR, PT ve ST’den aldığı işaretler yardımıyla işareti çözmeye çalışır. Ancak, ST’nin PT’den aldığı işareti doğru çözemediği durumda, PR sadece ilk zaman aralığında PT den gelen işarete dayanarak iletilen işareti çözmeye çalışır. Son olarak, ST üçüncü zaman aralığında kendi (ikincil) işaretini SR’ye iletir. Önerilen protokolde ikincil kullanıcıya ayrı bir zaman aralığı ayrılması iki kullanıcı arasındaki girişimi kaldırırken iki birincil işaretin CIOD yardımıyla iki zaman aralığında iletilmesi üç kanal kullanımı başına iki birincil işaretin iletilmesini sağlamakta, böylece iki kanal kullanımı başına bir birincil işaretin iletildiği referans sistemlere göre kanalın daha verimli kullanılmasını sağlamaktadır. PT ile ST arasında bir kritik uzaklık tanımlanmakta, ST, PT ye bu uzaklıktan daha yakın olduğu sürece PU nun servis kesilme olasılığı spektrum paylaşımı olmadığı durumdakine eşit veya daha düşük olmaktadır. Rayleigh sönümlemeli kanalda, PU ve SU nun servis kesilme olasılıkları için kapalı biçimde kuramsal ifadeler türetilmekte, hedeflenen farklı hızlar için protokolun başarımı değerlendirilmektedir. Kuramsal sonuçların bilgisayar benzetimleriyle bütünüyle uyum içerisinde olduğu görülmektedir. Önerilen protokol için hem PU nun hem de SU nun başarımında ST de toplamsal kodlamanın kullanıldığı literatürde verilen referans protokole göre önemli kazançlar elde edilmektedir. Diğer yandan birincil kullanıcının bit hata olasılığı için kuramsal bir üst sınır elde edilmekte, sonuçlar bilgisayar benzetimleriyle desteklenmektedir. Beklendiği gibi bilgisayar benzetim sonuçları artan işaret-gürültü oranı ile kuramsal üst sınıra yaklaşmaktadır. Son olarak, ikincil kullanıcının BER başarımı klasik doğrudan iletime eşdeğerdir. 4QAM ve 16QAM modülasyonları ve ST ile SR arasındaki uzaklığın farklı değerleri için elde edilen BER başarım eğrileri önerilen protokolun toplamsal kodlamalı referans protokole üstünlüğünü ortaya koymaktadır. İkincil protokolde birincil kullanıcı, birer antenli PT ve PR den oluşurken ikincil kullanıcı için ST iki antenli olup SR bir antenlidir. ST bir önceki protokolden farklı olarak en büyük oran birleştirme (MRC) ve Alamouti uzay-zaman kodlama tekniklerinden yararlanmaktadır. Protokol yine üstüne serme tekniğine dayalı olup spektral verimliliği artırma, çeşitleme sağlama ve alıcılarda girişimi önleme amacıyla CIOD ve Alamouti uzay zaman kodlama teknikleri bir arada kullanılmaktadır. Protokol PU nun iki, SU nun bir işaretini üç zaman aralığında iletmektedir. Birinci zaman aralığında PT iki birincil işaretin yalnız gerçel ve sanal kısımlarını PR ve ST ye iletmekte, ST iki anteni yardımıyla MRC uygulayarak bu iki birincil işareti yalnız gerçel ve sanal bileşenlerinden çözmekte, ikinci zaman aralığında ilişkin sanal ve gerçel bileşenleri bir araya getirerek birinci anteninden PR ye iletmektedir. Kendi ikincil işaretini ise aynı anda ikinci anteninden SR ye iletmektedir. Üçüncü zaman aralığında ise ikinci zaman aralığında ilettiği işaretlere Alamouti uzay zaman blok kodlaması uygulayarak her iki anteninde iletmektedir. ST, PT den gelen işareti çözemezse ikinci ve üçüncü zaman aralıklarında Alamouti koduna uygun biçimde kendi işaretini iletmektedir. Protokol hem PR hem de SR de Alamouti kodlamanın getirdiği tek simge çözme özelliğiyle girişimi ortadan kaldırmakta ayrıca her iki kullanıcı için uzay çeşitlemesi sağlamaktadır. Tezde birincil kullanıcının bit hata olasılığı için kuramsal bir üst sınır türetilmekte, üst sınırın geçerliliği bilgisayar benzetim sonuçlarıyla desteklenmektedir. PT, ST ve PR arasındaki farklı uzaklık değerleri için sonuçlar irdelenmekte, protokolun sağladığı BER başarım kazancı referans protokolle karşılaştırılarak ortaya konmaktadır. Diğer yandan, ikincil kullanıcının BER başarımı klasik Alamouti kodununkine eşdeğer olmakta, ST ile SR arasındaki uzaklığın çeşitli değerleri ve 16QAM modülasyonu için irdelenmekte, doğrudan iletim durumu ve toplamsal kodlamanın kullanıldığı referans protokolle karşılaştırılarak üstünlüğü ortaya konmaktadır.Next generation wireless communications and mobile systems demand higher data rates with maximum bandwidth utilization. Over the past years, some techniques in the literature are provided in various ways where wireless systems should support high data rates. However, this requirement is faced with spectrum scarcity accommodation problem as in spectrum allocation chart where majority of the spectrum is under license. Nevertheless, spectrum measurements show that most of the spectrum is not continuously used based on the frequency, geographical location and time. As a result, this requirement necessitates the efficient use of the available resources by managing spectrum distribution to provide acceptable service quality. Therefore, several approaches in wireless systems are introduced in literature for sharing the available spectrum to overcome the spectrum scarcity problem. Cognitive Radio (CR) is considered as a potential solution to boost the spectrum utilization and solve the spectrum scarcity in which two different wireless systems could operate in the same frequency band with respect to their priority. CR is an innovative technique and developing area of research for the next wireless generation systems. In CR, to access the licensed bands interweave, underlay and overlay patterns can be used by the Secondary Users (SUs). In the interweave protocol, SUs sense the existence or nonexistence of Primary Users (PUs) to use spectrum holes without causing interference to PUs. In the underlay protocol, SUs are certified to use the licensed spectrum if the interference caused at PUs is below a predetermined interference level. In the overlay protocol, unlicensed users generally pay a price to share a licensed spectrum by cooperating for the benefit of spectrum owners. Different kinds of spectrum sharing model such as hybrid and superposition coding techniques are proposed in the literature. In superposition coding SU combines the PU's and its own signal and then broadcast to both Primary Receiver (PR) and Secondary Receiver (SR). However, this technique causes severe interference in both receivers. Two CR patterns can be combined to approach the hybrid mode where in this case the system has flexibility to operate in different protocols to obtain benefits from the spectrum and cooperate with PU. One diversity technique that could mitigate the fading channels effect on the transmitted signal is Signal Space Diversity (SSD) also known as modulation diversity. SSD provides performance improvement over fading channels without using extra bandwidth or power. In SSD, constellation points of the modulation are rotated by an angle before the transmission which maximize the minimum product distance of the rotated constellation, and after applying Coordinate Interleaved Orthogonal Design (CIOD) on the rotated constellation an irregular modulation points are acquired. Normally, in cooperative communications overall system spectral efficiency and rate are decreased due to the fact that data takes more than one time slot to be transmitted to the receiver. However, using SSD and CIOD technique in the system configuration, one can easily enhance the overall spectral efficiency and rate in cooperative systems without adding any complexity to the system. In this thesis, two different spectrum sharing protocols for cognitive radio operating in overlay mode are proposed. In the first protocol, the primary and secondary system is comprised of PT, PR, ST and SR equipped all with one antenna. SU is allowed to use the shared spectrum band in accordance to cooperate with primary system. We take advantages of the SSD and CIOD concepts in this three-phase overlay protocol to enhance the spectral efficiency, rate and diversity as well as to provide single symbol decoding. In the first transmission time slot, PT broadcasts its signal to PR and ST where ST tries to decode the transmitted signal from PT. If ST correctly decodes the PU's signal, ST forwards the coordinate interleaved signal pair to PR in the second time slot and PR tries to estimate the symbol by received signals from PT and ST. However, in the case that ST could not correctly decode the signal received from PT, PR decodes the symbol only from PT. Finally, SU's signal is transmitted to SR by ST at the third time slot. Due to the fact that a specific time slot is dedicated to SU data transmission, this protocol avoids interference. A critical distance between PT and ST is obtained such that as long as ST is located within that distance the outage probability of PU will be equal or lower than the case that of without spectrum sharing and ST will benefit from the band. The outage probabilities for PU and SU over Rayleigh fading channels are derived in a closed-form expressions and depicted for different target rates. Note that, the theoretic outcomes match perfectly with simulation results. It is shown that a significant performance improvement in the proposed scheme is notable both for PU and SU in comparison to the reference protocol where superposition coding is used at ST. Furthermore, an upper bound on the Bit Error Probability (BEP) of primary system is obtained and supported via simulation results. The simulation results agree well with the theoretical upper bound in the high Signal to Noise Ratio (SNR), respectively. Finally, for the secondary system, BEP performance is the same as classical direct transmission. The BEP performance for 16-QAM and 4-QPSK modulation for different values of the distance between ST and SR are depicted where in both cases simulation. The results confirm the efficiency of the proposed spectrum sharing compared to the reference protocol. In the second protocol, PU consists of a pair of PT and PR with one antenna and for SU, ST is equipped with two antennas to use the benefits of Maximum Ratio Combining (MRC) and Alamouti techniques and SR has only one antenna. A CR protocol which is configured on overlay mode to share the spectrum of the primary system is presented. SSD, CIOD and Alamouti concepts are used together to benefit from the single symbol decoding, diversity gain and to increase the overall system rate and spectral efficiency. The protocol comprises of three time slots to transmit PU's and SU's data. In the first time slot, PT transmits the primary signal to PR and to both antennas of ST. Then, ST uses the MRC technique to decode the transmitted signal. If ST correctly decodes the transmitted signal from PT, it applies Alamouti coding to transmit the primary and its own symbols to PR and SR in the second and third time slots. Nevertheless, if ST could not correctly decode the signal pair received from PT, PR will estimate the symbol from the direct link PT$\to$PR. Meanwhile, secondary signal is transmitted in the second and third time slots which provides diversity which enhances SU system performance. This protocol guarantees an interference-free communication for both users by considering the fact that PR and SR could extract their own signal based on the single symbol decoding technique provided by Alamouti coding. An upper bound for the BEP of the primary system is derived and it is shown that computer simulation results are in perfectly match with the theoretical upper bound in high SNR which validates the theoretical derivations. Results for different values of the distance between PT, ST and PR are obtained where in all cases, they validate the significant improvement in the Bit Error Rate (BER) performance for the proposed protocol. For the secondary system, BEP performance is the same as classical Alamouti code and is depicted for various values of the distance between ST and SR for classical 16-QAM and is compared with the straightforward transmission scheme and with the reference scheme where SU uses nearly all of its power to transmit the PU's signal and SU is in outage in most cases and operates a relay.Yüksek LisansM.Sc

Energy Management and Size Optimization of Hybrid Energy Systems

Electricity is assumed as a significant driving force in people\u27s lives, ensuring comfort and boosting the quality of life. However, some remote communities have the least access to the national grid due to the far distance to the province\u27s s industrial and electrical sector. The lack of grid connection has led to antiquated methods of power production, which increases reliance on carbon-based fuels and pollutes the atmosphere. This study focuses on the techno-econo-environmental aspects of introducing hybrid renewable energy systems (HRES) in three energy-poor islands in Eastern Canada. the proposed HRES have been simulated based on real-time field data of solar irradiation, wind speed, ambient temperature, and load demand during 8760 hours in a year. Chapter II examines Pelee Island\u27s reliable and economical hybrid energy solutions by comparing conventional and state-of-the-art storage technologies, namely 1kWh Lead Acid, 1kWh Li-Ion, 100kWh Li-Ion, and Scenario IV: 2.5 kWh PowerSafe SBS (SBS). The optimization results indicate that 152 kW PV module, 200 kW DG, 190 kW CNV, when integrated with 853 1kWh Li-Ion batteries, have the lowest NPC. Fuel price and irradiance of Lead Acid -based systems have a greater impact on renewable fraction but have a lower effect on LCOE. Chapter III evaluates the ability of grid-connected renewable energy solutions to implement four different PV tracking technologies controlled by two energy management strategies(CC and LF). The assumed sun-tracking PV modules contain horizontal-axis monthly adjustment (HMA), horizontal-axis continuous adjustment (HCA), Vertical-Axis continuous adjustment (VCA), and Dual-axis-tracker (DAT). The results indicate that a CC-controlled system equipped with a vertical-axis PV tracker has the optimal solution. The LF-controlled system with a similar tracker has a higher net present cost (NPC), cost of energy (COE), and renewable fraction by ~$0.02M, ~$0.002/kWh, and 7.6%, respectively. In Chapter IV, techno-economic feasibility evaluation of simultaneous hydrogen and electricity production is discussed in three energy-poor islands in Canada: Pelee, Saint Pierre, and Wolfe Island, all located in separate directions in Eastern Canada. The optimal sizing for the electric load of 50 residential households and hydrogen for 50 fuel cell electric cars will be conducted in each location. The results show that the impact of load value in minimizing NPC is higher than the expected inflation rate. Paying attention to these research findings highly depends on the location and techno-economic data of the energy generation systems

Global, regional, and national burden of diabetes from 1990 to 2021, with projections of prevalence to 2050: a systematic analysis for the Global Burden of Disease Study 2021

Background Diabetes is one of the leading causes of death and disability worldwide, and affects people regardless of country, age group, or sex. Using the most recent evidentiary and analytical framework from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD), we produced location-specific, age-specific, and sex-specific estimates of diabetes prevalence and burden from 1990 to 2021, the proportion of type 1 and type 2 diabetes in 2021, the proportion of the type 2 diabetes burden attributable to selected risk factors, and projections of diabetes prevalence through 2050. Methods Estimates of diabetes prevalence and burden were computed in 204 countries and territories, across 25 age groups, for males and females separately and combined; these estimates comprised lost years of healthy life, measured in disability-adjusted life-years (DALYs; defined as the sum of years of life lost [YLLs] and years lived with disability [YLDs]). We used the Cause of Death Ensemble model (CODEm) approach to estimate deaths due to diabetes, incorporating 25 666 location-years of data from vital registration and verbal autopsy reports in separate total (including both type 1 and type 2 diabetes) and type-specific models. Other forms of diabetes, including gestational and monogenic diabetes, were not explicitly modelled. Total and type 1 diabetes prevalence was estimated by use of a Bayesian meta-regression modelling tool, DisMod-MR 2.1, to analyse 1527 location-years of data from the scientific literature, survey microdata, and insurance claims; type 2 diabetes estimates were computed by subtracting type 1 diabetes from total estimates. Mortality and prevalence estimates, along with standard life expectancy and disability weights, were used to calculate YLLs, YLDs, and DALYs. When appropriate, we extrapolated estimates to a hypothetical population with a standardised age structure to allow comparison in populations with different age structures. We used the comparative risk assessment framework to estimate the risk-attributable type 2 diabetes burden for 16 risk factors falling under risk categories including environmental and occupational factors, tobacco use, high alcohol use, high body-mass index (BMI), dietary factors, and low physical activity. Using a regression framework, we forecast type 1 and type 2 diabetes prevalence through 2050 with Socio-demographic Index (SDI) and high BMI as predictors, respectively. Findings In 2021, there were 529 million (95% uncertainty interval [UI] 500–564) people living with diabetes worldwide, and the global age-standardised total diabetes prevalence was 6·1% (5·8–6·5). At the super-region level, the highest age-standardised rates were observed in north Africa and the Middle East (9·3% [8·7–9·9]) and, at the regional level, in Oceania (12·3% [11·5–13·0]). Nationally, Qatar had the world's highest age-specific prevalence of diabetes, at 76·1% (73·1–79·5) in individuals aged 75–79 years. Total diabetes prevalence—especially among older adults—primarily reflects type 2 diabetes, which in 2021 accounted for 96·0% (95·1–96·8) of diabetes cases and 95·4% (94·9–95·9) of diabetes DALYs worldwide. In 2021, 52·2% (25·5–71·8) of global type 2 diabetes DALYs were attributable to high BMI. The contribution of high BMI to type 2 diabetes DALYs rose by 24·3% (18·5–30·4) worldwide between 1990 and 2021. By 2050, more than 1·31 billion (1·22–1·39) people are projected to have diabetes, with expected age-standardised total diabetes prevalence rates greater than 10% in two super-regions: 16·8% (16·1–17·6) in north Africa and the Middle East and 11·3% (10·8–11·9) in Latin America and Caribbean. By 2050, 89 (43·6%) of 204 countries and territories will have an age-standardised rate greater than 10%. Interpretation Diabetes remains a substantial public health issue. Type 2 diabetes, which makes up the bulk of diabetes cases, is largely preventable and, in some cases, potentially reversible if identified and managed early in the disease course. However, all evidence indicates that diabetes prevalence is increasing worldwide, primarily due to a rise in obesity caused by multiple factors. Preventing and controlling type 2 diabetes remains an ongoing challenge. It is essential to better understand disparities in risk factor profiles and diabetes burden across populations, to inform strategies to successfully control diabetes risk factors within the context of multiple and complex drivers.publishedVersio

Global, regional, and national burden of disorders affecting the nervous system, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BackgroundDisorders affecting the nervous system are diverse and include neurodevelopmental disorders, late-life neurodegeneration, and newly emergent conditions, such as cognitive impairment following COVID-19. Previous publications from the Global Burden of Disease, Injuries, and Risk Factor Study estimated the burden of 15 neurological conditions in 2015 and 2016, but these analyses did not include neurodevelopmental disorders, as defined by the International Classification of Diseases (ICD)-11, or a subset of cases of congenital, neonatal, and infectious conditions that cause neurological damage. Here, we estimate nervous system health loss caused by 37 unique conditions and their associated risk factors globally, regionally, and nationally from 1990 to 2021.MethodsWe estimated mortality, prevalence, years lived with disability (YLDs), years of life lost (YLLs), and disability-adjusted life-years (DALYs), with corresponding 95% uncertainty intervals (UIs), by age and sex in 204 countries and territories, from 1990 to 2021. We included morbidity and deaths due to neurological conditions, for which health loss is directly due to damage to the CNS or peripheral nervous system. We also isolated neurological health loss from conditions for which nervous system morbidity is a consequence, but not the primary feature, including a subset of congenital conditions (ie, chromosomal anomalies and congenital birth defects), neonatal conditions (ie, jaundice, preterm birth, and sepsis), infectious diseases (ie, COVID-19, cystic echinococcosis, malaria, syphilis, and Zika virus disease), and diabetic neuropathy. By conducting a sequela-level analysis of the health outcomes for these conditions, only cases where nervous system damage occurred were included, and YLDs were recalculated to isolate the non-fatal burden directly attributable to nervous system health loss. A comorbidity correction was used to calculate total prevalence of all conditions that affect the nervous system combined.FindingsGlobally, the 37 conditions affecting the nervous system were collectively ranked as the leading group cause of DALYs in 2021 (443 million, 95% UI 378–521), affecting 3·40 billion (3·20–3·62) individuals (43·1%, 40·5–45·9 of the global population); global DALY counts attributed to these conditions increased by 18·2% (8·7–26·7) between 1990 and 2021. Age-standardised rates of deaths per 100 000 people attributed to these conditions decreased from 1990 to 2021 by 33·6% (27·6–38·8), and age-standardised rates of DALYs attributed to these conditions decreased by 27·0% (21·5–32·4). Age-standardised prevalence was almost stable, with a change of 1·5% (0·7–2·4). The ten conditions with the highest age-standardised DALYs in 2021 were stroke, neonatal encephalopathy, migraine, Alzheimer's disease and other dementias, diabetic neuropathy, meningitis, epilepsy, neurological complications due to preterm birth, autism spectrum disorder, and nervous system cancer.InterpretationAs the leading cause of overall disease burden in the world, with increasing global DALY counts, effective prevention, treatment, and rehabilitation strategies for disorders affecting the nervous system are needed

Performance Analysis of Dual-Hop AF Relaying with Non-Linear/Linear Energy Harvesting

Massive device-to-device communication nodes and Internet of Things (IoT) devices are expected to be crucial components in next-generation wireless networks. However, the energy constraint of these nodes presents a challenge since the energy of the batteries is limited. Motivated by this, radio frequency energy harvesting (EH) has been developed as an efficient strategy to overcome the energy constraint of IoT devices and sensor networks. In this paper, a wireless-powered dual-hop amplify-and-forward relaying system, in the absence of a direct link between the source (S) and the destination (D), is considered. It is assumed that a dedicated power beacon (PB) transmits an energy-bearing signal from which the power-constrained S and relay (R) harvest energy. Theoretical derivations of bit error probability, outage probability, and throughput expressions are performed for both linear and non-linear energy harvesting models. Moreover, the theoretical results provided for different system parameters are validated via Monte Carlo simulations. The obtained results reveal the difference between the realistic non-linear EH model and the conventional linear EH model, which overestimates the system performance at high levels of harvested energy. Thus, it leads to misunderstanding the real performance of the EH systems. However, at low levels of harvested energy, both models behave similarly and provide realistic results

Survey of the Effect of Biotin on Glycemic Control and Plasma Lipid Concentrations in Type 1 Diabetic Patients in Kermanshah in Iran

Abstract Objective: Diabetes mellitus is the most common chronic endocrine disease worldwide. Intensive glycemic control plays an important role in decreasing morbidity and mortality rate of the disease. Preclinical studies have shown that biotin has an essential role in regulating blood glucose and serum lipid metabolism. This study aims to evaluate the effect of biotin on glycemic control and plasma lipids concentrations in type 1diabetic patients. methods: This randomized double-blind placebo-controlled clinical trial study was conducted 70 type 1 diabetic patients with an age range 5-25 years old with poorly controlled (glycosylated hemoglobin ≥8%). Subjects were randomly allocated into two groups. In the intervention group biotin (40 microgram/kg) was administered plus daily insulin, while the control group received placebo plus daily insulin regimen for three months. Laboratory tests including glycosylated hemoglobin (HbA1c), fasting blood sugar and plasma lipids were measured at the base and after 3 months. Results: In this study, seventy patients were evaluated, 35 were allocated to each group. There were no statistically significant differences between age, gender, duration of diabetes, BMI and BP between the two groups (p>0.05). HbA1c in the intervention (biotin) group was 9.84±1.80 at base and after 3 months treatment, it declined to 8.88±1.73 (p<0.001). In the control group HbA1c at base was 9.39±1.58, after 3 months it increased to10.11± 1.68. There were statistically significant differences in the mean of HbA1c in both the biotin and the control groups (p<0.001). FBS in the biotin group at base was 275±65.76 mg/dl and after 3 months it had reduced to 226± 41.31 (p<0.001). There were statistically significant differences in the mean of total cholesterol, low density lipoprotein cholesterol and triglyceride between the two groups at the end of 3 months (p<0.05). Conclusion: Results of this study showed that biotin administration as an adjuvant in addition to insulin regimen can improve glycemic management and decrease plasma lipids concentrations in poorly controlled type 1 diabetic patients

Quercetin in Food: Possible Mechanisms of Its Effect on Memory

Abstract: Quercetin (3,3�,4�,5,7-pentahydroxyflavone) is found in vegetables and fruits. It is one of the major flavonoids that is part of human diets. Quercetin has several pharmacological effects in the nervous system as a neuroprotective agent. In this review, we summarize the research on quercetin and its role in memory in both animals and humans. Articles were chosen from the Scopus, PubMed, and Web of Science databases. In this review, we describe and summarize the importance of quercetin’s presence in the body, particularly in the brain; its kinetics, including its absorption, metabolism, distribution, and excretion; its behavioral effects; and some of the possible mechanisms of action of quercetin on memory in different animal models. Several important pathways that may be involved in the processes of learning and memory, long-term potentiation, and cognition may be impaired during neurological diseases or other medical conditions. As dietary quercetin is important, provision of its best formulation for delivery to the brain as a nutraceutical and in clinical translational research for the prevention or treatment of Alzheimer’s disease and other types of dementia is necessary. Keywords: Alzheimer’s disease, flavonoids, food, memory, querceti

Natural convection of Al2O3-water nanofluid with variable properties in a square enclosure with heat source and heat sink on the vertical walls

The buoyancy-driven fluid flow and heat transfer in a square cavity with partially active side walls filled The buoyancy-driven fluid flow and heat transfer in a square cavity with partially active side walls filled which the length is equal to half of height and width is 0.1 of height respectively so that it contains Al_2 O_3âwater nanofluid which variable properties, has been investigated numerically. The active parts of the left and the right side walls of the cavity are maintained at temperatures Th and Tc , respectively, with Th>Tc . The enclosureâs top and bottom walls as well as the inactive parts of its side walls are kept insulated. The governing equations in the two-dimensional space are discretized using the control volume method. A proper upwinding scheme is employed to obtain stabilized solutions. Using the developed code, a parametric study is undertaken, and the effects of the Rayleigh number, the locations of the active parts of the side walls and the volume fraction of the nanoparticles on the fluid flow and heat transfer inside the cavity are investigated. It is observed from the results that the average Nusselt number increase with increasing the Rayleigh number and decrease with increasing the volume fraction of the nanoparticles. Moreover, the maximum average Nusselt number for the high and the low Rayleigh numbers occur for the bottomâmiddle locations of the thermally active parts, respectively

The Relationship of Cognitive Flexibility and Self-compassion With Depression and Anxiety Among Healthcare Staff During the COVID-19 Pandemic

Objectives: The COVID-19 outbreak has considerably affected various aspects of our lives and different groups of society. In this regard, healthcare staff is more affected by the pressure of heavy workloads and daily exposure to suspected COVID-19 cases. This study aimed to investigate depression and anxiety as two basic factors of mental health among healthcare workers and the role of self-compassion and cognitive flexibility during the pandemic.  Methods: A multi-center cross-sectional study was conducted. Healthcare workers were the target group, and the samples were collected through the online groups from healthcare staff of coronavirus hospitalized centers in Tehran. A convenience sampling method was used in this study. The general anxiety disorder-7 scale, patient health questionnaire, cognitive flexibility inventory, and self-compassion short-form scale were used online for data collection. Totally 551 respondents were entered into the analysis process of the current study.  Results: A total of 437 respondents (79.3%) had mild to severe anxiety symptoms, and 447(81.1%) had mild to severe depressive symptoms. Cognitive flexibility had a significant negative relationship with anxiety and depression (r=-0.40, r=-0.37, respectively, P<0.001). Similarly, the relationship between self-compassion and anxiety and depression was significantly negative (r=-0.48, r=-0. 47, respectively, P<0.001). Discussion: This study demonstrates the positive effects of cognitive flexibility and self-compassion on healthcare staff during COVID-19