Synthesis gas production using non-thermal plasma reactors

textToday we face the formidable challenge of meeting the fuel needs of a growing population while minimizing the adverse impacts on our environment. Thus, we search for technologies that can provide us with renewable fuels while mitigating the emission of global pollutants. To this end, use of non-thermal plasma processes can offer novel methods for efficiently and effectively converting carbon dioxide and water vapor into synthesis gas for the production of renewable fuels. Particularly, non-thermal plasma technologies offer distinct advantages over conventional methods including lower operating temperatures, reduced need for catalysts and potentially lower manufacturing and operation costs. The non-thermal plasma reactors have been studied for ozone generation, material synthesis, decontamination, thruster for microsatellites, and biomedical applications. This dissertation focuses on producing synthesis gas using a non-thermal, microhollow cathode discharge (MHCD) plasma reactor. The prototype MHCD reactor consisted of a mica plate as a dielectric layer that was in between two aluminum electrodes with a through hole. First, electrical characterization of the reactor was performed in the self-pulsing regime, and the reactor was modeled with an equivalent circuit which consisted of a constant capacitance and a variable, negative differential resistance. The values of the resistor and capacitors were recovered from experimental data, and the introduced circuit model was validated with independent experiments. Experimental data showed that increasing the applied voltage increased the current, self-pulsing frequency and average power consumption of the reactor, while it decreased the peak voltage. Subsequently, carbon dioxide and water vapor balanced with argon as the carrier gas were fed through the hole, and parametric experiments were conducted to investigate the effects of applied voltage (from 2.5 to 4.5 kV), flow rate (from 10 to 800 mL/min), CO₂ mole fraction in influent (from 9.95% to 99.5%), dielectric thickness (from 150 to 450 [mu]m) and discharge hole diameter (from 200 to 515 [mu]m) on the composition of the products, electrical-to-chemical energy conversion efficiency, and CO₂-to-CO conversion yield. Within the investigated parameter ranges, the maximum H2/CO ratio was about 0.14 when H2O and CO₂ were dissociated in different reactors. Additionally, at an applied voltage of 4.5 kV, the maximum yields were about 28.4% for H2 at a residence time of 128 [mu]s and 17.3% for CO at a residence time of 354 [mu]s. Increasing residence time increased the conversion yield, but decreased the energy conversion efficiency. The maximum energy conversion efficiency of about 18.5% was achieved for 99.5% pure CO₂ at a residence time of 6 [mu]s and an applied voltage of 4.5 kV. At the same applied voltage, the maximum efficiency was about 14.8% for saturated CO₂ at a residence time of 12.8 [mu]s. The future work should focus on optimizing the conversion yield and efficiency as well as analyzing the temporal and spatial changes in the gas composition in the plasma reactor.Mechanical Engineerin

Techno-Economic Comparative Analysis of Renewable Energy Systems: Case Study in Zimbabwe

Fluctuations in fossil fuel prices significantly affect the economies of countries, especially oil-importing countries, hence these countries are thoroughly investigating the increase in the utilization of renewable energy resources as it is abundant and locally available in all the countries despite challenges. Renewable energy systems (RES) such as solar and wind systems offer suitable alternatives for fossil fuels and could ensure the energy security of countries in a feasible way. Zimbabwe is one of the African countries that import a significant portion of its energy needs which endanger the energy security of the country. Several studies in the literature discussed the feasibility of different standalone and hybrid RES either with or without energy storage systems to either maximize the technical feasibility or the economic feasibility; however, none of the studies considered maximizing both feasibilities at the same time. Therefore, we present a techno-economic comparison of standalone wind and solar photovoltaic (PV) in addition to hybrid PV/wind systems based on maximizing the RES fraction with levelized cost of electricity (LCOE) being less than or equal to the local grid tariff where Gwanda, Zimbabwe, is the case study. The methodology suggested in this study could increase the utilization of renewable energy resources feasibly and at the same time increase the energy security of the country by decreasing dependency on imported energy. The results indicate that the PV/wind hybrid system does not only have the best economic benefits represented by the net present value (NPV) and the payback period (PBP), but also the best technical performance; where the maximum feasible size of the hybrid system-2 MW wind and 1 MW PV-has RES fraction of 65.07%, LCOE of 0.1 USD/kWh, PBP of 3.94 years, internal rate of return of 14.04% and NPV of 3.06 × 106 USD. Having similar systems for different cities in Zimbabwe will decrease the energy bill significantly and contribute toward the energy security of the country

Techno-economic comparative analysis of renewable energy systems: Case study in Zimbabwe

© 2020 by the authors. Licensee MDPI, Basel, Switzerland.Fluctuations in fossil fuel prices significantly affect the economies of countries, especially oil-importing countries, hence these countries are thoroughly investigating the increase in the utilization of renewable energy resources as it is abundant and locally available in all the countries despite challenges. Renewable energy systems (RES) such as solar and wind systems offer suitable alternatives for fossil fuels and could ensure the energy security of countries in a feasible way. Zimbabwe is one of the African countries that import a significant portion of its energy needs which endanger the energy security of the country. Several studies in the literature discussed the feasibility of different standalone and hybrid RES either with or without energy storage systems to either maximize the technical feasibility or the economic feasibility; however, none of the studies considered maximizing both feasibilities at the same time. Therefore, we present a techno-economic comparison of standalone wind and solar photovoltaic (PV) in addition to hybrid PV/wind systems based on maximizing the RES fraction with levelized cost of electricity (LCOE) being less than or equal to the local grid tariff where Gwanda, Zimbabwe, is the case study. The methodology suggested in this study could increase the utilization of renewable energy resources feasibly and at the same time increase the energy security of the country by decreasing dependency on imported energy. The results indicate that the PV/wind hybrid system does not only have the best economic benefits represented by the net present value (NPV) and the payback period (PBP), but also the best technical performance; where the maximum feasible size of the hybrid system-2 MW wind and 1 MW PV-has RES fraction of 65.07%, LCOE of 0.1 USD/kWh, PBP of 3.94 years, internal rate of return of 14.04% and NPV of 3.06 × 106 USD. Having similar systems for different cities in Zimbabwe will decrease the energy bill significantly and contribute toward the energy security of the country

100% Renewable Energy Grid for Rural Electrification of Remote Areas: A Case Study in Jordan

Many developing countries suffer from high energy-import dependency and inadequate electrification of rural areas, which aggravates the poverty problem. In this work, Al-Tafilah in Jordan was considered as a case study, where the technical, economic, and environmental benefits of a decentralized hybrid renewable energy system that can match 100% of the city demand were investigated. A tri-hybrid system of wind, solar, and hydropower was integrated with an energy storage system and optimized to maximize the match between the energy demand and production profiles. The optimization aimed at maximizing the renewable energy system (RES) fraction while keeping the levelized cost of electricity (LCOE) equal to the electricity purchase tariff. The techno-economic analysis showed that the optimal system in Al-Tafilah comprises a 28 MW wind system, 75.4 MW PV, and 1 MW hydropower, with a 259 MWh energy storage system, for which a RES fraction of 99% can be achieved, and 47,160 MtCO2 are avoided. This study can be easily extended to other rural cities in Jordan, as they have higher renewable energy system (RES) potential. The presented findings are essential not only for Jordan’s planning and economy-boosting but also for contributing to the ongoing force against climate change

Türkiye’de diş hekimlerinin bifosfonatlar konusundaki farkındalık ve bilgilerinin değerlendirilmesi

Aim: Bisphosphonates (BPs) are inorganic pyrophosphate analogs used for the treatment of various diseases. This study aimed to evaluate the knowledge and attitudes of general dental practitioners (GDP), specialist trainees (ST), and specialists (S) in Turkey toward medication-related osteonecrosis of the jaw (MRONJ) and to optimize future training programs in this field. Materials and Methods: A self-report questionnaire consisting of 7 questions about demographic data, knowledge about BPs, MRONJ and treatment modalities was prepared and send to the members of Turkish Dental Association via email. Results: A total of 209 participants were included in this survey. The mean age of the ST group was significantly lower than the mean ages of the GDP and S groups (P= 0.003, P= 0.038). GDP are less likely to think of BPs administration and radiotherapy treatment than S or ST upon observation of an exposed bone in the head-and-neck region (P=0.048, P=0.008). In comparison to the S and ST groups, the GDP group displayed less knowledge regarding the radiological and intraoral examination of patients undergoing BP therapy (P= 0.034). Conclusion: The increasing awareness of dentists about usage and side effects of BPs is important for preventing MRONJ. The GDP group displayed significantly less knowledge regarding the radiological and intraoral examinations of patients undergoing BP therapy. Greater efforts are required to increase education and knowledge of MRONJ and BPs among dental practitioners.Amaç: Bisfosfonatlar çeşitli hastalıkların tedavisinde kullanılan inorganik pirofosfat analoglarıdır. Bu çalışma uzman olmayan diş hekimlerinin, uzmanlık öğrencilerinin ve uzmanların ilaca bağlı gelişen çene osteonekrozuna yönelik bilgi ve tutumlarını değerlendirmenin yanında, gelecekteki eğitim programlarını optimize etmeyi amaçlamıştır. Materyal ve Metot: Çalışmaya 209 katılımcı dahil edilmiştir. Türk Dişhekimleri Birliği’nin desteğiyle bir anket hazırlanmış ve üyeler arasında e-posta ile paylaşılmıştır. Katılımcıların demografik bilgiler, ilaca bağlı çene osteonekrozları, bisfosfonatlar ve tedavi yaklaşımları ile ilgili 7 sorudan oluşan anketi yanıtlamaları istenmiştir. Bu anket sorularına hekimlerin verdiği cevaplar sayı ve yüzde ile tanımlanmıştır. Bulgular: Ankete katılan uzmanlık öğrencilerinin ortalama yaşı, uzman olmayan diş hekimleri ve uzmanlardan anlamlı olarak düşük bulunmuştur (P = 0.003, P = 0.038). Uzman olmayan diş hekimleri, baş-boyun bölgesinde gözlemlenen ekspoze kemiğin bisfosfonat tedavisi ya da radyoterapiye bağlı olabilme ihtimalini diğer gruplara göre daha az değerlendirmiştir (P=0.048, P=0.008). Uzman ve uzmanlık öğrencilerine kıyasla uzman olmayan diş hekimleri, bisfosfonat kullanan hastaların radyolojik ve ağız içi bulguları hakkında daha az bilgi sahibi olduğunu belirtmiştir (P = 0.034). Sonuç: Diş hekimlerinin bisfosfonatların kullanımı ve yan etkileri konusunda artan farkındalığı MRONJ’un önlenmesi için önemlidir. Diş hekimleri arasında MRONJ ve bisfosfonatlar ile ilgili bilincin artırılması için daha fazla çaba gösterilmesi ve hedef kitleye yönelik eğitim planları oluşturulması gerekmektedi

Güneş enerjisi destekli zeolit iklimlendirme sistemi

TÜBİTAK MAG01.01.2009Güneş enerjisi ekonomik, temiz ve yenilenebilir bir enerji türüdür. Çevresel faktörler ve artmakta olan enerji talepleri dikkate alındığında bu enerji türünün kullanımı büyük önem kazanmaktadır. Güneş enerjili adsorplanmalı soğutma (GEAS) sistemleri gelecekte yaygın olarak kullanılması düşünülen ve ticarileşmesi için yoğun bir şekilde çaba sarf edilen termal enerji destekli soğutma sistemlerindendir. Bu sistemlerin başarılı bir şekilde çalışması büyük ölçüde adsorban- adsorplanan çiftinin doğru seçimine bağlıdır. Zeolit-su, zeolit-organik soğutucular, silika jel-su ve activated karbon-methanol katı adsorplanmalı güneş enerjili soğutma sistemlerinde kulanılabilecek uygun adsorban- adsorplanan çiftlerinden bazılarıdır. Adsorban malzemenin adsorplama kapasitesi, x=f (P, T), adsorpsiyon basıncı ve adsorban malzemenin sıcaklığı ile değişmektedir ve bu değişim çoğunlukla eş sıcaklık eğrileri çizilerek ifade edilmektedir. Bu çalışmada ilk olarak, zeolit-su çalışma çiftine ait eş sıcaklık eğrilerini elde etmek için adsorpsiyon deney düzeneği tasarlanmış ve imal edilmiştir. Daha sonra, bu düzenek üzerinde bir takım deneyler yapılmıştır. Bu deneyler sonucunda, zeolit-su çalışma çiftine ait eş sıcaklık eğrileri, adsorpsiyon ve desorpsiyon prosesleri için farklı adsorban o sıcaklıkları(40-150 C)veadsorpsiyonbasınçları(0.87-7.38kPa)altındadeneyselolarakelde edilmiştir. Ayrıca, adsorpsiyon ve desorpsiyon prosesleri için elde edilen eş sıcaklık eğrilerine Dubinin–Astakhov denklemi uyarlanmıştır. Đkinci olarak, adsorpsiyon deneylerinden elde edilen sonuçlar çerçevesinde, zeolit-su çalışma çiftini kullanan güneş enerjisi destekli adsorpsiyonlu örnek soğutma grubu tasarlanmış ve imalatı gerçekleştirilmiştir. Daha sonra, adsorpsiyonlu örnek soğutma grubunun termal performansı farklı buharlaştırıcı sıcaklıklarında deneysel olarak incelenmiştir. Desorpsiyon prosesi sırasında zeolit yatağının yenilenmesi için gerekli enerji, güneş enerjisi yerine elektrik enerjisiyle ısıtılan ısı transfer sıvısının gövde ile adsorban yatak arasında dolaştırılmasıyla sağlanmıştır. Diğer bir ifade ile güneş enerjisi elektrik enerjisi kullanılarak benzeştirilmiştir. Deneyler sonucunda, soğutma grubunun COP değeri ortalama 0, 25 olarak bulunmuştur. Son olarak, GEAS sistemlerini başarısı çalışma çiftinin doğru seçiminin yanı sıra sistemde kullanılacak güneş toplaçlarının performansına ve ekonomik maliyetinede büyük ölçüde bağlıdır. Dolayısıyla bu çalışmada, soğutma sisteminin güneş enerjisi destekli olması sebebiyle bir yıl boyunca düzlemsel ve vakumlu boru tipi güneş toplaçlarının performansı Ankara ili iklim koşulları altında deneysel olarak incelenmiştir. Ayrıca, güneş enerjisi destekli zeolit-su çalışma çiftini kullanan xi adsorpsiyonlu soğutma sisteminin yıllık analizlerini yapmak üzere TRNSYS programı yardımıyla sayısal bir model tasarlanmıştır.Solar energy is economical, clean and renewable. The use of solar energy is gaining more attention due to environmental factors and increasing demand for energy. Solar powered adsorption cooling (SPAC) systems are considered to have a large potential for use in the future and extensive efforts have been expended to make the thermal powered adsorption cooling systems commercial. The successful operation of these systems mostly depends on the correct choice of the adsorbent-adsorbate working pair. Zeolite-water, zeolite-organic refrigerants, silica gel-water and activated carbon-methanol are some of the suitable adsorbent-adsorbate pairs that can be used in solar powered adsorption cooling systems. Adsorption capacity of the adsorbent material, x=f (P, T), varies with the adsorption pressure and adsorbent temperature and this variation is commonly represented by isotherms of the adsorbent investigated. In this study, firstly, an adsorption experimental set-up was designed and constructed to obtain the isotherms of a natural zeolite-water working pair. After that, a set of experiments was conducted using this set-up. As a result of these experiments, isotherms of the zeolite-water pair were obtained experimentally under various adsorbent o temperatures (40-150 C) and adsorption pressures (0.87-7.38 kPa). In addition, the Dubinin– Astakhov equation was used to fit the isotherm data that were obtained for adsorption and desorption processes. Secondly, within the framework of the results of the adsorption experiments, a prototype of the solar powered adsorption cooling system using the natural zeolite-water working pair was designed and constructed. Afterwards, the thermal performance of the prototype was investigated experimentally under different evaporation temperatures. In these experiments, during the desorption process, the solar energy that is needed to dry out the saturated adsorbent was simulated by using electrical energy. As a result, the average COP value of the prototype studied was found as 0,25. Finally, in addition to the correct choice of the adsorbent-adsorbate pair, the success of the (SPAC) systems depends largely on the thermal performance and cost of the solar collectors. Therefore, in this study, the performance of flat plate and evacuated tube collectors were investigated under the climatic conditions of Ankara for one year. Additionally, a numerical model of the solar powered adsorption cooling system using zeolite-water pair was developed with the help of the TRNSYS program to analyze the annual performance of this system

Determinants of high sensitivity troponin T concentration in chronic stable patients with heart failure: Ischemic heart failure versus non-ischemic dilated cardiomyopathy

Background: Cardiac troponin T is a marker of myocardial injury, especially when measured by means of the high-sensitivity assay (hs-cTnT). The echocardiographic and clinical predictors of hs-cTnT may be different in ischemic heart failure (IHF) and non-ischemic dilated cardiomyopathy (DCM).Methods: Sixty consecutive patients (19 female, 41 male; mean age 56.3 ± 13.9 years) with stable congestive heart failure (33 patient with IHF and 27 patients with DCM), with New York Heart Association functional class I–II symptoms, and left ventricular ejection fraction < 40% were included.Results: In patients with IHF peak early mitral inflow velocity (E), E/peak early diastolic mitral annular tissue Doppler velocity (Em) lateral, peak systolic mitral annular tissue Doppler velocity (Sm) lateral and logBNP were univariate predictors of hs-cTnT above median. But only E/Em lateral was an independent predictor of hs-cTnT above median (p = 0.04, HR: 1.2,CI: 1–1.4). In patients with DCM; left atrial volume index, male sex, Sm lateral and global longitudinal strain (LV-GLS) were included in multivariate model and LV-GLS was detected to be an independent predictor for hs-cTnT above median (p < 0.05, HR: 0.7, CI: 0.4–1.0).Conclusions: While LV-GLS is an independent predictor of hs-cTnT concentrations in patients with DCM, E/Em lateral predicted hs-TnT concentrations in patients with IHF

Diagnosis of comorbid migraine without aura in patients with idiopathic/genetic epilepsy based on the gray zone approach to the International Classification of Headache Disorders 3 criteria

BackgroundMigraine without aura (MwoA) is a very frequent and remarkable comorbidity in patients with idiopathic/genetic epilepsy (I/GE). Frequently in clinical practice, diagnosis of MwoA may be challenging despite the guidance of current diagnostic criteria of the International Classification of Headache Disorders 3 (ICHD-3). In this study, we aimed to disclose the diagnostic gaps in the diagnosis of comorbid MwoA, using a zone concept, in patients with I/GEs with headaches who were diagnosed by an experienced headache expert.MethodsIn this multicenter study including 809 consecutive patients with a diagnosis of I/GE with or without headache, 163 patients who were diagnosed by an experienced headache expert as having a comorbid MwoA were reevaluated. Eligible patients were divided into three subgroups, namely, full diagnosis, zone I, and zone II according to their status of fulfilling the ICHD-3 criteria. A Classification and Regression Tree (CART) analysis was performed to bring out the meaningful predictors when evaluating patients with I/GEs for MwoA comorbidity, using the variables that were significant in the univariate analysis.ResultsLonger headache duration (<4 h) followed by throbbing pain, higher visual analog scale (VAS) scores, increase of pain by physical activity, nausea/vomiting, and photophobia and/or phonophobia are the main distinguishing clinical characteristics of comorbid MwoA in patients with I/GE, for being classified in the full diagnosis group. Despite being not a part of the main ICHD-3 criteria, the presence of associated symptoms mainly osmophobia and also vertigo/dizziness had the distinguishing capability of being classified into zone subgroups. The most common epilepsy syndromes fulfilling full diagnosis criteria (n = 62) in the CART analysis were 48.39% Juvenile myoclonic epilepsy followed by 25.81% epilepsy with generalized tonic-clonic seizures alone.ConclusionLonger headache duration, throbbing pain, increase of pain by physical activity, photophobia and/or phonophobia, presence of vertigo/dizziness, osmophobia, and higher VAS scores are the main supportive associated factors when applying the ICHD-3 criteria for the comorbid MwoA diagnosis in patients with I/GEs. Evaluating these characteristics could be helpful to close the diagnostic gaps in everyday clinical practice and fasten the diagnostic process of comorbid MwoA in patients with I/GEs