1,720,975 research outputs found
Hydrothermal synthesis and characterization of Mg-doped CuCrO2 particles
No full textBu çalışmada, optoelektronik, foto-katalitik ve gaz-algılama uygulamalarına yönelik olarak p-tipi elektrik iletkenliği gösteren ve delafosit yapıya sahip, CuCr1-xMgxO2 (x=0, 0.01, 0.03, 0.05) kompozisyonlarında nano-kristallerin hidrotermal yöntemle üretimi hedeflenmiştir. Mg-aşılamanın yapısal, morfolojik, optik ve elektriksel özelliklere etkisi belirlenmiştir. X-ışınları kırınımı incelemeleri, hidrotermal sentez ile CuCrO2'nin saf halde üretilebildiğini göstermektedir. Deneysel veriler optimum Mg-aşılama miktarının atomca % 3 olduğunu ortaya koymuştur. Bu miktar üzerindeki aşılama, MgCr2O4 spinel fazının oluşmasına neden olmaktadır. Saf numunelerin ortalama kristalit boyutu 12 nm olarak bulunmuştur. Artan Mg-aşılama miktarı ile boyut 7 nm'ye kadar düşmektedir. Ayrıca, aşılama ile kristalit boyut dağılımında da bir artış meydana gelmektedir. UV-Vis spektrofotometre ölçümleri sonucu saf numunenin optik geçirgenlik değeri 700 nm dalga boyunda % 83 olarak bulunmuştur. Bu değer atomca % 1, 3 ve 5 Mg-aşılanmış numuneler için sırası ile % 85, 87 ve 90'a artmaktadır. Benzer şekilde, direk bant aralık değerleri saf numune için 3.00 eV, aşılanmış numuneler için sırası ile 3.01, 3.06 ve 3.07 eV olarak hesaplanmıştır. Elektriksel ölçümler, kompozisyondan bağımsız olarak tüm numunelerin yarı iletken davranış sergilediğini ortaya koymuştur. Çalışma kapsamında üretilen tüm kompozisyonlar için en düşük oda sıcaklığı elektriksel özdirenç değeri % 3 Mg-aşılanmış numunede elde edilmiş ve 68 Ω.cm olarak kaydedilmiştir. Bu değer saf numune için oda sıcaklığında ölçülen özdirenç değerinden (11,8 kΩ.cm) ~170 kat daha düşüktür.In this study, CuCr1-xMgxO2 (x=0, 0.01, 0.03, 0.05) nano-crystals with high surface area were prepared using hydrothermal synthesis. The effect of Mg+2 substitution for Cr+3 on the structural, morphological, optical and electrical characteristics of CuCrO2 nanoparticles was investigated. X-ray diffraction study showed that the solubility limit was around 3 at. % Mg and beyond this concentration the formation of MgCr2O4 spinel phase was observed. Transmission electron microscopy examination indicated that the average crystallite size, 12 nm for undoped sample, decreased with increasing doping amount of up to 5 at. % and reached 7 nm. Moreover, the introduction of Mg led to an increase in the size distribution of the crystallites. UV-vis spectrometry analysis showed that the optical transmittance of pure sample was 83 % at 700 nm wavelength and transmittance was enhanced for all doping concentrations. The optical transmittance of doped samples were 85, 87, and 90 %, respectively for 1,3, and 5 at. % doping. The corresponding optical bandgaps were determined to be 3.00, 3.05, 3.09, and 2.87 eV. All samples behaved like semiconductors. At room temperature, the minimum achieved electrical resistivity was measured to be 68 Ω.cm for at. 3 at. % Mg- doped sample. This value is lower by a factor of ~170 than that of the pure sample.Bu tez çalışması Öğretim Elemanı Yetiştirme Programı tarafından 2013-ÖYP-087 nolu proje ile desteklenmiştir
Çözelti ve Vakum Esaslı Yöntemler ile Perovskit Güneş Hücrelerinin Üretimi ve Karakterizasyonu
No full textBu tez çalışmasında, çözelti ve vakum esaslı biriktirme yöntemleri kullanılarak perovskit güneş hücrelerinin üretimi optimize edilmeye çalışılmıştır. Çözelti esaslı hücre üretiminde MAPbI3 ve Cs(0,05)FA(0,85)MA(0,1)PbI(2,7)Br(0,3) olmak üzere iki farklı kompozisyonda perovskit bileşimi kullanılmıştır. FTO/k-TiO2/m-TiO2/perovskit/Spiro-OMeTAD/Au (k-TiO2: kompakt TiO2, m-TiO2: mezoporoz TiO2) konfigürasyonunda üretilen hücrelerde Cs(0,05)FA(0,85)MA(0,1)PbI(2,7)Br(0,3) kompozisyonuna sahip perovskit bileşik ile Voc: 1,105 V, Jsc: 23,38 mA/cm2, FF: 0,66 ve verim değeri %17,0 olan hücreler başarı ile üretilmiştir. Ayrıca, k-TiO2/m-TiO2'ye alternatif olarak SnO2'nin elektron taşıyıcı olarak kullanıldığı düzlemsel hücrelerin üretimi yapılmış ve verim değeri %15,06 olan bu hücrenin Voc, Jsc ve FF değerlerinin sırasıyla 1,091 V, 22,63 mA/cm2 ve 0,54 olduğu tespit edilmiştir. Spiro-OMeTAD'a alternatif olarak önerilen inorganik boşluk taşıyıcı CuSbS2 ile üretilen hücreden elde edilen en yüksek verimin %4,3 olduğu ve düşük verimin CuSbS2'nin kaplanması sürecinde sürekli bir film oluşturacak şekilde paketlenememesinden kaynaklandığı belirlenmiştir. Isıl buhar biriktime yöntemi ile MoO3/TaTm, MoO3/H2, MoO3/PTAA, PTAA ve PolyTPD'nin boşluk taşıyıcı, C60/BCP'nin ise elektron taşıyıcı olarak kullanıldığı MAPbI3 esaslı hücreler üretilmiş ve PTAA tabakaya sahip hücrenin diğerlerine göre termal olarak daha kararlı olduğu gözlemlenmiştir. PTAA kullanılarak Voc, Jsc, FF ve verim değerleri sırasıyla 1,087 V, 22,12 mA/cm2, 0,79 ve %19,2 olan hücreler başarı ile üretilmiştir. Bu hücrelerin oda sıcaklığı ve 65 °C raf ömrü kararlılık deneylerinde 850 h sonunda sırasıyla ilk veriminin %92 ve %82'sini koruduğu tespit edilmiştir. Bunlara ek olarak, oda sıcaklığı ve 85 °C arasında 200 termal çevrime maruz bırakılan hücrenin ilk veriminin %95'ini koruduğu gözlemlenmiştir. Işık altında maksimum güç noktası takip edilerek yapılan çalışma durumu kararlılık testinde ise hücre 230 h içinde başlangıç veriminin %80'ini koruyabilmiştir. Çalışma durumunda meydana gelen verim kaybının perovskitin kristalinitesinde azalmaya bağlı olduğu tespit edilmiştir. Kristalinitede azalma, hem soğurmada düşüşe neden olmuş hem de kristal yapıdaki noktasal hata konsantrasyonunda artışa bağlı olarak Shockley-Read-Hall yeniden birleşme oranını artırmıştır. Böylece, çalışma durumunda verimde azalmanın perovskit tabakadan kaynaklandığı ortaya konulmuştur.In this thesis study, perovskite solar cells production was tried to be optimized using solution and vacuum based deposition methods. In solution deposition, two different perovskite compounds were used, i.e., MAPbI3 and Cs(0,05)FA(0,85)MA(0,1)PbI(2,7)Br(0,3). The cells with FTO/c-TiO2/m-TiO2/perovskite/Spiro-OMeTAD/Au configuration were fabricated via Cs(0,05)FA(0,85)MA(0,1)PbI(2,7)Br(0,3) composition as the absorbing layer and exhibited Voc of 1.105 V, Jsc of 23.38 mA/cm2, FF of 0.66, and PCE of 17.0%. In addition, planar cells were produced with SnO2 as a substitute for c-TiO2/m-TiO2 electron transporting layer. These cells displayed an efficiency of 15.06% with the corresponding photovoltaic parameters; Voc 1.091 V, Jsc 22.63 mA/cm2, and FF 0.54. Moreover, perovskite solar cells were fabricated with inorganic CuSbS2 hole transporting layer, however the efficiency of the cell was only 4.3%. This low efficiency was attributed to poor packing of the plate-like CuSbS2 particles on the perovskite layer with the formation of a noncontinous layer. In vacuum deposition method, MAPbI3 based perovskite solar cells with various hole transporting layers such as MoO3/TaTm, MoO3/H2, MoO3/PTAA, PTAA, and PolyTPD were fabricated by employing the C60/BCP as electron transporting layer. Among them, the cell produced with PTAA showed the highest stability under thermal stresses. This cell exhibited an efficiency of 19.2% with Voc of 1.087 V, Jsc of 22.12 mA/cm2, and FF of 0.79. The cell retained 92% and 82% of its initial PCE after aging for 850 h at room temperature and 65 °C, respectively. Even after thermal cycling between room temperature and 85 °C for 200 cycles, 95% of the initial PCE was maintained. Under continuous illumination and with maximum power point tracking (MPPT) Ts80 life time was obtained as 230 h. The decay of the initial efficiency under illumination was determined to be related with the decrease in the crystallinity of the perovskite layer. This also led to a decrease in the optical absorption of the cell. Moreover, Shockley-Read-Hall recombination rate was increased due to the increase in the concentration of defects or trap states in the crystal structure. Therefore, the study has clearly shown that the decrease in the efficiency of the cells under operating conditions was originated from the perovskite layer
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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