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排序方式: 共有368条查询结果,搜索用时 15 毫秒
81.
Mehmet Sankir Ramis Berkay SerinLevent Semiz Nurdan Demirci Sankir 《International Journal of Hydrogen Energy》2014
In this study, for the first time, hydrogen gas generation rate is dynamically measured by transferring required amount of sodium borohydride solution to maintain 1 or 2 normal liters of hydrogen gas generation per minute. Three different catalysts (iron, platinum and ruthenium) are used in order to investigate the critical catalyst concentration, catalyst amount and the rate relation and as well as the influence of the sodium borohydride concentration on the rate equations. It has been demonstrated that the linear approximation from the initial hydrogen gas generation data usually reported in the literature is not valid. Moreover, the actual rates reported here are higher and lower than the linear approximations depending on the type of the catalyst. It is about 60 percent lower than linear approximation when iron catalyst is used. Therefore, calculating hydrogen gas generation rate as NL min−1 g−1catalyst is invalid. On the other hand, it has been observed that the rate equation may not be dependent on the amount of the sodium borohydride concentration if the highest catalytic activity is achieved. Hence, most of the rate equations in the literature are only valid for a range, which is limited to the highest catalytic activity. Additionally, it has been concluded that the amount of catalyst and sodium borohydride concentration may be optimized to observe almost 100% efficiencies. 相似文献
82.
Herein we present and discuss the catalytic activity results of nickel-based bimetallic nanoparticles towards the two-step dehydrogenation of hydrazine borane N2H4BH3. Cobalt, iron and palladium were chosen as the second metal, and a series of Ni1−xMx nanocatalysts were prepared by surfactant-aided co-reduction method. The challenge was to find a nanocatalyst that is active in the decomposition of the N2H4 moiety of hydrazine borane. Of the 14 Ni1−xMx combinations, the best results were achieved with Ni0.7Fe0.3 and Ni0.7Pd0.3. At 50 °C, 3.9 and 4.3 mol H2 + N2 per mole of N2H4BH3 were measured, indicating an activity in the decomposition of the N2H4 moiety. Then, both nanocatalysts were characterized by XRD, SEM, EDX, TEM, SAED and XPS. Finally, the differences in catalytic activity were discussed in terms of electronic and geometric effects. 相似文献
83.
84.
In this study, various functions were evaluated and utilized to forecast observed values and kinetic parameters of the batch ethanol fabrication from carob extract in the suspended-cell stirred tank reactor (SCSTR). The best model was detected with the model comparison parameters (root-mean-square-error [RMSE], mean-absolute-error [MAE], and R2). The results indicated that the model Stannard (ST) successfully predicted biomass production data (RMSE = 0.26 g L−1, MAE = 0.18 g L−1, and R2 = 0.9910), ethanol fabrication data (RMSE = 2.44 g L−1, MAE = 1.88 g L−1, and R2 = 0.9809), and sugar depletion data (RMSE = 2.82 g L−1, MAE = 2.17 g L−1 and R2 = 0.9938). Nevertheless, the lowest value of the objective function (Φ-factor) was also yielded as 0.041 using the model ST. Additionally, in the estimation of the kinetic data, the model ST also gave well-directed results. Besides, when an independent set of the observed values was utilized to confirm the mathematical functions, the satisfactory consequences were achieved in terms of both the experimental and kinetic values. Consequently, the model ST can work as a universal function in predicting observed values and kinetics of batch ethanol generation from carob extract in an SCSTR. 相似文献
85.
Today there is a consensus regarding the potential of NaBH4 as a good candidate for hydrogen storage and release via hydrolysis reaction, especially for mobile, portable and niche applications. However as gone through in the present paper two main issues, which are the most investigated throughout the open literature, still avoid NaBH4 to be competitive. The first one is water handling. The second one is the catalytic material used to accelerate the hydrolysis reaction. Both issues are objects of great attentions as it can be noticed throughout the open literature. This review presents and discusses the various strategies which were considered until now by many studies to manage water and to improve catalysts performances (reactivity and durability). Published studies show real improvements and much more efforts might lead to significant overhangs. Nevertheless, the results show that we are still far from envisaging short‐term commercialisation. 相似文献
86.
Tu Nguyen Anh Huynh-The Thien Wong Kok-Seng Demirci M. Fatih Lee Young-Koo 《The Journal of supercomputing》2021,77(12):14374-14404
The Journal of Supercomputing - Nowadays, the explosion of CCTV cameras has resulted in an increasing demand for distributed solutions to efficiently process the vast volume of video data.... 相似文献
87.
88.
Dilek Küçük Özgül Salor Mennan Güder Turan Demirci Tolga İnan Yener Akkaya Işık Çadırcı Muammer Ermiş 《Electrical Engineering (Archiv fur Elektrotechnik)》2013,95(1):1-19
This paper describes countrywide electrical power quality (PQ) assessments of the Turkish Electricity Transmission System through a genuine PQ database. The database stores the output of mobile PQ measurement systems which are established at 172 transformer substations of the transmission system. At 601 measurement points in these substations, which are potentially critical in terms of PQ, measurements are carried out by the mobile systems for a period of 1 week. PQ parameters defined in the IEC-61000-4-30 standard in addition to power values are calculated from acquired raw data by the mobile-monitoring system and the resulting data are transferred to the PQ database. The database, based on a novel PQ data model, enables its users to take PQ snapshots of the transmission system countrywide and can be accessed through several interfaces including a visual query interface, a natural language interface, and a map interface. The overall PQ status of the measured points, representing the characteristics of the transmission system, is assessed through these interfaces and problematic points are determined while deriving important conclusions about the transmission system’s PQ behavior. Moreover, several novel PQ assessment methods are proposed and their applications on the PQ data are demonstrated especially through the map interface. 相似文献
89.
Murat?TasanEmail author Mehmet?Demirci 《Journal of the American Oil Chemists' Society》2003,80(8):825-828
The contents of total trans FA of sunflower oils at different stages of refining processes were determined by capillary GLC. The contents of 18∶1, 18∶2,
and 18∶3 trans acids were 0.22±0.03, 2.31±0.23, and 0.03±0.01%, respectively, in physically refined sunflower oils, and 0.05±0.01, 0.69±0.26,
and 0.02±0.01%, respectively, in chemically refined sunflower oils. The total trans FA contents drastically increased at the end of the physical refining process. The total trans FA contents of chemically refined sunflower oils were <1%. Because of the high temperature applied in the last stage of physical
refining, the content of total trans FA was higher than in chemically refined sunflower oils. The last-stage conditions should be carefully evaluated to reduce
the formation of trans FA during physical refining. 相似文献
90.
Neslihan Tekce Safa Tuncer Mustafa Demirci Emre Ozel Arzu Aykor 《Journal of Adhesion Science and Technology》2018,32(15):1700-1710
Purpose: To evaluate the effect of cavity preparation method (Er:YAG laser or diamond bur) and bulk-filled composite material type on marginal adaptation mesial occlusal (MO) class II cavities. Materials and Methods: Two-surface box cavities (4-mm proximal depth and 5-mm occlusal width) were prepared on 60 human mandibular molar teeth. Cavities were prepared using Er:YAG laser or diamond burs in an air-turbine hand-piece. All cavities were applied Single Bond Universal dentin bonding agent. The cavities were further subdivided into three subgroups according to the restorative material used; two bulk-filled composites [Filtek Bulk Fill Posterior (3M ESPE) and SonicFill 2 (Kerr)] and one traditional composite material Filtek Ultimate Universal Restorative (3M ESPE). Restorations were evaluated using scanning electron microscopy at ×200 magnification for their adaptation to the approximal margins of the tooth. Results were analyzed using the two-way ANOVA and Tukey Post Hoc Test (p < 0.05). Results: A total of 900 SEM figures were obtained from all groups. Filtek Bulk Fill Posterior, SonicFill 2, and Filtek Ultimate Universal Restorative exhibited statistically similar gapped margins. However, the lowest scores of gapped margins were observed with SonicFill 2 (4.22%). Conclusions: Completely gap-free margins were not obtained with any of the tested materials. Bulk-fill composite materials showed similar marginal adapatation compared with standard composite. Marginal adaptation of Er:YAG laser prepared cavities was more irregular and had more gaps, but was statistically similar to diamond bur-prepared cavities. 相似文献