Jan Hcker  Tevfik Onur Mente  Alessandro Sala  Andrea Locatelli  Thomas Schmidt  Jens Falta  Sanjaya D. Senanayake  Jan Ingo Flege 《Advanced Materials Interfaces》2015,2(18)

The interaction of molecular hydrogen with ceria is of important relevance for heterogeneous catalysis related to green chemistry and renewable energy. Here, the complex structural transformations of a well‐defined cerium oxide model catalyst are followed in situ and in real time when exposed to a reactive H₂ environment. By using electron spectromicroscopy and diffraction with chemical and structural sensitivities, it is demonstrated that the transition from CeO₂ to crystalline Ce₂O₃ occurs through a mixture of transient, coexisting phases on the nanoscale. The findings establish a clear relationship between structure and functionality for hydrogen dissociation over ceria(111), bearing profound implications on the nature of the reduction (Ce⁴⁺ → Ce³⁺) and mechanism for H₂ scission.  相似文献   

    

Mehmet Fidan  Fatih Onur Hocaoğlu  Ömer N. Gerek 《国际能源研究杂志》2012,36(13):1226-1237

In this paper, novel approaches for wind speed data generation using Mycielski algorithm are developed and presented. To show the accuracy of developed approaches, we used three‐year collected wind speed data belonging to deliberately selected two different regions of Turkey (Izmir and Kayseri) to generate artificial wind speed data. The data belonging to the first two years are used for training, whereas the remaining one‐year data are used for testing and accuracy comparison purposes. The concept of distinct synthetic data production with correlation‐wise and distribution‐wise similar statistical properties constitutes the main idea of the proposed methods for a successful artificial wind speed generation. Generated data are compared with test data for both regions in the sense of basic statistics, Weibull distribution parameters, transition probabilities, spectral densities, and autocorrelation functions; and are also compared with the data generated by the classical first‐order Markov chains method. Results indicate that the accuracy and realistic behavior of the proposed method is superior to the classical method in the literature. Comparisons and results are discussed in detail. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

    

Serkan Dag  Bora Yildirim  Onur Arslan  E. Erhan Arman 《热应力杂志》2013,36(7):596-613

A new computational method based on the J _k -integral is put forward for the purpose of conducting fracture analysis of orthotropic materials subjected to hygrothermal stresses. By utilizing the constitutive relations of plane orthotropic hygrothermoelasticity, an alternative expression for the J _k -integral is derived to replace the general limit definition. A numerical procedure is developed and integrated into a finite element analysis software to implement the proposed form of the J _k -integral. Temperature and specific moisture concentration fields, which are required in fracture calculations, are also computed through finite element analysis. Numerical results are generated by considering an embedded crack in a polymer matrix fibrous composite laminate, that is subjected to steady-state hygrothermal loading. Comparisons of the mixed-mode stress intensity factors computed by the J _k -integral based method to those evaluated via the displacement correlation technique demonstrate that, the proposed form of the J _k -integral is domain independent and leads to numerical results of high accuracy. Presented parametric analyses illustrate the influences of the fiber volume fraction and the crack location on the modes I and II stress intensity factors, the energy release rate, and the T-stress.  相似文献   

    

Tuğçe P. Öztürk  Onur B. Özdemir  Ali Gelir  Nahid A. Keshtiban  Önder Yargı  Selin Pıravadılı Mucur  Alper Seçgin 《应用聚合物科学杂志》2024,141(4):e54854

Solid-state electrolytes such a further novel finding is going to have great importance because of the disadvantages of liquid electrolytes such as electrochemical instability, low ion selectivity, and interface contact. It is anticipated that the use of solid-state electrolytes including supercapacitors (SCs) will become widespread with decreasing self-leakage and environmental damage more than liquid electrolytes. In this study, SCs with graphene/PEDOT: PSS coated electrodes and binary PVA gel electrolytes with a conductive layer were designed and the electrochemical performance of the configurations was characterized. The effects of the conductive layer between binary electrolytes and the concentration of the KOH solution in the electrolytes were studied. It was observed that the conductive layer used between the gel electrolytes causes additional charging at the electrolyte/conductive layer interface and behaves like a serially connected capacitor to the double-layer capacitor. Interestingly, at a slow sweep rate (5 mV/s), the specific capacitance values of the assembled SCs decreased when a conductive layer was used but it increased when the sweep rate was fast (100 mV/s).  相似文献   

    

Jaewon Choi  Jugal Kishore Sahoo  Onur Hasturk  Thomas Falcucci  Ya Yao  David L. Kaplan 《Advanced Materials Technologies》2023,8(7):2201392

A variety of artificial silk spinning approaches are attempted to mimic the natural spinning process found in silkworms and spiders, yet instantaneous silk fiber formation with hierarchical structure under physiological and ambient conditions without post-treatment procedures remains unaddressed. Here, this work reports a new strategy to fabricate silk protein-based aerosols and silk fibers instantaneously in situ using a spray device, avoiding complicated and costly advanced manufacturing techniques. The key to success is the instantaneous conformational transition of silk fibroin from random coil to β-sheet right before spraying by mixing silk and polyethylene glycol (PEG) solutions in the spray device, allowing aerosols and silk fibers to be sprayed, with further control achieved via the molecular weight of silk. The spinning process of the spray device is based on the use of green solvents, that is, all steps of instant conformational transition of silk fibroin are carried out in aqueous conditions or with buffers at ambient conditions, in combination with shear and elongational flow caused by the hydraulic pressure generated in the spray container. The system supports a portable and user-friendly system that could be used for drug delivery carriers, wound coating materials, and rapid silk fiber conformal coatings on surfaces.  相似文献   

    

Ahmet Polat  Onur Taskin  Nazmi Izli 《Journal of food science》2024,89(4):2332-2346

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Ümit Develer;Onur Cihan;Mehmet Akar; 《国际强度与非线性控制杂志
》2024,34(3):1921-1938

This paper investigates the cluster consensus problem for inherently nonlinear cooperative networks with first and second-order system dynamics. For a first order multi-agent network evolving over a directed graph, not necessarily containing a spanning tree, a sufficient condition based on Lyapunov theory is derived on the single controller parameter so that the system achieves cluster consensus. These stability results are extended to second-order nonlinear systems that utilize two parameters in the distributed control law. Furthermore, the total number of clusters and members of each cluster are explicitly computed from the primary and secondary layer subgraphs of the underlying directed graph. The results are the first in the literature to address the cluster consensus problem for inherently nonlinear cooperative networks evolving over directed graphs that do not contain a spanning tree.  相似文献   

    

Alixander Perzon  Cedric Dicko  Özgür Çobanoğlu  Onur Yükselen  Jitka Eryilmaz  Estera Szwajcer Dey 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2017,92(7):1645-1649

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Aslı Erdem Yayayürük  Onur Yayayürük 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2017,92(8):1891-1898

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H. H. G&#;ll&#;  M. Parlak 《半导体学报》2017,38(12):123001-6

The Cu-In-Zn-Se thin film was synthesized by changing the contribution of In in chalcopyrite CuInSe2 with Zn.The XRD spectra of the films showed the characteristic diffraction peaks in a good agreement with the quaternary Cu-In-Zn-Se compound.They were in the polycrystalline nature without any post-thermal process,and the main orientation was found to be in the (112) direction with tetragonal crystalline structure.With increasing annealing temperature,the peak intensities in preferred orientation became more pronounced and grain sizes were in increasing behavior from 6.0 to 25.0 nm.The samples had almost the same atomic composition of Cu0.5In0.5ZnSe2.However,EDS results of the deposited films indicated that there was Se re-evaporation and/or segregation with the annealing in the structure of the film.According to the optical analysis,the transmittance values of the films increased with the annealing temperature.The absorption coefficient of the films was calculated as around 105 cm-1 in the visible region.Moreover,optical band gap values were found to be changing in between 2.12 and 2.28 eV depending on annealing temperature.The temperature-dependent dark-and photo-conductivity measurements were carried out to investigate the electrical characteristics of the films.  相似文献