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排序方式: 共有419条查询结果,搜索用时 687 毫秒
111.
In this paper, we tackle the problem of designing an invariant observer for a chemostat model with adjustable and robust convergence. The main idea of the paper is to build a new class of observers for chemostat model using hidden symmetries. The effectiveness of the proposed observer is shown through simulations. 相似文献
112.
Andrei Kholkin Anna Morozovska Dmitry Kiselev Igor Bdikin Brian Rodriguez Pingping Wu Alexei Bokov Zuo‐Guang Ye Brahim Dkhil Long‐Qing Chen Marija Kosec Sergei V. Kalinin 《Advanced functional materials》2011,21(11):1977-1987
Relaxor ferroelectrics are a prototypical example of ferroic systems in which interplay between atomic disorder and order parameters gives rise to emergence of unusual properties, including non‐exponential relaxations, memory effects, polarization rotations, and broad spectrum of bias‐ and temperature‐induced phase transitions. Despite more than 40 years of extensive research following the original discovery of ferroelectric relaxors by the Smolensky group, the most basic aspect of these materials – the existence and nature of order parameter – has not been understood thoroughly. Using extensive imaging and spectroscopic studies by variable‐temperature and time resolved piezoresponse force microscopy, we find that the observed mesoscopic behavior is consistent with the presence of two effective order parameters describing dynamic and static parts of polarization, respectively. The static component gives rise to rich spatially ordered systems on the ~100 nm length scales, and are only weakly responsive to electric field. The surface of relaxors undergoes a mesoscopic symmetry breaking leading to the freezing of polarization fluctuations and shift of corresponding transition temperature. 相似文献
113.
114.
Kamel Msaada Karim Hosni Mouna Ben Taarit Thouraya Chahed Mohamed Elyes Kchouk Brahim Marzouk 《Food chemistry》2007,102(4):1131-1134
The essential oils composition of coriander (Coriandrum sativum L.) fruits obtained by hydrodistillation was studied at three stages of maturity by GC–FID and GC–MS. Essential oil yields showed marked increase during maturation process and forty one compounds were identified. Geranyl acetate (46.27%), linalool (10.96%), nerol (1.53%) and neral (1.42%) were the main compounds at the first stage of maturity (immature fruits). At the middle stage, linalool (76.33%), cis-dihydrocarvone (3.21%) and geranyl acetate (2.85%) were reported as the main constituents. Essential oils at the final stage of maturity (mature fruits) consist mainly on linalool (87.54%) and cis-dihydrocarvone (2.36%). Additionally, accumulation of monoterpene alcohols and ketones was observed during maturation process of coriander fruit. 相似文献
115.
Taazayet Wael Ben Zouari Ikbel Mallek Hosni Nabil Dkhil Brahim Mliki Najeh Thabet 《Journal of Materials Science: Materials in Electronics》2022,33(5):2518-2533
Journal of Materials Science: Materials in Electronics - In the present work, pure BiFeO3 and pure Bi2Fe4O9 single phases were successfully synthesized by tailoring hydrothermal synthesis route.... 相似文献
116.
Maazouzi Abdelhak Kettab Ahmed Badri Abdelkader Zahraoui Brahim Khelfaoui Rachid 《SILICON》2014,6(3):149-154
For a possible use of Saharan sands, representative samples were collected and analysed by several physicochemical methods. The results show that quartz (98 %) is the most represented mineral, while the oxides of aluminium, potassium, iron, chromium and manganese probably are included in a clay phase. The granular analysis enabled the determination of uniformity coefficient (CU) and equivalent diameter. On the other hand, a comparison of the Infrared spectrum of the sand (washed and unwashed) was carried out as well as Scanning Electron Microscopy observations and X-Ray analysis. 相似文献
117.
Brahim Boualy Mohamed Anouar HarradLarbi El Firdoussi Mustapha Ait AliSoufiane El Houssame Abdellah Karim 《Catalysis communications》2011,12(14):1295-1297
Various transition metal acetylacetonates have proven to be efficient catalytic systems for the Kharasch addition of tetrachloromethane to alkenes under mild conditions, providing 1:1 adducts in up to 87% yield, based on internal standard. The nature of metal, solvent, temperature, olefin/CCl4 ratio and the presence of nucleophilic co-catalysts were tested to evaluate the scope and limitation of the reaction. 相似文献
118.
Mouna Hamed Ali Fallah Ammar Ben Brahim 《International Journal of Hydrogen Energy》2017,42(13):8721-8732
This work aims to evaluate the performance of an integrated phase change material (PCM) solar collector. The dynamic behavior of the system is investigated via a theoretical model based on the first law of thermodynamics and oriented to deliver a maximum outlet water temperature. A parametric study is used to assess the effects of the inlet water temperature, the PCM thicknesses and properties and the mass flow rates on the outlet water temperature and the melt fraction. A comparison with a conventional solar water heater without heat storage is made. Results indicate that charging and discharging processes of PCM offer six stages. It is observed that the complete solidification time is longer than the melting one. The latent heat storage system increases the heating requirements at night. The rise is most enhanced for higher inlet water temperature, melting PCM temperature and PCM thickness and for lower mass flow rate. 相似文献
119.
Abdelhakim Settar Rachid Nebbali Brahim Madani Saïd Abboudi 《International Journal of Hydrogen Energy》2017,42(2):1490-1498
This paper deals with a numerical study on the steam methane reforming reaction performances into a wall-coated steam methane reformer (WC-SMR), intended to produce hydrogen. In this work a new catalytic pattern, purporting to enhance the WC-SMR efficiency, is proposed. A comparison study is made between the new inter-catalytic layers pattern and a conventional one with a continuous catalytic layer pattern. Both WC-SMR models operate at similar conditions and at the same design parameters, except the catalytic zone length which is monitored by taking into account the inter-catalytic layers spacing or not. Our results show that, by adopting a catalytic surface with an inter-catalytic spacing, the methane conversion could be enhanced and thus the hydrogen production is intensified. 相似文献
120.
Cemalettin Öztürk Semra Tunalı Brahim Hnich Arslan Örnek 《The International Journal of Advanced Manufacturing Technology》2013,67(9-12):2577-2591
In this paper, we study flexible mixed model assembly lines with serially connected stages where stages may have one or more parallel stations. Station parallelism in flexible mixed model assembly lines improves system reliability and enables rapid adaptability to customer demand fluctuations. However, in order to effectively manage such lines under real-world conditions, there is a need to extend traditional assembly line management methods. This study extends the current research by simultaneously considering the problems of task assignment and model scheduling on parallel stations. Furthermore, scheduling of assigned tasks on each station is considered. We formulate the problem context first as a mixed integer programming model and then develop a decomposition scheme for large scale applications. Finally, we compare the performance of the proposed model and decomposition scheme using various size test instances. 相似文献