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111.
Farzad Shayesteh Seyed Ali Delbari Zohre Ahmadi Mohammadreza Shokouhimehr Mehdi Shahedi Asl 《Ceramics International》2019,45(5):5306-5311
In this study, the impact of TiN as a sintering aid on the relative density and microstructure of TiB2 ceramic was investigated. Monolithic TiB2 and TiB2 doped with 5?wt% TiN were sintered at 1900?°C for 7?min dwell time under the pressure of 40?MPa by spark plasma. The addition of TiN affected the microstructure of TiB2-based sample considerably depicting the finer grains in the as-sintered ceramic. X-ray diffraction evaluation indicated that no interaction occurred between the initial materials. However, detail investigation by the map analysis and energy dispersive spectroscopy results revealed the formation of in-situ nano-sized hBN secondary phase in the TiN-doped TiB2. In addition, TiN played a remarkable role on increasing the relative density of TiN-doped TiB2 ceramic producing a nearly fully dense ceramic with relative density of 99.9% in comparison with the monolithic ceramic having 96.7% relative density. 相似文献
112.
Investigation of Hydrodynamics of High‐Temperature Fluidized Beds by Pressure Fluctuations 下载免费PDF全文
Hydrodynamics of a gas‐solid fluidized bed at elevated temperatures was investigated by analyzing pressure fluctuations in time and frequency domains. Sand particles were fluidized with air at various bed temperatures. At a constant gas velocity, the standard deviation, power spectrum density function, and wide‐band energy of pressure fluctuations reach a maximum at 300 °C. Increasing the temperature to this value causes larger bubble sizes and after the bubbles reach their maximum size, they break into smaller bubbles. The Archimedes number decreases with higher temperature and the type of fluidization becomes closer to that of Geldart A boundary at this maximum temperature. Based on estimation of the drag force acting on the emulsion phase, it was concluded that 300 °C was a transition temperature at which the drag force reaches a minimum due to a significant change of interparticle and hydrodynamic forces. 相似文献
113.
In this paper, we define a local version of Hudetz correction for the Yager entropy of dynamical systems. It is proved that the introduced function is indeed a local entropy map for the Hudetz correction of the Yager entropy, in the sense that, the Hudetz correction of the Yager entropy of a continuous map on a compact metric space is attained by integrating the introduced local entropy. 相似文献
114.
World Wide Web - In many cases, users are not familiar with their exact information needs while searching complicated data sources. This lack of understanding may cause the users to feel... 相似文献
115.
A conceptual design and statistical overview about passive direct methanol fuel cells that have been fabricated from 2002 to 2013, is performed [1–70]. The major components of passive DMFCs such as: active area, type of Nafion, catalyst loading on the anode and cathode side, characteristics and designs of current collectors (CC), and also the optimum methanol concentration which resulted in the best performance are categorized and studied statistically and individually. Finally, the best combination for the design and fabrication of a reliable passive DMFC is recommended. Obtained results indicated that a MEA with 4 cm2 active area, Nafion 117 and 4 mg/cm2 Pt/Ru at the anode and 2 mg/cm2 Pt black at the cathode (or 4 mg/cm2 Pt/Ru at the anode – 4 mg/cm2 Pt black at the cathode) as the catalyst loading, which is sandwiched between two stainless steel perforated current collectors that are coated by Pt (or Gold) could be a reliable design for a passive direct methanol single cell. 相似文献
116.
Abstract Each generation of programming languages has made applications easier to develop. In recent years, the use of fourth-generation languages (4GLs) has allowed many users, formerly alienated from the systems development process, to fulfill their own information needs. MIS professionals, however, have reacted negatively to the use of 4GLs. This article presents a survey of MIS professionals, who reveal their perceptions of the use and productivity of 4GLs as well as some of the obstacles that prevent them front using 4GLs in their organizations. 相似文献
117.
Manhal Abouzlam Régis Ouvrard Driss Mehdi Florence Pontlevoy Bertrand Gombert Nathalie Karpel Vel Leitner Sahidou Boukari 《Control Engineering Practice》2013,21(1):105-112
This paper deals with the control of a wastewater treatment pilot by catalytic ozonation. In general, catalytic ozonation processes operate with a deliberate ozone overproduction to obtain a treated water which respects discharge standards. But, in this case, the oxygen consumption is not optimal and the operating costs are important. The objective of this study focuses on the optimization of the catalytic ozonation reactor. A continuous-time transfer function model is identified to represent the pilot behavior, and an optimal control is proposed to obtain a significant abatement of the pollutant. In this application, the pollutant abatement is represented by the absorbance. 相似文献
118.
Alex Buchberger Harpinder Saini Kiarash Rahmani Eliato Azadeh Zare Ryan Merkley Yang Xu Julio Bernal Robert Ros Mehdi Nikkhah Dr. Nicholas Stephanopoulos 《Chembiochem : a European journal of chemical biology》2021,22(10):1755-1760
Biomaterials with dynamically tunable properties are critical for a range of applications in regenerative medicine and basic biology. In this work, we show the reversible control of gelatin methacrylate (GelMA) hydrogel stiffness through the use of DNA crosslinkers. We replaced some of the inter-GelMA crosslinks with double-stranded DNA, allowing for their removal through toehold-mediated strand displacement. The crosslinks could be restored by adding fresh dsDNA with complementary handles to those on the hydrogel. The elastic modulus (G’) of the hydrogels could be tuned between 500 and 1000 Pa, reversibly, over two cycles without degradation of performance. By functionalizing the gels with a second DNA strand, it was possible to control the crosslink density and a model ligand in an orthogonal fashion with two different displacement strands. Our results demonstrate the potential for DNA to reversibly control both stiffness and ligand presentation in a protein-based hydrogel, and will be useful for teasing apart the spatiotemporal behavior of encapsulated cells. 相似文献
119.
Computational Economics - This paper presents the numerical solution of the Black–Scholes partial differential equation (PDE) for the evaluation of European call and put options. The proposed... 相似文献
120.
In this study, a conventional steam power plant with two regenerative boilers is considered, and one of its boilers is replaced with parabolic solar dish collectors and storing the produced thermal energy by the phase change material (PCM) in a storage tank. The results show the necessity of the existence of an auxiliary fired‐gas boiler to provide constant load during the whole 24 hours. The performance of the proposed hybridized system is evaluated through energy and exergy analyses. It was demonstrated that substituting solar collectors with one of the boilers marginally lowers the energy efficiency but increases the exergy efficiency of the whole power plant up to 41.76%. Moreover, it is found out that this hybridization decreases the total irreversibility of the power plant in comparison with the base case, from 51.1 to 47.2 MW. The parametric analysis states that raising the mass flow rate of the heat transfer fluid in the solar collectors not only enhances the system performance but also increases the volume of the PCM tank. 相似文献