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排序方式: 共有724条查询结果,搜索用时 15 毫秒
101.
Olfat A. Fadali Mohamed Obaid Mohamed S. Mahmoud Taha E. Farrag Kim TaeWoo Khalil Abdelrazek Khalil Nasser A. M. Barakat 《化学工程与技术》2015,38(3):441-445
The effect of an electromagnetic field (EMF) on the rate of copper(II) cementation from copper sulfate solutions on a rotating iron cylinder was investigated. The studied variables were cylinder rotation speed, magnetic field strength, and magnetic field direction. The application of EMF increased the rate of cementation in both parallel and perpendicular direction of the magnetic field where the latter proved to be more effective. The rate of mass transfer under an EMF was found to be more than doubled. The enhancement of copper recovery in presence of the EMF is due to the induced motion of Fe+n in the solution which is limited to a certain range of cylinder rotation speed. The power consumption for cementation of copper could be significantly reduced by utilizing EMF. 相似文献
102.
Hosain Darvishi Nasser Behroozi-Khazaei Mahmoud Koushesh Saba Zakaria Alimohammadi Himan Nourbakhsh 《International Journal of Food Science & Technology》2021,56(9):4789-4798
The antioxidant, phenol, ascorbic acid, electrode corrosion and engineering factors of concentration process of kiwifruit juice by ohmic heating-vacuum conditions (OHVC) were evaluated and compared with ohmic heating under atmospheric conditions (OHAC). Results showed that the total phenol content was decreased with an increasing voltage gradient for both heating modes. The OHVC can better save the antioxidant capacity and ascorbic acid of concentrated samples than the OHAC. The processing time of OHVC was significantly higher than the OHAC at the same voltage gradient (P < 0.05). The electrode corrosion rate at the vacuum mode was 7- to 40-fold higher than the atmospheric mode. The energy efficiency at OHAC was lower than the OHVC. The energy consumption was found in the range of 3.37 to 3.75 MJ kg−1 water for OHAC and 4.08 to 11.09 MJ kg−1 water for OHVC. The electrical conductivity under the vacuum mode was lower than the atmospheric mode. 相似文献
103.
104.
Ashraf Mahmoud Ahmad Abo Naser Marwan Abu‐Amara Tarek Sheltami Nidal Nasser 《International Journal of Communication Systems》2018,31(1)
The evolved packet core (EPC) network is the mobile network standardized by the 3rd Generation Partnership Project and represents the recent evolution of mobile networks providing high‐speed data rates and on‐demand connectivity services. Software‐defined networking (SDN) is recently gaining momentum in network research as a new generation networking technique. An SDN‐based EPC is expected to introduce gains to the EPC control plane architecture in terms of simplified, and perhaps even software‐based, vendor independent infrastructure nodes. In this paper, we propose a novel SDN‐based EPC architecture along with the protocol‐level detailed implementation and provide a mechanism for identifying information fields exchanged between SDN‐EPC entities that maintains correct functionality with minimal impact on the conventional design. Furthermore, we present the first comprehensive network performance evaluation for the SDN‐based EPC versus the conventional EPC and provide a comparative analysis of 2 networks performances identifying potential bottlenecks and performance issues. The evaluation focuses on 2 network control operations, namely, the S1‐handover and registration operations, taking into account several factors, and assessing performance metrics such as end‐to‐end delay (E2ED) for completion of the respective control operation, and EPC nodes utilization figures. 相似文献
105.
N. Ouled Nasser A. Ezaami M. Koubaa W. Cheikhrouhou-Kaoubaa A. Cheikhrouhou 《Journal of Materials Science: Materials in Electronics》2018,29(24):20658-20667
An exhaustive study of structural, magnetic and magnetocaloric properties on La1.95Sr0.05BMnO6 (B?=?Ni and Co) double perovskite were performed. The samples were prepared by the sol–gel method. The crystallographic structure was studied by the X-ray diffraction patterns and Rietveld refinement which revealed that all samples crystallize in a monoclinic structure with P21/n space group. The magnetic behaviors of these double perovskite have been studied in detail. For La1.95Sr0.05NiMnO6, the M(T) curves exhibit double magnetization transition temperature at 68 K and 266 K which can be ascribed to Ni3+–O–Mn3+ and Ni2+–O–Mn4+ superexchange interaction, respectively. However, unique magnetic transition has been observed for the La1.95Sr0.05CoMnO6 double perovskite at 210 K due to Co2+–O–Mn4+ superexchange interaction. A deep investigation based on the Landau Theory and Arrot analysis confirmed a second order ferromagnetic phase transition for both samples. Besides, the magnetocaloric behaviors of these new samples have been studied by analysis the magnetic entropy change. This latter reached maximum values of 1.01 and 1.35 J/kg/K for La1.95Sr0.05NiMnO6 and La1.95Sr0.05CoMnO6, respectively, under µ0H?=?5 T. Moreover, the relative cooling power values for La1.95Sr0.05NiMnO6 and La1.95Sr0.05CoMnO6 are found to be 94 J/kg and 116 J/kg, respectively, under µ0H?=?5 T. Based on the obtained ΔSM data, we have also described the universal master curve for (ΔSM/\(\Delta S_{M}^{{\hbox{max} }}\)) versus rescaled temperature to confirm the order magnetic phase transition. Interestingly, all the ΔSM(T, H) data points are collapsed into a universal curve in the whole temperature range. The significant values of relative cooling power for both samples suggest that they might be an interesting candidate for exploring a new kind of magnetic refrigerants. 相似文献
106.
Asma Ezaami N. Ouled Nasser W. Cheikhrouhou-Koubaa A. Cheikhrouhou 《Journal of Materials Science: Materials in Electronics》2017,28(14):10056-10060
In this paper, we investigate the field dependence of the magnetocaloric properties of La0.7Ca0.2Sr0.1MnO3 powder sample using a phenomenological model. Our compound was elaborated by the conventional solid state reaction. The model parameters were determined from the magnetization data and were used to give better fits to magnetic transition and to calculate the magnetocaloric quantities. The magnetocaloric parameters such as the maximum of the magnetic entropy change \(\Delta S_M^{max}\) and the relative cooling power RCP, have been determined from the calculation of the magnetization as a function of temperature under several magnetic applied field. Thus, from the magnetocaloric results, such as RCP?≈?b(μ0H)1+1/δ and Tpeak???TC ≈ b (µ0H)1/Δ, the critical exponents values related to the magnetic transition have been determined. The estimated results are close to those expected by the tricritical mean-field model. Furthermore, the values of the ferromagnetic transition temperature TC, as well as the critical exponents β, γ and δ obtained by the theoretical model, are compared with those obtained by other various techniques (such as the modified Arrott plots, the Kouvel–Fisher method and the critical isotherm analysis). A good agreement has been found in the vicinity of the Curie temperature. 相似文献
107.
108.
Stability of gravitationally unstable double diffusive transient boundary layers with variable viscosity in porous media
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Nasser Sabet Hassan Hassanzadeh Jalal Abedi 《American Institute of Chemical Engineers》2017,63(6):2471-2482
We study the double diffusive convection (DDC) in porous media through linear stability analysis (LSA) and direct numerical simulations (DNS). Unlike the previous studies that assume static solutal or thermal fields, the developed model is able to capture the transient behavior of both fields. We show that under the assumption of static field, the role of Lewis number cannot be distinguished. Under transient fields, we conclude that higher Lewis numbers result in earlier instability of the boundary layers. Moreover, the effect of viscosity contrast is explained in terms of the mobility of the boundary layer. The DNS results confirm the validity of LSA predictions. We also obtain the critical Rayleigh number and show that in the presence of viscosity contrast, it can be much smaller than the conventional limit of 4π2. This study provides a better understanding of the transient nature of DDC in the presence of viscosity variations. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2471–2482, 2017 相似文献
109.
Anaerobic sewage treatment in a one-stage UASB reactor and a combined UASB-Digester system 总被引:3,自引:0,他引:3
The treatment of sewage at 15 degrees C was investigated in a one-stage upflow anaerobic sludge blanket (UASB) reactor and a UASB-Digester system. The latter consists of a UASB reactor complemented with a digester for mutual sewage treatment and sludge stabilisation. The UASB reactor was operated at a hydraulic retention time of 6h and a controlled temperature of 15 degrees C, the average sewage temperature during wintertime of some Middle East countries. The digester was operated at 35 degrees C. The UASB-Digester system provided significantly (significance level 5%) higher COD removal efficiencies than the one-stage UASB reactor. The achieved removal efficiencies in the UASB-Digester system and the one-stage UASB reactor for total, suspended, colloidal and dissolved COD were 66%, 87%, 44% and 30%, and 44%, 73%, 3% and 5% for both systems, respectively. The stability values of the wasted sludge from the one-stage UASB reactor and the UASB-Digester system were, respectively, 0.47 and 0.36g CH(4)-COD/g COD. Therefore, the anaerobic sewage treatment at low temperature in a UASB-Digester system is promising. 相似文献
110.
Anaerobic stabilisation and conversion of biopolymers in primary sludge--effect of temperature and sludge retention time 总被引:1,自引:0,他引:1
The effect of sludge retention time (SRT) and process temperature on the hydrolysis, acidification and methanogenesis of primary sludge was investigated in completely stirred tank reactors (CSTRs). The CSTRs were operated to maintain SRTs of 10, 15, 20 and 30 days at process temperatures of 25 degrees C and 35 degrees C. The rates of hydrolysis and the biodegradability of primary sludge were assessed in batch reactors incubated at 15 degrees C, 25 degrees C and 35 degrees C. The results revealed that the major amount of sludge stabilisation occurred between 0 and 10 days at 35 degrees C and 10 and 15 days at 25 degrees C. Hydrolysis was found to be the rate limiting-step of the overall digestion process, for the reactors operated at 35 degrees C and 25 degrees C, except for the reactor operated at 10 days and 25 degrees C. At the latter conditions, methanogenesis was the rate-limiting step of the overall digestion process. Proteins hydrolysis was limited to a maximum value of 39% at 30 days and 35 degrees C due to proteins availability in the form of biomass. The biodegradability of primary sludge was around 60%, and showed no temperature dependency. The hydrolysis of the main biopolymers and overall particulate COD of the primary sludge digested in CSTRs were well described by first-order kinetics, in case hydrolysis was the rate-limiting step. Similarly, the hydrolysis of the overall particulate COD of the primary sludge digested in batch reactors were described by first-order kinetics and revealed strong temperature dependency, which follows Arrhenius equation. 相似文献