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991.
Amal A. Hassan Faten H. Fahmy Abd El-Shafy A. Nafeh Mohamed A. Abu-elmagd 《国际可持续能源杂志》2017,36(6):545-562
The optimal design of renewable-based distributed generations (DGs) is a challenging issue in order to maximise their benefits and to overcome power quality problems. Therefore, this paper proposes a methodology for optimal allocation and sizing of renewable DG units to minimise total power losses over radial distribution systems. The planning problem is formulated as a single objective nonlinear mixed integer-constrained optimisation problem and is solved by using the augmented Lagrangian genetic algorithm (ALGA) by combining the objective function and the nonlinear constraints. In that case, the ALGA solves a sequence of sub-problems where the objective function penalises the constraints violation in order to obtain the best solution. The proposed technique is applied to IEEE radial test systems including 33-bus, 69-bus and 119-bus and is implemented with different scenarios including all possible combinations and various types of renewable DG units to prove the effectiveness of the proposed methodology. 相似文献
992.
Iman Farahbakhsh Amin Paknejad Hassan Ghassemi 《Journal of Mechanical Science and Technology》2012,26(10):3111-3117
This paper presents the numerical solutions of a two-dimensional laminar flow over a backward-facing step in the presence of the Lorentz body force. The Navier-Stokes equations in a vorticity-stream function formulation are numerically solved using a uniform grid mesh of 2001 × 51 points. A second-order central difference approximation is used for spatial derivatives. The solutions progress in time with a fourth-order Runge-Kutta method. The unsteady backward-facing step flow solution is computed for Reynolds numbers 100 to 800. The size and genesis of the recirculating regions are dramatically affected by applying the Lorentz force. The results demonstrate that using an appropriate configuration for applying the Lorentz force can make it an essential tool for controlling the flow in channels with a backward-facing step. 相似文献
993.
The influences of the performance parameters and the heat transfer characteristics of the absorption heat pump using ammonia–water mixture are theoretically carried out. There is a pronounced effect of the ammonia concentration ξ after rectifier on the temperature glides that has been investigated. At ξ = 0.9000 and saturation pressures of 75 and 0.5 bar, the temperature glides are 64.4°C and 81.21°C, respectively, whereas these glides are 0°C and 16.1°C at ξ = 0.9999 and at the same pressures. This mixture property considerably affects the absorption system performance and the design of the rectifier as well as other absorption components. A correlation of the Nusselt number, Nu, is developed and compared with some published work in the literature for plate type heat exchanger. The effects of ammonia concentration ξ, mass fraction spread Δξ, specific solution circulation ratio f, and pressure ratio Rp on the refrigerant mass flow rate, the pressure drop, and the heat transfer coefficients during the condensation, the evaporation, and the absorption processes are investigated. It was found that increasing ammonia mass fraction spread Δξ results in both specific circulation ratio f and Rp that have insignificant effects on the refrigerant mass flow rate. Mounting Δξ at constant f reduces the pressure drop gradually and subsequently starts to increase as Δξ escalates. The ammonia concentration ξ has insignificant effect on the evaporation heat transfer coefficient but has a little effect on the condensation and the absorber heat transfer coefficients. The ammonia mass fraction spread Δξ and f have considerable effects on the heat transfer coefficient for different absorption heat pump components. Rp has a pronounced effect on the evaporation heat transfer coefficient, although it has a slight effect on the condensation and the absorber heat transfer coefficients. The effect of Rp on the heat transfer coefficient may be eliminated in the absorber for Δξ > 0.18. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
994.
ABSTRACTIn recent decades, flax fibre has become a popular natural resource as reinforcement in polymeric composites. However, the pure mode characterisation of flax fibre composites is rather limited. Furthermore, the mixed-mode delamination is not yet available. Nevertheless, delamination behaviour is important to be characterised as it is a major problem in composite laminates. This study examined the delamination behaviour of a woven flax/epoxy composite. Specimens were tested using mode I double cantilever beam, mode II end-notched flexure and mixed-mode I+II single leg bending tests. Results showed that the mode I, mode II and mixed-mode I+II fracture toughness were 363.23, 962.17 and 649.06?N?m?1, respectively. When the fracture toughness values were fitted using Benzeggagh–Kenane criterion, it was found that the best-fit material parameter η was attained at 0.88. This information is useful to estimate the variation of fracture toughness with the mode ratio. Finally, through scanning electron micrographs, it was noticed that fibre/matrix debonding was the major fracture mechanism in all loading modes. In conclusion, the findings from this study suggested that the composite was suitable to be used for structural applications under mixed-mode loading. 相似文献
995.
996.
Lactoferrin (Lf), the main iron-binding protein of milk, has biological activities. We have evaluated the potential of camel milk lactoferrin for its ability to inhibit the proliferation of the colon cancer cell line, HCT-116, in vitro, DNA damage and its antioxidant activities for the first time. The antioxidant capacity of Lf was evaluated by different assays, including ferric-reducing/antioxidant power assay (FRAP), free radical-scavenging activity (DPPH), nitric oxide (NO) radical-scavenging assay, total antioxidant activity and DNA damage, compared with vitamin C and rutin. 相似文献
997.
Hammed H. A. M. Hassan Amel F. Elhusseiny Amr M. Sweyllam Robert J. Linhardt 《应用聚合物科学杂志》2013,128(1):310-321
We report the preparation of thermally stable spherical sulfonated aramides nanoparticles and their copper(II) complexes. Metal chelation with copper ions furnished polymeric complexes in a 1 : 2 ratio with square planar geometries as judged by their IR, UV, electron spin resonance, and elemental analysis data. The direct‐current electrical conductivities demonstrated the semiconducting nature of the polymeric particles and their copper complexes. Dielectric loss analysis studies showed spectral peaks appearing at characteristic frequencies, which suggested the presence of relaxing dipoles in all of the polymers. All loss peaks were shown on a linear frequency scale and appeared in the range of 1 decade, and no overlap was observed in any of the samples, whereas in the normal polymer's dielectric loss behavior, each peak covered more than 1 decade. Moreover, the peak positions did not change with increasing temperature; this indicated a nonactivated process. The reported dielectric results revealed anomalous behavior, which has not been reported before for such polymeric analogues, as the polarization in these cases was limited by nonthermal forces, and a steady‐state constant polarization was produced by an applied field. A simple method for the formation of a microporous semiconducting thin film of a polymer derived from isophthalic acid and diaminodiphenylsulfone is described. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
998.
Numerical Simulations of Solid Circulation Characteristics in an Internally Circulating Elevated Fluidized Bed
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Muhammad Hassan M. Philip Schwarz Muhammad Rafique Yuqing Feng Guodong Liu Peter J. Witt Shuai Wang Huilin Lu 《化学工程与技术》2017,40(4):769-777
A twin‐chamber internally circulating elevated fluidized bed (EFB) with one chamber elevated higher than the other within a single vessel is simulated using a two‐fluid model. Two EFB configurations termed as reaction chamber (RC)‐elevated and heat exchange chamber (HEC)‐elevated is evaluated. The effect of chamber elevation, variation of superficial velocities, and interchanging the two chambers are investigated and the results are quantified in terms of solid flux Gs. By increasing the RC gas velocity UR at constant HEC velocity UH, Gs is increased in both EFBs while an opposite behavior is observed by increasing UH at constant UR. Variation of the chamber elevation as well as interchanging the chambers also affects the performance of the two EFBs. 相似文献
999.
Hassan Aldeeb 《组合铁电体》2014,157(1):95-100
A tunable double band band-stop filter based on BST is presented. This configuration has a coplanar microstrip loaded with stepped impedance resonators. Ferroelectric BST parallel plate capacitors were loaded at the end of the stepped impedance resonators. When a DC voltage is applied to the BST capacitors, the change in capacitance shifts the resonance frequency of the stepped impedance transformers. The filters were designed with notch frequencies at 1.5 GHz and 3.5 GHz without loading them with BST capacitors. The filter circuits were simulated with Agilent ADS and were fabricated on FR-4 substrates. By loading the resonators with BST capacitors with no DC applied voltage, the first and second notch frequency shifts significantly. The first notch frequency can be tuned from 570 MHz to 781 MHz and the second notch frequency from 2.16 GHz to 2.55 GHz by applying the bias voltage of 5volts. The performance of the BST tuned filters were compared with filters tuned with p-n junction varactors. 相似文献
1000.
Wallied Orabi Ahmed B. Senouci Khaled El-Rayes Hassan Al-Derham 《Canadian Metallurgical Quarterly》2010,26(4):237-246
Postdisaster recovery efforts of damaged civil infrastructure systems need to be optimized in order to alleviate the adverse impacts of natural disasters on local societies and economies. This paper presents an innovative framework that integrates two newly developed models for resource utilization and multiobjective optimization that are designed to optimize these recovery efforts. The developed models provide new and unique capabilities, including (1) allocating limited reconstruction resources to competing recovery projects, (2) estimating the reconstruction duration and cost associated with implementing specific recovery plans, and (3) generating optimal trade-offs between minimizing the reconstruction duration and cost. An application example is analyzed to evaluate the performance of the developed models and demonstrate their capabilities in identifying a wide spectrum of optimal reconstruction plans, where each provides a unique and nondominated trade-off between minimizing the recovery duration and cost. This allows decision makers in emergency management agencies to select and implement reconstruction plans that address various societal and economical needs in the aftermath of natural disasters. 相似文献