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排序方式: 共有650条查询结果,搜索用时 462 毫秒
51.
Abdelkarim Kelleche Nasser-eddine Tatar Ammar Khemmoudj 《Journal of Dynamical and Control Systems》2017,23(2):237-247
In this paper, we study the stabilization of solutions of an axially moving string of kirchhoff type by a viscoelastic boundary control. We prove that the dissipation produced by the viscoelastic term is sufficient to suppress the transversal vibrations that occur during the axial motion of the string, and we also show that the string displacement decays in an arbitrary rate. When comparing with immobile strings, we conclude that the movement of the string itself produces enough extra damping ensuring the stabilization. 相似文献
52.
Mourad Mordjaoui Salim Haddad Ammar Medoued Abderrezak Laouafi 《International Journal of Hydrogen Energy》2017,42(28):17655-17663
Electrical energy is fundamental for the wellbeing and for the economic development of any country. However, all countries must ensure access to essential resources and ensure the continuity of its supply. Due to the non-storable nature of electrical energy, the amount of consumed active power should always be equal the produced active power just to avoid power system frequency deviation problem. In order to keep the relationship production–consumption relation in compliance with different standards and to secure profitable operations of power system, electric load consumption must be predicted and controlled instantaneously. Several statistical and classical techniques are proposed in the literature but unfortunately all these methods are not accurate in a satisfactory manner. In this paper, a dynamic neural network is used for the prediction of daily power consumption. The suitability and the performance of the proposed approach is illustrated and verified with simulations on load data collected from French Transmission System Operator (RTE) website. The obtained results show that the accuracy and the efficiency are improved comparatively to conventional methods widely used in this field of research. 相似文献
53.
The effect of high‐frequency (1.7 MHz) ultrasound waves on the mixing rate in a new continuous tubular sonoreactor was investigated by CFD modeling. Modeling of piezoelectric transducer (PZT) vibrations was done based on the dynamic mesh model. Results indicate that the acoustic streams were in the direction of wave propagation and their maximum velocity near the PZT surface agreed well with experimental measurements. The micromixing efficiency of the sonoreactor was studied by adopting the Villermaux/Dushman reaction in the modeling. Comparison of the calculated relative segregation index from modeling results with experimental data revealed reasonable accordance. 相似文献
54.
Ammar Al‐Bazi Nashwan Dawood 《Computer-Aided Civil and Infrastructure Engineering》2010,25(8):581-595
Abstract: The Precast Concrete Industry (PCI) is one of the major contributors to the national economy and can be categorized as labor‐intensive industry. It is currently experiencing shortcomings in terms of delivery products at a competitive cost and time. This is mainly due to the inefficiencies associate with planning and scheduling of skilled operators within crew configurations. This article presents a new strategy for efficient allocation of crews of workers in the precast concrete industry using Genetic Algorithms‐based simulation modeling. The aim of this study is to develop a crew allocation system that can efficiently allocate possible crews of workers to precast concrete labor‐intensive repetitive processes. Genetic algorithms (GAs) have been developed to solve this type of problem. Process mapping methodologies were used to identify and document the processes involved in producing precast components. Then process simulation was used to model and simulate all these processes and GAs were tailored to be embedded with the simulation model for a better search of promising solutions. GA operators were designed to suit this type of allocation problem. “Class Interval” selection strategy was developed to give a greater opportunity for the promising chromosomes to be chosen for further investigation. Dynamic crossover and mutation operators were developed to add more randomness to the search mechanism. The results showed that adopting different combinations of crews of workers had a substantial impact on reducing the process throughput time, minimizing resources cost, and achieving the required operatives utilization. 相似文献
55.
In this paper we study the convergence of the well-known Greedy Rank-One Update Algorithm. It is used to construct the rank-one
series solution for full-rank linear systems. The existence of the rank one approximations is also not new, but surprisingly
the focus there has been more on the applications side more that in the convergence analysis. Our main contribution is to
prove the convergence of the algorithm and also we study the required rank one approximation in each step. We also give some
numerical examples and describe its relationship with the Finite Element Method for High-Dimensional Partial Differential
Equations based on the tensorial product of one-dimensional bases. We illustrate this situation taking as a model problem
the multidimensional Poisson equation with homogeneous Dirichlet boundary condition. 相似文献
56.
Mohamed Ammar Abbassi Najla Grioui Kamel Halouani Andr Zoulalian Belkacem Zeghmati 《Fuel Processing Technology》2009,90(10):1278-1285
A pilot plant of biomass pyrolysis using pyrolysis products as fuel has been tested and shown to improve energy balance of the process and to be environmentally friendly by avoiding rejection of pyrolysis pollutants fumes into the atmosphere. The high number of parameters involved in a pyrolysis process makes it difficult to specify an optimum procedure for charcoal yield and pyrolysis cycle durability. So the knowledge of the essential parameters which govern the kinetics mechanisms of the biomass thermal decomposition and the combustion of pyrolysis gases is very useful to understand the operating cycle of the plant. In the present study a thermochemical model is developed in order to simulate and control the operating cycle of the system. The effect of the inlet molar air flow rate on the temporal evolution of biomass mass loss rate and temperatures in the different active zones of the pilot plant as well as the determination of the critical inlet molar air flow rate for which accidental runaway of combustion reactions occurs are presented. To avoid this accidental phenomenon a Proportional-Integral-Derived (PID) anticipated regulation is used in order to control temperatures evolution in the different zones of the device and avoid the runaway of combustion reactions. 相似文献
57.
Muhammad Iman Utama Abdul Aziz Ammar Nokeun Park Eung Ryul Baek 《Metals and Materials International》2018,24(2):291-299
We studied the origin of different characteristics and properties of a Ti–10V–2Fe–3Al beta (β) titanium alloy with surface height irregularities that occurred during machining. The height differences were observed in two different regions, labeled as “soft region” and “hard region.” The present study showed a higher Fe and a lower Al content in the hard region, which resulted in higher β-phase stability to resist primary alpha (αp) phase precipitation caused by a failure of the solution treatment process. In contrast, the soft region contained a higher volume fraction of αp phase and a lower volume fraction of the matrix, which consisted of a combination of β and secondary alpha (αs) phase. A high number of αs/β interface in the matrix with a predicted hardness of 520 HV generated an improvement of hardness in the hard region. Therefore, the hard and the soft regions had different abilities to resist wear during machining process, resulting in surface height irregularities. 相似文献
58.
Hawbani Ammar Wang Xingfu Kuhlani Hassan Karmoshi Saleem Ghoul Rafia Sharabi Yaser Torbosh Esa 《Wireless Networks》2018,24(7):2723-2734
Wireless Networks - Data dissemination toward static sinks causes the nearby nodes to deplete their energy quicker than the other nodes in the field (i.e., this is referred to as the hotspot... 相似文献
59.
Ammar Wakil Grahame Mackenzie Alberto Diego-Taboada J. Gordon Bell Stephen L. Atkin 《Lipids》2010,45(7):645-649
Benefits of eicosapentaenoic acid (EPA) can be enhanced by raising their bioavailability through microencapsulation. Pollen
can be emptied to form hollow shells, known as exines, and then used to encapsulate material, such as oils in a dry powder
form. Six healthy volunteers ingested 4.6 g of fish oil containing 20% EPA in the form of ethyl ester first alone and then
as 1:1 microencapsulated powder of exines and fish oil. Serum bioavailability of EPA was measured by area under curve (AUC0–24). The mean AUC0–24 of EPA from ethyl ester with exine (M = 19.7, SD = 4.3) was significantly higher than ethyl ester without exines (M = 2, SD = 1.4, p < 0.01).The bioavailability of EPA is enhanced by encapsulation by pollen exines. 相似文献
60.
Amine Ammar Emmanuelle Abisset-Chavanne Francisco Chinesta Roland Keunings 《International Journal of Material Forming》2017,10(4):547-556
Permeability is the fundamental macroscopic material property needed to quantify the flow in a fibrous medium viewed as a porous medium. Composite processing models require the permeability as input data to predict flow patterns and pressure fields. In a previous work, the expressions of macroscopic permeability were derived in a double-scale porosity medium for both Newtonian and generalized Newtonian (shear-thinning) resins. In the linear case, only a microscopic calculation on a representative volume is required, implying as many microscopic calculations as there are representative microscopic volumes in the whole fibrous structure. In the non-linear case, and even when the porous microstructure can be described by a unique representative volume, a large number of microscopic calculations must be carried out as the microscale resin viscosity depends on the macroscopic velocity, which in turn depends on the permeability that results from a microscopic calculation. An original and efficient offline-online procedure was proposed for the solution of non-linear flow problems related to generalized Newtonian fluids in porous media. In this paper, this procedure is generalized to quasi-Newtonian fluids in order to evaluate the effect of extensional viscosity on the resulting upscaled permeability. This work constitutes a natural step forward in the definition of equivalent saturated permeabilities for linear and non-linear fluids. 相似文献