In this paper, the resonance and radiation characteristics of rectangular microstrip patch printed on suspended and composite substrates are investigated theoretically. The analysis approach is based on the spectral-domain method of moments in conjunction with the stationary phase method. The complex resonant frequency of the microstrip antenna on suspended and composite substrates is studied with sinusoidal functions as basis functions, which show fast numerical convergence. Using a matrix representation of each layer, the far-field pattern of the suspended-composite configuration is efficiently determined by the (TM, TE) representation. The validity of the solution is tested by comparison of the computed results with experimental data. Finally, numerical results for the effects of suspended and composite substrates on the resonant frequency and half-power bandwidth are also presented.

This paper deals with robust direct power control of a grid-connected brushless doubly-fed induction generator(BDFIG). Using a nonlinear feedback linearization strategy, an attempt is made to improve the desired performances by controlling the generated stator active and reactive power in a linear and decoupled manner. Therefore, to achieve this objective, the Lyapunov approach is used associated with a sliding mode control to guarantee the global asymptotical stability. Thus, an optimal operation of the BDFIG in sub-synchronous operation is obtained as well as the stator power flows with the possibility of keeping stator power factor at a unity. The proposed method is tested with the Matlab/Simulink software. Simulation results illustrate the performances and the feasibility of the designed control.

In this paper, an optimized ultra-low power phototransistor design based on gradual gate doping engineering is proposed. Using an analytical investigation and numerical simulation, an overall performance comparison of the proposed phototransistor design and conventional structure has been studied, in order to show the improved characteristics provided by the proposed design in terms of increased \(I_ON/I_OFF\) ratio and superior photoresponsivity capability. The results obtained from our analytical investigation are validated by comparison with the numerical simulations, thus establishing the accuracy of our analytical investigation. Moreover, the developed analytical models are used to optimize the proposed design using a genetic algorithm (GA) based-computation. The advantages offered by the proposed design suggest the possibility to overcome the most challenging problem with the power requirements of the optical interconnect: power consumption in the light emitter and in the receiver. In this context, the proposed phototransistor owing to the high responsivity requires less optical power from the light emitter to achieve an acceptable signal-to-noise ratio compared to the phototransistor with conventional design.

In this paper, the impact of the surface-textured front glass on the absorption of TiO 2 /glass thin-film ultraviolet (UV) photodetector is investigated, in order to achieve the dual role of increasing the scattering of UV-light as well as reducing the refracting UV-light in the glass. The efficient control of these phenomena may lead to more electric field confinement and UV-light trapping in TiO 2 absorber layer. Moreover, semianalytical modeling combined with particle swarm optimization is carried out for studying and enhancing the metal-semiconductor-metal photodetector optical and electrical performances. The results obtained from our semianalytical investigation are validated by comparison with the experimental data. It is found that the absorbance increases significantly by about 51% in optimized design over the planar structure, which is expected to improve the photodetector figures of merit. In this context, photodetector with optimized grooves texturization exhibits a 341% improvement, in terms of responsivity, in comparison with the planar structure and 275% improvement with respect to the textured device without optimization. The obtained results make the proposed design methodology a promising alternative for high-performance optoelectronic applications.

In this paper, we present a simple new human activity recognition method using discrete cosine transform (DCT). The scheme uses the DCT coefficients extracted from silhouettes as descriptors (features) and performs frame-by-frame recognition, which make it simple and suitable for real time applications. We carried out several tests using radial basis neural network (RBF) for classification, a comparative study against stat-of-the-art methods shows that our technique is faster, simple and gives higher accuracy performance comparing to discrete transform based techniques and other methods proposed in literature.

Redundant data retransmission problem in wireless sensor networks (WSNs) can be eliminated using the data aggregation process which combines similar data to reduce the resource-consumption and consequently, saves energy during data transmission. In the recent days, many researchers have focused on securing this paradigm despite the constraints it imposes such as the limited resources. Most of the solutions proposed to secure the data aggregation process in WSNs are essentially based on the use of encryption keys to protect data during their transmission in the network. Indeed, the key generation and distribution mechanisms involve additional computation costs and consume more of energy. Considering this, in this paper, we propose a new security mechanism to secure data aggregation in WSNs called SDAW (secure data aggregation watermarking-based scheme in homogeneous WSNs). Our mechanism aims to secure the data aggregation process while saving energy. For this, the mechanism uses a lightweight fragile watermarking technique without encryption to insure the authentication and the integrity of the sensed data while saving the energy. The links between the sensor nodes and the aggregation nodes, and also the links between the aggregation nodes and the base station are secured by using the watermarking mechanism.

This paper proposes a semi-structured information retrieval model based on a new method for calculation of similarity. We have developed CASISS (Calculation of Similarity of Semi-Structured documents) method to quantify how two given texts are similar. This new method identifies elements of semi-structured documents using elements descriptors. Each semi-structured document is pre-processed before the extraction of a set of descriptors for each element, which characterize the contents of elements.It can be used to increase the accuracy of the information retrieval process by taking into account not only the presence of query terms in the given document but also the topology (position continuity) of these terms.

Nowadays, the dissemination of information touches the distributed world, where selecting the relevant servers to a user request is an important problem in distributed information retrieval. During the last decade, several research studies on this issue have been launched to find optimal solutions and many approaches of collection selection have been proposed. In this paper, we propose a new collection selection approach that takes into consideration the number of documents in a collection that contains terms of the query and the weights of those terms in these documents. We tested our method and our studies show that this technique can compete with other state-of-the-art algorithms that we choose to test the performance of our approach.