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31.
New numerical quasi-static model for the computer aided design (CAD) and analysis of suspended microstrip lines is reported. This model is applicable up to εr = 20 and over the range 0.001 ≤ u ≤ 1000, where u = w/h 1 is the structure’s variable (w is the width of the strip and h 1 is the air gap’s thickness). The practical cases are limited to a thickness h 1 of the same order of h 2 which is the dielectric’s thickness. This yields to choose 0.5 ≤ m ≤ 1.5. The parameter m is dependent on the structure’s variable u. This model is conceived to corroborate the results of the variational approach in any point of its ranges of validity, with a raised error with 1.2%. Although the variational approach allows accurate values of the effective permittivity, but the computing time is relatively high which quickly becomes prohibitory if the Finished Coupled Elementary Lines method is used. The present model is an improvement over the previous variational method as it not only takes lower computing time but it also valid up to high values of εr and over the range 0.001 ≤ u ≤ 1000. This work is important by the fact that it seeks to visualise the formal model of the effective permittivity, generally masked in a direct variational treatment. 相似文献
32.
The increasing pollution of the electromagnetic environment has prompted the study of array pattern nulling techniques. These techniques are very important in radar, sonar and communication systems for minimising degradation in signal-to-noise ratio performance due to undesired interferences. Adaptive array antennas backed by strong signal processing algorithms are able to automatically change the beam pattern in accordance with the changing signal environment. It not only directs maximum radiation in the direction of the desired mobile user but also introduces nulls for interfering directions while tracking the desired mobile user at the same time. The adaptation is achieved by multiplying the incoming signals with complex weights and then summing them together to obtain the desired radiation pattern. Adaptive array optimization is an NP-hardproblem. In this paper, a technique based on the coupling between tabu search and simulated annealing methods is presented to solve this problem. Several illustrative examples of patterns with imposed single and multiple null directions are given to show the versatility of the present method. 相似文献
33.
Nils-Erik Wiberg Fethi Abdulwahab Saulius Ziukas 《International journal for numerical methods in engineering》1994,37(20):3417-3440
Patch recovery based on superconvergent derivatives and equilibrium (SPRE), an enhancement of the Superconvergent Patch Recovery (SPR), is studied for linear elasticity problems. The paper also presents a further improvement for recovery of derivatives near boundaries, SPREB, where either tractions or displacements are prescribed. This is made by inclusion of weighted residual errors at boundary points in the patch recovery. A pronounced improvement in the post processed gradients of the finite element solution is observed by this method. 相似文献
34.
An accurate modelling of static effective permittivity ?eff of a uniform suspended microstrip line is presented. This modelling is built on the variational method of moments (Vm). But this method requires high times computing for line of arbitrary shape, the width w of the uniforme line is reduced by the thickness h1 of the air gap. The stratified microstrip patch antennas with an air gap, of arbitrary shape present this type of situation in the analysis with the method of the Finished Coupled Elementary Lines (F.c.e.l). A formal model proposed in this work, is free of integration and derivation, and is connecting the physical parameters (such as the relative permittivities ?ri of the mediums i = 1,2…) with those of the geometrical structure (u = w/h1 and m — h2/h1 where h2 is the thickness of dielectric). The new model is valid for the full 1 ≤ ?r ≤20, 0.5 ≤m≤ 1.5, 10?2 ≤ult; +∞ ranges. The model is successfully compared with mesured data. This work give an accurate evaluation of ?eff then the frequency dependence of the effective permittivity can be easily determined. 相似文献
35.
36.
Shrestha Bibek Alsadoon Abeer Prasad P. W. C. Al-Naymat Ghazi Al-Dala’in Thair Rashid Tarik A. Alsadoon Omar Hisham 《Multimedia Tools and Applications》2022,81(27):38945-38969
Multimedia Tools and Applications - The natural population-based prediction of type 2 diabetes is costly since it needs a high number of resources. Even though much research has used machine... 相似文献
37.
Kitchah Fethi Benmebarek Sadok Djabri Mohamed 《Bulletin of Engineering Geology and the Environment》2021,80(8):6161-6176
Bulletin of Engineering Geology and the Environment - Construction of long tunnels in difficult sites is associated with various risks. Such risks are usually resulted on one hand from the lack of... 相似文献
38.
Aissaoui Ferhi Leila Sethom Kaouthar Choubani Fethi 《Wireless Personal Communications》2019,109(3):1769-1779
Wireless Personal Communications - With the attractive applications in e-Health, a booming interest is granted to wireless body area network (WBAN). Through WBAN, healthcare professionals can... 相似文献
39.
This paper focuses on applying a wireless power transfer WPT technology in an electric vehicle battery charger. The wireless charger system is based on the principle of resonance inductive coupling power through a coreless transformer. The WPT system is considered as a multi parameter and multi constrained nonlinear system. The main contribution in this paper is the use of PSO and GA metaheuristic algorithms in the optimization of a transformer design regarding the impact of a lateral misalignment and the separation distance between the primary and secondary coils. To find the best global solution which is considered as the maximum efficiency in the complex system, both algorithms are compared. A perturbation-and-observation-based tracking system is developed through an efficiency sensing system to act on the misalignment issue and the car position. An additional PSO controller is performed to control the duty cycle of the boost converter in order to follows the maximum efficiency operating points of a WPT system. The discrepancy is the use of the resonant inductive coupling as a source of the MPPT so as to perturb the car position and observe the transferred. Furthermore, the modeling of a contactless transformer is optimized using metaheuristic algorithm. 相似文献
40.
Microsystem Technologies - This paper reports ion sensitive field effect transistor (IS-FET) with graphene/ionophore hybrid membrane for phosphate detection. CVD graphene is used as a sensing... 相似文献