Ming‐Sze Tong, Tae‐Gyu Chang and Ronan Sauleau
To perform studies and comparisons on the electromagnetic band‐gap (EBG) structures, which are constructed by using a combination of inductive and capacitive elements printed on…
Abstract
Purpose
To perform studies and comparisons on the electromagnetic band‐gap (EBG) structures, which are constructed by using a combination of inductive and capacitive elements printed on guided‐wave transmission lines, and by applying a chirping‐and‐tapering technique.
Design/methodology/approach
An in‐house solver based on finite‐difference time‐domain (FDTD) method is adopted for analysis. Conventionally, EBG characteristics are formed by a series of perforations, considered as capacitive elements, on the ground plane(s). To enhance the performance, an additional inductive element is implemented, which is realized by narrowing the strip over the respective perforated regions. For further enhancement, a chirping‐and‐tapering technique is applied on the combined EBG structures for comparisons.
Findings
Through scattering parameter analysis, it was found that the EBG structures using combined inductive and capacitive elements exhibit a band‐gap behavior superior to the ones built with only inductive or capacitive elements. In another set of comparisons, the modified EBG structures combined with a chirping‐and‐tapering technique resulted in further widening of band‐gap, as well as lower side‐lobes and a smoother transition towards the band‐gap region.
Research limitations/implications
Research was mainly limited to studying solely the EBG structures printed on guided‐wave transmission lines.
Practical implications
The proposed EBG structures may be applied into various areas, such as microelectronics and mobile communications for harmonic suppressions, and into other practical electronic circuit structures.
Originality/value
The ideas on applying combined inductive and capacitive elements on various guided‐wave transmission lines to induce EBG characteristics, together with applications of a chirping‐and‐tapering technique on the combined EBG structures give rise to the research originality.
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Keywords
Ming‐Sze Tong, Yinchao Chen, Yilong Lu, Hyeong‐Seok Kim, Tae‐Gyu Chang and Ronan Sauleau
To study the photonic band‐gap (PBG) characteristics constructed by periodic conducting vias on various guided transmission‐line structures.
Abstract
Purpose
To study the photonic band‐gap (PBG) characteristics constructed by periodic conducting vias on various guided transmission‐line structures.
Design/methodology/approach
The finite difference time domain (FDTD) method is adopted to analyze various PBG via structures. Conventionally, PBG characteristics on guided‐wave structures, such as microstrip lines or coplanar waveguides (CPW), are constructed through a series of perforations on the ground plane(s). PBG characteristics can, however, also be realized through periodic arrangements of conducting vias located on the respective ground planes.
Findings
Through studies of the scattering parameters, it has been found that all analyzed PBG via structures exhibit strong band‐gap characteristics in a particular frequency range. Different harmonic patterns are also observed when the dimensional sizes of the conducting vias vary with respect to the PBG period.
Research limitations/implications
Research has been mainly limited to study solely the PBG via structures, guided‐wave transmission lines. More studies may be conducted in analyzing the overall performance when they are combined with other microwave components.
Practical implications
The proposed PBG via structures can be applied to various microwave areas, ranging from signal suppressions in microelectronics and mobile communications, to electro‐magnetic interference studies in other practical electronic circuit structures.
Originality/value
The ideas of applying conducting vias on the guided‐wave transmission lines and the proposed via patterns to induce the PBG characteristics are the research's claim to originality one.
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Ming‐Sze Tong, Yinchao Chen, Yilong Lu, Viktor Krozer, Kenichi Kagoshima, Hyeong‐Seok Kim and Tae‐Gyu Chang
To demonstrate the flexibility and advantages of a non‐uniform pseudo‐spectral time domain (nu‐PSTD) method through studies of the wave propagation characteristics on photonic…
Abstract
Purpose
To demonstrate the flexibility and advantages of a non‐uniform pseudo‐spectral time domain (nu‐PSTD) method through studies of the wave propagation characteristics on photonic band‐gap (PBG) structures in stratified medium
Design/methodology/approach
A nu‐PSTD method is proposed in solving the Maxwell's equations numerically. It expands the temporal derivatives using the finite differences, while it adopts the Fourier transform (FT) properties to expand the spatial derivatives in Maxwell's equations. In addition, the method makes use of the chain‐rule property in calculus together with the transformed space technique in order to make the algorithm flexible in terms of non‐uniform spatial sampling.
Findings
Through the studies of the wave propagation characteristics on PBG structures in stratified medium, it has been found that the proposed method retains excellent accuracy in the occasions where the spatial distributions contain step of up to five times larger than the original size, while simultaneously the flexibility of non‐uniform sampling offers further savings on computational storage.
Research limitations/implications
Research has been mainly limited to the simple one‐dimensional (1D) periodic and defective cases of PBG structures. Nevertheless, the findings reveal strong implications that flexibility of sampling and memory savings can be realized in multi‐dimensional structures.
Practical implications
The proposed method can be applied to various practical structures in electromagnetic and microwave applications once the Maxwell's equations are appropriately modeled.
Originality/value
The method validates its values and properties through extensive studies on regular and defective 1D PBG structures in stratified medium, and it can be further extended to solving more complicated structures.
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Ouafae El Yahyaoui, Bahia Bouabid, Nabil Ait Ouaaziz, Mohamed El Bakkali, Hanae El Harche, Lalla Aicha Lrhorfi, Kamal Nakari and Rachid Bengueddour
Within the framework of the valorization of natural resources, a characterization of the biochemical composition of the edible parts of Adansonia Digitata is applied. The…
Abstract
Purpose
Within the framework of the valorization of natural resources, a characterization of the biochemical composition of the edible parts of Adansonia Digitata is applied. The antibacterial effect against bacteria is also realized and compared to some synthetic antibiotics.
Design/methodology/approach
The biochemical characterization is carried out according to the norms of the French Association of Normalization, methods of Association of Official Analytical Chemists (AOAC International) and gas chromatography (GC). The antibacterial activity is tested by disk diffusion on a solid medium. Parametric tests are used to compare the differences between groups and heat maps to show the expression of the mean inhibitions according to the studied parameters. Multivariate logistic modeling is applied to study the effect of extracts and antibiotics on bacteria.
Findings
Biochemical characterization showed a variable importance of proteins, fibers and total sugars, with the presence of highly desired fatty acids such as palmitic, oleic, stearic, linoleic and a-linolenic acids. This gives the tested parts important energy values, especially in the seeds very rich in fatty acids. Methanol proved to be a better extraction solvent than dichloromethane. Antibacterial activity showed that pulp and leaves extracted with methanol had quite similar inhibitory activities against Enterococcus faecalis ATCC29212 and that this effect was better than some antibiotics. Multivariate analysis showed that the leaves had a similar effect to antibiotics, and a significant effect against Staphylococcus aureus ATCC29213.
Originality/value
This important activity and the attractive nutritional value of this plant could justify its extensive use in the traditional pharmacopoeia.