Wyniki wyszukiwania - BazTech

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Dual-band Textile AMC Antenna for WLAN/WBAN Applications on the Human Arm

Bouamra Wahida, Sfar Imen, Mersani Ameni, Osman Lotfi, Ribero Jean-Marc

International Journal of Electronics and Telecommunications

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2022

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Vol. 68, No. 2

209--216

EN

This article presents a low-profile and flexible dualband AMC Antenna operating at 2.45/ 5.8 GHz for wireless local area network (WLAN) on-body antenna applications using textile materials. A dual-band artificial magnetic conductor (AMC) structure with a dual hexagonal shape was used to reduce back radiation, therefore specific absorption rate (SAR), and improve the antenna performance parameters. To study the antenna/body interaction, a suitable comprehension and detailed studies of the wave propagation in the vicinity of the human arm in different meteorological conditions were carried out to demonstrate the effects of the skin condition on the antenna performance parameters. The simulation and measurement results indicate that electromagnetic communication on wet skin is viable. Acceptable SAR values were obtained, revealing that the body is well immune from the antenna electromagnetic radiation in functional wearable conditions. The proposed wearable AMC antenna provided engaging simulation and measurement results. It satisfies users' comfort and safety properties, making it a good candidate for WLAN/WBAN applications.

2

Study on the applicability of the SCS CN based models to simulate foods in the semi arid watersheds of northern Algeria

Abdi Ishak, Meddi Mohamed

Acta Geophysica

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2021

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Vol. 69, no. 1

217--230

EN

Algeria has experienced catastrophic foods over the second half of the twentieth century, causing many deaths and extensive material damage. This study was conducted to fnd a suitable event-based rainfall-runof (RR) model for semi-arid conditions, where continuous data are not available in all regional basins. The study compared, based on data availability, the SCS-CN model based on the antecedent moisture conditions (AMC) and four modifed SCS-CN models incorporating antecedent moisture amounts (AMA) in order to fnd the best model to reproduce the food hydrographs in two catchments. The modi fed models were predominant over the SCS-CN method. Nonetheless, the Singh et al. (Water Resour Manag 29:4111–4127, 2015. https://doi.org/10.1007/s11269-015-1048-1) model (M4) and the Verma et al. (Environ Earth Sci 76:736, 2017a. https ://doi.org/10.1007/s12665-017-7062-2) model (M5) were superior and demonstrated more stable structures. Coupled with the Hayami routing model, the models showed promising results and were able to reproduce the observed hydrographs’ shape. However, it was impossible to choose the preferred model since they each excelled as to a criterion. Therefore, the corresponding outputs were combined using the simple average (SA) method and the weighted average (WA) method. We found that the WA method showed better results in the two catchments and allowed a more accurate prediction according to the performance criteria.

3

Wpływ parametrów mielenia wysokoenergetycznego na właściwości proszków kompozytowych aluminiowo-ceramicznych

Witkowska A., Pawlik T., Michalik D., Sopicka-Lizer M.

Inżynieria Materiałowa

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2015

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Vol. 36, nr 4

166--175

PL

Drobnoziarniste kompozyty na osnowie aluminium i jego stopów wzmacniane cząstkami ceramicznymi, stanowiące alternatywę dla kompozytów otrzymywanych metodami odlewniczymi, charakteryzuje submikroskopowy stopień rozdrobnienia i wysoka reaktywność. Celem prezentowanych badań było określenie wpływu parametrów mielenia w młynie planetarnym na powstawanie i właściwości proszku kompozytowego składającego się z siluminu, azotku krzemu i węgla szklistego. Analizowane parametry mielenia to: czas mielenia, prędkość obrotowa, średnica mielników, materiał wyłożenia oraz średnica misy mielącej. Zastosowano metody badawcze umożliwiające określenie rozkładu ziarnowego proszku kompozytowego, powierzchni właściwej, zawartości tlenu w proszku metalicznym i w azotku krzemu oraz składu fazowego. Przeprowadzone analizy wykazały zróżnicowany wpływ parametrów na efekt rozdrobnienia i właściwości rozdrobnionego materiału. Wysokoenergetyczne mielenie wieloskładnikowego proszku kompozytowego wywołuje reakcje chemiczne między składnikami proszku i aglomerację rozdrobnionych cząstek, których intensywność zależy od analizowanych parametrów mielenia. Analogiczne mielenie jednoskładnikowego proszku siluminowego dało odmienne wyniki.

EN

Fine-grained composites based on an aluminum matrix or its alloys, reinforced with submicron ceramic particles obtained by the powder metallurgy method are an alternative to the composites obtained by casting method and they can provide the submicrometer scale of reinforcement distribution. The aim of this study was to determine the impact of the milling parameters in a planetary mill on the formation and properties of the composite powder consisting of silumin, silicon nitride and glassy carbon. The analyzed parameters of milling are: the time of milling, the rotational speed, the diameter of the grinding media, the jar lining material and the diameter of the grinding bowl. Research methods enabling to determine the particle size distribution of the composite powder, the specific surface area, oxygen content in both, the metallic and silicon nitride powder, as well as phase composition changes induced by high-energy milling, were applied. The obtained results revealed a varying impact of milling parameters on the refining effect and on the properties of particulate material. High energy milling of the multi-component composite powder induced chemical reactions between the powder particles of various chemical composition and agglomeration of fine particles, with various intensity depending on the analyzed grinding parameters. Analogous milling of the sole silumin powder without ceramic reinforcement gave different results.

4

Usefulness of the Modified NRCS-CN Method for the Assessment of Direct Runoff in a Mountain Catchment

Wałęga A., Rutkowska A.

Acta Geophysica

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2015

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Vol. 63, no. 5

1423--1446

EN

The aim of this study was to evaluate the usefulness of modified methods, developed on the basis of NRCS-CN method, in determining the size of an effective rainfall (direct runoff). The analyses were performed for the mountain catchment of the Kamienica river, right-hand tributary of the Dunajec. The amount of direct runoff was calculated using the following methods: (1) Original NRCS-CN model, (2) Mishra- Singh model (MS model), (3) Sahu-Mishra-Eldho model (SME model), (4) Sahu 1-p model, (5) Sahu 3-p model, and (6) Q_base model. The study results indicated that the amount of direct runoff, determined on the basis of the original NRCS-CN method, may differ significantly from the actually observed values. The best results were achieved when the direct runoff was determined using the SME and Sahu 3-p model.

5

Techniki szybkiej transmisji danych w systemie UMTS (HSDPA, HSUPA)

Moszczyk S., Kołakowski J., Cichocki J.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

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2005

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nr 10

362-367

PL

Poruszono tematykę związaną z wprowadzaniem nowych technik transmisji w łączu radiowym systemu UMTS. W ostatnich latach zostały opracowane i standaryzowane odrębne techniki przeznaczone do szybkiej transmisji w łączu w dół HSDPA (High Speed Downlink Packet Access) i w łączu w górę HSUPA (High Speed Uplink Packet Access). Artykuł zawiera opis tych rozwiązań oraz przegląd oferowanych przez nie możliwości.

EN

The paper deals with new techniques used for fast transmission of packet data in UMTS radio interface. Recently two solutions were developed and introduced into UMTS specifications: HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access). The paper contains description of these standards as well as review of opportunities offered by these solutions.