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- 저자 : Ahmed Mekki (검색결과 4 건)
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Generalised Ricci Solitons on Sasakian Manifolds
Mekki, Mohammed El Amine,Cherif, Ahmed Mohammed Department of Mathematics 2017 Kyungpook mathematical journal Vol.57 No.4
In this paper, we show that a Sasakian manifold which also satisfies the generalised gradient Ricci soliton equation, satisfying some conditions, is necessarily Einstein.
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Soumia Benhouhou,Ahmed Mekki,Maha Ayat,Noureddine Gabouze 한국고분자학회 2021 Macromolecular Research Vol.29 No.4
Conducting polymers, are still fascinating the industrial applications area since their discovery, particularly in the field of chemical sensors. For this purpose, flexible and highly sensitive based polyaniline-strontium (PANI-Sr) films were successfully prepared via a facile in-situ chemical polymerization process of aniline in presence of Sr (NO3)2 deposited on biaxially oriented polyethylene terephthalate (BOPET) flexible substrates with prior surface treatment using (3-aminopropyl) trimethoxysilane. Spectral, structural, morphological, and surface behavior characterizations were carried out using Fourier transform infrared spectroscopy (FTIR-ATR), X-ray fluorescence (XRF), raman spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and surface wettability. The electrical conductivity was measured by the usual four probes technique. Noticeably, the prepared films with Sr (NO3)2 ~2M have shown a highest conductivity of 0.3 S·cm-1 over the other samples. This conductivity feature has been exploited to test the sensitivity and the performances of the obtained films toward different type of gas. The PANI-Sr sensor demonstrates an outstanding selectivity and an excellent sensitivity towards the ammonia (498% response to 100 ppm) within a detection limit of 0.013 ppm, and a fast response/recovery time (1 s /42 s) toward 50 ppm at room temperature. The PANI-Sr sensor also showed a good reproducibility during five cycles. The interaction mechanism of PANI-Sr sensor film and the NH3 vapors was discussed basing on the impedance spectroscopy analysis results. The obtained results highlight the paramount role played by the strontium particle in enhancing the ammonia detection performances, when they are imbedded into PANI matrix through facile preparation process, and they emphasize their prominence over the similar study.
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Fateh Merdj,Ahmed Mekki,Djamil Guettiche,Boualem Mettai,Zakaria Bekkar Djeloul Sayah,Zitouni Safidine,Abderrazak Abdi,Rachid Mahmoud,Mohamed M. Chehimi 한국고분자학회 2018 Macromolecular Research Vol.26 No.6
Air quality monitoring is of major concern as it is directly linked to public health. It requires the development of high sensitive devices with fast response towards hazardous gas and volatile compounds. Such performances depend on the nature and quality of deposition of the sensing layer. Herein, adherent polypyrroledodecylbenzene sulfonic acid (PPy–DBSA) films were deposited on a N-(3-trimethoxysilylpropyl) pyrrole modified ITO coated polyethylene teraphtalate (PET) flexible substrate by facile direct electrochemical oxidation of pyrrole in an aqueous solution of sulfonic acid. The obtained PPy-DBSA films were subjected to various characterization techniques such as, FTIR, Raman, SEM and conductivity measurements. Chemiresistive gas sensing tests have demonstrated selectivity and sensitivity of films toward ammonia vapors over the other vapors (nitrogen dioxide, carbon dioxide, hydrogen sulfide, acetone, methanol and ethanol) with higher response at 20 ppm, reasonably fast response time of 3 min and reaching detection limit of 3ppm. The response of the sensor can reasonably be related to the strong electrostatic interactions between vapor molecules and the dopant agents within PPy films. In comparison PPy- DBSA films prepared on pristine ITO/PET has exhibited lower response at 20 ppm of ammonia exposure, which highlights the role of surface modification and the contribution from the dopant agent nature for ammonia sensing. Moreover, chemiresistive response performances have been tested in the presence of humidity, under varied temperatures, and finally their behaviors were featured by an impedance spectroscopy in both presence and absence of gas. This work conclusively shows that the sensing performances are not only driven by the molecular interactions between the sensor and the analyte but also by the quality of deposition and adhesion of the former to the transducer. The latter feature can be controlled by appropriate chemical surface modification.
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Fateh Merdj,Ahmed Mekki,Djamil Guettiche,Boualem Mettai,Zakaria Bekkar Djeloul Sayah,Zitouni Safidine,Abderrazak Abdi,Rachid Mahmoud,Mohamed M. Chehimi 한국고분자학회 2018 Macromolecular Research Vol.25 No.6
Air quality monitoring is of major concern as it is directly linked to public health. It requires the development of high sensitive devices with fast response towards hazardous gas and volatile compounds. Such performances depend on the nature and quality of deposition of the sensing layer. Herein, adherent polypyrroledodecylbenzene sulfonic acid (PPy–DBSA) films were deposited on a N-(3-trimethoxysilylpropyl) pyrrole modified ITO coated polyethylene teraphtalate (PET) flexible substrate by facile direct electrochemical oxidation of pyrrole in an aqueous solution of sulfonic acid. The obtained PPy-DBSA films were subjected to various characterization techniques such as, FTIR, Raman, SEM and conductivity measurements. Chemiresistive gas sensing tests have demonstrated selectivity and sensitivity of films toward ammonia vapors over the other vapors (nitrogen dioxide, carbon dioxide, hydrogen sulfide, acetone, methanol and ethanol) with higher response at 20 ppm, reasonably fast response time of 3 min and reaching detection limit of 3ppm. The response of the sensor can reasonably be related to the strong electrostatic interactions between vapor molecules and the dopant agents within PPy films. In comparison PPy- DBSA films prepared on pristine ITO/PET has exhibited lower response at 20 ppm of ammonia exposure, which highlights the role of surface modification and the contribution from the dopant agent nature for ammonia sensing. Moreover, chemiresistive response performances have been tested in the presence of humidity, under varied temperatures, and finally their behaviors were featured by an impedance spectroscopy in both presence and absence of gas. This work conclusively shows that the sensing performances are not only driven by the molecular interactions between the sensor and the analyte but also by the quality of deposition and adhesion of the former to the transducer. The latter feature can be controlled by appropriate chemical surface modification.
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