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排序方式: 共有143条查询结果,搜索用时 31 毫秒
111.
Ridha Ziani Ahmed Hammami Fakher Chaari Ahmed Felkaoui Mohamed Haddar 《Comptes Rendus Mecanique》2019,347(9):663-675
Condition monitoring of gearboxes running under non-stationary operating conditions is a very difficult task. In this study, a signal processing technique is developed for damage detection of a bevel gearbox running under variable load and speed conditions. The proposed technique is applied on simulated vibration data computed through a dynamic model of bevel gearbox. The procedure used in this technique is based on the extraction of the shock related to the defect using the Shock Detector (SD) method. Firstly, vibration signals are decomposed into IMFs using Empirical Mode Decomposition (EMD). Then, the Teager–Kaiser Energy Operator (TKEO) is used to assess the instantaneous energy of the signal. Afterwards, SD is applied to examine and quantify the shock contents of the TKEO signal, which reflect the effect of the defect. 相似文献
112.
Hasna Ettis Melek Hajji Ridha Touati 《Phosphorus, sulfur, and silicon and the related elements》2016,191(5):765-771
A novel organic sulfate (C4H16N3)SO4?HSO4 has been prepared and characterized by single-crystal X-ray diffraction, infrared spectroscopy, thermogravimetric analysis and differential scanning calorimetry (DSC). The structure consists of linked HSO4? and SO42? anions assembled into clusters. Organic triple-protonated diethylene triammonium cations are interconnected to these clusters via N–H?O hydrogen bonds to create the three dimensional arrangement. The Hirshfeld surface and associated fingerprint plots of the compound were presented to explore the nature of intermolecular interactions and their relative contributions to building the solid-state architecture. TG-DTA and DSC studies showed the presence of two phase transitions. Infrared spectrum is reported and discussed on the basis of group theoretical analysis and on Density Functional Theory calculations. 相似文献
113.
Peter Nwabuzor Collins Edet Akpan Ndem Ikot Uduakobong Okorie Morris Ramantswana Ridha Horchani Abdel-Haleem Abdel-Aty Gaotsiwe Rampho 《Entropy (Basel, Switzerland)》2021,23(8)
In this study, the impacts of TD on the energy spectra and thermal properties of LiH, TiC and I2 diatomic molecules is considered. The Schrodinger equation in cosmic string spacetime is solved with the generalized Morse potential using the well-known (NU) method. The energy spectra and eigenfunction are obtained respectively. The energy spectra is used to obtain the partition function which is then used to evaluate the thermal properties of the system is evaluated accordingly. We find that the energy spectra in the presence of the TD differ from their flat Minkowski spacetime analogue. The effects of the deformation parameter and TD on the thermal properties of the system is also analysed in detail. We observe that the specific heat capacity of the system tends to exhibit quasi-saturation as the deformation parameter and topological defect approaches unity. The results of our study can be applied in the astrophysical situation where these modifications exist in the understanding of spectroscopical data and it may be used as a probe of the presence of a cosmic string or a global monopole in the Universe. 相似文献
114.
115.
R. Zouari 《Phase Transitions》2017,90(2):167-174
The present work is devoted to a review of the phenomenological model proposed by Mahmoud Aly Hamad (M. Aly Hamad, Phase Transitions 85 (2012) 106–112) to predict the magnetocaloric effect in ferromagnetic material from the only measure of its magnetization as a function of temperature under an applied magnetic field. We questioned the reliability of that model. Based on some experimental data available in the literature, we have shown that, contrary to what is expected, the prediction of the magnetocaloric effect by this model is poor. 相似文献
116.
3,4‐Dihydropyrimidinone and derivatives were synthesized by the one‐pot, three‐component Biginelli condensation of an aldehyde, β‐dicarbonyl compound and urea. Synthesis was carried out in aqueous sodium hydroxide using Aliquat‐336 as a phase transfer agent. Compared to the classical Biginelli reaction conditions, this new method cousistently has the advantage of excellent yields and short reaction time. 相似文献
117.
Muhammed Mizher Radhi Firas K. Mohamad Alosfur Noor J. Ridha 《Russian Journal of Electrochemistry》2018,54(1):27-32
In this study, a grafted polymer (GP) with ZnO nanoparticles (GP/ZnO NPs) was attached on the surface of glassy carbon electrode (GCE), in order to produce a new modified electrode (GP/ZnO NPs-GCE). The gamma irradiation method was used to grafted polystyrene (polymer) with acrylonitrile (monomer), while slow evaporation process was used to prepare the new modified electrode. The cyclic voltammetry (CV) of K4[Fe(CN)6] was used to study the electrochemical properties GP/ZnO NPs-GCE. The peak separation (ΔEpa-c) was 500 mV between the redox peaks of Fe(II)/Fe(III) in an aqueous solution of 1 M KCl and the current ratio of redox current peaks (Ipa/Ipc) was ≈ 1 for the modified electrode. This indicated that the modified electrode has s good reversibility and conductivity, wherefore; it was applied in the voltammetric filed. It was found that the modified electrode GP/ZnO NPs-GCE have a reasonable solubility and stability at various pH medium. Additionally, the sensitivity of the electrochemical analysis by cyclic voltammetric (CV) method is extensively subjected to the pH medium and the scan rate (SR). A couple of redox current peaks of K4[Fe(CN)6] in KCl solution was observed with a reversible process: Fe3+/Fe2+. Finally a good diffusion coefficient of electroactive species (D) for the new modified electrode was found in this study by chronoamperometry method using Cottrell equation. 相似文献
118.
119.
The present paper accounts for the synthesis, crystal structure, differential scanning calorimetry and vibrational spectroscopy of a new compound (1,3,5-triazinidium-2,4,6-triamine) hexabromidodicuprate (II) grown at room temperature by slow evaporation of aqueous solution. From X-ray diffraction data collected at room temperature, it is concluded that it crystallizes in the monoclinic system (P21/c space group). The anion and the cation are linked by N–H···Br hydrogen bonds. Furthermore, the room temperature IR and Raman spectra of the title compound were recorded and analyzed. The differential scanning calorimetric has also been investigated. Hirshfeld surfaces were used to confirm the existence of inter-molecular interactions in the compound. 相似文献
120.
Saoussen Hammami Zhenzhen Li Mingjie Huang Ridha El Mokni Hatem Dhaouadi 《Natural product research》2016,30(19):2142-2148
A phytochemical investigation of the ethanol extract of Marrubium aschersonii Magnus (Lamiaceae) collected from Tunisia led to the isolation and identification of two new labdane diterpenoids, marrubaschs A (1) and B (2), along with two known compounds (3 and 4). Their structures were elucidated by spectroscopic methods including HRESIMS and NMR techniques. All compounds were evaluated for their inhibitory effects on the nitric oxide (NO) production induced by lipopolysaccharide in RAW 264.7 macrophage cells. Compound 2 exhibited weak inhibition of NO production with an IC50 value of 35 ± 1.0 μM. 相似文献