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Reduction of vibration by periodically stitched sandwich panel

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Chinese Journal of Aeronautics 2021年第7期34卷 39-49页

作者： Nan LI mabrouk BEN tahar Liang MENG Fusheng SUI Key Laboratory of Noise and Vibration Research Institute of AcousticsChinese Academy of SciencesBeijing 100190China Sorbonne Universites Universitede Technologie de CompiegneCNRSUMR 7337 RobervalCentre de Recherche RoyallieuCS 60319Compiegne Cedex 60203France State IJR Center of Aerospace Design and Additive Manufacturing Northwestern Polytechnical UniversityXi’an 710072China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China

This work reveals that the addition of periodically distributed stitches to sandwich structure enables a significant reduction of vibration in stop-band and this new functionality is systematically ***,a finite element model which is capable of taking into consideration the three layers of the sandwich as well as the stitches is *** diagram of dispersion is calculated by applying Floquet-Bloch theorem to the boundaries of unit *** properly chosen properties of stitches,a stop-band for flexural wave is *** stop-band is further confirmed by the forced response of a large stitched sandwich panel under point *** level of vibration in the stop-band is significantly *** influence of the stitch rigidity and density on upper and lower limits of stop-band is also examined,which confirms that stitched sandwich can be tuned to mitigate vibration in a certain frequency band with appropriate stitch *** investigations have demonstrated the potential application of stitched sandwich in the area of vibration reduction.

关键词： Composite structure Parametric study Periodic structures Reduction of vibration Stitched sandwich

ACOUSTIC ANALYSIS OF HYDRODYNAMIC AND ELASTO-HYDRODYNAMIC OIL LUBRICATED JOURNAL BEARINGS

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Journal of Hydrodynamics 2012年第2期24卷 250-256页

作者： BOUAZIZ Slim FAKHFAKH tahar HADDAR mohamed Dynamic of Mechanical Systems Research Unit (UDSM) University of Sfax Mechanics Modelling and Production Research Unit (U2MP) and National School of Engineers of Sfax (ENIS) BP.11733038University of Sfax

The purpose of the present paper is to investigate the effect of elastic deformation of bearing liner on the acoustic behavior of oil lubricated journal *** is performed for hydrodynamic（HD） and elasto-hydrodynamic （EHD） *** behavior and acoustical properties are investigated through an analysis of pressure fluctuation calculated from the Reynolds equation governing the flow in the clearance space of the journal *** is solved numerically using the finite difference method with the successive over relaxation *** elasto-hydrodynamic lubrication,the finite element method with in iteration scheme is adopted to solve both Reynolds equation and the three-dimensional elasticity equation representing the displacement field in the bearing *** results show that the sound pressure level of the bearing is markedly influenced by the flexibility of the bearing liner,the viscosity of lubricant and the load applied to *** analysis shows that the journal centre＇s orbit,from a disturbed position,converges to the static equilibrium position faster than EHD *** results of the present paper could aid in the design of low-noise rotor-bearing systems supported by oil lubricated journal bearings.

关键词： vibration amplitude pressure level lubricated bearing sound pressure

Robust design and analysis for opto-mechanical two array laser warning system

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Defence Technology(防务技术) 2023年第9期27卷 46-52页

作者： Mazhar Tayel mohamed Shehata mohamed mabrouk Abdlarhman Adel mohamed Shady Shokry Mostafa Alshershby Faculty of Engineering Alexandria UniversityAlexandriaEgypt Egyptian Air Defense Collage AlexandriaEgypt Laser and Optoelectronics Department Technical Research CenterEgypt

In the past three decades,laser warning systems(LWS)have emerged in great importance,as the development of laser-guided weapons,such as airborne Hellfire missiles,has increased,posing an imminent threat to vital areas and *** laser warning station(LWS)can detect,classify,identify,and give alarm from laser threat at a very short time with high ***,the designers of this system must take into account the detectability and field of view to cover the area to be *** main contribution in this research is an analytical design of LWS that consists of 24 detector elements,distributed in two arrays(2×12)***,calculating the best distance between the detectors according to the laser beam spot *** addition,enhancement laser warring sensor detection capability and detection performance FOV between the detectors to increase coverage area up to 360°.Moreover,decreasing dead zone area between the laser detectors *** calculations and illustrations made to reach the best systematic design.

关键词： LWS Field of view Detector elements

Structural Characterization, Vibrational Studies and Electrical Properties of 2-Amino-3-benzyloxy Pyridinium Perchlorate

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Chemical Research in Chinese Universities 2015年第5期31卷 693-698页

作者： SAMI Soukrata mohamed Belhouchet tahar Mhiri Laboratory of Solid State Faculty of Sciences University of Sfax 3000 Sfax Tunisia

A title organic-inorganic hybrid material 2-amino-3-benzyloxy pyridinium perchlorate was synthesized by slow evaporation at room temperature using 2-amino-3-benzyloxypyridine as the structure-directing agent. The structure of the title compound was determined by means of single-crystal X-ray diffraction at 293 K. The results show that this compound crystallizes in the centrosymetric monoclinic system with a space group of P2 1/n and lattice parameters of a=0.7025（5） nm, b=1.2635（5） nm, c=1.5766（5） nm, Z=4 and V=1.3905（2） nm^3. The crystal structure has been determined and refined to R1=0.0367 and wR2=0.1022 using 2326 independent reflections and can be described as a succession of organic and inorganic layers parallel to the bc plane. In this arrangement, hydrogen bonds and van der Waals interactions between different species play an important role in the two-dimensional（2D） network cohesion. This compound was also characterized by means of infrared spectroscopy, Raman spectroscopy and thermogravimetric analysis-differential thermal analysis（TG-DTA）. Moreover, protonic conduction of this compound determined by an impedance analyzer has been studied in the temperature range of 303--373 K.

关键词： Organic-inorganic hybrid Chemical synthesis Infrared and Raman spectroscopy Thermal analysis Electrical property

HYDRODYNAMIC AND ELASTOHYDRODYNAMIC STUDIES OF A CYLINDRICAL JOURNAL BEARING

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Journal of Hydrodynamics 2010年第2期22卷 155-163页

作者： ATTIA HILI Molka BOUAZIZ Slim MAATAR mohamed FAKHFAKH tahar HADDAR mohamed Mechanics Modelling and Production Research Unit (U2MP)National School of Engineers of Sfax(ENIS)BP.11733038sfaxTunisia

In this article,the effect of the bearing elastic deformation on the performance characteristics of a cylindrical journal bearing is *** variety of simulation models covers hydrodynamic（HD） and elastohydrodynamic（EHD） lubrication *** Reynolds equations governing the flow in the clearance space of the journal bearing are obtained by considering the effect of mass transfer across the fluid *** finite element method with an iteration scheme was employed to solve both the Reynolds equation and the three-dimensional elasticity equation representing the displacement field in the bearing *** converged solutions for the lubricant flow and elastic deformation vector are *** characteristics of the journal bearing are computed for HD and EHD *** simulation results show that the flexibility of bearing liner has a significant influence on the performance of a cylindrical journal ***,the elastic deformations of the bearing liner extend the pressure area in the bearing and increase the minimum film ***,dynamic coefficient,load capacity and attitude angle decrease.

关键词： Reynolds equation hydrodynamic(HD) and elastohydrodynamic(EHD) lubrication theories dynamic coefficients relative eccentricity deformation coefficient

NuMDG:A New Tool for Multiway Decision Graphs Construction

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Journal of Computer Science & Technology 2011年第1期26卷 139-152页

作者： Sa'ed Abed Yassine Mokhtari Otmane Ait-mohamed Sofiene tahar Department of Computer Engineering Hashemite UniversityZarqaJordan Department of Electrical and Computer Engineering Concordia UniversityMontrealCanada

Multiway Decision Graphs （MDGs） are a canonical representation of a subset of many-sorted first-order logic. This subset generalizes the logic of equality with abstract types and uninterpreted function symbols. The distinction between abstract and concrete sorts mirrors the hardware distinction between data path and control. Here we consider ways to improve MDGs construction. Efficiency is achieved through the use of the Generalized-If-Then-Else （GITE） commonly operator in Binary Decision Diagram packages. Consequently, we review the main algorithms used for MDGs verification techniques. In particular, Relational Product and Pruning by Subsumption are algorithms defined uniformly through this single CITE operator which will lead to a more efficient implementation. Moreover, we provide their correctness proof. This work can be viewed as a way to accommodate the ROBBD algorithms to the realm of abstract sorts and uninterpreted functions. The new tool, called NuMDG, accepts an extended SMV language, supporting abstract data sorts. Finally, we present experimental results demonstrating the efficiency of the NuMDG tool and evaluating its performance using a set of benchmarks from the SMV package.

关键词： infinite state model checking multiway decision graphs uninterpreted functions

Robust Interactive Method for Hand Gestures Recognition Using Machine Learning

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Computers, Materials & Continua 2022年第7期72卷 577-595页

作者： Amal Abdullah Mohammed Alteaimi mohamed.tahar Ben Othman Department of Computer Science College of ComputerQassim UniversityBuraydah51452Saudi Arabia BIND Research Group College of ComputerQassim UniversityBuraydah51452Saudi Arabia

The Hand Gestures Recognition(HGR)System can be employed to facilitate communication between humans and computers instead of using special input and output *** devices may complicate communication with computers especially for people with *** gestures can be defined as a natural human-to-human communication method,which also can be used in human-computer *** researchers developed various techniques and methods that aimed to understand and recognize specific hand gestures by employing one or two machine learning algorithms with a reasonable *** aims to develop a powerful hand gesture recognition model with a 100%recognition *** proposed an ensemble classification model that combines the most powerful machine learning classifiers to obtain diversity and improve *** majority voting method was used to aggregate accuracies produced by each classifier and get the final classification *** model was trained using a self-constructed dataset containing 1600 images of ten different hand *** employing of canny’s edge detector and histogram of oriented gradient method was a great combination with the ensemble classifier and the recognition *** experimental results had shown the robustness of our proposed *** Regression and Support Vector Machine have achieved 100%*** developed model was validated using two public datasets,and the findings have proved that our model outperformed other compared studies.

关键词： Hand gesture recognition canny edge detector histogram of oriented gradient ensemble classifier majority voting

Online Postcolumn Indirect Detection for Determination of Ibandronate in Pharmaceutical Tablets by HPLC/DAD

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Journal of Analysis and Testing 2019年第4期3卷 322-330页

作者： Mokhtar mabrouk Sherin F.Hammad mohamed A.Abdelaziz Fotouh R.Mansour Department of Pharmaceutical Analytical Chemistry Faculty of PharmacyTanta UniversityElgeish StreetTanta 31111Egypt Pharmaceutical Services Center Faculty of PharmacyTanta UniversityTanta 31111Egypt Department of Pharmaceutical Analytical Chemistry Faculty of PharmacyKafrelsheikh UniversityKafrelsheikh 33511Egypt

Ibandronate sodium monohydrate is a highly polar aliphatic compound that belongs to the bisphosphonate class,a widely used bone resorption *** aliphatic nature of ibandronate precludes direct photometric detection and its high polar-ity urged analysts to use ion-pairing agents in the mobile phase to promote retention in reversed-phase *** this work,a reversed-phase method for determination of ibandronate sodium monohydrate in pharmaceutical tablets is introduced by employing an online postcolumn ligand exchange reaction to enable photometric *** method offers for the first time the ability to separate the drug from its well-known impurities on conventional reversed-phase *** detection reac-tion depends on the ability of ibandronate and its degradation products to displace salicylate in the iron(III)salicylate complex,forming various colorless iron(III)complexes and showing a negative chromatographic signal for ibandronate and its degra-dants atλ_(max)=525 *** chromatographic separation was achieved using a Hypersil BDS C_(8) column(5μm particle size,150 mm×4.6 mm i.d.)and a mobile phase consisting of a mixture of aqueous formate buffer pH 3(pH 3,5 mM)and methanol in a ratio of 80:20%(v/v),delivered at a flow rate of 0.8 mL/*** postcolumn iron(III)salicylate reagent was prepared at 250μM in aqueous formate buffer,delivered using a syringe pump at a flow rate of 0.5 mL/*** proposed method was validated as per the guidelines of the International Conference on Harmonization Q2(R1)and was found linear over the range 40-120μg/mL(r=0.9995)with a limit of detection of 3.19μg/*** to currently reported methods,the proposed method is considerably simpler,faster,cheaper,and adequately sensitive and makes use of the most popular LC detectors.

关键词： Bisphosphonates Non-chromophoric drugs Highly polar compounds High-performance liquid chromatography Reversed phase

The Multifractal Formalism for Measures, Review and Extension to Mixed Cases

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Analysis in Theory and Applications 2016年第4期32卷 303-332页

作者： mohamed Menceur Anouar Ben mabrouk Kamel Betina Algerba and Number Theory Laboratory Faculty of Mathematics University of Sciences and Technology Houari Boumediene Computational Mathematics Laboratory Department of Mathematics Faculty of Sciences Department of Mathematics HIgher Institute of Applied Mathematics and Informatics Street of Assad Ibn Alfourat Kairouan University

The multifractal formalism for single measure is reviewed. Next, a mixed generalized multifractal formalism is introduced which extends the multifractal formalism of a single measure based on generalizations of the Hausdorff and packing measures to a vector of simultaneously many measures. Borel-Cantelli and Large deviations Theorems are extended to higher orders and thus applied for the validity of the new variant of the multifractal formalism for some special cases of multi-doubling type measures.

关键词： Hausdorff measures packing measures Hausdorff dimension packing dimension renyi dimension multifractal formalism vector valued measures mixed cases Holderian measures doubling measures Borel-Cantelli large deviations