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A numerical study of anti-vortex film-cooling holes designs in a 1-1/2 turbine stage using LES

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Propulsion and Power Research 2019年第4期8卷 275-299页

作者： Nabeel Al-zurfi Ali Turan Adel Nasser ahmed Alhusseny Department of Mechanical Engineering Faculty of EngineeringUniversity of KufaNajafIraq Visiting Researcher Department of MechanicalAerospace and Civil EngineeringSchool of EngineeringFaculty of Science and EngineeringThe University of ManchesterManchesterM139PLUK Department of Mechanical Aerospace and Civil EngineeringSchool of EngineeringFaculty of Science and EngineeringThe University of ManchesterManchesterM139PLUK

The primary focus of the present study is to investigate the impact of anti-vortex holes design on the film-cooling performance in a film-cooled rotor blade model using the large eddy simulation method(LES).One row of the film holes was positioned on the pressure surface of the rotor *** row had three cylindrical holes(the main hole in the present study)with a diameter(D)of 4 mm and a tangential injection angle of 28 *** main hole supplemented with the addition of two symmetrical side holes(anti-vortex holes),which branch out from the same main *** positions for the anti-vortex side holes were considered;namely:upstream to the outlet of the main hole;in line with the main hole;and downstream of the main *** Reynolds number was fixed at Re z 1.92105 and the speed of the rotor blade was taken to be 1800 *** blowing ratio varied from 1.0 to 5.0 and the density ratio of coolant to mainstream was *** to the base hole,the film cooling performance of the all anti-vortex cases showed obvious improvement at all blowing *** middle stream side holes and downstream side holes each demonstrated good film cooling performance at all blowing ratios,while the upstream side holes perform well only at a lower blowing *** presence of side holes can restrain the CRVP(counter rotating vortex pairs)intensity of the main hole and reduce the coolant lift-off,improving the film coverage and film cooling *** downstream side holes can perform better in reducing the CRVP intensity.

关键词： Rotor blade Large eddy simulation Film-cooling effectiveness Turbulence Rotation Anti-vortex hole

Syntheses, Characterization and Crystal Structures of Two Novel Oxazoline Based Titanium Complexes

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Chinese Journal of Structural Chemistry 2015年第7期34卷 1121-1134页

作者： MUHAMMAD Hafeez MUHAMMAD Naeem ahmed SONJA Lippert WINFRIED P.Krtetschmer Department of Chemistry The University of Azad Jammu and Kashmir Inorganic Chemistry II University of Bayreuth

Two novel titanium compounds [（E）-N＇-（2,6-diisopropylphenyl）-N-（2-（4,4-dimethyl-4,5-dihydrooxazol-2-yl）phenyl）benzimidamido]titanium trichloride（1） and [N-（2-（4,4-dimethyl-4,5-dihydrooxaz-ol-2-yl）phenyl）-6-（2,4,6-triisopropyl-phenyl） pyridin-2-amido]titanium trichloride（2） were synthesized by reacting the corresponding ligand with diethylaminetitaniumtrichloride in equal molar ratios. The compounds were characterized with 1H, 13 C NMR, elemental analysis and single-crystal X-ray diffraction analysis. The geometry of both compounds is distorted octahedron. The three nitrogen and one chlorine atoms are in the equatorial plane. Compound 1 crystallizes in orthorhombic system, space group P212121 with a = 10.3520（4）, b = 16.5750（7）, c = 17.1530（7） , z = 4 and V = 2943.2（2）3. Compound 2 crystalizes in the monoclinic system, space group P21/n with a = 15.6400（11）, b = 10.12.60（7）, c = 22.9120（14）, z = 4 and V = 3558.5（4）3. The synthesized compounds were employed for ethylene polymerization catalysis. Both complexes showed moderate activity when activated with dry methylaluminoxane（d MAO） and complex 1 produced very high molecular weight polyethylene.

关键词： octahedron polymerization titanium trichloride X-ray

Measuring Audit Firms＇ Intellectual Capital as a Determinant of Audit Quality： A Suggested Model

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Journal of Modern Accounting and Auditing 2014年第1期10卷 59-79页

作者： Amr N. Abdelrhman Khaled z. Labib ahmed F. Elbayoumi Cairo University Cairo Egypt Cairo University Cairo EgyptThe American University in Cairo Cairo Egypt

The intellectual capital is a main source of competing advantage. Many studies developed measure（s） of intellectual capital of industrial and service firms. Few studies have tried to develop a reliable measure of intellectual capital in audit firms. This study extends the current models to provide more insight into the role of intellectual capital in audit firms. The aim of this study is to develop a quantitative model to measure audit firms＇ intellectual capital. The suggested model can be used to explore the relationship between the intellectual capital in audit firms and audit quality. The model combines the main components of intellectual capital （human capital, structural capital, and relational capital）. The suggested model provides a tool that may help to better manage the intellectual capital in audit firms. As this is a theoretical study, a number of hypotheses are presented for testing in the future.

关键词： intellectual capital human capital structural capital relational capital audit quality audit firms

Performance analysis of a random ARQ initialized cooperative communication protocol in shadowed Nakagami-m wireless channel

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Science in China(Series F) 2009年第6期52卷 1027-1036页

作者： ahmed Irfan PENG MuGen WANG WenBo SHAH Syed Ismail Wireless Signal Processing and Network Laboratory Beijing University of Posts and Telecommunications Real-Time MIMO Test-Bed Laboratory Iqra University Islamabad Pakistan

In this paper, we develop and analyze an energy efficient ARQ （automatic repeat request） initialized transmit diversity protocol for cooperative *** access control （MAC） layer packet retransmission limit （similar to aShortRetryLimit or aLongRetryLimit [802.11-1997]） has been used as an actuator for transmit cooperative diversity *** take the channel state information （CSI） as a function of retransmission tries and the number of retransmission tries is modeled as a random *** close to the source node are chosen for the transmit *** form expressions are obtained for symbol error rate （SER）, outage capacity and outage probability for the proposed scheme in shadowed fading *** cooperative scheme achieves lower signal-to-noise ratio （SNR）, stumpy outage probability, higher bandwidth, and transmit energy efficiencies for desired average symbol error rate （ASER） than the preceding ARQ based cooperative ***, the results of computer simulations are included to demonstrate the efficacy of the proposed scheme and to verify the accuracy of the analytical expressions.

关键词： automatic repeat request (ARQ) cooperative transmit diversity composite shadowed fading channel wireless networks

Muon-pair Production in the Left-right Symmetric Model at z 0-factory

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Muon-pair Production in the Left-right Symmetric Model at Z ...

作者： Mahfoudh ahmed Beiba 中国科学技术大学

学位级别：硕士

The potential for probing the impacts of the left-right symmetric model（LRM） onthe process e

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Protective Coatings Containing znMOF-BTA Metal–Organic Framework for Active Protection of AA2024-T3

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Acta Metallurgica Sinica(English Letters) 2023年第11期36卷 1893-1908页

作者： Izuchukwu K.Nwokolo Hongwei Shi Paul CUzoma Sharjeel ahmed Jiwen Li Fuchun Liu CAS Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei230026China School of Materials Science and Engineering Shenyang University of TechnologyShenyang110870China zJU-UIUC Institute International CampusZhejiang UniversityHaining314400China Institute of Corrosion Science and Technology Guangzhou510530China

znMOF-BTA,a new metal–organic framework with excellent anti-corrosion properties was prepared and *** and immersion tests in 3.5 wt%NaCl were performed on AA2024-T3 alloy to assess the corrosion inhibition ability of *** showed an inhibition efficiency of more than 90%,indicating excellent corrosion inhibition of znMOF-BTA on AA 2024-T3 in ***,znMOF-BTA particles were incorporated into polyurethane coatings to create corrosion-resistant *** tests and neutral salt spray analysis were used to assess the corrosion protection ability of znMOF-BTA-laden polyurethane *** results of electrochemical impedance spectra clearly showed the outstanding corrosion resistance and durability of znMOF-BTA coatings after 1440 h of immersion with a high pore resistance(Rpo)of 1.76×10^(10)Ωcm^(2).In addition,during the cross-cut adhesion test,the coating did not detach from the substrate,and after the impact test,there was scarcely any indication of a fracture,which further supports the notion that the coating has strong adhesion to the substrate.

关键词： Aluminum alloy Benzotriazole Corrosion inhibition Electrochemical impedance spectroscopy(EIS) Metal-organic framework Organic coatings

Factors affecting improvement of fluorescence intensity of quartet and doublet state of NO diatomic molecule excited by glow discharge

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Chinese Physics B 2018年第8期27卷 356-363页

作者： ahmed Asaad I Khalilt Reem A1-Tuwirqi Mohamed Gondal Noura A1-Suliman Department of Laser Sciences and Interactions National Institute of Laser Enhanced Sciences(NILES)Cairo UniversityGiza12613 Egypt Department of Physics Faculty of ScienceKing Abdulaziz UniversityJeddah 21551Saudi Arabia Department of Physics King Fahd University of Petroleum&MineralsDhahran 31261Saudi Arabia Department of Physics Faculty of Science for GirlsImam Abdulrahman Ben Faisal UniversityDammam 31441Saudi Arabia

We report on the observation of new fluorescence emission spectral transitions obtained from NO diatomic molecule in the region from ultraviolet （UV） to near infrared （NIR） in a low power glow discharge system. This glow discharge electronic excitation populates different quartet and doublet states of NO in its proximity such as the A2z （/9 = 2）, b4∑- （υ= 3）, B2М （1） = 4）, and X2Л （u= 33-32） states. Due to inter-system crossing, emission lines originating from these levels to lower lying states are recorded and spectral line assignments are performed. The observed systems include b4∑- a4∏, B21∏-a4∏, a4∏-X2I∏, A2∑X2∏, X2∏-X2∏ （33-15）, X2∏-X2∏ （33-17）, X2∏-X2∏ （33-20）, and X2∏-X2∏ （33- 18）. This new information will conduce to the better understanding of the interesting features of NO molecule. Such parameters that affect the recording of low density of NO molecules are also discussed In addition to the factors such as the time evolution, argon gas concentration relative to NO mixture, the percentage of NO molecular gas concentration, discharge electric current signals and discharge applied voltage are studied. Those factors would enhance the fluorescence signal intensity of NO molecules. The recent results might be significant as reference data for optimizing the glow discharge spectrometer and diagnostics of NO gas.

关键词： fluorescence emission NO molecule quartet states intersystem crossing glow discharge

Dimethylformamide Dimethyl Acetal (DMFDMA) in Heterocyclic Synthesis: Synthesis of Polysubstituted Pyridines, Pyrimidines, Pyridazine and Their Fused Derivatives

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International Journal of Organic Chemistry 2011年第4期1卷 207-214页

作者： Fathi A. Abu-Shanab Sayed A. S. Mousa E. A. Eshak ahmed z. Sayed ahmed Al-Harrasi 不详

Reaction of N,N’-dimethylformamide dimethyl acetal (DMFDMA) with malononitrile dimer 8 (1:1) mole afforded 9 while, this reaction when carried out in (2:1) mole to give amidine 11 which can be used for the preparation of pyrimidine 13, amidine 14 and pyridine 19 when reacted with 4-nitroaniline, 4-methylaniline and alkoxide respectively. Malononitrile dimer reacted with diazonium chloride to give pyridazine 21, which can be reacted with DMFDMA, AcOH/HCl and cyanoacetamide to give pyridazine 22, 23 and pyrido[4,3-c] pyridazine 24 respectively. The latter reacted with DMFDMA to afford tricyclic compound 25.

关键词： DMFDMA Malononitrile Dimer Pyridazine-3 5-carbonitrile Pyridine-4-alkoxide

Magnetic transitions and butterfly-shaped hysteresis of Sm-Fe-Al-based perovskite-type orthoferrite

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Journal of Rare Earths 2015年第9期33卷 965-971页

作者： M.A.ahmed N.G.Imam M.K.Abdelmaksoud Y.A.Saeid Materials Science Lab. Physics Department Faculty of Science Cairo University Materials Science Lab. Experimental Physics Department Nuclear Research Center Atomic Energy Authority

A1 doped SmFeO3 （SmFel_xmlxO3; 0.0〈x〈0.15; step 0.05） were prepared by double sintering ceramic technique. The obtained samples were crystallized in single phase structure except the sample with x=0.15. The unit cell volume was found to decrease with increasing AI substitution in orthoferrite. The effective magnetic moment （μeff） and the Curie constant （C） were calculated from the reciprocal of the molar magnetic susceptibility （z-1） versus absolute temperature plot and found to attain maximum value for the parent sample. The magnetic behavior showed two different magnetic transitions, viz, N6el temperature （TN） and spin reorientation （TsR） transitions. The M-H hysteresis loop of the parent sample took butterfly-shape as a result of different contributions anisotropies. From the magnetic properties measurements, it was obviously found that B-site cation dilution resulted in a drastic decrease in the magnetization. Surprisingly large value of the coercive field was obtained for the undoped sample;Hc=6198.80e. Based on the mentioned results, one can recommend the use of such orthoferrite in magnetic recording media and as pining layer in spin valve for spin- tronic applications.

关键词： SmFeO3 magnetization FESEM crystal structure spintronics spin reorientation butterfly-shaped hysteresis anisotropy rare earths