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Intermediate HSS bracing members during seismic excitations： modeling, design, and behavior

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Frontiers of Structural and Civil Engineering 2018年第1期12卷 148-162页

作者： Madhar haddad Department of Architectural Engineering United Arab Emirates University P. O. Box 15551 AI Ain UAE

Concentric hollow structural section （HSS） bracing members are used frequently in steel framed structural systems to resist seismic excitations. Finite element modeling of the HSS braces that utilizes the true stress- strain curves produces hysteresis responses that are reasonable matches to the experimental response. True stress-strain curves are obtained from coupon tests or stub-column tests while utilizing an exponential function or strain hardening role with a trial and error procedure to obtain the hysteresis behavior. In the current study, the true stress-strain curves are directly obtained from tests on stub-columns extracted from the full scale HSS bracing members away from the mid- length plastic hinge after cyclic testing. Two experimental tests （Shaback 2001 and haddad 2004） were used to validate the model. Results indicate that the stress-strain curves for these braces are not unique. A refined damage accumulation model for ultra-low-cycle fatigue is implemented to predict fracture of the brace tests. The refined damage model is then used in the finite element modeling to predict fracture of braces in a chevron braced frame of an eight-storey building subjected to selected ground motions analyzed using OpenSees program. Results indicate that all braces could sustain the selected earthquake records without fracture.

关键词： HSS FEM stress-strain curves damage model

Mediterranean Sea level trends from long-period tide gauge time series

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Acta Oceanologica Sinica 2020年第1期39卷 157-165页

作者： haddad Mahdi Taibi Hebib Centre of Space Techniques Algerian Space Agency

The main purpose of this study is to highlight, on the basis of statistical tests, the significant long-term changes of the Mediterranean Sea level, through the analysis of historical tide gauge records. In this framework, 14 tide gauge monthly series selected from the Permanent Service of the Mean Sea Level(PSMSL) database were used. The search for the presence or not of trends within these series, that have a temporal coverage from 59 to 142 years, was carried out using the Mann-Kendall test and the Sen’s slope estimator. The obtained results show that the Split Rt Marjana series are the only ones which does not exhibit a significant trend. The other 13 series show significant increasing trends. This result seems sufficient to suppose the presence, in the past century, of a new climatic phase on the scale of the Mediterranean basin, where the rising sea level is one of the consequences.

关键词： sea level tidal heights trend analysis Mann-Kendall test Sen’s slope estimates

Estimating trends of the Mediterranean Sea level changes from tide gauge and satellite altimetry data (1993-2015)

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Journal of Oceanology and Limnology 2019年第4期37卷 1176-1185页

作者： TAIBI Hebib haddad Mahdi Centre of Space Techniques(CTS)

The impact of climate change on sea level has received a great deal of attention by scientists worldwide. In this context, the problem of sea levels on global and regional scales have been analyzed in a number of studies based on tide gauges observations and satellite altimetry measurements. This study focuses on trend estimates from 18 high-quality tide gauge stations along the Mediterranean Sea coast. The seasonal Mann-Kendall test was run at a 5% significance level for each of the 18 stations for the period of 1993-2015 (satellite altimetry era). The results of this test indicate that the trends for 17 stations were statistically significant and showed an increase (no significant trend was observed only at one station). The rates of sea level change for the 17 stations that exhibit significant trends, estimated using seasonal Sen's approach, range after correction for Vertical Land Motion (VLM) from 1.48 to 8.72 mm/a for the period 1993-2015. Furthermore, the magnitude of change at the location of each tide gauge station was estimated using the satellite altimetry measurements. Thus, the results obtained agree with those from the tide-gauge data analysis.

关键词： sea level tidal height satellite altimetry trend analysis Mann-Kendall test Sen's slope estimates

Shaking table tests on the liquefaction-induced uplift displacement of circular tunnel structure

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Underground Space 2023年第3期10卷 182-198页

作者： Saber Nokande Yaser Jafarian Abdolhosein haddad Department of Civil Engineering Semnan UniversitySemnan 35131-19111Iran International Institute of Earthquake Engineering and Seismology(IIEES) Tehran 19537-14453Iran Deltares Boussinesqweg 1DelftSouth Hollands 2629 HVNetherlands

Underground structures are susceptible to float and move upward during earthquakes when located in a liquefiable soil *** are examples of this phenomenon in past major earthquake *** this study,the uplift of circular tunnels in a liquefiable sand layer was investigated with a series of shaking table *** research has focused on the buried depth of the tunnel,tunnel diameter,tunnel weight,liquefaction extent,uplift mechanism,and factor of safety against liquefaction-induced *** to the test results,the shallow buried depth,larger diameter,and lower weight can intensify the tunnel uplift,so the displacement in post-liquefaction time continues at the same rate as during the shaking *** to the shear-induced dilation,pore water pressure generation around the tunnel was reduced compared with that of the free *** excess pore water pressure dissipation in the soil overlying the uplifted tun-nel was significant,which leads to suction in the soil ***,the acceleration response of overlying soil with the uplifted tunnel was similar to that of the free ***,the soil acceleration response around the tunnel without uplift was similar to the base motion.

关键词： Liquefaction Tunnel uplift Underground structures Shaking table test Circular tunnel

A review of fluid displacement mechanisms in surfactant-based chemical enhanced oil recovery processes:Analyses of key influencing factors

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Petroleum Science 2022年第3期19卷 1211-1235页

作者： Ahmed Bashir Amin Sharifi haddad Roozbeh Rafati School of Engineering Kings CollegeUniversity of AberdeenAB243UEUK

Surfactant-based oil recovery processes are employed to lower the interfacial tension in immiscible displacement processes,change the wettability of rock to a more water-wet system and emulsify the oil to displace it in subsurface porous ***,these phenomena can reduce the capillary pressure and enhance spontaneous *** key factors affecting such immiscible displacement process are temperature,salinity and p H of the fluids,surfactant concentration and ***,before any surfactant flooding process is applied,extensive studies of fluid-fluid and rock-fluid interactions are *** use of other chemicals along with surfactants in chemical enhanced oil recovery(c EOR)processes have been widely considered to exploit the synergy of individual chemicals and complement the weakness arises from each of them during immiscible displacement of fluids in porous ***,such combinations of chemicals lead to alkaline-surfactant(AS),surfactantpolymer(SP),alkaline-surfactant-polymer(ASP),and nanoparticle-surfactant(NS)flooding processes,among *** this review study,we categorised the role and displacement mechanisms of surfactants and discussed the key factors to be considered for analysing the fluid displacement in porous media.

关键词： Alkaline surfactant(AS)flooding Alkaline-surfactant-polymer(ASP)flooding Enhanced oil recovery(EOR) Interfacial tension(IFT) Nanoparticle-surfactant(NS)flooding Surfactant adsorption Surfactant-polymer(SP)flooding Wettability alteration

Microstructural characteristics and mechanical properties of Al-2024 alloy processed via a rheocasting route

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International Journal of Minerals,Metallurgy and Materials 2015年第1期22卷 59-67页

作者： Behnam Rahimi Hamed Khosravi Mohsen haddad-Sabzevar Department of Metallurgy and Materials Engineering Faculty of EngineeringFerdowsi University of Mashhad Faculty of Materials Science and Engineering K.N.Toosi University of Technology

This article reports the effects of stirring speed and T6 heat treatment on the microstructure and mechanical properties of Al-2024 alloy synthesized by a rheocasting process. There was a decrease in grain size ofα-Al particles corresponding to an increase in stirring speed. By increasing the stirring speed, however, the globularity of matrix particles first increased and then declined. It was also found that the hardness, compressive strength, and compressive strain increased with the increase of stirring speed. Microstructural studies revealed the presence of nonsoluble Al15（CuFeMn）3Si2 phase in the vicinity of CuAl2 in the rheocast samples. The required time for the solution treatment stage was also influenced by stirring speed;the solution treatment time decreased with the increase in stirring speed. Furthermore, the rheo-cast samples required a longer homogenization period compared to conventionally wrought alloys. Improvements in hardness and compres-sive properties were observed after T6 heat treatment.

关键词： aluminum alloys rheocasting microstructure mechanical properties

ON THE IDENTIFICATION OF RESIDUAL IMPACT PROPERTIES OF MATERIALS BY ACOUSTO-ULTRASONICS——A PATTERN RECOGNITION APPROACH

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Acta Mechanica Sinica 1995年第1期11卷 34-43页

作者： G.J.Molina Y.M.haddad Dept.of Mechanical Engineering University of OttawaOttawaCanada K1N 6N5

This paper deals with the application of Acousto-ultrasonics,in con- junction with Pattern Recognition and Classification techniques,to the identification of residual impact properties of a class of polymeric material,namely,Polyvinylchlo- ride(PVC).PVC specimens of different low-energy repeated impact damage states are processed by Acousto-ultrasonics(AU)to retrieve AU signals in the form of dig- italized *** AU signals are grouped as distinct classes,each pertaining to a known level of repeated impact *** features of these AU signals are used to build Pattern Recognition(PR)*** classifiers are used to identify unknown damage states in other PVC specimens by classifying the re- trieved AU signals as belonging to one of the *** obtained results indicate that Acousto-ultrasonics in combination with Pattern Recognition and Classification techniques can be used for the quantitative non-destructive identification of damage states in PVC specimens of unknown low-energy repeated impact conditions.

关键词： pattern recognition acousto-ultrasonics impact damage quantitative non-destructive examination

Fabrication of Fe–TiC–Al_2O_3 composites on the surface of steel using a TiO_2–Al–C–Fe combustion reaction induced by gas tungsten arc cladding

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International Journal of Minerals,Metallurgy and Materials 2016年第2期23卷 193-204页

作者： Mahmood Sharifitabar Jalil Vahdati Khaki Mohsen haddad Sabzevar Department of Metallurgical and Materials Engineering Faculty of Engineering Ferdowsi University of Mashhad Department of Materials Engineering Faculty of Engineering University of Sistan and Baluchestan

The aim of the present study was to fabricate Fe-TiC-Al2O3 composites on the surface of medium carbon *** this purpose,TiO2-3C and 3TiO2-4Al-3C-xFe（0 ≤ x ≤ 4.6 by mole） mixtures were pre-placed on the surface of a medium carbon steel *** mixtures and substrate were then melted using a gas tungsten arc cladding *** results show that the martensite forms in the layer produced by the TiO2-3C ***,ferrite-Fe3C-TiC phases are the main phases in the microstructure of the clad layer produced by the 3TiO2-4Al-3C *** addition of Fe to the TiO2-4Al-3C reactants with the content from 0 to 20wt%increases the volume fraction of particles,and a composite containing approximately 9vol%TiC and A12O3 particles *** composite substantially improves the substrate *** mechanism by which Fe particles enhance the TiC ＋ A12O3 volume fraction in the composite is determined.

关键词： composite coatings iron-based materials combustion cladding microstructure microhardness

Endoscopic ultrasound guided fine needle tissue acquisition:Where we stand in 2013?

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World Journal of Gastroenterology 2014年第9期20卷 2176-2185页

作者： Zeid Karadsheh Mohammad Al-haddad Signature Healthcare Brockton Hospital Brockton MA 02320 United States Division of Gastroenterology and Hepatology Indiana University School of Medicine IN 46202 United States

Since its introduction,endoscopic ultrasound(EUS)guided fine needle aspiration and fine needle biopsy have become an indispensable tool for the diagnosis of lesions within the gastrointestinal tract and surrounding *** has proved to be an effective diagnostic method with high accuracy and low complication *** factors can influence the accuracy and the diagnostic yield of this procedure including experience of the endosonographer,availability of onsite cytopathology services,the method of cytopathology preparation,the location and physical characteristics of the lesion,sampling techniques and the type and size of the needle *** this review we will outline the recent studies evaluating EUS-guided tissue acquisition and will provide practical recommendations to maximize tissue yield.

关键词： Endoscopic ultrasound Fine needle aspiration Endoscopic ultrasound guided sampling techniques Cytological diagnosis Core biopsy device Gastrointestinal endoscopy