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Electrical and mechanical properties of (Bi, Pb)-2223 substituted by holmium

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Journal of Advanced Ceramics 2016年第1期5卷 54-69页

作者： W.ABDEEN S.MARAhBA R.AWAD A.i.ABOU ALY i.h.i.rahi. M.MATAR Superconductivity and Metallic Glass Lab Physics Department Faculty of ScienceAlexandria University Alexandria EgyptPhysics Department University College at Al-Gamom Umm Al-Qura University Saudi Arabia Physics Department Faculty of Science Beirut Arab University(BA U) Beirut Lebanon Superconductivity and Metallic Glass Lab Physics Department Faculty of ScienceAlexandria University Alexandria Egypt

The effect of the partial substitution of Ca2+ by ho3+ ions on the electrical and mechanical properties of the superconducting phase (Bi,Pb)-2223 was studied. Superconducting samples of the type (Bi1.8Pb0.4)Sr2Ca2.1?x ho xCu3.1O10+δ were prepared by solid-state reaction technique under ambient pressure, and characterized by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The superconducting transition temperature T c and pseudogap temperature T* were estimated from electrical resistivity measurements, while the critical current density J c was determined from i-V curves. The electrical resistivity data were discussed according to bipolaron model in the absence of thermally excited individual polarons. The sample with x = 0.025 showed the highest phase volume fraction, T c, and J c. Room temperature Vickers microhardness measurements were carried out at different applied loads (0.25-5 N) in order to investigate the performance of the mechanical properties of (Bi1.8Pb0.4)Sr2Ca2.1?x ho xCu3.1O10+δ phase. it was found that all the samples exhibit normal indentation size effect (iSE). The Vickers microhardness number h V increased as x increased from 0 to 0.025. The experimental results were discussed in view of Meyer’s law, hays-Kendall (hK) approach, elastic/plastic deformation (EPD) model, and proportional specimen resistance (PSR) model. The load independent (true) microhardness of (Bi1.8Pb0.4)Sr2Ca2.1?x ho xCu3.1O10+δ superconducting samples showed identical behavior to that of the PSR model.

关键词： (Bi,Pb)-2223 phase ho substitution Vickers microhardness bipolaron model pesudogap temperature

Mini-loop ligation of a bleeding duodenal Dieulafoy's lesion

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World Journal of Gastroenterology 2013年第22期19卷 3505-3507页

作者： Marija Gomeri Pali Neven Ljubii Division of Gastro-enterology and hepatology Department of Internal Medicine Medical and Dental Faculty "Sestre Milosrdnice" University Hospital Center University of Zagreb 10000 Zagreb Croatia

Two percent of gastrointestinal hemorrhages are caused by Dieulafoy's lesions, which are located in duodenum in only 15% of cases. There are no recommendations regarding the prime endoscopic treatment technique for this condition. A 61-year-old woman presented with melena without signs of hemodynamic instability. During an urgent upper endoscopy, blood oozing from the normal mucosa of the duodenum was seen and this was classified as a Dieulafoy's lesion. A mini-loop was opened at the rim of a transparent ligation chamber, at the end of the endoscope, and after aspiration of the lesion, closed and detached. Complete hemostasis was achieved without early or postponed complications. in every day clinical practice, mini-loop ligation is rarely used because of possible complications, such as site ulceration, organ perforation, re-bleeding and possible inexperience of the operator. To the best of our knowledge this is the first case of successful treatment of bleeding duodenal Dieulafoy's lesion by mini-loop ligation.

关键词： Dieulafoy’s lesion Duodenum Endoscopy Mini-loop hemostasis

Cohomology of Associative h-Pseudoalgebras

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Algebra Colloquium 2023年第4期30卷 541-554页

作者： José i.Liberati Ciem-CONiCET Medina Allende y Haya de la TorreCiudad Universitaria(5000)CórdobaArgentina

We define the cohomology of associative h-pseudoalgebras,and we show that it describes module extensions,abelian pseudoalgebra extensions,and pseudoalgebra first-order *** same results for the special case of associat... 详细信息

关键词： associative pseudoalgebra associative conformal algebra cohomology

Distortion Analysis of Single V-groove Butt Welding on heat Treatable Aluminum Alloys

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Journal of Materials Science & Technology 2005年第5期21卷 738-742页

作者： i.K.Lee Department of Mechanical Engineering National Chiao Tung UniversityHsinchu TaiwanChina

in this study we conducted single V-groove butt welding （GTAW） on three types of heat treatable aluminum alloys 2024-T351, 6061-T6 and 7075-T6 and compared the angular distortion levels of the three aluminum alloys at different Vee preparation angles with or without restraint. Experimental results demonstrated that when the Vee preparation angle was 0° （i-shaped groove）, the angular distortion level of the restrained weldment can exceed that of the unrestrained weldments. Moreover, when the Vee preparation angle was 45°, 60° or 90°, the restrained weldment had lower angular distortion than the unrestrained weldments. The single Vee preparation angle （amount of filler metal） in butt welding affected the angular distortion of the weldment. Without restraint, the angular distortion tended to increase with the single Vee preparation angle. Meanwhile, the angular distortion tended to decrease when the single Vee preparation angle was 60% Additionally, a restrained weldment had high angular distortion when the single Vee preparation angle was 0°. Notably, the angular distortion tended to reduce with increasing single Vee preparation angle. The angular distortion of the weldment was minimized at an angle of 60°. however, the angular distortion increased when the Vee preparation angle exceeded 60% The high-temperature yield strength of a material also affected its angular distortion. Angular distortion increased with high-temperature yield strength. Experimental results also showed that, from the strongest to the weakest, the high-temperature yield strength of the three types of aluminum alloys followed the order 6061-T6 and 2024-T351〉7075-T6.

关键词： Angular distortion Aluminum alloy Single-V-groove

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The current status and future development of high-temperature conventional superconductivity

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National Science Review 2024年第7期11卷 18-20页

作者： Mikhail i.Eremets high Pressure Chemistry and Physics Group Max-Planck-Institut für Chemie

This survey highlights key advancements in high-temperature superconductivity in hydrogen-rich materials, emphasizing the robust evidence and reproducibility of superconductivity under challenging experimental conditions of megabar pressures. in the near future, achieving room-temperature superconductivity is highly probable, and the field is expected to transition towards near-ambient-pressure superconductivity.

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Flat limit of the de Sitter QFT in the rest frame vacuum

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Chinese Physics C 2021年第1期45卷 97-108页

作者： ion i.Cotaescu West University of Timisoara V.Parvan Ave.4RO-300223 TimisoaraRomania

The problem of the flat limits of the scalar and spinor fields on the de Sitter expanding universe is considered in the traditional adiabatic vacuum and in the new rest frame vacuum we proposed recently,in which the frequencies are separated in the rest frames as in special *** is shown that only in the rest frame vacuum can the Minkowskian flat limit be reached naturally fbr any momentum,whereas in the adiabatic vacuum,this limit remains undefined in rest frames in which the momentum *** important role is played by the phases of the fundamental solutions in the rest frame vacuum,which must be regularized to obtain the desired Minkowskian flat *** procedure fixes the phases of the scalar mode functions and Dirac spinors,resulting in their definitive expressions derived *** physical consequenee is that,in the rest frame vacuum,the flat limits of the oneparticle operators are simply the corresponding operators of special relativity.

关键词： de Sitter space-time Klein-Gordon field Dirac field flat limit approximation method phase regularization

Using fracture-based continuum modeling of coupled geomechanical-hydrological processes for numerical simulation of hydraulic fracturing

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第5期16卷 1582-1599页

作者： Goodluck i.Ofoegbu GNO Modeling Research LLC. San AntonioTX78253USA

This paper describes numerical simulation of hydraulic fracturing using fracture-based continuum modeling(FBCM)of coupled geomechanical-hydrological processes to evaluate a technique for high-density fracturing and fracture *** simulations are innovative because of modeling discrete fractures explicitly in continuum analysis.A key advantage of FBCM is that fracture initiation and propagation are modeled explicitly without changing the domain grid(*** re-meshing).Further,multiple realizations of a preexisting fracture distribution can be analyzed using the same domain *** simulated hydraulic fracturing technique consists of pressurizing multiple wells simultaneously:initially without permeating fluids into the rock,to seed fractures uniformly and at high density in the wall rock of the wells;followed by fluid injection to propagate the seeded fracture density *** combines the ease of continuum modeling with the potential accuracy of modeling discrete fractures and fracturing *** are modeled as piecewise planar based on intersections with domain elements;fracture geometry stored as continuum properties is used to calculate parameters needed to model individual fractures;and rock behavior is modeled through tensorial aggregation of the behavior of discrete fractures and unfractured *** are presented for previously unfractured rock and for rock with preexisting fractures of horizontal,shallow-dipping,steeply dipping,or vertical *** of a single-well model are used to determine the pattern and spacing for a multiple-well *** results illustrate high-density fracturing and fracture caging through simultaneous fluid injection in multiple wells:for previously unfractured rock or rock with preexisting shallow-dipping or horizontal fractures,and in situ vertical compressive stress greater than *** preexisting fractures are steeply dipping or vertical,and considering the same in situ

关键词： Discrete fracture Fracture-based continuum modeling Fracture caging high-density fracturing hydraulic fracturing Preexisting fracture

Viscous Dark Energy Models with Variable G and A

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Chinese Physics Letters 2008年第10期25卷 3834-3836页

作者： Arbab i. Arbab Department of Physics Faculty of Science University of Khartoum PO Box 321 Khartoum 11115 SudanDepartment of Physics and Applied Mathematics Faculty of Applied Sciences and Computer Omdurman Ahlia University PO Box 7S6 Omdurman Sudan

We consider a cosmological model with bulk viscosity η and variable cosmological A ∝p^-α, alpha = const and gravitational G constants. The model exhibits many interesting cosmological features. inflation proceeds du to the presence of bulk viscosity and dark energy without requiring the equation of state p =-p. During the inflationary era the energy density p does not remain constant, as in the de-Sitter type. Moreover, the cosmological and gravitational constants increase exponentially with time, whereas the energy density and viscosity decrease exponentially with time. The rate of mass creation during inflation is found to be very huge suggesting that all matter in the universe is created during inflation.

关键词： the power-law exponents precipitation durative abrupt precipitation change

hardness of Mn_2V_2O_7 thin films and its influential factors

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international Journal of Minerals,Metallurgy and Materials 2015年第9期22卷 987-991页

作者： i. Aft in Kariper Department of Science Education Faculty of Education Erciyes University Kayseri 38039 Turkey

Mn2V2O7 thin films were deposited onto amorphous glass substrates using a chemical bath deposition method and different deposition time. X-ray diffraction （XRD） analysis was used to define the structure of the films. Their roughness, thickness, and surface properties were evaluated through atomic force microscopy （AFM）. The hardness of the films was measured using a nanohardness tester The film thickness, average grain size, and roughness were positively correlated with each other. These three parameters were observed to increase with the deposition time. The film thickness and average grain size were inversely correlated with the hardness and rough- ness. in addition, the number of crystallites per unit area and the dislocation density were observed to be positively correlated with the hardness and roughness. This study was designed to elucidate and formalize the underlying reasons for these relationships.

关键词： manganese vanadate thin films nanohardness influencing factors

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