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Insights into kinetic inhibition effects of MEG,PVP,and L-tyrosine aqueous solutions on natural gas hydrate formation

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Petroleum Science 2021年第2期18卷 495-508页

作者： amir Saberi Abdolmohammad Alamdari Ali Rasoolzadeh amir H.Mohammadi Department of Natural Gas Engineering School of Chemical and Petroleum EngineeringShiraz UniversityShiraz71345Iran Department of Process Engineering National Iranian Gas Company(NIGC)South Pars Gas Complex(SPGC)Phases 4&5Bushehr75391/311Iran Discipline of Chemical Engineering School of EngineeringUniversity of KwaZulu-NatalHoward College CampusKing George V AvenueDurban4041South Africa

It is necessary to understand all the prerequisites, which result in gas hydrate formation for safe design and control of a variety of processes in petroleum industry. Thermodynamic hydrate inhibitors (THIs) are normally used to preclude gas hydrate formation by shifting hydrate stability region to lower temperatures and higher pressures. Sometimes, it is difficult to avoid hydrate formation and hydrates will form anyway. In this situation, kinetic hydrate inhibitors (KHIs) can be used to postpone formation of gas hydrates by retarding hydrate nucleation and growth rate. In this study, two kinetic parameters including natural gas hydrate formation induction time and the rate of gas consumption were experimentally investigated in the presence of monoethylene glycol (MEG), L-tyrosine, and polyvinylpyrrolidone (PVP) at various concentrations in aqueous solutions. Since hydrate formation is a stochastic phenomenon, the repeatability of each kinetic parameter was evaluated several times and the average values for the hydrate formation induction times and the rates of gas consumption are reported. The results indicate that from the view point of hydrate formation induction time, 2 wt% PVP and 20 wt% MEG aqueous solutions have the highest values and are the best choices. It is also interpreted from the results that from the view point of the rate of gas consumption, 20 wt% MEG aqueous solution yields the lowest value and is the best choice. Finally, it is concluded that the combination of PVP and MEG in an aqueous solution has a simultaneous synergistic impact on natural gas hydrate formation induction time and the rate of gas consumption. Furthermore, a semi-empirical model based on chemical kinetic theory is applied to evaluate the hydrate formation induction time data. A good agreement between the experimental and calculated hydrate formation induction time data is observed.

关键词： Gas hydrate Clathrate hydrate Natural gas Kinetic hydrate inhibitor(KHI) Induction time Kinetics

Fischer–Tropsch synthesis using Co and Co-Ru bifunctional nanocatalyst supported on carbon nanotube prepared via chemical reduction method

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Journal of Energy Chemistry 2019年第1期28卷 9-22页

作者： Jafar Shariati Ali Haghtalab amir Mosayebi Department of Chemical Engineering Tarbiat Modares University Department of Chemical Engineering Tafresh University

We used a chemical reduction method to synthesize the catalysts of cobalt(Co) and cobalt-ruthenium(Co-Ru) bifunctional supported on carbon nanotubes(CNTs) for Fischer–Tropsch synthesis(FTS) in a fixedbed reactor. These Co-Ru/CNTs catalysts were synthesized with various weight proportions of Ru/Co(0.1 to 0.4 wt%) with keeping a fixed amount of cobalt(10 wt%). Moreover, for comparison purpose, CNTs supported Co-and Co(Ru)-based catalysts at same loading as the above catalysts were prepared through impregnation method. We characterize the present catalysts through the various techniques such as Energy–dispersive X-ray(EDX), Transmission Electron Microscopy(TEM), Brunauer–Emmett–Teller(BET),Hydrogen-Temperature-Programmed Reduction(H_2-TPR), Hydrogen-Temperature-Programmed Desorption(H_2-TPD) and O_2 titration. Thus using the chemical reduction method, a narrow particle size distribution was obtained so that the small cobalt particles were confined inside the CNTs. The Co-based catalyst prepared by impregnation was compared with the Co-Ru catalysts at the same loading. The results demonstrated that the use of chemical reduction method led to decrease the average Co oxide cluster size to8.7 nm so that the reduction enhanced about 24% and stabilized an earlier time at the stream. Among the prepared catalysts, the results indicated that the Co-Ru/CNTs catalysts demonstrated high catalytic activity with the highest long-chain hydrocarbons(C_(5+)), selectivity up to 74.76%, which was higher than those we obtained by the Co-Ru/γ-Al_2O_3(61._20%), Co/CNTs(43.68%) and Co/γ-Al_2O_3(37.69%). At the same time, comparing with those catalyst synthesized by impregnation, the use of chemical reduction led to enhancement of the C_(5+) selectivity from 59.30% to 68.83% and increment in FTS rate about 11% for the Co-Ru/CNTs catalyst.

关键词： Cobalt-ruthenium Carbon nanotubes Fischer-Tropsch synthesis Catalyst nanoparticles Chemical reduction method

Innate phase behavior in the desert locust, Schistocerca gregaria

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Insect Science 2012年第6期19卷 649-656页

作者： Moshe Guershon amir Ayali Department of Zoology Tel Aviv University Ramat Aviv 69978 Israel

Detailed aspects of the transition from the solitarious to the gregarious phase in the framework of locust ecology are undoubtedly most important for understanding locust phase polyphenism. Nevertheless, due to obvious difficulties in studying the solitarious phase in nature, such information is limited and mostly available from research carried out under laboratory conditions. In the current study, we examined the dispersal patterns of newly hatched locust nymphs in a laboratory setup that simulated seminatural conditions. This was carried out with no previous manipulation of the nymphs other than controlling their parental density. We comparatively tested the spatial distribution of newly hatched nymphs on perches located at different ranges within an emergence arena, and the expected Poisson （random） distribution. Hatchlings were found to disperse among the perches in a pattern significantly different from that expected by random. Irrespective of their parents＇ phase, the observed distributions of all nymphs were clearly clumped, similar or close to those expected for gregarious locusts. It seems that rather than emerging with a parentally derived and predetermined phase, hatchlings have an independent default or innate behavioral state, which reflects at least tolerance if not attraction to conspecifics. The typical phase behavior may later become dominant under the appropriate environmental conditions. These results imply novel perspectives on locust phase transformation, which contribute to our understanding of the formation of locust crowds under field conditions. These should be considered in any rationale for developing a preventative management strategy of locust populations.

关键词： desert locust hatchlings innate behavior phase polymorphism

A constitutive model for evaluation of mechanical behavior of fiber-reinforced cemented sand

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第2期11卷 349-360页

作者： Hadi Abioghli amir Hamidi Department of Civil Engineering School of EngineeringKharazmi University

The aim of this study is to present a constitutive model for prediction of the mechanical behavior of fiberreinforced cemented sand. For this purpose, a generalized plasticity constitutive model of sandy soil is selected and the parameters of the model are determined for three types of sandy soils using the results of triaxial tests. Next, the proposed model is developed using the existing models based on the physicomechanical characteristics of fiber-reinforced cemented sand. The elastic parameters, flow rule and hardening law of the base model are modified for fiber-reinforced cemented sand. To verify the proposed model, the predicted results are compared with those of triaxial tests performed on fiber-reinforced cemented sand. Finally, the efficiency of the proposed model is studied at different confining pressures, and cement and fiber contents.

关键词： Fiber-reinforced cemented sand Constitutive model Hardening law Flow rule

Coherent States of Nonlinear Oscillators with Position-Dependent Mass:Temporal Stability and Fractional Revivals

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Communications in Theoretical Physics 2017年第8期68卷 181-190页

作者： Naila amir Shahid Iqbal School of Electrical Engineering and Computer Sciences National University of Sciences and Technology Department of Physics School of Natural Sciences National University of Sciences and Technology

We develop generalized coherent states for a class of nonlinear oscillators with position-dependent effective mass in the context of the Gazeau–Klauder formalism and discuss some of their properties. In order to investigate the temporal evolution we first explore the statistical properties by means of weighting distribution and the Mandel parameter. It is found that the temporal evolution of the coherent states may exhibit the phenomena of quantum revivals and fractional revivals for a particular choice of position-dependent mass oscillator.

关键词： position-dependent effective mass nonlinear oscillators Gazeau–Klauder coherent states Mandel parameter sub-Poissonian statistics temporal stability quantum revivals fractional revivals

Generalized Coherent States for Position-Dependent Effective Mass Systems

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Communications in Theoretical Physics 2016年第12期65卷 615-620页

作者： Naila amir Shahid Iqbal School of Electrical Engineering and Computer Sciences National University of Sciences and Technology School of Natural Sciences National University of Sciences and Technology

A generalized scheme for the construction of coherent states in the context of position-dependent effective mass systems has been presented. This formalism is based on the ladder operators and associated algebra of the system which are obtained using the concepts of supersymmetric quantum mechanics and the property of shape invariance. In order to exemplify the general results and to analyze the properties of the coherent states, several examples have been considered.

关键词： generalized coherent states supersymmetric quantum mechanics shape invariance ladder operators position-dependent effective mass systems non-linear oscillators Mandel parameter subPoissonian statistics

At-will chromatic dispersion by prescribing light trajectories with cascaded metasurfaces

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Light(Science & Applications) 2020年第1期9卷 1108-1116页

作者： Andrew McClung Mahdad Mansouree amir Arbabi Department of Electrical and Computer Engineering University of Massachusetts Amherst151 Holdsworth WayAmherstMA 01003USA

Chromatic dispersion spatially separates white light into colours,producing rainbows and similar *** to imaging but essential to spectroscopy,chromatic dispersion is the result of material properties in refractive optics and is considered an inherent characteristic of diffractive devices such as gratings and flat ***,we present a fundamental relation connecting an optical system’s dispersion to the trajectories light takes through it and show that arbitrary control over dispersion may be achieved by prescribing specific trajectories,even in diffractive *** cascaded metasurfaces(2D arrays of sub-micron scatterers)to direct light along predetermined trajectories,we present an achromatic twisted metalens and experimentally demonstrate beam deflectors with arbitrary *** new insight and design approach usher in a new class of optical systems with wide-ranging applications.

关键词： dispersion light trajectories

Reduction of Ideals Relative to an Artinian Module and the Dual of Burch,s Inequality

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Algebra Colloquium 2019年第1期26卷 113-122页

作者： Fatemeh Cheraghi amir Mafi Department of Mathematics University of Kurdistan P.O. Box: 416 Sanandaj Iran

Let (A,m) be a commutative quasi-local ring with non-zero identity and M be an Artinian A-module with dim M = d. If I is an ideal of A with l(0 :m I) 0. Moreover, we study the dual of Burch's inequality. In particular... 详细信息

Let (A,m) be a commutative quasi-local ring with non-zero identity and M be an Artinian A-module with dim M = d. If I is an ideal of A with l(0 :m I)y if l(0:M I^n+1)=l(0:m J)^(n+d/d)-l(0 :M J)/(0 :M I))(n+d-1/d-1) for all n≥> 0. Moreover, we study the dual of Burch's inequality. In particular, the Burch's inequality becomes an equality if G(I,M) is co-Cohen-Macaulay.

关键词： reduction of ideals Artinian modules co-Cohen-Macaulay

Design adaptations in a large and deep urban excavation: Case study

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第2期11卷 389-399页

作者： amir Alipour Abolfazl Eslami Department of Civil and Environmental Engineering Amirkabir University of Technology

In this paper, design, re-design, and performance of a long-standing very deep excavation, which was originally planned to depth of 38 m, are presented. Over-digging was not planned in the original design,thus the reassessment was performed. Two main topics were followed: deepening to increase the maximum depth of an existent excavation from 38 m to 42.5 m, and feasibility for upgrading a predesigned support system from temporary to permanent support system. The geological investigations in the project site illustrated a type of stiff and cemented coarse-grained alluvium. An observational approach with additional geotechnical investigations and in situ tests was applied. Back analyses of stability of an unsupported access ramp, as well as deformation monitoring of walls, were used in order to review geotechnical design parameters that represent the full-scale behavior of the ground. Additional nails and soldier piles together with building mat foundation were implemented as a complementary lateral support in the retaining system. From an engineering point of view, by assuming a corrosion rate of 0.065 mm/a for existent rebars, according to chemical and electrical resistivity tests, the long-term performance of the revised retaining system was verified by static and pseudo-dynamic ultimate limit state analyses. Performance monitoring during the construction shows that the measured deformation is in the lower limit of the prediction.

关键词： Deep excavation Field observations In situ tests Support system Adaptive design Inverse analysis