3,197 research outputs found
Eighth-order phase-field-crystal model for two-dimensional crystallization
We present a derivation of the recently proposed eighth order phase field
crystal model [Jaatinen et al., Phys. Rev. E 80, 031602 (2009)] for the
crystallization of a solid from an undercooled melt. The model is used to study
the planar growth of a two dimensional hexagonal crystal, and the results are
compared against similar results from dynamical density functional theory of
Marconi and Tarazona, as well as other phase field crystal models. We find that
among the phase field crystal models studied, the eighth order fitting scheme
gives results in good agreement with the density functional theory for both
static and dynamic properties, suggesting it is an accurate and computationally
efficient approximation to the density functional theory
Influence of Disorder Strength on Phase Field Models of Interfacial Growth
We study the influence of disorder strength on the interface roughening
process in a phase-field model with locally conserved dynamics. We consider two
cases where the mobility coefficient multiplying the locally conserved current
is either constant throughout the system (the two-sided model) or becomes zero
in the phase into which the interface advances (one-sided model). In the limit
of weak disorder, both models are completely equivalent and can reproduce the
physical process of a fluid diffusively invading a porous media, where
super-rough scaling of the interface fluctuations occurs. On the other hand,
increasing disorder causes the scaling properties to change to intrinsic
anomalous scaling. In the limit of strong disorder this behavior prevails for
the one-sided model, whereas for the two-sided case, nucleation of domains in
front of the invading front are observed.Comment: Accepted for publication in PR
Corrosion Inhibition of Mild-Steel in (1M) HCl using Spands Reagent
The effect of Spands Reagent on the dissolution of Mild-steel in 1M HCl solution was studied using weight loss and galvanostatic polarization techniques. The inhibition efficiency of inhibitor increases with concentration to attain (75.26%) at concentration 1—10-2 M ,and standing time for 180 min at 25°C. Temperature effect on the corrosion behavior was studied at temperature range from 25-45°C, the results showed that inhibition efficiency decreased with increasing temperature to attain (64.53%) at concentration 1—10-2 M at 45°C and with standing time equal to 180 min. The effect of temperature on the rate of corrosion in the absence and presence of Spands Reagent was also studied. The Kinetic Parameters were calculated and discussed. The polarization curves revealed that the studied inhibitor represent a mixed type inhibitors. Adsorption of inhibitor was isotherm physisorption type
Intrinsic versus super-rough anomalous scaling in spontaneous imbibition
We study spontaneous imbibition using a phase field model in a two
dimensional system with a dichotomic quenched noise. By imposing a constant
pressure at the origin, we study the case when the interface
advances at low velocities, obtaining the scaling exponents ,
and within the intrinsic
anomalous scaling scenario. These results are in quite good agreement with
experimental data recently published. Likewise, when we increase the interface
velocity, the resulting scaling exponents are , and . Moreover, we observe that the local
properties of the interface change from a super-rough to an intrinsic anomalous
description when the contrast between the two values of the dichotomic noise is
increased. From a linearized interface equation we can compute analytically the
global scaling exponents which are comparable to the numerical results,
introducing some properties of the quenched noise.Comment: Accepted for publication in Physical Review
Integrated depositional model of the Carbonate Kirkuk Group of Southern Kurdistan-Iraq
The carbonate Kirkuk Group succession hosts major hydrocarbon reserves in the southern Kurdistan-Northen Iraq. This is why investigations into this succession started a long time ago, especially for oil exploration. In this research numerous microfacies were identified from the Kirkuk Group and interpreted as having been deposited in a ramp setting based on lateral variations of the microfacies; gradual deepening with no evidence of slope break or effective barriers. A depositional model has been generated from the overall palaeoenvironmental interpretations of the microfacies in which the analysed microfacies indicate palaeoenvironments ranging from terrestrial to open marine settings; nine major depositional environmental zones have been identified and correlated with the standard Cenozoic carbonate ramp model. These zones distributed across the ramp setting, dipping southwest, in which zone 1 is a terrestrial deposit; zone 2, 3, 4 and 5 belong to the inner ramp; zone 6, 7 and 8 belong to the middle ramp and zone 9 belong to the outer ramp and basinal settings. Key words: Kirkuk Group, microfacies, Oligocene, Carbonate, Kurdistan, Iraq
Interface Equations for Capillary Rise in Random Environment
We consider the influence of quenched noise upon interface dynamics in 2D and
3D capillary rise with rough walls by using phase-field approach, where the
local conservation of mass in the bulk is explicitly included. In the 2D case
the disorder is assumed to be in the effective mobility coefficient, while in
the 3D case we explicitly consider the influence of locally fluctuating
geometry along a solid wall using a generalized curvilinear coordinate
transformation. To obtain the equations of motion for meniscus and contact
lines, we develop a systematic projection formalism which allows inclusion of
disorder. Using this formalism, we derive linearized equations of motion for
the meniscus and contact line variables, which become local in the Fourier
space representation. These dispersion relations contain effective noise that
is linearly proportional to the velocity. The deterministic parts of our
dispersion relations agree with results obtained from other similar studies in
the proper limits. However, the forms of the noise terms derived here are
quantitatively different from the other studies
Online Job Recruitment Model for Universiti Utara Malaysia
Requirements play an important part in system development project. It is because requirement forms the backbone of any success project and provides the measure of success or failure of a certain project. Misinterpreted of requirements
will make the system development does not meet the customer's expectation and increasing cost. Therefore, it is necessary to present the requirement in an understandable and meaningful way. The main purposes of this project are to capture the requirements of online job
recruitment for Universiti Utara Malaysia and defined requirement model for the captured requirements of online job recruitment for Universiti Utara Malaysia. A
requirement model is important as it serves as a good starting point for system development. Requirement model will give a complete view of a system and represent idea without having to build an actual system. Requirement model help the developer to understand user's requirement, and it saves time and cost, reduce risk, and improves effectiveness and efficiency. Project methodology would use object-oriented requirement capture and analysis phase, which consists of domain understanding, requirement capture,
classification and validation. The requirements captured modeled using Unified Modeling Language's (UML) notation. Requirements model is validated by using system requirements testing and horizontal prototype
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