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 $\mu_{a}<0$ at the origin, we study the case when the interface advances at low velocities, obtaining the scaling exponents $z=3.0\pm 0.1$, $\alpha=1.50\pm 0.02$ and $\alpha_{loc}= 0.95\pm 0.03$ 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 $z=4.0 \pm 0.1$, $\alpha=1.25\pm 0.02$ and $\alpha_{loc}= 0.95\pm 0.03$. 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

Enhancing the performance of energy harvesting wireless communications using optimization and machine learning

The motivation behind this thesis is to provide efficient solutions for energy harvesting communications. Firstly, an energy harvesting underlay cognitive radio relaying network is investigated. In this context, the secondary network is an energy harvesting network. Closed-form expressions are derived for transmission power of secondary source and relay that maximizes the secondary network throughput. Secondly, a practical scenario in terms of information availability about the environment is investigated. We consider a communications system with a source capable of harvesting solar energy. Two cases are considered based on the knowledge availability about the underlying processes. When this knowledge is available, an algorithm using this knowledge is designed to maximize the expected throughput, while reducing the complexity of traditional methods. For the second case, when the knowledge about the underlying processes is unavailable, reinforcement learning is used. Thirdly, a number of learning architectures for reinforcement learning are introduced. They are called selector-actor-critic, tuner-actor-critic, and estimator-selector-actor-critic. The goal of the selector-actor-critic architecture is to increase the speed and the efficiency of learning an optimal policy by approximating the most promising action at the current state. The tuner-actor-critic aims at improving the learning process by providing the actor with a more accurate estimation about the value function. Estimator-selector-actor-critic is introduced to support intelligent agents. This architecture mimics rational humans in the way of analyzing available information, and making decisions. Then, a harvesting communications system working in an unknown environment is evaluated when it is supported by the proposed architectures. Fourthly, a realistic energy harvesting communications system is investigated. The state and action spaces of the underlying Markov decision process are continuous. Actor-critic is used to optimize the system performance. The critic uses a neural network to approximate the action-value function. The actor uses policy gradient to optimize the policy\u27s parameters to maximize the throughput