Aamir Shahzad

By Aamir Shahzad and Maogang He

Understanding of thermophysical properties of complex liquids under various conditions is of practical interest in the field of science and technology. Thermal conductivity of nonideal complex (dusty) plasmas (NICDPs) is investigated by using homogeneous nonequilibrium molecular dynamics (HNEMD) simulation method. New investigations have shown, for the first time, that Yukawa dusty plasma liquids (YDPLs) exhibit a non-Newtonian behavior expressed with the increase of plasma conductivity with increasing external force field strength Fext. The observations for lattice correlation functions Ψ (t) show, that our YDPL system remains in strongly coupled regime for a complete range of plasma states of (Γ, κ), where (Γ) Coulomb coupling and (κ) Debye screening length. It is demonstrated, that the present NICDP system follows a simple scaling law of thermal conductivity. It has been shown, that our new simulations extend the range of Fext used in the earlier studies in order to find out the size of the linear ranges. It has been shown that obtained results at near equilibrium (Fext = 0.005) are in satisfactory agreement with the earlier simulation results and with the presented reference set of data showed deviations within less than ±15% for most of the present data points and generally overpredicted thermal conductivity by 3–22%, depending on (Γ, κ).

Part of the book: Thermoelectrics for Power Generation

By Aamir Shahzad, Muhammad Asif Shakoori, Maogang He and Sajid Bashir

Wave properties of strongly coupled complex dusty (SCCD) plasmas evaluated using the equilibrium molecular dynamics (EMD) simulation technique. In this work, the plasma normalized longitudinal current correlation function CL(k,t) and transverse current CT(k,t) are calculated for a large range of plasma parameters of Coulomb coupling parameter (Γ) and screening strength (κ) with varying wave’s number (k). In EMD simulations, we have analysed different modes of wave propagation in SCCD plasmas with increasing and decreasing sequences of different combinations of plasmas parameters (κ, Γ) at varying simulation time step (Δt). Our simulation results show that the fluctuation of waves increases with an increase of Γ and decreases with increasing κ. Additional test shows that the presented results for waves are slightly dependent on number of particles (N). The amplitude and time period of CL(k,t) and CT(k,t) also depend on different influenced parameters of κ, Γ, k and N. The new results obtained through the presented EMD method for complex dusty plasma discussed and compared with earlier simulation results based on different numerical methods. It is demonstrated that the presented model is the best tool for estimating the behaviour of waves in strongly coupled complex system (dusty plasmas) over a suitable range of parameters.

Part of the book: Computational and Experimental Studies of Acoustic Waves

By Muzamal Hussain, Aamir Shahzad, Muhammad Nawaz Naeem and Maogang He

Vibration analysis of fluid-filled functionally graded material (FGM) cylindrical shells (CSs) is investigated with ring supports. The shell problem is formulated by deriving strain and kinetic energies of a vibrating cylindrical shell (CS). The method of variations of Hamiltonian principle is utilized to change the shell integral problem into the differential equation (DE) expression. Three differential equations (DE) in three unknown for displacement functions form a system of partial differential equations (PDEs). The shells are restricted along the thickness direction by ring supports. The polynomial functions describe the influence of the ring supports and have the degree equal to the number of ring supports. Fluid loaded terms (FLT) are affixed with the shell motion equations. The acoustic wave equation states the fluid pressure designated by the Bessel functions of first kind. Axial modal deformation functions are specified by characteristic beam functions which meet end conditions imposed on two ends of the shell. The Galerkin method is employed to get the shell frequency equation. Natural frequency of FGM cylindrical shell is investigated by placing the ring support at different position with fluid for a number of physical parameters. For validity and accuracy, results are obtained and compared with the data in open literature. A good agreement is achieved between two sets of numerical results.

Part of the book: Computational Fluid Dynamics

By Aamir Shahzad, Syed Irfan Haider, Maogang He and Yan Feng

Part of the book: Impact of Thermal Conductivity on Energy Technologies

By Aamir Shahzad, Muhammad Asif Shakoori, Mao-Gang HE and Yan Feng

The dynamical structure factor [S(k,ω)] gives the information about static and dynamic properties of complex dusty plasma (CDPs). We have used the equilibrium molecular dynamic (EMD) simulations for the investigation of S(k,ω) of strongly coupled CDPs (SCCDPs). In this work, we have computed all possible values of dynamical density with increasing and decreasing sequences of plasma frequency (ωp) and wave number (k) over a wide range of different combinations of the plasma parameters (κ, Γ). Our new simulation results show that the fluctuation of S(k,ω) increases with increasing Г and it decreases with an increase of κ and N. Moreover, investigation shows that the amplitude of S(k,ω) increases by increasing screening (κ) and wave number (k), and it decreases with increasing Г. Our EMD simulation shows that dynamical density of SCCDPs is slightly dependent on N; however, it is nearly independent of other parameters. The presented results obtained through EMD approach are in reasonable agreement with earlier known results based on different numerical methods and plasma states. It is demonstrated that the presented model is the best tool for estimating the density fluctuation in the SCCDPs over a suitable range of parameters.

Part of the book: Plasma Science and Technology

By Aamir Shahzad and Fang Yang

Transport properties of complex system under various conditions are of practical interest in the field of science and technology. Homogenous nonequilibrium molecular dynamics (HNEMD) simulations have been employed to calculate the thermal conductivity (λ) of three-dimensional (3D) strongly coupled complex nonideal plasmas (SCCNPs) over a suitable range of plasma parameters (Γ, κ). New investigations show that the λ depending on plasma parameters and minimum value of λ exists at nearly same plasma states. In the present case, the non-Newtonian behavior is checked with different system sizes and it is found that the λ behavior is well matched with earlier numerical work. It is demonstrated that the present outcomes are more consistent than those obtained earlier known simulations. It is revealed that our outcomes can be acceptable for a low range of force field in order to find out the size of linear ranges, and it explains the nature of nonlinearity of SCCNPs. It has been shown that the measured outcomes at steady states of external field of F* (=0.005) are in acceptable agreement with previous numerical outcomes, and it showed that the deviations are within less than 12% for most of the data and depend on plasma states.

Part of the book: Non-Equilibrium Particle Dynamics

By Aamir Shahzad

Part of the book: Nuclear Medicine Physics

By Aamir Shahzad and Sajid Bashir

The concepts of diagnostic reference levels (DRLs) and achievable doses (ADs) have been developed to optimize the imaging procedures, both diagnostic and interventional, involving ionizing radiation. These are not dose limits but are used to evaluate the performance of clinical exams. Most countries have developed their own DRLs and ADs depending on the medical practice of administrating radioactivity to patients. In this project, the intent was to establish these quantities in nuclear medicine according to the prevailing practices of our country. Data were collected for all gamma ray imaging procedures both for adults as well as for children. An attempt was made to include as many hospitals and patients as possible to get good statistics. The survey data showed the range of minimum and maximum administered activities is quite large for many commonly performed nuclear medicine studies. DRLs and ADs are selected at the 75th and 50th percentiles of the survey data to represent state-of-the-practice. DRLs are not regulatory limits or to establish legal standards of care. In addition, DRLs are not applicable to the doses for individual patients. It is essential to ensure that the appropriate clinical information is available in the image throughout the optimization process.

Part of the book: Nuclear Medicine Physics

By Aamir Shahzad, Muhammad Asif Shakoori and Mao-Gang He

Wave’s spectra are investigated through an equilibrium molecular dynamic (EMD) simulation of three-dimensional (3D) strongly-coupled complex-dusty plasmas (SCCDPs). In this chapter, we have analyzed the correlation functions over a wide range of plasma parameters of Γ (≡1, 100) and of κ (≡4.5, 5.5) along with a higher wave’s numbers of k (≡1, 4). In EMD simulations, we have examined the propagation modes of wave in the longitudinal CL(k, t) and transverse CT(k, t) current direction at higher screening (κ). We have also analyzed the wave’s spectra in different regimes of plasma states of SCCDPs. A new simulation shows that the longitudinal (CL) and transverse (CT) waves in SCCDPs are damped for low values of Γ. However, these damping affects decrease comparatively with an increasing Γ. Outcomes show that amplitude and frequency modes of the CL and CT depend on κ, Γ, k and probably on a number of particles (N). The results obtained from EMD are in reasonable agreement with earlier known theoretical and experimental data. It has been shown that the present EMD method is the best tool for computing CL and CT in the SCCDPs over a suitable range of plasma parameters.

Part of the book: Fusion Energy

By Aamir Shahzad, Muhammad Qasim Khan, Muhammad Asif Shakoori, Maogang He and Yan Feng

The studies of strongly coupled complex plasmas are of significant in the area of science and technology. The plasma thermal conductivity strongly coupled (complex) plasmas is of significant in scientific technology, because it behaves as complex fluids. The two-dimensional (2D) plasma thermal conductivity of strongly coupled complex dusty plasmas (SCCDPs) has been investigated by using the homogenous nonequilibrium molecular dynamics (HNEMD) simulations, proposed by Evan-Gillan scheme, at higher screening parameter к. In our case, we have chosen particularly higher screening strength (к) for calculating plasma thermal conductivity. The new simulations of plasma thermal conductivity are computed over an extensive range of plasma states (Г, к) for suitable system sizes by applying the HNEMD simulation method at constant external force field strength (F*). It is found that the plasma thermal conductivity of SCCDPS decreases by increasing plasma states (Г, к). The calculations show that the kinetic energy of SCCDPS depends upon the system temperature (1/Г) and it is independent of к for higher screening parameter. The new results of thermal conductivity obtained from an improved HNEMD algorithm are in satisfactory agreement with earlier known numerical results and experimental data for 2D SCCDPS. It is depicted that the HNEMD method is a powerful tool to calculate an accurate plasma thermal conductivity of 2D SCCDPS.

Part of the book: Thermophysical Properties of Complex Materials