In recent years the energy shortage and environmental impact from consuming fossil fuels have led to the development of renewable energy source systems. Since these sources are not reliable and are usually time dependent, an energy storing system likehydrogen production is required. In this regard, a PEM electrolyzer can be efficiently used to decompose liquid water into hydrogen and oxygen. Because of the dynamic nature of renewable sources, a dynamic model of a PEM electrolyzer is a necessity for investigating its performance. In this paper, a new one-dimensional dynamic model PEM electrolyzer which solves electrochemical and two phase fluid flow equations at each time step is proposed. The finite volume method with an upwind scheme is used to solve a set of nonlinear partial differential equations of fluid flowfor discretization. The obtained algebraic set of equations is implicitly solved to ensure good stability at large time steps as well as low mesh nodes which provide the capability of system level simulation. Storing gas produced by the electrolysis process continuously increases vessels pressure and leads to dynamic behavior of the electrolyzer. This phenomenon is investigated in this research using the proposed model. Results show that although the concentration of produced gas was raised by increasing vessel pressure, the hydrogen concentration was essentially constant along the electrolyzer on the cathode side. It was also observed that increasing vessel pressure results in high power consumption. However, when the pressure on the anode side reaches the moderate level the water mass flow rate can be reduced, which causes a reduction in pump energy consumption.

In the present paper, a laminar counter-flow flame has been numerically investigated under the transcritical and supercritical conditions. The Cantera open source code has been used to calculate the flow field and the kinetic combustion solution. Furthermore, the energy equation, the thermodynamics and the transport properties have been modified for real gas solution. The thermodynamics properties, including density, enthalpy, and specific heat at constant pressure, are evaluated based on fundamental thermodynamics theories and the modified SRK equation of state (EOS). Transport properties, including thermal conductivity and dynamic viscosity, are estimated using Chung method. It can be seen that the pseudo-boiling phenomenon has been appeared in transcritical condition with real gas equations. The ideal gas solution is unable to capture this phenomenon. In the mixture fraction field, there is no major difference between the real gas and the ideal gas, which is important for solving the turbulent reacting flow by the flamelet models. However In the physical field, the difference between the real gas condition and the ideal gas is significant in terms of the position and dimensions of the flame for the transcritical state. For supercritical conditions in the physical field similar to mixture fraction field, there is no significant difference in the flame situation.

In this paper we consider a nonlinear two-phase Stefan problem in onedimensional space. The problem is mapped into a nonlinear Volterra integral equation for the free boundary.

In present study, the effect of different defect layer refractive indices and thicknesses on group velocity has been studied in onedimensional photonic crystal. It is found that the increase of refractive index, number of defects and defect layer thickness will induce the decrease of group velocity. Taking advantage of these results, a novel technique has been introduced to tune and control the slowing light in photonic crystal.

The effect of the frequency variation of laser pulse in uniform magnetized plasma is considered in onedimensional laser wakefield acceleration and carried out particle simulation. It is shown that wakefield amplitude is increased threefold for the negative Gaussian chirped laser pulse in the magnetized plasma. In our simulation, electrons with initial energy about 0.3 MeV with initial energy spread about 10 % were trapped, effectively compressed in longitudinal direction and accelerated to ultra-relativistic energy about 1.3 GeV with final energy spread about 6%.

Wax crystallisation and deposition from offshore reservoirs have been causing serious problems such as plugged pipelines and reduced production flow rates. This issue is receiving more attention from the researchers and for commercial applications due to the shift in trend from using offshore production facilities to pipelines utilization. The aim of this study is the implementation of the Avrami theory to comprehend the mechanism of wax crystallisation to reveal the morphology of wax crystal using gravimetric and differential scanning calorimetry (DSC) analyses. The experiment values obtained from the Avrami’ s theory for both gravimetric and DSC techniques shows that the crystals were onedimensional with rod-like structures.