Effect Of Initial Parameters Research Articles

State of charge estimation for lithium-ion battery based on an Intelligent Adaptive Extended Kalman Filter with improved noise estimator

Adaptive extended Kalman filter (AEKF) is widely used for lithium-ion battery (LIBs) state of charge (SOC) estimation. Innovation covariance matrix (ICM) of AEKF is estimated by fixed-length error innovation sequence (EIS) (the difference between measured and estimated voltages), which doesn’t consider the distribution change of EIS. However, the distribution of EIS will change due to load current dynamics or error of battery model. Failing to consider the distribution change of EIS will lead to SOC estimation inaccuracy. To address this problem, this paper proposed an intelligent adaptive extended Kalman filter (IAEKF) method that can detect the moment of distribution change of EIS by the maximum likelihood function. Then, the ICM is updated based on the EIS after that moment to improve the SOC estimation accuracy. Results show that the proposed IAEKF method improves SOC estimation accuracy. Compared to that of the AEKF, the Root Mean Squared Error (RMSE) and the Mean Absolute Error (MAE) of SOC based on IAEKF decrease significantly by 43.34% and 55.80%, respectively, while the computation time only increases by 4.59%. In the end, the effect of initial parameters on the SOC estimation accuracy was analysed. It is found that the proposed IAEKF method is robust against parameter uncertainties.

Relativistic longitudinal self-compression of ultra-intense Gaussian laser pulses in magnetized plasma

AbstractThis article presents a preliminary study of the longitudinal self-compression of ultra-intense Gaussian laser pulse in a magnetized plasma, when relativistic nonlinearity is active. This study has been carried out in 1D geometry under a nonlinear Schrodinger equation and higher-order paraxial (nonparaxial) approximation. The nonlinear differential equations for self-compression and self-focusing have been derived and solved by the analytical and numerical methods. The dielectric function and the eikonal have been expanded up to the fourth power of r (radial distance). The effect of initial parameters, namely incident laser intensity, magnetic field, and initial pulse duration on the compression of a relativistic Gaussian laser pulse have been explored. The results are compared with paraxial-ray approximation. It is found that the compression of pulse and pulse intensity of the compressed pulse is significantly enhanced in the nonparaxial region. It is observed that the compression of the high-intensity laser pulse depends on the intensity of laser beam (a0), magnetic field (ωc), and initial pulse width (τ0). The preliminary results show that the pulse is more compressed by increasing the values of a0, ωc, and τ0.

Effect of initial parameter on thermodynamic performance in a liquid oxygen tank with pressurized helium gas

Heat and mass transfer occurs among different species during the pressurization process with helium gas in cryogenic storage tanks, for which detailed investigations are necessary. In this article, the influence of initial parameters on the thermodynamic performance in a liquid oxygen tank is investigated. Both liquid–vapor interfacial evaporation and mass diffusion are considered. Different initial parameters are compared and analyzed. With the initial liquid temperature increasing from 94.0 to 96.0 K, the total phase change quality decreases by 20%. The initial tank wall temperature ranges from 104.0 to 106.0 K, and the final phase change quality increases by 14.01%. With the oxygen component kept constant, the tank pressure rise was reduced by 23.33% and the total phase change quantity increased by 4.25 times with the helium component ranging from 0.00 to 0.20 kg. When the initial tank pressure remained constant by adjusting the species components of the mixture, the tank pressure rise and the total phase change quantity increased by 17.6% and 8.87 times, with the initial helium increasing from 0.00 to 0.50 kg. The present study provides important conclusion that may supply some technique reference for the design of cryogenic propellant systems.

Numerical investigation of diesel spray flame structures under diesel engine-relevant conditions using large eddy simulation

ABSTRACTLarge eddy simulation coupled with the third-order Monotone Upstream-centered Schemes for Conservation Laws (MUSCL) differencing scheme was employed for investigating the ignition processes and flame structures of the reacting n-heptane spray over a wider range of diesel engine-relevant conditions. First, the effects of numerical schemes on the mixing and combustion processes are analyzed in detail. Comparisons of the mixture fraction profiles with experimental data from the Engine Combustion Network website show that the MUSCL gives a better prediction compared with Quasi-second-order upwind scheme. The mixing between fuel and air is much better using MUSCL scheme. As a result, ignition is initiated at fuel-leaner regions, but still richer than stoichiometric equivalence ratio. Second, the predicted ignition delay times and flame lift-off lengths are compared with experimental data under different initial conditions. The predicted results show good agreements with experimental results at different temperatures, oxygen concentrations, and densities. Finally, the effects of initial conditions on the spray flame structures are comprehensively analyzed using the temperature-equivalence ratio maps. The effects of initial parameters on the reacting spray structures and important radicals, such as OH and CO are investigated carefully. Results show that initial oxygen concentration has the greatest influence on the flame structures than ambient gas temperature and density.

The Characteristics of Frustum of Cone Parachute-Airbag for Aircraft Recovery System

The aircraft recovery systems have been drawn more attention for its ability on offering cushioning landing in recent years. However, many previous researches mainly focus on the cylinder or rectangle air bags where the upper surface is orthogonal to the flank side. This kind of airbag will not meet the requisite stability and security because it might be bended by payload under the misalignment forces. In this light, a more stable frustum of cone parachute-airbag system is proposed and the cushioning mathematical model is established. Based on the theories of thermodynamics and mechanics, the expressions of velocity and deceleration are derived. The effects of initial parameters on airbag cushioning properties are analyzed and the simulation results are shown. The results can provide references for the future design of aircraft recovery system.

The effect of initial parameters on particle size distribution inverted using the laser diffraction technique and a non-linear iterative method

The Twomey non-linear iteration (NLI) method is known by the simple algorithm. However, the performance of the inversion is strongly depended on parameters of the NLI algorithm. Major parameters in the algorithm are the initial size distribution, weight parameter, and the number of iteration. In the study, we show how values of initial parameters affect to the result of size distribution in the algorithm by the laser diffraction scattering method. Computer simulations and experimental method are carried out to observe the influence of the parameters in the algorithm. Scattering pattern is calculated by Mie scattering model in the range of 5.0×10−4−2.5rad. Experimental results were measured mono-distribution polystyrene latex (50μm) and poly-distribution glass beads (3–30μm, and 10–100μm). The number of iteration is a most influence parameter in the NLI algorithm. If the number of iteration is too high for calculation, calculated result will lose the smoothness. We also introduced a new parameter C (combination of the sum of residual squares of scattering signals and sum of secondary differentiation of size distribution) to monitor the suitable stop criterion for the NLI method. The parameter C is a useful index for the poly dispersion sample to find the suitable stop criterion.

Improvement of harmony search algorithm by using statistical analysis

In this article, we suggest a new method to improve the harmony search meta-heuristic algorithm. Several approaches are presented for improving the harmony search algorithm. These approaches consider different values for initial parameters in each optimization problem. Differences between the proposed algorithm and the harmony search algorithm are as follows. First, we add a new step to create a new harmony vector, which increases the accuracy and convergence rate and reduces the impact of the initial parameters in achieving an optimal solution. Second, we set introduce a parameter called bandwidth (bw), which is an important factor with great influence on the convergence rate toward optimal solutions. To prove the efficiency and robustness of the proposed algorithm, we argument about statistical analysis of proposed algorithm and examine it through a variety of optimization problems, including constrained and unconstrained functions, mathematical problems with high dimensions and engineering and reliability problems. In all of these problems, the convergence rate and accuracy of the answer are equal to or better than other methods. In addition, in our proposed method, the effect of initial parameters has been reduced with respect to the optimal solution.

Formation of fast shocks by magnetic reconnection in the solar corona

Reconnections of magnetic fields over the solar surface are expected to generate abundant magnetohydrodynamic (MHD) discontinuities and shocks, including slow shocks and rotational discontinuities. However, the generation of fast shocks by magnetic reconnection process is relatively not well studied. In this paper, magnetic reconnection in a current sheet is studied based on two-dimensional resistive MHD numerical simulations. Magnetic reconnections in the current sheet lead to the formation of plasma jets and plasma bulges. It is further found that the plasma bulges, the leading part of plasma jets, in turn lead to the generation of fast shocks on flanks of the bulges. The simulation results show that during the magnetic reconnection process, the plasma forms a series of structures: plasma jets, plasma bulges, and fast shocks. As time increases, the bulges spread out along the current sheet (±z direction) and the fast shocks move just ahead of the bulges. The effects of initial parameters ρs/ρm, β∞, and trec on the fast shock generation are also examined, where ρs/ρm is the ratio of plasma densities on two sides of the initial current sheet, β∞=P∞/(B∞2/2μ0), P∞ is the plasma pressure and B∞ is the magnetic field magnitude far from the current sheet, and trec is the reconnection duration. In the asymmetric case with ρs/ρm=2, β∞=0.01 and trec=1000, the maximum Alfvén Mach number of fast shocks (MA1 max) is MA1 max≅1.1, where MA1=Vn1/VA1, and Vn1 and VA1 are, respectively, the normal upstream fluid velocity and the upstream Alfvén speed in the fast shocks frame. As the density ratio ρs/ρm (=1–8) and plasma beta β∞ (=0.0001–1) increase, MA1 max varies slightly. For the case with a large plasma beta β∞ (=5), the fast shock is very weak. As the reconnection duration trec increases, the bulges lead to generation of fast shocks with a higher MA1 max. The present results can be applied to the mechanism of coronal heating by fast shocks.

Reaching High Temperatures by Compressing a Vapor Bubble

The process of compression of a vapor bubble under the action of an instantaneously applied pressure is considered. The effect of initial parameters on compression dynamics is analyzed. Conditions of emergence of a shock wave inside the bubble are considered. It is shown that the temperature in the bubble is lower than 104 K under uniform compression.