Quantum Fisher information of two atoms with dipole–dipole interaction under the environment of phase noise lasers

We investigate the parameter estimation problems of two-atom system driven by the phase noise lasers (PNLs) environment. And we give a general method of numeric solution to handle the problems of atom system under the PNLs environment. The calculation results of this method on Quantum Fisher Information (QFI) are consistent with our former results. Moreover, we consider the dipole–dipole (d–d) interaction between the atoms under PNLs environment with the collective decay, and the results show that larger d–d interaction and smaller collective decay rate lead to larger QFI of the two-atom system. So the collective decay will destroy the QFI while the d–d interaction will preserve the QFI, these results can be used to protect the QFI of two-atom system driven by the PNLs environment.

Modeling of the COVID-19 pandemic in the limit of no acquired immunity

We propose the SEIRS compartmental epidemiology model aimed at modeling the COVID-19 pandemy dynamics. The limit case of no acquired immunity (neither natural nor via vaccination) is considered mimicking the situation (i) when no effective vaccine being developed or available yet, and (ii) the virus strongly mutates causing massive reinfections. Therefore, the only means of suppressing the virus spread are via quarantine measures and effective identification and isolation of infected individuals. We found both the disease-free and the endemic fixed points and examined their stability. The basic reproduction ratio is obtained and its dependence on the parameters of the model is discussed. We found the presence of the contact rate threshold beyond which the disease-free fixed point cannot be reached. Using the numeric solution, the approximate analytic solution of the model, characterized by rescaled contact rate, is obtained. Several possible "quarantine on"/"quarantine off" scenarios are considered and the one combined with flexible adjustment of the identification and isolation rates is found to be the most effective in bringing the second and consequent waves down. The study can be interpreted as a reference point for the case when the natural or acquired immunity, as well as vaccination, are taken into account. It will be a topic of a separate study.

A Numeric Solution of the Quantum Rigid Rotor

The Variable Fixed Grid Method (VFGM) combines numerical techniques of differentiation and integration to solve the Schrödinger equation in its integral form. The method is extremely simple and allows to overcome difficulties found in conventional resolutions and when coupled equations are produced. However, difficulties arise when curvilinear coordinate systems are used because there are no well-defined boundary conditions for the angular functions. Systematic numerical alternatives were performed using the rigid rotor model. A transformation of variables proved to be efficient for calculating energy and the wave function. The difficulties are located at the poles where the Jacobian of the curvilinear coordinate system is canceled. The method used in this work allows a greater application of VFGM for systems in different curvilinear coordinate systems.

Solusi Numerik Model SIR pada Penyebaran Penyakit Hepatitis B dengan Metode Perturbasi Homotopi di Provinsi Sulawesi Selatan

Penelitian ini membahas mengenai solusi secara numerik dari model SIR pada penyebaran penyakit Hepatitis B dengan Metode Perturbasi Homotopi. Data yang digunakan adalah data sekunder dari penelitian Rosdiana (2015) yang berupa model SIR dan jumlah penderita Hepatitis B di Provinsi Sulawesi Selatan tahun 2015 dari Dinas Kesehatan Provinsi Sulawesi Selatan. Pembahasan dimulai dari penentuan solusi umum dengan Metode Perturbasi Homotopi, penentuan parameter, simulasi dan analisis hasil. Setelah dilakukan analisis dari simulasi numerik terlihat bahwa Metode Perturbasi Homotopi dapat digunakan untuk melihat kecenderungan perlakuan penyakit Hepatitis B di Provinsi Sulawesi Selatan dan menjadi bahan pertimbangan untuk tindakan pencegahan penyakit Hepatitis B. Dalam penelitian ini diperoleh grafik pergerakan dari model SIR dengan data riil.Kata kunci : Solusi Numerik, Model SIR, Hepatitis B, Metode Perturbasi Homotopi, PemodelanThis research aims to find out the numerical solustion from a SIR model on the spread of Hepatitis B by Homotopy Perturbation Method. This research used a secundary data from Rosdiana’s research (2015) focused on SIR model and number of Hepatitis B in South Sulawesi 2015 from Health Department of South Sulawesi. The discussion started by determining general solution with Homotopy Perturbation Method, parameter decision, simulation and result analyzis. After conducting an analyzis from numeric simulation it shows that the Homotopy Perturbation Method can be used to analyze the preference of Hepatitis B treatment in South Sulawesi also can be a consideration for preventing action of infectious disease of Hepatitis B. This research gets movement grafic and result analyzis from SIR model by riil data.Keywords : Numeric Solution, SIR Model, Hepatitis B, Homotopy Perturbation Method, Modeling

Multiple Bragg reflection by a thick mosaic crystal. II. Simplified transport equation solved on a grid

The generalized Darwin–Hamilton equations [Wuttke (2014). Acta Cryst. A70, 429–440] describe multiple Bragg reflection from a thick, ideally imperfect crystal. These equations are simplified by making full use of energy conservation, and it is demonstrated that the conventional two-ray Darwin–Hamilton equations are obtained as a first-order approximation. Then an efficient numeric solution method is presented, based on a transfer matrix for discretized directional distribution functions and on spectral collocation in the depth coordinate. Example solutions illustrate the orientational spread of multiply reflected rays and the distortion of rocking curves, especially if the detector only covers a finite solid angle.

Numerical study for mixed convection flow of Oldroyd-B nanofluid subject to activation energy and binary chemical reaction

This attempt discusses mixed convection Oldroyd-B nanoliquid flow over a doubly stratified surface in existence of activation energy. Impacts of Brownian diffusion and thermophoretic are additionally accounted. The non-linear frameworks are simplified by suitable variables. Shooting method is utilized to develop numeric solution of resulting issue. Graphs have been composed just to explore that how concentration and the temperature are impacted by different developing flow factors. Mass and heat transport rates are additionally tabulated and dissected. Furthermore, the temperature and concentration distributions are enhanced for larger thermophoresis parameter.

Utilization of Maple-based Physics Computation in Determining the Dynamics of Tippe Top

Tippe top is an example of simple moving system of rigid body with non-holonomic constraint, but the analysis of this system is not simple. A tippe top equation has been derived with Routhian reduction method and Poincaré equation, and physics computation in finding numeric solution of the dynamics of the tippe top has also been utilized by using Maple program. However, the Poincaré equation required that quasi-coordinate of the quasi-velocity is found, while in the case of the dynamics of tippe top, there is not any exact solution of the quasi-coordinate of the quasi-velocity was found. Therefore, the tippe top equation should be reduced to solve the problem. In this research, Routhian reduction was employed so that the Routhian reduction-based Poincaré equation was used to derive the tippe top equation. The method was able to derive a tippe top equation on a flat plane and tube inner surface clearly represented differential equations.