Mathematical modeling of the magnetic properties of axisymmetric hard superconductors of the second kind in the Kim model

Authors perform mathematical modeling of magnetic properties, such as current distribution, intrinsic magnetic field and magnetization of a number of axisymmetric superconductors of the second kind, for example, of a sphere with the dependence of the critical current density on the local magnetic field in the Kim model. The simulation is based on equation that is integral with respect to coordinate and differential with respect to time. The equation describes time evolution of the critical current density and is solved numerically for a uniformly varying external magnetic field. The shape of the sample is set using a distorted rectangular irregular mesh with compaction to the edges of the sample. While solving the equation of current motion, the total magnetic field iscalculated at the points of the superconductor to calculate the value of the critical current density. In the article, the obtained solutions are used to visualize the current distribution in the volume of a superconductor and to construct magnetization hysteresis loops. Also, thanks to the calculations of the magnetic field in the center of the sample, the dependencies of the total penetration field for samples with different aspect ratios are obtained.

DETEKCIJA SARKAZMA U KOMENTARIMA SA REDDIT STRANICE

Analiza sentimenta je veoma zastup­ljena u istraživanjima danas. Deo problema određivanja sentimenta predstavlja detekcija sarkazma, jer on često može da navede model da zaključuje suprotno od tačnog. Ovaj fenomen se javlja zbog same prirode sarkazma: upotreba pozitivnih reči u cilju izražavanja negativnih osećanja. Tema ovog rada je detekcija sarkazma u komentarima, gde se on češće javlja u odnosu na druge tekstualne sadržaje. U ovom radu prikazani su različiti pristupi u rešavanju datog problema. Predloženi su razli­čiti klasifikacioni modeli – metod slučajnih šuma (engl. Random Forest), metod potpornih vektora (engl. Support Vector Machines - SVM), logistička regresija, kao i različite arhitekture neuronskih mreža – Yoon Kim model, konvolucioni model, rekurentni model i konvoluciono-rekurentni. Uporedo sa srodnim istraživanjima i ovim radom je pokazano da je detekcija sarkazma moguća i da se daljim unapređenjem modela tačnost može povećati i time doprineti značajnom poboljšanju analize sentimenta.

Optimation Free Space Optic (FSO) Design with Kim Model Using Space Diversity

The development of communication services in remote rural areas is difficult to use cable-based systems such as Digital Subscriber Line (DSL) and FTTx. One solution to solve this problem is to use a wireless system such as radio communication. Free Space Optic (FSO) communication system is a better choice compared to radio communication because of the flexibility of frequency usage. One of the problems of the FSO communication system is the range not too far. The range of the FSO can be increased by using the space diversity method. This study compared FSO systems that not use space diversity and FSO systems that use space diversity in three weather conditions, namely clear, haze, and fog. In taking data results using Kim model propagation with variations in the range between 100 – 2000 meters. The modulation used in this study is external modulation. The result of the analysis of FSO performance after adding space diversity, the range of FSO increases as far as 1200 meters when the condition is clear. During the haze condition, the FSO range increase as far as 800 meters. During the fog condition, the FSO range has increased as far as 300 meters. By adding space diversity, the Q-factor value has increased, and BER (Bit Error Rate) has decreased.

Roles of Clustering Coefficient for the Network Reconstruction

It is important to establish relations between the network reconstruction and the topological dynamical structure of networks. In this article, we quantify the effect for two types of network topologies on the performance of network reconstruction. First, we generate two network modes with variable clustering coefficient based on Holme-Kim model and Newman-Watts small-world model, then we reconstruct the artificial networks by using a novel framework called L1-norm minimization algorithm based on a theory called compressive sensing (CS), a framework for recovering sparse signals. The results of the simulation experiment show that the accuracy rate for the network reconstruction is a monotonically increasing function of the clustering coefficient in Holme-Kim model, whereas the opposite occurs in Newman-Watts small-world network. And this yet demonstrates that the larger the network size, the higher the accuracy rate. Morever, we compare the results of CS with orthogonal matching pursuit (OMP), a greedy algorithm. The results show that the accuracy rate of L1-norm minimization method is 10% higher than that of OMP, and OMP yields 1.2 times the computation speed of L1-norm minimization. Our work demonstrates that the topological structure of network has influence on the accurate reconstruction and it is helpful for offering proper method for the network reconstruction.

Coupled Numerical Approach for Automotive Battery Pack Lifetime Estimates With Thermal Management

This study combined a simple two-dimensional (2D) finite volume model (Kim model), which employs Ohm's law along with charge conservation over the electrodes and Butler–Volmer charge transfer kinetics for prismatic battery cells coupled with the single particle model (SPM) in order to model the thermal state of automotive battery packs. The objective here was to determine the effects of liquid cooling applied to the packs under standard driving cycles. A model developed by Kim provided a means for determining a nonuniform current distribution over the surface of the current collectors. The Kim model is based on the application of Ohm's law over a conducting medium, with empirical source terms representing current flowing into or out of an adjacent electrode layer. Here, a modeling advance is presented where empirical source terms in the Kim model were replaced with ones based on the chemistry and physics occurring inside the battery. As such, fundamental battery function was imparted to the model by integrating the SPM into the 2D finite volume Kim model. The 2D procedure described above was carried out on electrode sheets at different positions inside the cell, and determined thermal generation values that were mapped volumetrically into a heat transfer simulation, which, in turn, updated the electrochemical simulation. Capacity fade kinetics were determined by fitting experimental data to simulated results. With time-temperature profiles produced as described above for different pack cooling levels and varying degrees of cell degradation, a basic SPM simulation was then used with thermal overlays to estimate automotive cell life under various driving scenarios and various cooling levels. With these simulations, scenarios representing different thermal management regimes along with driving behavior were able to show the combined impact on automotive battery pack lifetimes.

The Calculation of Fourth-Rank Constitutive Parameters of Consistent Tangent Modulus and Plastic Modulus in Finite Element Analysis

Newton-Raphson method is used in global equilibrium for the numerical solution of elasto-plastic problems. It is necessary to determine the fourth-rank constitutive parameters of consistent tangent modulus in each integration point. Euler backward method and implicit stress integration is applied while constitutive model is implemented into ANSYS software. Take Chen, Jiao, and Kim model (2005) as an example, comparison of fourth-rank constitutive parameters and without fourth-rank constitutive parameters of consistent tangent modulus indicates that the convergence is obviously influenced by fourth-rank constitutive parameters of consistent tangent modulus for the larger load case, whereas the influence of plastic modulus is almost neglected.