Tài liệu miễn phí Toán học

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Về vành nửa hoàn chỉnh có đế cốt yếu thỏa mãn điều kiện nội xạ bé

Một vành R được gọi là giả-Frobenius phải (gọi tắt là PF) nếu R là tự nội xạ phải, nửa hoàn chỉnh với đế phải cốt yếu. Bài viết đưa ra một số tính chất của vành nửa hoàn chỉnh với đế phải cốt yếu thỏa một số điều kiện về nội xạ bé.

9/25/2020 1:08:50 AM +00:00

Dạy học toán theo định hướng giáo dục quan điểm toàn diện cho sinh viên

Bài viết trình bày khái niệm về quan điểm toàn diện, cơ sở lý luận và yêu cầu của quan điểm toàn diện và việc giáo dục quan điểm toàn diện cho sinh viên (SV) Sư phạm Toán thông qua dạy học các học phần Toán ở các trường đại học.

9/25/2020 1:06:04 AM +00:00

Thiết kế một số hoạt động học tập phát triển năng lực tìm tòi, khám phá thế giới tự nhiên trong dạy học môn Khoa học lớp 4

Thiết kế một số hoạt động học tập phát triển năng lực tìm tòi, khám phá thế giới tự nhiên trong dạy học môn Khoa học lớp 4 là một trong những biện pháp thiết thực, đáp ứng được yêu cầu chương trình giáo dục phổ thông tổng thể hiện nay. Bài viết này gợi mở cho giáo viên dạy học môn khoa học lớp 4 thiết kế, thực hiện một số hoạt động học tập góp phần phát triển năng lực tìm tòi, khám phá thế giới tự nhiên cho học sinh lớp 4.

9/25/2020 1:05:58 AM +00:00

A survey of high efficiency context addaptive binary arithmetic coding hardware implementations in high efficiency video coding standard

This paper provides an overview of CABAC hardware implementations for HEVC targeting high quality, low power video applications, addresses challenges of exploiting it in different application scenarios and then recommends several predictive research trends in the future.

9/24/2020 9:40:57 PM +00:00

A comparison theorem for stability of linear stochastic implicit difference equations of index 1

In this paper we study linear stochastic implicit difference equations (LSIDEs for short) of index-1. We give a definition of solution and introduce an index-1 concept for these equations. The mean square stability of LSIDEs is studied by using the method of solution evaluation. An example is given to illustrate the obtained results.

9/24/2020 9:40:51 PM +00:00

The effect of residual la on crystal structure and magnetic properties of La1+ơFe11.05Si1.95 Compounds

In this paper, we present the results of the study of the effect of residual La on crystal structure, magnetic properties of La1+ơFe11.05Si1.95 (ơ= 0.00; 0.03; 0.06 and 0.09) compounds. The analysis of X-ray diffractions showed that when the La content increases to 9, the structure still remains cubic in a typical NaZn13 arrangement with unchanged lattice constant (about 0.5).

9/24/2020 9:40:45 PM +00:00

ℋ∞ Finite time boundedness for discrete time delay neural networks via reciprocally convex approach

This paper addresses the problem of ℋ∞ finite-time boundedness for discrete-time neural networks with interval-like time-varying delays. First, a delay-dependent finite-time boundedness criterion under the finite-time ℋ ∞ performance index for the system is given based on constructing a set of adjusted Lyapunov–Krasovskii functionals and using reciprocally convex approach.

9/24/2020 9:40:39 PM +00:00

Absorption of isopropanol on surface of defect silicene

In this work, we investigate the defect structure of silicene with a vancacy and the adsorption mechanism of isopropanol on the surface of defected silicene by employing the Density Functional Theory method.

9/24/2020 9:40:33 PM +00:00

A comparative study on two different methods for calculating gravity effect of an uneven layer: Application to computation of bouguer gravity anomaly in the east Vietnam sea and adjacent areas

This paper presents a comparative study of two different forward methods such as the space domain method and the frequency domain method. The performance of each method was evaluated on two synthetic models. Finally, the more effective method was applied to calculate Bouguer gravity anomaly in the East Vietnam Sea and adjacent areas using the latest available dataset from the TOPEX mission.

9/24/2020 9:40:27 PM +00:00

Optimization of laminated composite plates for maximum biaxial buckling load

This paper proposes an optimization procedure for maximization of the biaxial buckling load of laminated composite plates using the gradient-based interior-point optimization algorithm. The fiber orientation angle and the thickness of each lamina are considered as continuous design variables of the problem.

9/24/2020 9:40:20 PM +00:00

Ovalbumin based microlasers

In this work, biomaterial based microlasers were successfully fabricated by a cost effective, simple and environmental friendly method. The as-fabricated microlasers were made of biocompatible material including ovalbumin doped Rhodamine B at low weight percentage.

9/24/2020 9:40:14 PM +00:00

Hot filament CVD growth of vertically aligned carbon nanotubes on support materials for field electron emitters

In this work, we report a direct growth of the VACNTs on several substrates by using hot-filament chemical vapor deposition (hot-filament CVD) and a catalytic buffer-layer structure. The buffer layer was the aluminum (Al) thin film used together with iron (Fe) as the catalyst.

9/24/2020 9:40:08 PM +00:00

Synthesis and optical characterizations of the fluorescence silica nanoparticles containing quantum dots

The quantum dots coated by silica is fluorescence material class with great biocompatibility, low toxicity and water-solubility, that is suitable for bioapplications. This work presents the synthesis of SiO2 coated CdTe/ZnSe (named CdTe) quantum dots (CdTeaSiO2 nanoparticles) via a wet chemmical route called modified Stöber method.

9/24/2020 9:40:01 PM +00:00

Electronic thermal conductivity and thermoelectric performance of n-type PbBi4Te7

In this work, in the framework of density functional theory, we study the electronic thermal conductivity of the compound by employing the solution of Boltzmann Transport Equation in a constant relaxationtime approximation. The results show that the electronic thermal conductivity drastically increases with the increase of temperature and carrier concentration which have a detrimental effect on the thermoelectric performance.

9/24/2020 9:39:55 PM +00:00

Fabrication of sers substrates using au nanoparticles prepared by laser ablation in distilled water and detection of tetracycline at low concentrations

The high sensitivity of the AuNPs/Si substrates was confirmed by the SERS spectra of malachite green detected with high quality at concentrations of 0.1ppm. The SERS substrates can detect SERS spectra of tetracycline at low concentrations of around 1ppm.

9/24/2020 9:39:49 PM +00:00

Machine learning representation for atomic forces and energies

We present machine learning models for fast estimating atomic forces and energies. In our method, the total energy of a system is approximated as the summation of atomic energy which is the interaction energy with its surrounding chemical environment within a certain cutoff radius.

9/24/2020 9:39:43 PM +00:00

Toxic gases on B12 Borophene: The selective adsorption

In this work, the adsorption ability of β12 borophene towards some main harmful gases was investigated. The first-principles calculations were employed to obtain the adsorption configurations and the adsorption energies of CO, NO, CO2, NH3, and NO2 on 12 borophene. The vdW interactions are taken into account by using three functionals: revPBE-vdW, optPBE-vdW, and vdW-DF2.

9/24/2020 9:39:36 PM +00:00

DFT study on adsorption of acetone and toluene on silicene

In this work, we investigated the adsorption mechanism of acetone and toluene on the surface of silicene by the quantum simulation method. The images of the potential energy surfaces for different positions of the adsorbate on the silicene surface were explored by Computational DFTbased Nanoscope tool for determination of the most stable configurations and diffusion possibilities.

9/24/2020 9:39:30 PM +00:00

Microstructure and electrical properties of low-temperature Solution-processed Sol-gel KNN thin films

We report on an environmentally friendly and versatile chemical solution deposition route to K0.5Na0.5NbO3 (KNN) thin films. The excess amounts of K and Na in KNN precursor solutions was found to be strong influence on perovskite KNN single-phase thin films. It was revealed from Raman spectroscopic analysis data that a change in scattering mode was observed for the KNN thin films fabricated under various processing conditions.

9/24/2020 9:39:24 PM +00:00

Wavelet transform application based on matlab simulation

In this thesis, the two systems are simulated with particular parameters and the performance of Bit Error Rate (BER) is evaluated to determine the different types of wavelets in various channel conditions with separate modulation methods (8, 16, 32-QAM). Therefore, MIMO-OFDM system based on DWT algorithm will be compared with MIMO-OFDM system based on FFT algorithm by using MATLAB simulation software.

9/24/2020 9:39:18 PM +00:00

Theoretical kinetics study of The HO2 and C2H5OH: Hydrogen abstraction reaction

C2H5OH has been using as an alternative fuel for decades; HO2 also plays a pivotal role in the combustion. The kinetics and mechanism for the reaction between C2H5OH and HO2 radical have been investigated using the molecular parameters for the reactants, transition states and products predicted at the CCSD(T)//B3LYP/6-311++G(3df,2p) level of theory.

9/24/2020 9:39:12 PM +00:00

Adsorption of 2-butanone on pristine graphene: A first-principles study

This study investigates the adsorption mechanism of 2-butanone (ethyl methyl ketone) on the surface of graphene by using Density Functionals Theory (DFT). A 2-butanone molecule was chosen as a selected example of main volatile organic compounds (VOCs) in exhaled breath.

9/24/2020 9:39:05 PM +00:00

An efficient method for automatic recognizing text fields on identification card

It has obtained great results in theory as well as practical applications. However, the accuracy of identification is still limited, especially in the case of low-quality input images. In this article, we propose an efficient method to recognize information fields for identification in ID card using Convolutional Neural Network (CNN) and Long Short-Term Memory networks (LSTM).

9/24/2020 9:38:59 PM +00:00

Optical back propagation for nonlinear compensation in OFDM based long range passive optical networks

In this study, we propose an optical back propagation (OBP) approach for compensation of the nonlinear and dispersion distortions in direct-detection optical OFDM system. The proposed OBP using split-step Fourier method is implemented at transmitter that is suitable for high-rate OFDM-based LR-PONs applications.

9/24/2020 9:38:53 PM +00:00

Gas sensors based on u shaped graphene nanoribbons: A first principles study

In this paper, I present first-principle calculations which are performed by using combination of DFT and NEGF methods to investigate the adsorption of CO2 and NH3 molecules on straight and U-shaped GNRs junctions. The density of state, molecular orbital, adsorption energy, transmission spectrum, and current-voltage characteristics were analyzed.

9/24/2020 9:38:47 PM +00:00

Impact of parallel computing on study of time evolution of a quantum impurity system in response to a quench

In this paper, we estimate the scale of time consumption of such calculation in comparison to that of time-independent calculation, and present our solution to the problem by using parallel computing as implementing both MPI and OpenMP to the calculation. We also discuss the possibility to exploit parallel computing with GPU in the near future, and the preliminary results of time-dependent spectral function.

9/24/2020 9:38:41 PM +00:00

Phonon characterization, structural and optical properties of Type-II CdSe/CdTe core/shell and Type-II/type-I CdSe/CdTe/ZnS core/shell/shell quantum dots

The CdSe, type-II CdSe/CdTe core/shell and type-II/type-I CdSe/CdTe/ZnS core/shell/shell quantum dots (QDs) were successfully synthesized in a noncoordinating solvent. The phonon characterizations, optical properties and structures of the synthesized QDs were characterized by Raman scattering (RS) spectra, photoluminescence (PL) spectroscopy, PL-decay lifetime, absorption spectroscopy (Abs), and X-ray diffraction (XRD).

9/24/2020 9:38:34 PM +00:00

Gelation of anisotropic colloids with short range attraction

Colloidal gels are space-spanning networks that form solids at dilute particle volume fractions. The kinetic process of gelation is central to understand the flow of complex fluids. Here, we report a simulation study of colloidal gelation of anisotropic colloids with attractive Lennard Jones potential.

9/24/2020 9:38:28 PM +00:00

The ettingshausen effect in doped semiconductor superlattice under the influence of confined optical phonon

The electron – optical phonon scattering is considered in detail to studying the Ettingshausen effect in doped semiconductor superlattice under the influence of phonon confinement and laser radiation. The analytical expressions for tensors and the Ettingshausen coefficient are obtained by using the kinetic equation method.

9/24/2020 9:38:22 PM +00:00

Maximal inequalities for fractional brownian motion with variable drift

Let BH be a fractional Brownian motion with H∈ (0, 1) and g be a deterministic function. We study the asymptotic behaviour of the tail probability as for fixed x and as for fixed T. Our results partially generalise those obtained by Prakasa Rao in.

9/24/2020 9:38:16 PM +00:00