Exploration of the helimagnetic and skyrmion lattice phase diagram inCu2OSeO3using magnetoelectric susceptibility

Omrani, A. A.,White, J. S.,Prš,a, K.,Ž,ivković,, I.,Berger, H.,Magrez, A.,Liu, Ye-Hua,Han, J. H.,Rønnow, H. M. American Physical Society 2014 Physical review. B, Condensed matter and materials Vol.89 No.6

Using superconducting quantum interference device magnetometry techniques, we have studied the change in magnetization versus applied ac electric field, i.e. the magnetoelectric (ME) susceptibility dM/dE, in the chiral-lattice ME insulator Cu2OSeO3. Measurements of the dM/dE response provide a sensitive and efficient probe of the magnetic phase diagram, and we observe clearly distinct responses for the different magnetic phases, including the skyrmion lattice phase. By combining our results with theoretical calculation, we estimate quantitatively the ME coupling strength as lambda = 0.0146 meV/(V/nm) in the conical phase. Our study demonstrates the ME susceptibility to be a powerful, sensitive, and efficient technique for both characterizing and discovering new multiferroic materials and phases.

ERROR ESTIMATES FOR A GALERKIN METHOD FOR A COUPLED NONLINEAR SCHRÖDINGER EQUATIONS

Omrani, Khaled,Rahmeni, Mohamed Korean Mathematical Society 2020 대한수학회보 Vol.57 No.1

In this paper, we approximate the solution of the coupled nonlinear Schrödinger equations by using a fully discrete finite element scheme based on the standard Galerkin method in space and implicit midpoint discretization in time. The proposed scheme guarantees the conservation of the total mass and the energy. First, a priori error estimates for the fully discrete Galerkin method is derived. Second, the existence of the approximated solution is proved by virtue of the Brouwer fixed point theorem. Moreover, the uniqueness of the solution is shown. Finally, convergence orders of the fully discrete Crank-Nicolson scheme are discussed. The end of the paper is devoted to some numerical experiments.

Effects of needle punching process and structural parameters on mechanical behavior of flax nonwovens preforms

Omrani, Fatma,Soulat, Damien,Ferreira, Manuela,Wang, Peng Techno-Press 2019 Advances in aircraft and spacecraft science Vol.6 No.2

The production of nonwoven fabrics from natural fibers is already expanding at an industrial level for simple curvature semi-structural part in the automotive industry. To develop their use for technical applications, this paper provides an experimental study of the mechanical behavior of flax-fiber nonwoven preforms. A comparison between different sets of carded needle-punched nonwoven has been used to study the influence of manufacturing parameters such as fibers' directions, the area and the needle punching densities. We have found that the anisotropy observed between both directions can be reduced depending on these parameters. Furthermore, this work investigates the possibility to form double curvature parts such as a hemisphere as well as a more complex shape such as a square box which possesses four triple curvature points. We propose a forming process adapted to the features of the nonwoven structure. The purpose is to determine their behavior under high stress during various forming settings. The preforming tests allowed us to observe in real time the manufacturing defects as well as the high deformability potential of flax nonwoven.

Improve the performance of CZTSSe solar cells by applying a SnS BSF layer

Omrani, Mir Kazem,Minbashi, Mehran,Memarian, Nafiseh,Kim, Dae-Hwan Elsevier 2018 Solid-State Electronics Vol.141 No.-

<P><B>Abstract</B></P> <P>In this study, the CZTSSe (Cu<SUB>2</SUB>ZnSn(S,Se)<SUB>4</SUB>) solar cells, with Al/ZnO:Al/ZnO (i)/CdS/CZTSSe/Mo structure, have been simulated. The simulation results have been compared and validated with real experimental results. Next, suggestions for improving the performance of CZTSSe solar cell have been provided. A SnS layer has been used as back surface field (BSF) layer. Different physical parameters of SnS layer are investigated, and the optimum values are selected. It has been found that by inserting a BSF layer with optimum parameters, the efficiency of CZTSSe solar cell increases from 12.3% to 17.25% due to enhancement of both short-circuit current density (Jsc) and open circuit voltage (Voc). For this optimized cell structure, the maximum Jsc = 37.37 mA<I>/</I>cm<SUP>2</SUP>, Voc = 0.605 V, and fill factor = 76.28% are obtained under 1.5 AM illumination.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highest achieved efficiency for CZTSSe. </LI> <LI> Comparison and validation of simulation with an experimental case. </LI> <LI> Proposing a simple, experimentally available and structurally matched BSF to increase the efficiency. </LI> <LI> Optimization of the BSF layer parameters. </LI> </UL> </P>

Error estimates for a Galerkin method for a coupled nonlinear Schr\"{o}dinger equations

Khaled Omrani,Mohamed Rahmeni 대한수학회 2020 대한수학회보 Vol.57 No.1

In this paper, we approximate the solution of the coupled nonlinear Schr\"odinger equations by using a fully discrete finite element scheme based on the standard Galerkin method in space and implicit midpoint discretization in time. The proposed scheme guarantees the conservation of the total mass and the energy. First, a priori error estimates for the fully discrete Galerkin method is derived. Second, the existence of the approximated solution is proved by virtue of the Brouwer fixed point theorem. Moreover, the uniqueness of the solution is shown. Finally, convergence orders of the fully discrete Crank-Nicolson scheme are discussed. The end of the paper is devoted to some numerical experiments.

Structure–rheology characterization of whey-less Feta cheese containing milk protein concentrate/soy protein isolate

Newsha Omrani Khiabanian,Ali Motamedzadegan,Shahram Naghizadeh Raisi,Mazdak Alimi 한국유변학회 2022 Korea-Australia rheology journal Vol.34 No.1

In this study, the properties of whey-less Feta cheese (WLFC) manufactured from milk protein concentrate (MPC) with the addition of soy protein isolate (SPI) were investigated. Six treatments were made using different ratios of MPC:SPI (12:0,10:2, 9:3, 8:4, 7:5, 6:6% w/v) and stored for 45 days. Then, the textural properties, rheological behavior of samples, and microstructural and sensory features were evaluated. Furthermore, FTIR spectroscopy was used to provide spectral data on the protein, acids, carbohydrates, lipids, and water. The results showed that different concentrations of SPI significantly affected pH, acidity, total solids (TS), and color parameters. So that, by increasing SPI concentration, the lightness and greenness decreased, and the yellowness increased. The viscoelastic behavior of all samples demonstrated a higher G ′ compared to G ″. The replacement of MPC with SPI decreased G ′, G ″, and texture parameters. The images of the microstructure indicated a weak structure with a more open protein network in WLFCs fortified with high levels of SPI (5, 6%). In conclusion, results showed that SPI could be a good substitution for MPC at a 2–3% concentration without negative effects on WLFCs.

Characterization and Comparison of TiN Coatings Deposited on Coarse- and Nano-grained Substrates

Mahla Seifzadeh Omrani,Mohsen Karimi,Mansoor Bozorg 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.2

In this study, TiN layers were deposited on coarse- and nano-grained (CG and NG) AISI 301 stainless steel sheets using theCathodic arc physical vapor deposition method. X-ray diffraction, Scanning electron microscopy, atomic force microscopy,Rockwell-C adhesion test, static contact angle test, electrochemical impedance spectroscopy, and polarization measurementwere employed to characterize and compare the coatings on different substrates. Under the same coating conditions (currentof 120 Amp, bias voltage of 100 V, pressure of 0.001 Torr, temperature range of 300–350 °C, and time of 90 min), muchgreater coating thickness was observed on the NG substrate. This was attributed to the epitaxial growth of the coatings onsubstrates and the difference in density of substrate grain-boundaries as high-energy nucleation sites for the TiN grains. Surface morphology observations showed a finer structure for the coating on the NG sample. Also, according to the resultsof the contact angle test the coating on the NG sample had more hydrophobicity, due to the higher density of the grainboundaries, and it confirmed the results of microscopic investigations. The coating layer exhibited an excellent adhesionquality to both substrates. The corrosion resistance was improved by grain refinement and also applying TiN coating so thatcoated NG sample had the best corrosion resistance.

GeneXpert MTB/RIF Testing in the Management of Patients with Active Tuberculosis; A Real Life Experience from Saudi Arabia

Ali S. Omrani,Mohammed F. Al-Otaibi,Souad M. Al-Ateah,Fahad M. Al-Onazi,Kamran Baig,Noura A. El-Khizzi,Ali M. Albarrak 대한감염학회 2014 Infection and Chemotherapy Vol.46 No.1

Background: GeneXpert MTB/RIF is a real-time PCR assay with established diagnostic performance in pulmonary and extra-pulmonaryforms of tuberculosis. The aim of this study was to assess the contribution of GeneXpert MTB/RIF assay to the management ofpatients with any form of active tuberculosis in a single large tertiary center in Saudi Arabia, with a special focus on the impact ontime to start of antituberculous therapy compared with Ziehl-Neelsen (ZN) smears and mycobacterial cultures. Materials and Methods: Clinical, radiological and laboratory records for all patients who were commenced on antituberculous therapybetween March 2011 and February 2013 were retrospectively reviewed. Results: A total of 140 patients were included, 38.6% of which had pulmonary tuberculosis. GeneXpert MTB/RIF was requested for only39.2% of patients and was the only reason for starting antituberculous therapy for only 12.1%. The median time to a positive GeneXpertMTB/RIF result was 0 days (IQR 3) compared with 0 day (IQR 1) for smear microscopy (P > 0.999) and 22 days (IQR 21) for mycobacterialcultures (P < 0.001). No patients discontinued antituberculous therapy because of a negative GeneXpert MTB/RIF result. Conclusions: In a setting wherein physicians are highly experienced in the diagnosis and treatment of tuberculosis, GeneXpertMTB/RIF was remarkably under-utilized and had only a limited impact on decisions related to starting or stopping antituberculoustherapy. Cost-effectiveness and clinical utility of routine testing of all smear-negative clinical samples submitted for tuberculosisinvestigations by GeneXpert MTB/RIF warrant further study.

Evaluation of stability in maize hybrids using univariate parametric methods

Seyed Habib Shojaei,Mostafavi Khodadad,Lak Amirparviz,Omrani Ali,Omrani Saeed,Mousavi Seyed Mohammad Nasir,Illés Árpád,Bojtor Csaba,János Nagy 한국작물학회 2022 Journal of crop science and biotechnology Vol.25 No.3

Genotype × environment interaction is one of the complex issues of breeding programs to produce high-yielding and compatible cultivars. Interaction of genotype × environment and make the more accurate selection, the performance and stability of hybrids need to be considered simultaneously. This study aimed to investigate stable genotypes with yield using 12 maize hybrids in different climatic conditions of Iran. The experimental design used was a randomized complete blocks design in three replications in two cropping years in Karaj, Birjand, Shiraz, and Arak stations. The simple analysis of variance performed on grain yield of genotypes indicated that all hybrids studied each year and station were significantly different in grain yield. Also, the combined analysis results showed a significant effect on the environment, the effects of genotype, and the interaction of genotype × environment and t in the studied hybrids different. Comparing Duncan's mean on the data obtained from the research, KSC705 genotypes with an average yield of 7.21 and KSC704 genotype with an average yield of 7.04 were identified as high yield cultivars. In order to identify stable cultivars, six stability parameters were used. KSC260 and KSC707 genotypes had stability Based on the environmental variance, also had stability based KSC705, KSC707 genotype on environmental the coefficient of variation, and KSC260 genotypes had stability based methods of genotype and environment interaction. As well as based on Eberhart and Russell regression coefficient had the stability to KSC400 and SC647 genotypes. Also, they were identified as the most stable genotypes based on the detection coefficient method, KSC707, and KSC703 genotypes.

A FOURTH-ORDER ACCURATE FINITE DIFFERENCE SCHEME FOR THE EXTENDED-FISHER-KOLMOGOROV EQUATION

Kadri, Tlili,Omrani, Khaled Korean Mathematical Society 2018 대한수학회보 Vol.55 No.1

In this paper, a nonlinear high-order difference scheme is proposed to solve the Extended-Fisher-Kolmogorov equation. The existence, uniqueness of difference solution and priori estimates are obtained. Furthermore, the convergence of the difference scheme is proved by utilizing the energy method to be of fourth-order in space and second-order in time in the discrete $L^{\infty}-norm$. Some numerical examples are given in order to validate the theoretical results.