A control volume finite‐element method for numerical simulating incompressible fluid flows without pressure correction

This paper presents a numerical model to study the laminar flows induced in confined spaces by natural convection. A control volume finite‐element method (CVFEM) with equal‐order meshing is employed to discretize the governing equations in the pressure–velocity formulation. In the proposed model, unknown variables are calculated in the same grid system using different specific interpolation functions without pressure correction. To manage memory storage requirements, a data storage format is developed for generated sparse banded matrices. The performance of various Krylov techniques, including Bi‐CGSTAB (Bi‐Conjugate Gradient STABilized) with an incomplete LU (ILU) factorization preconditioner is verified by applying it to three well‐known test problems. The results are compared to those of independent numerical or theoretical solutions in literature. The iterative computer procedure is improved by using a coupled strategy, which consists of solving simultaneously the momentum and the continuity equation transformed in a pressure equation. Results show that the strategy provides useful benefits with respect to both reduction of storage requirements and central processing unit runtime. Copyright © 2006 John Wiley & Sons, Ltd.     

Amino acids in the syntheses of heterocyclic systems: Syntheses and radiostability of novel biologically active triazoles containing the sulfonamide moiety

A number of novel triazoles 2a–f, 4, 9, 10, 12, 15 ; triazolothiadiazoles 6, 8, 11, 16 ; triazolothiadiazine 5 ; and triazolotriazine 14 were synthesized and characterized by elemental analyses and spectral data. Six of the compounds showed antifungal activity compared with the fungicide Mycostatine. Radiosterilization of the biologically active compounds 4, 8, 9b , and 10 in the dry state may prove to be applicable at the sterile dose 25 kGy. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:316–323, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10037     

Boosting COVID-19 Image Classification Using MobileNetV3 and Aquila Optimizer Algorithm

Currently, the world is still facing a COVID-19 (coronavirus disease 2019) classified as a highly infectious disease due to its rapid spreading. The shortage of X-ray machines may lead to critical situations and delay the diagnosis results, increasing the number of deaths. Therefore, the exploitation of deep learning (DL) and optimization algorithms can be advantageous in early diagnosis and COVID-19 detection. In this paper, we propose a framework for COVID-19 images classification using hybridization of DL and swarm-based algorithms. The MobileNetV3 is used as a backbone feature extraction to learn and extract relevant image representations as a DL model. As a swarm-based algorithm, the Aquila Optimizer (Aqu) is used as a feature selector to reduce the dimensionality of the image representations and improve the classification accuracy using only the most essential selected features. To validate the proposed framework, two datasets with X-ray and CT COVID-19 images are used. The obtained results from the experiments show a good performance of the proposed framework in terms of classification accuracy and dimensionality reduction during the feature extraction and selection phases. The Aqu feature selection algorithm achieves accuracy better than other methods in terms of performance metrics.     

Synthesis and properties of derivatives of sym-triazine. 5. Synthesis and mass spectrometric study of carbamide derivatives of sym-triazine

The reaction of 2-amino- and 2,4-diamino-sym-triazines with nitrourea and phenyl isocyanate was studied; it gives N-mono- and N,N-disubstituted ureas that contain sym-triazine segments. General features were established for the decomposition of carbamide derivatives of sym-triazine under electron impact.For communication 4, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 356–362, March, 1987.     

Effect of the server capacity distribution on the optimal control of a bulk service queueing system

In this paper the optimal control of a single-channel bulk service queueing system with random server capacity is investigated. Given an accumulation level r, the server stops processing new customers whenever the queue falls below r and resumes service when the queue reaches level r again. Server capacity becomes random following an idle period. A quick search procedure is designed to determine the value of r that yields the minimum expected total cost per unit of time. The effect of the server capacity distribution on the optimal control is then studied. Finally, a sensitivity analysis is conducted in order to assess the extent to which our results are valid.     

Gold and Silver Thin Film Analysis by Optical and Neutron Activation Techniques

Thicknesses of gold and silver thin films have been determined by NAA technique. Reasonable agreement with conventional optical method has been obtained, but the lower detection limit in the case of NAA is far better than in the optical method.

Es wurde die Dicke von Gold- und Silberfilmen mittels NAA-Technik bestimmt. Dabei konnte eine vernünftige Übereinstimmung mit der konventionellen optischen Methode erzielt werden, wobei im Falle der NAA die untere Nachweis grenze wescntlich besser war als vergleichsweise die optische Methode.     

The geometry of matrix eigenvalue methods

This paper explores the relations between the matrix Riccati equation and the standard matrix eigenvalue methods. It is demonstrated that the mathematics of the analysis of the two objects is essentially the same; consisting of the analysis of flows on the homogeneous spaces of various Lie groups.Supported in part by DOE Contract DE-ACOL-80RA-5256.Supported in part by DOE Contract DE-ACOL-80RA-5256 and by NASA Grant DAG2-82.     

Laser-based characterization of a flame-assisted plasma

A well-characterized flame-assisted plasma was developed to understand the role of flow nonuniformities and plasma/wall interactions in plasma devices for use in validation of laser-based Doppler shift spectroscopic methods. A hydrogen/oxygen capillary diffusion flame burner was used as a plasma source, with barium seeded into the reactants to provide a source of ions and electrons. For analysis the plasma was assumed to be a stationary, partially ionized, collision dominated, thermal plasma consisting of barium ions, electrons, and neutrals between two parallel-plate electrodes. The plasma was examined in terms of the continuum equations for ions and electrons, together with Poisson's equation to predict spatial profiles of electron and positive ion density and potential as functions of applied potential. First an analytic solution based on constant plasma properties and negligible difusion was introduced. The model was then extended by including effects of diffusion and variable plasma properties. Experimentally, current/voltage characteristics of the plasma were measured conventionally, relative ion concentration and temperature were measured with laser-induced fluorescence, and local potential distribution was measured using an electrostatic probe. The diffusionless theory predicted well the bulk behavior of the plasma, but not the correct spatial distributions of ion concentration and potential. The extended model produced a more satisfactory fit to the data. At conditions of 1.4 equivalence ratio, 70 torn pressure, 300 ppm seed concentration, and 100–400 V applied potentials, electric fields of the order of 10², 10³ V/cm were observed near the powered electrode, and of few tens of V/cm in the hulk of tire plasma. The field strength in the sheath ensures the operation of the Doppler shift diagnostics, once the recommendations tor LIF signal detectability are fulfilled.     

Gel-type polyacrylic resins cross-linked with trimethylolpropanetrimethacrylate: the issue of their nanostructure and molecular accessibility unveiled with a combination of inverse steric exclusion chromatography (ISEC), and ESR and CP-MAS 13C NMR spectroscopy

Six gel-type functional resins, that is, three poly-DMAA-co-TMPTP (DMAA = N,N-dimethylacrylamide, TMPTP = trimethylolpropyltrimethacrylate) samples with different degrees of cross-linking (0.6, 1.2, 1.7 % mol) and three poly-DMAA-co-MA-co-TMPTP (MA = methacrylic acid, ca. 5.5 % mol) samples with 1.7, 3.5, and 7 % mol cross-linking were investigated with ISEC (inverse steric exclusion chromatography), and ESR and CP-MAS (cross polarization magic angle spinning) 13C NMR spectroscopy after swelling in water and other solvents. This unprecedented combination of conceptually independent physicochemical techniques provides a thorough overall consistent picture of the morphology of the resins on the nanometer scale and of the molecular accessibility of the swollen polymer framework to the paramagnetic probe TEMPONE (2,2,6,6-tetramethyl-4-oxo-1-oxypiperidine) and to selected solvents.