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Modeling and optimization of cylindrical antennas using the mode-expansion method and genetic algorithms

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 6 2005
Dawei Shen
Abstract For monopole antennas with cylindrically symmetric structures, a mode-expansion method is highly time efficient, which is a realistic approach for integrating function-optimization tools, such as genetic algorithms (GAs), in order to extract the best bandwidth property. In this article, a mode-expansion method is used to simulate the impedance characteristics of the cylindrical antennas. As examples, two new types of monopole antennas are presented, one of which possesses a two-step top-hat structure while the other has an annulus around the stem. After the modeling scheme is examined for convergence and data validity, the associated optimization problem, with dimensions as decision variables, structural limitations as linear constraints, and desired bandwidth performance as an objective function, is solved using GAs. The effects of the geometric parameters on the impedance characteristics are investigated in order to demonstrate the optimality of the calculated solutions. Two optimized practical antennas are designed based on our numerical studies. One has a broad bandwidth of 3 GHz while the other shows a dual-band property, which can satisfy the bandwidth requirements for both Bluetooth (2.45-GHz band) and WLAN (5-GHz band) systems. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. [source]

Inclusion of the ligand field contribution in a polarizable molecular mechanics: SIBFA-LF,

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 16 2003
Jean-Philip Piquemal
Abstract To account for the distortion of the coordination sphere that takes place in complexes containing open-shell metal cations such as Cu(II), we implemented, in sum of interactions between fragments ab initio computed (SIBFA) molecular mechanics, an additional contribution to take into account the ligand field splitting of the metal d orbitals. This term, based on the angular overlap model, has been parameterized for Cu(II) coordinated to oxygen and nitrogen ligands. The comparison of the results obtained from density functional theory computations on the one hand and SIBFA or SIBFA-LF on the other shows that SIBFA-LF gives geometric arrangements similar to those obtained from quantum mechanical computations. Moreover, the geometric improvement takes place without downgrading the energetic agreement obtained from SIBFA. The systems considered are Cu(II) interacting with six water molecules, four ammonia or four imidazoles, and four water plus two formate anions. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1963,1970, 2003 [source]

Experiment, Experience and Observation in Eighteenth-Century Anthropology and Psychology , the Examples of Krüger's Experimentalseelenlehre and Moritz' Erfahrungsseelenkunde

ORBIS LITERARUM, Issue 2 2001
Carsten Zelle
This article situates the role of Johann Gottlieb Krüger (1715,1759), one representative of Halle's "reasonable doctors", as a link between Christian Wolff's empirical psychology and the anthropology of the late Enlightenment. Krüger's "Experimental Psychology" (1756) is analyzed, particularly the distinction drawn in his work between ,observation' and ,experiment' as experiential modi. Comparison between these modi and Karl Philipp Moritz' terminology of self-observation and observation of the other shows that experimental and empirical psychology are closer than previous research has assumed. [source]

Quinolin-6-ol at 100,K

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2009
Anna Michta
The title compound, C9H7NO, has two symmetry-independent molecules in the asymmetric unit, which have different conformations of the hydroxy group with respect to the quinoline ring. One of the molecules adopts a cis conformation, while the other shows a trans conformation. Each type of independent molecule links into a separate infinite O,H...N hydrogen-bonded chain with the graph-set notation C(7). These chains are perpendicular in the unit cell, one extended in the a -axis direction and the other in the b -axis direction. There is also a weak C,H...O hydrogen bond with graph-set notation D(2), which runs in the c -axis direction and joins the two separate O,H...N chains. The significance of this study lies in the comparison drawn between the experimental and calculated data of the crystal structure of the title compound and the data of several other derivatives possessing the hydroxy group or the quinoline ring. The correlation between the IR spectrum of this compound and the hydrogen-bond energy is also discussed. [source]