Subwavelength imaging with two symmetrical interfaces by dielectric-tube photonic crystals

As distinct from coated photonic crystals, in this paper we propose a novel one that is made of dielectric tubes arranged in a close-packet square lattice. Without metallic cores, this structure is low-loss and convenient to fabricate. A left-handed frequency region is found in the second band by dispersion characteristic analysis. Without inactive modes for the transverse electric mode, negative refraction and subwavelength imaging are demonstrated by the finite-difference time-domain simulations with two symmetrical interfaces, i.e. Gamma X and Gamma M.

Enhancement of three-photon absorption cross-sections in a novel class of symmetrical charge transfer fluorene-based molecules

The three-photon absorption effect (3PA) of two novel symmetrical charge transfer fluorene-based molecules (abbreviated as BASF and BMOSF) has been determined by using a Q-switched Nd:YAG laser pumped with 38 ps pulses at 1064 nm in DMF. The measured 3PA cross-sections are 84 x 10(-78) and 114 x 10(-78) cm(6) s(2), respectively. The geometries and electronic excitations of these two molecules are systematically studied by PM3 and ZINDO/S methods. The relationships between 3PA cross-sections and intramolecular charge transfer are discussed micromechanically. The experimental and theoretical results have shown that the larger intramolecular charge transfer, which was characterized by the charge density difference between the ground state (SO) and the first excited state (S-I), the greater enhancement of the 3PA cross-sections. (c) 2005 Elsevier B.V. All rights reserved.

Theoretical investigation on the one- and two-photon absorption properties for a series of symmetrical charge transfer fluorene-phenylene and fluorene-thiophene derivatives

One- and two-photon absorption properties of a series of fluorene derivatives with symmetrical charge transfer D-IT-D and A-IT-A structural motifs have been theoretically investigated with ZINDO/S method. The optimized structures and the characterization of frontier molecular orbitals were obtained by using AMI calculations. Two-photon absorption properties of molecules have been studied using three-state model. The calculation results have shown that fluorene-thiophene derivatives exhibit larger two-photon absorption cross-section as compared with other studied molecules. To illustrate the results, the crucial effects of thiophene ring on fluorenethiophene derivatives and the net charge changes on the pi-conjugated bridges are analyzed theoretically. (c) 2006 Elsevier B.V. All rights reserved.

ETCS protokoloaren hedatzea simulazio hibridodun ingurune batean System-in-the-loop erreminta erabiliz.

[EU]Gaur egun, Europa mailan European Rail Traffic Management System (ERTMS) seinaleztapen-sistema bateratua hedatzen ari dira trenbide sare desberdinen arteko elkar eragintasuna bultzatzeko. Proiektu honen helburua da ERTMS sistemaren barneko ETCS protokoloa hedatzea simulazio hibridodun ingurune batean, ERTMS sistemaren hedatzea azkartuko duten erakusleak sortuz. Horretarako, OPNET simulagailuaren System-in-the-loop erreminta erabili da. Erreminta hau baliatuz ETCS protokoloaren pakete errealak ingurune simulatuan integratzeko funtzioen liburutegi bat idatzi da. Amaitzeko, liburutegi hori baliatuz ETCS protokoloak sareko arazoen aurrean duen errendimenduaren analisi bat burutu da eta liburutegi berri horrek pakete errealak simulatuetara itzultzean (eta kontrakoa) duen errendimendua zein den aztertu da.