Power spectral density analysis

Equations for power spectral density function, and for root mean square of power spectral density functio

Analysis of the excited-state absorption spectral bandshape of oligofluorenes

We present ultrafast transient absorption spectra of two oligofluorene derivatives in dilute solution. These spectra display clear vibronic structure, which we analyze rigorously using a time-dependent formalism of absorption to extract the principal excited-state vibrational normal-mode frequencies that couple to the electronic transition, the configurational displacement of the higher-lying excited state, and the reorganization energies. We can model the excited-state absorption spectrum using two totally symmetric vibrational modes with frequencies 450 (dimer) or 400 cm$^{-1}$ (trimer), and 1666 cm$^{-1}$. The reorganization energy of the ground-state absorption is rather insensitive to the oligomer length at 230 meV. However, that of the excited-state absorption evolves from 58 to 166 meV between the oligofluorene dimer and trimer. Based on previous theoretical work [Shukla et al., Phys. Rev. B \textbf{67}, 245203 (2003)], we assign the absorption spectra to a transition from the $1B_u$ excited state to a higher-lying $mA_g$ state, and find that the energy of the excited-state transition with respect to the ground-state transition energy is in excellent agreement with the theoretical predictions for both oligomers studied here. These results and analysis permit profound understanding of the nature of excited-state absorption in $\pi$-conjugated polymers, which are the subject of general interest as organic semiconductors in the solid state.Comment: Resubmitted to J. Chem. Phys on 28 April 2010; 31 pages, 7 figure

Stability and control characteristics of an air-breathing missile configuration having a forward located inlet

An investigation was made to determine the aerodynamic characteristics of an airbreathing missile configuration having a forward located inlet. Control was provided by cruciform tail surfaces. Aerodynamic data were obtained for the body-tail configuration alone and with planar or cruciform wings. At Mach numbers from 2.86 to 4.63, the model had internal flow. At Mach numbers from 1.70 to 2.86, the internal duct was closed, and an inlet fairing was installed to simulate boost conditions

The Influence of Religion and Ethnonationalism on Public Attitudes towards Amnesty : Northern Ireland as a Case Study

The 2011 Northern Ireland Social and Political Attitudes Survey was collected by John D. Brewer and Bernadette C. Hayes and was funded by the Leverhulme Trust under the Compromise After Conflict Programme (Grant no. F/00/152/AK).Peer reviewedPostprin

Illuminance and luminance distributions of a prototype ambient illumination system for Space Station Freedom

Preliminary results of research conducted in the late 1970's indicate that perceptual qualities of an enclosure can be influenced by the distribution of illumination within the enclosure. Subjective impressions such as spaciousness, perceptual clarity, and relaxation or tenseness, among others, appear to be related to different combinations of surface luminance. A prototype indirect ambient illumination system was developed which will allow crew members to alter surface luminance distributions within an enclosed module, thus modifying perceptual cues to match crew preferences. A traditional lensed direct lighting system was compared to the prototype utilizing the full-scale mockup of Space Station Freedom developed by Marshall Space Flight Center. The direct lensed system was installed in the habitation module with the indirect prototype deployed in the U.S. laboratory module. Analysis centered on the illuminance and luminance distributions resultant from these systems and the implications of various luminaire spacing options. All test configurations were evaluated for compliance with NASA Standard 3000, Man-System Integration Standards