25,647 research outputs found
PanelWhiz - Efficient Data Extraction of Complex Panel Data Sets: An Example Using the German SOEP
This paper outlines a panel data retrieval program written for Stata/SE 10 or better, which allows easier accessing of complex panel data sets. Using a drop-down menu and mouse click system, the researcher selects variables from any and all available years of a panel study. The data is automatically retrieved and merged to form a "long file", which can be directly used by the Stata panel estimators. The system implements modular data cleaning programs called "plugins". Yearly updates to the data retrievals can be made automatically. Projects can be stored in libraries allowing modular administration and appending. The paper exemplifies the power of PanelWhiz using the example of the German SOEP (German Socio-Economic Panel Study).Panel data, storage, retrieval
Permeability measurements of two low-density phenolic-nylon chars Final report
Permeability measurements of low-density phenolic-nylon chars in gaseous nitrogen and heliu
On the relative intensity of Poisson’s spot
The Fresnel diffraction phenomenon referred to as Poisson’s spot or spot of Arago has, beside its
historical significance, become relevant in a number of fields. Among them are for example
fundamental tests of the super-position principle in the transition from quantum to classical physics
and the search for extra-solar planets using star shades. Poisson’s spot refers to the positive on-axis
wave interference in the shadow of any spherical or circular obstacle. While the spot’s intensity is equal
to the undisturbed field in the plane wave picture, its intensity in general depends on a number of
factors, namely the size and wavelength of the source, the size and surface corrugation of the
diffraction obstacle, and the distances between source, obstacle and detector. The intensity can be
calculated by solving the Fresnel–Kirchhoff diffraction integral numerically, which however tends to
be computationally expensive. We have therefore devised an analytical model for the on-axis intensity
of Poisson’s spot relative to the intensity of the undisturbed wave field and successfully validated it
both using a simple light diffraction setup and numerical methods. The model will be useful for
optimizing future Poisson-spot matter-wave diffraction experiments and determining under what
experimental conditions the spot can be observed
First-principles study on scanning tunneling microscopy images of hydrogen-terminated Si(110) surfaces
Scanning tunneling microscopy images of hydrogen-terminated Si(110) surfaces
are studied using first-principles calculations. Our results show that the
calculated filled-state images and local density of states are consistent with
recent experimental results, and the empty-state images appear significantly
different from the filled-state ones. To elucidate the origin of this
difference, we examined in detail the local density of states, which affects
the images, and found that the bonding and antibonding states of surface
silicon atoms largely affect the difference between the filled- and empty-state
images.Comment: 4 pages, and 4 figure
Determination of Strong-Interaction Widths and Shifts of Pionic X-Rays with a Crystal Spectrometer
Pionic 3d-2p atomic transitions in F, Na, and Mg have been studied using a bent crystal spectrometer. The pionic atoms were formed in the production target placed in the external proton beam of the Space Radiation Effects Laboratory synchrocyclotron. The observed energies and widths of the transitions are E=41679(3) eV and Γ=21(8) eV, E=62434(18) eV and Γ=22(80) eV, E=74389(9) eV and Γ=67(35) eV, in F, Na, and Mg, respectively. The results are compared with calculations based on a pion-nucleus optical potential
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