7,739 research outputs found
PCPro a Novel Technology for Rapid Prototyping and Rapid Manufacturing
PCPro stands for Precise Cast Prototyping, which is a combination of casting technologies and
milling. This method was developed at Fraunhofer IWS in Dresden, Germany. It is patented in
Germany [1] and is applied in the USA under US 10/794,936. The main goal for this
development was to shorten the process chain for making plastic prototypes accompanied by
higher quality. The casting technology was integrated in a machining center in order to enable a
high degree of automation and to avoid an external casting system. This means that Rapid
Manufacturing can be easily implemented using such an automated combination of casting and
machining.
This article describes the PCPro method by means of the fabrication of sample parts. The
advantages and the limitations in comparison to common Rapid Prototyping and Rapid
Manufacturing process chains will be discussed. In addition, the manufacturing of a prototype
machine is presented.Mechanical Engineerin
Few-Body States in Fermi-Systems and Condensation Phenomena
Residual interactions in many particle systems lead to strong correlations. A
multitude of spectacular phenomenae in many particle systems are connected to
correlation effects in such systems, e.g. pairing, superconductivity,
superfluidity, Bose-Einstein condensation etc. Here we focus on few-body bound
states in a many-body surrounding.Comment: 10 pages, proceedings 1st Asian-Pacific Few-Body Conference, needs
fbssuppl.sty of Few-Body System
Blood product transfusion in emergency department patients: A case-control study of practice patterns and impact on outcome
Definitions of comorbid conditions. (DOCX 13 kb
Investigation of nonlinear absorption processes with femtosecond light pulses in lithium niobate crystals
The propagation of high-power femtosecond light pulses in lithium niobate crystals (LiNbO3) is investigated experimentally and theoretically in collinear pump-probe transmission experiments. It is found within a wide intensity range that a strong decrease of the pump transmission coefficient at wavelength 388 nm fully complies with the model of two-photon absorption; the corresponding nonlinear absorption coefficient is betap~=3.5 cm/GW. Furthermore, strong pump pulses induce a considerable absorption for the probe at 776 nm. The dependence of the probe transmission coefficient on the time delay Deltat between probe and pump pulses is characterized by a narrow dip (at Deltat~=0) and a long (on the picosecond time scale) lasting plateau. The dip is due to direct two-photon transitions involving pump and probe photons; the corresponding nonlinear absorption coefficient is betar~=0.9 cm/GW. The plateau absorption is caused by the presence of pump-excited charge carriers; the effective absorption cross section at 776 nm is sigmar~=8×10^–18 cm^2. The above nonlinear absorption parameters are not strongly polarization sensitive. No specific manifestations of the relaxation of hot carriers are found for a pulse duration of ~=0.24 ps
Feynman versus Bakamjian-Thomas in Light Front Dynamics
We compare the Bakamjian-Thomas (BT) formulation of relativistic few-body
systems with light front field theories that maintain closer contact with
Feynman diagrams. We find that Feynman diagrams distinguish Melosh rotations
and other kinematical quantities belonging to various composite subsystem
frames that correspond to different loop integrals. The BT formalism knows only
the rest frame of the whole composite system, where everything is evaluated.Comment: 5 page
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