279,248 research outputs found
Design of a smart turning tool with application to in-process cutting force measurement in ultraprecision and micro cutting
In modern micromachining, there is a need to measure and monitor certain machining process parameters in process so as to detect tool wear in real time, to optimize the process parameters setup, and to render the machining process some level of smartness and intelligence. This paper presents the innovative design of a smart turning tool using two pieces of piezoelectric films to measure cutting and feed force in real time. The tool was tested on its performance through the calibration and cutting trials against the commercial dynamometer. The results show the smart turning tool has achieved the performance as designed
Every Good Virtue You Ever Wanted in a Q-switched Solid-state Laser and More: Monolithic, Diode-pumped, Self-q-switched, Highly Reproducible, Diffraction-limited Nd:yag Laser
The applications of Q-switched lasers are well known, for example, laser radar, laser remote sensing, satellite orbit determination, Moon orbit and 'moon quake' determination, satellite laser communication, and many nonlinear optics applications. Most of the applications require additional properties of the Q-switched lasers, such as single-axial and/or single-transverse mode, high repetition rate, stable pulse shape and pulse width, or ultra compact and rugged oscillators. Furthermore, space based and airborne lasers for lidar and laser communication applications require efficient, compact, lightweight, long-lived, and stable-pulsed laser sources. Diode-pumped solid-state lasers (DPSSL) have recently shown the potential for satisfying all of these requirements. We will report on the operating characteristics of a diode-pumped, monolithic, self-Q-switched Cr,Nd:YAG laser where the chromium ions act as a saturable absorber for the laser emission at 1064 nm. The pulse duration is 3.5 ns and the output is highly polarized with an extinction ratio of 700:1. It is further shown that the output is single-longitudinal-mode with transform-limited spectral line width without pulse-to-pulse mode competition. Consequently, the pulse-to-pulse intensity fluctuation is less than the instrument resolution of 0.25 percent. This self-stabilization mechanism is because the lasing mode bleaches the distributed absorber and establishes a gain-loss grating similar to that used in the distributed feedback semiconductor lasers. A repetition rate above 5 KHz has also been demonstrated. For higher power, this laser can be used for injection seeding an amplifier (or amplifier chain) or injection locking of a power oscillator pumped by diode lasers. We will discuss some research directions on the master oscillator for higher output energy per pulse as well as how to scale the output power of the diode-pumped amplifier(s) to multi-kilowatt average power
Simple choreographies of the planar Newtonian -body Problem
In the -body problem, a simple choreography is a periodic solution, where
all masses chase each other on a single loop. In this paper we prove that for
the planar Newtonian -body problem with equal masses, , there are
at least different main simple choreographies. This
confirms a conjecture given by Chenciner and etc. in \cite{CGMS02}.Comment: 31pages, 6 figures. Refinements in notations and proof
Plasma Lens Backgrounds at a Future Linear Collider
A 'plasma lens' might be used to enhance the luminosity of future linear
colliders. However, its utility for this purpose depends largely on the
potential backgrounds that may be induced by the insertion of such a device in
the interaction region of the detector. In this note we identify different
sources of such backgrounds, calculate their event rates from the elementary
interaction processes, and evaluate their effects on the major parts of a
hypothetical Next Linear Collider (NLC) detector. For plasma lens parameters
which give a factor of seven enhancement of the luminosity, and using the NLC
design for beam parameters as a reference, we find that the background yields
are fairly high, and require further study and improvements in detector
technology to avoid their impact.Comment: 14 pages incl. 3 figures; contributed to the 4th International
Workshop, Electron-Electron Interactions at TeV Energies, Santa Cruz,
California, Dec. 7 - 9, 2001. To be published in Int.Journ. Mod. Phys.
Recrystallization of epitaxial GaN under indentation
We report recrystallization of epitaxial (epi-) GaN(0001) film under
indentation.Hardness value is measured close to 10 GPa, using a Berkovich
indenter. Pop-in burst in the loading line indicates nucleation of dislocations
setting in plastic motion of lattice atoms under stress field for the
recrystallization process. Micro-Raman studies are used to identify the
recrystallization process. Raman area mapping indicates the crystallized
region. Phonon mode corresponding to E2(high) close to 570 cm-1 in the as-grown
epi-GaN is redshifted to stress free value close to 567 cm-1 in the indented
region. Evolution of A1(TO) and E1(TO) phonon modes are also reported to
signify the recrystallization process.Comment: 10 pages, 3 figures
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