30,226 research outputs found
Instrument accurately measures weld angle and offset
Weld angle is measured to the nearest arc minute and offset to one thousandth of an inch by an instrument designed to use a reference plane at two locations on a test coupon. A special table for computation has been prepared for use with the instrument
Tempered Fermions in the Hybrid Monte Carlo Algorithm
Parallel tempering simulates at many quark masses simultaneously, by changing
the mass during the simulation while remaining in equilibrium. The algorithm is
faster than pure HMC if more than one mass is needed, and works better the
smaller the smallest mass is.Comment: 4 pages, 2 figures, Combined proceedings for Lattice 97, Edinburgh
and the International Workshop 'Lattice QCD on Parallel Computers',
University of Tsukuba, Japa
Relaxed damage threshold intensity conditions and nonlinear increase in the conversion efficiency of an optical parametric oscillator using a bi-directional pump geometry
A novel bi-directional pump geometry that nonlinearly increases the nonlinear optical conversion efficiency of a synchronously pumped optical parametric oscillator (OPO) is reported. This bi-directional pumping method synchronizes the circulating signal pulse with two counter-propagating pump pulses within a linear OPO resonator. Through this pump scheme, an increase in nonlinear optical conversion efficiency of 22% was achieved at the signal wavelength, corresponding to a 95% overall increase in average power. Given an almost unchanged measured pulse duration of 260 fs under optimal performance conditions, this related to a signal wavelength peak power output of 18.8 kW, compared with 10 kW using the traditional single-pass geometry. In this study, a total effective peak intensity pump-field of 7.11 GW/cm(2) (corresponding to 3.55 GW/cm(2) from each pump beam) was applied to a 3 mm long periodically poled lithium niobate crystal, which had a damage threshold intensity of 4 GW/cm(2), without impairing crystal integrity. We therefore prove the application of this novel pump geometry provides opportunities for power-scaling of synchronously pumped OPO systems together with enhanced nonlinear conversion efficiency through relaxed damage threshold intensity conditions
Strong monotonicity in mixed-state entanglement manipulation
A strong entanglement monotone, which never increases under local operations
and classical communications (LOCC), restricts quantum entanglement
manipulation more strongly than the usual monotone since the usual one does not
increase on average under LOCC. We propose new strong monotones in mixed-state
entanglement manipulation under LOCC. These are related to the decomposability
and 1-positivity of an operator constructed from a quantum state, and reveal
geometrical characteristics of entangled states. These are lower bounded by the
negativity or generalized robustness of entanglement.Comment: 6 pages and 1 figure. A brief discussion about the connection to
asymptotic distillability was adde
X-Ray Diffraction Study of the Internal Structure of Supercooled Water
A Bragg X-ray spectrometer equipped with a volume-sensitive Geiger counter and Soller slits and employing filtered molybdenum Ka radiation was used to obtain a set of diffracted intensity curves as a Punction of angle for supercooled water. Diffracted intensity curves in the temperature region of 21 to -16 C were obtained. The minimum between the two main diffraction peaks deepened continuously with lowering temperature, indicating a gradual change in the internal structure of the water. No discontinuity in this trend was noted at the melting point. The internal structure of supercooled water was concluded to become progressively more ice-like as the temperature is lowered
Gluon Condensate and Non-Perturbative Quark-Photon Vertex
We evaluate the quark-photon vertex non-perturbatively taking into account
the gluon condensate at finite temperature. This vertex is related to the
previously derived effective quark propagator by a QED like Ward-Takahashi
identity. The importance of the effective vertex for the dilepton production
rate from a quark-gluon plasma is stressed.Comment: 9 pages including two figure
True Airspeed Measurement by Ionization-Tracer Technique
Ion bundles produced in a pulse-excited corona discharge are used as tracers with a radar-like pulse transit-time measuring instrument in order to provide a measurement of airspeed that is independent of all variables except time and distance. The resulting instrumentation need not project into the air stream and, therefore, will not cause any interference in supersonic flow. The instrument was tested at Mach numbers ranging from 0.3 to 3.8. Use of the proper instrumentation and technique results in accuracy of the order of 1 percent
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