52 research outputs found
Thermally Induced Clamping Force Deviations in a Sensory Chuck for Thin-Walled Workpieces
Deviations between nominal and actual tolerances are a challenging problem during turning processes of thin-walled workpieces. One main cause of these deviations is the clamping force applied by the turning chuck to hold the workpiece. Due to the low stiffness of thin-walled workpieces, large workpiece deformations can occur even when clamping forces are low. For this reason, the clamping force needs to be precisely adjusted. A possible approach are chucks with integrated actuators. As a result of the more direct power transmission, these chucks have a potentially higher clamping force accuracy compared to conventional external actuation. However, integrated actuators are additional heart sources resulting in thermal loads and thermally induced deformations of the chuck components. Due to the resulting mechanical distortion of the chuck system, the precise adjustment of clamping forces is not possible. Thus, this paper evaluates the thermally induced clamping force deviations on a novel turning chuck with four integrated electric drives. A test bench is used to analyse both a single drive and the combination of all four drives regarding the temperature effect on the clamping force adjustability. A clamping force deviation of up to 26% is observed. Based on the measured chuck temperature, a compensation method is introduced leading to a clamping force accuracy of 96.9%
Microresonator Soliton Dual-Comb Spectroscopy
Rapid characterization of optical and vibrational spectra with high
resolution can identify species in cluttered environments and is important for
assays and early alerts. In this regard, dual-comb spectroscopy has emerged as
a powerful approach to acquire nearly instantaneous Raman and optical spectra
with unprecedented resolution. Spectra are generated directly in the electrical
domain and avoid bulky mechanical spectrometers. Recently, a miniature
soliton-based comb has emerged that can potentially transfer the dual-comb
method to a chip platform. Unlike earlier microcombs, these new devices achieve
high-coherence, pulsed mode locking. They generate broad, reproducible spectral
envelopes, which is essential for dual-comb spectroscopy. Here, dual-comb
spectroscopy is demonstrated using these devices. This work shows the potential
for integrated, high signal-to-noise spectroscopy with fast acquisition rates.Comment: 7 pages, 4 figure
Conclusions and implications of automation in space
Space facilities and programs are reviewed. Space program planning is discussed
Pulsed squeezed vacuum characterization without homodyning
Direct photon detection is experimentally implemented to measure the
squeezing and purity of a single-mode squeezed vacuum state without an
interferometric homodyne detection. Following a recent theoretical proposal
[arXiv quant-ph/0311119], the setup only requires a tunable beamsplitter and a
single-photon detector to fully characterize the generated Gaussian states. The
experimental implementation of this procedure is discussed and compared with
other reference methods.Comment: 8 pages, 7 figure
NASA Space applications of high-temperature superconductors
The application of superconducting technology in space has been limited by the requirement of cooling to near liquid helium temperatures. The only means of obtaining these temperatures has been with cryogenic fluids which severely limit mission lifetime. The development of materials with superconducting transition temperatures above 77 K has made superconducting technology more attractive and feasible for employment in aerospace systems. Here, potential applications of high temperature superconducting technology in cryocoolers, remote sensing, communications, and power systems are discussed
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The role of large-scale energy storage design and dispatch in the power grid: A study of very high grid penetration of variable renewable resources
We present a result of hourly simulation performed using hourly load data and the corresponding simulated output of wind and solar technologies distributed throughout the state of California. We examined how we could achieve very high-energy penetration from intermittent renewable system into the electricity grid. This study shows that the maximum threshold for the storage need is significantly less than the daily average demand. In the present study, we found that the approximate network energy storage is of the order of 186. GW. h/22. GW (approximately 22% of the average daily demands of California). Allowing energy dumping was shown to increase storage use, and by that way, increases grid penetration and reduces the required backup conventional capacity requirements. Using the 186. GW. h/22. GW storage and at 20% total energy loss, grid penetration was increased to approximately 85% of the annual demand of the year while also reducing the conventional backup capacity requirement to 35. GW. This capacity was sufficient to supply the year round hourly demand, including 59 GW peak demand, plus a distribution loss of about 5.3%. We conclude that designing an efficient and least cost grid may require the capability to capture diverse physical and operational policy scenarios of the future grid. © 2014 Elsevier Ltd
Quantum Chaotic Scattering in Microwave Resonators
In a frequency range where a microwave resonator simulates a chaotic quantum
billiard, we have measured moduli and phases of reflection and transmission
amplitudes in the regimes of both isolated and of weakly overlapping resonances
and for resonators with and without time-reversal invariance. Statistical
measures for S-matrix fluctuations were determined from the data and compared
with extant and/or newly derived theoretical results obtained from the
random-matrix approach to quantum chaotic scattering. The latter contained a
small number of fit parameters. The large data sets taken made it possible to
test the theoretical expressions with unprecedented accuracy. The theory is
confirmed by both, a goodness-of-fit-test and the agreement of predicted values
for those statistical measures that were not used for the fits, with the data
Perturbative regime of terahertz high-harmonics generation in topological insulators
In this Letter, terahertz high harmonic generation processes in topological
insulators of the bismuth and antimony chalcogenides family are investigated.
Field conversion efficiencies are determined and clean cubic and quintic
power-law scaling is observed for third and fifth harmonics, up to driving
terahertz fields of 140 kV/cm. This is in contrast to all previous experiments
on terahertz harmonics generation in Dirac materials where a non-perturbative
regime has been observed already at few 10s kV/cm driving fields. Our nonlinear
THz spectroscopy experiments are complemented by THz pump - optical probe
measurements showing distinctly different relaxation dynamics of the carriers
in the topologically-protected Dirac states at the surfaces and the bulk. The
THz-induced dynamics of surface states reveal ultrafast relaxation that
prevents accumulation effects, and results in a clear perturbative regime of
THz harmonics generation that is different to graphene or Dirac semimetals with
their slower relaxation times in the few ps regime
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