492 research outputs found
Optimization of Zero Net-mass Flow Actuators for Aero-optics Applications
Using experimental methods, zero net-mass flow actuators were optimized to manipulate flow around an airborne laser turret in order to reduce destructive aero-optics effects. Synthetic jets are created by 50 mm and 27 mm piezoelectric disk actuators. Our optimization process involved identifying an actuator’s cavity size, driving frequency, and amplitude to achieve the strongest, most consistent jet possible. The effects of driving a single actuator versus driving two actuators in or out of phase with one another were also investigated. An initial cavity depth was determined using the Helmholtz resonator cavity approximation which estimates the ideal cavity depth for a given resonance frequency. Hotwires were used to collect data and time series for the velocity profile of each actuator at different cavity depths, driving frequencies, and amplitudes. The length and area of the resonance cavity’s opening slot are being held constant throughout our optimization process. When operating at optimized cavity and input settings, the piezoelectric disk actuators were found to produce synthetic jets with velocities as high as 90 m/s. Two local maxima for synthetic jet velocities were located at driving frequencies approximating those of the piezoelectric actuators and resonance cavity. Changing the phase and number of actuators resulted in similar velocities, but at a different distribution of driving frequencies. The effects of the synthetic jets produced by these actuators on the flow acting over a spherical turret is being analyzed in wind tunnel testing utilizing flow visualization and pressure measurements
Optimization of Zero Net-mass Flow Actuators for Aero-optics Applications
Using experimental methods, zero net-mass flow actuators were optimized to manipulate flow around an airborne laser turret in order to reduce destructive aero-optics effects. Synthetic jets are created by 50 mm and 27 mm piezoelectric disk actuators. Our optimization process involved identifying an actuator’s cavity size, driving frequency, and amplitude to achieve the strongest, most consistent jet possible. The effects of driving a single actuator versus driving two actuators in or out of phase with one another were also investigated. An initial cavity depth was determined using the Helmholtz resonator cavity approximation which estimates the ideal cavity depth for a given resonance frequency. Hotwires were used to collect data and time series for the velocity profile of each actuator at different cavity depths, driving frequencies, and amplitudes. The length and area of the resonance cavity’s opening slot are being held constant throughout our optimization process. When operating at optimized cavity and input settings, the piezoelectric disk actuators were found to produce synthetic jets with velocities as high as 90 m/s. Two local maxima for synthetic jet velocities were located at driving frequencies approximating those of the piezoelectric actuators and resonance cavity. Changing the phase and number of actuators resulted in similar velocities, but at a different distribution of driving frequencies. The effects of the synthetic jets produced by these actuators on the flow acting over a spherical turret is being analyzed in wind tunnel testing utilizing flow visualization and pressure measurements
Cricket and yellow mealworm powders promote higher bioaccessible fractions of mineral elements in functional bread
The application of cricket and yellow mealworm powders to improve the mineral bioaccessibility of bread was investigated. Breads enriched with 10% cricket (CPB-10%) and 10% yellow mealworm (YMPB-10%) powders showed a 1.5-, 2.95-, and 1.22-fold increase in proteins, total lipids, and fibers, respectively, compared to the reference white wheat bread (WFB-100%). Compared to reference bread, a significant increase in the essential amino acids valine (9.72%) and tyrosine (1.86%) contents was observed in the CPB-10% and YMPB-10%. The
MUFAs account for 35.22% in CPB-10%, 30.77% in YMPB-10%, and 32.34% in WFB-100%. In vitro digestion experiments showed a higher bioaccessibility of Na, K, Ca, Mg, P, Fe, Zn, Mn, and Li from insect bread than from white bread. Only Cu was more bioaccessible from FB-100% than from insect bread. The results shed light on the possible contribution of insect bread consumption to mitigate deficiencies in several important macro- and microelements
Fermi liquid identities for the Infinite U Anderson Model
We show how the electron gas methods of Luttinger, Ward and Nozi\`eres can be
applied to the infinite U Anderson impurity model within a Schwinger boson
treatment. Working to all orders in a 1/N expansion, we show how the Friedel
Langreth relationship, the Yamada-Yosida-Yoshimori and the Shiba-Korringa
relations can be derived, under the assumption that the spinon and holon fields
are gapped. One of the remarkable features of this treatment, is that the
Landau amplitudes depend on the exchange of low energy virtual spinons and
holons. We end the paper with a discussion on the extension of our approach to
the lattice, where the spinon-holon is expected to close at a quantum critical
point.Comment: 18 pages. Version 2 revised after referees comment
The effect of irradiation-induced disorder on the conductivity and critical temperature of the organic superconductor -(BEDT-TTF)Cu(SCN)
We have introduced defects into clean samples of the organic superconductor
-(BEDT-TTF)Cu(SCN) in order to determine their effect on the
temperature dependence of the conductivity and the critical temperature . We find a violation of Matthiessen's rule that can be explained by a model
of the conductivity involving a defect-assisted interlayer channel which acts
in parallel with the band-like conductivity. We observe an unusual dependence
of on residual resistivity which is not consistent with the
generalised Abrikosov-Gor'kov theory for an order parameter with a single
component, providing an important constraint on models of the superconductivity
in this material
Large scale Optimal Transportation Meshfree (OTM) Simulations of Hypervelocity Impact
Large scale three-dimensional numerical simulations of hypervelocity impact of Aluminum alloy 6061-T6 plates by Nylon 6/6 cylindrical
projectile have been performed using the Optimal Transportation Meshfree (OTM) method of Li et al. [7] along with the seizing contact
and variational material point failure algorithm [17, 18]. The dynamic response of the Al6061-T6 plate including phase transition in the
high strain rate, high pressure and high temperature regime expected in our numerical analysis is described by the use of a variational
thermomechanical coupling constitutive model with SESAME equation of state, rate-dependent J2 plasticity with power law hardening
and thermal softening and temperature dependent Newtonian viscosity. A polytropic type of equation of state fit to in-house ReaxFF
calculations is employed to model the Nylon 6/6 projectile under extreme conditions. The evaluation of the performance of the numerical
model takes the form of a conventional validation analysis. In support of the analysis, we have conducted experiments over a range of
plate thicknesses of [0.5, 3.0] mm, a range of impact velocities of [5.0, 7.0]km/s and a range of obliquities of [0, 70]° at Caltech's Small
Particle Hypervelocity Range (SPHIR) Facility. Large scale three-dimensional OTM simulations of hypervelocity impact are performed
on departmental class systems using a dynamic load balancing MPI/PThreads parallel implementation of the OTM method. We find
excellent full field agreement between measured and computed perforation areas, debris cloud and temperature field
Innovative interstellar explorer
An interstellar "precursor" mission has been under discussion in the scientific community for at least 30 years. Fundamental scientific questions about the interaction of the Sun with the interstellar medium can only be answered with in situ measurements that such a mission can provide. The Innovative Interstellar Explorer (IIE) and its use of Radioisotope Electric Propulsion (REP) is being studied under a NASA "Vision Mission" grant. Speed is provided by a combination of a high-energy launch, using current launch vehicle technology, a Jupiter gravity assist, and long-term, low-thrust, continuous acceleration provided by an ion thruster running off electricity provided by advanced radioisotope electric generators. A payload of ten instruments with an aggregate mass of ~35 kg and requiring ~30 W has been carefully chosen to address the compelling science questions. The nominal 20-day launch window opens on 22 October 2014 followed by a Jupiter gravity assist on 5 February 2016. The REP system accelerates the spacecraft to a "burnout" speed of 7.8 AU per year at 104 AU on 13 October 2032 (Voyager 1's current speed is ~3.6 AU/yr). The spacecraft will return at least 500 bits per second from at least 200 AU ~30 years after launch. Additional (backup) launch opportunities occur every 13 months to early 2018. In addition to addressing basic heliospheric science, the mission will ensure continued information on the far-heliospheric galactic cosmic ray population after the Voyagers have fallen silent and as the era of human Mars exploration begins
No Far-Infrared-Spectroscopic Gap in Clean and Dirty High-T Superconductors
We report far infrared transmission measurements on single crystal samples
derived from BiSrCaCuO. The impurity scattering rate of
the samples was varied by electron-beam irradiation, 50MeV O ion
irradiation, heat treatment in vacuum, and Y doping. Although substantial
changes in the infrared spectra were produced, in no case was a feature
observed that could be associated with the superconducting energy gap. These
results all but rule out ``clean limit'' explanations for the absence of the
spectroscopic gap in this material, and provide evidence that the
superconductivity in BiSrCaCuO is gapless.Comment: 4 pages and 3 postscript figures attached. REVTEX v3.0. Accepted for
publication in Phys. Rev. Lett. IRDIRT
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