10,636 research outputs found
Thermoelastic analysis of solar cell arrays and their material properties
Announced report discusses experimental test program in which five different solar cell array designs were evaluated by subjecting them to 60 thermal cycles from minus 190 deg to 0.0 deg. Results indicate that solder-coated cells combined with Kovar n-interconnectors and p-interconnectors are more durable under thermal loading than other configurations
Coherent state triplets and their inner products
It is shown that if H is a Hilbert space for a representation of a group G,
then there are triplets of spaces F_H, H, F^H, in which F^H is a space of
coherent state or vector coherent state wave functions and F_H is its dual
relative to a conveniently defined measure. It is shown also that there is a
sequence of maps F_H -> H -> F^H which facilitates the construction of the
corresponding inner products. After completion if necessary, the F_H, H, and
F^H, become isomorphic Hilbert spaces. It is shown that the inner product for H
is often easier to evaluate in F_H than F^H. Thus, we obtain integral
expressions for the inner products of coherent state and vector coherent state
representations. These expressions are equivalent to the algebraic expressions
of K-matrix theory, but they are frequently more efficient to apply. The
construction is illustrated by many examples.Comment: 33 pages, RevTex (Latex2.09) This paper is withdrawn because it
contained errors that are being correcte
Nozzle performance calibration and turbomachinery operational analysis of Turbo-Powered Simulators (TPS) for the NASA-Langley EET propulsion airframe integration investigation
The Boeing flight simulator chamber facility energy efficient transport (EET) propulsion/airframe integration investigation was tested. Two turbopowered simulators (TPS) were calibrated with four different nacelle configurations. Two nacelle configurations were calibrated on each TPS, each calibration simulating the full nozzle pressure ratio range encountered in a one atmosphere total pressure wind tunnel operating over a Mach number range from 0.70 to 0.90 Mach. The results of the calibration test are in the form of velocity and discharge coefficient which is used in determining the simulator thrust while the TPS is operating in the wind tunnel
The Tamm-Dancoff Approximation as the boson limit of the Richardson-Gaudin equations for pairing
A connection is made between the exact eigen states of the BCS Hamiltonian
and the predictions made by the Tamm-Dancoff Approximation. This connection is
made by means of a parametrised algebra, which gives the exact quasi-spin
algebra in one limit of the parameter and the Heisenberg-Weyl algebra in the
other. Using this algebra to construct the Bethe Ansatz solution of the BCS
Hamiltonian, we obtain parametrised Richardson-Gaudin equations, leading to the
secular equation of the Tamm-Dancoff Approximation in the bosonic limit. An
example is discussed in depth.Comment: Submitted to the proceedings of the Group28 conference
(Newcastle-upon-Tyne, UK). Journal of Physics: Conference Serie
An exactly solvable model of a superconducting to rotational phase transition
We consider a many-fermion model which exhibits a transition from a
superconducting to a rotational phase with variation of a parameter in its
Hamiltonian. The model has analytical solutions in its two limits due to the
presence of dynamical symmetries. However, the symmetries are basically
incompatible with one another; no simple solution exists in intermediate
situations. Exact (numerical) solutions are possible and enable one to study
the behavior of competing but incompatible symmetries and the phase transitions
that result in a semirealistic situation. The results are remarkably simple and
shed light on the nature of phase transitions.Comment: 11 pages including 1 figur
Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Diagnosis and Management in Young People: A Primer
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex disease that affects children and adolescents as well as adults. The etiology has not been established. While many pediatricians and other health-care providers are aware of ME/CFS, they often lack essential knowledge that is necessary for diagnosis and treatment. Many young patients experience symptoms for years before receiving a diagnosis. This primer, written by the International Writing Group for Pediatric ME/CFS, provides information necessary to understand, diagnose, and manage the symptoms of ME/CFS in children and adolescents. ME/CFS is characterized by overwhelming fatigue with a substantial loss of physical and mental stamina. Cardinal features are malaise and a worsening of symptoms following minimal physical or mental exertion. These post-exertional symptoms can persist for hours, days, or weeks and are not relieved by rest or sleep. Other symptoms include cognitive problems, unrefreshing or disturbed sleep, generalized or localized pain, lightheadedness, and additional symptoms in multiple organ systems. While some young patients can attend school, on a full or part-time basis, many others are wheelchair dependent, housebound, or bedbound. Prevalence estimates for pediatric ME/CFS vary from 0.1 to 0.5%. Because there is no diagnostic test for ME/CFS, diagnosis is purely clinical, based on the history and the exclusion of other fatiguing illnesses by physical examination and medical testing. Co-existing medical conditions including orthostatic intolerance (OI) are common. Successful management is based on determining the optimum balance of rest and activity to help prevent post-exertional symptom worsening. Medications are helpful to treat pain, insomnia, OI and other symptoms. The published literature on ME/CFS and specifically that describing the diagnosis and management of pediatric ME/CFS is very limited. Where published studies are lacking, recommendations are based on the clinical observations and practices of the authors
Control of trapped-ion quantum states with optical pulses
We present new results on the quantum control of systems with infinitely
large Hilbert spaces. A control-theoretic analysis of the control of trapped
ion quantum states via optical pulses is performed. We demonstrate how resonant
bichromatic fields can be applied in two contrasting ways -- one that makes the
system completely uncontrollable, and the other that makes the system
controllable. In some interesting cases, the Hilbert space of the
qubit-harmonic oscillator can be made finite, and the Schr\"{o}dinger equation
controllable via bichromatic resonant pulses. Extending this analysis to the
quantum states of two ions, a new scheme for producing entangled qubits is
discovered.Comment: Submitted to Physical Review Letter
Gamow-Teller transitions and deformation in the proton-neutron random phase approximation
We investigate reliability of Gamow-Teller transition strengths computed in
the proton-neutron random phase approximation, comparing with exact results
from diagonalization in full shell-model spaces. By allowing the
Hartree-Fock state to be deformed, we obtain good results for a wide variety of
nuclides, even though we do not project onto good angular momentum. We suggest
that deformation is as important or more so than pairing for Gamow-Teller
transitions.Comment: 8 pages, 5 figures; added references, clarified discussion with
regards to stabilit
- …