38,926 research outputs found
Numerical Studies of the Compressible Ising Spin Glass
We study a two-dimensional compressible Ising spin glass at constant volume.
The spin interactions are coupled to the distance between neighboring particles
in the Edwards-Anderson model with +/- J interactions. We find that the energy
of a given spin configuration is shifted from its incompressible value, E_0, by
an amount quadratic in E_0 and proportional to the coupling strength. We then
construct a simple model expressed only in terms of spin variables that
predicts the existence of a critical value of the coupling above which the
spin-glass transition disappears.Comment: REVTeX, 4 pages, 4 figures. Submitted to Phys. Rev. Let
Evaluation of analysis techniques for low frequency interior noise and vibration of commercial aircraft
The application of selected analysis techniques to low frequency cabin noise associated with advanced propeller engine installations is evaluated. Three design analysis techniques were chosen for evaluation including finite element analysis, statistical energy analysis (SEA), and a power flow method using element of SEA (computer program Propeller Aircraft Interior Noise). An overview of the three procedures is provided. Data from tests of a 727 airplane (modified to accept a propeller engine) were used to compare with predictions. Comparisons of predicted and measured levels at the end of the first year's effort showed reasonable agreement leading to the conclusion that each technique had value for propeller engine noise predictions on large commercial transports. However, variations in agreement were large enough to remain cautious and to lead to recommendations for further work with each technique. Assessment of the second year's results leads to the conclusion that the selected techniques can accurately predict trends and can be useful to a designer, but that absolute level predictions remain unreliable due to complexity of the aircraft structure and low modal densities
CP nonconservation in the leptonic sector
In this paper we use an exact method to impose unitarity on moduli of
neutrino PMNS matrix recently determined, and show how one could obtain
information on CP nonconservation from a limited experimental information. One
suggests a novel type of global fit by expressing all theoretical quantities in
terms of convention independent parameters: the Jarlskog invariant and the
moduli , able to resolve the positivity problem of .
In this way the fit will directly provide a value for , and if it is
different from zero it will prove the existence of CP violation in the
available experimental data. If the best fit result, , from M.
Maltoni {\em et al}, [New J.Phys. {\bf 6} (2004) 122] is confirmed, it will
imply a new physics in the leptonic sector
HEAO 1 measurements of the galactic ridge
The HEAO A2 experiment data was systematically searched for unresolved galactic disc emission. Although there were suggestions of non-uniformities in the emission, the data were consistent with a disc of half-thickness 241 + 22 pc and surface emissivity (2-10 keV) at galactic radius R(kpc) of 2.2 10 to the minus 7th power exp(-R/3.5) erg/sq cm to the (-2)power/s (R 7.8 kpc). giving a luminosity of approximately 4.4 10 to the 37th power erg S to the (-1) power. If the model is extrapolated to radii less than 7.8 kpc, the unresolved disc emission is approximately 1.4 10 to the 38th power erg S to the (-1) power (2-10 keV) i.e., a few percent of the luminosity of the galaxy in resolved sources. the disc emission has a spectrum which is significantly softer than that of the high galactic latitude diffuse X-ray background and it is most probably of discrete source origin
A Census of X-ray gas in NGC 1068: Results from 450ks of Chandra HETG Observation
We present models for the X-ray spectrum of the Seyfert 2 galaxy NGC 1068.
These are fitted to data obtained using the High Energy Transmission Grating
(HETG) on the Chandra X-ray observatory. The data show line and radiative
recombination continuum (RRC) emission from a broad range of ions and elements.
The models explore the importance of excitation processes for these lines
including photoionization followed by recombination, radiative excitation by
absorption of continuum radiation and inner shell fluorescence. The models show
that the relative importance of these processes depends on the conditions in
the emitting gas, and that no single emitting component can fit the entire
spectrum. In particular, the relative importance of radiative excitation and
photoionization/recombination differs according to the element and ion stage
emitting the line. This in turn implies a diversity of values for the
ionization parameter of the various components of gas responsible for the
emission, ranging from log(xi)=1 -- 3. Using this, we obtain an estimate for
the total amount of gas responsible for the observed emission. The mass flux
through the region included in the HETG extraction region is approximately 0.3
Msun/yr assuming ordered flow at the speed characterizing the line widths. This
can be compared with what is known about this object from other techniques.Comment: 39 pages, 12 figures, Ap. J. in pres
QAA subject benchmark statement architecture : version for consultation December 2019
The Statement is intended to guide lecturers and course leaders in the design of academic courses leading to qualifications in architecture, it will also be useful to those developing other related courses.
Higher education providers may need to consider other reference points in addition to this Statement in designing, delivering and reviewing courses. These may include requirements set out by the Architects Registration Board (ARB), the Royal Institute of British Architects (RIBA) and the Institute for Apprenticeships and Technical Education (IfATE). Providers may also need to consider industry or employer expectations. Individual higher education providers will decide how they use this information.
The broad subject of architecture is both academic and vocational. The bachelor's award for architecture is the first stage of the typical education of an architect. This is typically either a BSc or a BA degree. The second stage of academic qualification is a master's level degree, typically in the form of a two-year MArch, which is defined as an undergraduate master's award.
Architecture qualifications typically require a total of 360 (Credit Accumulation and Transfer Scheme, or CATS) credits at bachelor's level and 240 (CATS) credits within a master's level degree. While this may equate to five years of 120 (CATS) credits each, higher education providers may construct alternatives to enable flexibility in student learning.
This Statement seeks to encapsulate the nature of a rich and diverse academic discipline. It is not intended to prescribe a curriculum, but rather describes the broad intellectual territory within which individual higher education providers will locate their courses of study in architecture
Scaling Symmetries of Scatterers of Classical Zero-Point Radiation
Classical radiation equilibrium (the blackbody problem) is investigated by
the use of an analogy. Scaling symmetries are noted for systems of classical
charged particles moving in circular orbits in central potentials V(r)=-k/r^n
when the particles are held in uniform circular motion against radiative
collapse by a circularly polarized incident plane wave. Only in the case of a
Coulomb potential n=1 with fixed charge e is there a unique scale-invariant
spectrum of radiation versus frequency (analogous to zero-point radiation)
obtained from the stable scattering arrangement. These results suggest that
non-electromagnetic potentials are not appropriate for discussions of classical
radiation equilibrium.Comment: 13 page
- …