9,111 research outputs found
Application of a virtual watershed in academic education
International audienceHydrologic models of watersheds often represent complex systems which are difficult to understand regarding to their structure and dynamics. Virtual watersheds, i.e. watersheds which exist only in the virtual reality of a computer system, are an approach to simplify access to this real-world complexity. In this study we present the virtual watershed KIELSHED-1, a 117 km2 v-shaped valley with grassland on a "Cambisol" soil type. Two weather scenarios are delivered with the watershed: a simplified artificial weather scenario based on long-term data of a German weather station as well as an unmodified data record. The input data and parameters are compiled according to the conventions of the SWAT 2000 hydrological model. KIELSHED-1 is mainly used for education, and illustrative application examples, i.e. calculation of water balance, model calibration, development of land use scenarios, give an insight to the capabilities of the virtual watershed
Theory of impedance networks: The two-point impedance and LC resonances
We present a formulation of the determination of the impedance between any
two nodes in an impedance network. An impedance network is described by its
Laplacian matrix L which has generally complex matrix elements. We show that by
solving the equation L u_a = lambda_a u_a^* with orthonormal vectors u_a, the
effective impedance between nodes p and q of the network is Z = Sum_a [u_{a,p}
- u_{a,q}]^2/lambda_a where the summation is over all lambda_a not identically
equal to zero and u_{a,p} is the p-th component of u_a. For networks consisting
of inductances (L) and capacitances (C), the formulation leads to the
occurrence of resonances at frequencies associated with the vanishing of
lambda_a. This curious result suggests the possibility of practical
applications to resonant circuits. Our formulation is illustrated by explicit
examples.Comment: 21 pages, 3 figures; v4: typesetting corrected; v5: Eq. (63)
correcte
Fuel-Supply-Limited Stellar Relaxation Oscillations: Application to Multiple Rings around AGB Stars and Planetary Nebulae
We describe a new mechanism for pulsations in evolved stars: relaxation
oscillations driven by a coupling between the luminosity-dependent mass-loss
rate and the H fuel abundance in a nuclear-burning shell. When mass loss is
included, the outward flow of matter can modulate the flow of fuel into the
shell when the stellar luminosity is close to the Eddington luminosity . When the luminosity drops below , the mass outflow declines
and the shell is re-supplied with fuel. This process can be repetitive. We
demonstrate the existence of such oscillations and discuss the dependence of
the results on the stellar parameters. In particular, we show that the
oscillation period scales specifically with the mass of the H-burning
relaxation shell (HBRS), defined as the part of the H-burning shell above the
minimum radius at which the luminosity from below first exceeds the Eddington
threshold at the onset of the mass loss phase. For a stellar mass M_*\sim
0.7\Msun, luminosity L_*\sim 10^4\Lsun, and mass loss rate |\dot M|\sim
10^{-5}\Msun yr, the oscillations have a recurrence time
years , where is the timescale for
modulation of the fuel supply in the HBRS by the varying mass-loss rate. This
period agrees with the 1400-year period inferred for the spacings
between the shells surrounding some planetary nebulae, and the the predictied
shell thickness, of order 0.4 times the spacing, also agrees reasonably well.Comment: 15 pages TeX, 1 ps figure submitted to Ap
Testing the Antelope software suite to realize a distributed seismic database among Austria, Northeastern Italy and Slovenia
Since 2002 the Zentralanstalt für Meteorologie und Geodynamik (ZAMG, http://www.zamg.ac.at/), the Centro di Ricerche Sismologiche (CRS, http://www.crs.inogs.it) of the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), the Dipartimento di Scienze della Terra (DST, http://www.dst.univ.trieste.it/) of the Università di Trieste and the Agencija Republike Slovenije Za Okolje (ARSO, http://www.arso.gov.si/) are involved in the EU INTERREG IIIA project “Trans-national seismological networks in the South-Eastern Alps”.
The Antelope software suite has been chosen as the common basis for real time data exchange, rapid location of earthquakes and alerting. The Antelope software suite has the capability to exchange data in real time among data centres: for this purpose the standard “orb2orb” software module is used. It uses a proprietary protocol and a point-to-point client/server architecture to exchange data. The last release of the Antelope software suite contains a more sophisticated version of this data exchange module: it is named “orbxchange”. “orbxchange” is a multithreaded version of “orb2orb” which supervises multiple “orb2orb” copies specified in a parameter file; it has the option of switching to alternate servers when no data is being copied from the primary. A distributed real time seismic database has been so established by connecting ZAMG, CRS/OGS, DST/UTS and ARSO Antelope servers with “orbxchange” modules. A test of the above described “orbxchange” features has been conducted artificially shutting down the Antelope servers and/or the data links between them: the results in the data coverage of the multiple copies of the distributed database will be shown. The expected improvement in data availability not only will be very useful for the institutional activities (like rapid earthquake location with magnitude estimation) of the four institutions involved in this test, but moreover its natural extension will be in more mission critical applications, like in public civil protection applications and rapid notification of inherent authorities
Quantum authentication with unitary coding sets
A general class of authentication schemes for arbitrary quantum messages is
proposed. The class is based on the use of sets of unitary quantum operations
in both transmission and reception, and on appending a quantum tag to the
quantum message used in transmission. The previous secret between partners
required for any authentication is a classical key. We obtain the minimal
requirements on the unitary operations that lead to a probability of failure of
the scheme less than one. This failure may be caused by someone performing a
unitary operation on the message in the channel between the communicating
partners, or by a potential forger impersonating the transmitter.Comment: RevTeX4, 10 page
A simple method for the induction of high levels of tyrosinase activity
A simple method for the induction of high levels of tyrosinase activit
Collective fluctuations in networks of noisy components
Collective dynamics result from interactions among noisy dynamical
components. Examples include heartbeats, circadian rhythms, and various pattern
formations. Because of noise in each component, collective dynamics inevitably
involve fluctuations, which may crucially affect functioning of the system.
However, the relation between the fluctuations in isolated individual
components and those in collective dynamics is unclear. Here we study a linear
dynamical system of networked components subjected to independent Gaussian
noise and analytically show that the connectivity of networks determines the
intensity of fluctuations in the collective dynamics. Remarkably, in general
directed networks including scale-free networks, the fluctuations decrease more
slowly with the system size than the standard law stated by the central limit
theorem. They even remain finite for a large system size when global
directionality of the network exists. Moreover, such nontrivial behavior
appears even in undirected networks when nonlinear dynamical systems are
considered. We demonstrate it with a coupled oscillator system.Comment: 5 figure
Equivalence of particle-particle random phase approximation correlation energy and ladder-coupled-cluster doubles
We present an analytical proof and numerical demonstrations of the
equivalence of the correlation energy from particle-particle random phase
approximation (pp-RPA) and ladder-couple-cluster-doubles (ladder-CCD). These
two theories reduce to the identical algebraic matrix equation and correlation
energy expressions, under the assumption that the pp-RPA equation is stable.
The numerical examples illustrate that the correlation energy missed by pp-RPA
in comparison with couple-cluster single and double is largely canceled out
when considering reaction energies. This theoretical connection will be
beneficial to future pp-RPA studies based on the well established couple
cluster theory
- …