7,857 research outputs found
An Elliptical Galaxy Luminosity Function and Velocity Dispersion Sample of Relevance for Gravitational Lensing Statistics
We have selected 42 elliptical galaxies from the literature and estimated
their velocity dispersions at the effective radius (\sigma_{\re}) and at 0.54
effective radii (\vff). We find by a dynamical analysis that the normalized
velocity dispersion of the dark halo of an elliptical galaxy \vdm is roughly
\sigma_{\re} multiplied by a constant, which is almost independent of the
core radius or the anisotropy parameter of each galaxy. Our sample analysis
suggests that \vdm^{*} lies in the range 178-198 km s. The power law
relation we find between the luminosity and the dark matter velocity dispersion
measured in this way is (L/L^{*}) = (\vdm/\vdm^{*})^\gamma, where is
between 2-3. These results are of interest for strong gravitational lensing
statistics studies.
In order to determine the value of \vdm^{*}, we calculate \mstar in the
same \bt band in which \vdm^{*} has been estimated. We select 131
elliptical galaxies as a complete sample set with apparent magnitudes \bt
between 9.26 and 12.19. We find that the luminosity function is well fitted to
the Schechter form, with parameters \mstar = -19.66 + 5, , and the normalization constant Mpc, with the Hubble constant
\hnot = 100 km s Mpc. This normalization implies that
morphology type E galaxies make up (10.8 1.2) per cent of all galaxies.Comment: 18 pages latex, with ps figs included. accepted by New Astronomy
(revised to incorporate referees comments
An Algorithmic Framework for Efficient Large-Scale Circuit Simulation Using Exponential Integrators
We propose an efficient algorithmic framework for time domain circuit
simulation using exponential integrator. This work addresses several critical
issues exposed by previous matrix exponential based circuit simulation
research, and makes it capable of simulating stiff nonlinear circuit system at
a large scale. In this framework, the system's nonlinearity is treated with
exponential Rosenbrock-Euler formulation. The matrix exponential and vector
product is computed using invert Krylov subspace method. Our proposed method
has several distinguished advantages over conventional formulations (e.g., the
well-known backward Euler with Newton-Raphson method). The matrix factorization
is performed only for the conductance/resistance matrix G, without being
performed for the combinations of the capacitance/inductance matrix C and
matrix G, which are used in traditional implicit formulations. Furthermore, due
to the explicit nature of our formulation, we do not need to repeat LU
decompositions when adjusting the length of time steps for error controls. Our
algorithm is better suited to solving tightly coupled post-layout circuits in
the pursuit for full-chip simulation. Our experimental results validate the
advantages of our framework.Comment: 6 pages; ACM/IEEE DAC 201
Information System Development Team Collaboration Antecedents
Despite information system development companies have invested substantial resources to support the success of information system development (ISD) projects, the failure rate is still high. Extant studies indicated that the constant changes from socio-technical environments are the main causes of the low success rate. This study argues that team collaboration is a key factor to effectively cope with unexpected disruptions that would have negative effect on overall software product success. This study proposes a research model exploring factors that influence the development of team collaboration. These factors include the team commitment, transactive memory systems (TMS), and collective mind. In addition, the study suggests that the collective mind has an intermediate effect on the team commitment, TMS, and team collaboration. This study takes the information development teams of various companies in Taiwan as its subjects
CO2 Capture by Aqueous Solution Containing Mixed Alkanolamines and Diethylene Glycol in a Rotating Packed Bed
AbstractIn this study, an effective absorbent, 23.5% diethylenetriamine (DETA)/19.6% piperazine (PZ)/37.7% diethylene glycol (DEG)/19.2% H2 O, was proposed to capture CO2 from a nitrogen gas stream containing 10% of CO2 in a rotating packed bed (RPB). The addition of DEG could improve the solubility of PZ in absorbent, and there was no precipitation observed in CO2 - rich solution after CO2 absorption for the proposed absorbent. The regeneration energy could be reduced because the heat capacity and vapor pressure of DEG are lower than that of water. The higher gas-liquid contact area and mass transfer rate as well as the smaller size were observed in a RPB as compared with a packed bed to achieve the same CO2 capture efficiency
Motion Compensation Along All Three Different Directions
This unit addresses how one can deal with phase perturbations that arise due to the presence of motion. Techniques to reduce or remove their associated artifacts are explained in detail. Artifacts due to phase changes that come from the read gradient, from the slice select gradient and from the phase encoding gradient are also discussed.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145397/1/cpmib0702.pd
Discrimination of quantum states under locality constraints in the many-copy setting
We study the discrimination of a pair of orthogonal quantum states in the
many-copy setting. This is not a problem when arbitrary quantum measurements
are allowed, as then the states can be distinguished perfectly even with one
copy. However, it becomes highly nontrivial when we consider states of a
multipartite system and locality constraints are imposed. We hence focus on the
restricted families of measurements such as local operation and classical
communication (LOCC), separable operations (SEP), and the
positive-partial-transpose operations (PPT) in this paper.
We first study asymptotic discrimination of an arbitrary multipartite
entangled pure state against its orthogonal complement using LOCC/SEP/PPT
measurements. We prove that the incurred optimal average error probability
always decays exponentially in the number of copies, by proving upper and lower
bounds on the exponent. In the special case of discriminating a maximally
entangled state against its orthogonal complement, we determine the explicit
expression for the optimal average error probability and the optimal trade-off
between the type-I and type-II errors, thus establishing the associated
Chernoff, Stein, Hoeffding, and the strong converse exponents. Our technique is
based on the idea of using PPT operations to approximate LOCC.
Then, we show an infinite separation between SEP and PPT operations by
providing a pair of states constructed from an unextendible product basis
(UPB): they can be distinguished perfectly by PPT measurements, while the
optimal error probability using SEP measurements admits an exponential lower
bound. On the technical side, we prove this result by providing a quantitative
version of the well-known statement that the tensor product of UPBs is UPB.Comment: Comments are welcom
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