18,145 research outputs found
A Criterion for Comparing Measurement Results and Determining Conformity with Specifications
In this paper a new criterion for comparing measurement results and determining conformity with specifications is proposed, which essentially is a strategy of estimating the empirical relationships of objects. Comparing with traditional methods given in GUM: 2008 and ISO 14253-1, this criterion improves the resolution of comparison by reducing the sizes of the coverage intervals to be compared. Interval order (a binary relation) is used for comparing the coverage intervals of the measurand and represents the empirical relations. The systematic effects of measurement are classified into two types: monotonic and non-monotonic effects, so that, without correcting the monotonic effects, a biased measurand can be specified to represent the empirical relations. Thereby the uncertainty components arising from the monotonic effects can be removed from the combined uncertainty. A strategy is given for determining the relationships among measurement results and specification limits. An example is given to demonstrate the application of the criterion
Vegetation NDVI Linked to Temperature and Precipitation in the Upper Catchments of Yellow River
Vegetation in the upper catchment of Yellow River is critical for the ecological stability of the whole watershed. The dominant vegetation cover types in this region are grassland and forest, which can strongly influence the eco-environmental status of the whole watershed. The normalized difference vegetation index (NDVI) for grassland and forest has been calculated and its daily correlation models were deduced by Moderate Resolution Imaging Spectroradiometer products on 12 dates in 2000, 2003, and 2006. The responses of the NDVI values with the inter-annual grassland and forest to three climatic indices (i.e., yearly precipitation and highest and lowest temperature) were analyzed showing that, except for the lowest temperature, the yearly precipitation and highest temperature had close correlations with the NDVI values of the two vegetation communities. The value of correlation coefficients ranged from 0.815 to 0.951 (p <0.01). Furthermore, the interactions of NDVI values of vegetation with the climatic indicators at monthly interval were analyzed. The NDVI of vegetation and three climatic indices had strong positive correlations (larger than 0.733, p <0.01). The monthly correlations also provided the threshold values for the three climatic indictors, to be used for simulating vegetation growth grassland under different climate features, which is essential for the assessment of the vegetation growth and for regional environmental management
Gauged Q ball in a piecewise parabolic potential
Q ball solutions are considered within the theory of a complex scalar field
with a gauged
U(1) symmetry and a parabolic-type potential. In the thin-walled limit, we
show explicitly that there is a maximum size for these objects because of the
repulsive Coulomb force. The size of Q ball will increase with the decrease of
local minimum of the potential. And when the two minima degenerate, the energy
stored within the surface of the Q ball becomes significant.
Furthermore, we find an analytic expression for gauged Q ball, which is
beyond the conventional thin-walled limit.Comment: 1 figure
Exceptionally large room-temperature ferroelectric polarization in the novel PbNiO3 multiferroic oxide
We present a study based on several advanced First-Principles methods, of the
recently synthesized PbNiO3 [J. Am. Chem. Soc 133, 16920 (2011)], a
rhombohedral antiferromagnetic insulator which crystallizes in the highly
distorted R3c crystal structure. We find this compound electrically polarized,
with a very large electric polarization of about 100 (\muC/cm)^2, thus even
exceeding the polarization of well-known BiFeO3. PbNiO3 is a proper
ferroelectric, with polarization driven by large Pb-O polar displacements along
the [111] direction. Contrarily to naive expectations, a definite ionic charge
of 4+ for Pb ion can not be assigned, and in fact the large Pb 6s-O 2p
hybridization drives the ferroelectric distortion through a lone-pair mechanism
similar to that of other Pb- and Bi-based multiferroic
Application of Association Rule Mining Theory in Sina Weibo
A user profile contains information about a user. A substantial effort has been made so as to understand users’ behavior through analyzing their profile data. Online social networks provide an enormous amount of such information for researchers. Sina Weibo, a Twitter-like microblogging platform, has achieved a great success in China although studies on it are still in an initial state. This paper aims to explore the relationships among different profile attributes in Sina Weibo. We use the techniques of association rule mining to identify the dependency among the attributes and we found that if a user’s posts are welcomed, he or she is more likely to have a large number of followers. Our results demonstrate how the relationships among the profile attributes are affected by a user’s verified type. We also put some efforts on data transformation and analyze the influence of the statistical properties of the data distribution on data discretization
Cosmological dynamics of scalar fields with O(N) symmetry
In this paper, we study the cosmological dynamics of scalar fields with O(N)
symmetry in general potentials. We compare the phase space of the dynamical
systems of the quintessence and phantom and give the conditions for the
existence of various attractors as well as their cosmological implications. We
also show that the existence of tracking attractor in O(N) phantom models
require the potential with , which makes the models with
exponential potential possess no tracking attractor.Comment: 9 pages, 4 figures; Replaced with the version to be published in
Classical and Quantum Gravity. Reference adde
Derivation of Electroweak Chiral Lagrangian from One Family Technicolor Model
Based on previous studies deriving the chiral Lagrangian for pseudo scalar
mesons from the first principle of QCD in the path integral formalism, we
derive the electroweak chiral Lagrangian and dynamically compute all its
coefficients from the one family technicolor model. The numerical results of
the order coefficients obtained in this paper are proportional to the
technicolor number and the technifermion number ,
which agrees with the arguments in previous works, and which confirms the
reliability of this dynamical computation.Comment: 6 page
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