68,986 research outputs found
On Non-Squashing Partitions
A partition n = p_1 + p_2 + ... + p_k with 1 <= p_1 <= p_2 <= ... <= p_k is
called non-squashing if p_1 + ... + p_j <= p_{j+1} for 1 <= j <= k-1.
Hirschhorn and Sellers showed that the number of non-squashing partitions of n
is equal to the number of binary partitions of n. Here we exhibit an explicit
bijection between the two families, and determine the number of non-squashing
partitions with distinct parts, with a specified number of parts, or with a
specified maximal part. We use the results to solve a certain box-stacking
problem.Comment: 15 pages, 2 fig
The chaetognatha of the Eastropic Expedition, with notes as to their possible value as indicators of hydrographic conditions
ENGLISH: The purpose of this study was to investigate the possibility that certain species of Chaetognatha found in Eastern Tropical Pacific waters can serve as biological indicators of oceanographic features. "Indicator" organisms have been found useful in identifying water types, in tracing the pattern of current systems, and in tracing the origin of moving water masses. To be of use in this type of study, the organisms must be sufficiently abundant to be readily sampled, and easily identified to species; they must also, at least partially, fulfill the additional requisites listed and discussed by Sverdrup, Johnson, and Fleming (1942, pp. 866-867). Among several groups of organisms fulfilling these requirements are the Chaetognatha. Specimens of this group of animals occurred in large numbers in the plankton samples used for this study. The works of Thomson (1947), Fraser (1942), Ritter-Zahony (1911), and Sund (1959) were used for identification.
SPANISH: El objetivo de este estudio ha sido el de investigar la posibilidad de utilizar ciertas especies de quetognatos encontrados en el PacÃfico Oriental Tropical como indicadoras biológicas de caracterÃsticas oceanográficas. Organismos "indicadores" fueron encontrados útiles para la identificación de tipos de agua, el trazado del régimen de los sistemas de corrientes y la determinación del origen de masas de agua en movimiento. Para servir a este tipo de estudios, los organismos deben ser lo suficientemente abundantes como para ser fácilmente muestreados e identificados hasta la especie; también deben satisfacer, por lo menos parcialmente, los requerimientos indicados y discutidos par Sverdrup, Johnson y Fleming (1942, pags. 866-867)
A simple test for thermomechanical evaluation of ceramic fibers
A simple bend stress relaxation (BSR) test was developed to measure the creep related properties of ceramic fibers and whiskers. The test was applied to a variety of commercial and developmental Si based fibers to demonstrate capabilities and to evaluate the relative creep resistance of the fibers at 1200 to 1400 C. The implications of these results and the advantages of the BSR test over typical tensile creep tests are discussed
Quantum Confinement Induced Metal-Insulator Transition in Strongly Correlated Quantum Wells of SrVO Superlattice
Dynamical mean-field theory (DMFT) has been employed in conjunction with
density functional theory (DFT+DMFT) to investigate the metal-insulator
transition (MIT) of strongly correlated electrons due to quantum
confinement. We shed new light on the microscopic mechanism of the MIT and
previously reported anomalous subband mass enhancement, both of which arise as
a direct consequence of the quantization of V states in the SrVO
layers. We therefore show that quantum confinement can sensitively tune the
strength of electron correlations, leading the way to applying such approaches
in other correlated materials
Security Policy Specification Using a Graphical Approach
A security policy states the acceptable actions of an information system, as
the actions bear on security. There is a pressing need for organizations to
declare their security policies, even informal statements would be better than
the current practice. But, formal policy statements are preferable to support
(1) reasoning about policies, e.g., for consistency and completeness, (2)
automated enforcement of the policy, e.g., using wrappers around legacy systems
or after the fact with an intrusion detection system, and (3) other formal
manipulation of policies, e.g., the composition of policies. We present LaSCO,
the Language for Security Constraints on Objects, in which a policy consists of
two parts: the domain (assumptions about the system) and the requirement (what
is allowed assuming the domain is satisfied). Thus policies defined in LaSCO
have the appearance of conditional access control statements. LaSCO policies
are specified as expressions in logic and as directed graphs, giving a visual
view of policy. LaSCO has a simple semantics in first order logic (which we
provide), thus permitting policies we write, even for complex policies, to be
very perspicuous. LaSCO has syntax to express many of the situations we have
found to be useful on policies or, more interesting, the composition of
policies. LaSCO has an object-oriented structure, permitting it to be useful to
describe policies on the objects and methods of an application written in an
object-oriented language, in addition to the traditional policies on operating
system objects. A LaSCO specification can be automatically translated into
executable code that checks an invocation of a program with respect to a
policy. The implementation of LaSCO is in Java, and generates wrappers to check
Java programs with respect to a policy.Comment: 28 pages, 22 figures, in color (but color is not essential for
viewing); UC Davis CS department technical report (July 22, 1998
Remote sensing and GIS analysis for demarcation of coastal hazard line along the highly eroding Krishna-Godavari delta front
Coastal regions, especially river deltas are highly resourceful and hence densely populated; but these extremely low-lying lands are vulnerable to rising sea levels due to global warming threatening the life and property in these regions. Recent IPCC (2013) predictions of 26-82cm global sea level rise are now considered conservative as subsequent investigations such as by Met Office, UK indicated a vertical rise of about 190cm, which would displace 10% of the world’s population living within 10 meters above the sea level. Therefore, predictive models showing the hazard line are necessary for efficient coastal zone management. Remote sensing and GIS technologies form the mainstay of such predictive models on coastal retreat and inundation to future sea-level rise. This study is an attempt to estimate the varying trends along the Krishna–Godavari (K–G) delta region. Detailed maps showing various coastal landforms in the K-G delta region were prepared using the IRS-P6 LISS 3 images. The rate of shoreline shift during a 31-year period along different sectors of the 330km long K-G delta coast was estimated using Landsat-2 and IRS-P6 LISS 3 images between 1977 and 2008. With reference to a selected baseline from along an inland position, End Point Rate (EPR), Shoreline Change Envelope (SCE) and Net Shoreline Movement (NSM) were calculated, using a GIS–based Digital Shoreline Analysis System (DSAS). The results showed that the shoreline migrated landward up to a maximum distance of 3.13km resulting in a net loss of about 42.10km2 area during this 31-year period. Further, considering the nature of landforms and EPR, the future hazard line is predicted for the area, which also indicated a net erosion of about 57.68km2 along the K-G delta coast by 2050 AD
The Organizational Evolution of Markets for Wood Products in the Southern United States
This paper represents the first case study attempt to develop a transaction cost conceptual model to describe industry evolution of the paper and lumber industries in the Southern United States around the late 1800s and early 1900s. We use transaction cost theory to explain the co-evolution of markets for wood products noting that variation in the level and type of investments made in physical and human capital assets needed to manage paper and lumber miller operations had a significant influence on the use of wood dealer systems compared to more vertically organized business arrangements. We identify some testable hypotheses and areas of future research.Industry Evolution, Contracting, Property Rights, Vertical Integration, Forest Products, Industrial Organization, Research Methods/ Statistical Methods, L14, L24, L73, J24,
Deep Optical Observations of Compact Groups of Galaxies
Compact groups of galaxies appear to be extremely dense, making them likely
sites of intense galaxy interaction, while their small populations make them
relatively simple to analyze. In order to search for optical interaction
tracers such as diffuse light and galaxy tidal features in Hickson compact
groups (HCGs), we carried out deep photometry in three filters on a sample of
HCGs with observations. Using a modeling procedure to subtract the
light of bright early-type galaxies, we found shell systems and extended
envelopes around many, but not all, of those galaxies. Only one group in our
sample, HCG 94, has diffuse light in the group potential (with a luminosity of
7 L); the other groups do not contain more than 1/3 L in diffuse light.
With the exception of HCG 94 (which is the most X-ray--luminous HCG), we found
no correlation between the presence of shells or other tidal features and the
X-ray luminosity of a group. Better predictors of detectable group X-ray
emission are a low spiral fraction and belonging to a larger galaxy
condensation---neither of which are correlated with optical disturbances in the
group galaxies. Two elliptical galaxies that are extremely optically luminous
but X-ray--faint are found to have shells and very complex color structures.
This is likely due to recent infall of gas-rich material into the galaxies,
which would produce both the disruption of stellar orbits and a significant
amount of star formation.Comment: 24 pages, to appear in October 1995 Astronomical Journal; postscript
text and figures (low resolution scans, tar'ed and compressed) available at
ftp://astro.lsa.umich.edu/pub/get/pildis
Environmental Impact on the Southeast Limb of the Cygnus Loop
We analyze observations from the Chandra X-ray Observatory of the southeast
knot of the Cygnus Loop supernova remnant. In this region, the blast wave
propagates through an inhomogeneous environment. Extrinsic differences and
subsequent multiple projections along the line of sight rather than intrinsic
shock variations, such as fluid instabilities, account for the apparent
complexity of the images. Interactions between the supernova blast wave and
density enhancements of a large interstellar cloud can produce the
morphological and spectral characteristics. Most of the X-ray flux arises in
such interactions, not in the diffuse interior of the supernova remnant.
Additional observations at optical and radio wavelengths support this account
of the existing interstellar medium and its role in shaping the Cygnus Loop,
and they demonstrate that the southeast knot is not a small cloud that the
blast wave has engulfed. These data are consistent with rapid equilibration of
electron and ion temperatures behind the shock front, and the current blast
wave velocity v_{bw} approx 330 km/s. Most of this area does not show strong
evidence for non-equilibrium ionization conditions, which may be a consequence
of the high densities of the bright emission regions.Comment: To appear in ApJ, April 1, 200
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