7,723 research outputs found
The regularity of the boundary of a multidimensional aggregation patch
Let and let be the fundamental solution of the Laplace
equation in We consider the aggregation equation with
initial data , where is the indicator
function of a bounded domain We now fix and
take to be a bounded domain (a domain with smooth boundary
of class ). Then we have Theorem: If is a
domain, then the initial value problem above has a solution given by
where is a domain for all
Characterization of radially symmetric finite time blowup in multidimensional aggregation equations,
This paper studies the transport of a mass in by a
flow field . We focus on kernels for
for which the smooth densities are known to develop
singularities in finite time. For this range This paper studies the transport
of a mass in by a flow field . We
focus on kernels for for which the
smooth densities are known to develop singularities in finite time. For this
range we prove the existence for all time of radially symmetric measure
solutions that are monotone decreasing as a function of the radius, thus
allowing for continuation of the solution past the blowup time. The monotone
constraint on the data is consistent with the typical blowup profiles observed
in recent numerical studies of these singularities. We prove monotonicity is
preserved for all time, even after blowup, in contrast to the case
where radially symmetric solutions are known to lose monotonicity. In the case
of the Newtonian potential (), under the assumption of radial
symmetry the equation can be transformed into the inviscid Burgers equation on
a half line. This enables us to prove preservation of monotonicity using the
classical theory of conservation laws. In the case and at
the critical exponent we exhibit initial data in for which the
solution immediately develops a Dirac mass singularity. This extends recent
work on the local ill-posedness of solutions at the critical exponent.Comment: 30 page
Diablo Canyon power plant site ecological study Annual Report July 1, 1976 - June 30, 1977 and Quarterly Report no. 16 April 1, 1977 - June 30, 1977
More stations were surveyed during this report period
than during any previous period. A total of 818 mandays
was spent surveying 18 permanent and 67 random
subtidal stations, 19 permanent and 50 random intertidal
stations, and 64 sportfish catch-per-unit-of-effort
stations, as well as conducting corollary laboratory
work.
In the subtidal areas, Laminaria dentigera and Pterygophora
californica, both important subsurface kelp
species, increased in their combined total numbers from
the 1976 survey. However, Nereocystis luetkeana, the
bull kelp, declined substantially in all study areas.
Population trends of many of the dominant subtidal
macro-invertebrates have varied depending on the species
and on the type of method utilized. Regression analyses
have been performed on selected species for numbers
versus depth. Red algal abundance and diversity appear
to have increased in both subtidal study areas.
Of the three observation areas, sea otters were observed
least frequently in Diablo Cove. However, there continues
to be fresh evidence of otter foraging within
Diablo Cove.
Several seasons' data for intertidal algae and invertebrates have been summarized for one study area. While the algae biomass shows a fairly clear seasonality of
abundance, the trends in numbers of the six invertebrate
species considered are not as well defined.
Because of high variability in the data, the sportfish
catch-per-unit-of-effort and hook-and-line study was
cancelled in December.
Populations of intertidal red and black abalones,
Haliotis rufescens and H. cracherodii, respectively,
appear to have remained fairly stable during the
1976-77 period.
Two other ancillary studies were also terminated during
this period: interviews of commercial abalone and
urchin fishermen, and observations of foam in Diablo Cove. (107pp.
Diablo Canyon power plant site ecological study Quarterly Report no. 22: October 1 - December 31, 1978
Field work for this quarter consisted of completion of random 1/4-m2 subtidal stations from the summer sampling season. In addition, one permanent subtidal station was surveyed. No intertidal stations were surveyed. Sea otters, Enhydra lutris, remained scarce in the vicinity of the power plant.
Lab work was comprised of processing subtidal algae
samples and sorting and identifying invertebrates from
intertidal samples. Analysis of preoperational data
for final report proceeded apace. (7pp.
Diablo Canyon power plant site ecological study Quarterly Report no. 19: January 1 - March 31, 1978
Field work was limited to monitoring permanent
intertidal and subtidal stations. Only a few
stations were surveyed due to a long series of
winter storms which produced large seas.
Office and laboratory work was devoted to completing computer data sheets for keypunching, completing the 1976/77 annual report and several quarterly reports, and processing the remaining algae samples collected at subtidal and intertidal stations in 1977.
Sea otter activity increased in South Cove and
Diablo Cove where sea otters were observed on
five out of 20 observation days. (11pp.
Diablo Canyon power plant site ecological study Quarterly Report no. 18; October 1 - December 31, 1977
Large storm-generated swells prevented us from
completing the random stations in the North Control.
The project has shifted to a low level of field work to allow for analysis of all data and preparation of the final report. Field work during the next year will be confined to monitoring permanent stations.
Four permanent subtidal stations were surveyed during the quarter, including a new station located at the entrance of Diablo Cove. Nine random 30m2 stations and 32 - 1/4m2 quadrats were also completed. It appears, from this year's subtidal studies, that there has been a decline in the
abundance of lingcod, Ophiodon elongatus, and kelp greenling, Hexagrammos decagrammus, in the Diablo Canyon area since our studies began in 1974.
A few sea otters continue to raft and forage in
Lion Rock Cove. (12pp.
Diablo Canyon power plant site ecological study Quarterly Report No. 21: July 1 - September 30, 1978
Rough seas and the hiring freeze further delayed completion
of our field and laboratory work.
All random 1/4-m2 stations were completed in Diablo Cove
but ten stations remain in the North Control. Nine
random fish species counts were conducted in Diablo Cove.
Very few sea otters, Enhydra lutris, were observed during
this quarter, none in Diablo Cove. (10pp.
- …