15,509 research outputs found
The Effect of the Bulk Sales Article on Existing Commercial Practices
Power control is considered as an important means to combat near-far fading effects and maintain acceptable connections in wireless communications systems. When applying power control in practice, the performance is restricted by a number of fundamental limitations. Here, these are addressed from a control theory perspective. Limited update rate, limited feedback bandwidth, time delays, measurement errors, feedback errors, and filtering effects among other aspects all affect the resulting performance, and are related to radio channnel characteristics. Simulations further illustrate the hampering effects
Optimal designs which are efficient for lack of fit tests
Linear regression models are among the models most used in practice, although
the practitioners are often not sure whether their assumed linear regression
model is at least approximately true. In such situations, only designs for
which the linear model can be checked are accepted in practice. For important
linear regression models such as polynomial regression, optimal designs do not
have this property. To get practically attractive designs, we suggest the
following strategy. One part of the design points is used to allow one to carry
out a lack of fit test with good power for practically interesting
alternatives. The rest of the design points are determined in such a way that
the whole design is optimal for inference on the unknown parameter in case the
lack of fit test does not reject the linear regression model. To solve this
problem, we introduce efficient lack of fit designs. Then we explicitly
determine the -optimal design in the class of efficient lack of
fit designs for polynomial regression of degree .Comment: Published at http://dx.doi.org/10.1214/009053606000000597 in the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Conditional Estimation in Two-stage Adaptive Designs
We consider conditional estimation in two-stage sample size adjustable
designs and the following bias. More specifically, we consider a design which
permits raising the sample size when interim results look rather promising,
and, which keeps the originally planned sample size when results look very
promising. The estimation procedures reported comprise the unconditional
maximum likelihood, the conditionally unbiased Rao-Blackwell estimator, the
conditional median unbiased estimator, and the conditional maximum likelihood
with and without bias correction. We compare these estimators based on
analytical results and by a simulation study. We show in a real clinical trial
setting how they can be applied
Observations on the Nesting of \u3ci\u3eCrabro Tenuis\u3c/i\u3e (Hymenoptera: Sphecidae)
Three nests of Crabro tenuis were studied during June 1971-1972 in Oswego County, New York. Females constructed shallow but lengthy, multicelled nests in sand with the cells being built in clusters, sometimes in series. Females plugged the entrances with damp sand and occupied the burrows during midday. Paralyzed prey were stored head inward at the end of the burrow. The deeper cells in a cluster were excavated and provisioned first and the shallower cells built and stored later, as determined by the developmental stages of the wasps within the cells. From four to seven paralyzed, adult male flies were placed in a fully provisioned cell with their venters toward the center. Such a cell usually held only one species of fly. Provisions consisted of the suborders Brachycera and Cyclorrhapha and comprised the families Rhagionidae, Anthomyiidae and Tachinidae. An egg was affixed about equally to the left or right side of the neck of a fly and this prey was placed against or near the wall of the cell. The nesting traits of C. tenuis were compared with those of other members of the Cribrarius group, C. advena of the Advena, group, C. venator of the Tumidus group and species in the Hilaris group
Range Extensions for Species of Sphecidae (Hymenoptera) in the Northeastern United States
The ranges of 10 Nearctic species of Sphecidae, Spilomena pusilla, Tachytes parvus, Solierella plenoculoides, Pison agile, Entomognathus lenapeorum, Rhopalum clavipes, Crabro hilaris, C. tenuis, Alysson conicus and Lestiphorus cockerelli, are extended in the northeastern U.S. based upon collections made in Pennsylvania and New York. The first prey record for a North American species of Lestiphorus, cockerelli, is included
Age estimates of isochronous reflection horizons by combining ice core, survey, and synthetic radar data.
Ice core records and ice-penetrating radar data contain complementary information on glacial subsurface structure and composition, providing various opportunities for interpreting past and present environmental conditions. To exploit the full range of possible applications, accurate dating of internal radar reflection horizons and knowledge about their constituting features is required. On the basis of three ice core records from Dronning Maud Land, Antarctica, and surface-based radar profiles connecting the drilling locations, we investigate the accuracies involved in transferring age-depth relationships obtained from the ice cores to continuous radar reflections. Two methods are used to date five internal reflection horizons: (1) conventional dating is carried out by converting the travel time of the tracked reflection to a single depth, which is then associated with an age at each core location, and (2) forward modeling of electromagnetic wave propagation is based on dielectric profiling of ice cores and performed to identify the depth ranges from which tracked reflections originate, yielding an age range at each drill site. Statistical analysis of all age estimates results in age uncertainties of 5 10 years for conventional dating and an error range of 1 16 years for forward modeling. For our radar operations at 200 and 250 MHz in the upper 100 m of the ice sheet, comprising some 1000 1500 years of deposition history, final age uncertainties are 8 years in favorable cases and 21 years at the limit of feasibility. About one third of the uncertainty is associated with the initial ice core dating; the remaining part is associated with radar data quality and analysis
Solving Graph Coloring Problems with Abstraction and Symmetry
This paper introduces a general methodology, based on abstraction and
symmetry, that applies to solve hard graph edge-coloring problems and
demonstrates its use to provide further evidence that the Ramsey number
. The number is often presented as the unknown Ramsey
number with the best chances of being found "soon". Yet, its precise value has
remained unknown for more than 50 years. We illustrate our approach by showing
that: (1) there are precisely 78{,}892 Ramsey colorings; and (2)
if there exists a Ramsey coloring then it is (13,8,8) regular.
Specifically each node has 13 edges in the first color, 8 in the second, and 8
in the third. We conjecture that these two results will help provide a proof
that no Ramsey coloring exists implying that
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