University of Maryland, Baltimore County

About: University of Maryland, Baltimore County is a education organization based out in Baltimore, Maryland, United States. It is known for research contribution in the topics: Population & Galaxy. The organization has 8749 authors who have published 20843 publications receiving 795706 citations. The organization is also known as: UMBC.

Testing the Gamma-Ray Burst Energy Relationships

Abstract: Building on Nakar & Piran's analysis of the Amati relation relating gamma-ray burst peak energies E(sub p) and isotropic energies E(sub iso ) we test the consistency of a large sample of BATSE bursts with the Amati and Ghirlanda (which relates peak energies and actual gamma-ray energies E(sub gamma)) relations. Each of these relations can be exp ressed as a ratio of the different energies that is a function of red shift (for both the Amati and Ghirlanda relations) and beaming fraction f(sub B) (for the Ghirlanda relation). The most rigorous test, whic h allows bursts to be at any redshift, corroborates Nakar & Piran's r esult - 88% of the BATSE bursts are inconsistent with the Amati relat ion - while only l.6% of the bursts are inconsistent with the Ghirlan da relation if f(sub B) = 1. Modelling the redshift distribution resu lts in an energy ratio distribution for the Amati relation that is sh ifted by an order of magnitude relative to the observed distributions; any sub-population satisfying the Amati relation can comprise at mos t approx. 18% of our burst sample. A similar analysis of the Ghirland a relation depends sensitively on the beaming fraction distribution f or small values of f(sub B); for reasonable estimates of this distrib ution about a third of the burst sample is inconsistent with the Ghir landa relation. Our results indicate that these relations are an artifact of the selection effects of the burst sample in which they were f ound; these selection effects may favor sub-populations for which the se relations are valid.

From El Niño to La Niña: Vegetation Response Patterns over East and Southern Africa during the 1997-2000 Period.

Abstract: During the period 1997–2000, the global climate system experienced a transition from the strongest ENSO warm event this century in 1997/98 to a strong cold event in 1999/2000. Normalized difference vegetation index (NDVI) time series data derived from the Advanced Very High Resolution Radiometer (AVHRR) instrument aboard the NOAA polar-orbiting satellite series were analyzed to resolve the land surface response patterns over Africa during this period. The rearrangement of precipitation patterns induced by the change from El Nino to La Nina conditions had significant effects on biomass production in arid and semiarid lands of Africa as revealed by NDVI anomaly patterns, particularly in equatorial East Africa and southern Africa where the ENSO–precipitation linkage is most pronounced. In general, there was a reversal in NDVI response patterns in East (southern) Africa from positive (negative) during the El Nino in 1997/98 to negative (positive) during the La Nina event in 1999/2000. These changes c...

DReggie: Semantic Service Discovery for M-Commerce Applications

Abstract: The emergence of mobile devices and wireless networks has created a new path in the field of e-commerce: ``m-commerce''. Significant research needs to be done in the field of service discovery to support m-commerce applications. Various new applications, that would use services available to a mobile device from both the fixed network backbone and peer mobile devices in its proximity, are being developed. M-commerce applications have the challenging task of discovering services in a dynamically changing environment. To support dynamic service discovery, existing mechanisms need to move beyond trivial attribute or interface matching. Recently the DARPA Agent Markup Language (DAML) has been developed to semantically describe the content of the web. In this paper, we describe ongoing work in developing a dynamic service discovery infrastructure using DAML. This architecture is built on the Jini service discovery framework. Our service discovery infrastructure can find services in a semantically richer way, instead of using simple attribute or interface based matching. This increased flexibility in service discovery has the potential to enable a broad range of m-commerce applications.

The genesis, classification, and mapping of soils in urban areas

Abstract: This paper discusses the concept of soil in both urban and rural environments, and along the urban-rural land use gradient, to illustrate the obvious need to increase our understanding of urban soils. Spatial variability of the urban landscape is illustrated with "Soil series - Urban land complexes" from Baltimore County, Maryland. The World Reference Base for Soil Resources (ISSS-ISRIC-FAO, 1994) proposed Anthrosol and Regosol major soil groups are discussed to show modern approaches to soil classification and to illustrate how the classification of urban soils is essentially undeveloped. Models of soil genesis help identify the processes and functions of the soil system. A conceptual model using Jenny's (1941) state factor approach for human impact on soil formation details the "anthroposequence." The benchmark anthroposequence model may be applied to studying soil systems along urban-rural land use gradients. The process of "anthropedogenesis" is supported to quantify the role of human activity in changing the "natural" direction of soil formation. Future directions of soil research in the urban landscape should involve large scale soil mapping (e.g. 1:6000), benchmark anthroposequences, improved soil classification, and refined characterization of the role of human activities in soil formation.