Giving You back Control of Your Data: Digital Signing Practical Issues and the eCert Solution

As technologies develop rapidly, digital signing is commonly used in eDocument security. However, unaddressed issues exist. An eCertificate system represents the problem situation, and therefore is being used as case study, in a project called eCert, to research for the solution. This paper addresses these issues, explores the gap between current tools and the desired system, through analysis of the existing services and eCertificate use cases, and the identified requirements, thereby presenting an approach which solves the above problems. Preliminary results indicate that the recommendation from this research meets the design requirements, and could form the foundation of future study of solving digital signing issues

Age, growth, mortality, and radiometric age validation of gray snapper (Lutjanus griseus) from Louisiana

The gray snapper (Lutjanus griseus) is a temperate and tropical reef fish that is found along the Gulf of Mexico and Atlantic coasts of the southeastern United States. The recreational fishery for gray snapper has developed rapidly in south Louisiana with the advent of harvest and seasonal restrictions on the established red snapper (L. campechanus) fishery. We examined the age and growth of gray snapper in Louisiana with the use of cross-sectioned sagittae. A total of 833 specimens, (441 males, 387 females, and 5 of unknown sex) were opportunistically sampled from the recreational fishery from August 1998 to August 2002. Males ranged in size from 222 to 732 mm total length (TL) and from 280 g to 5700 g total weight (TW) and females ranged from 254 to 756 mm TL and from 340 g to 5800 g TW. Both edge analysis and bomb radiocarbon analyses were used to validate otolith-based age estimates. Ages were estimated for 718 individuals; both males and females ranged from 1 to 28 years. The von Bertalanffy growth models derived from TL at age were Lt = 655.4{1–e[–0.23(t)]} for males, Lt = 657.3{1–e[– 0.21(t)]} for females, and L t = 656.4{1–e[– 0.22 (t)]} for all specimens of known sex. Catch curves were used to produce a total mortality (Z) estimate of 0.17. Estimates of M calculated with various methods ranged from 0.15 to 0.50; however we felt that M= 0.15 was the most appropriate estimate based on our estimate of Z. Full recruitment to the gray snapper recreational fishery began at age 4, was completed by age 8, and there was no discernible peak in the catch curve dome

A generic study of strip mining impacts on groundwater resources

Originally presented as the first author's thesis, (M.S.) in the M.I.T. Dept. of Civil Engineering, 1977.This report evaluates the influence of strip mining features, commonly found in the Northern Great Plains Coal Region, on ground water hydrology. The features examined are: reclaimed mine geometry, relative transmissivity between the reclaimed spoil and the surrounding unmined coal bed aquifer, anisotropy, the gravity sorted rubble layer, coal wedges left between trench cuts, and the position and size of an operational mine in the regional flow system. A finite element computer model was used to simulate the groundwater flow field from three frames of reference: a local plan view of the mine site (local hydrology), a cross sectional view of flow through the reclaimed mine interior (interior flow), and a cross sectional view of a regional flow system (regional hydrology). The simulation model solved for the piezometric head distribution in each system. For each simulation the piezometric head contours were plotted, and in some cases, the increase in flux induced by the mine properties, and the contact time of water passing through the reclaimed spoil were calculated. Although only the flow of water through the spoil was modeled, water quality effects were inferred through a set of indices dealing with the reclaimed mine size and amount of water passing through it. The effects of a reclaimed mine were studied in the local and interior flow simulations. The influence of an operational mine was examined in the regional simulation. In all cases, the long term impacts were simulated by solving for the steady state condition. Regional location is found to be the most important factor in the influence of an operational mine on groundwater resources. Relative transmissivity is the most important factor in determining the influence of a reclaimed mine. When present, the rubble layer dominates the flow pattern through the mine spoil. The coal wedges are apparently of little hydrologic consequence. Equidimensional mine shapes are preferred to elongated shapes because they induce the least amount of flow through the spoil per unit extracted coal.Prepared with the support of the M.I.T. Energy Laboratory's institutional funds from the U.S. Energy Research and Development Administration and the National Science Foundation