633 Matching Results

Search Results

Advanced search parameters have been applied.

New Security Results on Encrypted Key Exchange

Description: Schemes for encrypted key exchange are designed to provide two entities communicating over a public network, and sharing a (short) password only, with a session key to be used to achieve data integrity and/or message confidentiality. An example of a very efficient and ''elegant'' scheme for encrypted key exchange considered for standardization by the IEEE P1363 Standard working group is AuthA. This scheme was conjectured secure when the symmetric-encryption primitive is instantiated via either a cipher that closely behaves like an ''ideal cipher,'' or a mask generation function that is the product of the message with a hash of the password. While the security of this scheme in the former case has been recently proven, the latter case was still an open problem. For the first time we prove in this paper that this scheme is secure under the assumptions that the hash function closely behaves like a random oracle and that the computational Diffie-Hellman problem is difficult. Furthermore, since Denial-of-Service (DoS) attacks have become a common threat we enhance AuthA with a mechanism to protect against them.
Date: December 15, 2003
Creator: Bresson, Emmanuel; Chevassut, Olivier & Pointcheval, David
Partner: UNT Libraries Government Documents Department

Fermi Timing and Synchronization System

Description: The Fermi FEL will depend critically on precise timing of its RF, laser and diagnostic subsystems. The timing subsystem to coordinate these functions will need to reliably maintain sub-100fs synchronicity between distant points up to 300m apart in the Fermi facility. The technology to do this is not commercially available, and has not been experimentally demonstrated in a working facility. Therefore, new technology must be developed to meet these needs. Two approaches have been researched by different groups working with the Fermi staff. At MIT, a pulse transmission scheme has been developed for synchronization of RF and laser devices. And at LBL, a CW transmission scheme has been developed for RF and laser synchronization. These respective schemes have advantages and disadvantages that will become better understood in coming years. This document presents the work done by both teams, and suggests a possible system design which integrates them both. The integrated system design provides an example of how choices can be made between the different approaches without significantly changing the basic infrastructure of the system. Overall system issues common to any synchronization scheme are also discussed.
Date: July 19, 2006
Creator: Wilcox, R.; Staples, J.; Doolittle, L.; Byrd, J.; Ratti, A.; Kaertner, F.X. et al.
Partner: UNT Libraries Government Documents Department

Observation of field-induced domain wall propagation in magnetic nanowires by magnetic transmission X-ray microscopy

Description: Magnetic transmission X-ray microscopy (M-TXM) is used to image domain walls in magnetic ring structures formed by a 300 nm wide, 24 nm thick Ni{sub 81}Fe{sub 19} nanowire. Both transverse and vortex type domain walls are observed after application of different field sequences. Domain walls can be observed by comparing images obtained from opposite field sequences, or else domain wall propagation observed by comparing successive images in a particular field sequence. This demonstrates the potential use of M-TXM in developing and understanding planar magnetic nanowire behavior.
Date: December 1, 2007
Creator: Bryan, M. T.; Fry, P. W.; Fischer, P. & Allwood, D. A.
Partner: UNT Libraries Government Documents Department

MOSAIC: a new wavefront metrology

Description: MOSAIC is a new wavefront metrology that enables complete wavefront characterization from print or aerial image based measurements. Here we describe MOSAIC and verify its utility with a model-based proof of principle.
Date: February 2, 2009
Creator: Anderson, Christopher & Naulleau, Patrick
Partner: UNT Libraries Government Documents Department

UC Assurance Plan For Lawrence Berkeley National Laboratory July2007

Description: This Division ES&H Self-Assessment Manual describes how the Laboratory administers a division self-assessment program that conforms to the institutional requirements promulgated in the 'LBNL Environment, Safety and Health Self-Assessment Program' (LBNL/PUB-5344, latest revision). The institutional program comprises all appraisal and reporting activities that identify environmental, safety, and health deficiencies and associated corrective actions. It is designed to meet U.S. Department of Energy (DOE) requirements for self-assessment. Self-assessment is a continuous process of information gathering and evaluation. A division selfassessment program should describe methods for gathering and documenting information, and methods to analyze these performance data to identify trends and root causes and their corrections.
Date: July 9, 2007
Creator: Chernowski, John
Partner: UNT Libraries Government Documents Department

Accelerating the Payment of PACE Assessments By Mark Zimring and Merrian Fulle

Description: The 'acceleration' of land-secured assessments allows municipalities to declare the entire value (not just the late payments) of a property owner's outstanding balance payable if a default occurs. State laws vary on whether acceleration is required, permitted, or prohibited. Acceleration can be attractive to bond investors because it strips out non-performing assessments, and may avoid delays in debt service payments to investors. The risk that non-acceleration will negatively impact bond investors is a particular issue in states without a process for rapidly resolving defaults. However, acceleration may also increase the risk to mortgage holders, as the full amount of the outstanding assessment becomes due and traditionally has priority over other lien holders. Acceleration also places a greater burden on the property owner.
Date: May 4, 2010
Creator: Zimring, Mark & Fuller, Merrian
Partner: UNT Libraries Government Documents Department

Architecture Concepts and Technical Issues for an Open,Interoperable Automated Demand Response Infrastructure

Description: This paper presents the technical and architectural issues associated with automating Demand Response (DR) programs. The paper focuses on a description of the Demand Response Automation Server (DRAS), which is the main component used to automate the interactions between the Utilities and their customers for DR programs. Use cases are presented that show the role of the DRAS in automating various aspects of DR programs. This paper also describes the various technical aspects of the DRAS including its interfaces and major modes of operation. This includes how the DRAS supports automating such Utility/Customer interactions as automated DR bidding, automated DR event handling, and finally real-time pricing.
Date: October 1, 2007
Creator: Koch, Ed & Piette, Mary Ann
Partner: UNT Libraries Government Documents Department

ATLAS TrackingEvent Data Model -- 12.0.0

Description: In this report the event data model (EDM) relevant for tracking in the ATLAS experiment is presented. The core component of the tracking EDM is a common track object which is suited to describe tracks in the innermost tracking sub-detectors and in the muon detectors in offline as well as online reconstruction. The design of the EDM was driven by a demand for modularity and extensibility while taking into account the different requirements of the clients. The structure of the track object and the representation of the tracking-relevant information are described in detail.
Date: July 23, 2006
Creator: ATLAS; Akesson, F.; Atkinson, T.; Costa, M.J.; Elsing, M.; Fleischmann, S. et al.
Partner: UNT Libraries Government Documents Department

DNAPL invasion into a partially saturated dead-end fracture

Description: The critical height for DNAPL entry into a partially watersaturated, dead-end fracture is derived and compared to laboratoryobservations. Experiments conducted in an analog, parallel-plate fracturedemonstrate that DNAPL accumulates above the water until the height ofthe DNAPL overcomes the sum of the capillary forces at the DNAPL-airinterface and at the DNAPL-water interface. These experiments also showthat DNAPL preferentially enters the water at locations where DNAPL haspreviously entered, and the entry heights for these subsequent entriesare lower than the heights measured for the initial invasion. The wettingcontact angle at the DNAPL-water interface becomes larger at thelocations where the DNAPL has already entered the water because ofresidual DNAPL on the fracture walls, which results in lowering thecritical entry height at those locations. The experiments alsodemonstrate that a DNAPL lens can remain nearly immobile above the waterfor a period of time before eventually redistributing itself and enteringthe water.
Date: June 17, 2004
Creator: gwsu@lbl.gov
Partner: UNT Libraries Government Documents Department

BDDC for nonsymmetric positive definite and symmetric indefinite problems

Description: The balancing domain decomposition methods by constraints are extended to solving both nonsymmetric, positive definite and symmetric, indefinite linear systems. In both cases, certain nonstandard primal constraints are included in the coarse problems of BDDC algorithms to accelerate the convergence. Under the assumption that the subdomain size is small enough, a convergence rate estimate for the GMRES iteration is established that the rate is independent of the number of subdomains and depends only slightly on the subdomain problem size. Numerical experiments for several two-dimensional examples illustrate the fast convergence of the proposed algorithms.
Date: December 10, 2008
Creator: Tu, Xuemin & Li, Jing
Partner: UNT Libraries Government Documents Department

Fast marching methods for the continuous traveling salesman problem

Description: We consider a problem in which we are given a domain, a cost function which depends on position at each point in the domain, and a subset of points ('cities') in the domain. The goal is to determine the cheapest closed path that visits each city in the domain once. This can be thought of as a version of the Traveling Salesman Problem, in which an underlying known metric determines the cost of moving through each point of the domain, but in which the actual shortest path between cities is unknown at the outset. We describe algorithms for both a heuristic and an optimal solution to this problem. The order of the heuristic algorithm is at worst case M * N logN, where M is the number of cities, and N the size of the computational mesh used to approximate the solutions to the shortest paths problems. The average runtime of the heuristic algorithm is linear in the number of cities and O(N log N) in the size N of the mesh.
Date: December 1, 2008
Creator: Andrews, J. & Sethian, J.A.
Partner: UNT Libraries Government Documents Department

A Three-level BDDC algorithm for saddle point problems

Description: BDDC algorithms have previously been extended to the saddle point problems arising from mixed formulations of elliptic and incompressible Stokes problems. In these two-level BDDC algorithms, all iterates are required to be in a benign space, a subspace in which the preconditioned operators are positive definite. This requirement can lead to large coarse problems, which have to be generated and factored by a direct solver at the beginning of the computation and they can ultimately become a bottleneck. An additional level is introduced in this paper to solve the coarse problem approximately and to remove this difficulty. This three-level BDDC algorithm keeps all iterates in the benign space and the conjugate gradient methods can therefore be used to accelerate the convergence. This work is an extension of the three-level BDDC methods for standard finite element discretization of elliptic problems and the same rate of convergence is obtained for the mixed formulation of the same problems. Estimate of the condition number for this three-level BDDC methods is provided and numerical experiments are discussed.
Date: December 10, 2008
Creator: Tu, X.
Partner: UNT Libraries Government Documents Department