Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 8 of 8

Full-Text Articles in Physical Sciences and Mathematics

Applications Of Underground Structures For The Protection Of Critical Infrastructure, George H. Baker, Richard G. Little, Don A. Linger Nov 2002

Applications Of Underground Structures For The Protection Of Critical Infrastructure, George H. Baker, Richard G. Little, Don A. Linger

George H Baker

The U.S. President’s Commission on Critical Infrastructure Protection (PCCIP), convened in the wake of the bombing of the Murrah Federal Building in Oklahoma City, concluded that the nation’s physical security and economic security depend on our critical energy, communications, and computer infrastructures. While a primary motivating event for the establishment of the commission was the catastrophic physical attack of the Murrah Building, it is ironic that the commission focused its attention primarily on cyber threats. Their rationale was that cyber vulnerabilities posed a new, unaddressed challenge to infrastructure security. This approach was further questioned by the events of September 11, …


Supervisory Control And Data Acquisition (Scada) Systems, George H. Baker, Allan Berg Nov 2002

Supervisory Control And Data Acquisition (Scada) Systems, George H. Baker, Allan Berg

George H Baker

Our critical national infrastructure systems have become almost universally dependent upon computer-based control systems technically referred to as supervisory control and data acquisition (SCADA) systems. SCADA systems evolved from the telemetry and event-alarm systems developed in the early days of utilities. With the widespread use of SCADA systems, computers have become the "basis element" for much of our critical infrastructure. Thus, the disruption of controlling computer terminals and networks due to natural disasters, electric power failure, accidents or malicious activity can have catastrophic consequences.


The Seabed Auv — A Platform For High Resolution Imaging, Hanumant Singh, Ryan Eustice, Christopher Roman, Oscar Pizarro Aug 2002

The Seabed Auv — A Platform For High Resolution Imaging, Hanumant Singh, Ryan Eustice, Christopher Roman, Oscar Pizarro

Christopher N. Roman

No abstract provided.


Maximization Of The Open Circuit Voltage For Hydrogenated Amorphous Silicon N–I–P Solar Cells By Incorporation Of Protocrystalline Silicon P-Type Layers, R. J. Koval, Chi Chen, G. M. Ferreira, A. S. Ferlauto, Joshua M. Pearce, P. I. Rovira, C. R. Wronski, R. W. Collins Aug 2002

Maximization Of The Open Circuit Voltage For Hydrogenated Amorphous Silicon N–I–P Solar Cells By Incorporation Of Protocrystalline Silicon P-Type Layers, R. J. Koval, Chi Chen, G. M. Ferreira, A. S. Ferlauto, Joshua M. Pearce, P. I. Rovira, C. R. Wronski, R. W. Collins

Joshua M. Pearce

In studies of hydrogenated amorphous silicon(a-Si:H) n–i–psolar cells fabricated by rf plasma-enhanced chemical vapor deposition (PECVD), we have found that the maximum open circuit voltage (Voc) is obtained by incorporating p-type doped Si:H layers that are protocrystalline in nature. Specifically, these optimum p layers are prepared by PECVD in the a-Si:H growth regime using the maximum hydrogen-to-silane flow ratio possible without crossing the thickness-dependent transition into the mixed-phase (amorphous+microcrystalline) growth regime for the ∼200 Å p-layer thickness. The strong dependence of the p-layer phase and solar cell Voc on the underlying i-layer phase also confirms the protocrystalline nature of the …


Photovoltaics — A Path To Sustainable Futures, Joshua M. Pearce Apr 2002

Photovoltaics — A Path To Sustainable Futures, Joshua M. Pearce

Joshua M. Pearce

As both population and energy use per capita increase, modern society is approaching physical limits to its continued fossil fuel consumption. The immediate limits are set by the planet’s ability to adapt to a changing atmospheric chemical composition, not the availability of resources. In order for a future society to be sustainable while operating at or above our current standard of living a shift away from carbon based energy sources must occur. An overview of the current state of active solar (photovoltaic, PV) energy technology is provided here to outline a partial solution for the environmental problems caused by accelerating …


Multiscalar, Multisensor Search And Survey With Hovering Auvs, Christopher Roman, Hanumant Singh Apr 2002

Multiscalar, Multisensor Search And Survey With Hovering Auvs, Christopher Roman, Hanumant Singh

Christopher N. Roman

No abstract provided.


Transparent Fault Tolerance For Web Services Based Architectures, Vijay Dialani, Simon Miles, Luc Moreau, David De Roure, Michael Luck Dec 2001

Transparent Fault Tolerance For Web Services Based Architectures, Vijay Dialani, Simon Miles, Luc Moreau, David De Roure, Michael Luck

Vijay Dialani

Service-based architectures enable the development of new classes of Grid and distributed applications. One of the main capabilities provided by such systems is the dynamic and flexible integration of services, according to which services are allowed to be a part of more than one distributed system and simultaneously serve different applications. This increased flexibility in system composition makes it difficult to address classical distributed system issues such as fault-tolerance. While it is relatively easy to make an individual service fault-tolerant, improving fault-tolerance of services collaborating in multiple application scenarios is a challenging task. In this paper, we look at the …


Logic, Optimization And Constraint Programming, John Hooker Dec 2001

Logic, Optimization And Constraint Programming, John Hooker

John Hooker

No abstract provided.