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2002

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Articles 1 - 18 of 18

Full-Text Articles in Engineering

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, …

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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.

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On The Nature Of The Electrochemically Synthesized Hard Fe-0.96 Mass Pct C Alloy Film Nov 2002

On The Nature Of The Electrochemically Synthesized Hard Fe-0.96 Mass Pct C Alloy Film

A.S. Md Abdul Haseeb

A hard Fe-0.96 mass pet C alloy with a hardness value of 810 HV has been electrochemically synthesized from a ferrous sulfate bath containing a small amount of citric acid and L-ascorbic acid. The nature of the alloy has been investigated by a number of techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Mössbauer spectroscopy, differential scanning calorimetry (DSC), and magnetic measurements. The decomposition behavior of the alloy is also studied and compared with that of thermally prepared martensite. It has been found that the electrochemically deposited Fe-C alloy exists in …

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Roentgen's First Public Lecture, Fathi Habashi Oct 2002

Roentgen's First Public Lecture, Fathi Habashi

Fathi Habashi

The Birmingham artist Robert Alan Thom (1915-1979) painted a picture in 1966 showing Wilhelm Conard Roentgen at his first public demonstration of the newly discovered X-rays in the evening of January 23, 1896. The lecture took place at the Physics Department Auditorium of the University of Würzburg in Germany where Roentgen was the rector. The painting shows Albert von Kölliker, professor of anatomy at the University putting his hand on a photographic plate to make an X-ray picture. The painting is published in an interesting book entitled Great Moments in Medicine by Parke, Davis & Company, Northwood Institute Press, Detroit …

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Delivering On The 256 Qam Promise, Ron D. Katznelson Oct 2002

Delivering On The 256 Qam Promise, Ron D. Katznelson

Ron D. Katznelson

The accumulation of degradation factors in the downstream channels is reviewed with focus on headend/hub transmission-related noise aggregation due to a plurality of downstream Quadrature Amplitude Modulation (QAM) transmitters and upconverters. Substantial increase in the number of QAM transmitters based on frequency agile upconverters is expected. Unlike fixed channel upconverters, these do not have narrow band filters at their output, consequently imparting appreciable levels of broadband noise on the network when several such units are combined. Based on these factors and other noise contributions, it is shown that additional impairments due to fluctuations associated with composite distortion terms on the …

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Method Of Manufacturing A Semiconductor Wafer Level Package, Us Patent # 6,465,281, Daxue Xu, Henry H. Hughes, Paul L. Bergstorm, Frank A. Shemansky, Hak-Yam Tsoi Sep 2002

Method Of Manufacturing A Semiconductor Wafer Level Package, Us Patent # 6,465,281, Daxue Xu, Henry H. Hughes, Paul L. Bergstorm, Frank A. Shemansky, Hak-Yam Tsoi

Paul Bergstrom

A semiconductor wafer level package used to encapsulate a device fabricated on a semiconductor substrate wafer before dicing of the wafer into individual chips. A cap wafer may be bonded to the semiconductor substrate using a low temperature frit glass layer as a bonding agent. The frit glass layer is in direct contact with the device. A hermetic seal is formed by a combination of the semiconductor substrate wafer, the cap wafer and the frit glass layer. A second embodiment of the package does not contain a cap wafer.

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Analytical Model For The Optical Functions Of Amorphous Semiconductors From The Near-Infrared To Ultraviolet: Applications In Thin Film Photovoltaics, A. S. Ferlauto, G. M. Ferreira, Joshua M. Pearce, C. R. Wronski, R. W. Collins, Xunming Deng, Gautam Ganguly Aug 2002

Analytical Model For The Optical Functions Of Amorphous Semiconductors From The Near-Infrared To Ultraviolet: Applications In Thin Film Photovoltaics, A. S. Ferlauto, G. M. Ferreira, Joshua M. Pearce, C. R. Wronski, R. W. Collins, Xunming Deng, Gautam Ganguly

Joshua M. Pearce

We have developed a Kramers–Kronig consistent analytical expression to fit the measured optical functions of hydrogenated amorphous silicon(a-Si:H) based alloys, i.e., the real and imaginary parts of the dielectric function(ε1,ε2) (or the index of refractionn and absorption coefficient α) versus photon energy E for the alloys. The alloys of interest include amorphous silicon–germanium (a-Si1−xGex:H) and silicon–carbon (a-Si1−xCx:H), with band gaps ranging continuously from ∼1.30 to 1.95 eV. The analytical expression incorporates the minimum number of physically meaningful, E independent parameters required to fit (ε1,ε2) versus E. The fit is performed simultaneously throughout the following three regions: (i) the below-band gap …

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Struggles Of The ‘Father’, Aimee Dechambeau Aug 2002

Struggles Of The ‘Father’, Aimee Dechambeau

Aimée L. deChambeau

Biographical account of Konstantin Eduardovich Tsiolkovsky, the father of Soviet cosmonautics.

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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 …

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Functional Profiling Of The Saccharomyces Cerevisiae Genome, Patrick Flaherty Jul 2002

Functional Profiling Of The Saccharomyces Cerevisiae Genome, Patrick Flaherty

Patrick Flaherty

Determining the effect of gene deletion is a fundamental approach to understanding gene function. Conventional genetic screens exhibit biases, and genes contributing to a phenotype are often missed. We systematically constructed a nearly complete collection of gene-deletion mutants (96% of annotated open reading frames, or ORFs) of the yeast Saccharomyces cerevisiae. DNA sequences dubbed 'molecular bar codes' uniquely identify each strain, enabling their growth to be analysed in parallel and the fitness contribution of each gene to be quantitatively assessed by hybridization to high-density oligonucleotide arrays. We show that previously known and new genes are necessary for optimal growth …

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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 …

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Mobility Gap Profiles In Si:H Intrinsic Layers Prepared By H2 Dilution Of Sih4: Effects On The Performance Of P-I-N Solar Cells, R. J. Koval, A. S. Ferlauto, Joshua M. Pearce, R. W. Collins, C. R. Wronski Jan 2002

Mobility Gap Profiles In Si:H Intrinsic Layers Prepared By H2 Dilution Of Sih4: Effects On The Performance Of P-I-N Solar Cells, R. J. Koval, A. S. Ferlauto, Joshua M. Pearce, R. W. Collins, C. R. Wronski

Joshua M. Pearce

Insights into the growth processes and microstructural evolution for intrinsic (i) hydrogenated silicon (Si:H) films obtained from real-time spectroscopic ellipsometry (RTSE) are extended to the characterization of the optoelectronic properties of the corresponding solar cells. Numerical modeling of the J–V characteristics and their temperature dependences support the RTSE results and provide new information about the optoelectronic properties of the i-layer materials. Experimental results are presented that strongly suggest changes in the mobility gap of the i-layer materials as their microstructure evolves with thickness, further confirming the important effect of the hydrogen dilution ratio Full-size image (<1 >K) on the transitions …

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Results Of Audio-Visual Winter Road Condition Sensor Prototype, Kevin Mcfall, T. Niittula Dec 2001

Results Of Audio-Visual Winter Road Condition Sensor Prototype, Kevin Mcfall, T. Niittula

Kevin McFall

After several years of research in winter road condition classification, an automated prototype has been tested. Classification is achieved with artificial neural networks based on data from either images of the road, acoustic signals of vehicles passing the sensor, or a combination of the two. Systems based on either images or signals give good results for some road condition classes, but the most reliable results are for the hybrid system. Hybrid results are reliable for icy, snowy, and wet road conditions but not for dry. Dry results can be improved with more
representative training data and/or further integration with other …

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Effects Of Concentration And Temperature On The Coupled Heat And Mass Transport In Liquid Mixtures, Yasar Demirel, S.I. Sandler Dec 2001

Effects Of Concentration And Temperature On The Coupled Heat And Mass Transport In Liquid Mixtures, Yasar Demirel, S.I. Sandler

YASAR DEMIREL

Using published experimental data on the thermal conductivity, mutual diffusivity, and heats of transport, the degree of coupling between heat and mass flows has been calculated for binary and ternary nonideal liquid mixtures.

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Thermodynamics And Bioenergetics, Yasar Demirel Dec 2001

Thermodynamics And Bioenergetics, Yasar Demirel

YASAR DEMIREL

Bioenergetics is concerned with the energy conservation and conversion processes in a living cell, particularly in the inner membrane of the mitochondrion. This review summarizes the role of thermodynamics in understanding the coupling between the chemical reactions and the transport of substances in bioenergetics. Thermodynamics has the advantages of identifying possible pathways, providing a measure of the efficiency of energy conversion, and of the coupling between various processes without requiring a detailed knowledge of the underlying mechanisms. In the last five decades, various new approaches in thermodynamics, non-equilibrium thermodynamics and network thermodynamics have been developed to understand the transport and …

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On The Origin Of High Phosphorus Contents In Ancient Indian Iron, Vikas Kumar, R. Balasubramaniam Dec 2001

On The Origin Of High Phosphorus Contents In Ancient Indian Iron, Vikas Kumar, R. Balasubramaniam

Vikas Kumar

No abstract provided.

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Deconvolution Of Compartmental Water Diffusion Coefficients In Yeast-Cell Suspensions Using Combined T1 And Diffusion Measurements, Matthew D. Silva, Karl G. Helmer, Jing-Huei Lee, Sam S. Han, Charles S. Springer, Christopher H. Sotak Dec 2001

Deconvolution Of Compartmental Water Diffusion Coefficients In Yeast-Cell Suspensions Using Combined T1 And Diffusion Measurements, Matthew D. Silva, Karl G. Helmer, Jing-Huei Lee, Sam S. Han, Charles S. Springer, Christopher H. Sotak

Sam Han

Deconvolution of Compartmental Water Diffusion Coefficients in Yeast-Cell Suspensions Using Combined T1 and Diffusion Measurements

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Prediction Of Splitting Tensile Strength Of High-Performance Concrete, Hilmi Mahmud Dec 2001

Prediction Of Splitting Tensile Strength Of High-Performance Concrete, Hilmi Mahmud

Hilmi Mahmud

Splitting tensile strength (STS) is one of the concrete mechanical properties that are used in structural design. It can be related to numerous parameters, which include compressive strength, water/binder (W/B) ratio and concrete age. Until now, most researchers estimated the STS directly from compressive strength data. This paper suggests formulae that relate STS with that of compressive strength, W/B ratio and concrete age. The predicted STS can be obtained accurately using these formulae. It is proposed that the equation with the concrete age (t) parameter be used in predicting the STS of high-performance concrete (HPC). © 2002 Elsevier Science Ltd. …

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