Publications

The authors present a compact, robust, solid-state blue light (490 nm) source capable of greater than 5 mW of output in a TEM{sub 00} mode. This device is an optically pumped, vertical external-cavity surface-emitting laser (VECSEL) with an intracavity frequency doubling crystal.

Deposition parameters were found to have a marked effect on piezoelectric response of reactive radio frequency (RF) sputtered AlN thin films. The authors observed peizoelectric response values ranging from {minus}3.5 to +4.2 pm/V for 1 {micro}m thick AlN films deposited onto Ti/Ru electrode stacks. An investigation of the effects of deposition parameters, in particular the nature of the Ru/AlN interface, was conducted. The lag time between deposition of adjacent thin film layers appeared to have the greatest affect on the value of the piezoelectric response. This suggests that chemical reaction occurring on the Ru thin film surface is responsible for changing an important thin film property such as dipole orientation within the overlying AlN thin film.

In this paper, we introduce a new approach for altering the properties of bridged polysilsesquioxane xerogels using post-processing modification of the polymeric network. The bridging organic group contains latent functionalities that can be liberated thermally, photochemically, or by chemical means after the gel has been processed to a xerogel. These modifications can produce changes in density, volubility, porosity, and or chemical properties of the material. Since every monomer possesses two latent functional groups, the technique allows for the introduction of high levels of functionality in hybrid organic-inorganic materials. Dialkylenecarbonate-bridged polysilsesquioxane gels were prepared by the sol-gel polymerization of bis(triethoxysilylpropyl)carbonate (1) and bis(triethoxysilylisobutyl)-carbonate (2). Thermal treatment of the resulting non-porous xerogels and aerogels at 300-350 C resulted in quantitative decarboxylation of the dialkylenecarbonate bridging groups to give new hydroxyalkyl and olefinic substituted polysilsesquioxane monolithic xerogels and aerogels that can not be directly prepared through direct sol-gel polymerization of organotrialkoxysilanes.

JavaScript allows the definition and use of large, complex objects. Unlike some other object-oriented languages, it also allows run-time modifications not only of the values of object components, but also of the very structure of the object itself. This feature is powerful and sometimes very convenient, but it can be difficult to keep track of the object's structure and values throughout program execution. What's needed is a simple way to view the current state of an object at any point during execution. There is a debug function that is included in the Netscape server-side JavaScript environment. The function outputs the value(s) of the expression given as the argument to the function in the JavaScript Application Manager's debug window [SSJS].

Traditional safety and reliability analysis methods are applicable to many standard problems, including those examples illustrated in most formal courses. However, there are many real-world situations for which non-traditional methods appear to be more appropriate, mainly because most practical problems involve substantial subjectivity about the inputs and models used. This paper surveys some of the most applicable approaches found in a recent research study. Each approach is developed individually and is illuminated by selecting example situations of apparent applicability. Then, the combinational blending of the approaches with each other and with traditional methodology is discussed.

Work of adhesion (Wa) measurements are being studied for several types of polymer/metal combinations in order to obtain a better understanding of the adhesive failure mechanisms for systems containing encapsulated and bonded components. A primary concern is whether studies of model systems can be extended to systems of technological interest. One study performed in our laboratory involved the determination of Wa between silicone (PDMS) and Al surfaces in order to establish potential adhesive failure mechanisms. Our initial work with PDMS was based on Dow Corning 170 Sylgard. PDMS hemispheres were synthesized following the procedure outlined by Chaudhury and Whitesides where the filler was stripped from the commercial silicone by centrifuging. Wa between PDMS surfaces was determined using the JKR method. Our results for the Wa of PDMS were in agreement with those reported by Chaudhury and Whitesides. However, further JKR studies using these PDMS hemispheres on flat Al surfaces were fraught with difficulty. We could not discriminate hydrogen-bonding effects between Al{sub 2}O{sub 3} and hydroxyl groups in the PDMS and other possible bonding mechanisms. It was suggested that commercial systems contain inhibitors and additives that interfere with understanding the PMDS/Al interface. Therefore, the current study uses pure PDMS networks synthesized in our lab. Also, two contact mechanics methods were deployed to measure the Wa--JKR method using two hemispheres and a LEFM method using a cylinder containing a circumferential crack. This paper contains a description of the synthesis of the PDMS used for these studies and the determination of Wa between PDMS surfaces using the JKR method, contact angle measurements, and a LEFM method that consists of a cylinder containing a circumferential crack.

This editorial paper presents a vision for intelligent health care in the home of the future, focusing on technologies with the highest potential payoff given targeted government funding over the next ten years. A secure, plug-and-play information framework provides the starting point for identifying technologies that must be developed before home-based devices can know their context and assimilate information to support care decisions.

We propose an object-oriented information architecture for telemedicine systems that promotes secure `plug-and-play' interaction between system components through standardized interfaces, communication protocols, messaging formats, and data definitions. In this architecture, each component functions as a black box, and components plug together in a ''lego-like'' fashion to achieve the desired device or system functionality. Introduction Telemedicine systems today rely increasingly on distributed, collaborative information technology during the care delivery process. While these leading-edge systems are bellwethers for highly advanced telemedicine, most are custom-designed and do not interoperate with other commercial offerings. Users are limited to a set of functionality that a single vendor provides and must often pay high prices to obtain this functionality, since vendors in this marketplace must deliver en- tire systems in order to compete. Besides increasing corporate research and development costs, this inhibits the ability of the user to make intelligent purchasing decisions regarding best-of-breed technologies. This paper proposes a reference architecture for plug-and-play telemedicine systems that addresses these issues.

Global Nuclear Materials Management (GNMM) anticipates and supports a growing international recognition of the importance of uniform, effective management of civilian, excess defense, and nuclear weapons materials. We expect thereto be a continuing increase in both the number of international agreements and conventions on safety, security, and transparency of nuclear materials, and the number of U.S.-Russian agreements for the safety, protection, and transparency of weapons and excess defense materials. This inventory of agreements and conventions may soon expand into broad, mandatory, international programs that will include provisions for inspection, verification, and transparency, To meet such demand the community must build on the resources we have, including State agencies, the IAEA and regional organizations. By these measures we will meet the future expectations for monitoring and inspection of materials, maintenance of safety and security, and implementation of transparency measures.

Sandia has implemented a formal process to verify that new or modified facilities and operations are ready to safely operate. The readiness review process focuses on the status of management systems, personnel, and systems, structures, and components to do work safely. The scope and depth of the review are tailored to match the potential consequences and the likelihood that the consequences could occur. The precepts and methodology of the process are applicable to verifying the readiness of enterprise systems, and should comprise the final element in developing and implementing an enterprise system. This paper describes the readiness review process, the key elements for success, lessons learned from Sandia's readiness assessment process, and outlines how the process can be applied to enterprise systems. Specific topics addressed include selecting the criteria, approach, and lines of inquiry to be used for the review; selecting members for the review team; team leader responsibilities; reporting and closing deficiencies; and, responsibilities of the facility/project owner and management.

Irradiation of red meat and poultry has been approved by the U.S. FDA, and the U.S. Department of Agriculture's rule for processing red meat is out for comment. Looking beyond the current issues of packaging materials, labeling, and consumer acceptance, this paper reviews the next step of implementation and how to remove, or at least reduce, the barriers to utilization. Polls of the user community identified their requirements for electron beam or x-ray processing of meat or poultry and their concerns about implementation for on-line processing. These needs and issues are compared to the capabilities of the accelerator industry. The critical issues of beam utilization and dose uniformity, factors affecting floor space requirements, and treatment costs are examined.

Boolean logic expressions are often derived in safety and reliability analysis. Since the values of the operands are rarely exact, accounting for uncertainty with the tightest justifiable bounds is important. Accurate determination of result bounds is difficult when the inputs have constraints. One example of a constraint is that an uncertain variable that appears multiple times in a Boolean expression must always have the same value, although the value cannot be exactly specified. A solution for this repeated variable problem is demonstrated for two Boolean classes. The classes, termed functions with unate variables (including, but not limited to unate functions), and exclusive-or functions, frequently appear in Boolean equations for uncertain outcomes portrayed by logic trees (event trees and fault trees).

This paper presents results from a series of preliminary tests to evaluate a scannerless range-imaging device as a potential sensory enhancement tool for divers and as a potential identification sensor for deployment on small unmanned underwater vehicles. The device, developed by Sandia National Laboratories, forms an image on the basis of point-to-point range to the target rather than an intensity map. The range image is constructed through a classical continuous wave phase detection technique in which the light source is amplitude modulated at radio frequencies. The receiver incorporates a gain-modulated image intensifier, and range information is calculated on the basis of the phase difference between the transmitted and reflected signal. The initial feasibility test at the Coastal Systems Station showed the device to be effective at imaging low-contrast underwater targets such as concertina wire. It also demonstrated success at imaging a 21-inch sphere at a depth of 10 feet in the water column through a wavy air-water interface.

In 1991, the Federal Aviation Administration (FAA) established an Airworthiness Assurance NDI Validation Center (AANC) at Sandia National Laboratories. Its primary mission is to support technology development, validation, and transfer to industry in order to enhance the airworthiness and improve the aircraft maintenance practices of the U.S. commercial aviation industry. The Center conducts projects in a myriad of engineering disciplines. The results are placed in the public domain so that the industry at-large can reap the benefits of FAA-funded Research and Development efforts. To support the Center's goals, the FAA/AANC has set up a hangar facility at the Albuquerque International Airport which contains a collection of transport and commuter aircraft as well as other test specimens. The facility replicates a working maintenance environment by incorporating both the physical inspection difficulties as well as the environmental factors which influence maintenance reliability.

Over a period of 15 months, five sets of adhesively-bonded butt joints were fabricated and tested. This previously unreported data is used to assess the variability of measured interface corner toughness values, K{sub ac}, as well as the dependence of K{sub ac} on surface preparation. A correlation between K{sub ac} and the size of the adhesive failure zone is also noted.

The authors consider a chain of elastic (Hertzian) grains that repel upon contact according to the potential V = a{delta}{sup u}, u > 2, where {delta} is the overlap between the grains. They present numerical and analytical results to show that an impulse initiated at an end of a chain of Hertzian grains in contact eventually propagates as a soliton for all n > 2 and that no solitons are possible for n {le} 2. Unlike continuous, they find that colliding solitons in discrete media initiative multiple weak solitons at the point of crossing.

Abstract not provided.

This paper outlines general physical and computational issues associated with performing numerical simulation of fire suppression. Fire suppression encompasses a broad range of chemistry and physics over a large range of time and length scales. The authors discuss the dominant physical/chemical processes important to fire suppression that must be captured by a fire suppression model to be of engineering usefulness. First-principles solutions are not possible due to computational limitations, even with the new generation of tera-flop computers. A basic strategy combining computational fluid dynamics (CFD) simulation techniques with sub-grid model approximations for processes that have length scales unresolvable by gridding is presented.

As we enter the new millennium, let us recognize that the losses resulting from natural or malevolent events that cause major property damage, severe injuries, and unnecessary death are not always due to forces beyond our control. We can prevent these losses by changing the way we think and act about design and construction projects. New tools, technologies, and techniques can improve structural safety, security, and reliability and protect owners, occupants, and users against loss and casualties. Hurricane Mitch, the African embassy bombings, the ice storms in Canada and the northeastern US last winter, the Oklahoma City bombing, flooding and earthquakes in California, tornadoes and flooding in Florida, and wildfires in the Southwest are threats to the safety and security of the public and the reliability of our constructed environment. Today's engineering design community must recognize these threats and address them in our standards, building codes, and designs. We know that disasters will continue to strike and we must reduce their impact on the public. We must demand and create innovative solutions that assure a higher level of structural performance when disasters strike.

Z-pinches created using the Z accelerator generate {approximately}220 TW, 1.7 MJ radiation pulses that heat large ({approximately}10 cm{sup 3}) hohlraums to 100-150 eV temperatures for times of order 10 nsec. We are performing experiments exploiting this intense radiation to drive shock waves for equation of state studies. The shock pressures are typically 1-10 Mbar with 10 nsec duration in 6-mm-diameter samples. In this paper we demonstrate the ability to perform optical spectroscopy measurements on shocked samples located in close proximity to the z-pinch. These experiments are particularly well suited to optical spectroscopy measurements because of the relatively large sample size and long duration. The optical emission is collected using fiber optics and recorded with a streaked spectrograph. Other diagnostics include VISAR and active shock breakout measurements of the shocked sample and a suite of diagnostics that characterize the radiation drive. Our near term goal is to use the spectral emission to obtain the temperature of the shocked material. Longer term objectives include the examination of deviations of the spectrum from blackbody, line emission from lower density regions, determination of kinetic processes in molecular systems, evaluation of phase transitions such as the onset of metalization in transparent materials, and characterization of the plasma formed when the shock exits the rear surface. An initial set of data illustrating both the potential and the challenge of these measurements is described.

Sandia Laboratories' computational scientists are addressing a very important question: How do we get insight from the human combined with the computer-generated information? The answer inevitably leads to using scientific visualization. Going one technology leap further is teraflop visualization, where the computing model and interactive graphics are an integral whole to provide computing for insight. In order to implement our teraflop visualization architecture, all hardware installed or software coded will be based on open modules and dynamic extensibility principles. We will illustrate these concepts with examples in our three main research areas: (1) authoring content (the computer), (2) enhancing precision and resolution (the human), and (3) adding behaviors (the physics).

Over the past two years, New Mexico has been engaged in a significant new approach to implement large purchases of solar power. This effort followed a regulatory process that treated solar power generation similar to conventional generation obtained by an investor-owned utility under the regulation of a public utility commission. In 1997, Public Service Company of New Mexico (PNM) gained approval to purchase power from a 100-MW combustion turbine facility that would be owned and operated by a wholesale generator. At the same time it issued the approval, and following discussions with the utility, the New Mexico Public Utility Commission (NMPUC) also required PNM to issue a request for proposal for a 5-MW central station solar facility, a major step for solar technologies in the state, in what would be the world's largest of its technology type. In cooperation with the staff of the NMPUC, PNM reviewed the proposals received, and Applied Power Corporation was selected for the photovoltaic portion of the proposed plan; retaining ownership of the plant, assuming the risks connected with the technology, and operating the plant in exchange for a power purchase agreement in a first-of-its-kind contract for photovoltaics. During the NMPUC hearings, various parties raised significant opposition to the cost-recovery mechanism that was proposed and voiced issues about the type of solar plant, its size, cost and the tiding approaches to building it. Because of these issues, alternative proposals were put forth that reduced the size and costs of the plant and had implied changes in ownership and risks. The order issued by the NMPUC on October 21, 1998, requires PNM to impose a charge of 0.5% on its retail electric customers' monthly bills to be used to acquire the solar facilities, but also to obtain other renewable electric power resources, both on a pay-as-you-go basis. This paper identifies the issues and their resolution that similar projects are expected to encounter.

We conducted three sets of depth-of-penetration experiments with limestone targets and 3.0 caliber-radius-head (CRH), ogive-nose steel rod projectiles. The limestone targets had a nominal unconfined compressive strength of 60 MPa, a density of 2.31 kg/m{sup 3}, a porosity of 15%, and a water content less than 0.4%. The ogive-nose rod projectiles with length-to-diameter ratios often were machined from 4340 R{sub c} 45 and Aer Met 100 R{sub c} 53 steel, round stock and had diameters and masses of 7.1 mm, 0.020 kg; 12.7 mm, 0.117 kg; and 25.4 mm, 0.931 kg. Powder guns or a two-stage, light-gas gun launched the projectiles at normal impacts to striking velocities between 0.4 and 1.9 km/s. For the 4340 R{sub c} 45 and Aer Met 100 R{sub c} 53 steel projectiles, penetration depth increased as striking velocity increased to a striking velocity of 1.5 and 1.7 km/s, respectively. For larger striking velocities, the projectiles deformed during penetration without nose erosion, deviated from the shot line, and exited the sides of the target. We also developed an analytical penetration equation that described the target resistance by its density and a strength parameter determined from depth of penetration versus striking velocity data.

The delivery of the first one tera-operations/sec computer has significantly impacted production data visualization, affecting data transfer, post processing, and rendering. Terascale computing has motivated a need to consider the entire data visualization system; improving a single algorithm is not sufficient. This paper presents a systems approach to decrease by a factor of four the time required to prepare large data sets for visualization.For daily production use, all stages in the processing pipeline from physics simulation code to pixels on a screen, must be balanced to yield good overall performance. Also, to complete the data path from screen to the analyst's eye, user display systems for individuals and teams are examined. Performance of the initial visualization system is compared with recent improvements. Lessons learned from the coordinated deployment of improved algorithms are also discussed, including the need for 64 bit addressing and a fully parallel data visualization pipeline.

An evaluation of biotic and abiotic attenuation processes potentially important to chlorinated and non-chlorinated volatile organic compound (VOC) fate and transport in the 148 meter thick vadose zone beneath the Chemical Waste Landfill (CWL) was conducted. A unique feature of this evaluation is the comparison of two estimates of VOC mass present in the soil gas, pore-water, and solid phases (but not including mass as non-aqueous phase liquid [NAPL]) of the vadose zone in 1993. One estimate, 1,800 kg, was obtained from vadose zone transport modeling that incorporated molecular diffusion and volatilization to the atmosphere, but not biotic or chemical processes. The other estimate, 2,120 kg, was obtained from the sum of VOC mass physically removed during soil vapor extraction and an estimate of VOC mass remaining in the vadose zone in 1998, both adjusted to exclude NAPL mass. This comparison indicates that biogeochemical processes were at best slightly important to historical VOC plume development. Some evidence of aerobic degradation of non-chlorinated VOCs and abiotic transformation of 1,1,1-Trichloroethane was identified. Despite potentially amenable site conditions, no evidence was found of cometabolic and anaerobic transformation pathways. Relying principally on soil-gas analytical results, an upper-bound estimate of 21% mass reduction due to natural biogeochemical processes was developed. Although available information for the CWL indicates that natural attenuation processes other than volatilization to the atmosphere did not effective y enhance groundwater protection, these processes could be important in significantly reducing groundwater contamination and exposure risks at other sites. More laboratory and field research is required to improve our collective ability to characterize and exploit natural VOC attenuation processes, especially with respect to the combination of relatively thick and dry vadose zones and chlorinated VOCs.