Progress in Biomedical Optics and Imaging - Proceedings of SPIE
Greenberg, Melisa R.; Chen, Weiliang; Pulford, Ben N.; Smolyakov, Gennady A.; Jiang, Ying B.; Bunge, Scott D.; Boyle, Timothy J.; Osiński, Marek
InP quantum dots (QDs) with zinc blende structure and InN QDs with hexagonal structure were synthesized from appropriate organometallic precursors in a noncoordinating solvent using myristic acid as a ligand. The QDs were characterized by TEM, the associated energy dispersive spectroscopy (EDS), electron diffraction, and steady state UV-VIS optical absorption and photoluminescence spectroscopy. To our best knowledge, this paper reports synthesis of InN colloidal quantum dots for the first time.
A decomposition chemistry and heat transfer model to predict the response of removable epoxy foam (REF) exposed to fire-like heat fluxes is described. The epoxy foam was created using a perfluorohexane blowing agent with a surfactant. The model includes desorption of the blowing agent and surfactant, thermal degradation of the epoxy polymer, polymer fragment transport, and vapor-liquid equilibrium. An effective thermal conductivity model describes changes in thermal conductivity with reaction extent. Pressurization is modeled assuming: (1) no strain in the condensed-phase, (2) no resistance to gas-phase transport, (3) spatially uniform stress fields, and (4) no mass loss from the system due to venting. The model has been used to predict mass loss, pressure rise, and decomposition front locations for various small-scale and large-scale experiments performed by others. The framework of the model is suitable for polymeric foams with absorbed gases. Published by Elsevier Ltd.
The peridynamic model was introduced by Silling in 1998. In this paper, we demonstrate the application of the quasistatic peridynamic model to two-dimensional, linear elastic, plane stress and plane strain problems, with special attention to the modeling of plain and reinforced concrete structures. We consider just one deviation from linearity--that which arises due to the irreversible sudden breaking of bonds between particles. The peridynamic model starts with the assumption that Newton's second law holds true on every infinitesimally small free body (or particle) within the domain of analysis. A specified force density function, called the pairwise force function, (with units of force per unit volume per unit volume) between each pair of infinitesimally small particles is postulated to act if the particles are closer together than some finite distance, called the material horizon. The pairwise force function may be assumed to be a function of the relative position and the relative displacement between the two particles. In this paper, we assume that for two particles closer together than the specified 'material horizon' the pairwise force function increases linearly with respect to the stretch, but at some specified stretch, the pairwise force function is irreversibly reduced to zero.
The US Department of Energy requires a periodic assessment of the Microsystems Program at Sandia National Laboratories. An external review of this program is held approximately every 18 months to 24 months. The report from the External Review Panel serves as the basis for Sandia's ''self assessment'' and is a specific deliverable of the governance contract between Lockheed Martin and the Department of Energy. The External Review of Microelectronics and Microsystems for Fiscal Year 2004 was held September 27-29, 2004 at Sandia National Laboratories, Albuquerque, NM. The external review panel consisted of experts in the fields of microelectronics, photonics and microsystems from universities, industry and other Government agencies. A complete list of the panel members is included as Appendix A of the attached report. The review assessed four areas: relevance to national needs and agency mission; quality of science, technology and engineering; performance in the operation of a major facility; and program performance management and planning. Relevance to national needs and agency mission was rated as ''outstanding''. The quality of science, technology, and engineering was rated as ''outstanding''. Operation of a major facility was rated as ''outstanding'', and the category of program performance, management, and planning was rated as ''outstanding''. Sandia's Microsystems Program thus received an overall rating of ''outstanding'' [the highest possible rating].
This report describes the features of monolithic, series connected silicon (Si) photovoltaic (PV) cells which have been developed for applications requiring higher voltages than obtained with conventional single junction solar cells. These devices are intended to play a significant role in micro / mini firing systems and fuzing systems for DOE and DOD applications. They are also appropriate for other applications (such as micro-electro-mechanical-systems (MEMS) actuation as demonstrated by Bellew et. al.) where electric power is required in remote regions and electrical connection to the region is unavailable or deemed detrimental for whatever reason. Our monolithic device consists of a large number of small PV cells, combined in series and fabricated using standard CMOS processing on silicon-on-insulator (SOI) wafers with 0.4 to 3 micron thick buried oxide (BOX) and top Si thickness of 5 and 10 microns. Individual cell isolation is achieved using the BOX layer of the SOI wafer on the bottom. Isolation along the sides is produced by trenching the top Si and subsequently filling the trench by deposition of dielectric films such as oxide, silicon nitride, or oxynitride. Multiple electrically isolated PV cells are connected in series to produce voltages ranging from approximately 0.5 volts for a single cell to several thousands of volts for strings of thousands of cells.
With the increasing role of computational modeling in engineering design, performance estimation, and safety assessment, improved methods are needed for comparing computational results and experimental measurements. Traditional methods of graphically comparing computational and experimental results, though valuable, are essentially qualitative. Computable measures are needed that can quantitatively compare computational and experimental results over a range of input, or control, variables and sharpen assessment of computational accuracy. This type of measure has been recently referred to as a validation metric. We discuss various features that we believe should be incorporated in a validation metric and also features that should be excluded. We develop a new validation metric that is based on the statistical concept of confidence intervals. Using this fundamental concept, we construct two specific metrics: one that requires interpolation of experimental data and one that requires regression (curve fitting) of experimental data. We apply the metrics to three example problems: thermal decomposition of a polyurethane foam, a turbulent buoyant plume of helium, and compressibility effects on the growth rate of a turbulent free-shear layer. We discuss how the present metrics are easily interpretable for assessing computational model accuracy, as well as the impact of experimental measurement uncertainty on the accuracy assessment.
Crude oil storage caverns at the U.S. Strategic Petroleum Reserve (SPR) are solution-mined from subsurface salt domes along the U.S. Gulf Coast. While these salt domes exhibit many attractive characteristics for large-volume, long-term storage of oil such as low cost for construction, low permeability for effective fluids containment, and secure location deep underground, they also present unique technical challenges for maintaining oil quality within delivery standards. The vapor pressures of the crude oils stored at SPR tend to increase with storage time due to the combined effects of geothermal heating and gas intrusion from the surrounding salt. This presents a problem for oil delivery offsite because high vapor-pressure oil may lead to excessive atmospheric emissions of hydrocarbon gases that present explosion hazards, health hazards, and handling problems at atmospheric pressure. Recognizing this potential hazard, the U.S. Department of Energy, owner and operator of the SPR, implemented a crude oil vapor pressure monitoring program that collects vapor pressure data for all the storage caverns. From these data, DOE evaluates the rate of change in vapor pressures of its oils in the SPR. Moreover, DOE implemented a vapor pressure mitigation program in which the oils are degassed periodically and will be cooled immediately prior to delivery in order to reduce the vapor pressure to safe handling levels. The work described in this report evaluates the entire database since its origin in 1993, and determines the current levels of vapor pressure around the SPR, as well as the rate of change for purposes of optimizing both the mitigation program and meeting safe delivery standards. Generally, the rate of vapor pressure increase appears to be lower in this analysis than reported in the past and, problematic gas intrusion seems to be limited to just a few caverns. This being said, much of the current SPR inventory exceeds vapor pressure delivery guidelines and must be degassed and cooled in order to meet current delivery standards.
This report documents the results of a six month test program of an Alternative Configuration (ACONF) power management system design for a typical United States Coast Guard (USCG) National Distress System (NDS) site. The USCG/USDOE funded work was performed at Sandia National Laboratories to evaluate the effect of a Sandia developed battery management technology known as ACONF on the performance of energy storage systems at NDS sites. This report demonstrates the savings of propane gas, and the improvement of battery performance when utilizing the new ACONF designs. The fuel savings and battery performance improvements resulting from ACONF use would be applicable to all current NDS sites in the field. The inherent savings realized when using the ACONF battery management design was found to be significant when compared to battery replacement and propane refueling at the remote NDS sites.
The Design-through-Analysis Realization Team (DART) is chartered with reducing the time Sandia analysts require to complete the engineering analysis process. The DART system analysis team studied the engineering analysis processes employed by analysts in Centers 9100 and 8700 at Sandia to identify opportunities for reducing overall design-through-analysis process time. The team created and implemented a rigorous analysis methodology based on a generic process flow model parameterized by information obtained from analysts. They also collected data from analysis department managers to quantify the problem type and complexity distribution throughout Sandia's analyst community. They then used this information to develop a community model, which enables a simple characterization of processes that span the analyst community. The results indicate that equal opportunity for reducing analysis process time is available both by reducing the ''once-through'' time required to complete a process step and by reducing the probability of backward iteration. In addition, reducing the rework fraction (i.e., improving the engineering efficiency of subsequent iterations) offers approximately 40% to 80% of the benefit of reducing the ''once-through'' time or iteration probability, depending upon the process step being considered. Further, the results indicate that geometry manipulation and meshing is the largest portion of an analyst's effort, especially for structural problems, and offers significant opportunity for overall time reduction. Iteration loops initiated late in the process are more costly than others because they increase ''inner loop'' iterations. Identifying and correcting problems as early as possible in the process offers significant opportunity for time savings.
This report examines the problem of an antenna radiating from a cylindrical hole in the earth and the subsequent far-zone field produced in the upper air half space. The approach used for this analysis was to first examine propagation characteristics along the hole for surrounding geologic material properties. Three cases of sand with various levels of moisture content were considered as the surrounding material to the hole. For the hole diameters and sand cases examined, the radiation through the earth medium was found to be the dominant contribution to the radiation transmitted through to the upper half-space. In the analysis presented, the radiation from a vertical and a horizontal dipole source within the hole is used to determine a closed-form expression for the radiation in the earth medium which represents a modified element factor for the source and hole combination. As the final step, the well-known results for a dipole below a half space, in conjunction with the use of Snell's law to transform the modified element factor to the upper half space, determine closed-form expressions for the far-zone radiated fields in the air region above the earth.
Total X-ray power measurements using aluminum block calorimetry and other techniques were made at LIGA X-ray scanner synchrotron beamlines located at both the Advanced Light Source (ALS) and the Advanced Photon Source (APS). This block calorimetry work was initially performed on the LIGA beamline 3.3.1 of the ALS to provide experimental checks of predictions of the LEX-D (LIGA Exposure- Development) code for LIGA X-ray exposures, version 7.56, the version of the code in use at the time calorimetry was done. These experiments showed that it was necessary to use bend magnet field strengths and electron storage ring energies different from the default values originally in the code in order to obtain good agreement between experiment and theory. The results indicated that agreement between LEX-D predictions and experiment could be as good as 5% only if (1) more accurate values of the ring energies, (2) local values of the magnet field at the beamline source point, and (3) the NIST database for X-ray/materials interactions were used as code inputs. These local magnetic field value and accurate ring energies, together with NIST database, are now defaults in the newest release of LEX-D, version 7.61. Three dimensional simulations of the temperature distributions in the aluminum calorimeter block for a typical ALS power measurement were made with the ABAQUS code and found to be in good agreement with the experimental temperature data. As an application of the block calorimetry technique, the X-ray power exiting the mirror in place at a LIGA scanner located at the APS beamline 10 BM was measured with a calorimeter similar to the one used at the ALS. The overall results at the APS demonstrated the utility of calorimetry in helping to characterize the total X-ray power in LIGA beamlines. In addition to the block calorimetry work at the ALS and APS, a preliminary comparison of the use of heat flux sensors, photodiodes and modified beam calorimeters as total X-ray power monitors was made at the ALS, beamline 3.3.1. This work showed that a modification of a commercially available, heat flux sensor could result in a simple, direct reading beam power meter that could be a useful for monitoring total X-ray power in Sandia's LIGA exposure stations at the ALS, APS and Stanford Synchrotron Radiation Laboratory (SSRL).
With the continuing trend of decreasing feature sizes in flip-chip assemblies, the reliability tolerance to interfacial flaws is also decreasing. Small-scale disbonds will become more of a concern, pointing to the need for a better understanding of the initiation stage of interfacial delamination. With most accepted adhesion metric methodologies tailored to predict failure under the prior existence of a disbond, the study of the initiation phenomenon is open to development and standardization of new testing procedures. Traditional fracture mechanics approaches are not suitable, as the mathematics assume failure to originate at a disbond or crack tip. Disbond initiation is believed to first occur at free edges and corners, which act as high stress concentration sites and exhibit singular stresses similar to a crack tip, though less severe in intensity. As such, a 'fracture mechanics-like' approach may be employed which defines a material parameter--a critical stress intensity factor (K{sub c})--that can be used to predict when initiation of a disbond at an interface will occur. The factors affecting the adhesion of underfill/polyimide interfaces relevant to flip-chip assemblies were investigated in this study. The study consisted of two distinct parts: a comparison of the initiation and propagation phenomena and a comparison of the relationship between sub-critical and critical initiation of interfacial failure. The initiation of underfill interfacial failure was studied by characterizing failure at a free-edge with a critical stress intensity factor. In comparison with the interfacial fracture toughness testing, it was shown that a good correlation exists between the initiation and propagation of interfacial failures. Such a correlation justifies the continuing use of fracture mechanics to predict the reliability of flip-chip packages. The second aspect of the research involved fatigue testing of tensile butt joint specimens to determine lifetimes at sub-critical load levels. The results display an interfacial strength ranking similar to that observed during monotonic testing. The fatigue results indicate that monotonic fracture mechanics testing may be an adequate screening tool to help predict cyclic underfill failure; however lifetime data is required to predict reliability.