STDEM is the structured mesh time-domain electromagnetic and plasma physics component of Emphasis/Nevada. This report provides a guide on using STDEM. Emphasis, the electromagnetic physics analysis system, is a suite of codes for the simulation of electromagnetic and plasma physics phenomena. The time-dependent components of Emphasis have been implemented using the Nevada framework [1]. The notation Emphasis/Nevada is used to highlight this relationship and/or distinguish the time-dependent components of Emphasis. In theory the underlying framework should have little influence on the user's interaction with the application. In practice the framework tends to be more invasive as it provides key services such as input parsing and defines fundamental concepts and terminology. While the framework offers many technological advancements from a software development point of view, from a user's perspective the key benefits of the underlying framework are the common interface for all framework physics modules as well as the ability to perform coupled physics simulations. STDEM is the structured time-domain electromagnetic and plasma physics component of Emphasis/Nevada. STDEM provides for the full-wave solution to Maxwell's equations on multi-block three-dimensional structured grids using finite-difference time-domain (FDTD) algorithms. Additionally STDEM provides for the fully relativistic, self-consistent simulation of charged particles using particle-in-cell (PIC) algorithms.
The shock compaction behavior of a tungsten carbide powder was investigated using a new experimental design for gas-gun experiments. This design allows the Hugoniot properties to be measured with reasonably good accuracy despite the inherent difficulties involved with distended powders. The experiments also provide the first reshock state for the compacted powder. Experiments were conducted at impact velocities of 245, 500, and 711 m/s. A steady shock wave was observed for some of the sample thicknesses, but the remainder were attenuated due to release from the back of the impactor or the edge of the sample. The shock velocity for the powder was found to be quite low, and the propagating shock waves were seen to be very dispersive. The Hugoniot density for the 711 m/s experiment was close to ambient crystal density for tungsten carbide, indicating nearly complete compaction. When compared with quasi-static compaction results for the same material, the dynamic compaction data is seen to be significantly stiffer for the regime over which they overlap. Based on these initial results, recommendations are made for improving the experimental technique and for future work to improve our understanding of powder compaction.
Numerical models of complex phenomena often contain approximations due to our inability to fully model the underlying physics, the excessive computational resources required to fully resolve the physics, the need to calibrate constitutive models, or in some cases, our ability to only bound behavior. Here we illustrate the relationship between approximation, calibration, extrapolation, and model validation through a series of examples that use the linear transient convective/dispersion equation to represent the nonlinear behavior of Burgers equation. While the use of these models represents a simplification relative to the types of systems we normally address in engineering and science, the present examples do support the tutorial nature of this document without obscuring the basic issues presented with unnecessarily complex models.
One critical aspect of any denuclearization of the Democratic People’s Republic of Korea (DPRK) involves dismantlement of its nuclear facilities and management of their associated radioactive wastes. The decommissioning problem for its two principal operational plutonium facilities at Yongbyun, the 5MWe nuclear reactor and the Radiochemical Laboratory reprocessing facility, alone present a formidable challenge. Dismantling those facilities will create radioactive waste in addition to existing inventories of spent fuel and reprocessing wastes. Negotiations with the DPRK, such as the Six Party Talks, need to appreciate the enormous scale of the radioactive waste management problem resulting from dismantlement. The two operating plutonium facilities, along with their legacy wastes, will result in anywhere from 50 to 100 metric tons of uranium spent fuel, as much as 500,000 liters of liquid high-level waste, as well as miscellaneous high-level waste sources from the Radiochemical Laboratory. A substantial quantity of intermediate-level waste will result from disposing 600 metric tons of graphite from the reactor, an undetermined quantity of chemical decladding liquid waste from reprocessing, and hundreds of tons of contaminated concrete and metal from facility dismantlement. Various facilities for dismantlement, decontamination, waste treatment and packaging, and storage will be needed. The shipment of spent fuel and liquid high level waste out of the DPRK is also likely to be required. Nuclear facility dismantlement and radioactive waste management in the DPRK are all the more difficult because of nuclear nonproliferation constraints, including the call by the United States for “complete, verifiable and irreversible dismantlement,” or “CVID.” It is desirable to accomplish dismantlement quickly, but many aspects of the radioactive waste management cannot be achieved without careful assessment, planning and preparation, sustained commitment, and long completion times. The radioactive waste management problem in fact offers a prospect for international participation to engage the DPRK constructively. DPRK nuclear dismantlement, when accompanied with a concerted effort for effective radioactive waste management, can be a mutually beneficial goal.
The Bryan Mound salt dome, located near Freeport, Texas, is home to one of four underground crude oil-storage facilities managed by the U. S. Department of Energy Strategic Petroleum Reserve (SPR) Program. Sandia National Laboratories, as the geotechnical advisor to the SPR, conducts site-characterization investigations and other longer-term geotechnical and engineering studies in support of the program. This report describes the conversion of two-dimensional geologic interpretations of the Bryan Mound site into three-dimensional geologic models. The new models include the geometry of the salt dome, the surrounding sedimentary units, mapped faults, and the 20 oil-storage caverns at the site. This work provides an internally consistent geologic model of the Bryan Mound site that can be used in support of future work.
Sandia is undergoing tremendous change. Sandia's executive management recognized the need for leadership development. About ten years ago the Business, Leadership, and Management Development department in partnership with executive management developed and implemented the organizational leadership Success Profile Competencies to help address some of the changes on the horizon such as workforce losses and lack of a skill set in the area of interpersonal skills. This study addresses the need for the Business, Leadership, and Management Development department to provide statistically sound data in two areas. One is to demonstrate that the organizational 360-degree success profile assessment tool has made a difference for leaders. A second area is to demonstrate the presence of high performing leaders at the Labs. The study utilized two tools to address these two areas. Study participants were made up of individuals who have solid data on Sandia's 360-degree success profile assessment tool. The second assessment tool was comprised of those leaders who participated in the Lockheed Martin Corporation Employee Preferences Survey. Statistical data supports the connection between leader indicators and the 360-degree assessment tool. The study also indicates the presence of high performing leaders at Sandia.
The thrust from a multi-cycle, pulse detonation engine operating at practical flight altitudes will vary with the surrounding environment pressure. We have carried out the first experimental study using a detonation tube hung in a ballistic pendulum arrangement within a large pressure vessel in order to determine the effect that the environment has on the single-cycle impulse. The air pressure inside the vessel surrounding the detonation tube varied between 100 and 1.4 kPa while the initial pressure of the stoichiometric ethylene-oxygen mixture inside the tube varied between 100 and 30 kPa. The original impulse model (Wintenberger et al., Journal of Propulsion and Power, Vol. 19, No. 1, 2002) was modified to predict the observed increase in impulse and blow down time as the environment pressure decreased below one atmosphere. Comparisons between the impulse from detonation tubes and ideal, steady flow rockets indicate incomplete expansion of the detonation tube exhaust, resulting in a 37% difference in impulse at a pressure ratio (ratio of pressure behind the Taylor wave to the environment pressure) of 100.
Smart polymeric materials, such as piezoelectric polymers which deform by application of an electric field, are of interest for use in controllable mirrors as large, lightweight space optics. An important consideration when using any organic material in a space application is their extreme vulnerability to the space environment. In LEO the presence of atomic oxygen, large thermal extremes, hard vacuum, short wavelength ultraviolet and particulate radiation can result in erosion, cracking and outgassing of most polymers. While much research has been performed examining the physical and chemical changes incurred by polymers exposed to actual and simulated LEO environments, little work has focused on the effects of the space environment on the performance of piezoelectric polymers. The most widely used piezoelectric polymers are those based on poly(vinylidene fluoride) (PVDF) and include copolymers synthesized from vinylidene fluoride and trifluoroethylene, hexafluoropropylene or chlorotrifluoroethylene. The presence of a comonomer group can greatly influence on the crystalline phase, melting point, Curie point, modulus and processing required for piezoelectricity. After a rigorous pre-selection process only two polymers, namely the PVDF homopolymer and a TrFE copolymer (80% comonomer content), satisfied most of the requirements for operation in the temperature/radiation environment of LEO. Based on this initial materials selection, we have now performed a detailed study of the effects of temperature, atomic oxygen and vacuum UV radiation simulating low Earth orbit conditions on these two polymers. Both polymers exhibited diminished but very stable piezoelectric performance up to 130 C despite the upper use temperatures suggested by industry of 80 C (PVDF) and 100 C (P(VDF-TrFE)). We believe that the loss of piezoelectric response in samples conditioned at 130 C compared with non-exposed samples is partly due to the depoling process which occurs when the highly stressed films undergo contraction via relaxation. The TrFE copolymer, which does not need to be stretched for the polar phase to be present, has better retention of piezoelectric properties at 130 C compared with the highly oriented homopolymer. AO/VUV exposure caused significant surface erosion and pattern development for both polymers. Erosion yields were 2.8 x 10{sup -24} cm{sup 3}/atom for PVDF and 2.5 x 10{sup -24} cm{sup 3}/atom for P(VDF-TrFE). The piezoelectric properties of the residual material for both polymers were largely unchanged after exposure, although a slight shift in the Curie transition of the P(VDF-TrFE) was observed. A lightly crosslinked network was formed in the copolymer, presumably due to penetrating VUV radiation, while the homopolymer remained uncrosslinked. These differences were attributed to different levels of crystallinity and increased VUV absorption by P(VDF-TrFE) over PVDF. In this paper a summary of the performance limiting effects of temperature, radiation, atomic oxygen and VUV on the piezoelectric response of PVDF based polymers will be presented.
With multipath routing in mobile ad hoc networks (MANETs), a source can establish multiple routes to a destination for routing data. In MANETs, mulitpath routing can be used to provide route resilience, smaller end-to-end delay, and better load balancing. However, when the multiple paths are close together, transmissions of different paths may interfere with each other, causing degradation in performance. Besides interference, the physical diversity of paths also improves fault tolerance. We present a purely distributed multipath protocol based on the AODV-Multipath (AODVM) protocol called AODVM with Path Diversity (AODVM/PD) that finds multiple paths with a desired degree of correlation between paths specified as an input parameter to the algorithm. We demonstrate through detailed simulation analysis that multiple paths with low degree of correlation determined by AODVM/PD provides both smaller end-to-end delay than AODVM in networks with low mobility and better route resilience in the presence of correlated node failures.