Science.gov

Sample records for slab assembly work

  1. 62. SUPPORT CARRIAGE ASSEMBLY AT BASE OF VAL LAUNCHING SLAB ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    62. SUPPORT CARRIAGE ASSEMBLY AT BASE OF VAL LAUNCHING SLAB AFTER TRANSFER FROM BARGE IN FOREGROUND, February, 11, 1948. (Original photograph in possession of Dave Willis, San Diego, California.) - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  2. Slab pull, mantle convection, and Pangaean assembly and dispersal

    NASA Astrophysics Data System (ADS)

    Collins, W. J.

    2003-01-01

    Two global-scale mantle convection cells presently exist on Earth, centred on upwelling zones in the South Pacific Ocean and northeast Africa: one cell (Panthalassan) contains only oceanic plates, the other (Pangaean) contains all the continental plates. They have remained fixed relative to one another for >400 Ma. A transverse (Rheic-Tethyian) subduction system splits the Pangaean cell. Poloidal plate motion in the oceanic cell reflects circumferential pull of Panthalassan slabs, but toroidal flow in the Pangaean cell, reflected by vortex-type motion of continents toward the Altaids of central-east Asia throughout the Phanerozoic, has resulted from the competing slab-pull forces of both cells. The combined slab-pull effects from both cells also controlled Pangaean assembly and dispersal. Assembly occurred during Palaeozoic clockwise toroidal motion in the Pangaean cell, when Gondwana was pulled into Pangaea by the NE-trending Rheic subduction zone, forming the Appalachian-Variscide-Altaid chain. Pangaean dispersal occurred when the Rheic trench re-aligned in the Jurassic to form the NW-trending Tethyside subduction system, which pulled east Gondwanan fragments in the opposite direction to form the Cimmerian-Himalayan-Alpine chain. This re-alignment also generated a new set of (Indian) mid-ocean ridge systems which dissected east Gondwana and facilitated breakup. 100-200-Myr-long Phanerozoic Wilson cycles reflect rifting and northerly migration of Gondwanan fragments across the Pangaean cell into the Rheic-Tethyian trench. Pangaean dispersal was amplified by retreat of the Panthalassan slab away from Europe and Africa, which generated mantle counterflow currents capable of pulling the Americas westward to create the Atlantic Ocean. Thermal blanketing beneath Pangaea and related hotspot activity were part of a complex feedback mechanism that established the breakup pattern, but slab retreat is considered to have been the main driving force. The size and longevity of

  3. Electronic Properties and Work Functions of Metallic Hexaboride Rods and Slabs

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Luo, Guangfu; Sabirianov, Renat F.; Mei, Wai-Ning; Lu, Jing; Cheung, Chin Li

    2011-03-01

    In this work, we performed electronic structure calculations of quasi one-dimensional metallic hexaboride XB6 nanorods, where X are mostly rare-earth metals with 4f levels such as La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. In addition we included Ca, Sr, Ba, Sc, Y, and Si for comparison and then complimented those with calculations of LaB6 slabs with different boundaries and low index surfaces. Our purpose is to facilitate the research and manufacture of metal boride probes, thus we study extensively the size-dependence and element-specificity of the electronic properties, particularly the work functions, in nanorods and slabs composed of the rare-earth metal borides, which usually regarded as good thermoelectric materials. We uncovered few general features that elucidate their excellent thermionic and field emission property. To accomplish our calculations, we applied density functional theory together with minimization scheme based on the ensemble density functional theory to facilitate convergence when optimizing structures of these rare-earth metallic haxaboride rods, which have plenty of 4f levels at the Fermi levels.

  4. Benchmark experiment on a copper slab assembly bombarded by D-T neutrons

    NASA Astrophysics Data System (ADS)

    Maekawa, Fujio; Oyama, Yukio; Konno, Chikara; Ikeda, Yujiro; Maekawa, Hiroshi; Kosako, Kazuaki

    1994-03-01

    Copper is a very important material for fusion reactor because it is used in superconducting magnets or first walls and so on. To verify nuclear data of copper, a benchmark experiment was performed using the D-T neutron source of the FNS facility in Japan Atomic Energy Research Institute. An cylindrical experimental assembly of 629 mm in diameter and 608 mm in thickness made of pure copper was located at 200 mm from the D-T neutron source. In the assembly, the following quantities were measured: (1) neutron spectra in energy regions of MeV and keV, (2) neutron reaction rates, (3) prompt and decay gamma-ray spectra, and (4) gamma-ray heating rates. The obtained experimental data were compiled in this report.

  5. Internal Aspects of the Skill Transfer of Manual Assembly Work

    ERIC Educational Resources Information Center

    Doyo, Daisuke

    2009-01-01

    In manual assembly work, parts are often assembled by applying force with a simple tool or by hand. A worker thus needs control the force he or she applies in working, as an appropriate level of force is requisite for minimizing work failures and improving efficiency. The object of this study is to clarify the relationship between the level of…

  6. 35. OUTLET WORKS: GATE HOIST ASSEMBLY. Sheet 44, August 20, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    35. OUTLET WORKS: GATE HOIST ASSEMBLY. Sheet 44, August 20, 1938. File no. SA 121/84(?). - Prado Dam, Outlet Works, Santa Ana River near junction of State Highways 71 & 91, Corona, Riverside County, CA

  7. Parametric performance of circumferentially grooved heat pipes with homogeneous and graded-porosity slab wicks at cryogenic temperatures. [methane and ethane working fluids

    NASA Technical Reports Server (NTRS)

    Groll, M.; Pittman, R. B.; Eninger, J. E.

    1976-01-01

    A recently developed, potentially high-performance nonarterial wick was extensively tested. This slab wick has an axially varying porosity which can be tailored to match the local stress imposed on the wick. The purpose of the tests was to establish the usefulness of the graded-porosity slab wick at cryogenic temperatures between 110 and 260 K, with methane and ethane as working fluids. For comparison, a homogeneous (i.e., uniform porosity) slab wick was also tested. The tests included: maximum heat pipe performance as a function of fluid inventory, maximum performance as a function of operating temperature, maximum performance as a function of evaporator elevation, and influence of slab wick orientation on performance. The experimental data were compared with theoretical predictions obtained with the GRADE computer program.

  8. Astronaut Alan Bean works on Modular Equipment Stowage Assembly

    NASA Technical Reports Server (NTRS)

    1969-01-01

    Astronaut Alan L. Bean, lunar module pilot for the Apollo 12 lunar landing mission, works at the Modular Equipment Stowage Assembly (MESA) on the Apollo 12 Lunar Module during the mission's first extravehicular activity, EVA-1, on November 19, 1969.

  9. Slab photonic crystals with dimer colloid bases

    SciTech Connect

    Riley, Erin K.; Liddell Watson, Chekesha M.

    2014-06-14

    The photonic band gap properties for centered rectangular monolayers of asymmetric dimers are reported. Colloids in suspension have been organized into the phase under confinement. The theoretical model is inspired by the range of asymmetric dimers synthesized via seeded emulsion polymerization and explores, in particular, the band structures as a function of degree of lobe symmetry and degree of lobe fusion. These parameters are varied incrementally from spheres to lobe-tangent dimers over morphologies yielding physically realizable particles. The work addresses the relative scarcity of theoretical studies on photonic crystal slabs with vertical variation that is consistent with colloidal self-assembly. Odd, even and polarization independent gaps in the guided modes are determined for direct slab structures. A wide range of lobe symmetry and degree of lobe fusion combinations having Brillouin zones with moderate to high isotropy support gaps between odd mode band indices 3-4 and even mode band indices 1-2 and 2-3.

  10. Slab reformer

    NASA Technical Reports Server (NTRS)

    Spurrier, Francis R. (Inventor); DeZubay, Egon A. (Inventor); Murray, Alexander P. (Inventor); Vidt, Edward J. (Inventor)

    1984-01-01

    Slab-shaped high efficiency catalytic reformer configurations particularly useful for generation of fuels to be used in fuel cell based generation systems. A plurality of structures forming a generally rectangular peripheral envelope are spaced about one another to form annular regions, an interior annular region containing a catalytic bed and being regeneratively heated on one side by a hot comubstion gas and on the other side by the gaseous products of the reformation. An integrally mounted combustor is cooled by impingement of incoming oxidant.

  11. Slab reformer

    DOEpatents

    Spurrier, Francis R.; DeZubay, Egon A.; Murray, Alexander P.; Vidt, Edward J.

    1985-03-12

    Slab-shaped high efficiency catalytic reformer configurations particularly useful for generation of fuels to be used in fuel cell based generation systems. A plurality of structures forming a generally rectangular peripheral envelope are spaced about one another to form annular regions, an interior annular region containing a catalytic bed and being regeneratively heated on one side by a hot combustion gas and on the other side by the gaseous products of the reformation. An integrally mounted combustor is cooled by impingement of incoming oxidant.

  12. Slab reformer

    DOEpatents

    Spurrier, Francis R.; DeZubay, Egon A.; Murray, Alexander P.; Vidt, Edward J.

    1984-02-07

    Slab-shaped high efficiency catalytic reformer configurations particularly useful for generation of fuels to be used in fuel cell based generation systems. A plurality of structures forming a generally rectangular peripheral envelope are spaced about one another to form annular regions, an interior annular region containing a catalytic bed and being regeneratively heated on one side by a hot comubstion gas and on the other side by the gaseous products of the reformation. An integrally mounted combustor is cooled by impingement of incoming oxidant.

  13. Slab reformer

    DOEpatents

    Spurrier, F.R.; DeZubay, E.A.; Murray, A.P.; Vidt, E.J.

    1984-02-07

    Slab-shaped high efficiency catalytic reformer configurations are disclosed particularly useful for generation of fuels to be used in fuel cell based generation systems. A plurality of structures forming a generally rectangular peripheral envelope are spaced about one another to form annular regions, an interior annular region containing a catalytic bed and being regeneratively heated on one side by a hot combustion gas and on the other side by the gaseous products of the reformation. An integrally mounted combustor is cooled by impingement of incoming oxidant. 14 figs.

  14. Mobile work station concept for assembly of large space structures (zero gravity simulation tests)

    NASA Astrophysics Data System (ADS)

    Heard, W. L., Jr.; Bush, H. G.; Wallsom, R. E.; Jensen, J. K.

    1982-03-01

    The concept presented is intended to enhance astronaut assembly of truss structure that is either too large or complex to fold for efficient Shuttle delivery to orbit. The potential of augmented astronaut assembly is illustrated by applying the result of the tests to a barebones assembly of a truss structure. If this structure were assembled from the same nestable struts that were used in the Mobile Work Station assembly tests, the spacecraft would be 55 meters in diameter and consist of about 500 struts. The struts could be packaged in less than 1/2% of the Shuttle cargo bay volume and would take up approximately 3% of the mass lift capability. They could be assembled in approximately four hours. This assembly concept for erectable structures is not only feasible, but could be used to significant economic advantage by permitting the superior packaging feature of erectable structures to be exploited and thereby reduce expensive Shuttle delivery flights.

  15. Comparison of the thoracic flexion relaxation ratio and pressure pain threshold after overhead assembly work and below knee assembly work

    PubMed Central

    Yoo, Won-gyu

    2016-01-01

    [Purpose] The purpose of this study was to compare the thoracic flexion relaxation ratio following overhead work and below-knee work. [Subjects and Methods] Ten men (20–30 years) were recruited to this study. The thoracic flexion relaxation ratio and pressure pain threshold was measured after both overhead work and below-knee work. [Results] The pressure-pain thresholds of the thoracic erector spinae muscle decreased significantly from initial, to overhead, to below-knee work. Similarly, the thoracic flexion relaxation ratio decreased significantly from initial, to overhead, to below-knee work. [Conclusion] Below-knee work results in greater thoracic pain than overhead work. Future studies should investigate below-knee work in detail. This study confirmed the thoracic relaxation phenomenon in the mid-position of the thoracic erector spinae. PMID:26957744

  16. A mobile work station concept for mechanically aided astronaut assembly of large space trusses

    NASA Technical Reports Server (NTRS)

    Heard, W. L., Jr.; Bush, H. G.; Wallson, R. E.; Jensen, J. K.

    1983-01-01

    This report presents results of a series of truss assembly tests conducted to evaluate a mobile work station concept intended to mechanically assist astronaut manual assembly of erectable space trusses. The tests involved assembly of a tetrahedral truss beam by a pair of test subjects with and without pressure (space) suits, both in Earth gravity and in simulated zero gravity (neutral buoyancy in water). The beam was assembled from 38 identical graphite-epoxy nestable struts, 5.4 m in length with aluminum quick-attachment structural joints. Struts and joints were designed to closely simulate flight hardware. The assembled beam was approximately 16.5 m long and 4.5 m on each of the four sides of its diamond-shaped cross section. The results show that average in-space assembly rates of approximately 38 seconds per strut can be expected for struts of comparable size. This result is virtually independent of the overall size of the structure being assembled. The mobile work station concept would improve astronaut efficiency for on-orbit manual assembly of truss structures, and also this assembly-line method is highly competitive with other construction methods being considered for large space structures.

  17. Subducting slabs: Jellyfishes in the Earth's mantle

    NASA Astrophysics Data System (ADS)

    Loiselet, Christelle; Braun, Jean; Husson, Laurent; Le Carlier de Veslud, Christian; Thieulot, Cedric; Yamato, Philippe; Grujic, Djordje

    2010-08-01

    The constantly improving resolution of geophysical data, seismic tomography and seismicity in particular, shows that the lithosphere does not subduct as a slab of uniform thickness but is rather thinned in the upper mantle and thickened around the transition zone between the upper and lower mantle. This observation has traditionally been interpreted as evidence for the buckling and piling of slabs at the boundary between the upper and lower mantle, where a strong contrast in viscosity may exist and cause resistance to the penetration of slabs into the lower mantle. The distribution and character of seismicity reveal, however, that slabs undergo vertical extension in the upper mantle and compression near the transition zone. In this paper, we demonstrate that during the subduction process, the shape of low viscosity slabs (1 to 100 times more viscous than the surrounding mantle) evolves toward an inverted plume shape that we coin jellyfish. Results of a 3D numerical model show that the leading tip of slabs deform toward a rounded head skirted by lateral tentacles that emerge from the sides of the jellyfish head. The head is linked to the body of the subducting slab by a thin tail. A complete parametric study reveals that subducting slabs may achieve a variety of shapes, in good agreement with the diversity of natural slab shapes evidenced by seismic tomography. Our work also suggests that the slab to mantle viscosity ratio in the Earth is most likely to be lower than 100. However, the sensitivity of slab shapes to upper and lower mantle viscosities and densities, which remain poorly constrained by independent evidence, precludes any systematic deciphering of the observations.

  18. Subducting Slabs: Jellyfishes in the Earth's Mantle

    NASA Astrophysics Data System (ADS)

    Loiselet, C.; Braun, J.; Husson, L.; Le Carlier de Veslud, C.; Thieulot, C.; Yamato, P.; Grujic, D.

    2010-12-01

    The constantly improving resolution of geophysical data, seismic tomography and seismicity in particular, shows that the lithosphere does not subduct as a slab of uniform thickness but is rather thinned in the upper mantle and thickened around the transition zone between the upper and lower mantle. This observation has traditionally been interpreted as evidence for the buckling and piling of slabs at the boundary between the upper and lower mantle, where a strong contrast in viscosity may exist and cause resistance to the penetration of slabs into the lower mantle. The distribution and character of seismicity reveal, however, that slabs undergo vertical extension in the upper mantle and compression near the transition zone. In this paper, we demonstrate that during the subduction process, the shape of low viscosity slabs (1 to 100 times more viscous than the surrounding mantle) evolves toward an inverted plume shape that we coin jellyfish. Results of a 3D numerical model show that the leading tip of slabs deform toward a rounded head skirted by lateral tentacles that emerge from the sides of the jellyfish head. The head is linked to the body of the subducting slab by a thin tail. A complete parametric study reveals that subducting slabs may achieve a variety of shapes, in good agreement with the diversity of natural slab shapes evidenced by seismic tomography. Our work also suggests that the slab to mantle viscosity ratio in the Earth is most likely to be lower than 100. However, the sensitivity of slab shapes to upper and lower mantle viscosities and densities, which remain poorly constrained by independent evidence, precludes any systematic deciphering of the observations.

  19. The Lipid A Assembly Pathway: The Work of Christian Raetz

    PubMed Central

    Kresge, Nicole; Simoni, Robert D.; Hill, Robert L.

    2011-01-01

    During his career, Christian Raetz has characterized many enzymes responsible for synthesizing or modifying lipid molecules, including the entire nine-enzyme pathway for the biosynthesis of lipid A, an essential part of bacterial outer membranes that plays a role in making many Gram-negative bacteria toxic. The findings from the two Journal of Biological Chemistry (JBC) Classic articles reprinted here were the start of Raetz' elucidation of the enzymology, genetics, and structural biology of lipid A assembly. Fatty Acyl Derivatives of Glucosamine 1-Phosphate in Escherichia coli and Their Relation to Lipid A. Complete Structure of a Diacyl GlcN-1-P Found in a Phosphatidylglycerol-deficient Mutant (Takayama, K., Qureshi, N., Mascagni, P., Nashed, M. A., Anderson, L., and Raetz, C. R. H. (1983) J. Biol. Chem. 258, 7379–7385) The Biosynthesis of Gram-negative Endotoxin. Formation of Lipid A Precursors from UDP-GlcNAc in Extracts of Escherichia coli (Anderson, M. S., Bulawa, C. E., and Raetz, C. R. H. (1985) J. Biol. Chem. 260, 15536–15541) PMID:21887864

  20. Design options for improving protective gloves for industrial assembly work.

    PubMed

    Dianat, Iman; Haslegrave, Christine M; Stedmon, Alex W

    2014-07-01

    The study investigated the effects of wearing two new designs of cotton glove on several hand performance capabilities and compared them against the effects of barehanded, single-layered and double cotton glove conditions when working with hand tools (screwdriver and pliers). The new glove designs were based on the findings of subjective hand discomfort assessments for this type of work and aimed to match the glove thickness to the localised pressure and sensitivity in different areas of the hand as well as to provide adequate dexterity for fine manipulative tasks. The results showed that the first prototype glove and the barehanded condition were comparable and provided better dexterity and higher handgrip strength than double thickness gloves. The results support the hypothesis that selective thickness in different areas of the hand could be applied by glove manufacturers to improve the glove design, so that it can protect the hands from the environment and at the same time allow optimal hand performance capabilities.

  1. The effect of subducting slabs in global shear wave tomography

    NASA Astrophysics Data System (ADS)

    Lu, Chang; Grand, Stephen P.

    2016-05-01

    Subducting slabs create strong short wavelength seismic anomalies in the upper mantle where much of Earth's seismicity is located. As such, they have the potential to bias longer wavelength seismic tomography models. To evaluate the effect of subducting slabs in global tomography, we performed a series of inversions using a global synthetic shear wave traveltime data set for a theoretical slab model based on predicted thermal anomalies within slabs. The spectral element method was applied to predict the traveltime anomalies produced by the 3-D slab model for paths corresponding to our current data used in actual tomography models. Inversion tests have been conducted first using the raw traveltime anomalies to check how well the slabs can be imaged in global tomography without the effect of earthquake mislocation. Our results indicate that most of the slabs can be identified in the inversion result but with smoothed and reduced amplitude. The recovery of the total mass anomaly in slab regions is about 88 per cent. We then performed another inversion test to investigate the effect of mislocation caused by subducting slabs. We found that source mislocation largely removes slab signal and significantly degrades the imaging of subducting slabs-potentially reducing the recovery of mass anomalies in slab regions to only 41 per cent. We tested two source relocation procedures-an iterative relocation inversion and joint relocation inversion. Both methods partially recover the true source locations and improve the inversion results, but the joint inversion method worked significantly better than the iterative method. In all of our inversion tests, the amplitudes of artefact structures in the lower mantle caused by the incorrect imaging of slabs (up to ˜0.5 per cent S velocity anomalies) are comparable to some large-scale lower-mantle heterogeneities seen in global tomography studies. Based on our inversion tests, we suggest including a-priori subducting slabs in the

  2. MULTIPLE SETS OF TWIN SLABS ON THE RUN OUT. THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    MULTIPLE SETS OF TWIN SLABS ON THE RUN OUT. THE RUN OUT INCLUDES THE TRAVELING TORCH WHICH CUTS SLABS TO DESIRED LENGTH, AN IDENTIFICATION SYSTEM TO INDICATE HEAT NUMBER AND TRACE IDENTITY OF EVERY SLAB, AND A DEBURRING DEVICE TO SMOOTH SLABS. AT LEFT OF ROLLS IS THE DUMMY BAR. DUMMY BAR IS INSERTED UP THROUGH CONTAINMENT SECTION INTO MOLD PRIOR TO START OF CAST. WHEN STEEL IS INTRODUCED INTO MOLD IT CONNECTS WITH BAR AS CAST BEGINS, AT RUN OUT DUMMY BAR DISCONNECTS AND IS STORED. - U.S. Steel, Fairfield Works, Continuous Caster, Fairfield, Jefferson County, AL

  3. MULTIPLE SETS OF TWIN SLABS ON THE RUN OUT. THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    MULTIPLE SETS OF TWIN SLABS ON THE RUN OUT. THE RUN OUT INCLUDES THE TRAVELING TORCH WHICH CUTS SLABS TO DESIRED LENGTH, AN IDENTIFICATION SYSTEM TO INDICATE HEAT NUMBER AND TRACE IDENTITY OF EVERY SLAB, AND A DEBURRING DEVICE TO SMOOTH SLABS. AT LEFT OF ROLLS IS THE DUMMY BAR. DUMMY BAR IS INSERTED UP THROUGH CONTAINMENT SECTION INTO MOLD PRIOR TO START OF CAST. WHEN STEEL IS INTRODUCED INTO MOLD IT CONNECTS WITH BAR AS CAST BEGINS, AT RUN OUT DUMMY BAR DISCONNECTS AND IS STORED - U.S. Steel, Fairfield Works, Continuous Caster, Fairfield, Jefferson County, AL

  4. Inter-worker variability in lower body postures during assembly line work: implications for exposure assessment.

    PubMed

    Keyserling, W Monroe; Wiggermann, Neal; Werner, Robert A; Gell, Nancy

    2010-05-01

    This study evaluated inter-worker variability in lower body posture and work activity during highly-structured assembly line work. Data were collected from 79 unique assembly line workstations in an engine manufacturing plant. Because the plant utilized work teams, 4-8 workers rotated through each workstation. At least 30 min of videotape was collected from at least three workers at each workstation. A computer-assisted work sampling procedure randomly selected 200 video "freeze-frames" for each worker. Lower body posture/movement (e.g., sit, stand, walk, etc.) was determined for each frame and used to estimate the percentage of time the worker spent in various postures and activities. Chi-square analyses were performed for each workstation to assess the significance of inter-worker differences. Due to variations in individual work methods, significant differences (p <.05) were found at 57 out of 79 workstations (72%). The greatest differences occurred when workers had the option to choose between standing and sitting (significant in 8 of 8 cases; in extreme examples, sit time ranged between 0-100% on one job, and 6.5-98% on another). Studying a single worker (or "proxy") can contribute to substantial error when estimating exposures in workplace studies of ergonomic stressors, since the proxy may not be representative of all workers who perform the job. Individual measurements are preferable, particularly for jobs where workers have substantial latitude to develop individualized work methods.

  5. Slab Leaf Bowls

    ERIC Educational Resources Information Center

    Suitor, Cheryl

    2012-01-01

    In science class, fourth graders investigate the structure of plants and leaves from trees and how the process of photosynthesis turns sunlight into sugar proteins. In this article, the author fuses art and science for a creative and successful clay slab project in her elementary art classroom. (Contains 1 online resource.)

  6. Evaluation of the changes in working limits in an automobile assembly line using simulation

    NASA Astrophysics Data System (ADS)

    Ferreira, L. P.; Ares, E.; Peláez, G.; Resano, A.; Luis, C. J.; Tjahjono, B.

    2012-04-01

    The aim of the work presented in this paper consists of the development of a decision-making support system, based on discrete-event simulation models, of an automobile assembly line which was implemented within an Arena simulation environment and focused at a very specific class of production lines with a four closed-loop network configuration. This layout system reflects one of the most common configurations of automobile assembly and preassembly lines formed by conveyors. The sum of the number of pallets on the intermediate buffers, remains constant, except for the fourth closed-loop, which depends on the four-door car ratio (x) implemented between the door disassembly and assembly stations of the car body. Some governing equations of the four closed-loops are not compatible with the capacities of several intermediate buffers for certain values of variable x. This incompatibility shows how the assembly line cannot operate in practice for x< 0,37 and for x>0,97 in a stationary regime, due to the starvation phenomenon or the failure of supply to the machines on the production line. We have evaluated the impact of the pallet numbers circulating on the first closed-loop on the performance of the production line, translated into the number of cars produced/hour, in order to improve the availability of the entire manufacturing system for any value of x. Until the present date, these facts have not been presented in specialized literature.

  7. Ross Works on the Assembly Concept for Construction of Erectable Space Structure (ACCESS) During

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The crew assigned to the STS-61B mission included Bryan D. O'Conner, pilot; Brewster H. Shaw, commander; Charles D. Walker, payload specialist; mission specialists Jerry L. Ross, Mary L. Cleave, and Sherwood C. Spring; and Rodolpho Neri Vela, payload specialist. Launched aboard the Space Shuttle Atlantis November 28, 1985 at 7:29:00 pm (EST), the STS-61B mission's primary payload included three communications satellites: MORELOS-B (Mexico); AUSSAT-2 (Australia); and SATCOM KU-2 (RCA Americom). Two experiments were conducted to test assembling erectable structures in space: EASE (Experimental Assembly of Structures in Extravehicular Activity), and ACCESS (Assembly Concept for Construction of Erectable Space Structure). In a joint venture between NASA/Langley Research Center in Hampton, Virginia, and the Marshall Space Flight Center (MSFC), EASE and ACCESS were developed and demonstrated at MSFC's Neutral Buoyancy Simulator (NBS). In this STS-61B onboard photo, astronaut Ross works on ACCESS high above the orbiter. The primary objective of these experiments was to test the structural assembly concepts for suitability as the framework for larger space structures and to identify ways to improve the productivity of space construction.

  8. 42. PRESSING A SLAB OF CLAY ONTO A MOSAIC MOLD. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    42. PRESSING A SLAB OF CLAY ONTO A MOSAIC MOLD. THE MOLD, WHICH HAS A RAISED DESIGN, LEAVES AND OUTLINE IN THE SLAB, THE PIECES THUS DEFINED, ARE THEN CUT APART TO BE FIRED SEPARATELY AND REASSEMBLED. - Moravian Pottery & Tile Works, Southwest side of State Route 313 (Swamp Road), Northwest of East Court Street, Doylestown, Bucks County, PA

  9. Effect of Subducting Slabs in Global Shear Wave Tomography

    NASA Astrophysics Data System (ADS)

    Lu, C.; Grand, S. P.

    2015-12-01

    Subducting slabs represent strong short wavelength seismic anomalies in the upper mantle where much of Earth's seismicity is located. As such, they have the potential to bias longer wavelength seismic tomography models. To evaluate the effect of subducting slabs in global tomography, we performed a series of inversion tests using a global synthetic shear wave travel time dataset for a theoretical slab model based on predicted thermal anomalies within slabs. The spectral element method (SEM) was applied to predict the travel time anomalies produced by the 3D slab model for paths corresponding to our current data used in actual tomography models. Inversion tests have been conducted first using the raw travel time anomalies to check how well the slabs can be imaged in global tomography without the effect of mislocation. Our results indicate that most of the slabs can be identified in the inversion result but with smoothed and reduced amplitude. The recovery of the total mass anomaly in slab regions is about 84%. We then performed another inversion test to investigate the effect of mislocation caused by subducting slabs. We found that source mislocation significantly degrades the imaging of subducting slabs - potentially reducimg the recovery of mass anomalies in slab regions to only 39%. We tested two source relocation procedures - an iterative relocation inversion and joint relocation inversion. Both methods partially recover the true source locations and improve the inversion results, but the joint inversion method worked significantly better than the iterative method. In all of our inversion tests, the amplitude of artifact structures in the lower mantle caused by the incorrect imaging of slabs (up to ~0.5% S velocity anomalies) are comparable to large scale lower mantle heterogeneities seen in global tomography studies.

  10. Influence of weak layer heterogeneity and slab properties on slab tensile failure propensity and avalanche release area

    NASA Astrophysics Data System (ADS)

    Gaume, J.; Chambon, G.; Eckert, N.; Naaim, M.; Schweizer, J.

    2015-04-01

    Dry-snow slab avalanches are generally caused by a sequence of fracture processes, including failure initiation in a weak snow layer underlying a cohesive slab followed by crack propagation within the weak layer (WL) and tensile fracture through the slab. During past decades, theoretical and experimental work has gradually increased our knowledge of the fracture process in snow. However, our limited understanding of crack propagation and fracture arrest propensity prevents the evaluation of avalanche release sizes and thus impedes hazard assessment. To address this issue, slab tensile failure propensity is examined using a mechanically based statistical model of the slab-WL system based on the finite element method. This model accounts for WL heterogeneity, stress redistribution by slab elasticity and possible tensile failure of the slab. Two types of avalanche release are distinguished in the simulations: (1) full-slope release if the heterogeneity is not sufficient to stop crack propagation and trigger a tensile failure within the slab; (2) partial-slope release if fracture arrest and slab tensile failure occur due to the WL heterogeneity. The probability of these two release types is presented as a function of the characteristics of WL heterogeneity and the slab. One of the main outcomes is that, for realistic values of the parameters, the tensile failure propensity is mainly influenced by slab properties. Hard and thick snow slabs are more prone to wide-scale crack propagation and thus lead to larger avalanches (full-slope release). In this case, the avalanche size is mainly influenced by topographical and morphological features such as rocks, trees, slope curvature and the spatial variability of the snow depth as often claimed in the literature.

  11. Carbon dioxide slab laser

    SciTech Connect

    Tulip, J.

    1988-01-12

    A gas slab laser is described comprising: first and second elongated electrodes each including a planar light reflecting surface disposed so as to form a light guide only in a plane perpendicular to the planar surface and to define a gas discharge gap therebetween; a laser gas disposed in the gap; and means for applying a radio frequency current between the first and second electrodes to establish a laser-exciting discharge in the laser gas.

  12. Using augmented reality in AIRBUS A400M shop floor assembly work instructions

    NASA Astrophysics Data System (ADS)

    Serván, J.; Mas, F.; Menéndez, J. L.; Ríos, J.

    2012-04-01

    The assembly of components in the aerospace industry is currently supported through procedures based on the generation of work instructions. This documentation describes both the sequence of operations to be performed by operators, and fundamental and critical parameters of operation (drawings of components, torques to be applied, sealing system characteristics or paste, etc.). Currently, workers use this information to ensure that the tasks are performed correctly. However, sometimes the documentation is difficult to manage, either by the difficulty of interpreting the drawings or because the process is too complex, for example in the installation of electrical harnesses. This document shows the results of the Project MOON (asseMbly Oriented authOring augmeNted reality) developed by AIRBUS Military in 2010. MOON uses 3D information from the iDMU (industrial Digital Mock-Up) to generate assembly instructions by applying Augmented Reality technology. A demonstrator was developed for the electrical harness routing in the frame 36 of the AIRBUS A400M. The techniques and methods here described are 'patent pending'.

  13. OVERVIEW LOOKING SOUTH OF CONTAINMENT SYSTEM (TOP), SLAB CASTING MACHINE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    OVERVIEW LOOKING SOUTH OF CONTAINMENT SYSTEM (TOP), SLAB CASTING MACHINE AND RUN OUT WITH TRAVELING TORCH. MACHINE IS CASTING IN TWIN MOLD. - U.S. Steel, Fairfield Works, Continuous Caster, Fairfield, Jefferson County, AL

  14. 18. RADAR BED/SLAB AND ROOF OPENING FOR BEAM, WITH MIRROR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. RADAR BED/SLAB AND ROOF OPENING FOR BEAM, WITH MIRROR ABOVE, ROOM 3001, PENTHOUSE. - Hughes Aircraft Company, Assembly & Manufacturing Building, 6775 Centinela Avenue, Los Angeles, Los Angeles County, CA

  15. Mobile Launch Platform Vehicle Assembly Area (SWMU 056) Biosparge Expansion Interim Measures Work Plan

    NASA Technical Reports Server (NTRS)

    Burcham, Michael S.; Daprato, Rebecca C.

    2016-01-01

    This document presents the design details for an Interim Measure (IM) Work Plan (IMWP) for the Mobile Launch Platform/Vehicle Assembly Building (MLPV) Area, located at the John F. Kennedy Space Center (KSC), Florida. The MLPV Area has been designated Solid Waste Management Unit Number 056 (SWMU 056) under KSC's Resource Conservation and Recovery Act (RCRA) Corrective Action Program. This report was prepared by Geosyntec Consultants (Geosyntec) for the National Aeronautics and Space Administration (NASA) under contract number NNK09CA02B and NNK12CA13B, project control number ENV1642. The Advanced Data Package (ADP) presentation covering the elements of this IMWP report received KSC Remediation Team (KSCRT) approval at the December 2015 Team Meeting; the meeting minutes are included in Appendix A.

  16. Definition of spacecraft standard interfaces by the NASA Space Assembly and Servicing Working Group (SASWG)

    NASA Technical Reports Server (NTRS)

    Radtke, Robert; Woolley, Charles; Arnold, Lana

    1993-01-01

    The purpose of the NASA Space Assembly and Servicing Working Group (SASWG) is to study enabling technologies for on-orbit spacecraft maintenance and servicing. One key technology required for effective space logistics activity is the development of standard spacecraft interfaces, including the 'Basic Set' defined by NASA, the U.S. Space Command, and industry panelists to be the following: (1) navigation aids; (2) grasping, berthing, and docking; and (3) utility connections for power, data, and fluids. Draft standards have been prepared and referred to professional standards organizations, including the AIAA, EIA, and SAE space standards committee. The objective of the SASWG is to support these committees with the technical expertise required to prepare standards, guidelines, and recommended practices which will be accepted by the ANSI and international standards organizations, including the ISO, IEC, and PASC.

  17. SUB-SLAB PROBE INSTALLATION

    EPA Science Inventory

    Sub-slab sampling has become an integral part of vapor intrusion investigations. It is now recommended in guidance documents developed by EPA and most states. A method for sub-slab probe installation was devised in 2002, presented at conferences through 2005, and finally docume...

  18. [Thermoluminescence Slab Dosimeter].

    PubMed

    Shinsho, Kiyomitsu; Koba, Yusuke; Tamatsu, Satoshi; Sakurai, Noboru; Wakabayashi, Genichiro; Fukuda, Kazusige

    2013-01-01

    In 1953 F. Daniels et al. used the property of thermoluminescence in dosimetry for the first time. Since then, numerous TLD have been developed. 2D TLD was investigated for the first time in 1972 by P Broadhead. However, due to excessive fading, difficulties with handling and the time required for measurements, development stalled. At the current time, the majority of TLD are used in small scale, localized dosimetry with a wide dynamic range and personal dosimeters for exposure management. Urushiyama et. al. have taken advantage of the commoditization of CCD cameras in recent years--making large area, high resolution imaging easier--to introduce and develop a 2D TLD. It is expected that these developments will give rise to a new generation of applications for 2D TL dosimetry. This paper introduces the "TL Slab Dosimeter" developed jointly by Urushiyama et. al. and our team, its measurement system and several typical usage scenarios.

  19. Impact Resistance Behaviour of Banana Fiber Reinforced Slabs

    NASA Astrophysics Data System (ADS)

    Che Muda, Zakaria; Syamsir, Agusril; Nasharuddin Mustapha, Kamal; Rifdy Samsudin, Muhamad; Thiruchelvam, Sivadass; Usman, Fathoni; Beddu, Salmia; Liyana Mohd Kamal, Nur; Ashraful Alam, Md; Birima, Ahmed H.; Zaroog, O. S.

    2016-03-01

    This paper investigate the performance of banana fibre reinforced slabs 300mm × 300mm size with varied thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.25 kg drop at 1 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance against the BF contents and slab thickness. A linear relationship has been established between first and ultimate crack resistance against BF contents and slab thickness by the experiment. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the BF contents for a constant spacing for various banana fibre reinforced slab thickness. The increment in BF content has more effect on the first crack resistance than the ultimate crack resistance. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the various slab thickness. Overall 1.5% BF content with slab thickness of 40 mm exhibit better first and ultimate crack resistance up to 16 times and up to 17 times respectively against control slab (without BF)

  20. Seismic constraints on the morphology of deep slabs

    NASA Astrophysics Data System (ADS)

    Fischer, Karen M.; Jordan, Thomas H.; Creager, Kenneth C.

    1988-05-01

    Residual sphere images from deep earthquakes not only detect the presence of slab-associated velocity anomalies but also lend insight into the flow and deformation of lithosphere subducted into the lower mantle. We have compared travel times from deep events in the Kuril and Mariana arcs with the seismic velocity anomalies implied by kinematical models that thicken the slab perpendicular to its plane by reducing the vertical velocity of the flow with depth. We assume that the details of the deformation (whether the slab buckles, imbricates, fragments, etc.) are averaged out along the ray paths, and hence our models constrain the scale, not the mode, of slab thickening. The deep event travel times are best fit by undeformed models, but the ability of the residual sphere method to resolve slab thickness is limited by ray bending effects. Although the Mariana times are consistent with advective thickening factors of 5 or more, factors larger than 3 are ruled out by the Kuril data. For all models examined, the data require that slab material extends to depths of 900-1000 km. Global tomographic models and regional studies which delineate high-velocity anomalies in the lower mantle beneath zones of Cenozoic subduction are consistent with our results, as is recent work on pulse distortion by slab gradients. Comparison of observed and predicted rates of seismic moment release suggests that if substantial advective thickening does occur, it is largely aseismic.

  1. Aircraft Assembly, Riveting and Surface Repair 2; Sheet Metal Work 2: 9855.03.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    This course provides experience in assembly techniques, including repairs on aircraft structures, utilizing all methods from basic layout to surface protection of finished parts. Course content includes goals, specific objectives, metal fasteners, general structural repairs, and aircraft assembly. A bibliography and post-test are appended. Prior…

  2. Deep earthquakes beneath the Fiji Basin, SW Pacific: Earth's most intense deep seismicity in stagnant slabs

    USGS Publications Warehouse

    Okal, E.A.; Kirby, S.H.

    1998-01-01

    Previous work has suggested that many of the deep earthquakes beneath the Fiji Basin occur in slab material that has been detached and foundered to the bottom of the transition zone or has been laid down by trench migration in a similar recumbent position. Since nowhere else in the Earth do so many earthquakes occur in slabs stagnated in the transition zone, these earthquakes merit closer study. Accordingly, we have assembled from historical and modern data a comprehensive catalogue of the relocated hypocenters and focal mechanisms of well-located deep events in the geographic area between the bottoms of the main Vanuatu and Tonga Wadati-Benioff zones. Two regions of deep seismogenesis are recognized there: (i) 163 deep shocks have occurred north of 15??S in the Vityaz Group from 1949 to 1996. These seismological observations and the absence of other features characteristic of active subduction suggest that the Vityaz group represents deep failure in a detached slab that has foundered to a horizontal orientation near the bottom of the transition zone. (ii) Another group of nearly 50 'outboard' deep shocks occur between about 450 and 660 km depth, west of the complexly buckled and offset western edge of the Tonga Wadati-Benioff zone. Their geometry is in the form of two or possibly three small-circle arcs that roughly parallel the inferred motion of Tonga trench migration. Earthquakes in the southernmost of these arcs occur in a recumbent high-seismic-wavespeed slab anomaly that connects both to the main inclined Tonga anomaly to the east and a lower mantle anomaly to the west [Van der Hilst, R., 1995. Complex morphology of subducted lithosphere in the mantle beneath the Tonga trench. Nature, Vol. 374, pp. 154-157.]. Both groups show complexity in their focal mechanisms. The major question raised by these observations is the cause of this apparent temporary arrest in the descent of the Tonga slab into the lower mantle. We approach these questions by considering the

  3. New Packaging for Amplifier Slabs

    SciTech Connect

    Riley, M.; Thorsness, C.; Suratwala, T.; Steele, R.; Rogowski, G.

    2015-03-18

    The following memo provides a discussion and detailed procedure for a new finished amplifier slab shipping and storage container. The new package is designed to maintain an environment of <5% RH to minimize weathering.

  4. Optimization of reinforced concrete slabs

    NASA Technical Reports Server (NTRS)

    Ferritto, J. M.

    1979-01-01

    Reinforced concrete cells composed of concrete slabs and used to limit the effects of accidental explosions during hazardous explosives operations are analyzed. An automated design procedure which considers the dynamic nonlinear behavior of the reinforced concrete of arbitrary geometrical and structural configuration subjected to dynamic pressure loading is discussed. The optimum design of the slab is examined using an interior penalty function. The optimization procedure is presented and the results are discussed and compared with finite element analysis.

  5. Fast Waves in Smooth Coronal Slab

    NASA Astrophysics Data System (ADS)

    Lopin, I.; Nagorny, I.

    2015-03-01

    This work investigates the effect of transverse density structuring in coronal slab-like waveguides on the properties of fast waves. We generalized previous results obtained for the exponential and Epstein profiles to the case of an arbitrary transverse density distribution. The criteria are given to determine the possible (trapped or leaky) wave regime, depending on the type of density profile function. In particular, there are plasma slabs with transverse density structuring that support pure trapped fast waves for all wavelengths. Their phase speed is nearly equal to the external Alfvén speed for the typical parameters of coronal loops. Our findings are obtained on the basis of Kneser’s oscillation theorem. To confirm the results, we analytically solved the wave equation evaluated at the cutoff point and the original wave equation for particular cases of transverse density distribution. We also used the WKB method and obtained approximate solutions of the wave equation at the cutoff point for an arbitrary transverse density profile. The analytic results were supplemented by numerical solutions of the obtained dispersion relations. The observed high-quality quasi-periodic pulsations of flaring loops are interpreted in terms of the trapped fundamental fast-sausage mode in a slab-like coronal waveguide.

  6. STS-61B Astronaut Ross Works on Assembly Concept for Construction of Erectable Space Structure

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The crew assigned to the STS-61B mission included Bryan D. O'Conner, pilot; Brewster H. Shaw, commander; Charles D. Walker, payload specialist; mission specialists Jerry L. Ross, Mary L. Cleave, and Sherwood C. Spring; and Rodolpho Neri Vela, payload specialist. Launched aboard the Space Shuttle Atlantis November 28, 1985 at 7:29:00 pm (EST), the STS-61B mission's primary payload included three communications satellites: MORELOS-B (Mexico); AUSSAT-2 (Australia); and SATCOM KU-2 (RCA Americom). Two experiments were conducted to test assembling erectable structures in space: EASE (Experimental Assembly of Structures in Extravehicular Activity), and ACCESS (Assembly Concept for Construction of Erectable Space Structure). In a joint venture between NASA/Langley Research Center in Hampton, Virginia and the Marshall Space Flight Center (MSFC), EASE and ACCESS were developed and demonstrated at MSFC's Neutral Buoyancy Simulator (NBS). In this STS-61B onboard photo astronaut Ross, located on the Manipulator Foot Restraint (MFR) over the cargo bay, erects ACCESS. The primary objective of this experiment was to test the structural assembly concepts for suitability as the framework for larger space structures and to identify ways to improve the productivity of space construction.

  7. A Work of ARTE: The Newsletter of the Assembly of Rural Teachers of English, 1993.

    ERIC Educational Resources Information Center

    Work of ARTE, 1993

    1993-01-01

    This document consists of the three issues of the ARTE newsletter published during 1993. This newsletter describes organizational objectives and activities of the Assembly of Rural Teachers of English (ARTE), and presents articles of interest to rural English teachers. Articles discuss: (1) promoting and capitalizing on positive feelings of family…

  8. Large work function shift of gold induced by a novel perfluorinated azobenzene-based self-assembled monolayer.

    PubMed

    Crivillers, Núria; Osella, Silvio; Van Dyck, Colin; Lazzerini, Giovanni M; Cornil, David; Liscio, Andrea; Di Stasio, Francesco; Mian, Shabbir; Fenwick, Oliver; Reinders, Federica; Neuburger, Markus; Treossi, Emanuele; Mayor, Marcel; Palermo, Vincenzo; Cacialli, Franco; Cornil, Jérôme; Samorì, Paolo

    2013-01-18

    Tune it with light! Self-assembled monolayers on gold based on a chemisorbed novel azobenzene derivative with a perfluorinated terminal phenyl ring are prepared. The modified substrate shows a significant work function increase compared to the bare metal. The photo-conversion between trans and cis isomers chemisorbed on the surface shows great perspectives for being an accessible route to tune the gold properties by means of light.

  9. Spatially Modulating Interfacial Properties of Transparent Conductive Oxides: Patterning Work Function with Phosphonic Acid Self-Assembled Monolayers

    SciTech Connect

    Knesting, Kristina M.; Hotchkiss, Peter J.; MacLeod, Bradley A.; Marder, Seth R.; Ginger, David S.

    2011-09-29

    The interface between an organic semiconductor and a transparent conducting oxide is crucial to the performance of organic optoelectronics. We use microcontact printing to pattern pentafluorobenzyl phosphonic acid self-assembled monolayers (SAMs) on indium tin oxide (ITO). We obtain high-fidelity patterns with sharply defined edges and with large work function contrast (comparable to that obtained from phosphonic acid SAMs deposited from solution).

  10. How mantle slabs drive plate tectonics.

    PubMed

    Conrad, Clinton P; Lithgow-Bertelloni, Carolina

    2002-10-01

    The gravitational pull of subducted slabs is thought to drive the motions of Earth's tectonic plates, but the coupling between slabs and plates is not well established. If a slab is mechanically attached to a subducting plate, it can exert a direct pull on the plate. Alternatively, a detached slab may drive a plate by exciting flow in the mantle that exerts a shear traction on the base of the plate. From the geologic history of subduction, we estimated the relative importance of "pull" versus "suction" for the present-day plates. Observed plate motions are best predicted if slabs in the upper mantle are attached to plates and generate slab pull forces that account for about half of the total driving force on plates. Slabs in the lower mantle are supported by viscous mantle forces and drive plates through slab suction. PMID:12364804

  11. How mantle slabs drive plate tectonics.

    PubMed

    Conrad, Clinton P; Lithgow-Bertelloni, Carolina

    2002-10-01

    The gravitational pull of subducted slabs is thought to drive the motions of Earth's tectonic plates, but the coupling between slabs and plates is not well established. If a slab is mechanically attached to a subducting plate, it can exert a direct pull on the plate. Alternatively, a detached slab may drive a plate by exciting flow in the mantle that exerts a shear traction on the base of the plate. From the geologic history of subduction, we estimated the relative importance of "pull" versus "suction" for the present-day plates. Observed plate motions are best predicted if slabs in the upper mantle are attached to plates and generate slab pull forces that account for about half of the total driving force on plates. Slabs in the lower mantle are supported by viscous mantle forces and drive plates through slab suction.

  12. Recent Segmental Duplications in the Working Draft Assembly of the Brown Norway Rat

    PubMed Central

    Tuzun, Eray; Bailey, Jeffrey A.; Eichler, Evan E.

    2004-01-01

    We assessed the content, structure, and distribution of segmental duplications (≥90% sequence identity, ≥5 kb length) within the published version of the Rattus norvegicus genome assembly (v.3.1). The overall fraction of duplicated sequence within the rat assembly (2.92%) is greater than that of the mouse (1%–1.2%) but significantly less than that of human (∼5%). Duplications were nonuniformly distributed, occurring predominantly as tandem and tightly clustered intrachromosomal duplications. Regions containing extensive interchromosomal duplications were observed, particularly within subtelomeric and pericentromeric regions. We identified 41 discrete genomic regions greater than 1 Mb in size, termed “duplication blocks.” These appear to have been the target of extensive duplication over millions of years of evolution. Gene content within duplicated regions (∼1%) was lower than expected based on the genome representation. Interestingly, sequence contigs lacking chromosome assignment (“the unplaced chromosome”) showed a marked enrichment for segmental duplication (45% of 75.2 Mb), indicating that segmental duplications have been problematic for sequence and assembly of the rat genome. Further targeted efforts are required to resolve the organization and complexity of these regions. PMID:15059990

  13. Mantle flow and dynamic topography associated with slab window opening

    NASA Astrophysics Data System (ADS)

    Guillaume, Benjamin; Moroni, Monica; Funiciello, Francesca; Martinod, Joseph; Faccenna, Claudio

    2010-05-01

    A slab window is defined as an 'hole' in the subducting lithosphere. In the classical view, slab windows develop where a spreading ridge intersects a subduction zone. The main consequences of this phenomenon are the modifications of the physical, chemical and thermal conditions in the backarc mantle that in turn affect the tectonic and magmatic evolution of the overriding plate. In this work, we perform dynamically self-consistent mantle-scale laboratory models, to evaluate how the opening of a window in the subducting panel influences the geometry and the kinematics of the slab, the mantle circulation pattern and, finally, the overriding plate dynamic topography. The adopted setup consists in a two-layer linearly viscous system simulating the roll-back of a fixed subducting plate (simulated using silicone putty) into the upper mantle (simulated using glucose syrup). Our experimental setting is also characterized by a constant-width rectangular window located at the center of a laterally confined slab, modeling the case of the interaction of a trench-parallel spreading ridge with a wide subduction zone. We find that the geometry and the kinematics of the slab are only minorly affected by the opening of a slab window. On the contrary, slab induced mantle circulation, quantified using Feature Tracking image analysis technique, is strongly modified and produces a peculiar non-isostatic topographic signal on the overriding plate. Assuming that our modeling results can be representative of the natural behavior of subduction zones, we compare them to the Patagonian subduction zone finding that anomalous backarc volcanism that developed since middle Miocene could result from the lateral flowage of subslab mantle, and that part of the Patagonian uplift could be dynamically supported.

  14. Modeling the surface photovoltage of silicon slabs with varying thickness.

    PubMed

    Vazhappilly, Tijo; Kilin, Dmitri S; Micha, David A

    2015-04-10

    The variation with thickness of the energy band gap and photovoltage at the surface of a thin semiconductor film are of great interest in connection with their surface electronic structure and optical properties. In this work, the change of a surface photovoltage (SPV) with the number of layers of a crystalline silicon slab is extracted from models based on their atomic structure. Electronic properties of photoexcited slabs are investigated using generalized gradient and hybrid density functionals, and plane wave basis sets. Si(1 1 1) surfaces have been terminated by hydrogen atoms to compensate for dangling bonds and have been described by large supercells with periodic boundary conditions. Calculations of the SPV of the Si slabs have been done in terms of the reduced density matrix of the photoactive electrons including dissipative effects due to their interaction with medium phonons and excitons. Surface photovoltages have been calculated for model Si slabs with 4-12, and 16 layers, to determine convergence trends versus slab thickness. Band gaps and the inverse of the SPVs have been found to scale nearly linearly with the inverse thickness of the slab, while the electronic density of states increases quadratically with thickness. Our calculations show the same trends as experimental values indicating band gap reduction and absorption enhancement for Si films of increasing thickness. Simple arguments on confined electronic structures have been used to explain the main effects of changes with slab thickness. A procedure involving shifted electron excitation energies is described to improve results from generalized gradient functionals so they can be in better agreement with the more accurate but also more computer intensive values from screened exchange hybrid functionals.

  15. Evaluation of the possibility to use thick slabs of reconstructed outer breast tomosynthesis slice images

    NASA Astrophysics Data System (ADS)

    Petersson, Hannie; Dustler, Magnus; Tingberg, Anders; Timberg, Pontus

    2016-03-01

    The large image volumes in breast tomosynthesis (BT) have led to large amounts of data and a heavy workload for breast radiologists. The number of slice images can be decreased by combining adjacent image planes (slabbing) but the decrease in depth resolution can considerably affect the detection of lesions. The aim of this work was to assess if thicker slabbing of the outer slice images (where lesions seldom are present) could be a viable alternative in order to reduce the number of slice images in BT image volumes. The suggested slabbing (an image volume with thick outer slabs and thin slices between) were evaluated in two steps. Firstly, a survey of the depth of 65 cancer lesions within the breast was performed to estimate how many lesions would be affected by outer slabs of different thicknesses. Secondly, a selection of 24 lesions was reconstructed with 2, 6 and 10 mm slab thickness to evaluate how the appearance of lesions located in the thicker slabs would be affected. The results show that few malignant breast lesions are located at a depth less than 10 mm from the surface (especially for breast thicknesses of 50 mm and above). Reconstruction of BT volumes with 6 mm slab thickness yields an image quality that is sufficient for lesion detection for a majority of the investigated cases. Together, this indicates that thicker slabbing of the outer slice images is a promising option in order to reduce the number of slice images in BT image volumes.

  16. A Comparative Study of Strength of Two-Way Rectangular Slabs with and without Openings

    NASA Astrophysics Data System (ADS)

    Ravindra, M.; Rakesh, V.; Rambabu, K.

    2016-09-01

    The present work uses yield-line theory to find the strength of uniformly loaded rectangular reinforced concrete slabs with and without rectangular openings. Five positions of openings are considered, i.e. the slab centre, the slab corner, the centre of a short side, the centre of a long side and the opening eccentric to the slab centre. All possible admissible yield line patterns are considered for all given configurations of the slab subjected to uniformly distributed load keeping in view the basic principles of yield line theory. The ratios of the corresponding lengths of the sides of the opening and the slab are different and sizes of opening up to 0.4× the length of the slab sides are considered. Symmetric edge conditions like continuous slab, simply supported, two long sides continuous and two short sides continuous are considered for various sizes of openings in order to plot the design charts for isotropic reinforcement coefficients only. Affine transformation is also performed for slab with openings.

  17. 6. NO. 2 CONTINUOUS SLAB REHEATING FURNACE OF THE 160' ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. NO. 2 CONTINUOUS SLAB REHEATING FURNACE OF THE 160' PLATE MILL. FURNACE SHOWING DURING DEMOLITION. C HOOK USED TO CHANGE ROLLS IS VISIBLE IN FRONT OF FURNACE. - U.S. Steel Homestead Works, 160" Plate Mill, Along Monongahela River, Homestead, Allegheny County, PA

  18. Free subduction dynamics of a thermo-mechanical slab with non-linear rheology

    NASA Astrophysics Data System (ADS)

    Holt, A. F.; Becker, T. W.; Buffett, B. A.

    2012-12-01

    We investigate the dynamic controls on single plate subduction in a visco-plastic rheology using a 2D set up of the finite element code, CitcomCU. In contrast to previous studies, which focus largely on compositional slabs (e.g. Enns et al., 2005), we focus on thermal slabs (i.e. include effects of thermal diffusion). We analyse slabs that develop from plates both with uniform initial thicknesses and half-space cooling plates with thicknesses that vary with sqrt(x). A pseudo-plastic rheology facilitates the decoupling of the slab from the free slip upper surface. It is found that thermal slabs have lower strain rates in the bending region, due to the cooling upper boundary temperature condition, and so lower yield stresses are required to decouple thermal slabs than compositional slabs. As in previous work, it is found that stronger, thicker slabs promote trench advance (after the initial advancing phase). Both boundary conditions (basal and side) and incorporating a plate with half-space cooling thickness variations are shown to have a significant effect on slab dynamics, particularly on the maximum amount of trench retreat. Subsequently, models with non-Newtonian, stress-dependent rheologies are compared to Newtonian models with equivalent slab-mantle viscosity contrasts. Models with power law exponents of both 3, corresponding to dislocation creep, and a large exponent of 14, corresponding to near-pure plasticity (see Buffett and Becker, 2012), are analysed. It is found that, particularly for the n=14 case, the inclusion of a stress dependent rheology dramatically reduces the timescales of both trench migration and slab descent, while modifying slab morphology to a much lesser degree. Using a temperature threshold to confine the non-Newtonian rheology to within the slab prevents weakening in the surrounding mantle and so increases the subduction timescales to values that lie between the equivalent Newtonian and non-Newtonian (non-confined) timescales. While all

  19. Intersecting Work and Learning: Assembling Advanced Liberal Regimes of Governing Workers in Australia

    ERIC Educational Resources Information Center

    Reich, Ann

    2008-01-01

    Much had been written over the past few years on the intersections of work and learning. This article suggests that the analysis of the intersections of work and learning can benefit greatly from understanding the ways in which governing workers as individuals and populations has changed in Western liberal democracies in the latter part of the…

  20. Dithiocarbamate Self-Assembled Monolayers as Efficient Surface Modifiers for Low Work Function Noble Metals.

    PubMed

    Meyer, Dominik; Schäfer, Tobias; Schulz, Philip; Jung, Sebastian; Rittich, Julia; Mokros, Daniel; Segger, Ingolf; Maercks, Franziska; Effertz, Christian; Mazzarello, Riccardo; Wuttig, Matthias

    2016-09-01

    Tuning the work function of the electrode is one of the crucial steps to improve charge extraction in organic electronic devices. Here, we show that N,N-dialkyl dithiocarbamates (DTC) can be effectively employed to produce low work function noble metal electrodes. Work functions between 3.1 and 3.5 eV are observed for all metals investigated (Cu, Ag, and Au). Ultraviolet photoemission spectroscopy (UPS) reveals a maximum decrease in work function by 2.1 eV as compared to the bare metal surface. Electronic structure calculations elucidate how the complex interplay between intrinsic dipoles and dipoles induced by bond formation generates such large work function shifts. Subsequently, we quantify the improvement in contact resistance of organic thin film transistor devices with DTC coated source and drain electrodes. These findings demonstrate that DTC molecules can be employed as universal surface modifiers to produce stable electrodes for electron injection in high performance hybrid organic optoelectronics. PMID:27504721

  1. The Spindle Assembly Checkpoint works like a rheostat not a toggle-switch

    PubMed Central

    Collin, Philippe; Nashchekina, Oxana; Walker, Rachael; Pines, Jonathon

    2013-01-01

    The Spindle Assembly Checkpoint (SAC) is essential in mammalian mitosis to ensure the equal segregation of sister chromatids1, 2. The SAC generates a Mitotic Checkpoint Complex (MCC) to prevent the Anaphase Promoting Complex/Cyclosome (APC/C) from targeting key mitotic regulators for destruction until all the chromosomes have attached to the mitotic apparatus1, 3, 4. A single unattached kinetochore can delay anaphase for several hours5, but how it is able to block the APC/C throughout the cell is not understood. Current concepts of the SAC posit that it exhibits either an ‘all or nothing’ response6 or there is a minimum threshold sufficient to block the APC/C7. Here, we have used gene targeting to measure SAC activity and find that it does not have an ‘all or nothing’ response. Instead, the strength of the SAC depends on the amount of Mad2 recruited to kinetochores and on the amount of MCC formed. Furthermore, we show that different drugs activate the SAC to different extents, which may be relevant to their efficacy in chemotherapy. PMID:24096242

  2. Analog Modeling of the Juan Fernández Ridge, Central Chile, and Implications for Flat-Slab Subduction Dynamics

    NASA Astrophysics Data System (ADS)

    Woodell, D.; Anderson, M. L.

    2009-12-01

    This study compares the strain experienced by the subducting lithosphere in analog models to the strain recorded by earthquakes in the subduction zone that includes the Juan Fernández Ridge (JFR), near 33 S, 73 W, off the coast of central Chile. The JFR is an aseismic hot spot ridge that has a thickened oceanic crust. The overthickened crust reduces the total density of the slab when compared to the surrounding slab areas, and thus increases the buoyancy of the subducting Nazca plate at this particular location. It is hypothesized that the Nazca plate experiences “flat-slab” subduction at the JFR subduction zone due to this buoyancy. Brudzinski and Chen (2005) argue that, due to the poorly aligned direction of maximum extension (T axes) for earthquakes in the subducting slab in flat-slab subduction zones, the theory of “slab pull” may not be valid for flat-slab subduction zones, and there must be other forces at work. However, Anderson et al. (2007) develop new, more precise slab contours from newly determined earthquake locations and use these contours to qualitatively compare the earthquake data to slab dip directions and thus expected slab-pull directions. They conclude that T axes are parallel to slab dip, and thus slab pull is the only force necessary for explaining the T axis direction. In this study, we quantitatively compare extension produced in analog "flat-slab" models in the laboratory to T axes from the Anderson et al. (2007) study, extending and further testing their idea. Several materials comprise the analog models. Light corn syrup represents the asthenosphere, while silicon putty represents the lithosphere. Recreating the dynamics of the buoyant JFR necessitates two different densities of silly putty: a denser one for the bulk of the slab, and a less dense one for the buoyant ridge. Shallow circular indentations (strain ellipses) on the slab facilitate recording of the strain in the subducting slab. Video and still pictures record each

  3. Tethyan subducted slabs under India

    NASA Astrophysics Data System (ADS)

    Van der Voo, Rob; Spakman, Wim; Bijwaard, Harmen

    1999-08-01

    Tomographic imaging of the mantle under Tibet, India and the adjacent Indian Ocean reveals several zones of relatively high P-wave velocities at various depths. Under the Hindu Kush region in northeastern Afghanistan and southern Tajikistan, a regional northward-dipping slab is seen in the entire upper 600 km of the mantle and is apparently still attached to the lithosphere of the Indian plate. Under northern Pakistan this same slab shows a roll-over structure with the deeper portion overturned and dipping southward, as can also be seen in the distribution of earthquake hypocenters. Farther east-southeast (e.g., in the vicinity of Nepal), a well-resolved anomaly below 450 km depth is connected to the slab under the Hindu Kush, but seems to be separated from the lithosphere above 350 km. These upper-mantle anomalies are interpreted as the remnants of delaminated sub-continental lithosphere that went down when Greater India continued to converge northward with Asia after ˜45 Ma. The deeper high-velocity anomalies under the Indian sub-continent appear clearly separated from the shallower ones as well as from each other, and are inferred to represent remnants of oceanic lithospheric slabs that have sunk into the lower mantle and were subsequently overridden by the Indian plate. They occur at depths between 1000 and 2300 km and occasionally descend down to the core-mantle boundary. The anomalies form three parallel WNW-ESE striking zones. We interpret the two southern zones as remnants of oceanic lithosphere that was subducted when the Neo-Tethys Ocean closed between India and Tibet in the Cretaceous and earliest Tertiary. The northern deep-mantle zone under northern Afghanistan, the Himalayas and the Lhasa block in southern Tibet may represent the last-subducted remnant of the Paleo-Tethys Ocean, which is thought to have closed before the Hauterivian stage of the Early Cretaceous. The middle zone continues southeastward as a rather straight high-velocity zone towards

  4. Slab melting versus slab dehydration in subduction-zone magmatism

    PubMed Central

    Mibe, Kenji; Kawamoto, Tatsuhiko; Matsukage, Kyoko N.; Fei, Yingwei; Ono, Shigeaki

    2011-01-01

    The second critical endpoint in the basalt-H2O system was directly determined by a high-pressure and high-temperature X-ray radiography technique. We found that the second critical endpoint occurs at around 3.4 GPa and 770 °C (corresponding to a depth of approximately 100 km in a subducting slab), which is much shallower than the previously estimated conditions. Our results indicate that the melting temperature of the subducting oceanic crust can no longer be defined beyond this critical condition and that the fluid released from subducting oceanic crust at depths greater than 100 km under volcanic arcs is supercritical fluid rather than aqueous fluid and/or hydrous melts. The position of the second critical endpoint explains why there is a limitation to the slab depth at which adakitic magmas are produced, as well as the origin of across-arc geochemical variations of trace elements in volcanic rocks in subduction zones. PMID:21536910

  5. Perforation of thin unreinforced concrete slabs

    SciTech Connect

    Cargile, J.D.; Giltrud, M.E.; Luk, V.K.

    1993-10-01

    This report discusses fourteen tests which were conducted to investigate the perforation of thin unreinforced concrete slabs. The 4340-steel projectile used in the test series is 50.8 mm in diameter, 355.6 mm in length, has a mass of 2.34 kg. and an ogive nose with caliber radius head of 3. The slabs, contained within steel culverts, are 1.52 m in diameter and consist of concrete with a nominal unconfined compressive strength of 38.2 MPa and maxima aggregate size of 9.5 mm. Slab thicknesses are 284.4, 254.0, 215.9 and 127.0 mm. Tests were conducted at impact velocities of about 313 m/s on all slab thicknesses and about 379 and 471 m/s on the 254.0-mm-thick slab. All tests were conducted at normal incidence to the slab. All tests were conducted at normal incidence to the slab. Information obtained from the tests used to determine the loading (deceleration) on the projectile during the perforation process, the velocity-displacement of the projectile as it perforated the slab, and the projectile position as damage occurred on the backface of the slab. The test projectile behaved essentially as a rigid body for all of the tests.

  6. The slab geometry laser. I - Theory

    NASA Technical Reports Server (NTRS)

    Eggleston, J. M.; Kane, T. J.; Kuhn, K.; Byer, R. L.; Unternahrer, J.

    1984-01-01

    Slab geometry solid-state lasers offer significant performance improvements over conventional rod-geometry lasers. A detailed theoretical description of the thermal, stress, and beam-propagation characteristics of a slab laser is presented. The analysis includes consideration of the effects of the zig-zag optical path, which eliminates thermal and stress focusing and reduces residual birefringence.

  7. Slab Houses: Reflections of the Past.

    ERIC Educational Resources Information Center

    Cappetta, Ann

    1990-01-01

    Describes how students, influenced by Victorian architecture, created ceramic slab houses. Students devised a solution to depict the reflective nature of Victorian bay windows. Project incorporates art history, handbuilding, and surface ornamentation. Outlines and illustrates steps involved in making slab houses that can be adapted for use by…

  8. Fracture of solid state laser slabs

    SciTech Connect

    Marion, J.E.

    1986-07-01

    Fracture due to thermal stress limits the power output potential of modern, high average power slab lasers. Here the criteria for slab fracture and the nature of the surface flaws which constitute the strength-controlling defects are reviewed. Specific fracture data for gadolinium scandium gallium garnet and LHG-5 phosphate glass with different surface finishes are evaluated in the context of assigning appropriate slab operating parameters using Wiebull statistics. These examples illustrate both the danger of design using brittle components without adequate fracture testing, and the inadequacy of design methods which use a fixed safety factor, for this class of materials. Further consideration reveals that operation of slab lasers in contact with an aqueous coolant may lead to strength degradation with time. Finally, the evolution of the failure process in which a characteristic midplane crack forms is outlined, and the pertinent parameters for avoiding slab fracture are identified.

  9. Software Analytical Instrument for Assessment of the Process of Casting Slabs

    SciTech Connect

    Franek, Zdenek; Kavicka, Frantisek; Stetina, Josef; Masarik, Milos

    2010-06-15

    The paper describes the original proposal of ways of solution and function of the program equipment for assessment of the process of casting slabs. The program system LITIOS was developed and implemented in EVRAZ Vitkovice Steel Ostrava on the equipment of continuous casting of steel (further only ECC). This program system works on the data warehouse of technological parameters of casting and quality parameters of slabs. It enables an ECC technologist to analyze the course of casting melt and with using statistics methods to set the influence of single technological parameters on the duality of final slabs. The system also enables long term monitoring and optimization of the production.

  10. Slab stagnation and detachment under northeast China

    NASA Astrophysics Data System (ADS)

    Honda, Satoru

    2016-03-01

    Results of tomography models around the Japanese Islands show the existence of a gap between the horizontally lying (stagnant) slab extending under northeastern China and the fast seismic velocity anomaly in the lower mantle. A simple conversion from the fast velocity anomaly to the low-temperature anomaly shows a similar feature. This feature appears to be inconsistent with the results of numerical simulations on the interaction between the slab and phase transitions with temperature-dependent viscosity. Such numerical models predict a continuous slab throughout the mantle. I extend previous analyses of the tomography model and model calculations to infer the origins of the gap beneath northeastern China. Results of numerical simulations that take the geologic history of the subduction zone into account suggest two possible origins for the gap: (1) the opening of the Japan Sea led to a breaking off of the otherwise continuous subducting slab, or (2) the western edge of the stagnant slab is the previous subducted ridge, which was the plate boundary between the extinct Izanagi and the Pacific plates. Origin (2) suggesting the present horizontally lying slab has accumulated since the ridge subduction, is preferable for explaining the present length of the horizontally lying slab in the upper mantle. Numerical models of origin (1) predict a stagnant slab in the upper mantle that is too short, and a narrow or non-existent gap. Preferred models require rather stronger flow resistance of the 660-km phase change than expected from current estimates of the phase transition property. Future detailed estimates of the amount of the subducted Izanagi plate and the present stagnant slab would be useful to constrain models. A systematic along-arc variation of the slab morphology from the northeast Japan to Kurile arcs is also recognized, and its understanding may constrain the 3D mantle flow there.

  11. Turbulence in the cylindrical slab

    SciTech Connect

    Gentle, K. W.; Rowan, W. L.; Williams, C. B.; Brookman, M. W.

    2014-09-15

    The cylindrical slab was the first and simplest model of intrinsically unstable microturbulence. The Helimak is an experimental realization of this model. Although finite, it is sufficiently large to escape boundary effects, with dimensionless parameters similar to those of a tokamak edge or scrape off layer. The essential drive is interchange-like, a pressure gradient with unfavorable magnetic curvature, leading to a non-linearly saturated state of large-amplitude turbulence, Δn{sub rms}/n ∼ 0.5. The nonlinear processes governing this saturation are unique, unlike any of those posited for the much weaker turbulence typical of confined plasma, e.g., in a tokamak. Neither linear stability theory, quasi-linear theory, zonal flows, nor flow shear stabilization is consistent with the observations. The mechanisms determining the non-linearly saturated state constitute an important challenge to our understanding of strongly nonlinear systems.

  12. Slab melting and magma formation beneath the southern Cascade arc

    NASA Astrophysics Data System (ADS)

    Walowski, K. J.; Wallace, P. J.; Clynne, M. A.; Rasmussen, D. J.; Weis, D.

    2016-07-01

    The processes that drive magma formation beneath the Cascade arc and other warm-slab subduction zones have been debated because young oceanic crust is predicted to largely dehydrate beneath the forearc during subduction. In addition, geochemical variability along strike in the Cascades has led to contrasting interpretations about the role of volatiles in magma generation. Here, we focus on the Lassen segment of the Cascade arc, where previous work has demonstrated across-arc geochemical variations related to subduction enrichment, and H-isotope data suggest that H2O in basaltic magmas is derived from the final breakdown of chlorite in the mantle portion of the slab. We use naturally glassy, olivine-hosted melt inclusions (MI) from the tephra deposits of eight primitive (MgO > 7 wt%) basaltic cinder cones to quantify the pre-eruptive volatile contents of mantle-derived melts in this region. The melt inclusions have B concentrations and isotope ratios that are similar to mid-ocean ridge basalt (MORB), suggesting extensive dehydration of the downgoing plate prior to reaching sub-arc depths and little input of slab-derived B into the mantle wedge. However, correlations of volatile and trace element ratios (H2O/Ce, Cl/Nb, Sr/Nd) in the melt inclusions demonstrate that geochemical variability is the result of variable addition of a hydrous subduction component to the mantle wedge. Furthermore, correlations between subduction component tracers and radiogenic isotope ratios show that the subduction component has less radiogenic Sr and Pb than the Lassen sub-arc mantle, which can be explained by melting of subducted Gorda MORB beneath the arc. Agreement between pMELTS melting models and melt inclusion volatile, major, and trace element data suggests that hydrous slab melt addition to the mantle wedge can produce the range in primitive compositions erupted in the Lassen region. Our results provide further evidence that chlorite-derived fluids from the mantle portion of the

  13. Slab melting and magma generation beneath the southern Cascade Arc

    NASA Astrophysics Data System (ADS)

    Walowski, K. J.; Wallace, P. J.; Clynne, M. A.

    2014-12-01

    Magma formation in subduction zones is interpreted to be caused by flux melting of the mantle wedge by fluids derived from dehydration of the downgoing oceanic lithosphere. In the Cascade Arc and other hot-slab subduction zones, however, most dehydration reactions occur beneath the forearc, necessitating a closer investigation of magma generation processes in this setting. Recent work combining 2-D steady state thermal models and the hydrogen isotope composition of olivine-hosted melt inclusions from the Lassen segment of the Cascades (Walowski et al., 2014; in review) has shown that partial melting of the subducted basaltic crust may be a key part of the subduction component in hot arcs. In this model, fluids from the slab interior (hydrated upper mantle) rise through the slab and cause flux-melting of the already dehydrated MORB volcanics in the upper oceanic crust. In the Shasta and Lassen segments of the southern Cascades, support for this interpretation comes from primitive magmas that have MORB-like Sr isotope compositions that correlate with subduction component tracers (H2O/Ce, Sr/P) (Grove et al. 2002, Borg et al. 2002). In addition, mass balance calculations of the composition of subduction components show ratios of trace elements to H2O that are at the high end of the global arc array (Ruscitto et al. 2012), consistent with the role of a slab-derived melt. Melting of the subducted basaltic crust should contribute a hydrous dacitic or rhyolitic melt (e.g. Jego and Dasgupta, 2013) to the mantle wedge rather than an H2O-rich aqueous fluid. We are using pHMELTS and pMELTS to model the reaction of hydrous slab melts with mantle peridotite as the melts rise through the inverted thermal gradient in the mantle wedge. The results of the modeling will be useful for understanding magma generation processes in arcs that are associated with subduction of relatively young oceanic lithosphere.

  14. Oscillation modes and transmission into a Fibonacci slab

    NASA Astrophysics Data System (ADS)

    Castro-Arce, Lamberto; Molinar-Tabares, Martin; Campos-Garcia, Julio; Figueroa-Navarro, Carlos; Isasi-Siqueiros, Leonardo; Manzanares-Martinez, Betsabe

    In our contribution we developed a study on the behavior of the transmission modes and a Pt / Zn slab of a Fibonacci array of longitudinal and transverse acoustic waves. We have worked with arrangements from n = 1 to10 and has managed to find the energy bands and transmission, filling factor 0.4 observing the appearance of Pseudo-Gaps in the evolution of the study when the arrangement Fibonacci increases. We acknowledge the support of SNI CONACYT.

  15. Commensurate germanium light emitters in silicon-on-insulator photonic crystal slabs.

    PubMed

    Jannesari, R; Schatzl, M; Hackl, F; Glaser, M; Hingerl, K; Fromherz, T; Schäffler, F

    2014-10-20

    We report on the fabrication and characterization of silicon-on-insulator (SOI) photonic crystal slabs (PCS) with commensurately embedded germanium quantum dot (QD) emitters for near-infrared light emission. Substrate pre-patterning defines preferential nucleation sites for the self-assembly of Ge QDs during epitaxial growth. Aligned two-dimensional photonic crystal slabs are then etched into the SOI layer. QD ordering enhances the photoluminescence output as compared to PCSs with randomly embedded QDs. Rigorously coupled wave analysis shows that coupling of the QD emitters to leaky modes of the PCS can be tuned via their location within the unit cell of the PCS.

  16. The Effect of Mortar Grade and Thickness on the Impact Resistance of Ferrocement Slab

    NASA Astrophysics Data System (ADS)

    Che Muda, Zakaria; Syamsir, Agusril; Nasharuddin Mustapha, Kamal; Sulleman, Sorefan; Beddu, Salmia; Thiruchelvam, Sivadass; Ismail, Firas B.; Usman, Fathoni; Liyana Mohd Kamal, Nur; Ashraful Alam, Md; Birima, Ahmed H.; Itam, Zarina; Zaroog, O. S.

    2016-03-01

    This paper investigate the effect of the thickness and mesh spacing on the impact of ferrocement for the concrete slab of 300mm × 300mm size reinforced subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at height of 150 mm, 350mm, and 500mm has been used in this research work. The objective of this research is to study the relationship of impact resistance of ferrocement against the mortar grade and slab thickness. There is a good linear correlation between impact resistance of ferrocement against the mortar grade and the thickness of ferrocement slab. The first and ultimate crack impact resistance of mortar grade 43 (for 40 mm thick slab with mesh reinforcement) are 1.60 times and 1.53 times respectively against the mortar grade 17 slab (of same thickness with mesh reinforcement). The first and ultimate crack impact resistance for 40 mm thick slab (mortar grade 43 with mesh reinforcement) are 3.55 times and 4.49 times respectively against the 20 mm thick slab (of same mortar grade with mesh reinforcement).

  17. Meteorological variables associated with deep slab avalanches on persistent weak layers

    USGS Publications Warehouse

    Marienthal, Alex; Hendrikx, Jordy; Birkeland, Karl; Irvine, Kathryn M.

    2014-01-01

    Deep slab avalanches are a particularly challenging avalanche forecasting problem. These avalanches are typically difficult to trigger, yet when they are triggered they tend to propagate far and result in large and destructive avalanches. For this work we define deep slab avalanches as those that fail on persistent weak layers deeper than 0.9m (3 feet), and that occur after February 1st. We utilized a 44-year record of avalanche control and meteorological data from Bridger Bowl Ski Area to test the usefulness of meteorological variables for predicting deep slab avalanches. As in previous studies, we used data from the days preceding deep slab cycles, but we also considered meteorological metrics over the early months of the season. We utilized classification trees for our analyses. Our results showed warmer temperatures in the prior twenty-four hours and more loading over the seven days before days with deep slab avalanches on persistent weak layers. In line with previous research, extended periods of above freezing temperatures led to days with deep wet slab avalanches on persistent weak layers. Seasons with either dry or wet avalanches on deep persistent weak layers typically had drier early months, and often had some significant snow depth prior to those dry months. This paper provides insights for ski patrollers, guides, and avalanche forecasters who struggle to forecast deep slab avalanches on persistent weak layers late in the season.

  18. The study of the transition regime between slab and mixed slab-toroidal electron temperature gradient modes in a basic experiment

    NASA Astrophysics Data System (ADS)

    Balbaky, Abed; Sokolov, Vladimir; Sen, Amiya K.

    2015-05-01

    Electron temperature gradient (ETG) modes are suspected sources of anomalous electron thermal transport in magnetically confined plasmas as in tokamaks. Prior work in the Columbia Linear Machine (CLM) has been able to produce and identify slab ETG modes in a slab geometry [Wei et al., Phys. Plasmas 17, 042108 (2010)]. Now by modifying CLM to introduce curvature to the confining axial magnetic field, we have excited mixed slab-toroidal modes. Linear theory predicts a transition between slab and toroidal ETG modes when /k ∥ R c k y ρ ˜ 1 [J. Kim and W. Horton, Phys. Fluids B 3, 1167 (1991)]. We observe changes in the mode amplitude for levels of curvature Rc - 1 ≪ /k ∥ , s l a b k ⊥ ρ , which may be explained by reductions in k ∥ in the transition from slab to mixed slab-toroidal modes, as also predicted by theory. We present mode amplitude scaling as a function of magnetic field curvature. Over the range of curvature available in CLM experimentally we find a modest increase in saturated ETG potential fluctuations (˜1.5×), and a substantial increase in the power density of individual mode peaks (˜4-5×).

  19. Sausage oscillations of coronal plasma slabs

    NASA Astrophysics Data System (ADS)

    Hornsey, C.; Nakariakov, V. M.; Fludra, A.

    2014-07-01

    Context. Sausage oscillations are observed in plasma non-uniformities of the solar corona as axisymmetric perturbations of the non-uniformity. Often, these non-uniformities can be modelled as field-aligned slabs of the density enhancement. Aims: We perform parametric studies of sausage oscillations of plasma slabs, aiming to determine the dependence of the oscillation period on its parameters, and the onset of leaky and trapped regimes of the oscillations. Methods: Slabs with smooth transverse profiles of the density of a zero-beta plasma are perturbed by an impulsive localised perturbation of the sausage symmetry. In particular, the slab can contain an infinitely thin current sheet in its centre. The initial value problem is then solved numerically. The numerical results are subject to spectral analysis. The results are compared with analytical solutions for a slab with a step-function profile and also with sausage oscillations of a plasma cylinder. Results: We established that sausage oscillations in slabs generally have the same properties as in plasma cylinders. In the trapped regime, the sausage oscillation period increases with the increase in the longitudinal wavelength. In the leaky regime, the dependence of the period on the wavelength experiences saturation, and the period becomes independent of the wavelength in the long-wavelength limit. In the leaky regime the period is always longer than in the trapped regime. The sausage oscillation period in a slab is always longer than in a cylinder with the same transverse profile. In slabs with steeper transverse profiles, sausage oscillations have longer periods. The leaky regime occurs at shorter wavelengths in slabs with smoother profiles.

  20. Depth to the Juan De Fuca slab beneath the Cascadia subduction margin - a 3-D model for sorting earthquakes

    USGS Publications Warehouse

    McCrory, Patricia A.; Blair, J. Luke; Oppenheimer, David H.; Walter, Stephen R.

    2004-01-01

    We present an updated model of the Juan de Fuca slab beneath southern British Columbia, Washington, Oregon, and northern California, and use this model to separate earthquakes occurring above and below the slab surface. The model is based on depth contours previously published by Fluck and others (1997). Our model attempts to rectify a number of shortcomings in the original model and update it with new work. The most significant improvements include (1) a gridded slab surface in geo-referenced (ArcGIS) format, (2) continuation of the slab surface to its full northern and southern edges, (3) extension of the slab surface from 50-km depth down to 110-km beneath the Cascade arc volcanoes, and (4) revision of the slab shape based on new seismic-reflection and seismic-refraction studies. We have used this surface to sort earthquakes and present some general observations and interpretations of seismicity patterns revealed by our analysis. For example, deep earthquakes within the Juan de Fuca Plate beneath western Washington define a linear trend that may mark a tear within the subducting plate Also earthquakes associated with the northern stands of the San Andreas Fault abruptly terminate at the inferred southern boundary of the Juan de Fuca slab. In addition, we provide files of earthquakes above and below the slab surface and a 3-D animation or fly-through showing a shaded-relief map with plate boundaries, the slab surface, and hypocenters for use as a visualization tool.

  1. Rotational flow in tapered slab rocket motors

    NASA Astrophysics Data System (ADS)

    Saad, Tony; Sams, Oliver C.; Majdalani, Joseph

    2006-10-01

    Internal flow modeling is a requisite for obtaining critical parameters in the design and fabrication of modern solid rocket motors. In this work, the analytical formulation of internal flows particular to motors with tapered sidewalls is pursued. The analysis employs the vorticity-streamfunction approach to treat this problem assuming steady, incompressible, inviscid, and nonreactive flow conditions. The resulting solution is rotational following the analyses presented by Culick for a cylindrical motor. In an extension to Culick's work, Clayton has recently managed to incorporate the effect of tapered walls. Here, an approach similar to that of Clayton is applied to a slab motor in which the chamber is modeled as a rectangular channel with tapered sidewalls. The solutions are shown to be reducible, at leading order, to Taylor's inviscid profile in a porous channel. The analysis also captures the generation of vorticity at the surface of the propellant and its transport along the streamlines. It is from the axial pressure gradient that the proper form of the vorticity is ascertained. Regular perturbations are then used to solve the vorticity equation that prescribes the mean flow motion. Subsequently, numerical simulations via a finite volume solver are carried out to gain further confidence in the analytical approximations. In illustrating the effects of the taper on flow conditions, comparisons of total pressure and velocity profiles in tapered and nontapered chambers are entertained. Finally, a comparison with the axisymmetric flow analog is presented.

  2. Microwave and THz sensing using slab-pair-based metamaterials

    SciTech Connect

    Kenanakis, G.; Shen, Nianhai; Mavidis, Ch.; Katsarakis, N.; Kafesaki, M.; Soukoulis, Costas M.; Economou, E.N.

    2012-10-15

    In this work the sensing capability of an artificial magnetic metamaterial based on pairs of metal slabs is demonstrated, both theoretically and experimentally, in the microwave regime. The demonstration is based on transmission measurements and simulations monitoring the shift of the magnetic resonance frequency as one changes a thin dielectric layer placed between the slabs of the pairs. Strong dependence of the magnetic resonance frequency on both the permittivity and the thickness of the dielectric layer under detection was observed. The sensitivity to the dielectrics′ permittivity (ε) is larger for dielectrics of low ε values, which makes the approach suitable for sensing organic materials also in the THz regime. The capability of our approach for THz sensing is also demonstrated through simulations.

  3. Constraints of subducted slab geometries on trench migration and subduction velocities: flat slabs and slab curtains in the mantle under Asia

    NASA Astrophysics Data System (ADS)

    Wu, J. E.; Suppe, J.; Renqi, L.; Lin, C.; Kanda, R. V.

    2013-12-01

    The past locations, shapes and polarity of subduction trenches provide first-order constraints for plate tectonic reconstructions. Analogue and numerical models of subduction zones suggest that relative subducting (Vs) and overriding (Vor) plate velocities may strongly influence final subducted slab geometries. Here we have mapped the 3D geometries of subducted slabs in the upper and lower mantle of Asia from global seismic tomography. We have incorporated these slabs into plate tectonic models, which allows us to infer the subducting and overriding plate velocities. We describe two distinct slab geometry styles, ';flat slabs' and ';slab curtains', and show their implications for paleo-trench positions and subduction geometries in plate tectonic reconstructions. When compared to analogue and numerical models, the mapped slab styles show similarities to modeled slabs that occupy very different locations within Vs:Vor parameter space. ';Flat slabs' include large swaths of sub-horizontal slabs in the lower mantle that underlie the well-known northward paths of India and Australia from Eastern Gondwana, viewed in a moving hotspot reference. At India the flat slabs account for a significant proportion of the predicted lost Ceno-Tethys Ocean since ~100 Ma, whereas at Australia they record the existence of a major 8000km by 2500-3000km ocean that existed at ~43 Ma between East Asia, the Pacific and Australia. Plate reconstructions incorporating the slab constraints imply these flat slab geometries were generated when continent overran oceanic lithosphere to produce rapid trench retreat, or in other words, when subducting and overriding velocities were equal (i.e. Vs ~ Vor). ';Slab curtains' include subvertical Pacific slabs near the Izu-Bonin and Marianas trenches that extend from the surface down to 1500 km in the lower mantle and are 400 to 500 km thick. Reconstructed slab lengths were assessed from tomographic volumes calculated at serial cross-sections. The ';slab

  4. Prediction of temperature distribution in the hot rolling of slabs

    NASA Astrophysics Data System (ADS)

    Serajzadeh, S.; Karimi Taheri, A.; Mucciardi, F.

    2002-03-01

    In the process of continuous hot slab rolling, it is vital to know the temperature distribution within the slab along the length of the rolling mill because temperature is the dominant parameter controlling the kinetics of metallurgical transformations and the flow stress of the rolled metal. In other words, the microstructural changes, the mechanical properties as well as the final dimensions of the product and roll-force depend on the temperature distribution within the metal being rolled. In this paper, a mathematical model based on the finite element method is utilized to predict the temperature distribution and microstructural changes during the continuous hot slab rolling process. The effects of various parameters such as the heat of deformation, the work-roll temperature, the rolling speed, and the heat transfer coefficient between the work-roll and the metal are all taken into account in the analyses. To verify the validity of the model and the generated computer code, a comparison is carried out between the theoretical and plant-recorded results.

  5. Sensitivity enhancement in photonic crystal slab biosensors.

    PubMed

    El Beheiry, Mohamed; Liu, Victor; Fan, Shanhui; Levi, Ofer

    2010-10-25

    Refractive index sensitivity of guided resonances in photonic crystal slabs is analyzed. We show that modal properties of guided resonances strongly affect spectral sensitivity and quality factors, resulting in substantial enhancement of refractive index sensitivity. A three-fold spectral sensitivity enhancement is demonstrated for suspended slab designs, in contrast to designs with a slab resting over a substrate. Spectral sensitivity values are additionally shown to be unaffected by quality factor reductions, which are common to fabricated photonic crystal nano-structures. Finally, we determine that proper selection of photonic crystal slab design parameters permits biosensing of a wide range of analytes, including proteins, antigens, and cells. These photonic crystals are compatible with large-area biosensor designs, permitting direct access to externally incident optical beams in a microfluidic device.

  6. Crust rheology, slab detachment and topography

    NASA Astrophysics Data System (ADS)

    Duretz, T.; Gerya, T. V.

    2012-04-01

    The collision between continents following the closure of an ocean can lead to the subduction of continental crust. The introduction of buoyant crust within subduction zones triggers the development of extensional stresses in slabs which eventually result in their detachment. The dynamic consequences of slab detachment affects the development of topography, the exhumation of high-pressure rocks and the geodynamic evolution of collision zones. We employ two-dimensional thermo-mechanical modelling in order to study the importance of crustal rheology on the evolution of spontaneous subduction-collision systems and the occurrence of slab detachment. The modelling results indicate that varying the rheological structure of the crust can results in a broad range of collisional evolutions involving slab detachment, delamination (associated to slab rollback), or the combination of both mechanisms. By enhancing mechanical coupling at the Moho, a strong crust leads to the deep subduction of the crust (180 km). These collisions are subjected to slab detachment and subsequent coherent exhumation of the crust accommodated by eduction (inversion of subduction sense) and thrusting. In these conditions, slab detachment promotes the development of a high (> 4.5 km) and narrow (< 200 km) topographic plateau located in the vicinity of the suture. A contrasting style of collision is obtained by employing a weak crustal rheology. The weak mechanical coupling at the Moho promotes the widespread delamination of the lithosphere, preventing slab detachment to occur. Further shortening leads to buckling and thickening of the crust resulting in the development of topographic bulging on the lower plate. Collisions involving rheologically layered crust are characterised by a decoupling level at mid-crustal depths. These initial condition favours the delamination of the upper crust as well as the deep subduction of the lower crust. These collisions are thus successively affected by delamination

  7. Photocatalytic, highly hydrophilic porcelain stoneware slabs

    NASA Astrophysics Data System (ADS)

    Raimondo, M.; Guarini, G.; Zanelli, C.; Marani, F.; Fossa, L.; Dondi, M.

    2011-10-01

    Photocatalytic, highly hydrophilic industrial porcelain stoneware large slabs were realized by deposition of nanostructured TiO2 coatings. Different surface finishing and experimental conditions were considered in order to assess the industrial feasibility. Photocatalytic and wetting behaviour of functionalized slabs mainly depends on surface phase composition in terms of anatase/rutile ratio, this involving - as a key issue - the deposition of TiO2 on industrially sintered products with an additional annealing step to strengthen coatings' performances and durability.

  8. 68. COMPLETED ASSEMBLY SHOWING BARGES, BRIDGE AND SUPPORT CARRIAGE AT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    68. COMPLETED ASSEMBLY SHOWING BARGES, BRIDGE AND SUPPORT CARRIAGE AT THE BASE OF THE LAUNCHING SLAB LOOKING EAST, April 26, 1948. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  9. Repetitively pulsed Nd-glass slab lasers

    NASA Astrophysics Data System (ADS)

    Denker, B. I.; Kir'ianov, A. V.; Maliutin, A. A.; Kertesz, I.; Kroo, N.

    1989-09-01

    The possibility of obtaining high laser output energies at 1.32 micron using thin LiNdLa phosphate glass slabs with a high Nd(3+) concentration is discussed. Comparison data for 1.054 micron are also given. In the experiments, 3 x 14 x 125-mm slabs were prepared from LiNdLa phosphate glass with Nd concentration 1.2 x 10 to the 21st/cu cm. The uncoated slab facets were tested in a silver-coated quartz tube reflector pumped by 450-microsec flash-lamp pulses. The light passing through the slab returns to it after reflection from the tube surface. Most of the radiation falls on the wider side of the slab at large angles of incidence, thus maximizing its path inside the slab. The 150-mm laser resonator was formed by two flat mirrors. At 1.32 microns an output mirror of reflectivity r = 95 percent was used (with r less than 10 percent at 1.054 micron), while at 1.054 micron, r(output) = 50 percent was chosen. The pump-energy dependence of the output energy was measured.

  10. Three-dimensional necking during viscous slab detachment

    NASA Astrophysics Data System (ADS)

    Tscharner, M.; Schmalholz, S. M.; Duretz, T.

    2014-06-01

    We study the three-dimensional (3-D) deformation during detachment of a lithospheric slab with simple numerical models using the finite element method. An initially vertical layer of power law viscous fluid mimics the slab and is surrounded by a linear or power law viscous fluid representing asthenospheric mantle. We quantify the impact of slab size and shape (symmetric/asymmetric) on slab detachment and identify two processes that control the lateral (i.e., along-trench) slab deformation: (1) the horizontal deflection of the lateral, vertical slab sides (> 100 km with velocities up to 16 mm/yr) and (2) the propagation of localized thinning (necking) inside the slab (with velocities >9 cm/yr). The lateral propagation velocity is approximately constant during slab detachment. Larger slabs (here wider than approximately 300 km) detach with rates similar to those predicted by 2-D models, whereas smaller slabs detach slower. Implications for geodynamic processes and interpretations of seismic tomography are discussed.

  11. Was there a Laramide "flat slab"?

    NASA Astrophysics Data System (ADS)

    Jones, C. H.

    2014-12-01

    Slab-continent interactions drive most non-collisional orogenies; this has led us to usually anticipate that temporal changes or spatial variations in orogenic style are related to changes in the slab, most especially in the slab's dip. This is most dramatically evident for orogenies in the foreland, well away from the trench, such as the Laramide orogeny. However, the physical means of connecting slab geometry to crustal deformation remain obscure. Dickinson and Snyder (1978) and Bird (1984) laid out a conceptually elegant means of creating foreland deformation from shear between a slab and overriding continental lithosphere, but such strong shear removed all of the continental lithosphere in the western U.S. when included in a numerical simulation of flat slab subduction (Bird, 1988), a removal in conflict with observations of volcanic rocks and xenoliths in many locations. Relying on an increase in edge normal stresses results, for the Laramide, in requiring the little-deformed Colorado Plateau to either be unusually strong or to have risen rapidly enough and high enough to balance edge stresses with body forces. Early deformation in the Plateau rules out unusual strength, and the accumulation and preservation of Late Cretaceous near-sea level sedimentary rocks makes profound uplift unlikely (though not impossible). Relying on comparisons with the Sierras Pampeanas is also fraught with problems: the Sierras are not separated from the Andean fold-and-thrust belt by several hundred kilometers of little-deformed crust, nor were they buried under kilometers of marine muds as were large parts of the Laramide foreland. We have instead suggested that some unusual interactions of an obliquely subducting plate with a thick Archean continental root might provide a better explanation than a truly flat slab (Jones et al., 2011). From this, and given that several flat-slab segments today are not associated with foreland orogenesis and noting that direct evidence for truly

  12. Time domain evolution of diffuse fields in heterogeneous slabs

    NASA Astrophysics Data System (ADS)

    Turner, Joseph A.

    2005-09-01

    Fundamental studies of elastic wave scattering in heterogeneous media are applicable for problems at several length scales from ultrasonic to seismic waves. The intermediate scattering regime that lies between the single scattering and the diffusion limits is perhaps the least understood. Experiments of elastic wave scattering through a heterogeneous slab have been studied in the time domain using diffusion theory to fit the data. However, numerical solutions of the elastic wave radiative transfer equation (RTE) in the steady state have shown that the conditions for validity of the diffusion limit are only satisfied in the interior of the slab, many mean free paths away from the boundaries. Thus, an examination of the time domain multiple scattering in heterogeneous slabs is important to this class of experiments. The spatial distribution, temporal evolution, and partitioning of the diffuse longitudinal and shear energies are studied as a function of direction and frequency for several types of microstructure including polycrystalline metals and two-phase media using numerical solutions of the RTE. Finally, the ability of a diffusion-type solution to fit RTE solutions is also discussed with applications to inversion of experimental results. [Work supported by DOE.

  13. Application Improvements of Slab-Coupled Optical Fiber Sensors

    NASA Astrophysics Data System (ADS)

    Chadderdon, Spencer Lee

    This dissertation explores techniques for improving slab-coupled optical fiber sensor (SCOS) technology for use in specific applications and sensing configurations. SCOS are advantageous for their small size and all-dielectric composition which permit non-intrusive measurement of electric fields within compact environments; however, their small size also limits their sensitivity. This work performs a thorough analysis of the factors contributing to the performance of SCOS and demonstrates methods which improve SCOS, while maintaining its small dimensions and high level of directional sensitivity. These improvements include increasing the sensitivity by 9x, improving the frequency response to include sub 300 kHz frequencies, and developing a method to tune the resonances. The analysis shows that the best material for the slab waveguide is an electro-optic polymer because of its low RF permittivity combined with high electro-optic coefficient. Additional improvements are based on changing the crystal orientation to a transverse configuration, which enhances the sensitivity due to a combined increase in the effective electro-optic coefficient and electric field penetration into the slab. The transverse SCOS configuration not only improves the overall sensitivity but increases the directional sensitivity of the SCOS. Lithium niobate and electro-optic polymer are both experimentally shown to exhibit minimal frequency dependent sensitivity making them suitable for broad frequency applications. Simultaneous interrogation of multiple SCOS with a single tunable laser is achieved by tuning the resonant wavelengths of KTP SCOS so their resonances overlap.

  14. Using pliers in assembly work: short and long task duration effects of gloves on hand performance capabilities and subjective assessments of discomfort and ease of tool manipulation.

    PubMed

    Dianat, Iman; Haslegrave, Christine M; Stedmon, Alex W

    2012-03-01

    The present study investigated the effects of wearing typical industrial gloves on hand performance capabilities (muscle activity, wrist posture, touch sensitivity, hand grip and forearm torque strength) and subjective assessments for an extended duration of performing a common assembly task, wire tying with pliers, which requires a combination of manipulation and force exertion. Three commercially available gloves (cotton, nylon and nitrile gloves) were tested and compared with a bare hand condition while participants performed the simulated assembly task for 2 h. The results showed that wearing gloves significantly increased the muscle activity, wrist deviation, and discomfort whilst reducing hand grip strength, forearm torque strength and touch sensitivity. The combined results showed that the length of time for which gloves are worn does affect hand performance capability and that gloves need to be evaluated in a realistic working context. The results are discussed in terms of selection of gloves for industrial assembly tasks involving pliers.

  15. Task design, psycho-social work climate and upper extremity pain disorders--effects of an organisational redesign on manual repetitive assembly jobs.

    PubMed

    Christmansson, M; Fridén, J; Sollerman, C

    1999-10-01

    A company redesign was carried out to improve production efficiency and minimise the prevalence of work-related musculoskeletal disorders and sick leave. The redesign was evaluated on the basis of studies of assembly workers before (17 workers) and after (12 workers) the redesign. The redesign resulted in more varied, less repetitive, and more autonomous assembly jobs. The psycho-social work climate was both improved and impaired. A medical examination showed that eight of 17 workers before and nine of 12 workers after the redesign suffered from upper extremity pain disorders. Neither the production goals nor the goals of the redesign were fulfilled. Our conclusion was that the increased task variation and impaired psycho-social work climate, combined with a lack of skill and competence, actually increased the physical stress, risk for disorders and difficulties in fulfilling the production goals.

  16. Cracking behavior of structural slab bridge decks

    NASA Astrophysics Data System (ADS)

    Baah, Prince

    Bridge deck cracking is a common problem throughout the United States, and it affects the durability and service life of concrete bridges. Several departments of transportation (DOTs) in the United States prefer using continuous three-span solid structural slab bridges without stringers over typical four-lane highways. Recent inspections of such bridges in Ohio revealed cracks as wide as 0.125 in. These measured crack widths are more than ten times the maximum limit recommended in ACI 224R-01 for bridge decks exposed to de-icing salts. Measurements using digital image correlation revealed that the cracks widened under truck loading, and in some cases, the cracks did not fully close after unloading. This dissertation includes details of an experimental investigation of the cracking behavior of structural concrete. Prism tests revealed that the concrete with epoxy-coated bars (ECB) develops the first crack at smaller loads, and develops larger crack widths compared to the corresponding specimens with uncoated (black) bars. Slab tests revealed that the slabs with longitudinal ECB developed first crack at smaller loads, exhibited wider cracks and a larger number of cracks, and failed at smaller ultimate loads compared to the corresponding test slabs with black bars. To develop a preventive measure, slabs with basalt and polypropylene fiber reinforced concrete were also included in the test program. These test slabs exhibited higher cracking loads, smaller crack widths, and higher ultimate loads at failure compared to the corresponding slab specimens without fibers. Merely satisfying the reinforcement spacing requirements given in AASHTO or ACI 318-11 is not adequate to limit cracking below the ACI 224R-01 recommended maximum limit, even though all the relevant design requirements are otherwise met. Addition of fiber to concrete without changing any steel reinforcing details is expected to reduce the severity and extent of cracking in reinforced concrete bridge decks.

  17. History vs. snapshot: how slab morphology relates to slab age evolution

    NASA Astrophysics Data System (ADS)

    Garel, Fanny; Goes, Saskia; Davies, Rhodri; Davies, Huw; Lallemand, Serge; Kramer, Stephan; Wilson, Cian

    2016-04-01

    The age of the subducting plate at the trench ("slab age") spans a wide range, from less than 10 Myr in Central and South America to 150 Myr in the Marianas. The morphology of subducting slab in the upper mantle is also very variable, from slabs stagnating at the top of the lower mantle to slabs penetrating well beyond 1000 km depth. People have looked rather unsucessfully for correlations between slab morphology and subduction parameters, including age at the trench, on the basic assumption that old (thick) plates are likely to generate a large slab pull force that would influence slab dip. Thermo-mechanical models reveal complex feedbacks between temperature, strain rate and rheology, and are able to reproduce the evolution of plate ages as a function of time, subducting plate velocity and trench velocity. In particular, we show how initially young subducting plates can rapidly age at the surface because of a slow sinking velocity. As a consequence, different slab morphologies can exhibit similar ages at the trench provided that subduction history is different. We illustrate how models provide insights into Earth subduction zones for which we have to consider their history (evolution of trench velocity, relative plate ages at time of initiation) in order to unravel their present-day geometry.

  18. Slab tears and intermediate-depth seismicity

    USGS Publications Warehouse

    Meighan, Hallie E.; Ten Brink, Uri; Pulliam, Jay

    2013-01-01

    Active tectonic regions where plate boundaries transition from subduction to strike slip can take several forms, such as triple junctions, acute, and obtuse corners. Well-documented slab tears that are associated with high rates of intermediate-depth seismicity are considered here: Gibraltar arc, the southern and northern ends of the Lesser Antilles arc, and the northern end of Tonga trench. Seismicity at each of these locations occurs, at times, in the form of swarms or clusters, and various authors have proposed that each marks an active locus of tear propagation. The swarms and clusters start at the top of the slab below the asthenospheric wedge and extend 30–60 km vertically downward within the slab. We propose that these swarms and clusters are generated by fluid-related embrittlement of mantle rocks. Focal mechanisms of these swarms generally fit the shear motion that is thought to be associated with the tearing process.

  19. How to measure slab-off and reverse slab prism in spectacle lenses.

    PubMed

    Christoff, Alexander; Guyton, David L

    2007-08-01

    It is well known that new spectacle lenses for the correction of anisometropia can induce diplopia with reading. The difference in the powers of the lenses induces a net prismatic effect that can cause double vision through off-center areas of the lenses. This is particularly bothersome when patients try to read, often noting vertical double vision in attempted downgaze, especially through multifocal add segments. This induced prismatic effect can be compensated at one level of downgaze by the use of slab-off or reverse slab prism. Typically the slab-off correction is ground into the stronger minus, or weaker plus lens. Reverse slab is ground into the weaker minus, or stronger plus, lens. Unfortunately, determining the amount of slab-off prism already incorporated into spectacle lenses is nonintuitive and inconvenient. This usually requires the use of a lens clock, which is not widely accessible to many ophthalmology practices. A simple technique, described in the past but poorly known, is illustrated here for quickly measuring slab-off and reverse slab prism prescription lenses in the clinic with a common manual lens meter.

  20. Oceanic slab melting and mantle metasomatism.

    PubMed

    Scaillet, B; Prouteau, G

    2001-01-01

    Modern plate tectonic brings down oceanic crust along subduction zones where it either dehydrates or melts. Those hydrous fluids or melts migrate into the overlying mantle wedge trigerring its melting which produces arc magmas and thus additional continental crust. Nowadays, melting seems to be restricted to cases of young (< 50 Ma) subducted plates. Slab melts are silicic and strongly sodic (trondhjemitic). They are produced at low temperatures (< 1000 degrees C) and under water excess conditions. Their interaction with mantle peridotite produces hydrous metasomatic phases such as amphibole and phlogopite that can be more or less sodium rich. Upon interaction the slab melt becomes less silicic (dacitic to andesitic), and Mg, Ni and Cr richer. Virtually all exposed slab melts display geochemical evidence of ingestion of mantle material. Modern slab melts are thus unlike Archean Trondhjemite-Tonalite-Granodiorite rocks (TTG), which suggests that both types of magmas were generated via different petrogenetic pathways which may imply an Archean tectonic model of crust production different from that of the present-day, subduction-related, one. PMID:11838241

  1. A Simple Vertical Slab Gel Electrophoresis Apparatus.

    ERIC Educational Resources Information Center

    Carter, J. B.; And Others

    1983-01-01

    Describes an inexpensive, easily constructed, and safe vertical slab gel kit used routinely for sodium dodecyl sulphate-polyacrylamide gel electrophoresis research and student experiments. Five kits are run from a single transformer. Because toxic solutions are used, students are given plastic gloves and closely supervised during laboratory…

  2. Slab Ice Characterization on Martian Richardson Crater

    NASA Astrophysics Data System (ADS)

    Schmidt, F.; Andrieu, F.; Douté, S.

    2016-09-01

    We compare two models: granular and slab in order to study the ice properties in the Richardson crater using spectroscopy. Thanks to radiative transfer modeling, we determine compactness of CO2 ice, grain size, and abundances of water ice and dust.

  3. Oceanic slab melting and mantle metasomatism.

    PubMed

    Scaillet, B; Prouteau, G

    2001-01-01

    Modern plate tectonic brings down oceanic crust along subduction zones where it either dehydrates or melts. Those hydrous fluids or melts migrate into the overlying mantle wedge trigerring its melting which produces arc magmas and thus additional continental crust. Nowadays, melting seems to be restricted to cases of young (< 50 Ma) subducted plates. Slab melts are silicic and strongly sodic (trondhjemitic). They are produced at low temperatures (< 1000 degrees C) and under water excess conditions. Their interaction with mantle peridotite produces hydrous metasomatic phases such as amphibole and phlogopite that can be more or less sodium rich. Upon interaction the slab melt becomes less silicic (dacitic to andesitic), and Mg, Ni and Cr richer. Virtually all exposed slab melts display geochemical evidence of ingestion of mantle material. Modern slab melts are thus unlike Archean Trondhjemite-Tonalite-Granodiorite rocks (TTG), which suggests that both types of magmas were generated via different petrogenetic pathways which may imply an Archean tectonic model of crust production different from that of the present-day, subduction-related, one.

  4. 3-D Transient Heat Transfer Analysis of Slab Heating Characteristics in a Reheating Furnace in Hot Strip Mills

    NASA Astrophysics Data System (ADS)

    Jang, J. Y.; Lee, Y. W.; Lin, C. N.; Wang, C. H.

    2016-05-01

    A three-dimensional mathematical transient heat transfer model for the prediction of temperature distribution within the slab has been developed by considering the thermal radiation in the walking-beam-type reheating furnace chamber. The steel slabs are heated up through the non-firing, preheating, 1st-heating, 2nd-heating, and soaking zones in the furnace, respectively, where the furnace wall temperature is function of time. Comparison with the in-situ experimental data from Steel Company in Taiwan shows that the present heat transfer model works well for the prediction of thermal behavior of the slab in the reheating furnace. The effects of different skid button height (H=60mm, 90mm, and 120mm) and different gap distance between two slabs (S=50mm, 75mm, and 100mm) on the slab skid mark formation and temperature profiles are investigated. It is found that the skid mark severity decreases with an increase in the skid button height. The effect of gap distance is important only for the slab edge planes, while it is insignificant for the slab central planes.

  5. Impact resistance performance of green construction material using light weight oil palm shells reinforced bamboo concrete slab

    NASA Astrophysics Data System (ADS)

    Muda, Z. C.; Usman, F.; Beddu, S.; Alam, M. A.; Thiruchelvam, S.; Sidek, L. M.; Basri, H.; Saadi, S.

    2013-06-01

    This paper investigate the performance of lightweight oil palm shells (OPS) concrete with varied bamboo reinforcement content for the concrete slab of 300mm x 300mm size reinforced with different thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.2 kg drop at 1 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance against the amount of bamboo reinforcement and slab thickness. A linear relationship has been established between first and ultimate crack resistance against bamboo diameters and slab thickness by the experiment. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the bamboo reinforcement diameter for a constant spacing for various slab thickness using 0.45 OPS and 0.6 OPS bamboo reinforced concrete. The increment in bamboo diameter has more effect on the first crack resistance than the ultimate crack resistance. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the various slab thickness. Increment in slab thickness of the slab has more effect on the crack resistance as compare to the increment in the diameter of the bamboo reinforcement.

  6. Mantle Response to a Slab Gap and Three-dimensional Slab Interaction in Central America

    NASA Astrophysics Data System (ADS)

    Jadamec, M. A.; Fischer, K. M.

    2013-12-01

    Seismically constrained global slab geometries suggest the Middle America-South American subduction system contains a gap on the order of 500 km separating the east-dipping Cocos and Nazca slabs at depth (Gudmundsson and Sambridge, 1998; Syracuse and Abers, 2006; Hayes et al., 2012). The location of the gap correlates with tectonic features impinging on the Pacific side of the Middle America trench, in particular the incoming young buoyant oceanic lithosphere and oceanic ridges associated with the Galapagos hotspot and Cocos-Nazca spreading center (Protti et al., 1994; Mann et al., 2007; Muller et al., 2008). Moreover, geochemical studies focusing on the arc chemistry in the Central American volcanic front argue for a slab window of some kind in this region (Johnston and Thorkelson, 1997; Abratis and Worner, 2001; Hoernle et al., 2008). We use high-resolution, three-dimensional (3D) geodynamic modeling of the Middle America-South American subduction system to investigate the role of the incoming young oceanic lithosphere and a gap between the Cocos and Nazca slabs in controlling mantle flow velocity and geochemical signatures beneath Central America. The geodynamic models are geographically referenced with the geometry and thermal structure for the overriding and subducting plates based on geological and geophysical observables and constructed with the multi-plate subduction generator code, SlabGenerator (Jadamec and Billen, 2010; Jadamec et al., 2012; Jadamec and Billen, 2012). The viscous flow simulations are solved using the mantle convection finite-element code, CitcomCU (Zhong, 2006), modified by Jadamec and Billen (2010) to take into account the experimentally derived flow law for olivine and allow for variable 3D plate interface geometries and magnitudes of inter-plate coupling. The 3D numerical models indicate the gap between the Cocos and Nazca slabs serves as a conduit for Pacific-Cocos mantle to pass into the Caribbean, with toroidal flow around the

  7. Impact resistance of sustainable construction material using light weight oil palm shells reinforced geogrid concrete slab

    NASA Astrophysics Data System (ADS)

    Muda, Z. C.; Malik, G.; Usman, F.; Beddu, S.; Alam, M. A.; Mustapha, K. N.; Birima, A. H.; Zarroq, O. S.; Sidek, L. M.; Rashid, M. A.

    2013-06-01

    This paper investigate the performance of lightweight oil palm shells (OPS) concrete slab with geogrid reinforcement of 300mm × 300mm size with 20mm, 30mm and 40 mm thick casted with different geogrid orientation and boundary conditions subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.2 kg drop at 1 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance the slab thickness, boundary conditions and geogrid reinforcement orientation. Test results indicate that the used of the geogrid reinforcement increased the impact resistance under service (first) limit crack up to 5.9 times and at ultimate limit crack up to 20.1 times against the control sample (without geogrid). A good linear relationship has been established between first and ultimate crack resistance against the slab thickness. The orientation of the geogrid has minor significant to the crack resistance of the OPS concrete slab. OPS geogrid reinforced slab has a good crack resistance properties that can be utilized as a sustainable impact resistance construction materials.

  8. Millimeter-wave imaging with slab focusing lens made of electromagnetic-induction materials.

    PubMed

    Yang, Kui; Wang, Jinbang; Zhao, Lu; Liu, Zhiguo; Zhang, Tao

    2016-01-11

    A slab focusing lens in this work has been designed, which consists of electromagnetic-induction materials (cage-shaped granules of conductor materials) and polymethyl methacrylate (PMMA) materials. A compound lens with a thickness of 32 mm is composed of two slab focusing lenses, and has a refractive index of 1.41 at 35 GHz. Millimeter-wave (MMW) images of metallic objects have been obtained with the compound lens. The image quality has been compared by means of the compound lens and the polyethylene lens. The experimental results show good feasibility of the compound lens in MMW imaging.

  9. Technology Solutions Case Study: Capillary Break Beneath a Slab: Polyethylene Sheeting over Aggregate, Southwestern Pennsylvania

    SciTech Connect

    2014-07-01

    In this project, Building America team IBACOS worked with a builder of single- and multifamily homes in southwestern Pennsylvania (climate zone 5) to understand its methods of successfully using polyethylene sheeting over aggregate as a capillary break beneath the slab in new construction. This builder’s homes vary in terms of whether they have crawlspaces or basements. However, in both cases, the strategy protects the home from water intrusion via capillary action (e.g., water wicking into cracks and spaces in the slab), thereby helping to preserve the durability of the home.

  10. Millimeter-wave imaging with slab focusing lens made of electromagnetic-induction materials.

    PubMed

    Yang, Kui; Wang, Jinbang; Zhao, Lu; Liu, Zhiguo; Zhang, Tao

    2016-01-11

    A slab focusing lens in this work has been designed, which consists of electromagnetic-induction materials (cage-shaped granules of conductor materials) and polymethyl methacrylate (PMMA) materials. A compound lens with a thickness of 32 mm is composed of two slab focusing lenses, and has a refractive index of 1.41 at 35 GHz. Millimeter-wave (MMW) images of metallic objects have been obtained with the compound lens. The image quality has been compared by means of the compound lens and the polyethylene lens. The experimental results show good feasibility of the compound lens in MMW imaging. PMID:26832287

  11. Laboratory Experiments Concerning Upwellings From the Slab-Graveyard: Implications For Geochemical and Seismic Models

    NASA Astrophysics Data System (ADS)

    Harris, A. C.; Kincaid, C.; Hall, P.

    2005-12-01

    The ongoing plume debate appears to focus on upwellings characterized by large heads and smaller tails, that form from a deep or basal thermal boundary layer (BTBL), which are driven by temperature excesses in the range of 200° C. We use 3-D laboratory experiments to explore how upwellings might differ from this common plume description when BTBLs are influenced by subducted plates. An important aspect of the models is the representation of ridge chemical differentiation processes resulting in slabs with two distinct layers; a lighter, depleted upper mantle component (Harzburgite:H) and a heavier, iron-rich crustal component (Basalt/Eclogite:B/E). Laboratory experiments utilize a working fluid of glucose syrup with temperature dependent density and viscosity. Compositionally distinct mantle reservoirs are represented through isothermal density/viscosity contrasts controlled by water content. The ambient fluid (AF) is contained within a rectangular tank that is heated from below and cooled from above to produce background convection with a Rayleigh number of 10-5-10-6. Highly viscous, tabular slabs are produced by pouring compositionally distinct syrup from two slab reservoirs (B/E and H) into a mold which is chilled to -5° C. The viscous layered slab is emplaced at the fluid surface and subsequently sinks through, stalls and spreads within a BTBL roughly twice the slab thickness (1 cm). Results show that a wide variety in upwelling morphologies form when layered slabs reside within the BTBL and that plume heads/tails are largely dissimilar to those of the standard plume model. The manner in which the slab laminae vs. AF in the BTBL combine (or segregate) within upwellings depends on viscosity/density contrasts, how slabs collapse in the BTBL, and time. End-member regimes include: experiments dominated by a very light H-slab component with early, cold H-plumes and late, hot B/E-AF plumes and experiments where density differences between H, B/E and AF are small and

  12. Subduction zone earthquakes and stress in slabs

    NASA Technical Reports Server (NTRS)

    Vassiliou, M. S.; Hager, B. H.

    1988-01-01

    Simple viscous fluid models of subducting slabs are used to explain observations of the distribution of earthquakes as a function of depth and the orientation of stress axes of deep (greater than 300 km) and intermediate (70-300 km) earthquakes. Results suggest the following features in the distribution of earthquakes with depth: (1) an exponential decrease from shallow depths down to 250 to 300 km, (2) a minimum near 250 to 300 km, and (3) a deep peak below 300 km. Many shallow subducting slabs show only the first characteristic, while deeper extending regions tend to show all three features, with the deep peak varying in position and intensity. These data, combined with the results on the stress orientations of various-depth earthquakes, are consistent with the existence of a barrier of some sort at 670-km depth and a uniform viscosity mantle above this barrier.

  13. Radiation characteristics of tapered slab waveguides

    NASA Astrophysics Data System (ADS)

    Scheggi, A. M.; Falciai, R.; Brenci, M.

    1983-01-01

    The application of ray optics to the evaluation of near- and far-field radiation patterns of a slab waveguide taper is discussed, noting the importance of calculating the power that can be extracted from the core at the end of the waveguide related to the near-field configurations. A multimode, tapered slab waveguide with a homogeneous core and unlimited cladding is considered. It is pointed out that as the ray proceeds on its zigzag path down the taper, its propagation angle increases from reflection to reflection and eventually surpasses the limit angle of total reflection. To obtain an overall idea of the range of ray angles accepted at the smaller end of the taper, the Williamson (1952) method is used; this makes it possible, through a simple geometrical construction, to trace the ray in a linear cone. It is found that the ray-tracing technique can constitute an adequate tool in the analysis and design of tapered multimode waveguides.

  14. Imaging a Remnant Slab Beneath Southeastern US: New Results from Teleseismic, Finite-frequency Tomography.

    NASA Astrophysics Data System (ADS)

    Biryol, C. B.; Wagner, L. S.; Fischer, K. M.; Hawman, R. B.

    2014-12-01

    Our new results from teleseismic, finite-frequency, body-wave tomography analysis reveal a relatively steep east-dipping fast velocity anomaly beneath the Southeastern US. The resolving power of our dataset is good enough to retrieve major mantle anomalies, such as this fast velocity body, owing to the dense receiver coverage provided by US Transportable Array (TA) and the SouthEastern Suture of the Appalachian Margin Experiment (SESAME). Various resolution and recovery tests demonstrate the robustness of this anomaly in our tomographic model between the depths of 60 and 660 km. Our images reveal that the dip of this structure decreases significantly in the mantle transition zone where it terminates. We also observe major gaps in the lateral continuity of this structure. Based on the amplitude, location and geometry of the velocity perturbation, we interpret this anomaly as remnant subducted lithosphere, suspended in the upper mantle after a subduction phase as young as 100-110 Ma or as old as 1Ga. Basic calculations and evaluations on the geometry and location of this anomaly help us to narrow down the origin of this slab to the Farallon flat-slab subduction in the west and Grenville Subduction during assembly of supercontinent Rodinia. Our images reveal possible mechanisms that would allow this slab to remain in the upper mantle without sinking into deeper mantle for such extended periods of time. We believe the flat geometry of the slab near the transition zone and the fragmented nature provide important clues about processes that could delay/resist the sinking while providing necessary time for it to transform into a more neutrally buoyant state. In this respect, we believe our results have broad implications for subduction processes and piece-meal slab failure, as well as tectonic implications for characteristics of former subduction zones that help shape North American Plate.

  15. Implementing slab solar water heating system

    NASA Astrophysics Data System (ADS)

    Raveendran, S. K.; Shen, C. Q.

    2015-08-01

    Water heating contributes a significant part of energy consumption in typical household. One of the most employed technologies today that helps in reducing the energy consumption of water heating would be conventional solar water heating system. However, this system is expensive and less affordable by most family. The main objective of this project is to design and implement an alternative type of solar water heating system that utilize only passive solar energy which is known as slab solar water heating system. Slab solar water heating system is a system that heat up cold water using the solar radiance from the sun. The unique part of this system is that it does not require any form of electricity in order to operate. Solar radiance is converted into heat energy through convection method and cold water will be heated up by using conduction method [1]. The design of this system is governed by the criteria of low implementation cost and energy saving. Selection of material in the construction of a slab solar water heating system is important as it will directly affect the efficiency and performance of the system. A prototype has been built to realize the idea and it had been proven that this system was able to provide sufficient hot water supply for typical household usage at any given time.

  16. Convection in Slab and Spheroidal Geometries

    NASA Technical Reports Server (NTRS)

    Porter, David H.; Woodward, Paul R.; Jacobs, Michael L.

    2000-01-01

    Three-dimensional numerical simulations of compressible turbulent thermally driven convection, in both slab and spheroidal geometries, are reviewed and analyzed in terms of velocity spectra and mixing-length theory. The same ideal gas model is used in both geometries, and resulting flows are compared. The piecewise-parabolic method (PPM), with either thermal conductivity or photospheric boundary conditions, is used to solve the fluid equations of motion. Fluid motions in both geometries exhibit a Kolmogorov-like k(sup -5/3) range in their velocity spectra. The longest wavelength modes are energetically dominant in both geometries, typically leading to one convection cell dominating the flow. In spheroidal geometry, a dipolar flow dominates the largest scale convective motions. Downflows are intensely turbulent and up drafts are relatively laminar in both geometries. In slab geometry, correlations between temperature and velocity fluctuations, which lead to the enthalpy flux, are fairly independent of depth. In spheroidal geometry this same correlation increases linearly with radius over the inner 70 percent by radius, in which the local pressure scale heights are a sizable fraction of the radius. The effects from the impenetrable boundary conditions in the slab geometry models are confused with the effects from non-local convection. In spheroidal geometry nonlocal effects, due to coherent plumes, are seen as far as several pressure scale heights from the lower boundary and are clearly distinguishable from boundary effects.

  17. Thermal-induced wavefront aberration in sapphire-cooled Nd:glass slab

    NASA Astrophysics Data System (ADS)

    Huang, Tingrui; Huang, Wenfa; Wang, Jiangfeng; Lu, Xinghua; Li, Xuechun

    2016-07-01

    We demonstrate for the first time a sapphire-cooled Nd:glass composite assembly based on optical bonding of two thin sapphire plates to a Nd:glass slab for efficient heat removal. The distributions of temperature, stress, depolarization loss, and wavefront aberration were obtained by finite element analysis. The simulation results were verified experimentally. Although the heat generation rate was 4.5 W/cm3, the temperature increase was within 5.7 °C at the center of the sapphire surface, and the whole wavefront aberration was 1.21 λ ( λ = 1053 nm). This demonstration opens up a viable path toward novel repetition rate Nd:glass laser amplifier designs with efficient double-sided room-temperature heat sinking on both sides of the slab.

  18. Parametric performance of circumferentially grooved heat pipes with homogeneous and graded-porosity slab wicks at cryogenic temperatures

    NASA Technical Reports Server (NTRS)

    Groll, M.; Pittman, R. B.; Eninger, J. E.

    1975-01-01

    A recently developed, potentially high-performance nonarterial wick has been extensively tested. This slab wick has an axially varying porosity which can be tailored to match the local stress imposed on the wick. The purpose of the tests was to establish the usefulness of the graded-porosity slab wick at cryogenic temperatures between 110 K and 260 K, with methane and ethane as working fluids. For comparison, a homogeneous (i.e., uniform porosity) slab wick was also tested. The tests included: (1) maximum heat pipe performance as a function of fluid inventory, (2) maximum performance as a function of operating temperature, (3) maximum performance as a function of evaporator elevation, and (4) influence of slab wick orientation on performance. The experimental data was compared with theoretical predictions obtained with the computer program GRADE.

  19. Viscous Dissipation and Criticality of Subducting Slabs

    NASA Astrophysics Data System (ADS)

    Riedel, Mike; Karato, Shun; Yuen, Dave

    2016-04-01

    Rheology of subducting lithosphere appears to be complicated. In the shallow part, deformation is largely accomodated by brittle failure, whereas at greater depth, at higher confining pressures, ductile creep is expected to control slab strength. The amount of viscous dissipation ΔQ during subduction at greater depth, as constrained by experimental rock mechanics, can be estimated on the basis of a simple bending moment equation [1,2] 2ɛ˙0(z) ∫ +h/2 2 M (z) = h ṡ -h/2 4μ(y,z)y dy , (1) for a complex multi-phase rheology in the mantle transition zone, including the effects of a metastable phase transition as well as the pressure, temperature, grain-size and stress dependency of the relevant creep mechanisms; μ is here the effective viscosity and ɛ˙0(z) is a (reference) strain rate. Numerical analysis shows that the maximum bending moment, Mcrit, that can be sustained by a slab is of the order of 1019 Nm per m according to Mcrit˜=σp ∗h2/4, where σp is the Peierl's stress limit of slab materials and h is the slab thickness. Near Mcrit, the amount of viscous dissipation grows strongly as a consequence of a lattice instability of mantle minerals (dislocation glide in olivine), suggesting that thermo-mechanical instabilities become prone to occur at places where a critical shear-heating rate is exceeded, see figure. This implies that the lithosphere behaves in such cases like a perfectly plastic solid [3]. Recently available detailed data related to deep seismicity [4,5] seems to provide support to our conclusion. It shows, e.g., that thermal shear instabilities, and not transformational faulting, is likely the dominating mechanism for deep-focus earthquakes at the bottom of the transition zone, in accordance with this suggested "deep criticality" model. These new findings are therefore briefly outlined and possible implications are discussed. References [1] Riedel, M. R., Karato, S., Yuen, D. A. Criticality of Subducting Slabs. University of Minnesota

  20. Viscous Dissipation and Criticality of Subducting Slabs

    NASA Astrophysics Data System (ADS)

    Riedel, Mike; Karato, Shun; Yuen, Dave

    2016-04-01

    Rheology of subducting lithosphere appears to be complicated. In the shallow part, deformation is largely accomodated by brittle failure, whereas at greater depth, at higher confining pressures, ductile creep is expected to control slab strength. The amount of viscous dissipation ΔQ during subduction at greater depth, as constrained by experimental rock mechanics, can be estimated on the basis of a simple bending moment equation [1,2] 2ɛ˙0(z) ∫ +h/2 2 M (z) = h ṡ ‑h/2 4μ(y,z)y dy , (1) for a complex multi-phase rheology in the mantle transition zone, including the effects of a metastable phase transition as well as the pressure, temperature, grain-size and stress dependency of the relevant creep mechanisms; μ is here the effective viscosity and ɛ˙0(z) is a (reference) strain rate. Numerical analysis shows that the maximum bending moment, Mcrit, that can be sustained by a slab is of the order of 1019 Nm per m according to Mcrit˜=σp ∗h2/4, where σp is the Peierl's stress limit of slab materials and h is the slab thickness. Near Mcrit, the amount of viscous dissipation grows strongly as a consequence of a lattice instability of mantle minerals (dislocation glide in olivine), suggesting that thermo-mechanical instabilities become prone to occur at places where a critical shear-heating rate is exceeded, see figure. This implies that the lithosphere behaves in such cases like a perfectly plastic solid [3]. Recently available detailed data related to deep seismicity [4,5] seems to provide support to our conclusion. It shows, e.g., that thermal shear instabilities, and not transformational faulting, is likely the dominating mechanism for deep-focus earthquakes at the bottom of the transition zone, in accordance with this suggested "deep criticality" model. These new findings are therefore briefly outlined and possible implications are discussed. References [1] Riedel, M. R., Karato, S., Yuen, D. A. Criticality of Subducting Slabs. University of Minnesota

  1. Tectonic controls on earthquake size distribution and seismicity rate: slab buoyancy and slab bending

    NASA Astrophysics Data System (ADS)

    Nishikawa, T.; Ide, S.

    2014-12-01

    There are clear variations in maximum earthquake magnitude among Earth's subduction zones. These variations have been studied extensively and attributed to differences in tectonic properties in subduction zones, such as relative plate velocity and subducting plate age [Ruff and Kanamori, 1980]. In addition to maximum earthquake magnitude, the seismicity of medium to large earthquakes also differs among subduction zones, such as the b-value (i.e., the slope of the earthquake size distribution) and the frequency of seismic events. However, the casual relationship between the seismicity of medium to large earthquakes and subduction zone tectonics has been unclear. Here we divide Earth's subduction zones into over 100 study regions following Ide [2013] and estimate b-values and the background seismicity rate—the frequency of seismic events excluding aftershocks—for subduction zones worldwide using the maximum likelihood method [Utsu, 1965; Aki, 1965] and the epidemic type aftershock sequence (ETAS) model [Ogata, 1988]. We demonstrate that the b-value varies as a function of subducting plate age and trench depth, and that the background seismicity rate is related to the degree of slab bending at the trench. Large earthquakes tend to occur relatively frequently (lower b-values) in shallower subduction zones with younger slabs, and more earthquakes occur in subduction zones with deeper trench and steeper dip angle. These results suggest that slab buoyancy, which depends on subducting plate age, controls the earthquake size distribution, and that intra-slab faults due to slab bending, which increase with the steepness of the slab dip angle, have influence on the frequency of seismic events, because they produce heterogeneity in plate coupling and efficiently inject fluid to elevate pore fluid pressure on the plate interface. This study reveals tectonic factors that control earthquake size distribution and seismicity rate, and these relationships between seismicity and

  2. Development of a Press-Hardened Steel Suitable for Thin Slab Direct Rolling Processing

    NASA Astrophysics Data System (ADS)

    Lee, Jewoong; De Cooman, Bruno C.

    2015-01-01

    The thin slab casting and direct rolling process is a hot-rolled strip production method which has maintained commercial quality steel grades as a major material in many industrial applications due to its low processing cost. Few innovative products have however been developed specifically for production by thin slab direct rolling. Press hardening or hot press forming steel grades which are now widely used to produce structural automotive steel parts requiring ultra-high strength and formability may however offer an opportunity for thin slab direct rolling-specific ultra-high strength products. In this work, a newly designed press hardening steel grade developed specifically for thin slab direct rolling processing is presented. The press hardening steel has a high nitrogen content compared with press hardening steel grades produced by conventional steelmaking routes. Boron and titanium which are key alloying additions in conventional press hardening steel such as the 22MnB5 press hardening steel grade are not utilized. Cr is added in the press hardening steel to obtain the required hardenability. The properties of the new thin slab direct rolling-specific 22MnCrN5 press hardening steel grade are reviewed. The evolution of the microstructure and mechanical properties with increasing amounts of Cr additions from 0.6 to 1.4 wt pct and the effect of the cooling rate during die-quenching were studied by means of laboratory simulations. The selection of the optimum chemical composition range for the thin slab direct rolling-specific 22MnCrN5 steel in press hardening heat treatment conditions is discussed.

  3. A Numerical Method for Obtaining Monoenergetic Neutron Flux Distributions and Transmissions in Multiple-Region Slabs

    NASA Technical Reports Server (NTRS)

    Schneider, Harold

    1959-01-01

    This method is investigated for semi-infinite multiple-slab configurations of arbitrary width, composition, and source distribution. Isotropic scattering in the laboratory system is assumed. Isotropic scattering implies that the fraction of neutrons scattered in the i(sup th) volume element or subregion that will make their next collision in the j(sup th) volume element or subregion is the same for all collisions. These so-called "transfer probabilities" between subregions are calculated and used to obtain successive-collision densities from which the flux and transmission probabilities directly follow. For a thick slab with little or no absorption, a successive-collisions technique proves impractical because an unreasonably large number of collisions must be followed in order to obtain the flux. Here the appropriate integral equation is converted into a set of linear simultaneous algebraic equations that are solved for the average total flux in each subregion. When ordinary diffusion theory applies with satisfactory precision in a portion of the multiple-slab configuration, the problem is solved by ordinary diffusion theory, but the flux is plotted only in the region of validity. The angular distribution of neutrons entering the remaining portion is determined from the known diffusion flux and the remaining region is solved by higher order theory. Several procedures for applying the numerical method are presented and discussed. To illustrate the calculational procedure, a symmetrical slab ia vacuum is worked by the numerical, Monte Carlo, and P(sub 3) spherical harmonics methods. In addition, an unsymmetrical double-slab problem is solved by the numerical and Monte Carlo methods. The numerical approach proved faster and more accurate in these examples. Adaptation of the method to anisotropic scattering in slabs is indicated, although no example is included in this paper.

  4. Reflection mode two-dimensional photonic-crystal-slab-waveguide-based micropressure sensor

    NASA Astrophysics Data System (ADS)

    Wang, Yi; Bakhtazad, Aref; Sabarinathan, Jayshri

    2011-08-01

    Photonic crystals (PhCs) have recently been the focus for the developing micro- and nano-optical sensors, due to its capability to control and manipulate light on planar devices. This paper presents a novel design of micro-optical pressure sensor based on 2-dimensional PhC slab suspended on Si substrate. A line defect was introduced to the PhC slab to guide and reflect light with frequency in the photonic bandgap in the plane of the slab. The structure, with certain surface treatment, can be used in miro-scale pressure catheters in heart ablation surgeries and other biomedical applications. The working principle of the device is to modify light reflection in the PhC line defect waveguide by moving a substrate vertically in the evanescent field of the PhC waveguide. Evanescent field coupling is the critical step that affects light transmission and reflection. High resolution electron-beam lithography and isotropic wet etching have been used to realize the device on the top layer of a Si-On-Insulator (SOI) wafer. The PhC slab is released by isotropic wet etch of the berried oxide layer. The output reflection spectrum of the device under different pressure conditions is simulated using 3-dimensional finite difference time domain (FDTD) method. The result showed that when the PhC slab is close enough to the substrate (less than 400 nm), the reflected light intensity decreases sharply when the substrate moves towards the PhC slab. Mechanical response of the sensor is also studied.

  5. Studies on Punching Shear Resistance of Two Way Slab Specimens with Partial Replacement of Cement by GGBS with Different Edge Conditions

    NASA Astrophysics Data System (ADS)

    Nemani, Ravi Dakshina Murthy; Rao, M. V. S.; Grandhe, Veera Venkata Satya Naranyana

    2016-09-01

    The present work is an effort to quantify the punching shear load resistance effect on two way simply supported slab specimens with replacement of cement by Ground Granulated Blast Furnace Slag (GGBS) with different edge conditions at various replacement levels and evaluate its efficiency. GGBS replacement has emerged as a major alternative to conventional concrete and has rapidly drawn the concrete industry attention due to its cement savings, cost savings, environmental and socio-economic benefits. The two way slab specimens were subjected to punching shear load by in house fabricated apparatus. The slab specimens were cast using M30 grade concrete with HYSD bars. The cement was partially replaced with GGBS at different percentages i.e., 0 to 30 % at regular intervals of 10 %. The test results indicate that the two way slab specimens with partial replacement of cement by GGBS exhibit high resistance against punching shear when compared with conventional concretes slab specimens.

  6. Experimental and computational study of plasma bullet reignition behind a thin dielectric slab

    NASA Astrophysics Data System (ADS)

    Ranieri, Pietro; Babaeva, Natalia; Foster, John

    2013-09-01

    Ionization waves (IWs) propagating through plasma jets and helium channels are often observed as luminous fronts of the IWs and conventionally termed as plasma bullets. The preliminary experiments show that if a thin dielectric slab is placed in the helium channel as an obstacle for the bullet propagation, the discharge may reignite below the slab. This process is perceived as though the bullets propagate through the obstacle. The goal of this work is to find conditions under which the bullet can reignite behind the dielectric. The experimental setup consists of a corona discharge, with a single metal electrode, within a quartz tube. We study the influence of the dielectric constant, thickness and the length of the mica slab on the plasma jet behavior. We show that after the impact on the mica surface, the bullet partially reflects from the surface and plasma spreads along the surface. Depending on the location of the mica relative to the tube exit, its capacitance and opacity to photoionizing radiation, a second bullet can emerge below the slab. The computational model used in this work, nonPDPSIM, is a plasma hydrodynamics model in which continuity, momentum and energy equations are solved for charged and neutral species with solution of Poisson's equation for the electric potential.

  7. The thermal influence of the subducting slab beneath South America from 410 and 660 km discontinuity observations

    NASA Astrophysics Data System (ADS)

    Collier, J. D.; Helffrich, G. R.

    2001-11-01

    Regional seismic network data from deep South American earthquakes to western United States and western European seismic arrays is slant stacked to detect weak near-source interactions with upper mantle discontinuities. These observations are complemented by an analysis of earlier work by Sacks & Snoke (1977) who observed S to P conversions from deep events to stations in South America, and similar observations from 1994-95 events using the BANJO and SEDA networks. Observations of the depth of the 410km discontinuity are made beneath central South America in the vicinity of the aseismic region of the subducting Nazca Plate. These results image the 410km discontinuity over a lateral extent of up to 850km perpendicular to the slab and over a distance of 2700km along the length of the slab. Away from the subducting slab the discontinuity is mainly seen near its global average depth, whilst inside the slab there is evidence for its elevation by up to around 60km but with significant scatter in the data. These results are consistent with the presence of a continuous slab through the aseismic region with a thermal anomaly of 900°C at 350km depth. This value is in good agreement with simple thermal models though our data are too sparse to accurately constrain them. Sparse observations of the 660km discontinuity agree with tomographic models suggesting penetration of the lower mantle by the slab in the north but stagnation at the base of the transition zone in the south. The geographical distribution of the data, however, does not allow us to rule out the possibility of slab stagnation at the base of the transition zone in the north. These observations, together with the presence of deep earthquakes, require more complicated thermal models than previously used to explain them, possibly including changes in slab dip and age with depth.

  8. A two- and three-dimensional numerical modelling benchmark of slab detachment

    NASA Astrophysics Data System (ADS)

    Thieulot, Cedric; Glerum, Anne; Hillebrand, Bram; Schmalholz, Stefan; Spakman, Wim; Torsvik, Trond

    2014-05-01

    Subduction is likely to be the most studied phenomenon in Numerical Geodynamics. Over the past 20 years, hundreds of publications have focused on its various aspects (influence of the rheology and thermal state of the plates, slab-mantle coupling, roll-back, mantle wedge evolution, buoyancy changes due to phase change, ...) and results were obtained with a variety of codes. Slab detachment has recently received some attention (e.g. Duretz, 2012) but remains a field worth exploring due to its profound influence on dynamic topography, mantle flow and subsequent stress state of the plates, and is believed to have occured in the Zagros, Carpathians and beneath eastern Anatolia, to name only a few regions. Following the work of Schmalholz (2011), we propose a two- and three-dimensional numerical benchmark of slab detachment. The geometry is simple: a power-law T-shaped plate including an already subducted slab overlies the mantle whose viscosity is either linear or power-law. Boundary conditions are free-slip on the top and the bottom of the domain, and no-slip on the sides. When the system evolves in time, the slab stretches out vertically and shows buoyancy-driven necking, until it finally detaches. The benchmark is subdivided into several sub-experiments with gradually increase in complexity (free surface, coupling of the rheology with temperature, ...). An array of objective measurements is recorded throughout the simulation such as the width of the necked slab over time and the exact time of detachment. The experiments will be run in two-dimensions and repeated in three-dimensional, the latter case being designed so as to allow both poloidal and toroidal flow. We show results obtained with a multitude of Finite Element and Finite Difference codes, using either compositional fields, level sets or tracers to track the compositions. A good agreement is found for most of the measurements in the two-dimensional case, and preliminary three-dimensional measurements will

  9. Mechanisms of deep slab hydration: numerical modeling and implications

    NASA Astrophysics Data System (ADS)

    Faccenda, M.; Gerya, T.; Burlini, L.

    2009-12-01

    Water is a fundamental component of the Earth, affecting its internal structures and dynamics. Sea-water enters the subduction factory via slab hydration that occurs mainly at the trench and is subsequently released in the upper mantle wedge because of slab warming and de-hydration. In the last decades, the scientific research has focused mainly on geophysical processes related to the de-hydration of the slab. However, not much is known on how and to which extent the subducting oceanic plate get hydrated. In order to investigate hydration of the slab, we performed 2D numerical models of a spontaneously bending oceanic plate using I2ELVIS code that account for visco-elasto-plastic rheologies and where fluid flow is regulated by Darci’s law. At the outer rise, bending-related slab faulting occurs, providing a pathway for water percolation in the slab. Faults generally deep trenchward, but antithetic faults are also common. Downward deep fluid flow establishes during brittle extensional deformation at the trench outer rise producing strong variation of the tectonic pressure and causing sub-hydrostatic or even negative pressure gradients along bending related normal faults through which fluids are pumped. The results of the numerical experiment indicate that water can be transported down and stored in the bending area via serpentinization of the normal faults. Deep slab hydration has important implications for the rheological structure, seismicity and seismic anisotropy of the upper mantle because: 1) more water can be stored in the slab producing more enhanced weakening of the mantle wedge, 2) intermediate and deep intra-slab earthquakes can be triggered by slab de-hydration, 3) DHMS phases, able to bring fluids down to the transition zone and lower mantle, could form in the cold core of the slab, 4) the slab could acquire a strong anisotropic fabric responsible for the anisotropic patterns observed at subduction zones.

  10. Hybrid slab-microchannel gel electrophoresis system

    DOEpatents

    Balch, Joseph W.; Carrano, Anthony V.; Davidson, James C.; Koo, Jackson C.

    1998-01-01

    A hybrid slab-microchannel gel electrophoresis system. The hybrid system permits the fabrication of isolated microchannels for biomolecule separations without imposing the constraint of a totally sealed system. The hybrid system is reusable and ultimately much simpler and less costly to manufacture than a closed channel plate system. The hybrid system incorporates a microslab portion of the separation medium above the microchannels, thus at least substantially reducing the possibility of non-uniform field distribution and breakdown due to uncontrollable leakage. A microslab of the sieving matrix is built into the system by using plastic spacer materials and is used to uniformly couple the top plate with the bottom microchannel plate.

  11. Photonic crystal slab quantum cascade detector

    NASA Astrophysics Data System (ADS)

    Reininger, Peter; Schwarz, Benedikt; Harrer, Andreas; Zederbauer, Tobias; Detz, Hermann; Maxwell Andrews, Aaron; Gansch, Roman; Schrenk, Werner; Strasser, Gottfried

    2013-12-01

    In this Letter, we demonstrate the design, fabrication, and characterization of a photonic crystal slab quantum cascade detector (PCS-QCD). By employing a specifically designed resonant cavity, the performance of the photodetector is improved in three distinct ways. The PCS makes the QCD sensitive to surface normal incident light. It resonantly enhances the photon lifetime inside the active zone, thus increasing the photocurrent significantly. And, the construction form of the device inherently decreases the noise. Finally, we compare the characteristics of the PCS-QCD to a PCS - quantum well infrared photodetector and outline the advantages for certain fields of applications.

  12. Numerical quadrature for slab geometry transport algorithms

    SciTech Connect

    Hennart, J.P.; Valle, E. del

    1995-12-31

    In recent papers, a generalized nodal finite element formalism has been presented for virtually all known linear finite difference approximations to the discrete ordinates equations in slab geometry. For a particular angular directions {mu}, the neutron flux {Phi} is approximated by a piecewise function Oh, which over each space interval can be polynomial or quasipolynomial. Here we shall restrict ourselves to the polynomial case. Over each space interval, {Phi} is a polynomial of degree k, interpolating parameters given by in the continuous and discontinuous cases, respectively. The angular flux at the left and right ends and the k`th Legendre moment of {Phi} over the cell considered are represented as.

  13. Automated inspection of hot steel slabs

    DOEpatents

    Martin, Ronald J.

    1985-01-01

    The disclosure relates to a real time digital image enhancement system for performing the image enhancement segmentation processing required for a real time automated system for detecting and classifying surface imperfections in hot steel slabs. The system provides for simultaneous execution of edge detection processing and intensity threshold processing in parallel on the same image data produced by a sensor device such as a scanning camera. The results of each process are utilized to validate the results of the other process and a resulting image is generated that contains only corresponding segmentation that is produced by both processes.

  14. Automated inspection of hot steel slabs

    DOEpatents

    Martin, R.J.

    1985-12-24

    The disclosure relates to a real time digital image enhancement system for performing the image enhancement segmentation processing required for a real time automated system for detecting and classifying surface imperfections in hot steel slabs. The system provides for simultaneous execution of edge detection processing and intensity threshold processing in parallel on the same image data produced by a sensor device such as a scanning camera. The results of each process are utilized to validate the results of the other process and a resulting image is generated that contains only corresponding segmentation that is produced by both processes. 5 figs.

  15. Photonic crystal slab quantum cascade detector

    SciTech Connect

    Reininger, Peter Schwarz, Benedikt; Harrer, Andreas; Zederbauer, Tobias; Detz, Hermann; Maxwell Andrews, Aaron; Gansch, Roman; Schrenk, Werner; Strasser, Gottfried

    2013-12-09

    In this Letter, we demonstrate the design, fabrication, and characterization of a photonic crystal slab quantum cascade detector (PCS-QCD). By employing a specifically designed resonant cavity, the performance of the photodetector is improved in three distinct ways. The PCS makes the QCD sensitive to surface normal incident light. It resonantly enhances the photon lifetime inside the active zone, thus increasing the photocurrent significantly. And, the construction form of the device inherently decreases the noise. Finally, we compare the characteristics of the PCS-QCD to a PCS - quantum well infrared photodetector and outline the advantages for certain fields of applications.

  16. Thermally induced birefringence in Nd:YAG slab lasers

    SciTech Connect

    Ostermeyer, Martin; Mudge, Damien; Veitch, Peter J.; Munch, Jesper

    2006-07-20

    We study thermally induced birefringence in crystalline Nd:YAG zigzag slab lasers and the associated depolarization losses. The optimum crystallographic orientation of the zigzag slab within the Nd:YAG boule and photoelastic effects in crystalline Nd:YAG slabs are briefly discussed. The depolarization is evaluated using the temperature and stress distributions, calculated using a finite element model, for realistically pumped and cooled slabs of finite dimensions. Jones matrices are then used to calculate the depolarization of the zigzag laser mode. We compare the predictions with measurements of depolarization, and suggest useful criteria for the design of the gain media for such lasers.

  17. Pyrometer method for measuring slab temperature in a reheat furnace

    SciTech Connect

    Rudzki, E.M.; Jackson, R.W.; Martocci, A.P.

    1984-02-21

    A method and apparatus to measure the temperature of a slab in a reheat furnace with increased accuracy using either a single or dual pyrometer system through use of a multiplicity of temperature correction functions involving temperatures of slab and wall, distance between a pyrometer and the slab at which it is aimed, a ratio of air and fuel supplying the furnace heat and radiation interferences. The functions are chosen by a micro-processor in the system dependent on temperature differentials, emissivity setting of the pyrometer, target distance between pyrometer and slab, and air and fuel flow rates existing and fluctuating in the system.

  18. Sub-slab vs. Near-slab Soil Vapor Profiles at a Chlorinated Solvent Site (1)

    EPA Science Inventory

    A critical issue in assessing the vapor intrusion pathway is the distribution and migration of VOCs from the subsurface source to the near surface environment. Of particular importance is the influence of a slab. Therefore, EPA/ORD is funding a research program with the primary...

  19. Plate deformation at depth under northern California: Slab gap or stretched slab?

    USGS Publications Warehouse

    ten Brink, U.S.; Shimizu, N.; Molzer, P.C.

    1999-01-01

    Plate kinematic interpretations for northern California predict a gap in the underlying subducted slab caused by the northward migration of the Pacific-North America-Juan de Fuca triple junction. However, large-scale decompression melting and asthenospheric upwelling to the base of the overlying plate within the postulated gap are not supported by geophysical and geochemical observations. We suggest a model for the interaction between the three plates which is compatible with the observations. In this 'slab stretch' model the Juan de Fuca plate under coastal northern California deforms by stretching and thinning to fill the geometrical gap formed in the wake of the northward migrating Mendocino triple junction. The stretching is in response to boundary forces acting on the plate. The thinning results in an elevated geothermal gradient, which may be roughly equivalent to a 4 Ma oceanic lithosphere, still much cooler than that inferred by the slab gap model. We show that reequilibration of this geothermal gradient under 20-30 km thick overlying plate can explain the minor Neogene volcanic activity, its chemical composition, and the heat flow. In contrast to northern California, geochemical and geophysical consequences of a 'true' slab gap can be observed in the California Inner Continental Borderland offshore Los Angeles, where local asthenospheric upwelling probably took place during the Miocene as a result of horizontal extension and rotation of the overlying plate. The elevated heat flow in central California can be explained by thermal reequilibration of the stalled Monterey microplate under the Coast Ranges, rather than by a slab gap or viscous shear heating in the mantle.

  20. Telerobotic truss assembly

    NASA Technical Reports Server (NTRS)

    Sheridan, Philip L.

    1987-01-01

    The ACCESS truss was telerobotically assembled in order to gain experience with robotic assembly of hardware designed for astronaut extravehicular (EVA) assembly. Tight alignment constraints of the ACCESS hardware made telerobotic assembly difficult. A wider alignment envelope and a compliant end effector would have reduced the problem. The manipulator had no linear motion capability, but many of the assembly operations required straight line motion. The manipulator was attached to a motion table in order to provide the X, Y, and Z translations needed. A programmable robot with linear translation capability would have eliminated the need for the motion table and streamlined the assembly. Poor depth perception was a major problem. Shaded paint schemes and alignment lines were helpful in reducing this problem. The four cameras used worked well for only some operations. It was not possible to identify camera locations that worked well for all assembly steps. More cameras or movable cameras would have simplified some operations. The audio feedback system was useful.

  1. Seeing lumps, sticks, and slabs in silhouettes.

    PubMed

    Willats, J

    1992-01-01

    Marr has suggested that we see three-dimensional (3-D) shapes in silhouettes because we make the implicit assumption that the viewed shapes are generalized cones. One difficulty with this suggestion is that it cannot deal with silhouettes of irregular 3-D shapes like clouds and trees; another is that it only applies to generalized cones with a relatively high length:width ratio. An alternative explanation, suggested by evidence from cross-cultural studies of language, from children's early speech, and from children's early drawings, is that the scene primitives actually used by humans are not generalized cones but 'lumps', 'sticks', and 'slabs', that is, primitives whose only shape properties are their relative extensions in 3-D space. In this paper it is proposed that the implicit assumption we make in interpreting silhouettes is that the extendedness of the silhouette reflects the extendedness of the viewed shape, so that a round region is seen as a lump and a long region is seen as a stick; and that such views seem "natural" because they are the views most likely to be encountered in normal environments. This account is more general than that of Marr because it explains how we interpret silhouettes of all kinds of 3-D shapes, even very irregular ones. Unlike Marr's account, it also deals with flat shapes like slabs and discs, and shows why it is difficult to see these shapes in silhouettes.

  2. Subduction in eastern Indonesia: how many slabs?

    NASA Astrophysics Data System (ADS)

    Milsom, John

    2001-08-01

    Seismicity associated with arc-continent collision in eastern Indonesia testifies to past north-directed subduction of Indian Ocean lithosphere beneath the Banda Sea. The complex patterns of deep seismicity have been cited as evidence for simultaneous south-directed subduction at the northern margin of the sea but this interpretation has not been universally accepted. Recently available recomputations of hypocentre locations have provided increased resolution of eastern Indonesian Wadati-Benioff Zones (WBZs). Shallow to intermediate depth seismic activity around the Banda Arc appears to support models involving subduction of two separate and distinct lithospheric slabs, but between 150 and 500 km the WBZ has a continuous 'shoehorn' shape. This shape confirms the presence of subducted lithosphere beneath Seram, in the north, as well as beneath Timor, in the south, is incompatible with independent subduction of two unconnected plates and implies rapid eastwards retreat of the subduction trace across a now vanished northern spur of the Indian Ocean. This 'roll-back' is unlikely to have been driven by local gravitational forces alone and may have been sustained by injection behind the Banda slab of asthenospheric material escaping from the Molucca Sea arc-arc collision.

  3. Radiative transfer model for contaminated rough slabs.

    PubMed

    Andrieu, François; Douté, Sylvain; Schmidt, Frédéric; Schmitt, Bernard

    2015-11-01

    We present a semi-analytical model to simulate the bidirectional reflectance distribution function (BRDF) of a rough slab layer containing impurities. This model has been optimized for fast computation in order to analyze massive hyperspectral data by a Bayesian approach. We designed it for planetary surface ice studies but it could be used for other purposes. It estimates the bidirectional reflectance of a rough slab of material containing inclusions, overlaying an optically thick media (semi-infinite media or stratified media, for instance granular material). The inclusions are assumed to be close to spherical and constituted of any type of material other than the ice matrix. It can be any other type of ice, mineral, or even bubbles defined by their optical constants. We assume a low roughness and we consider the geometrical optics conditions. This model is thus applicable for inclusions larger than the considered wavelength. The scattering on the inclusions is assumed to be isotropic. This model has a fast computation implementation and thus is suitable for high-resolution hyperspectral data analysis. PMID:26560577

  4. Electrochemical fabrication of surface chemical gradients in thiol self-assembled monolayers with tailored work-functions.

    PubMed

    Fioravanti, Giulia; Lugli, Francesca; Gentili, Denis; Mucciante, Vittoria; Leonardi, Francesca; Pasquali, Luca; Liscio, Andrea; Murgia, Mauro; Zerbetto, Francesco; Cavallini, Massimiliano

    2014-10-01

    The studies on surface chemical gradients are constantly gaining interest both for fundamental studies and for technological implications in materials science, nanofluidics, dewetting, and biological systems. Here we report on a new approach that is very simple and very efficient, to fabricate surface chemical gradients of alkanethiols, which combines electrochemical desorption/partial readsorption, with the withdrawal of the surface from the solution. The gradient is then stabilized by adding a complementary thiol terminated with a hydroxyl group with a chain length comparable to desorbed thiols. This procedure allows us to fabricate a chemical gradient of the wetting properties and the substrate work-function along a few centimeters with a gradient slope higher than 5°/cm. Samples were characterized by cyclic voltammetry during desorption, static contact angle, XPS analysis, and Kelvin probe. Computer simulations based on the Dissipative Particle Dynamics methods were carried out considering a water droplet on a mixed SAM surface. The results help to rationalize the composition of the chemical gradient at different position on the Au surface.

  5. Damage assessment of two-way bending RC slabs subjected to blast loadings.

    PubMed

    Jia, Haokai; Yu, Ling; Wu, Guiying

    2014-01-01

    Terrorist attacks on vulnerable structures and their individual structural members may cause considerable damage and loss of life. However, the research work on response and damage analysis of single structural components, for example, a slab to blast loadings, is limited in the literature and this is necessary for assessing its vulnerability. This study investigates the blast response and damage assessment of a two-way bending reinforced concrete (RC) slab subjected to blast loadings. Numerical modeling and analysis are carried out using the commercial finite element code LS-DYNA 971. A damage assessment criterion for the two-way bending RC slab is defined based on the original and residual uniformly distributed load-carrying capacity. Parametric studies are carried out to investigate the effects of explosive weight and explosive position on the damage mode of the two-way RC slab. Some design parameters, such as the boundary conditions and the negative reinforcement steel bar length, are also discussed. The illustrated results show that the proposed criterion can apply to all failure modes. The damage assessment results are more accurate than the ones due to the conventional deformation criterion.

  6. Damage Assessment of Two-Way Bending RC Slabs Subjected to Blast Loadings

    PubMed Central

    Jia, Haokai; Wu, Guiying

    2014-01-01

    Terrorist attacks on vulnerable structures and their individual structural members may cause considerable damage and loss of life. However, the research work on response and damage analysis of single structural components, for example, a slab to blast loadings, is limited in the literature and this is necessary for assessing its vulnerability. This study investigates the blast response and damage assessment of a two-way bending reinforced concrete (RC) slab subjected to blast loadings. Numerical modeling and analysis are carried out using the commercial finite element code LS-DYNA 971. A damage assessment criterion for the two-way bending RC slab is defined based on the original and residual uniformly distributed load-carrying capacity. Parametric studies are carried out to investigate the effects of explosive weight and explosive position on the damage mode of the two-way RC slab. Some design parameters, such as the boundary conditions and the negative reinforcement steel bar length, are also discussed. The illustrated results show that the proposed criterion can apply to all failure modes. The damage assessment results are more accurate than the ones due to the conventional deformation criterion. PMID:25121134

  7. Scattering of electromagnetic waves from a turbulent plasma slab.

    NASA Technical Reports Server (NTRS)

    Liu, C. H.

    1972-01-01

    Scattering of electromagnetic waves from a turbulent plasma slab is studied. Part of the effects of the multiple scattering is taken into account. The reflection coefficient is found to be increased and its variation with respect to the slab thickness is smoothed out by the random scattering.

  8. Advanced parameter retrievals for metamaterial slabs using an inhomogeneous model

    NASA Astrophysics Data System (ADS)

    Li Hou, Ling; Chin, Jessie Yao; Yang, Xin Mi; Lin, Xian Qi; Liu, Ruopeng; Xu, Fu Yong; Cui, Tie Jun

    2008-03-01

    The S-parameter retrieval has proved to be an efficient approach to obtain electromagnetic parameters of metamaterials from reflection and transmission coefficients, where a slab of metamaterial with finite thickness is regarded as a homogeneous medium slab with the same thickness [D. R. Smith and S. Schultz, Phys. Rev. B 65, 195104 (2002)]. However, metamaterial structures composed of subwavelength unit cells are different from homogeneous materials, and the conventional retrieval method is, under certain circumstances, not accurate enough. In this paper, we propose an advanced parameter retrieval method for metamaterial slabs using an inhomogeneous model. Due to the coupling effects of unit cells in a metamaterial slab, the roles of edge and inner cells in the slab are different. Hence, the corresponding equivalent medium parameters are different, which results in the inhomogeneous property of the metamaterial slab. We propose the retrievals of medium parameters for edge and inner cells from S parameters by considering two- and three-cell metamaterial slabs, respectively. Then we set up an inhomogeneous three-layer model for arbitrary metamaterial slabs, which is much more accurate than the conventional homogeneous model. Numerical simulations verify the above conclusions.

  9. Flat slab deformation caused by interplate suction force

    NASA Astrophysics Data System (ADS)

    Ma, Yiran; Clayton, Robert W.

    2015-09-01

    We image the structure at the southern end of the Peruvian flat subduction zone, using receiver function and surface wave methods. The Nazca slab subducts to ~100 km depth and then remains flat for ~300 km distance before it resumes the dipping subduction. The flat slab closely follows the topography of the continental Moho above, indicating a strong suction force between the slab and the overriding plate. A high-velocity mantle wedge exists above the initial half of the flat slab, and the velocity resumes to normal values before the slab steepens again, indicating the resumption of dehydration and ecologitization. Two prominent midcrust structures are revealed in the 70 km thick crust under the Central Andes: molten rocks beneath the Western Cordillera and the underthrusting Brazilian Shield beneath the Eastern Cordillera.

  10. The Role of Subducting Ridges in the Formation of Flat Slabs: Insights from the Peruvian Flat Slab

    NASA Astrophysics Data System (ADS)

    Knezevic Antonijevic, Sanja; Wagner, Lara; Kumar, Abhash; Beck, Susan; Long, Maureen; Zandt, George; Eakin, Caroline M.

    2015-04-01

    Flattening of the subducting plate is often used to explain various geological features removed far from the subducting margins, including basement-cored uplifts, the cessation of arc volcanism, ignimbrite flare-ups, and the formation of high plateaus and ore deposits [Humphreys et al., 2003; Gutscher et al., 2000; Rosenbaum et al., 2005, Kay and Mpodozis, 2001]. Today, flat slab subduction is observed in central Chile and Peru, representing the modern analogues to the immense paleo-flat slab that subducted beneath the North American continent during the Laramide orogeny (80-55 Ma) [English et al., 2003]. However, how flat slabs form and what controls their inboard and along-strike extent is still poorly understood. To better understand modern and paleo-flat slabs, we focus on the Peruvian flat slab, where the Nazca plate starts to bend at ~90 km depth and travels horizontally for several hundred kilometers beneath the South American plate. Earlier studies propose a correlation between the flat slab and the subducting Nazca Ridge that has been migrating to the south over the past 11 ~Ma [Hampel et al., 2004, Gutscher et al., 2003]. Combining 3D shear wave velocity structure and Rayleigh wave phase anisotropy between ~10° and 18° S, we find that the flat slab has the greatest inboard extent along the track of the subducting Nazca Ridge. North of the ridge track, where the flat slab was initially formed, the flat slab starts to sag, tear and re-initiate steep slab subduction, allowing inflow of warm asthenosphere. Based on our new constraints on the geometry of the subducted plate, we find that the subduction of buoyant oceanic features with overthickened oceanic crust plays a vital role in the formation of flat slabs. We further develop a model of temporal evolution of the Peruvian flab slab that forms as a result of the combined effects of the subducting ridge, trench retreat, and suction forces. Once the buoyant ridge subducts to ~90 km depth, it will fail to

  11. Lithosphere-Mantle Interactions Associated with Flat-Slab Subduction

    NASA Astrophysics Data System (ADS)

    Gerault, M.; Becker, T. W.; Husson, L.; Humphreys, E.

    2014-12-01

    Episodes of flat-slab subduction along the western margin of the Americas may have lead to the formation of intra-continental basins and seas, as well as mountain belts and continental plateaux. Here, we explore some of the consequences of a flat slab morphology, linking dynamic topography and stress patterns in continents to slab and mantle dynamics. Using a 2-D cylindrical code, we develop general models and apply them to the North and South America plates. The results are primarily controlled by the coupling along the slab-continent interface (due to geometry and viscosity), the viscosity of the mantle wedge, and the buoyancy of the subducted lithosphere. All models predict broad subsidence, large deviatoric stresses, and horizontal compression above the tip of the flat slab and the deep slab hinge. In models where the slab lays horizontally for hundreds of kilometers, overriding plate compression focuses on both ends of the flat segment, where normal-dip subduction exerts a direct downward pull. In between, a broad low-stress region gets uplifted proportionally to the amount of coupling between the slab and the continent. Anomalously buoyant seafloor enhances this effect but is not required. The downward bending of the flat slab extremities causes its upper part to undergo extension and the lower part to compress. These results have potential for explaining the existence of relatively undeformed, uplifted regions surrounded by mountain belts, such as in the western U.S. and parts of the Andes. Adequately modeling topography and stress in the unusual setting of southwestern Mexico requires a low-viscosity subduction interface and mantle wedge. Our results are only partially controlled by the buoyancy of the subducting plate, suggesting that the viscosity and the morphology of the slab are important, and that the often-used low resolution and "Stokeslet" models may be missing substantial effects.

  12. Hybrid slab-microchannel gel electrophoresis system

    DOEpatents

    Balch, J.W.; Carrano, A.V.; Davidson, J.C.; Koo, J.C.

    1998-05-05

    A hybrid slab-microchannel gel electrophoresis system is described. The hybrid system permits the fabrication of isolated microchannels for biomolecule separations without imposing the constraint of a totally sealed system. The hybrid system is reusable and ultimately much simpler and less costly to manufacture than a closed channel plate system. The hybrid system incorporates a microslab portion of the separation medium above the microchannels, thus at least substantially reducing the possibility of non-uniform field distribution and breakdown due to uncontrollable leakage. A microslab of the sieving matrix is built into the system by using plastic spacer materials and is used to uniformly couple the top plate with the bottom microchannel plate. 4 figs.

  13. All-polymer photonic crystal slab sensor.

    PubMed

    Hermannsson, Pétur G; Sørensen, Kristian T; Vannahme, Christoph; Smith, Cameron L C; Klein, Jan J; Russew, Maria-Melanie; Grützner, Gabi; Kristensen, Anders

    2015-06-29

    An all-polymer photonic crystal slab sensor is presented, and shown to exhibit narrow resonant reflection with a FWHM of less than 1 nm and a sensitivity of 31 nm/RIU when sensing media with refractive indices around that of water. This results in a detection limit of 4.5 × 10(-6) RIU when measured in conjunction with a spectrometer of 12 pm/pixel resolution. The device is a two-layer structure, composed of a low refractive index polymer with a periodically modulated surface height, covered with a smooth upper-surface high refractive index inorganic-organic hybrid polymer modified with ZrO2based nanoparticles. Furthermore, it is fabricated using inexpensive vacuum-less techniques involving only UV nanoreplication and polymer spin-casting, and is thus well suited for single-use biological and refractive index sensing applications. PMID:26191664

  14. Laser applications in machining slab materials

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoping

    1990-10-01

    Since the invention of the laser back in 1960, laser technology has been extensively applied in many fields of science and technology. These has been a history of nearly two decades of using lasers as an energy source in machining materials, such as cutting, welding, ruling and boring, among other operations. With the development of flexible automation in production, the advantages of laser machining have has grown more and more obvious. The combination of laser technology and computer science further promotes the enhancement and upgrading of laser machining and related equipment. At present, many countries are building high quality laser equipment for machining slab materials, such as the Coherent and Spectra Physics corporations in the United States, the Trumpf Corporation in West Germany, the Amada Corporation in Japan, and the Bystronic Corporation in Switzerland, among other companies.

  15. A two- and three-dimensional numerical comparison study of slab detachment

    NASA Astrophysics Data System (ADS)

    Thieulot, Cedric; Buiter, Susanne; Brune, Sascha; Davies, Rhodri; Duretz, Thibault; Gerbault, Muriel; Glerum, Anne; Quinteros, Javier; Schmalholz, Stefan; Spakman, Wim

    2015-04-01

    Subduction is likely to be the most studied phenomenon in Numerical Geodynamics. Over the past 20 years, hundreds of publications have focused on its various aspects (influence of the rheology and thermal state of the plates, slab-mantle coupling, roll-back, mantle wedge evolution, buoyancy changes due to phase change, ...) and results were obtained with a variety of codes. Slab detachment has recently received some attention but remains a field worth exploring due to its profound influence on dynamic topography, mantle flow and subsequent stress state of the plates, and is believed to have occured in the Zagros, Carpathians and beneath eastern Anatolia, to name only a few regions. Following the work of Schmalholz (2011), we propose a two- and three-dimensional numerical benchmark of slab detachment. The geometry is simple: a power-law T-shaped plate including an already subducted slab overlies the mantle whose viscosity is either linear or power-law. Boundary conditions are free-slip on the top and the bottom of the domain, and no-slip on the sides. When the system evolves in time, the slab stretches out vertically and shows buoyancy-driven necking, until it finally detaches. The benchmark is subdivided into several sub-experiments with gradually increase in complexity (free surface, coupling of the rheology with temperature, ...). An array of objective measurements is recorded throughout the simulation such as the width of the necked slab over time and the exact time of detachment. The experiments will be run in two-dimensions and repeated in three-dimensional, the latter case being designed so as to allow both poloidal and toroidal flow. We show results obtained with a multitude of Finite Element and Finite Difference codes, using either compositional fields, level sets or tracers to track the compositions. A good agreement is found for most of the measurements in the two-dimensional case, and preliminary three-dimensional measurements will be shown. Schmalholz

  16. Complex geometry of the subducted Pacific slab inferred from receiver function

    NASA Astrophysics Data System (ADS)

    Zhang, Ruiqing; Wu, Qingju; Zhang, Guangcheng

    2014-05-01

    In recent years, slab tear has received considerable attention and been reported in many arc-arc junctures in Pacific plate subdution zones. From 2009 to 2011, we deployed two portable experiments equipped with CMG-3ESPC seismometers and the recorders of REFTEK-130B in NE China. The two linear seismic arrays were designed nearly parallel, and each of them containing about 60 seismic stations extended about 1200 km from west to east spanning all surface geological terrains of NE China. The south one was firstly set up and continually operated over two year, while the north deployment worked only about one year. By using the teleseismic data collected by these two arrays, we calculate the P receiver functions to map topographic variation of the upper mantle discontinuities. Our sampled region is located where the juncture between the subducting Kuril and Japan slabs reaches the 660-km discontinuity. Distinct variation of the 660-km discontinuity is mapped beneath the regions. A deeper-than-normal 660 km discontinuity is observed locally in the southeastern part of our sampled region. The depression of the 660 km discontinuity may be resulted from an oceanic lithospheric slab deflected in the mantle transition zone, in good agreement with the result of earlier tomographic and other seismic studies in this region. The northeastern portion of our sampled region, however, does not show clearly the deflection of the slab. The variation of the tomography of the 660-km discontinuity in our sampled regions may indicate a complex geometry of the subducted Pacific slab.

  17. 'Let the phage do the work': Using the phage P22 coat protein structures as a framework to understand its folding and assembly mutants

    SciTech Connect

    Teschke, Carolyn M.; Parent, Kristin N.

    2010-06-05

    The amino acid sequence of viral capsid proteins contains information about their folding, structure and self-assembly processes. While some viruses assemble from small preformed oligomers of coat proteins, other viruses such as phage P22 and herpesvirus assemble from monomeric proteins (Fuller and King, 1980). The subunit assembly process is strictly controlled through protein:protein interactions such that icosahedral structures are formed with specific symmetries, rather than aberrant structures. dsDNA viruses commonly assemble by first forming a precursor capsid that serves as a DNA packaging machine. DNA packaging is accompanied by a conformational transition of the small precursor procapsid into a larger capsid for isometric viruses. Here we highlight the pseudo-atomic structures of phage P22 coat protein and rationalize several decades of data about P22 coat protein folding, assembly and maturation generated from a combination of genetics and biochemistry.

  18. Bound state in the continuum in the one-dimensional photonic crystal slab

    NASA Astrophysics Data System (ADS)

    Sadrieva, Z. F.; Bogdanov, A. A.

    2016-08-01

    In this work we developed a design of one-dimensional Si/SiO2 photonic crystal slab supporting so called optical bound states in the continuum - infinitely high-Q optical states with energies lying above the light line of the surrounding space. Such high-Q states are very perspective for many potential applications ranging from on-chip photonics and optical communications to biological sensing and photovoltaics.

  19. Imaging the transition from flat to normal subduction: variations in the structure of the Nazca slab and upper mantle under southern Peru and northwestern Bolivia

    NASA Astrophysics Data System (ADS)

    Scire, Alissa; Zandt, George; Beck, Susan; Long, Maureen; Wagner, Lara; Minaya, Estela; Tavera, Hernando

    2016-01-01

    Two arrays of broad-band seismic stations were deployed in the north central Andes between 8° and 21°S, the CAUGHT array over the normally subducting slab in northwestern Bolivia and southern Peru, and the PULSE array over the southern part of the Peruvian flat slab where the Nazca Ridge is subducting under South America. We apply finite frequency teleseismic P- and S-wave tomography to data from these arrays to investigate the subducting Nazca plate and the surrounding mantle in this region where the subduction angle changes from flat north of 14°S to normally dipping in the south. We present new constraints on the location and geometry of the Nazca slab under southern Peru and northwestern Bolivia from 95 to 660 km depth. Our tomographic images show that the Peruvian flat slab extends further inland than previously proposed along the projection of the Nazca Ridge. Once the slab re-steepens inboard of the flat slab region, the Nazca slab dips very steeply (˜70°) from about 150 km depth to 410 km depth. Below this the slab thickens and deforms in the mantle transition zone. We tentatively propose a ridge-parallel slab tear along the north edge of the Nazca Ridge between 130 and 350 km depth based on the offset between the slab anomaly north of the ridge and the location of the re-steepened Nazca slab inboard of the flat slab region, although additional work is needed to confirm the existence of this feature. The subslab mantle directly below the inboard projection of the Nazca Ridge is characterized by a prominent low-velocity anomaly. South of the Peruvian flat slab, fast anomalies are imaged in an area confined to the Eastern Cordillera and bounded to the east by well-resolved low-velocity anomalies. These low-velocity anomalies at depths greater than 100 km suggest that thick mantle lithosphere associated with underthrusting of cratonic crust from the east is not present. In northwestern Bolivia a vertically elongated fast anomaly under the Subandean Zone

  20. A modularized pulse forming line using glass-ceramic slabs.

    PubMed

    Wang, Songsong; Shu, Ting; Yang, Hanwu

    2012-08-01

    In our lab, a kind of glass-ceramic slab has been chosen to study the issues of applying solid-state dielectrics to pulse forming lines (PFLs). Limited by the manufacture of the glass-ceramic bulk with large sizes, a single ceramic slab is hard to store sufficient power for the PFL. Therefore, a modularized PFL design concept is proposed in this paper. We regard a single ceramic slab as a module to form each single Blumlein PFL. We connect ceramic slabs in series to enlarge pulse width, and stack the ceramic Blumlein PFLs in parallel to increase the output voltage amplitude. Testing results of a single Blumlein PFL indicate that one ceramic slab contributes about 11 ns to the total pulse width which has a linear relation to the number of the ceramic slabs. We have developed a prototype facility of the 2-stage stacked Blumlein PFL with a length of 2 ceramic slabs. The PFL is dc charged up to 5 kV, and the output voltage pulse of 10 kV, 22 ns is measured across an 8 Ω load. Simulation and experiment results in good agreement demonstrate that the modularized design is reasonable. PMID:22938320

  1. A modularized pulse forming line using glass-ceramic slabs.

    PubMed

    Wang, Songsong; Shu, Ting; Yang, Hanwu

    2012-08-01

    In our lab, a kind of glass-ceramic slab has been chosen to study the issues of applying solid-state dielectrics to pulse forming lines (PFLs). Limited by the manufacture of the glass-ceramic bulk with large sizes, a single ceramic slab is hard to store sufficient power for the PFL. Therefore, a modularized PFL design concept is proposed in this paper. We regard a single ceramic slab as a module to form each single Blumlein PFL. We connect ceramic slabs in series to enlarge pulse width, and stack the ceramic Blumlein PFLs in parallel to increase the output voltage amplitude. Testing results of a single Blumlein PFL indicate that one ceramic slab contributes about 11 ns to the total pulse width which has a linear relation to the number of the ceramic slabs. We have developed a prototype facility of the 2-stage stacked Blumlein PFL with a length of 2 ceramic slabs. The PFL is dc charged up to 5 kV, and the output voltage pulse of 10 kV, 22 ns is measured across an 8 Ω load. Simulation and experiment results in good agreement demonstrate that the modularized design is reasonable.

  2. May eclogite dehydration cause slab fracturation ?

    NASA Astrophysics Data System (ADS)

    Loury, Chloé; Lanari, Pierre; Rolland, Yann; Guillot, Stéphane; Ganino, Clément

    2015-04-01

    Petrological and geophysical evidences strongly indicate that fluids releases play a fundamental role in subduction zones as in subduction-related seismicity and arc magmatism. It is thus important to assess quantitatively their origin and to try to quantify the amount of such fluids. In HP metamorphism, it is well known that pressure-dependent dehydration reactions occur during the prograde path. Many geophysical models show that the variations in slab physical properties along depth could be linked to these fluid occurrences. However it remains tricky to test such models on natural sample, as it is difficult to assess or model the water content evolution in HP metamorphic rocks. This difficulty is bound to the fact that these rocks are generally heterogeneous, with zoned minerals and preservation of different paragenesis reflecting changing P-T conditions. To decipher the P-T-X(H2O) path of such heterogeneous rocks the concept of local effective bulk (LEB) composition is essential. Here we show how standardized X-ray maps can be used to constrain the scale of the equilibration volume of a garnet porphyroblast and to measure its composition. The composition of this equilibrium volume may be seen as the proportion of the rock likely to react at a given time to reach a thermodynamic equilibrium with the growing garnet. The studied sample is an eclogite coming from the carboniferous South-Tianshan suture (Central Asia) (Loury et al. in press). Compositional maps of a garnet and its surrounding matrix were obtained from standardized X-ray maps processed with the program XMapTools (Lanari et al, 2014). The initial equilibration volume was modeled using LEB compositions combined together with Gibbs free energy minimization. P-T sections were calculated for the next stages of garnet growth taking into account the fractionation of the composition at each stage of garnet growth. The modeled P-T-X(H2O) path indicates that the rock progressively dehydrates during the

  3. Lower mantle seismic scatterers below the subducting Tonga slab: Evidence for slab entrainment of transition zone materials

    NASA Astrophysics Data System (ADS)

    Kaneshima, Satoshi

    2013-09-01

    We show evidence that materials with significantly different elastic properties are juxtaposed in the lower mantle immediately below the subducting Tonga slab (depths ⩽1000 km), like the anomalies preferentially located beneath the lower mantle slabs at other Pacific subduction zones (Kaneshima, 2009). Array analyses of wave form data of short period seismic networks at western United States and Japan for deep earthquakes at the Tonga slab reveal S-to-P scatterers with a size less than the wavelengths (˜10 km). The scatterers are located mostly outside of the slab by several tens of kilometers. Assuming a locally planar interface for the geometry of the scatterers, the amplitudes and polarities of the S-to-P waves are modeled to constrain the properties of the scatterers. We find that the scatterers are steeply dipping, the Vs increases oceanward across the interface, and the Vs contrasts are at least comparable to that associated with the post-spinel transformation (⩾6%). It is unclear at this stage what these subslab scatterers represent, so we discuss about three mechanisms which seem plausible from mantle dynamics viewpoints: (1) they may represent basaltic rocks which were emplaced by partial melting immediately beneath the former oceanic lithosphere-asthenosphere boundary (LAB) before the slab started subducting; (2) alternatively the elastic anomalies of the scatterers may be caused by localized presence of dehydrated water; or (3) the scatterers may correspond to a sharp boundary between fine-grained isotropic rocks in the immediate vicinity of the slab and coarse grained anisotropic rocks more distant from the slab. The presence of pronounced and localized elastic anomalies preferentially beneath the slabs in the shallow lower mantle, whatever its mechanism is, implies that a geophysically observable amount of transition zone material is entrained by the subducting slabs into the lower mantle.

  4. Effective bichromatic potential for ultra-high Q-factor photonic crystal slab cavities

    SciTech Connect

    Alpeggiani, Filippo Andreani, Lucio Claudio; Gerace, Dario

    2015-12-28

    We introduce a confinement mechanism in photonic crystal slab cavities, which relies on the superposition of two incommensurate one-dimensional lattices in a line-defect waveguide. It is shown that the resulting photonic profile realizes an effective quasi-periodic bichromatic potential for the electromagnetic field confinement yielding extremely high quality (Q) factor nanocavities, while simultaneously keeping the mode volume close to the diffraction limit. We apply these concepts to pillar- and hole-based photonic crystal slab cavities, respectively, and a Q-factor improvement by over an order of magnitude is shown over existing designs, especially in pillar-based structures. Thanks to the generality and easy adaptation of such confinement mechanism to a broad class of cavity designs and photonic lattices, this work opens interesting routes for applications where enhanced light–matter interaction in photonic crystal structures is required.

  5. Effects of magnetic field on the interaction between terahertz wave and non-uniform plasma slab

    SciTech Connect

    Tian, Yuan; Han, YiPing; Guo, LiXin; Ai, Xia

    2015-10-15

    In this paper, the interaction between terahertz electromagnetic wave and a non-uniform magnetized plasma slab is investigated. Different from most of the published literatures, the plasma employed in this work is inhomogeneous in both collision frequency and electron density. Profiles are introduced to describe the non-uniformity of the plasma slab. At the same time, magnetic field is applied to the background of the plasma slab. It came out with an interesting phenomenon that there would be a valley in the absorption band as the plasma's electromagnetic characteristic is affected by the magnetic field. In addition, the valley located just near the middle of the absorption peak. The cause of the valley's appearance is inferred in this paper. And the influences of the variables, such as magnetic field strength, electron density, and collision frequency, are discussed in detail. The objective of this work is also pointed out, such as the applications in flight communication, stealth, emissivity, plasma diagnose, and other areas of plasma.

  6. Effects of magnetic field on the interaction between terahertz wave and non-uniform plasma slab

    NASA Astrophysics Data System (ADS)

    Tian, Yuan; Ai, Xia; Han, YiPing; Guo, LiXin

    2015-10-01

    In this paper, the interaction between terahertz electromagnetic wave and a non-uniform magnetized plasma slab is investigated. Different from most of the published literatures, the plasma employed in this work is inhomogeneous in both collision frequency and electron density. Profiles are introduced to describe the non-uniformity of the plasma slab. At the same time, magnetic field is applied to the background of the plasma slab. It came out with an interesting phenomenon that there would be a valley in the absorption band as the plasma's electromagnetic characteristic is affected by the magnetic field. In addition, the valley located just near the middle of the absorption peak. The cause of the valley's appearance is inferred in this paper. And the influences of the variables, such as magnetic field strength, electron density, and collision frequency, are discussed in detail. The objective of this work is also pointed out, such as the applications in flight communication, stealth, emissivity, plasma diagnose, and other areas of plasma.

  7. Hybrid Heat Capacity - Moving Slab Laser Concept

    SciTech Connect

    Stappaerts, E A

    2002-04-01

    A hybrid configuration of a heat capacity laser (HCL) and a moving slab laser (MSL) has been studied. Multiple volumes of solid-state laser material are sequentially diode-pumped and their energy extracted. When a volume reaches a maximum temperature after a ''sub-magazine depth'', it is moved out of the pumping region into a cooling region, and a new volume is introduced. The total magazine depth equals the submagazine depth times the number of volumes. The design parameters are chosen to provide high duty factor operation, resulting in effective use of the diode arrays. The concept significantly reduces diode array cost over conventional heat capacity lasers, and it is considered enabling for many potential applications. A conceptual design study of the hybrid configuration has been carried out. Three concepts were evaluated using CAD tools. The concepts are described and their relative merits discussed. Because of reduced disk size and diode cost, the hybrid concept may allow scaling to average powers on the order of 0.5 MW/module.

  8. Magnetoelectric sensor excitations in hexaferrite slabs

    NASA Astrophysics Data System (ADS)

    Zare, Saba; Izadkhah, Hessam; Somu, Sivasubramanian; Vittoria, Carmine

    2015-06-01

    We developed techniques for H- and E-field sensors utilizing single phase magnetoelectric (ME) hexaferrite slabs in the frequency range of 100 Hz to 10 MHz. Novel circuit designs incorporating both spiral and solenoid coils and single and multi-capacitor banks were developed to probe the physics and properties of ME hexaferrites and explore ME effects for sensor detections. Fundamental measurements of the anisotropic tensor elements of the magneto-electric coupling parameter were performed using these novel techniques. In addition, for H-field sensing experiments we measured sensitivity of about 3000 Vm-1/G using solenoid coils and 8000 Vm-1/G using spiral coils. For E-field, sensing the sensitivity was 10-4 G/Vm-1 and using single capacitor detector. Sensitivity for multi-capacitor detectors was measured to be in the order of 10-3 G/Vm-1 and frequency dependent exhibiting a maximum value at ˜1 MHz. Tunability of 0.1%-90% was achieved for tunable inductor applications using both single and multi-capacitors excitation. We believe that significant (˜106) improvements in sensitivity and tunability are feasible with simple modifications of the fabrication process.

  9. Streamlined Approach for Environmental Restoration Work Plan for Corrective Action Unit 461: Joint Test Assembly Sites and Corrective Action Unit 495: Unconfirmed Joint Test Assembly Sites Tonopah Test Range, Nevada

    SciTech Connect

    Jeff Smith

    1998-08-01

    This Streamlined Approach for Environmental Restoration plan addresses the action necessary for the clean closure of Corrective Action Unit 461 (Test Area Joint Test Assembly Sites) and Corrective Action Unit 495 (Unconfirmed Joint Test Assembly Sites). The Corrective Action Units are located at the Tonopah Test Range in south central Nevada. Closure for these sites will be completed by excavating and evaluating the condition of each artillery round (if found); detonating the rounds (if necessary); excavating the impacted soil and debris; collecting verification samples; backfilling the excavations; disposing of the impacted soil and debris at an approved low-level waste repository at the Nevada Test Site

  10. 23. Surrender interview site, showing Pemberton Avenue concrete slab road ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    23. Surrender interview site, showing Pemberton Avenue concrete slab road type with gutter (asphalt construction typical on Union and Confederate Avenues), view to the sw. - Vicksburg National Military Park Roads & Bridges, Vicksburg, Warren County, MS

  11. 2. FLAME DEFLECTOR FROM THE REINFORCED CONCRETE SLAB ROOF, VIEW ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. FLAME DEFLECTOR FROM THE REINFORCED CONCRETE SLAB ROOF, VIEW TOWARDS SOUTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-2, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  12. 9. FLAME DEFLECTOR FROM REINFORCED CONCRETE SLAB ROOF, VIEW TOWARDS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. FLAME DEFLECTOR FROM REINFORCED CONCRETE SLAB ROOF, VIEW TOWARDS NORTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  13. Segmented Hellenic slab rollback driving Aegean deformation and seismicity

    NASA Astrophysics Data System (ADS)

    Sachpazi, M.; Laigle, M.; Charalampakis, M.; Diaz, J.; Kissling, E.; Gesret, A.; Becel, A.; Flueh, E.; Miles, P.; Hirn, A.

    2016-01-01

    The NE dipping slab of the Hellenic subduction is imaged in unprecedented detail using teleseismic receiver function analysis on a dense 2-D seismic array. Mapping of slab geometry for over 300 km along strike and down to 100 km depth reveals a segmentation into dipping panels by along-dip faults. Resolved intermediate-depth seismicity commonly attributed to dehydration embrittlement is shown to be clustered along these faults. Large earthquakes occurrence within the upper and lower plate and at the interplate megathrust boundary show a striking correlation with the slab faults suggesting high mechanical coupling between the two plates. Our results imply that the general slab rollback occurs here in a differential piecewise manner imposing its specific stress and deformation pattern onto the overriding Aegean plate.

  14. DETAIL OF NORTH GUARDRAIL AND EXPANSION JOINT IN CONCRETE SLAB, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF NORTH GUARDRAIL AND EXPANSION JOINT IN CONCRETE SLAB, SHOWING DAMAGED SECTION OF GUARDRAIL AND ALUMINUM REPLACEMENT. VIEW TO NORTHWEST. - Hassayampa Bridge, Spanning Hassayampa River at old U.S. Highway 80, Arlington, Maricopa County, AZ

  15. Radiative Transfer Model for Translucent Slab Ice on Mars

    NASA Astrophysics Data System (ADS)

    Andrieu, F.; Schmidt, F.; Douté, S.; Schmitt, B.; Brissaud, O.

    2016-09-01

    We developed a radiative transfer model that simulates in VIS/NIR the bidirectional reflectance of a contaminated slab layer of ice overlaying a granular medium, under geometrical optics conditions to study martian ices.

  16. Waveform effects of a metastable olivine tongue in subducting slabs

    NASA Technical Reports Server (NTRS)

    Vidale, John E.; Williams, Quentin; Houston, Heidi

    1991-01-01

    Velocity models of subducting slabs with a kinetically-depressed olivine to beta- and gamma-spinel transition are constructed, and the effect that such structures would have on teleseismic P waveforms are examined using a full-wave finite-difference method. These 2D calculations yielded waveforms at a range of distances in the downdip direction. The slab models included a wedge-shaped, low-velocity metastable olivine tongue (MOTO) to a depth of 670 km, as well as a plausible thermal anomaly; one model further included a 10-km-thick fast layer on the surface of the slab. The principal effect of MOTO is to produce grazing reflections at wide angles off the phase boundary, generating a secondary arrival 0 to 4 seconds after the initial arrival depending on the take-off angle. The amplitude and timing of this feature vary with the lateral location of the seismic source within the slab cross-section.

  17. Benchmark study for total enery electrons in thick slabs

    NASA Technical Reports Server (NTRS)

    Jun, I.

    2002-01-01

    The total energy deposition profiles when highenergy electrons impinge on a thick slab of elemental aluminum, copper, and tungsten have been computed using representative Monte Carlo codes (NOVICE, TIGER, MCNP), and compared in this paper.

  18. Analytical and Numerical Solution for a Solidifying Liquid Alloy Slab

    NASA Technical Reports Server (NTRS)

    Antar, B. N.

    1983-01-01

    Numerical and analytical solutions are presented for the temperature and concentration distributions during the solidification of a binary liquid alloy slab. The slab is taken to be of a finite depth but infinite in the horizontal direction. The solidification process is started by withdrawing a fixed amount of heat from the lower surface of the slab. The upper surface of the slab is subjected to both radiation and convective conditions. The solution gives the concentration and temperature profiles and the interface position as a function of time. Due to the smallness of the mass diffusion coefficient in the solid, the numerical solution method breaks down whenever the ratio of the diffusivities in the solid and the liquid falls below a certain value. An analytical method is developed which gives accurate solution for any value of the diffusivity ratio.

  19. 7. REINFORCED CONCRETE SLAB ROOF FROM NORTHWEST EDGE, FLAME DEFLECTOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. REINFORCED CONCRETE SLAB ROOF FROM NORTHWEST EDGE, FLAME DEFLECTOR AT RIGHT, VIEW TOWARDS SOUTHEAST. - Glenn L. Martin Company, Titan Missile Test Facilities, CaptiveTest Stand D-3, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  20. 11. REINFORCED CONCRETE SLAB ROOF, FLAME DEFLECTOR AT RIGHT, CONTROL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. REINFORCED CONCRETE SLAB ROOF, FLAME DEFLECTOR AT RIGHT, CONTROL BUILDING B AT FAR CENTER RIGHT. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-4, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  1. 9. STONE SLAB CULVERT UNDER CARRIAGE ROAD AT HORSESHOE CURVE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. STONE SLAB CULVERT UNDER CARRIAGE ROAD AT HORSESHOE CURVE NEAR GIANT SLIDE TRAIL MARKER ON AROUND-THE-MOUNTAIN LOOP. - Rockefeller Carriage Roads, Mount Desert Island, Bar Harbor, Hancock County, ME

  2. Interior view of groundfloor porch showing exposed concrete floor slab ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Interior view of ground-floor porch showing exposed concrete floor slab system, facing west. - Albrook Air Force Station, Field Officer's Quarters, West side of Dargue Avenue Circle, Balboa, Former Panama Canal Zone, CZ

  3. 31. VIEW OF CONCRETE SLAB AT WEST ENTRANCE OF WALKWAY. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    31. VIEW OF CONCRETE SLAB AT WEST ENTRANCE OF WALKWAY. '1944 JOE LANDETA' SCRATCHED INTO FRESH CONCRETE. March 1987 - Verde River Sheep Bridge, Spanning Verde River (Tonto National Forest), Cave Creek, Maricopa County, AZ

  4. 27. VAL, DETAIL OF LAUNCHER SLAB AND LAUNCHER RAIL WITH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    27. VAL, DETAIL OF LAUNCHER SLAB AND LAUNCHER RAIL WITH 7 INCH DIAMETER HOLE FOR SUPPORT CARRIAGE LOCKING PIN. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  5. 34. VAL, DETAIL OF STAIRS ON COUNTERWEIGHT SLAB WITH COUNTERWEIGHT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    34. VAL, DETAIL OF STAIRS ON COUNTERWEIGHT SLAB WITH COUNTERWEIGHT CAR RAILS ON RIGHT AND PERSONNEL CAR RAILS ON LEFT. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  6. 5. VAL LAUNCHER BRIDGE OVER LAUNCHER SLAB TAKEN FROM RESERVOIR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. VAL LAUNCHER BRIDGE OVER LAUNCHER SLAB TAKEN FROM RESERVOIR LOOKING NORTH. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  7. 49. DETAIL VIEW OF SLOPE PREPARATION FOR VARIABLEANGLE LAUNCHER SLAB ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    49. DETAIL VIEW OF SLOPE PREPARATION FOR VARIABLE-ANGLE LAUNCHER SLAB LOOKING NORTH, November 6, 1946. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  8. 8. VAL COUNTERWEIGHT CAR ON COUNTERWEIGHT SLAB AND CAMERA TOWER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. VAL COUNTERWEIGHT CAR ON COUNTERWEIGHT SLAB AND CAMERA TOWER TAKEN FROM RESERVOIR LOOKING SOUTHWEST. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  9. Casimir effect for two lossy dispersive dielectric slabs

    NASA Astrophysics Data System (ADS)

    Matloob, R.; Keshavarz, A.; Sedighi, D.

    1999-11-01

    The electromagnetic field is quantized using the Green's-function method for the geometry of a Fabry-Perot cavity, made up of two identical lossy dispersive slabs of finite thickness. The dielectric functions of the slabs are assumed to be an arbitrary complex function of frequency obeying causality requirements. The attractive Casimir force between the two slabs is calculated by the help of the latter field operators, via evaluating the difference between the vacuum pressures on both sides of each slab. Special attention is paid to the limiting case of the Casimir effect for two conducting plates. The Lorentz model of the dielectric function is used to demonstrate the variation of the force in terms of plasma frequency. The Casimir force expression is also related to the imaginary part of the response function. The latter expression is used to introduce the repulsive Casimir force between two conducting plates located inside a Fabry-Perot cavity.

  10. An enhanced HOWFARLESS option for DOSXYZnrc simulations of slab geometries

    SciTech Connect

    Babcock, Kerry; Cranmer-Sargison, Gavin; Sidhu, Narinder

    2008-09-15

    The Monte Carlo code DOSXYZnrc is a valuable instrument for calculating absorbed dose within a three-dimensional Cartesian geometry. DOSXYZnrc includes several variance reduction techniques used to increase the efficiency of the Monte Carlo calculation. One such technique is HOWFARLESS which is used to increase the efficiency of beam commissioning calculations in homogeneous phantoms. The authors present an enhanced version of HOWFARLESS which extends the application to include phantoms inhomogeneous in one dimension. When the enhanced HOWFARLESS was used, efficiency increases as high as 14 times were observed without any loss in dose accuracy. The efficiency gains of an enhanced HOWFARLESS simulation was found to be dependent on both slab geometry and slab density. As the number of two-dimensional voxel layers per slab increases, so does the efficiency gain. Also, as the mass density of a slab is decreased, the efficiency gains increase.

  11. High frequency seismic waves and slab structures beneath Italy

    NASA Astrophysics Data System (ADS)

    Sun, Daoyuan; Miller, Meghan S.; Piana Agostinetti, Nicola; Asimow, Paul D.; Li, Dunzhu

    2014-04-01

    Tomographic images indicate a complicated subducted slab structure beneath the central Mediterranean where gaps in fast velocity anomalies in the upper mantle are interpreted as slab tears. The detailed shape and location of these tears are important for kinematic reconstructions and understanding the evolution of the subduction system. However, tomographic images, which are produced by smoothed, damped inversions, will underestimate the sharpness of the structures. Here, we use the records from the Italian National Seismic Network (IV) to study the detailed slab structure. The waveform records for stations in Calabria show large amplitude, high frequency (f>5 Hz) late arrivals with long coda after a relatively low-frequency onset for both P and S waves. In contrast, the stations in the southern and central Apennines lack such high frequency arrivals, which correlate spatially with the central Apennines slab window inferred from tomography and receiver function studies. Thus, studying the high frequency arrivals provides an effective way to investigate the structure of slab and detect possible slab tears. The observed high frequency arrivals in the southern Italy are the strongest for events from 300 km depth and greater whose hypocenters are located within the slab inferred from fast P-wave velocity perturbations. This characteristic behavior agrees with previous studies from other tectonic regions, suggesting the high frequency energy is generated by small scale heterogeneities within the slab which act as scatterers. Furthermore, using a 2-D finite difference (FD) code, we calculate synthetic seismograms to search for the scale, shape and velocity perturbations of the heterogeneities that may explain features observed in the data. Our preferred model of the slab heterogeneities beneath the Tyrrhenian Sea has laminar structure parallel to the slab dip and can be described by a von Kármán function with a down-dip correlation length of 10 km and 0.5 km in

  12. The fundamental constants of orthotropic affine plate/slab equations

    NASA Technical Reports Server (NTRS)

    Brunelle, E. J.

    1984-01-01

    The global constants associated with orthotropic slab/plate equations are discussed, and the rotational behavior of the modulus/compliance components associated with orthotropic slabs/plates are addressed. It is concluded that one cluster constant is less than or equal to unity for all physically possible materials. Rotationally anomalous behavior is found in two materials, and a simple inequality which can be used to identify regular or anomalous behavior is presented and discussed in detail.

  13. Development of common conversion point stacking of receiver functions for detecting subducted slabs

    NASA Astrophysics Data System (ADS)

    Abe, Y.; Ohkura, T.; Hirahara, K.; Shibutani, T.

    2010-12-01

    In subduction zones, the subducting slabs are thought to convey fluid into the mantle wedge to cause arc volcanism (Hasegawa et al., 2008. Iwamori, 2007). Kawakatsu & Watada (2007) examined the Pacific slab subducting beneath northeast Japan with receiver function (RF) analysis, and revealed where the hydrated oceanic crust and the serpentinized mantle wedge exist. In the other subduction zones, it is also essential to examine subducting slabs for better understanding of water transportation and volcanic activities. In this study, we develop a new method to migrate RFs in order to examine subducting slabs with high dip angle (Abe et al., submitted to GJI) and apply this method to examination of the Philippine Sea slab (PHS). The RF technique is one of the useful methods to obtain seismic velocity discontinuities. Ps phases converted at discontinuities in a teleseismic coda can be detected by RF analysis. RFs are usually converted to depth domain assuming a 1-d velocity structure, and the geometry of discontinuities is obtained (e.g. Yamauchi et al., 2003). In subduction zones, however, subducting slabs usually dip, and we should take into account the refraction of seismic waves at dipping interfaces. Therefore, we use the multi-stage fast marching method (FMM, de Kool et al., 2006) to convert RFs into depth domain. We stack transverse RFs, since polarity of them does not change depending on their dip angles and they are better at detecting phases converted at dipping interfaces than radial RFs. We have confirmed that this method works properly with synthetic test. We apply our method to waveform data observed in Kyushu, Japan, where PHS is subducting toward WNW and the Wadati-Benioff zone dips at 30° at depths up to 80 km, and dips at 70° at depths between 80 km and 170 km. We obtain a vertical section, on which RF amplitude is projected, across central part of Kyushu perpendicular to the depth contour of the Wadati-Benioff zone. On the section, positive peaks of

  14. Characterizing Seismic Anisotropy across the Peruvian Flat-Slab Subduction Zone: Implications for the Dynamics of Flat-Slabs

    NASA Astrophysics Data System (ADS)

    Eakin, Caroline; Long, Maureen; Beck, Susan; Wagner, Lara; Tavera, Hernando

    2014-05-01

    Although 10% of subduction zones worldwide today exhibit shallow or flat subduction, we are yet to fully understand how and why these slabs go flat. An excellent study location for such a problem is in Peru, where the largest region of flat-subduction currently exists, extending ~1500 km in length (from 3 °S to 15 °S) and ~300 km in width. Across this region we investigate the pattern of seismic anisotropy, an indicator for past and/or ongoing deformation in the upper mantle. To achieve this we conduct shear wave splitting analyzes at 40 broadband stations from the PULSE project (PerU Lithosphere and Slab Experiment). These stations were deployed for 2+ years across the southern half of the Peruvian flat-slab region. We present detailed shear wave splitting results for both teleseismic events (such as SKS, SKKS, PKS, sSKS) that sample the upper mantle column beneath the stations as well as direct S from local events that constrain anisotropy in the upper portion of the subduction zone. We analyze the variability of our results with respect to initial polarizations, ray paths, and frequency content as well as spatial variability between stations as the underlying slab morphology changes. Teleseismic results show predominately NW-SE fast polarizations (trench oblique to sub-parallel) over the flat-slab region east of Lima. These results are consistent with observations of more complex multi-layered anisotropy beneath a nearby permanent station (NNA) that suggests a trench-perpendicular fast direction in the lowest layer in the sub-slab mantle. Further south, towards the transition to steeper subduction, the splitting pattern becomes increasingly dominated by null measurements. Over to the east however, beyond Cuzco, where the mantle wedge might begin to play a role, we record fast polarizations quasi-parallel to the local slab contours. Local S results indicate the presence of weak (delay times typically less than 0.5 seconds) and heterogeneous supra-slab

  15. Scaling of Electron Thermal Conductivity during the Transition between Slab and Mixed Slab-Toroidal ETG Mode

    NASA Astrophysics Data System (ADS)

    Sokolov, Vladimir; Balbaky, Abed; Sen, Amiya K.

    2015-11-01

    Transition from the slab to the toroidal branch of the electron temperature gradient (ETG) mode has been successfully achieved in a basic experiment in Columbia Linear Machine CLM. We found a modest increase in saturated ETG potential fluctuations (~ 2 ×) and a substantial increase in the power density of individual mode peaks (~ 4 - 5 ×) with increased levels of curvature. We have obtained a set of experimental scalings for electron thermal conductivity χ⊥e as a function of the inverse radius of curvature Rc-1 for different fluctuation levels of the initial slab ETG mode. We found that thermal conductivity for pure slab modes is larger than it is for mixed slab-toroidal ETG modes with the same level of mode fluctuation. This effective reduction in diffusive transport can be partly explained by the flute nature of the toroidal ETG mode. This research was supported by the Department of Electrical Engineering of Columbia University.

  16. Coherent combination of slab-coupled optical waveguide lasers

    NASA Astrophysics Data System (ADS)

    Huang, Robin K.; Chann, Bien; Missaggia, Leo J.; Augst, Steven J.; Connors, Michael K.; Turner, George W.; Sanchez-Rubio, Antonio; Donnelly, Joseph P.; Hostetler, John L.; Miester, Carl; Dorsch, Friedhelm

    2009-02-01

    A long-standing challenge for semiconductor lasers is scaling the optical power and brightness of many diode lasers by coherent beam combination. Because single-mode semiconductor lasers have limited power available from a single element, there is a strong motivation to coherently combine the outputs of many elements for applications including industrial lasers for materials processing, free space optical communications, and defense. Despite the fact that such a coherently-combined source is potentially the most efficient laser, coherent combination of semiconductor lasers is generally considered to be difficult, since precise phase control is required between elements. We describe our approach to coherent combination of semiconductor lasers. The Slab-Coupled Optical Waveguide Laser (SCOWL), invented at Lincoln Laboratory, is used as the single-mode diode laser element for coherent combination. With a 10-element SCOWL array, coherently combined output power as high as 7 W in continuous wave using an external cavity has been demonstrated, which is the highest output level achieved using a coherent array of semiconductor lasers. We are currently working on a related approach to scale the coherent power up to 100 W.

  17. Standing sausage modes in curved coronal slabs

    NASA Astrophysics Data System (ADS)

    Pascoe, D. J.; Nakariakov, V. M.

    2016-09-01

    Context. Magnetohydrodynamic waveguides such as dense coronal loops can support standing modes. The ratios of the periods of oscillations for different longitudinal harmonics depend on the dispersive nature of the waveguide and so may be used as a seismological tool to determine coronal parameters. Aims: We extend models of standing sausage modes in low β coronal loops to include the effects of loop curvature. The behaviour of standing sausage modes in this geometry is used to explain the properties of observed oscillations that cannot be accounted for using straight loop models. Methods: We perform 2D numerical simulations of an oscillating coronal loop, modelled as a dense slab embedded in a potential magnetic field. The loop is field-aligned and so experiences expansion with height in addition to being curved. Standing sausage modes are excited by compressive perturbations of the loop and their properties are studied. Results: The spatial profiles of standing sausage modes are found to be modified by the expanding loop geometry typical for flaring loops and modelled by a potential magnetic field in our simulations. Longitudinal harmonics of order n > 1 have anti-nodes that are shifted towards the loop apex and the amplitude of anti-nodes near the loop apex is smaller than those near the loop footpoints. Conclusions: We find that the observation of standing sausage modes by the Nobeyama Radioheliograph in a flaring coronal loop on 12 January 2000 is consistent with interpretation in terms of the global mode (n = 1) and third harmonic (n = 3). This interpretation accounts for the period ratio and spatial structure of the observed oscillations.

  18. An ancient slab visible from the transition zone to the deep mantle beneath the southern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Sandvol, E. A.; Skobeltsyn, G.; Turkelli, N.; Polat, G.; Yetirmishli, G.; Godoladze, T.; Mellors, R. J.; Gok, R.

    2014-12-01

    Ancient subducted tectonic plates have been observed in past seismic images of the mantle beneath North America and Eurasia including some that subducted before the end of the Mesozoic Era. It is likely that other ancient slab structures have remained largely hidden, particularly in the seismic-data-limited regions beneath the vast oceans in the southern hemisphere. Here we present a new global tomographic image, which shows a slab-like structure beneath the southern Indian Ocean with coherency from the upper mantle transition zone to the core-mantle boundary region - with striking similarities to past and current images of the Farallon slab. Based on the image and additional geoscientific observations, we postulate that the structure is an oceanic plate that sank into the mantle along a 7000-km intra-oceanic subduction zone that migrated southwestward across the ancient Tethys Ocean in the Mesozoic Era, perhaps beginning prior to 200 Ma. Slab material still trapped in the transition zone is positioned near the former edge of East Gondwana ca. 140 Ma suggesting that subduction terminated near the margin of the ancient continent prior to breakup and subsequent dispersal of its subcontinents. If our interpretation is correct, the slab likely represents the first of its kind with extensive transition zone stagnation (exceeding 100 million years) followed by eventual penetration into the lower mantle. It suggests that some slabs may sink through the mantle much slower than previously believed and may reside intact in the shallow mantle if left undisturbed by subsequent subduction episodes. We postulate other dynamic mechanisms that may be involved and a potential link to Indian Ocean MORB chemistry. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-675725

  19. An ancient slab visible from the transition zone to the deep mantle beneath the southern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Simmons, N. A.; Myers, S.; Johannesson, G.; Matzel, E.; Grand, S.

    2015-12-01

    Ancient subducted tectonic plates have been observed in past seismic images of the mantle beneath North America and Eurasia including some that subducted before the end of the Mesozoic Era. It is likely that other ancient slab structures have remained largely hidden, particularly in the seismic-data-limited regions beneath the vast oceans in the southern hemisphere. Here we present a new global tomographic image, which shows a slab-like structure beneath the southern Indian Ocean with coherency from the upper mantle transition zone to the core-mantle boundary region - with striking similarities to past and current images of the Farallon slab. Based on the image and additional geoscientific observations, we postulate that the structure is an oceanic plate that sank into the mantle along a 7000-km intra-oceanic subduction zone that migrated southwestward across the ancient Tethys Ocean in the Mesozoic Era, perhaps beginning prior to 200 Ma. Slab material still trapped in the transition zone is positioned near the former edge of East Gondwana ca. 140 Ma suggesting that subduction terminated near the margin of the ancient continent prior to breakup and subsequent dispersal of its subcontinents. If our interpretation is correct, the slab likely represents the first of its kind with extensive transition zone stagnation (exceeding 100 million years) followed by eventual penetration into the lower mantle. It suggests that some slabs may sink through the mantle much slower than previously believed and may reside intact in the shallow mantle if left undisturbed by subsequent subduction episodes. We postulate other dynamic mechanisms that may be involved and a potential link to Indian Ocean MORB chemistry. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-675725

  20. Multiphase Modeling in the Fate of Detached Slabs in the India-Asia Collision

    NASA Astrophysics Data System (ADS)

    Shahnas, M.

    2004-05-01

    P-wave velocity anomalies under Tibet, India and north of Indian Ocean reveals the existence of cold patches at different depths ranging from one to two thousand km. These are interpreted as fossil detached slabs due to former subducting Tethyan oceanic lithosphere, while a regional northward-dipping slab under the Hindu Kush region in northeastern Afghanistan and southern Tajikistan in the entire upper mantle is believed to be the remnants of delaminated sub-continental Indian lithosphere (Van der Voo et al., 1999). In our previous studies we have shown the influence of depth-dependent viscosity profiles on the fate of these descending slabs which were believed to have been recycled in deep mantle during the last 45 Myr, past from India-Asia collision. In this work we study the influence of double-phase transition at 400 km and 670 km depths and its contribution for this retarding effect. Employing finite differences in a full cylindrical shell we compare the results of double-phase and single-phase boundary models with the results of no-phase boundary models with both constant and depth-dependent viscosity profiles.

  1. Exterior Rigid Foam Insulation at the Edge of a Slab Foundation, Fresno, California (Fact Sheet)

    SciTech Connect

    Not Available

    2013-10-01

    Exterior rigid foam insulation at the edge of the slab foundation was a unique feature for this low-load, unoccupied test house in a hot-dry climate and may be more appropriate for climates with higher heating loads. U.S. Department of Energy Building America research team IBACOS worked with National Housing Quality Award winner Wathen-Castanos Hybrid Homes, Inc., to assess the performance of this feature in a single-family detached ranch house with three bedrooms and two full bathrooms constructed on a slab-on-grade foundation in Fresno, California. One challenge during installation of the system was the attachment of the butyl flashing to the open framing. To solve this constructability issue, the team added a nailer to the base of the wall to properly attach and lap the flashing. In this strategy, R-7.5, 1.5-in.-thick extruded polystyrene was installed on the exterior of the slab for a modeled savings of 4,500 Btu/h on the heating load.

  2. The development of slabs in the upper mantle: Insights from numerical and laboratory experiments

    NASA Astrophysics Data System (ADS)

    Becker, Thorsten W.; Faccenna, Caludio; O'Connell, Richard J.; Giardini, Domenico

    1999-07-01

    We have performed numerical and laboratory experiments to model subduction of oceanic lithosphere in the upper mantle from its beginnings as a gravitational instability to the fully developed slab. A two-dimensional finite element code is applied to model Newtonian creep in the numerical experiments. Scaled analog media are used in the laboratory, a sand mixture models the brittle crust, silicone putty simulates creep in the lower crust and mantle lithosphere, and glucose syrup is the asthenosphere analog. Both model approaches show similar results and reproduce first-order observations of the subduction process in nature based on density and viscosity heterogeneities in a Stokes flow model. Subduction nucleates slowly and a pronounced slab forms only when the viscosity contrast between oceanic plate and mantle is below a threshold. We find that the subduction velocity and angle are time-dependent and increase roughly exponentially over tens of millions of years before the slab reaches the 670-km discontinuity. The style of subduction is controlled by the prescribed velocity of convergence, the density contrast between the plates, and the viscosity contrast between the oceanic plate and the mantle. These factors can be combined in the buoyancy number F which expresses the ratio between driving slab pull and resisting viscous dissipation in the oceanic plate. Variations in F control the stress in the plates, the speed and the dip of subduction, and the rate of trench retreat, reproducing the contrasting styles of subduction observed in nature. The subduction rate is strongly influenced by the work of bending the lithosphere as it subducts.

  3. Modeling the thin-slab continuous-casting mold

    SciTech Connect

    O'Connor, T.G. . Applied Superconductivity Group); Dantzig, J.A. . Dept. of Mechanical and Industrial Engineering)

    1994-06-01

    A three-dimensional mathematical model has been developed to compute the thermomechanical state in the mold of thin-slab continuous casters. The thin-slab mold differs from those used in conventional slab casters in that the upper portion of the broad side walls defines a funnel-shaped chamber which allows the nozzle to be submerged into the liquid metal. The chamber converges with distance down the mold, reducing to the rectangular cross section of the finished casting near the mold exit. The new mold, along with casting speeds up to 6 m/min, allows slabs to be cast 50--60 mm thick, compared with 150 to 350 mm in conventional continuous slab casting. However, the mold shape and high casting speed lead to higher mold temperatures and shorter mold life than are found in conventional slab casters. In this article, the author develop mathematical models of the process to determine the role of various process parameters in determining the mold life. Finite-element analysis is used to determine the temperatures in the mold and cast slab, and these data are then used in an elastic-viscoplastic analysis to investigate the deformation of the mold wall in service. Cyclic inelastic strains up to 1.75 pct are found in a region below the meniscus along the funnel edge. These large strains result from the combination of locally high temperatures coupled with geometric restraint of the mold. The deformation leads to short mold life because of thermal fatigue cracking of the mold. The computed locations and time to failure of the mold in fatigue agree very well with observations of the appearance of mold surface cracks in an operating caster. The models are also used to develop an improved mold design.

  4. Modeling the thin-slab continuous-casting mold

    NASA Astrophysics Data System (ADS)

    Oconnor, Thomas G.; Dantzig, Jonathan A.

    1994-06-01

    A three-dimensional mathematical model has been developed to compute the thermomechanical state in the mold of thin-slab continuous casters. The thin-slab mold differs from those used in conventional slab casters in that the upper portion of the broad side walls defines a funnel-shaped chamber which allows the nozzle to be submerged into the liquid metal. The chamber converges with distance down the mold, reducing to the rectangular cross section of the finished casting near the mold exit. The new mold, along with casting speeds up to 6 m/min, allows slabs to be cast 50 60 mm thick, compared with 150 to 350 mm in conventional continuous slab casting. However, the mold shape and high casting speed lead to higher mold temperatures and shorter mold life than are found in conventional slab casters. In this article, we develop mathematical models of the process to determine the role of various process parameters in determining the mold life. Finite-element analysis is used to determine the temperatures in the mold and cast slab, and these data are then used in an elastic-viscoplastic analysis to investigate the deformation of the mold wall in service. Cyclic inelastic strains up to 1.75 Pct are found in a region below the meniscus along the funnel edge. These large strains result from the combination of locally high temperatures coupled with geometric restraint of the mold. The deformation leads to short mold life because of thermal fatigue cracking of the mold. The computed locations and time to failure of the mold in fatigue agree very well with observations of the appearance of mold surface cracks in an operating caster. The models are also used to develop an improved mold design.

  5. Can slabs melt beneath forearcs in hot subduction zones?

    NASA Astrophysics Data System (ADS)

    Ribeiro, J.; Maury, R.; Gregoire, M.

    2015-12-01

    At subduction zones, thermal modeling predict that the shallow part of the downgoing oceanic crust (< 80 - 100 km depth to the slab) is usually too cold to cross the water-rich solidus and melts beneath the forearc. Yet, the occasional occurrence of adakites, commonly considered as slab melts, in the forearc region challenges our understanding of the shallow subduction processes. Adakites are unusual felsic rocks commonly associated with asthenospheric slab window opening or fast subduction of young (< 25 Ma) oceanic plate that enable slab melting at shallow depths; but their genesis has remained controversial. Here, we present a new approach that provides new constraints on adakite petrogenesis in hot subduction zones (the Philippines) and above an asthenospheric window (Baja California, Mexico). We use amphibole compositions to estimate the magma storage depths and the composition of the parental melts to test the hypothesis that adakites are pristine slab melts. We find that adakites from Baja California and Philippines formed by two distinct petrogenetic scenarios. In Baja California, hydrous mantle melts mixed/mingled with high-pressure (HP) adakite-type, slab melts within a lower crustal (~30 km depth) magma storage region before stalling into the upper arc crust (~7-15 km depth). In contrast, in the Philippines, primitive mantle melts stalled and crystallized within lower and upper crustal magma storage regions to produce silica-rich melts with an adakitic signature. Thereby, slab melting is not required to produce an adakitic geochemical fingerprint in hot subduction zones. However, our results also suggest that the downgoing crust potentially melted beneath Baja California.

  6. Continental collision and slab break-off: A comparison of 3-D numerical models with observations

    NASA Astrophysics Data System (ADS)

    van Hunen, Jeroen; Allen, Mark B.

    2011-02-01

    Conditions and dynamics of subduction-collision and subsequent 3-D slab break-off and slab tear propagation are quantified, for the first time, using fully dynamic numerical models. Model results indicate that collision after the subduction of old, strong subducting oceanic slab leads to slab break-off at 20-25 Myr after the onset of continental collision, and subsequently a slab tear migrates more or less horizontally through the slab with a propagation speed of 100-150 mm/yr. In contrast, young, weak oceanic slabs show the first break-off already 10 Myr after continental collision, and can experience tear migration rates up to 800 mm/yr. Slab strength plays a more important role in the timing of slab break-off and the speed of a propagating slab tear than (negative) slab buoyancy does. Slab break-off is viable even for slabs that are supported by the viscosity jump and phase change between the upper and lower mantle. The density of the oceanic slab and the subducting continental block is important for the amount of continental subduction and the depth of slab break-off. A 40-km thick continental crust can be buried to depths greater than 200 km, although this maximum depth is significantly less for younger or very weak slabs, or thicker continental crust. Slab break-off typically starts at a depth of 300 km, mostly independent of mantle rheology, but, like continental crustal burial, can be shallower for young or buoyant plates. Our 3-D models illustrate how, due to the difference in necking in 2-D and 3-D, break-off has an intrinsic small preference to start as a slab window within the slab's interior, rather than as a slab tear at the slab edge. However, any significant asymmetry in the collision setting, e.g. earlier collision at one end of the subduction zone, would override this, and leads to slab tearing starting near one edge of the slab. These results put important new constraints on the dynamics of the collision and subsequent slab break-off for modern

  7. Effects of Crustal Densification in Warm Slabs on In-slab Earthquakes and Episodic Tremors and Slips

    NASA Astrophysics Data System (ADS)

    Wang, K.

    2003-12-01

    During subduction, dehydration may facilitate earthquake rupture in both the slab crust and slab mantle. The up to 15% rock densification that accompanies the metabasalt-eclogite transformation is expected to have several mechanical consequences. In warm slabs such as Cascadia and Nankai, this transformation and mantle serpentine breakdown begin at rather shallow depths (30 - 50 km). The pervasively hydrated upper crust transforms to eclogite under equilibrium conditions, but the transformation of the anhydrous parts of the lower crust is kinetically delayed to greater depths. Therefore, densification begins in a thin layer along the top of the slab. Volume reduction gives rise to an equivalent stretching force in the thin layer in all slab-parallel directions, activating existing faults and developing new fractures. Analogous to a weak layer sandwiched between, and bonded to, two strong layers under stretching, fracture spacing in the weak layer scales with the layer thickness. The theory predicts that the densified thin layer must be ~{!0~}shattered~{!1~}. The shattered upper crust may have numerous small earthquakes but does not favor large ruptures. In contrast, the much more uniform lower crust and mantle can host larger ruptures, although seismic ruptures occur only in the limited hydrated parts. This explains the observation that relatively few earthquakes deeper inside the slab tend to have larger magnitudes than those just below the slab surface. For example, three recent damaging events (1999 Oaxaca, Mexico; 2001 Geiyo, Nankai; 2001 Nisqually, Cascadia) in warm slabs all occurred in the lower crust or mantle. The densification is generally a steady state process: An increasingly thinner slab moves into an increasingly thinner subduction "slot" continuously, with the downdip width of transition from normal to thinned crust scaling linearly with the subduction rate. However, at the fracture scale, the process is highly nonlinear, and there must be small

  8. Tomographic imaging of the effects of Peruvian flat slab subduction on the Nazca slab and surrounding mantle under central and southern Peru

    NASA Astrophysics Data System (ADS)

    Scire, A. C.; Zandt, G.; Beck, S. L.; Bishop, B.; Biryol, C. B.; Wagner, L. S.; Long, M. D.; Minaya, E.; Tavera, H.

    2014-12-01

    The modern central Peruvian Andes are dominated by a laterally extensive region of flat slab subduction. The Peruvian flat slab extends for ~1500 km along the strike of the Andes, correlating with the subduction of the Nazca Ridge in the south and the theorized Inca Plateau in the north. We have used data from the CAUGHT and PULSE experiments for finite frequency teleseismic P- and S-wave tomography to image the Nazca slab in the upper mantle below 95 km depth under central Peru between 10°S and 18°S as well as the surrounding mantle. Since the slab inboard of the subducting Nazca Ridge is mostly aseismic, our results provide important constraints on the geometry of the subducting Nazca slab in this region. Our images of the Nazca slab suggest that steepening of the slab inboard of the subducting Nazca Ridge locally occurs ~100 km further inland than was indicated in previous studies. The region where we have imaged the steepening of the Nazca slab inboard of the Nazca Ridge correlates with the location of the Fitzcarrald Arch, a long wavelength upper plate topographic feature which has been suggested to be a consequence of ridge subduction. When the slab steepens inboard of the flat slab region, it does so at a very steep (~70°) angle. The transition from the Peruvian flat slab to the more normally dipping slab south of 16°S below Bolivia is characterized by an abrupt bending of the slab anomaly in the mantle in response to the shift from flat to normal subduction. The slab anomaly appears to be intact south of the Nazca Ridge with no evidence for tearing of the slab in response to the abrupt change in slab dip. A potential tear in the slab is inferred from an observed offset in the slab anomaly north of the Nazca Ridge extending subparallel to the ridge axis between 130 and 300 km depth. A high amplitude (-5-6%) slow S-wave velocity anomaly is observed below the projection of the Nazca Ridge. This anomaly appears to be laterally confined to the mantle

  9. ORNL Soils Remediation and Slabs Removal - The Bridge from D and D to Redevelopment - 12342

    SciTech Connect

    Travaglini, Mike; Halsey, Pat; Conger, Malinda; Schneider, Ken

    2012-07-01

    The landscape of the Oak Ridge National Laboratory (ORNL) has dramatically changed over the past 2 years with demolition of aging facilities in the Central Campus. Removal of these infrastructure legacies was possible due to an influx of DOE-Environmental Management funding through the American Recovery and Reinvestment Act of 2009 (ARRA). Facility D and D traditionally removes everything down to the building slab, and the Soils and Sediments Program is responsible for slabs, below-grade footers and sub-grade structures, abandoned waste utilities, and soils contaminated above certain risk levels that must be removed before the site can be considered for redevelopment. DOE-EM has used a combination of base and ARRA funding to facilitate the clean-up process in ORNL's 2000 Area. Demolition of 13 buildings in the area was funded by the ARRA. Characterization of the remaining slabs, underground pipelines and soils was funded by DOE-EM base funding. Additional ARRA funding was provided for the removal of the slabs, pipelines and contaminated soils. Removal work is in progress and consists of removing and disposing of approximately 7,650 cubic meters (m{sup 3}) of concrete, 2,000 m{sup 3} of debris, and 400 m{sup 3} of contaminated soil. Immediately adjacent to the 2000 Area is the Oak Ridge Science and Technology Park and the modernized ORNL western campus. The Science and Technology Park is the only private sector business and technology park located within the footprint of a national laboratory. The completion of this work will not only greatly reduce the risk to the ORNL campus occupants but also allow this much sought after space to be available for redevelopment and site reuse efforts at ORNL. Demolition of aging facilities enabled by injection of ARRA funding has significantly altered the landscape at ORNL while reducing risk to laboratory personnel and operations and providing valuable central campus land parcels for redevelopment to expand and enhance the

  10. Fossil slabs attached to unsubducted fragments of the Farallon plate

    PubMed Central

    Wang, Yun; Forsyth, Donald W.; Rau, Christina J.; Carriero, Nina; Schmandt, Brandon; Gaherty, James B.; Savage, Brian

    2013-01-01

    As the Pacific–Farallon spreading center approached North America, the Farallon plate fragmented into a number of small plates. Some of the microplate fragments ceased subducting before the spreading center reached the trench. Most tectonic models have assumed that the subducting oceanic slab detached from these microplates close to the trench, but recent seismic tomography studies have revealed a high-velocity anomaly beneath Baja California that appears to be a fossil slab still attached to the Guadalupe and Magdalena microplates. Here, using surface wave tomography, we establish the lateral extent of this fossil slab and show that it is correlated with the distribution of high-Mg andesites thought to derive from partial melting of the subducted oceanic crust. We also reinterpret the high seismic velocity anomaly beneath the southern central valley of California as another fossil slab extending to a depth of 200 km or more that is attached to the former Monterey microplate. The existence of these fossil slabs may force a reexamination of models of the tectonic evolution of western North America over the last 30 My. PMID:23509274

  11. Fossil slabs attached to unsubducted fragments of the Farallon plate.

    PubMed

    Wang, Yun; Forsyth, Donald W; Rau, Christina J; Carriero, Nina; Schmandt, Brandon; Gaherty, James B; Savage, Brian

    2013-04-01

    As the Pacific-Farallon spreading center approached North America, the Farallon plate fragmented into a number of small plates. Some of the microplate fragments ceased subducting before the spreading center reached the trench. Most tectonic models have assumed that the subducting oceanic slab detached from these microplates close to the trench, but recent seismic tomography studies have revealed a high-velocity anomaly beneath Baja California that appears to be a fossil slab still attached to the Guadalupe and Magdalena microplates. Here, using surface wave tomography, we establish the lateral extent of this fossil slab and show that it is correlated with the distribution of high-Mg andesites thought to derive from partial melting of the subducted oceanic crust. We also reinterpret the high seismic velocity anomaly beneath the southern central valley of California as another fossil slab extending to a depth of 200 km or more that is attached to the former Monterey microplate. The existence of these fossil slabs may force a reexamination of models of the tectonic evolution of western North America over the last 30 My.

  12. Systematic variation in the depths of slabs beneath arc volcanoes

    USGS Publications Warehouse

    England, P.; Engdahl, R.; Thatcher, W.

    2004-01-01

    The depths to the tops of the zones of intermediate-depth seismicity beneath arc volcanoes are determined using the hypocentral locations of Engdahl et al. These depths are constant, to within a few kilometres, within individual arc segments, but differ by tens of kilometres from one arc segment to another. The range in depths is from 65 km to 130 km, inconsistent with the common belief that the volcanoes directly overlie the places where the slabs reach a critical depth that is roughly constant for all arcs. The depth to the top of the intermediate-depth seismicity beneath volcanoes correlates neither with age of the descending ocean floor nor with the thermal parameter of the slab. This depth does, however, exhibit an inverse correlation with the descent speed of the subducting plate, which is the controlling factor both for the thermal structure of the wedge of mantle above the slab and for the temperature at the top of the slab. We interpret this result as indicating that the location of arc volcanoes is controlled by a process that depends critically upon the temperature at the top of the slab, or in the wedge of mantle, immediately below the volcanic arc.

  13. Fossil slabs attached to unsubducted fragments of the Farallon plate.

    PubMed

    Wang, Yun; Forsyth, Donald W; Rau, Christina J; Carriero, Nina; Schmandt, Brandon; Gaherty, James B; Savage, Brian

    2013-04-01

    As the Pacific-Farallon spreading center approached North America, the Farallon plate fragmented into a number of small plates. Some of the microplate fragments ceased subducting before the spreading center reached the trench. Most tectonic models have assumed that the subducting oceanic slab detached from these microplates close to the trench, but recent seismic tomography studies have revealed a high-velocity anomaly beneath Baja California that appears to be a fossil slab still attached to the Guadalupe and Magdalena microplates. Here, using surface wave tomography, we establish the lateral extent of this fossil slab and show that it is correlated with the distribution of high-Mg andesites thought to derive from partial melting of the subducted oceanic crust. We also reinterpret the high seismic velocity anomaly beneath the southern central valley of California as another fossil slab extending to a depth of 200 km or more that is attached to the former Monterey microplate. The existence of these fossil slabs may force a reexamination of models of the tectonic evolution of western North America over the last 30 My. PMID:23509274

  14. Optical distortions in end-pumped zigzag slab lasers.

    PubMed

    Tang, Bing; Zhou, Tangjian; Wang, Dan; Li, Mi

    2015-04-01

    Ray tracing is performed to investigate the optical distortions in the end-pumped, zigzag slab. Optical path differences caused by temperature, slab deformation, and stress birefringence are calculated under uniform pumping; the results show a steep edge in the width dimension and a thermal lens with an effective focal length as short as several meters in the thickness dimension. Dependence of depolarization on total internal reflection phase retardance as well as the slab's cut angle is studied by the Jones matrix technique; results show that although at the pumping power of 10 kW, the mean depolarization of the 2.5  mm×30  mm×150.2  mm Nd:YAG slab is generally below 3%, and it increases rapidly with pumping power. Besides, for the 0°- or 60°-cut slab, an optimal phase retardance range of 5° to 13° exists, in which the depolarization loss can be lower than 0.5%. Finally, experiments on temperature and depolarization measurements verify the numerical results. PMID:25967178

  15. Cenozoic Plume-Slab Interaction Beneath the Pacific Northwest

    NASA Astrophysics Data System (ADS)

    Obrebski, M. J.; Allen, R. M.; Hung, S.; Pollitz, F. F.

    2009-12-01

    Here we present new images of the structure beneath the Pacific Northwest obtained by inverting both compressional and shear teleseismic body waves and using finite-frequency sensitivity kernels. The models use all available seismic data from the Earthscope Transportable Array, regional seismic networks and two Flexible Array experiments (Mendocino and FACES experiments) deployed on the west coast. By picking P, S and SKS arrivals manually and estimating station-to-station relative arrival times through cross correlation of the waveforms, we select only the highest quality data. East from the Juan de Fuca slab and north from the Mendocino Triple Junction, the mantle structure is dominated by high velocity blocks that are likely to be fragments of the Farallon slab. In the middle of the slab fragments, both our compressional (DNA09-P) and shear (DNA09-S) velocity models show a continuous low velocity anomaly that extends from the Yellowstone Caldera down into the lower mantle. We interpret this feature as a deep-seated mantle plume. The striking contrast between the slab-dominated mantle north from the MTJ and the continuous deep-seated Yellowstone mantle plume suggests the plume disrupted the Farallon slab during its ascent to the surface.

  16. Effects of edge restraint on slab behavior. Final report

    SciTech Connect

    Guice, L.K.

    1986-02-01

    This study was performed in conjunction with a Federal Emergency Management Agency program to plan, design, and construct keyworker blast shelters which would be used in high-risk areas of the country during and after a nuclear attack. The shelters considered in this study were box-type structures in which damage is much more likely to occur in the roof slab than in the walls or floor. In this part of the program, the effect of edge restraint on slab behavior was investigated. The primary objective was to determine the effects of partial rotational restraint on slab strength, ductility, and mechanism of failure. Sixteen one-way, reinforced concrete plate elements were tested in a reaction structure under uniform static water pressure.

  17. Abrupt tectonics and rapid slab detachment with grain damage.

    PubMed

    Bercovici, David; Schubert, Gerald; Ricard, Yanick

    2015-02-01

    A simple model for necking and detachment of subducting slabs is developed to include the coupling between grain-sensitive rheology and grain-size evolution with damage. Necking is triggered by thickened buoyant crust entrained into a subduction zone, in which case grain damage accelerates necking and allows for relatively rapid slab detachment, i.e., within 1 My, depending on the size of the crustal plug. Thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking; oceanic lithosphere with normal or slightly thickened crust subducts without necking. The model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and/or induce abrupt continental rebound. PMID:25605890

  18. Role of Hydrogen in stagnant slabs and big mantle wedge

    NASA Astrophysics Data System (ADS)

    Ohtani, E.; Zhao, D.

    2008-12-01

    Recent seismic tomography data imply that subducting slabs are stagnant at some regions such as beneath Japan and Northeast China [1, 2]. The stagnant slab can have an important effect on the overlying transition zone and upper mantle. A big mantle wedge (BMW) model has been proposed by Zhao [2], in which the stagnant slab in the transition zone could play an essential role in the intra-plate volcanic activities overlying the slab. Water released by the stagnant slab could be important for such igneous activities, such as Mt. Changbai in Northeast China. In cold subducting slabs, several hydrous minerals together with nominally anhydrous minerals accommodate OH and transport water into the transition zone [3]. The effect of dehydration of the stagnant slab has been analyzed by Richard et al. [4]. They argued that warming of the stagnant slab due to heat conduction could play an important role for the slab dehydration, and local oversaturation could be achieved due to decrease of the water solubility in minerals with temperature, and fluid can be formed in the overlying transition zone. We determined the hydrogen diffusion in wadsleyite and ringwoodite under the transition zone conditions in order to clarify the deep processes of the stagnant slabs, and found that diffusion rates of hydrogen are comparable with that of olivine [5]. We also determined the dihedral angle of aqueous fluid between wadsleyite grains and majorite grains under the transition zone conditions. The dihedral angles are very small, around 20-40 degrees, indicating that the oversaturated fluids can move rapidly by the percolation mechanism in the transition zone. The fluids moved to the top of the 410 km discontinuity can generate heavy hydrous melts due to a larger depression of the wet solidus at the base of the upper mantle [6]. Gravitationally stable hydrous melts can be formed at the base of the upper mantle, which is consistent with seismological observations of the low velocity beneath

  19. Abrupt tectonics and rapid slab detachment with grain damage.

    PubMed

    Bercovici, David; Schubert, Gerald; Ricard, Yanick

    2015-02-01

    A simple model for necking and detachment of subducting slabs is developed to include the coupling between grain-sensitive rheology and grain-size evolution with damage. Necking is triggered by thickened buoyant crust entrained into a subduction zone, in which case grain damage accelerates necking and allows for relatively rapid slab detachment, i.e., within 1 My, depending on the size of the crustal plug. Thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking; oceanic lithosphere with normal or slightly thickened crust subducts without necking. The model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and/or induce abrupt continental rebound.

  20. Requalification analysis of a circular composite slab for seismic load

    SciTech Connect

    Srinivasan, M.G.; Kot, C.A.

    1992-11-01

    The circular roof slab of an existing facility was analyzed to requalify the structure for supporting a significant seismic load that it was not originally designed for. The slab has a clear span of 66 ft and consists of a 48 in thick reinforced concrete member and a steel liner plate. Besides a number of smaller penetrations, the slab contains two significant cutouts: a 9 ft square opening and a 3 ft dia hole. The issues that complicated the analysis of this non-typical structure, i.e., composite action and nonlinear stiffness of reinforced concrete (R. C.) sections, are discussed. It was possible to circumvent the difficulties by making conservative and simplifying assumptions. If codes incorporate guidelines on practical methods for dynamic analysis of R. C. structures, some of the unneeded conservatism could be eliminated in future designs.

  1. Dynamic triggering of deep earthquakes within a fossil slab

    NASA Astrophysics Data System (ADS)

    Cai, Chen; Wiens, Douglas A.

    2016-09-01

    The 9 November 2009 Mw 7.3 Fiji deep earthquake is the largest event in a region west of the Tonga slab defined by scattered seismicity and velocity anomalies. The main shock rupture was compact, but the aftershocks were distributed along a linear feature at distances of up to 126 km. The aftershocks and some background seismicity define a sharp northern boundary to the zone of outboard earthquakes, extending westward toward the Vitiaz deep earthquake cluster. The northern earthquake lineament is geometrically similar to tectonic reconstructions of the relict Vitiaz subduction zone at 8-10 Ma, suggesting the earthquakes are occurring in the final portion of the slab subducted at the now inactive Vitiaz trench. A Coulomb stress change calculation suggests many of the aftershocks were dynamically triggered. We propose that fossil slabs contain material that is too warm for earthquake nucleation but may be near the critical stress susceptible to dynamic triggering.

  2. Abrupt tectonics and rapid slab detachment with grain damage

    PubMed Central

    Bercovici, David; Schubert, Gerald; Ricard, Yanick

    2015-01-01

    A simple model for necking and detachment of subducting slabs is developed to include the coupling between grain-sensitive rheology and grain-size evolution with damage. Necking is triggered by thickened buoyant crust entrained into a subduction zone, in which case grain damage accelerates necking and allows for relatively rapid slab detachment, i.e., within 1 My, depending on the size of the crustal plug. Thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking; oceanic lithosphere with normal or slightly thickened crust subducts without necking. The model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and/or induce abrupt continental rebound. PMID:25605890

  3. Systematic effects induced by a flat isotropic dielectric slab.

    PubMed

    Macculi, Claudio; Zannoni, Mario; Peverini, Oscar Antonio; Carretti, Ettore; Tascone, Riccardo; Cortiglioni, Stefano

    2006-07-20

    The instrumental polarization induced by a flat isotropic dielectric slab in microwave frequencies is discussed. We find that, in spite of its isotropic nature, such a dielectric can produce spurious polarization either by transmitting incoming anisotropic diffuse radiation or emitting when it is thermally inhomogeneous. We present evaluations of instrumental polarization generated by materials usually adopted in radio astronomy, by using the Mueller matrix formalism. As an application, results for different slabs in front of a 32 GHz receiver are discussed. Such results are based on measurements of their complex dielectric constants. We evaluate that a 0.33 cm thick Teflon slab introduces negligible spurious polarization (<2.6 x 10(-5) in transmission and <6 x 10(-7) in emission), even minimizing the leakage (<10(-8) from Q to U Stokes parameters, and vice versa) and the depolarization (approximately 1.3 x 10(-3)).

  4. Slab detachment of subducted Indo-Australian plate beneath Sunda arc, Indonesia

    NASA Astrophysics Data System (ADS)

    Kundu, Bhaskar; Gahalaut, V. K.

    2011-04-01

    Necking, tearing, slab detachment and subsequently slab loss complicate the subduction zone processes and slab architecture. Based on evidences which include patterns of seismicity, seismic tomography and geochemistry of arc volcanoes, we have identified a horizontal slab tear in the subducted Indo-Australian slab beneath the Sunda arc. It strongly reflects on trench migration, and causes along-strike variations in vertical motion and geochemically distinct subduction-related arc magmatism. We also propose a model for the geodynamic evolution of slab detachment.

  5. Waveform modeling the deep slab beneath northernmost Nevada

    NASA Astrophysics Data System (ADS)

    Helmberger, D. V.; Sun, D.

    2011-12-01

    The interactions between subducted slab and transition zone are crucial issues in dynamic modeling. Previous mantle convection studies have shown that various viscosity structures can result in various slab shape, width, and edge sharpness. Recent tomographic images based on USArray data reveals strong multi-scale heterogeneous upper mantle beneath western US. Among those features, a slab-like fast anomaly extends from 300 to 600 km depth below Nevada and western Utah, which was suggested as a segmented chunk of the Farallon slab. But we still missing key information about the details of this structure and whether this structure flatten outs in the transition zone, where various tomographic models display inconsistent images. The study of multipathing and waveform broadening around sharp features have been proved a efficient way to study such features. Here, we use both P and S waveform data from High Lava Plains seismic experiments and USArray to produce a detailed image. If we amplify the Schmandt and Humphreys [2010] 's S-wave tomography model by 1.5, we can produce excellent travel-time fits. But the waveform distortions are not as strong as those observed in data for events coming from the southeast, which suggest a much sharper anomaly. The waveform broadening features are not observed for events arriving from northwestern. By fitting the SH waveform data, we suggest that this slab-like structure dips ~35° to the southeast, extending to a depth near 660 km with a velocity increase of about 5 per cent. To generate corresponding P model, we adapt the SH wave model and scale the model using a suite of R (=dlnVs/dlnVp) values. We find that synthetics from the model with R ≈ 2 can fit the observed data, which confirms the segmented slab interpretation of this high velocity anomaly.

  6. Numerical modeling on the temperature fluctuation and thermo-stress development of the continuously cast steel thin-slab

    SciTech Connect

    Yang, B.J.; Liu, W.T.; Su, J.Y.

    1995-12-31

    The present paper is aimed on modeling the fluctuation of surface temperature and thermo-stress development of the continuously cast steel thin-slab in the secondary cooling system. In the heat transfer model, the spray cooling feature, roll contact and so on are considered to reveal the temperature fluctuation on the solidified surface of thin slab during passing through the secondary cooling zones. The slice-traveling method was used for solidification process to calculate the temperature distribution. The thermo-stress in the solidified shell has simulated by using 2-dimensional thermo-elastic and viscoplastic model incorporating the temperature dependent material properties. The effects of the ferropressure, roll constraint, temperature fluctuation of slab surface on stress development are considered according to the practical operating variables, and a comparison of the stress development at the different temperature distributions has been performed. The computed results have shown that the stress development and surface crack tendency under the conditions of the smooth temperature distribution and real fluctuation distribution are significantly different. In addition, the time-step automatically controlling method for the simulation of the thermo-stress fluctuation development has developed, and it works well to guarantee the computational stability and convergence in modeling the stress development of continuously cast thin-slab at a high casting speed when loading the big fluctuation of temperature.

  7. Space assembly fixtures and aids

    NASA Technical Reports Server (NTRS)

    Bloom, K. A.; Lillenas, A. N.

    1980-01-01

    Concepts and requirements for assembly fixtures and aids necessary for the assembly and maintenance of spare platforms were studied. Emphasis was placed on erectable and deployable type structures with the shuttle orbiter as the assembly base. Both single and multiple orbiter flight cases for the platform assembly were considered. Applicable space platform assembly studies were reviewed to provide a data base for establishing the assembly fixture and aids design requirements, assembly constraints, and the development of representative design concepts. Conclusions indicated that fixture requirements will vary with platform size. Larger platforms will require translation relative to the orbiter RMS working volume. The installation of platform payloads and subsystems (e.g., utility distribution) must also be considered in the specification of assembly fixtures and aids.

  8. Joint assembly

    NASA Technical Reports Server (NTRS)

    Wilson, Andrew (Inventor); Punnoose, Andrew (Inventor); Strausser, Katherine (Inventor); Parikh, Neil (Inventor)

    2010-01-01

    A joint assembly is provided which includes a drive assembly and a swivel mechanism. The drive assembly features a motor operatively associated with a plurality of drive shafts for driving auxiliary elements, and a plurality of swivel shafts for pivoting the drive assembly. The swivel mechanism engages the swivel shafts and has a fixable element that may be attached to a foundation. The swivel mechanism is adapted to cooperate with the swivel shafts to pivot the drive assembly with at least two degrees of freedom relative to the foundation. The joint assembly allows for all components to remain encased in a tight, compact, and sealed package, making it ideal for space, exploratory, and commercial applications.

  9. Expansion of a cold non-neutral plasma slab

    SciTech Connect

    Karimov, A. R.; Yu, M. Y.; Stenflo, L.

    2014-12-15

    Expansion of the ion and electron fronts of a cold non-neutral plasma slab with a quasi-neutral core bounded by layers containing only ions is investigated analytically and exact solutions are obtained. It is found that on average, the plasma expansion time scales linearly with the initial inverse ion plasma frequency as well as the degree of charge imbalance, and no expansion occurs if the cold plasma slab is stationary and overall neutral. However, in both cases, there can exist prominent oscillations on the electron front.

  10. Seismic Behaviour of Masonry Vault-Slab Structures

    SciTech Connect

    Chesi, Claudio; Butti, Ferdinando; Ferrari, Marco

    2008-07-08

    Spandrel walls typically play a structural role in masonry buildings, transferring load from a slab to the supporting vault. Some indications are given in the literature on the behaviour of spandrels under the effect of vertical loads, but little attention is given to the effect coming from lateral forces acting on the building. An opportunity to investigate this problem has come from the need of analyzing a monumental building which was damaged by the Nov. 24, 2004 Val Sabbia earthquake in the north of Italy. The finite element model set up for the analysis of the vault-spandrel-slab system is presented and the structural role resulting for the spandrels is discussed.

  11. Investigating the Farallon Slab with Probabilistic Traveltime Tomography

    NASA Astrophysics Data System (ADS)

    Burdick, S.; Lekic, V.

    2015-12-01

    Subduction of the Farallon Plate beneath North America played a key role in its tectonic development. Seismic constraints on the subducted remnants of the Farallon slab provide evidence needed to better understand the polarity and timing of subduction, the structure of the plate, and its relation to tectonic events like the uplift of the Rocky Mountains. Over the course of its deployment, the USArray Transportable Array (TA) has offered ideal data coverage for investigating the Farallon and related slabs in the upper mantle using seismic tomography and converted wave imaging. With its arrival in the east, data from the TA provides the crossing paths necessary to image the upper reaches of the oldest parts of the plate at mid-mantle depths. We perform a global tomographic inversion using the latest P-wave traveltime picks from TA combined with global catalogue data. While the new velocity model resolves upper mantle slab structure at unprecedented detail in the east, a quantitative grasp of model uncertainty is needed to reliably relate velocity variations to the thermal and mechanical properties of the slabs. In order to quantify the uncertainty of our tomographic model, we employ Transdimensional Hierarchical Bayesian (THB) inversion. THB tomography uses Markov chain Monte Carlo to create an ensemble of velocity models that can be analyzed to statistically infer the best-fit velocities, their uncertainties, and tradeoffs. We present and discuss various representations of uncertainty quantified by THB tomography—error bars, model covariance, multimodal distributions of velocity values—and demonstrate its importance for furthering our understanding of the slab fragments beneath North America. We illustrate how we are able to distinguish between spurious slab fragments from those required by the data. By examining bimodal velocity distributions, we put error bars on the spatial extent of the slabs that can then be analyzed using thermal diffusion modeling. By

  12. Links between fluid circulation, temperature, and metamorphism in subducting slabs

    USGS Publications Warehouse

    Spinelli, G.A.; Wang, K.

    2009-01-01

    The location and timing of metamorphic reactions in subducting lithosph??re are influenced by thermal effects of fluid circulation in the ocean crust aquifer. Fluid circulation in subducting crust extracts heat from the Nankai subduction zone, causing the crust to pass through cooler metamorphic faci??s than if no fluid circulation occurs. This fluid circulation shifts the basalt-to-eclogite transition and the associated slab dehydration 14 km deeper (35 km farther landward) than would be predicted with no fluid flow. For most subduction zones, hydrothermal cooling of the subducting slab will delay eclogitization relative to estimates made without considering fluid circulation. Copyright 2009 by the American Geophysical Union.

  13. Slab Driven Mantle Deformation and Plate-Mantle Decoupling

    NASA Astrophysics Data System (ADS)

    Jadamec, M. A.; MacDougall, J.; Fischer, K. M.

    2015-12-01

    Observations of shear wave splitting derived from local sources in subduction zones suggest viscous flow in the mantle wedge is commonly non-parallel to both the subducting plate velocity vector and the motion of the overriding plate. However, far from the subduction zone trench, observations indicate the fast axis of shear wave splitting tends to align with the velocity vector of the surface plates. Similarly, previous 3D geodynamic models show the slab can drive local decoupling of the mantle and surface plates, in both direction and speed. This suggests that there is some distance from the trench over which there is significant decoupling of the mantle flow from surface plate motion, and that this decoupling zone then decays with continued distance from the trench, resulting in far-field plate-mantle coupling. Here we present results from geodynamic models of subduction coupled with calculations of olivine fabric deformation and synthetic splitting to 1) examine the influence of slab strength, slab dip, and non-Newtonian viscosity on the deformation fabric in the mantle wedge and subslab mantle and 2) quantify the spatial extent and intensity of this slab driven decoupling zone. We compare the deformation fabric in a 2D corner flow solution with varying dip to that of a 2D free subduction model with varying initial dip and slab strength. The results show that using an experimentally derived flow law to define viscosity (both diffusion creep and dislocation creep deformation mechanisms) has a first order effect on the viscosity structure and flow velocity in the upper mantle. The free subduction models using the composite viscosity formulation produce a zone of subduction induced mantle weakening that results in reduced viscous support of the slab and lateral variability in coupling of the mantle to the base of the surface plates. The maximum yield stress, which places an upper bound on the slab strength, can also have a significant impact on the viscosity

  14. Spatial Stability of the Expanding Magnetized Slab Jet

    NASA Astrophysics Data System (ADS)

    Cooper, M. A.; Hardee, P. E.; Clarke, D. A.

    1993-12-01

    A spatial stability analysis of the Kelvin-Helmholtz instability in an expanding axially magnetized slab jet is presented. The results are then compared with numerical simulations to see if the perturbation theory correctly describes global instabilities. Provided the jet is highly super-Alfvenic and highly supersonic then the dispersion relation describing the propagation and growth of a perturbation admits the same type of solutions as those found for purely fluid jets. However, in the region where the jet is only slightly super-Alfvenic or slightly supersonic, the expansion of the jet causes the solution to split into a growing and damped pair. This splitting occurs for both sonic and Alfvenic disturbances which propagate along the flow direction. At high frequencies, the growing solutions of the fundamental sinusoidal mode correspond to sound waves and Alfven waves propagating in the flow direction, while the damped solutions correspond to sound waves and Alfven waves propagating against the flow. Those solutions which are damped at high frequencies become growing as the frequency is decreased. The opposite is true for growing solutions at high frequencies. When the jet is sub-Alfvenic, at least one solution of the fundamental mode is not stabilized. However, the simulations suggest that any instabilities that arise when the jet is sub- or trans-Alfvenic will be damped out as the jet becomes fully super-Alfvenic. Therefore, for sub-Alfvenic jets it may be necessary to consider the effects of expansion on the stability of the jet. This work was supported by NSF grant AST-8919180 and EPSCoR grant EHR-9108761.

  15. Slab fluid release: localized in space and time

    NASA Astrophysics Data System (ADS)

    John, T.; Gussone, N. C.; Podladchikov, Y. Y.

    2012-12-01

    As subducting oceanic plates descend into the Earth's mantle, increasing pressures and temperatures lead to the progressive destabilization of hydrous mineral phases and the release of H2O-rich fluids. Some fraction of these fluids ascend into the overlying mantle wedge, inducing partial melting, and their "chemical freight" is thought to contribute to the distinctive chemical signature of the resulting arc magmas. Field evidences suggest that channelized fluid flow may be the dominant mechanism for intra-slab fluid flow. Along their pathways within slabs, these fluids can trigger mineral reactions and produce chemical changes in rocks with which they interact. However, the spatial and temporal scales of this fluid flow remain largely unknown. We employed the Ca and Li isotope systems on a fossil high-pressure fluid pathway and its associated reaction halo (Chinese Tianshan), formed at ~70 km depth during subduction of a coherent oceanic slab, allowing us to constrain the fluid flux, fluid source and the duration of the fluid-rock interaction. In the reaction halo, the degree of eclogitization along with Ca concentration increases towards the vein. A high fluid flux is required to obtain the observed Ca increase and changes in δ44/40Ca. The Ca isotope composition indicate mixing of two distinct Ca sources, the wall-rock blueschist and an external fluid source, the latter of which is enriched in heavy Ca isotopes. The relatively high δ44/40Ca (>1.3‰) of the infiltrating fluid is suggestive of partially hydrated slab mantle as the fluid source. Alternatively, Ca derived from MORB, (0.7 to 0.9‰) and AOC (0.6 to 1.0‰) might evolve towards heavier Ca isotope values while it is ascending through the slab and reacting with wall-rocks and forming carbonates, which are usually associated with the flow structures. This is because calcium carbonate precipitation preferentially removes light Ca from the fluid while the residual fluid will get heavier proportional to

  16. Welding and mechanical properties of cast FAPY (Fe-16 at. % Al-based) alloy slabs

    SciTech Connect

    Sikka, V.K.; Goodwin, G.M.; Alexander, D.J.; Howell, C.R.

    1995-08-01

    The low-aluminum-content iron-aluminum program deals with the development of a Fe-Al alloy with aluminum content such as a produce the minimum environmental effect at room temperature. The FAPY is an Fe-16 at. % Al-based alloy developed at the Oak Ridge National Laboratory as the highest aluminum-containing alloy with essentially no environmental effect. The chemical composition for FAPY in weight percent is: aluminum = 8.46, chromium = 5.50, zirconium = 0.20, carbon = 0.03, molybdenum = 2.00, yttrium = 0.10, and iron = 83.71. The cast ingots of the alloy can be hot worked by extrusion, forging, and rolling processes. The hot- worked cast structure can be cold worked with intermediate anneals at 800{degrees}C. Typical room-temperature ductility of the fine-grained wrought structure is 20 to 25% for this alloy. In contrast to the wrought structure, the cast ductility at room temperature is approximately 1% with a transition temperature of approximately 100 to 150{degrees}C, above which ductility values exceed 20%. The alloy has been melted and processed into bar, sheet, and foil. The alloy has also been cast into slabs, step-blocks of varying thicknesses, and shapes. The purpose of this section is to describe the welding response of cast slabs of three different thicknesses of FAPY alloy. Tensile, creep, and Charpy-impact data of the welded plates are also presented.

  17. RAW COPPER SLABS USED IN CASTING OPERATIONS AT BUFFALO PLANT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    RAW COPPER SLABS USED IN CASTING OPERATIONS AT BUFFALO PLANT OF AMERICAN BRASS COMPANY. MATERIALS STORAGE FOR THE CAST SHOP NOW OCCUPIES A PORTION OF THE ORIGINAL BRASS MILL BUILT BY THE BUFFALO COPPER AND BRASS ROLLING MILL IN 1906-07 AND EXPANDED IN 1911. - American Brass Foundry, 70 Sayre Street, Buffalo, Erie County, NY

  18. Topological optical Bloch oscillations in a deformed slab waveguide.

    PubMed

    Longhi, Stefano

    2007-09-15

    Spatial Bloch oscillations of light waves of purely topological origin are theoretically shown to exist in weakly deformed slab waveguides. As the optical rays trapped in the deformed waveguide can roll freely, wave diffraction is strongly affected by the topology of the deformed surface, which can be tailored to simulate the effect of a tilted periodic refractive index.

  19. 8. WEST FLAME DEFLECTOR FROM REINFORCED CONCRETE SLAB ROOF, FORMER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. WEST FLAME DEFLECTOR FROM REINFORCED CONCRETE SLAB ROOF, FORMER DRAINAGE AREA IN THE DISTANCE, VIEW TOWARDS NORTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  20. 52. SLABBING AND BLOOMING MILLS AND FOUNDRY (IN FOREGROUND), AS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    52. SLABBING AND BLOOMING MILLS AND FOUNDRY (IN FOREGROUND), AS SEEN FROM THE CLARK AVENUE BRIDGE. AT RIGHT, REAR, IS THE BASIC OXYGEN FURNACE. VIEW LOOKING NORTH. - Corrigan, McKinney Steel Company, 3100 East Forty-fifth Street, Cleveland, Cuyahoga County, OH

  1. Workmen and Crawler Crane pouring roof slab and parapet wall ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Workmen and Crawler Crane pouring roof slab and parapet wall of building - looking northwest. Taken Nov. 15, 1929. 14th Naval District Photo Collection Item No. 7165 - U.S. Naval Base, Pearl Harbor, Exterior Cranes, Waterfront Crane Track System, Pearl City, Honolulu County, HI

  2. Subduction of the Indian Lithospheric Slab Beneath Tibet

    NASA Astrophysics Data System (ADS)

    Zhou, H.; Murphy, M. A.

    2001-12-01

    In order to characterize the dynamics of continent-continent collisions, it is essential to define its present geometry and physical state. We report the results of a seismic tomography study of the Tibet-Himalayan collision zone, using a global data set, which indicates that the Indian lithospheric slab has been subducted subhorizontally beneath nearly the entire Tibetan plateau to depths of 165-260 km. Tibetan velocity structure is low in the crust and high in mantle lithosphere at depths between 75-120 km. An asthenospheric layer overlies the subducted Indian slab at depths between 120-165 km beneath the Tibetan plateau. There is a large low-velocity anomaly north of the Indus-Yalu suture zone between 85ºE and 93ºE that extends from the crust down to at least 310 km depth beneath the plateau. This low-velocity anomaly is indicative of mantle upwelling through a weakened zone of the subducted slab. The extent to which India has subducted beneath Tibet, as revealed by these seismic images, is comparable to estimates of crustal shortening across the Himalaya. Moreover, we hypothesize that the buoyancy due to heating of the subducted Indian slab and the existence of the asthenospheric layer contribute to the elevation and flatness of the Tibetan plateau.

  3. 18. FOURTH FLOOR BLDG. 28, RAISED CONCRETE SLAB FLOOR WITH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. FOURTH FLOOR BLDG. 28, RAISED CONCRETE SLAB FLOOR WITH BLOCKS AND PULLEYS OVERHEAD LOOKING NORTHEAST. - Fafnir Bearing Plant, Bounded on North side by Myrtle Street, on South side by Orange Street, on East side by Booth Street & on West side by Grove Street, New Britain, Hartford County, CT

  4. Photonic-crystal slab for terahertz-wave technology platform

    NASA Astrophysics Data System (ADS)

    Fujita, Masayuki

    2016-03-01

    Photonic crystals manipulate photons in a manner analogous to solid-state crystals, and are composed of a dielectric material with a periodic refractive index distribution. In particular, two-dimensional photonic-crystal slabs with high index contrasts (semiconductor/air) are promising for practical applications, owing to the strong optical confinement in simple, thin planar structures. This paper presents the recent progress on a silicon photonic-crystal slab as a technology platform in the terahertz-wave region, which is located between the radio and light wave regions (0.1-10 THz). Extremely low-loss (<0.1 dB/cm) terahertz waveguides based on the photonic-bandgap effect as well as dynamic control and modulation of a terahertz-wave transmission in a photonic-crystal slab by the effective interaction between photoexcited carriers and the terahertz-wave trapping due to the photonic band-edge effect are demonstrated. Terahertz photonic-crystal slabs hold the potential for developing ultralow-loss, compact terahertz components and integrated devices used in applications including wireless communication, spectroscopic sensing, and imaging.

  5. Tensor-guided fitting of subduction slab depths

    USGS Publications Warehouse

    Bazargani, Farhad; Hayes, Gavin P.

    2013-01-01

    Geophysical measurements are often acquired at scattered locations in space. Therefore, interpolating or fitting the sparsely sampled data as a uniform function of space (a procedure commonly known as gridding) is a ubiquitous problem in geophysics. Most gridding methods require a model of spatial correlation for data. This spatial correlation model can often be inferred from some sort of secondary information, which may also be sparsely sampled in space. In this paper, we present a new method to model the geometry of a subducting slab in which we use a data‐fitting approach to address the problem. Earthquakes and active‐source seismic surveys provide estimates of depths of subducting slabs but only at scattered locations. In addition to estimates of depths from earthquake locations, focal mechanisms of subduction zone earthquakes also provide estimates of the strikes of the subducting slab on which they occur. We use these spatially sparse strike samples and the Earth’s curved surface geometry to infer a model for spatial correlation that guides a blended neighbor interpolation of slab depths. We then modify the interpolation method to account for the uncertainties associated with the depth estimates.

  6. 30. VAL LOOKING DOWN THE LAUNCHER SLAB STAIRS AT THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    30. VAL LOOKING DOWN THE LAUNCHER SLAB STAIRS AT THE PROJECTILE LOADING CAR AND LOADING PLATFORM ADJACENT TO THE PROJECTILE LOADING DECK AND LAUNCHER BRIDGE. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  7. 63. VIEW LOOKING DOWN VAL LAUNCHING SLAB SHOWING DRIVE GEARS, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    63. VIEW LOOKING DOWN VAL LAUNCHING SLAB SHOWING DRIVE GEARS, CABLES, LAUNCHER RAILS, PROJECTILE CAR AND SUPPORT CARRIAGE, April 8, 1948. (Original photograph in possession of Dave Willis, San Diego, California.) - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  8. Enhancement of polarizabilities of cylinders with cylinder-slab resonances

    PubMed Central

    Xiao, Meng; Huang, Xueqin; Liu, H.; Chan, C. T.

    2015-01-01

    If an object is very small in size compared with the wavelength of light, it does not scatter light efficiently. It is hence difficult to detect a very small object with light. We show using analytic theory as well as full wave numerical calculation that the effective polarizability of a small cylinder can be greatly enhanced by coupling it with a superlens type metamaterial slab. This kind of enhancement is not due to the individual resonance effect of the metamaterial slab, nor due to that of the object, but is caused by a collective resonant mode between the cylinder and the slab. We show that this type of particle-slab resonance which makes a small two-dimensional object much “brighter” is actually closely related to the reverse effect known in the literature as “cloaking by anomalous resonance” which can make a small cylinder undetectable. We also show that the enhancement of polarizability can lead to strongly enhanced electromagnetic forces that can be attractive or repulsive, depending on the material properties of the cylinder. PMID:25641391

  9. Applications of acoustics in the measurement of coal slab thickness

    NASA Technical Reports Server (NTRS)

    Hadden, W. J., Jr.; Mills, J. M.; Pierce, A. D.

    1980-01-01

    The determination of the possibility of employing acoustic waves at ultrasonic frequencies for measurements of thicknesses of slabs of coal backed by shale is investigated. Fundamental information concerning the acoustical properties of coal, and the relationship between these properties and the structural and compositional parameters used to characterize coal samples was also sought. The testing device, which utilizes two matched transducers, is described.

  10. Emplacement of the Kodiak batholith and slab-window migration

    USGS Publications Warehouse

    Farris, David W.; Haeussler, P.; Friedman, R.; Paterson, S.R.; Saltus, R.W.; Ayuso, R.

    2006-01-01

    The Kodiak batholith is one of the largest, most elongate intrusive bodies in the forearc Sanak-Baranof plutonic belt located in southern Alaska. This belt is interpreted to have formed during the subduction of an oceanic spreading center and the associated migration of a slab window. Individual plutons of the Kodiak batholith track the location and evolution of the underlying slab window. Six U/Pb zircon ages from the axis of the batholith exhibit a northeastward-decreasing age progression of 59.2 ± 0.2 Ma at the southwest end to 58.4 ± 0.2 Ma at the northeast tip. The trench-parallel rate of age progression is within error of the average slab-window migration rate for the entire Sanak-Baranof belt (~19 cm/yr). Structural relationships, U/Pb ages, and a model of new gravity data indicate that magma from the Kodiak batholith ascended 5-10 km as a northeastward-younging series of 1-8-km-diameter viscoelastic diapirs. Individual plutons ascended by multiple emplacement mechanisms including downward flow, collapse of wall rock, stoping, and diking. Stokes flow xenolith calculations suggest ascent rates of 5-100 m/yr and an effective magmatic viscosity of 107-108 Pa s. Pre-existing structural or lithologic heterogeneities did not dominantly control the location of the main batholith. Instead, its location was determined by migration of the slab window at depth. 

  11. 11. VIEW OF PLACING STEEL FOR POURING OF FIRST SLABS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. VIEW OF PLACING STEEL FOR POURING OF FIRST SLABS OF SPILLWAY CHUTE FROM VICINITY OF WESTERN SIDE OF SPILLWAY APRON, FACING SOUTH. September 1928 - Cushman No. 1 Hydroelectric Power Plant, Spillway, North Fork of Skokomish River, 5 miles West of Hood Canal, Hoodsport, Mason County, WA

  12. DETAIL OF THE IMPRESSION IN THE CONCRETE SLAB OF THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF THE IMPRESSION IN THE CONCRETE SLAB OF THE SOUTH END OF THE ABOVE-GROUND PORTION. NOTE STEP DOWN TO THE STEEL PLATE IN BACKGROUND. VIEW FACING NORTH - U.S. Naval Base, Pearl Harbor, Ford Island 5-Inch Antiaircraft Battery, Battery Command Center, Ford Island, Pearl City, Honolulu County, HI

  13. DETAIL OF STEEL PLATE SET INTO THE CONCRETE SLAB OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF STEEL PLATE SET INTO THE CONCRETE SLAB OF THE NORTH END OF THE ABOVE-GROUND PORTION. VIEW FACING NORTH - U.S. Naval Base, Pearl Harbor, Ford Island 5-Inch Antiaircraft Battery, Battery Command Center, Ford Island, Pearl City, Honolulu County, HI

  14. Equilibrium Slab Models of Lyman-Alpha Clouds

    NASA Technical Reports Server (NTRS)

    Charlton, Jane C.; Salpeter, Edwin E.; Hogan, Craig J.

    1993-01-01

    We model the L(sub y(alpha)) clouds as slabs of hydrogen with an ionizing extragalactic radiation field incident from both sides. In general, the equilibrium configuration of a slab at redshift z approx. less than 5 is determined by a balance of the gas pressure, gravity (including the effects of a dark matter halo), and the pressure exerted by the inter-galactic medium, P(sub ext). These models have been used to make predictions of the number of slabs as a function of the neutral hydrogen column density, N(sub H). A break in the curve is predicted at the transition between regimes where gravity and pressure are the dominant confining forces, with a less rapid decrease at larger N(sub H). The transition from optically thin to optically thick slabs leads to a gap in the distribution, whose location is governed largely by the spectrum of ionizing radiation. There are certain parallels between lines of sight through the outer HI disk of spiral galaxy with increasing radius, and the progression from damped, to Lyman limit, to forest clouds. We discuss briefly the possibility that at least some of the observed low z forest clouds may be a separate population, associated with galaxies, as suggested by the observations of Bahcall et al. This population could dominate the forest at present if the dark matter attached to galaxies should lead to gravity confinement for this disk population, while the isolated clouds remain pressure confined. The formalism developed in this paper will allow a more detailed study. We also discuss a more general parameter study of the equilibrium configuration of slabs, including mock gravity and L(sub y(alpha)) photon trapping.

  15. Assimilating lithosphere and slab history in 4-D Earth models

    NASA Astrophysics Data System (ADS)

    Bower, Dan J.; Gurnis, Michael; Flament, Nicolas

    2015-01-01

    We develop methods to incorporate paleogeographical constraints into numerical models of mantle convection. Through the solution of the convection equations, the models honor geophysical and geological data near the surface while predicting mantle flow and structure at depth and associated surface deformation. The methods consist of four constraints determined a priori from a plate history model: (1) plate velocities, (2) thermal structure of the lithosphere, (3) thermal structure of slabs in the upper mantle, and (4) velocity of slabs in the upper mantle. These constraints are implemented as temporally- and spatially-dependent conditions that are blended with the solution of the convection equations at each time step. We construct Earth-like regional models with oceanic and continental lithosphere, trench migration, oblique subduction, and asymmetric subduction to test the robustness of the methods by computing the temperature, velocity, and buoyancy flux of the lithosphere and slab. Full sphere convection models demonstrate how the methods can determine the flow associated with specific tectonic environments (e.g., back-arc basins, intraoceanic subduction zones) to address geological questions and compare with independent data, both at present-day and in the geological past (e.g., seismology, residual topography, stratigraphy). Using global models with paleogeographical constraints we demonstrate (1) subduction initiation at the Izu-Bonin-Mariana convergent margin and flat slab subduction beneath North America, (2) enhanced correlation of model slabs and fast anomalies in seismic tomography beneath North and South America, and (3) comparable amplitude of dynamic and residual topography in addition to improved spatial correlation of dynamic and residual topography lows.

  16. Crew Assembly

    NASA Video Gallery

    Train to improve your dexterity and hand-eye coordination by assembling a puzzle.The Train Like an Astronaut project uses the excitement of exploration to challenge students to set goals, practice ...

  17. Enhanced output of soft X-ray lasers using double slab targets

    SciTech Connect

    Moreno, J.C.; Nilsen, J.; Chandler, E.

    1994-06-01

    Double slab neon-like niobium soft x-ray laser experiments have been performed using the Nova laser. The two slabs have their front surfaces facing in opposite directions with either a 300 {mu}m planar separation between them. Separate laser beams irradiate each slab with an intensity on target of 1.3 {times} 10{sup 14} W/cm{sup 2}. Best coupling was observed using a 300 {mu}m separation. The angular divergence of the laser is measured for single slab and double slab configurations. Comparisons to numerical models are discussed.

  18. Seal assembly

    SciTech Connect

    Johnson, Roger Neal; Longfritz, William David

    2001-01-01

    A seal assembly that seals a gap formed by a groove comprises a seal body, a biasing element, and a connection that connects the seal body to the biasing element to form the seal assembly. The seal assembly further comprises a concave-shaped center section and convex-shaped contact portions at each end of the seal body. The biasing element is formed from an elastic material and comprises a convex-shaped center section and concave-shaped biasing zones that are opposed to the convex-shaped contact portions. The biasing element is adapted to be compressed to change a width of the seal assembly from a first width to a second width that is smaller than the first width. In the compressed state, the seal assembly can be disposed in the groove. After release of the compressing force, the seal assembly expands. The contact portions will move toward a surface of the groove and the biasing zones will move into contact with another surface of the groove. The biasing zones will bias the contact portions of the seal body against the surface of the groove.

  19. Optical properties of crystalline and amorphous silicon slabs with adsorbed metal clusters and with dopants: A combined ab-initio electronic structure and density matrix treatment

    NASA Astrophysics Data System (ADS)

    Kilin, Dimitri; Micha, David; Ramirez, Jessica

    2011-03-01

    The optical absorbance and surface photovoltage of slabs of Si with varying number of layers have been calculated starting from their atomic structure. Results have been obtained for nanostructured surfaces with adsorbed metal clusters and for group III and V dopants, from ab initio DFT with periodic boundary conditions for extended systems, and from time-dependent DFT for supercells. Density matrix equations of motion (EOM) have been parametrized in a basis set of Kohn-Sham orbitals, for both crystalline and amorphous Si slabs. Results for properties and from electronic charge distributions provide insight on slab confinement effects for electronically excited states and for particle-hole creation. In addition, the integrodifferential EOMs have been solved for an initial femtosecond pulse excitation to analyze the nature of electron transfer at the surfaces, relevant to photovoltaics. Work supported by the NSF and by the Dreyfus Foundation to DM.

  20. The Role of Serpentinization and Deserpentinization In Bending and Unbending A Subducting Slab

    NASA Astrophysics Data System (ADS)

    Phipps Morgan, J.; Ruepke, L.; Ranero, C.

    mechanism. The inferred lithospheric stress distribution can explain a puzzling feature of Tongan `outer-rise' seismicity ­ the apparent coexistance of shal- low compressional and tensional EQs at shallow depths between the outer rise and trench axis (Garcia-Castellanos, GJI, 2000). The observation that intermediate depth seismic slip occurs on the faultplane directions of previous outer-rise faulting is also consistent (Jiao et al., JGR,2000), while providing a similar volume-decreasing trans- 1 formation faulting mechanism that could link the physics of 100-350-km depth de- serpentinization transformation faulting and even deeper olivine-spinel tranformation faulting (H. Green II, EOS, 2001). Furthermore, serpentinization-linked slab-bending significantly eases the mechanical work needed to subduct a plate, providing a possible resolution to the apparent paradox (Conrad and Hager, JGR, 1999) that the bending and unbending of the downgoing plate could consume even more energy than that available from the negative buoyancy of subducting lithosphere. 2

  1. Mantle-slab interaction and redox mechanism of diamond formation.

    PubMed

    Palyanov, Yuri N; Bataleva, Yuliya V; Sokol, Alexander G; Borzdov, Yuri M; Kupriyanov, Igor N; Reutsky, Vadim N; Sobolev, Nikolai V

    2013-12-17

    Subduction tectonics imposes an important role in the evolution of the interior of the Earth and its global carbon cycle; however, the mechanism of the mantle-slab interaction remains unclear. Here, we demonstrate the results of high-pressure redox-gradient experiments on the interactions between Mg-Ca-carbonate and metallic iron, modeling the processes at the mantle-slab boundary; thereby, we present mechanisms of diamond formation both ahead of and behind the redox front. It is determined that, at oxidized conditions, a low-temperature Ca-rich carbonate melt is generated. This melt acts as both the carbon source and crystallization medium for diamond, whereas at reduced conditions, diamond crystallizes only from the Fe-C melt. The redox mechanism revealed in this study is used to explain the contrasting heterogeneity of natural diamonds, as seen in the composition of inclusions, carbon isotopic composition, and nitrogen impurity content. PMID:24297876

  2. Equilibrium slab models of Lyman-alpha clouds

    NASA Technical Reports Server (NTRS)

    Charlton, Jane C.; Salpeter, Edwin E.; Hogan, Craig J.

    1993-01-01

    Solutions for the equilibrium configuration of a slab with ionizing radiation incident equally from both sides are explored. Radiation effects (photoionization, Ly-alpha photon trapping, and mock gravity) as well as external pressure and self gravity (with and without dark matter) are included. The general formalism is applied to structure growth on small scales at very high z due to mock gravity on dust. Emphasis is placed on the application of slab models at z of less than 5, particularly those that may correspond to Ly-alpha forest, Lyman limit, and damped Ly-alpha systems. The regime with a dominant outward force contributed by trapping of Ly-alpha photons is discussed. General expressions are given for the equilibrium, including dark matter, assuming various relationships between the density of the dark matter halo and the total gas column density.

  3. Non-Fourier heat conduction in an exponentially graded slab

    NASA Astrophysics Data System (ADS)

    Raveshi, M. R.

    2016-03-01

    The present article investigates one-dimensional non-Fourier heat conduction in a functionally graded material by using the differential transformation method. The studied geometry is a finite functionally graded slab, which is initially at a uniform temperature and suddenly experiences a temperature rise at one side, while the other side is kept insulated. A general non-Fourier heat transfer equation related to the functionally graded slab is derived. The problem is solved in the Laplace domain analytically, and the final results in the time domain are obtained by using numerical inversion of the Laplace transform. The obtained results are compared with the exact solution to verify the accuracy of the proposed method, which shows excellent agreement.

  4. Mantle–slab interaction and redox mechanism of diamond formation

    PubMed Central

    Palyanov, Yuri N.; Bataleva, Yuliya V.; Sokol, Alexander G.; Borzdov, Yuri M.; Kupriyanov, Igor N.; Reutsky, Vadim N.; Sobolev, Nikolai V.

    2013-01-01

    Subduction tectonics imposes an important role in the evolution of the interior of the Earth and its global carbon cycle; however, the mechanism of the mantle–slab interaction remains unclear. Here, we demonstrate the results of high-pressure redox-gradient experiments on the interactions between Mg-Ca-carbonate and metallic iron, modeling the processes at the mantle–slab boundary; thereby, we present mechanisms of diamond formation both ahead of and behind the redox front. It is determined that, at oxidized conditions, a low-temperature Ca-rich carbonate melt is generated. This melt acts as both the carbon source and crystallization medium for diamond, whereas at reduced conditions, diamond crystallizes only from the Fe-C melt. The redox mechanism revealed in this study is used to explain the contrasting heterogeneity of natural diamonds, as seen in the composition of inclusions, carbon isotopic composition, and nitrogen impurity content. PMID:24297876

  5. Nonlocal microscopic theory of quantum friction between parallel metallic slabs

    SciTech Connect

    Despoja, Vito

    2011-05-15

    We present a new derivation of the friction force between two metallic slabs moving with constant relative parallel velocity, based on T=0 quantum-field theory formalism. By including a fully nonlocal description of dynamically screened electron fluctuations in the slab, and avoiding the usual matching-condition procedure, we generalize previous expressions for the friction force, to which our results reduce in the local limit. Analyzing the friction force calculated in the two local models and in the nonlocal theory, we show that for physically relevant velocities local theories using the plasmon and Drude models of dielectric response are inappropriate to describe friction, which is due to excitation of low-energy electron-hole pairs, which are properly included in nonlocal theory. We also show that inclusion of dissipation in the nonlocal electronic response has negligible influence on friction.

  6. Scattering by dielectric circular cylinders in a dielectric slab.

    PubMed

    Frezza, Fabrizio; Pajewski, Lara; Ponti, Cristina; Schettini, Giuseppe

    2010-04-01

    An analytical-numerical technique for the solution of the plane-wave scattering problem by a set of dielectric cylinders embedded in a dielectric slab is presented. Scattered fields are expressed by means of expansions into cylindrical functions, and the concept of plane-wave spectrum of a cylindrical function is employed to define reflection and transmission through the planar interfaces. Multiple reflection phenomena due to the presence of a layered geometry are taken into account. Solutions can be obtained for both TM and TE polarizations and for near- and far-field regions. The numerical approach is described and the method is validated by comparison with examples given in the literature, with very good agreement. Results are presented for the scattering by a finite grid of three cylinders embedded in a slab.

  7. Negotiating Multicollinearity with Spike-and-Slab Priors.

    PubMed

    Ročková, Veronika; George, Edward I

    2014-08-01

    In multiple regression under the normal linear model, the presence of multicollinearity is well known to lead to unreliable and unstable maximum likelihood estimates. This can be particularly troublesome for the problem of variable selection where it becomes more difficult to distinguish between subset models. Here we show how adding a spike-and-slab prior mitigates this difficulty by filtering the likelihood surface into a posterior distribution that allocates the relevant likelihood information to each of the subset model modes. For identification of promising high posterior models in this setting, we consider three EM algorithms, the fast closed form EMVS version of Rockova and George (2014) and two new versions designed for variants of the spike-and-slab formulation. For a multimodal posterior under multicollinearity, we compare the regions of convergence of these three algorithms. Deterministic annealing versions of the EMVS algorithm are seen to substantially mitigate this multimodality. A single simple running example is used for illustration throughout.

  8. Slab2 - Providing updated subduction zone geometries and modeling tools to the community

    NASA Astrophysics Data System (ADS)

    Hayes, G. P.; Hearne, M. G.; Portner, D. E.; Borjas, C.; Moore, G.; Flamme, H.

    2015-12-01

    The U.S. Geological Survey database of global subduction zone geometries (Slab1.0) combines a variety of geophysical data sets (earthquake hypocenters, moment tensors, active source seismic survey images of the shallow subduction zone, bathymetry, trench locations, and sediment thickness information) to image the shape of subducting slabs in three dimensions, at approximately 85% of the world's convergent margins. The database is used extensively for a variety of purposes, from earthquake source imaging, to magnetotelluric modeling. Gaps in Slab1.0 exist where input data are sparse and/or where slabs are geometrically complex (and difficult to image with an automated approach). Slab1.0 also does not include information on the uncertainty in the modeled geometrical parameters, or the input data used to image them, and provides no means to reproduce the models it described. Currently underway, Slab2 will update and replace Slab1.0 by: (1) extending modeled slab geometries to all global subduction zones; (2) incorporating regional data sets that may describe slab geometry in finer detail than do previously used teleseismic data; (3) providing information on the uncertainties in each modeled slab surface; (4) modifying our modeling approach to a fully-three dimensional data interpolation, rather than following the 2-D to 3-D steps of Slab1.0; (5) migrating the slab modeling code base to a more universally distributable language, Python; and (6) providing the code base and input data we use to create our models, such that the community can both reproduce the slab geometries, and add their own data sets to ours to further improve upon those models in the future. In this presentation we describe our vision for Slab2, and the first results of this modeling process.

  9. Density Structures of Oceanic Slabs and Surrounding Mantle Around the 660 km Discontinuity: Implications for the Fate of Old and Young Slabs

    NASA Astrophysics Data System (ADS)

    Ganguly, J.; Saxena, S. K.; Freed, A. M.

    2007-05-01

    We calculated density variations as a function of temperature around the 660 km deep seismic discontinuity in the Earth's mantle in different types of compositional units associated with a subducting slab and the ambient mantle. The calculations are based on computational thermodynamic approach of minimization of Gibbs free energy at a specified P-T condition, subject to the bulk compositional constraints of the system, that simultaneously yield stable mineral assemblage, mineral compositions and modal abundances. These results are converted to density profiles using appropriate data for physical properties and equations of state that are applicable to high P-T conditions. In addition, we also calculated thermal structures of several slabs, with the extremes being given by Tonga (140 Myr at trench, vertical velocity: 14 cm/yr; average dip: 60 degrees) and Peru (41 Myr, 4.4 cm/yr, 35 degrees). A slab was assumed to be lithologically stratified with a top basaltic crust, followed downwards by residual harzburgite and slightly depleted pyrolite. The surrounding mantle is taken to be undepleted pyrolite. Integration of the results of thermal and density calculations show that that all components of the Tonga slab are heavier than both ambient and thermally perturbed adjacent mantle, which has been cooled due to contact with the slab. Thus, old slabs with thermal minimum below 750 C, as in Tonga, should easily penetrate into the lower mantle unless resisted by slab roll back and/or a viscosity jump at the top of the lower mantle. In contrast, the harzburgite layer in warmer slabs, such as Peru, Marianas and Izu-Bonin, is slightly lighter than ambient mantle, causing near neutral or marginally negative net buoyancy of the slab. In this case, other factors, such as rollback and slab dip angle, may explain why some slabs in the northwest Pacific appear to penetrate into the lower mantle while others do not. In Peru-type warm slabs, buoyancy of the harzburgite layer may

  10. Dynamics of Mantle Circulation Associated with Slab Window Formation: Insights from 3D Laboratory Models

    NASA Astrophysics Data System (ADS)

    Guillaume, B.; Funiciello, F.; Moroni, M.; Faccenna, C.; Martinod, J.

    2009-12-01

    Slab window can form either by the intersection of a spreading ridge with a subduction zone or because of internal deformation of the slab that leads to its disruption. The main consequences of this phenomenon are the modifications of the physical, chemical and thermal conditions in the backarc mantle that in turn affect the tectonic and magmatic evolution of the overriding plate. We performed laboratory models of a two-layer linear viscous slab (silicone putty)-upper mantle (glucose syrup) system to quantitatively investigate the pattern of mantle circulation within the slab window (using Feature Tracking image analysis technique) and its influence on the kinematics of the system. Two different geometries have been tested considering a window located (a) at slab edges or (b) within the slab. Kinematic consequences of slab window have been explored to understand the dynamics of the mantle-slab interaction. Configuration (a) implies a reduction of the slab width (W) during subduction and is characterized by toroidal fluxes around the slab edges. The abrupt opening of lateral slab windows produces an acceleration of the trench retreat and subduction velocity, such as 40% for a three-fold width reduction. We interpret this behavior as mostly due to the decrease in the toroidal flow inside subduction windows, scaling with W2. Configuration (b) has been designed to explore the pattern of mantle flow within the window in the case of a laterally constrained subduction system. Slab window, which had a width (Ww) fixed to 15 % of the slab width, opened in the trench-perpendicular direction. It produced the formation of two toroidal mantle cells, centered on the slab midpoint and laterally growing as the slab window enlarged. Particles extruded through the slab window did not mix with particles located in the mantle wedge, the boundary between both reaching distances from the trench up to 3×Ww in the trench-perpendicular direction, and up to 1.5×Ww from the window edge in

  11. Comments on Work-Study as an Academic Tool: A Selection from Resource Materials Provided to the Joint Committee on Education Appropriations of the Iowa General Assembly

    ERIC Educational Resources Information Center

    Greiner, Keith

    2007-01-01

    This is a one-page summary of work-study assistance as an academic tool for college and university students. The summary includes references to on-line resource documents that provide additional details.

  12. Slab detachment under the Eastern Alps seen by seismic anisotropy

    PubMed Central

    Qorbani, Ehsan; Bianchi, Irene; Bokelmann, Götz

    2015-01-01

    We analyze seismic anisotropy for the Eastern Alpine region by inspecting shear-wave splitting from SKS and SKKS phases. The Eastern Alpine region is characterized by a breakdown of the clear mountain-chain-parallel fast orientation pattern that has been previously documented for the Western Alps and for the western part of the Eastern Alps. The main interest of this paper is a more detailed analysis of the anisotropic character of the Eastern Alps, and the transition to the Carpathian–Pannonian region. SK(K)S splitting measurements reveal a rather remarkable lateral change in the anisotropy pattern from the west to the east of the Eastern Alps with a transition area at about 12°E. We also model the backazimuthal variation of the measurements by a vertical change of anisotropy. We find that the eastern part of the study area is characterized by the presence of two layers of anisotropy, where the deeper layer has characteristics similar to those of the Central Alps, in particular SW–NE fast orientations of anisotropic axes. We attribute the deeper layer to a detached slab from the European plate. Comparison with tomographic studies of the area indicates that the detached slab might possibly connect with the lithosphere that is still in place to the west of our study area, and may also connect with the slab graveyard to the East, at the depth of the upper mantle transition zone. On the other hand, the upper layer has NW–SE fast orientations coinciding with a low-velocity layer which is found above a more-or-less eastward dipping high-velocity body. The anisotropy of the upper layer shows large-scale NW–SE fast orientation, which is consistent with the presence of asthenospheric flow above the detached slab foundering into the deeper mantle. PMID:25843968

  13. Slab pull and the seismotectonics of subducting lithosphere.

    USGS Publications Warehouse

    Spence, W.

    1987-01-01

    This synthesis links many seismic and tectonic processes at subduction zones, including great subduction earthquakes, to the sinking of subducted plate. Earthquake data and tectonic modeling for subduction zones indicate that the slab pull force is much larger than the ridge push force. Interactions between the forces that drive and resist plate motions cause spatially and temporally localized stress that lead to characteristic earthquake activity, providing details on how subduction occurs.-from Author

  14. Project B: Improved Liquid Steel Feed For Slab Casters

    SciTech Connect

    Brent S. Isaacson; Mike Slepian; Thomas Richter

    1998-10-01

    This report describes the completion of the development of an electromagnetic valve to control liquid steel flow for improved liquid steel feeding for slab casters. Achievements result from a joint research effort between Westinghouse Science and Technology Center, North American Refractories and U.S. Steel. This effort is part of the American Iron and Steel Institute's (AISI) Advanced Process Control Program, a collaboration between the U.S. Department of Energy (DOE) and fifteen North American steel makers.

  15. Block-slider model for ductile instabilities in subducting slabs

    NASA Astrophysics Data System (ADS)

    Riedel, M. R.

    2003-04-01

    It has been suggested that the occurence of ductile (or plastic) instabilities in the deeper portion of subducting slabs is the dominating mechanism for the generation of intermediate-depth and deep-focus earthquakes. Heat generated during viscous deformation provides a positive feedback to creep and eventually faulting under high pressure. Recent detailed receiver function images of the structure of the Japan subduction zone seem to provide support for this notion. First, there is no indication of an existing metastable olivine wedge. Second, the intermediate-depth seismicity seems to be located in the strong and colder portions of the downgoing slab, about 30 km below the oceanic Moho. This suggests that instead of dehydration or phase transformation triggered events, ductile faulting is its predominating cause. In a recent paper, we have discussed the necessary conditions for ductile instabilities to develop in the bended subducting mantle lithosphere, based on the available experimental data on viscous creep of olivine resp. spinel (*). The present paper aims at a numerical study of the time evolution of a nucleated instability. For this purpose, we develop a cellular block-slider model for ductile instabilities in the mantle lithosphere, in analogy to the frequently used and highly successful block-slider models for brittle fracture of the crust. The block-slider approach is numerically much less demanding than solutions based on the corresponding, thermal-mechanically coupled continuum equations. Furthermore, it allows a straightforward inclusion of possible non-equilibrium effects associated with mineral phase transformations in a subducting slab (kinetic overshoot, grainsize reduction). The obtained numerical results are compared with seismological observation. It is shown, e.g., that the existence of metastable olivine in the deeper portion of a slab (below 500 km) is not a necessary condition for the generation of deep-focus earthquakes. (*) S. Karato, M

  16. Human Assisted Assembly Processes

    SciTech Connect

    CALTON,TERRI L.; PETERS,RALPH R.

    2000-01-01

    Automatic assembly sequencing and visualization tools are valuable in determining the best assembly sequences, but without Human Factors and Figure Models (HFFMs) it is difficult to evaluate or visualize human interaction. In industry, accelerating technological advances and shorter market windows have forced companies to turn to an agile manufacturing paradigm. This trend has promoted computerized automation of product design and manufacturing processes, such as automated assembly planning. However, all automated assembly planning software tools assume that the individual components fly into their assembled configuration and generate what appear to be a perfectly valid operations, but in reality the operations cannot physically be carried out by a human. Similarly, human figure modeling algorithms may indicate that assembly operations are not feasible and consequently force design modifications; however, if they had the capability to quickly generate alternative assembly sequences, they might have identified a feasible solution. To solve this problem HFFMs must be integrated with automated assembly planning to allow engineers to verify that assembly operations are possible and to see ways to make the designs even better. Factories will very likely put humans and robots together in cooperative environments to meet the demands for customized products, for purposes including robotic and automated assembly. For robots to work harmoniously within an integrated environment with humans the robots must have cooperative operational skills. For example, in a human only environment, humans may tolerate collisions with one another if they did not cause much pain. This level of tolerance may or may not apply to robot-human environments. Humans expect that robots will be able to operate and navigate in their environments without collisions or interference. The ability to accomplish this is linked to the sensing capabilities available. Current work in the field of cooperative

  17. Comparison of Cluster, Slab, and Analytic Potential Models for the Dimethyl Methylphosphonate (DMMP)/TiO2 (110) Intermolecular Interaction

    SciTech Connect

    Yang, Li; Tunega, Daniel; Xu, Lai; Govind, Niranjan; Sun, Rui; Taylor, Ramona; Lischka, Hans; De Jong, Wibe A.; Hase, William L.

    2013-08-29

    In a previous study (J. Phys. Chem. C 2011, 115, 12403) cluster models for the TiO2 rutile (110) surface and MP2 calculations were used to develop an analytic potential energy function for dimethyl methylphosphonate (DMMP) interacting with this surface. In the work presented here, this analytic potential and MP2 cluster models are compared with DFT "slab" calculations for DMMP interacting with the TiO2 (110) surface and with DFT cluster models for the TiO2 (110) surface. The DFT slab calculations were performed with the PW91 and PBE functionals. The analytic potential gives DMMP/ TiO2 (110) potential energy curves in excellent agreement with those obtained from the slab calculations. The cluster models for the TiO2 (110) surface, used for the MP2 calculations, were extended to DFT calculations with the B3LYP, PW91, and PBE functional. These DFT calculations do not give DMMP/TiO2 (110) interaction energies which agree with those from the DFT slab calculations. Analyses of the wave functions for these cluster models show that they do not accurately represent the HOMO and LUMO for the surface, which should be 2p and 3d orbitals, respectively, and the models also do not give an accurate band gap. The MP2 cluster models do not accurately represent the LUMO and that they give accurate DMMP/TiO2 (110) interaction energies is apparently fortuitous, arising from their highly inaccurate band gaps. Accurate cluster models, consisting of 7, 10, and 15 Ti-atoms and which have the correct HOMO and LUMO properties, are proposed. The work presented here illustrates the care that must be taken in "constructing" cluster models which accurately model surfaces.

  18. Water-Moderated and -Reflected Slabs of Uranium Oxyfluoride

    SciTech Connect

    Margaret A. Marshall; John D. Bess; J. Blair Briggs; Clinton Gross

    2010-09-01

    A series of ten experiments were conducted at the Oak Ridge National Laboratory Critical Experiment Facility in December 1955, and January 1956, in an attempt to determine critical conditions for a slab of aqueous uranium oxyfluoride (UO2F2). These experiments were recorded in an Oak Ridge Critical Experiments Logbook and results were published in a journal of the American Nuclear Society, Nuclear Science and Engineering, by J. K. Fox, L. W. Gilley, and J. H. Marable (Reference 1). The purpose of these experiments was to obtain the minimum critical thickness of an effectively infinite slab of UO2F2 solution by extrapolation of experimental data. To do this the slab thickness was varied and critical solution and water-reflector heights were measured using two different fuel solutions. Of the ten conducted experiments eight of the experiments reached critical conditions but the results of only six of the experiments were published in Reference 1. All ten experiments were evaluated from which five critical configurations were judged as acceptable criticality safety benchmarks. The total uncertainty in the acceptable benchmarks is between 0.25 and 0.33 % ?k/keff. UO2F2 fuel is also evaluated in HEU-SOL-THERM-043, HEU-SOL-THERM-011, and HEU-SOL-THERM-012, but these those evaluation reports are for large reflected and unreflected spheres. Aluminum cylinders of UO2F2 are evaluated in HEU-SOL-THERM-050.

  19. Ionospheric slab thickness in middle and low latitudes

    SciTech Connect

    Davies, K.; Liu, X.M. )

    1991-08-01

    The equivalent slab thickness of the ionosphere at 15 stations in middle and low latitudes was studied to determine its dependence on solar cycle and location. The data were grouped by season. The following are the major conclusions. There appears to be little or no geographical, or geomagnetic, dependence. The slab thickness varies approximately linearly with the 12-month smoothed values of the 10.7-cm solar radio flux. In middle latitudes the winter midnight thickness is essentially independent of the flux, whereas in summer and equinox the midnight thickness increases with increase of solar flux. The noon thickness increases with increase of solar flux in all seasons. The zero-order Fourier coeffficients for the diurnal curves at all 15 stations were expressed as linear functions of the 10.7-cm flux. The higher harmonic coefficients showed no appreciable dependence on solar flux. The pronounced predawn increase in slab thickness is caused by low values of the maximum electron density, not by increase of total electron content. 10 refs.

  20. Electromagnetic and ultrasonic investigations on a roman marble slab

    NASA Astrophysics Data System (ADS)

    Capizzi, Patrizia; Cosentino, Pietro L.

    2010-05-01

    The archaeological Museum of Rome (Museo delle Terme di Diocleziano) asked our group about the physical consistency of a marble slab (II - III century AD) that has recently fallen down during the transportation for an exhibition. In fact, due to insurance conflict, it was necessary to control the new fractures due to the recent accident and distinguish them from the ancient ones. The sculptured slab (today's size is 1280 x 70 x 9 cm), cut at the ends for a re-use as an inscription in the rear face, was restored (assemblage of different broken parts and cleaning) in contemporary times. We used different methodologies to investigate the slab: namely a pacometer (Protovale Elcometer) to individuate internal coupling pins, GPR (2000 MHz) and Ultrasonic (55 kHz) tomographic high-density surveys to investigate the internal extension of all the visible fractures and to search for the unknown internal ones. For every methodology used the quality of the acquired data was relatively high. They have been processed and compared to give a set of information useful for the bureaucratic problems of the Museum. Later on, the data have been processed in depth, for studying how to improve the data processing and for extracting all the information contained in the whole set of experimental data. Finally, the results of such a study in depth are exposed in detail.

  1. System for loading slab-gel holders for electrophoresis separation

    DOEpatents

    Anderson, Norman G.; Anderson, Norman L.

    1979-01-01

    A slab-gel loading system includes a prismatic chamber for filling a plurality of slab-gel holders simultaneously. Each slab-gel holder comprises a pair of spaced apart plates defining an intermediate volume for gel containment. The holders are vertically positioned in the chamber with their major surfaces parallel to the chamber end walls. A liquid inlet is provided at the corner between the bottom and a side wall of the chamber for distributing a polymerizable monomer solution or a coagulable colloidal solution into each of the holders. The chamber is rotatably supported so that filling can begin with the corner having the liquid inlet directed downwardly such that the solution is gently funneled upwardly, without mixing, along the diverging side and bottom surfaces. As filling proceeds, the chamber is gradually rotated to position the bottom wall in a horizontal mode. The liquid filling means includes a plastic envelope with a septum dividing it into two compartments for intermixing two solutions of different density and thereby providing a liquid flow having a density gradient. The resulting gels have a density gradient between opposite edges for subsequent use in electrophoresis separations.

  2. High Performance Slab-on-Grade Foundation Insulation Retrofits

    SciTech Connect

    Goldberg, Louise F.; Mosiman, Garrett E.

    2015-09-01

    ?A more accurate assessment of SOG foundation insulation energy savings than traditionally possible is now feasible. This has been enabled by advances in whole building energy simulation with 3-dimensional foundation modelling integration at each time step together with an experimental measurement of the site energy savings of SOG foundation insulation. Ten SOG insulation strategies were evaluated on a test building to identify an optimum retrofit insulation strategy in a zone 6 climate (Minneapolis, MN). The optimum insulation strategy in terms of energy savings and cost effectiveness consisted of two components: (a) R-20 XPS insulation above grade, and, (b) R-20 insulation at grade (comprising an outer layer of R-10 insulation and an interior layer of R-12 poured polyurethane insulation) tapering to R-10 XPS insulation at half the below-grade wall height (the lower half of the stem wall was uninsulated). The optimum insulation strategy was applied to single and multi-family residential buildings in climate zone 4 - 7. The highest site energy savings of 5% was realized for a single family home in Duluth, MN, and the lowest savings of 1.4 % for a 4-unit townhouse in Richmond, VA. SOG foundation insulation retrofit simple paybacks ranged from 18 to 47 years. There are other benefits of SOG foundation insulation resulting from the increase in the slab surface temperatures. These include increased occupant thermal comfort, and a decrease in slab surface condensation particularly around the slab perimeter.

  3. Ionospheric slab thickness and its seasonal variations observed by GPS

    NASA Astrophysics Data System (ADS)

    Jin, Shuanggen; Cho, Jung-Ho; Park, Jung-Uk

    2007-11-01

    The ionospheric slab thickness, the ratio of the total electron content (TEC) to the F2-layer peak electron density (NmF2), is closely related to the shape of the ionospheric electron density profile Ne (h) and the TEC. Therefore, the ionospheric slab thickness is a significant parameter representative of the ionosphere. In this paper, the continuous GPS observations in South Korea are firstly used to study the equivalent slab thickness (EST) and its seasonal variability. The averaged diurnal medians of December January February (DJF), March April May (MAM), June July August (JJA) and September October November (SON) in 2003 have been considered to represent the winter, spring, summer and autumn seasons, respectively. The results show that the systematic diurnal changes of TEC, NmF2 and EST significantly appeared in each season and the higher values of TEC and NmF2 are observed during the equinoxes (semiannual anomaly) as well as in the mid-daytime of each season. The EST is significantly smaller in winter than in summer, but with a consistent variation pattern. During 14 16 LT in daytime, the larger EST values are observed in spring and autumn, while the smaller ones are in summer and winter. The peaks of EST diurnal variation are around 10 18 LT which are probably caused by the action of the thermospheric wind and the plasmapheric flow into the F2-region.

  4. Electromagnetic and ultrasonic investigations on a Roman marble slab

    NASA Astrophysics Data System (ADS)

    Capizzi, P.; Cosentino, P. L.

    2011-09-01

    The archaeological museum of Rome asked our group about the physical consistency of a marble slab (second to third century AD) that recently fell during its travel as part of an exhibition. We decided to use different methodologies to investigate the slab: namely a pacometer (Protovale Elcometer) to individuate the internal coupling pins, and ground-penetrating radar (GPR) (2000 MHz) and ultrasonic (55 kHz) tomographic high-density surveys to investigate the internal extension of all the visible fractures and to search for the hidden ones. For the ultrasonic data, tests were carried out to optimize the inversion parameters, in particular the cell dimensions. Surely, the choice of cell size for the inversion process must take into account the size of the acquisition grid and the ray number acquired. We proposed to calculate a minimum Fresnel's radius using the sampling frequency instead of that of the probes. For every methodology used, the quality of the acquired data was relatively high. This was then processed and compared to provide information that was useful for some of the insurance problems of the museum. Later on, the data was processed in depth to see how to improve the data processing and interpretation. Finally, the results of this in-depth study were exposed in detail. Ultrasonic and GPR tomographies show a strong correlation, and in particular, the inhomogeneous areas are located in correspondence to the slab injuries.

  5. Studies on the progress of occupational cervicobrachial disorder by analysing the subjective symptoms of work-women in assembly lines of a cigarette factory.

    PubMed

    Maeda, K; Hirayama, H; Chang, C P; Takamatsu, M

    1979-09-01

    The Committee on Cervicobrachial Syndrome in Japan Association of Industrial Health (JAIH) made a report on the questionnaires for checking for the complaints of patients suffering from Occupational Cervicobrachial Disorder (OCD). In order to reveal how the complaints develop in the progress of OCD, we analysed the complaints of 117 workwomen in assembly lines of a cigarette factory by using the questionnaires. And the followings were made clear: 1) At the mild stage of OCD, stiffness or dullness at the neck and shoulders, and eyestrain become remarkable. 2) At the moderate stage, pain at the neck, shoulders, arms and hands, dullness at extremities, general fatigue, pain or heavy feeling in the head, increased irritability etc. become remarkable in addition to the mild stage complaints. 3) At the severe stage, pain and dullness at the back, numbness at arms and hands, hand coldness, sleep disturbance etc. become remarkable in addition to the moderate stage complaints. 4) Various sufferings in daily life such as "I want to lie down at rest time," "I lack patience to go on reading long," "It is hard for me to go on writing long," and "Fixed sitting soon tires me" become more and more frequent as the stage advances. We consider it is important in the diagnosis of OCD to pay attention to the general symptoms such as general fatigue, pain or heavy feeling in the head, increased irritability and sleep disturbance, together with complaints at the neck, shoulders, arms and hands.

  6. Surface turbulence in a physical model of a steel thin slab continuous caster

    NASA Astrophysics Data System (ADS)

    Hajari, A.; Meratian, M.

    2010-12-01

    In the thin slab continuous casting (TSCC) of steel, the issue of optimum fluid flow is very important due to higher casting speeds and has direct influence on the formation of solidified shells and the quality of final products. In the current work, a full-scale physical modeling of a thin slab caster on the basis of dimensionless Reynolds and Froude similarity criteria was constructed. The flow pattern in the funnel shaped mold with a new tetra-furcated submerged entry nozzle (SEN) was investigated. To determinate optimum operational parameters, some experiments were carried out under various casting conditions. The results show that the tetra-furcated design of the nozzle leads to a special flow pattern in the mold cavity with three-dimensional recirculating flow. It is also shown that the increase of casting speed and gas injection results in surface turbulence. On the other hand, using a higher depth of SEN decreases the vortex in the free surface of the caster. To avoid surface turbulent and related casting problems, it is recommended to use 30-cm and 40-cm SEN depth at the casting speeds of 3.5 and 4.5 m/min, respectively.

  7. Modeling of the flow-solidification interaction in thin slab casting

    NASA Astrophysics Data System (ADS)

    Vakhrushev, A.; Wu, M.; Ludwig, A.; Tang, Y.; Hackl, G.; Nitzl, G.

    2012-07-01

    A key issue for modelling the thin slab casting (TSC) is to consider the evolution of the solid shell, which strongly interacts with the turbulent flow and in the meantime is subject to continuous deformation due to the funnel shape (curvature) of the mould. Here an enthalpy-based mixture solidification model with consideration of turbulent flow [Prescott and Incropera, ASME HTD, vol. 280, 1994, pp. 59] is employed, and further enhanced to include the deforming solid shell. The solid velocity in the fully-solidified strand shell and partially-solidified mushy zone is estimated by solving the Laplace's equation. Primary goals of this work are to examine the sensitivity of the modelling result to different model implementation schemes, and to explore the importance of the deforming and moving solid shell in the solidification. Therefore, a 2D benchmark, to mimic the solidification and deformation behaviour of the thin slab casting, is firstly simulated and evaluated. An example of 3D TSC is also presented. Due to the limitation of the current computation resources additional numerical techniques like parallel computing and mesh adaptation are necessarily applied to ensure the calculation accuracy for the full-3D TSC.

  8. Restoration of s-polarized evanescent waves and subwavelength imaging by a single dielectric slab

    NASA Astrophysics Data System (ADS)

    El Gawhary, Omar; Schilder, Nick J.; da Costa Assafrao, Alberto; Pereira, Silvania F.; Urbach, H. Paul

    2012-05-01

    It was predicted a few years ago that a medium with negative index of refraction would allow for perfect imaging. Although no material has been found so far that behaves as a perfect lens, some experiments confirmed the theoretical predictions in the near-field, or quasi-static, regime where the behaviour of a negative index medium can be mimicked by a thin layer of noble metal, such as silver. These results are normally attributed to the excitation of surface plasmons in the metal, which only leads to the restoration of p-polarized evanescent waves. In this work, we show that the restoration of s-polarized evanescent waves and, correspondingly, sub-wavelength imaging by a single dielectric slab are possible. Specifically, we show that at λ = 632 nm a thin layer of GaAs behaves as a superlens for s-polarized waves. Replacing the single-metal slab by a dielectric is not only convenient from a technical point of view, it being much easier to deposit and control the thickness and flatness of dielectric films than metal ones, but also invites us to re-think the connection between surface plasmon excitation and the theory of negative refraction.

  9. Transmission of evanescent wave modes through a slab of negative-refractive-index material.

    PubMed

    de Wolf, David A

    2011-02-01

    There has been a long-standing argument about Pendry's suggestion that a plane harmonic evanescent (surface) wave along the interface between free space and a slab of ɛ=-1, μ=-1 double-negative (DNG) medium will emerge on the far side with recovery of phase and amplitude. While this is possible, it is subject to parameter restrictions. This work generalizes previous work and now gives analytical criteria for when to expect such a recovery in a Smith-Kroll DNG medium. Basically this requires, among other things, a relatively narrow bandwidth and relatively small transverse-mode component. There also is a very strong dependence on the ratio of slabwidth to plasma wavelength.

  10. Hinge assembly

    DOEpatents

    Vandergriff, D.H.

    1999-08-31

    A hinge assembly is disclosed having a first leaf, a second leaf and linking member. The first leaf has a contact surface. The second leaf has a first contact surface and a second contact surface. The linking member pivotally connects to the first leaf and to the second leaf. The hinge assembly is capable of moving from a closed position to an open position. In the closed position, the contact surface of the first leaf merges with the first contact surface of the second leaf. In the open position, the contact surface of the first leaf merges with the second contact surface of the second leaf. The hinge assembly can include a seal on the contact surface of the first leaf. 8 figs.

  11. Hinge assembly

    DOEpatents

    Vandergriff, David Houston

    1999-01-01

    A hinge assembly having a first leaf, a second leaf and linking member. The first leaf has a contact surface. The second leaf has a first contact surface and a second contact surface. The linking member pivotally connects to the first leaf and to the second leaf. The hinge assembly is capable of moving from a closed position to an open position. In the closed position, the contact surface of the first leaf merges with the first contact surface of the second leaf. In the open position, the contact surface of the first leaf merges with the second contact surface of the second leaf. The hinge assembly can include a seal on the contact surface of the first leaf.

  12. Detecting lower-mantle slabs beneath Asia and the Aleutians

    NASA Astrophysics Data System (ADS)

    Schumacher, L.; Thomas, C.

    2016-06-01

    To investigate the descend of subducted slabs we search for and analyse seismic arrivals that reflected off the surface of the slab. In order to distinguish between such arrivals and other seismic phases, we search for waves that reach a seismic array with a backazimuth deviating from the theoretical backazimuth of the earthquake. Source-receiver combinations are chosen in a way that their great circle paths do not intersect the slab region, hence the direct arrivals can serve as reference. We focus on the North and Northwest Pacific region by using earthquakes from Japan, the Philippines and the Hindu Kush area recorded at North American networks (e.g. USArray, Alaska and Canada). Using seismic array techniques for analysing the data and record information on slowness, backazimuth and traveltime of the observed out-of-plane arrivals we use these measurements to trace the wave back through a 1-D velocity model to its scattering/reflection location. We find a number of out-of-plane reflections. Assuming only single scattering, most out-of-plane signals have to travel as P-to-P phases and only a few as S-to-P phases, due to the length of the seismograms we processed. The located reflection points present a view of the 3-D structures within the mantle. In the upper mantle and the transition zone they correlate well with the edges of fast velocity regions in tomographic images. We also find reflection points in the mid- and lower mantle and their locations generally agree with fast velocities mapped by seismic tomography models suggesting that in the subduction regions we map, slabs enter the lower mantle. To validate our approach, we calculate and process synthetic seismograms for 3-D wave field propagation through a model containing a slab-like heterogeneity. We show, that depending on the source-receiver geometry relative to the reflection plane, it is indeed possible to observe and back-trace out-of-plane signals.

  13. Opening and closing slab windows in congested subduction zones

    NASA Astrophysics Data System (ADS)

    Moresi, Louis

    2013-04-01

    Subduction zones often try to swallow buoyant material which is embedded in the oceanic lithosphere: plume material or hotspot residues, oceanic plateaux, and fragments of continental material. This often results in the formation of a slab window and it has been shown (Mason et al, 2010; Betts et al, 2012) that this window strongly influences the subsequent evolution of the slab and the advance/retreat rate of the trench. The buoyant material typically pushes the trench into a local state of advance, and the creation of the slab window allows the rest of the trench to retreat as the mantle behind the slab flows in through the window. This situation is inherently unstable: if the buoyancy anomaly is finite in size, then the retreating trench will soon move behind the anomaly and juxtapose negatively buoyant oceanic lithosphere with active subduction. This creates the potential to close the slab window and, in doing so, transfer the buoyant material to the over-riding plate. Models show that this closure of the window initially occurs through a lateral rollback process followed by a catastrophic re-initiation of subduction behind the colliding buoyant anomaly. This rollback leaves a characteristic, tightly rolled remnant in the mantle and significant rotation in the over-riding plate and the newly-docked block. The over-riding plate is thrown into extension perpendicular to the original orientation of the trench. This same situation applies at the late-stages of a closing ocean due to the passive margin geometry and the presence of debris collected from the closing ocean floor and it seems likely that these models can also be applied to the complicated geometry of subduction in such environments. Mason, W. G.; Moresi, L.; Betts, P. G. & Miller, M. S. Three-dimensional numerical models of the influence of a buoyant oceanic plateau on subduction zones Tectonophysics, 2010, 483, 71-79 P. Betts, W. Mason, L. Moresi, The influence of mantle plumes on subduction zone

  14. Design of energy efficient building with radiant slab cooling

    NASA Astrophysics Data System (ADS)

    Tian, Zhen

    2007-12-01

    Air-conditioning comprises a substantial fraction of commercial building energy use because of compressor-driven refrigeration and fan-driven air circulation. Core regions of large buildings require year-round cooling due to heat gains from people, lights and equipment. Negative environmental impacts include CO2 emissions from electric generation and leakage of ozone-depleting refrigerants. Some argue that radiant cooling simultaneously improves building efficiency and occupant thermal comfort, and that current thermal comfort models fail to reflect occupant experience with radiant thermal control systems. There is little field evidence to test these claims. The University of Calgary's Information and Communications Technology (ICT) Building, is a pioneering radiant slab cooling installation in North America. Thermal comfort and energy performance were evaluated. Measurements included: (1) heating and cooling energy use, (2) electrical energy use for lighting and equipment, and (3) indoor temperatures. Accuracy of a whole building energy simulation model was evaluated with these data. Simulation was then used to compare the radiant slab design with a conventional (variable air volume) system. The radiant system energy performance was found to be poorer mainly due to: (1) simultaneous cooling by the slab and heating by other systems, (2) omission of low-exergy (e.g., groundwater) cooling possible with the high cooling water temperatures possible with radiant slabs and (3) excessive solar gain and conductive heat loss due to the wall and fenestration design. Occupant thermal comfort was evaluated through questionnaires and concurrent measurement of workstation comfort parameters. Analysis of 116 sets of data from 82 occupants showed that occupant assessment was consistent with estimates based on current thermal comfort models. The main thermal comfort improvements were reductions in (1) local discomfort from draft and (2) vertical air temperature stratification. The

  15. Latch assembly

    DOEpatents

    Frederickson, James R.; Harper, William H.; Perez, Raymond

    1986-01-01

    A latch assembly for releasably securing an article in the form of a canister within a container housing. The assembly includes a cam pivotally mounted on the housing wall and biased into the housing interior. The cam is urged into a disabled position by the canister as it enters the housing and a latch release plate maintains the cam disabled when the canister is properly seated in the housing. Upon displacement of the release plate, the cam snaps into latching engagement against the canister for securing the same within the housing.

  16. Latch assembly

    DOEpatents

    Frederickson, J.R.; Harper, W.H.; Perez, R.

    1984-08-17

    A latch assembly for releasably securing an article in the form of a canister within a container housing. The assembly includes a cam pivotally mounted on the housing wall and biased into the housing interior. The cam is urged into a disabled position by the canister as it enters the housing and a latch release plate maintains the cam disabled when the canister is properly seated in the housing. Upon displacement of the release plate, the cam snaps into latching engagement against the canister for securing the same within the housing. 2 figs.

  17. Valve assembly

    SciTech Connect

    Marshala, D.L.

    1986-12-16

    This patent describes a subsurface pump actuated by a reciprocatable sucker rod for producing well liquids from a subsurface reservoir involving a piston adapted to reciprocate within a cylinder immersed in the reservoir, the piston being provided with a traveling valve. The improvement described here comprises valve means connected to the sucker tod for lifting a body of fluid during upstrokes of the sucker rod, the valve means comprising: a barrel assembly having an internal bore and comprising: a lower barrel member; and an upper barrel assembly connected to the lower barrel and having a beveled seating surface with at least one fluid port therethrough.

  18. The Work Group on Early Childhood Report on Reform of the Early Childhood System. Report to the Governor and the Illinois General Assembly.

    ERIC Educational Resources Information Center

    Voices for Illinois Children, Chicago.

    Illinois Senate Joint Resolution 173 resulted in the appointment in 1994 of a 53-member Work Group on Early Childhood Education. This group was mandated to report to the Senate on the development and implementation of a statewide early childhood education and care program. The group identified key issues, delimited legislative objectives, offered…

  19. School-to-Work Transition Programs. Report of the Department of Education to the Governor and the General Assembly of Virginia. Senate Document No. 7.

    ERIC Educational Resources Information Center

    Virginia State Dept. of Education, Richmond.

    A team of representatives of Virginia state agencies involved in career preparation and employment examined the development and establishment of school-to-work transition (SWT) programs in Virginia. The team conducted a literature review and analyzed 42 selected state programs. The 16 school-based programs primarily provided classroom instruction…

  20. Assembling the evidence jigsaw: insights from a systematic review of UK studies of individual-focused return to work initiatives for disabled and long-term ill people

    PubMed Central

    2011-01-01

    Background Employment rates of long-term ill and disabled people in the UK are low and 2.63 million are on disability-related state benefits. Since the mid-1990 s, UK governments have experimented with a range of active labour market policies aimed to move disabled people off benefits and into work to reduce the risk of poverty and social exclusion. This systematic review asks what employment impact have these interventions had and how might they work better? Methods A systematic review of observational and qualitative empirical studies and systematic reviews published between 2002 and mid-2008 reporting employment effects and/or process evaluations of national UK government interventions focused on helping long-term sick or disabled people (aged 16-64) into the open labour market. This built on our previous systematic review which covered the years 1970 to 2001. Results Searches identified 42 studies, 31 of which evaluated initiatives with an individual focus (improving an individual's employability or providing financial support in returning to work) while 11 evaluated initiatives with an environmental focus (directed at the employment environment or changing the behaviour of employers). This paper synthesises evidence from the 31 studies with an individual focus. The use of personal advisors and individual case management in these schemes helped some participants back to work. Qualitative studies, however, revealed that time pressures and job outcome targets influenced advisors to select 'easier-to-place' claimants into programmes and also inhibited the development of mutual trust, which was needed for individual case management to work effectively. Financial incentives can help with lasting transitions into work, but the incentives were often set too low or were too short-term to have an effect. Many of the studies suffered from selection bias into these programmes of more work-ready claimants. Even though these were national programmes, they had very low

  1. Tomographic imaging of the Cascadia subduction zone: Constraints on the Juan de Fuca slab

    NASA Astrophysics Data System (ADS)

    Chen, Chuanxu; Zhao, Dapeng; Wu, Shiguo

    2015-04-01

    We used 40,343 P-wave arrival times from 1883 local earthquakes and 105,455 P-wave arrivals from 6361 teleseismic events to study the detailed structure of the Cascadia subduction zone. We conducted tomographic inversions using a starting velocity model which includes the high-velocity subducting Juan de Fuca slab as a priori information. A number of such slab-constrained inversions are conducted by changing the slab thickness and the velocity contrast between the slab and the surrounding mantle. Our optimal 3-D velocity model fits the data much better than that determined by an inversion with a 1-D homogeneous starting model. Our results show that the subducting Juan de Fuca slab has a thickness of 30-50 km and a P-wave velocity of 1-3% higher than that of the surrounding mantle. Beneath the northern and southern parts of the Cascadia, P-wave velocity is lower in the slab and along the slab interface, which may reflect a more hydrated slab and more active slab dehydration there. The lateral velocity variations may indicate different degrees of slab dehydration and forearc mantle serpentinization. The segmentation in episodic tremor and slip (ETS) is also spatially coincident with the velocity heterogeneities, indicating that the ETS occurrence and recurrence interval are controlled by fluid activity in and around the mantle wedge corner.

  2. Furnace assembly

    DOEpatents

    Panayotou, N.F.; Green, D.R.; Price, L.S.

    A method of and apparatus for heating test specimens to desired elevated temperatures for irradiation by a high energy neutron source. A furnace assembly is provided for heating two separate groups of specimens to substantially different, elevated, isothermal temperatures in a high vacuum environment while positioning the two specimen groups symmetrically at equivalent neutron irradiating positions.

  3. Furnace assembly

    DOEpatents

    Panayotou, Nicholas F.; Green, Donald R.; Price, Larry S.

    1985-01-01

    A method of and apparatus for heating test specimens to desired elevated temperatures for irradiation by a high energy neutron source. A furnace assembly is provided for heating two separate groups of specimens to substantially different, elevated, isothermal temperatures in a high vacuum environment while positioning the two specimen groups symmetrically at equivalent neutron irradiating positions.

  4. Global Subducting Slab Entrainment of Oceanic Asthenosphere: Re-examination of Sub-Slab Shear-Wave Splitting Patterns

    NASA Astrophysics Data System (ADS)

    Song, T.; Liu, L.; Kawakatsu, H.

    2011-12-01

    Oceanic asthenosphere is characterized as a low seismic velocity, low viscosity, and strongly anisotropic channel separating from the oceanic lithosphere through a sharp shear wave velocity contrast. It has been a great challenge to reconcile all these observations and ultimately illuminate the fate of oceanic asthenosphere near convergent plate margins. Sub-slab shear wave splitting patterns are particularly useful to address the fate of oceanic asthenosphere since they are directly linked to deformation induced by the mantle flow beneath the subducting slab. To address slab entrainment of oceanic asthenosphere through shear wave splitting, it is important to recognize that oceanic asthenosphere is characterized by azimuthal anisotropy (1-3%) as well as strong P wave and S wave radial anisotropy (3-7%) for horizontally travelling P wave (VPH > VPV) and S wave (VSH > VSV), making it effectively an orthorhombic medium. Here we show that entrained asthenosphere predicts sub-slab SKS splitting pattern, where the fast splitting direction changes from predominantly trench-normal under shallow subduction zones to predominantly trench-parallel under relatively steep subduction zones. This result can be recognized by the 90 degrees shift in the polarization of the fast wave at about 20 degrees incident angle, where VSH equals to VSV forming a classical point singularity (Crampin, 1991). The thickness of the entrained asthenosphere is estimated to be on the order of 100 km, which predicts SKS splitting time varying from 0.5 seconds to 2 seconds. After briefly discussing improvement of the millefeuille model (Kawakatsu et al. 2009) of the asthenosphere upon this new constraint and long wave Backus averaging of orthorhombic solid and melt, we will illustrate that, in the range of observed trench migration speed, dynamic models of 2-D mantle convection with temperature-dependent viscosity do support thick subducting slab entrainment of asthenosphere under ranges of

  5. New Whole-House Solutions Case Study: Exterior Rigid Foam Insulation at the Edge of a Slab Foundation, Fresno, California

    SciTech Connect

    2013-10-01

    Exterior rigid foam insulation at the edge of the slab foundation was a unique feature for this low-load, unoccupied test house in a hot-dry climate and may be more appropriate for climates with higher heating loads. U.S. Department of Energy Building America research team IBACOS worked with National Housing Quality Award winner Wathen-Castanos Hybrid Homes, Inc., to assess the performance of this feature in a single-family detached ranch house with three bedrooms and two full bathrooms constructed on a slab-on-grade foundation in Fresno, California. One challenge during installation of the system was the attachment of the butyl flashing to the open framing. To solve this constructability issue, the team added a nailer to the base of the wall to properly attach and lap the flashing. In this strategy, R-7.5, 1.5-in.-thick extruded polystyrene was installed on the exterior of the slab for a modeled savings of 4,500 Btu/h on the heating load.

  6. Plate kinematics, slab shape and back-arc stress: A comparison between laboratory models and current subduction zones

    NASA Astrophysics Data System (ADS)

    Heuret, A.; Funiciello, F.; Faccenna, C.; Lallemand, S.

    2007-04-01

    A combination of statistical studies on present-day subduction zones and three-dimensional (3D) laboratory models is performed with the aim to clarify the way that plate kinematics control the geometry of the slab and the overriding plate deformation in subduction zones. In 3D laboratory models, the analogue of a two layer linearly viscous lithosphere-upper mantle system is achieved by means of silicon putty glucose syrup tank experiment. The subducting and overriding plate velocities are systematically changed by exploring the variability field of natural plate kinematics. Both statistical and modelling approaches recognize the importance of overriding plate motion on subduction process behavior: (1) trenches migrate at a rate close to the overriding plate motion, but always move slower than the overriding plates. The mechanism at work is a direct consequence of "slab anchoring" opposed by both lithosphere and mantle viscous resistance and is responsible for overriding plate deformation and slab geometry variability. (2) An overriding plate shortens when the overriding plate moves toward the trench and conditions that are favourable for overriding plate extension are created when the overriding plate moves away from the trench. (3) Shallow and steep dips are found if the overriding plate moves toward and away from the trench, respectively.

  7. Planning Assembly Of Large Truss Structures In Outer Space

    NASA Technical Reports Server (NTRS)

    De Mello, Luiz S. Homem; Desai, Rajiv S.

    1992-01-01

    Report dicusses developmental algorithm used in systematic planning of sequences of operations in which large truss structures assembled in outer space. Assembly sequence represented by directed graph called "assembly graph", in which each arc represents joining of two parts or subassemblies. Algorithm generates assembly graph, working backward from state of complete assembly to initial state, in which all parts disassembled. Working backward more efficient than working forward because it avoids intermediate dead ends.

  8. Linking Slab Break-Off, Hellenic Trench Retreat, and Uplift of the Central and Eastern Anatolian Plateaus

    NASA Astrophysics Data System (ADS)

    Schildgen, T. F.; Yildirim, C.; Cosentino, D.; Strecker, M. R.

    2015-12-01

    The Central and Eastern Anatolian plateaus are integral parts of the world's third largest orogenic plateau. Geophysical surveys that have provided insights into the crust, lithosphere, and mantle beneath Eastern Anatolia are now accompanied by recent work in Central Anatolia constraining uplift along its northern and southern margins. Together with predictions from geodynamic models, the observations can be integrated to identify probable mechanisms of plateau growth. A changeover from shortening to extension along the southern margin of Central Anatolia coeval with the start of uplift in the latest Miocene is likely associated with oceanic slab break-off following Arabia-Eurasia collision. This interpretation is supported by tomography, seismicity, and the pattern of uplift. Based on geological observations and model predictions, slab break-off likely occurred first beneath Eastern Anatolia in middle Miocene time and propagated westward toward Cyprus by the latest Miocene. Uplift at the northern margin of Central Anatolia appears to result from crustal shortening starting in the late Miocene, which has been linked to the broad restraining bend of the North Anatolian Fault (NAF). The uplift history of the Central Anatolian interior is unclear, although shortening was superseded by extension in the late Miocene. This change in the deformation style coincides with faster retreat of the Hellenic trench as well as uplift of the northern and southern margins of Central Anatolia. These different events may be linked, as faster retreat of the Hellenic trench has been predicted to occur after slab break-off, which could have induced extension of Central Anatolia and helped to form the NAF through accelerated westward escape of Anatolia. Overall, geochronologic evidence supports the hypothesis that tectonic and geodynamic plateau-forming activity throughout the Aegean-Anatolian domain in the Miocene defines a series of events that may all be linked to slab break-off.

  9. Photovoltaic self-assembly.

    SciTech Connect

    Lavin, Judith; Kemp, Richard Alan; Stewart, Constantine A.

    2010-10-01

    This late-start LDRD was focused on the application of chemical principles of self-assembly on the ordering and placement of photovoltaic cells in a module. The drive for this chemical-based self-assembly stems from the escalating prices in the 'pick-and-place' technology currently used in the MEMS industries as the size of chips decreases. The chemical self-assembly principles are well-known on a molecular scale in other material science systems but to date had not been applied to the assembly of cells in a photovoltaic array or module. We explored several types of chemical-based self-assembly techniques, including gold-thiol interactions, liquid polymer binding, and hydrophobic-hydrophilic interactions designed to array both Si and GaAs PV chips onto a substrate. Additional research was focused on the modification of PV cells in an effort to gain control over the facial directionality of the cells in a solvent-based environment. Despite being a small footprint research project worked on for only a short time, the technical results and scientific accomplishments were significant and could prove to be enabling technology in the disruptive advancement of the microelectronic photovoltaics industry.

  10. Transition from slab stagnation to penetration beneath the northwestern Pacific and South America (Invited)

    NASA Astrophysics Data System (ADS)

    Fukao, Y.; Obayashi, M.

    2010-12-01

    Subducting slabs tend to once deflect horizontally in the transition zone as stagnant slabs and then to penetrate into the lower mantle across the 660-km discontinuity. Here we present the detailed tomographic images of transition from stagnant-slab mode to penetrating-slab mode, based on the global ISC travel time data to which regional network data and long-term array observation data including ocean bottom data are added. The targets are the subducted slabs beneath South America and the northwestern Pacific. In South America the transition occurs across the northeastward extension of the sharp bend of the Peru-Chili trench. The slab to the south of this extension is stagnant above the 660, and to the north it plunges into the lower mantle across the 660. The transition is sharp as if the originally flat slab in the northern part was rotated into the present configuration by hinge faulting along the extension. We suspect that this hinge faulting either triggered the northward propagation of or truncated the southward propagation of the plunging motion of the slab into the lower mantle. Along the Kurile arc, the slab is flattened above the 660 in the southwest, penetrating in the northeast, with a transitional feature in between. In southern Kurile the flattened part has a deepest bottom near the junction with the dipping part. Such an along-arc change of slab configuration is indicative of a process of transition from stagnant-slab mode to penetrating-slab mode: the flattened part and dipping part of the slab begin to sink into the lower mantle at their junction so that the horizontal part is progressively dragged to and is eventually united to the dipping part as a penetrating slab. Along the Izu-Bonin-Mariana (IBM) arc, the slab is flattened above the 660 in the north (Izu-Bonin) and is penetrating the 660 in the south (Mariana) leaving the horizontal part in the transition zone. In the Izu-Bonin the flattened part has a deepest bottom near the junction with

  11. A Systematic Study on the Formation of South American Flat-Slab Subduction

    NASA Astrophysics Data System (ADS)

    Hu, J.; Liu, L.

    2015-12-01

    The South American subduction zone is characterized by its along-strike variation from flat to steeply dipping slabs. Both formation mechanisms and geometry of flat slabs in South America remain unclear. To evaluate the relative contribution of different mechanisms to flat slab formation, we simulate the post-100 Ma subduction history below South America using 3-D geodynamic models by progressively incorporating key tectonic features including seafloor ages, buoyant oceanic crusts, thickened oceanic plateaus (i.e. the Inca plateau, Nazca Ridge and Juan Fernandez Ridge), continental cratons, as well as deformable trench profiles according to recent geological reconstructions. With a uniform seafloor age of 30 Ma (i.e., the spatial average of the Nazca Plate since 20 Ma), we get steep (>30°, measured at 200 km depth) subduction everywhere except at 25°S -35°S, where the slab dip is affected by earlier subduction at depth. With the actual reconstructed seafloor ages, the slab dip angle is systematically reduced with an average of ~25°; the long-wavelength lateral variation of slab dip angle that resembles the observation results from the spatial variation of slab buoyancy and strength. The addition of a uniformly thick overriding plate, with enhanced dynamic suction in the mantle wedge, further reduces the slab dip angle (<23°) along the entire trench, where the young slab portions are affected more than the old one. Realization of the 3D geometry of cratonic roots enhances along-trench variation of suction force, which results in an additional reduction of slab dip (<20°), especially next to the cratons. While dynamic suction from the overriding plate reduces the long-wavelength slab dip angle, subducting oceanic plateau and aseismic ridges lead to more localized flat-slabs (as low as 15°) as observed. The subduction of aseismic ridges also generates tears within the flat slabs, due to the accumulation of strain at the down-dip end of the ridge. These slab

  12. Too much slab waving in South America? Wet plumes as an alternative to flat slab steepening as the cause of back arc large volcanic provinces

    NASA Astrophysics Data System (ADS)

    Booker, J. R.; Burd, A. I.

    2013-12-01

    A widely held view is that the Nazca Slab under western S. America acts like a tattered flag waving in the wind: It is segmented and the dip angle of segments flap up and down with time. There are presently two flat segments - one under Peru and the other, the "Pampean" flat slab (centered around 31S) under central Chile and Argentina. Both are correlated with subduction of buoyant crust of oceanic aseismic ridges, complete cessation of Andean arc volcanism and very thick crust. It has been argued that the waxing and waning of flat subduction is responsible for much of the time variations in tectonics and volcanism up to 800 km east of the S. American coast for at least 100 MA. For instance, the back arc Payenia igneous plateau (35-38S) and the Somuncura igneous plateau (40.5-43S) are both thought to follow from the steepening of flat slabs at about 2 and 27 MA. Each flat slab existed for more than 5 MA. However, the case for the existence of these flat slabs rests heavily on volcanism with "arc signature" hundreds of km east of the modern volcanic arc at a time when an asthenospheric wedge would be in its final stages of being squeezed out of the space between the slab and the lithosphere. Arc signature can be summarized as the geochemical consequence of mantle melting in the presence of water. If there is a source of water in the mantle other than a shallow slab, the strongest argument for a flat slab dissolves. We have found two electrically conductive plumes rising from below 350 km near the top of the Mantle Transition Zone (MTZ). One passes through a window in the Pampean flat slab but does not penetrate the lithosphere. The other rises under Payenia. The maximum resistivity at the core of these plumes is less than 10 Ohm-m. Partial melt can explain such low resistivity, but will not be buoyant and rise from below 350 km. We propose that the low resistivity is more likely due to water and that we are seeing "wet plumes" that have been proposed to explain

  13. Mini-Brayton heat source assembly development

    NASA Technical Reports Server (NTRS)

    Wein, D.; Zimmerman, W. F.

    1978-01-01

    The work accomplished on the Mini-Brayton Heat Source Assembly program is summarized. Required technologies to design, fabricate and assemble components for a high temperature Heat Source Assembly (HSA) which would generate and transfer the thermal energy for a spaceborne Brayton Isotope Power System (BIPS) were developed.

  14. Cenozoic tectonics of western North America controlled by evolving width of Farallon slab.

    PubMed

    Schellart, W P; Stegman, D R; Farrington, R J; Freeman, J; Moresi, L

    2010-07-16

    Subduction of oceanic lithosphere occurs through two modes: subducting plate motion and trench migration. Using a global subduction zone data set and three-dimensional numerical subduction models, we show that slab width (W) controls these modes and the partitioning of subduction between them. Subducting plate velocity scales with W(2/3), whereas trench velocity scales with 1/W. These findings explain the Cenozoic slowdown of the Farallon plate and the decrease in subduction partitioning by its decreasing slab width. The change from Sevier-Laramide orogenesis to Basin and Range extension in North America is also explained by slab width; shortening occurred during wide-slab subduction and overriding-plate-driven trench retreat, whereas extension occurred during intermediate to narrow-slab subduction and slab-driven trench retreat. PMID:20647465

  15. Cenozoic tectonics of western North America controlled by evolving width of Farallon slab.

    PubMed

    Schellart, W P; Stegman, D R; Farrington, R J; Freeman, J; Moresi, L

    2010-07-16

    Subduction of oceanic lithosphere occurs through two modes: subducting plate motion and trench migration. Using a global subduction zone data set and three-dimensional numerical subduction models, we show that slab width (W) controls these modes and the partitioning of subduction between them. Subducting plate velocity scales with W(2/3), whereas trench velocity scales with 1/W. These findings explain the Cenozoic slowdown of the Farallon plate and the decrease in subduction partitioning by its decreasing slab width. The change from Sevier-Laramide orogenesis to Basin and Range extension in North America is also explained by slab width; shortening occurred during wide-slab subduction and overriding-plate-driven trench retreat, whereas extension occurred during intermediate to narrow-slab subduction and slab-driven trench retreat.

  16. Deep subduction of hot young oceanic slab required by the Syros eclogites

    NASA Astrophysics Data System (ADS)

    Flemetakis, Stamatis; Moulas, Evangelos; Kostopoulos, Dimitrios; Chatzitheodoridis, Elias

    2014-05-01

    calculated for a subduction velocity of 3 cm/yr, a subduction angle of 30° and an age of incoming lithosphere of ~20 Ma with a shear stress of 80 MPa at the slab-mantle interface [5]. The above are in excellent agreement with published isotopic work on zircons and garnets from Syros eclogites suggesting crystallisation from magmas derived from a depleted mantle at ~80 Ma and constraining the event of eclogitic metamorphism at ~55 Ma. Diffusion modelling of the garnet outermost rims suggests a brief heating pulse of only ~1,000 years at peak T. [1] Van der Molen (1981) Tectonophysics 73, 323-342 .[2] Koons and Thompson (1985) Chemical Geology 50, 3-30. [3] Baxter and Caddick (2013) Geology 41, 6, 643-646. [4] Poli et al. (2009) Earth and Planetary Science Letters 278, 350-360. [5] Peacock (1993) Geol. Soc. Am. Bull. 105, 684-694 .

  17. Slab Deformation in the Mantle Transition Zone: The Effect of Plate Age and Strength Evolution

    NASA Astrophysics Data System (ADS)

    Goes, S. D. B.; Garel, F.; Davies, R.; Davies, J. H.; Kramer, S. C.; Wilson, C. R.

    2014-12-01

    The deformation encountered by subducted tectonic plates at the base of the upper mantle influences Earth's thermal, chemical, and tectonic evolution. Yet the mechanisms responsible for the wide range of imaged slab morphologies, either stagnating in the transition zone or penetrating into the lower mantle, remain debated. We use 2-D thermo-mechanical models of a two-plate subduction system, modeled with the finite-element, adaptive-mesh code Fluidity. We implement a temperature- and stress-dependent rheology, and viscosity increases 30-fold from upper to lower mantle. Trench position evolves freely in response to plate dynamics. Such an approach self-consistently captures feedbacks between temperature, density, flow, strength and deformation. Our results indicate that key controls on subduction dynamics and slab morphology are: (i) the evolution of slab strength; and (ii) the slab's ability to induce trench motion. We build a regime diagram that distinguishes four subduction styles: (1) a "vertical folding" mode with stationary trench; (2) young slabs that are "horizontally deflected" along the 660-km deep viscosity jump ; (3) an inclined slab morphology, resulting from strong trench retreat (old slabs and thinner overriding plates); and (4) a two-stage mode, displaying bent (rolled-over) slabs at the end of upper-mantle descent, that subsequently unbend and achieve inclined morphologies, with late trench retreat (strong overriding plates). We find that the interplay between trench motion and slab deformation at depth dictates the subduction style, both being controlled by slab strength. We show that all seismically observed slab morphologies in the transition zone can arise just by changing the subducting-plate ages. However, to understand present-day slab morphologies, we have to analyse subduction history rather than just current age at the trench.

  18. Arc Interrupted: The birth, life, and death of the Peruvian flat slab

    NASA Astrophysics Data System (ADS)

    Wagner, Lara; Knezevic Antonijevic, Sanja; Kumar, Abhash; Beck, Susan; Long, Maureen; Zandt, George; Tavera, Hernando; Minaya, Estela

    2016-04-01

    The Peruvian flat slab is a unique natural laboratory for investigating the temporal evolution of flat slab subduction and its associated thermal, tectonic, and seismic implications. This is because the flat slab has been hypothesized to have first formed further north (at approximately the latitude of Lima, Peru), but broadened to the south over the past 11 Ma. This means that areas further to the north represent an older, more evolved flat slab setting, whereas the southernmost edge of the modern flat slab reflects conditions experienced by a newly formed flat slab. Here we present findings from a suite of recent temporary broadband seismic deployments that spanned this entire region. Results from intermediate depth earthquake locations, surface wave tomography (ballistic and ambient Rayleigh wave), and Rayleigh wave anisotropy all indicate that the flat slab did indeed first form further to the north and broadened to the south, along with the southward migration of the Nazca ridge. Subsequently, a trench-parallel tear developed in the older portions of the flat slab north of the ridge, resulting in a resumption of normal subduction geometry where once a flat slab had existed. This tear allows for an interchange of mantle material from beneath the slab to the south to above the slab to the north. This mantle flow has significant thermal implications, both beneath the flat slab and in the lower continental crust located above the relatively newly formed tear. Our results provide unique constraints on the thermal and tectonic evolution of this unusual subduction geometry that may help us to understand better subduction zone processes everywhere.

  19. Surface waves on a grounded dielectric slab covered by a resistive sheet

    NASA Technical Reports Server (NTRS)

    Shively, David

    1993-01-01

    This paper examines surface wave propagation in a grounded dielectric slab covered with a resistive sheet. Transcendental equations are derived for each polarization and are solved using iterative techniques. Attention and phase velocity are shown for a representative geometry. The results are applicable to both a grounded slab covered with a resistive sheet and an ungrounded slab covered on each side with a resistive sheet.

  20. The dynamics of double slab subduction from numerical and semi-analytic models

    NASA Astrophysics Data System (ADS)

    Holt, A.; Royden, L.; Becker, T. W.

    2015-12-01

    Regional interactions between multiple subducting slabs have been proposed to explain enigmatic slab kinematics in a number of subduction zones, a pertinent example being the rapid pre-collisional plate convergence of India and Eurasia. However, dynamically consistent 3-D numerical models of double subduction have yet to be explored, and so the physics of such double slab systems remain poorly understood. Here we build on the comparison of a fully numerical finite element model (CitcomCU) and a time-dependent semi-analytic subduction models (FAST) presented for single subduction systems (Royden et. al., 2015 AGU Fall Abstract) to explore how subducting slab kinematics, particularly trench and plate motions, can be affected by the presence of an additional slab, with all of the possible slab dip direction permutations. A second subducting slab gives rise to a more complex dynamic pressure and mantle flow fields, and an additional slab pull force that is transmitted across the subduction zone interface. While the general relationships among plate velocity, trench velocity, asthenospheric pressure drop, and plate coupling modes are similar to those observed for the single slab case, we find that multiple subducting slabs can interact with each other and indeed induce slab kinematics that deviate significantly from those observed for the equivalent single slab models. References Jagoutz, O., Royden, L. H., Holt, A. F. & Becker, T. W., 2015, Nature Geo., 8, 10.1038/NGEO2418. Moresi, L. N. & Gurnis, M., 1996, Earth Planet. Sci. Lett., 138, 15-28. Royden, L. H. & Husson, L., 2006, Geophys. J. Int. 167, 881-905. Zhong, S., 2006, J. Geophys. Res., 111, doi: 10.1029/2005JB003972.

  1. Slab dehydration recorded in subducted serpentine sea-mount

    NASA Astrophysics Data System (ADS)

    Okamoto, K.; Fukumura, S.; Ishimori, C.; Jung, H.

    2014-12-01

    It has been considered that there is a correlation between the double seismic zones and metamorphic dehydration reaction in deep slab. The lower seismic plane of the double seismic zone is considered to be located on the 600 oC isotherm in the subducting lithosphere. Antigorite terminal reaction is highly temperature sensitive around 600 oC. Therefore it has been proposed that the oceanic lithosphere was hydrated forming serpentine prior to subduction, then serpentine was decomposed to release fluid causing dehydration embrittlement in the slab. In order to unravel relation between dehydration and seismic deformation, we have investigated dehydration process of natural metamorphic rocks recording very cold geothermal history in the crust and lithosphere in the slab. Metamorphic olivine after antigorite has been described in Italian Alps and also from the Mt. Shiraga, Japan [1]. However, the olivine was formed with talc and fluid by antigorite breakdown reaction in pressures lower than 1.5 GPa. Spinifex olivine with opx in the Cerro del Almirez [2], is the product at pressures (P > 1.5 GPa) relevant to the lower seismic plane beneath Northeast Japan. It clearly indicates the presence of large amount of water facilitate crystallization of elongated olivine with opx. It is also supported by LPO pattern of olivines determined by EBSD. Fine-grained olivine-rich samples shows that Type-C fabric pattern is dominant, suggesting deformation under water-rich condition [3]. With metamorphic olivines, chlorite was also recrystallized, suggesting that water would be transported farther down to deep. The estimated dehydration reaction has a negative P-T slope at pressures higher than 1.5 GPa. The reaction is volume reducing reaction and the olivine-opx spinifex texture was formed under volume reducing reaction. In the warm slab beneath SW Japan, the reaction has a positive slope in P-T space and forms olivine+talc+fluid. From microstrucral and petrological analysis of the

  2. Wave propagation through a random medium - The random slab problem

    NASA Technical Reports Server (NTRS)

    Acquista, C.

    1978-01-01

    The first-order smoothing approximation yields integral equations for the mean and the two-point correlation function of a wave in a random medium. A method is presented for the approximate solution of these equations that combines features of the eiconal approximation and of the Born expansion. This method is applied to the problem of reflection and transmission of a plane wave by a slab of a random medium. Both the mean wave and the covariance are calculated to determine the reflected and transmitted amplitudes and intensities.

  3. Diffraction and electron energy loss to plasmons in silicon slabs

    NASA Astrophysics Data System (ADS)

    Levine, Zachary H.

    2008-03-01

    Dynamical diffraction patterns were calculated for 25nm slabs of silicon with [001], [111], and [110] faces for a 120keV electron beam. The calculation used the mixed dynamical form factor in the dielectric formulation. Dielectric matrices with wave vector and frequency dependence were calculated within the local density approximation using the random phase approximation. The energy losses, 10-25eV , span the plasmon peak. Near the zone axes, the results show the preservation of elastic contrast and both excess and deficit Kikuchi lines.

  4. WORKERS FABRICATE ROOF SLABS FOR MTR BUILDING AT THE CONSTRUCTION ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    WORKERS FABRICATE ROOF SLABS FOR MTR BUILDING AT THE CONSTRUCTION SITE. FORMS WERE MADE OF STEEL. AFTER AN INCH OF CONCRETE HAD BEEN POURED IN THE FORM, A MAT OF REINFORCING STEEL WAS PLACED ON IT. THE REMAINDER OF THE FORM WAS FILLED, AND THE CONCRETE WAS VIBRATED, STRUCK, AND TROWELED. GROOVES AT CORNER WILL HAVE 1/4 INCH RODS WELDED INTO THE EYE OF THE STEEL MAT FOR GROUNDING. INL NEGATIVE NO. 578. Unknown Photographer, 9/1/1950 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

  5. Stability of Alfven oscillations in a plane plasma slab

    SciTech Connect

    Patudin, V.M.; Sagalakov, A.M.

    1983-05-01

    The stability of the natural Alfven oscillations of a plane slab of a collisional, slightly nonequilibrium plasma in a uniform magnetic field is studied. An effective numerical method, a special version of the differential sweepout method, is proposed. A calculation procedure has been developed. The small-oscillation spectrum is analyzed for parabolic plasma density profiles, and neutral curves are plotted. The growth rates and critical parameters are determined. At a high plasma conductivity, both strongly and weakly localized perturbations near the axis can go unstable. For a density profile with an inflection point, weakly damped oscillations are observed near the inflection point. These oscillations can also be excited by an ion beam.

  6. Radiative flux emitted by a burning PMMA slab

    NASA Astrophysics Data System (ADS)

    Parent, G.; Acem, Z.; Collin, A.; Berfroi, R.; Boulet, P.; Pizzo, Y.; Mindykowski, P.; Kaiss, A.; Porterie, B.

    2012-11-01

    The degradation of a PMMA sample has been studied based on experimental results obtained for the radiation emission by a burning slab. Observations of the infrared emission perpendicular to the plate, in the range where the optically thin flame is weakly emitting, indicate a plate temperature close to 680 K which is an indication on the surface temperature during the degradation process. Observations from the side allow a flame characterization without the plate emission superimposition. This is a promising way for evaluating data regarding the flame characteristics: temperature, gaz concentration and soot volumetric fraction.

  7. Surface polaritons of a metal-insulator-metal curved slab

    NASA Astrophysics Data System (ADS)

    Moradi, Afshin

    2016-09-01

    The properties of s- and p-polarized surface polariton modes propagating circumferentially around a portion of a cylindrical metal-insulator-metal structure are studied, theoretically. By using the Maxwell equations in conjunction with the Drude model for the dielectric function of the metals and applying the appropriate boundary conditions, the dispersion relations of surface waves for two types of modes, are derived and numerically solved. The effects of the slab curvature and insulator thickness on the propagation of electromagnetic modes are investigated. The differences of the s- and p-polarized surface modes are also shown.

  8. Quasiparticle electronic structure of bulk and slab Bi2Se3 and Bi2Te3

    NASA Astrophysics Data System (ADS)

    Barker, Bradford; Deslippe, Jack; Yazyev, Oleg; Louie, Steven G.

    2014-03-01

    We present ab initio calculations of the quasiparticle electronic band structure of three-dimensional topological insulator materials Bi2Se3 and Bi2Te3. The mean-field DFT calculation is performed with fully relativistic pseudopotentials, generating spinor wavefunctions in a plane-wave basis. Quasiparticle properties are computed with a one-shot ab initio GW calculation. We use both bulk and slab forms of the materials to better understand the quasiparticle band gaps and Fermi velocities of the topological surface states of these materials. This work was supported by NSF grant No. DMR10-1006184 and U.S. DOE under Contract No. DE-AC02-05CH11231. Computational resources have been provided by DOE at LBNL's NERSC facility and the NSF through XSEDE resources at NICS.

  9. Fracture problem of a nonhomogeneous high temperature superconductor slab based on real fundamental solutions

    NASA Astrophysics Data System (ADS)

    Gao, Zhiwen; Zheng, Zhiye; Li, Xueyi

    2015-12-01

    To analyze the fracture problem of the nonhomogeneous high temperature superconductor (HTS) slab under electromagnetic force, we derive the real fundamental solutions based on eigenvalue and eigenvector analyses. The superconductor E-J constitutive law is characterized by the Bean model where the critical current density is independent of the flux density. Fracture analysis is performed by the methods of singular integral equations which are solved numerically by Lobatto-Chybeshev collocation method. Numerical results of the stress intensity factor (SIF) are obtained. Moreover, the crack opening displacement (COD) can be obtained by numerical integration dislocation density functions. The effects of the thickness ratio, HTS material nonhomogeneous parameters, applied magnetic field and critical current density on SIF and COD are discussed. The present work could theoretically provide quantitative predictions of the fracture mechanism of the nonhomogeneous HTS.

  10. Abnormal seismological and magmatic processes controlled by the tearing South American flat slabs

    NASA Astrophysics Data System (ADS)

    Hu, Jiashun; Liu, Lijun

    2016-09-01

    The influence of flat slab subduction on the formation of intra-slab earthquakes, volcanic activities and mantle seismic velocity anomalies remains unclear. We attempt to better understand these processes by simulating the two flat slabs in Peru and Chile using data-orientated geodynamic models. Our results successfully reproduce the observed flat slabs as mainly due to two subducting aseismic ridges. In contrast to the traditional view of flat-slab subduction, we find that these slabs are internally torn, as is due to the 3D nature of the subducting buoyancy features. This broken slab configuration, confirmed by regional tomography, naturally explains the abnormal distribution of and stress regimes associated with the intermediate-depth earthquakes. We further show that the slab tearing process could also better explain the formation of adakitic and ore-forming magmatism, the evolution of the magmatic arc, and the enigmatic mantle seismic structures beneath these regions. We propose that slab tearing may represent a common result of buoyancy feature subduction and that the resulting mantle processes could affect the long-term geodynamic evolution of continents.

  11. Analysis of surface wave propagation in a grounded dielectric slab covered by a resistive sheet

    NASA Technical Reports Server (NTRS)

    Shively, David G.

    1992-01-01

    Both parallel and perpendicular polarized surface waves are known to propagate on lossless and lossy grounded dielectric slabs. Surface wave propagation on a grounded dielectric slab covered with a resistive sheet is considered. Both parallel and perpendicular polarizations are examined. Transcendental equations are derived for each polarization and are solved using iterative techniques. Attenuation and phase velocity are shown for representative geometries. The results are applicable to both a grounded slab with a resistive sheet and an ungrounded slab covered on each side with a resistive sheet.

  12. Meteorological variables to aid forecasting deep slab avalanches on persistent weak layers

    USGS Publications Warehouse

    Marienthal, Alex; Hendrikx, Jordy; Birkeland, Karl; Irvine, Kathryn M.

    2015-01-01

    Deep slab avalanches are particularly challenging to forecast. These avalanches are difficult to trigger, yet when they release they tend to propagate far and can result in large and destructive avalanches. We utilized a 44-year record of avalanche control and meteorological data from Bridger Bowl ski area in southwest Montana to test the usefulness of meteorological variables for predicting seasons and days with deep slab avalanches. We defined deep slab avalanches as those that failed on persistent weak layers deeper than 0.9 m, and that occurred after February 1st. Previous studies often used meteorological variables from days prior to avalanches, but we also considered meteorological variables over the early months of the season. We used classification trees and random forests for our analyses. Our results showed seasons with either dry or wet deep slabs on persistent weak layers typically had less precipitation from November through January than seasons without deep slabs on persistent weak layers. Days with deep slab avalanches on persistent weak layers often had warmer minimum 24-hour air temperatures, and more precipitation over the prior seven days, than days without deep slabs on persistent weak layers. Days with deep wet slab avalanches on persistent weak layers were typically preceded by three days of above freezing air temperatures. Seasonal and daily meteorological variables were found useful to aid forecasting dry and wet deep slab avalanches on persistent weak layers, and should be used in combination with continuous observation of the snowpack and avalanche activity.

  13. Leaky unstable modes and electromagnetic radiation amplification by an anisotropic plasma slab

    SciTech Connect

    Vagin, K. Yu. Uryupin, S. A.

    2015-09-15

    The interaction between electromagnetic radiation and a photoionized plasma slab with an anisotropic electron velocity distribution is studied. It is shown that the fields of leaky modes are amplified due to the development of aperiodic instability in the slab, which leads to an increase in both the reflected and transmitted fields. The transmitted field can significantly increase only if the slab thickness does not exceed the ratio of the speed of light to the electron plasma frequency, whereas there is no upper bound on the slab thickness for the reflected signal to be amplified.

  14. High energy efficient solid state laser sources. [slab geometry laser sources

    NASA Technical Reports Server (NTRS)

    Byer, R. L.

    1983-01-01

    Slab glass performance studies demonstate 18 J of output at 2 Hz with 2.3% wall plug efficiency. The goal is to achieve 10 J per pulse at 10 Hz and 3% wall plug efficiency during the next annual period. The slab concept was extended to Nd:YAG and to Nd:GGG. To date over 80 W of CW output power at 2% efficiency was generated in slab Nd:YAG. A multiplexed slab Nd:YAG pre-amplifier was invented and a Nd:YAG oscillator was demonstrated with 100kHz linewidth for eventual use in wind velocity measurements.

  15. Structured mass density slab as a waveguide of fast magnetoacoustic waves

    NASA Astrophysics Data System (ADS)

    Jelínek, P.; Karlický, M.

    Coronal loops are waveguides for magnetohydrodynamic (MHD) waves. These loops are expected to be structured. Therefore, in the present paper, we numerically studied the propagation of the fast MHD waves in the structured density slab (composed from a broad density slab with one axisymmetric narrow sub-slab superposed), and analysed the wave signals. Then, this structured slab was divided into its components, i.e., to simple broad and narrow slabs and the same analysis was made. We compared results of both these cases. For the calculations we adopted a two-dimensional (2D) magnetohydrodynamic (MHD) model, in which we solved a full set of ideal time-dependent MHD equations using the FLASH code, applying the adaptive mesh refinement (AMR) method. To initiate the fast sausage magnetoacoustic waves, we used axisymmetric Gaussian velocity perturbation. Wave signals were detected in different locations along the slab and as a diagnostic tool of these waves, the wavelet analysis method has been used. We found that for the structured density slab with sufficiently sharp boundaries, i.e., for good quality waveguides (without an energy leakage), the guided waves in the structured slab behave similarly as in its separated (simple slab) components.

  16. Displacement-based seismic design of flat slab-shear wall buildings

    NASA Astrophysics Data System (ADS)

    Sen, Subhajit; Singh, Yogendra

    2016-06-01

    Flat slab system is becoming widely popular for multistory buildings due to its several advantages. However, the performance of flat slab buildings under earthquake loading is unsatisfactory due to their vulnerability to punching shear failure. Several national design codes provide guidelines for designing flat slab system under gravity load only. Nevertheless, flat slab buildings are also being constructed in high seismicity regions. In this paper, performance of flat slab buildings of various heights, designed for gravity load alone according to code, is evaluated under earthquake loading as per ASCE/SEI 41 methodology. Continuity of slab bottom reinforcement through column cage improves the performance of flat slab buildings to some extent, but it is observed that these flat slab systems are not adequate in high seismicity areas and need additional primary lateral load resisting systems such as shear walls. A displacement-based method is proposed to proportion shear walls as primary lateral load resisting elements to ensure satisfactory performance. The methodology is validated using design examples of flat slab buildings with various heights.

  17. Optical pulling force on a particle near the surface of a dielectric slab waveguide

    NASA Astrophysics Data System (ADS)

    Paul, Nayan Kumar; Kemp, Brandon A.

    2016-01-01

    Optical forces on a Rayleigh particle near the surface of a dielectric slab waveguide are considered. A light wave of the lowest-order TE0 mode is used to excite the particle. The transverse and longitudinal forces acting on the particle are studied. The particle is always trapped near the surface of the slab, where the electric field intensity is high. The particle can be pushed away from or pulled toward the light source along the surface of the slab by tuning the frequency around a switching frequency. This phenomenon switches between scattering and gradient forces near the switching frequency of the dielectric slab waveguide.

  18. Calculation and comparison of thermal effect in laser diode pumped slab lasers with different pumping structures

    NASA Astrophysics Data System (ADS)

    Huang, Feng; Jiang, Nan; Wang, Yuefeng; Dong, Wei; Niu, Yanxiong

    2008-03-01

    Laser diode (LD) pumped slab laser, as an important high average power solid-state laser, is a promising laser source in military and industrial fields. The different laser diode pumping structures lead to different thermal effect in the slab gain medium. The thermal and stress analysis of slab laser with different pumping structure are performed by finite element analysis (FEA) with the software program ANSYS. The calculation results show that the face pumped and cooled laser results in a near one-dimension temperature distribution and eliminates thermal stress induced depolarization. But the structure is low pump efficiency due to the small thickness of slabs and the requirement to cool and pump through the same faces. End-pumped slab laser is high pump efficiency and excellent mode match, but its pumping arrangement is fairly complicated. The edge-pumped face-cooling slab laser's pump efficiency is better than face-pumping, and its pumping structure is simpler than end-pumped laser, but the tensile stress on surfaces may initiate failure of the gain medium so it is important to design so that the stress is well below the stress fracture limit. The comparison of the thermal effects with different pumping structure shows that, the edge-pumped slab laser has engineering advantages in high power slab laser's application. Furthermore, the end-pumped slab laser tends to get the best beam quality, so it is fit for the application which has a special requirement on laser beam quality.

  19. Sensor assembly

    DOEpatents

    Bennett, Thomas E.; Nelson, Drew V.

    2004-04-13

    A ribbon-like sensor assembly is described wherein a length of an optical fiber embedded within a similar lengths of a prepreg tow. The fiber is ""sandwiched"" by two layers of the prepreg tow which are merged to form a single consolidated ribbon. The consolidated ribbon achieving a generally uniform distribution of composite filaments near the embedded fiber such that excess resin does not ""pool"" around the periphery of the embedded fiber.

  20. Mobile Launch Platform Vehicle Assembly Building Area (SWMU 056) Hot Spot 3 Bioremediation Interim Measures Work Plan, Kennedy Space Center, Florida

    NASA Technical Reports Server (NTRS)

    Whitney L. Morrison; Daprato, Rebecca C.

    2016-01-01

    This Interim Measures Work Plan (IMWP) presents an approach and design for the remediation of chlorinated volatile organic compound (CVOC) groundwater impacts using bioremediation (biostimulation and bioaugmentation) in Hot Spot 3, which is defined by the area where CVOC (trichloroethene [TCE], cis-1,2-dichloroethene [cDCE], and vinyl chloride [VC]) concentrations are greater than 10 times their respective Florida Department of Environmental Protection (FDEP) Natural Attenuation Default Concentration (NADC) [10xNADC] near the western Mobile Launch Platform (MLP) structure. The IM treatment area is the Hot Spot 3 area, which is approximately 0.07 acres and extends from approximately 6 to 22 and 41 to 55 feet below land surface (ft BLS). Within Hot Spot 3, a source zone (SZ; area with TCE concentrations greater than 1% solubility [11,000 micrograms per liter (micrograms/L)]) was delineated and is approximately 0.02 acres and extends from approximately 6 to 16 and 41 to 50 ft BLS.

  1. Ray tracing calculations of the output from germanium slab lasers

    SciTech Connect

    Plowes, J. A.; Holden, P. B.; Pert, G. J.; Healy, S. B.; Kingston, A. E.; Roberts, E.

    1995-05-01

    A 3D Raytracing code is used, as a post processor, to simulate experimental observables, such as divergences, deflected angle, and output intensity, from a 1 1/2 D fluid code. The latter self consistently treats the plasma expansion with the atomic physics of the Ne-like ion. The results presented relate to two separate experiments. First, an experiment carried out at R. A. L. where Ge slab targets, of varying lengths, were irradiated at driving laser intensities in the range 0.8{yields}2.3x10{sup 13} W cm{sup -2}. Results presented here are for the 236 A line and good agreement is found with experiment. Also presented, are simulations which relate to an experiment carried out at Osaka University, where a 4 cm Ge slab target, with a curvature from 0 to 20 mrad, along the lasing axis, was irradiated. General agreement with experiment is obtained. Tightening in the output beam, with increasing curvature, can clearly be seen.

  2. Trench migration, net rotation and slab mantle coupling

    NASA Astrophysics Data System (ADS)

    Funiciello, F.; Faccenna, C.; Heuret, A.; Lallemand, S.; Di Giuseppe, E.; Becker, T. W.

    2008-07-01

    Laboratory models have been conducted to improve our understanding of the role that the resistance of the slab to bending and its coupling to the ambient mantle play in subduction dynamics over geological time scales. Our models are set up with a viscous plate of silicone (lithosphere) subducting under negative buoyancy in a viscous layer of glucose syrup (mantle). For our study, the lithosphere/upper mantle viscosity contrast has been systematically varied, from ~ 10 to ~ 10 5 in order to explore the parameter space between weak and strong slab dynamics. We found that subduction is characterized by a retreating mode for viscosity ratios > 10 4, by the coexistence of a retreating mode and an advancing mode for viscosity ratios between ~ 10 4 and ~ 10 2, and quasi-stationary, Rayleigh-Taylor like behaviour for ratios < 10 2. By combining our experimental results and kinematic data from current subduction zones in four reference frames which differ in the amount of net rotation, we infer that a lithosphere/upper mantle viscosity contrast of 150-500 is necessary to obtain realistic trench/subducting plate velocity ratios as well as the variability of subduction styles observed in nature.

  3. Effects of subduction and slab gaps on mantle flow beneath the Lesser Antilles based on observations of seismic anisotropy

    NASA Astrophysics Data System (ADS)

    Schlaphorst, David; Kendall, J.-Michael; Baptie, Brian; Latchman, Joan L.; Bouin, Marie-Paule

    2016-04-01

    Subduction is a key process in the formation of continental crust. However, the interaction of the mantle with the subducting slab is not fully understood and varies between subduction zones. The flow geometry and stress patterns influence seismic anisotropy; since anisotropic layers lead to variations in the speed of seismic waves as a function of the direction of wave propagation, mantle flow can be constrained by investigating the structure of these anisotropic layers. In this study we investigate seismic anisotropy in the eastern Greater and the Lesser Antilles along a subduction environment, including the crust and the upper mantle as regions of interest. We use a combination of teleseismic and local events recorded at three-component broadband seismic stations on every major island in the area to observe and distinguish between anisotropy in the crust, the mantle wedge and the sub-slab mantle. Local event delay times (0.21±0.12s) do not increase with depth, indicating a crustal origin and an isotropic mantle wedge. Teleseismic delay times are larger (1.34±0.47s), indicating sub-slab anisotropy. The results suggest trench-parallel mantle flow, with the exception of trench-perpendicular alignment in narrow regions east of Puerto Rico and south of Martinique, suggesting mantle flow through gaps in the slab. This agrees with the continuous northward mantle flow that is caused by the subducting slab proposed by previous studies of that region. We were able to identify a pattern previously unseen by other studies; on St. Lucia a trench-perpendicular trend also indicated by the stations around can be observed. This pattern can be explained by a mantle flow through a gap induced by the subduction of the boundary zone between the North and South American plates. This feature has been proposed for that area using tomographic modelling (van Benthem et al., 2013). It is based on previous results by Wadge & Shepherd (1984), who observed a vertical gap in the Wadati

  4. Spherical disharmonics in the Earth sciences and the spatial solution: Ridges, hotspots, slabs, geochemistry and tomography correlations

    NASA Technical Reports Server (NTRS)

    Ray, Terrill W.; Anderson, Don L.

    1994-01-01

    There is increasing use of statistical correlations between geophysical fields and between geochemical and geophysical fields in attempts to understand how the Earth works. Typically, such correlations have been based on spherical harmonic expansions. The expression of functions on the sphere as spherical harmonic series has many pitfalls, especially if the data are nonuniformly and/or sparsely sampled. Many of the difficulties involved in the use of spherical harmonic expansion techniques can be avoided through the use of spatial domain correlations, but this introduces other complications, such as the choice of a sampling lattice. Additionally, many geophysical and geochemical fields fail to satisfy the assumptions of standard statistical significance tests. This is especially problematic when the data values to be correlated with a geophysical field were collected at sample locations which themselves correlate with that field. This paper examines many correlations which have been claimed in the past between geochemistry and mantle tomography and between hotspot, ridge, and slab locations and tomography using both spherical harmonic coefficient correlations and spatial domain correlations. No conclusively significant correlations are found between isotopic geochemistry and mantle tomography. The Crough and Jurdy (short) hotspot location list shows statistically significant correlation with lowermost mantle tomography for degree 2 of the spherical harmonic expansion, but there are no statistically significant correlations in the spatial case. The Vogt (long) hotspot location list does not correlate with tomography anywhere in the mantle using either technique. Both hotspot lists show a strong correlation between hotspot locations and geoid highs when spatially correlated, but no correlations are revealed by spherical harmonic techniques. Ridge locations do not show any statistically significant correlations with tomography, slab locations, or the geoid; the

  5. The role of ridges in the formation and longevity of flat slabs.

    PubMed

    Antonijevic, Sanja Knezevic; Wagner, Lara S; Kumar, Abhash; Beck, Susan L; Long, Maureen D; Zandt, George; Tavera, Hernando; Condori, Cristobal

    2015-08-13

    Flat-slab subduction occurs when the descending plate becomes horizontal at some depth before resuming its descent into the mantle. It is often proposed as a mechanism for the uplifting of deep crustal rocks ('thick-skinned' deformation) far from plate boundaries, and for causing unusual patterns of volcanism, as far back as the Proterozoic eon. For example, the formation of the expansive Rocky Mountains and the subsequent voluminous volcanism across much of the western USA has been attributed to a broad region of flat-slab subduction beneath North America that occurred during the Laramide orogeny (80-55 million years ago). Here we study the largest modern flat slab, located in Peru, to better understand the processes controlling the formation and extent of flat slabs. We present new data that indicate that the subducting Nazca Ridge is necessary for the development and continued support of the horizontal plate at a depth of about 90 kilometres. By combining constraints from Rayleigh wave phase velocities with improved earthquake locations, we find that the flat slab is shallowest along the ridge, while to the northwest of the ridge, the slab is sagging, tearing, and re-initiating normal subduction. On the basis of our observations, we propose a conceptual model for the temporal evolution of the Peruvian flat slab in which the flat slab forms because of the combined effects of trench retreat along the Peruvian plate boundary, suction, and ridge subduction. We find that while the ridge is necessary but not sufficient for the formation of the flat slab, its removal is sufficient for the flat slab to fail. This provides new constraints on our understanding of the processes controlling the beginning and end of the Laramide orogeny and other putative episodes of flat-slab subduction. PMID:26268192

  6. Two-way interaction between plume and slab: The Hainan-Manila example

    NASA Astrophysics Data System (ADS)

    Mériaux, Catherine; Duarte, João; Schellart, Wouter

    2015-04-01

    Three-dimensional upper-mantle laboratory models consisting of a compositional plume that is initiated underneath an entirely dynamically driven dense plate fixed at the surface along its trailing edge exhibit a two-way interaction between plume and slab. The slab influence on the plume is driven by the induced mantle flow generated by the plate motion, which includes a sinking and a retreating phase. Slab/Plume buoyancy flux ratios ranged between 7 and 18. In all models, the plume is being swept away from the slab during its rise, and once it has reached the surface, its head spreads towards the trench as a gravity current while its conduit keeps being deflected away. The plume influence on the slab is seen later, when the slab in its retreat gets closer to the plume. The plume buoyancy spreading under the slab then weakens the subduction rate. The degree to which the subduction rate is lessened is conditioned by the level of asymmetry, which the slab may develop along its free edge during its impact at the bottom surface. A lasting symmetric plate causes maximum disturbance of the plume to the slab retreat rate, while plate asymmetry alleviates the plume influence as the plume buoyancy is no longer trapped underneath the plate in its centreline but can escape sideways. Our laboratory model configuration applies to the Hainan plume and Manila subduction system. The geophysical and seismic observations showing the existence of a NW-SE tilting plume-like mantle low-velocity structure in the crust and in the mantle beneath the north Hainan Island-Leizhou Peninsula basalt province are explained by slab rollback induced toroidal mantle flow from the Manila subduction zone. On the basis of our models, it can be foreseen that the Hainan plume is to spread out under the Manila slab towards the mantle wedge in the future, which could lessen the Manila subduction rate.

  7. The role of ridges in the formation and longevity of flat slabs

    NASA Astrophysics Data System (ADS)

    Antonijevic, Sanja Knezevic; Wagner, Lara S.; Kumar, Abhash; Beck, Susan L.; Long, Maureen D.; Zandt, George; Tavera, Hernando; Condori, Cristobal

    2015-08-01

    Flat-slab subduction occurs when the descending plate becomes horizontal at some depth before resuming its descent into the mantle. It is often proposed as a mechanism for the uplifting of deep crustal rocks (`thick-skinned' deformation) far from plate boundaries, and for causing unusual patterns of volcanism, as far back as the Proterozoic eon. For example, the formation of the expansive Rocky Mountains and the subsequent voluminous volcanism across much of the western USA has been attributed to a broad region of flat-slab subduction beneath North America that occurred during the Laramide orogeny (80-55 million years ago). Here we study the largest modern flat slab, located in Peru, to better understand the processes controlling the formation and extent of flat slabs. We present new data that indicate that the subducting Nazca Ridge is necessary for the development and continued support of the horizontal plate at a depth of about 90 kilometres. By combining constraints from Rayleigh wave phase velocities with improved earthquake locations, we find that the flat slab is shallowest along the ridge, while to the northwest of the ridge, the slab is sagging, tearing, and re-initiating normal subduction. On the basis of our observations, we propose a conceptual model for the temporal evolution of the Peruvian flat slab in which the flat slab forms because of the combined effects of trench retreat along the Peruvian plate boundary, suction, and ridge subduction. We find that while the ridge is necessary but not sufficient for the formation of the flat slab, its removal is sufficient for the flat slab to fail. This provides new constraints on our understanding of the processes controlling the beginning and end of the Laramide orogeny and other putative episodes of flat-slab subduction.

  8. Mantle flow and dynamic topography associated with slab window opening: Insights from laboratory models

    NASA Astrophysics Data System (ADS)

    Guillaume, Benjamin; Moroni, Monica; Funiciello, Francesca; Martinod, Joseph; Faccenna, Claudio

    2010-12-01

    We present dynamically self-consistent mantle-scale laboratory models that have been conducted to improve our understanding of the influence of slab window opening on subduction dynamics, mantle flow and associated dynamic topography over geological time scales. The adopted setup consists of a two-layer linearly viscous system simulating the subduction of a fixed plate of silicone (lithosphere) under negative buoyancy in a viscous layer of glucose syrup (mantle). Our experimental setting is also characterized by a constant-width rectangular window located at the center of a laterally confined slab, modeling the case of the interaction of a trench-parallel spreading ridge with a wide subduction zone. We found that the opening of a slab window does not produce consistent changes of the geometry and the kinematics of the slab. On the contrary, slab-induced mantle circulation, quantified both in the vertical and horizontal sections using the Feature Tracking image analysis technique, is strongly modified. In particular, rollback subduction and the opening of the slab window generate a complex mantle circulation pattern characterized by the presence of poloidal and toroidal components, with the importance of each evolving according to kinematic stages. Mantle coming from the oceanic domain floods through the slab window, indenting the supra-slab mantle zone and producing its deformation without any mixing between mantle portions. The opening of the slab window and the upwelling of sub-slab mantle produce a regional-scale non-isostatic topographic uplift of the overriding plate that would correspond to values ranging between ca. 1 and 5 km in nature. Assuming that our modeling results can be representative of the natural behavior of subduction zones, we compared them to the tectonics and volcanism of the Patagonian subduction zone. We found that the anomalous backarc volcanism that has been developing since the middle Miocene could result from the lateral flow of sub-slab

  9. Rheologic Controls on the Dynamic Evolution of Slabs in the Upper Mantle

    NASA Astrophysics Data System (ADS)

    Billen, M.; Hirth, G.

    2004-12-01

    Subduction of tectonic plates is characterized by long-lived subduction zones, asymmetric subduction and slab dip angles of 25--80o in the upper mantle. Several mechanisms proposed to explain the variation in observed dip include large-scale mantle flow, trench roll-back, and interaction of the slab with the transition zone. Previous dynamic models of subduction that include only Newtonian viscosity and moderately strong slabs generally fail to predict subduction angles less than 60--90o at shallow depths (100--300 km). We find that the observed characteristics of subduction are reproduced by viscous flow models, in which the rheologic structure is consistent with experimentally determined flow laws for Newtonian and non-Newtonian visco-plastic deformation of olivine. The properties of the models required to match the observed characteristics of slabs are: non-Newtonian viscosity in the mantle producing a weak mantle wedge (1018--1019~Pa s), a stiff slab interior (1025~Pa s) limited by a plastic yield criterion and a weak plate boundary shear zone (1020--1021~Pa s). The shallow slab dip reaches a minimum of 25--30o for high convergence rates and a stiff slab, without trench roll-back or relative motion of the entire lithosphere with respect to the mantle, suggesting these other mechanisms are not the primary controls on slab geometry. The deep slab dip (350--650 km) decreases as the slab penetrates the stiffer (x10), Newtonian viscosity lower mantle, eventually stabilizing the upper mantle slab geometry.

  10. Pushrod assembly

    DOEpatents

    Potter, J.D.

    1984-03-30

    A pushrod assembly including a carriage mounted on a shaft for movement therealong and carrying a pushrod engageable with a load to be moved is described. A magnet is mounted on a supporting bracket for movement along such shaft. Means are provided for adjustably spacing magnet away from the carriage to obtain a selected magnetic attractive or coupling force therebetween. Movement of the supporting bracket and the magnet carried thereby pulls the carriage along with it until the selected magnetic force is exceeded by a resistance load acting on the carriage.

  11. Pushrod assembly

    DOEpatents

    Potter, Jerry D.

    1987-01-01

    A pushrod assembly including a carriage mounted on a shaft for movement therealong and carrying a pushrod engageable with a load to be moved. A magnet is mounted on a supporting bracket for movement along such shaft. Means are provided for adjustably spacing said magnet away from said carriage to obtain a selected magnetic attractive or coupling force therebetween. Movement of the supporting bracket and the magnet carried thereby pulls the carriage along with it until the selected magnetic force is exceeded by a resistance load acting on the carriage.

  12. Shingle assembly

    DOEpatents

    Dinwoodie, Thomas L.

    2007-02-20

    A barrier, such as a PV module, is secured to a base by a support to create a shingle assembly with a venting region defined between the barrier and base for temperature regulation. The first edge of one base may be interengageable with the second edge of an adjacent base to be capable of resisting first and second disengaging forces oriented perpendicular to the edges and along planes oriented parallel to and perpendicular to the base. A deflector may be used to help reduce wind uplift forces.

  13. Dump assembly

    DOEpatents

    Goldmann, L.H.

    1984-12-06

    This is a claim for a dump assembly having a fixed conduit and a rotatable conduit provided with overlapping plates, respectively, at their adjacent ends. The plates are formed with openings, respectively, normally offset from each other to block flow. The other end of the rotatable conduit is provided with means for securing the open end of a filled container thereto. Rotation of the rotatable conduit raises and inverts the container to empty the contents while concurrently aligning the conduit openings to permit flow of material therethrough. 4 figs.

  14. A Markov Chain-based quantitative study of angular distribution of photons through turbid slabs via isotropic light scattering

    NASA Astrophysics Data System (ADS)

    Li, Xuesong; Northrop, William F.

    2016-04-01

    This paper describes a quantitative approach to approximate multiple scattering through an isotropic turbid slab based on Markov Chain theorem. There is an increasing need to utilize multiple scattering for optical diagnostic purposes; however, existing methods are either inaccurate or computationally expensive. Here, we develop a novel Markov Chain approximation approach to solve multiple scattering angular distribution (AD) that can accurately calculate AD while significantly reducing computational cost compared to Monte Carlo simulation. We expect this work to stimulate ongoing multiple scattering research and deterministic reconstruction algorithm development with AD measurements.

  15. Design of a Slab Waveguide Multiaperture Fourier Spectrometer for Water Vapor Measurements in Earth's Atmosphere

    NASA Astrophysics Data System (ADS)

    Sinclair, Kenneth; Florjańczyk, Mirosław; Solheim, Brian; Scott, Alan; Quine, Ben; Cheben, Pavel

    Concept, theory and design of a new type of waveguide device, a multiaperture Fourier-transform planar waveguide spectrometer[1], implemented as a prototype instrument is pre-sented. The spectrometer's objective is to demonstrate the ability of the new slab waveguide technology for application in remote sensing instruments[2]. The spectrometer will use a limb viewing configuration to detect the 1.36um waveband allowing concentrations of water vapor in earth's atmosphere to be measured[3]. The most challenging aspects of the design, assembly and calibration are presented. Focus will be given to the effects of packaging the spectrometer and interfacing to the detector array. Stress-induced birefringence will affect the performance of the waveguides, therefore the design of a stress-free mounting over a range of temperatures is important. Spectral retrieval algo-rithms will have to correct for expected fabrication errors in the waveguides. Data processing algorithms will also be developed to correct for non-uniformities of input brightness through the array, making use of MMI output couplers to capture both the in-phase and anti-phase interferometer outputs. A performance assessment of an existing breadboard spectrometer will demonstrate the capability of the instrument. REFERENCES 1. M. Florjáczyk, P. Cheben, S. Janz, A. Scott, B. Solheim, and D.-X. Xu, "Multiaper-n ture planar waveguide spectrometer formed by arrayed Mach-Zehnder interferometers," Opt. Expr. 15(26), 18176-18189 (2007). 2. M. Florjáczyk, P. Cheben, S. Janz, B. Lamontagne, J. n Lapointe, A. Scott, B. Solheim, and D.-X. Xu, "Slab waveguiode spatial heterodyne spectrom-eters for remote sensing from space," Optical sensors 2009. Proceedings of the SPIE, Volume 7356 (2009)., pp. 73560V-73560V-7 (2009). 3. A. Scott, M. Florjáczyk, P. Cheben, S. Janz, n B. Solheim, and D.-X. Xu, "Micro-interferometer with high throughput for remote sensing." MOEMS and Miniaturized Systems VIII. Proceedings of the SPIE

  16. The impact of slab dip variations, gaps and rollback on mantle wedge flow: insights from fluids experiments

    NASA Astrophysics Data System (ADS)

    MacDougall, Julia G.; Kincaid, Chris; Szwaja, Sara; Fischer, Karen M.

    2014-05-01

    Observed seismic anisotropy and geochemical anomalies indicate the presence of 3-D flow around and above subducting slabs. To investigate how slab geometry and velocity affect mantle flow, we conducted a set of experiments using a subduction apparatus in a fluid-filled tank. Our models comprise two independently adjustable, continuous belts to represent discrete sections of subducting slabs that kinematically drive flow in the surrounding glucose syrup that represents the upper mantle. We analyse how slab dip (ranging from 30° to 80°), slab dip difference between slab segments (ranging from 20° to 50°), rates of subduction (4-8 cm yr-1) and slab/trench rollback (0-3 cm yr-1) affect mantle flow. Whiskers were used to approximate mineral alignment induced by the flow, as well as to predict directions of seismic anisotropy. We find that dip variations between slab segments generate 3-D flow in the mantle wedge, where the path lines of trenchward moving mantle material above the slab are deflected towards the slab segment with the shallower dip. The degree of path line deflection increases as the difference in slab dip between the segments increases, and, for a fixed dip difference, as slab dip decreases. In cases of slab rollback and large slab dip differences, we observe intrusion of subslab material through the gap and into the wedge. Flow through the gap remains largely horizontal before eventual downward entrainment. Whisker alignment in the wedge flow is largely trench-normal, except near the lateral edges of the slab where toroidal flow dominates. In addition, whisker azimuths located above the slab gap deviate most strongly from trench-normal orientations when slab rollback does not occur. Such flow field complexities are likely sufficient to affect deep melt production and shallow melt delivery. However, none of the experiments produced flow fields that explain the trench-parallel shear wave splitting fast directions observed over broad arc and backarc

  17. Two-Pass, Diode-Pumped Nd:YAG Slab Laser Head

    NASA Technical Reports Server (NTRS)

    Coyle, D. Barry

    1992-01-01

    Neodymium/yttrium aluminum garnet (Nd:YAG) ring-laser head designed for compactness, simplicity, and increased efficiency for side pumping by diode lasers. Laser head includes two linear arrays of diode lasers, two fused-silica collimating rods, and Nd:YAG slab. Slab mounted on finned copper block, providing good thermal dissipation.

  18. Convective instability rising out of the underbelly of stagnant slabs in the Mantle Transition Zone

    NASA Astrophysics Data System (ADS)

    Ballmer, Maxim D.; Motoki, Matthew H.

    2016-04-01

    The study of volcanism can further our understanding of Earth's mantle processes and composition. Continental intraplate volcanism commonly occurs above subducted slabs that stagnate in the Mantle Transition Zone (MTZ), such as in Europe, eastern China, and western North America. Here, we use two-dimensional numerical models to explore the evolution of stagnant slabs in the MTZ and their potential to sustain mantle upwellings that can support volcanism. We find [1] that weak slabs may go convectively unstable within tens of Myr. Upwellings rise out of the relatively warm underbelly of the slab, are entrained by ambient-mantle flow and reach the base of the lithosphere. The first and most vigorous upwellings rise adjacent to lateral heterogeneity within the slab. Ultimately, convective instability also acts to separate the compositional components of the slab, harzburgite and eclogite, from each other with harzburgite rising into the upper mantle and eclogite sinking toward the base of the MTZ, and potentially into the lower mantle. Such a physical filtering process may sustain a long-term compositional stratification across the mantle [2]. [1] Motoki, M. H. and M. D. Ballmer (2015): Convective instability of Stagnant Slabs in the Mantle Transition Zone, Geochem. Geophys. Geosys., doi:10.1002/2014GC005608. [2] Ballmer, M. D., N. C. Schmerr, T. Nakagawa, and J. Ritsema (2015): Compositional mantle layering revealed by slab stagnation at ~1,000 km depth, Science Advances, doi:10.1126/sciadv.1500815

  19. Degradation and mechanism of the mechanics and durability of reinforced concrete slab in a marine environment

    NASA Astrophysics Data System (ADS)

    Wu, Sheng-xing; Liu, Guan-guo; Bian, Han-bing; Lv, Wei-bo; Jiang, Jian-hua

    2016-04-01

    An experimental research was conducted to determine the corrosion and bearing capacity of a reinforced concrete (RC) slab at different ages in a marine environment. Results show that the development of corrosion-induced cracks on a slab in a marine environment can be divided into three stages according to crack morphology at the bottom of the slab. In the first stage, cracks appear. In the second stage, cracks develop from the edges to the middle of the slab. In the third stage, longitudinal and transverse corrosion-induced cracks coexist. The corrosion ratio of reinforcements nonlinearly increases with the age, and the relationship between the corrosion ratio of the reinforcements and the corrosion-induced crack width of the concrete is established. The flexural capacity of the corroded RC slab nonlinearly decreases with the age, and the model for the bearing capacity factor of the corroded RC slab is established. The mid-span deflection of the corroded RC slab that corresponds to the yield of the reinforcements linearly increases with the increase in corrosion ratio. Finally, the mechanisms of corrosion morphology and the degradation of the mechanical properties of an RC slab in a marine environment are discussed on the basis of the basic theories of steel corrosion in concrete and concrete structure design.

  20. Juan de Fuca slab geometry and its relation to Wadati-Benioff zone seismicity

    USGS Publications Warehouse

    McCrory, Patricia A.; Blair, J. Luke; Waldhause, Felix; Oppenheimer, David H.

    2012-01-01

    A new model of the subducted Juan de Fuca plate beneath western North America allows first-order correlations between the occurrence of Wadati-Benioff zone earthquakes and slab geometry, temperature, and hydration state. The geo-referenced 3D model, constructed from weighted control points, integrates depth information from earthquake locations and regional seismic velocity studies. We use the model to separate earthquakes that occur in the Cascadia forearc from those that occur within the underlying Juan de Fuca plate and thereby reveal previously obscured details regarding the spatial distribution of earthquakes. Seismicity within the slab is most prevalent where the slab is warped beneath northwestern California and western Washington suggesting that slab flexure, in addition to expected metamorphic dehydration processes, promotes earthquake occurrence within the subducted oceanic plate. Earthquake patterns beneath western Vancouver Island are consistent with slab dehydration processes. Conversely, the lack of slab earthquakes beneath western Oregon is consistent with an anhydrous slab. Double-differenced relocated seismicity resolves a double seismic zone within the slab beneath northwestern California that strongly constrains the location of the plate interface and delineates a cluster of seismicity 10 km above the surface that includes the 1992 M7.1 Mendocino earthquake. We infer that this earthquake ruptured a surface within the Cascadia accretionary margin above the Juan de Fuca plate. We further speculate that this earthquake is associated with a detached fragment of former Farallon plate. Other subsurface tectonic elements within the forearc may have the potential to generate similar damaging earthquakes.

  1. ENGINEERING DESIGN CRITERIA FOR SUB-SLAB DEPRESSURIZATION SYSTEMS IN LOW-PERMEABILTY SOLIDS

    EPA Science Inventory

    The report describes the development of engineering design criteria for the successful design, installation, and operation of sub-slab depressurization systems, based on radon (Rn) mitigation experience on 14 slab-on-grade houses in South Central Florida. The Florida houses are c...

  2. A numerical model for calculating vibration due to a harmonic moving load on a floating-slab track with discontinuous slabs in an underground railway tunnel

    NASA Astrophysics Data System (ADS)

    Hussein, M. F. M.; Hunt, H. E. M.

    2009-03-01

    This paper presents a new method for modelling floating-slab tracks with discontinuous slabs in underground railway tunnels. The track is subjected to a harmonic load moving with a constant velocity. The model consists of two sub-models. The first is an infinite track with periodic double-beam unit formulated as a periodic infinite structure. The second is modelled with a new version of the Pipe-in-Pipe (PiP) model that accounts for a tunnel wall embedded in a half-space. The two sub-models are coupled by writing the force transmitted from the track to the tunnel as a continuous function using Fourier series representation and satisfying the compatibility condition. The displacements at the free surface are calculated for a track with discontinuous slab and compared with those of a track with continuous slab. The results show that the far-field vibration can be significantly increased due to resonance frequencies of slabs for tracks with discontinuous slabs.

  3. Overriding plate thickness control on subducting slab curvature

    NASA Astrophysics Data System (ADS)

    Holt, A.; Buffett, B. A.; Becker, T. W.

    2014-12-01

    The curvature of subducting lithosphere controls deformation due to bending at the trench, which results in a force that dissipates gravitational potential energy and may affect seismic coupling. We use 2-D, thermo-mechanical subduction models to explore the dependence of the radius of curvature on the thickness of the subducting and overriding plates for models with both viscous and effectively plastic lithospheric rheologies. Such a plastic rheology has been shown to reproduce the bending stresses/moment computed using a kinematic strain rate description and a laboratory derived composite rheology. Laboratory and numerical models show that the bending geometry of subducting slabs with a viscous rheology is strongly dependent on slab thickness; thicker plates have a larger radius of curvature. However, the curvature of subducting plates on Earth, illuminated by the distribution of earthquake hypocenters, shows little to no dependence on the plate thickness or age. Such an observation is instead compatible with plates that have a plastic rheology. Indeed, our numerical models show that the radius of curvature of viscous plates has a stronger dependence on subducting plate thickness than in equivalent plastic models. In viscous plates, the bending moment produces a torque, which balances the torque exerted by buoyancy. However, for the plastic plate case the bending moment saturates at a maximum value and so cannot balance the gravitational torque. The saturation of bending moment means that, (a) the radius of curvature of the bending region is not constrained by this torque balance, and, (b) other forces are required to balance the gravitational torque. We explore the role that the overriding plate could play in controlling the subducting plate curvature in plastic plate models where the bending stresses have saturated. For such plates, we find that increasing the thickness of the overriding plate causes the radius of curvature to increase. The same correlation is

  4. Seismic imaging of the stagnant Pacific slab in the mantle transition zone under East Asia

    NASA Astrophysics Data System (ADS)

    Zhao, D.

    2008-12-01

    We used regional and global seismic tomography to determine high-resolution 3-D P-wave velocity structure of the crust and mantle down to 1200 km depth under Western Pacific to East Asia (Zhao, 2004, 2007; Huang and Zhao, 2006). A large number of arrival times of P, pP, PP and PcP waves recorded by many seismic stations in East Asia are used in the tomographic inversions. The subducting Pacific slab is imaged clearly as a high-velocity zone from the oceanic trenches down to 670-km depth, and intermediate-depth and deep earthquakes are located within the slab. The Pacific slab becomes stagnant in the mantle transition zone under eastern China. The western edge of the stagnant slab is generally parallel with the Japan trench and the Ryukyu trench and roughly coincides with a prominent surface topographic boundary in East China. Although there are some discrepancies between the topographic boundary and the western edge of the stagnant slab, both of them are located approximately 1800 km west of the trenches. The entire Pacific slab is stagnant in the mantle transition zone under Northeast China (53-37 degree north latitude). Under 37-28 degree north latitude, however, some of the slab materials are visible below the 670-km discontinuity, though most of the slab materials are still in the transition zone, suggesting that part of the slab materials have started to drop down to the lower mantle. Under the Mariana arc, the Pacific slab penetrates directly down to the lower mantle. It is also visible that the Philippine Sea slab has subducted down to the mantle transition zone depth under western Japan and the Ryukyu back-arc region (Abdelwahed and Zhao, 2007). There are three active intraplate volcanoes in China. The Changbai and Wudalianchi volcanoes in Northeast China are underlain by significant slow anomalies in the upper mantle, above the stagnant Pacific slab, suggesting that the two active volcanoes are not hot spots but a kind of back-arc volcanoes associated with

  5. Farallon slab detachment and deformation of the Magdalena Shelf, southern Baja California

    USGS Publications Warehouse

    Brothers, Daniel S.; Harding, Alistair J.; Gonzalez-Fernandez, Antonio; Holbrook, W.S. Steven; Kent, Graham M.; Driscoll, Neal W.; Fletcher, John M.; Lizarralde, Daniel; Umhoefer, Paul J.; Axen, Gary

    2012-01-01

    Subduction of the Farallon plate beneath northwestern Mexico stalled by ~12 Ma when the Pacific-Farallon spreading-ridge approached the subduction zone. Coupling between remnant slab and the overriding North American plate played an important role in the capture of the Baja California (BC) microplate by the Pacific Plate. Active-source seismic reflection and wide-angle seismic refraction profiles across southwestern BC (~24.5°N) are used to image the extent of remnant slab and study its impact on the overriding plate. We infer that the hot, buoyant slab detached ~40 km landward of the fossil trench. Isostatic rebound following slab detachment uplifted the margin and exposed the Magdalena Shelf to wave-base erosion. Subsequent cooling, subsidence and transtensional opening along the shelf (starting ~8 Ma) starved the fossil trench of terrigenous sediment input. Slab detachment and the resultant rebound of the margin provide a mechanism for rapid uplift and exhumation of forearc subduction complexes.

  6. Experimental validation of systematically designed acoustic hyperbolic meta material slab exhibiting negative refraction

    NASA Astrophysics Data System (ADS)

    Christiansen, Rasmus E.; Sigmund, Ole

    2016-09-01

    This Letter reports on the experimental validation of a two-dimensional acoustic hyperbolic metamaterial slab optimized to exhibit negative refractive behavior. The slab was designed using a topology optimization based systematic design method allowing for tailoring the refractive behavior. The experimental results confirm the predicted refractive capability as well as the predicted transmission at an interface. The study simultaneously provides an estimate of the attenuation inside the slab stemming from the boundary layer effects—insight which can be utilized in the further design of the metamaterial slabs. The capability of tailoring the refractive behavior opens possibilities for different applications. For instance, a slab exhibiting zero refraction across a wide angular range is capable of funneling acoustic energy through it, while a material exhibiting the negative refractive behavior across a wide angular range provides lensing and collimating capabilities.

  7. The output beam quality of a Q-switched Nd:glass slab laser

    NASA Technical Reports Server (NTRS)

    Reed, Murray K.; Byer, Robert L.

    1990-01-01

    The authors have constructed and tested a flashlamp pumped, Q-switched, Nd:glass zigzag slab laser. The thermally induced optical distortion through the slab is minimized by uniform pumping and cooling and the use of corrective pump shields at the slab ends. The laser spatial output for Q-switched resonators has been measured and modeled. It is shown that a larger aperture planar oscillator has an output divergence many times above the diffraction limit. Operation as a one-dimensional unstable resonator in the wide direction of the slab allows the efficient extraction of energy in a high-quality beam. Near-diffraction-limited laser output of 5 J at 4 Hz is achieved with a resonator that includes an intracavity telescope to correct for residual defocusing in the thin direction of the slab.

  8. Series solution to coupled nonlinear heat and moisture transfer in slabs with temperature-dependent diffusivities

    NASA Astrophysics Data System (ADS)

    Chiba, Ryoichi

    2014-12-01

    The two-dimensional differential transform method (DTM) is applied to solve the one-dimensional coupled heat and moisture diffusion problem for a slab with temperature-dependent thermal and moisture diffusivities, which are expressed by a linear function and an exponential function of temperature, respectively. One surface of the slab is subjected to convective hygrothermal loading and the other has constant prescribed temperature and moisture. Approximate analytical (series) solutions for the temperature and moisture profiles in the slab are derived. The transformed functions included in the solutions are obtained through a simple recursive procedure. Numerical results for a slab subjected to a sudden change in surface temperature illustrate the effects of temperature-dependent diffusivities on the transient temperature and moisture profiles of the slab. The results indicate that the nonlinear effect originating from the varying moisture diffusivity is not negligible for resin composites. The DTMis a useful new analytical method for solving nonlinear coupled transient problems.

  9. Insights on slab-driven mantle flow from advances in three-dimensional modelling

    NASA Astrophysics Data System (ADS)

    Jadamec, Margarete A.

    2016-10-01

    The wealth of seismic observations collected over the past 20 years has raised intriguing questions about the three-dimensional (3D) nature of the mantle flow field close to subduction zones and provided a valuable constraint for how the plate geometry may influence mantle flow proximal to the slab. In geodynamics, there has been a new direction of subduction zone modelling that has explored the 3D nature of slab-driven mantle flow, motivated in part by the observations from shear wave splitting, but also by the observed variations in slab geometries worldwide. Advances in high-performance computing are now allowing for an unprecedented level of detail to be incorporated into numerical models of subduction. This paper summarizes recent advances from 3D geodynamic models that reveal the complex nature of slab-driven mantle flow, including trench parallel flow, toroidal flow around slab edges, mantle upwelling at lateral slab edges, and small scale convection within the mantle wedge. This implies slab-driven mantle deformation zones occur in the asthenosphere proximal to the slab, wherein the mantle may commonly flow in a different direction and rate than the surface plates, implying laterally variable plate-mantle coupling. The 3D slab-driven mantle flow can explain, in part, the lateral transport of geochemical signatures in subduction zones. In addition, high-resolution geographically referenced models can inform the interpretation of slab structure, where seismic data are lacking. The incorporation of complex plate boundaries into high-resolution, 3D numerical models opens the door to a new avenue of research in model construction, data assimilation, and modelling workflows, and gives 3D immersive visualization a new role in scientific discovery.

  10. Slab detachment during continental collision: Influence of crustal rheology and interaction with lithospheric delamination

    NASA Astrophysics Data System (ADS)

    Duretz, T.; Gerya, T. V.

    2013-08-01

    Collision between continents can lead to the subduction of continental material. If the crust remains coupled to the downgoing slab, a large buoyancy force is generated. This force slows down convergence and promotes slab detachment. If the crust resists to subduction, it may decouple from the downgoing slab and be subjected to buoyant extrusion. We employ two-dimensional thermo-mechanical modelling to study the importance of crustal rheology on the evolution of subduction-collision systems. We propose simple quantifications of the mechanical decoupling between lithospheric levels (σ*) and the potential for buoyant extrusion of the crust (ξ*). The modelling results indicate that a variable crustal rheological structure results in slab detachment, delamination, or the combination of both mechanisms. A strong crust provides coupling at the Moho (low σ*) and remains coherent during subduction (low ξ). It promotes deep subduction of the crust (180 km) and slab detachment. Exhumation occurs in coherent manners via eduction and thrusting. Slab detachment triggers the development of topography (> 4.5 km) close to the suture. A contrasting style of collision occurs using a weak crustal rheology. Mechanical decoupling at the Moho (high σ*) promotes the extrusion of the crust (high ξ), disabling slab detachment. Ongoing shortening leads to buckling of the crust and development of topography on the lower plate. Collisions involving rheologically layered crust allow decoupling at mid-crustal depths. This structure favours both the extrusion of upper crust and the subduction of the lower crust. Such collisions are successively affected by delamination and slab detachment. Topography develops together with the buoyant extrusion of crust onto the foreland and is further amplified by slab detachment. Our results suggest that the occurrence of both delamination (Apennines) and slab detachment (Himalayas) in orogens may indicate differences in the initial crustal structure of

  11. Mechanisms controlling the modes of the sinking slab into the transition zone

    NASA Astrophysics Data System (ADS)

    Agrusta, Roberto; Goes, Saskia; van Hunen, Jeroen

    2016-04-01

    It is generally accepted that subducting slabs can either sink into the lower mantle, lie down in the mantle transition zone, or even stagnate beneath it. Several studies have looked at correlations between subduction zone parameters and the ability of the slabs to penetrate into the lower mantle. These studies have suggested that the key parameters to control whether slabs stagnate or penetrate are trench motions, slab strength, buoyant features and/or the overriding plate. For example, there is evidence that older lithospheres show significant trench retreat, and tend to lie down flat above the transition zone (northwest Pacific), whereas younger lithospheres, less able to drive trench retreat, tend to sink into the lower mantle (central America). Moreover, numerical modelling studies have shown further correlations with parameters that cannot be directly observed. For example, slab penetration is inhibited by density and viscosity increases associated with post-spinel phase transition. Numerical modelling has been one of the key tools to investigate slab penetration, and a lot of insight has been gained from these studies. But most of these studies assume (statistical) steady ­state scenarios, in which slab stagnation or slab penetration is more or less a permanent feature. However, on Earth different modes of slab - transition zone interaction probably need to be able to change in time from penetrating to stagnant and also vice versa. In this study, using 2D self-consistent numerical subduction models, we test plausible mechanisms which may trigger different modes of slab deformation in the transition zone and may explain both spatial and temporal variability.

  12. Planar prism spectrometer based on adiabatically connected waveguiding slabs

    NASA Astrophysics Data System (ADS)

    Civitci, F.; Hammer, M.; Hoekstra, H. J. W. M.

    2016-04-01

    The device principle of a prism-based on-chip spectrometer for TE polarization is introduced. The spectrometer exploits the modal dispersion in planar waveguides in a layout with slab regions having two different thicknesses of the guiding layer. The set-up uses parabolic mirrors, for the collimation of light of the input waveguide and focusing of the light to the receiver waveguides, which relies on total internal reflection at the interface between two such regions. These regions are connected adiabatically to prevent unwanted mode conversion and loss at the edges of the prism. The structure can be fabricated with two wet etching steps. The paper presents basic theory and a general approach for device optimization. The latter is illustrated with a numerical example assuming SiON technology.

  13. Diffusive Propagation of Exciton-Polaritons through Thin Crystal Slabs.

    PubMed

    Zaitsev, D A; Il'ynskaya, N D; Koudinov, A V; Poletaev, N K; Nikitina, E V; Egorov, A Yu; Kavokin, A V; Seisyan, R P

    2015-01-01

    If light beam propagates through matter containing point impurity centers, the amount of energy absorbed by the media is expected to be either independent of the impurity concentration N or proportional to N, corresponding to the intrinsic absorption or impurity absorption, respectively. Comparative studies of the resonant transmission of light in the vicinity of exciton resonances measured for 15 few-micron GaAs crystal slabs with different values of N, reveal a surprising tendency. While N spans almost five decimal orders of magnitude, the normalized spectrally-integrated absorption of light scales with the impurity concentration as N(1/6). We show analytically that this dependence is a signature of the diffusive mechanism of propagation of exciton-polaritons in a semiconductor. PMID:26088555

  14. High-Performance Slab-on-Grade Foundation Insulation Retrofits

    SciTech Connect

    Goldberg, Louise F.; Mosiman, Garrett E.

    2015-09-01

    A more accurate assessment of slab-on-grade foundation insulation energy savings than traditionally possible is now feasible. This has been enabled by advances in whole building energy simulation with 3-dimensional foundation modelling integration at each time step together with an experimental measurement of the site energy savings of SOG foundation insulation. Ten SOG insulation strategies were evaluated on a test building to identify an optimum retrofit insulation strategy in a zone 6 climate (Minneapolis, MN). The optimum insulation strategy in terms of energy savings and cost effectiveness consisted of two components: (a) R-20 XPS insulation above grade, and, (b) R-20 insulation at grade (comprising an outer layer of R-10 insulation and an interior layer of R-12 poured polyurethane insulation) tapering to R-10 XPS insulation at half the below-grade wall height (the lower half of the stem wall was uninsulated).

  15. Slab waveguide theory for general multi-slot waveguide

    NASA Astrophysics Data System (ADS)

    Le, ZiChun; Yin, LiXiang; Zou, Yu; Wu, Xiang

    2016-07-01

    Optical devices based on slot waveguide are of considerable interest in numerous applications due to the distinct feature of strong electric field confinement in a low-refractive index region. A theoretical model based on multi-slab waveguide theory is used to reveal the physical mechanism of the slot waveguide. The calculation results derived from the basic Helmholtz equation for the conventional single-slot waveguide with a ~2% validation of the effective refractive index are compared to the former experiment results by the Cornell University group. Moreover, we extend the theoretical model to a general multi-slot waveguide. Its electric field distribution and key properties such as optical power confinement factor and enhancement factor in slot are deduced theoretically and fully discussed.

  16. Where has the Flat-Fattened-Farallon Slab gone?

    NASA Astrophysics Data System (ADS)

    Helmberger, D. V.; Sun, D.; Bai, K.; Gurnis, M.

    2014-12-01

    It has been hypothesized that much of the Laramide orogeny producing the Rock Mountain Front was caused by dynamic effects induced by flat-slabs during a period of subducting plateaus. It has further been hypothesized that a particularly flat block containing the Shatsky Rise conjugate left a foot print from Southern California to Colorado with dimensions of about 500 km in width and 1000km in length. Here we rediscovered this block beneath the Midwest at a depth of about 660km and dipping northeastward at about 35°. This resolution was accomplished by exploiting the USArray seismic observations where detailed waveform modeling allowed both the shape and sharpness of a candidate tomographic image as box-like. This structure when migrated back in time to California (using G-plate mapping) fits the above hypothesized block quite well lending strong support for the above hypothesis.

  17. Diffusive Propagation of Exciton-Polaritons through Thin Crystal Slabs

    PubMed Central

    Zaitsev, D. A.; Il’ynskaya, N. D.; Koudinov, A. V.; Poletaev, N. K.; Nikitina, E. V.; Egorov, A. Yu.; Kavokin, A. V.; Seisyan, R. P.

    2015-01-01

    If light beam propagates through matter containing point impurity centers, the amount of energy absorbed by the media is expected to be either independent of the impurity concentration N or proportional to N, corresponding to the intrinsic absorption or impurity absorption, respectively. Comparative studies of the resonant transmission of light in the vicinity of exciton resonances measured for 15 few-micron GaAs crystal slabs with different values of N, reveal a surprising tendency. While N spans almost five decimal orders of magnitude, the normalized spectrally-integrated absorption of light scales with the impurity concentration as N1/6. We show analytically that this dependence is a signature of the diffusive mechanism of propagation of exciton-polaritons in a semiconductor. PMID:26088555

  18. Experimental investigation of heat transfer and pressure drop characteristics of water and glycol-water mixture in multi-port serpentine microchannel slab heat exchangers

    NASA Astrophysics Data System (ADS)

    Khan, Md Mesbah-ul Ghani

    Microchannels have several advantages over traditional large tubes. Heat transfer using microchannels recently have attracted significant research and industrial design interests. Open literatures leave with question on the applicability of classical macroscale theory in microchannels. Better understanding of heat transfer in various microchannel geometries and building experimental database are continuously urged. The purpose of this study is to contribute the findings and data to this emerging area through carefully designed and well controlled experimental works. The commercially important glycol-water mixture heat transfer fluid and multiport slab serpentine heat exchangers are encountered in heating and cooling areas, e.g. in automotive, aircraft, and HVAC industries. For a given heat duty, the large diameter tubes experience turbulent flow whereas the narrow channels face laminar flow and often developing flow. Study of low Reynolds number developing glycol-water mixture laminar flow in serpentine microchannel heat exchanger with parallel multi-port slab is not available in the open literature. Current research therefore experimentally investigates glycol-water mixture and water in simultaneously developing laminar flows. Three multiport microchannel heat exchangers; straight and serpentine slabs, are used for each fluid. Friction factors of glycol-water mixture and water flows in straight slabs are higher than conventional fully developed laminar flow. If a comprehensive pressure balance is introduced, the results are well compared with conventional Poiseuille theory. Similar results are found in serpentine slab. The pressure drop for the straight core is the highest, manifolds are the intermediate, and serpentine is the least; which are beneficial for heat exchangers. The heat transfer results in serpentine slab for glycol-water mixture and water are higher and could not be compared with conventional fully developed and developing flow correlations. New

  19. A generalized 2D pencil beam scaling algorithm for proton dose calculation in heterogeneous slab geometries

    SciTech Connect

    Westerly, David C.; Mo Xiaohu; DeLuca, Paul M. Jr.; Tome, Wolfgang A.; Mackie, Thomas R.

    2013-06-15

    Purpose: Pencil beam algorithms are commonly used for proton therapy dose calculations. Szymanowski and Oelfke ['Two-dimensional pencil beam scaling: An improved proton dose algorithm for heterogeneous media,' Phys. Med. Biol. 47, 3313-3330 (2002)] developed a two-dimensional (2D) scaling algorithm which accurately models the radial pencil beam width as a function of depth in heterogeneous slab geometries using a scaled expression for the radial kernel width in water as a function of depth and kinetic energy. However, an assumption made in the derivation of the technique limits its range of validity to cases where the input expression for the radial kernel width in water is derived from a local scattering power model. The goal of this work is to derive a generalized form of 2D pencil beam scaling that is independent of the scattering power model and appropriate for use with any expression for the radial kernel width in water as a function of depth. Methods: Using Fermi-Eyges transport theory, the authors derive an expression for the radial pencil beam width in heterogeneous slab geometries which is independent of the proton scattering power and related quantities. The authors then perform test calculations in homogeneous and heterogeneous slab phantoms using both the original 2D scaling model and the new model with expressions for the radial kernel width in water computed from both local and nonlocal scattering power models, as well as a nonlocal parameterization of Moliere scattering theory. In addition to kernel width calculations, dose calculations are also performed for a narrow Gaussian proton beam. Results: Pencil beam width calculations indicate that both 2D scaling formalisms perform well when the radial kernel width in water is derived from a local scattering power model. Computing the radial kernel width from a nonlocal scattering model results in the local 2D scaling formula under-predicting the pencil beam width by as much as 1.4 mm (21%) at the depth

  20. A generalized 2D pencil beam scaling algorithm for proton dose calculation in heterogeneous slab geometries

    PubMed Central

    Westerly, David C.; Mo, Xiaohu; Tomé, Wolfgang A.; Mackie, Thomas R.; DeLuca, Paul M.

    2013-01-01

    Purpose: Pencil beam algorithms are commonly used for proton therapy dose calculations. Szymanowski and Oelfke [“Two-dimensional pencil beam scaling: An improved proton dose algorithm for heterogeneous media,” Phys. Med. Biol. 47, 3313–3330 (2002)10.1088/0031-9155/47/18/304] developed a two-dimensional (2D) scaling algorithm which accurately models the radial pencil beam width as a function of depth in heterogeneous slab geometries using a scaled expression for the radial kernel width in water as a function of depth and kinetic energy. However, an assumption made in the derivation of the technique limits its range of validity to cases where the input expression for the radial kernel width in water is derived from a local scattering power model. The goal of this work is to derive a generalized form of 2D pencil beam scaling that is independent of the scattering power model and appropriate for use with any expression for the radial kernel width in water as a function of depth. Methods: Using Fermi-Eyges transport theory, the authors derive an expression for the radial pencil beam width in heterogeneous slab geometries which is independent of the proton scattering power and related quantities. The authors then perform test calculations in homogeneous and heterogeneous slab phantoms using both the original 2D scaling model and the new model with expressions for the radial kernel width in water computed from both local and nonlocal scattering power models, as well as a nonlocal parameterization of Molière scattering theory. In addition to kernel width calculations, dose calculations are also performed for a narrow Gaussian proton beam. Results: Pencil beam width calculations indicate that both 2D scaling formalisms perform well when the radial kernel width in water is derived from a local scattering power model. Computing the radial kernel width from a nonlocal scattering model results in the local 2D scaling formula under-predicting the pencil beam width by as

  1. Thermocouple assembly

    DOEpatents

    Thermos, Anthony Constantine; Rahal, Fadi Elias

    2002-01-01

    A thermocouple assembly includes a thermocouple; a plurality of lead wires extending from the thermocouple; an insulating jacket extending along and enclosing the plurality of leads; and at least one internally sealed area within the insulating jacket to prevent fluid leakage along and within the insulating jacket. The invention also provides a method of preventing leakage of a fluid along and through an insulating jacket of a thermocouple including the steps of a) attaching a plurality of lead wires to a thermocouple; b) adding a heat sensitive pseudo-wire to extend along the plurality of lead wires; c) enclosing the lead wires and pseudo-wire inside an insulating jacket; d) locally heating axially spaced portions of the insulating jacket to a temperature which melts the pseudo-wire and fuses it with an interior surface of the jacket.

  2. Swivel assembly

    DOEpatents

    Hall, David R.; Pixton, David S.; Briscoe, Michael; Bradford, Kline; Rawle, Michael; Bartholomew, David B.; McPherson, James

    2007-03-20

    A swivel assembly for a downhole tool string comprises a first and second coaxial housing cooperatively arranged. The first housing comprises a first transmission element in communication with surface equipment. The second housing comprises a second transmission element in communication with the first transmission element. The second housing further comprises a third transmission element adapted for communication with a network integrated into the downhole tool string. The second housing may be rotational and adapted to transmit a signal between the downhole network and the first housing. Electronic circuitry is in communication with at least one of the transmission elements. The electronic circuitry may be externally mounted to the first or second housing. Further, the electronic circuitry may be internally mounted in the second housing. The electronic circuitry may be disposed in a recess in either first or second housing of the swivel.

  3. Ingestion resistant seal assembly

    SciTech Connect

    Little, David A.

    2011-12-13

    A seal assembly limits gas leakage from a hot gas path to one or more disc cavities in a gas turbine engine. The seal assembly includes a seal apparatus associated with a blade structure including a row of airfoils. The seal apparatus includes an annular inner shroud associated with adjacent stationary components, a wing member, and a first wing flange. The wing member extends axially from the blade structure toward the annular inner shroud. The first wing flange extends radially outwardly from the wing member toward the annular inner shroud. A plurality of regions including one or more recirculation zones are defined between the blade structure and the annular inner shroud that recirculate working gas therein back toward the hot gas path.

  4. Imaging variations in the central Andean mantle and the subducting Nazca slab with teleseismic tomography

    NASA Astrophysics Data System (ADS)

    Scire, Alissa

    The Nazca-South America convergent margin is marked by the presence of the Andean mountain belt, which stretches along the 8000-km long western margin of the South American plate. The subduction zone is characterized by significant along-strike changes in both upper plate structure and slab geometry that make it an ideal region to study the relationship between the subducting slab, the surrounding mantle, and the overriding plate. This dissertation summarizes the results of three finite frequency teleseismic tomography studies of the central Nazca-South America subduction zone which improve our understanding of how along-strike variations in the Andean mountain belt and the subducting Nazca plate interact with each other and with the surrounding mantle. This is accomplished by first focusing on two smaller adjacent regions of the central Andes to explore upper mantle variations and then by using a combined dataset, which covers a larger region, to image the deeply subducted Nazca slab to investigate the fate of the slab. The first study focuses on the central Andean upper mantle under the Altiplano-Puna Plateau where normally dipping subduction of the Nazca plate is occurring (18° to 28°S). The shallow mantle under the Eastern Cordillera is generally fast, consistent with either underthrusting of the Brazilian cratonic lithosphere from the east or a localized "curtain" of delaminating material. Additional evidence for delamination is seen in the form of high amplitude low velocities under the Puna Plateau, consistent with proposed asthenospheric influx following lithospheric removal. In the second study, we explore the transition between normal and flat subduction along the north edge of the Altiplano Plateau (8° to 21°S). We find that the Peruvian flat slab extends further inland along the projection of the Nazca Ridge than was previously proposed and that when re-steepening of the slab occurs, the slab dips very steeply (˜70°) down through the mantle

  5. Efficient exhumation of (ultra) high-pressure rocks by slab extraction

    NASA Astrophysics Data System (ADS)

    Zhao, Zhongbao; Bons, Paul; Gomez-Rivas, Enrique; Soesoo, Alvar; Evgueni, Burov

    2015-04-01

    A range of mechanisms has been proposed for the enigmatic exhumation of (ultra) high-pressure (UHP) rocks from great depths. These include channel flow, wedge extrusion, diapiric rise, metamorphic core complexes and eduction. Most current models envisage exhumation to occur in a subduction setting, where exhumation of UHP rocks takes place in the context of the downward movement of the subducting slab. In addition, removal of the downward pull on the subducting slab (by slab break-off and slab retreat) may lead to buoyant rise of the UHP material, especially in case of subduction of continental crust. Here we consider the alternative scenario of slab extraction, where subduction is reversed and the slab is pulled up and away from the overriding plate, instead of sliding down into the mantle. UHP rocks are then exhumed together with the ascending plate. Slab extraction occurs when the downward pull of the subducted slab is exceeded by an opposite force, for example in case of plate divergence. Another case is a divergent double subduction zone (DDSZ), where the two hinges inevitably converge by rollback. At some point the pull of one slab can exceed that of the other one if it is short enough, leading to the extraction of the shorter slab and concomitant exhumation of UHP rocks. The evolution of a DDSZ with one short slab was modelled with the thermo-mechanical code FLAMAR, varying the relative movement of the two overriding plates. If the two overriding plates do not converge too fast, the short slab is pulled up and away from its suture and is eventually pulled down at the opposite suture. UHP rocks are exhumed at rates exceeding cms/yr in what is effectively a lithospheric-scale core complex. This mechanism may explain the exhumation of UHP rocks in the Tibetan Qiangtang Metamorphic Belt and the d'Entercasteaux Islands. If the sutures converge slower than the long slab slides down, an oceanic basin forms, which we suggest is the cause for the rapid opening of the

  6. Investigation of compressive membrane action in ultra high performance concrete slab strips

    NASA Astrophysics Data System (ADS)

    Foust, Bradley Wade

    Reinforced concrete slabs are found in very common structural systems in both civilian and military applications. The boundary conditions that support the slab play an important role in the response to a particular load. Specifically, the amount of lateral and rotational restraint dictates how a slab responds to a particular load. Compressive membrane (i.e., in-plane) forces are present in slabs when the boundaries are sufficiently stiff, therefore restricting the slab from both lateral translations and rotations. Advancements have been made to account for the additional capacity due to compressive membrane forces in conventional strength concrete. In today's world, concrete performance is improving because of increasing compressive strengths and additional ductility present in concrete members. As a result of this current improvement, there is an urgent need to investigate compressive membrane theory in ultra-high-performance concrete (UHPC) slabs to better understand their behavior. Existing compressive membrane theory should be revisited to determine if current theory is applicable, or if it is not, what modifications should be made. This study will provide insight into the validity of existing theory that is currently used to predict the ultimate capacity in conventional-strength concrete slabs and attempt to modify the existing equations to account for high-strength concrete materials. A matrix of 14 normal-strength concrete (NSC) and 13 UHPC slabs was tested both statically and dynamically to better understand the behavior of each material set and the effects that boundary conditions have on slab response. The results from these experiments were then compared to response calculations made from existing theory as well as finite element analyses. Valuable data sets on rigidly restrained UHPC slab response were obtained through an experimental research program. The experiments helped to validate the associated numerical analysis that was performed. It was

  7. Tears in subducting slabs: Examples from central Mexico and southern Peru

    NASA Astrophysics Data System (ADS)

    Dougherty, S. L.; Clayton, R. W.

    2013-12-01

    Slab tears are tectonically important morphological features of subducted plates that have been proposed to occur in numerous subduction zones. We examine the transitions from flat to normal subduction that occur in central Mexico and southern Peru for seismic evidence of such proposed tearing. The fine-scale seismic structure of these subduction zones is studied using moderate-sized (M4-6) intraslab earthquakes. Regional waveforms from temporary and permanent seismic arrays are complicated and contain detailed information about the subduction zone structure, including evidence of lateral heterogeneity, which is used to model the structure of the subducted plates. The lateral extent of a thin ultra-slow velocity layer (USL) imaged atop the Cocos slab in central Mexico in recent studies and evident atop the Nazca slab in southern Peru is mapped and examined for its relationship to the possible slab tears in each region. In central Mexico, there are two transitions from flat to normal subduction located in the west and east, respectively. In the west, recent tectonic studies have shown evidence for possible slab tearing along the projection of the Orozco Fracture Zone (OFZ), while in the east, observations of a sudden change in slab dip coupled with the abrupt end of the Trans Mexican Volcanic Belt (TMVB) suggest a second possible slab tear. In the west, we find an edge to the USL which is coincident with the western boundary of the projected OFZ region. Forward modeling of the 2D structure of the subducted Rivera and Cocos plates using a finite-difference algorithm provides constraints on the velocity and geometry of each slab's seismic structure in this region and confirms the location of the USL edge. Coupled with the results of recent plate motion studies showing that the Cocos plate moves differently on either side of the OFZ, we propose that the Cocos slab is currently fragmenting into a North Cocos plate and a South Cocos plate along the projection of the OFZ

  8. Analysis of Distribution of Nonmetallic Inclusions in Aluminum DC-Cast Billets and Slabs

    NASA Astrophysics Data System (ADS)

    Jaradeh, Majed M.; Carlberg, Torbjorn

    2012-02-01

    Inclusion distribution was studied in commercial aluminum DC-cast billets and slabs using a newly developed deep-etching method. Analyses revealed a nonuniform distribution of nonmetallic inclusions across billet diameters and lengths, and also across slab thicknesses and widths. In as-cast billets, more inclusions were found at the beginning and end of the billet length; more were present near the cross-section center than near the surface. In slabs, inclusions were located mostly within 13 mm of the surface and in a band between the centerline and the surface. Few inclusions were found 60 to 100 mm from the slab surface or at the centerline. In addition, comparing slab quality after casting using three types of ceramic foam filters (CFFs; i.e., 30 ppi, 50 ppi, and 50 ppi + HF) revealed significant differences in inclusion size, number, and distribution. Casting slabs using a finer pore-size filter (50 ppi) reduced the number of non-metallic inclusions greatly. The inclusion distribution patterns observed in the solidified slabs are discussed in terms of melt flow during casting.

  9. Exploring the connection between intermediate-depth seismicity, slab hydration, and dehydration

    NASA Astrophysics Data System (ADS)

    Syracuse, E. M.; Pesicek, J. D.; Zhang, H.; Thurber, C. H.

    2013-12-01

    The dehydration of hydrous minerals has commonly been cited as the cause of intermediate-depth seismicity in subducted crust and mantle, through the process known as dehydration embrittlement. However, recent laboratory and empirical studies have called both the mechanism and seismological observation of this phenomenon into question. In order to assess the global relationship between seismicity, the presence of hydrous and dehydrating minerals, and the thermal state of slabs, we perform double-difference earthquake relocation of earthquakes at the majority of Earth's subduction zones, which reduces the scatter and improves the accuracy of the distributions of slab seismicity. The double-difference relocations are systematically calculated for each subduction zone in a version of the algorithm tomoDD that has been modified to include absolute and differential catalog P, S, and depth phase arrival times from local and teleseismic stations, as well as a three-dimensional global velocity model. Preliminary relocations demonstrate shifts of up to 15 km due to the use of a three-dimensional global velocity model. These relocations also illuminate various types of slab structures, including a range of slab morphologies, potential double seismic zones, and evidence of fault zones within slabs. At each subduction zone, these distributions are compared to previously published two-dimensional thermal and mineralogical models that have been calculated for that particular slab. The findings of these comparisons will be used to develop a set of slab conditions that describe where intermediate-depth seismicity is possible (and observed) at subduction zones.

  10. Seismic response to slab rupture and variation in lithospheric structure beneath the Savu Sea, Indonesia

    NASA Astrophysics Data System (ADS)

    Ely, Kim S.; Sandiford, Mike

    2010-03-01

    Variations in seismic moment release and stress state across the transition from subduction of oceanic crust to arc-continent collision in the Banda Arc are constrained by focal mechanism solutions from the CMT earthquake catalogue. In particular the slab under the western Savu Sea is unusual in that intermediate depth (70-300 km) events indicate that at this depth range the slab is largely in down-dip compression. This contrasts with the intermediate depth, down-dip tension that typifies the Sunda slab to the west and the far eastern Banda slab to the east. Down-dip compression beneath the Savu Sea reflects subduction of transitional crust of the Scott Plateau, more buoyant than the Indian Ocean crust subducting further west. In this region, enhanced magma flux is indicated by unusually narrow volcano spacing in the overlying arc, and suggests that down-dip compression reflects not only more buoyant transitional crust but also a reduction in slab-wedge coupling induced by enhanced magma flux. East of the Savu Sea, the near complete absence of intermediate depth seismicity is attributed to a slab window that has opened where Australian continental crust has collided with the arc. Differences in seismic moment release around this slab window indicate asymmetric rupture, propagating to the east at a much faster rate than to the west.

  11. Surface deformation and slab-mantle interaction during Banda arc subduction rollback

    NASA Astrophysics Data System (ADS)

    Spakman, Wim; Hall, Robert

    2010-08-01

    The spectacularly curved Banda arc comprises young oceanic crust enclosed by a volcanic inner arc, outer arc islands and a trough parallel to the Australian continental margin. Strong seismic activity in the upper mantle defines a folded surface, for which there are two contrasting explanations: deformation of a single slab or two separate slabs subducting from the north and south. Here we combine seismic tomography with the plate tectonic evolution of the region to infer that the Banda arc results from subduction of a single slab. Our palaeogeographic reconstruction shows that a Jurassic embayment, which consisted of dense oceanic lithosphere enclosed by continental crust, once existed within the Australian plate. Banda subduction began about 15million years ago when active Java subduction tore eastwards into the embayment. The present morphology of the subducting slab is only partially controlled by the shape of the embayment. As the Australian plate moved northward at a high speed of about 7cmyr-1, the Banda oceanic slab rolled back towards the south-southeast accompanied by active delamination separating the crust from the denser mantle. Increasing resistance of the mantle to plate motion progressively folded the slab and caused strong deformation of the crust. The Banda arc represents an outstanding example of large-scale deformation of the Earth's crust in response to coupling between the crust, slab and surrounding mantle.

  12. Construction of a polarization insensitive lens from a quasi-isotropic metamaterial slab

    NASA Astrophysics Data System (ADS)

    Luo, Hailu; Ren, Zhongzhou; Shu, Weixing; Li, Fei

    2007-02-01

    We propose to employ the quasi-isotropic metamaterial (QIMM) slab to construct a polarization insensitive lens, in which both E - and H -polarized waves exhibit the same refocusing effect. For shallow incident angles, the QIMM slab will provide some degree of refocusing in the same manner as an isotropic negative index material. The refocusing effect allows us to introduce the ideas of paraxial beam focusing and phase compensation by the QIMM slab. On the basis of angular spectrum representation, a formalism describing paraxial beams propagating through a QIMM slab is presented. Because of the negative phase velocity in the QIMM slab, the inverse Gouy phase shift and the negative Rayleigh length of paraxial Gaussian beam are proposed. We find that the phase difference caused by the Gouy phase shift in vacuum can be compensated by that caused by the inverse Gouy phase shift in the QIMM slab. If certain matching conditions are satisfied, the intensity and phase distributions at object plane can be completely reconstructed at image plane. Our simulation results show that the superlensing effect with subwavelength image resolution could be achieved in the form of a QIMM slab.

  13. Extraordinary wavelength reduction in terahertz graphene-cladded photonic crystal slabs

    PubMed Central

    Williamson, Ian A. D.; Mousavi, S. Hossein; Wang, Zheng

    2016-01-01

    Photonic crystal slabs have been widely used in nanophotonics for light confinement, dispersion engineering, nonlinearity enhancement, and other unusual effects arising from their structural periodicity. Sub-micron device sizes and mode volumes are routine for silicon-based photonic crystal slabs, however spectrally they are limited to operate in the near infrared. Here, we show that two single-layer graphene sheets allow silicon photonic crystal slabs with submicron periodicity to operate in the terahertz regime, with an extreme 100× wavelength reduction from graphene’s large kinetic inductance. The atomically thin graphene further leads to excellent out-of-plane confinement, and consequently photonic-crystal-slab band structures that closely resemble those of ideal two-dimensional photonic crystals, with broad band gaps even when the slab thickness approaches zero. The overall photonic band structure not only scales with the graphene Fermi level, but more importantly scales to lower frequencies with reduced slab thickness. Just like ideal 2D photonic crystals, graphene-cladded photonic crystal slabs confine light along line defects, forming waveguides with the propagation lengths on the order of tens of lattice constants. The proposed structure opens up the possibility to dramatically reduce the size of terahertz photonic systems by orders of magnitude. PMID:27143314

  14. High-quality slab-based intermixing method for fusion rendering of multiple medical objects.

    PubMed

    Kim, Dong-Joon; Kim, Bohyoung; Lee, Jeongjin; Shin, Juneseuk; Kim, Kyoung Won; Shin, Yeong-Gil

    2016-01-01

    The visualization of multiple 3D objects has been increasingly required for recent applications in medical fields. Due to the heterogeneity in data representation or data configuration, it is difficult to efficiently render multiple medical objects in high quality. In this paper, we present a novel intermixing scheme for fusion rendering of multiple medical objects while preserving the real-time performance. First, we present an in-slab visibility interpolation method for the representation of subdivided slabs. Second, we introduce virtual zSlab, which extends an infinitely thin boundary (such as polygonal objects) into a slab with a finite thickness. Finally, based on virtual zSlab and in-slab visibility interpolation, we propose a slab-based visibility intermixing method with the newly proposed rendering pipeline. Experimental results demonstrate that the proposed method delivers more effective multiple-object renderings in terms of rendering quality, compared to conventional approaches. And proposed intermixing scheme provides high-quality intermixing results for the visualization of intersecting and overlapping surfaces by resolving aliasing and z-fighting problems. Moreover, two case studies are presented that apply the proposed method to the real clinical applications. These case studies manifest that the proposed method has the outstanding advantages of the rendering independency and reusability.

  15. Low electrical resistivity associated with plunging of the Nazca flat slab beneath Argentina.

    PubMed

    Booker, John R; Favetto, Alicia; Pomposiello, M Cristina

    2004-05-27

    Beneath much of the Andes, oceanic lithosphere descends eastward into the mantle at an angle of about 30 degrees (ref. 1). A partially molten region is thought to form in a wedge between this descending slab and the overlying continental lithosphere as volatiles given off by the slab lower the melting temperature of mantle material. This wedge is the ultimate source for magma erupted at the active volcanoes that characterize the Andean margin. But between 28 degrees and 33 degrees S the subducted Nazca plate appears to be anomalously buoyant, as it levels out at about 100 km depth and extends nearly horizontally under the continent. Above this 'flat slab', volcanic activity in the main Andean Cordillera terminated about 9 million years ago as the flattening slab presumably squeezed out the mantle wedge. But it is unknown where slab volatiles go once this happens, and why the flat slab finally rolls over to descend steeply into the mantle 600 km further eastward. Here we present results from a magnetotelluric profile in central Argentina, from which we infer enhanced electrical conductivity along the eastern side of the plunging slab, indicative of the presence of partial melt. This conductivity structure may imply that partial melting occurs to at least 250 km and perhaps to more than 400 km depth, or that melt is supplied from the 410 km discontinuity, consistent with the transition-zone 'water-filter' model of Bercovici and Karato.

  16. Simulation of late Cenozoic South American flat-slab subduction using geodynamic models with data assimilation

    NASA Astrophysics Data System (ADS)

    Hu, Jiashun; Liu, Lijun; Hermosillo, Armando; Zhou, Quan

    2016-03-01

    The formation mechanisms of flat slabs in South America remain unclear. To quantitatively evaluate the earlier proposed mechanisms, we simulate the post-100 Ma subduction history below South America using 4-D geodynamic models by progressively incorporating plate kinematics, seafloor ages and key tectonic features including the buoyant oceanic crust, continental cratons, oceanic plateaus (i.e. the inferred Inca plateau, subducting Nazca Ridge and Juan Fernandez Ridge), as well as deformable trench profiles according to recent geological reconstructions. We find that, in the absence of an overriding plate and subducting buoyancy features, the seafloor age affects slab dip angle by controlling the slab's mechanical strength (i.e., the resistance to bending) and negative buoyancy (integrated positive density anomaly that enhances bending). Our models show that slab strength dominates its buoyancy at age >30 Ma and the opposite for younger ages. The existence of a thick overriding plate reduces the slab dip by increasing dynamic suction, and individual cratonic roots further lead to along-trench variations of dip angle reduction. While dynamic suction from the overriding plate generates a permanent reduction of the long-wavelength slab dip angle, it is the final addition of subducting oceanic plateau and aseismic ridges that produces the transient and localized flat-slabs as observed. These results suggest that all mechanisms except the buoyancy features affect the slab dip only at large spatial scales. Our best-fit model with all the above tectonic features included provides a good match to both the upper mantle Benioff zones and the temporal evolution of volcanic arcs since the mid-Miocene. The imperfect match of the Peruvian flat-slab is likely associated with the uncertain 3-D configuration of the Amazonian craton.

  17. Boron-isotope systematics of Halmahera arc (Indonesia) lava: Evidence for involvement of the subducted slab

    SciTech Connect

    Palmer, M.R. )

    1991-03-01

    Dehydration of sediments and oceanic crust within the subducting slab at convergent plate margins is probably a ubiquitous feature. This leads to fractionation of elements between fluids and solids so that the slab-derived component of island-arc lavas is modified from the originally subducted material. Sediments and altered oceanic crust are enriched in boron and cesium relative to uncontaminated mantle products, and these elements are highly mobile during fluid-rock interaction. The combination of B-isotope systematics and Cs concentrations in lavas from the Halmahera arc (Indonesia) suggests that they have been influenced by fluids derived from dehydration and/or melting of the subducted slab.

  18. Experimental and numerical investigation of slabs on ground subjected to concentrated loads

    NASA Astrophysics Data System (ADS)

    Øverli, Jan

    2014-09-01

    An experimental program is presented where a slab on ground is subjected to concentrated loading at the centre, the edges and at the corners. Analytical solutions for the ultimate load capacity fit well with the results obtained in the tests. The non-linear behaviour of the slab is captured by performing nonlinear finite element analyses. The soil is modelled as a no-tension bedding and a smeared crack approach is employed for the concrete. Through a parametric study, the finite element model has been used to assess the influence of subgrade stiffness and shrinkage. The results indicate that drying shrinkage can cause severe cracking in slabs on grade.

  19. Out-of-plane resonances in terahertz photonic crystal slabs modulated by optical pumping.

    PubMed

    Shi, Yulei; Zhou, Qing-Li; Liu, Wei; Zhang, Cunlin

    2011-10-10

    This paper describes detailed optical-pump-terahertz-probe studies of two-dimensional photonic crystal slabs for propagation perpendicular to the slabs. When the slabs are excited by an 800 nm pump pulse and the effect of shielding by photocarriers is removed, we find that the decaying tail in the transmitted terahertz radiation is strikingly enhanced. The photocarriers weaken guided resonances, but they also greatly enhance the excitation efficiency of guided resonances and the ability of the guided resonances to transfer energy back to the radiation field. This increases the resonance-assisted contribution to transmitted field. The photoinduced resonant extremes agree well with the Fano model. PMID:21997090

  20. A high speed profiler based slab curvature index for jointed concrete pavement curling and warping analysis

    NASA Astrophysics Data System (ADS)

    Byrum, Christopher Ronald

    One of the biggest gaps of missing knowledge between accurate structural modeling of concrete pavement slab behavior and real pavement behavior is accounting for slab warping (locked-in curvature and moisture gradient effects) and curling (temperature gradient effects). Curling and warping are curvatures that can be present in a PCC slab that can cause corners and edges, or mid panel, of the slab to lift off of the ground resulting in relatively high deflection and stress in the system. The least understood type of curvature in slabs is apparent locked-in curvature, which can become excessive and control the overall behavior of the pavement system. This project is focused on quantifying slab curvatures and the effects of apparent locked-in curvature on the behavior and long-term performance of pavement systems. A high-speed profile analysis technique for detecting the amount of slab curvatures along pavement wheel paths is described. This signal processing technique can detect relatively small curvature variations in high-speed pavement elevation profiles obtained at normal highway operating speeds using special vehicles. A resulting curvature detection algorithm is applied to the Federal Highway Administration (FHWA) Long Term Pavement Performance (LTPP) database high-speed pavement profiles for jointed concrete pavements. The range and nature of slab curvatures detected in the profiles is described. The calculated locked-in curvature at the various pavement sites is compared to LTPP database information to evaluate curvature effects on pavement deterioration rates and the relation between site parameters and locked-in curvature. The significance of slab curvature is shown through statistics and predictive models developed for various pavement distress modes. It is shown that the amount of curvature locked into concrete slabs is one of the strongest factors in the FHWA LTPP data correlated to deterioration of pavements. This study shows that preventing locked

  1. Investigation of complete bandgaps in a piezoelectric slab covered with periodically structured coatings.

    PubMed

    Zou, Kui; Ma, Tian-Xue; Wang, Yue-Sheng

    2016-02-01

    The propagation of elastic waves in a piezoelectric slab covered with periodically structured coatings or the so-called stubbed phononic crystal slab is investigated. Four different models are selected and the effects of distribution forms and geometrical parameters of the structured coatings on complete bandgaps are discussed. The phononic crystal slab with symmetric coatings can generate wider complete bandgaps while that with asymmetric coatings is favorable for the generation of multi-bandgaps. The complete bandgaps, which are induced by locally resonant effects, change significantly as the geometry of the coatings changes. Moreover, the piezoelectric effects benefit the opening of the complete bandgaps.

  2. INDEPENDENT VERIFICATION OF THE BUILDING 3550 SLAB AT OAK RIDGE NATIONAL LABORATORY OAK RIDGE, TENNESSEE

    SciTech Connect

    Weaver, Phyllis C.

    2012-05-08

    The Oak Ridge Institute for Science and Education (ORISE) has completed the independent verification survey of the Building 3550 Slab. The results of this effort are provided. The objective of this verification survey is to provide independent review and field assessment of remediation actions conducted by Safety and Ecology Corporation (SEC) to document that the final radiological condition of the slab meets the release guidelines. Verification survey activities on the Building 3550 Slab that included scans, measurements, and the collection of smears. Scans for alpha, alpha plus beta, and gamma activity identified several areas that were investigated.

  3. Three-dimensional Numerical Models of Mantle Flow Through the Cocos-Nazca Slab Gap

    NASA Astrophysics Data System (ADS)

    Jadamec, M.; Fischer, K. M.

    2013-05-01

    Global slab geometry models suggest a 350 km to 1000 km spacing between the southern extent of the Cocos slab and the northern extent of the Nazca slab (Gudmundsson and Sambridge, 1998; Syracuse and Abers, 2006; Hayes et al., 2012). The apparent gap between the east-dipping Cocos and Nazca slabs at depth correlates to several tectonic features on the Pacific side of Central and northern South America that may limit subduction, namely the (a) Panama Fault zone, (b) incoming young lithosphere associated with the Cocos-Nazca spreading center, and (c) the Cocos, Coiba, Malpelo, and Carnegie ridges associated with the Galapogos hotspot and Cocos-Nazca spreading center (Protti et al., 1994; Johnston and Thorkelson, 1997; Gutscher et al., 1999; Abratis and Worner, 2001; Sdrolias and Muller, 2006; Mann et al., 2007; Gazel et al., 2011). In addition, on the Caribbean side of Central and northern South America, seismic data suggest that part of the Caribbean plate is subducting and dipping in a direction opposite to the Cocos and Nazca slabs (van der Hilst and Mann, 1994; Camacho et al., 2010). We construct high-resolution three-dimensional numerical models of the Cocos-Nazca subduction system to test the effects of a slab gap and variable overriding plate thickness on surface plate motion and mantle flow. The 3D tectonic configuration is generated with SlabGenerator (Jadamec and Billen, 2010, 2012) and the mantle convection code CitcomCU is used to solve for the viscous flow (Moresi and Solomatov, 1995; Zhong, 2006). The negative thermal buoyancy of the slabs drive the flow. No driving velocities are applied to the plates or any of the slabs in the model. The detailed geometries of the Cocos and Nazca slabs are constructed from seismicity and seismic tomography (Protti et al., 1994; Colombo et al., 1997; Gudmundsson and Sambridge, 1998; Rogers et al., 2002; Husen et al., 2003; Syracuse and Abers, 2006; Syracuse et al., 2008; Dzierma et al., 2011). Seismic tomography

  4. Nanoparticle interfacial assembly in liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Rahimi, Mohammad; Roberts, Tyler; Armas-Perez, Julio; Wang, Xiaoguang; Bukusoglu, Emre; Abbott, Nicholas L.; de Pablo, Juan J.

    2015-03-01

    Controlled assembly of nanoparticles at liquid crystal interfaces could lead to easily manufacturable building blocks for assembly of materials with tunable mechanical, optical, and electronic properties. Past work has examined nanoparticle assembly at planar liquid crystal interfaces. In this work we show that nanoparticle assembly on curved interfaces is drastically different, and arises for conditions under which assembly is too weak to occur on planar interfaces. We also demonstrate that LC-mediated nanoparticle interactions are strong, are remarkably sensitive to surface anchoring, and lead to hexagonal arrangements that do not arise in bulk systems. All these elements form the basis for a highly tunable, predictable, and versatile platform for hierarchical materials assembly. National Science Foundation through the UW MRSEC.

  5. Surface expression of Eastern Mediterranean slab dynamics: Uplift at the SW margin of the Central Anatolian Plateau

    NASA Astrophysics Data System (ADS)

    Schildgen, T. F.; Cosentino, D.; Caruso, A.; Yildirim, C.; Echtler, H.; Strecker, M. R.

    2011-12-01

    that these phenomena may have been linked with a change in the tectonic stress field associated with the process(es) causing post-7 Ma surface uplift. The complex geometry of lithospheric slabs beneath the southern plateau margin, early Pliocene to recent alkaline volcanism, and the localized uplift pattern with accompanying tensional/transtensional stresses point toward slab tearing and localized heating at the base of the lithosphere as a probable mechanism for post-7 Ma uplift of the SW margin. Considering previous work in the region, slab break-off is more likely responsible for non-contractional uplift along the S and SE margins. Overall there appears to be an important link between slab dynamics and surface uplift across the whole southern margin of the Central Anatolian plateau.

  6. Across-arc variation of Magma Composition in Central Sunda Arc, Indonesia: A test of slab influence to mantle source

    NASA Astrophysics Data System (ADS)

    Wibowo, H.; Hasenaka, T.; Handini, E.; Harijoko, A.

    2011-12-01

    Sunda arc, a part of Pacific ring of fire, extends from West Java to Flores. The arc developed since Tertiary period at a convergent tectonic plate margin, where India-Australian plate is subducted northward beneath Eurasian plate. Central Sunda Arc (CSA) is represented by a series of Quartenary volcanoes from the fore arc toward the back arc including Merapi, Merbabu, Telomoyo, Ungaran and Muria. Estimated depth of Wadati-Benioff zone beneath CSA ranges from 190 km for Merapi to 350 km for Muria. Field works have been conducted for brief geologic observation and rock sample collection from Merbabu, Telomoyo, Muria, including Genuk on the north and Patiayam on the south of Muria. Data from Merapi is compiled from previous studies. X-Ray Fluorescence, Prompt Gamma Ray and Instrumental Neutron Activation Analyses were used to obtain whole rock compositions. Previously reported trace element of Altered Oceanic Crust (AOC) and Indian Ocean sediment are employed to estimate the derived fluid composition, by considering mobility of the elements and assuming 1.5% weight fraction of hydrous fluid extracted from them. By applying subduction component elements, we tried to estimate the slab influence to mantle source in magma genesis of CSA. High Al2O3 (~18 wt%), low Cr (~29 ppm) and Ni (~27 ppm) of the volcanic rocks characterize CSA. K2O content increases gradually with the depth of Benioff zone from each volcano. Most samples from Merapi, Merbabu, Telomoyo and Ungaran are classified as subalkaline, whereas Muria samples fall on both alkaline and subalkaline fields. In detail, Merapi samples could be divided into medium-K and high-K, Merbabu medium-K, Telomoyo and Ungaran high-K, and Muria samples range from high-K to shosonitic. We only selected unfractionated lavas to avoid assimilation, including basalt, basaltic andesite, basanite, and trachy basaltic andesite. We also exclude samples with hornblende, micas, and K-feldspar to avoid boron fractionation and assimilation

  7. Identifying wrong assemblies in de novo short read primary sequence assembly contigs.

    PubMed

    Chawla, Vandna; Kumar, Rajnish; Shankar, Ravi

    2016-09-01

    With the advent of short-reads-based genome sequencing approaches, large number of organisms are being sequenced all over the world. Most of these assemblies are done using some de novo short read assemblers and other related approaches. However, the contigs produced this way are prone to wrong assembly. So far, there is a conspicuous dearth of reliable tools to identify mis-assembled contigs. Mis-assemblies could result from incorrectly deleted or wrongly arranged genomic sequences. In the present work various factors related to sequence, sequencing and assembling have been assessed for their role in causing mis-assembly by using different genome sequencing data. Finally, some mis-assembly detecting tools have been evaluated for their ability to detect the wrongly assembled primary contigs, suggesting a lot of scope for improvement in this area. The present work also proposes a simple unsupervised learning-based novel approach to identify mis-assemblies in the contigs which was found performing reasonably well when compared to the already existing tools to report mis-assembled contigs. It was observed that the proposed methodology may work as a complementary system to the existing tools to enhance their accuracy. PMID:27581937

  8. Assembly auxiliary system for narrow cabins of spacecraft

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Li, Shiqi; Wang, Junfeng

    2015-09-01

    Due to the narrow space and complex structure of spacecraft cabin, the existing asssembly systems can not well suit for the assembly process of cabin products. This paper aims to introduce an assembly auxiliary system for cabin products. A hierarchical-classification method is proposed to re-adjust the initial assembly relationship of cabin into a new hierarchical structure for efficient assembly planning. An improved ant colony algorithm based on three assembly principles is established for searching a optimizational assembly sequence of cabin parts. A mixed reality assembly environment is constructed with enhanced information to promote interaction efficiency of assembly training and guidance. Based on the machine vision technology, the inspection of left redundant objects and measurement of parts distance in inner cabin are efficiently performed. The proposed system has been applied to the assembly work of a spacecraft cabin with 107 parts, which includes cabin assembly planning, assembly training and assembly quality inspection. The application result indicates that the proposed system can be an effective assistant tool to cabin assembly works and provide an intuitive and real assembly experience for workers. This paper presents an assembly auxiliary system for spacecraft cabin products, which can provide technical support to the spacecraft cabin assembly industry.

  9. Slab melting as a barrier to deep carbon subduction.

    PubMed

    Thomson, Andrew R; Walter, Michael J; Kohn, Simon C; Brooker, Richard A

    2016-01-01

    Interactions between crustal and mantle reservoirs dominate the surface inventory of volatile elements over geological time, moderating atmospheric composition and maintaining a life-supporting planet. While volcanoes expel volatile components into surface reservoirs, subduction of oceanic crust is responsible for replenishment of mantle reservoirs. Many natural, 'superdeep' diamonds originating in the deep upper mantle and transition zone host mineral inclusions, indicating an affinity to subducted oceanic crust. Here we show that the majority of slab geotherms will intersect a deep depression along the melting curve of carbonated oceanic crust at depths of approximately 300 to 700 kilometres, creating a barrier to direct carbonate recycling into the deep mantle. Low-degree partial melts are alkaline carbonatites that are highly reactive with reduced ambient mantle, producing diamond. Many inclusions in superdeep diamonds are best explained by carbonate melt-peridotite reaction. A deep carbon barrier may dominate the recycling of carbon in the mantle and contribute to chemical and isotopic heterogeneity of the mantle reservoir. PMID:26738593

  10. Maximizing Photoluminescence Extraction in Silicon Photonic Crystal Slabs

    NASA Astrophysics Data System (ADS)

    Mahdavi, Ali; Sarau, George; Xavier, Jolly; Paraïso, Taofiq K.; Christiansen, Silke; Vollmer, Frank

    2016-04-01

    Photonic crystal modes can be tailored for increasing light matter interactions and light extraction efficiencies. These PhC properties have been explored for improving the device performance of LEDs, solar cells and precision biosensors. Tuning the extended band structure of 2D PhC provides a means for increasing light extraction throughout a planar device. This requires careful design and fabrication of PhC with a desirable mode structure overlapping with the spectral region of emission. We show a method for predicting and maximizing light extraction from 2D photonic crystal slabs, exemplified by maximizing silicon photoluminescence (PL). Systematically varying the lattice constant and filling factor, we predict the increases in PL intensity from band structure calculations and confirm predictions in micro-PL experiments. With the near optimal design parameters of PhC, we demonstrate more than 500-fold increase in PL intensity, measured near band edge of silicon at room temperature, an enhancement by an order of magnitude more than what has been reported.

  11. Maximizing Photoluminescence Extraction in Silicon Photonic Crystal Slabs

    PubMed Central

    Mahdavi, Ali; Sarau, George; Xavier, Jolly; Paraïso, Taofiq K.; Christiansen, Silke; Vollmer, Frank

    2016-01-01

    Photonic crystal modes can be tailored for increasing light matter interactions and light extraction efficiencies. These PhC properties have been explored for improving the device performance of LEDs, solar cells and precision biosensors. Tuning the extended band structure of 2D PhC provides a means for increasing light extraction throughout a planar device. This requires careful design and fabrication of PhC with a desirable mode structure overlapping with the spectral region of emission. We show a method for predicting and maximizing light extraction from 2D photonic crystal slabs, exemplified by maximizing silicon photoluminescence (PL). Systematically varying the lattice constant and filling factor, we predict the increases in PL intensity from band structure calculations and confirm predictions in micro-PL experiments. With the near optimal design parameters of PhC, we demonstrate more than 500-fold increase in PL intensity, measured near band edge of silicon at room temperature, an enhancement by an order of magnitude more than what has been reported. PMID:27113674

  12. Treacherous Pavements: Paving Slab Patterns Modify Intended Walking Directions.

    PubMed

    Leonards, Ute; Fennell, John G; Oliva, Gaby; Drake, Alex; Redmill, David W

    2015-01-01

    Current understanding in locomotion research is that, for humans, navigating natural environments relies heavily on visual input; in contrast, walking on even ground in man-made obstacle and hazard-free environments is so highly automated that visual information derived from floor patterns should not affect locomotion and in particular have no impact on the direction of travel. The vision literature on motion perception would suggest otherwise; specifically that oblique floor patterns may induce substantial veering away from the intended direction of travel due to the so-called aperture problem. Here, we tested these contrasting predictions by letting participants walk over commonly encountered floor patterns (paving slabs) and investigating participants' ability to walk "straight ahead" for different pattern orientations. We show that, depending on pattern orientation, participants veered considerably over the measured travel distance (up to 8% across trials), in line with predictions derived from the literature on motion perception. We argue that these findings are important to the study of locomotion, and, if also observed in real world environments, might have implications for architectural design.

  13. Maximizing Photoluminescence Extraction in Silicon Photonic Crystal Slabs.

    PubMed

    Mahdavi, Ali; Sarau, George; Xavier, Jolly; Paraïso, Taofiq K; Christiansen, Silke; Vollmer, Frank

    2016-01-01

    Photonic crystal modes can be tailored for increasing light matter interactions and light extraction efficiencies. These PhC properties have been explored for improving the device performance of LEDs, solar cells and precision biosensors. Tuning the extended band structure of 2D PhC provides a means for increasing light extraction throughout a planar device. This requires careful design and fabrication of PhC with a desirable mode structure overlapping with the spectral region of emission. We show a method for predicting and maximizing light extraction from 2D photonic crystal slabs, exemplified by maximizing silicon photoluminescence (PL). Systematically varying the lattice constant and filling factor, we predict the increases in PL intensity from band structure calculations and confirm predictions in micro-PL experiments. With the near optimal design parameters of PhC, we demonstrate more than 500-fold increase in PL intensity, measured near band edge of silicon at room temperature, an enhancement by an order of magnitude more than what has been reported. PMID:27113674

  14. Slab melting as a barrier to deep carbon subduction

    NASA Astrophysics Data System (ADS)

    Thomson, Andrew R.; Walter, Michael J.; Kohn, Simon C.; Brooker, Richard A.

    2016-01-01

    Interactions between crustal and mantle reservoirs dominate the surface inventory of volatile elements over geological time, moderating atmospheric composition and maintaining a life-supporting planet. While volcanoes expel volatile components into surface reservoirs, subduction of oceanic crust is responsible for replenishment of mantle reservoirs. Many natural, ‘superdeep’ diamonds originating in the deep upper mantle and transition zone host mineral inclusions, indicating an affinity to subducted oceanic crust. Here we show that the majority of slab geotherms will intersect a deep depression along the melting curve of carbonated oceanic crust at depths of approximately 300 to 700 kilometres, creating a barrier to direct carbonate recycling into the deep mantle. Low-degree partial melts are alkaline carbonatites that are highly reactive with reduced ambient mantle, producing diamond. Many inclusions in superdeep diamonds are best explained by carbonate melt-peridotite reaction. A deep carbon barrier may dominate the recycling of carbon in the mantle and contribute to chemical and isotopic heterogeneity of the mantle reservoir.

  15. Slab melting as a barrier to deep carbon subduction.

    PubMed

    Thomson, Andrew R; Walter, Michael J; Kohn, Simon C; Brooker, Richard A

    2016-01-01

    Interactions between crustal and mantle reservoirs dominate the surface inventory of volatile elements over geological time, moderating atmospheric composition and maintaining a life-supporting planet. While volcanoes expel volatile components into surface reservoirs, subduction of oceanic crust is responsible for replenishment of mantle reservoirs. Many natural, 'superdeep' diamonds originating in the deep upper mantle and transition zone host mineral inclusions, indicating an affinity to subducted oceanic crust. Here we show that the majority of slab geotherms will intersect a deep depression along the melting curve of carbonated oceanic crust at depths of approximately 300 to 700 kilometres, creating a barrier to direct carbonate recycling into the deep mantle. Low-degree partial melts are alkaline carbonatites that are highly reactive with reduced ambient mantle, producing diamond. Many inclusions in superdeep diamonds are best explained by carbonate melt-peridotite reaction. A deep carbon barrier may dominate the recycling of carbon in the mantle and contribute to chemical and isotopic heterogeneity of the mantle reservoir.

  16. Metamaterial slab-based super-absorbers and perfect nanodetectors for single dipole sources.

    PubMed

    Guo, Guang-Yu; Klimov, Vasily; Sun, Shulin; Zheng, Wei-Jin

    2013-05-01

    We propose to use double negative (DNG) metamaterial slabs to build effective super-absorbers and perfect nanodetectors for single divergent sources. We demonstrate by numerical simulations that an absorbing nanoparticle properly placed inside a DNG slab back-covered with a perfect electric conductor or perfect magnetic conductor mirror can absorb up to 100% radiation energy of a single dipole source placed outside the slab. Furthermore, we also show that even the simple DNG slab without any absorbing nanoparticle could be used as a perfect absorber for both plane and divergent beams. The proposed systems may focus the radiation in nanoscale and thus have applications in optical nanodevices for a variety of different purposes. PMID:23669990

  17. Oblique incidence of semi-guided waves on rectangular slab waveguide discontinuities: A vectorial QUEP solver

    NASA Astrophysics Data System (ADS)

    Hammer, Manfred

    2015-03-01

    The incidence of thin-film-guided, in-plane unguided waves at oblique angles on straight discontinuities of dielectric slab waveguides, an early problem of integrated optics, is being re-considered. The 3-D frequency domain Maxwell equations reduce to a parametrized inhomogeneous vectorial problem on a 2-D computational domain, with transparent-influx boundary conditions. We propose a rigorous vectorial solver based on simultaneous expansions into polarized local slab eigenmodes along the two orthogonal cross section coordinates (quadridirectional eigenmode propagation QUEP). The quasi-analytical scheme is applicable to configurations with - in principle - arbitrary cross section geometries. Examples for a high-contrast facet of an asymmetric slab waveguide, for the lateral excitation of a channel waveguide, and for a step discontinuity between slab waveguides of different thicknesses are discussed.

  18. Effects of triggering mechanism on snow avalanche slope angles and slab depths from field data

    NASA Astrophysics Data System (ADS)

    McClung, David M.

    2013-04-01

    Field data from snow avalanche fracture lines for slope angle and slab depth (measured perpendicular to the weak layer) were analyzed for different triggering mechanisms. For slope angle, the results showed that the same probability density function (pdf) (of log-logistic type) and range (25 - 55 degrees) apply independent of triggering mechanism. For slab depth, the same pdf (generalized extreme value) applies independent of triggering mechanism. For both slope angle and slab depth, the data skewness differentiated between triggering mechanism and increased with applied triggering load. For slope angle, skewness is lowest for natural triggering by snow loads and highest for triggering from human intervention. For slab depth, the skewness is lowest for natural triggering and highest for a mix of triggers including explosive control with skier triggering being intermediate. The results reveal the effects of triggering mechanism which are important for risk analyses and to guide avalanche forecasting.

  19. Quasi-phase matching of high-order harmonics in modulated slab waveguide

    NASA Astrophysics Data System (ADS)

    Gu, Peng; Liu, Shi-Bing; Song, Hai-Ying

    2016-11-01

    A femtosecond Ti:sapphire laser is focused into a modulated He-filled slab waveguide to generate high-order harmonics. The modulated slab waveguide is used to periodically vary the intensity of the laser pulse along the direction of propagation in order to implement quasi-phase matching of the high-order harmonics. Experimental results show that compared with the spectra emitted from an unmodulated slab waveguide, there is an obvious increase in the yield of high harmonics at wavelengths close to the cutoff region. This finding is in agreement with theory and calculations reported in previous research. Therefore, our experiment indicates that, as with the modulated hollow-core waveguide, a slab waveguide can also achieve quasi-phase matched high-order harmonics.

  20. Reasonable Temperature Schedules for Cold or Hot Charging of Continuously Cast Steel Slabs

    NASA Astrophysics Data System (ADS)

    Li, Yang; Chen, Xin; Liu, Ke; Wang, Jing; Wen, Jin; Zhang, Jiaquan

    2013-12-01

    Some continuously cast steel slabs are sensitive to transverse fracture problems during transportation or handling away from their storage state, while some steel slabs are sensitive to surface transverse cracks during the following rolling process in a certain hot charging temperature range. It is revealed that the investigated steel slabs with high fracture tendency under room cooling condition always contain pearlite transformation delayed elements, which lead to the internal brittle bainitic structure formation, while some microalloyed steels exhibit high surface crack susceptibility to hot charging temperatures due to carbonitride precipitation. According to the calculated internal cooling rates and CCT diagrams, the slabs with high fracture tendency during cold charging should be slowly cooled after cutting to length from hot strand or charged to the reheating furnace directly above their bainite formation temperatures. Based on a thermodynamic calculation for carbonitride precipitation in austenite, the sensitive hot charging temperature range of related steels was revealed for the determination of reasonable temperature schedules.

  1. Goos-Haenchen shifts of the reflected waves from a cold, inhomogeneous, and magnetized plasma slab

    SciTech Connect

    Xu Guoding; Zang Taocheng; Pan Tao

    2010-01-15

    We discuss theoretically the Goos-Haenchen (GH) shifts of the reflected waves from a cold, inhomogeneous, and magnetized plasma slab by using the invariant imbedding approach. Aiming at the linear and parabolic electron-density profiles, we demonstrate numerically the dependences of the co- and cross-polarized GH shifts on the angle of incidence, external static magnetic field, and the thickness of the plasma slab. The results show that the different electron-density profiles of plasma can result in the very different dependences of the GH shifts on the angle of incidence, external magnetic field, and the slab's thickness; the GH shifts can be switched between the considerably large positive and negative values under certain conditions. Particularly, without altering the structure of the plasma slab, the GH shifts can be manipulated by modifying the angle of incident or the external static magnetic field.

  2. Evidence for slab material under Greenland and links to Cretaceous High Arctic magmatism

    NASA Astrophysics Data System (ADS)

    Shephard, G. E.; Trønnes, R. G.; Spakman, W.; Panet, I.; Gaina, C.

    2016-04-01

    Understanding the evolution of extinct ocean basins through time and space demands the integration of surface kinematics and mantle dynamics. We explore the existence, origin, and implications of a proposed oceanic slab burial ground under Greenland through a comparison of seismic tomography, slab sinking rates, regional plate reconstructions, and satellite-derived gravity gradients. Our preferred interpretation stipulates that anomalous, fast seismic velocities at 1000-1600 km depth imaged in independent global tomographic models, coupled with gravity gradient perturbations, represent paleo-Arctic oceanic slabs that subducted in the Mesozoic. We suggest a novel connection between slab-related arc mantle and geochemical signatures in some of the tholeiitic and mildly alkaline magmas of the Cretaceous High Arctic Large Igneous Province in the Sverdrup Basin. However, continental crustal contributions are noted in these evolved basaltic rocks. The integration of independent, yet complementary, data sets provides insight into present-day mantle structure, magmatic events, and relict oceans.

  3. Evolution of attached and detached slabs and their associated mantle dynamics

    NASA Technical Reports Server (NTRS)

    Hsui, Albert T.

    1992-01-01

    Over the two years of the NASA grant, this project has produced a significant amount of research results related to the plate subduction process and the surface crustal deformation at convergent boundaries (i.e., above subduction zones). While some research objectives are completely accomplished, other research tasks remain active and continue to be investigated at present. A steady state analytic thermal model for subducting slabs was used to examine the torques acting on a descending slab. It is found that gravitational torque vanishes when a slab is dipping either vertically or horizontally, unlike previous studies indicating that the magnitude of gravitational torque decreases as dip angle increases. Subsequently, a new time-dependent, analytic thermal model for a subducting slab was developed. The new model enables us to study transient phenomena associated with plate subduction analytically. On the basis of this model, the nature of slab dip angles was evaluated. Slab dip angles are found to be transient features. As they penetrate into the mantle and increase their lengths, the associated gravitational torque also increases resulting in a downward pulling of the slab to the steeper dip angle. This is especially true once a slab penetrates the olivine-spinel phase boundary at about 400 km depth. However, if the phase transformation does not follow the equilibrium condition, the gravitational torque may have a different behavior. This problem was investigated. Except for fast descending slabs, non-equilibrium phase transformation can only slow down the transient increase of slab dip angles discussed earlier. Its effect is not sufficiently strong to reverse the downward pulling for most of the slabs. However, when slabs subducting at 10 cm/yr or faster, a sufficient amount of metastable olivine can exist beneath 400 km. Because of its low density compared with the surrounding spinel, an upward buoyancy is produced resulting in an upward bending of the slab and

  4. 29. SPILLWAY BUCKET SLAB: REINFORCEMENT DETAILS NO. 3. Sheet S40, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    29. SPILLWAY BUCKET SLAB: REINFORCEMENT DETAILS NO. 3. Sheet S-40, December, 1939. File no. SA 342/49. - Prado Dam, Spillway, Santa Ana River near junction of State Highways 71 & 91, Corona, Riverside County, CA

  5. 28. SPILLWAY BUCKET SLAB: REINFORCEMENT DETAILS NO. 1. Sheet S37, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    28. SPILLWAY BUCKET SLAB: REINFORCEMENT DETAILS NO. 1. Sheet S-37, December, 1939. File no. SA 342/47. - Prado Dam, Spillway, Santa Ana River near junction of State Highways 71 & 91, Corona, Riverside County, CA

  6. 22. SPILLWAY CHANNEL SLAB REINFORCEMENT DETAILS, NO. 1. Sheet S4, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    22. SPILLWAY CHANNEL SLAB REINFORCEMENT DETAILS, NO. 1. Sheet S-4, February, 1939. File no. SA 343/67. - Prado Dam, Spillway, Santa Ana River near junction of State Highways 71 & 91, Corona, Riverside County, CA

  7. 30. SPILLWAY BUCKET SLAB: REINFORCEMENT DETAILS NO. 4. Sheet S44, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    30. SPILLWAY BUCKET SLAB: REINFORCEMENT DETAILS NO. 4. Sheet S-44, December, 1939. File no. SA 342/50. - Prado Dam, Spillway, Santa Ana River near junction of State Highways 71 & 91, Corona, Riverside County, CA

  8. Deformation of the overriding slab during incipient subduction in centrifuge modeling and its tectonic significance

    NASA Astrophysics Data System (ADS)

    Mart, Yossi; Goren, Liran; Koyi, Hemin

    2015-04-01

    Analog models of subduction-related structural deformation emphasize the significance of differences in density and friction between the adjacent plates on the distortion of the overriding slab and its possible effect on the subduction procedure. Centrifuge experiments juxtaposed miniaturized lighter and denser lithospheres, which were floating on denser but less viscous asthenosphere. The lithosphere in the tests comprised brittle and ductile strata, which showed diversified styles of deformation, while factors of equivocal tectonic significance, such as lateral push or negative buoyancy, were not introduced into the experiments. The tests show that the juxtaposition of lighter and denser lithospheres would suffice to drive the denser lithosphere as a wedge between the asthenosphere and the lighter lithosphere, and that the rate of the process would depend on the rate of friction between the slabs, as well as on differential viscosity. It seems that the reduced friction in Nature was derived from the generation of serpentinites, which could be the main agent of lubrication. The underthrusting of the denser lithosphere leads to the uplift and collapse of the edge of the lighter slab, where extension, thinning, normal faulting and rifting took place, and diapiric ascent of parts of the ductile layer of the lighter slab occurred along several rifts. The analog experiments were carried out only to the stage where the denser slab was thrust under the lighter one, but the penetration of the lithosphere into the asthenosphere was not achieved. It seems plausible therefore, that only after eclogitization, and the upward motion of serpentinites, increased the density of the underthrust slab, would it dive and penetrate into the asthenosphere. The experiments indicate the plausibility of the constraints imposed on the subduction process by the deformation of the overthrust slab. The normal faults and rifts in the overthrust block could serve as conduits for the ascent of

  9. Pacific slab beneath northeast China revealed by regional and teleseismic waveform modeling

    NASA Astrophysics Data System (ADS)

    WANG, X.; Chen, Q. F.; Wei, S.

    2015-12-01

    Accurate velocity and geometry of the slab is essential for better understanding of the thermal, chemical structure of the mantle earth, as well as geodynamics. Recent tomography studies show similar morphology of the subducting Pacific slab beneath northeast China, which was stagnant in the mantle transition zone with thickness of more than 200km and an average velocity perturbation of ~1.5% [Fukao and Obayashi, 2013]. Meanwhile, waveform-modeling studies reveal that the Pacific slab beneath Japan and Kuril Island has velocity perturbation up to 5% and thickness up to 90km [Chen et al., 2007; Zhan et al., 2014]. These discrepancies are probably caused by the smoothing and limited data coverage in the tomographic inversions. Here we adopted 1D and 2D waveform modeling methods to study the fine structure of Pacific slab beneath northeast China using dense regional permanent and temporary broadband seismic records. The residual S- and P-wave travel time, difference between data and 1D synthetics, shows significant difference between the eastern and western stations. S-wave travel time residuals indicate 5-10s earlier arrivals for stations whose ray path lies within the slab, compared with those out of the slab. Teleseimic waveforms were used to rule out the major contribution of the possible low velocity structure above 200km. Furthermore, we use 2D finite-difference waveform modeling to confirm the velocity perturbation and geometry of the slab. Our result shows that the velocity perturbation in the slab is significantly higher than those reported in travel-time tomography studies. ReferencesChen, M., J. Tromp, D. Helmberger, and H. Kanamori (2007), Waveform modeling of the slab beneath Japan, J. Geophys. Res.-Solid Earth, 112(B2), 19, doi:10.1029/2006jb004394.Fukao, Y., and M. Obayashi (2013), Subducted slabs stagnant above, penetrating through, and trapped below the 660 km discontinuity, J. Geophys. Res.-Solid Earth, 118(11), 5920-5938, doi:10.1002/2013jb010466

  10. Mantle compositional layering revealed by slab stagnation in the uppermost lower mantle

    NASA Astrophysics Data System (ADS)

    Ballmer, Maxim; Ritsema, Jeroen; Schmerr, Nicholas; Motoki, Matthew

    2015-04-01

    Seismic tomography reveals three different modes of slab sinking behavior. Some slabs segments (1) descend through the upper mantle to stagnate in the transition zone (e.g., Japan slab), others (2) sink into the deep mantle (e.g., Tethys slab), and yet others (3) sink through the upper mantle and transition zone to stagnate at ~1000 km depth (e.g., Peru, Kermadec, Sunda and Nicaragua slabs) [Fukao and Obayashi, 2013]. Whereas stagnation in the transition zone is well explained by the supporting effect of the spinel-to-perovskite phase transition at ~660 km depth ("the 660"), a scenario for equilibrium stagnation in the uppermost lower mantle, where no endothermic phase transitions occur, remains to be proposed. Here, we explore slab sinking behavior using two-dimensional numerical models. We show that slabs stagnate at 900~1000 km depth if the lower mantle be intrinsically dense, for example due to enrichment in Si and/or Fe relative to Mg. A gradual and moderate compositional contrast across the 660 in a heterogeneous mantle is (at least locally) able to provide sufficient support for long-term slab stagnation. While such a contrast is expected to result from early-Earth processes (e.g., differential crystallization of the magma ocean), its maintenance over 4.5 Gyrs of mantle convection and stirring requires ongoing geodynamic mechanism(s) to sustain it. One such mechanism is stagnant slab disintegration, in which a superplastic slab that stagnates above or below the 660 undergoes convective instability to separate into its (enriched) basaltic and (depleted) harzburgitic components. As dense basaltic material and buoyant harzburgite tend to sink and rise, respectively, this mechanism sets up an efficient compositional filter across the transition zone. Thus, the fate of subducted slabs can sustain (disintegration) - as well as provide evidence for (stagnation at ~1000 km depth) - relative enrichment of the lower compared to the upper mantle. Such an enrichment is

  11. Demise of Flat-slab Subduction at the end of the Laramide Orogeny (Invited)

    NASA Astrophysics Data System (ADS)

    Humphreys, E.

    2013-12-01

    Increasingly constrained interpretations for how the Laramide orogeny ended, and how the ignimbrite flareup followed, are derived from recent upper mantle tomograms in conjunction with the volcanic and tectonic record. Tomography is used to identify subducted slab, magmatic re-initiation indicates removal of the Laramide flat slab from the base of North America, and vertical motions are used to infer the evolving sub-crustal density distribution. The general story is not so much one of flat-slab rollback, but rather one of progressive abandonment of large fragments of ocean lithosphere at North America's base and a subsequent foundering of this slab. I infer the following history. Subduction of a large ocean plateau (Shatsky conjugate) occurred beneath southern California, the Colorado Plateau and Wyoming, where it stopped ~75 Ma and where it resides today (below ~150 km of Wyoming craton). Its buoyant lithosphere has elevated Wyoming; its (dense eclogite) crust is absent, probably lost at ~75 Ma when rapid subsidence of Wyoming ended, followed by uplift. The next major event was the ~53 Ma accretion of Farallon ocean lithosphere to the margin of NW U.S. and beneath much of NW U.S. This accretion ended the Laramide orogeny at this latitude, from where it propagated southward. Immediately, thrusting switched to (core complex) extension and magmatic quiescence switched to volcanic flareup (Challis-Absoraka volcanism) as the slab delaminated from North America. This slab is imaged as a vertical curtain extending from the Idaho batholith down into the transition zone. Subduction jumped outboard to create Cascadia, and the Cascade arc soon followed, indicating normal-dip subduction. Flat-slab subduction continued south of central Oregon, necessitating a slab tear across central Oregon. The volcanic flareup propagated south from the tear across the northern Basin and Range, indicating a progressive N-to-S removal of the flat slab, probably by sideways rollback. An

  12. Upper plate absolute motion and slab-anchor force control on back-arc deformation

    NASA Astrophysics Data System (ADS)

    Heuret, A.; Lallemand, S.

    2003-04-01

    In order to test how the combined effects of overriding plate motion and trench migration can account for the variability of back-arc tectonic regimes, their "normal to the trench" absolute motion components and the strain regime of all oceanic subduction zones were compiled. Strain regime was estimated following Jarrard (1986), in a semiquantitative way. The upper plate absolute motion (Vup) is calculated in the hotspot HS3-NUVEL1A (Gripp and Gordon, 2002) reference frame and trench migration (Vt) from Vup, corrected from deformation rate of back-arc region, mainly given by GPS data. As slabs tend to sink because of their age-related-mass-excess relative to the surrounding mantle, it is generally assumed that most of the trenches have a spontaneous seaward motion (trench rollback). Ages at trench have thus also been compiled ( from Muller et al, 1997) to test a possible control of trench migration with slab age. Our values underline a high control of strain regime by Vup, but inconsistencies still remain with this single parameter. To account for all the observed deformations, trench migration is needed. There are more or less as much subduction zones with seaward Vt as landward ones, and, for 90% of subduction zones, Vt never reach 50 mm/y in the two directions. The expected relation between trench migration and slab age is far to be verified: landward trench migrations exist in many subduction zones, and, among them, many have old slabs. Several examples indicate that the slab tend to follow the trench migration and, so, to move transversely in the surrounding mantle. As a consequence, Vt is close to the "normal to the trench" slab migration and gives informations about the slab anchor force : slabs are not perfectly anchored but their possible motions appear to be limited. This 50 mm/y limitation of slab migration may provide new constraints on the poorly known slab-anchor force. No evidence of age related trench rollback have beeen found. It does not

  13. Present-day stress field on the South American slab underneath the Sandwich Plate (Southern Atlantic Ocean)

    NASA Astrophysics Data System (ADS)

    Giner-Robles, J. L.; Pérez-López, R.; Álvarez-Gómez, J. A.; Martínez-Díaz, J. J.; Rodríguez-Pascua, M. A.

    2009-04-01

    This work confirms the present-day principal stress orientation on the South Sandwich Plate (SSP) from the analysis of 331 earthquake focal mechanisms (Harvard catalog, HCMT). Principal stress orientation was deduced from earthquake focal mechanisms, examined by fault population analysis methods. The SSP plate is composed by oceanic crust limits an elliptical trench to the east (South Sandwich Trench), a ridge to the west and transforms faults towards the northern and southern boundaries. Within the trench region, the maximum horizontal shortening direction (SHMAX) rotates in trend in a clockwise direction, from NNE, in the northern boundary, to SSE in the southern boundary. Therefore, and keeping in mind the gradual rotation of SHMAX along the trench, three different areas were defined according to the prevailing focal mechanism type: (1) the North Zone, with SHMAX oriented N060°E and reverse and strike-slip focal mechanisms; (2) the Central Zone, with only reverse focal mechanism and SHMAX striking N080°E; (3) the South Zone, with SHMAX oriented N110°E and reverse and strike-slip focal geometry. Furthermore, the accommodation of the strain field in the Northern Zone of the South Sandwich Plate generates a subduction decoupling of the slab at, approximately, 70 km depth. In contrast, the South Zone slab exhibits a gradual stress and strain magnitude decreasing in depth. Finally, we define a sinistral strike-slip parallel to the southern boundary between the South Sandwich Plate and the Antarctic Plate, the South Sandwich Fault Zone.

  14. Characterizing Seismic Anisotropy across the Peruvian Flat-Slab Subduction Zone: Shear Wave Splitting from PULSE

    NASA Astrophysics Data System (ADS)

    Eakin, C. M.; Long, M. D.; Beck, S. L.; Wagner, L. S.; Tavera, H.

    2013-12-01

    Although 10% of subduction zones worldwide today exhibit shallow or flat subduction, we are yet to fully understand how and why these slabs go flat. An excellent study location for such a problem is in Peru, where the largest region of flat-subduction currently exists, extending ~1500 km in length (from 3 °S to 15 °S) and ~300 km in width. Across this region we investigate the pattern of seismic anisotropy, an indicator for past and/or ongoing deformation in the upper mantle. To achieve this we conduct shear wave splitting analyzes at 40 broadband stations from the PULSE project (PerU Lithosphere and Slab Experiment). These stations were deployed for 2+ years across the southern half of the Peruvian flat-slab region. We present detailed shear wave splitting results for deep and teleseismic events, making use of a wide variety of available phases that sample the upper mantle directly beneath the stations (such as SKS, SKKS, PKS, sSKS, SKiKS, ScS and local/direct S). We analyze the variability of our results with respect to initial polarizations and ray paths, as well as spatial variability between stations as the underlying slab morphology changes. Preliminary results show predominately NW-SE fast polarizations (trench oblique to sub-parallel) over the flat-slab region east of Lima. These results are consistent with observations of more complex multi-layered anisotropy beneath a nearby permanent station (NNA). Further south, towards the transition to steeper subduction, the splitting pattern becomes increasingly dominated by null measurements. Over to the east however, beyond Cuzco, where the mantle wedge might begin to play a role, we record fast polarizations quasi-parallel to the local slab contours. We carefully evaluate the different possible source locations within the subduction zone for this seismic anisotropy and observe increasing evidence for distinct anisotropy within the slab as well as the sub-slab mantle.

  15. Method for fabricating zig-zag slabs for solid state lasers

    NASA Technical Reports Server (NTRS)

    Sridharan, Arun Kumar (Inventor); Saraf, Shailendhar (Inventor); Byer, Robert L. (Inventor)

    2006-01-01

    A method for batch manufacturing of slabs for zig-zag lasers including steps of bonding two non-active media to either side of an active medium to form a sandwich, dicing the sandwich to provide slices, rendering two surfaces of each slice into total-internal-reflection (TIR) surfaces, and then dicing the slices perpendicular to the TIR surfaces to provide a plurality of zig-zag slabs.

  16. Compositional mantle layering revealed by slab stagnation at ~1,000 km depth

    NASA Astrophysics Data System (ADS)

    Ballmer, M. D.; Nakagawa, T.; Schmerr, N. C.; Ritsema, J.; Motoki, M.

    2015-12-01

    Improved constraints on lower-mantle composition are fundamental to understand the accretion, differentiation and thermochemical evolution of our planet. Whereas cosmochemical arguments indicate that lower-mantle rocks may be enriched in Si relative to upper-mantle pyrolite, seismic tomography images suggest whole-mantle convection and efficient mantle mixing. This study reconciles cosmochemical and geophysical constraints using the stagnation of some slab segments at ~1,000 km depth as the key observation. Whereas slab stagnation at ~660 km depth is well explained by the effects of the spinel-perovskite endothermic phase transition, flattening of slabs in the uppermost lower mantle remains poorly understood. Through numerical modeling of subduction, we show that enrichment of the lower mantle in intrinsically dense basaltic heterogeneity can render slabs neutrally buoyant at ~1,000 km depth. Slab stagnation (at ~660 and ~1,000 km depth) as well as unimpeded slab sinking to great depths can only coexist as three different modes of slab sinking behavior on Earth if the basalt fraction is ~8% higher in the lower than in the upper mantle, equivalent to a lower-mantle Mg/Si of ~1.18. Geodynamic models demonstrate that such a moderate compositional gradient can be sustained by compositional filtering of both slabs and plumes as they cross the transition zone, and thus persist over billions of years of whole-mantle convection. Whereas basaltic heterogeneity tends to get trapped in the transition zone and ultimately sink into the lower mantle, harzburgitic heterogeneity tends to rise into the uppermost mantle.

  17. Evidences of a Stalled-slab Beneath the Coast Ranges, California, From Seismicity and Converted Phases

    NASA Astrophysics Data System (ADS)

    Cao, A.; Liu, K. H.; Gao, S. S.

    2001-12-01

    In spite of numerous geophysical studies, the existence and geometry of a stalled slab beneath the Coast Ranges remains vague. In this study we use the distribution of mantle earthquakes and P-to-S converted phases from tilt interfaces to address the problem. Based on the CNSS catalog, in the period between 01/1960 and 04/2001, there were about 450 earthquakes occurred at depth larger than 35 km in the vicinity of the Coast Ranges. When plotted along east-west cross-sections, those earthquakes show a clear slab-like image, similar to the upper part of classic Benioff zones along subducting oceanic slabs. One of such cross-sections, which has a width of 20 km and a latitude of 39N, is located in the so-called 'slabless window' suggested by several previous geologic and geophysic studies, implying the existence of a stalled-slab along the cross-section. The mantle earthquakes can be explained as the result of stress concentration caused by heterogeneities in elastic properties associated with the cold slab, and of changes in mineralogical phases in the upper-most mantle in and around the slab. The existence of the slab is supported by clear azimuthal variations of the amplitude and arrival time of P-to-S converted phases from a tilt interface at about 70 km depth recorded by a broadband seismic station in the area. Our analysis shows that the converted phase is probably from a subducted oceanic lithosphere dipping to the east. The strike of the slab is approximately parallel to the Coast Ranges.

  18. Latching relay switch assembly

    DOEpatents

    Duimstra, Frederick A.

    1991-01-01

    A latching relay switch assembly which includes a coil section and a switch or contact section. The coil section includes at least one permanent magnet and at least one electromagnet. The respective sections are, generally, arranged in separate locations or cavities in the assembly. The switch is latched by a permanent magnet assembly and selectively switched by an overriding electromagnetic assembly.

  19. A theoretical investigation on influences of slab tracks on vertical dynamic responses of railway viaducts

    NASA Astrophysics Data System (ADS)

    Shi, Li; Cai, Yuanqiang; Wang, Peng; Sun, Honglei

    2016-07-01

    A railway viaduct model consisting of infinite spans of elastically-supported girders carrying a slab track of infinite length is established to investigate the influence of the slabs on the vertical dynamic response of the viaduct, when a moving harmonic point load or a moving sprung wheel is applied. The infinite rail, the discontinuous slabs and girders of identical span lengths are idealized as Euler-Bernoulli beams. The rail fasteners, the cushion layer beneath the slab and the elastic bearings at the girder supports are represented by discretely distributed springs of hysteretic damping. Due to the repetitive nature of the girders, the model can be divided into periodic three-beam units by the span length of the girder, and then solved analytically in the frequency domain using the property of periodic structure. Besides the first natural frequency of the girder with elastic bearings, it is found that the resonance frequency of the slab on the cushion layer has a significant influence on the dynamic response of the track and the girder. Parametric excitations due to the moving wheel periodically passing the discontinuous slabs contribute significantly to the wheel/rail interactions.

  20. Seismic evidence for hydration of the Central American slab: Guatemala through Costa Rica

    NASA Astrophysics Data System (ADS)

    Syracuse, E. M.; Thurber, C. H.

    2011-12-01

    The Central American subduction zone exhibits a wide variability in along-arc slab hydration as indicated by geochemical studies. These studies generally show maximum slab contributions to magma beneath Nicaragua and minimum contributions beneath Costa Rica, while intermediate slab fluid contributions are found beneath El Salvador and Guatemala. Geophysical studies suggest strong slab serpentinization and fluid release beneath Nicaragua, and little serpentinization beneath Costa Rica, but the remainder of the subduction zone is poorly characterized seismically. To obtain an integrated seismic model for the Central American subduction zone, we combine 250,000 local seismic arrivals and 1,000,000 differential arrivals for 6,500 shallow and intermediate-depth earthquakes from the International Seismic Centre, the Central American Seismic Center, and the temporary PASSCAL TUCAN array. Using this dataset, we invert for Vp, Vs, and hypocenters using a variable-mesh double-difference tomography algorithm. By observing low-Vp areas within the normally high-Vp slab, we identify portions of the slab that are likely to contain serpentinized mantle, and thus contribute to higher degrees of melting and higher volatile components observable in arc lavas.

  1. Retrieving the characteristics of slab ice covering snow by remote sensing

    NASA Astrophysics Data System (ADS)

    Andrieu, François; Schmidt, Frédéric; Schmitt, Bernard; Douté, Sylvain; Brissaud, Olivier

    2016-09-01

    We present an effort to validate a previously developed radiative transfer model, and an innovative Bayesian inversion method designed to retrieve the properties of slab-ice-covered surfaces. This retrieval method is adapted to satellite data, and is able to provide uncertainties on the results of the inversions. We focused on surfaces composed of a pure slab of water ice covering an optically thick layer of snow in this study. We sought to retrieve the roughness of the ice-air interface, the thickness of the slab layer and the mean grain diameter of the underlying snow. Numerical validations have been conducted on the method, and showed that if the thickness of the slab layer is above 5 mm and the noise on the signal is above 3 %, then it is not possible to invert the grain diameter of the snow. In contrast, the roughness and the thickness of the slab can be determined, even with high levels of noise up to 20 %. Experimental validations have been conducted on spectra collected from laboratory samples of water ice on snow using a spectro-radiogoniometer. The results are in agreement with the numerical validations, and show that a grain diameter can be correctly retrieved for low slab thicknesses, but not for bigger ones, and that the roughness and thickness are correctly inverted in every case.

  2. Imaging properties of dielectric photonic crystal slabs for large object distances.

    PubMed

    Sun, Guilin; Jugessur, Aju S; Kirk, Andrew G

    2006-07-24

    We extend the understanding of the imaging properties of dielectric photonic crystal slabs to object distances that are larger than the slab thickness. We specifically consider hexagonal crystal lattices in the second band. For object distances smaller than the slab thickness, the image distance is a negative linear function of the object distance as expected for negative refractive index materials. The effective refractive index extracted from this linear object-image relation is close to the negative unity value calculated for infinite photonic crystal using the plane wave expansion method. In contrast to previous predictions, we find that a real image can still be formed for object distances up to twice the slab thickness. In this regime the image distance changes little as the object distance increases, and can thus be described as the saturated image regime. Sub-wavelength resolution performance can be approximately maintained even for these larger object distances. The full-width half-maximum spot size at the image is approximately (0.43-0.55)lambda up to object distances 1.5 times the slab thickness. By evaluating the image angular frequency spectrum we show that this sub-wavelength resolution imaging at larger object distances is due to evanescent waves that arise within the slab, rather than being directly transferred from the object. The eventual loss of image resolution is due to interference side lobes which enter the image plane.

  3. Mechanical Consequences of Metamorphism and Their Effects on In-slab Earthquakes

    NASA Astrophysics Data System (ADS)

    Wang, K.; Kao, H.; Cassidy, J. F.; Wada, I.

    2004-05-01

    The relatively few earthquakes deeper inside a subducting slab tend to have larger magnitudes than those just below the slab surface. For example, three recent damaging events (1999 Oaxaca, Mexico; 2001 Geiyo, Nankai; 2001 Nisqually, Cascadia) in warm slabs all occurred in the lower crust or mantle. We propose that this is controlled by slab metamorphic processes. The metabasalt-eclogite transformation of the subducting oceanic crust causes up to 15% volume reduction. Because of temperature and kinetics, the densification begins in a thin layer along the top of the slab. Volume reduction gives rise to an equivalent stretching force in the thin layer in all slab-parallel directions, activating existing faults and developing new fractures. The theory of fracture spacing predicts that the densified thin layer must be "shattered". The shattered upper crust may have numerous small earthquakes but does not favor large ruptures. In contrast, the much more uniform lower crust and mantle can host larger ruptures, although seismic ruptures may occur only in limited hydrated parts. Earthquakes that rupture the subducting mantle, such as the M 6.8 2001 Nisqually earthquake at Cascadia, appear to require serpentine dehydration along pre-existing deep faults.

  4. Seismicity and state of stress in the central and southern Peruvian flat slab

    NASA Astrophysics Data System (ADS)

    Kumar, Abhash; Wagner, Lara S.; Beck, Susan L.; Long, Maureen D.; Zandt, George; Young, Bissett; Tavera, Hernando; Minaya, Estella

    2016-05-01

    We have determined the Wadati-Benioff Zone seismicity and state of stress of the subducting Nazca slab beneath central and southern Peru using data from three recently deployed local seismic networks. Our relocated hypocenters are consistent with a flat slab geometry that is shallowest near the Nazca Ridge, and changes from steep to normal without tearing to the south. These locations also indicate numerous abrupt along-strike changes in seismicity, most notably an absence of seismicity along the projected location of subducting Nazca Ridge. This stands in stark contrast to the very high seismicity observed along the Juan Fernandez ridge beneath central Chile where, a similar flat slab geometry is observed. We interpret this as indicative of an absence of water in the mantle beneath the overthickened crust of the Nazca Ridge. This may provide important new constraints on the conditions required to produce intermediate depth seismicity. Our focal mechanisms and stress tensor inversions indicate dominantly down-dip extension, consistent with slab pull, with minor variations that are likely due to the variable slab geometry and stress from adjacent regions. We observe significantly greater variability in the P-axis orientations and maximum compressive stress directions. The along strike change in the orientation of maximum compressive stress is likely related to slab bending and unbending south of the Nazca Ridge.

  5. Modified creep and shrinkage prediction model B3 for serviceability limit state analysis of composite slabs

    NASA Astrophysics Data System (ADS)

    Gholamhoseini, Alireza

    2016-03-01

    Relatively little research has been reported on the time-dependent in-service behavior of composite concrete slabs with profiled steel decking as permanent formwork and little guidance is available for calculating long-term deflections. The drying shrinkage profile through the thickness of a composite slab is greatly affected by the impermeable steel deck at the slab soffit, and this has only recently been quantified. This paper presents the results of long-term laboratory tests on composite slabs subjected to both drying shrinkage and sustained loads. Based on laboratory measurements, a design model for the shrinkage strain profile through the thickness of a slab is proposed. The design model is based on some modifications to an existing creep and shrinkage prediction model B3. In addition, an analytical model is developed to calculate the time-dependent deflection of composite slabs taking into account the time-dependent effects of creep and shrinkage. The calculated deflections are shown to be in good agreement with the experimental measurements.

  6. Motion of a distant solid particle in a shear flow along a porous slab

    NASA Astrophysics Data System (ADS)

    Khabthani, S.; Sellier, A.; Feuillebois, F.

    2013-12-01

    The motion of a solid and no-slipping particle immersed in a shear flow along a sufficiently porous slab is investigated. The fluid flow outside and inside of the slab is governed by the Stokes and Darcy equations, respectively, and the so-called Beavers and Joseph slip boundary conditions are enforced on the slab surface. The problem is solved for a distant particle with length scale a in terms of the small parameter a/ d where d designates the large particle-slab separation. This is achieved by asymptotically inverting a relevant boundary-integral equation on the particle surface, which has been recently proposed for any particle location (distant or close particle) in Khabthani et al. (J Fluid Mech 713:271-306, 2012). It is found that at order O( a/ d) the slab behaves for any particle shape as a solid plane no-slip wall while the slab properties (thickness, permeability, associated slip length) solely enter at O(( a/ d)2). Moreover, for a spherical particle, the numerical results published in Khabthani et al. (J Fluid Mech 713:271-306, 2012) perfectly agree with the present asymptotic analysis.

  7. Diverse magmatic effects of subducting a hot slab in SW Japan: Results from forward modeling

    NASA Astrophysics Data System (ADS)

    Kimura, Jun-Ichi; Gill, James B.; Kunikiyo, Tomoyuki; Osaka, Isaku; Shimoshioiri, Yusuke; Katakuse, Maiko; Kakubuchi, Susumu; Nagao, Takashi; Furuyama, Katsuhiko; Kamei, Atsushi; Kawabata, Hiroshi; Nakajima, Junichi; van Keken, Peter E.; Stern, Robert J.

    2014-03-01

    response to the subduction of the young Shikoku Basin of the Philippine Sea Plate, arc magmas erupted in SW Japan throughout the late Cenozoic. Many magma types are present including ocean island basalt (OIB), shoshonite (SHO), arc-type alkali basalt (AB), typical subalkalic arc basalt (SAB), high-Mg andesite (HMA), and adakite (ADK). OIB erupted since the Japan Sea back-arc basin opened, whereas subsequent arc magmas accompanied subduction of the Shikoku Basin. However, there the origin of the magmas in relation to hot subduction is debated. Using new major and trace element and Sr-Nd-Pb-Hf isotope analyses of 324 lava samples from seven Quaternary volcanoes, we investigated the genetic conditions of the magma suites using a geochemical mass balance model, Arc Basalt Simulator version 4 (ABS4), that uses these data to solve for the parameters such as pressure/temperature of slab dehydration/melting and slab flux fraction, pressure, and temperature of mantle melting. The calculations suggest that those magmas originated from slab melts that induced flux melting of mantle peridotite. The suites differ mostly in the mass fraction of slab-melt flux, increasing from SHO through AB, SAB, HMA, to ADK. The pressure and temperature of mantle melting decreases in the same order. The suites differ secondarily in the ratio of altered oceanic crust to sediment in the source of the slab melt. The atypical suites associated with hot subduction result from unusually large mass fractions of slab melt and unusually cool mantle temperatures.

  8. The Assembly, Integration, and Verification (AIV) team

    NASA Astrophysics Data System (ADS)

    2009-06-01

    Assembly, Integration, and Verification (AIV) is the process by which the software and hardware deliveries from the distributed ALMA partners (North America, South America, Europe, and East Asia) are assembled and integrated into a working system, and the initial technical capabilities tested to insure that they will meet the observatories exacting requirements for science.

  9. Slab rollback orogeny in the Alps inferred from the stratigraphic evolution of the Swiss Molasse basin

    NASA Astrophysics Data System (ADS)

    Schlunegger, Fritz; Kissling, Edi

    2016-04-01

    The stratigraphic development of foreland basins have been related to orogenic processes, where continent- continent collision resulted in the construction of topography and the downwarping of the foreland plate. These mechanisms have been used to explain the Oligocene to Miocene evolution of the Molasse basin, situated on the northern side of the European Alps. Continuous flexural bending of the subducting European lithosphere as a consequence of topographic loads alone would imply that the Alpine topography would have increased at least between 30 Ma and ca. 5-10 Ma when the basin accumulated the erosional detritus. This, however, is neither consistent with observations nor with isostatic mass balancing models. In particular, the use of empirical relationships between the spacing of alluvial megafans, orogen width and morphometric properties of stream channels feeding the fans imply a general trend towards an increasing total fluvial relief until 1,900±1,000 m at ca. 20 Ma, followed by a prolonged period of time during which this variable has remained nearly constant. Accordingly, larger topographic loads cannot be invoked to explain the continuous deflection of the foreland plate. Alternatively, a scenario where horizontal forces cause a downward dragging of the foreland plate would offer a valuable explanation for the decoupling between basin depth and topographic loads. However, such a scenario would be associated with the occurrence of compressional forces within the foreland plate, which is not in agreement with observations in the Molasse Basin, at least for the present, where focal mechanisms of current seismic events imply the occurrence of extensional forces at work. We suggest that rollback orogeny, driven by the gravitational pull of the European slab, provides a mechanism to explain the increasing deflection of the foreland in the absence of larger topographic forcing, and it agrees with the geologic record that the subducting European plate did not

  10. Seismological Features of the Subducting Slab Beneath the Kii Peninsula, Central Japan, Revealed by Receiver Functions

    NASA Astrophysics Data System (ADS)

    Shiomi, K.; Park, J.

    2007-12-01

    We report seismological evidence that the subducting Philippine Sea slab (PHS) beneath the Kii Peninsula, central Japan, can be divided into three segments. Offshore the Kii Peninsula, the "Tonankai" and "Nankai" fault segments suffer mega-thrust earthquakes that repeat every 100 to 150 years. The structure of the young, thin, contorted PHS is important to the seismo-tectonics in this region. We apply the receiver function (RF) analysis to 26 Hi-net short-period and 4 F-net broad-band seismographic stations. In the case that dipping velocity discontinuities and/or anisotropic media exist beneath seismometer, both radial RFs and transverse RFs contain useful information to estimate underground structure. For isotropic media with a dipping-slab interface, back- azimuthal variation in RFs depends largely on three parameters, the downdip azimuth, dip angle and the depth of the interface. We stack both radial and transverse RFs with allowance a time-shift caused by the dipping interface, searching for optimal parameters based on the grid-search technique at each station. At some stations located near the eastern coastline of the Kii Peninsula, the dip angle of the interface inferred from RF stacking is much steeper than that estimated by the local seismicity. This discrepancy arises from the interference of two slab-converted phases, suggesting a layer atop the slab. In these cases we refine the stack to distinguish two slab phases and estimate three parameters of each dipping interface separately. Two interfaces with the same dip direction and low dip angle are estimated at these stations, with depth difference near 6 km. Thus, the shallower interface may be related to the layer within the oceanic crust and the deeper one is the slab Moho. These double-layered interfaces are detected only at stations located up-dip of a belt-like distribution of non- volcanic low-frequency tremor. Comparing the interface dips estimated in this study with the direction of slab motion

  11. Inlet nozzle assembly

    DOEpatents

    Christiansen, David W.; Karnesky, Richard A.; Precechtel, Donald R.; Smith, Bob G.; Knight, Ronald C.

    1987-01-01

    An inlet nozzle assembly for directing coolant into the duct tube of a fuel assembly attached thereto. The nozzle assembly includes a shell for housing separable components including an orifice plate assembly, a neutron shield block, a neutron shield plug, and a diffuser block. The orifice plate assembly includes a plurality of stacked plates of differently configurated and sized openings for directing coolant therethrough in a predesigned flow pattern.

  12. Inlet nozzle assembly

    DOEpatents

    Christiansen, D.W.; Karnesky, R.A.; Knight, R.C.; Precechtel, D.R.; Smith, B.G.

    1985-09-09

    An inlet nozzle assembly for directing coolant into the duct tube of a fuel assembly attached thereto. The nozzle assembly includes a shell for housing separable components including an orifice plate assembly, a neutron shield block, a neutron shield plug, and a diffuser block. The orifice plate assembly includes a plurality of stacked plates of differently configurated and sized openings for directing coolant therethrough in a predesigned flow pattern.

  13. Structural assembly in space

    NASA Technical Reports Server (NTRS)

    Stokes, J. W.; Pruett, E. C.

    1980-01-01

    A cost algorithm for predicting assembly costs for large space structures is given. Assembly scenarios are summarized which describe the erection, deployment, and fabrication tasks for five large space structures. The major activities that impact total costs for structure assembly from launch through deployment and assembly to scientific instrument installation and checkout are described. Individual cost elements such as assembly fixtures, handrails, or remote minipulators are also presented.

  14. Tilt assembly for tracking solar collector assembly

    DOEpatents

    Almy, Charles; Peurach, John; Sandler, Reuben

    2012-01-24

    A tilt assembly is used with a solar collector assembly of the type comprising a frame, supporting a solar collector, for movement about a tilt axis by pivoting a drive element between first and second orientations. The tilt assembly comprises a drive element coupler connected to the drive element and a driver, the driver comprising a drive frame, a drive arm and a drive arm driver. The drive arm is mounted to the drive frame for pivotal movement about a drive arm axis. Movement on the drive arm mimics movement of the drive element. Drive element couplers can extend in opposite directions from the outer portion of the drive arm, whereby the assembly can be used between adjacent solar collector assemblies in a row of solar collector assemblies.

  15. Structure of turbulent flow in a slab mold

    NASA Astrophysics Data System (ADS)

    Ramírez-López, Pável; Demedices, L. G.; Dávila, O.; Sánchez-Pérez, R.; Morales, R. D.

    2005-12-01

    The structure of the turbulent flow in a slab mold is studied using a water model, various experimental techniques, and mathematical simulations. The meniscus stability depends on the turbulence structure of the flow in the mold; mathematical simulations using the k-ɛ model and the Reynolds-stress model (RSM) indicate that the latter is better at predicting the meniscus profile for a given casting speed. Reynolds stresses and flow vorticity measured through the particle-image velocimetry (PIV) technique are very close to those predicted by the RSM model, and maximum and minimum values across the jet diameter are reported. The backflow in the upper side of the submerged entry nozzle (SEN) port (for a fixed SEN design) depends on the casting speed and disappears, increasing this process parameter. At low casting speeds, the jet does not report enough dissipation of energy, so the upper flow roll is able to reach the SEN port. At high casting speeds, the jet energy is strongly dissipated inside the SEN port, the narrow wall, and in the mold corner, weakening the momentum transfer of the upper flow roll, which is unable to reach the SEN port. At low casting speeds, meniscus instability is observed very close to the SEN, while at high casting speeds, this instability is observed in the mold corner. An optimum casting speed is reported where complete meniscus stability was observed. The flow structure at the free surface indicates a composite structure of islands with large gradients of velocity at high casting speeds. These velocity gradients are responsible for the meniscus instability.

  16. Proton transfer in liquid water confined inside graphene slabs

    NASA Astrophysics Data System (ADS)

    Tahat, Amani; Martí, Jordi

    2015-09-01

    The microscopic structure and dynamics of an excess proton in water constrained in narrow graphene slabs between 0.7 and 3.1 nm wide has been studied by means of a series of molecular dynamics simulations. Interaction of water and carbon with the proton species was modeled using a multistate empirical valence bond Hamiltonian model. The analysis of the effects of confinement on proton solvation structure and on its dynamical properties has been considered for varying densities. The system is organized in one interfacial and a bulk-like region, both of variable size. In the widest interplate separations, the lone proton shows a marked tendency to place itself in the bulk phase of the system, due to the repulsive interaction with the carbon atoms. However, as the system is compressed and the proton is forced to move to the vicinity of graphene walls it moves closer to the interface, producing a neat enhancement of the local structure. We found a marked slowdown of proton transfer when the separation of the two graphene plates is reduced. In the case of lowest distances between graphene plates (0.7 and 0.9 nm), only one or two water layers persist and the two-dimensional character of water structure becomes evident. By means of spectroscopical analysis, we observed the persistence of Zundel and Eigen structures in all cases, although at low interplate separations a signature frequency band around 2500 cm-1 suffers a blue shift and moves to characteristic values of asymmetric hydronium ion vibrations, indicating some unstability of the typical Zundel-Eigen moieties and their eventual conversion to a single hydronium species solvated by water.

  17. Advancing Design-for-Assembly: The Next Generation in Assembly Planning

    SciTech Connect

    Calton, T.L.

    1998-12-09

    At the 1995 IEEE Symposium on Assembly and Task Planning, Sandia National Laboratories introduced the Archimedes 2 Software Tool [2]. The system was described as a second-generation assembly planning system that allowed preliminmy application of awembly planning for industry, while solidly supporting further research in planning techniques. Sandia has worked closely with indust~ and academia over the last four years. The results of these working relationships have bridged a gap for the next generation in assembly planning. Zke goal of this paper is to share Sandia 's technological advancements in assembly planning over the last four years and the impact these advancements have made on the manufacturing communip.

  18. Development of a Leave-in-Place Slab Edge Insulating Form System

    SciTech Connect

    Marc Hoeschele; Eric Lee

    2009-08-31

    Concrete slabs represent the primary foundation type in residential buildings in the fast-growing markets throughout the southern and southwestern United States. Nearly 75% of the 2005 U.S. population growth occurred in these southern tier states. Virtually all of these homes have uninsulated slab perimeters that transfer a small, but steady, flow of heat from conditioned space to outdoors during the heating season. It is estimated that new home foundations constructed each year add 0.016 quads annually to U.S. national energy consumption; we project that roughly one quarter of this amount can be attributed to heat loss through the slab edge and the remaining three quarters to deep ground transfers, depending upon climate. With rising concern over national energy use and the impact of greenhouse gas emissions, it is becoming increasingly imperative that all cost-effective efforts to improve building energy efficiency be implemented. Unlike other building envelope components that have experienced efficiency improvements over the years, slab edge heat loss has largely been overlooked. From our vantage point, a marketable slab edge insulation system would offer significant benefits to homeowners, builders, and the society as a whole. Conventional slab forming involves the process of digging foundation trenches and setting forms prior to the concrete pour. Conventional wood form boards (usually 2 x 10's) are supported by vertical stakes on the outer form board surface, and by supporting 'kickers' driven diagonally from the top of the form board into soil outside the trench. Typically, 2 x 10's can be used only twice before they become waste material, contributing to an additional 400 pounds of construction waste per house. Removal of the form boards and stakes also requires a follow-up trip to the jobsite by the concrete subcontractor and handling (storage/disposal) of the used boards. In the rare cases where the slab is insulated (typically custom homes with radiant

  19. Circum-Slab Mantle Deformation: Insights from Finite Strain and Seismic Anisotropy

    NASA Astrophysics Data System (ADS)

    Di Leo, J. F.; Li, Z. H.; Ribe, N. M.; Walker, A.; Wookey, J. M.; Kendall, J. M.

    2014-12-01

    Recent numerical modeling studies of the time-dependent development of texture and seismic anisotropy during subduction have shed light on how the mantle deforms as a slab subducts. It is thus becoming more and more clear that the term "mantle flow" may be too ambiguous in the context of subduction. For instance, it has been suggested that trench-parallel shear wave splitting fast directions (from SKS and source-side S splitting) on the seaward side need not necessarily be the result of trench-parallel movement (i.e., "flow") of mantle material, but are rather due to pure shear deformation in the sub-slab mantle. Here we present results of a numerical modeling study where we have systematically investigated how mantle propagation, finite strain, olivine lattice-preferred orientation (LPO), and SKS splitting vary with slab width in a fully dynamic 3-D subduction model. We find that even in the complex circum-slab flow field, the finite strain ellipsoid (FSE) is a good proxy for LPO. However, it does not necessarily align with the instantaneous mantle flow velocity vector. We identify two distinct domains with different deformation types in the central sub-slab upper mantle: simple shear induced by plate advance dominates at shallow depths and results in trench-normal fast splitting, while pure shear due to slab rollback dominates in the deeper mantle (above 410 km) and produces trench-parallel fast orientations. In our models, the SKS splitting pattern strongly depends on these two competing effects as well as the subduction partition ratio, γ = Xp/Xt, where Xp and Xt are the lengths of plate advance and trench retreat, respectively. If γ < 1 (narrow slabs, < 1000 km), trench-parallel fast directions are produced. In contrast, γ > 1 (wide slabs, > 1000 km), results in trench-normal fast splitting. This may explain the observed dichotomy in natural subduction zones of sub-slab fast splitting patterns (away from slab edges) usually being either trench-parallel or

  20. Self-assembling amphiphilic peptides†

    PubMed Central

    Dehsorkhi, Ashkan; Castelletto, Valeria; Hamley, Ian W

    2014-01-01

    The self-assembly of several classes of amphiphilic peptides is reviewed, and selected applications are discussed. We discuss recent work on the self-assembly of lipopeptides, surfactant-like peptides and amyloid peptides derived from the amyloid-β peptide. The influence of environmental variables such as pH and temperature on aggregate nanostructure is discussed. Enzyme-induced remodelling due to peptide cleavage and nanostructure control through photocleavage or photo-cross-linking are also considered. Lastly, selected applications of amphiphilic peptides in biomedicine and materials science are outlined. © 2014 The Authors. Journal of Peptide Science published by European Peptide Society and John Wiley & Sons, Ltd. PMID:24729276

  1. Pathways for virus assembly around nucleic acids

    PubMed Central

    Perlmutter, Jason D; Perkett, Matthew R

    2014-01-01

    Understanding the pathways by which viral capsid proteins assemble around their genomes could identify key intermediates as potential drug targets. In this work we use computer simulations to characterize assembly over a wide range of capsid protein-protein interaction strengths and solution ionic strengths. We find that assembly pathways can be categorized into two classes, in which intermediates are either predominantly ordered or disordered. Our results suggest that estimating the protein-protein and the protein-genome binding affinities may be sufficient to predict which pathway occurs. Furthermore, the calculated phase diagrams suggest that knowledge of the dominant assembly pathway and its relationship to control parameters could identify optimal strategies to thwart or redirect assembly to block infection. Finally, analysis of simulation trajectories suggests that the two classes of assembly pathways can be distinguished in single molecule fluorescence correlation spectroscopy or bulk time resolved small angle x-ray scattering experiments. PMID:25036288

  2. Evolution of the slab bending radius and the bending dissipation in three-dimensional subduction models with a variable slab to upper mantle viscosity ratio

    NASA Astrophysics Data System (ADS)

    Schellart, W. P.

    2009-10-01

    Three-dimensional laboratory subduction models are presented investigating the influence of the slab/upper mantle viscosity ratio (η SP/η UM) on the slab bending radius ( RB), with η SP/η UM = 66-1375. Here, RB is non-dimensionalized by dividing it by the upper mantle thickness ( TUM). The results show that RB/ TUM varies with time, reaching a maximum when the subduction velocity is maximum. Furthermore, RB/ TUM increases approximately linearly with increasing η SP/η UM for the investigated viscosity range. The model results show that the slab bending force ( FBe) and the energy dissipation during bending (Ф Be) are small compared to the negative buoyancy force of the slab ( FBu) and the potential energy release during sinking (Ф Bu). Maxima in Ф Be/Ф Bu (≈ FBe/ FBu) are reached in the early stage of subduction when RB/ TUM is minimum and the slab tip is at 220-440 km depth. Maximum Ф Be/Ф Bu increases with increasing η SP/η UM, with Ф Be/Ф Bu(max) = 0.06, 0.11, 0.18 and 0.22 for η SP/η UM = 66, 217, 709 and 1375, respectively. For subduction depths > 220-440 km, Ф Be/Ф Bu = 0.02-0.11 for all viscosity ratios. Assuming that in nature η SP/η UM < 1000, and that viscous dissipation during plan view curvature of the slab is ≤ 1%, the models predict that in nature most of the slab's potential energy is used to drive mantle flow (on average 88%-97% and minimally 81%), whilst only a small component is used to bend the subducting plate at the hinge (on average 2-11% and maximally 18%). Applying the model predictions for RB/ TUM and Ф Be/Ф Bu to natural subduction zones implies that in nature η SP/η UM = 1-7 × 10 2 and η UM = 0.8-2.7 × 10 20 Pa·s. Finally, the laboratory models, which use glucose syrup and silicone oil as modelling materials, highlight the importance of accurate control on temperature during an experiment. New material investigations show that the viscosity of these two materials decreases exponentially with temperature in

  3. Slab dragging and the recent geodynamic evolution of the western Mediterranean plate boundary region

    NASA Astrophysics Data System (ADS)

    Spakman, Wim; Chertova, Maria V.; van den Berg, Arie P.; Thieulot, Cedric; van Hinsbergen, Douwe J. J.

    2016-04-01

    The Tortonian-Present geodynamic evolution of the plate boundary between North Africa and Iberia is characterized by first-order enigmas. This concerns, e.g., the diffuse tectonic activity of the plate boundary; the crustal thickening below the Rif; the closing of the northern Moroccan marine gateways prior to the Messinian Salinity Crisis; crustal extension of the central to eastern Betics; the origin and sense of motion of the large left-lateral Trans Alboran Shear Zone (TASZ) and Eastern Betic Shear Zone (EBSZ); and lithosphere delamination of the North African continental edge. Many explanations have been given for each of these seemingly disparate tectonic features, which invariably have been addressed in the plate tectonic context of the NW-SE relative plate convergence between the major plates since the Tortonian, mostly independently from each other. Usually there is no clear role for the subducted slab underlying the region, except for presumed rollback, either to SW or to the W, depending on the type of observations that require explanation. Here we integrate the dynamic role of the slab with the NW-SE relative plate convergence by 3-D numerical modelling of the slab evolution constrained by absolute plate motions (Chertova et al., JGR,2014 & Gcubed 2014). By combining observations and predictions from seismology, geology, and geodesy, with our numerical 3-D slab-mantle dynamics modelling, we developed a new and promising geodynamic framework that provides explanations of all noted tectonic enigmas in a coherent and connected way. From the Tortonian until today, we propose that mantle-resisted slab dragging combines with the NW-SE plate convergence across the (largely) unbroken plate boundary to drive the crustal deformation of the region. Slab dragging is the lateral transport, pushing or pulling, of slab through the mantle by the absolute motion of the subducting plate (Chertova et al., Gcubed, 2014). Because the slab is connected to both the Iberian

  4. Signature of slab fragmentation beneath Anatolia from full-waveform tomography

    NASA Astrophysics Data System (ADS)

    Govers, Rob; Fichtner, Andreas

    2016-09-01

    When oceanic basins close after a long period of convergence and subduction, continental collision and mountain building is a common consequence. Slab segmentation is expected to have been relatively common just prior to closure of other oceans in the geological past, and may explain some of the complexity that geologists have documented in the Tibetan plateau also. We focus on the eastern Mediterranean basin, which is the last remainder of a once hemispherical neo-Tethys ocean that has nearly disappeared due to convergence of the India and Africa/Arabia plates with the Eurasia plate. We present new results of full-waveform tomography that allow us to image both the crust and upper mantle in great detail. We show that a major discontinuity exists between western Anatolia lithosphere and the region to the east of it. Also, the correlation of geological features and the crustal velocities is substantially stronger in the west than in the east. We interpret these observations as the imprint in the overriding plate of fragmentation of the neo-Tethys slab below it. This north-dipping slab may have fragmented following the Eocene (about 35 million years ago) arrival of a continental promontory (Central Anatolian Core Complex) at the subduction contact. From the Eocene through the Miocene, slab roll-back ensued in the Aegean and west Anatolia, while the Cyprus-Bitlis slab subducted horizontally beneath central and east Anatolia. Following collision of Arabia (about 16 million years ago), the Cyprus-Bitlis slab steepened, exposing the crust of central and east Anatolia to high temperature, and resulting in the velocity structure that we image today. Slab fragmentation thus was a major driver of the evolution of the overriding plate as collision unfolded.

  5. A simple new device to examine human stance: the totter-slab.

    PubMed

    Roth, Robin; Wank, Veit; Müller, Otto; Hochwald, Harald; Günther, Michael

    2010-02-01

    This article describes a new measuring device to investigate balancing strategies of human stance: the totter-slab, i.e., a standing plate suspended with steel cables to hooks on a steel frame. First, we analysed the physical properties of the device by recording free oscillations under different conditions [varying amplitude, mass and centre of mass (COM) height]. This allowed us to determine the eigenfrequency f and the damping coefficient D<1 Ns/m for each trial. The trials showed that the measured damped eigenfrequency of f is approximately 0.63 Hz is barely dependent on the mass loaded. The ratio D/M is approximately 0.015 1/s is a constant almost independent of the different conditions. Furthermore, we determined the stiffnesses of the suspending cables and their suspension points to check for potential energy storage capacity of the totter-slab. We found that the totter-slab is a useful, well-defined, reliable and developable measuring device for different non-rigid-ground stance conditions. In a second part of the investigation, we compared the frequency spectra of six subjects balancing on the totter-slab with their spectra while standing quietly on a force plate fixed to the ground. The totter-slab spectra showed two distinct, dominant peak regions at approximately 0.3 and 1.1 Hz. This finding enforces the double inverted pendulum to be an adequate model particularly for balancing on the totter-slab. Compared with the firm ground condition, these two peak regions were more pronounced when balancing on the totter-slab. However, there is a variety of frequencies in the region 0.2...1.5 Hz specific for an individual subject in both balancing conditions. PMID:20128743

  6. Polarization of Lyman α Emergent from a Thick Slab of Neutral Hydrogen

    NASA Astrophysics Data System (ADS)

    Ahn, Sang-Hyeon; Lee, Hee-Won

    2015-06-01

    Star forming galaxies found in the early universe exhibit asymmetric Lyα emission line that results from multiple scattering in a neutral thick medium surrounding the Lyα emission source. It is expected that emergent Lyα will be significantly polarized through a large number of resonance scattering events followed by a number of successive wing scatterings. In this study we adopt a Monte Carlo method to calculate the polarization of Lyα transferred in a very thick static slab of HI. Resonantly scattered radiation associated with transitions between 1S 1/2 - 2P 1/2, 3/2 is only weakly polarized and therefore linear polarization of the emergent Lyα is mainly dependent on the number of off-resonant wing scattering events. The number of wing scattering events just before escape from the slab is determined by the product of the Doppler parameter a and the line center optical depth τ0, which, in turn, determines the behavior of the linear polarization of Lyα. This result is analogous to the study of polarized radiative transfer of Thomson scattered photons in an electron slab, where the emergent photons are polarized in the direction perpendicular to the slab when the scattering optical depth is small and polarized in the parallel direction when the slab is optically thick. Our simulated spectropolarimetry of Lyα shows that the line center is negligibly polarized, the near wing parts polarized in the direction parallel to the slab and the far wing parts are polarized in the direction perpendicular to the slab. We emphasize that the flip of polarization direction in the wing parts of Lyα naturally reflects the diffusive nature of the Lyα transfer process in thick neutral media.

  7. Workload analyse of assembling process

    NASA Astrophysics Data System (ADS)

    Ghenghea, L. D.

    2015-11-01

    The workload is the most important indicator for managers responsible of industrial technological processes no matter if these are automated, mechanized or simply manual in each case, machines or workers will be in the focus of workload measurements. The paper deals with workload analyses made to a most part manual assembling technology for roller bearings assembling process, executed in a big company, with integrated bearings manufacturing processes. In this analyses the delay sample technique have been used to identify and divide all bearing assemblers activities, to get information about time parts from 480 minutes day work time that workers allow to each activity. The developed study shows some ways to increase the process productivity without supplementary investments and also indicated the process automation could be the solution to gain maximum productivity.

  8. Autonomous electrochromic assembly

    SciTech Connect

    Berland, Brian Spencer; Lanning, Bruce Roy; Stowell, Jr., Michael Wayne

    2015-03-10

    This disclosure describes system and methods for creating an autonomous electrochromic assembly, and systems and methods for use of the autonomous electrochromic assembly in combination with a window. Embodiments described herein include an electrochromic assembly that has an electrochromic device, an energy storage device, an energy collection device, and an electrochromic controller device. These devices may be combined into a unitary electrochromic insert assembly. The electrochromic assembly may have the capability of generating power sufficient to operate and control an electrochromic device. This control may occur through the application of a voltage to an electrochromic device to change its opacity state. The electrochromic assembly may be used in combination with a window.

  9. Firearm trigger assembly

    SciTech Connect

    Crandall, David L.; Watson, Richard W.

    2010-02-16

    A firearm trigger assembly for use with a firearm includes a trigger mounted to a forestock of the firearm so that the trigger is movable between a rest position and a triggering position by a forwardly placed support hand of a user. An elongated trigger member operatively associated with the trigger operates a sear assembly of the firearm when the trigger is moved to the triggering position. An action release assembly operatively associated with the firearm trigger assembly and a movable assembly of the firearm prevents the trigger from being moved to the triggering position when the movable assembly is not in the locked position.

  10. Guided plasmonic modes in nanorod assemblies: strong electromagnetic coupling regime.

    PubMed

    Wurtz, G A; Dickson, W; O'Connor, D; Atkinson, R; Hendren, W; Evans, P; Pollard, R; Zayats, A V

    2008-05-12

    We demonstrate that the coupling between plasmonic modes of oriented metallic nanorods results in the formation of an extended (guided) plasmonic mode of the nanorod array. The electromagnetic field distribution associated to this mode is found to be concentrated between the nanorods within the assembly and propagates normally to the nanorod long axes, similar to a photonic mode waveguided by an anisotropic slab. This collective plasmonic mode determines the optical properties of nanorod assemblies and can be tuned in a wide spectral range by changing the nanorod array geometry. This geometry represents a unique opportunity for light guiding applications and manipulation at the nanoscale as well as sensing applications and development of molecular plasmonic devices.

  11. Plumes, Hotspot & Slabs Imaged by Global Adjoint Tomography

    NASA Astrophysics Data System (ADS)

    Bozdag, E.; Lefebvre, M. P.; Lei, W.; Peter, D. B.; Smith, J. A.; Komatitsch, D.; Tromp, J.

    2015-12-01

    We present the "first generation" global adjoint tomography model based on 3D wave simulations, which is the result of 15 conjugate-gradient iterations with confined transverse isotropy to the upper mantle. Our starting model is the 3D mantle and crustal models S362ANI (Kustowski et al. 2008) and Crust2.0 (Bassin et al. 2000), respectively. We take into account the full nonlinearity of wave propagation in numerical simulations including attenuation (both in forward and adjoint simulations), topography/bathymetry, etc., using the GPU version of the SPECFEM3D_GLOBE package. We invert for crust and mantle together without crustal corrections to avoid any bias in mantle structure. We started with an initial selection of 253 global CMT events within the magnitude range 5.8 ≤ Mw ≤ 7.0 with numerical simulations having resolution down to 27 s combining 30-s body and 60-s surface waves. After the 12th iteration we increased the resolution to 17 s, including higher-frequency body waves as well as going down to 45 s in surface-wave measurements. We run 180-min seismograms and assimilate all minor- and major-arc body and surface waves. Our 15th iteration model update shows a tantalisingly enhanced image of the Tahiti plume as well as various other plumes and hotspots, such as Caroline, Galapagos, Yellowstone, Erebus, etc. Furthermore, we see clear improvements in slab resolution along the Hellenic and Japan Arcs, as well as subduction along the East of Scotia Plate, which does not exist in the initial model. Point-spread function tests (Fichtner & Trampert 2011) suggest that we are close to the resolution of continental-scale studies in our global inversions and able to confidently map features, for instance, at the scale of the Yellowstone hotspot. This is a clear consequence of our multi-scale smoothing strategy, in which we define our smoothing operator as a function of the approximate Hessian kernel and smooth our gradients less wherever we have good ray coverage

  12. Tomographically-imaged subducted slabs and magmatic history of Caribbean and Pacific subduction beneath Colombia

    NASA Astrophysics Data System (ADS)

    Bernal-Olaya, R.; Mann, P.; Vargas, C. A.; Koulakov, I.

    2013-12-01

    We define the length and geometry of eastward and southeastward-subducting slabs beneath northwestern South America in Colombia using ~100,000 earthquake events recorded by the Colombian National Seismic Network from 1993 to 2012. Methods include: hypocenter relocation, compilation of focal mechanisms, and P and S wave tomographic calculations performed using LOTOS and Seisan. The margins of Colombia include four distinct subduction zones based on slab dip: 1) in northern Colombia, 12-16-km-thick oceanic crust subducts at a modern GPS rate of 20 mm/yr in a direction of 110 degrees at a shallow angle of 8 degrees; as a result of its low dip, Pliocene-Pleistocene volcanic rocks are present 400 km from the frontal thrust; magmatic arc migration to the east records 800 km of subduction since 58 Ma ago (Paleocene) with shallow subduction of the Caribbean oceanic plateau starting ~24-33 Ma (Miocene); at depths of 90-150 km, the slab exhibits a negative velocity anomaly we associate with pervasive fracturing; 2) in the central Colombia-Panama area, we define an area of 30-km-thick crust of the Panama arc colliding/subducting at a modern 30/mm in a direction of 95 degrees; the length of this slab shows subduction/collision initiated after 20 Ma (Middle Miocene); we call this feature the Panama indenter since it has produced a V-shaped indentation of the Colombian margin and responsible for widespread crustal deformation and topographic uplift in Colombia; an incipient subduction area is forming near the Panama border with intermediate earthquakes at an eastward dip of 70 degrees to depths of ~150 km; this zone is not visible on tomographic images; 3) a 250-km-wide zone of Miocene oceanic crust of the Nazca plate flanking the Panama indenter subducts at a rate of 25 mm/yr in a direction of 55 degrees and at a normal dip of 40 degrees; the length of this slab suggests subduction began at ~5 Ma; 4) the Caldas tear defines a major dip change to the south where a 35 degrees

  13. Silicic Arc Magmas And Silicic Slab Melts: The Melt-Rock Reaction Link

    NASA Astrophysics Data System (ADS)

    Straub, S. M.; Gomez-Tuena, A.; Bolge, L. L.; Espinasa-Perena, R.; Bindeman, I. N.; Stuart, F. M.; Zellmer, G. F.

    2013-12-01

    While a genetic link between silicic arc magmas and silicic melts from the subducted slab has long been proposed, this hypothesis is commonly refuted because most arc magmas lack a 'garnet-signature' which such slab melts must have. A comprehensive geochemical study of high-Mg# arc magmas from the Quaternary central Mexican Volcanic Belt (MVB), however, shows that this conflict can be reconciled if melt-rock reaction processes in the mantle wedge were essential to arc magma formation. In the central MVB, monogenetic and composite volcanoes erupt high-Mg# basalts to andesites with highly variable trace element patterns. These magmas contain high-Ni olivines (olivine Ni higher than permissible for olivines in partial peridotite melts) with high 3He/4He = 7-8 Ra that provide strong evidence for silicic slab components that infiltrate the subarc mantle to produce olivine-free segregations of 'reaction pyroxenite' in the sources of individual volcanoes. Melting of silica-excess and silica-deficient reaction pyroxenites can then produce high-Mg# basaltic and dacitic primary melts that mix during ascent through mantle and crust to form high-Mg# andesites. Mass balance requires that reaction pyroxenites contain at least >15-18 wt%, and likely more, of slab component. However, because the HREE of the slab component are efficiently retained in the eclogitic slab, elements Ho to Lu in partial melts from reaction pyroxenites remain controlled by the mantle and maintain MORB-normalized Ho/Lun ˜1.15 close to unity. In contrast, the MREE to LREE and fluid mobile LILE of the arc magmas are either controlled, or strongly influenced, by slab-contributions. The origin from hybrid sources also shows in the major elements that are blends of mantle-derived elements (Mg, Ca, Mn, Fe, Ti) and elements augmented by slab contributions (Si, Na, K, P, and possibly Al). Moreover, strong correlations between bulk rock SiO2, 87Sr/86Sr and δ18O (olivines) can be interpreted as mixtures of subarc

  14. Preliminary performance analysis of a transverse flow spectrally selective two-slab packed bed volumetric receiver

    NASA Astrophysics Data System (ADS)

    Roos, Thomas H.; Harms, Thomas M.

    2016-05-01

    A new volumetric receiver concept has been investigated, based on an adaptation of the spectrally selective, two-slab packed bed volumetric receiver concept of Flamant et al. Both slabs comprise spheres of identical size - borosilicate for the transparent slab 1 and SiC for the opaque slab 2 - which are ordered in a hexagonally close-packed bed. The flow direction has been changed from parallel to the incident radiation and perpendicular to the window, to parallel to the window and perpendicular to the incident radiation (transverse flow). The gap between the window and slab 1 has been removed, so the bed is held in place by the sidewalls, the floor and the window, allowing arbitrary orientation and dispensing with the need for beam-down operation. The receiver has been subjected to constant solar radiative load of approximately 70 suns, and the effect of variations in flowrate, the degree of air preheating as well as the thickness of slab 2 on the outlet air temperature distributions have been measured. The effect of reducing the flowrate for both slab 2 thicknesses is to increase temperature everywhere relative to the maximum temperature, having the effect of "flattening" the pattern factor and tending towards more uniform temperature distribution. The effect of preheating for both slab 2 thicknesses is to move the location of maximum temperature deeper into the bed (away from the window). No significant effect is observed on pattern factor in the transparent region of the bed (slab 1), but temperatures in the opaque region increase relative to the maximum temperature. The results are consistent with the increasing contribution of radiative heat transfer relative to convective and conductive heat transfer as the bed temperature rises. In all cases, the air temperature closest to the window is lower than the maximum temperature, demonstrating the volumetric heating effect. Increasing the outlet air temperature (either due to preheating or due to decreasing

  15. ZPR-3 Assembly 6F : A spherical assembly of highly enriched uranium, depleted uranium, aluminum and steel with an average {sup 235}U enrichment of 47 atom %.

    SciTech Connect

    Lell, R. M.; McKnight, R. D; Schaefer, R. W.; Nuclear Engineering Division

    2010-09-30

    Over a period of 30 years, more than a hundred Zero Power Reactor (ZPR) critical assemblies were constructed at Argonne National Laboratory. The ZPR facilities, ZPR-3, ZPR-6, ZPR-9 and ZPPR, were all fast critical assembly facilities. The ZPR critical assemblies were constructed to support fast reactor development, but data from some of these assemblies are also well suited for nuclear data validation and to form the basis for criticality safety benchmarks. A number of the Argonne ZPR/ZPPR critical assemblies have been evaluated as ICSBEP and IRPhEP benchmarks. Of the three classes of ZPR assemblies, engineering mockups, engineering benchmarks and physics benchmarks, the last group tends to be most useful for criticality safety. Because physics benchmarks were designed to test fast reactor physics data and methods, they were as simple as possible in geometry and composition. The principal fissile species was {sup 235}U or {sup 239}Pu. Fuel enrichments ranged from 9% to 95%. Often there were only one or two main core diluent materials, such as aluminum, graphite, iron, sodium or stainless steel. The cores were reflected (and insulated from room return effects) by one or two layers of materials such as depleted uranium, lead or stainless steel. Despite their more complex nature, a small number of assemblies from the other two classes would make useful criticality safety benchmarks because they have features related to criticality safety issues, such as reflection by soil-like material. ZPR-3 Assembly 6 consisted of six phases, A through F. In each phase a critical configuration was constructed to simulate a very simple shape such as a slab, cylinder or sphere that could be analyzed with the limited analytical tools available in the 1950s. In each case the configuration consisted of a core region of metal plates surrounded by a thick depleted uranium metal reflector. The average compositions of the core configurations were essentially identical in phases A - F. ZPR-3

  16. A School That Works.

    ERIC Educational Resources Information Center

    Paglin, Catherine

    2001-01-01

    Alpha High School in urban Gresham (Oregon) houses a school-to-work program and was designed, with student involvement, as a business. Movable walls and cabinetry provide the flexibility to accommodate general assemblies, combine classes for team teaching, or break classes up into small working groups. A business lab enables businesses to set up…

  17. Numerical Modelling of Reinforced Concrete Slabs under Blast Loads of Close-in Detonations Using the Lagrangian Approach

    NASA Astrophysics Data System (ADS)

    Shuaib, M.; Daoud, O.

    2015-07-01

    This paper includes an investigation for the deformations, including deflections and damage modes, which occur in reinforced concrete (RC) slabs when subjected to blast loads of explosions. The slab considered for the investigation is a one-way square RC slab with the dimensions of 1000 x 1000 x 40 mm, fixed supported at two opposite sides. It was subjected to close-in detonations of three different charge weights for a constant standoff distance. For the study, the slab was analysed using the numerical method by means of nonlinear finite element analysis. The slab was modelled as 3-D structural continuum using LS-DYNA software. For concrete modelling, two constitutive models were selected, namely the KCC and Winfrith concrete models. Blast loads were applied to the slab through the Lagrangian approach, and the blast command available in the software, namely LOAD_BLAST_ENHANCED, was selected for the application. The deflections and damage modes results obtained were compared to those from a previously published experiment. From the study, both the KCC and Winfrith concrete models effectively and satisfactorily estimated the actual slab maximum deflection. For damage modes, the KCC model appeared to be capable to capture satisfactorily the general damage mode including flexural cracks. However, the model could not capture the local shear mode at the middle of slab (spallation) because the Lagrangian approach does not simulate the interaction between the ambient air and the solid slab.

  18. Seismicity and structure in central Mexico: Evidence for a possible slab tear in the South Cocos plate

    NASA Astrophysics Data System (ADS)

    Dougherty, Sara L.; Clayton, Robert W.

    2014-04-01

    The morphology of the transition from flat to normal subduction in eastern central Mexico is explored using intraslab earthquakes recorded by temporary and permanent regional seismic arrays. Observations of a sharp transition in slab dip near the abrupt end of the Trans-Mexican Volcanic Belt (TMVB) suggest a possible slab tear located within the subducted South Cocos plate. The eastern lateral extent of a thin ultra-slow velocity layer (USL) imaged atop the Cocos slab in recent studies along the Meso America Subduction Experiment array is examined here using additional data. We find an end to this USL which is coincident with the western boundary of a zone of decreased seismicity and the end of the TMVB near the sharp transition in slab dip. Waveform modeling of the 2-D structure in this region using a finite difference algorithm provides constraints on the velocity and geometry of the slab's seismic structure and confirms the location of the USL. Analysis of intraslab seismicity patterns reveals clustering, sudden increase in depth, variable focal mechanism orientations and faulting types, and alignment of source mechanisms along the sharp transition in slab dip. The seismicity and structural evidence suggests a possible tear in the South Cocos slab. This potential tear, together with the tear along the Orozco Fracture Zone to the northwest, indicates a slab rollback mechanism in which separate slab segments move independently, allowing for mantle flow between the segments.

  19. Arc Basalt Simulator version 3: Spreadsheet mass balance for exploring on element behavior between subducted slab, mantle wedge, and magma

    NASA Astrophysics Data System (ADS)

    Kimura, J.; Kawabata, H.; Hacker, B. R.; van Keken, P. E.; Gill, J. B.; Stern, R. J.

    2010-12-01

    We have developed the Arc Basalt Simulator version 3 (ABS3), a quantitative calculator to examine the mass balance of (1) slab-dehydration and melting, and (2) slab fluid/melt-fluxed mantle melting, and to quantitatively evaluate magma genesis beneath arcs. Calculation results from the ABS3 model suggest that element re-distribution between the subducted slab and slab-derived liquid controls distinctive trace element signatures found in arc magmas and crust. The slab liquid is derived from various mixtures of fluids and melts from sediment and altered oceanic crust, dependent on the thermal structure of the subducted slab. Slab fluids are mostly generated by slab-dehydration to form the volcanic front (VF) magmas with slab P-T conditions around 3 GPa/ 750°C, whereas slab may melt at 3-6 GPa > 830°C contributing either to the VF or to rear arc (RA) magmas. Compositions of slab fluids and melts are controlled primarily by breakdown of amphibole and lawsonite for VF and phengite for RA slab depths in association with the residual eclogite mineral phases including garnet, clinopyroxenes, and quartz. Temperature dependent partition coefficients and different partition coefficients between melt/fluid and minerals are additional controls. Minor mineral phases such as zircon and titanite also play important roles for certain elements. The slab liquid fluxed melting of depleted mantle wedge peridotite plays additional role to element re-distribution in subduction zone. The degree of partial melting varies between 17-28 % (VF) and 3-22 % (RA), with a slab flux fraction of 2-4.5 % (e.g., VF fluid) to 1-1.5 % (e.g., RA melt), and at melting depths corresponding to 1-2.5 GPa (VF) and 2.4-2.8 GPa (RA). Addition of luid-immobile elements from the mantle contributes 78-98 % of the magma mass and controls certain isotopes such as Nd and Hf in arc magmas. However, element addition from the slab liquid modifies the liquid mobile elements/isotopes in the arc magmas significantly

  20. A global survey of stress orientations in subducting slabs as revealed by intermediate-depth earthquakes

    NASA Astrophysics Data System (ADS)

    Chen, Po-Fei; Bina, Craig R.; Okal, Emile A.

    2004-11-01

    We examine a variety of mechanisms that have been proposed as contributors to the stress fields expressed as intermediate-depth seismicity in subducting slabs. To this end, we study principal stress orientations for a global data set of 1900 intermediate-depth focal solutions, determining the patterns of events characterized primarily by downdip compression, downdip tension, or neither. In regions dominated by downdip principal stresses, we find that conjugate stress axes exhibit preferential slab-normal orientations. Furthermore, we observe a clear trend of thermal control, in which colder slabs exhibit greater components of downdip compression while warmer slabs display greater downdip tension. In those regions not dominated by downdip principal stresses, a significant number of events exhibit lateral stresses in the form of subhorizontal principal axes in the plane of the slab. We conclude that the evidently complementary roles played by lithospheric age and subduction rate in constraining stress regimes support thermomechanical and petrological buoyancy models for control of intermediate-depth stresses. Moreover, observed lateral stresses support the traditional model of a squeezed ping-pong ball and stress patterns overall are consistent with some influence by reactivated fossil faults.

  1. Plate interface rheological switches during subduction infancy: Control on slab penetration and metamorphic sole formation

    NASA Astrophysics Data System (ADS)

    Agard, P.; Yamato, P.; Soret, M.; Prigent, C.; Guillot, S.; Plunder, A.; Dubacq, B.; Chauvet, A.; Monié, P.

    2016-10-01

    Subduction infancy corresponds to the first few million years following subduction initiation, when slabs start their descent into the mantle. It coincides with the transient (yet systematic) transfer of material from the top of the slab to the upper plate, as witnessed by metamorphic soles welded beneath obducted ophiolites. Combining structure-lithology-pressure-temperature-time data from metamorphic soles with flow laws derived from experimental rock mechanics, this study highlights two main successive rheological switches across the subduction interface (mantle wedge vs. basalts, then mantle wedge vs. sediments; at ∼800 °C and ∼600 °C, respectively), during which interplate mechanical coupling is maximized by the existence of transiently similar rheologies across the plate contact. We propose that these rheological switches hinder slab penetration and are responsible for slicing the top of the slab and welding crustal pieces (high- then low-temperature metamorphic soles) to the base of the mantle wedge during subduction infancy. This mechanism has implications for the rheological properties of the crust and mantle (and for transient episodes of accretion/exhumation of HP-LT rocks in mature subduction systems) and highlights the role of fluids in enabling subduction to overcome the early resistance to slab penetration.

  2. Collision-induced light scattering in a thin xenon layer between graphite slabs - MD study.

    PubMed

    Dawid, A; Górny, K; Wojcieszyk, D; Dendzik, Z; Gburski, Z

    2014-08-14

    The collision-induced light scattering many-body correlation functions and their spectra in thin xenon layer located between two parallel graphite slabs have been investigated by molecular dynamics computer simulations. The results have been obtained at three different distances (densities) between graphite slabs. Our simulations show the increased intensity of the interaction-induced light scattering spectra at low frequencies for xenon atoms in confined space, in comparison to the bulk xenon sample. Moreover, we show substantial dependence of the interaction-induced light scattering correlation functions of xenon on the distances between graphite slabs. The dynamics of xenon atoms in a confined space was also investigated by calculating the mean square displacement functions and related diffusion coefficients. The structural property of confined xenon layer was studied by calculating the density profile, perpendicular to the graphite slabs. Building of a fluid phase of xenon in the innermost part of the slot was observed. The nonlinear dependence of xenon diffusion coefficient on the separation distance between graphite slabs has been found.

  3. Assessing the role of slab rheology in coupled plate-mantle convection models

    NASA Astrophysics Data System (ADS)

    Bello, Léa; Coltice, Nicolas; Tackley, Paul J.; Dietmar Müller, R.; Cannon, John

    2015-11-01

    Reconstructing the 3D structure of the Earth's mantle has been a challenge for geodynamicists for about 40 yr. Although numerical models and computational capabilities have substantially progressed, parameterizations used for modeling convection forced by plate motions are far from being Earth-like. Among the set of parameters, rheology is fundamental because it defines in a non-linear way the dynamics of slabs and plumes, and the organization of lithosphere deformation. In this study, we evaluate the role of the temperature dependence of viscosity (variations up to 6 orders of magnitude) and the importance of pseudo-plasticity on reconstructing slab evolution in 3D spherical models of convection driven by plate history models. Pseudo-plasticity, which produces plate-like behavior in convection models, allows a consistent coupling between imposed plate motions and global convection, which is not possible with temperature-dependent viscosity alone. Using test case models, we show that increasing temperature dependence of viscosity enhances vertical and lateral coherence of slabs, but leads to unrealistic slab morphologies for large viscosity contrasts. Introducing pseudo-plasticity partially solves this issue, producing thin laterally and vertically more continuous slabs, and flat subduction where trench retreat is fast. We evaluate the differences between convection reconstructions employing different viscosity laws to be very large, and similar to the differences between two models with the same rheology but using two different plate histories or initial conditions.

  4. Geomorphic Response to Flat Slab Subduction along the Eastern Foothills of the Colombian Andes

    NASA Astrophysics Data System (ADS)

    Veloza, G.; Taylor, M. H.; Gosse, J. C.; Mora, A.; Becker, T. W.

    2013-12-01

    It is thought that in northwest South America flat slab subduction plays a key role in the recent development of the eastern Colombian Andes. Here we show that the geomorphic response to flat slab subduction is presently occurring >500 km inboard of the subduction zone plate boundary. The Llanos basin located along the eastern edge of the Colombian Andes is experiencing active uplift along the seismically active Cusiana, Yopal, Paz de Ariporo and Tame thrust faults, which we refer to as the Llanos Foothills thrust system (LFTS). The LFTS is comprised of east-directed thrust faults that are listric in geometry with shallowly west-dipping decollements. Locally, actively growing north-south plunging folds are cored by blind thrust faults, and are being incised by antecedent east-flowing streams. Using a combination of field-based observations on the geometry of faulted and folded fluvial terraces, and geochronology from terrestrial cosmogenic nuclides, we show that the fluvial terraces have been uplifted, and locally, incised >200 meters at incision rates exceeding 3 mm/yr. The field observations in combination with earthquakes and geodynamic simulations can be reconciled by flat slab subduction, but it is presently unknown whether the flat slab has a Caribbean or Nazca plate affinity. Different geodynamic scenarios can be tested to understand how the leading edge of the flat slab interacts with the South American craton, and how that interaction controls upper crustal deformation.

  5. Simulating the effect of slab features on vapor intrusion of crack entry.

    PubMed

    Yao, Yijun; Pennell, Kelly G; Suuberg, Eric M

    2013-01-01

    In vapor intrusion screening models, a most widely employed assumption in simulating the entry of contaminant into a building is that of a crack in the building foundation slab. Some modelers employed a perimeter crack hypothesis while others chose not to identify the crack type. However, few studies have systematically investigated the influence on vapor intrusion predictions of slab crack features, such as the shape and distribution of slab cracks and related to this overall building foundation footprint size. In this paper, predictions from a three-dimensional model of vapor intrusion are used to compare the contaminant mass flow rates into buildings with different foundation slab crack features. The simulations show that the contaminant mass flow rate into the building does not change much for different assumed slab crack shapes and locations, and the foundation footprint size does not play a significant role in determining contaminant mass flow rate through a unit area of crack. Moreover, the simulation helped reveal the distribution of subslab contaminant soil vapor concentration beneath the foundation, and the results suggest that in most cases involving no biodegradation, the variation in subslab concentration should not exceed an order of magnitude, and is often significantly less than this. PMID:23359620

  6. Lateral detachment in progress within the Vrancea slab (Romania): inferences from intermediate-depth seismicity patterns

    NASA Astrophysics Data System (ADS)

    Mitrofan, Horia; Anghelache, Mirela-Adriana; Chitea, Florina; Damian, Alexandru; Cadicheanu, Nicoleta; Vişan, Mădălina

    2016-05-01

    Within a slab experiencing present-day lateral break-off, a particular type of earthquakes is expected to cluster at the detachment horizon tip: namely, events generated by reverse faulting, with the approximately horizontal compression involved acting along the strike of the slab. Such a cluster of moderate magnitude earthquakes (4.7 ≤ mb ≤ 5.0) was identified in this study at the 160-175 km depth range of the Vrancea seismogenic body, in the Southeast Carpathians mountains collision environment. The corresponding cluster epicentres were systematically positioned at the boundary between a region being subject (cf. published GPS records), to present-day upward movements, and another one that underwent present-day subsidence. Such an overall setting seems to suggest that a lateral break-off is currently developing at the indicated depth within the Vrancea slab, leading to topographic uplift above the already detached slab section, and to enhanced subsidence above the section to which the gravitational slab pull was being transferred. In addition, by taking into account some systematic time correspondence which we documented between moderate magnitude events of the 160-175 km depth cluster and the subsequent strong Vrancea shocks (Mw ≥ 6.9), it appears that the latter, although occurring at much shallower depths (roughly, in the 80-140 km range), were also controlled by the break-off progress.

  7. Slab mantle dehydrates beneath Kamchatka—Yet recycles water into the deep mantle

    NASA Astrophysics Data System (ADS)

    Konrad-Schmolke, Matthias; Halama, Ralf; Manea, Vlad C.

    2016-08-01

    The subduction of hydrated slab mantle is the most important and yet weakly constrained factor in the quantification of the Earth's deep geologic water cycle. The most critical unknowns are the initial hydration state and the dehydration behavior of the subducted oceanic mantle. Here we present a combined thermomechanical, thermodynamic, and geochemical model of the Kamchatka subduction zone that indicates significant dehydration of subducted slab mantle beneath Kamchatka. Evidence for the subduction of hydrated oceanic mantle comes from across-arc trends of boron concentrations and isotopic compositions in arc volcanic rocks. Our thermodynamic-geochemical models successfully predict the complex geochemical patterns and the spatial distribution of arc volcanoes in Kamchatka assuming the subduction of hydrated oceanic mantle. Our results show that water content and dehydration behavior of the slab mantle beneath Kamchatka can be directly linked to compositional features in arc volcanic rocks. Depending on hydration depth of the slab mantle, our models yield water recycling rates between 1.1 × 103 and 7.4 × 103 Tg/Ma/km corresponding to values between 0.75 × 106 and 5.2 × 106 Tg/Ma for the entire Kamchatkan subduction zone. These values are up to one order of magnitude lower than previous estimates for Kamchatka, but clearly show that subducted hydrated slab mantle significantly contributes to the water budget in the Kamchatkan subduction zone.

  8. Initial measurements of BN-350 spent fuel in dry storage casks using the dual slab verification detonator

    SciTech Connect

    Santi, Peter Angelo; Browne, Michael C; Freeman, Corey R; Parker, Robert F; Williams, Richard B

    2010-01-01

    The Dual Slab Verification Detector (DSVD) has been developed, built, and characterized by Los Alamos National Laboratory in cooperation with the International Atomic Energy Agency (IAEA) as part of the dry storage safeguards system for the spent fuel from the BN-350 fast reactor. The detector consists of two rows of 3He tubes embedded in a slab of polyethylene which has been designed to be placed on the outer surface of the dry storage cask. By performing DSVD measurements at several different locations around the outer surface of the DUC, a signature 'fingerprint' can be established for each DUC based on the neutron flux emanating from inside the dry storage cask. The neutron fingerprint for each individual DUC will be dependent upon the spatial distribution of nuclear material within the cask, thus making it sensitive to the removal of a certain amount of material from the cask. An initial set of DSVD measurements have been performed on the first set of dry storage casks that have been loaded with canisters of spent fuel and moved onto the dry storage pad to both establish an initial fingerprint for these casks as well as to quantify systematic uncertainties associated with these measurements. The results from these measurements will be presented and compared with the expected results that were determined based on MCNPX simulations of the dry storage facility. The ability to safeguard spent nuclear fuel is strongly dependent on the technical capabilities of establishing and maintaining continuity of knowledge (COK) of the spent fuel as it is released from the reactor core and either reprocessed or packaged and stored at a storage facility. While the maintenance of COK is often done using continuous containment and surveillance (C/S) on the spent fuel, it is important that the measurement capabilities exist to re-establish the COK in the event of a significant gap in the continuous CIS by performing measurements that independently confirm the presence and content

  9. Membrane module assembly

    DOEpatents

    Kaschemekat, Jurgen

    1994-01-01

    A membrane module assembly adapted to provide a flow path for the incoming feed stream that forces it into prolonged heat-exchanging contact with a heating or cooling mechanism. Membrane separation processes employing the module assembly are also disclosed. The assembly is particularly useful for gas separation or pervaporation.

  10. Cage redesign explains assembly

    PubMed Central

    Theil, Elizabeth C; Turano, Paola

    2013-01-01

    Control of protein self-assembly and disassembly, which is central to metabolism and engineering applications, remains challenging. Here, a perspicacious redesign of interfaces in the multisubunit ferritin protein cage provides single, modifiable subunits that assemble with Cu2+ templating and give insights into the cage assembly code. PMID:23416399

  11. Membrane module assembly

    DOEpatents

    Kaschemekat, J.

    1994-03-15

    A membrane module assembly is described which is adapted to provide a flow path for the incoming feed stream that forces it into prolonged heat-exchanging contact with a heating or cooling mechanism. Membrane separation processes employing the module assembly are also disclosed. The assembly is particularly useful for gas separation or pervaporation. 2 figures.

  12. Sensor mount assemblies and sensor assemblies

    DOEpatents

    Miller, David H.

    2012-04-10

    Sensor mount assemblies and sensor assemblies are provided. In an embodiment, by way of example only, a sensor mount assembly includes a busbar, a main body, a backing surface, and a first finger. The busbar has a first end and a second end. The main body is overmolded onto the busbar. The backing surface extends radially outwardly relative to the main body. The first finger extends axially from the backing surface, and the first finger has a first end, a second end, and a tooth. The first end of the first finger is disposed on the backing surface, and the tooth is formed on the second end of the first finger.

  13. Validation of Predicted Residual Stresses within Direct Chill Cast Magnesium Alloy Slab

    NASA Astrophysics Data System (ADS)

    Turski, Mark; Paradowska, Anna; Zhang, Shu-Yan; Mortensen, Dag; Fjaer, Hallvard; Grandfield, John; Davis, Bruce; DeLorme, Rick

    2012-05-01

    A significant level of cold cracking has been observed within direct chill (DC) cast, high-strength magnesium alloy Elektron WE43. These cracks have been attributed to the formation of significant residual stresses during casting. A finite-element modeling (FEM) code, which is called ALSIM, has been used to predict the residual stress within the DC-cast slab. Verification of the predicted residual stress field within an 870 × 315-mm sized slab has been carried out using neutron diffraction measurements. Given that measurements in such large-scale components using diffraction measurements are particularly challenging and expensive, the efficient use of neutron diffraction measurements is emphasized. This has included the use of sectioning, allowing the residual stress within the slab to be mapped in detail.

  14. Dual-mode characteristics of the Buneman instability in a bounded slab plasma

    SciTech Connect

    Hong, Woo-Pyo; Jung, Young-Dae

    2015-06-15

    The dual-mode characteristics of the Buneman instability are investigated in a slab plasma, including the geometric effects. The dual symmetric and anti-symmetric dispersion modes of the Buneman instability are obtained by the plasma dielectric function with the spectral reflection conditions for the slab geometry. The result shows that the magnitudes of the growth rate for the symmetric mode are always greater than those for the anti-symmetric mode. It is also found that the geometric effect suppresses the position of the maximum growth rate for the Buneman instability in bounded slab plasmas since the maximum conditions for the symmetric and anti-symmetric modes of the Buneman instability are given by 0.60

  15. Controllable optical bistability and multistability in a slab defected with monolayer graphene nanostructure

    NASA Astrophysics Data System (ADS)

    Solookinejad, Gh.

    2016-05-01

    In this paper, the optical bistability (OB) and optical multistability (OM) properties of weak probe light in a defect dielectric medium doped by four-level graphene nanostructure is theoretically discussed. The double dark resonance can arise by linear polarized control laser fields which consist of linear left and right circularly polarized light. We show that by adjusting the Rabi-frequencies of control fields, frequency detuning of bichromatic electric fields, the intensity threshold and hysteric curves of OB and OM can be manipulated. Moreover, the thickness of the slab is considered as a controllable parameter which can impact the OB and OM behaviors of weak probe light in a defect slab. We find that the transition from OB to OM or vice versa can be possible by adjusting the thickness of the slab. Our results may provide some new application on Nano-scale devices in future all-optical communication and quantum information technologies.

  16. Deep dehydration and physical and chemical nature of the mantle above the stagnant slab (Invited)

    NASA Astrophysics Data System (ADS)

    Ohtani, E.; Zhao, D.; Kuritani, T.; Tajima, F. C.

    2010-12-01

    Recent seismic tomography studies imply that the slab is stagnant in some regions such as beneath Japan and NE China [1]. Dehydration is expected from the slabs due to decomposition of hydrous and nominally anhydrous minerals in the slabs. There are two phase boundaries between the phases with a large contrast of the water contents; i.e., the olivine-wadsleyite boundary and the decomposition boundary of ringwoodite. Dehydration could occur at the boundaries in plumes or slabs crossing the boundaries. The low velocity beneath Eastern China and United State (e.g., [2]) suggests existence of gravitationally stable hydrous melts at the base of the upper mantle. Body waveforms analysis suggested existence of highly localized low velocity anomalies at the base of the transition zone [3], which are consistent with decomposition of hydrous ringwoodite in slabs. Measurement of hydrogen diffusion in wadsleyite and ringwoodite revealed that the diffusion rates of hydrogen are comparable with that of olivine suggesting heterogeneity in hydrogen contents in the transition zone [4]. Based on hydrogen diffusion coefficients together with reported electrical conductivity of mantle minerals [5] the water content in the mantle transition zone and upper mantle can be estimated combining the electrical conductivity observations and seismic tomography data. These analyses indicate that transition zone is generally more hydrous beneath Japan compared to beneath Europe [6], and the water is localized within the wet transition zone [7]. The stagnant slabs have an important effect on the overlying transition zone and upper mantle. A big mantle wedge (BMW) model has been proposed by Zhao [1], in which the stagnant slab in the transition zone could play an essential role in the intra-plate volcanic activities overlying the slab. Water released by the stagnant slab could be important for these igneous activities, such as Changbaishan in Northeast China. The recent isotopic data of basaltic

  17. Low-damping epsilon-near-zero slabs: Nonlinear and nonlocal optical properties

    NASA Astrophysics Data System (ADS)

    de Ceglia, Domenico; Campione, Salvatore; Vincenti, Maria Antonietta; Capolino, Filippo; Scalora, Michael

    2013-04-01

    We investigate second-harmonic generation, low-threshold multistability, all-optical switching, and inherently nonlocal effects due to the free-electron gas pressure in an epsilon-near-zero (ENZ) metamaterial slab made of cylindrical, plasmonic nanoshells illuminated by TM-polarized light. Damping compensation in the ENZ frequency region, achieved by using gain medium inside the nanoshells’ dielectric cores, enhances the nonlinear properties. Reflection is inhibited, and the electric field component normal to the slab interface is enhanced near the effective pseudo-Brewster angle, where the effective ɛ≈0 condition triggers a nonresonant, impedance-matching phenomenon. We show that the slab displays a strong effective, spatial nonlocality associated with leaky modes that are mediated by the compensation of damping. The presence of these leaky modes then induces further spectral and angular conditions, where the local fields are enhanced, thus opening new windows of opportunity for the enhancement of nonlinear optical processes.

  18. Large complete band gap in two-dimensional phononic crystal slabs with elliptic inclusions

    NASA Astrophysics Data System (ADS)

    Li, Yongsen; Chen, Jiujiu; Han, Xu; Huang, Kan; Peng, Jianguo

    2012-04-01

    Phononic band structure with periodic elliptic inclusions for the square lattice is investigated based on the plane wave expansion method. The numerical results show the systems composed of tungsten (W) elliptic rods embedded in a silicon (Si) matrix can exhibit a larger complete band gap than the conventional circular phononic crystal (PC) slabs. The phononic band structure of the plate-mode waves and the width of the first complete band gap can be tuned by varying the ratio of the minor axis and the major axis, the orientation angle of the elliptic rods and the thickness of the PC slabs. We also study the band structure of plate-mode waves propagating in two-dimensional (2D) slabs with periodic elliptic inclusions coated on uniform substrate.

  19. The distribution of earthquakes with depth and stress in subducting slabs

    NASA Technical Reports Server (NTRS)

    Vassiliou, M. S.; Hager, B. H.; Raefsky, A.

    1984-01-01

    The global variation of Benioff zone seismicity with depth and the orientation of stress axes of deep and intermediate earthquakes is explained using numerical models of subducting slabs. Models that match the seismicity and stress require a barrier to flow at the 670 km seismic discontinuity. The barrier may be a viscosity increase of at least an order of magnitude or a chemical discontinuity. Instantaneous flow is subparallel to the slabs for models with a viscosity increase but contorted for models with a chemical barrier. Log N (number of earthquakes) decreases linearly to 250-300 km depth and increases thereafter. Stress magnitude in the models shows the same pattern, in accord with experiments showing N proportional to e(k-sigma), with k a constant and sigma the stress magnitude. The models predict downdip compression in the slabs at depths below 300-400 km, as observed for earthquake stress axes.

  20. Seismic Behavior and Force-Displacement Characterization of Neotype Column-Slab High Piers

    PubMed Central

    Zhou, YanQun; Zhang, YeZhi; Ye, MeiXin; Zhan, MengSi

    2014-01-01

    The seismic behavior and plasticity spreading of a neotype column-slab high pier are researched in this paper. Four scale model tests of a web slab with two boundary columns are carried out under cyclic inelastic lateral displacements simulating seismic response. The test results show that the neotype column-slab high pier has strong and stable bearing capacity, good ductility, and energy dissipation capacity. The experimental values pertaining to the spread of plasticity are derived. An approach for deriving the spread of plasticity analytically is deduced and applied to the four tests. This method accurately assesses a pier's spread of plasticity for most ductility levels. At nearly all ductility levels, the mean difference between analytical assessments of the spread of plasticity and results from 4 large-scale tests is 12% with a 9% coefficient of variation. PMID:24883420