Science.gov

Sample records for slab assembly work

  1. 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

  2. Progress on slab lasers

    NASA Astrophysics Data System (ADS)

    Albrecht, G. F.; Eggleston, J. M.; Petr, R. A.

    1986-01-01

    After a brief overview of slab geometry work published to date, zig-zag optical path slab laser development toward a 100-Hz slab YAG system ('Centurion') and a 10-Hz dual slab glass system ('Gemini') is described. Some of the major diagnostic work performed and in the process is also described to illustrate the major mechanisms responsible for beam distortion observed in these types of slab lasers.

  3. WHAT ABOUT WHEN SUB-SLAB DEPRESSURIZATION DOESN'T WORK WELL?

    EPA Science Inventory

    The paper discusses the mitigation of radon levels in basementhouses when sub-slab depressurization (SSD), a widely usedmitigation technique, is not a viable option. or example, in somehouses the slab is poured directly on the soil, resulting inpoor-to-nonexistent communication u...

  4. 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…

  5. 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.

  6. 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.

  7. Looking east inside of the 44" slab mill building at ...

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

    Looking east inside of the 44" slab mill building at the red hot slabs being conveyed to the hot beds. - U.S. Steel Edgar Thomson Works, 44" Slab Mill, Along Monongahela River, Braddock, Allegheny County, PA

  8. 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.

  9. 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.

  10. 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.

  11. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    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.

  13. 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

  14. A case study of smoke detector assembly work method intervention and evaluation.

    PubMed

    Sun, Chuan; Buchholz, Bryan; Thomas, Jeff

    2012-01-01

    The study aimed to evaluate a work method intervention in a smoke detector assembly line. High hand gripping forces and extreme wrist postures were found in the smoke detector assembly line at UTC Fire & Security Company in Maine. A fixture was introduced to replace the old assembly method. Electromyography (EMG) and electrogoniometry were used to measure the workers' hand gripping force and wrist motions with both the old and new assembly methods. Results show both hand gripping forces and wrist postures improved significantly with the new method. PMID:22317738

  15. 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.

  16. Manipulation of graphene work function using a self-assembled monolayer

    NASA Astrophysics Data System (ADS)

    Seo, Jung-Tak; Bong, Jihye; Cha, Janghwan; Lim, Taekyung; Son, Junyoung; Park, Sung Ha; Hwang, Jungseek; Hong, Suklyun; Ju, Sanghyun

    2014-08-01

    We report an effective and reliable method to increase the work function of graphene to as high as 5.50 eV by applying a self-assembled monolayer on its surface. The work function of pristine graphene (4.56 eV) was increased by approximately +0.94 eV following trichlorosilane (HDF-S) self-assembly. This increase in the work function was confirmed by ab initio calculations. HDF-S self-assembled graphene exhibited no significant changes in structural, optical, or electrical characteristics compared with pristine graphene. In addition, we verified that the modified work function of HDF-S self-assembled graphene was not affected by the underlying substrates.

  17. 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

  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. 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.

  20. On the Viability of Slab Melting

    NASA Astrophysics Data System (ADS)

    Van Hunen, J.; Bouilhol, P.; Magni, V.; Maunder, B. L.

    2014-12-01

    Melting subducted mafic crust is commonly assumed to be the main process leading to silicic melts with an adakitic signature, which may form Archaean granitoids and generate early continental crust. Alternatively, melting of the overriding lower mafic crust and near-Moho depth fractional crystallisation of mantle melts can form differentiated magmas with an adakitic signature. Previous work shows how only very young slabs melt through dehydration melting, or depict melting of dry eclogites via water addition from deeper slab dehydration. Alternatively, underplated subducted material via delamination and diapirism may be important in the generation of felsic continental crust. We quantify subduction dehydration and melting reactions in a warm subduction system using a thermo-mechanical subduction model with a thermodynamic database. We find that even young (hot) slabs dehydrate before reaching their solidus, which suppresses any slab dehydration melting and creates significant amounts of mantle wedge melting irrespective of slab age. Significant slab crust melting is only achieved in young slabs via water present melting if metamorphic fluids from the subducted mantle flux through the dry eclogites. These slab melts, however, interfere with massive mantle wedge melting and unlikely to participate in the overriding plate felsic magmatism, unlike the shallower, primitive mantle wedge melts. We also explore the conditions for delaminating the mafic subducted crust. For a wide range of ages, the uppermost part of the subducted slab might delaminate to form compositionally buoyant plumes that rise through the mantle wedge. Thick crust on young slabs (as perhaps representative for a hotter, early Earth) may delaminate entirely and reside in the mantle wedge. Under such conditions, this ponded crust might melts subsequently, forming "adakitic" felsic melts contributing to a significant amount of the overriding plate crustal volumes.

  1. Engineering work plan for container venting system drill press assembly troubleshooting. Revision 1

    SciTech Connect

    Prather, M.C.

    1994-11-01

    This work plan is for troubleshooting the current CVS drill press to ensure that the drill bit assembly doesn`t bind in the press plate. A drill press assembly has been fabricated for the Container Venting System (CVS). The drill bit assembly has bound in the press plate in previous revisions of this design. Initial troubleshooting of the drill press per Rev. 0 of this work plan was performed at the 200W Kaiser Machine Shop under Work Package 2H9401670F, Internal Work Order E20027. The drill press operated without jamming. Then, during the pre-operational test on 11/14/17 and the operational test on 11/17/94, two drum lids were drilled. Immediately after the test on 11/17/94, the drill was again operated, and it jammed. An inspection found shavings at the bottom of the drill bit assembly, between the drill bit sleeve and the press plate bore. This revised work plan provides direction for the machine shop to diagnose and correct this recent problem.

  2. Assembling in Sequence: A Saleable Work Skill. Occupation Simulation Packet. Grades 3rd-4th.

    ERIC Educational Resources Information Center

    Hueston, Jean

    This teacher's guide for grades 3 and 4 contains simulated work experiences for students using the isolated skill concept - assembling in sequence. Teacher instructions include objectives, evaluation, and sequence of activities. The guide contains pre-tests and post-tests with instructions and answer keys. Three pre-skill activities are suggested,…

  3. Deepest hypocentral distributions associated with stagnant slabs and penetrated slabs

    NASA Astrophysics Data System (ADS)

    Fukao, Y.; Obayashi, M.

    2013-12-01

    We constructed a new P-wave tomographic model of the mantle, GAP_P4, using more than ten millions of travel time data, including waveform-based differential travel times from ocean bottoms, to all of which the finite frequency kernels were applied in the inversion. Based on this model, we made a systematic survey for subducted slab images around the Circum Pacific. This survey revealed a progressive lateral variation of slab configuration along arc(s), where a subducted slab is in general in one or two of the following four stages: I. slab stagnant above the 660, II. slab penetrating the 660, III. slab trapped in the uppermost lower mantle (660 to ˜1000 km in depth), and IV. slab descending well into the deep lower mantle. The majority of the slab images are either at stage I or III. We interpret I to IV as the successive stages of slab subduction through the transition region with the 660 at the middle. There is a remarkable correlation of the slab configuration with the deepest shock hypocentral distribution. Subhorizontal distributions of deepest shocks are associated with stagnant slabs in the transition zone (slabs at stage I). Their focal depths are limited to shallower than ˜620 km. Steeply dipping deepest shock distributions are associated with penetrating slabs across the 660-km discontinuity or trapped slabs below it (slabs at stages II and III). Their focal depths extend well beyond ˜620 km. There are no cases of association of either a stagnant slab (at stage I) with subvertical distribution of deepest shocks or a trapped slab (at stage II or III) with their subhorizontal distribution. Only steeply dipping slabs appear to penetrate the 660 to be trapped in the uppermost lower mantle. The along-arc variations of stagnant-slab configuration and deepest shock distribution beneath the Bonin arc indicate a process of how the slab begins to penetrate the 660-km discontinuity after the slab stagnation. Those beneath the Java arc and Kermadec arc commonly

  4. Enabling Light Work in Helical Self-Assembly for Dynamic Amplification of Chirality with Photoreversibility.

    PubMed

    Cai, Yunsong; Guo, Zhiqian; Chen, Jianmei; Li, Wenlong; Zhong, Liubiao; Gao, Ya; Jiang, Lin; Chi, Lifeng; Tian, He; Zhu, Wei-Hong

    2016-02-24

    Light-driven transcription and replication are always subordinate to a delicate chirality transfer. Enabling light work in construction of the helical self-assembly with reversible chiral transformation becomes attractive. Herein we demonstrate that a helical hydrogen-bonded self-assembly is reversibly photoswitched between photochromic open and closed forms upon irradiation with alternative UV and visible light, in which molecular chirality is amplified with the formation of helixes at supramolecular level. The characteristics in these superhelixes such as left-handed or right-handed twist and helical length, height, and pitch are revealed by SEM and AFM. The helical photoswitchable nanostructure provides an easily accessible route to an unprecedented photoreversible modulation in morphology, fluorescence, and helicity, with precise assembly/disassembly architectures similar to biological systems such as protein and DNA. PMID:26709946

  5. The Effect of Subducting Slabs in Global Shear Wave Tomography

    NASA Astrophysics Data System (ADS)

    Lu, Chang; Grand, Stephen P.

    2016-03-01

    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 travel time dataset for a theoretical slab model based on predicted thermal anomalies within slabs. The spectral element method 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 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%. 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%. 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 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 starting models in global

  6. 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

  7. Impact of increasing productivity on work content and psychosocial work characteristics in Chaku-Chaku assembly lines - a follow-up study in a German automotive manufacturing company.

    PubMed

    Enríquez-Díaz, José-Alonso; Kotzab, Daniel; Sytch, Alina; Frieling, Ekkehart

    2012-01-01

    The current study aims at evaluating the reorganization of work processes on the basis of studies of three assembly lines in a well known component manufacture of the German automotive industry. It is of particular interest to evaluate the impact of the introduction of Chaku-Chaku assembly lines on the production goals, distribution of activities during one typical work day and psychosocial characteristics of the work environment. Findings indicate that the Chaku-Chaku assembly lines could represent a successful production strategy in order to enhance the output levels of work systems. However, the data show that interviewed assembly workers have spent more time on value added activities than before. The intensive perception of the time spent on main work activities (direct value added activities) and a simultaneous decrease of available discretionary time between work tasks seem to be related to the low level of the reported psychosocial work characteristics. PMID:22317514

  8. Cordilleran slab windows

    SciTech Connect

    Thorkelson, D.J.; Taylor, R.P. )

    1989-09-01

    The geometry and geologic implications of subducted spreading ridges are topics that have bedeviled earth scientists ever since the recognition of plate tectonics. As a consequence of subduction of the Kula-Farallon and East Pacific rises, slab windows formed and migrated beneath the North American Cordillera. The probable shape and extent of these windows, which represent the asthenosphere-filled gaps between two separating, subducting oceanic plates, are depicted from the Late Cretaceous to the present. Possible effects of the existence and migration of slab windows on the Cordillera at various times include cessation of arc volcanism and replacement by rift or plate-edge volcanism; lithospheric uplift, attenuation, and extension; and increased intensity of compressional tectonism. Eocene extensional tectonism and alkaline magmatism in southern British Columbia and the northwestern United States were facilitated by slab-window development.

  9. Along-strike translation of a fossil slab

    NASA Astrophysics Data System (ADS)

    Pikser, Jacob E.; Forsyth, Donald W.; Hirth, Greg

    2012-05-01

    The Isabella anomaly is a high seismic velocity anomaly beneath the southern Central Valley of California that has previously been interpreted to represent a lithospheric drip or delaminated Sierra Nevada root. However, recent work suggests that the anomaly is a remnant slab, left over from Cenozoic subduction, attached to the Pacific plate underneath the edge of the North American plate. This hypothesis requires the slab to translate hundreds of kilometers along-strike while remaining intact and attached to the Pacific plate despite drag from the surrounding asthenosphere and overriding lithosphere. We use 3-D finite element models to simulate this scenario, and calculate the viscosity ratio between the slab and the surrounding asthenosphere required for the slab to translate undeformed. The required viscosity ratio increases with increasing downdip extent of the slab, and decreases with increasing slab dip; for geometries approximating that of our proposed slab, the required ratio ranges from 102 to 104. Given the thermal and petrologic history of the slab, mantle flow laws predict viscosity contrasts greater than or equal to these requirements. As such, we conclude that along-strike translation of a remnant slab is feasible, and serves as a possible explanation of the Isabella anomaly. The significance of this finding extends beyond our general understanding of subduction dynamics, in that the presence of such a slab could have implications for the water budget of the San Andreas Fault and its role in aseismic slip.

  10. 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.

  11. 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.

  12. STS-61B Astronauts Ross and Spring Work on Experimental Assembly of Structures in Extravehicular

    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). This STS-61B onboard photo depicts astronauts Ross and Spring working on EASE. 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.

  13. 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

  14. 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

  15. 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.)

  16. Ergonomic risk assessment with DesignCheck to evaluate assembly work in different phases of the vehicle development process.

    PubMed

    Winter, Gabriele; Schaub, Karlheinz G; Großmann, Kay; Laun, Gerhard; Landau, Kurt; Bruder, Ralph

    2012-01-01

    Occupational hazards exist, if the design of the work situation is not in accordance with ergonomic design principles. At assembly lines ergonomics is applied to the design of work equipment and tasks and to work organisation. The ignoring of ergonomic principles in planning and design of assembly work leads to unfavourable working posture, action force and material handling. Disorders of the musculoskeletal system are of a common occurrence throughout Europe. Musculoskeletal disorders are a challenge against the background of disabled workers. The changes in a worker's capability have to be regarded in the conception of redesigned and new assembly lines. In this way ergonomics becomes progressively more important in planning and design of vehicles: The objective of ergonomic design in different stages of the vehicles development process is to achieve an optimal adaptation of the assembly work to workers. Hence the ergonomic screening tool "Design Check" (DC) was developed to identify ergonomic deficits in workplace layouts. The screening-tool is based on the current ergonomic state of the art in the design of physical work and relevant EU legal requirements. It was tested within a federal German research project at selected work stations at the assembly lines at Dr.-Ing. h.c. F. Porsche AG / Stuttgart. Meanwhile the application of the screening-tool DC is transferred in other parts of the Porsche AG, Stuttgart. It is also realized as an ergonomic standard method to perform assembly work in different phases of the vehicle development process. PMID:22317393

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 7. NO. 2 CONTINUOUS SLAB REHEATING FURNACE OF THE 160' ...

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

    7. NO. 2 CONTINUOUS SLAB REHEATING FURNACE OF THE 160' PLATE MILL. INTERIOR REFRACTORY LINING VISIBLE BECAUSE OF DEMOLITION. - U.S. Steel Homestead Works, 160" Plate Mill, Along Monongahela River, Homestead, Allegheny County, PA

  2. 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

  3. Preliminary control/structure interaction study of coupled Space Station Freedom/Assembly Work Platform/orbiter

    NASA Technical Reports Server (NTRS)

    Singh, Sudeep K.; Lindenmoyer, Alan J.

    1989-01-01

    Results are presented from a preliminary control/structure interaction study of the Space Station, the Assembly Work Platform, and the STS orbiter dynamics coupled with the orbiter and station control systems. The first three Space Station assembly flight configurations and their finite element representations are illustrated. These configurations are compared in terms of control authority in each axis and propellant usage. The control systems design parameters during assembly are computed. Although the rigid body response was acceptable with the orbiter Primary Reaction Control System, the flexible body response showed large structural deflections and loads. It was found that severe control/structure interaction occurred if the stiffness of the Assembly Work Platform was equal to that of the station truss. Also, the response of the orbiter Vernier Reaction Control System to small changes in inertia properties is examined.

  4. Effects of Below-knee Assembly Work at Different Reach Distances on Upper-extremity Muscle Activity.

    PubMed

    Shin, Seung-Je; Yoo, Won-Gyu

    2014-08-01

    [Purpose] We investigated upper-extremity muscle activity during below-knee assembly work performed by healthy adults at three different reach distances evaluate the physical risk factors associated with neck and shoulder disorders of reach distances. [Subjects] Sixteen young male workers were recruited. [Methods] Activities of the right upper trapezius, anterior deltoid, and biceps brachii muscles were measured during below-knee assembly work at the three different reach distances. [Results] The normalized EMG data of the upper trapezius, anterior deltoid, and biceps brachii muscles generally increased significantly as the reach distance at which the assembly work was performed increased. [Conclusion] Below-knee workers should engage in work that involves shorter (nearer) reach distances. PMID:25202196

  5. 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

  6. 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...

  7. [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. PMID:24893451

  8. 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)

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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…

  14. 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).

  15. Phase conjugated slab laser designator

    SciTech Connect

    Chandra, S.; Paul, J.L.

    1989-06-06

    A laser designator is described comprising a laser pump means; a high power phase conjugated slab laser amplifier formed of GSGG:Cr:Nd as a lasing material on one side of the pump means; a low power rod shaped laser oscillator on the opposite side of the pump means; and a first plurality of optical reflecting and refracting means for directing and shaping a laser beam which surrounds the pump means and passes through the rod and slab; and a telescope means coupled to the beam to direct it to a distant target.

  16. A wrinkly phononic crystal slab

    NASA Astrophysics Data System (ADS)

    Bayat, Alireza; Gordaninejad, Faramarz

    2015-03-01

    The buckling induced surface instability is employed to propose a tunable phononic crystal slab composed of a stiff thin film bonded on a soft elastomer. Wrinkles formation is used to generate one-dimensional periodic scatterers at the surface of a finitely thick slab. Wrinkles' pattern change and corresponding stress is employed to control wave propagation triggered by a compressive strain. Simulation results show that the periodic wrinkly structure can be used as a transformative phononic crystal which can switch band diagram of the structure in a reversible behavior. Results of this study provide opportunities for the smart design of tunable switch and elastic wave filters at ultrasonic and hypersonic frequency ranges.

  17. 49. VIEW OF WOOD FRAME STUCCO STRUCTURES ON CONCRETE SLABS, ...

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

    49. VIEW OF WOOD FRAME STUCCO STRUCTURES ON CONCRETE SLABS, REPUTED HOUSES FOR PROSTITUTES, LOOKING NORTH. NOTICE SIMILAR RUIN IN BACKGROUND RIGHT. THREE OR FOUR SIMILAR RUINS ALONG RIVER ROAD NORTH OF MINE WORKINGS. - Mariscal Quicksilver Mine & Reduction Works, Terlingua, Brewster County, TX

  18. 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

  19. 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

  20. The footwear factory's assembly sector: opposing organizational structure and quality from the ergonomic work analysis.

    PubMed

    Silva, Kláudia M M N; Coelho, Bernardo G P; Junior, Josemir V S; Faria, Luiz F M; Dutra, Ludmila; Alvarenga, Marília; Roggini, Renan; Echternach, Eliza Helena de Oliveira

    2012-01-01

    Data from 2006 indicated that Brazilian footwear leather industry was composed of approximately 9,488 formally registered establishments, considering the leather industry, footwear and leather goods. It was responsible for 211,582 people employed. However, in spite of having many employees, this kind of organization found several problems when analyzed from the ergonomics view. With this premise, then, in order to identify bottlenecks and other engineering problems that could cause discomfort and motivation lack among workers, leading directly to the loss of the product quality, the assembly sector of women's shoes factory was characterized. PMID:22316956

  1. 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. PMID:25767101

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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.

  3. 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

  4. 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.

  5. Vibration characteristics of floating slab track

    NASA Astrophysics Data System (ADS)

    Kuo, Chen-Ming; Huang, Cheng-Hao; Chen, Yi-Yi

    2008-11-01

    Coupled equilibrium equations of suspended wheels and floating slab track system were solved with the fourth-order Runge-Kutta method to obtain the deflections, vibration velocities, and wheel-rail contact forces. The program was validated through several aspects. Cases with various vehicle speed, slab mass, and stiffness of slab bearing were analyzed to reveal the effects of slab bearing on track responses. The correlation between wheel-rail resonance and train speed was also discussed. It was found that rail deflections increase significantly as train speed increases. Although large slab mass may lower tuning frequency, it could also result in higher wheel-rail contact force and rail deflections. The floating slab track is effective in isolating loading above 10 Hz, which might present in some railway sections with irregularities. Adopting floating slab track for vibration control for environment along the railway may cause concerns about ride quality and track damages.

  6. 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

  7. Preface: Deep Slab and Mantle Dynamics

    NASA Astrophysics Data System (ADS)

    Suetsugu, Daisuke; Bina, Craig R.; Inoue, Toru; Wiens, Douglas A.

    2010-11-01

    We are pleased to publish this special issue of the journal Physics of the Earth and Planetary Interiors entitled "Deep Slab and Mantle Dynamics". This issue is an outgrowth of the international symposium "Deep Slab and Mantle Dynamics", which was held on February 25-27, 2009, in Kyoto, Japan. This symposium was organized by the "Stagnant Slab Project" (SSP) research group to present the results of the 5-year project and to facilitate intensive discussion with well-known international researchers in related fields. The SSP and the symposium were supported by a Grant-in-Aid for Scientific Research (16075101) from the Ministry of Education, Culture, Sports, Science and Technology of the Japanese Government. In the symposium, key issues discussed by participants included: transportation of water into the deep mantle and its role in slab-related dynamics; observational and experimental constraints on deep slab properties and the slab environment; modeling of slab stagnation to constrain its mechanisms in comparison with observational and experimental data; observational, experimental and modeling constraints on the fate of stagnant slabs; eventual accumulation of stagnant slabs on the core-mantle boundary and its geodynamic implications. This special issue is a collection of papers presented in the symposium and other papers related to the subject of the symposium. The collected papers provide an overview of the wide range of multidisciplinary studies of mantle dynamics, particularly in the context of subduction, stagnation, and the fate of deep slabs.

  8. Numerical Models of Subduction and Slab Detachment: Placing a Lower Bound on the Strength of Slabs

    NASA Astrophysics Data System (ADS)

    Billen, M. I.; Andrews, E.

    2007-12-01

    Subduction provides the main driving force for the motion of tectonic plates at the Earth's surface through slab- pull and sinking-induced flow in the surrounding mantle. The ability of the slab to directly transmit slab-pull forces to the tectonic plate at the surface depends on the minimum strength and rheology (e.g., viscous, plastic) of the slab. Previous models have shown that observations including the state of stress in slabs, dynamic topography and the geoid above slabs, the evolution of slab and the kinematic history of subduction can be well-matched by a variety of models with either low viscosity (i.e., 100-1,000 times more viscous than the surrounding mantle) or high viscosity slabs (i.e., more than 10,000 times more viscous than the surrounding mantle). However, in many of the models in which a good match to observations is found for low viscosity slabs, the maximum slab viscosity is imposed as a cut-off value, which forces the entire slab to have a more or less uniform viscosity independent of strain-rate or stress magnitude, rather than a plastic yielding-type rheology. We present numerical models demonstrating that when the non-Newtonian viscosity of the upper mantle and plastic yielding behavior of slabs are taken into account, the minimum yield strength that allows for continuous subduction is approximately 300- 500 MPa, which leads to high viscosity slabs with some localized lower viscosity regions. A yield stress of 10-100 MPa is required to form uniformly low viscosity slabs, but these slabs detach from the subducting plate, due to localized weakening, when the slab reaches a length of 200-300 km, even when subduction is facilitated by a low viscosity shear zone and kinematically-imposed surface velocities. In contrast, detachment of higher strength slabs in fully-dynamic models only occurs when the shear zone is removed and prevents further subduction.

  9. 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

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

    PubMed

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

    2011-05-17

    The second critical endpoint in the basalt-H(2)O 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

  11. Reversible work function changes induced by photoisomerization of asymmetric azobenzene dithiol self-assembled monolayers on gold

    SciTech Connect

    Ah Qune, Lloyd F. N.; Wee, Andrew T. S.; Akiyama, H.; Nagahiro, T.; Tamada, K.

    2008-08-25

    We measured reversible changes in the work function ({delta}{phi}{sub Au}) of gold substrates modified by asymmetric azobenzene dithiol self-assembled monolayers (SAMs) following photoisomerization and thermal recovery of the azo unit. The azobenzene derivative SAMs were photoisomerized to cis form by UV irradiation. {delta}{phi}{sub Au} was monitored in real time during thermal recovery to trans form by ultraviolet photoelectron spectroscopy using a synchrotron light source. Changing the substituted functional group in the p{sup '} position of the azobenzene from electron donating to electron withdrawing resulted in opposite responses of {delta}{phi}{sub Au} against photoisomerization. Hence, a direct correlation between {delta}{phi}{sub Au} and changes in molecular dipole moments was obtained.

  12. 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

  13. The Effect of Thickness and Mesh Spacing on the Impact Resistance of Ferrocement Slab

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    This paper investigates the effect of the thickness and mesh spacing on the impact of ferrocement for the concrete slab of 300mm x 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 slab thickness and mesh reinforcement spacing. There is a good linear correlation between impact resistance of ferrocement against slab thickness and its mesh spacing. The first and ultimate crack impact resistance for 40 mm slab are 2.00 times and 1.84 times respectively against the 20 mm slab with the same mesh spacing. The first and ultimate crack impact resistance for 40 mm slab with 20 mm mesh spacing are 2.24 times and 3.70 times respectively against 50 mm mesh spacing with the same slab thickness. The mesh with higher content of reinforcement provides more contribution to the slab resistance as compare with the thickness.

  14. Dynamic uplift during slab flattening

    NASA Astrophysics Data System (ADS)

    Dávila, Federico M.; Lithgow-Bertelloni, Carolina

    2015-09-01

    Subduction exerts a strong control on surface topography and is the main cause of large vertical motions in continents, including past events of large-scale marine flooding and tilting. The mechanism is dynamic deflection: the sinking of dense subducted lithosphere gives rise to stresses that directly pull down the surface. Here we show that subduction does not always lead to downward deflections of the Earth's surface. Subduction of young lithosphere at shallow angles (flat subduction) leaves it neutrally or even positively buoyant with respect to underlying mantle because the lithosphere is relatively warm compared with older lithosphere, and because the thickened and hence drier oceanic crust does not undergo the transformation of basalt to denser eclogite. Accounting for neutrally buoyant flat segments along with large variations in slab morphology in the South American subduction zone explains along-strike and temporal changes in dynamic topography observed in the geologic record since the beginning of the Cenozoic. Our results show that the transition from normal subduction to slab flattening generates dynamic uplift, preventing back-arc marine flooding.

  15. 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.

  16. A cryogenic slab CO laser

    SciTech Connect

    Ionin, Andrei A; Kozlov, A Yu; Seleznev, L V; Sinitsyn, D V

    2009-03-31

    A compact capacitive transverse RF-discharge-pumped slab CO laser with cryogenically cooled electrodes, which operates both in the cw and repetitively pulsed regimes, is fabricated. The laser operation is studied in the free running multifrequency regime at the vibrational - rotational transitions of the fundamental (V + 1 {yields} V) vibrational bands of the CO molecule in the spectral region from 5.1 to 5.4 {mu}m. Optimal operation conditions (gas mixture composition and pressure, RF pump parameters) are determined. It is shown that only gas mixtures with a high content of oxygen (up to 20% with respect to the concentration of CO molecules) can be used as an active medium of this laser. It is demonstrated that repetitively pulsed pumping is more efficient compared to cw pumping. In this case, quasi-cw lasing regime can be obtained. The maximum average output power of {approx}12 W was obtained for this laser operating on fundamental bands and its efficiency achieved {approx}14 %. The frequency-selective operation regime of the slab RF-discharge-pumped CO laser was realised at {approx} 100 laser lines in the spectral region from 5.0 to 6.5 {mu}m with the average output power of up to several tens of milliwatts in each line. Lasing at the transitions of the first vibrational overtone (V + 2 {yields} V) of the CO molecule is obtained in the spectral region from 2.5 to 3.9 {mu}m. The average output power of the overtone laser achieved 0.3 W. All the results were obtained without the forced gas mixture exchange in the discharge chamber. Under fixed experimental conditions, repetitively pulsed lasing (with fluctuations of the output characteristics no more than {+-}10 %) was stable for more than an hour. (lasers)

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. Cretaceous Arctic magmatism: Slab vs. plume? Or slab and plume?

    NASA Astrophysics Data System (ADS)

    Gottlieb, E. S.; Miller, E. L.; Andronikov, A. V.; Brumley, K.; Mayer, L. A.; Mukasa, S. B.

    2010-12-01

    Tectonic models for the Cretaceous paleogeographic evolution of the Arctic Ocean and its adjacent landmasses propose that rifting in the Amerasia Basin (AB) began in Jura-Cretaceous time, accompanied by the development of the High Arctic Large Igneous Province (HALIP). During the same timespan, deformation and slab-related magmatism, followed by intra-arc rifting, took place along the Pacific side of what was to become the Arctic Ocean. A compilation and comparison of the ages, characteristics and space-time variation of circum-Arctic magmatism allows for a better understanding of the role of Pacific margin versus Arctic-Atlantic plate tectonics and the role of plume-related magmatism in the origin of the Arctic Ocean. In Jura-Cretaceous time, an arc built upon older terranes overthrust the Arctic continental margins of North America and Eurasia, shedding debris into foreland basins in the Brooks Range, Alaska, across Chukotka, Russia, to the Lena Delta and New Siberian Islands region of the Russian Arctic. These syn-tectonic sediments have some common sources (e.g., ~250-300 Ma magmatic rocks) as determined by U-Pb detrital zircon geochronology. They are as young as Valanginian-Berriasian (~136 Ma, Gradstein et al., 2004) and place a lower limit on the age of formation of the AB. Subsequent intrusions of granitoid plutons, inferred to be ultimately slab-retreat related, form a belt along the far eastern Russian Arctic continental margin onto Seward Peninsula and have yielded a continuous succession of zircon U-Pb ages from ~137-95 Ma (n=28) and a younger suite ~91-82 Ma (n=16). All plutons dated were intruded in an extensional tectonic setting based on their relations to wall-rock deformation. Regional distribution of ages shows a southward migration of the locus of magmatism during Cretaceous time. Basaltic lavas as old as 130 Ma and as young as 80 Ma (40Ar/39Ar)) erupted across the Canadian Arctic Islands, Svalbard and Franz Josef Land and are associated with

  2. 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.

  3. Investigation of Ionospheric Slab Thickness behaviour over Rome during high solar activity period

    NASA Astrophysics Data System (ADS)

    Trivedi, Richa; Gwal, Ashok Kumar; Jain, Sudhir

    The subject of the present study is to analyze the characteristic variations of the ionospheric slab thickness at Rome (41°N, 12°E, LT= (UT+1h), DIP=57°.4) for the period August, 2011 to July, 2012. The work deals with diurnal, seasonal, solar and magnetic activity variations of slab thickness. We observed that the seasonal mean value of slab thickness is higher during summer months than equinox and winter months and the mean diurnal variations of the slab thickness characterised with night-time values that are substantially higher than the day-time values during winter (night-to-day ratio between 1.01), but higher day-time and lower night-time values during summer (night-to-day ratio of 0.65). The slab thickness decreases with increase in solar flux value for mid-latitude. The results have been compared with the earlier ones and discussed in terms of possible source mechanism responsible for the variation of slab thickness at mid-latitude region. Keywords: F2 layer critical frequency (foF2); F2-layer electron density (NmF2); Slab thickness (τ); Solar Flux.

  4. 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.

  5. 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).

  6. 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.

  7. Detecting slab structure beneath the Mediterranean

    NASA Astrophysics Data System (ADS)

    Miller, Meghan S.; Sun, Daoyuan; Piana Agostinetti, Nicola

    2013-04-01

    The presence of subducted slabs in the Mediterranean has been well documented with seismic tomography, however, these images, which are produced by smoothed, damped inversions, underestimate the sharpness of the structures. The position and extent of the slabs and the presence possible tears or gaps in the subducted lithosphere are still debated, yet the shape and location these structures are important for kinematic reconstructions and evolution of the entire subduction zone system. Extensive distribution of broadband seismic instrumentation in the Mediterranean (Italian National Seismic Network in Italy and the NSF-PICASSO project in Spain and Morocco) has allowed us to use alternative methodologies to detect the position of the slabs and slab tears beneath the Central and Western Mediterranean. Using S receiver functions we are able to identify S-to-p conversions from the bottom of the subducted slab and a lack of these signals where there are gaps or tears in the slab. We also analyze broadband waveforms for changes in P wave coda from deep (> 300 km depth) local earthquakes. The waveform records for stations in southern Italy and around the Betic-Rif show large amplitude, high frequency (f > 5 Hz) late arrivals with long coda after relatively low-frequency onset. High frequency arrivals are the strongest from events whose raypaths travel within the slab to the stations where they are recorded allowing for mapping of where the subducted material is located within the upper mantle. These two methods, along with inferring the slab position from fast P-wave velocity perturbations in tomography and intermediate depth seismicity, provide additional geophysical evidence to aid in interpretation of the complex, segmented slab structure beneath the Mediterranean.

  8. Andean flat subduction maintained by slab tunneling

    NASA Astrophysics Data System (ADS)

    Schepers, Gerben; van Hinsbergen, Douwe; Kosters, Martha; Boschman, Lydian; McQuarrie, Nadine; Spakman, Wim

    2016-04-01

    In two segments below the Andean mountain belt, the Nazca Plate is currently subducting sub-horizontally below South America over a distance of 200-300 km before the plate bends into the mantle. Such flat slab segments have pronounced effects on orogenesis and magmatism and are widely believed to be caused by the downgoing plate resisting subduction due to its local positive buoyancy. In contrast, here we show that flat slabs primarily result from a local resistance against rollback rather than against subduction. From a kinematic reconstruction of the Andean fold-thrust belt we determine up to ~390 km of shortening since ~50 Ma. During this time the South American Plate moved ~1400 km westward relative to the mantle, thus forcing ~1000 km of trench retreat. Importantly, since the 11-12 Ma onset of flat slab formation, ~1000 km of Nazca Plate subduction occurred, much more than the flat slab lengths, which leads to our main finding that the flat slabs, while being initiated by arrival of buoyant material at the trench, are primarily maintained by locally impeded rollback. We suggest that dynamic support of flat subduction comes from the formation of slab tunnels below segments with the most buoyant material. These tunnels trap mantle material until tearing of the tunnel wall provides an escape route. Fast subduction of this tear is followed by a continuous slab and the process can recur during ongoing rollback of the 7000 km wide Nazca slab at segments with the most buoyant subducting material, explaining the regional and transient character of flat slabs. Our study highlights the importance of studying subduction dynamics in absolute plate motion context.

  9. 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.

  10. 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.

  11. Hot Slab Surface Inspection By Laser Scanning Method

    NASA Astrophysics Data System (ADS)

    Matsubara, Toshiro; Toyota, Toshio; Fujiyama, Akihiro

    1986-10-01

    An optical flaw detector with laser as the external light source, which is called LST ( laser scanning tester ), has been developed. This equipment automatically inspects the entire surface of hot slabs. The results are used to examine the suitability of those slabs for hot charge rolling. The characteristics of LST are its high optical resolving power and the signal processing method with which two-dimensional information on the type of the flaw is processed. For the opening width of O.4mm and over, the detection ratio is nearly 100%. This equipment started commercial operation in January 1983 in Nippon Steel's Yawata Works and its application has increased the hot charge rolling ratio.

  12. 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.

  13. 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

  14. 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.

  15. Work.

    ERIC Educational Resources Information Center

    Haines, Annette M.

    2003-01-01

    Draws upon Maria Montessori's writings to examine work as a universal human tendency throughout life. Discusses the work of adaptation of the infant, work of "psycho-muscular organism" for the preschooler, work of the imagination for the elementary child, community work of the adolescent, and work of the adult. Asserts that Montessorians' role is…

  16. Spontaneous emission interference enhancement with a {mu}-negative metamaterial slab

    SciTech Connect

    Zeng Xiaodong; Xu Jingping; Yang Yaping

    2011-09-15

    The spontaneous decay and quantum interference of a V-type Zeeman atom placed near a {mu}-negative metamaterial (MNG) slab are investigated. Based on the fact that MNG slab supports only TE-polarized surface-plasmon polariton (SPP) modes, the decay rate of the dipole component parallel to the interface would be much larger than that normal to the interface, because one can couple while another decouple to TE modes. Consequently, high-level anisotropic environment is created and the two dipoles can interfere with each other strongly by sharing such SPP modes even if they are orthogonal. In our work, we analyze the influence of the parameters of the MNG slab as well as the atomic location on the interference intensity in detail. In addition, the dissipation of the slab is considered, and the quantum interference is still excellent even with large absorption.

  17. The Casimir force between an ideal metal plate and a dissipative dielectric slab

    NASA Astrophysics Data System (ADS)

    Falinejad, H.; Bayat, F.

    2014-09-01

    In this research, a general formula for the Casimir force between ideal metal plate and a dissipative dielectric slab has been obtained. The dielectric function of the slab is assumed to be an arbitrary complex function of frequency satisfying Kramers-Kronig relations. A classical expression for the radiation pressure of the vacuum fields on the slab is presented by using the Maxwell stress tensor. With the transition to the quantum domain and using the fluctuation dissipation theorem and Kubo's formula, the resulting expression is written in terms of the imaginary part of the vector potential Green functions components of the system. Finally, by computing the Green function, the Casimir force on the slab is obtained. This formalism enables us to calculate the Casimir force without resorting to the explicit form of the field operators. The general expression is confirmed by limiting and comparing with one of the previous works.

  18. 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.

  19. 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

  20. Water in the Slab: a Trilogy

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    In this presentation we summarize the results of a project started in 2007 from a brilliant intuition of Luigi Burlini that suggested an additional anisotropy source for the interpretation of seismic anisotropy patterns observed at subduction zones. Such an anisotropic body located in the upper part of the slab would result from the hydration of the oceanic plate at the trench outer-rise. The natural continuation of the project was to understand the mechanical processes behind slab hydration and the fluid flow patterns established during slab dehydration. In both cases, we found that tectonic pressure gradients due to the bending and unbending of the subducting oceanic plate are fundamental in driving fluid flow. This last part of the project led to the other two chapters of the final trilogy about the long route of water in the slab. This trilogy is here described in detail and a chronologically ordered series of events presented below. The first episode is related to slab hydration occurring during bending at the trench-outer rise. Here, fluids are driven downward along active normal faults by bending-related, sub-hydrostatic pressure gradients. Water can percolate down to 15-20 km below the seafloor, triggering hydrothermal reactions and the formation of hydrous minerals. This results in an elongated pattern of mostly trench-dipping hydrated faults with a strike parallel to the trench and whose orientation below the forearc becomes sub-vertical. The second episode is related to the geophysical implications of a hydrated slab below the forearc. Indeed, both the subvertical layering of closely spaced hydrated and dry levels (SPO) and the syn-deformational, fault-parallel alignment of highly anisotropic minerals (CPO) such as serpentine and talc may contribute to the SKS splitting patterns observed in the forearc. We suggest that the upper part of the slab may have a strong seismic anisotropy that can be approximated by a transverse isotropic body with a sub

  1. Contribution of Elasticity in Slab Bending

    NASA Astrophysics Data System (ADS)

    Fourel, L.; Goes, S. D. B.; Morra, G.

    2014-12-01

    Previous studies have shown that plate rheology exerts a dominant control on the shape and velocity of subducting plates. Here, we perform a systematic investigation of the, often disregarded, role of elasticity in slab bending at the trench, using simple, yet fully dynamic, set of 2.5D models where an elastic, visco-elastic or visco-elasto-plastic plate subducts freely into a purely viscous mantle. We derive a scaling relationship between the bending radius of visco-elastic slabs and the Deborah number, De, which is the ratio of Maxwell time over deformation time. We show that De controls the ratio of elastically stored energy over viscously dissipated energy and find that at De exceeding 10-2, it requires substantially less energy to bend a visco-elastic slab to the same shape as a purely viscous slab with the same viscosity (90% less for De=0.1). Elastically stored energy at higher De facilitates slab unbending and hence favours retreating modes of subduction, while trench advance only occurs for some cases with De<10-2. We use our scaling relation to estimate apparent Deborah numbers, Deapp, from a global compilation of subduction-zone parameters. Values range from 10-3 to >1, where most zones have low Deapp<10-2, but a few young plates have Deapp>0.1. Slabs with Deapp ≤ 10-2 either have very low viscosities, ≤10 times mantle viscosity, or they may be yielding, in which case our apparent Deborah number may underestimate actual De by up to an order of magnitude. If a significant portion of the low Deapp slabs yield, then elastically stored energy may actually be important in quite a large number of subduction zones. Interestingly, increasing Deapp correlates with increasing proportion of larger seismic events (b-value) in both instrumental and historic catalogues, indicating that increased contribution of elasticity may facilitate rupture in larger, less frequent earthquakes.

  2. 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.

  3. 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.

  4. Accidents due to falls from roof slabs.

    PubMed

    Rudelli, Bruno Alves; Silva, Marcelo Valerio Alabarce da; Akkari, Miguel; Santili, Claudio

    2013-01-01

    CONTEXT AND OBJECTIVE Falls from the roof slabs of houses are accidents of high potential severity that occur in large Brazilian cities and often affect children and adolescents. The aims of this study were to characterize the factors that predispose towards this type of fall involving children and adolescents, quantify the severity of associated lesions and suggest preventive measures. DESIGN AND SETTING Descriptive observational prospective longitudinal study in two hospitals in the metropolitan region of São Paulo. METHODS Data were collected from 29 cases of falls from roof slabs involving children and adolescents between October 2008 and October 2009. RESULTS Cases involving males were more prevalent, accounting for 84%. The predominant age group was schoolchildren (7 to 12 years old; 44%). Leisure activities were most frequently being practiced on the roof slab at the time of the fall (86%), and flying a kite was the most prevalent game (37.9%). In 72% of the cases, the children were unaccompanied by an adult responsible for them. Severe conditions such as multiple trauma and traumatic brain injuries resulted from 79% of the accidents. CONCLUSION Falls from roof slabs are accidents of high potential severity, and preventive measures aimed towards informing parents and guardians about the dangers and risk factors associated with this type of accident are needed, along with physical protective measures, such as low walls around the slab and gates with locks to restrict free access to these places. PMID:23903263

  5. Fluorescence losses from Yb:YAG slab lasers.

    PubMed

    Chen, Ying; Rapaport, Alexandra; Chung, Te-yuan; Chen, Bin; Bass, Michael

    2003-12-20

    We report on the distribution of fluorescence that can be emitted through the surfaces of a ytterbium-doped yttrium aluminum garnet (Yb:YAG) slab-shaped high-power solid-state laser. Slab shapes considered include parallel or antiparallel Brewster endfaced slabs and rectangular parallelepiped slabs. We treat cases in which all the faces of these slabs are in air, or with water or another coating on the largest faces. The fraction of the fluorescence emitted through each face, its distribution over that face, and the directions in which it travels are shown to be important to the design of high-power slab lasers. PMID:14717292

  6. Fatigue of concrete beams and slabs

    NASA Astrophysics Data System (ADS)

    Roesler, Jeffrey Raphael

    Traditionally, simply supported concrete beam (SSB) fatigue results have been used to characterize the fatigue resistance of fully supported concrete slabs (FSS). SSB concrete fatigue tests have been assumed to be equivalent to the fatigue resistance of concrete slabs in the field. The effect specimen size, boundary conditions, and loading configurations have on the fatigue of concrete beams and slabs have not been considered in the design of concrete pavements against fatigue. A laboratory study was undertaken to determine if the fatigue behavior of FSS and SSB were similar. A fully supported beam (FSB) was also tested under repeated loading, since it represented an intermediate specimen size and testing configuration between SSB and FSS. The best way to present fatigue results for all specimens was a stress ratio (S) to number of cycles to failure (N) curve (S-N curve). SSB fatigue behavior was similar to results obtained from the literature. FSB had similar fatigue behavior to SSB. The fatigue curve derived from repeated loading of FSS was 30 percent higher than the SSB fatigue curve. This suggested for a given number of cycles to failure, FSS could take a 30 percent higher bending stress as compared to SSB and FSB. The concrete modulus of rupture from a FSS test configuration was 30 percent greater than the concrete modulus of rupture from a SSB test setup. If the concrete modulus of rupture from a FSS test configuration was used in the slab's stress ratio, the slab's fatigue curve was the same as the SSB and FSB. This meant concrete behaved the same under fatigue loading, irrespective of specimen size and test configuration, as long as the correct concrete modulus of rupture was used in the stress ratio. Strain gages, attached to all specimens tested, indicated cracking in concrete occurred in a narrow band. Regions of high plastic strain were found in the plane of cracking, while adjacent areas experienced decreases in strain levels with cracking. Strain

  7. 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…

  8. 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

  9. INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS AND SLAB BEING PROCESSED ...

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

    INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS AND SLAB BEING PROCESSED THROUGH PRESS/STECKLER (RIGHT). HEATED SLABS MAKE SEVERAL PASSES THROUGH THE STECKLER WITH THICKNESS OF THE SLAB DECREASED UNTIL REQUIRED GAGE IS REACHED. - Central Iron Foundry, Hot Strip Mill Building, 1700 Holt Road, Holt, Tuscaloosa County, AL

  10. Necessity of the Ridge for the Flat Slab Subduction: Insights from the Peruvian Flat Slab

    NASA Astrophysics Data System (ADS)

    Knezevic Antonijevic, S.; Wagner, L. S.; Beck, S. L.; Long, M. D.; Zandt, G.; Tavera, H.

    2014-12-01

    Flattening of the subducting plate has been linked to the formation of various geological features, 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]. However, the mechanism responsible for the slab flattening is still poorly understood. Here we focus on the Peruvian flat slab, where the Nazca plate starts to bend at ~80 km depth and travels horizontally for several hundred kilometers, at which point steep subduction resumes. Based on a 1500 km long volcanic gap and intermediate depth seismicity patterns, the Peruvian flat slab appears to have the greatest along-strike extent and, therefore, has been suggested as a modern analogue to the putative flat slab during the Laramide orogeny in the western United States (~80-55 Ma). Combining 3D shear wave velocity structure and Rayleigh wave phase anisotropy between ~10° and 18° S, we find that the subducting Nazca plate is not uniformly flat along the entire region, but fails to the north of the subducting Nazca Ridge. Our results show that, in combination with trench retreat, rapid overriding plate motion, and/or presence of a thick cratonic root, the subduction of buoyant overthickened oceanic crust, such as the Nazca Ridge, is necessary for the formation and sustainability of flat slabs. This finding has important implications for the formation of flat slabs both past and present.

  11. Experimental Investigations on Ferrocement Roof Slab System for Low Cost Housing

    NASA Astrophysics Data System (ADS)

    Ahmad, T.; Arif, M.; Masood, A.

    2014-01-01

    The work presents the results of an experimental investigation carried out to assess the strength of pre-cast roof slab system comprising of ferrocement slab panels resting over RC beams. In the ferrocement panels, the cement was replaced by 0 and 20 % fly ash. This roof slab system proves out to be a cost effective and structurally safe and viable alternative for low cost housing, much better than the conventional roofing system comprising of steel girder and brittle sand stone panels commonly used in regions where sand stone panels are easily available. The testing includes three sets of roof system comprising of 12 ferrocement panels placed on two pre-cast RC beams, and an enclosure of brick walls on four sides. A similar set of roof slab system comprising of 12 sand stone panels in place of ferrocement panels were also tested for comparison. The testing was continued till the cracks were pronounced. It was observed that load carrying capacity of RC beam and ferrocement panel system with same thickness is higher as compared to similar arrangement of RC beam and sand stone panels. The crack propagation phenomenon was also studied. The ferrocement roof slab system exhibited ductile failure whereas brittle failure was observed in case of sand stone roof slab system. Cost analysis reveals that two pre-cast systems of RC beams and ferrocement panels with and without fly ash are economical as compared to red sand stone panels or RC slab system. The theoretical calculations have also been carried out to establish the adequacy of the sections to sustain the flexural loading applied in the present investigation.

  12. 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

  13. A Global Model of Mantle Convection that Incorporates Plate Bending Forces, Slab Pull, and Seismic Constraints on the Plate Stress.

    NASA Astrophysics Data System (ADS)

    Lewis, K.; Buffett, B.; Becker, T.

    2008-12-01

    We introduce a global mantle convection model employing mantle density anomalies inferred from seismic tomography to determine present day plate motions. Our approach addresses two aspects that are not usually considered in previous work. First, we include forces associated with the bending of subducting plates. The bending forces oppose the plate motion, and may be comparable in magnitude to other important forces at subduction zones, including slab pull. Second, our model incorporates data from the Global CMT Catalog. We use the focal mechanisms of earthquakes associated with subducting slabs to estimate the relative occurrence of compressional and tensional axes in the down-dip direction of subducting slabs. This information is used to infer the state of stress in the subducting slab, which we use to calculate slab pull forces. We investigate regional variations in slab pull by comparing plate motions derived using seismic constraints with those derived using slab pull forces based solely on the age of subducting plates. Furthermore, we constrain the rheology of subducted plates by comparing plate motions predicted with and without bending forces. Although our current model uses only radial variations in mantle viscosity, we include the capability of permitting lateral variations in viscosity by calculating buoyancy and plate-driven flows using Citcom

  14. 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.

  15. Measuring snow properties relevant to slab avalanche release

    NASA Astrophysics Data System (ADS)

    Reuter, Benjamin; Proksch, Martin; Löwe, Henning; van Herwijnen, Alec; Schweizer, Jürg

    2014-05-01

    The release of a slab avalanche is preceded by a sequence of fractures. The main material properties relevant for the fracture processes are the specific fracture energy of the weak layer, as also the elastic modulus and the density of the overlying slab layers. The snow micro-penetrometer (SMP) is the method of choice for snow stratigraphy measurements in the field with high resolution. Recent advances in signal processing allow us to derive the most needed material properties to model the fracture behaviour of snow. On a smaller scale, the three dimensional structure of snow samples is obtained from snow micro-tomography (CT) providing snow density directly. By modelling the mechanical behaviour of the ice matrix the elastic properties of the snow sample can be calculated. At the macro-scale, fracture mechanical field tests with particle tracking velocimetry (PTV) allow observing the in-situ fracture behaviour. Specific fracture energy and slab stiffness are derived from PTV measurement by fitting an analytical beam equation to the observed deformation field. Over the past years we were able to generate two datasets of overlapping SMP and CT as well as SMP and PTV measurements. SMP measurements and micro-tomography of snow samples show that snow density is well reproduced with current SMP signal processing algorithms. Also the specific fracture energy as derived from the SMP signal is in agreement with PTV results. The effective modulus, however, being the most sensitive parameter in fracture covers three orders of magnitude depending on measurement method. The present work discusses observed similarities and differences arising from measurement methods, theoretical assumptions and process scales. Reliable methods to determine the parameters describing the fracture process are key to snow instability modelling based on either snow cover simulations or field measurements. Preliminary modelling results from ongoing spatial variability studies illustrate the

  16. 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

  17. 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.

  18. Constraining Slab Sinking on a Whole-Mantle Scale: Quantitative Integration of Surface and Sub-Surface Observations from Geophysics and Geology

    NASA Astrophysics Data System (ADS)

    Sigloch, K.; Mihalynuk, M. G.

    2014-12-01

    How rapidly slabs sink, which trajectories they follow, and how they deform in the process, presents an inferential challenge to geophysics. Mantle rheologies remain highly uncertain, and seismic tomography can merely offer present-day snapshots of a process defined by temporal evolution. Thus observational constraints on slab sinking have tended to remain non-unique. Subduction zones are complex litho-consumers whose time-variant activity can be reconstructed from geological observations on paleo-arcs, but the association of arcs to their subducted, tomographically imaged lithosphere is iffy. Except for young slabs that can be reliably linked with coeval paleo-arc activity a priori, deeper geological time information cannot be exploited with certainty. As long as slab geometries remain "undated", few constraints on slab sinking behavior and hence mantle rheology can be extracted. Sigloch & Mihalynuk (2013) demonstrated a quantitative method to tighten constraints on slab sinking in the lower mantle by investigating the least ambiguous slab geometries observed. Extremely massive and almost vertical slab walls should have been deposited by vertical sinking beneath (intra-oceanic) trenches that remained stationary for a long time (~100 m.y.). We showed how this hypothesis of vertical sinking can be tested quantitatively and successfully, making only minimal assumptions on mantle rheology, and with proper error propagation for all observations (tomography, plate reconstructions, geology). Here the discussion of sinking trajectories and rates is extended to more challenging geometries. Dipping slabs in the lower mantle, and laterally extensive "stagnant slabs" in the transition zone can also be rendered dateable and trackable by (re-)investigation of their paleo-trenches. We discuss examples and link to recent geodynamic modeling of viscous sheet sinking. Reference: Sigloch K & Mihalynuk MG (2013), Intra-oceanic subduction shaped the assembly of Cordilleran North

  19. Engineering solution to the problem of ingot solidification in slab continuous-casting machines

    NASA Astrophysics Data System (ADS)

    Shichkov, A. N.; Bykasova, E. N.; Bashirov, N. G.; Klochai, V. V.; Bystrov, L. G.

    1995-03-01

    An engineering solution to ingot solidification and the regularities of growth of an ingot envelope thickness and the coordinate of the end of slab solidification directly on slab continuous-casting machines (SCCM) are given, and ingot solidification conditions are determined. Examples of calculation of the envelope thickness and the coordinate of the end of solidification are provided for slab continuous-casting machines utilized at the Cherepovetsk integrated metallurgical complex (CherMC) and at the cast-and-iron works of the Aisenhüttenstadt Joint-Stock Company. A graphical algorithm for determining the cooling capacity of the secondary cooling zone is presented, and a nomogram for calibration of the cooling capacity of forced secondary cooling against the major and minor radii of an SCCM is developed.

  20. 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.

  1. Effects of Thermodynamic Properties on Slab Evolution

    NASA Astrophysics Data System (ADS)

    Wada, I.; King, S. D.; Caddick, M. J.; Ross, N.

    2012-12-01

    We perform a series of numerical experiments to investigate the effects of thermodynamic properties on the geometrical evolution of subducting slabs. We calculate density (ρ), thermal expansivity (α), and heat capacity (cp) of mantle mineral assemblages of a harzburgite composition over a range of pressure and temperature conditions applicable to the Earth's mantle, using the thermodynamic database of Stixrude and Lithgow-Bertelloni [2011] and the thermodynamic calculation code Perple_X [Connolly, 2009]. Following Nakagawa et al. [2009], we assume that thermal diffusivity (κ) follows a power-law relationship with density (κ=κ0(ρ/ρ0)3, where κ0 and ρ0 are reference diffusivity and density, respectively). The calculations show that ρ, α, and κ change significantly along mantle geotherms; the ranges of their values are 3300-5100 km/m3, 1.5-3.5 10-5/K, and 3-17 W/m K, respectively. The change in cp is small (< 5%). We incorporate the pressure and temperature (PT) dependence of these thermodynamic properties into a 2-D finite element code with compressible convection formulations under the truncated anelastic liquid approximation [Lee and King, 2009] and develop a dynamic subduction model with kinematic boundary conditions. In the model, we use a composite mantle rheology that accounts for both diffusion and dislocation creep with flow law parameterization of wet olivine [Hirth and Kohlstedt, 2003]. Following Billen and Hirth [2007] and Lee and King [2011], we adjust the flow law parameter values for the lower mantle to test the effects of viscosity contrast between the upper and lower mantle on slab evolution. We use a reference model with a constant ρ, κ α, and cp, which is equivalent to using the incompressible extended Bousisnesq approximation. Preliminary results show that incorporating PT-dependent ρ enhances the vigor of the buoyancy driven flow compared to the reference model. Further, lithostatic pressure at a given depth is higher than in the

  2. The effect of metastable pyroxene on the slab dynamics

    NASA Astrophysics Data System (ADS)

    Agrusta, Roberto; Hunen, Jeroen; Goes, Saskia

    2014-12-01

    Seismic studies show that some subducting slabs penetrate straight into the lower mantle, whereas others seem to flatten near the base of the mantle transition zone. Slab stagnation is often attributed to an increase in viscosity and phase transformations in the olivine system. However, recent mineral physics studies showed that due to extremely low transformational diffusion rates, low-density metastable pyroxene may persist into the transition zone in cool slabs. Here we use a dynamically fully self-consistent subduction model to investigate the influence of metastable pyroxene on the dynamics of subducting oceanic lithosphere. Our results show that metastable pyroxene affects slab buoyancy at least as much as olivine metastability. However, unlike metastable olivine, which can inhibit slab penetration in the lower mantle only for cold, old, and fast slabs, metastable pyroxene is likely to also affect sinking of relatively young and slow slabs.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. Dynamic buckling of subducting slabs reconciles geological and geophysical observations

    NASA Astrophysics Data System (ADS)

    Lee, Changyeol; King, Scott D.

    2011-12-01

    Ever since the early days of the development of plate tectonic theory, subduction zones have been engrained in geological thinking as the place where steady, linear slabs descend into the mantle at a constant, uniform dip angle beneath volcanic arcs. However, growing evidence from geological and geophysical observations as well as analog and numerical modeling indicates that subducting slabs buckle in a time-dependent manner, in contrast to the steady-state, linear cartoons that dominate the literature. To evaluate the implication of time-dependent slab buckling of geological events, we conduct a series of 2-D numerical dynamic/kinematic subduction experiments by varying the viscosity increase across the 660 km discontinuity and the strength of the subducting slab. Our results show that slab buckling is a universal figure in all the experiments when rate of the trench migration ( Vtrench) is relatively slow ( Vtrench| < 2 cm/a) and viscosity increases across the 660 km discontinuity are greater than a factor of 30. Slab buckling is expressed as alternate shallowing and steepening dip of the subducting slab (from ~ 40 to ~ 100°) which is correlated with increasing and decreasing convergent rate of the incoming oceanic plate toward the trench. Further, the slab buckling in our experiments is consistent with the previously developed scaling laws for slab buckling; using reasonable parameters from subducted slabs the buckling amplitude and period are ~ 400 km and ~ 25 Myr, respectively. The slab buckling behavior in our experiments explains a variety of puzzling geological and geophysical observations. First, the period of slab buckling is consistent with short periodic variations (~ 25 Myr) in the motions of the oceanic plates that are anchored by subduction zones. Second, the scattered distributions of slab dips (from ~ 20 to ~ 90°) in the upper mantle are snapshots of time-dependent slab dip. Third, the current compressional and extensional stress environments in

  9. Buoyancy, bending, and seismic visibility in deep slab stagnation

    NASA Astrophysics Data System (ADS)

    Bina, Craig R.; Kawakatsu, Hitoshi; Suetsugu, D.; Bina, C.; Inoue, T.; Wiens, D.; Jellinek, M.

    2010-11-01

    The petrological consequences of deep subhorizontal deflection ("stagnation") of subducting slabs should affect both apparent seismic velocity structures and slab morphology. We construct kinematic thermal models of stagnant slabs and perform thermodynamic modeling of the consequent perturbation of high-pressure phase transitions in mantle minerals, focusing upon Japan as our study area. We calculate associated thermo-petrological buoyancy forces and bending moments which (along with other factors such as viscosity variations and rollback dynamics) may contribute to slab deformation. We consider effects of variations in depth of stagnation, post-stagnation dip angle, phase transition sharpness, transition triplication due to multiple intersection of geotherms with phase boundaries, and potential persistence of metastable phases due to kinetic hindrance. We also estimate seismic velocity anomalies, as might be imaged by seismic tomography, and corresponding seismic velocity gradients, as might be imaged by receiver-function analysis. We find that buoyant bending moment gradients of petrological origin at the base of the transition zone may contribute to slab stagnation. Such buoyancy forces vary with the depth at which stagnation occurs, so that slabs may seek an equilibrium slab stagnation depth. Metastable phase bending moment gradients further enhance slab stagnation, but they thermally decay after ∱/4600•700 km of horizontal travel, potentially allowing stagnant slabs to descend into the lower mantle. Stagnant slabs superimpose zones of negative velocity gradient onto a depressed 660-km seismic discontinuity, affecting the seismological visibility of such features. Seismologically resolvable details should depend upon both stagnation depth and the nature of the imaging technique (travel-time tomography vs. boundary-interaction phases). While seismic tomography appears to yield images of stagnant slabs, discontinuity topography beneath Japan resolved by

  10. Evolution and diversity of subduction zones controlled by slab width.

    PubMed

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

    2007-03-15

    Subducting slabs provide the main driving force for plate motion and flow in the Earth's mantle, and geodynamic, seismic and geochemical studies offer insight into slab dynamics and subduction-induced flow. Most previous geodynamic studies treat subduction zones as either infinite in trench-parallel extent (that is, two-dimensional) or finite in width but fixed in space. Subduction zones and their associated slabs are, however, limited in lateral extent (250-7,400 km) and their three-dimensional geometry evolves over time. Here we show that slab width controls two first-order features of plate tectonics-the curvature of subduction zones and their tendency to retreat backwards with time. Using three-dimensional numerical simulations of free subduction, we show that trench migration rate is inversely related to slab width and depends on proximity to a lateral slab edge. These results are consistent with retreat velocities observed globally, with maximum velocities (6-16 cm yr(-1)) only observed close to slab edges (<1,200 km), whereas far from edges (>2,000 km) retreat velocities are always slow (<2.0 cm yr(-1)). Models with narrow slabs (< or =1,500 km) retreat fast and develop a curved geometry, concave towards the mantle wedge side. Models with slabs intermediate in width ( approximately 2,000-3,000 km) are sublinear and retreat more slowly. Models with wide slabs (> or =4,000 km) are nearly stationary in the centre and develop a convex geometry, whereas trench retreat increases towards concave-shaped edges. Additionally, we identify periods (5-10 Myr) of slow trench advance at the centre of wide slabs. Such wide-slab behaviour may explain mountain building in the central Andes, as being a consequence of its tectonic setting, far from slab edges. PMID:17361181

  11. 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

  12. 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.

  13. 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.

  14. ORNL Soils Remediation and Slabs Removal The Bridge from D&D to Redevelopment

    SciTech Connect

    Conger, M Malinda; Schneider, Ken R

    2012-01-01

    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&D traditionally removes everything down to the building slab, and the Soils and Sediments Program is responsible for slabs, below-grade footers, 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 10,000 cubic yards (CY) of concrete, 2,500 CY of debris, and 500 CY of contaminated soil. The completion of this work will allow the site to be available for redevelopment and site reuse efforts at ORNL.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Slab coupled optical fiber sensor calibration

    NASA Astrophysics Data System (ADS)

    Whitaker, B.; Noren, J.; Chadderdon, S.; Wang, W.; Forber, R.; Selfridge, R.; Schultz, S.

    2013-02-01

    This paper presents a method for calibrating slab coupled optical fiber sensors (SCOS). An automated system is presented for selecting the optimal laser wavelength for use in SCOS interrogation. The wavelength calibration technique uses a computer sound card for both the creation of the applied electric field and the signal detection. The method used to determine the ratio between the measured SCOS signal and the applied electric field is also described along with a demonstration of the calibrated SCOS involving measuring the dielectric breakdown of air.

  1. Ergonomic development work: co-education as a support for user participation at a car assembly plant. A case study.

    PubMed

    Garmer, K; Dahlman, S; Sperling, L

    1995-12-01

    This study deals with the design, trials and evaluation of a co-education programme at the Volvo Uddevalla plant in Sweden. Involving operators, manufacturing engineers and managers, the programme served as a support for the creation of a participatory ergonomics process, intended for continuous use at the plant. It consisted of a basic ergonomics knowledge package, and a dialogue model defining the roles and relations of actors involved. As a practical part of the programme, trial development projects were also carried out by the participants. The main and long term objective of the project was to start the participants cooperating in a continuous change and development process on the shop-floor. The outcome of the co-education programme was evaluated immediately after the first two regular courses, and, as a longterm follow-up, after seven subsequent courses shortly after the closing of the Uddevalla plant. The co-education programme was shown to be successful. Later on, the expertize of both operators and manufacturing engineers became obvious to everyone at the plant, and the cooperation between operators and manufacturing engineers increased steadily. The main conclusion drawn was that the co-education programme is a good starting point for a process of participation and industrial change work. However, in order to get a permanent impact, the whole organization must nurse and nourish the further development, and implementation of the process. PMID:15677043

  2. Observation of the Early Transition from Slab to mixed Slab-Toroidal ETG Turbulence

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    Parametric studies of the transition between the slab branch of electron temperature gradient (ETG) mode and the mixed slab-toroidal branch of the ETG mode in CLM are reported. CLM was operated in a mirror machine configuration with a cell length of 50--100 cm, and a mirror ratio of 1--2. For typical CLM parameters and a mode localized at r = 2 cm this provides a range for inverse radius of curvature Rc - 1 between 0 and .006 cm-1. Under normal conditions theory predicts transition between slab and toroidal modes would occur when the parameter k| |Rc / 2k⊥ ρ ~ 1. Recent experiments have obtained an experimental scaling of mode amplitude and frequency as a function of Rc - 1. They indicate that even for much more modest levels of k| |Rc / 2k⊥ ρ ~ . 1 , there are substantial increases in saturated mode, up to 5 times larger than the pure slab mode. Changes in real frequency in the mode are generally small, on the order of <5%. This research was supported by the Department of Electrical Engineering of Columbia University.

  3. 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.

  4. 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.

  5. Assembly and maintenance of full scale NIF amplifiers in the amplifier module prototype laboratory (AMPLAB)

    SciTech Connect

    Horvath, J. A.

    1998-07-16

    Mechanical assembly and maintenance of the prototype National Ignition Facility amplifiers in the Amplifier Module Prototype Laboratory (AMPLAB) at Lawrence Livermore National Laboratory requires specialized equipment designed to manipulate large and delicate amplifier components in a safe and clean manner. Observations made during the operation of this assembly and maintenance equipment in AMPLAB provide design guidance for similar tools being built for the National Ignition Facility. Fixtures used for amplifier frame installation, laser slab and flashlamp cassette assembly, transport, and installation, and in-situ blastshield exchange are presented. Examples include a vacuum slab gripper, slab handling clean crane, slab cassette assembly fixture, sealed transport vehicle for slab cassette movement between the cleanroom and amplifier, slab cassette transfer fixture between the cleanroom and transport vehicle, and equipment needed for frame assembly unit, blastshield, an d flashlamp cassette installation and removal. The use of these tools for amplifier assembly, system reconfiguration, reflector replacement, and recovery from an abnormal occurrence such as a flashlamp explosion is described. Observations are made on the design and operation of these tools and their contribution to the final design.

  6. Assembly and maintenance of full-scale NIF amplifiers in the Amplifier Module Prototype Laboratory (AMPLAB)

    NASA Astrophysics Data System (ADS)

    Horvath, John A.

    1999-07-01

    Mechanical assembly and maintenance of the prototype NIF amplifiers in the AMPLAB at LLNL requires specialized equipment designed to manipulate large and delicate component in a safe and clean manner. Observations made during the operation of this assembly and maintenance equipment in AMPLAB provide design guidance for similar tools being built for the NIF. Fixtures used for amplifier frame installation, laser slab and flashlamp cassette assembly, transport, and installation, and in-situ blastshield exchange are presented. Examples include a vacuum slab gripper, slab handling clean crane, slab cassette assembly fixture, sealed transport vehicle for slab cassette movement between the cleanroom and amplifier, slab cassette transfer fixture between the cleanroom and transport vehicle, and equipment needed for frame assembly unit, blastshield, and flashlamp cassette installation and removal. The use of these tools for amplifier assembly , system reconfiguration, reflector replacement, and recovery from an abnormal occurrence such as a flashlamp explosion is described. Observations are made on the design and operation of these tools and their contribution to the final design of their NIF counterparts.

  7. 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.

  8. GNSS tomography, assembled multi model solution, initial results from first experiment of IAG GNSS tomography working group

    NASA Astrophysics Data System (ADS)

    Rohm, W.; Gaiger, A.; Brenot, H.; Bender, M.; Shangguan, M.; Bosy, J.

    2012-12-01

    The Global Navigation Satellite Systems (GNSS) troposphere delay, standard product of GNSS processing, among all other applications can be used as a data source for GNSS tomography. The path delays in the direction of satellites can be converted to a 3D distribution of atmospheric refractivity (total or wet), or water vapor density using Radon inverse transform. Although problem is linear the ill - conditionedess and ill-posedness of the equations, results in complexity of the problem. In the frame of IAG Sub-Commission SC 4.3 - "Remote sensing and modelling of the atmosphere", we proposed a Working Group "Inter-comparison and cross-validation of tomography models". The group aim is to tackle current challenges of GNSS tomography modeling like how to find best way to include space based GNSS observations, to deliver more reliable slant delay processing methods, to test robust algorithms to account for outliers in observations, to determine trustworthy precision and accuracy measures, to address problems linked with near real time processing, and how to provide effective cooperation channels with meteorological agencies. In this study the same GNSS data set has been processed for each tomographic model. To study the differences between obtained solutions, each solution step of GNSS tomography has been carefully analyzed. The methodical framework has been developed to allow comprehensive comparison and validation. In the GNSS tomography process flow several critical points have been selected, for each node a validation has been performed. This validation was based on meteorological observations carefully selected from in situ measurements, satellite measurements, and Numerical Weather Prediction models. Following nodes of GNSS tomography processing have been considered: GNSS raw data processing and preprocessing of path delays, voxel model outline and construction, observation selection, raytracing algorithms, a priori observations, observations noise, inversion

  9. 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

  10. The Equivalent Slab Thickness of Mars' Ionosphere

    NASA Astrophysics Data System (ADS)

    Mendillo, M.; Lawler, G.; Narvaez, C.; Kofman, W.; Mouginot, J.; Morgan, D.; Gurnett, D.

    2014-04-01

    The integral with height of an electron density profile, called the ionospheric total electron content (TEC), is dominated by plasma near the height of maximum electron density (Nmax). The ratio τ = TEC/Nmax has a unit of distance, representing the thickness of a slab of plasma of uniform density (Nmax) with the same TEC. At Earth, the parameter τ has been found to vary far less than either Nmax or TEC, and thus models of τ can be used to generate values of TEC or Nmax when only one is observed. For an ionospheric layer dominated by photo-chemical processes, τ has also been related to the scale height of the neutral gas (H = kT/mg) that is ionized by sunlight. The MARSIS radio science package on the Mars Express satellite has produced large independent data sets of TEC and Nmax. We have used them to form slab thickness patterns versus phase of the solar cycle and solar zenith angle. The overall sample average for daytime (SZA < 90o) conditions is < τ >day = 71 ± 21 km, and for SZA between 90o - 100o, < τ >terminator = 55 ± 25 km. We will report on the possible use of τ patterns to infer characteristics of the martian ionosphere and thermosphere.

  11. Slab Profile Encoding (PEN) for Minimizing Slab Boundary Artifact in 3D Diffusion-Weighted Multislab Acquisition*

    PubMed Central

    Van, Anh T; Aksoy, Murat; Holdsworth, Samantha J; Kopeinigg, Daniel; Vos, Sjoerd B; Bammer, Roland

    2014-01-01

    Purpose To propose a method for mitigating slab boundary artifacts in 3D multislab diffusion imaging with no or minimal increases in scan time. Methods The multislab acquisition was treated as parallel imaging acquisition where the slab profiles acted as the traditional receiver sensitivity profiles. All the slabs were then reconstructed simultaneously along the slab direction using Cartesian-based sensitivity encoding (SENSE) reconstruction. The slab profile estimation was performed using either a Bloch simulation or a calibration scan. Results Both phantom and in vivo results showed negligible slab boundary artifacts after reconstruction using the proposed method. The performance of the proposed method is comparable to the state-of-the-art slab combination method without the scan time penalty that depends on the number of acquired volumes. The obtained g-factor map of the SENSE reconstruction problem showed a maximum g-factor of 1.7 in the region of interest. Conclusion We proposed a novel method for mitigating slab boundary artifacts in 3D diffusion imaging by treating the multislab acquisition as a parallel imaging acquisition and reconstructing all slabs simultaneously using Cartesian SENSE. Unlike existing methods, the scan time increase, if any, does not scale with the number of image volumes acquired. PMID:24691843

  12. Characterization of Yb:YAG active slab media based on a layered structure with different doping

    NASA Astrophysics Data System (ADS)

    Lapucci, A.; Ciofini, M.; Esposito, L.; Ferrara, P.; Gizzi, L. A.; Hostaša, J.; Labate, L.; Pirri, A.; Toci, G.; Vannini, M.

    2013-05-01

    Slabs with non-uniform doping distribution are studied with the aim of reducing thermal deformations in high-energy high-average-power Yb:YAG slab systems. We present a numerical analysis based on Finite Element Mesh (FEM) methods suitable to model non-uniform devices. The thermal variation of the refractive index, the end-faces deformations and the photo-elastic effect have been calculated in order to estimate the total thermal-lens effect. The stress distributions are also obtained. Some results of this numerical approach are compared to experimental thermal lens measurements in a simple geometry for both uniform and structured samples, in order to validate the numerical procedures. Finally we compare numerical simulations for different single- or double-sided pumping and cooling geometries. They show that structured slabs can reduce thermal gradients with respect to uniformly doped means with comparable absorption and geometry. This means a reduction of thermal lens effect and thus an increase of maximum allowed pump power loading. Previous literature reports some work made with structured slabs where higher doping was located in layers with lower pump radiation levels, in order to get a more uniform absorption. Interestingly our modeling indicates that reduced thermal effects are instead obtained when a higher doping is located close to the cooled surfaces.

  13. 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

  14. 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. PMID:25121134

  15. '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.

  16. 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.

  17. 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.

  18. The gravitational field of an infinite flat slab

    NASA Astrophysics Data System (ADS)

    Fulling, S. A.; Bouas, J. D.; Carter, H. B.

    2015-08-01

    We study Einstein's equations with a localized plane-symmetric source, with close attention to gauge freedom/fixing and to listing all physically distinct solutions. In the vacuum regions there are only two qualitatively different solutions, one curved and one flat; in addition, on each of the two sides there is a free parameter describing how the slab is embedded into the vacuum region. Surprisingly, for a generic slab source the solution must be curved on one side and flat on the other. We treat infinitely thin slabs in full detail and indicate how thick slabs can increase the variety of external geometry pairs. Positive energy density seems to force external geometries with curvature singularities at some distance from the slab; we speculate that such singularities occur in regions where the solution cannot be physically relevant anyway.

  19. Nonlinear Shear Instabilities in an Infinite Slab

    NASA Astrophysics Data System (ADS)

    Nepveu, M.

    1982-08-01

    The dynamical evolution of an infinite slab moving in denser and noisy (turbulent) surroundings is investigated with a 2D hydrodynamic code. The applicability of the results to astrophysical jets is discussed. Inviscid beams show internal shocks at regular intervals of a few beamwidths. Kinks are not obvious. In viscous beams shocks are less outspoken, but turbulence is triggered with maximum scales of a few beamwidths. These viscous beams broaden. Linear stability analysis may hold up to a few e-folding times, although the seed disturbance field is not infinitesimal. The computations suggest that viscous astrophysical beams may become blurred quite suddenly and may give rise to sudden change in radiation patterns (NGC 1265).

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. Slab anisotropy from subduction zone guided waves in Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, K. H.; Tseng, Y. L.; Hu, J. C.

    2014-12-01

    Frozen-in anisotropic structure in the oceanic lithosphere and faulting/hydration in the upper layer of the slab are expected to play an important role in anisotropic signature of the subducted slab. Over the past several decades, despite the advances in characterizing anisotropy using shear wave splitting method and its developments, the character of slab anisotropy remains poorly understood. In this study we investigate the slab anisotropy using subduction zone guided waves characterized by long path length in the slab. In the southernmost Ryukyu subduction zone, seismic waves from events deeper than 100 km offshore northern Taiwan reveal wave guide behavior: (1) a low-frequency (< 1 Hz) first arrival recognized on vertical and radial components but not transverse component (2) large, sustained high-frequency (3-10 Hz) signal in P and S wave trains. The depth dependent high-frequency content (3-10Hz) confirms the association with a waveguide effect in the subducting slab rather than localized site amplification effects. Using the selected subduction zone guided wave events, we further analyzed the shear wave splitting for intermediate-depth earthquakes in different frequency bands, to provide the statistically meaningful shear wave splitting parameters. We determine shear wave splitting parameters from the 34 PSP guided events that are deeper than 100 km with ray path traveling along the subducted slab. From shear wave splitting analysis, the slab and crust effects reveal consistent polarization pattern of fast directions of EN-WS and delay time of 0.13 - 0.27 sec. This implies that slab anisotropy is stronger than the crust effect (<0.1 s) but weaker than the mantle wedge and sub-slab mantle effect (0.3-1.3 s) in Taiwan.

  5. Along-strike translation of a fossil slab

    NASA Astrophysics Data System (ADS)

    Eichenbaum-Pikser, J. M.; Forsyth, D. W.; Hirth, G.

    2011-12-01

    The Isabella anomaly is a high seismic velocity anomaly beneath the southern Central Valley of California. Breaking from previous interpretations of the anomaly as a lithospheric drip (Zandt and Carrigan, 1993) or delaminated Sierra Nevada root (Zandt et al., 2004), Forsyth et al. (2011) propose that it is a remnant slab, left over from Cenozoic subduction, attached to the Monterey microplate and translating along-strike with the Pacific plate underneath the edge of the North American plate. This hypothesis requires the slab to translate hundreds of kilometers along strike while remaining intact and attached to the Pacific plate despite drag from the surrounding asthenosphere and overriding lithosphere. Using COMSOL Multiphysics, we design 3-D finite element fluid flow models to simulate this scenario, and calculate the viscosity ratio required between the slab and the surrounding asthenosphere in order for the slab to translate undeformed. The ratio needed increases with downdip extent of the slab, and decreases with slab dip; for geometries approximating that of our proposed slab, it ranges from 10^2 to 10^4. Given the thermal and hydrological history of the slab, mantle flow laws predict viscosity contrasts greater than or equal to these requirements. As such, we conclude that along-strike translation of a remnant slab is entirely feasible, and serves as possible explanation of the Isabella anomaly. The significance of this finding extends beyond our general understanding of subduction dynamics, in that the presence of such a slab could have interesting implications for the water budget of the San Andreas Fault and its role in aseismic slip.

  6. THE EFFECT OF INTERMITTENT GYRO-SCALE SLAB TURBULENCE ON PARALLEL AND PERPENDICULAR COSMIC-RAY TRANSPORT

    SciTech Connect

    Le Roux, J. A.

    2011-12-10

    Earlier work based on nonlinear guiding center (NLGC) theory suggested that perpendicular cosmic-ray transport is diffusive when cosmic rays encounter random three-dimensional magnetohydrodynamic turbulence dominated by uniform two-dimensional (2D) turbulence with a minor uniform slab turbulence component. In this approach large-scale perpendicular cosmic-ray transport is due to cosmic rays microscopically diffusing along the meandering magnetic field dominated by 2D turbulence because of gyroresonant interactions with slab turbulence. However, turbulence in the solar wind is intermittent and it has been suggested that intermittent turbulence might be responsible for the observation of 'dropout' events in solar energetic particle fluxes on small scales. In a previous paper le Roux et al. suggested, using NLGC theory as a basis, that if gyro-scale slab turbulence is intermittent, large-scale perpendicular cosmic-ray transport in weak uniform 2D turbulence will be superdiffusive or subdiffusive depending on the statistical characteristics of the intermittent slab turbulence. In this paper we expand and refine our previous work further by investigating how both parallel and perpendicular transport are affected by intermittent slab turbulence for weak as well as strong uniform 2D turbulence. The main new finding is that both parallel and perpendicular transport are the net effect of an interplay between diffusive and nondiffusive (superdiffusive or subdiffusive) transport effects as a consequence of this intermittency.

  7. 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

  8. Capture of the Canary mantle plume material by the Gibraltar arc mantle wedge during slab rollback

    NASA Astrophysics Data System (ADS)

    Mériaux, C. A.; Duarte, J. C.; Duarte, S. S.; Schellart, W. P.; Chen, Z.; Rosas, F.; Mata, J.; Terrinha, P.

    2015-06-01

    Recent evidence suggests that a portion of the Canary plume travelled northeastwards below the lithosphere of the Atlas Mountains in North Africa towards the Alboran domain and was captured ˜10 Ma ago by the Gibraltar subduction system in the Western Mediterranean. The capture would have been associated with the mantle return flow induced by the westward-retreating slab that would have dragged and trapped a portion of the plume material in the mantle wedge of the Gibraltar subduction zone. Such material eventually contaminated the subduction related volcanism in the Alboran region. In this work, we use scaled analogue models of slab-plume interaction to investigate the plausibility of the plume capture. An upper-mantle-scaled model combines a narrow (400 km) edge-fixed subduction plate with a laterally offset compositional plume. The subduction dominated by slab rollback and toroidal mantle flow is seen to increasingly impact on the plume dynamics as the area of influence of the toroidal flow cells at the surface is up to 500 × 1350 km2. While the plume head initially spreads axisymmetrically, it starts being distorted parallel to the plate in the direction of the trench as the slab trench approaches the plume edge at a separation distance of about 500 km, before getting dragged towards mantle wedge. When applied to the Canary plume-Gibraltar subduction system, our model supports the observationally based conceptual model that mantle plume material may have been dragged towards the mantle wedge by slab rollback-induced toroidal mantle flow. Using a scaling argument for the spreading of a gravity current within a channel, we also show that more than 1500 km of plume propagation in the sublithospheric Atlas corridor is dynamically plausible.

  9. 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.

  10. Melting features along the western Ryukyu slab edge (northeast Taiwan) and Ryukyu slab tear (southernmost Okinawa Trough): Seismic evidence

    NASA Astrophysics Data System (ADS)

    Lin, J.; Hsu, S.; Sibuet, J.

    2003-12-01

    Behind the sedimentary Ryukyu arc lies the Okinawa Trough whose termination is located at the tip of the Ilan plain (northern Taiwan), just above the Ryukyu slab edge. The present-day active volcanic front, located 80-100 km above the Ryukyu slab, extends from Japan to Kueishantao Island, an islet situated 10-km offshore the Ilan plain. 3370 earthquakes recorded in northern Taiwan by 65 seismic land stations between December 1990 and May 1999 were used to determine the 3-D Vp and Vs velocity structures and Vp/Vs ratios. A low Vp, low Vs and high Vp/Vs sausage like body, about 20 km in diameter, lies within the Eurasian mantle wedge, on top of the western Ryukyu slab extremity, from depths ranging between 20 km and 100 km. We suggest that the friction of the Ryukyu slab edge against the Eurasian lithosphere and/or the upwelling of the underlying Philippine Sea plate lithospheric mantle around the slab edge would cause an abnormal heating resulting in the formation of partial melt. Part of this melt feeds obliquely the Kueishantao andesitic Island. An abnormal amount of volcanism occurs within the Okinawa Trough, east of a slab tear located 140 km from the Ryukyu slab edge. The power spectrum analysis of magnetic data shows the presence of a thick crust located above the slab tear, suggesting that a similar pattern to the one identified above of the Ryukyu slab edge might exist in the slab tear region, feeding obliquely this area of abnormal volcanism.

  11. Unusually Deep Bonin Earthquake (M7.9) of May 30, 2015 Suggests that Stagnant Slab Transforms into Penetration Stage

    NASA Astrophysics Data System (ADS)

    Obayashi, M.; Fukao, Y.; Yoshimitsu, J.

    2015-12-01

    A great shock occurred at an unusual depth of 678 km far away from the well-defined Wadati-Benioff zone of the Izu-Bonin arc (Fig.1). To the north of this region the slab is stagnant above the 660 km discontinuity and to the south it penetrates the discontinuity (Fig.2). Thus, the slab in this region can be viewed as in a transitional state from the stagnant to penetrating slab. Here, the steeply dipping part of the slab bends sharply to horizontal and the great shock happened at the lowest corner of this bending. The CMT indicates a pure normal faulting with the trench-normal near horizontal tensional axis and the near vertical compressional axis (Fig.1). We suggest that this mechanism reflects a transitional state of slab deformation from the bending-dominant mode to the penetration-dominant mode. The mechanism is consistent with either of these two two modes. We show that the mechanism is also consistent with the resultant stress field generated by many deep shocks occurring along the Wadati-Benioff zone. The calculated stress field changes rapidly along a trench-normal profile at a depth of 680 km and becomes similar to that generated by the great shock at points near the hypocenter (Fig.3). Thus, the stress field due to the Wadati-Benioff zone earthquakes works to enhance the occurrence of deep shocks of the type of the 2015 great shock, which represents slab deformation associated with the transition from stagnant to penetrating slab.

  12. A dipping, thick Farallon slab below central United States

    NASA Astrophysics Data System (ADS)

    Sun, D.; Gurnis, M.; Saleeby, J.; Helmberger, D. V.

    2015-12-01

    It has been hypothesized that much of the Laramide orogeny was caused by dynamic effects induced by an extensive flat slab during a period of plateau subduction. A particularly thick block containing the Shatsky Rise conjugate, now in the mid-mantle, left a distinctive deformation footprint from southern California to Denver, Colorado. Thus mid-mantle, relic slabs can provide fundamental information about past subduction and the history of plate tectonics if properly imaged. Here we find clear evidence for a northeastward dipping (35° dip), slab-like, but fat (up to 400-500 km thick) seismic anomaly within the top of the lower mantle below the central United States. Using a deep focus earthquake below Spain with direct seismic paths that propagate along the top and bottom of the anomaly, we find that the observed, stacked seismic waveforms recorded with the dense USArray show multi-pathing indicative of sharp top and bottom surfaces. Plate tectonic reconstructions in which the slab is migrated back in time suggest strong coupling of the slab to North America. In combination with the reconstructions, we interpret the structure as arising from eastward dipping Farallon subduction at the western margin of North America during the Cretaceous, in contrast with recent interpretations. The slab could have been fattened through a combination of pure shear thickening during flat-slab subduction and a folding instability during penetration into the lower mantle.

  13. 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

  14. 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

  15. 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

  16. Sliding interleaved kY (SLINKY) acquisition: a novel 3D MRA technique with suppressed slab boundary artifact.

    PubMed

    Liu, K; Rutt, B K

    1998-01-01

    This work addresses the elimination of the slab boundary artifact (SBA) or venetian blind artifact in three-dimensional multiple overlapped thin slab acquisition (3D MOTSA) for magnetic resonance angiography (MRA). Our method uses a sliding-slab, interleaved kY (SLINKY) data acquisition strategy, equalizing flow-related signal intensity weighting across the entire slab dimension. This technique demodulates signal intensity changes along the slab direction and can essentially eliminate the SBA while retaining the same or better imaging time efficiency than that of conventional MOTSA, providing robustness to complicated flow patterns and thereby resulting in more accurate depiction of vascular morphology. In addition, this technique does not need specialized reconstruction and extra computation. The unique penalty of this technique is the sensitivity to phase inconsistency in the data. Both phantom and in vivo experiments verify the clinical significance of the technique. The new MRA images acquired with this imaging technique show highly reliable mapping of vascular morphology without the SBA and reduction of signal voids in complex/slow flow regions. PMID:9702893

  17. 3-D numerical simulation of Yb:YAG active slabs with longitudinal doping gradient for thermal load effects assessment.

    PubMed

    Ferrara, P; Ciofini, M; Esposito, L; Hostaša, J; Labate, L; Lapucci, A; Pirri, A; Toci, G; Vannini, M; Gizzi, L A

    2014-03-10

    We present a study of Yb:YAG active media slabs, based on a ceramic layered structure with different doping levels. We developed a procedure allowing 3D numerical analysis of the slab optical properties as a consequence of the thermal load induced by the pump process. The simulations are compared with a set of experimental results in order to validate the procedure. These structured ceramics appear promising in appropriate geometrical configurations, and thus are intended to be applied in the construction of High Energy Diode Pumped Solid State Laser (DPSSL) systems working in high repetition-rate pulsed regimes. PMID:24663877

  18. Tunable one-dimensional photonic crystal slabs

    NASA Astrophysics Data System (ADS)

    Beccherelli, R.; Bellini, B.; Zografopoulos, D.; Kriezis, E.

    2007-05-01

    A 1D photonic crystal slab based on preferential etching of commercially available silicon-on-insulator wafers is presented. Compared to dry etching, anisotropic wet etching is more tolerant to errors as it is self-stopping on crystallographic {111} planes and it produces a more precise geometry with symmetries and homothetic properties, with surface roughness close to 1 nm. The resulting grooves are infiltrated by low viscosity liquid crystal having large positive optical anisotropy. The use of slanted grooves provides advantages: first of all the complete filling of slanted grooves is simplified when compared to vertical walls structures. Furthermore alignment is significantly facilitated. Indeed the liquid crystal molecules tend to align with their long axis along the submicron grooves. Therefore by forcing reorientation out of a rest position, the liquid crystal presents a choice of refractive indices to the propagating optical field. The liquid crystal behavior is simulated by a finite element method, and coupled to a finite difference time domain method. We investigate different photonic crystal configurations. Large tunability of bandgap edge for TE polarization is demonstrated when switching the liquid crystal with an applied voltage. We have also studied the use of the same device geometry as a very compact microfluidic refractometric sensor.

  19. 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.

  20. 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.

  1. Diode-pumped efficient slab laser with two Nd:YLF crystals and second-harmonic generation by slab LBO.

    PubMed

    Li, Daijun; Ma, Zhe; Haas, Rüdiger; Schell, Alexander; Simon, Janosch; Diart, Robert; Shi, Peng; Hu, Peixin; Loosen, Peter; Du, Keming

    2007-05-15

    We demonstrate a diode-pumped electro-optical Q-switched slab laser with a high optical efficiency, high pulse energy, and short pulse width with two Nd:YLF crystals inside one resonator. The single compact slab resonator can generate a 1D top-hat beam at both the far field and the near field. With a slab-geometry-design lithium triborate (LBO) crystal, efficient critical phase-matching second-harmonic generation for a 1D top-hat beam with multiple transverse modes is achieved. PMID:17440558

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. PERSPECTIVE OF UNDERSIDE SHOWING ARCHED GIRDER AND SLAB CONSTRUCTION. NOTE ...

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

    PERSPECTIVE OF UNDERSIDE SHOWING ARCHED GIRDER AND SLAB CONSTRUCTION. NOTE TWISTED BAR STOCK REINFORCING CAN BE SEEN. - Keggereis Ford Bridge, Spanning West Branch Conococheague Creek at State Route 4006, Willow Hill, Franklin County, PA

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 14. LOOKING NORTHWEST THROUGH WOODS TOWARD THE SLAB AND BUTTRESS ...

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

    14. LOOKING NORTHWEST THROUGH WOODS TOWARD THE SLAB AND BUTTRESS SECTION. NEW DAM MODIFICATIONS WILL IMPACT THIS AREA. - Pit 4 Diversion Dam, Pit River west of State Highway 89, Big Bend, Shasta County, CA

  13. 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.

  14. 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

  15. 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

  16. A VIEW OF FOUNDATION (SLAB ON GRADE) WITH SCALE POLE ...

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

    A VIEW OF FOUNDATION (SLAB ON GRADE) WITH SCALE POLE LOOKING INTO SPRINKLER BOX ON EAST SIDE OF BUILDING (01/03/2008) - Wake Island Airfield, Terminal Building, West Side of Wake Avenue, Wake Island, Wake Island, UM

  17. 10. REINFORCED CONCRETE SLAB ROOF FROM SOUTHEASTERN EDGE, ACCESS RAMPS ...

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

    10. REINFORCED CONCRETE SLAB ROOF FROM SOUTHEASTERN EDGE, ACCESS RAMPS AT LEFT AND RIGHT, 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

  18. 11. REINFORCED CONCRETE SLAB ROOF FROM THE SOUTHERN EDGE, VIEW ...

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

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

  19. 12. REINFORCED CONCRETE SLAB ROOF FROM NORTHEASTERN EDGE, VIEW TOWARDS ...

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

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

  20. 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

  1. 13. REINFORCED CONCRETE SLAB ROOF FROM SOUTHWESTERN EDGE, VIEW TOWARDS ...

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

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

  2. 13. REINFORCED CONCRETE SLAB ROOF FROM THE NORTHERN EDGE, VIEW ...

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

    13. REINFORCED CONCRETE SLAB ROOF FROM THE NORTHERN EDGE, 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

  3. 9. REINFORCED CONCRETE SLAB ROOF FROM NORTHEAST EDGE, VIEW TOWARDS ...

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

    9. REINFORCED CONCRETE SLAB ROOF FROM NORTHEAST EDGE, VIEW TOWARDS SOUTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-4, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  4. 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

  5. 10. REINFORCED CONCRETE SLAB ROOF FROM SOUTHEAST EDGE, VIEW TOWARDS ...

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

    10. REINFORCED CONCRETE SLAB ROOF FROM SOUTHEAST EDGE, VIEW TOWARDS NORTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-4, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  6. 12. REINFORCED CONCRETE SLAB ROOF FROM THE NORTHERN EDGE, VIEW ...

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

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

  7. 8. REINFORCED CONCRETE SLAB ROOF FROM NORTHWEST EDGE, ACCESS RAMP ...

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

    8. REINFORCED CONCRETE SLAB ROOF FROM NORTHWEST EDGE, ACCESS RAMP IN FOREGROUND, 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

  8. 11. REINFORCED CONCRETE SLAB ROOF, GUARD RAIL AT CENTER, VIEW ...

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

    11. REINFORCED CONCRETE SLAB ROOF, GUARD RAIL AT CENTER, 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

  9. INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS AND STEEL SLAB EXITING ...

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

    INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS AND STEEL SLAB EXITING (LEFT) AND EDGING MACHINE/PRESS (RIGHT). - Central Iron Foundry, Hot Strip Mill Building, 1700 Holt Road, Holt, Tuscaloosa County, AL

  10. INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS AND STEEL SLAB HAVING ...

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

    INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS AND STEEL SLAB HAVING EXITED (LEFT) AND PROCEEDING TO EDGER (RIGHT). - Central Iron Foundry, Hot Strip Mill Building, 1700 Holt Road, Holt, Tuscaloosa County, AL

  11. INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS (LEFT) AND SLAB BEING ...

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

    INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS (LEFT) AND SLAB BEING PROCESSED THROUGH PRESS/STECKLER (RIGHT). - Central Iron Foundry, Hot Strip Mill Building, 1700 Holt Road, Holt, Tuscaloosa County, AL

  12. EXTERIOR VIEW, LOOKING NORTHEAST, WITH SLAB YARD. AT RIGHT IS ...

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

    EXTERIOR VIEW, LOOKING NORTHEAST, WITH SLAB YARD. AT RIGHT IS HOT STRIP MILL BUILDING AND FURNACE. VIEW AT LEFT IS TOWARD CUT TO LENGTH BUILDING. - Central Iron Foundry Site, 1700 Holt Road, Holt, Tuscaloosa County, AL

  13. Estimation of dielectric slab permittivity using a flared coaxial line

    NASA Astrophysics Data System (ADS)

    Shin, Dong H.; Eom, Hyo J.

    2003-04-01

    Estimation of dielectric slab permittivity is considered by using a flared coaxial line. A problem of reflection from a flared coaxial line that radiates into a dielectric slab with a flange is solved. A flared coaxial line is modeled with multiply stepped coaxial lines with different inner and outer conductors. A set of simultaneous equations for the modal coefficients is constituted based on the boundary conditions. Computations are performed to illustrate the reflection behavior in terms of the coaxial line geometry, frequency, and permittivity of a dielectric slab. Nomograms are developed to estimate the permittivity from the measured reflection coefficients. The utility of a flared coaxial line for the determination of slab permittivity is discussed.

  14. 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

  15. Decarbonation of subducting slabs: insight from thermomechanical-petrological numerical modelling

    NASA Astrophysics Data System (ADS)

    Gonzalez, Christopher M.; Gorczyk, Weronika; Gerya, Taras

    2015-04-01

    This work extends a numerical geodynamic modelling code (I2VIS) to simulate subduction of carbonated lithologies (altered basalts and carbonated sediments) into the mantle. Code modifications now consider devolatilisation of H2O-CO2 fluids, a CO2-melt solubility parameterisation for molten sediments, and allows for carbonation of mantle peridotites. The purpose is to better understand slab generated CO2 fluxes and consequent subduction of carbonates into the deep mantle via numerical simulation. Specifically, we vary two key model parameters: 1) slab convergence rate (1,2,3,4,5 cm y-1) and 2) converging oceanic slab age (20,40,60,80 Ma) based on a half-space cooling model. The aim is to elucidate the role subduction dynamics has (i.e., spontaneous sedimentary diapirism, slab roll-back, and shear heating) with respect to slab decarbonation trends not entirely captured in previous experimental and thermodynamic investigations. This is accomplished within a fully coupled petrological-thermomechanical modelling framework utilising a characteristics-based marker-in-cell technique capable of solving visco-plastic rheologies. The thermodynamic database is modified from its original state to reflect the addition of carbonate as CO2 added to the rock's overall bulk composition. Modifications to original lithological units and volatile bulk compositions are as follows: GLOSS average sediments (H2O: 7.29 wt% & CO2: 3.01 wt%), altered basalts (H2O: 2.63 wt% & CO2: 2.90 wt%), and metasomatised peridotite (H2O: 1.98 wt% & CO2: 1.5 wt%). We resolve stable mineralogy and extract rock properties via PerpleX at a resolution of 5K and 25 MPa. Devolatilisation/consumption and stability of H2O-CO2 fluid is determined by accessing the thermodynamic database. When fluid is released due to unstable conditions, it is tracked via markers that freely advect within the velocity field until consumed. 56 numerical models were completed and our results show excellent agreement in dynamics with

  16. Modeling the effects of 3-D slab geometry and oblique subduction on subduction zone thermal structure

    NASA Astrophysics Data System (ADS)

    Wada, I.; Wang, K.; He, J.

    2013-12-01

    In this study, we revisit the effects of along-strike variation in slab geometry and oblique subduction on subduction zone thermal structures. Along-strike variations in slab dip cause changes in the descending rate of the slab and generate trench-parallel pressure gradients that drive trench-parallel mantle flow (e.g., Kneller and van Keken, 2007). Oblique subduction also drives trench-parallel mantle flow. In this study, we use a finite element code PGCtherm3D and examine a range of generic subduction geometries and parameters to investigate the effects of the above two factors. This exercise is part of foundational work towards developing detailed 3-D thermal models for NE Japan, Nankai, and Cascadia to better constrain their 3-D thermal structures and to understand the role of temperature in controlling metamorphic, seismogenic, and volcanic processes. The 3-D geometry of the subducting slabs in the forearc and arc regions are well delineated at these three subduction zones. Further, relatively large compilations of surface heat flow data at these subduction zones make them excellent candidates for this study. At NE Japan, a megathrust earthquake occurred on March 11, 2011; at Nankai and Cascadia, there has been a great effort to constrain the scale of the next subduction thrust earthquake for the purpose of disaster prevention. Temperature influences the slip behavior of subduction faults by (1) affecting the rheology of the interface material and (2) controlling dehydration reactions, which can lead to elevated pore fluid pressure. Beyond the depths of subduction thrust earthquakes, the thermal structure is affected strongly by the pattern of mantle wedge flow. This flow is driven by viscous coupling between the subducting slab and the overriding mantle, and it brings in hot flowing mantle into the wedge. The trench-ward (up-dip) extent of the slab-mantle coupling is thus a key factor that controls the thermal structure. Slab-mantle decoupling at shallow

  17. Carrier transport in Bi2Se3 topological insulator slab

    NASA Astrophysics Data System (ADS)

    Gupta, Gaurav; Lin, Hsin; Bansil, Arun; Jalil, Mansoor Bin Abdul; Liang, Gengchiau

    2015-11-01

    Electron transport in Bi2Se3 topological insulator slabs is investigated in the thermal activation regime (>50 K) both in the absence (ballistic) and presence of weak and strong acoustic phonon scattering using the non-equilibrium Green function approach. Resistance of the slab is simulated as a function of temperature for a range of slab thicknesses and effective doping in order to gain a handle on how various factors interact and compete to determine the overall resistance of the slab. If the Bi2Se3 slab is biased at the Dirac point, resistance is found to display an insulating trend even for strong electron-phonon coupling strength. However, when the Fermi-level lies close to the bulk conduction band (heavy electron doping), phonon scattering can dominate and result in a metallic behavior, although the insulating trend is retained in the limit of ballistic transport. Depending on values of the operating parameters, the temperature dependence of the slab is found to exhibit a remarkably complex behavior, which ranges from insulating to metallic, and includes cases where the resistance exhibits a local maximum, much like the contradictory behaviors seen experimentally in various experiments.

  18. Double seismic zone and dehydration embrittlement of the subducting slab

    NASA Astrophysics Data System (ADS)

    Yamasaki, Tadashi; Seno, Tetsuzo

    2003-04-01

    Dehydration embrittlement of metamorphosed oceanic crust and mantle in the subducting slab may be responsible for the occurrence of intermediate-depth earthquakes. We explore the possibility that this hypothesis can explain the morphology of the double seismic zones observed in northeast Japan, southwest Japan, northeast Taiwan, northern Chile, Cape Mendocino, and eastern Aleutians. We calculate transient temperature structures of slabs based on geologically estimated subduction histories of these regions. We then determine dehydration loci of metamorphosed oceanic crust and serpentinized mantle using experimentally derived phase diagrams. The depth range of the dehydration loci of metamorphosed oceanic crust and serpentine is dependent on slab age. The dehydration loci of serpentine produce a double-layered structure. Because the upper dehydration loci of serpentine are mostly located in the wedge mantle above the slab, we regard the upper plane seismicity representing dehydration embrittlement in the oceanic crust, and we fix the slab geometry so that the upper plane seismicity is just below the upper surface of the slab. We find that the lower plane seismicity is located at the lower dehydration loci of serpentine, which indicates that the morphology of the double seismic zones is consistent with the dehydration embrittlement.

  19. 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

  20. Structural vulnerability assessment using reliability of slabs in avalanche area

    NASA Astrophysics Data System (ADS)

    Favier, Philomène; Bertrand, David; Eckert, Nicolas; Naaim, Mohamed

    2013-04-01

    Improvement of risk assessment or hazard zoning requires a better understanding of the physical vulnerability of structures. To consider natural hazard issue such as snow avalanches, once the flow is characterized, highlight on the mechanical behaviour of the structure is a decisive step. A challenging approach is to quantify the physical vulnerability of impacted structures according to various avalanche loadings. The main objective of this presentation is to introduce methodology and outcomes regarding the assessment of vulnerability of reinforced concrete buildings using reliability methods. Reinforced concrete has been chosen as it is one of the usual material used to build structures exposed to potential avalanche loadings. In avalanche blue zones, structures have to resist to a pressure up to 30kPa. Thus, by providing systematic fragility relations linked to the global failure of the structure, this method may serve the avalanche risk assessment. To do so, a slab was numerically designed. It represented the avalanche facing wall of a house. Different configuration cases of the element in stake have been treated to quantify numerical aspects of the problem, such as the boundary conditions or the mechanical behaviour of the structure. The structure is analysed according to four different limit states, semi-local and global failures are considered to describe the slab behaviour. The first state is attained when cracks appear in the tensile zone, then the two next states are described consistent with the Eurocode, the final state is the total collapse of the structure characterized by the yield line theory. Failure probability is estimated in accordance to the reliability framework. Monte Carlo simulations were conducted to quantify the fragility to different loadings. Sensitivity of models in terms of input distributions were defined with statistical tools such as confidence intervals and Sobol's indexes. Conclusion and discussion of this work are established to

  1. Nd:glass slab laser for x-ray lithography

    NASA Astrophysics Data System (ADS)

    Reed, Murray K.; Byer, Robert L.

    1990-08-01

    A Nd:Glass laser has been used to generate laser produced plasmas (LLP). The plasma emission in the keV range useful for X-ray lithography has been measured. Lithography with sub-micron linewidths has been demonstrated with a thin absorbing mask. The Nd:Glass slab laser is operated in a Q-switched one-dimensional unstable resonator. The resulting beam quality is a few times diffraction limited and is focused to an area less than the lO cm2 in our vacuum chamber. We have operated at 5 J up to 4 Hz repetition rate without any degradation of the laser output. Injection mode locking of the Nd:Glass laser with 0.7 ns pulses increases the intensity of the Q-switched laser output by about a factor of 10 and allows us to achieve a total integrated pulse length of less than 10 ns. Optical damage limits the laser intensity. The damage threshold for injection mode locked pulses focused into a Nd:Glass slab outside the laser cavity is about 20 J/cm2. However, we have observed another damage mechanism at lower intensities in Nd:Glass slabs in use in the laser head. Brown discoloration occurs in filaments along the laser beam path and we believe solarization with the help of self-focusing and the ultra- violet flashlamp radiation may be occuring. We are still investigating this phenomenon but at present it is limiting the laser output to only 2 J per pulse. The focused laser intensity is 2.1013 W/cm2 on a solid copper target in our vacuum chamber. The plasma emission in the keV X-ray range has been measured through a variety of thin film X-ray filters with a Hamamatsu micro-channel plate detector. Using the published values for the detector quantum efficiency, the micro-channel plate gain, and the filter's transmission spectra, we estimate that the conversion efficiency in the plasma from laser radiation to soft X-rays of energy greater than 0.5 keV is around 2%. We have performed single-level demonstration exposures of PNMA resist through a 10 im thick aluminised Kapton debris

  2. 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

  3. 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.

  4. 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

  5. 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

  6. Polarization effects in active Fresnel rhomb zig-zag slab amplifier

    SciTech Connect

    Bikmatov, R.G.; Chernyak, V.M.; Ignat`ev, L.P.; Kuznetsov, V.G.; Pergament, M.I.; Smirnov, R.V.; Sokolov, V.I.; Hunt, J.T.; Manes, K.

    1997-01-27

    The concept to use a slab as active element, working in zig-zag geometry, and also as Fresnel rhomb, seems to be rather attractive. However, in this case different depolarization effects in active element arc of crucial importance. We have carried out the estimations of depolarization effects arising both due to mechanical loading of an active element at its fastening and due to thermooptical distortions. To check up these rigid requirements to depolarization (0.1 % - 0.01 %) careful measurements of depolarization effects and their sources are being carried out. Mechanical loading gives one of the main contributions in depolarization at fastening of active element. Using model experiments with glass Fresnel rhomb under mechanical loading we have measured depolarization effects. It is proposed to use additional glass plate to compensate beam depolarization in zig-zag slab. The received results allow to expect successful use of the slab amplifier as a Fresnel rhomb providing rather high quality of optical material of active clement.

  7. Analytical and numerical treatment of drift-tearing and resistive drift instabilities in plasma slab

    NASA Astrophysics Data System (ADS)

    Mirnov, V. V.; Hegna, C. C.; Sauppe, J. P.; Sovinec, C. R.

    2015-11-01

    We consider modification to linear resistive MHD instability theory in a slab due to two categories of non-MHD effects: (1) electron and ion diamagnetic flows caused by equilibrium pressure gradients and (2) electron and ion decoupling on short scales associated with kinetic Alfven and whistler waves. The relationship between the expected stabilizing response due to the effects (1) and the destabilizing contribution caused by the dispersive waves (2) is investigated. An analytic solution combining the effect of diamagnetic flows and the ion-sound gyroradius contribution is derived using a perturbative approach. Linear numerical simulations using the NIMROD code are performed with cold ions and hot electrons in plasma slab with a doubly periodic box bounded by two perfectly conducting walls. Configurations with magnetic shear are unstable to current-driven drift-tearing instability. A second linearly unstable resistive drift type mode with largely electrostatic perturbations is also observed in simulations. The resistive-drift mode is suppressed by magnetic shear in unbounded domains but can remain unstable in the simulations with finite slab thickness and perfectly conducting wall. Additionally, the growth rate is sensitive to the magnetic shear length. We analyze whether these modes can be unstable in cylindrical configurations with magnetic shear typical for reversed field pinches. The material is based on work supported by the U.S. DOE and NSF.

  8. 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.

  9. Ignition transient of a polymethylmethacrylate slab in a sudden-expansion combustor

    SciTech Connect

    Yang, J.T.; Wu, C.Y.Y.; Din, S.J. . Dept. of Power Mechanical Engineering)

    1994-08-01

    Ignition and the subsequent flame development of a polymethylmethacrylate (PMMA) slab in a sudden-expansion combustor was observed experimentally. The solid fuel was ignited by a hot oxidizing flow stream that was supplied by a wind tunnel. The controlled variables of the experiment were: step height (17--29 mm), inlet flow velocity (15--30 m/s), and inlet gas temperature (700--850 C). The oxygen concentration of the gas stream was 13%. The ignition process generally initiated in the recirculation zone, but occasionally occurred near the end of the fuel slab at high temperature of the gas and small velocity of the flow. The results show that high temperature and a high step height favored ignition, broadened the ignition limits and abbreviated the ignition delay. The interval of the flame development was about 0.1 s when ignition occurred in the recirculation zone but 0.9 s for ignition near the end of the fuel slab. As the step height increased, the opposed flame spread rate increased, but the rate of concurrent flame spread decreased. In this work, the rate of opposed flame spread was 0.2--7.7 m/s and that of concurrent flame spread was 9.6--18.3 m/s.

  10. Imaging the slab beneath central Chile using the Spectral Elements Method and adjoint techniques

    NASA Astrophysics Data System (ADS)

    Mercerat, E. D.; Nolet, G.; Marot, M.; Deshayes, P.; Monfret, T.

    2010-12-01

    This work focuses on imaging the subducting slab beneath Central Chile using novel inversion techniques based on the adjoint method and accurate wave propagation simulations using the Spectral Elements Method. The study area comprises the flat slab portion of the Nazca plate between 29 S and 34 S subducting beneath South America. We will use a database of regional seismicity consisting of both crustal and deep slab earthquakes with magnitude 3 < Mw < 6 recorded by different temporary and permanent seismological networks. Our main goal is to determine both the kinematics and the geometry of the subducting slab in order to help the geodynamical interpretation of such particular active margin. The Spectral Elements Method (SPECFEM3D code) is used to generate the synthetic seismograms and it will be applied for the iterative minimization based on adjoint techniques. The numerical mesh is 600 km x 600 km in horizontal coordinates and 220 km depth. As a first step, we are faced to well-known issues concerning mesh generation (resolution, quality, absorbing boundary conditions). In particular, we must evaluate the influence of free surface topography, as well as the MOHO and other geological interfaces in the synthetic seismograms. The initial velocity model from a previous travel-time tomography study, is linearly interpolated to the Gauss-Lobatto-Legendre grid. The comparison between the first forward simulations (up to 4 seconds minimum period) validate the initial velocity model of the study area, although many features not reproduced by the initial model have already been identified. Next step will concentrate in the comparison between finite-frequency kernels calculated by travel-time methods with ones based on adjoint methods, in order to highlight advantages and disadvantages in terms of resolution, accuracy, but also computational cost.

  11. Aegean tectonics: Strain localisation, slab tearing and trench retreat

    NASA Astrophysics Data System (ADS)

    Jolivet, Laurent; Faccenna, Claudio; Huet, Benjamin; Labrousse, Loïc; Le Pourhiet, Laetitia; Lacombe, Olivier; Lecomte, Emmanuel; Burov, Evguenii; Denèle, Yoann; Brun, Jean-Pierre; Philippon, Mélody; Paul, Anne; Salaün, Gwenaëlle; Karabulut, Hayrullah; Piromallo, Claudia; Monié, Patrick; Gueydan, Frédéric; Okay, Aral I.; Oberhänsli, Roland; Pourteau, Amaury; Augier, Romain; Gadenne, Leslie; Driussi, Olivier

    2013-06-01

    We review the geodynamic evolution of the Aegean-Anatolia region and discuss strain localisation there over geological times. From Late Eocene to Present, crustal deformation in the Aegean backarc has localised progressively during slab retreat. Extension started with the formation of the Rhodope Metamorphic Core Complex (Eocene) and migrated to the Cyclades and the northern Menderes Massif (Oligocene and Miocene), accommodated by crustal-scale detachments and a first series of core complexes (MCCs). Extension then localised in Western Turkey, the Corinth Rift and the external Hellenic arc after Messinian times, while the North Anatolian Fault penetrated the Aegean Sea. Through time the direction and style of extension have not changed significantly except in terms of localisation. The contributions of progressive slab retreat and tearing, basal drag, extrusion tectonics and tectonic inheritance are discussed and we favour a model (1) where slab retreat is the main driving engine, (2) successive slab tearing episodes are the main causes of this stepwise strain localisation and (3) the inherited heterogeneity of the crust is a major factor for localising detachments. The continental crust has an inherited strong heterogeneity and crustal-scale contacts such as major thrust planes act as weak zones or as zones of contrast of resistance and viscosity that can localise later deformation. The dynamics of slabs at depth and the asthenospheric flow due to slab retreat also have influence strain localisation in the upper plate. Successive slab ruptures from the Middle Miocene to the Late Miocene have isolated a narrow strip of lithosphere, still attached to the African lithosphere below Crete. The formation of the North Anatolian Fault is partly a consequence of this evolution. The extrusion of Anatolia and the Aegean extension are partly driven from below (asthenospheric flow) and from above (extrusion of a lid of rigid crust).

  12. 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.

  13. Transverse Crack Modeling of Continuously Casted Slabs through Finite Element Method in Roughing Rolling at Wide Strip Mill

    NASA Astrophysics Data System (ADS)

    Pesin, A.; Salganik, V.; Pustovoytov, D.

    2010-06-01

    In the pipe billet production at the wide strip mills of hot rolling big metal losses are caused by surface defects that affect most parts of the finished strips. The rolling surface defects are referred to the breach of steelmaking technology. Specialists mostly face defects of metal surface such as "scab" and "crack". The only area suffered from these defects is a slab edge. This area has the least surface temperature at the unbending of the continuous-casting machine, and together with deep buckles made by reciprocating motion of the crystallizer it is mostly subjected to transverse cracks that can be up to several millimeters. Each surface defect of the continuously casted slab will further turn into the surface defect of the strip bar. For some grade sets, mostly made of pipe steel grades the amount of strips with these defects can reach up to 60-70%. The area that is mostly prone to these defects is the edge of the strip. The work reveals investigation of the form change peculiarities in the transverse cracks of the continuously casted slab in roughing rolling in the horizontal rollers. The finite element method with software DEFORM 3D V6.1 has been applied in modeling. The work gives a form change mechanism of transverse cracks of slabs in deformation. Further crack growth in rolling is assessed due to Cockroft-Latham criteria.

  14. 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

  15. 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

  16. Slab laser development at MSNW - The Gemini and Centurion systems

    NASA Astrophysics Data System (ADS)

    Eggleston, J. M.; Albrecht, G. F.

    Two, zig-zag-optical-path, slab-geometry, solid-state lasers, referred to as Gemini and Centurion, are described. The Nd:glass laser (Gemini) uses a pump geometry in which the flash lamps are located between two slabs in the same laser head. The dimensions and functions of the glass slabs are studied and the single-sided pumping of the Nd:glass laser is examined. The system is verified using the Nd:YAG laser system (Centurion). The Centurion system uses four flash lamps to pump a single 6 mm x 2 cm x 15.5 cm Nd:YAG slab; the reflector structure of the system is analyzed. The thermal-optical model for the Nd:glass laser and the Trace 3D, a three-dimensional flashlamp-slab coupling code, are evaluated. The oscillation performance and defocusing of a single-pass beam are measured; it is observed that the single-sided pump output is 30 percent more efficient than the standard configuration and no major defocusing effect is detected. The use of the Trace 3D code to design a reflector system for Gemini is discussed.

  17. The effect of metastable pyroxene on the slab dynamics

    NASA Astrophysics Data System (ADS)

    Agrusta, R.; Van Hunen, J.; Goes, S. D. B.

    2014-12-01

    Global seismic studies show variations near the base of mantle transition zone, where some slabs penetrate straight into the lower mantle, whereas others seem to flatten. The dynamics of cold subducting slabs are mainly controlled by negative thermal buoyancy forces and by buoyancy anomalies due to density contrasts of the different mineralogical phases. Recent experiments show that pyroxene dissolves into the denser garnet, forming the majorite-garnet, at very slow rates, and pyroxene can remain metastable to temperatures as high as 1400 °C.Because metastable pyroxene may potentially persist in subduction zones over large volumes and to great depths, a self-consistent subduction model has been used to investigate the influence of metastable phase on the dynamics of subducting oceanic lithosphere. The phase boundary of pyroxene to garnet (300 km equilibrium depth) is considered together with the phase transition of olivine to wadsleyite (410 km equilibrium), and ringwoodite to perovskite-magnesiowustite (670 km equilibrium). The kinetics of the phase transition for ol-wd and in px-gt are treated considering a temperature-dependent diffusion rate. To quantify the buoyant contributions of the metastable phase on the subduction dynamics, an extensive parameter sensitivity study has been performed.Results from this study illustrate that metastable pyroxene affects slab buoyancy at least as much as olivine metastability. Slab age and phase change kinetics are the most dominant parameters, and buoyancy effects are stronger for old subducting lithosphere and for low diffusion rates, favouring slab stagnation in the transition zone.

  18. 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

  19. 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

  20. 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.

  1. Numerical modeling of outer rise deformation in the Tonga subduction system: Coupling between outer rise deformation, slab weakening and plate velocities

    NASA Astrophysics Data System (ADS)

    Naliboff, J. B.; Billen, M. I.; Gerya, T.; Saunders, J. K.

    2012-12-01

    During subduction, bending and flexure of oceanic lithosphere generates a topographic bulge seaward of the trench known as the outer rise, which commonly exhibits extensional deformation attributed to slab pull forces and bending stresses. The resulting brittle and viscous deformation may play a significant role in long-term geodynamic processes by limiting the ability of subducted oceanic lithosphere to act as a stress guide driving surface plate motions through slab pull. Recent numerical studies provide varying estimates of slab pull's contribution to surface plate motions [e.g., van Summeren et al. 2012, Ghosh & Holt 2012], while observational constraints suggest old oceanic lithosphere may weaken by 3-4 orders of magnitude as it bends and descends beneath the overriding plate [Arredondo & Billen, 2012]. Preliminary numerical models of outer rise deformation during oceanic-continental convergence (40 Myr oceanic lithosphere) exhibit 10x-150x viscous weakening in the upper plate near the trench, with time-dependent variations related to both changes in slab depth and downgoing-overriding plate coupling (Naliboff et al., in prep). In order to more closely examine the relationship between outer rise deformation, geophysical observations and plate velocities, we consider 2D subduction models of the Tonga subduction system where flow will be strictly driven by upper mantle slab buoyancy as defined by the Slab1.0 model [Hayes et al. 2012]. The resulting subducting plate deformation patterns are compared to observations of outer rise faulting, elastic thickness measurements and outer rise seismicity. While keeping buoyancy forces fixed, we will examine the role of brittle rheology, hydration and downgoing-overriding plate coupling in patterns of subducting plate deformation. These results will provide improved physical understanding of the relationship between slab pull, plate velocities and downgoing plate weakening, and a basis for future work examining the role of

  2. The Tonga-Vanuatu Subduction Complex -- a Self-Optimized 3D Slab-Slab-Mantle Heat Pump

    NASA Astrophysics Data System (ADS)

    McCreary, J. A.

    2008-12-01

    Recently published geophysical and geochemical data and increasingly actualistic free subduction models prompted a fresh look at 2 classics hinting, in combination, that a coupled 3D slab-slab-upper mantle interaction (Scholz and Campos, 1995; full citations at URL below) might power the prodigious surface heat dissipation (Lagabrielle et al., 1997) characterizing one of Earth's most remarkable tectonomagmatic systems, the Tonga-Vanuatu Subduction Complex (TVSC). The 3D TVSC includes (1) the kinematically, magmatically, and bathymetrically distinct North Tonga (NT, 14-26° S) and South Vanuatu (SV, 16-23° S) trenches and slabs, (2) the shared NT-SV backarc, and (3) entrained mobile upper mantle (MUM). That Earth's greatest convergence, rollback, and spreading rates; most disseminated spreading (the North Fiji Basin (NFB) ridge swarm); and greatest concentration of aggregate active ridge length coincide in a 1,500 km TVSC can't be accidental. To the north and south, the respective active NT and SV trenches swing abruptly 90° counterclockwise into continuity with the Vitiaz and Hunter fossil trenches, both active in the Late Miocene but now sinistral strike-slip loci standing over long exposed PA and AU slab edges. These 2 active-fossil trench pairs bracket a hot, shallow and geophysically and geochemically exceptional TVSC interior consisting of 2 rapidly spreading backarcs set back-to-back in free sublithospheric communication: The Lau-Havre NT backarc on the east and the ridge-infested SV backarc (NFB) on the west. The NFB and adjacent North Fiji Plateau make up the unplatelike New Hebrides-Fiji Orogen (Bird, 2003). As in the western Aleutians, the NT-Vitiaz and SV-Hunter subduction-to-strike-slip transitions (SSSTs) stand above toroidal fluxes of hot, dry PA and AU MUM driven along-trench and around the free NT and SV slab edges from subslab to supraslab regions by dynamic pressure gradients powered by slab free-fall and induced viscous couplings. These edge

  3. 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.

  4. Search for deep slabs in the Northwest Pacific mantle.

    PubMed

    Zhou, H W; Anderson, D L

    1989-11-01

    A residual sphere is formed by projecting seismic ray travel-time anomalies, relative to a reference Earth model, onto an imaginary sphere around an earthquake. Any dominant slab-like fast band can be determined with spherical harmonic expansion. The technique is useful in detecting trends associated with high-velocity slabs beneath deep earthquakes after deep-mantle and near-receiver effects are removed. Two types of corrections are used. The first uses a tomographic global mantle model; the second uses teleseismic station averages of residuals from many events over a large area centered on the events of interest. Under the Mariana, Izu-Bonin, and Japan trenches, the dominant fast bands are generally consistent with seismicity trends. The results are unstable and differ from the seismicity trend for Kurile events. The predominant fast band for most deep earthquakes under Japan is subhorizontal rather than near vertical. We find little support for the deep slab penetration hypothesis. PMID:16594080

  5. 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

  6. Controlling of optical bistability and multistability in a defect slab

    NASA Astrophysics Data System (ADS)

    Jabbari, Masoud

    2016-02-01

    Optical bistability (OB) and optical multistability (OM) due to wide applications in all-optical switching and transistors is studied in this paper. Here, we study the OB and OM properties of incident light in a defect slab doped by a GaAs quantum well (QW) nanostructure. It is shown that OB and OM features can be manipulated by spin coherence created by circular polarized laser fields in GaAs QWs. The impacts of laser field features, such as intensity, frequency detuning, and relative phase, on OB and OM are simulated. Moreover, the dependence of OB and OM features of a probe light on the thickness of the slab, then, are analyzed. It is found that the thickness of the slab can provide a new way to optimize the intensity threshold of OB and OM. We hope that our proposed model may be useful for developing all-optical devices on nanoscales.

  7. 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

  8. 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

  9. 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.

  10. 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.