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Sample records for ailao shan shear

  1. Midcrustal shearing and doming in a Cenozoic compressive setting along the Ailao Shan-Red River shear zone

    NASA Astrophysics Data System (ADS)

    Zhang, B.; Yin, C. Y.; Zhang, J. J.; Wang, J. M.; Zhong, D. L.; Wang, Y.; Lai, Q. Z.; Yue, Y. H.; Zhou, Q. Y.

    2017-01-01

    The Cenozoic Xuelong Shan antiformal dome is located along the northern segment of the Ailao Shan-Red River shear zone in Yunnan, China. Subhorizontal foliation in the gneiss core is recognized, representing a broad top-to-NE shear initiated under amphibolite facies conditions and propagating into greenschist facies in the mantling schist and strike-slip shear zone. Microfabrics of crystallographic-preferred orientations (CPOs) in quartz suggest that the deformation temperatures increased with increasing structural depth from the upper crust (300-500°C) in the mantling schist to the midcrust (15 km or more, ≥650°C) in the gneissic core. This trend is mirrored by variations in the metamorphic grade of the syn-kinematic mineral assemblages and microstructures, which range from garnet + amphibole + biotite + sillimanite + rutile + feldspar in the core to garnet + staurolite + biotite + epidote + muscovite within the limb units. The dome experienced the following deformation history: (1) a broad top-to-NE shear in the subhorizontal foliation of the gneiss core during the first stage of deformation (D1); (2) opposing reverse-sense shear along the two schist limbs of the dome during contraction-related doming (D2-D3); (3) sinistral strike-slip shearing within the eastern limb (D4); and (4) extensional deformation (D5). The structural-thermal patterns suggest the antiformal dome formation was roughly coeval with top-to-NE ductile shearing in the midcrust of Tibet at 32 Ma or earlier. A major implication is that there was a phase of contractional ductile deformation in the region prior to the initiation of strike-slip deformation.

  2. Timing of initiation of left-lateral shearing along the Ailao Shan-Red River shear zone: microstructural and geochronological constraints from high temperature mylonites in Diancang Shan, SW China

    NASA Astrophysics Data System (ADS)

    Cao, S.; Liu, J.; Leiss, B.; Neubauer, F.; Genser, J.

    2009-04-01

    The high grade metamorphic massifs (e.g. Xuelong Shan, Diancang Shan, Ailao Shan in China and Day Nui Con Voi metamorphic massif in Vietnam) along the Ailao Shan-Red River shear zone in Southwestern China bear much information on the large-scale left-lateral strike-slip shearing in eastern Tibet during Indian-Eurasian plate collision and post-collisional accommodation process in late Oligocene-early Miocene. The metamorphic massifs are narrow zones bounded by brittle faults. Low-grade metamorphic rocks are lying on the west and sedimentary rocks to the east. Rocks in these massifs are partly sheared with widespread occurrence of high temperature mylonites that have subhorizontal stretching lineations. Left-lateral shearing is indicated by mesoscale and microscale shear indicators in the mylonites. Debates exist on the timing of initiation and duration of left-lateral shearing, and mechanism of exhumation of the high grade metamorphic rocks along Ailao Shan Red River shear zone. The Diancang Shan complex, a typical metamorphic massif, is constituted by three units, i.e. a central high strain shear zone, a western low-grade metamorphic volcanic-sedimentary sequence in the Lanping basin, and an eastern superimposed retrograde metamorphic belt. The central high grade metamorphic complex consists of metamorphic rocks of amphibolite facies conditions. High-grade metamorphic mineral assemblages and structural elements indicate a deep level crustal metamorphism and deformation of the rocks. L-tectonites are typical indicators of high-temperature deformation in the highly sheared granitic mylonites. Widespread occurrence of different shear criteria (e.g. sheared veins, sigmoid and delta -porphyroclasts) suggests that these gneisses experienced very intensive high-temperature progressive left-lateral strike-slip shearing. A large synkinematic augen monzogranitic intrusion is recognized in the central belt by the present work. The intrusion has an obvious porphyritic texture

  3. Ductile and Brittle Neogene Deformation of Late Permian Orthogneiss in the Northern Ailao Shan-Red River Shear Zone: View from the Xuelong Shan Block

    NASA Astrophysics Data System (ADS)

    Wintsch, R. P.; Yi, D.; Yi, K.; Wang, Q. F.; Wang, G. H.

    2014-12-01

    ASRRSZ based on data obtained in the southern Diancang Shan block. Permian granitoids were intruded and ductily deformed in the Early Triassic. The left lateral shearing that brought these blocks to the surface was delayed until the Neogene extrusion of the Indochina block.

  4. Petrology, geochemistry, and metamorphic evolution of meta-sedimentary rocks in the Diancang Shan-Ailao Shan metamorphic complex, Southeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Wang, Fang; Liu, Fulai; Liu, Pinghua; Shi, Jianrong; Cai, Jia

    2016-07-01

    -grained biotite-muscovite-bearing symplectites were formed, which occur at the grain boundaries of garnet and felsic minerals; such assemblage as Bt + Ms + Pl ± Kfs ± Grt + Qz were formed at 553-613 °C and 4.0-5.0 kb. The metamorphic history of the Diancang Shan-Ailao Shan metamorphic complex is thus defined by a clockwise P-T trajectory which includes a nearly isothermal decompression recording the subduction, collision and exhumation events between the Yangtze and Indochina blocks at Oligocene to Early Miocene, prior to the regional strong left-lateral shearing along the Ailao Shan-Red River Fault.

  5. Late Cenozoic tectonic evolution of the Ailao Shan-Red River fault (SE Tibet): Implications for kinematic change during plateau growth

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Zhang, Bo; Schoenbohm, Lindsay M.; Zhang, Jinjiang; Zhou, Renjie; Hou, Jianjun; Ai, Sheng

    2016-08-01

    Surface uplift, river incision, shear zone exhumation, and displacement along active faults have all interacted to shape the modern landscape in the southeastern margin of the Tibetan Plateau. The Ailao Shan-Red River fault, a major structure in the tectonic evolution of southeastern Asia, is an excellent recorder of these processes. We present new stratigraphic, structural, and low-temperature thermochronologic data to explore its late Cenozoic tectonic and geomorphic evolution. The stratigraphic and structural observations indicate that the major bend in the fault was a releasing bend with significant Miocene sedimentation in the early-middle Miocene but became a restraining bend with abundant shortening structures developed after the late Miocene reversal of displacement. We also document exhumation of the shear zone from two low-temperature thermochronologic transects. New apatite (U-Th)/He(AHe) data and published thermochronologic results reveal two accelerated cooling episodes, backed by stratigraphic and geomorphic observations. The first rapid cooling phase occurred from ca. 27 to 17 Ma with removal of cover rocks and exhumation of the shear zone. The second accelerated cooling episode revealed by our AHe data commenced at 14-13 Ma, lasting 2-3 Myr. The Ailao Shan range may have risen to its modern elevation with high-relief topography developing due to river incision. We interpret the onset of this rapid exhumation to reflect renewed plateau growth associated with lower crustal flow.

  6. Potassic magma genesis and the Ailao Shan-Red River fault

    NASA Astrophysics Data System (ADS)

    Flower, Martin F. J.; Hoàng, Nguyễn; Lo, Chinh-hua; Chí, Cung Thu'ọ'ng; Cu'ò'ng, Nguyễn Quốc; Liu, Fu-tian; Deng, Jin-fu; Mo, Xuan-xue

    2013-09-01

    Two types of K-rich magma of Eocene to Early Oligocene (ca. 40-30) and Plio-Pleistocene (ca. 5-0.1 Ma) age were emplaced prior to and following left-lateral slip on the Ailao Shan-Red River (ASRR) fault, a regional shear zone extending between southwest China and the Tonkin Gulf (South China Sea) that accommodated 'escape' of the Indochina block. The first type is exposed in the Dali-Lijiang and adjacent regions of western Yunnan and Sichuan and comprises ultramafic potassic to ultrapotassic 'absarokites' and their shoshonite, banakite, and SiO2-rich derivatives which were emplaced immediately prior to activation of the ASRR fault. They are characterized by high Mg.-nos, and low contents of fusible oxides (FeO*, CaO, Al2O3), for equivalent MgO content, and pronounced primitive mantle-normalized high-field strength element (HFSE) depletions. In contrast, 'post-escape' K-rich magmas were erupted in the Puer, Maguan-Pingbian regions of south and southeast Yunnan. Apart from their relative enrichments in potassium they show typical HFSE-rich intra-plate compositional affinity. Geological and geomorphic evidence, and thermochronologic age dating of metamorphisc events, suggest that left-lateral shearing occurred between ca. 30 and 17 Ma; thereby accommodating the southeastward 'escape' of Indochina and (possibly) two episodes of spreading in the South China Sea. The southwestern part of Dali-Lijiang magmatic products was detached and offset by ca. 600 km and are now located in Phan Xi Pang in northern Viet Nam. The same is true for the Permo-Triassic Emeishan flood basalts, whose western exposures were likewise displaced by the same amount and are now represented by the Song Da complex, also in northern Viet Nam. Here, we report geochemical, isotopic, and 40Ar/39Ar age data for samples from both the 'pre-escape' Dali-Lijiang magmas and the 'post-escape' K-rich Puer, Maguan-Pingbian basalts and basanites, with a view to comparing and contrasting their interpolated source

  7. Shear velocity model for the Kyrgyz Tien Shan from joint inversion of receiver function and surface wave data

    NASA Astrophysics Data System (ADS)

    Gilligan, Amy; Roecker, Steven W.; Priestley, Keith F.; Nunn, Ceri

    2014-10-01

    The Tien Shan is the largest active intracontinental orogenic belt on Earth. To better understand the processes causing mountains to form at great distances from a plate boundary, we analyse passive source seismic data collected on 40 broad-band stations of the MANAS project (2005-2007) and 12 stations of the permanent KRNET seismic network to determine variations in crustal thickness and shear wave speed across the range. We jointly invert P- and S-wave receiver functions with surface wave observations from both earthquakes and ambient noise to reduce the ambiguity inherent in the images obtained from the techniques applied individually. Inclusion of ambient noise data improves constraints on the upper crust by allowing dispersion measurements to be made at shorter periods. Joint inversion can also reduce the ambiguity in interpretation by revealing the extent to which various features in the receiver functions are amplified or eliminated by interference from multiples. The resulting wave speed model shows a variation in crustal thickness across the range. We find that crustal velocities extend to ˜75 km beneath the Kokshaal Range, which we attribute to underthrusting of the Tarim Basin beneath the southern Tien Shan. This result supports the plate model of intracontinental convergence. Crustal thickness elsewhere beneath the range is about 50 km, including beneath the Naryn Valley in the central Tien Shan where previous studies reported a shallow Moho. This difference apparently is the result of wave speed variations in the upper crust that were not previously taken into account. Finally, a high velocity lid appears in the upper mantle of the Central and Northern part of the Tien Shan, which we interpret as a remnant of material that may have delaminated elsewhere under the range.

  8. Orientation-related deformation mechanisms of naturally deformed amphibole in amphibolite mylonites from the Diancang Shan, SW Yunnan, China

    NASA Astrophysics Data System (ADS)

    Cao, Shuyun; Liu, Junlai; Leiss, Bernd

    2010-05-01

    Sheared amphibolite rocks from Diancang Shan high-grade metamorphic complex along the Ailao Shan-Red River shear zone, southwestern Yunnan, China, show typical mylonitic microstructures. The mylonites are characterized by porphyroclastic microstructures and the ultramylonites are highly lineated with alternating amphibole- and quartzofeldspathic domains. Microstructural analysis and P/T estimation suggest that the amphibole grains in the mylonitic rocks are deformed and dynamically recrystallized at amphibolite facies. In the mylonitic amphibolites, there are two types of amphibole porphyroclasts, i.e. type I "hard" and type II "soft" porphyroclasts. They have their [001] crystallographic orientations subnormal and sub-parallel to the stretching lineation of the rocks, respectively. The two types of porphyroclasts show distinct deformation microstructures and sub-microstructures formed by various deformation mechanisms, which contribute in different ways to the generation of the fine-grained matrix. Shape preferred orientation analysis, misorientation analysis of the two types of porphyroclasts and new fine grains around them further prove the generation of the fine grains in matrix from the type II porphyroclasts. The type I "hard" porphyroclasts are deformed mainly by mechanical rotation, work hardening and intragranular microfracturing. In contrast, the deformation of the type II "soft" porphyroclasts is mainly attributed to crystalline plasticity, i.e. twinning, dislocation creep and dynamic recrystallization. During the deformation of the type II porphyroclasts, the (100) [001] slip system plays a dominant role during deformation and grain size reduction of amphibole. Twinning along the active (100) slip system, in combination with dislocation creep (gliding and climbing) governs the nucleation of subgrains and formation of dynamically recrystallized fine grains, a process here named Twinning Nucleation Recrystallization.

  9. New thermochronological constraints on the timing of shear from the Khlong Marui and Ranong faults, Peninsular Thailand: implications for Himalayan lateral extrusion.

    NASA Astrophysics Data System (ADS)

    Watkinson, I.; Elders, C.; Hall, R.

    2009-04-01

    New Ar-Ar data from the strike-slip faults of Peninsular Thailand indicate rapid uplift of mid-crustal ductile shear zones during the Eocene. The cooling ages are consistent with a northwards younging pattern of Ar-Ar cooling ages from the NW-trending Three Pagodas and Mae Ping faults in Northern Thailand, to the Ailao Shan-Red River fault in Vietnam and Yunnan, taken to reflect the northwards movement of India during the Cenozoic. The peninsular structures: the Khlong Marui fault (KMF) and Ranong fault (RF), are major NNE trending strike-slip faults of respectively 220 km and 420 km length. Exposed mylonitic rocks bear consistently dextral kinematic indicators, unlike the sinistral mylonites of the NW-trending structures to the north. Brittle strike-slip and dip-slip faults overprint all the shear zones. Rocks ranging from low grade mylonites to syn-kinematic amphibolite facies migmatites from the RF and KMF yield similar biotite Ar-Ar cooling ages, suggesting that uplift from all depths in the shear zone was rapid. Retrograde shear fabrics in places show that dextral shear may have continued during uplift. While the new thermochronological data show that the peninsular mylonites cooled during the Eocene, constraint from pre- and post-kinematic granitoids strongly suggests that ductile shear occurred during the Late-Cretaceous to Paleocene. Since this is well before the onset of India-Eurasia collision, much of the ductile shear must pre-date that orogeny, and therefore cannot be related to Himalayan lateral extrusion, as has been speculated. The regional cooling pattern, however, shows that Indian indentation may have triggered progressive northward exhumation of mylonitic rocks. If the model of the peninsular faults is applied to the NW-trending faults in northern Thailand, then a pre-Himalayan history may also be recorded by those mylonites, rather than a simple, lateral extrusion-related history.

  10. Exhumation history of the Red River shear zone in northern Vietnam: New insights from zircon and apatite fission-track analysis

    NASA Astrophysics Data System (ADS)

    Viola, G.; Anczkiewicz, R.

    2008-06-01

    A new set of zircon and apatite fission-track ages from the Ailao Shan and Day Nui Con Voi (DNCV) metamorphic massifs of the Red River shear zone (RRSZ) and neighboring rocks in northern Vietnam is presented. A complex, along-strike diachronous, denudation history is revealed. The southern sector of the DNCV cooled to about 100 °C by the Late Oligocene, whereas its central compartment was affected by the later thermotectonic evolution of the Song Chay dome to the E of the RRSZ, whose final exhumation occurred during the Early Miocene. The northern sector of the RRSZ is characterized by the 35 Ma Phan Si Pang pre- to synkinematic intrusion. Fission-track ages from a vertical section within the Phan Si Pang granite indicate rapid exhumation and cooling. The Paleozoic tectonic block to the west of the RRSZ (fission-track ages between 40 and 30 Ma) was exhumed and cooled earlier than the fault mylonite belt (fission track ages of 30 Ma and younger) and also than the eastern block. Its structural level is consistent with field observations that suggest the RRSZ in northern Vietnam to be a transtensional system, with a regional NE-SW oriented extension component.

  11. [Population and distribution of western black crested gibbon (Nomascus concolor) at Ailao Mountain, Xinping, Yunnan].

    PubMed

    Li, Guo-Song; Yang, Xian-Ming; Zhang, Hong-Yu; Li, Wei

    2011-12-01

    The western black crested gibbon (Nomascus concolor) is mainly distributed in Yunnan, China. Ailao Mountain is located in central Yunnan and divided into three prefectures and six counties. This mountain forms the principle distribution range for western black crested gibbon; however, there are no published data on the gibbon population inhabiting the Xinping administrative. Take the interview results conducted in 2007 and 2009 with local people as the reference, this study conducted an extensive field survey covering all possible habitats from November 2009 to January 2010 using call surveys. Among the one hundred and twenty-four gibbon groups which were confirmed across the Ailao Mountain, the largest known population of western black crested gibbons yet, 85 groups inhabit the national nature reserve and adjacent national forest, 30 groups inhabit the provincial nature reserve and nine groups inhabit the collective forest located outside the reserve and national forest. We found that the western black crested gibbons here have a patchy distribution pattern and occur at higher densities in certain areas. Moreover, the population distribution density and elevation gradient distribution decline from north to south. The results also demonstrated the importance of Ailao Mountain in the western black crested gibbon protection.

  12. Measuring Local Strain Rates In Ductile Shear Zones: A New Approach From Deformed Syntectonic Dykes

    NASA Astrophysics Data System (ADS)

    Sassier, C.; Leloup, P.; Rubatto, D.; Galland, O.; Yue, Y.; Ding, L.

    2006-12-01

    At the Earth surface, deformation is mostly localized in fault zones in between tectonic plates. In the upper crust, the deformation is brittle and the faults are narrow and produce earthquakes. In contrast, deformation in the lower ductile crust results in larger shear zones. While it is relatively easy to measure in situ deformation rates at the surface using for example GPS data, it is more difficult to determinate in situ values of strain rate in the ductile crust. Such strain rates can only be estimated in paleo-shear zones. Various methods have been used to assess paleo-strain rates in paleo-shear zones. For instance, cooling and/or decompression rates associated with assumptions on geothermic gradients and shear zone geometry can lead to such estimates. Another way to estimate strain rates is the integration of paleo-stress measurements in a power flow law. But these methods are indirect and imply strong assumptions. Dating of helicitic garnets or syntectonic fibres are more direct estimates. However these last techniques have been only applied in zones of low deformation and not in major shear zones. We propose a new direct method to measure local strain rates in major ductile shear zones from syntectonic dykes by coupling quantification of deformation and geochronology. We test our method in a major shear zone in a well constrained tectonic setting: the Ailao-Shan - Red River Shear Zone (ASRRsz) located in SE Asia. For this 10 km wide shear zone, large-scale fault rates, determined in three independent ways, imply strain rates between 1.17×10^{-13 s-1 and 1.52×10^{-13 s-1 between 35 and 16 Ma. Our study focused on one outcrop where different generations of syntectonic dykes are observed. First, we quantified the minimum shear strain γ for each dyke using several methods: (1) by measuring the stretching of dykes with a surface restoration method (2) by measuring the final angle of the dykes with respect to the shear direction and (3) by combining the two

  13. EDIBE PLANTS OF SHAN TRIBE OF ASSAM

    PubMed Central

    Pandey, Ashok K; Bora, H.R

    1997-01-01

    The Paper presents an accounts of wild edible food plants used by shan tribe of Assam. The shan tribe of Assam is Sino-Tibetan race of Mongoloid stock whose ancestors migrated from South –west china. They depend upon forest products for their day to day needs, i.e, food, fodder and shelter etc. Their food include leaves, tubers, bulbs, rhizomes, flowers fruits and seeds of various wild plants species which they collect from the forest. The present study was conducted during the year 1991-94 in Golaghat, Karbi-Anglong, Lakhimpur, Dibrugarh and jorhat districts of Assam. About 143 plants species were collected which are being used by shan tribe as their supplementary source of food material. PMID:22556801

  14. The coexistence of seven sympatric fulvettas in Ailao Mountains, Ejia Town, Yunnan Province

    PubMed Central

    XIA, Ji; WU, Fei; HU, Wan-Zhao; FANG, Jian-Ling; YANG, Xiao-Jun

    2015-01-01

    The coexistence of ecologically similar species sharing sympatric areas is a central issue of community ecology. Niche differentiation is required at least in one dimension to avoid competitive exclusion. From 2012-2014, by adopting the methods of mist-nets and point counts to evaluate spatial niche partitioning and morphological differentiations, we explored the coexistence mechanisms of seven sympatric fulvettas in Ailao Mountains, Ejia town, Yunnan Province, China. The microhabitats of these seven fulvettas were significantly different in elevation, roost site height and vegetation coverage, indicating a spatial niche segregation in different levels. Approximately, 90.30% of the samples were correctly classified by linear discriminant analysis (LDA) with correct rates at 91.20%-100%, except the White-browed fulvetta (Alcippe vinipectus) (65.4%) and the Streak-throated fulvetta (A. cinereiceps) (74.6%). The seven fulvettas were classified into four guilds based on their specific morphological characters, suggesting that the species in each guild use their unique feeding ways to realize resource partitioning in the overlapped areas. These finding indicate that through multi-dimensional spatial niche segregation and divergence in resource utilizing, the inter-specific competition among these seven fulvettas is minimized, whereas, coexistence is promoted. PMID:25730457

  15. Jurassic evolution of the Tien-Shan

    SciTech Connect

    Bebeshev, I.I.

    1994-09-01

    Complex studies led to identification of three stages in Jurassic deposits. The stages reflect development periods of the studied deposits. Each stage is represented by a paleogeographic map that indicates the evolution of ancient landforms in the Tien-Shan region in time and space.

  16. Cenozoic intracontinental deformation and exhumation at the northwestern tip of the India-Asia collision—southwestern Tian Shan, Tajikistan, and Kyrgyzstan

    NASA Astrophysics Data System (ADS)

    Käßner, Alexandra; Ratschbacher, Lothar; Jonckheere, Raymond; Enkelmann, Eva; Khan, Jahanzeb; Sonntag, Benita-Lisette; Gloaguen, Richard; Gadoev, Mustafo; Oimahmadov, Ilhomjon

    2016-09-01

    Along the Ghissar-Alai Range of the southwestern Tian Shan (southwestern Kyrgyzstan, northern Tajikistan), the deformation front of the India-Asia collision—the Pamir-Tibet orogen—is interacting with the intracontinental Tian Shan orogen without the intervening Tarim Craton. Apatite fission track (n = 33, 3.3-145.6 Ma, 27% <10 Ma) and (U-Th)/He (n = 32, 1.9-26.1 Ma, 56% <10 Ma) thermochronologic ages suggest approximate isothermal holding (very slow cooling to weak reheating) during relative tectonic quiescence between 150 and 15 Ma. Accelerated exhumation ( 0.2-1.0 km/Myr, median 0.5 km/Myr) and cooling (11-16°C/Myr) occurred over the last 10 Myr. Geomorphologic parameters—incision, river steepness, and concavity—confirm the youth of the southwestern Tian Shan's mountain building. High exhumation/cooling rates are correlated with pronounced local relief, produced by Cenozoic faults reactivating inherited (Late Paleozoic) structures. Regions with similarly young exhumation are centered along rims of rigid crustal blocks in the central and eastern Tian Shan. Structurally, the Ghissar-Alai Range is a broad, east trending zone of dextral transpression that includes the northern Tajik Basin (Illiak Fault Zone) and the Pamir Thrust System of the frontal northern Pamir. It is the particular deformation field at the northwestern tip of the India-Asia collision—the interaction of the westward gravitational collapse of the Pamir Plateau into the Tajik Basin with the bulk northward motion of the Pamir—that transformed the southwestern Tian Shan into a dextral transpression belt. The dextral transpression in the southwestern Tian Shan contrasts with sinistral strike-slip shear localized along inherited fault zones, accommodating dominant north-south shortening, in the central and eastern Tian Shan. The deformation field influenced by the Pamir and the associated young exhumation make the Ghissar-Alai Range a unique feature in the Tian Shan orogen.

  17. Tien Shan Geohazards Database: Earthquakes and landslides

    NASA Astrophysics Data System (ADS)

    Havenith, H. B.; Strom, A.; Torgoev, I.; Torgoev, A.; Lamair, L.; Ischuk, A.; Abdrakhmatov, K.

    2015-11-01

    In this paper we present new and review already existing landslide and earthquake data for a large part of the Tien Shan, Central Asia. For the same area, only partial databases for sub-regions have been presented previously. They were compiled and new data were added to fill the gaps between the databases. Major new inputs are products of the Central Asia Seismic Risk Initiative (CASRI): a tentative digital map of active faults (even with indication of characteristic or possible maximum magnitude) and the earthquake catalogue of Central Asia until 2009 that was now updated with USGS data (to May 2014). The new compiled landslide inventory contains existing records of 1600 previously mapped mass movements and more than 1800 new landslide data. Considering presently available seismo-tectonic and landslide data, a target region of 1200 km (E-W) by 600 km (N-S) was defined for the production of more or less continuous geohazards information. This target region includes the entire Kyrgyz Tien Shan, the South-Western Tien Shan in Tajikistan, the Fergana Basin (Kyrgyzstan, Tajikistan and Uzbekistan) as well as the Western part in Uzbekistan, the North-Easternmost part in Kazakhstan and a small part of the Eastern Chinese Tien Shan (for the zones outside Kyrgyzstan and Tajikistan, only limited information was available and compiled). On the basis of the new landslide inventory and the updated earthquake catalogue, the link between landslide and earthquake activity is analysed. First, size-frequency relationships are studied for both types of geohazards, in terms of Gutenberg-Richter Law for the earthquakes and in terms of probability density function for the landslides. For several regions and major earthquake events, case histories are presented to outline further the close connection between earthquake and landslide hazards in the Tien Shan. From this study, we concluded first that a major hazard component is still now insufficiently known for both types of geohazards

  18. GPS survey of the western Tien Shan

    NASA Technical Reports Server (NTRS)

    Molnar, Peter H.

    1994-01-01

    This report summarizes the background, field work, data collection and analysis, and future plans associated with a collaborative GPS experiment in the Tien Shan of the former Soviet Union. This project involves the amalgamation of two, separately funded projects, which were proposed separately by PIs Hamburger and Reilinger (NSF number EAR-9115159 and NASA number NAG5-1941) and Molnar and Hager (NSF number EAR9117889 and NASA number NAG5-1947). In addition, the work is being conducted under the auspices of the US-USSR Agreement on Cooperation in the Field of Environmental Protection, with support from the United States Geological Survey.

  19. GPS survey of the western Tien Shan

    NASA Technical Reports Server (NTRS)

    Hager, Bradford H.; Molnar, Peter H.; Hamburger, Michael W.; Reilinger, Robert E.

    1995-01-01

    There were two major developments in 1994 in our collaborative GPS experiment in the Tien Shan of the Former Soviet Union (FSU). Both were motivated by our expectation that we will ultimately obtain better science at lower cost if we involve our colleagues in the FSU more deeply in (1) the collection and (2) the analysis of data. As an experimental test of the concept of having our local collaborators carry out the field work semi-autonomously, we sent 6 MIT receivers to the Tien Shan for a period of 3 months. To enable our collaborators to have the capability for data analysis, we provided computers for two data analysis centers and organized a two-week training session. This report emphasizes the rationale for deeper involvement of FSU scientists, describes the training sessions, discusses the data collection, and presents the results. We also discuss future plans. More detailed discussion of background, general scientific objectives, discussions with collaborators, and results for the campaigns in 1992 and 1993 have been given in previous reports.

  20. The Bogeda Shan uplifting: Evidence from multiple phases of deformation

    NASA Astrophysics Data System (ADS)

    Chen, Ke; Lin, Wei; Wang, Qingchen

    2015-03-01

    The current topography of Central Asia is considered to have resulted from crustal shortening related to the ongoing India-Asia collision that started in the Early Tertiary period. The Bogeda Shan, a northeastern branch of the Tian Shan located in northwest China, has several summits higher than 5000 m. The northern piedmont of the Bogeda Shan exhibits remarkable deformation features that remain poorly studied. This study documents three phases of tectonic deformation in the Bogeda Shan that are related to the far-field effects of collisions along the southern Eurasian margin. Detailed field observations show that the intensively folded Upper Permian strata are covered by a subhorizontal Lower Jurassic layer, thus indicating a Triassic tectonic event that is probably related to the onset of the uplift in the Bogeda Shan during a Cimmerian orogenic episode (D1). A seismic profile suggests that this deformation episode was followed by the Late Jurassic-Early Cretaceous deformation (D2), which is characterized by wide wavelength folds overlaid by undeformed Cretaceous layers. Cenozoic thrusts were also observed in the northern piedmont of the Bogeda Shan (D3). This study demonstrates that the onset of uplift in the Bogeda Shan began in the Early Mesozoic and separated the Turfan-Hami Basin from the Junggar Basin. A new tectonic evolution model of the Bogeda Shan was reconstructed by these three tectonic phases. This work indicates that the current topography of the Bogeda Shan and its surrounding area was the result of multiple phases of deformation related to successive collisions at the southern Eurasian margin.

  1. Full Waveform 2.5D Teleseismic Surface Wave Tomography with Application to the Tien Shan

    NASA Astrophysics Data System (ADS)

    Roecker, S. W.; Priestley, K. F.; Baker, B. I.

    2011-12-01

    We adapt the 2.5D spectral domain finite difference waveform tomography algorithm of Roecker et al. (2010) to permit the analysis of teleseismically recorded surface waves. The teleseismic body wave technique of generating synthetic waveforms by specifying an analytic solution for a background wavefield in a 1D model and solving for a scattered field excited by this background is equally applicable to surface waves. We use the locked mode approach of Gomberg and Masters (1988) to calculate the background Greens functions at each point of the finite difference (FD) grid. Because of the much greater concentration of energy at the surface, we adopt the cell-based FD operators of Min et al. (2004) to calculate the free surface boundary conditions, and the generalized stretching function of Komatitch and Martin (2007) to improve the absorption in the PML. We use this algorithm to analyze broad band seismograms of events in Sumatra recorded by the MANAS array in the Tien Shan. Our results show that the upper mantle beneath much of the central Tien Shan has shear wavespeeds at least 10% lower than the lithosphere beneath the Tarim basin to the south or the Kazach shield to the north. At the same time, there appears to be a remnant lithospheric lid beneath the Kyrgyz range in the north, an observation consistent with previous receiver function studies in this area.

  2. Lithospheric structure across the central Tien Shan constrained by gravity anomalies and joint inversions of receiver function and Rayleigh wave dispersion

    NASA Astrophysics Data System (ADS)

    Li, Yonghua; Shi, Lei; Gao, Jiayi

    2016-07-01

    Shear wave velocity structure across the central Tien Shan orogeny was generated by jointly inverting Rayleigh wave phase and group velocity with teleseismic P-wave receiver functions at 40 broadband seismic stations. The inferred seismic structure was validated by forward modeling of the complete Bouguer anomaly data. The joint inversion result reveals larger crust thicknesses beneath the Kokshaal (∼68-72 km) and Kyrgyz ranges (∼62-64 km), while other units have crustal thicknesses between 48 and 58 km. A fast velocity layer (Vs = 3.6-3.9 km/s) in the upper crust is found in some seismic stations within the Kazakh Shield. Our models show the presence of high velocity and density layers in the lowermost crust throughout the region, consistent with the presence of mafic/ultramafic lithologies. The large crustal thickness is associated with a thickened mafic layer in the lower crust, indicating that the thickened crust may be partly caused by magmatic underplating. The low velocity and density anomaly in the middle crust, and low upper mantle velocity observed in our model beneath the middle Tien Shan reflect the presence of partial melt in the crust due to the intrusion of hot mantle material. The lack of correlation between Moho depth and topography, together with the gravity results, suggests that the topographic compensation in the central Tien Shan is not confined to the crust. This requires significant support from the mantle to account for the relative high elevation of the middle Tien Shan.

  3. [Microbial community and its activities in canopy- and understory humus of two montane forest types in Ailao Mountains, Northwest China].

    PubMed

    Liu, Yong-jie; Liu, Wen-yao; Chen, Lin; Zhang, Han-bo; Wang, Gao-sheng

    2010-09-01

    Mid-montane moist evergreen broadleaved forest (MMF) and top-montane dwarf mossy forest (DMF) are the two major natural forest types in subtropical mountainous area of Ailao Mountains, Northwest China. In this paper, a comparative study was made on the microbial composition, quantity, biochemical activity, metabolic activity, and their seasonal dynamics in the canopy- and understory humus of the two forest types. The composition, quantity, and metabolic activity of the microbes in the canopy humus of dominant tree species in MMF and DMF were also analyzed. In the canopy humus of the two forest types, the amounts of fungi and actinomycetes, microbial biomass C and N, and intensities of nitrogen fixation and cellulose decomposition were significantly higher than those in understory humus. Meanwhile, the amount of cellulose-decomposing microbes (ACDM), cellulose decomposition intensity, microbial biomass C and N, and metabolic activity in the canopy humus of MMF were significantly higher than those of DMF. The amounts of bacteria, fungi, and aerobic nitrogen-fixing bacteria (ANFB) and the metabolic activity in the canopy humus of MMF and DMF were significantly higher in wet season than in dry season, while a contradictory trend was observed on the amount of actinomycetes. No significant difference was observed on the amount of ACDM between wet season and dry season. For the two forest types, the amounts of microbes and their biochemical activities in canopy humus had a larger seasonal variation range than those in understory humus. There was a significant difference in the amounts of the microbes in canopy humus among the dominant tree species in MMF and DMF, especially in wet season. The microbes in canopy humus played important roles in maintaining the biodiversity of epiphytes in the canopy, and in supplying the needed nutrients for the vigorous growth of the epiphytes.

  4. Climatic and hydrologic changes in the Tien Shan, central Asia

    SciTech Connect

    Aizen, V.B.; Aizen, E.M.; Melack, J.M.; Dozier, J.

    1997-06-01

    The authors analyze climatic hydrologic data from 110 sites collected from the middle of the twentieth century to the present in the Tien Shan, one of the largest mountain systems of central Asia. In spite of a few confounding interregional variations in the temporal changes of surface air temperature, precipitation, runoff, glacier mass, and snow thickness in the Tien Shan, it has been possible to establish statistically significant long-range, with slightly lower values below 2000-m elevation. The precipitation in the Tien Shan increased 1.2 mm yr{sup -1} over the past half-century. The precipitation increase is larger at low altitudes in the northern and western regions than at altitudes above 2000 m. A decrease in snow resources occurred almost everywhere in the Tien Shan; the maximum snow thickness an snow duration have decreased on average 10 cm and 9 days, respectively. The annual runoff is the type of precipitation (liquid or solid). Over the last few decades, periods of glacier decline have coincided with declining river runoff. 45 refs., 8 figs., 2 tabs.

  5. A Guide to the Tai-shan Dialect.

    ERIC Educational Resources Information Center

    Hashimoto, Anne Yue

    This document provides a description of the Tai-shan dialect of Chinese. Maps illustrate the area where the dialect is spoken, and introductory remarks concern previous study of the dialect, sources of current information, and relationship to other dialects. The phonological description provides information on syllable structure, initials, finals,…

  6. INVESTIGATION OF CRUSTAL MOTION IN THE TIEN SHAN USING INSAR

    SciTech Connect

    Mellors, R J

    2011-02-25

    The northern Tien Shan of Central Asia is an area of active mid-continent deformation. Although far from a plate boundary, this region has experienced 5 earthquakes larger than magnitude 7 in the past century and includes one event that may as be as large as Mw 8.0. Previous studies based on GPS measurements indicate on the order of 23 mm/yr of shortening across the entire Tien Shan and up to 15 mm/year in the northern Tien Shan (Figure 1). The seismic moment release rate appears comparable with the geodetic measured slip, at least to first order, suggesting that geodetic rates can be considered a proxy for accumulation rates of stress for seismic hazard estimation. Interferometric synthetic aperture radar may provide a means to make detailed spatial measurements and hence in identifying block boundaries and assisting in seismic hazard. Therefore, we hoped to define block boundaries by direct measurement and by identifying and resolving earthquake slip. Due to political instability in Kyrgzystan, the existing seismic network has not performed as well as required to precisely determine earthquake hypocenters in remote areas and hence InSAR is highly useful. In this paper we present the result of three earthquake studies and show that InSAR is useful for refining locations of teleseismically located earthquakes. ALOS PALSAR data is used to investigate crustal motion in the Tien Shan mountains of Central Asia. As part of the work, considerable software development was undertaken to process PALSAR data. This software has been made freely available. Two damaging earthquakes have been imaged in the Tien Shan and the locations provided by ALOS InSAR have helped to refine seismological velocity models. A third earthquake south of Kyrgyzstan was also imaged. The use of InSAR data and especially L band is therefore very useful in providing groundtruth for earthquake locations.

  7. Coseismic and postseismic deformation studies of the Wenchuan earthquake and seismo-tectonics of the Longmen Shan fault system (Invited)

    NASA Astrophysics Data System (ADS)

    Shen, Z.; Wang, M.; Sun, J.; Wang, F.; Wang, Y.; Tao, W.; Zhang, P.; Liao, H.; Hao, M.; Wang, Q.

    2011-12-01

    The 2008 Mw 7.9 Wenchuan earthquake is a devastating tragic event. In the meantime it also provided a rare opportunity for the study of seismo-tectonic processes of the Longmen Shan fault system. After the quake we collected GPS and InSAR data to deduce its coseismic and postseismic deformation fields, and combined that with geological and seismic observations to invert for the fault geometry, coseismic slip distribution, and postseismic deformation sources. Our results show the following. The Longmen Shan fault system has two major segments. The southern segment is listric in shape, and deforms primarily through reverse faulting. The northern segment is near vertical in shape, and deforms primarily through dextral shear. The Minjiang-Huya fault system branches obliquely off the central Longmen Shan fault, absorbing a portion of the ESEward extrusion of the eastern Tibet and causing slip partition between itself and the northern segment of the Longmen Shan fault. The Wenchuan earthquake ruptured a cluster of 'asperities' in a cascade style. These 'asperities' are stress strongholds not because of their friction properties on fault plane as interpreted for most of the large strike-slip and/or subduction zone faults, but because of their being geometric barriers. These geometric barriers were created due to complexity of the crust materials under tectonic loading and faulting, and could not be smoothed out by aberration in the fault process because its faulting direction is at high oblique angle with the fault strike direction and the overall aberration ranges are relatively short comparing to that of large strike-slip and subduction zone faults. Aftershocks of the Wenchuan earthquake concentrated mainly around the geometric barriers in upper crust, which cannot be explained by a conventional asperity model used to explain aftershock locations of strike-slip and/or subduction zone earthquakes, but can be interpreted as caused by secondary faulting around these

  8. Coseismic and postseismic deformation studies of the Wenchuan earthquake and seismo-tectonics of the Longmen Shan fault system (Invited)

    NASA Astrophysics Data System (ADS)

    Shen, Z.; Wang, M.; Sun, J.; Wang, F.; Wang, Y.; Tao, W.; Zhang, P.; Liao, H.; Hao, M.; Wang, Q.

    2013-12-01

    The 2008 Mw 7.9 Wenchuan earthquake is a devastating tragic event. In the meantime it also provided a rare opportunity for the study of seismo-tectonic processes of the Longmen Shan fault system. After the quake we collected GPS and InSAR data to deduce its coseismic and postseismic deformation fields, and combined that with geological and seismic observations to invert for the fault geometry, coseismic slip distribution, and postseismic deformation sources. Our results show the following. The Longmen Shan fault system has two major segments. The southern segment is listric in shape, and deforms primarily through reverse faulting. The northern segment is near vertical in shape, and deforms primarily through dextral shear. The Minjiang-Huya fault system branches obliquely off the central Longmen Shan fault, absorbing a portion of the ESEward extrusion of the eastern Tibet and causing slip partition between itself and the northern segment of the Longmen Shan fault. The Wenchuan earthquake ruptured a cluster of 'asperities' in a cascade style. These 'asperities' are stress strongholds not because of their friction properties on fault plane as interpreted for most of the large strike-slip and/or subduction zone faults, but because of their being geometric barriers. These geometric barriers were created due to complexity of the crust materials under tectonic loading and faulting, and could not be smoothed out by aberration in the fault process because its faulting direction is at high oblique angle with the fault strike direction and the overall aberration ranges are relatively short comparing to that of large strike-slip and subduction zone faults. Aftershocks of the Wenchuan earthquake concentrated mainly around the geometric barriers in upper crust, which cannot be explained by a conventional asperity model used to explain aftershock locations of strike-slip and/or subduction zone earthquakes, but can be interpreted as caused by secondary faulting around these

  9. Paleoglaciology of the Tian Shan and Altai Mountains, Central Asia

    NASA Astrophysics Data System (ADS)

    Blomdin, Robin

    Central Asia is home to some of the highest and most spectacular mountain ranges in the world, including the Tian Shan and Altai Mountains, and plays a major role in global and regional climate and hydrology. Understanding the glacial history of this vast region is important for several reasons, but in particular there is a general lack of paleoclimatic data from this highly continental region, at the confluence of major climate systems, and glaciers are sensitive monitors of climate change. This thesis examines the pattern and history of glacial deposition and erosion in the Tian Shan and Altai Mountains using a combined approach including 1) geomorphological mapping, 2) spatial analysis of glacial geomorphology, 3) hypsometry, 4) Equilibrium Line Altitudes (ELA), and 5) 10Be exposure dating of erratic boulders on glacial landforms. Preliminary mapping of the Altai Mountains suggests the area mainly experienced alpine style glaciations, with glacial centers as ice caps and ice fields located around the higher mountainous areas. This is consistent with previous work on the Tian Shan. For the Tian Shan we have new apparent minimum 10Be exposure ages from ~0.2 ka to ~ 180 ka, with large site-specific scatter. Most of our apparent exposure ages come from boulders with an age range between 30 ka to 0.2 ka. Although we recognize that more studies combining mapping, dating and modeling are needed to understand the full history of past glaciation in this region, our conclusions to date include: 1) The oldest recorded glacial event occurred in the Taragay Basin in the Tian Shan, dated to 92.1+/-11.4 ka, and two MIS 2 glacial advances have been recorded on opposite sides of the Ak-Shyrak Range, dated to 16.0+/-3.4 and 17.3+/-4.7 ka respectively. 2) Remote-sensing-based mapping and cosmogenic nuclide dating indicate that Pleistocene glaciations were restricted to the mountains and plateau areas of the Tian Shan. 3) Glaciation ages indicate that glacial events occurred during

  10. Lithospheric structure across the central Tien Shan constrained by gravity anomalies and joint inversions of receiver function and Rayleigh group velocity data

    NASA Astrophysics Data System (ADS)

    Li, Yonghua; Shi, Lei; Gao, Jiayi

    2016-04-01

    Shear wave velocity structure across the central Tien Shan orogeny was generated by jointly inverting Rayleigh wave phase and group velocity with teleseismic P-wave receiver functions at 40 broad band seismic stations of the MANAS project. The inferred seismic structure was validated by forward modeling of the complete Bouguer anomaly data. The joint inversion result reveals larger crust thicknesses beneath the Kokshaal (~68-72 km) and Kyrgyz ranges (~62-64 km), while other units have crustal thicknesses between 48 and 58 km. A fast velocity layer (Vs = 3.6-3.9 km/s) in the upper crust is found in some seismic stations within the Kazakh Shield. Our models show the presence of high velocity and density layers in the lowermost crust throughout the region, consistent with the presence of mafic/ultramafic lithologies. The large crustal thickness is associated with a thickened mafic layer in the lower crust, indicating that the thickened crust may be partly caused by magmatic underplating. The low velocity and density anomaly in the middle crust, and low upper mantle velocity observed in our model beneath the middle Tien Shan reflects the presence of partial melt in the crust due to the intrusion of hot mantle material. The lack of correlation between Moho depth and topography, together with the gravity results, suggests that the topographic compensation in the central Tien Shan is not confined to the crust. This requires significant support from the mantle to account for the relative high elevation of the middle Tien Shan.

  11. [Biography of the outstanding acupuncturist DU Xiao-shan].

    PubMed

    Ding, Min; Lu, Rui-Qin; Du, Liang-Dong; Cao, Li; Lin, Tian-Yun

    2012-09-01

    Professor DU Xiao-shan 's academic thought and clinical experiences was introduced in this paper. He has noble medical ethics and is fair to the patients without distinction. He has great learning and rich practical experiences, and he specializes in all kinds of common diseases as well as many difficult and complicated cases. He never stops studying the ancients to make innovation and he creates the technique of the quick-puncture and slow-twist and DU's heat-reinforce method. He teaches to carry forward acupuncture and moxibustion and his achievements have become an important part of acupuncture and moxibustion science.

  12. HIV-1 in ethnic Shan migrant workers in northern Thailand.

    PubMed

    Srithanaviboonchai, Kriengkrai; Choi, Kyung-Hee; van Griensven, Frits; Hudes, Esther S; Visaruratana, Surasing; Mandel, Jeffrey S

    2002-04-12

    Northern Thailand has one of the highest rates of HIV-1 infection in Southeast Asia. It is also home to a large number of Burmese migrants, believed to be at high risk of HIV. Our 1999 survey of 429 Burmese migrant workers of Shan ethnic origin in Chiang Mai province found a 4.9% rate of HIV-1 prevalence (5.7% men, 3.8% women). This figure is almost double that of comparable population groups in Chiang Mai, e.g. pregnant women and military recruits. HIV prevention programmes are urgently needed for this vulnerable population.

  13. [Characteristics of floor litter and soil arthropod community in different types ot subtropical forest in Ailao Mountain of Yunnan, Southwest China].

    PubMed

    Yang, Zhao; Yang, Xiao-Dong

    2011-11-01

    By using line transect method, an investigation was conducted on the floor litter and soil arthropod community in a mid mountain wet evergreen broad-leaved forest, a mossy dwarf forest, and a Populus bonatii forest in Ailao Mountain of Yunnan in April (dry and hot season), June (rainy season), and December (dry and cold season), 2005. In both dry and rainy seasons, the existing floor litter mass, C storage, and C/N ratio in the three forests all increased in the order of mossy dwarf forest > P. bonatii forest > evergreen broad-leaved forest, but the N storage had less difference. In the floor litter layer of the forests, Acari and Collembola were the dominant groups of soil arthropod community, while Diptera larvae, Coleoptera, ants, and Homoptera were the common groups. The Sorenson coefficients of soil arthropod community in the three forests were extremely great. No significant differences were observed in the soil arthropod density (ind x m(-2)) in the floor litter layer among the three forests, but the relative density (ind x g(-1)) of soil arthropods was higher in the evergreen broad-leaved forest and P. bonatii forest than in the mossy dwarf forest. In the three forests, the density of soil arthropods was significantly higher in dry season than in rainy season, but the Shannon diversity index had less difference. There were significant positive correlations between the existing floor litter mass and the individual density (ind x m(-2)) and dominant groups of soil arthropod communities in dry and hot season (April), but negative correlations between the existing floor litter mass and the relative density (ind x g(-1)) of soil arthropod communities and Acari in dry and cold season (December). The individual densities of Collembola and Coleoptera also had positive correlations with the N storage of the existing floor litter mass in the three forests. It was considered that the floor litter and the development of soil arthropod community in the litter layer of

  14. [Composition and carbon storage of woody debris in moist evergreen broad-leaved forest and its secondary forests in Ailao Mountains of Yunnan Provinve].

    PubMed

    Yang, Li-Pan; Liu, Wen-Yao; Yang, Guo-Ping; Ma, Wen-Zhang; Li, Da-Wen

    2007-10-01

    This paper studied the composition and carbon storage of woody debris in the primary moist evergreen broad-leaved forest and its main secondary forests (regenerated Lithocarpus forest, Populus bonatii forest, and Alnus nepalensis forest) in Ailao Moutains of Yunnan Province. The results showed that in the primary forest, the carbon storage of woody debris amounted to 36.56 t x hm(-2). Castanopsis wattii, Lithocarpus xylocarpus and L. chintungensis were the main contributors, and most of them were the logs with larger diameter and at intermediate stage of decay. The unique environment of richer precipitation, higher humidity and lower temperature in the study area, and the decay-resistance of hardwood were favorable to the accumulation of woody debris. The three secondary forests had a carbon storage of 1.2-5.0 t x hm(-2), which decreased in the order of regenerated Lithocaropus forest > P. bonatii forest > A. nepalensis forest, showing a tendency of increasing carbon storage with succession course.

  15. A crustal model of the ultrahigh-pressure Dabie Shan orogenic belt, China, derived from deep seismic refraction profiling

    USGS Publications Warehouse

    Wang, Chun-Yong; Zeng, Rong-Sheng; Mooney, W.D.; Hacker, B.R.

    2000-01-01

    We present a new crustal cross section through the east-west trending ultrahigh-pressure (UHP) Dabie Shan orogenic belt, east central China, based on a 400-km-long seismic refraction profile. Data from our profile reveal that the cratonal blocks north and south of the orogen are composed of 35-km-thick crust consisting of three layers (upper, middle, and lower crust) with average seismic velocities of 6.0±0.2 km/s, 6.5±0.1 km/s, and 6.8±0.1 km/s. The crust reaches a maximum thickness of 41.5 km beneath the northern margin of the orogen, and thus the present-day root beneath the orogen is only 6.5 km thick. The upper mantle velocity is 8.0±0.1 km/s. Modeling of shear wave data indicate that Poisson's ratio increases from 0.24±0.02 in the upper crust to 0.27±0.03 in the lower crust. This result is consistent with a dominantly felsic upper crustal composition and a mafic lower crustal composition within the amphibolite or granulite metamorphic facies. Our seismic model indicates that eclogite, which is abundant in surface exposures within the orogen, is not a volumetrically significant component in the middle or lower crust. Much of the Triassic structure associated with the formation of the UHP rocks of the Dabie Shan has been obscured by post-Triassic igneous activity, extension and large-offset strike-slip faulting. Nevertheless, we can identify a high-velocity (6.3 km/s) zone in the upper (<5 km depth) crustal core of the orogen which we interpret as a zone of ultrahigh-pressure rocks, a north dipping suture, and an apparent Moho offset that marks a likely active strike-slip fault.

  16. Upper Paleozoic tectonics in the Tien Shan (Central Asian Orogenic Belt): insight from new structural data (Kyrgyzstan)

    NASA Astrophysics Data System (ADS)

    Jourdon, Anthony; Petit, Carole; Rolland, Yann; Loury, Chloé; Bellahsen, Nicolas; Guillot, Stéphane; Ganino, Clément

    2016-04-01

    Due to successive block accretions, the polarity of structures and tectonic evolution of the Central Asian Orogenic Belt (CAOB) are still a matter of debate. There are several conflicting models about the polarity of subduction during the Paleozoic, the number of microplates and oceanic basins and the timing of tectonic events in Kyrgyz and Chinese Tien Shan. In this study, we propose new structural maps and cross-sections of Middle and South Kyrgyz Tien Shan (MTS and STS respectively). These cross-sections highlight an overall dextral strike-slip shear zone in the MTS and a north verging structure related to south-dipping subduction in the STS. These structures are Carboniferous in age and sealed by Mesozoic and Cenozoic deposits. In detail, the STS exhibits two deformation phases. The first one is characterized by coeval top-to-the north thrusting and top-to-the-South normal shearing at the boundaries of large continental unit that underwent High-Pressure (Eclogite facies) metamorphism. We ascribe this phase to the exhumation of underthrusted passive margin units of the MTS. The second one corresponds to a top to the North nappe stacking that we link to the last collisional events between the MTS and the Tarim block. Later on, during the Late Carboniferous, a major deformation stage is characterized by the deformation of the MTS and its thrusting over the NTS. This deformation occurred on a large dextral shear zone between the NTS and the MTS known as Song-Kul Zone or Nikolaiev Line as a "side effect" of the Tarim/MTS collision. Based on these observations, we propose a new interpretation of the tectonic evolution of the CAOB. The resulting model comprises the underthrusting of the MTS-Kazakh platform beneath the Tarim and its exhumation followed by the folding, shortening and thickening of the internal metamorphic units during the last collisional events which partitioned the deformation between the STS and the MTS. Finally, the docking of the large Tarim Craton

  17. Proposed approximation for contact angles in Shan-and-Chen-type multicomponent multiphase lattice Boltzmann models

    NASA Astrophysics Data System (ADS)

    Huang, Haibo; Thorne, Daniel T., Jr.; Schaap, Marcel G.; Sukop, Michael C.

    2007-12-01

    We propose a method for approximating the adhesion parameters in the Shan and Chen multicomponent, multiphase lattice Boltzmann model that leads to the desired fluid-solid contact angle. The method is a straightforward application of Young’s equation with substitution of the Shan and Chen cohesion parameter and a density factor for the fluid-fluid interfacial tension, and the adhesion parameters for the corresponding fluid-solid interfacial tensions.

  18. Displacement and disease: The Shan exodus and infectious disease implications for Thailand

    PubMed Central

    Suwanvanichkij, Voravit

    2008-01-01

    Decades of neglect and abuses by the Burmese government have decimated the health of the peoples of Burma, particularly along her eastern frontiers, overwhelmingly populated by ethnic minorities such as the Shan. Vast areas of traditional Shan homelands have been systematically depopulated by the Burmese military regime as part of its counter-insurgency policy, which also employs widespread abuses of civilians by Burmese soldiers, including rape, torture, and extrajudicial executions. These abuses, coupled with Burmese government economic mismanagement which has further entrenched already pervasive poverty in rural Burma, have spawned a humanitarian catastrophe, forcing hundreds of thousands of ethnic Shan villagers to flee their homes for Thailand. In Thailand, they are denied refugee status and its legal protections, living at constant risk for arrest and deportation. Classified as "economic migrants," many are forced to work in exploitative conditions, including in the Thai sex industry, and Shan migrants often lack access to basic health services in Thailand. Available health data on Shan migrants in Thailand already indicates that this population bears a disproportionately high burden of infectious diseases, particularly HIV, tuberculosis, lymphatic filariasis, and some vaccine-preventable illnesses, undermining progress made by Thailand's public health system in controlling such entities. The ongoing failure to address the root political causes of migration and poor health in eastern Burma, coupled with the many barriers to accessing health programs in Thailand by undocumented migrants, particularly the Shan, virtually guarantees Thailand's inability to sustainably control many infectious disease entities, especially along her borders with Burma. PMID:18341695

  19. Displacement and disease: The Shan exodus and infectious disease implications for Thailand.

    PubMed

    Suwanvanichkij, Voravit

    2008-03-14

    Decades of neglect and abuses by the Burmese government have decimated the health of the peoples of Burma, particularly along her eastern frontiers, overwhelmingly populated by ethnic minorities such as the Shan. Vast areas of traditional Shan homelands have been systematically depopulated by the Burmese military regime as part of its counter-insurgency policy, which also employs widespread abuses of civilians by Burmese soldiers, including rape, torture, and extrajudicial executions. These abuses, coupled with Burmese government economic mismanagement which has further entrenched already pervasive poverty in rural Burma, have spawned a humanitarian catastrophe, forcing hundreds of thousands of ethnic Shan villagers to flee their homes for Thailand. In Thailand, they are denied refugee status and its legal protections, living at constant risk for arrest and deportation. Classified as "economic migrants," many are forced to work in exploitative conditions, including in the Thai sex industry, and Shan migrants often lack access to basic health services in Thailand. Available health data on Shan migrants in Thailand already indicates that this population bears a disproportionately high burden of infectious diseases, particularly HIV, tuberculosis, lymphatic filariasis, and some vaccine-preventable illnesses, undermining progress made by Thailand's public health system in controlling such entities. The ongoing failure to address the root political causes of migration and poor health in eastern Burma, coupled with the many barriers to accessing health programs in Thailand by undocumented migrants, particularly the Shan, virtually guarantees Thailand's inability to sustainably control many infectious disease entities, especially along her borders with Burma.

  20. The End Of Chi-Shan Fault:Tectonic of Transtensional Fault

    NASA Astrophysics Data System (ADS)

    Chou, H.; Song, G.

    2011-12-01

    Chishan fault is an active strike-slip fault that located at the Southwestern Taiwan and extend to the offshore area of SouShan in Kaohsiung. The strike and dip of the fault is N80E,50N. It's believed that the Wushan Formation of Chishan fault, which is composed of sandstone, thrusts upon the Northwestern Kutingkeng Formation, which is composed of mudstone. Chishan fault is acting as a reversal fault with sinistral motion. (Tsan and Keng,1968; Hsieh, 1970; Wen-Pu Geng, 1981). This left-lateral strike-slip fault extend to shelf break and stop, with a transtensional basin at the termination. The transtensional basin has stopped extending to open sea, whereas it is spreading toward the inshore area. Therefore, we can know that a young extensional activity is developing at the offshore seabed of Tsoying Naval Port and the activity is relative to the transtension of left-lateral fault. ( Gwo-Shyh Song, 2010). Tectonic of transtensional basin deformed in strike-slip settings overland have been described by many authors, but the field outcrop could be distoryed by Weathering and made the tectonic features incomplete. Hence, this research use multibeam bathymetry and 3.5-kHz sub-bottom profiler data data collected from the offshore extended part of Chishan fault in Kaohsiung to define the transtensional characteristics of Chishan fault. At first, we use the multibeam bathymetry data to make a Geomorphological map of our research area and we can see a triangulate depressed area near shelf break. Then, we use Fledermaus to print 3D diagram for understanding the distribution of the major normal faults(fig.1). Furthermore, we find that there are amount of listric normal fault and the area between the listric faults is curving. After that, we use the 3.5-kHz sub-bottom profiler data to understand the subsurface structure of the normal faults and the curved area between the listric normal fault, which seems to be En e'chelon folds. As the amount of displacement on the wrench

  1. Structural framework of a major intracontinental orogenic termination zone: The easternmost Tien Shan, China

    USGS Publications Warehouse

    Cunningham, D.; Owen, L.A.; Snee, L.W.; Li, J.

    2003-01-01

    The Barkol Tagh and Karlik Tagh ranges of the easternmost Tien Shan are a natural laboratory for studying the fault architecture of an active termination zone of a major intracontinental mountain range. Barkol and Karlik Tagh and lesser ranges to the north are bounded by active thrust faults that locally deform Quaternary sediments. Major thrusts in Karlik Tagh connect along strike to the east with the left-lateral Gobi-Tien Shan Fault System in SW Mongolia. From a Mongolian perspective. Karlik Tagh represents a large restraining bend for this regional strike-slip fault system, and the entire system of thrusts and strike-slip faults in the Karlik Tagh region defines a horsetail splay fault geometry. Regionally, there appears to be a kinematic transition from thrust-dominated deformation in the central Tien Shan to left-lateral transpressional deformation in the easternmost Tien Shan. This transition correlates with a general eastward decrease in mountain belt width and average elevation and a change in the angular relationship between the NNE-directed maximum horizontal stress in the region and the pre-existing basement structural grain, which is northwesterly in the central Tien Shan (orthogonal to SHmax) but more east-west in the eastern Tien Shan (acute angular relationship with SHmax . Ar-Ar ages indicate that major range-bounding thrusts in Barkol and Karlik Tagh are latest Permian-Triassic ductile thrust zones that underwent brittle reactivation in the Late Cenozoic. It is estimated that the modern mountain ranges of the extreme easternmost Tien Shan could have been constructed by only 10-15 km of Late Cenozoic horizontal shortening.

  2. Ozone and nitrogen dioxide above the northern Tien Shan

    NASA Technical Reports Server (NTRS)

    Arefev, Vladimir N.; Volkovitsky, Oleg A.; Kamenogradsky, Nikita E.; Semyonov, Vladimir K.; Sinyakov, Valery P.

    1994-01-01

    The results of systematic perennial measurements of the total ozone (since 1979) and nitrogen dioxide column (since 1983) in the atmosphere in the European-Asian continent center above the mountainmass of the Tien Shan are given. This region is distinguished by a great number of sunny days during a year. The observation station is at the Northern shore of Issyk Kul Lake (42.56 N 77.04 E 1650 m above the sea level). The measurement results are presented as the monthly averaged atmospheric total ozone and NO2 stratospheric column abundances (morning and evening). The peculiarities of seasonal variations of ozone and nitrogen dioxide atmospheric contents, their regular variances with a quasi-biennial cycles and trends have been noticed. Irregular variances of ozone and nitrogen dioxide atmospheric contents, i.e. their positive and negative anomalies in the monthly averaged contents relative to the perennial averaged monthly means, have been analyzed. The synchronous and opposite in phase anomalies in variations of ozone and nitrogen dioxide atmospheric contents were explained by the transport and zonal circulation in the stratosphere (Kamenogradsky et al., 1990).

  3. Dynamic support of the Tien Shan lithosphere based on flexural and rheological modeling

    NASA Astrophysics Data System (ADS)

    Jiang, Xiaodian

    2014-10-01

    The Tien Shan is a high, young and seismically active intracontinental mountain belt in central Asia that has been uplifted approximately 3 km over the past 10 Ma. A flexural analysis using Bouguer gravity and topographic data was used to determine the dynamic lithospheric mechanisms that are responsible for the topographic uplift and crustal thickening of the range. Bouguer gravity anomalies were used to constrain flexural models for isostatic compensation associated with the large relief of the Tien Shan. This is explained by significant underthrusting of a continuous elastic plate below the Tien Shan, with an effective elastic thicknesses (Te) that gradually changes from 40 to 50 km in the Tarim and Junggar basins and the Kazakh plate to 20-23 km beneath the Tien Shan. Horizontal shortening due to folding and thrusting of the upper-middle crust causes uplift and crustal thickening of the margin of the Tien Shan. The regional and local compensation occur at the eastern and western parts of the Tien Shan respectively. Rheological modeling using a simple geothermal structure for the Tien Shan reveals that the base of the strong upper crust of Tibet is at a depth of 30-35 km, which is consistent with the depths of 7776 earthquakes between 1970 and 2011, which serve as constraints on the brittle failure domain of the area. The Moho depths are used to determine the thickness of the lower crust (17-25 km) and to understand the mobility of the lower-crustal flow of the Tien Shan. The tendency for the strong upper crust to flow over the weak, ductile lower crust (or middle-lower crust) depends on the thickness of the lower crust. In other words, its strength depends on the depths of the base of the upper crust and the Moho. The larger the difference, the easier it is for the upper crust to flow relative to the strong upper-mantle lithosphere. The crustal deformation is decoupled from deformation of the upper-mantle lithosphere by the weak, ductile lower crust of the Tien

  4. Depth localized azimuthal anisotropy from SKS and P receiver functions: The Tien Shan

    NASA Astrophysics Data System (ADS)

    Vinnik, L. P.; Aleshin, I. M.; Kiselev, S. G.; Kosarev, G. L.; Makeyeva, L. I.

    2007-06-01

    Shear wave splitting in the seismic SKS phase provides a unique possibility to judge on deformations at depths inaccessible for direct observations. Fast S wave polarization direction in collisional belts is often parallel to the trend of the belt, although deformations of the mantle lithosphere in low-angle thrusts would lead to the fast polarization direction normal to the trend of the belt. These considerations suggested that the upper mantle in collisional belts is decoupled from the crust. However, SKS technique is notable by a poor depth resolution, and usually it assumes that the fast polarization direction is the same at any depth, which is hard to justify. Here, to investigate depth dependent azimuthal anisotropy in the mantle, we invert jointly P receiver functions and SKS particle motions at a number of seismograph stations. The technique involves azimuthal filtering of the receiver functions and provides a criterion to discriminate between the effects of azimuthal anisotropy and lateral heterogeneity of isotropic medium. A search for the optimum models is conducted with a technique similar to simulated annealing. Testing with synthetics demonstrates that this approach is robust. The results for 10 seismograph stations in the Tien Shan, the world's most active intracontinental collisional belt in Central Asia, reveal a pronounced change in the patterns of azimuthal anisotropy at a depth around 100 km. In the mantle lithosphere (at depths less than 100 km), anisotropy is relatively weak and fast wave polarization direction varies laterally in a broad range. This layer is not necessarily decoupled from the crust: its anisotropy can be a combined effect of present day thrusting and of deformations of the geologic past. In the lower layer (asthenosphere) the average azimuth of fast wave polarization is close to the trend of the belt, whereas magnitude of S wave anisotropy is stable and large (between 5 and 6 per cent). This anisotropy is a likely result of

  5. Thermotectonic evolution of the northern Kyrgyz Tien Shan intrusives

    NASA Astrophysics Data System (ADS)

    Glorie, Stijn; de Grave, Johan; Buslov, Mikhail

    2010-05-01

    The northern Kyrgyz Tien Shan (nKTS) encloses a large number of granitoid intrusions. These plutons intruded during the Palaeozoic and are geodynamical related to either Caledonian or Hercynian collisions. The most voluminous, i.e. the Caledonian intrusion phase is associated with the evolution and closure of the Early Palaeozoic Terskey Ocean (branch of the Turkestan Ocean). Hercynian plutons, smaller in both abundance and dimensions, are thought to have formed during the final closure of the Turkestan Ocean when the Tarim microcontinent eventually collided with the Kazakhstan plate. In the Late Palaeozoic - Early Mesozoic, the nKTS experienced tectonic quiescence. This geodynamic environment abruptly changed in the Mesozoic, when the Central Asian Orogenic System - including the nKTS - was reactivated as an intracontinental orogen (Cimmerian orogeny). The granitoids embedded in the basement record this phase as a cooling event. This cooling is a consequence of denudation and exhumation of the nKTS basement associated with this orogeny. The Late Mesozoic - Early Cenozoic introduced again a period of thermal stability. In the Cenozoic, a new phase of cooling, linked to renewed denudation as a tectonic far-field effect of the India-Eurasia collision, affected the nKTS basement. In this study, we dated each of the aforementioned events and reveal the thermotectonic history of the nKTS granitoids from emplacement to exhumation. Zircon SHRIMP and LA-ICP-MS U/Pb concordia ages suggest a Middle to Late Ordovician crystallization age (440-470 Ma) for the Caledonian intrusion phase, however the presence of additional Early Ordovician - Cambrian U/Pb samples, points towards a more prolonged production of granitoids during the entire Early Palaeozoic. Hercynian samples are constrained to the Late Carboniferous - Permian (260-300 Ma). 40Ar/39Ar stepwise heating plateau-ages (biotite: 400-440 Ma; K-feldspar: 235-375 Ma) bear witness to rapid Silurian - Early Devonian post

  6. [Morphological and histological studies on the Chinese drug shan-dou-gen].

    PubMed

    Fang, L Q; Guo, J X

    1992-01-01

    The Chinese drug "Shan-Dou-Gen" has been used for removing toxic heat, promoting the subsidence of swelling and soothing the sore throat since the ancient time. The authors made a survey of the drug "Shan-Dou-Gen" available in drug markets as well as the plant origin from the drug producing districts. The results showed that the drug "Shan-Dou-Gen" used in different regions in China at present are the roots or rhizomes derived from 9 species: Sophora tonkinensis Gagnep. (Leguminosae), Menispermum dauricum DC. (Menispermaceae), Indigofera amblyantha Craib (Leguminosae), I. carlesii Carib, I., fortunei Craib, I. decoa Lindl. var. ichangensis Y. Y. Fang et C. Z. Zheng, I. kirilowii Maxim. et Palibin, I. potaninii Craib, and Beesia calthaefolia (Maxim.) Ulbr. (Ranuculaceae). In this paper, the morphological characters of the crude drugs are described, compared and illustrated with photographs. The histological structures of the used parts are described, compared and illustrated with line drawings. The morphological and histological similarities and differences found among the above 9 species are summarized, and the key for the identification of the crude drugs is provided. As the drug "Shan-Dou-Gen" derived from different species has different actions and dosages, it is necessary to give different names to different species and use them correctly.

  7. Improvement of supporting electronics system of H-clock at Sher Shan VLBI station.

    NASA Astrophysics Data System (ADS)

    Zhang, Weiqun

    1990-12-01

    The supporting electronics system is a very important part of the H-clock. The author improves the supporting electronics system of the two sets of H-clock at Sher Shan VLBI station. Some design ideas and results are described.

  8. Yu-Gong Yi Shan: Exploring Some Possibilities of Designing Tomorrow's Foreign Language Textbook.

    ERIC Educational Resources Information Center

    Chan, Chung; Liu, Li-chia

    1992-01-01

    An electronic version of Yu-gong Yi Shan, an ancient Chinese fable, is discussed as a prototype of the use of technology for Chinese teaching and learning. Yu-gong demonstrates how hypermedia can be designed to overcome the linear, static, and silent constraints of book technology. (four references) (Author/LB)

  9. Limnocentropus kritsaneepaibooni new species (Limnocentropodidae: Trichoptera) from Shan State, Myanmar, with faunistic data for the family.

    PubMed

    Laudee, Pongsak; Malicky, Hans

    2016-07-12

    A new species of Limnocentropus, Limnocentropus kritsaneepaibooni n. sp. from Keng Tung Province, Shan State, Myanmar, is described and figured. Three other, previously described species of Limnocentropus are newly recorded for Myanmar, including L. apollon Malicky 1999, L. sammuanensis Malicky & Chantaramongkol 1989, and L. siribhumensis Malicky & Chantaramongkol 1989, resulting in 7 species of the family found in Myanmar.

  10. Empirical Relationship between particulate matter and Aerosol Optical Depth over Northern Tien-Shan, Central Asia

    EPA Science Inventory

    Measurements were obtained at two sites in northern Tien-Shan in Central Asia during a 1-year period beginning July 2008 to examine the statistical relationship between aerosol optical depth (AOD) and of fine [PM2.5, particles less than 2.5 μm aerodynamic diameter (AD)] and coars...

  11. Source parameters for 11 earthquakes in the Tien Shan, central Asia, determined by P and SH waveform inversion

    NASA Technical Reports Server (NTRS)

    Nelson, Michael R.; Mccaffrey, Robert; Molnar, Peter

    1987-01-01

    The style and the distribution of faulting occurring today in the Tien Shan region were studied, by digitizing long-period World-Wide Standard Seismograph Network P and SH waveforms of 11 of the largest Tien Shan earthquakes between 1965 and 1982 and then using a least squares inversion routine to constrain their fault plane solutions and depths. The results of the examination indicate that north-south shortening is presently occurring in the Tien Shan, with the formation of basement uplifts flanked by moderately dipping thrust faults. The present-day tectonics of the Tien Shan seem to be analogous to those of the Rocky Mountains in Colorado, Wyoming, and Utah during the Laramide orogeny in Late Cretaceous and Early Tertiary time.

  12. Source processes of strong earthquakes in the North Tien-Shan region

    NASA Astrophysics Data System (ADS)

    Kulikova, G.; Krueger, F.

    2013-12-01

    Tien-Shan region attracts attention of scientists worldwide due to its complexity and tectonic uniqueness. A series of very strong destructive earthquakes occurred in Tien-Shan at the turn of XIX and XX centuries. Such large intraplate earthquakes are rare in seismology, which increases the interest in the Tien-Shan region. The presented study focuses on the source processes of large earthquakes in Tien-Shan. The amount of seismic data is limited for those early times. In 1889, when a major earthquake has occurred in Tien-Shan, seismic instruments were installed in very few locations in the world and these analog records did not survive till nowadays. Although around a hundred seismic stations were operating at the beginning of XIX century worldwide, it is not always possible to get high quality analog seismograms. Digitizing seismograms is a very important step in the work with analog seismic records. While working with historical seismic records one has to take into account all the aspects and uncertainties of manual digitizing and the lack of accurate timing and instrument characteristics. In this study, we develop an easy-to-handle and fast digitization program on the basis of already existing software which allows to speed up digitizing process and to account for all the recoding system uncertainties. Owing to the lack of absolute timing for the historical earthquakes (due to the absence of a universal clock at that time), we used time differences between P and S phases to relocate the earthquakes in North Tien-Shan and the body-wave amplitudes to estimate their magnitudes. Combining our results with geological data, five earthquakes in North Tien-Shan were precisely relocated. The digitizing of records can introduce steps into the seismograms which makes restitution (removal of instrument response) undesirable. To avoid the restitution, we simulated historic seismograph recordings with given values for damping and free period of the respective instrument and

  13. Tectonic evolution of Kazakhstan and Tien Shan in Neoproterozoic and Early-Middle Paleozoic

    NASA Astrophysics Data System (ADS)

    Samygin, S. G.; Kheraskova, T. N.; Kurchavov, A. M.

    2015-05-01

    Geological information on Kazakhstan and the Tien Shan obtained up to the present time has been considered and integrated in order to demonstrate the main features of continental massifs, basins with oceanic crust, island arcs, marginal volcanic-plutonic belts, and transform fault zones differing in type and age. We ascertained the character and probable causes of their evolution and transformations resulting in the origination and development of mosaic structural assembly at margin of the Paleoasian ocean that existed from Neoproterozoic. The main stages of the geodynamic history of Paleozoides in Kazakhstan and Tien Shan are characterized, and a model of the probable course of regional tectonic events has been proposed. This model is illustrated by published paleomagnetic data and a series of paleotectonic reconstructions for time intervals 950-900, 850-800, 750-700, 650-630, 570-550, 530-515, 500-470, 460-440, and 390-380 Ma.

  14. Diamond from the dabie shan metamorphic rocks and its implication for tectonic setting.

    PubMed

    Shutong, X; Wen, S; Yican, L; Laili, J; Shouyuan, J; Okay, A I; Sengör, A M

    1992-04-03

    Diamond occurs in ultrahigh pressure metamorphic rocks from Dabie Shan, Anhui Province, eastern China. Diamond-bearing rocks include eclogite, gamet-pyroxenite, and jadeitite. Diamond occurs in a mineral assemblage with coesite and jadeite. The diamonds and diamondiferous rocks of Dabie Shan are interpreted to be the products of ultrahigh pressure metamorphism in the undérthrust basement of the Yangtze continental plate during the early Mesozoic, at greater than 4.0 gigapascals and 900 degrees C. This interpretation is based on the distribution of rock units, the stability field of diamond, and isotopic data indicating a crustal origin for the rocks. Most diamonds occur as euhedral inclusions in garnets and are 10 to 60 micrometers across, although some are up to 700 micrometers across.

  15. Tomographic Imaging of the Crust and Upper Mantle Beneath the Western Tien Shan

    NASA Astrophysics Data System (ADS)

    Li, Z.; Roecker, S.

    2007-12-01

    We combine P and S wave arrival times from the recent MANAS deployment of broad band sensors with the prior GENGHIS deployment and analogue observations from the Kyrgyz Institute of Seismology to generate a high resolution (5-20 km) image of elastic wavespeeds in the crust and upper mantle beneath the western Tien Shan. The total data set consists of 29,006 P and 21,491 S arrivals from 2176 local events along with 27,196 P arrivals from 2631 teleseismic events recorded at 144 stations. Near surface structure is constrained by a combination of arrival times from local and regional events, Moho depths determined from receiver functions, and travel times from the 2007 MANAS active source profile. Our principal finding is a large high wavespeed region in the mantle beneath most of western Tien Shan dipping to the north to depths as great as 600 km. This region appears to be continuous to shallow depths and surfaces at the southern range front near where the Tarim Basin is being overthrust by the Kokshal range. This result suggests that the Tarim Basin continues to actively subduct beneath the Tien Shan. We do not see any similar feature associated with underthrusting of the Kazach shield to the south. We also inverted a subset of regionally located events for Pn wavespeed and anisotropy. Similar to the larger scale results, Pn wavespeeds in the uppermost mantle are 3-4 percent lower than normal under most of the Tien Shan. The fast direction of Pn anisotropy is predominantly north-south in agreement with the sparser sampling of previous SKS studies. Taken with the tomographic image, we suggest that the anisotropy is most likely due to flow in the asthenosphere induced by the subduction of the Tarim basin.

  16. Tectonic interaction between the Pamir and Tien Shan observed by GPS

    NASA Astrophysics Data System (ADS)

    Zubovich, A.; Schöne, T.; Metzger, S.; Mosienko, O.; Mukhamediev, Sh.; Sharshebaev, A.; Zech, C.

    2016-02-01

    The complex tectonic interplay between the Central Asian Southwest Tien Shan and the north advancing Pamir as well as the role of the Pamir Frontal Thrust (PFT) separating these two orogens along the intervening Alai Valley is yet unclear. In this paper we present data of the newly installed Western Alai GPS profile (WAGP), capturing the deformation signal of both mountain ranges. The 20 km long WAGP records a maximum displacement rate of 9.3 ± 0.8 mm yr-1. The lion's share of displacement (6.0 ± 0.8 mm yr-1) is accommodated between the two stations located directly north and south of the PFT in 5 km distance. The WAGP data nicely complement the existing South Tien Shan and the Pamir GPS network data, which we present here in a combined reference frame and use it as input for horizontal block rotation/strain models. The model results show that both the Southwest Tien Shan and the Pamir behave as uniformly strained blocks and rotate counterclockwise (with respect to Eurasia) by 0.93 ± 0.11° Myr-1 and 0.62 ± 0.05° Myr-1, respectively. The Southwest Tien Shan undergoes NNE-SSW shortening of -22.1 ± 1.5 × 10-9 year-1 with an insignificant perpendicular extension. The Pamir is shortening with a rate of -10.2 ± 3.8 × 10-9 year-1 in a NNE-SSW direction, which is nearly 2.5 times less than its lateral extension rate. A band of increased deformation along the PFT is bounded to the north by the northern rim of the Alai Valley and extends up to 30-50 km south into the Pamir.

  17. Intraplate mountain building in response to continent continent collision—the Ancestral Rocky Mountains (North America) and inferences drawn from the Tien Shan (Central Asia)

    NASA Astrophysics Data System (ADS)

    Dickerson, Patricia Wood

    2003-04-01

    The intraplate Ancestral Rocky Mountains of western North America extend from British Columbia, Canada, to Chihuahua, Mexico, and formed during Early Carboniferous through Early Permian time in response to continent-continent collision of Laurentia with Gondwana—the conjoined masses of Africa and South America, including Yucatán and Florida. Uplifts and flanking basins also formed within the Laurentian Midcontinent. On the Gondwanan continent, well inboard from the marginal fold belts, a counterpart structural array developed during the same period. Intraplate deformation began when full collisional plate coupling had been achieved along the continental margin; the intervening ocean had been closed and subduction had ceased—that is, the distinction between upper versus lower plates became moot. Ancestral Rockies deformation was not accompanied by volcanism. Basement shear zones that formed during Mesoproterozoic rifting of Laurentia were reactivated and exerted significant control on the locations, orientations, and modes of displacement on late Paleozoic faults. Ancestral Rocky Mountain uplifts extend as far south as Chihuahua and west Texas (28° to 33°N, 102° to 109°W) and include the Florida-Moyotes, Placer de Guadalupe-Carrizalillo, Ojinaga-Tascotal and Hueco Mountain blocks, as well as the Diablo and Central Basin Platforms. All are cored with Laurentian Proterozoic crystalline basement rocks and host correlative Paleozoic stratigraphic successions. Pre-late Paleozoic deformational, thermal, and metamorphic histories are similar as well. Southern Ancestral Rocky Mountain structures terminate along a line that trends approximately N 40°E (present coordinates), a common orientation for Mesoproterozoic extensional structures throughout southern to central North America. Continuing Tien Shan intraplate deformation (Central Asia) has created an analogous array of uplifts and basins in response to the collision of India with Eurasia, beginning in late

  18. Enhancing shear thickening

    NASA Astrophysics Data System (ADS)

    Madraki, Yasaman; Hormozi, Sarah; Ovarlez, Guillaume; Guazzelli, Élisabeth; Pouliquen, Olivier

    2017-03-01

    A cornstarch suspension is the quintessential particulate system that exhibits shear thickening. By adding large non-Brownian spheres to a cornstarch suspension, we show that shear thickening can be significantly enhanced. More precisely, the shear-thickening transition is found to be increasingly shifted to lower critical shear rates. This influence of the large particles on the discontinuous shear-thickening transition is shown to be more dramatic than that on the viscosity or the yield stress of the suspension.

  19. The numerical simulation study of the dynamic evolutionary processes in an earthquake cycle on the Longmen Shan Fault

    NASA Astrophysics Data System (ADS)

    Tao, Wei; Shen, Zheng-Kang; Zhang, Yong

    2016-04-01

    The Longmen Shan, located in the conjunction of the eastern margin the Tibet plateau and Sichuan basin, is a typical area for studying the deformation pattern of the Tibet plateau. Following the 2008 Mw 7.9 Wenchuan earthquake (WE) rupturing the Longmen Shan Fault (LSF), a great deal of observations and studies on geology, geophysics, and geodesy have been carried out for this region, with results published successively in recent years. Using the 2D viscoelastic finite element model, introducing the rate-state friction law to the fault, this thesis makes modeling of the earthquake recurrence process and the dynamic evolutionary processes in an earthquake cycle of 10 thousand years. By analyzing the displacement, velocity, stresses, strain energy and strain energy increment fields, this work obtains the following conclusions: (1) The maximum coseismic displacement on the fault is on the surface, and the damage on the hanging wall is much more serious than that on the foot wall of the fault. If the detachment layer is absent, the coseismic displacement would be smaller and the relative displacement between the hanging wall and foot wall would also be smaller. (2) In every stage of the earthquake cycle, the velocities (especially the vertical velocities) on the hanging wall of the fault are larger than that on the food wall, and the values and the distribution patterns of the velocity fields are similar. While in the locking stage prior to the earthquake, the velocities in crust and the relative velocities between hanging wall and foot wall decrease. For the model without the detachment layer, the velocities in crust in the post-seismic stage is much larger than those in other stages. (3) The maximum principle stress and the maximum shear stress concentrate around the joint of the fault and detachment layer, therefore the earthquake would nucleate and start here. (4) The strain density distribution patterns in stages of the earthquake cycle are similar. There are two

  20. The Whole Tien Shan Glacier Area Changes Between 1973 and 2003 Estimated From Corona and ASTER Satellite Imagery

    NASA Astrophysics Data System (ADS)

    Surazakov, A. B.; Aizen, V. B.; Aizen, E. M.

    2007-12-01

    Changes in glacier covered area of the Tien Shan Mountains (western, central and eastern) was estimated between 1973-2003 using Corona KH-9 (9 m) and ASTER (15 m) imagery. Large spatial coverage of a single Corona KH-9 photograph (almost eight ASTER images) and accurate geometric qualities of the KH-9 frame- mapping camera provide a unique opportunity for reconstruction of the glacier covered area during the last 30 years with comparable spatial resolution. The images were orthorectified using SRTM DEM with void areas filled with ASTER DEM and ground control points collected from 1:25,000 and 1:50,000 topographic maps. The Corona and ASTER orthorectification RMS residuals were in the same order of 7-15 m. Glacier boundaries were derived using segmentation of ASTER 3N/4 band ratio and manual digitizing with error-checking in stereo viewing. Since the middle of 1970s, Tien Shan was experiencing abrupt increase in air temperature, that accelerated glacier recession particularly in the mountain ranges lower than 5,000 m a.s.l. From 1973 to 2003 all Tien Shan glaciers have significant recession trend. The most notable recession has been observed in the western and southern Tien Shan: from 20% to 17.1% of the total glacier area. The eastern and northern Tien Shan glaciers have lost 12.6% - 11% of their total area while the largest and highest (up to 7,000 m) central Tien Shan remained nearly the same glacierized area: only 1% of the total glacier area reduction. The large dendritic glaciers in the central Tien Shan are heavily covered by moraine debris, which protect glaciers from intensive ablation. The Tien Shan mountain ranges longitudinally spans more than 2,000 km and glaciers exist in different geo-morphological and climatic conditions determining the difference in glacier recession. However, the Tien Shan glacier surface has decreased in all regions and has to be measured by GPS and satellite altimetry to estimate real changes in glacier ice water resources.

  1. Application of Global Positioning Measurements to Continental Collision in the Pamir-Tien Shan Region, Central Asia and GPS Survey of the Western Tien Shan

    NASA Technical Reports Server (NTRS)

    Hamburger, Michael W.; Reilinger, Robert E.; Hager, Bradford H.; Molnar, Peter

    1997-01-01

    In this report, we summarize what we have accomplished with five years of funding from NASA under its DOSE program, and with a comparable level of funding from NSF. We describe the development of a GPS network in the Tien Shan of Kyrgyzstan and Kazakhstan of the former Soviet Union, the analysis of data, and the main results. This discussion presents the state of the current network, which has grown significantly since the termination of our DOSE grants, with continued support both from NSF through its continental dynamics program and from NASA's SENH program. Although grants from NASA's DOSE program did not support this growth not directly, it did so indirectly by building the infrastructure that has enabled further expansion in an area where otherwise there would be only a small GPS presence. We note how the network has grown over time, but the emphasis of this discussion is on the quantity and quality of measurements that we have made.

  2. Deciphering the coupled Paleozoic and Cenozoic tectonic history of the Qilian Shan, northeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Zuza, A. V.; Yin, A.; Li, J.

    2014-12-01

    The Cenozoic Qilian Shan--the widest thrust belt on the Tibetan Plateau--exposes a record of early Paleozoic subduction-accretion associated with closure of the Qilian Ocean as the Qaidam microcontinent converged with North China. Despite decades of intense research, there is little consensus regarding the nature of the Qilian orogen (e.g., subduction polarity or number of arcs). For example, are the scattered ophiolite-bearing mélange complexes in the Qilian Shan the result of multiple arcs colliding along several suture zones in the Paleozoic or Cenozoic thrust duplication of a single Paleozoic suture zone? A major problem is that existing hypotheses neglect Cenozoic reorganization of the earlier tectonic framework, and the coupling between Paleozoic and Cenozoic structures has yet to be systematically investigated. To address this issue, we examine the Paleozoic Qilian Shan in the context of Cenozoic deformation. We conducted detailed field mapping (~1:50,000), balanced cross-section construction and restoration, U-Pb-Th zircon geochronology, Th-Pb dating of monazite inclusions in garnet, thermobarometry, and whole-rock geochemistry across the central Qilian Shan and in the Hexi Corridor foreland near Jinchan, where the North China craton abuts directly against the Qilian orogen. Successions of juxtaposed amphibolite facies Proterozoic gneiss (T: 725 ± 53°C, P: 7.9 ± 0.9 kbar), Cambrian oceanic material (U-Pb zircon ages: 530-520 Ma), and Ordovician-Silurian arc-derived granite (U-Pb zircon ages: 475-445 Ma) are exposed in the hanging walls of south-directed Cenozoic thrusts that place this basement over younger strata. A regionally correlative unconformity at the base of Carboniferous-Triassic strata is duplicated by this deformation and is used as marker horizon in our restoration. Initial estimates indicate a minimum post-Triassic shortening strain of ~42-45% across the range. By removing this deformation on mapped faults and adhering to observed field

  3. Reduced shear power spectrum

    SciTech Connect

    Dodelson, Scott; Shapiro, Charles; White, Martin J.; /UC, Berkeley, Astron. Dept. /UC, Berkeley

    2005-08-01

    Measurements of ellipticities of background galaxies are sensitive to the reduced shear, the cosmic shear divided by (1-{kappa}) where {kappa} is the projected density field. They compute the difference between shear and reduced shear both analytically and with simulations. The difference becomes more important an smaller scales, and will impact cosmological parameter estimation from upcoming experiments. A simple recipe is presented to carry out the required correction.

  4. Rotatable shear plate interferometer

    DOEpatents

    Duffus, Richard C.

    1988-01-01

    A rotatable shear plate interferometer comprises a transparent shear plate mounted obliquely in a tubular supporting member at 45.degree. with respect to its horizontal center axis. This tubular supporting member is supported rotatably around its center axis and a collimated laser beam is made incident on the shear plate along this center axis such that defocus in different directions can be easily measured.

  5. Timing of initiation of extension in the Tianshan, based on structural, geochemical and geochronological analyses of bimodal volcanism and olistostrome in the Bogda Shan (NW China)

    NASA Astrophysics Data System (ADS)

    Shu, Liangshu; Wang, Bo; Zhu, Wenbin; Guo, Zhaojie; Charvet, Jacques; Zhang, Yuan

    2011-10-01

    This paper describes an olistostrome formation and accompanied bimodal volcanic rocks occurring in the Baiyanggou area, south of Bogda Shan. The main lithotectonic units consist of olistostrome, volcanic rocks and turbidite. The olistostrome is tectonically underlain by Upper Carboniferous limestone and sandstone along a NEE-trending detachment fault. Paleo-growth fault is locally observed. The olistostrome unit includes plenty of blocks of limestone, sandstone, rhyolite and volcaniclastic rocks, and a matrix of graywacke. Limestone blocks are dated as Pennsylvanian-Bashkirian in age by the coral and brachiopod fossils that are extensively recognized in the Upper Carboniferous strata. The volcanic unit consists of pillowed and massive basalt and rhyolite, the latter occur as an 8- to 10-meter-thick layer above the olistostrome unit. The turbidite unit is mainly composed of chert, siliceous mudstone and sandstone, within which the Bouma sequence can be locally recognized. Meter-wide gabbro and diabase dykes intrude these three units. Geochemically, rhyolites are characterized by high ACNK value of >1.1, depletion of Ba, Nb and Sm, and enrichment in Rb, Th and Zr. Basaltic rocks are rich in K2O, they show a LREE-enriched pattern and depletion in Ba, Nb and Zr, and enrichment in Ti, Ce and Hf, similar to continental rift-type tholeiite series. A gabbro porphyrite intruding the olistostrome was dated at 288 ± 3 Ma by a sensitive high-resolution ion microprobe (SHRIMP) zircon U-Pb method, and a rhyolite at 297 ± 2 Ma by a laser ablation inductively coupled plasma mass spectrometer (LA-ICPMS) zircon U-Pb method. The Baiyanggou olistostrome and accompanying bimodal volcanic series are linked to an extensional setting that developed in the south of the Bogda Shan. Several lines of evidence, e.g. occurrence of large-scale strike-slip shear zones, large number of mantle-derived magmatic rocks and available geochronological data, demonstrate a significant geodynamic change

  6. Structural evolution of the Ural-Tian Shan junction: A view from Karatau ridge, South Kazakhstan

    USGS Publications Warehouse

    Alexeiev, D.V.; Cook, H.E.; Buvtyshkin, V.M.; Golub, L.Y.

    2009-01-01

    The deformation history of the Late Palaeozoic Ural-Tian Shan junction is discussed for the example of the Karatau ridge in southern Kazakhstan. Three deformation events are recognized. The Late Carboniferous D1 event is characterized by Laramide-style thrust-and-fold structures on the southern margin of Kazakhstan with shortening in a NE-SW direction. The Latest Permian and Triassic D2 event is controlled by compression in an east-west direction, which reflects collisional deformation in the Urals. The main structures are submeridional folds and north-west-striking sinistral strike-slip faults. The Triassic D3 event with shortening in a north-south direction reflects collision of the Turan microcontinent against the southern margin of Kazakhstan. The main structures are north-west-striking dextral strike-slip faults. Our new data provides important clues for the reconstruction of pre-Cretaceous structures between the Urals and the Tian Shan. ?? 2008 Acad??mie des sciences.

  7. Timing and process of river and lake terrace formation in the Kyrgyz Tien Shan

    NASA Astrophysics Data System (ADS)

    Burgette, Reed J.; Weldon, Ray J.; Abdrakhmatov, Kanatbek Ye.; Ormukov, Cholponbek; Owen, Lewis A.; Thompson, Stephen C.

    2017-03-01

    Well-preserved flights of river and lake terraces traverse an actively deforming rangefront, and form a link between glaciated mountains and a large intermontane lake in the Issyk-Kul basin of the Kyrgyz Tien Shan. We investigated the history and geometry of these lake and river terraces using geologic mapping, surveying, and radiocarbon and terrestrial cosmogenic nuclide dating. A prominent late Pleistocene highstand of the lake occurred over at least the period of 43-25 ka, followed by a period of deep regression and subsequent rise of the lake to the modern sill level in the late Holocene. Major aggradation of the most prominent latest Quaternary river terrace along the Ak-Terek and Barskaun rivers likely started at ∼70-60 ka, coincident to the local last glacial maximum in this region. In contrast to some models of aggradation and incision, the rivers appear to have stayed near the top of the fill for >20 ka, incising subtly below the top of this fill by ∼37 ka, locally. Deep incision likely did not occur until the peak deglaciation in the latest Pleistocene. Older dated terrace surfaces are consistent with one major terrace-forming event per glacial, constant deformation and incision rates, and typical fluvial gradients lower than the modern incising streams. The dating confirms regional terrace correlations for the most prominent late Quaternary terraces, but correlating higher terraces is complicated by spatially varying uplift rates and preferential terrace preservation between basins in the Tien Shan.

  8. Basin evolution in a folding lithosphere: Altai-Sayan and Tien Shan belts in Central Asia

    NASA Astrophysics Data System (ADS)

    Delvaux, D.; Cloetingh, S.; Beekman, F.; Sokoutis, D.; Burov, E.; Buslov, M. M.; Abdrakhmatov, K. E.

    2013-08-01

    Central Asia is a classical example for continental lithospheric folding. In particular, the Altay-Sayan belt in South-Siberia and the Kyrgyz Tien Shan display a special mode of lithospheric deformation, involving decoupled lithospheric mantle folding and upper crustal folding and faulting. Both areas have a heterogenous crust with a long history of accretion-collision, subsequently reactivated as a far-field effect of the Indian-Eurasian collision. Thanks to the youthfulness of the tectonic deformation in this region (peak deformation in late Pliocene-early Pleistocene), the surface expression of lithospheric deformation is well documented by the surface topography and superficial tectonic structures. A review of the paleostress data and tectono-stratigraphic evolution of the Kurai-Chuya basin in Siberian Altai, Zaisan basin in Kazakh South Altai and Issyk-Kul basin in Kyrgyz Tien Shan suggests that they were initiated in an extensional context and inverted by a combination of fault-controlled deformation and flexural folding. In these basins, fault-controlled deformation alone appears largely insufficient to explain their architecture. Lithospheric buckling inducing surface tilting, uplift and subsidence also played an important role. They form typical basins in a folding lithosphere (FLB). Their characteristic basin fill and symmetry, inner structure, folding wavelength and amplitude, thermal regime, time frame are examined in relation to basement structure, stress field, strain rate, timing of deformation, and compared to existing modelling results.

  9. Dynamics of a high viscosity layer in response to shear flow

    NASA Astrophysics Data System (ADS)

    Esmaili, Ehsan; Staples, Anne

    2016-11-01

    We use the Shan-Chen multicomponent Lattice Boltzmann method (LBM) to investigate the time evolution of a thin liquid film (phase I) coating a solid surface under the action of a shearing force imposed by a surrounding fluid (phase II), whose viscosity is significantly lower than that of the film. The goal of this study is to use LBM to capture the contact line motion and interfacial dynamics for an oil-like liquid film which is driven by the upper phase (water) movement as a first approach to modeling thin film dewetting in wave swept marine environments. Lubrication theory is used to validate the results for the driven thin film, and the LBM simulations investigate the effects of the upper phase movement, lower phase thickness, and angle of the imposed shearing force on the thin film profile. This work was supported by the National Science Foundation under Grant Number 1437387.

  10. Importance of Reactivation in the Thickening of the Eastern Tibetan Plateau (Longmen Shan, Sichuan, China)

    NASA Astrophysics Data System (ADS)

    de Sigoyer, J.; Robert, A.; Pubellier, M. F.; Deldicque, D.; Li, Y.; Yi, Z.

    2013-12-01

    The modalities of thickening and uplift of the Tibetan plateau have been often debated. Ages of thickening and of uplift all over the plateau seem to vary with the geological inheritance and reactivation of each area. The Longmen Shan, located on the eastern edge of Tibet, presents an important topographic gradient (from 5000 m to 500 m along 50 km) that overhangs a sharp Moho offset of 20km between the thick Tibetan crust (the Songpan Garze unit) (~67 km-thick) and the resistant 45 km-thick South China crust. Paradoxically the convergence rate across the Longmen Shan measured from geodetic data remains very low (3×3 mm/yr), and this has led to an underestimation of the seismic hazard in this area, and difficulties to explain the thickness of the Tibetan crust underneath. We have documented the thickening processes of the eastern Tibetan border in the Longmen Shan area by unravelling its polyphase evolution via Pressure Temperature (PT) estimates. The first phase of thickening of the Songpan Garze unit and the Longmen Shan occurred by the end of Triassic time during the closure of the Paleotethys. Structural, microstructural, metamorphic observations, PT studies (graphitization of carbonaceous material, quantified X-ray images, chlorite-phengite-quartz-water multi-equilibrium and thermodynamic modelling of phases equilibrium) and U-Pb geochronology are used to describe the tectono-metamorphic evolution of the internal part of the Longmen Shan belt along the Xuelongbao crystalline massif. The Xuelongbao granite is dated 765×7 Ma (in situ U/Pb dating on zircon), suggesting it forms part of the Neoproterozoic South China basement. The intense deformation observed in the sedimentary cover above the Xuelongbao massif, with step cleavage, twisted fold axes and CS structures with top to the SE thrusting vergence are associated to the decollement of the sedimentary pile over the basement. Four stages of deformation are described; three of them being related to the

  11. Response of native and exotic bark beetles to high-energy wind event in the Tian Shan Mountains, Kazakhstan

    NASA Astrophysics Data System (ADS)

    Mukhamadiev, N.; Lynch, A.; O'Connor, C.; Sagitov, A.; Panyushkina, I. P.

    2012-12-01

    On May 17, 2011, the spruce forest of Yile-Alatausky and Medeo National Parks in southeast Kazakhstan was surged by a high-energy cyclonic storm. Severe blowdown damaged several thousand hectare of Tian Shan spruce forest (Picea schrenkiana), with over 90% of trees killed in extensive areas. Bark beetle populations are increasing rapidly, particularly Ips hauseri, I. typographis, I. sexdentatus, and Pityogenes perfossus (all Coleoptera: Curculionidae). Little is known about the frequency or extent of either large storm events or bark beetle outbreaks in the Tian Shan Mountains, nor about associations between outbreaks of these species and temperature and precipitation regimes. Local managers are concerned that triggering bark beetle outbreaks during current unusually warm, dry conditions will have devastating consequences for the residual forest and forest outside of the blowdown. We characterize the bark beetle population response to the 2011 event to date, and reconstruct the temporal and spatial dynamics of historical disturbance events in the area using dendrochronology. Additionally temperature and precipitation-sensitive tree-ring width chronologies from the Tian Shan Mountains are analyzed to determine high- and low-frequency variability of climate for the past 200 years. Catastrophic windstorm disturbances may play a crucial role in determining forest structure across the mountains. We hypothesize that the Tian Shan spruce forest could be prone to severe storm winds and subsequent bark beetle outbreaks and never reach an old-growth phase between events.

  12. Association between atmospheric circulation patterns and firn-ice core records from the Inilchek glacierized area, central Tien Shan, Asia

    USGS Publications Warehouse

    Aizen, V.B.; Aizen, E.M.; Melack, J.M.; Kreutz, K.J.; Cecil, L.D.

    2004-01-01

    Glacioclimatological research in the central Tien Shan was performed in the summers of 1998 and 1999 on the South Inilchek Glacier at 5100-5460 m. A 14.36 m firn-ice core and snow samples were collected and used for stratigraphic, isotopic, and chemical analyses. The firn-ice core and snow records were related to snow pit measurements at an event scale and to meteorological data and synoptic indices of atmospheric circulation at annual and seasonal scales. Linear relationships between the seasonal air temperature and seasonal isotopic composition in accumulated precipitation were established. Changes in the ??18O air temperature relationship, in major ion concentration and in the ratios between chemical species, were used to identify different sources of moisture and investigate changes in atmospheric circulation patterns. Precipitation over the central Tien Shan is characterized by the lowest ionic content among the Tien Shan glaciers and indicates its mainly marine origin. In seasons of minimum precipitation, autumn and winter, water vapor was derived from the and and semiarid regions in central Eurasia and contributed annual maximal solute content to snow accumulation in Tien Shan. The lowest content of major ions was observed in spring and summer layers, which represent maximum seasonal accumulation when moisture originates over the Atlantic Ocean and Mediterranean and Black Seas. Copyright 2004 by the American Geophysical Union.

  13. Quaternary activity of the range front thrust system in the Longmen Shan piedmont, China, revealed by seismic imaging and growth strata

    NASA Astrophysics Data System (ADS)

    Li, Zhigang; Liu-Zeng, Jing; Jia, Dong; Sun, Chuang; Wang, Wei; Yuan, Zhaode; Liu, Baojin

    2016-12-01

    Reliable estimates of Quaternary or Cenozoic upper crustal shortening in the Longmen Shan fold-and-thrust belt are rare. In this paper, we report on our use of high-resolution 2-D and 3-D seismic reflection profiles at various scales, together with borehole data, to investigate the structural geometry of the Longmen Shan piedmont. The results reveal a thrust system beneath the Longmen Shan, termed the range front thrust system, which consists of the range front blind thrust and its upward splay faults. Moreover, on these faults we identified growth strata that provide an excellent opportunity for assessing the activity of this thrust system. Analyses of the growth strata reveal early to late Pleistocene activity on the range front blind thrust, with minimum dip slip and horizontal shortening rates of 1.1 ± 0.2 mm/yr and 1 mm/yr. Accordingly, the maximum accumulated slip on the range front blind thrust is calculated to be 7.5 ± 0.3 km in the Longmen Shan. Using the new horizontal shortening rate and other published data, we also estimated that the long-term shortening rate across the Longmen Shan fold-and-thrust belt is 1-3 mm/yr, which is comparable to the short-term GPS rate. The similarity of these rates suggests that the Longmen Shan attained a steady state condition over the past 2 Myr. An additional highlight of our results is that we show Quaternary activity around the Tibetan Plateau to have been nearly synchronous in different regions, including in the Longmen Shan, the Himalayas, the western Kunlun Shan, and the northern Qilian Shan.

  14. Evaluating the timing of former glacier expansions in the Tian Shan: A key step towards robust spatial correlations

    NASA Astrophysics Data System (ADS)

    Blomdin, R.; Stroeven, A. P.; Harbor, J. M.; Lifton, N. A.; Heyman, J.; Gribenski, N.; Petrakov, D. A.; Caffee, M. W.; Ivanov, M. N.; Hättestrand, C.; Rogozhina, I.; Usubaliev, R.

    2016-12-01

    The timing of past glaciation across the Tian Shan provides a proxy for past climate change in this critical area. Correlating glacial stages across the region is difficult but cosmogenic exposure ages have considerable potential. A drawback is the large observed scatter in 10Be surface exposure data. To quantify the robustness of the dating, we compile, recalculate, and perform statistical analyses on sets of 10Be surface exposure ages from 25 moraines, consisting of 114 new and previously published ages. We assess boulder age scatter by dividing boulder groups into quality classes and rejecting boulder groups of poor quality. This allows us to distinguish and correlate robustly dated glacier limits, resulting in a more conservative chronology than advanced in previous publications. Our analysis shows that only one regional glacial stage can be reliably correlated across the Tian Shan, with glacier expansions occurring between 15 and 28 ka during marine oxygen isotope stage (MIS) 2. However, there are examples of older more extensive indicators of glacial stages between MIS 3 and MIS 6. Paleoglacier extent during MIS 2 was mainly restricted to valley glaciation. Local deviations occur: in the central Kyrgyz Tian Shan paleoglaciers were more extensive and we propose that the topographic context explains this pattern. Correlation between glacial stages prior to late MIS 2 is less reliable, because of the low number of samples and/or the poor resolution of the dating. With the current resolution and spatial coverage of robustly-dated glacier limits we advise that paleoclimatic implications for the Tian Shan glacial chronology beyond MIS 2 are speculative and that continued work toward robust glacial chronologies is needed to resolve questions regarding drivers of past glaciation in the Tian Shan and Central Asia.

  15. Very fast Uplifting in the Kongur Shan, NE Pamir during Marine Isotope Stage 5 (MIS 5)

    NASA Astrophysics Data System (ADS)

    Chen, J.; Liu, C.; Qin, J.; Yang, H.; Luo, M.; Huang, M.; Li, W.

    2014-12-01

    Understanding the evolution of relief in active regions in response to climate change is of particular importance because of the potential linkages between climate and tectonics, such as in the case of the highly debated late Cenozoic uplift of the Himalayas and Tibetan plateau in relation to the onset of Quaternary Glaciations (Molnar and England, 1990; Whipple et al., 1999).Using paramagnetic centers in quartz measured by electron spin resonance (ESR) has shown a potential to quantify late-stage exhumation rates in the range of about 10 ka to 1 Ma due to their relatively low closure temperatures (Grün et al., 1999). However, successful field case study has rarely been documented. Here, we explore the potential ESR dating to provide multiple-thermochronometers using the Al and Ti center in quartz in the Kongur Shan, NE Pamir, to measure how the landscape of a tectonically active range has responded to a change in climatic conditions at the timescale of Quaternary glacial cycles. The Kongur Shan is located in NE Pamir, at the western end of the Himalayan-Tibetan orogenic belt, and presents exhumation rates of ~5 mm/a since 7-8 Ma (Robinson et al., 2010). Bedrock samples were collected from an elevation transect (between 3380 m and 4850 m above sea level) across the Kongur Shan normal fault and along the east-flowing Ghez river. We investigated both the ESR Al center (a hole center located at AlO-) and the Ti center (an electron center: Ti3++e- substituting silicon and stabilized by H+, Li+ in channels near the edge of the silicon-oxygen tetrahedron) in quartz. Our preliminary results show that the quartz Al and Ti centers signals are bright enough for dating. There is a clear age offset between samples from the hanging wall and footwall of the fault, suggesting that the fault is still active. In general, the apparent exhumation rate of the footwall from the ESR Al center is quite similar to that of zircon (U-Th)/He (Thiede et al., 2013), however, there is a clear

  16. Climatic vs. Seismic Controlled Rockglacier Advances in Northern Tien Shan - Insights from Lichenometry

    NASA Astrophysics Data System (ADS)

    Rosenwinkel, S.; Korup, O.; Landgraf, A.; Dzhumabaeva, A.

    2014-12-01

    Glaciers and permafrost landforms in high mountain areas are of major importance for storing and providing fresh water for the surroundings, especially in arid or semi-arid areas as Central Asia. Rockglaciers have been traditionally used as landform proxies of the distribution of alpine permafrost. In the northern Tien Shan mountains, the most distinct lobes of >200 rockglaciers that we mapped from satellite imagery occur at minimum elevations between 2500 and 3700 m. However, individual and particularly low-lying lobes extend down to well below 3000 m, and seem difficult to reconcile with regional paleoclimatic fluctuations. To support ground based and satellite imagery estimates on rockglacier advances (1 to 10 m/yr) and to gain information on their morphological characteristics, we present results of terrestrial LiDAR measurements on six rockglaciers in four steep mountain valleys in the Kyrgyz and Kazakh Tien Shan. Having the ability to destabilize, and thus provide massive sediment input from hillslopes, we hypothesize that strong earthquakes may also have influenced the formation or advance of some of the region's rockglaciers. This hypothesis is based on the observation that the tectonically active area was affected by a series of major earthquakes in the late 19th and earliest 20th centuries, which have subsequently triggered numerous landslides and rock falls. Using lichenometry, we aim to resolve age patterns on lobes of different rockglaciers located both, in the vicinity and distal from large young historic earthquakes. This method has been used successfully to reconstruct glaciation histories, and paleoseismicity. To gain information about and to compare advance histories of the rockglaciers from the relative ages of their lobes, we compiled a dataset of several thousand lichen diameter measurements of different species (e.g., Rhizocarpon geographicum, Aspicilia tianshanica, Lecanora muralis, and Xanthoria elegans). Results show that lichen age

  17. Shearing stability of lubricants

    NASA Technical Reports Server (NTRS)

    Shiba, Y.; Gijyutsu, G.

    1984-01-01

    Shearing stabilities of lubricating oils containing a high mol. wt. polymer as a viscosity index improver were studied by use of ultrasound. The oils were degraded by cavitation and the degradation generally followed first order kinetics with the rate of degradation increasing with the intensity of the ultrasonic irradiation and the cumulative energy applied. The shear stability was mainly affected by the mol. wt. of the polymer additive and could be determined in a short time by mechanical shearing with ultrasound.

  18. Enhancing Shear Thickening

    NASA Astrophysics Data System (ADS)

    Madraki, Fatemeh; Hormozi, Sarah; Ovarlez, Guillaume; Guazzelli, Elisabeth; Pouliquen, Olivier

    2016-11-01

    A cornstarch suspension is the quintessential particulate system that exhibits shear thickening. By adding large non-Brownian spheres to a cornstarch suspension, we show that shear thickening can be significantly enhanced. More precisely, the shear thickening transition is found to be increasingly shifted to lower critical shear rates. This enhancement is found to be mainly controlled by the concentration of the large particles. ANR(ANR-13-IS09-0005-01), ANR(ANR-11-LABX-0092), MIDEX (ANR-11-IDEX-0001-02), NSF (CBET-1554044-CAREER).

  19. Shear Thinning in Xenon

    NASA Technical Reports Server (NTRS)

    Bergm Robert F.; Moldover, Michael R.; Yao, Minwu; Zimmerli, Gregory A.

    2009-01-01

    We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids such as molten plastics or ketchup, near the critical point of xenon. The data span a wide range of dimensionless shear rate: the product of the shear rate and the relaxation time of critical fluctuations was greater than 0.001 and was less than 700. As predicted by theory, shear thinning occurred when this product was greater than 1. The measurements were conducted aboard the Space Shuttle Columbia to avoid the density stratification caused by Earth's gravity.

  20. Dissolved Chemical Ions in an Ice Core of Grigoriev Ice Cap, Kyrgyz Tien Shan

    NASA Astrophysics Data System (ADS)

    SHUN, A.; Takeuchi, N.; Sera, S.; Fujita, K.; Okamoto, S.; Naoki, K.; Aizen, V. B.

    2012-12-01

    Snow and ice of glaciers contain various chemical ions supplied through the atmosphere and preserve them for a long period of time. Thus, analysis of soluble ions in glaciers is important to reveal material circulation and climate change in the cryosphere. Many glaciers are distributed over the mountains of the Central Asia. Chemical analysis of ice cores recovered from there play an important role to understand the atmosphere and material circulation peculiar to the Eurasian Continent. In this study, we analyzed the concentration of major ions in the ice core drilled on Grigoriev Ice Cap, Kyrgys Tien Shan, located in the northwestern part of Central Asia. We aim to understand material circulation in this area based on the chemical records. Then, we have attempted to reconstruct the environmental change of Central Asia, combining the chronology, hydrogen and oxygen stable isotope ratio, and density of dust in the ice core analyzed by prior researches. In this study, we used 2,176 samples of a snow pit and ice core from the surface to bed (86.87 m total length) on the top of Grigoriev Ice Cap (4,660 m high), Kyrgys Tien Shan in September, 2007. Samples were cut every 1-5 cm and scraped thinly, and transported frozen to Chiba University, Japan. After that, we dispensed those for various experiments, and analyzed the concentration of major ions using ion chromatography. By the way, it is estimated that the date of the bottom of this ice core is approximately 12,000 years ago by prior researches. The concentration of major ions dissolved in the ice core of Grigoriev Ice Cap revealed that Ca is the most dominant species in the measured ions and it accounted for more than 50 % (Eq ratio) of the mean of the entire core. This suggests that CaCO3 included in mineral dust derived from deserts around Tien Shan strongly influence the chemical composition of the Ice Cap. In addition, this composition is similar to those of Urumqi No.1 Glacier (Tien Shan), Mustagh Ata Glacier

  1. Climate change impacts on glaciers and runoff in Tien Shan (Central Asia)

    NASA Astrophysics Data System (ADS)

    Sorg, A. F.; Bolch, T.; Stoffel, M.; Solomina, O.; Beniston, M.

    2012-12-01

    Climate-driven changes in glacier-fed streamflow regimes have direct implications on freshwater supply, irrigation and hydropower potential. Reliable information about current and future glaciation and runoff is crucial for water allocation and, hence, for social and ecological stability. Although the impacts of climate change on glaciation and runoff have been addressed in previous work undertaken in the Tien Shan (known as the 'water tower of Central Asia'), a coherent, regional perspective of these findings has not been presented until now. In our study, we explore the range of changes in glaciation in different climatic regions of the Tien Shan based on existing data. We show that the majority of Tien Shan glaciers experienced accelerated glacier wasting since the mid-1970s and that glacier shrinkage is most pronounced in peripheral, lower-elevation ranges near the densely populated forelands, where summers are dry and where snow and glacial meltwater is essential for water availability. The annual glacier area shrinkage rates since the middle of the twentieth century are 0.38-0.76% per year in the outer ranges, 0.15-0.40% per year in the inner ranges and 0.05-0.31% per year in the eastern ranges. This regionally non-uniform response to climate change implies that glacier shrinkage is less severe in the continental inner ranges than in the more humid outer ranges. Glaciers in the inner ranges react with larger time lags to climate change, because accumulation and thus mass turnover of the mainly cold glaciers are relatively small. Moreover, shrinkage is especially pronounced on small or fragmented glaciers, which are widely represented in the outer regions. The relative insensitivity of glaciers in the inner ranges is further accentuated by the higher average altitude, as the equilibrium line altitude ranges from 3'500 to 3'600 masl in the outer ranges to 4'400 masl in the inner ranges. For our study, we used glacier change assessments based both on direct data

  2. Late Paleozoic tectonomagmatic evolution of the western southern Tian Shan, Tajikistan

    NASA Astrophysics Data System (ADS)

    Worthington, James R.; Kapp, Paul; Minaev, Vladislav; Chapman, James B.; Oimahmadov, Ilhomjon; Gadoev, Mustafo

    2015-04-01

    The 2500-km-long Tian Shan orogenic belt constitutes a dominantly Paleozoic amalgmation of Eurasia that has been overprinted by the Mesozoic and Cenozoic Cimmerian and Indo-Eurasian collisions. This southernmost unit of the Central Asian Orogenic System (CAOS) is divided N-S by discontinuous suture zones that reflect its complex assemblage and E-W by the Talas-Fergana dextral (modern kinematics) fault zone. The western southern Tian Shan in Tajikistan/Uzbekistan is poorly studied compared to the rest of the orogen in Kyrgyzstan/China, but a dominant signal of late Paleozoic magmatism synchronous to widespread magmatism documented along strike provides an intriguing opportunity to investigate regional tectonic processes at this time. The late Carboniferous-early Permian Gissar batholith is the southern Tian Shan's southernmost lithotectonic unit. Zircon U-Pb weighted-mean crystallization ages for Gissar granitoids range from ~310-290 Ma, are youngest in the east, and define a primary stage of arc magmatism related to closure of the Turkestan ocean. A ~280 Ma crystallization age was obtained for a Ne syenite, which corresponds to small, 'post-collisional,' alkaline intrusions in 1:200,000 Soviet geologic maps. Zircon ɛHf in Gissar granitoids generally decreases with decreasing zircon U-Pb age from +5'10. Zircon ɛHf in the young Ne syenite is +1-+6. Taken together, these trends indicate a progressive shift from juvenile to intermediate magmatism over 20 Myr, followed by a marked return to juvenile magmatism within 10 Myr. The Garm 'metamorphic' massif is situated within the eastern Gissar batholith and is derived from greater depths than the rest of the batholith, as indicated by its defining features: (i) Discontinuous outcrops of Bt+Grt quartzofeldspathic gneisses/schists; and (ii) Presence of igneous garnet in granitoids. Zircons from the Garm quartzofeldspathic gneisses/schists exhibit pronounced Pb-loss discordia that are consistent with ~amphibolite

  3. Tien Shan geohazards database: Landslides versus other geomorphic features, seismic versus climatic triggering

    NASA Astrophysics Data System (ADS)

    Havenith, Hans-Balder; Strom, Alexander

    2015-04-01

    Recently, we compiled a new landslide inventory for the Tien Shan, Central Asia, containing about 3500 mapped mass movements within a target region of 1200 km (E-W) by 600 km (N-S). While compiling this inventory, we met several problems: which features need to be combined to identify a landslide - combination of scarp and depositional area? Are all deposits below scarps landslide deposits? Should we map scarps as a landslide feature even if no deposits are found below it? How to clearly distinguish landslide from moraine deposits in the higher mountain areas? ... and finally, as the Tien Shan is prone to strong earthquakes (and comparatively less to severe climatic events), can we consider that most giant landslides are triggered by large seismic events .. and, then, could they be used a paleoseismic markers? Identification problems are partly due to the low resolution of imagery that was used for the landslide mapping (mainly based on Google Earth imagery); the other main reason for related uncertainties is the likely great age (> 1000 years) of the mapped features (even though conservation of geomorphic features can be considered as good in those semi-arid areas - much better than in the Alps). For some of those 'old' features, the uncertainty of their origin remained even after having visited the sites. The tendency was that 'landslide geologists' generally considered the mapped features as landslide deposits while some other geoscientists preferred the moraine hypothesis. The problem of the possible seismic origin of proved landslide morphologies is either directly solved if the triggering earthquake event is known (in recent historical times, after 1885) or indirectly in the other (more frequent) case. We consider that most giant landslides (>107 m3) in the Tien Shan had been triggered by earthquakes - while most occurred in 'pre-historic' times (here, before 1885) and a direct proof is thus missing. Actually, several hard rock slopes and many soft rock

  4. Palaeogegraphic and palaeotopography evolution of the chinese Tien Shan during the Mesozoic : a sedimentological synthesis

    NASA Astrophysics Data System (ADS)

    Heilbronn, Gloria; Jolivet, Marc; Robin, Cécile; Barrier, Laurie; Bourquin, Sylvie; Jia, Yingying; Fu, Bihong

    2014-05-01

    The Tian Shan is one of the main ranges of Central Asia Orogenic Belt. The Tertiary deformation is driven by the India-Asia collision stress field. However, the deformation appears localised along inherited tectonic structures formed during the Palaeozoic - Early Mesozoic history of the range (e.g. Jolivet et al., 2010). Our aim is to reconstruct the pre-Tertiary history of relief building in the Chinese Tian Shan. We use the sedimentary facies, sediment provenances and paleocurrent directions of the exposed Mesozoic sections in the northern and southern piedmonts and inside the range. This will be used to understand the long-term reactivation pattern of the main inherited structures and to assess their influence on the localisation and propagation of the deformation. We first established 6 complete reference sections spanning from the Upper Triassic to the Palaeogene. These sections are interpreted in terms of sedimentary facies, palaeoenvironments and prograding-retrograding sequences. The correlation of these 6 sections allows us to propose some palaeogeographic maps for the middle Jurassic, the upper Jurassic - lower Cretaceous transition, the upper Cretaceous and the late Cretaceous - Paleogene transition. The dismantling of reliefs associated to the late-paleozoic range stops in the upper Trias. The Jurassic is characterised by a low tectonic activity and results in a general planation phase of the Tian Shan area. The supposed low relief is possibly associated to local activity of normal faults : this is attested by alluvial fan deposits on the internal sections, as well as paleocurrent directions to the North in the northern foothills and to the south in the southern foothills. These faults could belong to pull apart basins opening in a transtensive tectonic régime, under a humid climate, what is testified by numerous organic matter layers. The upper Jurassic - lower Cretaceous transition is characterized by a huge conglomeratic event at the scale of all

  5. Denudation rates from mass balance on alluvial fans in the chinese Tian Shan

    NASA Astrophysics Data System (ADS)

    Guerit, Laure; Barrier, Laurie; Métivier, François; Jolivet, Marc; Fu, Bihong

    2015-04-01

    Denudation is a key process for mountain ranges evolution as it is an essential parameter to study the mass transfer over the Earth surface, the evolution of reliefs, or the complex relationships between climate, erosion and landscape changes. Several methods have been develop to quantify denudation such as the estimation of paleo-sediment fluxes from mass budget. In fact, markers of erosion within drainage areas are often scarce, temporary and difficult to reach. At the outlet of mountain belts, more continuous and perennial records of deposition can be found in sedimentary basins. Sediment budget is thus a powerful approach, generally used at the scale of sedimentary basins. However, this method can also be applied on smaller sedimentary systems, such as alluvial fans. Yet, it is seldom used on these systems, and consequently, its accuracy is barely questioned. We propose to implement such a method on several alluvial fan systems in the Chinese part of the Tian Shan Range, where estimations of denudation rates have already been proposed. Based on the reconstruction of two generations of alluvial fans, we estimate the volume of sediment exported out of the drainage system of the range for the Middle- Late Pleistocene (300 000 to ~11 000 y) and for the Holocene (~11 000 y to present). From these volumes, we derive denudation rates of ~135 m/My at maximum for these two periods, in good agreement with previous mass balance studies. Despite a strong change in the morphology of the piedmont at the onset of the Holocene, denudation rate seems quite stable within the hinterland mountains. This value is quite low for such a range. Based on a comparison of denudation rates observed in other areas over the world with comparable shortening or precipitation rates, we suggest that the low denudation rate observed in the chinese Tian Shan is related to the limited amount of precipitation.

  6. Adding the Long-Term Perspective: Tien Shan's Glacier Mass Change during 1961-2012

    NASA Astrophysics Data System (ADS)

    Farinotti, D.; Longuevergne, L.; Moholdt, G.; Duethmann, D.; Bolch, T.; Vorogushyn, S.; Guntner, A.; Gafurov, A.

    2014-12-01

    The Tien Shan, Central Asia's major mountain range, has recently been the focus of a series of studies targeting changes in meteorological variables, glacier mass and extent, as well as runoff. Reviews have repeatedly highlighted the importance of glacier melt for total runoff on the one hand, but the scarcity of direct glaciological observation on the other. At the regional to global scale, the lack of such direct observations has been tackled by using remotely sensed products such as satellite gravimetry and altimetry, but the covered time frame is typically in the order of one decade, thus hampering robust assessments. Here, an ensemble of approaches based on the Gravity Recovery and Climate Experiment (GRACE), the Ice, Cloud and land Elevation Satellite (ICESat), and in-situ glacier mass balance measurements is used for estimating glacier mass changes in the Tien Shan during the last decade, and for validating a glacier mass balance model that we subsequently use for reconstructing a continuous mass balance time series over the last half-century. The model ensemble is designed to take into account a wide range of uncertainty sources including often-neglected differences such as data sources or model structure. We cross-validate our different approaches during the period 2003-2009, and find an average glacier mass change of -6.1±4.4 Gt/a, thus confirming previously published estimates. We use the glaciological modelling approach to extend our estimates over the period 1961-2012, and gain insights in the spatial and temporal evolution of the regional glacier melt. Estimated melt rates are in turn used for assessing the contribution of glacier melt to the total runoff of major hydrological basins, and indicate that the contribution from glaciers has likely been overestimated in a series of previous studies.

  7. Cosmogenic 10Be constraints on Little Ice Age glacial advances in the eastern Tian Shan, China

    NASA Astrophysics Data System (ADS)

    Li, Yanan; Li, Yingkui; Harbor, Jon; Liu, Gengnian; Yi, Chaolu; Caffee, Marc W.

    2016-04-01

    Presumed Little Ice Age (LIA) glacial advances, represented by a set of fresh, sharp-crested, boulder covered and compact moraines a few hundred meters downstream from modern glaciers, have been widely recognized in the Central Asian highlands. However, few studies have constrained the formation ages of these moraines. We report 31 10Be exposure ages from presumed LIA moraines in six glacial valleys in the Urumqi River headwater area and the Haxilegen Pass area of the eastern Tian Shan, China. Our results reveal that the maximum LIA glacial extent occurred mainly around 430 ± 100 yr, a cold and wet period as indicated by proxy data from ice cores, tree rings, and lake sediments in Central Asia. We also dated a later glacial advance to 270 ± 55 yr. However, 10Be exposure ages on several presumed LIA moraines in front of small, thin glaciers are widely scattered and much older than the globally recognized timing of the LIA. Historical topographic maps indicate that most glaciers were more extensive in the early 1960s, and two of our 10Be sample sites were located close to the ice front at that time. Boulders transported by these small and thin glaciers may be reworked from deposits originally formed prior to the LIA glacial advances, producing apparently old and widely scattered exposure ages due to varied nuclide inheritance. Other published ages indicated an earlier LIA advance around 790 ± 300 yr in the easternmost Tian Shan, but in our study area the more extensive advance around 430 ± 100 yr likely reworked or covered deposits from this earlier event.

  8. Paleoglaciology of the Ala-Archa and Ak-Shyrak areas, Kyrgyz Tian Shan

    NASA Astrophysics Data System (ADS)

    Blomdin, R.; Beel, C.; Caffee, M. W.; Codilean, A.; Gribenski, N.; Harbor, J.; Heyman, J.; Hattestrand, C.; Ivanov, M.; Kassab, C.; Lifton, N. A.; Petrakov, D.; Rogozhina, I.; Stroeven, A. P.; Usubaliev, R.

    2012-12-01

    We employed detailed glacial geomorphological mapping of the Ala-Archa and Ak-Shyrak areas, Kyrgyz Tian Shan (Shan = Mountains) to build a paleoglaciological reconstruction. These two areas were selected because their glaciers constitute important freshwater reservoirs for downstream communities (the Kyrgyz capital Bishkek, and cities along the Syr Darja which drains towards the Aral Sea, respectively), and because fluctuations in their extent cause both variations in water supply and risks for glacial hazards. Five landform categories were mapped; glacial valleys, marginal moraines, glacial lineations, hummocky terrain, and melt-water channels. These landforms were mapped using a SRTM digital elevation model (DEM) with a 90 m resolution, Landsat 7 ETM+ satellite imagery with a 30 m resolution, Aster GDEM with a 30 m resolution, and Google Earth. This remotely sensed mapping was also checked and complemented by field mapping. The distribution of mapped landforms indicates restricted glaciations, mainly concentrated to the mountain areas. In both ranges marginal moraines extend beyond the furthest extent of glacial valleys. Furthermore, extensive areas of hummocky moraine in Ak-Shyrak extending beyond montane glacial valleys indicate glacial extents into the intermontane basins. Several series of lateral and terminal moraines in the Ala-Archa and Ak-Shyrak ranges have been identified and sampled for cosmogenic nuclide 10Be dating, while associated glaciofluvial sediment was sampled for optically-stimulated luminescence (OSL) and electron spin resonance (ESR) dating. Future work will involve using these samples to build a consistent chronology for glaciation and investigation of contrasts between paleoglaciological reconstructions of valleys within a single range but with different aspects, as well as between ranges. In the final stages of the project we will use intermediate complexity glacier flow models to examine paleoclimatic implications of the observed spatial

  9. Shear flexibility for structures

    NASA Technical Reports Server (NTRS)

    Stangeland, Maynard L. (Inventor)

    1976-01-01

    This device comprises a flexible sheet member having cross convolutions oriented 45.degree. to the shear vector with spherical reliefs at the convolution junctions. The spherical reliefs are essential to the shear flexibility by interrupting the principal stress lines that act along the ridges of the convolutions. The spherical reliefs provide convolutions in both directions in the plane of the cross-convolution ridges.

  10. Shear flexibility for structures

    NASA Technical Reports Server (NTRS)

    Stangeland, Maynard L. (Inventor)

    1977-01-01

    This device comprises a flexible sheet member having cross convolutions oriented 45.degree. to the shear vector with spherical reliefs at the convolution junctions. The spherical reliefs are essential to the shear flexibility by interrupting the principal stress lines that act along the ridges of the convolutions. The spherical reliefs provide convolutions in both directions in the plane of the cross-convolution ridges.

  11. Magnetostratigraphic Record of the Early Evolution of the Southwestern Tian Shan Foreland Basin (Ulugqat Area), Interactions with Pamir Indentation and India-Asia Collision

    NASA Astrophysics Data System (ADS)

    Yang, W.; Wang, S.

    2015-12-01

    The Tian Shan range is an inherited intracontinental structure reactivated by the far-field effects of India-Asia collision. A growing body of thermochronology and magnetostratigraphy datasets shows the range grew through several tectonic pulses since ~25 Ma, however the early Cenozoic history remains poorly constrained. Particularly enigmatic is the time-lag between the Eocene India-Asia collision and the Miocene onset of Tian Shan exhumation. This peculiar period is potentially recorded along the southwestern Tian Shan piedmont. There, recently dated late Eocene marine deposits of the proto-Paratethys epicontinental sea transition to continental foreland basin sediments of unknown age. We provide magnetostratigraphic dating of these continental sediments from the 1700-m-thick Mine section integrated with previously published detrital apatite fission track and U/Pb zircon ages. The most likely correlation to the geomagnetic polarity time scale indicates an age span from 20.8 to 13.3 Ma with a marked accumulation rate increase at 19-18 Ma. This implies the entire Oligocene period is missing between the last marine and first continental sediments, as suggested by previous southwestern Tian Shan results. This differs from the southwestern Tarim basin where Eocene marine deposits are continuously overlain by late Eocene-Oligocene continental sediments. This supports a simple evolution model of the western Tarim basin with Eocene-Oligocene foreland basin activation to the south related to northward thrusting of the Kunlun Shan, followed by early Miocene activation of northern foreland basin related to overthrusting of the south Tian Shan. Our data also support southward propagation of the Tian Shan piedmont from 20-18 Ma that may relate to motion on the Talas Fergana Fault. The coeval activation of a major right-lateral strike-slip system allowing indentation of the Pamir Salient into the Tarim basin, suggest far-field deformation from the India-Asia collision zone

  12. Dynamics of intracontinental convergence between the western Tarim basin and central Tien Shan constrained by centroid moment tensors of regional earthquakes

    NASA Astrophysics Data System (ADS)

    Huang, Guo-chin Dino; Roecker, Steven W.; Levin, Vadim; Wang, Haitao; Li, Zhihai

    2017-01-01

    Among the outstanding tectonic questions regarding the convergence between the Tien Shan and Tarim basin in northwestern China are the manner in which deformation is accommodated within their lithospheres, and the extent that the Tarim lithosphere underthrusts the Tien Shan. In particular, the amount and type of deformation within the Tarim basin is poorly understood. It is also uncertain if the convergence between the Tarim and the Tien Shan takes place mainly along a discrete boundary, or if the Tarim lithosphere simply indents into the Kazach shield, forming the Tien Shan through crustal thickening accommodated by a distributed series of thrust faults. In this study we use hypocentres from published earthquake catalogues and waveforms recorded by regional seismic networks to determine earthquake source parameters through regional centroid moment tensor inversion. The entire dataset consists of 160 earthquakes that occurred between 1969 and 2009 and with moment magnitudes between 3.5 and 7 distributed throughout the central Tien Shan and northwestern Tarim Basin. The estimated focal depths of these earthquakes range from the near-surface to about 44 km. Focal mechanisms throughout much of the Tien Shan indicate active deformation accommodated by thrust faults from at least the upper crust to 30 km depth. South of the Tien Shan, the Jia-shi earthquake sequence within the Tarim basin suggests that both crustal shortening and localized flexure are part of a complicated process involving rotational convergence. Inside the Tarim basin, two earthquakes with thrust faulting mechanisms near the crust-mantle boundary beneath the Bachu uplift imply a brittle rheology of the lower crust. High-angle thrust events occur broadly across the Tien Shan, suggesting that the Tarim lithosphere as a whole is strong and indents into the Kazach shield to create the mountain range.

  13. Dynamics of Intra-Continental Convergence Between the Western Tarim Basin and Central Tien Shan Constrained by Centroid Moment Tensors of Regional Earthquakes

    NASA Astrophysics Data System (ADS)

    Huang, Guo-chin Dino; Roecker, Steven W.; Levin, Vadim; Wang, Haitao; Li, Zhihai

    2016-11-01

    Among the outstanding tectonic questions regarding the convergence between the Tien Shan and Tarim basin in northwestern China are the manner in which deformation is accommodated within their lithospheres, and the extent that the Tarim lithosphere underthrusts the Tien Shan. In particular, the amount and type of deformation within the Tarim basin is poorly understood. It is also uncertain if the convergence between the Tarim and the Tien Shan takes place mainly along a discrete boundary, or if the Tarim lithosphere simply indents into the Kazach shield, forming the Tien Shan through crustal thickening accommodated by a distributed series of thrust faults. In this study we use hypocenters from published earthquake catalogs and waveforms recorded by regional seismic networks to determine earthquake source parameters through regional centroid moment tensor inversion. The entire dataset consists of 160 earthquakes that occurred between 1969 and 2009 and with moment magnitudes between 3.5 and 7 distributed throughout the central Tien Shan and northwestern Tarim Basin. The estimated focal depths of these earthquakes range from the near-surface to about 44 km. Focal mechanisms throughout much of the Tien Shan indicate active deformation accommodated by thrust faults from at least the upper crust to 30 km depth. South of the Tien Shan, the Jia-shi earthquake sequence within the Tarim basin suggests that both crustal shortening and localized flexure are part of a complicated process involving rotational convergence. Inside the Tarim basin, two earthquakes with thrust faulting mechanisms near the crust-mantle boundary beneath the Bachu uplift imply a brittle rheology of the lower crust. High-angle thrust events occur broadly across the Tien Shan, suggesting that the Tarim lithosphere as a whole is strong and indents into the Kazach shield to create the mountain range.

  14. Hercynian post-collisional magmatism in the context of Paleozoic magmatic evolution of the Tien Shan orogenic belt

    NASA Astrophysics Data System (ADS)

    Seltmann, Reimar; Konopelko, Dmitry; Biske, Georgy; Divaev, Farid; Sergeev, Sergei

    2011-10-01

    The Hercynian Tien Shan (Tianshan) orogen formed during Late Palaeozoic collision between the Karakum-Tarim and the Kazakhstan paleo-continents. In order to constrain timing of Hercynian post-collisional magmatism, 27 intrusions were sampled for U-Pb zircon dating along a ca. 2000 km - long profile in Uzbekistan and Kyrgyzstan. The samples were dated utilizing sensitive high resolution ion microprobe (SHRIMP-II). The obtained ages, together with previously published age data, allowed the timing of Hercynian post-collisional magmatism to be constrained and interpreted in the context of the Paleozoic magmatic evolution of the region. Apart from Hercynian post-collisional magmatism, two older magmatic episodes have been recognized, and the following sequence of events has been established: (1) approximately 10 Ma after cessation of continuous Caledonian magmatism a number of Late Silurian-Early Devonian intrusions were emplaced in the Middle and Northern Tien Shan terranes between 420 and 390 Ma. The intrusions probably formed in an extensional back arc setting during coeval subduction under the margins of Caledonian Paleo-Kazakhstan continent; (2) the next relatively short Late Carboniferous episode of subduction under Paleo-Kazakhstan was registered in the Kurama range of the Middle Tien Shan. Calc-alkaline volcanics and granitoids with ages 315-300 Ma have distinct metallogenic affinities typical for subduction-related rocks and are not found anywhere outside the Middle Tien Shan terrane west of the Talas-Farghona fault; (3) the Early Permian Hercynian post-collisional magmatism culminated after the closure of the Paleo-Turkestan ocean and affected the whole region across terrane boundaries. The post-collisional intrusions formed within a relatively short time span between 295 and 280 Ma. The model for Hercynian post-collisional evolution suggests that after collision the Tien Shan was affected by trans-crustal strike-slip motions which provided suitable conduits

  15. Topographic status of the central Longmen Shan region''the role of the 2008 Mw 7.9 Wenchuan earthquake

    NASA Astrophysics Data System (ADS)

    Ren, Zhikun; Zhang, Zhuqi; Dai, Fuchu; Yin, Jinhui; Zhang, Huiping

    2015-04-01

    Landscape evolution in active orogenic regions is inevitably affected by the repeated strong earthquakes triggered by the corresponding active faults. However, the lack of adequate methods for the documentation and monitoring of mountain-building processes has resulted in a shortage of quantitative estimates of orogenic and eroded volumes. A strong earthquake and its associated co-seismic landslides represent a sudden pulse in landscape evolution in tectonically active areas. The 2008 Mw 7.9 Wenchuan earthquake dramatically modified the topography of the Longmen Shan region. Based on topographic data before the earthquake and stereo pairs of post-earthquake remote sensing imagery, we derived pre- and post-earthquake DEMs (digital elevation models) of the three regions along the Longmen Shan Thrust Belt. By comparing the geomorphic features before and after the earthquake, we find that the Wenchuan earthquake smoothed the steep relief and caused a co-seismic uplift of the Longmen Shan region. The medium-relief regions increased; however, the high-relief regions decreased, indicating that the local relief is controlled by repeated strong earthquakes. The changed slope aspect indicates that the formation and modification of the east- and west-facing slopes are controlled by tectonic events in the Longmen Shan region, which might be associated with the regional stress field. However, the unchanged aspects of other slopes might be controlled by long-term erosion rather than tectonic events. The topographic changes, landslide volume and co-seismic uplift indicate that the greatest seismically induced denudation occurred in association with a thrust faulting mechanismand low-angle fault geometry. Our findings reveal that the local relief has been shaped by the localized, seismically induced high rate of denudation within the plateau margins, and that the formation of local relief is also related to tectonic events, especially the events that have occurred on low

  16. Fighting wind shear

    NASA Astrophysics Data System (ADS)

    A “coherent and sustained program” of improved radar detection of weather, pilot training, and better communication between pilots and air controllers can greatly reduce the risk of wind shear to airplanes landing or taking off, according to a National Research Council (NRC) committee.Wind shear, characterized by winds rapidly changing direction and speed, has caused several serious accidents in recent years; among the most notable is the July 8, 1982, crash of a Pan American World Airlines jetliner at the New Orleans International Airport, which killed 153 persons. Following the accident, Congress directed the Federal Aviation Administration (FAA) to contract with the NRC to study wind shear.

  17. Internal deformation of the Shan-Thai block inferred from paleomagnetism of Jurassic sedimentary rocks in Northern Thailand

    NASA Astrophysics Data System (ADS)

    Aihara, Kazuyoshi; Takemoto, Kazuhiro; Zaman, Haider; Inokuchi, Hiroo; Miura, Daisuke; Surinkum, Adichat; Paiyarom, Apichat; Phajuy, Burapha; Chantraprasert, Sarawute; Panjasawatwong, Yuenyong; Wongpornchai, Pisanu; Otofuji, Yo-ichiro

    2007-05-01

    Paleomagnetic samples of red sandstones were collected at 16 sites from the Lower to Upper Jurassic Phu Kradung formation and the Upper Jurassic Phra Wihan formation around Nan City (19.2°N, 101.0°E) in the southern region of the Shan-Thai block. After stepwise thermal demagnetization, a high-temperature component with an unblocking temperature of about 680 °C is isolated from 11 sites. We interpret this to be a prefold characteristic remanent magnetization because of a positive fold test at the 95% confidence level. The tilt-corrected mean paleomagnetic direction from 11 sites is D = 32.3°, I = 33.3°, α95 = 12.2°, k = 15.0, which gives a paleomagnetic pole for this area of 60.1°N, 186.5°E with A95 = 11.7°. Compared with a Jurassic paleopole for the stable part of the Yangtze block, we observe a clockwise tectonic rotation of 12.8°, which is similar to the observed rotation (18-28°) of the northern region of the Shan-Thai block. This amount contrasts with a large rotation of more than 45° that is estimated from the narrow zone extending from Luxi to Mengla in the central region of this block. This declination aspect suggests that a coherent whole block rotation by about 20° of the Shan-Thai block took place in an earlier phase during indentation of India into Asia and that an internal deformation with additional local rotation between 25° and 77° followed within a limited zone in the central part. The internal deformation of the Shan-Thai block absorbed the stress on the Asian continent induced by indentation of India as well as its coherent whole block motions of clockwise rotation and southward displacement.

  18. Shan women and girls and the sex industry in Southeast Asia; political causes and human rights implications.

    PubMed

    Beyrer, C

    2001-08-01

    The human rights abuses which occur during civil conflicts pose special threats to the health and lives of women. These can include rape, sexual violence, increased vulnerability to trafficking into prostitution, and exposure to HIV infection. The long-standing civil conflict in the Shan States of Burma is investigated as a contributing cause to the trafficking of ethnic Shan women and girls into the Southeast Asian sex industry, and to the subsequent high rates of HIV infection found among these women. The context of chronic human rights abuses in the Shan states is explored, as well as the effects of recent forced population transfers on the part of the Burmese Military Regime. Rights abuses specific to trafficked women may further increase their vulnerability to HIV and other STD. The need for a political resolution to the crisis in Burma is discussed, as are approaches aimed at preventing trafficking, empowering women already in the sex industry, and reducing the risks of HIV and other STD among these women and girls.

  19. Geodynamics of late Paleozoic magmatism in the Tien Shan and its framework

    NASA Astrophysics Data System (ADS)

    Biske, Yu. S.; Konopelko, D. L.; Seltmann, R.

    2013-07-01

    The Devonian-Permian history of magmatic activity in the Tien Shan and its framework has been considered using new isotopic datings. It has been shown that the intensity of magmatism and composition of igneous rocks are controlled by interaction of the local thermal upper mantle state (plumes) and dynamics of the lithosphere on a broader regional scale (plate motion). The Kazakhstan paleocontinent, which partly included the present-day Tien Shan and Kyzylkum, was formed in the Late Ordovician-Early Silurian as a result of amalgamation of ancient continental masses and island arcs. In the Early Devonian, heating of the mantle resulted in the within-plate basaltic volcanism in the southern framework of the Kazakhstan paleocontinent (Turkestan paleoocean) and development of suprasubduction magmatism over an extensive area at its margin. In the Middle-Late Devonian, the margins of the Turkestan paleoocean were passive; the area of within-plate oceanic magmatism shifted eastward, and the active margin was retained at the junction with the Balkhash-Junggar paleoocean. A new period of active magmatism was induced by an overall shortening of the region under the settings of plate convergence. The process started in the Early Carboniferous at the Junggar-Balkhash margin of the Kazakhstan paleocontinent and the southern (Paleotethian) margin of the Karakum-Tajik paleocontinent. In the Late Carboniferous, magmatism developed along the northern boundary of the Turkestan paleoocean, which was closing between them. The disappearance of deepwater oceanic basins by the end of the Carboniferous was accompanied by collisional granitic magmatism, which inherited the paleolocations of subduction zones. Postcollision magmatism fell in the Early Permian with a peak at 280 Ma ago. In contrast to Late Carboniferous granitic rocks, the localization of Early Permian granitoids is more independent of collision sutures. The magmatism of this time comprises: (1) continuation of the

  20. Assessing the Mesozoic paleorelief of the NE Tian Shan (China): Constraints from sedimentological marker strata.

    NASA Astrophysics Data System (ADS)

    Heilbronn, G.; Jolivet, M.; Robin, C.; Bourquin, S.; Barrier, L.; Jia, Y.; Guerit, L.; Fu, B.

    2012-04-01

    The Tian Shan is one of the main ranges of Central Asia Orogenic Belt. The Tertiary deformation is driven by the India-Asia collision stress field (e.g., [1], [2]). However, the deformation appears localised along inherited tectonic structures formed during the Palaeozoic - Early Mesozoic history of the range (e.g., [3]). Some of these structures have been reactivated during the early stages of the India-Asia collision which diverge from the model of northward propagation of the Tertiary deformation through time (e.g., [4]). Our aim is to reconstruct the pre-Tertiary history of relief building in the Chinese Tian Shan. We use the sedimentary facies, depositional environments, sediment provenances and palaeocurrent directions of the exposed Mesozoic sections in the northern piedmont and inside the range. This will be used to understand the long-term reactivation pattern of the main inherited structures and to assess their influence on the localisation and propagation of the deformation. We first established a nearly complete reference section spanning from the Upper Triassic to the Palaeogene, in the northern piedmont of the Tian shan range. This section, localised between the Ningjia and Manas rivers, west of Urumqi was previously studied by Hendrix et al. [5] and is thus well documented. We then studied two other sections, one in Wusu (100 km to the West) and one along the Toutun River (100 km to the East). Those sections, mostly covering the Jurassic and Cretaceous are used to assess potential lateral variations in the sedimentary facies and depositional environments along the actual piedmont. Finally, we investigated the Mesozoic sections (Jurassic and Cretaceous ?) exposed within the intramontane Yili and Bayanbulak basins and compared them with the results obtained on the northern piedmont. This comparison should allow assessing the continuity or disconnection between the internal basins and the Junggar basin. Preliminary results along the reference section

  1. Reconstruction of glacial lake outburst floods in northern Tien Shan: Implications for hazard assessment

    NASA Astrophysics Data System (ADS)

    Zaginaev, V.; Ballesteros-Cánovas, J. A.; Erokhin, S.; Matov, E.; Petrakov, D.; Stoffel, M.

    2016-09-01

    Glacier lake outburst floods (GLOFs) and related debris flows are among the most significant natural threats in the Tien Shan Mountains of Kyrgyzstan and have even caused the loss of life and damage to infrastructure in its capital Bishkek. An improved understanding of the occurrence of this process is essential so as to be able to design reliable disaster risk reduction strategies, even more so in view of ongoing climate change and scenarios of future evolutions. Here, we apply a dendrogeomorphic approach to reconstruct past debris-flow activity on the Aksay cone (Ala-Archa valley, Kyrgyz range), where outbursting glacier lakes and intense rainfalls have triggered huge debris flows over the past decades. A total of 96 Picea abies (L.) Karst. trees growing on the cone and along the main channel have been selected based on the evidence of past debris-flow damage in their trunks; these trees were then sampled using increment borers. The dating of past events was based on the assessment of growth disturbances (GD) in the tree-ring records and included the detection of injuries, tangential rows of traumatic resin ducts, reaction wood, and abrupt growth changes. In total, 320 GD were identified in the tree-ring samples. In combination with aerial imagery and geomorphic recognition in the field, reactions in trees and their position on the cone have allowed reconstruction of the main spatial patterns of past events on the Aksay cone. Our findings suggest that at least 27 debris flows have occurred on the site between 1877 and 2015 and point to the occurrence of at least 17 events that were not documented prior to this study. We also observe high process activity during the 1950s and 1960s, with major events on the cone in 1950, 1966, and 1968, coinciding with phases of slight glacier advance. The spatial analyses of events also point to two different spatial patterns, suggesting that quite dissimilar magnitudes probably occurred during glacier lake outburst floods and

  2. Association between Social Integration and Health among Internal Migrants in ZhongShan, China.

    PubMed

    Lin, Yanwei; Zhang, Qi; Chen, Wen; Shi, Jingrong; Han, Siqi; Song, Xiaolei; Xu, Yong; Ling, Li

    2016-01-01

    Internal migrants are the individuals who migrate between regions in one country. The number of internal migrants were estimated at 245 million in China in 2013. Results were inconsistent in the literature about the relationship between their health statuses and social integration. The main difference exists on how to measure the social integration and whether health statuses of internal migrants improve with years of residence. To complement the existing literature, this study measured social integration more comprehensively and estimated the internal migrants' health statuses with varying years of residence, and explored the associations between the migrants' social integration and health. We used the data from 2014 Internal Migrant Dynamic Monitoring Survey of Health and Family Planning in ZhongShan, China. Health status was measured from four aspects: self-reported health, subjective well-being, perception of stress, mental health. We measured social integration through four dimensions: economy, social communication, acculturation, and self-identity. The analyses used multiple linear regressions to examine the associations between self-reported health, subjective well-being, and perception of stress, mental health and social integration. The analytical sample included 1,999 households of the internal migrants and 1,997 local registered households, who were permanent residents in ZhongShan. Among the internal migrants, Adults in the labor force, who were aged 25 to 44 years old, accounted for 91.2% of the internal migrant population, while 74.6% of the registered population were in that age group. Median residential time among migrants was 2.8 (1.3-6.2) years, and 20.2% of them were migrating in the same Guangdong province. Except for mental health, other health statuses among migrants had significant differences compared with local registered population, e.g. self-reported health was better, but subjective well-being was worse. However, these health

  3. Association between Social Integration and Health among Internal Migrants in ZhongShan, China

    PubMed Central

    Lin, Yanwei; Zhang, Qi; Chen, Wen; Shi, Jingrong; Han, Siqi; Song, Xiaolei; Xu, Yong; Ling, Li

    2016-01-01

    Internal migrants are the individuals who migrate between regions in one country. The number of internal migrants were estimated at 245 million in China in 2013. Results were inconsistent in the literature about the relationship between their health statuses and social integration. The main difference exists on how to measure the social integration and whether health statuses of internal migrants improve with years of residence. To complement the existing literature, this study measured social integration more comprehensively and estimated the internal migrants’ health statuses with varying years of residence, and explored the associations between the migrants’ social integration and health. We used the data from 2014 Internal Migrant Dynamic Monitoring Survey of Health and Family Planning in ZhongShan, China. Health status was measured from four aspects: self-reported health, subjective well-being, perception of stress, mental health. We measured social integration through four dimensions: economy, social communication, acculturation, and self-identity. The analyses used multiple linear regressions to examine the associations between self-reported health, subjective well-being, and perception of stress, mental health and social integration. The analytical sample included 1,999 households of the internal migrants and 1,997 local registered households, who were permanent residents in ZhongShan. Among the internal migrants, Adults in the labor force, who were aged 25 to 44 years old, accounted for 91.2% of the internal migrant population, while 74.6% of the registered population were in that age group. Median residential time among migrants was 2.8 (1.3–6.2) years, and 20.2% of them were migrating in the same Guangdong province. Except for mental health, other health statuses among migrants had significant differences compared with local registered population, e.g. self-reported health was better, but subjective well-being was worse. However, these health

  4. Tectonic deformation around the eastern Himalayan syntaxis: constraints from the Cretaceous palaeomagnetic data of the Shan-Thai Block

    NASA Astrophysics Data System (ADS)

    Tanaka, Kenji; Mu, Chuanlong; Sato, Ken; Takemoto, Kazuhiro; Miura, Daisuke; Liu, Yuyan; Zaman, Haider; Yang, Zhenyu; Yokoyama, Masahiko; Iwamoto, Hisanori; Uno, Koji; Otofuji, Yo-ichiro

    2008-11-01

    Lower to Middle Cretaceous red sandstones were sampled at four localities in the Lanpin-Simao fold belt of the Shan-Thai Block to describe its regional deformational features. Most of the samples revealed a characteristic remanent magnetization with unblocking temperatures around 680 °C. Primary natures of magnetization are ascertained through positive fold test. A tilt-corrected formation-mean direction for the Jingdong (24.5°N, 100.8°E) locality, which is located at a distance of 25 km from the Ailaoshan-Red River Fault, revealed northerly declination with steep inclination (Dec./Inc. = 8.3°/48.8°, α95 = 7.7°, N = 13). However, mean directions obtained from the Zhengyuan (24.0°N, 101.1°E), West Zhengyuan (24.0°N, 101.1°E) and South Mengla (21.4°N, 101.6°E) localities indicate an easterly deflection in declination; such as Dec./Inc. = 61.8°/46.1°, α95 = 8.1° (N = 7), Dec./Inc. = 324.2°/-49.4°, α95 = 6.4° (N = 4) and Dec./Inc. = 51.2°/46.4°, α95 = 5.6° (N = 13), respectively. The palaeomagnetic directions obtained from these four localities are incorporated into a palaeomagnetic database for the Shan-Thai Block. When combined with geological, geochronological and GPS data, the processes of deformation in the Shan-Thai Block is described as follows: Subsequent to its rigid block clockwise rotation of about 20° in the early stage of India-Asia collision, the Shan-Thai Block experienced a coherent but southward displacement along the Red River Fault prior to 32 Ma. This block was then subjected to a north-south compressive stresses during the 32-27 Ma period, which played a key role in shaping the structure of Chongshan-Lancang-Chiang Mai Belt. Following this some local clockwise rotational motion has occurred during the Pliocene-Quaternary time in central part of the Shan-Thai Block as a result of internal block movements along the reactivated network of faults.

  5. The relationship between the age and depth of the oceanic crust in the central South China Sea

    NASA Astrophysics Data System (ADS)

    Peng, Yi-Jui; Hsu, Shu-Kun; Chiao, Ling-Yun

    2016-04-01

    South China Sea (SCS) is the largest marginal basin in the western Pacific. The onset of seafloor spreading in the central part of the SCS was suggested at 32 Ma. After a ridge jump around 25 Ma, the southwestern sub-basin started to open. The spreading of the entire basin ended at ~16 Ma, then a phase of post-magmatic seamount formation occurred (eg., Taylor and Hayes, 1983; Briais et al.,1993; Barckhausen et al., 2014). In this study, we want to find the relationship between the age and depth of the oceanic crust in the central SCS. We will also study a fracture zone trending NW-SE near to Manila trench and to understand how did the fracture zone affect the development of the SCS. We have analyzed five reflection seismic profiles collected by R/V Ocean Researcher 1 during the cruise ORI-1115. We have correlated the age of seismic strata in the central SCS by comparing to the seismic phase of profile MCS1115-7 that has crossed the IODP drilling site U1431. To understand the characteristics of the fracture zone, we have also applied the analytic signal and Euler deconvolution methods to the gravity and magnetic anomalies related to the fracture zone. We suggest that the fraction zone was formed in order to accommodate the spreading in the east sub-basin. However, this fracture zone is somewhat curved concave southwestward. According to the collision-extrusion model of Tapponnier et al. (1982), the formation of Indochina is followed with the constitution of Ailao Shan-Red River Shear Zone. We suppose that the formation of the fracture zone in this study is similar to the Ailao Shan-Red River Shear Zone. The fan-shaped crustal fabric is distinct in the younger portions of the oceanic basin. Both Ailao Shan-Red River Shear Zone and the fracture zone in northeastern SCS may share the same rotation pole. Furthermore, we have tried to find a relationship between oceanic crust depth and age in this area. The preliminary result shows that the relationship between depth and

  6. Coherence of the Dabie Shan UHPM terrane investigated by Lu-Hf and 40Ar/39Ar dating of eclogites

    NASA Astrophysics Data System (ADS)

    Brouwer, F. M.; Groen, M.; Nebel, O.; Wijbrans, J. R.; Qiu, H.

    2009-12-01

    The Central China Orogenic Belt is the largest known ultrahigh-pressure metamorphic (UHPM) belt. Currently exposed UHP metamorphic rocks reflect subduction of massive swathes of continental crust to depths exceeding 100 km. Subsequent uplift exposed the voluminous sequence more or less intact. Deciphering responsible exhumation processes requires well constrained P-T-time paths. Most workers accept Triassic (~240 and 220-200 Ma) peak UHP metamorphism on the basis of zircon U-Pb ages in Central and Eastern Dabie Shan, while Western Dabie Shan, Qinling, North Qaidam and Altyn Tagh exhibit Ordovician (420-500 Ma) UHPM. However, contrasting reports of Carboniferous and Ordovian UHPM in Eastern Dabie Shan (Jian et al. 2001; Qiu & Wijbrans, 2006, 2008), and Ordovician, Carboniferous and Triassic (U)HPM in Western Dabie Shan (Wu et al. 2009) question this simple East-West gradient. Here, we investigate PTt-paths for localities throughout Dabie Shan to determine how far west the Triassic UHP event is documented, and how far east the Carboniferous and Ordovician events can be traced. Based on this distribution we aim to establish whether the Dabie Shan terrane is an amalgam of blocks that underwent UHPM at different times rather than a single coherent terrane. Eclogite samples are investigated for thermobarometry, Lu-Hf Grt-Cpx geochronology, and 40Ar/39Ar thermochronology. For fresh eclogites Thermocalc was used to establish equilibration conditions of the UHPM assemblage, Grt and Cpx of which were subsequently used for Lu-Hf isotope analysis. In addition, retrogressed eclogites, two fresh eclogites and two orthogneisses were analysed for 40Ar/39Ar isotope distributions in Phg, Bt, Amp and Kfs. Four fresh eclogites, all collected at reported UHP-localities confirm established PT-estimates for peak-metamorphism above the Coe-in reaction at 450-680 °C, with higher T for eastern Dabie. In one sample this is confirmed by the presence of a Coe inclusion in Cpx. Lu-Hf Grt

  7. Stress drop in the sources of intermediate-magnitude earthquakes in northern Tien Shan

    NASA Astrophysics Data System (ADS)

    Sycheva, N. A.; Bogomolov, L. M.

    2014-05-01

    The paper is devoted to estimating the dynamical parameters of 14 earthquakes with intermediate magnitudes (energy class 11 to 14), which occurred in the Northern Tien Shan. For obtaining the estimates of these parameters, including the stress drop, which could be then applied in crustal stress reconstruction by the technique suggested by Yu.L. Rebetsky (Schmidt Institute of Physics of the Earth, Russian Academy of Sciences), we have improved the algorithms and programs for calculating the spectra of the seismograms. The updated products allow for the site responses and spectral transformations during the propagation of seismic waves through the medium (the effect of finite Q-factor). By applying the new approach to the analysis of seismograms recorded by the seismic KNET network, we calculated the radii of the sources (Brune radius), scalar seismic moment, and stress drop (release) for the studied 14 earthquakes. The analysis revealed a scatter in the source radii and stress drop even among the earthquakes that have almost identical energy classes. The stress drop by different earthquakes ranges from one to 75 bar. We have also determined the focal mechanisms and stress regime of the Earth's crust. It is worth noting that during the considered period, strong seismic events with energy class above 14 were absent within the segment covered by the KNET stations.

  8. Ordovician-Carboniferous tectono-sedimentary evolution of the North Nuratau region, Uzbekistan (Westernmost Tien Shan)

    NASA Astrophysics Data System (ADS)

    McCann, T.; Nurtaev, B.; Kharin, V.; Valdivia-Manchego, M.

    2013-04-01

    The Tien Shan is a c. 2500 km long orogenic belt of which the Nuratau region of eastern Uzbekistan forms the western part. Petrographical and field analysis of the Ordovician-Carboniferous succession in the North Nuratau region provided the basis for a reconstruction of the depositional settings along part of the northern margin of the Alai continent and their evolution during the period of closure of the Turkestan Ocean, which separated the Alai and the Kazakh-Kyrgyz continents. Initial sedimentation (Ordovician) was broadly carbonate dominated, although by Mid-Late Ordovician times siliciclastic input predominated in some areas. These variations, between clastic- and carbonate-dominated regions may have been related to tectonic activity within the Alai continent. Carbonate sedimentation was reestablished in the ?Wenlock, with broad shelf systems forming along the continental margin. Volcanic activity in the Early Devonian records a period of tectonic instability, and this was followed by the reestablishment of the carbonate mosaic, albeit with a greater degree of instability (as indicated by stratigraphic gaps) than in the Silurian. This pattern extended up into the Carboniferous culminating in backarc-related magmatic activity. Final closure of the Turkestan Ocean involved significant folding and thrusting, as well as a major change from compressional to strike-slip movement.

  9. Alpine tectonics of granites in basement of Ysyk-Köl Basin, northern Tien Shan

    NASA Astrophysics Data System (ADS)

    Leonov, M. G.; Przhiyalgovsky, E. S.; Lavrushina, E. V.; Poleshchuk, A. V.; Rybin, A. K.

    2016-07-01

    The Ysyk-Köl Basin filled with Lower Jurassic-Quaternary sedimentary rocks is the largest intermontane negative structural unit of the northern Tien Shan. The basement of this basin is composed of Precambrian-Paleozoic rocks, largely of Ordovician and Silurian granitoids exposed in mountain ranges of the basin framework and as separate anticlinal domes situated in areas occupied by the Mesozoic-Cenozoic sedimentary cover. The postmagmatic tectonic internalstructure of the Chonkurchak (Chunkurchak), Kyzyl-Choku, Kyzyl-Bulak, and Prishib massifs emplaced in the basement, as well as their relationships to the sedimentary cover, are described in the paper. The study was carried out using the morphostructural method, detailed geological mapping, structural kinematic analysis, and petrographic examination of rocks. The internalstructure of Paleozoic granites in the basement and indications of their 3D tectonic flow are characterized. It is shown that granites underwent 3D deformation after their emplacement in the consolidated crust, and this process had a substantial influence on tectonic processes at the plate and orogenic stages of regional evolution.

  10. Shear strength of metals under uniaxial deformation and pure shear

    NASA Astrophysics Data System (ADS)

    Latypov, F. T.; Mayer, A. E.

    2015-11-01

    In this paper, we investigate the dynamic shear strength of perfect monocrystalline metals using the molecular dynamics simulation. Three types of deformation (single shear, uniaxial compression and tension) are investigated for five metals of different crystallographic systems (fcc, bcc and hcp). A strong dependence of the calculated shear strength on the deformation type is observed. In the case of bcc (iron) and hcp (titanium) metals, the maximal shear strength is achieved at the uniaxial compression, while the minimal shear strength is observed at the uniaxial tension. In the case of fcc metals (aluminum, copper, nickel) the largest strength is achieved at the pure shear, the lowest strength is obtained at the uniaxial compression.

  11. Ultrasonic shear wave couplant

    DOEpatents

    Kupperman, David S.; Lanham, Ronald N.

    1985-01-01

    Ultrasonically testing of an article at high temperatures is accomplished by the use of a compact layer of a dry ceramic powder as a couplant in a method which involves providing an ultrasonic transducer as a probe capable of transmitting shear waves, coupling the probe to the article through a thin compact layer of a dry ceramic powder, propagating a shear wave from the probe through the ceramic powder and into the article to develop echo signals, and analyzing the echo signals to determine at least one physical characteristic of the article.

  12. Shear wave transmissivity measurement by color Doppler shear wave imaging

    NASA Astrophysics Data System (ADS)

    Yamakoshi, Yoshiki; Yamazaki, Mayuko; Kasahara, Toshihiro; Sunaguchi, Naoki; Yuminaka, Yasushi

    2016-07-01

    Shear wave elastography is a useful method for evaluating tissue stiffness. We have proposed a novel shear wave imaging method (color Doppler shear wave imaging: CD SWI), which utilizes a signal processing unit in ultrasound color flow imaging in order to detect the shear wave wavefront in real time. Shear wave velocity is adopted to characterize tissue stiffness; however, it is difficult to measure tissue stiffness with high spatial resolution because of the artifact produced by shear wave diffraction. Spatial average processing in the image reconstruction method also degrades the spatial resolution. In this paper, we propose a novel measurement method for the shear wave transmissivity of a tissue boundary. Shear wave wavefront maps are acquired by changing the displacement amplitude of the shear wave and the transmissivity of the shear wave, which gives the difference in shear wave velocity between two mediums separated by the boundary, is measured from the ratio of two threshold voltages required to form the shear wave wavefronts in the two mediums. From this method, a high-resolution shear wave amplitude imaging method that reconstructs a tissue boundary is proposed.

  13. Measuring the reduced shear

    NASA Astrophysics Data System (ADS)

    Zhang, Jun

    2011-11-01

    Neglecting the second order corrections in weak lensing measurements can lead to a few percent uncertainties on cosmic shears, and becomes more important for cluster lensing mass reconstructions. Existing methods which claim to measure the reduced shears are not necessarily accurate to the second order when a point spread function (PSF) is present. We show that the method of Zhang (2008) exactly measures the reduced shears at the second order level in the presence of PSF. A simple theorem is provided for further confirming our calculation, and for judging the accuracy of any shear measurement method at the second order based on its properties at the first order. The method of Zhang (2008) is well defined mathematically. It does not require assumptions on the morphologies of galaxies and the PSF. To reach a sub-percent level accuracy, the CCD pixel size is required to be not larger than 1/3 of the Full Width at Half Maximum (FWHM) of the PSF, regardless of whether the PSF has a power-law or exponential profile at large distances. Using a large ensemble (gtrsim107) of mock galaxies of unrestricted morphologies, we study the shear recovery accuracy under different noise conditions. We find that contaminations to the shear signals from the noise of background photons can be removed in a well defined way because they are not correlated with the source shapes. The residual shear measurement errors due to background noise are consistent with zero at the sub-percent level even when the amplitude of such noise reaches about 1/10 of the source flux within the half-light radius of the source. This limit can in principle be extended further with a larger galaxy ensemble in our simulations. On the other hand, the source Poisson noise remains to be a cause of systematic errors. For a sub-percent level accuracy, our method requires the amplitude of the source Poisson noise to be less than 1/80 ~ 1/100 of the source flux within the half-light radius of the source, corresponding to

  14. Measuring the reduced shear

    SciTech Connect

    Zhang, Jun

    2011-11-01

    Neglecting the second order corrections in weak lensing measurements can lead to a few percent uncertainties on cosmic shears, and becomes more important for cluster lensing mass reconstructions. Existing methods which claim to measure the reduced shears are not necessarily accurate to the second order when a point spread function (PSF) is present. We show that the method of Zhang (2008) exactly measures the reduced shears at the second order level in the presence of PSF. A simple theorem is provided for further confirming our calculation, and for judging the accuracy of any shear measurement method at the second order based on its properties at the first order. The method of Zhang (2008) is well defined mathematically. It does not require assumptions on the morphologies of galaxies and the PSF. To reach a sub-percent level accuracy, the CCD pixel size is required to be not larger than 1/3 of the Full Width at Half Maximum (FWHM) of the PSF, regardless of whether the PSF has a power-law or exponential profile at large distances. Using a large ensemble (∼>10{sup 7}) of mock galaxies of unrestricted morphologies, we study the shear recovery accuracy under different noise conditions. We find that contaminations to the shear signals from the noise of background photons can be removed in a well defined way because they are not correlated with the source shapes. The residual shear measurement errors due to background noise are consistent with zero at the sub-percent level even when the amplitude of such noise reaches about 1/10 of the source flux within the half-light radius of the source. This limit can in principle be extended further with a larger galaxy ensemble in our simulations. On the other hand, the source Poisson noise remains to be a cause of systematic errors. For a sub-percent level accuracy, our method requires the amplitude of the source Poisson noise to be less than 1/80 ∼ 1/100 of the source flux within the half-light radius of the source

  15. Chronology and tectonic controls of late tertiary deposition in the southwestern Tian Shan foreland, NW China

    USGS Publications Warehouse

    Heermance, R.V.; Chen, J.; Burbank, D.W.; Wang, C.

    2007-01-01

    Magnetostratigraphy from the Kashi foreland basin along the southern margin of the Tian Shan in Western China defines the chronology of both sedimentation and the structural evolution of this collisional mountain belt. Eleven magnetostratigraphic sections representing ???13 km of basin strata provide a two- and three-dimensional record of continuous deposition since ???18 Ma. The distinctive Xiyu conglomerate makes up the uppermost strata in eight of 11 magnetostratigraphic sections within the foreland and forms a wedge that thins southward. The basal age of the conglomerate varies from 15.5??0.5 Ma at the northernmost part of the foreland, to 8.6??0.1 Ma in the central (medial) part of the foreland and to 1.9??0.2, ???1.04 and 0.7??0.1 Ma along the southern deformation front of the foreland basin. These data indicate the Xiyu conglomerate is highly time-transgressive and has prograded south since just after the initial uplift of the Kashi Basin Thrust (KBT) at 18.9??3.3 Ma. Southward progradation occurred at an average rate of ???3 mm year -1 between 15.5 and 2 Ma, before accelerating to ???10 mm year-1. Abrupt changes in sediment-accumulation rates are observed at 16.3 and 13.5 Ma in the northern part of the foreland and are interpreted to correspond to southward stepping deformation. A subtle decrease in the sedimentation rate above the Keketamu anticline is determined at ???4.0 Ma and was synchronous with an increase in sedimentation rate further south above the Atushi Anticline. Magnetostratigraphy also dates growth strata at <4.0, 1.4??0.1 and 1.4??0.2 Ma on the southern flanks the Keketamu, Atushi and Kashi anticlines, respectively. Together, sedimentation rate changes and growth strata indicate stepped migration of deformation into the Kashi foreland at least at 16.3, 13.5, 4.0 and 1.4 Ma. Progressive reconstruction of a seismically controlled cross-section through the foreland produces total shortening of 13-21 km and migration of the deformation front at

  16. Tectonic and sedimentary evolution of the Ili Basin (northern Tien Shan, Kazakhstan)

    NASA Astrophysics Data System (ADS)

    Kley, J.; Voigt, T.; Seib, N.; Kober, M.

    2010-12-01

    The Tien Shan active intraplate orogen of Central Asia exhibits strong along-strike variations in structure. Its northern front in southeastern Kazakhstan is characterized by a fragmented array of anticlinal basement highs whose wavelengths range from c. 5 to 30 km. Range-bounding faults are mostly E- to ENE-trending thrust or reverse faults and SE-trending dextral strike-slip faults. Faults of large displacement (more than several tens of meters) are conspicuously absent. The synclinal lows between the basement highs preserve Cenozoic strata of Oligocene to Quaternary age, probably deposited in a once continuous basin (the Ili Basin) and recording the entire history of Tien Shan uplift. Very gentle, long-wavelength folds affect the Cenozoic strata. As far as visible, the basement is always folded conformably. The basin fill starts in the middle Oligocene (mammal fossils; Indricotherium horizon). The facies of these oldest deposits is characterized by fluvial deposits of a large river system and varying flood-plain deposits with intense soil formation (calcretes and gypsisols). Transport directions and quartz content of the sediments suggest they were not sourced from the nearby mountain ranges present today. The fluvial succession is followed by late Oligocene to early Miocene lake deposits which reflect the transition from an evaporitic lake/playa system to freshwater lacustrine conditions. The Oligocene to Early Miocene deposits are limited to a small area in the core of the Aktau anticline and show no relationship to the sediment succession overlying the basement in the uplifts surrounding the Aktau mountains in the north and west. There, alluvial and fluvial deposits of middle Miocene(?) age rest on deeply weathered paleosurfaces. Transport is mainly to the south. Changes in colour, grain size and ratio of channel to interchannel deposits probably reflect climatic changes. Rapid facies and thickness-changes allow the reconstruction of several alluvial fans

  17. Towards an improved glacier monitoring program in the Kyrgyz Tien Shan and Pamir Mountains

    NASA Astrophysics Data System (ADS)

    Barandun, Martina; Huss, Matthias; Azisov, Erlan; Gafurov, Abror; Vorogushyn, Sergiy; Usubaliev, Ryskul; Kronenberg, Marlene; Hoelzle, Martin

    2014-05-01

    The monitoring of glacier mass balance in remote regions is important to understand the response of glaciers to climate change. The coverage of monitored glaciers in Central Asia has been very limited for the past 15 years; however the necessity of enhanced understanding regarding glacier dynamics and long term evolution in this particular region is crucial. Moisture availability importantly determines glacier response. Glaciers located in the Northern Tien Shan and Pamir Mountains are likely not to be directly influenced by monsoon such as most monitored Peri-Himalayan glaciers. However, not only scientific reasons make glacier monitoring to be of great relevance, also the link to political and socio-economic constraints on water scarcity carries high importance. First steps towards the establishment of a new glacier monitoring network were performed in 2010/2011 and since then modernization and extension of the monitoring strategies are continuously aspired. Close cooperation of international and local scientists build the basis of the program. Today four glaciers located in the Kyrgyz Tien Shan (Golubin Glacier, Suek Zapadniy Glacier, Glacier No. 354) and the North-Western Pamir (Abramov Glacier) are regularly monitored. The network is planned to be extended in the next years to cover selected glaciers in Uzbekistan and Tajikistan. Further, we intend to develop new approaches to remotely monitor sub-seasonal glacier mass balance at a regional scale. In-situ mass balance measurements are taken at all four glaciers continuously in late summer. Automatic weather stations installed at Abramov Glacier in 2011 and at Golubin Glacier in 2013 deliver daily meteorological data allowing the application of a simple mass balance model driven with local precipitation and temperature data. Model calibration is performed using glaciological measurements and results are validated with snowline observations based on remote imagery. Automatic cameras at Abramov Glacier take

  18. Cenozoic tectonic history of the Western Tien Shan constrained by low-temperature thermochronology

    NASA Astrophysics Data System (ADS)

    Bande, Alejandro; Sobel, Edward; Mikolaichuk, Alexander

    2014-05-01

    The NW-SE trending dextral Talas-Fergana fault (TFF) separates the Western Tien Shan from the Central Kyrgyz Tien Shan. This ~2000 km long structure extends from western Tarim basin in the southeast to the Turgay basin in the northwest. The TFF formed in the late Paleozoic - Early Mesozoic and was reactivated in the Jurassic and Cenozoic. Cenozoic displacement only occurred along the southern segment of the fault and is poorly constrained; Thomas et al. (1993) suggested 100 ± 60 km Cenozoic displacement based on vertical-axis rotation of Tertiary red beds in the Fergana basin. AFT analysis was carried out on 26 samples collected from vertical profiles and spot samples in the Chatkal, Shandalash, Ugam, Talas and Fergana Ranges associated with structures that merge with the northern active end of the TFF with the goal of constraining the timing of slip. Sampling and thermal modeling of the Talas Range, on the east side of the TFF, show that the range was rapidly being exhumed by the latest Oligocene both near the TFF and at its northern termination. Based on this data and the geometrical relation of the TFF and the structural lineaments of the Talas Range, we interpret the zone as a transpressional pop-up structure kinematically-related to the TFF. A vertical profile in the Shandalash Range, directly to the west across the TFF, suggests a rapid exhumation event at Oligo-Miocene boundary. In this sector, the geometrical relationship of the reverse faults with the main TFF suggests a restraining bend connected to the TFF. Moreover, the timing of exhumation in these two areas suggests that strike-slip movement along the TFF is responsible for the uplift of the Talas pop-up and the development of restraining bends in the Ugam, Shandalash and Chatkal Ranges. Farther south along the west side of the TFF, we collected a vertical profile in the Fergana range in the hanging wall of a thrust sheet that roots into the TFF. A kink in an age-elevation plot suggests the onset of

  19. Status and habitat preferences for endemic inhabitants of fiddler crab Uca formosensis in Hsiang-Shan wetland, Taiwan.

    PubMed

    Liao, Shao-Wei; Chang, Wen-Liang; Lin, Shih-Wei

    2008-08-01

    This article reports on soil samples collected from Hsiang-Shan wetland, Taiwan. Canonical discriminant analysis (CDA) was applied to identify an existing habitat type's scheme by identifying the physico-chemical properties of sediment in Hsiang-Shan wetland. The three constructed discriminant functions (CDFs) showed a marked contribution by most of the discriminant variables, and the recognition capacities in these three CDFs were 49.5, 32.8 and 17.7%. Our study revealed that the most important latent factors in Hsiang-Shan wetland are soil texture-caused factor, ocean current-caused factor, nutrient-caused factor, and the redox reaction-caused factor. And the most sensitivity parameters in this habitat followed the descending order: OBD, EC, Eh, sand, TN, porosity, STP, silt, VCP and pH. And the inhabited sediment properties for U. formosensis in terms of soil texture are sand, silt, and clay (34.05, 29.72, and 32.35%, respectively): that is clay loam soil. We also found that U. formosensis preferred to inhabit the upper intertidal zone, spending 8.41% of the time submerged. Vegetation coverage on the ground was less than 2.20%, showing that it preferred to live in a bare intertidal habitat. Concerning nest choosing, excavating burrows is more difficult when a high soil penetration force is required, and in this study the soil penetration force for 20 cm was found to be is 45.98 N/cm(2). The results will be helpful in developing a methodology for use by the government in refining its management programs.

  20. Tectonic control on denudation across the eastern Tibetan Plateau from the Longriba fault zone to the Longmen Shan

    NASA Astrophysics Data System (ADS)

    Ansberque, C.; Godard, V.; Bellier, O.; Ren, Z.; Xu, X.; Liu, J.; Li, Y.; De Sigoyer, J.; Bourles, D. L.

    2013-12-01

    The deformation distribution across the eastern margin of the Tibetan Plateau is still highly debated. Whereas a major part of the present strain appears to be focused at the Longmen Shan front range, recently discovered active faults such as the Longriba fault zone suggest a wider deformation accommodation area and complex partitioning mechanisms. 10Be-derived denudation rates have recently demonstrated their utility to unravel the deformation pattern and distribution of uplift rates in tectonically active areas (e.g. Cyr et al., 2010; Gudmundsdottir et al., 2013), and applying this approach across the eastern Tibetan Plateau margin can provide key insights on eventual uplift gradients. Here, we present 10Be-derived denudation rates for 20 small basins across this area. We observe a clear denudation gradient with rates ranging from 0.04mm/yr to 0.14mm/yr, west of the Longriba fault zone and increasing up to 0.4mm/yr towards the Longmen Shan front range. We do not observe any significant relationship between rainfall and denudation rates, while relief and denudation appears to be correlated, suggesting a non climatic control on denudation distribution in the study domain. We use an empirical power law relationship between average hillslope angles (below the critical domain) and denudation rates to predict denudation. The results further support the idea of a slowly increasing denudation gradient from the Longriba fault zone to the Longmen Shan front suggesting progressive rock uplift across the eastern Tibetan Plateau margin, as suggested by previous authors on the basis of stream profile analysis (Kirby et al., 2003). Our study suggests that the Longriba fault zone is an important tectonic boundary for the eastern Tibetan Plateau margin. It probably marks the western boundary of the actively deforming domain.

  1. 2.5D Full Waveform Inversion of Teleseismic Body and Surface Waves in the Tien Shan

    NASA Astrophysics Data System (ADS)

    Baker, B. I.; Roecker, S. W.

    2013-12-01

    The Tien Shan is the best contemporary example of intracontinental shortening resulting from continental collision, a process believed to have been significant in the evolution of a number of ancient orogens. Previous tomographic studies of the Tien Shan implicate structures in the crust and upper mantle as key to understanding the dynamics of the region. In this study we apply recently developed full waveform inversion (FWI) techniques to passive data collected by the linear dense MANAS array between 2005 to 2007 in order to obtain higher resolution images of lateral heterogeneity beneath the Tien Shan than have previously been available. Our technique is an extension of that proposed by Roecker et al (2010); specifically the forward problem can now account for topographic features with a new 2.5D p-adaptive finite element solver. We incorporate a method developed by Bielak et. al. (2003) to input an appropriate force distribution to accommodate sources external to our model. The p-adaptivity allows us to suit element size to expected resolution as a function of depth and reduce the number of variables in inversion. Consequently, we can now explicitly calculate Frechet derivatives and generate the corresponding Gauss-Newton form with a model covariance regularization matrix all for modest additional computational expense. In order to take advantage of the complimentary sensitivities of different kinds of observations, we simultaneously invert fundamental mode Rayleigh waves and teleseismic P-wave coda. Our strategy is a multiscale approach by which we fit the longer period surface waves first followed by inclusion of body wave data.

  2. Source parameters of the major historical earthquakes in the Tien-Shan region from the late 19th to the early 20th century.

    NASA Astrophysics Data System (ADS)

    Kulikova, Galina; Krüger, Frank

    2016-04-01

    The Tien-Shan is one of the largest mountain belts in the world. Its deformation is dominated by intermontane basins bounded by active thrust and reverse faulting. The Tien-Shan mountain belt is characterized by a very high rate of seismicity along its margins as well as within the Tien-Shan interior. The study area of the here presented work, the western part of the Tien-Shan region, is currently seismically active with small and moderate sized earthquakes. However, at the end of 19th beginning of 20th century, this region was struck by a remarkable series of large magnitude (M>7) earthquakes, two of them reached magnitude 8. These large earthquakes occurred before the global digital seismic network was installed and therefore were recorded only by analog seismic instruments. The processing of the analog is complicated especially due to the digitization of the records - a very time-consuming and delicate part. Therefore a special set of techniques is developed and modern methods are adapted for the digitized instrumental data analysis. Here presented study evaluates the impact of large magnitude M>7.0 earthquakes, in the Tien-Shan region, on the overall regional tectonics. It also investigates the accuracy of previously estimated source parameters for those earthquakes, which were mainly based on macroseismic observations, and re-estimate them based on the instrumental data. Ten strongest and most interesting historical earthquakes in Tien-Shan region are analyzed with in presented work. With the developed techniques, the source parameters of these major earthquakes are determined and their impact on the regional tectonics was investigated. The large magnitudes of the earthquakes are confirmed by instrumental data. The focal mechanisms of these earthquakes were determined providing evidence for responsible faults or fault systems.

  3. Shear Thinning of Noncolloidal Suspensions

    NASA Astrophysics Data System (ADS)

    Vázquez-Quesada, Adolfo; Tanner, Roger I.; Ellero, Marco

    2016-09-01

    Shear thinning—a reduction in suspension viscosity with increasing shear rates—is understood to arise in colloidal systems from a decrease in the relative contribution of entropic forces. The shear-thinning phenomenon has also been often reported in experiments with noncolloidal systems at high volume fractions. However its origin is an open theoretical question and the behavior is difficult to reproduce in numerical simulations where shear thickening is typically observed instead. In this letter we propose a non-Newtonian model of interparticle lubrication forces to explain shear thinning in noncolloidal suspensions. We show that hidden shear-thinning effects of the suspending medium, which occur at shear rates orders of magnitude larger than the range investigated experimentally, lead to significant shear thinning of the overall suspension at much smaller shear rates. At high particle volume fractions the local shear rates experienced by the fluid situated in the narrow gaps between particles are much larger than the averaged shear rate of the whole suspension. This allows the suspending medium to probe its high-shear non-Newtonian regime and it means that the matrix fluid rheology must be considered over a wide range of shear rates.

  4. Assessment of HIV testing among young methamphetamine users in Muse, Northern Shan State, Myanmar

    PubMed Central

    2014-01-01

    Background Methamphetamine (MA) use has a strong correlation with risky sexual behaviors, and thus may be triggering the growing HIV epidemic in Myanmar. Although methamphetamine use is a serious public health concern, only a few studies have examined HIV testing among young drug users. This study aimed to examine how predisposing, enabling and need factors affect HIV testing among young MA users. Methods A cross-sectional study was conducted from January to March 2013 in Muse city in the Northern Shan State of Myanmar. Using a respondent-driven sampling method, 776 MA users aged 18-24 years were recruited. The main outcome of interest was whether participants had ever been tested for HIV. Descriptive statistics and multivariate logistic regression were applied in this study. Results Approximately 14.7% of young MA users had ever been tested for HIV. Significant positive predictors of HIV testing included predisposing factors such as being a female MA user, having had higher education, and currently living with one’s spouse/sexual partner. Significant enabling factors included being employed and having ever visited NGO clinics or met NGO workers. Significant need factors were having ever been diagnosed with an STI and having ever wanted to receive help to stop drug use. Conclusions Predisposing, enabling and need factors were significant contributors affecting uptake of HIV testing among young MA users. Integrating HIV testing into STI treatment programs, alongside general expansion of HIV testing services may be effective in increasing HIV testing uptake among young MA users. PMID:25042697

  5. Tien Shan geohazards database: earthquake and landslide size-frequency statistics

    NASA Astrophysics Data System (ADS)

    Havenith, Hans-Balder

    2015-04-01

    Recently compiled landslide and earthquake data covering a large part of the Tien Shan, Central Asia, are analysed with respect to their size-frequency behaviour. For the same area, only partial databases for sub-regions had been presented previously. They were combined and new data were added to fill the gaps between the databases. The new compiled landslide inventory contains existing records of 1600 previously identified mass movements and more than 1800 new landslide data mapped over a target region of 1200 km (E-W) by 600 km (N-S). On the basis of the new landslide inventory and an updated earthquake catalogue (> 10000 records), the link between landslide and earthquake activity is analysed. Here we focus on the size-frequency relationships developed for both types of geohazards, in terms of Gutenberg-Richter Law for the earthquakes and in terms of probability density function for the landslides. Some similarities can be found in the spatially changing b-value of earthquake events and the power law exponent of the landslide data - lowest values are found in mountain areas where very large mass movements had occurred near major fault zones. The supra-regional landslide inventory will also be compared with sub-regional ones. For one of them, we also possess a multi-temporal landslide inventory and assessed landslide size-frequency relationships for each time period. Those show a decreasing power law exponent with time - due to the coalescence of smaller landslides to form fewer larger ones. However, at (supra-)regional scale, temporal data are very scarce; thus, a major hazard component is still insufficiently known and scaling in time is almost impossible. We may only counteract this problem by dating rockslides and any large mass movement. Finally, we would like to emphasize the role of coupling effects related to various types of geohazards that may also be expressed by similarities between size-frequency relationships.

  6. New complex EAS installation of the Tien Shan mountain cosmic ray station

    NASA Astrophysics Data System (ADS)

    Chubenko, A. P.; Shepetov, A. L.; Antonova, V. P.; Beisembayev, R. U.; Borisov, A. S.; Dalkarov, O. D.; Kryakunova, O. N.; Mukashev, K. M.; Mukhamedshin, R. A.; Nam, R. A.; Nikolaevsky, N. F.; Pavlyuchenko, V. P.; Piscal, V. V.; Puchkov, V. S.; Ryabov, V. A.; Sadykov, T. Kh.; Saduev, N. O.; Salikhov, N. M.; Shaulov, S. B.; Stepanov, A. V.; Vildanov, N. G.; Vildanova, L. I.; Vildanova, M. I.; Zastrozhnova, N. N.; Zhukov, V. V.

    2016-10-01

    In this paper we present a description of the new complex installation for the study of extensive air showers which was created at the Tien Shan mountain cosmic ray station, as well as the results of the test measurements made there in 2014-2016. At present, the system for registration of electromagnetic shower component consists of ∼100 detector points built on the basis of plastic scintillator plates with the sensitive area of 0.25 m2 and 1 m2, spread equidistantly over ∼104m2 space. The dynamic range of scintillation amplitude measurements is currently about (3 - 7) ·104, and there is a prospect of it being extended up to ∼106. The direction of shower arrival is defined by signal delays from a number of the scintillators placed cross-wise at the periphery of the detector system. For the investigation of nuclear active shower components a multi-tier 55 m2 ionization-neutron calorimeter with a sum absorber thickness of ∼1000 g/cm2, typical spatial resolution of the order of 10 cm, and dynamic range of ionization measurement channel about ∼105 was created. Also, the use of saturation-free neutron detectors is anticipated for registration of the high- and low-energy hadron components in the region of shower core. A complex of underground detectors is designed for the study of muonic and penetrative nuclear-active components of the shower. The full stack of data acquisition, detector calibration, and shower parameters restoration procedures are now completed, and the newly obtained shower size spectrum and lateral distribution of shower particles occur in agreement with conventional data. Future studies in the field of 1014 -1017 eV cosmic ray physics to be held at the new shower installation are discussed.

  7. Underthrusting of Tarim beneath the Tien Shan and deep structure of their junction zone: Main results of seismic experiment along MANAS Profile Kashgar-Song-Köl

    NASA Astrophysics Data System (ADS)

    Makarov, V. I.; Alekseev, D. V.; Batalev, V. Yu.; Bataleva, E. A.; Belyaev, I. V.; Bragin, V. D.; Dergunov, N. T.; Efimova, N. N.; Leonov, M. G.; Munirova, L. M.; Pavlenkin, A. D.; Roecker, S.; Roslov, Yu. V.; Rybin, A. K.; Shchelochkov, G. G.

    2010-03-01

    The results of reflection CMP seismic profiling of the Central Tien Shan in the meridional tract 75-76° E from Lake Song-Köl in Kyrgyzstan to the town of Kashgar in China are considered. The seismic section demonstrating complex heterogeneous structure of the Earth’s crust and reflecting its near-horizontal delamination with vertical and inclined zones of compositional and structural differentiation was constructed from processing of initial data of reflection CMP seismic profiling, earthquake converted-wave method (ECWM), and seismic tomography. The most important is the large zone of underthrusting of the Tarim Massif beneath the Tien Shan.

  8. CAT LIDAR wind shear studies

    NASA Technical Reports Server (NTRS)

    Goff, R. W.

    1978-01-01

    The studies considered the major meteorological factors producing wind shear, methods to define and classify wind shear in terms significant from an aircraft perturbation standpoint, the significance of sensor location and scan geometry on the detection and measurement of wind shear, and the tradeoffs involved in sensor performance such as range/velocity resolution, update frequency and data averaging interval.

  9. Shear bands in concentrated bacterial suspensions under oscillatory shear

    NASA Astrophysics Data System (ADS)

    Cheng, Xiang; Samanta, Devranjan; Xu, Xinliang

    2016-11-01

    Bacterial suspensions show interesting rheological behaviors such as a remarkable "superfluidic" state with vanishing viscosity. Although the bulk rheology of bacterial suspensions has been experimentally studied, shear profiles within bacterial suspensions have not been systematically explored so far. Here, by combining confocal rheometry with PIV, we investigated the flow behaviors of concentrated E. coli suspensions under planar oscillatory shear. We found that concentrated bacterial suspensions exhibit strong non-homogeneous flow profiles at low shear rates, where shear rates vanish away from the moving shear plate. We characterized the shape of the nonlinear shear profiles at different applied shear rates and bacterial concentrations and activities. The shear profiles follow a simple scaling relation with the applied shear rates and the enstrophy of suspensions, unexpected from the current hydrodynamic models of active fluids. We demonstrated that this scaling relation can be quantitatively understood by considering the power output of bacteria at different orientations with respect to shear flows. Our experiments reveal a profound influence of shear flows on the locomotion of bacteria and provide new insights into the dynamics of active fluids. The research is funded by ACS Petroleum Research Fund (54168-DNI9) and by the David & Lucile Packard Foundation. X. X. acknowledges support by the National Natural Science Foundation of China No. 11575020.

  10. Shear Yielding and Shear Jamming of Dense Hard Sphere Glasses

    NASA Astrophysics Data System (ADS)

    Urbani, Pierfrancesco; Zamponi, Francesco

    2017-01-01

    We investigate the response of dense hard sphere glasses to a shear strain in a wide range of pressures ranging from the glass transition to the infinite-pressure jamming point. The phase diagram in the density-shear strain plane is calculated analytically using the mean-field infinite-dimensional solution. We find that just above the glass transition, the glass generically yields at a finite shear strain. The yielding transition in the mean-field picture is a spinodal point in presence of disorder. At higher densities, instead, we find that the glass generically jams at a finite shear strain: the jamming transition prevents yielding. The shear yielding and shear jamming lines merge in a critical point, close to which the system yields at extremely large shear stress. Around this point, highly nontrivial yielding dynamics, characterized by system-spanning disordered fractures, is expected.

  11. Gelation under shear

    SciTech Connect

    Butler, B.D.; Hanley, H.J.M.; Straty, G.C.; Muzny, C.D.

    1995-12-31

    An experimental small angle neutron scattering (SANS) study of dense silica gels, prepared from suspensions of 24 nm colloidal silica particles at several volume fractions {theta} is discussed. Provided that {theta}{approx_lt}0.18, the scattered intensity at small wave vectors q increases as the gelation proceeds, and the structure factor S(q, t {yields} {infinity}) of the gel exhibits apparent power law behavior. Power law behavior is also observed, even for samples with {theta}>0.18, when the gel is formed under an applied shear. Shear also enhances the diffraction maximum corresponding to the inter-particle contact distance of the gel. Difficulties encountered when trying to interpret SANS data from these dense systems are outlined. Results of computer simulations intended to mimic gel formation, including computations of S(q, t), are discussed. Comments on a method to extract a fractal dimension characterizing the gel are included.

  12. Shear-thinning Fluid

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Whipped cream and the filling for pumpkin pie are two familiar materials that exhibit the shear-thinning effect seen in a range of industrial applications. It is thick enough to stand on its own atop a piece of pie, yet flows readily when pushed through a tube. This demonstrates the shear-thinning effect that was studied with the Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002. CVX observed the behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. The principal investigator was Dr. Robert Berg of the National Institutes of Standards and Technology in Gaithersburg, MD.

  13. Shear Roll Mill Reactivation

    DTIC Science & Technology

    2012-09-13

    process equipment sprinkler protection systems , and the 5 psig steam supply serving the building heating and make-up air systems . It also included...control system can be run for maintenance and/or checkout while the fire alarm panel is bypassed. A sprinkler line and gate valve serving the Primac...the 440 v. electrical system providing power for process equipment motors, shear roll hydraulic pump motors, the air compressor motor, as well as

  14. Micromechanics of shear banding

    SciTech Connect

    Gilman, J.J.

    1992-08-01

    Shear-banding is one of many instabilities observed during the plastic flow of solids. It is a consequence of the dislocation mechanism which makes plastic flow fundamentally inhomogeneous, and is exacerbated by local adiabatic heating. Dislocation lines tend to be clustered on sets of neighboring glide planes because they are heterogeneously generated; especially through the Koehler multiple-cross-glide mechanism. Factors that influence their mobilities also play a role. Strain-hardening decreases the mobilities within shear bands thereby tending to spread (delocalize) them. Strain-softening has the inverse effect. This paper reviews the micro-mechanisms of these phenomena. It will be shown that heat production is also a consequence of the heterogeneous nature of the microscopic flow, and that dislocation dipoles play an important role. They are often not directly observable, but their presence may be inferred from changes in thermal conductivity. It is argued that after deformation at low temperatures dipoles are distributed a la Pareto so there are many more small than large ones. Instability at upper yield point, the shapes of shear-band fronts, and mechanism of heat generation are also considered. It is shown that strain-rate acceleration plays a more important role than strain-rate itself in adiabatic instability.

  15. Folded Lithospheric Basins in Central Asia: Altai-Sayan and Tien Shan basins in a folding lithosphere

    NASA Astrophysics Data System (ADS)

    Delvaux, Damien; Cloetingh, Sierd; Beekman, Fred; Sokoutis, Dimitrios; Burov, Evguenii; Buslov, Misha; Abdrakhmatov, Kanatbeck

    2014-05-01

    Central Asia is a classic example for continental lithospheric folding. In particular, the Altay-Sayan belt in South-Siberia and the Kyrgyz Tien Shan display a special mode of lithospheric deformation, involving decoupled lithospheric mantle folding and upper crustal folding and faulting. A review of the paleostress data and tectono-stratigraphic evolution of the Kurai-Chuya basin in Siberian Altai, Zaisan basin in Kazakh South Altai and Issyk-Kul basin in Kyrgyz Tien Shan suggests that these basins were initiated in an extensional context and later inverted by a combination of fault-controlled deformation and flexural folding. They deformed by a combination of lithospheric buckling inducing surface tilting, uplift and subsidence, together with upper crustal fault-controlled deformation. They are good examples of Folded Lithospheric Basins (FLB) which typically form in a buckling lithosphere. Their characteristic basin fill and symmetry, inner structure, folding wavelength and amplitude, thermal regime and time frame are examined in relation to basement structure, stress field, strain rate, timing of deformation, and compared to existing modelling results. Both regions of active lithospheric folding have a heterogeneous crust with a long history of accretion-collision, subsequently reactivated as a far-field effect of the Indian-Eurasian collision. Thanks to the youthfulness of the tectonic deformation in this region (peak deformation in late Pliocene - early Pleistocene), the surface expression of lithospheric deformation is well documented by the surface topography and superficial tectonic structures.

  16. Monitoring of lake level changes on the Tibetan Plateau and Tian Shan by retracking Cryosat SARIn waveforms

    NASA Astrophysics Data System (ADS)

    Kleinherenbrink, M.; Lindenbergh, R. C.; Ditmar, P. G.

    2015-02-01

    In this study we present, for the first time, the application of Cryosat SARIn mode data to monitor lakes in mountainous areas and to find their water balance. By applying a novel retracker, tailored for lake level observations, we find at least four useable passes for 125 lakes on the Tibetan Plateau and Tian Shan areas over the period February 2012 to January 2014. From these 125 lakes, 30 are passed at least ten times, for which we compute trends and periodic variations, and 16 lakes more then twenty times, for which we additionally apply a water slope correction. This slope correction accounts for geoid inaccuracies or wind effects. We compared the results over two lakes, Langa Co and Bosten, with Jason-2 measurements. Over Langa Co we find an RMS difference of 0.55 m, while for Lake Bosten this is only 0.26 m. For Lake Bosten, the estimated trends, annual and semi-annual variations from the Cryosat and Jason-2 datasets are compared as well. The estimated amplitudes are comparable, while derived phases differ by a few days. Using the trends of all lakes passed at least ten times, a water volume balance of natural lakes is estimated. A loss of 1.51 ± 0.11 km3 y-1 is observed in the lakes in the Tian Shan area. In Tibet, a positive mass balance is estimated of 1.76 ± 0.24 km3 y-1.

  17. Autonomous geodynamics of the Pamir-Tien Shan junction zone from seismology data

    NASA Astrophysics Data System (ADS)

    Lukk, A. A.; Shevchenko, V. I.; Leonova, V. G.

    2015-11-01

    The geodynamics of the Tajik Depression, the junction zone of the Pamirs and Tien Shan, is typically considered in the context of plate tectonic concept, which implies intense subhorizontal compression of the zone resulting from the subduction of the Indian and Eurasian lithospheric plates. This convergence has been reliably confirmed by the GPS measurements. However, the joint analysis of the geological structure, seismicity, and geodimeter measurements conducted during a few years at the Garm geodynamical testing site of the Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, demonstrates a widening of the Tajik Depression instead of its shortening, as should be expected from the subhorizontal compression predominant in the present-day stress-state of this region. This conclusion, together with the data from the other regions, suggests that, along with the plate tectonic mechanisms, there are also other, local, autonomous drivers that contribute to the tectogenesis of this region. Besides, the probable existence of these autonomous sources within the Tajik Depression directly follows from the seismology data. Among them is the crustal spreading within the depression suggested by the seismotectonic displacements in the focal mechanisms of the earthquakes. These displacements are directed in different azimuths off the axial's most subsided part of the depression at a depth of 20-30 km. Above this region the distribution of seismotectonic deformations (STD) is chaotic. This pattern of deformation is barely accounted for by a simple model of subhorizontal compression of the Earth's crust in the region. In our opinion, these features of the seismotectonic deformation in the crust within the studied part of the Tajik Depression is probably associated with the gain in the volume of the rocks due to the inflow of the additional material, which is supplied from the bottom crust or upper mantle by the deep fluids. This increase in the rock volume

  18. Instabilities in shear and simple shear deformations of gold crystals

    NASA Astrophysics Data System (ADS)

    Pacheco, A. A.; Batra, R. C.

    We use the tight-binding potential and molecular mechanics simulations to study local and global instabilities in shear and simple shear deformations of three initially defect-free finite cubes of gold single crystal containing 3480, 7813, and 58,825 atoms. Displacements on all bounding surfaces are prescribed while studying simple shear deformations, but displacements on only two opposite surfaces are assigned during simulations of shear deformations with the remaining four surfaces kept free of external forces. The criteria used to delineate local instabilities in the system include the following: (i) a component of the second-order spatial gradients of the displacement field having large values relative to its average value in the body, (ii) the minimum eigenvalue of the Hessian of the energy of an atom becoming non-positive, and (iii) structural changes represented by a high value of the common neighborhood parameter. It is found that these criteria are met essentially simultaneously at the same atomic position. Effects of free surfaces are evidenced by different deformation patterns for the same specimen deformed in shear and simple shear. The shear strength of a specimen deformed in simple shear is more than three times that of the same specimen deformed in shear. It is found that for each cubic specimen deformed in simple shear the evolution with the shear strain of the average shear stress, prior to the onset of instabilities, is almost identical to that in an equivalent hyperelastic material with strain energy density derived from the tight-binding potential and the assumption that it obeys the Cauchy-Born rule. Even though the material response of the hyperelastic body predicted from the strain energy density is stable over the range of the shear strain simulated in this work, the molecular mechanics simulations predict local and global instabilities in the three specimens.

  19. Local climate differences between the adjacent Linxia and Xunhua basins, NE Tibet reveal 11 Ma history of relief in the intervening Jishi Shan

    NASA Astrophysics Data System (ADS)

    Hough, B.; Garzione, C.; Wang, Z.; Zheng, W.; Yuan, D.; Zhang, P.; Molnar, P.

    2008-12-01

    The 3500-4000 m high Jishi Shan located on the boarder between Gansu and Qinghai Provinces along the northeast margin of the Tibetan Plateau stands as an orographic barrier to easterly derived summer rainfall. Comparison of stable isotope compositions of modern rainfall (δ18O and δ2H) and paleo-soil carbonate (δ18O and δ13C) from the leeward Xunhua basin and the windward Linxia basin provides a method for the interpretation of changes in local climate related to the formation of relief in the intervening Jishi Shan. Rayleigh distillation models suggest that a vapor mass experiencing orographic rainout should be relatively depleted in 18O on the lee side of the range. However, increased aridity in the rain shadow of the Jishi Shan results in a net 2‰ enrichment in the δ18O values of modern rainfall in the Xunhua basin due to evaporative enrichment of 18O. Using the stable isotope compositions of pedogenic and lacustrine carbonates in the Xunhua and Linxia basins as a proxy for paleoclimate, we find that the aridity difference between these basins has existed throughout at least the past 11 Ma, implying the presence of the Jishi Shan. These data indicate that intra- basin comparisons of the stable isotope composition of sedimentary carbonates can be used to assess the timing of emergence of basin-segmenting mountain ranges between the sub-basins of northeastern Tibet.

  20. Estimation of recurrence interval of large earthquakes on the central Longmen Shan fault zone based on seismic moment accumulation/release model.

    PubMed

    Ren, Junjie; Zhang, Shimin

    2013-01-01

    Recurrence interval of large earthquake on an active fault zone is an important parameter in assessing seismic hazard. The 2008 Wenchuan earthquake (Mw 7.9) occurred on the central Longmen Shan fault zone and ruptured the Yingxiu-Beichuan fault (YBF) and the Guanxian-Jiangyou fault (GJF). However, there is a considerable discrepancy among recurrence intervals of large earthquake in preseismic and postseismic estimates based on slip rate and paleoseismologic results. Post-seismic trenches showed that the central Longmen Shan fault zone probably undertakes an event similar to the 2008 quake, suggesting a characteristic earthquake model. In this paper, we use the published seismogenic model of the 2008 earthquake based on Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data and construct a characteristic seismic moment accumulation/release model to estimate recurrence interval of large earthquakes on the central Longmen Shan fault zone. Our results show that the seismogenic zone accommodates a moment rate of (2.7 ± 0.3) × 10¹⁷ N m/yr, and a recurrence interval of 3900 ± 400 yrs is necessary for accumulation of strain energy equivalent to the 2008 earthquake. This study provides a preferred interval estimation of large earthquakes for seismic hazard analysis in the Longmen Shan region.

  1. Estimation of Recurrence Interval of Large Earthquakes on the Central Longmen Shan Fault Zone Based on Seismic Moment Accumulation/Release Model

    PubMed Central

    Zhang, Shimin

    2013-01-01

    Recurrence interval of large earthquake on an active fault zone is an important parameter in assessing seismic hazard. The 2008 Wenchuan earthquake (Mw 7.9) occurred on the central Longmen Shan fault zone and ruptured the Yingxiu-Beichuan fault (YBF) and the Guanxian-Jiangyou fault (GJF). However, there is a considerable discrepancy among recurrence intervals of large earthquake in preseismic and postseismic estimates based on slip rate and paleoseismologic results. Post-seismic trenches showed that the central Longmen Shan fault zone probably undertakes an event similar to the 2008 quake, suggesting a characteristic earthquake model. In this paper, we use the published seismogenic model of the 2008 earthquake based on Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data and construct a characteristic seismic moment accumulation/release model to estimate recurrence interval of large earthquakes on the central Longmen Shan fault zone. Our results show that the seismogenic zone accommodates a moment rate of (2.7 ± 0.3) × 1017 N m/yr, and a recurrence interval of 3900 ± 400 yrs is necessary for accumulation of strain energy equivalent to the 2008 earthquake. This study provides a preferred interval estimation of large earthquakes for seismic hazard analysis in the Longmen Shan region. PMID:23878524

  2. Active thrusting and folding along the northern Tien Shan and Late Cenozoic rotation of the Tarim relative to Dzungaria and Kazakhstan

    NASA Astrophysics Data System (ADS)

    Avouac, Jean-Philippe; Tapponnier, P.; Bai, M.; You, H.; Wang, G.

    1993-04-01

    Geometries and rates of Late Cenozoic thrust faulting and folding along the northern piedmont of the Tien Shan mountain belt, which was the location of the 1906 Manas earthquake, are studied. A flexural foredeep of the Dzungarian basement, filled with up to 11,000 m of sediment, is overthrusted by the 5,000 m northern range of the Tien Shan. The active thrust is found to reach the surface 30 km north of the front range, within a 200-km-long zone of Neogene-Quaternary anticlines. Cenozoic shortening of the folded Dzungarian sediments is estimated to be on the order of 30 km, and the Cenozoic shortening rate is found to have been 3.0 +/- 1.5 mm/yr. Reactivation of the Tien Shan by the collision of India and Asia is determined to have taken place in the early to middle Miocene. This is consistent with the existence of thick late Neogene and Quaternary deposits. Reactivation of the Tien Shan roughly coincides with the great mid-Miocene changes in tectonic regimes, denudation, and sedimentation rates seen in southeast Asia.

  3. A fluvial terrace record of late Quaternary folding rate of the Anjihai anticline in the northern piedmont of Tian Shan, China

    NASA Astrophysics Data System (ADS)

    Fu, Xiao; Li, Sheng-Hua; Li, Bo; Fu, Bihong

    2017-02-01

    Crustal shortening of the Tian Shan Range in northwest China has largely been accommodated by fold-and-thrust belts that mark the northern and southern mountain boundaries, which were formed during the basinward propagation of the deformation front of Tian Shan. Investigating the deformation rates of active folds (anticlines) in the mountain piedmonts within different timescales is important for understanding the mountain building and front propagation processes of the Tian Shan. In this study, we investigate the late Quaternary folding rate of the Anjihai anticline, one of the major anticlines in the northern piedmont of Tian Shan. Our study is based on optically stimulated luminescence (OSL) dating and topographic measurements of folded river terraces. Three well-preserved fluvial terraces across the Anjihai anticline were identified and dated to be 3.6 ± 0.1 ka, 9.0 ± 0.6 ka and 53.3 ± 2.2 ka, respectively. These terrace ages are combined with shortening and uplift of the terraces estimated using an area-conservation method and the terrace height profiles to evaluate the average shortening and uplift rates. Our results show that the minimum shortening rate of the Anjihai anticline is 0.4 mm/a between 53 ka and 9 ka and 1.1 mm/a over the past 9 ka, and the corresponding minimum uplift rates are 0.5 mm/a and 1.4 mm/a, respectively. If a local sedimentation rate of 0.3 mm/a is taken into consideration, the shortening rate is 0.7 mm/a between 53 ka and 9 ka and 1.3 mm/a since 9 ka, and the corresponding uplift rates are 0.8 mm/a and 1.5 mm/a, respectively. These data suggest that the Anjihai anticline has accommodated 20-25% of the total shortening across the whole eastern Tian Shan ( 5 mm/a) in the Holocene. Our results suggest that the Holocene is a relatively tectonically active time interval since the late Pleistocene. The late Quaternary shortening rate of the Anjihai anticline is much higher than its long-term average shortening rate (0.2 mm/a) since its

  4. Uplift and denudation rates of an actively growing mountain range inferred from in-situ produced cosmogenic 10Be: the Yumu Shan (NE Tibetan Plateau)

    NASA Astrophysics Data System (ADS)

    Palumbo, L.; Hetzel, R.; Minxing, T.; Li, X.; Guo, J.

    2009-04-01

    Located in the foreland of the Quilian Shan (NE Tibet), the Yumu Shan is an isolated mountain range bounded by an active NW-SE striking thrust fault. Geomorphic and structural features such as fault scarps and wind gaps suggest that the ~70 km long range is actively growing (Hetzel et al., 2004; Tapponnier et al., 1990), hence the tectonic uplift should exceed the rate of denudation. Here we quantify the rate of these two competing processes using in-situ produced cosmogenic 10Be. Catchment-wide denudation rates are derived from 10Be concentrations in stream sediments, whereas rock uplift rates are obtained by combining scarp topographic profiles with dating of geomorphic surfaces deformed by active thrust faults at the Yumu Shan mountain front. Both denudation and rock uplift rates integrate over a similar temporal scale (~10-100 ka) and thus over many earthquake cycles. Our data document that catchment wide-denudation rates vary from ~100 to ~400 mm ka-1 as a function of morphology and lithology, while rock uplift takes place at the rate of ~0.7 mm ka-1. The difference between these values confirms that the Yumu Shan is in a topographic pre-steady state and in accordance with geomorphic and structural features. Tectonic features indicate that over few millions of years the Yumu Shan may rise to a similar height as the main ranges of the Qilian Shan farther south, which have peaks with elevations between ~5 and ~5.5 km. References: Hetzel R., Tao M., Niedermann S., Strecker M.R., Ivy-Ochs S., Kubik P.W., Gao B. (2004). Implications of the fault scaling law for the growth of topography: Mountain ranges in the broken foreland of NE Tibet, Terra Nova, 16, 157-162. Tapponnier P., Meyer B., Avouac J.P., Peltzer G., Gaudemer Y., Guo S., Xiang H., Yin K., Chen Z., Cai S., Dai H. (1990). Active thrusting and folding in the Quilian Shan, and decoupling between upper crust and mantle in northeastern Tibet, Earth Planet. Sci. Lett., 97, 382-403.

  5. Shear mode grinding

    SciTech Connect

    Brown, N.J.; Fuchs, B.A.

    1989-04-24

    The thesis of this paper is that shear mode grinding of glass (1) occurs with abrasive particle sizes less than 1/mu/m, (2) that it is the mechanical limit of the the more common mechanical-chemical glass polishing, and (3) that the debris is insufficient in size to perform the function of eroding the binder in the grinding wheel and thus necessitates the addition of an abrasive and/or chemical additions to the coolant to effect wheel-dressing. 13 refs.

  6. The evolution of a terrace sequence along the Manas River in the northern foreland basin of Tian Shan, China, as inferred from optical dating

    NASA Astrophysics Data System (ADS)

    Gong, Zhijun; Li, Sheng-Hua; Li, Bo

    2014-05-01

    The Tian Shan range lies in the actively deforming part of the India-Asia collision zone. The uplift rate and deformation pattern of the Tian Shan are important for understanding the dynamics of crustal deformation in the region. The river terraces in northern Tian Shan provide key records of past changes in climate and/or regional tectonics. In this study, a terrace sequence along the Manas River in a tectonically active zone in the northern foreland basin of Tian Shan is investigated. Six river terraces were identified and dated using optically stimulated luminescence (OSL). The results show that the six terraces were abandoned at ~ 0.5 ka, ~ 1.4 ka, ~ 3.1 ka, ~ 4.0 ka, ~ 12.4 ka and ~ 19.9 ka, respectively. Together with high resolution Global Positioning System (GPS) measurements on the terrace treads, the fluvial history of Manas River is reconstructed. From ~ 20 ka to ~ 4.8 ka, the height of the fluvial bed of Manas River decreased at an average rate of 2.2 ± 0.6 mm/yr. From ~ 4.8 ka to the present, the height of the fluvial bed decreased at an average rate of 13.5 ± 0.6 mm/yr, corresponding to intensified incision of Manas River during the late Holocene. This accelerated incision is very likely caused by the tectonic forces rather than climatic influences alone, suggesting that the tectonic uplift activity was significantly intensified since ~ 4.8 ka in the northern piedmont of Tian Shan. Other controlling factors on the incision of Manas River are also discussed.

  7. Crustal structure of the northern margin of the eastern Tien Shan, China, and its tectonic implications for the 1906 M~7.7 Manas earthquake

    USGS Publications Warehouse

    Wang, Chun-Yong; Yang, Zhu-En; Luo, Hai; Mooney, W.D.

    2004-01-01

    The Tien Shan orogenic belt is the most active intracontinental mountain belt in the world. We describe an 86-km-long N–S-trending deep seismic reflection profile (which passes through the southern Junggar basin) located on the northeastern Tien Shan piedmont. Two distinct anticlines beneath the northern margin of the Tien Shan are clearly imaged in the seismic section. In addition, we have imaged two detachment surfaces at depths of ∼7 and ∼16 km. The detachment surface at 16-km depth corresponds to the main detachment that converges with the steep angle reverse fault (the Junggar Southern Marginal Fault) on which the 1906 M~7.7 Manas earthquake occurred. A 12–14-km-thick sedimentary basin is imaged beneath the southern Junggar basin near Shihezi. The crust beneath the northern margin of the Tien Shan is 50–55-km thick, and decreases beneath the Junggar basin to 40–45-km thick. The crustal image of the deep seismic reflection profile is consistent with models derived from nearby seismic refraction data and Bouguer gravity anomalies in the same region. The faulting associated with the 1906 Manas earthquake also fits within the structural framework imaged by the seismic reflection profile. Present-day micro-seismicity shows a hypocentral depth-distribution between 5 and 35 km, with a peak at 20 km. We hypothesize that the 1906 Manas earthquake initiated at a depth of ∼20 km and propagated upwards, causing northward slip on the sub-horizontal detachments beneath the southern Junggar basin. Thus, in accord with regional geological mapping, the current shortening within the eastern Tien Shan is accommodated both by high-angle reverse faulting and detachment faulting that can be clearly imaged at depth in seismic reflection data.

  8. Crustal structure of the northern margin of the eastern Tien Shan, China, and its tectonic implications for the 1906 M~7.7 Manas earthquake

    NASA Astrophysics Data System (ADS)

    Wang, Chun-Yong; Yang, Zhu-En; Luo, Hai; Mooney, W. D.

    2004-06-01

    The Tien Shan orogenic belt is the most active intracontinental mountain belt in the world. We describe an 86-km-long N-S-trending deep seismic reflection profile (which passes through the southern Junggar basin) located on the northeastern Tien Shan piedmont. Two distinct anticlines beneath the northern margin of the Tien Shan are clearly imaged in the seismic section. In addition, we have imaged two detachment surfaces at depths of ˜7 and ˜16 km. The detachment surface at 16-km depth corresponds to the main detachment that converges with the steep angle reverse fault (the Junggar Southern Marginal Fault) on which the 1906 M~7.7 Manas earthquake occurred. A 12-14-km-thick sedimentary basin is imaged beneath the southern Junggar basin near Shihezi. The crust beneath the northern margin of the Tien Shan is 50-55-km thick, and decreases beneath the Junggar basin to 40-45-km thick. The crustal image of the deep seismic reflection profile is consistent with models derived from nearby seismic refraction data and Bouguer gravity anomalies in the same region. The faulting associated with the 1906 Manas earthquake also fits within the structural framework imaged by the seismic reflection profile. Present-day micro-seismicity shows a hypocentral depth-distribution between 5 and 35 km, with a peak at 20 km. We hypothesize that the 1906 Manas earthquake initiated at a depth of ˜20 km and propagated upwards, causing northward slip on the sub-horizontal detachments beneath the southern Junggar basin. Thus, in accord with regional geological mapping, the current shortening within the eastern Tien Shan is accommodated both by high-angle reverse faulting and detachment faulting that can be clearly imaged at depth in seismic reflection data.

  9. Geologic Hazards Associated with Longmen Shan Fault zone, During and After the Mw 8.0, May 12, 2008 Earthquake

    NASA Astrophysics Data System (ADS)

    Xu, X.; Kusky, T.; Li, Z.

    2008-12-01

    A magnitude 8.0 earthquake shook the northeastern margin of the Tibetan plateau, on May 12, 2008 along the Longmen Shan orogenic belt that marks the boundary between the Songpan Ganzi terrane and Yangtze block. The Tibetan plateau is expanding eastwards, and GPS observations show that surface motion directions are northeast relative to the Sizhuan basin where the earthquake occurred. This sense of motion of crustal blocks is the reason why the main faults in Longmen Shan are oblique thrust-dextral strike slip faults. There are three main parallel thrust/ dextral-slip faults in Longmen Shan. All three faults strike northeast and dip to northwest. The May 12 rupture extends 270 km along the fault zone, and the epicenter of the magnitude 8.0 earthquake was located in Wenchuan, 90 km WNW of Chengdu, Sichuan, China. The devastating earthquake killed at least 87,652 people and destroyed all the buildings in epicenter. The victims of the earthquake zone want to rebuild their homes immediately, but they need more suggestions about the geologic hazards to help them withstand future possible earthquakes. So after earthquake, we went to disaster areas from July 5th to 10th to get first-hand field data, which include observations of surface ruptures, landslides, features of X joints on the damaged buildings, parameters of the active faults and landslides. If we only depend on the field data in accessible locations, we can only know the information of the ruptures in these positions, and we can't learn more information about the whole area affected by the earthquake. The earthquake zone shows surface rupture features of both thrust and strike-slip fault activities, indicating oblique slip followed by thrusting during the May 12 earthquake. In my talk, I will show the general regional geological disaster information by processing the pro- and post-earthquake satellite data. Then we combine the raw field data and regional geology as the restrictive conditions to determine the

  10. Glaciation in a tectonically active environment: Preliminary observations from the Inylchek and Sary-Dzaz Valleys, Kyrgyz Tian Shan

    NASA Astrophysics Data System (ADS)

    Lifton, N. A.; Beel, C.; Blomdin, R.; Caffee, M. W.; Chen, Y.; Codilean, A.; Goehring, B. M.; Gribenski, N.; Harbor, J.; Hattestrand, C.; Heyman, J.; Ivanov, M.; Kassab, C.; Li, Y.; Petrakov, D.; Rogozhina, I.; Stroeven, A. P.; Usubaliev, R.; Wetzel, H.

    2012-12-01

    The Tian Shan comprises a series of generally east-northeast trending mountain ranges and intermontane basins in Central Asia, formed in response to northward propagation of stresses associated with the India-Asia collision and focused between the Tarim Basin and the Kazakh Shield. These ranges are typically bounded by seismically active reverse or oblique-slip faults occupying reactivated zones of crustal weakness formed during prior deformational episodes. Neogene deformation distributed across the Tian Shan has resulted in some of the world's highest peaks outside the Himalaya, particularly in eastern Kyrgyzstan along the border with China and Kazakhstan. Major glaciers drain these peaks - one of the largest is the glacier that occupies the Inylchek Valley. This glacier is currently the focus of an intensive monitoring effort by Kyrgyz, German and Austrian groups to understand its mass balance in response to climate change, yet not much is known about its response to previous glaciations. Much of the Inylchek Valley lies along the Atbashi-Inylchek fault (also known as the South Tian Shan Suture), a major left-oblique slip fault that forms the southern boundary of the Sary-Dzaz range. Recent thermochronologic work has shown this range to be uplifting rapidly since ca. 2-3 Ma. This portion of the Inylchek Valley is linear but transitions to a southward-trending releasing bend at its western end, forming what has been mapped as a pull-apart basin. This end of the Inylchek Valley contains a moraine complex that we sampled for surface exposure dating by 10Be and 26Al in 2011. Results for both nuclides from two large boulders on this moraine indicate a preliminary age of approximately 20 ka (Lal/Stone scaling). The southern slope of the Sary-Dzaz range is characterized by a series of ridges and terraces spanning ca. 800 m in altitude from the present valley bottom, yet glaciers within the range and their associated deposits are restricted to the uppermost sections of

  11. Wind shear test

    NASA Astrophysics Data System (ADS)

    Techniques for forecasting and detecting a type of wind shear called microbursts are being tested this month in an operational program at Denver's Stapleton International Airport as part of an effort to reduce hazards to airplanes and passengers.Wind shear, which can be spawned by convective storms, can occur as a microburst. These downbursts of cool air are usually recognizable as a visible rain shaft beneath a thundercloud. Sometimes, however, the rain shaft evaporates before reaching the ground, leaving the downdraft invisible. Although thunderstorms are traditionally avoided by airplane pilots, these invisible downdrafts also harbor hazards in what usually appear to be safe skies. When the downdraft reaches the earth's surface, the downdraft spreads out horizontally, much like a stream of water gushing from a garden hose on a concrete surface, explained John McCarthy, director of the operational program. Airplanes can encounter trouble when the downdraft from the microburst causes sudden shifts in wind direction, which may reduce lift on the wing, an especially dangerous situation during takeoff.

  12. TUBE SHEARING VALVE

    DOEpatents

    Wilner, L.B.

    1960-05-24

    Explosive operated valves can be used to join two or more containers in fluid flow relationship, one such container being a sealed reservoir. The valve is most simply disposed by mounting it on the reservoir so thst a tube extends from the interior of the reservoir through the valve body, terminating at the bottom of the bore in a closed end; other containers may be similarly connected or may be open connected, as desired. The piston of the valve has a cutting edge at its lower end which shears off the closed tube ends and a recess above the cutting edge to provide a flow channel. Intermixing of the fluid being transferred with the explosion gases is prevented by a copper ring at the top of the piston which is force fitted into the bore at the beginning of the stroke. Although designed to avoid backing up of the piston at pressures up to 10,000 psi in the transferred fluid, proper operation is independent of piston position, once the tube ends were sheared.

  13. Excited waves in shear layers

    NASA Technical Reports Server (NTRS)

    Bechert, D. W.

    1982-01-01

    The generation of instability waves in free shear layers is investigated. The model assumes an infinitesimally thin shear layer shed from a semi-infinite plate which is exposed to sound excitation. The acoustical shear layer excitation by a source further away from the plate edge in the downstream direction is very weak while upstream from the plate edge the excitation is relatively efficient. A special solution is given for the source at the plate edge. The theory is then extended to two streams on both sides of the shear layer having different velocities and densities. Furthermore, the excitation of a shear layer in a channel is calculated. A reference quantity is found for the magnitude of the excited instability waves. For a comparison with measurements, numerical computations of the velocity field outside the shear layer were carried out.

  14. Inductive shearing of drilling pipe

    SciTech Connect

    Ludtka, Gerard M.; Wilgen, John; Kisner, Roger; Mcintyre, Timothy

    2016-04-19

    Induction shearing may be used to cut a drillpipe at an undersea well. Electromagnetic rings may be built into a blow-out preventer (BOP) at the seafloor. The electromagnetic rings create a magnetic field through the drillpipe and may transfer sufficient energy to change the state of the metal drillpipe to shear the drillpipe. After shearing the drillpipe, the drillpipe may be sealed to prevent further leakage of well contents.

  15. True Shear Parallel Plate Viscometer

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin; Kaukler, William

    2010-01-01

    This viscometer (which can also be used as a rheometer) is designed for use with liquids over a large temperature range. The device consists of horizontally disposed, similarly sized, parallel plates with a precisely known gap. The lower plate is driven laterally with a motor to apply shear to the liquid in the gap. The upper plate is freely suspended from a double-arm pendulum with a sufficiently long radius to reduce height variations during the swing to negligible levels. A sensitive load cell measures the shear force applied by the liquid to the upper plate. Viscosity is measured by taking the ratio of shear stress to shear rate.

  16. Failure During Sheared Edge Stretching

    NASA Astrophysics Data System (ADS)

    Levy, B. S.; van Tyne, C. J.

    2008-12-01

    Failure during sheared edge stretching of sheet steels is a serious concern, especially in advanced high-strength steel (AHSS) grades. The shearing process produces a shear face and a zone of deformation behind the shear face, which is the shear-affected zone (SAZ). A failure during sheared edge stretching depends on prior deformation in the sheet, the shearing process, and the subsequent strain path in the SAZ during stretching. Data from laboratory hole expansion tests and hole extrusion tests for multiple lots of fourteen grades of steel were analyzed. The forming limit curve (FLC), regression equations, measurement uncertainty calculations, and difference calculations were used in the analyses. From these analyses, an assessment of the primary factors that contribute to the fracture during sheared edge stretching was made. It was found that the forming limit strain with consideration of strain path in the SAZ is a major factor that contributes to the failure of a sheared edge during stretching. Although metallurgical factors are important, they appear to play a somewhat lesser role.

  17. Shearing dynamics and jamming density

    NASA Astrophysics Data System (ADS)

    Olsson, Peter; Vâgberg, Daniel; Teitel, Stephen

    2009-03-01

    We study the effect of a shearing dynamics on the properties of a granular system, by examining how the jamming density depends on the preparation of the starting configurations. Whereas the jamming density at point J was obtained by relaxing random configurations [O'Hern et al, Phys. Rev. E 68, 011306 (2003)], we apply this method to configurations obtained after shearing the system at a certain shear rate. We find that the jamming density increases somewhat and that this effect is more pronounced for configurations produced at smaller shear rates. Different measures of the order of the jammed configurations are also discussed.

  18. Tunable shear thickening in suspensions

    PubMed Central

    Lin, Neil Y.C.; Ness, Christopher; Cates, Michael E.; Sun, Jin; Cohen, Itai

    2016-01-01

    Shear thickening, an increase of viscosity with shear rate, is a ubiquitous phenomenon in suspended materials that has implications for broad technological applications. Controlling this thickening behavior remains a major challenge and has led to empirical strategies ranging from altering the particle surfaces and shape to modifying the solvent properties. However, none of these methods allows for tuning of flow properties during shear itself. Here, we demonstrate that by strategic imposition of a high-frequency and low-amplitude shear perturbation orthogonal to the primary shearing flow, we can largely eradicate shear thickening. The orthogonal shear effectively becomes a regulator for controlling thickening in the suspension, allowing the viscosity to be reduced by up to 2 decades on demand. In a separate setup, we show that such effects can be induced by simply agitating the sample transversely to the primary shear direction. Overall, the ability of in situ manipulation of shear thickening paves a route toward creating materials whose mechanical properties can be controlled. PMID:27621472

  19. Results from the 2009 Investigations at the Global Change Observatory "Gottfried Merzbacher" (Tien Shan, Kyrgyz Republic)

    NASA Astrophysics Data System (ADS)

    Häusler, Hermann; Leber, Diethard; Scheibz, Jürgen; Kopecny, Alexander; Wetzel, Hans-Ulrich; Echtler, Helmut; Moldobekov, Bolot

    2010-05-01

    The Global Change Observatory "Gottfried Merzbacher", which was installed near the former confluence of the Southern and Northern Inylchek Glacier, served as a platform for intensive field work in August 2009. "Peremitschka" (meaning "the area between") is a test site in front of the retreating Northern Inylchek Glacier, which regularly is flooded by the increasing glacier-dammed Lake Merzbacher, before it bursts out. Mapping the micro-geomorphology and conducting electrical resistivity tomography (ERT) profiles resulted in a sound interpretation of the surface morphology and of subsurface layers of the Peremitschka plain, which probably is underlain by both, permafrost and dead ice of the retreating Northern Inylchek Glacier. The flat 780 meters long high resolution ERT-profile reveals an undulated multilayer resistivity distribution. The uppermost 3-5 m of the profile show low resistivities ranging from 10 to about 200 ohm.m, indicating fine clastic sediments. In this area the surface of the whole test area is covered by silt and sand, the weathered material from the surrounding hills, which mainly consist of shists and calcareous shists of Upper Silurian to Lower Devonian age (Jamansu-Formation). The second "layer" below this low resistivity zone is characterized by resistivities up to 30.000 ohm.m to the final depth of the profile in approximately 45 m, and probably portraits permafrost overlying dead ice of the retreating Northern Inylchek Glacier. The geophysical measurements enable sound interpretations of the local geomorphology which consequently can be mapped in remote sensing images as flooded plain directly underlain by melting permafrost. Time series analysis of oblique aerial photos and remote sensing images allowed for a detailed reconstruction of the glacier retreat from 1943 to nowadays. It is still under discussion, however, if the Northern Inylchek Glacier surged in the late 1990ies. Compared to other regions in the Tien Shan range the youngest

  20. Heavy Metals in Sediment from Bei Shan River: Distribution, Relationship with Soil Characteristics and Multivariate Assessment of Contamination Sources.

    PubMed

    Xun, Yan; Xuegang, Luo

    2015-07-01

    The concentrations and correlation between some heavy metals (Mn, Cd, Cr, Cu, Ni, Zn and Pb) measured in sediments in part of Bei shan River near uranium mill tailings were studied. The mean concentration of Cr (57.7 mg/g) was more than the mean values established for uncultivated areas worldwide (46.3 mg/g). Negative correlations with pH and positive correlations with organic matter have been observed for most of elements analyzed in this study. Correlation analysis showed that all metals except Cr are highly correlated (p ≤ 0.01, p ≤ 0.05). This may indicate the different origin or controlling factors of Cr in analyzed sediments. Cluster analysis highlighted the lithogenic origin of heavy metals (Mn, Cd, Cu, Ni, Zn and Pb) and pointed out the primary input of Cr from anthropogenic sources.

  1. The role of shear in the transition from continuous shear thickening to discontinuous shear thickening

    NASA Astrophysics Data System (ADS)

    Jiang, Weifeng; Xuan, Shouhu; Gong, Xinglong

    2015-04-01

    Dense non-Brownian suspension has rich rheology and is hard to understand, especially for distinguishing continuous shear thickening (CST) from discontinuous shear thickening (DST). By studying the shear stress dependent rheology of a well-known DST suspension of cornstarch in water, we find that the transition from CST to DST could occur not only by increasing the volume fraction ϕ but also by increasing the shear stress σ. For the recovery process of jammed suspension, we observe that the shear activates the time-dependent nature of particle rearrangement. DST can then be interpreted as the consequence of shear-induced jamming. Based on the test data, we plot the schematic phase diagram in the ϕ-σ plane and find out that ϕ and σ perform almost the same effect on flow-state transition.

  2. Research on the Quaternary fluvial geomorphological surface sequence of the foreland region in southern Longmen Shan, eastern Tibet

    NASA Astrophysics Data System (ADS)

    Jiang, Dawei; Zhang, Shimin; Li, Wei

    2016-09-01

    Research on the complex structure of the Longmen Shan foreland is of great significance for understanding the tectonism of the eastern Tibetan Plateau. Therefore, using field survey of abandoned alluvial fans that developed during the middle Pleistocene and the terraces of the modern Qingyi River, a geomorphological surface sequence for the foreland region was established to study the tectonic surface processes. We know that the deformations of river terraces can serve as foundations for the study of tectonic activity. Because the Qingyi River ran through the foreland region in the south range of Longmen Shan, it is an appropriate research area and was adopted to solve these problems. However, in the humid temperate region, the terraces are strongly eroded and hardly retain continuous morphological surfaces. In addition, no marker horizons are available that can be utilized to restrain the corresponding relationships among terraces at the same level. To solve these problems, high-precision field measurements of the terraces and alluvial fan were made, and a series of long cross sections were acquired to determine the spatial relationships between the geomorphological surfaces; moreover, based on major element tests and grain size analyses, we found that the sediments of the geomorphological surfaces at all levels had favorable corresponding relationships. Using those specific analyses of geomorphological surfaces and sediments, a geomorphological surface sequence was derived for the foreland region. The surface sequence can be employed to study the tectonism of the foreland region over larger spatial and temporal ranges rather than using the limited modern terraces. In addition, after the ages of the geomorphological surfaces at various levels were further tested, the evolution of Qingyi River especially its two migrations since the middle Pleistocene in the foreland was determined.

  3. Repeated large-magnitude earthquakes in a tectonically active, low-strain continental interior: The northern Tien Shan, Kyrgyzstan

    NASA Astrophysics Data System (ADS)

    Landgraf, A.; Dzhumabaeva, A.; Abdrakhmatov, K. E.; Strecker, M. R.; Macaulay, E. A.; Arrowsmith, Jr.; Sudhaus, H.; Preusser, F.; Rugel, G.; Merchel, S.

    2016-05-01

    The northern Tien Shan of Kyrgyzstan and Kazakhstan has been affected by a series of major earthquakes in the late 19th and early 20th centuries. To assess the significance of such a pulse of strain release in a continental interior, it is important to analyze and quantify strain release over multiple time scales. We have undertaken paleoseismological investigations at two geomorphically distinct sites (Panfilovkoe and Rot Front) near the Kyrgyz capital Bishkek. Although located near the historic epicenters, both sites were not affected by these earthquakes. Trenching was accompanied by dating stratigraphy and offset surfaces using luminescence, radiocarbon, and 10Be terrestrial cosmogenic nuclide methods. At Rot Front, trenching of a small scarp did not reveal evidence for surface rupture during the last 5000 years. The scarp rather resembles an extensive debris-flow lobe. At Panfilovkoe, we estimate a Late Pleistocene minimum slip rate of 0.2 ± 0.1 mm/a, averaged over at least two, probably three earthquake cycles. Dip-slip reverse motion along segmented, moderately steep faults resulted in hanging wall collapse scarps during different events. The most recent earthquake occurred around 3.6 ± 1.3 kyr ago (1σ), with dip-slip offsets between 1.2 and 1.4 m. We calculate a probabilistic paleomagnitude to be between 6.7 and 7.2, which is in agreement with regional data from the Kyrgyz range. The morphotectonic signals in the northern Tien Shan are a prime example of deformation in a tectonically active intracontinental mountain belt and as such can help understand the longer-term coevolution of topography and seismogenic processes in similar structural settings worldwide.

  4. Sandbox modeling of evolving thrust wedges with different preexisting topographic relief: Implications for the Longmen Shan thrust belt, eastern Tibet

    NASA Astrophysics Data System (ADS)

    Sun, Chuang; Jia, Dong; Yin, Hongwei; Chen, Zhuxin; Li, Zhigang; Shen, Li; Wei, Dongtao; Li, Yiquan; Yan, Bin; Wang, Maomao; Fang, Shaozhi; Cui, Jian

    2016-06-01

    To understand the effects of substantial topographic relief on deformation localization in the seismically active mountains, like the Longmen Shan thrust belt in the eastern Tibet, sandbox experiments were performed based on the framework of the critical taper theory. First, a reference experiment revealed that the critical taper angle was 12° for our experimental materials. Subsequently, different proto wedges (subcritical (6° in taper angle), critical (12°), and supercritical (20°)) were introduced to cover the range of natural topographic relief, and we used two setups: setup A considered only across-strike topographic relief, whereas setup B investigated along-strike segmentation of topography, consist of two adjacent proto wedges. In all experiments, thrust wedges grew by in-sequence accretion of thrust sheets. Setup A revealed an alternating mode of slip partitioning on the accreted thrusts, with large-displacement thrust and small-displacement thrust developing in turn. And contrasting wedge evolutions occurred according to whether the proto wedge was subcritical or critical-supercritical. In setup B, the differential deformation along the strike produced transverse structures such as tear fault and lateral ramp during frontal accretion. The observed tear fault and its associated thrust system resemble the seismogenic fault system of the 2008 Mw7.9 Wenchuan earthquake. Our experimental results could also explain first-order deformation features observed in the Longmen Shan. Consequently, we conclude that topographic features, including topographic relief across the range and along-strike segmentation of topography, contribute significantly to the kinematics and deformation localization in such active mountains.

  5. Late Quaternary faulting on the Manas and Hutubi reverse faults in the northern foreland basin of Tian Shan, China

    NASA Astrophysics Data System (ADS)

    Gong, Zhijun; Li, Sheng-Hua; Li, Bo

    2015-08-01

    The Tian Shan Range lies in the actively deforming part of the India-Asia collision zone. In the northern foreland basin of Tian Shan, the strata were intensively deformed by Cenozoic folding and faulting. Slip rate studies along these faults are important for understanding the dynamics of crustal deformation and evaluating the seismic hazards in the region. Two reverse faults (the Manas and Hutubi faults) in the northern foreland basin were investigated. Due to past faulting events along these faults, the terrace treads along the Manas River were ruptured, forming fault scarps several meters in height. Loess deposits were trapped and preserved at the surface ruptures along these scarps. The thickness of the trapped loess is dependent on the size of the ruptures. The minimum and maximum ages of these scarps are constrained by dating the loess preserved at the surface ruptures and the terrace treads, respectively, using the quartz optically stimulated luminescence (OSL) dating technique. Our dating results suggest that the loess trapped at the ruptures was deposited from the early to mid-Holocene at the Hutubi Fault, and from the mid- to late-Holocene at the Manas Fault. The vertical displacements of the faults were evaluated by measuring the topographic profiles across the investigated fault scarps using the differential global position system (DGPS). Our results suggest that, during the late Quaternary in the studied region, the vertical slip rates of the Manas Fault were between ˜ 0.74 mm /yr and ˜ 1.6 mm /yr, while the Hutubi Fault had a much lower vertical slip rate between ˜ 0.34 mm /yr and ˜ 0.40 mm /yr. The tectonic implications of our results are discussed.

  6. Predictability of Sheared Tropical Cyclones

    NASA Astrophysics Data System (ADS)

    Zhang, F.; Tao, D.

    2015-12-01

    Predictability of the formation, rapid intensification and eyewall replacement of sheared tropical cyclones (TCs) are explored through a series of convection-permitting ensemble simulations using the Weather Research and Forecasting (WRF) model with different environmental vertical wind shear, sea-surface temperature (SST), and ambient moisture conditions. It is found that the intrinsic predictability of the RI onset time is more limited with increasing shear magnitude until the shear magnitude is large enough to prevent the TC formation. Based on ensemble sensitivity and correlation analysis, the RI onset timing within one set is largely related to the vortex tilt magnitude, the diabatic heating distribution and the strength of the primary vortex circulation. Systematic differences amongst the ensemble members begin to arise right after the initial burst of moist convection associated with the incipient vortex. This difference from the randomness inherent in moist convection in terms of both location and intensity first changes the TC vortex structure subtly and then leads to the deviations in system scales and eventually in the development (and precession) of the TC. On average, a higher SST has a positive effect on the TC formation and reduces the uncertainty of development under all shear conditions, while a drier environment has a negative impact on the TCs development and either broadens the ensemble spread of RI onset time or prevents the storm from forming when the shear-induced tilt is large. Nevertheless, the uncertainty in environmental shear magnitudes may dominate over the effect of randomness in moist convection in terms of TC formation and predictability. A byproduct of tropical cyclones under vertical wind shear is the secondary eyewall formation (SEF). It is found that the eyewall formation is more often observed in TCs with moderate to high shear, which was inherently more unpredictable. The inward contraction/axisymmeterization of shear

  7. Shear rotation numbers

    NASA Astrophysics Data System (ADS)

    Doeff, E.; Misiurewicz, M.

    1997-11-01

    This paper presents results on rotation numbers for orientation-preserving torus homeomorphisms homotopic to a Dehn twist. Rotation numbers and the rotation set for such homeomorphisms have been defined and initially investigated by the first author in a previous paper. Here we prove that each rotation number 0951-7715/10/6/017/img5 in the interior of the rotation set is realized by some compact invariant set, and that there is an ergodic measure on that set with mean rotation number 0951-7715/10/6/017/img5. It is also proved that the function which assigns its rotation set to such a homeomorphism is continuous. Finally, a counterexample is presented that shows that rational extremal points of the shear rotation set do not necessarily correspond to any periodic orbits.

  8. Models of fluid saturated zones according magnetotellurics and seismics data on Tien-Shan crust and mantle along transect MANAS

    NASA Astrophysics Data System (ADS)

    Bataleva, E.; Rybin, A.; Batalev, V.; Matyukov, V.

    2009-04-01

    Recognized as one of the highest, youngest, and most active orogenic systems on the Earth the Tien Shan is situated internal to the Eurasian continent. New deep seismic data acquired from 2004 to 2007 constitute an -400 km lithospheric transect located from the northwestern Tarim Basin in China to the northern Tien Shan in Kyrgyzstan. This seismic profile consists of 40 seismic stations "Quanterra" containing STS-2 (Streckeisen, Switzerland) and CMG - 3T (Güralp Systems Ltd) broadband seismic receivers. Registration of the seismic data in each station was conducted with sampling frequency of 40 Hz. Time service based on GPS clock was applied on each station. Average distance between the seismic stations along the profile is 10-15 km. Observations were held on 30 stations in Kyrgyzstan and on 10 of them in China. As a result of seismic investigations wave speeds cross-section was calculated. A 450 km long north-south magnetotelluric profile spanning the Tien Shan from Kazakhstan to western China reveals lateral variations in the resistivity of the Earth crust and mantle lithosphere to depths of 140 km. MT profile consisting of 19 long period MT soundings (20-20,000 s periods) were combined with 30 broadband stations (0.1-1600 s periods). Broadband measurements (0.001-100 s periods) were also acquired at the 14 long period sites in Kazakhstan and Kyrgyzstan. [Bielinski, et al 2003] Conductivity changes of up to one order of magnitude are a result from variations in temperature or composition, or both. Previous magneto telluric (MT) studies [Trapeznikov et al., 1997] partly show that some low velocity layers also have low resistivity, lending support to the fluid hypothesis. Studies of wave speeds reveal sections of the crust that have pronounced low velocity zones in the thicker portions of the crust which are attributed to crustal metasomatism [Ghose et al., 1998] or fluid filled fractures in pervasively deformed rocks [Vinnik et al., 2002]. Comparing an obtained

  9. Role of Lithosphere structural inheritance in the localization of intraplate deformation: the example of the Tien Shan (Central Asian Orogenic Belt)

    NASA Astrophysics Data System (ADS)

    Jourdon, Anthony; Le Pourhiet, Laetitia; Petit, Carole; Rolland, Yann

    2016-04-01

    Due to the India-Asia collision, the deformation of the Eurasian continent extends over several thousand kilometers, far away from the Himalayan belt. However, some areas like the Tarim craton are poorly deformed while others, as the Tien Shan belt or Tibet plateau, display large deformation rates. These actively deforming areas correspond to ancient plate boundaries which were previously involved in the construction of large orogenic belts. The Tien Shan is a relevant example to study the role of structural inheritance in the localization of recent deformation because of its Paleozoic tectonic history. Indeed, the Tien Shan has been built during two consecutive orogenies (Caledonian and Variscan) which formed large scale structures (as suture zones) clearly identifiable on the field. These structures are now reworked as active deformation zones where large earthquakes can occur. In order to improve our understanding of the role of this strong structural inheritance on the Cenozoic deformation, this study couples two approaches: 1-A field study which allowed us to identify the major Paleozoic structures, their geometry and the main lithologies involved. Our new findings include the reconnaissance of a transcurrent system in Middle Tien Shan, and a south-dipping structure of the major suture zone of the South Tien Shan/ North Tarim. 2-Based on a reconstruction of the pre-Cenozoic structure geometries, we use the thermomechanical modeling code Ptatin to simulate the lithospheric deformation of the belt depending on the geometry and rheology of inherited structures. Our results show that inherited structures first localize the deformation before that antithetic neoformed structures develop on the outer parts of the belt. This result is consistent with seismologic, seismic and GPS data, which show that the deformation is now localized on the borders of the belt, and especially propagates in the South Tien Shan/ North Tarim boundary along a N-dipping top-to-the South

  10. The Middle AsiaN Active Source (MANAS) Profile: Preliminary Results From A Deep Seismic Transect in the Tien Shan of Kyrgyzstan and China

    NASA Astrophysics Data System (ADS)

    Knapp, J. H.; Roecker, S. W.; Park, S. K.; Schelochkov, G.; He, R.

    2007-12-01

    New near-vertical deep seismic reflection data, acquired during the summer of 2007, constitute an ~350 km lithospheric transect from the northwestern Tarim Basin in China to the central Tien Shan of Kyrgyzstan. Recognized as one of the highest, youngest, and most active orogenic systems on Earth, the Tien Shan are situated internal to the Eurasian continent, removed up to 3000 km from the former plate boundary with the Indian subcontinent. Existing geologic constraints imply that up to 200 km of shortening may have occurred in Late Tertiary to Recent time. Additionally, geologic, topographic, and gravimetric data suggest that continental lithosphere of the Tarim basin may presently be subducting beneath the southern margin of the Tien Shan, in the absence of an oceanic slab. While geodetic measurements document that the Tien Shan currently record about half of the shortening between India and Eurasia, geologic data dictate that active faults are restricted to only several of the individual ranges that make up the mountain belt. Passive-source seismological studies have shown the surprising result that the orogenic crust is thickest (65-70 km) at both the southern and northern margins of the Tien Shan, and thins dramatically to ~35 km within the internal part of the orogen. Key targets of the MANAS (Middle AsiaN Active Source) Profile include (1) the top of the Tarim crust as it descends beneath the southern Tien Shan, (2) an inferred crustal-scale frontal ramp, representing where the continental plate may have broken and is now descending into the upper mantle, (3) the geometry of demonstrably active faults below the shallow depths to which they can be inferred from surface geologic constraints, (4) the topography and seismic reflection signature of the Moho, especially given the unexpected variations in crustal thickness across the orogen, and (5) the significance of both crustal and upper mantle conductivity anomalies previously identified through magnetotelluric

  11. APPARATUS FOR SHEARING TUBULAR JACKETS

    DOEpatents

    Simon, J.P.

    1962-09-01

    A machine is designed for removing the jacket from the core of a used rod-like fuel element by shearing the jacket into a spiral ribbon. Three skewed rolls move the fuel element axially and rotatively, and a tool cooperates with one of the rolls to carry out the shearing action. (AEC)

  12. A Piezoelectric Shear Stress Sensor

    NASA Technical Reports Server (NTRS)

    Kim, Taeyang; Saini, Aditya; Kim, Jinwook; Gopalarathnam, Ashok; Zhu, Yong; Palmieri, Frank L.; Wohl, Christopher J.; Jiang, Xiaoning

    2016-01-01

    In this paper, a piezoelectric sensor with a floating element was developed for shear stress measurement. The piezoelectric sensor was designed to detect the pure shear stress suppressing effects of normal stress generated from the vortex lift-up by applying opposite poling vectors to the: piezoelectric elements. The sensor was first calibrated in the lab by applying shear forces and it showed high sensitivity to shear stress (=91.3 +/- 2.1 pC/Pa) due to the high piezoelectric coefficients of PMN-33%PT (d31=-1330 pC/N). The sensor also showed almost no sensitivity to normal stress (less than 1.2 pC/Pa) because of the electromechanical symmetry of the device. The usable frequency range of the sensor is 0-800 Hz. Keywords: Piezoelectric sensor, shear stress, floating element, electromechanical symmetry

  13. Electroosmotic shear flow in microchannels.

    PubMed

    Mampallil, Dileep; van den Ende, Dirk

    2013-01-15

    We generate and study electroosmotic shear flow in microchannels. By chemically or electrically modifying the surface potential of the channel walls a shear flow component with controllable velocity gradient can be added to the electroosmotic flow caused by double layer effects at the channel walls. Chemical modification is obtained by treating the channel wall with a cationic polymer. In case of electric modification, we used gate electrodes embedded in the channel wall. By applying a voltage to the gate electrode, the zeta potential can be varied and a controllable, uniform shear stress can be applied to the liquid in the channel. The strength of the shear stress depends on both the gate voltage and the applied field which drives the electroosmotic shear flow. Although the stress range is still limited, such a microchannel device can be used in principle as an in situ micro-rheometer for lab on a chip purposes.

  14. Shear jamming in highly strained granular system without shear banding

    NASA Astrophysics Data System (ADS)

    Zhao, Yiqiu; Barés, Jonathan; Zheng, Hu; Behringer, Robert

    2016-11-01

    Bi et al. have shown that, if sheared, a granular material can jam even if its packing fraction (ϕ) is lower than the critical isotropic jamming point ϕJ. They have introduced a new critical packing fraction value ϕS such that for ϕS< ϕ< ϕJ the system jams if sheared. Nevertheless, the value of ϕS as a function of the shear profile or the strain necessary to observe jamming remain poorly understood because of the experimental complexity to access high strain without shear band. We present a novel 2D periodic shear apparatus made of 21 independent, aligned and mirrored glass rings. Each ring can be moved independently which permits us to impose any desired shear profile. The circular geometry allows access to any strain value. The forces between grains are measured using reflective photoelasticity. By performing different shear profiles for different packing fractions we explored the details of jamming diagram including the location of the yield surface. This work is supported by NSF No.DMR1206351, NASA No.NNX15AD38G and W. M. Keck Foundation.

  15. Macroscopic Discontinuous Shear Thickening versus Local Shear Jamming in Cornstarch

    NASA Astrophysics Data System (ADS)

    Fall, A.; Bertrand, F.; Hautemayou, D.; Mezière, C.; Moucheront, P.; Lemaître, A.; Ovarlez, G.

    2015-03-01

    We study the emergence of discontinuous shear thickening (DST) in cornstarch by combining macroscopic rheometry with local magnetic resonance imaging measurements. We bring evidence that macroscopic DST is observed only when the flow separates into a low-density flowing and a high-density jammed region. In the shear-thickened steady state, the local rheology in the flowing region is not DST but, strikingly, is often shear thinning. Our data thus show that the stress jump measured during DST, in cornstarch, does not capture a secondary, high-viscosity branch of the local steady rheology but results from the existence of a shear jamming limit at volume fractions quite significantly below random close packing.

  16. Permian to Late Triassic evolution of the Longmen Shan Foreland Basin (Western Sichuan): Model results from both the lithospheric extension and flexure

    NASA Astrophysics Data System (ADS)

    He, Lijuan

    2014-10-01

    The lithosphere was extended during the Permian-Middle Triassic in the Yangtze Craton where the Sichuan Basin located, and then bent due to thrusting of the Longmen Shan orogen, leading to formation of the Longmen Shan Foreland Basin (Western Sichuan) during the Late Triassic Indosinian orogeny. The lateral variation of the lithospheric strength resulted by former differential extension would inevitably influence the subsequent evolution of the foreland basin. In order to investigate this, both extensional and flexural models were applied in modeling Permian-Late Triassic basin evolution. A 2D kinematic extensional model was initially developed along a profile crossing the Yangtze Craton to simulate the lithospheric thermal evolution during the Permian-Middle Triassic. Based on the thermal results, the thermal-rheological structure, as well as the effective elastic thickness of the lithosphere (Te), was then determined. Extension model show that the stretching factors decrease gradually from Songpan-Ganzi to the Sichuan Basin, leading to variable thermal-rheological structure and increased Te from west to east. Taking into account of the Te variation, a flexural model was finally constructed to investigate the evolution of the Longmen Shan Foreland Basin during the Late Triassic spanning the time period c. 227-206 Ma. Three episodes were divided according to the corresponding tectonostratigraphic units. By matching the stratigraphic observations, three phase advance distances eastward of the Longmen Shan along the Qingchuan-Maowen Fault turned out to be 18, 22, and 18 km. It implied a slow and similar thrust advance rate of 3.6 (c.227-222 Ma), 2.2 (c.222-212 Ma), and 3 mm/yr (c.212-206 Ma), respectively.

  17. Mesozoic tectonic evolution of the Daba Shan Thrust Belt in the southern Qinling orogen, central China: Constraints from surface geology and reflection seismology

    NASA Astrophysics Data System (ADS)

    Li, Jianhua; Dong, Shuwen; Yin, An; Zhang, Yueqiao; Shi, Wei

    2015-08-01

    The Daba Shan Thrust Belt is located along the southern margin of the Qinling orogen that separates the north China block in the north from the south China block in the south. Despite decades of research, the total magnitude of shortening accommodated by continent-continent convergence across the Qinling orogen after Triassic ocean closure between north and south China remains poorly constrained. The lack of knowledge on the shortening magnitude in turn limits our ability to test a wide array of tectonic models for the development of the Qinling orogen and thus the convergence history between north and south China. In order to address this issue, we construct a balanced cross section and develop a new kinematic model for the evolution of the Daba Shan Thrust Belt. This work was accomplished by integrating (1) surface geologic mapping, (2) detailed kinematic analysis of key structures, (3) existing geochronologic and thermochronological data, and (4) a recently obtained lithospheric-scale seismic reflection profile. Restoration of the cross section indicates that the minimum shortening strain increases northward from ~10% in the foreland to >45% in the thrust belt interior. The estimated amount of upper crustal shortening across the Daba Shan Thrust Belt is >130 km, which is sufficient to allow the inferred mafic lower crust of the subducted south China lithosphere to have experienced eclogite phase transition. Thus, our work supports that the development of the Daba Shan Thrust Belt may have been driven by slab pull of the subducted mafic lower crust at the leading edge of the down-plunging south China continental lithosphere.

  18. Parametric Study of Rockbolt Shear Behaviour by Double Shear Test

    NASA Astrophysics Data System (ADS)

    Li, L.; Hagan, P. C.; Saydam, S.; Hebblewhite, B.; Li, Y.

    2016-12-01

    Failure of rockbolts as a result of shear or bending loads can often be found in underground excavations. The response of rock anchorage systems has been studied in shear, both by laboratory tests as well as numerical modelling in this study. A double shear test was developed to examine the shear behaviour of a bolt installed across two joints at different angles. To investigate the influence of various parameters in the double shear test, a numerical model of a fully grouted rockbolt installed in concrete was constructed and analysed using FLAC3D code. A number of parameters were considered including concrete strength, inclination between rockbolt and joints and rockbolt diameter. The numerical model considered three material types (steel, grout and concrete) and three interfaces (concrete-concrete, grout-concrete and grout-rockbolt). The main conclusions drawn from the study were that the level of bolt resistance to shear was influenced by rock strength, inclination angle, and diameter of the rockbolt. The numerical simulation of the bolt/grout interaction and deformational behaviour was found to be in close agreement with earlier experimental test results.

  19. Tomographic image of the crust and upper mantle beneath the western Tien Shan from the MANAS broadband deployment: Possible evidence for lithospheric delamination

    NASA Astrophysics Data System (ADS)

    Zhiwei, Li; Roecker, Steve; Zhihai, Li; Bin, Wei; Haitao, Wang; Schelochkov, Gennady; Bragin, Vitaly

    2009-11-01

    We combine teleseismic P arrival times from the recent MANAS deployment of broadband sensors with P and S arrival times from local events recorded by the GENGHIS deployment and analog observations from the Kyrgyz Institute of Seismology to generate a high resolution (~ 20 km) image of elastic wavespeeds in the crust and upper mantle beneath the western Tien Shan. The total data set consists of 29,006 P and 21,491 S arrivals from 2176 local events recorded at 144 stations along with 5202 P arrivals from 263 teleseismic events recorded at 40 stations. The most significant feature in our image of the mantle beneath the Tien Shan is a pair of large, elongated high wavespeed regions dipping in opposite directions from the near surface to depths of at least 400 km. These regions appear to be continuous and extend upwards to bounding range fronts where the Tarim Basin is being overthrust by the Kokshal range on the south side, and the Kazach shield underthrusts the Kyrgyz range on the north side. While it is tempting to interpret these high wavespeed anomalies as evidence for contemporary subduction of continental lithosphere, such a scenario is difficult to reconcile with both the timing of the orogen and the size of the wavespeed anomaly. We suggest instead that they represent downwelling side-limbs of a lithospheric delamination beneath the central part of the Tien Shan, possibly by siphoning of the bordering continental lithosphere as the central part descends.

  20. Three-dimensional velocity structure and earthquake locations beneath the northern Tien Shan of Kyrgyzstan, central Asia

    NASA Astrophysics Data System (ADS)

    Ghose, Sujoy; Hamburger, Michael W.; Virieux, Jean

    1998-02-01

    We used the arrival times of local earthquakes and quarry blasts recorded by the Kyrgyzstan Broadband Network (KNET) to obtain three-dimensional (3-D) P and S wave velocity models of the upper crust beneath an actively deforming mountain front and its associated foreland in the Kyrgyz Tien Shan. The continuous velocity models, described by cubic B spline interpolation of the squared slowness over a regular 3-D grid, were computed by simultaneous inversion of hypocenter and medium parameters. Exact ray tracing was done in the smooth 3-D medium by shooting rays from the sources to the stations by an analytical perturbation method based on the paraxial ray theory. The deduced large, sparse, linear system was solved using the damped, iterative, least squares algorithm LSQR. The stability and resolution of the result was qualitatively tested by two synthetic tests: the spike test and the checkerboard resolution test. We found that the models are well resolved up to a depth of ˜27 km for most parts of our image domain. The P and S wave velocity models are consistent with each other and provide evidence for marked heterogeneity in the upper crustal structure beneath the northern Tien Shan. At shallower depths (<7 km) the sediment-filled foreland is imaged as a relatively lower velocity feature compared to the mountains, which are cored by crystalline basement rocks. In contrast, at midcrustal depths the mountains are underlain by relatively lower velocity materials compared to the foreland. A distinct contrast in velocity structure is also observed between the eastern and western parts of the Kyrgyz Range at midcrustal depths, with the presence of relatively higher velocities toward the east. The seismicity is concentrated near the traces of major active faults and extends deeper beneath the foreland compared to the mountains. The regional compression in the Tien Shan is accommodated along a series of high-angle reverse faults distributed throughout the orogenic system

  1. Shear thinning of nanoparticle suspensions.

    SciTech Connect

    Grest, Gary Stephen; Petersen, Matthew K.; in't Veld, Pieter J.

    2008-08-01

    Results of large scale non-equilibrium molecular dynamics (NEMD) simulations are presented for nanoparticles in an explicit solvent. The nanoparticles are modeled as a uniform distribution of Lennard-Jones particles, while the solvent is represented by standard Lennard-Jones particles. Here we present results for the shear rheology of spherical nanoparticles of size 5 to 20 times that of the solvent for a range of nanoparticle volume fractions and interactions. Results from NEMD simulations suggest that for strongly interacting nanoparticle that form a colloidal gel, the shear rheology of the suspension depends only weakly on the size of the nanoparticle, even for nanoparticles as small as 5 times that of the solvent. However for hard sphere-like colloids the size of the nanoparticles strongly affects the shear rheology. The shear rheology for dumbbell nanoparticles made of two fused spheres is also compared to spherical nanoparticles and found to be similar except at very high volume fractions.

  2. Grafted polymer under shear flow

    NASA Astrophysics Data System (ADS)

    Kumar, Sanjiv; Foster, Damien P.; Giri, Debaprasad; Kumar, Sanjay

    2016-04-01

    A self-attracting-self-avoiding walk model of polymer chain on a square lattice has been used to gain an insight into the behaviour of a polymer chain under shear flow in a slit of width L. Using exact enumeration technique, we show that at high temperature, the polymer acquires the extended state continuously increasing with shear stress. However, at low temperature the polymer exhibits two transitions: a transition from the coiled to the globule state and a transition to a stem-flower like state. For a chain of finite length, we obtained the exact monomer density distributions across the layers at different temperatures. The change in density profile with shear stress suggests that the polymer under shear flow can be used as a molecular gate with potential application as a sensor.

  3. The aeolian sedimentary system in the northern Qilian Shan and Hexi Corridor (N-China) - geomorphologic, sedimentologic and climatic drivers

    NASA Astrophysics Data System (ADS)

    Nottebaum, Veit; Lehmkuhl, Frank; Stauch, Georg

    2015-04-01

    The formation of aeolian deposits depends on the influence of climatic factors but also on non-climatic controls, such as local geomorphological setting and tectonic activity. Unravelling the environmental history needs a careful consideration of a set of sections to capture spatial variability and a detailed investigation of depositing processes and chronology. Along the northern margin of the Qilian Shan mountain range 22 OSL-dated loess and aeolian sand sections and additional surface samples reveal the interactions between climatic, geomorphologic and sedimentologic factors. Thin loess covers (~1-2 m) occur in elevations of 2000 to 3800 m asl, which were mainly accumulated during the Holocene. End-member modelling of loess grain size data exhibits three dominant aeolian transport pathways representing local transport from fluvial storages, dust storm contribution and background dust deposition. Their relative contributions show a clear dependence on geomorphological setting, and additionally, synchronous trends throughout the Holocene. Their relative changes allow conclusions about Holocene environmental conditions. Discontinuous archives (aeolian sand, lacustrine, and alluvial deposition) in the lower forelands of the Qilian Shan show a distinct spatial pattern contrasting western and eastern forelands. The comparison of OSL ages exhibits high sediment accumulation (~2 m/ka) in the drier western part during the Late Glacial, while the lack of Holocene ages indicates sediment discharge / deflation. In contrast, moister areas in the eastern foreland yield scattered Holocene ages. This indicates high sediment dynamics, benefiting from fluvial reworking and thus provided sediment availability. Fluvial sediment supply plays an important role in sediment recycling. Meanwhile, western forelands lack efficient sand sources and fluvial reworking agents. The study exemplifies the complex sedimentary systems acting along mountain to foreland transects which often host

  4. Genetic parameters of body weight, egg production, and shell quality traits in the Shan Ma laying duck (Anas platyrhynchos).

    PubMed

    Lin, R L; Chen, H P; Rouvier, R; Marie-Etancelin, C

    2016-11-01

    Three hundred and four female ducks of the Chinese indigenous Shan Ma breed, progeny of 11 sires and 104 dams, were used to study laying traits. Among them, 264 ducks were used to study the egg shell quality traits of eggs laid at 300 days of age. The mean age at first egg was 109 days with an average egg weight of 49.6 ± 3.7 g. Between 210 and 300 days of age, egg weight increased from 65.0 ± 3.9 g to 67.0 ± 4.2 g and the mean of the number of eggs laid up to 300 days was 161 ± 15.0. Egg length was 59.57 ± 3.01 mm and egg width was 45.02 ± 1.98 mm, leading to a shape index of 1.32 ± 0.08. Egg shell thickness was about 0.31 mm whatever the shell region, and the breaking strength was 28.80 ± 8.29 N. The heritability's estimated using restricted maximum likelihood ( REML: ) methodology were high for egg weights (ranging from 0.43 to 0.61), intermediate for the number of eggs laid (ranging from 0.38 to 0.43), and low for the age at first egg (0.13). Heritability's for egg shell quality traits varied from 0.20 for the breaking strength to 0.44 for egg length, with in-between values of 0.28 for shell thickness and 0.34 for the shape index. The number of eggs laid was not genetically correlated with the age at first egg or egg weight, but was correlated with body weight (rg = +0.54 ± 0.23). High positive correlations were found between egg weight and body weight traits, and both of these traits (except egg weight at first egg) were highly and positively correlated with egg length and width. Breaking strength was genetically correlated with egg shell thickness (rg = +0.54 ± 0.19) and the shape index (rg = +0.71 ± 0.23). These results suggest that an efficient selection strategy could be implemented to improve the egg production of the pure Shan Ma duck line.

  5. Shear shocks in fragile networks.

    PubMed

    Ulrich, Stephan; Upadhyaya, Nitin; van Opheusden, Bas; Vitelli, Vincenzo

    2013-12-24

    A minimal model for studying the mechanical properties of amorphous solids is a disordered network of point masses connected by unbreakable springs. At a critical value of its mean connectivity, such a network becomes fragile: it undergoes a rigidity transition signaled by a vanishing shear modulus and transverse sound speed. We investigate analytically and numerically the linear and nonlinear visco-elastic response of these fragile solids by probing how shear fronts propagate through them. Our approach, which we tentatively label shear front rheology, provides an alternative route to standard oscillatory rheology. In the linear regime, we observe at late times a diffusive broadening of the fronts controlled by an effective shear viscosity that diverges at the critical point. No matter how small the microscopic coefficient of dissipation, strongly disordered networks behave as if they were overdamped because energy is irreversibly leaked into diverging nonaffine fluctuations. Close to the transition, the regime of linear response becomes vanishingly small: the tiniest shear strains generate strongly nonlinear shear shock waves qualitatively different from their compressional counterparts in granular media. The inherent nonlinearities trigger an energy cascade from low to high frequency components that keep the network away from attaining the quasi-static limit. This mechanism, reminiscent of acoustic turbulence, causes a superdiffusive broadening of the shock width.

  6. Simulation of projected water demand and ground-water levels in the Coffee Sand and Eutaw-McShan aquifers in Union County, Mississippi, 2010 through 2050

    USGS Publications Warehouse

    Hutson, Susan S.; Strom, E.W.; Burt, D.E.; Mallory, M.J.

    2000-01-01

    Ground water from the Eutaw-McShan and the Coffee Sand aquifers is the major source of supply for residential, commercial, and industrial purposes in Union County, Mississippi. Unbiased, scientifically sound data and assessments are needed to assist agencies in better understanding and managing available water resources as continuing development and growth places more stress on available resources. The U.S. Geological Survey, in cooperation with the Tennessee Valley Authority, conducted an investigation using water-demand and ground-water models to evaluate the effect of future water demand on groundwater levels. Data collected for the 12 public-supply facilities and the self-supplied commercial and industrial facilities in Union County were used to construct water-demand models. The estimates of water demand to year 2050 were then input to a ground-water model based on the U.S. Geological Survey finite-difference computer code, MODFLOW. Total ground-water withdrawals for Union County in 1998 were estimated as 2.85 million gallons per day (Mgal/d). Of that amount, municipal withdrawals were 2.55 Mgal/d with about 1.50 Mgal/d (59 percent) delivered to residential users. Nonmunicipal withdrawals were 0.296 Mgal/d. About 80 percent (2.27 Mgal/d) of the total ground-water withdrawal is produced from the Eutaw-McShan aquifer and about 13 percent (0.371 Mgal/d) from the Coffee Sand aquifer. Between normal- and high-growth conditions, total water demand could increase from 72 to 131 percent (2.9 Mgal/d in 1998 to 6.7 Mgal/d in year 2050) with municipal demand increasing from 77 to 146 percent (2.6 to 6.4 Mgal/d). Increased pumping to meet the demand for water was simulated to determine the effect on water levels in the Coffee Sand and Eutaw- McShan aquifers. Under baseline-growth conditions, increased water use by year 2050 could result in an additional 65 feet of drawdown in the New Albany area below year 2000 water levels in the Coffee Sand aquifer and about 120 feet of

  7. Seasonal deuterium excess in a Tien Shan ice core: Influence of moisture transport and recycling in Central Asia

    USGS Publications Warehouse

    Kreutz, K.J.; Wake, C.P.; Aizen, V.B.; DeWayne, Cecil L.; Synal, H.-A.

    2003-01-01

    Stable water isotope (??18O, ??D) data from a high elevation (5100 masl) ice core recovered from the Tien Shan Mountains, Kyrgyzstan, display a seasonal cycle in deuterium excess (d = ??D - 8*??18O) related to changes in the regional hydrologic cycle during 1994-2000. While there is a strong correlation (r2 = 0.98) between ??18O and ??D in the ice core samples, the regression slope (6.9) and mean d value (23.0) are significantly different than the global meteoric water line values. The resulting time-series ice core d profile contains distinct winter maxima and summer minima, with a yearly d amplitude of ???15-20???. Local-scale processes that may affect d values preserved in the ice core are not consistent with the observed seasonal variability. Data from Central Asian monitoring sites in the Global Network of Isotopes in Precipitation (GNIP) have similar seasonal d changes. We suggest that regional-scale hydrological conditions, including seasonal changes in moisture source, transport, and recycling in the Caspian/Aral Sea region, are responsible for the observed spatial and temporal d variability.

  8. New geochronology constraints on timing and depth of the ancient earthquakes along the Longmen Shan fault belt, eastern Tibet

    NASA Astrophysics Data System (ADS)

    Zheng, Yong; Li, Haibing; Sun, Zhiming; Wang, Huan; Zhang, Jiajia; Li, Chenglong; Cao, Yong

    2016-12-01

    Pseudotachylyte is an ideal target to directly date ancient earthquake associated with regional faulting. Here we perform step-heating 40Ar/39Ar, clay mineral K-Ar, and zircon fission track (ZFT) analyses on the pseudotachylyte samples collected from the Yingxiu-Beichuan coseismic rupture of the Longmen Shan fault belt (LSFB) to provide time constraints for the tectonic evolution of the LSFB during the Indosinian orogeny. 40Ar/39Ar results from the matrix show that the frictional melting occurred 226-235 Ma ago. Combined with mylonite dating of the host rock, the age of the ancient earthquakes is constrained at 231-238 Ma, with a formation depth of 10-14 km. As a response to the earthquakes, a series of soft-sediment deformation structures are widely preserved in the Middle and Late Triassic strata along the Yingxiu-Beichuan fault (YBF), indicating that the LSFB was seismically active since the Late Anisian and persisted episodically until the end of the Indosinian orogeny. Both clay mineral K-Ar and ZFT analyses record a younger deformation or alteration with an age of approximately 195 Ma, corresponding to a postcollisional orogeny. These new data represent the first direct evidence of the regional thrusting (YBF) in the central LSFB during the Indosinian orogeny, concurrent with the initial ductile deformation of the western boundary fault. Tectonic inheritance then strongly influenced the evolution of the LSFB as most of the Mesozoic faults are reactivated by major Tertiary tectonic deformations.

  9. Protective Effects of Hong Shan Capsule against Lethal Total-Body Irradiation-Induced Damage in Wistar Rats

    PubMed Central

    Li, Jianzhong; Xu, Jing; Xu, Weiheng; Qi, Yang; Lu, Yiming; Qiu, Lei; Hu, Zhenlin; Chu, Zhiyong; Chai, Yifeng; Zhang, Junping

    2015-01-01

    Hong Shan Capsule (HSC), a crude drug of 11 medicinal herbs, was used in clinical practice for the treatment of radiation injuries in China. In this study, we investigated its protection in rats against acute lethal total-body irradiation (TBI). Pre-administration of HSC reduced the radiation sickness characteristics, while increasing the 30-day survival of the irradiated rats. Administration of HSC also reduced the radiation sickness characteristics and increased the 30-day survival of mice after exposure to lethal TBI. Ultrastructural observation illustrated that the pretreatment of rats with HSC significantly attenuated the TBI-induced morphological changes in the different organs of irradiated rats. Gene expression profiles revealed the dramatic effect of HSC on alterations of gene expression caused by lethal TBI. Pretreatment with HSC prevented differential expression of 66% (1398 genes) of 2126 genes differentially expressed in response to TBI. Pathway enrichment analysis indicated that these genes were mainly involved in a total of 32 pathways, such as pathways in cancer and the mitogen-activated protein kinase (MAPK) signaling pathway. Our analysis indicated that the pretreatment of rats with HSC modulated these pathways induced by lethal TBI, such as multiple MAPK pathways, suggesting that pretreatment with HSC might provide protective effects on lethal TBI mainly or partially through the modulation of these pathways. Our data suggest that HSC has the potential to be used as an effective therapeutic or radio-protective agent to minimize irradiation damage. PMID:26274957

  10. The disappearance of glaciers in the Tien Shan Mountains in Central Asia at the end of Pleistocene

    NASA Astrophysics Data System (ADS)

    Takeuchi, Nozomu; Fujita, Koji; Aizen, Vladimir B.; Narama, Chiyuki; Yokoyama, Yusuke; Okamoto, Sachiko; Naoki, Kazuhiro; Kubota, Jumpei

    2014-11-01

    Glaciers in Central Asia are among the largest ice masses in the Eurasian continent and have supplied vital water to local inhabitants for thousands of years. The glaciers in this region are generally believed to be remnants of the last deglaciation, however, glacier variability in the central Asian mountains since the Last Glacial Maximum (LGM) has not been well documented. Here, we report an 86.87 m-deep ice core record drilled on an ice cap in the Tien Shan Mountains of Central Asia. Radiocarbon dating of organic soil from the bottom of the ice-core borehole showed that the age of the soil was 12,656 - 12,434 cal years before present, coincident with the beginning of the Younger Dryas cold period (YD). This result indicates that the ice cap did not exist in the Bølling-Allerød period (BA), which was the warm period before the YD, and that the BA climate was significantly warmer than at present. It also indicates that the ice cap has never entirely disappeared in any warm periods throughout the Holocene. We estimated that during the BA its extent was 43% or less of the present glacier coverage in the mountains. Our results suggest that this region at the end of Pleistocene was considerably warmer than at present, and that most of the present glaciers in this region are not relics of the Last Glacial period, but are composed of ice formed during the YD and Holocene.

  11. Paleomagnetic age of the Tangxian planation surface, northwestern Zhongtiao Shan of the Shanxi Graben System, North China

    NASA Astrophysics Data System (ADS)

    Xiong, Jianguo; Li, Youli; Zhong, Yuezhi; Si, Supei; Lei, Jinghao; Xin, Weilin; Hu, Xiu; Yao, Yifan

    2017-04-01

    A numerical formation age for the Tangxian planation surface (TXPS) in North China is still controversial. The TXPS, beveled across paleoarchean basement rocks, is overlain by late Cenozoic conglomerate, aeolian red clay, and loess. The magnetostratigraphy of two late Cenozoic deposition sections is established, and two other sections are recorded and measured in this work. The magnetostratigraphy indicates six normal magnetozones (N1 to N6) and six reverse magnetozones (R1 to R6). These magnetozones are correlated to chron C1n through C2An.1r, indicating that the TXPS was formed at 3.12-3.03 Ma. The characteristics of the Zhongtiao Shan tectonic uplift and its relationship with the Tibetan Plateau and Ordos Block are discussed in terms of tectonic uplift. The TXPS formation and accumulation of the late Cenozoic sediments are mainly controlled by tectonic activities. The formation and uplift of the TXPS with a lag in the Shanxi Graben System is consistent with the activities of the Tibetan Plateau and Ordos Block, implying that the NE extension of the Tibetan Plateau epeirogenic uplift advances successively.

  12. Millennium recurrence interval of morphogenic earthquakes on the Qingchuan fault, northeastern segment of the Longmen Shan Thrust Belt, China

    NASA Astrophysics Data System (ADS)

    Lin, Aiming; Yan, Bing; Rao, Gang

    2016-04-01

    The 2008 M w 7.9 Wenchuan produced a ˜285-300-km-long coseismic surface rupture zone, including a 60-km-long segment along the Qingchuan fault, the northeastern segment of the Longmen Shan Thrust Belt (LSTB), Sichuan Basin, central China. Field investigations, trench excavations, and radiocarbon dating results reveal that (i) the Qingchuan fault is currently active as a seismogenic fault, along which four morphogenic earthquakes including the 2008 Wenchuan earthquake occurred in the past ca. 3500 years, suggesting an average millennium recurrence interval of morphogenic earthquakes in the late Holocene; (ii) the most recent event prior to the 2008 Wenchuan earthquake took place in the period between AD 1400 and AD 1100; (iii) the penultimate paleoseismic event occurred in the period around 2000 years BP in the Han Dynasty (206 BC-AD 220); (iv) the third paleoseismic event occurred in the period between 900 and 1800 BC; and (v) at least three seismic faulting events occurred in the early Holocene. The present results are comparable with those inferred in the central and southwestern segments of the LSTB within which the Wenchuan magnitude earthquakes occurred in a millennium recurrence interval, that are in contrast with previous estimates of 2000-10,000 years for the recurrence interval of morphogenic earthquakes within the LSTB and thereby necessitating substantial modifications to existing seismic hazard models for the densely populated region at the Sichuan region.

  13. The Cenozoic growth of the Qilian Shan in the northeastern Tibetan Plateau: A sedimentary archive from the Jiuxi Basin

    NASA Astrophysics Data System (ADS)

    Wang, Weitao; Zhang, Peizhen; Pang, Jianzhang; Garzione, Carmala; Zhang, Huiping; Liu, Caicai; Zheng, Dewen; Zheng, Wenjun; Yu, Jingxing

    2016-04-01

    Sedimentary deposits in Tibetan Basins archive the spatial-temporal patterns of the deformation and surface uplift processes that created the area's high topography during the Cenozoic India-Asia collision. In this study, new stratigraphic investigation of the Caogou section from the Jiuxi Basin in the northeasternmost part of Tibetan Plateau provides chronologic constraints on the deformation and northward growth of the plateau. Magnetostratigraphic analysis results suggest that the age of the studied ~1000 m thick section spans from ~24.2 Ma to 2.8 Ma. Detailed sedimentology and apatite fission track (AFT) analyses reveal that variations in the clast provenance, lithofacies, sediment accumulation rates, and AFT lag times occurred at ~13.5-10.5 Ma. We interpret these changes as in response to the initial uplift of the North Qilian Shan. In addition, paleomagnetic declination results from the section indicate a clockwise rotation of the Jiuxi Basin before ~13.5 Ma, which was followed by a subsequent counterclockwise rotation during 13.5-9 Ma. This reversal in rotation direction may be directly related to left-lateral strike-slip activity along the easternmost segment of the Altyn Tagh Fault. Combined with previous studies, we suggest that movement on the western part of the Altyn Tagh Fault was probably initiated during the Oligocene (>30 Ma) and that fault propagation to its eastern tip occurred during the middle-late Miocene.

  14. Yield shear stress and disaggregating shear stress of human blood

    NASA Astrophysics Data System (ADS)

    Jung, Jinmu; Lee, Byoung-Kwon; Shin, Sehyun

    2014-05-01

    This review presents two distinct rheological parameters of blood that have the potential to indicate blood circulation adequacy: yield shear stress (YSS) and disaggregating shear stress (DSS). YSS and DSS reflect the strength of red blood cell (RBC) aggregation in suspension under static and dynamic conditions, respectively. YSS, defined as the critical stress to disperse RBC aggregates under static conditions, was found to be dependent upon hematocrit, fibrinogen, and red cell deformability, but not temperature. DSS, defined as the minimum shear stress to disperse RBC aggregates under dynamic conditions, is dependent upon fibrinogen, red cell deformability, and temperature but not hematocrit. Owing to recent advances in measurement technology, these two parameters can be easily measured, and thus, their clinical significance in blood circulation can be verified.

  15. Transport suppression by shear reduction

    NASA Astrophysics Data System (ADS)

    Martinell, Julio; Del-Castillo-Negrete, Diego

    2009-11-01

    The relationship between transport and shear is a problem of considerable interest to magnetically confined plasmas. It is well known that there are cases in which an increase of flow shear can lead to a reduction of turbulent transport. However, this is not a generic result, and there are transport problems in which the opposite is the case. In particular, as originally discussed in Ref. footnotetextdel-Castillo-Negrete and Morrison, Phys. Fluids A 5, 948 (1993), barriers to chaotic transport typically form in regions of vanishing shear. This property, which is generic to the so-called non-twist Hamiltonian systems footnotetextdel-Castillo-Negrete, Greene, and Morrison, Physica D 91, 1 (1996), explains the observed resilience of transport barriers in non-monotonic zonal flows in plasmas and fluids and the robustness of shearless magnetic surfaces in reverse shear configurations. Here we study the role of finite Larmor radius (FLR) effects on the suppression of chaotic transport by shear reduction in a simplified model. Following Ref. footnotetextdel-Castillo-Negrete, Phys. Plasmas, 7, 1702 (2000) we consider a model consisting of a superposition of drift waves and a non-monotonic zonal flow. The FLR effects are incorporated by gyroaveraging the E xB velocity, and transport is studied by following the evolution of ensembles of test particles.

  16. Shear Brillouin light scattering microscope

    PubMed Central

    Kim, Moonseok; Besner, Sebastien; Ramier, Antoine; Kwok, Sheldon J. J.; An, Jeesoo; Scarcelli, Giuliano; Yun, Seok Hyun

    2016-01-01

    Brillouin spectroscopy has been used to characterize shear acoustic phonons in materials. However, conventional instruments had slow acquisition times over 10 min per 1 mW of input optical power, and they required two objective lenses to form a 90° scattering geometry necessary for polarization coupling by shear phonons. Here, we demonstrate a confocal Brillouin microscope capable of detecting both shear and longitudinal phonons with improved speeds and with a single objective lens. Brillouin scattering spectra were measured from polycarbonate, fused quartz, and borosilicate in 1-10 s at an optical power level of 10 mW. The elastic constants, phonon mean free path and the ratio of the Pockels coefficients were determined at microscopic resolution. PMID:26832263

  17. Squirming through shear thinning fluids

    NASA Astrophysics Data System (ADS)

    Datt, Charu; Zhu, Lailai; Elfring, Gwynn J.; Pak, On Shun

    2015-11-01

    Many microorganisms find themselves surrounded by fluids which are non-Newtonian in nature; human spermatozoa in female reproductive tract and motile bacteria in mucosa of animals are common examples. These biological fluids can display shear-thinning rheology whose effects on the locomotion of microorganisms remain largely unexplored. Here we study the self-propulsion of a squirmer in shear-thinning fluids described by the Carreau-Yasuda model. The squirmer undergoes surface distortions and utilizes apparent slip-velocities around its surface to swim through a fluid medium. In this talk, we will discuss how the nonlinear rheological properties of a shear-thinning fluid affect the propulsion of a swimmer compared with swimming in Newtonian fluids.

  18. Shear Acceleration in Expanding Flows

    NASA Astrophysics Data System (ADS)

    Rieger, F. M.; Duffy, P.

    2016-12-01

    Shear flows are naturally expected to occur in astrophysical environments and potential sites of continuous non-thermal Fermi-type particle acceleration. Here we investigate the efficiency of expanding relativistic outflows to facilitate the acceleration of energetic charged particles to higher energies. To this end, the gradual shear acceleration coefficient is derived based on an analytical treatment. The results are applied to the context of the relativistic jets from active galactic nuclei. The inferred acceleration timescale is investigated for a variety of conical flow profiles (i.e., power law, Gaussian, Fermi-Dirac) and compared to the relevant radiative and non-radiative loss timescales. The results exemplify that relativistic shear flows are capable of boosting cosmic-rays to extreme energies. Efficient electron acceleration, on the other hand, requires weak magnetic fields and may thus be accompanied by a delayed onset of particle energization and affect the overall jet appearance (e.g., core, ridge line, and limb-brightening).

  19. Shearing Effectiveness of Integral Stiffening

    NASA Technical Reports Server (NTRS)

    Crawford, Robert F; Libove, Charles

    1955-01-01

    Values of coefficients for defining the effectiveness of integral stiffeners in resisting shear deformations of the plate of which they are an integral part are presented for a variety of proportions of rectangular stiffeners with circular fillets. Formulas are given in which these coefficients may be employed to calculate the elastic constants associated with the twisting and shearing of integrally stiffened plates. The size of fillet radius is shown to contribute appreciably to the degree of penetration of the stresses from the skin into the stiffener.

  20. On poro-hyperelastic shear

    NASA Astrophysics Data System (ADS)

    Suvorov, A. P.; Selvadurai, A. P. S.

    2016-11-01

    The paper examines the problem of the shear of a porous hyperelastic material, the pore space of which is saturated with an incompressible fluid. Poro-hyperelasticity provides a suitable approach for modelling the mechanical behaviour of highly deformable materials in engineering applications and particularly soft tissues encountered in biomechanical applications. Unlike with the infinitesimal theory of poroelasticity, the application of pure shear generates pore fluid pressures that dissipate with time as fluid migrates either from or into the pore space due to the generated fluid pressure gradients. The analytical results provide benchmark problems that can be used to examine the accuracy of computational approaches.

  1. Decadal deformation rates from SAR interferometry in the eastern Pamir-Tian Shan collision zone and implication for the growth and erosion of detachment folds

    NASA Astrophysics Data System (ADS)

    Bufe, A.; Burbank, D. W.; Bookhagen, B.

    2012-12-01

    The Cenozoic Indo-Asian collision caused the impingement of the north-verging Pamir orogen with the south-verging Tian Shan. Rapid convergence rates of 8-12 mm/y across the Pamir-Tian Shan boundary are suggested by GPS measurements and broadly match Holocene and Quaternary shortening rates. The shortening is dominantly accommodated by a series of oppositely verging thrust faults that interfere to form a complex pattern of temporal and spatial variation in deformation style and rate. Cosmogenic radionuclide (CRN) dating and optically stimulated luminescence (OSL) dating suggest late Quaternary shortening rates of 3-7 mm/y on individual structures. To the east, the rigid Tarim basin is translated northward alongside the Pamir and subducted beneath the Tian Shan. Since ~16 Ma deformation has stepped southward into the Tarim basin from the Tian Shan range-bounding fault. Most recently a series of detachment folds with inferred shortening rates of 1-5 mm/y and lateral propagation rates of up to 50-80 mm/y formed and continue to be active today. We present (1) new decadal deformation rates in the Pamir - Tian Shan and Tarim - Tian Shan collision zone in westernmost China inferred from Interferometric Synthetic Aperture Radar (InSAR) and (2) digital topography and fluvial network analysis to constrain deformation on longer timescales. These data are integrated with (3), published GPS data, (4) published Quaternary shortening rates, and (5) geologic mapping in order to identify spatial patterns of modern deformation, investigate temporal variations in deformation rate and show the response of the river network to active deformation. Preliminary InSAR results reveal interseismic deformation of 1-6 mm/y that is concentrated on thrust faults and detachment folds. However, current deformation appears localized on particular segments of the structures, a pattern that is likely to change with time. We speculate that rapid Quaternary growth of detachment folds in the Kashi

  2. Tectonically controlled relief evolution in the Northern Tien Shan and Junggar Alatau from the Eocene to the Present

    NASA Astrophysics Data System (ADS)

    Seib, N.; Kley, J.; Voigt, T.; Kober, M.

    2012-04-01

    The Cenozoic Tien Shan and Junggar Alatau mountains developed on the southern part of the Paleozoic Altaid orogen as a far-field effect of the collision of the Indian and Eurasian plates. Highland terrain, active seismicity, and fast GPS-derived motions are evidence of rapid ongoing mountain growth today. Variations in relief energy, hight-to-width ratio of ranges and apatite fission track (AFT) exhumation ages suggest they rose at different times. The strong dissection of the higher ridges (heights of up to 2km), indicates an earlier onset and higher rates of uplift. At the other end of the spectrum are low, little dissected ridges. According to AFT ages, exhumation in the Junggar Range began at 9 Ma (Jolivet et al., 2010), circa 11 Ma in the central Kyrgyz Range (Sobel et al., 2006) and 10 Ma in the Terskey Alatau. An AFT age of the low Sogety range is 77 Ma, suggesting that the Cenozic exhumation of the ridge was insufficient to expose rocks from below c.3 km depth. The synclinal lows between the basement highs preserve Cenozoic strata of Eocene to Quaternary age, probably deposited in a once continuous basin (the Ili Basin) and recording the entire history of Tien Shan uplift. Facies pattern of proximal alluvial fans are strictly related to the recent higher mountain areas in the north and in the south. During Middle Miocene, a large lake developed in the basin center. Up to the Middle Miocene sedimentation was accompanied by normal faulting of small magnitude. The main Cenozoic folding and thrusting occurred after that time and before deposition of the Chorgos formation. Shortening was accommodated by reactivation of inherited basement structures, by a switch to reverse or strike-slip motion on normal faults, and the nucleation of new thrusts. The majority of faults which emplace basement rocks over upper Cenozoic sediments dip steeply at angles of 60-70˚, and some have throws of more than 200 m. They are marked by topographic steps and contrasting morphology

  3. Regional based modeling approach for rainfall-induced debris flows in the continental-climatic Northern Tien Shan (SE Kazakhstan)

    NASA Astrophysics Data System (ADS)

    Fischer, Thomas; Küfmann, Carola; Haas, Florian; Baume, Otfried; Becht, Michael

    2013-04-01

    The high mountain systems of Central Asia (Hindukush, Pamir and Tien Shan) are dominated by continental-climatic conditions. Nevertheless, westerly maritime air circulation and convective rainfalls during the summer season result in high rainfall intensities. In combination with a high availability of unconsolidated material rainfall triggered debris flows are prominent and intensive geomorphologic processes in these mountain areas. The presented study aims to figure out a regional based modeling approach for rainfall-induced debris flow processes based on combination of a disposition model for debris flow starting zones with process-flow models. The investigation area has a size of about 700 square kilometers and is situated in the Northern Tien Shan mountains in SE Kazakhstan (investigation areas: valleys of Prochadnaja, Big Almatinka, Little Almatinka and Left Talgar). The area is characterized by mountain forest zone, alpine meadows and high-alpine glaciated areas with the highest peaks at 4500m. In a first step the disposition (point of process triggering) of actual debris flows was analyzed. Due to different triggering mechanisms, the processes were divided into channel-type and slope-type debris flows. Detailed mapping of actual debris flows initiation areas and a GIS-based geostatistical disposition analysis are used to identify the main geofactor-variables and geofactor combinations which enhance the triggering of rainfall-induced debris flows. It can be shown that both, longtime variable geofactors (such as local geomorphology and hydrology) plays a significant role for triggering debris flows, as well as mid- and short time variable geofactors. Especially actual permafrost distribution and degradation plus glacier retreat comes into the focus of interest. This is most notably for rainfall induced slope-type debris flows which primarily are triggered in the discontinuous and continuous permafrost areas eroding younger unconsolidated material from actual

  4. Active Seismicity and Tectonics in Central Asia from Seismological Data Recorded in the Pamir and Tien Shan Mountain Ranges

    NASA Astrophysics Data System (ADS)

    Sippl, Christian; Schurr, Bernd; Schneider, Felix M.; Yuan, Xiaohui; Mechie, James; Minaev, Vladislav; Abdybachaev, Ulan A.; Gadoev, Mustafo; Oimahmadov, Ilhomjon

    2010-05-01

    Active tectonics in the Pamir mountains in central Asia, the westernmost part of the India-Eurasia collision zone, are controlled by ongoing convergence (about 20 mm/yr), causing substantial crustal shortening and compressional deformation. This leads to high seismicity rates throughout the region. Whereas seismic activity along the rim of the Pamir plateau is mostly compressional and concentrated along the Main Pamir Thrust, the distribution and focal mechanisms of earthquakes in its interior are more diffuse, with extensional events occurring along North-South trending rift zones (Kara Kul, Wachan). Seismicity in the south-western Pamir and in the Hindu Kush features frequent intermediate-depth earthquakes, reaching hypocentral depths of 300 km, which is rare for regions not obviously related to active subduction of oceanic lithosphere. These mantle earthquakes, which are not observed beneath the Himalayas and Tibet further east, form a rather well-defined Wadati-Benioff zone that was readily interpreted as subducted lithosphere present below the current collisional orogen. Earlier seismological studies showed the presence of a northward-dipping lithospheric slab under the Hindu Kush and a southward-dipping one beneath the Pamirs, with a small seismic gap in-between. Different hypotheses concerning the nature of these slabs (oceanic or continental lithosphere) and tectonic geometry in general (two slabs subducting in opposite directions or a single, hugely contorted slab) have been proposed in literature. Political instability in the region in the last two decades hampered on-site studies and field work, leaving many key issues poorly understood. In the framework of the multidisciplinary project TIPAGE (Tien Shan Pamir Geodynamic Programme), for the first time, new field campaigns collecting high quality data have been made possible. Local seismicity in the Pamir and Tien Shan mountain ranges (Tajikistan and Kyrgyzstan) is currently being recorded by a temporary

  5. Short-term glacier velocity changes as evidence for efficient erosion at West Kunlun Shan, NW Tibet

    NASA Astrophysics Data System (ADS)

    Furuya, M.; Yasuda, T.

    2011-12-01

    Glacier surface velocity is a combination of plastic internal deformation of the ice and basal slip, the latter of which consists of basal sliding over the bed and deformation of the bed itself. Because plastic ice cannot deform rapidly, short-term surface velocity variations are attributed to basal slip caused by reduction of the effective overburden pressure associated with changes in the hydrologic system. Such rapid signals detected over the past decade across the polar region, including Greenland Ice sheet, have been attracting a great deal of attention, because surface melting in response to global warming could further accelerate the glacier flow and potentially lead to a significant loss of glacier mass. It remains uncertain, however, how much short-term variability exists in other glaciers, particularly those in High Asia, that are equally important contributors to the eustatic sea-level rise. Moreover, short-term glacier velocity changes in tectonically active areas should have an important implication for the interaction between mountain building and surface erosion processes. This is because glacial erosion are directly controlled by basal slip rates and will limit the general height of mountain ranges according to the glacial buzz-saw hypothesis. The West Kunlun Shan (WKS) is the highest region in the world when averaged over 1000 km2, but has received less attention as a potential field for the interaction between tectonics and surface processes. This is probably due to the facts that not only is direct monitoring by fieldwork difficult in this region, but that no significant erosion was expected at such high-altitude cold and arid glaciers. Here, we report analysis of satellite radar imagery that reveals seasonal velocity fluctuations at the largest glacier (Duofeng glacier) in the West Kunlun Shan with deviations from the winter values by more than ~20 m/yr, which provides with a lower limit on basal slip; we processed Phased Array-type L

  6. Spatial variability of recent glacier area changes in the Tien Shan Mountains, Central Asia, using Corona (~ 1970), Landsat (~ 2000), and ALOS (~ 2007) satellite data

    NASA Astrophysics Data System (ADS)

    Narama, Chiyuki; Kääb, Andreas; Duishonakunov, Murataly; Abdrakhmatov, Kanatbek

    2010-03-01

    Geographic variability of the recent changes of glacier coverage in the Tien Shan Mountains, Central Asia, is assessed using Corona KH-4B satellite photographs for 1968-1971, Landsat 7 ETM+data for 1999-2002, and ALOS/PRISM and AVNIR data for 2006-2008. The four mountain regions investigated (Pskem, Ili-Kungöy, At-Bashy, and SE-Fergana) cover several distributed glacierized areas in the Tien Shan Mountain system, a region that is affected by highly variable local precipitation regimes. Over the 30 years investigated between ~ 1970 and ~ 2000, glacier area decreased by 19% in the Pskem region, 12% in the Ili-Kungöy region, 12% in the At-Bashy region, and 9% in the SE-Fergana region. In the last 7 years (~ 2000 to ~ 2007), glacier area shrank by 5% in the Pskem region, 4% in the Ili-Kungöy region, 4% in the At-Bashy region, and 0% in the SE-Fergana region. Glacier behavior has varied markedly in these regions. The most dramatic glacier shrinkage has occurred in the outer ranges of the Tien Shan Mountains. Recent glacier area loss has resulted from rising summer temperatures. Regional differences of glacier-area changes related to local climate conditions, to the altitudinal distribution of glacier areas, and to the relative proportion of glaciers in different size classes. The observed accelerated glacier shrinkage is expected to have two impacts on the more populated outer ranges: 1) water shortages during summer and 2) increased threat from glacier hazards such as glacier lake outburst floods (GLOFs) and ice avalanches.

  7. Rock magnetic expression of fluid infiltration in the Yingxiu-Beichuan fault (Longmen Shan thrust belt, China)

    NASA Astrophysics Data System (ADS)

    Yang, Tao; Yang, Xiaosong; Duan, Qingbao; Chen, Jianye; Dekkers, Mark J.

    2016-03-01

    Fluid infiltration within fault zones is an important process in earthquake rupture. Magnetic properties of fault rocks convey essential clues pertaining to physicochemical processes in fault zones. In 2011, two shallow holes (134 and 54 m depth, respectively) were drilled into the Yingxiu-Beichuan fault (Longmen Shan thrust belt, China), which accommodated most of the displacement of the 2008 Mw 7.9 Wenchuan earthquake. Fifty-eight drill core samples, including granitic host rock and various fault rocks, were analyzed rock-magnetically, mineralogically, and geochemically. The magnetic behavior of fault rocks appears to be dominated by paramagnetic clay minerals. Magnetite in trace amounts is identified as the predominant ferrimagnetic fraction in all samples, decreasing from the host rock, via fault breccia to (proto-)cataclasite. Significant mass-losses (10.7-45.6%) are determined for the latter two with the "isocon" method. Volatile contents and alteration products (i.e., chlorite) are enriched toward the fault core relative to the host rocks. These observations suggest that magnetite depletion occurred in these fault rocks—exhumed from the shallow crust—plumbed by fluid-assisted processes. Chlorite, interpreted to result from hydrothermal activity, occurs throughout almost the entire fault core and shows high coefficients of determination (R2 > 0.6) with both low and high-field magnetic susceptibility. Close relationships, with R2 > 0.70, are also observed between both low and high-field magnetic susceptibility and the immobile elements (e.g., TiO2, P2O5, MnO), H2O+, and the calculated mass-losses of fault rocks. Hence, magnetic properties of fault rocks can serve as proxy indicators of fluid infiltration within shallow fault zones.

  8. Seasonal Deuterium Excess in a Tien Shan Ice Core: Influence of Moisture Transport and Recycling in Central Asia

    NASA Astrophysics Data System (ADS)

    Kreutz, K. J.; Wake, C. P.; Aizen, V. B.; Cecil, D.; Green, J.; Synal, H.; Introne, D. S.

    2002-12-01

    Stable water isotope (δ18O, δD) data from a high elevation (5100 masl) ice core recovered from the Tien Shan Mountains, Kyrgyzstan, display a seasonal cycle in deuterium excess (d = δD - 8*δ18O) related to changes in the regional hydrologic cycle during 1994-2000. While there is a strong correlation (r2 = 0.98) between δ18O and δD in the ice core samples, the regression slope (6.9) and mean d value (23.0) are significantly different than the global meteoric water line slope of 8 and global d value of 10. The resulting time-series ice core d profile contains distinct winter maxima and summer minima, with a yearly d amplitude of ~15-20 \\permil. Local-scale processes (i.e., sublimation, partial summer melting, snow formation temperature) that may affect d values preserved in the ice core are not consistent with the observed seasonal variability. Rather, we suggest that regional-scale hydrological conditions, including seasonal changes in moisture source, transport, and recycling in the Caspian/Aral Sea region, are responsible for the observed d variability. Examination of data from the Global Network of Isotopes in Precipitation (GNIP) indicates similar seasonal changes in southwestern Central Asian (Afghanistan and Tajikistan), likely related to moisture supply from the Mediterranean Sea during summer. The two years with the highest d values in the ice core record are 1997 and 1998, suggesting a possible link to ENSO ocean/atmosphere variability. The isotope data presented here provide a basis for interpreting centennial-scale ice core d records currently being developed from the region, and highlight the complexity of time-series isotope records from mid-latitude ice cores.

  9. A twentieth century major soluble ion record of dust and anthropogenic pollutants from Inilchek Glacier, Tien Shan

    NASA Astrophysics Data System (ADS)

    Grigholm, B.; Mayewski, P. A.; Aizen, V.; Kreutz, K.; Aizen, E.; Kang, S.; Maasch, K. A.; Sneed, S. B.

    2017-02-01

    Using a high-resolution ( 18 samples/year) major soluble ion record (Na+, K+, Mg2+, Ca2+, Cl-, NO3-, and SO42-) covering the period 1908-1995 A.D. from the Inilchek Glacier, Tien Shan, Kyrgyzstan, we provide a detailed climate and environmental proxy record for the region. Chemical concentrations, empirical orthogonal function analyses, and noncrustal excess calculations are used to identify natural and potential anthropogenic depositional trends. Dominant dust proxy species (i.e., Ca2+) reveal highest concentrations during the 1950s-1970s, with declining decadal trends through the end of the record. These trends likely reflect decreases in central Asian dust storm activity post-1950, which has been associated with coupled atmospheric circulation variability and anthropogenic activities. Comparison between Ca2+ and ERA-Interim (1979-1995) climate reanalysis data indicates a strong relationship to spring (March-May) geopotential height patterns in northwest China and southern Siberia associated with the Siberian High. Noncrustal contribution (excess) estimates of NO3-, K+, SO42-, and Cl- concentrations suggest discernable anthropogenic inputs began between the 1950s and 1970s, increased into the middle/late 1980s, and declined in the 1990s. Excess trends coincide with Former Soviet Union consumption, production, and emission of fossil fuels and fertilizers, reflecting the rapid growth of agriculture and industry, as well as economic declines in the middle to late 1980s/early 1990s. Excess-Cl- trends reflect timings that coincide with the construction of the Pavlodar Chemical Plant and the military production of Cl2 in Kazakhstan. NOAA Hybrid Single-Particle Lagrangian Integrated Trajectory back trajectory frequency analysis suggests eastern Uzbekistan (e.g., Fergana Valley), Kyrgyzstan, and southern Kazakhstan as the primary pollutant sources to the study region.

  10. Lattice Boltzmann simulation of the flow of binary immiscible fluids with different viscosities using the Shan-Chen microscopic interaction model.

    PubMed

    Chin, Jonathan; Boek, Edo S; Coveney, Peter V

    2002-03-15

    We present a lattice Boltzmann study of the flow of a binary fluid where the fluid components have different viscosities. For this purpose, a microscopic interaction model (due to Shan & Chen) is used. The model is validated for Poiseuille flow of layered immiscible binary fluids and the dispersion of a capillary wave. We then study the unstable displacement of a viscous fluid by a less viscous fluid in a two-dimensional channel. Although a finger-like structure was observed in many simulations, it is not clear if this structure was produced due to viscous fingering or due to other effects.

  11. Zipper and freeway shear zone junctions

    NASA Astrophysics Data System (ADS)

    Passchier, Cees; Platt, John

    2016-04-01

    Ductile shear zones are usually presented as isolated planar high-strain domains in a less deformed wall rock, characterised by shear sense indicators such as characteristic deflected foliation traces. Many shear zones, however, form branched systems and if movement on such branches is contemporaneous, the resulting geometry can be complicated and lead to unusual fabric geometries in the wall rock. For Y-shaped shear zone junctions with three simultaneously operating branches, and with slip directions at a high angle to the branch line, eight basic types of shear zone triple junctions are possible, divided into three groups. The simplest type, called freeway junctions, have similar shear sense on all three branches. If shear sense is different on the three branches, this can lead to space problems. Some of these junctions have shear zone branches that join to form a single branch, named zipper junctions, or a single shear zone which splits to form two, known as wedge junctions. Closing zipper junctions are most unusual, since they form a non-active high-strain zone with opposite deflection of foliations. Shear zipper and shear wedge junctions have two shear zones with similar shear sense, and one with the opposite sense. All categories of shear zone junctions show characteristic flow patterns in the shear zone and its wall rock. Shear zone junctions with slip directions normal to the branch line can easily be studied, since ideal sections of shear sense indicators lie in the plane normal to the shear zone branches and the branch line. Expanding the model to allow slip oblique and parallel to the branch line in a full 3D setting gives rise to a large number of geometries in three main groups. Slip directions can be parallel on all branches but oblique to the branch line: two slip directions can be parallel and a third oblique, or all three branches can have slip in different directions. Such more complex shear zone junctions cannot be studied to advantage in a

  12. Transiently Jammed State in Shear Thickening Suspensions under Shear

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Shomeek; Allen, Benjamin; Brown, Eric

    2014-03-01

    We examine the response of a suspension of cornstarch and water under normal impact at controlled velocities. This is a model system to understand why a person can run on the surface of a discontinuous shear thickening fluid. Using simultaneous high-speed imaging of the top and bottom surfaces along with normal force measurements allows us to investigate whether the force response is a result of system spanning structures. We observe a shear thickening transition where above a critical velocity the normal force increases by orders of magnitude. In the high force regime the force response is displacement dependent like a solid rather than velocity dependent like a liquid. The stresses are on the order of 106 Pa which is enough to hold up a person's weight. In this regime imaging shows the existence of a solid like structure that extends to the bottom interface.

  13. Dynamics of Sheared Granular Materials

    NASA Technical Reports Server (NTRS)

    Kondic, Lou; Utter, Brian; Behringer, Robert P.

    2002-01-01

    This work focuses on the properties of sheared granular materials near the jamming transition. The project currently involves two aspects. The first of these is an experiment that is a prototype for a planned ISS (International Space Station) flight. The second is discrete element simulations (DES) that can give insight into the behavior one might expect in a reduced-g environment. The experimental arrangement consists of an annular channel that contains the granular material. One surface, say the upper surface, rotates so as to shear the material contained in the annulus. The lower surface controls the mean density/mean stress on the sample through an actuator or other control system. A novel feature under development is the ability to 'thermalize' the layer, i.e. create a larger amount of random motion in the material, by using the actuating system to provide vibrations as well control the mean volume of the annulus. The stress states of the system are determined by transducers on the non-rotating wall. These measure both shear and normal components of the stress on different size scales. Here, the idea is to characterize the system as the density varies through values spanning dense almost solid to relatively mobile granular states. This transition regime encompasses the regime usually thought of as the glass transition, and/or the jamming transition. Motivation for this experiment springs from ideas of a granular glass transition, a related jamming transition, and from recent experiments. In particular, we note recent experiments carried out by our group to characterize this type of transition and also to demonstrate/ characterize fluctuations in slowly sheared systems. These experiments give key insights into what one might expect in near-zero g. In particular, they show that the compressibility of granular systems diverges at a transition or critical point. It is this divergence, coupled to gravity, that makes it extremely difficult if not impossible to

  14. Shear piezoelectricity in bone at the nanoscale

    NASA Astrophysics Data System (ADS)

    Minary-Jolandan, Majid; Yu, Min-Feng

    2010-10-01

    Recent demonstration of shear piezoelectricity in an isolated collagen fibril, which is the origin of piezoelectricity in bone, necessitates investigation of shear piezoelectric behavior in bone at the nanoscale. Using high resolution lateral piezoresponse force microcopy (PFM), shear piezoelectricity in a cortical bone sample was studied at the nanoscale. Subfibrillar structure of individual collagen fibrils with a periodicity of 60-70 nm were revealed in PFM map, indicating the direct contribution of collagen fibrils to the shear piezoelectricity of bone.

  15. Simple phase-shifting lateral shearing interferometer.

    PubMed

    Mihaylova, Emilia; Whelan, Maurice; Toal, Vincent

    2004-06-01

    A phase-shifting electronic speckle pattern shearing interferometer with a very simple shearing device is proposed. Two partially reflective glass plates are used to introduce the shear in this new interferometer. The reflection coefficients of the coatings on the two plates are 0.3 and 0.7. The distance between the two glass plates controls the size of the shear. The proposed new interferometric system is simple, flexible, and low cost.

  16. Structure of wind-shear turbulence

    NASA Technical Reports Server (NTRS)

    Trevino, G.; Laituri, T. R.

    1989-01-01

    The statistical characteristics of wind shear turbulence are modelled. Isotropic turbulence serves as the basis of comparison for the anisotropic turbulence which exists in wind shear. The question of turbulence scales in wind shear is addressed from the perspective of power spectral density.

  17. Controlled shear/tension fixture

    DOEpatents

    Hsueh, Chun-Hway [Knoxville, TN; Liu, Chain-tsuan [Knoxville, TN; George, Easo P [Knoxville, TN

    2012-07-24

    A test fixture for simultaneously testing two material test samples is provided. The fixture provides substantially equal shear and tensile stresses in each test specimens. By gradually applying a load force to the fixture only one of the two specimens fractures. Upon fracture of the one specimen, the fixture and the load train lose contact and the second specimen is preserved in a state of upset just prior to fracture. Particular advantages of the fixture are (1) to control the tensile to shear load on the specimen for understanding the effect of these stresses on the deformation behavior of advanced materials, (2) to control the location of fracture for accessing localized material properties including the variation of the mechanical properties and residual stresses across the thickness of advanced materials, (3) to yield a fractured specimen for strength measurement and an unfractured specimen for examining the microstructure just prior to fracture.

  18. Turbulent Shear and Internal Waves

    NASA Astrophysics Data System (ADS)

    Munroe, James; Sutherland, Bruce

    2008-11-01

    A series of experiments is presented that model the generation of non-hydrostatic internal gravity waves in upper ocean by the forcing of wind driven turbulent eddies in the surface mixed layer. A turbulent shear layer is forced by a conveyor belt with affixed flat plates near the surface of a stratified fluid and downward propagating internal waves are generated. The turbulence in the shear layer is characterized using particle image velocimetry to measure the kinetic energy as well as length and time scales. The internal waves are measured using synthetic schlieren to determine the amplitudes, frequencies, momentum fluxes, and the energy of the generated waves. The fraction of energy that leaks from the mixed layer to the internal wave field is presented. Consistent with other studies, it is found that the frequencies of internal waves generated by turbulence are an approximate constant fraction of the buoyancy frequency. Implications to internal waves propagating into the deep ocean will be discussed.

  19. Paleo-Climate and Glaciological Reconstruction in Central Asia through the Collection and Analysis of Ice Cores and Instrumental Data from the Tien Shan

    SciTech Connect

    Vladimir Aizen; Donald Bren; Karl Kreutz; Cameron Wake

    2001-05-30

    While the majority of ice core investigations have been undertaken in the polar regions, a few ice cores recovered from carefully selected high altitude/mid-to-low latitude glaciers have also provided valuable records of climate variability in these regions. A regional array of high resolution, multi-parameter ice core records developed from temperate and tropical regions of the globe can be used to document regional climate and environmental change in the latitudes which are home to the vase majority of the Earth's human population. In addition, these records can be directly compared with ice core records available from the polar regions and can therefore expand our understanding of inter-hemispheric dynamics of past climate changes. The main objectives of our paleoclimate research in the Tien Shan mountains of middle Asia combine the development of detailed paleoenvironmental records via the physical and chemical analysis of ice cores with the analysis of modern meteorological and hydrological data. The first step in this research was the collection of ice cores from the accumulation zone of the Inylchek Glacier and the collection of meteorological data from a variety of stations throughout the Tien Shan. The research effort described in this report was part of a collaborative effort with the United State Geological Survey's (USGS) Global Environmental Research Program which began studying radionuclide deposition in mid-latitude glaciers in 1995.

  20. Shear Strength of Aluminum Oxynitride

    NASA Astrophysics Data System (ADS)

    Dandekar, Dattatraya P.; Vaughan, Brian A. M.; Proud, William G.

    2007-06-01

    Aluminum oxynitride (AlON) is a transparent, polycrystalline cubic spinel. The results of investigations^1-4 on shock response of AlON permit determination of the equation of state, and shear strength retained under shock compression. Whereas the values of the HEL of AlON holds no surprises, the inelastic response of AlON reported in Ref. 1-4 differ significantly and is stress dependent. The results of Ref. 1-2 show that AlON retains a shear strength of 3 to 4 GPa when shocked up to around 20 GPa, but the results of Ref, 3-4 seem to suggest a possible loss of shear strength when shocked to 16 GPa and beyond. Our analysis examines the observed differences in the inelastic response of AlON reported in these four studies . 1. J. U. Cazamias, et. al., in Fundamental Issues and Applications of Shock-Wave and High Strain Rate Phenomena, Eds. Staudhammer, Murr, and Meyers, Elsevier, NY, 173 (2001). 2. B. A. M. Vaughn, et.al., Shock Physics, Cavendish Laboratory, Report SP/1092 (2001) 3. T. Sekine, et.al., J. Appl. Phys. 94, 4803 (2003). 4. T. F. Thornhill, et.al., Shock Compression of Matter-2005, Eds. Furnish, Elert, Russell, White, AIP, NY, 143 (2006).

  1. Minimum cut and shear bands

    NASA Astrophysics Data System (ADS)

    Tordesillas, Antoinette; Cramer, Andrew; Walker, David M.

    2013-06-01

    We explore the efficacy of network optimisation theory for minimum cut to quantify the evolution of granular fabric and its functionality as a transmission medium in deforming dense granular media. Our focus here is on force transmission in a sheared assembly of polydisperse particles, in a biaxial compression test under constant confining pressure. The granular fabric is examined with respect to the material's force-bearing contact network over that regime when the material has reached its residual strength, and is deforming under a near constant volume in the presence of a fully developed shear band. The structural evolution of the fabric is quantitatively characterized using a representative weighted-directed network that is similarly evolving as the sample deforms. The edges or links, representing the interparticle contacts, are each weighted by the capacity of the contact to transmit force: a scalar that depends solely on the relative motion of the contacting grains. In the large strain failure regime, the minimum cut which represents the bottleneck in force transmission is found to lie in the persistent shear band. This study paves the way for the future analysis of flows and force transmission through an evolving contact network and, in turn, the characterisation of the relationship between the material's contact topology and its capacity to transmit forces through its contact network.

  2. Haptic Edge Detection Through Shear

    NASA Astrophysics Data System (ADS)

    Platkiewicz, Jonathan; Lipson, Hod; Hayward, Vincent

    2016-03-01

    Most tactile sensors are based on the assumption that touch depends on measuring pressure. However, the pressure distribution at the surface of a tactile sensor cannot be acquired directly and must be inferred from the deformation field induced by the touched object in the sensor medium. Currently, there is no consensus as to which components of strain are most informative for tactile sensing. Here, we propose that shape-related tactile information is more suitably recovered from shear strain than normal strain. Based on a contact mechanics analysis, we demonstrate that the elastic behavior of a haptic probe provides a robust edge detection mechanism when shear strain is sensed. We used a jamming-based robot gripper as a tactile sensor to empirically validate that shear strain processing gives accurate edge information that is invariant to changes in pressure, as predicted by the contact mechanics study. This result has implications for the design of effective tactile sensors as well as for the understanding of the early somatosensory processing in mammals.

  3. Haptic Edge Detection Through Shear

    PubMed Central

    Platkiewicz, Jonathan; Lipson, Hod; Hayward, Vincent

    2016-01-01

    Most tactile sensors are based on the assumption that touch depends on measuring pressure. However, the pressure distribution at the surface of a tactile sensor cannot be acquired directly and must be inferred from the deformation field induced by the touched object in the sensor medium. Currently, there is no consensus as to which components of strain are most informative for tactile sensing. Here, we propose that shape-related tactile information is more suitably recovered from shear strain than normal strain. Based on a contact mechanics analysis, we demonstrate that the elastic behavior of a haptic probe provides a robust edge detection mechanism when shear strain is sensed. We used a jamming-based robot gripper as a tactile sensor to empirically validate that shear strain processing gives accurate edge information that is invariant to changes in pressure, as predicted by the contact mechanics study. This result has implications for the design of effective tactile sensors as well as for the understanding of the early somatosensory processing in mammals. PMID:27009331

  4. Elastic clearance change in axisymmetric shearing process

    NASA Astrophysics Data System (ADS)

    Yoshida, Yoshinori

    2016-10-01

    An axisymmetric shearing experiment is conducted for a sheet of low carbon steel and stainless steel. Elastic change in the clearance between punch and die is measured. The increase of the clearance in shearing is confirmed and the influence of sheared material's flow stress on the clearance change is shown. Finite element analysis (FEA) of shearing with Gurson-Tvergaard-Needlman model (GTN model) is conducted for shearing of the carbon steels with rigid tools as a numerical experiment. Burr height is predicted in the FEA and the result is compared with the experimental result. In addition, the influence of the clearance on stress state in the material is investigated.

  5. Fracture structure near a longitudinal shear macrorupture

    NASA Astrophysics Data System (ADS)

    Goldstein, R. V.; Osipenko, N. M.

    2012-09-01

    Fracture evolution the near a main longitudinal shear in the presence of normal stresses is studied. Experiments with model materials (gypsum, cheese) showed that a multiscale echelon structure of cracks feathering the main rupture is formed under the shear domination conditions. A system of small cracks in the initial echelon is replaced by an echelon of larger and sparser cracks. Intensive transverse compression along the normal to the shear plane, which imitates the initial stress concentrator, takes the fracture region away from the shear plane. A model of evolution development of the observed echelon structure along the main rupture front under the shear domination conditions is proposed.

  6. Apparatus for shearing spent nuclear fuel assemblies

    DOEpatents

    Weil, Bradley S.; Metz, III, Curtis F.

    1980-01-01

    A method and apparatus are described for shearing spent nuclear fuel assemblies of the type comprising an array of fuel pins disposed within an outer metal shell or shroud. A spent fuel assembly is first compacted in a known manner and then incrementally sheared using fixed and movable shear blades having matched laterally projecting teeth which slidably intermesh to provide the desired shearing action. Incremental advancement of the fuel assembly after each shear cycle is limited to a distance corresponding to the lateral projection of the teeth to ensure fuel assembly breakup into small uniform segments which are amenable to remote chemical processing.

  7. Shear fatigue crack growth - A literature survey

    NASA Technical Reports Server (NTRS)

    Liu, H. W.

    1985-01-01

    Recent studies of shear crack growth are reviewed, emphasizing test methods and data analyses. The combined mode I and mode II elastic crack tip stress fields are considered. The development and design of the compact shear specimen are described, and the results of fatigue crack growth tests using compact shear specimens are reviewed. The fatigue crack growth tests are discussed and the results of inclined cracks in tensile panels, center cracks in plates under biaxial loading, cracked beam specimens with combined bending and shear loading, center-cracked panels and double edge-cracked plates under cyclic shear loading are examined and analyzed in detail.

  8. Steady incompressible variable thickness shear layer aerodynamics

    NASA Technical Reports Server (NTRS)

    Chi, M. R.

    1976-01-01

    A shear flow aerodynamic theory for steady incompressible flows is presented for both the lifting and non lifting problems. The slow variation of the boundary layer thickness is considered. The slowly varying behavior is treated by using multitime scales. The analysis begins with the elementary wavy wall problem and, through Fourier superpositions over the wave number space, the shear flow equivalents to the aerodynamic transfer functions of classical potential flow are obtained. The aerodynamic transfer functions provide integral equations which relate the wall pressure and the upwash. Computational results are presented for the pressure distribution, the lift coefficient, and the center of pressure travel along a two dimensional flat plate in a shear flow. The aerodynamic load is decreased by the shear layer, compared to the potential flow. The variable thickness shear layer decreases it less than the uniform thickness shear layer based upon equal maximum shear layer thicknesses.

  9. Shear Fractures of Extreme Dynamics

    NASA Astrophysics Data System (ADS)

    Tarasov, Boris

    2016-10-01

    Natural and laboratory observations show that shear ruptures (faults) can propagate with extreme dynamics (up to intersonic rupture velocities) through intact materials and along pre-existing faults with frictional and coherent (bonded) interfaces. The rupture propagation is accompanied by significant fault strength weakening in the rupture head. Although essential for understanding earthquakes, rock mechanics, tribology and fractures, the question of what physical processes determine how that weakening occurs is still unresolved. The general approach today to explain the fault weakening is based upon the strong velocity-weakening friction law according to which the fault strength drops rapidly with slip velocity. Different mechanisms of strength weakening caused by slip velocity have been proposed including thermal effect, high-frequency compressional waves, expansion of pore fluid, macroscopic melting and gel formation. This paper proposes that shear ruptures of extreme dynamics propagating in intact materials and in pre-existing frictional and coherent interfaces are governed by the same recently identified mechanism which is associated with an intensive microcracking process in the rupture tip observed for all types of extreme ruptures. The microcracking process creates, in certain conditions, a special fan-like microstructure shear resistance of which is extremely low (up to an order of magnitude less than the frictional strength). The fan-structure representing the rupture head provides strong interface weakening and causes high slip and rupture velocities. In contrast with the velocity-weakening dependency, this mechanism provides the opposite weakening-velocity effect. The fan-mechanism differs remarkably from all reported earlier mechanisms, and it can provide such important features observed in extreme ruptures as: extreme slip and rupture velocities, high slip velocity without heating, off-fault tensile cracking, transition from crack-like to pulse

  10. Phoresis in a Shearing Gas

    NASA Astrophysics Data System (ADS)

    Söderholm, Lars H.; Borg, Karl I.

    2003-05-01

    An axially symmetric body small compared with the mean free path is free to move in a shearing gas. The body is treated as a test particle. The force and torque acting on the body are calculated. This force and torque will set the body in motion, which asymptotically will take place in one of the eigendirections of the rate of deformation tensor. The axis of the body then points in the same direction. For a velocity field vx(y) the final motion is parallel to one of the lines x = y and x = -y, and the speed of the motion is given by V = 9μβN/8p (2πkBT/m)1/2 ατb1/4 + 1/2πατ + [8 - (6 - πατ)]b3vx,y. Here μ is the viscosity of the gas, p is the pressure, βN is a number close to unity, T is the temperature, m is the mass of a gas molecule, and ατ is parameter in the boundary conditions close to unity. The non-dimensional numbers b1 and b3 depends on the shape of the body. This speed is of the order of the mean free path of the gas multiplied by the shearing. There will be no motion for a body, which is reflection symmetric in a plane orthogonal to the axis of symmetry. This means that there is a phenomenon of phoresis in a shearing gas, which is analogous to thermophoresis in a gas with a temperature gradient.

  11. Nucleation of shear bands in amorphous alloys

    PubMed Central

    Perepezko, John H.; Imhoff, Seth D.; Chen, Ming-Wei; Wang, Jun-Qiang; Gonzalez, Sergio

    2014-01-01

    The initiation and propagation of shear bands is an important mode of localized inhomogeneous deformation that occurs in a wide range of materials. In metallic glasses, shear band development is considered to center on a structural heterogeneity, a shear transformation zone that evolves into a rapidly propagating shear band under a shear stress above a threshold. Deformation by shear bands is a nucleation-controlled process, but the initiation process is unclear. Here we use nanoindentation to probe shear band nucleation during loading by measuring the first pop-in event in the load–depth curve which is demonstrated to be associated with shear band formation. We analyze a large number of independent measurements on four different bulk metallic glasses (BMGs) alloys and reveal the operation of a bimodal distribution of the first pop-in loads that are associated with different shear band nucleation sites that operate at different stress levels below the glass transition temperature, Tg. The nucleation kinetics, the nucleation barriers, and the density for each site type have been determined. The discovery of multiple shear band nucleation sites challenges the current view of nucleation at a single type of site and offers opportunities for controlling the ductility of BMG alloys. PMID:24594599

  12. Does Shear Thickening Occur in Semisolid Metals?

    NASA Astrophysics Data System (ADS)

    Atkinson, Helen V.; Favier, Veronique

    2016-04-01

    In the various forms of semisolid processing such as thixoforming and thixoforging, the entry into the die occurs in a fraction of a second so it is the transient rheological behavior which governs the initial stages of flow. In experiments in the literature, this rheological behavior is probed through applying rapid transitions in shear rate under isothermal conditions. There is contradictory evidence as to whether the behavior during these transitions is shear thinning or shear thickening, although it is clear that once in the die the material is thinning. Here the data in the literature are reanalyzed to obtain a rationalization of the contradictions which has not previously been available. It is argued that if a suspension is initially in a disagglomerated state ( i.e., one which is initially sheared), the instantaneous behavior with a jump-up in shear rate is shear thickening (even if the long-term steady-state behavior is shear thinning) provided the fraction solid is greater than about 0.36 and the final shear rate at the end of the jump is greater than about 100 s-1. If the jump-up in shear rate is made from rest then yield masks the shear thickening.

  13. Shear zone junctions: Of zippers and freeways

    NASA Astrophysics Data System (ADS)

    Passchier, Cees W.; Platt, John P.

    2017-02-01

    Ductile shear zones are commonly treated as straight high-strain domains with uniform shear sense and characteristic curved foliation trails, bounded by non-deforming wall rock. Many shear zones, however, are branched, and if movement on such branches is contemporaneous, the resulting shape can be complicated and lead to unusual shear sense arrangement and foliation geometries in the wall rock. For Y-shaped shear zone triple junctions with three joining branches and transport direction at a high angle to the branchline, only eight basic types of junction are thought to be stable and to produce significant displacement. The simplest type, called freeway junctions, have similar shear sense in all three branches. The other types show joining or separating behaviour of shear zone branches similar to the action of a zipper. Such junctions may have shear zone branches that join to form a single branch (closing zipper junction), or a single shear zone that splits to form two branches, (opening zipper junction). All categories of shear zone junctions show characteristic foliation patterns and deflection of markers in the wall rock. Closing zipper junctions are unusual, since they form a non-active zone with opposite deflection of foliations in the wall rock known as an extraction fault or wake. Shear zipper junctions can form domains of overprinting shear sense along their flanks. A small and large field example are given from NE Spain and Eastern Anatolia. The geometry of more complex, 3D shear zone junctions with slip parallel and oblique to the branchline is briefly discussed.

  14. Conductor shears as iceberg encroaches

    SciTech Connect

    Not Available

    1984-10-01

    Operators in the Arctic regions must protect wellheads from encroaching icebergs and icepack sheets. Diverting ice masses and excavating large holes below scour depth is expensive. Now an alternate approach allows the conductor to shear, shuts in the well, and provides a method of re-entering the well. The new system has been successfully used by Mobil on two exploratory wells in the Hibernia field off eastern Canada. The wells used 18 3/4-in. wellheads rated at 10,000 psi with 36-in. conductor pipe. The performance of the system is discussed.

  15. Compactness of lateral shearing interferometers

    NASA Astrophysics Data System (ADS)

    Ferrec, Yann; Taboury, Jean; Sauer, Hervé; Chavel, Pierre

    2011-08-01

    Imaging lateral shearing interferometers are good candidates for airborne or spaceborne Fourier-transform spectral imaging. For such applications, compactness is one key parameter. In this article, we compare the size of four mirror-based interferometers, the Michelson interferometer with roof-top (or corner-cube) mirrors, and the cyclic interferometers with two, three, and four mirrors, focusing more particularly on the last two designs. We give the expression of the translation they induce between the two exiting rays. We then show that the cyclic interferometer with three mirrors can be made quite compact. Nevertheless, the Michelson interferometer is the most compact solution, especially for highly diverging beams.

  16. Gravity waves on shear flows

    NASA Astrophysics Data System (ADS)

    Miles, John

    2001-09-01

    The eigenvalue problem for gravity waves on a shear flow of depth h and non-inflected velocity profile U(y) (typically parabolic) is revisited, following Burns (1953) and Yih (1972). Complementary variational formulations that provide upper and lower bounds to the Froude number F as a function of the wave speed c and wavenumber k are constructed. These formulations are used to improve Burns's long-wave approximation and to determine Yih's critical wavenumber k[low asterisk], for which the wave is stationary (c = 0) and to which k must be inferior for the existence of an upstream running wave.

  17. Invariant Quantities in Shear Flow

    NASA Astrophysics Data System (ADS)

    Baule, A.; Evans, R. M. L.

    2008-12-01

    The dynamics of systems out of thermal equilibrium is usually treated on a case-by-case basis without knowledge of fundamental and universal principles. We address this problem for a class of driven steady states, namely, those mechanically driven at the boundaries such as complex fluids under shear. From a nonequilibrium counterpart to detailed balance (NCDB) we derive a remarkably simple set of invariant quantities which remain unchanged when the system is driven. These new nonequilibrium relations are both exact and valid arbitrarily far from equilibrium. Furthermore, they enable the systematic calculation of transition rates in driven systems with state spaces of arbitrary connectivity.

  18. Paleozoic structure of Middle Tien Shan (Kyrgyzstan Central Asian Orogenic Belt): Insights on the polarity and timing of tectonic motions, subductions, and lateral correlations

    NASA Astrophysics Data System (ADS)

    Jourdon, Anthony; Loury, Chloé; Rolland, Yann; Petit, Carole; Bellahsen, Nicolas

    2015-04-01

    The structure and Palaeozoic tectonic evolution in Kyrgyz and Chinese Tien Shan Central Asian Orogenic Belt (CAOB) are still a matter of debate. There are numerous and conflicting models about the polarity of tectonic motions in the Paleozoic, the number of continental blocks and oceanic basins involved and the timing of tectonic events. In this study we propose new maps and structural cross-sections of Middle and South Kyrgyz Tien Shan (TS). These cross-sections allow us to highlight an overall South-verging structure in the Middle TS, with a thick-skin style involving the crystalline basement. This deformation occurred during the Early Carboniferous, and is sealed by an Upper Carboniferous unconformity. We ascribe this structure to an Upper Plate deformation linked to north-dipping subduction below Middle TS. In contrast, the South TS exhibits a north-verging structure, linked to south-dipping subduction, which is evidenced by an accretionary prism, a volcanic arc, and high-pressure rocks (Loury et al., 2015), and is correlated to similar structures in the Chinese TS (e.g., Charvet et al., 2011). Based on these observations, we propose a new interpretation of the tectonic evolution of the Middle and South TS CAOB. The resulting model comprises a long-lived north-dipping subduction of the Turkestan Ocean below the Middle TS-Karazakh Platform and a short-lived south-dipping subduction of a marginal back-arc basin below the Tarim. Consequently, the South TS is interpreted as a rifted block from the Tarim. Finally, the docking of the large Tarim Craton to the CAOB corresponds to a rapid collision phase (320-300 Ma). This put an end to the long-lived Paleozoic subduction history in the CAOB. Charvet, J., Shu, L., et al., 2011. Palaeozoic tectonic evolution of the Tianshan belt, NW China. Science China Earth Sciences, 54, 166-184. Loury, C. , Rolland, Y., Guillot S., Mikolaichuk, A.V., Lanari, P., Bruguier, O., D.Bosch, 2015. Crustal-scale structure of South Tien Shan

  19. Origin of Late Mesozoic granitoids in the newly discovered Zha-Shan porphyry Cu district, South Qinling, central China, and implications for regional metallogeny

    NASA Astrophysics Data System (ADS)

    Xie, Guiqing; Mao, Jingwen; Wang, Ruiting; Ren, Tao; Li, Jianbi; Da, Junzhi

    2015-05-01

    The newly discovered porphyry Cu deposits in the South Qinling Belt (SQB) have not been well researched as compared with the large porphyry Mo province in the southern North China Block (S-NCB), and the origin of granitoids associated with porphyry Cu mineralization in the Zha-Shan district, SQB is poorly constrained. Here, we present detailed zircon U-Pb geochronological, whole rock elemental and Sr-Nd isotopic data for important Late Mesozoic granitoid stocks associated with porphyry Cu deposits in the Zha-Shan district; these data are used to constrain the age and the source of magmas that formed these granitoids, and implication of regional metallogeny. The new zircon LA-ICPMS U-Pb ages presented here indicate that the granitoids related to porphyry Cu system at Chigou, Beishagou, Shuangyuangou and Yuanjiagou developed at 148-144 Ma, 144 Ma, 145-144 Ma and 146 Ma, respectively. These rocks are high-K calc-alkaline I-type granitoids, which are enriched in large ion lithophile elements (e.g., Th, U, and Pb) and light rare earth elements, are depleted in Nb, Ta and Ti, characterizing by wide variations in initial εNd(t) (-3.8 to -9.5), and moderate radiogenic Sr isotopes ((87Sr/86Sr)i = 0.7046 to 0.7093). These features indicate that the magmas that formed the granitoids related to porphyry Cu system in the Zha-Shan district formed as a result of variable degrees of mixing between crustal and metasomatic lithospheric mantle. The new zircon LA-ICPMS U-Pb ages in this study, combined with previous published data, suggest that regional-scale Late Jurassic to Early Cretaceous granitoid stocks, and associated porphyry Cu and Mo systems in both the S-NCB and SQB formed almost contemporaneously, with 147-139 Ma porphyry Mo deposits in the S-NCB and 148-145 Ma porphyry Cu deposits in the SQB. The Cu-related intrusions contained a greater contribution of lithospheric mantle component than the Mo-related intrusions in the East Qinling Orogeny.

  20. Joint Inversion of Receiver Functions and Surface Wave Group Velocities from the MANAS data set to Determine Custal Thickness Variations in theTien Shan

    NASA Astrophysics Data System (ADS)

    Gilligan, A.; Priestley, K. F.; Roecker, S. W.

    2012-12-01

    The Tien Shan is the largest active intracontinental orgogenic belt on the Earth. To better understand the processes causing mountains to form in this location distant from a plate boundary, we analyze passive source seismic data collected on 40 broad band stations of the MANAS project (2005-2007) to determine variations in crustal thickness and wavespeed across the range. The linear MANAS array transects the Tien Shan just to the east of the Talas Fergana fault and extends from the Tarim Basin north over the Kokshal Range and across the Naryn Valley to the Kyrgyz Range and the Kazakh Shield. This data set has a denser station spacing (~10 km) than that available in previous studies. We combine P- and S-wave receiver functions with surface wave observations from both earthquakes and ambient noise analysis to reduce the ambiguity inherent in the images obtained from the techniques applied individually. In particular, fundamental-mode surface-wave dispersion observations are sensitive to absolute wavespeed averages rather than contrasts, while receiver functions are primarily sensitive to wavespeed contrasts and vertically integrated travel times rather than absolute wavespeeds. Moreover, analysis of the ambient noise allows dispersion measurements at shorter periods which improves constraints for the upper crust. We jointly invert P- and S-wave receiver functions, fundamental mode Rayleigh wave group velocity determined from 1.75 years of continuous seismic ambient noise for periods 4-28s, and group velocity data for periods 10-70s from the surface wave study of Acton et al. (2010). The resulting crustal model show a strong variation in the Moho depth across the range. We find the thickest crust (~60 km) beneath the Kokshal range, while that beneath the Naryn Valley, in the middle of the Tien Shan is thin (~45 km) and is of similar thickness to that beneath the Tarim Basin and Kazakh shield. This suggests a lack of crustal shortening, or shortening of a previously

  1. Optical Beam-Shear Sensors

    NASA Technical Reports Server (NTRS)

    Martin, Stefan; Szwaykowski, Piotr

    2007-01-01

    A technique for measuring optical beam shear is based on collecting light from the four quadrants of the beam and comparing the optical power collected from each quadrant with that from the other three quadrants. As used here, "shear" signifies lateral displacement of a beam of light from a nominal optical axis. A sensor for implementing this technique consists of a modified focusing lens and a quad-cell photodetector, both centered on the nominal optical axis. The modification of the lens consists in cutting the lens into four sectors (corresponding to the four quadrants) by sawing along two orthogonal diameters, then reassembling the lens following either of two approaches described next. In one approach, the lens is reassembled by gluing the sectors back together. In the simplest variant of this approach, the kerf of the saw matches the spacing of the photodetector cells, so that the focus of each sector crosses the axis of symmetry to fall on the opposite photodetector cell (see figure). In another variant of this approach, the lens sectors are spaced apart to make their individual foci to fall on separate photodetector cells, without crossing the optical axis. In the case of a sufficiently wide beam, the modified lens could be replaced with four independent lenses placed in a square array, each focusing onto an independent photodetector

  2. Shear wall ultimate drift limits

    SciTech Connect

    Duffey, T.A.; Goldman, A.; Farrar, C.R.

    1994-04-01

    Drift limits for reinforced-concrete shear walls are investigated by reviewing the open literature for appropriate experimental data. Drift values at ultimate are determined for walls with aspect ratios ranging up to a maximum of 3.53 and undergoing different types of lateral loading (cyclic static, monotonic static, and dynamic). Based on the geometry of actual nuclear power plant structures exclusive of containments and concerns regarding their response during seismic (i.e.,cyclic) loading, data are obtained from pertinent references for which the wall aspect ratio is less than or equal to approximately 1, and for which testing is cyclic in nature (typically displacement controlled). In particular, lateral deflections at ultimate load, and at points in the softening region beyond ultimate for which the load has dropped to 90, 80, 70, 60, and 50 percent of its ultimate value, are obtained and converted to drift information. The statistical nature of the data is also investigated. These data are shown to be lognormally distributed, and an analysis of variance is performed. The use of statistics to estimate Probability of Failure for a shear wall structure is illustrated.

  3. Shear-Induced Reactive Gelation.

    PubMed

    Brand, Bastian; Morbidelli, Massimo; Soos, Miroslav

    2015-11-24

    In this work, we describe a method for the production of porous polymer materials in the form of particles characterized by narrow pore size distribution using the principle of shear-induced reactive gelation. Poly(styrene-co-divinylbenzene) primary particles with diameter ranging from 80 to 200 nm are used as building blocks, which are assembled into fractal-like clusters when exposed to high shear rates generated in a microchannel. It was found that independent of the primary particle size, it is possible to modulate the internal structure of formed fractal-like aggregates having fractal dimension ranging from 2.4 to 2.7 by varying the residence time in the microchannel. Thermally induced postpolymerization was used to increase the mechanical resilience of such formed clusters. Primary particle interpenetration was observed by SEM and confirmed by light scattering resulting in an increase of fractal dimension. Nitrogen sorption measurements and mercury porosimetry confirmed formation of a porous material with surface area ranging from 20 to 40 m(2)/g characterized by porosity of 70% and narrow pore size distribution with an average diameter around 700 nm without the presence of any micropores. The strong perfusive character of the synthesized material was confirmed by the existence of a plateau of the height equivalent to a theoretical plate measured at high reduced velocities using a chromatographic column packed with the synthesized microclusters.

  4. Shear dynamo problem: Quasilinear kinematic theory.

    PubMed

    Sridhar, S; Subramanian, Kandaswamy

    2009-04-01

    Large-scale dynamo action due to turbulence in the presence of a linear shear flow is studied. Our treatment is quasilinear and kinematic but is nonperturbative in the shear strength. We derive the integrodifferential equation for the evolution of the mean magnetic field by systematic use of the shearing coordinate transformation and the Galilean invariance of the linear shear flow. For nonhelical turbulence the time evolution of the cross-shear components of the mean field does not depend on any other components excepting themselves. This is valid for any Galilean-invariant velocity field, independent of its dynamics. Hence the shear-current assisted dynamo is essentially absent, although large-scale nonhelical dynamo action is not ruled out.

  5. Double-Diffusive Convection in Rotational Shear

    DTIC Science & Technology

    2015-03-01

    CONVECTION IN ROTATIONAL SHEAR by James S. Ball March 2015 Thesis Advisor: Timour Radko Second Reader: John Colosi THIS PAGE...AND SUBTITLE 5. FUNDING NUMBERS DOUBLE-DIFFUSIVE CONVECTION IN ROTATIONAL SHEAR 6. AUTHOR(S) James S. Ball 7. PERFORMING ORGANIZATION NAME(S) AND...INTENTIONALLY LEFT BLANK ii Approved for public release;distribution is unlimited DOUBLE-DIFFUSIVE CONVECTION IN ROTATIONAL SHEAR James S. Ball

  6. Shear wall experiments and design in Japan

    SciTech Connect

    Park, Y.J.; Hofmayer, C.

    1994-12-01

    This paper summarizes the results of recent survey studies on the available experimental data bases and design codes/standards for reinforced concrete (RC) shear wall structures in Japan. Information related to the seismic design of RC reactor buildings and containment structures was emphasized in the survey. The seismic requirements for concrete structures, particularly those related to shear strength design, are outlined. Detailed descriptions are presented on the development of Japanese shear wall equations, design requirements for containment structures, and ductility requirements.

  7. Continuous wave laser for wind shear detection

    NASA Technical Reports Server (NTRS)

    Nelson, Loren

    1991-01-01

    Details of the design and development of a continuous-wave heterodyne carbon dioxide laser which has wind shear detection capabilities are given in viewgraph form. The goal of the development was to investigate the lower cost CW (rather than pulsed) lidar option for look-ahead wind shear detection from aircraft. The device has potential utility for ground based wind shear detection at secondary airports where the high cost of a Terminal Doppler Weather Radar system is not justifiable.

  8. Carbonate clumped isotope paleothermometry and stable isotope results from the Eocene Fenghuo Shan Group, Hoh Xil Basin, Central Tibet

    NASA Astrophysics Data System (ADS)

    Snell, K. E.; Lippert, P. C.; Eiler, J. M.

    2009-12-01

    We present preliminary clumped isotope temperatures, calcite δ13C and δ18O values, and reconstructed water δ18O values from paleosol carbonates and calcite cemented siltstones and mudstones of the Fenghuo Shan Group from stratigraphic sections in the TouTou He subbasin of Hoh Xil Basin on the northern Tibetan Plateau. Models of plateau growth vary in the timing of initial plateau growth, and in their description of the spatial distribution of the plateau through time. Oxygen isotope paleoaltimetry studies have been used to estimate the elevation of the plateau in the past, but this technique requires assumptions about the temperature of mineral formation. Independent estimates of the temperature of mineral formation are potentially useful for identifying samples in which carbonate has undergone post-depositional recrystallization and/or isotopic exchange, and, when plausible primary depositional temperatures are found, for making more accurate estimates of δ18O of the waters from which the calcite precipitated. The calcite δ18O and δ13C values for the cements are relatively invariant with stratigraphic level, averaging -10.1±1.2‰ and -4.5±2.5‰ (PDB), respectively. These values are similar to lacustrine carbonates of similar age from the same region. The paleosol carbonates, in contrast, are 18O- and 13C-enriched relative to the cements, with average δ18O and δ13C values of -2.4±0.8 and -2.8±0.7‰. Carbonate clumped isotope paleotemperatures for the cements and the paleosol carbonates are also markedly different. The cement samples vary from 26 to 83°C and increase consistently with increasing depth, at a steep gradient of ~100°C/km. Paleosol carbonates from depths at which cements recorded 60°C, preserve temperatures of 35°C and 41°C. A calcite spar-filled fracture in one paleosol carbonate had a temperature of 41°C. Finally the reconstructed cement water δ18O values range from 2.8 to -7.6‰(SMOW), with a trend of 0.2‰/°C. The

  9. Origins of Shear Jamming for Frictional Grains

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Zheng, Hu; Ren, Jie; Dijksman, Joshua; Bares, Jonathan; Behringer, Robert

    2016-11-01

    Granular systems have been shown to be able to behave like solids, under shear, even when their densities are below the critical packing fraction for frictionless isotropic jamming. To understand such a phenomena, called shear jamming, the question we address here is: how does shear bring a system from a unjammed state to a jammed state, where the coordination number, Z, is no less than 3, the isotropic jamming point for frictional grains? Since Z can be used to distinguish jammed states from unjammed ones, it is vital to understand how shear increases Z. We here propose a set of three particles in contact, denoted as a trimer, as the basic unit to characterize the deformation of the system. Trimers, stabilized by inter-grain friction, fail under a certain amount of shear and bend to make extra contacts to regain stability. By defining a projection operator of the opening angle of the trimer to the compression direction in the shear, O, we see a systematically linear decrease of this quantity with respect to shear strain, demonstrating the bending of trimers as expected. In addition, the average change of O from one shear step to the next shows a good collapse when plotted against Z, indicating a universal behavior in the process of shear jamming. We acknowledge support from NSF DMR1206351, NASA NNX15AD38G, the William M. Keck Foundation and a RT-MRSEC Fellowship.

  10. Periodically sheared 2D Yukawa systems

    SciTech Connect

    Kovács, Anikó Zsuzsa; Hartmann, Peter; Donkó, Zoltán

    2015-10-15

    We present non-equilibrium molecular dynamics simulation studies on the dynamic (complex) shear viscosity of a 2D Yukawa system. We have identified a non-monotonic frequency dependence of the viscosity at high frequencies and shear rates, an energy absorption maximum (local resonance) at the Einstein frequency of the system at medium shear rates, an enhanced collective wave activity, when the excitation is near the plateau frequency of the longitudinal wave dispersion, and the emergence of significant configurational anisotropy at small frequencies and high shear rates.

  11. Dynamic shear deformation in high purity Fe

    SciTech Connect

    Cerreta, Ellen K; Bingert, John F; Trujillo, Carl P; Lopez, Mike F; Gray, George T

    2009-01-01

    The forced shear test specimen, first developed by Meyer et al. [Meyer L. et al., Critical Adiabatic Shear Strength of Low Alloyed Steel Under Compressive Loading, Metallurgical Applications of Shock Wave and High Strain Rate Phenomena (Marcel Decker, 1986), 657; Hartmann K. et al., Metallurgical Effects on Impact Loaded Materials, Shock Waves and High Strain rate Phenomena in Metals (Plenum, 1981), 325-337.], has been utilized in a number of studies. While the geometry of this specimen does not allow for the microstructure to exactly define the location of shear band formation and the overall mechanical response of a specimen is highly sensitive to the geometry utilized, the forced shear specimen is useful for characterizing the influence of parameters such as strain rate, temperature, strain, and load on the microstructural evolution within a shear band. Additionally, many studies have utilized this geometry to advance the understanding of shear band development. In this study, by varying the geometry, specifically the ratio of the inner hole to the outer hat diameter, the dynamic shear localization response of high purity Fe was examined. Post mortem characterization was performed to quantify the width of the localizations and examine the microstructural and textural evolution of shear deformation in a bcc metal. Increased instability in mechanical response is strongly linked with development of enhanced intergranular misorientations, high angle boundaries, and classical shear textures characterized through orientation distribution functions.

  12. Multisegment rupture in the 11 July 1889 Chilik earthquake (Mw 8.0-8.3), Kazakh Tien Shan, interpreted from remote sensing, field survey, and paleoseismic trenching

    NASA Astrophysics Data System (ADS)

    Abdrakhmatov, K. E.; Walker, R. T.; Campbell, G. E.; Carr, A. S.; Elliott, A.; Hillemann, C.; Hollingsworth, J.; Landgraf, A.; Mackenzie, D.; Mukambayev, A.; Rizza, M.; Sloan, R. A.

    2016-06-01

    The 11 July 1889 Chilik earthquake (Mw 8.0-8.3) forms part of a remarkable sequence of large earthquakes in the late nineteenth and early twentieth centuries in the northern Tien Shan. Despite its importance, the source of the 1889 earthquake remains unknown, though the macroseismic epicenter is sited in the Chilik valley, ~100 km southeast of Almaty, Kazakhstan (~2 million population). Several short fault segments that have been inferred to have ruptured in 1889 are too short on their own to account for the estimated magnitude. In this paper we perform detailed surveying and trenching of the ~30 km long Saty fault, one of the previously inferred sources, and find that it was formed in a single earthquake within the last 700 years, involving surface slip of up to 10 m. The scarp-forming event, likely to be the 1889 earthquake, was the only surface-rupturing event for at least 5000 years and potentially for much longer. From satellite imagery we extend the mapped length of fresh scarps within the 1889 epicentral zone to a total of ~175 km, which we also suggest as candidate ruptures from the 1889 earthquake. The 175 km of rupture involves conjugate oblique left-lateral and right-lateral slip on three separate faults, with step overs of several kilometers between them. All three faults were essentially invisible in the Holocene geomorphology prior to the last slip. The recurrence interval between large earthquakes on any of these faults, and presumably on other faults of the Tien Shan, may be longer than the timescale over which the landscape is reset, providing a challenge for delineating sources of future hazard.

  13. Extensional step-over between the Zhongdian and Red River faults: kinematics of the Daju normal fault constrained by cosmogenic dating of the Yangtze terraces (Yulong Shan, Yunnan)

    NASA Astrophysics Data System (ADS)

    van der Woerd, J.; Perrineau, A.; Gaudemer, Y.; Leloup, P.-H.; Liu-Zeng, J.; Barrier, L.; Thuizat, R.

    2012-04-01

    Extension in western Yunnan, southeastern Tibet, is limited by two dextral strike-slip faults, the Zhongdian and Red River faults, to the north and south, respectively, and is characterized by N-S directed normal faults and basins. In the northwestern corner of this large extensional step-over, the Yangtze River crosses the Daju normal fault at the foot of the Yulong Shan. Due to uplift of the Yulong Shan, the Yangtze carved the huge Huxiao Jia (Tiger Leap) Gorges (˜3500 m deep) and abandoned sets of fluvial terraces across the fault zone and in the Daju basin to the north. Cosmogenic dating of blocks sampled on top of the terraces provide ages ranging from 8 to 30 ka. In the hanging wall basin to the north, the terraces may have been abandoned after the breach of a natural dam formed in the river (moraine or landslide) during the last glacial period. The average incision rate of the river in the basin is about 5.9 mm/yr, the vertical slip-rate on the Daju fault is 4.9±1.3 mm/yr, thus implying an incision rate of the river inside the gorge reaching about 11 mm/year. These rates may explain the exceptional size and steepness of the gorge. These results show that active faulting plays a major role in shaping the present relief of this region and that recent strain changes involve movement along the largest strike-slip faults of the region, in accordance with models implying large-scale block extrusion.

  14. Metamorphic Study along the Wenchuan Thrust (Longmen Shan, Sichuan, China); a Key to Understand the Two Phases of Thickening of the Eastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    de Sigoyer, J.

    2015-12-01

    The Longmen Shan mountain belt, represents the eastern margin of Tibetan plateau (Sichuan, China) and culminated over 7000m. Despite very low convergent rate observed across his belt, it is active as attested by the Wenchuan earthquake Mw 7.9 (2008) that rupture and out of sequence thrust in this belt. The formation of this mountain bet results from two orogenic phase, one at the end of Trias (due to the closure of the Paleotethys), and one during Cenozoic time following the Indian Asia collision. This study aims to identify the deformation and metamorphism related to Mesozoic event and those relate to Cenozoic evolution. Structural, microstructural, metamorphic observations, PT estimates (graphitization of carbonaceous material, quantified X-ray images, chlorite-phengite-quartz-water multi-equilibrium and thermodynamic modelling) and U-Pb geochronology are used to describe the tectono-metamorphic evolution of the Xuelongbao area in the internal part of the Longmen Shan belt (eastern border of the Tibetan plateau, Sichuan, China). The Xuelongbao granite is dated at 765±7 Ma (in situ U/Pb dating on zircon), indicating that it forms part of the western Neoproterozoic South China block basement. The deformation in the western sedimentary cover above the Xuelongbao massif is intense, with step cleavage, twisted fold axes and CS structures with top to the SE thrusting vergence. Four stages of deformation are described, three of them are related to the Mesozoic wedge thickening, and the last one is due to the Cenozoic deformation. An inverted metamorphic gradient from 470°C, 8 kbar to 620°C, 13 kbar is identified in the cover above the Xuelongbao basement, suggesting a stack of sedimentary slices during the propagation of the Mesozoic accretionary wedge on the South China block margin. This decollement zone has been exhumed during the Cenozoic D4 exhumation of the Xuelongbao basement along the Wenchuan thrust, where greenschist overprint is observed.

  15. Behavior of granular materials under cyclic shear.

    PubMed

    Mueggenburg, Nathan W

    2005-03-01

    The design and development of a parallel plate shear cell for the study of large-scale shear flows in granular materials is presented. The parallel plate geometry allows for shear studies without the effects of curvature found in the more common Couette experiments. A system of independently movable slats creates a well with side walls that deform in response to the motions of grains within the pack. This allows for true parallel plate shear with minimal interference from the containing geometry. The motions of the side walls also allow for a direct measurement of the velocity profile across the granular pack. Results are presented for applying this system to the study of transients in granular shear and for shear-induced crystallization. Initial shear profiles are found to vary from packing to packing, ranging from a linear profile across the entire system to an exponential decay with a width of approximately six bead diameters. As the system is sheared, the velocity profile becomes much sharper, resembling an exponential decay with a width of roughly three bead diameters. Further shearing produces velocity profiles which can no longer be fit to an exponential decay, but are better represented as a Gaussian decay or error function profile. Cyclic shear is found to produce large-scale ordering of the granular pack, which has a profound impact on the shear profile. There exist periods of time in which there is slipping between layers as well as periods of time in which the layered particles lock together resulting in very little relative motion.

  16. Tuning graphene properties by shear

    NASA Astrophysics Data System (ADS)

    Concha, Andres; Cheng, Shengfeng; Covaci, Lucian; Mahadevan, L.

    2014-03-01

    Graphene being the thinnest possible membrane made out of carbon atoms is prone to deformations under slight external forcing. Here, we take advantage of this proneness to deformations to manipulate transport properties of graphene ribbons. We analyze the effect on conductance and LDOS of the spontaneous pattern produced when a wide ribbon is subject to shear. The deformation of the ribbon produces pseudo-magnetic fields, scalar potentials, and Fermi velocity renormalization resulting in the modification of transmission properties without the need of an external gate potential. Our proposal paves the way for producing electronic waveguides by using an elastic instability that spans from the nano to macro-scales. AC was partially supported by Conicyt PAI 79112004 and Fondecyt iniciacion 11130075. LC acknowledges individual support from FWO-Vlaanderen.

  17. Quadruple Lap Shear Processing Evaluation

    NASA Technical Reports Server (NTRS)

    Thornton, Tony N.; McCool, A. (Technical Monitor)

    2000-01-01

    The Thiokol, Science and Engineering Huntsville Operations (SEHO) Laboratory has previously experienced significant levels of variation in testing Quadruple Lap Shear (QLS) specimens. The QLS test is used at Thiokol / Utah for the qualification of Reusable Solid Rocket Motor (RSRM) nozzle flex bearing materials. A test was conducted to verify that process changes instituted by SEHO personnel effectively reduced variability, even with normal processing variables introduced. A test matrix was designed to progress in a series of steps; the first establishing a baseline, then introducing additional solvents or other variables. Variables included normal test plan delay times, pre-bond solvent hand-wipes and contaminants. Each condition tested utilized standard QLS hardware bonded with natural rubber, two separate technicians and three replicates. This paper will report the results and conclusions of this investigation.

  18. Magnetoconvection in sheared magnetic fields

    SciTech Connect

    Bian, N. H.; Garcia, O. E.

    2008-10-15

    The development of magnetoconvection in a sheared magnetic field is investigated. The equilibrium magnetic field B{sub 0} is horizontal and its orientation varies linearly along the vertical axis. Preliminary consideration of the transition from the inertial to the viscous regime of the gravitational resistive interchange instability, reveals that the latter is characterized by the existence of viscoresistive boundary layers of vertical width which scales as Q{sup -1/6}, where Q is the Chandrasekhar number. The situation is analogous to the one encountered in magnetically confined laboratory plasmas, where convective flows are constrained by the magnetic shear to develop in boundary layers located around resonant magnetic surfaces in order to fulfill the 'interchange condition'k{center_dot}B{sub 0}=0, where k is the wave vector of the magnetic perturbation. It follows that when the effect of thermal diffusion is taken into account in the process, convection can only occur above a certain critical value of the Rayleigh number which scales as Q{sup 2/3} for large Q. At the onset, the convection pattern is a superposition of identically thin convective rolls everywhere aligned with the local magnetic field lines and which therefore adopt the magnetic field geometry, a situation also reminiscent of the penumbra of sunspots. Using this degeneracy, equations describing the weakly nonlinear state are obtained and discussed. A reduced magnetohydrodynamic description of magnetoconvection is introduced. Since it is valid for arbitrary magnetic field configurations, it allows a simple extension to the case where there exists an inclination between the direction of gravity and the plane spanned by the equilibrium magnetic field. These reduced magnetohydrodynamic equations are proposed as a powerful tool for further investigations of magnetoconvection in more complex field line geometries.

  19. The Multi-Dimensional Nature of Wind Shear Investigations

    NASA Technical Reports Server (NTRS)

    Cox, W. J.

    1977-01-01

    The impact of air carrier accidents has lead to investigations into the wind shear phenomenon. This report includes such topics as wind shear characterization, aircraft pilot performance in shear conditions, terminology and language development, wind shear forecasting, ground and flight wind shear displays, wind shear data collection and dissemination, and pilot factors associated with wind shear encounters. Some areas which show promise for short term solutions to the wind shear hazards includes: (1) improved gust front warning through ground based sensors; (2) greater pilot awareness of wind shear through improved training; and (3) airborne displays based on groundspeed/airspeed comparisons.

  20. Crosswind Shear Gradient Affect on Wake Vortices

    NASA Technical Reports Server (NTRS)

    Proctor, Fred H.; Ahmad, Nashat N.

    2011-01-01

    Parametric simulations with a Large Eddy Simulation (LES) model are used to explore the influence of crosswind shear on aircraft wake vortices. Previous studies based on field measurements, laboratory experiments, as well as LES, have shown that the vertical gradient of crosswind shear, i.e. the second vertical derivative of the environmental crosswind, can influence wake vortex transport. The presence of nonlinear vertical shear of the crosswind velocity can reduce the descent rate, causing a wake vortex pair to tilt and change in its lateral separation. The LES parametric studies confirm that the vertical gradient of crosswind shear does influence vortex trajectories. The parametric results also show that vortex decay from the effects of shear are complex since the crosswind shear, along with the vertical gradient of crosswind shear, can affect whether the lateral separation between wake vortices is increased or decreased. If the separation is decreased, the vortex linking time is decreased, and a more rapid decay of wake vortex circulation occurs. If the separation is increased, the time to link is increased, and at least one of the vortices of the vortex pair may have a longer life time than in the case without shear. In some cases, the wake vortices may never link.

  1. Shear alters motility of Escherichia coli

    NASA Astrophysics Data System (ADS)

    Molaei, Mehdi; Jalali, Maryam; Sheng, Jian

    2013-11-01

    Understanding of locomotion of microorganisms in shear flows drew a wide range of interests in microbial related topics such as biological process including pathogenic infection and biophysical interactions like biofilm formation on engineering surfaces. We employed microfluidics and digital holography microscopy to study motility of E. coli in shear flows. We controlled the shear flow in three different shear rates: 0.28 s-1, 2.8 s-1, and 28 s-1 in a straight channel with the depth of 200 μm. Magnified holograms, recorded at 15 fps with a CCD camera over more than 20 minutes, are analyzed to obtain 3D swimming trajectories and subsequently used to extract shear responses of E.coli. Thousands of 3-D bacterial trajectories are tracked. The change of bacteria swimming characteristics including swimming velocity, reorientation, and dispersion coefficient are computed directly for individual trajectory and ensemble averaged over thousands of realizations. The results show that shear suppresses the bacterial dispersions in bulk but promote dispersions near the surface contrary to those in quiescent flow condition. Ongoing analyses are focusing to quantify effect of shear rates on tumbling frequency and reorientation of cell body, and its implication in locating the hydrodynamic mechanisms for shear enhanced angular scattering. NIH, NSF, GoMRI.

  2. Finite element modelling of fabric shear

    NASA Astrophysics Data System (ADS)

    Lin, Hua; Clifford, Mike J.; Long, Andrew C.; Sherburn, Martin

    2009-01-01

    In this study, a finite element model to predict shear force versus shear angle for woven fabrics is developed. The model is based on the TexGen geometric modelling schema, developed at the University of Nottingham and orthotropic constitutive models for yarn behaviour, coupled with a unified displacement-difference periodic boundary condition. A major distinction from prior modelling of fabric shear is that the details of picture frame kinematics are included in the model, which allows the mechanisms of fabric shear to be represented more accurately. Meso- and micro-mechanisms of deformation are modelled to determine their contributions to energy dissipation during shear. The model is evaluated using results obtained for a glass fibre plain woven fabric, and the importance of boundary conditions in the analysis of deformation mechanisms is highlighted. The simulation results show that the simple rotation boundary condition is adequate for predicting shear force at large deformations, with most of the energy being dissipated at higher shear angles due to yarn compaction. For small deformations, a detailed kinematic analysis is needed, enabling the yarn shear and rotation deformation mechanisms to be modelled accurately.

  3. Study of shear-stiffened elastomers

    NASA Astrophysics Data System (ADS)

    Tian, Tongfei; Li, Weihua; Ding, Jie; Alici, Gursel; Du, Haiping

    2013-06-01

    Shear thickening fluids, which are usually concentrated colloidal suspensions composed of non-aggregating solid particles suspended in fluids, exhibit a marked increase in viscosity beyond a critical shear rate. This increased viscosity is seen as being both 'field-activated', due to the dependence on shearing rate, as well as reversible. Shear thickening fluids have found good applications as protection materials, such as in liquid body armor, vibration absorber or dampers. This research aims to expand the protection material family by developing a novel solid status shear thickening material, called shear-stiffened elastomers. These new shear-stiffened elastomers were fabricated with the mixture of silicone rubber and silicone oil. A total of four SSE samples were fabricated in this study. Their mechanical and rheological properties under both steady-state and dynamic loading conditions were tested with a parallel-plate. The effects of silicone oil composition and angular frequency were summarized. When raising the angular frequency in dynamic shear test, the storage modulus of conventional silicone rubber shows a small increasing trend with the frequency. However, if silicone oil is selected to be mixed with silicone rubber, the storage modulus increases dramatically when the frequency and strain are both beyond the critical values.

  4. The formation of multiple adiabatic shear bands

    NASA Astrophysics Data System (ADS)

    Zhou, F.; Wright, T. W.; Ramesh, K. T.

    2006-07-01

    In a previous paper, Zhou et al. [2006. A numerical methodology for investigating adiabatic shear band formation. J. Mech. Phys. Solids, 54, 904-926] developed a numerical method for analyzing one-dimensional deformation of thermoviscoplastic materials. The method uses a second order algorithm for integration along characteristic lines, and computes the plastic flow after complete localization with high resolution and efficiency. We apply this numerical scheme to analyze localization in a thermoviscoplastic material where multiple shear bands are allowed to form at random locations in a large specimen. As a shear band develops, it unloads neighboring regions and interacts with other bands. Beginning with a random distribution of imperfections, which might be imagined as arising qualitatively from the microstructure, we obtain the average spacing of shear bands through calculations and compare our results with previously existing theoretical estimates. It is found that the spacing between nucleating shear bands follows the perturbation theory due to Wright and Ockendon [1996. A scaling law for the effect of inertia on the formation of adiabatic shear bands. Int. J. Plasticity 12, 927-934], whereas the spacing between mature shear bands is closer to that predicted by the momentum diffusion theory of Grady and Kipp [1987. The growth of unstable thermoplastic shear with application to steady-wave shock compression in solids. J. Mech. Phys. Solids 35, 95-119]. Scaling laws for the dependence of band spacing on material parameters differ in many respects from either theory.

  5. Simple shear deformation of partially molten aplite

    NASA Astrophysics Data System (ADS)

    Stipp, Michael; Tullis, Jan; Berger, Alfons

    2013-04-01

    The tectonic processes which are important for melt distribution and transport in the intermediate and lower crust and which can result in crustal weakening are not yet well understood. Natural migmatites are usually overprinted by annealing and retrogression during uplift and exhumation, largely obliterating the deformation structures and microstructures of their partially molten history. Deformation experiments on partially molten crustal rocks have so far been conducted in pure shear geometry and mostly under low confining pressures in the brittle deformation field, both of which are not representative of nature. We carried out deformation experiments in simple shear that predominates in the crust and especially crustal shear zones. Undrained experiments were carried out on Enfield aplite at ~1.5 GPa, 900° -1000° C, and ˜ 5*10-6 s-1, conditions which favor crystal plastic deformation of quartz and feldspar (Dell'Angelo and Tullis, 1988). Sample slices 1.0-1.5 mm thick were placed between the shear pistons with the shear plane at a 45° -angle to the compression direction. Maximum shear strain in the experiments is ? ?2.8. Despite difficulties in controlling the melt content by varying the amount of added water, we were able to achieve the full range of brittle to crystal plastic deformation mechanisms. With decreasing melt content Enfield aplite displays a transition from discrete fracturing at a high angle (~70-90° ) to the shear plane (>20 vol.% melt), to cataclastic shearing (10-20 vol.% melt) and to crystal plastic deformation (

  6. Steel shear walls, behavior, modeling and design

    SciTech Connect

    Astaneh-Asl, Abolhassan

    2008-07-08

    In recent years steel shear walls have become one of the more efficient lateral load resisting systems in tall buildings. The basic steel shear wall system consists of a steel plate welded to boundary steel columns and boundary steel beams. In some cases the boundary columns have been concrete-filled steel tubes. Seismic behavior of steel shear wall systems during actual earthquakes and based on laboratory cyclic tests indicates that the systems are quite ductile and can be designed in an economical way to have sufficient stiffness, strength, ductility and energy dissipation capacity to resist seismic effects of strong earthquakes. This paper, after summarizing the past research, presents the results of two tests of an innovative steel shear wall system where the boundary elements are concrete-filled tubes. Then, a review of currently available analytical models of steel shear walls is provided with a discussion of capabilities and limitations of each model. We have observed that the tension only 'strip model', forming the basis of the current AISC seismic design provisions for steel shear walls, is not capable of predicting the behavior of steel shear walls with length-to-thickness ratio less than about 600 which is the range most common in buildings. The main reasons for such shortcomings of the AISC seismic design provisions for steel shear walls is that it ignores the compression field in the shear walls, which can be significant in typical shear walls. The AISC method also is not capable of incorporating stresses in the shear wall due to overturning moments. A more rational seismic design procedure for design of shear walls proposed in 2000 by the author is summarized in the paper. The design method, based on procedures used for design of steel plate girders, takes into account both tension and compression stress fields and is applicable to all values of length-to-thickness ratios of steel shear walls. The method is also capable of including the effect of

  7. Shear accommodation in dirty grain boundaries

    NASA Astrophysics Data System (ADS)

    Wang, C.; Upmanyu, M.

    2014-04-01

    The effect of solutes (dirt) on the mechanics of crystalline interfaces remains unexplored. Here, we perform atomic-scale simulations to study the effect of carbon segregation on the shear accommodation at select grain boundaries in the classical α-Fe/C system. For shear velocities larger than the solute diffusion rate, we observe a transition from coupled motion to sliding. Below a critical solute excess, the boundaries break away from the solute cloud and exhibit in a coupled motion. At smaller shear velocities, the extrinsic coupled motion is jerky, occurs at relatively small shear stresses, and is aided by fast convective solute diffusion along the boundary. Our studies underscore the combined effect of energetics and kinetics of solutes in modifying the bicrystallography, temperature and rate dependence of shear accommodation at grain boundaries.

  8. Turbulence structure at high shear rate

    NASA Technical Reports Server (NTRS)

    Lee, Moon Joo; Kim, John; Moin, Parviz

    1987-01-01

    The structure of homogeneous turbulence in the presence of a high shear rate is studied using results obtained from three-dimensional time-dependent numerical simulations of the Navier-Stokes equations on a grid of 512 x 128 x 128 node points. It is shown that high shear rate enhances the streamwise fluctuating motion to such an extent that a highly anisotropic turbulence state with a one-dimensional velocity field and two-dimensional small-scale turbulence develops asymptotically as total shear increases. Instantaneous velocity fields show that high shear rate in homogeneous turbulent shear flow produces structures which are similar to the streaks present in the viscous sublayer of turbulent boundary layers.

  9. Structure of turbulence at high shear rate

    NASA Technical Reports Server (NTRS)

    Lee, Moon Joo; Kim, John; Moin, Parviz

    1990-01-01

    The structure of homogeneous turbulence subject to high shear rate has been investigated by using three-dimensional, time-dependent numerical simulations of the Navier-Stokes equations. This study indicates that high shear rate alone is sufficient for generation of the streaky structures, and that the presence of a solid boundary is not necessary. Evolution of the statistical correlations is examined to determine the effect of high shear rate on the development of anisotropy in turbulence. It is shown that the streamwise fluctuating motions are enhanced so profoundly that a highly anisotropic turbulence state with a 'one-component' velocity field and 'two-component' vorticity field develops asymptotically as total shear increases. Because of high-shear rate, rapid distortion theory predicts remarkably well the anisotropic behavior of the structural quantities.

  10. WEAK LENSING MASS RECONSTRUCTION: FLEXION VERSUS SHEAR

    SciTech Connect

    Pires, S.

    2010-11-10

    Weak gravitational lensing has proven to be a powerful tool to map directly the distribution of dark matter in the universe. The technique, currently used, relies on the accurate measurement of the gravitational shear that corresponds to the first-order distortion of the background galaxy images. More recently, a new technique has been introduced that relies on the accurate measurement of the gravitational flexion that corresponds to the second-order distortion of the background galaxy images. This technique should probe structures on smaller scales than that of shear analysis. The goal of this paper is to compare the ability of shear and flexion to reconstruct the dark matter distribution by taking into account the dispersion in shear and flexion measurements. Our results show that the flexion is less sensitive than shear for constructing the convergence maps on scales that are physically feasible for mapping, meaning that flexion alone should not be used to do convergence map reconstruction, even on small scales.

  11. Vortex simulation of reacting shear flow

    NASA Astrophysics Data System (ADS)

    Ghoniem, Ahmed F.

    Issues involved in the vortex simulation of reacting shear flow are discussed. It is shown that maintaining accuracy in the vortex methods requires the application of elaborate vorticity-updating schemes as vortex elements are moved along particle trajectories when shear or a strong strain field is represented. Solutions using 2D and 3D methods are discussed to illustrate some of the most common instabilities encountered in nonreacting and reacting shear flows and to reveal the mechanisms by which the maturation of these instabilities enhance mixing and hence burning in a reacting flow. The transport element method is developed and its application to compute scalar mixing in a shear layer is reviewed. The method is then combined with the vortex method to solve the problem of nonuniform-density shear flow. The results of incompressible reacting flow models are used to examine reaction extinction due to the formation of localized regions of strong strains as instabilities grow into their nonlinear range.

  12. Shear layer excitation, experiment versus theory

    NASA Technical Reports Server (NTRS)

    Bechert, D. W.; Stahl, B.

    1984-01-01

    The acoustical excitation of shear layers is investigated. Acoustical excitation causes the so-called orderly structures in shear layers and jets. Also, the deviations in the spreading rate between different shear layer experiments are due to the same excitation mechanism. Measurements in the linear interaction region close to the edge from which the shear layer is shed are examined. Two sets of experiments (Houston 1981 and Berlin 1983/84) are discussed. The measurements were carried out with shear layers in air using hot wire anemometers and microphones. The agreement between these measurements and the theory is good. Even details of the fluctuating flow field correspond to theoretical predictions, such as the local occurrence of negative phase speeds.

  13. Determining Shear Stress Distribution in a Laminate

    NASA Technical Reports Server (NTRS)

    Bednarcyk, Brett A.; Aboudi, Jacob; Yarrington, Phillip W.

    2010-01-01

    A "simplified shear solution" method approximates the through-thickness shear stress distribution within a composite laminate based on an extension of laminated beam theory. The method does not consider the solution of a particular boundary value problem; rather, it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply-level stresses can be efficiently determined from global load resultants at a given location in a structure and used to evaluate the margin of safety on a ply-by-ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. The method has been incorporated within the HyperSizer commercial structural sizing software to improve its predictive capability for designing composite structures. The HyperSizer structural sizing software is used extensively by NASA to design composite structures. In the case of through-thickness shear loading on panels, HyperSizer previously included a basic, industry-standard, method for approximating the resulting shear stress distribution in sandwich panels. However, no such method was employed for solid laminate panels. The purpose of the innovation is to provide an approximation of the through-thickness shear stresses in a solid laminate given the through-thickness shear loads (Qx and Qy) on the panel. The method was needed for implementation within the HyperSizer structural sizing software so that the approximated ply-level shear stresses could be utilized in a failure theory to assess the adequacy of a panel design. The simplified shear solution method was developed based on extending and generalizing bi-material beam theory to plate-like structures. It is assumed that the through-thickness shear stresses arise due to local bending of the laminate induced by the through-thickness shear load, and by imposing

  14. Petrogenesis of late Eocene high Ba-Sr potassic rocks from western Yangtze Block, SE Tibet: A magmatic response to the Indo-Asian collision

    NASA Astrophysics Data System (ADS)

    Liu, Zheng; Liao, Shi-Yong; Wang, Jin-Rong; Ma, Zhen; Liu, Yi-Xin; Wang, Dong-Bing; Tang, Yuan; Yang, Jing

    2017-03-01

    The Indo-Asian collision resulted in extrusion of the Indochina Block along the Ailao Shan-Red River (ASRR) shear zone in the Cenozoic, with the emplacement of widespread potassic magmatic rocks. In this contribution, we investigated five potassic felsic intrusions exposed in the western Yangtze Block adjacent to the ASRR shear zone, including the Xiaoqiaotou, Jianchuan, Yuzhaokuai, Laojunshan and South Taohuacun intrusions. New LA-ICP-MS zircon U-Pb results in combination with previous data indicate that these felsic rocks have identical crystallization ages of ∼36-35 Ma. They are characterized by high Ba (mostly >1500 ppm) and Sr (mostly >1000 ppm) abundances, with high K2O contents and K2O/Na2O ratios. They exhibit similar Sr-Nd isotopic components as the coeval shoshonitic mafic rocks exposed in the studied area. Elemental and isotopic data suggest that the five intrusions were likely derived from fractional crystallization of shoshonitic mafic magmas originating from an enriched lithospheric mantle. On the basis of previously published data and results in this paper, we considered that the lithospheric mantle underneath the western Yangtze might have undergone enrichment events twice at least, including the Neoproterozoic oceanic subduction and the Neo-Tethyan oceanic subduction.

  15. Periodic Viscous Shear Heating Instability in Fine-Grained Shear Zones: Mechanism for Intermediate Depth Earthquakes

    NASA Astrophysics Data System (ADS)

    Coon, E.; Kelemen, P.; Hirth, G.; Spiegelman, M.

    2005-12-01

    Kelemen and Hirth (Fall 2004 AGU) presented a model for periodic, viscous shear heating instabilities along pre-existing, fine grained shear zones. This provides an attractive alternative to dehydration embrittlement for explaining intermediate-depth earthquakes, especially those in a narrow thermal window within the mantle section of subducting oceanic plates (Hacker et al JGR03). Ductile shear zones with widths of cm to m are common in shallow mantle massifs and peridotite along oceanic fracture zones. Pseudotachylites in a mantle shear zone show that shear heating temperatures exceeded the mantle solidus (Obata & Karato Tectonophys95). Olivine grain growth in shear zones is pinned by closely spaced pyroxenes; thus, once formed, these features do not `heal' on geological time scales in the absence of melt or fluid (Warren & Hirth EPSL05). Grain-size sensitive creep will be localized within these shear zones, in preference to host rocks with olivine grain size from 1 to 10 mm. Inspired by the work of Whitehead & Gans (GJRAS74), we proposed that such pre-existing shear zones might undergo repeated shear heating instabilities. This is not a new concept; what is new is that viscous deformation is limited to a narrow shear zone, because grain boundary sliding, sensitive to both stress and grain size, may accommodate creep even at high stress and high temperature. These new ideas yield a new result: simple models for a periodic shear heating instability. Last year, we presented a 1D numerical model using olivine flow laws, assuming that viscous deformation remains localized in shear zones, surrounded by host rocks undergoing elastic deformation. Stress evolves due to elastic strain and drives viscous deformation in a shear zone of specified width. Shear heating and thermal diffusion control T. A maximum of 1400 C (substantial melting of peridotite ) was imposed. Grain size evolves due to recrystallization and diffusion. For strain rates of E-13 to E-14 per sec and

  16. Shear coaxial injector instability mechanisms

    NASA Technical Reports Server (NTRS)

    Puissant, C.; Kaltz, T.; Glogowski, M.; Micci, M.

    1994-01-01

    There is no definitive knowledge of which of several concurrent processes ultimately results in unstable combustion within liquid rocket chambers employing shear coaxial injectors. Possible explanations are a detrimental change in the atomization characteristics due to a decrease in the gas-to-liquid velocity ratio, a change in the gas side injector pressure drop allowing acoustic coupling to the propellant feed system or the disappearance of a stabilizing recirculation region at the base of the LOX post. The aim of this research effort is to investigate these proposed mechanisms under conditions comparable to actual engine operation. Spray characterization was accomplished with flash photography and planar laser imaging to examine the overall spray morphology and liquid jet breakup processes and with a PDPA to quantify the spatial distribution of droplet size and mean axial velocity. A simplified stability model based on the Rayleigh criterion was constructed for the flow dynamics occurring within the chamber and injector to evaluate the potential coupling between the chamber and injector acoustic modes and was supported by high frequency measurements of chamber and injector pressure oscillations. To examine recirculation within the LOX post recess, velocity measurements were performed in the recess region by means of LDV. Present experiments were performed under noncombusting conditions using LOX/GH2 stimulants at pressures up to 4 MPa.

  17. Inverse magnetic/shear catalysis

    NASA Astrophysics Data System (ADS)

    McInnes, Brett

    2016-05-01

    It is well known that very large magnetic fields are generated when the Quark-Gluon Plasma is formed during peripheral heavy-ion collisions. Lattice, holographic, and other studies strongly suggest that these fields may, for observationally relevant field values, induce ;inverse magnetic catalysis;, signalled by a lowering of the critical temperature for the chiral/deconfinement transition. The theoretical basis of this effect has recently attracted much attention; yet so far these investigations have not included another, equally dramatic consequence of the peripheral collision geometry: the QGP acquires a large angular momentum vector, parallel to the magnetic field. Here we use holographic techniques to argue that the angular momentum can also, independently, have an effect on transition temperatures, and we obtain a rough estimate of the relative effects of the presence of both a magnetic field and an angular momentum density. We find that the shearing angular momentum reinforces the effect of the magnetic field at low values of the baryonic chemical potential, but that it can actually decrease that effect at high chemical potentials.

  18. Sheared magnetofluids and Bernoulli confinement

    NASA Astrophysics Data System (ADS)

    Quevado, H. J.; Bengtson, Roger; Mahajan, S. M.; Valanju, P. M.

    2001-10-01

    New magnetofluid states that differ qualitatively from those accessible to either neutral fluids or to conventional MHD plasmas have been predited theoretically. They are predicted to appear if plasmas with strong velocity shear flows (with large initial values of both magnetic and magnetofluid helicity) are created and allowed to relax. The dynamic invariance of these two helicities will force the plasma to self-organize and relax to a long-lived quasi equilibrium state away from thermal equilibrium. The investigation of these states bears critically upon basic plasma confinement and heating issues in both natural and laboratory plasmas. We have built a magnetic mirror device designed to create and investigate these theoretically predicted pressure-confining magnetofluid states. The primary experimental challenge is to create an initial plasma (with significant flows and currents) which is relatively isolated from walls and embedded in a modest magnetic external field. Our machine has a central bias rod to create a radial electric field for generating fast plasma flow, a large mirror ratio for good centrifugal confinement, and magnetic, Langmuir, and Mach probes to measure the evolution of plasma rotation profiles and fluctuations. Initial results will be presented demonstrating plasma rotation.

  19. Wind shear and turbulence simulation

    NASA Technical Reports Server (NTRS)

    Bowles, Roland L.

    1987-01-01

    The aviation community is increasing its reliance on flight simulators. This is true both in pilot training and in research and development. In moving research concepts through the development pipeline, there is a sequence of events which take place: analysis, ground based simulation, inflight simulation, and flight testing. Increasing fidelity as progress toward the flight testing arena is accompanied by increasing cost. The question that seems to be posed in relation to the meteorological aspects of flight simulation is, How much fidelity is enough and can it be quantified. As a part of the Langley Simulation Technology Program, there are three principal areas of focus, one being improved simulation of weather hazards. A close liaison with the JAWS project was established because of the Langley Simulation Technology interests regarding reliable simulation of severe convective weather phenomena and their impact on aviation systems. Simulation offers the only feasible approach for examining the utility of new technology and new procedures for coping with severe convective weather phenomena such as wind shear. These simulation concepts are discussed in detail.

  20. Impact response of shear thickening suspensions

    NASA Astrophysics Data System (ADS)

    Brown, Eric; Ozgen, Oktar; Kallmann, Marcelo; Allen, Benjamin

    2013-11-01

    Dense suspensions of hard particles such as cornstarch in water exhibit shear thickening, in which the energy dissipation rate under shear dramatically increases with increasing shear rate. Recent work has established that in steady-state shear this phenomena is a result of a dynamic jamming of the particles in suspension. Several dynamic phenomena observed in such suspensions have long been assumed to be a consequence of this shear thickening; strong impact resistance, the ability of a person to run on the fluid surface, fingering and hole instabilities under vibration, and oscillations in the speed of sinking of an object in the fluid. However, I will present results of experiments consisting of an indenter impacting a dense suspension which demonstrate that the strong impact resistance cannot be explained by existing models for steady-state shear thickening. I will show these dynamic phenomena can be reproduced by graphical simulations based on a minimal phenomenological model in which the fluid has a stiffness with a dependence on velocity history. These and other recent results suggest a need for new models to understand the dynamic phenomena associated with shear thickening fluids.

  1. Surface shear inviscidity of soluble surfactants

    PubMed Central

    Zell, Zachary A.; Nowbahar, Arash; Mansard, Vincent; Leal, L. Gary; Deshmukh, Suraj S.; Mecca, Jodi M.; Tucker, Christopher J.; Squires, Todd M.

    2014-01-01

    Foam and emulsion stability has long been believed to correlate with the surface shear viscosity of the surfactant used to stabilize them. Many subtleties arise in interpreting surface shear viscosity measurements, however, and correlations do not necessarily indicate causation. Using a sensitive technique designed to excite purely surface shear deformations, we make the most sensitive and precise measurements to date of the surface shear viscosity of a variety of soluble surfactants, focusing on SDS in particular. Our measurements reveal the surface shear viscosity of SDS to be below the sensitivity limit of our technique, giving an upper bound of order 0.01 μN·s/m. This conflicts directly with almost all previous studies, which reported values up to 103–104 times higher. Multiple control and complementary measurements confirm this result, including direct visualization of monolayer deformation, for SDS and a wide variety of soluble polymeric, ionic, and nonionic surfactants of high- and low-foaming character. No soluble, small-molecule surfactant was found to have a measurable surface shear viscosity, which seriously undermines most support for any correlation between foam stability and surface shear rheology of soluble surfactants. PMID:24563383

  2. Hierarchical cosmic shear power spectrum inference

    NASA Astrophysics Data System (ADS)

    Alsing, Justin; Heavens, Alan; Jaffe, Andrew H.; Kiessling, Alina; Wandelt, Benjamin; Hoffmann, Till

    2016-02-01

    We develop a Bayesian hierarchical modelling approach for cosmic shear power spectrum inference, jointly sampling from the posterior distribution of the cosmic shear field and its (tomographic) power spectra. Inference of the shear power spectrum is a powerful intermediate product for a cosmic shear analysis, since it requires very few model assumptions and can be used to perform inference on a wide range of cosmological models a posteriori without loss of information. We show that joint posterior for the shear map and power spectrum can be sampled effectively by Gibbs sampling, iteratively drawing samples from the map and power spectrum, each conditional on the other. This approach neatly circumvents difficulties associated with complicated survey geometry and masks that plague frequentist power spectrum estimators, since the power spectrum inference provides prior information about the field in masked regions at every sampling step. We demonstrate this approach for inference of tomographic shear E-mode, B-mode and EB-cross power spectra from a simulated galaxy shear catalogue with a number of important features; galaxies distributed on the sky and in redshift with photometric redshift uncertainties, realistic random ellipticity noise for every galaxy and a complicated survey mask. The obtained posterior distributions for the tomographic power spectrum coefficients recover the underlying simulated power spectra for both E- and B-modes.

  3. Fluid shear stress threshold regulates angiogenic sprouting.

    PubMed

    Galie, Peter A; Nguyen, Duc-Huy T; Choi, Colin K; Cohen, Daniel M; Janmey, Paul A; Chen, Christopher S

    2014-06-03

    The density and architecture of capillary beds that form within a tissue depend on many factors, including local metabolic demand and blood flow. Here, using microfluidic control of local fluid mechanics, we show the existence of a previously unappreciated flow-induced shear stress threshold that triggers angiogenic sprouting. Both intraluminal shear stress over the endothelium and transmural flow through the endothelium above 10 dyn/cm(2) triggered endothelial cells to sprout and invade into the underlying matrix, and this threshold is not impacted by the maturation of cell-cell junctions or pressure gradient across the monolayer. Antagonizing VE-cadherin widened cell-cell junctions and reduced the applied shear stress for a given transmural flow rate, but did not affect the shear threshold for sprouting. Furthermore, both transmural and luminal flow induced expression of matrix metalloproteinase 1, and this up-regulation was required for the flow-induced sprouting. Once sprouting was initiated, continuous flow was needed to both sustain sprouting and prevent retraction. To explore the potential ramifications of a shear threshold on the spatial patterning of new sprouts, we used finite-element modeling to predict fluid shear in a variety of geometric settings and then experimentally demonstrated that transmural flow guided preferential sprouting toward paths of draining interstitial fluid flow as might occur to connect capillary beds to venules or lymphatics. In addition, we show that luminal shear increases in local narrowings of vessels to trigger sprouting, perhaps ultimately to normalize shear stress across the vasculature. Together, these studies highlight the role of shear stress in controlling angiogenic sprouting and offer a potential homeostatic mechanism for regulating vascular density.

  4. Fan-structure waves in shear ruptures

    NASA Astrophysics Data System (ADS)

    Tarasov, Boris

    2016-04-01

    This presentation introduces a recently identified shear rupture mechanism providing a paradoxical feature of hard rocks - the possibility of shear rupture propagation through the highly confined intact rock mass at shear stress levels significantly less than frictional strength. According to the fan-mechanism the shear rupture propagation is associated with consecutive creation of small slabs in the fracture tip which, due to rotation caused by shear displacement of the fracture interfaces, form a fan-structure representing the fracture head. The fan-head combines such unique features as: extremely low shear resistance (below the frictional strength), self-sustaining stress intensification in the rupture tip (providing easy formation of new slabs), and self-unbalancing conditions in the fan-head (making the failure process inevitably spontaneous and violent). An important feature of the fan-mechanism is the fact that for the initial formation of the fan-structure an enhanced local shear stress is required, however, after completion of the fan-structure it can propagate as a dynamic wave through intact rock mass at shear stresses below the frictional strength. Paradoxically low shear strength of pristine rocks provided by the fan-mechanism determines the correspondingly low transient strength of the lithosphere, which favours generation of new earthquake faults in the intact rock mass adjoining pre-existing faults in preference to frictional stick-slip instability along these faults. The new approach reveals an alternative role of pre-existing faults in earthquake activity: they represent local stress concentrates in pristine rock adjoining the fault where special conditions for the fan-mechanism nucleation are created, while further dynamic propagation of the new fault (earthquake) occurs at low field stresses even below the frictional strength.

  5. Method for shearing spent nuclear fuel assemblies

    DOEpatents

    Weil, Bradley S.; Watson, Clyde D.

    1977-01-01

    A method is disclosed for shearing spent nuclear fuel assemblies of the type wherein a plurality of long metal tubes packed with ceramic fuel are supported in a spaced apart relationship within an outer metal shell or shroud which provides structural support to the assembly. Spent nuclear fuel assemblies are first compacted in a stepwise manner between specially designed gag-compactors and then sheared into short segments amenable to chemical processing by shear blades contoured to mate with the compacted surface of the fuel assembly.

  6. Modeling of shear localization in materials

    SciTech Connect

    Lesuer, D.; LeBlanc, M.; Riddle, B.; Jorgensen, B.

    1998-02-11

    The deformation response of a Ti alloy, Ti-6Al-4V, has been studied during shear localization. The study has involved well-controlled laboratory tests involving a double-notch shear sample. The results have been used to provide a comparison between experiment and the predicted response using DYNA2D and two material models (the Johnson-Cook model and an isotropic elastic-plastic-hydrodynamic model). The work will serve as the basis for the development of a new material model which represents the different deformation mechanisms active during shear localization.

  7. Time accurate simulations of compressible shear flows

    NASA Technical Reports Server (NTRS)

    Givi, Peyman; Steinberger, Craig J.; Vidoni, Thomas J.; Madnia, Cyrus K.

    1993-01-01

    The objectives of this research are to employ direct numerical simulation (DNS) to study the phenomenon of mixing (or lack thereof) in compressible free shear flows and to suggest new means of enhancing mixing in such flows. The shear flow configurations under investigation are those of parallel mixing layers and planar jets under both non-reacting and reacting nonpremixed conditions. During the three-years of this research program, several important issues regarding mixing and chemical reactions in compressible shear flows were investigated.

  8. Coherent motion in excited free shear flows

    NASA Technical Reports Server (NTRS)

    Wygnanski, Israel J.; Petersen, Robert A.

    1987-01-01

    The application of the inviscid instability approach to externally excited turbulent free shear flows at high Reynolds numbers is explored. Attention is given to the cases of a small-deficit plane turbulent wake, a plane turbulent jet, an axisymmetric jet, the nonlinear evolution of instabilities in free shear flows, the concept of the 'preferred mode', vortex pairing in turbulent mixing layers, and experimental results for the control of free turbulent shear layers. The special features often attributed to pairing or to the preferred mode are found to be difficult to comprehend; the concept of feedback requires further substantiation in the case of incompressible flow.

  9. Determination of the Shear Stress Distribution in a Laminate from the Applied Shear Resultant--A Simplified Shear Solution

    NASA Technical Reports Server (NTRS)

    Bednarcyk, Brett A.; Aboudi, Jacob; Yarrington, Phillip W.

    2007-01-01

    The simplified shear solution method is presented for approximating the through-thickness shear stress distribution within a composite laminate based on laminated beam theory. The method does not consider the solution of a particular boundary value problem, rather it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply level stresses can be efficiently determined from global load resultants (as determined, for instance, by finite element analysis) at a given location in a structure and used to evaluate the margin of safety on a ply by ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. Comparisons to existing theories are made for a variety of laminates, and design examples are provided illustrating the use of the method for determining through-thickness shear stress margins in several types of composite panels and in the context of a finite element structural analysis.

  10. Magnetized stratified rotating shear waves.

    PubMed

    Salhi, A; Lehner, T; Godeferd, F; Cambon, C

    2012-02-01

    We present a spectral linear analysis in terms of advected Fourier modes to describe the behavior of a fluid submitted to four constraints: shear (with rate S), rotation (with angular velocity Ω), stratification, and magnetic field within the linear spectral theory or the shearing box model in astrophysics. As a consequence of the fact that the base flow must be a solution of the Euler-Boussinesq equations, only radial and/or vertical density gradients can be taken into account. Ertel's theorem no longer is valid to show the conservation of potential vorticity, in the presence of the Lorentz force, but a similar theorem can be applied to a potential magnetic induction: The scalar product of the density gradient by the magnetic field is a Lagrangian invariant for an inviscid and nondiffusive fluid. The linear system with a minimal number of solenoidal components, two for both velocity and magnetic disturbance fields, is eventually expressed as a four-component inhomogeneous linear differential system in which the buoyancy scalar is a combination of solenoidal components (variables) and the (constant) potential magnetic induction. We study the stability of such a system for both an infinite streamwise wavelength (k(1) = 0, axisymmetric disturbances) and a finite one (k(1) ≠ 0, nonaxisymmetric disturbances). In the former case (k(1) = 0), we recover and extend previous results characterizing the magnetorotational instability (MRI) for combined effects of radial and vertical magnetic fields and combined effects of radial and vertical density gradients. We derive an expression for the MRI growth rate in terms of the stratification strength, which indicates that purely radial stratification can inhibit the MRI instability, while purely vertical stratification cannot completely suppress the MRI instability. In the case of nonaxisymmetric disturbances (k(1) ≠ 0), we only consider the effect of vertical stratification, and we use Levinson's theorem to demonstrate the

  11. Localization in inelastic rate dependent shearing deformations

    NASA Astrophysics Data System (ADS)

    Katsaounis, Theodoros; Lee, Min-Gi; Tzavaras, Athanasios

    2017-01-01

    Metals deformed at high strain rates can exhibit failure through formation of shear bands, a phenomenon often attributed to Hadamard instability and localization of the strain into an emerging coherent structure. We verify formation of shear bands for a nonlinear model exhibiting strain softening and strain rate sensitivity. The effects of strain softening and strain rate sensitivity are first assessed by linearized analysis, indicating that the combined effect leads to Turing instability. For the nonlinear model a class of self-similar solutions is constructed, that depicts a coherent localizing structure and the formation of a shear band. This solution is associated to a heteroclinic orbit of a dynamical system. The orbit is constructed numerically and yields explicit shear localizing solutions.

  12. Wind shear related research at Princeton University

    NASA Technical Reports Server (NTRS)

    Stengel, Robert

    1992-01-01

    The topics addressed are: (1) real-time decision aiding-aircraft guidance for wind shear avoidance; (2) reducing the thrust-manual recovery strategies; and (3) dynamic behaviour of and aircraft encountering a single axis vortex.

  13. Shear-Joint Capability Versus Bolt Clearance

    NASA Technical Reports Server (NTRS)

    Lee, H. M.

    1994-01-01

    NASA Technical Memorandum presents theoretical study of relationships between load-bearing capabilities of shear joints that comprise plates clamped together by multiple bolts and clearances between bolts and boltholes in those joints.

  14. Turbulent shear stresses in compressible boundary layers

    NASA Technical Reports Server (NTRS)

    Laderman, A. J.; Demetriades, A.

    1979-01-01

    Hot-wire anemometer measurements of turbulent shear stresses in a Mach 3 compressible boundary layer were performed in order to investigate the effects of heat transfer on turbulence. Measurements were obtained by an x-probe in a flat plate, zero pressure gradient, two dimensional boundary layer in a wind tunnel with wall to freestream temperature ratios of 0.94 and 0.71. The measured shear stress distributions are found to be in good agreement with previous results, supporting the contention that the shear stress distribution is essentially independent of Mach number and heat transfer for Mach numbers from incompressible to hypersonic and wall to freestream temperature ratios of 0.4 to 1.0. It is also found that corrections for frequency response limitations of the electronic equipment are necessary to determine the correct shear stress distribution, particularly at the walls.

  15. Stress analysis of shear/compression test

    SciTech Connect

    Nishijima, S.; Okada, T.; Ueno, S.

    1997-06-01

    Stress analysis has been made on the glass fiber reinforced plastics (GFRP) subjected to the combined shear and compression stresses by means of finite element method. The two types of experimental set up were analyzed, that is parallel and series method where the specimen were compressed by tilted jigs which enable to apply the combined stresses, to the specimen. Modified Tsai-Hill criterion was employed to judge the failure under the combined stresses that is the shear strength under the compressive stress. The different failure envelopes were obtained between the two set ups. In the parallel system the shear strength once increased with compressive stress then decreased. On the contrary in the series system the shear strength decreased monotonicly with compressive stress. The difference is caused by the different stress distribution due to the different constraint conditions. The basic parameters which control the failure under the combined stresses will be discussed.

  16. Remote Sensing Wind and Wind Shear System.

    DTIC Science & Technology

    Contents: Remote sensing of wind shear and the theory and development of acoustic doppler; Wind studies; A comparison of methods for the remote detection of winds in the airport environment; Acoustic doppler system development; System calibration; Airport operational tests.

  17. Shear joint capability versus bolt clearance

    NASA Technical Reports Server (NTRS)

    Lee, H. M.

    1992-01-01

    The results of a conservative analysis approach into the determination of shear joint strength capability for typical space-flight hardware as a function of the bolt-hole clearance specified in the design are presented. These joints are comprised of high-strength steel fasteners and abutments constructed of aluminum alloys familiar to the aerospace industry. A general analytical expression was first arrived at which relates bolt-hole clearance to the bolt shear load required to place all joint fasteners into a shear transferring position. Extension of this work allowed the analytical development of joint load capability as a function of the number of fasteners, shear strength of the bolt, bolt-hole clearance, and the desired factor of safety. Analysis results clearly indicate that a typical space-flight hardware joint can withstand significant loading when less than ideal bolt hole clearances are used in the design.

  18. Dynamo quenching due to shear flow.

    PubMed

    Leprovost, Nicolas; Kim, Eun-jin

    2008-04-11

    We provide a theory of dynamo (alpha effect) and momentum transport in three-dimensional magnetohydrodynamics. For the first time, we show that the alpha effect is reduced by the shear even in the absence of magnetic field. The alpha effect is further suppressed by magnetic fields well below equipartition (with the large-scale flow) with different scalings depending on the relative strength of shear and magnetic field. The turbulent viscosity is also found to be significantly reduced by shear and magnetic fields, with positive value. These results suggest a crucial effect of shear and magnetic field on dynamo quenching and momentum transport reduction, with important implications for laboratory and astrophysical plasmas, in particular, for the dynamics of the Sun.

  19. Shear wave velocity measurements in marine sediments

    NASA Astrophysics Data System (ADS)

    Matthews, J. E.

    1982-09-01

    Pulsed ultrasonic techniques for the measurement of sound speed are reliable and well documented. Extension of these techniques to the measurement of shear wave velocities in marine sediments, generally was unsuccessful. Recently developed shear wave transducers, based upon piezoelectric benders operated at sonic frequencies, provide significantly improved transducer-sample mechanical coupling. This improved coupling allows the application of pulsed techniques to the measurement of shear wave velocities in marine sediments, and the rapid determination of sediment dynamic elastic properties. Two types of bender-based shear wave transducer and preliminary data are described: 1) a probe configuration for box core samples, and 2) a modification to the Hamilton Frame Velocimeter for cut samples.

  20. Effect of shear on aircraft landing

    NASA Technical Reports Server (NTRS)

    Luers, J. K.; Reeves, J. B.

    1973-01-01

    A simulation study was conducted to determine the effect of wind shear on aircraft landings. The landing of various type of commercial and military aircraft was digitally simulated starting from an initial altitude of 300 feet. Assuming no pilot feedback during descent, the deviation in touchdown point due to vertical profiles of wind shear was determined. The vertical profiles of wind shear are defined in terms of surface roughness, Z sub 0, and stability, L, parameters. The effects on touchdown due to Z sub 0 and L have been calculated for the different type aircraft. Comparisons were made between the following types of aircraft: (1) C-130E, (2) C-135A, (3) C-141, (4) DC-8, (5) Boeing 747, and (6) an augmentor-wing STOL. In addition, the wind shear effect on touchdown resulting from different locations of the center of gravity and gross weights was also analyzed.

  1. Flight in low-level wind shear

    NASA Technical Reports Server (NTRS)

    Frost, W.

    1983-01-01

    Results of studies of wind shear hazard to aircraft operation are summarized. Existing wind shear profiles currently used in computer and flight simulator studies are reviewed. The governing equations of motion for an aircraft are derived incorporating the variable wind effects. Quantitative discussions of the effects of wind shear on aircraft performance are presented. These are followed by a review of mathematical solutions to both the linear and nonlinear forms of the governing equations. Solutions with and without control laws are presented. The application of detailed analysis to develop warning and detection systems based on Doppler radar measuring wind speed along the flight path is given. A number of flight path deterioration parameters are defined and evaluated. Comparison of computer-predicted flight paths with those measured in a manned flight simulator is made. Some proposed airborne and ground-based wind shear hazard warning and detection systems are reviewed. The advantages and disadvantages of both types of systems are discussed.

  2. Summary Proceedings of a Wind Shear Workshop

    NASA Technical Reports Server (NTRS)

    Enders, J. H.; Melvin, W. W.; Frost, W.; Camp, D. W.

    1983-01-01

    A number of recent program results and current issues were addressed: the data collection phase of the highly successful Joint Airport Weather Study (JAWS) Project and the NASA-B5f7B Gust Gradient Program, the use of these data for flight crew training through educational programs (e.g., films) and with manned flight training simulators, methods for post-accident determination of wind conditions from flight data recorders, the microburst wind shear phenomenon which was positively measured and described the ring vortex as a possible generating mechanism, the optimum flight procedure for use during an unexpected wind shear encounter, evaluation of the low-level wind shear alert system (LLWSAS), and assessment of the demonstrated and viable application of Doppler radar as an operational wind shear warning and detection system.

  3. Electrostatic ion cyclotron velocity shear instability

    NASA Technical Reports Server (NTRS)

    Lemons, D. S.; Winske, D.; Gary, S. P.

    1992-01-01

    A local electrostatic dispersion equation is derived for a shear flow perpendicular to an ambient magnetic field, which includes all kinetic effects and involves only one important parameter. The dispersion equation is cast in the form of Gordeyev integrals and is solved numerically. Numerical solutions indicate that an ion cyclotron instability is excited. The instability occurs roughly at multiples of the ion cyclotron frequency (modified by the shear), with the growth rate or the individual harmonics overlapping in the wavenumber. At large values of the shear parameter, the instability is confined to long wavelengths, but at smaller shear, a second distinct branch at shorter wavelengths also appears. The properties of the instability obtained are compared with those obtained in the nonlocal limit by Ganguli et al. (1985, 1988).

  4. Geomorphology and Ice Content of Glacier - Rock Glacier &ndash; Moraine Complexes in Ak-Shiirak Range (Inner Tien Shan, Kyrgyzstan)

    NASA Astrophysics Data System (ADS)

    Bolch, Tobias; Kutuzov, Stanislav; Rohrbach, Nico; Fischer, Andrea; Osmonov, Azamat

    2015-04-01

    Meltwater originating from the Tien Shan is of high importance for the runoff to the arid and semi-arid region of Central Asia. Previous studies estimate a glaciers' contribution of about 40% for the Aksu-Tarim Catchment, a transboundary watershed between Kyrgyzstan and China. Large parts of the Ak-Shiirak Range drain into this watershed. Glaciers in Central and Inner Tien Shan are typically polythermal or even cold and surrounded by permafrost. Several glaciers terminate into large moraine complexes which show geomorphological indicators of ice content such as thermo-karst like depressions, and further downvalley signs of creep such as ridges and furrows and a fresh, steep rock front which are typical indicators for permafrost creep ("rock glacier"). Hence, glaciers and permafrost co-exist in this region and their interactions are important to consider, e.g. for the understanding of glacial and periglacial processes. It can also be assumed that the ice stored in these relatively large dead-ice/moraine-complexes is a significant amount of the total ice storage. However, no detailed investigations exist so far. In an initial study, we investigated the structure and ice content of two typical glacier-moraine complexes in the Ak-Shiirak-Range using different ground penetrating radar (GPR) devices. In addition, the geomorphology was mapped using high resolution satellite imagery. The structure of the moraine-rock glacier complex is in general heterogeneous. Several dead ice bodies with different thicknesses and moraine-derived rock glaciers with different stages of activities could be identified. Few parts of these "rock glaciers" contain also massive ice but the largest parts are likely characterised by rock-ice layers of different thickness and ice contents. In one glacier forefield, the thickness of the rock-ice mixture is partly more than 300 m. This is only slightly lower than the maximum thickness of the glacier ice. Our measurements revealed that up to 20% of

  5. Rock magnetic properties of an 8-Ma terrigenous succession from the northern Tian Shan foreland basin, northwestern China and aridification of the Asian inland

    NASA Astrophysics Data System (ADS)

    Lu, H.; Zhang, W.; Li, Y.; Dong, C.; Zhang, T.; Zhou, Z.; Zheng, X.

    2013-12-01

    The Asian inland is characterized by exceptional topographic relief and widespread deserts and semi-deserts. Its environmental evolution during the late Cenozoic is featured by two processes: (1) growth and uplift of the Tibetan Plateau (including the hinterland to the north) and (2) stepwise development of dry climate. Many previous investigations have attempted to reconstruct the process of plateau uplift or constrain the aridification history. The relative role of the Tibetan Plateau uplift and Cenozoic global cooling in the aridification process of the Asian interior, however, remains an issue of debate. More detailed paleoclimatic/tectonic investigations over a broad area should be beneficial to better answer this question. In the northern Tian Shan foreland basin, northwestern China was deposited thick Cenozoic terrigenous succession, which is crucial for paleoenvironmental reconstruction of the Asian interior. Here we present a detailed rock magnetic investigation on 245 samples from the ~1,200-m-thick Neogene Taxi He section with a magnetostratigraphic age span of ca. 8.0 to 2.0 Ma in the northern Tian Shan foreland basin. Our rock magnetic results indicate that the significant variations in composition, concentration and grain size of magnetic minerals occurred at ca. 6.0, 3.7 and 2.7 Ma. The comparable compositions of rare earth elements (REEs) throughout the Neogene Taxi He section suggest no significant modification of the source materials during the interval between ca. 8.0 and 2.0 Ma, and thus sediment provenance is not regarded as responsible for these observed variations in rock magnetic properties. Our further analyses show that the variations in magnetic property of the Neogene Taxi He deposits are casually linked mainly with lithofacies transition due to range encroachment into foreland basin as well as climate aridification. Identified enhancement of aridification was chronologically constrained at ca. 6.0 and 2.7 Ma based on the variations of

  6. Title of abstract - Different approaches to the determining of 3-d P and S wave velocity structures of the crust beneath Northern Tien Shan

    NASA Astrophysics Data System (ADS)

    Kryukova, O.

    2003-04-01

    The seismic images of the crust beneath Northern Tien Shan (NTS) are obtained with using of different sets of data and several algorithms for solution of local earthquake tomography problem. The NTS is a very interesting region from geophysical point if view due to high seismic activity caused by interplate collision: Tien Shan and Kazakh. A rectangular region under investigation is constrained by lines 41.90o N - 43.40o N and 73.50o E- 76.50o E. 14661 P and 14436 S wave arrival times recorded 12 seismic stations of the Kyrgyzstan Broadband Network (KNET) from local earthquake in 1991-1999 years are used. In addition, data from 267 local earthquake recorded over a period of about 20 years by a regional arrays of 93 seismographs in NTS are involved in inversions. 1-d optimal velocity models and stations delays are estimated with help of program VELEST (E.Kissling, 1995). Block parameterization of model and ray tracing described by Thurber and Ellsworth (1980) are used for determination of 3-d velocity structure and relocation of events as one of the approaches (programs S.Roecker Sphypit90 and Sphrel3d). Other approach consists in application linear or cubic B spline interpolation of velocity function and ray tracing Um and Thurber (1987) for the solution of forward problem (program C.Thurber et al. Simulps and own program). The data resolution analysis and statistical analysis of models was carried out. Calculated P wave tomographic models were compared with tomographic models S.Roecker et al. (1993), S.Ghose et al. (1998) and T.Sabitova (1996). The main result is the confirmation of existence of different seismic velocity structure beneath Kyrgyz Range and Chu Basin. Using various sets of date and methods for reconstruction velocity model is effective in reveal of more reliable velocity heterogeneities in the domain of research. The author is grateful to dr. I. Kitov for help and to dr. I.Sanina for useful discussion.

  7. Effects of transverse shearing flexibility on the postbuckling of plates loaded by inplane shear

    NASA Technical Reports Server (NTRS)

    Stein, Manuel

    1987-01-01

    This paper presents buckling and postbuckling results for plates loaded by inplane shear. The buckling results have been plotted to show the effects of thickness on the stress coefficient for aluminum plates. Results are given for various length-to-width ratios. Postbuckling results for thin plates with transverse shearing flexibility are compared to results from classical theory. The problems considered are the postbuckling response of plates in shear made of aluminum and of a + or - 45 deg graphite-epoxy laminate. Thus the materials are isotropic and orthotropic, respectively. The plates are considered to be long with side edges simply supported, with various inplane edge conditions, and the plates are subject to a constant shearing displacement along the side edges. Characteristic curves presenting the average shear stress resultant as a function of the applied displacement are given. These curves indicate that change in inplane edge conditions influence plate postbuckling stiffness and that transverse shearing is important in some cases.

  8. Shear wavelength estimation based on inverse filtering and multiple-point shear wave generation

    NASA Astrophysics Data System (ADS)

    Kitazaki, Tomoaki; Kondo, Kengo; Yamakawa, Makoto; Shiina, Tsuyoshi

    2016-07-01

    Elastography provides important diagnostic information because tissue elasticity is related to pathological conditions. For example, in a mammary gland, higher grade malignancies yield harder tumors. Estimating shear wave speed enables the quantification of tissue elasticity imaging using time-of-flight. However, time-of-flight measurement is based on an assumption about the propagation direction of a shear wave which is highly affected by reflection and refraction, and thus might cause an artifact. An alternative elasticity estimation approach based on shear wavelength was proposed and applied to passive configurations. To determine the elasticity of tissue more quickly and more accurately, we proposed a new method for shear wave elasticity imaging that combines the shear wavelength approach and inverse filtering with multiple shear wave sources induced by acoustic radiation force (ARF). The feasibility of the proposed method was verified using an elasticity phantom with a hard inclusion.

  9. Shear band foliation as an indicator of sense of shear: Field observations in central Spain

    NASA Astrophysics Data System (ADS)

    Weijermars, Ruud; Rondeel, Harm E.

    1984-10-01

    The Macizo de Nevera, a Paleozoic basement inlier surrounded by essentially flat-lying Mesozoic cover rocks of central Spain, exhibits an extremely consistent system of steep, dextral strike-slip faults. Different faults have a variable amount of displacement, but their en echelon arrangement and similar sense of displacement imply a cogenetic origin. A maximum displacement of 1.0 km, corresponding to an averaged angular shear strain of 1.5 and peak values of 6.6, occurs along the central part of the 6-km-long Truchas ductile shear zone. An early axial-plane cleavage is locally deflected into the Truchas shear zone and superposed by coarse shear band foliation. The consistent angular relationship between the new foliation and the shear zone boundary confirms the megascopic sense of shear.

  10. Lateral shearing interferometer with variable shearing for measurement of a small beam.

    PubMed

    Liu, Lei; Zeng, Aijun; Zhu, Linglin; Huang, Huijie

    2014-04-01

    A lateral shearing interferometer with variable shearing for measurement of a small beam is proposed. The interferometer is composed of a polarization beam splitter, a thick birefringent plate, a quarter-wave plate, a mirror, and an image sensor. The shearing amount can be tiny by using the thick birefringent plate as the shear generator. The shearing amount of the interferometer can be continuously adjusted by rotating the thick birefringent plate, and 2D interferograms can be obtained by rotating the thick birefringent plate along the mutually perpendicular directions. The optical path difference is compensated with a double lateral shearing by using a quarter-wave plate and a mirror. The interferometer is verified by simulation and experiment; the experiment result is well coincident with the simulation result. The usefulness of the interferometer is verified.

  11. Mathematical interpretation of radial shearing interferometers.

    PubMed

    Malacara, D

    1974-08-01

    The procedure for computing a radial shearing interferometric pattern is given. The interferometric pattern is analyzed to obtain the wavefront shape. Restricting the discussion to wavefronts having rotational symmetry, we give two different methods of finding the wavefront. One approach is to scan along a diameter of the interferometric pattern and the other is to examine the shape of the fringes. The relative sensitivity of a radial shearing interferometer with respect to that of a Twyman-Green interferometer is also analyzed.

  12. Large Amplitude Oscillatory Shear near Jamming

    NASA Astrophysics Data System (ADS)

    Tighe, Brian; Dagois-Bohy, Simon; Somfai, Ellak; van Hecke, Martin

    2014-11-01

    Jammed solids such as foams and emulsions can be driven with oscillatory shear at finite strain amplitude and frequency. On a macro scale, this induces nonlinearities such as strain softening and shear thinning. On the micro scale one observes the onset of irreversibility, caging, and long-time diffusion. Using simulations of soft viscous spheres, we systematically vary the distance to the jamming transition. We correlate crossovers in the microscopic and macroscopic response, and construct scaling arguments to explain their relationships.

  13. Thermodynamics of dilute gases in shear flow

    NASA Astrophysics Data System (ADS)

    Jou, D.; Criado-Sancho, M.

    2001-03-01

    We consider the effect of shear and normal viscous pressures on the non-equilibrium entropy of ideal gases in Couette flow. These results extend the previous ones (Bidar et al., Physica A 233 (1996) 163), where normal pressure effects were ignored. Furthermore, we analyze the non-equilibrium contributions to the chemical potential, which may be useful in the analysis of shear-induced effects on colligative properties and chemical equilibrium.

  14. Combined Pressure-Shear Ignition Sensitivity Test

    DTIC Science & Technology

    1988-07-01

    anrCIDB* propellant showing that sensitivity increase ( from TNT to Comp B to CMDB . The maximum pressure an~d shear velocity were around 1.0 GPa and 60...shear velocity required for ignition. * CMDB is an acronyin for Composite Modified Double Base. S IA I S i-A2 TABLE OF CONTENTS Page LIST OF FIGURES...Reaction ...................... 15 IOA.CMDB slid against CKDB. No reaction ....................... 17 10B.CMDB slid againbt CMDB . Reaction

  15. Modeling and implementation of wind shear data

    NASA Technical Reports Server (NTRS)

    Frost, Walter

    1987-01-01

    The problems of implementing the JAWS wind shear data are discussed. The data sets are described from the view of utilizing them in an aircraft performance computer program. Then, some of the problems of nonstandard procedures are described in terms of programming the equations of aircraft motion when the effects of temporal and spatially variable winds are included. Finally, some of the computed effects of the various wind shear terms are shown.

  16. Shear-stabilized emulsion flooding process

    SciTech Connect

    Carpenter, C.W.; Reed, R.L.

    1982-06-29

    Additional amounts of crude oil are recovered from a subterranean formation by flooding with a translucent emulsion comprising an upper- or middle-phase microemulsion as an external phase and a polymer-containing brine solution as an internal phase. The translucent emulsion tends to coalesce into its component phases under conditions of no shear, but is stabilized by low shears such as those imposed on fluids flowing through a subterranean formation.

  17. Shear Strength Behavior of Human Trabecular Bone

    PubMed Central

    Sanyal, Arnav; Gupta, Atul; Bayraktar, Harun H.; Kwon, Ronald Y.; Keaveny, Tony M.

    2012-01-01

    The shear strength of human trabecular bone may influence overall bone strength under fall loading conditions and failure at bone-implant interfaces. Here, we sought to compare shear and compressive yield strengths of human trabecular bone and elucidate the underlying failure mechanisms. We analyzed 54 specimens (5-mm cubes), all aligned with the main trabecular orientation and spanning four anatomic sites, 44 different cadavers, and a wide range of bone volume fraction (0.06–0.38). Micro-CT-based non-linear finite element analysis was used to assess the compressive and shear strengths and the spatial distribution of yielded tissue; the tissue-level constitutive model allowed for kinematic non-linearity and yielding with strength asymmetry. We found that the computed values of both the shear and compressive strengths depended on bone volume fraction via power law relations having an exponent of 1.7 (R2=0.95 shear; R2=0.97 compression). The ratio of shear to compressive strengths (mean ± SD, 0.44 ± 0.16) did not depend on bone volume fraction (p=0.24) but did depend on microarchitecture, most notably the intra-trabecular standard deviation in trabecular spacing (R2=0.23, p<0.005). For shear, the main tissue-level failure mode was tensile yield of the obliquely oriented trabeculae. By contrast, for compression, specimens having low bone volume fraction failed primarily by large-deformation-related tensile yield of horizontal trabeculae and those having high bone volume failed primarily by compressive yield of vertical trabeculae. We conclude that human trabecular bone is generally much weaker in shear than compression at the apparent level, reflecting different failure mechanisms at the tissue level. PMID:22884967

  18. Shear dispersion in dense granular flows

    DOE PAGES

    Christov, Ivan C.; Stone, Howard A.

    2014-04-18

    We formulate and solve a model problem of dispersion of dense granular materials in rapid shear flow down an incline. The effective dispersivity of the depth-averaged concentration of the dispersing powder is shown to vary as the Péclet number squared, as in classical Taylor–Aris dispersion of molecular solutes. An extension to generic shear profiles is presented, and possible applications to industrial and geological granular flows are noted.

  19. Shear modulus of kaolin containing methane bubbles

    SciTech Connect

    Duffy, S.M. ); Wheeler, S.J. . Dept. of Engineering Science); Bennell, J.D. )

    1994-05-01

    Measurements of undrained shear moduli are reported from a program of laboratory tests on reconstituted kaolin samples containing relatively large bubbles of methane gas. The experimental program included low-frequency torsional stress-strain loops and torsional resonant column tests, providing values of shear moduli for shear-strain similitudes from 0.0004% to 0.1%. At all values of strain amplitude, the reduction of shear moduli caused by the presence of gas bubbles was greater than predicted by a theoretical elastic expression. This pattern of behavior was attributed to te formation of local yield zones around the gas-bubble cavities during consolidation prior to shear testing (a phenomenon that would also occur in-situ within offshore sediments). The results of the research program suggest that reductions in shear moduli of up to 50% could be caused by relatively small volumes of gas bubbles, occupying just a few percent of the total soil volume. This would have considerable significance for the displacements of offshore foundations constructed on sediments containing undissolved gas.

  20. Accurate shear measurement with faint sources

    SciTech Connect

    Zhang, Jun; Foucaud, Sebastien; Luo, Wentao E-mail: walt@shao.ac.cn

    2015-01-01

    For cosmic shear to become an accurate cosmological probe, systematic errors in the shear measurement method must be unambiguously identified and corrected for. Previous work of this series has demonstrated that cosmic shears can be measured accurately in Fourier space in the presence of background noise and finite pixel size, without assumptions on the morphologies of galaxy and PSF. The remaining major source of error is source Poisson noise, due to the finiteness of source photon number. This problem is particularly important for faint galaxies in space-based weak lensing measurements, and for ground-based images of short exposure times. In this work, we propose a simple and rigorous way of removing the shear bias from the source Poisson noise. Our noise treatment can be generalized for images made of multiple exposures through MultiDrizzle. This is demonstrated with the SDSS and COSMOS/ACS data. With a large ensemble of mock galaxy images of unrestricted morphologies, we show that our shear measurement method can achieve sub-percent level accuracy even for images of signal-to-noise ratio less than 5 in general, making it the most promising technique for cosmic shear measurement in the ongoing and upcoming large scale galaxy surveys.

  1. An expert system for wind shear avoidance

    NASA Technical Reports Server (NTRS)

    Stengel, Robert F.; Stratton, D. Alexander

    1990-01-01

    A study of intelligent guidance and control concepts for protecting against the adverse effects of wind shear during aircraft takeoffs and landings is being conducted, with current emphasis on developing an expert system for wind shear avoidance. Principal objectives are to develop methods for assessing the likelihood of wind shear encounter (based on real-time information in the cockpit), for deciding what flight path to pursue (e.g., takeoff abort, landing go-around, or normal climbout or glide slope), and for using the aircraft's full potential for combating wind shear. This study requires the definition of both deterministic and statistical techniques for fusing internal and external information , for making go/no-go decisions, and for generating commands to the manually controlled flight. The program has begun with the development of the WindShear Safety Advisor, an expert system for pilot aiding that is based on the FAA Windshear Training Aid; a two-volume manual that presents an overview , pilot guide, training program, and substantiating data provides guidelines for this initial development. The WindShear Safety Advisor expert system currently contains over 200 rules and is coded in the LISP programming language.

  2. Shear induced structures in crystallizing cocoa butter

    NASA Astrophysics Data System (ADS)

    Mazzanti, Gianfranco; Guthrie, Sarah E.; Sirota, Eric B.; Marangoni, Alejandro G.; Idziak, Stefan H. J.

    2004-03-01

    Cocoa butter is the main structural component of chocolate and many cosmetics. It crystallizes in several polymorphs, called phases I to VI. We used Synchrotron X-ray diffraction to study the effect of shear on its crystallization. A previously unreported phase (phase X) was found and a crystallization path through phase IV under shear was observed. Samples were crystallized under shear from the melt in temperature controlled Couette cells, at final crystallization temperatures of 17.5^oC, 20^oC and 22.5^oC in Beamline X10A of NSLS. The formation of phase X was observed at low shear rates (90 s-1) and low crystallization temperature (17.5^oC), but was absent at high shear (720 s-1) and high temperature (20^oC). The d-spacing and melting point suggest that this new phase is a mixture rich on two of the three major components of cocoa butter. We also found that, contrary to previous reports, the transition from phase II to phase V can happen through the intermediate phase IV, at high shear rates and temperature.

  3. On shearing fluids with homogeneous densities

    NASA Astrophysics Data System (ADS)

    Srivastava, D. C.; Srivastava, V. C.; Kumar, Rajesh

    2016-06-01

    In this paper, we study shearing spherically symmetric homogeneous density fluids in comoving coordinates. It is found that the expansion of the four-velocity of a perfect fluid is homogeneous, whereas its shear is generated by an arbitrary function of time M( t), related to the mass function of the distribution. This function is found to bear a functional relationship with density. The field equations are reduced to two coupled first order ordinary differential equations for the metric coefficients g_{11} and g_{22}. We have explored a class of solutions assuming that M is a linear function of the density. This class embodies, as a subcase, the complete class of shear-free solutions. We have discussed the off quoted work of Kustaanheimo (Comment Phys Math XIII:12, 1, 1947) and have noted that it deals with shear-free fluids having anisotropic pressure. It is shown that the anisotropy of the fluid is characterized by an arbitrary function of time. We have discussed some issues of historical priorities and credentials related to shear-free solutions. Recent controversial claims by Mitra (Astrophys Space Sci 333:351, 2011 and Gravit Cosmol 18:17, 2012) have also been addressed. We found that the singularity and the shearing motion of the fluid are closely related. Hence, there is a need for fresh look to the solutions obtained earlier in comoving coordinates.

  4. Effect of micellar topology on shear rheology

    NASA Astrophysics Data System (ADS)

    Rogers, Simon; Calabrese, Michelle; Wagner, Norman

    2014-03-01

    Micellar topology affects the nonlinear shear rheology of self-assembled surfactant solutions. Segmental alignment of wormlike micelles (WLMs) exhibiting varying degrees of branching was investigated under shear in the flow-gradient and flow-vorticity planes using new small angle neutron scattering (SANS) sample environments. The degree of branching in mixed cationic/anionic surfactant (CTAT/SDBS) WLMs is controlled via the addition of the hydrotropic salt sodium tosylate. Shear-induced segmental alignment of the micelles is characterized by spatially-resolved flow-small angle neutron scattering (flow-SANS). Our ability to resolve structural projections in both planes provides insight to branch behavior and kinematics under shear flows. Local segmental orientation and alignment in the flow-gradient plane is a non-monotonic function of branching level and radial position. Alignment in the flow-gradient plane is significantly higher than that observed in the flow-vorticity plane, suggesting that branches may simultaneously migrate into the vorticity direction and inhibit spatially localized flows. Shear and normal stresses calculated from micellar alignment using the stress-SANS law are favorably compared with rheological measurements under identical conditions. The results provide evidence for the effects of micellar topology on the nonlinear shear rheology of WLM solutions.

  5. Vesicle dynamics in shear and capillary flows

    NASA Astrophysics Data System (ADS)

    Noguchi, Hiroshi; Gompper, Gerhard

    2005-11-01

    The deformation of vesicles in flow is studied by a mesoscopic simulation technique, which combines multi-particle collision dynamics for the solvent with a dynamically triangulated surface model for the membrane. Shape transitions are investigated both in simple shear flows and in cylindrical capillary flows. We focus on reduced volumes, where the discocyte shape of fluid vesicles is stable, and the prolate shape is metastable. In simple shear flow at low membrane viscosity, the shear induces a transformation from discocyte to prolate with increasing shear rate, while at high membrane viscosity, the shear induces a transformation from prolate to discocyte, or tumbling motion accompanied by oscillations between these two morphologies. In capillary flow, at small flow velocities the symmetry axis of the discocyte is found not to be oriented perpendicular to the cylinder axis. With increasing flow velocity, a transition to a prolate shape occurs for fluid vesicles, while vesicles with shear-elastic membranes (like red blood cells) transform into a coaxial parachute-like shape.

  6. A new look on blood shear thinning

    NASA Astrophysics Data System (ADS)

    Abkarian, Manouk; Lanotte, Luca; Fromental, Jean-Marc; Mendez, Simon; Fedosov, Dmitry; Gompper, Gerhard; Mauer, Johannes; Claveria, Viviana

    2015-11-01

    Blood is a shear-thinning fluid. At shear rates γ˙ < 1 s-1 , its drop of viscosity has been related primarily to the breaking-up of networks of ``rouleaux'' formed by stacked red blood cells (RBCs). For higher γ˙ in the range 10 - 1000 s-1 , where RBCs flow as single elements, studies demonstrated that RBCs suspended in a viscous fluid mimicking the viscosity of whole blood, deformed into ellipsoids aligned steadily in the direction of the flow, while their membrane rotated about their center of mass like a tank-tread. Such drop-like behavior seemed to explain shear-thinning. Here, using rheometers, microfluidics and simulations, we show that the dynamics of single RBCs in plasma-like fluids display a different sequence of deformation for increasing shear rates going from discocytes to successively, stomatocytes, folded stomatocytes, trilobes and tetralobes, but never ellipsoids. This result is also identical for physiological hematocrits. We correlate this shape diagram to the different regimes in blood rheology for high shear rates and propose a new-look on the interpretation of blood shear-thinning behavior.

  7. Analysis of shear banding in twelve materials

    NASA Astrophysics Data System (ADS)

    Batra, R. C.; Kim, C. H.

    The problem of the initiation and growth of shear bands in 12 different materials, namely, OFHC copper, Cartridge brass, Nickel 200, Armco IF (interstitial free) iron, Carpenter electric iron, 1006 steel, 2024-T351 aluminum, 7039 aluminum, low alloy steel, S-7 tool steel, Tungsten alloy, and Depleted Uranium (DU -0.75 Ti) is studied with the objectives of finding out when a shear band initiates, and upon what parameters does the band width depend. The nonlinear coupled partial differential equations governing the overall simple shearing deformations of a thermally softening viscoplastic block are analyzed. It is assumed that the thermomechanical response of these materials can be adequately represented by the Johnson-Cook law, and the only inhomogeneity present in the block is the variation in its thickness. The effect of the defect size on the initiation and subsequent growth of the band is also studied. It is found that, for each one of these 12 materials, the deformation has become nonhomogeneous by the time the maximum shear stress occurs. Also the band width, computed when the shear stress has dropped to 85 percent of its peak value, does not correlate well with the thermal conductivity of the material. The band begins to grow rapidly when the shear stress has dropped to 90 percent of its maximum value.

  8. Cosmology with cosmic shear observations: a review.

    PubMed

    Kilbinger, Martin

    2015-07-01

    Cosmic shear is the distortion of images of distant galaxies due to weak gravitational lensing by the large-scale structure in the Universe. Such images are coherently deformed by the tidal field of matter inhomogeneities along the line of sight. By measuring galaxy shape correlations, we can study the properties and evolution of structure on large scales as well as the geometry of the Universe. Thus, cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. We review here the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then we give an overview of weak-lensing measurements, and present the main observational cosmic-shear results since it was discovered 15 years ago, as well as the implications for cosmology. We then conclude with an outlook on the various future surveys and missions, for which cosmic shear is one of the main science drivers, and discuss promising new weak cosmological lensing techniques for future observations.

  9. Dynamic shear jamming in dense suspensions

    NASA Astrophysics Data System (ADS)

    Peters, Ivo; Majumdar, Sayantan; Jaeger, Heinrich

    Shear a dense suspension of cornstarch and water hard enough, and the system seems to solidify as a result. Indeed, previous studies have shown that a jamming front propagates through these systems until, after interaction with boundaries, a jammed solid spans across the system. Because these fully jammed states are only observed if the deformation is fast enough, a natural question to ask is how this phenomenon is related to the discontinuous shear thickening (DST) behavior of these suspensions. We present a single experimental setup in which we on the one hand can measure the rheological flow curves, but on the other hand also determine if the suspension is in a jammed state. This we do by using a large-gap cylindrical Couette cell, where we control the applied shear stress using a rheometer. Because our setup only applies shear, the jammed states we observe are shear-jammed, and cannot be a result of an overall increase in packing fraction. We probe for jammed states by dropping small steel spheres on the surface of the suspension, and identify elastic responses. Our experiments reveal a clear distinction between the onset of DST and Shear-Jammed states, which have qualitatively different trends with packing fraction close to the isotropic jamming point.

  10. A Controlled Shear Decorrelation Experiment (CSDX)

    NASA Astrophysics Data System (ADS)

    Tynan, George

    1999-11-01

    The controlled shear de-correlation experiment (CSDX) is being designed to study the effect of sheared flows on: (1) known linear pressure gradient-driven drift and/or effective gravity-driven flute eigenmodes; (2) the nonlinear three-wave coupling of a finite number of large amplitude coherent modes; and (3) on the rate of electrostatic turbulent fluctuation energy cascades. This research is motivated by magnetic confinement experiments and theory which suggest that sheared E x B shear flows lead to a nonlinear de-correlation of plasma turbulence. The plasma state (i.e. quiescent, single small-amplitude drift wave, nonlinearly coupled modes, or strongly turbulent) will be controlled by varying the magnetic field strength, collisionality, parallel current, and/or effective gravity due to solid-body plasma rotation driven by azimuthal ExB drifts. The radial electric field strength and shear rate will be controlled independently of the plasma state by the application of externally controlled voltages to concentric annular rings which will form the ends of the experimental region. Diagnostics include azimuthal, radial, and axial Langmuir probe arrays, laser induced flourescence (LIF) for ion temperature and equilibrium ExB flow velocities. Bi-spectral analysis techniques will be used to measure k-space resolved linear growth rates and nonlinear energy cascading due to three-wave coupling in the presence of flow shear. Designs and experimental plans will be presented and discussed.

  11. Behavior of Tilted Angle Shear Connectors

    PubMed Central

    Khorramian, Koosha; Maleki, Shervin; Shariati, Mahdi; Ramli Sulong, N. H.

    2015-01-01

    According to recent researches, angle shear connectors are appropriate to transfer longitudinal shear forces across the steel-concrete interface. Angle steel profile has been used in different positions as L-shaped or C-shaped shear connectors. The application of angle shear connectors in tilted positions is of interest in this study. This study investigates the behaviour of tilted-shaped angle shear connectors under monotonic loading using experimental push out tests. Eight push-out specimens are tested to investigate the effects of different angle parameters on the ultimate load capacity of connectors. Two different tilted angles of 112.5 and 135 degrees between the angle leg and steel beam are considered. In addition, angle sizes and lengths are varied. Two different failure modes were observed consisting of concrete crushing-splitting and connector fracture. By increasing the size of connector, the maximum load increased for most cases. In general, the 135 degrees tilted angle shear connectors have a higher strength and stiffness than the 112.5 degrees type. PMID:26642193

  12. Stability of an accelerated shear layer

    SciTech Connect

    Mjolsness, R.C.; Ruppel, H.M.

    1986-07-01

    A fluid shear layer with free boundary conditions is subject to a Kelvin--Helmholtz-like instability. When the shear layer is accelerated by a difference in applied pressures it is also subject to a Rayleigh--Taylor-like instability. The combined action of these instabilities leads to at most one unstable mode at each wavelength, whose behavior depends in detail on fluid parameters, the fluid acceleration and the perturbation wavelength. Typically, at longest wavelengths the instability is essentially of Rayleigh--Taylor form; its behavior resembles the Kelvin--Helmholtz-like mode at shorter wavelengths, near the thickness of the shear layer, cutting off when the Kelvin--Helmholtz-like mode does. At still shorter wavelengths, the shear layer is subject to a Rayleigh--Taylor-like instability. Careful control of fluid parameters could place the most unstable wavelength for Rayleigh--Taylor instability, calculated from viscous theory, in the range of wavelengths where the accelerated shear layer has no unstable mode. However, this may be difficult to achieve in practice. If this can be realized, the most unstable growth rate may be reduced by about an order of magnitude by the presence of shear.

  13. Wall shear stress in collapsed tubes

    NASA Astrophysics Data System (ADS)

    Naili, S.; Ribreau, C.

    1999-01-01

    A small flexural wall rigidity brings unique features to cross-sectional shapes and blood flow within veins, which are characterised by a non-uniform hemodynamical environment acting upon endothelial cells. Velocity fields and related wall shear stress were numerically determined for a large number of conditions, assuming a fully developed, steady, incompressible laminar flow through an uniform smooth pipe with a constant cross-section. It was shown that the flatness greatly influences the resulting distribution of the wall shear stresses along the lumen perimeter. For instance, under a steady longitudinal pressure gradient at about 500 Pascal per meter inside a constant oval-shaped tube, with a lumen perimeter of the order of 5 × 10^{-2} meter, the maximum wall shear stress is found at about 2 Pascal where the local curvature is minimal. On the other hand, the minimal wall shear stress of the order of 1 Pascal is found where the local curvature is maximal. Clear indications have been reported showing that the hemodynamical wall shear stress does alter endothelial cell morphology and orientation. These results are being used for developing an experimental set-up in order to locally map out the characteristic shear stresses looking for endothelial shape modifications whenever a viscous fluid flow is applied.

  14. Resolution of axial shear strain elastography

    NASA Astrophysics Data System (ADS)

    Thitaikumar, Arun; Righetti, Raffaella; Krouskop, Thomas A.; Ophir, Jonathan

    2006-10-01

    The technique of mapping the local axial component of the shear strain due to quasi-static axial compression is defined as axial shear strain elastography. In this paper, the spatial resolution of axial shear strain elastography is investigated through simulations, using an elastically stiff cylindrical lesion embedded in a homogeneously softer background. Resolution was defined as the smallest size of the inclusion for which the strain value at the inclusion/background interface was greater than the average of the axial shear strain values at the interface and inside the inclusion. The resolution was measured from the axial shear strain profile oriented at 45° to the axis of beam propagation, due to the absence of axial shear strain along the normal directions. The effects of the ultrasound system parameters such as bandwidth, beamwidth and transducer element pitch along with signal processing parameters such as correlation window length (W) and axial shift (ΔW) on the estimated resolution were investigated. The results show that the resolution (at 45° orientation) is determined by the bandwidth and the beamwidth. However, the upper bound on the resolution is limited by the larger of the beamwidth and the window length, which is scaled inversely to the bandwidth. The results also show that the resolution is proportional to the pitch and not significantly affected by the axial window shift.

  15. The shear-stress intensity factor for a centrally cracked stiff-flanged shear web

    NASA Technical Reports Server (NTRS)

    Fichter, W. B.

    1976-01-01

    By use of the principle of superposition the stiff-flanged shear web is modeled mathematically by an infinite elastic strip with fixed longitudinal edges. The shear-stress intensity factor for a central longitudinal crack is calculated for various values of the ratio of strip width to crack length, h/a, in the range 0.1-10. The interaction of the crack with the boundaries is illustrated by boundary shear-stress distributions for three values of h/a. Some implications of the results for the design of damage-tolerant shear webs are discussed briefly.

  16. Mid-Late Miocene deformation of the northern Kuqa fold-and-thrust belt (southern Chinese Tian Shan): An apatite (U-Th-Sm)/He study

    NASA Astrophysics Data System (ADS)

    Chang, Jian; Tian, Yuntao; Qiu, Nansheng

    2017-01-01

    The Kuqa fold-and-thrust belt developed in response to Cenozoic southward shortening between the Chinese Tian Shan and the Tarim Basin. This study aims to constrain the timing of the Late Cenozoic deformation by determining the onset time of enhanced rock cooling using apatite (U-Th-Sm)/He thermochronometry. Eight sedimentary samples were collected from Triassic to Cretaceous strata exposed along a 17 km N-S transect, cross-cutting the northern Kuqa fold-and-thrust belt. Single-grain AHe ages from these samples mostly cluster around 8-16 Ma and are younger than their depositional ages. Older AHe ages show a positive relationship with [eU], a proxy for radiation damage. Modelling of the observed age-eU relationships suggest a phase of enhanced cooling and erosion initiated at Mid-Late Miocene time (10-20 Ma) in the northern Kuqa fold-and-thrust belt. This result is consistent with a coeval abrupt increase of sedimentation rate in the foreland Kuqa depression, south of the study area, indicating a Mid-Late Miocene phase of shortening in the northern Kuqa fold-and-thrust belt.

  17. Shear rheology of molten crumb chocolate.

    PubMed

    Taylor, J E; Van Damme, I; Johns, M L; Routh, A F; Wilson, D I

    2009-03-01

    The shear rheology of fresh molten chocolate produced from crumb was studied over 5 decades of shear rate using controlled stress devices. The Carreau model was found to be a more accurate description than the traditional Casson model, especially at shear rates between 0.1 and 1 s(-1). At shear rates around 0.1 s(-1) (shear stress approximately 7 Pa) the material exhibited a transition to a solid regime, similar to the behavior reported by Coussot (2005) for other granular suspensions. The nature of the suspension was explored by investigating the effect of solids concentration (0.20 < phi < 0.75) and the nature of the particles. The rheology of the chocolate was then compared with the rheology of (1) a synthetic chocolate, which contained sunflower oil in place of cocoa butter, and (2) a suspension of sugar of a similar size distribution (volume mean 15 mum) in cocoa butter and emulsifier. The chocolate and synthetic chocolate showed very similar rheological profiles under both steady shear and oscillatory shear. The chocolate and the sugar suspension showed similar Krieger-Dougherty dependency on volume fraction, and a noticeable transition to a stiff state at solids volume fractions above approximately 0.5. Similar behavior has been reported by Citerne and others (2001) for a smooth peanut butter, which had a similar particle size distribution and solids loading to chocolate. The results indicate that the melt rheology of the chocolate is dominated by hydrodynamic interactions, although at high solids volume fractions the emulsifier may contribute to the departure of the apparent viscosity from the predicted trend.

  18. Boundary Shear Stress Along Vegetated Streambanks

    NASA Astrophysics Data System (ADS)

    Clark, L. A.; Wynn, T.

    2007-12-01

    Sediment, a leading cause of water quality impairment, damages aquatic ecosystems and interferes with recreational uses and water treatment processes. Streambank retreat can contribute as much as 85% of watershed sediment yield. Vegetation is an important component of stream restoration designs used to control streambank retreat, but vegetation effects on streambank boundary shear stress (SBSS) need to be quantified. The overall goal of this experiment is to predict boundary shear stress along vegetated streambanks. This goal will be met by determining a method for measuring boundary shear stress in the field along hydraulically rough streambanks, evaluating the effects of streambank vegetation on boundary shear stress in the field, and developing predictive methods based on measurable vegetative properties. First, three streambank vegetation types (herbaceous, shrubbery, and woody) will be modeled in a flume study to examine both boundary shear stress measurement theory and instruments for field use. An appropriate method (law of the wall, Reynold's stresses, TKE, or average wall shear stress) and field instrument (ADV, propeller, or Pitot tube) will be selected, resulting in a field technique to measure SBSS. Predictive methods for estimating SBSS, based on common vegetation measurements, will be developed in the flume study and validated with field data. This research is intended to improve our understanding of the role of riparian vegetation in stream morphology by evaluating the effects of vegetation on boundary shear stress, providing insight to the type and density of vegetation required for streambank stability. The results will also aide in quantifying sediment inputs from streambanks, providing quantitative information for stream restoration projects and watershed management planning.

  19. Experimental shear zones and magnetic fabrics

    NASA Astrophysics Data System (ADS)

    Borradaile, G. J.; Alford, C.

    Magnetic fabric analysis has been used as a non-destructive means of detecting petrofabric development during experimentally produced multi-stage, transpressive deformations in 'shear zones'. Artificial, magnetic-bearing silicate sands and calcite sands, bonded with Portland cement, were deformed at room temperature and at 100 and 150 MPa confining pressure. The slip-rate for the shear zone walls was 0.73 × 10 -4 mm s -1 and the maximum shear strains were about 0.38, across zones that were initially about 5 mm thick. The magnetic fabric ellipsoid rapidly spins so that the maximum and intermediate susceptibilities tend to become parallel to the shear zone walls throughout the sheared zone. The ellipsoid becomes increasingly oblate with progressive deformation. However, in all cases, the anisotropy is strongly influenced by the pre-deformation magnetic fabric. During deformation the cement gel collapses so that cataclasis of the mineral grains is suppressed. In the quartz-feldspar aggregates the magnetite's alignment is accommodated by particulate flow (intergranular displacements) of the grains. In the calcite aggregates stronger magnetic fabrics develop due to plastic deformation of calcite grains as well as particulate flow. However, the calcite grain fabrics are somewhat linear ( L ≥ S) whereas the magnetic fabrics are planar ( S > L). The preferred dimensional orientations of magnetite are weak and it is possible that the magnetic fabrics are due to intragranular rearrangements of magnetic domains. The transpressive shear zones are much more efficient than axial-symmetric shortening in the increase of anisotropy of the magnetic fabrics, especially in the case of the calcite aggregates. This suggests that flow laws derived for axial-symmetric shortening experiments may not be appropriate for non-coaxial strain histories such as those of shear zones.

  20. Mechanical Response and Shear Initiation of Double-Base Propellants

    DTIC Science & Technology

    2009-08-01

    dynamic shear punch test using a modified split- Hopkinson bar. Varying the striker bar’s velocity and length controls the shear rate and duration. Shear...for double-base propellants and computational results of the shear punch test . For the simulations, the viscoSCRAM constitutive model was used to...initiation is determined based on their ability to predict the observed response from the dynamic shear punch test . 15. SUBJECT TERMS insensitive

  1. Compact forced simple-shear sample for studying shear localization in materials

    DOE PAGES

    Gray, George Thompson; Vecchio, K. S.; Livescu, Veronica

    2015-11-06

    In this paper, a new specimen geometry, the compact forced-simple-shear specimen (CFSS), has been developed as a means to achieve simple shear testing of materials over a range of temperatures and strain rates. The stress and strain state in the gage section is designed to produce essentially “pure” simple shear, mode II in-plane shear, in a compact-sample geometry. The 2-D plane of shear can be directly aligned along specified directional aspects of a material's microstructure of interest; i.e., systematic shear loading parallel, at 45°, and orthogonal to anisotropic microstructural features in a material such as the pancake-shaped grains typical inmore » many rolled structural metals, or to specified directions in fiber-reinforced composites. Finally, the shear-stress shear-strain response and the damage evolution parallel and orthogonal to the pancake grain morphology in 7039-Al are shown to vary significantly as a function of orientation to the microstructure.« less

  2. Compact forced simple-shear sample for studying shear localization in materials

    SciTech Connect

    Gray, George Thompson; Vecchio, K. S.; Livescu, Veronica

    2015-11-06

    In this paper, a new specimen geometry, the compact forced-simple-shear specimen (CFSS), has been developed as a means to achieve simple shear testing of materials over a range of temperatures and strain rates. The stress and strain state in the gage section is designed to produce essentially “pure” simple shear, mode II in-plane shear, in a compact-sample geometry. The 2-D plane of shear can be directly aligned along specified directional aspects of a material's microstructure of interest; i.e., systematic shear loading parallel, at 45°, and orthogonal to anisotropic microstructural features in a material such as the pancake-shaped grains typical in many rolled structural metals, or to specified directions in fiber-reinforced composites. Finally, the shear-stress shear-strain response and the damage evolution parallel and orthogonal to the pancake grain morphology in 7039-Al are shown to vary significantly as a function of orientation to the microstructure.

  3. Dynamics of Discontinuous Shear Thickening suspensions

    NASA Astrophysics Data System (ADS)

    Brown, Eric

    2015-03-01

    Concentrated suspensions of hard particles such as cornstarch in water exhibit Discontinuous Shear Thickening, in which an increasing shear rate drives a transition from liquid- to solid-like mechanical behavior. In steady-state shear this phenomena is a result of a dynamic version of jamming in which forces are transmitted along particle contact networks that span to system boundaries and repeatedly form and break up. Several dynamic phenomena observed in such suspensions have long been assumed to be a consequence of this shear thickening, but cannot be explained as a direct result of shear thickening; for example a uniquely strong impact response which allows a person to run on the fluid surface. We perform experiments in which a concentrated suspension is subjected to transient impact. We find that the strong impact response is due a short-lived jammed contact network spanning to the boundaries and a delay time required for this dynamically jammed region to propagate to the boundary. The resulting ability of this system-spanning solid-like region to support loads can explain the ability of a person to run on the surface of these fluids. This delay before a solid-like response may also explain several other dynamic phenomena observed in these fluids.

  4. Internal hydraulic jumps with large upstream shear

    NASA Astrophysics Data System (ADS)

    Ogden, Kelly; Helfrich, Karl

    2015-11-01

    Internal hydraulic jumps in approximately two-layered flows with large upstream shear are investigated using numerical simulations. The simulations allow continuous density and velocity profiles, and a jump is forced to develop by downstream topography, similar to the experiments conducted by Wilkinson and Wood (1971). High shear jumps are found to exhibit significantly more entrainment than low shear jumps. Furthermore, the downstream structure of the flow has an important effect on the jump properties. Jumps with a slow upper (inactive) layer exhibit a velocity minimum downstream of the jump, resulting in a sub-critical downstream state, while flows with the same upstream vertical shear and a larger barotropic velocity remain super-critical downstream of the jump. A two-layer theory is modified to account for the vertical structure of the downstream density and velocity profiles and entrainment is allowed through a modification of the approach of Holland et al. (2002). The resulting theory can be matched reasonably well with the numerical simulations. However, the results are very sensitive to how the downstream vertical profiles of velocity and density are incorporated into the layered model, highlighting the difficulty of the two layer approximation when the shear is large.

  5. Shear-Driven Reconnection in Kinetic Models

    NASA Astrophysics Data System (ADS)

    Black, C.; Antiochos, S. K.; Germaschewski, K.; Karpen, J. T.; DeVore, C. R.; Bessho, N.

    2015-12-01

    The explosive energy release in solar eruptive phenomena is believed to be due to magnetic reconnection. In the standard model for coronal mass ejections (CME) and/or solar flares, the free energy for the event resides in the strongly sheared magnetic field of a filament channel. The pre-eruption force balance consists of an upward force due to the magnetic pressure of the sheared field countered by a downward tension due to overlying unsheared field. Magnetic reconnection disrupts this force balance; therefore, it is critical for understanding CME/flare initiation, to model the onset of reconnection driven by the build-up of magnetic shear. In MHD simulations, the application of a magnetic-field shear is a trivial matter. However, kinetic effects are dominant in the diffusion region and thus, it is important to examine this process with PIC simulations as well. The implementation of such a driver in PIC methods is challenging, however, and indicates the necessity of a true multiscale model for such processes in the solar environment. The field must be sheared self-consistently and indirectly to prevent the generation of waves that destroy the desired system. Plasma instabilities can arise nonetheless. In the work presented here, we show that we can control this instability and generate a predicted out-of-plane magnetic flux. This material is based upon work supported by the National Science Foundation under Award No. AGS-1331356.

  6. Colloidal Aggregate Structure under Shear by USANS

    NASA Astrophysics Data System (ADS)

    Chatterjee, Tirtha; van Dyk, Antony K.; Ginzburg, Valeriy V.; Nakatani, Alan I.

    2015-03-01

    Paints are complex formulations of polymeric binders, inorganic pigments, dispersants, surfactants, colorants, rheology modifiers, and other additives. A commercially successful paint exhibits a desired viscosity profile over a wide shear rate range from 10-5 s-1 for settling to >104 s-1 for rolling, and spray applications. Understanding paint formulation structure is critical as it governs the paint viscosity profile. However, probing paint formulation structure under shear is a challenging task due to the formulation complexity containing structures with different hierarchical length scales and their alterations under the influence of an external flow field. In this work mesoscale structures of paint formulations under shear are investigated using Ultra Small-Angle Neutron Scattering (rheo-USANS). Contrast match conditions were utilized to independently probe the structure of latex binder particle aggregates and the TiO2 pigment particle aggregates. Rheo-USANS data revealed that the aggregates are fractal in nature and their self-similarity dimensions and correlations lengths depend on the chemistry of the binder particles, the type of rheology modifier present and the shear stress imposed upon the formulation. These results can be explained in the framework of diffusion and reaction limited transient aggregates structure evolution under simple shear.

  7. Pressure-shear experiments on granular materials.

    SciTech Connect

    Reinhart, William Dodd; Thornhill, Tom Finley, III; Vogler, Tracy John; Alexander, C. Scott

    2011-10-01

    Pressure-shear experiments were performed on granular tungsten carbide and sand using a newly-refurbished slotted barrel gun. The sample is a thin layer of the granular material sandwiched between driver and anvil plates that remain elastic. Because of the obliquity, impact generates both a longitudinal wave, which compresses the sample, and a shear wave that probes the strength of the sample. Laser velocity interferometry is employed to measure the velocity history of the free surface of the anvil. Since the driver and anvil remain elastic, analysis of the results is, in principal, straightforward. Experiments were performed at pressures up to nearly 2 GPa using titanium plates and at higher pressure using zirconium plates. Those done with the titanium plates produced values of shear stress of 0.1-0.2 GPa, with the value increasing with pressure. On the other hand, those experiments conducted with zirconia anvils display results that may be related to slipping at an interface and shear stresses mostly at 0.1 GPa or less. Recovered samples display much greater particle fracture than is observed in planar loading, suggesting that shearing is a very effective mechanism for comminution of the grains.

  8. The shear fracture toughness, KIIc, of graphite

    DOE PAGES

    Burchell, Timothy D.; Erdman, III, Donald L.

    2015-11-05

    In this study, the critical shear stress intensity factor, KIIc, here-in referred to as the shear fracture toughness, KIIc (MPa m), of two grades of graphite are reported. The range of specimen volumes was selected to elucidate any specimen size effect, but smaller volume specimen tests were largely unsuccessful, shear failure did not occur between the notches as expected. This was probably due to the specimen geometry causing the shear fracture stress to exceed the compressive failure stress. In subsequent testing the specimen geometry was altered to reduce the compressive footprint and the notches (slits) made deeper to reduce themore » specimen's ligament length. Additionally, we added the collection of Acoustic Emission (AE) during testing to assist with the identification of the shear fracture load. The means of KIIc from large specimens for PCEA and NBG-18 are 2.26 MPa m with an SD of 0.37 MPa m and 2.20 MPa m with an SD of 0.53 MPa m, respectively. The value of KIIc for both graphite grades was similar, although the scatter was large. In this work we found the ratio of KIIc/KIc ≈ 1.6. .« less

  9. Particle Distribution in Suspension Shear Flow

    NASA Technical Reports Server (NTRS)

    Buyevich, Yu A.; Webbon, Bruce W. (Technical Monitor)

    1994-01-01

    An earlier proposed constitutive relation for normal stresses originated by random particle fluctuations is used to describe a joint effect of thermal and shear-induced fluctuations on concentrational distributions in suspension flow. Averaged products of components of the fluctuation velocity are evaluated on a basis of the rational mechanics approach combined with a simple kinematic consideration. The equation of momentum conservation of the dispersed phase of a suspension closed with this constitutive relation is applied to unidirectional shear flow in the gravity field and to rotational Couette flow. Coupling of the thermal and shear-induced fluctuations results in that the ability of shear flow to suspend particles has a minimum at a certain particle size, all other things being equal. The developed model provides also for a reasonable explanation of particle distributions observed in Couette flow. The approach based on the consideration of momentum balance for the dispersed phase is proved to lead to an effective equation of convective diffusion of the suspended particles. Coefficients of mutual diffusion due to both thermal and shear-induced fluctuations are drastically different from corresponding self-diffusivities as regards both their scaling and their concentrational dependence.

  10. Viscoelasticity and shear thinning of nanoconfined water

    NASA Astrophysics Data System (ADS)

    Kapoor, Karan; Amandeep, Patil, Shivprasad

    2014-01-01

    Understanding flow properties and phase behavior of water confined to nanometer-sized pores and slits is central to a wide range of problems in science, such as percolation in geology, lubrication of future nano-machines, self-assembly and interactions of biomolecules, and transport through porous media in filtration processes. Experiments with different techniques in the past have reported that viscosity of nanoconfined water increases, decreases, or remains close to bulk water. Here we show that water confined to less than 20-nm-thick films exhibits both viscoelasticity and shear thinning. Typically viscoelasticity and shear thinning appear due to shearing of complex non-Newtonian mixtures possessing a slowly relaxing microstructure. The shear response of nanoconfined water in a range of shear frequencies (5 to 25 KHz) reveals that relaxation time diverges with reducing film thickness. It suggests that slow relaxation under confinement possibly arises due to existence of a critical point with respect to slit width. This criticality is similar to the capillary condensation in porous media.

  11. Nonmonotonic flow curves of shear thickening suspensions

    NASA Astrophysics Data System (ADS)

    Mari, Romain; Seto, Ryohei; Morris, Jeffrey F.; Denn, Morton M.

    2015-05-01

    The discontinuous shear thickening (DST) of dense suspensions is a remarkable phenomenon in which the viscosity can increase by several orders of magnitude at a critical shear rate. It has the appearance of a first-order phase transition between two hypothetical "states" that we have recently identified as Stokes flows with lubricated or frictional contacts, respectively. Here we extend the analogy further by means of stress-controlled simulations and show the existence of a nonmonotonic steady-state flow curve analogous to a nonmonotonic equation of state. While we associate DST with an S -shaped flow curve, at volume fractions above the shear jamming transition the frictional state loses flowability and the flow curve reduces to an arch, permitting the system to flow only at small stresses. Whereas a thermodynamic transition leads to phase separation in the coexistence region, we observe a uniform shear flow all along the thickening transition. A stability analysis suggests that uniform shear may be mechanically stable for the small Reynolds numbers and system sizes in a rheometer.

  12. Nonmonotonic flow curves of shear thickening suspensions.

    PubMed

    Mari, Romain; Seto, Ryohei; Morris, Jeffrey F; Denn, Morton M

    2015-05-01

    The discontinuous shear thickening (DST) of dense suspensions is a remarkable phenomenon in which the viscosity can increase by several orders of magnitude at a critical shear rate. It has the appearance of a first-order phase transition between two hypothetical "states" that we have recently identified as Stokes flows with lubricated or frictional contacts, respectively. Here we extend the analogy further by means of stress-controlled simulations and show the existence of a nonmonotonic steady-state flow curve analogous to a nonmonotonic equation of state. While we associate DST with an S-shaped flow curve, at volume fractions above the shear jamming transition the frictional state loses flowability and the flow curve reduces to an arch, permitting the system to flow only at small stresses. Whereas a thermodynamic transition leads to phase separation in the coexistence region, we observe a uniform shear flow all along the thickening transition. A stability analysis suggests that uniform shear may be mechanically stable for the small Reynolds numbers and system sizes in a rheometer.

  13. Electrostatic ion cyclotron velocity shear instability

    SciTech Connect

    Lemons, D.S.; Winske, D.; Gary, S.P. )

    1992-12-01

    An electrostatic ion cyclotron instability driven by sheared velocity flow perpendicular to a uniform magnetic field is investigated in the local approximation. The dispersion equation, which includes all kinetic effects and involves only one important parameter, is cast in the form of Gordeyev integrals and solved numerically. The instability occurs roughly at multiples of the ion cyclotron frequency (but modified by the shear) with the growth rate of the individual harmonics overlapping in wavenumber. At small values of the shear parameter, the instability exists in two branches, one at long wavelength, [kappa][rho][sub i] [approximately] 0.5, and one at short wavelength, [kappa][rho][sub i] > 1.5 ([kappa][rho][sub i] is the wavenumber normalized to the ion gyroradius). At larger values of the shear parameter only the longer wavelength branch persists. The growth rate of the long wavelength mode, maximized over wavenumber and frequency, increases monotonically with the shear parameter. Properties of the instability are compared to those of Ganguli et al. obtained in the nonlocal limit.

  14. Bacterial motility and chemotaxis in shear

    NASA Astrophysics Data System (ADS)

    Rusconi, Roberto; Guasto, Jeffrey S.; Son, Kwangmin; Stocker, Roman

    2011-11-01

    Bacteria often exhibit directed motility (``taxis'') in response to gradients of dissolved resources, like nutrients or oxygen. While we have a detailed understanding of chemotaxis in quiescent environments, it has been largely overlooked how this behavior is affected by fluid flow, despite the ubiquity of flow in bacterial habitats. Here we present experiments on aerotaxis (attraction to dissolved oxygen) of Bacillus subtilis in controlled shear flows. Using novel microfluidic devices we expose bacterial suspensions to steady oxygen gradients, with independent control over shear rates. From single-cell trajectories and the spatial distribution of bacteria, we show that the cell rotation induced by shear reduces the aerotactic performance, demonstrating that hydrodynamic conditions affect bacterial fitness.

  15. Scaling effects in direct shear tests

    USGS Publications Warehouse

    Orlando, A.D.; Hanes, D.M.; Shen, H.H.

    2009-01-01

    Laboratory experiments of the direct shear test were performed on spherical particles of different materials and diameters. Results of the bulk friction vs. non-dimensional shear displacement are presented as a function of the non-dimensional particle diameter. Simulations of the direct shear test were performed using the Discrete Element Method (DEM). The simulation results show Considerable differences with the physical experiments. Particle level material properties, such as the coefficients of static friction, restitution and rolling friction need to be known a priori in order to guarantee that the simulation results are an accurate representation of the physical phenomenon. Furthermore, laboratory results show a clear size dependency on the results, with smaller particles having a higher bulk friction than larger ones. ?? 2009 American Institute of Physics.

  16. Mitigating shear lag in tall buildings

    NASA Astrophysics Data System (ADS)

    Gaur, Himanshu; Goliya, Ravindra K.

    2015-09-01

    As the height of building increases, effect of shear lag also becomes considerable in the design of high-rise buildings. In this paper, shear lag effect in tall buildings of heights, i.e., 120, 96, 72, 48 and 36 stories of which aspect ratio ranges from 3 to 10 is studied. Tube-in-tube structural system with façade bracing is used for designing the building of height 120 story. It is found that bracing system considerably reduces the shear lag effect and hence increases the building stiffness to withstand lateral loads. Different geometric patterns of bracing system are considered. The best effective geometric configuration of bracing system is concluded in this study. Lateral force, as wind load is applied on the buildings as it is the most dominating lateral force for such heights. Wind load is set as per Indian standard code of practice IS 875 Part-3. For analysis purpose SAP 2000 software program is used.

  17. Active dynamics of tissue shear flow

    NASA Astrophysics Data System (ADS)

    Popović, Marko; Nandi, Amitabha; Merkel, Matthias; Etournay, Raphaël; Eaton, Suzanne; Jülicher, Frank; Salbreux, Guillaume

    2017-03-01

    We present a hydrodynamic theory to describe shear flows in developing epithelial tissues. We introduce hydrodynamic fields corresponding to state properties of constituent cells as well as a contribution to overall tissue shear flow due to rearrangements in cell network topology. We then construct a generic linear constitutive equation for the shear rate due to topological rearrangements and we investigate a novel rheological behaviour resulting from memory effects in the tissue. We identify two distinct active cellular processes: generation of active stress in the tissue, and actively driven topological rearrangements. We find that these two active processes can produce distinct cellular and tissue shape changes, depending on boundary conditions applied on the tissue. Our findings have consequences for the understanding of tissue morphogenesis during development.

  18. Streamline curvature in supersonic shear layers

    NASA Technical Reports Server (NTRS)

    Kibens, V.

    1992-01-01

    Results of an experimental investigation in which a curved shear layer was generated between supersonic flow from a rectangular converging/diverging nozzle and the freestream in a series of open channels with varying radii of curvature are reported. The shear layers exhibit unsteady large-scale activity at supersonic pressure ratios, indicating increased mixing efficiency. This effect contrasts with supersonic flow in a straight channel, for which no large-scale vortical structure development occurs. Curvature must exceed a minimum level before it begins to affect the dynamics of the supersonic shear layer appreciably. The curved channel flows are compared with reference flows consisting of a free jet, a straight channel, and wall jets without sidewalls on a flat and a curved plate.

  19. Bioinspired Sensory Systems for Shear Flow Detection

    NASA Astrophysics Data System (ADS)

    Colvert, Brendan; Chen, Kevin K.; Kanso, Eva

    2017-03-01

    Aquatic organisms such as copepods exhibit remarkable responses to changes in ambient flows, especially shear gradients, when foraging, mating and escaping. To accomplish these tasks, the sensory system of the organism must decode the local sensory measurements to detect the flow properties. Evidence suggests that organisms sense differences in the hydrodynamic signal rather than absolute values of the ambient flow. In this paper, we develop a mathematical framework for shear flow detection using a bioinspired sensory system that measures only differences in velocity. We show that the sensory system is capable of reconstructing the properties of the ambient shear flow under certain conditions on the flow sensors. We discuss these conditions and provide explicit expressions for processing the sensory measurements and extracting the flow properties. These findings suggest that by combining suitable velocity sensors and physics-based methods for decoding sensory measurements, we obtain a powerful approach for understanding and developing underwater sensory systems.

  20. Tethered DNA dynamics in shear flow.

    PubMed

    Zhang, Yu; Donev, Aleksandar; Weisgraber, Todd; Alder, Berni J; Graham, Michael D; de Pablo, Juan J

    2009-06-21

    We study the cyclic dynamics of a single polymer tethered to a hard wall in shear flow using Brownian dynamics, the lattice Boltzmann method, and a recent stochastic event-driven molecular dynamics algorithm. We focus on the dynamics of the free end (last bead) of the tethered chain and we examine the cross-correlation function and power spectral density of the chain extensions in the flow and gradient directions as a function of chain length N and dimensionless shear rate Wi. Extensive simulation results suggest a classical fluctuation-dissipation stochastic process and question the existence of periodicity of the cyclic dynamics, as previously claimed. We support our numerical findings with a simple analytical calculation for a harmonic dimer in shear flow.

  1. Strength of Footing with Punching Shear Preventers

    PubMed Central

    Lee, Sang-Sup; Moon, Jiho; Park, Keum-Sung; Bae, Kyu-Woong

    2014-01-01

    The punching shear failure often governs the strength of the footing-to-column connection. The punching shear failure is an undesirable failure mode, since it results in a brittle failure of the footing. In this study, a new method to increase the strength and ductility of the footing was proposed by inserting the punching shear preventers (PSPs) into the footing. The validation and effectiveness of PSP were verified through a series of experimental studies. The nonlinear finite element analysis was then performed to demonstrate the failure mechanism of the footing with PSPs in depth and to investigate the key parameters that affect the behavior of the footing with PSPs. Finally, the design recommendations for the footing with PSPs were suggested. PMID:25401141

  2. Shear and extensional properties of kefiran.

    PubMed

    Piermaría, Judith; Bengoechea, Carlos; Abraham, Analía Graciela; Guerrero, Antonio

    2016-11-05

    Kefiran is a neutral polysaccharide constituted by glucose and galactose produced by Lactobacillus kefiranofaciens. It is included into kefir grains and has several health promoting properties. In the present work, shear and extensional properties of different kefiran aqueous dispersions (0.5, 1 and 2% wt.) were assessed and compared to other neutral gums commonly used in food, cosmetic and pharmaceutics industries (methylcellulose, locust bean gum and guar gum). Kefiran showed shear flow characteristics similar to that displayed by other representative neutral gums, although it always yielded lower viscosities at a given concentration. For each gum system it was possible to find a correlation between dynamic and steady shear properties by a master curve including both the apparent and complex viscosities. When studying extensional properties of selected gums at 2% wt. by means of a capillary break-up rheometer, kefiran solutions did not show important extensional properties, displaying a behaviour close the Newtonian.

  3. Sheared DNA fragment sizing: comparison of techniques.

    PubMed Central

    Ordahl, C P; Johnson, T R; Caplan, A I

    1976-01-01

    DNA fragmented by conventional French press shearing procedures (30,000 lbs/in2) has a number-average fragment size of 230 base pairs. This is considerably smaller than the 450 base pairs typically reported for DNA sheared by this method. Comparison of 5 sizing techniques indicates that sheared DNA fragment size is overestimated by either measurement of velocity sedimentation or Kleinschmidt Electron Microscopic visualization. Both adsorption grid electron microscopic visualization and gel electrophoresis yield the most reliable estimates of the mean size of small DNA fragment populations. In addition, the assessment of fragment size distribution (not possible from sedimentation analysis) potentially allows more critical evaluation of DNA hybridization and reassociation kinetic and measurement parameters. Images PMID:1034292

  4. Measuring shear modulus of individual fibers

    NASA Astrophysics Data System (ADS)

    Behlow, Herbert; Saini, Deepika; Oliviera, Luciana; Skove, Malcolm; Rao, Apparao

    2014-03-01

    Fiber technology has advanced to new heights enabling tailored mechanical properties. For reliable fiber applications their mechanical properties must be well characterized at the individual fiber level. Unlike the tensile modulus, which can be well studied in a single fiber, the present indirect and dynamic methods of measuring the shear properties of fibers suffer from various disadvantages such as the interaction between fibers and the influence of damping. In this talk, we introduce a quasi-static method to directly measure the shear modulus of a single micron-sized fiber. Our simple and inexpensive setup yields a shear modulus of 16 and 2 GPa for a single IM7 carbon fiber and a Kevlar fiber, respectively. Furthermore, our setup is also capable of measuring the creep, hysteresis and the torsion coefficient, and examples of these will be presented.

  5. Observations of velocity shear driven plasma turbulence

    NASA Technical Reports Server (NTRS)

    Kintner, P. M., Jr.

    1976-01-01

    Electrostatic and magnetic turbulence observations from HAWKEYE-1 during the low altitude portion of its elliptical orbit over the Southern Hemisphere are presented. The magnetic turbulence is confined near the auroral zone and is similar to that seen at higher altitudes by HEOS-2 in the polar cusp. The electrostatic turbulence is composed of a background component with a power spectral index of 1.89 + or - .26 and an intense component with a power spectral index of 2.80 + or - .34. The intense electrostatic turbulence and the magnetic turbulence correlate with velocity shears in the convective plasma flow. Since velocity shear instabilities are most unstable to wave vectors perpendicular to the magnetic field, the shear correlated turbulence is anticipated to be two dimensional in character and to have a power spectral index of 3 which agrees with that observed in the intense electrostatic turbulence.

  6. Physical models of tissue in shear fields.

    PubMed

    Carstensen, Edwin L; Parker, Kevin J

    2014-04-01

    This review considers three general classes of physical as opposed to phenomenological models of the shear elasticity of tissues. The first is simple viscoelasticity. This model has a special role in elastography because it is the language in which experimental and clinical data are communicated. The second class of models involves acoustic relaxation, in which the medium contains inner time-dependent systems that are driven through the external bulk medium. Hysteresis, the phenomenon characterizing the third class of models, involves losses that are related to strain rather than time rate of change of strain. In contrast to the vast efforts given to tissue characterization through their bulk moduli over the last half-century, similar research using low-frequency shear data is in its infancy. Rather than a neat summary of existing facts, this essay is a framework for hypothesis generation-guessing what physical mechanisms give tissues their shear properties.

  7. Shear banding in soft glassy materials.

    PubMed

    Fielding, S M

    2014-10-01

    Many soft materials, including microgels, dense colloidal emulsions, star polymers, dense packings of multilamellar vesicles, and textured morphologies of liquid crystals, share the basic 'glassy' features of structural disorder and metastability. These in turn give rise to several notable features in the low frequency shear rheology (deformation and flow properties) of these materials: in particular, the existence of a yield stress below which the material behaves like a solid, and above which it flows like a liquid. In the last decade, intense experimental activity has also revealed that these materials often display a phenomenon known as shear banding, in which the flow profile across the shear cell exhibits macroscopic bands of different viscosity. Two distinct classes of yield stress fluid have been identified: those in which the shear bands apparently persist permanently (for as long as the flow remains applied), and those in which banding arises only transiently during a process in which a steady flowing state is established out of an initial rest state (for example, in a shear startup or step stress experiment). Despite being technically transient, such bands may in practice persist for a very long time and so be mistaken for the true steady state response of the material in experimental practice. After surveying the motivating experimental data, we describe recent progress in addressing it theoretically, using the soft glassy rheology model and a simple fluidity model. We also briefly place these theoretical approaches in the context of others in the literature, including elasto-plastic models, shear transformation zone theories, and molecular dynamics simulations. We discuss finally some challenges that remain open to theory and experiment alike.

  8. Shear banding in soft glassy materials

    NASA Astrophysics Data System (ADS)

    Fielding, S. M.

    2014-10-01

    Many soft materials, including microgels, dense colloidal emulsions, star polymers, dense packings of multilamellar vesicles, and textured morphologies of liquid crystals, share the basic ‘glassy’ features of structural disorder and metastability. These in turn give rise to several notable features in the low frequency shear rheology (deformation and flow properties) of these materials: in particular, the existence of a yield stress below which the material behaves like a solid, and above which it flows like a liquid. In the last decade, intense experimental activity has also revealed that these materials often display a phenomenon known as shear banding, in which the flow profile across the shear cell exhibits macroscopic bands of different viscosity. Two distinct classes of yield stress fluid have been identified: those in which the shear bands apparently persist permanently (for as long as the flow remains applied), and those in which banding arises only transiently during a process in which a steady flowing state is established out of an initial rest state (for example, in a shear startup or step stress experiment). Despite being technically transient, such bands may in practice persist for a very long time and so be mistaken for the true steady state response of the material in experimental practice. After surveying the motivating experimental data, we describe recent progress in addressing it theoretically, using the soft glassy rheology model and a simple fluidity model. We also briefly place these theoretical approaches in the context of others in the literature, including elasto-plastic models, shear transformation zone theories, and molecular dynamics simulations. We discuss finally some challenges that remain open to theory and experiment alike.

  9. Unresolved issues in wind shear encounters

    NASA Technical Reports Server (NTRS)

    Stengel, Robert F.

    1987-01-01

    Much remains to be learned about the hazards of low altitude wind shear to aviation. New research should be conducted on the nature of the atmospheric environment, on aircraft performance, and on guidance and control aids. In conducting this research, it is important to distinguish between near-term and far-term objectives, between basic and applied research, and between uses of results for aircraft design or for real-time implementation. Advances in on-board electronics can be applied to assuring that aircraft of all classes have near optimal protection against wind shear hazards.

  10. Shear Viscosity in a Gluon Gas

    SciTech Connect

    Xu Zhe; Greiner, Carsten

    2008-05-02

    The relation of the shear viscosity coefficient to the recently introduced transport rate is derived within relativistic kinetic theory. We calculate the shear viscosity over entropy ratio {eta}/s for a gluon gas, which involves elastic gg{yields}gg perturbative QCD (PQCD) scatterings as well as inelastic gg{r_reversible}ggg PQCD bremsstrahlung. For {alpha}{sub s}=0.3 we find {eta}/s=0.13 and for {alpha}{sub s}=0.6, {eta}/s=0.076. The small {eta}/s values, which suggest strongly coupled systems, are due to the gluon bremsstrahlung incorporated.

  11. Transition in compressible free shear layers.

    NASA Technical Reports Server (NTRS)

    Birch, S. F.; Keyes, J. W.

    1972-01-01

    The transition Reynolds number for shear layers produced by interactions between weak and strong shock waves is determined on the basis of experiments performed in a 20-in. (Mach 6) and an 11-in. (Mach 6.9) hypersonic tunnel. A variable angle wedge was used to generate a planar shock wave which interacted with the bow wave of a blunt body. An average value of the transition length (defined as the length along the shear layer from the shock interaction to the point where turbulence became visible on schlieren photographs) was used to determine the transition Reynolds number.

  12. Enhancing Rotational Diffusion Using Oscillatory Shear

    NASA Astrophysics Data System (ADS)

    Leahy, Brian D.; Cheng, Xiang; Ong, Desmond C.; Liddell-Watson, Chekesha; Cohen, Itai

    2013-05-01

    Taylor dispersion—shear-induced enhancement of translational diffusion—is an important phenomenon with applications ranging from pharmacology to geology. Through experiments and simulations, we show that rotational diffusion is also enhanced for anisotropic particles in oscillatory shear. This enhancement arises from variations in the particle’s rotation (Jeffery orbit) and depends on the strain amplitude, rate, and particle aspect ratio in a manner that is distinct from the translational diffusion. This separate tunability of translational and rotational diffusion opens the door to new techniques for controlling positions and orientations of suspended anisotropic colloids.

  13. Compressible homogeneous shear: Simulation and modeling

    NASA Technical Reports Server (NTRS)

    Sarkar, S.; Erlebacher, G.; Hussaini, M. Y.

    1992-01-01

    Compressibility effects were studied on turbulence by direct numerical simulation of homogeneous shear flow. A primary observation is that the growth of the turbulent kinetic energy decreases with increasing turbulent Mach number. The sinks provided by compressible dissipation and the pressure dilatation, along with reduced Reynolds shear stress, are shown to contribute to the reduced growth of kinetic energy. Models are proposed for these dilatational terms and verified by direct comparison with the simulations. The differences between the incompressible and compressible fields are brought out by the examination of spectra, statistical moments, and structure of the rate of strain tensor.

  14. Shear-flow Effects in Open Traps

    SciTech Connect

    Beklemishev, A. D.

    2008-11-01

    Interaction between shear flows and plasma instabilities and turbulence in open traps can lead to improved confinement both in experiments and in simulations. Shear flows, driven by biasing end-plates and limiters or by off-axis electron heating, in combination with the finite-larmor-radius (FLR) effects are shown to be efficient in confining plasmas even with unstable flute modes. Interpretation of the observed effects as the ''vortex confinement,'' i.e., confinement of the plasma core in the dead-flow zone of the driven vortex, is shown to agree well with simulations.

  15. Low shear viscosity of dilute polymer solutions

    SciTech Connect

    Chiou, C.S.; Gordon, R.J.

    1980-09-01

    A modification of a viscometer originally proposed by Zimm and Crothers is studied, which may be used to measure ultra low shear viscosity for highly dilute polymer solutions. This may provide useful information on polymer coil dimensions and relaxation time. Use of the low shear viscosity data leads to large value of relaxation time induced by polymer addition to a concentration of only 2 to 3 ppM by wt. This finding is consistent with the marked viscoelastic effects exhibited by these solutions.

  16. Shear viscosity coefficient of liquid lanthanides

    SciTech Connect

    Patel, H. P. Thakor, P. B. Prajapati, A. V.; Sonvane, Y. A.

    2015-05-15

    Present paper deals with the computation of shear viscosity coefficient (η) of liquid lanthanides. The effective pair potential v(r) is calculated through our newly constructed model potential. The Pair distribution function g(r) is calculated from PYHS reference system. To see the influence of local field correction function, Hartree (H), Tailor (T) and Sarkar et al (S) local field correction function are used. Present results are compared with available experimental as well as theoretical data. Lastly, we found that our newly constructed model potential successfully explains the shear viscosity coefficient (η) of liquid lanthanides.

  17. Iosipescu shear properties of graphite fabric/epoxy composite laminates

    NASA Technical Reports Server (NTRS)

    Walrath, D. E.; Adams, D. F.

    1985-01-01

    The Iosipescu shear test method is used to measure the in-plane and interlaminar shear properties of four T300 graphite fabric/934 epoxy composite materials. Different weave geometries tested include an Oxford weave, a 5-harness satin weave, an 8-harness satin weave, and a plain weave with auxiliary warp yarns. Both orthogonal and quasi-isotropic layup laminates were tested. In-plane and interlaminar shear properties are obtained for laminates of all four fabric types. Overall, little difference in shear properties attributable to the fabric weave pattern is observed. The auxiliary warp material is significantly weaker and less stiff in interlaminar shear parallel to its fill direction. A conventional strain gage extensometer is modified to measure shear strains for use with the Iosipescu shear test. While preliminary results are encouraging, several design iterations failed to produce a reliable shear transducer prototype. Strain gages are still the most reliable shear strain transducers for use with this test method.

  18. A dynamic jamming point for shear thickening suspensions

    NASA Astrophysics Data System (ADS)

    Brown, Eric; Jaeger, Heinrich

    2008-11-01

    Densely packed suspensions can shear thicken, in which the viscosity increases with shear rate. We performed rheometry measurements on two model systems: corn starch in water and glass spheres in oils. In both systems we observed shear thickening up to a critical packing fraction φc (=0.55 for spherical grains) above which the flow abruptly transitions to shear thinning. The viscosity and yield stress diverge as power laws at φc. Extrapolating the dynamic ranges of shear rate and stress in the shear thickening regime up to φc suggests a finite change in shear stress with zero change in shear rate. This is a dynamic analog to the jamming point with a yield stress at zero shear rate.

  19. High-shear-rate capillary viscometer for inkjet inks

    SciTech Connect

    Wang Xi; Carr, Wallace W.; Bucknall, David G.; Morris, Jeffrey F.

    2010-06-15

    A capillary viscometer developed to measure the apparent shear viscosity of inkjet inks at high apparent shear rates encountered during inkjet printing is described. By using the Weissenberg-Rabinowitsch equation, true shear viscosity versus true shear rate is obtained. The device is comprised of a constant-flow generator, a static pressure monitoring device, a high precision submillimeter capillary die, and a high stiffness flow path. The system, which is calibrated using standard Newtonian low-viscosity silicone oil, can be easily operated and maintained. Results for measurement of the shear-rate-dependent viscosity of carbon-black pigmented water-based inkjet inks at shear rates up to 2x10{sup 5} s{sup -1} are discussed. The Cross model was found to closely fit the experimental data. Inkjet ink samples with similar low-shear-rate viscosities exhibited significantly different shear viscosities at high shear rates depending on particle loading.

  20. Shear stress regulates HUVEC hydraulic conductivity by occludin phosphorylation.

    PubMed

    Pang, Zhengyu; Antonetti, David A; Tarbell, John M

    2005-11-01

    Human umbilical vein endothelial cells (HUVECs) display hydraulic conductivity (L(P)) responses to shear stress that differ markedly from the responses of bovine aortic endothelial cells (BAECs). In HUVECs, 5, 10, and 20 dyn cm(-2) steady shear stress transiently increased L(P) with a return to preshear baseline after a 2-h exposure to shear stress. Pure oscillatory shear stress of 0 +/- 20 dyn cm(-2) (mean+/-amplitude) had no effect on L(P), whereas superposition of oscillatory shear stress on steady shear stress suppressed the effect induced by steady shear stress alone. Shear reversal (amplitude greater than mean) was not necessary for the inhibitory influence of oscillatory shear stress. The transient increase of L(P) by steady shear stress was not affected by incubation with BAPTA-AM (10 microM), suggesting calcium independence of the shear response. Decreasing nitric oxide (NO) concentration with L-NMMA (100 microM), a nitric oxide synthase (NOS) inhibitor, did not inhibit the HUVEC L(P) response to shear stress. At the protein level, 10 dyn cm(-2) shear stress did not affect the total content of occludin, but it did elevate the phosphorylation level transiently. The positive correlation between occludin phosphorylation and hydraulic conductivity parallels observations in BAECs and suggests that occludin phosphorylation may be a general mediator of shear-L(P) responses in diverse endothelial cell types.

  1. A new method for shear wave speed estimation in shear wave elastography.

    PubMed

    Engel, Aaron J; Bashford, Gregory R

    2015-12-01

    Visualization of mechanical properties of tissue can aid in noninvasive pathology diagnosis. Shear wave elastography (SWE) measures the elastic properties of soft tissues by estimation of local shear wave propagation speed. In this paper, a new robust method for estimation of shear wave speed is introduced which has the potential for simplifying continuous filtering and real-time elasticity processing. Shear waves were generated by external mechanical excitation and imaged at a high frame rate. Three homogeneous phantoms of varying elastic moduli and one inclusion phantom were imaged. Waves propagating in separate directions were filtered and shear wave speed was estimated by inversion of the 1-D first-order wave equation. Final 2-D shear wave speed maps were constructed by weighted averaging of estimates from opposite traveling directions. Shear wave speed results for phantoms with gelatin concentrations of 5%, 7%, and 9% were 1.52 ± 0.10 m/s, 1.86 ± 0.10 m/s, and 2.37 ± 0.15 m/s, respectively, which were consistent with estimates computed from three other conventional methods, as well as compression tests done with a commercial texture analyzer. The method was shown to be able to reconstruct a 2-D speed map of an inclusion phantom with good image quality and variance comparable to conventional methods. Suggestions for further work are given.

  2. Shear Wave Propagation Across Filled Joints with the Effect of Interfacial Shear Strength

    NASA Astrophysics Data System (ADS)

    Li, J. C.; Liu, T. T.; Li, H. B.; Liu, Y. Q.; Liu, B.; Xia, X.

    2015-07-01

    The thin-layer interface model for filled joints is extended to analyze shear wave propagation across filled rock joints when the interfacial shear strength between the filling material and the rocks is taken into account. During the wave propagation process, the two sides of the filled joint are welded with the adjacent rocks first and slide on each other when the shear stress on the joint is greater than the interfacial shear strength. By back analysis, the relation between the shear stress and the relative tangential deformation of the filled joints is obtained from the present approach, which is shown as a cycle parallelogram. Comparison between the present approach and the existing method based on the zero-thickness interface model indicates that the present approach is efficient to analyze shear wave propagation across rock joints with slippery behavior. The calculation results show that the slippery behavior of joints is related to the interfacial failure. In addition, the interaction between the shear stress wave and the two sides of the filling joint influences not only the wave propagation process but also the dynamic response of the filled joint.

  3. Orientation of shear bands for a rigid plastic frictional material in simple shear

    NASA Astrophysics Data System (ADS)

    Papon, A.; Liu, X.; Muhlhaus, H.; Gross, L.

    2012-10-01

    The orientation of shear bands is investigated analytically and numerically for a rigid plastic frictional material in simple shear. The model is based on co-axial flow rule, incompressible deformations and a friction factor which depends on the strain history. Since we are focussing on geological timescales, the influence of elasticity is neglected. Firstly, a linear stability analysis is performed confirming Rice's 1976 assertion [The localization of plastic deformation, in Proceedings of the 14th International Congress on Theoretical and Applied Mechanics, W.T. Koiter, ed., North Holland, Amsterdam, 1976, p.207] that, in the hardening regime, bifurcation is possible at every stage. Orientation of shear bands against the less compressive principal axis lies anywhere between the Roscoe and Coulomb angles, namely between π/4+ψ/2 and π/4 + ϕ/2, where ϕ and ψ are the mobilised angles of friction and dilatancy, respectively (in our study, we assume ψ = 0). The linear stability analysis leaves open the question of which orientation will actually emerge in a boundary value problem that consider all nonlinearities. This question is addressed in a finite element study of simple shear with periodic boundary conditions in the shear direction. Our simulations show temporary inclined shear bands in the hardening regime followed by a persistent horizontal shear band. A sensitivity study with respect to geometric and constitutive parameters indicates that the height of the sample controls the orientation of the inclined shear bands. Finally, we extend our analytical and numerical studies to Cosserat plasticity. It turns out that inclined shear bands are suppressed for large values of the internal length R (narrow bands). The case of a standard continuum is gradually recovered for small R (wide bands).

  4. Laboratory Investigation on Shear Behavior of Rock Joints and a New Peak Shear Strength Criterion

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaobo; Jiang, Qinghui; Chen, Na; Wei, Wei; Feng, Xixia

    2016-09-01

    In this study, shear tests on artificial rock joints with different roughness were conducted under five normal stress levels. Test results showed that the shear strength of rock joints had a positive correlation with roughness and the applied normal stress. Observation of joint specimens after shear tests indicated that asperity damage was mainly located in the steep areas facing the shear direction. The damaged joint surfaces tend to be rough, which implies that tensile failure plays an important role in shear behavior. As a result of the anisotropic characteristic of joint roughness, two quantitative 2D roughness parameters, i.e., the revised root-mean-square of asperity angle tan-1( Z 2r) and the maximum contact coefficient C m, were proposed considering the shear direction. The proposed roughness parameters can capture the difference of roughness in forward and reverse directions along a single joint profile. The normalized tensile strength and the proposed roughness parameters were used to perform a rational derivation of peak dilatancy angle. A negative exponential-type function was found to be appropriate to model the peak dilatancy angle. Using the new model of peak dilatancy angle, we obtained a new criterion for peak shear strength of rock joints. The good agreement between test results and predicted results by the new criterion indicated that the proposed criterion is capable of estimating the peak shear strength of rock joints. Comparisons between the new criterion and published models from available literature revealed that the proposed criterion has a good accuracy for predicting the peak shear strength of joints investigated in this study.

  5. An XPS study on the valence states of arsenic in arsenian pyrite: Implications for Au deposition mechanism of the Yang-shan Carlin-type gold deposit, western Qinling belt

    NASA Astrophysics Data System (ADS)

    Liang, Jin-long; Sun, Wei-dong; Li, Yi-liang; Zhu, San-yuan; Li, He; Liu, Yu-long; Zhai, Wei

    2013-01-01

    The enrichment of gold in arsenian pyrite is usually associated closely with the enrichment of arsenic in the mineral, generally known as As1--pyrite [Fe(As, S)2]. Direct analyses of the valence state of Au in pyrite are, however, difficult due to generally low (˜ppm level) Au concentrations. By means of X-ray photoelectron spectroscopy (XPS), this study obtained reliable valence states of As in pyrite from the Yang-shan gold deposit, a giant "Carlin-type" Au deposit in the western Qinling orogen, central China. The arsenian pyrite specimens were sputtered with Ar+ beam in the vacuum chamber of an XPS to obtain pristine surfaces and to avoid As oxidation during sample preparation. Analyses before and after sputtering show that the As3+ peak are only present on surface that was once exposed to the air. In contrast, the peak of As-1 was essentially unchanged during continuous sputtering. The results indicated that As- is the predominant state on the pristine surface of arsenian pyrite; the peak of As3+ previously reported for Au-bearing arsenian pyrite was probably due to oxidation when exposed to air during sample preparation. It is unlikely that the coupled substitution of (Au+ + As3+) for 2Fe2+ takes place in the pyrite lattice. The so-called As3+-pyrite proposed by previous studies may occur in some special (oxidizing) geologic settings, but it is not observed in the Yang-shan gold deposit, and is unlikely to be important in typical orogenic or Carlin-type gold deposits, in which arsenian pyrite is a dominant Au carrier. Combining previous studies on Carlin-type Au deposits with our XPS experimental results, we suggest that the most likely state of Au in the Yang-shan Au deposit is lattice-bounded Au with or without nanoparticles (Au0).

  6. Evaluation of large aberrations using a lateral-shear interferometer having variable shear.

    PubMed

    Rimmer, M P; Wyant, J C

    1975-01-01

    A variable shear lateral shearing interferometer consisting of two holographically produced crossed diffraction gratings is used to test nonrotationally symmetric wavefronts having aberrations greater than 100 wavelengths and slope variations of more than 400 wavelengths/diameter. Comparisons are made with results of Twyman-Green interferometric tests for wavefront aberrations of up to thirty wavelengths. The results indicate that small wavefront aberrations can be measured as accurately with the lateral-shear interferometer as with the Twyman-Green interferometer and that aberrations that cannot be measured at all with a Twyman-Green interferometer can be measured to about 1% accuracy or better.

  7. Chirality-specific lift forces of helix under shear flows: Helix perpendicular to shear plane.

    PubMed

    Zhang, Qi-Yi

    2017-02-01

    Chiral objects in shear flow experience a chirality-specific lift force. Shear flows past helices in a low Reynolds number regime were studied using slender-body theory. The chirality-specific lift forces in the vorticity direction experienced by helices are dominated by a set of helix geometry parameters: helix radius, pitch length, number of turns, and helix phase angle. Its analytical formula is given. The chirality-specific forces are the physical reasons for the chiral separation of helices in shear flow. Our results are well supported by the latest experimental observations.

  8. Measurement of surface shear stress vector distribution using shear-sensitive liquid crystal coatings

    NASA Astrophysics Data System (ADS)

    Zhao, Ji-Song; Scholz, Peter; Gu, Liang-Xian

    2012-10-01

    The global wall shear stress measurement technique using shear-sensitive liquid crystal (SSLC) is extended to wind tunnel measurements. Simple and common everyday equipment is used in the measurement; in particular a tungsten-halogen light bulb provides illumination and a saturation of SSLC coating color change with time is found. Spatial wall shear stress distributions of several typical flows are obtained using this technique, including wall-jet flow, vortex flow generated by a delta wing and junction flow behind a thin cylinder, although the magnitudes are not fully calibrated. The results demonstrate that SSLC technique can be extended to wind tunnel measurements with no complicated facilities used.

  9. Shear heating in continental strike-slip shear zones:model and field examples

    NASA Astrophysics Data System (ADS)

    Leloup, Philippe Hervé; Ricard, Yannick; Battaglia, Jean; Lacassin, Robin

    1999-01-01

    A two-layer (crust and upper mantle), finite difference steady-state thermomechanical model of a long-lived (several million years) lithospheric strike-slip fault is presented, and its predictions compared with field observations from various major fault zones. In order to estimate the maximum amount of shear heating, all mechanical energy is assumed to be dissipated in heat, in ductile as well as in brittle layers. Deformation follows a friction law in the brittle layer(s), and a power-flow law in the ductile one(s). Variations of several independent parameters and their influence on the thermo-mechanical state of the fault zone and on shear heating are systematically explored. Shear heating is found to be more important in fault zones affecting an initially cold lithosphere, and increases with slip rate, friction coefficient and stiffness of materials. In extreme cases (slip rate of 10 cm yr^-1, stiff lithosphere), shear heating could lead to temperature increases close to 590 degC at the Moho, and 475 degC at 20 km depth. For more common cases, shear heating leads to smaller temperature increases, but can still explain high-grade metamorphic conditions encountered in strike-slip shear zones. However, modelled temperature conditions often fall short of those observed. This could be due to heat transport by mechanisms more efficient than conduction. Common syntectonic emplacement of granitic melts in ductile strike-slip shear zones can be explained by lower crust partial melting induced by shear heating in the upper mantle. Besides slip rate, the possibility of such melting depends mostly on the upper mantle rheology and on the fertility of the lower crust: for hard upper mantle and highly fertile lower crust, partial melting could occur at rates of 1 cm yr^-1, while in most cases it would result from the breakdown of micas for slip rates over 3 cm yr^-1. As a result of shear heating, partial melting of the upper mantle could occur in the presence of small amounts

  10. Trace element characteristics of clinozoisite pseudomorphs after lawsonite in talc-garnet-chloritoid schists from the Makbal UHP Complex, northern Kyrgyz Tian-Shan

    NASA Astrophysics Data System (ADS)

    Orozbaev, Rustam; Hirajima, Takao; Bakirov, Apas; Takasu, Akira; Maki, Kenshi; Yoshida, Kenta; Sakiev, Kadyrbek; Bakirov, Azamat; Hirata, Takafumi; Tagiri, Michio; Togonbaeva, Asel

    2015-06-01

    Polyphase mineral aggregates (PMAs) composed of clinozoisite + kyanite + quartz ± chlorite ± paragonite ± phengite have been found within garnet and in the matrix of talc-garnet-chloritoid schists from the Makbal ultrahigh-pressure complex in the northern Kyrgyz Tian-Shan. These mineral textures are interpreted as pseudomorphs after lawsonite, and we reconstructed the compositions of PMAs of clinozoisite + kyanite + quartz, consistent with lawsonite. Petrological study demonstrated that lawsonite was stable during the prograde to the UHP peak stage (P = 28-33 kbar and T = 530-580 °C) and decomposed to the PMAs during isothermal decompression around P = 16-20 kbar and T = 510-580 °C. Trace element characteristics of the clinozoisite grains in the PMAs (former lawsonite) show a flat rare earth element (REE) chondrite-normalized pattern, comparable with the typical reported REE pattern of lawsonite, although the abundance of REE varied from sample to sample. Thus, the REE content of clinozoisite in the PMAs included in garnet was likely inherited from the former lawsonite as the decomposition reaction took place isolated from the matrix. Discrete clinozoisite grains in the matrix have high light REE enrichment over heavy REE in the chondrite-normalized pattern, consistent with the typical epidote pattern. Our results indicate that the talc-garnet-chloritoid schists in the Makbal complex were buried to great depth (> 100 km) with a low geothermal gradient (< 6 °C/km) during the Early Paleozoic (480-509 Ma). Lawsonite decomposition and clinozoisite-forming reactions accompany fluid release during the isothermal decompression stage, implying that the fluids can be generated not only during subduction, but also during exhumation of ultrahigh-pressure rocks in cold subduction settings.

  11. Sedimentary record and climatic implications of recurrent deformation in the Tian Shan: Evidence from Mesozoic strata of the north Tarim, south Junggar, and Turpan basins, northwest China

    SciTech Connect

    Hendrix, M.S.; Graham, S.A.; Sobel, E.R.

    1992-01-01

    Detailed stratigraphic, sedimentologic, paleocurrent, and subsidence analyses were conducted on Mesozoic nonmarine sedimentary sections of the south Junggar, north Tarim, and Turpan basins, Xinjang Uygur Autonomous Region, northwest China. These three basins have been foreland basins throughout the Mesozoic and Cenozoic eras, as demonstrated by asymmetrically distributed basinwide sediment accumulations, foreland-style subsidence profiles, and a variety of outcrop and subsurface facies data. Mesozoic paleocurrent indicators measured in the south Junggar and north Tarim basins, as well as Mesozoic sandstone compositions from both basins, indicate that the intervening Tian Shan has existed as a positive physiographic feature partitioning the two basins throughout Mesozoic and Cenozoic time. Paleocurrent, facies, and subsurface isopach data suggest that the Turpan basin was established as a discrete feature by the Early Jurassic period. The timing and style of depositional systems within the north Tarim Mesozoic depocenter, the south Junggar Mesozoic depocenter, and the central Turpan basin are remarkably similar. Upper Triassic strata of each basin consist of alluvial conglomerate and associated braided-fluvial sandstone and siltstone which fine upward into lower through Middle Jurassic, locally organic-rich, meandering-fluvial, and lacustrine strata. Upper Jurassic braided-fluvial red beds in each basin are overlain by a distinct pulse of uppermost Jurassic alluvial conglomerate. Lower Cretaceous exposures consist of fine-grained red beds in north Tarim and Turpan and interbedded red and gray shale with local silty carbonates in south Junggar. Upper Cretaceous strata of the north Tarim and south Junggar basins are composed of alluvial conglomerate with associated braided-fluvial sandstone and siltstone. 94 refs., 17 figs.

  12. Recycling of sediments from the last 300 kyr in the modern sediment flux during transfer across the north Tian Shan alluvial piedmont.

    NASA Astrophysics Data System (ADS)

    Malatesta, Luca C.; Avouac, Jean-Philippe; Brown, Nathan; Rhodes, Edward; Prancevic, Jeffrey P.; Pan, Jiawei; Chevalier, Marie-Luce; Saint-Carlier, Dimitri; Zhang, Wenjing; Berger, Quentin

    2016-04-01

    Climatic changes can force a fast-paced increase or decrease in erosion rates and sediment production (relative to geological times) and can modify the transport rate and mixing of these sediments from source to sink. To decipher the tectonic and climatic history recorded in sedimentary sequences we need to constrain the sensitivity of sediment fluxes to climatic variations. We set here to investigate quantitatively how climatic forcing at a glacial cycle scale affects the evolution of a mountain piedmont with field work, and in which way this cyclic forcing controls the flux and nature of sediments into the basin with a sediment mixing model. We choose the depositional fold-and-thrust belt in the northern piedmont of the Northeast Tian Shan (Xinjiang, China) as a case study for its well-constrained tectonics and climate. The piedmont experienced several important cycles of incision and aggradation in the Pleistocene. New OSL dating of terrace abandonment and fan aggradation suggests a broad correlation between glacial cycles and incision-aggradation on the alluvial piedmont. As a consequence, a significant fraction of sediments produced in that period is temporarily deposited in the piedmont before a later incision phase can deliver it to the basin, illustrating a stepwise progression of coarse material towards the basin to the beat of climate cycles. We build a sediment mixing model informed by field dating and propose that the modern sediment flux entering the basin contains recycled material as old as 300 ka that can significantly skew geochemical or provenance studies if ignored.

  13. Sediment from the Last Two Glacial Periods Amalgamated and Re-Entrained in the Alluvial Piedmont of the North Tian Shan

    NASA Astrophysics Data System (ADS)

    Malatesta, L. C.; Avouac, J. P.; Brown, N.; Rhodes, E. J.; Prancevic, J.; Pan, J.; Chevalier, M. L.; Saint-Carlier, D.; Zhang, W.

    2015-12-01

    The history of the planet is recorded in its sedimentary basins where the product of mountain erosion is stored, reflecting climatic and tectonic forcing. Were the sediments and the signal they carry to be immediately deposited in a basin, paleo-reconstructions would be straightforward as the age and nature of a deposit would be a testimony of the source and transfer conditions. The sometime intricate path of clastic material along the sediment routing system complicates greatly the situation. We set here to investigate quantitatively the effect of an alluvial piedmont on the sediment flux that crosses it en route to a basin. We focus on the northern piedmont of the Tian Shan (Xinjiang, China). The piedmont is actively deformed by a fold-and-thrust system and experienced several cycles of incision and aggradation in the Pleistocene. We present new OSL dating of terrace and fan material. These data suggest that the most prominent terraces match three glacial maxima 100 kyr apart; thereby the landscape would primarily react to eccentricity cycles. As a consequence, a significant fraction of sediments produced in that period is temporarily deposited in the piedmont before a later incision phase can deliver it to the basin. The OSL ages of alluvial fan strata exposed and recently eroded by the incising river hint at two aggradation phases during the last two glacial periods. Furthermore lose sediment dated at 300 ka is found to be available along the transport route of the sediments and likely entrained during incision phases. We expect the modern sediment flux entering the basin to contain a significant amount of recycled material as old as 180 ka and a non-negligible amount of recycled material as old as 300 ka that can significantly skew geochemical or provenance studies if ignored.

  14. Holocene River Dynamics, Climate Change and Floodwater Farming in the Watersheds of the Pamir and Tien Shan Mountains of Inner Asia

    NASA Astrophysics Data System (ADS)

    Macklin, M. G.; Panyushkina, I. P.; Toonen, W. H. J.

    2014-12-01

    The Ili, Syr Dayra and Amu Dayra rivers of Inner Asia are emerging as critical areas for the development of irrigation-based agriculture in the ancient world. Following research by Russian archaeologists in the 1970s it is evident that these watersheds had flourishing riverine civilizations comparable to those in Mesopotamia and the Indus Valley. But unlike these areas where the relationship between Holocene river dynamics, climate change and floodwater farming is increasingly underpinned by radiometric dating, the alluvial archaeology of Inner Asia is significantly under researched. To address this, a major multi-disciplinary research program was begun in 2011 centred on the Talgar catchment, a south-bank tributary of the Ili river, southeast Kazakhstan. Building on archaeological excavations and surveys conducted over the past 20 years, we have undertaken one of the most detailed investigations of Holocene people-river environment interactions in Inner Asia. River development has been reconstructed over the last 20,000 years and human settlement histories from the Eneolithic to the Medieval period documented. Periods of Holocene river aggradation and high water levels in Lake Balkhash and Aral Sea correspond with cooler and wetter neoglacial episodes while river entrenchment and floodplain soil development are associated with warmer and drier conditions. Floodwater farming in the Talgar river reached its acme in the late Iron Age (400-200 cal. BC) with more than 60 settlement sites and 550 burial mounds. This corresponds to a period of reduced flood flows, river stability and glacier retreat in the Tien Shan headwaters. A new hydroclimatic-based model for the spatial and temporal dynamics of floodwater farming in the Ili, Syr Dayra and Amu Dayra watersheds is proposed, which explains the large scale expansion (down-river) and contraction (up-river) of settlements since the first use of irrigation in the Neolithic through to the late Medieval period.

  15. Mid-twentieth century increases in anthropogenic Pb, Cd and Cu in central Asia set in hemispheric perspective using Tien Shan ice core

    NASA Astrophysics Data System (ADS)

    Grigholm, B.; Mayewski, P. A.; Aizen, V.; Kreutz, K.; Wake, C. P.; Aizen, E.; Kang, S.; Maasch, K. A.; Handley, M. J.; Sneed, S. B.

    2016-04-01

    High-resolution major and trace element (Al, As, Ca, Cd, Co, Cr, Cu, Fe, Li, Mn, Na, Pb, S, Ti, and V) ice core records from Inilchek glacier (5120 m above sea level) on the northwestern margin of the Tibetan Plateau provide the first multi-decadal ice core record spanning the period 1908-1995 AD in central Tien Shan. The trace element records reveal pronounced temporal baseline trends and concentration maxima characteristic of post-1950 anthropogenic emissions. Examination of Pb, Cd and Cu concentrations, along with non-crustal calculation estimates (i.e. excess (ex) and enrichment factor (EF)), reveal that discernable anthropogenic inputs began during the 1950s and rapidly increased to the late-1970s and early 1980s, by factors up to of 5, 6 and 3, respectively, relative to a 1910-1950 means. Pb, Cd and Cu concentrations between the 1950s-1980s are reflective of large-scale Soviet industrial and agricultural development, including the growth of production and/or consumption of the non-ferrous metals, coal and phosphate fertilizers. NOAA HYSPLIT back-trajectory frequency analysis suggests pollutant sources originating primarily from southern Kazakhstan (e.g. Shymkent and Balkhash) and the Fergana Valley (located in Kazakhstan, Uzbekistan and Kyrgyzstan). Inilchek ice core Pb, Cd and Cu reveals declines during the 1980s concurrent with Soviet economic declines, however, due to the rapid industrial and agricultural growth of western China, Pb, Cd and Cu trends increase during the 1990s reflecting a transition from primarily central Asian sources to emission sources from western China (e.g. Xinjiang Province).

  16. Estimating the terrestrial N processes in subtropical mountainous forestry catchment through INCA-N: A case study in FuShan catchment, Taiwan

    NASA Astrophysics Data System (ADS)

    Lu, Meng-Chang; Huang, -Chuan, Jr.; Chang, Chung-Te; Shih, Yu-Ting; Lin, Teng-Chiu

    2016-04-01

    The riverine DIN is a crucial indicator for eutrophication in river network. The riverine DIN export in Taiwan is featured by the extremely high yield, ~3800 kg-N km-2yr-1, nearly 20-fold than the global average, showing the interesting terrestrial N process yet rarely documented. In this study we collected the DIN samples in rainwater, soil water, and stream water in a mountainous forest watershed, FuShan experimental forest watershed 1 (WS1) which is a natural broadleaf forest without human activities. Based on the intensive observations, we applied the INCA-N to simulate the riverine DIN response and thus estimate the terrestrial N processes in a global synthesis. The result showed that both discharge and DIN yield were simulated well with the average Nash-Sutcliffe efficiency coefficient of 0.83 and 0.76 , respectively. Among all N processes, N uptake, mineralization, nitrification, denitrfication, and immobilization are significantly positive correlated with soil moisture (R2>0.99), which indicates that soil moisture greatly influences N cycle processes. The average rate of mineralization and nitrification in wet years are consistent with documented values, whereas the rates in dry years are lower than the observations. Despite the high nitrification rate, the secondary forest may uptake abundant N indicating the plant uptake, which responds for removing considerable nitrate, is a controlling factor in forest ecosystem. Our simulated denitrification rate falls between the documented rates of temperate forest and agricultural area, and that may be affected by the high N-deposition in Taiwan. Simulated in-stream denitrification rate is less than 10% of the rate in soil, and is a little lower than that in temperate forest. This preliminary simulation provides an insightful guide to establish the monitoring programme and improve the understanding of N cycle in subtropical.

  17. Analysis of shear test method for composite laminates

    NASA Technical Reports Server (NTRS)

    Bergner, H. W., Jr.; Davis, J. G., Jr.; Herakovich, C. T.

    1977-01-01

    An elastic plane stress finite element analysis of the stress distributions in four flat test specimens for in-plane shear response of composite materials subjected to mechanical or thermal loads is presented. The shear test specimens investigated include: slotted coupon, cross beam, losipescu, and rail shear. Results are presented in the form of normalized shear contour plots for all three in-plane stess components. It is shown that the cross beam, losipescu, and rail shear specimens have stress distributions which are more than adequate for determining linear shear behavior of composite materials. Laminate properties, core effects, and fixture configurations are among the factors which were found to influence the stress distributions.

  18. Integration of the TDWR and LLWAS wind shear detection system

    NASA Technical Reports Server (NTRS)

    Cornman, Larry

    1991-01-01

    Operational demonstrations of a prototype TDWR/LLWAS (Terminal Doppler Weather Radar/Low Level Wind shear Alarm System) integrated wind shear detection system were conducted. The integration of wind shear detection systems is needed to provide end-users with a single, consensus source of information. A properly implemented integrated system provides wind shear warnings of a higher quality than stand-alone LLWAS or TDWR systems. The algorithmic concept used to generate the TDWR/LLWAS integrated products and several case studies are discussed, indicating the viability and potential of integrated wind shear detection systems. Implications for integrating ground and airborne wind shear detection systems are briefly examined.

  19. Shear buckling analysis of a hat-stiffened panel

    NASA Technical Reports Server (NTRS)

    Ko, William L.; Jackson, Raymond H.

    1994-01-01

    A buckling analysis was performed on a hat-stiffened panel subjected to shear loading. Both local buckling and global buckling were analyzed. The global shear buckling load was found to be several times higher than the local shear buckling load. The classical shear buckling theory for a flat plate was found to be useful in predicting the local shear buckling load of the hat-stiffened panel, and the predicted local shear buckling loads thus obtained compare favorably with the results of finite element analysis.

  20. Ultrasound velocimetry in a shear-thickening wormlike micellar solution: evidence for the coexistence of radial and vorticity shear bands.

    PubMed

    Herle, V; Manneville, S; Fischer, P

    2008-01-01

    We carried out pointwise local velocity measurements on 40 mM cetylpyridinium chloride-sodium salicylate (CPyCl-NaSal) wormlike micellar solution using high-frequency ultrasound velocimetry in a Couette shear cell. The studied wormlike solution exhibits Newtonian, shear-thinning and shear-thickening rheological behavior in a stress-controlled environment. Previous rheology, flow visualization and small-angle light/neutron scattering experiments in the shear-thickening regime of this system showed the presence of stress-driven alternating transparent and turbid rings or vorticity bands along the axis of the Couette geometry. Through local velocity measurements we observe a homogeneous flow inside the 1mm gap of the Couette cell in the shear-thinning (stress-plateau) region. Only when the solution is sheared beyond the critical shear stress (shear-thickening regime) in a stress-controlled experiment, we observe inhomogeneous flow characterized by radial or velocity gradient shear bands with a highly sheared band near the rotor and a weakly sheared band near the stator of the Couette geometry. Furthermore, fast measurements performed in the shear-thickening regime to capture the temporal evolution of local velocities indicate coexistence of both radial and vorticity shear bands. However the same measurements carried out in shear rate controlled mode of the rheometer do not show such rheological complexity.

  1. Colloidal polycrystalline monolayers under oscillatory shear

    NASA Astrophysics Data System (ADS)

    Buttinoni, Ivo; Steinacher, Mathias; Spanke, Hendrik Th.; Pokki, Juho; Bahmann, Severin; Nelson, Bradley; Foffi, Giuseppe; Isa, Lucio

    2017-01-01

    In this paper we probe the structural response to oscillatory shear deformations of polycrystalline monolayers of soft repulsive colloids with varying area fraction over a broad range of frequencies and amplitudes. The particles are confined at a fluid interface, sheared using a magnetic microdisk, and imaged through optical microscopy. The structural and mechanical response of soft materials is highly dependent on their microstructure. If crystals are well understood and deform through the creation and mobilization of specific defects, the situation is much more complex for disordered jammed materials, where identifying structural motifs defining plastically rearranging regions remains an elusive task. Our materials fall between these two classes and allow the identification of clear pathways for structural evolution. In particular, we demonstrate that large enough strains are able to fluidize the system, identifying critical strains that fulfill a local Lindemann criterion. Conversely, smaller strains lead to localized and erratic irreversible particle rearrangements due to the motion of structural defects. In this regime, oscillatory shear promotes defect annealing and leads to the growth of large crystalline domains. Numerical simulations help identify the population of rearranging particles with those exhibiting the largest deviatoric stresses and indicate that structural evolution proceeds towards the minimization of the stress stored in the system. The particles showing high deviatoric stresses are localized around grain boundaries and defects, providing a simple criterion to spot regions likely to rearrange plastically under oscillatory shear.

  2. Shear of ordinary and elongated granular mixtures

    NASA Astrophysics Data System (ADS)

    Hensley, Alexander; Kern, Matthew; Marschall, Theodore; Teitel, Stephen; Franklin, Scott

    2015-03-01

    We present an experimental and computational study of a mixture of discs and moderate aspect-ratio ellipses under two-dimensional annular planar Couette shear. Experimental particles are cut from acrylic sheet, are essentially incompressible, and constrained in the thin gap between two concentric cylinders. The annular radius of curvature is much larger than the particles, and so the experiment is quasi-2d and allows for arbitrarily large pure-shear strains. Synchronized video cameras and software identify all particles and track them as they move from the field of view of one camera to another. We are particularly interested in the global and local properties as the mixture ratio of discs to ellipses varies. Global quantities include average shear rate and distribution of particle species as functions of height, while locally we investigate the orientation of the ellipses and non-affine events that can be characterized as shear transformational zones or possess a quadrupole signature observed previously in systems of purely circular particles. Discrete Element Method simulations on mixtures of circles and spherocylinders extend the study to the dynamics of the force network and energy dissipated as the system evolves. Supported by NSF CBET #1243571 and PRF #51438-UR10.

  3. MEMS shear stress sensors for cardiovascular diagnostics.

    PubMed

    Soundararajan, Gopikrishnan; Hsiai, Tzung K; DeMaio, Lucas; Chang, Michael; Chang, Stanley

    2004-01-01

    Coronary artery disease is the leading cause of morbidity and mortality in the industrialized nations. Both biochemical and biomechanical stimuli modulate the pathogenesis of coronary artery diseases. Shear stress acting on the lumen of blood vessels intimately modulates the biological activities of vascular endothelial cells (ECs). We hereby develop microelectro mechanical system (MEMS)-based sensors at the dimension comparable to a single EC to monitor realtime shear stress in fluidic channel. Our goal is to fabricate sensors for ex vivo or in vivo shear stress measurement at Reynolds number commonly encountered in human circulation. The MEMS sensors were designed based on the previously described heat transfer principles. The polysilicon was doped with phosphorous to render the sensing element a high resistivity at 2.5 KOmega. The development of backside wire bonding enabled the application for the vascular geometry. The small dimension (80x2 mum) and the gain amplitude at 71 KHz offered an entry point to measure shear stress with high spatial and temporal resolution.

  4. Dynamics of High Pressure Reacting Shear Flows

    DTIC Science & Technology

    2015-10-02

    side recirculation zone should be present DISTRIBUTION A: Approved for public release; distribution unlimited 13 Convection Velocities x y Extract...column of pixels at each time along shear layer edge as a function of time, dark streaks represent convecting liquid structures Positive slope streaks...represent upstream traveling features Structures convect at apparent constant velocity Structures start at slow speed and gradually accelerate

  5. Aeroacoustics of subsonic turbulent shear flows

    NASA Technical Reports Server (NTRS)

    Goldstein, Marvin E.

    1987-01-01

    Sound generation in turbulent shear flows is examined. The emphasis is on simultaneous calculation of the turbulent flow along with the resulting sound generation rather than the alternative acoustic analogy approach. The first part of the paper is concerned with solid surface interaction. The second part concentrates on the sound generated by turbulence interacting with itself.

  6. Integrated Shear Stress/Temperature Micromachined Sensors

    NASA Technical Reports Server (NTRS)

    Sheplak, Mark; Cattafesta, Louis N., III; Nishida, Toshikazu

    2002-01-01

    During this project we were able to design and initiate the fabrication of an integrated Micro ElectroMechanical Systems (MEMS)-based shear stress/temperature sensor for flow control applications. A brief summary of the completed activities during this project is presented.

  7. Wind Shear Modeling for Aircraft Hazard Definition.

    DTIC Science & Technology

    1978-02-01

    11 . Lewellen , W. S., G. G. Will iamson , and N. E . Teske . “Es tima tes of the Low Level Win d Shear and Turbulence in the Vicinity of Kennedy...E. Teske . “Model Predictions of Wind and Turbines Profiles Associated wi th an Ensemble of Aircraf t Accidents ,” NASA CR-2884, July 1977. 37 2—21

  8. Shear and Pressure Driven Flow in Microchannels

    NASA Astrophysics Data System (ADS)

    Jaluria, Yogesh

    2013-11-01

    In many important circumstances, microchannel flows driven by moving surfaces that impart shear to the fluid and by an imposed pressure difference across the channel are of interest. The pressure may aid or oppose the flow due to the moving surface. One such problem is the optical fiber coating process, where the entrance of the moving fiber into a reservoir of fluid, as well as its exit, results in shear driven flow in microchannels. An additional aiding or opposing pressure head is also usually applied. The transport processes influence the resulting coating very substantially. This paper discusses the basic considerations that arise in such processes, particularly the resulting flow and the menisci that are observed at the inlet and outlet regions of the two microchannels. Visualization has been an important approach to the basic understanding of these flows. Detailed flow and thermal transport results are often obtained by numerical modeling. Another important circumstance is the pressure rise in the channel for narrowing flow domains, such as those employed in dies and extruders. It is found that, in practical problems, high pressures are generated that oppose the shear effects. Then the resulting transport is affected by both shear and pressure. On the other hand, cooling of electronic systems often employs pressure-driven microchannel flows. Comparisons between the results obtained for these different flow situations indicate many interesting features, which are discussed in terms of the basic mechanisms.

  9. Dilatancy and shear thickening of particle suspensions

    NASA Astrophysics Data System (ADS)

    Bonn, Daniel

    2013-03-01

    Shear thickening is a fascinating subject, as 99.9% of complex fluids are thinning; thickening systems thus are the ``exception to the rule'' that needs to be understood. Moreover, such tunable systems show very promising applications, e.g. to block large underground pores in oil recovery to maintain a constant oil flow by plugging water filled pores (an approach used in oil recovery by e.g. Shell), or to manufacture bulletproof vests that are comfortable to wear, but stop bullets nonetheless. We study the rheology of non-Brownian particle suspensions (notably, cornstarch) that exhibit shear thickening. Using magnetic resonance imaging (MRI), the local properties of the flow are obtained by the determination of local velocity profiles and concentrations in a Couette cell. We also perform macroscopic rheology experiments in different geometries. The results suggest that the shear thickening is a consequence of dilatancy: the system under flow attempts to dilate but instead undergoes a jamming transition, because it is confined. This proposition is confirmed by an independent measurement of the dilation of the suspension as a function of the shear rate.

  10. Piston measurement by quadriwave lateral shearing interferometry.

    PubMed

    Mousset, Soazic; Rouyer, Claude; Marre, Gabrielle; Blanchot, Nathalie; Montant, Sébastien; Wattellier, Benoit

    2006-09-01

    We present what is to our knowledge a new method for measuring the relative piston between two independent beams separated by a physical gap, typical of petawatt facilities. The feasibility of this measurement, based on quadriwave lateral shearing interferometry, has been demonstrated experimentally: piston has been measured with accuracy and sensitivity better than 50 nm.

  11. Shear flow induced unfolding of collapsed polymers.

    NASA Astrophysics Data System (ADS)

    Alexander-Katz, Alfredo; Netz, Roland

    2006-03-01

    In the process of clotting in small vessels, platelets form a plug in an injured zone only in the presence of a protein known as the von Willebrand Factor (vWF). The absence or malfunction of the vWF leads to a bleeding disorder, the so-called von Willebrand disease. It is believed that the protein is collapsed (or globular) when released into the blood flow, and that it undergoes a transition at high shear rates that allows it to bind platelets. Using hydrodynamic simulations of a simple model of the vWF in shear flow, we show that a globular polymer undergoes a globule-stretch transition at a critical shear rate. Below this threshold shear rate the polymer remains collapsed and slightly deformed, while above it the chain displays strong elongations in the direction of the flow. Finally, we discuss the relevance of our results in the case of blood flow, and compare them to the physiological values present in the body.

  12. Shear deformation in thick auxetic plates

    NASA Astrophysics Data System (ADS)

    Lim, Teik-Cheng

    2013-08-01

    This paper aims to understand the effect of auxeticity on shear deformation in thick plates. Three models for the shear correction factor of plates as a function of Poisson’s ratio were proposed: an analytical model, a cubic fit model and a modified model. Of these three, the cubic fit model exhibits the best accuracy over the entire range of Poisson’s ratio from -1 to 0.5. The extent of shear deformation is herein investigated using the example of uniformly loaded circular plates. It was found that the maximum deformation of such plates based on Mindlin theory approximates to those according to Kirchhoff theory when the Poisson’s ratio of the plate material is highly negative. When the Poisson’s ratio of the plate material is -1 and the edge of the plate is simply supported, the calculation of the maximum deflection by Mindlin theory simplifies into that by Kirchhoff theory. These results suggest that auxeticity reduces shear deformation in thick plates, permitting the use of classical plate theory for thick plates only if the plate material is highly auxetic.

  13. Shearing DNA for genomic library construction.

    PubMed

    Hengen, P N

    1997-07-01

    Methods and reagents is a unique monthly column that highlights current discussion in the newsgroup bionet.molibio.methds-reagnts, available on the internet. This month's column discusses the pros and cons of various techniques used to shear DNA for shotgun cloning. For details on how to partake in the newsgroup, see the accompanying box.

  14. 'Slings' enable neutrophil rolling at high shear.

    PubMed

    Sundd, Prithu; Gutierrez, Edgar; Koltsova, Ekaterina K; Kuwano, Yoshihiro; Fukuda, Satoru; Pospieszalska, Maria K; Groisman, Alex; Ley, Klaus

    2012-08-16

    Most leukocytes can roll along the walls of venules at low shear stress (1 dyn cm−2), but neutrophils have the ability to roll at tenfold higher shear stress in microvessels in vivo. The mechanisms involved in this shear-resistant rolling are known to involve cell flattening and pulling of long membrane tethers at the rear. Here we show that these long tethers do not retract as postulated, but instead persist and appear as 'slings' at the front of rolling cells. We demonstrate slings in a model of acute inflammation in vivo and on P-selectin in vitro, where P-selectin-glycoprotein-ligand-1 (PSGL-1) is found in discrete sticky patches whereas LFA-1 is expressed over the entire length on slings. As neutrophils roll forward, slings wrap around the rolling cells and undergo a step-wise peeling from the P-selectin substrate enabled by the failure of PSGL-1 patches under hydrodynamic forces. The 'step-wise peeling of slings' is distinct from the 'pulling of tethers' reported previously. Each sling effectively lays out a cell-autonomous adhesive substrate in front of neutrophils rolling at high shear stress during inflammation.

  15. Modeling of Turbulent Free Shear Flows

    NASA Technical Reports Server (NTRS)

    Yoder, Dennis A.; DeBonis, James R.; Georgiadis, Nicolas J.

    2013-01-01

    The modeling of turbulent free shear flows is crucial to the simulation of many aerospace applications, yet often receives less attention than the modeling of wall boundary layers. Thus, while turbulence model development in general has proceeded very slowly in the past twenty years, progress for free shear flows has been even more so. This paper highlights some of the fundamental issues in modeling free shear flows for propulsion applications, presents a review of past modeling efforts, and identifies areas where further research is needed. Among the topics discussed are differences between planar and axisymmetric flows, development versus self-similar regions, the effect of compressibility and the evolution of compressibility corrections, the effect of temperature on jets, and the significance of turbulent Prandtl and Schmidt numbers for reacting shear flows. Large eddy simulation greatly reduces the amount of empiricism in the physical modeling, but is sensitive to a number of numerical issues. This paper includes an overview of the importance of numerical scheme, mesh resolution, boundary treatment, sub-grid modeling, and filtering in conducting a successful simulation.

  16. Infrared low-level wind shear work

    NASA Technical Reports Server (NTRS)

    Adamson, Pat

    1988-01-01

    Results of field experiments for the detection of clear air disturbance and low level wind shear utilizing an infrared airborne system are given in vugraph form. The hits, misses and nuisance alarms scores are given. Information is given on the infrared spatial resolution technique. The popular index of aircraft hazard (F= WX over g - VN over AS) is developed for a remote temperature sensor.

  17. Effects of shear load on frictional healing

    NASA Astrophysics Data System (ADS)

    Ryan, K. L.; Marone, C.

    2014-12-01

    During the seismic cycle of repeated earthquake failure, faults regain strength in a process known as frictional healing. Laboratory studies have played a central role in illuminating the processes of frictional healing and fault re-strengthening. These studies have also provided the foundation for laboratory-derived friction constitutive laws, which have been used extensively to model earthquake dynamics. We conducted laboratory experiments to assess the affect of shear load on frictional healing. Frictional healing is quantified during slide-hold-slide (SHS) tests, which serve as a simple laboratory analog for the seismic cycle in which earthquakes (slide) are followed by interseismic quiescence (hold). We studied bare surfaces of Westerly granite and layers of Westerly granite gouge (thickness of 3 mm) at normal stresses from 4-25 MPa, relative humidity of 40-60%, and loading and unloading velocities of 10-300 μm/s. During the hold period of SHS tests, shear stress on the sample was partially removed to investigate the effects of shear load on frictional healing and to isolate time- and slip-dependent effects on fault healing. Preliminary results are consistent with existing works and indicate that frictional healing increases with the logarithm of hold time and decreases with normalized shear stress τ/τf during the hold. During SHS tests with hold periods of 100 seconds, healing values ranged from (0.013-0.014) for τ/τf = 1 to (0.059-0.063) for τ/τf = 0, where τ is the shear stress during the hold period and τf is the shear stress during steady frictional sliding. Experiments on bare rock surfaces and with natural and synthetic fault gouge materials are in progress. Conventional SHS tests (i.e. τ/τf = 1) are adequately described by the rate and state friction laws. However, previous experiments in granular quartz suggest that zero-stress SHS tests are not well characterized by either the Dieterich or Ruina state evolution laws. We are investigating

  18. Buoyancy Driven Shear Flows of Bubble Suspensions

    NASA Technical Reports Server (NTRS)

    Koch, D. L.; Hill, R. J.; Chellppannair, T.; Zenit, R.; Zenit, R.; Spelt, P. D. M.

    1999-01-01

    In this work the gas volume fraction and the root-mean-squared fluid velocity are measured in buoyancy driven shear flows of bubble suspensions in a tall, inclined, rectangular channel. The experiments are performed under conditions where We << 1a nd Re >> 1, for which comparisons are made with kinetic theory and numerical simulations. Here Re = gamma(a(exp 2)/nu is the Reynolds number and We = rho(gamma(exp 2))a(exp 3)/sigma is the Weber number; gamma is the shear rate, a is the bubble radius, nu is the kinematic viscosity of the liquid, rho is the density of the liquid, and sigma is the surface tension of the gas/liquid interface. Kang et al. calculated the bubble phase pressure and velocity variance of sheared bubble suspensions under conditions where the bubbles are spherical and the liquid phase velocity field can be approximated using potential flow theory, i.e. We= 0 and Re >> 1. Such conditions can be achieved in an experiment using gas bubbles, with a radius of O(0.5mm), in water. The theory requires that there be no average relative motion of the gas and liquid phases, hence the motivation for an experimental program in microgravity. The necessity of performing preliminary, Earth based experiments, however, requires performing experiments where the gas phase rises in the liquid, which significantly complicates the comparison of experiments with theory. Rather than comparing experimental results with theory for a uniform, homogeneous shear flow, experiments can be compared directly with solutions of the averaged equations of motion for bubble suspensions. This requires accounting for the significant lift force acting on the gas phase when the bubbles rise parallel to the average velocity of the sheared suspension. Shear flows can be produced in which the bubble phase pressure gradient, arising from shear induced collisions amongst the bubbles, balances a body force (centrifugal or gravitational) on the gas phase. A steady, non-uniform gas volume fraction

  19. Direct shear of olivine single crystals

    NASA Astrophysics Data System (ADS)

    Tielke, Jacob A.; Zimmerman, Mark E.; Kohlstedt, David L.

    2016-12-01

    Knowledge of the strengths of the individual dislocation slip systems in olivine is fundamental to understanding the flow behavior and the development of lattice-preferred orientation in olivine-rich rocks. The most direct measurements of the strengths of individual slip systems are from triaxial compression experiments on olivine single crystals. However, such experiments only allow for determination of flow laws for two of the four dominant slip systems in olivine. In order to measure the strengths of the (001)[100] and (100)[001] slip systems independently, we performed deformation experiments on single crystals of San Carlos olivine in a direct shear geometry. Experiments were carried out at temperatures of 1000 ° to 1300 °C, a confining pressure of 300 MPa, shear stresses of 60 to 334 MPa, and resultant shear strain rates of 7.4 × 10-6 to 2.1 × 10-3 s-1. At high-temperature (≥1200 °C) and low-stress (≤200 MPa) conditions, the strain rate of crystals oriented for direct shear on either the (001)[100] or the (100)[001] slip system follows a power law relationship with stress, whereas at lower temperatures and higher stresses, strain rate depends exponentially on stress. The flow laws derived from the mechanical data in this study are consistent with a transition from the operation of a climb-controlled dislocation mechanism during power-law creep to the operation of a glide-controlled dislocation mechanism during exponential creep. In the climb-controlled regime, crystals oriented for shear on the (001)[100] slip system are weaker than crystals orientated for shear on the (100)[001] slip system. In contrast, in the glide-controlled regime the opposite is observed. Extrapolation of flow laws determined for crystals sheared in orientations favorable for slip on these two slip systems to upper mantle conditions reveals that the (001)[100] slip system is weaker at temperatures and stresses that are typical of the asthenospheric mantle, whereas the (100

  20. Direct Shear of Olivine Single Crystals

    NASA Astrophysics Data System (ADS)

    Tielke, Jacob; Zimmerman, Mark; Kohlstedt, David

    2016-04-01

    Knowledge of the strength of individual dislocation slip systems in olivine is fundamental to understanding the flow behavior and the development of lattice-preferred orientation in olivine-rich rocks. The most direct measurements of the strengths of individual slip systems are from triaxial compression experiments on olivine single crystals. However, such experiments only allow for determination of flow laws for two of the four dominate slip systems in olivine. In order to measure the strengths of the (001)[100] and (100)[001] slip systems independently, we performed deformation experiments on single crystals of San Carlos olivine in a direct shear geometry. Experiments were carried out at temperatures of 1000° to 1300°C, a confining pressure of 300 MPa, shear stresses of 60 to 334 MPa, and resultant shear strain rates of 7.4 x 10-6 to 6.7 x 10-4 s-1. At high-temperature (≥1200°C) and low-stress (≤200 MPa) conditions, the strain rate of crystals oriented for direct shear on either the (001)[100] or the (100)[001] slip system follows a power law relationship with stress, whereas at lower temperatures and higher stresses, strain rate depends exponentially on stress. The flow laws derived from the mechanical data in this study are consistent with a transition from the operation of a climb-controlled dislocation mechanism during power-law creep to the operation of a glide-controlled dislocation mechanism during exponential creep. In the climb-controlled regime, crystals oriented for shear on the (001)[100] slip system are weaker than crystals orientated for shear on the (100)[001] slip system. In contrast, in the glide-controlled regime the opposite is observed. Extrapolation of flow laws determined for crystals sheared in orientations favorable for slip on these two slip systems to upper mantle conditions reveals that the (001)[100] slip system is weaker at temperatures and stresses that are typical of the asthenospheric mantle, whereas the (100)[001] slip

  1. Predicting km-scale shear zone formation

    NASA Astrophysics Data System (ADS)

    Gerbi, Christopher; Culshaw, Nicholas; Shulman, Deborah; Foley, Maura; Marsh, Jeffrey

    2015-04-01

    Because km-scale shear zones play a first-order role in lithospheric kinematics, accurate conceptual and numerical models of orogenic development require predicting when and where they form. Although a strain-based algorithm in the upper crust for weakening due to faulting appears to succeed (e.g., Koons et al., 2010, doi:10.1029/2009TC002463), a comparable general rule for the viscous crust remains unestablished. Here we consider two aspects of the geological argument for a similar algorithm in the viscous regime, namely (1) whether predicting km-scale shear zone development based on a single parameter (such as strain or shear heating) is reasonable; and (2) whether lithologic variability inherent in most orogenic systems precludes a simple predictive rule. A review of tectonically significant shear zones worldwide and more detailed investigations in the Central Gneiss belt of the Ontario segment of the Grenville Province reveals that most km-scale shear zones occur at lithological boundaries and involve mass transfer, but have fairly little else in common. As examples, the relatively flat-lying Twelve Mile Bay shear zone in the western Central Gneiss belt bounds the Parry Sound domain and is likely the product of both localized anatexis and later retrograde hydration with attendant metamorphism. Moderately dipping shear zones in granitoids of the Grenville Front Tectonic Zone apparently resulted from cooperation among several complementary microstructural processes, such as grain size reduction, enhanced diffusion, and a small degree of metamorphic reaction. Localization into shear zones requires the operation of some spatially restricted processes such as stress concentration, metamorphism/fluid access, textural evolution, and thermal perturbation. All of these could be due in part to strain, but not necessarily linearly related to strain. Stress concentrations, such as those that form at rheological boundaries, may be sufficient to nucleate high strain

  2. Spurious Shear in Weak Lensing with LSST

    SciTech Connect

    Chang, C.; Kahn, S.M.; Jernigan, J.G.; Peterson, J.R.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R.R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M.A.; Jee, M.J.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, P.J.; Marshall, S.; Meert, A.

    2012-09-19

    The complete 10-year survey from the Large Synoptic Survey Telescope (LSST) will image {approx} 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to r {approx} 27.5, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of algorithm-independent, additive systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing analysis techniques. We find that the main source of the errors comes from an inability to adequately characterise the atmospheric point spread function (PSF) due to its high frequency spatial variation on angular scales smaller than {approx} 10{prime} in the single short exposures, which propagates into a spurious shear correlation function at the 10{sup -4}-10{sup -3} level on these scales. With the large multi-epoch dataset that will be acquired by LSST, the stochastic errors average out, bringing the final spurious shear correlation function to a level very close to the statistical errors. Our results imply that the cosmological constraints from LSST will not be severely limited by these algorithm-independent, additive systematic effects.

  3. Shear dynamics of an inverted nematic emulsion.

    PubMed

    Tiribocchi, A; Da Re, M; Marenduzzo, D; Orlandini, E

    2016-10-04

    Here we study theoretically the dynamics of a 2D and a 3D isotropic droplet in a nematic liquid crystal under a shear flow. We find a large repertoire of possible nonequilibrium steady states as a function of the shear rate and of the anchoring of the nematic director field at the droplet surface. We first discuss homeotropic anchoring. For weak anchoring, we recover the typical behaviour of a sheared isotropic droplet in a binary fluid, which rotates, stretches and can be broken by the applied flow. For intermediate anchoring, new possibilities arise due to elastic effects in the nematic fluid. We find that in this regime the 2D droplet can tilt and move in the flow, or tumble incessantly at the centre of the channel. For sufficiently strong anchoring, finally, one or both of the topological defects which form close to the surface of the isotropic droplet in equilibrium detach from it and get dragged deep into the nematic state by the flow. In 3D, instead, the Saturn ring associated with the normal anchoring disclination line can be deformed and shifted downstream by the flow, but remains always localized in the proximity of the droplet, at least for the parameter range we explored. Tangential anchoring in 2D leads to a different dynamic response, as the boojum defects characteristic of this situation can unbind from the droplet under a weaker shear with respect to the normal anchoring case. Our results should stimulate further experiments with inverted liquid crystal emulsions under shear, as most of the predictions can be testable in principle by monitoring the evolution of liquid crystalline orientation patterns or by tracking the position and shape of the droplet over time.

  4. Creep Cavitation in Lower Crustal Shear Zones

    NASA Astrophysics Data System (ADS)

    Menegon, L. M.; Fusseis, F.; Stunitz, H. H.

    2014-12-01

    Shear zones channelize fluid flow in the Earth's crust. A number of mechanisms have been suggested to control fluid migration pathways in upper- and mid-crustal shear zones, amongst them creep cavitation, which is well-known from deforming metals and ceramics. However, little is known on deep crustal fluid migration and on how fluids are channelized and distributed in actively deforming lower crustal shear zones.This study investigates the deformation mechanisms, fluid-rock interaction, and development of porosity in a monzonite ultramylonite from Lofoten, northern Norway. The rock was deformed under lower crustal conditions (T=700-730° C, P=0.65-0.8 GPa). The ultramylonite consists of feldspathic layers and of domains of amphibole + quartz + calcite, which represent the products of hydration reactions of magmatic clinopyroxene. The average grain size in both domains is <25 μm. Microstructural observations and EBSD analysis are consistent with diffusion creep as the dominant deformation mechanism in both domains. In feldspathic layers, isolated quartz grains without a crystallographic preferred orientation occur along C'-type shear bands. All microstructures suggest that quartz precipitated in cavities. The orientation of such quartz bands overlaps with the preferred orientation of pores in the ultramylonites, as evidenced from synchrotron X-ray microtomography. Such C'-type shear bands are interpreted as high-strain cavitation bands resulting from diffusion creep deformation associated with grain boundary sliding. Mass-balance calculation indicates a 2% volume increase during the protolith-ultramylonite transformation. The volume increase is consistent with a synkinematic formation of cavities. Thus, this study presents clear evidence that high-strain cavitation bands may control deep crustal porosity and fluid flow. Nucleation of new phases in cavitation bands inhibits grain growth and enhances the activity of grain-size sensitive creep, thereby maintaining

  5. Shear alignment of a disordered lamellar mesophase.

    PubMed

    Kumaran, V; Raman, D S S

    2011-03-01

    The shear alignment of an initially disordered lamellar phase is examined using lattice Boltzmann simulations of a mesoscopic model based on a free-energy functional for the concentration modulation. For a small shear cell of width 8λ, the qualitative features of the alignment process are strongly dependent on the Schmidt number Sc=ν/D (ratio of kinematic viscosity and mass diffusion coefficient). Here, λ is the wavelength of the concentration modulation. At low Schmidt number, it is found that there is a significant initial increase in the viscosity, coinciding with the alignment of layers along the extensional axis, followed by a decrease at long times due to the alignment along the flow direction. At high Schmidt number, alignment takes place due to the breakage and reformation of layers because diffusion is slow compared to shear deformation; this results in faster alignment. The system size has a strong effect on the alignment process; perfect alignment takes place for a small systems of width 8λ and 16λ, while a larger system of width 32λ does not align completely even at long times. In the larger system, there appears to be a dynamical steady state in which the layers are not perfectly aligned--where there is a balance between the annealing of defects due to shear and the creation due to an instability of the aligned lamellar phase under shear. We observe two types of defect creation mechanisms: the buckling instability under dilation, which was reported earlier, as well as a second mechanism due to layer compression.

  6. Theory of activated-rate processes under shear with application to shear-induced aggregation of colloids.

    PubMed

    Zaccone, Alessio; Wu, Hua; Gentili, Daniele; Morbidelli, Massimo

    2009-11-01

    Using an approximation scheme within the convective diffusion (two-body Smoluchowski) equation framework, we unveil the shear-driven aggregation mechanism at the origin of structure formation in sheared colloidal systems. The theory, verified against numerics and experiments, explains the induction time followed by explosive (irreversible) rise of viscosity observed in charge-stabilized colloidal and protein systems under steady shear. The Arrhenius-type equation with shear derived here, extending Kramers' theory in the presence of shear, clearly demonstrates the important role of shear drive in activated-rate processes as they are encountered in soft condensed matter.

  7. High strength semi-active energy absorbers using shear- and mixedmode operation at high shear rates

    NASA Astrophysics Data System (ADS)

    Becnel, Andrew C.

    This body of research expands the design space of semi-active energy absorbers for shock isolation and crash safety by investigating and characterizing magnetorheological fluids (MRFs) at high shear rates ( > 25,000 1/s) under shear and mixed-mode operation. Magnetorheological energy absorbers (MREAs) work well as adaptive isolators due to their ability to quickly and controllably adjust to changes in system mass or impact speed while providing fail-safe operation. However, typical linear stroking MREAs using pressure-driven flows have been shown to exhibit reduced controllability as impact speed (shear rate) increases. The objective of this work is to develop MREAs that improve controllability at high shear rates by using pure shear and mixed shear-squeeze modes of operation, and to present the fundamental theory and models of MR fluids under these conditions. A proof of concept instrument verified that the MR effect persists in shear mode devices at shear rates corresponding to low speed impacts. This instrument, a concentric cylinder Searle cell magnetorheometer, was then used to characterize three commercially available MRFs across a wide range of shear rates, applied magnetic fields, and temperatures. Characterization results are presented both as flow curves according to established practice, and as an alternate nondimensionalized analysis based on Mason number. The Mason number plots show that, with appropriate correction coefficients for operating temperature, the varied flow curve data can be collapsed to a single master curve. This work represents the first shear mode characterization of MRFs at shear rates over 10 times greater than available with commercial rheometers, as well as the first validation of Mason number analysis to high shear rate flows in MRFs. Using the results from the magnetorheometer, a full scale rotary vane MREA was developed as part of the Lightweight Magnetorheological Energy Absorber System (LMEAS) for an SH-60 Seahawk helicopter

  8. Study of shear banding in simulated amorphous solids in the context of shear transformation zone theory

    NASA Astrophysics Data System (ADS)

    Alix-Williams, Darius; Falk, Michael L.

    2015-03-01

    We examine the general framework of the effective temperature formalism of the shear transformation zone (STZ) theory of plasticity via molecular dynamics simulation of two distinct amorphous systems - Silicon and Cu-Zr. In both systems strain localization is observed during simple shear loading. The shear bands differ in the rate of broadening and the sharpness of the interface between the flowing and jammed material. We examine both systems for scaling expected to arise between effective temperature and shear rate. For each system a local dimensionless effective temperature that quantifies structural disorder is extracted by assuming a linear relation to the local potential energy per atom. Research possible through support from National Science Foundation Grant No. 0801471.

  9. Shear horizontal guided wave modes to infer the shear stiffness of adhesive bond layers.

    PubMed

    Le Crom, Bénédicte; Castaings, Michel

    2010-04-01

    This paper presents a non-destructive, ultrasonic technique to evaluate the quality of bonds between substrates. Shear-horizontally polarized (SH) wave modes are investigated to infer the shear stiffness of bonds, which is necessarily linked to the shear resistance that is a critical parameter for bonded structures. Numerical simulations are run for selecting the most appropriate SH wave modes, i.e., with higher sensitivity to the bond than to other components, and experiments are made for generating-detecting pre-selected SH wave modes and for measuring their phase velocities. An inverse problem is finally solved, consisting of the evaluation of the shear stiffness modulus of a bond layer at different curing times between a metallic plate and a composite patch, such assembly being investigated in the context of repair of aeronautical structures.

  10. Anchoring-Induced Texture & Shear Banding of Nematic Polymers in Shear Cells

    DTIC Science & Technology

    2007-10-01

    Other simulations highlight unsteady flow -nematic structures over 3 decades of the Ericksen number, comparisons of shear banding and texture features...qualitative features of the space-time attractor, are again strongly dependent on wall anchoring conditions. Other simulations highlight unsteady flow -nematic...the correlations between texture and flow lengthscales. A remarkable feature predicted by the model simulations reported here is the contrast in shear

  11. The effect of shearing rate and slope angle on the simple shear response of marine clays

    NASA Astrophysics Data System (ADS)

    Biscontin, G.; Rutherford, C.

    2010-12-01

    The response of submarine slopes to seismic or storm loading has become an important element in the risk assessment for offshore structures and local tsunami hazard. Evaluation of submarine slope stability requires characterization of soil behavior and relies on the selection of appropriate parameter values. Although the traditional simple shear device has been used to investigate cyclic loading effects on marine clay, it does not allow for complex loading conditions which often contribute to the failure on submarine slopes. Understanding the interaction between the initial shear stress, the slope angle, and the multi-directional shaking due to earthquakes or storm loading is an important aspect to understanding the failure mechanisms of submarine slope failures. The initial static driving force on the slope is combined with the dynamic loading by storms and earthquakes to create complex loading paths. Therefore, the ability to apply complex stress or strain paths is important to fully study the shear response of marine clays on submarine slopes. A new multi-directional simple shear device developed at Texas A&M University allows loading along three independent axes, two perpendicular horizontal directions to allow any stress or strain paths in the horizontal plane, and a third in the vertical direction. This device is used to investigate the response of Gulf of Mexico marine deposits to different loading conditions. To study the effect of slope angle on the shear response of the soil, samples are subjected to a shear stress during consolidation, Kα consolidation. One-dimensional monotonic and cyclic shearing of Ko consolidated specimens is used to simulate level ground conditions, whereas sloping surfaces were simulated using Kα consolidation for both monotonic and cyclic tests. The effects of shearing rate on the soil response are investigated using strain controlled tests at varying frequencies.

  12. Molecular origins of higher harmonics in large-amplitude oscillatory shear flow: Shear stress response

    NASA Astrophysics Data System (ADS)

    Gilbert, P. H.; Giacomin, A. J.

    2016-10-01

    Recent work has focused on deepening our understanding of the molecular origins of the higher harmonics that arise in the shear stress response of polymeric liquids in large-amplitude oscillatory shear flow. For instance, these higher harmonics have been explained by just considering the orientation distribution of rigid dumbbells suspended in a Newtonian solvent. These dumbbells, when in dilute suspension, form the simplest relevant molecular model of polymer viscoelasticity, and this model specifically neglects interactions between the polymer molecules [R. B. Bird et al., "Dilute rigid dumbbell suspensions in large-amplitude oscillatory shear flow: Shear stress response," J. Chem. Phys. 140, 074904 (2014)]. In this paper, we explore these interactions by examining the Curtiss-Bird model, a kinetic molecular theory designed specifically to account for the restricted motions that arise when polymer chains are concentrated, thus interacting and specifically, entangled. We begin our comparison using a heretofore ignored explicit analytical solution [X.-J. Fan and R. B. Bird, "A kinetic theory for polymer melts. VI. Calculation of additional material functions," J. Non-Newtonian Fluid Mech. 15, 341 (1984)]. For concentrated systems, the chain motion transverse to the chain axis is more restricted than along the axis. This anisotropy is described by the link tension coefficient, ɛ, for which several special cases arise: ɛ = 0 corresponds to reptation, ɛ > 1/8 to rod-climbing, 1/5 ≤ ɛ ≤ 3/4 to reasonable predictions for shear-thinning in steady simple shear flow, and ɛ = 1 to the dilute solution without hydrodynamic interaction. In this paper, we examine the shapes of the shear stress versus shear rate loops for the special cases ɛ = (" separators=" 0 , 1 / 8 , 3 / 8 , 1 ) , and we compare these with those of rigid dumbbell and reptation model predictions.

  13. Adaptive Estimation of Intravascular Shear Rate Based on Parameter Optimization

    NASA Astrophysics Data System (ADS)

    Nitta, Naotaka; Takeda, Naoto

    2008-05-01

    The relationships between the intravascular wall shear stress, controlled by flow dynamics, and the progress of arteriosclerosis plaque have been clarified by various studies. Since the shear stress is determined by the viscosity coefficient and shear rate, both factors must be estimated accurately. In this paper, an adaptive method for improving the accuracy of quantitative shear rate estimation was investigated. First, the parameter dependence of the estimated shear rate was investigated in terms of the differential window width and the number of averaged velocity profiles based on simulation and experimental data, and then the shear rate calculation was optimized. The optimized result revealed that the proposed adaptive method of shear rate estimation was effective for improving the accuracy of shear rate calculation.

  14. 3. INTERIOR VIEW LOOKING SOUTH SHOWING PUNCH AND SHEAR MACHINE ...

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

    3. INTERIOR VIEW LOOKING SOUTH SHOWING PUNCH AND SHEAR MACHINE (manufactured by Cleveland Punch and Shear Works Company, USA) - Cambria & Indiana Railroad, Blacksmith Shop, .25 miles northwest of Colver, Colver, Cambria County, PA

  15. Thermochronology of the PoSen complex, northern Vietnam: Implications for tectonic evolution in SE Asia

    NASA Astrophysics Data System (ADS)

    Wang, Pei-Ling; Lo, Ching-Hua; Lan, Ching-Ying; Chung, Sun-Lin; Lee, Tung-Yi; Nam, Tran Ngoc; Sano, Yuji

    2011-03-01

    The PoSen complex, located closely adjacent to the southwestern margin of the Red River shear zone represents the uplifted basement of north Vietnam and may record the motion of the shear zone. However, its thermochronological history has not been fully examined yet. Here we applied U-Pb and 40Ar/ 39Ar dating methods to reveal its thermochronological history. U-Pb analysis of composite zircon grains by TIMS yielded an average age of 760 ± 25 Ma, clustering on the concordia line. Twelve SHRIMP U-Pb analyses also yielded a consistent result of 751 ± 7 Ma. Along with the geochemical features, the U-Pb dating results suggest the PoSen complex was a late Proterozoic magmatic complex, which could correspond to the Chengjiang orogeny, a widespread thermal event in southwest China. Results of 40Ar/ 39Ar dating of micas and K-feldspars were in the range of 36-30 Ma, revealing a rapid cooling and exhumation history of the PoSen complex during the late Paleogene. The time span of cooling and exhumation of the PoSen complex is slightly older than the main cooling phases of the Ailao Shan-Red River (ASRR) metamorphic massifs (28-17 Ma), but is synchronous with the early igneous activity stage in the eastern Indo-Asian collision zone of southeast China and north Vietnam. Owing to the ongoing debate about the initiation and offset of the ASRR shear zone, the tectonic force for the late Paleogene cooling of the PoSen complex is still inconclusive. The rapid exhumation of the PoSen complex could be in response to either the detachment of the Neo-Tethyan slab or a transpressional phase of continental subduction along the ASRR shear system in the eastern Indo-Asian collision zone.

  16. Shear Banding of Soft Glassy Materials in Large Amplitude Oscillatory Shear

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, Rangarajan; Fielding, Suzanne M.

    2016-10-01

    We study shear banding in soft glassy materials subject to a large amplitude oscillatory shear flow (LAOS). By numerical simulations of the widely used soft glassy rheology model, supplemented by more general physical arguments, we demonstrate strong banding over an extensive range of amplitudes and frequencies of the imposed shear rate γ ˙(t )=γ˙0cos (ω t ), even in materials that do not permit banding as their steady state response to a steadily imposed shear flow γ ˙=γ˙0=const. Highly counterintuitively, banding persists in LAOS even in the limit of zero frequency ω →0 , where one might a priori have expected a homogeneous flow response in a material that does not display banding under conditions of steadily imposed shear. We explain this finding in terms of an alternating competition within each cycle between glassy aging and flow rejuvenation. Our predictions have far-reaching implications for the flow behavior of aging yield stress fluids, suggesting a generic expectation of shear banding in flows of even arbitrarily slow time variation.

  17. Flexible Micropost Arrays for Shear Stress Measurement

    NASA Technical Reports Server (NTRS)

    Wohl, Christopher J.; Palmieri, Frank L.; Hopkins, John W.; Jackson, Allen M.; Connell, John W.; Lin, Yi; Cisotto, Alexxandra A.

    2015-01-01

    Increased fuel costs, heightened environmental protection requirements, and noise abatement continue to place drag reduction at the forefront of aerospace research priorities. Unfortunately, shortfalls still exist in the fundamental understanding of boundary-layer airflow over aerodynamic surfaces, especially regarding drag arising from skin friction. For example, there is insufficient availability of instrumentation to adequately characterize complex flows with strong pressure gradients, heat transfer, wall mass flux, three-dimensionality, separation, shock waves, and transient phenomena. One example is the acoustic liner efficacy on aircraft engine nacelle walls. Active measurement of shear stress in boundary layer airflow would enable a better understanding of how aircraft structure and flight dynamics affect skin friction. Current shear stress measurement techniques suffer from reliability, complexity, and airflow disruption, thereby compromising resultant shear stress data. The state-of-the-art for shear stress sensing uses indirect or direct measurement techniques. Indirect measurements (e.g., hot-wire, heat flux gages, oil interferometry, laser Doppler anemometry, small scale pressure drag surfaces, i.e., fences) require intricate knowledge of the studied flow, restrictive instrument arrangements, large surface areas, flow disruption, or seeding material; with smaller, higher bandwidth probes under development. Direct measurements involve strain displacement of a sensor element and require no prior knowledge of the flow. Unfortunately, conventional "floating" recessed components for direct measurements are mm to cm in size. Whispering gallery mode devices and Fiber Bragg Gratings are examples of recent additions to this type of sensor with much smaller (?m) sensor components. Direct detection techniques are often single point measurements and difficult to calibrate and implement in wind tunnel experiments. In addition, the wiring, packaging, and installation

  18. Turbulent transport across shear layers in magnetically confined plasmas

    SciTech Connect

    Nold, B.; Ramisch, M.; Manz, P.; Birkenmeier, G.; Ribeiro, T. T.; Müller, H. W.; Scott, B. D.; Fuchert, G.; Stroth, U.

    2014-10-15

    Shear layers modify the turbulence in diverse ways and do not only suppress it. A spatial-temporal investigation of gyrofluid simulations in comparison with experiments allows to identify further details of the transport process across shear layers. Blobs in and outside a shear layer merge, thereby exchange particles and heat and subsequently break up. Via this mechanism particles and heat are transported radially across shear layers. Turbulence spreading is the immanent mechanism behind this process.

  19. Band crossing in a shears band of {sup 108}Cd

    SciTech Connect

    Roy, Santosh; Datta, Pradip; Pal, S.; Chattopadhyay, S.; Bhattacharya, S.; Goswami, A.; Jain, H. C.; Joshi, P. K.; Bhowmik, R. K.; Kumar, R.; Muralithar, S.; Singh, R. P.; Madhavan, N.; Rao, P. V. Madhusudhana

    2010-05-15

    The level lifetimes have been measured for a shears band of {sup 108}Cd that exhibits band crossing. The observed level energies and B(M1) rates have been successfully described by a semiclassical geometric model based on shear mechanism. In this geometric model, the band crossing in the shears band has been described as the reopening of the angle between the blades of a shear.

  20. A microcomputer-based data acquisition and control system for the direct shear, ring shear, triaxial shear, and consolidation tests

    USGS Publications Warehouse

    Powers, Philip S.

    1983-01-01

    This report is intended to provide internal documentation for the U.S. Geological Survey laboratory's automatic data acquisition system. The operating procedures for each type of test are designed to independently lead a first-time user through the various stages of using the computer to control the test. Continuing advances in computer technology and the availability of desktop microcomputers with a wide variety of peripheral equipment at a reasonable cost can create an efficient automated geotechnical testing environment. A geotechnical testing environment is shown in figure 1. Using an automatic data acquisition system, laboratory test data from a variety of sensors can be collected, and manually or automatically recorded on a magnetic device at the same apparent time. The responses of a test can be displayed graphically on a CRT in a matter of seconds, giving the investigator an opportunity to evaluate the test data, and to make timely, informed decisions on such matters as whether to continue testing, abandon a test, or modify procedures. Data can be retrieved and results reported in tabular form, or graphic plots, suitable for publication. Thermistors, thermocouples, load cells, pressure transducers, and linear variable differential transformers are typical sensors which are incorporated in automated systems. The geotechnical tests which are most practical to automate are the long-term tests which often require readings to be recorded outside normal work hours and on weekends. Automation applications include incremental load consolidation tests, constant-rate-of-strain consolidation tests, direct shear tests, ring shear tests, and triaxial shear tests.

  1. Wind shear training applications for 91/135

    NASA Technical Reports Server (NTRS)

    Arbon, ED

    1991-01-01

    The requirement for wind shear training of all pilots has been demonstrated too often by the accident statistics of past years. Documents were developed to train airline crews on specific aircraft and to teach recognition of the meteorological conditions that are conducive to wind shear and microburst formation. A Wind Shear Training Aid program is discussed.

  2. Nonperturbative quasilinear approach to the shear dynamo problem

    SciTech Connect

    Sridhar, S.; Subramanian, Kandaswamy

    2009-12-15

    We study large-scale dynamo action due to turbulence in the presence of a linear shear flow. Our treatment is quasilinear and equivalent to the standard 'first-order smoothing approximation'. However it is non perturbative in the shear strength. We first derive an integrodifferential equation for the evolution of the mean magnetic field, by systematic use of the shearing coordinate transformation and the Galilean invariance of the linear shear flow. We show that, for nonhelical turbulence, the time evolution of the cross-shear components of the mean field do not depend on any other components excepting themselves; this is valid for any Galilean-invariant velocity field, independent of its dynamics. Hence, to all orders in the shear parameter, there is no shear-current-type effect for non helical turbulence in a linear shear flow in quasilinear theory in the limit of zero resistivity. We then develop a systematic approximation of the integro-differential equation for the case when the mean magnetic field varies slowly compared to the turbulence correlation time. For nonhelical turbulence, the resulting partial differential equations can again be solved by making a shearing coordinate transformation in Fourier space. The resulting solutions are in the form of shearing waves, labeled by the wave number in the sheared coordinates. These shearing waves can grow at early and intermediate times but are expected to decay in the long time limit.

  3. Nonperturbative quasilinear approach to the shear dynamo problem.

    PubMed

    Sridhar, S; Subramanian, Kandaswamy

    2009-12-01

    We study large-scale dynamo action due to turbulence in the presence of a linear shear flow. Our treatment is quasilinear and equivalent to the standard "first-order smoothing approximation." However it is non perturbative in the shear strength. We first derive an integrodifferential equation for the evolution of the mean magnetic field, by systematic use of the shearing coordinate transformation and the Galilean invariance of the linear shear flow. We show that, for nonhelical turbulence, the time evolution of the cross-shear components of the mean field do not depend on any other components excepting themselves; this is valid for any Galilean-invariant velocity field, independent of its dynamics. Hence, to all orders in the shear parameter, there is no shear-current-type effect for non helical turbulence in a linear shear flow in quasilinear theory in the limit of zero resistivity. We then develop a systematic approximation of the integro-differential equation for the case when the mean magnetic field varies slowly compared to the turbulence correlation time. For nonhelical turbulence, the resulting partial differential equations can again be solved by making a shearing coordinate transformation in Fourier space. The resulting solutions are in the form of shearing waves, labeled by the wave number in the sheared coordinates. These shearing waves can grow at early and intermediate times but are expected to decay in the long time limit.

  4. Wrinkling of reinforced plates subjected to shear stresses

    NASA Technical Reports Server (NTRS)

    Seydel, Edgar

    1931-01-01

    An analysis is made here of the problem of long plates with transverse stiffeners subject to shear. A typical example would be a long Wagner beam. The shear stress is calculated at which the web wrinkles and shear stress becomes a maximum. The equation is solved for both a condition of free support and rigidity of support on the edges.

  5. 49 CFR 230.27 - Maximum shearing strength of rivets.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Appurtenances Strength of Materials § 230.27 Maximum shearing strength of rivets. The maximum shearing strength... 49 Transportation 4 2011-10-01 2011-10-01 false Maximum shearing strength of rivets. 230.27 Section 230.27 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL...

  6. 49 CFR 230.27 - Maximum shearing strength of rivets.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Appurtenances Strength of Materials § 230.27 Maximum shearing strength of rivets. The maximum shearing strength... 49 Transportation 4 2014-10-01 2014-10-01 false Maximum shearing strength of rivets. 230.27 Section 230.27 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL...

  7. 49 CFR 230.28 - Higher shearing strength of rivets.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Appurtenances Strength of Materials § 230.28 Higher shearing strength of rivets. A higher shearing strength may be used for rivets when it can be shown through testing that the rivet material used is of such... 49 Transportation 4 2013-10-01 2013-10-01 false Higher shearing strength of rivets. 230.28...

  8. 49 CFR 230.27 - Maximum shearing strength of rivets.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Appurtenances Strength of Materials § 230.27 Maximum shearing strength of rivets. The maximum shearing strength... 49 Transportation 4 2010-10-01 2010-10-01 false Maximum shearing strength of rivets. 230.27 Section 230.27 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL...

  9. 49 CFR 230.28 - Higher shearing strength of rivets.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Appurtenances Strength of Materials § 230.28 Higher shearing strength of rivets. A higher shearing strength may be used for rivets when it can be shown through testing that the rivet material used is of such... 49 Transportation 4 2011-10-01 2011-10-01 false Higher shearing strength of rivets. 230.28...

  10. 49 CFR 230.27 - Maximum shearing strength of rivets.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Appurtenances Strength of Materials § 230.27 Maximum shearing strength of rivets. The maximum shearing strength... 49 Transportation 4 2013-10-01 2013-10-01 false Maximum shearing strength of rivets. 230.27 Section 230.27 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL...

  11. 49 CFR 230.27 - Maximum shearing strength of rivets.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Appurtenances Strength of Materials § 230.27 Maximum shearing strength of rivets. The maximum shearing strength... 49 Transportation 4 2012-10-01 2012-10-01 false Maximum shearing strength of rivets. 230.27 Section 230.27 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL...

  12. 49 CFR 230.28 - Higher shearing strength of rivets.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Appurtenances Strength of Materials § 230.28 Higher shearing strength of rivets. A higher shearing strength may be used for rivets when it can be shown through testing that the rivet material used is of such... 49 Transportation 4 2014-10-01 2014-10-01 false Higher shearing strength of rivets. 230.28...

  13. 49 CFR 230.28 - Higher shearing strength of rivets.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Appurtenances Strength of Materials § 230.28 Higher shearing strength of rivets. A higher shearing strength may be used for rivets when it can be shown through testing that the rivet material used is of such... 49 Transportation 4 2012-10-01 2012-10-01 false Higher shearing strength of rivets. 230.28...

  14. 49 CFR 230.28 - Higher shearing strength of rivets.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Appurtenances Strength of Materials § 230.28 Higher shearing strength of rivets. A higher shearing strength may be used for rivets when it can be shown through testing that the rivet material used is of such... 49 Transportation 4 2010-10-01 2010-10-01 false Higher shearing strength of rivets. 230.28...

  15. Shear-Sensitive Liquid Crystal Coating Method: Surface-Inclination Effects on Shear Vector Measurements

    NASA Technical Reports Server (NTRS)

    Reda, Daniel C.; Wilder, Michael C.; Nixon, David (Technical Monitor)

    1998-01-01

    The shear-sensitive liquid crystal coating (SSLCC) method is an image-based technique for both visualizing dynamic surface-flow phenomena, such as transition and separation, and for measuring the continuous shear-stress vector distribution acting on an aerodynamic surface. Under proper lighting and viewing conditions (discussed below), the coating changes color in response to an applied aerodynamic shear. This color-change response is continuous and reversible, with a response time of milliseconds, and is a function of both the shear magnitude and the shear vector orientation relative to the observer. The liquid crystal phase of matter is a weakly-ordered, viscous, non-Newtonian fluid state that exists between the nonuniform liquid phase and the ordered solid phase of certain organic compounds. Cholesteric liquid crystal compounds possess a helical molecular arrangement that selectively scatters white light, incident along the helical axis, as a three-dimensional spectrum. This property is linked to the helical pitch length, which is within the range of wavelengths in the visible spectrum. The pitch length, and hence the wavelength of the scattered light, is influenced by shear stress normal to the helical axis. This unique optical property produces a measurable color change in response to an applied shearing force. The full-surface shear stress vector measurement method, developed at NASA-Ames, is schematically illustrated. As with the visualization method, the coated test surface is illuminated from the normal direction with white light and the camera is positioned at an above-plane view angle of approximately 30 deg. Experiments have been initiated at NASA Ames to begin the process of quantifying surface-inclination (surface-curvature) effects on shear vector measurement accuracy. In preliminary experiments, surface-inclination angles theta(sub x), theta(sub y) of 0, +/-5, +/-10, and +/-15 deg were employed. In this arrangement, white-light illumination was

  16. The VviMYB80 Gene is Abnormally Expressed in Vitis vinifera L. cv. 'Zhong Shan Hong' and its Expression in Tobacco Driven by the 35S Promoter Causes Male Sterility.

    PubMed

    Zheng, Huan; Yu, Xiaojuan; Yuan, Yue; Zhang, Yaguang; Zhang, Zhen; Zhang, Jiyu; Zhang, Meng; Ji, Chenfei; Liu, Qian; Tao, Jianmin

    2016-03-01

    Anther development is a very precise and complicated process. In Arabidopsis, the AtMYB80 transcription factor regulates genes involved in pollen development and controls the timing of tapetal programmed cell death (PCD). In this study, we isolated and characterized cDNA for VviMYB80 expressed in flower buds of male-sterile Vitis vinifera L. cv. 'Zhong Shan Hong', a late-maturing cultivar derived from self-progeny of cv. 'Wink'. VviMYB80 belongs to the MYB80 subfamily and clusters with AtMYB35/TDF1 in a distinct clade. We found that in flower buds, expression of the VviMYB80 gene in cv. 'Zhong Shan Hong' sharply increased at the tetrad stage, resulting in a higher and earlier transcript level than that found in cv. 'Wink'. Expression of the VviMYB80 gene, driven by the 35S promoter, caused pleiotropic effects on the stamens, including smaller and shriveled anthers, delayed dehiscence, fewer seeds, shorter anther filaments, distorted pollen shape and a lack of cytoplasm, with the tapetum exhibiting hypertrophy in transformed tobacco. These results suggest that VviMYB80 may play an important role in stamen development and that expression of VviMYB80 driven by the 35S promoter in tobacco induces male sterility.

  17. Interfacial Shear Rheology of Coffee Samples

    NASA Astrophysics Data System (ADS)

    Läuger, Jörg; Heyer, Patrick

    2008-07-01

    Both oscillatory and rotational measurements on the film formation process and on interfacial rheological properties of the final film of coffee samples with different concentrations are presented. As higher the concentration as faster the film formation process is, whereas the concentration does not have a large effect on the visco-elastic properties of the final films. Two geometries, a biconical geometry and a Du Noüy ring have been employed. The presented results show that interfacial shear rheology allows detailed investigations on coffee films. Although with a Du Noüy ring it is possible to measure the qualitative behavior and relative differences only the biconical geometry is sensitive enough to test weak films and to reveal real absolute values for the interfacial shear rheological quantities.

  18. Implications of Orientation in Sheared Cocoa Butter

    NASA Astrophysics Data System (ADS)

    Guthrie, Sarah E.; Mazzanti, Gianfranco; Marangoni, Alejandro; Idziak, Stefan H. J.

    2004-03-01

    We will present x-ray and mechanical studies of oriented phases of cocoa butter. The structural elements of foods play an important role in determining such things as quality and shelf stability. The specific structure and properties of cocoa butter, however, are complicated due to the ability of the cocoa butter to form crystals in six polymorphic forms. Recent work has shown that the application of shear not only accelerates the transitions to more stable polymorphs, but also causes orientation of the crystallites[1]. The implications of orientation on the structures formed under conditions of shear and cooling will be described using x-ray diffraction and mechanical measurements. 1 G. Mazzanti, S. E. Guthrie, E. B. Sirota et al., Crystal Growth & Design 3 (5), 721 (2003).

  19. Flocculation of model algae under shear.

    SciTech Connect

    Pierce, Flint; Lechman, Jeremy B.

    2010-11-01

    We present results of molecular dynamics simulations of the flocculation of model algae particles under shear. We study the evolution of the cluster size distribution as well as the steady-state distribution as a function of shear rates and algae interaction parameters. Algal interactions are modeled through a DLVO-type potential, a combination of a HS colloid potential (Everaers) and a yukawa/colloid electrostatic potential. The effect of hydrodynamic interactions on aggregation is explored. Cluster strucuture is determined from the algae-algae radial distribution function as well as the structure factor. DLVO parameters including size, salt concentration, surface potential, initial volume fraction, etc. are varied to model different species of algae under a variety of environmental conditions.

  20. Fiber optic plantar pressure/shear sensor

    NASA Astrophysics Data System (ADS)

    Soetanto, William; Nguyen, Ngoc T.; Wang, Wei-Chih

    2011-04-01

    A full-scale foot pressure/shear sensor that has been developed to help diagnose the cause of ulcer formation in diabetic patients is presented. The design involves a tactile sensor array using intersecting optical fibers embedded in soft elastomer. The basic configuration incorporates a mesh that is comprised of two sets of parallel optical fiber plane; the planes are configured so the parallel rows of fiber of the top and bottom planes are perpendicular to each other. Threedimensional information is determined by measuring the loss of light from each of the waveguide to map the overall pressure distribution and the shifting of the layers relative to each other. In this paper we will present the latest development on the fiber optic plantar pressure/shear sensor which can measure normal force up from 19.09 kPa to 1000 kPa.

  1. Shear Stress Sensing with Elastic Microfence Structures

    NASA Technical Reports Server (NTRS)

    Cisotto, Alexxandra; Palmieri, Frank L.; Saini, Aditya; Lin, Yi; Thurman, Christopher S; Kim, Jinwook; Kim, Taeyang; Connell, John W.; Zhu, Yong; Gopalarathnam, Ashok; Jiang, Xiaoning; Wohl, Christopher J.

    2015-01-01

    In this work, elastic microfences were generated for the purpose of measuring shear forces acting on a wind tunnel model. The microfences were fabricated in a two part process involving laser ablation patterning to generate a template in a polymer film followed by soft lithography with a two-part silicone. Incorporation of a fluorescent dye was demonstrated as a method to enhance contrast between the sensing elements and the substrate. Sensing elements consisted of multiple microfences prepared at different orientations to enable determination of both shear force and directionality. Microfence arrays were integrated into an optical microscope with sub-micrometer resolution. Initial experiments were conducted on a flat plate wind tunnel model. Both image stabilization algorithms and digital image correlation were utilized to determine the amount of fence deflection as a result of airflow. Initial free jet experiments indicated that the microfences could be readily displaced and this displacement was recorded through the microscope.

  2. APPLYING SHEAR STRESS TO PLURIPOTENT STEM CELLS

    PubMed Central

    Wolfe, Russell P.; Guidry, Julia B.; Messina, Stephanie L.; Ahsan, Tabassum

    2016-01-01

    Summary Thorough understanding of the effects of shear stress on stem cells is critical for the rationale design of large-scale production of cell-based therapies. This is of growing importance as emerging tissue engineering and regenerative medicine applications drive the need for clinically-relevant numbers of both pluripotent stem cells (PSCs) and cells derived from PSCs. Here we describe the use of a custom parallel plate bioreactor system to impose fluid shear stress on a layer of PSCs adhered to protein-coated glass slides. This system can be useful both for basic science studies in mechanotransduction and as a surrogate model for bioreactors used in large-scale production. PMID:25762292

  3. Pulsatile Fluid Shear in Bone Remodeling

    NASA Technical Reports Server (NTRS)

    Frangos, John A.

    1997-01-01

    The objective of this investigation was to elucidate the sensitivity to transients in fluid shear stress in bone remodeling. Bone remodeling is clearly a function of the local mechanical environment which includes interstitial fluid flow. Traditionally, load-induced remodeling has been associated with low frequency (1-2 Hz) signals attributed to normal locomotion. McLeod and Rubin, however, demonstrated in vivo remodeling events associated with high frequency (15-30 Hz) loading. Likewise, other in vivo studies demonstrated that slowly applied strains did not trigger remodeling events. We therefore hypothesized that the mechanosensitive pathways which control bone maintenance and remodeling are differentially sensitive to varying rates of applied fluid shear stress.

  4. Bac clones generated from sheared dna

    SciTech Connect

    Osoegawa, Kazutoyo; Vessere, Gery M.; Shu, Chung Li; Hoskins,Roger A.; Abad, Jose P.; de Pablos, Beatriz; Villasante, Alfredo; deJong, Pieter J.

    2006-08-09

    BAC libraries generated from restriction-digested genomic DNA display representational bias and lack some sequences. To facilitate completion of genome projects, procedures have been developed to create BACs from DNA physically sheared to create fragments extending up to 200kb. The DNA fragments were repaired to create blunt ends and ligated to a new BAC vector. This approach has been tested by generating BAC libraries from Drosophila DNA, with insert lengths of 50 kb to 150 kb. The libraries lack chimeric clone problems as determined by mapping paired BAC-end sequences of one library to the D. melanogaster genome sequence. The utility of ''sheared'' libraries was demonstrated by closure of a previous clone gap and by isolation of clones from telomeric regions, which were notably absent from previous Drosophila BAC libraries.

  5. Behavior of Rapidly Sheared Bubble Suspensions

    NASA Technical Reports Server (NTRS)

    Sangani, A. S.; Kushch, V. I.; Hoffmann, M.; Nahra, H.; Koch, D. L.; Tsang, Y.

    2002-01-01

    An experiment to be carried out aboard the International Space Station is described. A suspension consisting of millimeter-sized bubbles in water containing some dissolved salt, which prevents bubbles from coalescing, will be sheared in a Couette cylindrical cell. Rotation of the outer cylinder will produce centrifugal force which will tend to accumulate the bubbles near the inner wall. The shearing will enhance collisions among bubbles creating thereby bubble phase pressure that will resist the tendency of the bubbles to accumulate near the inner wall. The bubble volume fraction and velocity profiles will be measured and compared with the theoretical predictions. Ground-based research on measurement of bubble phase properties and flow in vertical channel are described.

  6. Viscosity of Sheared Helical filament Suspensions

    NASA Astrophysics Data System (ADS)

    Sartucci, Matthew; Urbach, Jeff; Blair, Dan; Schwenger, Walter

    The viscosity of suspensions can be dramatically affected by high aspect ratio particles. Understanding these systems provides insight into key biological functions and can be manipulated for many technological applications. In this talk, the viscosity as a function of shear rate of suspensions of helical filaments is compared to that of suspensions of straight rod-like filaments. Our goal is to determine the impact of filament geometry on low volume fraction colloidal suspensions in order to identify strategies for altering viscosity with minimal volume fraction. In this research, the detached flagella of the bacteria Salmonella Typhimurium are used as a model system of helical filaments and compared to mutated straight flagella of the Salmonella. We compare rheological measurements of the suspension viscosity in response to shear flow and use a combination of the rheology and fluorescence microscopy to identify the microstructural changes responsible for the observed rheological response.

  7. Wind shear predictive detector technology study status

    NASA Technical Reports Server (NTRS)

    Gandolfi, C.

    1990-01-01

    Among the different elements to be investigated when considering the Wind Shear hazard, the Aeronautical Navigation Technical Service (STNA/3E), whose task is to participate in the development of new technologies and equipments, focused its effort on airborne and ground sensors for the detection of low-level wind shear. The first task, initiated in 1986, consists in the evaluation of three candidate techniques for forward-looking sensors: lidar, sodar, and radar. No development is presently foreseen for an infrared based air turbulence advance warning system although some flight experiments took place in the 70's. A Thomson infrared radiometer was then installed on an Air France Boeing 707 to evaluate its capability of detecting clear air turbulence. The conclusion showed that this technique was apparently able to detect cloud layers but that additional experiments were needed; on the other hand, the rarity of the phenomenon and the difficulty in operating on a commercial aircraft were also mentioned.

  8. Direct measurement of shear properties of microfibers

    SciTech Connect

    Behlow, H.; Saini, D.; Durham, L.; Simpson, J.; Skove, M. J.; Rao, A. M.; Oliveira, L.; Serkiz, S. M.

    2014-09-15

    As novel fibers with enhanced mechanical properties continue to be synthesized and developed, the ability to easily and accurately characterize these materials becomes increasingly important. Here we present a design for an inexpensive tabletop instrument to measure shear modulus (G) and other longitudinal shear properties of a micrometer-sized monofilament fiber sample, such as nonlinearities and hysteresis. This automated system applies twist to the sample and measures the resulting torque using a sensitive optical detector that tracks a torsion reference. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers, for which G is well known. Two industrially important fibers, IM7 carbon fiber and Kevlar{sup ®} 119, were also characterized with this system and were found to have G = 16.5 ± 2.1 and 2.42 ± 0.32 GPa, respectively.

  9. Direct measurement of shear properties of microfibers.

    PubMed

    Behlow, H; Saini, D; Oliveira, L; Durham, L; Simpson, J; Serkiz, S M; Skove, M J; Rao, A M

    2014-09-01

    As novel fibers with enhanced mechanical properties continue to be synthesized and developed, the ability to easily and accurately characterize these materials becomes increasingly important. Here we present a design for an inexpensive tabletop instrument to measure shear modulus (G) and other longitudinal shear properties of a micrometer-sized monofilament fiber sample, such as nonlinearities and hysteresis. This automated system applies twist to the sample and measures the resulting torque using a sensitive optical detector that tracks a torsion reference. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers, for which G is well known. Two industrially important fibers, IM7 carbon fiber and Kevlar(®) 119, were also characterized with this system and were found to have G = 16.5 ± 2.1 and 2.42 ± 0.32 GPa, respectively.

  10. Direct measurement of shear properties of microfibers

    NASA Astrophysics Data System (ADS)

    Behlow, H.; Saini, D.; Oliveira, L.; Durham, L.; Simpson, J.; Serkiz, S. M.; Skove, M. J.; Rao, A. M.

    2014-09-01

    As novel fibers with enhanced mechanical properties continue to be synthesized and developed, the ability to easily and accurately characterize these materials becomes increasingly important. Here we present a design for an inexpensive tabletop instrument to measure shear modulus (G) and other longitudinal shear properties of a micrometer-sized monofilament fiber sample, such as nonlinearities and hysteresis. This automated system applies twist to the sample and measures the resulting torque using a sensitive optical detector that tracks a torsion reference. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers, for which G is well known. Two industrially important fibers, IM7 carbon fiber and Kevlar® 119, were also characterized with this system and were found to have G = 16.5 ± 2.1 and 2.42 ± 0.32 GPa, respectively.

  11. Radiative instabilities in sheared magnetic field

    NASA Technical Reports Server (NTRS)

    Drake, J. F.; Sparks, L.; Van Hoven, G.

    1988-01-01

    The structure and growth rate of the radiative instability in a sheared magnetic field B have been calculated analytically using the Braginskii fluid equations. In a shear layer, temperature and density perturbations are linked by the propagation of sound waves parallel to the local magnetic field. As a consequence, density clumping or condensation plays an important role in driving the instability. Parallel thermal conduction localizes the mode to a narrow layer where K(parallel) is small and stabilizes short wavelengths k larger-than(c) where k(c) depends on the local radiation and conduction rates. Thermal coupling to ions also limits the width of the unstable spectrum. It is shown that a broad spectrum of modes is typically unstable in tokamak edge plasmas and it is argued that this instability is sufficiently robust to drive the large-amplitude density fluctuations often measured there.

  12. Supercritical Mixing in a Shear Coaxial Injector

    DTIC Science & Technology

    2016-07-27

    bottom, a circular hole acts as an outlet to the injected fluid, discharging into the outer chamber. The shear co-axial injector consists of inner...as to enable such an investigation. A line contour of 80% inner fluid is shown in black , indicating the intact core flow. The drop in the inner fluid...core( black line). D. Acoustic Excitation Two cases are chosen to examine the impact of acoustic excitation on the mixing of the coaxial jets. The

  13. Axisymmetric single shear element combustion instability experiment

    NASA Technical Reports Server (NTRS)

    Breisacher, Kevin J.

    1993-01-01

    The combustion stability characteristics of a combustor consisting of a single shear element and a cylindrical chamber utilizing LOX and gaseous hydrogen as propellants are presented. The combustor geometry and the resulting longitudinal mode instability are axisymmetric. Hydrogen injection temperature and pyrotechnic pulsing were used to determine stability boundaries. Mixture ratio, fuel annulus gap, and LOX post configuration were varied. Performance and stability data were obtained for chamber pressures of 300 and 1000 psia.

  14. Axisymmetric single shear element combustion instability experiment

    NASA Technical Reports Server (NTRS)

    Breisacher, Kevin J.

    1993-01-01

    The combustion stability characteristics of a combustor consisting of a single shear element and a cylindrical chamber utilizing LOX and gaseous hydrogen as propellants are presented. The combustor geometry and the resulting longitudinal mode instability are axisymmetric. Hydrogen injection temperature and pyrotechnic pulsing were used to determine stability boundaries. Mixture ratio, fuel annulus gap, and LOX post configuration were varied. Performance and stability data are presented for chamber pressures of 300 and 1000 psia.

  15. Shear Stabilization of a Solidifying Front

    NASA Technical Reports Server (NTRS)

    Davis, Stephen H.; Schulze, Timothy P.

    1996-01-01

    The manufacturing of multi-component single crystals with uniform material properties is frequently hampered by the presence of morphological instabilities during the solidification. We discuss the influence of shear flows on the linear and nonlinear stability of the solid/liquid interface during the directional solidification of binary alloys. The flows are generated by nonplanar harmonic translations of the crystal parallel to the mean interface position. Oscillations with physically realizable amplitudes and frequencies are found useful for stabilization purposes.

  16. Wind shear measuring on board an airliner

    NASA Technical Reports Server (NTRS)

    Krauspe, P.

    1984-01-01

    A measurement technique which continuously determines the wind vector on board an airliner during takeoff and landing is introduced. Its implementation is intended to deliver sufficient statistical background concerning low frequency wind changes in the atmospheric boundary layer and extended knowledge about deterministic wind shear modeling. The wind measurement scheme is described and the adaptation of apparatus onboard an A300 airbus is shown. Preliminary measurements made during level flight demonstrate the validity of the method.

  17. Standing shear waves in anisotropic viscoelastic media

    NASA Astrophysics Data System (ADS)

    Krit, T.; Golubkova, I.; Andreev, V.

    2015-10-01

    We studied standing shear waves in anisotropic resonator represented by a rectangular parallelepiped (layer) fixed without slipping between two wooden plates of finite mass. The viscoelastic layer with edges of 70 mm × 40 mm × 15 mm was made of a rubber-like polymer plastisol with rubber bands inside. The bands were placed vertical between the top and the bottom plate. Mechanical properties of the plastisol itself were carefully measured previously. It was found that plastisol shows a cubic nonlinear behavior, i.e. the stress-strain curve could be represented as: σ = μɛ + βμɛ3, where ɛ stands for shear strain and σ is an applied shear stress. The value of shear modulus μ depends on frequency and was found to be several kilopascals which is common for such soft solids. Nonlinear parameter β is frequency dependent too and varies in range from tenths to unity at 1-100 Hz frequency range, decreasing with frequency growth. Stretching the rubber bands inside the layer leads to change of elastic properties in resonator. Such effect could be noticed due to frequency response of the resonator. The numerical model of the resonator was based on finite elements method (FEM) and performed in MatLab. The resonator was cut in hundreds of right triangular prisms. Each prism was provided with viscoelastic properties of the layer except for the top prisms provided with the wooden plate properties and the prisms at the site of the rubber bands provided with the rubber properties. The boundary conditions on each prism satisfied the requirements that resonator is inseparable and all its boundaries but bottom are free. The bottom boundary was set to move horizontally with constant acceleration amplitude. It was shown numerically that the resonator shows anisotropic behavior expressed in different frequency response to oscillations applied to a bottom boundary in different directions.

  18. Buoyancy Driven Shear Flows of Bubble Suspensions

    NASA Astrophysics Data System (ADS)

    Hill, R. J.; Zenit, R.; Chellppannair, T.; Koch, D. L.; Spelt, P. D. M.; Sangani, A.

    1998-11-01

    In this work the gas volume fraction and the root-mean-squared fluid velocity are measured in buoyancy driven shear flows of bubble suspensions in a tall, inclined, rectangular channel. The experiments are performed under conditions where We << 1 and Re >> 1 , so that the bubbles are relatively undeformed and the flow is inviscid and approximately irrotational. Nitrogen is introduced through an array of capillaries at the base of a .2x.02x2 m channel filled with an aqueous electrolyte solution (0.06 molL-1 MgSO_4). The rising bubbles generate a unidirectional shear flow, where the denser suspension at the lower surface of the channel falls, while the less dense suspension at the upper surface rises. Hot-film anemometry is used to measure the resulting gas volume fraction and fluid velocity profiles. The bubble collision rate with the sensor is related to the gas volume fraction and the mean and variance of the bubble velocity using an experimentally measured collision surface area for the sensor. Bubble collisions with the sensor are identified by the characteristic slope of the hot-film anemometer signal when bubbles collide with the sensor. It is observed that the steady shear flow develops a bubble phase pressure gradient across the channel gap as the bubbles interchange momentum through direct collisions. The discrete phase presssure gradient balances the buoyancy force driving bubbles toward the upper surface resulting in a steady void fraction profile across the gap width. The strength of the shear flow is controlled by the extent of bubble segregation and by the effective viscosity of the bubble phase. The measurements are compared with solutions of the averaged equations of motion (Kang et al. 1997; Spelt and Sangani, 1998), for a range of gas volume fractions and channel inclination angles.

  19. Rotations in shear bands and polydisperse packings

    NASA Astrophysics Data System (ADS)

    Herrmann, H. J.; Astrøm, J. A.; Mahmoodi Baram, R.

    2004-12-01

    High resistance concrete or hard ceramics needs extremely dense granular packings which can only be realised when the size distribution of grains follows a powerlaw. We discuss the perfectly dense limit, namely Apollonian packings in three dimensions and show in particular the existence of space filling bearings rotating without slip and without torsion. When a dense packing like tectonic gouge is deformed, it glides internally on shear bands. The existence of rotations in shearbands is evidenced by molecular dynamics simulations of disks.

  20. Testing modified gravity with cosmic shear

    NASA Astrophysics Data System (ADS)

    Harnois-Déraps, J.; Munshi, D.; Valageas, P.; van Waerbeke, L.; Brax, P.; Coles, P.; Rizzo, L.

    2015-12-01

    We use the cosmic shear data from the Canada-France-Hawaii Telescope Lensing Survey to place constraints on f(R) and Generalized Dilaton models of modified gravity. This is highly complementary to other probes since the constraints mainly come from the non-linear scales: maximal deviations with respects to the General Relativity (GR) + Λ cold dark matter (ΛCDM) scenario occurs at k ˜ 1 h Mpc-1. At these scales, it becomes necessary to account for known degeneracies with baryon feedback and massive neutrinos, hence we place constraints jointly on these three physical effects. To achieve this, we formulate these modified gravity theories within a common tomographic parametrization, we compute their impact on the clustering properties relative to a GR universe, and propagate the observed modifications into the weak lensing ξ± quantity. Confronted against the cosmic shear data, we reject the f(R) \\lbrace |f_{R_0}| = 10^{-4}, n = 1\\rbrace model with more than 99.9 per cent confidence interval (CI) when assuming a ΛCDM dark matter only model. In the presence of baryonic feedback processes and massive neutrinos with total mass up to 0.2 eV, the model is disfavoured with at least 94 per cent CI in all different combinations studied. Constraints on the \\lbrace |f_{R_0}| = 10^{-4}, n = 2\\rbrace model are weaker, but nevertheless disfavoured with at least 89 per cent CI. We identify several specific combinations of neutrino mass, baryon feedback and f(R) or Dilaton gravity models that are excluded by the current cosmic shear data. Notably, universes with three massless neutrinos and no baryon feedback are strongly disfavoured in all modified gravity scenarios studied. These results indicate that competitive constraints may be achieved with future cosmic shear data.

  1. Modeling shear wave splitting observations from Iceland

    NASA Astrophysics Data System (ADS)

    Fu, Y. V.; Li, A.; Ito, G.; Hung, S.

    2010-12-01

    The goal of this research is to investigate the sources of shear-wave splitting in Iceland using synthetic waveforms generated from a variety of models. We employ a pseudospectral method in waveform modeling that allows 3-D heterogeneity and anisotropy. Several 1-D and 2-D models have been tested for a vertically propagating plane shear wave. For the two-layer models with horizontal symmetry axes, our results show that the apparent fast direction is towards the fast orientation in the upper layer. This experiment may explain why shear wave splitting measurements tend to be correlated with surface geology. We have also tested models with lateral anisotropic variations including a dike and a plume. The anisotropic boundary can be well resolved based on the change of fast directions and delay times. The splitting parameters near the boundary are affected by the laterally varied structure and the affected distance depends on wavelength, which is about 40 km for periods of 4-6 s and 50 km for periods of 8-10 s. We are currently performing experiments on a radial flow model from a plume stem. Synthetic shear-wave splitting measurements will be conducted from two more realistic geodynamic models. The first one is the “radial flow” model with low Rayleigh number. The pounding plume material is much thicker than the lithosphere and therefore does not strongly “feel” the lithosphere thickening away from the axis. Thus the plume spreads as fast away from the axis as it does along it. The other one is the “channel flow” model with high Rayleigh number. In this model the plume stem is much narrower and the thickness of the pounding plume material beneath the lithosphere much thinner. Thus the very low viscosity plume material is channeled more along axis by the thickening lithosphere. Combing the synthetic with the observed splitting results, we expect to determine the best geodynamic models for Iceland that fit seismic constraints.

  2. Stent implantation influence wall shear stress evolution

    NASA Astrophysics Data System (ADS)

    Bernad, S. I.; Totorean, A. F.; Bosioc, A. I.; Petre, I.; Bernad, E. S.

    2016-06-01

    Local hemodynamic factors are known affect the natural history of the restenosis critically after coronary stenting of atherosclerosis. Stent-induced flows disturbance magnitude dependent directly on the strut design. The impact of flow alterations around struts vary as the strut geometrical parameters change. Our results provide data regarding the hemodynamic parameters for the blood flow in both stenosed and stented coronary artery under physiological conditions, namely wall shear stress and pressure drop.

  3. Shear Wave Attenuation in Unconsolidated Laboratory Sediments.

    DTIC Science & Technology

    1983-06-01

    pressure) exponent of one-fourth for prediction of shear wave velocities in sands. This recommendation is based upon both in situ and laboratory...measurements. However, as we have seen from the data presented, there is consider- able scatter in the pressure exponent with values varying from...standard deviation of 0.98. Hamilton 5 4 takes % . -. ... .... . ...... .. ............ ...... 21 exception to this frequency exponent , pointing out

  4. Effect of shear on duct wall impedance.

    NASA Technical Reports Server (NTRS)

    Goldstein, M.; Rice, E.

    1973-01-01

    The solution to the equation governing the propagation of sound in a uniform shear layer is expressed in terms of parabolic cylinder functions. This result is used to develop a closed-form solution for acoustic wall impedance which accounts for both the duct liner and the presence of a boundary layer in the duct. The effective wall impedance can then be used as the boundary condition for the much simpler problem of sound propagation in uniform flow.

  5. Shear rheological characterization of motor oils

    NASA Technical Reports Server (NTRS)

    Bair, Scott; Winer, Ward O.

    1988-01-01

    Measurements of high pressure viscosity, traction coefficient, and EHD film thickness were performed on twelve commercial automotive engine oils, a reference oil, two unformulated base oils and two unformated base oil and polymer blends. An effective high shear rate inlet viscosity was calculated from film thickness and pressure viscosity coefficient. The difference between measured and effective viscosity is a function of the polymer type and concentration. Traction measurements did not discriminate mileage formulated oils from those not so designated.

  6. [Study of shear rate in modified airlift nitrifying bioreactor].

    PubMed

    Jin, Ren-cun; Zheng, Ping

    2006-06-01

    The characteristics of shear rate in an airlift nitrifying bioreactor and its influencing factors were studied. The results showed that the shear rate was different in different sections of the bioreactor. With inlet gas flowrate at 430 approximately 2700 L x h(-1), the overall shear rate was (0.702 approximately 3.13) x 10(5) s(-1), shear rate in riser was (1.07 approximately 31.3) x 10(5) s(-1) and in gas-liquid separator was (1.12 approximately 25.0) x 10(5) s(-1), respectively. It indicates that the highest shear rates prevailed in the riser part of bioreactor. The operational variables and the bioreactor configurations exerted a significant influence on the shear level of the bioreactor. When inlet gas flowrate was raised from 1300 to 2700 L x h(-1), shear rate in riser and separator ascended first and then descended subsequently. The diameter of draft tube (d) was negatively correlated with shear rate. When the draft tube with diameter of 5.5 cm was installed, the shear rates in riser, separator and overall shear rate were 85.5%, 82.3% and 80.6%, respectively less as compared with that with diameter of 4.0 cm. The number of static mixers (N) was positively correlated with the shear rate. When d was set at 4.0 cm, with N of 10 and 39, the shear rates in riser were 6.14 and 7.97 times higher respectively, than that of conventional bioreactor. The ratio of maximum local shear rate to overall shear rate was 3.68 approximately 7.66, and the homogeneity of the shear field in airlift bioreactors could be improved if d and N were set at 5.5 cm and 10 approximately 13, respectively.

  7. Intersonic shear cracks and fault ruptures

    NASA Astrophysics Data System (ADS)

    Rosakis, Ares J.

    2002-06-01

    Recent experimental observations of intersonic shear rupture events that occur in a variety of material systems have rekindled interest in the intersonic failure phenomenon. Since the early 1990s, engineers and scientists working in all length scales, from the atomistic, the structural, all the way up to the scale of the earth's deformation processes, have undertaken joint efforts to study this unexplored area of fracture mechanics. The analysis in the present article emphasizes the cooperative and complementary manner in which experimental observations and analytical and numerical developments have proceeded. The article first reviews early contributions to the theoretical literature of dynamic subsonic and intersonic fracture and highlights the significant differences between tensile and shear cracks. The article then uses direct laboratory observations as a framework for discussing the physics of intersonic shear rupture occurring in constitutively homogeneous (isotropic and anisotropic) as well as in inhomogeneous systems, all containing preferable crack paths or faults. Experiments, models, and field evidence at a variety of length scales (from the atomistic, the continuum, and up to the scale of geological ruptures) are used to discuss processes such as (1) shock wave formation, (2) large-scale frictional contact and sliding at the rupture faces, and (3) maximum attainable rupture speeds and rupture speed stability. Particular emphasis is given to geophysical field evidence and to the exploration of the possibility of intersonic fault rupture during shallow crustal earthquake events.

  8. The genesis of adiabatic shear bands

    PubMed Central

    Landau, P.; Osovski, S.; Venkert, A.; Gärtnerová, V.; Rittel, D.

    2016-01-01

    Adiabatic shear banding (ASB) is a unique dynamic failure mechanism that results in an unpredicted catastrophic failure due to a concentrated shear deformation mode. It is universally considered as a material or structural instability and as such, ASB is hardly controllable or predictable to some extent. ASB is modeled on the premise of stability analyses. The leading paradigm is that a competition between strain (rate) hardening and thermal softening determines the onset of the failure. It was recently shown that microstructural softening transformations, such as dynamic recrystallization, are responsible for adiabatic shear failure. These are dictated by the stored energy of cold work, so that energy considerations can be used to macroscopically model the failure mechanism. The initial mechanisms that lead to final failure are still unknown, as well as the ASB formation mechanism(s). Most of all - is ASB an abrupt instability or rather a gradual transition as would be dictated by microstructural evolutions? This paper reports thorough microstructural characterizations that clearly show the gradual character of the phenomenon, best described as a nucleation and growth failure mechanism, and not as an abrupt instability as previously thought. These observations are coupled to a simple numerical model that illustrates them. PMID:27849023

  9. HIERARCHICAL PROBABILISTIC INFERENCE OF COSMIC SHEAR

    SciTech Connect

    Schneider, Michael D.; Dawson, William A.; Hogg, David W.; Marshall, Philip J.; Bard, Deborah J.; Meyers, Joshua; Lang, Dustin

    2015-07-01

    Point estimators for the shearing of galaxy images induced by gravitational lensing involve a complex inverse problem in the presence of noise, pixelization, and model uncertainties. We present a probabilistic forward modeling approach to gravitational lensing inference that has the potential to mitigate the biased inferences in most common point estimators and is practical for upcoming lensing surveys. The first part of our statistical framework requires specification of a likelihood function for the pixel data in an imaging survey given parameterized models for the galaxies in the images. We derive the lensing shear posterior by marginalizing over all intrinsic galaxy properties that contribute to the pixel data (i.e., not limited to galaxy ellipticities) and learn the distributions for the intrinsic galaxy properties via hierarchical inference with a suitably flexible conditional probabilitiy distribution specification. We use importance sampling to separate the modeling of small imaging areas from the global shear inference, thereby rendering our algorithm computationally tractable for large surveys. With simple numerical examples we demonstrate the improvements in accuracy from our importance sampling approach, as well as the significance of the conditional distribution specification for the intrinsic galaxy properties when the data are generated from an unknown number of distinct galaxy populations with different morphological characteristics.

  10. Shear Stress Sensing using Elastomer Micropillar Arrays

    NASA Technical Reports Server (NTRS)

    Wohl, Christopher J.; Palmieri, Frank L.; Lin, Yi; Jackson, Allen M.; Cissoto, Alexxandra; Sheplak, Mark; Connell, John W.

    2013-01-01

    The measurement of shear stress developed as a fluid moves around a solid body is difficult to measure. Stresses at the fluid-solid interface are very small and the nature of the fluid flow is easily disturbed by introducing sensor components to the interface. To address these challenges, an array of direct and indirect techniques have been investigated with various advantages and challenges. Hot wire sensors and other indirect sensors all protrude significantly into the fluid flow. Microelectromechanical systems (MEMS) devices, although facilitating very accurate measurements, are not durable, are prone to contamination, and are difficult to implement into existing model geometries. One promising approach is the use of engineered surfaces that interact with fluid flow in a detectable manner. To this end, standard lithographic techniques have been utilized to generate elastomeric micropillar arrays of various lengths and diameters. Micropillars of controlled length and width were generated in polydimethylsiloxane (PDMS) elastomer using a soft-lithography technique. The 3D mold for micropillar replication was fabricated using laser ablative micromachining and contact lithography. Micropillar dimensions and mechanical properties were characterized and compared to shear sensing requirements. The results of this characterization as well as shear stress detection techniques will be discussed.

  11. Horizontal Shear Wave Imaging of Large Optics

    SciTech Connect

    Quarry, M J

    2007-09-05

    When complete the National Ignition Facility (NIF) will be the world's largest and most energetic laser and will be capable of achieving for the first time fusion ignition in the laboratory. Detecting optics features within the laser beamlines and sizing them at diameters of 0.1 mm to 10 mm allows timely decisions concerning refurbishment and will help with the routine operation of the system. Horizontally polarized shear waves at 10 MHz were shown to accurately detect, locate, and size features created by laser operations from 0.5 mm to 8 mm by placing sensors at the edge of the optic. The shear wave technique utilizes highly directed beams. The outer edge of an optic can be covered with shear wave transducers on four sides. Each transducer sends a pulse into the optic and any damage reflects the pulse back to the transmitter. The transducers are multiplexed, and the collected time waveforms are enveloped and replicated across the width of the element. Multiplying the data sets from four directions produces a map of reflected amplitude to the fourth power, which images the surface of the optic. Surface area can be measured directly from the image, and maximum depth was shown to be correlated to maximum amplitude of the reflected waveform.

  12. Shear sensitive silicon piezoresistive tactile sensor prototype

    NASA Astrophysics Data System (ADS)

    Wang, Lin; Beebe, David J.

    1998-09-01

    Shear sensing ability it important in many fields such as robotics, rehabilitation, teleoperation and human computer interfaces. A shear sensitive tactile sensor prototype is developed based on the principles of the piezoresistive effect in silicon, and using microfabrication technology. Analogous to the conventional silicon piezoresistive pressure sensor, piezoresistive resistors embedded in a silicon diaphragm are used to sense stress change. An additional mesa is fabricated on the top of the diaphragm and serves to transform an applied force to a stress. Both the shear and normal components of the force are resolved by measuring the resistance changes of the four resistors placed at the corners of a prism mesa. The prototype is tested both statically and dynamically when a spatial force of 0 - 300 gram is applied. Good linearity (R > 0.98) and high repeatability are observed. In this paper, the force sensing mechanism and force determination approach are described. The fabrication process is presented. The preliminary testing results are presented and discussed.

  13. Amyloid fibril networks nucleated under oscillatory shear

    NASA Astrophysics Data System (ADS)

    Batzli, Kiersten; Love, Brian

    2013-03-01

    The process of amyloid fibril formation is of interest due to the link between these self-aggregating proteins and the progression of neurodegenerative disease. More recently, research has been directed at the exploitation of self-assembly properties of amyloid proteins for use as templates for nanowires and fibrillar networks. Insulin is an ideal protein for these purposes due to the ease of aggregation, as well as the large aspect ratio and high chemical stability of the produced fibrils. Insulin in pH 2 solution quickly forms aggregates in the presence of 65 °C heat. We have investigated the effect of oscillatory shear on the nucleation and growth of amyloid fibrillar networks using rheology and TEM to characterize the mechanical properties and structure of the network respectively. We contrast networks nucleated under oscillatory shear with networks nucleated in static and agitated conditions, and discuss network properties in the context of use in templating nanostructures. We find that the structural characteristics of the formed networks, including the density of fibrils, are affected by shear during the nucleation phase of amyloid growth.

  14. Geology, mineralization, and fluid inclusion characteristics of the Kumbel oxidized W-Cu-Mo skarn and Au-W stockwork deposit in Kyrgyzstan, Tien Shan

    NASA Astrophysics Data System (ADS)

    Soloviev, Serguei G.

    2015-02-01

    The Kumbel deposit is located within a metallogenic belt of W-Mo, Cu-Mo, Au-W, and Au deposits along the Late Paleozoic active continental margin of Tien Shan. The deposit is related to a Late Carboniferous multiphase pluton, with successive intrusive phases from early olivine monzogabbro through monzonite-quartz monzonite to granodiorite and granite, with the latest monzogabbro-porphyry dikes. The deposit represents an example of a complex W-Cu-Mo-Au magmatic-hydrothermal system related to magnetite-series high-K calc-alkaline to shoshonitic igneous suite. It contains large bodies of W-Cu-Mo oxidized prograde and retrograde skarns, with abundant andradite garnet, magnetite, and especially hematite, as well as K-feldspar, molybdoscheelite, chalcopyrite, and molybdenite, with transitions to zones of intense quartz-K-feldspar (with minor andradite and hematite) veining. The skarns are cut by quartz-carbonate ± adularia ± sericite veins (locally sheeted) and stockworks bearing scheelite and minor Cu, Zn, Pb sulfides, as well as Au, Bi, Te, and As mineralization. The association of these veins with the oxidized skarns and magnetite-series intrusion is consistent with the general oxidized, intrusion-related W-Mo-Cu-Au type of deposit, with an affinity to the alkalic (silica-saturated) Cu-Au ± Mo porphyry deposits. The fluid inclusion data show the predominance of magmatic-hydrothermal aqueous chloride fluid during the formation of skarns and quartz-carbonate-scheelite-sulfide veins. The high fluid pressures (˜1,750 bars), together with their high temperature (up to 600 °C) and high salinity (˜50-60 wt% NaCl-equiv.), suggest the formation of skarns and quartz-K-feldspar-andradite-hematite veins under conditions typical of magmatic-hydrothermal transition (depth of ≥4-5 km) of intrusion-related mineralized system, possibly by exsolution of the fluids from crystallizing magma. The auriferous quartz-carbonate-scheelite-sulfide veins formed from high to moderate

  15. Atmospheric circulation patterns and geochemistry time series from ice/firn cores and snow samples of central Asian glaciers (Pamir, Tien Shan and Altai).

    NASA Astrophysics Data System (ADS)

    Aizen, E. M.; Aizen, V. B.; Joswiak, D. R.; Mayewski, P. A.

    2008-12-01

    from Aral region are for the Tien Shan; 3. Western and central Gobi and Kazakhstan dust are for the Altai. The Aral region is the source of dust aerosol for Altai also. Based on in-situ data in the western Central Asia and Altai ice core records of particle number content there is tendency on decrease of dust storms frequency from the 30th in central and eastern Asia.

  16. Interpreting date-eU correlations in zircon (U-Th)/He datasets: a case study from the Longmen Shan, China

    NASA Astrophysics Data System (ADS)

    Guenthner, William R.; Reiners, Peter W.; Tian, Yuntao

    2014-10-01

    Zircon (U-Th)/He (zircon He) dates from the Longmen Shan (LMS, on the eastern margin of the Tibetan Plateau) show a distinctive compositional dependence consistent with a strong effect of radiation damage on He diffusion. Using a new model accounting for the evolution of damage and diffusivity as a function of time and temperature, we use these data, together with constraints from other low-T thermochronometers, to interpret the Precambrian to Neogene thermal and exhumation histories of LMS basement rocks. For most samples, several features of the inverse correlations between single-grain zircon He dates and effective uranium (eU) concentrations, combined with geologic constraints, require near-surface exposure in the Precambrian, followed by burial and heating to temperatures less than about 200 °C over hundreds of Ma, and a final episode of cooling (exhumation) to surface temperatures after ∼30 Ma. In contrast, samples from the hanging wall of the Wenchuan-Maowen thrust fault in the LMS show weak or no date-eU correlations, requiring exhumation from greater depths than corresponding footwall rocks. Our modeling focuses particularly on maximum temperatures prior to Cenozoic exhumation, as well as the timing of the Cenozoic rapid cooling event, as these thermal history segments are most pertinent to debates about the timing and kinematics of recent exhumation in the LMS. Models for one sample near the front of the range in the central LMS (LME-18) require rapid Cenozoic cooling from ∼180 °C to less than ∼50 °C from ∼30-25 Ma. Model results from a more hinterland transect in the central LMS (Wenchuan) require a later rapid cooling event from ∼190 °C to the surface, beginning at ∼15 Ma. Finally, our models for samples from the southern LMS (WMF footwall transect) require rapid cooling from ∼200 °C to the surface beginning at ∼12 Ma. Taken together, these reinterpretations of previously published results lead to a cohesive burial and exhumation

  17. Holocene climate variability in arid Central Asia as revealed from high-resolution sedimentological and geochemical analyses of laminated sediments from Lake Chatyr Kol (Central Tian Shan, Kyrgyzstan)

    NASA Astrophysics Data System (ADS)

    Lauterbach, S.; Plessen, B.; Dulski, P.; Mingram, J.; Prasad, S.

    2013-12-01

    A pronounced trend from a predominantly wet climate during the early Holocene towards significantly drier conditions since the mid-Holocene, mainly attributed to the weakening of the Asian summer monsoon (ASM), is documented in numerous palaeoclimate records from the monsoon-influenced parts of Asia, e.g. the Tibetan Plateau and north- and southeastern China. In contrast, climate in the adjacent regions of mid-latitude arid Central Asia, located north and northwest of the Tibetan Plateau, is supposed to have been characterized by pronounced dry conditions during the early Holocene, wet conditions during the mid-Holocene and a rather moderate drying during the late Holocene, which is mainly attributed to the complex interplay between the mid-latitude Westerlies and the ASM. However, although mid-latitude Central Asia thus might represent a key region for the understanding of teleconnections between the ASM system and the Westerlies, knowledge about past climate development in this region is still ambiguous due to the limited number of high-resolution palaeoclimate records. Hence, new well-dated and highly resolved palaeoclimate records from this region are expected to provide important information about spatio-temporal changes in the regional interplay between Westerlies and ASM and thus aid the understanding of global climate teleconnections. As a part of the project CADY (Central Asian Climate Dynamics), aiming at reconstructing past climatic and hydrological variability in Central Asia, a sediment core of about 6.25 m length has been recovered from alpine Lake Chatyr Kol (40°36' N, 75°14' E, 3530 m a. s. l., surface area ~170 km2, maximum depth ~20 m), located in the Central Tian Shan of Kyrgyzstan. Sediment microfacies analysis on large-scale petrographic thin sections reveals continuously sub-mm scale laminated sediments throughout the record except for the uppermost ca. 60 cm. Microsedimentological characterization of these laminae, which are most probably

  18. Constraints on timing and rates of strath terrace formation on actively uplifting anticlines in the foreland of the Chinese Tien Shan.

    NASA Astrophysics Data System (ADS)

    Bufe, A.; Burbank, D. W.; Chen, J.; Liu, L.; Li, T.; Thompson, J. A.

    2014-12-01

    The formation of strath surfaces (fluvially created, sub-horizontal erosion surfaces) requires that the rate of lateral erosion outpaces the rate of incision of a river. The change from incision to strath cutting has commonly been linked to a decrease of incision rates due to shielding of the river bed by a thick sediment cover1. Straths are abandoned when the bed cover is reduced and incision resumes. A more recent study suggests that strath terrace formation might be linked to a change between a braided and a single-thread river2. Finally, several models have explored strath formation due to inherent dynamics of meandering systems3,4. In the foreland of the Tian Shan in northwest China, weakly consolidated Pliocene sand and siltstones are being actively uplifted at rates of 1 - 3 mm/y by a series of detachment anticlines. A number of elevated, several-kilometer-wide planation surfaces bear witness to a history of multiple strath cutting events by braided streams. In contrast, modern rivers incise into the uplifting folds creating 10 - 200 m deep canyons while the up- and downstream alluvial fans remain unincised. We use GIS analysis, field mapping, and OSL dating to describe incision and beveling of the folds. Our chronologic data reveal at least 2 - 3 beveling events over the last 40 ky on the Mutule fold. We find that lateral erosion of the bedrock during beveling events occurs at rates that are more than an order of magnitude higher than average incision rates. During times of incision (which can be tens of thousands of years long), lateral erosion rates need to be considerably lower in order to explain the formation of narrow canyons. Thus, our observations of scale, rate, and intermittency of strath cutting, seem difficult to reconcile with models that explain strath formation by variations of the incision rate1 or intrinsic meandering dynamics under steady forcing3,4. The critical requirement to explain our observations appears to be repeated changes in the

  19. Studying solutions at high shear rates: a dedicated microfluidics setup.

    PubMed

    Wieland, D C F; Garamus, V M; Zander, T; Krywka, C; Wang, M; Dedinaite, A; Claesson, P M; Willumeit-Römer, R

    2016-03-01

    The development of a dedicated small-angle X-ray scattering setup for the investigation of complex fluids at different controlled shear conditions is reported. The setup utilizes a microfluidics chip with a narrowing channel. As a consequence, a shear gradient is generated within the channel and the effect of shear rate on structure and interactions is mapped spatially. In a first experiment small-angle X-ray scattering is utilized to investigate highly concentrated protein solutions up to a shear rate of 300000 s(-1). These data demonstrate that equilibrium clusters of lysozyme are destabilized at high shear rates.

  20. Shear induced orientation of edible fat and chocolate crystals

    NASA Astrophysics Data System (ADS)

    Mazzanti, Gianfranco; Welch, Sarah E.; Marangoni, Alejandro G.; Sirota, Eric B.; Idziak, Stefan H. J.

    2003-03-01

    Shear-induced orientation of fat crystallites was observed during crystallization of cocoa butter, milk fat, stripped milk fat and palm oil. This universal effect was observed in systems crystallized under high shear. The minor polar components naturally present in milk fat were found to decrease the shear-induced orientation effect in this system. The competition between Brownian and shear forces, described by the Peclet number, determines the crystallite orientation. The critical radius size, from the Gibbs-Thomson equation, provides a tool to understand the effect of shear at the onset stages of crystallization.