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Understanding Himalayan erosion and the significance of the Nicobar Fan
McNeill, Lisa C.,Dugan, Brandon,Backman, Jan,Pickering, Kevin T.,Pouderoux, Hugo F.A.,Henstock, Timothy J.,Petronotis, Katerina E.,Carter, Andrew,Chemale Jr., Farid,Milliken Jr., Kitty L.,Kutterolf Jr Elsevier 2017 Earth and planetary science letters Vol.475 No.-
<P><B>Abstract</B></P> <P>A holistic view of the Bengal–Nicobar Fan system requires sampling the full sedimentary section of the Nicobar Fan, which was achieved for the first time by International Ocean Discovery Program (IODP) Expedition 362 west of North Sumatra. We identified a distinct rise in sediment accumulation rate (SAR) beginning ∼9.5 Ma and reaching 250–350 m/Myr in the 9.5–2 Ma interval, which equal or far exceed rates on the Bengal Fan at similar latitudes. This marked rise in SAR and a constant Himalayan-derived provenance necessitates a major restructuring of sediment routing in the Bengal–Nicobar submarine fan. This coincides with the inversion of the Eastern Himalayan Shillong Plateau and encroachment of the west-propagating Indo–Burmese wedge, which reduced continental accommodation space and increased sediment supply directly to the fan. Our results challenge a commonly held view that changes in sediment flux seen in the Bengal–Nicobar submarine fan were caused by discrete tectonic or climatic events acting on the Himalayan–Tibetan Plateau. Instead, an interplay of tectonic and climatic processes caused the fan system to develop by punctuated changes rather than gradual progradation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Sediment accumulation rates in Nicobar Fan abruptly increase 9.5 Ma. </LI> <LI> Increased sediment flux to eastern Indian Ocean and restructuring of sediment routing. </LI> <LI> Nicobar Fan holds significant record of Indian Ocean sedimentation in late Neogene. </LI> <LI> Shillong Plateau and Indo–Burmese wedge uplift drive sediment south in late Miocene. </LI> </UL> </P>
Active-Sensing Lamb Wave Propagations for Damage Identification in Honeycomb Aluminum Panels
Flynn, Eric B.,Swartz, R.Andrew,Backman, Daniel E.,Park, Gyu-Hae,Farrar, Charles R. The Korean Society for Nondestructive Testing 2009 한국비파괴검사학회지 Vol.29 No.4
This paper presents a novel approach for Lamb wave based structural health monitoring(SHM) in honeycomb aluminum panels. In this study, a suite of three signal processing algorithms are employed to improve the damage detection capability. The signal processing algorithms used include wavelet attenuation, correlation coefficients of power density spectra, and triangulation of reflected waves. Piezoelectric transducers are utilized as both sensors and actuators for Lamb wave propagation. These SHM algorithms are built into a MatLab interface that integrates and automates the hardware and software operations and displays the results for each algorithm to the analyst for side by side comparison. The effectiveness of each of these signal processing algorithms for SHM in honeycomb aluminum panels under a variety of damage conditions is then demonstrated.
Active-Sensing Lamb Wave Propagations for Damage Identification in Honeycomb Aluminum Panels
Eric B. Flynn,R. Andrew Swartz,Daniel E. Backman,Gyuhae Park,Charles R. Farrar 한국비파괴검사학회 2009 한국비파괴검사학회지 Vol.29 No.4
This paper presents a novel approach for Lamb wave based structural health monitoring(SHM) in honeycomb aluminum panels. In this study, a suite of three signal processing algorithms are employed to improve the damage detection capability. The signal processing algorithms used include wavelet attenuation, correlation coefficients of power density spectra, and triangulation of reflected waves. Piezoelectric transducers are utilized as both sensors and actuators for Lamb wave propagation. These SHM algorithms are built into a MatLab interface that integrates and automates the hardware and software operations and displays the results for each algorithm to the analyst for side by side comparison. The effectiveness of each of these signal processing algorithms for SHM in honeycomb aluminum panels under a variety of damage conditions is then demonstrated.
A Cenozoic record of the equatorial Pacific carbonate compensation depth
P채like, Heiko,Lyle, Mitchell W.,Nishi, Hiroshi,Raffi, Isabella,Ridgwell, Andy,Gamage, Kusali,Klaus, Adam,Acton, Gary,Anderson, Louise,Backman, Jan,Baldauf, Jack,Beltran, Catherine,Bohaty, Steven M.,Bo Nature Publishing Group, a division of Macmillan P 2012 Nature Vol.488 No.7413
Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0??3.5??kilometres during the early Cenozoic (approximately 55??million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.
Centrifugal compressor tip clearance and impeller flow
Ahti Jaatinen-Värri,Jonna Tiainen,Teemu Turunen-Saaresti,Aki Grönman,Alireza Ameli,ABRAHAM ENGEDA,Jari Backman 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.11
Compressors consume a considerable portion of the electricity used in the industrial sector. Hence, improvements in compressor efficiency lead to energy savings and reduce environmental impacts. The efficiency of an unshrouded centrifugal compressor suffers from leakage flow over the blade tips. The effect of tip leakage flow on the passage flow differs between the full and splitter blade passages. In this study, the differences in the flow fields between the full and splitter blade passages were studied numerically in detail. An industrial high-speed compressor with a design pressure ratio of 1.78 was modelled. Numerical studies were conducted with six different tip clearances and three different diffuser widths. The results show that increasing tip clearance considerably increases the reversed flow into the impeller with an unpinched diffuser. The reversed flow then partly mixes into the flow in the same blade passage it entered the impeller and the rest migrates over the blade, mixing with the tip clearance flow. Furthermore, as the reversed and clearance flow mix into the wake, the wake is weakened. As pinch reduces both the reversed flow and clearance flow, the passage wakes are stronger with pinches. However, the pinch is beneficial as the losses at the impeller outlet decrease.
Release of mineral-bound water prior to subduction tied to shallow seismogenic slip off Sumatra
Hupers, Andre,Torres, Marta E.,Owari, Satoko,McNeill, Lisa C.,Dugan, Brandon,Henstock, Timothy J.,Milliken, Kitty L.,Petronotis, Katerina E.,Backman, Jan,Bourlange, Sylvain,Chemale Jr., Farid,Chen, We American Association for the Advancement of Scienc 2017 Science Vol.356 No.6340
<P>Plate-boundary fault rupture during the 2004 Sumatra-Andaman subduction earthquake extended closer to the trench than expected, increasing earthquake and tsunami size. International Ocean Discovery Program Expedition 362 sampled incoming sediments offshore northern Sumatra, revealing recent release of fresh water within the deep sediments. Thermal modeling links this freshening to amorphous silica dehydration driven by rapid burial-induced temperature increases in the past 9 million years. Complete dehydration of silicates is expected before plate subduction, contrasting with prevailing models for subduction seismogenesis calling for fluid production during subduction. Shallow slip offshore Sumatra appears driven by diagenetic strengthening of deeply buried fault-forming sediments, contrasting with weakening proposed for the shallow Tohoku-Oki 2011 rupture, but our results are applicable to other thickly sedimented subduction zones including those with limited earthquake records.</P>