scholarly journals The Kuroshio flowing over seamounts and associated submesoscale flows drive 100-km-wide 100-1000-fold enhancement of turbulence

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Takeyoshi Nagai ◽  
Daisuke Hasegawa ◽  
Eisuke Tsutsumi ◽  
Hirohiko Nakamura ◽  
Ayako Nishina ◽  
...  
Keyword(s):  
Near Field ◽  
Mixing Processes ◽  
Phytoplankton Primary Production ◽  
Topographic Features ◽  
Close Proximity ◽  
Tokara Strait ◽  
Generation Mechanisms ◽  
Turbulence Generation ◽  
The Kuroshio

AbstractAlthough previous studies reported that currents over topographic features, such as seamounts and ridges, cause strong turbulence in close proximity, it has been elusive how far intense turbulence spreads toward the downstream. Here, we conducted a series of intensive in-situ turbulence observations using a state-of-the-art tow-yo microstructure profiler in the Kuroshio flowing over the seamounts of the Tokara Strait, south of Kyusyu Japan, in November 2017, June 2018, and November 2019, and employed a high-resolution numerical model to elucidate the turbulence generation mechanisms. We find that the Kuroshio flowing over seamounts generates streaks of negative potential vorticity and near-inertial waves. With these long-persisting mechanisms in addition to other near-field mixing processes, intense mixing hotspots are formed over a 100-km scale with the elevated energy dissipation by 100- to 1000-fold. The observed turbulence could supply nutrients to sunlit layers, promoting phytoplankton primary production and CO2 uptake.

scholarly journals Oceanic Eddy Characteristics and Generation Mechanisms in the Kuroshio Extension Region

2018 ◽  
Vol 123 (11) ◽  
pp. 8548-8567 ◽  
Author(s):  
Jinlin Ji ◽  
Changming Dong ◽  
Biao Zhang ◽  
Yu Liu ◽  
Bin Zou ◽  
...  
Keyword(s):  
Kuroshio Extension ◽  
Eddy Characteristics ◽  
Oceanic Eddy ◽  
Generation Mechanisms ◽  
The Kuroshio ◽  
Kuroshio Extension Region

Emissions and Noise Pollution Diagnosis of a Turbogas Power Plant During Commissioning Service

2010 ◽  
Author(s):  
Norberto Pe´rez Rodri´guez ◽  
Erik Rosado Tamariz ◽  
Rafael Garci´a Illescas
Keyword(s):  
Power Plant ◽  
Cooling System ◽  
Near Field ◽  
Noise Pollution ◽  
Point Of View ◽  
International Standards ◽  
Partial Load ◽  
The City ◽  
Permissible Deviation

This work is focused on the diagnosis of behavior, from the point of view of control emissions and noise level, of a power Turbogas plant during the process of commissioning, to guarantee that its operation complies with national and international standards. The environmental diagnosis of the power plant was developed as part of the performance evaluation of the unit. The conditions of the unit evaluation include operation at base load and partial load, as well as time periods for load changes. The evaluated power plant consists of an aeroderivative gas turbine installed in a simple cycle, operating with a cooling system (chiller) installed in the urban zone of Mexico City. Therefore, it should comply with the legislation and regulations of the city concerning air pollution and allowed noise, besides the international standards established by the manufacturer. The study includes emissions measurements using a Continuous Emissions Monitoring System installed in-situ, previously calibrated and checked during and after the test which was found inside the permissible deviation of 3%. Measurements were recorded at intervals of 5 minutes during test periods of 110 minutes for each load and 45 minutes for load changes. On the other hand, noise pressure evaluation was carried out in near field as well as far field produced by the power plant during operation. Measurements were carried out by using precision instruments installed specifically for it. A temporary system for obtaining data was used to monitoring the environmental conditions every 30 seconds. It was possible to verify that the turbogenerator complies with all noise levels and contaminant emissions requirements and regulations according to the limits established by the manufacturer and national and international standards.

Evaluating the temperature dependence of bedrock hillslope erosion in the Mont Blanc massif using in situ cosmogenic 3He-10Be-14C

2021 ◽  
Author(s):  
Donovan P. Dennis ◽  
Dirk Scherler ◽  
Samuel Niedermann ◽  
Kristina Hippe ◽  
Hella Wittmann ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Erosion Rates ◽  
Close Proximity ◽  
Order Of Magnitude ◽  
Stochastic Events ◽  
Exposure Ages ◽  
Alpine Environments ◽  
Magnitude Difference ◽  
Mont Blanc Massif

<p>The erosion of cold bedrock hillslopes in alpine environments depends not only on rates of frost weathering and accumulated rock damage, but additionally on the removal of the weathered material from the bedrock surface. In the Mont Blanc massif, steep bedrock faces with exposure ages sometimes much older than 50,000 years sit in close proximity to actively-eroding rockwalls, suggesting a more complex relationship between temperature and erosion rates than encompassed by the proposed “frost-cracking window.” Stochastic events like rockfalls and rock avalanches, despite their rarity, contribute a non-trivial proportion of the total sediment budget in alpine permafrost regions, adding to the contribution from background “steady-state” erosion. Employing a methodology based on the combination of in-situ cosmogenic nuclides <sup>3</sup>He -<sup>10</sup>Be-<sup>14</sup>C, we test the temperature-dependence of high-alpine erosion while taking into account erosional stochasticity.</p><p>From cosmogenic <sup>10</sup>Be concentrations of amalgamated samples collected on the Aiguille du Midi (3842 m a.s.l.) in the Mont Blanc massif, we find an order of magnitude difference in erosion rate across the peak’s surface. Our preliminary measured erosion rates, ranging between appx. 0.03 mm yr<sup>-1</sup> and 1.0 mm yr<sup>-1</sup>, correlate neither with modern temperature measurements from borehole thermistors, nor with our current estimates of bedrock cosmogenic <sup>3</sup>He-derived paleotemperatures. The corresponding cosmogenic <sup>14</sup>C/<sup>10</sup>Be ratios (between 1.70 and 4.0) for these erosion rates indicate that our measurements are not biased by recent stochastic rockfall events. Our current results therefore suggest that on geomorphic timescales, bedrock hillslope erosion rates are not set solely by rates of frost-cracking, but rather by the combined effects of frost-cracking and permafrost thaw-induced rockfalls. These insights are relevant both for short-term monitoring of alpine permafrost and associated geohazards under a warming climate, as well as studies of proposed “buzzsaws” operating on glacial-interglacial timescales.</p>

Study on the Properties of Aerodynamic Reference Sound Sources

2019 ◽  
Vol 105 (6) ◽  
pp. 960-969 ◽  
Author(s):  
Spyros Brezas ◽  
Volker Wittstock
Keyword(s):  
Ambient Temperature ◽  
Atmospheric Pressure ◽  
Rotation Speed ◽  
Near Field ◽  
Sound Power ◽  
Sound Sources ◽  
The Core ◽  
In Situ Conditions ◽  
Calibration Condition

Towards the establishment of traceability in sound power in airborne sound, the present study focuses on the dissemination procedure. Aerodynamic reference sound sources were studied as potential transfer standards. Initially, the sources were examined in the up-to-present requirements. The core of the study is the correction required for the transition from calibration to in situ conditions. The influence of atmospheric pressure, ambient temperature and fan rotation speed was investigated and the corresponding correction was determined. A comparison to an existing correction was also performed. Near field effects were another part of the study. The related uncertainty was estimated in a transparent approach. The dependency of the uncertainty on the in situ and calibration condition values is also presented.

scholarly journals A comparison between the two lobes of comet 67P/Churyumov–Gerasimenko based on D/H ratios in H2O measured with the Rosetta/ROSINA DFMS

2019 ◽  
Vol 489 (4) ◽  
pp. 4734-4740 ◽  
Author(s):  
Isaac R H G Schroeder ◽  
Kathrin Altwegg ◽  
Hans Balsiger ◽  
Jean-Jacques Berthelier ◽  
Michael R Combi ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
European Space Agency ◽  
Cometary Nucleus ◽  
The Other ◽  
Appreciable Difference ◽  
Space Agency ◽  
Close Proximity ◽  
Double Focusing ◽  
Comet 67P

ABSTRACT The nucleus of the Jupiter-family comet 67P/Churyumov–Gerasimenko was discovered to be bi-lobate in shape when the European Space Agency spacecraft Rosetta first approached it in 2014 July. The bi-lobate structure of the cometary nucleus has led to much discussion regarding the possible manner of its formation and on how the composition of each lobe might compare with that of the other. During its two-year-long mission from 2014 to 2016, Rosetta remained in close proximity to 67P/Churyumov–Gerasimenko, studying its coma and nucleus in situ. Based on lobe-specific measurements of HDO and H2O performed with the ROSINA Double Focusing Mass Spectrometer (DFMS) on board Rosetta, the deuterium-to-hydrogen (D/H) ratios in water from the two lobes can be compared. No appreciable difference was observed, suggesting that both lobes formed in the same region and are homogeneous in their D/H ratios.

scholarly journals Reduction of charge offset drift using plasma oxidized aluminum in SETs

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yanxue Hong ◽  
Ryan Stein ◽  
M. D. Stewart ◽  
Neil M. Zimmerman ◽  
J. M. Pomeroy
Keyword(s):  
High Vacuum ◽  
Ultra High Vacuum ◽  
Tunnel Barrier ◽  
Plasma Oxidation ◽  
Single Electron Transistors ◽  
Tunnel Barriers ◽  
Close Proximity ◽  
Electron Transistors ◽  
Charge Defect

Abstract Aluminum oxide ($${\text {AlO}}_x$$ AlO x )-based single-electron transistors (SETs) fabricated in ultra-high vacuum (UHV) chambers using in situ plasma oxidation show excellent stabilities over more than a week, enabling applications as tunnel barriers, capacitor dielectrics or gate insulators in close proximity to qubit devices. Historically, $${\text {AlO}}_x$$ AlO x -based SETs exhibit time instabilities due to charge defect rearrangements and defects in $${\text {AlO}}_x$$ AlO x often dominate the loss mechanisms in superconducting quantum computation. To characterize the charge offset stability of our $${\text {AlO}}_x$$ AlO x -based devices, we fabricate SETs with sub-1 e charge sensitivity and utilize charge offset drift measurements (measuring voltage shifts in the SET control curve). The charge offset drift ($$\Delta {Q_0}$$ Δ Q 0 ) measured from the plasma oxidized $${\text {AlO}}_x$$ AlO x SETs in this work is remarkably reduced (best $$\Delta {Q_0}=0.13 \, \hbox {e} \, \pm \, 0.01 \, \hbox {e}$$ Δ Q 0 = 0.13 e ± 0.01 e over $$\approx 7.6$$ ≈ 7.6 days and no observation of $$\Delta {Q_0}$$ Δ Q 0 exceeding $$1\, \hbox {e}$$ 1 e ), compared to the results of conventionally fabricated $${\text {AlO}}_x$$ AlO x tunnel barriers in previous studies (best $$\Delta {Q_0}=0.43 \, \hbox {e} \, \pm \, 0.007 \, \hbox {e}$$ Δ Q 0 = 0.43 e ± 0.007 e over $$\approx 9$$ ≈ 9 days and most $$\Delta {Q_0}\ge 1\, \hbox {e}$$ Δ Q 0 ≥ 1 e within one day). We attribute this improvement primarily to using plasma oxidation, which forms the tunnel barrier with fewer two-level system (TLS) defects, and secondarily to fabricating the devices entirely within a UHV system.

scholarly journals Vertical Migration of the Along-Slope Counter-Flow and Its Relation with the Kuroshio Intrusion off Northeastern Taiwan

2019 ◽  
Vol 11 (22) ◽  
pp. 2624
Author(s):  
Yuanshou He ◽  
Po Hu ◽  
Yuqi Yin ◽  
Ze Liu ◽  
Yahao Liu ◽  
...  
Keyword(s):  
Vertical Migration ◽  
Subsurface Layer ◽  
Analysis Data ◽  
Kuroshio Intrusion ◽  
Counter Flow ◽  
Velocity Anomaly ◽  
Biochemical Systems ◽  
Marine Economy ◽  
The Kuroshio

Based on satellite and analysis data and in situ observations acquired during May 23, 2017 to May 19, 2018, the spatiotemporal variations of the along-slope counter-flow off northeastern Taiwan were investigated. It was observed that the along-slope counter-flow in the subsurface layer was uplifted and lowered significantly during the study period. The counter-flow was significantly uplifted (lowered) while the sea surface was during an interval of positive (negative) geostrophic velocity anomaly (GVA) curl. The vertical migration of the counter-flow was also found closely linked with the Kuroshio intrusion (KI) to the northeast of Taiwan. The depths of both the upper boundary and the axis of the counter-flow were found proportional to the KI variance along the western continental slope off northeastern Taiwan. More importantly, it was established that the variation of the KI to the northeast of Taiwan had better correlation with the counter-flow than the Kuroshio derived from altimetry data. Thus, further study of the variation and mechanism of the along-slope counter-flow is needed to improve the understanding and prediction of the KI in the area of northeastern Taiwan, as well as the biochemical systems and marine economy in the East China Sea in the future.

Sign in / Sign up

Export Citation Format

Share Document