Influence of Large-Scale Pressure Changes on Preconditioned Solutions at Low Speeds

AIAA Journal ◽  
2004 ◽  
Vol 42 (12) ◽  
pp. 2490-2498 ◽  
Author(s):  
Venkateswaran Sankaran ◽  
Charles L. Merkle ◽  
XiaoQiang Zeng ◽  
Ding Li
Keyword(s):  
Large Scale ◽  
Low Speeds ◽  
Pressure Changes

scholarly journals Climate variability reduces employment in New England fisheries

2019 ◽  
Vol 116 (52) ◽  
pp. 26444-26449
Author(s):  
Kimberly L. Oremus
Keyword(s):  
Climate Variability ◽  
New England ◽  
Large Scale ◽  
County Level ◽  
Atlantic Region ◽  
Quantitative Evidence ◽  
The North ◽  
Fishing Sector ◽  
Pressure Changes ◽  
Climate Shocks

Climate change is already affecting fish productivity and distributions worldwide, yet its impact on fishing labor has not been examined. Here I directly link large-scale climate variability with fishery employment by studying the effects of sea-surface pressure changes in the North Atlantic region, whose waters are among the world’s fastest warming. I find that climate shocks reduce not only regional catch and revenue in the New England fishing sector, but also ultimately county-level wages and employment among commercial harvesters. Each SD increase from the climatic mean decreases county-level fishing employment by 13%, on average. The South Atlantic region serves as a control due to its different ecological response to climate. Overall, I estimate that climate variability from 1996 to 2017 is responsible for a 16% (95% CI: 10% to 22%) decline in county-level fishing employment in New England, beyond the changes in employment attributable to management or other factors. This quantitative evidence linking climate variability and fishing labor has important implications for management in New England, which employs 20% of US commercial harvesters. Because the results are mediated by the local biology and institutions, they cannot be directly extrapolated to other regions. But they show that climate can impact fishing outcomes in ways unaccounted by management and offer a template for study of this relationship in fisheries around the world.

Microstructure Evolution Across Interfaces of Heterogeneous Metal Systems Under Ultrasonic Impact

2004 ◽  
Vol 854 ◽  
Author(s):  
Youhong Li ◽  
Yinon Ashkenazy ◽  
Robert S. Averback
Keyword(s):  
Large Scale ◽  
Shock Loading ◽  
Interfacial Strength ◽  
Interface Layer ◽  
Structural Defects ◽  
Interfacial Region ◽  
Heterogeneous Model ◽  
Interfacial Defects ◽  
Temperature And Pressure ◽  
Pressure Changes

ABSTRACTLarge-scale Molecular Dynamics (MD) studies on heterogeneous, model metal systems subjected to intense shock loading by a flyer plate were carried out. Of interest here is the effect of structural defects on interfacial strength under these extreme conditions. The metal target and flyer were essentially single crystals of Cu, but an interface layer was created by varying the mass of the Cu atoms in part of the sample. Interfacial defects in the form of vacancies, and at different concentrations, were introduced into the interfacial region. In addition to microstructural evolution of damage in this system, the shock induced temperature and pressure changes were also analyzed.

On the prospects for increasing dynamic lift

1988 ◽  
Vol 92 (913) ◽  
pp. 95-106 ◽  
Author(s):  
D. G. Mabey
Keyword(s):  
Experimental Evidence ◽  
Large Scale ◽  
Separated Flow ◽  
Controversial Issues ◽  
Dynamic Effects ◽  
Low Speeds ◽  
Large Scale Flow ◽  
Aerodynamic Surfaces ◽  
Swept Wings

Summary A review is given of some recent research, mainly at low speeds, into the development of dynamic lift. Sudden movement of aerodynamic surfaces can generate dynamic lift due to the transient development of separated flow. These dynamic effects are large and well established for aerofoils. They are considered likely to be small for highly swept wings and negligible for slender wings, but there is little experimental evidence to support this inference. The dynamic lift might be increased if conventional sinusoidal motions can be replaced by appropriate periodic saw-tooth motions. The control of large-scale flow separations by rapid movements of aerodynamic surfaces requires further investigation to resolve some of the controversial issues raised in the review.

scholarly journals Hydrogeologic Property Estimation in Plate Boundary Observatory Boreholes Using Tidal Response Analysis

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Jacob B. Simon ◽  
Patrick M. Fulton ◽  
Lian Xue
Keyword(s):  
Large Scale ◽  
Seismic Waves ◽  
Plate Boundary ◽  
Earth Tides ◽  
Cascadia Subduction Zone ◽  
Response Analysis ◽  
Specific Storage ◽  
Permeability Enhancement ◽  
Control Fluid ◽  
Pressure Changes

Because of the influence pore pressures have on effective stress, understanding hydrogeologic properties that control fluid flow and pressure distribution is important in characterizing earthquake and deformation processes. Here, we utilize borehole pressure changes in response to earth tides to determine hydrogeologic properties and their time variations for 17 boreholes within the NSF Earthscope’s Plate Boundary Observatory (PBO) network along the San Andreas fault and Cascadia subduction zone. Our analysis considers solutions for both confined and unconfined aquiares. Resulting permeability and hydraulic diffusivity values range from 6.4 × 10 − 16 – 8.4 × 10 − 14  m2 and 1 × 10 − 4 – 9 × 10 − 1   m 2 s − 1 , respectively, whereas specific storage values are generally ~ 1 × 10 − 6   m − 1 . The values are fairly consistent through time, reasonable given lithology, and are comparable to other regional studies. For one borehole, values are also comparable to those determined with traditional aquifer test data. In contrast with previous determinations of the high-frequency poroelastic response to seismic waves, no obvious spatial trends in hydrogeologic properties determined from long-wavelength tidal perturbations are observed. Within the recurring time-series estimates, only one borehole exhibits clear permeability enhancement by earthquakes, whereas nearby boreholes with similar lithology and hydrogeologic property values do not. This highlights the variable susceptibility of rocks to permeability enhancement. Together, these results provide quantitative constraints useful for models of large-scale groundwater flow around large fault systems and the potential hydrologic influence on deformation and fault slip behavior.

scholarly journals Thermally controlled microfluidic back pressure regulator

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Karolina Svensson ◽  
Simon Södergren ◽  
Klas Hjort
Keyword(s):  
Large Scale ◽  
Pressure Control ◽  
Back Pressure ◽  
Dead Volume ◽  
Pressure Regulator ◽  
Total Analysis System ◽  
Elevated Pressures ◽  
Upstream Pressure ◽  
Analysis System ◽  
Pressure Changes

AbstractBy using the temperature dependence of viscosity, we introduce a novel type of microfluidic lab-on-a-chip back pressure regulator (BPR) that can be integrated into a micro-total-analysis-system. A BPR is an important component used to gain pressure control and maintain elevated pressures in e.g. chemical extractions, synthesis, and analyses. Such applications have been limited in microfluidics, since the back pressure regularly has been attained by passive restrictors or external large-scale BPRs. Herein, an active microfluidic BPR is presented, consisting of a glass chip with integrated thin-film heaters and thermal sensors. It has no moving parts but a fluid restrictor where the flow resistance is controlled by the change of viscosity with temperature. Performance was evaluated by regulating the upstream pressure of methanol or water using a PID controller. The developed BPR has the smallest reported dead volume of 3 nL and the thermal actuation has time constants of a few seconds. The pressure regulation were reproducible with a precision in the millibar range, limited by the pressure sensor. The time constant of the pressure changes was evaluated and its dependence of the total upstream volume and the compressibility of the liquids is introduced.

Finite Element Modeling of a Microdroplet Generator With Integrated Sensing

2011 ◽  
Author(s):  
William S. Rone ◽  
Pinhas Ben-Tzvi
Keyword(s):  
Finite Element ◽  
Large Scale ◽  
Open Loop ◽  
Liquid Droplets ◽  
Gas Reservoir ◽  
Element Simulation ◽  
Droplet Liquid ◽  
Pressure Changes ◽  
Dominant Paradigm ◽  
Compressible Gas

This paper describes the analysis of a novel microdroplet generator’s integrated sensing capability using finite element simulation. The dominant paradigm for utilizing droplet generation is with either open-loop or externally-sensed closed-loop methods, each with significant disadvantages in terms of reliability and large-scale implementation, respectively. This work utilizes a system designed with a compressible gas reservoir adjacent to the incompressible droplet liquid reservoir. The compressible gas pressure changes as liquid droplets are dispensed from the constant volume fluid reservoir. This change was found to be linearly dependent on the size of the droplet that was ejected, validating this gas reservoir pressure as a useful means of indirectly measuring droplet size internally within the system.

scholarly journals Mountain Torque Events at the Tibetan Plateau

2008 ◽  
Vol 136 (2) ◽  
pp. 389-404 ◽  
Author(s):  
Joseph Egger ◽  
Klaus-Peter Hoinka
Keyword(s):  
Tibetan Plateau ◽  
Large Scale ◽  
Potential Temperature ◽  
Vertical Motion ◽  
The Tibetan Plateau ◽  
Eastern Slope ◽  
Pressure Potential ◽  
Initial Depression ◽  
Pressure Changes ◽  
Maximum Minimum

Abstract The interaction of large-scale wave systems with the Tibetan Plateau (TP) is investigated by regressing pressure, potential temperature, winds, precipitation, and selected fluxes in winter onto the three components Toi of this massif’s mountain torque on the basis of the 40-yr ECMWF reanalysis (ERA-40) data. Events with respect to the equatorial “Greenwich” axis of the global angular momentum exhibit by far the largest torques (To1,), which essentially represent north–south pressure differences across the TP. The axial torque To3 peaks when the surface pressure is high at the eastern slope of the TP. The torque To2 with respect to the 90°E axis is closely related to To3 with To2 ∼ −To3. The maximum (minimum) of To1 tends to occur about 1 day earlier than the minimum (maximum) of To2. All torque events are initiated by equivalent barotropic perturbations moving eastward along the northern rim of the TP. In general, the initial depression, for example, forms a southward-protruding extension at the eastern slope of the TP and a new high grows near Japan. Later, the perturbation near Japan moves eastward in To2 events but extends northward in To1 events. These flow developments cannot be explained by theories of topographic instability. The observed vertical motion at the lee slope is at best partly consistent with theories of linear quasigeostrophic wave motion along mountain slopes. These findings lead the authors to test the eventual usefulness of linear theories by fitting the linear terms of a novel statistical equation for the potential temperature θ to the observed changes of θ and the torque to the observations. This test indicates that the evolving regression patterns of θ can be explained by linear terms at least in specific domains. In turn, pressure tendency regressions at a selected level can be calculated on the basis of the linear θ tendencies above that level. The formation of the lee trough appears to be mainly caused by horizontal warm-air advection along the slopes, but changes of the potential temperature above the height of the TP also contribute significantly to the pressure changes in the lee. Cold-air advection aloft strengthens the Japan high. “Turbulent” transports appear to be mainly responsible for the decay of the perturbations but data accuracy problems impede the analysis. In particular, the noisiness of the vertical motion fields affects the skill of the linear calculations.

On the Buckling of Thin Walled Tubes Under Axial Impact

1964 ◽  
Vol 68 (642) ◽  
pp. 418-419 ◽  
Author(s):  
R. C. Redwood
Keyword(s):  
Central Region ◽  
Short Wavelength ◽  
Large Scale ◽  
Axial Impact ◽  
Low Speed ◽  
Impact Tests ◽  
High Speeds ◽  
Thin Walled ◽  
Low Speeds ◽  
The Impact

In some recent impact tests in which thin walled square tubes were loaded axially to produce large scale buckling of the walls, a difference occurred between the behaviour at high speeds and that at low speeds. The tubes, standing on an anvil, were struck by a falling steel tup which was guided to strike the tubes approximately axially. At the higher speeds damage was confined to the impact end of the tube, with a short wavelength buckle adjacent to the end and longer waves farther from the end. At lower speeds damage occurred at either end, or, jn many cases, in the central region of the tube. The wavelengths in these low speed tests were longer than those occurring at high speeds. These two types of behaviour are illustrated on Fig. 1.

Classification and analysis of VMS data in vertical line fisheries: incorporating uncertainty into spatial distributions

2017 ◽  
Vol 74 (11) ◽  
pp. 1749-1764 ◽  
Author(s):  
Nicholas D. Ducharme-Barth ◽  
Robert N.M. Ahrens
Keyword(s):  
Large Scale ◽  
Critical Role ◽  
Fishing Effort ◽  
Vertical Line ◽  
Commercial Fishing ◽  
Spatial Distributions ◽  
Fishing Pressure ◽  
Modeling Process ◽  
Fishing Fleets ◽  
Pressure Changes

Commercial fishing fleets play a critical role in the population dynamics of exploited stocks. Understanding the spatial distribution of fleets allows managers to anticipate how fishing pressure on exploited stocks changes in response to fishing regulations or to large-scale perturbations. By anticipating how fishing pressure changes, managers can develop proactive responses to better protect stocks that are vulnerable to overfishing. Modern fisheries monitoring techniques, including vessel monitoring systems (VMS), have advanced this endeavor. This paper presents a framework for using VMS data to develop spatial distributions of catch, fishing effort, and catch per unit of effort (CPUE) as well as associated estimates of uncertainty in a vertical line fishery. VMS data are classified as fishing using a random forest (RF) model. Uncertainty is calculated using a two-step approach to account for uncertainty arising from the RF modeling process and the classification accuracy of the model. This framework is applied to investigate changes in the Gulf of Mexico reef fish fishery during a period of 6 years, including the 2010 Deepwater Horizon oil spill.

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