The impact of twin lamella thickness distribution on strength and endurance limit in nanotwinned copper

2015 ◽  
Vol 84 ◽  
pp. 91-99 ◽  
Author(s):  
C. Xie ◽  
Q.H. Fang ◽  
L.X. Li ◽  
J.K. Chen ◽  
Y.W. Liu ◽  
...  
Keyword(s):  
Endurance Limit ◽  
Thickness Distribution ◽  
Twin Lamella ◽  
Lamella Thickness ◽  
The Impact

scholarly journals Cable Tensile Forces Associated to Winch Design in Tethered Harvesting Operations: A Case Study from the Pacific North West

Forests ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 827
Author(s):  
Omar Mologni ◽  
Eric D. T. Nance ◽  
C. Kevin Lyons ◽  
Luca Marchi ◽  
Stefano Grigolato ◽  
...  
Keyword(s):  
Endurance Limit ◽  
Tensile Force ◽  
Force Analysis ◽  
North West ◽  
The Pacific ◽  
Work Tasks ◽  
Tensile Forces ◽  
System Activation ◽  
The Impact

Cable tensile forces in winch-assist harvesting have been investigated in order to assess the safety concerns of the technology. However, the literature is lacking, particularly in regards to the impact of winch design. In this study, a Summit Winch Assist tethering a feller-director on ground slopes up to 77% was monitored for four days. The cable tensile forces were simultaneously recorded at the harvesting and anchor machine at a frequency of 100 Hz. Cameras and GNSS devices enabled a time study of the operations and the recording of machine positions. Winch functionality and design were disclosed by the manufacturer and used for the interpretation of the results. The cable tensile forces reached 296 kN at the harvesting machine and 260 kN at the anchor machine. The slow negotiation of obstacles while moving downhill recorded the highest peaks, mainly due to threshold settings of the winch in the brake system activation. Lower but significant peaks were also recorded during stationary work tasks. The peaks, however, were limited to a few events and never exceeded the endurance limit of the cable. Overall, the study confirmed recent findings in cable tensile force analysis of active winch-assist operations and provided evidence of the underlaying mechanisms that contribute to cable tensile forces.

Optimization and Investigation on the Impact of Centrifugal Impeller Blade Thickness Distribution on Hydro-Induced Vibration

2018 ◽  
Author(s):  
B. Qian ◽  
D. Z. Wu
Keyword(s):  
Secondary Flow ◽  
Thickness Distribution ◽  
Suction Side ◽  
Centrifugal Impeller ◽  
Impeller Blade ◽  
Streamwise Location ◽  
Unbalanced Rotor ◽  
Blade Thickness ◽  
Vibration Performance ◽  
The Impact

The vibration performance of centrifugal impellers is of great importance for pumps in some application areas such as automobiles and ships. Apart from mechanical excitations for instance, unbalanced rotor and misalignment, attentions should be concentrated on the hydraulic excitations. The complex internal secondary flow in the centrifugal impeller brings degradation on both hydraulic and vibration performances. On the purpose of repressing the internal secondary flow and alleviating vibration, an attempt of optimization by controlling the thickness distribution of centrifugal impeller blade is given. The vibration performances of the impellers are investigated numerically and experimentally. Meanwhile, further study on the mechanism of the influence of the thickness distribution optimization on vibration is conducted. There is a relative velocity gradient from suction side (SS) to pressure side (PS) due to the Coriolis force, which causes non-uniformity of energy distribution. By means of thickness distribution optimization, the impeller blade angle on the PS and SS along the blade-aligned (BA) streamwise location is respectively modified and therefore the flow field can be improved.

scholarly journals New insight from CryoSat-2 sea ice thickness for sea ice modelling

2018 ◽  
Author(s):  
David Schröder ◽  
Danny L. Feltham ◽  
Michel Tsamados ◽  
Andy Ridout ◽  
Rachel Tilling
Keyword(s):  
Sea Ice ◽  
Thickness Distribution ◽  
Arctic Sea Ice ◽  
Ice Thickness ◽  
Atmospheric Conditions ◽  
Sea Ice Concentration ◽  
Sea Ice Thickness ◽  
Ice Growth ◽  
Melt Pond ◽  
The Impact

Abstract. Estimates of Arctic sea ice thickness are available from the CryoSat-2 (CS2) radar altimetry mission during ice growth seasons since 2010. We derive the sub-grid scale ice thickness distribution (ITD) with respect to 5 ice thickness categories used in a sea ice component (CICE) of climate simulations. This allows us to initialize the ITD in stand-alone simulations with CICE and to verify the simulated cycle of ice thickness. We find that a default CICE simulation strongly underestimates ice thickness, despite reproducing the inter-annual variability of summer sea ice extent. We can identify the underestimation of winter ice growth as being responsible and show that increasing the ice conductive flux for lower temperatures (bubbly brine scheme) and accounting for the loss of drifting snow results in the simulated sea ice growth being more realistic. Sensitivity studies provide insight into the impact of initial and atmospheric conditions and, thus, on the role of positive and negative feedback processes. During summer, atmospheric conditions are responsible for 50 % of September sea ice thickness variability through the positive sea ice and melt pond albedo feedback. However, atmospheric winter conditions have little impact on winter ice growth due to the dominating negative conductive feedback process: the thinner the ice and snow in autumn, the stronger the ice growth in winter. We conclude that the fate of Arctic summer sea ice is largely controlled by atmospheric conditions during the melting season rather than by winter temperature. Our optimal model configuration does not only improve the simulated sea ice thickness, but also summer sea ice concentration, melt pond fraction, and length of the melt season. It is the first time CS2 sea ice thickness data have been applied successfully to improve sea ice model physics.

scholarly journals Glacier thickness estimations of alpine glaciers using data and modeling constraints

2019 ◽  
Vol 13 (8) ◽  
pp. 2189-2202 ◽  
Author(s):  
Lisbeth Langhammer ◽  
Melchior Grab ◽  
Andreas Bauder ◽  
Hansruedi Maurer
Keyword(s):  
Water Resource Management ◽  
Thickness Distribution ◽  
Cost Benefit ◽  
Estimation Algorithm ◽  
Ice Surface ◽  
Alpine Glaciers ◽  
Inversion Procedure ◽  
Using Data ◽  
The Individual ◽  
The Impact

Abstract. Advanced knowledge of the ice thickness distribution within glaciers is of fundamental importance for several purposes, such as water resource management and the study of the impact of climate change. Ice thicknesses can be modeled using ice surface features, but the resulting models can be prone to considerable uncertainties. Alternatively, it is possible to measure ice thicknesses, for example, with ground-penetrating radar (GPR). Such measurements are typically restricted to a few profiles, with which it is not possible to obtain spatially unaliased subsurface images. We developed the Glacier Thickness Estimation algorithm (GlaTE), which optimally combines modeling results and measured ice thicknesses in an inversion procedure to obtain overall thickness distributions. GlaTE offers the flexibility of being able to add any existing modeling algorithm, and any further constraints can be added in a straightforward manner. Furthermore, it accounts for the uncertainties associated with the individual constraints. Properties and benefits of GlaTE are demonstrated with three case studies performed on different types of alpine glaciers. In all three cases, subsurface models could be found that are consistent with glaciological modeling and GPR data constraints. Since acquiring GPR data on glaciers can be an expensive endeavor, we additionally employed elements of sequential optimized experimental design (SOED) for determining cost-optimized GPR survey layouts. The calculated cost–benefit curves indicate that a relatively large amount of data can be acquired before redundant information is collected with any additional profiles, and it becomes increasingly expensive to obtain further information.

Effect of oil starvation on the isothermal impact problem

2017 ◽  
Vol 232 (10) ◽  
pp. 1332-1339
Author(s):  
Duohuan Wu ◽  
Jing Wang ◽  
Peiran Yang ◽  
Ton Lubrecht
Keyword(s):  
Film Thickness ◽  
Pressure Gradient ◽  
Thickness Distribution ◽  
Elastohydrodynamic Lubrication ◽  
Maximum Pressure ◽  
Numerical Techniques ◽  
Minimum Film Thickness ◽  
The Impact ◽  
Impact Motion ◽  
Impact Problem

In this study, the effect of oil starvation on isothermal elastohydrodynamic lubrication of an impact motion is explored with the aid of numerical techniques. During the impact process, on comparison with the fully lubricated results, the pressure and film thickness are much lower and the entrapped film shape does not happen. The rebound is delayed by the oil starvation assumption. During the rebound process, a periphery entrapment is seen in the starved film thickness distribution. Under the starved condition, the maximum pressure gradient is higher. The central film thickness and minimum film thickness exhibit different variations compared with the results by fully flooded assumption.

Long period analysis in blends of high-density and lowdensity polyethylene

e-Polymers ◽  
2001 ◽  
Vol 1 (1) ◽  
Author(s):  
Fadhel Ben Cheikh Larbi ◽  
Jean Louis Halary
Keyword(s):  
Distribution Function ◽  
Thickness Distribution ◽  
High Density ◽  
Period Analysis ◽  
Polymeric Systems ◽  
Long Period ◽  
X Ray Scattering ◽  
Saxs Intensity ◽  
Amorphous Domain ◽  
Lamella Thickness

AbstractLong period calculations from small angle X-ray scattering experiments (SAXS) is a well-known way to describe biphasic polymeric systems. In the case of semi-crystalline homopolymers, more and more sophisticated models have been proposed to account for the SAXS intensity profiles. However, they use too many parameters to be applied to systems including two crystalline phases and an amorphous phase. Therefore, we propose a crude alternative, based on a generalization of the old paracrystalline Hoseman model, in order to consider the case of blends of high-density (HDPE) and low-density (LDPE) polyethylene. The crystalline lamella thickness distribution function is taken as the sum of two Gaussians (bimodal function 2G). As far as the amorphous domain thickness distribution function is concerned, either an exponential distribution (E) or a Gaussian distribution (G) is used. The model 2G/G proves to be much more realistic than the model 2G/E, with respect to the long period evolution as a function of HDPE/LDPE blend composition.

scholarly journals Impact of frontal ablation on the ice thickness estimation of marine-terminating glaciers in Alaska

2019 ◽  
Vol 13 (10) ◽  
pp. 2657-2672 ◽  
Author(s):  
Beatriz Recinos ◽  
Fabien Maussion ◽  
Timo Rothenpieler ◽  
Ben Marzeion
Keyword(s):  
Sea Level ◽  
Thickness Distribution ◽  
Regional Scale ◽  
Ice Thickness ◽  
Potential Contribution ◽  
Volume Estimate ◽  
Tidewater Glaciers ◽  
Thickness Estimation ◽  
The Impact ◽  
Frontal Ablation

Abstract. Frontal ablation is a major component of the mass budget of calving glaciers, strongly affecting their dynamics. Most global-scale ice volume estimates to date still suffer from considerable uncertainties related to (i) the implemented frontal ablation parameterization or (ii) not accounting for frontal ablation at all in the glacier model. To improve estimates of the ice thickness distribution of glaciers, it is thus important to identify and test low-cost and robust parameterizations of this process. By implementing such parameterization into the ice thickness estimation module of the Open Global Glacier Model (OGGM v1.1.2), we conduct a first assessment of the impact of accounting for frontal ablation on the estimate of ice stored in glaciers in Alaska. We find that inversion methods based on mass conservation systematically underestimate the mass turnover and, therefore, the thickness of tidewater glaciers when neglecting frontal ablation. This underestimation can amount to up to 19 % on a regional scale and up to 30 % for individual glaciers. The effect is independent of the size of the glacier. Additionally, we perform different sensitivity experiments to study the influence of (i) a constant of proportionality (k) used in the frontal ablation parameterization, (ii) Glen's temperature-dependent creep parameter (A) and (iii) a sliding velocity parameter (fs) on the regional dynamics of Alaska tidewater glaciers. OGGM is able to reproduce previous regional frontal ablation estimates, applying a number of combinations of values for k, Glen's A and fs. Our sensitivity studies also show that differences in thickness between accounting for and not accounting for frontal ablation occur mainly at the lower parts of the glacier, both above and below sea level. This indicates that not accounting for frontal ablation will have an impact on the estimate of the glaciers' potential contribution to sea-level rise. Introducing frontal ablation increases the volume estimate of Alaska marine-terminating glaciers from 9.18±0.62 to 10.61±0.75 mm s.l.e, of which 1.52±0.31 mm s.l.e (0.59±0.08 mm s.l.e when ignoring frontal ablation) are found to be below sea level.

Towards a swath-to-swath sea-ice drift product for the Copernicus Imaging Microwave Radiometer (CIMR) mission.

2021 ◽  
Author(s):  
Thomas Lavergne ◽  
Montserrat Piñol Solé ◽  
Emily Down ◽  
Craig Donlon
Keyword(s):  
Sea Ice ◽  
Thickness Distribution ◽  
Microwave Radiometer ◽  
Arctic Sea Ice ◽  
Sea Ice Thickness ◽  
Spatial And Temporal Scales ◽  
Location Uncertainty ◽  
Ice Drift ◽  
Sea Ice Drift ◽  
The Impact

<p>Across spatial and temporal scales, sea-ice motion has implications on ship navigation, the sea-ice thickness distribution, sea ice export to lower latitudes and re-circulation in the polar seas, among others. Satellite remote sensing is an effective way to monitor sea-ice drift globally and daily, especially using the wide swaths of passive microwave missions. Since the late 1990s, many algorithms and products have been developed for this task. Here, we investigate how processing sea-ice drift vectors from the intersection of individual swaths of the Advanced Microwave Scanning Radiometer 2 (AMSR2) mission compares to today’s status-quo (processing from daily averaged maps of brightness temperature).</p><p>We document that the “swath-to-swath” (S2S) approach results in many more (two orders of magnitude) sea-ice drift vectors than the “daily-maps” (DM) approach. These S2S vectors also validate better when compared to trajectories of on-ice drifters. For example, the RMSE of the 24 hour Arctic sea-ice drift is 0.9 km for S2S vectors, and 1.3 km for DM vectors from the 36.5 GHz imagery of AMSR2.</p><p>Through a series of experiments with actual AMSR2 data and simulated Copernicus Imaging Microwave Radiometer (CIMR) data, we study the impact that geo-location uncertainty and imaging resolution have on the accuracy of the sea-ice drift vectors. We conclude by recommending that a “swath-to-swath” approach is adopted for the future operational Level-2 sea-ice drift product of the CIMR mission. We outline some potential next steps towards further improving the algorithms, and making the user community ready to fully take advantage of such a product.</p><p>This work is currently under revision at EGU The Cryosphere as https://tc.copernicus.org/preprints/tc-2020-332/</p>

Martian Dichotomy from a Giant Impact: Mantle Convection Models

2021 ◽  
Author(s):  
Kar Wai Cheng ◽  
Antoine B. Rozel ◽  
Gregor J. Golabek ◽  
Harry Ballantyne ◽  
Martin Jutzi
Keyword(s):  
Mantle Convection ◽  
Thickness Distribution ◽  
Thermal Anomaly ◽  
Crustal Thickness ◽  
Annual Review ◽  
Physical Parameters ◽  
Geophysical Research ◽  
Giant Impact ◽  
The Impact ◽  
Crustal Dichotomy

<p>The Martian crustal dichotomy is one of the most prominent features on the planet, featuring a ≈5.5 km difference in topography and a ≈25 km difference in crustal thickness between the southern highland and northern lowland [1]. It Is thought to have formed within the first 400-500 Myr of Martian history [2]. While its formation process remains unclear, there have been different hypotheses to explain it, including an endothermic degree-1 convection mode [3, 4], and the excavation of the lowland crust by a giant impact [5]. In this study we focus on the hybrid hypothesis, where an early giant impact created a magma pond, and subsequent mantle convection alters the internal mantle structure as well as crustal distribution in the next 4 billion years [6, 7].  By imposing a parametrized giant impact as a thermal anomaly as an initial condition, we simulate the long-term evolution of the crust and mantle using the thermochemical convection code StagYY [8]. In particular, we investigate the effect of physical parameters of both the solid mantle and the impact-induced magma pond, as well as those of the crust production process, on the crystallisation of such pond, its interaction with surrounding mantle and the preservation of impact signature. Diagnostics including topography and crust thickness from these different models will be presented and compared.</p><p> </p><p>[1] Watters, T., McGovern, P., & Irwin III, R. (2007). Hemispheres Apart: The Crustal Dichotomy on Mars. Annual Review of Earth and Planetary Sciences, 35(1), 621-652.</p><p>[2] Taylor, S., & McLennan, S. (2009). Planetary crusts. Cambridge, UK: Cambridge University Press.</p><p>[3] Roberts, J., & Zhong, S. (2006). Degree-1 convection in the Martian mantle and the origin of the hemispheric dichotomy. Journal of Geophysical Research, 111(E6).</p><p>[4] Keller, T., & Tackley, P. (2009). Towards self-consistent modeling of the martian dichotomy: The influence of one- ridge convection on crustal thickness distribution. Icarus, 202(2), 429-443.</p><p>[5] Andrews-Hanna, J., Zuber, M., & Banerdt, W. (2008). The Borealis basin and the origin of the martian crustal dichotomy. Nature, 453(7199), 1212-1215.</p><p>[6] Golabek, G., Keller, T., Gerya, T., Zhu, G., Tackley, P., & Connolly, J. (2011). Origin of the martian dichotomy and Tharsis from a giant impact causing massive magmatism. Icarus, 215(1), 346-357.</p><p>[7] Reese, C., Orth, C., & Solomatov, V. (2011). Impact megadomes and the origin of the martian crustal dichotomy. Icarus, 213(2), 433-442.</p><p>[8] Tackley, P. (2008). Modelling compressible mantle convection with large viscosity contrasts in a three- dimensional spherical shell using the yin-yang grid. Physics of The Earth and Planetary Interiors, 171(1-4), 7-18</p><p> </p><p> </p>

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