Spatial distribution of surficial sediments in part of the Kingston basin of northeastern Lake Ontario, Canada

2000 ◽  
Vol 37 (6) ◽  
pp. 901-911 ◽  
Author(s):  
Joachim W Härtling ◽  
Robert Gilbert
Keyword(s):  
Lake Ontario ◽  
Surficial Sediments ◽  
Study Region ◽  
Fine Grained ◽  
Sedimentary Environments ◽  
Wind Speeds ◽  
Grain Sizes ◽  
Fine Grain ◽  
Strong Winds ◽  
Kingston Harbour

The distribution of surficial sediments in the interisland area of northeastern Lake Ontario is characterized by a generally homogeneous composition of fine grained muds with some local exceptions at the gaps leading into Kingston basin and in parts of North Channel. This pattern reflects principally differing levels of wave energy from the exposed areas of outer Kingston basin and Upper and Lower gaps to the more protected interisland area. Additional processes responsible for the distribution are currents at the Upper and Lower gaps and local slumping. The observed deposition of surficial sediments in the northern Kingston basin shows generally good agreement with the wave base calculations employing wind speeds of 60 km·h-1. The study region consists of three sedimentary environments. Above the wave base related to winds of less than 60 km·h-1 continual erosion and transport of all grain sizes leads to a constant source of sediment to the deeper parts of the Kingston basin. Above the wave base related to infrequent strong winds of more than 60 km·h-1, episodic removal of the fine grain sizes leads to winnowing of the fines and their being transported into North Channel and Kingston Harbour while the sands are left in place. Below the wave base the sediments are undistributed. Thus, there is no proximal-distal differentiation outward from the coasts nor along the channels. The sediment is transported with currents moving through North Channel and Kingston Harbour with similarly low velocities across the entire section.

scholarly journals The effect of fluvial environments on sediment bleaching and Holocene luminescence ages — A case study from the German Alpine Foreland

2013 ◽  
Vol 40 (4) ◽  
pp. 283-293 ◽  
Author(s):  
Patrick Schielein ◽  
Johanna Lomax
Keyword(s):  
Statistical Modelling ◽  
Moderate Degree ◽  
Point Bar ◽  
Fine Grained ◽  
Sedimentary Environments ◽  
Fine Grain ◽  
Floodplain Deposits ◽  
Crevasse Splay ◽  
Channel Deposits ◽  
Floodplain Sediments

Abstract This study investigates the potential of luminescence to date deposits from different fluvial sedimentary environments; namely point bar deposits, sandy and silty channel fills and floodplain sediments. Samples were taken from Holocene (<5 ka) terraces of the Lech and Danube rivers, for which independent age constraint is available through 14C ages, archaeological data and historical maps. OSL-ages were obtained using small aliquots of coarse grain quartz for the majority of samples. Two further samples were dated by the IRSL-signals of polymineral fine grain extracts, as no sufficient number of coarse grains could be extracted from these sediments. In order to detect and ac-count for incomplete bleaching, we used the decision process suggested by Bailey and Arnold [Statistical modelling of single grain quartz De distributions and an assessment of procedures for estimating burial dose. Quaternary Science Reviews 25, 2475–2502, 2006]. Although their model was designed for single grains of quartz, our study shows that it is also applicable to multiple grains of quartz, pro-vided that a low number of luminescent grains is present on one aliquot. Luminescence ages of point bar deposits and a sandy channel fill correspond most closely to the independent age control. In the floodplain, sand-striped floodplain channel deposits were incompletely bleached to a moderate degree, yielding ages with acceptable overestimations, while fine-grained floodplain deposits were worst bleached. One crevasse splay deposit was so severely incompletely bleached that none of the age models was able to yield accurate ages.

Effect of precipitate volume fraction on fracture toughness of extruded Mg–Zn alloys

2008 ◽  
Vol 23 (4) ◽  
pp. 1128-1135 ◽  
Author(s):  
Hidetoshi Somekawa ◽  
Yoshiaki Osawa ◽  
Alok Singh ◽  
Toshiji Mukai
Keyword(s):  
Fracture Toughness ◽  
Volume Fraction ◽  
Void Formation ◽  
Zinc Content ◽  
Precipitate Volume Fraction ◽  
Fine Grained ◽  
Grain Sizes ◽  
Fine Grain ◽  
Ductile Fracture Model ◽  
Zn Alloy

Four kinds of extruded Mg–X at.% Zn binary alloys (X = 1.9, 2.4, 3.0, and 3.4) were used to examine the effect of precipitate volume fraction on fracture toughness. All the alloys had fine grain sizes of 1–3 μm and fine sphere-shaped precipitates of 50–60 nm. The volume fraction of precipitates increased with additional zinc content. The results of mechanical property tests showed that the extruded Mg–2.4 at.% Zn alloy exhibited the best balance of strength and fracture toughness. One of the reasons was the different volume fraction of precipitates at the grain boundaries, which was the source of void formation. According to the fracture surface observations and ductile fracture model analysis, the volume fraction of precipitates of 2%–4% was shown to be enough to improve the fracture toughness for the fine-grained magnesium alloys; i.e., higher contents of zinc atoms were not needed to enhance the mechanical properties.

scholarly journals Statistical Modeling of Fine Sediments Dredged Using a Variable Area Dredging Suction Head to Improve Water Quality

Hydrology ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 98
Author(s):  
Leigh A. Provost ◽  
Robert Weaver ◽  
Nezamoddin N. Kachouie
Keyword(s):  
Climate Change ◽  
Water Quality ◽  
Sedimentation Rates ◽  
Agricultural Lands ◽  
Design Efficiency ◽  
Fine Sediments ◽  
Grain Sizes ◽  
Fine Grain ◽  
Sediment Sampling ◽  
Improve Water Quality

The changing climate affects the agricultural lands, and, in turn, the changes in agricultural lands alter the watershed. A major concern regarding waterbodies is the increased sedimentation rates due to climate change. To improve the water quality, it is crucial to remove fine sediments. Using current environmental dredging methods is challenging because of the sediment volumes that must be dredged, the absence of nearby disposal sites, and the shoreline infrastructure at the dredging locations. To address these issues, we used a surgical dredging method with a variable area suction head that can easily maneuver around the docks, pilings, and other infrastructures. It can also isolate the fine grain material to better manage the dredged volumes in the seabed where nutrients are typically adhered. To this end, a statistical analysis of the dredged samples is essential to improve the design efficiency. In this work, we collected several samples using a variable area suction head with different design settings. The collected samples using each design setting were then used to model the distributions of the different grain sizes in the dredged sediments. The proposed statistical model can be effectively used for the prediction of sediment sampling outcomes to improve the gradation of the fine sediments.

scholarly journals Submarine lava deltas of the 2018 eruption of Kīlauea volcano

2021 ◽  
Vol 83 (4) ◽  
Author(s):  
S. Adam Soule ◽  
Michael Zoeller ◽  
Carolyn Parcheta
Keyword(s):  
Grain Size ◽  
Pore Pressure ◽  
Mechanistic Model ◽  
Large Fraction ◽  
Volcanic Hazards ◽  
Lava Flows ◽  
Coarse Grained ◽  
Fine Grained ◽  
Fine Grain ◽  
Delta Formation

AbstractHawaiian and other ocean island lava flows that reach the coastline can deposit significant volumes of lava in submarine deltas. The catastrophic collapse of these deltas represents one of the most significant, but least predictable, volcanic hazards at ocean islands. The volume of lava deposited below sea level in delta-forming eruptions and the mechanisms of delta construction and destruction are rarely documented. Here, we report on bathymetric surveys and ROV observations following the Kīlauea 2018 eruption that, along with a comparison to the deltas formed at Pu‘u ‘Ō‘ō over the past decade, provide new insight into delta formation. Bathymetric differencing reveals that the 2018 deltas contain more than half of the total volume of lava erupted. In addition, we find that the 2018 deltas are comprised largely of coarse-grained volcanic breccias and intact lava flows, which contrast with those at Pu‘u ‘Ō‘ō that contain a large fraction of fine-grained hyaloclastite. We attribute this difference to less efficient fragmentation of the 2018 ‘a‘ā flows leading to fragmentation by collapse rather than hydrovolcanic explosion. We suggest a mechanistic model where the characteristic grain size influences the form and stability of the delta with fine grain size deltas (Pu‘u ‘Ō‘ō) experiencing larger landslides with greater run-out supported by increased pore pressure and with coarse grain size deltas (Kīlauea 2018) experiencing smaller landslides that quickly stop as the pore pressure rapidly dissipates. This difference, if validated for other lava deltas, would provide a means to assess potential delta stability in future eruptions.

scholarly journals Air Movement in Snow Due to Windpumping

1989 ◽  
Vol 35 (120) ◽  
pp. 209-213 ◽  
Author(s):  
S.C. Colbeck
Keyword(s):  
Pore Space ◽  
Barometric Pressure ◽  
Surface Flows ◽  
Wind Speeds ◽  
Compression And Expansion ◽  
Strong Winds ◽  
Pressure Changes ◽  
Low Amplitude ◽  
Pressure Perturbations ◽  
Rapid Pressure

Abstract Strong winds can disrupt the thermal regime in seasonal snow because of the variation in surface pressure associated with surface features like dunes and ripples. Topographical features of shorter wavelengths produce stronger surface flows, but the flow decays rapidly with depth. Longer-wavelength features produce weaker surface flows but the flow decays more slowly with depth. The flow may only be strong enough to disrupt the temperature field for features of wavelengths on the scale of meters or tens of meters at wind speeds of 10 m/s or more. Other possible causes of windpumping have been examined but they do not appear to be as significant. Rapid pressure perturbations due to turbulence produce very little displacement of the air because of the high frequency and low amplitude. Barometric pressure changes cause compression and expansion of the air in the pore space, but the rate is too low to have much effect.

Climate Conditions at Perennially Ice-Covered Lake Untersee, East Antarctica

2015 ◽  
Vol 54 (7) ◽  
pp. 1393-1412 ◽  
Author(s):  
Dale T. Andersen ◽  
Christopher P. McKay ◽  
Victor Lagun
Keyword(s):  
Wind Speed ◽  
Austral Summer ◽  
Solar Flux ◽  
East Antarctica ◽  
Daily Maximum ◽  
Mean Annual Temperature ◽  
Secondary Source ◽  
Climate Conditions ◽  
Wind Speeds ◽  
Strong Winds

AbstractIn November 2008 an automated meteorological station was established at Lake Untersee in East Antarctica, producing a 5-yr data record of meteorological conditions at the lake. This dataset includes five austral summer seasons composed of December, January, and February (DJF). The average solar flux at Lake Untersee for the four years with complete solar flux data is 99.2 ± 0.6 W m−2. The mean annual temperature at Lake Untersee was determined to be −10.6° ± 0.6°C. The annual degree-days above freezing for the five years were 9.7, 37.7, 22.4, 7.0, and 48.8, respectively, with summer (DJF) accounting for virtually all of this. For these five summers the average DJF temperatures were −3.5°, −1.9°, −2.2°, −2.6°, and −2.5°C. The maximum (minimum) temperatures were +5.3°, +7.6°, +5.7°, +4.4°, and +9.0°C (−13.8°, −12.8°, −12.9°, −13.5°, and −12.1°C). The average of the wind speed recorded was 5.4 m s−1, the maximum was 35.7 m s−1, and the average daily maximum was 15 m s−1. The wind speed was higher in the winter, averaging 6.4 m s−1. Summer winds averaged 4.7 m s−1. The dominant wind direction for strong winds is from the south for all seasons, with a secondary source of strong winds in the summer from the east-northeast. Relative humidity averages 37%; however, high values will occur with an average period of ~10 days, providing a strong indicator of the quasi-periodic passage of storms across the site. Low summer temperatures and high wind speeds create conditions at the surface of the lake ice resulting in sublimation rather than melting as the main mass-loss process.

The Method of Eliminating Banded Structure and the Effects of Banded Structure on the Transverse Properties in 20G Steel

2013 ◽  
Vol 347-350 ◽  
pp. 1171-1175 ◽  
Author(s):  
Bin Wang ◽  
Hong Mei Hu ◽  
Cui Zhou
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Stress Concentration ◽  
Base Metal ◽  
Metallic Inclusion ◽  
Banded Structure ◽  
Grain Sizes ◽  
Fine Grain ◽  
Treatment Processes ◽  
Metallic Inclusions

The transverse properties were inferior to the longitudinal properties for the existence of banded structure in 20G steel. In order to eliminate the banded structure and improve the transverse performance of 20G steel, different heat treatment processes were adopted. The results showed that conventional normalizing could reduce the banded structure and refine the grain sizes. When 20G was heated with 10°C/min heating rated and then held at 920°C for 2h, the banded structure in the steel was almost eliminated and the microstructure was homogeneous with fine grain size, the strength increased by 14%. The non-metallic inclusion and carbide in the microstructure leaded to stress concentration and separation with the base metal. To some extent, heat treatment can improve the distribution and form of non-metallic inclusions.

scholarly journals THE IDEAL DISTRIBUTION OF FARMERS: EXPLAINING THE EURO-AMERICAN SETTLEMENT OF UTAH

2017 ◽  
Vol 83 (1) ◽  
pp. 75-90 ◽  
Author(s):  
Peter M. Yaworsky ◽  
Brian F. Codding
Keyword(s):  
Population Density ◽  
Ideal Free Distribution ◽  
Negative Relationship ◽  
Coarse Grained ◽  
Distribution Model ◽  
Test Model ◽  
Fine Grained ◽  
Fine Grain ◽  
Model Predictions ◽  
The Ideal

Explaining how and why populations settle a new landscape is central to many questions in American archaeology. Recent advances in settlement research have adopted predictions from the Ideal Free Distribution model (IFD). While tests of IFD predictions to date rely either on archaeologically derived coarse-grained diachronic data or ethnographically derived fine-grained synchronic data, here we provide the first test using historically derived data that is both fine-grained and diachronic. Fine-grain diachronic data allow us to test model predictions at a temporal scale in line with human settlement decisions and to validate proxies for application in archaeological contexts. To test model predictions pertaining to the relationship between population density and habitat quality, we use data from the historical settlement of Utah. The results demonstrate a negative relationship between population density and the quality of habitats occupied. These results are consistent with IFD predictions, suggesting that Euro-American settlement of Utah resulted from individuals attempting to maximize individual returns via agricultural productivity. Our results provide a quantitative and testable explanation for population dispersion over time and explain the spatial distribution of population density today. The results support predictions derived from a general theory of behavior, providing an explanatory framework for colonization events worldwide.

scholarly journals Initial-Condition Sensitivities and the Predictability of Downslope Winds

2009 ◽  
Vol 66 (11) ◽  
pp. 3401-3418 ◽  
Author(s):  
Patrick A. Reinecke ◽  
Dale R. Durran
Keyword(s):  
Wave Breaking ◽  
Initial Conditions ◽  
Static Stability ◽  
Synoptic Scale ◽  
Wind Speeds ◽  
Downslope Winds ◽  
First Case ◽  
Downslope Wind ◽  
The Difference ◽  
Strong Winds

Abstract The sensitivity of downslope wind forecasts to small changes in initial conditions is explored by using 70-member ensemble simulations of two prototypical windstorms observed during the Terrain-Induced Rotor Experiment (T-REX). The 10 weakest and 10 strongest ensemble members are composited and compared for each event. In the first case, the 6-h ensemble-mean forecast shows a large-amplitude breaking mountain wave and severe downslope winds. Nevertheless, the forecasts are very sensitive to the initial conditions because the difference in the downslope wind speeds predicted by the strong- and weak-member composites grows to larger than 28 m s−1 over the 6-h forecast. The structure of the synoptic-scale flow one hour prior to the windstorm and during the windstorm is very similar in both the weak- and strong-member composites. Wave breaking is not a significant factor in the second case, in which the strong winds are generated by a layer of high static stability flowing beneath a layer of weaker mid- and upper-tropospheric stability. In this case, the sensitivity to initial conditions is weaker but still significant. The difference in downslope wind speeds between the weak- and strong-member composites grows to 22 m s−1 over 12 h. During and one hour before the windstorm, the synoptic-scale flow exhibits appreciable differences between the strong- and weak-member composites. Although this case appears to be more predictable than the wave-breaking event, neither case suggests that much confidence should be placed in the intensity of downslope winds forecast 12 or more hours in advance.

scholarly journals Incremental and Modular Context-sensitive Analysis

2021 ◽  
pp. 1-48
Author(s):  
ISABEL GARCIA-CONTRERAS ◽  
JOSÉ F. MORALES ◽  
MANUEL V. HERMENEGILDO
Keyword(s):  
Global Analysis ◽  
Memory Consumption ◽  
Sensitive Analysis ◽  
Analysis Techniques ◽  
Context Sensitive ◽  
Fine Grained ◽  
Fine Grain ◽  
Modular Analysis ◽  
Modular Algorithm ◽  
Modular Structures

Abstract Context-sensitive global analysis of large code bases can be expensive, which can make its use impractical during software development. However, there are many situations in which modifications are small and isolated within a few components, and it is desirable to reuse as much as possible previous analysis results. This has been achieved to date through incremental global analysis fixpoint algorithms that achieve cost reductions at fine levels of granularity, such as changes in program lines. However, these fine-grained techniques are neither directly applicable to modular programs nor are they designed to take advantage of modular structures. This paper describes, implements, and evaluates an algorithm that performs efficient context-sensitive analysis incrementally on modular partitions of programs. The experimental results show that the proposed modular algorithm shows significant improvements, in both time and memory consumption, when compared to existing non-modular, fine-grain incremental analysis techniques. Furthermore, thanks to the proposed intermodular propagation of analysis information, our algorithm also outperforms traditional modular analysis even when analyzing from scratch.

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