scholarly journals Emplacement of a silicic lava dome through a crater glacier: Mount St Helens, 2004–06

2007 ◽  
Vol 45 ◽  
pp. 14-20 ◽  
Author(s):  
Joseph S. Walder ◽  
Richard G. LaHusen ◽  
James W. Vallance ◽  
Steve P. Schilling
Keyword(s):  
Lava Dome ◽  
Thick Layer ◽  
Drainage Network ◽  
Strain Rates ◽  
Crater Wall ◽  
Groundwater System ◽  
Speed Up ◽  
Speed Fluctuations ◽  
First Time ◽  
Mount St Helens

AbstractThe process of lava-dome emplacement through a glacier was observed for the first time after Mount St Helens reawakened in September 2004. The glacier that had grown in the crater since the cataclysmic 1980 eruption was split in two by the new lava dome. The two parts of the glacier were successively squeezed against the crater wall. Photography, photogrammetry and geodetic measurements document glacier deformation of an extreme variety, with strain rates of extraordinary magnitude as compared to normal alpine glaciers. Unlike normal temperate glaciers, the crater glacier shows no evidence of either speed-up at the beginning of the ablation season or diurnal speed fluctuations during the ablation season. Thus there is evidently no slip of the glacier over its bed. The most reasonable explanation for this anomaly is that meltwater penetrating the glacier is captured by a thick layer of coarse rubble at the bed and then enters the volcano’s groundwater system rather than flowing through a drainage network along the bed.

scholarly journals Modeling the dynamic response of a crater glacier to lava-dome emplacement: Mount St Helens, Washington, USA

2007 ◽  
Vol 45 ◽  
pp. 21-28 ◽  
Author(s):  
Stephen F. Price ◽  
Joseph S. Walder
Keyword(s):  
Lava Dome ◽  
High Strain ◽  
Strain Rates ◽  
Field Scale ◽  
Glacier Surface ◽  
Surface Motion ◽  
Sequence Of Events ◽  
Dome Growth ◽  
Scale Experiment ◽  
Mount St Helens

AbstractThe debris-rich glacier that grew in the crater of Mount St Helens after the volcano’s cataclysmic 1980 eruption was split in two by a new lava dome in 2004. For nearly six months, the eastern part of the glacier was squeezed against the crater wall as the lava dome expanded. Glacier thickness nearly doubled locally and surface speed increased substantially. As squeezing slowed and then stopped, surface speed fell and ice was redistributed downglacier. This sequence of events, which amounts to a field-scale experiment on the deformation of debris-rich ice at high strain rates, was interpreted using a two-dimensional flowband model. The best match between modeled and observed glacier surface motion, both vertical and horizontal, requires ice that is about 5 times stiffer and 1.2 times denser than normal, temperate ice. Results also indicate that lateral squeezing, and by inference lava-dome growth adjacent to the glacier, likely slowed over a period of about 30 days rather than stopping abruptly. This finding is supported by geodetic data documenting dome growth.

scholarly journals Preloading Effect On The Strength of Cement Mass Mixing Treated Salty Sand

2021 ◽  
Author(s):  
Rasoul Alipour
Keyword(s):  
Thick Layer ◽  
Test Results ◽  
Cement Slurry ◽  
Sem Images ◽  
Treated Soil ◽  
Pure Salt ◽  
Ucs Test ◽  
Southwest Of Iran ◽  
First Time ◽  
Electronic Microscope

Abstract Existing problematic sub-layers in mixing technologies are a challenge, and for the first time, the effects of salt sub-layers in mass mixing technology have been investigated in this study for sandy salt in the southwest of Iran. This paper discusses the influence of adding various cement contents, Aw, and imposing different preloading values on the salty sand soil. First, salt and sand samples were dried, then, 90 % sand was mixed with 10% salt. After that, 30 % water was mixed thoroughly with the mixture of salty sand to obtain slurries. Cement slurry at a water-cement ratio (w/c) of 0.6 was then added to the sample and thoroughly mixed. The amount of cement in a slurry form that was added to the salty soil was 2, 4, 6, 8, and 10% by mass of dry soil. Each treated soil preloaded by 0, 9, and 45 kPa. After 120 days, the unconfined compressive strength of the sample was determined. Furthermore, by Scanning Electronic Microscope, SEM, the microstructures of treated samples were analyzed. At the end Unconfined Compression Strength, UCS, test results normalized to the non-preloaded treated soil. By increasing cement content, the effect of preloading in increasing UCS will decrease. In the SEM images for Aw=2%, the effect of preloading indicates porous shape for non-preloaded samples. Vice versa by Aw=8%, porous shape in the SEM images will disappear. In the end, treatability studies of pure salt in the thick layer have been investigated.

Fast Solution of Transient Elastohydrodynamic Line Contact Problems Using the Trajectory Piecewise Linear Approach

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Daniel Maier ◽  
Corinna Hager ◽  
Hartmut Hetzler ◽  
Nicolas Fillot ◽  
Philippe Vergne ◽  
...  
Keyword(s):  
Piecewise Linear ◽  
Contact Problems ◽  
Galerkin Projection ◽  
Line Contact ◽  
Reduced Order ◽  
Fast Solution ◽  
Speed Up ◽  
Newton Raphson ◽  
First Time ◽  
Piecewise Linear Approach

In order to obtain a fast solution scheme, the trajectory piecewise linear (TPWL) method is applied to the transient elastohydrodynamic (EHD) line contact problem for the first time. TPWL approximates the nonlinearity of a dynamical system by a weighted superposition of reduced linearized systems along specified trajectories. The method is compared to another reduced order model (ROM), based on Galerkin projection, Newton–Raphson scheme and an approximation of the nonlinear reduced system functions. The TPWL model provides further speed-up compared to the Newton–Raphson based method at a high accuracy.

Improving Matsui’s Search Algorithm For The Best Differential/Linear Trails And Its Applications For DES, DESL And GIFT

2020 ◽  
Author(s):  
Fulei Ji ◽  
Wentao Zhang ◽  
Tianyou Ding
Keyword(s):  
Search Algorithm ◽  
Search Space ◽  
Search Methods ◽  
New Methods ◽  
Linear Layer ◽  
Speed Up ◽  
Automatic Search ◽  
The Cost ◽  
First Time ◽  
Improved Algorithm

Abstract Automatic search methods have been widely used for cryptanalysis of block ciphers, especially for the most classic cryptanalysis methods—differential and linear cryptanalysis. However, the automatic search methods, no matter based on MILP, SMT/SAT or CP techniques, can be inefficient when the search space is too large. In this paper, we propose three new methods to improve Matsui’s branch-and-bound search algorithm, which is known as the first generic algorithm for finding the best differential and linear trails. The three methods, named reconstructing DDT and LAT according to weight, executing linear layer operations in minimal cost and merging two 4-bit S-boxes into one 8-bit S-box, respectively, can efficiently speed up the search process by reducing the search space as much as possible and reducing the cost of executing linear layer operations. We apply our improved algorithm to DESL and GIFT, which are still the hard instances for the automatic search methods. As a result, we find the best differential trails for DESL (up to 14-round) and GIFT-128 (up to 19-round). The best linear trails for DESL (up to 16-round), GIFT-128 (up to 10-round) and GIFT-64 (up to 15-round) are also found. To the best of our knowledge, these security bounds for DESL and GIFT under single-key scenario are given for the first time. Meanwhile, it is the longest exploitable (differential or linear) trails for DESL and GIFT. Furthermore, benefiting from the efficiency of the improved algorithm, we do experiments to demonstrate that the clustering effect of differential trails for 13-round DES and DESL are both weak.

Growth of Cubic Silicon Carbide on Silicon Using Hot Filament CVD

2017 ◽  
Vol 897 ◽  
pp. 91-94
Author(s):  
Philip Hens ◽  
Ryan Brow ◽  
Hannah Robinson ◽  
Michael Cromar ◽  
Bart van Zeghbroeck
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Degrees Of Freedom ◽  
Thick Layer ◽  
Chemical Vapor ◽  
Silicon Substrates ◽  
X Ray Diffraction ◽  
Hot Filament ◽  
Cubic Silicon Carbide ◽  
First Time

In this paper, we report, for the first time, growth of high-quality single-crystalline 3C-SiC on silicon substrates using Hot Filament Chemical Vapor Deposition (HF-CVD). Rocking curve X-Ray diffraction (XRD) measurements revealed a full-width at half maximum (FWHM) as low as 333 arcsec for a 15 μm thick layer. Low tensile strain, below 0.1%, was measured using Raman spectroscopy. This quality was achieved with a carefully optimized process making use of the additional degrees of freedom the hot filaments create. For example, the hot filaments allow for precursor pre-cracking. Additionally, they allow a tuning of the vertical thermal gradient which creates an improved thermal field compared to classic Chemical Vapor Deposition techniques used for the deposition of this material today.

scholarly journals Dartagnan: Leveraging Compiler Optimizations and the Price of Precision (Competition Contribution)

2021 ◽  
pp. 428-432
Author(s):  
Hernán Ponce-de-León ◽  
Thomas Haas ◽  
Roland Meyer
Keyword(s):  
Model Checking ◽  
Bounded Model Checking ◽  
Model Checker ◽  
Compiler Optimizations ◽  
Sequential Programs ◽  
Input Program ◽  
Order Of Magnitude ◽  
Speed Up ◽  
First Time ◽  
Bitwise Operations

AbstractWe describe the new features of the bounded model checker Dartagnan for SV-COMP ’21. We participate, for the first time, in the ReachSafety category on the verification of sequential programs. In some of these verification tasks, bugs only show up after many loop iterations, which is a challenge for bounded model checking. We address the challenge by simplifying the structure of the input program while preserving its semantics. For simplification, we leverage common compiler optimizations, which we get for free by using LLVM. Yet, there is a price to pay. Compiler optimizations may introduce bitwise operations, which require bit-precise reasoning. We evaluated an SMT encoding based on the theory of integers + bit conversions against one based on the theory of bit-vectors and found that the latter yields better performance. Compared to the unoptimized version of Dartagnan, the combination of compiler optimizations and bit-vectors yields a speed-up of an order of magnitude on average.

scholarly journals GTA Weld Brazing a Joint of Aluminum to Stainless Steel

2019 ◽  
Vol 98 (12) ◽  
pp. 365s-378s
Author(s):  
HUAN HE ◽  
◽  
WENQIN GOU ◽  
PATRICIO F. MENDEZ ◽  
SANBAO LIN ◽  
...  
Keyword(s):  
Heat Input ◽  
Joint Strength ◽  
Pure Aluminum ◽  
Thick Layer ◽  
Total Thickness ◽  
Gas Tungsten Arc ◽  
Interfacial Kinetics ◽  
Maximum Value ◽  
First Time ◽  
The Relationship

The relationship between heat input, microstructures, and mechanical properties was studied in the gas tungsten arc (GTA) weld brazing process of aluminum alloy and stain-less steel dissimilar metals with a pure aluminum core wire (ER1100). The mechanisms involved were further revealed by hot-dip aluminizing experiments. The intermetallic compounds (IMCs) of the brazing interface consisted of a thin layer of -Fe2Al5 next to the steel, and a thick layer of -Fe4Al13 adjacent to the Al joint, surrounded by eutectic identified to be Al-FeAl6 and Al-Fe2Al9 distributed uniformly in the weld metal. With increasing heat input, the total thickness of the IMCs decreased first, reaching a minimum value of 3.5 m, and then increased. The decrease in IMC thickness with heat input was observed for the first time and had never been reported before in welding or brazing processes. The joint strength increased to a maximum value of 238 MPa and then declined, suggesting an inverse relationship between IMC thickness and joint strength. The results of the hot-dip aluminizing, regarding the relationship between IMC thickness and temperature, were consistent with the change of IMC thickness in the welds. A possible mechanism in action is that interfacial kinetics and thermodynamics play a role in the dissolution and decomposition of the thick layer of -Fe4Al13 into the FeAl6 and Fe2Al9 phase. Promoting the IMC dissolution or decomposition by adjusting welding procedures is a promising new way to control the IMC growth and improve the joint strength.

scholarly journals Deep COVID 19: Deep Learning for COVID 19 Detection from X ray Images

2021 ◽  
Vol 11 (1) ◽  
pp. 1-6
Author(s):  
Ahmed Hashem El Fiky ◽  
Keyword(s):  
Machine Learning Algorithms ◽  
Diagnostic Process ◽  
X Rays ◽  
Virus Spread ◽  
Large Dataset ◽  
X Ray ◽  
Support Mechanism ◽  
Proposed Model ◽  
Speed Up ◽  
First Time

The COVID-19 will take place for the first time in December 2019 in Wuhan, China. After that, the virus spread all over the world, with over 4.7 million confirmed cases and over 315000 deaths as of the time of writing this report. Radiologists can employ machine learning algorithms developed on radiography pictures as a decision support mechanism to help them speed up the diagnostic process. The goal of this study is to conduct a quantitative evaluation of six off-the-shelf convolutional neural networks (CNNs) for COVID-19 X-ray image analysis. Due to the limited amount of images available for analysis, the CNN transfer learning approach was used. We also developed a simple CNN architecture with a modest number of parameters that does a good job of differentiating COVID-19 from regular X-rays. in this paper, we are used large dataset which contained CXR images of normal patients and patients with COVID-19. the number of CXR images for normal patients are 10,192 image and the number of CXR images for COVID-19 patients are 3,616 images. The results of experiments show the effectiveness and robustness of Deep-COVID-19 and pretrained models like VGG16, VGG19, and MobileNets. Our proposed Model Deep-COVID-19 achieved over 94.5% accuracy.

scholarly journals Spatial patterns of glacier motion during a high-velocity event: Haut Glacier d’Arolla, Switzerland

2001 ◽  
Vol 47 (156) ◽  
pp. 9-20 ◽  
Author(s):  
Douglas Mair ◽  
Peter Nienow ◽  
Ian Willis ◽  
Martin Sharp
Keyword(s):  
Spatial Distribution ◽  
Horizontal Stress ◽  
Surface Strain ◽  
Strain Rates ◽  
Surface Motion ◽  
Local Forcing ◽  
Speed Up ◽  
Non Local ◽  
Glacier Motion ◽  
Resolution Data

AbstractThe surface motion of Haut Glacier d’Arolla, Switzerland, was monitored at a high spatial and temporal resolution. Data are analyzed to calculate surface velocities, surface strain rates and the components of the glacier force budget before, during and after an early melt season speed-up or “spring event”. We investigate the extent to which variations in glacier motion can be attributed to hydrologically induced local forcing or to non-local forcing transmitted via horizontal stress gradients. Enhanced glacier motion is dependent on a change in the spatial distribution of areas of high drag across the glacier.

scholarly journals Multi-Steps Registration Protocol for Multimodal MR Images of Hip Skeletal Muscles in a Longitudinal Study

2020 ◽  
Vol 10 (21) ◽  
pp. 7823
Author(s):  
Lucia Fontana ◽  
Alfonso Mastropietro ◽  
Elisa Scalco ◽  
Denis Peruzzo ◽  
Elena Beretta ◽  
...  
Keyword(s):  
Longitudinal Study ◽  
Image Registration ◽  
Mr Images ◽  
Learning Rates ◽  
Speed Up ◽  
Muscle Magnetic Resonance Imaging ◽  
Magnetic Resonance Imaging Mri ◽  
First Time ◽  
Tesla Scanner

Image registration is crucial in multimodal longitudinal skeletal muscle Magnetic Resonance Imaging (MRI) studies to extract reliable parameters that can be used as indicators for physio/pathological characterization of muscle tissue and for assessing the effectiveness of treatments. This paper aims at proposing a reliable registration protocol and evaluating its accuracy in a longitudinal study. The hips of 6 subjects were scanned, in a multimodal protocol, at 2 different time points by a 3 Tesla scanner; the proposed multi-step registration pipeline is based on rigid and elastic transformations implemented in SimpleITK using a multi-resolution technique. The effects of different image pre-processing (muscle masks, isotropic voxels) and different parameters’ values (learning rates and mesh sizes) were quantitatively assessed using standard accuracy indexes. Rigid registration alone does not provide satisfactory accuracy for inter-sessions alignment and a further elastic step is needed. The use of isotropic voxels, combined with the muscle masking, provides the best result in terms of accuracy. Learning rates can be increased to speed up the process without affecting the final results. The protocol described in this paper, complemented by open-source software, can be a useful guide for researchers that approach for the first time the issues related to the muscle MR image registration.

Sign in / Sign up

Export Citation Format

Share Document