Confining pressure reduction experiments: a new method for measuring frictional strength over a wide range of normal stress

1986 ◽  
Vol 23 (2) ◽  
pp. 44
Keyword(s):  
Normal Stress ◽  
Confining Pressure ◽  
New Method ◽  
Pressure Reduction ◽  
Frictional Strength ◽  
Wide Range

scholarly journals Frictional behaviour of carbonate bearing faults at brittle-ductile transition

2021 ◽  
Author(s):  
Francesco Figura ◽  
Carolina Giorgetti ◽  
Mathias Lebihain ◽  
Marie Violay
Keyword(s):  
Normal Stress ◽  
Principal Stress ◽  
Fluid Pressure ◽  
Confining Pressure ◽  
Shear Loading ◽  
Experimental Results ◽  
Ductile Deformation ◽  
Critical Conditions ◽  
Brittle Ductile Transition ◽  
Wide Range

<p>One of the most alarming recent findings in geo-science is the dramatic rise in the rate of human-induced earthquakes in the past decade. This is due to the fluid injection or extraction in deep reservoirs for hydrocarbon production, wastewater and CO<sub>2</sub> storage and exploitation of geothermal resources which result in the reactivation of nearby faults. These reservoirs are often located 2-3 km depth (i.e. 30 MPa), and are hosted in or covered by sedimentary carbonate layers. As carbonate undergoes a brittle-ductile transition with increasing confining pressure from values of around 20 MPa, ductile deformation can play an important role on the nucleation and propagation of earthquakes on carbonate faults. Here, we investigate the role of increasing ductile behaviour on fault frictional parameters. The research is performed through the new biaxial apparatus installed at EPFL, the <em>HighSTEPS </em>(High Strain TEmperature Pressure Speed) apparatus, able to measure frictional parameters in a wide range of shearing velocities (10<sup>-6</sup> m/s – 0.2 m/s) and under unique boundary conditions representative of the Earth’s crust, i.e., normal stress up to 100 MPa, confining pressure up to 100 MPa, pore fluid pressure up to 100 MPa and temperature up to 120°. The induced stress state in bare surface samples was previously studied by a comparison between results of FEM numerical analyses and experimental ones. Under shear loading conditions, the principal stress σ1 is oriented at about 25° to the vertical axis, and the confining pressure corresponds to the principal stress σ2. Tests are performed under different values of applied confining pressure (1 - 60 MPa) and normal stress (1.5 – 90 MPa) on the faults, keeping constant the ratio between σn/σ3 around ~ 3, to mimic faults at different depth. We present experimental results mapping carbonate fault mechanical behaviour from low shearing velocity 10<sup>-6</sup> m/s to high shearing velocity 10<sup>-1</sup> m/s. Moreover, experimental results are modelled with rate-and-state friction laws (RSFLs) to define rate and state parameters related to the critical conditions for fault stability and its dependence on the presence of ductile deformation. These results shed new light on the nucleation and propagation of earthquake within the brittle-ductile transition in carbonate bearing rocks.</p>

scholarly journals Design of Personalized Devices—The Tradeoff between Individual Value and Personalization Workload

2020 ◽  
Vol 11 (1) ◽  
pp. 241
Author(s):  
Juliane Kuhl ◽  
Andreas Ding ◽  
Ngoc Tuan Ngo ◽  
Andres Braschkat ◽  
Jens Fiehler ◽  
...  
Keyword(s):  
Customer Value ◽  
Early Stage ◽  
Treatment Success ◽  
Product Family ◽  
Flow Diverter ◽  
New Method ◽  
Product Families ◽  
Wide Range ◽  
The Individual ◽  
Individual Value

Personalized medical devices adapted to the anatomy of the individual promise greater treatment success for patients, thus increasing the individual value of the product. In order to cater to individual adaptations, however, medical device companies need to be able to handle a wide range of internal processes and components. These are here referred to collectively as the personalization workload. Consequently, support is required in order to evaluate how best to target product personalization. Since the approaches presented in the literature are not able to sufficiently meet this demand, this paper introduces a new method that can be used to define an appropriate variety level for a product family taking into account standardized, variant, and personalized attributes. The new method enables the identification and evaluation of personalizable attributes within an existing product family. The method is based on established steps and tools from the field of variant-oriented product design, and is applied using a flow diverter—an implant for the treatment of aneurysm diseases—as an example product. The personalization relevance and adaptation workload for the product characteristics that constitute the differentiating product properties were analyzed and compared in order to determine a tradeoff between customer value and personalization workload. This will consequently help companies to employ targeted, deliberate personalization when designing their product families by enabling them to factor variety-induced complexity and customer value into their thinking at an early stage, thus allowing them to critically evaluate a personalization project.

scholarly journals Evolution of Friction and Permeability in a Propped Fracture under Shear

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Fengshou Zhang ◽  
Yi Fang ◽  
Derek Elsworth ◽  
Chaoyi Wang ◽  
Xiaofeng Yang
Keyword(s):  
Normal Stress ◽  
Shear Loading ◽  
Particle Crushing ◽  
Normal Loading ◽  
Fracture Surfaces ◽  
Frictional Strength ◽  
Transport Response ◽  
Shear Slip ◽  
High Normal Stress ◽  
Proppant Embedment

We explore the evolution of friction and permeability of a propped fracture under shear. We examine the effects of normal stress, proppant thickness, proppant size, and fracture wall texture on the frictional and transport response of proppant packs confined between planar fracture surfaces. The proppant-absent and proppant-filled fractures show different frictional strength. For fractures with proppants, the frictional response is mainly controlled by the normal stress and proppant thickness. The depth of shearing-concurrent striations on fracture surfaces suggests that the magnitude of proppant embedment is controlled by the applied normal stress. Under high normal stress, the reduced friction implies that shear slip is more likely to occur on propped fractures in deeper reservoirs. The increase in the number of proppant layers, from monolayer to triple layers, significantly increases the friction of the propped fracture due to the interlocking of the particles and jamming. Permeability of the propped fracture is mainly controlled by the magnitude of the normal stress, the proppant thickness, and the proppant grain size. Permeability of the propped fracture decreases during shearing due to proppant particle crushing and related clogging. Proppants are prone to crushing if the shear loading evolves concurrently with the normal loading.

Cholinium-amino acid based ionic liquids: a new method of synthesis and physico-chemical characterization

2015 ◽  
Vol 17 (32) ◽  
pp. 20687-20698 ◽  
Author(s):  
Serena De Santis ◽  
Giancarlo Masci ◽  
Francesco Casciotta ◽  
Ruggero Caminiti ◽  
Eleonora Scarpellini ◽  
...  
Keyword(s):  
Ionic Liquids ◽  
Amino Acid ◽  
Room Temperature ◽  
Chemical Characterization ◽  
New Method ◽  
Room Temperature Ionic Liquids ◽  
Synthetic Method ◽  
Chemical Structures ◽  
Physico Chemical ◽  
Wide Range

Fourteen cholinium-amino acid based room temperature ionic liquids were prepared using a cleaner synthetic method. Chemicophysical properties were well correlated with the wide range of amino acid chemical structures.

scholarly journals A new entropy-variable-based discretization method for minimum entropy moment approximations of linear kinetic equations

2021 ◽  
Author(s):  
Tobias Leibner ◽  
Mario Ohlberger
Keyword(s):  
Optimization Problems ◽  
Hessian Matrix ◽  
Computational Cost ◽  
Kinetic Equations ◽  
New Method ◽  
Minimum Entropy ◽  
Reduced Basis ◽  
Simple Task ◽  
Wide Range ◽  
The Moment

In this contribution we derive and analyze a new numerical method for kinetic equations based on a variable transformation of the moment approximation. Classical minimum-entropy moment closures are a class of reduced models for kinetic equations that conserve many of the fundamental physical properties of solutions. However, their practical use is limited by their high computational cost, as an optimization problem has to be solved for every cell in the space-time grid. In addition, implementation of numerical solvers for these models is hampered by the fact that the optimization problems are only well-defined if the moment vectors stay within the realizable set. For the same reason, further reducing these models by, e.g., reduced-basis methods is not a simple task. Our new method overcomes these disadvantages of classical approaches. The transformation is performed on the semi-discretized level which makes them applicable to a wide range of kinetic schemes and replaces the nonlinear optimization problems by inversion of the positive-definite Hessian matrix. As a result, the new scheme gets rid of the realizability-related problems. Moreover, a discrete entropy law can be enforced by modifying the time stepping scheme. Our numerical experiments demonstrate that our new method is often several times faster than the standard optimization-based scheme.

Urinary protein as measured with a pyrogallol red-molybdate complex, manually and in a Hitachi 726 automated analyzer.

1986 ◽  
Vol 32 (8) ◽  
pp. 1551-1554 ◽  
Author(s):  
N Watanabe ◽  
S Kamei ◽  
A Ohkubo ◽  
M Yamanaka ◽  
S Ohsawa ◽  
...  
Keyword(s):  
Trichloroacetic Acid ◽  
Protein Concentration ◽  
Urinary Protein ◽  
New Method ◽  
Normal Range ◽  
Pyrogallol Red ◽  
Wide Range ◽  
Biuret Method

Abstract In this new method for determining urinary protein, the reaction is complete within 10 min at 37 degrees C. This method is applicable to automated as well as manual measurements. Protein concentration and absorbance at 600 nm are linearly related throughout a wide range of concentrations, 10 to 16 000 mg/L. However, the chromogenicity of the gamma-globulins in this method is 70% of that of albumin, as estimated from results by a biuret method. Within-run CVs were less than 3.3%; the day-to-day CV was 2.9%. Errors due to interfering components in urine are less than 2%. The normal range for urinary protein as measured by this method was from 28 to 141 mg/day. Results by this method (y) and by a trichloroacetic acid-biuret method (x) correlated well (n = 80, r = 0.995; y = 0.99x - 2.9).

scholarly journals Development of a shutterless continuous rotation method using an X-ray CMOS detector for protein crystallography

2009 ◽  
Vol 42 (6) ◽  
pp. 1165-1175 ◽  
Author(s):  
Kazuya Hasegawa ◽  
Kunio Hirata ◽  
Tetsuya Shimizu ◽  
Nobutaka Shimizu ◽  
Takaaki Hikima ◽  
...  
Keyword(s):  
Data Collection ◽  
Dynamic Range ◽  
Protein Structures ◽  
Protein Crystallography ◽  
New Method ◽  
Oxide Semiconductor ◽  
X Ray ◽  
Rotation Method ◽  
Continuous Rotation ◽  
Wide Range

A new shutterless continuous rotation method using an X-ray complementary metal-oxide semiconductor (CMOS) detector has been developed for high-speed, precise data collection in protein crystallography. The principle of operation and the basic performance of the X-ray CMOS detector (Hamamatsu Photonics KK C10158DK) have been shown to be appropriate to the shutterless continuous rotation method. The data quality of the continuous rotation method is comparable to that of the conventional oscillation method using a CCD detector and, furthermore, the combination with fine φ slicing improves the data accuracy without increasing the data-collection time. The new method is more sensitive to diffraction intensity because of the narrow dynamic range of the CMOS detector. However, the strong diffraction spots were found to be precisely measured by recording them on successive multiple images by selecting an adequate rotation step. The new method has been used to successfully determine three protein structures by multi- and single-wavelength anomalous diffraction phasing and has thereby been proved applicable in protein crystallography. The apparatus and method may become a powerful tool at synchrotron protein crystallography beamlines with important potential across a wide range of X-ray wavelengths.

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