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Search Publications by

Nicos Martys (Fed)

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Displaying 26 - 50 of 92

Advancing the materials science of concrete with supercomputers

January 24, 2011
Jeffrey W. Bullard, Edward Garboczi, William L. George, Nicos Martys, Steven G. Satterfield, Judith E. Terrill
Supercomputers are renowned for being used on grand challenge problems like global weather patterns, nuclear device virtual testing, galaxy formation, unraveling molecular structure - and now concrete! Why do the mysteries of concrete form this kind of a

A Numerical Study of the Flow of Bingham-Like Fluids In Two Dimensional Vane And Cylinder Rheometers Using a Smoothed Particle Hydrodynamic (SPH) Based Method

April 7, 2010
Huaning Zhu, Nicos Martys, Chiara C. Ferraris, Daniel De Kee
A vane rheometer is commonly used to determine the rheological properties of suspensions, colloids such as cement-based materials, many of which can be described as a Bingham fluid. Due to the complex flow geometry of the vane rheometer, relating measured

Virtual Testing of Concrete Transport Properties

October 1, 2009
Dale P. Bentz, Edward J. Garboczi, Nicos Martys, Kenneth A. Snyder, W. S. Guthrie, Konstantinos Kyritsis, Narayanan Neithalath
The transport properties of concrete are critical to its field performance. Commonly encountered degradation mechanisms are dependent on ionic diffusivity, sorptivity, and permeability. In this paper, virtual testing of two of these concrete transport

Contact and Stress Anisotropies in Start Up Flows of Collodial Suspensions

September 11, 2009
Nicos Martys, William L. George, Didier Lootens, Pascal Hebraud
Spatio-temporal correlations in start-up flows of attractive colloids are explored by numerical simulations. The suspension is first allowed to flocculate during a time tw, then the stress necessary to induce its flow is computed. Whereas at low volume

Building Plumbing System Decontamination - First Report on Recommendations

September 6, 2009
Stephen J. Treado, Mark A. Kedzierski, Stephanie S. Watson, Nicos Martys, Kenneth D. Cole
This report summarizes the measurement results and recommended procedures for responding to building plumbing system contamination incidents and restoring the water system to safe operation. The recommendations are based on analysis of the results of a

Virtual Cement and Concrete

September 1, 2009
Jeffrey W. Bullard, Chiara C. Ferraris, Edward Garboczi, Nicos Martys, Paul E. Stutzman, Judith E. Terrill
Design and optimization of cement or concrete mixes typically is accomplished by intensive trial-and-error experimentation, primarily because the design space has many parameters and because interactions between these parameters are incompletely understood

Extending Measurement Science to Interactive Visualization Environments

January 30, 2009
Judith E. Terrill, William L. George, Terence J. Griffin, John G. Hagedorn, John T. Kelso, Thomas M. Olano, Adele P. Peskin, Steven G. Satterfield, James S. Sims, Jeffrey W. Bullard, Joy P. Dunkers, Nicos Martys, Agnes A. O'Gallagher, Gillian Haemer
We describe a method for creating a visual laboratory to interactively measure and analyze scientific data. We move the normal activities that scientists perform to understand their data into the visualization environment. The visualization environment is

Standards Development for Gas Phase Air Cleaning Equipment in Buildings

November 3, 2008
Andrew K. Persily, Cynthia H. Reed, Stephanie S. Watson, Nicos Martys, Edward J. Garboczi, Heather Davis
Concerns about building security have resulted in increasing interest in gas phase air cleaning (GPAC) and the need for standard methods to determine the effectiveness of these systems. Similarly, the ability to predict their installed performance, based

A Comparison of Viscosity-Concentration Relationships for Emulsions

November 1, 2008
Jeffrey W. Bullard, A T. Pauli, Edward J. Garboczi, Nicos Martys
Differential Effective Medium Theory (D-EMT) is applied to derive expressions for the viscosity of a colloidal suspension or an emulsion as a function of the volume fraction of the dispersed phase. The application of D-EMT to this problem depends on how

Spatial-Temporal Correlations at the Onset of Flow in Concentrated Suspensions

July 7, 2008
Nicos Martys, Didier Lootens, William L. George, Steven G. Satterfield, Pascal Hebraud
Spatial-temporal correlations in the startup-up flow of colloidal suspensions composed of attractive spherical particles under static and shear conditions are studied by computer simulation. The evolution of particle organization with time is followed as

Stress chains formation under shear of concentrated suspension

July 7, 2008
Didier Lootens, Nicos Martys, William L. George, Steven G. Satterfield, Pascal Hebraud
Results comparing experiments on a model system of mono-disperse silica-particles with the numerical simulation of highly concentrated suspension of spherical particles subject to a constant rate of strain are presented. Giant fluctuations of the shear

Parallel-Plate Rheometer Calibration Using Oil and Lattice Boltzmann Simulation

October 11, 2007
Chiara F. Ferraris, Nicos Martys, M R. Geiker, N V. Muzzatti
The flow in traditional rotational rheometers is well known and rheological parameters such as viscosity can be calculated relatively easily. On the other hand, when the fluid is a suspension that contains particles with a diameter up to 2 mm, these

Cement and Concrete Materials Research at the National Institute of Standards and Technology (NIST)

September 5, 2007
Edward J. Garboczi, Dale P. Bentz, Jeffrey W. Bullard, Chiara F. Ferraris, Nicos Martys, Max A. Peltz, Sudalin Rodrigues, Paul E. Stutzman, Kenneth A. Snyder, John A. Winpigler
The materials science of cement and concrete is the focus of the Inorganic Materials Group at the National Institute of Standards and Technology (NIST). These experimental and computational research efforts include component and finished materials

Computational Model Predictions of Suspension Rheology: Comparison to Experiment

July 25, 2007
Nicos Martys, Chiara F. Ferraris, V Gupta, Josephine H. Cheung
Predicting the rheological properties of fresh concrete, mortars, and cement paste from first principles remains a great challenge. While progress has been made in modeling the rheological properties of idealized hard sphere-like suspensions, there is

A Stokes Permeability Solver for Three-Dimensional Porous Media

April 4, 2007
Dale P. Bentz, Nicos Martys
A set of C and Fortran computer programs have been developed for computing the permeability of three-dimensional porous media under incompressible Stokes flow conditions. In this NISTIR, the background for developing these codes is reviewed and the

Virtual Testing of Cement and Concrete

May 10, 2006
Dale P. Bentz, Edward J. Garboczi, Jeffrey W. Bullard, Chiara F. Ferraris, Nicos Martys, Paul E. Stutzman
Concrete is a unique multi-phase, random, complex, and composite material that provides both strength and impermeability to engineered structures. Unlike most construction materials, the properties of concrete continue to develop over time and in place an

Cross-Property Correlations and Permeability Estimation in Sandstone

October 26, 2005
C H. Arns, M A. Knackstedt, Nicos Martys
Results from a numerical study examining the cross-property correlations linking fluid permeability to conductive properties and to a number of pore size parameters based on 3D digitized images of sedimentary rock are presented. In particular we focus on