Automated Identification of Compression-Induced Cracking in Cement Paste
The development of image analysis techniques to identify cracks using scanning electron microscope images of hydrated cement paste is described. Cracks are identified based on both the...
Sensitivity of Lifeline Response to Models for the Spatial Incoherence of the Seismic Ground Motions
The sensitivity of the response of above-ground and buried lifelines to different models describing the spatial variability of the seismic ground motions is examined. It is shown that...
First Order Importance Sampling Method and its Variance Reduction
This paper proposes an Importance Sampling method for structural system reliability problems with linearized modal failure surfaces. It has the advantage of locating all samples in the...
Nonstationary Response Characteristics of Linear MDOF Systems
A new approximate methodology for nonstationary random vibration analysis of multi-degree-of-freedom linear systems is developed. Simple analytical expressions for the covariance response...
Highly Accurate Adaptive hp-Methods for Linear Elastostatics
A new class of highly accurate, self-adaptive computational methods for two- and three-dimensional elastostatics problems is presented which can deliver solutions to general boundary-value...
Bifurcations and Chaos in Structural Control
We study a harmonically forced oscillator with nonlinear soft spring subjected to a linear feedback control with time delay. This system can be written as a three dimensional dynamical...
Regularization Methods for Identification of Structural Damage
Generally, various non-unique solutions may be obtained from ill-conditioned equations. Several methods are available to obtain a unique (minimum energy) solution to a modified and thus...
Updating Dynamic Models and Their Associated Uncertainties for Structural Systems
The problem of updating a structural model and its associated uncertainties using dynamic test data is addressed, considering uncertainties which arise from measurement noise, modeling...
Computer Simulation of Dry Layered Granular Flow Down an Incline Composed of Grains
Experiments show that gravity-driven dry granular flows are essentially layered for smooth spheres. This paper describes layer-to-layer interaction in the flow. Assuming two-dimensional...
Full Scale Application of Active Bracing Systems
A full scale active bracing system has been installed in a structure in Tokyo, Japan. The practical problems associated with the implementation of this system, and the corresponding solutions...
Recent Findings in Active Structural Control
Over the past decade, tremendous advancements have been made in the development of structural control paradigms and in the necessary supporting technologies. The fundamental paradigm that...
Inflation Instability of Cylindrical Membranes
A new procedure which investigates inflation instability of cylindrical nonlinear membranes is developed. The general characteristics of inflation instability are described. An efficient...
Nonlinear Eigensolver for Exact Vibration Analysis
Vibration analysis of structural systems is concerned with accurately predicting the free vibration modes and frequencies of the vibrating system. This analysis process involves two general...
An Expert System for Impeller Mechanical Design and Analysis
Impeller is the most critical component of centrifugal compressors. The mechanical efficiency and durability of the impeller determines the performance of the compressors. The shapes and...
Lunar Oasis
The Lunar Oasis emphasizes development toward self-sufficiency in order to reduce dependence on the Earth for resupply and to enable expansion utilizing indigenous resources. The Oasis...
A Horizontal Inflatable Habitat for SEI
The inflatable habitat described in this paper is a horizontally-oriented cylindrical pneumatic structure. It is part of NASA's ongoing effort to study inflatables as alternative habitats...
Cables and Cranes for a Flexible Lunar Transportation System
This paper will discuss the results of preliminary research on a cable-based transportation system for the moon. The paper will address the principles of cableway design and will present...
The Application of Open System Architecture to Planetary Surface Systems
This paper investigates the issues that future planet surface activities must confront, defines the basic concepts that provide the basis for establishing an Open System Architecture,...
Chemical Analysis in Space Exploration: A Lunar-based Chemical Analysis Laboratory (LBCAL)
Many questions need to be answered before humans can be supported for extended periods in space - an environment inimical to terrestrial life. While some questions of a physiological nature...
A Modified Sulfate Process to Lunar Oxygen
A modified sulfate process which produces oxygen from iron oxide-bearing minerals in lunar soil is under development. Reaction rates of ilmenite in varying strength sulfuric acid have...
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