751 research outputs found
Concurrent processing simulation of the space station
The development of a new capability for the time-domain simulation of multibody dynamic systems and its application to the study of a large angle rotational maneuvers of the Space Station is described. The effort was divided into three sequential tasks, which required significant advancements of the state-of-the art to accomplish. These were: (1) the development of an explicit mathematical model via symbol manipulation of a flexible, multibody dynamic system; (2) the development of a methodology for balancing the computational load of an explicit mathematical model for concurrent processing; and (3) the implementation and successful simulation of the above on a prototype Custom Architectured Parallel Processing System (CAPPS) containing eight processors. The throughput rate achieved by the CAPPS operating at only 70 percent efficiency, was 3.9 times greater than that obtained sequentially by the IBM 3090 supercomputer simulating the same problem. More significantly, analysis of the results leads to the conclusion that the relative cost effectiveness of concurrent vs. sequential digital computation will grow substantially as the computational load is increased. This is a welcomed development in an era when very complex and cumbersome mathematical models of large space vehicles must be used as substitutes for full scale testing which has become impractical
A modular software architecture for UAVs
There have been several attempts to create scalable and hardware independent software architectures for Unmanned Aerial Vehicles (UAV). In this work, we propose an onboard architecture for UAVs where hardware abstraction, data storage and communication between modules are efficiently maintained. All processing and software development is done on the UAV while state and mission status of the UAV is monitored from a ground station. The architecture also allows rapid development of mission-specific third party applications on the vehicle with the help of the core module
Engineering toughening mechanisms in architectured ceramic-based bioinspired materials
Abstract Ceramics offer many attractive properties including low-density, high compressive strength, remarkable thermal stability, and high oxidation/corrosion resistance. However, these materials suffer from brittleness, which substantially limits the range of their applications, where high toughness is required. This investigation draws inspiration from a concept of architectures with three-dimensional (3D) networks of weak interfaces targeting high toughness ceramics. In this study, a comprehensive method combining an advanced computational model with 3D digital image correlation (DIC) was developed to engineer bioinspired multilayered architectured ceramics and assesses their toughening and deformation mechanisms when subjected to a low-velocity impact load regime. A complete finite element (FE) analysis was conducted to precisely evaluate the crack growth and displacement field of the architectured ceramics and is compared to those of plain ceramics. The damage and displacement evolution results from FE analysis and experimental testing revealed that the primary source of toughening of the architectured ceramic systems is extrinsic, resulting from extensive crack deflection and delamination. Crack propagation along an irregular long path at the weak interfaces of architectured layers increased the toughness of the plain ceramics by two orders of magnitude. Based on the DIC data, both extrinsic and intrinsic toughening mechanisms were captured: sliding of the tiles in the architectured ceramics and channel plastic deformation in adhesive interlayers, respectively
Combining Commerce and Culture
It seldom happens that new firms, new industries, and new business systems need to be developed simultaneously. This, however, is the situation in transition economies such as China. Irrespective of product and technology used, incentives and governance structures need to be formulated that give business endeavours an organisational form. The survivability of firms depends further on the ability to start and maintain long-term business relations between contracting parties, while only a broad consensus within the community of entrepreneurs and firms on the procedures that co-ordinate business relations and sanctions transgression promises a decline in transaction costs sufficiently enough to trigger off the quick expansion of markets
Review of the Synergies Between Computational Modeling and Experimental Characterization of Materials Across Length Scales
With the increasing interplay between experimental and computational
approaches at multiple length scales, new research directions are emerging in
materials science and computational mechanics. Such cooperative interactions
find many applications in the development, characterization and design of
complex material systems. This manuscript provides a broad and comprehensive
overview of recent trends where predictive modeling capabilities are developed
in conjunction with experiments and advanced characterization to gain a greater
insight into structure-properties relationships and study various physical
phenomena and mechanisms. The focus of this review is on the intersections of
multiscale materials experiments and modeling relevant to the materials
mechanics community. After a general discussion on the perspective from various
communities, the article focuses on the latest experimental and theoretical
opportunities. Emphasis is given to the role of experiments in multiscale
models, including insights into how computations can be used as discovery tools
for materials engineering, rather than to "simply" support experimental work.
This is illustrated by examples from several application areas on structural
materials. This manuscript ends with a discussion on some problems and open
scientific questions that are being explored in order to advance this
relatively new field of research.Comment: 25 pages, 11 figures, review article accepted for publication in J.
Mater. Sc
Elastostatics of star-polygon tile-based architectured planar lattices
We showed a panoptic view of architectured planar lattices based on
star-polygon tilings. Four star-polygon-based lattice sub-families were
investigated numerically and experimentally. Finite element-based
homogenization allowed computation of Poisson's ratio, elastic modulus, shear
modulus, and planar bulk modulus. A comprehensive understanding of the range of
properties and micromechanical deformation mechanisms was developed. By
adjusting the star angle from to the uniqueness limit ( to
), our results showed an over 250-fold range in elastic modulus,
over a 10-fold range in density, and a range of to for
Poisson's ratio. Additively manufactured lattices showed good agreement in
properties. The additive manufacturing procedure for each lattice is available
on www.fullcontrol.xyz/#/models/1d3528. Three of the four sub-families
exhibited in-plane elastic isotropy. One showed high stiffness with auxeticity
at low density with a primarily axial deformation mode as opposed to bending
deformation for the other three lattices. The range of achievable properties,
demonstrated with property maps, proves the extension of the conventional
material-property space. Lattice metamaterials with Triangle-Triangle, Kagome,
Hexagonal, Square, Truncated Archimedean, Triangular, and Truncated Hexagonal
topologies have been studied in the literature individually. We show that all
these structures belong to the presented overarching lattices
The Scalability-Efficiency/Maintainability-Portability Trade-off in Simulation Software Engineering: Examples and a Preliminary Systematic Literature Review
Large-scale simulations play a central role in science and the industry.
Several challenges occur when building simulation software, because simulations
require complex software developed in a dynamic construction process. That is
why simulation software engineering (SSE) is emerging lately as a research
focus. The dichotomous trade-off between scalability and efficiency (SE) on the
one hand and maintainability and portability (MP) on the other hand is one of
the core challenges. We report on the SE/MP trade-off in the context of an
ongoing systematic literature review (SLR). After characterizing the issue of
the SE/MP trade-off using two examples from our own research, we (1) review the
33 identified articles that assess the trade-off, (2) summarize the proposed
solutions for the trade-off, and (3) discuss the findings for SSE and future
work. Overall, we see evidence for the SE/MP trade-off and first solution
approaches. However, a strong empirical foundation has yet to be established;
general quantitative metrics and methods supporting software developers in
addressing the trade-off have to be developed. We foresee considerable future
work in SSE across scientific communities.Comment: 9 pages, 2 figures. Accepted for presentation at the Fourth
International Workshop on Software Engineering for High Performance Computing
in Computational Science and Engineering (SEHPCCSE 2016
Graphene/Li-Ion battery
Density function theory calculations were carried out to clarify storage
states of Lithium (Li) ions in graphene clusters. The adsorption energy, spin
polarization, charge distribution, electronic gap, surface curvature and dipole
momentum were calculated for each cluster. Li-ion adsorbed graphene, doped by
one Li atom is spin polarized, so there would be different gaps for different
spin polarization in electrons. Calculation results demonstrated that a smaller
cluster between each two larger clusters is preferable, because it could
improve graphene Li-ion batteries; consequently, the most proper graphene anode
structure has been proposed.Comment: 19 pages, 7 figures, 1 tabl
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