516 research outputs found
Analysis of Harvesting Energy from Mistuned Multiple Harvesters with and without Coupling
AbstractEnergy harvesting has received a lot of attention in the recent past. At present a single device does not harvested energy enough to power up an electronic sensors. In order to increase the power output multiple identical harvesters are used. When multiple harvesters are used, they bring in non-uniformity in their physical parameters due to variability during manufacturing or even during deployment. Therefore, ânâ numbers of harvesters do not necessary produce ânâ times the harvested power of a single device. The variability in parameters is less enough to be coined as mistuning. In this paper, an analysis of multiple energy harvesters is studied. The harvesters are assumed to show mistuning. The study is further extended to understand the effect of mechanical coupling between the harvesters. For simplification, pendulums are considered as the harvesters, with magnetic tip masses for the electromagnetic energy harvesting. Mistuning is achieved by varying the length of the pendulums. A generalized mathematical model for n coupled harvesters with mistuning is developed. Simulations are performed with the number of harvesters varying from 2 to 6 with ±1% non-repetitive mistuning in the lengths of the harvesters, and a comparison of the power harvested between mechanically coupled and uncoupled harvesters is presented
Elastic effects of vacancies in strontium titanate: Short- and long-range strain fields, elastic dipole tensors, and chemical strain
We present a study of the local strain effects associated with vacancy
defects in strontium titanate and report the first calculations of elastic
dipole tensors and chemical strains for point defects in perovskites. The
combination of local and long-range results will enable determination of x-ray
scattering signatures that can be compared with experiments. We find that the
oxygen vacancy possesses a special property -- a highly anisotropic elastic
dipole tensor which almost vanishes upon averaging over all possible defect
orientations. Moreover, through direct comparison with experimental
measurements of chemical strain, we place constraints on the possible defects
present in oxygen-poor strontium titanate and introduce a conjecture regarding
the nature of the predominant defect in strontium-poor stoichiometries in
samples grown via pulsed laser deposition. Finally, during the review process,
we learned of recent experimental data, from strontium titanate films deposited
via molecular-beam epitaxy, that show good agreement with our calculated value
of the chemical strain associated with strontium vacancies.Comment: 14 pages, 11 figures, 4 table
The Evolution of Family Level Sales Forecasts into Product Level Forecasts
The Evolution of Family Level Sales Forecasts into Product Level Forecast
A micro electromagnetic generator for vibration energy harvesting
Vibration energy harvesting is receiving a considerable amount of interest as a means for powering wireless sensor nodes. This paper presents a small (component volume 0.1 cm3, practical volume 0.15 cm3) electromagnetic generator utilizing discrete components and optimized for a low ambient vibration level based upon real application data. The generator uses four magnets arranged on an etched cantilever with a wound coil located within the moving magnetic field. Magnet size and coil properties were optimized, with the final device producing 46 ”W in a resistive load of 4 k? from just 0.59 m s-2 acceleration levels at its resonant frequency of 52 Hz. A voltage of 428 mVrms was obtained from the generator with a 2300 turn coil which has proved sufficient for subsequent rectification and voltage step-up circuitry. The generator delivers 30% of the power supplied from the environment to useful electrical power in the load. This generator compares very favourably with other demonstrated examples in the literature, both in terms of normalized power density and efficiency
ACT/ICAPS: Thermoplastic composite activities
McDonnell Aircraft Company (MCAIR) is teamed with Douglas Aircraft Company (DAC) under NASA's Advanced Composite Technology (ACT) initiative in a program entitled Innovative Composite Aircraft Primary Structures (ICAPS). Efforts at MCAIR have focused on the use of thermoplastic composite materials in the development of structural details associated with an advanced fighter fuselage section with applicability to transport design. Based on innovative design/manufacturing concepts for the fuselage section primary structure, elements were designed, fabricated, and structurally tested. These elements focused on key issues such as thick composite lugs and low cost forming of fastenerless, stiffener/moldline concepts. Manufacturing techniques included autoclave consideration, single diaphragm co-consolidation (SDCC), and roll-forming
Joint density-functional theory for electronic structure of solvated systems
We introduce a new form of density functional theory for the {\em ab initio}
description of electronic systems in contact with a molecular liquid
environment. This theory rigorously joins an electron density-functional for
the electrons of a solute with a classical density-functional theory for the
liquid into a single variational principle for the free energy of the combined
system. A simple approximate functional predicts, without any fitting of
parameters to solvation data, solvation energies as well as state-of-the-art
quantum-chemical cavity approaches, which require such fitting.Comment: Fixed typos and minor updates to tex
Treatment Longevity and Changes in Surface Fuel Loads After PinyonâJuniper Mastication
In the Intermountain West, land managers masticate pinyon pine (Pinus spp.) and juniper (Juniperus spp.) trees that have encroached sagebrush steppe communities to reduce canopy fuels, alter potential fire behavior, and promote growth of understory grasses, forbs, and shrubs. At three study sites in Utah, 45 sampling plots spanning a range of tree cover from 5% to 50% were masticated. We measured surface fuel load components three times over a 10âyr period. We also measured tree cover, density, and height as indicators of treatment longevity. Changes in these variables were analyzed across the range of preâtreatment tree cover using linear mixed effects modeling. We detected decreases in 1âh down woody debris by 5â6 yr postâtreatment, and from 5â6 to 10 yr postâtreatment, but did not detect changes in 10âh or 100 + 1000âh down woody debris. By 10 yr postâtreatment, there was very little duff and tree litter left for all preâtreatment tree cover values. Herbaceous fuels (all standing live and dead biomass) increased through 10 yr postâtreatment. At 10 yr postâtreatment, pinyonâjuniper cover ranged 0â2.6%, and the majority of trees were1âh fuels were the only class of down woody debris that decreased, it may be beneficial to masticate woody fuels to the finest size possible. Decreases in 1âh down woody debris and duff + litter fuels over time may have important implications for fire behavior and effects, but increases in herbaceous and shrub fuel loads should also be taken into account. At 10 yr postâtreatment, understory grasses and shrubs were not being outcompeted by trees, and average pinyonâjuniper canopy cover wa
Transitioning ECP Software Technology into a Foundation for Sustainable Research Software
Research software plays a crucial role in advancing scientific knowledge, but
ensuring its sustainability, maintainability, and long-term viability is an
ongoing challenge. The Sustainable Research Software Institute (SRSI) Model has
been designed to address the concerns, and presents a comprehensive framework
designed to promote sustainable practices in the research software community.
However the SRSI Model does not address the transitional requirements for the
Exascale Computing Project (ECP) Software Technology (ECP-ST) focus area
specifically. This white paper provides an overview and detailed description of
how ECP-ST will transition into the SRSI in a compressed time frame that a)
meets the needs of the ECP end-of-technical-activities deadline; and b) ensures
the continuity of the sustainability efforts that are already underway.Comment: 7 pages, 1 figur
An Open Community-Driven Model For Sustainable Research Software: Sustainable Research Software Institute
Research software plays a crucial role in advancing scientific knowledge, but
ensuring its sustainability, maintainability, and long-term viability is an
ongoing challenge. To address these concerns, the Sustainable Research Software
Institute (SRSI) Model presents a comprehensive framework designed to promote
sustainable practices in the research software community. This white paper
provides an in-depth overview of the SRSI Model, outlining its objectives,
services, funding mechanisms, collaborations, and the significant potential
impact it could have on the research software community. It explores the wide
range of services offered, diverse funding sources, extensive collaboration
opportunities, and the transformative influence of the SRSI Model on the
research software landscapeComment: 13 pages, 1 figur
Power processing circuits for electromagnetic, electrostatic and piezoelectric inertial energy scavengers
Accepted versio
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