913 research outputs found
Analytical Model for the Optical Functions of Indium Gallium Nitride with Application to Thin Film Solar Photovoltaic Cells
This paper presents the preliminary results of optical characterization using
spectroscopic ellipsometry of wurtzite indium gallium nitride (InxGa1-xN) thin
films with medium indium content (0.38<x<0.68) that were deposited on silicon
dioxide using plasma-enhanced evaporation. A Kramers-Kronig consistent
parametric analytical model using Gaussian oscillators to describe the
absorption spectra has been developed to extract the real and imaginary
components of the dielectric function ({\epsilon}1, {\epsilon}2) of InxGa1-xN
films. Scanning electron microscope (SEM) images are presented to examine film
microstructure and verify film thicknesses determined from ellipsometry
modelling. This fitting procedure, model, and parameters can be employed in the
future to extract physical parameters from ellipsometric data from other
InxGa1-xN films
Reducing the Threat of a Nuclear Iran with Photovoltaic Technology: The Generous Solar Option
International audienc
National Academy of Engineering: Introduction to Open Hardware in Science and Engineering
International audienc
Defense for Covert Administrative Techniques for Neutralizing American Highly Qualified Personnel
International audiencePh.D. scientists and engineers are highly qualified personnel (HQP) that improve U.S. economic efficiency and generate new products including weapons of interest to the intelligence community. HQP represent a small fraction of the population, which make them favorable targets to compromise. This study analyzes how to defend against a novel approach of covert infiltration that uses administrative techniques to neutralize HQP without recruiting them directly. The approach follows five hierarchical strategies to replace the innovation cycle with administrative time expenditures. This approach is critically analyzed to further national security goals by providing intelligence service guidelines for defensive measures needed against this new weapon
Create, Share, and Save Money Using Open-Source Projects
Prepare to explore an amazing collection of open-source projects shared by others—that literally create millions of dollars of wealth. You can do all these projects yourself by following in the footsteps of other Creative Commons users. Perhaps best of all—it is all free! Regardless of your experience, in doing your own projects, you have already benefited from this open-source sharing, even without knowing it. The internet is perhaps the best example because it is a massive collection of wildly successful open-source projects put together by millions of people sharing their time and talent. In these pages, you will learn about how to be a more proactive sharer in the Creative Commons to reap the benefits of enormous wealth for yourself and others, even if you have only a modest amount of money to start
Distributed manufacturing of open source medical hardware for pandemics
Distributed digital manufacturing offers a solution to medical supply and technology shortages during pandemics. To prepare for the next pandemic, this study reviews the state-of-the-art of open hardware designs needed in a COVID-19-like pandemic. It evaluates the readiness of the top twenty technologies requested by the Government of India. The results show that the majority of the actual medical products have some open source development, however, only 15% of the supporting technologies required to produce them are freely available. The results show there is still considerable research needed to provide open source paths for the development of all the medical hardware needed during pandemics. Five core areas of future research are discussed, which include (i) technical development of a wide-range of open source solutions for all medical supplies and devices, (ii) policies that protect the productivity of laboratories, makerspaces, and fabrication facilities during a pandemic, as well as (iii) streamlining the regulatory process, (iv) developing Good-Samaritan laws to protect makers and designers of open medical hardware, as well as to compel those with knowledge that will save lives to share it, and (v) requiring all citizen-funded research to be released with free and open source licenses
Distributed Manufacturing of Flexible Products: Technical Feasibility and Economic Viability
International audienceDistributed manufacturing even at the household level is now well established with the combined use of open source designs and self-replicating rapid prototyper (RepRap) 3-D printers. Previous work has shown substantial economic consumer benefits for producing their own polymer products. Now flexible filaments are available at roughly 3-times the cost of more conventional 3-D printing materials. To provide some insight into the potential for flexible filament to be both technically feasible and economically viable for distributed digital manufacturing at the consumer level this study investigates 20 common flexible household products. The 3-D printed products were quantified by print time, electrical energy use and filament consumption by mass to determine the cost to fabricate with a commercial RepRap 3-D printer. Printed parts were inspected and when necessary tested for their targeted application to ensure technical feasibility. Then, the experimentally measured cost to DIY manufacturers was compared to low and high market prices for comparable commercially available products. In addition, the markup and potential for long-term price declines was estimated for flexible filaments by converting thermoplastic elastomer (TPE) pellets into filament and reground TPE from a local recycling center into filament using an open source recyclebot. This study found that commercial flexible filament is economically as well as technically feasible for providing a means of distributed home-scale manufacturing of flexible products. The results found a 75% savings when compared to the least expensive commercially equivalent products and 92% when compared to high market priced products. Roughly, 160 flexible objects must be substituted to recover the capital costs to print flexible materials. However, as previous work has shown the Lulzbot Mini 3-D printer used in this study would provide more than a 100% ROI printing one object a week from hard thermoplastics, the upgrade needed to provide flexible filament capabilities can be accomplished with 37 average substitution flexible prints. This, again easily provides a triple digit return on investment printing one product a week. Although these savings, which are created by printing objects at home are substantial, the results also have shown the savings could be further increased to 93% when the use of a pellet extruder and TPE pellets, and 99% if recycled TPE filament made with a recyclebot is used. The capital costs of a recyclebot can be recovered in the manufacturing of about 9 kg of TPE filament, which can be accomplished in less than a week, enabling improved environmental impact as well as a strong financial return for heavy 3-D printer users
Expanded microchannel heat exchanger: design, fabrication and preliminary experimental test
This paper first reviews non-traditional heat exchanger geometry, laser
welding, practical issues with microchannel heat exchangers, and high
effectiveness heat exchangers. Existing microchannel heat exchangers have low
material costs, but high manufacturing costs. This paper presents a new
expanded microchannel heat exchanger design and accompanying continuous
manufacturing technique for potential low-cost production. Polymer heat
exchangers have the potential for high effectiveness. The paper discusses one
possible joining method - a new type of laser welding named "forward conduction
welding," used to fabricate the prototype. The expanded heat exchanger has the
potential to have counter-flow, cross-flow, or parallel-flow configurations, be
used for all types of fluids, and be made of polymers, metals, or
polymer-ceramic precursors. The cost and ineffectiveness reduction may be an
order of magnitude or more, saving a large fraction of primary energy. The
measured effectiveness of the prototype with 28 micron thick black low density
polyethylene walls and counterflow, water-to-water heat transfer in 2 mm
channels was 72%, but multiple low-cost stages could realize the potential of
higher effectiveness
Measuring the Effects of Childbearing on Labor Market Outcomes
Decisions about childbearing and market work are significantly interrelated. Although there are many estimates of the effects of fertility on labor supply, few of them have adequately addressed the problems of simultaneity inherent in these choices. In our research we use exogenous variations in fertility due to twin births to measure the impact of an unplanned child on labor supply and earnings. We contrast these results to those for closely-spaced births (one year or less). We consider effects for married and unmarried mothers separately, and for married fathers. We discuss the implications of these measurements for estimating the magnitude of the rise in female labor supply and earnings as birthrates decline.fertility, labor supply, earnings
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