136 research outputs found
Optical and Electronic Simulation of Silicon / Germanium Tandem Four Terminal Solar Cells
No full textA tandem solar cell architecture of silicon and germanium solar cells in a mechanical (stack like) arrangement is evaluated to increase the efficiency of light absorption in the far infra-red region from 1107 nm to 1907 nm wavelength which constitutes about 14.5% of the power intensity in the solar AM 1.5 spectrum. In this work the technical feasibility of tandem solar cells is investigated. Here we report on detailed electrical and optical simulations of this structure quantifying the various theoretical and practical loss mechanisms in the encapsulation, interfaces and in the device and indicate that a relative efficiency improvement of 20% may be attainable with silicon and germanium solar cells in this configuration. The optical and electrical parameters for silicon and germanium simulation models were extracted from experimental devices and material vendors. The developed simulation models were validated by comparing the performance of standalone silicon and germanium solar cells with experimental devices reported in the literature.This article, by Vishnuvardhanan Vijayakuman and Dunbar P. Birnie, III, was originally published in Journal of Solar Energy Engineering, copyright 2014 by ASME. It may be used for non-commercial purposes only.Peer reviewe
E-journals in a networked environment : its impact on academic libraries in the digital millennium
No full textThis paper tries to describe the Advantages of E-journals in terms of Accessibility, Speed distribution and production, Subscription Cost, Multimedia Capabilities, Internal and External Links etc and also tries to find out the Technological, Socio-cultural and Economic Barriers. The issues like Refereeing, Copyright and Licensing, Longevity and Storage and recent trends in E-journal publication and its implication on Academic Libraries in selection and acquisition, Cataloguing, archiving, user's access, training and support to staff and users are discussed in this paper
Optical and Electronic Simulation of Gallium Arsenide/Silicon Tandem Four Terminal Solar Cells
No full textA tandem solar cell in a mechanical (stack like) arrangement of gallium arsenide and silicon solar cells is evaluated as a pathway towards higher efficiency terrestrial solar cells. In this work the technical feasibility of the tandem solar cell is investigated. Here we report on the detailed electrical and optical simulations of this structure quantifying various theoretical and practical loss mechanisms in the interface and in the device and indicate that an efficiency improvement of 5.13% would be attainable with present generation of gallium arsenide and silicon solar cells in this configuration. The optical and electrical parameters for gallium arsenide and silicon simulation models were extracted from experimental devices and material vendors. The developed simulation models were validated by comparing the performance of standalone gallium arsenide and silicon solar cells with experimental devices reported in the literature.NOTICE: this is the author’s version of a work that was accepted for publication in Solar Energy. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Solar Energy, 97 (2013), DOI:10.1016/j.solener.2013.07.033Peer reviewe
The accumulation of particles in ureteric stents is mediated by flow dynamics: Full-scale computational and experimental modeling of the occluded and unoccluded ureter
No full textUreteric stents are clinically deployed to restore urinary drainage in the presence of ureteric occlusions. They consist of a hollow tube with multiple side-holes that enhance urinary drainage. The stent surface is often subject to encrustation (induced by crystals-forming bacteria such as Proteus mirabilis) or particle accumulation, which may compromise stent's drainage performance. Limited research has, however, been conducted to evaluate the relationship between flow dynamics and accumulation of crystals in stents. Here, we employed a full-scale architecture of the urinary system to computationally investigate the flow performance of a ureteric stent and experimentally determine the level of particle accumulation over the stent surface. Particular attention was given to side-holes, as they play a pivotal role in enhancing urinary drainage. Results demonstrated that there exists an inverse correlation between wall shear stress (WSS) and crystal accumulation at side-holes. Specifically, side-holes with greater WSS levels were those characterized by inter-compartmental fluid exchange between the stent and ureter. These "active " side-holes were located either nearby ureteric obstructions or at regions characterized by a physiological constriction of the ureter. Results also revealed that the majority of side-holes (> 60%) suffer from low WSS levels and are, thus, prone to crystals accumulation. Moreover, side-holes located toward the proximal region of the ureter presented lower WSS levels compared to more distal ones, thus suffering from greater particle accumulation. Overall, findings corroborate the role of WSS in modulating the localization and extent of particle accumulation in ureteric stents. (C) 2022 Author(s)
Body & Evironment
No full text122 pagesEssays:
Waves of Whales - Sadie Trush / Bionic Rhythm - Kirsten Vinyeta / Counting Stomata - Allyson Woodard
Fiction:
To Hear the Earth Speak - Francesca Varela / Interview
“To Make Change You Need to be Inspired” - Jessica Rojas / Poetry: Us. -
Anonymous / Adama -
Christa Linz / Pump -
Lisa Lombardo / On a Cross-Country Bus - J. Pazamàdjigan
/ Mountain Hemlock -
Susanne Twight-Alexander / The Garden of Earthly Delights -
Chithira Vijayakumar
/ Ambrose -
Gayla WardWel
Lymph Node T Cell Dynamics and Novel Strategies for HIV Cure
No full textThis eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contac
Lymph Node T Cell Dynamics and Novel Strategies for HIV Cure
No full textThis eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contac
Sustainable poly(lactic acid) transformation: Leveraging agri-food waste-compatibilization strategies nexus for enhanced properties
No full textThe paper comprehensively reviews the upcycling and utilization of agri-food loss and wastes (FLWs) in poly(lactic acid) (PLA)-based biocomposites from the perspective of material circularity. The massive volume of unwanted and unvalued FLWs contributed from fruit producers (durian husk, pineapple leaf, orange peel, and apple), post-consumer products (spent coffee ground, sugarcane bagasse, coconut husk, crustacean shells), and agricultural sectors (rick husk, rice straw, wheat straw, and corn stover) is generally discarded and incinerated. Notably, these FLWs can be collected and upcycled into valuable products depending on the final application, endowing them with a meaningful second life. This upcycling approach promotes environment-friendliness and reduces the product’s carbon footprint. However, gaps and challenges in creating high-performance biocomposites remain critical to a translatable product. To address that, this review comprehensively discussed the recent progress and strategies to enhance the compatibility of PLA and the various FLW biocomposites, such as improved processability, well-balanced properties, heat resistance, and increased interfacial adhesion. The overall mechanical, thermal, processability, and biodegradability performances are further examined and elaborated. Furthermore, the current and prospective applications, such as packaging, automotive, construction, and 3D printing of FLWs/PLA products, are discussed. Finally, the prospects and opportunities of these FLWs/PLA biocomposites are shared to give a view into the future. Graphical Abstract: (Figure presented.)Author: J. C. C. Yeo, funder: Agency for Science, Technology and Research (A*STAR), GAP Grant (Grant No. I22D1AG014). Author: J. K. Muiruri, no funder. Author: P. S. K. Lee, no funder. Author: R. Vijayakumar, no funder. Author: T. T. Lin, no funder. Author: X. Zhang, no funder. Author: W. Thitsartarn, no funder. Author: C. He, No funder. Author: N. Hadjichristidis, no funder. Author: Z. Li, Agency for Science, Technology and Research (A*STAR), RIE2025 Manufacturing, Trade and Connectivity (MTC) Programmatic Fund (M22K9b0049)
On-chip Switched-Capacitor DC-DC converter for CMUT Biasing
No full textCapacitive micromachined ultrasonic transducer (CMUT) technology has been considered as a promising alternative for the conventional piezo electric-based technology in ultrasound imaging systems. Its potential advantages include better image quality, higher operational frequency, and ease of fabrication andintegration with CMOS read-out circuitry. However, CMUTs usually need high-voltage DC bias in order to transmit and receive acoustic waves. This work presents the design of a DC-DC converter to bias a CMUT for ultrasound imaging systems. Two different cases have been investigated: biasing at 63 V from an input of 5 V using a fully-integrated converter realized in a 180nm BCD technology that can handle up to 65V; and biasing at 120 V by employing minimal off-chip components. The proposed work explores the transient properties of a conventional on-chip switched capacitor DC-DC converter: the Dickson charge pump. A MATLAB model of the Dickson charge pump is developed to understand the relation between dynamic efficiency and the charge pump capacitor. Prior research works suggest that the dynamic efficiency of the Dickson charge pump is limited for a particular number of stages. However, the results obtained from the MATLAB model suggests that the dynamic efficiency can be improved by making the charge pump capacitor smaller. Various circuit simulations have been done to understand the results obtained from the MATLAB model. When the charge pump capacitor becomes very small, the parasitics start dominating and affect the overall efficiency of the Dickson charge pump. An optimization strategy is discussed to find the optimum number of stages and charge pump capacitor value to maximize the dynamic efficiency and minimize the circuit area. Based on the results obtained from this study, a DC-DC converter is designed to bias the CMUT at 63V, which consumes an estimated circuit area of 0.6586mm2 and has a simulated efficiency of 0.752. In addition, a new design idea that incorporates two DC-DC converters to bias the CMUT beyond the process voltage limitations is also discussed in this thesis. This hybrid converter involves the optimized DC DC converter designed earlier to generate 63V from an input of 5V, a control unit circuit, and some off-chipcomponents. The hybrid converter designed consumes an estimated circuit area of 0.842mm2 and has a simulated efficiency of 0.577Electrical Engineering | Microelectronic
Time Provoked: Interrogating the Past, Imagining the Future
No full text54 pagesFeatures: Tapestried in Green: When the Trees
Came Down at Camp -
Melissa Sexton /
Time for Justice - Julie Bacon / Generational Sovereignty
and the Land - John Edward Davidson /
Salmon Seasons - Rick Gurule / The Sabbath Pastoral - Robert Zandstra / Pictograph - Bennett Battaile / Traditional Ecological
Knowledge and the
California Condor - T. Bird Wicks / The Memory of Persistance - Chithira Vijayakumar / Prosthetic Desire: Bodily
Enhancement and Longing
in Science Fiction - Samuel VanNest / Take Me Amtrak:
Notes on a Train Trip - Lisa Lombardo / Taking Turns - John Edward Davidson
/ In Passing - Gayla Wardw
- …
