196,044 research outputs found
Cost and environmental analyses of reinforcement alternatives for a concrete bridge
No full textReinforced Concrete (RC) and Prestressed Concrete (PC) structures using conventional materials in aggressive exposure conditions are susceptible to corrosion. Non-corrosive reinforcement materials such as: Glass Fiber-Reinforced Polymer (GFRP) rebars; Carbon Fiber-Reinforced Polymer (CFRP) strands; Stainless-Steel (SS); and Epoxy-coated steel (ECS) reinforcing bars, are attracting attention as more appropriate options in concrete structures. This paper addresses a Life Cycle Cost (LCC) analysis that verifies the cost performance of four different alternative reinforcement bars for the design of a demonstration FRP-RC/PC bridge in Florida, namely Halls River Bridge (HRB). The four different alternatives to be compared are namely Carbon Steel (CS), SS, FRP, and ECS, and the analysis is performed over 100-years. Additionally, a Life-Cycle Assessment (LCA) is included in the analysis to investigate the environmental credentials of the four design alternatives. Cost sensitivity analyses over specific parameters are included. The parameters analyzed are: reinforcement cost, changes in chloride concentration levels over the bridge service life, and discount rate values. Conclusions and recommendations for standard practices and design of future alternative solutions are then presented
Developments in X-ray diffraction microscopy with applications for biological imaging
No full text© 2014 Dr. Guido Andrew CadenazziPublications included in thesis:Williams, G. J., Hanssen, E., Peele, A. G., Pfeifer, M. A., Clark, J., Abbey, B., & Cadenazzi, G. et al. (2008). High resolution X-ray imaging of Plasmodium falciparum infectedred blood cells. Cytometry, Part A (73), 949-957. DOI: 10.1002/cyto.a.20616Putkunz, C. T., Clark, J. N., Vine, D. J., Williams, G. J., Balaur, E., Cadenazzi, G. A. et al. (2011). Mapping granular structure in the biological adhesive of Phragmatopomacalifornica using phase diverse coherent diffractive imaging. Ultramicroscopy, 111(8), 1184-1188. DOI: 10.1016/j.ultramic.2011.03.022Abbey, B., Whitehead, L. W., Quiney, H. M., Vine, D. J., Cadenazzi, G. A., Henderson, C. A. et al. (2011). Lensless imaging using broadband X-ray sources. Nature Photonics, 5, 420-424. DOI: doi:10.1038/nphoton.2011.125Vartanyants, I. A., Singer, A., Mancuso, A. P., Yefanov, O., Sakdinawat, A., Liu, Y. et al. (2011). Coherence properties of individual femtosecond pulses of an X-rayfree-electron laser. Physical Review Letters, 107(14), 144801. DOI: 10.1103/PhysRevLett.107.144801Schlotter, W. F., Turner, J. J., Rowen, M., Heimann, P., Holmes, M., Krupin, O. et al. (2012). The soft X-ray instrument for materials studies at the linac coherentlight source X-ray free-electron laser. Review of Scientifc Instruments, 83(4), 043107. DOI: 10.1063/1.3698294Peterson, I., Abbey, B., Putkunz, C. T., Vine, D. J., van Riessen, G., Cadenazzi, G. A. et al. (2012). Nanoscale Fresnel coherent diffraction tomography using ptychography. Optics Express, 20(22), 24678-24685. DOI: 10.1364/OE.20.024678.Luu, M. B., van Riessen, G. A., Phillips, N. W., Elgass, K., Junker, M., Abbey, B. et al. (2014). Fresnel coherent diffractive imaging tomography of whole cells in capillaries. New Journal of Physics, 16. DOI: 10.1088/1367-2630/16/9/093012Macroscopic dynamics in biological systems are driven by signalling events between a host of microscopic sub-structures. At the molecular level, signals propagate along molecular circuitry that is mediated by signalling and receptor agents such as hormones, enzymes, neurotransmitters, cell membrane proteins, ion channels and others. At a cellular level, organelle functionality is crucial for cellular respiration and cellular division as well as protein synthesis and trafficking. Clearly, much can be learned from the size, shape and composition of the microscopic structures that regulate homeostasis.
X-ray microscopy has established itself as a highly capable technique that surpasses the resolution limits of optical microscopy while circumventing the weak penetration and extensive sample preparation characteristic of electron microscopy. Lens based, optical microscopes have the advantage of producing images in real time but, apart from some forms of fluorescence microscopy, their resolution is fundamentally limited to the quality of the lens. We here discuss a powerful alternative known as X-ray Diffraction Microscopy (XDM). Removing the focussing optic means that XDM is unaffected by issues such as lens quality. Images are reconstructed from the diffraction
pattern meaning that image resolution is given by the largest scattered angle detected. For biological materials the ability to record high angle is limited by radiation damage however, new techniques demonstrate that if the scattering is recorded sufficiently rapidly, radiation damage can be circumvented and wavelength limited resolution could be possible.
Chapters 1 to 4 comprise introductory and review chapters that outline the theory and experimental work necessary to describe the original work presented in this thesis. In Chapter 5 we discuss the application of curved beam XDM to malaria infected red blood cells. The life cycle of this deadly disease is still not fully understood and we approach the problem from a structural biology perspective. Using a variety of infected blood cells, we explore the possibility of imaging intact cells to high resolution and without extensive sample preparation. The method is shown to be sensitive to internal cellular structure and to return high resolution images that are consistent with the accompanying SEM and optical micrographs at a resolution of ∼ 40 nm. In Chapter 6 we discuss the importance of 3D imaging and present a simple method for mounting samples in heat-thinned glass capillaries. To support the premise that this method is ideal for tomographic analysis we present preliminary results of tomographic curved beam XDM of malaria infected red blood cells mounted in glass capillaries.
To address the data collection overhead imposed by imaging weakly scattering samples in a tomographic format, we challenge the notion that XDM requires fully coherent flux. Standard XDM implicitly assumes full temporal and spatial coherence. These conditions are achieved using spatial and spectral filters that remove the overwhelming majority of the radiation available. We explore the possibility of relaxing the spatial and temporal coherence requirements in order to exploit a larger fraction of the undulator radiation. In Chapter 7 we present the first demonstration of XDM data collection and image reconstruction using a broadband x-ray beam. A multi-modal reconstruction algorithm is then used to propagate the beam between real and reciprocal space. The analysis shows that by imaging structures with a partially temporally coherent beam, the data acquisition times are reduced by a factor of 60. Chapter 8 extends this work in a simulation study by analysing the effect of partial spatial coherence. We demonstrate that a reconstruction algorithm that includes the spatial coherence properties can recover a simple object with no a priori information. The results from both chapters show that if the coherence properties are accounted for in the reconstruction, significant departures from full coherence are tolerable with commensurate decreases in the required exposure time.
The final chapter changes tack and focuses on the source of radiation itself. A surge of investment in new x-ray sources over the last decade is representative of the growing interest in the field. New x-ray facilities known as X-ray Free Electron Lasers (XFELs) are currently being developed and will allow methods of biological imaging that are impossible at 3rd generation sources. Unlike synchrotron sources, XFELs provide ultra short pulses of intrinsically coherent radiation. Chapter 9 describes spatial coherence measurements of individual femto-second pulses of a hard x-ray free electron laser. Using the well known “diffract and destroy” technique, we apply the classic Young’s double pinhole experiment to probe the coherence of individual pulses. Our results show that in the absence of spatial filters, the majority of the x-ray flux is contained within the fundamental spatial coherence mode and thus confirms the coherent nature of XFEL pulses
Utilizzo di acqua di mare in calcestruzzo armato. Comportamento a lungo termine di due strutture prototipo
No full textIl progetto SEACON, finanziato dal programma INFRAVATION per l’innovazione nell’ambito delle infrastrutture e recentemente concluso, ha sviluppato l’idea di combinare l’utilizzo di acqua di mare e altri materiali contaminati da cloruri, attualmente proibito da norme e codici, per la realizzazione di strutture in calcestruzzo armato durevoli, in combinazione con diversi tipi di armatura resistenti alla corrosione. Il presente lavoro descrive le due strutture prototipo realizzate nel corso del progetto: una canaletta drenante per l’allontanamento delle acque meteoriche dalla pavimentazione stradale adiacente, costruita in Italia, e un ponte sul fiume Halls in Florida. I due prototipi sono stati realizzati con lo scopo di monitorare il comportamento a lungo termine delle armature di rinforzo delle due strutture; pertanto, in questo articolo vengono illustrate anche le strategie di monitoraggio e i risultati preliminari ottenuti
Resilience and economical sustainability of a FRP reinforced concrete bridge in Florida: LCC analysis at the design stage
No full textFiber-Reinforced Polymers (FRP) play a major role in civil engineering applications. FRP reinforcement
guarantees resilience and corrosion-resistance to reinforced concrete (RC) and prestressed concrete
(PC) structures. Glass FRP (GFRP) and Carbon FRP (CFRP) reinforcement represent proven non-metallic
solutions, able to ensure the required mechanical resistance to RC and PC structures. The research presented
hereinafter addresses the Life Cycle Cost (LCC) analysis of an FRP-RC/PC bridge in Florida, at the design
stage. The structure is designed for a 100-year service life. The analysis is performed in compliance with the
international standard ISO 15686-5 (ISO, 2008).
The bridge main structure consists of CFRP square PC bearing piles, CFRP-PC/GFRP-RC sheet piles, GFRPRC
girders, GFRP-RC bent caps, GFRP-RC bulkhead caps, traffic railings and approach slabs and a 20m long
GFRP-RC gravity wall, resulting in the absence of any steel reinforcement in the entire design.
According to ISO (2008) the costs that should be included in LCC analysis are those relative to the construction,
operation, maintenance, and end-of-life. Generally, maintenance includes replacement or repair. Externally
bonded reinforcement or cathodic protection are also common solutions applied to restore/strengthen the existing
structure, or to prevent further strength degradation. These solutions are relatively expensive and, in some cases,
require challenging over-water or in-water working activities.
This paper focuses on the construction costs. The initial cost of the FRP reinforcement is recovered thanks
to their long-term durability. Further savings are expected to be achieved with FRP if maintenance costs are
included in the analysis
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
Simulation of thermal plant optimization and hydraulic aspects of thermal distribution loops for large campuses
No full textFollowing an introduction, the author describes Texas A&M University and its utilities system. After that, the author presents how to construct simulation models for chilled water and heating hot water distribution systems. The simulation model was used in a $2.3 million Ross Street chilled water pipe replacement project at Texas A&M University. A second project conducted at the University of Texas at San Antonio was used as an example to demonstrate how to identify and design an optimal distribution system by using a simulation model. The author found that the minor losses of these closed loop thermal distribution systems are significantly higher than potable water distribution systems. In the second part of the report, the author presents the latest development of software called the Plant Optimization Program, which can simulate cogeneration plant operation, estimate its operation cost and provide optimized operation suggestions. The author also developed detailed simulation models for a gas turbine and heat recovery steam generator and identified significant potential savings. Finally, the author also used a steam turbine as an example to present a multi-regression method on constructing simulation models by using basic statistics and optimization algorithms. This report presents a survey of the author??s working experience at the Energy Systems Laboratory (ESL) at Texas A&M University during the period of January 2002 through March 2004. The purpose of the above work was to allow the author to become familiar with the practice of engineering. The result is that the author knows how to complete a project from start to finish and understands how both technical and nontechnical aspects of a project need to be considered in order to ensure a quality deliverable and bring a project to successful completion. This report concludes that the objectives of the internship were successfully accomplished and that the requirements for the degree of Degree of Engineering have been satisfied
Intern experience at CH���M Hill, Inc.: an internship report
No full textIncludes author's vita"Submitted to the College of Engineering of Texas A&M University in partial
fulfillment of the requirement for the degree of Doctor of Engineering."Includes bibliographical referencesA review of the author's internship experience with CH���M HILL, Inc.
during the period September 1975 through May 1976 is presented. During this nine month
internship the author worked as an Engineer II in the Industrial Processes discipline of this
large consulting engineering firm... The author's prime responsibility was as one of three
lead design engineers on the design of a large wastewater treatment facility for a pulp mill
in Hoquiam, Washington owned by ITT Rayonier Inc. The work generally consisted of the design
of individual treatment units and associated piping and pumping. The purpose of the project
was to provide wastewater treatment capabilities that would satisfy the effluent limitations
(standards) imposed upon the mill by the State of Washington Department of Ecology and the
U.S. Environmental Protection Agency. The author's assignment also entailed necessary
interaction with the project manager and other CH���M HILL design engineers and support staff
members, the client's representatives, and representatives of two other consulting engineering
firms working on the project. Thus, the internship position at CH���M HILL provided considerable
experience coordinating the author's work with the work of other engineers, guiding the design
and administrative efforts of a support staff, and interacting regularly with the client and
other consulting firms. This broad exposure to a variety of engineering and organizational
problems provided a valuable educational experience
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