196,275 research outputs found
Optimization of mechanical properties for pulsed anodizing of aluminum
No full textMechanical properties such as thickness, hardness, and wear resistance of an anodic oxide layer on aluminum must be high enough for industrial purposes. Due to burning phenomenon, hardness and wear resistance of anodic oxide layer decrease as the thickness of the layer increases. These properties of oxide layer fabricated by regular anodizing on aluminum in mixed sulfuric-oxalic acid electrolyte were optimized using pulsed currents. For this purpose, four variable response surface design (duty cycle, frequency, maximum and minimum current densities) was utilized. Desirability function was used to maximize thickness, microhardness and wear resistance of the anodic oxide layer. Wear resistance of the layer was measured by means of ‘pin on disk’ method according to ASTM G89 standard. The determined optimal anodizing conditions were: duty cycle = 65%, frequency = 326 Hz, imax = 3.5 and imin = 0.5 A/dm2, while the corresponding estimated responses values were 170 μm, 526 Hv0.1 and 2.12 × 10− 7 g/N.m for thickness, microhardness, and wear rate, respectively. Frictional behavior of optimized pulsed, and direct current anodic oxide layers was discussed in terms of friction coefficient and examination of worn surfaces
Miniaturized Wilkinson power divider with suppressed harmonics
No full textA Wilkinson power divider (WPD) with good novelty has been presented in this letter. To achieve this design, each quarter-wavelength lines of the conventional WPD have been replaced by two symmetrical comb-shaped resonators. These resonators create two rejection bands near their passbands, which can guarantee a good harmonics suppression for a power divider. By applying and computing the even-/odd-modes analysis, the suggested PD has been analyzed. In the proposed PD, the extra harmonics from second to 10th are suppressed. The normalized circuit size for operation in the center frequency of 1.1 GHz is about 0.06 x 0.07 lambda g. Eventually, fabrication of the power divider has been done on Rogers type RT-Duroid 5880 substrate and tested. The measured return loss is about 16 dB in the fundamental frequency. The obtained experimental S-parameters validated the primal design results. Therefore, the proposed WPD is a high performance one, which can be applied for applications such as the signal splitter in a Doherty power amplifier
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
Elucidation of local and global structural properties of packed bed configurations
No full textSome of the most common unit operations being used in the chemical industry are based upon packed bed configurations. Multi-tubular catalytic reactors are a prominent example of such systems which are believed by many experts to be the heart of the chemical profession and frequently the most
expensive units of the plant. They offer extensive surface area between phases of the matter in a compact physical manner, and also are relatively easy to construct
and maintain. The successfuld esign of such systems depends on models, which should describe the processes occurring within the fixed bed and must also be able to accurately represent the intrinsic behaviour of the reactor quantitatively. It is therefore necessary to have good estimates of the associated transport parameters,
namely the wall heat transfer coefficient, effective radial and axial thermal conductivity coefficients and radial and axial dispersion coefficients, in order to design efficiently. Unfortunately, the accuracy of the design data for the prediction of these parameters are in doubt. They are considered to be unreliable because of being based on poorly defined packed bed models in terms of structure
of the packing. The non-uniformities of voidage in the packing matrix must be appreciated and hence be included in descriptive models of the physical system in order to establish reliable design data.
As the roles of modelling and experimentation are complementary, a number of beds comprised of equilateral cylindrical particles were prepared to examine their global and local structural properties, with a view to identifying and characterising features which could be used for prediction purposes. The microstructural details within packed beds were studied by means of an image analyser,
so that the local variations of voidage in angular, axial and radial directions could be portrayed. It is only on the basis of this kind of information that a well-defined
description of the bed structure becomes accessible. This research activity has been concerned with the study of several factors influencing the packing structure such as entrance/exit and wall effects, reproducibility and scaling problems. Also succeeding the accurate data acquisition stage, a number of correlations have been developed for a wide scope of diameter ratios covering the industrial range. These correlations allow the mean and local voidage distributions to be predicted reliably
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
Electric vehicle scheduling: State of the art, critical challenges, and future research opportunities
No full textElectric vehicles can be perceived as a means to achieve carbon reduction, energy efficiency, and sustainable development of the transportation industry. Electric vehicle sales and deployment are increasing rapidly over time. However, electric vehicle deployment should be conducted in a planned manner, as electric vehicles have some limitations (e.g., limited driving range, refueling capacity, carrying capacity). The electric vehicle scheduling problem should be studied in detail to overcome such limitations, as it addresses them while optimizing the paths and timetables of electric vehicles. A number of studies have been dedicated towards electric vehicle scheduling. Yet, there is a lack of survey studies that cover a structural recapitulation of the electric vehicle scheduling efforts and provide a thorough overview of the existing tendencies, operations research aspects, problem-specific properties, and future research needs. For this reason, this study offers a structured survey of the existing research studies, which assessed electric vehicle scheduling. The collected studies are grouped into three categories for a detailed review, namely general electric vehicle scheduling, electric vehicle scheduling with power grid considerations, and electric vehicle scheduling with environmental considerations. A detailed description of the relevant studies along with a summary of findings and future research needs are provided for each of the study categories. In addition, a representative mathematical model is outlined for each study category in order to guide the future research. The outcomes of this research are expected to provide interesting and important insights to different groups of professionals in the field of electric vehicles
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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