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Verona, WI, United States

Kim D.,Washington State University | Beal A.,Epic | Kwon P.,Michigan State University
Journal of Manufacturing Science and Engineering, Transactions of the ASME | Year: 2016

This paper reviews the nature of hole defects and postulates the cause of hole defects resulting from the drilling process of carbon fiber reinforced plastic-titanium alloy stacked panels (CFRP-Ti stacks) using tungsten carbide (WC) and polycrystalline diamond (PCD) twist drills. The parameters that describe the hole quality of the CFRP-Ti stacks include CFRP entry hole delamination, hole diameter and roundness, inner hole surface roughness, CFRP hole profile, CFRP-Ti interplate damage, and Ti exit burr. They are caused by heat generation during drilling as well as hot Ti chips and adhesion, Ti burr formation, tool instability, and tool geometry change due to tool wear. For the WC drills, large flank wear and margin wear occurred at the high spindle speed condition, resulting in a reduction of the hole size and an increase of the hole roundness and CFRP-Ti interface damage. At the low spindle speed condition, tool geometry was changed due to the large edge rounding. This resulted in large fiber pull-out at the CFRP hole surface. Ti entry burrs caused damage associated with fiber removal and matrix discoloring at the bottom of the CFRP panel and this interplate damage was observed to increase with tool wear. When compared with the WC tool at the same speed condition, the PCD drill maintained relatively small hole defects under all parameters. Copyright © 2016 by ASME. Source

Dong Y.,Southern Methodist University | Olinick E.V.,Southern Methodist University | Jason Kratz T.,Epic | Matula D.W.,Southern Methodist University
Networks | Year: 2015

We present an alternative linear programming formulation of the maximum concurrent flow problem (MCFP) termed the triples formulation. The standard formulations in the literature are the edge-path and node-edge formulations, which are known to be equivalent due to the Flow Decomposition Theorem.We present algorithms for deriving a triples solution from an edge-path solution and vice versa, and hence show that all three formulations are equivalent. Our new formulation leads to more compact linear programs than either the edge-path or node-path formulations. We show that the triples formulation often has half the number of rows and half the number of columns compared to the node-edge formulation. We report computational results comparing the solution times using the three formulations and the state-of-the-art linear programming solver CPLEX on a set of popular problem instances from the literature and a set of instances defined on random geometric graphs. The results indicate that the triples formulation can be solved more efficiently than the other two. We found that the CPLEX linear programming solvers solved 89% of the MCFP instances in our computational study faster with the triples formulation than it did with the other two formulations, typically two to four times faster than the node-edge formulation when available computer memory allowed both to be solved. The triples formulation appears to be particularly well suited for problem instances defined on dense graphs; on average, CPLEX solved these types of problems in our study 10 times faster with the triples formulation. © 2014 Wiley Periodicals, Inc. Source

Butler E.K.,Ohio State University | Joseph H.,Epic | Ruiz N.,Ohio State University
Journal of Bacteriology | Year: 2014

Peptidoglycan (PG) is an extracytoplasmic glycopeptide matrix essential for the integrity of the envelope of most bacteria. The PG building block is a disaccharide-pentapeptide that is synthesized as a lipid-linked precursor called lipid II. The translocation of the amphipathic lipid II across the cytoplasmic membrane is required for subsequent incorporation of the disaccharide-pentapeptide into PG. In Escherichia coli, the essential inner membrane protein MurJ is the lipid II flippase. Previous studies showed that 8 charged residues in the central cavity region of MurJ are crucial for function. Here, we completed the functional analysis of all 57 charged residues in MurJ and demonstrated that the respective positive or negative charge of the 8 aforementioned residues is required for proper MurJ function. Loss of the negative charge in one of these residues, D39, causes a severe defect in MurJ biogenesis; by engineering an intragenic suppressor mutation that restores MurJ biogenesis, we found that this charge is also essential for MurJ function. Because of the low level of homology between MurJ and putative orthologs from Gram-positive bacteria, we explored the conservation of these 8 charged residues in YtgP, a homolog from Streptococcus pyogenes. We found that only 3 positive charges are similarly positioned and essential in YtgP; YtgP possesses additional charged residues within its predicted cavity that are essential for function and conserved among Gram-positive bacteria. From these data, we hypothesize that some charged residues in the cavity region of MurJ homologs are required for interaction with lipid II and/or energy coupling during transport. © 2014, American Society for Microbiology. Source

Cochard J.,Ecole Polytechnique - Palaiseau | Lee C.,Epic
Biophotonics International | Year: 2013

Biophotonic technologies have received more and more attention in recent years, highly touted as more-effective, cost-saving methods with applications ranging from medicine to life sciences research and beyond. Diagnostic and monitoring applications are paving the way for new optical technologies. Over the past 20 years, countries within the Organization for Economic Cooperation and Development (OECD) have faced increased growth of the pensioner population as well as recurrent epidemics, chronic diseases and economic issues linked to unsustainable, unbalanced health care systems. Miniaturization is a major trend in every industry sector, and health care is no exception. The agriculture industry faces growing demand from consumers for safer, healthier and more cost-effective nourishment and from policy makers, for new sustainable food and fish methods of production. Source

Preuss C.,Washington State University | Morway C.,Epic
Language Learning and Technology | Year: 2012

This paper explores university student access to and use of technology in Azerbaijan in the context of hegemony in computer-assisted language learning (CALL). Due to perceptions of a lack of technology access in the university context, the instructors in this study did not initially pursue a CALL agenda. Based on data sources that included a questionnaire, photographs, documents, journals, and interviews, the results of the study indicated that despite instructor perceptions, many students used and had access to various forms of technology on a regular basis. For example, students used computers and mobile devices to pursue different kinds of knowledge outside of the university. Implications include the importance of the deconstruction of instructor assumptions so that they can be critical educators and make choices that can lead to social change. © 2012. Source

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