198 research outputs found

    Reconstructing conductivities with boundary corrected D-bar method

    Full text link
    The aim of electrical impedance tomography is to form an image of the conductivity distribution inside an unknown body using electric boundary measurements. The computation of the image from measurement data is a non-linear ill-posed inverse problem and calls for a special regularized algorithm. One such algorithm, the so-called D-bar method, is improved in this work by introducing new computational steps that remove the so far necessary requirement that the conductivity should be constant near the boundary. The numerical experiments presented suggest two conclusions. First, for most conductivities arising in medical imaging, it seems the previous approach of using a best possible constant near the boundary is sufficient. Second, for conductivities that have high contrast features at the boundary, the new approach produces reconstructions with smaller quantitative error and with better visual quality

    Positive-energy D-bar method for acoustic tomography: a computational study

    Full text link
    A new computational method for reconstructing a potential from the Dirichlet-to-Neumann map at positive energy is developed. The method is based on D-bar techniques and it works in absence of exceptional points -- in particular, if the potential is small enough compared to the energy. Numerical tests reveal exceptional points for perturbed, radial potentials. Reconstructions for several potentials are computed using simulated Dirichlet-to-Neumann maps with and without added noise. The new reconstruction method is shown to work well for energy values between 10−510^{-5} and 55, smaller values giving better results

    A direct D-bar reconstruction algorithm for recovering a complex conductivity in 2-D

    Get PDF
    A direct reconstruction algorithm for complex conductivities in W2,∞(Ω)W^{2,\infty}(\Omega), where Ω\Omega is a bounded, simply connected Lipschitz domain in R2\mathbb{R}^2, is presented. The framework is based on the uniqueness proof by Francini [Inverse Problems 20 2000], but equations relating the Dirichlet-to-Neumann to the scattering transform and the exponentially growing solutions are not present in that work, and are derived here. The algorithm constitutes the first D-bar method for the reconstruction of conductivities and permittivities in two dimensions. Reconstructions of numerically simulated chest phantoms with discontinuities at the organ boundaries are included.Comment: This is an author-created, un-copyedited version of an article accepted for publication in [insert name of journal]. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at 10.1088/0266-5611/28/9/09500

    Discovery of small molecules that activate RNA-methylation through cooperative binding to the METTL3/14/WTAP complex active site

    Get PDF
    Chemical modifications of RNA provide an additional, epitranscriptomic, level of control over cellular functions. N-6-methylated adenosines (m6As) are found in several types of RNA, and their amounts are regulated by methyltransferases and demethylases. One of the most important enzymes catalyzing generation of m6A on mRNA is the trimer N-6-methyltransferase METTL3-14-WTAP complex. Its activity has been linked to such critical biological processes as cell differentiation, proliferation, and death. We used in silico-based discovery to identify small-molecule ligands that bind to METTL3-14-WTAP and determined experimentally their binding affinity and kinetics, as well as their effect on enzymatic function. We show that these ligands serve as activators of the METTL3-14-WTAP complex

    Synchronous communication in PLM environments using annotated CAD models

    Full text link
    The connection of resources, data, and knowledge through communication technology plays a vital role in current collaborative design methodologies and Product Lifecycle Management (PLM) systems, as these elements act as channels for information and meaning. Despite significant advances in the area of PLM, most communication tools are used as separate services that are disconnected from existing development environments. Consequently, during a communication session, the specific elements being discussed are usually not linked to the context of the discussion, which may result in important information getting lost or becoming difficult to access. In this paper, we present a method to add synchronous communication functionality to a PLM system based on annotated information embedded in the CAD model. This approach provides users a communication channel that is built directly into the CAD interface and is valuable when individuals need to be contacted regarding the annotated aspects of a CAD model. We present the architecture of a new system and its integration with existing PLM systems, and describe the implementation details of an annotation-based video conferencing module for a commercial CAD application.This work was supported by the Spanish Ministry of Economy and Competitiveness and the FEDER Funds, through the ANNOTA project (Ref. TIN2013-46036-C3-1-R).Camba, JD.; Contero, M.; Salvador Herranz, GM.; Plumed, R. (2016). Synchronous communication in PLM environments using annotated CAD models. Journal of Systems Science and Systems Engineering. 25(2):142-158. https://doi.org/10.1007/s11518-016-5305-5S142158252Abrahamson, S., Wallace, D., Senin, N. & Sferro, P. (2000). Integrated design in a service marketplace. Computer-Aided Design, 32(2):97–107.Ahmed, S. (2005). Encouraging reuse of design knowledge: a method to index knowledge. Design Studies, 26:565–592.Alavi, M. & Tiwana, A (2002). Knowledge integration in virtual teams: the potential role of KMS. Journal of the American Society for Information Science and Technology, 53:1029–1037.Ameri, F. & Dutta, D. (2005). Product lifecycle management: closing the knowledge loops. Computer-Aided Design and Applications, 2(5):577–590.Anderson, A.H., Smallwood, L., MacDonald, R., Mullin, J., Fleming, A. & O'Malley, C. (2000). Video data and video links in mediated communication: what do users value? International Journal of Human-Computer Studies, 52(1):165–187.Arias, E., Eden, H., Fischer, G., Gorman, A. & Scharff, E. (2000). Transcending the individual human mind–creating shared understanding through collaborative design. ACM Transactions on Computer-Human Interaction (TOCHI) 7(1): 84–113.Barley, W.C., Leonardi, P.M., & Bailey, D.E. (2012). Engineering objects for collaboration: strategies of ambiguity and clarity at knowledge boundaries. Human Communication Research, 38:280–308.Boujut, J.F. & Dugdale, J. (2006). Design of a 3D annotation tool for supporting evaluation activities in engineering design. Cooperative Systems Design, COOP 6:1–8.Camba, J., Contero, M., Johnson, M. & Company, P. (2014). Extended 3D annotations as a new mechanism to explicitly communicate geometric design intent and increase CAD model reusability. Computer-Aided Design, 57:61–73.Camba, J., Contero, M. & Salvador-Herranz, G. (2014). Speak with the annotator: promoting interaction in a knowledge-based CAD environment built on the extended annotation concept. Proceedings of the 2014 IEEE 18th International Conference on Computer Supported Cooperative Work in Design (CSCWD), 196–201.Chudoba, K.M., Wynn, E., Lu, M. & Watson-Manheim, M.B. (2005). How virtual are we? Measuring virtuality and understanding its impact in a global organization. Information Systems Journal, 15(4):279–306.Danesi, F., Gardan, N. & Gardan, Y. (2006). Collaborative Design: from Concept to Application. Geometric Modeling and Imaging—New Trends, 90–96.Durstewitz, M., Kiefner, B., Kueke, R., Putkonen, H., Repo, P. & Tuikka, T. (2002). Virtual collaboration environment for aircraft design. Proceedings of the IEEE 6th International Conference on Information Visualisation, 502–507.Fisher, D., Brush, A.J., Gleave, E. & Smith, M.A. (2006). Revisiting Whittaker and Sidner’s email overload ten years later. Proceedings of the 2006 20th Anniversary Conference on Computer Supported Cooperative Work. ACM, BanffFonseca, M.J., Henriques, E., Silva, N., Cardoso, T. & Jorge, J.A. (2006). A collaborative CAD conference tool to support mobile engineering. Rapid Product Development (RPD’06), Marinha Grande, Portugal.Frechette, S.P. (2011). Model based enterprise for manufacturing. Proceedings of the 44th CIRP International Conference on Manufacturing Systems.Fu, W.X., Bian, J. & Xu, Y.M. (2013). A video conferencing system for collaborative engineering design. Applied Mechanics and Materials, 344:246–252.Fuh, J.Y.H. & Li, W.D. (2005). Advances in collaborative CAD: the-state-of-the art. Computer-Aided Design, 37:571–581.Fussell, S.R., Kraut, R.E. & Siegel, J. (2000). Coordination of communication: effects of shared visual context on collaborative work. Proceedings of the 2000 ACM Conference on Computer Supported Cooperative Work, 21–30.Gajewska, H., Kistler, J., Manasse, M.S. & Redell, D. (1994). Argo: a system for distributed collaboration. Proceedings of the ACM Second International Conference on Multimedia, San Francisco, CA, USA. 433–440.Gantz, J., Reinsel, D., Chute, C., Schlichting, W., Mcarthur, J., Minton, S., Xheneti, I., Toncheva, A. & Manfrediz, A. (2007). The expanding digital universe: a forecast of worldwide information growth through 2010. IDC, Massachusetts.Gowan, Jr. J.A. & Downs, J.M. (1994). Video conferencing human-machine interface: a field study. Information and Management, 27(6):341–356.Gupta, A., Mattarelli, E., Seshasai, S. & Broschak, J. (2009). Use of collaborative technologies and knowledge sharing in co-located and distributed teams: towards the 24-h knowledge factory. The Journal of Strategic Information Systems, 18:147–161.Hickson, I. (2009). The Web Socket Protocol IETF, Standards Track.Hong, J., Toye, G. & Leifer, L.J. (1996). Engineering design notebook for sharing and reuse. Computers in Industry, 29:27–35.Isaacs, E.A. & Tang, J.C. (1994). What video can and cannot do for collaboration: a case study. Multimedia Systems, 2(2):63–73.Karsenty, L. (1999). Cooperative work and shared visual context: an empirical study of comprehension problems in side-by-side and remote help dialogues. Human Computer Interaction, 14(3): 283–315.Lahti, H., Seitamaa-Hakkarainen, P. & Hakkarainen, K. (2004). Collaboration patterns in computer supported collaborative designing. Design Studies, 25:351–371.Leenders, R.T.A., Van Engelen, J.M. & Kratzer, J. (2003). Virtuality, communication, and new product team creativity: a social network perspective. Journal of Engineering and Technology Management, 20(1):69–92.Levitt, R.E., Jin, Y. & Dym, C.L. (1991). Knowledge-based support for management of concurrent, multidisciplinary design. Artificial Intelligence for Engineering, Design, Analysis and Manufacturing, 5(2):77–95.Li, C., McMahon, C. & Newnes, L. (2009). Annotation in product lifecycle management: a review of approaches. Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, DETC2009. Vol. 2. New York: ASME, 797–806.Li, W.D., Lu, W.F., Fuh, J.Y. & Wong, Y.S. (2005). Collaborative computer-aided design-research and development status. Computer-Aided Design, 37(9):931–940.Londono, F., Cleetus, K.J., Nichols, D.M., Iyer, S., Karandikar, H.M., Reddy, S.M., Potnis, S.M., Massey, B., Reddy, A. & Ganti, V. (1992). Coordinating a virtual team. CERC-TR-RN-92-005, Concurrent Engineering Research Centre, West Virginia University, West Virginia.Lubell, J., Chen, K., Horst, J., Frechette, S., & Huang, P. (2012). Model based enterprise/technical data package summit report. NIST Technical Note, 1753.May, A. & Carter, C. (2001). A case study of virtual team working in the European automotive industry. International Journal of Industrial Ergonomics, 27(3):171–186.Olson, J.S., Olson, G.M. & Meader, D.K. (1995). What mix of video and audio is useful for small groups doing remote real-time design work? Proceedings of the SIGCHI Conference on Human Factors in Computing Systems. ACM Press, Addison-Wesley Publishing Co.Ping-Hung, H., Mishra, C.S. & Gobeli, D.H. (2003). The return on R&D versus capital expenditures in pharmaceutical and chemical industries. IEEE Transactions on Engineering Management, 50:141–150.Sharma, A. (2005). Collaborative product innovation: integrating elements of CPI via PLM framework. Computer-Aided Design, 37(13):1425–1434.Shum, S.J.B., Selvin, A.M., Sierhuis, M., Conklin, J., Haley, C.B. & Nuseibeh, B. (2006). Hypermedia support for argumentation-based rationale: 15 Years on from Gibis and Qoc. Rationale Management in Software Engineering, 111–132.Siltanen, P. & Valli, S. (2013). Web-based 3D Mediated Communication in Manufacturing Industry. Concurrent Engineering Approaches for Sustainable Product Development in a Multidisciplinary Environment, 1181–1192. Springer London.Stark, J. (2011). Product Lifecycle Management. 1–16. Springer London.Tavcar, J., Potocnik, U. & Duhovnik, J. (2013). PLM used as a backbone for concurrent engineering in supply chain. Concurrent Engineering Approaches for Sustainable Product Development in a Multi-Disciplinary Environment, 681–692.Tay, F.E.H. & Ming, C. (2001). A shared multi-media design environment for concurrent engineering over the internet. Concurrent Engineering, 9(1):55–63.Tay, F.E.H. & Roy, A. (2003). CyberCAD: a collaborative approach in 3D-CAD technology in a multimedia-supported environment. Computers in Industry, 52(2):127–145.Toussaint, J. & Cheng, K. (2002). Design agility and manufacturing responsiveness on the web. Integrated Manufacturing Systems, 13(5):328–339.Tsoi, K.N. & Rahman, S.M. (1996). Media-on-demand multimedia electronic mail: a tool for collaboration on the web. Proceedings of the 5th IEEE International Symposium on High Performance Distributed Computing.Upton, D.M. & Mcafee, A. (1999). The Real Virtual Factory. Harvard Business School Press, 69–89.Vila, C., Estruch, A., Siller, H.R., Abellán, J.V. & Romero, F. (2007). Workflow methodology for collaborative design and manufacturing. Cooperative Design, Visualization, and Engineering 42–49, Springer Berlin Heidelberg.Wasiak, J., Hicks, B., Newnes, L., Dong, A., & Burrow, L. (2010). Understanding engineering email: the development of a taxonomy for identifying and classifying engineering work. Research in Engineering Design, 21(1):43–64.Wasko, M.M. & Faraj, S. (2005). Why should I share? Examining social capital and knowledge contribution in electronic networks of practice. MIS Quarterly: Management Information Systems, 29:35–57.Yang, Q.Z., Zhang, Y., Miao, C.Y. & Shen, Z.Q. (2008). Semantic annotation of digital engineering resources for multidisciplinary design collaboration. ASME 2008 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, 617–624. American Society of Mechanical Engineers.You, C.F. & Chao, S.N. (2006). Multilayer architecture in collaborative environment. Concurrent Engineering Research and Applications, 14(4):273–281.Yuan, Y.C., Fulk, J., Monge, P.R. & Contractor, N. (2010). Expertise directory development, shared task interdependence, and strength of communication network ties as multilevel predictors of expertise exchange in transactive memory work groups. Communication Research, 37: 20–47
    • 

    corecore