School of Civil and Construction Engineering

Heart Motion Prediction in Robotic- Assisted Beating Heart Surgery: A Nonlinear Fast Adaptive Approach

2013-05-22T16:37:52Z

Heart Motion Prediction in Robotic- Assisted Beating Heart Surgery: A Nonlinear Fast Adaptive Approach Liang, Fan; Yu, Yang; Wang, Haizhong; Meng, Xiaofeng Off-pump Coronary Artery Bypass Graft (CABG) surgery outperforms traditional on-pump surgery because the assisted robotic tools can alleviate the relative motion between the beating heart and robotic tools. Therefore, it is possible for the surgeon to operate on the beating heart and thus lessens post surgery complications for the patients. Due to the highly irregular and non-stationary nature of heart motion, it is critical that the beating heart motion is predicted in the model-based track control procedures. It is technically preferable to model heart motion in a nonlinear way because the characteristic analysis of 3D heart motion data through Bi-spectral analysis and Fourier methods demonstrates the involved nonlinearity of heart motion. We propose an adaptive nonlinear heart motion model based on the Volterra Series in this paper. We also design a fast lattice structure to achieve computational-efficiency for real-time online predictions. We argue that the quadratic term of the Volterra Series can improve the prediction accuracy by covering sharp change points and including the motion with sufficient detail. The experiment results indicate that the adaptive nonlinear heart motion prediction algorithm outperforms the autoregressive (AR) and the time-varying Fourier-series models in terms of the root mean square of the prediction error and the prediction error in extreme cases. This is the publisher’s final pdf. The published article is copyrighted by InTech — Open Access Company and can be found at: http://www.intechopen.com/.

A high-resolution study of tides in the Delaware Bay: Past conditions and future scenarios

2013-05-22T16:37:29Z

A high-resolution study of tides in the Delaware Bay: Past conditions and future scenarios Hall, George F.; Hill, David F.; Horton, Benjamin P.; Engelhart, Simon E.; Peltier, W. R. Tides in the Delaware Bay (USA) have been modeled from 7000 years before present (7 ka) to the present day and for selected future sea-level rise scenarios (100 years, 300 years). Historic bathymetries were constructed through use of glacial isostatic adjustment models and a very high spatial resolution (< 100 m) was used at the shoreline. Future bathymetries were obtained by extrapolating these glacial isostatic adjustment models and applying an additional eustatic sea-level rise. It was found that tides in the lower bay have remained fairly constant through time but that tides in the upper bay have increased steadily from about 4 ka to the present day; a nearly 100% increase in total. The future runs demonstrated spatially complex behavior with tidal-range changes of up to 10%. Citation: Hall, G. F., D. F. Hill, B. P. Horton, S. E. Engelhart, and W. R. Peltier (2013), A high-resolution study of tides in the Delaware Bay: Past conditions and future scenarios, Geophys. Res. Lett., 40, 338-242, doi:10.1029/2012GL054675. The article is copyrighted by American Geophysical Union and published by Wiley-Blackwell and can be found at: http://onlinelibrary.wiley.com/.

Spatial identification and optimization of upland wetlands in agricultural watersheds

2013-05-13T17:13:51Z

Spatial identification and optimization of upland wetlands in agricultural watersheds Babbar-Sebens, Meghna; Barr, Robert C.; Tedesco, Lenore P.; Anderson, Milo Wetland ecosystems are considered as potential ecological solutions for increasing the capacity of watersheds to store runoff waters upstream, and thereby, decrease risk of downstream flooding. Especially in tile-drained agricultural landscapes, wetlands constructed to intercept these tiles can serve as storage basins for agricultural runoff, leading to both reduction in peak runoff flows and diminished transport of agricultural nutrients. The objective of this study was to develop a watershed-scale methodology for identifying potential sites for wetlands in a tile-drained landscape in the Midwestern USA, and for optimizing the spatial distribution of these wetlands for reductions in peak runoff flows. The benefits of this methodology is demonstrated by using it for selecting appropriate wetland restoration and/or creation sites in Eagle Creek Watershed (ECW), located 10 miles northwest of Indianapolis, IN, USA. Results show that a large number of potential sites could be identified (e.g., 2953 sites in ECW), and with a choice of effective wetland design parameters and with spatial optimization of their areas, locations, and drainage areas, it is possible to achieve significant peak flow reductions with fewer sites and smaller wetlands. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.elsevier.com/.

Adjacent structure response sensitivity to seismic events using the direct differentiation method

2013-05-10T20:52:13Z

Adjacent structure response sensitivity to seismic events using the direct differentiation method White, William S. (William Schaffer) The response of adjacent structural systems to earthquake motions is investigated using the finite element framework OpenSees. Results of sensitivity analyses demonstrate that structural response quantities can increase in either or both of the adjacent structures for specific configurations. The structural models used include steel moment-resisting frames and rigid shear walls. The soil that underlies both buildings is modeled with a "structure-soil- structure spring" that connects the structural models. Due to the variety of building heights in urban environments, all combinations of four-, eight-, and twenty-story buildings are analyzed. Six shallow crustal earthquake motions are selected to model the dynamic responses of structural models. Sensitivity analyses are carried out using the direct differentiation method (DDM) with respect to parameters associated with the structure-foundation-soil systems, including floor mass, story stiffness, and soil stiffness. The DDM allows for computation of the time history of response sensitivity with respect to each parameter, in addition to the deterministic, or mean, time history response computed as part of an ordinary, non-linear, dynamic analysis. The response time histories can then be used to make a first-order approximation of the change in building response with respect to prescribed changes in a given parameter. The results of these analyses demonstrate that the effects of structure-soil-structure interaction are generally negligible for the steel, moment-resisting frame structure pairs investigated. The rigid shear walls demonstrated effects of structure-soil-structure interaction, particularly in the smaller wall mimicking the motion of the larger wall. Further research is needed in this area, particularly in refining the soil model to more fully reflect the response of realistic soil. Graduation date: 2013