D. D. Duncan

Portland State University

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i-10 index

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Co-Authors

Sheila K. West

Johns Hopkins University

Beatriz Muñoz

Johns Hopkins Medicine

Jessica C. Ramella‐Roman

Florida International University

S. K. West

University of Sydney

Quan Dong Nguyen

Princeton University

F. Mark

University of Zimbabwe

Oliver D. Schein

Johns Hopkins Medicine

Morton H. Friedman

George Washington University

Sean J. Kirkpatrick

Michigan Technological University

C. B. Bargeron

Johns Hopkins University

Cooperative Institutions

Johns Hopkins University

Harvard University

University of Washington

University of Pennsylvania

Stanford University

Johns Hopkins University Applied Physics Laboratory

Washington University in St. Louis

Yale University

University College London

Harvard University Press

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Effects of Arterial Compliance and Non-Newtonian Rheology on Correlations Between Intimal Thickness and Wall Shear

Journal of Biomechanical Engineering (1992)

Morton H. Friedman C. B. Bargeron D. D. Duncan Grover M. Hutchins F. Mark

A minimally diseased (mean intimal thickness = 56 μm) human aortic bifurcation was replicated in rigid and compliant flow-through casts. Both casts were perfused with physiological flow waves having the same Reynolds and unsteadiness numbers; the pulse pressure in the compliant cast produced radial strains similar to those expected from post-mortem measurements of the compliance of the original tissue. The compliant cast was perfused with a Newtonian fluid and one whose rheology was closer to that of blood. Wall shear rate histories were estimated from near-wall velocities obtained by laser Doppler velocimetry at identical sites in both casts. Intimal thickness was measured at corresponding sites in the original vessel and linear regressions were performed between these thicknesses and several normalized shear rate measures obtained from the histories. The correlations showed a positive slope—that is, the intima was thicker at sites exposed to higher shear rates—consistent with earlier results for relatively healthy vessels, but their significance was often poor. There was no significant effect of either model compliance or fluid rheology on the slopes of the correlations of intimal thickness against any normalized shear rate measure.

Arterial wall

Pulse pressure

10.1115/1.2891389

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Citations (113)

Dynamic Beam-to-Beam Optical Communication Link

Marc B. Airola Bradley G. Boone J.R. Bruzzi D. D. Duncan Raymond M. Sova

A duplex optical, free space communication system was developed to track and stabilize beam perturbations such as those resulting from atmospheric or platform disturbances. The system uses two-beam dynamic tracking and active alignment to maintain direct fiber-to-fiber beam coupling in a communication link. Encompassing the system are galvanometer optical scanners and CMOS imagers and it employs visible laser diodes as track channels

Galvanometer

Free-Space Optical Communication

Optical link

Link (geometry)

10.1109/milcom.2005.1605878

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The heritability of age-related cortical cataract

Investigative Ophthalmology & Visual Science (2001)

Christopher J. Hammond D. D. Duncan Harold Snieder Marlies de Lange Sheila K. West

Source

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Comparative prevalence assessment of nuclear cataract using objective and subjective means

D. D. Duncan O. B. Shukla Oliver D. Schein S. K. West

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Oximetry and Blood Flow in the Retina

IFMBE proceedings (2010)

Paul Lemaillet Art Lompado D. D. Duncan Quan Dong Nguyen Jessica C. Ramella‐Roman

Fundus camera

Fundus (uterus)

10.1007/978-3-642-14998-6_82

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Physics-based processing for terahertz reflection spectroscopy and imaging

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2010)

Lisa M. Zurk S. C. Henry Scott Schecklman D. D. Duncan

The spectra obtained from Terahertz (THz) reflection imaging can be distorted by scattering from rough interfaces, layers, and granular inclusions. Since the facets of the object being imaged are not generally aligned normal to the THz beam, the received signal is produced from diffuse scattering, which can be appreciably lower in signal strength than specular returns. These challenges can be addressed with advanced signal processing approaches based upon the coherent and incoherent combination of returns from multiple sensors and frequencies. This paper presents two examples of physics-based processing strategies applied to THz imaging spectroscopy. The first method is based on synthetic aperture processing of a 2D sensor array to provide variable depth focused images of buried inclusions (a ball bearing embedded in polyethylene sample). The second method uses correlation processing to coherently combine multiple sensors and multiple frequencies to extract material signatures from measurements of THz scattering from rough interfaces. Results for both methods show an increase in performance relative to conventional imaging or spectroscopy approaches.

Reflection

SIGNAL (programming language)

Imaging Spectroscopy

10.1117/12.870664

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Cortical Cataract Grading: A Comparison of Human and Computerized Grading Methods Using Simulated Retro-Illumination Images

Andrea Abraham D. D. Duncan Savannah J. West

Grading (engineering)

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Research Effort in Atmospheric Propagation.

Final Technical Report (1975)

Stuart A. Collins D. D. Duncan Y. J. Liu

Abstract : This report presents work performed on: (1) The propagation of light through aircraft boundary layers; (2) The measurement and interpretation of refractive index spectra at high altitudes; and (3) The temporal spectra of angle-of-arrival fluctuations. A method of analyzing the data from the experiment on light beams propagating through aircraft boundary layers to obtain the boundary layer MTF was presented. Next a calculation of the effects of velocity and air mean free path on wire microthermal measurements was reported. The results were that the procedure of calibrating a microthermal sensor at zero velocity and making measurements at low altitude at Mach 1 can have up to 17% error. Further, flying at an altitude of 20 km where the air molecular mean free path is larger can increase the error another 4%. A discussion of refractive index spectra obtained from airborne microthermal measurements resulted in an empirical formula which could be made to fit the data. The formula involved the addition of two von Karman type of spatial spectra. The data showed outer scales between 300 to 1000 meters. Finally, results of an analysis on the temporal spectrum of angle-of-arrival fluctuations were presented. The model included a moving source, and a position proportional detector. The resulting curve showed a peak contribution from refractive index fluctuations of size equal to one fifth the source height.

Position (finance)

Optical path

Source

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Performance of a gradient‐based shift estimator in a spatially sparse data environment: tracking the sub‐pixel motion of fluorescent particles

Journal of Microscopy (2008)

Sean J. Kirkpatrick D. D. Duncan

Summary Through a series of numerical simulations, we investigate the suitability of a relatively new gradient‐based particle‐tracking algorithm for efficiently quantifying sub‐pixel shifts of fluorescently labelled cells or particles from a sequence of video microscopy images. The algorithm excels at estimating sub‐0.5 pixel per frame shifts in both data‐dense (e.g. laser speckle imaging) and data‐sparse (e.g. fluorescence imaging) applications. No upsampling (i.e. interpolation) is required to achieve the sub‐pixel shift resolution, and thus the approach avoids the complexity and potential errors associated with the interpolation process. An efficient matlab sub‐routine is provided for implementing the algorithm.

Upsampling

Interpolation

Tracking (education)

10.1111/j.1365-2818.2008.02087.x

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Use of spectroscopic imager for the assessment of optical properties and 3-D reconstruction of biological media

Thu A. Nguyen Ali Basiri Jeffrey W. Shupp J. A. Jordan D. D. Duncan

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text T. A. Nguyen, A. Basiri, J. Shupp, J. Jordan, D. D. Duncan, and J. C. Ramella-Roman, "Use of spectroscopic imager for the assessment of optical properties and 3-D reconstruction of biological media," in CLEO:2011 - Laser Applications to Photonic Applications, OSA Technical Digest (CD) (Optica Publishing Group, 2011), paper ATuB2. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

10.1364/cleo_at.2011.atub2

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