Exploration of applying a theory-based user classification model to inform personalised content-based image retrieval system design

© ACM, 2016. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published at http://dl.acm.org/citation.cfm?id=2903636To better understand users and create more personalised search experiences, a number of user models have been developed, usually based on different theories or empirical data study. After developing the user models, it is important to effectively utilise them in the design, development and evaluation of search systems to improve users’ overall search experiences. However there is a lack of research has been done on the utilisation of the user models especially theory-based models, because of the challenges on the utilization methodologies when applying the model to different search systems. This paper explores and states how to apply an Information Foraging Theory (IFT) based user classification model called ISE to effectively identify user’s search characteristics and create user groups, based on an empirically-driven methodology for content-based image retrieval (CBIR) systems and how the preferences of different user types inform the personalized design of the CBIR systems

Volume-based Estimates of Left Ventricular Blood Pool Volume and Ejection Fraction from Multi-plane 2D Ultrasound Images

Accurate estimations of left ventricular (LV) blood pool volume and left ventricular ejection fraction (LVEF) are crucial for the clinical diagnosis of cardiac disease, patient management, or other therapeutic treatment decisions, especially given a patient’s LVEF often affects his or her candidacy for cardiovascular intervention. Ultrasound (US) imaging is the most common and least expensive imaging modalities used to non-invasively image the heart to estimate the LV blood pool volume and assess LVEF. Despite advances in 3D US imaging, 2D US images are routinely used by cardiologists to image the heart and their interpretation is inherently based on the 2D LV blood pool area information immediately available in the US images, rather than 3D LV blood pool volume information. This work proposes a method to reconstruct the 3D geometry of the LV blood pool from three tri-plane 2D US images to estimate the LV blood pool volume and subsequently the LVEF. This technique uses a statistical shape model (SSM) of the LV blood pool characterized by several anchor points – the mitral valve hinges, apex, and apex-to-mitral valve midpoints – identified from the three multi-plane 2D US images. Given a new patient image dataset, the diastolic and systolic LV blood pool volumes are estimated using the SSM either as a linear combination of the n-closest LV geometries according to the Mahalanobis distance or based on the n-most dominant principal components identified after projecting the new patient into the principal component space defined by the training dataset. The performance of the proposed method was assessed by comparing the estimated LV blood pool volume and LVEF to those measured using the EchoPac PC clinical software on a dataset consisting of 66 patients, and several combinations of 50-16 used for training and validation, respectively. The studies show the proposed method achieves LV volume and LVEF estimates within 5% of those computed using the clinical software. Lastly, this work proposes an approach that requires minimal user interaction to obtain accurate 3D estimates of LV blood pool volume and LVEF using multi-plane 2D US images and confirms its performance similar to the ground truth clinical measurements

Quantifying Fluid Shear Stress in a Rocking Culture Dish

Fluid shear stress (FSS) is an important stimulus for cell functions. Compared with the well established parallel-plate and cone-and-plate systems, a rocking “see-saw” system offers some advantages such as easy operation, low cost, and high throughput. However, the FSS spatiotemporal pattern in the system has not been quantified. In the present study, we developed a lubrication-based model to analyze the FSS distributions in a rocking rectangular culture dish. We identified an important parameter (the critical flip angle) that dictates the overall FSS behaviors and suggested the right conditions to achieving temporally oscillating and spatially relatively uniform FSS. If the maximal rocking angle is kept smaller than the critical flip angle, which is defined as the angle when the fluid free surface intersects the outer edge of the dish bottom, the dish bottom remains covered with a thin layer of culture medium. The spatial variations of the peak FSS within the central 84% and 50% dish bottom are limited to 41% and 17%, respectively. The magnitude of FSS was found to be proportional to the fluid viscosity and the maximal rocking angle, and inversely proportional to the square of the fluid depth-to-length ratio and the rocking period. For a commercial rectangular dish (length of 37.6 mm) filled with ∼2 mL culture medium, the FSS at the center of the dish bottom is expected to be on the order of 0.9 dyn/cm2 when the dish is rocked +5° at 1 cycle/s. Our analysis suggests that a rocking “see-saw” system, if controlled well, can be used as an alternative method to provide low-magnitude, dynamic FSS to cultured cells

Experimental and numerical study of radio fequency atmospheric pressure glow discharges

Radio frequency (rf) atmospheric pressure glow discharges (APGDs) have received growing attention for their exciting scope of new science and their immense potential for widespread applications. While geometrically similar to conventional low-pressure discharges used in the semiconductor industry for decades, rf APGDs present new physics that require investigation. This thesis presents an experimental and computational study of helium rfAPGDs aimed at making a contribution to the current understanding of these discharges and enabling their optimization for different applications. The timely interest and significance of this work is highlighted by the publication of different parts of this thesis in 10 peer-reviewed international journals. Starting with the electron trapping in rf APGDs, the thesis looks into the electron heating mechanism responsible for sustaining the discharges, the influence of the rf excitation frequency on the discharge characteristics, the role of impurities in the discharge chemistry as well as the evolution of the discharge as the size is reduced down to microplasma dimensions. The findings of this research are based on the synergistic use of electrical measurements, optical diagnostics and self-developed computational models. With the knowledge gained from this thesis, rf-APGDs can be readily used for a wide-range of applications including biological decontaminations, nanostructure fabrication and portable gas analyzers