Andrew Lewis

Model reduction for real-time fluids

We present a new model reduction approach to fluid simulation, enabling large, real-time, detailed flows with continuous user interaction. Our reduced model can also handle moving obstacles immersed in the flow. We create separate models for the velocity field and for each moving boundary, and show that the coupling forces may be reduced as well. Our results indicate that surprisingly few basis functions are needed to resolve small but visually important features such as spinning vortices.

Measurement of the cable-pulley Coulomb and viscous friction for a cable-driven surgical robotic system

In this paper we present experimentally obtained cable-pulley Coulomb and viscous friction for cable-driven surgical robotic systems including the RAVEN II surgical robotic research platform. In the study of controlling cable-driven systems a simple mathematical model which does not capture physical behavior well is often employed. Even though control of such systems is achievable without an accurate model, fully understanding the behavior of the system will potentially realize more robust control. A surgical robot is one of the systems that often relies on cables as an actuation method as well as pulleys to guide them. Systems with such structure encounter frictional force related to conditions of cable and pulley such as cable velocity, tension, type and number of pulley, and angle of cable wrapping around pulley. Using a couple of test platforms that incorporate cable, pulleys, and other experimental conditions corresponding to the RAVEN II system, it is shown that cable-pulley friction is function of tension, wrap angle, and number of pulleys and not of magnitude of cable velocity.

A Lifecycle Approach to HIV Prevention in African Women and Children

Effective biomedical and structural HIV prevention approaches are being implemented throughout sub-Saharan Africa. A “lifecycle approach” to HIV prevention recognizes the interconnectedness of the health of women, children and adolescents, and prioritizes interventions that have benefits across these populations. We review new biomedical prevention strategies for women, adolescents and children, structural prevention approaches, and new modalities for eliminating infant HIV infection, and discuss the implications of a lifecycle approach for the success of these methods. Some examples of the lifecycle approach include evaluating education and HIV prevention strategies among adolescent girls not only for their role in reducing risk of HIV infection and early pregnancy, but also to promote healthy adolescents who will have healthier future children. Similarly, early childhood interventions such as exclusive breastfeeding not only prevent HIV, but also contribute to better child and adolescent health outcomes. The most ambitious biomedical infant HIV prevention effort, Option B+, also represents a lifecycle approach by leveraging the prevention benefits of optimal HIV treatment for mothers; maternal survival benefits from Option B+ may have ultimately more health impact on children than the prevention of infant HIV in isolation. The potential for synergistic and additive benefits of lifecycle interventions should be considered when scaling up HIV prevention efforts in sub-Saharan Africa.

Raven surgical robot training in preparation for da vinci.

The rapid adoption of robotic assisted surgery challenges the pace at which adequate robotic training can occur due to access limitations to the da Vinci robot. Thirty medical students completed a randomized controlled trial evaluating whether the Raven robot could be used as an alternative training tool for the Fundamentals of Laparoscopic Surgery (FLS) block transfer task on the da Vinci robot. Two groups, one trained on the da Vinci and one trained on the Raven, were tested on a criterion FLS block transfer task on the da Vinci. After robotic FLS block transfer proficiency training there was no statistically significant difference between path length (p=0.39) and economy of motion scores (p=0.06) between the two groups, but those trained on the da Vinci did have faster task times (p=0.01). These results provide evidence for the value of using the Raven robot for training prior to using the da Vinci surgical system for similar tasks.

Dynamically evaluated gravity compensation for the RAVEN surgical robot

Using an accelerometer on the base of a robot, it is possible to calculate the torque required from each actuator in order to maintain a known pose regardless of base orientation with respect to the direction or magnitude of gravity. A simple and novel method has been developed and implemented for overcoming gravity induced torques on the RAVENTM surgical research robot. This innovation will allow for accurate control of serial robot manipulators with re-orientable bases or for those operating in non-stationary environments such as boats, space stations, or moving vehicles.

Improving Archaeologists’ Online Archive Experiences Through User-Centred Design

Traditionally, the preservation of archaeological data has been limited by the cost of materials and the physical space required to store them, but for the last 20 years, increasing amounts of digital data have been generated and stored online. New techniques in digital photography and document scanning have dramatically increased the amount of data that can be retained in digital format, while at the same time reducing the physical cost of production and storage. Vast numbers of hand written notes, grey literature documents, images of assemblages, contexts, and artefacts have been made available online. However, accessing these repositories is not always straightforward. Superficial interaction design, sparsely populated metadata, and heterogeneous schemas may prevent users from working the data that they need within archaeological archives. In this article, we present the work of the Digging into Archaeological Data and Image Search Metadata project (DADAISM), a multidisciplinary project that draws together the work of researchers from the fields of archaeology, interaction design, image processing and text mining to create an interactive system that supports archaeologists in their tasks in online archives. By adopting a user-centred approach with techniques grounded in contextual design, we identified the phases of archaeologists work in online archives, which are distinctive to this user group. The insights from this work drove the design and evaluation of an interactive system that successfully integrates content-based image based retrieval and improved metadata searching to deliver a positive user experience when working with online archives.

Assistive Technology Abandonment: Research Realities and Potentials.

Abandonment of assistive technologies (ATs) is a serious problem – rates of abandonment can be high, 78% has been reported for hearing aids. The paper argues for the importance of studying the abandonment of ATs by collecting real-time data about the use and non-use of ATs in the lived experience of their users. In the AART-BC Project, we are studying the use and abandonment of mobility ATs including wheelchairs, walkers and prostheses. We present two apps, ESMMobilityAT and ProbMobilityAT to facilitate the collection of real-time data about mobility AT use and problems encountered with these ATs. ESMMobilityAT is based on the experience sampling method (ESM) and asks mobility AT users to answer a short questionnaire about their AT use seven times a day. ProbMobilityAT allows mobility AT users to report problems with their AT when they occur. The apps have been successfully piloted on Android and IOS smartphones, although a number of problems with deployment have been highlighted. They will now be used in a field study with mobility AT uses and can be adapted for other AT domains.

Image-based search and retrieval for biface artefacts using features capturing archaeologically significant characteristics

Archaeologists are currently producing huge numbers of digitized photographs to record and preserve artefact finds. These images are used to identify and categorize artefacts and reason about connections between artefacts and perform outreach to the public. However, finding specific types of images within collections remains a major challenge. Often, the metadata associated with images is sparse or is inconsistent. This makes keyword-based exploratory search difficult, leaving researchers to rely on serendipity and slowing down the research process. We present an image-based retrieval system that addresses this problem for biface artefacts. In order to identify artefact characteristics that need to be captured by image features, we conducted a contextual inquiry study with experts in bifaces. We then devised several descriptors for matching images of bifaces with similar artefacts. We evaluated the performance of these descriptors using measures that specifically look at the differences between the sets of images returned by the search system using different descriptors. Through this nuanced approach, we have provided a comprehensive analysis of the strengths and weaknesses of the different descriptors and identified implications for design in the search systems for archaeology.

Obtaining Experiential Data on Assistive Technology Device Abandonment

There have been few studies of abandonment of Assistive Technology, typically based on surveys and best practices expertise. This paper describes the application of classic experience sampling techniques to gather timely information about mobility aiding assistive technology in day-to-day use especially with respect to causes of abandonment. The paper describes the technical understructure of the system, which uses smartphones to gather, and web services to store, data. Also described is the setup and branching of the question set presented on the smartphone. Beyond details of use of the assistive technology, the system collects a verified scale of responses to determine the emotional affect of the participant. Sampling is taken several times during the day by actively pushing a set of questions that are tailored to the users technology and responses. There is also provision for the participant to push the information to the system when desired.