Browsing by Author "Engineer, Bhavin"

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    Calculation of guided wave dispersion characteristics using a three-transducer measurement system
    (MDPI, 2018-07-29) Hernandez Crespo, Borja; Courtney, Charles R. P.; Engineer, Bhavin
    Guided ultrasonic waves are of significant interest in the health monitoring of thin structures, and dispersion curves are important tools in the deployment of any guided wave application. Most methods of determining dispersion curves require accurate knowledge of the material properties and thickness of the structure to be inspected, or extensive experimental tests. This paper presents an experimental technique that allows rapid generation of dispersion curves for guided wave applications when knowledge of the material properties and thickness of the structure to be inspected are unknown. The technique uses a single source and measurements at two points, making it experimentally simple. A formulation is presented that allows calculation of phase and group velocities if the wavepacket propagation time and relative phase shift can be measured. The methodology for determining the wavepacket propagation time and relative phase shift from the acquired signals is described. The technique is validated using synthesized signals, finite element model-generated signals and experimental signals from a 3 mm-thick aluminium plate. Accuracies to within 1% are achieved in the experimental measurements.
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    Field testing of a prototype mechanical dry toilet flush
    (Elsevier, 2019-02-17) Hennigs, Jan; Ravndal, Kristin T.; Blose, Thubelihle; Toolaram, Anju; Sindall, Rebecca C.; Barrington, Dani J.; Collins, Matt; Engineer, Bhavin; Kolios, Athanasios J.; McAdam, Ewan; Parker, Alison; Williams, Leon; Tyrrel, Sean
    A prototype of a non-fluid based mechanical toilet flush was tested in a semi-public, institutional setting and in selected peri-urban households in eThekwini municipality, Republic of South Africa. The mechanism's functionality and users' perception of the flush were assessed. User perception varied depending on background: Users accustomed to porcelain water flush toilets were open to, yet reserved about the idea of using a waterless flush in their homes. Those who commonly use Urine Diversion Dehydration Toilets were far more receptive. The user-centred field trials were complemented by a controlled laboratory experiment, using synthetic urine, -faeces, and -menstrual blood, to systematically assess the efficiency of three swipe materials to clean the rotating bowl of the flush. A silicone rubber with oil-bleed-effect was found to be the best performing material for the swipe. Lubrication of the bowl prior to use further reduced fouling. A mechanical waterless flush that does not require consumables, like plastic wrappers, is a novelty and could – implemented in existing dry toilet systems – improve acceptance and thus the success of waterless sanitation.
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    Multi-sectoral participatory design of a babyWASH playspace for rural Ethiopian households
    (American Society of Tropical Medicine and Hygiene, 2021-03-03) Budge, Sophie; Parker, Alison; Hutchings, Paul; Garbutt, Camila; Rosenbaum, Julia; Tulu, Tizita; Woldemedhin, Fitsume; Jemal, Mohammedyasin; Engineer, Bhavin; Williams, Leon
    Growing evidence suggests current water, sanitation, and hygiene interventions do not improve domestic hygiene sufficiently to improve infant health, nor consider the age-specific behaviors which increase infection risk. A household playspace (HPS) is described as one critical intervention to reduce direct fecal–oral transmission within formative growth periods. This article details both the design and development (materials and methods), and testing (results) of a HPS for rural Ethiopian households. Design and testing followed a multi-sectoral, multistep participatory process. This included a focus group discussion (FGD), two user-centered and participatory design workshops in the United Kingdom and Ethiopia, discussions with local manufacturers, and a Trials by Improved Practices (TIPs) leading to a final prototype design. Testing included the FGD and TIPs study and a subsequent randomized controlled feasibility trial in Ethiopian households. This multi-sectoral, multistage development process demonstrated a HPS is an acceptable and feasible intervention in these low-income, rural subsistence Ethiopian households. A HPS may help reduce fecal–oral transmission and infection—particularly in settings where free-range domestic livestock present an increased risk. With the need to better tailor interventions to improve infant health, this article also provides a framework for future groups developing similar material inputs and highlights the value of participatory design in this field