Browsing by Subject "Simulation"

Now showing 1 - 7 of 7
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    Construct validity testing of a low cost vitreoretinal surgical simulator
    (2020) van Der Westhuizen, Dean; Rice, James
    Objective: To test the construct validity of a low cost, low fidelity vitreoretinal surgical simulator Design: Construct validity study. Six microsurgical dexterity tasks, performed on a low cost vitreoretinal surgical simulator, were graded using a scoring rubric designed to assess microsurgical dexterity. Tasks one and two were dominant hand exercises, tasks three-five required bimanual dexterity and task six assessed visualization through a retinal viewing system The scores of a novice group (Ophthalmology residents who had never performed a pars planar vitrectomy) were compared to an expert group (Vitreoretinal surgeons who had performed in excess of 20 pars planar vitrectomies). Scores were graded via video recordings of the tasks, by blinded independent graders using a scoring rubric. Participants: The novice group of surgeons included 8 ophthalmology residents training at the Groote Schuur hospital department of Ophthalmology. The expert group of surgeons included 5 vitreoretinal surgeons working at the Groote Schuur hospital department of Ophthalmology, and 2 vitreoretinal surgeons working in the private sector in Cape Town, South Africa. Results: Expert surgeons performed significantly better( P=< 0.05) than the novice surgeons across all six microsurgical dexterity tasks. Greater differences were seen in bimanual tasks(tasks three-five) and in task six that was designed specifically to assess the surgeon's ability to ensure good visualisation through a retinal viewing system. Conclusions: The microsurgical dexterity tasks performed on This low cost, low-fidelity vitreoretinal surgical simulator can distinguish between novice and expert retinal surgeons demonstrating significant construct validity. Its use can be encouraged in the training of novice vitreoretinal surgeons.
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    Inductive Coupled Transfer Functions for Four Major Topologies, and their Relevant Design Equations
    (2021) Mouton, Hendrik D
    The four major topologies for inductive couplers (such as transformers with air gaps used for wireless power transfer), are discussed in many articles widely available. In this article all the relevant transfer functions and design equations for all four topologies are given and derived. It contains Bode plots showing gain and phase characteristics against frequency with different load resistances, demonstrating clearly that each topology has its own specific characteristics so that the best one for a particular application can be selected. The author used the Laplace s-parameter in all derivations, and only convert later to the frequency domain when required. The concept of reflected impedances due to the transformer in all the designs is used, because it simplifies the derivations significantly, though care must be taken to apply it correctly. Therefore, the basic der-ivation of reflected impedances is also given. A novel set of formulas is derived for calculating the capacitance of the capacitor on the secondary side of the transformer. It is demonstrated to give satisfactory results even though the resultant formulas are relatively simple.
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    Investigating the Effectiveness of Supermarket Transmission Control Measures on the Spread of COVID-19 in the Presence of Super-Spreaders through Agent-Based Modelling
    (2022) Mountford, Timothy; Silal, Sheetal
    An examination of the effectiveness of transmission control measures for COVID-19 in a supermarket setting, factoring for the inclusion of Super-Spreaders, must extend beyond the direct effects the control measure has on transmission in order to account for the indirect effects changes in human movement dynamics have on the spread of disease. The analysis makes use of Agent-Based Modelling simulation techniques to model changes in customer movement and disease transmission dynamics resulting from the isolated and combined implementation of COVID-19 transmission control measures. The bottom-up approach of agent-based modelling allows for the inclusion of heterogeneous, individual-level chances of infectiousness, compliance, and consumer behaviours, allowing for a more realistic representation of real-world behaviours. The model used for analysis is built entirely in the NetLogo environment, designed to be interactive, adaptable to user-varied inputs, and visually engaging. This allows for the model to adapt to changes in disease parameters and easily communicate model effects in a manner accessible to users in and out of the field. Control measures considered include: Vaccinations, Capacity Limiting, Social Distancing, Staff COVID-19 Testing, and the use of Sanitizers. Results indicate high levels of effectiveness for the use of Vaccinations at reducing transmission with minimal impact on customer dynamics. The results also highlight the negative effects changes in customer dynamics can have on transmission, indicated by increased shop-queue transmissions resulting from the use of Capacity Limiting or other measures slowing customer entrance to the shop. The positive effects of interactions between control measures are highlighted by the additional implementation of Social Distancing in reducing these increases. The implications of these findings involve the need to factor for changes in human movement dynamics when assessing the effectiveness of transmission control measures implemented in any environment. The findings further reinforce the benefits of implementing social distancing practises in conjunction with mechanisms that reduce the flow of movement, as well as the benefits of increased vaccination coverage in the population. Lastly, the findings provide an effective comparison of the control measures considered, allowing for the direct assessment of their implementation and the resulting effects on transmission and customer dynamics.
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    Primary refrigeration system commissioning based on a transcritical 2- stage R744 cycle
    (2024) Teixeira, Daniella; Boje, Edward; Yacoob, Sahal
    This report gives a brief background into the use of carbon dioxide as a refrigerant (R744) and describes the development of a two-stage trans-critical cooling system that is intended to be used as a chiller for the detectors at CERN's Large Hadron Collider (LHC). It then goes on to describe the steps taken to prepare the system for start-up. These steps include the process of defining how the system should operate and translating this into actuator and PLC logic; identifying the safety limits and implementing alarms to prevent accidents; testing the PLC redundancy to understand its failure modes; testing the programmed logic and wiring; and testing the alarms before clearing the system for start-up. Once the system is started, the controllers are manually tuned by an operator to achieve stable and reliable performance. However, this project aims to determine whether a better performance can be achieved by first modelling the system, determining the transfer function of each control loop and designing the controllers mathematically. To do this, the system is modelled in Simulink, and the performance of the model is verified by comparing the outputs of the model to that of the physical system while running with the same operating conditions. With the verified model, the transfer function of each control loop can be determined, and various control methods can be used to design the PI controllers. Due to the complexity of the control problem, and the interaction between the multiple control loops, care is taken when defining the desired performance of the controllers to maximise disturbance rejection and ensure that the controllers can operate independently without causing instability in other control loops. The designed controllers are implemented in the simulated model of the plant to verify the performance of the control loops under different operating conditions and with realistic disturbances. This is compared to the performance of the physical system with its manually tuned controllers. The comparison finds that the designed controllers perform better, with less oscillation and better disturbance rejection than the manually tuned controllers. From this it can be concluded that the process of simulating the system and designing the controllers mathematically provides more stable performance than the manual operator tuning. However, this process is much more time-consuming and requires a deep understanding of the instabilities, disturbances, and possible failures of the system. This may not be practical for the commissioning of multiple, large, complex systems with restrictive deadlines but may be worthwhile for systems that will be multiplied several times as the Primary R744 chiller at CERN will be.
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    Simulating therapeutic drug monitoring results for dose individualisation to maintain investigator blinding in a randomised controlled trial
    (BioMed Central, 2017-06-07) Lesosky, Maia; Joska, John; Decloedt, Eric
    Background: Therapeutic drug monitoring (TDM) is essential practice when dosing drugs with a narrow therapeutic index in order to achieve a plasma drug concentration within a narrow target range above the efficacy concentration but below the toxicity concentration. However, TDM with dose individualisation is challenging during a double-blind clinical trial with laboratory staff and investigators blinded to treatment arm allocation. Methods: Drug concentrations were simulated for participants in the placebo arm by an unblinded independent statistician, utilising the measured values from the treatment arm participants. Simulated and actual concentrations were re-blinded and passed on to a dose-adjusting investigator, who made dose adjustment recommendations but was not directly responsible for clinical care of participants. Results: A total of 257 sham lithium plasma concentrations were simulated utilising 242 true lithium plasma concentrations in real time as the trial progressed. The simulated values had a median (interquartile range) of 0.59 (0.46, 0.72) compared to 0.53 (0.39, 0.72) in the treatment arm. Blinding of the laboratory staff and dose-adjusting investigator was maintained successfully. Conclusions: We succeeded in simulating sham lithium plasma concentrations while maintaining blinding. Our simulated values have a smaller range than the observed data, which can be explained by the challenges with respect to drug adherence and dose timing that were experienced. Trial registration: Pan African Clinical Trials Registry, PACTR201310000635418. Registered on 30 August 2013.
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    Simulation-based low-dose, high-frequency plus mobile mentoring versus traditional group-based training approaches on day of birth care among maternal and newborn healthcare providers in Ebonyi and Kogi States, Nigeria; a randomized controlled trial
    (BioMed Central, 2018-08-13) Ugwa, Emmanuel; Otolorin, Emmanuel; Kabue, Mark; Ishola, Gbenga; Evans, Cherrie; Oniyire, Adetiloye; Olisaekee, Gladys; Onwe, Boniface; LeFevre, Amnesty E; Bluestone, Julia; Orji, Bright; Yenokyan, Gayane; Okoli, Ugo
    Abstract Background There is limited information from low and middle-income countries on learning outcomes, provider satisfaction and cost-effectiveness on the day of birth care among maternal and newborn health workers trained using onsite simulation-based low-dose high frequency (LDHF) plus mentoring approach compared to the commonly employed offsite traditional group-based training (TRAD). The LDHF approach uses in-service learning updates to deliver information based on local needs during short, structured, onsite, interactive learning activities that involve the entire team and are spaced over time to optimize learning. The aim of this study will be to compare the effectiveness and cost of LDHF versus TRAD approaches in improving knowledge and skill in maternal and newborn care and to determine trainees’ satisfaction with the approaches in Ebonyi and Kogi states, Nigeria. Methods This will be a prospective cluster randomized control trial. Sixty health facilities will be randomly assigned for day of birth care health providers training through either LDHF plus mobile mentoring (intervention arm) or TRAD (control arm). There will be 150 trainees in each arm. Multiple choices questionnaires (MCQs), objective structured clinical examinations (OSCEs), cost and satisfaction surveys will be administered before and after the trainings. Quantitative data collection will be done at months 0 (baseline), 3 and 12. Qualitative data will also be collected at 12-month from the LDHF arm only. Descriptive and inferential statistics will be used as appropriate. Composite scores will be computed for selected variables to determine areas where service providers have good skills as against areas where their skills are poor and to compare skills and knowledge outcomes between the two groups at 0.05 level of statistical significance. Discussion There is some evidence that LDHF, simulation and practice-based training approach plus mobile mentoring results in improved skills and health outcomes and is cost-effective. By comparing intervention and control arms the authors hope to replicate similar results, evaluate the approach in Nigeria and provide evidence to Ministry of Health on how and which training approach, frequency and setting will result in the greatest return on investment. Trial registration The trial was retrospectively registered on 24th August, 2017 at ClinicalTrials.Gov: NCT03269240 .
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    The evaluation of a simulated theatre scenario as a tool to promote inter-professional collaboration and engender a culture of increased awareness of patient safety in South African hospitals
    (2022) Robertson, Caroline Helen; Duys, Rowan
    Background: Errors related to patient safety are a major contributor to adverse incidents and preventable deaths. Interventions aimed at changing team behaviour and implementing World Health Organisation Safe Surgical Checklists (WHO SSCL) have been associated with improved outcomes. We required a cost- and timeefficient vehicle to address low adoption rates of the WHO SSCL, barriers to interdisciplinary teamwork, and inadequate attention to patient safety. Method: We aimed to test the feasibility and efficacy of a simulation-based intervention to improve behaviour influencing patient safety in operating theatres. We performed a prospective cohort study using survey tools for attendee feedback immediately after the event and at 6 weeks. We report feasibility and efficacy data plus qualitative feedback from the education team describing the advantages of this instructional design. The intervention was a 2-stage simulation. First, learners watched a 5-minute film, set in the operating theatre, depicting an error-filled WHO SSCL timeout. Second, learners entered a simulated operating theatre environment with multiple errors and risks to patient safety. Learners identified errors and prioritised them in order of importance. Their observations were discussed in a small group debrief session facilitated by novice debriefers before a whole group plenary discussion. Results: One hundred and three health workers attended the education event and 77 (75%) responded to the Immediate Questionnaire. Surgeons (27), Anaesthetists (18) and Scrub Nurses (12) made up the majority of respondents. Sixty-seven (87%) participants agreed or strongly agreed that they “now have an increased awareness of patient safety”, while 75 (97%) agreed or strongly agreed that they “feel more committed to ensuring a team approach to patient safety”. Thirty (29%) attendees responded to the Delayed Questionnaire distributed via email 6 weeks after the event. Twenty-eight (93%) agreed or strongly agreed that they felt more committed to ensuring a team approach to patient safety. Conclusion: The total cost of the event was low. Faculty reported that the instructional design afforded deliberate targeting of the importance of multi-disciplinary teamwork in patient safety. The simulation event was feasible at low monetary, time, and human resource costs. This approach offers a scalable instructional design that targets inter-professional learning.