A modular design architecture for application to community-scale photovoltaic-powered reverse osmosis systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2013.This electronic version was submitted and approved by the author's academic department as part of an electronic thesis pilot project. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from department-submitted PDF version of thesis.Includes bibliographical references (p. 151-158).Access to safe, clean drinking water is a major challenge for many communities. These communities are often near seawater and/or brackish groundwater sources, making desalination a possible solution. Unfortunately, desalination is energy intensive and a reliable, inexpensive power supply is also challenging for remote locations. Photovoltaic reverse osmosis systems (PVRO) can be used to provide water for underserved communities. A feasibility study which demonstrates the economic viability of such systems is discussed here. PVRO systems are assembled from mass-produced modular components. This approach reduces manufacturing costs. However, designing a system optimized for a specific location is difficult. For even a small inventory of components, the number of design choices is enormous. A designer with significant expertise is required to tailor a PVRO system for a given location, putting this technology out of reach of many communities. This thesis develops a modular design architecture which can be implemented in a computer program to enable non-experts to configure systems from inventories of modular components. This architecture is not limited to PVRO systems, but can also be used to design other systems composed of modular components such as cars, electronics, and computers. The method uses a hierarchy of filters to limit the design space based on design principles and calculations. The system is then configured from the reduced design space using optimization methods and detailed system models. In this thesis, the modular design architecture is implemented for PVRO systems. A set of detailed physics-based system models are developed to enable this process. A novel method of representing a PVRO system using a graph is developed to enable rapid evaluation of different system configurations. This modeling technique is validated using the MIT Experimental PVRO system constructed as part of this research. A series of case studies are conducted to validate the modular design approach for PVRO systems. The first set of case studies considers a deterministic solar input and water demand. The design goal is to determine the lowest cost system that meets the water demand requirements. It is shown that the method is able to tailor systems for a wide range of locations and water demands from a large system inventory. The validity of these solutions is demonstrated by simulating a custom designed system in the wrong location. Another case study shows that the approach can be used to determine market potential of new components. The second set of case studies considers variations in the solar radiation and water demand. The design goal is to determine the lowest cost PVRO system that meets the water demand profile with a specified probability. Two methods that use historical solar insolation and water demand to account for variations are presented. The first method characterizes the historical data and develops models to synthetically generate solar insolation and water demand profiles, and then simulates the system performance over 100 years to calculate the loss-of-water probability. In the second method, distributions of solar radiation and water demand are calculated from historical data and used to directly calculate the probability of running out of water in the worst month of the year. Both methods are implemented and shown to produce feasible system configurations. The direct calculation method is shown to reduce the required computation time and is suitable for different systems with variable inputs.by Amy M. Bilton.Ph.D

Fusion of remote vision and on-board acceleration data for the vibration estimation of large space structures

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006.Includes bibliographical references (leaves 81-84).Future space structures such as solar power stations and telescopes are expected to be very large. These structures will require on-orbit construction. Due to the risks and costs of human extravehicular work, teams of robots will be essential for the on-orbit assembly of the large space structures. There are a number of technical challenges presented by such robotic construction. The structures will need to be made of lightweight materials and will be very flexible. Autonomous robots will require information about the vibrations of the flexible structures and their dynamic parameters in order to perform the construction efficiently. Often models of the structures are imperfect, therefore the magnitude of the vibrations of the structure must be estimated on-orbit. This thesis presents a method for estimating the shape and dynamic parameters of a vibrating large space structure. This technique is a cooperative sensing approach using remote free-flying robot observers equipped with vision sensors and structure-mounted accelerometers. This approach exploits the complementary nature of the two types of sensors.(cont.) Vision sensors are able to measure structure deflections at a high spatial frequency but are bandwidth limited. Accelerometers are able to make measurements at high temporal frequency, but are sparsely located on the structure. The fused estimation occurs in three steps. First, the vision data is condensed in a modal decomposition that results in coarse estimates of modal coefficients. In the second step, the coarse estimates of the modal coefficients obtained from vision data are fused with the accelerometer measurements in a multi-rate nonlinear Kalman filter, resulting in a refined estimate of the modal coefficients and dynamic properties of the structure. In the final step, the estimated modal coefficients are combined with the mode shapes to provide a shape estimate of the entire structure. Simulation and experimental results demonstrate that the performance of this fused estimation approach is superior to the performance achieved when using only a single type of sensor.by Amy M. Bilton.S.M

Convalescent plasma in patients admitted to hospital with COVID-19 (RECOVERY): a randomised controlled, open-label, platform trial

Background: Many patients with COVID-19 have been treated with plasma containing anti-SARS-CoV-2 antibodies. We aimed to evaluate the safety and efficacy of convalescent plasma therapy in patients admitted to hospital with COVID-19. Methods: This randomised, controlled, open-label, platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]) is assessing several possible treatments in patients hospitalised with COVID-19 in the UK. The trial is underway at 177 NHS hospitals from across the UK. Eligible and consenting patients were randomly assigned (1:1) to receive either usual care alone (usual care group) or usual care plus high-titre convalescent plasma (convalescent plasma group). The primary outcome was 28-day mortality, analysed on an intention-to-treat basis. The trial is registered with ISRCTN, 50189673, and ClinicalTrials.gov, NCT04381936. Findings: Between May 28, 2020, and Jan 15, 2021, 11558 (71%) of 16287 patients enrolled in RECOVERY were eligible to receive convalescent plasma and were assigned to either the convalescent plasma group or the usual care group. There was no significant difference in 28-day mortality between the two groups: 1399 (24%) of 5795 patients in the convalescent plasma group and 1408 (24%) of 5763 patients in the usual care group died within 28 days (rate ratio 1·00, 95% CI 0·93–1·07; p=0·95). The 28-day mortality rate ratio was similar in all prespecified subgroups of patients, including in those patients without detectable SARS-CoV-2 antibodies at randomisation. Allocation to convalescent plasma had no significant effect on the proportion of patients discharged from hospital within 28 days (3832 [66%] patients in the convalescent plasma group vs 3822 [66%] patients in the usual care group; rate ratio 0·99, 95% CI 0·94–1·03; p=0·57). Among those not on invasive mechanical ventilation at randomisation, there was no significant difference in the proportion of patients meeting the composite endpoint of progression to invasive mechanical ventilation or death (1568 [29%] of 5493 patients in the convalescent plasma group vs 1568 [29%] of 5448 patients in the usual care group; rate ratio 0·99, 95% CI 0·93–1·05; p=0·79). Interpretation: In patients hospitalised with COVID-19, high-titre convalescent plasma did not improve survival or other prespecified clinical outcomes. Funding: UK Research and Innovation (Medical Research Council) and National Institute of Health Research

Increasing frailty is associated with higher prevalence and reduced recognition of delirium in older hospitalised inpatients: results of a multi-centre study

Purpose: Delirium is a neuropsychiatric disorder delineated by an acute change in cognition, attention, and consciousness. It is common, particularly in older adults, but poorly recognised. Frailty is the accumulation of deficits conferring an increased risk of adverse outcomes. We set out to determine how severity of frailty, as measured using the CFS, affected delirium rates, and recognition in hospitalised older people in the United Kingdom. Methods: Adults over 65 years were included in an observational multi-centre audit across UK hospitals, two prospective rounds, and one retrospective note review. Clinical Frailty Scale (CFS), delirium status, and 30-day outcomes were recorded. Results: The overall prevalence of delirium was 16.3% (483). Patients with delirium were more frail than patients without delirium (median CFS 6 vs 4). The risk of delirium was greater with increasing frailty [OR 2.9 (1.8–4.6) in CFS 4 vs 1–3; OR 12.4 (6.2–24.5) in CFS 8 vs 1–3]. Higher CFS was associated with reduced recognition of delirium (OR of 0.7 (0.3–1.9) in CFS 4 compared to 0.2 (0.1–0.7) in CFS 8). These risks were both independent of age and dementia. Conclusion: We have demonstrated an incremental increase in risk of delirium with increasing frailty. This has important clinical implications, suggesting that frailty may provide a more nuanced measure of vulnerability to delirium and poor outcomes. However, the most frail patients are least likely to have their delirium diagnosed and there is a significant lack of research into the underlying pathophysiology of both of these common geriatric syndromes

Convalescent plasma in patients admitted to hospital with COVID-19 (RECOVERY): a randomised controlled, open-label, platform trial

SummaryBackground Azithromycin has been proposed as a treatment for COVID-19 on the basis of its immunomodulatoryactions. We aimed to evaluate the safety and efficacy of azithromycin in patients admitted to hospital with COVID-19.Methods In this randomised, controlled, open-label, adaptive platform trial (Randomised Evaluation of COVID-19Therapy [RECOVERY]), several possible treatments were compared with usual care in patients admitted to hospitalwith COVID-19 in the UK. The trial is underway at 176 hospitals in the UK. Eligible and consenting patients wererandomly allocated to either usual standard of care alone or usual standard of care plus azithromycin 500 mg once perday by mouth or intravenously for 10 days or until discharge (or allocation to one of the other RECOVERY treatmentgroups). Patients were assigned via web-based simple (unstratified) randomisation with allocation concealment andwere twice as likely to be randomly assigned to usual care than to any of the active treatment groups. Participants andlocal study staff were not masked to the allocated treatment, but all others involved in the trial were masked to theoutcome data during the trial. The primary outcome was 28-day all-cause mortality, assessed in the intention-to-treatpopulation. The trial is registered with ISRCTN, 50189673, and ClinicalTrials.gov, NCT04381936.Findings Between April 7 and Nov 27, 2020, of 16 442 patients enrolled in the RECOVERY trial, 9433 (57%) wereeligible and 7763 were included in the assessment of azithromycin. The mean age of these study participants was65·3 years (SD 15·7) and approximately a third were women (2944 [38%] of 7763). 2582 patients were randomlyallocated to receive azithromycin and 5181 patients were randomly allocated to usual care alone. Overall,561 (22%) patients allocated to azithromycin and 1162 (22%) patients allocated to usual care died within 28 days(rate ratio 0·97, 95% CI 0·87–1·07; p=0·50). No significant difference was seen in duration of hospital stay (median10 days [IQR 5 to >28] vs 11 days [5 to >28]) or the proportion of patients discharged from hospital alive within 28 days(rate ratio 1·04, 95% CI 0·98–1·10; p=0·19). Among those not on invasive mechanical ventilation at baseline, nosignificant difference was seen in the proportion meeting the composite endpoint of invasive mechanical ventilationor death (risk ratio 0·95, 95% CI 0·87–1·03; p=0·24).Interpretation In patients admitted to hospital with COVID-19, azithromycin did not improve survival or otherprespecified clinical outcomes. Azithromycin use in patients admitted to hospital with COVID-19 should be restrictedto patients in whom there is a clear antimicrobial indication

Ultrafast reclamation of fracking effluents using surface-engineered nanosilicon sponges

Effluents from the fracking process are typically discharged at elevated temperatures and are a major environmental concern. We applied a surface-engineered sponge (SEnS) with thermal stability up to 220 ºC to reclaim emulsified oily wastewater at discharge temperatures between 30-100 ºC. The sponge achieved 92-96% removal efficiency within 5 minutes, where speed increased by 27% by melting waxes. The adsorbed oil from the SEnS was also recovered within 1-2 minutes by diluent wash. These performance metrics suggest that SEnS could emerge as a practical solution to achieve fracking water reclamation processes’ Net-Zero goals

Adsorptive Recovery of Crude Oil Microdroplets from Wastewater Using Surface Engineered Sponges

In the US, the oil industry produces over 15 billion barrels of wastewater contaminated with crude oil microdroplets annually. Current technologies are unable to remove these microdroplets at different pH conditions. Herein, an innovative surface engineered sponge (SenS) was designed by combining surface chemistry, surface charge, roughness, and surface energy. Under all pH conditions, the SEnS rapidly adsorbed oil microdroplets with 95-99% removal efficiency. The adsorbed oil was recovered at ambient conditions while the cleaned SEnS was reused for five times for crude oil adsorption. Due to the process efficacy, sponge reuse, and oil recovery, this adsorptive-recovery method using SEnS demonstrates great potential for the industrial recovery of oil from wastewater

Acid–Base Polymeric Foams for the Adsorption of Micro-oil Droplets from Industrial Effluents

Separation of toxic organic pollutants from industrial effluents is a great environmental challenge. Herein, an acid–base engineered foam is employed for separation of micro-oil droplets from an aqueous solution. In acidic or basic environments, acid–base polymers acquire surface charge due to protonation or dissociation of surface active functional groups. This property is invoked to adsorb crude oil microdroplets from water using polyester polyurethane (PESPU) foam. The physicochemical surface properties of the foam were characterized using X-ray photoelectron spectroscopy, inverse gas chromatography, electrokinetic analysis, and micro-computed tomography. Using the surface charge of the foam and oil droplets, the solution pH (5.6) for maximum separation efficacy was predicted. This optimal pH was verified through underwater wetting behavior and adsorption experiments. The droplet adsorption onto the foam was governed by physisorption, and the driving forces were attributed to electrostatic attraction and Lifshitz–van der Waals forces. The foam was regenerated and reused multiple times by simple compression. The lowest trace oil content in the retentate was 3.6 mg L^–1, and all oil droplets larger than 140 nm were removed. This work lays the foundation for the development of a new class of engineered foam adsorbents with the potential to revolutionize water treatment technologies