Usable Lifetime Research Articles

Entropy generation analysis on hybrid dusty nanofluid flow over a heated stretching sheet: aerospace technology

Over the last few decades, many kinds of advanced substances that are acceptable for specific aerospace applications have been developed. An aircraft engine has a number of duties that are performed by kerosene oil. These responsibilities include oiling, air conditioning, servicing, preventing corrosion and reducing loudness. Maintenance is a matter of extreme importance. Without maintenance, it is only inevitable that any moving component might have the capacity to run away quickly. This project’s efforts are focused on reducing expenditures by extending the usable lifetimes of aviation components. Additionally, the initiative aims to improve fuel efficiency, load capacity and travel distance. The importance of the heat transfer investigation on MHD dusty hybrid nanofluid across a porous stretching sheet with entropy generation and thermal radiation is examined in the current research. We used the self-similarity transformation to transform the partial differential equation into ordinary differential equations. After applying transformations, for graphical purposes we have used the Bvp4c technique in MATLAB solver. The effect of active important parameters affecting the fluid’s capacity to transfer importance is shown in graphs and tables. For higher values of the magnetic field parameter, the velocity outline decreased, while the opposite nature was noticed in the energy profile. Based on our investigation, we found that mixed nanofluids are more effective in transferring energy carriers compared to dusty tiny fluids.

Coupling Nuclear Predictions into Damage Simulations with SPECTRA-PKA

Modern nuclear physics software is well validated, providing advanced capabilities to support the engineering of the future generations of fission and fusion reactors. Transport simulators can model the transport of neutrons through reactor geometries, and inventory codes can accurately predict transmutation and activation. Meanwhile, material modeling applies a variety of techniques to understand how structural damage and composition changes will alter the properties of materials, ultimately limiting their usable lifetime in a reactor. Bridging the gap between nuclear simulation tools and materials modeling is a necessary step if these lifetimes are to be accurately predicted, which, for fusion, is critical to provide the necessary assurance of commercial viability. SPECTRA-PKA is a tool developed to compute the rates of structural damage source events, i.e. the primary knock-on atoms (PKAs), using the same nuclear data as used by transport and inventory simulations. Now, it has been interfaced with the binary collision approximation code SDTrimSP, allowing those PKA events, distributed spatially and temporally in an atomic system, to be converted into damage cascades. This computational infrastructure provides insight into the variation in damage distributions between different materials under the same nuclear environment. Example simulations for materials under fusion reactor conditions demonstrate how the rich detail of the nuclear environment can be applied directly to modeling, without the need for integral-average measures that omit those details.

A novel post-weld treatment using nanostructured metallic multilayer for superior fatigue strength

Welded joints exhibit fatigue failure potential from weld geometry and characteristics of the heat affected zone. In order to counteract fatigue, structures and components require larger thicknesses resulting in heavier designs exhausting the finite natural resources. We hereby introduce a novel post-weld treatment, which postpones or even prevents fatigue failure of the welded connection. A Cu/Ni nanostructured metallic multilayer (NMM) is applied via electrodeposition and a 300–600% increase in usable lifetime compared to the untreated weld is observed. A FAT class 190 with a slope of k = 6 is proposed for the design of NMM treated butt welds. Material mechanisms responsible for the fatigue strength increase are introduced herein. A case study shows that the design of offshore wind turbine support structures applying NMM post-weld treatment enables a lifetime extension as well as a 28% weight reduction compared to the structure without post-weld treatment.

Operando Li metal plating diagnostics via MHz band electromagnetics

A nondestructive detection method for internal Li-metal plating in lithium-ion batteries is essential to improve their lifetime. Here, we demonstrate a direct Li-metal detection technology that focuses on electromagnetic behaviour. Through an interdisciplinary approach combining the ionic behaviour of electrochemical reactions at the negative electrode and the electromagnetic behaviour of electrons based on Maxwell’s equations, we find that internal Li-metal plating can be detected by the decrease in real part of the impedance at high-frequency. This finding enables simpler diagnostics when compared to data-driven analysis because we can correlate a direct response from the electronic behaviour to the metallic material property rather changes in the ionic behaviour. We test this response using commercial Li-ion batteries subject to extremely fast charging conditions to induce Li-metal plating. From this, we develop a battery sensor that detects and monitors the cycle-by-cycle growth of Li-metal plating. This work not only contributes to advancing future Li-ion battery development but may also serve as a tool for Li-metal plating monitoring in real-field applications to increase the useable lifetime of Li-ion batteries and to prevent detrimental Li-metal plating.

Stretchable, self-healing, biocompatible, and durable ionogel for continuous wearable strain and physiological signal monitoring

Electronic textiles (e-textiles) have great potential for use in wearable systems worn next to skin for continuous physiological monitoring, owing to their flexibility and conformability to the body. However, challenges exist in the long-term functionality and durability of these materials. This work presents a highly stretchable, self-healing, and biocompatible chloride-based ionogel fabricated from polymerization of thioctic acid, and 1-n-Butyl-3-methylimidazolium chloride ([BMIM]Cl) ionic liquid. With its adaptable mechanical properties and tunable viscosity by simple dilution, the ionogel precursor can be either cast into an ionogel film used for strain sensing applications up to 500% strain, or directly sprayed as a coating for e-textile electrodes for biopotential signal monitoring. The ionogel can reform at room temperature, demonstrating 73.5% stress recovery, and 84.8% modulus recovery after a 30-minute healing period. When used as a spray barrier coating on e-textiles, the ionogel displayed high resistance to abrasion, and reformed after adding ethanol to the surface. The electrical properties of the ionogel coated e-textiles satisfies the performance range desired for textile sensing electrodes. Further development and application of this ionogel material system can address long-term durability concerns by extending the usable lifetime of the sensors for wearable applications.

Degradation of Polyacrylates by One-Pot Sequential Dehydrodecarboxylation and Ozonolysis

We establish a synthetically convenient method to degrade polyacrylate homopolymers. Carboxylic acids are installed along the polymer backbone by partial hydrolysis of the ester side chains, and then, in a one-pot sequential procedure, the carboxylic acids are converted into alkenes and oxidatively cleaved. This process enables the robustness and properties of polyacrylates to be maintained during their usable lifetime. The ability to tune the degree of degradation was demonstrated by varying the carboxylic acid content of the polymers. This method is compatible with a wide range of polymers prepared from vinyl monomers through copolymerization of acrylic acid with different monomers including acrylates, acrylamides, and styrenics.

Validation of a balancing model based on master-slave battery management system architecture

The battery management system (BMS) performs the monitoring and control of the charging/discharging process of the cell, state of charge estimation, battery safety and protection, state of health estimation, cell balancing, and thermal management. These control operations ensure accurate, safe, and reliable operating conditions, individual cell damage on battery string, and increase the cell life. Battery balancing is one of the key technologies in the BMS, which affects the actual usable capacity range, performance, and lifetime of the entire battery module. However, it is difficult to evaluate or compare the performance of the overall BMS under the multi-series battery module structure. Most of the proposed battery energy storage system (ESS) models focus on energy distribution and system estimation (microgrid or renewable energy). This study develops a balancing model for estimating the balancing performance of the BMS. A Master-Slave BMS (MS-BMS) is proposed to validate the balancing model. The Master and Slaves of the BMS employed a traditional flyback converter with a MOSFET switching array and bidirectional flyback converters with photoMOS arrays, respectively, to perform the balancing behavior. The balancing skill, balancing circuit power, equalization speed, control simplicity, modularization simplicity, and cost has been considered in designing the proposed BMS. The simulation results are verified with the experimental results, which are then compared with the balancing model's results under the five balancing conditions, and the average absolute error of the balancing duration results is 3.12%. The performance of the proposed BMS is also compared with the existing modular BMS architecture, which validates the advantages of the proposed BMS including equalization speed, control simplicity, modularization simplicity, and cost.

Operando monitoring of single-particle kinetic state-of-charge heterogeneities and cracking in high-rate Li-ion anodes

To rationalize and improve the performance of newly developed high-rate battery electrode materials, it is crucial to understand the ion intercalation and degradation mechanisms occurring during realistic battery operation. Here we apply a laboratory-based operando optical scattering microscopy method to study micrometre-sized rod-like particles of the anode material Nb14W3O44 during high-rate cycling. We directly visualize elongation of the particles, which, by comparison with ensemble X-ray diffraction, allows us to determine changes in the state of charge of individual particles. A continuous change in scattering intensity with state of charge enables the observation of non-equilibrium kinetic phase separations within individual particles. Phase field modelling (informed by pulsed-field-gradient nuclear magnetic resonance and electrochemical experiments) supports the kinetic origin of this separation, which arises from the state-of-charge dependence of the Li-ion diffusion coefficient. The non-equilibrium phase separations lead to particle cracking at high rates of delithiation, particularly in longer particles, with some of the resulting fragments becoming electrically disconnected on subsequent cycling. These results demonstrate the power of optical scattering microscopy to track rapid non-equilibrium processes that would be inaccessible with established characterization techniques.

Towards in-situ State of Health Monitoring of Lithium-Ion Batteries Using Internal Fiber-Optic Sensors

We demonstrate a fiberoptic sensor for measuring the lithium-ion concentration inside a lithium-ion battery (LiB), live during charge and discharge. The goal is to monitor the health of the battery based on the dynamic and state-of-charge dependent concentration of lithium ions in the electrolyte.An important factor to improve the sustainability of LiBs is to prolong the usable lifetime of the batteries, as it directly reduces the environmental footprint per functional unit (e.g., per kilometer driven). Batteries lose capacity over time, both due to charging/discharging and to shelf ageing (calendar ageing). This ageing is caused either by i) unwanted chemical reactions, reducing the number of available lithium-ions or increasing the impedance, or ii) by physical changes that reduces the available lithium storage capacity of the electrodes.Generally, ageing is studied through monitoring the operational performance (e.g., coulombic capacity, internal resistance), or through post-mortem investigations. Alternatively, advanced equipment such as thermal neutron imaging or X-ray tomography has been used to take snapshots of the internal composition of the battery [1,2]. In this study we propose to monitor and study the health of LiBs through internal measurements using fiber-optic sensors, specifically through live measurements of the internal lithium concentration.The intrinsic properties of optical fibers (e.g., small, chemically inert, electrically insulating) make them ideal for internal sensing in the chemically harsh interior of a battery. Multiple sensors can also be produced on a single fiber, enabling multi-point or multi-parameter sensing with only one entry point in the cell. Alternatively, the whole fiber can be used as a sensor, giving a continuous measurement along the fiber. In this study, the lithium concentration is measured by immobilizing a lithium-sensitive fluorophore at the tip of an optical fiber.Multiple fluorophores that exhibit increased fluorescence in the presence of lithium ions have been described in the literature [3–5]. Padilla et al. synthesized such a turn-on type fluorophore with a red-shifted absorption/emission spectrum to reduce UV photobleaching [5]. However, they did not demonstrate the Li-sensitivity in a setup suitable for internal health monitoring in LiBs, which will be done in this study using optical fibers.The experimental setup used in this study can be seen in Figure 1a. The fluorophore (2-(2-hydroxyphenyl)-naphthoxazole, HPNO) is synthesized according to Padilla et al.When the fluorophore (HPNO) binds a lithium-ion (see Figure 1b), the absorption edge redshifts enough to enable excitation at 405 nm. This increases the fluorescence intensity, which therefore becomes sensitive to the Li-ion concentration (Figure 1c). The fluorophore concentration used in this plot was 5 mM, with the Li-ion concentration varying from 0 to 14 mM. The sensitivity range therefore needs to be shifted to higher concentrations to reach typical conditions in LiBs (~1 M). The fluorophore shows minimal photo-bleaching, making the sensing principle suitable also in long term cycling studies. Siegel, J.B.; Lin, X.; Stefanopoulou, A.G.; Hussey, D.S.; Jacobson, D.L.; Gorsich, D. Neutron Imaging of Lithium Concentration in LFP Pouch Cell Battery. J. Electrochem. Soc. 2011, 158, A523, doi:10.1149/1.3566341.Senyshyn, A.; Mühlbauer, M.J.; Dolotko, O.; Hofmann, M.; Ehrenberg, H. Homogeneity of lithium distribution in cylinder-type Li-ion batteries. Sci. Rep. 2015, 5, 1–9, doi:10.1038/srep18380.Qin, W.; Obare, S.O.; Murphy, C.J.; Angel, S.M. A fiber-optic fluorescence sensor for lithium ion in acetonitrile. Anal. Chem. 2002, 74, 4757–4762, doi:10.1021/ac020365x.Langmuir, M.E.; Laura, R. Fluorescent lipophilic lithium ionophores. In Proceedings of the Advances in Fluorescence Sensing Technology; Lakowicz, J.R., Thompson, R.B., Eds.; 1993; Vol. 1885, pp. 337–348.Padilla, N.A.; Rea, M.T.; Foy, M.; Upadhyay, S.P.; Desrochers, K.A.; Derus, T.; Knapper, K.A.; Hunter, N.H.; Wood, S.; Hinton, D.A.; et al. Tracking lithium ions via widefield fluorescence microscopy for battery diagnostics. ACS Sensors 2017, 2, 903–908, doi:10.1021/acssensors.7b00087. Figure 1

Boosting the lifespan of magneto-mechano-electric generator via vertical installation for sustainable powering of Internet of Things sensor

Sustainability is essential for magneto-mechano-electric (MME) energy harvesters that convert low-frequency magnetic noise into useful electrical energy to be considered a practical power source for implementing real-life Internet of Things (IoT) sensor networks. In this study, we propose a vertically installed MME energy harvester based on a piezoelectric lead magnesium niobate-lead zirconate titanate (Pb(Mn1/3Nb2/3)O3-Pb(Zr,Ti)O3, PMN-PZT) single-crystal macro fiber composite cantilever. The MME harvester generates 12.2 mW output power from a low-amplitude stray magnetic field of 2.5 Oe and exhibits a long-term usable lifetime of 2.5 × 109 cycles while maintaining over 90 % of its output. An accelerated life test method is employed to predict the usable lifetime of the MME harvester using an inverse power law-Weibull model with accelerating stress of magneto-mechanical vibration-induced strain. In addition, a standalone wireless environmental monitoring system is demonstrated to operate for 10 weeks by exploiting the harvested power from stray magnetic fields (~2.2 Oe) near the power cables of home appliances. This study paves the way for lifetime assessment and prediction of sustainable MME harvesters to increase the practicability of self-powered IoT devices in smart infrastructures.

Quantifying the Impact of Lagged Hydrological Responses on the Effectiveness of Groundwater Conservation

AbstractMany irrigated agricultural areas seek to prolong the lifetime of their groundwater resources by reducing pumping. However, it is unclear how lagged responses, such as reduced groundwater recharge caused by more efficient irrigation, may impact the long‐term effectiveness of conservation initiatives. Here, we use a variably saturated, simplified surrogate groundwater model to: (a) analyze aquifer responses to pumping reductions, (b) quantify time lags between reductions and groundwater level responses, and (c) identify the physical controls on lagged responses. We explore a range of plausible model parameters for an area of the High Plains aquifer (USA) where stakeholder‐driven conservation has slowed groundwater depletion. We identify two types of lagged responses that reduce the long‐term effectiveness of groundwater conservation, recharge‐dominated and lateral‐flow‐dominated, with vertical hydraulic conductivity (KZ) the major controlling variable. When high KZ allows percolation to reach the aquifer, more efficient irrigation reduces groundwater recharge. By contrast, when low KZ impedes vertical flow, short term changes in recharge are negligible, but pumping reductions alter the lateral flow between the groundwater conservation area and the surrounding regions (lateral‐flow‐dominated response). For the modeled area, we found that a pumping reduction of 30% resulted in median usable lifetime extensions of 20 or 25 years, depending on the dominant lagged response mechanism (recharge‐ vs. lateral‐flow‐dominated). These estimates are far shorter than estimates that do not account for lagged responses. Results indicate that conservation‐based pumping reductions can extend aquifer lifetimes, but lagged responses can create a sizable difference between the initially perceived and actual long‐term effectiveness.

Modelling the antimicrobial pharmacodynamics for bacterial strains with versus without acquired resistance to fluoroquinolones or cephalosporins

Antimicrobial resistance threatens therapeutic options for human and animal bacterial diseases worldwide. Current antimicrobial treatment regimens were designed against bacterial strains that were fully susceptible to them. To expand the useable lifetime of existing antimicrobial drug classes by modifying treatment regimens, data are needed on the antimicrobial pharmacodynamics (PD) against strains with reduced susceptibility. In this study, we generated and mathematically modelled the PD of the fluoroquinolone ciprofloxacin and the cephalosporin ceftriaxone against non-typhoidal Salmonella enterica subsp. enterica strains with varying levels of acquired resistance. We included Salmonella strains across categories of reduced susceptibility to fluoroquinolones or cephalosporins reported to date, including isolates from human infections, food-animal products sold in retail, and food-animal production. We generated PD data for each drug and strain via time-kill assay. Mathematical models were compared in their fit to represent the PD. The best-fit model's parameter values across the strain susceptibility categories were compared. The inhibitory baseline sigmoid Imax (or Emax) model was best fit for the PD of each antimicrobial against a majority of the strains. There were statistically significant differences in the PD parameter values across the strain susceptibility categories for each antimicrobial. The results demonstrate predictable multiparameter changes in the PD of these first-line antimicrobials depending on the Salmonella strain's susceptibility phenotype and specific genes conferring reduced susceptibility. The generated PD parameter estimates could be used to optimise treatment regimens against infections by strains with reduced susceptibility.

Lifetime estimation of single crystal macro-fiber composite-based piezoelectric energy harvesters using accelerated life testing

Piezoelectric energy harvesters (PEHs) based on single crystal macro fiber composites (SFCs) have been widely utilized in vibration sensing, energy conversion, and power portable/wearable electronic devices. Despite growing attention to improve the output power of PEHs, few dedicated studies on reliability, especially on estimation of the usable lifetime of PEHs, have been reported. In this paper, an accelerated life test is applied to d32-type hard SFC-based PEHs to efficiently estimate usable lifetime in a short period of time. High temperature is used as environmental stress to accelerate the life of the PEHs, and time-to-failures are collected according to the criterion of a 10% drop in output power at 45, 55, and 70 °C under a mechanical vibration of 4.9 m/s2. The statistical failures distribution is analyzed using the Arrhenius-Weibull model with an activation energy (Ea) of 2.36 eV and a shape parameter (β) of 1.44. Accordingly, the average lifetime to failure of the PEHs in normal use (i.e., at room temperature) is determined as 4.3 × 109 vibration cycles. In addition, each failure mode is assessed to identify vulnerable points that reduce the lifespan of SFC-based PEHs. This study provides insight for evaluating and enhancing the reliability of PEHs as a basis for future practical application.

Nitric Oxide Release for Enhanced Biocompatibility and Analytical Performance of Implantable Electrochemical Sensors

AbstractThe real‐time, continuous monitoring of glucose/lactate, blood gases and electrolytes by implantable electrochemical sensors holds significant value for critically ill and diabetic patients. However, the wide‐spread use of such devices has been seriously hampered by implant‐initiated host responses (e. g., thrombus formation, inflammatory responses and bacterial infection) when sensors are implanted in blood or tissue. As a result, the accuracy and usable lifetime of in vivo sensors are often compromised. Nitric oxide (NO) is an endogenous gas molecule able to inhibit platelet adhesion/activation, inflammatory responses and bacterial growth. As such, the release of NO from the surfaces of in vivo sensors is a promising strategy for enhancement of their biocompatibility and analytical performance. In this review, the physiological functions of NO to improve the biocompatibility of implantable electrochemical sensors are introduced, followed by a brief analysis of chemical approaches to realize NO release from such devices. A detailed summary of the various types of NO releasing electrochemical sensors reported to date and their performance in benchtop and/or in vivo testing are also provided. Finally, the prospects of future developments to further advance NO releasing sensor technology for clinical use are discussed.

Performance Assessment of Polymeric Composite Wrap to Repair Damaged Pipelines Exposed under Accelerated Environment Conditions

Fiber-reinforced polymer composites are used as emerging materials to repair oil and gas transmission pipelines without stopping the flow of fluids inside. These pipelines are subjected to harsh environment conditions such as being buried under soil and being exposed to high humidity, high temperatures, and different chemicals. It is important to predict the useful life of composite repairs in these harsh conditions in order to design better and to have robust repair solutions. This study evaluates mechanical properties, namely tensile strength tensile modulus, flexural strength, flexural modulus, and lap shear strength, of composite laminates when exposed to harsh environmental conditions such as hot-wet [70°C/85% relative humidity (RH)] for 0, 2, 4, and 6 weeks, steam autoclave [121°C and 1,05,000 Pa (1.05 bar)] for 0, 6, and 12 h, and ultraviolet (UV) ray exposure of type UVA-340 at 50°C for 0 and 2 weeks. The glass fiber–reinforced polymer (GFRP) composite laminates are prepared by hand layup process and are cut using a water-jet cutting process to avoid machining defects and to keep a good surface finish. The specimens are exposed to these corresponding environmental conditions for different periods of time, and the changes in their mechanical properties are studied. The tensile strength, flexural modulus, and lap shear strength values are compared with unexposed specimens. Decreases in strength and modulus values are observed for exposed specimens. A simple empirical expression is developed to predict the usable lifetime of a composite repair system exposed to such different harsh environmental conditions.

In-situ 4D visualization and analysis of temperature-driven creep in an oil shale propped fracture

The proppant embedment due to creep in shales is a known issue affecting the useable lifetime of wells in unconventional oil and gas recovery. One of the factors influencing creep is the presence of organics, whose properties can be very sensitive to temperature. In this work we investigated for the first time the role of temperature-induced creep increase in proppant embedment in an organics-rich Green River oil shale sample via in-situ synchrotron X-ray micro-computed tomography. We observed that temperatures as low as 75 °C already induce fast creep, with a fracture aperture closing rate of 13 μm/h and a loss of fracture conductivity rate of 8.7%/h, due only to proppant embedment, in the measured interval at the first heating stage. Local displacement data analysis provided evidence for markedly plastic deformation around the proppant-shale contacts, in contrast with the brittle proppant embedment observed on more cemented and less organics-rich shales at room temperature. The results highlight how the problem of temperature-dependent mechanical behavior might be more important than previously thought, in shales with a high content in organics, and that in-situ micro-imaging techniques can play a key role in understanding the underlying mechanisms, contributing to solve creep-related problems associated with hydraulic fracturing in complex scenarios.

Self-referencing optical fiber pH sensor for marine microenvironments

This study presents the development of an optical fiber pH sensor based on evanescent wave absorbance for continuous pH measurements in marine microenvironments. The sensing layer consists of an optimized sol-gel matrix of tetraethoxysilane and dimethyldiethoxysilane, which substantially improves the entrapment efficiency of the pH indicator meta-cresol purple, leading to a long useable lifetime. The optical fiber pH sensor conforms to the Global Ocean Acidification Observing Network “weather” measurement quality guideline with precision of approximately 0.02 pH units, has a dynamic pHT range of 7.4–9.7 in seawater, a response time of 2.5–6.5 min and a useable lifetime of 7 days. The optical fiber pH sensor has additional advantages of being self-referencing, without the need of an external sensor reference, having a simple fabrication method and basic spectrometer instrumentation. The suitability of the optical fiber pH sensor was demonstrated in real-time measurements of the ecologically significant green seaweed Ulva sp. The optical fiber pH sensor monitored pH variations due to metabolic activity over 7 days within the seaweed canopy and 4 days within the diffusion boundary layer interface, demonstrating the suitability for measurements in marine microenvironments.

Designing a bidirectional, adaptive neural interface incorporating machine learning capabilities and memristor-enhanced hardware

Abstract Building bidirectional biointerfaces is one of the key challenges of modern engineering and medicine, with dramatic potential impact on bioprosthetics. Two of the major challenges of biointerface design concern signal stability and power efficiency. The former entails: a) ensuring that biosignal inputs corresponding to the same ground truth (e.g. patient “intentions”) are recorded and interpreted consistently and b) maintaining the mapping from biointerface stimulation outputs to behavioral outputs (e.g. muscle movements). In this work we demonstrate how machine learning techniques, state-of-art nanoelectronics and microfluidics can combine forces to build and test low-power, adaptable biointerfaces that address both key challenges. Specifically, we demonstrate that: 1) we can emulate the input/output transfer characteristics of a structure biological neural network (BNN) with an artificial one (ANN), 2) it is possible to translate the resulting, “ideally trained” ANN into a hardware network using RRAM devices as synapses without significant loss of accuracy, despite concerns in the community about RRAM device reliability and 3) using a very simple mechanism of shifting the active stimulation electrode can fully restore functionality after the initial stimulation site degrades, prolonging the usable lifetime of the biointerface significantly. In this manner we place a key stepping stone towards building self-adjusting, low-power biointerfaces, themselves a foundational stepping stone towards adaptable, low-power bioprostheses.

Light propagation within N95 filtered face respirators: A simulation study for UVC decontamination.

This study presents numerical simulations of UVC light propagation through seven different filtered face respirators (FFR) to determine their suitability for Ultraviolet germicidal inactivation (UVGI). UV propagation was modeled using the FullMonte program for two external light illuminations. The optical properties of the dominant three layers were determined using the inverse adding doubling method. The resulting fluence rate volume histograms and the lowest fluence rate recorded in the modeled volume, sometimes in the nW cm-2 , provide feedback on a respirator's suitability for UVGI and the required exposure time for a given light source. While UVGI can present an economical approach to extend an FFR's useable lifetime, it requires careful optimization of the illumination setup and selection of appropriate respirators.

Rotation Optimized Filter for Longevity (ROFL): Increasing the Lifetime of Swift/UVOT Simply

Abstract I demonstrate that a very simple and safe change to the planning software filter assignment algorithm for the Ultraviolet/Optical Telescope (UVOT) onboard the Neil Gehrels Swift Observatory can reduce the number of filter wheel rotations by >10%, and its adoption is thus likely to significantly extend the usable lifetime of the UVOT instrument.