Publications by authors named "James S Bennett"

10 Publications

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Precision Magnetometers for Aerospace Applications: A Review.

Sensors (Basel) 2021 Aug 18;21(16). Epub 2021 Aug 18.

School of Mathematics and Physics, The University of Queensland, St. Lucia, QLD 4072, Australia.

Aerospace technologies are crucial for modern civilization; space-based infrastructure underpins weather forecasting, communications, terrestrial navigation and logistics, planetary observations, solar monitoring, and other indispensable capabilities. Extraplanetary exploration-including orbital surveys and (more recently) roving, flying, or submersible unmanned vehicles-is also a key scientific and technological frontier, believed by many to be paramount to the long-term survival and prosperity of humanity. All of these aerospace applications require reliable control of the craft and the ability to record high-precision measurements of physical quantities. Magnetometers deliver on both of these aspects and have been vital to the success of numerous missions. In this review paper, we provide an introduction to the relevant instruments and their applications. We consider past and present magnetometers, their proven aerospace applications, and emerging uses. We then look to the future, reviewing recent progress in magnetometer technology. We particularly focus on magnetometers that use optical readout, including atomic magnetometers, magnetometers based on quantum defects in diamond, and optomechanical magnetometers. These optical magnetometers offer a combination of field sensitivity, size, weight, and power consumption that allows them to reach performance regimes that are inaccessible with existing techniques. This promises to enable new applications in areas ranging from unmanned vehicles to navigation and exploration.
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http://dx.doi.org/10.3390/s21165568DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8402258PMC
August 2021

Laboratory Modeling of SARS-CoV-2 Exposure Reduction Through Physically Distanced Seating in Aircraft Cabins Using Bacteriophage Aerosol - November 2020.

MMWR Morb Mortal Wkly Rep 2021 Apr 23;70(16):595-599. Epub 2021 Apr 23.

Aircraft can hold large numbers of persons in close proximity for long periods, which can increase the risk for transmission of infectious disease.* Current CDC guidelines recommend against travel for persons who have not been vaccinated against COVID-19, and a January 2021 CDC order requires masking for all persons while on airplanes. Research suggests that seating proximity on aircraft is associated with increased risk for infection with SARS-CoV-2, the virus that causes COVID-19 (1,2). However, studies quantifying the benefit of specific distancing strategies to prevent transmission, such as keeping aircraft cabin middle seats vacant, are limited. Using bacteriophage MS2 virus as a surrogate for airborne SARS-CoV-2, CDC and Kansas State University (KSU) modeled the relationship between SARS-CoV-2 exposure and aircraft seating proximity, including full occupancy and vacant middle seat occupancy scenarios. Compared with exposures in full occupancy scenarios, relative exposure in vacant middle seat scenarios was reduced by 23% to 57% depending upon the modeling approach. A 23% exposure reduction was observed for a single passenger who was in the same row and two seats away from the SARS-COV-2 source, rather than in an adjacent middle seat. When quantifying exposure reduction to a full 120-passenger cabin rather than to a single person, exposure reductions ranging from 35.0% to 39.4% were predicted. A 57% exposure reduction was observed under the vacant middle seat condition in a scenario involving a three-row section that contained a mix of SARS-CoV-2 sources and other passengers. Based on this laboratory model, a vacant middle seat reduces risk for exposure to SARS-CoV-2 from nearby passengers. These data suggest that increasing physical distance between passengers and lowering passenger density could help reduce potential COVID-19 exposures during air travel. Physical distancing of airplane passengers, including through policies such as middle seat vacancy, could provide additional reductions in SARS-CoV-2 exposure risk.
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http://dx.doi.org/10.15585/mmwr.mm7016e1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8061797PMC
April 2021

Mechanical Squeezing via Fast Continuous Measurement.

Phys Rev Lett 2020 Jul;125(4):043604

Australian Research Council Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, University of Queensland, St Lucia, Queensland 4072, Australia.

We revisit quantum state preparation of an oscillator by continuous linear position measurement. Quite general analytical expressions are derived for the conditioned state of the oscillator. Remarkably, we predict that quantum squeezing is possible outside of both the backaction dominated and quantum coherent oscillation regimes, relaxing experimental requirements even compared to ground-state cooling. This provides a new way to generate nonclassical states of macroscopic mechanical oscillators, and opens the door to quantum sensing and tests of quantum macroscopicity at room temperature.
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http://dx.doi.org/10.1103/PhysRevLett.125.043604DOI Listing
July 2020

Hexavalent chromium and isocyanate exposures during military aircraft painting under crossflow ventilation.

J Occup Environ Hyg 2016 ;13(5):356-71

a National Institute for Occupational Health, Division of Applied Research Technology , Cincinnati Ohio.

Exposure control systems performance was investigated in an aircraft painting hangar. The ability of the ventilation system and respiratory protection program to limit worker exposures was examined through air sampling during painting of F/A-18C/D strike fighter aircraft, in four field surveys. Air velocities were measured across the supply filter, exhaust filter, and hangar midplane under crossflow ventilation. Air sampling conducted during painting process phases (wipe-down, primer spraying, and topcoat spraying) encompassed volatile organic compounds, total particulate matter, Cr[VI], metals, nitroethane, and hexamethylene diisocyanate, for two worker groups: sprayers and sprayer helpers ("hosemen"). One of six methyl ethyl ketone and two of six methyl isobutyl ketone samples exceeded the short term exposure limits of 300 and 75 ppm, with means 57 ppm and 63 ppm, respectively. All 12 Cr[VI] 8-hr time-weighted averages exceeded the recommended exposure limit of 1 µg/m3, 11 out of 12 exceeded the permissible exposure limit of 5 µg/m3, and 7 out of 12 exceeded the threshold limit value of 10 µg/m3, with means 38 µg/m3 for sprayers and 8.3 µg/m3 for hosemen. Hexamethylene diisocyanate means were 5.95 µg/m3 for sprayers and 0.645 µg/m3 for hosemen. Total reactive isocyanate group--the total of monomer and oligomer as NCO group mass--showed 6 of 15 personal samples exceeded the United Kingdom Health and Safety Executive workplace exposure limit of 20 µg/m3, with means 50.9 µg/m3 for sprayers and 7.29 µg/m3 for hosemen. Several exposure limits were exceeded, reinforcing continued use of personal protective equipment. The supply rate, 94.4 m3/s (200,000 cfm), produced a velocity of 8.58 m/s (157 fpm) at the supply filter, while the exhaust rate, 68.7 m3/s (146,000 cfm), drew 1.34 m/s (264 fpm) at the exhaust filter. Midway between supply and exhaust locations, the velocity was 0.528 m/s (104 fpm). Supply rate exceeding exhaust rate created re-circulations, turbulence, and fugitive emissions, while wasting energy. Smoke releases showing more effective ventilation here than in other aircraft painting facilities carries technical feasibility relevance.
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http://dx.doi.org/10.1080/15459624.2015.1117617DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4916860PMC
December 2016

Evaluation of leakage from fume hoods using tracer gas, tracer nanoparticles and nanopowder handling test methodologies.

J Occup Environ Hyg 2014 ;11(10):D164-73

a Division of Applied Research and Technology, Engineering and Physical Hazards Branch , National Institute for Occupational Safety and Health , Cincinnati , Ohio.

The most commonly reported control used to minimize workplace exposures to nanomaterials is the chemical fume hood. Studies have shown, however, that significant releases of nanoparticles can occur when materials are handled inside fume hoods. This study evaluated the performance of a new commercially available nano fume hood using three different test protocols. Tracer gas, tracer nanoparticle, and nanopowder handling protocols were used to evaluate the hood. A static test procedure using tracer gas (sulfur hexafluoride) and nanoparticles as well as an active test using an operator handling nanoalumina were conducted. A commercially available particle generator was used to produce sodium chloride tracer nanoparticles. Containment effectiveness was evaluated by sampling both in the breathing zone (BZ) of a mannequin and operator as well as across the hood opening. These containment tests were conducted across a range of hood face velocities (60, 80, and 100 ft/min) and with the room ventilation system turned off and on. For the tracer gas and tracer nanoparticle tests, leakage was much more prominent on the left side of the hood (closest to the room supply air diffuser) although some leakage was noted on the right side and in the BZ sample locations. During the tracer gas and tracer nanoparticle tests, leakage was primarily noted when the room air conditioner was on for both the low and medium hood exhaust airflows. When the room air conditioner was turned off, the static tracer gas tests showed good containment across most test conditions. The tracer gas and nanoparticle test results were well correlated showing hood leakage under the same conditions and at the same sample locations. The impact of a room air conditioner was demonstrated with containment being adversely impacted during the use of room air ventilation. The tracer nanoparticle approach is a simple method requiring minimal setup and instrumentation. However, the method requires the reduction in background concentrations to allow for increased sensitivity.
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http://dx.doi.org/10.1080/15459624.2014.933959DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4539248PMC
June 2015

Airborne exposure patterns from a passenger source in aircraft cabins.

HVAC&R Res 2013 22;19(8):962-73. Epub 2013 Nov 22.

National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, U.S. Department of Health and Human Services, 4676 Columbia Parkway, MS R5, Cincinnati, OH 45226-1998, USA.

Airflow is a critical factor that influences air quality, airborne contaminant distribution, and disease transmission in commercial airliner cabins. The general aircraft-cabin air-contaminant transport effect model seeks to build exposure-spatial relationships between contaminant sources and receptors, quantify the uncertainty, and provide a platform for incorporation of data from a variety of studies. Knowledge of infection risk to flight crews and passengers is needed to form a coherent response to an unfolding epidemic, and infection risk may have an airborne pathogen exposure component. The general aircraf-tcabin air-contaminant transport effect model was applied to datasets from the University of Illinois and Kansas State University and also to case study information from a flight with probable severe acute respiratory syndrome transmission. Data were fit to regression curves, where the dependent variable was contaminant concentration (normalized for source strength and ventilation rate), and the independent variable was distance between source and measurement locations. The data-driven model showed exposure to viable small droplets and post-evaporation nuclei at a source distance of several rows in a mock-up of a twin-aisle airliner with seven seats per row. Similar behavior was observed in tracer gas, particle experiments, and flight infection data for severe acute respiratory syndrome. The study supports the airborne pathway as part of the matrix of possible disease transmission modes in aircraft cabins.
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http://dx.doi.org/10.1080/10789669.2013.838990DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4626449PMC
November 2015

Comparison of emission models with computational fluid dynamic simulation and a proposed improved model.

AIHA J (Fairfax, Va) 2003 Nov-Dec;64(6):739-54

Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Division of Applied Research and Technology, Engineering and Physical Hazards Branch, 4676 Columbia Parkway MS-R5, Cincinnati, OH 45226, USA.

Understanding source behavior is important in controlling exposure to airborne contaminants. Industrial hygienists are often asked to infer emission information from room concentration data. This is not easily done, but models that make simplifying assumptions regarding contaminant transport are frequently used. The errors resulting from these assumptions are not yet well understood. This study compares emission estimates from the single-zone completely mixed (CM-1), two-zone completely mixed (CM-2), and uniform diffusivity (UD) models with the emissions set as boundary conditions in computational fluid dynamic (CFD) simulations of a workplace. The room airflow and concentration fields were computed using Fluent 4. These numerical experiments were factorial combinations of three source locations, five receptor locations, three dilution airflow rates, and two generation rate profiles, constant and time-varying. The aim was to compute plausible concentration fields, not to simulate exactly the processes in a real workroom. Thus, error is defined here as the difference between model and CFD predictions. For the steady-state case the UD model had the lowest error. When the source near-field contained the breathing zone receptor, the CM-2 model was applied. Then, in decreasing agreement with CFD were UD, CM-2, and CM-1. Averaging over all source and receptor locations (CM-2 applied for only one), in decreasing order of agreement with CFD were UD, CM-1, and CM-2. Source and receptor location had large effects on emission estimates using the CM-1 model and some effect using the UD model. A location-specific mixing factor (location factor) derived from steady-state concentration gradients was used to build a more accurate time-dependent emission model, CM-L. Total mass emitted from a time-varying source was modeled most accurately by CM-L, followed by CM-1 and CM-2.
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http://dx.doi.org/10.1202/457.1DOI Listing
March 2004

Control of wake-induced exposure using an interrupted oscillating jet.

AIHA J (Fairfax, Va) 2003 Jan-Feb;64(1):24-9

Engineering and Physical Hazards Branch, MS R5, Division of Applied Research and Technology, National Institute for Occupational Safety and Health, 4676 Columbia Parkway, Cincinnati, OH 45226, USA.

A problem may arise in ventilation design when the contaminant source is located in the worker's wake, where turbulence and vortex formation can carry the contaminant into the breathing zone even though the source is downwind. It was found previously that forced directional variations in the flow can reduce or eliminate the vortex formation that causes these local reversals. Reported here is a simple realization of this concept, in which an oscillating jet of air was directed at a mannequin in an otherwise steady flow of air. A 50th percentile male mannequin was placed in a nearly uniform flow of approximately 0.18 m/sec (36 ft/min). A low-velocity tracer gas source (isobutylene) was held in the standing mannequin's hands with the upper arms vertical and the elbows at 90 degrees. Four ventilation scenarios were compared by concentration measurements in the breathing zone, using photoionization detectors: (A) uniform flow; (B) addition of a steady jet with initial velocity 5.1 m/sec (1.0 x 10(3) ft/min) directed at the mannequin's back, parallel to the main flow; (C) making the jet oscillate to 45 degrees on either side of the centerline with a period of 13 sec; and (D) introducing a blockage at the centerline so the oscillating jet never blew directly at the worker. At the 97.5% confidence level the interrupted oscillating jet (case D) achieved at least 99% exposure reduction compared with the uniform flow by itself (case A), at least 93% compared with the steady jet (case B), and at least 45% exposure reduction compared with the unblocked oscillating jet (case C).
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http://dx.doi.org/10.1080/15428110308984779DOI Listing
May 2003

Performance of deterministic workplace exposure assessment models for various contaminant source, air inlet, and exhaust locations.

AIHA J (Fairfax, Va) 2002 Jul-Aug;63(4):402-12

Department of Environmental Health Sciences, HESC, Room 311, School of Public Health, University of South Carolina, Columbia, SC 29208, USA.

Contaminant concentration estimates from simple models were compared with concentration fields obtained by computational fluid dynamic (CFD) simulations for various room and source configurations under steady-state conditions. Airflow and contaminant distributions in a 10 x 3 x 7-m room with a single contaminant source on a 1-m high table were simulated using CFD for steady, isothermal conditions. For a high wall jet inlet, simulations were performed for nine room air exhaust locations and eight source locations. For a ceiling diffuser inlet the impact of two exhaust locations and eight source locations were investigated. Because CFD treats determinants of contaminant transport explicitly and agreed well with experimental results, it was used as the standard for comparison. Parameters of the one- and two-zone completely mixed models (CM-1 and CM-2) and the uniform turbulent diffusivity model (UD) were determined from CFD simulation results. Concentration estimates from these were compared with CFD results in the breathing zone (BZ) plane (1.5 m above the floor) for the entire BZ, the source "near field," and the source "far field." In the near field the mean percentage difference between the model concentration estimates and the CFD results for all room configurations were -21.9, 32.3, and 126% for the CM-1, CM-2, and UD models, respectively, with standard deviations of 26.8, 111, and 103%. In the far field the mean percentage difference between the model estimates and CFD results were -4.8, -2.3, and -36.3%. The CM-1 model had generally the best performance for applications such as occupational epidemiology for the conditions and configurations studied. However, CM-1 tended to underestimate the near field concentration; thus, CM-2 was judged to be better in the near field when underestimation is undesirable, such as when determining compliance with occupational exposure limits. The agreement of CM-2 estimates with CFD results in the near field was more variable than that of the CM-1. The UD model performed poorly on average in both near and far fields, and the difficulty in accurately estimating the turbulent diffusivity presents a significant impediment to UD model use for exposure estimation.
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http://dx.doi.org/10.1080/15428110208984728DOI Listing
March 2003

Improving the use of mixing factors for dilution ventilation design.

Appl Occup Environ Hyg 2002 May;17(5):333-43

Department of Environmental Health Sciences, School of Public Health, University of South Carolina, Columbia, USA.

In specifying dilution ventilation flow rate, a safety factor, K, is often used to provide a margin of safety and to compensate for uncertainties and health impact severity. In current practice, the selection of K is very subjective. Here the component of K accounting for imperfect mixing, Km, was studied to develop more effective and efficient design procedures. Air flow and contaminant distribution in a 10 m x 3 m x 7 m room with a single contaminant source on a 1-m high table were simulated for steady, isothermal conditions using computational fluid dynamics. A series of 10 simulations explored factorial combinations of air exchange rates (1, 2,4, 8, 16 ACH) and inlet types (a high wall jet and a ceiling diffuser). Nine additional simulations explored exhaust opening location effects and 13 other simulations investigated source location effects. Km was calculated at each of 25,600 grid locations within the room by linear regression of emission rate/flow rate (G/Q) on concentration (C). The linear relationship between C and G/Q at each of the points was nearly perfect (R2 > 0.97). For the simulations with varying dilution flow rate, Km ranged from 0.19 to 2.86 for the wall jet and from 0.94 to 4.34 for the ceiling diffuser. Holding G/Q at 100 ppm and varying source and exhaust location produced room average concentrations from 55.7 to 173 ppm. Unlike orthodox design approaches, this work suggests that air monitoring data often can be used to calculate dilution flow rate requirements. Also, dilution flow rate requirements may be reduced by enhancing room mixing with fans or altering air inlet configuration. However, mixing should not be increased if the altered room air currents could transport contaminant to an occupant's breathing zone or interfere with other control methods that depend on segregation of incoming air and contaminant.
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http://dx.doi.org/10.1080/10473220252864932DOI Listing
May 2002
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