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Sample records for efficiency aerosol filters

  1. Leaks in nuclear grade high efficiency aerosol filters

    SciTech Connect

    Scripsick, R.C.

    1994-07-01

    Nuclear grade high efficiency aerosol filters, also known as high efficiency particulate air (HEPA) filters, are commonly used in air cleaning systems for removal of hazardous aerosols. Performance of the filter units is important in assuring health and environmental protection. The filter units are constructed from pleated packs of fiberglass filter media sealed into rigid frames. Results of previous studies on such filter units indicate that their performance may not be completely predicted by ideal performance of the fibrous filter media. In this study, departure from ideal performance is linked to leaks existing in filter units and overall filter unit performance is derived from independent performance of the individual filter unit components. The performance of 14 nuclear grade HEPA filter units (size 1, 25 cfm) with plywood frames was evaluated with a test system that permitted independent determination of penetration as a function of particle size for the whole filter unit, the filter unit frame, and the filter media pack. Tests were performed using a polydisperse aerosol of di-2-ethylhexyl phthalate with a count median diameter of 0.2 {mu}m and geometric standard deviation of 1.6. Flow rate and differential pressure were controlled from 1% to 100% of design values. Particle counts were made upstream and downstream of the filter unit with an optical particle counter (OPC). The OPC provided count information in 28 size channels over the particle diameter range from 0.1 to 0.7 {mu}m. Results provide evidence for a two component leak model of filler unit performance with: (1) external leaks through filter unit frames, and (2) internal leaks through defects in the media and through the seal between the media pack and frame. For the filter units evaluated, these leaks dominate overall filter unit performance over much of the flow rate and particle size ranges tested.

  2. High-efficiency particulate air filter test stand and aerosol generator for particle loading studies.

    PubMed

    Arunkumar, R; Hogancamp, Kristina U; Parsons, Michael S; Rogers, Donna M; Norton, Olin P; Nagel, Brian A; Alderman, Steven L; Waggoner, Charles A

    2007-08-01

    This manuscript describes the design, characterization, and operational range of a test stand and high-output aerosol generator developed to evaluate the performance of 30 x 30 x 29 cm(3) nuclear grade high-efficiency particulate air (HEPA) filters under variable, highly controlled conditions. The test stand system is operable at volumetric flow rates ranging from 1.5 to 12 standard m(3)/min. Relative humidity levels are controllable from 5%-90% and the temperature of the aerosol stream is variable from ambient to 150 degrees C. Test aerosols are produced through spray drying source material solutions that are introduced into a heated stainless steel evaporation chamber through an air-atomizing nozzle. Regulation of the particle size distribution of the aerosol challenge is achieved by varying source solution concentrations and through the use of a postgeneration cyclone. The aerosol generation system is unique in that it facilitates the testing of standard HEPA filters at and beyond rated media velocities by consistently providing, into a nominal flow of 7 standard m(3)/min, high mass concentrations (approximately 25 mg/m(3)) of dry aerosol streams having count mean diameters centered near the most penetrating particle size for HEPA filters (120-160 nm). Aerosol streams that have been generated and characterized include those derived from various concentrations of KCl, NaCl, and sucrose solutions. Additionally, a water insoluble aerosol stream in which the solid component is predominantly iron (III) has been produced. Multiple ports are available on the test stand for making simultaneous aerosol measurements upstream and downstream of the test filter. Types of filter performance related studies that can be performed using this test stand system include filter lifetime studies, filtering efficiency testing, media velocity testing, evaluations under high mass loading and high humidity conditions, and determination of the downstream particle size distributions. PMID

  3. High-efficiency particulate air filter test stand and aerosol generator for particle loading studies

    NASA Astrophysics Data System (ADS)

    Arunkumar, R.; Hogancamp, Kristina U.; Parsons, Michael S.; Rogers, Donna M.; Norton, Olin P.; Nagel, Brian A.; Alderman, Steven L.; Waggoner, Charles A.

    2007-08-01

    This manuscript describes the design, characterization, and operational range of a test stand and high-output aerosol generator developed to evaluate the performance of 30×30×29cm3 nuclear grade high-efficiency particulate air (HEPA) filters under variable, highly controlled conditions. The test stand system is operable at volumetric flow rates ranging from 1.5to12standardm3/min. Relative humidity levels are controllable from 5%-90% and the temperature of the aerosol stream is variable from ambient to 150°C. Test aerosols are produced through spray drying source material solutions that are introduced into a heated stainless steel evaporation chamber through an air-atomizing nozzle. Regulation of the particle size distribution of the aerosol challenge is achieved by varying source solution concentrations and through the use of a postgeneration cyclone. The aerosol generation system is unique in that it facilitates the testing of standard HEPA filters at and beyond rated media velocities by consistently providing, into a nominal flow of 7standardm3/min, high mass concentrations (˜25mg/m3) of dry aerosol streams having count mean diameters centered near the most penetrating particle size for HEPA filters (120-160nm). Aerosol streams that have been generated and characterized include those derived from various concentrations of KCl, NaCl, and sucrose solutions. Additionally, a water insoluble aerosol stream in which the solid component is predominantly iron (III) has been produced. Multiple ports are available on the test stand for making simultaneous aerosol measurements upstream and downstream of the test filter. Types of filter performance related studies that can be performed using this test stand system include filter lifetime studies, filtering efficiency testing, media velocity testing, evaluations under high mass loading and high humidity conditions, and determination of the downstream particle size distributions.

  4. Evaluation of Ag nanoparticle coated air filter against aerosolized virus: Anti-viral efficiency with dust loading.

    PubMed

    Joe, Yun Haeng; Park, Dae Hoon; Hwang, Jungho

    2016-01-15

    In this study, the effect of dust loading on the anti-viral ability of an anti-viral air filter was investigated. Silver nanoparticles approximately 11 nm in diameter were synthesized via a spark discharge generation system and were used as anti-viral agents coated onto a medium air filter. The pressure drop, filtration efficiency, and anti-viral ability of the filter against aerosolized bacteriophage MS2 virus particles were tested with dust loading. The filtration efficiency and pressure drop increased with dust loading, while the anti-viral ability decreased. Theoretical analysis of anti-viral ability with dust loading was carried out using a mathematical model based on that presented by Joe et al. (J. Hazard. Mater.; 280: 356-363, 2014). Our model can be used to compare anti-viral abilities of various anti-viral agents, determine appropriate coating areal density of anti-viral agent on a filter, and predict the life cycle of an anti-viral filter. PMID:26434534

  5. Aerosol filtration with steel fiber filters

    SciTech Connect

    Bergman, W.; Wilson, K.; Larsen, G.; Lopez, R.

    1993-04-01

    We have conducted an experimental study of aerosol penetration through a new high efficiency steel fiber filter and filter media that we developed in cooperation with Pall Corporation. Our previous studies have shown that sintered steel fiber media have significant improvements in higher filter efficiency and lower pressure drop than the previous steel filter technology based on sintered powder metal media. In the present study, we have measured the penetration of dioctyl sebacate (DOS) aerosols through flat sheet samples, pleated cartridge filters and a 1000 cfm filter having 64 cartridges housed in a 2 {times} 2 {times} 1 ft. frame. The steel fiber media used in our study consists of 2 {mu}m diameter stainless steel (316L) fibers sintered together into sheets.

  6. Aerosol filtration with steel fiber filters

    NASA Astrophysics Data System (ADS)

    Bergman, W.; Wilson, K.; Larsen, G.; Lopez, R.

    1993-04-01

    An experimental study has been conducted of aerosol penetration through a new high efficiency steel fiber filter and filter media that was developed in cooperation with Pall Corporation. Previous studies have shown that sintered steel fiber media have significant improvements in higher filter efficiency and lower pressure drop than the previous steel filter technology based on sintered powder metal media. In the present study, measurements were made of the penetration of dioctyl sebacate (DOS) aerosols through flat sheet samples, pleated cartridge filters, and a 1000 cfm filter having 64 cartridges housed in a 2 x 2 x 1 ft. frame. The steel fiber media used in our study consists of 2 micron diameter stainless steel (316 L) fibers sintered together into sheets.

  7. Penetration of Combustion Aerosol Particles Through Filters of NIOSH-Certified Filtering Facepiece Respirators (FFRs).

    PubMed

    Gao, Shuang; Kim, Jinyong; Yermakov, Michael; Elmashae, Yousef; He, Xinjian; Reponen, Tiina; Grinshpun, Sergey A

    2015-01-01

    . The findings of this study suggest that the efficiency of N95 respirator filters obtained with the NaCl aerosol challenge may not accurately predict (and rather overestimate) the filter efficiency against combustion particles. PMID:26010982

  8. Chemical characterization of challenge aerosols for HEPA filter penetration testing

    SciTech Connect

    Strandberg, S.W.

    1985-04-01

    Quality assurance penetration testing of high efficiency particulate air (HEPA) filters use oil mists as challenge aerosols. Concern over the carcinogenic risk associated with the use of di-(2-ethylhexyl)phthalate (DEHP) has led to the investigation of alternative materials and generation methods for these aerosols. Since several commonly used generation methods for quality assurance testing of HEPA filters utilize heating of the starting material, it was determined essential to evaluate the starting material and the resultant aerosol which might contain thermal degradation by-products. A penetrometer utilizing flash vaporization has been developed by A.D. Little, Inc., for the US Government as a possible alternative generation method to the Q-127 thermally generated DEHP penetrometer. Tetraethylene glycol, oleic acid, and DEHP aerosols were generated in this unit, and particulate and vapor samples were collected and identified using gas chromatography/mass spectrometry techniques. Thermally generated DEHP by-products were also sampled and identified using a Q-107 penetrometer used in the testing of large HEPA filters. Determination of the toxicological hazards of starting materials and all of the identified compounds was made by reviewing available literature obtained on the Toxline system of the National Library of Medicine. No major degradation products were found in the flash vaporization penetrometer although a number of thermally generated by-products were found in the Q-107 penetrometer. Toxicologically, no hazards were found to preclude the use of either tetraethylene glycol or oleic acid as tested in the A.D. Little penetrometer. 133 refs., 5 figs., 9 tabs.

  9. Development and evaluation of a cleanable high efficiency steel filter

    SciTech Connect

    Bergman, W.; Larsen, G.; Weber, F.; Wilson, P.; Lopez, R.; Valha, G.; Conner, J.; Garr, J.; Williams, K.; Biermann, A.; Wilson, K.; Moore, P.; Gellner, C.; Rapchun, D. ); Simon, K.; Turley, J.; Frye, L.; Monroe, D. )

    1993-01-01

    We have developed a high efficiency steel filter that can be cleaned in-situ by reverse air pulses. The filter consists of 64 pleated cylindrical filter elements packaged into a 6l0 [times] 6l0 [times] 292 mm aluminum frame and has 13.5 m[sup 2] of filter area. The filter media consists of a sintered steel fiber mat using 2 [mu]m diameter fibers. We conducted an optimization study for filter efficiency and pressure drop to determine the filter design parameters of pleat width, pleat depth, outside diameter of the cylinder, and the total number of cylinders. Several prototype cylinders were then built and evaluated in terms of filter cleaning by reverse air pulses. The results of these studies were used to build the high efficiency steel filter. We evaluated the prototype filter for efficiency and cleanability. The DOP filter certification test showed the filter has a passing efficiency of 99.99% but a failing pressure drop of 0.80 kPa at 1,700 m[sup 3]/hr. Since we were not able to achieve a pressure drop less than 0.25 kPa, the steel filter does not meet all the criteria for a HEPA filter. Filter loading and cleaning tests using AC Fine dust showed the filter could be repeatedly cleaned by reverse air pulses. The next phase of the prototype evaluation consisted of installing the unit and support housing in the exhaust duct work of a uranium grit blaster for a field evaluation at the Y-12 Plant in Oak Ridge, TN. The grit blaster is used to clean the surface of uranium parts and generates a cloud of UO[sub 2] aerosols. We used a 1,700 m[sup 3]/hr slip stream from the 10,200 m[sup 3]/hr exhaust system.

  10. Development and evaluation of a cleanable high efficiency steel filter

    SciTech Connect

    Bergman, W.; Larsen, G.; Weber, F.; Wilson, P.; Lopez, R.; Valha, G.; Conner, J.; Garr, J.; Williams, K.; Biermann, A.; Wilson, K.; Moore, P.; Gellner, C.; Rapchun, D.; Simon, K.; Turley, J.; Frye, L.; Monroe, D.

    1993-01-01

    We have developed a high efficiency steel filter that can be cleaned in-situ by reverse air pulses. The filter consists of 64 pleated cylindrical filter elements packaged into a 6l0 {times} 6l0 {times} 292 mm aluminum frame and has 13.5 m{sup 2} of filter area. The filter media consists of a sintered steel fiber mat using 2 {mu}m diameter fibers. We conducted an optimization study for filter efficiency and pressure drop to determine the filter design parameters of pleat width, pleat depth, outside diameter of the cylinder, and the total number of cylinders. Several prototype cylinders were then built and evaluated in terms of filter cleaning by reverse air pulses. The results of these studies were used to build the high efficiency steel filter. We evaluated the prototype filter for efficiency and cleanability. The DOP filter certification test showed the filter has a passing efficiency of 99.99% but a failing pressure drop of 0.80 kPa at 1,700 m{sup 3}/hr. Since we were not able to achieve a pressure drop less than 0.25 kPa, the steel filter does not meet all the criteria for a HEPA filter. Filter loading and cleaning tests using AC Fine dust showed the filter could be repeatedly cleaned by reverse air pulses. The next phase of the prototype evaluation consisted of installing the unit and support housing in the exhaust duct work of a uranium grit blaster for a field evaluation at the Y-12 Plant in Oak Ridge, TN. The grit blaster is used to clean the surface of uranium parts and generates a cloud of UO{sub 2} aerosols. We used a 1,700 m{sup 3}/hr slip stream from the 10,200 m{sup 3}/hr exhaust system.

  11. 42 CFR 84.181 - Non-powered air-purifying particulate filter efficiency level determination.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... sodium chloride or equivalent solid aerosol at 25 ±5 °C and relative humidity of 30 ±10 percent that has... further decrease in efficiency. (g) The sodium chloride test aerosol shall have a particle size...-purifying particulate respirator model shall be tested for filter efficiency against: (1) A solid...

  12. 42 CFR 84.181 - Non-powered air-purifying particulate filter efficiency level determination.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... sodium chloride or equivalent solid aerosol at 25 ±5 °C and relative humidity of 30 ±10 percent that has... further decrease in efficiency. (g) The sodium chloride test aerosol shall have a particle size...-purifying particulate respirator model shall be tested for filter efficiency against: (1) A solid...

  13. 42 CFR 84.181 - Non-powered air-purifying particulate filter efficiency level determination.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... sodium chloride or equivalent solid aerosol at 25 ±5 °C and relative humidity of 30 ±10 percent that has... further decrease in efficiency. (g) The sodium chloride test aerosol shall have a particle size...-purifying particulate respirator model shall be tested for filter efficiency against: (1) A solid...

  14. Antimicrobial nanoparticle-coated electrostatic air filter with high filtration efficiency and low pressure drop.

    PubMed

    Sim, Kyoung Mi; Park, Hyun-Seol; Bae, Gwi-Nam; Jung, Jae Hee

    2015-11-15

    In this study, we demonstrated an antimicrobial nanoparticle-coated electrostatic (ES) air filter. Antimicrobial natural-product Sophora flavescens nanoparticles were produced using an aerosol process, and were continuously deposited onto the surface of air filter media. For the electrostatic activation of the filter medium, a corona discharge electrification system was used before and after antimicrobial treatment of the filter. In the antimicrobial treatment process, the deposition efficiency of S. flavescens nanoparticles on the ES filter was ~12% higher than that on the pristine (Non-ES) filter. In the evaluation of filtration performance using test particles (a nanosized KCl aerosol and submicron-sized Staphylococcus epidermidis bioaerosol), the ES filter showed better filtration efficiency than the Non-ES filter. However, antimicrobial treatment with S. flavescens nanoparticles affected the filtration efficiency of the filter differently depending on the size of the test particles. While the filtration efficiency of the KCl nanoparticles was reduced on the ES filter after the antimicrobial treatment, the filtration efficiency was improved after the recharging process. In summary, we prepared an antimicrobial ES air filter with >99% antimicrobial activity, ~92.5% filtration efficiency (for a 300-nm KCl aerosol), and a ~0.8 mmAq pressure drop (at 13 cm/s). This study provides valuable information for the development of a hybrid air purification system that can serve various functions and be used in an indoor environment. PMID:26172593

  15. In-place testing of tandem HEPA filter stages using fluorescent aerosols

    SciTech Connect

    Elder, J.C.; Kyle, T.G.; Tillery, M.I.; Ettinger, H.J.

    1981-04-01

    Fluorescent test aerosols have been incorporated into an in-place two-stage high-efficiency particulate air (HEPA) filter test method to improve sensitivity and eliminate interference by background aerosol leaking into the downstream sampling location. The method has been demonstrated by field testing large two-stage HEPA systems, one with a flow rate of 22 m/sup 3//s (48,500 cfm) and a decontamination factor (DF) of approximately 10/sup 8/. Advantages of the method, such as DF measurement more representative of actual filter performance and potential savings in construction and testing costs, make the fluorescent particle method a useful test method. A laser fluorescent particle spectrometer suitable for testing by this method was developed in conjunction with an instrument manufacturer and is commercially available. An improved dilution system was developed to reduce upstream aerosol concentration into the operating range of the spectrometer. Generation of a fluorescent dye-tagged DOP aerosol was accomplished by high-capacity, gas-thermal generator. Aerosol concentration of approximately 2 x 10/sup 6/ particles per cm/sup 3/ was maintained in the plenum upstream of the first stage. Other in-place test methods using fluorescent particles collected on sampling filters were investigated with only limited success and could not be extended to two-stage testing. The potentially most sensitive method, counting of solid fluorescent particles on sample filters taken upstream and downstream of HEPA filter stages, was restricted by particle losses in the resuspension operation. Maximum DF measurable by a solid fluorescent particle method was predicted to be 3 x 10/sup 3/, which would be adequate for testing one high-quality HEPA filter stage without excessive filter loading.

  16. Method for HEPA filter leak scanning with differentiating aerosol detector

    SciTech Connect

    Kovach, B.J.; Banks, E.M.; Wikoff, W.O.

    1997-08-01

    While scanning HEPA filters for leaks with {open_quotes}Off the Shelf{close_quote} aerosol detection equipment, the operator`s scanning speed is limited by the time constant and threshold sensitivity of the detector. This is based on detection of the aerosol density, where the maximum signal is achieved when the scanning probe resides over the pinhole longer than several detector time-constants. Since the differential value of the changing signal can be determined by observing only the first small fraction of the rising signal, using a differentiating amplifier will speed up the locating process. The other advantage of differentiation is that slow signal drift or zero offset will not interfere with the process of locating the leak, since they are not detected. A scanning hand-probe attachable to any NUCON{reg_sign} Aerosol Detector displaying the combination of both aerosol density and differentiated signal was designed. 3 refs., 1 fig.

  17. Amphiphobic Polytetrafluoroethylene Membranes for Efficient Organic Aerosol Removal.

    PubMed

    Feng, Shasha; Zhong, Zhaoxiang; Zhang, Feng; Wang, Yong; Xing, Weihong

    2016-04-01

    Polytetrafluoroethylene (PTFE) membrane is an extensively used air filter, but its oleophilicity leads to severe fouling of the membrane surface due to organic aerosol deposition. Herein, we report the fabrication of a new amphiphobic 1H,1H,2H,2H-perfluorodecyl acrylate (PFDAE)-grafted ZnO@PTFE membrane with enhanced antifouling functionality and high removal efficiency. We use atomic-layer deposition (ALD) to uniformly coat a layer of nanosized ZnO particles onto porous PTFE matrix to increase surface area and then subsequently graft PFDAE with plasma. Consequently, the membrane surface showed both superhydrophobicity and oleophobicity with a water contact angle (WCA) and an oil contact angle (OCA) of 150° and 125°, respectively. The membrane air permeation rate of 513 (m(3) m(-2) h(-1) kPa(-1)) was lower than the pristine membrane rate of 550 (m(3) m(-2) h(-1) kPa(-1)), which indicates the surface modification slightly decreased the membrane air permeation. Significantly, the filtration resistance of this amphiphobic membrane to the oil aerosol system was much lower than the initial one. Moreover, the filter exhibited exceptional organic aerosol removal efficiencies that were greater than 99.5%. These results make the amphiphobic PTFE membranes very promising for organic aerosol-laden air-filtration applications. PMID:27002786

  18. Filter and electrostatic samplers for semivolatile aerosols: physical artifacts.

    PubMed

    Volckens, John; Leith, David

    2002-11-01

    Adsorptive and evaporative artifacts often bias measurements of semivolatile aerosols. Adsorption occurs when the sampling method disrupts the gas-particle partitioning equilibrium. Evaporation occurs because concentrations of semivolatiles are rarely constant over time. Filtration is subject to both adsorptive and evaporative artifacts. By comparison, electrostatic precipitation reduces these artifacts by minimizing the surface area of collected particles without substantially disrupting the gas-particle equilibrium. The extent of these artifacts was determined for filter samplers and electrostatic precipitator samplers for semivolatile alkane aerosols in the laboratory. Adsorption of gas-phase semivolatiles was lower in electrostatic precipitators by factors of 5-100 compared to the filter method. Particle evaporation from the electrostatic sampler was 2.3 times lower than that from TFE-coated glass-fiber filters. Use of a backup filter to correct for compound-specific adsorption artifacts can introduce positive or negative errors to the measured particle-phase concentration due to competition among the adsorbates for available adsorption sites. Adsorption of evaporated particles from the front filter onto the backup filter increased the measured evaporative artifact by a factor of 1.5-2. PMID:12433172

  19. Self-cleaning, maintenance-free aerosol filter by non-thermal plasma at atmospheric pressure.

    PubMed

    Jidenko, N; Borra, J P

    2012-10-15

    Two lab-scale self-cleaning filters based on dielectric barrier discharges in air at atmospheric pressure have been developed and tested. Experimental results on aerosol removal by charging and electro-collection are presented versus plasma and hydrodynamic parameters for monodisperse aerosol from 20 nm to 1.2 μm. For classical atmospheric aerosol, the average mass and number filtration efficiencies exceed 95% and 87%, respectively in the most penetrating size range (100-700 nm). The frequency of the applied voltage controls the amplitude of the oscillation of charged particle and can be adjusted to favour either filtration or cleaning. Low frequency (1 kHz) is suitable for electro-collection, while high frequency (60 kHz) is favourable for filter cleaning. Electrical characterization and filter efficiency are two indicators of the filter loading. The durations of both filtration step at maximal efficiency and cleaning step depends on the deposited mass, the surface input power and subsequent dielectric surface temperature. PMID:22951224

  20. Compact Efficient Lidar Receiver for Measuring Atmospheric Aerosols

    NASA Technical Reports Server (NTRS)

    Gili, Christopher; De Young, Russell

    2006-01-01

    A small, light weight, and efficient aerosol lidar receiver was constructed and tested. Weight and space savings were realized by using rigid optic tubes and mounting cubes to package the steering optics and detectors in a compact assembly. The receiver had a 1064nm channel using an APD detector. The 532nm channel was split (90/10) into an analog channel (90%) and a photon counting channel (10%). The efficiency of the 1064nm channel with optical filter was 44.0%. The efficiency of the analog 532nm channel was 61.4% with the optical filter, and the efficiency of the 532nm photon counting channel was 7.6% with the optical filter. The results of the atmospheric tests show that the detectors were able to consistently return accurate results. The lidar receiver was able to detect distinct cloud layers, and the lidar returns also agreed across the different detectors. The use of a light weight fiber-coupled telescope reduced weight and allowed great latitude in detector assembly positioning due to the flexibility enabled by the use of fiber optics. The receiver is now ready to be deployed for aircraft or ground based aerosol lidar measurements.

  1. Effects of Relative Humidity and Spraying Medium on UV Decontamination of Filters Loaded with Viral Aerosols

    PubMed Central

    Woo, Myung-Heui; Grippin, Adam; Anwar, Diandra; Smith, Tamara; Wander, Joseph D.

    2012-01-01

    Although respirators and filters are designed to prevent the spread of pathogenic aerosols, a stockpile shortage is anticipated during the next flu pandemic. Contact transfer and reaerosolization of collected microbes from used respirators are also a concern. An option to address these potential problems is UV irradiation, which inactivates microbes by dimerizing thymine/uracil in nucleic acids. The objective of this study was to determine the effects of transmission mode and environmental conditions on decontamination efficiency by UV. In this study, filters were contaminated by different transmission pathways (droplet and aerosol) using three spraying media (deionized water [DI], beef extract [BE], and artificial saliva [AS]) under different humidity levels (30% [low relative humidity {LRH}], 60% [MRH], and 90% [HRH]). UV irradiation at constant intensity was applied for two time intervals at each relative humidity condition. The highest inactivation efficiency (IE), around 5.8 logs, was seen for DI aerosols containing MS2 on filters at LRH after applying a UV intensity of 1.0 mW/cm2 for 30 min. The IE of droplets containing MS2 was lower than that of aerosols containing MS2. Absorption of UV by high water content and shielding of viruses near the center of the aggregate are considered responsible for this trend. Across the different media, IEs in AS and in BE were much lower than in DI for both aerosol and droplet transmission, indicating that solids present in AS and BE exhibited a protective effect. For particles sprayed in a protective medium, RH is not a significant parameter. PMID:22685135

  2. Challenge of N95 Filtering Facepiece Respirators with Viable H1N1 Influenza Aerosols

    PubMed Central

    Harnish, Delbert A.; Heimbuch, Brian K.; Husband, Michael; Lumley, April E.; Kinney, Kimberly; Shaffer, Ronald E.; Wander, Joseph D.

    2015-01-01

    OBJECTIVE Specification of appropriate personal protective equipment for respiratory protection against influenza is somewhat controversial. In a clinical environment, N95 filtering facepiece respirators (FFRs) are often recommended for respiratory protection against infectious aerosols. This study evaluates the ability of N95 FFRs to capture viable H1N1 influenza aerosols. METHODS Five N95 FFR models were challenged with aerosolized viable H1N1 influenza and inert polystyrene latex particles at continuous flow rates of 85 and 170 liters per minute. Virus was assayed using Madin-Darby canine kidney cells to determine the median tissue culture infective dose (TCID50). Aerosols were generated using a Collison nebulizer containing H1N1 influenza virus at 1 × 108 TCID50/mL. To determine filtration efficiency, viable sampling was performed upstream and downstream of the FFR. RESULTS N95 FFRs filtered 0.8-µm particles of both H1N1 influenza and inert origins with more than 95% efficiency. With the exception of 1 model, no statistically significant difference in filtration performance was observed between influenza and inert particles of similar size. Although statistically significant differences were observed for 2 models when comparing the 2 flow rates, the differences have no significance to protection. CONCLUSIONS This study empirically demonstrates that a National Institute for Occupational Safety and Health–approved N95 FFR captures viable H1N1 influenza aerosols as well as or better than its N95 rating, suggesting that a properly fitted FFR reduces inhalation exposure to airborne influenza virus. This study also provides evidence that filtration efficiency is based primarily on particle size rather than the nature of the particle’s origin. PMID:23571366

  3. High efficiency CIP 10-I personal inhalable aerosol sampler

    NASA Astrophysics Data System (ADS)

    Görner, P.; Wrobel, R.; Simon, X.

    2009-02-01

    The CIP 10 personal aerosol sampler was first developed by Courbon for sampling the respirable fraction of mining dust. This respirable aerosol sampler was further improved by Fabries, then selectors for sampling thoracic and inhalable aerosols were designed. Kenny et al. evaluated the particle-size dependent sampling efficiency of the inhalable version in a large-scale wind tunnel using a life-size dummy. The authors found that the overall sampling efficiency decreases more rapidly than the CEN-ISO-ACGIH target efficiency curve. Görner and Witschger measured the aspiration efficiency of the CIP 10 omni-directional inlet. They found that the aspiration efficiency was high enough for inhalable aerosol sampling. This result led to the conclusion that the low sampling efficiency is due to some internal losses of the aspirated particles before they reach the final sampling stage, namely the CIP 10 rotating filter. Based on the assumption that the inhalable particles are selected at selector aspiration level, an experimental research project was conducted to improve particle transmission to the collection stage of the sampler. Two different inhalable selectors were designed by Görner and tested in a laboratory wind tunnel. The transmission efficiency of both models was measured by Roger following an experimental protocol described by Witschger. The T-shaped air flow circuit was finally adopted to draw the aspirated particles into the final collection stage of the CIP 10. Actually, in this selector, the almost horizontally aspirated particles should be conducted vertically to the rotating cup. In two previous prototypes, particles could be deposited in certain places by inertia (where the aerosol was forced to deviate drastically) or by sedimentation (where the aerosol decelerated). The aerodynamic behaviour of the adopted solution causes the particles to accelerate radially between two horizontal plates before they enter a vertical tube. This acceleration avoids the

  4. Highly efficient spin filtering of ballistic electrons

    NASA Astrophysics Data System (ADS)

    Steinmuller, S. J.; Trypiniotis, T.; Cho, W. S.; Hirohata, A.; Lew, W. S.; Vaz, C. A.; Bland, J. A.

    2004-04-01

    Spin dependent electron transport in hybrid Au/Co/Cu/NiFe/n-GaAs spin valve Schottky barrier structures was investigated using photoexcitation at various wavelengths. For excitation with the photon energy well above the Schottky barrier height we found a ˜2400% increase in helicity dependent photocurrent on switching the spin valve from parallel to antiparallel alignment. Our observations provide clear evidence for highly efficient spin filtering of spin polarized ballistic electrons.

  5. Efficient Anisotropic Filtering of Diffusion Tensor Images

    PubMed Central

    Xu, Qing; Anderson, Adam W.; Gore, John C.; Ding, Zhaohua

    2009-01-01

    To improve the accuracy of structural and architectural characterization of living tissue with diffusion tensor imaging, an efficient smoothing algorithm is presented for reducing noise in diffusion tensor images. The algorithm is based on anisotropic diffusion filtering, which allows both image detail preservation and noise reduction. However, traditional numerical schemes for anisotropic filtering have the drawback of inefficiency and inaccuracy due to their poor stability and first order time accuracy. To address this, an unconditionally stable and second order time accuracy semi-implicit Craig-Sneyd scheme is adapted in our anisotropic filtering. By using large step size, unconditional stability allows this scheme to take much fewer iterations and thus less computation time than the explicit scheme to achieve a certain degree of smoothing. Second order time accuracy makes the algorithm reduce noise more effectively than a first order scheme with the same total iteration time. Both the efficiency and effectiveness are quantitatively evaluated based on synthetic and in vivo human brain diffusion tensor images, and these tests demonstrate that our algorithm is an efficient and effective tool for denoising diffusion tensor images. PMID:20061113

  6. Particle size for greatest penetration of HEPA filters - and their true efficiency

    SciTech Connect

    da Roza, R.A.

    1982-12-01

    The particle size that most greatly penetrates a filter is a function of filter media construction, aerosol density, and air velocity. In this paper the published results of several experiments are compared with a modern filtration theory that predicts single-fiber efficiency and the particle size of maximum penetration. For high-efficiency particulate air (HEPA) filters used under design conditions this size is calculated to be 0.21 ..mu..m diam. This is in good agreement with the experimental data. The penetration at 0.21 ..mu..m is calculated to be seven times greater than at the 0.3 ..mu..m used for testing HEPA filters. Several mechanisms by which filters may have a lower efficiency in use than when tested are discussed.

  7. Survival of microorganisms on antimicrobial filters and the removal efficiency of bioaerosols in an environmental chamber.

    PubMed

    Kim, Sung Yeon; Kim, Misoon; Lee, Sunghee; Lee, JungEun; Ko, GwangPyo

    2012-09-01

    Exposure to bioaerosols causes various adverse health effects including infectious and respiratory diseases, and hypersensitivity. Controlling exposure to bioaerosols is important for disease control and prevention. In this study, we evaluated the efficacies of various functional filters coated with antimicrobial chemicals in deactivating representative microorganisms on filters or as bioaerosols. Tested functional filters were coated with different chemicals that included (i) Ginkgo and sumac, (ii) Ag-apatite and guanidine phosphate, (iii) SiO2, ZnO, and Al2O3, and (iv) zeolite. To evaluate the filters, we used a model ventilation system (1) to evaluate the removal efficiency of bacteria (Escherichia coli and Legionella pneumophila), bacterial spores (Bacillus subtilis spore), and viruses (MS2 bacteriophage) on various functional filters, and (2) to characterize the removal efficiency of these bioaerosols. All experiments were performed at a constant temperature of 25 degrees C and humidity of 50%. Most bacteria (excluding B. subtilis) rapidly decreased on the functional filter. Therefore, we confirmed that functional filters have antimicrobial effects. Additionally, we evaluated the removal efficiency of various bioaerosols by these filters. We used a six-jet collision nebulizer to generate microbial aerosols and introduced it into the environmental chamber. We then measured the removal efficiency of functional filters with and without a medium-efficiency filter. Most bioaerosol concentrations did not significantly decrease by the functional filter only but decreased by a combination of functional and medium-efficiency filter. In conclusion, functional filters could facilitate biological removal of various bioaerosols, but physical removal of these by functional was minimal. Proper use of chemical-coated filter materials could reduce exposure to these agents. PMID:22814505

  8. Spatially Refined Aerosol Direct Radiative Forcing Efficiencies

    NASA Technical Reports Server (NTRS)

    Henze, Daven K.; Shindell, Drew Todd; Akhtar, Farhan; Spurr, Robert J. D.; Pinder, Robert W.; Loughlin, Dan; Kopacz, Monika; Singh, Kumaresh; Shim, Changsub

    2012-01-01

    Global aerosol direct radiative forcing (DRF) is an important metric for assessing potential climate impacts of future emissions changes. However, the radiative consequences of emissions perturbations are not readily quantified nor well understood at the level of detail necessary to assess realistic policy options. To address this challenge, here we show how adjoint model sensitivities can be used to provide highly spatially resolved estimates of the DRF from emissions of black carbon (BC), primary organic carbon (OC), sulfur dioxide (SO2), and ammonia (NH3), using the example of emissions from each sector and country following multiple Representative Concentration Pathway (RCPs). The radiative forcing efficiencies of many individual emissions are found to differ considerably from regional or sectoral averages for NH3, SO2 from the power sector, and BC from domestic, industrial, transportation and biomass burning sources. Consequently, the amount of emissions controls required to attain a specific DRF varies at intracontinental scales by up to a factor of 4. These results thus demonstrate both a need and means for incorporating spatially refined aerosol DRF into analysis of future emissions scenario and design of air quality and climate change mitigation policies.

  9. A Computationally Efficient Algorithm for Aerosol Phase Equilibrium

    SciTech Connect

    Zaveri, Rahul A.; Easter, Richard C.; Peters, Len K.; Wexler, Anthony S.

    2004-10-04

    Three-dimensional models of atmospheric inorganic aerosols need an accurate yet computationally efficient thermodynamic module that is repeatedly used to compute internal aerosol phase state equilibrium. In this paper, we describe the development and evaluation of a computationally efficient numerical solver called MESA (Multicomponent Equilibrium Solver for Aerosols). The unique formulation of MESA allows iteration of all the equilibrium equations simultaneously while maintaining overall mass conservation and electroneutrality in both the solid and liquid phases. MESA is unconditionally stable, shows robust convergence, and typically requires only 10 to 20 single-level iterations (where all activity coefficients and aerosol water content are updated) per internal aerosol phase equilibrium calculation. Accuracy of MESA is comparable to that of the highly accurate Aerosol Inorganics Model (AIM), which uses a rigorous Gibbs free energy minimization approach. Performance evaluation will be presented for a number of complex multicomponent mixtures commonly found in urban and marine tropospheric aerosols.

  10. Evaluation of the effect of media velocity on filter efficiency and most penetrating particle size of nuclear grade high-efficiency particulate air filters.

    PubMed

    Alderman, Steven L; Parsons, Michael S; Hogancamp, Kristina U; Waggoner, Charles A

    2008-11-01

    High-efficiency particulate air (HEPA) filters are widely used to control particulate matter emissions from processes that involve management or treatment of radioactive materials. Section FC of the American Society of Mechanical Engineers AG-1 Code on Nuclear Air and Gas Treatment currently restricts media velocity to a maximum of 2.5 cm/sec in any application where this standard is invoked. There is some desire to eliminate or increase this media velocity limit. A concern is that increasing media velocity will result in higher emissions of ultrafine particles; thus, it is unlikely that higher media velocities will be allowed without data to demonstrate the effect of media velocity on removal of ultrafine particles. In this study, the performance of nuclear grade HEPA filters, with respect to filter efficiency and most penetrating particle size, was evaluated as a function of media velocity. Deep-pleat nuclear grade HEPA filters (31 cm x 31 cm x 29 cm) were evaluated at media velocities ranging from 2.0 to 4.5 cm/sec using a potassium chloride aerosol challenge having a particle size distribution centered near the HEPA filter most penetrating particle size. Filters were challenged under two distinct mass loading rate regimes through the use of or exclusion of a 3 microm aerodynamic diameter cut point cyclone. Filter efficiency and most penetrating particle size measurements were made throughout the duration of filter testing. Filter efficiency measured at the onset of aerosol challenge was noted to decrease with increasing media velocity, with values ranging from 99.999 to 99.977%. The filter most penetrating particle size recorded at the onset of testing was noted to decrease slightly as media velocity was increased and was typically in the range of 110-130 nm. Although additional testing is needed, these findings indicate that filters operating at media velocities up to 4.5 cm/sec will meet or exceed current filter efficiency requirements. Additionally

  11. X-RAY FLUORESCENCE ANALYSIS OF FILTER-COLLECTED AEROSOL PARTICLES

    EPA Science Inventory

    X-ray fluorescence (XRF) has become an effective technique for determining the elemental content of aerosol samples. For quantitative analysis, the aerosol particles must be collected as uniform deposits on the surface of Teflon membrane filters. An energy dispersive XRF spectrom...

  12. Sub-wavelength efficient polarization filter (SWEP filter)

    DOEpatents

    Simpson, Marcus L.; Simpson, John T.

    2003-12-09

    A polarization sensitive filter includes a first sub-wavelength resonant grating structure (SWS) for receiving incident light, and a second SWS. The SWS are disposed relative to one another such that incident light which is transmitted by the first SWS passes through the second SWS. The filter has a polarization sensitive resonance, the polarization sensitive resonance substantially reflecting a first polarization component of incident light while substantially transmitting a second polarization component of the incident light, the polarization components being orthogonal to one another. A method for forming polarization filters includes the steps of forming first and second SWS, the first and second SWS disposed relative to one another such that a portion of incident light applied to the first SWS passes through the second SWS. A method for separating polarizations of light, includes the steps of providing a filter formed from a first and second SWS, shining incident light having orthogonal polarization components on the first SWS, and substantially reflecting one of the orthogonal polarization components while substantially transmitting the other orthogonal polarization component. A high Q narrowband filter includes a first and second SWS, the first and second SWS are spaced apart a distance being at least one half an optical wavelength.

  13. Spatially Refined Aerosol Direct Radiative Forcing Efficiencies

    EPA Science Inventory

    Global aerosol direct radiative forcing (DRF) is an important metric for assessing potential climate impacts of future emissions changes. However, the radiative consequences of emissions perturbations are not readily quantified nor well understood at the level of detail necessary...

  14. Spatially Refined Aerosol Direct Radiative Focusing Efficiencies

    EPA Science Inventory

    Global aerosol direct radiative forcing (DRF) is an important metric for assessing potential climate impacts of future emissions changes. However, the radiative consequences of emissions perturbations are not readily quantified nor well understood at the level of detail necessary...

  15. Efficiency of aerosol collection on wires exposed in the stratosphere

    NASA Technical Reports Server (NTRS)

    Lem, H. Y.; Farlow, N. H.

    1979-01-01

    The theory of inertial impaction is briefly presented. Stratospheric aerosol research experiments were performed duplicating Wong et al. experiments. The use of the curve of inertial parameters vs particle collection efficiency, derived from Wong et al., was found to be justified. The results show that stratospheric aerosol particles of all sizes are collectible by wire impaction technique. Curves and tables are presented and used to correct particle counts for collection efficiencies less than 100%.

  16. The high efficiency steel filters for nuclear air cleaning

    SciTech Connect

    Bergman, W.; Larsen, G.; Lopez, R.; Williams, K.; Violet, C.

    1990-08-01

    We have, in cooperation with industry, developed high-efficiency filters made from sintered stainless-steel fibers for use in several air-cleaning applications in the nuclear industry. These filters were developed to overcome the failure modes in present high-efficiency particulate air (HEPA) filters. HEPA filters are made from glass paper and glue, and they may fail when they get hot or wet and when they are overpressured. In developing our steel filters, we first evaluated the commercially available stainless-steel filter media made from sintered powder and sintered fiber. The sintered-fiber media performed much better than sintered-powder media, and the best media had the smallest fiber diameter. Using the best media, we then built prototype filters for venting compressed gases and evaluated them in our automated filter tester. 12 refs., 20 figs.

  17. Aerosol detection efficiency in inductively coupled plasma mass spectrometry

    DOE PAGESBeta

    Hubbard, Joshua A.; Zigmond, Joseph A.

    2016-03-02

    We used an electrostatic size classification technique to segregate particles of known composition prior to being injected into an inductively coupled plasma mass spectrometer (ICP-MS). Moreover, we counted size-segregated particles with a condensation nuclei counter as well as sampled with an ICP-MS. By injecting particles of known size, composition, and aerosol concentration into the ICP-MS, efficiencies of the order of magnitude aerosol detection were calculated, and the particle size dependencies for volatile and refractory species were quantified. Similar to laser ablation ICP-MS, aerosol detection efficiency was defined as the rate at which atoms were detected in the ICP-MS normalized bymore » the rate at which atoms were injected in the form of particles. This method adds valuable insight into the development of technologies like laser ablation ICP-MS where aerosol particles (of relatively unknown size and gas concentration) are generated during ablation and then transported into the plasma of an ICP-MS. In this study, we characterized aerosol detection efficiencies of volatile species gold and silver along with refractory species aluminum oxide, cerium oxide, and yttrium oxide. Aerosols were generated with electrical mobility diameters ranging from 100 to 1000 nm. In general, it was observed that refractory species had lower aerosol detection efficiencies than volatile species, and there were strong dependencies on particle size and plasma torch residence time. Volatile species showed a distinct transition point at which aerosol detection efficiency began decreasing with increasing particle size. This critical diameter indicated the largest particle size for which complete particle detection should be expected and agreed with theories published in other works. Aerosol detection efficiencies also displayed power law dependencies on particle size. Aerosol detection efficiencies ranged from 10-5 to 10-11. Free molecular heat and mass transfer theory was

  18. Aerosol detection efficiency in inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Hubbard, Joshua A.; Zigmond, Joseph A.

    2016-05-01

    An electrostatic size classification technique was used to segregate particles of known composition prior to being injected into an inductively coupled plasma mass spectrometer (ICP-MS). Size-segregated particles were counted with a condensation nuclei counter as well as sampled with an ICP-MS. By injecting particles of known size, composition, and aerosol concentration into the ICP-MS, efficiencies of the order of magnitude aerosol detection were calculated, and the particle size dependencies for volatile and refractory species were quantified. Similar to laser ablation ICP-MS, aerosol detection efficiency was defined as the rate at which atoms were detected in the ICP-MS normalized by the rate at which atoms were injected in the form of particles. This method adds valuable insight into the development of technologies like laser ablation ICP-MS where aerosol particles (of relatively unknown size and gas concentration) are generated during ablation and then transported into the plasma of an ICP-MS. In this study, we characterized aerosol detection efficiencies of volatile species gold and silver along with refractory species aluminum oxide, cerium oxide, and yttrium oxide. Aerosols were generated with electrical mobility diameters ranging from 100 to 1000 nm. In general, it was observed that refractory species had lower aerosol detection efficiencies than volatile species, and there were strong dependencies on particle size and plasma torch residence time. Volatile species showed a distinct transition point at which aerosol detection efficiency began decreasing with increasing particle size. This critical diameter indicated the largest particle size for which complete particle detection should be expected and agreed with theories published in other works. Aerosol detection efficiencies also displayed power law dependencies on particle size. Aerosol detection efficiencies ranged from 10- 5 to 10- 11. Free molecular heat and mass transfer theory was applied, but

  19. Define and Quantify the Physics of Air Flow, Pressure Drop and Aerosol Collection in Nuclear Grade HEPA Filters

    SciTech Connect

    Moore, Murray E.

    2015-02-23

    Objective: Develop a set of peer-review and verified analytical methods to adjust HEPA filter performance to different flow rates, temperatures and altitudes. Experimental testing will measure HEPA filter flow rate, pressure drop and efficiency to verify the analytical approach. Nuclear facilities utilize HEPA (High Efficiency Particulate Air) filters to purify air flow for workspace ventilation. However, the ASME AG-1 technical standard (Code on Nuclear Air and Gas Treatment) does not adequately describe air flow measurement units for HEPA filter systems. Specifically, the AG-1 standard does not differentiate between volumetric air flow in ACFM (actual cubic feet per minute)compared to mass flow measured in SCFM (standard cubic feet per minute). More importantly, the AG-1 standard has an overall deficiency for using HEPA filter devices at different air flow rates, temperatures, and altitudes. Technical Approach: The collection efficiency and pressure drops of 18 different HEPA filters will be measured over a range of flow rates, temperatures and altitudes. The experimental results will be compared to analytical scoping calculations. Three manufacturers have allocated six HEPA filters each for this effort. The 18 filters will be tested at two different flow rates, two different temperatures and two different altitudes. The 36 total tests will be conducted at two different facilities: the ATI Test facilities (Baltimore MD) and the Los Alamos National Laboratory (Los Alamos NM). The Radiation Protection RP-SVS group at Los Alamos has an aerosol wind tunnel that was originally designed to evaluate small air samplers. In 2010, modifications were started to convert the wind tunnel for HEPA filter testing. (Extensive changes were necessary for the required aerosol generators, HEPA test fixtures, temperature control devices and measurement capabilities.) To this date, none of these modification activities have been funded through a specific DOE or NNSA program. This is

  20. Preliminary field evaluation of high efficiency steel filters

    SciTech Connect

    Bergman, W.; Larsen, G.; Lopez, R.; Wilson, K.; Simon, K.; Frye, L.

    1994-11-01

    The authors have conducted an evaluation of two high efficiency steel filters in the exhaust of an uranium oxide grit blaster at the Y-12 Plant in Oak Ridge Tennessee. The filters were installed in a specially designed filter housing with a reverse air-pulse cleaning system for automatically cleaning the filters in-place. Previous tests conducted on the same filters and housing at LLNL under controlled conditions using Arizona road dust showed good cleanability with reverse air pulses. Two high efficiency steel filters, containing 64 pleated cartridge elements housed in the standard 2{prime} x 2{prime} {times} l{prime} HEPA frame, were evaluated in the filter test housing using a 1,000 cfm slip stream containing a high concentration of depleted uranium oxide dust. One filter had the pleated cartridges manufactured to the authors specifications by the Pall Corporation and the other by Memtec Corporation. Test results showed both filters had a rapid increase in pressure drop with time, and reverse air pulses could not decrease the pressure drop. The authors suspected moisture accumulation in the filters was the problem since there were heavy rains during the evaluations, and the pressure drop of the Memtec filter decreased dramatically after passing clean, dry air through the filter and after the filter sat idle for one week. Subsequent laboratory tests on a single filter cartridge confirmed that water accumulation in the filter was responsible for the increase in filter pressure drop and the inability to lower the pressure drop by reverse air pulses. No effort was made to identify the source of the water accumulation and correct the problem because the available funds were exhausted.

  1. Preliminary field evaluation of high efficiency steel filters

    SciTech Connect

    Bergman, W.; Larsen, G.; Lopez, R.

    1995-02-01

    We have conducted an evaluation of two high efficiency steel filters in the exhaust of an uranium oxide grit blaster at the Y-12 Plant in Oak Ridge Tennessee. The filters were installed in a specially designed filter housing with a reverse air-pulse cleaning system for automatically cleaning the filters in-place. Previous tests conducted on the same filters and housing at LLNL under controlled conditions using Arizona road dust showed good cleanability with reverse air pulses. Two high efficiency steel filters, containing 64 pleated cartridge elements housed in the standard 2` x 2` x 1` HEPA frame, were evaluated in the filter test housing using a 1,000 cfm slip stream containing a high concentration of depleted uranium oxide dust. One filter had the pleated cartridges manufactured to our specifications by the Pall Corporation and the other by Memtec Corporation. Test results showed both filters had a rapid increase in pressure drop with time, and reverse air pulses could not decrease the pressure drop. We suspected moisture accumulation in the filters was the problem since there were heavy rains during the evaluations, and the pressure drop of the Memtec filter decreased dramatically after passing clean, dry air through the filter and after the filter sat idle for one week. Subsequent laboratory tests on a single filter cartridge confirmed that water accumulation in the filter was responsible for the increase in filter pressure drop and the inability to lower the pressure drop by reverse air pulses. No effort was made to identify the source of the water accumulation and correct the problem because the available funds were exhausted.

  2. Bacterial filtration efficiency of green soy protein based nanofiber air filter.

    PubMed

    Lubasova, D; Netravali, A; Parker, J; Ingel, B

    2014-07-01

    High bacterial filtration efficiency (BFE) filters, based on nanofibers derived from blends of grain proteins and poly-ethylene-oxide (PEO), were produced by an electrospinning process. Specifically, polymer blends consisting of purified soy flour/PEO with a ratio of 7/3 were spun into nanofibers and characterized. A new laboratory based experimental apparatus for testing BFE was designed and used to test BFE of bacterial aerosols consisting of Escherichia coli (E. coli). Performances of soy protein based nanofiber filters with nanofiber mass varying from 1 to 5 g/m2 as well as a nanofiber filters prepared from pure PEO were compared. The results showed that BFE values for filters containing 5 g/m2 protein based nanofibers and PEO nanofiber filter were 100 and 81.5%, respectively. The results also indicated that the BFE increased as the protein content in the nanofiber filter increased. These novel protein based nanofiber filters have demonstrated a clear potential for effective removal and retention of E. coli bacteria during air-filtration. These filters can be effectively deployed in environments such as hospitals and senior residential areas to reduce bacterial infections. PMID:24757959

  3. Summary of efficiency testing of standard and high-capacity high-efficiency particulate air filters subjected to simulated tornado depressurization and explosive shock waves

    SciTech Connect

    Smith, P.R.; Gregory, W.S.

    1985-04-01

    Pressure transients in nuclear facility air cleaning systems can originate from natural phenomena such as tornadoes or from accident-induced explosive blast waves. This study was concerned with the effective efficiency of high-efficiency particulate air (HEPA) filters during pressure surges resulting from simulated tornado and explosion transients. The primary objective of the study was to examine filter efficiencies at pressure levels below the point of structural failure. Both standard and high-capacity 0.61-m by 0.61-m HEPA filters were evaluated, as were several 0.2-m by 0.2-m HEPA filters. For a particular manufacturer, the material release when subjected to tornado transients is the same (per unit area) for both the 0.2-m by 0.2-m and the 0.61-m by 0.61-m filters. For tornado transients, the material release was on the order of micrograms per square meter. When subjecting clean HEPA filters to simulated tornado transients with aerosol entrained in the pressure pulse, all filters tested showed a degradation of filter efficiency. For explosive transients, the material release from preloaded high-capacity filters was as much as 340 g. When preloaded high-capacity filters were subjected to shock waves approximately 50% of the structural limit level, 1 to 2 mg of particulate was released.

  4. Is There a Common Correction for Biases in Historic Filter-Based Aerosol Absorption Measurements?

    NASA Astrophysics Data System (ADS)

    McComiskey, A. C.; Jefferson, A.; Dubey, M. K.; Aiken, A. C.; Fast, J. D.; Flynn, C. J.; Kassianov, E.

    2014-12-01

    Improved characterization of aerosol absorption is a pressing need for improving estimates of climate forcing by aerosols. Measurements of aerosol absorption are difficult to make with the accuracy and precision demanded by climate science. While several different approaches have been employed and new techniques have emerged, none can yet be considered a true 'gold standard'. Instruments that use filter-based methods have been the most widely used and are the basis of historic records. However, several studies using direct photoacoustic techniques have shown that filter-based measurements can be biased relative to these direct measurements. It has been demonstrated that this bias depends strongly on aerosol chemical composition, specifically concentration of organic mass. The wealth of information in the extensive set of historical filter-based data demands that this bias be diagnosed and corrected. A correction is critical for proper evaluation and development of chemical transport models, improved retrievals from remote sensing measurements, and integrating aerosol absorption surface and sub-orbital in situ measurements with knowledge gained from these other approaches. We have performed an intercomparison of absorption coefficients from a photoacoustic and two filter-based instruments with co-located organic mass concentrations from continuous, half-hourly averaged measurements over six months at a remote, continental site in the US (ARM SGP). The results show a bias in the filter-based measurements with organic concentration that is consistent with previous studies. Previous results come from controlled lab studies or field campaigns where absorption coefficients and organic concentrations are high and may represent aerosol close to the source. The current study is important in that these quantities are much lower and the aerosol likely more aged, representing a larger portion of the global conditions, yet shows a similar bias. This site provides other measures

  5. Evaluation of the performance of the N95-companion: effects of filter penetration and comparison with other aerosol instruments.

    PubMed

    Rengasamy, Samy; Eimer, Benjamin C; Shaffer, Ronald E

    2012-01-01

    Fit factor is the ratio of the particle concentration outside (C(out)) to the inside (C(in)) of the respirator and assumes that filter penetration is negligible. For Class-95 respirators, concerns were raised that filter penetration could bias fit test measurements. The TSI N95-Companion was designed to overcome this limitation by measuring only 40-60 nm size particles. Recent research has shown that particles in this size range are the most penetrating for respirators containing electrostic filter media. The goal of this study was to better understand the performance of the N95-Companion by assessing the impact of filter penetration and by comparing C(out)/C(in) ratios measured by other aerosol instruments (nano-Differential Mobility Analyzer/Ultrafine Condensation Particle Counter (nano-DMA/UCPC) and the TSI PortaCount Plus) using N95 filtering facepiece respirators sealed to a manikin and with intentionally created leaks. Results confirmed that 40-60 nm-diameter size room air particles were most penetrating for the respirators tested. A nonlinear relationship was found between the N95-Companion-measured C(out)/C(in) ratios and the other instruments at the sealed condition and at the small leak sizes because the N95-Companion measures only charged particles that are preferentially captured by the electrostic filter media, while the other instrument configurations also measure uncharged particles, which are captured less efficiently. The C(out)/C(in) ratios from the N95-Companion for experiments conducted under sealed condition suggest that filter penetration of negatively charged 40-60 nm size particles was less than 0.05%. Thus, the N95-Companion measured C(out)/C(in) ratios are due primarily to particle penetration through leakage, not through filter media, while the C(out)/C(in) ratios for the PortaCount, nano-DMA/UCPC, and UCPC result from a combination of face seal leakage and filter penetration. PMID:22642759

  6. Effect of ethanol on droplet size, efficiency of delivery, and clearance characteristics of technetium-99m DTPA aerosol.

    PubMed

    Sirr, S A; Juenemann, P J; Tom, H; Boudreau, R J; Chandler, R P; Loken, M K

    1985-06-01

    With recent technical advances in aerosol technology, the study of regional ventilation using [99mTc]DTPA aerosol has become increasingly popular. Using a cascade impactor, we have assessed droplet size distribution from a newly designed nebulizer. Delivery efficiency of [99mTc]DTPA aerosol to normal subjects was improved 70% with a 10% concentration of ethanol in the nebulizer. Using filter paper fixed to the delivery end of the aerosol device, and varying ethanol concentrations from 0-10%, an 87% increase of deposited radioactivity is measured. Use of higher concentration of ethanol to the nebulizer solution did not further improve delivery efficiency. The addition of ethanol did not alter clearance characteristics of [99mTc]DTPA from the lung nor did it affect droplet size distribution. PMID:3889235

  7. Experiments with the assimilation of fine aerosols using an ensemble Kalman filter

    NASA Astrophysics Data System (ADS)

    Pagowski, Mariusz; Grell, Georg A.

    2012-11-01

    In a series of experiments we issue forecasts of fine aerosol concentration over the coterminous USA and southern Canada using the Weather Research and Forecasting - Chemistry model initialized with 3D-VAR or ensemble Kalman filter (EnKF) assimilation methods. Assimilated observations include surface measurements of fine aerosols from the United States Environmental Protection Agency AIRNow Data Exchange program. Evaluation statistics calculated over a month-and-half-long summer period demonstrate the advantage of EnKF over 3D-VAR and point to the limitations of applying a simple aerosol parameterization for predicting air quality over the forecast area. Strategies for further improvement of forecasting aerosol concentrations are discussed.

  8. Spatial filtering efficiency of monostatic biaxial lidar: analysis and applications.

    PubMed

    Agishev, Ravil R; Comeron, Adolfo

    2002-12-20

    Results of lidar modeling based on spatial-angular filtering efficiency criteria are presented. Their analysis shows that the low spatial-angular filtering efficiency of traditional visible and near-infrared systems is an important cause of low signal/background-radiation ratio (SBR) at the photodetector input The low SBR may be responsible for considerable measurement errors and ensuing the low accuracy of the retrieval of atmospheric optical parameters. As shown, the most effective protection against sky background radiation for groundbased biaxial lidars is the modifying of their angular field according to a spatial-angular filtering efficiency criterion. Some effective approaches to achieve a high filtering efficiency for the receiving system optimization are discussed. PMID:12510915

  9. Protection Factor for N95 Filtering Facepiece Respirators Exposed to Laboratory Aerosols Containing Different Concentrations of Nanoparticles

    PubMed Central

    Rengasamy, Samy; Walbert, Gary; Newcomb, William; Coffey, Christopher; Wassell, James Terrence; Szalajda, Jonathan

    2015-01-01

    A previous study used a PortaCount Plus to measure the ratio of particle concentrations outside (Cout) to inside (Cin) of filtering facepiece respirators (FFRs) worn by test subjects and calculated the total inward leakage (TIL) (Cin/Cout) to evaluate the reproducibility of the TIL test method between two different National Institute for Occupational Safety and Health laboratories (Laboratories 1 and 2) at the Pittsburgh Campus. The purpose of this study is to utilize the originally obtained PortaCount Cout/Cin ratio as a measure of protection factor (PF) and evaluate the influence of particle distribution and filter efficiency. PFs were obtained for five N95 model FFRs worn by 35 subjects for three donnings (5 models × 35 subjects × 3 donnings) for a total of 525 tests in each laboratory. The geometric mean of PFs, geometric standard deviation (GSD), and the 5th percentile values for the five N95 FFR models were calculated for the two laboratories. Filter efficiency was obtained by measuring the penetration for four models (A, B, C, and D) against Laboratory 2 aerosol using two condensation particle counters. Particle size distribution, measured using a Scanning Mobility Particle Sizer, showed a mean count median diameter (CMD) of 82 nm in Laboratory 1 and 131 nm in Laboratory 2. The smaller CMD showed relatively higher concentration of nanoparticles in Laboratory 1 than in Laboratory 2. Results showed that the PFs and 5th percentile values for two models (B and E) were larger than other three models (A, C, and D) in both laboratories. The PFs and 5th percentile values of models B and E in Laboratory 1 with a count median diameter (CMD) of 82 nm were smaller than in Laboratory 2 with a CMD of 131 nm, indicating an association between particle size distribution and PF. The three lower efficiency models (A, C, and D) showed lower PF values than the higher efficiency model B showing the influence of filter efficiency on PF value. Overall, the data show that

  10. Protection factor for N95 filtering facepiece respirators exposed to laboratory aerosols containing different concentrations of nanoparticles.

    PubMed

    Rengasamy, Samy; Walbert, Gary; Newcomb, William; Coffey, Christopher; Wassell, James Terrence; Szalajda, Jonathan

    2015-04-01

    A previous study used a PortaCount Plus to measure the ratio of particle concentrations outside (C out) to inside (C in) of filtering facepiece respirators (FFRs) worn by test subjects and calculated the total inward leakage (TIL) (C in/C out) to evaluate the reproducibility of the TIL test method between two different National Institute for Occupational Safety and Health laboratories (Laboratories 1 and 2) at the Pittsburgh Campus. The purpose of this study is to utilize the originally obtained PortaCount C out/C in ratio as a measure of protection factor (PF) and evaluate the influence of particle distribution and filter efficiency. PFs were obtained for five N95 model FFRs worn by 35 subjects for three donnings (5 models × 35 subjects × 3 donnings) for a total of 525 tests in each laboratory. The geometric mean of PFs, geometric standard deviation (GSD), and the 5th percentile values for the five N95 FFR models were calculated for the two laboratories. Filter efficiency was obtained by measuring the penetration for four models (A, B, C, and D) against Laboratory 2 aerosol using two condensation particle counters. Particle size distribution, measured using a Scanning Mobility Particle Sizer, showed a mean count median diameter (CMD) of 82 nm in Laboratory 1 and 131 nm in Laboratory 2. The smaller CMD showed relatively higher concentration of nanoparticles in Laboratory 1 than in Laboratory 2. Results showed that the PFs and 5th percentile values for two models (B and E) were larger than other three models (A, C, and D) in both laboratories. The PFs and 5th percentile values of models B and E in Laboratory 1 with a count median diameter (CMD) of 82 nm were smaller than in Laboratory 2 with a CMD of 131 nm, indicating an association between particle size distribution and PF. The three lower efficiency models (A, C, and D) showed lower PF values than the higher efficiency model B showing the influence of filter efficiency on PF value. Overall, the data show that

  11. Effect of ethanol on droplet size, efficiency of delivery, and clearance characteristics of technetium-99m DTPA aerosol

    SciTech Connect

    Sirr, S.A.; Juenemann, P.J.; Tom, H.; Boudreau, R.J.; Chandler, R.P.; Loken, M.K.

    1985-06-01

    With recent technical advances in aerosol technology, the study of regional ventilation using (/sup 99m/Tc)DTPA aerosol has become increasingly popular. Using a cascade impactor, the authors have assessed droplet size distribution from a newly designed nebulizer. Delivery efficiency of (/sup 99m/Tc)DTPA aerosol to normal subjects was improved 70% with a 10% concentration of ethanol in the nebulizer. Using filter paper fixed to the delivery end of the aerosol device, and varying ethanol concentrations from 0-10%, an 87% increase of deposited radioactivity is measured. The addition of ethanol did not alter clearance characteristics of (/sup 99m/Tc)DTPA from the lung nor did it affect droplet size distribution.

  12. Self-assembled magnetic filter for highly efficient immunomagnetic separation.

    PubMed

    Issadore, David; Shao, Huilin; Chung, Jaehoon; Newton, Andita; Pittet, Mikael; Weissleder, Ralph; Lee, Hakho

    2011-01-01

    We have developed a compact and inexpensive microfluidic chip, the self-assembled magnetic filter, to efficiently remove magnetically tagged cells from suspension. The self-assembled magnetic filter consists of a microfluidic channel built directly above a self-assembled NdFeB magnet. Micrometre-sized grains of NdFeB assemble to form alternating magnetic dipoles, creating a magnetic field with a very strong magnitude B (from the material) and field gradient ▽B (from the configuration) in the microfluidic channel. The magnetic force imparted on magnetic beads is measured to be comparable to state-of-the-art microfabricated magnets, allowing for efficient separations to be performed in a compact, simple device. The efficiency of the magnetic filter is characterized by sorting non-magnetic (polystyrene) beads from magnetic beads (iron oxide). The filter enriches the population of non-magnetic beads to magnetic beads by a factor of >10(5) with a recovery rate of 90% at 1 mL h(-1). The utility of the magnetic filter is demonstrated with a microfluidic device that sorts tumor cells from leukocytes using negative immunomagnetic selection, and concentrates the tumor cells on an integrated membrane filter for optical detection. PMID:20949198

  13. Large radiative forcing efficiency of atmospheric aerosols over the Himalaya

    NASA Astrophysics Data System (ADS)

    Gasbarra, Daniele; di Sarra, Alcide; Meloni, Daniela; Bonasoni, Paolo; Di Biagio, Claudia; Gobbi, Gian Paolo; Marinoni, Angela; Pietro Verza, Gian; Vuillermoz, Elisa

    2014-05-01

    , it becomes relatively large during elevated aerosol cases. The radiative forcing efficiency (radiative effect produced by a unit aerosol optical depth) is significantly larger than at other sites worldwide, reaching values above 360 W/m2 at about 50° solar zenith angle. The maximum radiative effect is about -90±18 Wm-2 (for τ=0.25), corresponding to a reduction by more than 10% of the solar radiation at the surface. During these elevated aerosol events high concentrations of pollutants were measured: PM10 and PM 2.5 showed concentrations higher than 50 ng m-3, while the black carbon concentration reached 3000 ng m-3. The backtrajectory analysis for the elevated aerosol cases shows that the polluted airmasses observed at NCO-P come from Indo-Gangetic plain and Punjab, regions characterized by the highest industrial and demographic concentration of the Indian subcontinent.

  14. An efficient interpolation filter VLSI architecture for HEVC standard

    NASA Astrophysics Data System (ADS)

    Zhou, Wei; Zhou, Xin; Lian, Xiaocong; Liu, Zhenyu; Liu, Xiaoxiang

    2015-12-01

    The next-generation video coding standard of High-Efficiency Video Coding (HEVC) is especially efficient for coding high-resolution video such as 8K-ultra-high-definition (UHD) video. Fractional motion estimation in HEVC presents a significant challenge in clock latency and area cost as it consumes more than 40 % of the total encoding time and thus results in high computational complexity. With aims at supporting 8K-UHD video applications, an efficient interpolation filter VLSI architecture for HEVC is proposed in this paper. Firstly, a new interpolation filter algorithm based on the 8-pixel interpolation unit is proposed in this paper. It can save 19.7 % processing time on average with acceptable coding quality degradation. Based on the proposed algorithm, an efficient interpolation filter VLSI architecture, composed of a reused data path of interpolation, an efficient memory organization, and a reconfigurable pipeline interpolation filter engine, is presented to reduce the implement hardware area and achieve high throughput. The final VLSI implementation only requires 37.2k gates in a standard 90-nm CMOS technology at an operating frequency of 240 MHz. The proposed architecture can be reused for either half-pixel interpolation or quarter-pixel interpolation, which can reduce the area cost for about 131,040 bits RAM. The processing latency of our proposed VLSI architecture can support the real-time processing of 4:2:0 format 7680 × 4320@78fps video sequences.

  15. Experimental studies of silver iodide pyrotechnic aerosol ice forming efficiency dynamics

    NASA Astrophysics Data System (ADS)

    Shilin, A. G.; Drofa, A. S.; Ivanov, V. N.; Savchenko, A. V.; Shilin, V. A.

    2013-05-01

    The study concerns the problems connected with the temporal variability of aerosol ice forming activity at introduction into the sub-cloud layer and the comparison of aerosol efficiency of produced pyrotechnic mixtures with different silver contents.

  16. Analysis of heavy metal aerosols on filters by laser-induced plasma spectroscopy

    NASA Astrophysics Data System (ADS)

    Panne, U.; Neuhauser, R. E.; Theisen, M.; Fink, H.; Niessner, R.

    2001-06-01

    Particulate heavy metals can lead to severe toxic and carcinogenic effects in humans when inhaled in higher concentrations. For the development of a quasi-continuous emission monitor based on automatic filter sampling on a filter band, laser-induced plasma spectroscopy (LIPS) was studied for analysis of heavy metal aerosols on quartz fiber filters. The system consists of a 19-inch laser and detector module connected to a miniaturized sensor head through fiber optics, allowing maximum flexibility of the set-up. Parameters for optimum time-resolved analysis, i.e. detection wavelength, timing and filter material, were established. The LIPS investigations were accompanied by a rigorous reference analysis based on total reflection X-ray fluorescence (TXRF) analysis. The detection limits for heavy metals (Cd, Ni, As, Co, Mn, Sb, Cr, Tl, Sn, V, Cu and Pb) on filters varied between 0.01 and approximately 0.91 μg cm -2, corresponding to volume detection limits of 0.02-2.73 μg m -3. Analysis of filter samples from waste incineration demonstrated the potential of the LIPS approach. In combination with an echelle spectrometer, ambient samples from environmental monitoring could be characterized in much better detail, due to the improved detection limits and the superior spectral resolution, and spectral range of the echelle.

  17. A CLOSURE STUDY OF AEROSOL MASS CONCENTRATION MEASUREMENTS: COMPARISON OF VALUES OBTAINED WITH FILTERS AND BY DIRECT MEASUREMENTS OF MASS DISTRIBUTIONS. (R826372)

    EPA Science Inventory

    We compare measurements of aerosol mass concentrations obtained gravimetrically using Teflon coated glass fiber filters and by integrating mass distributions measured with the differential mobility analyzer–aerosol particle mass analyzer (DMA–APM) technique (Aero...

  18. An intercomparison study of analytical methods used for quantification of levoglucosan in ambient aerosol filter samples

    NASA Astrophysics Data System (ADS)

    Yttri, K. E.; Schnelle-Kreiss, J.; Maenhaut, W.; Alves, C.; Bossi, R.; Bjerke, A.; Claeys, M.; Dye, C.; Evtyugina, M.; García-Gacio, D.; Gülcin, A.; Hillamo, R.; Hoffer, A.; Hyder, M.; Iinuma, Y.; Jaffrezo, J.-L.; Kasper-Giebl, A.; Kiss, G.; López-Mahia, P. L.; Pio, C.; Piot, C.; Ramirez-Santa-Cruz, C.; Sciare, J.; Teinilä, K.; Vermeylen, R.; Vicente, A.; Zimmermann, R.

    2014-07-01

    The monosaccharide anhydrides (MAs) levoglucosan, galactosan and mannosan are products of incomplete combustion and pyrolysis of cellulose and hemicelluloses, and are found to be major constituents of biomass burning aerosol particles. Hence, ambient aerosol particle concentrations of levoglucosan are commonly used to study the influence of residential wood burning, agricultural waste burning and wild fire emissions on ambient air quality. A European-wide intercomparison on the analysis of the three monosaccharide anhydrides was conducted based on ambient aerosol quartz fiber filter samples collected at a Norwegian urban background site during winter. Thus, the samples' content of MAs is representative for biomass burning particles originating from residential wood burning. The purpose of the intercomparison was to examine the comparability of the great diversity of analytical methods used for analysis of levoglucosan, mannosan and galactosan in ambient aerosol filter samples. Thirteen laboratories participated, of which three applied High-Performance Anion-Exchange Chromatography (HPAEC), four used High-Performance Liquid Chromatography (HPLC) or Ultra-Performance Liquid Chromatography (UPLC), and six resorted to Gas Chromatography (GC). The analytical methods used were of such diversity that they should be considered as thirteen different analytical methods. All of the thirteen laboratories reported levels of levoglucosan, whereas nine reported data for mannosan and/or galactosan. Eight of the thirteen laboratories reported levels for all three isomers. The accuracy for levoglucosan, presented as the mean percentage error (PE) for each participating laboratory, varied from -63 to 23%; however, for 62% of the laboratories the mean PE was within ±10%, and for 85% the mean PE was within ±20%. For mannosan, the corresponding range was -60 to 69%, but as for levoglucosan, the range was substantially smaller for a subselection of the laboratories; i.e., for 33% of

  19. An intercomparison study of analytical methods used for quantification of levoglucosan in ambient aerosol filter samples

    NASA Astrophysics Data System (ADS)

    Yttri, K. E.; Schnelle-Kreis, J.; Maenhaut, W.; Abbaszade, G.; Alves, C.; Bjerke, A.; Bonnier, N.; Bossi, R.; Claeys, M.; Dye, C.; Evtyugina, M.; García-Gacio, D.; Hillamo, R.; Hoffer, A.; Hyder, M.; Iinuma, Y.; Jaffrezo, J.-L.; Kasper-Giebl, A.; Kiss, G.; López-Mahia, P. L.; Pio, C.; Piot, C.; Ramirez-Santa-Cruz, C.; Sciare, J.; Teinilä, K.; Vermeylen, R.; Vicente, A.; Zimmermann, R.

    2015-01-01

    The monosaccharide anhydrides (MAs) levoglucosan, galactosan and mannosan are products of incomplete combustion and pyrolysis of cellulose and hemicelluloses, and are found to be major constituents of biomass burning (BB) aerosol particles. Hence, ambient aerosol particle concentrations of levoglucosan are commonly used to study the influence of residential wood burning, agricultural waste burning and wildfire emissions on ambient air quality. A European-wide intercomparison on the analysis of the three monosaccharide anhydrides was conducted based on ambient aerosol quartz fiber filter samples collected at a Norwegian urban background site during winter. Thus, the samples' content of MAs is representative for BB particles originating from residential wood burning. The purpose of the intercomparison was to examine the comparability of the great diversity of analytical methods used for analysis of levoglucosan, mannosan and galactosan in ambient aerosol filter samples. Thirteen laboratories participated, of which three applied high-performance anion-exchange chromatography (HPAEC), four used high-performance liquid chromatography (HPLC) or ultra-performance liquid chromatography (UPLC) and six resorted to gas chromatography (GC). The analytical methods used were of such diversity that they should be considered as thirteen different analytical methods. All of the thirteen laboratories reported levels of levoglucosan, whereas nine reported data for mannosan and/or galactosan. Eight of the thirteen laboratories reported levels for all three isomers. The accuracy for levoglucosan, presented as the mean percentage error (PE) for each participating laboratory, varied from -63 to 20%; however, for 62% of the laboratories the mean PE was within ±10%, and for 85% the mean PE was within ±20%. For mannosan, the corresponding range was -60 to 69%, but as for levoglucosan, the range was substantially smaller for a subselection of the laboratories; i.e. for 33% of the

  20. Design of Aerosol Particle Coating: Thickness, Texture and Efficiency

    PubMed Central

    Buesser, B.; Pratsinis, S.E.

    2013-01-01

    Core-shell particles preserve the performance (e.g. magnetic, plasmonic or opacifying) of a core material while modifying its surface with a shell that facilitates (e.g. by blocking its reactivity) their incorporation into a host liquid or polymer matrix. Here coating of titania (core) aerosol particles with thin silica shells (films or layers) is investigated at non-isothermal conditions by a trimodal aerosol dynamics model, accounting for SiO2 generation by gas phase and surface oxidation of hexamethyldisiloxane (HMDSO) vapor, coagulation and sintering. After TiO2 particles have reached their final primary particle size (e.g. upon completion of sintering during their flame synthesis), coating starts by uniformly mixing them with HMDSO vapor that is oxidized either in the gas phase or on the particles’ surface resulting in SiO2 aerosols or deposits, respectively. Sintering of SiO2 deposited onto the core TiO2 particles takes place transforming rough into smooth coating shells depending on process conditions. The core-shell characteristics (thickness, texture and efficiency) are calculated for two limiting cases of coating shells: perfectly smooth (e.g. hermetic) and fractal-like. At constant TiO2 core particle production rate, the influence of coating weight fraction, surface oxidation and core particle size on coating shell characteristics is investigated and compared to pertinent experimental data through coating diagrams. With an optimal temperature profile for complete precursor conversion, the TiO2 aerosol and SiO2-precursor (HMDSO) vapor concentrations have the strongest influence on product coating shell characteristics. PMID:23729833

  1. Efficiency tests of samplers for microbiological aerosols, a review

    NASA Technical Reports Server (NTRS)

    Henningson, E.; Faengmark, I.

    1984-01-01

    To obtain comparable results from studies using a variety of samplers of microbiological aerosols with different collection performances for various particle sizes, methods reported in the literature were surveyed, evaluated, and tabulated for testing the efficiency of the samplers. It is concluded that these samplers were not thoroughly tested, using reliable methods. Tests were conducted in static air chambers and in various outdoor and work environments. Results are not reliable as it is difficult to achieve stable and reproducible conditions in these test systems. Testing in a wind tunnel is recommended.

  2. High efficiency, down flow air filter sealing and support system

    SciTech Connect

    Mattison, A.H.

    1986-07-15

    An assembly of high efficiency air filter units through which essentially all air entering a clean space below the units must pass to remove particulate matter down to sub-micron size from the air, the assembly comprising: (a) a plurality of air filter units each having a filter core of pleated media sealed in air-tight engagement on four sides to a surrounding, box-like, rigid frame, having side and end members; (b) means for supporting the filter units adjacent the upper surfaces thereof from structure above the space with adjacent units having the side and end members thereof providing adjoining vertical surfaces in closely spaced relation with the lower surfaces of the units in essentially the same horizontal plane to form at least a portion of the top of the space; and (c) a caulking material filling all spaces between the adjoining vertical surfaces of adjacent filter units, effectively sealing the spaces and providing the sole means preventing passage of air around the units.

  3. An Efficient Conflict Detection Algorithm for Packet Filters

    NASA Astrophysics Data System (ADS)

    Lee, Chun-Liang; Lin, Guan-Yu; Chen, Yaw-Chung

    Packet classification is essential for supporting advanced network services such as firewalls, quality-of-service (QoS), virtual private networks (VPN), and policy-based routing. The rules that routers use to classify packets are called packet filters. If two or more filters overlap, a conflict occurs and leads to ambiguity in packet classification. This study proposes an algorithm that can efficiently detect and resolve filter conflicts using tuple based search. The time complexity of the proposed algorithm is O(nW+s), and the space complexity is O(nW), where n is the number of filters, W is the number of bits in a header field, and s is the number of conflicts. This study uses the synthetic filter databases generated by ClassBench to evaluate the proposed algorithm. Simulation results show that the proposed algorithm can achieve better performance than existing conflict detection algorithms both in time and space, particularly for databases with large numbers of conflicts.

  4. Eigenvector spatial filtering for image analysis: An efficient algorithm

    NASA Astrophysics Data System (ADS)

    Rura, Melissa J.

    Eigenvector Spatial Filtering (ESF) is an established method in social science literature for incorporating spatial information in model specifications. ESF computes spatial eigenvectors, which are defined by the spatial structure associated with a variable. One important limitation of this technique is that it becomes computationally intensive in image analysis because of the massive number of image pixels. This research develops an algorithm, which makes ESF more efficient, by using the analytical solution for the eigenvalues and spatial eigenvectors, which are essentially a series of orthogonal, uncorrelated map patterns that describe positively spatial autocorrelated patterns through negatively spatially autocorrelated patterns, and global, regional, and local patterns of spatial dependencies in a surface. A reformulation of the analytical solution reduces the required computations and allows the eigenvectors to be computed sequentially. Finally, a series of sampling methods are explored. This algorithm is applied to three example multispectral images of different sizes: small (i.e., ˜200,000 pixels), medium (i.e., ˜1,000,000 pixels) and large (i.e., ˜110,000,000 pixels) and is evaluated in terms of output for each sampling technique and the complete spectral information. The output spatial filters of these sampling techniques compare to the filter generated with the complete spectral information. In terms of efficiency evaluation, the time is required to construct filters through sampling versus through analysis of the complete image surface is evaluated and the complexity of set-up and execution of the sampled and distributed algorithms are assessed.

  5. Aerosol microphysical retrievals from precision filter radiometer direct solar radiation measurements and comparison with AERONET

    NASA Astrophysics Data System (ADS)

    Kazadzis, S.; Veselovskii, I.; Amiridis, V.; Gröbner, J.; Suvorina, A.; Nyeki, S.; Gerasopoulos, E.; Kouremeti, N.; Taylor, M.; Tsekeri, A.; Wehrli, C.

    2014-07-01

    Synchronized sun-photometric measurements from the AERONET-CIMEL (AErosol RObotic NETwork) and GAW-PFR (Global Atmospheric Watch-Precision Filter Radiometer) aerosol networks are used to compare retrievals of the aerosol optical depth (AOD), effective radius, and volume concentration during a high-temporal-resolution measurement campaign at the Athens site in the Mediterranean Basin from 14 to 22 July 2009. During this period, direct-sun AOD retrievals from both instruments exhibited small differences in the range 0.01-0.02. The AODs measured with CIMEL and PFR instruments were inverted to retrieve particle microphysical properties using the linear estimation (LE) technique. For low aerosol loads (AOD < 0.2), measurements of the effective radius by the PFR were found to be -20% to +30% different from CIMEL values for both direct-sun data and inversion data. At higher loads (AOD > 0.4), measurements of the effective radius by the PFR are consistently 20 % lower than CIMEL for both direct-sun and inversion data. Volume concentrations at low aerosol loads from the PFR are up to 80% higher than the CIMEL for direct-sun data but are up to 20% lower when derived from inversion data under these same conditions. At higher loads, the percentage difference in volume concentrations from the PFR and CIMEL is systematically negative, with inversion data predicting differences 30% lower than those obtained from direct-sun data. An assessment of the effect of errors in the AOD retrieval on the estimation of PFR bulk parameters was performed and demonstrates that it is possible to estimate the particle volume concentration and effective radius with an uncertainty < 65% when AOD < 0.2 and when input errors are as high as 10%.

  6. ATI TDA 5A aerosol generator evaluation

    SciTech Connect

    Gilles, D.A.

    1998-07-27

    Oil based aerosol ``Smoke`` commonly used for testing the efficiency and penetration of High Efficiency Particulate Air filters (HEPA) and HEPA systems can produce flammability hazards that may not have been previously considered. A combustion incident involving an aerosol generator has caused an investigation into the hazards of the aerosol used to test HEPA systems at Hanford.

  7. Dust Aerosol Analysis and Prediction with Lidar Observations and Ensemble Kalman Filter

    NASA Astrophysics Data System (ADS)

    Sekiyama, T. T.; Tanaka, T. Y.; Shimizu, A.; Miyoshi, T.

    2010-12-01

    We have developed a state-of-the-art data assimilation system for a global aerosol model with a four dimensional Ensemble Kalman Filter (4D-EnKF) in which Lidar observations, i.e., attenuated backscattering coefficient, depolarization ratio, and extinction coefficient, were successfully assimilated. The concentrations of dust, sulfate, and seasalt aerosols as well as the dust surface emission intensity were treated as control variables in this data assimilation system. The Lidar observations were obtained from the Level 1B dataset of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) or the dataset of the East Asian ground-based Lidar network operated by the National Institute for Environmental Studies of Japan (NIES). With the use of these Lidar observations and 4D-EnKF system, aerosol data assimilation and prediction experiments were globally performed in the spring (March - May) of 2007. In this paper, we especially focus on the analysis and prediction of Asian dust which is a seasonal meteorological phenomenon sporadically affecting East Asian countries during the springtime. The analysis and prediction results derived from satellite and ground-based observations were compared with each other, and validated by independent observations: 1) aerosol optical depth measured by the Moderate Resolution Imaging Spectro-radiometer (MODIS) over East Asia, and 2) weather reports on aeolian dust events in East Asia derived from the World Meteorological Organization (WMO) Surface Synoptic Observations (SYNOP). Forecast scores were estimated by phenomenal discrimination (i.e. hit or not) using the SYNOP weather reports and a threshold of modeled dust surface concentration, for example, 100 micrograms/m3. Detailed four-dimensional structures of dust outflows from source regions, such as Taklimakan or Gobi desert, to the Pacific Ocean over the Korean Peninsula or the Japanese Archipelago were well reproduced by this data assimilation system. The

  8. Aerosol transport and deposition efficiency in the respiratory airways

    NASA Astrophysics Data System (ADS)

    Nicolaou, Laura; Zaki, Tamer

    2015-11-01

    Prediction of aerosol deposition in the respiratory system is important for improving the efficiency of inhaled drug delivery and for assessing the toxicity of airborne pollutants. Particle deposition in the airways is typically described as a function of the Stokes number based on a reference flow timescale. This choice leads to significant scatter in deposition data since the velocity and length scales experienced by the particles as they are advected through the flow deviate considerably from the reference values in many sections of the airways. Therefore, the use of an instantaneous Stokes number based on the local properties of the flow field is proposed instead. We define the effective Stokes number as the time-average of the instantaneous value. Our results demonstrate that this average, or effective, Stokes number can deviate significantly from the reference value particularly in the intermediate Stokes number range. In addition, the effective Stokes number shows a very clear correlation with deposition efficiency, and is therefore a more appropriate parameter to describe aerosol transport.

  9. Criteria for calculating the efficiency of HEPA filters during and after design basis accidents

    SciTech Connect

    Bergman, W.; First, M.W.; Anderson, W.L.; Gilbert, H.; Jacox, J.W.

    1994-12-01

    We have reviewed the literature on the performance of high efficiency particulate air (HEPA) filters under normal and abnormal conditions to establish criteria for calculating the efficiency of HEPA filters in a DOE nonreactor nuclear facility during and after a Design Basis Accident (DBA). The literature review included the performance of new filters and parameters that may cause deterioration in the filter performance such as filter age, radiation, corrosive chemicals, seismic and rough handling, high temperature, moisture, particle clogging, high air flow and pressure pulses. The deterioration of the filter efficiency depends on the exposure parameters; in severe exposure conditions the filter will be structurally damaged and have a residual efficiency of 0%. Despite the many studies on HEPA filter performance under adverse conditions, there are large gaps and limitations in the data that introduce significant error in the estimates of HEPA filter efficiencies under DBA conditions. Because of this limitation, conservative values of filter efficiency were chosen when there was insufficient data.

  10. Best Practice for Energy Efficient Cleanrooms: Fan-FilterUnits

    SciTech Connect

    Xu, Tengfang

    2005-06-15

    The HVAC systems in cleanrooms may use 50 percent or more of the total cleanroom energy use. Fan energy use accounts for a significant portion (e.g., over 50%) of the HVAC energy use in cleanrooms such as ISO Classes 3, 4, or 5. Three types of air-handling systems for recirculating airflows are commonly used in cleanrooms: (1) fan-tower systems with pressurized plenum, (2) ducted HEPA systems with distributed-fans, and (3) systems with fan-filter units. Because energy efficiency of the recirculation systems could vary significantly from system type to system type, optimizing aerodynamic performance in air recirculation systems appears to be a useful approach to improve energy efficiency in cleanrooms. Providing optimal airflows through careful planning, design and operation, including air change rate, airflow uniformity, and airflow speed, is important for controlling particle contamination in cleanrooms. In practice, the use of fan-filter units (FFUs) in the air-handling system is becoming more and more popular because of this type of system may offer a number of advantages. Often modular and portable than traditional recirculation airflow systems, FFUs are easier to install, and can be easily controlled and monitored to maintain filtration performance. Energy efficiency of air handling systems using fan-filter units can, however, be lower than their counterparts and may vary significantly from system to system because of the difference in energy performance, airflow paths, and the operating conditions of FFUs.

  11. An automated baseline correction protocol for infrared spectra of atmospheric aerosols collected on polytetrafluoroethylene (Teflon) filters

    NASA Astrophysics Data System (ADS)

    Kuzmiakova, Adele; Dillner, Ann M.; Takahama, Satoshi

    2016-06-01

    A growing body of research on statistical applications for characterization of atmospheric aerosol Fourier transform infrared (FT-IR) samples collected on polytetrafluoroethylene (PTFE) filters (e.g., Russell et al., 2011; Ruthenburg et al., 2014) and a rising interest in analyzing FT-IR samples collected by air quality monitoring networks call for an automated PTFE baseline correction solution. The existing polynomial technique (Takahama et al., 2013) is not scalable to a project with a large number of aerosol samples because it contains many parameters and requires expert intervention. Therefore, the question of how to develop an automated method for baseline correcting hundreds to thousands of ambient aerosol spectra given the variability in both environmental mixture composition and PTFE baselines remains. This study approaches the question by detailing the statistical protocol, which allows for the precise definition of analyte and background subregions, applies nonparametric smoothing splines to reproduce sample-specific PTFE variations, and integrates performance metrics from atmospheric aerosol and blank samples alike in the smoothing parameter selection. Referencing 794 atmospheric aerosol samples from seven Interagency Monitoring of PROtected Visual Environment (IMPROVE) sites collected during 2011, we start by identifying key FT-IR signal characteristics, such as non-negative absorbance or analyte segment transformation, to capture sample-specific transitions between background and analyte. While referring to qualitative properties of PTFE background, the goal of smoothing splines interpolation is to learn the baseline structure in the background region to predict the baseline structure in the analyte region. We then validate the model by comparing smoothing splines baseline-corrected spectra with uncorrected and polynomial baseline (PB)-corrected equivalents via three statistical applications: (1) clustering analysis, (2) functional group quantification

  12. Thermodesorption of aerosol matter on multiple filters of different materials for a more detailed evaluation of sampling artifacts

    NASA Astrophysics Data System (ADS)

    Wittmaack, Klaus; Keck, Lothar

    2004-10-01

    Multiple, essentially identical samples of PM2.5, PM10 and TSP aerosol matter were collected on filters of cellulose acetate-nitrate membrane (CA), quartz fiber (QF) and glass fiber (GF) material. The samples were analyzed in terms of the gravimetric mass and the mass of nine inorganic ions. These parameters were also measured after step-wise thermodesorption of aerosol matter by 1-h heating in ambient air up to 350 °C. The observed thermograms of the analyzed ions were compared with results obtained using pure and mixed salts on filter. In summer the apparent mass concentration of aerosol matter collected on CA was always larger than on QF and GF filter. The excess mass on CA was found to be highly volatile, i.e. completely removable at 120 °C, and composed of both ionic and non-ionic matter. The apparent nitrate concentration sampled on QF and GF was almost an order of magnitude lower than on CA. The very pronounced nitrate losses from the fiber filters are attributed to volatilization of ammonium nitrate. In contrast, nitrate losses from CA were small or even negligible for two reasons, pile-up of aerosol matter predominantly on (rather than in) the filter ("cake" formation) and, more importantly, re-adsorption of volatilized ammonia and nitric acid in the filter. Sampling on GF filters was found to suffer from severe problems due to chemical reactions between Na+ of the glass and SO42- of the aerosol matter. A novel type of artifact was observed in sampling campaigns during fall. Presumably as a results of a high water content, the collected aerosol matter became liquefied and a large fraction of the water soluble components was driven through the filter into the support pad underneath. The negative "wetting artifact" was much more pronounced for the thin CA than for the relatively thick QF filters. The total amount of aerosol matter in the CA/pad and QF/pad combinations was the same, indicating that this kind of artifact can be corrected for. Ammonium

  13. Efficient selective filtering of seismic data using multiscale decomposition

    NASA Astrophysics Data System (ADS)

    Leite, F. E. A.; Henriques, M. V. C.; Gurgel, V. C.; Filho, J. M. S.

    2013-03-01

    Seismic signal processing is an important task in geophysics sounding and represents a permanent challenge in petroleum exploration. Although seismograms could in principle give us a picture of a geological structure, they are very contaminated by spurious signals and the ground roll noise is a strongly undesired signal present in the seismograms - it does not carry physical information about the deep geological structures. This fact demands a big effort in developing new filtering methodologies. Using discrete wavelet transform, an efficient filtering for suppression of the ground roll is presented. In this method, seismic data is decomposed in multiple scales. We can remove the noise as a surgical operation in each scale, just from the regions where they are present or strong, allowing us to preserve the maximum of relevant information.

  14. A quantitative assessment of the total inward leakage of NaCl aerosol representing submicron-size bioaerosol through N95 filtering facepiece respirators and surgical masks.

    PubMed

    Rengasamy, Samy; Eimer, Benjamin C; Szalajda, Jonathan

    2014-01-01

    Respiratory protection provided by a particulate respirator is a function of particle penetration through filter media and through faceseal leakage. Faceseal leakage largely contributes to the penetration of particles through a respirator and compromises protection. When faceseal leaks arise, filter penetration is assumed to be negligible. The contribution of filter penetration and faceseal leakage to total inward leakage (TIL) of submicron-size bioaerosols is not well studied. To address this issue, TIL values for two N95 filtering facepiece respirator (FFR) models and two surgical mask (SM) models sealed to a manikin were measured at 8 L and 40 L breathing minute volumes with different artificial leak sizes. TIL values for different size (20-800 nm, electrical mobility diameter) NaCl particles representing submicron-size bioaerosols were measured using a scanning mobility particle sizer. Efficiency of filtering devices was assessed by measuring the penetration against NaCl aerosol similar to the method used for NIOSH particulate filter certification. Results showed that the most penetrating particle size (MPPS) was ∼45 nm for both N95 FFR models and one of the two SM models, and ∼350 nm for the other SM model at sealed condition with no leaks as well as with different leak sizes. TIL values increased with increasing leak sizes and breathing minute volumes. Relatively, higher efficiency N95 and SM models showed lower TIL values. Filter efficiency of FFRs and SMs influenced the TIL at different flow rates and leak sizes. Overall, the data indicate that good fitting higher-efficiency FFRs may offer higher protection against submicron-size bioaerosols. PMID:24275016

  15. FRACTIONAL AEROSOL FILTRATION EFFICIENCY OF IN-DUCT VENTILATION AIR CLEANERS

    EPA Science Inventory

    The filtration efficiency of ventilation air cleaners is highly particle-size dependent over the 0.01 to 3 μm diameter size range. Current standardized test methods, which determine only overall efficiencies for ambient aerosol or other test aerosols, provide data of limited util...

  16. A New Electrospray Aerosol Generator with High Particle Transmission Efficiency

    PubMed Central

    Fu, Huijing; Patel, Anand C.; Holtzman, Michael J.; Chen, Da-Ren

    2012-01-01

    A new single-capillary electrospray (ES) aerosol generator has been developed for monodisperse particle production with maximal transmission efficiency. The new generator consists of both a spray chamber in a point-to-orifice-plate configuration and a charge reduction chamber that can hold up to 4 Nuclespot ionizers (Model P-2042, NRD Inc.). The 2 chambers are partitioned by an orifice plate. To optimize the particle transmission efficiency of the prototype, a systematic study was performed on the generator by varying the system setup and operation. Two key dimensions of the generator setup, the orifice diameter and the distance from the capillary tip to the orifice plate, were varied. Fluorescence analysis was applied to characterize the loss of ES-generated particles at different locations of the prototype. It was found that particle loss in the generator could be reduced by either increasing the orifice diameter or decreasing the distance between the capillary tip and the orifice plate. Increasing either the total radioactivity of the ionizers or the flowrate of the particle carrier gas also further decreased the particle loss in the system. The maximum particle transmission efficiency of 88.0% was obtained with the spray chamber fully opened to the charge reduction chamber, the capillary tip at the same level as the orifice plate, and 4 bipolar ionizers installed. PMID:22829715

  17. A New Electrospray Aerosol Generator with High Particle Transmission Efficiency.

    PubMed

    Fu, Huijing; Patel, Anand C; Holtzman, Michael J; Chen, Da-Ren

    2011-01-01

    A new single-capillary electrospray (ES) aerosol generator has been developed for monodisperse particle production with maximal transmission efficiency. The new generator consists of both a spray chamber in a point-to-orifice-plate configuration and a charge reduction chamber that can hold up to 4 Nuclespot ionizers (Model P-2042, NRD Inc.). The 2 chambers are partitioned by an orifice plate. To optimize the particle transmission efficiency of the prototype, a systematic study was performed on the generator by varying the system setup and operation. Two key dimensions of the generator setup, the orifice diameter and the distance from the capillary tip to the orifice plate, were varied. Fluorescence analysis was applied to characterize the loss of ES-generated particles at different locations of the prototype. It was found that particle loss in the generator could be reduced by either increasing the orifice diameter or decreasing the distance between the capillary tip and the orifice plate. Increasing either the total radioactivity of the ionizers or the flowrate of the particle carrier gas also further decreased the particle loss in the system. The maximum particle transmission efficiency of 88.0% was obtained with the spray chamber fully opened to the charge reduction chamber, the capillary tip at the same level as the orifice plate, and 4 bipolar ionizers installed. PMID:22829715

  18. A Computationally Efficient Multicomponent Equilibrium Solver for Aerosols (MESA)

    SciTech Connect

    Zaveri, Rahul A.; Easter, Richard C.; Peters, Len K.

    2005-12-23

    deliquescence points as well as mass growth factors for the sulfate-rich systems. The MESA-MTEM configuration required only 5 to 10 single-level iterations to obtain the equilibrium solution for ~44% of the 328 multiphase problems solved in the 16 test cases at RH values ranging between 20% and 90%, while ~85% of the problems solved required less than 20 iterations. Based on the accuracy and computational efficiency considerations, the MESA-MTEM configuration is attractive for use in 3-D aerosol/air quality models.

  19. EFFECT OF LOADING DUST TYPE ON THE FILTRATION EFFICIENCY OF ELECTROSTATICALLY CHARGED FILTERS

    EPA Science Inventory

    The paper gives results of an evaluation of the effect of loading dust type on the filtration efficiency of electrostatically charged filters. Three types of filters were evaluated: a rigid-cell filter charged using an electrodynamic spinning process, a pleated-panel filter cha...

  20. Evaluation of a high-efficiency, filter-bank system.

    PubMed

    Martin, Stephen B; Beamer, Bryan R; Moyer, Ernest S

    2006-04-01

    National Institute for Occupational Safety and Health (NIOSH) investigators evaluated filtration efficiencies at three U.S. Postal Service (USPS) facilities. Ventilation and filtration systems (VFSs) had been installed after the 2001 bioterrorist attacks when the USPS unknowingly processed letters laden with B. anthracis spores. The new VFS units included high-efficiency particulate air (HEPA) filters and were required by USPS contract specifications to provide an overall filtration efficiency of at least 99.97% for particles between 0.3 microm and 3.0 micro m. The USPS evaluation involved a modification of methodology used to test total filtration system efficiency in agricultural tractor cab enclosures. The modified sampling strategy not only proved effective for monitoring the total filtration system component of VFS performance but also distinguished between filtration systems performing to the high USPS performance criteria and those needing repair or replacement. The results clearly showed the importance of choosing a pair of optical particle counters that have been closely matched immediately prior to testing. The modified methodology is readily adaptable to any workplace wishing to evaluate air filtration systems, including high-efficiency systems. PMID:16531293

  1. High-efficiency spectral purity filter for EUV lithography

    DOEpatents

    Chapman, Henry N.

    2006-05-23

    An asymmetric-cut multilayer diffracts EUV light. A multilayer cut at an angle has the same properties as a blazed grating, and has been demonstrated to have near-perfect performance. Instead of having to nano-fabricate a grating structure with imperfections no greater than several tens of nanometers, a thick multilayer is grown on a substrate and then cut at an inclined angle using coarse and inexpensive methods. Effective grating periods can be produced this way that are 10 to 100 times smaller than those produced today, and the diffraction efficiency of these asymmetric multilayers is higher than conventional gratings. Besides their ease of manufacture, the use of an asymmetric multilayer as a spectral purity filter does not require that the design of an EUV optical system be modified in any way, unlike the proposed use of blazed gratings for such systems.

  2. A simple method for estimation of coagulation efficiency in mixed aerosols. [environmental pollution control

    NASA Technical Reports Server (NTRS)

    Dimmick, R. L.; Boyd, A.; Wolochow, H.

    1975-01-01

    Aerosols of KBr and AgNO3 were mixed, exposed to light in a glass tube and collected in the dark. About 15% of the collected material was reduced to silver upon development. Thus, two aerosols of particles that react to form a photo-reducible compound can be used to measure coagulation efficiency.

  3. Phase I characterization of the HEPA (High Efficiency Particulate Air) filter media used in the airborne activity confinement system at the Savannah River Site

    SciTech Connect

    Novick, V.J.; Higgins, P.J. )

    1989-01-01

    The purpose of this report was to characterize the HEPA filter media material. This work consisted of two major tasks. First, the pressure drop characteristics of the HEPA filter material were measured as a function of the aerosol mass loading. Particle size effects were studied by using three different particle size distributions to load the filter material. The second task was to determine the filtration efficiency spectrum for solid particles as a function of particle diameter. The filtration efficiency was measured at two different media velocities, one corresponding to the equivalent flow rate under normal operating conditions, the other corresponding to the minimum equivalent flow rate expected through the filter compartments. These tests were conducted at the Argonne National Laboratory between September 1988 and February 1989. 20 refs., 31 figs., 10 tabs.

  4. Evaluating the use of PAO (4 cSt polyalphaoelfin) oil instead of DOP (di-octyl phthalate) oil for measuring the aerosol capture of nuclear canister filters

    SciTech Connect

    Moore, Murray E.

    2014-07-18

    This document details the distinction between using PAO (4 cSt polyalphaoelfin) oil instead of DOP (di-octyl phthalate) oil for measuring the aerosol capture of filters. This document is developed to justify the use of PAO rather than DOP for evaluating the performance of filters in the SAVY 4000 and Hagan containers. The design criteria (Anderson et al, 2012) for purchasing SAVY 4000 containers and the Safety Analysis Report for the SAVY 4000 Container Series specified that the filter must “capture greater than 99.97% of 0.45 μm mean diameter dioctyl phthalate (DOP) aerosol at the rated flow with a DOP concentration of 65±15 micrograms per liter.”This corresponds to a leakage percent of 0.03% (3.0x10-2). The density of DOP oil is 985 kg/m3 and the density of PAO oil is 819 kg/m3. ATI Test Inc measured the mass mean diameter of aerosol distributions produced by a single Laskin type III-A nozzle operating at a 20 psig air pressure as 0.563 μm for DOP oil and 0.549 μm for PAO oil. (See Appendix A.) For both types of oil in this document, the single fiber method calculated the leakage percent to be 4.4x10-5 for DOP oil and 4.7x10-5 for PAO oil. Although the percent error between these two quantities is 7.7%, these calculated leakage percent values are more than two orders of magnitude less than the criterion specified in the SAVY canister SAR. As a point of reference, the photometer used to measure the SAVY canister filter performance cannot resolve values for the leakage percent below 1.0x10-5. Additionally, over a range of particle sizes from 0.01 μm to 3.0 μm, there was less than 4.0x10-5 error between the calculated filter efficiency for the two types of oil at any particular particle size diameter. In conclusion, the difference between using DOP and PAO for testing SAVY canister filters is of inconsequential concern.

  5. High-Efficiency Generation and Delivery of Aerosols Through Nasal Cannula During Noninvasive Ventilation

    PubMed Central

    Walenga, Ross L.; Son, Yoen-Ju; Hindle, Michael

    2013-01-01

    Abstract Background Previous studies have demonstrated the delivery of pharmaceutical aerosols through nasal cannula and the feasibility of enhanced condensational growth (ECG) with a nasal interface. The objectives of this study were to develop a device for generating submicrometer aerosols with minimal depositional loss in the formation process and to improve aerosol delivery efficiencies through nasal cannulas. Methods A combination of in vitro experiments and computational fluid dynamics (CFD) simulations that used the strengths of each method was applied. Aerosols were formed using a conventional mesh nebulizer, mixed with ventilation gas, and heated to produce submicrometer sizes. An improved version of the mixer and heater unit was developed based on CFD simulations, and performance was verified with experiments. Aerosol delivery was considered through a commercial large-bore adult cannula, a divided (D) design for use with ECG, and a divided and streamlined (DS) design. Results The improved mixer design reduced the total deposition fraction (DF) of drug within the mixer by a factor of 3 compared with an initial version, had a total DF of approximately 10%, and produced submicrometer aerosols at flow rates of 10 and 15 L/min. Compared with the commercial and D designs for submicrometer aerosols, the DS cannula reduced depositional losses by a factor of 2–3 and retained only approximately 5% or less of the nebulized dose at all flow rates considered. For conventional-sized aerosols (3.9 and 4.7 μm), the DS device provided delivery efficiencies of approximately 80% and above at flow rates of 2–15 L/min. Conclusions Submicrometer aerosols can be formed using a conventional mesh nebulizer and delivered through a nasal cannula with total delivery efficiencies of 80–90%. Streamlining the nasal cannula significantly improved the delivery efficiency of both submicrometer and micrometer aerosols; however, use of submicrometer particles with ECG delivery

  6. Total Optical Depth Analysis for NO2, O3 and Aerosols by a Multi-Filter Shadowband Radiometer

    NASA Technical Reports Server (NTRS)

    Williamson, Lorenzo; Mebane, Lloyd; Brathwaite, Kevin; Craig, R.

    2000-01-01

    The main focus of this research is the retrieval of tropospheric aerosol information using a Multi-filter Rotating Shadowband Radiometer, Model MFR-7, placed on the roof of the Science Building at Medgar Evers College. This instrument makes precise measurements of atmospheric extinction of the direct solar beam simultaneously at six wavelengths (475, 500, 615, 670, 840 and 940 nm) at one minute intervals throughout the day. We are interested in measuring the changes in the optical depth of ambient aerosols, mass, effective particle size, aerosol size distribution, and chemical composition of ambient particulate matter in the Greater New York City Area. Results will be compared with data obtained by A. Lacis, B. Carlson and B. Cairns at the NASA Goddard Institute for Space Studies.

  7. Thrombus-trapping efficiency of the LGM (Vena Tech) and titanium Greenfield filters in vivo.

    PubMed

    Millward, S F; Marsh, J I; Pon, C; Moher, D

    1992-02-01

    To assess the trapping efficiency of two vena cava filters, 326 radiopaque thrombi 5 mm in diameter were injected into adult sheep: four with LG-Medical (LGM) and four with titanium Greenfield (TG) filters. Thrombi were sequentially injected and not removed. Trapping was monitored fluoroscopically, and the pressure gradient across the filter was measured. The LGM filter trapped 70% of 5 x 5-mm and 100% of 5 x 10-mm thrombi; the TG, 26% of 5 x 5-mm, 34% of 5 x 10-mm, and 37% of 5 x 30-mm thrombi. The LGM filter required an average of 2.0 mL of trapped thrombus to occlude the filter, compared with 6.4 mL for the TG. These differences were statistically significant. These data indicate that in this model, the LGM filter traps thrombi more efficiently than the TG filter but is more likely to produce caval occlusion. PMID:1540709

  8. Water-resistant cellulosic filter for aerosol entrapment and water purification, Part I: production of water-resistant cellulosic filter.

    PubMed

    Heydarifard, Solmaz; Nazhad, Mousa M; Xiao, Huining; Shipin, Oleg; Olson, James

    2016-07-01

    Synthetic filters are neither biodegradable nor produced from renewable sources. Thus, their disposal has serious environmental impacts. There is a growing desire to produce filters from cellulosic fibers that are renewable, biodegradable, cheap and most importantly recyclable if the contamination is removed. Foam-laid process in papermaking is a promising process for the production of specialty papers. Filters produced using this process are capable of providing products with high specific surface area and tortuous structure favorable for entrapping particulate matters, while providing excellent permeability for incoming gas or liquid. Although the end product fulfills completely the requirement of a filter in a dry environment, it fails completely if it is exposed to a moist environment. This work reports on converting the hydrophilic cellulosic filter into a hydrophobic product without disturbing its original structure. PMID:26683534

  9. Depth Filters Containing Diatomite Achieve More Efficient Particle Retention than Filters Solely Containing Cellulose Fibers

    PubMed Central

    Buyel, Johannes F.; Gruchow, Hannah M.; Fischer, Rainer

    2015-01-01

    The clarification of biological feed stocks during the production of biopharmaceutical proteins is challenging when large quantities of particles must be removed, e.g., when processing crude plant extracts. Single-use depth filters are often preferred for clarification because they are simple to integrate and have a good safety profile. However, the combination of filter layers must be optimized in terms of nominal retention ratings to account for the unique particle size distribution in each feed stock. We have recently shown that predictive models can facilitate filter screening and the selection of appropriate filter layers. Here we expand our previous study by testing several filters with different retention ratings. The filters typically contain diatomite to facilitate the removal of fine particles. However, diatomite can interfere with the recovery of large biopharmaceutical molecules such as virus-like particles and aggregated proteins. Therefore, we also tested filtration devices composed solely of cellulose fibers and cohesive resin. The capacities of both filter types varied from 10 to 50 L m−2 when challenged with tobacco leaf extracts, but the filtrate turbidity was ~500-fold lower (~3.5 NTU) when diatomite filters were used. We also tested pre–coat filtration with dispersed diatomite, which achieved capacities of up to 120 L m−2 with turbidities of ~100 NTU using bulk plant extracts, and in contrast to the other depth filters did not require an upstream bag filter. Single pre-coat filtration devices can thus replace combinations of bag and depth filters to simplify the processing of plant extracts, potentially saving on time, labor and consumables. The protein concentrations of TSP, DsRed and antibody 2G12 were not affected by pre-coat filtration, indicating its general applicability during the manufacture of plant-derived biopharmaceutical proteins. PMID:26734037

  10. Regional Influence of Aerosol Emissions from Wildfires Driven by Combustion Efficiency: Insights from the BBOP Campaign.

    PubMed

    Collier, Sonya; Zhou, Shan; Onasch, Timothy B; Jaffe, Daniel A; Kleinman, Lawrence; Sedlacek, Arthur J; Briggs, Nicole L; Hee, Jonathan; Fortner, Edward; Shilling, John E; Worsnop, Douglas; Yokelson, Robert J; Parworth, Caroline; Ge, Xinlei; Xu, Jianzhong; Butterfield, Zachary; Chand, Duli; Dubey, Manvendra K; Pekour, Mikhail S; Springston, Stephen; Zhang, Qi

    2016-08-16

    Wildfires are important contributors to atmospheric aerosols and a large source of emissions that impact regional air quality and global climate. In this study, the regional and nearfield influences of wildfire emissions on ambient aerosol concentration and chemical properties in the Pacific Northwest region of the United States were studied using real-time measurements from a fixed ground site located in Central Oregon at the Mt. Bachelor Observatory (∼2700 m a.s.l.) as well as near their sources using an aircraft. The regional characteristics of biomass burning aerosols were found to depend strongly on the modified combustion efficiency (MCE), an index of the combustion processes of a fire. Organic aerosol emissions had negative correlations with MCE, whereas the oxidation state of organic aerosol increased with MCE and plume aging. The relationships between the aerosol properties and MCE were consistent between fresh emissions (∼1 h old) and emissions sampled after atmospheric transport (6-45 h), suggesting that biomass burning organic aerosol concentration and chemical properties were strongly influenced by combustion processes at the source and conserved to a significant extent during regional transport. These results suggest that MCE can be a useful metric for describing aerosol properties of wildfire emissions and their impacts on regional air quality and global climate. PMID:27398804

  11. Experimental Assessment of Collection Efficiency of Submicron Aerosol Particles by Cloud Droplets

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Ardon-Dryer, K.; Cziczo, D. J.

    2013-12-01

    The interplay between aerosol particles and water droplets in the atmosphere, especially in clouds, influences both aerosol and cloud properties. The major uncertainty in our understanding of climate arises in the indirect effect of aerosol and their ability to impact cloud formation and consequently alter the global radiative balance. The collision between a water droplet and aerosol particles that results in coalescence is termed 'collection' or 'coagulation'. Coagulation can lead to aerosol removal from the atmosphere or induce ice nucleation via contact freezing at temperatures below 0 C. Theoretical studies have shown that for aerosol particles smaller than 0.1 micrometers, Brownian motion is important, and for particles with diameters larger than 1 micrometer, inertial force dominates. There is a collection efficiency minimum for particles between 0.1-2 micrometers, called the 'Greenfield Gap'. Experimental efforts, however, have been limited to very large drizzle and rain drops until recently, and constrained parameters necessary to describe particle collection efficiency by cloud droplets have not been available. One reason is that laboratory setups that allow for coagulation to be observed on a single-particle basis have been lacking. Collection efficiency is also an important parameter for studying and assessing contact ice nucleation. Contact ice nucleation is currently the least understood ice nucleation mechanism and can be potentially important for mixed-phase cloud formation. The significance of experimentally assessing collection efficiency is therefore two-fold: to first understand the frequency of contacts and to then understand the fraction that lead to ice nucleation. We have constructed the MIT-Contact Freezing Chamber (MIT-CFC) to study collection efficiency of submicron aerosol particles by cloud droplets and contact freezing. A stream of 30-micron cloud droplets fall freely into the chamber and collide with aerosol particles. The outflow

  12. Culturability of Bacillus spores on aerosol collection filters exposed to airborne combustion products of Al, Mg, and B·Ti.

    PubMed

    Adhikari, Atin; Yermakov, Michael; Indugula, Reshmi; Reponen, Tiina; Driks, Adam; Grinshpun, Sergey A

    2016-05-01

    Destruction of bioweapon facilities due to explosion or fire could aerosolize highly pathogenic microorganisms. The post-event air quality assessment is conducted through air sampling. A bioaerosol sample (often collected on a filter for further culture-based analysis) also contains combustion products, which may influence the microbial culturability and, thus, impact the outcome. We have examined the interaction between spores deposited on collection filters using two simulants of Bacillus anthracis [B. thuringiensis (Bt) and B. atrophaeus (referred to as BG)] and incoming combustion products of Al as well as Mg and B·Ti (common ingredient of metalized explosives). Spores extracted from Teflon, polycarbonate, mixed cellulose ester (MCE), and gelatin filters (most common filter media for bioaerosol sampling), which were exposed to combustion products during a short-term sampling, were analyzed by cultivation. Surprisingly, we observed that aluminum combustion products enhanced the culturability of Bt (but not BG) spores on Teflon filters increasing the culturable count by more than an order of magnitude. Testing polycarbonate and MCE filter materials also revealed a moderate increase of culturability although gelatin did not. No effect was observed with either of the two species interacting on either filter media with products originated by combustion of Mg and B·Ti. Sample contamination, spore agglomeration, effect of a filter material on the spore survival, changes in the spore wall ultrastructure and germination, as well as other factors were explored to interpret the findings. The study raises a question about the reliability of certain filter materials for collecting airborne bio-threat agents in combustion environments. PMID:26914458

  13. Multi-prediction particle filter for efficient parallelized implementation

    NASA Astrophysics Data System (ADS)

    Chu, Chun-Yuan; Chao, Chih-Hao; Chao, Min-An; Wu, An-Yeu Andy

    2011-12-01

    Particle filter (PF) is an emerging signal processing methodology, which can effectively deal with nonlinear and non-Gaussian signals by a sample-based approximation of the state probability density function. The particle generation of the PF is a data-independent procedure and can be implemented in parallel. However, the resampling procedure in the PF is a sequential task in natural and difficult to be parallelized. Based on the Amdahl's law, the sequential portion of a task limits the maximum speed-up of the parallelized implementation. Moreover, large particle number is usually required to obtain an accurate estimation, and the complexity of the resampling procedure is highly related to the number of particles. In this article, we propose a multi-prediction (MP) framework with two selection approaches. The proposed MP framework can reduce the required particle number for target estimation accuracy, and the sequential operation of the resampling can be reduced. Besides, the overhead of the MP framework can be easily compensated by parallel implementation. The proposed MP-PF alleviates the global sequential operation by increasing the local parallel computation. In addition, the MP-PF is very suitable for multi-core graphics processing unit (GPU) platform, which is a popular parallel processing architecture. We give prototypical implementations of the MP-PFs on multi-core GPU platform. For the classic bearing-only tracking experiments, the proposed MP-PF can be 25.1 and 15.3 times faster than the sequential importance resampling-PF with 10,000 and 20,000 particles, respectively. Hence, the proposed MP-PF can enhance the efficiency of the parallelization.

  14. Efficient color display using low-absorption in-pixel color filters

    NASA Technical Reports Server (NTRS)

    Wang, Yu (Inventor)

    2000-01-01

    A display system having a non-absorbing and reflective color filtering array and a reflector to improve light utilization efficiency. One implementation of the color filtering array uses a surface plasmon filter having two symmetric metal-dielectric interfaces coupled with each other to produce a transmission optical wave at a surface plasmon resonance wavelength at one interface from a p-polarized input beam on the other interface. Another implementation of the color filtering array uses a metal-film interference filter having two dielectric layers and three metallic films.

  15. Algorithmic and architectural optimizations for computationally efficient particle filtering.

    PubMed

    Sankaranarayanan, Aswin C; Srivastava, Ankur; Chellappa, Rama

    2008-05-01

    In this paper, we analyze the computational challenges in implementing particle filtering, especially to video sequences. Particle filtering is a technique used for filtering nonlinear dynamical systems driven by non-Gaussian noise processes. It has found widespread applications in detection, navigation, and tracking problems. Although, in general, particle filtering methods yield improved results, it is difficult to achieve real time performance. In this paper, we analyze the computational drawbacks of traditional particle filtering algorithms, and present a method for implementing the particle filter using the Independent Metropolis Hastings sampler, that is highly amenable to pipelined implementations and parallelization. We analyze the implementations of the proposed algorithm, and, in particular, concentrate on implementations that have minimum processing times. It is shown that the design parameters for the fastest implementation can be chosen by solving a set of convex programs. The proposed computational methodology was verified using a cluster of PCs for the application of visual tracking. We demonstrate a linear speed-up of the algorithm using the methodology proposed in the paper. PMID:18390378

  16. Efficient Lane Boundary Detection with Spatial-Temporal Knowledge Filtering.

    PubMed

    Nan, Zhixiong; Wei, Ping; Xu, Linhai; Zheng, Nanning

    2016-01-01

    Lane boundary detection technology has progressed rapidly over the past few decades. However, many challenges that often lead to lane detection unavailability remain to be solved. In this paper, we propose a spatial-temporal knowledge filtering model to detect lane boundaries in videos. To address the challenges of structure variation, large noise and complex illumination, this model incorporates prior spatial-temporal knowledge with lane appearance features to jointly identify lane boundaries. The model first extracts line segments in video frames. Two novel filters-the Crossing Point Filter (CPF) and the Structure Triangle Filter (STF)-are proposed to filter out the noisy line segments. The two filters introduce spatial structure constraints and temporal location constraints into lane detection, which represent the spatial-temporal knowledge about lanes. A straight line or curve model determined by a state machine is used to fit the line segments to finally output the lane boundaries. We collected a challenging realistic traffic scene dataset. The experimental results on this dataset and other standard dataset demonstrate the strength of our method. The proposed method has been successfully applied to our autonomous experimental vehicle. PMID:27529248

  17. Fuel Efficient Diesel Particulate Filter (DPF) Modeling and Development

    SciTech Connect

    Stewart, Mark L.; Gallant, Thomas R.; Kim, Do Heui; Maupin, Gary D.; Zelenyuk, Alla

    2010-08-01

    The project described in this report seeks to promote effective diesel particulate filter technology with minimum fuel penalty by enhancing fundamental understanding of filtration mechanisms through targeted experiments and computer simulations. The overall backpressure of a filtration system depends upon complex interactions of particulate matter and ash with the microscopic pores in filter media. Better characterization of these phenomena is essential for exhaust system optimization. The acicular mullite (ACM) diesel particulate filter substrate is under continuing development by Dow Automotive. ACM is made up of long mullite crystals which intersect to form filter wall framework and protrude from the wall surface into the DPF channels. ACM filters have been demonstrated to effectively remove diesel exhaust particles while maintaining relatively low backpressure. Modeling approaches developed for more conventional ceramic filter materials, such as silicon carbide and cordierite, have been difficult to apply to ACM because of properties arising from its unique microstructure. Penetration of soot into the high-porosity region of projecting crystal structures leads to a somewhat extended depth filtration mode, but with less dramatic increases in pressure drop than are normally observed during depth filtration in cordierite or silicon carbide filters. Another consequence is greater contact between the soot and solid surfaces, which may enhance the action of some catalyst coatings in filter regeneration. The projecting crystals appear to provide a two-fold benefit for maintaining low backpressures during filter loading: they help prevent soot from being forced into the throats of pores in the lower porosity region of the filter wall, and they also tend to support the forming filter cake, resulting in lower average cake density and higher permeability. Other simulations suggest that soot deposits may also tend to form at the tips of projecting crystals due to the axial

  18. Capture of 0.1-μm aerosol particles containing viable H1N1 influenza virus by N95 filtering facepiece respirators.

    PubMed

    Harnish, Delbert A; Heimbuch, Brian K; Balzli, Charles; Choe, Melanie; Lumley, April E; Shaffer, Ronald E; Wander, Joseph D

    2016-01-01

    Nosocomial infections pose an escalating threat to both patients and healthcare workers (HCWs). A widely recommended device for individual respiratory protection, the N95 filtering facepiece respirator (FFR) has been shown to provide efficient filtration of inert particles larger and smaller than the nominal most-penetrating particle size (MPPS) range, 0.03-0.3 μm. Humans generate respiratory aerosols in the MPPS range, suggesting that short-range disease transmission could occur via small infectious particles. Data presented here show that the N95 FFR will afford a significant measure of protection against infectious particles as small as a bare H1N1 influenza virion, and that the capture mechanism does not discriminate in favor of, or against, biological particles. PMID:26554291

  19. In vitro comparison of Günther Tulip and Celect filters: testing filtering efficiency and pressure drop.

    PubMed

    Nicolas, M; Malvé, M; Peña, E; Martínez, M A; Leask, R

    2015-02-01

    In this study, the trapping ability of the Günther Tulip and Celect inferior vena cava filters was evaluated. Thrombus capture rates of the filters were tested in vitro in horizontal position with thrombus diameters of 3 and 6mm and tube diameter of 19mm. The filters were tested in centered and tilted positions. Sets of 30 clots were injected into the model and the same process was repeated 20 times for each different condition simulated. Pressure drop experienced along the system was also measured and the percentage of clots captured was recorded. The Günther Tulip filter showed superiority in all cases, trapping almost 100% of 6mm clots both in an eccentric and tilted position and trapping 81.7% of the 3mm clots in a centered position and 69.3% in a maximum tilted position. The efficiency of all filters tested decreased as the size of the embolus decreased and as the filter was tilted. The injection of 6 clots raised the pressure drop to 4.1mmHg, which is a reasonable value that does not cause the obstruction of blood flow through the system. PMID:25553669

  20. Experimental Assessment of Collection Efficiency of Submicron Aerosol Particles by Cloud Droplets

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Oo, K.; Brown, M. D.; Dhaniyala, S.; Cziczo, D. J.

    2012-12-01

    An experimental setup has been constructed to measure the collection efficiency of submicron aerosol particles by cloud droplets. The collection efficiency study is a prelude to studying contact nucleation, which is a potentially important ice nucleation mode that is not well-understood. This laboratory setup is a step closer to experimentally assessing the importance of contact nucleation. Water droplets with 20 micron diameter and submicron aerosol particles are brought into contact in an injector situated inside a chilled glass flow tube. The water droplets that collect aerosol particles are allowed to pass through a counterflow virtual impactor (CVI), which accepts large droplets and rejects aerosol particles that have not coagulated with the water droplets. The collected droplets are sent into the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument which performs in situ chemical analysis of a single particle. The number of aerosol particles collected by the single water droplet is quantified by calibrating the PALMS with known concentrations of aerosol particles. The water droplets contain a known amount of ammonium sulfate for identification purpose in the mass spectrometry. Preliminary results from the experiment will be discussed and compared with previous theoretical and experimental studies.

  1. Advanced Energy-Efficient Filtration: Fan Filter Unit

    SciTech Connect

    Xu, Tengfang

    2005-10-01

    The objective of this project is to provide assistance in development of a standard test procedure for fan-filter units, which are gaining popularity for use in California cleanrooms. In particular, LBNL carried out collaboration with various stakeholders in the industry and took a lead in developing a draft standard method for testing the energy performance of fan-filter units, and provided assistance to California public utility companies by testing the draft method in PG&E's testing facility. Through testing more units in the future with a robust standard method, baseline performance information can be developed for use in possible energy incentive programs.

  2. A TWO STAGE RESPIRABLE AEROSOL SAMPLER USING NUCLEPORE FILTERS IN SERIES

    EPA Science Inventory

    Respirable and nonrespirable particles are separately collected from the atmosphere in a size selective sampler consisting of two Nuclepore filters in series. The first filter has pore diameters of 12 micrometers and collects, to a close approximation, the nonrespirable fraction ...

  3. Shortwave radiative forcing and efficiency of key aerosol types using AERONET data

    NASA Astrophysics Data System (ADS)

    García, O. E.; Díaz, J. P.; Expósito, F. J.; Díaz, A. M.; Dubovik, O.; Derimian, Y.; Dubuisson, P.; Roger, J.-C.

    2011-12-01

    The shortwave radiative forcing (ΔF) and the radiative forcing efficiency (ΔFeff) of natural and anthropogenic aerosols have been analyzed using estimates of radiation both at the top (TOA) and at the bottom of atmosphere (BOA) modeled based on AERONET aerosol retrievals. In this study we have considered six main types of atmospheric aerosols: desert mineral dust, biomass burning, urban-industrial, continental background, oceanic and free troposphere. The ΔF averages obtained vary from -148 ± 44 Wm-2 (aerosol optical depth, AOD, at 0.55 μm, 0.85 ± 0.45) at the BOA for the mixture of desert mineral dust and biomass burning aerosols in Central Africa and -42 ± 22 Wm-2 (AOD = 0.86 ± 0.51) at the TOA for the pure mineral dust also in this region up to -6 ± 3 Wm-2 and -4 ± 2 Wm-2 (AOD = 0.03 ± 0.02) at the BOA and the TOA, respectively, for free troposphere conditions. This last result may be taken as reference on a global scale. Furthermore, we observe that the more absorbing aerosols are overall more efficient at the BOA in contrast to at the TOA, where they backscatter less solar energy into the space. The analysis of the radiative balance at the TOA shows that, together with the amount of aerosols and their absorptive capacity, it is essential to consider the surface albedo of the region on which they are. Thus, we document that in regions with high surface reflectivity (deserts and snow conditions) atmospheric aerosols lead to a warming of the Earth-atmosphere system, contributing to the greenhouse gas effect.

  4. Shortwave radiative forcing and efficiency of key aerosol types using AERONET data

    NASA Astrophysics Data System (ADS)

    García, O. E.; Díaz, J. P.; Expósito, F. J.; Díaz, A. M.; Dubovik, O.; Derimian, Y.; Dubuisson, P.; Roger, J.-C.

    2012-06-01

    The shortwave radiative forcing (ΔF) and the radiative forcing efficiency (ΔFeff) of natural and anthropogenic aerosols have been analyzed using estimates of radiation both at the Top (TOA) and at the Bottom Of Atmosphere (BOA) modeled based on AERONET aerosol retrievals. Six main types of atmospheric aerosols have been compared (desert mineral dust, biomass burning, urban-industrial, continental background, oceanic and free troposphere) in similar observational conditions (i.e., for solar zenith angles between 55° and 65°) in order to compare the nearly same solar geometry. The instantaneous ΔF averages obtained vary from -122 ± 37 Wm-2 (aerosol optical depth, AOD, at 0.55 μm, 0.85 ± 0.45) at the BOA for the mixture of desert mineral dust and biomass burning aerosols in West Africa and -42 ± 22 Wm-2 (AOD = 0.9 ± 0.5) at the TOA for the pure mineral dust also in this region up to -6 ± 3 Wm-2 and -4 ± 2 Wm-2 (AOD = 0.03 ± 0.02) at the BOA and the TOA, respectively, for free troposphere conditions. This last result may be taken as reference on a global scale. Furthermore, we observe that the more absorbing aerosols are overall more efficient at the BOA in contrast to at the TOA, where they backscatter less solar energy into the space. The analysis of the radiative balance at the TOA shows that, together with the amount of aerosols and their absorptive capacity, it is essential to consider the surface albedo of the region on which they are. Thus, we document that in regions with high surface reflectivity (deserts and snow conditions) atmospheric aerosols lead to a warming of the Earth-atmosphere system.

  5. Criteria for calculating the efficiency of deep-pleated HEPA filters with aluminum separators during and after design basis accidents

    SciTech Connect

    Bergman, W.; First, M.W.; Anderson, W.L.

    1995-02-01

    We have reviewed the literature on the performance of HEPA filters under normal and abnormal conditions to establish criteria for calculating the efficiency of HEPA filters in a DOE nonreactor nuclear facility during and after a Design Basis Accident (DBA). This study is only applicable to the standard deep-pleated HEPA filter with aluminum separators as specified in ASME N509[1]. Other HEPA filter designs such as the mini-pleat and separatorless filters are not included in this study. The literature review included the performance of new filters and parameters that may cause deterioration in the filter performance such as filter age, radiation, corrosive chemicals, seismic and rough handling, high temperature, moisture, particle clogging, high air flow and pressure pulses. The deterioration of the filter efficiency depends on the exposure parameters; in severe exposure conditions the filter will be damaged and have a residual efficiency of 0%. There are large gaps and limitations in the data that introduce significant error in the estimates of HEPA filter efficiencies under DBA conditions. Because of this limitation, conservative values of filter efficiency were chosen. The estimation of the efficiency of the HEPA filters under DBA conditions involves three steps: (1) The filter pressure drop and environmental parameters are determined during and after the DBA, (2) Comparing the filter pressure drop to a set of threshold values above which the filter is damaged. There is a different threshold value for each combination of environmental parameters, and (3) Determining the filter efficiency. If the filter pressure drop is greater than the threshold value, the filter is damaged and is assigned 0% efficiency. If the pressure drop is less, then the filter is not damaged and the efficiency is determined from literature values of the efficiency at the environmental conditions.

  6. Development of a High Spectral Resolution Lidar (HSRL) Based on a Confocal Optical Filter for Aerosol Studies

    NASA Astrophysics Data System (ADS)

    Repasky, K. S.; Hoffman, D. S.; Reagan, J. A.; Carlsten, J.

    2010-12-01

    Aerosols are an important constituent in atmospheric composition affecting climate, weather, and air quality. Active remote sensing instruments provide tools for in-situ studies of atmospheric aerosols that can help understand the role of aerosols on the radiative forcing of the climate system. In this paper, the design and initial performance of a high spectral resolution lidar (HSRL) based on a unique confocal cavity for optically filtering the aerosol and molecular returns is presented. An injection seeded pulsed Nd:YAG laser with a fundamental and frequency doubled output is used as the laser transmitter for the HSRL. A small portion of fiber coupled injection seeded signal at 1064 nm is split before the laser oscillator and, after modulation using an acousto-optic modulator, is used to produce a discriminating signal for locking a confocal cavity that is resonant at the 1064 and 532 nm wavelengths to the injection seeded source. Light scattered in the atmosphere is collected using a commercial telescope. After the telescope, the 1064 nm light is split from the 532 nm light using a dielectric mirror with the 1064 nm light monitored using a PMT. The 532 nm light is launched into a multimode fiber. The output from the fiber is next incident on a beamsplitter with part of the light sent to a PMT to monitor the total return for the 532 nm channel. The light that passes through the beamsplitter is mode matched into a confocal optical cavity that allows the light scattered by the atmospheric aerosols to be transmitted while the light scattered from the atmospheric molecules is reflected. The transmitted light from the aerosol scattering is incident on a PMT while the reflected molecular signal is incident on a PMT. The transmission of the confocal cavity is monitored before and after the data collection using a continuous wave frequency doubled Nd:YAG laser that is fiber coupled. Data is collected and processed in the following manner. Each of the four voltage

  7. Preparation of Fiber Based Binder Materials to Enhance the Gas Adsorption Efficiency of Carbon Air Filter.

    PubMed

    Lim, Tae Hwan; Choi, Jeong Rak; Lim, Dae Young; Lee, So Hee; Yeo, Sang Young

    2015-10-01

    Fiber binder adapted carbon air filter is prepared to increase gas adsorption efficiency and environmental stability. The filter prevents harmful gases, as well as particle dusts in the air from entering the body when a human inhales. The basic structure of carbon air filter is composed of spunbond/meltblown/activated carbon/bottom substrate. Activated carbons and meltblown layer are adapted to increase gas adsorption and dust filtration efficiency, respectively. Liquid type adhesive is used in the conventional carbon air filter as a binder material between activated carbons and other layers. However, it is thought that the liquid binder is not an ideal material with respect to its bonding strength and liquid flow behavior that reduce gas adsorption efficiency. To overcome these disadvantages, fiber type binder is introduced in our study. It is confirmed that fiber type binder adapted air filter media show higher strip strength, and their gas adsorption efficiencies are measured over 42% during 60 sec. These values are higher than those of conventional filter. Although the differential pressure of fiber binder adapted air filter is relatively high compared to the conventional one, short fibers have a good potential as a binder materials of activated carbon based air filter. PMID:26726459

  8. Microwave Band-Pass Filter with Aerosol-Deposited Al2O3-Polytetrafluoroethylene Composite Thick Films.

    PubMed

    Lee, Ji-Won; Koh, Jung-Hyuk

    2015-03-01

    Fabrication of microwave band-pass filter with coplanar waveguide with ground structure was realized by employing Al2O3-polytetrafluoroethylene (Al2O3-PTFE) composite thick films for integrated substrates produced by aerosol deposition (AD). In order to predict the performance of the band-pass filter, 3-D electromagnetic simulations were performed by high-frequency structure analysis. The thick Al2O3-PTFE composite films prepared by the AD process had submicron-sized Al2O3 crystallites due to the shock-absorbing effect of PTFE during the film growth. The thick films were characterized by X-ray diffraction and scanning electron microscopy. The Cu transmission lines with the thickness of 300 nm were deposited by electron-beam evaporation to form the band-pass filter. The fabricated band-pass filter showed similar characteristics to the simulation results. The insertion loss and resonance frequency were 9.5 dB and 2.3 GHz, respectively. PMID:26413656

  9. Efficient wavelength multiplexers based on asymmetric response filters.

    PubMed

    Wade, Mark T; Popović, Miloš A

    2013-05-01

    We propose integrated photonic wavelength multiplexers based on serially cascaded channel add-drop filters with an asymmetric frequency response. By utilizing the through-port rejection of the previous channel to advantage, the asymmetric response provides optimal rejection of the adjacent channels at each wavelength channel. We show theoretically the basic requirements to realize an asymmetric filter response, and propose and evaluate the possible implementations using coupled resonators. For one implementation, we provide detailed design formulas based on a coupled-mode theory model, and more generally we provide broad guidelines that enumerate all structures that can provide asymmetric passbands in the context of a pole-zero design approach to engineering the device response. Using second-order microring resonator filter stages as an example, we show that the asymmetric multiplexer can provide 2.4 times higher channel packing (bandwidth) density than a multiplexer using the same order stages (number of resonators) using conventional all-pole maximally-flat designs. We also address the sensitivities and constraints of various implementations of our proposed approach, as it affects their applicability to CMOS photonic interconnects. PMID:23669947

  10. Spermine-alt-poly(ethylene glycol) polyspermine as a safe and efficient aerosol gene carrier for lung cancer therapy.

    PubMed

    Kim, You-Kyoung; Cho, Chong-Su; Cho, Myung-Haing; Jiang, Hu-Lin

    2014-07-01

    The clinical success of gene therapy critically depends upon the safety and efficiency of delivery system used. Although polyethylenimine (PEI) has been commonly used as an efficient cationic polymeric gene carrier due to its high transfection efficiency, its cytotoxicity and nondegradability limit the polymer's therapeutic applications in clinical trials. In this study, biocompatible polyspermine based on spermine (SPE) and poly(ethylene glycol) (PEG) diacrylate (SPE-alt-PEG) was synthesized using a Michael-type addition reaction, and its ability as an alternative gene carrier for lung cancer therapy was evaluated. SPE-alt-PEG polyspermine was complexed with plasmid DNA, and the resulting complexes were characterized by particle size and surface charge by dynamic light scattering, complex formation and DNA protection ability by gel retardation, and complex shape by energy-filtering transmission electron microscopy. The SPE-alt-PEG copolymer showed low cytotoxicity, and SPE-alt-PEG/DNA complexes showed efficacious transfection efficiency compared with 25 kDa PEI (PEI 25K). Also SPE-alt-PEG/GFP complexes were efficiently transferred into the lungs after aerosol administration without toxicity, and delivery of Pdcd4 gene as a therapeutic gene with SPE-alt-PEG polyspermine greatly reduced tumor size as well as tumor numbers in K-ras(LA1) lung cancer model mice compared relative to the effect observed for PEI 25K. These results suggest that SPE-alt-PEG has potential as a gene carrier for lung cancer gene therapy. PMID:23929634

  11. An Efficient Adaptive Weighted Switching Median Filter for Removing High Density Impulse Noise

    NASA Astrophysics Data System (ADS)

    Nair, Madhu S.; Ameera Mol, P. M.

    2014-09-01

    Restoration of images corrupted by impulse noise is a very active research area in image processing. In this paper, an Efficient Adaptive Weighted Switching Median filter for restoration of images that are corrupted by high density impulse noise is proposed. The filtering is performed as a two phase process—a detection phase followed by a filtering phase. In the proposed method, noise detection is done by HEIND algorithm proposed by Duan et al. The filtering algorithm is then applied to the pixels which are detected as noisy by the detection algorithm. All uncorrupted pixels in the image are left unchanged. The filtering window size is chosen adaptively depending on the local noise distribution around each corrupted pixels. Noisy pixels are replaced by a weighted median value of uncorrupted pixels in the filtering window. The weight value assigned to each uncorrupted pixels depends on its closeness to the central pixel.

  12. Enhanced spectral efficiency using bandwidth switchable SAW filtering for mobile satellite communications systems

    NASA Technical Reports Server (NTRS)

    Peach, Robert; Malarky, Alastair

    1990-01-01

    Currently proposed mobile satellite communications systems require a high degree of flexibility in assignment of spectral capacity to different geographic locations. Conventionally this results in poor spectral efficiency which may be overcome by the use of bandwidth switchable filtering. Surface acoustic wave (SAW) technology makes it possible to provide banks of filters whose responses may be contiguously combined to form variable bandwidth filters with constant amplitude and phase responses across the entire band. The high selectivity possible with SAW filters, combined with the variable bandwidth capability, makes it possible to achieve spectral efficiencies over the allocated bandwidths of greater than 90 percent, while retaining full system flexibility. Bandwidth switchable SAW filtering (BSSF) achieves these gains with a negligible increase in hardware complexity.

  13. Experimental Assessment of Collection Efficiency of Submicron Aerosol Particles by Cloud Droplets

    NASA Astrophysics Data System (ADS)

    Huang, Y. W.; Ardon-Dryer, K.; Cziczo, D. J.

    2014-12-01

    The interplay between aerosol particles and water droplets in the atmosphere, especially in clouds, influences both aerosol and cloud properties. The major uncertainty in our understanding of climate arises in the indirect effect of aerosol and their ability to impact cloud formation and consequently alter the global radiative balance. The collision between a water droplet and aerosol particles that results in coalescence is termed "collection" or "coagulation". Coagulation can lead to aerosol removal from the atmosphere or induce ice nucleation via contact freezing. There is a theoretical collection efficiency minimum of particles with diameter between 0.1-2 µm, called the "Greenfield Gap". Experimental effort, however, was limited to drizzle and rain drops until recently, and has not constrained parameters that describe particle collection efficiency by cloud droplets. Collection efficiency is also an important parameter for assessing contact freezing, the least known ice nucleation mechanism today. Experimentally assessing collection efficiency can prove the existence of the "Greenfield Gap" and lay the foundation for studying contact freezing. We recently constructed the MIT-Contact Freezing Chamber (MIT-CFC) to study coagulation experimentally. A stream of 40 µm cloud droplets fall freely into the chamber and collide with aerosol particles with known size and concentration. The outflow goes through a series of dryers before entering the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument for chemical composition analysis. PALMS is a true single-particle instrument and gives information on the size and the chemical composition of each particle. Coagulated particles from the MIT-CFC have mass spectral signatures of both the aerosol particles and the droplet residuals, while the droplet residual contains no signature of the aerosol particles. To our knowledge, this is the first time coagulation has been seen on a single-particle basis. We will

  14. Single Wall Diesel Particulate Filter (DPF) Filtration Efficiency Studies Using Laboratory Generated Particles

    SciTech Connect

    Yang, Juan; Stewart, Marc; Maupin, Gary D.; Herling, Darrell R.; Zelenyuk, Alla

    2009-04-15

    Diesel offers higher fuel efficiency, but produces higher exhaust particulate matter. Diesel particulate filters are presently the most efficient means to reduce these emissions. These filters typically trap particles in two basic modes: at the beginning of the exposure cycle the particles are captured in the filter holes, and at longer times the particles form a "cake" on which particles are trapped. Eventually the "cake" removed by oxidation and the cycle is repeated. We have investigated the properties and behavior of two commonly used filters: silicon carbide (SiC) and cordierite (DuraTrap® RC) by exposing them to nearly-spherical ammonium sulfate particles. We show that the transition from deep bed filtration to "cake" filtration can easily be identified by recording the change in pressure across the filters as a function of exposure. We investigated performance of these filters as a function of flow rate and particle size. The filters trap small and large particles more efficiently than particles that are ~80 to 200 nm in aerodynamic diameter. A comparison between the experimental data and a simulation using incompressible lattice-Boltzmann model shows very good qualitative agreement, but the model overpredicts the filter’s trapping efficiency.

  15. Switching between filter settings reduces the efficient utilization of visual working memory.

    PubMed

    Jost, Kerstin; Mayr, Ulrich

    2016-04-01

    The capacity limitation of working memory requires that only relevant information gains access to the workspace, while irrelevant information is kept out. Thus, the ability to use attention to filter out irrelevant information is an important factor in how efficiently the limited storage space is used. Here, we examined to what degree the requirement to flexibly change filter settings affects filtering efficiency. Participants were presented with visual objects in different colors, and a cue presented in advance indicated which objects had to be stored. The contralateral delay activity, an event-related brain potential that reflects working-memory load was used to assess filtering efficiency during the retention interval. The data of two experiments showed that when filter settings had to be adjusted on a trial-by-trial basis, more irrelevant information passed the gate to working memory. Moreover, this switching-induced filtering deficit was restricted to those items that matched the previous, but currently irrelevant, filter settings. Thus, lingering effects of the selection history seem to counteract goal-directed encoding, and thus constitute an important attentional limitation for the efficient utilization of our limited workspace. PMID:26450507

  16. Final Report: Part 1. In-Place Filter Testing Instrument for Nuclear Material Containers. Part 2. Canister Filter Test Standards for Aerosol Capture Rates.

    SciTech Connect

    Brown, Austin Douglas; Runnels, Joel T.; Moore, Murray E.; Reeves, Kirk Patrick

    2014-11-02

    A portable instrument has been developed to assess the functionality of filter sand o-rings on nuclear material storage canisters, without requiring removal of the canister lid. Additionally, a set of fifteen filter standards were procured for verifying aerosol leakage and pressure drop measurements in the Los Alamos Filter Test System. The US Department of Energy uses several thousand canisters for storing nuclear material in different chemical and physical forms. Specialized filters are installed into canister lids to allow gases to escape, and to maintain an internal ambient pressure while containing radioactive contaminants. Diagnosing the condition of container filters and canister integrity is important to ensure worker and public safety and for determining the handling requirements of legacy apparatus. This report describes the In-Place-Filter-Tester, the Instrument Development Plan and the Instrument Operating Method that were developed at the Los Alamos National Laboratory to determine the “as found” condition of unopened storage canisters. The Instrument Operating Method provides instructions for future evaluations of as-found canisters packaged with nuclear material. Customized stainless steel canister interfaces were developed for pressure-port access and to apply a suction clamping force for the interface. These are compatible with selected Hagan-style and SAVY-4000 storage canisters that were purchased from NFT (Nuclear Filter Technology, Golden, CO). Two instruments were developed for this effort: an initial Los Alamos POC (Proof-of-Concept) unit and the final Los Alamos IPFT system. The Los Alamos POC was used to create the Instrument Development Plan: (1) to determine the air flow and pressure characteristics associated with canister filter clogging, and (2) to test simulated configurations that mimicked canister leakage paths. The canister leakage scenarios included quantifying: (A) air leakage due to foreign material (i.e. dust and hair

  17. Photoacoustic and filter-based ambient aerosol light absorption measurements: Instrument comparisons and the role of relative humidity

    NASA Astrophysics Data System (ADS)

    Arnott, W. P.; Moosmüller, H.; Sheridan, P. J.; Ogren, J. A.; Raspet, R.; Slaton, W. V.; Hand, J. L.; Kreidenweis, S. M.; Collett, J. L.

    2003-01-01

    Ambient measurements are reported of aerosol light absorption from photoacoustic and filter-based instruments (aethalometer and a particle soot absorption photometer (PSAP)) to provide insight on the measurement science. Measurements were obtained during the Big Bend Regional Aerosol and Visibility Observational Study at the Big Bend National Park in South Texas. The aethalometer measurements of black carbon concentration at this site correlate reasonably well with photoacoustic measurements of aerosol light absorption, with a slope of 8.1 m2/g and a small offset. Light absorption at this site never exceeded 2.1 Mm-1 during the month of collocated measurements. Measurements were also obtained, as a function of controlled relative humidity between 40% and 90%, during the Photoacoustic IOP in 2000 at the Department of Energy Southern Great Plains Cloud and Radiation Testbed site (SGP). PSAP measurements of aerosol light absorption correlated very well with photoacoustic measurements, but the slope of the correlation indicated the PSAP values were larger by a factor of 1.61. The photoacoustic measurements of light absorption exhibited a systematic decrease when the RH increased beyond 70%. This apparent decrease in light absorption with RH may be due to the contribution of mass transfer to the photoacoustic signal. Model results for the limiting case of full water saturation are used to evaluate this hypothesis. A second PSAP measured the light absorption for the same humidified samples, and indicated very erratic response as the RH changed, suggesting caution when interpreting PSAP data under conditions of rapid relative humidity change.

  18. Facile Preparation of Nanostructured, Superhydrophobic Filter Paper for Efficient Water/Oil Separation

    PubMed Central

    Wang, Jianhua; Wong, Jessica X. H.; Kwok, Honoria; Li, Xiaochun; Yu, Hua-Zhong

    2016-01-01

    In this paper, we present a facile and cost-effective method to obtain superhydrophobic filter paper and demonstrate its application for efficient water/oil separation. By coupling structurally distinct organosilane precursors (e.g., octadecyltrichlorosilane and methyltrichlorosilane) to paper fibers under controlled reaction conditions, we have formulated a simple, inexpensive, and efficient protocol to achieve a desirable superhydrophobic and superoleophilic surface on conventional filter paper. The silanized superhydrophobic filter paper showed nanostructured morphology and demonstrated great separation efficiency (up to 99.4%) for water/oil mixtures. The modified filter paper is stable in both aqueous solutions and organic solvents, and can be reused multiple times. The present study shows that our newly developed binary silanization is a promising method of modifying cellulose-based materials for practical applications, in particular the treatment of industrial waste water and ecosystem recovery. PMID:26982055

  19. Aerosol radiative forcing efficiency in the UV-B region over central Argentina

    NASA Astrophysics Data System (ADS)

    Palancar, Gustavo G.; Olcese, Luis E.; Lanzaco, Bethania L.; Achad, Mariana; López, María Laura; Toselli, Beatriz M.

    2016-07-01

    AEROSOL Robotic Network (AERONET), Moderate Resolution Imaging Spectroradiometer (MODIS) and global UV-B (280-315 nm) irradiance measurements and calculations were combined to investigate the effects of aerosol loading on the ultraviolet B radiation (UV-B) reaching the surface under cloudless conditions in Córdoba, Argentina. The aerosol radiative forcing (ARF) and the aerosol forcing efficiency (ARFE) were calculated for an extended period of time (2000-2013) at a ground-based monitoring site affected by different types and loading of aerosols. The ARFE was evaluated by using the aerosol optical depth (AOD) at 340 nm retrieved by AERONET at the Cordoba CETT site. The individual and combined effects of the single scattering albedo (SSA) and the solar zenith angle (SZA) on the ARFE were also analyzed. In addition, and for comparison purposes, the MODIS AOD at 550 nm was used as input in a machine learning method to better characterize the aerosol load at 340 nm and evaluate the ARFE retrieved from AOD satellite measurements. The ARFE at the surface calculated using AOD data from AERONET ranged from (-0.11 ± 0.01) to (-1.76 ± 0.20) Wm-2 with an average of -0.61 Wm-2; however, when using AOD data from MODIS (TERRA/AQUA satellites), it ranged from (-0.22 ± 0.03) to (-0.65 ± 0.07) Wm-2 with an average value of -0.43 Wm-2. At the same SZA and SSA, the maximum difference between ground and satellite-based was 0.22 Wm-2.

  20. Efficient Nose-to-Lung (N2L) Aerosol Delivery with a Dry Powder Inhaler

    PubMed Central

    Golshahi, Laleh; Behara, Srinivas R.B.; Tian, Geng; Farkas, Dale R.; Hindle, Michael

    2015-01-01

    Abstract Purpose: Delivering aerosols to the lungs through the nasal route has a number of advantages, but its use has been limited by high depositional loss in the extrathoracic airways. The objective of this study was to evaluate the nose-to-lung (N2L) delivery of excipient enhanced growth (EEG) formulation aerosols generated with a new inline dry powder inhaler (DPI). The device was also adapted to enable aerosol delivery to a patient simultaneously receiving respiratory support from high flow nasal cannula (HFNC) therapy. Methods: The inhaler delivered the antibiotic ciprofloxacin, which was formulated as submicrometer combination particles containing a hygroscopic excipient prepared by spray-drying. Nose-to-lung delivery was assessed using in vitro and computational fluid dynamics (CFD) methods in an airway model that continued through the upper tracheobronchial region. Results: The best performing device contained a 2.3 mm flow control orifice and a 3D rod array with a 3-4-3 rod pattern. Based on in vitro experiments, the emitted dose from the streamlined nasal cannula had a fine particle fraction <5 μm of 95.9% and mass median aerodynamic diameter of 1.4 μm, which was considered ideal for nose-to-lung EEG delivery. With the 2.3-343 device, condensational growth in the airways increased the aerosol size to 2.5–2.7 μm and extrathoracic deposition was <10%. CFD results closely matched the in vitro experiments and predicted that nasal deposition was <2%. Conclusions: The developed DPI produced high efficiency aerosolization with significant size increase of the aerosol within the airways that can be used to enable nose-to-lung delivery and aerosol administration during HFNC therapy. PMID:25192072

  1. Transparent air filter for high-efficiency PM2.5 capture

    NASA Astrophysics Data System (ADS)

    Liu, Chong; Hsu, Po-Chun; Lee, Hyun-Wook; Ye, Meng; Zheng, Guangyuan; Liu, Nian; Li, Weiyang; Cui, Yi

    2015-02-01

    Particulate matter (PM) pollution has raised serious concerns for public health. Although outdoor individual protection could be achieved by facial masks, indoor air usually relies on expensive and energy-intensive air-filtering devices. Here, we introduce a transparent air filter for indoor air protection through windows that uses natural passive ventilation to effectively protect the indoor air quality. By controlling the surface chemistry to enable strong PM adhesion and also the microstructure of the air filters to increase the capture possibilities, we achieve transparent, high air flow and highly effective air filters of ~90% transparency with >95.00% removal of PM2.5 under extreme hazardous air-quality conditions (PM2.5 mass concentration >250 μg m-3). A field test in Beijing shows that the polyacrylonitrile transparent air filter has the best PM2.5 removal efficiency of 98.69% at high transmittance of ~77% during haze occurrence.

  2. Estimation of Collection Efficiency Change of Moving Granular Bed Filter by Dust Load

    SciTech Connect

    Furuuchi, M.; Hata, M.; Kanaoka, C.; Kawaminami, Y.

    2002-09-18

    Final goal of this study is to theoretically describe effects of influencing factors on the performance of the coke bed filter as a material classifier and to predict its optimal operating condition. In this paper, the author focuses on the basic investigation on collection mechanism of a fixed coke bed filter on the basis of the depth filtration theory, in which an influence of dust load on the dust collection efficiency.

  3. Efficient design of two-dimensional recursive digital filters. Final report

    SciTech Connect

    Twogood, R.E.; Mitra, S.K.

    1980-01-01

    This report outlines the research progress during the period August 1978 to July 1979. This work can be divided into seven basic project areas. Project 1 deals with a comparative study of 2-D recursive and nonrecursive digital filters. The second project addresses a new design technique for 2-D half-plane recursive filters, and Projects 3 thru 5 deal with implementation issues. The sixth project presents our recent study of the applicability of array processors to 2-D digital signal processing. The final project involves our investigation into techniques for incorporating symmetry constraints on 2-D recursive filters in order to yield more efficient implementations.

  4. High-efficiency microwave photonic harmonic down-conversion with tunable and reconfigurable filtering.

    PubMed

    Liao, Jinxin; Zheng, Xiaoping; Li, Shangyuan; Zhang, Hanyi; Zhou, Bingkun

    2014-12-01

    A new optical-frequency comb-based microwave photonic harmonic down-convertor with tunable and reconfigurable filtering is proposed and experimentally demonstrated. The coherent evenly spaced optical carriers offer harmonic down-conversion for ultrahigh radio frequency signals with low-frequency local oscillator, and construct a tunable and reconfigurable bandpass filter for the intermediate-frequency (IF) signal combined with dispersion. This implementation features high conversion efficiency. Experimental results show the filtered output IF signal has a clean spectrum with high quality. Measured conversion loss is 8.3 dB without extra electrical amplification. PMID:25490622

  5. An Efficient Machine Learning Approach To Low-Complexity Filtering In Biological Sequences

    SciTech Connect

    Barber, Christopher A; Oehmen, Christopher S

    2012-06-09

    Biological sequences contain low-complexity regions (LCRs) which produce superfluous matches in homology searches, and lead to slow execution of database search algorithms such as BLAST. These regions are efficiently identified by low-complexity filtering algorithms such as SDUST and SEG, which are included in the BLAST tool-suite. These algorithms target differing notions of complexity, so an algorithm which combines their sensitivities is pursued. A variety of features are derived from these algorithms, as well as a new filtering algorithm based on Lempel-Ziv complexity. Artificial sequences with known LCRs are used to train and evaluate an SVM classifier, which significantly outperforms the standalone filtering algorithms.

  6. Design of efficient circularly symmetric two-dimensional variable digital FIR filters

    PubMed Central

    Bindima, Thayyil; Elias, Elizabeth

    2016-01-01

    Circularly symmetric two-dimensional (2D) finite impulse response (FIR) filters find extensive use in image and medical applications, especially for isotropic filtering. Moreover, the design and implementation of 2D digital filters with variable fractional delay and variable magnitude responses without redesigning the filter has become a crucial topic of interest due to its significance in low-cost applications. Recently the design using fixed word length coefficients has gained importance due to the replacement of multipliers by shifters and adders, which reduces the hardware complexity. Among the various approaches to 2D design, transforming a one-dimensional (1D) filter to 2D by transformation, is reported to be an efficient technique. In this paper, 1D variable digital filters (VDFs) with tunable cut-off frequencies are designed using Farrow structure based interpolation approach, and the sub-filter coefficients in the Farrow structure are made multiplier-less using canonic signed digit (CSD) representation. The resulting performance degradation in the filters is overcome by using artificial bee colony (ABC) optimization. Finally, the optimized 1D VDFs are mapped to 2D using generalized McClellan transformation resulting in low complexity, circularly symmetric 2D VDFs with real-time tunability. PMID:27222739

  7. Design of efficient circularly symmetric two-dimensional variable digital FIR filters.

    PubMed

    Bindima, Thayyil; Elias, Elizabeth

    2016-05-01

    Circularly symmetric two-dimensional (2D) finite impulse response (FIR) filters find extensive use in image and medical applications, especially for isotropic filtering. Moreover, the design and implementation of 2D digital filters with variable fractional delay and variable magnitude responses without redesigning the filter has become a crucial topic of interest due to its significance in low-cost applications. Recently the design using fixed word length coefficients has gained importance due to the replacement of multipliers by shifters and adders, which reduces the hardware complexity. Among the various approaches to 2D design, transforming a one-dimensional (1D) filter to 2D by transformation, is reported to be an efficient technique. In this paper, 1D variable digital filters (VDFs) with tunable cut-off frequencies are designed using Farrow structure based interpolation approach, and the sub-filter coefficients in the Farrow structure are made multiplier-less using canonic signed digit (CSD) representation. The resulting performance degradation in the filters is overcome by using artificial bee colony (ABC) optimization. Finally, the optimized 1D VDFs are mapped to 2D using generalized McClellan transformation resulting in low complexity, circularly symmetric 2D VDFs with real-time tunability. PMID:27222739

  8. Comparative study of spray booth filter system efficiency

    SciTech Connect

    Darvin, C.H.; Cox, L.S.; Smith, D.

    1997-12-31

    During recent years, greater emphasis has been placed on the control of particulate emissions from painting operations. This has gained importance as more is learned about the potential release of toxic metals to the atmosphere from painting operations. This has led to queries about the efficiency of various painting arrestor systems to reduce particulate discharges to the atmosphere. Even more important is the capability of the arrestor systems to control PM-10 emissions. In 1995, the USEPA initiated a study to evaluate various dry paint overspray arrestor systems. This study was designed to evaluate, not only the total emissions control capability of the arrestor, but also the PM-10 control capability of the various system designs. Paint overspray arrestor systems using five different filtration concepts and/or materials were selected. They include systems constructed of fiberglass, paper, styrofoam, and cardboard. These systems used filtration techniques incorporating the following filtration phenomena and designs: cyclone, baffle, bag systems, and mesh systems. The testing used an optical particle counting procedure to determine the concentration of particles of a given size fraction to penetrate a test arrestor system. The results of the testing indicated that there are significant differences in the efficiency of the tested system designs to capture and retain PM-10. This paper summarizes the results of the research conducted to determine the capability of the arrestor systems to capture particulate of particle sizes down to approximately 1 {micro}m in surface diameter.

  9. Inactivation efficiency to Bacillus subtilis and Escherichia coli bacterial aerosols of spraying neutral electrolyzed water.

    PubMed

    Chuang, Chi-Yu; Yang, Shinhao; Chang, Ming-Yih; Huang, Hsiao-Chien; Luo, Chin-Hsiang; Hung, Po-Chen; Fang, Wei

    2013-12-01

    The main objective of this study is to apply neutral electrolyzed water (NEW) spraying to inactivate bioaerosols. We evaluated the inactivation efficiency of NEW applied to inactivate two airborne bacterial Escherichia coli and Bacillus subtilis aerosols inside an environmental-controlled chamber in the study. Generated with electrolyzing 6.15 M sodium chloride brine, the NEW with free available chlorine (FAC) concentration 50, 100, and 200 ppm was pumped with an air pressure of 70 kg/cm2 through nozzle into the chamber to inactive E. coli and B. subtilis aerosols precontaminated air (initial counts of 3 x 10(4) colony-forming units [CFU]/m3). Bacterial aerosols were collected and cultured from chamber before and after NEW spray. The air exchange rate (ACH, hr(-1)) of the chamber was set to simulate fresh air ventilating dilution of indoor environment. First-order concentration decaying coefficients (Ka, min(-1)) of both bacterial aerosols were measured as an index of NEW inactivation efficiency. The result shows that higher FAC concentration of NEW spray caused better inactivation efficiency. The Ka values under ACH 1.0 hr(-1) were 0.537 and 0.598 for E. coli of FAC 50 and 100 ppm spraying, respectively. The Ka values of FAC 100 ppm and 200 ppm spraying for B. subtilis were 0.063 and 0.085 under ACH 1.0 hr(-1), respectively. The results indicated that NEW spray is likely to be effective in inactivation of bacterial airborne contamination. Moreover, it is observed in the study that the increase of ventilation rate and the use of a larger orifice-size nozzle may facilitate the inactivation efficiency. PMID:24558707

  10. Solid versus Liquid Particle Sampling Efficiency of Three Personal Aerosol Samplers when Facing the Wind

    PubMed Central

    Koehler, Kirsten A.; Anthony, T. Renee; Van Dyke, Michael

    2016-01-01

    The objective of this study was to examine the facing-the-wind sampling efficiency of three personal aerosol samplers as a function of particle phase (solid versus liquid). Samplers examined were the IOM, Button, and a prototype personal high-flow inhalable sampler head (PHISH). The prototype PHISH was designed to interface with the 37-mm closed-face cassette and provide an inhalable sample at 10 l min−1 of flow. Increased flow rate increases the amount of mass collected during a typical work shift and helps to ensure that limits of detection are met, particularly for well-controlled but highly toxic species. Two PHISH prototypes were tested: one with a screened inlet and one with a single-pore open-face inlet. Personal aerosol samplers were tested on a bluff-body disc that was rotated along the facing-the-wind axis to reduce spatiotemporal variability associated with sampling supermicron aerosol in low-velocity wind tunnels. When compared to published data for facing-wind aspiration efficiency for a mouth-breathing mannequin, the IOM oversampled relative to mannequin facing-the-wind aspiration efficiency for all sizes and particle types (solid and liquid). The sampling efficiency of the Button sampler was closer to the mannequin facing-the-wind aspiration efficiency than the IOM for solid particles, but the screened inlet removed most liquid particles, resulting in a large underestimation compared to the mannequin facing-the-wind aspiration efficiency. The open-face PHISH results showed overestimation for solid particles and underestimation for liquid particles when compared to the mannequin facing-the-wind aspiration efficiency. Substantial (and statistically significant) differences in sampling efficiency were observed between liquid and solid particles, particularly for the Button and screened-PHISH, with a majority of aerosol mass depositing on the screened inlets of these samplers. Our results suggest that large droplets have low penetration efficiencies

  11. Degradation of HEPA filters exposed to DMSO

    SciTech Connect

    Bergman, W.; Wilson, K.; Larsen, G.; Lopez, R.; LeMay, J.

    1994-07-11

    Dimethyl sulfoxide (DMSO) sprays are being used to remove the high explosive (HE) from nuclear weapons in the process of their dismantlement. A boxed 50 cfm HEPA filter with an integral prefilter was exposed to DMSO vapor and aerosols that were generated by a spray nozzle to simulate conditions expected in the HE dissolution operation. After 198 hours of operation, the pressure drop of the filter had increased from 1.15 inches to 2.85 inches, and the efficiency for 0.3 {mu}m dioctyl sebacate (DOS) aerosols decreased from 99.992% to 98.6%. Most of the DMSO aerosols had collected as a liquid pool inside the boxed HEPA. The liquid was blown out of the filter exit with 100 cfm air flow at the end of the test. Since the filter still met the minimum allowed efficiency of 99.97% after 166 hours of exposure, we recommend replacing the filter every 160 hours of operation or sooner if the pressure drop increases by 50%. Examination of the filter showed that visible cracks appeared at the joints of the wooden frame and a portion of the sealant had pulled away from the frame. Since all of the DMSO will be trapped in the first HEPA filter, the second HEPA filter should not suffer from DMSO degradation. Thus the combined efficiency for the first filter (98.6%) and the second filter (99.97%) is 99.99996% for 0.3{mu}m particles. If the first filter is replaced prior to its degradation, each of the filters will have 99.97% efficiency, and the combined efficiency will be 99.999991%. The collection efficiency for DMSO/HE aerosols will be much higher because the particle size is much greater.

  12. Degradation of HEPA filters exposed to DMSO

    SciTech Connect

    Bergman, W.; Wilson, K.; Larsen, G.

    1995-02-01

    Dimethyl sulfoxide (DMSO) sprays are being used to remove the high explosive (HE) from nuclear weapons in the process of their dismantlement. A boxed 50 cmf HEPA filter with an integral prefilter was exposed to DMSO vapor and aerosols that were generated by a spray nozzle to simulate conditions expected in the HE dissolution operation. After 198 hours of operation, the pressure drop of the filter had increased form 1.15 inches to 2,85 inches, and the efficiency for 0.3 {mu}m dioctyl sebacate (DOS) aerosols decreased form 99.992% to 98.6%. Most of the DMSO aerosols had collected as a liquid pool inside the boxed HEPA. The liquid was blown out of the filter exit with 100 cmf air flow at the end of the test. Since the filter still met the minimum allowed efficiency of 99.97% after 166 hours of exposure, we recommend replacing the filter every 160 hours of operation or sooner if the pressure drop increases by 50%. Examination of the filter showed that visible cracks appeared at the joints of the wooden frame and a portion of the sealant had pulled away from the frame. Since all of the DMSO will be trapped in the first HEPA filter, the second HEPA filter should not suffer from DMSO degradation. Thus the combined efficiency for the first filter (98.6%) and the second filter (99.97%) is 99.99996% for 0.3 {mu}m particles. If the first filter is replaced prior to its degradation, each of the filters will have 99.97% efficiency, and the combined efficiency will be 99.999991%. The collection efficiency for DMSO/HE aerosols will be much higher because the particle size is much greater.

  13. A Fast and Efficient Version of the TwO-Moment Aerosol Sectional (TOMAS) Global Aerosol Microphysics Model

    NASA Technical Reports Server (NTRS)

    Lee, Yunha; Adams, P. J.

    2012-01-01

    This study develops more computationally efficient versions of the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithms, collectively called Fast TOMAS. Several methods for speeding up the algorithm were attempted, but only reducing the number of size sections was adopted. Fast TOMAS models, coupled to the GISS GCM II-prime, require a new coagulation algorithm with less restrictive size resolution assumptions but only minor changes in other processes. Fast TOMAS models have been evaluated in a box model against analytical solutions of coagulation and condensation and in a 3-D model against the original TOMAS (TOMAS-30) model. Condensation and coagulation in the Fast TOMAS models agree well with the analytical solution but show slightly more bias than the TOMAS-30 box model. In the 3-D model, errors resulting from decreased size resolution in each process (i.e., emissions, cloud processing wet deposition, microphysics) are quantified in a series of model sensitivity simulations. Errors resulting from lower size resolution in condensation and coagulation, defined as the microphysics error, affect number and mass concentrations by only a few percent. The microphysics error in CN70CN100 (number concentrations of particles larger than 70100 nm diameter), proxies for cloud condensation nuclei, range from 5 to 5 in most regions. The largest errors are associated with decreasing the size resolution in the cloud processing wet deposition calculations, defined as cloud-processing error, and range from 20 to 15 in most regions for CN70CN100 concentrations. Overall, the Fast TOMAS models increase the computational speed by 2 to 3 times with only small numerical errors stemming from condensation and coagulation calculations when compared to TOMAS-30. The faster versions of the TOMAS model allow for the longer, multi-year simulations required to assess aerosol effects on cloud lifetime and precipitation.

  14. Tandem filters using frequency selective surfaces for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    DOEpatents

    Dziendziel, Randolph J.; Baldasaro, Paul F.; DePoy, David M.

    2010-09-07

    This invention relates to the field of thermophotovoltaic (TPV) direct energy conversion. In particular, TPV systems use filters to minimize parasitic absorption of below bandgap energy. This invention constitutes a novel combination of front surface filters to increase TPV conversion efficiency by reflecting useless below bandgap energy while transmitting a very high percentage of the useful above bandgap energy. In particular, a frequency selective surface is used in combination with an interference filter. The frequency selective surface provides high transmission of above bandgap energy and high reflection of long wavelength below bandgap energy. The interference filter maintains high transmission of above bandgap energy and provides high reflection of short wavelength below bandgap energy and a sharp transition from high transmission to high reflection.

  15. Tandem filters using frequency selective surfaces for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    DOEpatents

    Dziendziel, Randolph J.; DePoy, David Moore; Baldasaro, Paul Francis

    2007-01-23

    This invention relates to the field of thermophotovoltaic (TPV) direct energy conversion. In particular, TPV systems use filters to minimize parasitic absorption of below bandgap energy. This invention constitutes a novel combination of front surface filters to increase TPV conversion efficiency by reflecting useless below bandgap energy while transmitting a very high percentage of the useful above bandgap energy. In particular, a frequency selective surface is used in combination with an interference filter. The frequency selective surface provides high transmission of above bandgap energy and high reflection of long wavelength below bandgap energy. The interference filter maintains high transmission of above bandgap energy and provides high reflection of short wavelength below bandgap energy and a sharp transition from high transmission to high reflection.

  16. Criteria for calculating the efficiency of deep-pleated HEPA filters with aluminum separators during and after design basis accidents

    SciTech Connect

    Bergman, W.; First, M.W.; Anderson, W.L.; Gilbert, H.; Jacox, J.W.

    1995-02-01

    The authors have reviewed the literature on the performance of high efficiency particulate air (HEPA) filters under normal and abnormal conditions to establish criteria for calculating the efficiency of HEPA filters in a DOE nonreactor nuclear facility during and after a Design Basis Accident (DBA). This study is only applicable to the standard deep-pleated HEPA filter with aluminum separators as specified in ASME N509. The literature review included the performance of new filters and parameters that may cause deterioration in the filter performance such as filter age, radiation, corrosive chemicals, seismic and rough handling, high temperature, moisture, particle clogging, high air flow and pressure pulses. The deterioration of the filter efficiency depends on the exposure parameters; in severe exposure conditions the filter will be structurally damaged and have a residual efficiency of 0%. Despite the many studies on HEPA filter performance under adverse conditions, there are large gaps and limitations in the data that introduce significant error in the estimates of HEPA filter efficiencies under DBA conditions. Because of this limitation, conservative values of filter efficiency were chosen when there was insufficient data.

  17. Improving the treatment efficiency of constructed wetlands with zeolite-containing filter sands.

    PubMed

    Bruch, Ingo; Fritsche, Johannes; Bänninger, Dominik; Alewell, Ulrike; Sendelov, Michael; Hürlimann, Heinz; Hasselbach, Ralf; Alewell, Christine

    2011-01-01

    In this study the physical and chemical properties of three different lava sands used in constructed wetlands for municipal wastewater treatment were investigated. The aim was to identify those properties and mechanisms that render lava sands as highly efficient filter media which could substitute conventional, fluviatile sands. It was shown that although lava sands per se may be suitable filter materials, the presence of zeolite minerals within the lava sands enhances the purification efficiency tremendously. Zeolites not only increase the sorption capacity, but even more important, they are able to absorb water in large amounts, which in turn leads to stronger swelling. The latter reduces hydrological conductivity considerably, resulting in a longer contact time to eliminate pollutants. A simple mineralogical survey of filter materials for the presence of zeolites may render many installations of constructed wetlands successful. PMID:20933388

  18. AMS Measurements in National Parks of Aerosol Mass, Size and Composition, Comparison with Filter Samples and Correlation with Particle Hygroscopicity and Optical Extinction Properties

    NASA Astrophysics Data System (ADS)

    Alexander, M.; Taylor, N. F.; Collins, D. R.; Kumar, N.; Allen, J.; Newburn, M.; Lowenthal, D. H.; Zielinska, B.

    2011-12-01

    We report a comparison of results from aerosol studies at Great Smoky Mountain National Park (2006), Mt. Rainier National Park (2009) and Acadia National Park (2011), all class I visibility areas associated with IMPROVE (Interagency Monitoring of Protected Visual Environments) sites. This collaborative study was sponsored by the Electric Power Research Institute (EPRI) and was done with the cooperation of the National Park Service and the EPA. The atmospheric aerosol composition in these sites is influenced by a number of anthropogenic as well as biogenic sources, providing a rich environment for fundamental aerosol studies. The primary purpose of these studies was to add state-of-the-art aerosol instrumentation to the standard light extinction and aerosol measurements at the site, used to determine parameters for the IMPROVE light extinction reconstruction equation, adopted by the EPA to estimate light extinction from atmospheric aerosol concentrations and Rayleigh scattering. The combination of these diverse measurements also provides significant insight into fundamental aerosol properties such as aging and radiative forcing. New instrumentation included a quadrupole aerosol mass spectrometer (Aerodyne Q-AMS-Smoky Mountain Study), a high resolution aerosol time-of-flight mass spectrometer (Aerodyne HR-ToF-AMS - Mt. Rainier and Acadia studies) for real time measurements that directly address the relationship between sulfate, nitrate, and OC size and concentration, which is related to cloud and dry gas-to-particle conversion as air masses age during transport, the relationship between WSOC hygroscopic growth and oxygenated organic (OOA) composition, the OCM/OC ratio, and the chemical composition that determines the ambient hygroscopic state. The OCM/OC ratio and organic water uptake was addressed with high-volume and medium volume PM2.5 aerosol samples. Aerosols were collected daily on Teflon coated glass fiber filters (TGFF) in four high-volume PM2.5 samplers

  19. Probabilistic Evaluation of the Vegetated Filter Strip Efficiency With Respect to Pathogen Removal From Runoff

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vegetated filter strips (VFS) have become an important component of the water quality improvement in watersheds. Relatively little is known about the efficiency of VFSs in retention of manure-borne pathogens that can be important agricultural pollutants. The objective of this work was to evaluate th...

  20. Mathematical Model for Determinating the Efficiency of Separation of Aerosols in Dry and Sprayed Channels

    NASA Astrophysics Data System (ADS)

    Laptev, A. G.; Iskhakov, A. R.

    2014-05-01

    Turbulent fl ow of aerosols in a cylindrical channel has been investigated. Differential equations of transfer of dispersed particles have been considered, and a two-dimensional equation with a mass source has been solved. Different numerical experiments have been conducted on the basis of the model proposed. Air with water droplets was used as a gas-liquid mixture in the calculations. The influence of the spraying of the channel, the fl ow velocity, the diameter of dispersed particles, and the water concentration on the separation efficiency of an aerosol have been studied. Agreement with experimental data has been shown. A mathematical model has been developed that can be used in designing gas-cleaning apparatuses for enterprises of various industries.

  1. Numerical Study of Usage Efficiency of Multistage Filters on Mineral Leaching Process

    NASA Astrophysics Data System (ADS)

    Inkarbekov, Medet; Kuljabekov, Alibek; Alibayeva, Karlygash; Kaltayev, Aidarkhan

    2013-11-01

    The numerical study of the usage efficiency of the multistage filters setting technology is carried out on the basis of mathematical simulation. And its application on in-situ mineral leaching process is considered. So long as mineral bearing sandstone in deposit mostly is separated by interbedded layers of sands and clays, it's expedient to use multistage filters setting technology at the mineral extraction. A comparison of the extraction degree at single and multistage filters is implemented. The results of calculations show that the distribution of flow (inflow) on well height is not uniform. In the calculations the well accepted as high-permeability channel, depending on the construction of the filter. Obtained results for a multistage filters setting qualitatively conform to the experimental findings. Wellbore is considered as a surface with a constant reduced pressure in the bottomhole formation zone. But such assumption does not show a qualitative picture of the fluid flow in the bottomhole zone [Brovin K.G., Grabovnikov V.A., 1997]. To construct an accurate mathematical model it's necessary to use Navier-Stokes equation for the interior of a vertical wellbore, and the filtration law for modeling the filtration in the reservoir. Strictly speaking, it would have had to sew two laws on the contact surface of a rock and filter. Such review requires enormous computing, as far as computational grid must be sufficiently thick to cover the interior of the wellbore.

  2. High efficiency filter systems -- General observations, 1992--1993. Status report

    SciTech Connect

    Mauzy, A.; Mokler, B.V.; Scripsick, R.C.

    1994-05-01

    Reviews of air emission control systems have been conducted at selected facilities supported by the Department of Energy (DOE) Office of Nuclear Energy (NE). Large High efficiency particulate air (HEPA) filtration systems and their testing received particular emphasis. Although significant differences between the sites were found, there were also several common issues. These are discussed under four general topic areas: policy development, testing multiple state systems, guidance on in-place filter testing and system supervision, and uncertainty in in-place filter testing results. Two principal conclusions have emerged from these reviews. First, there is an immediate need to develop information on how filter mechanical integrity decreases with time and use this to establish limits on filter service life. Second, there is a general need to ensure the validity of in-place filter testing results and improve testing practices. A mathematical framework for describing the effects of nonideal system features on testing results is proposed as an aid in understanding the uncertainty in in-place filter testing results.

  3. Testing Air-Filtering Systems

    PubMed Central

    Songer, Joseph R.; Sullivan, James F.; Hurd, James W.

    1963-01-01

    A procedure was developed for evaluating high-efficiency filters mounted in exhaust ducts at the National Animal Disease Laboratory. An aerosol of the test organism, Escherichia coli B T3 bacteriophage, was generated in a chamber attached to a ceiling exhaust register in concentrations of at least 1000 viable organisms per ft3 of air. Samples were collected from both the pre- and postfilter areas, and the number of organisms per ft3 of air was determined. The efficiency of the filter was calculated from these figures. A total of 269 high-efficiency filters were tested. Of these, 249 had efficiencies of 98% or greater. The remaining 20, with efficiencies of less than 98%, were repaired and retested. No filter was accepted with an efficiency of less than 98%. Images Fig. 2 PMID:14063779

  4. Rhenium-phthalocyanine molecular nanojunction with high magnetic anisotropy and high spin filtering efficiency

    SciTech Connect

    Li, J.; Hu, J.; Wang, H.; Wu, R. Q.

    2015-07-20

    Using the density functional and non-equilibrium Green's function approaches, we studied the magnetic anisotropy and spin-filtering properties of various transition metal-Phthalocyanine molecular junctions across two Au electrodes. Our important finding is that the Au-RePc-Au junction has both large spin filtering efficiency (>80%) and large magnetic anisotropy energy, which makes it suitable for device applications. To provide insights for the further experimental work, we discussed the correlation between the transport property, magnetic anisotropy, and wave function features of the RePc molecule, and we also illustrated the possibility of controlling its magnetic state.

  5. Plutonium Finishing Plant (PFP) Waste Composition and High Efficiency Particulate Air Filter Loading

    SciTech Connect

    ZIMMERMAN, B.D.

    2000-12-11

    This analysis evaluates the effect of the Plutonium Finishing Plant (PFP) waste isotopic composition on Tank Farms Final Safety Analysis Report (FSAR) accidents involving high-efficiency particulate air (HEPA) filter failure in Double-Contained Receiver Tanks (DCRTs). The HEPA Filter Failure--Exposure to High Temperature or Pressure, and Steam Intrusion From Interfacing Systems accidents are considered. The analysis concludes that dose consequences based on the PFP waste isotopic composition are bounded by previous FSAR analyses. This supports USQD TF-00-0768.

  6. Efficiency of automotive cabin air filters to reduce acute health effects of diesel exhaust in human subjects

    PubMed Central

    Rudell, B.; Wass, U.; Horstedt, P.; Levin, J. O.; Lindahl, R.; Rannug, U.; Sunesson, A. L.; Ostberg, Y.; Sandstrom, T.

    1999-01-01

    OBJECTIVES: To evaluate the efficiency of different automotive cabin air filters to prevent penetration of components of diesel exhaust and thereby reduce biomedical effects in human subjects. Filtered air and unfiltered diluted diesel exhaust (DDE) were used as negative and positive controls, respectively, and were compared with exposure to DDE filtered with four different filter systems. METHODS: 32 Healthy non- smoking subjects (age 21-53) participated in the study. Each subject was exposed six times for 1 hour in a specially designed exposure chamber: once to air, once to unfiltered DDE, and once to DDE filtered with the four different cabin air filters. Particle concentrations during exposure to unfiltered DDE were kept at 300 micrograms/m3. Two of the filters were particle filters. The other two were particle filters combined with active charcoal filters that might reduce certain gaseous components. Subjective symptoms were recorded and nasal airway lavage (NAL), acoustic rhinometry, and lung function measurements were performed. RESULTS: The two particle filters decreased the concentrations of diesel exhaust particles by about half, but did not reduce the intensity of symptoms induced by exhaust. The combination of active charcoal filters and a particle filter significantly reduced the symptoms and discomfort caused by the diesel exhaust. The most noticable differences in efficacy between the filters were found in the reduction of detection of an unpleasant smell from the diesel exhaust. In this respect even the two charcoal filter combinations differed significantly. The efficacy to reduce symptoms may depend on the abilities of the filters investigated to reduce certain hydrocarbons. No acute effects on NAL, rhinometry, and lung function variables were found. CONCLUSIONS: This study has shown that the use of active charcoal filters, and a particle filter, clearly reduced the intensity of symptoms induced by diesel exhaust. Complementary studies on vehicle

  7. Simultaneous retrieval of total ozone column amounts and cloud/aerosol optical depths from multi-channel, moderate bandwidth filter instruments

    NASA Astrophysics Data System (ADS)

    Stamnes, Knut; Fan, Lingling; Li, Wei; Dahlback, Arne; Stamnes, Jakob; Stamnes, Snorre

    2015-04-01

    A new method is presented based on using neural networks (NN) to analyze ultraviolet (UV) irradiance data recorded by multi-channel, moderate bandwidth filter instruments. Application of the NN method to three years of data obtained by a NILU-UV multi-channel, moderate bandwidth filter instrument, revealed that compared to a traditional look-up table (LUT) method, the NN method yielded better agreement against the Ozone Monitoring Instrument (OMI) with a 1% decrease in relative difference and a significant increase in the correlation of total ozone column (TOC) values. Furthermore, this new method resulted in larger number of valid retrievals (daily average values within a meaningful range of 200-500 DU) than the LUT method. Compared with NN retrievals based on NILU-UV irradiance measurements, TOC values obtained from OMI were underestimated under cloudy conditions. Cloud optical depth (COD) values derived by the NN method were more reliable than corresponding results derived by the LUT method, the latter results were less accurate for heavy cloud cover, broken cloud situations or snow-covered ground. The potential for retrieving aerosol optical depth (AOD) values under cloud-free conditions will be discussed. The cloud-aerosol information obtained by irradiance instruments such as the NILU-UV can be used in conjunction with a radiative transfer model to estimate cloud/aerosol radiative forcing and hence the impact of clouds and aerosols on the radiative energy balance. Deployment of multi-channel, moderate bandwidth filter instruments at AERONET sites and analysis of such data in conjunction with AERONET and satellite remote sensing data can provide crucial information needed for the assessment of the influence of ozone, clouds, and aerosols on climate.

  8. Construction of filter vectors for the information-efficient spectral imaging sensor

    SciTech Connect

    Stallard, B.R.; Gentry, S.M.

    1998-12-01

    The information-efficient spectral imaging sensor (ISIS) seeks to improve system performance by processing hyperspectral information in the optical hardware. Its output may be a gray scale image in which one attempts to maximize the contrast between a given target and the background. Alternatively, its output may be a small number of images, rather than a full data cube, that retain the essential information required in the application. The principal advantage of ISIS is that it offers the discrimination of hyperspectral imaging while achieving the signal-to-noise ratio of multispectral imaging. The paper focuses on construction of the filter vectors that are needed to program ISIS. The instrument produces an image which is essentially a dot product of the scene and the filter vector. Both single vector and multiple vector approaches are considered. Also, they discuss some subtle points related to optimizing the filter vectors.

  9. Roll-to-Roll Transfer of Electrospun Nanofiber Film for High-Efficiency Transparent Air Filter.

    PubMed

    Xu, Jinwei; Liu, Chong; Hsu, Po-Chun; Liu, Kai; Zhang, Rufan; Liu, Yayuan; Cui, Yi

    2016-02-10

    Particulate matter (PM) pollution in air has become a serious environmental issue calling for new type of filter technologies. Recently, we have demonstrated a highly efficient air filter by direct electrospinning of polymer fibers onto supporting mesh although its throughput is limited. Here, we demonstrate a high throughput method based on fast transfer of electrospun nanofiber film from roughed metal foil to a receiving mesh substrate. Compared with the direct electrospinning method, the transfer method is 10 times faster and has better filtration performance at the same transmittance, owing to the uniformity of transferred nanofiber film (>99.97% removal of PM2.5 at ∼73% of transmittance). With these advantages, large area freestanding nanofiber film and roll-to-roll production of air filter are demonstrated. PMID:26789781

  10. Energy efficient in-network RFID data filtering scheme in wireless sensor networks.

    PubMed

    Bashir, Ali Kashif; Lim, Se-Jung; Hussain, Chauhdary Sajjad; Park, Myong-Soon

    2011-01-01

    RFID (Radio frequency identification) and wireless sensor networks are backbone technologies for pervasive environments. In integration of RFID and WSN, RFID data uses WSN protocols for multi-hop communications. Energy is a critical issue in WSNs; however, RFID data contains a lot of duplication. These duplications can be eliminated at the base station, but unnecessary transmissions of duplicate data within the network still occurs, which consumes nodes' energy and affects network lifetime. In this paper, we propose an in-network RFID data filtering scheme that efficiently eliminates the duplicate data. For this we use a clustering mechanism where cluster heads eliminate duplicate data and forward filtered data towards the base station. Simulation results prove that our approach saves considerable amounts of energy in terms of communication and computational cost, compared to existing filtering schemes. PMID:22163999

  11. Energy Efficient In-network RFID Data Filtering Scheme in Wireless Sensor Networks

    PubMed Central

    Bashir, Ali Kashif; Lim, Se-Jung; Hussain, Chauhdary Sajjad; Park, Myong-Soon

    2011-01-01

    RFID (Radio frequency identification) and wireless sensor networks are backbone technologies for pervasive environments. In integration of RFID and WSN, RFID data uses WSN protocols for multi-hop communications. Energy is a critical issue in WSNs; however, RFID data contains a lot of duplication. These duplications can be eliminated at the base station, but unnecessary transmissions of duplicate data within the network still occurs, which consumes nodes’ energy and affects network lifetime. In this paper, we propose an in-network RFID data filtering scheme that efficiently eliminates the duplicate data. For this we use a clustering mechanism where cluster heads eliminate duplicate data and forward filtered data towards the base station. Simulation results prove that our approach saves considerable amounts of energy in terms of communication and computational cost, compared to existing filtering schemes. PMID:22163999

  12. Efficient spin filter using multi-terminal quantum dot with spin-orbit interaction

    PubMed Central

    2011-01-01

    We propose a multi-terminal spin filter using a quantum dot with spin-orbit interaction. First, we formulate the spin Hall effect (SHE) in a quantum dot connected to three leads. We show that the SHE is significantly enhanced by the resonant tunneling if the level spacing in the quantum dot is smaller than the level broadening. We stress that the SHE is tunable by changing the tunnel coupling to the third lead. Next, we perform a numerical simulation for a multi-terminal spin filter using a quantum dot fabricated on semiconductor heterostructures. The spin filter shows an efficiency of more than 50% when the conditions for the enhanced SHE are satisfied. PACS numbers: 72.25.Dc,71.70.Ej,73.63.Kv,85.75.-d PMID:21711500

  13. GUIDE TO CALCULATING TRANSPORT EFFICIENCY OF AEROSOLS IN OCCUPATIONAL AIR SAMPLING SYSTEMS

    SciTech Connect

    Hogue, M.; Hadlock, D.; Thompson, M.; Farfan, E.

    2013-11-12

    This report will present hand calculations for transport efficiency based on aspiration efficiency and particle deposition losses. Because the hand calculations become long and tedious, especially for lognormal distributions of aerosols, an R script (R 2011) will be provided for each element examined. Calculations are provided for the most common elements in a remote air sampling system, including a thin-walled probe in ambient air, straight tubing, bends and a sample housing. One popular alternative approach would be to put such calculations in a spreadsheet, a thorough version of which is shared by Paul Baron via the Aerocalc spreadsheet (Baron 2012). To provide greater transparency and to avoid common spreadsheet vulnerabilities to errors (Burns 2012), this report uses R. The particle size is based on the concept of activity median aerodynamic diameter (AMAD). The AMAD is a particle size in an aerosol where fifty percent of the activity in the aerosol is associated with particles of aerodynamic diameter greater than the AMAD. This concept allows for the simplification of transport efficiency calculations where all particles are treated as spheres with the density of water (1g cm-3). In reality, particle densities depend on the actual material involved. Particle geometries can be very complicated. Dynamic shape factors are provided by Hinds (Hinds 1999). Some example factors are: 1.00 for a sphere, 1.08 for a cube, 1.68 for a long cylinder (10 times as long as it is wide), 1.05 to 1.11 for bituminous coal, 1.57 for sand and 1.88 for talc. Revision 1 is made to correct an error in the original version of this report. The particle distributions are based on activity weighting of particles rather than based on the number of particles of each size. Therefore, the mass correction made in the original version is removed from the text and the calculations. Results affected by the change are updated.

  14. Efficient implementations of pipelined CORDIC-based IIR digital filters using fast orthonormal μ-rotations

    NASA Astrophysics Data System (ADS)

    Ma, Jun; Parhi, Keshab K.; Hekstra, Gerben J.; Deprettere, Ed F. A.

    1998-10-01

    CORDIC based IIR digital filters are orthogonal filters whose internal computations consist of orthogonal transformations. These filters possess desirable properties for VLSI implementations such as regularity, local connection, low sensitivity to finite word-length implementation, and elimination of limit cycles. Recently, fine-grain pipelined CORDIC based IIR digital filter architectures which can perform the filtering operations at arbitrarily high sample rates at the cost of linear increase in hardware complexity have been developed. These pipelined architectures consists of only Givens rotations and a few additions which can be mapped onto CORDIC arithmetic based processors. However, in practical applications, implementations of GIvens rotations using traditional CORDIC arithmetic are quite expensive. For example, for 16 bit accuracy, using floating point data format with 16 bit mantissa and 5 bit exponent, it will require approximately 20 pairs of shift-add operations for one Givens rotation. In this paper, we propose an efficient implementation of pipelined CORDIC based IIR digital filters based on fast orthonormal (mu) -rotations. Using this method, the Givens rotations are approximated by angel corresponding to orthonormal (mu) -rotations, which are based on the idea of CORDIC and can perform rotation with minimal number of shift-add operations. We present various methods of construction for such orthonormal (mu) -rotations. A significant reduction of the number of required shift-add operations is achieved. All types of fast rotations can be implemented as a cascade of only four basic types of shift-add stages. These stages can be executed on a modified floating-point CORDIC architecture, making the pipelined filter highly suitable for VLSI implementations.

  15. Efficient variable bandwidth filters for digital hearing aid using Farrow structure

    PubMed Central

    Haridas, Nisha; Elias, Elizabeth

    2015-01-01

    Design of a digital hearing aid requires a set of filters that gives reasonable audiogram matching for the concerned type of hearing loss. This paper proposes the use of a variable bandwidth filter, using Farrow subfilters, for this purpose. The design of the variable bandwidth filter is carried out for a set of selected bandwidths. Each of these bands is frequency shifted and provided with sufficient magnitude gain, such that, the different bands combine to give a frequency response that closely matches the audiogram. Due to the adjustable bandedges in the basic filter, this technique allows the designer to add reconfigurability to the system. This technique is simple and efficient when compared with the existing methods. Results show that lower order filters and better audiogram matching with lesser matching errors are obtained using Farrow structure. This, in turn reduces implementation complexity. The cost effectiveness of this technique also comes from the fact that, the user can reprogram the same device, once his hearing loss pattern is found to have changed in due course of time, without the need to replace it completely. PMID:26966566

  16. Aerosol distribution apparatus

    DOEpatents

    Hanson, W.D.

    An apparatus for uniformly distributing an aerosol to a plurality of filters mounted in a plenum, wherein the aerosol and air are forced through a manifold system by means of a jet pump and released into the plenum through orifices in the manifold. The apparatus allows for the simultaneous aerosol-testing of all the filters in the plenum.

  17. Aerosol Direct Radiative Forcing and Forcing Efficiencies at Surface from the shortwave Irradiance Measurements in Abu Dhabi, UAE

    NASA Astrophysics Data System (ADS)

    Beegum S, N.; Ben Romdhane, H.; Ghedira, H.

    2013-12-01

    Atmospheric aerosols are known to affect the radiation balance of the Earth-Atmospheric system directly by scattering and absorbing the solar and terrestrial radiation, and indirectly by affecting the lifetime and albedo of the clouds. Continuous and simultaneous measurements of short wave global irradiance in combination with synchronous spectral aerosol optical depth (AOD) measurements (from 340 nm to 1640 nm in 8 channels), for a period of 1 year from June 2012 to May 2013, were used for the determination of the surface direct aerosol radiative forcing and forcing efficiencies under cloud free conditions in Abu Dhabi (24.42°N, 54.61o E, 7m MSL), a coastal location in United Arab Emirates (UAE) in the Arabian Peninsula. The Rotating Shadow band Pyranometer (RSP, LI-COR) was used for the irradiance measurements (in the spectral region 400-1100 nm), whereas the AOD measurements were carried out using CIMEL Sunphotometer (CE 318-2, under AERONET program). The differential method, which is neither sensitive to calibration uncertainties nor model assumptions, has been employed for estimating forcing efficiencies from the changes in the measured fluxes. The forcing efficiency, which quantifies the net change in irradiance per unit change in AOD, is an appropriate parameter for the characterization of the aerosol radiative effects even if the microphysical and optical properties of the aerosols are not completely understood. The corresponding forcing values were estimated from the forcing efficiencies. The estimated radiative forcing and forcing efficiencies exhibited strong monthly variations. The forcing efficiencies (absolute magnitudes) were highest during March, and showed continuous decrease thereafter to reach the lowest value during September. In contrast, the forcing followed a slightly different pattern of variability, with the highest solar dimming during April ( -60 W m-2) and the minimum during February ( -20 W m-2). The results indicate that the aerosol

  18. Arsenic removal from drinking water by a household sand filter in Vietnam--effect of filter usage practices on arsenic removal efficiency and microbiological water quality.

    PubMed

    Nitzsche, Katja Sonja; Lan, Vi Mai; Trang, Pham Thi Kim; Viet, Pham Hung; Berg, Michael; Voegelin, Andreas; Planer-Friedrich, Britta; Zahoransky, Jan; Müller, Stefanie-Katharina; Byrne, James Martin; Schröder, Christian; Behrens, Sebastian; Kappler, Andreas

    2015-01-01

    Household sand filters are applied to treat arsenic- and iron-containing anoxic groundwater that is used as drinking water in rural areas of North Vietnam. These filters immobilize poisonous arsenic (As) via co-oxidation with Fe(II) and sorption to or co-precipitation with the formed Fe(III) (oxyhydr)oxides. However, information is lacking regarding the effect of the frequency and duration of filter use as well as of filter sand replacement on the residual As concentrations in the filtered water and on the presence of potentially pathogenic bacteria in the filtered and stored water. We therefore scrutinized a household sand filter with respect to As removal efficiency and the presence of fecal indicator bacteria in treated water as a function of filter operation before and after sand replacement. Quantification of As in the filtered water showed that periods of intense daily use followed by periods of non-use and even sand replacement did not significantly (p<0.05) affect As removal efficiency. The As concentration was reduced during filtration from 115.1 ± 3.4 μg L(-1) in the groundwater to 5.3 ± 0.7 μg L(-1) in the filtered water (95% removal). The first flush of water from the filter contained As concentrations below the drinking water limit and suggests that this water can be used without risk for human health. Colony forming units (CFUs) of coliform bacteria increased during filtration and storage from 5 ± 4 per 100mL in the groundwater to 5.1 ± 1.5 × 10(3) and 15 ± 1.4 × 10(3) per 100mL in the filtered water and in the water from the storage tank, respectively. After filter sand replacement, CFUs of Escherichia coli of <100 per 100mL were quantified. None of the samples contained CFUs of Enterococcus spp. No critical enrichment of fecal indicator bacteria belonging to E. coli or Enterococcus spp. was observed in the treated drinking water by qPCR targeting the 23S rRNA gene. The results demonstrate the efficient and reliable performance of household

  19. Estimation of aerosol mass scattering efficiencies under high mass loading: case study for the megacity of Shanghai, China.

    PubMed

    Cheng, Zhen; Jiang, Jingkun; Chen, Changhong; Gao, Jian; Wang, Shuxiao; Watson, John G; Wang, Hongli; Deng, Jianguo; Wang, Buying; Zhou, Min; Chow, Judith C; Pitchford, Marc L; Hao, Jiming

    2015-01-20

    Aerosol mass scattering efficiency (MSE), used for the scattering coefficient apportionment of aerosol species, is often studied under the condition of low aerosol mass loading in developed countries. Severe pollution episodes with high particle concentration frequently happened in eastern urban China in recent years. Based on synchronous measurement of aerosol physical, chemical, and optical properties at the megacity of Shanghai for two months during autumn 2012, we studied MSE characteristics at high aerosol mass loading. Their relationships with mass concentrations and size distributions were examined. It was found that MSE values from the original US IMPROVE algorithm could not represent the actual aerosol characteristics in eastern China. It results in an underestimation of the measured ambient scattering coefficient by 36%. MSE values in Shanghai were estimated to be 3.5 ± 0.55 m(2)/g for ammonia sulfate, 4.3 ± 0.63 m(2)/g for ammonia nitrate, and 4.5 ± 0.73 m(2)/g for organic matter, respectively. MSEs for three components increased rapidly with increasing mass concentration in low aerosol mass loading, then kept at a stable level after a threshold mass concentration of 12–24 μg/m(3). During severe pollution episodes, particle growth from an initial peak diameter of 200–300 nm to a peak diameter of 500–600 nm accounts for the rapid increase in MSEs at high aerosol mass loading, that is, particle diameter becomes closer to the wavelength of visible lights. This study provides insights of aerosol scattering properties at high aerosol concentrations and implies the necessity of MSE localization for extinction apportionment, especially for the polluted regions. PMID:25495050

  20. Efficient dipolar double quantum filtering under magic angle spinning without a 1H decoupling field

    NASA Astrophysics Data System (ADS)

    Courtney, Joseph M.; Rienstra, Chad M.

    2016-08-01

    We present a systematic study of dipolar double quantum (DQ) filtering in 13C-labeled organic solids over a range of magic-angle spinning rates, using the SPC-n recoupling sequence element with a range of n symmetry values from 3 to 11. We find that efficient recoupling can be achieved for values n ⩾ 7, provided that the 13C nutation frequency is on the order of 100 kHz or greater. The decoupling-field dependence was investigated and explicit heteronuclear decoupling interference conditions identified. The major determinant of DQ filtering efficiency is the decoupling interference between 13C and 1H fields. For 13C nutation frequencies greater than 75 kHz, optimal performance is observed without an applied 1H field. At spinning rates exceeding 20 kHz, symmetry conditions as low as n = 3 were found to perform adequately.

  1. Efficient dipolar double quantum filtering under magic angle spinning without a (1)H decoupling field.

    PubMed

    Courtney, Joseph M; Rienstra, Chad M

    2016-08-01

    We present a systematic study of dipolar double quantum (DQ) filtering in (13)C-labeled organic solids over a range of magic-angle spinning rates, using the SPC-n recoupling sequence element with a range of n symmetry values from 3 to 11. We find that efficient recoupling can be achieved for values n⩾7, provided that the (13)C nutation frequency is on the order of 100kHz or greater. The decoupling-field dependence was investigated and explicit heteronuclear decoupling interference conditions identified. The major determinant of DQ filtering efficiency is the decoupling interference between (13)C and (1)H fields. For (13)C nutation frequencies greater than 75kHz, optimal performance is observed without an applied (1)H field. At spinning rates exceeding 20kHz, symmetry conditions as low as n=3 were found to perform adequately. PMID:27314744

  2. Set Up For Filter And Mirror Efficiencies Measurements In The UV and VUV Spectral Range

    NASA Astrophysics Data System (ADS)

    Pouey, M.; Malherbe, A.

    1986-10-01

    A vacuum reflectometer for the UV and VUV spectral range was developed for qualification of optical components below 400 nm. Typical performances, in the 120-320 nm spectral range, of filters and mirrors offered by MATRA will be presented. Fitted with various gratings and sources this device allows reflecting, transmitting power as well as scattered or diffracted flux measurements (gratings efficiency measurements) until 25 nm.

  3. In-place HEPA (high efficiency, particulate air) filter testing at Hanford: Operating experiences, calibrations, and lessons learned

    SciTech Connect

    Flores, D.S.; Decelis, D.G.

    1989-10-01

    High Efficiency, Particulate Air (HEPA) Filters provide a minimum of 99.97% removal efficiency for particles greater than or equal to .3 microns in diameter. Each HEPA filter installation at Hanford is, at specified intervals, functionally tested for leaks. The test procedure involves a dioctylphthalate (DOP) smoke generator and a calibrated airborne particle detector. The DOP generator produces smoke of a known quantitative particle size distribution upstream of the filter. The airborne particle detector is first placed upstream, and then downstream of the filter to determine percent penetration. The smoke generator is characterized using a calibrated laser spectrometer, and the particle detector is calibrated using a calibrated picoammeter. 2 refs., 4 figs.

  4. Nanoparticle filtration performance of filtering facepiece respirators and canister/cartridge filters.

    PubMed

    Rengasamy, Samy; BerryAnn, Roland; Szalajda, Jonathan

    2013-01-01

    Respiratory protection offered by a particulate respirator is a function of the filter efficiency and face seal leakage. A previous study in our laboratory measured the filter penetration and total inward leakage (TIL) of 20-1000 nm size particles for N95 filtering facepiece respirators (FFRs) using a breathing manikin. The results showed relatively higher filter penetration and TIL value under different leak sizes and flow rates at the most penetrating particle size (MPPS), ∼45 nm for electrostatic FFRs,and ∼150 nm for the same FFRs after charge removal. This indicates an advantage of mechanical filters over electrostatic filters rated for similar filter efficiencies in providing respiratory protection in nanoparticle workplaces. To better understand the influence of the MPPS, the filtration performance of commonly used one N95 and one N100 FFR models, and four P100 canister/cartridge models were measured with monodisperse NaCl aerosols, and polydisperse NaCl aerosols employed in the National Institute for Occupational Safety and Health (NIOSH) certification test method. As expected, the polydisperse aerosol penetration was below 5% for the N95 FFR, and below 0.03% for the N100 FFR and P100 canister/cartridge filters. Monodisperse aerosol penetration results showed a MPPS of ∼40 nm for both the N95 and N100 FFRs. All four P100 canister/cartridge filters had a MPPS of ≥150 nm, similar to expectations for mechanical filters. The P100 canister/cartridge filters showed lower penetration values for different size nanoparticles than the N100 FFRs. The results indicate that a mechanical filter would offer a relatively higher filtration performance for nanoparticles than an electrostatic counterpart rated for the same filter efficiency. Overall, the results obtained in the study suggest that MPPS should be considered as a key factor in the development of respirator standards and recommendations for protection against nanoparticles. PMID:23927008

  5. Ozone-removal efficiencies of activated carbon filters after more than three years of continuous service

    SciTech Connect

    Weschler, C.J.; Shields, H.C.; Naik, D.V.

    1994-12-31

    This paper evaluates the efficiency with which commercial charcoal filters remove ozone. Three different applications have been examined: a test plenum, an air handler providing outside air to a Class 100 clean room, and a plenum downstream of an air handler providing outside air to another Class 100 clean room. After 37 months, the charcoal in the test plenum has decreased in removal efficiency from 95% to 90%. After 37 months, the charcoal servicing the first clean room has decreased in efficiency from 85% to 60%. After 24 months, the charcoal servicing the second clean room is still removing 95% of the ozone in the airstream. The charcoal filters associated with the test plenum and the second clean room are better protected from submicron particles than those associated with the first clean room. The accumulation of fine particles on the charcoal appears to influence service life. This work is an extension of the preliminary results (20 months of service) that were reported for the filters associated with the test plenum and the first clean room (Weschler et al. 1993).

  6. An Efficient Identity-Based Key Management Scheme for Wireless Sensor Networks Using the Bloom Filter

    PubMed Central

    Qin, Zhongyuan; Zhang, Xinshuai; Feng, Kerong; Zhang, Qunfang; Huang, Jie

    2014-01-01

    With the rapid development and widespread adoption of wireless sensor networks (WSNs), security has become an increasingly prominent problem. How to establish a session key in node communication is a challenging task for WSNs. Considering the limitations in WSNs, such as low computing capacity, small memory, power supply limitations and price, we propose an efficient identity-based key management (IBKM) scheme, which exploits the Bloom filter to authenticate the communication sensor node with storage efficiency. The security analysis shows that IBKM can prevent several attacks effectively with acceptable computation and communication overhead. PMID:25264955

  7. An efficient identity-based key management scheme for wireless sensor networks using the Bloom filter.

    PubMed

    Qin, Zhongyuan; Zhang, Xinshuai; Feng, Kerong; Zhang, Qunfang; Huang, Jie

    2014-01-01

    With the rapid development and widespread adoption of wireless sensor networks (WSNs), security has become an increasingly prominent problem. How to establish a session key in node communication is a challenging task for WSNs. Considering the limitations in WSNs, such as low computing capacity, small memory, power supply limitations and price, we propose an efficient identity-based key management (IBKM) scheme, which exploits the Bloom filter to authenticate the communication sensor node with storage efficiency. The security analysis shows that IBKM can prevent several attacks effectively with acceptable computation and communication overhead. PMID:25264955

  8. The effect of ash and filter media characteristics on particle filtration efficiency in fluidized bed.

    PubMed

    Wey, Ming-Yen; Chen, Ke-Hao; Liu, Kuang-Yu

    2005-05-20

    The phenomenon of filtering particles by a fluidized bed is complex and the parameters that affect the control efficiency of filtration have not yet been clarified. The major objective of the study focuses on the effect of characteristics of ash and filter media on filtration efficiency in a fluidized bed. The performance of the fluidized bed for removal of particles in flue gas at various fluidized operating conditions, and then the mechanisms of collecting particles were studied. The evaluated parameters included (1) various ashes (coal ash and incinerator ash); (2) bed material size; (3) operating gas velocity; and (4) bed temperature. The results indicate that the removal efficiency of coal ash increases initially with gas velocity, then decreases gradually as velocity exceeds some specific value. Furthermore, the removal of coal ash enhance with silica sand size decreasing. When the fluidized bed is operated at high temperature, diffusion is a more important mechanism than at room temperature especially for small particles. Although the inertial impaction is the main collection mechanism, the "bounce off" effect when the particles collide with the bed material could reduce the removal efficiency significantly. Because of layer inversion in fluidized bed, the removal efficiency of incinerator ash is decreased with increasing of gas velocity. PMID:15885419

  9. CONTROL OF INTERFACIAL DUST CAKE TO IMPROVE EFFICIENCY OF MOVING BED GRANULAR FILTERS

    SciTech Connect

    Robert C. Brown; Gerald M. Colver

    2002-10-31

    The goal of this research is to improve the performance of moving bed granular filters for gas cleaning at high temperatures and pressures. A second objective is to better understand dust capture interfacial phenomena and cake formation in moving bed filters. The experimental bed tested in the present study has several unique design features configured as cold flow, axially symmetric, counter-current flow to simulate a filter operating at high temperatures (1088 K) and elevated pressures (10 atmospheres). The granular filter is evaluated in two separate performance studies: (1) optimization of particle collection efficiency and bed pressure drop in a factorial study at near-atmospheric operating pressures through appropriate use of granular bed materials, particle sizes, and feed rates; and (2) high temperature and high pressure model simulation conducted at above-atmospheric pressures and room temperature utilizing dust and granular flow rates, granular size, system pressure, and superficial velocity. The factorial study involves a composite design of 16 near-atmospheric tests, while the model simulation study is comprised of 7 above-atmospheric tests. Similarity rules were validated in tests at four different mass dust ratios and showed nearly constant collection efficiencies ({approx} 99.5 {+-} 0.3%) for operating pressures of 160 kPa gage (23.2 psig) at room temperature (20 C), which simulates the hydrodynamic conditions expected for typical gasification streams (1088 K, 10 atmospheres). An important outcome from the near-atmospheric pressure studies are relationships developed using central composite design between the independent variables, superficial velocity (0.16-0.22 m/s), dust feed rate (0.08-0.74 kg/hr), and granular flow rate (3.32-15.4 kg/hr). These operating equations were optimized in contour plots for bed conditions that simultaneously satisfy low-pressure drop and high particle collection efficiency.

  10. Non-iridescent Transmissive Structural Color Filter Featuring Highly Efficient Transmission and High Excitation Purity

    PubMed Central

    Shrestha, Vivek Raj; Lee, Sang-Shin; Kim, Eun-Soo; Choi, Duk-Yong

    2014-01-01

    Nanostructure based color filtering has been considered an attractive replacement for current colorant pigmentation in the display technologies, in view of its increased efficiencies, ease of fabrication and eco-friendliness. For such structural filtering, iridescence relevant to its angular dependency, which poses a detrimental barrier to the practical development of high performance display and sensing devices, should be mitigated. We report on a non-iridescent transmissive structural color filter, fabricated in a large area of 76.2 × 25.4 mm2, taking advantage of a stack of three etalon resonators in dielectric films based on a high-index cavity in amorphous silicon. The proposed filter features a high transmission above 80%, a high excitation purity of 0.93 and non-iridescence over a range of 160°, exhibiting no significant change in the center wavelength, dominant wavelength and excitation purity, which implies no change in hue and saturation of the output color. The proposed structure may find its potential applications to large-scale display and imaging sensor systems. PMID:24815530

  11. Adaptive Bloom Filter: A Space-Efficient Counting Algorithm for Unpredictable Network Traffic

    NASA Astrophysics Data System (ADS)

    Matsumoto, Yoshihide; Hazeyama, Hiroaki; Kadobayashi, Youki

    The Bloom Filter (BF), a space-and-time-efficient hashcoding method, is used as one of the fundamental modules in several network processing algorithms and applications such as route lookups, cache hits, packet classification, per-flow state management or network monitoring. BF is a simple space-efficient randomized data structure used to represent a data set in order to support membership queries. However, BF generates false positives, and cannot count the number of distinct elements. A counting Bloom Filter (CBF) can count the number of distinct elements, but CBF needs more space than BF. We propose an alternative data structure of CBF, and we called this structure an Adaptive Bloom Filter (ABF). Although ABF uses the same-sized bit-vector used in BF, the number of hash functions employed by ABF is dynamically changed to record the number of appearances of a each key element. Considering the hash collisions, the multiplicity of a each key element on ABF can be estimated from the number of hash functions used to decode the membership of the each key element. Although ABF can realize the same functionality as CBF, ABF requires the same memory size as BF. We describe the construction of ABF and IABF (Improved ABF), and provide a mathematical analysis and simulation using Zipf's distribution. Finally, we show that ABF can be used for an unpredictable data set such as real network traffic.

  12. Efficiency and adaptability of the benthic methane filter at Quepos Slide cold seeps, offshore Costa Rica

    NASA Astrophysics Data System (ADS)

    Steeb, P.; Krause, S.; Linke, P.; Hensen, C.; Dale, A. W.; Nuzzo, M.; Treude, T.

    2014-11-01

    Large amounts of methane are delivered by fluids through the erosive forearc of the convergent margin offshore Costa Rica and lead to the formation of cold seeps at the sediment surface. Besides mud extrusion, numerous cold seeps are created by landslides induced by seamount subduction or fluid migration along major faults. Most of the dissolved methane reaching the seafloor at cold seeps is oxidized within the benthic microbial methane filter by anaerobic oxidation of methane (AOM). Measurements of AOM and sulfate reduction as well as numerical modeling of porewater profiles revealed a highly active and efficient benthic methane filter at Quepos Slide site; a landslide on the continental slope between the Nicoya and Osa Peninsula. Integrated areal rates of AOM ranged from 12.9 ± 6.0 to 45.2 ± 11.5 mmol m-2 d-1, with only 1 to 2.5% of the upward methane flux being released into the water column. Additionally, two parallel sediment cores from Quepos Slide were used for in vitro experiments in a recently developed Sediment-F low-Through (SLOT) system to simulate an increased fluid and methane flux from the bottom of the sediment core. The benthic methane filter revealed a high adaptability whereby the methane oxidation efficiency responded to the increased fluid flow within 150-170 days. To our knowledge, this study provides the first estimation of the natural biogeochemical response of seep sediments to changes in fluid flow.

  13. A three-step test of phosphate sorption efficiency of potential agricultural drainage filter materials.

    PubMed

    Lyngsie, G; Borggaard, O K; Hansen, H C B

    2014-03-15

    Phosphorus (P) eutrophication of lakes and streams, coming from drained farmlands, is a serious problem in areas with intensive agriculture. Installation of P sorbing filters at drain outlets may be a solution. Efficient sorbents to be used for such filters must possess high P bonding affinity to retain ortho-phosphate (Pi) at low concentrations. In addition high P sorption capacity, fast bonding and low desorption is necessary. In this study five potential filter materials (Filtralite-P(®), limestone, calcinated diatomaceous earth, shell-sand and iron-oxide based CFH) in four particle size intervals were investigated under field relevant P concentrations (0-161 μM) and retentions times of 0-24 min. Of the five materials examined, the results from P sorption and desorption studies clearly demonstrate that the iron based CFH is superior as a filter material compared to calcium based materials when tested against criteria for sorption affinity, capacity and stability. The finest CFH and Filtralite-P(®) fractions (0.05-0.5 mm) were best with P retention of ≥90% of Pi from an initial concentration of 161 μM corresponding to 14.5 mmol/kg sorbed within 24 min. They were further capable to retain ≥90% of Pi from an initially 16 μM solution within 1½ min. However, only the finest CFH fraction was also able to retain ≥90% of Pi sorbed from the 16 μM solution against 4 times desorption sequences with 6 mM KNO3. Among the materials investigated, the finest CFH fraction is therefore the only suitable filter material, when very fast and strong bonding of high Pi concentrations is needed, e.g. in drains under P rich soils during extreme weather conditions. PMID:24275107

  14. An efficient algorithm for measurement of retinal vessel diameter from fundus images based on directional filtering

    NASA Astrophysics Data System (ADS)

    Wang, Xuchu; Niu, Yanmin

    2011-02-01

    Automatic measurement of vessels from fundus images is a crucial step for assessing vessel anomalies in ophthalmological community, where the change in retinal vessel diameters is believed to be indicative of the risk level of diabetic retinopathy. In this paper, a new retinal vessel diameter measurement method by combining vessel orientation estimation and filter response is proposed. Its interesting characteristics include: (1) different from the methods that only fit the vessel profiles, the proposed method extracts more stable and accurate vessel diameter by casting this problem as a maximal response problem of a variation of Gabor filter; (2) the proposed method can directly and efficiently estimate the vessel's orientation, which is usually captured by time-consuming multi-orientation fitting techniques in many existing methods. Experimental results shows that the proposed method both retains the computational simplicity and achieves stable and accurate estimation results.

  15. A computationally-efficient secondary organic aerosol module for three-dimensional air quality models

    NASA Astrophysics Data System (ADS)

    Liu, P.; Zhang, Y.

    2008-04-01

    Accurately simulating secondary organic aerosols (SOA) in three-dimensional (3-D) air quality models is challenging due to the complexity of the physics and chemistry involved and the high computational demand required. A computationally-efficient yet accurate SOA module is necessary in 3-D applications for long-term simulations and real-time air quality forecasting. A coupled gas and aerosol box model (i.e., 0-D CMAQ-MADRID 2) is used to optimize relevant processes in order to develop such a SOA module. Solving the partitioning equations for condensable volatile organic compounds (VOCs) and calculating their activity coefficients in the multicomponent mixtures are identified to be the most computationally-expensive processes. The two processes can be speeded up by relaxing the error tolerance levels and reducing the maximum number of iterations of the numerical solver for the partitioning equations for organic species; turning on organic-inorganic interactions only when the water content associated with organic compounds is significant; and parameterizing the calculation of activity coefficients for organic mixtures in the hydrophilic module. The optimal speed-up method can reduce the total CPU cost by up to a factor of 29.7 with ±15% deviation from benchmark results. These speedup methods are applicable to other SOA modules that are based on partitioning theories.

  16. A computationally-efficient secondary organic aerosol module for three-dimensional air quality models

    NASA Astrophysics Data System (ADS)

    Liu, P.; Zhang, Y.

    2008-07-01

    Accurately simulating secondary organic aerosols (SOA) in three-dimensional (3-D) air quality models is challenging due to the complexity of the physics and chemistry involved and the high computational demand required. A computationally-efficient yet accurate SOA module is necessary in 3-D applications for long-term simulations and real-time air quality forecasting. A coupled gas and aerosol box model (i.e., 0-D CMAQ-MADRID 2) is used to optimize relevant processes in order to develop such a SOA module. Solving the partitioning equations for condensable volatile organic compounds (VOCs) and calculating their activity coefficients in the multicomponent mixtures are identified to be the most computationally-expensive processes. The two processes can be speeded up by relaxing the error tolerance levels and reducing the maximum number of iterations of the numerical solver for the partitioning equations for organic species; conditionally activating organic-inorganic interactions; and parameterizing the calculation of activity coefficients for organic mixtures in the hydrophilic module. The optimal speed-up method can reduce the total CPU cost by up to a factor of 31.4 from benchmark under the rural conditions with 2 ppb isoprene and by factors of 10 71 under various test conditions with 2 10 ppb isoprene and >40% relative humidity while maintaining ±15% deviation. These speed-up methods are applicable to other SOA modules that are based on partitioning theories.

  17. Understanding the Role of Riming in Deep Convection Through Variability in Collection Efficiencies and Aerosol Effects

    NASA Astrophysics Data System (ADS)

    Saleeby, S. M.; van den Heever, S. C.; Marinescu, P. J.; Kreidenweis, S. M.; DeMott, P. J.; Tao, W. K.; Matsui, T.; Wu, D.

    2015-12-01

    In many mixed-phase cloud systems, the riming of cloud droplets is a key microphysical process in the growth of precipitation-sized hydrometeors. The relative importance of riming compared to other hydrometeor growth mechanisms depends on the type of cloud system and the mass, size, and number concentration of cloud droplets and ice species. In a perturbed climate state, the nature of deep convection may be altered through changes in the environmental conditions and aerosol concentrations. Such climate-induced variability can modify the dominant microphysical processes that generate precipitation through changes in hydrometeor size spectra. Such changes could either increase or decrease precipitation production and efficiency as well as impact associated morphology of clouds and convection. If the efficiency of the riming process is modified through these climate changes, it can alter the accumulated precipitation, precipitation intensity, spatial and temporal distribution of cloud and ice water, and the radiation budget through the modification of ice spectra and areal coverage of upper-level anvil clouds. The impacts of variability in aerosol concentration and collision efficiencies on the riming process in deep convection is explored through the use of high-resolution cloud resolving model simulations of a squall line that occurred May 20, 2011 over the U.S. central plains during the MC3E field project. Results thus far have demonstrated that changes in the riming rates strongly impact the intensity and partitioning of squall line precipitation between convective and stratiform, the lofting of condensate to upper levels, the vertical distribution of latent heating, and the area and optical thickness of stratiform anvil clouds. Analyses from direct tests of microphysical processes have revealed that a reduction in riming rates leads to less precipitation, greater amounts of lofted cloud water, and greater ice mass in cirrus anvils. Further, an increase in aerosol

  18. On detection of black hole quasinormal ringdowns: Detection efficiency and waveform parameter determination in matched filtering

    SciTech Connect

    Tsunesada, Yoshiki; Tatsumi, Daisuke; Kanda, Nobuyuki; Nakano, Hiroyuki; Ando, Masaki; Sasaki, Misao; Tagoshi, Hideyuki; Takahashi, Hirotaka

    2005-05-15

    Gravitational radiation from a slightly distorted black hole with ringdown waveform is well understood in general relativity. It provides a probe for direct observation of black holes and determination of their physical parameters, masses and angular momenta (Kerr parameters). For ringdown searches using data of gravitational wave detectors, matched filtering technique is useful. In this paper, we describe studies on problems in matched filtering analysis in realistic gravitational wave searches using observational data. Above all, we focus on template constructions, matches or signal-to-noise ratios (SNRs), detection probabilities for Galactic events, and accuracies in evaluation of waveform parameters or black hole hairs. In template design for matched filtering, search parameter ranges and template separations are determined by requirements from acceptable maximum loss of SNRs, detection efficiencies, and computational costs. In realistic searches using observational data, however, effects of nonstationary noises cause decreases of SNRs, and increases of errors in waveform parameter determinations. These problems will potentially arise in any matched filtering searches for any kind of waveforms. To investigate them, we have performed matched filtering analysis for artificial ringdown signals which are generated with Monte-Carlo technique and injected into the TAMA300 observational data. We employed an efficient method to construct a bank of ringdown filters recently proposed by Nakano et al., and use a template bank generated from a criterion such that losses of SNRs of any signals do not exceed 2%. We found that this criterion is fulfilled in ringdown searches using TAMA300 data, by examining distribution of SNRs of simulated signals. It is also shown that with TAMA300 sensitivity, the detection probability for Galactic ringdown events is about 50% for black holes of masses greater than 20M{sub {center_dot}} with SNR>10. The accuracies in waveform parameter

  19. Poly(ethylene glycol)-Modified Tapered-Slit Membrane Filter for Efficient Release of Captured Viable Circulating Tumor Cells.

    PubMed

    Kim, Young Jun; Kang, Yoon-Tae; Cho, Young-Ho

    2016-08-16

    The grafting of poly(ethylene glycol) (PEG) onto an SU8 microfilter has been demonstrated for efficient capture and release of circulating tumor cells (CTCs). Previous CTC filters showed low cell release efficiency due to hydrophobic surfaces, even though their capture efficiency was considerable. PEG, a hydrophilic polymeric compound mainly used to form nonfouling thin films on silicon surfaces, induces repulsive force so that the nonspecific adsorption of the surface is incomparably reduced in comparison with unmodified filter surfaces. The effectiveness of PEG-modified CTC filters was verified through lung (H358) and colorectal (SW620) cancer cells spiked, respectively, in phosphate-buffered saline (PBS) and unprocessed whole blood. The modified SU8 filters achieved approximately 37.7% and 22.8% improvement in release efficiency without significant changes in cell viability and capture efficiency. In order to verify the filter's potential for clinical applications, we extended our experiments using cancer patient blood samples. Six blood samples from colorectal and lung cancer patients were processed, and captured CTCs were efficiently released. From these experiments, the present PEG-modified filter captures and releases on average 14 ± 7.4 CTCs/mL, including EpCAM-negative CTCs, which could not be captured by previous single antibody-based methods. The antibody-free isolation with enhanced release efficiency facilitates viable cell retrieval, which is significant to CTC culture and comprehensive molecular study for verifying the mechanism of metastasis and cancer. PMID:27444512

  20. GEANT4 calibration of gamma spectrometry efficiency for measurements of airborne radioactivity on filter paper.

    PubMed

    Alrefae, Tareq

    2014-11-01

    A simple method of efficiency calibration for gamma spectrometry was performed. This method, which focused on measuring airborne radioactivity collected on filter paper, was based on Monte Carlo simulations using the toolkit GEANT4. Experimentally, the efficiency values of an HPGe detector were calculated for a multi-gamma disk source. These efficiency values were compared to their counterparts produced by a computer code that simulated experimental conditions. Such comparison revealed biases of 24, 10, 1, 3, 7, and 3% for the radionuclides (photon energies in keV) of Ce (166), Sn (392), Cs (662), Co (1,173), Co (1,333), and Y (1,836), respectively. The output of the simulation code was in acceptable agreement with the experimental findings, thus validating the proposed method. PMID:25271933

  1. A novel method for on-line analysis of gas and particle composition: description and evaluation of a Filter Inlet for Gases and AEROsols (FIGAERO)

    NASA Astrophysics Data System (ADS)

    Lopez-Hilfiker, F. D.; Mohr, C.; Ehn, M.; Rubach, F.; Kleist, E.; Wildt, J.; Mentel, T. F.; Lutz, A.; Hallquist, M.; Worsnop, D.; Thornton, J. A.

    2013-10-01

    We describe a novel inlet that allows measurement of both gas and particle molecular composition when coupled to mass spectrometric, chromatographic, or optical sensors: the Filter Inlet for Gas and AEROsol (FIGAERO). The design goals for the FIGAERO are to allow unperturbed observation of ambient air while simultaneously analyzing gases and collecting particulate matter on a Teflon filter via an entirely separate sampling port. The filter is analyzed periodically by the same sensor on hourly or faster timescales using temperature-programmed thermal desorption. We assess the performance of the FIGAERO by coupling it to a high-resolution time-of-flight chemical-ionization mass spectrometer (HRToF-CIMS) in laboratory chamber studies of α-pinene oxidation and field measurements at a boreal forest location. Low instrument backgrounds give detection limits of ppt or lower for compounds in the gas-phase and in the pg m-3 range for particle phase compounds. The FIGAERO-HRToF-CIMS provides molecular information about both gases and particle composition on the 1 Hz and hourly timescales, respectively for hundreds of compounds. The FIGAERO thermal desorptions are highly reproducible (better than 10%), allowing a calibrated assessment of the effective volatility of desorbing compounds and the role of thermal decomposition during the desorption process. We show that the often multi-modal desorption thermograms arising from secondary organic aerosol (SOA) provide additional insights into molecular composition and/or particle morphology, and exhibit changes with changes in SOA formation or aging pathways.

  2. NUMERICAL CALCULATION OF INERTIAL ASPIRATION EFFICIENCY OF AEROSOLS INTO THIN-WALLED SAMPLING INLETS

    EPA Science Inventory

    Unbiased sampling of airborne particulate from a flowing stream requires that the size distribution and concentration of aerosol collected be identical to that of the aerosol in the free stream. ampling errors occur during aspiration of the aerosol from the free stream to he face...

  3. High Efficiency Particulate Air (HEPA) Filter Generation, Characterization, and Disposal Experiences at the Oak Ridge National Laboratory

    SciTech Connect

    Coffey, D. E.

    2002-02-28

    High Efficiency Particulate Air filtration is an essential component of the containment and ventilation systems supporting the research and development activities at the Oak Ridge National Laboratory. High Efficiency Particulate Air filters range in size from 7.6cm (3 inch) by 10.2 cm (4 inch) cylindrical shape filters to filter array assemblies up to 2.1 m (7 feet) high by 1.5 m (5 feet) wide. Spent filters are grouped by contaminates trapped in the filter media and become one of the components in the respective waste stream. Waste minimization and pollution prevention efforts are applied for both radiological and non-radiological applications. Radiological applications include laboratory hoods, glove boxes, and hot cells. High Efficiency Particulate Air filters also are generated from intake or pre-filtering applications, decontamination activities, and asbestos abatement applications. The disposal avenues include sanitary/industrial waste, Resource Conservation and Recovery Act and Toxic Substance Control Act, regulated waste, solid low-level waste, contact handled transuranic, and remote handled transuranic waste. This paper discusses characterization and operational experiences associated with the disposal of the spent filters across multiple applications.

  4. High-solids paint overspray aerosols in a spray painting booth: particle size analysis and scrubber efficiency

    SciTech Connect

    Chan, T.L.; D'arcy, J.B.; Schreck, R.M.

    1986-07-01

    Particle size distributions of high-solids acrylic-enamel paint overspray aerosols were determined isokinetically in a typical downdraft spray painting booth in which a 7-stage cascade impactor was used. Three different industrial paint atomizers were used, and the paint aerosols were characterized before and after a paint both scrubber. The mass median aerodynamic diameter (MMAD) of a metallic basecoat and an acrylic clearcoat paint aerosol from air-atomized spray guns ranged from 4-12 ..mu..m and was dependent on atomization pressure. When the paint booth was operated under controlled conditions simulating those in a plant, the collection efficiency of paint overspray aerosols by a paint scrubber was found to be size dependent and decreased sharply for particles smaller than 2 ..mu..m to as low as 64% for clearcoat paint particles of 0.6 ..mu..m. Improvement in the overall particulate removal efficiency can be achieved by optimizing the spray painting operations so as to produce the least amount of fine overspray paint aerosols less than 2 ..mu..m. Maintaining a higher static pressure drop across the paint both scrubber also will improve scrubber performance.

  5. AEROSOL DEPOSITION EFFICIENCIES AND UPSTREAM RELEASE POSITIONS FOR DIFFERENT INHALATION MODES IN AN UPPER BRONCHIAL AIRWAY MODELS

    EPA Science Inventory

    Aerosol Deposition Efficiencies and Upstream Release Positions for Different Inhalation Modes in an Upper Bronchial Airway Model

    Zhe Zhang, Clement Kleinstreuer, and Chong S. Kim

    Center for Environmental Medicine and Lung Biology, University of North Carolina at Ch...

  6. CCN activation and efficiency of nucleation and impaction removal process of biomass burning aerosols in Brazil: preliminary results.

    NASA Astrophysics Data System (ADS)

    Sánchez Gácita, Madeleine; Longo, Karla M.; Freitas, Saulo R.; Martin, Scot T.

    2015-04-01

    The biomass burning activity constitutes an important source of aerosols and trace gases to the atmosphere globally. In South America, during the dry season, aerosols prevenient from biomass burning are typically transported to long distances from its sources before being removed though contributing significantly to the aerosol budget on a continental scale. The uncertainties in the magnitude of the impacts on the hydrological cycle, the radiation budget and the biogeochemical cycles on a continental scale are still noteworthy. The still unknowns on the efficiency of biomass burning aerosol to act as cloud condensation nuclei (CCN) and the effectiveness of the nucleation and impaction scavenging mechanisms in removing them from the atmosphere contribute to such uncertainties. In the present work, the explicit modelling of the early stages of cloud development using a parcel model for the typical conditions of the dry season and dry-to-wet transition periods in Amazonia allowed an estimation of the efficiency of nucleation scavenging process and the ability of South American biomass burning aerosol to act as CCN. Additionally, the impaction scavenging was simulated for the same aerosol population following a method based on the widely used concept of the efficiency of collision between a raindrop and an aerosol particle. DMPS and H-TDMA data available in the literature for biomass burning aerosol population in the region indicated the presence of a nearly hydrophobic fraction (on average, with specific hygroscopic parameter κ=0.04, and relative abundance of 73 %) and nearly hygroscopic fraction (κ=0.13, 27 %), externally mixed. The hygroscopic parameters and relative abundances of each hygroscopic group, as well as the weighted average specific hygroscopic parameter for the entire population κ=0.06, were used in calculations of aerosol activation and population mass and number concentration scavenged by nucleation. Results from both groups of simulations are

  7. Independent Evaluation of Air Filter Media from Chornobyl

    SciTech Connect

    MD Hoover; AF Fencl; GJ Vargo

    1999-12-21

    An independent evaluation was performed to assess the morphology, pressure drop characteristics, alpha spectroscopy characteristics, and collection efficiency of an air sampling filter media and two types of aerosol face masks provided from Chernobyl by Pacific Northwest National Laboratory. The evaluation included characterizing the filter morphology by scqg electron microscopy; measuring the filter pressure drop as a function of air flowrate; evaluating the spectroscopy characteristics of the filter for alpha-emitting radionuclides by sampling ambient radon progeny aerosols in an Eberline Alpha-6A alpha continuous air monitor; determining the particle collection efficiency of the filter media for 0.3 {micro}m aerodynamic diameter monodisperse particles at 1 and 2 cfm; and comparing the apparent construction, durability, and performance similarities of the filter media to other media commonly used for monitoring airborne alpha-emitting radionuclides.

  8. Active slag filters: rapid assessment of phosphorus removal efficiency from effluent as a function of retention time.

    PubMed

    Shilton, Andy; Chen, Leon; Elemetri, Ibrahim; Pratt, Chris; Pratt, Steven

    2013-01-01

    There is increasing pressure to upgrade effluent ponds for phosphorus removal. Active slag filters offer a solution, but design information is limited. Hydraulic retention time (HRT) is a key factor in filter design because it controls filter treatment efficiency as well the filter substrate lifespan. This paper reports on a rapid method of continual looping of effluent through a filter column to obtain a relationship between HRT and phosphorus removal efficiency. Phosphorus removal declined logarithmically with respect to retention time. While the mechanisms that yield this relationship involve complex mass transfer and adsorption of phosphorus to Fe oxyhydroxide sites, in general terms, the adsorption rate is proportional to the adsorbate effluent concentration. Waste stabilization pond effluent treated by the slag achieved phosphorus removal efficiencies over 90% at extended HRTs greater than 70 hours, while 80% removal was obtainable in 30 hours. Higher phosphorus removal was achieved for slag treating real effluent compared with synthetic phosphate solution. This can be explained by: (1) different starting phosphorus concentrations in the synthetic phosphate solution and real effluent; and (2) the presence of constituents in real effluent that can enhance phosphorus removal, such as oxidized iron compounds, cations, algae and humic complexes. This new technique, which proved capable of replicating treatment efficiencies obtained from long-term column studies, offers rapid assessment of phosphorus removal efficiency as a function of retention time and thus will enable design engineers to size active filters on the basis of achieving the required phosphorus removal standards. PMID:23530330

  9. Perfect blind restoration of images blurred by multiple filters: theory and efficient algorithms.

    PubMed

    Harikumar, G; Bresler, Y

    1999-01-01

    We address the problem of restoring an image from its noisy convolutions with two or more unknown finite impulse response (FIR) filters. We develop theoretical results about the existence and uniqueness of solutions, and show that under some generically true assumptions, both the filters and the image can be determined exactly in the absence of noise, and stably estimated in its presence. We present efficient algorithms to estimate the blur functions and their sizes. These algorithms are of two types, subspace-based and likelihood-based, and are extensions of techniques proposed for the solution of the multichannel blind deconvolution problem in one dimension. We present memory and computation-efficient techniques to handle the very large matrices arising in the two-dimensional (2-D) case. Once the blur functions are determined, they are used in a multichannel deconvolution step to reconstruct the unknown image. The theoretical and practical implications of edge effects, and "weakly exciting" images are examined. Finally, the algorithms are demonstrated on synthetic and real data. PMID:18267468

  10. Optimal color filter array design: quantitative conditions and an efficient search procedure

    NASA Astrophysics Data System (ADS)

    Lu, Yue M.; Vetterli, Martin

    2009-01-01

    Most digital cameras employ a spatial subsampling process, implemented as a color filter array (CFA), to capture color images. The choice of CFA patterns has a great impact on the performance of subsequent reconstruction (demosaicking) algorithms. In this work, we propose a quantitative theory for optimal CFA design. We view the CFA sampling process as an encoding (low-dimensional approximation) operation and, correspondingly, demosaicking as the best decoding (reconstruction) operation. Finding the optimal CFA is thus equivalent to finding the optimal approximation scheme for the original signals with minimum information loss. We present several quantitative conditions for optimal CFA design, and propose an efficient computational procedure to search for the best CFAs that satisfy these conditions. Numerical experiments show that the optimal CFA patterns designed from the proposed procedure can effectively retain the information of the original full-color images. In particular, with the designed CFA patterns, high quality demosaicking can be achieved by using simple and efficient linear filtering operations in the polyphase domain. The visual qualities of the reconstructed images are competitive to those obtained by the state-of-the-art adaptive demosaicking algorithms based on the Bayer pattern.

  11. Application of FIGAERO (Filter Inlet for Gases and AEROsol) coupled to a high resolution time of flight chemical ionization mass spectrometer to field and chamber organic aerosol: Implications for carboxylic acid formation and gas-particle partitioning from monoterpene oxidation

    NASA Astrophysics Data System (ADS)

    Lopez-Hilfiker, F.; Mohr, C.; Ehn, M.; Rubach, F.; Mentel, T. F.; Kleist, E.; Wildt, J.; Thornton, J. A.

    2013-12-01

    We present measurements of a large suite of gas and particle phase carboxylic acid containing compounds made with a Filter Inlet for Gas and AEROsol (FIGAERO) coupled to a high resolution time of flight chemical ionization mass spectrometer (HR-ToF-CIMS) developed at the University of Washington. A prototype operated with acetate negative ion proton transfer chemistry was deployed on the Julich Plant Atmosphere Chamber to study a-pinene oxidation, and a modified version was deployed at the SMEAR II forest station in Hyytiälä, Finland and SOAS, in Brent Alabama. We focus here on results from JPAC and Hyytiälä, where we utilized the same ionization method most selective towards carboxylic acids. In all locations, 100's of organic acid compounds were observed in the gas and particles and many of the same composition acids detected in the gas-phase were detected in the particles upon temperature programmed thermal desorption. Particulate organics detected by FIGAERO are highly correlated with organic aerosol mass measured by an AMS, providing additional volatility and molecular level information about collected aerosol. The fraction of a given compound measured in the particle phase follows expected trends with elemental composition, but many compounds would not be well described by an absorptive partitioning model assuming unity activity coefficients. Moreover the detailed structure in the thermal desorption signals reveals a contribution from thermal decomposition of large molecular weight organics and or oligomers with implications for partitioning measurements and model validation

  12. Efficiency of Respirator Filter Media against Diesel Particulate Matter: A Comparison Study Using Two Diesel Particulate Sources.

    PubMed

    Burton, Kerrie A; Whitelaw, Jane L; Jones, Alison L; Davies, Brian

    2016-07-01

    Diesel engines have been a mainstay within many industries since the early 1900s. Exposure to diesel particulate matter (DPM) is a major issue in many industrial workplaces given the potential for serious health impacts to exposed workers; including the potential for lung cancer and adverse irritant and cardiovascular effects. Personal respiratory protective devices are an accepted safety measure to mitigate worker exposure against the potentially damaging health impacts of DPM. To be protective, they need to act as effective filters against carbon and other particulates. In Australia, the filtering efficiency of respiratory protective devices is determined by challenging test filter media with aerosolised sodium chloride to determine penetration at designated flow rates. The methodology outlined in AS/NZS1716 (Standards Australia International Ltd and Standards New Zealand 2012. Respiratory protective devices. Sydney/Wellington: SAI Global Limited/Standards New Zealand) does not account for the differences between characteristics of workplace contaminants like DPM and sodium chloride such as structure, composition, and particle size. This study examined filtering efficiency for three commonly used AS/NZS certified respirator filter models, challenging them with two types of diesel emissions; those from a diesel generator and a diesel engine. Penetration through the filter media of elemental carbon (EC), total carbon (TC), and total suspended particulate (TSP) was calculated. Results indicate that filtering efficiency assumed by P2 certification in Australia was achieved for two of the three respirator models for DPM generated using the small diesel generator, whilst when the larger diesel engine was used, filtering efficiency requirements were met for all three filter models. These results suggest that the testing methodology specified for certification of personal respiratory protective devices by Standards Australia may not ensure adequate protection for

  13. Laboratory studies of collection efficiency of sub-micrometer aerosol particles by cloud droplets on a single-droplet basis

    NASA Astrophysics Data System (ADS)

    Ardon-Dryer, K.; Huang, Y.-W.; Cziczo, D. J.

    2015-08-01

    An experimental setup has been constructed to measure the collection efficiency (CE) of sub-micrometer aerosol particles by cloud droplets. Droplets of a dilute aqueous ammonium sulfate solution with an average radius of 21.6 μm fall freely into a chamber and collide with sub-micrometer polystyrene latex (PSL) sphere particles of known sizes and concentrations. Two relative humidity (RH) conditions, 15 ± 3 % and 88 ± 3 %, hereafter termed "low" and "high", respectively, were varied with different particles sizes and concentrations. After passing through the chamber, the droplets and aerosol particles were sent to the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument to determine chemical compositions on a single-droplet basis. "Coagulated droplets" (droplets that collected aerosols) had mass spectra that contained signatures from both an aerosol particle and a droplet residual. CE values range from 2.0 × 10-1 to 1.6 for the low-RH case and from 1.5 × 10-2 to 9.0 × 10-2 for the high-RH case. CE values were, within experimental uncertainty, independent of the aerosol concentrations. CE values in this study were found to be in agreement with previous experimental and theoretical studies. To our knowledge, this is the first collection experiment performed on a single-droplet basis with atmospherically relevant conditions such as droplet sizes, droplet charges and flow.

  14. Direct-detection Doppler wind measurements with a Cabannes Mie lidar: B. Impact of aerosol variation on iodine vapor filter methods

    NASA Astrophysics Data System (ADS)

    She, Chiao-Yao; Yue, Jia; Yan, Zhao-Ai; Hair, Johnathan W.; Guo, Jin-Jia; Wu, Song-Hua; Liu, Zhi-Shen

    2007-07-01

    Atmospheric line-of-sight (LOS) wind measurement by means of incoherent Cabannes- Mie lidar with three frequency analyzers, two double-edge Fabry-Perot interferometers, one at 1064 nm (IR-FPI) and another at 355 nm (UV-FPI), as well as an iodine vapor filter (IVF) at 532 nm, utilizing either a single absorption edge, single edge (se-IVF), or both absorption edges, double edge (de-IVF), was considered in a companion paper [Appl. Opt. 46, 4434 (2007)], assuming known atmospheric temperature and aerosol mixing ratio, Rb. The effects of temperature and aerosol variations on the uncertainty of LOS wind measurements are investigated and it is found that while the effect of temperature variation is small, the variation in Rb can cause significant errors in wind measurements with IVF systems. Thus the means to incorporate a credible determination of Rb into the wind measurement are presented as well as an assessment of the impact on wind measurement uncertainty. Unlike with IVF methods, researchers can take advantage of design flexibility with FPI methods to desensitize either molecular scattering for IR-FPI or aerosol scattering for UV-FPI. The additional wind measurement uncertainty caused by Rb variation with FPI methods is thus negligible for these configurations. Assuming 100,000 photons from Cabannes scattering, and accounting for the Rb measurement incorporated into the IVF method in this paper, it is found that the lowest wind uncertainty at low wind speeds in aerosol-free air is still with UV-FPI, ˜32% lower than with de-IVF. For 0.050.07, the IR-FPI outperforms all other methods. In addition to LOS wind uncertainty comparison under high wind speed conditions, the need of an appropriate and readily available narrowband filter for operating the wind lidar at visible wavelengths under sunlit condition is discussed; with such a filter the degradation of LOS wind measurement attributable to clear

  15. Optical-chemical-microphysical relationships and closure studies for mixed carbonaceous aerosols observed at Jeju Island; 3-laser photoacoustic spectrometer, particle sizing, and filter analysis

    NASA Astrophysics Data System (ADS)

    Flowers, B. A.; Dubey, M. K.; Mazzoleni, C.; Stone, E. A.; Schauer, J. J.; Kim, S.-W.; Yoon, S. C.

    2010-11-01

    Transport of aerosols in pollution plumes from the mainland Asian continent was observed in situ at Jeju, South Korea during the Cheju Asian Brown Cloud Plume-Asian Monsoon Experiment (CAPMEX) field campaign throughout August and September 2008 using a 3-laser photoacoustic spectrometer (PASS-3), chemical filter analysis, and size distributions. The PASS-3 directly measures the effects of morphology (e.g. coatings) on light absorption that traditional filter-based instruments are unable to address. Transport of mixed sulfate, carbonaceous, and nitrate aerosols from various Asian pollution plumes to Jeju accounted for 74% of the deployment days, showing large variations in their measured chemical and optical properties. Analysis of eight distinct episodes, spanning wide ranges of chemical composition, optical properties, and source regions, reveals that episodes with higher organic carbon (OC)/sulfate (SO42-) and nitrate (NO3-)/SO42- composition ratios exhibit lower single scatter albedo at shorter wavelengths (ω405). We infer complex refractive indices (n-ik) as a function of wavelength for the high, intermediate, and low OC/SO42- pollution episodes by using the observed particle size distributions and the measured optical properties. The smallest mean particle diameter corresponds to the high OC/SO42- aerosol episode. The imaginary part of the refractive index (k) is greater for the high OC/SO42- episode at all wavelengths. A distinct, sharp increase in k at short wavelength implies enhanced light absorption by OC, which accounts for 50% of the light absorption at 405 nm, in the high OC/SO42- episode. Idealized analysis indicates increased absorption at 781 nm by factors greater than 3 relative to denuded black carbon in the laboratory. We hypothesize that coatings of black carbon cores are the mechanism of this enhancement. This implies that climate warming and atmospheric heating rates from black carbon particles can be significantly larger than have been

  16. Hydraulic transmissivity and heat exchange efficiency of open fractures: a model based on lowpass filtered apertures

    NASA Astrophysics Data System (ADS)

    Neuville, Amélie; Toussaint, Renaud; Schmittbuhl, Jean

    2011-09-01

    Natural open joints in rocks commonly present multiscale self-affine apertures. This geometrical complexity affects fluid transport and heat exchange between the flowing fluid and the surrounding rock. In particular, long range correlations of self-affine apertures induce strong channelling of the flow which influences both mass and heat advection. A key question is to find a geometrical model of the complex aperture that describes at best the macroscopic properties (hydraulic conductivity, heat exchange) with the smallest number of parameters. Solving numerically the Stokes and heat equations with a lubrication approximation, we show that a low pass filtering of the aperture geometry provides efficient estimates of the effective hydraulic and thermal properties (apertures). A detailed study of the influence of the bandwidth of the lowpass filtering on these transport properties is also performed. For instance, keeping the information of amplitude only of the largest Fourier length scales allows us to reach already an accuracy of 9 per cent on the hydraulic and the thermal apertures.

  17. High spin-filter efficiency and Seebeck effect through spin-crossover iron-benzene complex

    NASA Astrophysics Data System (ADS)

    Yan, Qiang; Zhou, Liping; Cheng, Jue-Fei; Wen, Zhongqian; Han, Qin; Wang, Xue-Feng

    2016-04-01

    Electronic structures and coherent quantum transport properties are explored for spin-crossover molecule iron-benzene Fe(Bz)2 using density functional theory combined with non-equilibrium Green's function. High- and low-spin states are investigated for two different lead-molecule junctions. It is found that the asymmetrical T-shaped contact junction in the high-spin state behaves as an efficient spin filter while it has a smaller conductivity than that in the low-spin state. Large spin Seebeck effect is also observed in asymmetrical T-shaped junction. Spin-polarized properties are absent in the symmetrical H-shaped junction. These findings strongly suggest that both the electronic and contact configurations play significant roles in molecular devices and metal-benzene complexes are promising materials for spintronics and thermo-spintronics.

  18. High spin-filter efficiency and Seebeck effect through spin-crossover iron-benzene complex.

    PubMed

    Yan, Qiang; Zhou, Liping; Cheng, Jue-Fei; Wen, Zhongqian; Han, Qin; Wang, Xue-Feng

    2016-04-21

    Electronic structures and coherent quantum transport properties are explored for spin-crossover molecule iron-benzene Fe(Bz)2 using density functional theory combined with non-equilibrium Green's function. High- and low-spin states are investigated for two different lead-molecule junctions. It is found that the asymmetrical T-shaped contact junction in the high-spin state behaves as an efficient spin filter while it has a smaller conductivity than that in the low-spin state. Large spin Seebeck effect is also observed in asymmetrical T-shaped junction. Spin-polarized properties are absent in the symmetrical H-shaped junction. These findings strongly suggest that both the electronic and contact configurations play significant roles in molecular devices and metal-benzene complexes are promising materials for spintronics and thermo-spintronics. PMID:27389217

  19. Memory efficient and constant time 2D-recursive spatial averaging filter for embedded implementations

    NASA Astrophysics Data System (ADS)

    Gan, Qifeng; Seoud, Lama; Ben Tahar, Houssem; Langlois, J. M. Pierre

    2016-04-01

    Spatial Averaging Filters (SAF) are extensively used in image processing for image smoothing and denoising. Their latest implementations have already achieved constant time computational complexity regardless of kernel size. However, all the existing O(1) algorithms require additional memory for temporary data storage. In order to minimize memory usage in embedded systems, we introduce a new two-dimensional recursive SAF. It uses previous resultant pixel values along both rows and columns to calculate the current one. It can achieve constant time computational complexity without using any additional memory usage. Experimental comparisons with previous SAF implementations shows that the proposed 2D-Recursive SAF does not require any additional memory while offering a computational time similar to the most efficient existing SAF algorithm. These features make it especially suitable for embedded systems with limited memory capacity.

  20. Palm vein for efficient person recognition based on 2D Gabor filter

    NASA Astrophysics Data System (ADS)

    Wang, Jixing; He, Yuqing; Zhu, Jiadan; Gao, Xinru; Cui, Yongsheng

    2013-05-01

    Palm vein recognition is a relatively new method in biometrics. This paper presents an effective palm vein feature extraction approach for improving the efficiency of palm vein identification. In this paper, relevant preprocessing steps as rotation and extraction of the Region of Interest are presented. In feature extraction, multiple 2D Gabor filters with 4 orientations are employed to extract the phase information on a palm vein image, which is then merged into unique feature according to an encoding rule. Hamming distance is used for vein recognition. Experiments are carried on a selfmade palm vein database. Experimental results show that the method in this paper achieved a higher correct recognition rate and a faster speed.

  1. A novel method for online analysis of gas and particle composition: description and evaluation of a Filter Inlet for Gases and AEROsols (FIGAERO)

    NASA Astrophysics Data System (ADS)

    Lopez-Hilfiker, F. D.; Mohr, C.; Ehn, M.; Rubach, F.; Kleist, E.; Wildt, J.; Mentel, Th. F.; Lutz, A.; Hallquist, M.; Worsnop, D.; Thornton, J. A.

    2014-04-01

    We describe a novel inlet that allows measurement of both gas and particle molecular composition when coupled to mass spectrometric, chromatographic, or optical sensors: the Filter Inlet for Gases and AEROsols (FIGAERO). The design goals for the FIGAERO are to allow unperturbed observation of ambient air while simultaneously analyzing gases and collecting particulate matter on a Teflon® (hereafter Teflon) filter via an entirely separate sampling port. The filter is analyzed periodically by the same sensor on hourly or faster timescales using temperature-programmed thermal desorption. We assess the performance of the FIGAERO by coupling it to a high-resolution time-of-flight chemical-ionization mass spectrometer (HRToF-CIMS) in laboratory chamber studies of α-pinene oxidation and field measurements at a boreal forest location. Low instrument backgrounds give detection limits of ppt or lower for compounds in the gas-phase and in the picogram m-3 range for particle phase compounds. The FIGAERO-HRToF-CIMS provides molecular information about both gases and particle composition on the 1 Hz and hourly timescales, respectively for hundreds of compounds. The FIGAERO thermal desorptions are highly reproducible (better than 10%), allowing a calibrated assessment of the effective volatility of desorbing compounds and the role of thermal decomposition during the desorption process. We show that the often multi-modal desorption thermograms arising from secondary organic aerosol (SOA) provide additional insights into molecular composition and/or particle morphology, and exhibit changes with changes in SOA formation or aging pathways.

  2. Experimental study of elementary collection efficiency of aerosols by spray: Design of the experimental device

    SciTech Connect

    Ducret, D.; Vendel, J.; Garrec. S.L.

    1995-02-01

    The safety of a nuclear power plant containment building, in which pressure and temperature could increase because of a overheating reactor accident, can be achieved by spraying water drops. The spray reduces the pressure and the temperature levels by condensation of steam on cold water drops. The more stringent thermodynamic conditions are a pressure of 5.10{sup 5} Pa (due to steam emission) and a temperature of 413 K. Moreover its energy dissipation function, the spray leads to the washout of fission product particles emitted in the reactor building atmosphere. The present study includes a large program devoted to the evaluation of realistic washout rates. The aim of this work is to develop experiments in order to determine the collection efficiency of aerosols by a single drop. To do this, the experimental device has to be designed with fundamental criteria:-Thermodynamic conditions have to be representative of post-accident atmosphere. Thermodynamic equilibrium has to be attained between the water drops and the gaseous phase. Thermophoretic, diffusiophoretic and mechanical effects have to be studied independently. Operating conditions have to be homogenous and constant during each experiment. This paper presents the design of the experimental device. In practice, the consequences on the design of each of the criteria given previously and the necessity of being representative of the real conditions will be described.

  3. Disk filter

    DOEpatents

    Bergman, Werner

    1986-01-01

    An electric disk filter provides a high efficiency at high temperature. A hollow outer filter of fibrous stainless steel forms the ground electrode. A refractory filter material is placed between the outer electrode and the inner electrically isolated high voltage electrode. Air flows through the outer filter surfaces through the electrified refractory filter media and between the high voltage electrodes and is removed from a space in the high voltage electrode.

  4. Disk filter

    DOEpatents

    Bergman, W.

    1985-01-09

    An electric disk filter provides a high efficiency at high temperature. A hollow outer filter of fibrous stainless steel forms the ground electrode. A refractory filter material is placed between the outer electrode and the inner electrically isolated high voltage electrode. Air flows through the outer filter surfaces through the electrified refractory filter media and between the high voltage electrodes and is removed from a space in the high voltage electrode.

  5. Probabilistic Evaluation of the Vegetated Filter Strip Efficiency With Respect to Pathogen Removal From Runoff

    NASA Astrophysics Data System (ADS)

    Pachepsky, Y. A.; Guber, A. K.; Sadeghi, A. M.; Shelton, D. R.

    2007-12-01

    Vegetated filter strips (VFS) have become an important component of the water quality improvement in watersheds. Relatively little is known about the efficiency of VFSs in retention of manure-borne pathogens that can be important agricultural pollutants. The objective of this work was to evaluate the uncertainty in the VFS efficiency caused by variations in major pathogen retention factors, i.e. vegetation status, soil infiltration capacity, and rainfall intensity and duration. We have developed the model STIR to simulate the overland transport and loss to infiltration of manure-borne pathogens in VFS. This model was used in Latin Hypercube sampling-based simulations to evaluate the possible variability in pathogenic bacteria breakthrough in VFSs. The sampled model parameters were rainfall intensity, rainfall duration, initial soil water content, Manning roughness coefficient, saturated hydraulic conductivity, shape parameters of soil water retention curve, pathogen partitioning coefficient, pathogen attachment rate, pathogen straining rate, and the dispersivity in the overland flow. Probability distributions of the parameters were selected to represent the USDA-ARS experimental site in Beltsville, MD, where the STIR model was tested with data on E. coli bacteria. Relatively long high-intensity rainfalls, low hydraulic conductivities, high soil moisture contents before the rainfall, and high dispersivities were the main reasons of the strip partial failure. However, the unfavorable conditions and their combinations were relatively rare, and the removal efficiency of the 6-m long VFS at the edge of 200-m long field was less than 100 % for 5 % of simulation scenarios, and less than 75 % for 2.5 % of simulation scenarios. The probabilistic characterization of the VFS efficiency with site-specific soil and weather properties can be useful in making decisions on VFS placement with respect to manure-borne pathogens.

  6. Nanofiber Air Filters with High-Temperature Stability for Efficient PM2.5 Removal from the Pollution Sources.

    PubMed

    Zhang, Rufan; Liu, Chong; Hsu, Po-Chun; Zhang, Chaofan; Liu, Nian; Zhang, Jinsong; Lee, Hye Ryoung; Lu, Yingying; Qiu, Yongcai; Chu, Steven; Cui, Yi

    2016-06-01

    Here, we developed high-efficiency (>99.5%) polyimide-nanofiber air filters for the high temperature PM2.5 removal. The polyimide nanofibers exhibited high thermal stability, and the PM2.5 removal efficiency was kept unchanged when temperature ranged from 25-370 °C. These filters had high air flux with very low pressure drop. They could continuously work for >120 h for PM2.5 index >300. A field-test showed that they could effectively remove >99.5% PM particles from car exhaust at high temperature. PMID:27167892

  7. Efficiency of five chemical protective clothing materials against nano and submicron aerosols when submitted to mechanical deformations.

    PubMed

    Ben Salah, Mehdi; Hallé, Stéphane; Tuduri, Ludovic

    2016-01-01

    Due to their potential toxicity, the use of nanoparticles in the workplace is a growing concern. Some studies indicate that nanoparticles can penetrate the skin and lead to adverse health effects. Since chemical protective clothing is the last barrier to protect the skin, this study aims to better understand nanoparticle penetration behaviour in dermal protective clothing under mechanical deformation. For this purpose, five of the most common types of fabrics used in protective clothing, one woven and four nonwoven, were chosen and submitted to different simulated exposure conditions. They were tested against polydispersed NaCl aerosols having an electrical-mobility diameter between 14 and 400 nm. A bench-scale exposure setup and a sampling protocol was developed to measure the level of penetration of the aerosols through the material samples of disposable coveralls and lab coat, while subjecting them to mechanical deformations to simulate the conditions of usage in the workplace. Particle size distribution of the aerosol was determined upstream and downstream using a scanning mobility particle sizer (SMPS). The measured efficiencies demonstrated that the performances of nonwoven materials were similar. Three nonwovens had efficiencies above 99%, while the woven fabric was by far, the least effective. Moreover, the results established that mechanical deformations, as simulated for this study, did not have a significant effect on the fabrics' efficiencies. PMID:26786065

  8. Dry powder aerosols of polyethylenimine (PEI)-based gene vectors mediate efficient gene delivery to the lung.

    PubMed

    Pfeifer, Corinna; Hasenpusch, Guenther; Uezguen, Senta; Aneja, Manish Kumar; Reinhardt, Dietrich; Kirch, Julian; Schneider, Marc; Claus, Sarah; Friess, Wolfgang; Rudolph, Carsten

    2011-08-25

    Aerosol gene delivery holds great therapeutical potential for many inherited and acquired pulmonary diseases. The physical instability of aqueous suspensions of non-viral vector complexes is a major limitation for their successful application. In this study, we investigated dry powder aerosols as novel gene vector formulations for gene transfer in vitro and murine lungs in vivo. Lyophilization was used to produce dry powder cakes followed by powderization to produce dry powder aerosols. Different sugars, namely lactose, sucrose and trehalose, were tested as lyoprotectants for gene delivery complexes consisting of branched polyethylenimine 25 kDa and plasmid DNA. Biophysical particle characterization demonstrated that lyophilization and powderization in the presence of lyoprotectants were well tolerated. In vitro transfection efficiency remained unaffected by the choice of lyoprotectant and subsequent lyophilization and/or powderization. In vivo screening of powderized samples, by applying the powder with an insufflator, resulted in highest gene expression with lactose as lyoprotectant. Delivering a plasmid coding for murine erythropoietin together with lactose as lyoprotectant resulted in increased blood hematocrit values post application thereby demonstrating the potential of dry powder aerosol as a promising method for pulmonary gene delivery. PMID:21600251

  9. Laboratory studies of collection efficiency of sub-micrometer aerosol particles by cloud droplets on a single droplet basis

    NASA Astrophysics Data System (ADS)

    Ardon-Dryer, K.; Huang, Y.-W.; Cziczo, D. J.

    2015-03-01

    An experimental setup has been constructed to measure the Collection Efficiency (CE) of sub-micrometer aerosol particles by cloud droplets. Water droplets of a dilute aqueous ammonium sulfate solution with a radius of ~20 μm fall freely into a chamber and collide with sub-micrometer Polystyrene Latex Sphere (PSL) particles of variable size and concentrations. Two RH conditions, ~15 and ~88%, hereafter termed "Low" and "High", respectively, were varied with different particles size and concentrations. After passing through the chamber, the droplets and aerosol particles were sent to the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument to determine chemical compositions on a single particle basis. Coagulated droplets had mass spectra that contain signatures from both an aerosol particle and a droplet residual. CE values range from 5.7 × 10-3 to 4.6 × 10-2 for the Low RH and from 6.4 × 10-3 to 2.2 × 10-2 for the High RH cases. CE values were, within experimental uncertainty, independent of the aerosol concentrations. CE values in this work were found to be in agreement with previous experimental and theoretical studies. To our knowledge, this is the first coagulation experiment performed on a single droplet basis.

  10. Toward green systems for cleanrooms: Energy efficient fan-filter units

    SciTech Connect

    Jeng, Ming-Shan; Xu, Tengfang; Lan, Chao-Ho

    2004-07-12

    The paper presents results of laboratory-measured performance of fan-filter units (FFUs) used for cleanrooms. A total of twenty FFUs collected from the market were tested, including thirteen 1220 mm x 610 mm (or 4 ft x 2 ft) units and seven 1220 mm x 1220 mm (or 4 ft x 4 ft) units. The paper concludes that there are wide variations in FFUs energy performance, and that there are opportunities in improving energy efficiency and lowering operating costs of FFUs. Furthermore, the paper suggests the benefits of having a uniform method for testing and reporting FFU performance. Such a testing method and recommended practice guideline is under development, with heavy input from FFU suppliers, users, and independent institutions that include Lawrence Berkeley National Laboratory (LBNL), Industrial Technology Research Institute (ITRI), and Institute of Environmental Sciences and Technology (IEST). An integrated approach with the participation from designers, suppliers, users, and utility companies can help to identify energy-efficient FFUs that are required for many cleanroom applications.

  11. Evaluation of Filters for Removal of Bacteriophages from Air1

    PubMed Central

    Washam, C. J.; Black, C. H.; Sandine, W. E.; Elliker, P. R.

    1966-01-01

    Glass wool, nonabsorbent cotton, fiberglass filter medium, and a commercial absolute filter were tested for effectiveness in removing aerosolized bacterial viruses under low flow rate (1 ft3/min) and high flow rate (10 to 25 ft3/min) air-flow conditions. Special equipment was designed for measurement of filter efficiencies under the two air-flow conditions. Under low air-flow rate test conditions, glass wool was only 98.543 to 99.83% efficient, whereas cotton (five layers), fiberglass medium (three layers), and the commercial absolute filter were at least 99.900, 99.999, and 99.999 efficient, respectively. Glass wool and cotton were not used under higher air-flow conditions because they were difficult to assemble in leak-tight filters. The commercial absolute filter and fiberglass medium (three layers) were at least 99.990 and 99.999% efficient, respectively, under the higher air flow conditions. A stainless-steel filter of simple design and fitted with three layers of fiberglass medium was found to be greater than 99.999% efficient in removing high concentrations (20,000 to 70,000 plaque-forming units per cubic foot) of aerosolized bacteriophages from air moving at a low flow rate (1 ft3/min). Use of this filter on pressure-vacuum tanks in the fermentation industry is suggested. Several other uses of such a filter are proposed. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:5927020

  12. Limitations of using synthetic blood clots for measuring in vitro clot capture efficiency of inferior vena cava filters.

    PubMed

    Robinson, Ronald A; Herbertson, Luke H; Sarkar Das, Srilekha; Malinauskas, Richard A; Pritchard, William F; Grossman, Laurence W

    2013-01-01

    The purpose of this study was first to evaluate the clot capture efficiency and capture location of six currently-marketed vena cava filters in a physiological venous flow loop, using synthetic polyacrylamide hydrogel clots, which were intended to simulate actual blood clots. After observing a measured anomaly for one of the test filters, we redirected the focus of the study to identify the cause of poor clot capture performance for large synthetic hydrogel clots. We hypothesized that the uncharacteristic low clot capture efficiency observed when testing the outlying filter can be attributed to the inadvertent use of dense, stiff synthetic hydrogel clots, and not as a result of the filter design or filter orientation. To study this issue, sheep blood clots and polyacrylamide (PA) synthetic clots were injected into a mock venous flow loop containing a clinical inferior vena cava (IVC) filter, and their captures were observed. Testing was performed with clots of various diameters (3.2, 4.8, and 6.4 mm), length-to-diameter ratios (1:1, 3:1, 10:1), and stiffness. By adjusting the chemical formulation, PA clots were fabricated to be soft, moderately stiff, or stiff with elastic moduli of 805 ± 2, 1696 ± 10 and 3295 ± 37 Pa, respectively. In comparison, the elastic moduli for freshly prepared sheep blood clots were 1690 ± 360 Pa. The outlying filter had a design that was characterized by peripheral gaps (up to 14 mm) between its wire struts. While a low clot capture rate was observed using large, stiff synthetic clots, the filter effectively captured similarly sized sheep blood clots and soft PA clots. Because the stiffer synthetic clots remained straight when approaching the filter in the IVC model flow loop, they were more likely to pass between the peripheral filter struts, while the softer, physiological clots tended to fold and were captured by the filter. These experiments demonstrated that if synthetic clots are used as a surrogate for animal or human blood

  13. Limitations of using synthetic blood clots for measuring in vitro clot capture efficiency of inferior vena cava filters

    PubMed Central

    Robinson, Ronald A; Herbertson, Luke H; Das, Srilekha Sarkar; Malinauskas, Richard A; Pritchard, William F; Grossman, Laurence W

    2013-01-01

    The purpose of this study was first to evaluate the clot capture efficiency and capture location of six currently-marketed vena cava filters in a physiological venous flow loop, using synthetic polyacrylamide hydrogel clots, which were intended to simulate actual blood clots. After observing a measured anomaly for one of the test filters, we redirected the focus of the study to identify the cause of poor clot capture performance for large synthetic hydrogel clots. We hypothesized that the uncharacteristic low clot capture efficiency observed when testing the outlying filter can be attributed to the inadvertent use of dense, stiff synthetic hydrogel clots, and not as a result of the filter design or filter orientation. To study this issue, sheep blood clots and polyacrylamide (PA) synthetic clots were injected into a mock venous flow loop containing a clinical inferior vena cava (IVC) filter, and their captures were observed. Testing was performed with clots of various diameters (3.2, 4.8, and 6.4 mm), length-to-diameter ratios (1:1, 3:1, 10:1), and stiffness. By adjusting the chemical formulation, PA clots were fabricated to be soft, moderately stiff, or stiff with elastic moduli of 805 ± 2, 1696 ± 10 and 3295 ± 37 Pa, respectively. In comparison, the elastic moduli for freshly prepared sheep blood clots were 1690 ± 360 Pa. The outlying filter had a design that was characterized by peripheral gaps (up to 14 mm) between its wire struts. While a low clot capture rate was observed using large, stiff synthetic clots, the filter effectively captured similarly sized sheep blood clots and soft PA clots. Because the stiffer synthetic clots remained straight when approaching the filter in the IVC model flow loop, they were more likely to pass between the peripheral filter struts, while the softer, physiological clots tended to fold and were captured by the filter. These experiments demonstrated that if synthetic clots are used as a surrogate for animal or human blood

  14. Characteristics of face seal leakage in filtering facepieces.

    PubMed

    Chen, C C; Willeke, K

    1992-09-01

    Several studies have found that aerosol size, testing method, leak size, leak position, sampling probe location, and the mixing condition inside the respirator affect the results of fit factor measurements. This study focuses on the effect of leak shape and filter resistance because leaks have been reported to vary in shape from circular to slit-like. Four leaks of different shape but the same cross-sectional area were used to study their effect on aerosol penetration. Dust-mist and high-efficiency particulate air filtering facepieces provided different filter resistances. An aerodynamic particle sizer and a laser aerosol spectrometer were used to measure the particle size-dependent aerosol concentrations inside and outside the respirators. The filtering facepieces were sealed to a mannequin and artificial leaks were inserted near the right cheek. Aerosol penetration was measured for five flow rates ranging from 5 to 100 L/min. The pressure drop across the mask was monitored with an inclined manometer. At a given pressure differential, a slit-like leak and multiple circular leaks have been found to pass less aerosols than a single circular leak of equal cross-sectional area because the leak flow decreases with an increase in leak shape complexity. If there is substantial lack of face seal fit and the breathing rate is low, a HEPA respirator may provide less protection than a dust-mist respirator because the pressure drop is considerably higher for a HEPA respirator, resulting in more aerosol flow through the leak. PMID:1524028

  15. High Efficiency Bi-Directional DC-DC Converter With ZVS-ZCS Applied For Parallel Active Filtering

    NASA Astrophysics Data System (ADS)

    Romero, V.; Soto, A.

    2011-10-01

    In space missions, it is becoming more and more common to have strict EMC requirements to be met. Coping with this is a challenge for all those instruments and subsystems implementing AC loads. In particular, the driving of motors is one of the highest challenges due to the low frequency and high amplitude of the emissions. The driving of these motors without exceeding typical EMC levels implies adding an active filter at its input. Passive filtering approach is not useful due to bulk components required to filter such low frequencies. The aim of this paper is to show a parallel active filtering solution that implements significant advantages compared to other classical approaches in terms of mass and efficiency.

  16. The efficient separation of surfactant-stabilized water-in-oil emulsions with a superhydrophobic filter paper

    NASA Astrophysics Data System (ADS)

    Ge, Bo; Zhu, Xiaotao; Li, Yong; Men, Xuehu; Li, Peilong; Zhang, Zhaozhu

    2015-11-01

    The filtration membranes have been acknowledged as efficient way for separation of emulsion. Nevertheless, most of the methods have limitations of high cost and complex fabrication process. Here, we present a simple method for preparing superhydrophobic/superoleophilic filter paper by solution immersion process. The superhydrophobic filter paper exhibited high selectivity for oil-water mixture. Importantly, the filter paper can be applied to separate surfactant-stabilized water-in-oil emulsion. Separation process is achieved by one step under gravity. Moreover, the superhydrophobic filter paper maintains stable superhydrophobicity and emulsion separation property after using for five cycles. We expected that this low-cost process can be used for water-in-oil emulsion separation.

  17. An efficient closed-form design method for nearly perfect reconstruction of non-uniform filter bank.

    PubMed

    Kumar, A; Pooja, R; Singh, G K

    2016-03-01

    In this paper, an efficient closed form method for the design of multi-channel nearly perfect reconstruction of non-uniform filter bank with the prescribed stopband attenuation and channel overlapping is presented. In this method, the design problem of multi-channel non-uniform filter bank (NUFB) is considered as the design of a prototype filter whose magnitude response at quadrature frequency is 0.707, which is exploited for finding the optimum passband edge frequency through empirical formula instead of using single or multivariable optimization technique. Two main attributes used in assessing the performance of filter bank are peak reconstruction error (PRE) and computational time (CPU time). As compared to existing methods, this method is very simple and easy to implement for NUFBs. To implement this algorithm, a Matlab program has been developed, and several examples are presented to illustrate the performance of proposed method. PMID:26861726

  18. Particle Characterization and Ice Nucleation Efficiency of Field-Collected Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Wang, B.; Gilles, M. K.; Laskin, A.; Moffet, R.; Nizkorodov, S.; Roedel, T.; Sterckx, L.; Tivanski, A.; Knopf, D. A.

    2011-12-01

    Atmospheric ice formation by heterogeneous nucleation is one of the least understood processes resulting in cirrus and mixed-phase clouds which affect the global radiation budget, the hydrological cycle, and water vapor distribution. In particular, how organic aerosol affect ice nucleation is not well understood. Here we report on heterogeneous ice nucleation from particles collected during the CalNex campaign at the Caltech campus site, Pasadena, on May 19, 2010 at 6am-12pm (A2) and 12pm-6pm (A3) and May 23 at 6am-12pm (B2) and 6pm-12am (B4). The ice nucleation onsets and water uptake were determined as a function of temperature (200-273 K) and relative humidity with respect to ice (RHice). The ice nucleation efficiency was related to the particle chemical composition. Single particle characterization was provided by using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). The STXM/NEXAFS analysis indicates that the morning sample (A2) constitutes organic particles and organic particles with soot and inorganic inclusions. The afternoon sample (A3) is dominated by organic particles with a potentially higher degree of oxidation associated with soot. The B2 sample shows a higher number fraction of magnesium-containing particle indicative of a marine source and ~93% of the particles contained sulfur besides oxygen and carbon as derived from CCSEM/EDX analysis. The B4 sample lacks the strong marine influence and shows higher organic content. Above 230 K, we observed water uptake followed by condensation freezing at mean RH of 93-100% and 89-95% for A2 and A3, respectively. This indicates that the aged A3 particles are efficient ice nuclei (IN) for condensation freezing. Below 230 K A2 and A3 induced deposition ice nucleation between 125-155% RHice (at mean values of 134-150% RHice). The B2 and B4

  19. Effects of flattening filter-free and volumetric-modulated arc therapy delivery on treatment efficiency.

    PubMed

    Thomas, Evan M; Popple, Richard A; Prendergast, Brendan M; Clark, Grant M; Dobelbower, Michael C; Fiveash, John B

    2013-01-01

    Flattening filter-free (FFF) beams are available on an increasing number of commercial linear accelerators. FFF beams have higher dose rates than flattened beams of equivalent energy which can lead to increased efficiency of treatment delivery, especially in conjunction with increased FFF beam energy and arc-based delivery configurations. The purpose of this study is to quantify and assess the implications of improved treatment efficiency for several FFF delivery options on common types of linac applicable radiotherapy. Eleven characteristic cases representative of a variety of clinical treatment sites and prescription doses were selected from our patient population. Treatment plans were generated for a Varian TrueBeam linear accelerator. For each case, a reference plan was created using DMLC IMRT with 6MV flat beams. From the same initial objectives, plans were generated using DMLC IMRT and volumetric-modulated arc therapy (VMAT) with 6 MV FFF and 10 MV FFF beams (max. dose rates of 1400 and 2400 MU/min, respectively). The plans were delivered to a phantom; beam-on time, total treatment delivery time, monitor units (MUs), and integral dose were recorded. For plans with low dose fractionations (1.8-2.0 & 3.85 Gy/fraction), mean beam-on time difference between reference plan and most efficient FFF plan was 0.56 min (41.09% decrease); mean treatment delivery time difference between the reference plan and most efficient FFF plan was 1.54 min (range: 0.31-3.56 min), a relative improvement of 46.1% (range: 29.2%-59.2%). For plans with high dose fractionations (16-20 Gy/fraction), mean beam-on time difference was 6.79 min (74.9% decrease); mean treatment delivery time difference was 8.99 min (range: 5.40-13.05 min), a relative improvement of 71.1% (range: 53.4%- 82.4%). 10 MV FFF VMAT beams generated the most efficient plan, except in the spine SBRT case. The distribution of monitor unit counts did not vary by plan type. In cases where respiratory motion management would

  20. Photon harvesting, coloring and polarizing in photovoltaic cell integrated color filters: efficient energy routing strategies for power-saving displays.

    PubMed

    Wen, Long; Chen, Qin; Song, Shichao; Yu, Yan; Jin, Lin; Hu, Xin

    2015-07-01

    We describe the integral electro-optical strategies that combine the functionalities of photovoltaic (PV) electricity generation and color filtering as well as polarizing to realize more efficient energy routing in display technology. Unlike the conventional pigment-based filters and polarizers, which absorb substantial amounts of unwanted spectral components and dissipate them in the form of heat, we propose converting the energy of those photons into electricity by constructing PV cell-integrated color filters based on a selectively transmitting aluminum (Al) rear electrode perforated with nanoholes (NHs). Combining with a dielectric-metal-dielectric (DMD) front electrode, the devices were optimized to enable efficient cavity-enhanced photon recycling in the PV functional layers. We perform a comprehensive theoretical and numerical analysis to explore the extraordinary optical transmission (EOT) through the Al NHs and identify basic design rules for achieving structural coloring or polarizing in our PV color filters. We show that the addition of thin photoactive polymer layers on the symmetrically configured Al NH electrode narrows the bandwidth of the EOT-assisted high-pass light filtering due to the strongly damped anti-symmetric coupling of the surface modes excited on the front and rear surface of the Al NHs, which facilitates the whole visible coloring with relatively high purity for the devices. By engineering the cut-off characteristics of the plasmonic waveguide mode supported by the circular or ellipsoidal Al NHs, beyond the photon recycling capacity, PV color filters and PV polarizing color filters that allow polarization-insensitive and strong polarization-anisotropic color filtering were demonstrated. The findings presented here may shed some light on expanding the utilization of PV electricity generation across new-generation energy-saving electrical display devices. PMID:26062682

  1. Photon harvesting, coloring and polarizing in photovoltaic cell integrated color filters: efficient energy routing strategies for power-saving displays

    NASA Astrophysics Data System (ADS)

    Wen, Long; Chen, Qin; Song, Shichao; Yu, Yan; Jin, Lin; Hu, Xin

    2015-07-01

    We describe the integral electro-optical strategies that combine the functionalities of photovoltaic (PV) electricity generation and color filtering as well as polarizing to realize more efficient energy routing in display technology. Unlike the conventional pigment-based filters and polarizers, which absorb substantial amounts of unwanted spectral components and dissipate them in the form of heat, we propose converting the energy of those photons into electricity by constructing PV cell-integrated color filters based on a selectively transmitting aluminum (Al) rear electrode perforated with nanoholes (NHs). Combining with a dielectric-metal-dielectric (DMD) front electrode, the devices were optimized to enable efficient cavity-enhanced photon recycling in the PV functional layers. We perform a comprehensive theoretical and numerical analysis to explore the extraordinary optical transmission (EOT) through the Al NHs and identify basic design rules for achieving structural coloring or polarizing in our PV color filters. We show that the addition of thin photoactive polymer layers on the symmetrically configured Al NH electrode narrows the bandwidth of the EOT-assisted high-pass light filtering due to the strongly damped anti-symmetric coupling of the surface modes excited on the front and rear surface of the Al NHs, which facilitates the whole visible coloring with relatively high purity for the devices. By engineering the cut-off characteristics of the plasmonic waveguide mode supported by the circular or ellipsoidal Al NHs, beyond the photon recycling capacity, PV color filters and PV polarizing color filters that allow polarization-insensitive and strong polarization-anisotropic color filtering were demonstrated. The findings presented here may shed some light on expanding the utilization of PV electricity generation across new-generation energy-saving electrical display devices.

  2. Performance testing of HEPA filters: Progress towards a European standard procedure

    SciTech Connect

    Dyment, J.

    1997-08-01

    Proposals for a future European testing procedure for {open_quotes}High Efficiency Particulate Air Filters (HEPA and ULPA){close_quotes} are being developed by CEN (Comite Europeen de Normalisation). The new standard will be given the status of national standard in participating countries, conflicting national standards being withdrawn. The standard will comprise 5 parts covering the grouping and classification of HEPA and ULPA filters according to their efficiency, fundamental principles of testing, marking etc (in part 1). Part 2 will cover aerosol production, measurement principles, counting equipment and statistics. Parts 3-5 will cover testing flat sheet media, leak testing of filter elements and the efficiency testing of filter elements respectively. The efficiency test methods allow the use of either homogeneous monodisperse or polydisperse aerosols for the determination of particulate filtration efficiencies as a function of particle size. The particle size at which maximum penetration occurs is first determined in flat sheet media tests; tests on filter elements (constructed using the same filter medium) may be carried out using either a homogeneous monodisperse aerosol of the size at which maximum penetration occurs (MPPS) or a polydisperse aerosol whose median size is close to the MPPS. Tests with monodisperse aerosols may be conducted using condensation nucleus counting equipment; tests using polydisperse test aerosols require the use of optical sizing particle counters. When determining the efficiency of filter elements the downstream aerosol concentrations may be determined from air samples obtained using either an overall method (single point sampling after mixing) or a scan method. The scan method also allows {open_quotes}local{close_quotes} efficiency values to be determined. 1 ref., 1 fig., 1 tab.

  3. The influence of salt aerosol on alpha radiation detection by WIPP continuous air monitors

    SciTech Connect

    Bartlett, W.T.; Walker, B.A.

    1997-08-01

    Waste Isolation Pilot Plant (WIPP) alpha continuous air monitor (CAM) performance was evaluated to determine if CAMs could detect accidental releases of transuranic radioactivity from the underground repository. Anomalous alpha spectra and poor background subtraction were observed and attributed to salt deposits on the CAM sampling filters. Microscopic examination of salt laden sampling filters revealed that aerosol particles were forming dendritic structures on the surface of the sampling filters. Alpha CAM detection efficiency decreased exponentially as salt deposits increased on the sampling filters, suggesting that sampling-filter salt was performing like a fibrous filter rather than a membrane filter. Aerosol particles appeared to penetrate the sampling-filter salt deposits and alpha particle energy was reduced. These findings indicate that alpha CAMs may not be able to detect acute releases of radioactivity, and consequently CAMs are not used as part of the WIPP dynamic confinement system. 12 refs., 12 figs., 1 tab.

  4. Recovery efficiency and limit of detection of aerosolized Bacillus anthracis Sterne from environmental surface samples.

    PubMed

    Estill, Cheryl Fairfield; Baron, Paul A; Beard, Jeremy K; Hein, Misty J; Larsen, Lloyd D; Rose, Laura; Schaefer, Frank W; Noble-Wang, Judith; Hodges, Lisa; Lindquist, H D Alan; Deye, Gregory J; Arduino, Matthew J

    2009-07-01

    After the 2001 anthrax incidents, surface sampling techniques for biological agents were found to be inadequately validated, especially at low surface loadings. We aerosolized Bacillus anthracis Sterne spores within a chamber to achieve very low surface loading (ca. 3, 30, and 200 CFU per 100 cm(2)). Steel and carpet coupons seeded in the chamber were sampled with swab (103 cm(2)) or wipe or vacuum (929 cm(2)) surface sampling methods and analyzed at three laboratories. Agar settle plates (60 cm(2)) were the reference for determining recovery efficiency (RE). The minimum estimated surface concentrations to achieve a 95% response rate based on probit regression were 190, 15, and 44 CFU/100 cm(2) for sampling steel surfaces and 40, 9.2, and 28 CFU/100 cm(2) for sampling carpet surfaces with swab, wipe, and vacuum methods, respectively; however, these results should be cautiously interpreted because of high observed variability. Mean REs at the highest surface loading were 5.0%, 18%, and 3.7% on steel and 12%, 23%, and 4.7% on carpet for the swab, wipe, and vacuum methods, respectively. Precision (coefficient of variation) was poor at the lower surface concentrations but improved with increasing surface concentration. The best precision was obtained with wipe samples on carpet, achieving 38% at the highest surface concentration. The wipe sampling method detected B. anthracis at lower estimated surface concentrations and had higher RE and better precision than the other methods. These results may guide investigators to more meaningfully conduct environmental sampling, quantify contamination levels, and conduct risk assessment for humans. PMID:19429546

  5. Recovery Efficiency and Limit of Detection of Aerosolized Bacillus anthracis Sterne from Environmental Surface Samples ▿

    PubMed Central

    Estill, Cheryl Fairfield; Baron, Paul A.; Beard, Jeremy K.; Hein, Misty J.; Larsen, Lloyd D.; Rose, Laura; Schaefer, Frank W.; Noble-Wang, Judith; Hodges, Lisa; Lindquist, H. D. Alan; Deye, Gregory J.; Arduino, Matthew J.

    2009-01-01

    After the 2001 anthrax incidents, surface sampling techniques for biological agents were found to be inadequately validated, especially at low surface loadings. We aerosolized Bacillus anthracis Sterne spores within a chamber to achieve very low surface loading (ca. 3, 30, and 200 CFU per 100 cm2). Steel and carpet coupons seeded in the chamber were sampled with swab (103 cm2) or wipe or vacuum (929 cm2) surface sampling methods and analyzed at three laboratories. Agar settle plates (60 cm2) were the reference for determining recovery efficiency (RE). The minimum estimated surface concentrations to achieve a 95% response rate based on probit regression were 190, 15, and 44 CFU/100 cm2 for sampling steel surfaces and 40, 9.2, and 28 CFU/100 cm2 for sampling carpet surfaces with swab, wipe, and vacuum methods, respectively; however, these results should be cautiously interpreted because of high observed variability. Mean REs at the highest surface loading were 5.0%, 18%, and 3.7% on steel and 12%, 23%, and 4.7% on carpet for the swab, wipe, and vacuum methods, respectively. Precision (coefficient of variation) was poor at the lower surface concentrations but improved with increasing surface concentration. The best precision was obtained with wipe samples on carpet, achieving 38% at the highest surface concentration. The wipe sampling method detected B. anthracis at lower estimated surface concentrations and had higher RE and better precision than the other methods. These results may guide investigators to more meaningfully conduct environmental sampling, quantify contamination levels, and conduct risk assessment for humans. PMID:19429546

  6. Synthesis of Spherical Carbon Nitride-Based Polymer Composites by Continuous Aerosol-Photopolymerization with Efficient Light Harvesting.

    PubMed

    Poostforooshan, Jalal; Badiei, Alireza; Kolahdouz, Mohammadreza; Weber, Alfred P

    2016-08-24

    Here we report a novel, facile, and sustainable approach for the preparation of spherical submicrometer carbon nitride-based polymer composites by a continuous aerosol-photopolymerization process. In this regard, spherical mesoporous carbon nitride (SMCN) nanoparticles were initially prepared via a nanocasting approach using spray-drying synthesized spherical mesoporous silica (SMS) nanoparticles as hard templates. In addition to experimental characterization, the effect of porosity on the light absorption enhancement and consequently the generation rate of electron-hole pairs inside the SMCN was simulated using a three-dimensional finite difference time-domain (FDTD) method. To produce the carbon nitride-based polymer composite, SMCN nanoparticles exhibit excellent performance in photopolymerization of butyl acrylate (PBuA) monomer in the presence of n-methyldiethanolamine (MDEA) as a co-initiator in a continuous aerosol-based process. In this one-pot synthesis, SMCN nanoparticles act not only as photoinitiators but at the same time as fillers and templates. The average aerosol residence time in the photoreactor is about 90 s. The presented aerosol-photopolymerization process avoids the need for solvent and surfactant, operates at room temperature, and, more importantly, is suitable to produce the spherical composite with hydrophobic polymers. Furthermore, we simulated the condition of SMCN nanoparticles during illumination in the gas phase process, which can freely rotate. The results demonstrated that the hole (h(+)) density is almost equally distributed in the whole part of the SMCN nanoparticles due to their rotation, leading to efficient light harvesting and more homogeneous photoreaction. The combination of the outstanding features of environmentally friendly SMCN, photopolymerization, and aerosol processing might open new avenues, especially in green chemistry, to produce novel polymer composites with multifunctional properties. PMID:27483090

  7. Pollution transport efficiency toward the Arctic: Sensitivity to aerosol scavenging and source regions

    NASA Astrophysics Data System (ADS)

    Bourgeois, Quentin; Bey, Isabelle

    2011-04-01

    The processes driving current changes in Arctic atmospheric composition and climate are still uncertain. In particular the relative contributions of major source regions from the midlatitudes remain a matter of debate in the literature. The objectives of this study are to better quantify the relative contributions of different processes governing the transport of pollution from the midlatitudes to the Arctic and the relative contributions of different geopolitical source regions. We use a suite of observational data sets (including the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaigns and the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite instrument) to constrain a global aerosol simulation from the ECHAM5-HAMMOZ model. Preliminary comparison of model results with vertical profiles of sulfate and black carbon (BC) collected during the ARCTAS campaigns and with aerosol extinction time series retrieved from CALIOP indicates that the model underestimates export of aerosols from the planetary boundary layer to the free troposphere in the midlatitudes and long-range transport of aerosols from the midlatitudes toward the Arctic. In contrast, observed CO profiles are relatively well simulated, which points to a possible problem with wet scavenging. Decreasing the prescribed aerosol scavenging coefficients within the range of experimental data available in the literature significantly improves the agreement with observations. Sulfate and BC burdens in the Arctic increase by a factor 5-6. Annual global lifetimes of sulfate and BC increase from 3.1 to 4.6 days and from 4.4 to 5.9 days, respectively. Using the improved simulation, we find that 59% of sulfate in the Arctic troposphere comes from the oxidation of SO2 emitted in Siberia (19%), Europe (18%), Asia (13%), and North America (9%). Anthropogenic and biomass burning BC emitted in Siberia, Asia, Europe, and North America contributes 29, 27, 25, and

  8. On-Line Measurement of Beryllium, Chromium, and Mercury by Using Aerosol Beam Focused Laser-Induced Plasma Spectrometer and TIme-Integrated Filter Sampling and Reference Method

    SciTech Connect

    Cheng, M.-D.; Vannice, R.W.

    2003-05-20

    A novel real-time monitor for aerosol particles has been developed by the Oak Ridge National Laboratory (ORNL). The instrument is designed to perform in-situ measurement for the elemental composition of aerosol particles in flue gas. They had tested this monitor at the Eastman Chemical Company in July 2001 taking advantage of the emissions from a waste incinerator operated by the company as the background. To investigate the behavior and response of the monitor under simulated/known conditions, stock solutions of prepared metal concentration(s) were nebulized to provide spikes for the instrument testing. Strengths of the solutions were designed such that a reference method (RM) was able to collect sufficient material on filter samples that were analyzed in a laboratory to produce 30-minute average data points. Parallel aerosol measurements were performed by using the ORNL instrument. Recorded signal of an individual element was processed and the concentration calculated from a calibration curve established prior to the campaign. RM data were able to reflect the loads simulated in the spiked waste stream. However, it missed one beryllium sample. The possibility of bias exists in the RM determination of chromium that could lead to erroneous comparison between the RM and the real-time monitoring data. With the real-time detection capability, the ORNL instrument was able to reveal the emission variation by making seven measurements within a 30-minute cycle. The ability of the instrument also enables the reconstruction of the baseline chromium emission concentration. The measurements for mercury by both methods are in good agreement.

  9. On-Line Measurements of Beryllium, Chromium, and Mercury by Using Aerosol Beam Focused Laser-Induced Plasma Spectrometer and Time-Integrated Filter Sampling Reference Method

    SciTech Connect

    Cheng, M.D.

    2003-05-15

    A novel real-time monitor for aerosol particles has been developed by the Oak Ridge National Laboratory (ORNL). The instrument is designed to perform in-situ measurement for the elemental composition of aerosol particles in flue gas. We had tested this monitor at the Eastman Chemical Company in July 2001 taking advantage of the emissions from a waste incinerator operated by the company as the background. To investigate the behavior and response of the monitor under simulated/known conditions, stock solutions of prepared metal concentration(s) were nebulized to provide spikes for the instrument testing. Strengths of the solutions were designed such that a reference method (RM) was able to collect sufficient material on filter samples that were subsequently analyzed in a laboratory to produce 30-minute average data points. Parallel aerosol measurements were performed by using the ORNL instrument. Recorded signal of an individual element was processed and the concentration calculated from a calibration curve established prior to the campaign. RM data were able to reflect the loads simulated in the spiked waste stream. However, it missed one beryllium sample. The possibility of bias exists in the RM determination of chromium that could lead to erroneous comparison between the RM and the real-time monitoring data. With the real-time detection capability, the ORNL instrument was able to reveal the emission variation by making seven measurements within a 30-minute cycle. The ability of the instrument also enables the reconstruction of the baseline chromium emission concentration. The measurements for mercury by both methods are in good agreement.

  10. Assessing Modeled CO2 Retention and Rebreathing of a Facemask Designed for Efficient Delivery of Aerosols to Infants

    PubMed Central

    Mundt, Christian; Sventitskiy, Alexander; Cehelsky, Jeffrey E.; Patters, Andrea B.; Tservistas, Markus; Hahn, Michael C.; Juhl, Gerd; DeVincenzo, John P.

    2012-01-01

    Background. New aerosol drugs for infants may require more efficient delivery systems, including face masks. Maximizing delivery efficiency requires tight-fitting masks with minimal internal mask volumes, which could cause carbon dioxide (CO2) retention. An RNA-interference-based antiviral for treatment of respiratory syncytial virus in populations that may include young children is designed for aerosol administration. CO2 accumulation within inhalation face masks has not been evaluated. Methods. We simulated airflow and CO2 concentrations accumulating over time within a new facemask designed for infants and young children (PARI SMARTMASK® Baby). A one-dimensional model was first examined, followed by 3-dimensional unsteady computational fluid dynamics analyses. Normal infant breathing patterns and respiratory distress were simulated. Results. The maximum average modeled CO2 concentration within the mask reached steady state (3.2% and 3% for normal and distressed breathing patterns resp.) after approximately the 5th respiratory cycle. After steady state, the mean CO2 concentration inspired into the nostril was 2.24% and 2.26% for normal and distressed breathing patterns, respectively. Conclusion. The mask is predicted to cause minimal CO2 retention and rebreathing. Infants with normal and distressed breathing should tolerate the mask intermittently delivering aerosols over brief time frames. PMID:22792479

  11. Radiological/biological/aerosol removal system

    DOEpatents

    Haslam, Jeffery J

    2015-03-17

    An air filter replacement system for existing buildings, vehicles, arenas, and other enclosed airspaces includes a replacement air filter for replacing a standard air filter. The replacement air filter has dimensions and air flow specifications that allow it to replace the standard air filter. The replacement air filter includes a filter material that removes radiological or biological or aerosol particles.

  12. Aerosol mixing state, hygroscopic growth and cloud activation efficiency during MIRAGE 2006

    NASA Astrophysics Data System (ADS)

    Lance, S.; Raatikainen, T.; Onasch, T. B.; Worsnop, D. R.; Yu, X.-Y.; Alexander, M. L.; Stolzenburg, M. R.; McMurry, P. H.; Smith, J. N.; Nenes, A.

    2013-05-01

    Observations of aerosol hygroscopic growth and CCN activation spectra for submicron particles are reported for the T1 ground site outside of Mexico City during the MIRAGE 2006 campaign. κ-Köhler theory is used to evaluate the characteristic hygroscopicity parameter, κ*, for the CCN active aerosol population using both size-resolved HTMDA and size-resolved CCNc measurements. Organic mass fractions (forg) are evaluated from size-resolved aerosol mass spectrometer (AMS) measurements, from which predictions of the hygroscopicity parameter are compared against κ*. Strong diurnal changes in aerosol water uptake parameters and aerosol composition are observed. We find that new particle formation (NPF) events are correlated with an increased κ* and CCN-active fraction during the daytime, with greater impact on smaller particles. During NPF events, the number concentration of 40 nm particles acting as CCN at 0.51% ± 0.06% supersaturation can surpass by more than a factor of two the corresponding concentrations of 100 nm particles. We also find that at 06:00-08:00 LT throughout the campaign, fresh traffic emissions result in substantial changes to the chemical distribution of the aerosol, with on average 65% externally mixed fraction for 40 nm particles and 30% externally mixed fraction for 100 nm particles, whereas at midday nearly all particles of both sizes can be described as "internally mixed". Average activation spectra and growth factor distributions are analyzed for different time periods characterizing the daytime (with and without NPF events), the early morning "rush hour" and the entire campaign. We show that κ* derived from CCNc measurements decreases as a function of size during all time periods, while the CCN-active fraction increases as a function of size. Size-resolved AMS measurements do not predict the observed trend for κ* versus particle size, which can be attributed to unresolved mixing state and the presence of refractory material not measured

  13. Comparison of model results of collection efficiency of aerosol particles by individual water droplets and ice crystals in a subsaturated atmosphere

    NASA Astrophysics Data System (ADS)

    Wang, P. K.; Lin, H.

    The aerosol collection efficiencies of water droplets and ice crystals are compared based on the concept of equivalent geometrical kernel K ∗ which is the geometrical sweep-out volume per unit time by the collector. It is thought that the comparison based on this quantity reveals the real difference of the aerosol collecting abilities of different collectors and sheds lights on the precipitation scavenging mechanisms. The collection efficiencies are taken from theoretical model results computed by us previously at relative humidities of 95% for water droplets, columnar and hexagonal plate ice crystals. It is shown that the efficiencies are rather insensitive to collector shape for aerosol particles smaller than 0.01 μm. The shape factor becomes more important for larger aerosol particles, especially in the Greenfield-Gap size range.

  14. Common inorganic ions are efficient catalysts for organic reactions in atmospheric aerosols and other natural environments

    NASA Astrophysics Data System (ADS)

    Nozière, B.; Dziedzic, P.; Córdova, A.

    2009-01-01

    In this work, inorganic ammonium ions, NH4+, and carbonate ions, CO32-, are reported for the first time as catalysts for organic reactions in atmospheric aerosols and other natural environments at the Earth's surface. These reactions include the formation of C-C and C-O bonds by aldol condensation and acetal formation, and reveal a new aspect of the interactions between organic and inorganic materials in natural environments. The catalytic properties of inorganic ammonium ions, in particular, were not previously known in chemistry. The reactions were found to be as fast in tropospheric ammonium sulfate composition as in concentrated sulfuric acid. The ubiquitous presence and large concentrations of ammonium ions in tropospheric aerosols would make of ammonium catalysis a main consumption pathway for organic compounds in these aerosols, while acid catalysis would have a minor contribution. In particular, ammonium catalysis would account quantitatively for the aging of carbonyl compounds into secondary ''fulvic'' compounds in tropospheric aerosols, a transformation affecting the optical properties of these aerosols. In general, ammonium catalysis is likely to be responsible for many observations previously attributed to acid catalysis in the troposphere.

  15. Preparation of Nanofibrous Metal-Organic Framework Filters for Efficient Air Pollution Control.

    PubMed

    Zhang, Yuanyuan; Yuan, Shuai; Feng, Xiao; Li, Haiwei; Zhou, Junwen; Wang, Bo

    2016-05-11

    Environmental challenges especially air pollution (particulate matter (PM) and toxic gases) pose serious threats to public health globally. Metal-organic frameworks (MOFs) are crystalline materials with high porosity, tunable pore size, and rich functionalities, holding the promise for poisonous pollutants capture. Here, nanocrystals of four unique MOF structures are processed into nanofibrous filters (noted as MOFilter) with high MOF loadings (up to 60 wt %). The MOFilters show high PM removal efficiencies up to 88.33 ± 1.52% and 89.67 ± 1.33% for PM2.5 and PM10, respectively, in the hazy environment, and the performance remains largely unchanged over 48 h of continuous filtration. For the first time, the interactions between such porous crystalline material and particulate pollutants were explored. These thin MOFilters can further selectively capture and retain SO2 when exposed to a stream of SO2/N2 mixture, and their hierarchical nanostructures can easily permeate fresh air at high gas flow rate with the pressure drop <20 Pa. PMID:27090776

  16. A Computationally Efficient Mel-Filter Bank VAD Algorithm for Distributed Speech Recognition Systems

    NASA Astrophysics Data System (ADS)

    Vlaj, Damjan; Kotnik, Bojan; Horvat, Bogomir; Kačič, Zdravko

    2005-12-01

    This paper presents a novel computationally efficient voice activity detection (VAD) algorithm and emphasizes the importance of such algorithms in distributed speech recognition (DSR) systems. When using VAD algorithms in telecommunication systems, the required capacity of the speech transmission channel can be reduced if only the speech parts of the signal are transmitted. A similar objective can be adopted in DSR systems, where the nonspeech parameters are not sent over the transmission channel. A novel approach is proposed for VAD decisions based on mel-filter bank (MFB) outputs with the so-called Hangover criterion. Comparative tests are presented between the presented MFB VAD algorithm and three VAD algorithms used in the G.729, G.723.1, and DSR (advanced front-end) Standards. These tests were made on the Aurora 2 database, with different signal-to-noise (SNRs) ratios. In the speech recognition tests, the proposed MFB VAD outperformed all the three VAD algorithms used in the standards by [InlineEquation not available: see fulltext.] relative (G.723.1 VAD), by [InlineEquation not available: see fulltext.] relative (G.729 VAD), and by [InlineEquation not available: see fulltext.] relative (DSR VAD) in all SNRs.

  17. Photoacoustic determination of optical properties of aerosol particles collected on filters: development of a method taking into account substrate reflectivity.

    PubMed

    Röhl, R; McClenny, W A; Palmer, R A

    1982-02-01

    The absorptivity of soot and methylene blue particles collected on Teflon filters is derived from photoacoustic measurements by least squares fitting a simple expression based on Beer's law to the experimental data. Refinements of the expression take into account the diffuse reflection of light by the filter substrate, yielding a base 10 absorptivity at 600 nm for soot of 3.00 +/- 0.37 m(2)/g. This value is in close agreement with the result of transmission measurements performed on the same samples (3.08 +/- 0.05 m(2)/g). PMID:20372465

  18. Filtration of bioaerosols using a granular metallic filter with micrometer-sized collectors

    SciTech Connect

    Damit, Brian E; Bischoff, Brian L; Phelps, Tommy Joe; Wu, Dr. Chang-Yu; Cheng, Mengdawn

    2014-01-01

    Several experimental studies with granular bed filters composed of micrometer-sized spherical or sintered metallic granules have demonstrated their use in aerosol filtration. However, the effectiveness of these metallic membrane filters against bioaerosols has not been established. In this work, the filtration efficiency and filter quality of these filters against airborne B. subtilis endospore and MS2 virus were determined as a function of face velocity and loading time. In experiments, a physical removal efficiency greater than 99.9% and a viable removal efficiency of greater than 5-log were observed for both bacterial spore and viral aerosols. A lower face velocity produced both higher collection efficiency and filter quality for virus but was not statistically significant for spore filtration. Although the filter had high filtration efficiency of the test bioaerosols, the filter's high pressure drop resulted in a low filter quality (0.25-0.75 kPa- 1). Overall, filters with micrometer-sized collectors capture bioaerosols effectively but their applications in aerosol filtration may be limited by their high pressure drop.

  19. Effect of DOP heterodispersion on HEPA-filter-penetration measurements

    SciTech Connect

    Bergman, W.; Biermann, A.

    1984-08-09

    The accuracy of the standard US test method for certifying High-Efficiency Particulate Air (HEPA) filters has been in question since the finding by Hinds, et al. that the dioctyl phthalate (DOP) aerosol used in the test is not monodisperse as had been assumed and that particle-size analyzers, or owls, could not distinguish between different particle-size distributions with the same owl reading. We have studied theoretically and experimentally the filter efficiency for different DOP size distributions with the same owl reading. Our studies show that the effect of varying DOP size distributions on the measured HEPA-filter penetration depends on the light-scattering-photometer response and on the HEPA-filter penetration curve, both measured as a function of particle size. HEPA-filter penetration for a heterodisperse DOP aerosol may be increased, decreased, or remain the same when compared to the filter penetration for monodisperse aerosols. Using experimental HEPA-filter penetration and photometer response curves, we show that heterodisperse DOP aerosols (D/sub cmd/ 0.19 and sigma g = 1.4) yield 24% lower penetrations than that for monodisperse DOP aerosols (D/sub cmd/ = 0.3 and sigma g = 1.0). This surprisingly small effect of the DOP heterodispersion on HEPA-filter penetration is due to the response function of the owl that is similar to the response of the photometer. Changes in the particle-size distribution are therefore seen in a similar fashion by both the photometer and the owl. We also show that replacing the owl with modern particle-size spectrometers may lead to large errors in filter penetration because the particle-size spectrometers do not provide measurements that correspond to the photometer measurements. 15 references, 16 figures.

  20. PHOTOACOUSTIC DETERMINATION OF OPTICAL PROPERTIES OF AEROSOL PARTICLES COLLECTED ON FILTERS: DEVELOPMENT OF A METHOD TAKING INTO ACCOUNT SUBSTRATE REFLECTIVITY

    EPA Science Inventory

    The absorptivity and imaginary index of refraction for carbon and methylene blue particles were inferred from the photoacoustic spectra of samples collected on Teflon filter substrates. Three models of varying complexity were developed to describe the photoacoustic signal as a fu...

  1. Evaluation of N95 filtering facepiece respirator efficiency with cyclic and constant flows.

    PubMed

    Bahloul, Ali; Mahdavi, Alireza; Haghighat, Fariborz; Ostiguy, Claude

    2014-01-01

    An increasing demand for protecting workers against harmful inhalable ultrafine particles (UFPs), by means of filtering facepiece respirators (FFRs), necessitates assessing the efficiency of FFRs. This article evaluates the penetration of particles, mostly in the ultrafine range, through one model of N95 FFRs exposed to cyclic and constant flows, simulating breathing for moderate to heavy work loads. The generated particles were poly-dispersed NaCl, within the range of 10-205.4 nm. The tests were performed for several cyclic flows, with mean inhalation flows (MIFs) ranging from 42 to 360 L/min, and constant flows with the same range. The measurements were based on filter penetration and did not consider particle leakage. With the penetrations recorded for the selected constant and cyclic flows, the worst-case scenario penetrations at the most penetrating particle size (MPPS) were obtained. The MPPS penetrations measured with the cyclic and constant flows equivalent to minute volume, MIF and peak inhalation flow (PIF) of the cyclic flows were then compared. It was indicated that the constant flows equivalent to the minute volume or PIF of the cyclic flow could not accurately represent the penetration of the corresponding cyclic flow: the constant flow equal to the minute volume of the cyclic flow significantly underestimated the MPPS penetration of the corresponding cyclic flow, while the constant flow equal to the PIF of the cyclic flow overestimated it. On the other hand, for the constant flow equal to the MIF of the cyclic flow, the MPPS penetrations were almost equal for both the constant and cyclic flows, for the lower flow rates (42 to 170 L/min). For higher flow rates (230 to 360 L/min), however, the MPPS penetration was exceeded under the constant flows, compared with the corresponding cyclic flows. It was therefore concluded that the constant flow equal to the MIF of the cyclic flow could better predict the results of corresponding cyclic flow, since it

  2. Removal efficiency of silver impregnated filter materials and performance of iodie filters in the off-gas of the Karlsruhe reprocessing plant WAK

    SciTech Connect

    Herrmann, F.J.; Herrmann, B.; Hoeflich, V.

    1997-08-01

    An almost quantitative retention of iodine is required in reprocessing plants. For the iodine removal in the off-gas streams of a reprocessing plant various sorption materials had been tested under realistic conditions in the Karlsruhe reprocessing plant WAK in cooperation with the Karlsruhe research center FZK. The laboratory results achieved with different iodine sorption materials justified long time performance tests in the WAK Plant. Technical iodine filters and sorption materials for measurements of iodine had been tested from 1972 through 1992. This paper gives an overview over the most important results, Extended laboratory, pilot plant, hot cell and plant experiences have been performed concerning the behavior and the distribution of iodine-129 in chemical processing plants. In a conventional reprocessing plant for power reactor fuel, the bulk of iodine-129 and iodine-127 is evolved into the dissolver off-gas. The remainder is dispersed over many aqueous, organic and gaseous process and waste streams of the plant. Iodine filters with silver nitrate impregnated silica were installed in the dissolver off-gas of the Karlsruhe reprocessing plant WAK in 1975 and in two vessel vent systems in 1988. The aim of the Karlsruhe iodine research program was an almost quantitative evolution of the iodine during the dissolution process to remove as much iodine with the solid bed filters as possible. After shut down of the WAK plant in December 1990 the removal efficiency of the iodine filters at low iodine concentrations had been investigated during the following years. 12 refs., 2 figs., 2 tabs.

  3. Segregated tandem filter for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    SciTech Connect

    Brown, E.J.; Baldasaro, P.F.; Dziendziel, R.J.

    1996-12-31

    A filter system to transmit short wavelength radiation and reflect long wavelength radiation for a thermophotovoltaic energy conversion cell comprises an optically transparent substrate segregation layer with at least one coherent wavelength in optical thickness; a dielectric interference filter deposited on one side of the substrate segregation layer, the interference filter being disposed toward the source of radiation, the interference filter including a plurality of alternating layers of high and low optical index materials adapted to change from transmitting to reflecting at a nominal wavelength {lambda}{sub IF} approximately equal to the bandgap wavelength {lambda}{sub g} of the thermophotovoltaic cell, the interference filter being adapted to transmit incident radiation from about 0.5{lambda}{sub IF} to {lambda}{sub IF} and reflect from {lambda}{sub IF} to about 2{lambda}{sub IF}; and a high mobility plasma filter deposited on the opposite side of the substrate segregation layer, the plasma filter being adapted to start to become reflecting at a wavelength of about 1.5{lambda}{sub IF}.

  4. Segregated tandem filter for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    DOEpatents

    Brown, Edward J.; Baldasaro, Paul F.; Dziendziel, Randolph J.

    1997-01-01

    A filter system to transmit short wavelength radiation and reflect long wavelength radiation for a thermophotovoltaic energy conversion cell comprises an optically transparent substrate segregation layer with at least one coherent wavelength in optical thickness; a dielectric interference filter deposited on one side of the substrate segregation layer, the interference filter being disposed toward the source of radiation, the interference filter including a plurality of alternating layers of high and low optical index materials adapted to change from transmitting to reflecting at a nominal wavelength .lambda..sub.IF approximately equal to the bandgap wavelength .lambda..sub.g of the thermophotovoltaic cell, the interference filter being adapted to transmit incident radiation from about 0.5.lambda..sub.IF to .lambda..sub.IF and reflect from .lambda..sub.IF to about 2.lambda..sub.IF ; and a high mobility plasma filter deposited on the opposite side of the substrate segregation layer, the plasma filter being adapted to start to become reflecting at a wavelength of about 1.5.lambda..sub.IF.

  5. Segregated tandem filter for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    DOEpatents

    Brown, E.J.; Baldasaro, P.F.; Dziendziel, R.J.

    1997-12-23

    A filter system to transmit short wavelength radiation and reflect long wavelength radiation for a thermophotovoltaic energy conversion cell comprises an optically transparent substrate segregation layer with at least one coherent wavelength in optical thickness; a dielectric interference filter deposited on one side of the substrate segregation layer, the interference filter being disposed toward the source of radiation, the interference filter including a plurality of alternating layers of high and low optical index materials adapted to change from transmitting to reflecting at a nominal wavelength {lambda}{sub IF} approximately equal to the bandgap wavelength {lambda}{sub g} of the thermophotovoltaic cell, the interference filter being adapted to transmit incident radiation from about 0.5{lambda}{sub IF} to {lambda}{sub IF} and reflect from {lambda}{sub IF} to about 2{lambda}{sub IF}; and a high mobility plasma filter deposited on the opposite side of the substrate segregation layer, the plasma filter being adapted to start to become reflecting at a wavelength of about 1.5{lambda}{sub IF}. 10 figs.

  6. A new family of Gaussian filters with adaptive lobe location and smoothing strength for efficient image restoration

    NASA Astrophysics Data System (ADS)

    Seddik, Hassene

    2014-12-01

    Noise can occur during image capture, transmission, or processing phases. Image de-noising is a very important step in image processing, and many approaches are developed in order to achieve this goal such as the Gaussian filter which is efficient in noise removal. Its smoothing efficiency depends on the value of its standard deviation. The mask representing the filter presents generally static weights with invariant lobe. In this paper, an adaptive de-noising approach is proposed. The proposed approach uses a Gaussian kernel with variable width and direction called adaptive Gaussian kernel (AGK). In each processed window of the image, the smoothing strength changes according to the image content, noise kind, and intensity. In addition, the location of its lobe changes in eight different directions over the processed window. This directional variability avoids averaging details by the highest mask weights in order to preserve the edges and the borders. The recovered data is de-noised efficiently without introducing blur or losing details. A comparative study with the static Gaussian filter and other recent techniques is presented to prove the efficiency of the proposed approach.

  7. Aerosol mixing-state, hygroscopic growth and cloud activation efficiency during MIRAGE 2006

    NASA Astrophysics Data System (ADS)

    Lance, S.; Raatikainen, T.; Onasch, T.; Worsnop, D. R.; Yu, X.-Y.; Alexander, M. L.; Stolzenburg, M. R.; McMurry, P. H.; Smith, J. N.; Nenes, A.

    2012-06-01

    Observations of aerosol hygroscopic growth and CCN activation spectra for submicron particles are reported for the T1 ground site outside of Mexico City during the MIRAGE 2006 campaign. κ-Köhler theory is used to evaluate the characteristic water uptake coefficient, κ*, for the CCN active aerosol population using both size-resolved HTDMA and size-resolved CCNc measurements. Organic mass fractions, forg, are evaluated from size-resolved aerosol mass spectrometer (AMS) measurements, from which κAMS is inferred and compared against κ*. Strong diurnal profiles of aerosol water uptake parameters and aerosol composition are observed. We find that new particle formation (NPF) events are correlated with an increased κ* and CCN-active fraction during the daytime, with greater impact on smaller particles. During NPF events, the number concentration of 40 nm particles acting as CCN can surpass by more than a factor of two the concentrations of 100 nm particles acting as CCN, at supersaturations of 0.51% ± 0.06%. We also find that at 06:00-08:00 in the morning throughout the campaign, fresh traffic emissions result in substantial changes to the chemical distribution of the aerosol, with on average 65% externally-mixed fraction for 40 nm particles and 30% externally-mixed fraction for 100 nm particles, whereas at midday nearly all particles of both sizes can be described as internally-mixed. Average activation spectra and growth factor distributions are analyzed for different time periods characterizing the daytime (with and without NPF events), the early morning "rush hour", and the entire campaign. We show that κ* derived from CCNc measurements decreases as a function of size during all time periods, while the CCN-active fraction increases as a function of size. Size-resolved AMS measurements do not predict the observed trend for κ* versus particle size, which can be attributed to unresolved mixing-state and the presence of refractory material not measured by the AMS

  8. Aerosol mixingstate, hygroscopic growth and cloud activation efficiency during MIRAGE 2006

    SciTech Connect

    Lance, Sara; Raatikainen, T.; Onasch, Timothy B.; Worsnop, Douglas R.; Yu, Xiao-Ying; Alexander, M. L.; Stolzenberg, Mark; McMurry, Peter; Smith, James N.; Nenes, Athanasios

    2013-05-15

    Observations of aerosol hygroscopic growth and CCN activation spectra for submicron particles are reported for the T1 ground site outside of Mexico City during the MIRAGE 2006 campaign. K¨ohler theory is used to evaluate the characteristic water uptake coefficient, k*, for the CCN active aerosol population using both size-resolved HTMDA and size-resolved CCNc measurements. Organic mass fractions, (forg), are evaluated from size-resolved aerosol mass spectrometer (AMS) measurements, from which kAMS is inferred and compared against k*. Strong diurnal profiles of aerosol water uptake parameters and aerosol composition are observed. We find that new particle formation (NPF) events are correlated with an increased k* and CCN-active fraction during the daytime, with greater impact on smaller particles. During NPF events, the number concentration of 40 nm particles acting as CCN can surpass by more than a factor of two the concentrations of 100 nm particles acting as CCN, at supersaturations of 0.51% +/- 0.06%. We also find that at 0600-0800 in the morning throughout the campaign, fresh traffic emissions result in substantial changes to the chemical distribution of the aerosol, with on average 65% externally-mixed fraction for 40 nm particles and 30% externally-mixed fraction for 100 nm particles, whereas at midday nearly all particles of both sizes can be described as “internally-mixed”. Average activation spectra and growth factor distributions are analyzed for different time periods characterizing the daytime (with and without NPF events), the early morning “rush hour”, and the entire campaign. We show that k* derived from CCNc measurements decreases as a function of size during all time periods, while the CCN-active fraction increases as a function of size. Size-resolved AMS measurements do not predict the observed trend for k* versus particle size, which can be attributed to unresolved mixing-state and the presence of refractory material not measured by the

  9. Extraction of semivolatile organic compounds from high-efficiency particulate air (HEPA) filters by supercritical carbon dioxide

    SciTech Connect

    Schilling, J.B.

    1997-09-01

    Supercritical fluid extraction (SFE) using unmodified carbon dioxide has been explored as an alternative method for the extraction of semivolatile organic compounds from high-efficiency particulate air (HEPA) filters. HEPA filters provide the final stage of containment on many exhaust systems in US Department of Energy (DOE) facilities by preventing the escape of chemical and radioactive materials entrained in the exhausted air. The efficiency of the filters is tested by the manufacturer and DOE using dioctylphthalate (DOP), a substance regulated by the US Environmental Protection Agency under the Resource Conservation and Recovery Act. Therefore, the filters must be analyzed for semivolatile organics before disposal. Ninety-eight acid, base, and neutral semivolatile organics were spiked onto blank HEPA material and extracted using SFE, Soxhlet, automated Soxhlet, and sonication techniques. The SFE conditions were optimized using a Dionex SFE-703 instrument. Average recoveries for the 98 semivolatile compounds are 82.7% for Soxhlet, 74.0% for sonication, 70.2% for SFE, and 62.9% for Soxtec. Supercritical fluid extraction reduces the extraction solvent volume to 10--15 mL, a factor of 20--30 less than Soxhlet and more than 5 times less than Soxtec and sonication. Extraction times of 30--45 min are used compared to 16--18 h for Soxhlet extraction.

  10. Response of HEPA filters to simulated-accident conditions

    SciTech Connect

    Gregory, W.S.; Martin, R.A.; Smith, P.R.; Fenton, D.E.

    1982-01-01

    High-efficiency particulate air (HEPA) filters have been subjected to simulated accident conditions to determine their response to abnormal operating events. Both domestic and European standard and high-capacity filters have been evaluated to determine their response to simulated fire, explosion, and tornado conditions. The HEPA filter structural limitations for tornado and explosive loadings are discussed. In addition, filtration efficiencies during these accident conditions are reported for the first time. Our data indicate efficiencies between 80% and 90% for shock loadings below the structural limit level. We describe two types of testing for ineffective filtration - clean filters exposed to pulse-entrained aerosol and dirty filters exposed to tornado and shock pulses. Efficiency and material loss data are described. Also, the resonse of standard HEPA filters to simulated fire conditions is presented. We describe a unique method of measuring accumulated combustion products on the filter. Additionally, data relating to pressure drop vs accumulated mass during plugging are reported for simulated combustion aerosols. The effects of concentration and moisture levels on filter plugging were evaluated. We are obtaining all of the above data so that mathematical models can be developed for fire, explosion, and tornado accident analysis computer codes. These computer codes can be used to assess the response of nuclear air cleaning systems to accident conditions.