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At least 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Glass Frit Filters for Collecting Metal Oxide Nanoparticles

Filter disks made of glass frit have been found to be effective as means of high-throughput collection of metal oxide particles, ranging in size from a few to a few hundred nanometers, produced in gas-phase condensation reactors. In a typical application, a filter is placed downstream of the reactor and a valve is used to regulate the flow of reactor exhaust through the filter. The exhaust stream includes a carrier gas, particles, byproducts, and unreacted particle-precursor gas. The filter selectively traps the particles while allowing the carrier gas, the byproducts, and, in some cases, the unreacted precursor, to flow through unaffected. Although the pores in the filters are much larger than the particles, the particles are nevertheless trapped to a high degree: Anecdotal information from an experiment indicates that 6-nm-diameter particles of MnO2 were trapped with greater than 99-percent effectiveness by a filtering device comprising a glass-frit disk having pores 70 to 100 micrometer wide immobilized in an 8-cm-diameter glass tube equipped with a simple twist valve at its downstream end.

Ackerman, John↗
NASA NTRS2003

Compact, Pneumatically Actuated Filter Shuttle

A compact, pneumatically actuated filter shuttle has been invented to enable alternating imaging of a wind-tunnel model in two different spectral bands characteristic of the pressure and temperature responses of a pressure and temperature-sensitive paint. This filter shuttle could also be used in other settings in which there are requirements for alternating imaging in two spectral bands. Pneumatic actuation was chosen because of a need to exert control remotely (that is, from outside the wind tunnel) and because the power leads that would be needed for electrical actuation would pose an unacceptable hazard in the wind tunnel. The entire shuttle mechanism and its housing can be built relatively inexpensively [<$500 (prices as of year 2000)] from off-the-shelf parts. The shuttle mechanism (see Figure 1) is contained in a housing that has dimensions of 4 by 6 by 2 in. (about 10 by 15 by 5 cm). Two 2-in. (=5-cm)-diameter standard scientific-grade band-pass filters are mounted on sliding panels in a dual-track frame. The mechanism is positioned and oriented so the panels slide sideways with respect to the optical axis of a charge-coupled-device camera used for viewing the wind-tunnel model. The mechanism includes a pneumatic actuator connected to a linkage. The linkage converts the actuator stroke to a scissor-like motion that places one filter in front of the camera and the other filter out of the way. Optoelectronic sensors detect tabs on the sliding panels for verification of the proper positioning of the filters.

Leighy, Bradley D.↗
NASA NTRS2012

Recursive Implementations of the Consider Filter

One method to account for parameters errors in the Kalman filter is to consider their effect in the so-called Schmidt-Kalman filter. This work addresses issues that arise when implementing a consider Kalman filter as a real-time, recursive algorithm. A favorite implementation of the Kalman filter as an onboard navigation subsystem is the UDU formulation. A new way to implement a UDU consider filter is proposed. The non-optimality of the recursive consider filter is also analyzed, and a modified algorithm is proposed to overcome this limitation.

Zanetti, Renato↗
NASA NTRS2012

Blocking Filters with Enhanced Throughput for X-Ray Microcalorimetry

New and improved blocking filters (see figure) have been developed for microcalorimeters on several mission payloads, made of high-transmission polyimide support mesh, that can replace the nickel mesh used in previous blocking filter flight designs. To realize the resolution and signal sensitivity of today s x-ray microcalorimeters, significant improvements in the blocking filter stack are needed. Using high-transmission polyimide support mesh, it is possible to improve overall throughput on a typical microcalorimeter such as Suzaku s X-ray Spectrometer by 11%, compared to previous flight designs. Using polyimide to replace standard metal mesh means the mesh will be transparent to energies 3 keV and higher. Incorporating polyimide s advantageous strength-to-weight ratio, thermal stability, and transmission characteristics permits thinner filter materials, significantly enhancing through - put. A prototype contamination blocking filter for ASTRO-H has passed QT-level acoustic testing. Resistive traces can also be incorporated to provide decontamination capability to actively restore filter performance in orbit.

Grove, David↗
NASA NTRS2013

Mass Conservation and Positivity Preservation with Ensemble-type Kalman Filter Algorithms

Maintaining conservative physical laws numerically has long been recognized as being important in the development of numerical weather prediction (NWP) models. In the broader context of data assimilation, concerted efforts to maintain conservation laws numerically and to understand the significance of doing so have begun only recently. In order to enforce physically based conservation laws of total mass and positivity in the ensemble Kalman filter, we incorporate constraints to ensure that the filter ensemble members and the ensemble mean conserve mass and remain nonnegative through measurement updates. We show that the analysis steps of ensemble transform Kalman filter (ETKF) algorithm and ensemble Kalman filter algorithm (EnKF) can conserve the mass integral, but do not preserve positivity. Further, if localization is applied or if negative values are simply set to zero, then the total mass is not conserved either. In order to ensure mass conservation, a projection matrix that corrects for localization effects is constructed. In order to maintain both mass conservation and positivity preservation through the analysis step, we construct a data assimilation algorithms based on quadratic programming and ensemble Kalman filtering. Mass and positivity are both preserved by formulating the filter update as a set of quadratic programming problems that incorporate constraints. Some simple numerical experiments indicate that this approach can have a significant positive impact on the posterior ensemble distribution, giving results that are more physically plausible both for individual ensemble members and for the ensemble mean. The results show clear improvements in both analyses and forecasts, particularly in the presence of localized features. Behavior of the algorithm is also tested in presence of model error.

EnKR↗
NASA NTRS2009

Optimization of OT-MACH Filter Generation for Target Recognition

An automatic Optimum Trade-off Maximum Average Correlation Height (OT-MACH) filter generator for use in a gray-scale optical correlator (GOC) has been developed for improved target detection at JPL. While the OT-MACH filter has been shown to be an optimal filter for target detection, actually solving for the optimum is too computationally intensive for multiple targets. Instead, an adaptive step gradient descent method was tested to iteratively optimize the three OT-MACH parameters, alpha, beta, and gamma. The feedback for the gradient descent method was a composite of the performance measures, correlation peak height and peak to side lobe ratio. The automated method generated and tested multiple filters in order to approach the optimal filter quicker and more reliably than the current manual method. Initial usage and testing has shown preliminary success at finding an approximation of the optimal filter, in terms of alpha, beta, gamma values. This corresponded to a substantial improvement in detection performance where the true positive rate increased for the same average false positives per image.

false alarm reduction↗
NASA NTRS2015

Concentric Split Flow Filter

A concentric split flow filter may be configured to remove odor and/or bacteria from pumped air used to collect urine and fecal waste products. For instance, filter may be designed to effectively fill the volume that was previously considered wasted surrounding the transport tube of a waste management system. The concentric split flow filter may be configured to split the air flow, with substantially half of the air flow to be treated traveling through a first bed of filter media and substantially the other half of the air flow to be treated traveling through the second bed of filter media. This split flow design reduces the air velocity by 50%. In this way, the pressure drop of filter may be reduced by as much as a factor of 4 as compare to the conventional design.

Stapleton, Thomas J.↗
NASA NTRS2011

Sequential Probability Ratio Test for Collision Avoidance Maneuver Decisions Based on a Bank of Norm-Inequality-Constrained Epoch-State Filters

Sequential probability ratio tests explicitly allow decision makers to incorporate false alarm and missed detection risks, and are potentially less sensitive to modeling errors than a procedure that relies solely on a probability of collision threshold. Recent work on constrained Kalman filtering has suggested an approach to formulating such a test for collision avoidance maneuver decisions: a filter bank with two norm-inequality-constrained epoch-state extended Kalman filters. One filter models 1he null hypothesis 1ha1 the miss distance is inside the combined hard body radius at the predicted time of closest approach, and one filter models the alternative hypothesis. The epoch-state filter developed for this method explicitly accounts for any process noise present in the system. The method appears to work well using a realistic example based on an upcoming highly-elliptical orbit formation flying mission.

Carpenter, J. R.↗
NASA NTRS2018

Design, Implementation, and Performance of the Astro-H Soft X-Ray Spectrometer Aperture Assembly and Blocking Filters

The calorimeter array of the JAXA Astro-H (renamed Hitomi) soft x-ray spectrometer (SXS) was designed to provide unprecedented spectral resolution of spatially extended cosmic x-ray sources and of all cosmic x-ray sources in the Fe-K band around 6 keV. The properties that made the SXS array a powerful x-ray spectrometer also made it sensitive to photons from the entire electromagnetic band as well as particles. If characterized as a bolometer, it would have had a noise equivalent power of <4 × 10(exp −18) W/((Hz)(exp 0.5)). Thus, it was imperative to shield the detector from thermal radiation from the instrument and optical and UV photons from the sky. In addition, it was necessary to shield the coldest stages of the instrument from the thermal radiation emanating from the warmer stages. These needs were addressed by a series of five thin-film radiation-blocking filters, anchored to the nested temperature stages, that blocked long-wavelength radiation while minimizing x-ray attenuation. The aperture assembly was a system of barriers, baffles, filter carriers, and filter mounts that supported the filters and inhibited their potential contamination. The three outer filters also had been equipped with thermometers and heaters for decontamination. We present the requirements, design, implementation, and performance of the SXS aperture assembly and blocking filters.

Kilbourne, Caroline A.↗
NASA NTRS2019

Design of Optical/IR Blocking Filters for the Lynx X-Ray Microcalorimeter

The Lynx mission concept, under development ahead of the 2020 Astrophysics Decadal Review, includes the Lynx X-ray Microcalorimeter (LXM) as one of its primary instruments. The LXM uses a microcalorimeter array at the focus of a high-throughput soft x-ray telescope to enable high-resolution nondispersive spectroscopy in the soft x-ray waveband (0.2 to 15 keV) with exquisite angular resolution. Similar to other x-ray microcalorimeters, the LXM uses a set of blocking filters mounted within the dewar that pass the photons of interest (x-rays) while attenuating the out-of-band long-wavelength radiation. Such filters have been successfully used on previous orbital and suborbital instruments; however, the Lynx science objectives, which emphasize observations in the soft x-ray band (<1keV), pose more challenging requirements on the set of LXM blocking filters. We present an introduction to the design of the LXM optical/IR blocking filters and discuss recent advances in filter capability targeted at LXM. In addition, we briefly describe the external filters and the modulated x-ray sources to be used for onboard detector calibration.

Eckart, Megan E.↗
NASA NTRS2019

Fabrication of Phononic Filter Structures for Far-IR/sub-mm Detector Applications

A photon noise limited sub-mm/far-IR cold telescope in space will require detectors with noise equivalent power (NEP) less than 1x10-19W/Hz1/2for imaging applications and at least an order of magnitude lower for spectroscopic studies. The detector NEP can be reduced by lowering the operation temperature and improving the thermal isolation between the bolometer and a heat bath. We report on the fabrication of membrane isolated transition edge sensor bolometers incorporating compact (<50 μm) thermal isolation beams based on phononic filters. Phononic filters are created by etching quasi-periodic nanoscale structures into supporting thermo-mechanical beams. The cross-sectional dimensions of the etched features are less than the thermal wavelength at the operating temperature, enabling coherent phonon transport to take place in one dimension. The phonon stop-band can be tuned by adjusting the scale of the quasi-periodic structures. Cascading multiple filter stages can increase bandwidth and provide improved thermal isolation similar to the function of a multi-stage electrical filter. We describe the fabrication of AlMn based transition edge sensor bolometers on silicon and silicon nitride membranes isolated by one-and two-dimensional phononic filters. The phononic filters are patterned through electron beam lithography and isolated with deep reactive ion etching.

Phononic↗
NASA NTRSDate not supplied

Sequential Filtering in the Presence of Uniform Measurement Errors

This paper presents a sequential filtering strategy using observations corrupted with uniform measurement noise. While the Kalman filter remains the best linear estimator of the state, other filtering techniques provide minimum variance optimal estimates, a trait only enjoyed by the Kalman filter when the underlying noises are, in fact, Gaussian. This work develops a new approximate optimal estimator for uniform measurement noises. The resulting recursion requires just slightly more computational time to complete a measurement update than the Kalman filter, which generally cannot be claimed by other optimal strategies such as the particle or Gaussian mixture filters.

James S. McCabe↗
NASA NTRSDate not supplied

Sequential Filtering in the Presence of Uniform Measurement Errors

This paper presents a sequential filtering strategy using observations corrupted with uniform measurement noise. While the Kalman filter remains the best linear estimator of the state, other filtering techniques provide minimum variance optimal estimates, a trait only enjoyed by the Kalman filter when the underlying noises are, in fact, Gaussian. This work develops a new approximate optimal estimator for uniform measurement noises. The resulting recursion requires just slightly more computational time to complete a measurement update than the Kalman filter, which generally cannot be claimed by other optimal strategies such as the particle or Gaussian mixture filters.

James S McCabe↗
DOE OSTI2019

Variable bandwidth filter

A variable bandwidth filter is described herein, wherein a bandwidth of a passband of the variable bandwidth filter is dynamically tunable. The variable bandwidth tuner is implemented on a CMOS chip, and acts to filter analog signals. The variable bandwidth filter comprises a plurality of finite impulse response (FIR) filters, wherein each FIR filter comprises a plurality of tunable transconductors. The tunable transconductors are tunable in their gain.

Rodenbeck, Christopher T.↗
DOE OSTI2023

Method for concentrating solids and removing solids from a filter medium

Disclosed are methods for concentrating solids and removing solids from a filter medium. The method includes the step of concentrating first particles of a first solid by removing a fluid stream through a filter medium in a filter. At least some of the first particles become blocking particles that block pores of the filter medium. The method also includes the step of inserting second particles of a second solid into the filter. These second particles scrape, vibrate, agglomerate, or a combination thereof along the filter medium, thus dislodging at least a portion of the blocking particles.

Frankman, David↗
DOE OSTI2017

Hydrophobic Filter Material for Nuclear Material Transportation and Storage Containers - 17518

Los Alamos National Laboratory has begun development of hydrophobic or super-hydrophobic inorganic filter materials that resist water ingress after exposure to radiation and/or elevated temperature. Filters that are currently available depend on carbon composites and/or organic polymers for their water resistant/hydrophobic properties to minimize water ingress. However, facility and transportation accident scenarios often include fire, impact and subsequent water spray or flooding conditions. A purely inorganic hydrophobic filter material could have enhanced resistance to fire and radiation damage, and continue to minimize water ingress after such an accident. Such filters could broaden the use of filtered containers in the transportation and storage of nuclear materials, and could have broader implications in other industrial applications. The goal is to create a porous inorganic material with hydrophobic properties that maintains or exceeds the current performance criteria for particulate filtration efficiency, pressure differential, air flow and hydrogen diffusion. The materials developed in this project show promise in evaluations for use as enhancements to the SAVY 4000 nuclear storage container that is becoming widely used around the DOE complex. Preliminary results indicate that the treated filters provide resistance to a water column pressure test and have filtration efficiencies and air flow pressure drops that meet the current performance criteria. There are various treatment options being tested to help determine the best path forward. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Development of High Strength HEPA Filters for Use in Demanding Air and Gas Streams - 17644

High-efficiency particulate air (HEPA) filters are used in a wide variety of applications, including the removal of radioactive particulate from process off-gas streams and the venting of waste storage containers. Porvair Filtration Group, specializing in the design and manufacture of robust filters in numerous industries, has worked to develop HEPA filter designs for use in such high-demand nuclear process-gas and air streams. Using the requirements of section FK of the American Society of Mechanical Engineers AG-1 Code on Nuclear Air and Gas Treatment (ASME AG-1) as a guide, Porvair Filtration Group has designed filters which can withstand upset conditions to include elevated temperatures, high relative humidity, high particle-loading, and an unconventionally high differential pressure across the filter media; while maintaining excellent removal efficiencies. The process by which Porvair Filtration Group has reached optimized designs was based upon an extended test and development program. Design, manufacture, and testing of flat sheet media samples, geometrically equivalent model filters, and full-scale prototypes was performed at several Porvair Filtration Group facilities located in the United States and the United Kingdom. The methods and results of this development program are outlined in the following paper. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Nanomaterial-Treated Filters for the Uptake of Heavy Metals from Water Sources

We describe the synthesis and properties of ligand-modified gold nanoparticles (AuNPs) grown on stainless steel wool filters. Their selectivity and efficiency with regards to heavy metal uptake from groundwater and other sources of drinking water found at or near DOE facilities were also investigated. The nanomaterial-treated filters are advantageous because they serve as inactive supports that allow for efficient flow of the contaminated water, and can be easily replaced after heavy metal uptake. They are also comparable to nanomaterials free in solution with regards to the effectiveness of remediation of drinking water. Environmental stewardship is at the forefront of core competencies at SRNS. This includes treatment and remediation of contaminated groundwater. Among contaminants present in water resources, hazardous heavy metals and radioactive contaminants are the main concerns in the DOE complex. With the advent of nanotechnology, new remediation technologies have emerged. AuNPs have unique optical properties and enormous surface areas, making them good candidates for water remediation. They can be functionalized with ligands, e.g. citrate and L-cysteine, allowing them to serve as an excellent platform for environmental stewardship applications. Objectives: 1. Nanomaterial development and characterization Ligand-modified AuNPs: (a) in solution and (b) on stainless steel wool filters 2. Nanomaterial evaluation for efficiency and selectivity of heavy metal uptake, including Cu{sup 2+} and Zn{sup 2+}. Materials and Methods: Chloroauric acid (HAuCl{sub 4}), sodium citrate (reducing and capping agent); Stainless steel wool (SSW) was used as a support and filter; L-cysteine- ligand for surface functionalization; Zinc acetate and copper nitrate: heavy metal ions contaminants. Au NPs were prepared by wet chemistry methods. They were characterized by UV-Vis, Zeta sizer and potential, SEM, EDS and EDS mapping to understand their physico-chemical properties. Results and Discussions: Surface modification of AuNPs with surfactants changes their optical properties. Citrate capped AuNPs demonstrate high loading capacity for both heavy metals. L-cysteine capped AuNPs demonstrate high loading capacity for Zn{sup 2+}. Citrate capped AuNPs have excellent sensitivity towards heavy metal ions (0.05 mM can be detected). L-cysteine capped AuNPs can detect heavy metal ions at low concentrations, making them useful for sensing. Conclusions: AuNPs in solution and on SSW were successfully synthesized and characterized. Two functional sensing and remediation technologies - colorimetric sensor and AuNP-treated filters - were developed through wet chemistry methods. AuNP SSW filters exhibit different characteristics (size, shape, etc.) than AuNPs in solution and are efficient at the uptake of heavy metal ions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗