Open Filter Research Articles

Heavy-duty, off-road diesel engine low-load particle number emissions and particle control

Exhaust gas particle and ion size distributions were measured from an off-road diesel engine complying with the European Stage IIIB emission standard. The measurements were performed at idling and low load conditions on an engine dynamometer. Nucleation-mode particles dominated the diesel exhaust particle number emissions at idle load. The nonvolatile nucleation-mode geometric mean diameter was detected at 10 nm or below. The nonvolatile nucleation-mode charge state implied that it has evolved through a highly ionizing environment before emission from the engine. The determined charging probabilities were 10.0 ± 2.2% for negative and 8.0 ± 2.0% for positive polarity particles. The nonvolatile nucleation particle concentration and size was also shown to be dependent on the lubricant oil composition. The particle emissions were efficiently controlled with a partial filter or with partial filter + selective catalytic reduction (SCR) combination. The particle number removal efficiencies of the aftertreatment systems were over 95% for wet total particle number (>3nm) and over 85% for dry particle total number. Nevertheless, the aftertreatment systems’ efficiencies were around 50% for the soot-mode particles. The low-load nonvolatile nucleation particle emissions were also dependent on the engine load, speed, and fuel injection pressure. The low load particle number emissions followed the soot-core trade-off, similar to medium or high operating loads.Implications:Idling and low-load diesel engine exhaust emissions affect harmfully the ambient air quality. The low-load particle number emissions are here shown to peak in the 10-nm size range for a modern off-road engine. The particles are electrically charged and nonvolatile and they originate from the combustion process. Tailpipe particle control by open channel filter can remove more than 85% of the nonvolatile 10-nm particles and about 50% of the soot-mode particles, while the fuel injection pressure increase can lead to particle number increase. The study provides a new viewpoint for low-load particle emissions and control.

Mathematical morphology pre-processing for enhanced segmentation of heterogeneous spatial regions

The very high spatial resolution of Pleiades images allows for the detection of small spatial objects such as buildings or isolated trees. However, the delineation of spatial regions, defined as associations between different spatial objects (such as open canopy forests or urban areas), becomes more challenging with the high level of details. On one hand, automated image segmentation algorithms often yield over-segmented polygons due to due to the high spectral heterogeneity of those regions. On the other hand, manual delineation was shown to end up with a significant bias from the interpreter and even a lack of consistency when the same person works more than one hour on the same task. In this study, we aimed at implementing a new filter to increase the contextual consistency of automated segmentation while preserving the geometric precision of the delineation of spectrally homogeneous spatial regions. A new mathematical morphology approach is proposed, which consists in applying a set of rules to an image based on the presence of absence of vegetation pixels within a structuring element. Two composite filters were then built based on the new filters. The opening filter removes isolated vegetation patches inside heterogeneous spatial regions, while the closing filter fills the gaps between those vegetation patches. The filters have been tested on a Pleiades images located in Belgium around the city of Leuven. A composite image was then created with the NIR and Red filtered bands stacked with the original image bands. The composite and the original bands were then segmented using e-Cognition software with the same parameters. The results show that the segmentation of the filtered images is spatially more consistent than the segmentation based on the unfiltered image. The over-segmentation is reduced in the heterogeneous areas, while the precision of the delineation is improved. The objects derived from the filtered images are thus more appropriate for the monitoring of spatial regions.

Quasi-subtractive varieties: Open filters, congruences and the commutator

Quasi-subtractive varieties are a generalization of subtractive varieties, introduced to account for some correspondence theorems between ideals and congruences in the literature that are not corollaries of general theorems in the theory of subtractive varieties. The main tool for the investigation of quasi-subtractive varieties is the concept of open filter, that extends the notion of ideal due to Gumm and Ursini. In this paper, we explore further the fundamental properties of open filters and congruences in this context; moreover, we introduce and investigate a notion of commutator of open filters.

Measurement of nitrogen dioxide diffusive sampling rates for Palmes diffusion tubes using a controlled atmosphere test facility (CATFAC)

We report measurements of the 28 day NO2 diffusive sampling rates for seven designs of Palmes diffusion tubes (PDTs), which were exposed in a controlled atmosphere test facility (CATFAC) containing traceable concentrations of nitrogen dioxide, nitric oxide and water vapour under defined conditions of temperature (20 °C) and wind speed. One of the aims of the work was to implement low cost modifications to the conventional open tube PDT design, using either meshes or filters. This would potentially reduce some of the undesirable bias effects due to wind, which may lead to an over estimation of the NO2 concentration. Exposure tests in the CATFAC were carried out over a wide concentration range applicable to ambient monitoring, and also over a range of wind speeds at a constant concentration. For a given PDT design, the measured NO2 diffusive sampling rates were found to be effectively constant over the conditions tested. These rates were then applied to NO2 field measurements carried out at a monitoring station in central London, and three of the modified PDT designs were found to deliver improved repeatability and consequently reduced measurement uncertainty over the conventional open tubes.

Strength of fine grained carbon-bonded alumina (Al2O3–C) materials obtained by means of the small punch test

Ceramic open cell foam filters are utilized for the reduction of non-metallic inclusions during casting of steel components. Fine grained carbon-bonded alumina (Al2O3–C) is used for the production of these porous filters. A new generation of Al2O3–C materials has been developed. The material has to withstand high mechanical loads during casting. Mechanical testing has to be applied to the material in order to ensure mechanical integrity of the filter structure. Standard sized specimens for the evaluation of the cold modulus of rupture (CMOR) are fabricated by uniaxial and isostatic pressing. The amount of binder (Cabores®P) is varied from 10 to 20wt% in this study.The differences in the mechanical behavior between the various material compositions as well as differences between the different production routes are investigated by means of the small punch test.

Extraction of Boundaries of Rooftop Fenced Buildings From Airborne Laser Scanning Data Using Rectangle Models

We propose a building boundary modeling method using rectangles to overcome the zigzag boundary shapes of rooftop fenced buildings that are inherent in light detection and ranging (LiDAR) data. The method first finds 3-D patches through building detection using a morphological opening filter and histogram mode analysis. Then, rectangles that encase the traced boundaries of the 3-D patches are adjusted adaptively based on traced boundary coordinates and perpendicular constraints among the sides of the rectangles. The boundary of each 3-D patch is remodeled by subtracting void region rectangles from the parent rectangle. The superstructures of rooftops are also modeled with perpendicularity and adaptive constraints.

Groundwater treatment as a source of indoor radon

New Viimsi Parish water treatment plant (Northern Estonia) was investigated in order to determine whether the open filter columns serve as a source of 222Rn generation in the treatment process and whether they influence indoor air 222Rn activity concentrations. 222Rn measurements of indoor 222Rn were performed at different locations of the treatment plant; water samples from incoming raw water, from all the purification stages, consumers water and solid filter material from two filtration stages were analyzed.

Probing “ambivalent” snug-fit sites in the KcsA potassium channel using three-dimensional reference interaction site model (3D-RISM) theory

Abstract The potassium channel is highly selective for K+ over Na+, and the mechanism underlying this selectivity remains unclear. We show the three-dimensional distribution functions (3D-DFs) of small cations (Li+, Na+, and K+) and the free energy profile of ions inside the open selectivity filter (SF) of the KcsA channel. Our previous results [S. Phongphanphanee, N. Yoshida, S. Oiki, F. Hirata. Abstract Book of 5th International Symposium on Molecular Science of Fluctuations toward Biological Functions, P062 (2012)] indicate that the 3D-DF for K+ exhibits distinct peaks at the sites formed by the eight carbonyl oxygen atoms belonging to the surrounding peptide-backbone and residues (the cage site). Li+ has sharp distributions in the 3D-DF at the center of a quadruplex composed of four carbonyl oxygen atoms (the plane site). Na+ has a rather diffuse distribution throughout the SF region with peaks both in the plane and in cage sites. The results provide microscopic evidence of the phenomenological findings that Li+ and Na+ are not excluded from the SF region and that the binding affinity alone does not cause the ion selectivity of KcsA. In the present study, with an ion placed explicitly along the pore axis, the free energy profiles of the ions inside the SF were calculated; from these profiles we suggest a new mechanism for selective K+ permeation. According to the model, a K+ ion must overcome a free energy barrier that is approximately half that of Na+ to exit from either of the SF mouths due to the existence of an intermediate local minimum along the route for climbing the barriers.

Influence of the Microstructure on the Fracture Behavior of Carbon Bonded Alumina

Carbon bonded alumina (Al2O3-C) in various compositions are developed for the production of open cell filters, which are used for melt metal filtration processes [. The Small Punch Test (SPT) is used to determine the mechanical properties of such materials. Previous investigations showed two different types of fracture behavior [2,, which can be distinguished by typical features of the load deflection curves of the SPT. This paper clarifies this behavior by examining the fracture surfaces using scanning electron microscopy (SEM).

Performance Evaluation and Comparison of Network Firewalls under DDoS Attack

Network firewalls act as the first line of defense against unwanted and malicious traffic and also represent critical point of failure during DDoS attack. Predicting the overall firewall performance is crucial to network security administrators and designers in assessing the strength and effectiveness of network firewalls against DDoS attacks. In this paper, authors have made a humble attempt to study and compare DDoS performance of various types of firewalls in operation as on today. Analysis and detailed comparison is performed on open source packet filter (PF) firewall, Checkpoint SPLAT and Cisco ASA in a testing environment with laboratory generated DDoS traffic. It is attempted to identify various firewall DDoS performance parameters which can be considered during DDoS attack. Further, experiments are carried out to study effect of varying TCP Opening Timers on performance of stateful inspection firewall during Sync Flood attack. Also, in order to improve performance, intelligence is applied in PF firewall rulebase to mitigate DDoS.

Automated Processing of LASCO Coronal Images: Spurious Point-Source-Filtering and Missing-Blocks Correction

We report on automated procedures for correcting the images of the LASCO coronagraph for i) spurious quasi-point-sources such as the impacts of cosmic rays, stars, and planets, and ii) the absence of signal due to transmission errors or dropouts, which results in blocks of missing information in the images. Correcting for these undesirable artifacts is mandatory for all quantitative works on the solar corona that require data inversion and/or long series of images, for instance. The nonlinear filtering of spike noise or point-like objects is based on mathematical morphology and implements the procedure opening by morphological reconstruction. However, a simple opening filter is applied whenever the fractional area of corrupted pixels exceeds 50 % of the original image. We describe different strategies for reconstructing the missing information blocks. In general, it is possible to implement the method of averaged neighbors using the two images obtained immediately before and after the corrupted image. For the other cases, and in particular when missing blocks overlapped in three images, we developed an original procedure of weighted interpolation along radial profiles from the center of the Sun that intercept the missing block(s). This procedure is also adequate for the saturated images of bright planets (such as Venus) that bleed along the neighboring pixels. Missing blocks in polarized images may generally be reconstructed using the associated unpolarized image of the same format. But in the case of overlapping missing blocks, we implemented our procedure of weighted interpolation. All tests performed on numerous LASCO-C2 images at various periods of solar activity (i.e. varying complexity of the structure of the corona) demonstrate the excellent performance of these new procedures, with results vastly superior to the methods implemented so far in the pipeline-processing of the LASCO images.

Automatic content filtering and publishing by email for the UP Open University Doctor of Communication Programme learning management system

The DComm website is an electronic learning environment using the Joomla Content Management Framework (CMF), designed specifically for the Doctor of Communication Programme offered by the University of the Philippines Open University (UPOU). Previously, when a faculty member or staff wanted to publish content on the website, content was first emailed to the web administrator, who uploaded it manually. While this method ensured that proper content was published on the site, publishing was delayed at times due to the unavailability of the web administrator. To enable DComm faculty members and staff to directly publish content without having to study web publishing or going through the web administrator, publishing content through email was enabled using Post-by-Email, an extension for Joomla that allows such functionality. The resulting website now allows authorised users to publish information in a particular section of the site by emailing content to a specific email address. However, without quality control over content that gets published, this practice raises the possibility of inappropriate content publishing. To address this issue, a strategy for content filtering and publishing that uses existing technologies such as email filters and SpamAssasin, an open source mail filter based on content matching rules, was designed and implemented. The result is a learning environment where faculty members and staff can automatically publish filtered content through email, making it immediately accessible to the students, ultimately providing for a more dynamic learning environment.

Study on ASP-Based Anti-Spam Management System

A perfect spam filter would avoid ham misclassification. This paper describes the development and application of spam filter. Specifically, the evaluation methodology was designed on-line open source spam filters. Finally, ASP-based anti-spam management system was created to combine the results of multiple filters. We finally find that the filters of ASP-based anti-spam system also make mistakes but can be used in conjunction with users to minimize errors.

The existence of free ultrafilters on ω does not imply the extension of filters on ω to ultrafilters

Let X be an infinite set and let and denote the propositions “every filter on X can be extended to an ultrafilter” and “X has a free ultrafilter”, respectively. We denote by the Stone space of the Boolean algebra of all subsets of X. We show: For every well‐ordered cardinal number ℵ, (ℵ) iff (2ℵ). iff “ is a continuous image of ” iff “ has a free open ultrafilter ” iff “every countably infinite subset of has a limit point”. implies “every open filter on extends to an open ultrafilter” implies “has an open ultrafilter” implies It is relatively consistent with that (ω) holds, whereas (ω) fails. In particular, none of the statements given in (2) implies (ω).

The microglial activation state regulates migration and roles of matrix-dissolving enzymes for invasion

BackgroundMicroglial cells are highly mobile under many circumstances and, after central nervous system (CNS) damage, they must contend with the dense extracellular matrix (ECM) in order to reach their target sites. In response to damage or disease, microglia undergo complex activation processes that can be modulated by environmental cues and culminate in either detrimental or beneficial outcomes. Thus, there is considerable interest in comparing their pro-inflammatory (‘classical’ activation) and resolving ‘alternative’ activation states. Almost nothing is known about how these activation states affect the ability of microglia to migrate and degrade ECM, or the enzymes used for substrate degradation. This is the subject of the present study.MethodsPrimary cultured rat microglial cells were exposed to lipopolysaccharide (LPS) to evoke classical activation or IL4 to evoke alternative activation. High-resolution microscopy was used to monitor changes in cell morphology and aspects of the cytoskeleton. We quantified migration in a scratch-wound assay and through open filter holes, and invasion through Matrigel™. A panel of inhibitors was used to analyze contributions of different matrix-degrading enzymes to migration and invasion, and quantitative real-time reverse transcriptase PCR (qRT-PCR) was used to assess changes in their expression.ResultsVinculin- and F-actin-rich lamellae were prominent in untreated and IL4-treated microglia (but not after LPS). IL4 increased the migratory capacity of microglia but eliminated the preferential anterior nuclear-centrosomal axis polarity and location of the microtubule organizing center (MTOC). Microglia degraded fibronectin, regardless of treatment, but LPS-treated cells were relatively immobile and IL4-treated cells invaded much more effectively through Matrigel™. For invasion, untreated microglia primarily used cysteine proteases, but IL4-treated cells used a wider range of enzymes (cysteine proteases, cathepsin S and K, heparanase, and matrix metalloproteases). Untreated microglia expressed MMP2, MMP12, heparanase, and four cathepsins (B, K, L1, and S). Each activation stimulus upregulated a different subset of enzymes. IL4 increased MMP2 and cathepsins S and K; whereas LPS increased MMP9, MMP12, MMP14 (MT1-MMP), heparanase, and cathepsin L1.ConclusionsMicroglial cells migrate during CNS development and after CNS damage or disease. Thus, there are broad implications of the finding that classically and alternatively activated microglia differ in morphology, cytoskeleton, migratory and invasive capacity, and in the usage of ECM-degrading enzymes.

Capture of Automotive Particulate Matter in Open Substrates

Open filters (with low pressure drop) have potential for energy-efficient reduction of particulate matter (PM) from engines. In the work reported here, the capture efficiency of PM in open substrates has been investigated using PM from a real engine under various flow conditions and sampling settings. The observed capture efficiency (CE) confirmed the expected trends that increased residence time and increased temperature give better CE. However, the volatile content (assumed to be hydrocarbons, HC) can increase the apparent CE due to rapid evaporation and/or shrinkage of the PM. In order to quantify these effects, a conceptual model has been implemented that can be used as an in situ analyzer of the PM properties. The results show how exhaust treatment (heating and/or dilution) changes the characteristics of the PM. These properties affect CE and can be used for subsequent catalyst optimization. In addition, the method developed here was used to analyze nucleation-mode PM from a special fuel injection strategy. The results revealed that these particles were mainly nonvolatiles, demonstrating the usefulness of this characterization methodology. Furthermore, an equation for diffusion losses in the rotary dilutor for the DMS500 is presented.

Performance evaluation of a novel open trickling filter for the post-treatment of anaerobic effluents from small communities

The objective of the work is to evaluate the performance of an innovative design of a trickling filter for small population sizes, which has been implemented for the post-treatment of sanitary effluent from a UASB (upflow anaerobic sludge blanket) reactor. The unit, named open trickling filter (OTF), operates with no side walls, no perforated bottom slab and no secondary settler. The OTF packing was 3.5 m high, composed of crushed stone, with a fixed distribution system made of channels with V-notch weirs. The OTF was operated with mean surface hydraulic loading rates of 4.1 and 9.3 m³ m⁻² d⁻¹, corresponding to population equivalents of approximately 250 and 550 inhabitants, respectively. For the surface hydraulic loading rate of 4.1 m³ m⁻² d⁻¹, the median removal efficiencies obtained by the OTF and overall system (UASB + OTF) were, respectively, 24 and 83% for total suspended solids (TSS), 44 and 79% for chemical oxygen demand (COD), 42 and 82% for biochemical oxygen demand (BOD), 40 and 40% for N-ammonia. For the surface hydraulic loading rate of 9.3 m³ m⁻² d⁻¹, the median removal efficiencies obtained by the OTF and global system (UASB + OTF) were 14 and 76% for TSS, 28 and 76% for COD, 25 and 86% for BOD, 15 and 15% for N-ammonia. Considering the great simplicity, no mechanization and small footprint of the system, these results can be considered satisfactory, suggesting that the OTF is suitable for small communities, especially in developing countries.

In Vivo Optical Imaging of Interscapular Brown Adipose Tissue with 18F-FDG via Cerenkov Luminescence Imaging

ObjectiveBrown adipose tissue (BAT), a specialized tissue for thermogenesis, plays important roles for metabolism and energy expenditure. Recent studies validated BAT’s presence in human adults, making it an important re-emerging target for various pathologies. During this validation, PET images with 18F-FDG showed significant uptake of 18F-FDG by BAT under certain conditions. Here, we demonstrated that Cerenkov luminescence imaging (CLI) using 18F-FDG could be utilized for in vivo optical imaging of BAT in mice.MethodsMice were injected with 18F-FDG and imaged 60 minutes later with open filter and 2 minute acquisition. In vivo activation of BAT was performed by norepinephrine and cold treatment under isoflurane or ketamine anesthesia. Spectral unmixing and 3D imaging reconstruction were conducted with multiple-filter CLI images.Results1) It was feasible to use CLI with 18F-FDG to image interscapular BAT in mice, with the majority of the signal (>85%) at the interscapular site originating from BAT; 2) The method was reliable because excellent correlations between in vivo CLI, ex vivo CLI, and ex vivo radioactivity were observed; 3) CLI could be used for monitoring BAT activation under different conditions; 4) CLI signals from the group under short-term isoflurane anesthesia were significantly higher than that from the group under long-term anesthesia; 5) The CLI spectrum of 18F-FDG with a peak at 640 nm in BAT after spectral unmixing reflected the actual context of BAT; 6) Finally 3D reconstruction images showed excellent correlation between the source of the light signal and the location and physical shape of BAT.ConclusionCLI with 18F-FDG is a feasible and reliable method for imaging BAT in mice. Compared to PET imaging, CLI is significantly cheaper, faster for 2D planar imaging and easier to use. We believe that this method could be used as an important tool for researchers investigating BAT.

Control of output mode and passband location of an overmoded defected coaxial Bragg structure

By making use of coupled-wave theory, the transmission characteristics of a defected coaxial Bragg structure which operates in the vicinity of 100 GHz are investigated. Results reveal that the overmoded operation of the example structure excites serious interaction among the operating mode and its neighboring modes, which spoils the passband structure and causes hybrid-mode transmission. However, single-mode output can be ensured by applying Hamming-window-function distribution to the ripple amplitude of the example structure, and one or more desired narrow passbands can be generated and controlled by adjusting the localized ripple defect or/and the initial phase difference between the outer-wall and the inner-rod ripples. These peculiarities provide potential applications of defected coaxial Bragg waveguides in constructing high-Q open resonators and narrow passband filters in the sub-terahertz and terahertz frequency ranges.

A pilot plant study of the processes of filtration and adsorption of drinking water through granular activated carbons: a comparative study

This study reports a procedure for the evaluation and comparison of the adsorption and filtration capacities of commercial activated carbons in the treatment of drinking water and the design and operation of a pilot plant to simulate the behavior of fast open filters made of granular activated carbon. The milestone of this experimental work was to determine the adsorption and filtration capacities and the physicochemical properties of five commercial activated carbons with a view to determining which activated carbon might replace the open sand filters of the drinking water treatment plant (DWTP) of the city of Salamanca (western Spain). Compliance with the requirements and physicochemical characteristics stipulated in the EN 12915 European standard for the different activated carbons tested was analyzed, and studies of the prewashing and behavior of the carbons operating in the filters were performed. In this sense, filtration tests to study the saturation of the bed, the variations in pressure drop and the performance of the removal of organic matter in suspension were carried out. Furthermore, the optimal time and rate of the countercurrent washing of the filters and the expansion of the filter bed were evaluated. In the adsorption assays, the specific surface area, porosity, useful lifetime and capacity of adsorption of the dissolved organic matter –especially humic acids, the major precursors of water chlorination by-products – of the activated carbons were determined. The results not only provided an overview of the actual behavior of different types of commercial activated carbons from their initial installation up to the end of their useful life, but also permitted optimization of the filtration and adsorption processes that could lead to the corresponding economic savings and energy reduction in the use of such activated carbon filter-adsorbers.