Double Filter Research Articles

Monochromators in electron microscopy

Monochromators used in electron microscopes have been reviewed. There are three steps in its progress. At the first step, monochromator is used in retarding mode. Wien filter monochromator and analyzer are floating on the high voltage connected to the gun high voltage. It provides very high energy resolution of about 10meV at 60kV accelerating voltage. In the second step, various gun monochromators; the Wien filter (fringe field monochromator, single focus monochromator and double focus monochromator) and electrostatic omega type are proposed and some of which are commercialized. The double Wien filter and the electrostatic omega monochromators have functions of astigmatic focus on the slit plane and the compensation of the dispersion at the last focus.As the third step, the earth potential monochromator is proposed. Only highly stabilized beam can go through the earth potential monochromator slit, whose magnetic field is stabilized around the 10−8, even if the beam stability from the gun is not so high. This function will be useful in the future high spatial resolution electron microscopy.

Effectiveness of filters in reducing consolidation time in routine laboratory testing

The research reported here is based on the standard laboratory experiments routinely performed in order to measure various geotechnical parameters. These experiments require consolidation of fine-grained samples in triaxial or stress path apparatus. The time required for the consolidation is dependent on the permeability of the soil and the length of the drainage path. The consolidation time is often of the order of several weeks in large clay-dominated samples. Long testing periods can be problematic, as they can delay decisions on design and construction methods. Acceleration of the consolidation process would require a reduction in effective drainage length and this is usually achieved by placing filter drains around the sample. The purpose of the research reported in this paper is to assess if these filter drains work effectively and, if not, to determine what modifications to the filter drains are needed. The findings have shown that use of a double filter reduces the consolidation time several fold.

Design of Double Mode SAW Filters Using IDT/(100) ZnO/(111) Diamond Structure

Propagation characteristics of surface acoustic waves (SAWs) in interdigital transducers (IDT)/(100) ZnO/diamond structures are investigated in this study using the finite element method. The effects of electrodes on phase velocity, coupling coefficient, and reflectivity of SAWs in the layered structures are illustrated. The extracted coupling-of-mode parameters are then applied to calculate frequency responses of double mode SAW filters using the transmission matrix method. Simulation results show a tailored filter applicable for wideband code division multiple access systems can be achieved.

Spin switch based on double spin-filter tunnel junction geometry

Using the concept of spin filter tunneling, we propose a scheme to turn on and off the spin polarization of a transport current. This is achievable in a double spin filter tunneling geometry, where the net spin polarization of the transient current can be switched off when the two spin filters are aligned antiparallel to each other such that their filtering effects cancel out. When aligned parallel, the two spin filters strengthen each other and the transient current is thus highly spin polarized. This magnetic manipulation gives an additional degree of freedom to tune or even turn off a transport current’s spin polarization. We also show that, to some extent, the degree of spin polarization can be linearly varied with an applied bias voltage.

DESIGN AND REALIZATION OF CIRCULAR CONTOURLET TRANSFORM

In this paper, circular contourlet transform (CCT) is proposed, designed and realized. As in the classical contourlet transform (CT), a double filter bank structure is also considered in this work but in different manners. A circularly-decomposed filter bank is first used to capture the points of discontinuities in the image edges, and then followed by a directional filter bank to obtain smoothed contours. The resulting CCT contains a critically sampled filter bank that decomposes images into any power of two's number of directional subbands at multiple scales. The designed CCT is realized by 2-D lattice allpass sections with separable and non-separable 2-D functions of z1 and z2. The resulting structure preserves both modularity and regularity properties which are suitable for VLSI implementations. Objectively, the performances of the realized CCT are tested and proved to be better than the classical CT in detail image preservation. The resulting subband images also indicate the superiority of the proposed CCT. Keywords: Circular contourlet transform, Contourlet transform, Laplacian pyramid, Directional filter bank, 2-D lattice allpass sections, Multiresolution (multiscale & multidirection) analysis.

Do bilinguals have a different hemispheric lateralization in visual processing from monolinguals?

Previous bilingual studies showed reduced hemispheric asymmetry in visual tasks such as face perception in bilinguals compared with monolinguals, which suggested that hemispheric asymmetry in visual tasks could be modulated by experience in reading one or two languages. Here we examined whether difference in hemispheric asymmetry in visual tasks can also be observed in bilinguals who have different language backgrounds. We compared the behavior of three language groups in a tachistoscopic English word sequential matching task: English monolinguals (or alphabetic monolinguals, A-Ms), bilinguals with an alphabetic language L1 and English L2 (alphabetic-alphabetic bilinguals, AA-Bs), and bilinguals with a logographic language (Chinese) L1 and English L2 (logographic-alphabetic bilinguals, LA-Bs). The results showed that AA-Bs had a stronger right visual field/ left hemispheric (LH) advantage than A-Ms and LA-Bs, suggesting that different language learning experiences can influence how visual words are processed in the brain. In addition, we showed that this effect could be accounted for by a computational model that implements a theory of hemispheric asymmetry in perception (i.e. the Double Filtering by Frequency theory, Ivry & Robertson, 1998); the modeling data suggested that this difference may be due to both the difference in participants’ vocabulary size and the difference in word-to-sound mapping between alphabetic and logographic languages.

When pure is not so pure: Chloramine‐related hemolytic anemia in home hemodialysis patients

Worldwide, chloramines are used as the preferred disinfectant for city water supplies. Although they have distinct advantages compared with chlorine and are deemed harmless to the general population, hemodialysis (HD) patients are at risk from chloramine-induced hemolytic anemia. In recent years, this has been highlighted in regional dialysis units but not as frequently in the home HD group. We report on 2 home HD patients who succumbed to severe oxidative hemolysis due to high mains water chloramine concentrations. Both patients were extensively investigated for other cause of anemia before a definitive diagnosis was reached. Delays in diagnosing this uncommon condition can be costly in terms of significant morbidity and excessive usage of recombinant erythropoietin and blood transfusion. Prevention primarily involves enforcing strict water quality control and establishing regular communication with water supply boards and home HD patients. Double (inline) carbon filters should be installed in patient's homes as an effective means for removing high incoming chloramine concentrations.

Algorithm Based on Double Counter Bloom Filter for Large Flows Identification

An algorithm based on double counter bloom filter for long flows identification (CCBF) is proposed in this paper. Double counter bloom filter structure is used to distinguish the process of the long flow filtration from the long flow existence. The false positive rate of the algorithm is analyzed. The relationship of the memory requirement and the error rate is analyzed through simulation. It is shown that with the same restriction of the memory resource, the average error of this algorithm is less than the existing similar algorithms. The analysis of the time performance shows this algorithm is capable of dealing with traffic up to 1 500kpps.The results reflect that this algorithm can be used to monitor the long flows on backbone network.

Biochemical Conservation and Evolution of Germacrene A Oxidase in Asteraceae

Sesquiterpene lactones are characteristic natural products in Asteraceae, which constitutes approximately 8% of all plant species. Despite their physiological and pharmaceutical importance, the biochemistry and evolution of sesquiterpene lactones remain unexplored. Here we show that germacrene A oxidase (GAO), evolutionarily conserved in all major subfamilies of Asteraceae, catalyzes three consecutive oxidations of germacrene A to yield germacrene A acid. Furthermore, it is also capable of oxidizing non-natural substrate amorphadiene. Co-expression of lettuce GAO with germacrene synthase in engineered yeast synthesized aberrant products, costic acids and ilicic acid, in an acidic condition. However, cultivation in a neutral condition allowed the de novo synthesis of a single novel compound that was identified as germacrene A acid by gas and liquid chromatography and NMR analyses. To trace the evolutionary lineage of GAO in Asteraceae, homologous genes were further isolated from the representative species of three major subfamilies of Asteraceae (sunflower, chicory, and costus from Asteroideae, Cichorioideae, and Carduoideae, respectively) and also from the phylogenetically basal species, Barnadesia spinosa, from Barnadesioideae. The recombinant GAOs from these genes clearly showed germacrene A oxidase activities, suggesting that GAO activity is widely conserved in Asteraceae including the basal lineage. All GAOs could catalyze the three-step oxidation of non-natural substrate amorphadiene to artemisinic acid, whereas amorphadiene oxidase diverged from GAO displayed negligible activity for germacrene A oxidation. The observed amorphadiene oxidase activity in GAOs suggests that the catalytic plasticity is embedded in ancestral GAO enzymes that may contribute to the chemical and catalytic diversity in nature.

Spin filtering in double tunnel junctions: The two-band model of the electronic structure of magnetic insulators

The effect of the top of the valence band of an insulator on spin filtering in tunnel structures with nanometer magnetic dielectric layers is discussed. It has been shown that the effect disappears completely at a zero bias voltage and is significantly suppressed at finite voltages if the Fermi level lies in the middle of the band gap of the insulator. This is the main cause of the recently observed striking discrepancy between the theoretical values of the magnetoresistance of double tunneling spin filters and the respective experimental data.

Image Compression and Watermarking scheme using Scalar Quantization

This paper presents a new compression technique and image watermarking algorithm based on Contourlet Transform (CT). For image compression, an energy based quantization is used. Scalar quantization is explored for image watermarking. Double filter bank structure is used in CT. The Laplacian Pyramid (LP) is used to capture the point discontinuities, and then followed by a Directional Filter Bank (DFB) to link point discontinuities. The coefficients of down sampled low pass version of LP decomposed image are re-ordered in a pre-determined manner and prediction algorithm is used to reduce entropy (bits/pixel). In addition, the coefficients of CT are quantized based on the energy in the particular band. The superiority of proposed algorithm to JPEG is observed in terms of reduced blocking artifacts. The results are also compared with wavelet transform (WT). Superiority of CT to WT is observed when the image contains more contours. The watermark image is embedded in the low pass image of contourlet decomposition. The watermark can be extracted with minimum error. In terms of PSNR, the visual quality of the watermarked image is exceptional. The proposed algorithm is robust to many image attacks and suitable for copyright protection applications.

Frequency-wavelet domain deconvolution for terahertz reflection imaging and spectroscopy

In terahertz reflection imaging, a deconvolution process is often employed to extract the impulse function of the sample of interest. A band-pass filter such as a double Gaussian filter is typically incorporated into the inverse filtering to suppress the noise, but this can result in over-smoothing due to the loss of useful information. In this paper, with a view to improving the calculation of terahertz impulse response functions for systems with a low signal to noise ratio, we propose a hybrid Frequency-Wavelet Domain Deconvolution (FWDD) for terahertz reflection imaging. Our approach works well; it retrieves more accurate impulse response functions than existing approaches and these impulse functions can then also be used to better extract the terahertz spectroscopic properties of the sample.

Evaluation of filtration efficiency for single layer and double layers alumina filter using aqueous suspension

The quality of molten aluminum is dependent on the methods used for its treatment to remove impurities. Of these, rigid media tube filter (RMF) has been the most reliable. RMF bound coarse grain of alumina by 9Al2O3·2B2O3 has been used widely all over the world. The purpose of this study was to examine the filtration efficiency of RMF using an aqueous suspension of ceramic powder instead of molten aluminum. During actual operation, inclusions accumulate on the surface of RMF to form a cake layer. But the cake formation was not expected in aqueous suspension, since its filtration efficiency showed initial operational conditions, i.e. surface and internal filtration. The results of our experiment clearly showed that filtration efficiency of RMF depended upon pore size and the operation condition. Namely, the filtration efficiency of small pore RMF allowed as high as possible removal of fine inclusions. It was confirmed that maximum inclusion size that could possible be filtered, was approximately 10% of maximum RMF pore size. Also, the operation conditions for higher filtration efficiency, was a slower flow rate and an aqueous suspension of low inclusion concentration. The filtration performance for double layers RMF was influenced by a smaller pore size and the filtration resistance reduced as compared to single layer. As the result of aqueous suspension was similar to that of TiB2 added molten aluminum, it was assumed that the aqueous suspension examination method was reliable.

Double resonant stub bandstop filter with pseudo-elliptic response

A simple wideband bandstop filter that yields equal ripples in both the pass- and the stopbands is described. The filter comprises only two resonant stubs and a connecting transmission line and has a transmission response almost identical to that of a third-order elliptic function filter. The practical bandwidth is limited to 130–160%.

Anthracology and taphonomy, from wood gathering to charcoal analysis. A review of the taphonomic processes modifying charcoal assemblages, in archaeological contexts

A discussion on the representativeness of charcoal from archaeological contexts and their potential for palaeoecological reconstruction is presented. The charcoal deposits studied are the result of human activities and natural processes, difficult to separate on the basis of their effects only. This is why “taphonomy” should not be limited to the study of charcoal, after the extinction of fire. As a result our questioning has been widened to include the entire succession of processes, from past vegetation to the anthracological diagram. We propose a review of the taphonomic processes affecting anthracological assemblages in archaeological contexts, from wood gathering to the analysis of charcoal results. Human practices appear clearly as the first filter determining or conditioning the assemblage. The combustion process can induce a double filter by limiting the taxonomic information and by falsifying the initial quantity of burned wood. Post-depositional agents represent a third level of filters between the vegetation and the anthracological assemblage. Finally, sampling and quantification methods can also induce a distortion of the assemblage. The aim of this paper is to present the state of the discipline today, the problems already solved, and the questions that remain to be studied.

CONTROLLING CHAOS IN A CHUA'S CIRCUIT USING NOTCH FILTERS

This paper explores the use of notch filters for the purpose of damping out chaotic oscillations. The design of the filter and the way it is interfaced to the system are investigated from a signal-processing point of view. A Chua's circuit, that has typical applications in synchronization and secure communications, is used to exemplify the suggested methodology where both theoretical and experimental results are provided. The power spectrum of the original system is analyzed to selectively damp-out portions of the power spectrum, thus truncating period-doubling, the original cause of chaos. Both single and double notch filters are explored to examine their effect on the performance of the modified system. Steady state analysis as well as issues regarding practical implementation are addressed and advantages and limitations of the proposed method are highlighted.

DECONSTRUCTING ACTIVE REGION AR10961 USINGSTEREO,HINODE,TRACE, ANDSOHO

Active region 10961 was observed over a five-day period (2007 July 2-6) by instrumentation on-board STEREO, Hinode, TRACE, and SOHO. As it progressed from Sun's center to the solar limb, a comprehensive analysis of the extreme ultraviolet, X-ray, and magnetic field data reveals clearly observable changes in the global nature of the region. Temperature analyses undertaken using STEREO Extreme Ultraviolet Imager double filter ratios and X-ray imaging telescope single and combined filter ratios demonstrate an overall cooling of the region from between 1.6-3.0 MK to 1.0-2.0 MK over the five days. Similarly, Hinode Extreme Ultraviolet Imaging Spectrograph density measurements show a corresponding increase in density of 27%. Moss, cool (1 MK) outer loop areas, and hotter core loop regions were examined and compared with potential magnetic field extrapolations from SOHO Michelson Doppler Imager magnetogram data. In particular, it was found that the potential field model was able to predict the structure of the hotter X-ray loops and that the larger cool loops seen in 171 A images appeared to follow the separatrix surfaces. The reasons behind the high-density moss regions only observed on one side of the active region are examined further.

Clinical Efficacy of Two-Phase Leukocyte Filtration in High-Risk Patients Undergoing Coronary Revascularization with Cardiopul monary Bypass

The purpose of this study was to investigate the clinical outcome, inflammatory response and myocardial function in high-risk patients undergoing three different leukocyte depletion strategies. Over a four-month period, forty patients (EuroSCORE 6+) undergoing coronary revascularization were prospectively randomized to one of the four perfusion protocols: Group 1 (N = 10): Conventional circuits (ECC) + two leukocyte filters (LG6B, Pall, USA) with the method of two-phase (continuous + strategic) leukofiltration; Group 2 (N = 10): ECC + single leukocyte filter with the method of continuous leukofiltration; Group 3 (N = 10): ECC + single leukocyte filter with the method of strategic leukofiltration; Group 4 (N = 10) Control: ECC without leukocyte filtration. Blood samples were collected at T1: Baseline, T2: On CPB, T3: X-Clamp, T4: Off CPB, T5: ICU24 and T6: ICU48. Perioperative follow-up was thoroughly monitored. Leukocyte counts in double filter and strategic filtration groups demonstrated significant differences at T4 (p < .05 vs. control). TNF-alpha levels were significantly lower in Group 1 at T4 and procalcitonin levels at T5 and T6 (p < .05 vs. control). CKMB levels demonstrated well preserved myocardium in double filter group (p < .05 vs. control). Brain natriuretic peptide levels in double filter group were significantly lower at T5 and T6 with respect to Group 2 (p < .05) and control (p < .001). Matrixmetallopeptidase 9 and D-Dimer levels in double filter group were significantly lower at T5 and T6 (p < .05 vs. control). Two-phase leukofiltration is associated with some compound benefit over continuous deployment in high-risk patients. A larger more powerful study than this pilot one is warranted for further evaluation.

Spectral Polarimetric Radar Clutter Suppression to Enhance Atmospheric Echoes

Abstract The clutter present in the Doppler spectra of atmospheric targets can be removed by using polarimetry. The purpose is to suppress the Doppler velocity bins where spectral polarimetric parameters have atypical values. This procedure largely improves profiles of moments and polarimetric parameters of atmospheric targets. Several spectral polarimetric clutter-reduction techniques, which are based on thresholding and intended for real-time processing, are discussed in this paper. A new method, the double spectral linear depolarization ratio clutter-suppression technique, is proposed. Very satisfactory performances are obtained with this method, which can be used in the full range of elevations (0°–90°). Spectral polarimetric clutter-suppression techniques for real-time processing were studied for the S-band high-resolution Transportable Atmospheric Radar (TARA) profiler. For this study, precipitation, cloud, and clear-air scattering are considered examples of atmospheric echoes. After successful testing in 2008, the double spectral linear depolarization ratio filter was implemented in the real-time processing of the X-band scanning drizzle radar (IDRA).

An effective filtering for GRACE time‐variable gravity: Fan filter

Spatial low‐pass filtering is necessary for processing the GRACE time‐variable gravity (TVG) data which are otherwise plagued with short‐wavelength noises. Here we devise a new non‐isotropic filter, called the fan filter: In terms of the spherical harmonic spectrum, the fan filter is simply a 2‐D double filter consisting of a low‐pass along the degree n (the same as the conventional isotropic filter) simultaneously with a low‐pass along the order m, whose contour projection onto the (n, m) plane is fan‐shaped. It is deterministic and independent of a priori or external information, its implementation is straightforward, and the result is objective. Most importantly, we show that this simple filter performs well among its counterparts under similar conditions, in particular against the N‐S striping noises prevalent in the GRACE TVG solutions. We demonstrate this with Gaussian weights at filter length and hence spatial resolution as fine as 300 km. We also deduce the fan filter's nominal amplitude‐reduction factor as a function of the filter length for TVG signals that follow the Kaula rule.