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61.
62.
Kalyan Mondal Biplab Bag Partha Pratim Sarkar 《International Journal of Communication Systems》2024,37(5):e5688
A small size, dual-band and dual-sense monopole antenna is proposed to improve the axial ratio bandwidth (ARBW). The proposed antenna is considered on a low-cost lossy FR4 substrate with parasitic strips (PSs) and partial ground plane of half guided wavelength dimensions. The dimension of the antenna in terms of wavelength is , where is the wavelength at the lowest resonant frequency. The circularly polarized (CP) mode is created for strong orthogonal electric fields and . The obtained phase difference (PD) between two electric fields and is varied from to under ARBW. The achieved ARBW is 3.68–3.8 GHz, 4.84–12.58 GHz, and impedance bandwidth (IBW) is 3.51–3.82 GHz and 4.28–15 GHz. The applications of the proposed antenna are International Telecommunication Union (ITU) for 5G, C-band IEEE 802.11a wireless local area network (WLAN) at 5 GHz (5.15–5.825 GHz) and X-band wireless systems. 相似文献
63.
Durjoy Mallick Swapan Khanra Swades K. Chaudhuri 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1997,70(3):231-240
The potential of fly ash procured form coal-fired thermal power plants was studied as a heterogeneous catalyst in the oxidation of aqueous sodium sulfide solutions with hydrogen peroxide in the temperature range of 303–323 K. The effects of various parameters (source of fly ash, fly ash loading, initial concentrations of sodium sulfide and hydrogen peroxide, electrolyte and deactivation of catalytic effect of fly ash) were studied. For an initial sodium sulfide and hydrogen peroxide concentration of 26·98×10−2 kmol m−3 and 24·28×10−2 kmol m−3 respectively, only 4% (w/v) fly ash loading intensified the rate of oxidation by a factor of 4·52 over that without fly ash at 303 K. The deactivation of the catalytic effect of fly ash was found to be less than 20% even after six repeated uses. The kinetics of aqueous phase decomposition of hydrogen peroxide was also studied in the presence of fly ash in alkaline medium. ©1997 SCI 相似文献
64.
Mondal PP Rajan K Ahmad I 《Journal of the Optical Society of America. A, Optics, image science, and vision》2006,23(7):1678-1686
Image filtering techniques have numerous potential applications in biomedical imaging and image processing. The design of filters largely depends on the a priori, knowledge about the type of noise corrupting the image. This makes the standard filters application specific. Widely used filters such as average, Gaussian, and Wiener reduce noisy artifacts by smoothing. However, this operation normally results in smoothing of the edges as well. On the other hand, sharpening filters enhance the high-frequency details, making the image nonsmooth. An integrated general approach to design a finite impulse response filter based on Hebbian learning is proposed for optimal image filtering. This algorithm exploits the interpixel correlation by updating the filter coefficients using Hebbian learning. The algorithm is made iterative for achieving efficient learning from the neighborhood pixels. This algorithm performs optimal smoothing of the noisy image by preserving high-frequency as well as low-frequency features. Evaluation results show that the proposed finite impulse response filter is robust under various noise distributions such as Gaussian noise, salt-and-pepper noise, and speckle noise. Furthermore, the proposed approach does not require any a priori knowledge about the type of noise. The number of unknown parameters is few, and most of these parameters are adaptively obtained from the processed image. The proposed filter is successfully applied for image reconstruction in a positron emission tomography imaging modality. The images reconstructed by the proposed algorithm are found to be superior in quality compared with those reconstructed by existing PET image reconstruction methodologies. 相似文献
65.
Das PP Bhandari NK Wan J Charles J Cahay M Chetry KB Newrock RS Herbert ST 《Nanotechnology》2012,23(21):215201
We study of the appearance and evolution of several anomalous (i.e., G < G(0) D 2e(2)/h) conductance plateaus in an In(0.52)Al(0.48)As/InAs quantum point contact (QPC). This work was performed at T = 4:2 K as a function of the offset bias ΔV(G) between the two in-plane gates of the QPC. The number and location of the anomalous conductance plateaus strongly depend on the polarity of the offset bias. The anomalous plateaus appear only over an intermediate range of offset bias of several volts. They are quite robust, being observed over a maximum range of nearly 1 V for the common sweep voltage applied to the two gates. These results are interpreted as evidence for the sensitivity of the QPC spin polarization to defects (surface roughness and impurity (dangling bond) scattering) generated during the etching process that forms the QPC side walls. This assertion is supported by non-equilibrium Green function simulations of the conductance of a single QPC in the presence of dangling bonds on its walls. Our simulations show that a spin conductance polarization as high as 98% can be achieved despite the presence of dangling bonds. The maximum in is not necessarily reached where the conductance of the channel is equal to 0:5G(0). 相似文献
66.
Trivalent europium doped zinc oxide (ZnO:Eu3+) nanocrystals were synthesized via room temperature chemical co-precipitation and they were systematically characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and photoluminescence (PL) spectroscopy. The as-synthesized samples were found to have hexagonal wurtzite coexisted with the intermediate Zn5(OH)8Cl2·H2O phase, while the single hexagonal phase was facilitated due to the calcinations. The as obtained samples were broadly composed of nanoflakes while the highly crystalline nanorods were formed due to low temperature annealing of the as-synthesized samples. The crystallite size of the nanoflakes and nanorods (40-90 nm) were extracted from the XRD pattern which was found to be consistent with scanning electron microscopy (SEM) measurements. The photolumi-nescence (PL) spectra of nanophosphors showed bright red and orange emissions at 618 and 594 nm respectively with efficient broad blue green emission spectrum due to ZnO lattice. Further, a good energy transfer process from ZnO host to Eu3+ was observed in PL emission and excitation spectra of Eu3+ doped ZnO ions. In all, the present nanophosphors were found to have great potentiality for bio-applications. 相似文献
67.
In this paper, we propose Max Connectivity grooming in WDM mesh networks under static lightpath connection requests. The grooming and wavelength conversion resources are placed at the nodes having maximum connections. We propose a heuristic genetic algorithm (GA) model to solve grooming, routing and wavelength assignment. The GA algorithm has been used to optimize the cost of grooming and wavelength conversion resources. The blocking probability has been investigated under different lightpath connections. The performance of Max Connectivity grooming has been compared with other grooming policies. Our results indicate the improvement of resource utilization with minimum blocking probability. 相似文献
68.
Shen Y Guturu PP Buckles BP 《IEEE transactions on information technology in biomedicine》2012,16(1):98-105
Since wireless capsule endoscopy (WCE) is a novel technology for recording the videos of the digestive tract of a patient, the problem of segmenting the WCE video of the digestive tract into subvideos corresponding to the entrance, stomach, small intestine, and large intestine regions is not well addressed in the literature. A selected few papers addressing this problem follow supervised leaning approaches that presume availability of a large database of correctly labeled training samples. Considering the difficulties in procuring sizable WCE training data sets needed for achieving high classification accuracy, we introduce in this paper an unsupervised learning approach that employs Scale Invariant Feature Transform (SIFT) for extraction of local image features and the probabilistic latent semantic analysis (pLSA) model used in the linguistic content analysis for data clustering. Results of experimentation indicate that this method compares well in classification accuracy with the state-of-the-art supervised classification approaches to WCE video segmentation. 相似文献
69.
Partha Ghosh Prodyot Ghosal Swapnadip Thakur Patrice Lerouge Corinne Loutelier-Bourhis Azeddine Driouich Bimalendu Ray 《Food chemistry》2005,90(4):719-726
Defatted Sesamum indicum seed cake was extracted, following two separate sequences, and the effects of extraction medium on yield and composition of the extracts were compared. Polysaccharides extracted sequentially with dilute acid and alkali represented 250 mg/g of defatted meal. The isolated polymers contained arabinan, rhamnogalacturonan I (RG I) and arabinogalactan proteins. Polysaccharides extracted during chlorite treatment and with dilute alkali had a higher proportion of rhamnose, suggesting a more branched variety of polymer. Three extracts, which were further characterized by size exclusion chromatography, gave two overlapping peaks. Structural characterisation of hemicellulosic polysaccharides, isolated with KOH, using specific enzyme hydrolysis, ion exchange chromatography (HPAEC) and matrix assisted laser desorption ionisation-time-of-flight (MALDI-TOF) mass spectroscopy, showed that sesame meal xyloglucan (XG) contained XXXG, XXFG and XXLG, and XLLG (named according to Fry et al., 1993) as the major building sub-units in the ratio of 1:0.9:0.3. Hydrolysis with endo-β-(1 → 4)-d-xylanase and analysis of the xylan derived oligosaccharides showed the presence of monomeric xylose (40%), xylobiose (46%) and acidic xylan oligosaccharides containing 4-O-methyl-d-glucuronic acid residues (14%). 相似文献
70.
Biotransformation of 3-nitro-4-hydroxybenzene arsonic acid (roxarsone) and release of inorganic arsenic by Clostridium species 总被引:1,自引:0,他引:1
Stolz JF Perera E Kilonzo B Kail B Crable B Fisher E Ranganathan M Wormer L Basu P 《Environmental science & technology》2007,41(3):818-823
The extensive use of 3-nitro-4-hydroxybenzene arsonic acid (roxarsone) in the production of broiler chickens can lead to increased soil arsenic concentration and arsenic contaminated dust. While roxarsone is the dominant arsenic species in fresh litter, inorganic As (V) predominates in composted litter. Microbial activity has been implicated as the cause, but neither the specific processes nor the organisms have been identified. Here we demonstrate the rapid biotransformation of roxarsone under anaerobic conditions by Clostridium species in chicken litter enrichments and a pure culture of a fresh water arsenate respiring species (Clostridium sp. strain OhILAs). The main products were 3-amino-4-hydroxybenzene arsonic acid and inorganic arsenic. Growth experiments and genomic analysis indicate strain OhILAs may use roxarsone as a terminal electron acceptor for anaerobic respiration. Electronic structure analysis suggests that the reducing equivalents should go to the nitro group, while liberation of inorganic arsenic from the intact benzene ring by cleaving the C-As bond is unlikely. Clostridium and Lactobacillus species are common in the chicken cecum and litter. Thus, the organic-rich manure and anaerobic conditions typically associated with composting provide the conditions necessary for the native microbial populations to transform the roxarsone in the litter releasing the more toxic inorganic arsenic. 相似文献