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31.
32.
Das Peddada S. Hwang J.T.G. 《Geoscience and Remote Sensing, IEEE Transactions on》2002,40(8):1879-1884
Often, in synthetic aperture radar (SAR) images of polar ice, one encounters shadow-like features across the images. Such features make it difficult to classify pixels into ice and water. Accordingly, it becomes a challenge to determine the true size and boundaries of ice floes in an SAR image of polar ice. We develop a simple statistical procedure which classifies pixels of an image by eliminating the effects of shadow-like features. Methodology developed in this paper is illustrated using some noisy SAR images of ice floes in the Arctic sea. 相似文献
33.
Ganguly S. Navda V. Kim K. Kashyap A. Niculescu D. Izmailov R. Hong S. Das S.R. 《Selected Areas in Communications, IEEE Journal on》2006,24(11):2147-2158
In the recent past, there has been a tremendous increase in the popularity of VoIP services as a result of huge growth in broadband access. The same voice-over-Internet protocol (VoIP) service poses new challenges when deployed over a wireless mesh network, while enabling users to make voice calls using WiFi phones. Packet losses and delay due to interference in a multiple-hop mesh network with limited capacity can significantly degrade the end-to-end VoIP call quality. In this work, we discuss the basic requirements for efficient deployment of VoIP services over a mesh network. We present and evaluate practical optimizing techniques that can enhance the network capacity, maintain the VoIP quality and handle user mobility efficiently. Extensive experiments conducted on a real testbed and ns-2 provide insights into the performance issues and demonstrate the level of improvement that can be obtained by the proposed techniques. Specifically, we find that packet aggregation along with header compression can increase the number of supported VoIP calls in a multihop network by 2-3 times. The proposed fast path switching is highly effective in maintaining the VoIP quality. Our fast handoff scheme achieves almost negligible disruption during calls to roaming clients 相似文献
34.
35.
Jone W.-B. Der-Chen Huang Das S.R. 《IEEE transactions on instrumentation and measurement》2003,52(5):1381-1390
In this work, a built-in self-testing (BIST) method is proposed to detect nontraditional faults of embedded memory arrays for a system-on-chip (SoC) design. The nontraditional faults include single-cell read-sensitive faults and read coupling faults. The BIST method can efficiently deal with embedded memory arrays spatially distributed on the entire SoC chip. The concept of redundant read-write operations is applied to detect all embedded memory arrays with different sizes simultaneously. The redundant operations do not affect the fault coverage of all nontraditional faults discussed in this paper. The method has the advantages of low hardware overhead, short test time, and high fault coverage for nontraditional memory defects. 相似文献
36.
H. S. Tripathi B. Mukherjee S. K. Das A. Ghosh G. Banerjee 《Bulletin of Materials Science》2003,26(2):217-220
Mullite was developed by reaction sintering of sillimanite beach sand and calcined alumina. Two varieties of sillimanite beach
sand viz. S and Z having different compositions were selected. Synthesis and properties of mullite were very much dependent
on the sillimanite beach sand composition. Presence of higher amount of impurities in the Z-variety of sillimanite sand favours
the densification by liquid phase formation. Presence of zircon in Z-variety increases the hardness and fracture toughness.
Alumina addition improves the mechanical/thermomechanical properties of the samples. Mullite retains the usual orthorhombic
habit of sillimanite. Rounded to sub rounded zirconia dispersed within the mullite matrix of the sample ZA is noticed. 相似文献
37.
Anjana Bhattacharya Jagannath Das Swapan Mitra Sisir K. Roy 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,54(4):399-407
Silicoaluminophosphate (SAPO-5) molecular sieves have been synthesised from reaction mixtures having a molar composition of: 0.7–1.0 Al2O3:0.7–1.0 P2O5:0.01–2.0 SiO2:xR:40 H2O (where R = (C2H3)3N or (C2H3)4NOH and x = 1.5–2.5 for (C2H5)5N and 0.5 for (C2H5)4NOH, at 473 K using various sources of alumina and silica. The effects of (i) varying the crystallinity of the alumina source (boehmite) and (ii) the use of different silica sources such as freshly prepared silica either from sodium silicate or paddy husk extract, silica gel from commercial water-glass, and tetraethyl orthosilicate have been studied. The crystallinity of boehmite has been found to have a strong effect on its reactivity towards the formation of SAPO-5. The activity of boehmite for SAPO-5 formation increased with a decrease in its crystallinity (or with increase in its moisture content). Any silica source devoid of sodium ions could be employed for the synthesis of SAPO-5. The process of crystallisation started as early as within 1.5 h of reaction and incorporation of silicon into the AlPO4 framework has been noted at this stage. Formation of some tridymite phase as impurity has been observed under conditions such as (i) SiO2 concentration > 1.7 mole and (ii) x > 2.0 when R = (C2H5)3N. 相似文献
38.
A reverse phase high-performance liquid chromatography method for the quantitation of sulfacetamide, sulfadiazine, sulfamerazine, and sulfamethazine in various combinations has been developed. The method is simple, accurate, precise and reproducible. The percent relative standard deviations based on 6 injections were 2.1, 0.6, 1.9, and 1.6 for sulfacetamide, sulfadiazine, sulfamerazine, and sulfamethazine, respectively. The ratio of peak heights (drug/internal standard) wer closely related (r value 0.99 or better) to concentrations (± 20% of the standard solution concentrations). The results of synthetic mixtures showed quantitative recovery and method was successfully applied to commercial dosage forms (tablets and suspension). Extraction of sulfa drugs from the dosage forms required a very simple procedure. 相似文献
39.
Cocaine abuse today has reached greater heights than it did during the first cocaine epidemic in the late nineteenth century. It is estimated that one out of every four Americans has used cocaine and some six million people in the US use it regularly. Although cocaine affects all systems in the body, the central nervous system (CNS) is the primary target. Cocaine blocks the reuptake of neurotransmitters in the neuronal synapses. Almost all CNS effects of cocaine can be attributed to this mechanism. Euphoria, pharmacological pleasure and intense cocaine craving share basis in this system. The effects of cocaine on other organ systems, in addition to its effects on the CNS, account for the majority of the complications associated with cocaine abuse. In this paper, the CNS effects following cocaine administration and their treatment are discussed. 相似文献
40.
Debasmita Das Purabi Rani Samaddar Pratik Kumar Sen Kaushik Das 《Journal of Applied Electrochemistry》2008,38(6):743-749
Galvanostatic steady state current potential measurements were carried out for oxidation of a series of aliphatic alcohols
having varying number of hydroxyl groups. The anodically deposited layer of MnO2 on platinum was used as the electrode material. The deposit was characterised by scanning electron microscopy (SEM), energy
dispersive X-ray analysis (EDAX) and electrode potential measurements. The catalytic role of MnO2 in the electro-oxidation of alcohols was indicated by the chronopotentiograms and the cyclic voltammograms. An analysis of
the electrochemical data indicated a catalytic EC mechanism in which Mn (V) is generated electrochemically and consumed chemically
in succession. Based on this and the hydrogen bonding interaction between alcoholic hydroxyl groups and MnO2 layer, a mechanism was proposed which accounts for the variation in the observed electrochemical reaction orders. Tafel behaviour
was found to be followed only approximately. Current efficiency of the electrochemical oxidation of polyols was studied. Replacement
of platinum by carbon as current collector was found to leave the electrocatalytic activity of the MnO2 deposit practically unaltered. 相似文献