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271.
Effect of inorganic, synthetic and naturally occurring chelating agents on Fe(II) mediated advanced oxidation of chlorophenols 总被引:5,自引:0,他引:5
This study examines the feasibility and application of Advanced Oxidation Technologies (AOTs) for the treatment of chlorophenols that are included in US EPA priority pollutant list. A novel class of sulfate/hydroxyl radical-based homogeneous AOTs (Fe(II)/PS, Fe(II)/PMS, Fe(II)/H2O2) was successfully tested for the degradation of series of chlorophenols (4-CP, 2,4-CP, 2,4,6-CP, 2,3,4,5-CP). The major objective of the present study was to evaluate the effectiveness of three representative chelating agents (citrate, ethylenediaminedisuccinate (EDDS), and pyrophosphate) on Fe(II)-mediated activation of three common peroxide (peroxymonosulfate (PMS), persulfate (PS), and hydrogen peroxide (H2O2)) at neutral pH conditions. Short term (4 h) and long term (7 days) experiments were conducted to evaluate the kinetics and longevity of different oxidative systems for 4-chlorophenol degradation. Results showed that each of the iron-chelating agent couple was superior in activating a particular oxidant and consequently for 4-CP degradation. In case of Fe(II)/PMS system, the inorganic chelating agent pyrophosphate showed effective activation of PMS whereas very fast dissociation of PMS was recorded in the case of EDDS without any apparent 4-CP degradation. In Fe(II)/H2O2 system, EDDS was proven to be the most effective whereas pyrophosphate showed negligible activation of H2O2. Fe(II)/Citrate system showed moderate activation of all three oxidants. PMS was found to be the most universal oxidant, which was activated by all three iron-chelating agent systems and Fe(II)/Citrate was the most universal chelating agent system, which was able to activate all three oxidants to a certain extent. 相似文献
272.
273.
Pellet: A practical OWL-DL reasoner 总被引:20,自引:0,他引:20
Evren Sirin Bijan Parsia Bernardo Cuenca Grau Aditya Kalyanpur Yarden Katz 《Journal of Web Semantics》2007,5(2):51-53
In this paper, we present a brief overview of Pellet: a complete OWL-DL reasoner with acceptable to very good performance, extensive middleware, and a number of unique features. Pellet is the first sound and complete OWL-DL reasoner with extensive support for reasoning with individuals (including nominal support and conjunctive query), user-defined datatypes, and debugging support for ontologies. It implements several extensions to OWL-DL including a combination formalism for OWL-DL ontologies, a non-monotonic operator, and preliminary support for OWL/Rule hybrid reasoning. Pellet is written in Java and is open source. 相似文献
274.
Over the past few years, wireless networking technologies have made vast forays into our daily lives. Today, one can find
802.11 hardware and other personal wireless technology employed at homes, shopping malls, coffee shops and airports. Present-day
wireless network deployments bear two important properties: they are unplanned, with most access points (APs) deployed by users in a spontaneous manner, resulting in highly variable AP densities; and
they are unmanaged, since manually configuring and managing a wireless network is very complicated. We refer to such wireless deployments as
being chaotic.
In this paper, we present a study of the impact of interference in chaotic 802.11 deployments on end-client performance. First,
using large-scale measurement data from several cities, we show that it is not uncommon to have tens of APs deployed in close
proximity of each other. Moreover, most APs are not configured to minimize interference with their neighbors. We then perform
trace-driven simulations to show that the performance of end-clients could suffer significantly in chaotic deployments. We
argue that end-client experience could be significantly improved by making chaotic wireless networks self-managing. We design and evaluate automated power control and rate adaptation algorithms to minimize interference among neighboring
APs, while ensuring robust end-client performance.
This work was supported by the Army Research Office under grant number DAAD19-02-1-0389, and by the NSF under grant numbers
ANI-0092678, CCR-0205266, and CNS-0434824, as well as by IBM and Intel.
Aditya Akella obtained his Ph.D. in Computer Science from Carnegie Mellon University in September 2005. He obtained a B.Tech in Computer
Science and Engineering from IIT Madras in May 2000. Currently, Dr. Akella is a post-doctoral associate at Stanford University.
He will join the Computer Sciences faculty at the University of Wisconsin-Madison in Fall 2006. Dr. Akella's research interests
include Internet Routing, Network Protocol Design, Internet Security, and Wireless Networking. His web page is at .
Glenn Judd, is a Computer Science Ph.D. candidate at Carnegie Mellon University. His research interests include wireless networking
and pervasive computing. He has an M.S. and B.S. in Computer Science from Brigham Young University.
Srinivasan Seshan is currently an Associate Professor and holds the Finmeccanica chair at Carnegie Mellon University’s Computer Science Department.
Dr. Seshan received his Ph.D. in 1995 from the Computer Science Department at University of California, Berkeley. From 1995
to 2000, Dr. Seshan was a research staff member at IBM’s T.J. Watson Research Center. Dr. Seshan’s primary interests are in
the broad areas of network protocols and distributed network applications. In the past, he has worked on topics such as transport/routing
protocols for wireless networks, fast protocol stack implementations, RAID system design, performance prediction for Internet
transfers, Web server benchmarking, new approaches to congestion control, firewall design and improvements to the TCP protocol.
His current work explores new approaches in overlay networking, sensor networking, online multiplayer games and wide-area
Internet routing. His web page is at .
Peter Steenkiste is a Professor of Computer Science and of Electrical and Computer Engineering at Carnegie Mellon University. His research
interests include networking, distributed systems, and pervasive computing. He received an M.S. and Ph.D. in Electrical Engineering
from Stanford University and an Engineering degree from the University of Gent, Belgium. You can learn more about his research
from his home page . 相似文献
275.
Nonlinear Distortion Due to Cross-Phase Modulation in Microwave Fiber-Optic Links With Optical Single-Sideband or Electrooptical Upconversion 总被引:1,自引:0,他引:1
Cheng L. Aditya S. Li Z. Nirmalathas A. Alphones A. Ong L. C. 《Microwave Theory and Techniques》2007,55(1):176-184
A new analytical model is presented to study nonlinear distortion due to cross-phase modulation in dispersive and nonlinear wavelength-division-multiplexing microwave fiber-optic links. The model is not based on the pump-probe approach. Hence, it can be used to analyze a larger variety of links, including, in particular, electrooptical upconversion links. Our simulations and experiments show that the model predicts the nonlinear distortion due to cross-phase modulation quite accurately, even when the modulating microwave frequency is in tens of gigahertz and the fiber length is in tens of kilometers. Detailed analyses of the distortion due to cross-phase modulation for links with optical single-sideband modulation are presented. Measured results for optical single-sideband are shown to match our theoretical predictions very well. Our results show that the nonlinear distortion due to cross-phase modulation can be a limiting factor for optical launch power in wavelength-division-multiplexing microwave fiber-optic links; moreover, the maximum possible nonlinear distortion level for a higher frequency may be lower than that for a lower frequency. Also presented are some simple approximations for a quick estimate of the level of the nonlinear distortion 相似文献
276.
Aditya Mahabhai Vora 《Journal of Materials Science》2007,42(3):935-940
In the present paper, the computation of the phonon dynamics of binary Mg70Zn30 metallic glass is reported using the well-recognized model potential of Gajjar et al. The present study includes the phonon
dispersion curves (PDC), elastic and thermodynamic properties such as longitudinal sound velocity υL, transverse sound velocity υT, Debye temperature θD, isothermal bulk modulus B
T, modulus of rigidity G, Poisson’s ratio σ and Young’s modulus Y and specific heat capacity C
V
of the glass. Three theoretical models given by Hubbard–Beeby (HB), Takeno–Goda (TG) and Bhatia–Singh (BS) are used to compute
the PDC. Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru–Utsumi (IU), Farid et al. (F)
and Sarkar et al. (S) are employed for the first time to study the effect of exchange and correlation in the aforesaid properties.
The pseudo-alloy-atom (PAA) model is applied for the first time instead of Vegard’s Law. 相似文献
277.
Manzoor K Aditya V Vadera SR Kumar N Kutty TR 《Journal of nanoscience and nanotechnology》2007,7(2):463-473
A novel synthesis method is presented for the preparation of eco-friendly, doped semiconductor nanocrystals encapsulated within oxide-shells, both formed sequentially from a single-source solid-precursor. Highly luminescent ZnS nanoparticles, in situ doped with Cu(+)-Al3+ pairs and encapsulated with ZnO shells are prepared by the thermal decomposition of a solid-precursor compound, zinc sulfato-thiourea-oxyhydroxide, showing layered crystal structure. The precursor compound is prepared by an aqueous wet-chemical reaction involving necessary chemical reagents required for the precipitation, doping and inorganic surface capping of the nanoparticles. The elemental analysis (C, H, N, S, O, Zn), quantitative estimation of different chemical groups (SO4(2-) and NH4(-)) and infrared studies suggested that the precursor compound is formed by the intercalation of thiourea, and/or its derivatives thiocarbamate (CSNH2(-)), dithiocarbamate (CS2NH2(-)), etc., and ammonia into the gallery space of zinc-sulfato-oxyhydroxide corbel where the Zn(II) ions are both in the octahedral as well as tetrahedral coordination in the ratio 3 : 2 and the dopant ions are incorporated within octahedral voids. The powder X-ray diffraction of precursor compound shows high intensity basal reflection corresponding to the large lattice-plane spacing of d = 11.23 angstroms and the Rietveld analysis suggested orthorhombic structure with a = 9.71 angstroms, b = 12.48 angstroms, c = 26.43 angstroms, and beta = 90 degrees. Transmission electron microscopy studies show the presence of micrometer sized acicular monocrystallites with prismatic platy morphology. Controlled thermolysis of the solid-precursor at 70-110 degrees C leads to the collapse of layered structure due to the hydrolysis of interlayer thiourea molecules or its derivatives and the S2- ions liberated thereby reacts with the tetrahedral Zn(II) atoms leading to the precipitation of ZnS nanoparticles at the gallery space. During this process, the dopant ions situated at octahedral voids gets incorporated into the nano-ZnS lattice and results in bright photoluminescence. On further heat treatment above 1100 degrees C, the corbel zinc-oxyhydroxide sheets undergo dehydroxylation to form ZnO which eventually encapsulates the ZnS nanoparticles at the gallery leading to significant enhancement in the luminescence quantum efficiency, up to approximately 22%. The emission color of thus formed nano-ZnS/micro-ZnO composites could be tuned over wide spectral ranges from 480 to 618 nm and the spectral changes are attributed to a number of factors including lattice defects, Cu(+)-Al3+ dopant-pairs and iso-electronic oxygen in nano-ZnS and oxygen-vacancy or -interstitial centers in non-stoichiometric ZnO. 相似文献
278.
Aditya Narayan Singh A. Moitra Pragna Bhaskar Arup Dasgupta G. Sasikala A. K. Bhaduri 《Journal of Materials Engineering and Performance》2018,27(8):3812-3823
The simple power relationship σ?=?Κε p n satisfactorily expresses the tensile flow behavior of many metals and alloys in their uniform plastic strain regime. However, many FCC materials with low stacking fault energy have opposed such power law relationship. Alloy 617, an age-hardenable Ni-based superalloy is also observed not to obey the simple power law relationship neither in its solution-treated nor in its aged conditions. Various flow relationships were used to obtain the best fit for the tensile data, and different relationships were identified for the different aged conditions. The work-hardening rate (θ) demonstrates three distinct regions for all aged conditions, and there is an obvious change in the trend of θ versus σ. In the initial portion, θ decreases rapidly followed by a gradual increase in the second stage and again a decrease in its third stage is perceived in the Alloy 617. These three-stage characteristics are attributed to a commonly known precipitate, γ′: Ni3(Ti, Al) which evolves during aging treatment and well recognized under transmission electron microscopy (TEM) observation. TEM results also reveal a slight degree of coarsening in γ′ over aging. The tensile flow and the work-hardening behavior are well correlated with other microstructural evolution during the aging treatments. 相似文献
279.
Spandan Chaudhary Surendra K. Chikara Mahesh C. Sharma Abhinav Chaudhary Bakhtiyar Alam Syed Pooja S. Chaudhary Aditya Mehta Maulik Patel Arpita Ghosh Marcello Iriti 《International journal of molecular sciences》2015,16(12):29889-29899
The effects of methyl jasmonate (MeJA), an elicitor of plant defense mechanisms, on the biosynthesis of diosgenin, a steroidal saponin, were investigated in six fenugreek (Trigonella foenum-graecum) varieties (Gujarat Methi-2, Kasuri-1, Kasuri-2, Pusa Early Branching, Rajasthan Methi and Maharashtra Methi-5). Treatment with 0.01% MeJA increased diosgenin levels, in 12 days old seedlings, from 0.5%–0.9% to 1.1%–1.8%. In addition, MeJA upregulated the expression of two pivotal genes of the mevalonate pathway, the metabolic route leading to diosgenin: 3-hydroxy-3-methylglutaryl-CoA reductase (HMG) and sterol-3-β-glucosyl transferase (STRL). In particular, MeJA increased the expression of HMG and STRL genes by 3.2- and 22.2-fold, respectively, in the Gujarat Methi-2 variety, and by 25.4- and 28.4-fold, respectively, in the Kasuri-2 variety. Therefore, MeJA may be considered a promising elicitor for diosgenin production by fenugreek plants. 相似文献
280.
Compensation between adsorption entropies and enthalpies results in less than a two-fold variation in adsorption equilibrium constants for C3–C6 alkanes at temperatures relevant for monomolecular cracking; the size-independent activation energy for CC bond activation in C3–C6 alkanes indicates that the marked increase in monomolecular cracking turnover rates observed with alkane chain size reflects a concurrent increase in activation entropies. Thermodynamic treatments for non-ideal systems rigorously describe confinement effects within zeolite channels and show that pre-exponential factors depend on solvation effects of the zeolite-host environment through variations in the thermodynamic activity of the zeolitic proton. Observed differences in rates and selectivities of monomolecular alkane activation with zeolite structure, after normalization to intrazeolitic concentrations, reflect differences in intrinsic rate constants. 相似文献