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排序方式: 共有361条查询结果,搜索用时 250 毫秒
1.
The oxidation of chloro-5-10,15,20-tetramesitylporphyrinotoiron(III) with peroxyacids affords a reactive oxoiron(IV)-porphyrin cation radical species 2. The characterization of 2 and its oxochromium analogs 3, 4 and 5 are reviewed. The nature of reactive oxochromium species derived from chromyl reagents is also reviewed. The oxidation of triphenylphosphine by CrOTPP (11), CrOTTP (13) and CrOTMP (14) is described. Variations in the rate constants indicate that steric factors affect the rate of oxygen atom transfer. Activation parameters for the oxidation of triphenylphosphine by 14 are ΔH≠ = 6.96 kcal/mol and ΔS≠ = −39 eu. The oxidation of t-butylphenylcarbinol (18) by CrOTPP gave predominantly benzaldehyde via carbon—carbon bond cleavage while the chromium(III) porphyrin-catalyzed oxidation of 18 by iodosylbenzene afforded t-butylphenylketone. 相似文献
2.
New materials for diode laser pumping of solid-state lasers 总被引:4,自引:0,他引:4
The authors review recent progress in the development of new materials for III-V semiconductor diode lasers useful for pumping solid-state lasers. All of the diode lasers discussed are grown on GaAs substrates. Particular emphasis is placed on the performance and reliability of high-CW-power strained-layer InGaAs-AlGaAs diode lasers emitting in the wavelength range between 0.87 and 1.1 μm, improved resistance to degradation of 0.78 to 0.87 μm diode lasers afforded by the strained-layer AlInGaAs-AlGaAs and lattice-matched GaInAsP-GaInP materials systems, and improved performance of visible diode lasers utilizing the materials system GaInP-AlGaInP 相似文献
3.
Ian G. Richardson Adrian R. Brough Rik Brydson Geoffrey W. Groves Christopher M. Dobson 《Journal of the American Ceramic Society》1993,76(9):2285-2288
Solid-state 27 Al and 29 Si magic angle spinning NMR spectroscopy has been combined with electron energy loss spectroscopy carried out in the transmission electron microscope to determine the location of Al substituting in a semicrystalline C-S-H gel present in a hydrated synthetic slag glass. The gel is found to contain mainly pentameric silicate chains in which the central silicon is substituted by aluminum. 相似文献
4.
5.
Declan C. Nolan Chris M. Tierney Cecil G. Armstrong Trevor T. Robinson Jonathan E. Makem 《Engineering with Computers》2014,30(4):689-701
The creation of idealised, dimensionally reduced meshes for preliminary design and optimisation remains a time-consuming, manual task. A dimensionally reduced model is ideal for assessing design changes through modification of element properties without the need to create a new geometry or mesh. In this paper, a novel approach for automating the creation of mixed dimensional meshes is presented. The input to the process is a solid model which has been decomposed into a non-manifold assembly of smaller volumes with different meshing significance. Associativity between the original solid model and the dimensionally reduced equivalent is maintained. The approach is validated by means of a free-free modal analysis on an output mesh of a gas turbine engine component of industrial complexity. Extensions and enhancements to this work are also discussed. 相似文献
6.
Batch leaching tests have been performed on fly ashes collected from four Australian power stations fuelled by chemically different coals. Two acidic and two alkaline fly ashes were subjected to long-term (144 h) leaching tests, and the behaviour of As, B, Mo and Se was investigated to obtain data on their potential for mobilisation during fly ash-water interactions. All four elements are mobile under different conditions and over different leaching times. The concentrations of these elements released in leaching solutions with initial pH values of 4, 7 and 10 were used to assess the influence of pH conditions on element mobility from the acidic and alkaline fly ashes. The most mobile of the four elements leached were Mo from alkaline fly ashes and B from acidic fly ashes. Arsenic concentration increased with time in leachate solutions from acidic and alkaline fly ashes; however, in solutions in contact with alkaline fly ashes the As concentration, after reaching a maximum, later decreased with time. Selenium mobility shows a similar pattern to that of As, with similar leaching concentrations. Boron has the highest relative mobility of all four elements. A process possibly responsible for the decrease in concentration of B, As and Se in alkaline leaching solutions is the formation of ettringite. Equilibrium between the solid phase (ash) and the leaching solution was not reached in any of the leaching experiments. The pH of the leaching solution is the key factor affecting the mobility of these trace elements in these fly ashes. 相似文献
7.
Dong Quan Peter Moloney Declan Carolan Hisham Abourayana Calvin Ralph Alojz Ivankovic Denis Dowling Neal Murphy 《应用聚合物科学杂志》2021,138(1):49605
This work studied the effects of adding short basalt fibers (BFs) and multi-walled carbon nanotubes (MWCNTs), both separately and in combination, on the mechanical properties, fracture toughness, and electrical conductivity of an epoxy polymer. The surfaces of the short BFs were either treated using a silane coupling agent or further functionalized by atmospheric plasma to enhance the adhesion between the BFs and the epoxy. The results of a single fiber fragmentation test demonstrated a significantly improved BF/epoxy adhesion upon applying the plasma treatment to the BFs. This resulted in better mechanical properties and fracture toughness of the composites containing the plasma-activated BFs. The improved BF/epoxy adhesion also affected the hybrid toughening performance of the BFs and MWCNTs. In particular, synergistic toughening effects were observed when the plasma-activated BFs/MWCNTs hybrid modifiers were used, while only additive toughening effects occurred for the silane-sized BFs/MWCNTs hybrid modifiers. This work demonstrated a potential to develop strong, tough, and electrically conductive epoxy composites by adding hybrid BF/MWCNT modifiers. 相似文献
8.
John Strassner Sven van der Meer Declan O’Sullivan Simon Dobson 《Journal of Network and Systems Management》2009,17(3):255-284
The purpose of autonomic networking is to manage the business and technical complexity of networked components and systems.
However, existing network management data has no link to business concepts. This makes it very difficult to ensure that services
offered by the network are meeting business objectives. This paper describes a novel context-aware policy model that uses
a combination of modeled and ontological data to determine the current context, which policies are applicable to that context,
and what services and resources should be offered to which users and applications.
John Strassner is the director of autonomic research in the Telecommunications Systems & Software Group in Waterford Institute of Technology, and a Visiting Professor at POSTECH. His research interests are in autonomic systems, policy based management, machine learning, and semantic reasoning. He is the Chairman of the Autonomic Communications Forum, and the past chair of the TMF’s NGOSS SID, metamodel and policy working groups. He has authored two books, written chapters for five other books, and co-edited five journals on network and service management and autonomics. John is the recipient of the Daniel A. Stokesbury memorial award for excellence in network management, and has authored 211 refereed journal papers and publications. Sven van der Meer received his M.Sc in computer science and his Dr.-Ing. from Technical University Berlin (TUB), Germany, in 1996 and 2002. Since November 2002, Sven has been a research fellow at the Telecommunications Software & Systems Group at the Waterford Institute of Technology. Since October 2004 he is Senior Investigator of the Competence Centre for Communication Infrastructure Management at TSSG, involved in the Architecture and Information Modelling teams in the TMF, and has served as editor for Technological Neutral Architecture and Contracts specifications within the TM Forum. Declan O’Sullivan is the director of the Knowledge and Data Engineering (KDEG) research group in Trinity College Dublin (TCD). His research interests are in the use of semantic-driven approaches for network and service management, in particular to enable semantic interoperability. He is currently a Principal Investigator in the SFI funded research project investigating Federated Autonomic Management Environments (FAME). O’Sullivan has a Ph.D. and a M.Sc in computer science from TCD. Simon Dobson is a co-founder of the Systems Research Group at UCD Dublin. His research centers around adaptive pervasive computing and novel programming techniques. He is on the editorial boards of the Journal of Network and Systems Management and the International Journal of Autonomous and Adaptive Communications Systems, and participates in a number of EU strategic workshops and working groups. He is National Director and vice-president of the European Research Consortium for Informatics and Mathematics, a board member of the Autonomic Communication Forum, and a member of the IBEC/ICT Ireland standing committee on academic/industrial research and development. He holds a BSc and DPhil in computer science, is a Chartered Fellow of the British Computer Society, a Chartered Engineer, and member of the IEEE and ACM. 相似文献
Simon DobsonEmail: |
John Strassner is the director of autonomic research in the Telecommunications Systems & Software Group in Waterford Institute of Technology, and a Visiting Professor at POSTECH. His research interests are in autonomic systems, policy based management, machine learning, and semantic reasoning. He is the Chairman of the Autonomic Communications Forum, and the past chair of the TMF’s NGOSS SID, metamodel and policy working groups. He has authored two books, written chapters for five other books, and co-edited five journals on network and service management and autonomics. John is the recipient of the Daniel A. Stokesbury memorial award for excellence in network management, and has authored 211 refereed journal papers and publications. Sven van der Meer received his M.Sc in computer science and his Dr.-Ing. from Technical University Berlin (TUB), Germany, in 1996 and 2002. Since November 2002, Sven has been a research fellow at the Telecommunications Software & Systems Group at the Waterford Institute of Technology. Since October 2004 he is Senior Investigator of the Competence Centre for Communication Infrastructure Management at TSSG, involved in the Architecture and Information Modelling teams in the TMF, and has served as editor for Technological Neutral Architecture and Contracts specifications within the TM Forum. Declan O’Sullivan is the director of the Knowledge and Data Engineering (KDEG) research group in Trinity College Dublin (TCD). His research interests are in the use of semantic-driven approaches for network and service management, in particular to enable semantic interoperability. He is currently a Principal Investigator in the SFI funded research project investigating Federated Autonomic Management Environments (FAME). O’Sullivan has a Ph.D. and a M.Sc in computer science from TCD. Simon Dobson is a co-founder of the Systems Research Group at UCD Dublin. His research centers around adaptive pervasive computing and novel programming techniques. He is on the editorial boards of the Journal of Network and Systems Management and the International Journal of Autonomous and Adaptive Communications Systems, and participates in a number of EU strategic workshops and working groups. He is National Director and vice-president of the European Research Consortium for Informatics and Mathematics, a board member of the Autonomic Communication Forum, and a member of the IBEC/ICT Ireland standing committee on academic/industrial research and development. He holds a BSc and DPhil in computer science, is a Chartered Fellow of the British Computer Society, a Chartered Engineer, and member of the IEEE and ACM. 相似文献
9.
Enantioselective catalytic epoxidation of olefins is an important problem from both practical and mechanistic points of view. The origins of chiral induction by asymmetric porphyrin and salen complexes were investigated by FT-NMR T1 relaxation techniques. A new chiral vaulted porphyrin (1) that carries (S)-binaphthyl-L-alanine straps across both faces of the porphyrin macrocycle was synthesized and characterized. (R)-styrene oxide was obtained in > 90% ee in the initial stages of styrene epoxidation with F5PhIO catalyzed by 1-Fe(III)Cl. The transition state for olefin epoxidation with high-valent metal-oxo species was modeled by coordinating epoxides to paramagnetic copper complexes of the corresponding ligands. The epoxide enantiomer that better fit the chiral cavity of the catalyst, as revealed by T1 relaxation measurements, was also the major product of catalytic olefin epoxidation. These results are consistent with the "lock-and-key" mechanism of asymmetric catalysis by metalloporphyrins. The copper complex of a chiral salen ligand showed no differentiation in terms of T1 relaxation rates between the enantiomers of cis-beta-methylstyrene oxide in contrast to the high enantioselectivity observed for catalytic epoxidation. 相似文献
10.
Hardened ordinary Portland cement pastes of various ages have been examined by analytical transmission electron microscopy (TEM) and electron microprobe analysis (EMPA). The stability of the various hydrate phases in the electron microscope is discussed. Although all are subject to damage in varying degrees, even the least stable phase, AFt, can be recognized in relict form in the TEM. The basic framework of the microstructure and the differentiation into inner and outer hydration product are well-established at 24 h hydration. Although the dominant inner product formed within the boundaries of the original anhydrous grains is C-S-H gel, particles of AFt, AFm, Ca(OH)2, a magnesium-rich phase and an iron-rich phase are occasionally observed within the inner product. The CaSi ratio of the C-S-H gel determined by TEM shows significant variation from one region to another in a given paste. There is no relationship between the average CaSi ratio of the C-S-H and the maturity of the paste, although young pastes appear to show a bimodal distribution. Microanalysis by EMPA gives CaSi ratios in substantial agreement with those found by TEM but it is essentially impossible to obtain by EMPA analyses of outer product C-S-H without admixture of other phases, particularly sulphoaluminate phases. Despite the presence of small amounts of embedded phases as revealed by TEM, single-phase inner product C-S-H can be analysed by EMPA. The compositions of AFt and AFm phases have been obtained by TEM and the results do not require the substitution of silicon in the formulae. 相似文献