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991.
The CO + NO reaction is one of the profoundly important reactions that take place on Pd-based industrial three-way catalysts (TWC). In this review, we discuss results from polarization modulation infrared reflection absorption spectroscopy (PM-IRAS) and conventional IRAS experiments on CO adsorption, NO adsorption and the CO + NO reaction on a Pd(111) model catalyst surface within a wide range of pressures (10?6–450 Torr) and temperatures (80–650 K). It will be shown that these studies allow for a detailed understanding of the adsorption behavior of these species as well as the nature of the products that are formed during their reaction under realistic catalytic conditions. CO adsorption experiments on Pd(111) at elevated pressures reveal that CO overlayers exhibit similar adsorption structures as found for ultrahigh vacuum (UHV) conditions. On the other hand, in the case of the CO + NO reaction on Pd(111), the pressure dependent formation of isocyanate containing species' was observed. The importance of this observation and its effects on the improvement of the catalytic NO x abatement is discussed. The kinetics of the CO + NO reaction on Pd(111) were also investigated and the factors affecting its selectivity are addressed. 相似文献
992.
993.
994.
A computational framework of configurational-force-driven brittle fracture based on incremental energy minimization 总被引:1,自引:0,他引:1
A variational formulation of quasi-static brittle fracture in elastic solids at small strains is proposed and an associated
finite element implementation is presented. On the theoretical side, a consistent thermodynamic framework for brittle crack
propagation is outlined. It is shown that both the elastic equilibrium response as well as the local crack evolution follow
in a natural format by exploitation of a global Clausius–Planck inequality. Here, the canonical direction of the crack propagation
associated with the classical Griffith criterion is the direction of the material configurational force which maximizes the
local dissipation at the crack tip. On the numerical side, we first consider a standard finite element discretization in the
two-dimensional space which yields a discrete formulation of the global dissipation in terms of configurational nodal forces.
Next, consistent with the node-based setting, the discretization of the evolving crack discontinuity for two-dimensional problems
is performed by the doubling of critical nodes and interface segments of the mesh. A crucial step for the success of this
procedure is its embedding into a r-adaptive crack-segment re-orientation algorithm governed by configurational-force-based
directional indicators. Here, successive crack propagation is performed by a staggered loading-release algorithm of energy
minimization at frozen crack state followed by nodal releases at frozen deformation. We compare results obtained by the proposed
formulation with other crack propagation criteria. The computational method proposed is extremely robust and shows an excellent
performance for representative numerical simulations. 相似文献
995.
Kallahalla M. Uysal M. Swaminathan R. Lowell D.E. Wray M. Christian T. Edwards N. Dalton C.I. Gittler F. 《Computer》2004,37(11):38-46
Utility computing aims to aggregate server, network, and storage systems into a single, centrally managed pool of resources. SoftUDC, a virtual machine monitor, lets applications and administrative domains share physical resources while maintaining full functional isolation. 相似文献
996.
997.
KJ Stalder LL Christian MF Rothschild EC Lin 《Canadian Metallurgical Quarterly》1997,75(12):3114-3118
Differences between porcine stress syndrome (PSS) normal (NN) and carrier (Nn) Landrace dams were determined for adjusted number of pigs born alive, adjusted number of pigs at 21 d, adjusted 21-d litter weight, proportion of pigs surviving to 21 d, and farrowing interval. Data were analyzed from a total of 841 females, 623 normal (NN) and 218 carriers (Nn) having 2,231 and 869 records, respectively. Three susceptible (nn) females from two herds were dropped from the analysis because of their small contribution to the total number of records. Frequency of the recessive PSS allele ranged from .07 to .28 in the nine herds involved in this study. Data were adjusted using Landrace breed-specific adjustments and analyzed with mixed-model derivative-free REML procedures fitting the dams' PSS genotype as a fixed effect in the model. Only females having two or more successive parities were used in the analysis of farrowing interval, resulting in a reduction of total records analyzed to 2,201 (1,564 NN and 637 Nn records) from 632 females (445 NN and 187 Nn females). No differences between NN and Nn dams were observed for adjusted number of pigs born alive, adjusted number of pigs at 21 d, adjusted 21-d litter weight, proportion of pigs surviving to 21 d, and farrowing interval. The results of this investigation indicate no significant maternal performance differences between PSS NN or Nn Landrace dams. 相似文献
998.
The effects of co-administering polyanions on the pharmacokinetics of a 20-mer phosphorothioate oligodeoxynucleotide (CGP 69846A), and the role of scavenger receptors in its in vivo disposition, have been investigated. Following i.v. administration, CGP 69846A was rapidly cleared from the plasma and distributed amongst high (e.g. kidney, liver, spleen), low (e.g. skeletal muscle) and negligible (e.g. brain) accumulating tissues. In addition it was shown that: 1) dextran sulphate co-administration has a dose-dependent effect on the disposition of CGP 69846A; 2) CGP 69846A undergoes renal filtration and renal accumulation largely results from tubular reabsorption; 3) cross-inhibition studies are consistent with CGP 69846A being recognized by scavenger receptors in vitro and in vivo; and 4) the scavenger receptor may be an important determinant for the in vivo disposition of CGP 69846A in mice. These studies contribute toward an increased understanding of the mechanism underlying the pharmacokinetic behaviour of phosphorothioate oligodeoxynucleotides. 相似文献
999.
Among test techniques for analog circuits, DC test is one of the simplest method for BIST application since easy to integrate test pattern generator and response analyzer are conceivable. Precisely, this paper presents such an investigation for a CMOS operational amplifier that is latter extended to active analog filters. Since the computation of fault coverage is still a controversy question for analog cells, we develop first an evaluation technique for optimizing the tolerance band of the measurements to test. Then, using some DFT solutions we derive single DC pattern and discuss the minimal number of points to test for the detection of defects. A response analyzer is integrated with a Built-in Voltage Sensor (BIVS) and provides directly a logic pass/fail test result. Finally, the extra circuitry introduced by this BIST technique for analog modules does not exceed 5% of the total silicon area of the circuit under test and detects most of the faults. 相似文献
1000.
A competitive neural network model and a genetic algorithm are used to improve the initialization and construction phase of a parallel insertion heuristic for the vehicle routing problem with time windows. The neural network identifies seed customers that are distributed over the entire geographic area during the initialization phase, while the genetic algorithm finds good parameter settings in the route construction phase that follows. Computational results on a standard set of problems are also reported. 相似文献