This paper determines the optimal location of K connections in the plane, where a connection links pairs of existing facilities. Both uncapacitated and capacitated versions
of the problem are considered. Discretization results for general polyhedral gauges and other properties are established.
Two heuristic algorithms are developed for each case using the concept of a shortest path flow set coupled with a sequential
location and allocation approach. Computational results show that the algorithms are efficient and accurate. 相似文献
The physicochemical, surface and catalytic properties of pure and doped 0.25CuO-NiO solids prepared by sol-gel method were investigated. The dopant concentration was 2, 4 and 6 mol% ZrO2. The solids investigated were calcined at 400 and 600 °C. The techniques employed were XRD, EDX, TEM, surface excess oxygen, nitrogen adsorption at −196 °C and catalytic oxidation of CO by O2 using both static and flow methods. The results revealed that the investigated system dissolved 4 mol% ZrO2 by heating at 400 °C. This process was accompanied by a significant increase in the SBET and Vp with subsequent decrease in the (r) values of the doped adsorbent. ZrO2-doping of the system investigated followed by calcination at 400 and 600 °C led to a considerable increase in its catalytic activity in CO oxidation by O2 using static and flow methods. The doping process was not accompanied by any change in the activation energy of the catalyzed reaction. 相似文献
Summary A bivariate inverse Gaussian (IG) density function is constructed. Relations of the bivariate IG distribution to the normal
and χ2 distributions are established. The corresponding bivariate random walk (RW) density function is obtained. The properties
and behaviour of bivariate IG distribution are studied for large parametric values. Moment estimates of the five parameters
are given and applications are pointed out. A generalization to the multivariate IG distribution is proposed. 相似文献
The solid–solid interactions between pure and alumina-doped cobalt and ferric oxides have been investigated using DTA, IR and XRD techniques. Equimolar proportions of basic cobalt carbonate and ferric oxide and different amounts of aluminum nitrate were added as dopant substrate. The amounts of dopant were 0.75, 1.5, 3.0 and 4.5 mol% Al2O3.
The results obtained revealed that solid–solid interaction between Fe2O3 and Co3O4 takes place at temperatures starting from 700°C to produce cobalt ferrite. The degree of propagation of this reaction increases progressively as a function of precalcination temperature and Al2O3-doping of the reacting solids. However, the heating of pure mixed solids at 1000°C for 6 h. was not sufficient to effect the complete conversion of the reacting solids into CoFe2O4, while the addition of a small amount of Al2O3 (1.5 mol%) to ferric/cobalt mixed solids followed by precalcination at 1000°C for 6 h conducted the complete conversion of the reacting solids into cobalt ferrite. The heat treatment of pure and the 0.75 mol%-doped solids at 900 and 1000°C effected the disappearance of most of IR transmission bands of the free oxides with subsequent appearance of new bands characteristic for the CoFe2O4 structure. An increase in the amount of Al2O3 added from 1.5–4.5 mol% to the mixed solids precalcined at 1000°C led to the disappearance of all bands of free oxides and appearance of all bands of cobalt ferrite. The promotion effect of Al2O3 in cobalt ferrite formation was attributed to an effective increase in the mobility of the various reacting cations. The activation energy of formation (ΔE) of CoFe2O4 phase was determined for pure and doped solids. The computed values of ΔE were, respectively, 99.6, 87.8, 71.9, 64.7 and 48.7 kJ mol−1 for the pure solid and those treated with 0.75, 1.5, 3 and 4.5 mol% Al2O3. 相似文献
Upon CA, ESI generated [M + H]+ ions of chalcone (benzalacetophenone) and 3-phenyl-indanone both undergo losses of H2O, CO, and the elements of benzene. CA of the [M + H]+ ions of 2-methoxy and 2-hydroxychalcone, however, prompts instead a dominant loss of ketene. In addition, CA of the [M +
H]+ ions of 2-methoxy-β-methylchalcone produces an analogous loss of methylketene instead. Furthermore, the [M + D]+ ion of 2-methoxychalcone upon CA eliminates only unlabeled ketene, and the resultant product, the [M + D − ketene]+ ion, yields only the benzyl-d1 cation upon CA. We propose that the 2-methoxy and 2-hydroxy (ortho) substituents facilitate a Nazarov cyclization to the corresponding protonated 3-aryl-indanones by mediating a critical proton
transfer. The resultant protonated indanones then undergo a second proton transport catalysis facilitated by the same ortho substituents producing intermediates that eliminate ketene to yield 2-methoxy- or 2-hydroxyphenyl-phenyl-methylcarbocations,
respectively. The basicity of the ortho substituent is important; for example, replacement of the ortho function with a chloro substituent does not provide an efficient catalyst for the proton transports. The Nazarov cyclization
must compete with an alternate cyclization, driven by the protonated carbonyl group of the chalcone that results in losses
of H2O and CO. The assisted proton transfer mediated by the ortho substituent shifts the competition in favor of the Nazarov cyclization. The proposed mechanisms for cyclization and fragmentation
are supported by high-mass resolving power data, tandem mass spectra, deuterium labeling, and molecular orbital calculations. 相似文献
This paper addresses the problem of short-term supply chain design using the idle capacities of qualified partners in order to seize a new market opportunity. The new market opportunity is characterized by a deterministic forecast over a planning horizon. The production–distribution process is assumed to be organized in stages or echelons, and each echelon may have several qualified partners willing to participate. Partners within the echelon may differ in idle production capacity, operational cost, storage cost, etc, and we assume that idle capacity may be different from one period to another period. The objective is to design a supply chain by selecting one partner from each echelon to meet the forecasted demand without backlog and best possible production and logistics costs over the given planning horizon. The overall problem is formulated as a large mixed integer linear programming problem. We develop a decomposition-based solution approach that is capable of overcoming the complexity and dimensionality associated with the problem. Numerical results are presented to support the effectiveness of this approach. 相似文献