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71.
Queueing networks with negative customers (G-networks), Poisson flow of positive customers, multi-server exponential nodes, and dependent service at the different nodes are studied. Every customer arriving at the network is defined by a set of random parameters: customer route, the length of customer route, customer volume and his service time at each route stage as well. A killed positive customer is removed at the last place in the queue and quits the network just after his remaining service time will be elaborated. For such G-networks, the multidimensional stationary distribution of the network state probabilities is shown to be representable in product form. 相似文献
72.
Abstract In this paper we prove that a linear system of plane curves of degree d with n points of multiplicity m always has the expected dimension when n is a perfect square. We also prove some results on the dimension of the linear system when n is close to a perfect square.
Keywords: Interpolation, Nagata, Linear systems, Plane curves
Mathematics Subject Classification (2000): 14J26, 14N05 相似文献
73.
Formation of integrally skinned asymmetric polysulfone gas separation membranes by supercritical CO2
Alondra Torres-Trueba F. Alberto Ruiz-Trevio Gabriel Luna-Brcenas Ciro H. Ortiz-Estrada 《Journal of membrane science》2008,320(1-2):431-435
Integrally skinned asymmetric polysulfone membranes were prepared from originally dense films inducing asymmetry by the formation of the porous layer adding to one side of the membranes chloroform and supercritical CO2 (SCCO2), and then allowing the SCCO2 expansion to occur. The influence of the chloroform/polysulfone mass ratio (g CH3Cl/g PSF), SCCO2 density and depressurization rate over the thickness of both the porous and the dense skin layers, the morphology of the porous support and the pure O2 and N2 permeability and selectivity performance were studied.The results show that it is possible to induce a very-controlled asymmetry in a dense film following the procedure described in this work and as expected, the thickness of the porous layer increases while the dense skin layer decreases as the chloroform/polysulfone mass ratio increases. Images of the porous layer show that the average-pore size decreases at high SCCO2 densities and slightly decreases with increasing the CO2 depressurization rates. The O2 and N2 permeability coefficients, measured at 35 °C and 2 bar, for the polysulfone asymmetric membranes are practically the same of those determined in dense films, suggesting that the dense skins are essentially defect-free of pinholes. 相似文献
74.
Lorenzo De Napoli Luciano Mayol Simonetta Bartolucci Gennaro Piccialli Mos Rossi Ciro Santacroce 《Journal of heterocyclic chemistry》1988,25(3):1039-1042
The paper reports the synthesis and physico-chemical data of eight new pyrimidine nucleosides C-4 substituted and two imidazo[1,2-c]pyrimidine nucleosides as well as preliminary results of their biological effects on neuroblastoma cells in culture. 相似文献
75.
We describe representation theorems for local and perfect MV-algebras in terms of ultraproducts involving the unit interval
[0, 1]. Furthermore, we give a representation of local Abelian ℓ-groups with strong unit as quasi-constant functions on an ultraproduct of the reals. All the above theorems are proved to
have a uniform version, depending only on the cardinality of the algebra to be embedded, as well as a definable construction
in ZFC. 相似文献
76.
77.
78.
Flagellar sensilla of Quadraspidiotus perniciosus Comstock (Rhynchota: Diaspididae) male 总被引:1,自引:0,他引:1
The flagellar sensory structures of Quadraspidiotus perniciosus Comstock (Rhynchota: Diaspididae) male have been investigated, using scanning and transmission electron microscopy. Five categories of sensilla have been identified: three types of sensilla trichodea, a sensillum coeloconicum and a sensillum basiconicum. The possible function of sensilla is discussed, considering their location, morphology and ultrastructure. No gustatory sensilla have been detected. All the setae (sensilla trichodea) present on the flagellomeres, except for the three 'knobbed' ones that are mechanosensilla, are cuticular components of olfactory structures. These olfactory sensilla are of two distinct types, having fluted or smooth hairs; furthermore, the fluted ones present different typologies for a varied number of dendrites. They are conceivably used for perceiving female sexual pheromone. It might be that each of the different components of the female sexual pheromone is perceived by a specific sensillum. Two types of supposed thermo-hygroreceptors have been found, one sensillum coeloconicum and two sensilla basiconica. 相似文献
79.
In this paper we give the full classification of surfaces X such that the family of lines contained in a (k+1)-secant
to X has dimension smaller than the expected. 相似文献
80.
Nicholas D. Chiappini James B. C. Mack Prof. J. Du Bois 《Angewandte Chemie (International ed. in English)》2018,57(18):4956-4959
A general and operationally convenient method for intermolecular amination of C(sp3)?H bonds is described. This technology allows for efficient functionalization of complex molecules, including numerous pharmaceutical targets. The combination of pivalonitrile as a solvent, Al2O3 as an additive, and phenyl sulfamate as a nitrogen source affords differential reaction performance and substrate scope. Mechanistic data strongly implicate a pathway for catalyst decomposition that initiates with solvent oxidation, thus providing rationale for the marked influence of pivalonitrile on this reaction process. 相似文献