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201.
Abilio Fernandes Angelo E. M. Ciarlini Antonio L. Furtado Michael G. Hinchey Marco A. Casanova Karin K. Breitman 《Innovations in Systems and Software Engineering》2007,3(4):291-302
Workflow management systems usually interpret a workflow definition rigidly. However, there are real life situations where
users should be allowed to deviate from the prescribed static workflow definition for various reasons, including lack of information,
unavailability of the required resources and unanticipated situations. Furthermore, workflow complexity may grow exponentially
if all possible combinations of anticipated scenarios must be compiled into the workflow definition. To flexibilize workflow
execution and help reduce workflow complexity, this paper proposes a dual strategy that combines a library of predefined typical
workflows with a planner mechanism capable of incrementally synthesizing new workflows, at execution time. This dual strategy
is motivated by the difficulty of designing emergency plans, modeled as workflows, which account for real-life complex crisis
or accident scenarios. 相似文献
202.
Marcus Vinícius C. Alves Jader R. Barbosa Alvaro T. Prata 《International Journal of Refrigeration》2013,36(7):1905-1915
A model is presented for calculating the volume flow rate in an eccentric-tube centrifugal oil pump for reciprocating compressors. The oil pump assembly consists of a pick-up tube with an inclined inlet that is mounted off-center with the crankshaft symmetry axis. The pick-up tube is connected to the shaft channel, a helical groove machined on the crankshaft that facilitates the supply of lubricant to the bearings. The analytical models for the pick-up tube and shaft channel were developed independently and were coupled via a numerical procedure to determine the steady-state volume flow rate in the assembly. The steady-state results were verified against a CFD model, which was also used to evaluate the fluid flow in the oil pump assembly during a start-up transient. A parametric analysis was conducted to quantify the influence of some oil pump geometric parameters, such as the pick-up tube diameter and the shaft eccentricity. 相似文献
203.
Relations between microstructure, phase transformations and creep resistance of austenitic Fe–Ni–Cr alloys are investigated. As-cast alloys with different silicon contents and an ex-service tube are submitted to laboratory agings to trigger specific phase transformations, and subsequently creep-tested at 950°C under stresses of 24–48?MPa. As-cast microstructures contain interdendritic chromium-rich M7C3 carbides with niobium-rich MC carbides. After aging at 950°C, primary M7C3 carbides transform into chromium-rich M23C6 carbides, associated to a loss in creep strength. The G phase present in the ex-service alloy is reversed into MC carbides by a heat treatment at 1100°C, associated to a slight decrease in creep resistance. Besides, the addition of silicon is highly detrimental to creep strength. Results can be used for alloy design. 相似文献
204.
Vieira HS Andrada DM Mendonça R Santos AP Martins MD Macedo WA Gorgulho HF Pimenta LP Moreira RL Jorio A Pimenta MA Furtado CA 《Journal of nanoscience and nanotechnology》2007,7(10):3421-3430
A classical protocol widely used in organic chemistry of aromatic and polyaromatic molecules has been successfully applied in this work for the decarboxylation of oxidized single-wall carbon nanotube (SWNT) to rend C-H SWNT derivatives. SWNT produced by arc discharge method have been oxidized during a purification process using strongly oxidant agents, such as hydrogen peroxide and nitric acid. The decarboxylation of oxidized SWNT has been conduced with copper(I) oxide in a 50:50 solution of N-methylpyrrolidone and quinoline. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and acid-base potentiometric titration analyses were carried out to characterize quali and quantitatively the changes in the chemical environment on the SWNT surface in each step of the purification and the decarboxylation process. Those techniques showed the appearance of mainly carboxylic and phenolic groups after the purification process and the disappearance of the carboxylic groups after the decarboxylation reaction. Fourier transform infrared spectroscopy analysis indicated also the formation of aliphatic and aromatic C-H groups. X-ray photoelectron spectroscopy and potentiometric titration results determined an efficiency higher than 90% for our decarboxylation procedure. The purity and structural quality of the SWNT sample used in the decarboxylation process were evaluated by thermogravimetry and Raman spectroscopy. Thermogravimetric analysis identified a purified sample with approximately 80 wt% of SWNT, in fractions distributed in highly structured SWNTs (25 wt%), with distribution in composition, length and structural quality (35 wt%) and with very defective and short tubes (25 wt%). The damages on the purified SWNT walls were characterized by the Raman scattering analysis. 相似文献
205.
206.
The aim of this work was to develop a stable injectable formulation of the antimalarial drug halofantrine (Hf) based on nanocapsules (NC) prepared from biodegradable polymers with Miglyol 810N as the oily core. Poly(D,L-lactide) PLA and its copolymers with poly(ethyleneglycol) (PLA-PEG) were used together with the surfactants poloxamer 188 and lecithin to yield NC with different surface properties. Highly efficient loading of the free base form of Hf was obtained; zeta potential measurements indicated that a part of the associated Hf was at the NC surface, interacting with the lecithin. NC were 150-250 nm in diameter and more stable on storage than nanoemulsions formed from oil and lecithin without polymer. The most stable NC, showing minimal size changes and flocculation, were those with a high density of 20-kDa PEG chains covalently grafted at the surface. Hf release from NC occurred mainly by partition with the external medium. In PBS, even when Tween 80 was added, release was limited to 20% of the total content, whatever the formulation. Addition of serum to the medium allowed complete and rapid release from PLA NC stabilized with adsorbed poloxamer 188, because of the high affinity of Hf for lipoproteins. However, the presence of covalently grafted PEG chains at the surface limited release by providing a hydrophilic steric barrier at the particle surface. A dense coverage with long PEG chains provided the best reduction of release. Such systems could constitute a long-circulating intravenous formulation of Hf for treating severe malaria. 相似文献
207.
208.