Determination of water activities and osmotic and activity coefficients of the system NaCl–BaCl2–H2O at 298.15 K

The water activities of the mixed aqueous electrolyte NaCl–BaCl₂(aq) are measured at total molalities from 0.25 mol kg⁻¹ to about saturation for different ionic strength fractions (y) of NaCl with y=0.33,0.50,0.67. The results allow the deduction of osmotic coefficients. The experimental results are compared with the predictions of the Zdanovskii, Stokes, and Robinson (ZSR), Kusik and Meissner (KM), Robinson and Stokes (RS), Lietzke and Stoughton (LSII), Reilly, Wood, and Robinson (RWR), and Pitzer models. From these measurements, the Pitzer mixing ionic parameters are determined and used to predict the solute activity coefficients in the mixture. The excess Gibbs energy is also determined.     

Polyurethane foams with 1,3‐pyrimidine ring

Attempts of obtaining of polyurethane foams using polyetherols with 1,3‐pyrimidine ring (obtained in reactions of 6‐aminouracil with oxiranes) are reported. Properties of the foams are investigated, especially their thermal stability. The foams show an improved thermal stability up to 200°C for a long time. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Potentiometric studies of oxidation–reduction reactions with redox copolymers

Polymeric oxidants in the bead form that were macroporous styrene/divinylbenzene copolymers containing N‐chlorosulfonamide functional groups (in sodium or hydrogen form) or N‐bromosulfonamide groups (in sodium form) were synthesized and investigated to determine their oxidizing powers. The redox potentials of the N‐chlorosulfonamide/sulfonamide and N‐bromosulfonamide/sulfonamide systems were determined by potentiometric studies at different pH values with aqueous solutions of Na₂SO₃, KCN, and KSCN as reducers. The formal redox potentials of the N‐chlorosulfonamide copolymers were 0.79, 0.44, and ?0.12 V at pH's of 1.8, 8.45, and 13.6, respectively. The formal redox potential of the N‐bromosulfonamide copolymer was about 100 mV higher in comparable conditions and in solutions over pH = 5 (e.g., 0.56 V at pH = 8.56). The comparatively higher oxidizing power of the N‐bromosulfonamide copolymer was particularly evident in a strong alkaline medium (in which the N‐chlorosulfonamide copolymer was not reactive). In contrast, the N‐chlorosulfonamide copolymer showed strong oxidative properties in acidic media (in which the N‐bromosulfonamide copolymer decomposed itself). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Quantification of ageing of ultracapacitors during cycling tests with current profile characteristics of hybrid and electric vehicles applications

The ageing quantification of ultracapacitors in cycle-life tests has been studied. Current profiles and the characteristics of the ultracapacitors used in hybrid and electric vehicle applications are specified and validated. With these profiles, significant self-heating occurs but without exceeding the manufacturers' limits. Thus, ultracapacitors are aged in a short time with the same degradation mechanisms observed in normal use. Ageing evaluation is based on the measurement of the electrical parameter changes. A particular phenomenon is performance recovery during rest periods when power-cycling is interrupted for electrical characterisation. Therefore, an online characterisation procedure was added for more accurate evaluation of the ultracapacitors' ageing. A number of devices from two manufacturers are cycled with different current profiles. The obtained results are presented and discussed.     

Traffic classification and scheduling in ATM networks

Virtual paths (VPs) are an integral part of the resource management and control hierarchy of ATM (asynchronous transfer mode) networks. To improve the utilization of network resources and facilitate management and control, source types are organized into traffic classes. Each traffic class is transported by its own virtual path subnetwork. In this paper, we consider issues related to the design of traffic classes. We consider an ATM switch node to which cells arrive from a diverse set of source types. Traffic classes are assumed to be served according to a weighted round robin policy, while cells belonging to a given traffic class are served in first-come-first-served order. We consider the problem of determining the optimal set of traffic classes. Under suitable simplifying assumptions, it is shown that the above problem can be modeled as a set-partitioning problem. The structure of the problem at hand is then exploited to develop an efficient heuristic. Several examples are given to illustrate the developed methodology.Supported partially through NSF Grant NCR-891447 and AT&T Grant 5-23690.