bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic shortest paths minimizing travel times and costs
Authors: Ahuja Ravindra K. , Orlin James B. , Pallottino Stefano , Scutellà Maria G. 
Published: June 2003

AbstractIn this paper, we study dynamic shortest path problems that determine a shortest path from a specified source node to every other node in the network where arc travel times change dynamically. We consider two problems: the minimum‐time walk problem and the minimum‐cost walk problem. The minimum‐time walk problem is to find a walk with the minimum travel time. The minimum‐cost walk problem is to find a walk with the minimum weighted sum of the travel time and the excess travel time (over the minimum possible travel time). The minimum‐time walk problem is known to be polynomially solvable for a class of networks called FIFO networks. In this paper, (i) we show that the minimum‐cost walk problem is an NP‐hard problem; (ii) we develop a pseudopolynomial‐time algorithm to solve the minimum‐cost walk problem (for integer travel times); and (iii) we develop a polynomial‐time algorithm for the minimum‐time walk problem arising in road networks with traffic lights. © 2003 Wiley Periodicals, Inc.
A bicriterion approach for routing problems in multimedia networks
Authors: Clímaco João C. N. , Craveirinha José M. F. , Pascoal Marta M. B. 
Published: June 2003

AbstractRouting problems in communication networks supporting multiple services, namely, multimedia applications, involve the selection of paths satisfying multiple constraints (of a technical nature) and seeking simultaneously to “optimize” the associated metrics. Although traditional models in this area are single‐objective, in many situations, it is important to consider different, eventually conflicting, objectives. In this paper, we consider a bicriterion model dedicated to calculating nondominated paths for specific traffic flows (associated with video services) in multiservice high‐speed networks. The mathematical formulation of the problem and the bicriterion algorithmic approach developed for its resolution are presented together with computational tests regarding an application to video‐traffic routing in a high‐speed network. The algorithmic approach is an adaptation of recent work by Ernesto Martins and his collaborators, namely, the MPS algorithm. © 2003 Wiley Periodicals, Inc.
Upper bounds for single‐source uncapacitated concave minimum‐cost network flow problems
Authors: Fontes Dalila B. M. M. , Hadjiconstantinou Eleni , Christofides Nicos 
Published: June 2003

AbstractIn this paper, we describe a heuristic algorithm based on local search for the Single‐Source Uncapacitated (SSU) concave Minimum‐Cost Network Flow Problem (MCNFP). We present a new technique for creating different and informed initial solutions to restart the local search, thereby improving the quality of the resulting feasible solutions (upper bounds). Computational results on different classes of test problems indicate the effectiveness of the proposed method in generating basic feasible solutions for the SSU concave MCNFP very near to a global optimum. A maximum upper bound percentage error of 0.07% is reported for all problem instances for which an optimal solution has been found by a branch‐and‐bound method. © 2003 Wiley Periodicals, Inc.
The determination of the path with minimum‐cost norm value
Authors: Paixão José M. P. , de Queirós Vieira Martins Ernesto , Rosa Mário S. , Santos José Luis E. 
Published: June 2003

AbstractThe multiobjective shortest path problem (MSPP) consists of finding the best nondominated path linking two specified nodes in a network where k > 1 different criteria are considered for the arc costs. Solving the MSPP implies determining all the nondominated paths; there may be many such paths, making the selection process a very hard task to accomplish. A traditional way of dealing with such a difficulty is using a utility function where the parameters are aggregated with different weights. In this work, an alternative utility function based on the norm value associated with each path is considered. Two algorithms for solving the minimum‐cost norm path problem are then proposed and some computational results are presented. © 2003 Wiley Periodicals, Inc.
Incentives for pollution abatement: Regulation, regulatory threats, and non‐governmental pressures
Authors: Harrison Kathryn , Antweiler Werner 
Published: June 2003

AbstractIn the last decade, voluntary efforts by firms to reduce their environmental impacts have received increasing
attention from both policymakers and scholars. This article discusses polluters' incentives to reduce their
releases. In particular, using data from Canada's National Pollutant Release Inventory, it examines the
impacts of conventional regulation, threats of regulation, and non‐governmental pressures facilitated by
public dissemination of information about pollutant releases. The vast majority of reductions reported to the
inventory to date were found not to be voluntary, as has often been assumed, but are, rather, the result of
direct regulation of a relatively small number of polluters. Strong effects of federal regulation were found
among other sources, as well, with much weaker responses to the mere threat of regulation. However, of concern
are the growth of less visible waste streams—such as land disposal and underground injection—as well
as transfers of wastes to other communities. Finally, evidence is reported that some waste streams are
increasing in toxicity, an effect that may outweigh the benefits of reductions in releases. © 2003 by the
Association for Public Policy Analysis and Management.
Community environmental policing: Assessing new strategies of public participation in environmental regulation
Authors: O'Rourke Dara , Macey Gregg P. 
Published: June 2003

AbstractThis paper evaluates a new form of public participation in environmental monitoring and regulation advanced
through local “bucket brigades,” which allow community members to sample air emissions near
industrial facilities. These brigades represent a new form of community environmental policing, in which
residents participate in collecting, analyzing, and deploying environmental information, and more importantly,
in an array of public policy dialogues. Use of this sampling technology has had marked effects on local
residents' perceptions and participation in emergency response and citizens'
right‐to‐know. However, when viewed through the lens of the more developed literature on community
policing, the bucket brigades are currently limited in their ability to encourage
“co‐production” of environmental protection between citizens and the state. Means are
examined to strengthen the bucket brigades and to more broadly support community participation in environmental
regulation. © 2003 by the Association for Public Policy Analysis and Management.
Public transit and the spatial distribution of minority employment: Evidence from a natural experiment
Authors: Holzer Harry J. , Quigley John M. , Raphael Steven 
Published: June 2003

AbstractA recent expansion of the San Francisco Bay Area's heavy rail system represents an exogenous change in
the accessibility of inner‐city minority communities to a concentrated suburban employment center. We
evaluate this natural experiment by conducting a two‐wave longitudinal survey of firms, with the first
wave of interviews conducted immediately before the opening of service, and the second wave approximately a year
later. Within‐firm changes in the propensity to hire minority workers for firms near the station were
compared with those located farther away. Also estimated was the effect of employer distance to the new stations
on changes in propensity to hire minorities. Results indicate a sizable increase in the hiring of Latinos near
the new stations, but little evidence of an effect on black hiring rates. © 2003 by the Association for
Public Policy Analysis and Management.
Do child care regulations affect the child care and labor markets?
Authors: Blau David M. 
Published: June 2003

AbstractThe effect of child care regulations on outcomes in the child care market and the labor market for mothers of
young children is examined. The analysis uses a time series of cross sections and examines the robustness of
previous cross‐section findings to controls for state‐level heterogeneity. Child care regulations
as a group have statistically significant effects on most outcomes, with or without state fixed effects.
However, regulations do not vary enough within state over time to allow precise identification of most
individual regulation effects. The great majority of estimated regulation effects in all specifications are
small and insignificantly different from 0. Some of the estimated effects seem reasonable in sign and magnitude,
but others are clearly implausible. © 2003 by the Association for Public Policy Analysis and
Management.
Shape and diffusion of the monomer‐controlled copolymerization of ethylene and α‐olefins over Cp2ZrCl2 confined in the nanospace of the supercage of NaY
Authors: Ko Young Soo , Woo Seong Ihl 
Published: June 2003

AbstractCp2ZrCl2 confined inside the supercage of NaY zeolites [NaY/methylaluminoxane (MAO)/Cp2ZrCl2] exhibited the shape and diffusion of a monomer‐controlled copolymerization mechanism that strongly depended on the molecular structure of the monomer and its size. For the ethylene–propylene copolymerization, NaY/MAO/Cp2ZrCl2 showed the effect of the comonomer on the increase in the polymerization rate in the presence of propylene, whereas the ethylene/1‐hexene copolymerization showed little comonomer effect, and the ethylene/1‐octene copolymerization instead showed a comonomer depression effect on the polymerization rate. Isobutylene, having a larger kinetic diameter, had little influence on the copolymerization behaviors with NaY/MAO/Cp2ZrCl2 for the ethylene–isobutylene copolymerization, which showed evidence of the shape and diffusion of a monomer‐controlled mechanism. The content of the comonomer in the copolymer chain prepared with NaY/MAO/Cp2ZrCl2 decreased by about one‐half in comparison with that of Cp2ZrCl2. A differential scanning calorimetry study on the melting endotherms after the successive annealing of the copolymers showed that the copolymers of NaY/MAO/Cp2ZrCl2 had narrow comonomer distributions, whereas those of homogeneous Cp2ZrCl2 were broad. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2171–2179, 2003
Synthesis and copolymerization of new phosphorus‐containing acrylates
Authors: Avci Duygu , Albayrak Aylin Ziylan 
Published: June 2003

AbstractTwo phosphorus‐containing acrylate monomers were synthesized from the reaction of ethyl α‐chloromethyl acrylate and t‐butyl α‐bromomethyl acrylate with triethyl phosphite. The selective hydrolysis of the ethyl ester monomer with trimethylsilyl bromide (TMSBr) gave a phosphonic acid monomer. The attempted bulk polymerizations of the monomers at 57–60 °C with 2,2′‐azobisisobutyronitrile (AIBN) were unsuccessful; however, the monomers were copolymerized with methyl methacrylate (MMA) in bulk at 60 °C with AIBN. The resulting copolymers produced chars on burning, showing potential as flame‐retardant materials. Additionally, α‐(chloromethyl)acryloyl chloride (CMAC) was reacted with diethyl (hydroxymethyl)phosphonate to obtain a new monomer with identical ester and ether moieties. This monomer was hydrolyzed with TMSBr, homopolymerized, and copolymerized with MMA. The thermal stabilities of the copolymers increased with increasing amounts of the phosphonate monomer in the copolymers. A new route to highly reactive phosphorus‐containing acrylate monomers was developed. A new derivative of CMAC with mixed ester and ether groups was synthesized by substitution, first with diethyl (hydroxymethyl)phosphonate and then with sodium acetate. This monomer showed the highest reactivity and gave a crosslinked polymer. The incorporation of an ester group increased the rate of polymerization. The relative reactivities of the synthesized monomers in photopolymerizations were determined and compared with those of the other phosphorous‐containing acrylate monomers. Changing the monomer structure allowed control of the polymerization reactivity so that new phosphorus‐containing polymers with desirable properties could be obtained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2207–2217, 2003
Coarse‐grained models and collective phenomena in membranes: Computer simulation of membrane fusion
Authors: Müller M. , Katsov K. , Schick M. 
Published: June 2003

AbstractWe discuss the role coarse‐grained models play in investigating collective phenomena in bilayer membranes and place them in the context of alternative approaches. By reducing the degrees of freedom and applying simple effective potentials, coarse‐grained models can address the large time scales and length scales of collective phenomena in membranes. Although the mapping from a coarse‐grained model onto chemically realistic models is a challenge, such models provide a direct view on the phenomena that occur on the length scales of a few tens of nanometers. Their relevance is exemplified by the study of fusion of model membranes. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1441–1450, 2003
Utilization of prompt‐γ neutron activation analysis in the evaluation of Nafion membranes
Authors: Young Sandra K. , Trevino Samuel F. , Tan Nora C. Beck , Paul Rick L. 
Published: June 2003

AbstractResearchers have performed evaluations on Nafion membranes for many years. An important aspect of the membranes is their chemical composition and uniformity. One technique that could provide accurate and fast quantitative measurements of the chemical composition and water within the membranes is prompt‐γ neutron activation analysis (PGAA). In this work, PGAA was applied to the chemical characterization of Nafion membranes in various forms. The evaluation confirmed the necessity of pretreatment of the membranes for the elimination of contamination. A series of counterion‐exchanged membranes were examined so that we could determine the degree of conversion achieved under different conditions and residual water levels. The results indicated that the type of counterion was an important factor determining conversion levels, that partial conversion could be achieved, and that counterion displacement could be forced to occur in certain environments. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1485–1492, 2003
Positron annihilation and differential scanning calorimetry studies of polyacrylamide and poly(dimethylacrylamide)/poly(ethylene glycol) blends
Authors: Ribeiro E Silva M. E. S. , Machado J. Caetano , Mano V. , Silva G. Goulart 
Published: June 2003

AbstractPositron annihilation lifetime spectroscopy and differential scanning calorimetry (DSC) measurements were performed for blends of polyacrylamide (PAM) and poly(ethylene glycol) (PEG) and blends of poly(dimethylacrylamide) (PDMAM) and PEG. The samples were prepared by codissolution in a concentration range of 0–100 wt % PEG. The thermal behavior, characterized by DSC measurements, showed similar variations of the glass‐transition temperatures (Tg's) with the PEG concentration for the two systems. Pure PAM and PDMAM presented Tg's of 188 and 111 °C, respectively. A relatively small and nearly linearly decreasing Tg was observed for the two systems in the range of 20–80 wt % PEG. PEG crystals were present in all blend compositions, and no melting point depression was observed. The thermal results pointed to the partial miscibility of the blends. The degree of crystallinity of PEG increased with increasing PEG concentration for the PDMAM/PEG systems. The ortho‐positronium lifetime (τ3) increased with increasing PEG concentration for both blends. However, the parameter of the ortho‐positronium formation probability (I3) decreased with the PEG concentration. The product τI3, which was proportional to the total free volume fraction, was approximately constant with the PEG concentration for PDMAM blends and increased with the PEG concentration for PAM systems. This result may be interpreted as a consequence of a more heterogeneous structure in PAM blends. Scanning electron microscopy micrographs of blends with 40 and 80 wt % PEG provided evidence of the regions associated with PEG crystallites. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1493–1500, 2003
Melt‐processable blends of ionic poly(p‐phenylene terephthalamide) and poly(4‐vinylpyridine): Relaxation behavior
Authors: Chen W. C. , Sauer J. A. , Hara M. 
Published: June 2003

AbstractMelt‐processable blends were prepared from rigid molecules of an ionically modified poly(p‐phenylene terephthalamide) (PPTA) and flexible‐coil molecules of poly(4‐vinylpyridine) (PVP). Dynamic mechanical analyses of blends with 50% or more of the ionic PPTA component revealed the presence of two distinct phases. The glass‐transition temperature of the more stable, ionic PPTA‐rich phase increased linearly with the ionic PPTA content. The second phase present in these blends was an ionic PPTA‐poor, or a PVP‐rich, phase. For this phase, a reasonably good fit of the data, showing the glass‐transition temperature as a function of the ionic PPTA content, was achieved between the results of this study and the reported results of previous investigation of molecular composites of the same two components with ionic PPTA contents of 15 wt % or less. The possible influence of annealing on the blend structure of a 90/10 blend of ionic PPTA and PVP was examined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1468–1475, 2003
Numerical and experimental analysis of the plasma in the synthesis of polyaniline
Authors: Olayo M. G. , Morales J. , Cruz G. J. , Barocio S. R. , Olayo R. 
Published: June 2003

AbstractA numerical and experimental study of the plasma variables in the synthesis of polyaniline in radio‐frequency (RF) glow discharges is presented. The plasma variables were measured on the basis of data collected by electrostatic Langmuir probes placed along the reactor. The results showed the distribution of the electric potential and the electronic energy and density during the polymerization reactions. The region with the lowest energy was the zone adjoining the grounded electrode, whereas the maximum energy was located near the RF electrode. In the second zone, the energy was around twice that of the grounded zone, and both were beyond the typical atomic bonding energy found in most organic polymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1501–1508, 2003
Properties of epoxy networks derived from the reaction of diglycidyl ether of bisphenol A with polyhedral oligomeric silsesquioxanes bearing OH‐functionalized organic substituents
Authors: Pellice S. A. , Fasce D. P. , Williams R. J. J. 
Published: June 2003

AbstractA polyhedral oligomeric silsesquioxane (POSS), consisting mainly of a mixture of octahedra, nonahedra, and decahedra with bulky and flexible organic substituents, with three secondary hydroxyls per organic group, was used to modify epoxy networks produced by the homopolymerization of diglycidyl ether of bisphenol A in the presence of benzyldimethylamine. Several physical, thermal, and mechanical properties of the cured materials containing 0, 10, 30, and 50 wt % POSS were determined. The addition of POSS increased the elastic modulus and the yield stress measured in uniaxial compression tests, mainly because of the increase in the cohesive energy density produced by hydrogen bonding through the hydroxyl groups. A constant yield stress/elastic modulus ratio equal to 0.03 was observed for different POSS concentrations and test temperatures. The glass‐transition temperature decreased with POSS addition because of the flexibility of organic branches present in the POSS structure and the decrease in the crosslink density (determined from the rubbery modulus). Although a combination of a reduction in the glass‐transition temperature (plasticization) with an increase in the glassy modulus (antiplasticization) is a well‐known phenomenon, what is original is that in this case it was not the result of the suppression (or reduction in intensity) of subglass relaxations but was produced by an increase in the cohesive energy density. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1451–1461, 2003
Radiooxidation of fluoropolymers: Identification of oxidation products
Authors: Boullier I. , Esnouf S. , Moël A. Le 
Published: June 2003

AbstractRadiation effects on fluoropolymers induced by high‐energy irradiation were investigated. Poly(fluorovinylidene‐co‐hexafluoropropylene) [P(VDF‐HFP)] films were irradiated with γ rays in air. Peroxy radicals formed by irradiation in the presence of oxygen were partially converted into more stable products such as hydroperoxides, alcohols, and acids. These oxidation products were identified by Fourier transform infrared spectroscopy. Specific chemical treatments were carried out to identify and separate overlapping absorption bands. Model compounds were also used. On the basis of the results, a mechanism of degradation for γ‐irradiated P(VDF‐HFP) is proposed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1509–1517, 2003
States of water in poly(vinyl alcohol) derivative hydrogels
Authors: Ruiz J. , Mantecón A. , Cádiz V. 
Published: June 2003

AbstractWe studied the behavior of absorbed water in equilibrium‐swollen poly(vinyl alcohol) derivative hydrogels by differential scanning calorimetry (DSC), 1H nuclear magnetic resonance, and wide‐angle X‐ray diffraction. By DSC, three types of water were detected, and their relative fractions were estimated. With this technique we also calculated the pore size for every sample. From the nonexponential decay of the spin–spin relaxation data, we distinguished two environmental states of the absorbed water in the samples. The relaxation times were determined. From these data, we calculated the fractions of each type of water for every hydrogel and related them to the degree of crosslinking. The X‐ray study indicated that the water absorbed in these hydrogels forms a single crystalline phase on cooling. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1462–1467, 2003
CO2‐delayed crystallization of isotactic polypropylene: A kinetic study
Authors: Zhang Zhiyi , Nawaby A. Victoria , Day Michael 
Published: June 2003

AbstractThe effect of CO2 on the nonisothermal crystallization of isotactic polypropylene (iPP) was studied with high‐pressure differential scanning calorimetry at cooling rates of 0.2–5 °C/min. CO2 significantly delayed the melt crystallization of iPP, and both the crystallization temperature and the heat of crystallization decreased with increasing CO2 pressure. The crystallization rate of iPP, as characterized by the half‐time, was also prolonged by the presence of CO2. With a modified Ozawa model developed by Seo, the Avrami crystallization exponent n of iPP was calculated. This value was depressed by the addition of CO2 and was strongly dependent on the CO2 pressure at low cooling rates. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1518–1525, 2003
Electrospinning of poly(vinylidene fluoride)/dimethylformamide solutions with carbon nanotubes
Authors: Seoul Chang , Kim Yong‐Tae , Baek Chi‐Kyung 
Published: June 2003

AbstractFor conductive carbon nanotube (CN)/polymer composite fibers to be obtained, CNs were incorporated into poly(vinylidene fluoride) (PVDF) in dimethylformamide (DMF) solutions and electrospun to form CN/PVDF fiber mats. The thinnest fiber was 70 nm thick. The percolation threshold for the insulator‐to‐conductor transition was 0.003 wt % CN for CN/PVDF/DMF solutions, 0.015 wt % CN for CN/PVDF spin‐coated films, and 0.04 wt % CN for CN/PVDF electrospun fiber mats. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1572–1577, 2003