bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of the Linking Structure of Nonlinear Optical Side Groups on the Phase Behavior of an Aromatic Polyester Backbone
Authors: Lee Maeng‐Eun , Seong Seayeal , No Kyoung‐Tai , Kwon O‐Pil , Lee Suck‐Hyun 
Published: March 2004

AbstractSummary: The phase behavior of poly(p‐phenylene terephthalate)s (PPT) with pendant side groups, N‐(4‐nitrophenyl)ethylaminoethanol (NPE) and N‐(4‐nitrophenyl)‐L‐prolinol (NPP) has been studied by using differential scanning calorimetry (DSC), wide‐angle X‐ray scattering (WAXS), and second harmonic generation (SHG). PPT‐NPE showed a layered liquid crystalline morphology while PPT‐NPP showed a completely amorphous structure. Compressive or shear stress applied on the polymer melt surface at 210 °C induced a more prominent layered structure of PPT‐NPE whereas the amorphous structure of PPT‐NPP remained unchanged under the stress. In order to understand this phase difference in terms of the repeat structure, we attempted theoretical ab initio Hartree‐Fock, and DFT calculations for the monomers and molecular dynamics for the bulk state. The results indicated that molecular configurations are a good way of microscopically understanding the phases of rigid backbone polymers with functional side groups: The NPT (constant particle number, pressure, and temperature) simulation data at 210 °C agree qualitatively with the experimental data and the difference between PPT‐NPE and PPT‐NPP could be understood using rotational energy barrier, steric hindrance and inter‐chain interactions. X‐ray diffractometer (XRD) simulation patterns for the oligomers are also in qualitative agreement with the experimental WAXS data and the structural parameters of stacks of PPT‐NPE chains are estimated to be layer distance (4.6 Å), backbone distance (21.5 Å), and side distance (12 Å).image
Structural Changes in Block Copolymer Solutions under Shear Flow as Determined by Non‐Equilibrium Molecular Dynamics
Authors: Rychkov Igor , Yoshikawa Kenichi 
Published: March 2004

AbstractSummary: A non‐equilibrium molecular dynamics computer simulation on microsegregated solutions of symmetrical diblock copolymers is reported. As the polymer concentration increases, the system undergoes phase transitions in the following order: body centered cubic (BCC) micelles, hexagonal (HEX) cylinders, gyroid (GYR) bicontinuous networks and lamellae (L), which are the same morphology reported for block copolymer melts. Structural classification is based on the patterns of the anisotropic static structure factor and characteristic 3‐dimensional images. The systems in the BCC micellar (ρσ3 = 0.3) and HEX cylindrical (ρσ3 = 0.4) phases were then subjected to a steady planar shear flow. In weak shear flow, the segregated domains in both systems tend to rearrange into sliding parallel close‐packed layers with their normal in the direction of the shear gradient. At higher shear rates, both systems adopt a perpendicular lamellar structure with the normal along the neutral direction. A further increase in the shear rate results in a decrease in lamellar spacing without any further structural transitions. Two critical shear rate values that correspond to the demarcation of different structural behaviors were found.Shear‐induced BCC‐LAM phase transition.imageShear‐induced BCC‐LAM phase transition.
Effects of Reversible Chemical Reaction on Morphology and Domain Growth of Phase Separating Binary Mixtures with Viscosity Difference
Authors: Huo Yanli , Zhang Hongdong , Yang Yuliang 
Published: March 2004

AbstractSummary: The effects of a reversible chemical reaction on morphology and dynamics of phase separating binary mixtures with viscosity difference are studied by numerically solving modified time‐dependent Ginzburg‐Landau and Navier‐Stokes equations. Much more interesting morphologies are observed in the system due to the coupling of reversible chemical reaction and viscosity difference between two components. When the chemical reaction rate is relatively low, the impact of viscosity difference on morphologies is prominent, so that the resulting patterns are affected by both reversible chemical reaction and viscosity difference. However, increasing the chemical reaction rate weakens the impact of viscosity difference on morphologies. Similarly, increasing the chemical reaction rate also suppresses the effects of viscosity difference on domain growth dynamics, which is prominent at the early stage of phase separation when the chemical reaction rate is relatively low. For both cases with relatively low and high chemical reaction rates, the average domain size eventually attains an equilibrium value due to the competition between the mixing of reversible chemical reaction and demixing of phase separation.Domain patterns of a critical system with ϕini = 0, and Γ1 = Γ2 = 0.001.imageDomain patterns of a critical system with ϕini = 0, and Γ1 = Γ2 = 0.001.
Orientation of Polymer Chains in Dilute Solution under Shear: Effect of Chain Model and Excluded Volume
Authors: Hernández Cifre José G. , García de la Torre José 
Published: March 2004

AbstractSummary: Polymer orientation in dilute solutions undergoing shear flow is investigated computationally by means of the Brownian dynamics simulation technique applied to the bead‐spring chain model. The dependence of the degree of orientation on the shear intensity is evaluated through a quantity called orientation resistance. All simulations were performed using non‐preaveraged hydrodynamic interaction (HI). The spring type (Gaussian or FENE) is shown to strongly determine the shear flow behavior of the chain orientation. Solvent quality (Θ, good or bad), represented by a suitable Lennard‐Jones intramolecular potential, does not affect the flow behavior but influences the values of the orientation resistance. Hence, the orientability of the polymer molecule is, in a way, related to the flow intensity.Evolution of mG (orientational resistance parameter, open circles are simulation, dashed line is Gaussian approximation) and mτ (filled circles are simulation, dotted line is Gaussian approximation) with β for ideal Gaussian chains with N = 15.imageEvolution of mG (orientational resistance parameter, open circles are simulation, dashed line is Gaussian approximation) and mτ (filled circles are simulation, dotted line is Gaussian approximation) with β for ideal Gaussian chains with N = 15.
Crosslinking Kinetics: Partitioning According to Number of Crosslinks
Authors: Li Rujun , McCoy Benjamin J. 
Published: March 2004

AbstractSummary: To mathematically describe crosslinking kinetics for polymers, we have proposed a novel method that accounts for the number of crosslinks, that is, partitioning according to number of crosslinks (PANC). By contrast, the well‐known method of numerical fractionation tracks generations of crosslinked molecules, defined to include a range of crosslinks. The proposed crosslinking kinetics yield a population balance model that provides moments and hence measurable average properties such as number average molecular weight and weight average molecular weight, polydispersity and average crosslink number. The gel points for batch and continuous‐flow stirred‐tank reactors are derived. Because the usual closure methods do not yield satisfactory convergence, new representations for post‐gelation moments are proposed. The results realistically show how the moments change with time in the post‐gel region.The average number of crosslinks in the bulk and sol versus time in a batch reactor; the gel point is the dashed line.imageThe average number of crosslinks in the bulk and sol versus time in a batch reactor; the gel point is the dashed line.
Monte Carlo Simulations of Copolymer Adsorption at Planar Chemically Patterned Surfaces: Effect of Interfacial Interaction
Authors: Semler James J. , Genzer Jan 
Published: March 2004

AbstractSummary: Monte Carlo simulation utilizing the bond fluctuation model in conjunction with single and configurational biased Monte Carlo moves is used to study the adsorption of diblock (A‐block‐B) and alternating (A‐alt‐B) copolymers at flat, chemically heterogeneous surfaces comprising C and D domains. The main objective of this work is to address the effect of the strength of attraction between the adsorbing surface domains, D, and the copolymer adsorbing segments, B, on the copolymer's ability to recognize the chemical pattern on the surface. The results of our simulations reveal that both block and alternating copolymers have the ability to recognize the surface motif and transcribe it into the bulk material. The extent to which diblock copolymers transfer the chemical pattern from the surface to the bulk is relatively unaffected when the attractive B‐D potential is increased beyond a certain critical value. This behavior stems from the brush‐like conformation adopted by the diblock copolymer at the substrate. In contrast to the diblock copolymer, the adsorption of the alternating copolymer is influenced by the strength of the attraction between the copolymer's adsorbing segments and the adsorbing domains on the surface. Since the B segments are distributed evenly along the backbone, the alternating copolymers are more likely to adopt conformations in which the whole chain is “zipped” to the surface. The resultant entropic frustration is then alleviated through an increased formation of loops with little change to their length. Such conformational changes endow the alternating copolymer with the ability to invert the substrate pattern as the distance away from the surface is increased.image
Identification of the boundary surface of an interstellar cloud from a measurement of the photon far‐field
Authors: Belleni‐Morante A. , Mugelli F. 
Published: March 2004

AbstractWe study an inverse problem for photon transport in a host medium (e.g. an interstellar cloud), that occupies a bounded and strictly convex region Ω⊂R3. Under the assumption that the cross‐sections and the sources are known, we identify the boundary surface ∑ = ∂Ω(within a suitable family F of surfaces), provided that one value of the photon number density is measured at some given location far from Ω. Copyright © 2004 John Wiley & Sons, Ltd.
A characterization theorem for the evolution semigroup generated by the sum of two unbounded operators
Authors: Frosali Giovanni , van der Mee Cornelis V. M. , Mugelli Francesco 
Published: March 2004

AbstractWe consider a class of abstract evolution problems characterized by the sum of two unbounded linear operators A and B, where A is assumed to generate a positive semigroup of contractions on an L1‐space and B is positive. We study the relations between the semigroup generator G and the operator A+B. A characterization theorem for $G=\overline{A + B}$ is stated. The results are based on the spectral analysis of B(λ‐A)‐1. The main point is to study the conditions under which the value 1 belongs to the resolvent set, the continuous spectrum, or the residual spectrum of B(λ‐A) ‐1.Applications to the runaway problem in the kinetic theory of particle swarms and to the fragmentation problem describing polymer degradation are discussed in the light of the previous theory. Copyright © 2004 John Wiley & Sons, Ltd.
Existence and uniqueness results for the continuous coagulation and fragmentation equation
Authors: Lamb Wilson 
Published: March 2004

AbstractA non‐linear integro‐differential equation modelling coagulation and fragmentation is investigated using the theory of strongly continuous semigroups of operators. Under the assumptions that the coagulation kernel is bounded and the overall rate of fragmentation satisfies a linear growth condition, global existence and uniqueness of mass‐conserving solutions are established. This extends similar results obtained in earlier investigations. In the case of pure fragmentation, when no coagulation occurs, a precise characterization of the generator of the associated semigroup is also obtained by using perturbation results for substochastic semigroups due to Banasiak (Taiwanese J. Math. 2001; 5: 169–191) and Voigt (Transport Theory Statist. Phys. 1987; 16: 453–466). Copyright © 2004 John Wiley & Sons, Ltd.
On the convex compactness property for the strong operator topology and related topics
Authors: Mokhtar‐Kharroubi Mustapha 
Published: March 2004

AbstractWe give direct proofs of the convex compactness property for the strong operator topology in Lebesgue spaces for compact or weakly compact operators. We also show how this tool applies to spectral theory of perturbed semigroups. Some non‐weakly compact operators arising in perturbation theory of neutron transport are shown to be Dunford–Pettis operators. Copyright © 2004 John Wiley & Sons, Ltd.
Chaos for some infinite‐dimensional dynamical systems
Authors: Rudnicki Ryszard 
Published: March 2004

AbstractThis paper is devoted to the problem of chaotic behaviour of infinite‐dimensional dynamical systems. We give a survey of different approaches to study of chaotic behaviour of dynamical systems. We mainly discuss the ergodic‐theoretical approach to chaos which bases on the existence of invariant measures having strong analytic and mixing properties. This method is applied to study chaotic behaviour of semiflows generated by semilinear partial differential equations and linear transformations. Copyright © 2004 John Wiley & Sons, Ltd.
Two‐machine flow shop no‐wait scheduling with a nonavailability interval
Authors: Kubzin Mikhail A. , Strusevich Vitaly A. 
Published: March 2004

AbstractWe study a two‐machine flow shop scheduling problem with no‐wait in process, in which one of the machines is not available during a specified time interval. We consider three scenarios of handing the operation affected by the nonavailability interval. Its processing may (i) start from scratch after the interval, or (ii) be resumed from the point of interruption, or (iii) be partially restarted after the interval. The objective is to minimize the makespan. We present an approximation algorithm that for all these scenarios delivers a worst‐case ratio of 3/2. For the second scenario, we offer a 4/3‐approximation algorithm. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004
An adaptive forecasting algorithm and inventory policy for products with short life cycles
Authors: Zhu Kaijie , Thonemann Ulrich W. 
Published: March 2004

AbstractProducts with short life cycles are becoming increasingly common in many industries, such as the personal computer (PC) and mobile phone industries. Traditional forecasting methods and inventory policies can be inappropriate for forecasting demand and managing inventory for a product with a short life cycle because they usually do not take into account the characteristics of the product life cycle. This can result in inaccurate forecasts, high inventory cost, and low service levels. Besides, many forecasting methods require a significant demand history, which is available only after the product has been sold for some time. In this paper, we present an adaptive forecasting algorithm with two characteristics. First, it uses structural knowledge on the product life cycle to model the demand. Second, it combines knowledge on the demand that is available prior to the launch of the product with actual demand data that become available after the introduction of the product to generate and update demand forecasts. Based on the forecasting algorithm, we develop an optimal inventory policy. Since the optimal inventory policy is computationally expensive, we propose three heuristics and show in a numerical study that one of the heuristics generates near‐optimal solutions. The evaluation of our approach is based on demand data from a leading PC manufacturer in the United States, where the forecasting algorithm has been implemented. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004.
Lot streaming with supplier–manufacturer coordination
Authors: Li Chung‐Lun , Xiao Wen‐Qiang 
Published: March 2004

AbstractLot splitting refers to breaking a production lot into smaller sublots during production. Coordinating lot splitting decisions across multiple stages of a production process is a challenging task. Traditional lot splitting and lot streaming models implicitly assume that the entire system is operated and owned by the same firm, or there exists a coordinator who controls the operation of all machines in the system. In this paper, we consider the situation where the machines in a multiple‐stage production process are owned and managed by different companies. Every item in a given production lot has to go through the processing by the supplier's machine, followed by the manufacturer's machine, and so on. We develop and analyze coordination mechanisms that enable different parties in the supply chain to coordinate their lot splitting decisions so as to achieve a systemwide optimum. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004
A general approach to the shape of failure rate and MRL functions
Authors: Mi Jie 
Published: March 2004

AbstractFailure rate and mean residual life are two important characteristics for studying reliability of products. In literature, some work studied the shape of failure rate function based on the knowledge of the associated probability density function; some other work investigated the shape of mean residual life function based on the shape of the associated failure rate function separately for continuous case and discrete case. In this article, a general approach is developed which can be applied to the aforementioned studies. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004
Dichotomous categorical variable formation in mathematical programming discriminant analysis models
Authors: Glen J. J. 
Published: March 2004

AbstractClassification models, whether generated by statistical techniques or mathematical programming (MP) discriminant analysis methods, are often simplified by ad hoc formation of dichotomous categorical variables from the original variables with, for example, a dichotomous variable taking value 1 if the original variable is above a threshold level and 0 otherwise. In this paper an MP discriminant analysis method is developed for forming dichotomous categorical variables in problems with discriminant functions that are monotone in the original variables. For each of the original variables from which dichotomous variables may be formed, a set of possible threshold levels for dichotomous variable formation is defined. An MP model is then used to determine both the threshold level for forming each dichotomous variable and the associated discriminant function coefficient. The proposed MP approach is applied to a published problem and a number of simulated problem sets. It is shown that the discriminant functions in dichotomous categorical variables generated by this new MP approach can in some cases outperform the functions generated by standard MP discriminant analysis models using the original variables. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004.
Higher‐order Markov chain models for categorical data sequences*
Authors: Ching Wai Ki , Fung Eric S. , Ng Michael K. 
Published: March 2004

AbstractIn this paper we study higher‐order Markov chain models for analyzing categorical data sequences. We propose an efficient estimation method for the model parameters. Data sequences such as DNA and sales demand are used to illustrate the predicting power of our proposed models. In particular, we apply the developed higher‐order Markov chain model to the server logs data. The objective here is to model the users' behavior in accessing information and to predict their behavior in the future. Our tests are based on a realistic web log and our model shows an improvement in prediction. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004
Scurvy in adults and youngsters: the Dutch experience. A review of the history and pathology of a disregarded disease
Authors: Maat G. J. R. 
Published: March 2004

AbstractPrior to the Dutch maritime expansion of the 17th and 18th centuries, scurvy was known in the Low Countries as an endemic disease. From the end of the 16th century the disease started to draw much more attention due to increasing long sea journeys of sailors. Already in the Dutch medical literature of the 16th century, a strong relation was expressed between the prolonged taking of foodstuffs of poor quality and the risk of contracting scurvy. Although from that time, many Dutch physicians recommended oranges, scurvy grass and brook‐lime, it took 200 years before inadequate therapy on the fleet was replaced by systematic prevention. Why did the old time effective recommendations for the therapy of scurvy stay inadequate for mariners? To understand, maritime and medical history were unfolded and evaluated with respect to palaeopathological findings reported for 39 cases of active scurvy and one case of healed scurvy.The palaeopathology of scurvy in adults and still growing youngsters was investigated from the remains of 50 Dutch whalers who had been buried during the 17th and 18th centuries on an island of the Spitsbergen Archipelago. Conforming the clinical literature, the original haematomas from scurvy were found as a black staining at the tips of dental roots. In the weight‐bearing bones of the lower extremities large black stains were positioned bilaterally around endofractures of the metaphyses, bilaterally on joint surfaces and bilaterally at epiphyseal discs of youngsters. In the non‐weight‐bearing bones they were often found unilaterally, such as at insertions of muscles. Immunoenzymatic staining of microscopic sections proved that the black stains were from remnants of denatured haemoglobin. No microscopic bone repair activities had happened. In a case of healed scurvy it could even be demonstrated how many times the recovery process had taken place from the layers of appositional bone which had replaced the original subperiosteal haematomas. Copyright © 2004 John Wiley & Sons, Ltd.
Endocranial lesions in non‐adult skeletons: understanding their aetiology
Authors: Lewis M. E. 
Published: March 2004

AbstractReactive new bone on the endocranial surface of the skull in non‐adults has recently received a lot of attention in the palaeopathological literature. These features appear as layers of new bone on the original cortical surface, expanding around meningeal vessels, as isolated plaques, ‘hair‐on‐end’ extensions of the diploë or, as ‘capillary’ impressions extending into the inner lamina of the cranium. These lesions are commonly found on the occipital bone, outlining the cruciate eminence, but have also been recorded on the parietal and frontal bones, and appear to follow the areas of venous drainage. Although recognized as resulting from haemorrhage or inflammation, their precise aetiology is still a matter of controversy. This paper outlines their possible causes and examines their nature and distribution in a group of non‐adults from four archaeological sites in England. It is recommended that, when recording these lesions in the future, additional skeletal pathologies, the age of the child, and nature and distribution of the lesions also be taken into account. Copyright © 2004 John Wiley & Sons, Ltd.
A dystocic childbirth in the Spanish Bronze Age
Authors: Malgosa A. , Alesan A. , Safont S. , Ballbé M. , Ayala M. M. 
Published: March 2004

AbstractPrehistoric cases of maternal and fetal death during labour are difficult to document. However, this must have been a frequent cause of death among young women who lived in hard circumstances and precarious health conditions. In this paper, a case of a Bronze Age woman who probably died during childbirth due to unavoidable reasons is presented: her baby was lying transversely with the right fetal arm protracted. Death of both mother and child was inevitable. Copyright © 2004 John Wiley & Sons, Ltd.