bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimal Dynamic Pricing for Perishable Assets with Nonhomogeneous Demand
Authors: Zhao Wen , Zheng Yu-Sheng 
Published: April 2003

We consider a dynamic pricing model for selling a given stock of a perishable product over a finite time horizon. Customers, whose reservation price distribution changes over time, arrive according to a nonhomogeneous Poisson process. We show that at any given time, the optimal price decreases with inventory. We also identify a sufficient condition under which the optimal price decreases over time for a given inventory level. This sufficient condition requires that the willingness of a customer to pay a premium for the product does not increase over time. In addition to shedding managerial insight, these structural properties enable efficient computation of the optimal policy. Numerical studies are conducted to show the revenue impact of dynamic price policies. Price changes are set to compensate for statistical fluctuations of demand and to respond to shifts of the reservation price. For the former, our examples show that using optimal dynamic optimal policies achieves 2.4–7.3% revenue improvement over the optimal single price policy. For the latter, the revenue increase can be as high as 100%. These results explain why yield management has become so essential to fashion retailing and travel service industries.
Optimal Admission Control and Sequencing in a Make-to-Stock/Make-to-Order Production System
Authors: Carr Scott , Duenyas Izak 
Published: April 2003

In this paper, we address the problem of admission control and sequencing in a production system that produces two classes of products. The first class of products is made-to-stock, and the firm is contractually obliged to meet demand for this class of products. The second class of products is made-to-order, and the firm has the option to accept (admit) or reject a particular order. The problem is motivated by suppliers in many industries who sign contracts with large manufacturers to supply them with a given product and also can take on additional orders from other sources on a make-to-order basis. We model the joint admission control/sequencing decision in the context of a simple two-class M/M/1 queue to gain insight into the following problems: 1. How should a firm decide (a) when to accept or reject an additional order, and (b) which type of product to produce next? 2. How should a firm decide what annual quantity of orders to commit to when signing a contract to produce the make-to-stock products?
A Production/Inventory System Subject to Failure with Limited Repair Capacity
Authors: Iravani Seyed M.R. , Duenyas Izak , Olsen Tava Lennon 
Published: April 2003

We consider a production/inventory system consisting of M machines and K (K≤M) repair crews in which machines are subject to time dependent failures. The repair operations on each machine require one repair crew during the whole operation. In this production/inventory system, each machine is assigned to produce a different item according to a make-to-stock routine. Inventories of each item service a Poisson demand process, and the unsatisfied demands are lost. The objective is to minimize the sum of the average holding and lost-sales penalty costs. We formulate the joint problem of (1) allocating the limited number of repairmen to failed machines and (2) deciding how much finished goods inventory to keep as a Markov decision process. We show that the optimal policy has a very complicated structure. We introduce two models to compute optimal base-stock policies in systems with identical machines, where first break first repair (FBFR) or preemptive priority (PPRI) repair policies are used. Then we present two heuristics to perform the same optimization analysis in systems with different machines. Finally, we compare the combination of the optimal base-stock policy (as the production policy) and the FBFR and PPRI policies (as the repair policies) to the optimal dynamic policy, and through numerical examples we show that this integration creates a solution that is close to the optimal dynamic policy. The results indicate that simple policies for determining finished goods inventory levels and repair crew assignment to failed machines can work well as long as the two problems are addressed in a coordinated manner.
Making Connections: Complementary Influences on Communication Media Choices, Attitudes, and Use
Authors: Treviño Linda Klebe , Webster Jane , Stein Eric W. 
Published: April 2003

Theorizing about communication media attitudes and behaviors has drawn upon multiple theories (e.g., media richness, social influence). But these theories have often been pitted against each other rather than considered as complementary in more comprehensive studies. Furthermore, previous research has tended to focus more on newer communication media such as electronic mail rather than more traditional media. Finally, communication media research has studied attitudes toward media, use of media, and only occasionally media choice. Yet, all three dependent variables are important. This comprehensive survey hypothesized and tested multiple influences (based on multiple theories) in a study of media attitudes and behaviors. The media included electronic mail, fax, letters, and face-to-face meetings. The outcomes included media choice (an individual's decision to use a medium in a particular communication incident), media use (an individual's general pattern of use over time), and media attitudes (an individual's general subjective evaluation of media). Results suggested that a number of factors differentiated among media choices, including medium symbolism, message equivocality, distance between message partners, perceived media richness, number of message recipients, and perceived message recipients' attitudes. General attitudes toward the different media were influenced most consistently by perceived medium richness. New media attitudes were also influenced by person/technology interaction factors. General medium use was influenced by different factors for the different media. The results generally supported a comprehensive theoretical approach to understanding media attitudes and behaviors. All of the theories have some merit in explaining media attitudes and behaviors. But different factors, derived from different theories, were more important in accounting for each of the dependent variables'media choices, attitudes, and use. We hope that this investigation will help research in this area move toward the development of more integrative theoretical models.
Cultural Industries Revisited
Authors: Hirsch Paul M. 
Published: April 2003

In my early “Processing Fads and Fashions: An Organization-Set Analysis of Cultural Industry Systems” (1972), the middle “throughput” phase, or most organizational aspect of cultural industries, was emphasized. In this depoliticized exploration of what Adorno (1991) had earlier characterized as the industrialization of high culture, and Powdermaker (1950) as Hollywood's “dream factory,” I emphasized the key roles of gatekeeper and distributor organizations as critical in connecting the artist/creators to audience/consumers of mass, or “popular” culture (as it had more acceptingly come to be called). Altogether, this network of organizations—from creators (artists, musicians, actors, writers) and brokers (agents), through the cultural product's producers (publishers, studios), distributors (wholesalers, theaters), and media outlets—collectively constitute cultural industries. This article on industries producing “cultural products”—defined as “ ‘nonmaterial’ goods directed at a public of consumers, for whom they generally serve an esthetic or expressive, rather than a clearly utilitarian function” (Hirsch 1972 p. 641)—appeared at the same time that organizational sociology's focus on what became known as the “production of culture” took off, and continued to flourish into the 1990s (Peterson 1994, Crane 1992). How has the study of cultural industries changed over the last generation? A simple answer is that the subject—the key role of distribution and the importance of organizational middlemen in the making and sale of popular culture—remains analytically the same. From actors, musicians, and writers; through studios, labels and publishers, to videocassettes, movie theaters, record stores, and booksellers (in stores or via the Internet)—cultural products flow. How this sequence is organized and traversed remains a fascinating forest of power plays and techniques, employed by role-occupants in the same positions as have existed since the advent of mass media. While this substantive field has changed little analytically, what we also see is a wondrous expansion in the disciplinary approaches being taken to examine the multitude of topics available for examination under the broad rubric and framing of the term, “cultural industries.” Because I was a graduate student at the time (my roommate dared me to submit the “Processing…” paper to the American Journal of Sociology), it is a great pleasure to find the concept has retained its value for other researchers since that time. In this article, I will (1) reexamine and discuss the original framing of the term cultural industries; (2) briefly review some of the more recent complementary perspectives which expand the possible arenas for studying this topic; and (3) append a short note on how the more recent inclusion of nonprofit cultural products(e.g., symphonies, museums) in this framework poses interesting analytical questions and opportunities.
Occupational exposure of non‐smoking restaurant personnel to environmental tobacco smoke in Finland
Authors: Johnsson Tom , Tuomi Tapani , Hyvärinen Markku , Svinhufvud Juha , Rothberg Mari , Reijula Kari 
Published: April 2003

AbstractBackgroundEnvironmental tobacco smoke (ETS) exposure levels in different restaurant types in Finland were assessed before the National Tobacco Act restricting smoking in restaurants was activated.MethodsExposure to ETS was determined by measuring nicotine in the breathing zone of non‐smoking restaurant workers and by quantification of the nicotine metabolites cotinine and 3‐hydroxycotinine in the urine of these workers during one whole work week. Altogether 23 workers from 15 restaurants were included in the study.ResultsThe geometric mean (GM) breathing‐zone nicotine level was 3.9 μg/m3 (3.7 μg/m3 in pubs, 1.4 μg/m3 in dining restaurants, and 10.2 μg/m3 in nightclubs). The GM cotinine and trans‐3′‐hydroxycotinine level in urine were 3.3 ng/mg(creatinine) and 15.3 ng/mg(creatinine), respectively. The exposure to ETS of restaurant workers in dining restaurants was clearly lower than that of workers in pubs and nightclubs as indicated by all ETS‐markers used in the present study. During the work week, the cotinine and 3′‐hydroxycotinine levels in urine of the study subjects increased. The correlation between breathing zone nicotine and urine cotinine and hydroxycotinine was 0.66 for both compounds. Post‐shift cotinine and hydroxycotinine levels were not significantly higher than the pre‐shift levels.ConclusionsIf 9 ng cotinine/mg(creatinine) is considered as the level above which heavy exposure has occurred, then this level was exceeded by 14 (∼60%) subjects at least once during the work week. Nicotine metabolite concentrations in the urine increased during the work week in 80% of the subjects, and the increase was especially noticeable for subjects working in both pubs and nightclubs. The study indicates that measures to restrict ETS exposure in restaurants are needed. Am. J. Ind. Med. 43:523–531, 2003. © 2003 Wiley‐Liss, Inc.
Fine structure of acetal resins and its effect on mechanical properties
Authors: Hammer C. F. , Koch T. A. , Whitney J. F. 
Published: April 2003

AbstractStable, high molecular‐weight polyoxymethylene resins show the room temperature x‐ray crystalline patterns expected from early work on unstable or low molecular weight polyoxymethylene resins. High‐temperature studies show the specific features of this resin to be: (1) disappearance of crystalline peaks at 180°C., and (2) a super‐cooling of 15°C. (i.e., nucleation periods much greater than 15 minutes for temperatures above 165°C.). Studies utilizing optical birefringence show similar melting and freezing behavior. Birefringence studies show effect of quench temperature and melt time and temperature on the average spherulite size and appearance. Under suitable conditions, very large (1 mm. diameter) spherulites can be grown. The effect of variations in the fine structure (spherulite size, crystallite size, and degree of crystallinity) on mechanical properties of thin sections shows that: (1) an increase in crystallinity (by specific volume) gives higher moduli, higher yield strengths, and lower values of elongation to break; (2) smaller spherulites increase the ductility, or ability to retain ductility as the rate of strain of the test is increased; (3) changes in crystallite size over a twofold range have lesser effects on these properties.
γ‐irradiation of styrene copolymers
Authors: Burlant W. , Green D. , Taylor C. 
Published: April 2003

AbstractCopolymers of styrene‐methyl methacrylate were irradiated in vacuo with γ‐rays; viscosity changes and gas yields (moles gas per mole methyl methacrylate in copolymer) for H2, CO, CO2, CH4, HCOOCH3, and CH3OH were examined at doses of 1.0 Mrep to 10.0 Mrep. It was found that styrene molecules protect the copolymer from degrading while decreasing the gas yields up to a styrene concentration of about 0.5 mole fraction; above this concentration, these radiation effects are independent of composition. When styrene–methyl acrylate copolymers were irradiated, styrene offered protection aganist gelation but simultaneously increased the gas yields (gases liberated were identical with those from the first system).
Molecular weight distribution and polymerization kinetics in some new catalytic processes
Authors: Mussa C. I. V. 
Published: April 2003

AbstractSome features of the molecular weight distributions found by experiment for low pressure polyethylenes are examined; an analytical interpretation of them is suggested which is in agreement with the polymerization mechanism resulting from kinetic investigations of Natta and co‐workers. Such interpretation is based on the consideration of the distribution of the individual times of growth (or of the “lifetimes”) of the single macromolecules. It is assumed that (a) these lifetimes tend to be distributed according to the Gauss formula, such as a series of events tending to be distributed at random about a mean; and (b) the growth of any single macromolecule proceeds at a rate which can be considered as the rate of a chain reaction. Possible deviations from such simplified scheme are taken into account. A distribution formula of a generalized Lansing‐Kraemer type is deduced, giving an explanation of all the observed features of the molecular weight distribution.
The emulsion polymerization of methyl methacrylate
Authors: Zimmt W. S. 
Published: April 2003

AbstractThe kinetics of the emulsion polymerization of methyl methacrylate have been examined in the light of recent advances in theory. It has been found that, if allowance is made for the decrease in the termination rate, the kinetics of the reaction can be predicted up to the point where all monomer is absorbed by growing monomer‐polymer particles. In order to do this it must be assumed that the efficiency of initiation is low and is a function of the size and number of growing particles in the latex. A possible explanation for these observations is discussed.
Diffusion‐controlled mechanical properties of polyvinyl alcohol and polyvinyl formals
Authors: Yamamura Hitoshi , Kuramoto Naoya 
Published: April 2003

AbstractThe elongation of polyvinyl alcohol and of formalized polyvinyl alcohol films under constant load for a wide range of conditions of temperature and humidity seems to be affected predominantly by the diffusion of water molecules into these polymeric films, as these films have many water‐sensitive bonds. In order to obtain a perspective of the diffusion mechanism of water molecules into these polymer films, the theoretical analysis of creep curves is here worked out. Since the diffusion is a time‐dependent, non‐Fickian process, the time dependence of the diffusion coefficient is considered into our theoretical treatment. It is also assumed that the elongation is caused only by the breaking of hydrogen bonds due to the absorption of water molecules in amorphous regions of the polymer film.To evaluate theoretical equations for the creep curves in accordance with a simple Voigt model, the parameter α for the rate of diffusion is conveniently substituted for by K, the parameter for the rate of elongation. Experiments were performed at temperatures from 20 to 50°C. at 60% R. H., and also at different relative humidities ranging from 40 to 80% at a constant temperature of 30°C. A series of creep curves for PVA and PVF, the latter having a degree of formal substitution ranging from 6% to 42.5% were obtained.In analyzing the observed creep curves by the present theoretical treatment, we can easily compute the values of K through application of the condition for the characteristic inflection point of each curve, i.e., d2γ/dt2 = 0. By use of the values of K thus obtained and by application of the theory of absolute reaction rates, the activation energy and entropy for the diffusion process of water molecules are duly determined. The values thus obtained are also compared with those calculated by Hauser and McLaren. The activation energy and entropy are highest and lowest, respectively for PVF (6%); this is made adequately explicable by the fact that the proportion of amorphous polymer in these films is found to be maximum when the degree of formalization is between 10 and 20%.
Thermal‐oxidative degradation of poly(ethyl acrylate)
Authors: Steele Richard , Jacobs Harvey 
Published: April 2003

AbstractThe thermal‐oxidative degradation of films of poly(ethyl acrylate) about 35 μ thick were studied in the temperature range of 80 to 120°C. The degradation was followed by determining intrinsic viscosity changes, absorption of oxygen, and production of titratable acidity in the polymer. From viscosity results an apparent activation energy of 28.6 kcal. was calculated. Only very slight degradation occurred when the polymer was heated in a vacuum. In air, the reaction is inhibited by the presence of hydroquinone, while the addition of benzoyl peroxide caused a rapid degradation even in a vacuum. The rate of oxygen absorption was found to be similar to that typical of autocatalytic oxidations. Oxygen diffusion did not appear to be the rate‐determining factor in the degradation of films 10 to 70 μ thick. The weight loss during degradation was very small, but infrared and mass spectra indicated the presence of carbon dioxide, ethanol, formic acid, and water among the volatile products. A degradation mechanism based on hydroperoxide formation and decomposition is suggested.
Physical characteristics of osmotic membranes of organic polymers
Authors: Reid Charles E. , Kuppers James R. 
Published: April 2003

AbstractThe mechanism of water transport across cellulosic membranes under high pressure differentials was studied in an attempt to explain the semipermeability of these films when used as osmotic membranes for ionic solutions. Diffusion coefficients and activation entropy values for the diffusion of water and other fluids through various polymer films were determined, and compressive deformation of cellulose acetate and cellophane films was measured. Activation entropy values for the diffusion of water across both cellulose acetate and cellophane films illustrated that water molecules are constrained to states of high order as they are transported across the membrane under high pressure differentials. Activation entropy values for the diffusion of methanol through cellulose acetate film failed to support the proposition that chains of this polymer may actually be crosslinked by hydrogen‐bonded water. It appeared, rather, that but one hydrogen of the water molecule was involved in hydrogen bonding to the polymer. A significant reorientation of the polymer in the pressure interval in which cellulose acetate film is induced into a semipermeable condition was indicated by pressure‐dependent fluctuations of diffusion coefficients and activation entropy values in this interval. The greater elastic modulus of wet cellulose acetate film under a compressive force applied normal to the film surface demonstrated a strong interaction between water and polymer chains in the cellulose acetate‐water structure. The capacity of the film for bound water was also increased by repeated compression while wet. Wet cellophane films deformed plastically under compression. Crosslinking polymer chains of cellophane film with cupric ions prevented plastic flow and, at the same time, increased the semipermeability of the film for sodium chloride solutions.
Molecular weight distributions from gel‐sol ratios
Authors: Bueche F. , Harding S. W. 
Published: April 2003

AbstractA method for determining molecular weight distributions is presented, based upon the partition of polymer molecules between gel and sol in a partly crosslinked system. It is assumed that the polymer sample consists of a series of molecular weight species, and analysis of previously developed theories covering this situation yields an expression which equates the weight fraction of gel to a summation involving the weight fraction of the material in each species and the number of crosslinked units in the sample. The data are presented in the form of a graph showing how the weight fraction of gel varies as a function of the number of crosslinked units in the sample. Data for the graph are obtained from swelling measurements made in the usual manner. The procedure is outlined for using the information from the graph to make a step‐by‐step evaluation of the fractional weight of each molecular weight species in the sample for as many fractions as may be arbitrarily chosen. Both a first approximation method and a more refined second approximation method are outlined. The procedure has been applied to samples of natural rubber, synthetic rubbers, and to two known molecular weight distributions.
A gel point method for the estimation of overall apparent activation energies of polymerization
Authors: Gough L. J. , Smith I. T. 
Published: April 2003

AbstractThe gel time, measured under isothermal conditions, may be taken as a measure of the overall rate of polymerization of a given system under certain circumstances. This enables us to estimate the Arrhenius activation energy from such measurements. A simple piece of apparatus is described which has been used to measure the overall activation energy of some epoxy resin polymerizations. The agreement with previously published data is reasonable.
Single‐point determination of intrinsic viscosity
Authors: Valles R. J. , Otzinger M. C. , Levi D. W. 
Published: April 2003

AbstractThe Schulz and Blaschke equation in the rearranged form of Hart was used for reasonably precise calculation of the intrinsic viscosity from a single measured specific viscosity for stereoregular polybutene‐1 in Decalin and for a series of alkyl methacrylate polymers in good and poor solvents. A single value of N can be used for each system provided careful measurements are made at specific viscosities somewhat below 1.