bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improving Manufacturing Performance Through Process Change and Knowledge Creation
Authors: Carrillo Janice E. , Gaimon Cheryl 
Published: April 2003

A model is introduced to guide a profit maximizing firm in its quest to enhance performance through process change. The key benefit sought from process change is a long term increase in effective capacity. However, realizing success from process change is not trivial. First, while process change may increase effective capacity in the long run, the disruptions during implementation typically reduce short term capacity. Second, competitive forces such as decreasing revenue streams and shrinking product life cycles complicate the implementation of process change. Third, while knowledge may enhance the ultimate benefits derived from process change, the correct timing and means of knowledge creation are difficult to discern. Lastly, a variety of trade-offs must be evaluated when selecting the particular process change to pursue. For example, choices range from hardware and software replacements to modification of manufacturing procedures. The model introduced here explicitly considers both the short term loss due to disruption and the long term gain in effective capacity associated with the process change. In addition, investments in the accumulation of knowledge are investigated for their potential to enhance process change effectiveness. Knowledge is generated from investment in preparation and training (learning-before-doing) and as a by-product of process change (learning-by-doing). Analysis of the model provides managerial recommendations for several key decisions relating to process change implementation including: (i) the selection of an appropriate process change alternative, (ii) the rate and timing for investment in process change, and (iii) the rate and timing for investment in preparation and training. New results are reported reflecting the important relationship between process change and knowledge. For example, we show that under certain conditions, a firm should optimally delay investment in process change until sufficient accumulation of knowledge is achieved. More generally, we identify conditions whereby investment in process change occurs at an increasing rate over time. This result is particularly important since it demonstrates a limitation of the existing literature where process change always occurs at a decreasing rate.
Frictionless Commerce? A Comparison of Internet and Conventional Retailers
Authors: Brynjolfsson Erik , Smith Michael D. 
Published: April 2003

There have been many claims that the Internet represents a new nearly “frictionless market.” Our research empirically analyzes the characteristics of the Internet as a channel for two categories of homogeneous products—books and CDs. Using a data set of over 8,500 price observations collected over a period of 15 months, we compare pricing behavior at 41 Internet and conventional retail outlets. We find that prices on the Internet are 9–16% lower than prices in conventional outlets, depending on whether taxes, shipping, and shopping costs are included in the price. Additionally, we find that Internet retailers' price adjustments over time are up to 100 times smaller than conventional retailers' price adjustments—presumably reflecting lower menu costs in Internet channels. We also find that levels of price dispersion depend importantly on the measures employed. When we compare the prices posted by different Internet retailers we find substantial dispersion. Internet retailer prices differ by an average of 33% for books and 25% for CDs. However, when we weight these prices by proxies for market share, we find dispersion is lower in Internet channels than in conventional channels, reflecting the dominance of certain heavily branded retailers. We conclude that while there is lower friction in many dimensions of Internet competition, branding, awareness, and trust remain important sources of heterogeneity among Internet retailers.
Dynamics and Dilemmas of Women Leading Women
Authors: Bartunek Jean M. , Walsh Kate , Lacey Catherine A. 
Published: April 2003

Through examination of transcripts of the first five leadership succession discussions that occurred in a work group designed to empower teachers we explored dynamics and dilemmas associated with women leading a women's group based on feminist principles. We addressed three research questions: How is leadership, as reflected in leadership succession processes, experienced in such a group? What dynamics are associated with leadership succession in this type of group? What are outcomes of the process for members? Results indicated that the experience of leadership shifted considerably during the first six years of the group, with reflective images of leadership moving from the mythical to the pragmatic, from the powerful to the less powerful. Dynamics evolved in ways that were partially consistent and partially inconsistent with organizational life-cycle literature. The group experienced ambivalence and tension surrounding the type of authority given to designated leaders. Members dealt with discomfort by shifting the focus of the group coordinator's attention to external relations and by rotating internal leadership responsibilities. This approach resolved tensions associated with authority and increased members' senses of their own power, even as it decreased the range of initiative-taking that was implicitly allowable within the group. This analysis of leadership succession in a women's group with an empowerment agenda offers a salient case for the study of dilemmas likely to be present in many change efforts. Its results suggest that attempting to resolve contradictions and tensions is less helpful than acknowledging them and working within them.
How to measure reproductive success?
Authors: Strassmann Beverly I. , Gillespie Brenda 
Published: April 2003

AbstractTo date there have been few empirical comparisons between alternative methods for measuring reproductive success (RS). We consider the pros and cons of alternative measures of RS to provide guidance for the design of field studies in human behavioral ecology. We compare cross‐sectional measures that count offspring alive at the time of the interview and retrospective measures that require data on offspring age at death or censoring. We consider analyses that include adult women (yielding age‐specific estimates of RS) as well as analyses restricted to postreproductive women (yielding data on lifetime RS). These methods are applied to reproductive data for the Dogon of Mali, West Africa. Am. J. Hum. Biol. 15:361–369, 2003. © 2003 Wiley‐Liss, Inc.
Grandmothers and the evolution of human longevity
Authors: Hawkes Kristen 
Published: April 2003

AbstractGreat apes, our closest living relatives, live longer and mature later than most other mammals and modern humans are even later‐maturing and potentially longer‐lived. Evolutionary life‐history theory seeks to explain cross‐species differences in these variables and the covariation between them. That provides the foundation for a hypothesis that a novel role for grandmothers underlies the shift from an ape‐like ancestral pattern to one more like our own in the first widely successful members of genus Homo. This hypothesis links four distinctive features of human life histories: 1) our potential longevity, 2) our late maturity, 3) our midlife menopause, and 4) our early weaning with next offspring produced before the previous infant can feed itself. I discuss the problem, then, using modern humans and chimpanzees to represent, respectively, genus Homo and australopithecines, I focus on two corollaries of this grandmother hypothesis: 1) that ancestral age‐specific fertility declines persisted in our genus, while 2) senescence in other aspects of physiological performance slowed down. The data are scanty but they illustrate similarities in age‐specific fertility decline and differences in somatic durability that are consistent with the hypothesis that increased longevity in our genus is a legacy of the “reproductive” role of ancestral grandmothers. Am. J. Hum. Biol. 15:380–400, 2003. © 2003 Wiley‐Liss, Inc.
Water and ion flow across cellulosic membranes
Authors: Reid C. E. , Breton E. J. 
Published: April 2003

AbstractThe primary objective of this investigation has been to explain why cellulose acetate behaves as a semipermeable membrane in saline water. To explain this phenomenon, two different mechanisms for the transfer to water and ions through cellulose acetate membranes were formulated. Those ions and molecules that cannot enter into hydrogen bonding with the membrane are transferred by hole‐type diffusion. The rate of diffusion appears to be governed by a water‐cellulose acetate structure. The reaction between water and the cellulose polymers to form bound water regions is favored by compressing the membrane. As pressure is applied on the membrane, more bound water is produced, which causes the rate of hole‐type diffusion to decrease. On the other hand, those ions and molecules that can associate with the membrane and are transported through it by alignment‐type diffusion. The formation of the water‐cellulose acetate structure does not appreciably diminish the diffusion rate of water through the membrane. Cellulose acetate begins to behave as an effective semipermeable membrane in saline water when it is compressed sufficiently to retard greatly the diffusion of NaCl. Several types of experiments were conducted to support these hypotheses. The most important evidence was obtained from resistance experiments. The electrical resistances of specific ions was measured across cellulose acetate at various pressures by using permselective membranes to prevent migration of the ion of opposite charge. It was observed that the rate of diffusion of those ions that cannot combine with the membrane actually does decrease as the membrane is compressed. The rate of diffusion of H3O+, which can enter into hydrogen bonding with cellulose acetate, is much higher and is not appreciably reduced as the membrane is compressed. These resistance‐pressure relationships are correlated with the semipermeability of the cellulose acetate.
Time, temperature, and linear viscoelasticity
Authors: Haugh Eugene F. 
Published: April 2003

AbstractLinear viscoelastic bodies satisfy the Boltzmann superposition principle which permits the calculation of the effect of arbitrary stress or strain history in terms of creep or stress relaxation parameters, respectively. In such calculations, the temperature is not considered as an independent variable; rather, the temperature must be constant, and the stress relaxation and creep parameters used are for the given temperature. By assuming the validity of the time‐temperature superposition principle, it is shown how an arbitrary thermal history may be included. By employing spring‐dashpot model methods, Boltzmann's principle is generalized, leading to the concepts of equivalent stress σ(t) and equivalent time w(t), the latter concept having also been introduced for creep and stress relaxation by Hopkins. These quantities are defined by

where t = time, p = density, T = temperature, and a[T(t), T(0)] is the time‐temperature shift factor between temperatures T(0) and T(t). In terms of the equivalent stress and equivalent time, Boltzmann's principle for shear remains the same as for the isothermal case with stress relaxation or creep parameters at the initial temperature, T(0). In the case of tensile experiments, the observed strain must be corrected for thermal expansion.
The dynamic mechanical properties of hypalon‐20 synthetic rubber at small strains
Authors: Kurath S. F. , Passaglia E. , Pariser R. 
Published: April 2003

AbstractThe dynamic mechanical properties at small strains have been determined for Hypalon‐20 synthetic rubber, a commerical elastomer, by means of an electromagnetic transducer which is a modification of one described by Marvin, Fitzgerald, and Ferry. The measurements cover frequencies from 25 to 2500 cycles/sec. at twelve temperatures ranging from −8.4 to 68.4°C. Values of the real portion of the shear modulus (G′) vary from 7 × 106 to 2.1 × 109 dynes/cm.2, and those of the imaginary portion (G″) from 2.1 × 106 to 9 × 108 dynes/cm.2. The method of reduced variables (i.e., temperature‐frequency superposition) is applicable and is used to extend G′ and G″ over the range 10−1 to 109 radians/sec. At 25°C., G″/G′ = 1.3 at its maximum at 105 radians/sec. The general function for the temperature dependence of mechanical properties proposed by Williams, Landel, and Ferry is valid up to 35°C. if one uses −24.5°C. for the glass transition temperature (Tg); dilatometrically Tg = −28 ± 1°C. The distribution function of relaxation times H(τ) has a pronounced maximum at about τ = 10−8 sec., decreases with a slope of about −0.57 (for log H versus log τ) to about τ = 10−3 sec., and is nearly flat from τ = 10−2 to 10 sec. H (τ) for Hypalon‐20 is similar to those for polyisobutylene and polyhexene‐1.
Molecular structure of high molecular weight acetal resins
Authors: Koch T. A. , Lindvig P. E. 
Published: April 2003

AbstractStable, high molecular weight polymers of formaldehyde have been studied to determine their molecular structure. The polymer chain was shown to be a polyoxymethylene by chemical analysis and infrared absorption spectra. Infrared techniques also revealed hydroxyl end groups which were replaced by acetate groups on esterification. The endgroups, which were also measured by chemical methods, were used to determine the number‐average molecular weight over the range 20,000 to 98,000. Values obtained by assuming two endgroups per molecule agreed with osmotic pressure results, thus showing this to be an essentially unbranched polymer. Two theoretically possible branch‐point structures were investigated by chemical methods; none could be detected, further indicating a linear polymer structure. Indirect evidence of narrow molecular weight distribution was obtained by comparing melt viscosity properties with those of other polymers of known wide and narrow distribution.
Dielectric studies on cellulose fibers
Authors: Ishida Yoichi , Yōshino Masatsugu , Takayanagi Motowo , Irie Fujio 
Published: April 2003

AbstractA method for obtaining the intrinsic dielectric constant and loss factor of dry cellulose fiber along the fiber axis was developed, and the dielectric properties of viscose rayon, Bemberg (cuprammonium rayon), and cotton sliver were measured over the frequency range from 500 cycles/sec. to 3 Mcycles/sec. and the temperature range from −60 to + 20°C. by using the mutual inductance bridge. Only one dispersion could be observed in this temperature and frequency range. Cole‐Cole's circular are law could be satisfactorily applied to the data obtained, and the parameters of the are (ϵ0 – ϵ∞) and β for the three samples could be determined at each temperature. The value of (ϵ0 – ϵ∞), which is proportional to concentration of the dipoles contributing to the orientation, increased with rising temperature and reached a limiting value at about −20°C. The value of β relating to the width of the distribution of relaxation times also increased with rising temperature, showing a little rise in the degree of increase at temperatures above −20°C. On the other hand, the apparent activation energy for dipole orientation, as calculated from the temperature dependence of the dispersion frequency, reached a maximum around −20°C. All these facts suggest that some transition will take place in the neighborhood of −20°C. This temperature is not considered to be likely to be the glass transition temperature for dry cellulose, since −20°C. is too low for a primary transition in stiff molecules such as cellulose, and since the observed value of the apparent activation energy is too small to activate the segmental movement of the main chains. It might be possible to expect some secondary transition, probably of a thermodynamical nature, relating to the movement of local parts such as side chains, especially methylol groups on glucose residue, at about −20°C., though there is no other support for this expectation. Moreover, the effect of the fine structures on the dielectric properties is that the magnitude of (ϵ0 – ϵ∞) at each temperature decreases in the order, viscose rayon > Bemberg > cotton sliver, and this order parallels that of the accessibility of the three samples. This fact suggests that the dipoles in the amorphous region and on the surface of the crystallite provide the chief contribution to this dispersion.
Molecular weights of polymethyl methacrylate in rubber‐methyl methacrylate graft copolymers
Authors: Cooper W. , Vaughan G. , Madden R. W. 
Published: April 2003

AbstractMolecular weight distributions of homopolymer and graft polymer obtained from the gamma and photoinitiated polymerization of methyl methacrylate with natural rubber latex have been determined. Broad distributions were found with peaks of low and high molecular weight polymer. The distributions were insufficiently defined to make definite assignments to the speeds of the reactions involved but were not inconsistent with the mechanism proposed in an earlier paper from kinetic considerations. Details are given of the column fractionation apparatus employed.
The mechanism of radiation damage to elastomers. I. Chain scission and antirad action
Authors: Bauman Richard G. , Born John W. 
Published: April 2003

AbstractThe effect of antirads on the gamma radiation yields of scission in black loaded natural rubber stocks has been studied. The yield of chain scission has been measured by stress relaxation methods. The antirads were found to decrease the rate of chain scission, both in air and under nitrogen, with the antirad effectiveness being greater in the former case. The presence of oxygen accelerated the radiation induced chain scission. These results may be explained if it is assumed that (1) RO2 · radicals lead to chain scission more readily than do R · radicals, and (2) RO2 · radicals react with antirads leading to stabilized products more readily than do R · radicals.
The gelation of plastisols: An automatic method for the determination of plastisol temperature‐rheology characteristics
Authors: Alter Harvey 
Published: April 2003

AbstractA technique is described for the small scale evaluation of plastisol formulations for molding, casting, coating, and foam applications. The technique described rapidly measures and automatically records the viscosity of a plastisol as a function of temperature by means of a Bendix Ultra‐Viscoson and thermocouple. The measurements are made under conditions that closely approach process conditions. Small changes are accurately followed and the portion of the curve in the vicinity of gelation is amplified. The shape and position of the viscosity‐temperature plot are dependent on the chemical nature of the plasticizer as well as the intrinsic viscosity and molecular weight distribution of the dispersed polymer. The resulting curves can be used to choose plastisol compositions for a given application. The application of the curves to foam and rotational casting formulations is outlined.
A modification of the method of intermittent stress relaxation measurements on rubber vulcanizates
Authors: Ore Svein 
Published: April 2003

AbstractThe method of continuous and intermittent stress relaxation measurements on rubber vulcanizates developed by Tobolsky and co‐workers has been modified by the introduction of intermittent tangent modulus measurements during the continuous relaxation experiments. This allows rate of scission and crosslinking to be determined simultaneously and on the same specimen. The method is based on the use of small or moderate extension ratios α and on the fact that in this case the stress f in actual rubbers is represented more closely by the empirical relationship f = 3G(1−1/α) than by the theoretical f = G[α−(1/α2)], where 3G denotes Young's modulus at infinitesimally small strains.
The mechanism of radiation damage to elastomers. II. Crosslinking and antirad action
Authors: Bauman Richard G. 
Published: April 2003

AbstractThe effect of antirads (compounds added to reduce changes of polymer properties during irradiation) on the crosslink yields in black‐loaded natural rubber stocks during gamma irradiation has been measured. The crosslink yields were determined by swelling techniques. Antirads decrease the crosslink yields if oxygen is absent. Oxygen alone effectively decreases crosslink yields. In the presence of oxygen some antirads further decrease crosslink yields, while others increase crosslink yields by their presence. These results may be explained in terms of competitive reactions between R. radicals, the antirad, and oxygen. Evaluation of the ratios of crosslink yields and scission yields indicate that most of the scission is temporary in nature, the chain breaks being reformed rapidly.
A statistical study of the effect of formulation variables on the properties of sorbitol polyether‐based rigid urethane foam
Authors: Wilson J. E. , Truax H. M. , Dunn M. A. 
Published: April 2003

AbstractEach rigid urethane foam formulation must be carefully designed to meet the key requirements of its specific end use. For example, refrigerator insulation is an application which requires low thermal conductivity, low density, and excellent resistance to humid aging. The present investigation was carried out to determine variations in foam properties caused by changes in catalyst concentration, isocyanate/hydroxyl ratio in the quasi‐prepolymer, quasi‐prepolymer cooking time, dispersing agent concentration, and isocyanate/hydroxyl ratio in the total foam. The basic foam formulation contained sorbitol polyether (Hydroxyl Number 490), toluene diisocyanate, trichlorofluoromethane blowing agent, catalyst, and dispersing agent. The results showed that the tensile strength decreased as the isocyanate/hydroxyl ratio in the total foam increased. Shear strength was affected strongly by catalyst concentration, and by isocyanate/hydroxyl ratio in the prepolymer and in the total foam. Cure time (at room temperature) was strongly affected by catalyst concentration and technique of prepolymer preparation. The only factors having a significant effect on humid aging resistance were isocyanate/hydroxyl ratio in the prepolymer and in the total foam. The effects on thermal conductivity were complex, and included an interaction between dispersing agent concentration and catalyst concentration, and also between prepolymer preparation technique and isocyanate/hydroxyl ratio in the prepolymer. The compressive strength increased with catalyst concentration, and was strongly affected by prepolymer preparation techniques. Key effects and interactions were plotted in graphical form.