Showing papers by "University of Akron published in 1993"

Some Forms of the Strain Energy Function for Rubber

Abstract: According to Rivlin's Phenomenological Theory of Rubber Elasticity, the elastic properties of a rubber may be described in terms of a strain energy function which is an infinite power series in the strain invariants I1, I2 and I3. The simplest forms of Rivlin's strain energy function are the neo-Hookean, which is obtained by truncating the infinite series to just the first term in I1, and the Mooney-Rivlin, which retains the first terms in I1 and I2. Recently, we proposed a strain energy function which is a cubic in I1. Conceptually, the proposed function is a material model with a shear modulus that varies with deformation. In this paper, we compare the large strain behavior of rubber as predicted by these forms of the strain energy function. The elastic behavior of swollen rubber is also discussed.

Electrospinning process and applications of electrospun fibers

Abstract: An electric field is used to create a charged jet of polymer solution. As this jet travels in air, the solvent evaporates, leaving behind a charged fiber that can be electrically deflected or collected on a metal screen. Fibers with a variety of cross-sectional shapes and sizes were produced from different polymers. These fibers had diameters in the range of 0.05 to 5 microns. The authors describe the electrospinning process, the processing conditions, fiber morphology, and some possible uses of electrospun fibers. >

Validity of the dissociative experiences scale in screening for multiple personality disorder: A multicenter study

Abstract: OBJECTIVE The Dissociative Experiences Scale has proved a reliable and valid instrument to measure dissociation in many groups, but its capacity to distinguish patients with multiple personality disorder from patients with other psychiatric disorders has not yet been conclusively tested. METHOD A discriminant analysis was performed to classify 1,051 subjects as having or not having multiple personality disorder. Another discriminant analysis was performed on a subgroup of 883 subjects more closely representing patients in a typical psychiatric facility in terms of base rates of dissociative disorders. A cutoff score of 30 was also used to classify subjects, and Bayes's theorem, which allows for the calculation of the positive predictive value and the negative predictive value of a screening test, was applied. RESULTS According to discriminant analysis of the total study group, the scale's sensitivity was 76% and its specificity was also 76%; according to discriminant analysis of the more representative subgroup, the scale's sensitivity was 76% and its specificity was 85%. Use of the cutoff score of 30 produced similar results. Results of the application of Bayes's theorem showed that 17% of the subjects scoring 30 or higher would actually have multiple personality disorder and 99% of those scoring less than 30 would not have multiple personality disorder. CONCLUSIONS These results indicate that the Dissociative Experiences Scale performs quite well as a screening instrument to identify subjects with multiple personality disorder. In addition, the consistency of responses to scale items across centers indicates that the symptoms reported by patients with multiple personality disorder are highly similar across diverse geographic centers. This consistency supports the reliability and validity of the diagnosis of multiple personality disorder across centers.

Managing emotions on the job and at home: understanding the consequences of multiple emotional roles

Abstract: This article explores work-family relations from the perspective of the emotion management performed by participants in both spheres. We extend previous discussions of emotion management by considering how work and family roles vary in the types and degrees of emotion management they require. We then explore the implications of this conception of work-family role variations in type and degree of emotion management for women's and men's work-family relations, paying particular attention to gender differences in work-family conflict and work-family role overload. The framework developed here highlights the need to examine variability in the emotion-management requirements of social roles, and it calls for attention to workers' multiple role involvements in studies of emotion management and their effects on individuals.

Externalizing in preschoolers and early adolescents : a cross-study replication of a family model

Abstract: With families of 3'/2-year-olds, the direct and indirect links among parents' depression, marital quality, parenting style, and their children's externalizing behavior were examined using partial least squares analysis. No direct paths were found between parents' depression and their child's behavior. Instead, parents' depression was mediated by the quality of their relationship as a couple or by their parenting style, or by both. A replication with families of 9- to 13-year-olds supported these findings in the form of the interconnections among family variables and children's outcomes, although the magnitude of the family-child linkage was much lower than it was in the younger sample. Children's cognitive and social competence has been found to correlate with their parents' psychological adjustment, parenting style, and, more recently, the quality of their marriage (C. P. Cowan, Cowan, Heming, & Miller, 1991; Hetherington & Clingempeel, 1992). Although the direction of influence, from child to parent or parent to child, has not been clearly established, findings have been consistent in relating children's adaptive or maladaptive behavior to parent functioning in intrapersonal , parent-child, and marital domains. The task of describing pathways from adult functioning to children's adaptation raises both conceptual and statistical issues. Conceptually, the fact that there is a correlation between, for example, mothers' depression and children's aggression, does not tell us whether there is a direct link between maternal and child behavior or an indirect link resulting from the influence of mothers' depression on the quality of their relationships with their children. Statistically, the problem is how to analyze direct and indirect effects in nonexperiment al, observationbased family studies. The question of whether family models of children's development have the same form when children are at different developmental levels has not been given the attention it deserves. Part

Portable point of sale terminal

Abstract: A point of sale terminal (11) is disclosed that provides all of the usual point of sale terminal functions, but that is entirely field portable. Data pertinent to each purchase can be input to the terminal via a keyboard assembly (17), a touch-screen display (19) or a signature-capture screen assembly (25), or via an antenna (39) and radio link from an associated bar code scanner. Data may be communicated at any time to a remote host computer, also via a separate antenna and radio link. The communication links with the host computer and the bar code scanner operate independently and simultaneously, using mutually compatible modulation schemes such as a spread spectrum scheme for the host computer link and a narrowband or spread spectrum scheme for the bar code scanner link. The terminal thereby functions as a portable repeater or node in a data communications network.

Hidden Markov model approach to skill learning and its application in telerobotics

Abstract: In this paper, we discuss the problem of how human skill can be represented as a parametric model using a hidden Markov model (HMM), and how an HMM-based skill model can be used to learn human skill. HMM is feasible to characterize a doubly stochastic process-measurable action and immeasurable mental states-that is involved in the skill learning. We formulated the learning problem as a multidimensional HMM and developed a testbed for a variety of skill learning applications. Based on "the most likely performance" criterion, the best action sequence can be selected from all previously measured action data by modeling the skill as an HMM. The proposed method has been implemented in the teleoperation control of a space station robot system, and some important implementation issues have been discussed. The method allows a robot to learn human skill in certain tasks and to improve motion performance. >

Neutral products formed during backbone fragmentations of protonated peptides in tandem mass spectrometry

Abstract: Collisionally activated dissociation (CAD) of the protonated polyalanines Ala-Ala,Ala-Ala-Ala, and Ala-Ala-Ala-Ala causes breakup of the peptide bonds leading to sequence-indicative fragment ions. The neutral molecules eliminated during these reactions are identified here using neutralization-reionization mass spectrometry (NRMS). N-terminal acylium ions (bn) arise after the C-terminus is lost as an intact amino acid or peptide; further loss of CO leads to immonium ions (an). Upon generation of C-terminal sequence ions (yn), a hydrogen atom attached to a nitrogen rearranges from the N-terminal to the C-terminal side yielding a protonated amino acid (y1) or peptide (y > or = 2) as the ionic fragment; the complementary neutral fragment is an aziridinone if the N-terminal amino acid is cleaved and a diketopiperazine if two N-terminal amino acid units are eliminated. Detection of neutral dissociation products can reveal valuable structure information, as demonstrated with the tetrapeptides Val-Gly-Ser-Glu and Val-Gly-Asp-Glu.

Compatibilizing agents in polymer blends : interfacial tension, phase morphology, and mechanical properties

Abstract: The interfacial tension, phase morphology, and phase growth was determined for four polymer blend systems: polyethylene/polystyrene, polyethylene/polyamide-6, polystyrene/polyamide-6, and polystyrene/poly(ethylene terephthalate). Generally, high interfacial tension correlates with coarse phase morphology and rapid phase coalescence. The addition of various potential compatibilizing agents to these binary blend systems results in lowered interfacial tension, finer and stabilized phase morphologies. The characteristics of different compatibilizing agents were compared for several of the blend systems. We also look at the influences of compatibilizing agents on mechanical properties of the blend systems. Some compatibilizing agents are able to produce substantial improvements in ultimate properties.

Rheology of concentrated dispersed systems in a low molecular weight matrix

Abstract: The objective of this paper is to provide a complete theoretical and experimental study of shear rheology for concentrated dispersed systems in low molecular weight matrices. A new theoretical approach based on qualitative microstructural physics and thermodynamical arguments is devel- oped which considers flow, elastic deformations, ruptures and restorations of flocs. The approach was developed to study steady and transient phenomena and has predicted very different behaviours for various systems; one of them was a non-monotonic flow curve. The most remarkable feature of the theoretical model is that it contains no mathematical yield criterion but predicts anisotropic yield values with continuous transition from solid state to flow as a bifurcation. A complete set of experiments in simple shearing was carried out for two different dispersed systems: a granular grease and a water-clay platelet mixture. Also some disturbing phenomena were observed and experimental techniques were developed which made it possible to obtain reliable results. Additionally the clay-water system exhibited a minimum in the flow curve, and all the characteristics peculiar to the evolution from solid state to flow, as predicted by the theory. Despite the short time scale of transition phenomena for the materials tested, the general comparison of experimental results with theory showed good agreement.

Predicting and Managing Turnover in Human Service Agencies: A Case Study of an Organization in Crisis:

Abstract: This study uses logistical regression to identify employee and organizational attributes contributing to the probability of voluntary turnover among child protective service caseworkers in a large ...

An integrated approach to detection of cracks using vibration characteristics

Abstract: An integrated technique based on the vibration theory to nondestructively identify multiple discrete cracks in a structure is presented. Two damage modeling techniques, one involving the use of massless, infinitesimal springs to represent discrete cracks and the other one employing the continuum damage concept, are integrated to provide a crack-detection technique that utilizes the global vibration characteristics of a structure but offers local information on each individual crack, including location and extent of the cracks. In the spring model, the Castigliano's theorem and the perturbation technique are used to derive a theoretical relationship between the eigenfrequency changes and the location and extent of the discrete cracks. In the continuum damage model, the effective stress concept coupled with the Hamilton's principle are used to derive the similar relationship that is cast in a continuum form. A unified g(β) function emerges from the two model approaches. The g(β) function can be determined through the mode shapes of an intact structure by means of the modal strain energy density. In the proposed integrated approach, the continuum damage model can be used first to identify the discretizing elements of a structure that contain cracks. Then, the spring damage model can be used to quantify the location and severity of the discrete crack in each damaged element. An example of a simply-supported beam containing two discrete cracks is given to illustrate the application and accuracy of the proposed approach.

Arthrodesis of the first metatarsophalangeal joint: a biomechanical study of internal fixation techniques.

Abstract: This study compares the strength and rigidity of four methods of internal fixation for arthrodesis of the first metatarsophalangeal joint Ten matched pairs of cadaveric first rays were harvested and arthrodesis performed by one of four techniques: (1) planar excision of joint surfaces and fixation with crossed Kirschner wires, (2) planar excision of joint surfaces and internal fixation with a dorsal plate and screws, (3) planar excision of joint surfaces and internal fixation with an interfragmentary screw, or (4) excision of the joint surfaces using powered conical reamers and fixation with an interfragmentary lag screw Biomechanical testing with a Bionix 858 materials testing machine was carried out, applying a plantar force utilizing principles of cantilever loading Force applied and displacement of the arthrodesis were recorded Of the four methods tested, bony preparation with power conical reamers and supplementary interfragmentary screw fixation was the most stable

Microstructural evolution and mechanical properties of SiC/Al2O3 particulate-reinforced spray-deposited metal-matrix composites

Abstract: In this study, aluminium-copper-based metal-matrix composites were synthesized utilizing the spray atomization and co-deposition technique. Microstructural characterization studies were carried out with an emphasis on understanding the effects associated with the co-injection of silicon carbide and aluminium oxide particulates. The results demonstrate the ageing kinetics of the spray-deposited and hot-extruded metal-matrix composites to be the same as those of the monolithic aluminium-copper material. Results of ambient temperature mechanical tests demonstrate that the presence of particulate reinforcement in the metal matrix does little to improve strength, and degrades the ductility of the matrix material. A model is formulated to compute the critical volume fraction of reinforcement. The results obtained using this model suggest that an optimum volume fraction of silicon carbide is essential in order to realize a strength improvement in the metal-matrix composite, relative to their monolithic counterpart.

Dose dependency and wound healing aspects of the use of tissue plasminogen activator in the prevention of intra-abdominal adhesions

Abstract: Intra-abdominal adhesions have been shown to result from the impairment of peritoneal fibrinolysis by inhibitors present in ischemic tissue. A reproducible model for the formation of intra-abdominal adhesions was utilized for the evaluation of the effectiveness of intraperitoneal applications of recombinant tissue plasminogen activator (rtPA) in adhesion prevention. Concentrations of rtPA required to overcome the inhibition of fibrinolysis in this model were estimated by titration of that amount of rtPA required to lyse blood clot in the presence of a measured amount of ischemic tissue. Adhesions were graded, and the hydroxyproline content of the abdominal wounds was analyzed. The effect of intraperitoneal administration of rtPA on adhesion formation was strongly dose related. Levels of rtPA of 0.01 mg/mL showed no effect (p Concomitantly, wound hydroxyproline content was significantly reduced (p=0.004). Prior investigations have shown a strong correlation between wound bursting strength and hydroxyproline content. The results of this study indicated that the levels of rtPA required to alter or prevent intra-abdominal adhesion formation also produce a significant impairment of the early phase of wound healing as measured by the wound content of hydroxyproline.

Polymerization-induced phase separation in a liquid-crystal-polymer mixture.

Abstract: We have used light scattering to study the kinetics of polymerization-induced phase separation in a liquid-crystal--polymer mixture. The evolution of the structure factor is compared with scaling predictions for thermally quenched systems. We have also observed a cascading phenomenon where phase separated domains become unstable and undergo phase separation for a second time.

Continuous ultrasonic devulcanization of vulcanized elastomers

Abstract: This invention relates to a continuous ultrasonic method and apparatus for breaking the carbon-sulfur (C-S), sulfur-sulfur (S-S), and if desired, carbon-carbon (C-C) bonds in a vulcanized elastomer. It is well known that vulcanized elastomers having a three-dimensional chemical network, cannot flow under the effect of heat and/or pressure. This creates a huge problem in the recycling of used tires and other elastomeric products. Through the application of certain levels of ultrasonic amplitudes in the presence of pressure and optionally heat, the three-dimensional network of vulcanized elastomer can be broken down. As a most desirable consequence, ultrasonically treated cured rubber becomes soft, thereby enabling this material to be reprocessed and shaped in a manner similar to that employed with uncured elastomers. The apparatus relates to the ultrasonic reactor (20) (e.g. an extruder). The reactor (20) is connected to an ultrasonic die assembly (10); the die assembly (10) consists of a transducer portion (12), which includes a power converter (14) and booster (13), connected to a horn portion (15), the assembly being supported by mounting bracket (18), and being attached to the reactor (20) through an adaptor portion (19). The reactor (20) includes a barrel (22), fed through hopper (24), the screw (26) within the barrel portion being driven by a drive (25), energized by a motor (28) (not shown). The horn portion (15) includes a die portion (16) through which the devulcanized elastomer being extruded is forced at a pressure shown by a pressure gauge (21). The ultrasonic generator (10) of the ultrasonic die of the invention, movably attached by mounting bracket (18) through adaptor legs (19) to a reactor (20). The reactor (20) is surrounded by a heating jacket (42). Vulcanized material is fed into die (16) through reactor bore exit (36) of exit bore diameter (dr) and into die inlet bore (38) of diameter (di). The vulcanized material is moved under pressure toward die exit bore (37) and leaves through die inlet bore (38).

Process for making polymers containing a norbornene repeating unit by addition polymerization using an organo (nickel or palladium) complex

Abstract: A single component ionic catalyst consists essentially of an organonickel complex cation, and a weakly coordinating neutral counteranion. The cation is a neutral bidentate ligand removably attached to a Group VIII transition metal in an organometal complex. The ligand is easily displaced by a norbornene-type (NB-type) monomer in an insertion reaction which results in an unexpectedly facile addition polymerization. A NB-type monomer includes NB or substituted NB, or a multi-ringed cycloolefin having more than three rings in which one or more of the rings has a structure derived from NB, and a ring may have an alicyclic alkyl, alkylene or alkylidene substituent. The insertion reaction results in the formation of a unique propagating species more soluble in a polar than in a non-polar solvent and devoid of an available β-hydrogen for termination. The ensuing propagation of a polymer chain proceeds without measurable unsaturation. The chain continues to grow until the insertion of a monoolefinic chain transfer reagent results in substantially all chains being terminated with the residue of the chain transfer reagent. This unique chain transfer reaction allows one to control the molecular weight in a relatively narrow range. The reaction mixture for controlling the mol wt of the polymer chains may contain any other catalyst which generates a propagating species by an insertion reaction in an essentially anhydrous solvent. Both, mol wt and glass transition temperature Tg are tailored to provide a weight average mol wt Mw>20,000 but preferably not greater than about 500,000, and a T g in the range from about 150° C. to about 400° C. or higher, if desired.

Cortisol, Biochemical, and Galvanic Skin Responses to Music Stimuli of Different Preference Values by College Students in Biology and Music:

Abstract: The purpose of this study was to examine biochemical and galvanic skin responses to music stimuli. Specifically, 30 university biology and 30 music students' plasma levels of norepinephrine and cortisol and their galvanic skin responses were measured before and after listening to two different musical selections, one of which was preferred (liked) by the music students and not preferred (disliked) by the biology students. The music-listening sessions and the controlled silent sessions were done in an anechoic chamber. 30 biology majors and 30 music majors were in the experimental groups; 14 biology and 17 music majors comprised the control group. Analysis indicated that the cortisol levels and galvanic skin responses were significantly higher for the music majors than the biology majors. The data indicate that music majors listen more critically and analytically to music than biology majors, and cortisol levels are associated with this as increases in music majors and decreases in biology majors after the music.

On‐line small‐angle and wide‐angle x‐ray scattering studies on melt‐spinning poly(vinylidene fluoride) tape using synchrotron radiation

Abstract: On-line small-angle and wide-angle x-ray scattering experiments were performed during the melt spinning of polyvinylidene fluoride using the DESY synchrotron light source. In these studies, the melt-spinning apparatus consisting of a screw extruder, a metering pump, and a take-up motor system were assembled on two separate stepper-motor-driven platforms. To investigate the structure development during crystallization, the tape location at the desired distance from the die could be positioned at the beam level with synchronous vertical movement of extruder and take-up platforms

The significance of enthesopathy as a skeletal phenomenon.

Abstract: Enthesophytes and enthesopathy, while easy to define, represent a phenomenon of unclear clinical significance. As the high frequency in skeletal populations suggests that enthesopathy may not be disease-specific, the nature of the reaction was assessed in 872 individuals from a representative skeletal population, subdivided into groups characterized by the presence or absence of rheumatoid arthritis, spondyloarthropathy, calcium pyrophosphate deposition disease and diffuse idiopathic skeletal hyperostosis (DISH). Achilles, plantar fascia, patellar and iliac crest entheses were examined for evidence of calcific overgrowth or "erosions." Enthesophytes were found to be a phenomenon of aging in individuals, and unrelated to the presence of inflammatory arthritis or DISH. The frequency increased with age, independent of sex or the site examined, plateauing in frequency after age 60. Enthesophytes in individuals under age 60 were usually unrelated to any underlying disorder. The absence of effect of underlying forms of arthritis on the frequency of enthesophytes at the patellar, Achilles and plantar sites suggests that mechanical factors outweigh the "enthesis calcifying" impact of such disorders as spondyloarthropathy, calcium pyrophosphate deposition disease and DISH. Individuals with rheumatoid arthritis, however, manifested a less severe iliac crest enthesial reaction, in keeping with the minimal reactive new bone formation characteristic of its erosions. Analysis of Achilles, plantar, and patellar enthesial reactions as a function of underlying inflammatory arthritis or DISH also revealed no significant variation with the underlying process. Cortical discontinuity at enthesial sites was a relatively infrequent phenomenon. While calcaneal discontinuities were originally thought to be erosive in nature, these observations suggest the possibility of tendon avulsion injuries.

The Validity of Job Knowledge Measures

Abstract: The validity of written job knowledge tests as predictors of job performance and training success was examined. Based on a sample of 363,528 persons and 502 coefficients, meta-analyses were performed to investigate the extent of validity generalization and the effects of two hypothesized moderator variables: content similarity and job complexity. Corrected mean validities were 0.45 for studies predicting job performance and 0.47 for studies of training success. Support was found for both moderators since validities were higher for high complexity jobs and when job-test content similarity was high. The implications of this study for personnel selection and research in the area of work performance are discussed.

Fuzzy implementation of direct self-control of induction machines

Abstract: A system with fast torque response is very beneficial in applications where direct torque control is highly desirable. The response of direct self control is slower during start-up and during change in command torque. Fuzzy control is used for the implementation of direct self control to improve its slow response. Experimental implementation of the fuzzy logic controller was carried out to verify the behavior of the controller. The controller was implemented with a single board computer that uses a TMS320C14 DSP. The experimental results with fuzzy control are compared with those of the conventional direct self controller. The starting flux and torque response and the responses to step changes in command torque with fuzzy implementation showed a considerable improvement over the conventional control. The steady state response for both controllers are the same. >

The enzymatic baeyer-villiger oxidation: A study of 4-substituted cyclohexanones

Abstract: A study of the enzymatic Baeyer-Villiger oxidation of a number of 4-substituted cyclohexanones utilizing the enzyme cyclohexanone oxygenase (E.C.1.14.13.-), isolated from the bacteria Acinetobacter NCIB 9871, is described.

Snap mounted attachment device

Abstract: A one-piece attachment device (15,16) for mounting an end of a fluid actuated member (14) on a support component (12,13). The attachment device has a plurality of first flexible fingers (58,94) which terminate at a tip provided with an outwardly extending shoulder (66,102) and a tapered camming surface (64,100). The fingers are moved inwardly by engagement of the camming surfaces (64,100) with the support component (12,13) as the fingers (58,94) pass through an aperture (44,50) formed therein, and thereafter attempt to return toward their original position. The finger shoulders (66,102) engage the support component (12,13) to secure the attachment device to the support component (12,13). A second plurality of inwardly and upwardly extending flexible fingers (70,97) are also provided on the attachment device and define an interior opening (72,110). A mounting stud (34) of a fluid actuated member (14) is inserted through the interior opening and the second fingers (70,97) will move outwardly initially upon passage of the stud (34) therethrough, afterwhich the fingers attempt to return toward their original position securely gripping and retaining the stud (34) therebetween to secure the fluid actuated member (14) to the attachment device (15,16). In another embodiment the second fingers (70,97) have inwardly extending tangs (104), the tips of which form the interior opening for securing and gripping the mounting stud therein.

Method of recovering recyclable unsintered powder from the 'part' bed of a selective laser-sintering machine

Abstract: This method teaches how to recover and reuse a powder of a thermally degradable material which is used in a selective laser sintering (SLS) process. To recycle such a laser-sinterable powder successfully in an SLS machine it is protected against degradation by cooling the hot bed while layer-upon-layer (layer-wise) of powder is being sintered, seriatim, to form successive slices fused together to form an article of arbitrary shape (part). The process requires maintaining the powder which has more than 80 % of the number of particles ∫53 νm as a quiescent bed which is nevertheless porous enough to permit flowing a cooling gas downwardly through the bed without disrupting its surface. Since each slice is formed at the surface, and the part, as it is formed, is supported in a well-insulated bed, the powder adjacent the slice is at a much higher temperature than powder in the rest of the bed, which, but for the cooling gas, would get overheated. Overheated powder not only degrades but is fused to the surfaces of the hot part forming a 'growth' which makes the part unusable for its intended purpose. The process allows one to recycle the unused powder from the bed to extinction, economically. If the powder, when hot, is also sensitive to oxygen, an inert gas is used as the cooling gas.