bluuebunny/crossref_metadata_2025_split huggingface dataset:
Decomposition‐based quantitative electromyography: Effect of force on motor unit potentials and motor unit number estimates
Authors: Boe Shaun G. , Stashuk Daniel W. , Brown William F. , Doherty Timothy J. 
Published: December 2004

AbstractDecomposition‐based quantitative electromyography (DQEMG) allows for the collection of motor unit potentials (MUPs) over a broad range of force levels. Given the size principle of motor unit recruitment, it may be necessary to control for force when using DQEMG for the purpose of deriving a motor unit number estimate (MUNE). Therefore, this study was performed to examine the effect of force on the physiological characteristics of concentric needle‐ and surface‐detected MUPs and the subsequent impact on MUNEs obtained from the first dorsal interosseous (FDI) muscle sampled using DQEMG. Maximum M waves were elicited in 10 subjects with supramaximal stimulation of the ulnar nerve at the wrist. Intramuscular and surface‐detected EMG signals were collected simultaneously during 30‐s voluntary isometric contractions performed at specific percentages of maximal voluntary contraction (MVC). Decomposition algorithms were used to identify needle‐detected MUPs and their individual MU firing times. These MU firing times were used as triggers to extract their corresponding surface‐detected MUPs (S‐MUPs) using spike‐triggered averaging. A mean S‐MUP was then calculated, the size of which was divided into the maximum M‐wave size to derive a MUNE. Increased levels of contraction had a significant effect on needle‐ and surface‐detected MUP size, firing rate, and MUNE. These results suggest that force level is an important factor to consider when performing quantitative EMG, including MUNEs with this method. Muscle Nerve, 2005
Relationship between symptoms and functional performance in COPD
Authors: Reishtein Judith L. 
Published: December 2004

AbstractWe studied the relationships among functional performance and three symptoms—dyspnea, fatigue, and sleep difficulty—in a sample of 100 people with chronic obstructive pulmonary disease (COPD). All participants had an FEV1 60% or less of the predicted level for age, sex, and height. Consistent with the Theory of Unpleasant Symptoms, dyspnea correlated with both fatigue and sleep difficulty. Dyspnea and fatigue both had moderate negative correlations with functional performance, while sleep difficulty had a small nonsignificant negative correlation with functional performance. After controlling for age and oxygen use, dyspnea was the only symptom to predict variance in functional performance significantly. Of the three symptoms studied, only dyspnea was related to both the other symptoms and to functional performance. Focusing on dyspnea may be the best way to improve both symptom experience and functional performance in people with COPD. © 2004 Wiley Periodicals, Inc. Res Nurs Health 28:39–47, 2005
Group‐based HIV risk reduction intervention for adolescent girls: Evidence of feasibility and efficacy
Authors: Morrison‐Beedy Dianne , Carey Michael P. , Kowalski Jeanne , Tu Xin 
Published: December 2004

AbstractThe purposes of this pilot study were (a) to assess the feasibility of a community‐based, small group HIV risk reduction intervention with adolescent girls, and (b) to obtain preliminary evidence of the efficacy of this theoretically‐guided intervention using a controlled design. The feasibility of the intervention was demonstrated by successfully implementing it with 33 sexually‐active, single girls. Preliminary evidence of the efficacy of the intervention was obtained using a randomized trial with 62 sexually‐active, single girls. Data obtained at a 3‐month follow‐up assessment showed that girls who received the HIV‐related intervention improved their HIV‐related knowledge and enhanced their motivation for risk reduction compared to girls who received a control (health promotion) intervention. Effect sizes suggest that the HIV intervention also reduced several risk behaviors (e.g., vaginal sex without a condom, giving oral sex, and alcohol and drug use before sex). Challenges to implementation and suggestions for intervention enhancement are discussed. © 2004 Wiley Periodicals, Inc. Res Nurs Health 28:3–15, 2005
Impact of training on work‐related assault
Authors: Nachreiner Nancy M. , Gerberich Susan Goodwin , McGovern Patricia M. , Church Timothy R. , Hansen Helen E. , Geisser Mindy S. , Ryan Andrew D. 
Published: December 2004

AbstractAlthough training is often recommended as a part of a comprehensive approach to address occupational violence, little empirical literature exists to support this recommendation. Over 40% of nurses responding to the Minnesota Nurses Study reported being trained about occupational violence, involving seven different training topics. Although at the univariate level, an increased risk was identified for nurses trained in managing assaultive/violent patients, no statistically significant results remained at the multivariate level. This lack of protection from training is consistent with previous research, although the explanations for this lack of effect remain unclear. Additional research is necessary to obtain more specific details on occupational violence training, including training content and methods, to understand more thoroughly the impact of training on occupational violence. © 2004 Wiley Periodicals, Inc. Res Nurs Health 28:67–78, 2005
The effect of ambient moisture and temperature conditions on the mechanical properties of glass fiber/carbon fiber/nylon 6 sandwich hybrid composites consisting of skin‐core morphologies
Authors: Ishiaku U.S. , Hamada H. , Mizoguchi M. , Chow W.S. , Mohd Ishak Z.A. 
Published: December 2004

AbstractThe concept of skin‐core (SC) morphology was used to make sandwich hybrid composites in which the skin and core were composed of different fibers in the same matrix. The sandwich blends comprising glass skin with carbon core and vice versa were compared with those of the hybrid composite, while the respective carbon (CF) and glass fiber (GF) composites served as points of reference. The composites were compounded and fabricated into injection molded tensile specimens and 3‐mm thick plaques. The effect of ambient temperature and moisture was studied. The fracture mechanical characterization of the various materials was done by using notched compact tension (CT) specimens. Tensile properties were also used to characterize the composites. Morphogical studies based on scanning electron microscopy and light microscopy were used to elucidate fracture characteristics. Deterioration of properties was noticed under hot and humid conditions. Synergism in flexural properties was observed in the CF/GF/PA hybrid composite. The mechanical properties of the CF/GF/PA hybrid are closer to those of CF/PA, suggesting a cost advantage by substituting half of the carbon fibers with glass fibers. Dynamic mechanical analysis results revealed that synergism in Tg is attained by blending or sandwiching glass and carbon fibers. Morphological studies reaffirmed the skin‐core morphology of the composites. POLYM. COMPOS., 26:52–59, 2005. © 2004 Society of Plastics Engineers.
Processing of single polymer composites using the concept of constrained fibers
Authors: Barkoula Nektaria‐Marianthi , Peijs Ton , Schimanski Tilo , Loos Joachim 
Published: December 2004

AbstractThe concept of “overheating” is one of the known methods for manufacturing single polymer composites. This concept is validated on two categories of semi‐crystalline polymers: the drawable, apolar (i.e., isotactic polypropylene [iPP], ultra‐high molecular weight polyethylene [UHMWPE]) and the less drawable, polar ones (i.e., polyethyleneterephalate [PET] and polyamides [PA]). The interchain interactions in apolar polymers are relatively weak and therefore a high degree of drawability can be obtained. Polar polymers on the other hand have relative strong interchain interactions, they are therefore less drawable. A shift higher than 20°C of the melting temperature can be obtained in case of highly extended iPP (draw ratios >14). Ultra‐drawn PE shows only 10°C overheating upon constraining and this is mainly due to the change in chain mobility for PE in the hexagonal phase. In case of PET and PA6, only draw ratios of 4 could be reached; however, temperature shifts of about 10°C for constrained fibers compared to unconstrained fibers could be measured. A proof of principle of the potential of the constraining concept for the manufacturing of single polymer composites is obtained by the preparation of single fiber model composites. The effect of the post‐drawing conditions on overheating is examined in details on the example of iPP. It is concluded that both post‐drawing temperature and ultimate draw ratio have a significant influence on the degree of overheating. POLYM. COMPOS., 26:114–120, 2005. © 2004 Society of Plastics Engineers
Fatigue crack propagation in composites with spherical fillers—part 1
Authors: Gadaree K. P. , Salee G. 
Published: December 2004

AbstractA study of the effect of various percentages of a spherical filler in a brittle matrix resin on fatigue crack propagation rates was carried out. The resin was a low‐molecular‐weight [Mn‐8200;Mw/Mn= 2.04] Bisphenol A‐terephthalate/isophthalate thernmoplastic copolyester. The fly ash filler had a mean diameter of 20μ. Experiments were done with 10 to 40 wt.% filler compliance method. A paris law model fits the data for the unfilled and the 10 wt.% filled compositions. At higher percentages of filler, however, a pattern of increasing and decreasing crack growth rates is observed. The pattern is unique for a given specimen. A mechanism is proposed to explain this behavior.
Some effects of matrix and interface properties on the fatigue of short fiber‐reinforced thermoplastics
Authors: Mandell J. F. , McGarry F. J. , Huang D. D. , Li C. G. 
Published: December 2004

AbstractThe fatigue behavior of injection‐molded tensile bars of short‐fiber‐reinforced theromplastics is described and related to the fatigue behavior of the matrices and the strength of the fiber/matrix interface. A brittle matrix system based on polyphenylene sulfide is shown to behave in a similar manner to long‐fiber composites. Glass‐fiber reinforcement in this matrix gives fatigue sensitivity that correlaes with that of unimpregnated glass fiber strands, while carbon‐fiber rein‐forcement gives better fatigue resistance. A well‐bonded, due‐tile matrix system based on nylon 6,6 gives matrix‐controlled fatigue sensitivity. Fatigue data for glass‐ and carbon‐fiber‐reinfoced nylon 6,6 superimpose on the matrix fatigue data when normalized by the ultimate tensile strength. Another ductile matrix, polyetherther ketone, is very fatigue‐resistant, but its composite progressively loses its reinforcing effect in fatigue, apparently due to interface failure. A transitional matrix, polysulfone, shifts from ductile to fatigue‐crack‐dominated failure as the cyclic stress is reduced. Its composites show an analogous failure mode shift, and the high cycle‐fatigue response is correlated with fatigue‐crack‐growth data.
Effect of fiber‐aspect ratio and orientation on the stress‐strain behavior of aligned, short‐fiber‐reinforced, ductile epoxy
Authors: Masoumy E. , Kacir L. , Kardos J. L. 
Published: December 2004

AbstractIn the study of complex short‐fiber‐reinforced plastics behavior, it is helpful to begin with a well‐aligned short‐fiber system. This study isolates the effects of fiber‐aspect ratio and orientation distributions on the tensile stress‐ strain behavior and failure mechanisms for a system containing 50 vol% E‐glass fiber bundles in a ductileepoxy matrix. Using a system wherein the fiber orientation distribution was well‐characterized, it is shown that the fibers reinforced as bundles rather than as individual fibers. As the bundle‐aspect ratio varied from 185 to 557 for samples tasted in the longitudinal majoralignment direction, the modulus rose from 85 to 99 percent of the value for a continuous fiber system, while the strength rose only to about 60 percent of the continuous‐fiber system. The ductility of the matrix had no effect on the modulus or the longitudinal strengths, but the off‐axis strengths were significantly higher than has been reported for a comparable brittle‐matrix system. The effects of fiber orientation on modulus and strength were successfully fit with the Leknitskii and Azzi‐Tsai equations, respectively. SCanning electron micros‐copy showed excellent adhesion and no fiber brekage, except at the highest bundle‐aspect ratio. Even at off‐axis angles below 15°, a mixed mode failure mechanism occurs because of the fiber orientation distribution.
Temperature increase of sheet molding compound (SMC‐R65) in flexural fatigue test
Authors: Hoa S. V. , Nguyen Q. B. 
Published: December 2004

AbstractThe temperature increase in flexural fatigue testing of sheet‐molding compound SMC‐R65 is investigated within a range of testing frequencies from 1000 cpm to 2200 cpm. Variation of the testing frequency affects the temperature increase and, based on 10 percent reduction in flexural stiffness, the effect of changing frequency on the fatigue lives was not detected. Steady‐state temperatures are obtained in the case of specimens tested in air. A temperature analysis is carried out that gives reasonable agreement with experimental values.
Interlaminar shear properties of graphite fiber, high‐performance resin composites
Authors: Varma D. S. , Needles H. L. , Kourtides D. A. , Fish R. H. 
Published: December 2004

AbstractShear properties of laminates consisting of graphite fiber (Celion 6000, Celion 3000, and T‐300) and several resins (epoxy, hot melt‐bismaleimide, solvent bismaleimide, polyimide, and polystyrylpyridine (PSP)) were measured using the short‐beam test. The interlaminar shear strength of epoxy composites was hightest. All other resin composites showed considerably lower shear properties. The shear strengths deereased with temperature, with the loss up to 100°C being more pronounced. The PSP composites did not show a loss in strength in the temperature range investigated (room temperature to 250°C). Boiling the composite samples in water for 24 h resuled in negligible reduction in shear strength in all cases. The interlaminar shear properties depended on the fiberresin interfacial bond, the wetting characteristics of the resin, and the resin meechanical properties. Attempts were made to determine to what extent each of these factors controlled the shear properties of the composites studies. Thus, the interfacial bond between the resin and the single fiber was determined. Results showed that the lower shear strength of polyimide, bisimides and PSP composites, as compared to epoxy resin composites, seemed to be due to their corresponding low interfacial bond strengths. The subsequent decrease in shear strength with temperature appeared to be directly correlated to the decrease in bond strength. The wettability of carbon fiber tow with all these resins was also determined. The small variations in wetting characteristics of the resin did not seem to justify the rather large differences in shear‐strength properties observed.
Synthesis and characterization of bisimide amines and bisimide amine‐cured epoxy resins
Authors: Scola Daniel A. 
Published: December 2004

AbstractA series of novel bisimide amines were synthesized and characterized and then utilized as curing agents with a standard epoxy resin, N,N′‐ tetraglycidyl‐methylenedianiline (TGMDA), known commercially as MY720. The bisimide amines (BIA's) were synthesized by reaction of 4,4′‐hexa‐ffuoroisopropylidine (biphthalic acid dianhydride) (6F anhydride) with aromatic and aliphatic diamines in dimethyl formamide at reflux temperatures in yields ranging 24 to 99 percent. The diamines used were 3,3′‐diaminodiphenylsulfone (3,3′‐DDS), 4,4′‐diaminodiphenylsulfone (4,4′‐DDS), 1,12‐dodecanediamine (1,12‐DDA), alone and as mixtures to produce the BIA's 6F‐3,3′‐ DDS, 6F‐4,4′‐DDS, 6F‐3,3′‐DDS‐4,4′‐DDS, 6F‐3,3′‐DDS‐1, 12‐DDA with various compositions, depending on the mode of addition and stoichiometry. The BIA's are isolated as mixtures containing monomer, oligomer, and polymeric species. They were characterized by elemental analysis, and high pressure liquid chromatography (HPLC). Epoxy resin specimens were fabricated by reaction of the standard epoxy (MY720) with the BIA and in some cases, mixtures of BIA and aromatic diamine, such as 3,3′‐DDS. The bisimide amine cured epoxies (IME's) were characterized for moisture absorption, thermal properties, physical and mechanical properties. The bisimide amine epoxy (IME) resins were also characterized as matrices in Celion 6000/bisimide amine cured epoxy (IME) composites. The relative toughness characteristics of each IME formulation was measured by the 10° offaxis tensile test by measuring the uniaxial tensile, shear strengths and shear‐strain‐to‐failure of the composite systems.
Use of processing aids and coupling agents in mica‐reinforced polypropylene
Authors: Chun I. , Woodhams R. T. 
Published: December 2004

AbstractLow molecular weight waxes prepared by the maleation of thermally degraded polypropylene are effective substitutes for silane coupling agents in filled polypropylene resins. The addition of 1 to 5 percent maleated polypropylene wax increased the tensile and flexural strength of mica‐filled polypropylenes without significant changes in the modulus or fracture toughness. The waxes also aided dispersion, reduced melt viscosity, and permitted direct injection molding of powder blends without precompounding. The influence of maleated polypropylene wax coupling agents on the mechanical properties is similar to the published behavior of chlorinated paraffin waxes, but without the undesirable corrosiveness. The efficient utilization of untreated micas as reinforcing fillers for general purpose polypropylene homopolymers can have important cost savings in the fabrication of mica‐reinforced automotive components.
The effect of aspect ratio of inclusions on the elastic properties of unidirectionally aligned composites
Authors: Tandon G. P. , Weng G. J. 
Published: December 2004

AbstractThis paper examines the influence of aspect ratio α, from zero to infinity, on the effective elastic moduli of a transversely isotropic composite. The reinforcing inclusions, which could be flakes or short fibers, are assumed to be spheroidal and unidirectionally aligned. Of the five independent elastic constants, the longitudinal Young's modulus E11 and in‐plane shear modulus μ12 appear to increase with increasing aspect ratio, while the transverse Young's modulus E22, out‐plane shear modulus μ23, and plane‐strain bulk modulus K23, generally decrease. It is further noted that E11 is more sensitive to α when α > 1 but the others are more so when α < 1. The present analysis was carried out by the combination of Eshelby's and Mori‐Tanaka's theories of inclusions.
Polypropylene composites: Fracture mechanics analysis of impact strength
Authors: Bramuzzo M. , Savadori A. , Bacci D. 
Published: December 2004

AbstractAn investigation according to LEFM (Linear Elastic Fracture Mechanics) principles has been carried out to determine impact resistance of PP (polypropylene) containing calcium carbonate in comparison with other types of mineral fillers. The tests have also allowed us to emphasize the strong influence of matrix brittleness or ductility on decreasing or increasing of toughness. In any case, of those materials tested, the calcium‐carbonate‐filled polypropylene is the material with the best performance. Scanning microscope (SEM) analysis and comparison of the results with the theoretical models reported in the literature made it possible to point out some particular aspects of this type of behavior.
Fracture behavior of glass‐cloth‐reinforced composites
Authors: Agrawal D. C. , Agarwal B. D. , Banerji K. 
Published: December 2004

AbstractThe fracture behavior of glass‐cloth‐reinforced composites has been studied. Fracture of these composites proceeds by tensile failure of fibers rather than by the shear failure of the matrix or the interface. Although the spread of damage in these composites is restricted to small distances away from the crack path due to the interweaving of the fibers, this distance is found to be appreciably larger for the samples with smaller initial crack lengths. Characteristic distances associated with the Whitney‐Nuismer criteria are, in turn, found to be smaller for these composites than for the angle ply laminates or randomly oriented short‐fiber composites reported in literature in which the spread of the damage is much greater. Analysis through the crack growth resistance also supports this correlation with the extent of damage spread and indicates that the critical crack length for these composites may be equal to the best fit value of the characteristic distance of the average stress criterion.
Statistical aspects of tensile strength of aramid fibers and unidirectional composites
Authors: Kompaniets L. V. , Potapov V. V. , Grigorian G. A. , Prut E. V. , Enikolopian N. S. 
Published: December 2004

AbstractThe effect of gage length and temperature on tensile strength of aramid monofilaments, yarns, and strands has been studied in view of statistical models of the theory of strength. The tensile strength of monofilaments and yarns is found to decrease as the gage length is increased. The strength of strands remains constant. The temperature resistance of strands is determined by the glass transition temperature of a polymeric matrix.
Electrical resistivity behavior of solution‐cast metal‐filled composites
Authors: Singh Rajeev R. , Roberts Robert W. 
Published: December 2004

AbstractSolvent‐cast metal‐filled composites made of polymethyl methacrylate and aluminum or copper exhibited electrical resistance behavior as is predicted by the percolation and tunneling mechanisms. A precipitous change in volume resistivity of about 1010 ohm‐cm was found to be thermally dependent at volume concentration of filler in the range from 17 to 19.5 percent. Materials with compositions at the conductive‐non‐conductive threshold showed semi‐conductor behavior and exhibited memory switching.
Fracture behavior of mica‐reinforced polypropylene: Effects of coupling agent, flake orientation, and degradation
Authors: Vu‐Khanh T. , Fisa B. 
Published: December 2004

AbstractThe effects of such factors as flake size, orientation, and surface treatment on the fracture mechanism of mica‐reinforced polypropylene were investigated. Concepts of post‐yield fracture mechanics were used to characterize the crack initiation and propagation resistances of the composite. It was found that better flake alignment slightly increases the yield strength but does not affect the crack growth resistance of the material. Flake size degradation during processing leads to an increased crack initiation resistance but reduces the tearing capacity and the maximum crack growth resistance of the composite, due to a reduction of the extent of matrix deformation. In the same manner, the use of a coupling agent diminishes the effect of matrix drawing and the total energy dissipated during the fracture process, even though the crack initiation resistance can be increased.