University of Akron

About: University of Akron is a education organization based out in Akron, Ohio, United States. It is known for research contribution in the topics: Polymer & Polymerization. The organization has 17401 authors who have published 29127 publications receiving 702386 citations. The organization is also known as: The University of Akron.

Compression, bending, and shear of bonded rubber blocks

Abstract: An approximate theoretical treatment is given for small compressions of bonded rubber blocks. The component of the compressive force arising from the bonded condition at the loaded surfaces is obtained from a pressure distribution within the block, given by the solution of the corresponding torsion problem. The bending of blocks is treated in a similar way, the pressure distribution in this case being derived from the corresponding bending stress function. The apparent shear of relatively thick blocks is then treated as a combination of shear and bending displacements. The location of an internal rupture and the deformation at which it occurs are also derived from a critical (negative) value of the pressure developed within the block, at which a small cavity increases indefinitely in size. The corresponding critical deformations are calculated for extension and bending displacements. The shear stresses developed at the bonded surfaces under extension, compression or bending displacements are also evaluated.

Success and Failure: Static Concepts in a Dynamic Society.

Abstract: Since program participants are inclined to view evaluators as a threat to themselves and their program, and since such a perception can restrict the flow of information about a program to the evalu

Mullins effect and rubber–filler interaction†

Abstract: A previously reported theory for the Mullins softening effect has been used to interpret various new data for the behavior of filled SBR rubber under tensile load. The strength of the filler–rubber bond, the filler surface area per polymer molecule attachment, and the average filler surface separation have been determined for two fillers, HAF black and Hi Sil-233 (a silica). A styrene–butadiene type filler (Pliolite S-6) has also been investigated. The temperature dependence of the filler–rubber bond has been measured; results lead to the conclusion that the bonds to carbon black and silica are high energy bonds, probably chemical in nature. It is shown that the recovery of hardness in prestretched, filled SBR is a rate process having an activation energy of about 22 kcal./mole. It is inferred from this and from permanent set data that the recovery is the result of the chemical breaking and reforming of the rubber chain network at the higher temperatures where recovery occurs. Silica-filled rubbers are shown to possess a pseudoyield stress which gives rise to an anomalous shape for the stress–strain curve of this material when it is stretched for the first time. A prestretched, silica-filled rubber recovers its hardness when left at 115°C. for 20 hr., but the anomalous portion of the curve is replaced by more normal behavior. Possible interpretations of the observed results are given.

Behavioral observation scales for performance appraisal purposes

Abstract: Behavioral items (N= 78) critical to the job success of logging supervisors were developed from 1204 critical incidents, the frequency with which a supervisor (N= 300) engaged in each behavior was rated on a 5-point Likert type scale by two sets of observers. A factor analysis reduced the items to 38 and 33, respectively, for the two sets of observers which in turn constituted 10 and 11 factors or criteria for performance evaluation purposes. Multiple regression equations based on composite scores were used to predict cost-related measures of logging crew effectiveness. The shrinkage in Rs after double cross-validation was moderately small. Moreover, the behavioral observation scales (BOS) that were developed by factor analyzing the observation ratings had moderately high reliability and accounted for more variance in the cost-related measures than did the BOS developed by traditional judgmental clustering techniques. The similarities and differences between BOS and BES procedures are discussed.

Plumage Color Patterns of an Extinct Dinosaur

Abstract: For as long as dinosaurs have been known to exist, there has been speculation about their appearance. Fossil feathers can preserve the morphology of color-imparting melanosomes, which allow color patterns in feathered dinosaurs to be reconstructed. Here, we have mapped feather color patterns in a Late Jurassic basal paravian theropod dinosaur. Quantitative comparisons with melanosome shape and density in extant feathers indicate that the body was gray and dark and the face had rufous speckles. The crown was rufous, and the long limb feathers were white with distal black spangles. The evolution of melanin-based within-feather pigmentation patterns may coincide with that of elongate pennaceous feathers in the common ancestor of Maniraptora, before active powered flight. Feathers may thus have played a role in sexual selection or other communication.