Showing papers by "University of Akron published in 1971"

Viscoelastic Characterization of a Nonlinear Fiber-Reinforced Plastic

Abstract: The nonlinear, viscoelastic behavior of a unidirectional, glass fiber-epoxy composite material is characterized by using isothermal, uniaxial creep and recovery tests together with a constitutive equation based on thermodynamic theory. The nonlinear constitutive equation for uniaxial loading is described first, and then fourth-order tensor transformations relating principal linear viscoelastic creep compli ances, uniaxial creep compliance, and fiber angle are summarized. Following a discussion of experimental aspects, creep and recovery data obtained from several different specimens (each having a differ ent fiber orientation relative to the loading axis) are reduced using a graphical shifting procedure and tensor transformations to evaluate all material properties, including the principal creep compliances. As a check on the constitutive theory, the data are shown to be in ternally consistent. Some simplicity in the analytical representation of the data is found; viz. the nonlinear, uniaxial creep compli...

An Efficient Algorithm for Multi-Item Scheduling

Abstract: A number of resource-allocation problems, including that of multi-item scheduling, may be solved approximately as large linear programs, as in Manne [Management Sci. 4, 115-135 1958]. Dzielinski and Gomory [Management Sci. 11, 874-890 1965] applied the Dantzig-Wolfe decomposition principle to this problem. Here, the problem is attacked directly, using a column generation technique and Dantzig and Van Slyke's generalized upper-bounding method [J. Comp. and Syst. Sci. 1, 213-226 1967]. For problems involving I items and T time periods, one need deal with a basis matrix of dimension only T by T. A lower bound on the optimal cost may be developed, and intermediate solutions all have Manne's integer property loc. cit.. Computational experiments, including an option for pricing out subproblem solutions until none is useful, show a number of iterations to optimality of from one-half to one-ninth the number required by the decomposition principle with work per iteration remaining approximately the same. Extensions of the basic model are also described. These form the core of an automated production-scheduling and inventory-control system, currently being used by a major U. S. manufacturer. Computational experience with this extended model is presented.

The Park as a Determinant of Property Values

Abstract: THIS PAPER is the result of a three year study conducted in Dallas and Fort Worth, Texas, to determine the impact of parks of various types upon the values of residential properties.1 The proxy for value which was used was assessed value for properties in both cities as developed by the two City Assessors. The study of the situation in Dallas was undertaken first with the study in Ft. Worth a kind of followup on the results in Dallas to see if these results were applicable to another community. The analysis in the present study was limited to the impact that the individual park might have on property values of properties near or within the use area of the park. Thus, the park may be an external value determining factor on the values of properties near or adjacent to it. Parks might cause either an increase or a decrease in the values of such properties. The limitations to the property analysis include the fact that data was collected only on properties quite near the park (within about 5 blocks) and included only about 700 properties around each of the parks analyzed. This meant that the property analysis did not extend as far as did the zone of park use (service area). Thus the relations measured may not be taken as a complete analysis of the functional relationship between park proximity and property value. It is known that a segment of relationship was measured, but there were not sufficient means nor sufficient data collected to determine the extent of the total dimension or geographic area around each park in which property values are affected. Another limitation to the analysis was that there appeared to be no logical way to relate the study of property values to areas which were not primarily residential. Assessment data on housing in most communities is of considerably higher quality than assessment data on commercial properties. An additional problem was that logically, commercial properties themselves can be a significant determinant of the value of nearby residences; thus, the zone of use of a given park might well extend into a mixed residential and commercial area. In trying to eliminate all the value factors of an external nature except the influence of the park, the segment around each park was necessarily small, homogeneously residential in character.

Process for polymerizing conjugated dienes

Abstract: The process described herein involves a method of converting relatively low molecular weight polymers by postreaction with a mixture of divinyl benzene and a haloalkane having no more than one halogen atom on any carbon atom, in the presence of an alkali metal catalyst, such as butyl lithium to give higher molecular weight polymers having improved cold flow resistance, processibility, green strength, etc. The improvements are much greater than can be effected by postreaction with either divinyl benzene or the haloalkane individually, or by having divinyl benzene present during the copolymerization. The haloalkanes include chloro, bromo, and iodo compounds and can have 1-4 or even more halogen atoms per molecule provided there are no more than one halogen atom on any carbon atom.

Structural analysis: a theory of personality based on projective techniques.

Abstract: Summary A new theory, Structural Analysis, is presented which postulates that personality is mediated through two hypothetical structures, the Facade Self and the Introspective Self. Implications for understanding personality dynamics and psychopthology were discussed. Applications of the theory to the interpretation and integration of projective test data were considered.

Polymerisation and block copolymerisation of cyclic sulphides

Abstract: The organolithium-initiated ring-opening polymerisation of cyclic sulphides in polar, aprotic solvents was investigated. It was found that at −78°C thiiranes are attacked at the sulphur atom by the carbanion of the organolithium. This reaction is followed by elimination of an olefin and formation of a lithium alkylthiolate. The polymerisation reaction then involves bimolecular nucleophilic displacement at a carbon atom of the monomer by the propagating thiolate. Similarly, the initiation of the thietanes takes place through reaction of the carbanion at the sulphur atom. This is followed by ring-opening and the formation of a new carbanion rather than the thiolate-lithium species. The homopolymerisation of thiiranes and thietanes is essentially free of termination and chain-transfer reactions. Thus, it is possible to prepare polythioethers of well-defined molecular characteristics. In addition, block polymers of poly-α-methylstyrene-poly(propylene sulphide)-poly-α-methylstyrene were synthesised using phosgene to couple the active lithium thiolate chain ends. Molecular weight measurements and gel permeation chromatograms indicate that block polymers were prepared possessing predictable molecular weights and narrow molecular weight distributions. Several other block polymers involving cyclic sulphides were also synthesised.

Tire cure programmer and function generator

Abstract: An apparatus for controlling sequence and duration of the operational steps in processes such as vulcanization of a pneumatic tire is capable of operating under two basic modes or parameters. In one mode the operational steps are dictated by elapsed real time, while in the other mode, the operation can be dictated by elapsed cure equivalent factors. The desired length of each step or the cure, whether in time or cure equivalents, is set into an input program means. In the time mode, time generating circuitry provides an output proportonal to elapsed time which output is displayed on a counter and electrically compared with the information in the input program means. When a match occurs, the time generating circuitry and displays are reset and the input program means directs the tire vulcanization press to perform the next sequential function. Also disclosed is circuitry which is capable of performing secondary functions such as extending the length of a step, as necessary. If it is desired to operate in the cure equivalent mode, a signal proportional to elapsed cure equivalents is developed by a cure equivalent generating circuitry which performs digital integration of the Arrhenius function. The input to cure equivalent generating circuitry can be a signal proportional to tire temperature developed by internal thermocouples or can be a signal which is directly proportional to the Arrhenius function as generated by a thermistor sensor.

Compositions containing epoxy resin, chain extender, functionally terminated elastomer and curing agent

Abstract: Hard and strong epoxy resin products of high impact resistance are made from a di-epoxy compound, a smaller than equivalent proportion of chain extender which is preferably a bis-phenol, and about 5% (based on the amount of the di-epoxy compound) of a functionally terminated elastomer which is preferably a phenol terminated liquid copolymer of butadiene and acrylonitrile, together with a curing agent active at elevated temperatures.

Fundamental studies on cationic polymerizations: Molecular weights and molecular weight distributions of polyisobutylenes produced by γ-irradiation (free ions) and chemical catalysis (ion pairs)

Abstract: The molecular weights (Mn, Mv, and Mw) and molecular weight distributions of polyisobutylenes synthesized by γ-irradiation in the range 29 to −78°C have been determined. The plots of log Mn, log Mv, and log Mw versus 1/T are linear and parallel (EM = −6.36 ± 0.5), and Mw/Mn ≈ 3.0 ± 0.5 over this temperature range. The viscosity-average molecular weights of polyisobutylenes obtained by γ-irradiation were compared with those of polymers prepared by BF3, EtAlCl2, and AlCl3. It is found that, at the same polymerization temperature, the Mv of radiation-induced polyisobutylenes, which propagate by free carbonium ions, is significantly higher than those synthesized by the Lewis acids, which probably propagate via ion pairs. The implications of these findings are discussed, and it is concluded that the counterion in the proximity of the growing cation impedes propagation to a greater extent than it does the competing process of chain transfer to monomer.

Metallation of unsaturated polymers and formation of graft copolymers

Abstract: The use of N,N,N′,N′-tetramethylethylenediamine (TMEDA) is known to enhance the metallation of capability of butyllithium. It has been found that this TMEDA–BuLi reagent smoothly metallates olefins in high yields at 50°C in less than 4 hr by replacement of allylic hydrogen. This reaction has been applied to unsaturated polymers such as polybutadiene and polyisoprene. The resulting products have lithium atoms scattered along the chain. The amount of lithium on the chain can be varied over wide limits. Each lithium atom on the chain can act as a site for grafting or adding functional groups to the base polymer. Thus, this method allows the preparation of polymers having controlled amounts of branching as well as the introduction of functional groups into the polymer. Through the use of this metallation technique, polymers containing styrene and butadience grafts are specifically reported. In addition, polymers containing hydroxyl or carboxyl groups along the backbone are prepared by using this technique.

Reduction of composite NMR spectra by using an analog computer

Abstract: An analog computer program has been devised to resolve complex composite curves such as might be encountered in various forms of spectroscopy or chromatography. Seven Gaussian or Lorentzian curves, or any combination of seven curves, can be used and displayed simultaneously to resolve the composite curves. Various degrees of skew and truncation, as well as slanted and curved baselines, can be introduced. The peak amplitude, width and position can be determined from potentiometer settings. The integrated relative area of each of the peaks is read out on a digital voltmeter with a reproducibility of about ±0.1%. The utility of the technique is demonstrated by resolving highly overlapped peaks in NMR spectra of butadiene–styrene copolymers. It is necessary to use as many as eight curves to resolve the styrene aromatic proton resonance. This analysis yields styrene-centered distributions and styrene sequence distributions from the NMR spectra of butadiene–styrene copolymers. In addition, it is shown that a distinction can be made between short styrene sequences, which contain two and three styrene units, and long styrene sequences, which include all sequences longer than three units.

Friction member assembly

Abstract: An annular friction member assembly for a disc type brake or clutch having segments of heat absorbing material sandwiched between and supported by facing members of carbon composite material. The facing members have driving lugs located at positions spaced from the heat-swept area for transmitting torque forces directly from the friction surfaces of the facing members to an associated brake or clutch part. Reinforcing members are located at the driving lugs and provide additional bearing area as well as added support to the facing members of carbon composite material to prevent failure under torque loads at the fasteners holding the facing members and the segments of heat absorbing material together.

Observations on the Impact Behaviour of Polyurethane Foams :II. The Effect of Fluid Flow:

Abstract: W hen small oscillatory compressions are applied to a flexible open-cell foam the flow of fluid through the matrix makes a significant contribution to the stiffness and the damping. The response of such systems, for small strains, is fairly well understood and there is reasonable agreement between theory and experiment ( 1, 2, 3, 4). It is found that as the frequency of compression is increased the loss tangent passes through a maximum, and the storage modulus increases to an equilibrium value. Phenomenologically, the frequency response is similar to that of a viscoelastic

Familial pheochromocytoma. Association with von Hippel-Lindau's disease.

Abstract: von Hippel in 1904 as one or more hemangiomas of the retina, each supplied by a dilated arteriole and vein.’ These lesions tend to progress and eventually result in retinal detachment, secondary glaucoma and blindness. It was noted by Lindau in 1926 that approximately 20% of these patients developed symptoms of an intracranial tumor. 2, 3 The typical tumor was a cystic hemangioblastoma involving the cerebellum, although similar lesions could be found in other areas of the brain and spinal cord. Cystic lesions of the pancreas and kidneys have also been described.4 Glusheim, et al in 1953 is credited with the first documented report of the association of pheochromocytoma and angiomatosis retinae in 2 patients.5 Later, Chapman, et al in 1962 described a patient with multiple hemangiomas of the brain stem and a pheochromocytoma.4 To date there have been 6 reported familial cases with this association 6

Process for the separation of a gaseous mixture

Abstract: This process relates to the separation of a gaseous mixture on a continuously moving solid adsorbent bed and applies particularly to the separation of a gaseous mixture characterized by linear, or quasilinear, adsorption isotherms and applies most particularly to the separation of ethane from ethylene on activated carbon.