Effect of liquid media on fatigue strength of polyamides

The results of an experimental study of polyamide fatigue strength are presented. Multiple flexing tests were performed on specimens rotating at 3000 cycles/min with a symmetrical load cycle in various media, including air (with and without blowing), volatile liquids (petroleum ether, ethanol, water), glycerin, and transformer oil. Fatigue strength is determined from (N — log N) curves for 10⁶ cycles. Dissipation of heat is found to be the main factor determining the effect of slightly aggressive media on fatigue strength. Values of the ratio fatigue strength/static strength (coefficient K) are presented.Mekhanika polimerov, Vol. 1, No. 1, pp. 124–127, 1965     

Effect of loading regime on the heating of plastics subjected to cyclic deformation

In cyclic loading in the W = const and ₀ = const regimes, as in the ₀ = const regime, both a low-temperature and a high-temperature thermal regime may exist, with an abrupt transition from the former to the latter. The effect of the loading regime on the temperature dependence of the hysteresis temperature rise T, which depends on the elastohysteresis properties of the material, results in the following relationship between the critical temperature rises: T ₀ ^c T _W ^c T ^c .Scientific-Research Institute of Plastics, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 465–469, May–June, 1969.     

An efficient one—dimensional search procedure for barrier functions

In minimizing interior penalty functions, most of the computational time is spent on the one-dimensional search. This paper presents a method for performing this search on barrier functions which is significantly faster than current techniques. The method exploits the special structure of barrier functions. Comparative computational results are given for a set of six test problems.This research was partially supported by the National Aeronautics and Space Administration under Research Grant NSG 110-61 and by the Office of Naval Research under Grant No. N00014-67-A-0404-0010.     

Hydroxymercuration-demercuration of (±)-pinol

Conclusions The hydroxymercuration-demercuration of (±)-pinol leads to (±)-4-hydroxypinol.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1888–1890, August, 1981.     

Two point problems and analyticity of solutions of abstract parabolic equations

Fort ∈ [a, b], letA(t) be the unbounded operator inH ^0,p (G) associated with an elliptic-boundary value problem that satisfies Agmon’s conditions on the rays λ=±iτ, τ ≥0. Existence and uniqueness results are obtained for weak and strict solutions of two-point problems of the type (du/dt)−A(t) u(t) =f(t),E ₁(α)u (α)=u _α,E ₂ (β)u (β)=u _β. Here [α, β) χ- [a, b],E ₁ (α) andE ₂ (β) are spectral projections associated withA(α) andA(β) respectively, andA(α)E ₁ (α) and =A (β)E ₂ (β) are infinitesimal generators of analytic semigroups. WhenA(t) andf(t) are analytic in a convex, complex neighborhoodO of [a, b] we show that for someθ _i ,i=1,2, any solution ofdu/dt =A(t)u (t)=f(t) in [a, b] is analytic and satisfies the above equation in the setO∩{t; t ≠ a, t ≠ b, | arg (t −a) | <θ ₁, | arg (b −t) |θ ₂}. Research partially supported by N. N. F. grant at Brandeis University.     

Band structure of semiconductors with a famatinite lattice

The band structure of certain semiconducting compounds with a famatinite lattice is calculated by the pseudopotential method.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 27–33, February, 1973.     

High-capacitance organic nanodielectrics: effective medium models of their response

Molecular and macromolecular high-permittivity organic gate dielectric materials have been the focus of recent experimental research as a consequence of their promising properties for organic and inorganic field effect transistor (FET) applications. Two types of molecular thin films, self-assembled nanodielectrics (SANDs) and cross-linked polymer blends (CPBs), have been shown experimentally to afford high capacitances and low FET operating voltages. In an effort to design optimized nanostructures having even larger capacitances, lower leakage current densities, and further reduced FET operating voltages, we discuss approaches for computing the effective permittivities of each nanodielectric motif and investigate how molecular arrangements impact overall device capacitance. The calculated frequency-dependent capacitances, derived from Maxwell-Wagner theory applied to the Maxwell-Garnett effective medium approximation, agree fairly well with the experimental values for the two types of nanodielectrics. Predictions of larger capacitance SANDs are made with the two-capacitors-in-series equivalent circuit, where the layered, self-assembled structure is viewed as two different capacitors. The Maxwell-Garnett and Polder-Van Santen effective medium approximations are used to predict the dielectric response of higher permittivity polymer cross-linked blends. In calculations showing good agreement between theory and experiment, and with all parameters being equal, it is found that greater capacitances should be achievable with cross-linked composites than with layered composites.     

Stress-biased rearrangements and preyield behavior in glasses

On the basis of a physical picture of a glass as a mosaic of mesoscopic clusters differing in their yield characteristics, we propose a model for the preyield behavior in glassy materials; the model describes the stress-strain relationship at different strain rates in terms of one reduced variable. A test using experimental data for polycarbonate materials at different rates and temperatures appears favorable for the model. The model may be used to interpolate and extrapolate limited experimental data, and also provides a practical means to assess dynamic heterogeneities within polymeric glasses. When applied at different temperatures, the model gives insight into the dependence of the excitation energies on temperature (glassformer fragility) in the glassy state.