This paper describes the effect of cyclic loading upon the compressive strength, the stress-strain relationship, and the energy absorption and dissipation characteristics of short concrete columns (stub columns) at various slow strain rates. Comparison is made with columns loaded monotonically at similar strain rates. The columns were confined laterally by high-tensile steel bolts, inserted horizontally in two orthogonal directions through preformed ducts; the annular space between ducts and bolts was grouted with high-strength epoxy resin. Both steel and concrete deformational response was measured. Significant enhancement of the strength and ductility of the concrete was obtained. Columns displayed large energy absorption and dissipation capacity under cyclic loading. The validity of an envelope curve to describe cyclic behavior is discussed.

We have used the pulsed time structure of the Cornell High-Energy Synchrotron Source (CHESS) to carry out a nanosecond resolution time-resolved x-ray study of silicon during pulsed-laser irradiation. Time-resolved temperature distributions and interfacial overheating and undercooling were measured on 〈111〉 and 〈100〉 silicon during 25 ns UV laser pulses through the analysis of thermal expansion induced strain. The temperature gradients were found to be > 107 K/cm at the liquid-solid interface and the temperature distributions have been shown to be in agreement with numerical heat flow calculations for these laser conditions. The combined overheating and undercooling (during ∼ 10 m/s melting and ∼ 6 m/s regrowth) was measured to be 110 ± 30 K on 〈111〉 oriented silicon and 50 ± 25 K on 〈100〉 silicon. These values have been interpreted in terms of velocity coefficients of overheating and undercooling.

Fine-grain polycrystalline silicon has been produced by low-energy pulsed-laser irradiation of copper-implanted amorphous silicon. This fine-grained material can be regrown epitaxially on the (100) substrate using thermal annealing at temperatures ranging from 800°–1000 °C.

Knoop hardness measurements have been carried out as a function of azimuthal angle and temperature (in the range 20°–440°C) on {001} faces of n-type, p-type, and intrinsic Ge and GaAs. The degree of hardness anisotropy shown increases with increasing temperature and for Ge is undetectable below a certain temperature which depends on doping. In GaAs, asymmetry in hardness between [110] and [110] directions was found at high temperatures. A new model of hardness anisotropy has been developed, based on detailed modeling of the plastic zone. This relates the hardness to the degree of workhardening in different regions of the plastic zone. Using this model, detailed explanations are given of the hardness anisotropy behavior and of the plastic recovery around indentations.

The in-plane and c-axis structure of KHx—GIC's and KDy—GIC's is studied using transmission electron microscopy (TEM) and x-ray diffraction as a function of intercalation temperature and time. With the TEM, two commensurate in-plane phases are found to coexist in these compounds with relative concentrations depending on intercalation conditions. When the direct intercalation method is used, the first step of intercalation is the formation of a stage n potassium-GIC and the final compound is a stage n KHx—GIC (or KDy—GIC). Highresolution (00l) lattice images show direct evidence for intermediate phases in the intercalation process. These intermediate phases are hydrogen (deuterium) deficient and are found at the boundary between pure potassium regions and regions with high hydrogen (deuterium) content. A comparison of the structure for the two methods of intercalation of KH is also presented.

Monoclinic βZnP2 (black ZnP2) single crystals, synthesized in the presence of excess P, contain regions of polysynthetic lamellar-twinned structure, with dislocations and stacking fault-like features. The twin law is a* twin axis, (100) composition plane: (100) is also the slip plane. The twin composition plane migrates across (100) lattice fringes. In the revised βZnP2 crystal structure, Zn(1) and P(4) positions are related across a (100) twin composition plane at x = 0.84 by two twin operations, with axes through is also a possible slip plane, with three partial dislocations, ½[001], ½[001], and ½[001]. A third possible twin operation relates Zn(2) and P(1) positions across a (100) twin plane at x = 0.5, with twin axis through All twin and slip operations result in very little distortion in nearest- and nextnearest-neighbor coordination geometries. Twin and stacking fault mistakes may be facilitated by approach of the monoclinic cell parameter ratio c[α sin(β — π/2)] to 4 (which yields a pseudo-orthorhombic unit cell) and by Zn1-xP2 nonstoichiometry.

Elastic strain energy and forces on point defects in a two-phase medium with a planar interface are analyzed employing the surface dislocation analysis developed earlier for three-dimensional distortions. The important field components, namely, the tractions and the displacements arising due to the point source at the interface, are determined. Furthermore, the field components at the interface are used to determine the elastic strain energy associated with the point source in the two-phase medium and the elastic force exerted by the second phase on the point defect. The significance of these results to the force acting on a vacancy or an interstitial at the interface is emphasized.

The temperature dependence of the tracer diffusion coefficient D* of long deuterated polystyrene (d-PS) chains of molecular weight M>Mc, where Mc is the critical molecular weight for entanglement, diffusing into highly entangled PS matrices, each of molecular weight P = 2×107, is studied using forward recoil spectrometry. It is found that the temperature dependence of D*/T, reflected primarily in the monomeric friction coefficient, is accurately described by a Vogel equation. The constants that are used to fit these results are independent of M and are the same as those used to fit the temperature dependence of the zero shear rate viscosity of polystyrene.

The kinetics of silicide growth are classified into three different categories: (a) diffusion controlled, (b) nucleation controlled, (c) others (reaction rate controlled). These are analyzed with the aim of understanding both the phenomenology of growth and the specific atomic mechanisms of phase formation. Diffusion-controlled growth is discussed with respect to the Nernst-Einstein equation. Stress relaxation is considered as a possible cause of reaction-rate control. The relative merits of two different types of marker experiments are compared. A few silicides are discussed in terms of what can be inferred about diffusion mechanisms. The competition between reaction-rate and diffusion control phenomena is shown to have specific effects on the sequence of phase formation; it is also related to the formation of some amorphous compounds. Reactions between silicon and alloyed metal films are used to illustrate the respective influences of mobility and driving force factors on the kinetics of silicide growth; they can also be used to underline the dominance of nucleation over diffusion in some silicide formation processes.