Under-ice sonar surveys were carried out in pack-ice fields near Fletcher’s Ice Island and at two sites north of Pt. Barrow, Alaska, U.S.A. A narrow-beam scanning sonar was used to measure the location and relative back-scattering of features on the under surface of Arctic sea ice. The 48 kHz sonar had a 1.5° by 51 ° beam width. Graphic records displaying the range and relative scattering levels were assembled into sonar maps which display location and shape of under-ice features. Two distinct types of back-scattering were found: (1) very high-level back-scattering from well defined under-ice ridges and (2) very low back-scattering from areas between ridges. Higher scattering at ridges was probably due to an increase of roughness and tilting of the average plane of the scattering surface. To measure depths of features, the sonar transducer was adjusted to give a wide horizontal beam and a narrow vertical beam. Polar scans were taken at several depths of the transducer to determine depths of ridges. The tops and bottoms of features were compared and the average ratio of peak elevation to keel depth was about 1:7.

Fuller accounts of some of this work have been published elsewhere (Berkson and others, 1973; Clay and Leong, 1974; Kan and others, 1974}.

In the context of a locally compact abelian group, we establish maximal theorem counterparts for weak type (1,1) multipliers of the classical de Leeuw theorems for individual strong multipliers. Special methods are developed to handle the weak type (1,1) estimates involved since standard linearization methods such as Lorentz space duality do not apply to this case. In particular, our central result is a maximal theorem for convolutions with weak type (1,1) multipliers which opens avenues of approximation. These results complete a recent series of papers by the authors which extend the de Leeuw theorems to a full range of strong type and weak type maximal multiplier estimates in the abstract setting.

Let X be a closed subspace of LP (μ), where μ is an arbitrary measure and 1 < p < ∞. By extending the scope of spectral integration, we show that every invertible power-bounded linear mapping of X into X has a functional calculus implemented by the algebra of complex-valued functions on the unit circle satisfying the hypotheses of the Strong Marcinkiewicz Multiplier Theorem. This result expands the framework of the Strong Marcinkiewicz Multiplier Theorem to the setting of abstract measure spaces.

TiNi alloys have been extensively studied for their shape memory properties, arising from a martensitic transformation between the cubic B2 crystal structure and the monoclinic B19′ structure. However, only recently has the application of TiNi alloys as thin film actuators been considered. Well-controlled thicknesses of TiNi films have been deposited via d.c. magnetron ion sputtering, with as-deposited films exhibiting an amorphous structure. These ductile metallic glass films may be bent into various macroscopic shapes and then heated to crystallize the B2 structure, thereby determining its parent (memory) shape. In situ high voltage electron microscopy (HVEM) heating and cooling experiments are utilized to observe the crystallization of the B2 structure and the martensitic transformation from B2 to B19∼500°C to ∼600°C. Isothermal annealing determines the kinetics of the crystallization process to be nucleation limited. The nucleation of B2 crystallites in thicker regions of TEM specimens, which occurs prior to nucleation in thinner regions, indicates that nucleation does not occur preferentially at surfaces, but rather homogeneously. After crystallization is completed, the existence of random orientations of B2 grains provides films that will exhibit shape memory in any desired orientation. Video-recording of the crystallization processes has been acquired.

This research investigated the influence of heat treatment and precipitation on the phase transformation temperatures of sputter-deposited nickel-titanium films. Films 5 to 10 microns thick were subjected to isochronal and isothermal heat treatments in vacuum. Four-point resistance measutements were made and the TP, TR, Ma, and Mc temperatures identified. The correlation between transformation temperatures and the film's microstructure was studied using transmission electron microscopy. Existence of Ti2Ni and Ti11Ni14 precipitates was seen to adversely influence the phase transformation temperatures. It was concluded that precipitate-free film is preferable for mechanical actuator applications.

Let C be the complex plane, and U the disc |Z| < 1 in C. Cn denotes complex n-dimensional Euclidean space, <, > the inner product, and | · | the Euclidean norm in Cn;. Bn will be the open unit ball {z ∈ Cn:|z| < 1}, and Un will be the unit polydisc in Cn. For l ≤ p < ∞, p ≠ 2, Gp(Bn) (resp., Gp(Un)) will denote the group of all isometries of Hp(Bn) (resp., Hp(Un)) onto itself, where Hp(Bn) and HP(Un) are the usual Hardy spaces.

Let C be the complex plane, and U the disc |z| < 1 in C. Cn denotes complex n-dimensional Euclidean space, <, > the inner product, and | · | the Euclidean norm in Cn. Bn will be the open unit ball {z ∈ Cn: |z| < 1}, and Un will be the unit polydisc in Cn. For 1 ≤p<∞, p≠2, Gp(Bn) (resp., Gp (Un)) will denote the group of all isometries of Hp (Bn) (resp., Hp (Un)) onto itself, where Hp (Bn) and Hp (Un) are the usual Hardy spaces.