Binary sensor systems are various types of analog sensors (optical, MEMS, X-ray, gamma-ray, acoustic, electronic, etc.), based on the binary decision process. Typical examples of such "binary sensors" are X-ray luggage inspection systems, product quality control systems, automatic target recognition systems, numerous medical diagnostic systems, and many others. In all these systems, the binary decision process provides only two mutually exclusive responses: "signal" and "noise." There are also two types of key parameters that characterize either system (such as false positive and false negative), or a priori external-to-system conditions (such as absolute probabilities). In this paper, by using a strong medical analogy, we analyze a third type of key parameter that combines both system-like and a priori information, in the form of so called Bayesian Figures of Merit, and we show that the latter parameter, in the best way, characterizes a binary sensor system.

Planar (2-2) and fibular (1-3) composites were fabricated by embedding single crystal Ni49.9Mn29.1Ga21.0 in a polyurethane resin. Magnetic and mechanical testing was performed on all samples. Mechanical testing showed the twin boundary yield stress to be 1.0 and 0.3MPa for the monolithic and composites, respectively. Magnetic testing was performed to determine the magnetic field induced strain as a function of increasing compressive preloads (from 0to2.0MPa). Actuation strains without an external preload are 4.9% for the monolithic and 1.0% for the composite samples. The composite samples show considerable cyclic strain without the application of a compressive loading, unlike the monolithic material. A rule of mixture model is presented to predict the strain output of the composite samples under a magnetic field and explain the reduced twin boundary yield stress.

Thin film nitinol and single crystal Ni-Mn-Ga represent two new shape memory materials with potential to be used as percutaneously placed implant devices. However, the biocompatibility of these materials has not been adequately assessed. Immersion tests were conducted on both thin film nitinol and single crystal Ni-Mn-Ga in Hank's balanced salt solution at 37 degrees C and pH 7.4. After 12 h, large pits were found on the Ni-Mn-Ga samples while thin film nitinol displayed no signs of corrosion. Further electrochemical tests on thin film nitinol samples revealed breakdown potentials superior to a mechanically polished nitinol disc. These results suggest that passivation or electropolishing of thin film nitinol maybe unnecessary to promote corrosion resistance.

Tensile and compressive loading experiments were conducted at room temperature on a thin slab (1 mm) of Ni50Mn33Ga17 single crystal ferromagnetic shape memory alloy while subjected to cyclic magnetic field (up to 550 kA/m). Tensile loads ranged from 0.4 MPa to 0.8 MPa while compressive loads ranged from 0.4 MPa to 2.2 MPa, with increasing compressive loads resulting in a reduced overall strain. Results indicate that magnetic field produces significant strains (over 4%) within the material. Experimental data also show that a tensile load reduces the required magnetic field for actuation by almost 80%.

Mechanical testing of a bulk, single-crystal sample of Ni 50 Mn 29 Ga 21 produced large hysteresis loops indicating the potential for the material to be used as a damper. Damping capacity was measured as a function of energy absorbed by the material relative to the mechanical energy input to the system. Tan δ, the tangent of the phase lag between stress and strain, was calculated and shown to increase as a function of maximum strain level. Five strain levels were evaluated (1%, 2%, 3%, 3.5%, and 3.7%) with tan δ values increasing from 0.6 at 1% strain level to 1.1 at 3.7% strain level. The secant modulus of these curves was also evaluated at each strain level to characterize the sample in terms of both damping and stiffness. The maximum secant modulus of 285 MPa occurred at the 1% strain level and decreased to 56 MPa at 3.7% strain. Examining the stress and strain values in the time domain reveals a varying time lag and thus the reported values for tan δ are considered an average measure of the material's damping capacity.