A comparison of broad versus deep auditory menu structures

OBJECTIVE: The primary purpose of this experiment was to gain a greater understanding of the utilization of working memory when interacting with a speech-enabled interactive voice response (IVR) system. BACKGROUND: A widely promoted guideline advises limiting IVR menus to five or fewer items because of constraints of the human memory system, commonly citing Miller's (1956) paper. The authors argue that Miller's paper does not, in fact, support this guideline. Furthermore, applying modern theories of working memory leads to the opposite conclusion--that reducing menu length by creating a deeper structure is actually more demanding of users' working memories and leads to poorer performance and satisfaction. METHOD: Participants took a working memory capacity test and then attempted to complete a series of e-mail tasks using one of two IVR designs (functionally equivalent, but one with a broad menu structure and the other with a deep structure). RESULTS: Users of the broad-structure IVR performed better and were more satisfied than users of the deep-structure IVR. Furthermore, this effect was more pronounced for those with low working memory capacity. CONCLUSION: Results indicate that creating a deeper structure is more demanding of working memory resource than the alternative of longer, shallower menus. APPLICATION: This experiment has important practical implications for all systems with auditory menus (particularly IVRs) because it provides empirical evidence refuting a widely promoted design practice.     

A closed-loop cross-correlation method for detecting model mismatch in MIMO model-based controllers

Correlation between a dithering signal and the prediction error has been used for detecting model mismatch in univariate model based control systems. This paper extends that approach to MIMO control systems. A closed-loop cross-correlation method is presented to detect which specific input-output pairings of a model-based controller are mismatched. This method may be used in screening the complete set of models and in selecting candidate models for re-identification. The method first finds the rows and columns of the transfer function matrix that contain mismatch, and then the candidates are found by the intersection of the said rows and columns. Placing the system under partial control, whereby one or more of the manipulated variables are held constant, can be used to further reduce the set of candidate models.     

Structural study of titanium oxide films synthesized by ion beam-assisted deposition

The application of titanium dioxide (TiO(2)) films as surgical implant coatings for antibiotic attachment depends crucially on their available surface area and thus their surface morphology and crystallinity. Here, we report our fabrication of high Wenzel ratio TiO(2) films targeted to increase the film surface area using the ion beam-assisted deposition (IBAD) technique at high-deposition temperatures (approximately 610 degrees C). The modulation of the films' surface morphology was accomplished by varying the chemical identity of the concurrent ion beams bombarded on the films during the e-beam evaporation process. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were employed to investigate the surface morphology of the as-deposited films. X-ray diffractometry (XRD) revealed that these nanocrystalline films primarily consist of anatase phase TiO(2). Wenzel ratio, the ratio of the actual surface area to the projected area, of IBAD films prepared with argon, oxygen, and nitrogen ion beams was measured to be 1.52, 1.31 and 1.49, respectively. The effect of the differences in chemical reactivity and ion size of these three type ion beams are discussed to explain the present results.     

Rectification of legibility distance in a driving simulator

Visual differences lead to differences in the legibility distances of traffic signs between driving simulators and real road environments. To ensure that the legibility distance in a simulator is similar to that in the real world, this study proposes a theoretical equation for predicting legibility distance and a simple algorithm for determining the magnifying power of a traffic sign for a display system in a simulator. Experiments of traffic sign recognition using a simulator were conducted under quasi-static and dynamic driving conditions. On-road tests were also carried out under quasi-static and dynamic driving conditions. Thirty healthy and non-disabled volunteers were recruited. The experimental results showed that the proposed theoretical equation for predicting legibility distance and the simple algorithm for determining the magnifying power of traffic signs reduced the difference in legibility distances between the simulator and real road environment under quasi-static and dynamic driving conditions.     

Calcium chloride in vitro effects on isolated myofibrillar proteins

The objective of this study was to determine the effect of 30 mM CaCl(2) on the solubilization of those structural proteins that contribute to myofibril stability. Ovine M. longissimus dorsi (longissimus) samples were obtained immediately post-exsanguination, myofibrils were isolated, glycerated, and frozen until needed. Myofibrils were washed, diluted and incubated in 0·1 m KCl, 10 mm Tris, pH 7·0 buffer for 24, 48 and 72 h. Treatments consisted of: (1) control, (2) 1 mm E(64), (3) 30 mm CaCl(2), and (4) 1 mm E(64) + 30 mm CaCl(2). Results (SDS-PAGE) indicated that myosin heavy chain (though not to a great extent), M-protein, C-protein, α-actinin, actin, troponin-T, tropomyosin isoforms, troponin-I and 72, 70, 62, 33, 32, 30, and 22 kDa unidentified bands were solubilized from myofibrils incubated in KCl buffer for 72 h. The addition of CaCl(2) hastened the appearance of some of the proteins in the supernatant fractions, but no differences were observed at 72 h among the treatments. The addition of E(64) had no effect on which proteins were released. Thus, in the absence of proteolysis it appears that a general solubilization of thick-and-thin filament ancillary proteins occurs in the presence of 30 mm CaCl(2). However, the contribution to tenderness should be minimal, because solubilized proteins are not part of the cytoskeletal elements that are responsible for maintaining structural integrity of the tissue.     

Localization of absorbers in scattering media by use of frequency-domain measurements of time-dependent photon migration

Frequency-domain studies of time-dependent light propagation in tissuelike phantoms that contain optical heterogeneities are described. Specifically the phase shift and amplitude modulation of reemergent light were measured when illuminated by an amplitude-modulated light source. Changes in the phase angle and the extent of modulation revealed the presence of a light-absorbing object. Furthermore the magnitude and direction of these changes were sensitive to the absorber depth and the light modulation frequency in a manner that could be used to infer the location of the heterogeneity. These data suggest the feasibility of optical imaging by frequency-domain methods.     

Polarization control of a Q-switched, diode-pumped Nd:YAG laser

We describe control of the polarization state of a diode-pumped Nd:YAG laser that is Q switched with an acousto-optic modulator (AOM). One of two orthogonal linear polarization states can be made dominant, depending on the amount of loss introduced by the AOM. Heterodyne beating indicates that the two polarization states are of slightly different frequencies.