A probabilistic multidimensional scaling with unique axes1

Abstract: A probabilistic multidimensional scaling model is proposed. The model assumes that the coordinates of each stimulus are normally distributed with variance Σ_i = diag(σ²₁, … σ²_Ri). The advantage of this model is that axes are determined uniquely. The distribution of the distance between two stimuli is obtained by polar coordinates transformation. The method of maximum likelihood estimation for means and variances using the EM algorithm is discussed. Further, simulated annealing is suggested as a means of obtaining initial values in order to avoid local maxima. A simulation study shows that the estimates are accurate, and a numerical example concerning the location of Japanese cities shows that natural axes can be obtained without introducing individual parameters.     

A performance analysis of In-Car Music engagement as an indication of driver distraction and risk

Drivers engage in a host of driving-unrelated tasks while on the road. They listen to music, sing-along, and accompany songs by pounding-out drum-kicks and syncopated rhythms on the steering wheel. However, there is controversy over in-cabin music: Does background music facilitate driver performance via increased arousal leading to more focused concentration, or cause distraction placing drivers at greater risk. In an effort to shed light on the debate, the current study evaluated music engagement by employing Music Performance Analyses with audio recordings from three simulated driving conditions. The results indicate that as the perceptual demands of the primary driving task increased, the secondary music activity was hampered, and subsequently sub-optimal vocal and percussive performances were demonstrated consisting of intonation errors, rhythmic inaccuracy, lack of synchrony, inconsistent and unstable temporal flow, neglect of text, and lyric replacement. The findings seem to point out that drivers allocate greater reserves to music than previously considered, and as drivers do not withdraw altogether from music engagement under high-demand driving conditions, driving may be under-resourced. Exploring active music engagement while driving might assist traffic safety researchers in decoding the effects of In-Car Music on driver behavior.     

Catalyst incorporation in ZnSe nanowires

ZnSe nanowires, 5–10?nm wide and several microns long, were fabricated by Au-catalyzed molecular beam epitaxy. Specially designed silicon–silicon dioxide substrates allowed an examination of individual nanowires with a combination of phase-contrast high-resolution transmission electron microscopy, Z-contrast scanning transmission electron microscopy imaging and energy-dispersive X-ray spectroscopy using a low-current electron probe with a diameter of 0.2?nm. Experimental results demonstrate direct evidence of Au incorporation within single-crystal sphalerite ZnSe nanowires.     

Drivers’ performances and their subjective feelings about their driving during a 40-min test on a circuit versus a dynamic simulator

Car manufacturers expect driving simulators to be reliable research and development tools. Questions arise, however, as to whether drivers’ behavior on simulators exactly matches that observed when they are driving real cars. Drivers’ performances and their subjective feelings about their driving were compared between two groups during a 40-min driving test on the same circuit in a real car (n = 20) and a high-fidelity dynamic simulator (n = 27). Their speed and its variability, the braking force and the engine revolutions per minute (rpm) were recorded five times on a straight line and three times on a curve. The differences observed in these measurements between circuit driving (CD) and simulator driving (SD) from the 6th to 40th minute showed no significant changes during the drive. The drivers also completed the NASA Raw Task Load Index (NASA RTLX) questionnaire and the Simulator Sickness Questionnaire (SSQ) and estimated the ease and standard of their own driving performances. These subjective feelings differed significantly between the two groups throughout the experiment. The SD group’s scores on the NASA RTLX and SSQ questionnaires increased with time and the CD group’s perceived driving quality and ease increased with time, reaching non-significantly different levels from their usual car driving standards by the end of the drive. These findings show the existence of a fairly good match between real-life and simulated driving, which stabilized six minutes after the start of the test, regardless of whether the road was straight or curved. These objective findings and subjective assessments suggest possible ways of improving the match between drivers’ performances on simulators and their real-life driving behavior.     

The effects of confederate prompt delivery style in a standardized social simulation test

Role plays or social simulations are presently one of the most common methods for assessing social skills. Although social simulation techniques have become quite popular, little is known about the psychometric adequacy of many of the role-play instruments which have been developed. This investigation was an attempt to determine certain properties of one particular social skills assessment instrument: the Simulated Social Interaction Test. The effects of various confederate prompt delivery styles on the judged social competency level of subjects in the Simulated Social Interaction Test were examined. Two confederates, one male and one female, were trained to portray three confederate prompt delivery styles: (a) unreceptive, (b) neutral, and (c) receptive. In order to determine if judges would compensate for the different confederate prompt delivery styles, two sets of trained judges rated the levels of skill and anxiety generated by the 30 subjects tested. One set of judges was screened from the confererate delivery while observing the simulation; the other set of judges followed the more common rating procedure (i.e., they were not screened from the confederates' deliveries). Data analysis examined variation in subject performance under each condition and according to each set of judges for both overall social skills and anxiety ratings. Confederate prompt delivery style was found to affect subjects' rated performance. There was also suggestive evidence that judges were sometimes able to compensate for different confederate delivery styles. The practical and theoretical implications of the results are discussed.This study was funded in part by a research grant from the Veterans Administration.     

Optical characterization of spin-coated cobalt porphyrazine thin films: effect of annealing temperature

Cobalt porphyrazine thin films were prepared by the spin-coating technique. The coated substrates were annealed at different temperatures (373, 423 and 523 K). The optical properties of the films were investigated by measuring the transmittance and reflectance spectra. The refractive index, extinction coefficient, optical band gap, dielectric constant values and thickness of the films were determined. Results showed that the refractive index, the extinction coefficient and the dielectric constants increased on annealing the films at 373 K in comparison with films annealed at other temperatures. On the other hand, the values of the band gap energy and thickness of the annealed film at 373 K were found to be the lowest in comparison with films annealed at different temperatures.     

Measuring drivers’ takeover performance in varying levels of automation: Considering the influence of cognitive secondary task

Mixed control by driver and automated system will remain in use for decades until fully automated driving is perfected. Thus, drivers must be able to accurately regain control of vehicles in a timely manner when the automated system sends a takeover request (TOR) at its limitation. Therefore, determining the factors that affect drivers’ takeover quality at varying levels of automated driving is important. Previous studies have shown that visually distracting secondary tasks impair drivers’ takeover performance and increase the subjective workload. However, the influence of purely cognitive distracting secondary tasks on drivers’ takeover performance and how this influence varies at different levels of automation are still unknown. Hence, a 5 (driving modes) × 3 (cognitive secondary tasks) factorial design with the within-subject factors was adopted for this driving simulator experiment. The sample consisted of 21 participants. The participants’ subjective workloads were recorded by the NASA-Task Load Index (NASA-TLX). Results showed that compared to manual driving conditions, the drivers’ subjective workloads were significantly reduced in both partially and highly automated driving conditions, even with a TOR, confirming the benefit of the automated driving system in terms of reducing the driving workload. Moreover, the drivers exhibited a lower takeover behavior quality at high levels of automation than manual driving in terms of increased reaction time, abnormal performance, standard deviation of lane position, lane departure probability, and reduced minimum of time to collision. However, at the highly automated driving condition, the drivers’ longitudinal driving safety and ability to follow instructions improved when performing a highly cognitive secondary task. This phenomenon possibly occurred because automated driving conditions lead to an underload phenomenon, and the execution of highly cognitive tasks transfers drivers into moderate load, which helps with the drivers’ takeover performance.     

Abnormally high residual dislocation density in pure aluminum after Al/Ti/Al laminate annealing for seven days

We report an abnormally high residual dislocation density in aluminium in an Al/Ti/Al laminate annealed at 873 K for seven days. The residual dislocation density reaches 7.5 × 10¹⁴ m^?2, higher than that in aluminum after severe plastic deformation processes such as accumulative roll bonding and high-pressure torsion. It is proposed that the high residual dislocation density may result from obstruction of the movement of TiAl₃ nanoparticles by the grain boundary and Ti atoms conglomerating at vacancies distributed in the aluminium matrix at a high temperature for a sufficient time to allow a relatively stable crystal.     

Autochthony through self-organization: Interactivism and emergence in a virtual environment

In this paper we take an interactivist perspective on the computer-mediated classroom, and explore the autopoietic teaching approach in the context of emergence of diversity in the classroom. The POPSICLE (Patterns in Orientation: Pattern-Aided Simulated Interaction Context-Learning Experiment) is presented and discussed, as well as its multiple consequences. POPSICLE is a study of learning in human subjects, as well as of interaction and transfer of knowledge between subjects in a collaborative environment.