One of the ultimate goals of studies on visualization literacy is to improve users’ visualization literacy through education and training. Even though users’ cognitive characteristics may significantly affect learning and responding processes in general, studies have addressed the relationships between users’ cognitive characteristics and visualization literacy. As a first step toward discovering the relationships, we conducted an empirical study to investigate the correlation between cognitive characteristics and visualization literacy. Our first study focuses on testing the correlation between visualization and three cognitive characteristics: numeracy, need for cognition, and visualizer-verbalizer style. In this study, we measured 178 participants’ visualization literacy and the level of the three cognitive characteristics using the Visualization Literacy Assessment Test (VLAT), the Decision Research Numeracy Test (DRNT), the Need for Cognition Scale (NCS), and the Verbalizer-Visualizer Questionnaire (VVQ) through a crowdsourcing experiment. Our test results confirmed that a correlation exists between visualization literacy and both numeracy and need for cognition. Based on our test results, we discuss the implications for education to enhance visualization literacy and future studies to investigate on related user characteristics.

Wearable activity trackers can motivate older adults to engage in the recommended daily amount of physical activity (PA). However, individuals may not maintain their use of the trackers over a longer period. To investigate the attitudes of activity tracker adoption and their effects on actual PA performance, we conducted a three-month study. We gave activity trackers to 16 older adults and assessed attitudes on activity tracker adoption through a survey during the study period. We extracted participants’ PA measures, step counts, and moderate and vigorous physical activity (MVPA) times. We observed significant differences in adoption attitudes during the three different periods (χ²(2, 48) = 6.27, p < 0.05), and PA measures followed similar decreasing patterns (F(83, 1357) = 12.56, 13.94, p < 0.00001). However, the Pearson correlation analysis (r = 0.268, p = 0.284) and a Bland–Altman plot indicated a bias between two PA measures. Positive attitudes at the initial stage did not persist through the study period, and both step counts and length of MVPA time showed waning patterns in the study period. The longitudinal results from both measures demonstrated the patterns of old adults’ long-term use and adoption. Considering the accuracy of the activity tracker and older adults’ athletic ability, MVPA times are more likely to be a reliable measure of older adults’ long-term use and successful adoption of activity trackers than step counts. The results support the development of better activity tracker design guidelines that would facilitate long-term adoption among older adults.

Interruption is a widespread phenomenon in human–computer interaction in modern working environments. To minimize the adverse impact or to maximize possible benefits of interruptions, a reliable approach to evaluate interruption cost needs to be established. In this paper, we suggest a new approach to evaluate the interruption cost by cognitive workload and task performance measures. The cognitive workload is assessed by pupil diameter changes and National Aeronautics and Space Administration (NASA) task load index. Task performance includes task completion time and task accuracy in a series of controlled laboratory experiments. This integrated approach was applied to three interruption coordination modes (i.e., the immediate, the negotiated, and the scheduled modes), which were designed based on McFarlane’s interruption coordination modes. Each mode consists of cognitive and skill tasks depending on the degree of mental demands providing four different task sets of interruptive task environments. Our results demonstrate that the negotiated mode shows a lower interruption cost than other modes, and primary task type and task similarity between primary and peripheral tasks are crucial in the evaluation of the cost. This study suggests a new approach evaluating interruption cost by cognitive workload and task performance measures. Applying this approach to various interruptive environments, disruptiveness of interruption was evaluated considering interruption coordination modes and task types, and the outcomes can support development of strategies to reduce the detrimental effects of unexpected and unnecessary interruptions.

A magnetron-driven microtron injector has been developed for a terahertz free electron laser (FEL). An internal injection system was chosen for the microtron to achieve a compact and inexpensive design. The system provides acceleration of electrons with low emittance and energy spread that is highly important for the FEL. However, the intrapulse instabilities of the accelerated current and the bunch repetition rate inherent to the injection system make problems for the FEL operation. Simulations of the beam dynamics and the transient process allow one to compute the load characteristic of the accelerating cavity and the time-dependent accelerated current. The simulation techniques also allow one to calculate time-dependent deviations of the magnetron frequency in the coupled system of the accelerating and magnetron cavities, as well as deviations in the bunch repetition rate. The computations validate proposed concepts for increasing the intrapulse current stability with appropriate time-dependent variation of the magnetron power and decreasing the bunch repetition rate instability through a simple microwave scheme utilizing the microtron accelerating cavity concurrently as an external stabilizing resonator for the magnetron. The realized concepts and optimization of the microtron regimes using the simulated phase motion of the accelerated bunch provide stable operation of the terahertz FEL, tunable in the range of 1–3 THz with extracted macropulse power up to 50 Watts at the macropulse energy of $\sim 0.2\mathrm{mJ}$.