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Published in Seán M. Stewart, R. Barry Johnson, Blackbody Radiation, 2016
Seán M. Stewart, R. Barry Johnson
Before proceeding further it is worth recalling some of the terminology associated with slide rules which may not be familiar to the modern reader. Broadly speaking, slide rules are of three general types: linear, circular, or spiral. In construction, a typical linear slide rule consisted of a central slide that slides relative to two stationary stocks and was either of the open or closed frame type. For the closed frame type the two stocks were separated by a gutter forming a body around the slide while for the open frame type the two stocks were held together at either of their ends with end braces. For the latter design, as the slide moved, an open gap would appear, hence its name, while no such gap appeared in the former. It was also usual for a slide rule to be fitted with a movable cursor with at least one hairline etched onto it. Scales were inscribed on the slide and one or both of the stocks while other fixed markings which may be found on the rule for the purpose of special calculations are known as gauge marks.
Positioning Actions' Regulation Strategies
Published in Kay M. Stanney, Kelly S. Hale, Advances in Cognitive Engineering and Neuroergonomics, 2012
In manual tasks there is often a need to move small objects into a particular position. To complete such tasks, a worker performs various positioning motor actions. For example, an assembly-line worker needs to move parts into a certain position. In man-machine or human-computer interaction systems there is a need to move a joystick to a particular position, or put a cursor at a certain point on a screen. Such actions do not require physical efforts. The main requirements for these actions are time limit and precision of movement. Fitts (1954) investigated the relationship between three variables: time, accuracy (precision), and distance. In his study subjects had to move their hand from one target to another, and hit them with maximum speed. Fitts’ studies have shown that movement time is linearly related to the logarithm of the index of difficulty. His studies were summarized by an equation presently known as Fitts’ Law. Some authors suggest using Fitts’ Law to predict positioning actions performance time. When attempting to apply this Law to a work environment, one would assume that each operator’s action is independent, and each operator’s action is performed with maximum speed. It is difficult to agree with such assumptions. Actions during task performance are organized into a system, and influence each other. A subject does not react, but rather actively and purposefully acts during task performance. Pace of performance of such actions is much lower than stated in Fitts’ Law.
Controlling
Published in John Flach, Fred Voorhorst, A Meaning Processing Approach to Cognition, 2019
The critical experimental manipulation in the study was the plant dynamics. Three different plant dynamics were used: A position control in which the plant was simply a proportional element or gain. In this case, a step change in control position resulted in a proportional step change in the plant position (e.g., 1-degree displacement in stick position resulted in a 10-pixel change in cursor position). This is analogous to a position-sensitive computer mouse controlling a cursor on the screen. A velocity control in which the plant was a gain and an integrator. In this case, a step change in control position resulted in a proportional change in the plant velocity (e.g., 1-degree displacement of the stick position resulted in a cursor velocity of 10 pixels per sec). Some controllers for scanning documents use this type of control, where the scan rate is proportional to displacement of the control icon.An acceleration control in which the plant was a gain plus two integrators. In this case, a displacement in control position resulted in a proportional acceleration (e.g., 1-degree displacement of the stick position resulted in an acceleration of 10 pixels per sec2). This is roughly analogous to the initial response of pressing the accelerator in a car. Although the acceleration of the car would not remain constant for a fixed displacement, as it would for the simple acceleration control used in these experiments. The different plants are illustrated in Figure 7.6 using a sketch of their open-loop frequency response using the Bode plot format described in the previous section and the Laplace transform6 of the transfer function.
Hierarchical Pointing on Distant Displays with Smart Devices
Published in International Journal of Human–Computer Interaction, 2022
Linlin Li, Zhiyi Fang, Weiqin Jia, Fengjun Zhang
The cursor in generic concepts needs to be placed over the range of the selected object to complete the pointing interaction. The area cursor has a larger hotspot defined by the cursor boundary instead of a point cursor with a single hotspot, which facilitates the target acquisition task under the premise of satisfying Fitts’ Law (Kabbash & Buxton, 1995). The bubble cursor is a variant of the area cursor that dynamically adjusts the activation region to contain the nearest objects (Grossman & Balakrishnan, 2005). On this basis, DynaSpot conjugates the cursor’s activation region with its speed, which inspired us to adopt the area cursor for distant pointing tasks and dynamically map the area cursor size by pressure (Chapuis et al., 2009).