Semi-contingent Task Durations: Characterization and Controllability

2021 ◽  
pp. 246-261
Author(s):  
Marco Franceschetti ◽  
Johann Eder
Keyword(s):  
Task Durations

Development of a DSM-Based Methodology in an Academic Setting

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
George Platanitis ◽  
Remon Pop-Iliev ◽  
Ahmad Barari
Keyword(s):  
Engineering Design ◽  
Design Process ◽  
Engineering Students ◽  
Design Structure ◽  
Academic Settings ◽  
Task Durations ◽  
Random Disturbances ◽  
Process Convergence ◽  
Work Transformation

This paper proposes the use of a design structure matrix/work transformation matrix (DSM/WTM)-based methodology in academic settings to serve engineering educators as a facilitating tool for predetermining the difficulty and feasibility of design engineering projects they assign, given both the time constraints of the academic term and the expected skill level of the respective learners. By using a third-year engineering design project as a case study, engineering students actively participated in this comprehensive use of DSM methodologies. The engineering design process has been thoroughly analyzed to determine convergence characteristics based on the eigenvalues of the system followed by a sensitivity analysis on the originally determined DSM based on data provided by students in terms of task durations and number of iterations for each task. Finally, an investigation of the design process convergence due to unexpected events or random disturbances has been conducted. The obtained predictive model of the design process was compared to the actual dynamics of the project as experienced by the students and the effect of random disturbances at any point in the design process has thereby been evaluated.

Measurements of Trunk Sway for Stance and Gait Tasks 2 Years after Vestibular Neurectomy

2018 ◽  
Vol 23 (5) ◽  
pp. 298-308 ◽  
Author(s):  
Dominique Vibert ◽  
John H.J. Allum ◽  
Martin Kompis ◽  
Simona Wiedmer ◽  
Christof Stieger ◽  
...  
Keyword(s):  
Balance Control ◽  
Recovery Period ◽  
Subjective Assessment ◽  
Vestibular Neurectomy ◽  
Eyes Closed ◽  
Before And After ◽  
Task Durations ◽  
Trunk Sway ◽  
Central Compensation ◽  
Balance Problems

The aim of this study was to investigate changes in balance control for stance and gait tasks in patients 2 years before and after vestibular neurectomy (VN) performed to alleviate intractable Meniere’s disease. Amplitudes of trunk sway in roll and pitch directions were measured for stance and gait tasks in 19 patients using gyroscopes mounted at the lower-back. Measurements before VN and 2 years later were compared to those of healthy age-matched controls (HC). We also examined if changes in trunk sway amplitudes were correlated with patients’ subjective assessment of disability using the AAO-HNS scale. For patients with low AAO-HNS scores 0–2 (n = 14), trunk roll and pitch sway velocities, standing eyes closed on foam, increased 2 years post VN compared to HC values (p < 0.01). Trunk sway amplitudes remained at levels of HC for simple gait tasks, but task durations were longer and therefore gait slower. For complex gait tasks (stairs), balance control remained impaired at 2 years. In patients with AAO-HNS high scores level 6 (n = 5), balance control remained abnormal, compared to HC, 2 years postoperatively for all stance, several simple and all complex gait tasks. Trunk sway in the pitch and roll directions for stance tasks was correlated with clinical (AAO-HNS) scores (p ≤ 0.05). These results indicate that VN leads to chronic balance problems for stance and complex gait tasks. The problems are greater for patients with high compared to low AAO-HNS scores, thereby explaining the different symptoms reported by these patients. The lack of balance recovery in VN patients to levels of HCs after 2 years contrasts with the 3 months average recovery period for acute vestibular neuritis patients and is indicative of the effects of neurectomy on central compensation processes.

Reduced task durations in functional PET imaging with [18F]FDG approaching that of functional MRI

NeuroImage ◽  
2018 ◽  
Vol 181 ◽  
pp. 323-330 ◽  
Author(s):  
Lucas Rischka ◽  
Gregor Gryglewski ◽  
Sarah Pfaff ◽  
Thomas Vanicek ◽  
Marius Hienert ◽  
...  
Keyword(s):  
Functional Mri ◽  
Pet Imaging ◽  
Task Durations ◽  
18F Fdg

A labeling method for dynamic driver-task assignment with uncertain task durations

2005 ◽  
Vol 33 (4) ◽  
pp. 411-420 ◽  
Author(s):  
Raymond K. Cheung ◽  
Darren D. Hang ◽  
Ning Shi
Keyword(s):  
Task Assignment ◽  
Task Durations ◽  
Labeling Method

STALL: A Simple Model for Workload Analysis in Early System Development

1987 ◽  
Vol 31 (3) ◽  
pp. 363-367 ◽  
Author(s):  
Gerald P. Chubb ◽  
Noreen Stodolsky ◽  
Warren D. Fleming ◽  
John A. Hassoun
Keyword(s):  
Response Time ◽  
System Development ◽  
Arrival Rate ◽  
System Response ◽  
Service Rate ◽  
Workload Analysis ◽  
Task Durations ◽  
System Response Time ◽  
Quantitative Basis ◽  
Load Limits

The Saturation of Tactical Aviator Load Limits (STALL) is defined as the intersection of asymptotically high and low load limits. In a closed queuing system consisting of M homogeneous demand generators, it has been shown that response time becomes asymptotically linear as M increases. This provides a quantitative basis for specifying the saturation point if one knows both arrival rate and service rate (the inverse of task duration). Early in system development, one can typically estimate arrival rates based on mission analyses. But task durations cannot be estimated until procedures have been defined, based on system design. At this stage, it is useful to determine the design requirements. Given the imposed load, how fast must servicing be to keep up with demand? Logically, service rates must exceed arrival rates, but the question is: by how much? Two related criteria can apply: the number of backlogged demands, or the system response time. STALL computes statistics for both. Preliminary model validation has been accomplished, using simulation runs to study model robustness to systematic violations of assumptions. Predictive validity depends on being able to demonstrate that the assumptions are valid in a particular application. The simulations demonstrate what can happen when that match is not successfully achieved. These studies demonstrated that the predictions will typically be most robust for an over-saturated system. The model is least sensitive to violations of the servicing assumptions. Furthermore, it is easy to relax the assumption of homogeneous demand generators by developing planned model extensions.

Vibrotactile grasping force and hand aperture feedback for myoelectric forearm prosthesis users

2014 ◽  
Vol 39 (3) ◽  
pp. 204-212 ◽  
Author(s):  
Heidi JB Witteveen ◽  
Hans S Rietman ◽  
Peter H Veltink
Keyword(s):  
Upper Limb ◽  
Force Feedback ◽  
Feedback Condition ◽  
Limb Loss ◽  
Vibrotactile Stimulation ◽  
Vibrotactile Feedback ◽  
Task Durations ◽  
Grasping Force ◽  
Additional Value ◽  
Virtual Grasping

Background: User feedback about grasping force and hand aperture is very important in object handling with myoelectric forearm prostheses but is lacking in current prostheses. Vibrotactile feedback increases the performance of healthy subjects in virtual grasping tasks, but no extensive validation on potential users has been performed. Objectives: Investigate the performance of upper-limb loss subjects in grasping tasks with vibrotactile stimulation, providing hand aperture, and grasping force feedback. Study design: Cross-over trial. Methods: A total of 10 subjects with upper-limb loss performed virtual grasping tasks while perceiving vibrotactile feedback. Hand aperture feedback was provided through an array of coin motors and grasping force feedback through a single miniature stimulator or an array of coin motors. Objects with varying sizes and weights had to be grasped by a virtual hand. Results: Percentages correctly applied hand apertures and correct grasping force levels were all higher for the vibrotactile feedback condition compared to the no-feedback condition. With visual feedback, the results were always better compared to the vibrotactile feedback condition. Task durations were comparable for all feedback conditions. Conclusion: Vibrotactile grasping force and hand aperture feedback improves grasping performance of subjects with upper-limb loss. However, it should be investigated whether this is of additional value in daily-life tasks. Clinical relevance This study is a first step toward the implementation of sensory vibrotactile feedback for users of myoelectric forearm prostheses. Grasping force feedback is crucial for optimal object handling, and hand aperture feedback is essential for reduction of required visual attention. Grasping performance with feedback is evaluated for the potential users.

Effects of Display Curvature and Task Duration on Proofreading Task Performance, Visual Fatigue, Visual Discomfort, and Display Satisfaction

2016 ◽  
Vol 60 (1) ◽  
pp. 790-794 ◽  
Author(s):  
Sungryul Park ◽  
Jihhyeon Yi ◽  
Donghee Choi ◽  
Songil Lee ◽  
Gyouhyung Kyung ◽  
...  
Keyword(s):  
Error Rate ◽  
Polynomial Regression ◽  
Viewing Distance ◽  
Visual Fatigue ◽  
Visual Discomfort ◽  
Task Duration ◽  
Two Factors ◽  
Task Durations ◽  
The Mean ◽  
And Task

With more curved display products in the market and more exposure to such products, it is necessary to examine the effects of display curvature and task duration from the ergonomics perspective. The current study examined the effects of these two factors on visual performance, visual fatigue, visual discomfort, and display satisfaction during proofreading tasks. We incorporated five display curvatures (600R, 1140R, 2000R, 4000R, and flat) and five task durations (0, 15, 30, 45, and 60 min). Each of 50 individuals completed a 1-hr proofreading task at one of five display curvature conditions. The horizontal viewing distance was fixed at 600mm. Proofreading performance (speed and error rate), subjective visual fatigue [on ECQ (Eye Complaint Questionnaire)], physiological visual fatigue [CFF (Critical Fusion Frequency), blink duration, and blink frequency], visual discomfort (on VAS), and display satisfaction (on VAS) were measured. The highest mean proofreading speed was at 600R. The mean proofreading speed and error rate increased by 15.5% and 22.3%, respectively, over the 1-h task. The mean ECQ score and visual discomfort increased by 188.6% and 107.2% during 45 and 60 min of the task, respectively. The mean CFF and display satisfaction decreased by 0.49Hz and 11.2% during 15 and 15-45 min of the task. A polynomial regression model for subjective visual fatigue was developed (adjusted R2 = 0.6). These findings can be used when determining ergonomic display curvatures and predicting visual fatigue.

Repetitive Lifting Tasks in Logistics – Effects on Humans at Different Lifting Task Durations

2016 ◽  
Vol 60 (1) ◽  
pp. 2034-2038 ◽  
Author(s):  
Verena C. Knott ◽  
Alexander Wiest ◽  
Klaus Bengler
Keyword(s):  
Cardiopulmonary Exercise Testing ◽  
Cardiovascular Effects ◽  
Objective Data ◽  
Subjective Data ◽  
Cardiopulmonary Exercise ◽  
Repetitive Lifting ◽  
Volunteer Study ◽  
Task Durations ◽  
Manual Handling ◽  
Lifting Task

A volunteer study at the Chair of Ergonomics (TUM) investigates which cardiovascular effects on the human body are to be expected from repetitive lifting movements at different load times, and which requirements arise accordingly with respect to different lifting task durations by using the cardiopulmonary exercise testing (CPET) method. Two different weight classes and three different load times are combined with a conventional lifting task. In addition to the acquisition of objective data, such as oxygen consumption (V’O2/kg) or heart rate (HR), the subjective stress using the Borg RPE scale is determined and analyzed. 27 test persons (M=27.6 years, SD=±3.1) participated in the study. At 70.4% less than three quarter of the participants in the test were men. Both the objective and subjective data show significant differences between the mentioned weight classes. A load time of more than 10 minutes for analyzing manual handling tasks by using CPET is recommended.

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