Mahmut Ekşioğlu

Optimal work-rest cycles for an isometric intermittent gripping task as a function of force, posture and grip span.

The aim of this study was to investigate the maximum acceptable contraction frequencies (i.e. work–rest cycles) for an isometric-intermittent handgrip task as a function of grip span, applied force and shoulder posture using psychophysical and physiological approaches. Twelve healthy males served as subjects. The three grip spans investigated were the optimal, 2 cm narrower than the optimal, and 2 cm wider than the optimal. The grip force levels studied were 15% and 30% of maximum voluntary grip force and the two shoulder postures were 25° flexion and 30° abduction. The psychophysical results indicate that subjects work faster with the narrower grip span at 15% of maximum voluntary grip force level in comparison to working with the optimal and the wider spans. However, when the task required 30% of maximum grip force level, the subjects worked faster with the optimal grip span. These findings were supported by the results of electromyography, heart rate, blood pressure and perceived discomfort. The study suggests that grip span of a tool is an important factor to be considered in predicting optimal work–rest cycles for hand grip tasks, and the optimum setting of grip span of the hand-tool depends on the required task force level. That is, the optimality is relative rather than absolute. In addition, it appears that weaker subjects can work at a higher rate than stronger ones at the same relative force level.

Vibration reduction of pneumatic percussive rivet tools: Mechanical and ergonomic re-design approaches

This paper presents a systematic design approach, which is the result of years of research effort, to ergonomic re-design of rivet tools, i.e. rivet hammers and bucking bars. The investigation was carried out using both ergonomic approach and mechanical analysis of the rivet tools dynamic behavior. The optimal mechanical design parameters of the re-designed rivet tools were determined by Taguchi method. Two ergonomically re-designed rivet tools with vibration damping/isolation mechanisms were tested against two conventional rivet tools in both laboratory and field tests. Vibration characteristics of both types of tools were measured by laboratory tests using a custom-made test fixture. The subjective field evaluations of the tools were performed by six experienced riveters at an aircraft repair shop. Results indicate that the isolation spring and polymer damper are very effective in reducing the overall level of vibration under both unweighted and weighted acceleration conditions. The mass of the dolly head and the housing played a significant role in the vibration absorption of the bucking bars. Another important result was that the duct iron has better vibration reducing capability compared to steel and aluminum for bucking bars. Mathematical simulation results were also consistent with the experimental results. Overall conclusion obtained from the study was that by applying the design principles of ergonomics and by adding vibration damping/isolation mechanisms to the rivet tools, the vibration level can significantly be reduced and the tools become safer and user friendly. The details of the experience learned, design modifications, test methods, mathematical models and the results are included in the paper.

Heuristic evaluation and usability testing: case study

The goal of this user centered design (UCD) study was to to identify usability issues on the Bogazici University Industrial Engineering (BUIE) department website user interface (UI) and also to provide a re-design guideline for the website. In this context, the website was evalauted via using heuristic evaluation, remote usability testing, and post-test questionnaire methods. Every single screen of the BUIE website was evaluated, and design problems along with associated severity rankings were determined. Based on the heuristic evaluation findings, various task scenarios were created for the remote usability testing study. Four diffferent user groups were identified for the study: high school students, BUIE undergraduate students, BUIE Graduate students/academic staff, and other university students. The users were asked to perform tasks relavant to the group characteristics and expectations related to the website. Their performance were evaluated in terms of task completion success rate, number of clicks, and time spent till either accomplishment, failure, or quittance by a remote usability testing tool, Loop11. A post user testing questionnaire was also administered online where the user subjective rating data were collected for each task in terms of ease of use. The results indicated numerous UI design issues, as confirmed by both heuristic and usability testing methods. Further redesign study is required to implement the results of this sudy in order to enhance the ease of use of the BUIE department website.

An Estimation of Finger-Tapping Rates and Load Capacities and the Effects of Various Factors

Objective: The aim of this study was to estimate the finger-tapping rates and finger load capacities of eight fingers (excluding thumbs) for a healthy adult population and investigate the effects of various factors on tapping rate. Background: Finger-tapping rate, the total number of finger taps per unit of time, can be used as a design parameter of various products and also as a psychomotor test for evaluating patients with neurologic problems. Method: A 1-min tapping task was performed by 148 participants with maximum volitional tempo for each of eight fingers. For each of the tapping tasks, the participant with the corresponding finger tapped the associated key in the standard position on the home row of a conventional keyboard for touch typing. Results: The index and middle fingers were the fastest fingers for both hands, and little fingers the slowest. All dominant-hand fingers, except little finger, had higher tapping rates than the fastest finger of the nondominant hand. Tapping rate decreased with age and smokers tapped faster than nonsmokers. Tapping duration and exercise had also significant effect on tapping rate. Conclusion: Normative data of tapping rates and load capacities of eight fingers were estimated for the adult population. In designs of psychomotor tests that require the use of tapping rate or finger load capacity data, the effects of finger, age, smoking, and tapping duration need to be taken into account. Application: The findings can be used for ergonomic designs requiring finger-tapping capacity and also as a reference in psychomotor tests.

User Experience Design of a Prototype Kiosk: A Case for the İstanbul Public Transportation System

ABSTRACT In this study, user experience design (UXD) of a prototype kiosk for the İstanbul Public Transportation System (İPTS) was presented. The kiosk included the following modules: a guide for tourists and newcomers, route finder, İstanbulkart operations (the smart city card for transportation), purchasing tickets-tokens, and a coin machine. The methodology consisted of a user survey, persona and scenario generation, design heuristics, system architecture, and user experience testing. The survey conducted with 168 participants revealed the following key points: Majority (68%) of the users of the current public transportation system ended up at wrong destinations at least once; 98% of the users stated that they would like to access a kiosk for their route planning needs; and 55% of the users were even willing to pay for such a service. The users overall thought that: the proposed kiosk would improve their public transportation experience because it included everything needed for transportation, it would make route planning easier, it was intuitive and easy to use, and it was accessible in many places. The empirical evidence shown by this study validated the UXD approaches suggested in the literature. Survey, persona and scenario generation, user testing, and mind mapping all were proven to be very useful steps to achieve a successful UXD. The design framework presented in this article may serve as a reference for the designers.