• Journal of Institute of Control, Robotics and Systems
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• v.10 no.11
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• pp.961-970
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• 2004

Tactile sensation is one of the most important sensory functions along with the auditory sensation for the visually impaired since it replaces the visual one of the persons with sight. In this paper, we present a tactile display device as a dynamic Braille display that is the unique tool f3r exchanging information among them. The tactile cell of the Braille display proposed is based on the dielectric elastomer, which is one of the electroactive polymers. It has advantageous features over the existing ones with respect to intrinsic softness, ease of fabrication, cost effectiveness and miniaturization. We introduce a new idea for actuation as well as additional considerations such as the driving circuit that makes it possible to drive multiple tactile cells in a high speed. Also, we describe the actuating mechanism of the Braille pin in details capable of realizing the enhanced spatial density of the tactile cells. Finally, results of psychophysical experiments are given to evaluate its effectiveness.

• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.69-75
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• 2009

It is well-known that lifting capacity of a worker is influenced by body posture during the task. When a task analyst make use of RULA and REBA Trunk and upper arm angles are recorded in a separate item. It means that the interaction between the angles of two body segments may be ignored in a final score. The NLE(NIOSH Lifting Equation) has been used to supplement this problem. However, there is no study to validate the result of RWL (Recommended Workload Limit) under the existence of interactions between trunk and upper arm angles. The goal of this study was to assess the effect of the interaction between trunk and upper arm angles. Three responses, including NMVC(normalized maximum voluntary contraction), RWL(Recommended Weight Limit) and subjective judgment in psychophysical method (Borg's scale), were recorded according to the combinations of three trunk angles and nine upper arm angles. The results showed that lifting capacity is highly influenced by interaction of two body segments(trunk and upper arm). It means that the task workload has to be analyzed along with the interaction of trunk angles and upper arm angles when the task analyst assesses potential risk factors on the postures. This study may be able to be a fundamental study to develop an assessment method for lifting task analyses according to body postures.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.74-82
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• 2002

In this paper the start fuel index was developed to estimate ride quality of a forklift truck during the start motion. Through the consultation with test drivers, definition of start feel was made, and three parameters were selected to describe the start motion. They are engagement shock in the forwarding direction, vertical and pitch vibration respectively. To find out the relation between the measured motion and the subjective fueling, both the subjective rating and the measurement of vehicle motions were performed simultaneously. The correlation analysis between the two kinds of results showed start fuel was expressed by the measured accelerations with accuracy and reliability, Use of the new index has advantages of not only evaluating start fuel only by the measured signals but providing the consistent results which are not affected by physical and mental state of a test driver. Usefulness of the new index was confirmed by verification test on four new forklift trucks of a same model, which showed the order of preference by the index was coincided that by subjective evaluation.

• Journal of Electrical Engineering and information Science
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• v.3 no.2
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• pp.202-210
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• 1998

This paper is concerned with an efficient generation of stereoscopic views for complex virtual environments by exploiting frame coherence in visibility. The basic idea is to keep visible polygons throughout the rendering process. P-buffer, a buffer of image size, holds the id of the visible polygon for each pixel. This contrasts to the frame buffer and the Z-buffer which hold the color information and the depth information, respectively. For the generation of a consecutive image, the position and the orientation of the visible polygons in the current view are updated according to the viewer's movements, and re-rendered on the current image under the assumption that, when the viewer moves slightly, the visibility of polygons remains unchanged. In the case of stereoscopic views, it may not introduce much difficulty when we render the right(left) image using visible polygons on the (right) image only, The less difference in two images is, the easier the matching becomes in perceiving depth. Some psychophysical experiments have been conducted to support this claim. The computational complexity for generating a fight(left) image from the previous left(right) image is bounded by the size of image space, and accordingly. It is somewhat independent of the complexity of the 3-D scene.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.5
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• pp.445-450
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• 2005

In this paper, we suggest an integrated tactile display system that provides kinesthetic force, pressure distribution, vibration and slip/stretch. The system consists of two parts: a 2 DOF force feedback device for kinesthetic display and a tactile feedback device for displaying the normal stimulation to the skin and the skin slip/stretch. Psychophysical experiments measure the effects of fingerpad selection, the direction of finger movements and the texture width on tactile sensitivity. We also investigate the characteristics of lateral finger movement while subjects perceive different textures. From the experimental results, the principal parameters for designing a tactile display are suggested. A tactile display device, using eight piezoelectric bimorphs and a linear actuator, Is implemented and attached to a 2 DOF translational force feedback device to simultaneously simulate the texture and stiffness of the object. As a result, we find out that the capability of the suggested device is sufficient to display physical quantities to display the texture.

• Bulletin of the Korean Institute for Industrial Safety
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• v.3 no.1
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• pp.11-17
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• 2003

In recent years, work-related musculoskeletal disorders (WMSDs) are one of major issues in occupational safety and health in Korea, since the number of injured workers has rapidly increased and the related regulation was amended to improve the work conditions. Main risk factors of WMSDs in Korean industries include manual handling of heavy weight loads, awkward postures, repetitive tasks, prolonged static muscle contraction, and so on. in this article, some ergonomics case studies for identifying the risk factors of WMSDs and far their prevention were introduced. They include a biomechanical analysis for the heavy-weight handling task in a machine-repair shop, physiological evaluation of backpack-carrying tasks in a beverage delivery job, and a set of psychophysical studies to evaluate static-postural load. These studies showed that there are several different ergonomic approaches to identifying and evaluating risk factors of WMSDs and to eliminating them or reducing their levels, and that it is important to select proper methods and apply them in improving the work conditions according to the characteristics of the task. In addition, it needs to develop practical and effective ergonomic tools to prevent WMSDs and to provide these tools to the safety managers in the field so that they can improve the tasks by themselves.

• Journal of the Korean Society of Safety
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• v.27 no.3
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• pp.9-14
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• 2012

The objectives of this study were to compare the results of HSL (Health and Safety Laboratory) ramp test with perceived sense of slip onto the several different floor surfaces under contaminated conditions. There are a variety of approaches from biomechanical measurements to psychophysical test and human perception. However, controversies over these approaches still remain. Some widely accepted methods need to be improved. AHP (Analytic Hierarchy Process) was used to evaluate the perception of slipperiness of seven different floor surfaces under the contaminated condition with glycerol solution. Twelve subjects worn same footwear and walked with self-selected step and cadence along the test floors. The angle of inclination obtained for water wet condition using 5 l/min with HSL ramp test was compared to perception of slipperiness. The surface roughness ($R_z$) related very well both AHP (r=0.95) and ramp test (r=0.92). The high significant correlation (r=0.90) was found between AHP and HSL ramp test.The HSL ramp test values (Coefficient of Friction, COF) according to subjective evaluation were divided into two categories. There were high correlations between test results (subjective evaluation, HSL ramp test) and surface roughness in Rz. Perception rating obtained with AHP showed a high correlation with COF obtained with HSL ramp test.

• Journal of the Ergonomics Society of Korea
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• v.22 no.1
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• pp.43-56
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• 2003

Observational methods such as OWAS, RULA, and REBA have been widely used to identify posture-related risks of musculoskeletal disorders in industry, since they are useful and efficient in evaluating postural stresses. However. there are few studies comparing the methods and providing guidelines for selecting and using the methods. They have been developed based on different backgrounds and with different application areas. Each method has its own characteristics. which must be considered in selecting and using them. In this study. 17 male subjects evaluated 42 different working postures that frequently assumed in the automobile assembly line using a psychophysical method. The postures were then evaluated by different observational methods. The results of the observational methods were compared with psychophysically evaluated stresses. The observational methods resulted in different values of stresses for certain postures. For some postures showing high values of perceived discomfort. the observational methods showed different values of stresses. These results showed that the observational methods should be used differently according to application area and they have some weak points to be improved.

• Journal of Oral Medicine and Pain
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• v.22 no.1
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• pp.183-192
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• 1997

Pressure pain thresholds are routinely used in orofacial pain research to evaluate the response of deep orofacial tissues to mechanical stimulation. Like other psychophysical measurements, however, this technique must stimulate cutaneous tissues before stimulating deeper tissues. This study aimed at evaluating the influence of the cutaneous hypoesthesia on the pressure pain threshold in 30 healthy volunteers. PPTs were determined with electric pressure algometry over masseter, temporalis anterior, sternocleidomastoid, and trapezius muscle before and after skin hypoesthesia. A local anesthetic cream and a control cream were applied following a placebo-controlled double-blind design and PPTs were reassessed. Two examiners measured PPTs two times on each muscles, randomly. And the EMG activity of all muscles were measured to evaluate the relationship with PPTs. The collected data were processed by SAS/STAT program. The obtained results were as follows : 1. There were a tendency to increase PPTs after than before cutaneous hypoesthesia, but, there were no significant difference statistically. 2. PPTs were consistently higher in anterior temporalis than in masseter muscle. 3. In all occasions, PPTs were higher in males than in females(p<0.001). 4. A statistically significant correlation was obtained from values of intra-examiners and inter-examiners in all measured muscles. 5. A significantly positive correlation was not found between PPT and functional EMG activity.

• Safety and Health at Work
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• v.1 no.2
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• pp.112-123
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• 2010

The paper gives an overview of the problems to be tackled nowadays by occupational health with regards to shift work as well as the main guidelines at organizational and medical levels on how to protect workers' health and well-being. Working time organization is becoming a key factor on account of new technologies, market globalization, economic competition, and extension of social services to general populations, all of which involve more and more people in continuous assistance and control of work processes over the 24 hours in a day. The large increase of epidemiological and clinical studies on this issue document the severity of this risk factor on human health and well being, at both social and psychophysical levels, starting from a disruption of biological circadian rhythms and sleep/wake cycle and ending in several psychosomatic troubles and disorders, likely also including cancer, and extending to impairment of performance efficiency as well as family and social life. Appropriate interventions on the organization of shift schedules according to ergonomic criteria and careful health surveillance and social support for shift workers are important preventive and corrective measures that allow people to keep working without significant health impairment.