• Journal of the Korean Society of Safety
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• v.28 no.3
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• pp.33-38
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• 2013

Many occupational workers or professionals have to walk on the various floors for a long period of time. The objective of this study was to develop the safety shoes with increased traction through the material selection. In order to fulfill our objective, first, two kinds of filler were selected to compare the wear mechanism at outsole surface. The developed rubber materials were tested with two kinds of portable slip meters. The sample safety shoes with developed rubber materials were also tested with subject in the laboratory. During walking, the safety shoes were naturally abraded with counter surface. The coefficient of friction(COF) was gradually decreased with number of steps to 30,000, while the COF was abruptly increased from 30,000 to 40,000. The experimental results showed that COF tested with silica rubber was at least 10% higher than that with carbon black rubber in wet or detergent condition. It has been well recognized that filler properties play a important role in wet traction in the tire industry. However it has been unclear that filler properties would be decisive factor in safety shoes. Our study shows that silica exhibits a higher slip resistance than carbon black without reference to wear states in wet or detergent condition. So, this results will provide guides for outsole compounders to develop new products and improve product performance.

• 한국노년학
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• v.30 no.3
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• pp.843-853
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• 2010

The purpose of this study is to find out the characteristics of elderly pedestrian accidents and to suggest policy implications to enhance the level of elderly pedestrian safety. Although much efforts has made to enhance traffic safety environment, pedestrian traffic accidents among elderly population are not significantly decreased. This is mainly because current traffic safety measures do not much consider the characteristics of elderly pedestrians in the aspects of physical and psychological conditions. Main findings from vehicle-pedestrian traffic accident data and survey are as follows. First elderly pedestrians have high probability of traffic accident near crosswalks or cross streets rather than on crosswalk or cross streets. Second they need more green light time for crossing the streets. Third, they feel motor cycles running on the side walk and parked vehicles on the side walk are the most dangerous factors. Forth, general drivers do not have reasonable understanding for the walking behaviors of elderly pedestrians. Fifth, elderly pedestrians frequently need to rest while walking. Sixth, elderly people do not see clearly or understand traffic signs. Finally, many elderly pedestrians experience accidents or inconvenience while walking on the sidewalk.

• Safety and Health at Work
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• v.9 no.2
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• pp.180-183
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• 2018

Background: This research investigates the degrees of slipperiness felt by the participants who walk on contaminants applied to a floor surface to decide degrees of slipperiness for various contaminants. Methods: For the experiment, 30 participants walked on a floor to which six contaminants were applied. All participants took the analytic hierarchy process (AHP)-based slipperiness questionnaire survey for the six kinds of contaminants, and the results were compared with the coefficient of friction. Results: The results of slip risk from the AHP indicate that grease is the most slippery of the six contaminants, followed by diesel engine oil, hydraulic oil, cooking oil, water-soluble cutting oil, and water in a decreasing order of slipperiness. When the results of slip risk from the AHP are compared with the static coefficient of friction for each contaminant, the order of slip risk follows the same trend. Although the results of slip risk from the AHP coincide with the static coefficient of friction, further study would be needed to investigate this relationship. Conclusion: This study will contribute as reference material for future research on preventing industrial accidents that result in falls from high places due to slipping.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.825-836
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• 2019

One of the most challenging safety precautions for workers in dynamic, radioactive environments is avoiding radiation sources and sustaining low exposure. This paper presents a sampling-based algorithm, DL-RRT*, for minimum dose walk-path re-planning in radioactive environments, expedient for occupational workers in nuclear facilities to avoid unnecessary radiation exposure. The method combines the principle of random tree star ($RRT^*$) and $D^*$ Lite, and uses the expansion strength of grid search strategy from $D^*$ Lite to quickly find a high-quality initial path to accelerate convergence rate in $RRT^*$. The algorithm inherits probabilistic completeness and asymptotic optimality from $RRT^*$ to refine the existing paths continually by sampling the search-graph obtained from the grid search process. It can not only be applied to continuous cost spaces, but also make full use of the last planning information to avoid global re-planning, so as to improve the efficiency of path planning in frequently changing environments. The effectiveness and superiority of the proposed method was verified by simulating radiation field under varying obstacles and radioactive environments, and the results were compared with $RRT^*$ algorithm output.

• Fire Science and Engineering
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• v.25 no.1
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• pp.72-77
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• 2011

The effort of transferring some parts of urban functions to the underground space is growing trend among modem cities because of the limit of horizontal land use, the rise of land value, the diversification of human desire, etc. Thus, the basement of building and the subway station have deepened. It calls our attention to safety about evacuation from the underground space to the ground. Until now, the study about crowding walk in stairs has been progressed, focusing on the crowding walk that is going down the stairs, and there is no study about crowding walk that is going up the stairs. This study measured walking pace by crowd density that is going up the stairs in the subway station stairs making one-way movement of crowd. The actual survey showed that the mathematical relation 'V=0.638-0.0949p' determines going up walking velocity at a gradient of $23^{\circ}$, and the mathematical relation will be 'V=0.597-0.1067p' at a gradient of $30^{\circ}$, when it is converted, based on the average walking velocity of crowd by the slope of the stairs which is recommended by Architectural Institute of Japan.

• Journal of Mechanical Science and Technology
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• v.19 no.12
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• pp.2312-2320
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• 2005

The aerodynamic effects of leading-edge accretion can raise important safety concerns since the formulation of ice causes severe degradation in aerodynamic performance as compared with the clean airfoil. The objective of this study is to develop a numerical simulation strategy for predicting the particle trajectory around an MS-0317 airfoil in the test section of the NASA Glenn Icing Research Tunnel and to investigate the impingement characteristics of droplets on the airfoil surface. In particular, predictions of the mean velocity and turbulence diffusion using turbulent flow solver and Continuous Random Walk method were desired throughout this flow domain in order to investigate droplet dispersion. The collection efficiency distributions over the airfoil surface in simulations with different numbers of droplets, various integration time-steps and particle sizes were compared with experimental data. The large droplet impingement data indicated the trends in impingement characteristics with respect to particle size ; the maximum collection efficiency located at the upper surface near the leading edge, and the maximum value and total collection efficiency were increased as the particle size was increased. The extent of the area impinged on by particles also increased with the increment of the particle size, which is similar as compared with experimental data.

• Journal of the Korean Institute of Landscape Architecture
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• v.30 no.1
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• pp.52-60
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• 2002

This paper presents a streetscape design for "Dangiae-Gil"which is located at 126-1 Yangpyung-2dong, Yeongdeungpo-gu, Seoul and is about 500m in length and about 24m in width. The design goals are to make a green street on which people want to walk and people can walk and rest safely and pleasantly. To achieve these goals, concepts of environmentally-friendliness, placeness, safety, amenity, vitality, connectivity, and democracy are developed. For pedestrian safety, shared street concepts, such as crank, slalom etc. are adopted. The site is divided into 5 thematic spaces, such as "Village Entrance Space", "Culture Street", "Dangsan Park", "Nature Street", and "Ferry Space". The Village Entrance Space, which is an entrance of the Dangjae-Gil and a welcoming space, is for communicating information about the area. "Dangnamu"(zelkova tree) and signs are introduced here. The Culture Street is for experiencing past and present culture of the area. Colored tiles and plant boxes attached to benches are introduced. The Dangsan park is a sacred space where modem people can feel the sacredness of nature arid of being in a refuge. Dangjib, Dangnamu, multi-purpose plaza, athletic facilities, and playground for infants are introduced. The Nature Street is a space for feeling and teaming nature which has disappeared from the area leading to the river and a space for community participation. The elementary school walls were demolished and nature education spaces, such as butterfly and dragonfly garden, ecological pond, wildflower garden, etc., which are related to school education, are introduced. The Ferry Space is a space symbolizing a old ferry crossing and an entrance plaza to a bridge for "Sunyu-do\" . A boat-shaped deck, an elevator for handicap people, and parking space are introduced. In conclusion, sustainable management schemes for the site are suggested.sted.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.4
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• pp.467-478
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• 2016

In this paper, we try to find the optimal locations of NeNB(Nomadic evolved NodeB)s for maximizing the overall throughput of the PS-LTE networks. Since finding optimal locations of all NeNBs in a given area is NP-hard(Non-deterministic Polynomial time-hard) problem, we proposed a PSO-based heuristic approach. In order to evaluate the performance, we conducted two experiments. We compared performance with other schemes such as Exhaustive Search, Random Walk Search, and locating neighboring NeNBs with the same NeNB-to-NeNB distance. The proposed method showed the similar results to the exhaustive search method in terms of locating optimal position and user's data throughput. The proposed method, however, has the fast and consistent convergence time.

• Journal of the Korean Home Economics Association
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• v.48 no.3
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• pp.43-53
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• 2010

This study aimed to compare fear and prevention behaviors on accidents between mothers and teachers in family childcare centers. The participants were 117 mothers whose children were 0~2 year-olds and 121 teachers. Based on Hendrickson(2008) and Reichert & Henricks(1996), the scale was developed by the researcher, and it was composed of fear and prevention behaviors on accident. The data were analyzed using descriptive statistics and $x^2$ analysis. Results showed that mothers feared fall accidents and step-on-accidents while teachers feared suffocation accidents and liability for injury medical fee. Also, mothers did more prevention behaviors on use of car seats than teachers, whereas teachers did more behaviors on walk safety, custody of drugs and dangerous articles, and food safety.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.1
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• pp.158-167
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• 1997

For the use of a mobile robot in dynamic environment, a collision-avoidance algorithm with moving obsta- cle is necessary. In this paper, a collsion-avoidance algorithm of a mobile robot is presented, when a mobile robot detects the collision with moving obstacle on the navigational path. Using reported positions of moving obstacle with sensors, the mobile robot predicts the next position of moving obstacle with possibility of collision. The velocity of moving obstacle is modeled as random walk process with Gaussian distribution. The optimal collision-avoidance path in which turning motion of the mobile robot is considered is generated with relative velocity between the mobile robot and moving obstacle. For the safety of collision-avoidance path, attractive potential with the safety factor is suggested. The simulation results using this algorithm show the mobile robot avoids collision with moving obstacle in many cases.