• Current Optics and Photonics
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• v.3 no.3
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• pp.210-214
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• 2019

The allowable path-deviation time of aircraft in a free-space optical communication system has been estimated from various trajectories, using different values of aircraft speeds and turn rates. We assumed the existence of a link between the aircraft and a ground base station. First, the transmitter beam's divergence angle was calculated through two different approaches, one based on a simple optical-link equation, and the other based on an attenuation coefficient. From the calculations, the discrepancy between the two approaches was negligible when the link distance was approximately 110 km, and was under 5% when the link distance ranged from 80 to 140 km. Subsequently, the allowable path-deviation time of the aircraft within the tracking-error tolerance of the system was estimated, using different aircraft speeds, turn rates, and link distances. The results indicated that the allowable path-deviation time was primarily determined by the aircraft's speed and turn rate. For example, the allowable path-deviation time was estimated to be ~3.5 s for an aircraft speed of 166.68 km/h, a turn rate of $90^{\circ}/min$, and a link distance of 100 km. Furthermore, for a constant aircraft speed and turn rate, the path-deviation time was observed to be almost unchanged when the link distance ranged from 80 to 140 km.

• Journal of the military operations research society of Korea
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• v.25 no.1
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• pp.29-36
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• 1999

In this paper, we are concerned with the K-shortest loopless path problem. The MPS algorithm, recently proposed by Martins et al., finds paths efficiently because it solves the shortest path problem only one time unlike other algorithms. But its computational complexity has not been known yet. We propose a few techniques by which the MPS algorithm can be implemented efficiently. First, we use min-heap data structure for the storage of candidate paths in order to reduce searching time for finding minimum distance path. Second, we prevent the eliminated paths from reentering in the list of candidate paths by lower bounding technique. Finally, we choose the source mode as a deviation node, by which selection time for the deviation node is reduced and the performance is improved in spite of the increase of the total number of candidate paths.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.607-613
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• 2011

This paper reviews search methods of multiple reasonable paths to implement multimodal public transportation network of Seoul. Such a large scale multimodal public transportation network as Seoul, the computation time of path finding algorithm is a key and the result of path should reflect route choice behavior of public transportation passengers. Search method of alternative path is divided by removing path method and deviation path method. It analyzes previous researches based on the complexity of algorithm for large-scale network. Applying path finding algorithm in public transportation network, transfer and loop constraints must be included to be able to reflect real behavior. It constructs the generalized cost function based on the smart card data to reflect travel behavior of public transportation. To validate the availability of algorithm, experiments conducted with Seoul metropolitan public multimodal transportation network consisted with 22,109 nodes and 215,859 links by using the deviation path method, suitable for large-scale network.

• Journal of Biomedical Engineering Research
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• v.17 no.3
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• pp.313-318
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• 1996

We proposed a new system for the postural balance rehabilitation training. For the purpose, we used the virtual hiking system using virtual reality technology. We evaluated the system by measuring the parameters such as path deviation, path deviation velocity, cycling time, and head movement. From our results, we verified the usefulness of virtual reality technology in rehabilitation. Our results showed that this system was effective postural balance rehabilitation training device and might be useful as the clinical equipment.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10a
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• pp.72-75
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• 1988

Due to the fact that the set point regulation scheme by the variable structure control method concerns only the initial and final locations of a manipulator, many constraints may exist in the application of path tracking with obstracle avoidance. The variable structure parameter should be selected in the trajectory planning step by satisfying the constraints of the travel time and the path deviations This paper presents the selection algorithm of the variable structure parameters with the constraints of the system dynamics and the travel time and the path deviation. This study makes unify the trajectory planning and tracking control using the variable structure control method.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.19 no.4
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• pp.412-422
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• 2009

This study was conducted to assess exposure to musculoskeletal disorder(MSD) risk factors in hospital personnel who performed non-routinized work tasks. A tool ("PATH-KOSHA" version) was newly revised from PATH(Posture, Activity, Tools and Handling) method and uploaded into a personal digital assistant(PDA). The version was used, on a basis of direct-observation, to collect PATH data at the 2 hospital settings in different regions. Job analysis was performed to get various information (e.g., work and rest time, task type) as well. The data collected were visually checked for data cleaning and stored for future data analysis. A total of 1,992 PATH observations were made for 37 hospital workers. Exposure levels varied across 18 items of the MSD risk factors. The highest percent time spent on non-neutral postures was 53% for wrist deviation, followed by 47%(pinch grip), 35%(trunk posture), 23%(neck posture), and 20%(shoulder/arm posture). The highest percent time spent among hand activity level(HAL) variables was 55% for HAL-cat2 (HAL: 3.3 - <6.7). The percent time of items with respect to both loads with more than 5kg and contact stress was less than 4%. Vibration was not exposed in the study workers. Different aspects were discussed for findings. The study results showed that wrist deviation was highest in percent time spent on awkward posture while HAL-cat2 was highest in hand repetition. The study suggests that distal upper extremity posture and HAL should be primarily addressed and controlled in non-routinized work including the hospital settings.

• Journal of the Korea Institute of Building Construction
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• v.18 no.6
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• pp.595-602
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• 2018

Network-based scheduling methods can be classified into CPM method and PERT method. In the network scheduling chart, critical path can be estimated by performing the forward calculation and the backward calculation though the paths in the network chart. In PERT method, however, it is unreasonable to simply estimate the critical path by adding the sum of the activity durations in a specific path, since it does not incorporate probabilistic concept of PERT. The critical path of a PERT network can change according to the target period and deviation, and in some cases, the expected time of the critical path may not be the path with longest expected time. Based on this concept, this study proposes a technique to derive the most-likely critical path by comparing the sum of estimated time with the target time. It also proposes a method of systematically deriving all alternate paths for a network of repetitive activities. Case studies demonstrated that the most-likely critical path is not a fixed path and may vary according to the target period and standard deviation. It is expected that the proposed method of project duration forecasting will be useful in construction environment with varying target date situations.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.4 no.2
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• pp.4-10
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• 1993

In mobile radio communication, propagation paths are time or spacial varying because of the motion of mobile unit. The propagation path loss not only involves frequency and distance but also the antenna height at both the base station and the mobile unit, terrain configuration, and the man made en- vironment. Thhese additional factors make the prediction of propagation path loss of mobile radio signals more difficult. In this paper, it is measured field strenght of mobile radio signals in Daejeon and Seoul area, also calculated local median, 500m sample mean, and stadard deviation. As the result of analysis, it can be seen that propagation path loss of measured data is similiar to predicted field strength, especially local median is dependent upon base antenna height, terrain configuration and the man-made environment. The standard deviation has been noted to lie between 2 and 10 dBuV.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.1
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• pp.76-82
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• 2000

An arc sensor system to compensate positional errors was developed on the foundation of sensor interface system to make use of the on-line shift function of industrial welding robot. Investigating the on-line shift function, we examine the quantitative relationship between the deviation from programmed path and the correction data transferred from personal computer to robot controller. The number of input parameters for weld seam tracking can be reduced by making the relationship between the deviation and the correction data during half weaving be the function of only cross time. With the results of weld seam tracking for the butt joint with V-groove and fillet joint of sheet metal, good performance was implemented. By developing the sensor interface system to compensate the positional errors, industrial welding robot can be expected to contribute to the promotion of welding automation.

• Journal of the Ergonomics Society of Korea
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• v.28 no.4
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• pp.83-89
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• 2009

This study was conducted to assess exposure to musculoskeletal disorders risk factors in the cooking & housekeeping jobs in hotel work. PATH (posture, activity, tools and handling) method was used for data collection at the 6 hotel settings in different regions across Korea. From 26 workers, a total of 949 PATH observations were obtained. The highest percent time on non-neutral posture was 78% for pinch grip, followed by 74%(wrist deviation), 52%(trunk posture), 37%(shoulder/arm posture), and 30%(neck posture). The highest percent time in the three HAL variables was 47% for HAL-cat2. The percent time of items in relation to both loads with more than 5kg and contact stress was less than 2%. The hotel workers were not exposed to vibration.