• International Journal of Highway Engineering
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• v.10 no.4
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• pp.235-245
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• 2008

Since rapidly increase of tunnel with increasing of expressway, the study on safety improvement of safety device at entrance of expressway tunnels is necessary. The existence of tunnel occurs more speed reduction than an upward slope by itself, the collision accident of tunnel entrance causes heavier damage than that of general accident on the road. So, many kinds of safety devices such as poly-ethylene barrier, guard-rail are placed on the road side. But these devices affect the drivers as an obstacle. Although there are various safety devices that are placed at tunnel entrance, this study is related to following 2-cases. One is that the poly-ethylene barrier is placed and the other is that a safety devices is not placed. The reason that these two cases are selected, is that poly-ethylene barrier is usually placed at many tunnel entrances and safety devices can affect the drivers as an obstacle. This study is related to the difference of right-hand side clearance between inside tunnel and outside tunnel, too. The average difference observed car speed and VDS(vehicle detect system) speed nearby the tunnel is analysed. Through the statistical analysis of the average difference, this study suggests an alternatives on safety improvement of safety devices at entrance of expressway tunnels. It is concluded that the small difference of right-hand side clearance is desirable to drivers when a poly-ethylene barrier is placed. And when the difference of right-hand side clearance is large, no safety devices is desirable, and when the difference of right-hand side clearance is small, poly-ethylene barrier should be placed to improve safety.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.6
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• pp.1036-1043
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• 2022

This paper discusses about the development of a visual sensor that can be installed in an automatic mooring device to detect the berthing condition of a vessel. Despite controlling the ship's speed and confirming its location to prevent accidents while berthing a vessel, ship collision occurs at the pier every year, causing great economic and environmental damage. Therefore, it is important to develop a visual system that can quickly obtain the information on the speed and location of the vessel to ensure safety of the berthing vessel. In this study, a visual sensor was developed to observe a ship through an image while berthing, and to properly check the ship's status according to the surrounding environment. To obtain the adequacy of the visual sensor to be developed, the sensor characteristics were analyzed in terms of information provided from the existing sensors, that is, detection range, real-timeness, accuracy, and precision. Based on these analysis data, we developed a 3D visual module that can acquire information on objects in real time by conducting conceptual designs of LiDAR (Light Detection And Ranging) type 3D visual system, driving mechanism, and position and force controller for motion tilting system. Finally, performance evaluation of the control system and scan speed test were executed, and the effectiveness of the developed system was confirmed through experiments.

• Journal of Korean Society of Transportation
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• v.35 no.2
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• pp.116-128
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• 2017

Traffic accidents can be defined as a physical collision event of vehicles occurred instantaneously when drivers do not perceive the surrounding vehicles and roadway environments properly. Therefore, detecting the high potential events that cause traffic accidents with monitoring the interactions among the surroundings continuously by driver is the prerequisite for prevention the traffic accidents. For the analysis, basic data were collected to analyze interactions using a test vehicle which is equipped the GPS(Global Positioning System)-IMU(Inertial Measurement Unit), camera, radar and RiDAR. From the collected data, highway geometric information and the surrounding traffic situation were analyzed and then safety evaluation algorithm for driving vehicle was developed. In order to detect a dangerous event of interaction with surrounding vehicles, locations and speed data of surrounding vehicles acquired from the radar sensor were used. Using the collected data, the tangent and curve section were divided and the driving safety evaluation algorithm which is considered the highway geometric characteristic were developed. This study also proposed an algorithm that can assess the possibility of collision against surrounding vehicles considering the characteristics of geometric road structure. The methodology proposed in this study is expected to be utilized in the fields of autonomous vehicles in the future since this methodology can assess the driving safety using collectible data from vehicle's sensors.

• Journal of Navigation and Port Research
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• v.36 no.10
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• pp.851-856
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• 2012

There has been increasing the possibility of occurring the marine accident and become bigger the extent of damage with the growing number and high speed of ships. Also, there were tremendous loss of lives and properties in accidents of Hebei spirit in 2007 and Cheon Ahan war ship in 2010 with the insufficient salvage response and the lack of emergency response systems. When a ship has suffered an incident, the best way of preventing damage or pollution from its progressive deterioration would be to providing a place of refuge and to repair the damage rapidly. Therefore, it was examined the recent collision accident broken out near the Nam-Hae, and then suggested that it was necessary to be improved of the domestic salvage systems. It requires the procedures of providing a place of refuge, and the towing support system which make the damaged ship moved to the safe area, and joining of the ISU.

• Resources Recycling
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• v.13 no.5
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• pp.37-44
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• 2004

In this study, neodymium oxalate powders were prepared by injecting oxalic acid to the neodymium chloride solution resulted from the acid leaching solution of NdFeB magnet scrap. The effect of experimental conditions on the characteristics of neodymium oxalate powders were investigated. Neodymium oxalate was aggregated by primary particles formed by nucleation, and average size of aggregates was affected by experimental conditions. In a constant volume, increase of reactants affected the average size of aggregate formed by collision of primary particles. In a constant concentration of reactants, agitation speed decreased the size of aggregate due to breakage of particles attached on the surface of aggregate. The number of primary particles decreased with increasing reaction temperature, and the size of aggregates decreased due to the decrease of collision probability. From the results of decomposition behavior of neodymium oxalate, oxalate decomposed from $400^{\circ}C$, and neodymium oxide began to crystallize at above $620^{\circ}C$.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.1243-1244
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• 2022

In recent years, the growing interest in off-site construction has led to factories scaling up their manufacturing and production processes in the construction sector. Consequently, continuous large-scale site monitoring in low-variability environments, such as prefabricated components production plants (precast concrete production), has gained increasing importance. Although many studies on computer vision-based site monitoring have been conducted, challenges for deploying this technology for large-scale field applications still remain. One of the issues is collecting and transmitting vast amounts of video data. Continuous site monitoring systems are based on real-time video data collection and analysis, which requires excessive computational resources and network traffic. In addition, it is difficult to integrate various object information with different sizes and scales into a single scene. Various sizes and types of objects (e.g., workers, heavy equipment, and materials) exist in a plant production environment, and these objects should be detected simultaneously for effective site monitoring. However, with the existing object detection algorithms, it is difficult to simultaneously detect objects with significant differences in size because collecting and training massive amounts of object image data with various scales is necessary. This study thus developed a large-scale site monitoring system using edge computing and a small-object detection system to solve these problems. Edge computing is a distributed information technology architecture wherein the image or video data is processed near the originating source, not on a centralized server or cloud. By inferring information from the AI computing module equipped with CCTVs and communicating only the processed information with the server, it is possible to reduce excessive network traffic. Small-object detection is an innovative method to detect different-sized objects by cropping the raw image and setting the appropriate number of rows and columns for image splitting based on the target object size. This enables the detection of small objects from cropped and magnified images. The detected small objects can then be expressed in the original image. In the inference process, this study used the YOLO-v5 algorithm, known for its fast processing speed and widely used for real-time object detection. This method could effectively detect large and even small objects that were difficult to detect with the existing object detection algorithms. When the large-scale site monitoring system was tested, it performed well in detecting small objects, such as workers in a large-scale view of construction sites, which were inaccurately detected by the existing algorithms. Our next goal is to incorporate various safety monitoring and risk analysis algorithms into this system, such as collision risk estimation, based on the time-to-collision concept, enabling the optimization of safety routes by accumulating workers' paths and inferring the risky areas based on workers' trajectory patterns. Through such developments, this continuous large-scale site monitoring system can guide a construction plant's safety management system more effectively.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.8
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• pp.80-87
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• 2008

This paper investigated into the impact characteristics of the stainless sheet with thickness of 0.7 mm on the stretching boundary condition through three-dimensional finite element analysis. High speed tensile tests were carried out to obtain strain-stress relationships with the effects of the strain rate. The FE analysis was performed by the ABAQUS explicit code. In order to improve an accuracy of the FE analysis, the hyper-elastic model and the damping factor were introduced. Through the comparison of the results of the FE analyses and those of the impact tests, a proper FE model was obtained. The results of the FE analyses showed that the absorption rate of energy maintains almost 82.5-83.5% irrespective of the impact energy level and the diameter of the impact head. From the results of FE analyses, variations of stress, strain, dissipation energy, strain energy density, and local deformation characteristics in the stainless sheet during the collision and the rebound of the impact head were quantitatively examined. In addition, it was shown that the fracture of the specimen occurs when the plastic strain is 0.42 and the maximum value of the plastic dissipation energy of the specimen is nearly 1.83 J.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.3
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• pp.172-177
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• 2014

Low pressure air flotation (LAF) pilot plant for sludge thickening was installed in Chung Nam N.S. municipal waste water treatment plant to verify its application possibility. Effects of operating conditions such as coagulant dosages and microbubble water ratio on thickening of the mixed sludge were examined. Microbubbles which were generated in the chamber of $1.5kgf/cm^2$ by high speed collision method with foaming agent were used to float sludge. Solid loading of $30kg/m^2/hr$, solid contents in thickened sludge of 60,300 mg/L and SS removal efficiency of 99% were obtained through long period operating LAF in conditions of mixed sludge concentration of 14,400 mg/L, coagulant dosage of 27.6 mg/L, foaming agent addition of 4.0 mg/L and microbubble water injection ratio of 9.7%.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.168-173
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• 2003

In this paper, we will present a deeper look on optimal design methods that are related to path-planning for a mobile robot. To control the motion of a mobile robot in a clustered environment, it's necessary to know a suitable trajectory assuming certain start and goal point. Up to now, there are many literatures that concern optimal path planning for an obstacle avoided mobile robot. Among those literatures, we have chosen 2 novel methods for our further analysis. The first approach [4] is based on HJB(Hamilton-Jacobi-Bellman) equation whose solution is the return-function that helps to generate a shortest path to the goal. The later [5] is called polynomial-path-planning approach, in this method, a shortest polynomial-shape path would become a solution if it was a collision-free path. The camera network plays the role as sensors to generate updated map which locates the static and dynamic objects in the space. Therefore, the exhibition of both path planning and dynamic obstacle avoidance by the updated map would be accomplished simultaneously. As we mentioned before, our research will include the motion control of a true mobile robot on those optimal planned paths which were generated by above algorithms. Base on the kinematic and dynamic simulation results, we can realize the affection of moving speed to the stable of motion on each generated path. Also, we can verify the time-optimal trajectory through velocity tuning. To simplify for our analysis, we assumed the obstacles are cylindrical circular objects with the same size.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.49 no.3
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• pp.62-73
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• 2012

IEEE 802.15.4 standard which has low-speed, low-power, low-cost can be efficiently used in wireless sensor network environment. Among various topologies used in IEEE 802.15.4 standard, a cluster-tree topology which has many nodes in it, transmit delay, energy consumption and data loss due to traffic concentration around the sink node. In this paper, we propose the MRS-DCA algorithm that minimizes conflicts between packets for efficient data transmission, and dynamically allocates the active period for efficient use of limited energy. The MRS-DCA algorithm allocates RP(Reservation Period) to the active period of IEEE 802.15.4 and guarantees reliable data transmission by allocating RP and CAP dynamically which is based on prediction using EWMA. The comparison result shows that the MRS-DCA algorithm reduces power consumption by reducing active period, and increasing transmission rate by avoiding collision.