• The Journal of Korea Robotics Society
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• v.17 no.1
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• pp.76-85
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• 2022

One of the most fundamental challenges when designing controllers for dynamic systems is the adjustment of controller parameters. Usually the system model is used to get the initial controller, but eventually the controller parameters must be manually adjusted in the real system to achieve the best performance. To avoid this manual tuning step, data-driven methods such as machine learning were used. Recently, reinforcement learning became one alternative of this problem to be considered as an agent learns policies in large state space with trial-and-error Markov Decision Process (MDP) which is widely used in the field of robotics. However, on initial training step, as an agent tries to explore to the new state space with random action and acts directly on the controller parameters in real systems, MDP can lead the system safety-critical system failures. Therefore, the issue of 'safe exploration' became important. In this paper we meet 'safe exploration' condition with Control Barrier Function (CBF) which converts direct constraints on the state space to the implicit constraint of the control inputs. Given an initial low-performance controller, it automatically optimizes the parameters of the control law while ensuring safety by the CBF so that the agent can learn how to predict and control unknown and often stochastic environments. Simulation results on a quadrotor UAV indicate that the proposed method can safely optimize controller parameters quickly and automatically.

• The Journal of Korea Robotics Society
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• v.18 no.4
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• pp.487-495
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• 2023

This paper presents a method for autonomous exploration of indoor environments using a 2-dimensional Light Detection And Ranging (LiDAR) scanner. The proposed frontier-based exploration method considers navigability from the current robot position to extracted frontier targets. An approach to constructing the point cloud grid map that accurately reflects the occupancy probability of glass obstacles is proposed, enabling identification of safe frontier grids on the safety grid map calculated from the point cloud grid map. Navigability, indicating whether the robot can successfully navigate to each frontier target, is calculated by applying the skeletonization-informed rapidly exploring random tree algorithm to the safety grid map. While conventional exploration approaches have focused on frontier detection and target position/direction decision, the proposed method discusses a safe navigation approach for the overall exploration process until the completion of mapping. Real-world experiments have been conducted to verify that the proposed method leads the robot to avoid glass obstacles and safely navigate the entire environment, constructing the point cloud map and calculating the navigability with low computing time deviation.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.402-405
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• 2008

This paper is a proposal of Sentinel Asia for Environment (SAFE). The essential to this project is to help environmental agencies in Asia to set up an environmental monitoring system with satellite observation data. It is focused on an environmental issues originated from anthropogenic events detected as land cover and land use change in Asians' daily human life including; agriculture, global warming gas, urban environment and forest resources. It is leaded by Japan Aerospace Exploration Agency (JAXA) along with University of Tokyo and Asian Institute of Technology in Thailand under the umbrella of Sentinel Asia which is dedicated to disaster monitoring issues. It is expected to initiate a information outgoing through WWW for Asian countries to set up their national land information system focusing on environmental changes.

• 한국지구물리탐사학회:학술대회논문집
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• 2001.09a
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• pp.1-13
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• 2001

The role of geophysics in Environmental Earth Sciences and Engineering is considered. In the developing era since 60's in Japan, geophysics has mainly contributed to investigation of new constructions such as tunnels, dams and high-rise buildings. In the coming sustainable era, geophysics must be used for maintaining the safe and easy human life. Application examples of geophysics to investigations for disaster prevention, maintenance of existing constructions and soil and groundwater pollutions are presented to demonstrate their role in Environmental Geo-engineering. Future subjects in this field for geophysics and geophysicists are also discussed.

• Journal of Astronomy and Space Sciences
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• v.29 no.4
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• pp.375-380
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• 2012

It is a crucial matter to select a landing site for landers or rovers in planning the Mars exploration. The landing site must have not only a scientific value as a landing site, but also geographical features to lead a safe landing for Mars probes. In this regard, this study analyzed landing site of Mars probes and rovers in previous studies and discussed the adequacy of the landing site to scientific missions. Moreover, this study also examined domestic studies on the Mars. The frameworks of these studies will guide the selection of exploration sites and a landing site when sending Mars probe to the Mars through our own efforts. Additionally, this paper will be used as the preliminary data for selection of exploration site and a landing site.

• Archives of Reconstructive Microsurgery
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• v.9 no.1
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• pp.15-22
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• 2000

One hundred & seventy four consecutive free-flap transfers were reviewed to analyze distribution of the type of reconstructions, kinds of donor flaps as well incidence of complications. The role of emergent exploration and the effect of preoperative wound conditions in flap survival were evaluated. Free flap transfer for head and neck reconstruction was most common as 93 cases, followed by for upper extremity of 30 cases, for lower extremity 30 cases, 18 penile reconstructions and for trunk & breast 3 cases. Nine flaps exhibited signs of ciruclatory insufficiency between 5 hours and 7 days. Three were managed conservatively with ultimate partial necrosis of the flaps. Eight flaps required return to the operating room. On exploration, early arterial occlusion was revealed in 1 flap, late arterial occlusion in 2 flaps, early venous occlusion in 1 flap, late venous thrombosis in 2 flaps, prolonged venous spasm in 1 and hematoma in 1 flap. The average time from the first abnormal examination to exploration was 2.6 hours. There were no false-positive explorations. Four free flaps failed in spite of the correction of the cause of circulatory compromise. The remaining 4 flaps were salvaged following the correction the casuse. Recipient vessel problems such as irradiation and infection were the most common cause of circulatory crisis. Among the eight flaps requiring return to the operating room, single vein was anastomosed in three flaps and two veins in the remaining five. In the totally failed four flaps only single vein was anastomosed in three cases. The results of this study demonstrate the efficacy of clinical monitoring and the role of early exploration. Precautious selection of recipient vessels and two vein anastomosis are recommended for safe and better prognosis.

• Tunnel and Underground Space
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• v.31 no.1
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• pp.1-9
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• 2021

Recently, the development of underground space has been accelerated with rapid urbanization, and it is significantly important for safe construction to accurately understand the geological conditions of the section when excavating rocks. In this paper, a boring alignment tracking and geological exploration system have been developed to identify the geological conditions beyond the excavation face by utilizing a MSP method that bores a large empty hole to reduce blast-induced vibration. The major advantage of the proposed exploration system is that we can obtain the ground condition of 50 m ahead of the excavation face through exploration along blast cut-holes drilled for the NATM tunnel construction. In addition, we introduce several case histories regarding the assessment of the geological conditions beyond the tunnel face by monitoring the inside of large empty holes using the proposed hole exploration system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.5
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• pp.1030-1035
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• 2011

The remote control of mobile robot is widely used to perform dangerous and complex tasks such as underwater exploration and cleaning of nuclear reactor. For this purpose, the obstacle avoidance process will proceed to ensure a safe drive. In this paper, we tested that mobile robot drive in which replaced a pipe with a box. After we measured the distance around the obstacle through a sensor of robot, we got the information that changed haptic force from the distance of the obstacle.

• Strategy21
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• s.30
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• pp.200-235
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• 2012

Over the past few years, due to the climate change of the earth, the Arctic's sea ice cover is undergoing a historic transformation - thinning, extent reduction in all seasons, and mitigation in the area of multi-year ice in the central Arctic Ocean. These changes allow for increases in maritime access throughout the Arctic Ocean and for potential longer seasons of navigation and possibly transarctic voyage in the summer. These changes also allow more exploration for oil, gas, and other minerals. The Arctic is now an archetype of the complex, multi-dimensional global problems of the twenty-first century. Military security, environmental security, and economic security interact. The potentially enormous economic stakes, sufficient to change the strategic balance among the states of the region, set off competitive pressures for national advantage. Korea, which is heavily dependent upon the sea lane in terms of transportation of its exports and imports, is very much interested in the Arctic sea routes. Korea believes that the Artic sea route, particularly the Northern Sea Route (NSR), could serve as a new useful sea lane, which will enable shorter times between East Asia and Europe, thus resulting in substantial cost saving for ship operators. In addition to shipping, Korea is interested in other Arctic-related maritime industries. Korea, as a leading shipbuilder in the global market, is interested in building ice breakers, drill ships, and other vessels which can contribute to safe operation in Arctic resource development and exploration. Korea, as one of the future stakeholders in Arctic maritime activities, should be ready to foster international cooperation in the region.

• Advances in pediatric surgery
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• v.12 no.1
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• pp.11-16
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• 2006

Inguinal hernia is one of the most common surgical diseases in pediatric patients. But the management of the side opposite the clinically apparent inguinal hernia, the "silent side" is controversial. Four hundred fifty-eight cases of pediatric inguinal hernias, operated by one pediatric surgeon at the Divisionof Pediatric Surgery, Department of Surgery, Chonbuk National University Hospital from January 1998 to December 2002, were reviewed retrospectively to determine the characteristics and significances of the silk-glove test on the side opposite the clinically apparent inguinal hernia. Males were preponderant as 2.8:1. Allhernias were of the indirect type and were repaired by high ligation of the sac. There were 238 (52.0 %) right sided hernias, 160 (35.0 %) were on the left and 60 (13.0%) were bilateral. The number of patients with a positive silk-glove sign on the contralateral side was 158(39.7 %), and 133 of these had a contralateral patent processus vaginalis. Positive predictive value of Silk-glove test was 84.2 % (133/158). The silk-glove test is a simple, safe, and relatively accurate method for contralateral exploration in the unilateral inguinal hernias in children.