• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.9
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• pp.599-608
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• 2022

Urban air mobility (UAM) equipped with rotor system is subject to ground effect at vertiport during takeoff and landing. The aerodynamic performance of the aircraft in ground effect should be analyzed for the safe operation. In this study, The ground effects on the aerodynamic performance and wake structure of the quadcopter electric vertical takeoff and landing (eVTOL) configuration equipped with coaxial counter-rotating propellers were investigated by using the lattice Boltzmann method (LBM). The influence of the ground effect was observed differently in the upper and lower propellers of the coaxial counter-rotating propeller system. There was no significant change in the aerodynamic performance of the upper propeller even if the propeller height above the ground was changed, whereas the averaged thrust and torque of the lower propeller increased significantly as propeller height decreased. In addition, the amplitude of the thrust fluctuation tended to increase as the propeller height decreased. The propeller wake was not sufficiently propagated downstream and was diffused along the ground due to the outwash flow developed by the ground effect. The impingement of the rotor wakes on the ground and a fountain vortex structure were observed.

• Journal of Navigation and Port Research
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• v.46 no.1
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• pp.18-25
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• 2022

MOF strengthen the law and institutions for safety management after the capsize accident of passenger ship "Sewol" on April 16, 2014. Nevertheless, about 13 cases of marine accidents such as collisions, contact, and stranding have occurred in coastal passenger ships over the past 5 years. Particularly, according to the judgment of KMST, most of the main causes of passenger ship accidents occurred within harbor areas because of the master's improper ship-handling or inattention. And so, this study analyzed four cases of marine accidents on passenger ships that occurred in the port areas and examined the environmental, institutional, material, and human factors that contributed to the master's improper ship-handling and behavior, and the results are as follows. First, as an environmental factor, the size of the turning basin was not enough. Second, as an institutional factor, the VTS control was not properly supported, the master lacked sufficient training for safe ship-handling in the port area and up-to-date charts were not provided. Third, as a material factor, the digital type speed log capable of the ship's speed in real-time was not installed on the ship's wing bridge. Lastly, as a human factor, the master could not take proper bridge resources and the passage plan was not proper. Therefore, it is suggested in this paper that the size of the turning basin should be adjusted to meet the prescribed standards, the master of passenger ships should receive the ship-handling simulation training among other safety training to ensure safe ship-handling of the master in the port area as improvement measures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6D
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• pp.775-789
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• 2008

The Office for Government Policy Coordination announced in 2006, september that a scheme of pre-signal would show remarkable outcome to reduce traffic accidents. Therefore, the Ministry recommended applying preferentially the pre-signal scheme to enhancement projects for high accident frequency areas. In case that the suggested pre-signal was unilaterally introduced to the enhancement projects at intersections, it might rather cause a big trial and error in terms of traffic safety. Hence, on the basis of quantitative analysis, this study was to indicate a pre-signal's effectiveness to reduce the traffic accidents, to illustrate a trend of the accident type due to the pre-signal, and to introduce intersection type that could be appropriate for the pre-signal. The methodology adopted Comparison-Group Method which was developed by Hauer. Through this methodology, overall effectiveness to reduce the accidents is considered positive but individual effectiveness by intersection and by accident case was different. All cases of the accidents at small scale intersection demonstrated positive results to reduce its accidents, while in case of frontal collision and side-right angle collision out of the accident types, the installation of pre-signal rather caused a negative result increasing the accident in terms of the traffic safety. I hope that this study would be a useful reference for future development of the estimation of accident effectiveness. Thus, when the pre-signal is being installed in the big intersection, it is recommended operating the installation concerning carefully improvements about muliple aspects as traffic operation, traffic facility, human factor etc.

• Journal of the Daesoon Academy of Sciences
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• v.22
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• pp.87-131
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• 2014

한국은 백 년 이래로 군사적 침략과 경제적 대변혁을 맞았으며, 또한 종교와 문화적 측면에서 전통의 중흥기와 서학의 유입에 대한 문제를 경험하게 되었다. 이런 점에서 한국의 역사적 경험은 주변 국가의 국민들이 배울 만한 의미가 있다고 생각된다. 이와 연관하여 대순진리회가 역사를 계승하고 창신을 이루어나가는 측면의 문제는 정리해볼 만한 가치가 있다. 대순진리회의 종지는 '음양합덕, 신인조화, 해원상생, 도통진경'이다. 특히 대순진리회는 해원상생 사상으로 조화정신을 집중적으로 잘 나타내고 있다. 대순진리회의 해원은 고대 단주로부터의 원을 푸는 것에서 시작되며, 인류가 근본적으로 여러 세대에 걸친 원한을 풀어야만 행복하고 안락한 시대에 진입할 수 있다는 역사관을 보여주고 있다. 대순진리회가 해원을 푸는 방책으로 제시하는 상생은 당시의 갑오동학혁명이나 역사상 많은 종교에서 원한을 해결하는 방법과 구별되는 것이다. 과거에 있어서는 상극의 방법으로 원한을 해결하여 왔으나, 상극의 방식은 오히려 새로운 원한을 더욱 만들어 낼 수 있기 때문에, 현대에 있어 원한을 제거할 수 있는 방법은 악을 선으로써 대하는 것이라고 한다. 증산 성사 및 그 후학들은 사회의 질서를 새롭게 세우는 문제와 전통사회에서 인간 간의 조화를 방해하고 원한을 용인하는 구습을 개조하고 원을 소멸하는 문제에 주의를 기울였다. 이러한 변혁은 평등의 관념을 나타내고 있다. 증산께서는 전 세계적인 관점에서 민족과 국가 그리고 종교 간의 조화를 실현해야 할 것을 강조하셨다. 당시 동아시아 국가는 매우 폐쇄적인 상황에서 서양 국가의 침략을 받던 시기였는데, 증산 성사께서 미래의 세계는 마땅히 화합을 이루고 서로의 장점을 배우는 세계가 될 것임을 예견하셨다는 것은 그의 위대함을 보여주는 대목이다. 증산의 후천개벽사상 역시 조화의 정신을 나타내고 있다. 후천개벽사상은 전통적 참위를 현대적으로 개조한 것으로 민중을 적극적으로 인도하기 위한 것이다. 다음으로, 증산께서는 각 종교에 대해 관용적인 태도를 표하셨고, 또한 매우 진지한 태도로 타 종교로부터 자신이 주창하는 사상과 관련한 자원을 흡수하셨다. 동양의 전통적인 유불선 삼교를 가장 중요한 종교와 문화형태로 인정하시고, 그 삼교의 내용을 두로 포용하셨으며, 심지어 예수교와 서양문화까지 모두 아우르는 태도를 보여주셨다. 서양의 문화 역시 증산께서 추구하시는 신세계의 한 부분이었기 때문이다. 이러한 사실은 증산께서 당시 세계의 역사적 방향에 대해 통찰하고 있었고 이 통찰 속에서 종교 간의 관계가 조화롭게 되어야 함을 주창했음을 말해 준다. 대순사상에는 민간 무교의 내용 역시 풍부하게 들어있다. 부뚜막신, 사명, 아표신, 마장군, 백의군왕, 황천신 등 민간에서 유행했던 다양한 신령숭배의 내용을 흡수했을 뿐만 아니라, 주문과 부를 태우는 법술로 신명과 관련된 내용을 표현하고 있으며, 칠성과 관우의 신앙까지 수용하고 있다. 또한 증산 성사는 동학과 같은 신종교까지 받아들이셨다. 증산께서는 동학혁명의 비참한 최후를 완화시켰던 위대한 역사적 공적을 이루셨으며, 신종교 운동의 사회적 형태를 변화시켰을 뿐 아니라, 서로 다른 내력을 지닌 교도들간의 관계를 조화롭게 하였다. 이로 볼 때 결국 증산께서 주창한 대순사상은 사람들 간의 충돌과 모순을 소멸시키고, 조화와 상생의 사회 환경을 창조하고자 하는 것이었다고 할 수 있다.

• Journal of the Society of Disaster Information
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• v.20 no.1
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• pp.106-116
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• 2024

Purpose: This paper conducts IoT and CCTV-based safety monitoring to analyze accidents and potential risks occurring at construction sites, and detect and analyze risks such as falls and collisions or abnormalities and to establish a system for early warning using devices like a walkie-talkie and chatbot service. Method: A safety management service model is presented through smart construction technology case studies at the construction site and review a relevant literature analysis. Result: According to 'Construction Accident Statistics,' in 2021, there were 26,888 casualties in the construction industry, accounting for 26.3% of all reported accidents. Fatalities in construction-related accidents amounted to 417 individuals, representing 50.5% of all industrial accident-related deaths. This study suggests implementing AI chatbot services for construction site safety management utilizing IoT-based health monitoring technologies in smart construction practices. Construction sites where stakeholders such as workers participate were demonstrated by implementing an artificial intelligence chatbot system by selecting major risk areas within the workplace, such as scaffolding processes, openings, and access to hazardous machinery. Conclusion: The possibility of commercialization was confirmed by receiving more than 90 points in the satisfaction survey of participating workers regarding the empirical results of the artificial intelligence chatbot service at construction sites.

• Journal of Preventive Medicine and Public Health
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• v.15 no.1
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• pp.187-196
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• 1982

The followings are the results of the study on industrial accidents occurred at 12 factories manufacturing metal products during the period of 2 years from January 1980 to December 1981 in the area of Yong-Dung-Po in Seoul. The results of the study are as follows: 1. The incidence rate of industrial injuries was 45.7 per 1,000 workers of the sample group and the rate of male (54.0) was three times higher than that of female (17.5). 2. In age groups, the highest rate was observed in the group of under 19 years old with 83.5, while the lowest in the group of 40s. 3. It was found that those who had short term of work experience produced a higher rate of injuries, particularly, the group of workers with less than 1 year of experience showed the highest rate of it as 48.1%. 4. In working time, the highest incidence rate occurred 3 and 7 hours after the beginning of their working showing the rate of 6.0 and 6.1 per 1,000 workers, respectively. 5. The highest incidence rate was observed on Monday as 8.4 per 1,000 workers, and it was 18.3% in aspect of the days of a week. 6. In aspect of the months of a year, the highest incidence was observed on July 1,000 workers and the next was on March as 4.8. These figures account for 11.8% of total occurrence in respective month. as 5. 4 per and 10.5% 7. In causes of injuries, the accident caused by power driven machinery showed the highest rate with 37.5%, the second was due to handling without machinery with 17.2%, and the third was due to falling objects with 14.2%, and striking against objects with 10.2%, and so on. 8. By parts of the body affected, the most injuries 84.3% of them occurred on both upper and lower extremities with the rate of 58.8% for the former and 25.5% for the latter. Fingers were most frequently injured with a rate of 40.3%. Comparing the sites of extremities affected, rate of injuries on the right side was 55.0% and 45.0% on the left side. 9. In the nature of injury, laceration and open wound were the highest with 34. 0%, the next was fracture and dislocation with 31. 9%, and sprain was the third with 8.1%. 10. On the duration of treatment, it lasted less than one month in 68.9% of the injured cases, of which 14.5% of the cases were recovered within 2 weeks, and 54.4% of them were treated more than 2 weeks. And the duration of the treatment tended to be prolonged in larger industries. 11. The ratio of insured accidents to uninsured accidents was 1 to 4.7.

• Journal of the Korean Arthroscopy Society
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• v.6 no.1
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• pp.1-6
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• 2002

Purpose : Evaluation and analysis of the incidence and causes of intraoperative and postoperative complications after arthoscopic anterior cruciate ligament(ACL) reconstruction using bone-patella. tendon-bone (BPTB) auto graft. Materials and Methods : We reviewed 85 cases of arthroscopic ACL reconstruction using BPTB autograft which had been followed up for more than 1 year. Intraoperative complications had been recorded and corrected during the operation. Postoperative complications were analyzed and compared between 3 groups which were classified by the last follow-up period after the operation. Results : There were a few intraoperative complications including patellar fracture(1 case), contamination of harvested graft(1 case), impingement of graft(2 cases), blow-out of tile posterior wall of the femoral tunnel(1 case) and intraarticular retraction of the screw(1 case). The result of the comparison of postoperative complications among the groups shows that the incidence of anterior knee pain, donor site pain and patellofemoral crepitation were significantly decreased after 2 years. But there was no significant decrease in these complications after 3 years. Conclusion : Intraoperative complications after arthroscopic ACL reconstruction using BPTB autograft were due to incorrect technique and carelessness of the operation team, and can be prevented by improvement of surgical technique and accumulation of experience. Postoperative complication were somewhat unavoidable but gradually improved with time; hence, we should consider it for the selection of graft donor.

• Journal of Preventive Medicine and Public Health
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• v.14 no.1
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• pp.81-88
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• 1981

The present study was conducted to investigate the status of industrial injuries through a prospective study for a year from August 1980 to July 1981. The subjects were 15 textile industries which were selected by random sampling in Daegu. The results obtained are as follows: Anual over-all incidence rate of industrial injuries was 3.3 percent and the rate showed 6.7 percent in male and 2 percent in female. The rate showed decreasing tendency with larger scale of industries. By the age group, $15{\sim}19$ age group was the highest as 49.3 percent. Age specific incidence rate of industrial injuries revealed highest as 4.7 precent among the group the group of 30 years old and over. By the years of service, 57.1 percent of the total cases belonged to the the group less than 1 year and the rate revealed increasing tendency with shorter period of service. The highest frequency of industrial injuries was observed at the point of 3 hours after the beginning of the work in a day as 18.1 percent. Frequency of industrial injuries showed highest as 20.3 percent on Monday. Frequency of industrial injuries was highest as 27.7 percent in winter time and showed 14 percent and 11.8 percent in January and August, respectively. By the cause of injuries, machinery accidents showed the highest as 39.2 percent and followed by the accidents due to striking against object as 17.8 percent, fall of ground as 16.3 percent and hand tool as 7.2 percent. Frequency of injured parts of body was highest as 43.9 percent in fingers. The frequency was much higher in upper extremities (66.9%) than in lower extremities (17.6%). By the kind of injuries, laceration wound was highestas 35.7 percent and the next was superficial injury and contusion as 35.1 percent. By the duration of treatment, most of the cases was belonged to the group less than 1 month as 79.1 percent and the duration showed prolonging tendency with larger scale of industries.

• Journal of the Korea Concrete Institute
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• v.24 no.3
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• pp.293-303
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• 2012

Recently, as construction technology improved, concrete structures not only became larger, taller and longer but were able to perform various functions. However, if extreme loads such as impact, blast, and fire are applied to those structures, it would cause severe property damages and human casualties. Especially, the structural responses from extreme loading are totally different than that from quasi-static loading, because large pressure is applied to structures from mass acceleration effect of impact and blast loads. Therefore, the strain rate effect and damage levels should be considered when concrete structure is designed. In this study, the low velocity impact loading test of steel fiber reinforced concrete (SFRC) slabs including 0%~1.5% (by volume) of steel fibers, and strengthened with two types of FRP sheets was performed to develop an impact resistant structural member. From the test results, the maximum impact load, dissipated energy and the number of drop to failure increased, whereas the maximum displacement and support rotation were reduced by strengthening SFRC slab with FRP sheets in tensile zone. The test results showed that the impact resistance of concrete slab can be substantially improved by externally strengthening using FRP sheets. This result can be used in designing of primary facilities exposed to such extreme loads. The dynamic responses of SFRC slab strengthened with FRP sheets under low velocity impact load were also analyzed using LS-DYNA, a finite element analysis program with an explicit time integration scheme. The comparison of test and analytical results showed that they were within 5% of error with respect to maximum displacements.

• Journal of the Korean Institute of Landscape Architecture
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• v.51 no.2
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• pp.1-11
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• 2023

This study intended to develop a technique for quantitatively and 3-dimensionally predicting the potential failure zone and impulse that may occur when trees are fall down. The main outcomes of this study are as follows. First, this study established the potential failure zone and impulse calculation formula in order to quantitatively calculate the risks generated when trees are fallen down. When estimating the potential failure zone, the calculation was performed by magnifying the height of trees by 1.5 times, reflecting the likelihood of trees falling down and slipping. With regard to the slope of a tree, the range of 360° centered on the root collar was set in the case of trees that grow upright and the range of 180° from the inclined direction was set in the case of trees that grow inclined. The angular momentum was calculated by reflecting the rotational motion from the root collar when the trees fell down, and the impulse was calculated by converting it into the linear momentum. Second, the program to calculate a potential failure zone and impulse was developed using Rhino3D and Grasshopper. This study created the 3-dimensional models of the shapes for topography, buildings, and trees using the Rhino3D, thereby connecting them to Grasshopper to construct the spatial information. The algorithm was programmed using the calculation formula in the stage of risk calculation. This calculation considered the information on the trees' growth such as the height, inclination, and weight of trees and the surrounding environment including adjacent trees, damage targets, and analysis ranges. In the stage of risk inquiry, the calculation results were visualized into a three-dimensional model by summarizing them. For instance, the risk degrees were classified into various colors to efficiently determine the dangerous trees and dangerous areas.