• Journal of the Korea Institute of Building Construction
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• v.11 no.1
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• pp.51-59
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• 2011

With the increased demand for membrane structures in recent years, there have been many studies of their mechanical properties, to the extent that such structures have become recognized as independent structures with a level of safety and durability comparable to those of other general structures. But in reality, the study for the maintenance of membrane structures has not been as active. In particularly, the study of watertightness from the perspective of maintenance has been very limited. Accordingly, a study on securing watertightness performance and the guidelines for maintenance is necessary. In this study, through a case study of water leakage accidents in membrane structures overseas, causes of leakage were selected from the membrane material itself, joint parts and open door of roof part in membrane structure. The water leakage and deterioration elements were analyzed from those leakage causes. The degree of importance of the water leakage and deterioration index was also designated using the AHP (Analytic Hierarchy Process) method. As a result, the basic technical index was suggested for the maintenance of the roofs of large-span membrane structures to prevent water leakage. This index will be used to make a guideline for the long-term maintenance of the roofs of large-span membrane structures.

• Journal of Korean Society of Transportation
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• v.27 no.2
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• pp.95-105
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• 2009

Traffic accidents on highways are likely to happen when there is an imbalance in the complex relationships among key elements such as road geometries, driver related factors, and mechanical performances. The Demand-Effort Model (DEM), which evaluates highway safety, can be explained by the imbalance, which occurs when the level of demand of the driver's attention to the road environment exceeds that of the response from the driver. This study suggests a new model that improves the reliability of the current DEM through the reinterpretation on the physiological signals with the help of the Neural Network Model (NNM). The data were collected from 149 subjects, who drove a test vehicle on the Yongdong, Honam, and Seohaean Expressways in Korea. Three important results could be drawn from the recursive tests as follows; (1) Only 5 out of 10 parameters on the physiological signals which are currently used were proven to be meaningful through the Normality Test, Cluster Analysis, and Mann-Whitney Analysis. (2) The revised DEM, which internally uses the NNM, showed more reliable results than existing DEM. Group 1, which is based on the new DEM showed 80.0% of accuracy in measuring the level of driver's efforts, however, that of Group 2 based on the current DEM was 74.3%. (3) Field tests on the Honam Expressway showed lower 'type II error' with the new DEM (40.5%) than the old DEM (58.8%). The DEM is designed as a quick and easy way to determine highway safety prior to the minute road safety audit (RSA) by a professional audit team. Then a new DEM, which is based on the NNM, needs to be considered since it showed higher reliability and lower error.

• Journal of the Korean Institute of Gas
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• v.16 no.4
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• pp.38-43
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• 2012

The purpose of this study is to carry out the consequence analysis of an accident related to the release of Hydrogen chloride occurred in a petrochemical company in Korea and suggest the measures to prevent similar accidents from happening again. The total amount released through the safety valve of HCl Column was calculated based on the rated capacity of the safety valve, the ideal gas equation and mechanical energy balance, respectively. As a result of the calculation, we found that the amount of HCl released through the safety valve was at least 76.8 kg. Also, we predicted the dispersion concentration at the position of the injured workers(more than 350 m away from the accident location) using simulation programs such as PHAST. The results of ALOHA and K-CARM are 304 ppm and 1,700 ppm respectively. However, PHAST calculation indicated that the concentration is less than l ppm. From these results, we can understand that workers were injured by HCl gas released from the safe valve and the concentration of gas might be less than 1 ppm. Also, it is important for toxic gases such as HCl to be vented safely to the atmosphere after scrubbing.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.18 no.4
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• pp.746-757
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• 1996

Bony defects may be found as a result of congenital anomalies, traumatic injury, automobile collisions and industrial accidents in the maxillofacial area. Such conditions are often associated with severs functional and esthetic problem. Various surgical procedure has been utilized in attempts to repair and reconstruct bony defects. Bone is a complex, living, constantly changing tissue. The architecture and composition of cancellous and cortical bone allow the skeleton to perform its essential mechanical functions. Periosteum covers the external surface of bone and consists of two layers : an outer fibrous layer and an inner more cellular and vascular layer. The inner osteogenic layer or cambium layer can form new bone while the outer layer firms part of the insertions of tendons, ligaments and muscles. This study was under taken to evaluate bone healing process on partial defect of calvarial bone with or without periosteum in rat. We made calvarial defects of different size(4mm, 6mm, 8mm) with periosteum or without periosteum in rat to study the effect of defect size on healing process. Control and experimental groups sacrified at 1, 2, 4, 6, 8 weeks, postoperatively. We examed the specimens by gloss findings, light microscophy, and fluorescent microscophy. The results were as follows. 1. Gloss findings: Control groups are larger bony defects than experimental groups after 2 weeks, and than control groups advanced healing of defected bone but experimental groups are lesser after 4, 6 weeks. After 8 weeks, bone defect has not been identified in control and experimental groups. 2. Light microscope: All defects of control groups are larger bony defects than experimental groups after 2 weeks. And than control groups show smaller defect after 4 weeks. After 8 weeks, the control group reveal pin-point sized, hardly identifiable defect space and the experimental group reveal small, but definite defect space. 3. Fluorescent microscope : Each week, new bone formation of control group is very similar to the experimental group. In this study, Osteogenesis of calvarial bone defects with periosteum or without periosteum was examined for 8 weeks in rats. The replaced periosteum had batter new bone formation than the removed periosteum.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.2
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• pp.227-235
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• 2018

Along with the recent increase in traffic volume of vehicles, accidents involving rollover of vehicles have been rapidly increased, resulting in an increase casualties. And to prevent this, various technologies such as vehicle crash test equipment and analysis program development have been advanced. In this study, the applied vehicle model is FORD EXPLORER model, and PC-Crash program for vehicle collision analysis is used to predict the rollover accident behavior of SUV and the collision velocity. Compared with the actual rollover behavior of SUV through the FMVSS No 208 regulations, the analysis results showed similar results, the characteristics of the collision velocity and roll angle showed a tendency that the error rate slightly increased after 1000 msec. Then, as a result of considering using the database of NHTSA, it is shown that the rollover accident occur most frequently in the range of the collision velocity of 15~77 km/h and the collision angle of $22{\sim}74^{\circ}$. And it is possible to estimate the vehicle speed and collision time when the vehicle roof is broken by reconstructing the vehicle starting position, the roof failure position and the stop position by applying the actual accident case.

• Journal of Navigation and Port Research
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• v.39 no.1
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• pp.29-35
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• 2015

As the numbers of users of domestic passenger ships increased up to 14.5 millions at 2012, the numbers of ships accidents also increased as 2 times than ever. It will be very important to develop technologies related with safety design for onboard passengers and disclose the potential problems. This study performed consciousness survey on ordinary peoples' way finding who have not got any regular anti-disaster training, to develop evacuation models for evacuation feasibility studies. Followings are the results answered by 83 participants for 33 way finding questions. Respondents selected right ways more than 6~18% for 2 ways like T type, U type, Y type passages. But when there are some walkers and/or runners, respondents preferred to select the way where walkers or runners are. And more over the ratio of the ways that runners are on is comparatively higher than walkers. On 'ㅏ'type, 'ㅓ'type and 3 way type passages, even though the walkers and/or runners are affected to answerers, straight way were most preferred. And it is clear that peoples like bright passages. On the other hands, peoples responded as they like right, downward and near stairs more than left, upward and far stairs, respectively. and very few selected escalator and elevator for as evacuation stairs.

• Journal of Navigation and Port Research
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• v.38 no.3
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• pp.233-238
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• 2014

With the increasing needs on various leisure activities, the users of passenger ships and cruisers have been increased year by year. Although over 15 accidents per year betide on domestic passenger ships for last decade, the researches on the safety of crews and guests on boards are difficult to find. This study performed the comparative analysis by experiments on the evacuation characteristics between experience levels on board a training ship. The followings are the results. From the seniors' experiments, it is found that more various evacuation scenarios have to develope and drill as a part of education contents. And from the freshmen's trials, the importances of the evacuation education and the roles of existing crews on evacuation guides are pointed out as to increase the safety of new crews and/or guests who are not accustomed to onboard a ship. On the other, it is explained that the communications between evacuees are worthy and useful, and also save more evacuation times. And on the viewpoint of evacuation methodology, it is clear that captain and evacuation-related crews have to control all the evacuation passages and evacuees of each passages to save more lives.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.5
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• pp.574-580
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• 2016

In this paper, we will introduce the system that can control multiple vehicles on the road through Single Board Computers and V2I (Vehicle-To-Infrastructure). Also, we will propose the group evasive maneuver decision algorithm, which plays a critical role in deciding whether the vehicles in the system have to conduct evasive maneuvers to avoid obstacles on the road. In order to test this system, we have utilized Wi-Fi and TCP/IP for establishing the communication between multiple vehicles and the relay server, and observed their driving states on the road with obstacles. During the experiments, we have discovered that our original decision algorithm possesses high failure rate when there is frequency interference in ISM (Industrial Scientific Medical) band. In order to reduce this failure rate, we have implemented the data transition detector. This paper will focus on how the use of data transition detector can affect the reliability of the system under the frequency interference of ISM band. If this technology is improved and applied in the field, we will effectively deal with such dangerous situations as multiple collision accidents through vehicle-to-vehicle communication or vehicle-to-infrastructure communication. Furthermore, this can be applied to the autonomous driving technologies. This can be used as the reference data for the development of the similar system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.135-139
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• 2017

The main reason for heat accidents occurring at the after stern tube bearing (STB) is excessive local pressure caused by the deflection of the propulsion shaft due to propeller loads. The probability of a heat accident is increased by the low flexibility of the shaft system in very large crude oil carriers (VLCCs) as the engine power and shaft diameter increase and the distance decreases between the forward and after STBs. This study proposed shaft system with only an after STB and no forward STB for a flexibility acquisition method for a VLCC shaft system under hull deformation. A Hertzian contact condition was applied, which assumes a half-elliptical pressure distribution along the contact width for the calculation of the local squeeze pressure. The propeller loads, heat effect, and hull deflection under engine operating conditions are also considered. The results show that the required design criteria were satisfied by building a partial slope at the white metal, which is the material at the axial contact side in the after STB. This system could reduce building cost by simplification of the shaft system.

• Korean Journal of Remote Sensing
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• v.34 no.2_2
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• pp.419-429
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• 2018

An unmanned autonomous maritime surface system can move the vehicle to the areas for observing the ocean accidents, disasters, and severe weather conditions. Detection and monitoring technologies have been developed by the converging of the regional and local surveillance system. Wave Glider, one of the autonomous maritime surface systems, is ocean-wave propelled autonomous surface vehicle and controlled using Iridium satellite communication. In this study, we carried out two-time Wave Glider observations for 2016 and 2017 summer in the East China Sea that the area was influenced by low-salinity water. We observed the sea surface warming effect due to the low-salinity water using the regional (satellite) and local (Wave Glider) surveillance system. We also monitored the effect of the typhoon and understood the change of the ocean-atmosphere environments in real-time. New unmanned surface system with autonomous system and high endurance structure can measure comprehensively and usefully a long observation in complicated ocean environments because of connecting with other surveillance systems.