This paper proposes a method to improve the position control synchronization performance by synchronizing the controller operation between servo drives based on the synchronization signal of the EtherCAT(Ethernet for Control Automation Technology)distributed clock. In order to synchronize the operation of the controller between the servo drives, the phase of the operating frequency of the PWM(Pulse Width Modulation) module for motor control was synchronized based on the synchronization signal. At this time, the operation sequence of the current, speed, and position controller of the servo drive operating based on the PWM operating frequency was rearranged. Therefore, the servo drives on the network run the same controller at the same time. And the time at which the master's command is reflected to the drive's controller and the time at which the drive's status information is acquired coincided among the drives. After establishing an experimental environment in which servo drives are arranged in the EthercCAT network system, we verified that the position synchronization performance between servo drives applying the proposed method is improved.
In this paper, we proposed and tested an indoor obstacle recognition and avoidance algorithm using vision and ultrasonic sensors for effective operation of drone with low-power. In this paper, the indoor flight of a drone is mainly composed of two algorithms. First, for the indoor flight of the drone, the vanishing point and the center point of the image were extracted through Hough transform of the input image of the vision sensor. The drone moves along the extracted vanishing point. Second, we set an area of interest so that the drone can avoid obstacles. The area of interest is a space where the drone can fly after recognizing an obstacle at a distance from the ultrasonic sensor. When an obstacle is recognized in the drone's area of interest, the drone performs an obstacle avoidance action. To verify the algorithm proposed in this paper, a simple obstacle was installed in an indoor environment and the drone was flown. From the experimental results, the proposed algorithm confirmed the indoor flight and obstacle avoidance behavior of the drone according to the vanishing point.
This research is to study the solution to the defects in maintenance and inspection that can be predicted/prevented in advance among human factors that account for more than 70% of the causes of aviation accidents. Traditionally, mechanics have performed visual inspections of aircraft exteriors. Due to this, there were factors that affect the human ability of mechanics in aircraft maintenance and inspection, safety problems when performing the upper part of the aircraft inspection, and the difficulty of precise inspection. To improve these problems, we conduct a study on an AI drone inspection system that has deep-learned samples on aircraft damage/defects. In this paper, we describe the aircraft maintenance inspection checklist, non-destructive inspection types, types of aircraft damage and defects, deep-learning highly reliable AI drone inspection systems, and the expected effects of this technology and future applications. Through this system research, it is expected that mechanics will efficiently inspect the aircraft through the optimization of aircraft maintenance system technology to prevent aviation accidents in advance and reduce time and economic costs.
PURPOSES : This study evaluates the long-term performance of the asphalt overlay designed by the Seoul pavement design method which determines overlay thickness by considering existing pavement conditions, traffic volume, and bearing capacity of the pavement.
METHODS : A total of 76 sections including 17 control sections and 59 design sections were constructed under various traffic conditions, overlay thicknesses and asphalt mixtures. The performance of the pavements has been monitored up to 60 months in terms of surface distresses, rutting, and longitudinal roughness. The service life of the pavements was estimated to be the period when the Seoul pavement condition index (SPI) becomes 6.0, i.e., a rehabilitation level.
RESULTS : Overall, the service life of the pavements was 72 months in the control and 120 months for the design sections. For relatively thinner overlay sections than designed, the service life reduced significantly; 36 months for 15cm thick overlay and 120 months for 25cm thick overlay. The service life of the pavement in the bus-only lane was 78 months, which is 30 months shorter than that in mixed-traffic lanes. Out of the bus-only lanes, 56% of the pavement along bus stop was deteriorated early to be a poor condition while only 2% of the pavement in a driving lane was degraded to be poor. The overlay with Stone Mastic Asphalt (SMA) in the wearing surface had 38% longer life than that with conventional dense graded mixtures.
CONCLUSIONS : Most of the overlays sections designed by the Seoul pavement design method were expected to survive 10 years, except for bus-only lanes. The control sections having 5 to 10 cm thick overlays showed significant lower performance than the design sections. Thus proper thickness and materials considering the characteristics of existing pavement and traffic volumes should be applied to secure the service life of overlays.
This paper is to study the technology of inspection and history management systems for wind power that are continuously increasing around the world. In the past, inspections and analysis of major devices in renewable energy system have been operated in an analog way that identifies problems through photography and passive method. To improve this problem, we conduct a study on VR-based inspection history management system using 3D texturing technique of drone image. The paper describes the current status and prospects of wind power, research and development of wind power blade inspection and history management systems, experiments and reviews in the field, and expected effects and future utilization of this technology. It is expected that the latest technology for inspection and management of renewable system will be secured and introduced to the site through the development research of this system to reduce maintenance costs and power generation costs.
As the spread of new and renewable power generation facilities, the fixed investment cost CAPEX(Capital Expenditure) of solar power generation facilities decreases due to continuous technological development, and the impact of O&M costs that determine investment success has increased. For this reason, the importance of technologies such as accuracy of O&M cost calculation through ICT, failure prediction, and predictive maintenance have emerged. In the above paper, based on the cost-breakdown structure design and failure rate model design of the solar power generation facility using engineering estimation method, the maintenance cost of the solar power generation facility, which is a renewable power generation facility, is predicted and the maintenance cost used was compared and confirmed. In addition, the cost-breakdown structure and failure rate model of solar power generation facilities were designed and developed by incorporating them into a new program of economic evaluation of new and renewable power generation facilities.
As the frequency of seismic disasters in Korea has increased rapidly since 2016, interest in systematic maintenance and crisis response technologies for structures has been increasing. A data-based leading management system of Lifeline facilities is important for rapid disaster response. In particular, the water supply network, one of the major Lifeline facilities, must be operated by a systematic maintenance and emergency response system for stable water supply. As one of the methods for this, the importance of the structural health monitoring(SHM) technology has emerged as the recent continuous development of sensor and signal processing technology. Among the various types of SHM, because all machines generate vibration, research and application on the efficiency of a vibration-based SHM are expanding. This paper reviews a vibration-based pipeline SHM system for seismic disaster response of water supply pipelines including types of vibration sensors, the current status of vibration signal processing technology and domestic major research on structural pipeline health monitoring, additionally with application plan for existing pipeline operation system.
본 논문은 철계-형상기억합금(Fe-SMA)의 부식특성을 평가하기 위한 실험적 연구이다. 연구를 수행하기 위해 동전위 분극실험을 통해 Fe-SMA의 부식성능을 평가하였다. 시편을 3전극 플렛셀에 설치 후 전위차계를 이용하여 –200mV∼1000mV 구간의 전위를 2mV/s으 속도로 측정하였다. 기준전극 및 상대전극으로 각각 SCE 기준전극과 백금 와이어를 이용하였다. 동전위 분극곡선 및 타펠 피팅을 이용하여 부식전위 및 부식전류밀도를 측정하였다. Fe-SMA의 부식특성을 직관적으로 확인하기 위해 SD400 철근을 비교군으로 설정하였다. 염화물 환경에서 Fe-SMA의 부식성능을 확인하기 위해 3.5wt% 농도의 NaCl 용액에서 실험을 실시하였으며, 콘크리트 환경에서 Fe-SMA의 부식성능을 확인하기 위해 CaO를 이용하여 수용액의 pH를 13으로 조절하였다. 실험결과 Fe-SMA는 SD400 대비 모든 조건에서 우수한 내부식성이 나타났다. Fe-SMA의 콘크리트 환경에서 내부식성은 우수한 것으로 나타났다. 하지만 Fe-SMA가 염화물에 노출되면 부식저항이 급격히 감소되는 것으로 나타났다. 따라서 염화물에 직접적으로 노출되는 환경에서 Fe-SMA를 사용할 경우 부식을 방지하기 위한 적절한 조치가 필요할 것으로 사료된다.
This study was developed to recognize the occurrence of 250[m] of experimental distance, rain and nighttime as an educational and training device without any safety accidents by applying algorithms to optical filters and noise filters to be used in all weather environments and closest to actual shooting training using IR Laser. There are live-fire shooting using live ammunition, screen shooting using beam project and screen, MILES using IR Laser and sensor, BB shooting using compressed gas and BB bullet, and painting shooting using CO2 gas and paint bullet. Among them, the actual shooting training is not efficient in terms of management and operation because it requires considerable risk factors and large costs in preparation for the highest efficiency. Therefore, training that replaces these problems is needed, and various alternative shooting training is being implemented. Therefore, research and development was conducted to solve these problems by using it as one of efficient shooting training and education systems. This study was conducted to develop high-performance and low-cost precision shooting training equipment to contribute to strengthening the defense of the Republic of Korea.
PURPOSES : This study analyzes the service life of the repair methods of jointed plain concrete pavement (JPCP) on expressways in Korea using PMS data.
METHODS : The Korea Expressway Corporation PMS data acquired from five major expressways in Korea were used for the analysis. The service lives of the repair methods were considered for two different cases: 1) the previous repair methods had been completely rerepaired by another or the same method due to their damage, and 2) the current repair methods were still in use.
RESULTS : The service lives of D/G and section repair were shown to be at least 30 % and 50 % shorter than expected, respectively. Joint sealing and crack sealing exhibited a service life similar to that expected. The Mill-and-Asphalt-overlay method showed an approximately 30 % longer service life; this might be because some damage to the asphalt overlay is typically neglected until subsequent maintenance and repair. When multiple repairs were applied in series for an identical pavement section, the service life of repairs on previously damaged secti ons become even shorter compared to their first application.
CONCLUSIONS : It was found that the analyzed service life of most important repair methods did not reach the expected service life, and that the service life of the same repair method becomes shorter as applied to the previously repaired concrete pavement sections. These shorter service lives should be seriously considered in future JPCP repair strategy development.
The concentration of TVOCs in public transportation in the spring and summer of 2018 was measured. Public transportation measured the concentration of TVOCs on six subway lines in Seoul, two lines of high-speed trains, and intercity buses. The measurements were taken during the operation of each route of the surveyed public transportation from the origin to the destination. In addition, the measurement time was divided into the congestion time and the non-congestion time. In the spring of 2018, in the order of subway, train A, train B, and intercity buses, TVOC concentrations during the congestion time zone were 205.9 μg/m3, 121.3 μg/m3, 171.1 μg/m3, and 88.7 μg/m3, respectively. During the non-congestion time zone, the concentrations were 177.2 μg/m3, 108.8 μg/ m3, 118.2 μg/m3, and 126.1 μg/m3, respectively. In the summer of 2018, TVOC concentrations in the order of the aforementioned transportation modes during the congestion time zone were 169.8 μg/m3, 175.8 μg/m3, 78.0 μg/ m3, and 185.3 μg/m3, respectively. During the non-congestion time zone, the concentrations were 210.8 μg/m3, 116.1 μg/m3, and 162.7 μg/m3, respectively. An analysis of BTEX concentration among VOCs in public transportation in descending order were followed by toluene > xylene > ethylbenzene > benzene. Toluene, which has the highest concentration among the BTEX compounds, was found to be 12.86 μg/m3 to 91.41 μg/m3 during spring congestion time and 7.10 μg/m3 to 39.52 μg/m3 during non-congestion time. During the summer congestion time, the concentration was 6.68 μg/m3 to 249.48 μg/m3 and 13.23 μg/m3 to 214.5 μg/m3 during the non-congestion time. The concentration of benzene was mostly less than 5 μg/m3 in transportation. Particularly in the case of toluene, the concentration is significantly higher than that of other VOCs. Accordingly, further study of toluene exposure hazards will be needed. Five percent of the surveyed TVOC concentrations exceeded the recommended indoor air quality standard of 500 μg/m3, and all 13 cases representing this percentage were found in the subway. In addition, nine of the 13 cases that exceeded the recommended standard were measured during congestion time. Therefore, VOCs in public transportation vehicles during congestion time need to be managed.
본 연구는 국내에 자생하는 약용식물인 개똥쑥을 배지 재료로 활용하여 느타리 재배를 위한 적정 혼합비율을 설 정하였다. 개똥쑥의 첨가량에 따른 균사생육과 균사밀도를 조사한 결과 균사생육은 배양 23일 후 개똥쑥 5% 첨 가된 배지에서 12.7 cm였고, 대조구인 포플러톱밥+미강 (8:2)배지에서는 12.5 cm로 개똥쑥 첨가배지와 균사생육이 거의 비슷하였다. 그러나 개똥쑥 첨가량이 증가할수록 대조구 보다 균사생육이 느렸으며, 개똥쑥 70%에서는 2.1 cm로 거의 생육하지 못하였다. 개똥쑥 첨가량에 따른 균사밀도는 처리간에 뚜렷한 차이가 없이 높은 밀도를 보였다. 개똥쑥의 첨가량에 따른 느타리 자실체 특성을 조사한 결과 갓의 직경은 대조구보다 개똥쑥 첨가에서 높았지만, 갓의 두께는 대조구에서 조금 높았다. 대의 두께는 개똥쑥 15% 첨가에서 가장 높았고, 대의 길이는 개똥쑥 10%에서 가장 높았지만 대조구보다는 낮은 경향을 보였다. 수확기 자실체의 갓과 대의 색도를 측정한 결과 대의 L값은 개똥쑥 10%에서 가장 높았고, 갓의 L값은 개똥쑥 5%에서 가장 높은 경향을 보였고, a, b값은 처리간에 뚜렷한 차이가 없었다. 자실체 수량은 대조구가 119 g/850 ml였고, 개똥쑥 5%에서 122 g/850 ml으로 가장 높았고, 개똥쑥 첨가량이 증가할수록 수량은 감소되었다.
PURPOSES : The purpose of this study is to evaluate the performance characteristics of stone mastic asphalt (SMA) pavement by comparison with polymer modified asphalt (PMA) pavement and conventional asphalt pavement, to check the performance characteristics according to the pavement type, pavement materials, traffic volume, and environmental factors and to analyze the quality variation characteristics according to the pavement materials using data extracted from the database of the expressway long-term pavement performance.
METHODS : Approximately 10% outlier data of pavement performance data were excluded in order to increase the reliability of the analysis results before evaluating the asphalt pavement performance. The performance model was developed through linear regression analysis by setting the performance period as the independent variable and the highway pavement condition index (HPCI) as the dependent variable. Descriptive statistic analysis of HPCI using the static package for social science (SPSS) tool and the analysis of variance was performed to identify the quality variation characteristics according to the pavement materials. The amount of de-icing agent and traffic level of service were classified as two levels in order to check the influence of traffic volume and environmental factors on the performance characteristics of the asphalt pavement.
RESULTS : The tentative pavement performance lives were calculated at 19.3 years for new the SMA pavement (GPS-2), 14.3 years for the SMA overlay on the asphalt pavement (GPS-6), and 10.3 years for the SMA overlay on the concrete pavement (GPS-7). In case of the asphalt overlay, the tentative performance lives were calculated at 8.2 years for the PMA overlay on the asphalt pavement (GPS-6), 7.2 years for the PMA overlay on the concrete pavement (GPS-7), 7.2 years for the conventional asphalt overlay on the asphalt pavement (GPS-6), and 5.5 years for the conventional asphalt overlay on the concrete pavement (GPS-7).
CONCLUSIONS : It was confirmed that the SMA pavement showed better performance and quality variation characteristics than the PMA and conventional asphalt pavement. The performance characteristics of the asphalt pavement (GPS-2) was better than the asphalt overlay pavement, and the asphalt overlay on the asphalt pavement (GPS-6) had better performance characteristics than the asphalt overlay on the concrete pavement (GPS-7). It was observed that the asphalt overlay on the asphalt pavement (GPS-6) was strongly influenced by the traffic volume and the asphalt overlay on concrete pavement (GPS-7) was strongly influenced by the traffic volume and de-icing agent.
The purpose of this study is to provision the standard method for ensuring the reliability of measuring indoor air quality in public transportation. The objective is to determine the difference in the measured concentration values according to various conditions. These variables include measurement conditions, measurement equipment, measurement points, and measurement time. The value differences are determined by measuring the PM10 and CO2 concentration of subways, and express buses and trains, which are targets of indoor air quality management. The concentration of CO2 was measured by the NDIR method and that of PM10 was measured by the gravimetric method and light-scattering method. Statistically, the results of the concentration comparison according to the measurement points of the public transportation modes were not significantly different (p > 0.05), and it is deemed that the concentration is not affected by the measurement points. In terms of the concentration analysis results according to the measurement method, there was a difference of the concentration between the gravimetric and light scattering method. In the case of the light scattering method, the concentration differed depending on whether it was corrected with standard particles in the laboratory environment.