• Journal of the Korean Society for Heat Treatment
• /
• v.37 no.5
• /
• pp.207-214
• /
• 2024

This study examines the effects of post-oxidation treatment on the microstructure and corrosion resistance of GC250 cast iron. The nitriding process was conducted at 570℃ for 180 minutes with a fixed nitriding potential (Kn) of 1.5, followed by post-oxidation at 450℃, 500℃, and 550℃ for 120 minutes. The post-oxidized specimens showed increased surface hardness and case depth compared to the nitrided specimens, with a maximum surface hardness of approximately 890 HV0.1. The oxidation process increased the thickness of the nitrided layer by more than 3 ㎛, with the oxide layer thickness reaching up to 2.5㎛ as the oxidation temperature increased. XRD analysis identified the presence of ε-phase, γ'-phase, and Fe₃O⁴ phase on the surface. Polarization tests revealed that the specimen treated at the highest oxidation temperature had a corrosion current density of 20.26 ㎂/cm² and a corrosion potential of -0.22V, indicating enhanced corrosion resistance compared to the nitrided specimen. This improvement is attributed to the formation and increased thickness of the oxide layer, which enhances corrosion resistance. In conclusion, the oxide layer formed through post-oxidation treatment significantly improves the corrosion resistance of GC250 cast iron, with the effect becoming more pronounced at higher oxidation temperatures.

• Journal of Digital Convergence
• /
• v.18 no.3
• /
• pp.163-169
• /
• 2020

A smart key has been used in a variety of embedded environments and there also have been attacks from a remote place by amplifying signals at a location of a user. Existing studies on defence techniques suggest multiple sensors and hash functions to improve authentication speed; these, however, increase the electricity usage and the probability of type 1 error. For these reasons, I suggest an embedded security controller based on client authentication and user movement information improving the authentication method between a controller and a host device. I applied encryption algorithm to the suggested model for communication using an Arduino board, GPS, and Bluetooth and performed authentication through path analysis utilizing user movement information for the authentication. I found that the change in usability was nonsignificant when performing actions using the suggested model by evaluating the time to encode and decode. The embedded security controller in the model can be applied to the system of a remote controller for a two-wheeled vehicle or a mobile and stationary host device; in the process of studying, I found that encryption and decryption could take less then 100ms. The later study may deal with protocols to speed up the data communication including encryption and decryption and the path data management.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.20 no.3
• /
• pp.34-46
• /
• 2021

In order to accelerate the commercialization of self-driving cars, it is necessary to accurately identify the causes of deteriorating the driving safety of the current self-driving cars and try to improve them. This study conducted a questionnaire survey of experts studying autonomous driving in Korea to identify the causes of problems in the driving safety of autonomous vehicles and the level of autonomous driving technology in Korea. As a result of the survey, the construction section, heavy rain/heavy snow conditions, fine dust conditions, and the presence of potholes were less satisfied with the current technology level than their importance, and thus priority research and development was required. Among them, the failure of road/road facilities and the performance of the sensor itself in the construction section and the porthole, and the performance of the sensor and the absence of an algorithm were the most responsible for the situation connected to the weather. In order to realize safe autonomous driving as soon as possible, it is necessary to continuously identify and resolve the causes that hinder the driving safety of autonomous vehicles.

• Land and Housing Review
• /
• v.13 no.1
• /
• pp.99-112
• /
• 2022

There is growing significance in securing urban parks and enhancing their accessibility due to irrational residential developments and apartment construction. Accordingly, Daejeon Metropolitan City has carried out urban park management projects to improve the quality of parks and create new parks. Daejeon Metropolitan City generates and manages park data for the purpose of management by the administrative district. However, these datasets take different forms in each administrative district. This study integrates the park data in Daejeon, generated by administrative districts, into the same format and generates geographic information data with the area information of each park for analysis. Analysis results show that urban parks are severely imbalanced across administrative districts, requiring new policy measures. In addition, by normalizing the park analysis results and, then, creating their rankings, this study compares them with the actual park information in detail to confirm the soundness of the dataset. The analysis results provide implications to improve the management of urban parks. This study proposes integrated datasets and the continued management of them in each administrative district by including essential data that can feature the objective information of the parks along with park evaluation indicators based on previous studies.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.21 no.2
• /
• pp.62-73
• /
• 2022

As the competition among the autonomous vehicle (AV, here after) developers are getting fierce, Korean government has been supporting developers by deregulating safety standards and providing financial subsidies. Recently, some OEMs announced their plans to market Lv3 and Lv4 automated driving systems. However, these market changes raised concern among public road management sectors for monitoring road conditions and alleviating hazardous conditions for AVs and human drivers. In this regards, the authors proposed a methodology for monitoring road infrastructure to identify hazardous factors for AVs and categorizing the hazards based on their level of impact. To evaluate the degrees of the harm on AVs, the authors suggested a methodology for managing road hazard factors based on vehicle performance features including vehicle body, sensors, and algorithms. Furthermore, they proposed a method providing AVs and road management authorities with potential risk information on road by delivering them on the monitoring map with node and link structure.

• Korean Journal of Remote Sensing
• /
• v.38 no.5_2
• /
• pp.725-735
• /
• 2022

Currently, disasters occurring in Korea are characterized by unpredictability and complexity. Due to these features, property damage and human casualties are increasing. Since the initial response process of these disasters is directly related to the scale and the spread of damage, optimal decision-making is essential, and information of the site must be obtained through timely applicable sensors. However, it is difficult to make appropriate decisions because indiscriminate information is collected rather than necessary information in the currently operated Disaster and Safety Situation Office. In order to improve the current situation, this study proposed a framework that quickly collects various disaster image information, extracts information required to support decision-making, and utilizes it. To this end, a web-based display system and a smartphone application were proposed. Data were collected close to real time, and various analysis results were shared. Moreover, the capability of supporting decision-making was reviewed based on images of actual disaster sites acquired through CCTV, smartphones, and UAVs. In addition to the reviewed capability, it is expected that effective disaster management can be contributed if institutional mitigation of the acquisition and sharing of disaster-related data can be achieved together.

• Journal of Cadastre & Land InformatiX
• /
• v.52 no.1
• /
• pp.105-118
• /
• 2022

The demand for information related to 3D spatial objects model in metaverse, smart cities, digital twins, autonomous vehicles, urban air mobility will be increased. 3D model construction for spatial objects is possible with various equipments such as satellite-, aerial-, ground platforms and technologies such as modeling, artificial intelligence, image matching. However, it is not easy to quickly detect and convert spatial objects that need updating. In this study, based on spatial information (features) and attributes, using matching elements such as address code, number of floors, building name, and area, the converged building DB and the detected building DB are constructed. Both to support above and to verify the suitability of object selection that needs to be updated, one system prototype was developed. When constructing the converged building DB, the convergence of spatial information and attributes was impossible or failed in some buildings, and the matching rate was low at about 80%. It is believed that this is due to omitting of attributes about many building objects, especially in the pilot test area. This system prototype will support the establishment of an efficient drone shooting plan for the rapid update of 3D spatial objects, thereby preventing duplication and unnecessary construction of spatial objects, thereby greatly contributing to object improvement and cost reduction.

• Journal of Aerospace System Engineering
• /
• v.16 no.3
• /
• pp.42-51
• /
• 2022

An eVTOL aircraft, which is required to operate with low pollution/low noise in urban environments, mostly use battery-powered electric propulsion systems as power sources, not traditional propulsion systems such as reciprocating or turbine engines. Accordingly, certification preparation for the electric propulsion system and securing the safety of the electric propulsion system, are important issues. In the U.S., special technical standards equivalent to FAR Part 33 were issued to certify electric engines, and in Europe, various special conditions were established to certify electric propulsion systems. Thus, in Korea, the technical standards for the electric propulsion system for eVTOL aircraft must also be prepared in line with the U.S. and Europe. In this paper, SC E-19, the technical standard of the electric/hybrid propulsion system (EHPS) in special conditions, was analyzed. Additionally, securing the safety of the electric propulsion system of the aircraft are proposed, through the collaboration of SC E-19 technical standards with the existing aircraft safety evaluation procedure ARP 4761. Finally, through a case study of the Ehang 184 electric propulsion system, it has been confirmed that the proposed safety assurance method is applicable at the aircraft level.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.21 no.5
• /
• pp.28-41
• /
• 2022

A road system with CV(Connected Vehicle)s, which is often referred to as a cooperative intelligent transportation system (C-ITS), provides various road information to drivers using an in-vehicle warning system. Road environments with CVs induce drivers to reduce their speed or change lanes to avoid potential risks downstream. Such avoidance maneuvers can be considered to improve driving behaviors from a traffic safety point of view. Thus, empirically evaluating how a given in-vehicle warning information affects driving behaviors, and monitoring of the correlation between them are essential tasks for traffic operators. To quantitatively evaluate the effect of in-vehicle warning information, this study develops a method to calculate compliance rate of drivers where two groups of speed profile before and after road information is provided are compared. In addition, conventional indexes (e.g., jerk and acceleration noise) to measure comfort of passengers are examined. Empirical tests are conducted by using PVD (Probe Vehicle Data) and DTG (Digital Tacho Graph) data to verify the individual effects of warning information based on C-ITS constructed in Seoul metropolitan area in South Korea. The results in this study shows that drivers tend to decelerate their speed as a response to the in-vehicle warning information. Meanwhile, the in-vehicle warning information helps drivers to improve the safety and comport of passengers.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.22 no.1
• /
• pp.233-251
• /
• 2023

Metropolitan buses are managed as either a direct seat type or a metropolitan express type according to the 「Passenger Transport Service Act」. However, a management system that reflects the characteristics of metropolitan buses is not currently established. Therefore, in this study, the driving characteristics of metropolitan buses, dangerous driving behavior characteristics of metropolitan bus drivers, metropolitan bus accident characteristics, and the safety management system of domestic and foreign buses and other means were investigated. Through this, a plan for strengthening the safety management of metropolitan buses suitable for Korea was presented by dividing it into short-term and mid to long term. The short-term plan is a plan that can be carried out through consultation between metropolitan bus agencies and transportation companies, and the mid to long term plan is a plan that can be implemented only when related laws are revised. Through this study, it is expected to serve as an opportunity for in-depth discussions by the government, business operators, and related experts to strengthen the safety management of metropolitan buses.