• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.23 no.2
• /
• pp.106-118
• /
• 2024

Interest in personal mobility has increased with the growing significance of first-mile and last-mile connectivity in smart mobility services. This study aims to propose a methodology for setting the service area of free-floating personal mobility sharing services and determining the optimal fleet size for the selected shared service area to address first-mile and last-mile challenges. We utilize population data, smart card data, and building data. Additionally, we estimate latent demand by incorporating age-specific and distance-specific utilization rates based on personal mobility device data. Along with the latent demand, we determine the service area based on locations of transit stops and buildings. We apply the proposed methodology to Yeongjong Island, Incheon. As a result, dense residential areas and popular beachside locations are designated as personal mobility sharing service areas. The fleet size for personal mobility in the dense residential service area is determined to be 1,022 units, while the fleet size for the beachside service area is set at 269 units.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.21 no.1
• /
• pp.159-181
• /
• 2022

Today, people in cities use differentthe types of transportation that rangepeople use in cities have diversified from existing public transportation, cars, taxis to shared bicycles and shared electric kickboards. In addition, with the development of mobile platform -based search, order, and payment services, and transportation services have also begun to change into platform-based integrated services. In particular, MaaS, which has emerged as an integrated mobile service and, is currently being studied and operated worldwide., However, MaaS but remains at the level of the integrated provision of the existing public transportation. As a result of Specifically, the results of a literature review on this issue reveal that, the First/Last Mile problem raised at the current level of MaaS is likely to be solved by establishing an improved policy incorporating new means of transportation. Therefore, this study aims to establish a First/Last Mile transportation supply plan for successful MaaS provision. This establishment is realized by analyzing the traffic patterns of urban populations usingbased on the ABATA system,, an activity-based traffic analysis model withevaluated as having higher analysis power on people's traffic.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.42 no.1
• /
• pp.75-81
• /
• 2022

Public bicycles are a representative eco-friendly transportation means that can reduce carbon emissions and play an important role in first/last mile mobility and that can be linked to public transportation in the future MaaS era. In 2008, Changwon City started operating donor bicycles for the first time in Korea. However, as the infrastructure of public bicycles has expanded without a theoretical basis for over 10 years, operating costs are increasing due to a decrease in operational efficiency, which makes it difficult to quantitatively expand the service. In this study, a method for calculating the number of stands suitable for the use of public bicycles was presented, and an efficiency index was developed to evaluate the efficiency of public bicycle infrastructure. The method presented in this study was found by examining the relationship between numbers of rentals and returns of public bicycles and the number of bicycle holders. It is expected that the results can be used by other local governments.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.21 no.5
• /
• pp.183-196
• /
• 2022

Public transportation accessibility has been evaluated through minimum level of service for public transportation. However it is evaluated based operators rather than users. This study analyzed the users' accessibility(first-mile, last-mile) to public transportation using altteul transport card data. As a result of user's accessibility of public transportation, rural areas was lower than that in the urban areas. This study calssified type 1 and 2 based average approach time, and average approach time of Type 1 and 2 were more than average approach time of total area. We propsed an efficient introduction of autonomous public transportation on-demand service using delphi survey. As a result of delphi survey, experts agreed on 9 items regarding function, service item, route operation, approach distance, route mileage, punctuality.

• ETRI Journal
• /
• v.40 no.1
• /
• pp.89-100
• /
• 2018

Millimeter wave communication is one of the main disruptive technologies in upcoming 5G mobile networks. One of the first candidate applications, which will be commercially ready by 2020, is wireless backhaul links or wireless last mile communication. This paper provides an analysis of this use-case from radio engineering and implementation perspectives. Furthermore, preliminary experimental results are shown for a proof-of-concept wireless backhaul solution developed within the EU-KR 5GCHAMPION project, which will be showcased during the 2018 Winter Olympic Games in Korea. In this paper, we verify system level calculations and a theoretical link budget analysis with conductive and radiated over-the-air measurements. The results indicate that the implemented radio solution is able to achieve the target key performance indicator, namely, a 2.5 Gbps data rate on average, over a range of up to 200 m.

• Atmosphere
• /
• v.18 no.1
• /
• pp.43-53
• /
• 2008

A new proposition on the definition of the tropical cyclone (TC) which influences the Korean Peninsula (KP) is presented. The definition is based upon the TC track and intensity, 34 wind swath considering the TC size, and the line of 200 nautical mile (NM) from the KP shore which is the boundary of the official warning of Korea Meteorological Administration. Four types are proposed. First type is TC that hits the KP inland. Second is TC that falls within the 200-NM boundary. Third type is TC that passes outside the 200-NM boundary but large enough to significantly influence the KP. Last, the cases for a TC which are downgraded to the midlatitude cyclone and hit the KP are included. 30-year reanalysis reveals that 21 tropical cyclones should be included in the TC list that influenced the KP during the period from 1977 to 2006, which corresponds to 3.93 TCs per year. Among them, number of type I, II, III and IV TCs turn are to be 36, 47, 10, and 16, respectively. The net increase found in the current reanalysis is 2, 5, 7, and 7 for each type.

• Nuclear Engineering and Technology
• /
• v.41 no.5
• /
• pp.575-602
• /
• 2009

In the wake of the Three Mile Island accident, vigorous research efforts were initiated to acquire a basic knowledge of the progression and consequences of accidents that involve a substantial degree of core degradation and melting. The primary emphasis of this research was placed on containment integrity, with: i) hydrogen combustion-detonation, ii) steam explosion, iii) direct containment heating (DCH), and iv) melt attack on the BWR Mark-I containment shell identified as energetic processes that could lead to early containment failure (i.e., within the first 24 hours of the accident). Should the core melt fail the reactor vessel, then non-condensable gas production from Molten Core-Concrete Interaction (MCCI) was identified as a mechanism that could fail the containment by pressurization over the long term. One signification question that arose as part of this investigation was the effectiveness of water in terminating an MCCI by flooding the interacting masses from above, thereby quenching the molten core debris and rendering it permanently coolable. Successful quenching of the core melt would prevent basemat melt through, as well as continued containment pressurization by non-condensable gas production, and so the accident progression would be successfully terminated without release of radioactivity to the environment. Based on these potential merits, ex-vessel corium coolability has been the focus of extensive research over the last 20 years as a potential accident management strategy for current plants. In addition, outcomes from this research have impacted the accident management strategies for the Gen III+LWR plant designs that are currently being deployed around the world. This paper provides: i) an historical overview of corium coolability research, ii) summarizes the current status of research in this area, and iii) highlights trends in severe accident management strategies that have evolved based on the findings from this work.

• Nuclear Engineering and Technology
• /
• v.44 no.7
• /
• pp.807-816
• /
• 2012

The Three Mile Island Unit 2 (TMI-2) accident has been studied extensively, as part of both post-accident technical assessment and follow-up computer code calculations. The models used in computer codes for severe accidents have improved significantly over the years due to better understanding. It was decided to reanalyze the severe accident scenario using current state of the art codes and methodologies. This reanalysis was adopted as a part of the joint standard problem exercise for the Atomic Energy Regulatory Board (AERB) - United States Regulatory Commission (USNRC) bilateral safety meet. The accident scenario was divided into four phases for analysis viz., Phase 1 covers from the accident initiation to the shutdown of the last Reactor Coolant Pumps (RCPs) (0 to 100 min), Phase 2 covers initial fuel heat up and core degradation (100 to 174 min), Phase 3 is the period of recovery of the core water level by operating the reactor coolant pump, and the core reheat that followed (174 to 200 min) and Phase 4 covers refilling of the core by high pressure injection (200 to 300 min). The base case analysis was carried out for all four phases. The majority of the predicted parameters are in good agreement with the observed data. However, some parameters have significant deviations compared to the observed data. These discrepancies have arisen from uncertainties in boundary conditions, such as makeup flow, flow during the RCP 2B transient (Phase 3), models used in the code, the adopted nodalisation schemes, etc. In view of this, uncertainty and sensitivity analyses are carried out using simulation based techniques. The paper deals with uncertainty and sensitivity analyses carried out for the first three phases of the accident scenario.

• Journal of the Korea Society of Computer and Information
• /
• v.28 no.2
• /
• pp.131-142
• /
• 2023

In this paper, we propose a new station selection algorithm to solve the illegal parking problem of shared electric scooters and improve the service quality. Recently, as a solution to the urban transportation problem, shared electric scooters are attracting attention as the first and last mile means between public transportation and final destinations. As a result, the shared electric scooter market grew rapidly, problems caused by electric scooters are becoming serious. Therefore, in this study, text data are collected to understand the nature of the problem, and the problems related to shared scooters are viewed from the perspective of pedestrians and users in 'LDA Topic Modeling', and a station extension algorithm is based on this. Some parking lots have already been installed, but the existing parking lot location is different from the actual area of tow. Therefore, in this study, we propose an algorithm that can install stations at high actual tow density using mixed clustering technology using K-means after primary clustering by DBSCAN, reflecting the 'current state of electric scooter tow in Seoul'.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.22 no.3
• /
• pp.1-19
• /
• 2023

Bikes have recently emerged as an alternative to carbon neutrality. To understand the demand for public bikes, we endeavored to estimate travel frequency of public bike by considering the intermediate stops. Using the GPS trajectory data of 'Ttareungyi', a public bike service in Seoul, we identified a stay point and estimated travel frequency reflecting population, land use, and physical characteristics. Application of map matching and a stay point detection algorithm revealed that stay point appeared in about 12.1% of the total trips. Compared to a trip without stay point, the trip with stay point has a longer average travel distance and travel time and a higher occurrence rate during off-peak hours. According to visualization analysis, the stay points are mainly found in parks, leisure facilities, and business facilities. To consider the stay point, the unit of analysis was set as a hexagonal grid rather than the existing rental station base. Travel frequency considering the stay point were analyzed using the Zero-Inflated Negative Binomial (ZINB) model. Results of our analysis revealed that the travel frequency were higher in bike infrastructure where the safety of bike users was secured, such as 'Bikepath' and 'Bike and pedestrian path'. Also, public bikes play a role as first & last mile means of access to public transportation. The measure of travel frequency was also observed to increase in life and employment centers. Considering the results of this analysis, securing safety facilities and space for users should be given priority when planning any additional expansion of bike infrastructure. Moreover, there is a necessity to establish a plan to supply bike infrastructure facilities linked to public transportation, especially the subway.