Daisik Nam

Daisik Nam


Research Focus & Metrics

Academic Career Length

7Years (2020-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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11 September 2020 in Sustainability
Verified
Journal Article
Open access
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DNDaisik Nam
Daisik Nam
JCJaewoo Cho
Jaewoo Cho
Individual-level modeling is an essential requirement for effective deployment of smart urban mobility applications. Mode choice behavior is also a core feature in transportation planning models, which are used for analyzing future policies and sustainable plans such as greenhouse gas emissions reduction plans. Specifically, an agent-based model requires an individual level choice behavior, mode choice being one such example. However, traditional utility-based discrete choice models, such as logit models, are limited to aggregated behavior analysis. This paper develops a model employing a deep neural network structure that is applicable to the travel mode choice problem. This paper uses deep learning algorithms to highlight an individual-level mode choice behavior model, which leads us to take into account the inherent characteristics of choice models that all individuals have different choice options, an aspect not considered in the neural network models of the past that have led to poorer performance. Comparative analysis with existing behavior models indicates that the proposed model outperforms traditional discrete choice models in terms of prediction accuracy for both individual and aggregated behavior.

26 August 2020 in Sensors
Verified
Journal Article
Open access
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DNDaisik Nam
Daisik Nam
RLRiju Lavanya
Riju Lavanya
RJR. Jayakrishnan
R. Jayakrishnan
IYInchul Yang
Inchul Yang
WJWoo Hoon Jeon
Woo Hoon Jeon
The focus of this research is on the estimation of traffic density from data obtained from Connected and Autonomous Probes (CAPs). CAPs pose an advantage over expensive and invasive infrastructure such as loop detectors. CAPs maneuver their driving trajectories, sensing the presence of adjacent vehicles and distances to them by means of several electronic sensors, whose data can be used for more sophisticated traffic density estimation techniques. Traffic density has a highly nonlinear nature during on-congestion and queue-clearing conditions. Closed-mathematical forms of the traditional density estimation techniques are incapable of dealing with complex nonlinearities, which opens the door for data-driven approaches such as machine learning techniques. Deep learning algorithms excel in data-rich contexts, which recognize nonlinear and highly situation-dependent patterns. Our research is based on an LSTM (Long short-term memory) neural network for the nonlinearity associated with time dynamics of traffic flow. The proposed method is designed to learn the input-output relation of Edie’s definition. At the same time, the method recognizes a temporally nonlinear pattern of traffic. We evaluate our algorithm by using a microscopic simulation program (PARAMICS) and demonstrate that our model accurately estimates traffic density in Free-flow, Transition, and Congested conditions.

23 July 2020 in Sustainability
Verified
Journal Article
Open access
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JCJaeheon Choi
Jaeheon Choi
KLKyuil Lee
Kyuil Lee
HKHyunmyung Kim
Hyunmyung Kim
SASunghi An
Sunghi An
DNDaisik Nam
Daisik Nam
Fatigue-related crashes, which are mainly caused by drowsy or distracted driving, account for a significant portion of fatal accidents on highways. Smart vehicle technologies can address this issue of road safety to improve the sustainability of transportation systems. Advanced driver-assistance system (ADAS) can aid drowsy drivers by recommending and guiding them to rest locations. Past research shows a significant correlation between driving distance and driver fatigue, which has been actively studied in the analysis of resting behavior. Previous research efforts have mainly relied on survey methods at specific locations, such as rest areas or toll booths. However, such traditional methods, like field surveys, are expensive and often produce biased results, based on sample location and time. This research develops methods to better estimate travel resting behavior by utilizing a large-scale dataset obtained from car navigation systems, which contain 591,103 vehicle trajectories collected over a period of four months in 2014. We propose an algorithm to statistically categorize drivers according to driving distances and their number of rests. The main algorithm combines a statistical hypothesis test and a random sampling method based on the renowned Monte-Carlo simulation technique. We were able to verify that cumulative travel distance shares a significant relationship with one’s resting decisions. Furthermore, this research identifies the resting behavior pattern of drivers based upon their travel distances. Our methodology can be used by sustainable traffic safety operators to their driver guiding strategies criterion using their own data. Not only will our methodology be able to aid sustainable traffic safety operators in constructing their driver guidance strategies criterion using their own data, but it could also be implemented in actual car navigation systems as a mid-term solution. We expect that ADAS combined with the proposed algorithm will contribute to improving traffic safety and to assisting the sustainability of road systems.
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29 September 2020 in Sustainability
Verified
Journal Article
Open access
PDF file
DNDaisik Nam
Daisik Nam
MPMinyoung Park
Minyoung Park
This article proposes a mathematical model for integrating terminal operation strategies with shipment scheduling. We are motivated by findings from the literature on the integrated design of logistic systems. The objective of this research is to efficiently utilize the existing hub terminals and transport network by considering the minimization of costs related to terminal congestion, transport, and carbon dioxide (CO2) emissions. Cooperative behaviors of terminal managers and fleet assignment managers are modeled in a bi-level problem framework. The total cost includes a processing cost and transport cost, and CO2 related to the assigned fleets. We introduce a terminal cost function to capture the relationship between unit processing cost with respect to hub delay, which allows us to find the minimum cost path and efficiently distribute shipments to hub terminals. The case study shows that the collaborative logistics outperforms a single routing strategy and capacity expansions in minimization of both total cost and CO2 emissions.