Minyoung Park

Saving Power in Video Playback on OLED Displays by Acceptable Changes to Perceived Brightness

Displays based on organic light-emitting diodes (OLEDs) are now widely used in mobile devices, in which they are major power consumers. The power drawn by an OLED display increases nonlinearly with sub-pixel intensities-thus reducing brightness saves appreciable power, but can displease users. This paper examines this tradeoff, and proposes a color blending scheme in which each frame is darkened in a way that reduces power consumption significantly while limiting the visual impact. The target lightness of frames is determined, in the LAB color space, from average intensities of the original frames; and these average values are in turn obtained by adaptive sampling, so as to reduce the computational overhead. An Android smartphone uses 12%-36% less power when running this scheme, compared to standard video playback, while a user evaluation suggested that reducing brightness to a certain extent can be largely unnoticed, or readily tolerated.

Quantifying non-recurrent traffic congestion caused by freeway work zones using archived work zone and ITS traffic data

Non-recurrent traffic congestion has been estimated using the capacity and the number of closed lanes in work zones and the upstream traffic demand of work zones. However, the number of closed lanes may be meaningless due to operational strategies, such as using the shoulder area and composing an additional lane by temporarily reducing the existing lane width to mitigate traffic congestion. The objective of this study is to develop a method to quantify non-recurrent traffic congestion caused by freeway work zones based on traffic flow data and spatio-temporal work zone information. In addition, to demonstrate the efficacy of the developed method, a case study is performed using 1-year historical traffic data and work zone data on major freeways in Korea.

A comparative study on sampling strategies for truck destination choice model: case of Seoul Metropolitan Area

One of the major issues when applying truck destination choice models with a large number of alternatives is how to sample a set of non-chosen traffic analysis zones (TAZs) to construct a destinati...

Analysing the cost efficiency of parcel distribution networks with changes in demand

Demand for parcel delivery services has rapidly increased recently mainly due to the tremendous growth of e-commerce worldwide. Responding to changes in parcel volume with small-sized frequent shipments poses a great challenge to parcel delivery companies, as they need to rationalize the cost of operating and maintaining their physical distribution networks, while achieving acceptable level of on-time delivery rate throughout their large market areas. The objective of this paper is to analyse the impact of increasing demand on the parcel distribution network structures in terms of minimizing transportation and sortation costs. Based on the case of South Korean parcel delivery industry, this study simulated various types of networks including point-to-point, hub-and-spoke, and multiple hub structure with parcel demand changes. This study can provide well-prepared adaptive network design strategies to parcel delivery service providers for various possible demand changes over the long term.

Modelling Truck's Destination Choice Model Behaviour: Case Study of Seoul Metropolitan Area

This study was to develop a disaggregate trucks destination choice model as a sub-model of a tour-based truck demand model. For this purpose, two distinct destination choice models for the first trip and post-first trips were developed. To determine if there is a competition or agglomeration effect in the choice of next stop location, the accessibility index was included as an explanatory variable in the logit-based choice model. The destination choice model, including accessibility as an explanatory variable, was found to be superior to that without the accessibility variable. More importantly, although there was a competition effect for the first trips destination choice, the agglomeration effect exists for the post-first trips destination choice, indicating that there is a competition effect in the destination choice of truck movements. The agglomeration effect for the post-first trips for a small-sized truck was found to be more significant than that for a medium-sized truck.

Identifying differences of travel time budgets between the elderly and the nonelderly groups using PSL structural equation models: A case study for Seoul metropolitan area

ABSTRACT To date, aging is one of the most important issues in our society because of its significant socioeconomic impacts. Corresponding concerns about the transportation needs of the elderly have led to a focus on the mobility and quality of life of the elderly and motivated various studies of senior mobility. As the fastest aging country in the world, Korea will need to provide insightful information for an aging society. The purpose of this study is to investigate the difference in travel behavior between the elderly and the nonelderly groups by focusing on travel time budget (TTB), using the 2006 household travel diary survey data from the Seoul metropolitan area. We develop partial least square (PLS) structural equation models to identify major variables that affect the TTB of each of the two groups and then compare the differences between the models. Model results indicate that the significant explanatory variables differ between the two age groups, and the degree to which the variables affect the TTB differs by personal and household characteristics.