Sangkeon Lee

A Bayesian Approach for Estimating Link Travel Time on Urban Arterial Road Network

Recently, Korean Ministry of Construction and Transportation selects three cities as the Intelligent Transport Model City to build a test bed for research in Intelligent Transportation System (ITS). One of the most sought-after information in any ITS project is to provide arterial travel speed forecasts to travellers. To estimate the arterial travel speed, one needs to apply a mathematical model supplied with sensor data generated by roadside sensors and in-vehicle sensors. In this research effort, we develop a simple Bayesian estimator and an expanded neural network model to estimate arterial link travel speed. Input data used are from dual-loop detectors and probe vehicles with DSRC(Dedicated Short-range Communication) device. Data from one of model city, Jeonju, are used to generate test data for the simulation where the probe vehicle’s speed is random sampled from observed vehicles’ speed. Initial run shows that the neural network model developed can provide accurate estimates of arterial link speed using only probe vehicle’s speed data.

Real Time Estimation of Bus Arrival Time under Mobile Environment

Recently, several city governments of Korea developed Bus Information Sytem (BIS) as one of initiatives of ITS deployment efforts. The core function of BIS is to deliver the arrival time information of incoming transit bus at every bus station. In this research, we propose a computational model for estimating transit vehicle’s link travel time from data transmitted through wireless communication channel and outline major components of real BIS server program architecture. Our algorithm is based on a neural network algorithm tailored for each period of the day under mobile environment. In this model, link weights are updated every 7 days in order to provide feedback control based on bias between estimate and real measurement. Our system can be implemented using reasonable space resources and should provide good estimates of bus arrival time.

Meta services: abstract a workflow in computational grid environments

We define a concept of Meta services which describes a way of abstracting and mapping a workflow to a service in computational Grid environments. By using Meta services, a workflow in a Grid environment could adapt various service concepts such as Grid services, Web services, and portal services without modification to the workflow. And the converted Meta services could be shared and reused by users. Furthermore, historical performance data could be included in the Meta service, making effective execution of the workflow possible.

A Grid Middleware Framework Support for a Workflow Model Based on Virtualized Resources

Nowadays, the virtualization technologies are widely used to overcome the difficulty of managing Grid computing infrastructures. The virtual account and the virtual workspace are very optimistic to allocate Grid resources to specific user, but they lacks of capability of interaction between portal services and virtualized resources which required by Grid portal. The virtual application is fitted to wrap simple application as a Grid portal service, but integrating some applications to compose larger application service is difficult. In this paper, we present a Grid middleware framework which supports for a workflow model based on virtualized resources. Meta Services in the framework exposes workflow as a portal service and service call is converted different workflow according to parameter and workflow generated by the Meta Services is scheduled in a virtual cluster which configured by this framework. Because of virtual application service can be composed of workflow and service interface wraps the workflow providing a complex portal services composed by small application could effectively integrated to Grid portal and scheduled in virtual computing resources.

Agent-Based middleware architecture for workflow in grid portals

In this paper, we propose an agent-based middleware architecture for the workflows used in Grid portal. We combined workflow model, workflow management system, job distribution, parameter scheduling, and service inteface in the middleware architecture. The workflow model consists of three layers. The agent-based middleware architecture consists of five agents and three types of communication protocols. Users can design a lightweight, flexible and effective middleware, which can be used to construct a workflow-based Grid portal.

Design and implementation of a resource management system using on-demand software streaming on distributed computing environment

As distributed computing has become a large-scale environment such as grid computing, software resource management is rising as the key issue. In this paper, we propose a new resource management system, which manages software resources effectively, and its prototype implementation. This system uses an existing on-demand software streaming technology to manage software resources. This system greatly reduces traditional software deployment costs and associated installation problems. In this system, an added node can also execute a requested job without installation of applications.

Validation of real-time traffic information based on personal communication service network

This research demonstrates an efficient traffic information provision system for mitigating traffic congestion in the street networks based on multi-type traffic detectors which include inductive loop, image recognition, beacon, and personal communication service (PCS). A methodology is demonstrated in this study, which combines and processes data including vehicle location and speed from the wireless communication network, i.e. PCS in order to validate real time traffic information through PCS and internet.

Meta Service: Mapping of a Service Request to a Workflow in Grid Environments

Many jobs in Grid environments consist of several subtasks, and these subtasks can be represented by a workflow, which is executed effectively on a Grid. In this paper, we present Meta services which describe a mapping from a service request to a workflow in Grid environments. By using Meta services, a workflow in Grid environments could adapts various service concepts such as portal services, Grid services, and Web services. And the workflow can be shared and reused among workflow users. Furthermore, historical performance data can be included in Meta services, so effective scheduling of the workflow is also possible.

Web-published data searching system for grid environment

If a grid system is connected to a database and uses data in the database, it is required to develop a data manipulation module, which handles data and its indices in the database, and install it in the grid system. If there is a search system, which can directly manipulate data in a database on a Web, and if it is possible to integrate it with a grid system as a single resource, the resulting system would be very effective, easy to develop and use, and very adaptable to changes of the database structure. We present a searching system, which connects Web-published databases with grid systems. By using the system, developers could save developing time by integrating data in a database on grid environments.