Hugon Kim

On the ring loading problem with demand splitting

In this paper, we improve the rerouting step of Myung, Kim and Tchas algorithm for the ring loading problem with demand splitting and achieve a better running time. We also conduct a computational study to evaluate the practical performance of the proposed algorithm.

Subgradient Approach for Resource Management in Multiuser OFDM Systems

This paper studies the problem of finding an optimal subcarrier and power allocation for downlink communication in the orthogonal frequency division multiplexing (OFDM) wireless systems. With the constraints on the power consumption and transmission rates for users, the problem of maximizing total throughput is mathematically formulated. The developed mathematical model is so general as to include almost of existing ones in which the original problems have been usually divided into smaller and tractable ones to make a practical application of some simple greedy algorithms. In this study, developed is the subgradient dual optimization method for the problem. Extensive experiments with realistic data show that in a reasonable time the subgradient method converges to the stable point, almost feasible to the original problem. We proved that the subgradient method is applicable to the dynamic resource allocation, by showing that environmental changes at a stable state need much lesser additional iterations to converge.

Comparison of emission estimates for non-CO2 greenhouse gases from livestock and poultry in Korea from 1990 to 2010

It has often been claimed that non-carbon dioxide greenhouse gases (NCGGs), such as methane, nitrous oxide and fluorinated greenhouse gases, are significant contributors to climate change. Here we nvestigate emission estimates of methane and nitrous oxide from livestock and poultry production, which is recognized as a major source of those NCGGs, in Korea over the period of 1990 through 2010. Based on the data on livestock and poultry populations, emission estimates of methane and nitrous oxide are first derived based on the Tier 1 approach. Then, the Tier 2 approach is adopted to obtain emission estimates of methane and nitrous oxide from cattle, which are known to be the largest sources of these NCGGs and account for about 70% of emissions from livestock and poultry in Korea. The result indicates that the Tier 2 estimates of methane and nitrous oxide emissions from enteric fermentation and manure management are significantly different from the Tier 1 estimates over the analysis period.

Marginal Abatement Cost Analysis for the Korean Residential Sector Using Bottom-Up Modeling

A marginal abatement cost analysis has been conducte d to analyze the effects of abatement measures on greenhouse gas (GHG) emissions for the Korean residential sector. A bottom-up model using MESSAGE has been developed by defining the energy demand and constructing the reference energy system for the residential sector. A great amount of activity data has also been analyzed. Abatement potentials and related costs of individual abatement measures are investigated. The result from the marginal abatement cost analysis may provide general guidelines and proc edures for the establishment of GHG abatement polices.

A Bottom-up Approach for Greenhouse Gas Emission Analysis of Korean Shipbuilding Industry

This study presents a bottom-up approach for analyzing greenhouse gas (GHG) emissions for the shipbuilding industry in Korea. The overall procedures for deriving GHG emissions from the Korean shipbuilding industry are presented. Based on the long-term forecast on energy demands of the Korean shipbuilding industry, reference energy system (RES) and energy balance (EB) for the shipbuilding process are derived for bottom-up modeling.

Heuristics for the Access Network Design Problem in 3G Mobile Communication Networks

This study deals with the access network design problem in universal mobile telecommunication systems (UMTS) networks. We provide a mathematical formulation of the problem with constraints on RNC and node-B capacities, along with a lower bounding method. We also develop a heuristic algorithm with two different initial solution methods designed to strengthen the solution quality, and demonstrate the computational efficacy of these procedures with several test problems.

IN HEURISTICS FOR THE ACCESS NETWORK DESIGN PROBLEM IN UMTS MOBILE COMMUNICATION NETWORKS

In this paper we study the access network design problem in Universal Mobile Telecommunication Systems (UMTS) networks. Given the location of radio base stations (node-Bs), their traffic demands, and the candidate facility centers for locating radio network controllers (RNCs), the problem is to determine the configuration of access network, including the number and location of facility centers, the number of RNCs in each facility center, and the links between RNCs and node-Bs, with the objective being to design such a network at the minimum cost. We provide a mathematical formulation of the problem with constraints on RNC and node-B capacities, along with a lower bounding method. We develop a heuristic algorithm with two different initial solution methods designed to strengthen the solution quality. The computational efficacy of their procedures is then demonstrated on a number of test problems.