Fermentation of Oak Tree Sawdust affects Peanut Sprout Growth and Fungal Microbiomes

Kibum Kim,Kisung Ko,Yang Joo Kang,Taewon Yang,Soyeon Oh,Seung-Won Lee,Moon-Soo Kim,Young Koung Lee,Mi Kyung Kim 한국원예학회 2023 원예과학기술지 Vol.41 No.1

Economic-based approach for predicting optimal water pipe renewal period based on risk and failure rate

Kibum Kim,Jeewon Seo,Jinseok Hyung,Taehyeon Kim,Jaehag Kim,Jayong Koo 대한환경공학회 2019 Environmental Engineering Research Vol.24 No.1

This study suggests a method for calculating the benefits of water pipe renewal based on an estimate of the water supply suspension risk. The proposed method based on five benefit items is more direct and specific than other benefit estimation methods. In addition, a methodology evaluating the economics of pipe renewal based on pipe failure rate is proposed for estimating the optimal renewal point from an economic perspective. By estimating the optimal renewal period based on a yearly benefit cost ratio per pipe in a case study area, it was possible to draft an optimal renewal plan for the subject region from an economic perspective. Compared with other methodologies, a reasonable optimal renewal period was derived from an economic point of view. The result of this study may be used to develop future water pipe renewal plans. Moreover, the proposed methodologies and results derived from this study can be applied to asset management plans.

Reduction in Harmful Emissions Using a Two-Stage Injection-Type Premixed Charge Compression Ignition Engine

Kim, Hyungmin,Kim, Kibum,Lee, Kihyung Mary Ann Liebert 2009 ENVIRONMENTAL ENGINEERING SCIENCE Vol.26 No.11

Renewal prioritization of multi-regional water supply pipelines through water supply risk assessment

Kim, Kibum,Kim, Mincheol,Seo, Jeewon,Koo, Jayong IWA Publishing 2016 Water science & technology--water supply Vol.16 No.2

<P>In the Republic of Korea, multi-regional water supply pipelines were intensively laid during the rapid economic growth period; however, these pipelines are now aging. The cost of renewal of the aged pipelines would be enormous. Therefore, limited resources need to be distributed effectively in accordance with the priority of renewal. In this study, the risks involved in the multi-regional water supply pipeline of region K were calculated and assessed for setting the priority of renewal. The probability of failure of the pipeline was calculated through a quantification theory, and the effects of failure on the water supply pipeline were calculated by interpreting a pressure driven analysis. The risk considering the probability and consequence of failure comprehensively was found to be the largest at section A12. Three alternatives were considered for risk reduction, and the effect of each alternative on the risk reduction was analyzed. As a result, the construction of double piping by laying a new pipeline was found to be the most effective measure for risk reduction. The results of this study can be utilized as the basic data for establishing an investment plan for the renewal of the water supply pipeline and asset management plan.</P>

Characterization of products from Fe(CO)₅ seeded CO diffusion flame

Kim, Kibum,Kim, Hae Kwang Pergamon Press 2018 Energy Vol.148 No.-

<P><B>Abstract</B></P> <P>Although Iron Pentacarbonyl (Fe(CO)<SUB>5</SUB>), one of common metallic additives has been applied to soot emission suppression in a few decades, the correct mechanism on soot reduction is not well-understood and still far controversial. Particular species presented in the flame could provide valuable information on the mechanisms of chemical reactions. With the fact in mind, the state of the fuel additive was identified using a variety of laser-based diagnostics and spectroscopic methods such as <I>in situ</I> Raman spectroscopy, laser-induced fluorescence (LIF), laser-induced breakdown spectroscopy, absorption spectroscopy, and X-ray photoelectron spectroscopy. Preliminary sets of experiments were conducted with Fe(CO)<SUB>5</SUB> seeded CO diffusion flame for eliminating the external environment interferences and variations due to soot particles that are normally produced from hydrocarbon fuel combustion. Any specific form of iron oxide was hardly detected while strong Fe signal was observed with <I>in sit</I>u analyses. The analytical results indicate that elemental Fe play crucial role as heterogeneous catalyst on carbon oxidation in any carbon-based fuel diffusion flame.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The dominant iron species obtained from Fe(CO)<SUB>5</SUB> seeded CO flame was elemental Fe. </LI> <LI> The formation of iron oxide was not observed using <I>in situ</I> Raman spectroscopy. </LI> <LI> Fe atomic emissions were observed using Fe LIF spectroscopy. </LI> <LI> No FeO florescence signal was detected. </LI> <LI> Fe absorption spectroscopy supported that elemental Fe are the major species. </LI> </UL> </P>

Structural phase transition in a growing network model with tunable member intimacy

Kim, Kibum,Seong Jo, Woo,Kim, Beom Jun Editions de Physique 2017 Europhysics letters Vol.118 No.4

<P>Users of online communities become more intimate in time by writing posts and exchanging comments to each other. Although a certain level of intimacy among a group of members can be beneficial for the activity of the whole community, too strong intimacy among existing members can make newcomers feel alienated, driving them to leave the community. In this letter, we introduce a growing network model in which we systematically study the effect of member intimacy on the formation of connected component of the network. We introduce a parameter called clinginess and control how the member intimacy affects the communication activity. We observe that cumulative number of users who leave the community exhibits a transition-like behavior, similarly to the discontinuous transition in statistical mechanics models. Implication of our result in constructing a sustainable online community is also discussed. Copyright (C) EPLA, 2017</P>

A Stock Prediction System Based on News and Twitter

Kibum Kim,Seungmin Yang,Dongyoung Kim,Jeawon Park,Jaehyun Choi 보안공학연구지원센터 2016 International Journal of Software Engineering and Vol.10 No.6

As more concerns by the public about stock markets grow bigger, the more the people’s attention is drawn to a systematic method to predict stock prices that fluctuate. More importantly, as the modern stock markets react very sensitively to information for their stock prices, it is very important to predict the prices for investors. For that, this study shall utilize opinion mining and mechanical learning, which are widely used to analyze the meaning of information in systematic ways on analyzing data from news and Twitter to suggest a system that predicts stock prices. The stock price prediction system consists of a data collector, vocabulary analyzer, sentiment analyzer and stock price predictor. The stock price predicting steps consist of collecting contents of news and Twitter, extracting vocabularies by using morpheme analysis, executing sentiment analysis then predicting stock prices via mechanical learning. In order to evaluate the usefulness of the suggested method, we used the stock data for the last whole year on 7 companies in the bio industry that are most sensitive to information for the tests, and the accuracy of the results showed above 80%. The results of this study can be regarded as one of the methods to effectively predict stock prices of companies from various backgrounds in this modern information era that changes dramatically every moment.

The Emergence of the Sharing Economy

Kibum Kim,Jeong-Dong Lee 과학기술정책연구원 2016 STI Policy Review Vol.7 No.2

What impact does the sharing economy have on existing businesses? This paper empirically examines how Uber transformed the taxi industry in New York City. Using a regression model controlling various potential influencing factors, we find no direct evidence that daily trips or revenue per taxi driver decreased since Uber entered the taxi industry. However, a closer investigation into other dimensions of taxi trips reveals that taxi drivers were forced to change their way of doing businesses to retain existing daily trips and revenue. Since Uber crowded out yellow taxis from the central area of Manhattan, yellow taxis responded by serving customers outside of the Manhattan borough. From enlarging their geographical coverage and serving customers that were previously ignored, yellow taxis were able to retain their previous level of taxi trips and market share. We also find that yellow taxis responded by improving their service quality to better serve customers’ needs. Our result suggests that incumbents actively responded to Uber’s entry and provided substantial benefit to consumers. Combined with the incumbent’s response, the sharing economy transformed the existing market in a welfare-enhancing way. This paper provides managerial and policy implication on how incumbents affected by the disruptions of the sharing economy should respond. Even though it might be yet premature to examine the impact of Uber, results suggest that incumbents have effectively defended against Uber’s entry so far. We conclude that the sharing economy and the existing economy can create positive value in our society through well-intentioned competition, complementing each other’s weaknesses and strengths.

Analysis of Effects of Segmentation Cracks on Durability Enhancement of APS TBC

Kibum Park(박기범),Damhyun Kim(김담현),Keekeun Kim(김기근),Namgyu Jun(전남규),Jongmin Lee(이종민),Chang-Sung Seok(석창성) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11

Thermal barrier coating(TBC) is a coating technology used to protect key components of gas turbine from high-temperature operating conditions, and the durability of TBC has emerged as a major issue since the operating temperatures are getting higher for better efficiencies. The failure of TBCs is caused of the thermal stresses either due to temperature change or due to the growth of the oxide layer(thermally grown oxide, TGO) which forms and grows at high service temperature. In this study, the effect of segmentation cracks formed in the TBC on stress reduction and durability improvement was analyzed in detail. Finite element analysis simulating the operating conditions was conducted using a 3D unit cell model for TBC, and the stress and geometry changes of interlayer were investigated. As a result, segmentation cracks inhibited the increases of the interface rumpling during the TGO growth, and also reduced the magnitude of the stress accompanying at this process. Additionally, through the thermal fatigue test, the suppression of increases of interfacial rumpling and improvement of durability were confirmed in the presence of segmentation cracks.

Development of an investment efficiency evaluation model for waterworks maintenance through data envelopment analysis

Kim, Kibum,Kim, Juyeop,Park, Sanghyuk,Koo, Jayong Desalination Publications 2018 Desalination and Water Treatment Vol.104 No.-