건조수축에 따른 균열 억제를 위한 규사 혼입 CLC의 특성

이창우 ( Lee¸ Chang-woo ),이상수 ( Lee¸ Sang-soo ) 한국건축시공학회 2021 한국건축시공학회 학술발표대회 논문집 Vol.21 No.2

In order to improve the housing culture, construction changes for the utilization of diverse and multifunctional spaces are appearing in response to the increasing diverse needs of consumers. Cellular Light-weight Concrete (CLC) is being developed for use in fire-resistant heat-insulating walls and non-bearing walls. However, manufacturing non-uniformity has become a problem as a drawback due to the use of foamed bubbles and normal temperature curing, and additional research is required. Therefore, in order to suppress cracks due to drying shrinkage, silica sand is mixed with CLC to try to understand its characteristics. In the experiment, the compressive strength from 7 to 28 days of age was measured via a constant temperature and humidity chamber, and the drying shrinkage was analyzed according to each condition using a strain gauge. The compressive strength of matrix tends to decrease as the substitution rate of silica sand increases. This is judged by the result derived from the fact that the specific surface area of silica sand is smaller than that of slag. Based on KS F 2701 (ALC block), the compressive strength of 0.6 products is 4.9 MPa or more as a guide, so the maximum replacement rate of silica sand that satisfies this can be seen at 60%. Looking at the change in drying shrinkage for just 7 days, the shrinkage due to temperature change and drying is 0.7 mm, and the possibility of cracking due to shrinkage can be seen, and it seems that continuous improvement and supplementation are needed in the future.

Excessive CNO yield of the non-rotating massive Pop III stars

Changwoo Kye,Sung-Chul Yoon 한국천문학회 2016 天文學會報 Vol.41 No.1

Dynamic Scheduling of Irregular Stream Programs toward Many-Core Scalability

Changwoo Min,Young Ik Eom IEEE 2015 IEEE transactions on parallel and distributed syst Vol.26 No.6

<P>The stream programming model has received much interest because it naturally exposes task, data, and pipeline parallelism. However, most priorwork has focused on the static scheduling of regular stream programs. Therefore, irregular applications cannot be handled in static scheduling, and the load imbalance caused by static scheduling faces scalability limitations in many-core systems. In this paper, we introduce the DANBI programming model, which supports irregular stream programs, and propose dynamic scheduling techniques. Scheduling irregular stream programs is very challenging, and the load imbalance becomes a major hurdle to achieving scalability. Our dynamic load-balancing scheduler exploits producer-consumer relationships already expressed in the DANBI program to achieve scalability. Moreover, it effectively avoids the thundering-herd problem and dynamically adapts to load imbalance in a probabilistic manner. It surpasses prior static stream scheduling approaches which are vulnerable to load imbalance and also surpasses prior dynamic stream scheduling approaches which result in many restrictions on supported program types, on the scope of dynamic scheduling, and on data ordering preservation. Our experimental results on a 40-core server show that DANBI achieves an almost linear scalability and outperforms state-of-the-art parallel runtimes by up to 2.8 times.</P>

Improvement of Mechanical Properties of Zr‑Based Bulk Amorphous Alloys by High Temperature Heat Treatment

Changwoo Jeon,Min Chul Jo,Juho Lee,Eun Soo Park,Junho Park,Sang Yong Shin 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.8

Zr-based bulk amorphous alloys which were heat-treated from 673 to 1073 K were investigated, and compressive fracturemechanisms related with improvement of mechanical properties were investigated by observing how the type, size and volumefraction of crystalline particles which is generated during the heat treatment affected the fracture mode. The Zr-based bulkamorphous alloys contained nano-sized crystalline particles showed excellent mechanical properties of compressive fracturestrength over 2.0 GPa and compressive plastic strain of approximately 1%. The fracture modes of the alloys are changeddepending on the heat treatment temperature and their microstructure. When the alloy is heat-treated at 673 K, the nanosizedZr2Cuparticles are generated in amorphous matrix. According to the observation of fractured specimens, in the alloyheat-treated at 673 K, the fine and elongated vein patterns were well developed. The heat treatment temperature increasedabove Tx,the Zr2Cuparticles as well as complex crystalline particles are consist in the heat-treated alloy, which lead to thebrittle fracture and the alloy show the low strength of 605 MPa. In the fractured surface of the alloy, large cleavage facetswere evenly developed. When the heat treatment temperature up near Tm,the size of Zr2Cuand complex crystalline particlesincreased to approximately 1 μm and the volume fraction of complex crystalline particles increased up to 52.3%. As the sizeof crystalline particles change, the size of facet decreased similarly to the size of crystalline particles.

Kaurenoic acid, a natural substance from traditional herbal medicine, alleviates palmitate induced hepatic lipid accumulation via Nrf2 activation

Changwoo Han 대한한의학회 2020 대한한의학회지 Vol.41 No.4

Matching technology and design for R2R printed electronics

Changwoo Lee(이창우) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

R2R (Roll to roll) printed electronics has been an attractive technology for the mass production. In this paper, it is found that a printed pattern geometric quality which affects functional quality of printed electronic device could be changed with respect to operating tension of bare substrate even if local optimized ink, substrate, and printing process were applied. Additionally, ink transfer mechanism for R2R printed electronics is analyzed regarding a dynamic surface energy of a bare substrate under a tension in R2R printing systems. Through the results, it is presented that how to find an optimal operating tension in R2R printed electronics for guaranteeing a required thickness of R2R printed patterns..

A study on the fire propagation characteristics in large-opening multi-level limestone mines in Korea

Changwoo Lee,Vanduc Nguyen 한국자원공학회 2016 Geosystem engineering Vol.19 No.6

Recently, deployment of large-capacity diesel haulage trucks is rapidly increasing in the domestic large-opening limestone mines due to the high level of operational flexibility. However, in multi-level mines, this trend has raised the serious concern for the risk of diesel vehicle fire. Fire in a deep multi-level mine site is harder to control and likely to develop into disastrous results. Developing the emergency evacuation strategies and controlling the fire should presuppose a knowledge of the fire behavior in mines. This paper aims at studying the behavior of a 25-ton diesel truck fire showing approximately the maximum heat release rate of 30 MW by computational fluid dynamic analysis. Spatial and temporal distributions of the hot air stream, smoke layer, and CO gas layer in multi-level mine sites are evaluated, and the effects of fan operation are scrutinized to find the appropriate fan location and operating mode. In addition, several other aspects of the fire development such as backlayering and throttling effects are also studied. The ultimate goal is to provide fundamental information about fire propagating characteristics in multi-level large-opening underground limestone mines for developing the mine fire evacuation plan and protect the workers’ safety.

Dynamic Collaborative Cloud Service Platform: Opportunities and Challenges

Changwoo Yoon,Hyunwoo Lee,Won Ryu,Mohammad Mehedi Hassan,허의남 한국전자통신연구원 2010 ETRI Journal Vol.32 No.4

This letter presents a model for a dynamic collaboration (DC) platform among cloud providers (CPs) that prevents adverse business impacts, cloud vendor lock-in and violation of service level agreements with consumers, and also offers collaborative cloud services to consumers. We consider two major challenges. The first challenge is to find an appropriate market model in order to enable the DC platform. The second is to select suitable collaborative partners to provide services. We propose a novel combinatorial auction-based cloud market model that enables a DC platform among CPs. We also propose a new promising multi-objective optimization model to quantitatively evaluate the partners. Simulation experiments were conducted to verify both of the proposed models.

Advances in Sustainable Polymeric Sorbents for Chemical Spills

Changwoo Nam(남창우) 한국고분자학회 2023 한국고분자학회 학술대회 연구논문 초록집 Vol.48 No.2

What Motivates the Online Gamers' Demand and Playing Times?

Changwoo Suh(서창우) 성신여자대학교 경영연구소 2011 경영관리연구 Vol.4 No.2

온라인 게임에는 주로 두 가지 형태의 보상이 주어진다. 하나는 경험 포임트로 게임이나 현실의 거래 시장에서 거래 불가능하며, 다른 하나는 가상의 통화 가치로 게임이나 현실 거래 시장에서 거래가 가능하다. 그렇다면 어떤 요소가 온라인 게임 사용자에게 더 중요할까? 그리고 인구통계학적 혹은 성별에 따른 어떤 요소가 게임 플레이에 영향을 줄까? 우리는 한국의 한 회사의 대규모 온라인 게임(MMOG)의 로그 데이터를 분석하였다. 실 데이터를 분석하여 다음과 같은 결과를 얻었다. 온라인 게임 내에서 게임을 하는데 경험치는 유의하게 영향을 주지 않은데에 반해 통화 가치는 유의하면서 양의 영향을 주었다. 낮은 레벨의 사용자에서는 성별에 따른 플레이 시간의 차이가 있으나 이는 레벨이 높아짐에 따라 사라졌다. 이에 반해 아바타를 성장시킴에 있어서 상대적으로 어린 나이의 플레이어가 나이가 많은 사용자에 비해 같은 내용을 수행하는데 더 긴 시간이 필요한 것으로 나타났다. 결론에서 우리는 이 같은 연구 결과 온라인 게임 개발사에 어떤 함의를 가지고 있는지를 논하고, 연구 결과를 통해 플레이어가 더 나은 게임 경험을 얻을 수 있을지를 논한다. In the online games, there are two main rewards: experience points which cannot be traded in the game or real market and virtual monetary values traded in the game and real market. Which factor is more important than the other for the online game players? And which factors of demographic or gender influence to playing time? We analyze massively multiple online gaming log data from a Korean company. By analyzing the real data, we find that the experience points are not significant influence to choose gaming experience, but the monetary values are significant and positive influence to do their gaming life. We also show that low level players show gender differences, but higher level players do not show gender difference any more. On the contrary with nurturing their avatar, younger players consume more time to play a same quest than elderly players In the conclusion, we discuss implications for firms and better playing experience for players.