Distribution Contrast for Disentangled Fair Representation

Changdae Oh,Heeji Won,Junhyuk So,Taero Kim,Yewon Kim,Hosik Choi,Kyungwoo Song 한국자료분석학회 2022 한국자료분석학회 학술대회자료집 Vol.2022 No.7

Zebra Refresh: Value Transformation for Zero-Aware DRAM Refresh Reduction

Kim, Seikwon,Kwak, Wonsang,Kim, Changdae,Huh, Jaehyuk IEEE 2018 IEEE computer architecture letters Vol.17 No.2

<P>Refresh operations consume growing portions of DRAM power with increasing DRAM capacity. To reduce the power consumption of such refresh operations, this paper proposes a novel value-aware refresh reduction technique exploiting the abundance of zero values in the memory contents. The proposed <I>Zebra refresh</I> architecture transforms the value and mapping of DRAM data to increase consecutive zero values, and skips a refresh operation for a row containing zero values entirely. Zebra converts memory blocks to base and delta values, inspired by a prior compression technique. Once values are converted, bits are transposed to place consecutive zeros matching the refresh granularity. The experimental results show Zebra refresh can reduce DRAM refresh operations by 43 percent on average for a set of benchmark applications.</P>

GVTS: Global Virtual Time Fair Scheduling to Support Strict Fairness on Many Cores

Kim, Changdae,Choi, Seungbeom,Huh, Jaehyuk IEEE 2019 IEEE transactions on parallel and distributed syst Vol.30 No.1

<P>Proportional fairness in CPU scheduling has been widely adopted to fairly distribute CPU shares corresponding to their weights. With the emergence of cloud environments, the proportionally fair scheduling has been extended to groups of threads or nested groups to support virtual machines or containers. Such proportional fairness has been supported by popular schedulers, such as Linux Completely Fair Scheduler (CFS) through virtual time scheduling. However, CFS, with a distributed runqueue per CPU, implements the virtual time scheduling <I>locally</I>. Across different queues, the virtual times of threads are not strictly maintained to avoid potential scalability bottlenecks. The uneven fluctuation of CPU shares caused by the limitations of CFS not only violates the fairness support for CPU assignments, but also significantly increases the tail latencies of latency-sensitive applications. To mitigate the limitations of CFS, this paper proposes a <I>global virtual-time fair scheduler (GVTS)</I>, which enforces global virtual time fairness for threads and thread groups, even if they run across many physical cores. The new scheduler employs the hierarchical enforcement of target virtual time to enhance the scalability of schedulers, which is aware of the topology of CPU organization. We implemented GVTS in Linux kernel 4.6.4 with several optimizations to provide global virtual time efficiently. Our experimental results show that GVTS can almost eliminate the fairness violation of CFS for both non-grouped and grouped executions. Furthermore, GVTS can curtail the tail latency when latency-sensitive applications are co-running with batch tasks.</P>

The Relationship between Civic Humanism and Calvin’s View of the State

KIM Changdae(김창대) 장로회신학대학교 기독교사상과 문화연구원 2017 장신논단 Vol.49 No.3

Exploring the Design Space of Fair Scheduling Supports for Asymmetric Multicore Systems

Kim, Changdae,Huh, Jaehyuk IEEE 2018 IEEE Transactions on Computers Vol.67 No.8

<P>Although traditional CPU scheduling efficiently utilizes multiple cores with equal computing capacity, the advent of multicores with diverse capabilities pose challenges to CPU scheduling. For such asymmetric multi-core systems, scheduling is essential to exploit the efficiency of core asymmetry, by matching each application with the best core type. However, in addition to the efficiency, an important aspect of CPU scheduling is fairness in CPU provisioning. Such uneven core capability is inherently unfair to threads and causes performance variance, as applications running on fast cores receive higher capability than applications on slow cores. Depending on co-running applications and scheduling decisions, the performance of an application may vary significantly. This study investigates the fairness problem in asymmetric multi-cores, and explores the design space of OS schedulers supporting multiple fairness constraints. In this paper, we consider two fairness-oriented constraints, <I>minimum fairness</I> for the minimum guaranteed performance and <I>uniformity</I> for performance variation reduction. This study proposes four scheduling policies which guarantee a minimum performance bound while improving the overall throughput and reducing performance variation too. The proposed fairness-oriented schedulers are implemented for the Linux kernel with an online application monitoring technique. Using an emulated asymmetric multi-core with frequency scaling and a real asymmetric multi-core with the big.LITTLE architecture, the paper shows that the proposed schedulers can effectively support the specified fairness while improving overall system throughput.</P>

디젤산화촉매의 CO 활성 저하 원인 분석

김창대(Changdae Kim),권충일(Choongil Kwon),김석재(Seokjae Kim),여권구(Gwonkoo Yeo) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_1

To meet future EURO-III, IV emission standards, it is essential to develop catalyst technology that will reduce diesel engine exhaust gases. In this study, deactivation of diesel oxidation catalyst used in fleet vehicle test was mainly investigated To conform the surface characterization of catalyst, BET, IC & CO chemisorption were used.<br/> The causes of deactivation of a diesel catalyst were several but the main factors were sulfur poisoning, carbon coking & Pt sintering among them. Therefore, the LOT of an endurance sample was increased higher than thai of a fresh Especially, the change of pore diameter & volume by sulfur was observed.

새 언약 안에서 백성의 변형

김창대(Changdae Kim) 대한성서공회 2015 성경원문연구 Vol.- No.37

This study has attempted to elucidate the theological significance of Jeremiah’s new covenant with regard to the people in the Kingdom of God. The thesis is that the new covenant of Jeremiah seeks to make God’s people in the eschaton the ones that will actualize the ideal of the kingly priests as suggested in the Mosaic Covenant. In making a case for this, this study proposes that the new covenant has, among other theological meanings, the sense of consummating the kingdom of God by making God’s people kingly priests who practice justice and righteousness. In this attempt, our chief attention has been devoted to analyzing the text of Jeremiah 33:14-26 by using the method of textlinguistics. The hermeneutical method of textlinguistics is basically text-oriented in nature, with the assumption that the meanings of a text is embedded in the text when the author tries to convey his intentions to his reader (or audience) through the text. In this method, the intended meanings of a text are culled out from the view point of grammatical cohesion and semantic (or thematic) coherence. The method of textlinguistics also has its concern on how the author impacts the reader in such a way that the reader should respond to the intended meanings of the text. In this respect, a trend in this method focuses its attention on the structures of literary units through which the author arranges his emphases in order to facilitate the reader’s understanding of the communicative effects of the text. On the basis of the method of textlinguistics, this study pays its attention to the literary structure of Jeremiah 33:14-26, with the result of arguing that this unit forms a thematic peak in the context of Jeremiah 30-33. Furthermore, our textlinguistic analysis lends credence to the notion that the reference to Davidic descendants and Levites in this unit implies that in the kingdom of God, the people will be made kings and priests. In conclusion, from the above observations, it is clear that this way of making an exegesis of a text enhances our understanding of the unified relation between the Old and New Testaments from the perspective of the new covenant. The new covenant of the Old Testament connotes the making of God’s people into kingly priests, which is explicitly announced in the New Testament.

시편 1권의 문맥에서 본 시편 9-10편의 “아나브”(עָנָו)의 의미

김창대(Changdae Kim) 한국신학정보연구원 2020 Canon&Culture Vol.14 No.1

본 연구는 시편 9-10편에서 등장하는 “아나브”(עָנָו)의 의미가 시편 1권의 문맥에서 어떤 신학적 의미를 가지는 지를 살피는 데에 그 목적이 있다. 이를 위해 시편의 시들이 의도적으로 배열되었다는 구성적 방법을 사용하여, 시의 경계를 넘어 주위 시들의 문맥에서 עָנָו의 의미를 연구하였다. 구체적으로 9-10편의 문맥, 3-14편의 문맥, 더 나아가 시편 1권의 전체 문맥에서 이 단어가 어떤 신학적 의미를 가지는지에 초점을 맞췄다. 일차적으로 9-10편에서 “아나브”는 세상의 욕심을 멀리하고 인생의 연약함을 직시하여 하나님의 교제 속에서 하나님의 뜻인 공의와 의를 추구하는 자라는 신학적 의미를 가진다. 그래서 이런 자신의 정체성을 바탕으로 하나님을 의지하는 자로 제시된다. 다음으로 9-10편이 속해 있는 3-14의 문맥에서 이 단어의 의미는 더욱 확대되어, 하나님의 사랑을 체험하고, 자신도 하나님을 사랑하는 자의 모습을 갖는다(3-7편). 그리하여 하나님과 인격적 교제의 기쁨을 가지고 환난을 이기고자 하는 자임을 일깨워 준다(4:7, “주께서 내 마음에 두신 기쁨은”). 더 나아가 이 단어는 인생을 감찰하시는 하나님을 철저하게 신뢰하고 보호와 구원의 약속을 받는 축복의 사람이라는 이미지를 갖는다(11-14편) 다음으로 시편 1권의 문맥에서 이 단어의 신학적 의미를 관찰하면, 그 의미의 지평이 더욱 확장된다. 앞서 3-14편은 “아나브”가 하나님의 구원과 보호라는 복을 받을 것을 약속하였다. 그런데 15-24편은 그런 복을 시온의 복으로 병치시키고, 시온의 복을 받은 사람은 율법을 즐거워하여 율법을 묵상하는 자임을 밝히고 있다. 따라서 자연스럽게 “아나브”가 율법을 즐거워 하여 묵상하는 자라는 힌트를 준다. 이어 25-37편은 “아나브”가 언약과 도를 따라 땅 상속과 평강이라는 복을 받게 될 것을 강조한다(37:11, “온유한자는 땅을 차지하며 풍성한 화평으로 즐거워하리로다”). 끝으로 38-41편은 “아나브”가 고난을 통과하면서 자신이 죄인이며 아무것도 아닌 존재임을 깨닫고(38:4; 39:5-8), 율법을 즐거워하며 율법을 마음에 새기는 자임을 보여준다(40:8-9). 그리하여 “아나브”가 시편 1편이 복이 있는 자로 제시한 의인임을 깨닫게 해 준다(41:1). 결국 “아나브”는 고난 가운데서 인생의 덧없음과 자신이 아무것도 아님을 깨닫고, 하나님과의 교제의 기쁨 속에서 하나님을 의지하고 그분의 뜻을 자발적으로 행하고자 하여, 궁극적으로 참된 복을 받는 성도라고 정의할 수 있다. This work has its purpose in exploring the implications of the word עָנָו which occurs first in Psalms 9-10 throughout the entire Psalter. To this end, this study has used the compositional method in such a way of attending to the literary context surrounding Psalms 9-10 where the word is first mentioned. More specifically, in an effort to find the theological implications of עָנָו in the Psalms, our attention has been drawn to the context of Psalms 9-10, then to the context of Psalms 3-14, and finally to the broader context of Book I of the Psalter. In the process, the argument has been advanced that the word עָנָו in Psalms 9-10 has among other connotations the sense of pointing to a person who seeks the justice and righteousness of God in an intimate relationship with God, at the same time trusting in God. Within its immediate context of Psalms 3-14, the theological implications of the word עָנָו are further expanded in such a way that it includes the concept of a person who loves God in response to experiencing God’s love (Psalms 3-7). This leads to the notion that עָנָו implies also a person who overcomes any adversities with a joy coming from relationships with God. Furthermore, the contextual reading of Psalms 11-14 hints that עָנָו conveys the sense of a person who is blessed with the promise of salvation by God. Further observations of the implications of עָנָו within Book I of the Psalter, widen the horizons of our understanding of the theological implications of the word. In attending to the context of Psalms 15-24, the sense of עָנָו is revealed to embrace the concept of enjoying the law and meditating on it. From the contextual reading of the word in Psalms 25-37, it is evident that the identity of עָנָו is deeply related to a blessed person who is given the promises of God, that is to say, inheriting the earth as well as peace. Finally, when dealing with the implications of עָנָו in the context of Psalms 38-41, it is found that a picture of עָנָו is taken as a person who puts the law into his heart(40:8-9).

석탄 합성가스를 이용한 온도 및 압력변화에 대한 메탄화 반응 특성

김수현(Kim, Suhyun),유영돈(Yoo, Youngdon),류재홍(Ryu, Jaehong),변창대(Byun, Changdae),임효준(Lim, Hyojun),김형택(Kim, Hyungtaek) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.11

석탄가스화로부터 얻어진 합성가스는 CO, H₂가 주성분으로, 그 자체를 연료로 사용하여 발전을 하거나 또는 적절한 정제, 분리 및 합성을 통해 다양한 원료물질을 생산할 수 있다. 이러한 석탄의 청정 사용 기술은 최근의 에너지 분야에서 많은 관심을 불러일으키고 있는 고유가 현상 및 석유자원 고갈에 대비할 수 있는 현실적인 방법의 하나로 여겨지고 있다. 석유를 대체할 에너지원으로서 석탄을 이용하는 다양한 응용 방법 중의 하나로 가스화 반응을 통해 발생하는 합성가스를 이용한 SNG 제조 공정을 들 수 있는데, 이는 석탄 등의 고체 시료를 이용하여 메탄이 주성분인 연료가스를 생산하는 것이다. SNG(Synthesis Natural Gas 또는Substitute Natural Gas)는 합성천연가스 또는 대체천연가스로 불리어지는데 주로 석탄의 가스화를 통해 얻어진 합성가스(syngas 또는 synthesis gas)인 CO, H₂를 촉매에 의한 합성반응을 통해 얻을 수 있다. SNG 합성 반응(메탄화 반응)은 보통 수성가스 전환 공정과 가스 정제 공정을 거친 합성가스를 CH₄로 전환하는 것으로 석탄을 이용한 SNG 제조 공정에서 가장 핵심 공정인 메탄화 반응은 높은 발열반응으로 주로 니켈 촉매를 사용하며 250{sim}400?C에서 반응이 이루어진다. SNG 합성 반응은 공급되는 합성가스의 조성(H₂/CO 비), 공급되는 합성가스의 유량과 반응기에 충진된 촉매의 부피와의 관계를 나타낸 공간속도, 반응온도 등의 조건에 따라 반응 특성이 달라질 수 있다. 가스화 반응을 통해 생성되는 합성가스를 이용한 SNG 합성반응(메탄화 반응)의 특성을 파악하기 위하여 Lab-scale 규모의 고정층 반응기를 이용하여 Ni 함량이 다른 2종류의 촉매를 대상으로 반응온도 및 압력에 따른 CO 전환율, CH₄ 선택도, CH₄ 생산성 변화를 파악하였다. 실험 결과 반응기의 온도가 350도 이상의 조건에서 CO 전환율은 99.8%이상, CH₄ 선택도는 90.7%이상으로 나타났으며, 공간속도가 2,000 1/h 이상의 조건에서는 CH₄ 생산성이 500 ml/g-cat, h을 만족하였다.

[디젤엔진부문] 승용차용 디젤엔진 촉매시스템 개발

김창대(Changdae Kim),김석재(Seokjae Kim),여권구(Gyunkoo Yeo),류명석(Myungseok Lyu) 한국자동차공학회 2000 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

To meet future U.S. & European NOx emission standards, it is essential to develop catalyst technology that will reduce NOx emission in addition to the other three pollutants(HC, CO, Paticulate). Two materials that attracted great attention as De-NOx catalysts are the ZSM-5 and BaO contained the commercial DOC. The manufactured several catalysts showed the NOx conversion of about 20-28% but the temperature window of those was narrow as 300~400°C. In case of a general diesel passenger car, engine outlet gas temperature is lower than 250°C under ECE mode. Finally, a new low temperature lean NOx catalyst will be described. In this paper, the possibility of the ZSM-5 and BaO contained the commercial DOC under diesel engine conditions as the 4-way catalyst was investigated