Combining In Situ Synchrotron X‐Ray Diffraction and Absorption Techniques with Transmission Electron Microscopy to Study the Origin of Thermal Instability in Overcharged Cathode Materials for Lithium‐Ion Batteries

Nam, Kyung‐,Wan,Bak, Seong‐,Min,Hu, Enyuan,Yu, Xiqian,Zhou, Youngning,Wang, Xiaojian,Wu, Lijun,Zhu, Yimei,Chung, Kyung‐,Yoon,Yang, Xiao‐,Qing WILEY‐VCH Verlag 2013 Advanced Functional Materials Vol.23 No.8

<P><B>Abstract</B></P><P>The thermal instability of the cathode materials in lithium‐ion batteries is an important safety issue, requiring the incorporation of several approaches to prevent thermal runaway and combustion. Systematic studies, using combined well‐defined in situ techniques, are crucial to obtaining in‐depth understanding of the structural origin of this thermal instability in overcharged cathode materials. Here time‐resolved X‐ray diffraction, X‐ray absorption, mass spectroscopy, and high‐resolution transmission electron microscopy during heating are combined to detail the structural changes in overcharged Li<SUB><I>x</I></SUB>Ni<SUB>0.8</SUB>Co<SUB>0.15</SUB>Al<SUB>0.05</SUB>O<SUB>2</SUB> and Li<SUB><I>x</I></SUB>Ni<SUB>1/3</SUB>Co<SUB>1/3</SUB>Mn<SUB>1/3</SUB>O<SUB>2</SUB> cathode materials. By employing these several techniques in concert, various aspects of the structural changes are investigated in these two materials at an overcharged state; these include differences in phase‐distribution after overcharge, phase nucleation and propagation during heating, the preferred atomic sites and migration paths of Ni, Co, and Mn, and their individual contributions to thermal stability, together with measuring the oxygen release that accompanies these structural changes. These results provide valuable guidance for developing new cathode materials with improved safety characteristics.</P>

Portfolio, Consumption and Voluntary Retirement Optimization Problem with Disutility and Subsistence Consumption Constraints

Namkyung Lee,Kum-Hwan Roh 한국전산응용수학회 2021 Journal of Applied and Pure Mathematics Vol.3 No.5

In this paper, we obtain the optimal portfolio, consumption and voluntary retirement strategies of an investor with subsistence consumption constraints. And we apply subsistence consumption constraints to the investor's lifetime.

Outlier Tests in Sample Surveys

Namkyung, Pyong,Lee, Joon Suk 한국통계학회 2000 Communications for statistical applications and me Vol.7 No.2

In this paper, we considered three methods for outlier identification sample surveys. First, we studied method of handling and adjusting outliers in normal population. Second, we studied existing methods using mean, maximum and minimum and proposed a test using of median which well reflects characteristic of data regardless of sampling distribution. Finally, we showed our test using median works better than Dixon and mean test through simulation.

An Interactive Virtual Stone Skipping System

Namkyung Lee,Nakhoon Baek 보안공학연구지원센터 2013 International Journal of Multimedia and Ubiquitous Vol.8 No.1

Considerations for Web of Object Service Architecture on IoT Environment

NamKyung Lee,HyunWoo Lee,Won Ryu 보안공학연구지원센터 2015 International Journal of Smart Home Vol.9 No.1

The internet is an optimal place to human as a producer or a consumer for sharing information until now. In the future, not only the human-generated information but also things will be connected into internet and these will evolve into internet of things(IoT) which can share the information thing-in-itself and its environment. Firstly, this paper proposes a service architecture which includes various devices for providing web base IoT services. Secondly, this paper also proposes a service platform which supports service orchestration and composition with device objectification and finally describes structure and functionalities of web of object gateway.

[P8-298] Inhibition Effects of Osteoclast differentiation on BMMs cells of Medicinal herb Extracts

Namkyung Im,Hyunjeong Kim,Mijin Kim,Eunju Lee,Jiwon Lee,Inseon Lee 한국식품영양과학회 2009 한국식품영양과학회 학술대회발표집 Vol.2009 No.11

A Study on the Relationship of Human Factors Integration In the Defense

Ko, NamKyung,Kwon, YongSoo The Korean Society of Systems Engineering 2011 시스템엔지니어링학술지 Vol.7 No.2

This work presents the relationship between the domains of Human Factors Integration(HFI) to develop the weapon systems through integrating human factors into the defense acquisition program. The HFI is a systematic process for identifying, tracking and resolving human related issues ensuring a balanced development of both technologies and human aspects of capability. In this point of view, this paper identifies and analyzes the HFI domains. Based on the results, this paper presents the relationships between the domains of the HFI.

원자력 우주추진 기술 고찰

조남경(Namkyung Cho),양수석(Sooseok Yang) 한국추진공학회 2023 한국추진공학회지 Vol.27 No.5

Nuclear space propulsion has the advantage of superior specific impulse compared to the currently widely used chemical propulsion, the system can be simplified by omitting the oxidizer system, and has the ability to improve performance in the future. The high specific impulse makes missions that are only possible with large chemical propulsion launch vehicles possible with medium-sized launch vehicles. This paper describes the characteristics of nuclear propulsion that are different from chemical propulsion and introduces the nuclear propulsion system and key components. Nuclear thermal propulsion and electric propulsion, and a bimodal system and a hybrid system that combines chemical propulsion and nuclear propulsion are introduced. Also, the development aspects of nuclear propulsion as well as test facility and launch safety of the nuclear power propulsion system are discussed.

액체로켓 기체공급계의 추진제 진동특성 및 제어기술 동향

조남경(Namkyung Cho),고현석(Hyunseok Kho),한상엽(Sangyeop Han),조인현(Inhyun Cho) 한국추진공학회 2010 한국추진공학회 학술대회논문집 Vol.2010 No.5

액체로켓 기체공급계는 추진제를 요구되는 유량, 온도, 압력으로 엔진에 공급하여야 한다. 이를 위한 정상상태의 공급특성은 기존의 열역학 및 열전달, 유체역학 이론을 적용하여 해석하며 방법론이 잘 정립되어 있다. 발사체의 비행 중에 발생하는 탱크와 공급배관에서의 추진제의 진동은 정상상태의 공급 특성을 변하게 하며 추진제공급 요구조건을 만족시키지 못하게 한다. 이러한 진동을 발생시키는 것으로서 발사체의 가속도로 인한 슬로싱 및 엔진의 추력섭동에 의해 배관 내 추진제가 진동하는 포고 불안정이 있다. 포고와 슬로싱에 의한 발사체 제어와 구조측면에서 미치는 영향에 대해서는 기존에 많은 연구가 있으나 추진제 공급특성에 미치는 영향에 대해서는 잘 알려져 있지 않다. 본 연구에서는 추진제의 진동이 엔진으로의 추진제 공급에 미치는 영향을 기존 자료를 이용하여 살펴보고 진동을 제어하기 위한 기구를 살펴본다. Fuselage propellant feeding system should supply propellants to engine with required flow rate, temperature and pressure. Propellant vibration in engine and feeding line changes feeding characteristics, and frequently inhibits to satisfy the required feeding requirements. Sloshing and POGO vibration are known to be the major vibration phenomena. Concerning sloshing and POGO, vehicle control and structural dynamics aspects are extensively studied, whereas, its effect on propellant feeding performance is not clearly understood. This paper focuses on the deviation of required feeding performance due to propellant vibration. Overall characteristics of propellant vibration and its effect on propellant supply to engine are reviewed and control mechanism for suppressing vibration is introduced.

서비스 프로세스 내 고객유발성변동의 대응 전략에 관한 연구

이남경(Namkyung Lee),권혜정(Hyejeong Gwon) 한국생산관리학회 2021 한국생산관리학회지 Vol.32 No.4

서비스 프로세스에서 고객의 이질성(heterogeneity)에 의해 나타나는 고객유발성변동은 프로세스 내 불확실성과 복잡성을 증가시키는 원인이 된다. 서비스 제공자는 이러한 고객유발성변동을 축소하거나 수용하는 전략적 대응을 통해 부정적 영향을 최소화하려 하지만, 각각의 대응은 운영 효율성과 서비스 품질 성과 간 상충 효과를 일으키는 것으로 알려져 있어 적절한 전략의 선택이 필요하다. 이에 본 연구는 고객유발성변동 대응 전략이 운영 효율성 및 서비스 품질에 미치는 영향을 실증적으로 분석하여 전략적 선택과 관련된 시사점을 제공하고자 한다. 고객유발성변동 대응 전략을 변동축소전략과 변동수용전략으로 구분하여 각 전략이 운영 효율성과 서비스 품질에 미치는 영향을 분석하였으며, 서비스 프로세스에서 서비스 직원의 역할에 집중하여 각 대응 전략과 서비스 직원의 능력 간 상호작용 효과를 분석하였다. 분석 결과, 변동축소전략은 운영 효율성에 긍정적인 영향을 미치고 변동수용전략은 서비스 품질에 긍정적인 영향을 주는 것으로 나타났다. 고객유발성변동 대응 전략과 직원 능력 간 상호작용 효과는 변동축소전략에서만 유의하게 나타났으며, 모두 음의 회귀 계수를 보여 직원 능력이 변동축소전략의 성과 영향을 약화시키는 것으로 나타났다. 이와 같은 결과는 고객유발성변동 대응 전략의 선택에 있어 성과의 상충 관계 대신 상위 전략과의 정합성 및 직원 능력 수준을 더욱 고려해야 한다는 것을 시사한다. As customer-induced variability causes uncertainty and complexity of the service process, service providers try to minimize the negative effect by either reducing or accommodating such variability. It is acknowledged that there is a performance trade-off between these two strategic reactions, but little is known about the impact of strategic reaction to customer-induced variability on service performance. This study empirically tests this impact and the moderating effect of service employees’ capability on the relationship between the strategic reaction and performance. Using survey data of managers from the service industry, the regression results reveal that the variability reduction strategy has a positive effect on efficiency, while the variability accommodation strategy has a positive effect on service quality. In addition, the variability reduction strategy was found to negatively interact with employee capability to harm efficiency and service quality. This study provides empirical evidence that strategic reactions to customer-induced variability should align with performance orientation and employee capability.