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Ultralow thermal conductivity of β -Cu<sub>2</sub>Se by atomic fluidity and structure distortion
Kim, Hyoungchul,Ballikaya, Sedat,Chi, Hang,Ahn, Jae-Pyung,Ahn, Kiyong,Uher, Ctirad,Kaviany, Massoud Elsevier 2015 Acta materialia Vol.86 No.-
<P><B>Abstract</B></P> <P>We demonstrate a prototype thermal evolution path for liquid thermal conductivity in solids. Thermal evolution of β -Cu<SUB>2</SUB>Se shows large interstitial displacement of constituent atoms marked by glass-like transitions and an asymptotic liquid thermal transport. Using ab initio molecular dynamics (AIMD), we identify these transitions, and confirm them with in situ transmission electron microscopy and electron energy loss spectroscopy. The thermal disorder of the Cu<SUP>+</SUP> ions forms homopolar Cu–Cu bonds under a rigid Se framework, and at yet higher temperatures the Se framework undergoes thermal distortion. The non-equilibrium AIMD prediction of lattice thermal conductivity shows significant suppression of the phonon transport, in agreement with experiments and molecular behavior.</P>
남형철(Hyoungchul Nam),김창현(Chang-Hyun Kim),권순만(Soon-Man Kwon) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
The RTG(roller track gear) system for an arbitrary path transportation can be constructed by the combinations of three RGM(roller gear mechanism) systems including CRP(cam rack pinion) system, CRG(cam ring gear) and RPG(roller pinion gear) system. Three ways for exact RTG system design to avoid the intersection of teeth in a connecting point between two RGMs are presented in this paper. Among them, we propose the third method is the best way for the aspect of standardization and manufacturing.
남형철(Hyoungchul Nam),권순만(Soon-Man Kwon),신중호(Joong-Ho Shin) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.11
외접기어의 어느 한쪽 기어를 핀 또는 롤러로 대체한 롤러 피니언 기어 (RPG) 시스템은 기어 치물림 시 미끄럼 접촉을 줄이고 구름운동을 증대시켜 기어 내구성을 향상시킬 수 있다. 우선 본 논문에서는 전위계수(profile shift coefficient)를 고려하여 RPG 시스템의 캠 기어(cam gear)의 엄밀 치형설계 방법 및 치 꼬임으로 인한 간섭 방지조건을 제시하였다. 또 기어구동에 있어 치면에서 발생되는 진동이나 소음의 원인이 되는 피팅(pitting) 발생수명을 고려하기 위해, 설계인자의 변화에 따른 Hertz 접촉응력 및 하중응력계수(load stress factor)의 변화를 검토하였다. 이를 통해 RPG 시스템의 내구성을 향상시킬 수 있는 방안으로 전위계수의 증가를 제안하였다. A roller pinion gear (RPG) system composed of either a pin or a roller and its conjugated cam gear can improve the gear endurance from that of a conventional gear system by reducing the sliding contact while increasing the rolling motion. In this paper, we first proposed the exact cam gear profile and the self-intersection condition obtained when the profile shift coefficient is introduced. Then, we investigated the Hertzian contact stresses and the load stress factors while the varying the shape design parameters to predict the gear surface fatigue life, which is strongly related to the gear noise and vibration at the contact patch. The results show that the pitting life can be extended significantly by increasing the profile shift coefficient.
특급 호텔 종사원의 직무역량이 서비스 몰입과 고객지향성에 미치는 영향
신형철 ( Hyoungchul Shin ),신재원 ( Jaewon Shin ) 관광경영학회 2018 관광경영연구 Vol.82 No.-
This study aims to identify how deluxe hotel employee’s job competency affects service commitment and customer orientation. To accomplish the goal, this study conducted a survey on the service employees working at the deluxe hotels in Seoul, Gyeonggi, and Incheon regions. After the survey, this study analyzed the coded data in the order of frequency analysis, exploratory factor analysis, reliability analysis, confirmatory factor analysis, correlation analysis, and multiple regression analysis with SPSS 18.0 and AMOS 18.0. To accomplish the research goal, this study suggests job competency factors that can be related to service employees at the deluxe hotels. This study also conducted empirical analysis on influential relationship between service commitment and customer orientation. First of all, In the order of relationship competency, professional competency, and personality competency, those competences had a significant positive (+) effect on service value. Also, relationship competency and personality competency had a significant positive (+) effect on service commitment’s subfactor, job commitment. Secondly, job competency had a significant positive (+) effect on customer orientation in the order of personality competency, professional competency, and relationship competency. Thirdly, service commitment had a significant positive (+) effect on customer orientation. By putting together empirical analysis result, the study verified that service employee’s job competency increases service commitment and has excellent role in improving customer orientation.
남형철(Hyoungchul Nam),김창현(Chang-Hyun Kim),권순만(Soon-Man Kwon) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.11
하이포 트로코이드 기반의 CRG(Cam ring gear) 시스템은 핀 또는 롤러 치형을 가지는 기어와 공액인 캠 링기어로 구성된 내접기어 시스템이다. 본 논문에서는 CRG 시스템의 엄밀 치형설계를 바탕으로 기어 치면에서의 접촉특성을 분석하였으며 형상설계변수인 치형수정계수에 따른 기어의 내구수명을 검토하였다. 결과적으로 치형수정계수의 증가를 통해 기 설계된 CRG 시스템에 영향을 미치지 않으면서 기어의 접촉 피로수명을 향상시킬 수 있다. A cam ring gear (CRG) system based on a hypotrochoid curve consists of a pinion with roller teeth and its conjugated internal CRG. In this study, we investigated contact forces, contact stresses, and load stress factors to predict the surface pitting life using an exact CRG profile by introducing the profile modification coefficient. The results show that the pitting life can be extended significantly by increasing the profile modification coefficient without any other change of parameters in the CRG system.
남형철(Hyoungchul Nam),김창현(Chang-Hyun Kim),권순만(Soon-Man Kwon) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.5-3
Cam ring gear(CRG) system based on hypo trochoid curve consist of a pinion with roller teeth and its conjugated internal cam ring geear. In this paper, we investigated contact stress for surface pitting life using exact cam ring gear profile by introducing the profile modification factor to find characteristics of surface fatigue. Then, we present effective method to improve surface pitting life without any change of design parameters in CRG system. The results show that the pitting life can be extended significantly by increasing the profile modification factor.