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전은채,백민경,김성훈,박주승,권동일 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.12
Continuous indentation test is getting more used to derive indentation flow curve. The overall deriving algorithm is relatively well-established, the details of the algorithm are, however, still argued. One of the arguments is the definition of true strain which constitutes the indentation flow curve. In this study, work-hardening exponent was adopted for determining what definition is appropriate to obtain accurate indentation flow curve since work-hardening exponent is affected by only the definition of true strain not by other constants. The effect of calibrating contact depth was eliminated using finite element analysis. Finally, the definition based on tangent function was determined to be proper for deriving the indentation flow curve. (Received September 8, 2004)
Changhyun Cho,Seunghun Choi,Oh Min Kwon,Seungha Lee,Jong‑hwan Kim,Dongil Kwon 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7
Friction stir welding has the advantages of producing less material deformation and of simple joining of relatively thickmaterials, but the disadvantages of forming relatively large heat-affected zones around weld areas. In addition, in research onreductions in bulletproof performance in heat-affected zones, it is necessary to evaluate the ballistic limit velocity (V50), whichmeasures bulletproof performance, and this requires specimens of a certain minimum size and has only limited applicationto local areas such as heat-affected zones. Instrumented indentation testing (IIT), a method of measuring material propertiesby utilizing load-depth curves measured by a small indenter leaving fine marks on the material, has no specimen size requirements;in addition, it has simple test procedures and is nondestructive. Here a theoretical model is proposed for evaluatingV50 of aluminum alloys by ductile hole formation using IIT. Heat-affected zones generated after friction stir welding of for7000-series aluminum alloys were simulated, and the model was validated through comparison with the conventional V50test. In addition, there is currently no way to directly evaluate V50 for welded areas in 7000-series aluminum, but here IIT wasused to assess V50 for each local part of the welded specimen. The conventional V50 test takes 15 min per shot and cannot bereused of specimens, but the test using IIT takes 1 min to complete one test and has benefits in terms of time, cost and safety.
Microfabrication and characterization of spray-coated single-wall carbon nanotube film strain gauges
Lee, Dongil,Hong, Hyun Pyo,Lee, Chul Jin,Park, Chan Won,Min, Nam Ki IOP Pub 2011 Nanotechnology Vol.22 No.45
<P>We present the design, fabrication, and characterization results of single-wall carbon nanotube (SWCNT) film strain gauges for potential applications as highly sensitive strain, weight, or pressure sensors on the macro-scale. A batch microfabrication process was developed for practical device construction and packaging using spray-coated SWCNTs and a conventional semiconductor process. The prototype was characterized using a commercial metal foil gauge with tensile and compressive testing on a binocular load cell. Our test results demonstrated that the proposed SWCNT film gauges have a linear relationship between resistance changes and externally applied strain. The gauge factor ranged from 7.0 to 16.4 for four different micro-grid configurations, indicating that the maximum strain sensitivity of the prototype was approximately eight times greater than that of commercial gauges. </P>
Automatic Cell Production for Cellular Phone Packing Using Two Dual-arm Robots
Hyun Min Do,Taeyong Choi,Dongil Park,Jinho Kyung 제어로봇시스템학회 2015 제어로봇시스템학회 국제학술대회 논문집 Vol.2015 No.10
The demands for an automation in a cell production process of IT products are becoming increasingly sophisticated. In particular, a dual-arm robot draws an attention as a solution because it has a flexibility and it can work in a similar way with a human. In this paper, we propose the automated robotic cell production system for cellular phone packing processes using two dual-arm robots. To achieve a goal, a method of task allocation for efficient packing job of cellular phone is proposed. Finally, we implement some results which show the packing job of 5 unit box with 7 kinds of accessories.
Three-Dimensional Fin-Structured Semiconducting Carbon Nanotube Network Transistor
Lee, Dongil,Lee, Byung-Hyun,Yoon, Jinsu,Ahn, Dae-Chul,Park, Jun-Young,Hur, Jae,Kim, Myung-Su,Jeon, Seung-Bae,Kang, Min-Ho,Kim, Kwanghee,Lim, Meehyun,Choi, Sung-Jin,Choi, Yang-Kyu American Chemical Society 2016 ACS NANO Vol.10 No.12
<P>Three-dimensional (3-D) fin-structured carbon nanotube field-effect transistors (CNT-FETs) with purified 99.9% semiconducting CNTs were demonstrated on a large scale 8 in. silicon wafer. The fabricated 3-D CNT-FETs take advantage of the 3-D geometry and exhibit enhanced electrostatic gate controllability and superior charge transport. A trigated structure surrounding the randomly networked single-walled CNT channel was formed on a fin-like 3-D silicon frame, and as a result, the effective packing density increased to almost 600 CNTs/mu m. Additionally, highly sensitive controllability of the threshold voltage (V-TH) was achieved using a thin back gate oxide in the same silicon frame to control power. consumption and enhance performance. Our results are expected to broaden the design margin of CNT-based circuit architectures for versatile applications. The proposed 3-D CNT-FETs can potentially provide a desirable alternative to silicon based nanoelectronics and a blueprint for furthering the practical use of emerging low-dimensional materials other than CNTs.</P>
김민(Min Kim),최말옥(Malok Choi),전동일(Dongil Chun) 한국산학기술학회 2019 한국산학기술학회논문지 Vol.20 No.8
본 연구의 목적은 ICF-VR 코어셋과 가치판단 분석툴인 IPC를 이용하여 프리젠티즘 도구에 대한 내용분석을 실시하는 것이 목적이다. 이를 위해 현재 국내에서 프리젠티즘을 측정하는 자기보고식 도구인 KOSS-SF(한국인 직무스트레스 측정도구 단축형)와 PWI-SF(사회-심리적 건강측정도구 단축형)를 사용하였으며, 척도문항 분류와 문항에 포함되어 있는 코드를 분석하여 프리젠팀즘을 측정하기 위해 추가되어야 하는 직업재활 요인을 제안하였다. 2018년 12월부터 2019년 2월까지 연구가 수행되었다. 저자들은 ICF와 IPC의 연결규칙에 따라 2가지 도구들을 독립적으로 분석하였으며, 연구자 간 일치도는 90%로 나타났다. KOSS-SF는 60개, PWI-SF는 34개의 ICF-VR 코드와 연결되어 있으며, 활동과 참여, 신체기능을 측정하는 것으로 나타났다. IPC 분석틀에 따른 결과는 Rational-Social, Emotional-Psychological 영역을 측정하는 것으로 나타났다. 2가지 도구들은 ICF-VR 코어셋과 일치율이 30%이하로 나타나 직업재활 영역을 적절하게 반영하고 있지 않으며, 특히 환경영역 측정에 제한적인 것으로 나타났다. 프리젠티즘을 측정하기 위해 ICF 신체구조, 환경요인, 개인요인에 대한 문항들이 추가되어야 하며, 보다 명확한 응답수집을 위해 설문에 대한 기준점이나 가이드라인이 개발되어야 할 것이다. 이러한 연구결과를 기반으로 추후연구에 대한 제안과 논의를 제공하였다. This study analyzed the contents of KOSS-SF and PWI-SF by using ICF-VR core set and IPC framework for value judgment. The two instruments are self-report questionnaires commonly used for presenteeism in order to suggest vocational rehabilitation factors to predict presenteeism. The study was conducted from Dec 2018 to Feb 2019. For the analysis, the researchers independently linked the scales using the connection rules of ICF and IPC framework. The average agreement between the researchers was 90%. KOSS-SF was linked with 60 ICF-VR codes and PWI-SF with 34 ICF-VR codes, and mainly measured activities and participation, and body function domains. According to the IPC framework, the instruments were found to measure the Rational-Social, and Emotional-Psychological aspects. As a result, the two instruments did not adequately reflect the presenteeism (30% matched) and were particularly limited in ICF-VR environmental domains. Based on the results, questions of ICF body structure, environmental, and personal domains should be added to improve the validity of the presenteeism scale, and references and guidelines should be developed for collecting clearer data. Further study and discussion were provided.