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김찬일,양승한,김영석 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.2
In the automobile industry, reducing the weight is the most important objective for reducing air pollution and improving the fuel efficiency. For this reason, the application of aluminum sheets is increasing. When the sheets are applied to the automobile, using inappropriate variables for the material, product design, and press processing can generate tearing, wrinkling, and spring-back problems, which are the main types of failure in the manufacturing process. Therefore, it is necessary to reduce these failures by harmonizing the many variables and strictly managing the processes. In this research, we study the theoretical plasticity instability of Al5454 and obtain the forming limit diagram (FLD) using MATLAB. Moreover, we compare the theoretical FLD with an experimental FLD obtained from a stretching test. 자동차 산업에서 대기오염을 줄이고 연비를 향상시키기 위해 경량화가 중요한 과제로 여겨지고 있다. 이를 위해 알루미늄 소재의 적용이 증가하고 있다. 판재를 차체에 적용하기 위해서는 주로 프레스 가공 공정을 거치게 된다. 이때, 재료, 제품설계 및 프레스 공정의 부적절한 가공 변수의 사용으로 인하여 파단, 주름, 및 스프링 백 등에 의한 다양한 형태의 가공 불량이 발생한다. 따라서 이들 변수들의 적절한 조화 뿐 만 아니라 엄격한 공정 관리가 요구된다. 이에 본 연구에서는 자동차 판재에 주로 사용되는 Al5454 재료에 대한 이론적으로 유도한 소성 불안정 조건을 구하고, MATLAB을 이용하여 성형 한계도를 도출하였다. 또한, 장출 인장 실험을 통해 얻어진 실험값과 이론적으로 도출한 성형 한계도와의 비교를 수행하였다.
Analysis of forming limit in tube hydroforming
김찬일,양승한,김영석 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.12
The automotive industry has shown increasing interest in tube hydroforming. Despite many automobile structural parts being produced from cylindrical tubes, failures frequently occur during tube hydroforming under improper forming conditions. These problems include wrinkling, buckling, folding back, and bursting.We perform analytical studies to determine forming limits in tube hydroforming and demonstrate how these forming limits are influenced by the loading path. Theoretical results for the forming limits of wrinkling and bursting are compared with experimental results for an aluminum tube.
아두이노를 활용한 무선 탄성파 자료취득 모듈 구현 실험
김찬일,조상인,편석준 한국지구물리.물리탐사학회 2023 지구물리와 물리탐사 Vol.26 No.3
In the oil and gas exploration market, various cableless seismic systems have been developed as an alternative to improve data acquisition efficiency. However, developing such equipment at a small scale for academic research is not available owing to highly priced commercial products. Fortunately, building and experimenting with open-source hardware enable the academic utilization of cableless seismic equipment with relatively low cost. This study aims to develop a cableless seismic acquisition module using Arduino. A cableless seismic system requires the combination of signal sensing, simple pre-processing, and data storage in a single device. A conventional geophone is used as the sensor that detects the seismic wave signal. In addition, it is connected to an Arduino circuit that plays a role in implementing the processing and storing module for the detected signals. Three main functions are implemented in the Arduino module: preprocessing, A/D conversion, and data storage. The developed single-channel module can acquire a common receiver gather from multiple source experiments. 석유가스 탐사 분야에서는 자료 취득 효율성을 개선하기 위한 대안으로 다양한 무선 탄성파 탐사 장비들이 개발되었다. 그러나 현재 상 용화된 무선 탄성파 탐사 장비는 높은 가격대를 형성하고 있으므로 작은 규모의 연구용 장비 구축이 어렵다. 이 때 비교적 적은 비용으로 탐사 장비 제작 및 구현이 가능한 오픈소스 하드웨어를 통해 직접 장비를 만들어 실험하는 것이 무선 탄성파 장비의 학술적 활용을 위한 한가지 대안이 될 수 있다. 이 연구에서는 오픈소스 하드웨어 중 아두이노를 이용하여 무선으로 탄성파 자료를 취득하기 위한 모듈을 개 발하였다. 무선 탄성파 탐사 장비는 하나의 수신 장비에서 신호 감지, 간단한 전처리, 저장이 모두 이루어져야 한다. 탄성파 신호를 감지 하는 센서로는 육상 탄성파 탐사에서 사용되는 지오폰을 활용하였으며, 이를 아두이노 회로와 연결하여 감지된 신호를 처리하고 저장하 는 모듈을 구현하였다. 아두이노를 사용하여 구축된 모듈에는 전처리, 아날로그-디지털 변환, 자료저장 등 크게 3가지 기능이 포함된다. 제작한 단일 채널 모듈은 여러 송신원으로부터 취득한 신호를 취합하여 공통 수신점 모음을 구성할 수 있다.
김찬일,Seung Han Yang,Young Suk Kim 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.6
Molecular dynamics simulations are performed to verify the deformation characteristics of grain boundaries on the AFM-based nanolithography. The model used has about 750,000 (Cu) atoms and is composed of two different crystal orientations. The grain boundaries are located in the center of model and have 45, 90, 135, and -135 degree angles in the xz-plane. The tool is made of rigid diamond-like carbon and is in the shape of the Berkovich indenter. The simulation has four different stages: relaxation, indentation, re-relaxation, and lithography. The simulation results reveal that the lithography deforms the grain boundary shape by the tool. The deformation of grain boundary’s angle proceeds to minimize the total potential energy of whole system. Consequently, the grain boundary angle is changed about 90 degrees.
이중 방식에 의한 독립적 폐환기에 적용한 고빈도 Jet 환기법 및 지속적 기도
김찬,엄대자,박윤곤,임현교,최령 대한마취과학회 1990 Korean Journal of Anesthesiology Vol.23 No.3
The effects of oxygenation of differential independent lung ventilation using HFJV (High Frequency Jet Ventilation) and CPAP (Continuous Positive Airway Pressure) on PaO₂ and Qs/Qt were studied during one lung anesthesia in 11 mongrel dogs in left semilateral position with pentobarbital anesthesia. The dogs were divided into two groups. In group A(N = 7), following the conventional two lung ventilation, one lung ventilation, HFJV, one lung ventilation, cpap 5 cmH₂O, and CPAP 10 cmH₂0 were applied sequentially. In group B(N =4), following the conventional two lung ventilation the above applications were reversed. In group A PaO₂ revealed a similar increase among a two lung ventilation, CPAP 5 cmH₂O, CPAP 10 cmH₂O and HFJV. Intrapulmonary shunt showed the similar decrease among two lung ventilation, HFJV and CPAP 10cmH₂O, but CPAP 5 cmH₂O was higher than CPAP 10cmH₂O. Although there were no statistically significant differences in PaO₂ and shunt among each step in group B, HFJV showed a greate increas and shunt than one lung ventilation, CPAP 5 cmH 20) 20, and CPAP 10 cmH₂O. In conclusion, HFJV proved to be more effective than CPAP 5 cmH₂O in increasing PaO₂ and decreasing shunt in differential independent lung ventilation. Both CPAP and JFJV should be applied in the deflation phase of the nondependent lung to cause an effective increase in PaO₂. HFFV proved to be more effective than CPAP in recruiting the small airway closure.
김찬,김무영,박희연,이형철 한국초전도.저온공학회 2017 한국초전도저온공학회논문지 Vol.19 No.1
We studied the distribution of the current density and its magnetic-field dependence in GdBCO coated conductors with AC biascurrents using low temperature scanning Hall probe microscopy. We selectively measured magnetic field profiles from AC signalobtained by Lock-in technique and calculated current distributions by inversion calculation. In order to confirm the ACmeasurement results, we applied DC current corresponding to RMS value of AC current and compared distribution of AC and DCtransport current. We carried out the same measurements at various external DC magnetic fields, and investigated field dependenceof AC current distribution. We notice that the AC current distribution unaffected by external magnetic fields and preserved theirown path on the contrary to DC current.