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유사물질 실험을 위한 자동화 현미경 실험 기기의 적용과 노캠퍼를 이용한 입자 성장 및 단순 전단 변형 실험의 예
하창수,김성실,Ha, Changsu,Kim, Sungshil 대한자원환경지질학회 2021 자원환경지질 Vol.54 No.2
암석의 미세구조에 대한 많은 연구는 실제 암석 관찰 뿐만 아니라 다양한 실험 장비를 이용하여 미구조의 발달 과정과 그 메커니즘을 이해하기 위해 수행되어 왔다. 변성이나 변형 작용 중에 입자 성장이나 입도의 변화를 일으킬 수 있는 광물 군집 내 입자 경계 이동 작용은 주요한 재결정작용 메커니즘 중 하나이다. 특히, 변형 과정 중 나타날 수 있는 입자 경계 이동의 연속적 관찰은 암석 유사 실험을 이용하여 수행될 수 있었다. 이번 연구에서는 다양한 실험 방법 중 유사 물질을 이용한 입자 성장 및 변형 실험 방법에 대해 기존 방법을 개량할 수 있는 실험 장비의 개발과 이를 통한 효과적인 미구조 분석 방법을 제시하였다. 개발된 실험 장비는 유사 물질 실험이 가능한 변형 장치와 실체 현미경에 회전 조작이 가능한 편광판들을 장착하여 광학적 조작이 가능하도록 구성되었다. 이들 장치들은 마이크로 컨트롤러를 통해 온도 및 변형 속도 제어 및 실험 동안 관찰되는 미구조 변화를 연속적으로 촬영할 수 있도록 자동화하여 구성되었다. 또한 편광판 회전 조작을 통해 취득되고 합성된 디지털 이미지들은 보다 정확한 입자 경계를 구분하고 분석할 수 있게 해주었다. 실험 결과의 입도 및 형태와 같은 미구조 분석을 위해 선분 교점 측정 방법과 입자 경계 트레이싱 방식을 비교하여 적용하였다. 유사물질로써는 석영과 유사한 광학적 성질을 가지는 노캠퍼(Norcamphor, C7H10O)라는 물질을 사용하였다. 개발된 장비의 실효성을 검증하고자 노캠퍼를 이용한 정적 입자 성장 실험과 단순 전단 변형 실험 및 이에 대한 미구조 분석을 수행하였다. 정적 입자 성장 실험은 시간이 지남에 따라 입자 수의 감소와 입도가 증가하는 전형적인 입자 성장 작용의 특징과 온도에 따른 성장 곡선들의 명확한 차이를 보여주었다. 중온-저변형율 조건의 단순 전단 변형 실험 결과는 평균 입도의 큰 변화는 없었으나, 입자 형태에 대해 전단 변형이 증가함에 따라 전단력 방향에 수직한 방향에 대해 약 53°의 방향으로 신장률이 증가하는 변화를 보여주었다. 이러한 미구조의 발달과정은 주어진 실험 조건에서 변형에 의해 입자 내부의 소성 변형과 내부 회복 작용이 균형을 이루면서 진행된 것으로 해석된다. 개량화 및 자동화된 실험장치를 이용한 이들 입자 성장 작용 실험 및 변형 실험의 예는 유사물질 실험에서 목적하는 바와 같이 실험 과정 동안의 입자의 미구조 변화과정을 순차적으로 관찰할 수 있고, 전체 수행 과정동안 수동적 조작없이 효율적으로 실험을 진행할 수 있다는 장점을 보여주었다. Many studies on the microstructures in rocks have been conducted using experimental methods with various equipment as well as natural rock studies to see the development of microstructures and understand their mechanisms. Grain boundary migration of mineral aggregates in rocks could cause grain growth or grain size changes during metamorphism or deformation as one of the main recrystallization mechanisms. This study suggests improved ways regarding the analog material experiments with reformed equipment to see sequential observations of these grain boundary migration. It can be more efficient than the existing techniques and carry out an appropriate microstructure analysis. This reformed equipment was implemented to enable optical manipulation by mounting polarizing plates capable of rotating operation on a stereoscopic microscope and a deformation rig capable of experimenting with analog materials. The equipment can automatically control the temperature and strain rate of the deformation rig by microcontrollers and programming and can take digital photomicrographs with constant time intervals during the experiment to observe any microstructure changes. The composite images synthesized using images by rotated polarizing plates enable us to see more accurate grain boundaries. As a rock analog material, norcamphor(C7H10O) was used, which has similar birefringence to quartz. Static grain growth and simple shear deformation experiments were performed using the norcamphor to verify the effectiveness of the equipment. The static grain growth experiments showed the characteristics of typical grain growth behavior. The number of grains decreases and the average grain size increases over time. These case experiments also showed a clear difference between the growth curves with three temperature conditions. The result of the simple shear deformation experiment under the medium temperature-low strain rate showed no significant change in the average grain size but presented the increased elongation of grain shapes in the direction of about 53° regarding the direction perpendicular to the shearing direction as the shear strain increases over time. These microstructures are interpreted as both the plastic deformation and the internal recovery process in grains are balanced by the deformation under the given experimental conditions. These experiments using the reformed equipment represent the ability to sequentially observe changing the microstructure during experiments as desired in the tests with the analog material during the entire process.
피식자-포식자 군집행동 모사를 위한 인간 상호작용이 가능한 다중감각 피드백의 시뮬레이터 개발
홍성민(Seongmin Hong),하창수(ChangSu Ha),이동준(Dongjun Lee) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
We develop human interactive prey-predator simulation based on collective behavior, which can be used for observation of collective animal behavior. For the simulator, we deploy three flocking rules of Reynolds and add preys’ behavior to avoid predators’ attack, which is not relatively studied comparing to the free-flocking. In addition, we also propose another observed motion in nature, ‘separation-rejoining’ behavior, by modifying the Reynolds rules. Finally, we introduce the preliminary concept of human-interactive simulator interface. This allow the users to operate the predators to observe the preys’ behavior with multi-modal feedback.
Semi-Autonomous Haptic Teleoperation of Multiple Omni-directional Mobile Robots
Hyunjun Cho,Haan Kim,Changsu ha,Kyung Ho Ha,Chong Nam Chu,Dongjun Lee 제어로봇시스템학회 2013 제어로봇시스템학회 국제학술대회 논문집 Vol.2013 No.10
We present experimental results on semi-autonomous control of unmanned ground vehicles (UGVs), which makes it possible for multiple robots to follow teleoperated command and maintain the formation of them with collision avoidance at the same time. The implemented results are presented with theoretical preliminaries, and we use three Tri-Roller Observing Tracers (TROTs) in our implementation. It is omni-directional mobile robot which has natural-born agility.
동역학 분할 기법을 이용한 유연한 구조물 위에 장착된 로봇팔의 작업공간 추종 및 진동 저감 제어기법
김학찬(Hackchan Kim),하창수(Changsu Ha),이동준(Dongjun Lee) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
This paper presents workspace control framework of a manipulator which is supported by a flexible beam, while suppressing vibrational motion by using passive decomposition. We, first, derive the flexible beam-manipulator system dynamics, considering boundary conditions of the flexible part that includes the dynamic effects of the manipulator’s mass and inertia. Then, the passive decomposition is deployed to decompose the original dynamics into workspace and null-space dynamics. Finally, after designing the desired control laws in both spaces, we suggest a least-square solution of the desired control laws due to under-actuation property of the system. Real experiments are performed to verify the performance of the proposed control framework.
Semiautonomous Haptic Teleoperation Control Architecture of Multiple Unmanned Aerial Vehicles
Dongjun Lee,Franchi, Antonio,Hyoung Il Son,ChangSu Ha,Bulthoff, Heinrich H.,Giordano, Paolo Robuffo IEEE 2013 IEEE/ASME transactions on mechatronics Vol.18 No.4
<P>We propose a novel semiautonomous haptic teleoperation control architecture for multiple unmanned aerial vehicles (UAVs), consisting of three control layers: 1) UAV control layer, where each UAV is abstracted by, and is controlled to follow the trajectory of, its own kinematic Cartesian virtual point (VP); 2) VP control layer, which modulates each VP's motion according to the teleoperation commands and local artificial potentials (for VP-VP/VP-obstacle collision avoidance and VP-VP connectivity preservation); and 3) teleoperation layer, through which a single remote human user can command all (or some) of the VPs' velocity while haptically perceiving the state of all (or some) of the UAVs and obstacles. Master passivity/slave stability and some asymptotic performance measures are proved. Experimental results using four custom-built quadrotor-type UAVs are also presented to illustrate the theory.</P>
Han YoungHoon,Song YoungMin,Kim Geun Woo,Ha ChangSu,Lee JiSun,Kim MinHee,Son HyeYoung,Lee GiYong,Gautam Ravi,Heo Yong 한국독성학회 2021 Toxicological Research Vol.37 No.4
Microplastics (MPs) have been recently recognized as a global environmental threat and its exposure as a risk factor to human health. Health effects through MPs exposure have been recently reported, especially through oral route of exposure. Since MPs could be exposed to humans through routes other than oral, this study was designed to evaluate whether MPs exposed through the inhalation route could be delivered to fetal mice and exhibit systemic toxicity. Polyethylene (PE) with 10–45 μm diameter were administered at 0 (distilled water, vehicle control), 6 (low administration), and 60 (high administration) μg/ mouse/day to 3 pregnant dams per group from gestational day 9 to postnatal day (PND) 7 through intratracheal instillation. Dams and neonates were sacrificed at PND 7 and blood was collected. Various neonatal organs including brain, lung, heart, stomach, intestine, kidneys, and ovaries were collected for histopathological observation and weight measurement. No influence of PE-MPs administration was observed on the number of offsprings born, but the body and organs’ weight were heavier overall in the high administration group of dams and neonates than the other groups with statistical significance achieved in the heart and spleen weight. Level of serum acetylcholinesterase and glutathione peroxidase activity was decreased in the high administration group of dams and neonates compared with the other groups. Lung was the organ with highest number of PE-MPs present in the both administration groups of dams, and PE-MPs were also detected in liver and intestine of the high administration dams. Whereas, PND7 neonates showed accountable numbers of PE-MPs only in kidneys of the high administration group. Overall, the present study indicates that PE-MPs instilled intratracheally could be delivered to neonates from dams. Even though adverse effects from PE-MPs exposure during pregnant and lactational period are less prominent on both dam and neonate, potential of second-generation toxicity could be considered for further investigation.