• 비파괴검사학회지
• /
• 제34권6호
• /
• pp.435-440
• /
• 2014

Contact-guided-wave tests are impractical for investigating specimens with limited accessibility and rough surfaces or complex geometric features. A non-contact setup with a laser-ultrasonic transmitter and receiver is quite attractive for guided-wave inspection. In the present work, we developed a non-contact guided-wave tomography technique using the laser-ultrasonic technique in a plate. A method for Lamb-wave generation and detection in an aluminum plate with a pulsed laser-ultrasonic transmitter and Michelson-interferometer receiver was developed. The defect shape and area in the images obtained using laser scanning, showed good agreement with the actual defect. The proposed approach can be used as a non-contact online inspection and monitoring technique.

• 한국동물위생학회지
• /
• 제42권4호
• /
• pp.169-175
• /
• 2019

Naegleria fowleri, a pathogenic free-living amoeba, leads to a fatal infection known as primary amebic meningoencephalitis (PAM) in human and animals. PAM is an acute, fulminant, necrotizing, and hemorrhagic disease that leads to death in approximately seven days. In this study, we investigate the cytotoxicity of target cells and the secreted molecules of N. fowleri under the non-contact condition. The target cell (U87MG cell) treated with N. fowleri lysates showed no morphological changes and no cytotoxicity. By contrast, the U87MG cells co-cultured with N. fowleri trophozoites under the non-contact condition induced morphological changes and reduction in number. When U87MG cells were co-cultured with N. fowleri trophozoites under the non-contact condition for 30 min, 2 hr, and 4 hr, the levels of cytotoxicity of target cells were 32.3, 35.5, and 37.8%, respectively. Particularly, when the ratio of amoeba to target cells is 10 to 1, the level of cytotoxicity of target cells was 49.7% at 30 min. To show the proteins secreted from N. fowleri under the non-contact condition, we carried out 2D electrophoresis and observed 6 major proteins. Finally, these results suggest that the molecules released from N. fowleri under the non-contact condition induce the cell death and this process is an important step in pathogenesis of N. fowleri.

• Journal of Mechanical Science and Technology
• /
• 제14권7호
• /
• pp.705-714
• /
• 2000

The formulation of Smoothed Particle Hydrodynamics (SPH) and a shortcoming of traditional SPH in contact simulation are presented. A contact algorithm is proposed to treat contact phenomenon between two objects. We describe the boundary of the objects with non-mass artificial particles and set vectors normal to the contact surface. Contact criterion using non-mass particles is established in this study. In order to verify the contact algorithm, an algorithm is implemented in to an in-house program; elastic wave propagation is an analysed under low velocity axial impact of two rods. The results show that the contact algorithm eliminates the undesirable phenomena at the contact surface; numerical result with the contact algorithm is compared with theoretical one.

• 소음진동
• /
• 제7권3호
• /
• pp.499-509
• /
• 1997

During the process of oxide removal from work rolls in sheet metal manufacture, filamentary brushes frequently exhibit a bouncing or chatter behavior. The dynamics of this phenomenon is investigated through the development of expressions for the non-linear contact stiffness between the brush and the roll. With formulation of simple structural models, the time responses in the presence and absence of friction under random excitation are investigated. Possible solutions for the minimization or avoidance of this bouncing or chatter problem are also suggested.

• 대한수학회논문집
• /
• 제24권2호
• /
• pp.265-275
• /
• 2009

The object of the present paper is to study 3-dimensional normal almost contact metric manifolds satisfying certain curvature conditions. Among others it is proved that a parallel symmetric (0, 2) tensor field in a 3-dimensional non-cosympletic normal almost contact metric manifold is a constant multiple of the associated metric tensor and there does not exist a non-zero parallel 2-form. Also we obtain some equivalent conditions on a 3-dimensional normal almost contact metric manifold and we prove that if a 3-dimensional normal almost contact metric manifold which is not a ${\beta}$-Sasakian manifold satisfies cyclic parallel Ricci tensor, then the manifold is a manifold of constant curvature. Finally we prove the existence of such a manifold by a concrete example.

• KEPCO Journal on Electric Power and Energy
• /
• 제1권1호
• /
• pp.181-188
• /
• 2015

비접촉 영구자석 기어는 높은 효율과 신뢰성의 장점을 가지고 있다. 또한, 기계적인 마찰 손실이 없으며, 소음과 진동이 적고, 윤활유가 불필요 하다는 장점을 가지고 있다. 이러한 장점으로 인하여, 비접촉 영구자석 기어는 기계적 기어의 물리적인 접촉에 의한 문제를 해결할 수 있어 높은 관심을 받고 있다. 비접촉 영구자석 기어는 기계적 기어를 대체하여 접촉 없이 토크 전달이 가능하지만 낮은 토크밀도의 문제점을 가지고 있어, 이에 대한 개선이 요구된다. 따라서 본 논문에서는 비접촉 영구자석 기어의 낮은 토크밀도의 문제점을 개선하고자 새로운 폴피스 형상을 제안하였다. 제안된 폴피스 형상에 대한 설계변수와 토크 및 토크 리플과 같은 반응변수들 간의 함수 관계를 파악하기 위하여 반응표면법을 이용하였으며, 박스-벤켄 설계를 이용하여 실험계획법을 수립하였다. 이들의 관계를 예측하기 위해 필요한 실험데이터는 수치해석기반 2-D 유한요소법을 이용하였다. 따라서 본 논문에서는 비접촉 영구자석 기어의 토크밀도 및 출력밀도 향상을 위하여 형상에 대한 전달토크 분석을 수행하였으며, 박스-벤켄 설계를 이용하여 제안된 폴피스 형상을 최적설계 하였다.

• Parasites, Hosts and Diseases
• /
• 제46권4호
• /
• pp.217-221
• /
• 2008

Free-living Naegleria fowleri leads to a fatal infection known as primary amebic meningoencephalitis in humans. Previously, the target cell death could be induced by phagocytic activity of N. fowleri as a contact-dependent mechanism. However, in this study we investigated the target cell death under a non-contact system using a tissue-culture insert. The human microglial cells, U87MG cells, co-cultured with N. fowleri trophozoites for 30 min in a non-contact system showed morphological changes such as the cell membrane destruction and a reduction in the number. By fluorescence-activated cell sorter (FACS) analysis, U87MG cells co-cultured with N. fowleri trophozoites in a non-contact system showed a significant increase of apoptotic cells (16%) in comparison with that of the control or N. fowleri lysate. When U87MG cells were co-cultured with N. fowleri trophozoites in a non-contact system for 30 min, 2 hr, and 4 hr, the cytotoxicity of amebae against target cells was 40.5, 44.2, and 45.6%, respectively. By contrast, the cytotoxicity of non-pathogenic N. gruberi trophozoites was 10.2, 12.4, and 13.2%, respectively. These results suggest that the molecules released from N. fowleri in a contact-independent manner as well as phagocytosis in a contact-dependent manner may induce the host cell death.

• 한국인공지능학회지
• /
• 제11권1호
• /
• pp.9-15
• /
• 2023

As mobile devices such as smartphones, tablets, and kiosks become increasingly prevalent, there is growing interest in developing alternative input systems in addition to traditional tools such as keyboards and mouses. Many people use their own bodies as a pointer to enter simple information on a mobile device. However, methods using the body have limitations due to psychological factors that make the contact method unstable, especially during a pandemic, and the risk of shoulder surfing attacks. To overcome these limitations, we propose a simple information input system that utilizes gaze-tracking technology to input passwords and control web surfing using only non-contact gaze. Our proposed system is designed to recognize information input when the user stares at a specific location on the screen in real-time, using intelligent gaze-tracking technology. We present an analysis of the relationship between the gaze input box, gaze time, and average input time, and report experimental results on the effects of varying the size of the gaze input box and gaze time required to achieve 100% accuracy in inputting information. Through this paper, we demonstrate the effectiveness of our system in mitigating the challenges of contact-based input methods, and providing a non-contact alternative that is both secure and convenient.

• Journal of Electrical Engineering and Technology
• /
• 제13권4호
• /
• pp.1732-1739
• /
• 2018

With the explosion of digital devices, interaction technologies between human and devices are required more than ever. Especially, hand gesture recognition is advantageous in that it can be easily used. It is divided into the two groups: the contact sensor and the non-contact sensor. Compared with non-contact gesture recognition, the advantage of contact gesture recognition is that it is able to classify gestures that disappear from the sensor's sight. Also, since there is direct contacted with the user, relatively accurate information can be acquired. Electromyography (EMG) and force-sensitive resistors (FSRs) are the typical methods used for contact gesture recognition based on muscle activities. The sensors, however, are generally too sensitive to environmental disturbances such as electrical noises, electromagnetic signals and so on. In this paper, we propose a novel contact gesture recognition method based on Flexible Epidermal Tactile Sensor Array (FETSA) that is used to measure electrical signals according to movements of the wrist. To recognize gestures using FETSA, we extracted feature sets, and the gestures were subsequently classified using the support vector machine. The performance of the proposed gesture recognition method is very promising in comparison with two previous non-contact and contact gesture recognition studies.

• 한국생산제조학회지
• /
• 제22권4호
• /
• pp.652-657
• /
• 2013

In this study, we developed a counting method for non-contact ID cards using an optical fiber displacement sensor instead of the traditionally used friction counting method. The proposed method has the advantage of high speed and automated measurement. For counting non-contact ID cards, an H-type optical fiber sensor, jig part, and counting program are developed separately to build the system and adjust it. Through the experimental test results, it was confirmed that counting is possible with one type of international ID card and one type of financial security card based on ISO7810. Furthermore, by applying the proposed method to 100 ID cards 100 times repeatedly, it was confirmed that it has high accuracy and an error ratio of 0%. We experimentally demonstrated that the proposed counting method for non-contact ID cards using an optical fiber displacement sensor can perform measurements with high accuracy and high speed.