• Title/Summary/Keyword: accelerated motion

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Mechanisms of microparticle propulsion by laser ablation

  • Gojani, A.B.;Menezes, V.;Yoh, J.J.;Takayama, K.
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.03a
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    • pp.837-841
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    • 2008
  • Propulsion of gene coated micro-particles is desired for non-intrusive drug delivery inside biological tissue. This has been achieved by the development of a device that uses high power laser pulses. The present paper looks at the mechanisms of micro-particle acceleration. Initially, a high power laser pulse is focused onto the front side of a thin aluminium foil leading to its ablation. The ablation front drives a compression wave inside the foil, thus leading to the formation of a shock wave, which will later reflect from the rear side of the foil, due to acoustic impedance mismatch. The reflected wave will induce an opposite motion of the foil, characterized by a very high speed, of the order of several millimeters per microsecond. Micro-particles, which are deposited on the rear side of the foil, thus get accelerated and ejected as micro-projectiles and are able to penetrate several hundreds of micrometers inside tissue-like material. These processes have been observed experimentally by using high-speed shadowgraphy and considered analytically.

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Effects of Temperature on Tribological Properties of Polymer Material (온도 조건에 따른 폴리머 소재의 트라이볼로지 특성 연구)

  • Chi-Yoon An;Dae-Eun Kim
    • Tribology and Lubricants
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    • v.39 no.6
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    • pp.262-267
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    • 2023
  • Research to replace metal mechanical elements with polymer materials has recently accelerated. However, polymers exhibit less favorable mechanical properties than metal materials, and are often easily worn-out owing to frictional heat when their mechanical elements contact while in relative motion. Therefore, research on the polymer tribological properties is required to employ polymer materials in mechanical elements operating under harsh conditions. In this study, we examine the effect of mechanical part operating temperatures on the material friction and wear characteristics of polymer materials. We conduct ball-on-disk friction tests under dry conditions at various temperatures, using a metal ball with high hardness and a polymer as the counter surface. Each test is repeated at least three times to ensure the reliability of the test results. Before the friction test, we analyze the surface hardness and roughness of each polymer specimen; after the friction test, we use a three-dimensional confocal microscope to compare and analyze the polymer specimen wear characteristics. Based on this study, we systematically elucidate the polymer material tribological characteristics. This information should be useful for selecting and utilizing polymer materials at various temperatures.

The study on metareality expressed in digital fashion film (디지털 패션필름에 표현된 메타리얼리티)

  • Kim, Sejin;Ha, Jisoo
    • The Research Journal of the Costume Culture
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    • v.23 no.4
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    • pp.554-568
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    • 2015
  • Technological change leads to a value shift in human society. Various cultural experiences through the digital paradigm influence the expression of fashion. This article considers fashion film as a new form for presenting fashion and explores the distinctiveness of expression in digital fashion film. For the methodology, a literature review was conducted to examine the concepts and features of digital fashion film and metareality. Empirical research was also performed by drawing from Nick Knight's digital films, "Sans Couture", "#asif", and "The Elegant Universe" and by specifically analyzing the classification of the themes, visuals, and auditory expression. The results are as follows. The proliferation of fashion film has accelerated in the internet environment. New media in the digital era allows images to become more realistic and variable through immaterial conversion. Metareality is the notion of a reality beyond existence. A metarealistic image maintains the metaphysical nature of an object and transcends empirical appearance. It possesses immaterial, transboundary, and multidimensional features, and the image is realized by digital technology. The expression analysis identifies the metareality expressed in contemporary fashion film appearing as atypical forms, irrational combinations, and the playfulness of motion. It shows a positive attitude, transcending the immaterial limit of reality toward fashion. This study indicates how fashion as products challenges the metaphysical transformation in the digital era. The exploration of metareality in digital fashion film promotes a wider perspective and understanding of the concept of fashion.

Finite Element Analysis of a Newly Designed Screw Type Fixture for an Artificial Intervertebral Disc (새로운 방식의 나사형 인공디스크 고정체 해석)

  • Lim, Jong-Wan;Yang, Hyun-Ik
    • Journal of Biomedical Engineering Research
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    • v.31 no.1
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    • pp.56-66
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    • 2010
  • The various total replacement artificial discs have developed because spinal fusion has shown a lesser mobility of an operated segment and an accelerated degeneration at adjacent discs. But almost artificial discs have not yet been reached on the substitute surgery of fusion because many problems such as those clinical success rates were not more than them of fusion have not solved. In this paper, vertically inserted assemble-screw fixture in vertebrae was proposed to improve the fixed capability of artificial disc. And also, to evaluate the design suitability of newly designed screw-type, including fixtures of commercial discs such as wedge and plate type, the 1/4 finite element model with a vertebra and various implanted fixtures were generated, and next, 3 bending motions such as flexion, bending and twisting under the moment of 10Nm and compression under the force of 1000N were considered, respectively and finally, FE analyses were performed. Results of three fixture types were compared, such as Range of Motion and maximal stress, and so on. For ROM, the screw type was average 58% less than the wedge type and was average 42% less than the plate type under all loading conditions. For average stress ratio at closer nodes between vertebra and each fixture, the wedge type was the lowest as minimum 0.02 in twisting, screw types were the highest as maximum 0.28 in compression. As the results of using cement material, it was predicted that the instability problem of the wedge type was better solved. The screw type which could be increased by implanting depth according to the number of assembling mid screws, showed that the decreased tendency of ROMs and maximal cancellous bone stresses. In further study, controlling the number of assembling screws that was suitable for a patient's bone quality, development of surgical tools and keeping on design supplementations, which will be able to develop the competitive artificial disc.

The Effect of Balance Control and Vestibular Function by an Aquatic Rotation Control and the Obstacle Avoidance Underwater with Hemiplegia Patients (수중에서 회전조절과 장애물 훈련이 편마비 환자의 전정기능과 균형조절에 미치는 영향)

  • Kwon, Hye-Min;Kim, Su-Hyun;Kim, Hyun-Jin;Oh, Seok;Choi, Ji-Ho;Kim, Tae-Youl
    • Journal of the Korean Academy of Clinical Electrophysiology
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    • v.8 no.1
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    • pp.43-50
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    • 2010
  • Purpose : The objective of this study is to effect of an aquatic rotation control and obstacle avoidance when conducted underwater on hemiplegia patient's balance ability and vestibular function. Methods : Twelve hemiplegia patients participated and were randomly assigned to a control group(I) with standard physical therapy and an aquatic group(II) with an aquatic rotation control, obstacle avoidance and standard physical therapy as well. The aquatic group trained using a Halliwick rotation control and obstacle avoidance through 3 times per week over 6 weeks. For all subjects, vestibular function, their balance, the change of electrooculogram (EOG), the change of accelerometer axis and torsiometer according to visual sense, vestibular sense with galvanic vestibular stimulation (GVS) or not during leg close stance were measured. Results : The EOG in the vertical and horizontal (p<0.05) were both significantly lowered. The change was significantly lower in the trajectory range of motion of trunk and spine with torsiometer when leg close stand (p<0.01) and leg close stand with GVS (p<0.01). The centre of gravity accelerated, there were reduced significantly difference X and Y axis of accelerometer during the closing of the leg without vision (p<0.05). There were reduced significantly difference X and Z axis of accelerometer during the closing of the leg with GVS (p<0.05). There were reduced significantly difference X and Z axis of accelerometer during the closing of the leg and close eyes with GVS (p<0.05). Conclusion : The balance ability, vestibular system and postural control is improved.

Comparison of retention characteristics of ferroelectric capacitors with $Pb(Zr, Ti)O_3$ films deposited by various methods for high-density non-volatile memory.

  • Sangmin Shin;Mirko Hofmann;Lee, Yong-Kyun;Koo, June-Mo;Cho, Choong-Rae;Lee, June-Key;Park, Youngsoo;Lee, Kyu-Mann;Song, Yoon-Jong
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.3 no.3
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    • pp.132-138
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    • 2003
  • We investigated the polarization retention characteristics of ferroelectric capacitors with $Pb(Zr,Ti)O_3$ (PZT) thin films which were fabricated by different deposition methods. In thermally-accelerated retention tests, PZT films which were prepared by a chemical solution deposition (CSD) method showed rapid decay of retained polarization charges as the thickness of the films decreased down to 100 nm, while the films which were grown by metal organic chemical vapor deposition (MOCVD) retained relatively large non-volatile charges at the corresponding thickness. We concluded that in the CSD-grown films, the thicker interfacial passive layer compared with the MOCVD-grown films had an unfavorable effect on retention behavior. We observed the existence of such interfacial layers by extrapolation of the total capacitance with thickness of the films and the capacitance of these layers was larger in MOCVD-grown films than in CSD-grown films. Due to incomplete compensation of surface polarization charges by the free charges in the metal electrodes, the interfacial field activated the space charges inside the interfacial layers and deposited them at the boundary between the ferroelectric layer and the interfacial layer. Such space charges built up an internal field inside the films, which interfered with domain wall motion, so that retention property at last became degraded. We observed less imprint which was a result of less internal field in MOCVD-grown films while large imprint was observed in CSD-grown films.

Multi GPU Based Image Registration for Cerebrovascular Extraction and Interactive Visualization (뇌혈관 추출과 대화형 가시화를 위한 다중 GPU기반 영상정합)

  • Park, Seong-Jin;Shin, Yeong-Gil
    • Journal of KIISE:Computing Practices and Letters
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    • v.15 no.6
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    • pp.445-449
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    • 2009
  • In this paper, we propose a computationally efficient multi GPU accelerated image registration technique to correct the motion difference between the pre-contrast CT image and post-contrast CTA image. Our method consists of two steps: multi GPU based image registration and a cerebrovascular visualization. At first, it computes a similarity measure considering the parallelism between both GPUs as well as the parallelism inside GPU for performing the voxel-based registration. Then, it subtracts a CT image transformed by optimal transformation matrix from CTA image, and visualizes the subtracted volume using GPU based volume rendering technique. In this paper, we compare our proposed method with existing methods using 5 pairs of pre-contrast brain CT image and post-contrast brain CTA image in order to prove the superiority of our method in regard to visual quality and computational time. Experimental results show that our method well visualizes a brain vessel, so it well diagnose a vessel disease. Our multi GPU based approach is 11.6 times faster than CPU based approach and 1.4 times faster than single GPU based approach for total processing.

Improving Evaluation of the Basket-to-Handstand Mount by a Technical Training Program on Parallel Bars (평행봉 Basket to Handstand 기술 훈련 프로그램 적용을 통한 향상도 평가)

  • Lee, Chong-Hoon;Back, Jin-Ho
    • Korean Journal of Applied Biomechanics
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    • v.19 no.4
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    • pp.719-728
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    • 2009
  • In this study, a training program was conducted to improve the performance of the basic movement of the basket-to-handstand mount. After completion of the training program, the kinematic comparison of the before and after effects were investigated to provide scientific data about this technique. It is recommended that during P1, the center of body mass at the back should push the hip joint to flex quickly, and the shoulder joint should be maintained at a maximum angle. During P2, the body's center of mass must be accelerated so as to create enough momentum to rise efficiently for this, quick extension of both the hip and the shoulder is required. For safety during P3, it is advised that the speed upwards must be increased and that the hands, shoulders, and hip joint must be extended, as in the posture of a handstand. These results stress to coaches the importance of the bodies speed during the ascent in the motion.

A Kinetics Analysis of Forward 11/2 Somersault on the Platform Diving (플랫폼 다이빙 앞으로 서서 앞으로 11/2회전 동작의 운동역학적 분석)

  • Jeon, Kyoung-Kyu
    • Korean Journal of Applied Biomechanics
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    • v.23 no.3
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    • pp.209-218
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    • 2013
  • This study was to perform the kinetic analysis of forward $1\frac{1}{2}$ somersault on the platform diving. Six men's diving players of the Korea national reserve athletes participated in this study. The variables were analyzed response time, velocity, center of mass (COM), angle, center of pressure (COP) and ground reaction force (GRF) of motion. For measure and analysis of this study, used to synchronized to 4 camcorder and 1 force plate, used to the Kwon3D XP (Ver. 4.0, Visol, Korea) and Kwon GRF (Ver. 2.0, Visol, Korea) for analyzed of variables. The results were as follows; Time factor were observed in maximum knee flexion depending on the extent of use at phase 1 of take-off to execute the somersault. This enabled the subject to secure the highest possible body position in space at the moment of jumping to execute the somersault and prepare for the entry into the water with more ease. Regarding the displacement of COM, all subjects showed rightward movement in the lateral displacement during technical execution. Changes in forward and downward movements were observed in the horizontal and vertical displacements, respectively. In terms of angular shift, the shoulder joint angle tended to decrease on average, and the elbow joints showed gradually increasing angles. This finding can be explained by the shift of the coordinate points of body segments around the rotational axis in order to execute the half-bending movement that can be implemented by pulling the lower limb segments toward the trunk using the upper limb segments. The hip joint angles gradually decreased; this accelerated the rotational movement by narrowing the distance to the trunk. Movement-specific shifts in the COP occurred in the front of and vertical directions. Regarding the changes in GRF, which is influenced by the strong compressive load exerted by the supporting feet, efficient aerial movements were executed through a vertical jump, with no energy lost to the lateral GRF.

Study on a Fully Electrified Car Ferry Design Powered by Removable Battery Systems Considering Domestic Coastal Environment

  • Hong, Jang Pyo;Kim, Young-Shik;Shim, Hyung-Won;Kang, Hee-Jin;Kim, YunHo;Kim, Gyu Bum;Cho, Seongpil
    • Journal of Ocean Engineering and Technology
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    • v.35 no.1
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    • pp.1-12
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    • 2021
  • As increasing the international community's awareness of greenhouse gas reduction, the demand for eco-friendly ship fuel has accelerated recently. The fundamental aim of this study is to develop a new type of fully electrified ferry for passengers and cars considering Korean domestic coastal environmental conditions. Several technical difficulties are encountered in applying a fully electric propulsion system based on removable battery systems into a ship due to limitations imposed by the batteries' size and capacity. This paper reviews and analyzes marine environment regulations strengthened recently, technology trends related to fully electric propulsion vessels in each country, and Korean domestic coastal environments. We propose a new fully electrified car ferry design with a displacement of 400 t applied in Korea. It is powered by removable battery systems pre-charged in a safe inland charging station. The mobile battery system is developed to enable roll-on and roll-off using wheels. The characteristics of the ship motion are analyzed based on the weight and location of the battery systems. We expect our battery systems to be applicable to larger ships in the future.