135 research outputs found
Analysis of Electrode Configuration of Underwater Electric Field Sensor on Electric-Field-based Localization for Underwater Robots
No full textThis paper addresses the effects of electrode configurations of an underwater electric field sensor (EFS) on the localization of underwater robots when the robots used electric field measurements to estimate their positions. Around an underwater electric landmark that generates a known electric field signature, an underwater robot equipped with an EFS can measure the signature to localize itself by searching for the position that minimizes the difference between the actual measurement and the theoretical calculation that should be measured when the robot is located at the position. The underwater robot's localization accuracy was analyzed in simulations when the robot was equipped with EFSs with different electrode configurations. In general, the electric field measurement accuracy and the consequent robot localization accuracy were higher when the robot was equipped with the EFS that consists of more electrodes. Depending on the measurement conditions, however, the use EFSs with less electrodes was enough to perform sufficiently accurate localization of the robot. The proposed simulation method would contribute to suggest the optimal electrode configuration of the EFS, and therefore, the robot localization with the electric field measurements would become more energy-efficient with the use of the suggested cheap and small EFS.1
Analysis of Electrode Configuration for Underwater Robot’s Navigation Utilizing Underwater Electric Field Sensor
No full textWe studied effects of electrode configurations of underwater electric field sensors (EFS) on the electro-localization accuracy of underwater robots. An underwater robot equipped with an EFS measures 3-D electric field that is induced by an electric landmark; the electric landmark generates predefined electric field signatures around itself. The paths of the underwater robot are predicted by comparing the measured electric field signatures and their theoretical calculations at the same measurement conditions. In this study, computer simulations were conducted in which an underwater robot measured electric field signatures with EFSs of different electrode configurations and performed its localization with the measurements. The results show that if the underwater robot is sufficiently close to the electric landmark, the localization accuracy when using the EFS with less number of electrodes is similar to that when using the EFS with more number of electrodes. The results would contribute to suggest the use of smaller and cheaper EFSs for navigation of underwater robots according to the robots’ exploration range and other measurement conditions.2
Feasibility test of underwater robot's navigation by using underwater electric field sensor
No full textWe propose a method to localize underwater robots by using an underwater electric field sensor (EFS) that measures underwater electric field signals. The EFS is installed at an underwater robot and measured the three-dimensional electric field signals generated by an underwater electric landmark. The position of the underwater robot is predicted by comparing the measured electric field signals and the theoretical calculations at the same measurement conditions. The optimal position of the underwater robot was predicted by using the particle swarm optimization that minimized the difference between the measurements and the theoretical calculations. The proposed method was tested in computer simulations and the positions of the underwater robot could be predicted. The proposed method would be useful for underwater robots to serve various missions, such as underwater exploration and object detection.2
Axis Calibration Method of Underwater Electric Field Measurement Sensor for Underwater Robot
No full textThis paper proposes a method to calibrate axis misalignment of underwater electric field sensors (EFS) for accurate electric signal measurements of underwater robots. An EFS measured a known electric field and the measured values were compared to their theoretical values to approximate the axis misalignment of the sensor. The approximation was optimized by using the Levenberg's optimization algorithm. The optimization algorithm searched for the axis misalignment of the EFS that minimized the difference between the measured values and the theoretical values. After the optimization, the measurements with the EFS could be calibrated. The proposed method was tested in computer simulations. The results show that the proposed method could approximate the axis misalignment of the EFS and calibrate the measured electric fields. The calibration reduced the localization errors of an underwater robot when the robot electro localized its position by using electric field signals generated by an electric landmark. The proposed method would contribute to various applications that require accurate measurements of underwater electric signals, such as electro localization of underwater robots and detection of electric objects underwater.2
Machine-Learning Based Automatic and Real-time Detection of Mouse Scratching Behaviors
No full textScratching is a main behavioral response accompanied by acute and chronic itch conditions, and has been quantified as an objective correlate to assess itch in studies using laboratory animals. Scratching has been counted mostly by human annotators, which is a time-consuming and laborious process. It has been attempted to develop automated scoring methods using various strategies, but they often require specialized equipment, costly software, or implantation of device which may disturb animal behaviors. To complement limitations of those methods, we have adapted machine learning-based strategy to develop a novel automated and real-time method detecting mouse scratching from experimental movies captured using monochrome cameras such as a webcam. Scratching is identified by characteristic changes in pixels, body position, and body size by frame as well as the size of body. To build a training model, a novel two-step J48 decision tree-inducing algorithm along with a C4.5 post-pruning algorithm was applied to three 30-min video recordings in which a mouse exhibits scratching following an intradermal injection of a pruritogen, and the resultant frames were then used for the next round of training. The trained method exhibited, on average, a sensitivity and specificity of 95.19% and 92.96%, respectively, in a performance test with five new recordings. This result suggests that it can be used as a non-invasive, automated and objective tool to measure mouse scratching from video recordings captured in general experimental settings, permitting rapid and accurate analysis of scratching for preclinical studies and high throughput drug screening. © 2019 Experimental Neurobiology.1
ClaimDiff: Comparing and Contrasting Claims on Contentious Issues
No full textWith the growing importance of detecting misinformation, many studies have focused on verifying factual claims by retrieving evidence. However, canonical fact verification tasks do not apply to catching subtle differences in factually consistent claims, which might still bias the readers, especially on contentious political or economic issues. Our underlying assumption is that among the trusted sources, one's argument is not necessarily more true than the other, requiring comparison rather than verification. In this study, we propose ClaimDiff, a novel dataset that primarily focuses on comparing the nuance between claim pairs. In ClaimDiff, we provide 2,941 annotated claim pairs from 268 news articles. We observe that while humans are capable of detecting the nuances between claims, strong baselines struggle to detect them, showing over a 19% absolute gap with the humans. We hope this initial study could help readers to gain an unbiased grasp of contentious issues through machine-aided comparison
액체-액체 핀틀 분사기에서의 형상 변화에 따른 수류 특성 연구
Get PDF학위논문(박사) -- 서울대학교대학원 : 공과대학 항공우주공학과, 2024. 2. 윤영빈.The private launch market is experiencing rapid growth, keeping pace with the fast-expanding space tourism and exploration market. This growth in the commercial sector has made the reduction of launch costs a significant issue. Launch costs include development costs and operating costs, and since it is difficult to reduce development costs, the most efficient method is to reduce operating costs. Therefore, it is reasonable to reduce operating costs by reusing launch vehicles. The most common method for reusing launch vehicles is to control the thrust by controlling the spray flow rate of the propellant, and the method of controlling the injection area of the orifice for the propellant is known to be the most effective. The pintle injector, which is a representative system for the injection area control method, is effective for combustion instability and the its simple structure, which is effective for weight reduction. However, compared to the traditional injector shape, the swirl coaxial injector or the shear coaxial injector, research related to the pintle injector is relatively unknown, so research on the pintle injector is required to match the changes in the market.
Studies on pintle injectors are primarily categorized into research on cold flow and combustion characteristics. However, the most of recent studies focus on injectors that use liquid-gas propellants, and research on liquid-liquid pintle injectors is not conducted actively. Thus, the spray characteristics of variously geometry pintle injectors were analyzed by altering the spray conditions as part of a parametric study in this research.
First, the breakup modes were classified based on the spray patterns to comprehend the spray characteristics of the pintle injector. These modes can be divided into hollow cone, fishbone, and branch shapes. Each breakup process was chronologically measured using a high-speed camera and 2P-SLIPI image images, and the breakup characteristics was analyzed. A schematic was presented to understand the instantaneous breakup mechanism, and it was found that perforation, impact force, and shear force were the main factors influencing the breakup. It was observed that the breakup characteristics distinctly varied in each mode. Specifically, in Mode #2, dynamic characteristics such as breakup frequency, breakup length, breakup location, and peak height were strongly influenced by radial flow. Conversely, these unstable phenomena were able to be reduced when the flow rate of the Annular flow increased.
Second, the continuous type pintle, called plain orifice type, shows the unstable spray shape, therefore it can be expected that the research on another configuration, such as discrete orifice, is necessary. Meanwhile, a pintle is exposed to high temperature environments, and various methods are applied for cooling. In this study, an internal structure called an insert was added to form a forced flow path for cooling, and the characteristics according to the area ratio of the insert were analyzed experimentally and analytically. As the central area of the insert increases, the flow rate of the internal flow increases, and the spray direction of the radial flow also changes to upward flow. As a result, a recirculation zone occurs beneath the insert inside the pintle, and the cooling performance changes as the flow is anchored to the bottom surface by recirculation zone. In addition, to overcome the limitations associated with the addition of inserts, the area ratio of the orifice in the pintle post was varied to analyze the characteristics.
Finally, the plain orifice type injectors and discrete orifice type injectors are commonly used, but it is not known which injector is more efficient during the throttling process. Therefore, in the process of adjusting the injection area consistent, the spray patterns of plain orifice, single row orifice, and double row orifice type injectors were compared and reconstructed using the 2P-SLIPI technique. On the side of the spray angle, the tendency of spray angle changes of plain orifice type and discrete orifice type injectors is different depending on the controlling the throttling level. In particular, it was found that the change in spray angle is small when the discrete orifice type injector controls the throttling level. In addition, by understanding the spray structure according to the spray conditions and understanding the uniformity of the spray, the discrete orifice type injector shows relatively efficient characteristics than plain orifice type.최근 우주 여행과 우주 탐사 시장이 급속도로 성장하면서, 민간 발사시장도 함께 빠른 속도로 성장하고 있다. 이러한 민간시장의 성장에 따라 발사 비용을 줄이는 것이 중요한 이슈가 되고 있다. 발사 비용에는 개발 비용 및 운용 비용이 포함되며, 개발 비용을 저감 시키기는 어렵기 때문에 운용 비용을 절감하는 방식이 가장 효율적인 방법이라고 할 수 있다. 따라서 발사체를 재사용하여 운용 비용을 절감하는 방식이 합리적이다. 발사체의 재사용을 위해서는 추진제의 분사 유량 조절을 통해 추력을 조절하는 방식이 가장 일반적이며, 그 중에서도 추진제의 오리피스의 분사 면적을 제어하는 방식이 가장 효과적인 것으로 알려져 있다. 면적 조절 방식의 대표적 시스템인 핀틀 분사기는 연소불안정성에 효과적이며, 구조가 단순하여 중량절감에 효과적이다. 그러나 핀틀 분사기와 관련된 연구는 전통적인 분사기 형상인 스월 동축형 분사기 또는 전단 동축형 분사기에 비해 상대적으로 알려진 바가 거의 없기 때문에 시장의 변화에 맞추어 핀틀 분사기에 대한 연구가 필요하다.
핀틀 분사기에 관한 연구는 주로 수류 분사 성능 및 연소 성능에 대한 연구로 분류된다. 하지만 핀틀 분사기는 액체-기체 추진제를 사용하는 분사기에 대한 연구가 가장 많이 이뤄지고 있으며, 액체-액체 핀틀 분사기에 대한 연구는 상대적으로 부족한 실정이다. 따라서 본 연구에서는 매개변수적 연구의 일환으로 핀틀 분사기의 분사조건에서 다양한 형상을 변화시켜가며 수류 특성을 분석하였다.
우선 핀틀 분사기의 분사 특성을 이해하기 위해, 분무 형상에 따라 분열 모드를 분류하였다. 분열 모드는 hollow cone, fishbone, 그리고 branch 형상으로 구분된다. 각 분열 과정은 초고속 카메라와 2P-SLIPI 이미지를 사용하여 시간 순서대로 나열하고 미립화 성능을 분석하였다. 또한, 순간적인 분열 메커니즘을 이해하기 위해 도식도를 제시하였으며, 분열에 영향을 주는 주요 원인으로는 각각 천공, 충돌력 그리고 전단력으로 확인되었다. 각 모드에서 분열 특성이 명확하게 차이가 나타난다. 특히 Mode #2에서는 분열주파수, 분열 길이, 분열 위치, 최대점의 높이 등과 같은 동적 특성이 반경방향 유동에 의해 강하게 나타나는 것을 확인하였다. 한편, 축방향 유동의 유속이 증가하면 이러한 불안정한 현상들이 저감되는 것을 확인하였다.
앞서 확인한 연속형 핀틀 분사기에서는 불안정한 현상들이 확인되므로 다른 형상에 대한 연구가 필요하다고 할 수 있다. 실제 상황에서 핀틀이 고온 환경에 노출되며 냉각을 위해 다양한 방법이 적용되고 있다. 본 연구에서는 내부 구조물인 인서트를 추가하여 강제 유로를 형성하는 방법을 적용하였으며, 불연속형 핀틀에서 인서트의 면적비에 따라 특성을 실험적, 해석적으로 분석하였다. 인서트의 중심 면적이 증가함에 따라 내부 유동의 유속이 증가하고, 반경방향 유동의 분사 방향도 상승 유동으로 변화하게 된다. 이로 인해 핀틀 내부의 인서트 하류에 재순환 영역이 발생하고, 유동이 바닥면에 고정되면서 냉각 성능이 변화한다. 또한, 인서트 추가에 따른 한계점을 극복하기 위해, 핀틀 포스트 구멍의 면적비를 변화시켜 특성을 분석하였다. 이 연구의 결과는 앞으로 재사용 가능한 핀틀 분사기의 냉각 유로 설계에 도움이 될 것으로 예상된다.
연속형 분사기와 불연속형 분사기는 일반적으로 알려진 형상이지만, 추력조절 과정에서 어떤 분사기가 더 효율적인지는 아직 알려져 있지 않다. 따라서 분사 면적을 동일하게 조절하는 과정에서 연속형, 1열 불연속형, 그리고 2열 불연속형 핀틀 분사기의 분무 패턴을 분석하고 2P-SLIPI 기법을 적용하여 재구성하였다. 분무각 측면에서는 추력 수준을 조절함에 따라 연속형과 불연속형 분사기의 분무각 변화 경향성이 다르게 나타나는 것을 확인하였다. 특히, 불연속형 분사기가 추력 수준을 조절하는 과정에서는 분무각의 변화폭이 작게 나타났다. 또한 분사조건에 따른 분사기에서의 분무 구조를 파악하고 분무의 균일도를 파악한 결과, 2열 불연속형 분사기가 상대적으로 효율적인 특성을 보이는 것을 확인하였다.Abstract i
List iv
List of figures vii
List of tables xi
Nomenclature xii
Chapter 1 Introduction 1
Chapter 2 Experiment and measurement systems 8
2.1 Hardware setup 8
2.1.1 Instantaneous spray imaging 8
2.1.2 High speed imaging 9
2.1.3 Two Phase Structured Laser Induced Planar Imaging (2P-SLIPI) 10
2.1.4 Droplet sizing 11
2.2 Image processing method 13
2.2.1 Spray angle analysis 13
2.2.2 Structured Laser Illumination Planar Imaging analysis 14
2.2.3 Droplet size analysis 15
Chapter 3 Spray characteristics of plain orifice type pintle injectors 16
3.1 Background and objectives 16
3.2 Experimental setup and conditions 19
3.2.1 Injector design and test condition 19
3.2.2 Image processing method 20
3.3 Result and conclusion 22
3.3.1 Breakup mode classification of the liquid-liquid pintle 22
3.3.2 Breakup process of the liquid-liquid pintle 26
3.3.2 Periodic characteristics in breakup characteristics 30
3.4 Conclusion 40
Chapter 4 Cold flow characteristics of double row orifice type pintle with various flow passage 41
4.1 Background and objectives 41
4.2 Experimental setup and conditions 44
4.2.1 Injector design and test conditions 44
4.2.2 Numerical analysis conditions 47
4.3 Result and conclusion 49
4.3.1 Spray angle patterns and angle variations 49
4.3.2 Droplet size distribution 57
4.3.3 Effect of insert on cooling characteristics 63
4.4 Conclusion 69
Chapter 5 Comparison between plain orifice and discrete orifice type pintle injector in accordance with throttling process 71
5.1 Background and objectives 71
5.2 Experimental setup and conditions 73
5.2.1 Operating conditions 73
5.2.2 Injector configuration. 75
5.2.3 Spray structure measurement 77
5.3 Result and conclusion 79
5.3.1 Instantaneous images with various conditions 79
5.3.2 3D spray structure 84
5.3.3 Spray uniformity analysis 92
5.4 Conclusion 97
Chapter 6 Summary 99
References 101
Abstract in Korean 110박
Incantation Practice of Korean New Religions: Focused on Jeungsan groups and Eastern Learning groups
No full text본 논문은 한국 신종교 가운데 동학계와 증산계 신종교의 종교적 실천을 연구 주제로 삼고 있다. 이 신종교들은 모두 주문을 반복적으로 염송하는 것 즉 주문 수행을 종교적 수행의 중심으로 하고 있다. 그러한 원인은 주문이 동학계와 증산계 신종교의 교조인 수운 최제우와 증산 강일순의 종교적 체험 또는 교설과 관련이 깊기 때문이다. 본고에서는 동학계 신종교로 천도교, 천진교, 수운교를 다루었다. 천도교는 수운 -> 해월 -> 의암으로 이어지는 정통성을 주장하며, 수운의 가르침을 계승하여 21자주를 송독하는 것을 의례의 핵심으로 삼고 있다. 천진교는 수운 -> 해월 -> 구암으로 이어지는 정통성을 주장하며 21자의 송독과 영부수행을 종교적 실천으로 행하고 있다. 수운교는 해월의 정통성을 부정하며 이상룡이 수운의 환생이라고 여기고 있다. 수운교는 21자주 외에 불교식 주문과 염불을 통해서 수행을 하고 있다. 증산계 신종교의 많은 분파 가운데 본 논문에서는 증산교본부, 증산법종교, 대순진리회를 연구 대상으로 하였다. 증산교본부는 초기 증산사상의 확산에 중요한 역할을 하였던 이상호, 이정립에 의해 설립된 단체로 증산의 언설을 계승하여 태을주 염송을 중시하였다. 증산법종교는 증산의 여식인 강순임에 의해 창설되었으며, 태을주 수련과 함께 불교식 주문과 염불을 겸하여 수행한다. 증산계 최대 교단인 대순진리회는 조정산으로 이어지는 정통성을 주장하며 수련, 기도 시 주문을 염송하며 공부를 통해서 특별한 수행을 실시하고 있다. 이 신종교들이 각기 다른 정통성과 교리를 주장하며 그 차별성을 보이고 있지만, 주문 수행이라는 공통된 종교적 실천을 실행하고 있다. 사용하는 주문과 방식도 변이가 발생하였지만 일상의례, 정기의례, 특별 수련 등이 주문을 중심으로 실천되고 있다는 공통적 특성이 나타나고 있다.This thesis focuses on the religious practices of Jeungsan groups and Eastern Learning groups among Korean new religions. All of these new religions have been doing incantation practice as their central religious practice. The reason is that the incantations are deeply related to the religious experience or the teaching of the founders. In this thesis, I researched Chundogyo, Chunjingyo and Suungyo among Eastern Learning groups. Chundogyo insists on the legitimacy that is passed down from Suun to Haewol and to Uiam. And Chundogyo follows Suun`s teaching and takes the reciting 21-letter-incantation as the main religious practice. Chunjingyo claims that the legitimacy is from Suun to Haewol and to Guam and recites 21-letter-incantation while drawing spiritual charm called Yongbu as the religious practice. Suungyo denies the legitimacy of Haewol and claims that Lee Sangryong is the reincarnation of Suun. Suungyo recites 21-letter-incantation and chants a Buddhist prayer and mantra as the main religious practice. I studied Jeungsangyobonbu, Jeungsanbubjonggyo and Daesoonjinrihoe among Jeungsan groups. Jeungsangyobonbu was founded by Lee Sangho and Lee Junglip who played a key role of disseminating Jeungsan`s thought. It puts emphasis on reciting Taeulju as religious practice following Jeungsan`s word. Jeungsanbubjonggyo was founded by Kang Sunim who is the only daughter of Jeungsan. This organization recites Taeulju and does a Buddhist prayer as religious ritual and practice. Daesoon Jinrihoe is the biggest organization among Jeungsan groups and insists the legitimacy of Jo Jeongsan. And Daesoon Jinrihoe also lays emphasis on reciting Taeulju and formulates practice, prayer and special practice. These religious organizations insist their legitimacy respectively and spread their own doctrine differently. But they do incantation practice as religious activity in common. Recited incantations and the way of reciting are different among these organizations. But it is common characteristics that ordinary ritual, regular ritual and special practice are conducted mainly through reciting incantations
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K-pop in Korea: How the Pop Music Industry is Changing a Post-Developmental Society
Get PDFKorean popular songs, or kayo, are evolving from a musical genre created and performed only by Koreans into K-pop, a global musical genre produced and enjoyed by Koreans and those of other nationalities. This new development has revolutionized the perception of the popular music industry in Korea’s post-developmental society, as Korean children dream of becoming K-pop idols rather than entering traditionally esteemed careers in politics, medicine, or academia. The Korean government is also actively promoting Hallyu and K-pop, as though they constitute new export industries that could feed the entire nation in the twenty-first century. While the K-pop revolution has a lot to do with YouTube and other digital means of distributing music on a global scale, Korean television stations are now eager to tap into the booming market by showcasing live K-pop auditions in order to circumvent declining television loyalty among K-pop fans, who prefer watching music videos on YouTube. K-pop in Korea therefore illustrates three important aspects of social change: changes in social perceptions of the popular music industry, massive government support, and television stations actively recruiting new K-pop stars. All three aspects of social change reinforce one another and fuel the aspirations of young Koreans to become the next K-pop idols. Keywords: South Korea, pop culture, K-pop, social change, mass media Links to YouTube videos referenced in this article: Lee Mi-Ja's "Tongbaek Agassi" (1964) Shin Joong-Hyun’s "Miin" (1974
Electrophoresis Characterization of Nanoplastic Particle Surface Charge in Dilute Aqueous Electrolytes
No full textThis is the accepted version of the following article: Lin, Jui-Yen, Ingyu Lee, Cuijuan Feng, Hyunook Kim, and Chin-Pao Huang. “Electrophoresis Characterization of Nanoplastic Particle Surface Charge in Dilute Aqueous Electrolytes.” Environmental Engineering Science, July 8, 2024. https://doi.org/10.1089/ees.2024.0076, which has now been formally published in final form at Environmental Engineering Science at https://doi.org/10.1089/ees.2024.0076. This original submission version of the article may be used for non-commercial purposes in accordance with the Mary Ann Liebert, Inc., publishers’ self-archiving terms and conditions. © 2024, Mary Ann Liebert, Inc., publishers.Aggregation, adsorption, and biofilm formation are involved in the fate and transport of nanoplastics in the aquatic environment. These interfacial processes are closely related to surface charge and electrical double layer (EDL) structure. As it is experimentally difficult to obtain surface potential, laser doppler electrophoresis is currently the most popular technique to measure zeta potential, or the potential at shear plane. However, the determination of zeta potential by laser doppler electrophoresis is not a trivial undertaking. Inaccurate zeta potential values could potentially lead to misleading conclusions. This study aims to present a comprehensive method tailored for nanoplastics to accurately measure zeta potential and convert it to surface charge and potential with classical EDL theory. The effect of particle size and number concentration on zeta potential measurement was investigated using monodisperse polystyrene (PS) latex. An optimal number concentration was between 1010 and 1012 #/L to generate sufficient scattered light with minimal interparticle interaction. Six nanoplastics were synthesized from major polymers to acquire the zeta potential at various pH, including low-density polyethylene, high-density polyethylene, polypropylene, PS, polyvinyl chloride, and polyethylene terephthalate. Based on classical EDL theory, the zeta potential measured at various ionic strength was converted to surface potential, revealing that the shear plane was 0.4 to 2.1 nm away from the surface. Finally, the surface charge density of nanoplastics was acquired, which is essential to describe interfacial processes of nanoplastics in the environment.This work is supported by the National Research Foundation of Korea in a grant funded by the Korea government (MSIT) (No. 2020R1A2C2101347) and the Graduate Program for Plastic-free Society funded by Korea Environmental Industry and Technology Institute. Additional support was provided by the Ministry of Science and Technology, Taiwan, to Jui-Yen Lin, under contract No. MOST-110–2917-I-564-033
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