• Title/Summary/Keyword: bottom tracking

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Performance Experimentation and an Optimal Iterative Coding Algorithm for Underwater Acoustic Communication (수중음향통신에서 최적의 반복부호 알고리즘 및 성능 실험)

  • Park, Gun-Yeol;Lim, Byeong-Su;Jung, Ji-Won
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.16 no.11
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    • pp.2397-2404
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    • 2012
  • Underwater acoustic communication has multipath error because of reflection by sea-level and sea-bottom. The multipath of underwater channel causes signal distortion and error floor. In order to improve the performance, it is necessary to employ an iterative coding scheme. Among the iterative coding scheme, turbo codes and LDPC codes are dominant channel coding schemes in recent. This paper concluded that turbo coding scheme is optimal for underwater communications system in aspect to performance, coded word length, and equalizer combining. Also, decision directed phase recovery was used for correcting phase offset induced by multipath. Based on these algorithms, we confirmed the performance in the environment of oceanic experimentation.

Performance characteristics of a multi-directional underwater CCTV camera system to use in the artificial reef survey (인공어초 조사용 다방향 수중 CCTV 카메라 시스템의 성능 특성)

  • Lee, Dae-Jae
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.47 no.2
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    • pp.146-152
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    • 2011
  • Underwater CCTV camera systems are increasingly replaced the traditional net approach of assessing the species, numbers and aggregation patterns of marine animals distributing around the artificial reefs installed in the inshore fishing grounds, in particular, in relation to the biological investigation of behavior and distribution patterns of target fishes. In relation to these needs, we developed a multi-directional underwater CCTV camera system to use in detecting and tracking marine animals in the artificial reef ground. The marine targets to be investigated were independently tracked by using a camera module toward the bottom and four camera modules installed in the interval of $90^{\circ}$ in horizontal plane and inclination of $45^{\circ}$ in vertical plane of the CCTV system without the overlap of video frames by each camera module. From the results of several field tests at sea, we believe that the developed multi-directional underwater CCTV camera system will contribute to a better understanding in evaluating the effect of artificial reefs installed in the inshore fishing grounds.

Numerical analysis of particle transport in low-pressure, low-temperature plasma environment

  • Kim, Heon Chang
    • Particle and aerosol research
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    • v.5 no.3
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    • pp.123-131
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    • 2009
  • This paper presents simulation results of particle transport in low-pressure, low-temperature plasma environment. The size dependent transport of particles in the plasma is investigated with a two-dimensional simulation tool developed in-house for plasma chamber analysis and design. The plasma model consists of the first two and three moments of the Boltzmann equation for ion and electron fluids respectively, coupled to Poisson's equation for the self-consistent electric field. The particle transport model takes into account all important factors, such as gravitational, electrostatic, ion drag, neutral drag and Brownian forces, affecting the motion of particles in the plasma environment. The particle transport model coupled with both neutral fluid and plasma models is simulated through a Lagrangian approach tracking the individual trajectory of each particle by taking a force balance on the particle. The size dependant trap locations of particles ranging from a few nm to a few ${\mu}m$ are identified in both electropositive and electronegative plasmas. The simulation results show that particles are trapped at locations where the forces acting on them balance. While fine particles tend to be trapped in the bulk, large particles accumulate near bottom sheath boundaries and around material interfaces, such as wafer and electrode edges where a sudden change in electric field occurs. Overall, small particles form a "dome" shape around the center of the plasma reactor and are also trapped in a "ring" near the radial sheath boundaries, while larger particles accumulate only in the "ring". These simulation results are qualitatively in good agreement with experimental observation.

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A Study on Efficient Packet Design for Underwater Acoustic Communication (수중음향통신에서 효율적인 패킷 설계에 관한 연구)

  • Park, Tae-Doo;Jung, Ji-Won
    • Journal of Navigation and Port Research
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    • v.36 no.8
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    • pp.631-635
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    • 2012
  • Underwater acoustic communication has multipath error because of reflection by sea-level and sea-bottom. The multipath of underwater channel causes signal distortion and error floor. In this paper, in order to design an efficient packet structure, we employ channel coding scheme and phase recovery algorithm. For channel coding scheme, half rate LDPC channel coding scheme with N=1944 and K=972 was used. Also, decision directed phase recovery was used for correcting phase offset induced by multipath. Based on these algorithms, we propose length of data for optimal packet structure in the environment of oceanic experimentation.

Designing an Efficient Reward Function for Robot Reinforcement Learning of The Water Bottle Flipping Task (보틀플리핑의 로봇 강화학습을 위한 효과적인 보상 함수의 설계)

  • Yang, Young-Ha;Lee, Sang-Hyeok;Lee, Cheol-Soo
    • The Journal of Korea Robotics Society
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    • v.14 no.2
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    • pp.81-86
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    • 2019
  • Robots are used in various industrial sites, but traditional methods of operating a robot are limited at some kind of tasks. In order for a robot to accomplish a task, it is needed to find and solve accurate formula between a robot and environment and that is complicated work. Accordingly, reinforcement learning of robots is actively studied to overcome this difficulties. This study describes the process and results of learning and solving which applied reinforcement learning. The mission that the robot is going to learn is bottle flipping. Bottle flipping is an activity that involves throwing a plastic bottle in an attempt to land it upright on its bottom. Complexity of movement of liquid in the bottle when it thrown in the air, makes this task difficult to solve in traditional ways. Reinforcement learning process makes it easier. After 3-DOF robotic arm being instructed how to throwing the bottle, the robot find the better motion that make successful with the task. Two reward functions are designed and compared the result of learning. Finite difference method is used to obtain policy gradient. This paper focuses on the process of designing an efficient reward function to improve bottle flipping motion.

Study on Flow Interaction between Bubble and Phase Change Material according to Injection Location (주입 위치에 따른 기포와 상변화물질의 유동 상호 작용에 관한 연구)

  • Min Hyeok Kim;Yun Young Ji;Dong Kee Sohn;Han Seo Ko
    • Journal of the Korean Society of Visualization
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    • v.21 no.3
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    • pp.75-84
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    • 2023
  • In this study, we conducted analysis of bubble dynamics and flow of liquid phase change material(PCM) using shadowgraphy and particle image velocimetry(PIV). Characteristics of internal flow varied depending on locations of injection when solid PCM was liquefied from heated vertical wall. When bubbles rose immediately, they exhibited elliptical shape and zigzag trajectory. In contrast, when bubbles rose after merging at the bottom of solid PCM, with equivalent diameter for the inter-wall distance of 0.64 or greater, they showed a jellyfish shape and strong rocking behavior. It was observed by the PIV that the small ellipse bubbles made most strong flow inside the liquid PCM. Furthermore, the flow velocity was highest in the case of front injection, as the directions of temperature gradients and bubble-driven flow were aligned. The results underscore the significant influence of injection location on various characteristics, including bubble size, shape, rising path of bubbles, and internal flow.

Application of Eye Tracker for Study on the Effect of Analytic Proof Learning of Gifted Students (수학영재 학생들의 분석적 증명 학습 효과 검증을 위한 시선추적기의 활용)

  • Jung, Kyung-Woo;Yun, Jong-Gug;Lee, Kwang Ho
    • Communications of Mathematical Education
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    • v.32 no.3
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    • pp.275-296
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    • 2018
  • The purpose of this study is to investigate the change of gaze and the change of the proof learning achievement after learning the analytic method for proof to mathematical gifted students using eye tracking technique. In order to complete the purpose of this study, a mixed method research was used, that is a combination of quantitative and qualitative research methods. Quantitative analysis was conducted based on the data obtained through the eye tracker, and qualitative analysis was also done using post interview data to make up for the quantitative analysis. The subjects of this study were 8 mathematical gifted 3rd grade middle school students in the gifted education center. The conclusions of this study are as follows. First, the learning of analysis leads to a change of gaze in the proof learning of students. The students, after learning the analysis, moved their gaze from the bottom to the top when solving the proof problem, and the occupancy rate of the gaze to the bottom of the proof was higher than the higher part. Second, the change of gaze caused by the learning of the analysis have a correlation with the achievement of the proof learning and it can be seen that the method learning improves the achievement of the proof learning of the students.

Development of the Heuristic Attention Model Based on Analysis of Eye Movement of Elementary School Students on Discrimination task (변별과제에서 초등학생의 안구운동 분석을 통한 발견적 주의 모델 개발)

  • Shin, Won-Sub;Shin, Dong-Hoon
    • Journal of The Korean Association For Science Education
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    • v.33 no.7
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    • pp.1471-1485
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    • 2013
  • The purpose of this study was to develop a HAM (Heuristic Attention Model) by analyzing the difference between eye movements according to the science achievement of elementary school students on discrimination task. Science achievement was graded by the results of the Korea national achievement test conducted in 2012 for a random sampling of classes. As an assessment tool to check discrimination task, two discrimination measure problems from TSPS (Test of Science Process Skill, developed in 1994) which were suitable for an eye tracking system were adopted. The subjects of this study were 20 students from the sixth grade who agreed to participate in the research. SMI was used to collect EMD (eye movement data). Experiment 3.2 and BeGaze 3.2 programs were used to plan experiments and analyze EMD. As a result, eye movements of participants in discrimination tasks varied greatly in counts and duration of fixation, first fixation duration, and dwell time, according to students' science achievement and difficulty of the problems. By the analysis of EMD, strategies of the students' problem-solving could be found. During problem solving, subjects' eye movements were affected by visual attention; bottom-up attention, top-down attention and convert attention, and aflunter attention. In conclusion, HAM was developed, and it is believed to help in the development of a science learning program for underachievers.

Determination of radius of edge round cut of loading head for deformation strength test (변형강도 시험용 하중봉의 원형절삭반경 선정연구)

  • Park, Tae-W.;Doh, Young-S.;Kim, Kwang-W.
    • International Journal of Highway Engineering
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    • v.10 no.2
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    • pp.183-191
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    • 2008
  • This study evaluated influence of the loading head dimension on characteristics of deformation strength ($S_D$) of asphalt mixtures. Kim test and Wheel tracking (WT) test were conducted to evaluate $S_D$ characteristics with relation to WT results for various mixtures. The $S_D$ values and coefficient of variation of $S_D$ values of r=10mm were smaller than those of r=10.5mm. It was also found that $S_D$ values obtained using r=10mm loading head showed high correlations with rut parameters of WT test. It was indicated that the aggregate size and radius (r) of round cut were statistically significant variables on $S_D$ at = 0.05 level in the analysis of variance. However, in interaction of r and aggregate size showed no significance within $10{\sim}19mm$ aggregate size at the same level. Therefore, it was concluded that the diameter (D) of 40mm and the bottom edge radius (r) of 10mm was suitable dimension of loading head for deformation strength test.

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Analysis of the Sea Condition on the Patrol Ship Cheonan Sinking Waters (천안호 침몰해역의 해상조건 분석)

  • Kim, Kang-Min;Lee, Joong-Woo;Kim, Kyu-Kwang;Kwon, So-Hyung;Lee, Hyung-Ha
    • Journal of Navigation and Port Research
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    • v.34 no.5
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    • pp.349-354
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    • 2010
  • Cheonan, Republic of Korea Navy patrol ship sank had happened by an unknown incident in the vicinity of Baekryeongdo southwest 1.6km(1 mile) sea at 21:45 on March 26, 2010. In terms of coastal researcher's point of view, it is meaningful to provide the sea condition of basic data necessary for search and rescue, more detailed predictions and inference data through the numerical simulations. Thus, in this study, we investigated the weather, wave, tide, tidal current, bottom soil conditions, and suspended sediment are investigated at the coast of Baekryeong-Daechung islands. And based on these data, the characteristics of sea conditions were analyzed. The tidal period at the time of incident corresponds between neap tide to mean tide. Until April 3-4 after March 26, the date of incident, the strongest velocity was progressed towards the spring tide. Thus, it was considered to be difficult to search and rescue operations. Also, because the ebb tide was in progress during 21:00 to 22:00, mass transport seems to be prevailed to the southeast. In particular, as the sudden turbulence due to the irregular topography existed was anticipated, we had carried out particle tracking experiment. From this experiment, depending on the situation of flow, the initial movement of the particles were directed to the southeast but it turned out moving towards the offshore based on the long term prediction. Through this result, it is considered that the scope of the search operation should be expanded towards the open sea.