401 research outputs found
Numerical Simulations of a Wave Energy Conversion Device Used for Oceanographic Buoys
Moored buoy systems are often deployed by oceanographers to gather scientific information on local and global changes in the water column, weather patterns and climate change. The data they gather is first transmitted to satellites or passing oceanographic ships prior to transmission land based research facilities. Most buoy designs are powered by battery systems that provide ballast and some can be recharged by solar panels. At-sea maintenance may include regular battery replacement or repairs to the buoy system due to vandalism, each being expensive propositions. In order to reduce the costs and utilize green energy, this thesis research investigates the use of
incorporating a pendulum wave energy conversion (WEC) device as a permanent or semi-permanent power source for some oceanographic buoys having an average power consumption that can vary from 0.1W to 6.0W.
The main criteria for selecting a WEC device for this application are operational reliability, sustainability during operational and extreme weather conditions, and minimizing the opportunity for vandalism. A general analytical model was developed and simulations of the motions of the buoy were performed using the numerical code COUPLE, which was originally developed to simulate the coupled response behavior of a deepwater floating hull and the associated mooring/riser/tendon systems. Based upon the motion behavior from the numerical simulation, the electrical power output by the selected WEC device is estimated using an iterative scheme to estimate equivalent damping of a hydraulic Power Take-Off (PTO) system.
Several illustrative case studies are presented to verify that the electrical power output rate is in the range of the power demands needed by typical oceanographic buoys. It is concluded that the proposed pendulum WEC device is a feasible solution that can be designed to provide an alternative power system to power oceanographic buoys. The research study provides a way to approach the design and utilization of WEC devices to capture wave energy as a natural power source for a wide range of buoy shapes, sizes and configurations for existing and future buoy designs
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Όλ¬Έ(λ°μ¬) -- μμΈλνκ΅λνμ : 곡과λν κΈ°κ³ν곡곡νλΆ, 2021.8. μ΄λμ€.Hand-based interface is promising for realizing intuitive, natural and accurate human machine interaction (HMI), as the human hand is main source of dexterity in our daily activities.
For this, the thesis begins with the human perception study on the detection threshold of visuo-proprioceptive conflict (i.e., allowable tracking error) with or without cutantoues haptic feedback, and suggests tracking error specification for realistic and fluidic hand-based HMI. The thesis then proceeds to propose a novel wearable hand tracking module, which, to be compatible with the cutaneous haptic devices spewing magnetic noise, opportunistically employ heterogeneous sensors (IMU/compass module and soft sensor) reflecting the anatomical properties of human hand, which is suitable for specific application (i.e., finger-based interaction with finger-tip haptic devices).
This hand tracking module however loses its tracking when interacting with, or being nearby, electrical machines or ferromagnetic materials. For this, the thesis presents its main contribution, a novel visual-inertial skeleton tracking (VIST) framework, that can provide accurate and robust hand (and finger) motion tracking even for many challenging real-world scenarios and environments,
for which the state-of-the-art technologies are known to fail due to their respective fundamental limitations (e.g., severe occlusions for tracking purely with vision sensors; electromagnetic interference for tracking purely with IMUs (inertial measurement units) and compasses; and mechanical contacts for tracking purely with soft sensors).
The proposed VIST framework comprises a sensor glove with multiple IMUs and passive visual markers as well as a head-mounted stereo camera; and a tightly-coupled filtering-based visual-inertial fusion algorithm to estimate the hand/finger motion and auto-calibrate hand/glove-related kinematic parameters simultaneously while taking into account the hand anatomical constraints.
The VIST framework exhibits good tracking accuracy and robustness, affordable material cost, light hardware and software weights, and ruggedness/durability even to permit washing.
Quantitative and qualitative experiments are also performed to validate the advantages and properties of our VIST framework, thereby, clearly demonstrating its potential for real-world applications.μ λμμ κΈ°λ°μΌλ‘ ν μΈν°νμ΄μ€λ μΈκ°-κΈ°κ³ μνΈμμ© λΆμΌμμ μ§κ΄μ±, λͺ°μ
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μ΄λ₯Ό μν΄ λ§μ λ¬Έμ λ₯Ό μΌμΌν€λ μ§μκΈ° μΌμ μμ΄ μ보μ μΈ νΉμ±μ μ§λλ κ΄μ± μΌμμ μμ μΌμλ₯Ό μ΅ν©νκ³ , μ΄λ μμ 곡κ°μ λ€ μμ λμ μμ§μμ κ°λ μ λμμ μΆμ νκΈ° μν΄ λ€μμ ꡬλΆλμ§ μλ λ§μ»€λ€μ μ¬μ©νλ€.
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μ΄ μ μλ μμ-κ΄μ± μΌμ μ΅ν© κΈ°μ (Visual-Inertial Skeleton Tracking (VIST)) μ λ°μ΄λ μ±λ₯κ³Ό κ°κ±΄μ±μ΄ λ€μν μ λ/μ μ± μ€νμ ν΅ν΄ κ²μ¦λμκ³ , μ΄λ VISTμ λ€μν μΌμνκ²½μμ κΈ°μ‘΄ μμ€ν
μ΄ κ΅¬ννμ§ λͺ»νλ μ λμ μΆμ μ κ°λ₯μΌ ν¨μΌλ‘μ¨, λ§μ μΈκ°-κΈ°κ³ μνΈμμ© λΆμΌμμμ κ°λ₯μ±μ 보μ¬μ€λ€.1 Introduction 1
1.1. Motivation 1
1.2. Related Work 5
1.3. Contribution 12
2 Detection Threshold of Hand Tracking Error 16
2.1. Motivation 16
2.2. Experimental Environment 20
2.2.1. Hardware Setup 21
2.2.2. Virtual Environment Rendering 23
2.2.3. HMD Calibration 23
2.3. Identifying the Detection Threshold of Tracking Error 26
2.3.1. Experimental Setup 27
2.3.2. Procedure 27
2.3.3. Experimental Result 31
2.4. Enlarging the Detection Threshold of Tracking Error by Haptic Feedback 31
2.4.1. Experimental Setup 31
2.4.2. Procedure 32
2.4.3. Experimental Result 34
2.5. Discussion 34
3 Wearable Finger Tracking Module for Haptic Interaction 38
3.1. Motivation 38
3.2. Development of Finger Tracking Module 42
3.2.1. Hardware Setup 42
3.2.2. Tracking algorithm 45
3.2.3. Calibration method 48
3.3. Evaluation for VR Haptic Interaction Task 50
3.3.1. Quantitative evaluation of FTM 50
3.3.2. Implementation of Wearable Cutaneous Haptic Interface
51
3.3.3. Usability evaluation for VR peg-in-hole task 53
3.4. Discussion 57
4 Visual-Inertial Skeleton Tracking for Human Hand 59
4.1. Motivation 59
4.2. Hardware Setup and Hand Models 62
4.2.1. Human Hand Model 62
4.2.2. Wearable Sensor Glove 62
4.2.3. Stereo Camera 66
4.3. Visual Information Extraction 66
4.3.1. Marker Detection in Raw Images 68
4.3.2. Cost Function for Point Matching 68
4.3.3. Left-Right Stereo Matching 69
4.4. IMU-Aided Correspondence Search 72
4.5. Filtering-based Visual-Inertial Sensor Fusion 76
4.5.1. EKF States for Hand Tracking and Auto-Calibration 78
4.5.2. Prediction with IMU Information 79
4.5.3. Correction with Visual Information 82
4.5.4. Correction with Anatomical Constraints 84
4.6. Quantitative Evaluation for Free Hand Motion 87
4.6.1. Experimental Setup 87
4.6.2. Procedure 88
4.6.3. Experimental Result 90
4.7. Quantitative and Comparative Evaluation for Challenging Hand Motion 95
4.7.1. Experimental Setup 95
4.7.2. Procedure 96
4.7.3. Experimental Result 98
4.7.4. Performance Comparison with Existing Methods for Challenging Hand Motion 101
4.8. Qualitative Evaluation for Real-World Scenarios 105
4.8.1. Visually Complex Background 105
4.8.2. Object Interaction 106
4.8.3. Wearing Fingertip Cutaneous Haptic Devices 109
4.8.4. Outdoor Environment 111
4.9. Discussion 112
5 Conclusion 116
References 124
Abstract (in Korean) 139
Acknowledgment 141λ°
Electromagnetic production of vector mesons at low energies
We have investigated exclusive photoproduction of light vector mesons
(, and ) on the nucleon at low energies. In order to
explore the questions concerning the so-called missing nucleon resonances, we
first establish the predictions from a model based on the Pomeron and meson
exchange mechanisms. We have also explored the contributions due to the
mechanisms involving - and -channel intermediate nucleon state. Some
discrepancies found at the energies near threshold and large scattering angles
suggest a possibility of using this reaction to identify the nucleon
resonances.Comment: 9 pages, LaTeX with sprocl.sty, 5 figures (11 eps files), Talk
presented at the NSTAR2000 Workshop, The Physics of Excited Nucleons,
Jefferson Lab., Newport News, Feb. 16-19, 200
Study on the Fatigue Strength of a Suction Flapper Valve Used in a High Efficient Reciprocating Compressor
Horizontal and Vertical Polarization
We analyze the effect of technological change in a novel framework that integrates an economy's skill distribution with its occupational and industrial structure. Individuals become managers or workers based on their managerial vs. worker skills, and workers further sort into a continuum of tasks (occupations) ranked by skill content. Our theory dictates that faster technological progress for middle-skill tasks not only raises the employment shares and relative wages of lower- and higher-skill occupations among workers (horizontal polarization), but also raises those of managers over workers as a whole (vertical polarization). Both dimensions of polarization are faster within sectors that depend more on middle-skill tasks and less on managers. This endogenously leads to faster TFP growth of such sectors, whose employment and value-added shares shrink if sectoral goods are complementary (structural change). We present several novel facts that support our model, followed by a quantitative analysis showing that task specific technological progress|which was fastest for occupations embodying routinemanual tasks but not interpersonal skills|is important for understanding changes in the sectoral, occupational, and organizational structure of the U.S. economy since 1980
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