OCEANS 2014 - TAIPEI最新文献_第10页

Covariance analysis as a measure of policy robustness 协方差分析作为政策稳健性的度量

OCEANS 2014 - TAIPEI Pub Date : 2014-04-07 DOI: 10.1109/OCEANS-TAIPEI.2014.6964339

Nawid Jamali, Petar Kormushev, S. Ahmadzadeh, D. Caldwell

{"title":"Covariance analysis as a measure of policy robustness","authors":"Nawid Jamali, Petar Kormushev, S. Ahmadzadeh, D. Caldwell","doi":"10.1109/OCEANS-TAIPEI.2014.6964339","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964339","url":null,"abstract":"In this paper we propose covariance analysis as a metric for reinforcement learning to improve the robustness of a learned policy. The local optima found during the exploration are analyzed in terms of the total cumulative reward and the local behavior of the system in the neighborhood of the optima. The analysis is performed in the solution space to select a policy that exhibits robustness in uncertain and noisy environments. We demonstrate the utility of the method using our previously developed system where an autonomous underwater vehicle (AUV) has to recover from a thruster failure [1]. When a failure is detected the recovery system is invoked, which uses simulations to learn a new controller that utilizes the remaining functioning thrusters to achieve the goal of the AUV, that is, to reach a target position. In this paper, we use covariance analysis to examine the performance of the top, n, policies output by the previous algorithm. We propose a scoring metric that uses the output of the covariance analysis, the time it takes the AUV to reach the target position and the distance between the target position and the AUV's final position. The top polices are simulated in a noisy environment and evaluated using the proposed scoring metric to analyze the effect of noise on their performance. The policy that exhibits more tolerance to noise is selected. We show experimental results where covariance analysis successfully selects a more robust policy that was ranked lower by the original algorithm.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116767822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

Preliminary study on a concept of wave propulsion by an active pitch-oscillating fin 主动俯仰摆动鳍推进波浪概念的初步研究

OCEANS 2014 - TAIPEI Pub Date : 2014-04-07 DOI: 10.1109/OCEANS-TAIPEI.2014.6964558

F. Chiu, Wen-Fu Li, Wen-Chuan Tiao

{"title":"Preliminary study on a concept of wave propulsion by an active pitch-oscillating fin","authors":"F. Chiu, Wen-Fu Li, Wen-Chuan Tiao","doi":"10.1109/OCEANS-TAIPEI.2014.6964558","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964558","url":null,"abstract":"Rising fuel prices and regulations to reduce CO2 emission have become a strong driving force to push shipyards and ship owners to build and operate energy saving ships. To meet these increasing demands, many novel designs and devices have been developed for reducing drag or for improving propulsion efficiency of a ship in seaway. Furthermore, several approaches using passive or active oscillating fin to extract wave power to assist ship propulsion have also been explored. The objective of the present study is to investigate the feasibility of a concept using an active pitch-oscillating fin to harness wave power for propulsion enhancement of merchant ships. Experimental data of the NACA 0012 oscillating foil are adopted to validate the present CFD simulation. Dependence of propulsion performance on Reynolds number and submerged depth are investigated. It has been confirmed that thrust of a flapping fin increases but efficiency decreases with larger Reynolds number, and shallower submerged depth of fin has negative effect for propulsion. Through simulations, thrust and propulsion efficiency of a flapping fin equipped at bow in full-scale ship are assessed. An active pitch-oscillating fin together with heave motion driven by ship vertical response to waves may generate significant amount of thrust with relatively high efficiency. As an example shown in the paper, for a VLCC of 321 meter long, a bow fin with projected area to waterline area ratio of 1/143, pitching actively around its pivot axis, may save energy about 3.1%~9.5% in the ship speed ranges of 12~16.5 knot.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116901699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

Research of the coupling effect of span-can penetration and environmental loads on piles 跨罐贯入与环境荷载对桩的耦合效应研究

OCEANS 2014 - TAIPEI Pub Date : 2014-04-07 DOI: 10.1109/OCEANS-TAIPEI.2014.6964364

Jinghua Tao, Xu Jia, Jinlin Hou, Zhaoyang Wang

引用次数: 1

Image-based motion estimation of underwater tow body 基于图像的水下拖体运动估计

OCEANS 2014 - TAIPEI Pub Date : 2014-04-07 DOI: 10.1109/OCEANS-TAIPEI.2014.6964571

Chau-Chang Wang, Hsin-Hung Chen, Kun-Hung Li

{"title":"Image-based motion estimation of underwater tow body","authors":"Chau-Chang Wang, Hsin-Hung Chen, Kun-Hung Li","doi":"10.1109/OCEANS-TAIPEI.2014.6964571","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964571","url":null,"abstract":"During deep sea exploration, the motion of the deep tow system is influenced by that of the surface vessel, the change of the cable length and the current field in the water column. Though the towing vessel moves in a straight line on the sea surface, the heading of the tow body is not necessary collinear to the towing direction. If no devices are available to adjust the direction of the tow body, data collected by directional sensors, like camera or side scan sonar, will be skewed. It causes problems and difficulties in the post processing for mosaicing data sets into a map of a larger area. Moreover, the existence of the offset angle creates a staircase-like pattern on the map when the images are stitched together. The staircase pattern hampers the continuity of the data. The offset angle, in theory, can be computed from the USBL and the compass readings. But in practice, the refresh rates of USBL and the compass are not compatible such that the results are not good enough for maneuvering the tow system. In this paper, we propose using the feature points on the images acquired to estimate the offset angle of the tow system with respect to the trace of the motion. The computation is carried out with the OPENCV library implemented in Visual C. Currently, the refresh rate can be about 2 Hz with 30 fps camera acquisition, given the tow body is moving with 0.5 m/s speed.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115527411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Extreme sea hazards statistics and engineering applications 极端海难统计及工程应用

OCEANS 2014 - TAIPEI Pub Date : 2014-04-07 DOI: 10.1109/OCEANS-TAIPEI.2014.6964285

L. Defu, Liu Guilin, Shi Hongda, Wang Fengqing, Chen Ziyu

引用次数: 3

Underwater video streaming using adaptive frame decimation 使用自适应帧抽取的水下视频流

OCEANS 2014 - TAIPEI Pub Date : 2014-04-07 DOI: 10.1109/OCEANS-TAIPEI.2014.6964355

Gilad Avrashi, Shlomi Museri, Yaakov Bucris, Azriel Sinai, A. Amar

引用次数: 5

Long-term features of quartz pressure gauges inferred from experimental and in-situ observations 从实验和现场观测推断石英压力表的长期特征

OCEANS 2014 - TAIPEI Pub Date : 2014-04-07 DOI: 10.1109/OCEANS-TAIPEI.2014.6964447

H. Matsumoto, E. Araki, K. Kawaguchi, S. Nishida, Y. Kaneda

{"title":"Long-term features of quartz pressure gauges inferred from experimental and in-situ observations","authors":"H. Matsumoto, E. Araki, K. Kawaguchi, S. Nishida, Y. Kaneda","doi":"10.1109/OCEANS-TAIPEI.2014.6964447","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964447","url":null,"abstract":"DONET, i.e., the dense ocean-floor network system for earthquakes and tsunamis has started its operation in the Nankai Trough, SW Japan in the early of 2010, and followed by the extension to the westward region as DONET2 in near future. DONET observatory is composed of various sensors such as broadband seismometer, seismic accelerometer, tsunami meter, etc. The present study focuses on quartz pressure gauges being used as tsunami meters measuring water pressure change. In the present study, long-term pressure gauges' characteristics have been evaluated by using the JAMSTEC's high accuracy pressure standard before deploying into the deep-sea. The high accuracy pressure standard is mainly customized by a piston gauge, a pressure generator/controller, a reference pressure monitor, and a thermal controlled large capacity chamber, which virtually reproduces the deep-sea environment. 20 MPa hydraulic pressure was applied to the pressure gauges under the constant temperature of 2°C, which is equivalent to the ocean-bottom of 2,000 meters depth for the duration of approximately one month. As a result, sensors' drift varies among pressure gauges, however, which implies that the gradual drift possibly occurs a few centimeters per month in maximum. We also discuss the sensors' drift after deploying the deep-sea by analyzing the long-term in-situ observations, which shows that it continues at a rate of a few to ten centimeters per year in the early stage, then it tends to be reduced gradually.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115353509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 13

Probing the suspended marine algae using polarized-light scattering 利用偏振光散射探测悬浮海藻

OCEANS 2014 - TAIPEI Pub Date : 2014-04-07 DOI: 10.1109/OCEANS-TAIPEI.2014.6964437

Ran Liao, Hui Ma

引用次数: 3

Dynamics analysis of wave-driven unmanned surface vehicle in longitudinal profile 波浪驱动无人水面航行器纵剖面动力学分析

OCEANS 2014 - TAIPEI Pub Date : 2014-04-07 DOI: 10.1109/OCEANS-TAIPEI.2014.6964333

B. Tian, Jiancheng Yu, Aiqun Zhang, Fumin Zhang, Zhier Chen, K. Sun

引用次数: 18

Distributions of soft-decision symbols using channel-estimation based equalizers 使用基于信道估计的均衡器的软判决符号分布

OCEANS 2014 - TAIPEI Pub Date : 2014-04-07 DOI: 10.1109/OCEANS-TAIPEI.2014.6964326

S. H. Huang, T. C. Yang, J. Tsao

{"title":"Distributions of soft-decision symbols using channel-estimation based equalizers","authors":"S. H. Huang, T. C. Yang, J. Tsao","doi":"10.1109/OCEANS-TAIPEI.2014.6964326","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964326","url":null,"abstract":"For communications, the estimated symbols (the output of a channel equalizer) is sometimes referred to as soft-estimate of the (transmitted) symbols. The mean squared Euclidian distribution between the soft symbol and true symbols yields the mean squared symbol estimation error, sometimes referred to as the soft-decision error. The soft symbol distribution is a key measure of the equalizer performance and is used for calculating the probability of bit errors. In this paper, we apply a channel estimation (CE) based decision feedback equalizer (DFE) to at sea data. For CE-DFE, we assume channel estimation in the training mode to avoid the error feedback problem that often occurs in real data processing. The reason is to study the relationship between equalizer performance and channel estimation performance without the error feedback problem. Specifically, we investigate the relation between the soft-decision error and signal prediction error; the latter is used as a measure for the channel estimation error. For channel estimation, we used various algorithms based on signal subspace tracking as well as conventional full space tracking. For each channel estimation algorithm, we estimate the symbol distribution. We find the distributions of the soft-estimate symbols are well fitted by a Gaussian normal distribution, with a variance predictable by the signal prediction error.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"499 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122202343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2