检索结果-内蒙古大学图书馆

OCEANS

作者： C. Roman H. Singh MIT/WHOI Joint Program in Applied Ocean Science and Engineering Massachusetts Institute of Technology Cambridge MA USA Department of Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution Woods Hole MA USA

This work focuses on the creation of high resolution micro-bathymetric maps using a high frequency pencil beam sonar. These maps typically cover areas of 10's to 100's of square meters. Data is collected using a sonar mounted to an underwater vehicle that can be positioned at discrete locations on the sea floor or flown in a survey pattern above the bottom. Specifically, we are focused on improving the accuracy of these terrain maps by merging sonar pings taken from multiple vantage points over the same location. This requires the adaption of data registration techniques to handle errors related to the sonar sensor. The registration can also be modified to incorporate the navigation data available from an instrumented underwater vehicle. A two axis scanning sonar was used to gather data in the form of densely sampled range images. The data registration works on the 3D projection of these range images in a scan-matching manner. Through this process regions occluded in a single scan are filled with data available from other scans and individual pings which show a poor return are removed. Refined estimates of the scan vantage points are also generated during the registration. The initial estimates of these locations are provided by navigation data. The practical application of this work complements photographic mapping when visibility is limited. It also provides additional measurements which can be used to improve vehicle navigation.

关键词： Sonar navigation Sonar measurements Remotely operated vehicles Underwater vehicles Sea floor Underwater acoustics Layout Oceans Acoustical engineering Acoustic beams

来源：评论

学校读者我要写书评

暂无评论

Enabling Under-Ice Geochemical Observations with a Size, Weight, and Power-Constrained Robot

arXiv

引用

arXiv 2022年

作者： Horowitz, Jess Preston, Victoria Michel, Anna P.M. Mechanical Engineering Massachusetts Institute of Technology Cambridge United States MIT-WHOI Joint Program Massachussetts Institute of Technology Cambridge United States Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution Woods Hole United States

Estimates of greenhouse gas emissions from Arctic estuarine environments are dominated by in situ summer-time ice-free dissolved gas measurements due to the logistical ease of performing field observations in these conditions. Recent evidence in coastal Arctic environments, however, has demonstrated that dissolved methane (CH4) and carbon dioxide (CO2) are strongly seasonally variable, and at least one significant gas ventilation event occurs during the spring freshet. Whether the Arctic serves as a source or sink of greenhouse emissions has significant implications on modeling climate change and its feedback mechanisms. To enable higher resolution spatiotemporal measurements of dissolved gases in typically undersampled conditions, remotely operated vehicles (ROVs) can be used to extract near continuous water samples below ice before and during the spring freshet. Here, we present a size, weight, and power-constrained (SWAP) underwater vehicle (UV) and novel geochemical sampling system suitable for taking under-ice geochemical observations and demonstrate the proposed system in a field-analog setting for Arctic estuarine studies. Copyright © 2022, The Authors. All rights reserved.

关键词： Carbon dioxide

来源：评论

学校读者我要写书评

暂无评论

Exactly Sparse Delayed-State Filters

Exactly Sparse Delayed-State Filters

引用

IEEE International Conference on Robotics and Automation (ICRA)

作者： R.M. Eustice H. Singh J.J. Leonard MIT/WHOI Joint Program in Applied Ocean Science and Engineering Woods Hole Oceanographic Institution Woods Hole MA USA Department of Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution Woods Hole MA USA Department of Ocean Engineering Massachusetts Institute of Technology Cambridge MA USA

This paper presents the novel insight that the SLAM information matrix is exactly sparse in a delayed-state framework. Such a framework is used in view-based representations of the environment which rely upon scan-matching raw sensor data. Scan-matching raw data results in virtual observations of robot motion with respect to a place its previously been. The exact sparseness of the delayed-state information matrix is in contrast to other recent feature based SLAM information algorithms like Sparse Extended Information Filters or Thin Junction Tree Filters. These methods have to make approximations in order to force the feature-based SLAM information matrix to be sparse. The benefit of the exact sparseness of the delayed-state framework is that it allows one to take advantage of the information space parameterization without having to make any approximations. Therefore, it can produce equivalent results to the “full-covariance” solution.

关键词： Delay Simultaneous localization and mapping Navigation Cameras Oceans Information filters Sparse matrices Information filtering Remotely operated vehicles Robot vision systems

来源：评论

学校读者我要写书评

暂无评论

Tunable Diode Laser Absorption Spectroscopy Instrument for Flow-Through Measurement of Dissolved Carbon Dioxide in the Ocean

Tunable Diode Laser Absorption Spectroscopy Instrument for F...

引用

Conference on Lasers and Electro-Optics (CLEO)

作者： Beckett Colson Anna P. M. Michel Woods Hole Oceanographic Institution Woods Hole MA USA Massachusetts Institute of Technology Cambridge MA USA MIT-WHOI Joint Program in Oceanography/Applied Ocean Science & Engineering Cambridge and Woods Hole MA USA

The measurement of dissolved carbon dioxide is important for understanding many ocean processes. Here we present the design and field deployment of a TDLAS sensor for the measurement of dissolved carbon dioxide.

ISBN: (纸本)9781943580910

关键词： Spectroscopy Semiconductor lasers Oceans Instruments Sea measurements Measurement by laser beam Carbon dioxide

来源：评论

学校读者我要写书评

暂无评论

Vertical Glider Robots for Subsea Equipment Delivery

Vertical Glider Robots for Subsea Equipment Delivery

引用

2011 IEEE International Conference on Robotics and Automation(2011年IEEE世界机器人与自动化大会 ICRA 2011)

作者： Brooks Reed Charles Ambler Franz Hover Julio Guerrero Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program in Oceanogr Department of Mechanical Engineering at MIT CambridgeMA 02139 USA Department of Mechanical Engineering at MIT Cambridge MA 02138 USA

We have developed an underwater vehicle that offers significant performance improvements over existing subsea elevators. Our Vertical Glider Robot falls under its own weight to a precise location on the seafloor, employing streamlining, active steering, and basic navigation *** examine typical at-sea mission requirements, mention several key governing parameters, and outline our design approach. We then describe a prototype device, and present results from model-scale experiments.

关键词： Vehicles Cameras Elevators Navigation Sensors Sea measurements Marine vehicles

来源：评论

学校读者我要写书评

暂无评论

Robotic Planning under Uncertainty in Spatiotemporal Environments in Expeditionary Science

arXiv

引用

arXiv 2022年

作者： Preston, Victoria Flaspohler, Genevieve Michel, Anna P.M. Fisher, John W. Roy, Nicholas MIT-WHOI Joint Program Massachusetts Institute of Technology CambridgeMA02139 United States Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution United States Computer Science and Artificial Intelligence Laboratory Massachusetts Institute of Technology CambridgeMA02139 United States

In the expeditionary sciences, spatiotemporally varying environments - hydrothermal plumes, algal blooms, lava flows, or animal migrations - are ubiquitous. Mobile robots are uniquely well-suited to study these dynamic, mesoscale natural environments. We formalize expeditionary science as a sequential decision-making problem, modeled using the language of partially-observable Markov decision processes (POMDPs). Solving the expeditionary science POMDP under real-world constraints requires efficient probabilistic modeling and decision-making in problems with complex dynamics and observational models. Previous work in informative path planning, adaptive sampling, and experimental design have shown compelling results, largely in static environments, using data-driven models and information-based rewards. However, these methodologies do not trivially extend to expeditionary science in spatiotemporal environments: they generally do not make use of scientific knowledge such as equations of state dynamics, they focus on information gathering as opposed to scientific task execution, and they make use of decision-making approaches that scale poorly to large, continuous problems with long planning horizons and real-time operational constraints. In this work, we discuss these and other challenges related to probabilistic modeling and decision-making in expeditionary science, and present some of our preliminary work that addresses these gaps. We ground our results in a real expeditionary science deployment of an autonomous underwater vehicle (AUV) in the deep ocean for hydrothermal vent discovery and characterization. Our concluding thoughts highlight remaining work to be done, and the challenges that merit consideration by the reinforcement learning and decision-making community. Copyright © 2022, The Authors. All rights reserved.

关键词： Decision making

来源：评论

学校读者我要写书评

暂无评论

A technique for generating synthetic acoustic fields in shallow water

引用

The Journal of the Acoustical Society of America 2005年第S1期76卷 S11-S11页

作者： Michael S. Wengrovitz George V. Frisk MIT/WHOI Joint Program in Oceanography/Oceanographic Engineering Woods Hole MA 02543 Woods Hole Oceanographic Institution Woods Hole MA 02543

A numerical scheme for generating both the trapped mode and continuum portions of acoustic fields for a horizontally stratified ocean and bottom is presented. The technique is based on the fact that the branch line integral corresponding to the continuum portion of the field can be performed by Hankel transforming a modified Green's function. The modified Green's function is obtained by removing the pole contributions from the actual Green's function. The continuum portion is then added to the trapped mode portion to form the total synthetic field. The technique has the advantage that it is fast, accurate, and can be used for a more general geoacoustic model than the Pekeris waveguide. Synthetic results for several examples are presented and discussed.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Scattering off rough boundaries in ray and normal mode theory with applications to ocean acoustic tomography and shallow water acoustics

引用

The Journal of the Acoustical Society of America 2005年第S1期77卷 S101-S101页

作者： James F. Lynch George V. Frisk James H. Miller Woods Hole Oceanographic Institution Woods Hole MA 02543 MIT/WHOI Joint Program in Oceanography/Oceanographic Engineering Woods Hole MA 02543

Two quantities which can be important, both in acoustic tomography and in shallow water acoustics, are the spread and wander in time of received acoustic pulses due to boundary scattering. These effects limit the pulse travel time resolution one may achieve and then ultimately the resolution of features in the water column (tomography) or ocean bottom (shallow water acoustics). In order to calculate these effects, a breakup of the scattering into adiabatic (leading to pulse wander) and coupled (leading to pulse spreading) ray and mode components was made, and moments of the deterministic propagation results were generated. Applications of this work to coherent array processing and further extensions of this work will be discussed. [Work supported by ONR.]

关键词：

来源：评论

学校读者我要写书评

暂无评论

Estimating sea surface spectra with acoustic tomography

引用

The Journal of the Acoustical Society of America 2005年第S1期80卷 S82-S82页

作者： James H. Miller Ching‐Sang Chiu James F. Lynch MIT/WHOI Joint Program in Oceanographic Engineering Woods Hole Oceanographic Institution Woods Hole MA 02543 Woods Hole Oceanographic Institution Woods Hole MA 02543

A technique for estimating space‐ and time‐varying sea surface spectra using acoustic tomography is described. The technique uses acoustic (mode and/or ray) phase or travel time perturbations as data for the inversions. The inverse problems for spatially homogeneous and spatially nonhomogeneous frequency‐directional wave spectra are discussed. Resolution and accuracy of the technique are addressed. Results of inversions of synthetic data are presented as well as an application of this technique to data taken during the MIZEX '84 preliminary tomography experiment. Directions of future research are indicated.

关键词：

来源：评论

学校读者我要写书评

暂无评论

A modal/WKB inversion method for determining sound‐speed profiles in the ocean and ocean bottom

引用

The Journal of the Acoustical Society of America 2005年第S1期84卷 S175-S175页

作者： Kevin D. Casey George V. Frisk MIT/WHOI Joint Program in Oceanography/Oceanographic Engineering Woods Hole MA 02543 Department of Ocean Engineering Woods Hole Oceanographic Institute Woods Hole MA 02543

Two approaches to determining sound‐speed profiles in the ocean and ocean bottom using measured acoustic modal eigenvalues are examined. Both methods use measured eigenvalues and mode‐dependent assumed values of the WKB phase integral as input data and use the WKB phase integral as a starting point for relating the index of refraction to depth. Inversion method 1 is restricted to monotonic or symmetric sound‐speed profiles and requires a measurement of the sound speed at one depth to convert the index of refraction profile to a sound‐speed profile. Inversion method 2 assumes that the sound speed at the ocean surface and the minimum sound speed in the profile are known and is applicable to monotonic profiles and to general single duct sound‐speed profiles. For asymmetric profiles, inversion method 2 gives the depth difference between two points of equal sound speed in the portion of the profile having two turning points, and in the remainder of the profile it gives sound speed versus depth directly. A numerical implementation of the methods is demonstrated using idealized ocean sound‐speed profiles. The two methods are used also to determine the sediment sound‐speed profiles in two shallow water waveguide models, and inversion method 1 is used to find the sediment sound‐speed profile using data from an experiment perfomed in the Gulf of Mexico. [Work supported by ONR.]

关键词：

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：