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Evaporation duct is an anomalous atmospheric surface layer over the sea surface and has severe influence on the microwave propagation. The evaporation duct height, which implies the strength of the evaporation duct, is an important physical quantity. Based on National Centers for Environmental Prediction Climate Forecast System Reanalysis data and the evaporation duct model, high spatial resolution...
In this study, the hydrodynamic performance of a dish-shaped autonomous underwater helicopter (AUH) in waves near the sea surface is examined. The AUH is a novel type of autonomous underwater vehicle (AUV) that has excellent maneuverability and flexibility. The hydrodynamic performance of a dish-shaped autonomous underwater helicopter (AUH) in waves near the sea surface is estimated. An AUH is a novel...
A vectored thruster based on 3-RRRR parallel manipulator for small-size AUVs is designed to solve some drawbacks of conventional AUVs, which the control surfaces become ineffective at zero or slow forward speeds. Though this method, the thrust from duck propeller is controlled by the parallel manipulator. This approach has advantages of high stiffness, high mobile and large payload capacity. The parallel...
A known characteristic of the Tropical Pacific is the interaction between the zonal winds and the equatorial thermocline, which allows coupled variability like ENSO to evolve. However, this fundamental feedback is the least understood and most poorly modeled element of the tropical climate system. To increase our knowledge of the mechanisms controlling this feedback process, NOAA's National Data Buoy...
Limits of a comparative evaluation of the performance of a conventional X-band marine radar (MR) sigma S6 WaMoS® II used for surface current measurements are dicussed. Main focus of the paper is to address challenges when comparing current measurements from different measuring devices for evaluation purpose. Although the current measurement principles of MRs and acoustic Doppler current profilers...
This study aims at comparative analysis of ship speed-power performance based on the daily report and onboard logged sensor data. This paper shows how much difference exists between two results and proposes a proper methodology to analyze the ship performance. To evaluate and compare the performance, 130 days daily noon reports and logged sensor data from a bulk carrier were used and ISO 15016:2015[1],...
A coastal acoustic tomography (CAT) experiment was carried out using seven sets of CAT systems between September 6 to 9, 2009, in the Sanmen Bay region. Both assimilation and inversion of the data were used to reconstruct the current fields. The assimilated velocities agreed better with the independent acoustic Doppler current profiler (ADCP) data than the velocities obtained through inversion. Root...
Nowadays, ocean observatory networks, which gather and provide multidisciplinary, long-term, 3D continuous marine observations at multiple temporal spatial scales, play a more and more important role in ocean investigations. In this paper, we try to develop a portable smart device with online fish detection and tracking strategies by ARM7 microprocessor for ocean observatory networks, combining the...
This paper focuses on the inspection for sloping dam wall by a remotely operated vehicle (ROV). First, a dedicated ROV for dam inspection is described. Second, a fixed-distance tracking control strategy is proposed to guarantee the fixed camera-to-subject distance in sloping dam inspection, which is instrumental in sonar image fusion for the large-scale dam wall with a certain inclination. In addition,...
In this paper, we apply a block-based compressive sensing (BCS) architecture to address the reconstruction of underwater acoustic intensity fields. Although with anisotropic characteristics, underwater acoustic intensity fields can be compressed or represented in sparse transform domains. The distinct advantages of the BCS method include no need for any prior knowledge of the interested acoustic fields...
This paper proposes a spline interpolation method to map 2D Dubins paths into 3D for multiple Autonomous Underwater Vehicles (AUVs) to visit multiple targets. The multitarget assignment and path planning problem is first modeled as a multiple Traveling Salesmen Problem (mTSP) and a three-step algorithm is used to solve the NP-hard integer programming problem with affordable computational complexity...
Alaska's Kenai fisheries are managed for maximum efficiency while ensuring fair allocation across multiple stakeholder groups and long term sustainability of the fishery. Managers must work to meet the fishery's goals while adapting their commercial and subsistence eco-service management practices to meet changing ecological conditions. Pre- and in-season fishery management practices are supported...
The authors present a series of sea trails with autonomous systems using a long-range communication network. The continuous monitoring of the oceans and realtime data gathering/monitoring is a key issue in future marine challenges. To have long range communication, between land and ships at tens of kilometers', the authors used the BlueCom+ project research trials and tested their robotic systems...
We propose a general approach towards feature extraction for identifying sonar targets based on their composition and geometry. The key idea is to discover the geometric connections between braid-like features within acoustic color topography that includes magnitude and phase information. Specifically, we characterize each target as a graph of intersecting braided features, detected across the complex-valued...
This paper addresses the problem of compensating for motion-induced Doppler frequency offset in multicarrier acoustic communication systems based on orthogonal frequency division multiplexing (OFDM). In mobile acoustic systems, Doppler effect can be sever enough that the received OFDM signal experiences non-negligible frequency offsets even after initial resampling. To target these offsets, a practical...
The Ocean Observatories Initiative (OOI) is a project funded by the National Science Foundation which provides over 100,000 data products. OOI Cyberinfrastructure takes a two-pronged approach to data quality control: system level and human-in-the-loop. With system level, the system runs datasets through a series of six algorithms: global range, local range, stuck value, gradient, trend, and spike...
In this work we develop and demonstrate a probabilistic generative model for phytoplankton communities. The proposed model takes counts of a set of phytoplankton taxa in a timeseries as its training data, and models communities by learning sparse co-occurrence structure between the taxa. Our model is probabilistic, where communities are represented by probability distributions over the species, and...
Alaska's coastal communities are facing increased coastal hazards. Accurate predictive models are necessary to anticipate how various hazards may affect communities over time. Currently, erosion projections do not take into account the non-linear increase in erosion due to warming near-shore water, air, and permafrost. University of Alaska, Anchorage (UAA) is developing an arctic-capable coastal geomorphic...
In recent years, Unmanned Surface Vehicles (USVs) have grown in popularity, with an increasing number of applications in the civil, military and research domains. When the USVs are operating in the same area with other marine vessels, the collision avoidance algorithm is the key to keep the safety of both the ownship vehicle and the encountered vessels. This paper presents the development and validation...
This paper aims at investigating the effects of the ocean current in the thrusters closed-loop performance. In particular, the intervention case, and thus the vehicle slowly moving, is of interest. Vehicle controllers are commonly designed without taking into account both the thruster dynamics and the presence of ocean current which, however, influence the closed loop. A fixed gains PID and an adaptive...
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