Mapping Small-Scale Horizontal Velocity Field in Panzhinan Waterway by Coastal Acoustic Tomography

Mapping small-scale high-precision velocity fields is of great significance to oceanic environment research. Coastal acoustic tomography (CAT) is a frontier technology used to observe large-scale velocity field in the horizontal slice. Nonetheless, it is difficult to observe the velocity field using the CAT in small-scale areas, specifically where the flow field is complex such as ocean ranch and artificial upwelling areas. This paper conducted a sound transmission experiment using four 50 kHz CAT systems in the Panzhinan waterway. Notably, sound transmission based on the round-robin method was recommended for small-scale CAT observation. The travel time between stations, obtained by correlation of raw data, was applied to reconstruct the horizontal velocity fields using Tapered Least Square inversion. The minimum net volume transport was 8.7 m3/s at 12:32, 1.63% of the total inflow volume transport indicating that the observational errors were acceptable. The relative errors of the range-average velocity calculated by differential travel time were 1.54% (path 2) and 0.92% (path 6), respectively. Moreover, the inversion velocity root-mean-square errors (RMSEs) were 0.5163, 0.1494, 0.2103, 0.2804 and 0.2817 m/s for paths 1, 2, 3, 4 and 6, respectively. The feasibility and acceptable accuracy of the CAT method in the small-scale velocity profiling measurement were validated. Furthermore, a three-dimensional (3-D) velocity field mapping should be performed with combined analysis in horizontal and vertical slices

Water Temperature Observation by Coastal Acoustic Tomography in Artificial Upwelling Area

Artificial upwelling is a geoengineering method to repair and improve marine ecosystems, and its operation requires long-term and continuous temperature field observation. However, existing methods are rarely seen to accomplish such observation. In this study, we investigate the coastal acoustic tomography (CAT) to obtain the long-term horizontal temperature field of an artificial upwelling area in an anechoic tank. We conduct four sets of experiments with different CAT station numbers and compare their data with those collected from temperature sensors. By analyzing the travel time from the CAT experiments, the horizontal temperature field of the upwelling area could be mapped. The CAT results and the comparison results show that the surface temperature of the observed area decreases by approximately 3 °C after upwelling, while the temperature of where the CAT is deployed decreases by about 1 °C; the temperature is lowest at the center of the upwelling area. Increasing the number of stations and station spacing would improve the temperature mapping accuracy. Therefore, the feasibility of using the CAT system to observe artificial upwelling is proved valid. This study indicates the potential application of CAT in temperature field observation in artificial upwelling area in the sea

Design of the Depth Controller for a Floating Ocean Seismograph

Floating ocean seismograph (FOS) is a vertical underwater vehicle used to detect ocean earthquakes by observing P waves at teleseismic distances in the oceans. With the requirements of rising to the surface and transmitting data to the satellite in real time and diving to the desired depth and recording signals, the depth control of FOS needs to be zero overshoot and accurate with fast response. So far, it remains challenging to implement such depth control due to the variation of buoyancy caused by the seawater density varying with the depth. The deeper the water is, the greater the impacts on buoyancy are. To tackle it, a fuzzy sliding mode controller considering the influence of seawater density change is proposed and simulated in MATLAB/SIMULINK based on the variable buoyancy system and state space function of FOS. Compared with proportional-integral-derivative (PID) controller, fuzzy PID controller and sliding mode controller, the simulation results indicate that the proposed controller shows its superiority regardless of the disturbing force. Its advantages include smaller steady-state error, faster response time, smaller system chatter, and well robustness. This proves that the designed fuzzy sliding mode controller is able to meet the working requirements and thus, lays a foundation for FOS application

A new curvularin glycoside and its cytotoxic and antibacterial analogues from marine actinomycete <i>Pseudonocardia</i> sp. HS7

<p>Five curvularin macrolides (<b>1</b>–<b>5</b>) were isolated from the cultured broth of marine actinomycete <i>Pseudonocardia</i> sp. HS7 that was obtained from the cloacal aperture of sea cucumber <i>Holothuria moebii</i>. The structures of these isolates were characterized as (11<i>S</i>,15<i>R</i>)-11-hydroxycurvularin (<b>1</b>), (11<i>R</i>,15<i>R</i>)-11-hydroxycurvularin (<b>2</b>), curvularin-7-<i>O</i>-α-D-glucopyranoside (<b>3</b>), <i>trans</i>-dehydrocurvularin (<b>4</b>) and curvularin (<b>5</b>) based on their NMR and HRESIMS data as well as chemical degradation. Compound <b>3</b> is a new macrolide with a rare α-D-glucopyranose substituent. Compounds <b>1</b>–<b>4</b>, <b>5a</b> and <b>5c</b> (the acyl products of <b>5</b>), suppressed the proliferation of all six tested cancer cell lines and <b>4</b> is the most active compound with IC₅₀ values ranging from 0.59 to 3.39 μM. The 11-hydroxycurvularins <b>1</b> and <b>2</b> also showed antibacterial activity inhibiting the growth of <i>Escherichia coli</i>.</p