Design and Simulation of Flexible Underwater Acoustic Sensor Based on 3D Buckling Structure

The exploration of marine resources has become an essential part of the development of marine strategies of various countries. MEMS vector hydrophone has great application value in the exploration of marine resources. However, existing MEMS vector hydrophones have a narrow frequency bandwidth and are based on rigid substrates, which are not easy to be bent in the array of underwater robots. This paper introduces a new type of flexible buckling crossbeam–cilium flexible MEMS vector hydrophone, arranged on a curved surface by a flexible substrate. A hydrophone model in the fluid domain was established by COMSOL Multiphysics software. A flexible hydrophone with a bandwidth of 20~4992 Hz, a sensitivity of −193.7 dB, excellent “8” character directivity, and a depth of concave point of 41.5 dB was obtained through structured data optimization. This study plays a guiding role in the manufacture and application of flexible hydrophones and sheds light on a new way of marine exploration.

Factor Graph Weight Particles aided Distributed Underwater Cooperative Positioning Algorithm

The growing scale of marine exploration requires high-resolution underwater localization, which necessitates cooperation among underwater network nodes, considering the channel complexity and power efficiency. In this paper, we proposed factor graph weight particles aided distributed underwater nodes cooperative positioning algorithm (WP-DUCP). It capitalized on the factor graph and sum-product algorithm to decompose the global optimization to the product of several local optimization functions. Combined with the Gaussian parameters to construct the weighted particles and to realize the belief transfer, it shows low complexity and high efficiency, suitable to the energy-restricted and communication distance-limited underwater networks. In terms of convergence, localization resolution, and computation complexity, we conducted the simulation and real-test with comparison to the existing co-localization methods. The results verified a higher resolution of the proposed method with no extra computation burden.

Passive seismic interferometry of the ultraslow-spreading Southwest Indian Ridge

<p>Passive seismic interferometry (ambient-noise seismology) is an increasingly popular, eco-friendly, relatively inexpensive exploration geophysics tool, to map S-wave velocity in the Earth’s crust. This method has not yet been applied widely to marine exploration. The purpose of this study is to investigate the crustal structure of a quasi-amagmatic portion of the Southwest Indian Ridge by interferometry, and to examine the performance and reliability of interferometry in marine exploration. To achieve this goal, continuous vertical-component recordings from 43 ocean bottom seismometers (OBS) deployed during the SISMO-SMOOTH cruise (2014) were utilized. Recorded signals span frequencies between 0.1Hz and 3Hz. We show that reliable estimates of the Green’s function are obtained for many station pairs, by cross-correlation in the frequency domain. The comparison of the cross-correlations with the theoretical Green’s (Bessel) function provides one Rayleigh-wave dispersion curve per station pair; dispersion curves are then averaged, and inverted through a conditional neighborhood algorithm to determine a 1D S-wave velocity model, that we estimate to be well constrained within the crust. Our S-wave velocity model is analyzed and interpreted with geological information, and independent geophysical studies in the region of interest, as well as other areas characterized by similar tectonically-dominated, quasi amagmatic spreadings.</p>

A Novel Method to Estimate the Sea State for Recycling Work on the Sea Surface

The recycling of marine exploration equipment after it has surfaced is greatly affected by sea state. In order to estimate the sea state in real time, this paper proposes a method for measuring wave elevation, which modifies the integrated results of GNSS/SINS in the up direction by virtual horizontal lines to extract wave fluctuation information. From these wave information, the significant wave heights (SWH) can be calculated as the only input parameter of P-M spectrum, and a series of wave height data can be further simulated. When the GNSS is interrupted due to severe sea state, the simulated data can be integrated with the SINS to deal with the data distortion problem. The simulation results show that the application of wave spectrum in the GNSS intermittent situation has obvious improvement effect and important significance.

A model for predicting stress distribution and strain-force characteristics in regular braided ropes

Owing to the good mechanical properties of braided structures, regular braided ropes are increasingly being used in various fields, including marine exploration, aloft work, recreation activities, and oil prospecting. However, under certain severe conditions, they could break, a situation that is absolutely undesired. Thus, predicting their stress distribution and strain-force characteristics when they are subjected to different tensile loads is a pre-requisite for their application. Therefore, in this study, a mathematical model for ropes with regular braided structures is developed, and based on the model, this study reveals that uneven stress distributions in the different strands of regular braided ropes generate different stress distributions and strain-force characteristics in each of the strands. Additionally, the uneven stress distributions in the different strands also induce mechanical failure more readily. Finally, to ensure the reliability of braided ropes in different applications, different strand parameters are compared.

GROWTH, BIOMASS AND PHYTOCHEMICAL COMPOUND OF SEAGRASS (CASE STUDY: MALANG REGENCY COASTAL)

Seagrass known as Lamun in Bahasa is one of the species that are can live in submerged marine habitats. Seagrasses have an important role in the ecosystems, including as primary producers, living habitats of benthic organisms, stabilize bed sediments and carbon storage in shallow-water coastal. Monospecies community of seagrass was found in Malang, however, only limited number studies of seagrass have been done in the area. This study aimed to determine the growth rate and biomass of the seagrass, as well as the phytochemical compounds. Experiments were conducted during August-November in 2014 and 2015. Measurement of in situ growth and biomass leaf were made using marking techniques in one week also the data of leaf seagrass collected were using a random sampling method. Extracted materials were tested by methanol to get the phytochemical compound. Data were analyzed at the Fisheries and Marine Exploration Laboratory, FPIK-UB. The results of the present study showed that two species of seagrass, Syringodium isoetifolium at Kondang Merak and Thalassia hemprichii at Bale Kambang. The growth rate of the seagrass leaves of the former species had positive values with 0.45±0.19 cm/day, hile the later species had 0.25±0.14 cm/day. Furthermore, the biomass value of the two types seagrass obtained that in the below-ground was higher than the above-ground. Phytochemical tests showed that both of type seagrass contained bioactive compounds such as flavonoids and saponins.

Dynamics Simulation of Grasping Process of Underwater Vehicle-Manipulator System

Underwater vehicle-manipulator system (UVMS) can be applied to fulfill different complex underwater tasks such as grasping, drilling, sampling, etc. It is widely used in the field of oceanographic research, marine exploration, military and commercial applications. In this paper, the dynamic simulation of UVMS is presented in the process of grasping an object. Firstly, the dynamic model of UVMS, which considers the change of the load of manipulator when the end effector of manipulator grasps the object, is developed. To compare different control conditions, the numerical simulation of grasping processes without/with vehicle attitude control are carried out. The results show that the coupling dynamics between the vehicle and the manipulator in the grasping process are clearly illustrated. The tracking position error of end effector without vehicle control is large and UVMS cannot complete the grasping task under this condition. Vehicle control can compensate the motion of vehicle due to the coupling effect caused by the motion of manipulator. This study will contribute to underwater operation mission for UVMS with floating base.

Revitalisasi Maritim Dalam Pemantapan Geopolitik Indonesia

History records that the archipelago is an area with more waters than land. This has been realized by the royal leaders in the archipelago. Since the days of the Srivijaya Kingdom, the Singosari Kingdom and the Majapahit Kingdom have made the sea a real force to build a kingdom. Sea or maritime is not only a support for economic power but more than that. Mari- time has become a geopolitical force to unite the archipelago. Geopolitical power has strength- ened the steps of the kingdoms in the archipelago to increase their political bargaining power against countries in the surrounding region and countries in the world. The strengthening of maritime as a geopolitical force will of course have implications for other sectors, especially in the development sector of land transportation and sea transportation. This implication is very well understood by the leaders of this country. But still until now, maritime development must be put forward because the strength and bargaining value of this country rests on maritime affairs. Apart from being a geopolitical power, there is also a very large economic power contained in it. Even though Indonesia was late in realizing this, President Gus Dur had formed a Department of Marine Exploration which is now the Ministry of Maritime Affairs. Indonesia’s maritime geopolitical strength has been identified in three main straits which are used by the international community as a passage for various ships with large weights so that Indonesia must be more closely monitoring these sea lanes. The three straits are the Malacca Strait, the Sunda Strait and the Lombok Strait. Indonesia must be able to regulate international maritime shipping so that it can play a strategic role in the world political arena.

WAVE module for hybrid oceanographic Autonomous Underwater Vehicle–prototype experimental validation and characterisation

WAVE (Wave-powered Autonomous Vehicle for marine Exploration) is an Italian National Research Projects of Military interest (PNRM) concluded in October 2017. The final goal of the project was the enhancement of the endurance of a typical marine mission with Autonomous Underwater Vehicles (AUVs). To this aim, a system to provide a generic carrier AUV for both energy harvesting from the wave motion and low energy propulsion capabilities was developed. A first prototype of the WAVE module was realised and installed on a commercial AUVplatform. After a preliminary assessment of the integrated system at sea, a systematic experimental characterisation of the module capabilities was carried out in a controlled environment at the CNR-INSEAN test tank facility in Rome, Italy. During the three days experimentation, a considerable quantity of data related to different recreated sea conditions and WAVE module configurations was collected. This work details the energetic characterisation of the proposed system, presenting a comparison of the performance of the different WAVE module layouts in terms of average generated power. The main result emerged from the previous analysis is the identification of the most effective configuration of the WAVE module for the battery charging. A deeper processing of data will allow to critically tune the available dynamical model of the system. This way, it will be possible to evaluate, through simulations, the expected performance of the WAVE AUV under typical wave profiles of the Mediterranean sea.