Search

To investigate influence of underwater environment on the effect of underwater drilling and blasting, the action mechanism of underwater drilling and blasting was analyzed by taking the underwater blasting engineering of No.3 pier foundation of New Baishatuo Yangtze River Super-long Bridge in Chongqing, China as research object. Moreover, by using ANSYS/LS-DYNA finite element program, the processes of land drilling & blasting and underwater drilling & blasting were separately numerically simulated. Based on the which, the dynamic response characteristics of land and underwater drilling & blasting were compared by utilizing a blasting funnel test, characteristics of shock waves and inherent characteristics of aqueous medium. Therefore, the influence of underwater environment on drilling and blasting effect was acquired. The results showed that Mises equivalent stress near the water-bottom interface was lower than that of the same location subjected to land drilling and blasting due to the influence of hydraulic pressure from underwater environment. Under the same pressure, the volumes of underwater blasting-induced funnel pits were all lower than those of land blasting-induced funnel pits. With the same charge quantity, the deeper the water, the smaller the volume of blasting induced funnel pits. Compared with land drilling and blasting, the presence of underwater environment can accelerate the attenuation of explosion-induced shock waves to thus further weaken the effect of rock fragmentation in blasting. The research result can further enrich the underwater blasting theory system and provide practical guidance for the construction of underwater drilling and blasting projects. [ABSTRACT FROM AUTHOR]

In order to solve the problem of missing various targets due to the limited memory and computing power of underwater equipment and also the complexity of the underwater environment, a lightweight and efficient underwater target detection algorithm YOLO_GN (YOLO with Ghost network) is proposed. Based on the basic framework of YOLOv5s, the algorithm designs a new backbone using GhostNetV2 and proposes Ghost_BottleneckV2 combined with dynamic sparse attention BiFormer to reduce computational costs and improve detection accuracy. The lightweight multi-scale convolutional LW-GSConv combined with VOV-GSCSP is used to capture the complex features of the input data more accurately and improve the network expression ability. In view of the imbalance of a large number of detection samples in underwater targets, the SlideLoss function is introduced and the optimizer of original model is updated to Sophia, so that the algorithm model has better generalization ability. Finally, the YOLO_GN algorithm is equipped with the Raspberry Pi 4B development board, and the camera is called up to realize real-time detection of underwater targets. Simulation results show that the proposed method can achieve 85.35% detection accuracy on the URPC dataset, which is 2.43% higher than the most common architecture in underwater scenarios, and computational complexity is reduced by 46.47%. Moreover, it can achieve better object detection effect in embedded terminals. [ABSTRACT FROM AUTHOR]

Deep-sea underwater technology and equipment are crucial aspects to cognize the deep sea, exploit deep-sea resources, and protect the marine ecosystem. Expanding the deep-sea space faces complex environmental challenges and urgently requires support of high-level deep-sea underwater technologies and equipment. This study analyzes the components and demands for the deep-sea underwater technology and equipment and reviews the current status and development trends of the technology and equipment from four aspects: deep-sea observation/detection and perception, underwater construction, deep-sea oil and gas production, and deep-sea mineral resource collection. Moreover, this study analyzes the development status and engineering challenges in China, explores the key technology and equipment systems and key physical–mechanical mechanisms behind them, and summarizes the typical equipment and corresponding diagram. Additionally, the common key technologies of the deep-sea underwater equipment in China are summarized, including the intelligent and automation technology, precision component processing and manufacturing technology, high-precision positioning and navigation technology, high-speed communication technology, computational and analytical mechanics of large systems, and multiscale engineering design methods and technologies. Furthermore, countermeasures and suggestions are proposed aiming at achieving high-quality development of the deep-sea underwater technology and equipment in China: strengthening the top-level design of deep-sea underwater engineering to promote the establishment of a coordinating system for common key technologies, enhancing the industry influence of Chinese deep-sea underwater technical standards to explore the international market, promoting the construction of compatible and universal platforms with high quality, and training innovation professionals to provide support for the high-level development of the marine science and technology industry.

In this paper, a novel architecture of bidirectional underwater wireless optical communication (UWOC) system has been proposed to interconnect stationary and moving underwater sensor nodes for diverse applications. To achieve the bidirectional communication, wavelength division multiplexing (WDM) and remodulation approach have been used in this work. The proposed bidirectional UWOC system works at 40 Gbps data rate for both downlink (stationary node to moving node) and uplink (moving node to stationary node). Two distinct wavelengths of 532 nm and 531 nm have been used for uplink and downlink, the main attraction of the proposed architecture is that both the laser sources are placed at the stationary node. The moving node do not have any laser source and it remodulates the signal for sending data back to the stationary node. Because of this, the moving node contains lesser components which results in cost effectiveness, low power requirement and light weight. The proposed system successfully transmits the bidirectional information at a link range of 40 m under pure sea conditions in the presence of distinctive air bubble populations. The observed bit error rate (BER) values are 1.89 × 10− 13 and 1.19 × 10− 04 for the downlink and uplink respectively at a link range of 40 m, these BER values are under the acceptable forward error correction (FEC = 2 × 10− 3) limit. The proposed bidirectional UWOC system is beneficial for the development of a high-speed last-mile underwater solution. [ABSTRACT FROM AUTHOR]

Object detection and image restoration pose significant challenges in deep learning and computer vision. These tasks are widely employed in various applications, and there is an increasing demand for specialized environments where images are prone to blur or noise, which can adversely affect subsequent results. In recent years, significant breakthroughs have been achieved in object detection performance. While some previously proposed methods prioritize high accuracy at the cost of longer inference times, others prioritize speed. Therefore, it is crucial to design an efficient network architecture that maintains both inference speed and high accuracy. This research proposes a network architecture for underwater object detection with an attention mechanism. The proposed approach differentiates itself from other methods by employing a deblurring network as a preprocessing step to restore and enhance the image quality of the underwater dataset. Additionally, in the feature extraction stage of the detection network, channel and spatial feature information are individually enhanced. These adaptive attention features are then integrated into a multi-scale feature fusion. Finally, the cross-stage local method is combined to improve the learning ability of the convolutional neural network while reducing the size of the model. Based on the experimental results, our proposed model architecture achieves leading accuracy and strikes a favorable balance in terms of model size compared to previously proposed methods. Based on our structure, the metrics of AP and AP50 reach 66.8 and 87.6, respectively. [ABSTRACT FROM AUTHOR]

Caddisfly larvae produce silk containing heavy and light fibroins, similar to the silk of Lepidoptera, for the construction of underwater structures. We analyzed the silk of Limnephilus lunatus belonging to the case-forming suborder Integripalpia. We analyzed the transcriptome, mapped the transcripts to a reference genome and identified over 80 proteins using proteomic methods, and checked the specificity of their expression. For comparison, we also analyzed the transcriptome and silk proteome of Limnephilus flavicornis. Our results show that fibroins and adhesives are produced together in the middle and posterior parts of the silk glands, while the anterior part produces enzymes and an unknown protein AT24. The number of silk proteins of L. lunatus far exceeds that of the web-spinning Plectrocnemia conspersa, a previously described species from the suborder Annulipalpia. Our results support the idea of increasing the structural complexity of silk in rigid case builders compared to trap web builders. [ABSTRACT FROM AUTHOR]

Cofferdam is widely employed in the construction of underwater bridge foundations. Its crucial attribute lies in providing a dedicated platform for construction activities and enhancing the water resistance dimensions in structural design, consequently amplifying local scour. However, previous research on local scour has seldom investigated the effect of construction facilities on the life cycle development of local scour on foundations. This gap has led to a misunderstanding of protective strategies against local scour throughout the construction period. In this paper, a scour experiment platform was implemented with a unidirectional flume. Physical model experiments were conducted to scrutinize the protective impact of anti-scour rib structures against local scour. The experimentally determined scour depth was compared to assess the performance of the anti-scour rib protection system. Oblique photogrammetry was subsequently used to capture the morphology of the equilibrium scour pit in the experiments. The associated topographical data were imported into Fluent commercial fluid software for in-depth flow field analysis. A numerical flume model was established to examine the hydraulic characteristics under two distinct topographical conditions: a smooth riverbed during the initial stage of scour and a scoured riverbed at the equilibrium stage of scour. To further determine the protective mechanism of anti-scour rib protection, the influence of anti-scour rib protection on shear stress was investigated numerically. Analyses revealed that incorporating scour protection ribs during cofferdam construction alters the flow field characteristics, hindering the downward movement of subsurface flow beneath the structure, reducing bed shear stress, and consequently mitigating scour effects. The instantaneous protective effect of scour protection ribs strengthens as the scour topography develops. The protective effectiveness of scour protection ribs was mainly influenced by rib length, spacing, and shape. [ABSTRACT FROM AUTHOR]

The scarcity and difficulty in acquiring Side-scan sonar target images limit the application of deep learning algorithms in Side-scan sonar target detection. At present, there are few amplification methods for Side-scan sonar images, and the amplification image quality is not ideal, which is not suitable for the characteristics of Side-scan sonar images. Addressing the current shortage of sample augmentation methods for Side-scan sonar, this paper proposes a method for augmenting single underwater target images using the CBL-sinGAN network. Firstly, considering the low resolution and monochromatic nature of Side-scan sonar images while balancing training efficiency and image diversity, a sinGAN network is introduced and designed as an eight-layer pyramid structure. Secondly, the Convolutional Block Attention Module (CBAM) is integrated into the network generator to enhance target learning in images while reducing information diffusion. Finally, an L1 loss function is introduced in the network discriminator to ensure training stability and improve the realism of generated images. Experimental results show that the accuracy of shipwreck target detection increased by 4.9% after training with the Side-scan sonar sample dataset augmented by the proposed network. This method effectively retains the style of the images while achieving diversity augmentation of small-sample underwater target images, providing a new approach to improving the construction of underwater target detection models. [ABSTRACT FROM AUTHOR]

With the extensive application of sensor technology in scientific ocean research, ocean resource exploration, underwater engineering construction, and other fields, underwater target positioning technology has become an important support for the ocean field. This paper proposes a robust positioning algorithm that combines the disadvantages of distributed estimation and particle swarm optimization, which can solve the large localization error problem caused by uncertainties in underwater acoustic communication and sampling processes. Considering the presence of ranging anomalies and sampling packet loss in underwater acoustic measurements, a weighted coupling filling method is used to correct the outliers in an underwater acoustic ranging signal. Based on the mapping model from the element array to the underwater acoustic responder, an unconstrained optimization algorithm for one-time localization estimation of underwater acoustic targets was established. Based on the one-time localization estimation results of underwater acoustic targets, an improved multi-particle swarm optimization estimation based on interactive search is proposed, which improves the accuracy of underwater target localization. The numerical results show that the positioning accuracy of the proposed algorithm can be effectively enhanced in cases of distance measurement errors and azimuth measurement errors. Compared with the positioning error before optimization, the positioning error can be reduced after optimization. Additionally, the experiment was carried out in the underwater environment of Hangzhou Qiandao Lake, which verified the positioning performance of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Underwater construction, maintenance, and mapping use autonomous underwater vehicles (AUVs) for path planning, path following, and target tracking operations. However, dynamic position management and localization of AUVs are critical issues. Correct localization and dynamic position management to prevent drifts can be used to acquire information on energy efficiency, another crucial topic. In this paper, AUV dynamic modeling using experimental data and position control is studied. The experiments were implemented on a Delphin2 scaled AUV model belonging to the Engineering and Environment Faculty, University of Southampton, UK. Hover and flight style motions according to the different speeds of Delphin2 were implemented in the test tank. Nonlinear coupled mathematical models were studied using shallow neural networks. The models are formed into depth-pitch and heading motion black-box models using the shallow neural network (SNN) algorithm. Proportional integral derivative control of heading motions and depth-pitch motion simulation studies were applied to the SNN model. [ABSTRACT FROM AUTHOR]

The article provides an overview of the proposed USN SEAHAB project in 1966, which aimed to establish a permanent seafloor colony for 40 men at a depth of 600 feet on the continental shelf. It traces the origins of saturation diving, a technique where workers live and work under pressure for extended periods, back to World War II. Captain George F. Bond and his team conducted experiments with gas saturation diving, leading to the development of the SEALAB series. The SEAHAB project sought to build upon the experiences of the SEALAB series and create a permanent deep-sea base for long-duration saturation diving. The article also explores the technologies and challenges associated with the SEAHAB project, referencing the works "Living and Working in the Sea" by Miller/Koblick and the MTS Transactions of the Joint Symposium titled "Man's Extension into the Sea" from 1966. The authors express gratitude to Stephen Hardy for enhancing the quality of the images used in the article and mention that the next issue of the Journal of Diving History will focus on SEALAB III and be published in the fourth quarter of 2023. [Extracted from the article]

The construction of the underwater Internet of Things (UIoT) is crucial to marine resource development, environmental observation, and tactical surveillance. The underwater optical wireless communication (UOWC) system with its large bandwidth and wide coverage facilitates the high-capacity information interconnection within the UIoT networks over short and medium ranges. To enhance the coverage characteristics of the UOWC system, an optimized lemniscate-compensated layout of light-emitting diode (LED) array is proposed in this paper, which can ameliorate the received optical power and reliability at the receiving terminal. Compared with traditional circular and rectangular layouts, the received optical power and bit error rate (BER) performance of the proposed system are analyzed based on the Monte Carlo simulation method. The analysis results show that the proposed LED array achieves a smaller peak power deviation and mean square error of the received optical power under three typical seawater environments. Furthermore, the proposed LED-array scheme supports a better BER performance of the UOWC system. For example, in turbid seawater with a transmission depth of 9.5 m, the BER of the proposed LED array layout is 1 × 10−7, which is better than the BER of 3.5 × 10−6 and 1 × 10−4 under the other two traditional light source layouts. [ABSTRACT FROM AUTHOR]

Underwater object detection (UOD) suffers from low detection accuracy because of environmental degradations, such as haze-like effects, color distortions, and imaging noises. Therefore, we commit to resolving the issue of object detection with compounded environmental degradations that greatly challenges existing deep learning-based detectors. We propose a neural architecture search -based deep learning network to realize the UOD task, which can automatically discover the scene-oriented feature representation. Our network is accomplished through a unified macro-detector and a novel mixed anti-aliasing block (MAaB)-based search space. The macro-detector targets to learn intrinsic feature representations automatically from underwater images containing various environmental degradations and complete the subsequent detection tasks. The novel MAaB-based search space is proposed toward complex underwater scenes. The candidate operator MAaB has multiple kernels and anti-aliased convolutions in a single block for boosting the contextual representation capacity and the robustness of degraded factors. Finally, we use the differential search strategy guides the whole learning process to obtain the scene-friendly results. Extensive experiments demonstrate that our method outperforms the state-of-the-art detectors by a large margin. More importantly, in cases where environmental degradation is severely disturbed, our method is also superior to other popular detectors. [ABSTRACT FROM AUTHOR]

An improved multi-objective particle swarm optimization algorithm is combined with a machine learning classifier to meet the needs of underwater manned/unmanned cooperative warfare architecture evaluation. Firstly, based on the traditional Cauchy variation method, the particles in the population are disturbed in a dynamic way so that the particles trapped in the local optimal can jump out of the local optimal, and the convergence performance of the particle swarm optimization is improved. Secondly, the accuracy of the index set is analyzed based on the CART decision tree algorithm and the IWRF algorithm. A screening method of key indexes with fewer evaluation indexes and high evaluation accuracy is developed to solve the problem of a large number of evaluation indexes and unclear correlation of the underwater combat system. Through simulation, the extraction results of key indicators were verified, and the reliability coefficient of the final simulation experiment was 0.93, which can be considered as high reliability and effectiveness of the key indicators extracted in this study. By combining multi-objective optimization with machine learning and weighing evaluation efficiency and accuracy, a high-precision and rapid evaluation of a few indicators is achieved, which provides support for establishing an evaluation model of SoS architecture for underwater manned/unmanned cooperative operations. This research result can provide inspiration for the evaluation and evaluation of the system in order to analyze the accuracy of indicators and the evaluation effect and carry out research by simulating the actual system with tools with a high simulation degree. [ABSTRACT FROM AUTHOR]

In order to solve the problems of low information management level and large safety risks in the construction of caisson prefabrication and transportation in the construction of gravity wharf, and improve the safety management level of gravity wharf construction, the whole process technology innovation and analysis was carried out in the key construction of No.9and No.10 berths in the Dalanping South Operation Area of Qinzhou Port. Through the analysis of precast yard construction design, key technologies of caisson prefabrication and transportation, water and underwater construction technology, digital innovation and other technologies, the key points of construction management technology were summarized, and technical measures such as intelligent steel bar processing workshop, caisson steel bar segmented lashing overall lifting technology, electric roof transportation integrated trolley transfer large caisson technology, BIM digital simulation technology and other technical measures were proposed. The technical and management experience in the construction of gravity wharf was accumulated, the project meets the design and specification requirements was ensured, the level of engineering intrinsic safety management was greatly improved, which can provide reference for similar engineering projects. [ABSTRACT FROM AUTHOR]

In order to investigate the development scale and spatial morphology characteristics of karst in the sea area, ensure that shield tunneling can smoothly pass through the underwater karst area, and effectively reduce safety hazards during the construction process of underwater tunnels. In this paper, relying on the karst survey project in a certain section of Dalian Metro Line 5, the development of karst in the site area was first divided by the seismic reflection method and the transient electromagnetic method in the sea area, and then the cross hole elastic wave CT method was used to find out the characteristics and scale of single karst development, ultimately achieving the goal of high-precision detection of the scale of karst development, spatial morphological characteristics, etc. within the influence area of the submarine tunnel. The survey results indicate that: (1) The traditional water surface geophysical exploration method can divide karst development zones from a macroscopic perspective, using water seismic reflection method to divide 2 karst development zones, transient electromagnetic method to divide 36 karst development zones, and dividing the entire survey interval into 3 sections: karst micro development, karst medium development, and karst strong development; (2) Due to the constraints of seawater conductivity, traditional geophysical methods such as surface and inter hole electrical methods are not suitable for karst exploration in sea areas; (3) The cross hole elastic wave CT method can accurately detect the spatial morphology of individual karst in local areas, accurately scan the development of karst between two holes, and clearly reflect the relationship between karst caves and tunnel bodies on a two-dimensional profile. [ABSTRACT FROM AUTHOR]

A novel testing methodology was developed in this study to efficiently evaluate the non-dispersibility of Reactive Powder Concrete (RPC) that does not disperse (Non- Dispersive RPC or NDRPC) - a concrete variant derived from the amalgamation of RPC and non-dispersive concrete. To study the fresh behavior of NDRPC, a series of fourteen mixes were prepared, each incorporating an Anti-Wash Admixture (AWA) concentration ranging between 0.5% and 2%. Fresh state properties were identified through a series of Slump Flow, V Funnel, L-box, and Setting Time tests, while washout resistance was determined through modified Stream Test, Turbidity, and pH tests. The findings constitute the first efficient evaluation of the non-dispersibility of fresh Self-Compacted Mortar (SCM) or concrete mixtures when placed underwater, as ascertained by V Funnel and L-box tests under similar conditions. Experimental results indicated a synergistic effect between AWA and High Range Water Reducer Admixture (HRWRA) concentrations on the properties, which could be counterbalanced by increasing the incorporation of silica fume to 30%. Notably, a significant reduction in washout loss was observed when silica fume replacement was increased to 30%. [ABSTRACT FROM AUTHOR]

Here, the concept of "aerofluidics," in which a system uses microchannels to transport and manipulate trace gases at the microscopic scale to build a highly versatile integrated system based on gas‒gas or gas‒liquid microinteractions is proposed. A kind of underwater aerofluidic architecture is designed using superhydrophobic surface microgrooves written by a femtosecond laser. In the aqueous medium, a hollow microchannel is formed between the superhydrophobic microgrooves and the water environment, which allows gas to flow freely underwater for aerofluidic devices. Driven by Laplace pressure, gas can be self‐transported along various complex patterned paths, curved surfaces, and even across different aerofluidic devices, with an ultralong transportation distance of more than 1 m. The width of the superhydrophobic microchannels of the designed aerofluidic devices is only ≈42.1 µm, enabling the aerofluidic system to achieve accurate gas transportation and control. With the advantages of flexible self‐driving gas transportation and ultralong transportation distance, the underwater aerofluidic devices can realize a series of gas control functions, such as gas merging, gas aggregation, gas splitting, gas arrays, gas‒gas microreactions, and gas‒liquid microreactions. It is believed that underwater aerofluidic technology can have significant applications in gas‐involved microanalysis, microdetection, biomedical engineering, sensors, and environmental protection. [ABSTRACT FROM AUTHOR]

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Due to the complexity of the underwater environment, tracking underwater targets via traditional particle filters is a challenging task. To resolve the problem that the tracking accuracy of a traditional particle filter is low due to the sample impoverishment caused by resampling, in this paper, a new tracking algorithm using Harris-hawks-optimized particle filters (HHOPF) is proposed. At the same time, the problem of particle filter underwater target feature construction and underwater target scale transformation is addressed, the corrected background-weighted histogram method is introduced into underwater target feature recognition, and the scale filter is combined to realize target scaling transformation during tracking. In addition, to enhance the computational speed of underwater target tracking, this paper constructs a nonlinear escape energy using the Harris hawks algorithm in order to balance the exploration and exploitation processes. Based on the proposed HHOPF tracker, we performed detection and evaluation using the Underwater Object Tracking (UOT100) vision database. The proposed method is compared with evolution-based tracking algorithms and particle filters, as well as with recent tracker-based correlation filters and some other state-of-the-art tracking methods. By comparing the results of tracking using the test data sets, it is determined that the presented algorithm improves the overlap accuracy and tracking accuracy by 11% compared with other algorithms. The experiments demonstrate that the presented HHOPF visual tracking provides better tracking results. [ABSTRACT FROM AUTHOR]

This paper proposes an algorithm that provides operational strategies for multiple tethered autonomous underwater vehicle (T-AUV) systems for entanglement-free navigation. T-AUVs can perform underwater tasks under reliable communication and power supply, which is the most substantial benefit of their operation. Thus, if one can overcome the entanglement issues while utilizing multiple tethered vehicles, the potential applications of the system increase including ecosystem exploration, infrastructure inspection, maintenance, search and rescue, underwater construction, and surveillance. In this study, we focus on developing strategies for task allocation, path planning, and scheduling that ensure entanglement-free operations while considering workload balancing among the vehicles. We do not impose restrictions on the size or shape of the vehicles at this stage; our primary focus is on efficient tether management as an initial work on the topic. To achieve entanglement-free navigation, we propose a heuristic based on the primal-dual technique, which enables initial task allocation and path planning while minimizing the maximum travel cost of the vehicles. Although this heuristic often generates sectioned paths due to its workload-balancing nature, we also propose a mixed approach to provide feasible solutions for non-sectioned initial paths. This approach combines entanglement avoidance techniques with time scheduling and sectionalization methods. To evaluate the effectiveness of our algorithm, extensive simulations were conducted with varying problem sizes. The computational results demonstrate the potential of our algorithm to be applied in real-time operations, as it consistently generates reliable solutions within a reasonable time frame. [ABSTRACT FROM AUTHOR]

Unlike aerial or terrestrial navigation, the global navigation satellite system (GNSS) is not available underwater. This is a big challenge for underwater navigation. The inertial navigation system (INS) aided by the single-beacon acoustic positioning system (APS) provides one solution, but the long-range case is limited by low-SNR conditions. Inspired by passive synthetic aperture detection, we proposed a new tightly coupled navigation algorithm based on spatial synthesis and one-way-travel-time (OWTT) range measurement. We design two estimators: the DOA/range estimator using the model-based method and the tightly coupled INS/APS navigation estimator. Based on the improved UKF, all information is combined. Simulation is carried out in MATLAB. Compared with range-only tightly coupled INS/APS navigation, synthetic long baseline (SLBL) algorithm and Doppler velocity logger (DVL) aided centralized extended Kalman filter (CEKF) based single beacon INS/OWTT navigation, the proposed method's performance is proven. The main contributions of this work are: (1). Propose a new architecture of underwater integrated navigation; (2). Apply the passive acoustic detecting method in the navigation to improve accuracy. (3). Apply the tightly coupled method to improve availability. [ABSTRACT FROM AUTHOR]

The requirements of early strength gain in concrete are indispensable in various structural applications such as precast industry, underwater construction, construction at low temperatures, shotcrete concrete, and so on. Generally, to accelerate the strength gain process in concrete under such applications, conventional hardening accelerators are used, which often suffer from different limitations, such as lowering of ultimate strength and durability properties. Calcium silicate hydrate (C-S-H) seed-based accelerators have the potential to overcome the limitations associated with conventional accelerators. Therefore, they are gradually becoming popular. In this research work, a novel ion-exchange process-based method has been developed and validated for the synthesis of a C-S-H-based accelerator, which successfully eliminated the limitations associated with commercially available hardening accelerators. The synthesis process used inexpensive resources such as agricultural waste to produce a C-S-H seed suspension that is almost free from harmful chemical impurities. Different characterization studies were performed to determine the structural, morphological, and chemical properties of the synthesized C-S-H seed. The heat of hydration and compressive strength studies proved that the material is effective in achieving early strength gains in concrete. The presence of synthesized C-S-H seeds in concrete effectively accelerated the strength gain process by approximately 40% during the initial hours of setting. Therefore, the developed hardening accelerator, when incorporated in concrete, has the potential to reduce the formwork removal time, resulting in the acceleration of the production cycle of precast elements. [ABSTRACT FROM AUTHOR]

The most significant increase of current task is in the desire for operational flexibility and agility in large-scale underwater network application scenarios in recent years. In order to address the challenging problems in Underwater Wireless Sensor Networks (UWSNs), we propose a large-scale UWSN based on the cellular network architecture called Underwater Cellular (uw-Cellular) network. It is designed especially for application scenarios where a large number of both fixed and mobile network nodes exist in a wide area to monitor the underwater environment. We also design protocols in each network layer in order to ensure reasonable channel sharing, data forwarding path selection and data reliability. The purpose of the simulation study we implement is to evaluate the performance of the CLA routing strategy compared to the VBF and the MFLOOD protocols in the uw-Cellular network. We also deploy a twenty-node uw-Cellular network in the real-world environment as the field case study. The experimental results showed that the Data Rate between any nodes could reach above 500 bps, and the network Average Throughput was no less than 550 bps under various load situations. [ABSTRACT FROM AUTHOR]

Due to the functions of a water intake structure, its underwater structure has to be located relatively deep in water. In the silty coastal environment with limited construction water area and unclear sight under the water, it is necessary to optimize the scheme selection and the construction technology according to the geological conditions of the construction site and the construction experience in similar projects around. The technology for underwater pile installation, underwater welding of steel brackets, underwater construction of prefabricated beams and pile cores and underwater installation of prefabricated culverts is emphatically controlled by means of field practice and summary of data of the project, and necessary key measures were formulated for relevant supporting pre-tightening and post-tightening procedures. Reliable quality and safety control of the construction of the underwater structure of water intakes have been finally achieved. [ABSTRACT FROM AUTHOR]

Underwater wet welding is commonly used in joining pipelines and in underwater construction. Harmful and hazardous compounds are added to many flux-cored wires for underwater welding and cutting, and can have a negative impact on marine life. The specific objective of this study was to evaluate the aquatic toxicity of two suspension samples obtained using welding electrode and flux-cored wire in marine microalgae Attheya ussuriensis and Porphyridium purpureum. Growth rate inhibition, cell size, and biochemical changes in microalgae were evaluated by flow cytometry. The results of the bioassay demonstrated that the suspension obtained after welding with electrode had an acute toxic impact on diatomic microalgae A. ussuriensis, and both tested suspensions revealed chronic toxicity in this microalga with a 40% growth rate inhibition after exposure to 40–50% of prepared suspensions for 7 days. Red algae P. purpureum revealed tolerance to both suspensions caused by exopolysaccharide covering, which prevents the toxic impact of metal cations such as Al, Ti, Mn, Fe, and Zn, which are considered the main toxic components of underwater welding emissions. [ABSTRACT FROM AUTHOR]

Subsea geological exploration is the primary link to ensure the quality and safety of underwater engineering, and appropriate geophysical exploration means are the key to marine geological exploration. Based on the construction project of Dalian Bay Subsea Tunnel, in view of the possible karst caves below the foundation trench for the immersed tubes, which may endanger the construction safety, the single-channel seismic exploration method and the transient electromagnetic method were first used to carry out overall geophysical exploration for the planned alignment of the project and then boreholing was made to verify the results in selected localities. While determining the location, scale and depth of the karst caves, the seabed geological exploration method was explored to provide a reference for underwater engineering and construction. The results of geophisical exploration show that: 1) there are 49 anomalies in the exploration area, mainly reflections of dolomite dissolution fissures or karst development, but no large karst caves, which do not pose a threat to construction safety; 2) the integrated physical and boreholing exploration method can effectively improve the reliability and scientificity of the exploration results, and provide an accurate basis and strong support for underwater engineering in the design and exploration stage. [ABSTRACT FROM AUTHOR]

Batychron is a flexible underwater bell patented by the Gdynia Maritime University as a device used in hydro-technics engineering for underwater transport and diving while maintaining the safety of human life. This study aims to present the methods and results of strength tests and the conducted analysis of the selection of the most appropriate method of joining thermoplastic polyurethane film (TPU) and polypropylene belts for underwater use to obtain a device with a specific buoyancy force. A universal testing machine with a hydraulic drive was used for the tests. Various methods of joining polypropylene belts were tested to select the most favourable in terms of strength properties. For this purpose, two types of materials were selected: the TE324 polyester belt and the TS501_50 style belt. Various connection methods have been used: without seams; zig-zag stitch, straight cross; cross stitch, straight longitudinal; cross stitch, straight transverse, in order to select a joint with the highest strength parameters. In addition, the tensile strength of individual types of belts was tested. The methods of joining the TPU film were verified. The obtained results allowed us to determine that the strongest bond of TE324 material is a straight, longitudinal cross stitch. This is related to the load distribution in the belts tested in laboratory conditions, but also reflected in their practical application. Thanks to the results obtained, it was possible to select the optimal methods of joining (connection) and the construction of Batychron. [ABSTRACT FROM AUTHOR]

In the engineering construction of immersed tube tunnel, the foundation bed bathymetry is an important part of the foundation construction, and high -precision foundation bed bathymetry is an important guarantee for the quality of the foundation engineering. Relying on the gravel leveling test project of the submarine tunnel foundation bed of Shenzhen Zhongshan Link project, the research and application of high-precision detection technology based on multi-beam bathymetry system was carried out. The underwater same position parameter conversion comparison method was used to realize the testing and verification of the accuracy of multi-beam bathymetry system by geodetic high precision instruments. The calibration and error mandatory correction of the data processing model of multi -beam system by setting the underwater elevation ratio measurement steel plate effectively improves the accuracy of foundation bed laying. By comparing the multi-beam sweep data with the results of penetration measurement, the results are basically consistent, which indicates that the multi -beam bathymetry system meets the project needs. The high-precision detection technology of multi-beam bathymetry system for immersed tunnel foundation construction can provide reliable reference data for underwater foundation construction. [ABSTRACT FROM AUTHOR]

The safety of marine construction workers and marine pollution problems are occurring due to large-scale offshore construction. In particular, underwater construction work in the sea has a higher risk than other work, so it is necessary to apply an unmanned alternative system that considers the safety of the workers. In this paper, the ROV system for offshore construction has been developed for underwater unmanned work. A monitoring system was developed for position control through the control of underwater propellants, pneumatic gripper, and monitoring of underwater work. As a result of the performance evaluation, the underwater movement speed of the ROV was evaluated to be 0.89 m/s, and it was confirmed that the maximum load of the pneumatic gripper was 80 kg. In addition, the network bandwidth required for underwater ROV control and underwater video streaming was evaluated to be more than 300Mbps, wired communication at 92.7 ~ 95.0Mbit/s at 205m, and wireless communication at 78.3 ~ 84.8Mbit/s. [ABSTRACT FROM AUTHOR]

The need to design computing platforms with low water footprint and enhanced energy efficiency makes non-terrestrial computing platforms attractive. Large scale computing platforms in non-terrestrial environments are increasingly receiving attention. In this regard, underwater data centers (UDCs) are considered to have operational benefits due to their low cooling cost. Underwater data centers experience challenges due to marine heat waves. The occurrence of marine heat waves limits the amount of ocean water available for UDC cooling. This paper proposes a mechanism to detect marine heat waves, and ensure continued UDC functioning. The proposed mechanism utilizes reservoirs to store water and ensure continued functioning of underwater data center. In addition, the proposed research presents the reservoir as a service (RaaS) for ensuring UDC cooling. Furthermore, the presented research also describes modular form factor approach for UDC development. This is being done with the aim of enhancing UDC adoption and use in capital constrained contexts. The underwater data center operational duration is investigated. Evaluation shows that the proposed solution enhances the operational duration by an average of (5.5–12.3) % and (5.2–11.5) % given that marine heat waves span 10 epochs and 15 epochs during an operational phase, respectively. [ABSTRACT FROM AUTHOR]

This paper introduces the current situation of constructing the seafloor geodetic network from de‐ sign, layout, measurement, and data processing. Based on the requirements of national ocean strategy and the development of marine geodetic technology, the problems of the construction of seafloor geodetic net‐ works at the present stage are analyzed. According to the results, it can be concluded the coverage of the current seafloor geodetic network is limited, and the information sharing is insufficient. In addition, the de‐ sign and layout principles are not combined with the positioning precision of the network, which are mostly qualitative descriptions and lack operability. The accuracy and resolution of the sound velocity field are low and the measurement and data processing are difficult to meet the requirements of large-scale and high-pre‐ cision underwater PNT（positioning，navigation and timing）network construction. To solve the mentioned problems, the concept of constructing the underwater PNT network with remote communication, informa‐ tion interconnection and telemetry is put forward. Several key technologies, including the design and layout of the underwater PNT network, the construction of the ocean sound velocity field with high precision and high resolution, the measurement strategy, data processing method and the thought of self-calibration and self-maintenance for underwater control points, the function of target and environment telemetry and sensing services, are discussed to provide support for the new generation of high-performance marine geo‐ detic survey and the construction of underwater PNT network. It is believed that the proposed network sys‐ tem will lead to a revolution in underwater PNT construction when problems such as the optimal design of the large-scale network, enhancing positioning service, the accurate timing and time synchronization, re‐ mote communication and the extension of the application are broken through. [ABSTRACT FROM AUTHOR]

The cofferdam method is generally applied in the construction of underwater pier foundation in bridge engineering, and the pouring of bottom sealing concrete is one of the important links in the construction of the cofferdam. The bottom sealing concrete can prevent water seepage and balance the main body of the cofferdam, and its structural size and construction quality have a great influence on the above functions. Under the condition of large water level difference, it is difficult to determine the reasonable thickness of the bottom sealing concrete. There are few related studies in this field, and there is a lack of systematic summary of calculation theory. This work theoretically deduces the approximate solution of ultimate bending moment and ultimate stress of the bottom sealing concrete, introduces two different calculation methods, systematically summarizes the calculation methods of three kinds of ultimate stress, analyzes the calculation methods of ultimate bonding force, and uses ANSYS finite element software to simulate a specific bottom sealing concrete model, and compares it with the theoretical calculation results. The maximum stress obtained by the approximate solution is closer to the actual monitoring data than the traditional method, and the calculation method of the bonding force can be used to make a rough estimate. [ABSTRACT FROM AUTHOR]

Stainless steel tubes have excellent plasticity and ductility, and FRP grids have favorable advantages for application in specific structural reinforcements. For systems including underwater construction without drainage, underwater columns reinforced with stainless steel tube-FRP grids are proposed using nondispersive mortar (NDM) as the reinforcement layer to best leverage the material properties of all elements. This paper carried out axial compression tests on 18 underwater columns reinforced with stainless steel tube-FRP grids (SS-FGWCs), 6 columns reinforced with stainless steel tube-FRP grids on land (SS-FGLCs), 3 underwater columns reinforced with stainless steel tubes (SSWCs), and 3 unreinforced concrete columns. The research parameters include the number of FRP grid layers, the types of FRP grids, and the reinforcement layer mortar pouring environments. The test results showed that FRP grids can be combined with stainless steel tubes (SSs) and nondispersive mortar (NDM) to reinforce concrete columns in underwater construction without drainage. In addition, compared with those of the SSWC specimens, after the BFRP grid and CFRP grid were built in, the ultimate stresses of the specimens increased by 13.4% ∼ 20.8% and 19.5% ∼ 25.4%, respectively, and the ultimate strains increased by 6.8% ∼ 31.7% and 21.8% ∼ 59.1%, respectively. Compared to BFRP grids, CFRP grids provide better reinforcement of the underwater columns. Existing prediction models were evaluated for ultimate stress calculations, the calculation methods for the ultimate stress and ultimate strain applicable to the SS-FGWCs and SS-FGLCs were revised, and a calculation model for the FRP grid failure point was proposed. Finally, a corresponding full stress–strain curve model was established. • Underwater columns reinforced with stainless steel tube-FRP grids was presented. • Underwater reinforcement specimens can achieve favorable compression performance. • Calculation method for ultimate point was revised, and calculation model for FRP grid failure point was proposed. • Full stress–strain curves of SS-FGWCs and SS-FGLCs were established. [ABSTRACT FROM AUTHOR]

Copyright of Guangdong Architecture Civil Engineering is the property of Guangdong Architecture Civil Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The underwater wireless sensor network is an important component of the underwater three-dimensional monitoring system. Due to the high bit error rate, high delay, low bandwidth, limited energy, and high dynamic of underwater networks, it is very difficult to realize efficient and reliable data transmission. Therefore, this paper posits that it is not enough to design the routing algorithm only from the perspective of the transmission environment; the comprehensive design of the data transmission algorithm should also be combined with the application. An edge prediction-based adaptive data transmission algorithm (EP-ADTA) is proposed that can dynamically adapt to the needs of underwater monitoring applications and the changes in the transmission environment. EP-ADTA uses the end–edge–cloud architecture to define the underwater wireless sensor networks. The algorithm uses communication nodes as the agents, realizes the monitoring data prediction and compression according to the edge prediction, dynamically selects the transmission route, and controls the data transmission accuracy based on reinforcement learning. The simulation results show that EP-ADTA can meet the accuracy requirements of underwater monitoring applications, dynamically adapt to the changes in the transmission environment, and ensure efficient and reliable data transmission in underwater wireless sensor networks. [ABSTRACT FROM AUTHOR]

High fluvial input combined with specific topographic and oceanographic settings in the Caspian Sea create favorable conditions for contourite deposition. For the first time in its middle portion, contourite deposits have been observed in high-resolution seismic profiles. Various types of contourite drifts and mixed depositional systems have been revealed on the lower slope and in the adjacent basin, some of which are accompanied by sediment wave fields. The deposition of contourites or turbidites and their lateral distribution is controlled by sea-floor topography and oceanographic processes, as well as the modern activity of gravity flows downslope on the western Caucasian slope and in the channel system on the Mangyshlak Sill. The contourite drifts and sediment wave fields form several contourite depositional systems, which seem to merge in the Caspian contourite depositional complex. This occurs near the foot of slopes of the Derbent Basin and is related to the counterclockwise circum-Caspian current in the Middle Caspian Sea. The fact that the Caspian Sea is the largest lake in the world makes this region a significant area for research into the "lake contourites" issue. The Caspian Sea is an important oil-producing area, and sedimentary processes related to the contourite and turbidite can be a source of potential geohazards in the construction and exploitation of underwater engineering structures [ABSTRACT FROM AUTHOR]

The construction of underwater geodetic networks (UGN) is crucial in marine geodesy. To provide high-precision kinematic positioning for underwater submersibles, an underwater acoustic geodetic network configuration of three seafloor base stations, one subsurface buoy, and one sea surface buoy is proposed. The simulation results show that, for a 3 km-deep sea, based on the proposed UGN, the submersible positioning range and positioning accuracy are primarily affected by the size of the seafloor base station array, while the height of the subsurface buoy has a greater impact on the submersible positioning accuracy than the positioning range. Considering current acoustic ranging technology, the kinematic positioning performance of the UGN is optimal when the seafloor base stations are 9~13 km apart and the subsurface buoy is less than 2.5 km above the seafloor, which can achieve a submersible positioning accuracy of less than 30 m within an underwater space of 25 km × 25 km × 3 km. The proposed cost-effective UGN configuration can provide high-precision submersible kinematic positioning performance for seafloor surveying and ocean precision engineering. The impact of the underwater environment on the acoustic transmission characteristics should be further investigated. [ABSTRACT FROM AUTHOR]

Fast and accurate acquisition of underwater structures information has always been a hot spot in sonar detection,and has important application value in water transport engineering management, port engineering quality assurance and structure disaster prevention and reduction detection. In this paper, the multi-beam sounding system and the three-dimensional multi-beam scanning sonar system with the same beam principle were selected to detect two typical underwater port structures,namely, the plane engineering of foundation trench excavation and bedding leveling with deep geographic position and large detection target size, and the vertical shore wall engineering of caisson wharf with high precision requirements. The quality of underwater engineering was evaluated in combination with relevant detection specifications. The result shows that the multi-beam sounding system has high efficiency on detection, and it can meet the detection requirements of underwater port engineering. The combination of multi-beam sounding system and three-dimensional multi-beam scanning sonar system to carry out vertical shore wall detection can provide accurate guidance for the construction control and evaluation of wharf underwater wall engineering. Multi-beam sonar system can detect the construction deviation of underwater port engineering accurately, and evaluate the quality of underwater port construction in combination with relevant detection specifications. [ABSTRACT FROM AUTHOR]

Copyright of Tunel is the property of Ceska Tunelarska Asociace ITA-AITES, z.s and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper addresses the development of a modular software architecture for the design/construction/operation of a remotely operated vehicle (ROV), based on systems engineering. First, systems engineering and the Vee model are presented with the objective of defining the interactions of the stakeholders with the software architecture development team and establishing the baselines that must be met in each development phase. In the development stage, the definition of the architecture and its connection with the hardware is presented, taking into account the use of the actor model, which represents the high-level software architecture used to solve concurrency problems. Subsequently, the structure of the classes is defined both at high and low levels in the instruments using the object-oriented programming paradigm. Finally, unit tests are developed for each component in the software architecture, quality assessment tests are implemented for system functions fulfillment, and a field sea trial for testing different modules of the vehicle is described. This approach is well suited for the development of complex systems such as marine vehicles and those systems which require scalability and modularity to add functionalities. [ABSTRACT FROM AUTHOR]