Hasil untuk "Naval Science"

Surg Cdr Prabhat Chauhan, Col Amit Katyal, Deputy Commandent M. Uday Kumar et al.

Introduction: Vasoplegic syndrome (VS) is a distributive shock characterized by profound hypotension, low systemic vascular resistance, and inadequate response to conventional vasopressors. While commonly observed in cardiac surgery, its occurrence in renal transplant settings is rare. Methylene blue (MB), through inhibition of the nitric oxide–cyclic GMP pathway, has shown promise in managing vasoplegia by restoring vascular tone. Methods: We report two cases of vasoplegic shock managed with MB. The first case involved a patient who developed intraoperative vasoplegic shock during an ABO-compatible renal transplant. The second case involved a renal transplant recipient who presented two years post-transplant with septic shock and vasoplegia, refractory to high-dose vasopressors. Both patients were administered intravenous MB (1 mg/kg) following failure of standard therapy. Additionally, a review of literature was conducted to explore the clinical application, timing, and outcomes of MB use in vasoplegic shock. Results: In both cases, MB administration led to a significant improvement in hemodynamics, with reduction in vasopressor requirements and resolution of shock. No adverse effects attributable to MB were noted. Literature review revealed that MB is most effective when administered early (within 8 hours of shock onset), with growing evidence supporting its use in cardiac, liver transplant, and septic shock scenarios. However, reports of MB use in renal transplant patients remain sparse. Safety concerns, including potential serotonin syndrome, pulmonary vasoconstriction, and methemoglobinemia, have been noted in isolated reports but were not observed in our cases. Conclusion: These cases highlight the potential role of methylene blue as an adjunct in the management of refractory vasoplegic shock, including in the renal transplant population. While its use appears safe and effective in selected patients, further prospective studies are needed to standardize its role in transplant-associated vasoplegia.

Li Zhou, Runxin Xu, Jiayi Bian et al.

Collisions between ships and sea ice pose a significant threat to maritime safety, making it essential to detect sea ice and perform safety-oriented path planning for polar navigation. This paper utilizes an optimized You Only Look Once version 5 (YOLOv5) model, designated as YOLOv5-ICE, for the detection of sea ice in satellite imagery, with the resultant detection data being employed to input obstacle coordinates into a ship path planning system. The enhancements include the Squeeze-and-Excitation (SE) attention mechanism, improved spatial pyramid pooling, and the Flexible ReLU (FReLU) activation function. The improved YOLOv5-ICE shows enhanced performance, with its mAP increasing by 3.5% compared to the baseline YOLOv5 and also by 1.3% compared to YOLOv8. YOLOv5-ICE demonstrates robust performance in detecting small sea ice targets within large-scale satellite images and excels in high ice concentration regions. For path planning, the Any-Angle Path Planning on Grids algorithm is applied to simulate routes based on detected sea ice floes. The objective function incorporates the path length, number of ship turns, and sea ice risk value, enabling path planning under varying ice concentrations. By integrating detection and path planning, this work proposes a novel method to enhance navigational safety in polar regions.

Shijie LI, Taixu LIU, Jialun LIU et al.

ObjectiveThis study aims to solve the problem of path-following control under environmental disturbances and model uncertainties, especially the effects of external wind and wave environments. MethodBased on a model predictive control (MPC) controller, improved model-free adaptive control (IMFAC) is introduced as the path following control compensator. The error between the ship's actual state and predicted state is corrected to solve the problem of the insufficient accuracy of the model under environmental disturbances such as sudden crosswinds and external wind waves, thereby improving the precision of path-following control. ResultsShip path-following control simulation experiments are conducted with a scaled-down KVLCC2 ship model. As the results show, compared with traditional MPC control, the MPC-IMFAC method reduces the maximum absolute heading error of the ship by 25.4% under sudden disturbances, and the average absolute heading error decreases by 2.6% under time-varying environmental disturbances. ConclusionThe simulation results verify that this control method possesses superior anti-interference ability while ensuring path-following control accuracy.

Cheng-Wei Wang, Shau-Shiun Jan

Precise point positioning (PPP), which is characterized by reliable positioning accuracy and flexibility, has been regarded as a highly promising technique. Precise ephemeris is essential for PPP; however, the conventionally used standard product 3 components have an almost biweekly latency. The multi-global navigation satellite system (GNSS) advanced demonstration tool for orbit and clock analysis (MADOCA), a novel next-generation service, aims to provide real-time correction messages for rapid-convergence PPP in regional areas. Additionally, to ensure seamless navigation during signal-interrupted conditions, an inertial measurement unit (IMU) can be tightly integrated with the motion constraint models. This paper presents a comprehensive analysis of standalone MADOCA-PPP and MADOCA-enhanced tightly coupled PPP/IMU. The approaches were evaluated under multiple scenarios. In suburban regions, the horizontal root mean square error (RMSE) was 0.4 m, with a 95th percentile horizontal error of 0.6 m. In GNSS-challenging environments, the horizontal RMSE was 0.92 m, with a 95th percentile horizontal error of 1.6 m.

Zhiqiao Wu, Xueping Zhen, Gangshu (George) Cai et al.

AbstractThe extant literature has mostly blamed the setup costs and added transportation costs for the failures of relocating procurement centers overseas, whereas internal decentralization has long been ignored. In practice, issues such as the arm's length principle and information asymmetry can prevent the headquarters from fully centralizing its divisions when offshoring its procurement center overseas. To examine the impact of internal decentralization, we investigate the decision of a firm's headquarters regarding whether to set up an overseas procurement center and whether to further decentralize the procurement center. This article investigates a stylized model and reveals that, even without the setup and transportation costs, it is not always beneficial for the firm to offshore procurement centers under the impact of transfer pricing unless the tax advantage is big enough. An offshoring procurement system with a decentralized procurement center can outperform one with a centralized procurement center when the tax rate disparity is large, because the headquarters' procurement cost information screening makes it benefit more from a decentralized procurement center when the tax rate gap is big. Besides the intuitive trade‐off between the tax‐saving effect and the double marginalization effect caused by the internal decentralization, some indirect effects—cost‐saving effect of the procurement effort and the tax‐paying asymmetry effect (i.e., the procurement center still pays a positive tax even if the headquarters is not profitable)—are found to have a significant impact on the headquarters' choice. Screening the procurement cost information amplifies the advantage of the procurement independent accounting system when the tax rate disparity is big but decreases it otherwise.

Wenxiao Chu, Maria Vicidomini, Francesco Calise et al.

The present paper reviews the hot topics at the 18th Conference on Sustainable Development of Energy, Water, and Environment Systems (SDEWES) held from 24 to 29 September 2023 in Dubrovnik, Croatia. The selected papers, including aspects of biomass energy application, energy saving in building, low-carbon development and climate change adaptation, hybrid application of sustainable energy, energy storage system, and other measures in sustainable development, are published in this Special Issue of Energies. The 12 selected papers in Energies and corresponding literature that relates to the above topics and has been published in the most recent year are reviewed. In particular, diversifying energy applications are trending towards comprehensive integration with more efficient clean energy capacities for global energy procurement, which can also offer increased resilience and sustainability, reduce reliance on fossil fuels, mitigate environmental impacts, and enhance energy security through a mix of renewable sources and innovative technologies. Meanwhile, energy storage has become increasingly important, which can manage the intermittent of renewable energy, stabilize the grid, and improve energy security and resilience against disruptions. In addition to conventional solar energy storage, biomass energy storage, building energy storage, water storage, etc., can also reduce the overall energy costs, deferring investments in additional transmission infrastructure.

Zhenquan Wei, Jinfeng Ma, Gaowen He et al.

Shallow-water carbonate rocks constitute a crucial component of large guyots, arising in distinct environments and harboring valuable insights into the evolutionary stages of seamount islands as well as the tectonic conditions of the underlying oceanic plate. Laser Ablation Multi-Collector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS) was used to conduct in situ U–Pb isotope dating of carbonate minerals with low uranium content collected from Weijia Guyot. This dating approach yielded crucial evidence for the vertical development of the seamount. Our study indicates that shallow-water carbonate rocks in Weijia Guyot had a temporal range between 91 My and 137 My. The carbonate rocks underwent two growth phases, Hauterivian to Barremian and Cenomanian to Turonian, with a hiatus of approximately 20 My. Since the Hauterivian age, the shield volcano of Weijia Guyot is essentially complete, with its seamount top exposed at or near sea level and receiving its first stage of shallow-water carbonate sedimentation. Based on the dating of both shallow-water carbonate rocks and hawaiite within the Weijia Guyot, it is inferred that approximately 10 My elapsed from shield-building volcanism to late alkalic volcanism. During the Turonian age, the main reason for the second phase of shallow-water carbonate rocks in the seamounts was the regional tectonic uplift triggered by the drift of the Weijia Guyot along with the Pacific Plate toward the Society hotspot.

Pibo Su, Zhongquan Zhao, Kangshou Zhang

The Mesozoic subduction zone over the Dongsha Waters (DSWs) of the South China Sea (SCS) is a part of the westward subduction of the ancient Pacific plate. Based on the comprehensive interpretation of deep reflection seismic profile data and polar magnetic anomaly data, and the zircon dating results of igneous rocks drilled from well LF35-1-1, the Mesozoic subduction zone in the northeast SCS is accurately identified, and a Mesozoic subduction model is proposed. The accretion wedges, trenches, and igneous rock zones together form the Mesozoic subduction zone. The evolution of the Mesozoic subduction zone can be divided into two stages: continental subduction during the Late Jurassic and continental collision during the late Cretaceous. The Mesozoic subduction zone controlled the structural pattern and evolution of the Chaoshan depression (CSD) during the Mesozoic and Neogene eras. The gas source of the hydrate comes from thermogenic gas, which is accompanied by mud diapir activity and migrates along the fault. The gas accumulates to form gas hydrates at the bottom of the stable domain; BSR can be seen above the mud diapir structure; that is, hydrate deposits are formed under the influence of mud diapir structures, belonging to a typical leakage type genesis model.

Yawen He, Yanhua Liu, Duxian Feng et al.

With global warming and the gradual melting of Arctic sea ice, the navigation duration of the Northeast Passage (NEP) is gradually increasing. The dynamic changes in sea ice concentration (SIC) during navigation time are a critical factor affecting the navigation of the passage. This study uses multiple linear regression and random forest to analyze the navigation windows of the NEP from 1979 to 2022 and examines the critical factors affecting the dynamic changes in the SIC. The results suggest that there are 25 years of navigable windows from 1979 to 2022. The average start date of navigable windows is approximately between late July and early August, while the end date is approximately early and mid-October, with considerable variation in the duration of navigable windows. The explanatory power of RF is significantly better than MLR, while LMG is better at identifying extreme events, and RF is more suitable for assessing the combined effects of all variables on the sea ice concentration. This study also found that the 2 m temperature is the main influencing factor, and the sea ice movement, sea level pressure and 10 m wind speed also play a role in a specific period. By integrating traditional statistical methods with machine learning techniques, this study reveals the dynamic changes of the SIC during the navigation period of the NEP and identifies its driving factors. This provides a scientific reference for the development and utilization of the Arctic Passage.

Bo Wang, Jie Wang, Chen Zheng et al.

Due to the weak structural features of pipelines and underwater light attenuation, the complex and harsh environment of the seabed greatly increases the possibility of an underwater autonomous remotely operated vehicle losing a detected seabed-contacting segment during pipe-laying operations. To address this problem, we propose a cascade attention module and a prefusion module with a convolutional neural network. The cascade attention module samples the feature maps in a non-convolutional form to realize the interaction between structure and channels, and the attention map is generated by cascading attention. The prefusion module pre-fuses the three layers of feature maps from different stages in the backbone, and the delicate features of the shallow feature maps are fused with the deeper feature maps to generate richer feature maps with space location and semantic classification information. We conduct experiments to verify our modules, both on the underwater pipeline dataset and in a tank test. The results show that our modules can improve the performance of different neural network models for seabed-contacting segment detection. The target detection and instance segmentation performance of the best model is improved through a 6.3% increase in AP and a 3.8% increase in mean intersection over union compared with the baseline model.

Jing Liu, Zongyu Li, Hanming Huang et al.

In response to the deficiencies in existing bridge pier scour protection technologies, this paper introduces a novel protective device, namely a normal distribution-shaped surface (BND) protection devices formed by rotating a concave normal curve. A three-dimensional turbulent SST <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>k</mi><mo>−</mo><mi>ω</mi></mrow></semantics></math></inline-formula> model is constructed, and physical model experiments of conical surfaces are conducted to validate the mathematical model. The simulation analyzes longitudinal water flow, downflow, vorticity intensity, and shear stress within normal and conical surfaces. The results show that the downflow distribution in front of the pier spans a relative water depth of (−0.45, 0.67), with a peak velocity approximately 70% of the longitudinal flow velocity. Circulation forms within the surfaces, with the main vortex flux inside the BND being 33% lower than that inside the conical surface. The maximum shear stress coefficient inside the BND can reach 9, and the protective surface isolates the bed from the flow to prevent scouring by high shear stress. The velocity gradient at the edge of the surface is small, and the edge shear stress of the 3D normal distribution-shaped surface (BND) protection device is only one-third of that of the conical surface, preventing edge scouring. The large shear stress and its distribution area decrease monotonically with the increase in surface width. When the surface width is four times the diameter, the distribution range of the shear stress coefficient greater than 1 is very small. The study of three-Dimensional turbulence within the BND provides a numerical basis for an anti-scour design.

Fan Zhu, Meng Zhang, Fuxuan Ma et al.

Wind turbine towers experience complex dynamic loads during actual operation, and these loads are difficult to accurately predict in advance, which may lead to inaccurate structural fatigue and strength assessment during the structural design phase, thereby posing safety risks to the wind turbine tower. However, online monitoring of wind loads has become possible with the development of load identification technology. Therefore, an identification method for wind load exerted on wind turbine towers was developed in this study to estimate the wind loads using structural strain, which can be used for online monitoring of wind loads. The wind loads exerted on the wind turbine tower were simplified into six equivalent concentrated forces on the topside of the tower, and the initial mathematical model for wind load identification was established based on dynamic load identification theory in the frequency domain, in which many candidate sensor locations and directions were considered. Then, the initial mathematical model was expressed as a linear system of equations. A numerical example was used to verify the accuracy and stability of the initial mathematical model for the wind load identification, and the identification results indicate that the initial mathematical model combined with the Moore–Penrose inverse algorithm can provide stable and accurate reconstruction results. However, the initial mathematical model uses too many sensors, which is not conducive to engineering applications. Therefore, D-optimal and C-optimal design methods were used to reduce the dimension of the initial mathematical model and determine the location and direction of strain gauges. The C-optimal design method adopts a direct optimisation search strategy, while the D-optimal design method adopts an indirect optimisation search strategy. Then, four numerical examples of wind load identification show that dimensionality reduction of the mathematical model leads to high accuracy, in which the C-optimal design algorithm provides more robust identification results. Moreover, the fatigue damage calculated based on the load identification wind loads closely approximates that derived from finite element simulation wind load, with a relative error within 6%. Therefore, the load identification method developed in this study offers a pragmatic solution for the accurate acquisition of the actual wind load of a wind turbine tower.

WANG Hanyu, CHEN Zhen, ZHOU Di, CHEN Zhaoxiang, PAN Ershun

In the process of steel rolling, due to wear and other reasons, the working performance of the roll under long and complex working conditions has a gradual decline. Considering the characteristics of complex working conditions and strong random interference of the roll working environment, this paper proposed a kernel-based Wiener process (KWP) degradation model to characterize the strong randomness of the roll degradation trend by using the Wiener process, and to capture the nonlinear degradation path of the roll by using the kerna function. This paper derives the analytical expression of parameter estimation in the Bayesian framework, and constructs the health index of the roll working rotation, then predicts the remaining useful life (RUL) of the roll. In combination with the field data of 1580 hot rolling production line of an iron and steel company, the goodness of fit of the model built is 0.989, and the residual life prediction error is less than 4.7%. Compared with the common machine learning algorithm, it has achieved better results, which is helpful to improve the operating efficiency and safety of equipment and achieve maintenance as needed.

Jing-yun LIU, Yi LIU, Tao SUN et al.

After decades of development, China has gradually developed an independent design capability for underwater weapon power system technologies. However, there is a current need for a wide variety of products and a short research and development cycle; therefore, the original design and development model based on document-based system engineering cannot meet the demand for rapid design. Based on an analysis of the background requirements and current situation of the digital development of model-based system engineering, a three-step digital development scheme is proposed for the power system design of underwater weapons, including technological breakthroughs and solidification of key capabilities, model-driven collaborative design, and construction of digital twin prototypes. The architecture and key technologies of the digital collaborative design platform for the power system of underwater weapons are analyzed; the results can provide a reference for the digital development of power system design for underwater weapons.

Gongxing Wu, Xiaolong Zhao, Yushan Sun et al.

The towing operation of multi-tug-assisted ship navigation mainly relies on the experience of the captain, and there is no set of effective operation methods. Therefore, it is difficult to achieve accurate assisted navigation when multiple tugboats work in coordination. The calculation method of maneuverability of the towing system with multi-tug-assisted navigation is proposed in this paper. In view of the complexity of multi-tug-assisted large ship maneuvering, this article focuses on solving the problems of force analysis and maneuvering modeling between the multi-tug and ship systems. Firstly, a maneuvering mathematic model for towing ships is established, and the hydrodynamic force of the hull, rope force of the tugs, and force of wind interference are analyzed. The thrust and moment of the ducted azimuthal propeller are calculated, and the mathematical model of the tug’s cable tension is discussed. Then, the fourth-order Runge–Kutta method is used to solve the differential equations of the maneuvering motion of the ships and each tug. Based on the ship-towing process by multiple tugs, a multi-tug-assisted ship towing simulation platform was built by using the Visual Studio development tool. Finally, on the simulation platform, multi-tug longitudinal-towing-simulation experiments at different speeds were carried out, and the simulation of turning towing maneuvers under the influence of wind was done. The simulation results showed that as the towing speed increases, the initial towing speed fluctuates greatly. There is a significant drift effect on the ships by the wind force. And the wind will cause a fluctuation in the tug’s rope force. The simulation of the multi-tugs towing a ship entering the port was carried out in the port environment. The results showed that the multi-tug towing system and simulation platform may be used for the safety training of the tug’s crew.

Wenliang Qiu, Vikram Pakrashi, Bidisha Ghosh

Fishing net cleanliness plays a critical role for aquaculture industry as bio-fouled nets restrict the flow of water through the net leading to a build-up of toxins and reduced oxygen levels within the pen, thereby putting the fish under increased stress. In this paper, we proposed an underwater fishing Net Health State Estimation (NHSE) method, which can automatically analyze the degree of fouling on the net through underwater image analysis using remotely operated vehicles (ROV) images, and calculate a blocking percentage metric of each net opening. The level of fouling estimated through this method help the operators decide on the need of cleaning or maintenance schedule. There are mainly six modules in the proposed NHSE method, namely user interaction, distortion correction, underwater image dehazing, marine growth segmentation, net-opening structure analysis, and blocked percentage estimation. To evaluate the proposed NHSE method, we collected and labeled several underwater images in Mulroy Bay, Ireland with pixel-wise annotations. In order to verify the universality and robustness of the algorithm, we simulated and built a virtual fishing farm, and, on this basis, collected and labeled fishing net images under different environmental conditions. Seven evaluation metrics are introduced to demonstrate the effectiveness and advantages of the proposed method.

Göktuğ Dalgıç, Mehmet Şaban Kutay, Ahmet Raif Eryaşar

In the present study, the commercial (16 mm nominal mesh size) and experimental deep water cast nets with different mesh sizes (20 mm, 24 mm, 28 mm and 32 mm nominal mesh size) were tested to compare the captured fish lengths and catch amounts for whiting (Merlangius merlangus euxinus). Experiments were carried out between July, 11 and August, 29, 2018 in Rize province of the south-eastern Black Sea Region. A commercial fishing boat was chartered for 20-day sea trials and in total, 66 set operations were done for all nets. Generalized Linear Mixed Models (GLMM) was used to compare fish sizes caught with experimental and commercial deep water cast nets. Results showed that more than 70 percent of the individuals caught in cast nets with 16 mm, 20 mm and 24 mm size were below the minimum landing size of whiting (13 cm). Among tested nets, only cast net with 32 mm size caught significantly less individuals under the minimum landing size. Finally, the results obtained from this study are discussed in terms of sustainable fisheries of whiting in the Black Sea.

Lingen Chen, Chenqi Tang, Huijun Feng et al.

One or more isothermal heating process was introduced to modify single and regenerative Brayton cycles by some scholars, which effectively improved the thermal efficiency and significantly reduced the emissions. To analyze and optimize the performance of this type of Brayton cycle, a regenerative modified Brayton cycle with an isothermal heating process is established in this paper based on finite time thermodynamics. The isothermal pressure drop ratio is variable. The irreversibilities of the compressor, turbine and all heat exchangers are considered in the cycle, and the heat reservoirs are variable-temperature ones. The function expressions of four performance indexes; that is, dimensionless power output, thermal efficiency, dimensionless power density and dimensionless ecological function are obtained. With the dimensionless power density as the optimization objective, the heat conductance distributions among all heat exchangers and the thermal capacitance rate matching among the working fluid and heat reservoir are optimized. Based on the NSGA-II algorithm, the cycle’s double-, triple- and quadruple-objective optimization are conducted with the total pressure ratio and the heat conductance distributions among heat exchangers as design variables. The optimal value is chosen from the Pareto frontier by applying the LINMAP, TOPSIS and Shannon entropy methods. The results show that when the pressure ratio in the compressor is less than 12.0, it is beneficial to add the regenerator to improve the cycle performance; when the pressure ratio is greater than 12.0, adding the regenerator will reduce the cycle performance. For single-objective optimization, the four performance indexes could be maximized under the optimal pressure ratios, respectively. When the pressure ratio is greater than 9.2, the cycle is simplified to a closed irreversible simple modified Brayton cycle with one isothermal heating process and coupled to variable-temperature heat reservoirs. Therefore, when the regenerator is used, the range of pressure ratio is limited, and a suitable pressure ratio should be selected. The triple objective (dimensionless power output, dimensionless power density and dimensionless ecological function) optimization’ deviation index gained by LINMAP or TOPSIS method is the smallest. The optimization results gained in this paper could offer some new pointers for the regenerative Brayton cycles’ optimal designs.

Adam Kowalski

There are well-known specifics of ro-pax ferry shipping, such as the time factor as a consequence of keeping a regular timetable and the priority given to minimizing heeling, pitching, and rolling caused by maximum focus on passenger comfort and ro-ro cargo safety. It is also extremely important to control the ferry&#8217;s fuel consumption, being one of the most important cost components. The aim of the article is to draw the attention of shipping company managers to the great potential that lies in the use of routine operational data, collected exclusively on board the ferries. It is worth noting that the research in this paper is based on standard office software packages rather than advanced statistical methods of data analysis, which are usually not accessible for shipping managers. Contrary to typical ocean-going vessels, there are a number of factors that need to be taken into consideration when analyzing ro-pax ferry fuel consumption. Moreover, these factors occur, in many cases, accidentally and, thus, they are difficult to observe on board the ferry without utilizing expensive and time-consuming methods. The possibility of fuel control is important not only for economic reasons but also due to air pollution caused by engine exhausts. The article presents an estimation of increased fuel consumption caused by the degradation of the hull silicone anti-fouling coating. The presented estimations of fuel consumption may be treated as the base for calculations of the economic effectiveness of ferries. The attempt to resolve the above-mentioned problem was made on the basis of research on a real ferry, which took place on the Świnoujście-Trelleborg line between 2007 and 2019.

Antonio Chinhenha, Janusz Mindykowski

This paper deals with the assessment methodology for the impact of combined cycle plant characteristics on the quality of the produced electrical power. The aim of this work is to develop the assessment methodology with the use of an algorithm based on a flowchart of the system. The research methodology includes an analysis of the non-steady state phenomena with use of a MATLAB-Simulink environment and an analysis of the steady-state phenomena based on the theoretical calculations and analytical models of a combined cycle plant of the COGES type, connected with the processes of producing and converting of thermal and electrical power in the considered systems. A key point of the study is to check that the voltage frequency modulation on the shaft of the gas turbine is included in the limits defined by the appropriate requirements of the related IEEE Std 45TM-2002 standard.