_ The paper presents a novel approach of cooperative multiagent reinforcement learning (CMARL) combined with A* search to address ship multicabin equipment layout considering pipe route, aiming to minimize pipe cost while considering practical requirements. The formulation is established through equipment simplification and grid marking, and A* search is utilized to value the pipe route. By designing equipment states, the equipment layout in each cabin is solved using a CMARL approach that involves three actions. Subsequently, comparative experiments were conducted on an engine room case by CMARL against genetic algorithm and single multiagent reinforcement learning methods under the condition of coupling with A* search. The parameter values for these methods were sampled using Latin Hypercube. The findings demonstrate that CMARL has superior combination properties. Keywords ship equipment layout; multicabin layout; cooperative multiagent reinforcement learning; A* search; pipe route

_ The terrestrial laser scanning (TLS) technology, which has been widely used in recent years, provides a new approach to control the construction quality of hull blocks in shipyards. As the cloud-model registration problem plays the most significant role in the data processing stage of utilizing the TLS devices, this paper concentrates on developing a broadly applicable coarse alignment framework for the point cloud of hull blocks. This framework involves two steps: the recognition of the connection regions of the point clouds and the coarse registration method according to the classification results. To detect the connection regions automatically, a hand-crafted simple model of the connection regions of hull blocks is built and its supporting detection method is proposed, besides, considering the recent overwhelming success of deep learning methods, a deep learning network suitable for large hull block datasets is constructed according to the Point-Net, and convolutional neural networks paradigms. Then, the coarse alignment method based on the detected connection regions is proposed. Experimental results illustrate the good performance of the proposed framework. Keywords computers in construction; shipbuilding; automation

_ The International Maritime Organization (IMO) has been discussing technical issues by dividing the second-generation intact stability criteria for ships into five types. In this paper, we paid attention to the dead ship condition and introduced the process for the assessment of Levels 1 and 2 in detail. Dead ship condition refers to a case where a large angle of rolling motion occurs due to waves incident on the side of the ship’s hull after the ship’s engine has failed. Basically, in the dead ship condition, if the Level 1 criterion for analysis related to the GZ curve is not satisfied, an evaluation is performed against the Level 2 criterion considering the hydrodynamics of waves. The method for the effective wave slope function required to obtain the spectrum of the effective relative roll angle, which is the most important factor in the calculation of Level 2, was implemented. In particular, unlike existing ship types in terms of various experiences, this study performed stability evaluation using special ship data of a 5000HP tug boat and obtained results that satisfied both Level 1 and 2 standards. Through this example of dead ship condition evaluation for a tug boat, we aim to ensure the expansion of IMO second-generation intact stability evaluation targets for various types of ships. Keywords IMO second generation intact stability criteria; dead ship condition; GZ curve; effective wave slope function; tug boat

_ Traditional accuracy check methods for cargo hold in container ships rely solely on manual and visual operations, which are time-consuming and resource-intensive. Addressing the challenge of extracting and analyzing key data, such as cell guides and container pedestals, from large-scale point clouds obtained through three-dimensional (3D) laser scanning in container ship trial runs, this paper proposes an algorithmic framework based on 3D laser scanning. Building upon this framework, an improved coordinate-axis filtering RANSAC algorithm is employed to optimize the extraction of cell guide planes. Additionally, an algorithmic process based on Bhattacharyya distance is utilized to automatically extract container pedestal point clouds. Furthermore, a combination of the genetic algorithm and the ICP algorithm is proposed to achieve the fitting of the container pedestal edge contour through point cloud registration. Experimental results demonstrate the consistency between the extracted cell guide and container pedestal data and the actual results, indicating the high practical value of the proposed methodology. Keywords container ship loading test; cargo hold accuracy check; 3D point cloud processing

_ The paper proposes an innovative methodology of Human Cognitive Reliability- Cognitive Reliability and Error Analysis Method (HCR-CREAM) coupled with A* search and genetic algorithm (GA) to tackle ship cabin equipment layout considering human factor reliability optimization with the goal of minimizing human error probability (HEP) subjected to practical requirements. After establishing the mathematical model of cabin equipment inspection tasks in ship cabin equipment layout problem through HCR-CREAM and equipment geometric simplification, a method of the horizontal movement based on minimum distance is presented to avoid the equipment overlapping, then A* search is used for planning inspection paths and GA with selection, crossover, and mutation operators is applied to solve equipment layout results. A case of equipment layout in a certain ship engine room has been taken to carry out parameter sampling experiments by Latin Hypercube for GA. The results show the solution effect of GA is less affected by its parameter variation. And through the comparison with the initial equipment layout, the indicators influencing the HEP of the optimized result have been improved, thus significantly reducing HEP. Keywords ship cabin equipment layout; human factor reliability optimization; HCRCREAM; A* search; genetic algorithm

_ The melt-inert gas-shielded arc additive manufacturing experiment of Inconel 625 nickel-based alloy bulk was carried out. The influence of current mode, current, travel speed, weld bead spacing, deposition path, and arc length on the formation of overlapping weld beads was studied. The incomplete fusion near the bottom weld toe of adjacent weld beads was the main defect. The optimized parameters for bulk additive manufacturing obtained from the experiment were as follows: pulse current of 70 A, travel speed of 200 mm/min, weld bead spacing of 3 mm, dry extension of 10 mm, continuous deposition, and arc length of 1 mm. Due to the thermal influence during the deposition of adjacent weld beads, directional grains were formed inside the weld bead and at the boundary with adjacent weld beads. However, the direction of grain growth was not uniform throughout the entire weld bead, and a consistent texture of the entire weld bead was not formed. The tensile strengths of the specimens in the X, Y, and Z directions were 858.5, 838.7, and 827.2 MPa, respectively, and the fracture elongations were 53.3%, 37.6%, and 42.1%, respectively. The strength in the Z direction, which is the vertical direction, was the lowest. Keywords arc additive manufacturing; nickel-based alloy; incomplete fusion; texture

The ship construction process is characterized by a sequential workflow, with pivotal workstations playing a crucial role. Initially, steel plates are introduced to these stations in sheet form, undergoing a transformation process that culminates in the creation of segments known as blocks. These blocks are individually constructed and subsequently assembled at the final workstation, denoted as the block joining station. Upon completing block fabrication, a deliberate tolerance allowance is retained on the plates to accommodate deformations induced by heat treatment during the transformation from plates to blocks. The alignment process involves aligning the reference points (master reference line) of the blocks on a common axis, facilitating the identification of excess material and deformations. This alignment process encompasses aligning the blocks with each other, employing either a three-dimensional measurement device or manual methods to obtain necessary measurements for determining excess material. In an effort to optimize time spent on block alignment and machine usage, a comprehensive methodology has been developed. This methodology involves determining excess material cuts on the blocks, performing virtual alignment operations using laser scanning techniques in a virtual environment, and conducting the cutting process on the slipway prior to placing the block excesses on it.

The operation of marine vessels with high efficiency provides a great contribution within the scope of the International Maritime Organization and the sustainable development goals. In terms of the propulsion system, selecting the appropriate propeller is critical to effectively use the engine power installed in marine vessels because the biggest energy losses during transmission occur on the propeller and ship hull. Increasing propeller efficiencies above a certain level is quite a challenge by simply changing the number of blades, pitch, or propeller type. Therefore, various energy-saving device applications, such as propeller boss cap fins (PBCFs), are performed on the ship propeller. The effects of National Advisory Committee for Aeronautics 4415 profile PBCFs which have a different position and pitch angle integrated into the E698 model propeller have been investigated to describe efficiency, vortex, and pressure distributions based on the KRISO very large crude carrier 2 designed hull in this study. The E698 model propeller has been created by the 3D software and the validation has been performed by the computational fluid dynamic solver software based on the reference values of the propeller. The effect of four PBCF applications which have different pitches and positions on the model propeller has been revealed in terms of the efficiency, pressure distributions, and vortexes. Although P45-R45 and P45-R90 PBCF applications are quite close to the E698 propeller in terms of efficiency, no significant efficiency increase has been observed. In addition, the efficiency has decreased considerably in P90-R45 and P90-R90 applications. PBCFs application with P45-R90 has provided superiority to the base model in terms of pressure distributions and vortex formation. However, any improvement has not been achieved in the remaining three designs. Therefore, PBCF applications should be applied quite elaborately based on propeller types.

The potential impact of a ship’s outfit density on the labor hours required for production, sustainment, and upgrade has been discussed within the domain of warship design for decades. For fixed ship mission, systems capabilities, crew size, specification complexity and maturity, other producibility characteristics, and work schedule, as a ship’s size varies, required production labor hours are impacted in two ways—first by a change in work content and second by a change in worker productivity with available space. Because these impacts are inversely related, there exists an optimum ship size and outfit density that minimizes required labor hours. This paper describes an analysis of optimum outfit density to minimize production labor hours for complex modern surface combatants. The key relationship between available space and worker productivity is defined based on data from multiple industries. This relationship is then used along with knowledge of surface combatant design and shipbuilding processes and production labor requirements to identify an optimum range of overall outfit density to target during ship design. This derived optimum range is validated with other related research and reference to the outfit densities of existing modern surface combatants and what is known about their ease of build. Also discussed are 1) alternative ship design and production paradigms that might allow for ships with higher outfit densities while maintaining efficient production, maintenance, and upgrade and 2) implications of the relationship between available worker space and worker productivity for shipyard planning and work execution.

Endurance fuel calculations are used to determine the required volume of fuel tanks; annual fuel calculations are used to estimate the fuel consumed during a year of ship operations, primarily to estimate the projected cost of fuel as part of the life cycle cost estimate. These calculations depend on the fuel rates (kg/h) for different electrical and propulsion system configurations. The fuel rates in turn depend on factors, such as equipment efficiency, prime mover-specific fuel consumption curves, electrical loads, ambient temperature, propulsion loads, and the manner in which the power and propulsion systems, are operated. This paper details how to perform endurance fuel and annual fuel calculations, provides guidance for modeling system components based on data typically provided in data sheets, and provides guidance on the manner in which the power and propulsion systems are operated. Four examples are provided to illustrate the methods using the Smart Ship System Design modeling and simulation tool along with supporting spreadsheets.