The International Maritime Organization aims for net-zero carbon emissions in the maritime industry by 2050. Among various alternatives, route optimization holds an important place as it does not require any additional component-related costs. Especially for wind-assisted ships, the effectiveness of different sailing systems can be improved significantly through route optimization. However, finding the ship’s optimal route is computationally expensive when the totality of possible weather conditions is taken into consideration. To determine the optimal route that minimizes energy consumption, an energy model based on the environmental conditions, ship route and ship speed was built using artificial neural networks. The energy consumed for given input data was calculated using a ship dynamics model and a database was generated to train the artificial neural networks, which predict how much energy is consumed depending on the route followed in given environmental conditions. Then, such networks were exploited to derive the optimal routes for all the relevant operational conditions. It was found that route optimization can reduce the overall ship energy consumption depending on the weather conditions of the environment by up to 9.7% without any increase in voyage time and by up to 35% with a 10% delay in voyage time. The proposed methodology can be applied to any ship by training real weather conditions and provides a framework for reducing energy consumption and greenhouse gas emissions during the service life of ships.

To achieve the goal of a 50% reduction of CO₂ emission in the maritime industry by 2050, different systems and solutions were proposed by researchers. Rigid wind sails, rotor sails, suction wings, and kites were developed to contribute to cleaner and environment-friendly transportation by reducing total fuel and energy consumption. In the present study, a ship dynamics model of KVLCC2 consisting of hull, rudder, propeller, and sailing system was built considering the effects of wind and wave. Firstly, the amount of energy consumption reduction of both systems was examined under different wind directions and wind speeds. It was found that a single sailing system can reduce total energy consumption by up to 10%. Then, the effects of the ship speed, the position of the sailing system, and the number of sails on the reduction of energy consumption were examined. It was found that the amount of overall energy reduction reaches around 23% and 16% when the number of sails was increased to 10 rigid wind sails and 10 rotor sails, respectively. The effects of waves were also investigated, and it was revealed that wave forces decrease the percent energy reduction more when environmental conditions become more severe, starting from the Beaufort scale of 7.

Rotor sails are one of the promising solutions to reducing the energy consumption and CO₂ emissions of ships. Previous studies focused on how rotor sails affect ship dynamics and energy consumption. In the present study, an optimization-based workflow was proposed to find the optimal design of a rotor sail based on given environmental conditions for a target ship. Since the performance of a rotor sail depends on both operational conditions and the design of the rotor sail, a two-level optimization problem was proposed to separate the optimization of operational conditions and rotor sail design. At the operational level, the spin ratio of a given rotor sail was optimized at each time step under different environmental conditions. Then, the design of the rotor sail was optimized on the design level considering the initial cost of rotor sails and the average operational cost of the ship depending on the environmental conditions and their probabilities. The reductions in energy consumption of ships having optimal rotor sail designs, considering 5-year, 10-year, 15-year, and 20-year investment plans were found to be 0.34%, 2.7%, 3.91%, and 4.29%, respectively. When more severe environmental conditions were assumed for the 10-year investment plan, the diameter of the rotor sail increased and the reduction in energy consumption increased from 2.7% to 4.06%.

Human gait varies based on personal characteristics, the existence of walking problems, or variability of gait parameters. Identifying the sources of variations is significant in detecting walking problems, designing orthotic/prosthetic products, etc. What are the types of variations in joint angles and ground reaction forces? How do age, sex, height, weight, and walking speed affect the distribution of the modes? In this study, temporal variations in the joint angles and ground reaction forces were obtained using singular value decomposition. Then, the relationships among age, sex, height, weight, walking speed, and the coefficients obtained by singular value decomposition were investigated using Pearson’s correlation coefficient matrix. The first mode of joint angles and ground reaction forces represent the overall characteristics; the first six modes of joint angles and the first two modes of ground reaction forces express 99.9% of the gait parameter space. We concluded that the walking speed dramatically affects joint kinematics and ground reaction forces. In addition, the effects of age, gender, height, and weight on the joint kinematics and ground reaction forces were also found, but with less contribution. The temporal behavior of the joint angles and ground reaction forces was expressed using a few coefficients due to singular value decomposition. The effects of age, sex, weight, height, and walking speed on the modes were found. The proposed method can be applied to understand the progression of an abnormality, and design orthotic/prosthetic products etc. in future studies.

Wind-assisted ship propulsion is one of the solutions for reducing greenhouse gas emissions by generating additional thrust using renewable wind power. Various technologies utilizing wind power to generate thrust are being developed and adopted by the industry. In addition to the thrust, side forces are also generated as secondary outputs, and they significantly affect ship motion. Although many studies have been conducted on the effects of sails on ship dynamics and energy consumption, the impact of control strategies of wind-assisted ships on energy consumption has not been clearly identified. This study aimed to determine the bearings of different control strategies on ships in terms of motion and energy. When the heading control strategy is adopted, rotor sails can reduce energy consumption by up to 10%. However, course- and speed-controlled ships without any wind-assistance devices can reduce energy consumption by 15%, and a further reduction of up to 30% can be achieved through rotor sails depending on the wind direction. When the control of the rotor sails was changed from a stand-alone controller to a ship dynamics-integrated controller, the energy consumption can be reduced by approximately 1-2% for course- and speed-controlled ships.