An Optimization Model for Ship Speed Based on Maneuvering Control

The increasing frequency of serious environmental issues and high fuel costs have necessitated better energy efficiency in the shipping industry. According to a report by the International Maritime Organization (IMO), ship speed optimization has huge potential. This paper introduces an optimization model of ship speed based on maneuvering control. The trajectory tracking theory and sliding mode control method are applied to simulate the control load of a ship. The propeller mode and rudder mode are used to calculate the corresponding rotating speed of the propeller, the rudder angle and the energy consumption. The accuracy and robustness of the maneuvering control model are validated in a still water scenario and a level 5 sea state scenario. On this basis, a particle swarm optimization (PSO) algorithm is applied to determine the best speed combination. The result shows that sailing at a constant speed is the most energy-saving strategy in still water. Moreover, due to the effects of wind, waves and currents, ships should sail faster when the sea is calm and slower when the sea is rough. These results are consistent with the actual experiences of a captain

In situ preparation of nano cone-like structures of rutile titanium oxides on titanium implants by one-step femtosecond laser irradiation for enhanced mechanical properties and biocompatibility

Titanium oxides (TiO2) nanostructures coating is helpful in improving the utilization of titanium in many areas due to its multifunctional properties. This study introduces a novel approach for the in-situ fabrication of nano cones-like structures of rutile titanium oxides (NCS–TiO2) on the surface of titanium utilizing femtosecond laser technology. Rutile titanium oxides were synthesized with a height of around 80 nm and a diameter of 100 nm, forming NCS that imparts higher hardness, wear resistance, and biocompatibility. Molecular dynamic simulation provides valuable insights into the three-stage formation process of NCS-TiO2. Molecular dynamic simulation revealed that the growth of rutile titanium oxides and the formation of nano cones-like structures are attributed to the interplay between femtosecond laser ablation and the accumulation of thermal energy. The proposed method offers a versatile and straightforward approach for creating functional surfaces on metal substrates, enabling broad applicability and ease of implementation, specifically in titanium and its alloys. This advancement holds great potential for expanding the scope of titanium-based materials and their applications, paving the way for improved mechanical properties and biocompatibility in diverse fields

Laser Polishing of Ti6Al4V Fabricated by Selective Laser Melting

Selective laser melting (SLM) is emerging as a promising 3D printing method for orthopedic and dental applications. However, SLM-based Ti6Al4V components frequently exhibit high roughness values and partial surface defects. Laser polishing (LP) is a newly developed technology to improve the surface quality of metals. In this research, LP is applied to improve the surface finish of components. The results show that the laser beam can neatly ablate the aggregates of metallic globules and repair cracks and pores on the surface, resulting in a smooth surface with nanocomposites. Overall, the results indicate that using LP optimizes surface morphology to favor fatigue behavior and osteoblastic differentiation. These findings provide foundational data to improve the surface roughness of a laser-polished implant and pave the way for optimized mechanical behavior and biocompatibility via the laser process

Antibacterial Vancomycin@ZIF-8 Loaded PVA Nanofiber Membrane for Infected Bone Repair

Bone substitutes with strong antibacterial properties and bone regeneration effects have an inherent potential in the treatment of severe bone tissue infections, such as osteomyelitis. In this study, vancomycin (Van) was loaded into zeolitic imidazolate framework-8 (ZIF-8) to prepare composite particles, which is abbreviated as V@Z. As a pH-responsive particle, ZIF-8 can be cleaved in the weak acid environment caused by bacterial infection to realize the effective release of drugs. Then, V@Z was loaded into polyvinyl alcohol (PVA) fiber by electrospinning to prepare PVA/V@Z composite bone filler. The drug-loading rate of V@Z was about 6.735%. The membranes exhibited super hydrophilicity, water absorption and pH-controlled Van release behavior. The properties of anti E. coli and S. aureus were studied under the pH conditions of normal physiological tissues and infected tissues (pH 7.4 and pH 6.5, respectively). It was found that the material had good surface antibacterial adhesion and antibacterial property. The PVA/V@Z membrane had the more prominent bacteria-killing effect compared with the same amount of single antibacterial agent containing membrane such as ZIF-8 or Van loaded PVA, and the antibacterial rate was up to 99%. The electrospun membrane had good biocompatibility and can promote MC3T3-E1 cell spreading on it

Anion-Assisted Synthesis of TiO₂ Nanocrystals with Tunable Crystal Forms and Crystal Facets and Their Photocatalytic Redox Activities in Organic Reactions

In this work, we develop a facile and general strategy to control the crystal forms and crystal facets of TiO₂ nanocrystals. Ti­(OH)₄ was used as the precursor and different anions were used as capping agents without any other organic surfactants. These anions can selectively adsorb on the specific crystal facets of anatase, inducing the transformation of conventional {101} facets to unconventional {001} facets and {100} facets or even phase transformation to rutile and brookite. Rutile and brookite TiO₂ nanocrystals as well as anatase TiO₂ nanocrystals with different facets ({101}, {001}, and {100}) exposed are obtained. Photocatalytic selective reduction of nitrobenzene and selective oxidation of benzyl alcohol are employed as a probe reaction to test the redox properties of the as-prepared TiO₂ nanocrystals. The results show that the photocatalytic redox properties of TiO₂ NCs are dependent on their crystal forms and crystal facets. Specially the photocatalytic activities of different anatase crystal facets show different orders in reduction and oxidation reactions, respectively. The reduction ability of different anatase crystal facets can be ranked as {101} > {001} > {100}. While the oxidation ability of different facets can be ranked as {101} ≈ {001} ≈ {100}. Surface and electronic structures should be the origin that account for their different activity orders in different reactions. Based on the results in the two model reactions, one important principle should be pointed out. When we discuss the crystal-facet-dependent catalytic activities of TiO₂ nanocrystals, we should analyze the results based on specific reactions