Narrow Results

One of the main purposes of SHiP experiment is to shed light on neutrino mass generation mechanisms like the so-called seesaw. We consider a minimal type-I seesaw neutrino mass mechanism model with two heavy neutral leptons (right-handed or sterile neutrinos) with arbitrary masses. Extremely high active-sterile mixing angle requires a correlation between the phases of the Dirac neutrino couplings. Actual experimental limits on the half-life of neutrinoless double beta decay $0\nu \beta \beta$-rate on the active-sterile mixing angle are not significative in constraining the masses or the mixing measurable by SHiP.

The purpose of this study is to determine the correct estimation of laminate patterns for high-strength composites applied to a ship. Recently, the need for developing a ship component has been increasing to improve the capability of maritime operations. Composites with excellent specific strength and specific stiffness are emerging as next-generation materials. In the composite material, the mechanical properties vary depending on the laminated pattern of the reinforcing material. Therefore, in this study, the properties of the composite materials were calculated using the computer simulation program. The ply calibration performance results show that the initial values of the mechanical properties of the carbon/epoxy composites in the E11 direction are higher than the calculated values, and the remaining values are the same. The laminate mechanics results show that the tensile strength in the S11T direction was 1515 MPa, which is almost the same as the initial value of 1500 MPa.

In this study, the CFRP shafts made up of T700-SC multilayered composites have been designed to replace the steel shaft of a ship. An important design variable to be considered when designing composite material intermediate shafts is the natural frequency for resonance avoidance at critical rotational speed and torsional strength for axial load. In order to satisfy these, strength and modal analysis were performed. In order to minimize the deformation of the shape due to the residual stress after mandrel removal, it was laminated by axial symmetry. The fibers orientation angle has a great influence on the natural frequency of the drive shaft. The carbon fiber should be closely oriented at $30^{\circ }$ to improve the modulus of elasticity in the direction of length of the intermediate shaft and to increase the natural frequency. Also, the optimum fiber orientation for maximum torsional strength should be close to $45^{\circ }$. The stacking pattern and the stacking order were finally decided considering the results of the finite element analysis (FEA).

Unsteady aerodynamic interference between a rotorcraft and a ship occurs during shipboard launch and recovery operations and has a negative impact on the safety. An experiment of a reduced-scale model rotor and a CFD analysis in hover was carried out to investigate the performance and flow field of a rotor approaching a ship. In this paper, the thrust and pitching moment of the rotor hovering above the ground, deck were tested, and the influence of hangar door on the thrust, pitching moment, and flow field was also measured. A CFD method based on RANS and overset technology was used to investigate the flow field of the rotor operating on the model-scale ship. As the rotor approaches the deck, its thrust first decreases induced by a recirculation near the deck, and then increases induced by the effect of deck, and finally obviously decreases caused by the recirculation near hangar door. The deck and hangar door also affects the flow field to yield an intensive nose-down pitching moment. The status of the hangar door has a significant influence on the rotor thrust and pitching moment. The recirculation is weakened with an opened hangar door resulting in recovery of the rotor thrust and decrease of the nosed down pitching moment.

Risks associated with a vessel traffic system at sea are analyzed according to the elements in this system and a new method is developed to ensure safe ship operation. Based on Bayes' point estimation and probability influence diagram to estimate the traffic accidents related to vessel traffic, an analysis model is established for the quantitative risk assessment (QRA) of the vessel traffic system at sea. After the analysis on occurrence likelihood of the accidents related to ship traffic, a structure on the basis of Bayesian networks is developed to obtain the QRA of their relative risks. QRA is also put forward after analyzing the features and situations of the vessel traffic system and identifying the corresponding hazards including characteristics of those hazards. The risk distributions of ship traffic are described and results are presented on QRA in relation to various features by using this risk assessment model. This method, verified in the cases of QRA, turns out to be feasible by the use of identified posterior probability.

The distance between navigation ships is closely related with ship's safety. In this paper, the reasonable distance between navigation ships is researched, and the equation of distance between navigation ships is also put forward. The using method of this equation is also illuminated by example.