Design and Experimental Validation of a Control System for Dynamic Positioning of a Shuttle Tanker

In this paper, a dynamic positioning performance evaluation procedure for a shuttle tanker is discussed through experimental and numerical analyses. A dynamically positioned shuttle tanker with six thrusters (three tunnel thrusters, two azimuth thrusters, and one main propeller with a rudder), operated in deep water condition was considered. A conventional proportional-derivative control algorithm was adopted for the main feedback control algorithm to reduce the position error, and an anti-windup integral control algorithm was introduced to suppress the steady-state error in the dynamic positioning operation. A minimum power consumption algorithm, based on the Lagrange multiplier method, was utilised in the thrust allocation for the thruster systems. An extended Kalman filter was used in the experiment to separate the low-frequency motion from the measured vessel motion. A set of experiments and numerical analyses were conducted in this study under the same environmental conditions and with the same control methodology. The dynamic positioning operation results obtained by the experiments and numerical simulations were compared to evaluate the station-keeping performance of the dynamically positioned shuttle tanker

Electromagnetic Shielding Characteristics of Eco-Friendly Foamed Concrete Wall

The electromagnetic shielding characteristics according to the material composition of foamed concrete, which was manufactured to reduce environmental pollution and to economically apply it in actual building walls, were researched herein. Industrial by-products such as ladle furnace slag (LFS), gypsum, and blast furnace slag (BFS) were added to manufacture foamed concrete with enhanced functionalities such as lightweight, heat insulation, and sound insulation. The electrical characteristics such as permittivity and loss tangent according to the foam and BFS content were calculated and measured. Free space measurement was used to measure the electromagnetic shielding characteristics of the actually manufactured foamed concrete. It was confirmed that electromagnetic signals were better blocked when the foam content was low and the BFS content was high in the measured frequency bands (1–8 GHz) and that approximately 90% of the electromagnetic signals were blocked over 4 GHz

Lanczos exact diagonalization study of field-induced phase transition for Ising and Heisenberg antiferromagnets

Using an exact diagonalization treatment of Ising and Heisenberg model Hamiltonians, we study field-induced phase transition for two-dimensional antiferromagnets. For the system of Ising antiferromagnet the predicted field-induced phase transition is of first order, while for the system of Heisenberg antiferromagnet it is the second-order transition. We find from the exact diagonalization calculations that the second-order phase transition (metamagnetism) occurs through a spin-flop process as an intermediate step.Comment: 4 pages, 4 figure