Real-time and omnidirectional observation of the ocean is of great significance in protecting the marine environment while enabling mankind to effectively develop and utilize marine resources. In particular, ocean currents and wind observation are very important in the observation of marine environmental quality. Ocean currents are the large-scale and relatively stable flow of seawater, which is one of the most important and universal forms of motion of the sea water, playing an important role in the stability of the global climate and ecological balance, and having many adverse effects on the livelihood and production of coastal people and the exploitation and utilization of the ocean. As a result, current measurement technology has been one of the main focuses of the oceanography. In addition, ocean wind observation has important significances in ensuring navigation safety, preventing disasters, assisting climate research, improving environmental protection and promoting resource exploitation and fisheries production.

Currently, ocean observation is mainly carried out by oceanographic buoys, unmanned vessel surveillance and satellite remote sensing. Ocean observation buoys, which have the longest history of development, can be mainly divided into two types; underwater observation buoys for specified points and surface drifting buoys that drift along the ocean current.

Of course, observations by unmanned ships and satellite remote sensing have been applied in ocean water measurement, but they cannot accurately measure ocean water at exact locations required by users, and real-time and long-term measurements are more difficult. In ocean water measurement using observation buoys, accurate measurement data can be directly measured and wirelessly transmitted in real time at any location required by observers.

Kim Chol Min, a researcher at the Faculty of Naval Architecture and Ocean Engineering, analysed the influence of the yaw and pitch characteristics of observation buoys on the measurement of the direction of the ocean current and wind direction, proposed a simple and reasonable measurement method, and verified its effectiveness through simulations and experiments.

The simulations and experiments demonstrated high accuracy of ocean current and wind direction measurements. The absolute error of the ocean current direction measurement is less than 0.5%, and 16 wind directions were accurately measured.

For further details, please refer to his paper “One method to measuring ocean current and wind direction from marine buoys” in “Journal of Atmospheric and Oceanic Technology” (SCI).

The opinion dynamics model which is being widely investigated by physicists can be largely divided into two types: discrete opinion models and continuous opinion models. The former uses a finite number of values to express agents’ opinions. The latter, unlike the discrete opinion models, takes a real number to represent agents’ opinions.

Some researchers studied the SJT model, one of the continuous opinion models. They proposed two thresholds: an acceptance threshold (d1) and a repulsion threshold (d2). According to their rules, when the difference in the inner opinion between two randomly selected agents is smaller (or larger) than d1 (or d2), the agents simultaneously update their opinions in the direction where their difference gets smaller (or bigger).

Jang Paek San, a researcher at the Institute of Nano Science and Technology, proposed a modified SJT model with a new opinion updating mechanism. Unlike the previous works, every individual affects the others’ opinions and the extent of the influence depends only on the magnitude in the opinion difference. To incorporate the convergence parameter of the assimilation effect and the divergence parameter of the repulsion effect into one parameter, he introduced a new function and used Monte Carlo simulations to study the opinion evolution process of the new model.

The simulation results showed that as d1 increases, the number of opinion clusters increases, but with increasing d2, the opinion dynamics changes from a bipolarization of opinions to a consensus of opinions.

For more information, you can refer to his paper “Social Judgment Theory model with continuous interaction between assimilation and repulsion mechanisms” in “SN Social Sciences” (SCI).

The introduction of a self-mixing (SM) displacement sensor into the measurement of mechanical vibration is an effective choice due to the characteristics of the SM interferometry (SMI). This is because the SMI has very favorable advantages for field measurement, for instance, high measurement accuracy, adaptability to any reflective surface, low cost, etc. Moreover, the compactness of SM sensors makes it easy to develop a hand-held portable device.

The key to developing a hand-held SM sensor is how to remove the hand-induced parasitic vibration. Since the removal of parasitic vibration is important for the accuracy of SMI, there have been many studies, divided into hardware-based and software-based methods.

Jang Kum Hyang, a researcher at the Institute of Mirae Industrial Technology, proposed a method of removing the hand-induced parasitic vibration based on data fitting, which is very simple and suitable for a hand-held self-mixing displacement sensor for the measurement of mechanical vibration.

The measurement accuracy that the proposed method provides is less than 30 nm.

If further information is needed, please refer to his paper “Removal of parasitic vibration in a self-mixing measurement for mechanical vibration based on data fitting” in “Applied optics” (SCI).