The LNG price is basically determined based on the oil price, but other than that, it is also determined by the influence of the method of LNG transportation; storage; processes; and political, economic, and geographical instability. Liquefied natural gas (LNG) may not reflect its market value if the destination of the purchase is restricted or the purchase contract includes a take-or-pay clause. Furthermore, it is difficult for the buyer to flexibly manage procurement, resulting in the decoupling of oil and natural gas prices. Therefore, as the LNG bunker price is expected to be more volatile than the marine bunker price in the future, shipping companies need to prepare countermeasures based on scientific forecasting techniques. This study aims to be the first to analyze the forecasting of short-term LNG bunker prices using recurrent neural network (RNN) models suitable for highly volatile data such as time series. Predictive analysis was performed using simple RNN, long short-term memory (LSTM), and gated recurrent unit (GRU) models, which effectively forecast time-series data, and the prediction performance of LSTM among the three models was excellent. LSTM had relatively excellent prediction performance of outliers and beyond. In addition, it was possible to effectively manage ship operating costs with improved forecasting in practice. Furthermore, this study contributes to establishing a systematic strategy for supervisors in global shipping companies, port authorities, and LNG bunkering companies.

According to the International Maritime Organization, transitioning to alternative fuels is essential to achieving net-zero carbon emissions. Seafarers are at the frontline of this transition, and in this study, their attitude toward this strategy is analyzed using the technology acceptance model. The alternative fuels analyzed are liquefied natural gas (LNG) and methanol as short-term options and hydrogen and ammonia as long-term options. The analyzed seafarers are from South Korea, where alternative fuels are actively incorporated into shipbuilding and training. Across all fuels, perceived ease of use (PEOU) positively affected perceived usefulness (PU). PEOU and PU positively influenced attitude toward using (ATT). ATT and trust (TRU) significantly increased behavioral intention (BI), a finding that aligns with those of prior studies, while operational safety risk (OSR) also showed a positive effect on ATT. This indicates that seafarers became more aware of the need to use alternative fuels and expected improvements in managing related risks. Unlike OSR, environmental risk (ER) negatively affected ATT for hydrogen, consistent with prior risk perception studies. These findings suggest that to encourage alternative fuel use during the shipping industry’s energy transition, operational ease, enhanced risk management systems, and basic competency training and incentives are necessary to positively shape seafarers’ attitudes and behavioral intentions.

We prepared InGaN light-emitting diodes (LEDs) with the active layers grown from a mixed source of Ga–In–N materials on an n-type GaN substrate by a selective-area growth method and three fabrication steps: photolithography, epitaxial layer growth, and metallization. The preparation followed a previously developed experimental process using apparatus for mixed-source hydride vapor-phase epitaxy (HVPE), which consisted of a multi-graphite boat, for insulating against the high temperature and to control the growth rate of epilayers, filled with the mixed source on the inside and a radio-frequency (RF) heating coil for heating to a high temperature ( T > 900 °C) and for easy control of temperature outside the source zone. Two types of LEDs were prepared, with In compositions of 11.0 and 6.0% in the InGaN active layer, and room-temperature electroluminescence measurements exhibited a main peak corresponding to the In composition at either 420 or 390 nm. The consecutive growth of InGaN LEDs by the mixed-source HVPE method provides a technique for the production of LEDs with a wide range of In compositions in the active layer.

We report the characterization of the InGaN/GaN multi-quantum-well (MQW) light-emitting diode (LED) grown on a patterned sapphire substrate by metal organic chemical vapor deposition (MOCVD) using the selective area growth (SAG) method. The SAG patterns were designed to be circular and their diameters were 700 and 200 µm. After the growth, the InGaN/GaN MQW LED of 200 µm diameter had various crystal facets and a shape similar to volcanic craters, which were not observed in the 700-µm-diameter sample. We obtained an active layer with compositional nonuniformity and superior optical properties. We found wide electroluminescence (EL) spectral peaks near 470, 570, and 600 nm. The distribution of the EL spectrum of the sample was similar to that of a conventional phosphor-converted white LED.