An adaptive extended Gaussian peak derivative reweighted penalised least squares method for baseline correction.

Baseline drift is an important issue in spectral analysis (e.g., infrared, Raman, and laser-induced spectroscopy). Most common methods for baseline correction perform poorly in high noise, complex baselines, and overlapping peaks. To solve this problem, we proposed an adaptive extended Gaussian peak derivative reweighted penalised least squares (agdPLS) method for removing baseline drift from spectra. The method added extended Gaussian peaks to spectra, added derivative terms for spectral and baseline differences during iterations, and adaptively adjusted penalty coefficients λ. Experiments with simulated and measured spectra for methane and ethane were carried out to compare the performance of the different methods. agdPLS performed better than the other methods, with more accurate baseline estimation in low- and high-noise situations. Especially when the spectrum contained high noise, complex baselines and overlapping peaks, the agdPLS method performed significantly better than other methods. Moreover, agdPLS was computationally efficient. Results of actual spectral experiments showed that the proposed agdPLS method could be effective for baseline correction of spectra which, in turn, improved qualitative and quantitative spectral performances.

Assessment of ship speed, operational carbon intensity indicator penalty and charterer profit of time charter ships.

The operational carbon intensity indicator (CII) proposed by the International Maritime Organization (IMO) has been officially implemented on January 1, 2023. As an important way of ship operation, applicable time charter ships are subject to the CII regulation. How to properly deal with the CII regulation is a challenge for the shipowner and charterer of time charter ships. Speed reduction is an effective measure to reduce carbon emissions and carbon intensity of ships. This study establishes a speed model including CII penalty for time charter ships. Results show that speed reductions of a time charter ship of 10 %, 20 % and 30 % reduce carbon emissions by 27.1 %, 48.8 % and 65.7 % and carbon intensity by 19 %, 36 % and 51 %, respectively. Speed reduction leads to reductions of carbon emissions, carbon intensity and CII penalty, with greater reductions for larger ships. Under the optimal charterer profit, the speed of a time charter ship increases with the rise of freight rate and reduces with the decrease of freight rate. When the fluctuation range of freight rate is the same, the larger the ship type is, the smaller the speed adjustment range is. For the same ship type, when its freight rate decreases, it is suggested that the charterer reduces speed; otherwise, it is suggested that the charterer increases speed. For different ship types, if the shipping market is booming, the charterer should charter more large ships; otherwise, the charterer can choose more small ships.