With the growing application of unmanned surface vehicles (USVs) in marine explorations, high precision state estimation of USVs becomes increasingly important. However, sensors for consumer use are often with noise, and the real states cannot be inferred from a single sensor. Thus, GPS, IMU, and the Hydrodynamic Model of USV are combined here to achieve multi-sensor fusion and reduce the noise interference. This paper proposes a GPS/IMU/Hydrodynamic Model fusion state estimation strategy based on the moving horizon estimation (MHE) method. The performance of MHE is compared against the Extended Kalman Filter (EKF) in simulations of a traditional circular trajectory and a complex trajectory. In addition, the correlation between estimation horizon and MHE performance is studied. The results demonstrate that the designed estimator could substantially improve pose and velocity estimation accuracy compared to EKF when the real-time performance is required. © 2023 IEEE.

Underwater image denoising, as an important field of image enhancement in vision, has become an important and popular research field. Through image denoising, the texture features of the image will become clearer. In order to improve image quality, we present you a pseudo-siamese neural network based on self-supervised image denoising, which is specifically designed for underwater noise characteristics. Besides, the pyramid hierarchical are designed to consider the feature information under different scales at the same time in order to denoise the image noise. Totally, our model can reduce the noise caused by underwater impurities scattering significantly. We take not only the Structural Similarity (SSIM), Peak Signal-to-Noise Ratio (PSNR), Natural Image Quality Evaluator (NIQE) and Mean Opinion Score (MOS) but also the pose estimation (an important visual information during auto-underwater-vehicles docking)accuracy as evaluation criterion. Extensive experiments on self-built dataset and public datasets demonstrate the superior performance of our approach. © 2023 IEEE.

The optoacoustic pulses generated under the thermal expansion mechanism have good repeatability and high correlation coefficient, making them suitable as carriers for underwater communication. However, due to the unique properties of optoacoustic signals and the limitations of laser physical parameters, the pulse position modulation (PPM) is the only feasible modulation scheme at present. This paper proposes a pulse position demodulation method based on cepstrum-wavelet decomposition, which can achieve the separation of noise and optoacoustic pulses in the cepstrum domain, and complete comparative judgment by calculating entropy value. Finally, simulation results confirm that the performance of the cepstrum domain demodulation method is superior to traditional methods, and the feasibility has been verified through experiments at Zhoushan Pier. © 2023 IEEE.

6D pose estimation is the committed step of autonomous docking of underwater vehicles using executive guidance, and it is also an important research topic in recent years. This method provides RGB images and CAD models and calculates the pose of the object. The prediction model based on keypoints performs well in 6D object pose estimation. The method of this model is to select keypoints first, and then estimate 6D pose through keyoint estimation. Therefore, the position of selected keypoints profoundly affects the accuracy of pose estimation results. To reduce the positional errors of keypoints introduced in previous studies, we propose a new framework for using keypoints to determine pose. This framework includes a vector projection based estimation method (VPE) and a two-stage pose calculation based on reprojection to improve the accuracy of keypoint position estimation required for pose solution. The two-stage pose calculation based on reprojection first obtains the initial pose value, and then iteratively optimizes the final pose based on the reprojection distance. Compared with the original method based on RANSAC vector voting on the LINEMOD test set, the final ADD(-S) metric and 2D-projection perform 4.2% and 3.3% better after adding our VPE. © 2023 IEEE.

Chinese baijiu (liquor) is one of the oldest ditillates in the world and can be classified into 11 categories according to their aroma characteristics. Volatile compounds are extremely important to the flavor profile of baijiu. However, not all of these compounds are important to the aroma and flavor. The aroma and flavor compounds in baijiu was first studied using gas chromatography-olfactometry (GC-O) in 2004 by Qian and Fan. Since then, more than 300 aroma compounds of 10 different aroma type baijius were detected by GC-O coupled with gas chromatography-mass spectrometer (GC-MS), and key aromas of 5 aroma type baijius were confirmed using GC-O, OAV, recombinate, and omission tests. Esters were very important aroma compounds; these include ethyl hexanoate, ethyl butanoate, and ethyl acetate. Ethyl hexanoate was the key aroma compound in strong aroma and flavor type baijiu. Fatty acids were important aromas for Chinese baijiu. Some compounds are particularly important for certains types of baijiu. beta-Damascenone is a positive aroma compound for light aroma type of baijiu, whereas geosmin contributes a negative characteristic aroma for light aroma and flavor type baijiu. However, geosmin was a key aroma contributor for laobaiganxiang-aroma type baijiu. (E)-2-Enals are very important aroma compounds for chixiang-aroma type baijiu. Sulfur-containing compounds were very important aroma compounds. Many of the volatile compounds also affect the bitter taste and astringent mouthfeel. The knowledge obtained in the past decade about aromas and flavors of baijius has provided a direction for baijiu quality improvement and new technology implementation in industry.

Lactic acid bacteria (LAB) are valuable microorganisms which are wildly applied in production of food, feed, chemical, etc. Specially, LAB play an important role in fermentation of Chinese traditional vinegar. In our previous study, a strain of LAB Lactobacillus helveticus AAF1-5 that appeared a potential application in reinforcing vinegar fermentation was isolated from pei of Shanxi aged vinegar, a kind of famous Chinese traditional vinegars. In this present work, the preparation of direct vat set (DVS) of L. helveticus AAF1-5 was optimized. The optimized fermentation medium was consisted with glucose 2.0%, peptone 1.0%, beef extract 1.0%, yeast extract 0.5%, NaAc 0.5%, K2HPO4 0.2%, MgSO4 0.058%, malt wort 20%, the total number of viable cells was (2.35 ± 6.00) × 109 CFU/mL when it was cultured at 37 °C for 24 h. Then the DVS was prepared with lactose as protective agent. Under this condition the survival cells in DVS was (5.66 ± 0.07) × 1010 CFU/g which was 87.5% of initial cells. The survival cells of DVS were 58.7 and 69.0% after it was conversed for 6 months at 25 and 4 °C, respectively. © Springer Nature Singapore Pte Ltd. 2018.