L-VTP: Long-Term Vessel Trajectory Prediction Based on Multi-Source Data Analysis.

With the rapid development of marine IoT (Internet of Things), ocean MDTN (Mobile Delay Tolerant Network) has become a research hot spot. Long-term trajectory prediction is a key issue in MDTN. There are no long-term fine-grained trajectory prediction methods proposed for ocean vessels because a vessel's mobility pattern lacks map topology support and can be easily influenced by the fish moratorium, sunshine duration, etc. A traditional on-land trajectory prediction algorithm cannot be directly utilized in this field because trajectory characteristics of ocean vessels are far different from that on land. To address the problem above, we propose a novel long-term trajectory prediction algorithm for ocean vessels, called L-VTP, by utilizing multiple sailing related parameters and K-order multivariate Markov Chain. L-VTP utilizes multiple sailing related parameters to build multiple state-transition matrices for trajectory prediction based on quantitative uncertainty analysis of trajectories. Trajectories' sparsity of ocean vessels results in a critical state missing problem of a high-order state-transition matrix. L-VTP automatically traverses other matrices in a specific sequence in terms of quantitative uncertainty results to overcome this problem. Furthermore, the different mobility models of the same vessel during the day and the night are also exploited to improve the prediction accuracy. Privacy issues have been taken into consideration in this paper. A quantitative model considering Markov order, training metadata and privacy leak degree is proposed to help the participant make the trade-off based on their customized requirements. We have performed extensive experiments on two years of real-world trajectory data that include more than two thousand vessels. The experiment results demonstrate that L-VTP can realize fine-grained long-term trajectory prediction with the consideration of privacy issues. The average error of 4.5-hour fine-grained prediction is less than 500 m. In addition, the proposed method can be extended to 10-hour prediction with an average error of 2.16 km, which is also far less than the communication range of ocean vessel communication devices.

Chloroplast genome data of five Amygdalus species: Clarifying genome structure and phylogenetic relationships.

Amygdalus species have considerable ecological and economic value, however, the phylogenetic relationships among Amygdalus remain controversy. In this study, we sequenced and assembled the chloroplast (cp) genomes of five Amygdalus species: Prunus communis, P. mongolica, P. pedunculata, P. triloba, and P. mira. We then conducted comparative genomic analyses and constructed their phylogenetic relationships. The genome length ranged from 157,870 to 158,451 bp, and 131 genes were annotated (86 protein-coding genes, 37 tRNAs, and 8 rRNAs). Additionally, 49-57 simple sequence repeats were detected, with most in the large single-copy region and with AT base preferences. Comparative genomic analyses revealed high similarities in structure, order, and gene content. However, we identified four highly divergent sequences: trnR-UCU-atpA, nbdhC-trnV-UAC, ycf4-cemA, and rpl32-trnL-UAG. The phylogenomic relationship analysis suggested that the Amygdalus species were grouped together, in which P. pedunculata, P. triloba, and Prunus tangutica were categorized into a branch, P. mongolica and Prunus davidiana were clustered a branch. This study provides an improved understanding of the genetic relationships among the Amygdalus and provides a basis for the development and utilization of Amygdalus resources.

Effect of Aging Treatment on Microstructural Evolution and Mechanical Properties of the Electron Beam Cold Hearth Melting Ti-6Al-4V Alloy.

Ti-6Al-4V (Ti64 or TC4) alloy is widely used in the industrial field. However, there have been few studies of the TC4 alloy melted by electron beam cold hearth melting (EBCHM) technology. Aging treatment has a considerable influence on the secondary α-phase in titanium alloys. Therefore, TC4 alloy melted by EBCHM technology was investigated in this study. The effect of different aging times on the microstructural evolution and mechanical properties of titanium alloy sheets was evaluated. The results showed that, with increase in aging time, the primary α-phase enlarged and grain globularization occurred. In addition, some transformed ß-phases disappeared. The strength and Vickers hardness of the heat-treated sheets decreased, while the plasticity increased with increase in aging time, indicating that the mechanical properties developed with evolution of the microstructure. After aging at 560 °C for 2 h, the properties overall were optimal. The type of fracture of the samples was ductile fracture; the dimples became larger with increase in aging time. After heat treatment, the recrystallized nucleus, substructures and HAGBs increased, while the deformed structure and LAGBs decreased. Some grains had rotated following heat treatment, indicating that anisotropy was greatly reduced.

Variation in grain-size characteristics of simulated shrubs as a novel sand-barrier in a wind tunnel experiment.

Sand transport is the main manifestation of sand damage in the arid and semiarid regions globally. It is a huge challenge to stabilize mobile sandy and change them into stable productive ecosystems. The establishment of simulated shrubs is one of the most effective measures to solve the above difficulties as a novel sand-barrier. To clarify simulated shrubs' role in the process of ecological restoration. It will be greatly helpful to incorporate the shelter device proposed in the present work into landscape models for aeolian soil transport, to optimize the parameters associated with the sand-barrier characteristics for aeolian soil stabilization at the field scale. A series of wind tunnel experiments were conducted to analyze the variations of soil grain-size of simulated shrubs with different spatial configurations, row spaces, and net wind speeds. Further, the soil grain-size parameters were calculated by the classic method proposed by Folk and Ward to clarify the change of soil particles resulted from the blocking effects. The average grain-size content of simulated shrubs with different spatial configurations, row spaces, and net wind speeds was dominated by medium sand and fine sand, and the total percentage was more than 90%. Moreover, the sand deposition of simulated shrubs with different spatial configurations increased with the improvement of wind speeds. The average sand deposition of spindle-shaped simulated shrubs in 17.5 × 17.5 cm and broom-shaped simulated shrubs in 17.5 × 26.25 cm under different net wind speeds was the least. The effects of row spaces on average grain-size parameters increased with the improvement of net wind speeds. By calculating the correct characteristics of specific shelter devices proposed in the present work, all of these findings suggest that the application of simulated shrubs will be an important component to further extend ecological engineering projects in arid and semiarid regions.

The complete chloroplast genome of Salix psamaphila, a desert shrub in northwest China.

Salix psammophila C. Wang & Chang Y. Yang is a desert plant species distributed in Northwest China. Here, we report the complete choroplast genome sequences in order to enrich its genetic resource. The total genome is 155,278 bp in length and contains a typical quadripartite structure, including a large single copy (LSC) region of 84,457 bp, a small single copy (SSC) region of 15,891 bp, and a pair of inverted repeats (IRs) of 27,465 bp. There were 130 genes in the genome, including 85 protein-coding genes, 37 tRNA genes and eight rRNA genes. The overall CG content in the plastome of S. psammophila is 36.72%. The phylogenetic tree based on 18 complete plastomes of Salicaceae support close relationships among S. psammophila, Salix taoensis, and Salix rehderiana.