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Improving the autopilot capability of ships is particularly important to ensure the safety of maritime navigation.The unmanned surface vessel (USV) with autopilot capability is a development trend of the ship of the future. The objective of this paper is to investigate the path planning problem of USVs in uncertain environments, and a path planning strategy unified with a collision avoidance function based on deep reinforcement learning (DRL) is proposed. A Deep Q-learning network (DQN) is used to continuously interact with the visually simulated environment to obtain experience data, so that the agent learns the best action strategies in the visual simulated environment. To solve the collision avoidance problems that may occur during USV navigation, the location of the obstacle ship is divided into four collision avoidance zones according to the International Regulations for Preventing Collisions at Sea (COLREGS). To obtain an improved DRL algorithm, the artificial potential field (APF) algorithm is utilized to improve the action space and reward function of the DQN algorithm. A simulation experiments is utilized to test the effects of our method in various situations. It is also shown that the enhanced DRL can effectively realize autonomous collision avoidance path planning.

Chitin nanocrystal (ChNC) was used to prepare fully biodegradable nanocomposites with polylactide (PLA). The nucleation and melting behavior of nanocomposites were studied with the objective to correlate PLA-ChNC affinity to PLA crystallization. The results disclose that the PLA nanocomposites with pristine ChNCs and the ones with acetylated ChNCs show completely different nucleation and melting behavior because the role of ChNCs is altered after acetylation. Pristine ChNC acts as inert filler, with weak nucleating activity, while acetylated ChNCs as anti-nucleation agent, restraining crystallization of PLA. Accordingly, the nanocomposites with acetylated ChNCs show melting point depression, with reduced nucleation capability. The recrystallization and self-nucleation, as well as the double-melting behaviors were then studied in terms of acetylation levels of ChNCs and annealing temperatures, in order to better understand the relations between two-phase affinity and PLA chain dynamics. This work provides interesting information around designing thermal properties of the ChNC-filled PLA nanocomposites.

Hypothesis Using the platelet-like starch nanocrystals (SNCs) to stabilize emulsions is attractive because as-prepared emulsions have promising applications in cosmetics and food fields. Limited studies mainly focus on the oil-in-water system, and another important system, the water-in-water emulsions stabilized by SNCs, has not yet been unveiled. Experiments Two surface modification strategies, crosslinking and acetylation, were applied to tune surface property and aggregation of SNCs, and a common all-aqueous system (dextran/poly(ethylene glycol)) was used here as template. The viscoelasticity and morphology of emulsions were studied in terms of the SNC loadings and polymer ratios. Findings Crosslinking results in aggregation of SNCs, and the particle size increases (from 110 nm to 370 nm) with increased levels of substitution. This favors improving emulsifying ability of particles. Acetylation decreases the particle size (∼90 nm) and weakens the affinity of SNCs to the two aqueous phases, improving the emulsifying efficiency of SNCs. More intriguingly, the two emulsion systems show different phase inversion behaviors. The depletion-stabilization mechanism for the cross-linked SNCs and the diffusion-controlled mechanism for the acetylated SNCs are proposed using the emulsion viscoelasticity as probe. This study makes a comprehensive insight into the regulation of water-in-water emulsion morphology and types with the platelet-like SNCs.

As important biological functions of many creatures, structural colors and self-healing features play crucial roles in the survival of organisms. Inspired by these features, the intelligent self-he...

The sesame oil-in-water Pickering emulsions using cellulose nanofibers (CNF) as the emulsifier were prepared for the rheological study, aiming at establishing relationship between emulsion viscoelasticity and morphology. A droplet cluster structure forms in those systems due to multicomponent properties of sesame oil and fibrillar structure of CNF. Its deformation and relaxations result in weak strain overshoot behavior in large amplitude oscillatory shear (LAOS) flow, but not affect the scaling behavior of small amplitude oscillatory shear (SAOS) responses. The relaxation time scales can be evaluated by creep of emulsions. This structure can evolve during ramp shear flow, rearranged and oriented at the higher flow rates, which has evident influence on the thixotropic behavior of emulsions. The mechanisms of evolution and relaxations of droplet cluster structure are traced through rheo-optical way. This work presents some interesting results and paves a possible way to control morphology and viscoelasticity of edible Pickering emulsions.

A surface imprinting method is presented herein for the development of a highly selective yet highly permeable molecularly imprinted membrane for protein separation and purification. The resultant protein imprinted membrane was shown to exhibit great potential for the efficient separation of the template protein from a binary mixture and a cell lysate solution, while maintaining high transport flux for complementary molecules. Bovine Serum Albumin (BSA) and Lysozyme (Lys) were individually immobilized on a cellulose acetate membrane as template molecules. In situ surface crosslinking polymerization was then used for protein imprinting on the membrane for a controlled duration. Both membranes showed high adsorption capacity towards template proteins in the competitive batch rebinding tests. In addition, the adsorption capacity could be greatly enhanced in a continuous permeation procedure, where the resultant membrane specifically adsorbed the template protein for more than 40 h. Moreover, this is the first report of purification of a specific protein from the cell broth mixture using a molecularly imprinted membrane. The protein imprinted membrane enables the transport of multiple non-template proteins with high permeation rate in a complex system, thus opening the way for high efficiency protein separation at a low cost for the industry.

Developing dwarf watermelon is a major objective among breeders. The dsh dwarf watermelon germplasm developed in our laboratory is genetically stable. We previously produced preliminary evidence that Cla010726, which encodes a gibberellin 20-oxidase-like protein, is the primary gene controlling dwarfism in watermelon. However, the underlying genetic mechanism was unknown. In this study, we characterized the spontaneous recessive mutant dsh, which is a gibberellin (GA)-deficient mutant. Many of the phenotypic traits of dsh plants are similar to those of known GA-deficient mutants. The dsh plants were sensitive to exogenous bioactive GAs, which increased seedling height. Moreover, a quantitative analysis of endogenous GA3 proved that the bioactive GA3 content was substantially lower than normal in dsh. Additionally, the T5ClaGA20ox RNAi plants generally exhibited dwarfism, with short stems and internodes as well as small leaves and fruit. An examination of the transgenic plants carrying the ClaGA20ox1 promoter-GUS and mutant ClaGA20ox2 promoter-GUS constructs confirmed that two promoter sites are involved in the regulation of ClaGA20ox expression. Hence, mutations in the promoter of the GA20ox gene, which encodes a key enzyme involved in gibberellin biosynthesis, lead to the dwarfism of watermelon plants. The dsh mutant is a potentially useful germplasm resource for developing new watermelon varieties exhibiting dwarfism.

Dispersion states are vital for fibrous nanocelluloses to be used as reinforcements for polymers, which is highly dependent on geometry of nanocelluloses. Three types of nanocelluloses with various fiber aspect ratios were used to prepare target composite samples with poly(β-hydroxybutyrate) in this work. Viscoelasticity/elastoplasticity were used as probes to detect the flexibility-morphology relations of nanocelluloses in polymer. Cellulose nanocrystals (aspect ratio = 8) were rigid in polymer, retaining their rod-like shape, whereas bacterial celluloses (aspect ratio = 600) fully flexible, forming closely networked structure, and cellulose nanofibers (aspect ratio = 70) semi-flexible, dispersing as loosely flocculated clusters. Owing to these differences, the viscoelastic flow and elastoplastic deformation of three kinds of composites differed from one another. The strain-scaling and hysteresis work-scaling behaviors were then used to establish relaxation scale-structure correlations of target samples. This work provides interesting information around regulating the dispersion of nanocelluloses in polymer composites by tailoring aspect ratios of nanocelluloses.

Fractured horizontal wells have been widely used to develop unconventional oil and gas reservoirs. In previous studies, most studies on the transient pressure behavior of multistage horizontal wells were based on the assumption of single porosity medium, in which the coupling relationship of natural fractures and artificial fractures was not taken into account or artificial fractures were assumed to be infinitely conductive. In this paper, the fracture is finite conductive, which means that there is flow resistance in the fracture. Based on point-source method and superposition principle, a transient model for multistage fractured horizontal wells, which considers the couple of fracture flow and reservoir seepage, is built and solved with the Laplace transformation. The transient pressure behavior in multistage fractured horizontal wells is discussed, and effects of influence factors are analyzed. The result of this article can be used to identify the response characteristic of fracture conductivity to pressure and pressure differential and provide theoretical basis for effective development of tight oil reservoirs. The findings of this study can help for better understanding of transient pressure behavior of multistage fractured horizontal wells with finite conductivity in tight oil reservoirs.

Starch nanocrystals (SNCs) grafted with octenyl succinic anhydride (OSA) were used to stabilize caprylic/capric triglycerides (GTCC)-in-water emulsions. The morphology and viscoelasticity of emulsions were studied in terms of particle loadings and degrees of substitution (DSs). It is found that the emulsifying capacities of SNCs increase with increased DSs. Both the pristine SNC and modified ones can be well used to stabilize emulsions, whereas the emulsification follows different mechanisms. The platelet-like structure of SNCs, together with its improved amphiphilicity after surface treatments, are important to the formation and evolution of droplet clusters. The deformation and relaxation of those clusters result in weak flow overshoots and strong thixotropy in different shear flow fields, which favor storage and applications of GTCC-in-water emulsions as hydrocolloids. The mechanisms were then discussed in terms of rigidity of SNC and relaxations of clusters. This work proposes a promising application of SNC in food and cosmetic industries.

To investigate the relationship between functional groups on cellulose nanocrystals (CNC) and the performance of poly(β-hydroxybutyrate-co-valerate) (PHBV), the surface of CNC was modified by surface graft modification and PHBV/CNC biocomposites were prepared by melt blending. To demonstrate the interfacial adhesion difference between hydrophobic PHBV and hydrophilic CNC, palmitoyl chloride and e-caprolactone had been used to tailor the oleophilic property of CNC. Results showed that CNC had heterogeneous nucleation effect on the crystallization process of PHBV, while the entanglement of molecular chains weakened the promoting functions of CNC-g-C16 (CNC grafted with palmitoyl chloride) and CNC-g-CL (CNC grafted with e-caprolactone). Furthermore, CNC-g-CL exhibited better interfacial adhesion with PHBV when compared with CNC-g-C16. And 1 wt% CNC-g-CL improved the tensile strength of PHBV biocomposite to 38.09 MPa, which is 26.25% higher than PHBV.

Cellulose nanocrystal (CNC) particles were used as the solid emulsifier to stabilize poly(e-caprolactone) (PCL) solution-in-poly(vinyl alcohol) (PVA) solution emulsions (oil-in-water), with the objective to prepare ternary nanocomposites using as-obtained Pickering emulsions as the templates. The morphology of emulsions and mechanical properties of nanocomposites were studied, aiming at establishing a convenient route to regulate selective localization of CNCs and multiphase structures. The results show that emulsion stability depend strongly on CNC loadings and PVA concentrations in continuous phase. The evolution of multiphase morphology of emulsions from locally coalesced droplet structure to interfacial saturation one, and finally to droplet-particle interfacial flocculation, shows scaling characteristics with increasing CNC loadings, and can be detected through rheological way. The interfacial localization makes CNCs show excellent reinforcement to ternary nanocomposites because of their two-phase bridging effect. This work provides an interesting strategy of fabrication of the CNC reinforced polymer blend composites with controllable multiphase structures.

Particle reinforcement is a common approach to improve mechanical properties of thermoplastic polyester elastomer (TPEE). The improvement of strength is commonly accompanied by an evident increase of Young’s modulus, which is against the usage of TPEE as the elastomer material, however. The high-strength TPEE composites with low modulus are preferred. A composite particle technology was developed here to modify TPEE. Two-dimensional graphene nanoplatelets (GNP) and three-dimensional slag particles were bonded by pretreatment , and then mixed with TPEE. In this case, the Young’s modulus decreased by about 20% relative to the composite containing simply mixed particles. On the other hand, the former showed an evident increase of yielding strength by about 40% relative to TPEE, while the latter only by about 10%. The mechanism was then proposed in terms of alteration of closely packed structure of particles. This work opens a new door for structure and property design of polymer composites .

Vessels with a dynamic positioning system (DPS) are widely applied in ocean resource exploration. Because of the inaccuracy and coupling of the vessel dynamic model, it is important to design a controller that performs well in an oceanic environment. The active disturbance rejection controller (ADRC) is introduced in this study to control the vessel movement and positioning in the DPS. The merit of the ADRC is that it does not need an accurate plant and disturbance model. In the proposed method, an adaptive hybrid biogeography-based optimization (BBO) and differential evolution (DE) are developed. The orthogonal learning (OL) mechanism is employed to achieve adaptive switching to different searching mechanisms between BBO and DE. The proposed adaptive hybrid BBO-DE (AHBBODE) algorithm is then used to optimize the parameters of ADRC; these parameters are not easy to determine by using the trial and error method. Finally, the proposed method is compared with the BBO- and DE-based methods. The results show that better performance is obtained by the proposed method.

As green composites, cellulose nanofiber (CNF) reinforced polylactide (PLA) systems have attracted increasing attention recently. In this work, three forms of CNFs, including pristine, coupled and acetylated ones, were incorporated with PLA through solution casting and injection molding to prepare PLA nanocomposites with different polymer-fiber affinities, and with different dispersion states and orientation levels of fibers. Rheological and mechanical properties of those systems were studied then in terms of fiber loadings and phase compatibility. Some interesting results are shown here. Surface acetylation can improve phase affinity of CNFs to PLA more evidently as compared to coupling reaction, but it also has diluent effect on the shear flow of nanocomposites, and therefore acetylated CNFs show better dispersion and higher orientation levels relative to coupled ones. However, the linear dynamical shear flow responses of nanocomposites, especially the percolation behaviors, are not sensitive to improved fiber dispersion, but are highly dependent on fiber loadings. All three forms of CNFs exhibit good reinforcement of PLA, and acetylated CNFs provide the best outcome. The relationships between properties of nanocomposites and hierarchical structures of CNFs are then established through the mechanical model.

Poly(e-caprolactone) (PCL) was filled with a very small amount of starch nanocrystals (SNC), with the objective being to control its crystallization. Three kinds of SNC particles, including a prist...

The pristine and acetylated cellulose nanocrystal (CNC) particles were incorporated with poly(e-caprolactone) to prepare two kinds of green nanocomposite systems: the former is incompatible, while the latter compatible thermodynamically. A rheological study was then performed systematically with various flow fields, including linear and nonlinear dynamic shear flow, creep and start-up flow. Some interesting results were shown then. The pristine CNC filled system shows far lower percolation threshold than the acetylated CNC filled one because the improved phase affinity yields diluent effect. The formation and rebuild-up of percolated network is driven by the Brownian motion of particles, which are nearly independent of altered phase affinity. However, the improved phase affinity makes the system more sensitive to the strain-responded deformation, leading to the reinforced Maxwell spring unit during creep and to a weak strain overshoot during dynamic flow. The structural evolution and relaxations of two systems were further evaluated from different perspectives.

A high-reliability, low-cost buoy–chain–sprocket wave energy capture device is proposed. Resonance theory is used to improve its wave energy capture efficiency and reduce its cost. The testing principle of the buoy–chain–sprocket model is proposed, and comparable resonant and nonresonant experimental floating body models were constructed based on finite depth linear wave theory and the resonance principle. Then the methods and results of the model experiments are described. Based on using Morison equation to calculate wave load, simulation and verification of the model experiment were conducted by using AQWA and OrcaFlex software. Finally, to eliminate the size effect and the impact of one-way wave energy collection, based on the simulation technology described above, sea-state prototype models of resonant and nonresonant buoy–chain–sprocket wave energy capture devices with one-way and two-way acquisition characteristics were constructed. Simulations were then conducted to get the maximum wave energy gathering efficiency. The research result indicates that the nonresonant buoy–chain–sprocket wave energy capture device with one-way acquisition has higher wave energy capture efficiency than the resonant buoy–chain–sprocket wave energy capture device.

ArcAB is a two-component regulatory system that can help bacteria respond to and survive in a changing environment. To identify the function of ArcAB homologues in Serratia marcescens FS14, in-frame deletion mutants of the arcA, arcB and arcAB genes were constructed. Surprisingly, ArcB affects the motility of FS14, but ArcA does not. These results are the reverse of those found in Escherichia coli. Further studies demonstrated that ArcB could promote bacterial motility by activating the synthesis of flagella and particularly by activating the expression of the biosurfactant serrawettin W1. Our results suggest that ArcB may regulate FS14 motility by interacting with an unidentified response regulator other than ArcA. The regulation of ArcAB may be bacterial strain-specific, and the same regulatory system may participate in different mechanisms to adapt to different environments.

Based on the principle of piecewise linearization, the incremental forms of microstructure evolution models were integrated into the thermo-mechanical coupled finite element (FE) model to simulate non-linear microstructure evolution during multi-pass hot deformation. This is an unsteady-state deformation where dynamic recrystallization (DRX), meta-dynamic recrystallization (MDRX), static recrystallization (SRX) and grain growth (GG) take place during hot deformation or deformation interval. The distributions of deformation and microstructure for cylindrical AZ31 sample during single-pass and double-pass hot compressions were quantitatively calculated and compared with the metallographic observation. It is shown that both the deformation and microstructure are non-uniformly distributed due to the presence of friction between the die and the flat end of sample. The average grain size and its standard deviation under the double-pass hot compression are slightly smaller than those under single-pass compression. The simulated average grain sizes agree well with the experiments, which validates that the developed FE model on the basis of incremental forms of microstructure evolution models is reasonable.

Background/aims ErbB3 is an oncogene which has proliferation and metastasis promotion effects by several signaling pathways. However, the individual expression difference regulated by miRNA was almost still unknown. We focused on the miRNAs associated SNPs in the 3′-UTR of ErbB3 to investigate the further relationship of the SNPs with miRNAs among Chinese gastric cancer (GC) patients. Methods We performed case–control study including 851 GC patients and 799 cancer-free controls. Genotyping, real-time PCR assay, cell transfection, the dual luciferase reporter assay, western-blot, cell proliferation and trans-well based cell invasion assay were used to investigate the effects of the SNP on ErbB3 expression. Moreover, a 5-years-overall survival and relapse free survival were investigated between different genotypes. Results We found that patients suffering from Helicobacter pylori (Hp.) infection indicated to be the susceptible population by comparing with controls. Besides, SNP rs3202538 (G/T) in ErbB3 3′-UTR was involved in the occurrence of GC by acting as tumor risk factors. SNP rs3202538 (G/T) could be regulated by both miR-204 and miR-211 which caused an upregulation of ErbB3 in patients. Furthermore, the carriers of T genotype was related to the significantly high expression of ErbB3, and to big tumor size, poor differentiation as well as the high probability of metastasis. Both miR-211 and miR-204 can significantly decrease cell proliferation, metastasis as well as downstream AKT activation through G but not T allele of ErbB3 3′UTR. Moreover, the SNP of G/T was associated with shorter survival of post-surgery GC patients with 5 years of follow up study. Conclusion In conclusion, our findings have shown that the SNP rs3202538 (G/T) in ErbB3 3′-UTR acted as promotion factors in the GC development through disrupting the regulatory role of miR-204 and miR-211 in ErbB3 expression. Electronic supplementary material The online version of this article (doi:10.1186/s12935-017-0449-z) contains supplementary material, which is available to authorized users.

Basalt fiber (BF) was used to reinforce polylactide (PLA) to obtain new composites with potential structural or engineering applications. The composites with pristine BFs present evidently increased strength and modulus relative to neat PLA. After surface treatment, BF shows more evident reinforcing effect because the interfacial energy between BF and PLA decreases sharply from 27.40 to 8.58 mJ m −2 . The physical network structure of BFs is also improved after their surface treatment, and as a result, the composites with treated BF have more tensile cycles and higher elongation levels than the one with pristine BF. After solid annealing, the mechanical strengths of systems were further improved because of cold crystallization of PLA. But composites show higher improvement level relative to neat PLA because the nucleation effect of BF enhances fiber-matrix interfacial adhesion. This work provides useful information on the preparation of BF filled PLA composites with tailorable structure and properties.

Poly(e-caprolactone) composites containing the acetylated cellulose nanocrystal (aCNC) with various degrees of substitution (DS) were prepared for the phase compatibility study. An interesting phenomenon around the alteration of crystallization temperature (Tc) was reported here. Tc of PCL increases evidently in the presence of pristine CNC (DS = 0) due to its nucleation effect. However, for the composites with aCNCs, Tc decreases monotonously with increasing DSs of aCNCs and is even lower than that of the neat PCL at higher DSs. This is attributed to the improved compatibility between the matrix and particles, which is further evaluated by the Flory–Huggins parameters. Therefore, the alteration of Tc can be used as the probe to detect the compatibility between two phases in aliphatic polyester composites with chemically modified CNCs. From another perspective, crystallization of aliphatic polyesters can be controlled using aCNCs with different DSs.

Pristine cellulose nanocrystal (CNC) and acetylated one (aCNC) were used as the modifier to change the surface properties of poly(trimethylene terephthalate) (PTT) fibers for the transcrystallization study of polypropylene (PP). The results reveal that all three kinds of fibers, including the neat PTT, PTT/CNC and PTT/aCNC ones can induce PP transcrystallization. But the PTT/aCNC fiber-filled PP system shows the most remarkable transcrystallization behavior because of the highest nucleation density of PTT/aCNC fiber. The long period and lamellar thickness of two composite fiber-filled PP systems increase as compared with the neat PTT fiber-filled one, which is caused by the reduced system undercooling and higher surface energy level of composite fibers. Accordingly, the former two systems show the lower transcrystal growth rates than the latter, which is further analyzed by the secondary nucleation theory. This work can provide useful information on the control of PP transcrystallization using the CNC-filled polyester composite fibers.

A new approach to improve the thermal stability and mechanical strength of thermoplastic polyester elastomer (TPEE) using spodumene slag as the filler is reported here. The thermal decomposition temperature of TPEE increases from 277 °C to about 350 °C by about 26% in the presence of pristine spodumene slag. The surface graft reaction further improves its barrier effect. Besides, spodumene slag can be used as a good reinforcement to TPEE, and also the surface treatment favors further improvement of its reinforcing effect. However, the presence of spodumene slag reduces the elastoplasticity and viscoplasticity of the system, leading to decreased tensile cycles and elongation levels. The morphological and crystallographic methods were then employed to further reveal the alteration of the phase separation structure of TPEE in the presence of spodumene slag, aiming at establishing structure–property relations of composites. This work can provide useful information on the preparation of new TPEE composites wit...

This paper deals with the trajectory tracking problem of autonomous underwater vehicles (AUVs) in the presence of dynamic uncertainties and time-varying external disturbances. Three exponentially convergent robust controllers, namely, the min-max type controller, the saturation type controller and the smooth transition type controller are proposed to drive an AUV to track a predefined trajectory. It is shown that the filtered tracking errors, position tracking errors and velocity tracking errors for the three proposed controllers are exponentially convergent. Moreover, all the above tracking errors for the three proposed controllers can be shaped by specific analytic expressions and such expressions illustrate how the transient responses of the above tracking errors can be modified by adjusting the control parameters. The characteristics of the three proposed controllers are summarized and demonstrated with numerical simulations. Theoretical comparison analysis and comparative simulations with the existing RISE-based controller of AUV are presented to show the effectiveness of the three proposed exponentially convergent robust controllers.

The crystallization behavior of the basalt fibers (BF)-filled poly(e-caprolactone) (PCL) composites was studied. Both the pristine BF and the treated one have a remarkable nucleation effect on the crystallization of PCL, and the latter has a higher nucleation activity than the former. However, the PCL chain diffusion is restrained by the physical barrier effect of BF and the increased system viscosities. Yet nucleation dominates the overall kinetics because composites have far higher crystallization rates than neat PCL. The presence of BF does not alter lamellar structure, but favors the formation of the nuclei with a denser fold surface, especially in the treated BF-filled composite. The reinforcing effect of BF, together with the increased PCL crystallinity, results in increased mechanical strength of the composite system. This work can provide useful information on the structure and property control of novel PCL/BF composites.

Polylactide (PLA) composites with pristine cellulose nanocrystals (CNC) and acetylated one (aCNC) were prepared for the crystallization study. The roles of CNC and aCNC in cold and melt crystallization of PLA were explored. Both CNC and aCNC have good nucleation activity during cold crystallization of PLA, but also highly impede transport of adjacent chain segments to the growing surface, acting as the role of physical barrier in the glassy bulk. Within the experimental temperature range, growth dominates the overall kinetics, rather than nucleation. Therefore, barrier role overwhelms nucleation agent one and as a result, the cold crystallization rates of composites decrease as compared with neat PLA, accompanied by decreased degrees of crystallinity. During melt crystallization, although the presence of CNC and aCNC leads to sharply increased system viscosities, reducing chain mobility, nucleation is the dominant role as the systems crystallize from the melts. Thus, the presence of CNC and aCNC promotes melt crystallization of PLA, and the composites show far higher crystallization rates and degrees of crystallinity than neat PLA. Besides, the surface acetylation of CNC improves its nucleation ability during melt crystallization of PLA, and as a result, the composite with aCNC has denser fold surfaces relative to the one with CNC. But the presence of these two kinds of particles has no evident influence on the lamellar structure of PLA whether in the cold or in melt crystallization. This work can provide useful information on the crystallization control of PLA using CNC.

Poly(e-caprolactone) (PCL) composites with pristine nanocrystalline cellulose (NCC) and acetylated nanocrystalline cellulose (aNCC) (with 1.85 ± 0.15 degree of substitution) were prepared. Different roles of NCC and aNCC to the crystallization of PCL were explored. NCC acts as the nucleation agent, promoting the formation of thickened PCL lamellae. Thus, PCL-NCC sample shows higher melting point (Tm) and degree of crystallinity (Xc) than neat PCL. However, aNCC plays the role of antinucleation agent, decreasing Xc and crystallization temperature (Tc) of PCL. This is because the relaxation of PCL chain segments is restrained by the presence of aNCC through hydrogen bonding between two phases. As a result, the looser fold surfaces of lamellae form in PCL-aNCC sample, with decreased lamellar thickness. The ring-banded morphology is therefore observed on this sample because of good compatibility between aNCC and PCL and higher level of surface stress of PCL lamellae, which is not observed on PCL-NCC one.

Blending two biodegradable aliphatic polyesters with complementary bulk properties is an easy way of tuning their final properties. In this work, the ductile poly(butylene succinate) was mixed with polylactide, and as expectable, the blends show improved toughness with sharply reduced strengths. The pristine cellulose nanofibers were then used as the reinforcement for the blends. It is found that most nanofibers are dispersed in the polylactide phase because polylactide has better affinity to nanofibers, and the lower viscosity level of polylactide also favors driving nanofibers into the continuous polylactide phase during melting mixing. In this case, the strength and rigidity losses resulted from the presence of soft poly(butylene succinate) phase are compensated to some extent. To further improve mechanical properties, a two-step approach (reactive processing of blends, followed by the incorporation with nanofibers) was developed. This work provides an interesting way of fabricating fully biodegradable composites with well-balanced mechanical performance.

Starch nanocrystal (SNC), was used as the third component to prepare nanocomposites with biodegradable poly(β-hydroxybutyrate)/poly(butylene succinate) (PHB/PBS) blend. The results reveal that SNC shows strong nucleation to the two matrix polymers. However, the crystallization temperature of PHB is highly dependent on the SNC loadings, whereas that of PBS not. This is because SNCs have preferential localization in the immiscible matrix polymers: mainly dispersed in the continuous PHB phase and on PHB/PBS phase interfaces. Therefore, alteration trend of crystallization temperatures can be used as good probe to evaluate selective localization of SNCs in the immiscible blends containing two semicrystalline polymers. The nucleation activities of SNCs, and their interaction energy densities in the two polyesters, as well as the tensile behaviors of ternary nanocomposites, were then detected, aiming at establishing a simple route to prepare green nanocomposites with tailorable multi-phase morphology and balanced mechanical properties using starch and biodegradable aliphatic polyester blends.

It is well known that path planning has always been an important study area for intelligent ships, especially for unmanned surface vehicles (USVs). Therefore, it is necessary to study the path-planning algorithm for USVs. As one of the basic algorithms for USV path planning, the rapidly-exploring random tree (RRT) is popular due to its simple structure, high speed and ease of modification. However, it also has some obvious drawbacks and problems. Designed to perfect defects of the basic RRT and improve the performance of USVs, an enhanced algorithm of path planning is proposed in this study, called the adaptive hybrid dynamic stepsize and target attractive force-RRT(AHDSTAF-RRT). The ability to pass through a narrow area and the forward speed in open areas of USVs are improved by adopting the AHDSTAF-RRT in comparison to the basic RRT algorithm. The improved algorithm is also applied to an actual gulf map for simulation experiments, and the experimental data is collected and organized. Simulation experiments show that the proposed AHDSTAF-RRT in this paper outperforms several existing RRT algorithms, both in terms of path length and calculating speed.

Lead methacrylate ( Pb (MAA) 2 ) was synthesized through the reaction of lead oxide and methacrylic acid and characterized by FT-IR spectroscopy, XRD ， DSC. The non-isothermal and isothermal analysis were used to study the kinetics of self-polymerization of Pb (MAA) 2 . The monomer reactivity ratios of Pb (MMA) 2 /MMA, Pb(MAA) 2 /St and Pb(MAA) 2 /BA were calculated by K-T method. The results showed that Pb (MMA) 2 could be induced to self-polymerization initiated by thermal and free radical and the activation energy of polymerization was 150.10kJ/mol in solid state and 74.99kJ/mol in aqueous solution. The rate of polymerization under low conversion was governed by the expression at 70 ℃ : Rp=K[M] 1.02 [I] 0.37 . The values of r 1 ( Pb (MAA) 2 ) and r 2 ( MMA ) were 3.767 and 0.166, r 1 ( Pb (MAA) 2 ) and r 2 (St) were 26.856 and 0.294, r 1 ( Pb (MAA) 2 ) and r 2 ( BA ) were 10.822 and 0.089.

Due to their unique and excellent properties, nanopolysaccharides have been widely used in a variety of areas, including stabilizing agents in diet meals, active components in cosmetic products and important substances in polymer composites. This chapter covers the contents of nanopolysaccharides as green additives and the corresponding disciplines. Their roles in achieving enhanced performances in food, cosmetics, construction, paper industry, and some emerging fields will be discussed in general.

Crosslinking opens more possibilities of biodegradable poly (L-malic acid) (PLMA) as functional materials, and network structure is key to its mechanical states and final applications. In this work, the diols with various chain lengths, including six types of fatty diols and four types of polyethylene glycols, were used to construct networks in PLMA, aiming at establishing network structure-mechanical state-material function correlations. As the molecular weights of diols increased from 100 to 400, the samples experienced evident transition from high-strength plastic to low-loss rubber, finally to soft elastomer. The strengths and Young's moduli varied from 71 MPa to 0.6 MPa and from 2.3 GPa to 2.7 MPa, respectively, accompanied by a broad variation of glass transition temperature (Tg, 50 oC–7 oC). This brittle-ductile transition was revealed in terms of elastoplastic and dielectric relaxations, then. Using the samples with different network structures as components, the actuators with attractive capability to complete asynchronous actions were fabricated. This work proposes promising applications of cross-linked PLMA as functional or smart materials due to its easily-tuned mechanical states and Tg, together with its good antibactierial activity and shape memory effect.

When considering the characteristics of a dynamic positioning (DP) vessel involving uncertain modelling and unknown disturbances, the vessel control problem becomes a mismatched nonlinear control issue. To resolve this issue, this paper proposes a control method based on the sliding mode control (SMC) and the uncertainty and disturbance estimator (UDE). The total disturbance in the DP vessel is determined using the UDE, whereas the trajectory tracking function of the vessel is achieved via SMC. Moreover, the estimation error in the UDE and the tracking error of the SMC were found to converge based on the Lyapunov theory. The effectiveness of the proposed control strategy was verified via simulations. A comparative study involving the conventional SMC was also conducted, revealing that the proposed SMC unified with the UDE yielded a considerably superior performance.

Three types of nanocelluloses, including bacterial cellulose (BC), cellulose nanofiber (CNF) and cellulose nanocrystal (CNC), were used to prepare oil-in-water Pickering emulsions with the objective to disclose the effect of fiber flexibility on emulsification. In aqueous suspensions, the shortest CNC is rigid, while the longest BC fully flexible, which result in large difference in their dilute-to-semi-dilute concentrations, and in the rheological percolations. Thus, these cellulosic nanofibers play different roles during emulsification. Flexible BC nearly has no emulsifying capacity, whereas semi-flexible CNF and rigid CNC can be well used to stabilize emulsions. For the CNF-stabilized system, depletion effect is dominant, leading to the formation of droplet clusters easily, while for the CNC-stabilized one, repulsive effect plays more important role. Visible evidence regarding relaxation of long-term structure of droplets is further disclosed by dynamic rheology. This work proposes interesting views around tailoring morphology and viscoelasticity of Pickering emulsions by regulating fiber flexibility.

In practice, dynamic positioning (DP) vessels are subjected to complex disturbances as well as the magnitude and changing rate constraints of the thrusts and moments. This study applied a dynamic surface controller based on an uncertainty and disturbance estimator (UDE) to a DP vessel with complex disturbances and input constraints. The UDE was designed to estimate and handle the complex disturbances. An auxiliary dynamic system (ADS) and smooth switching function were employed to compensate for the input constraints and avoid the singularity phenomenon caused by the ADS, respectively. The combination of the UDE method and dynamic surface control (DSC) technology significantly simplified the design process for the control law and increased the practicability for DP vessels. The stability of the proposed control law was proved using the Lyapunov theory. The effectiveness of the control law and possibility of actually applying it to a DP vessel were verified using simulation experiments.

In this paper, we investigate an accurate trajectory tracking control of marine surface vessels (MSVs) under external disturbances. First, introducing an auxiliary velocity vector, a complicated MSV models can be further simplified. Then, a fixed-time disturbance observer (FDO) is employed to identify external disturbances to enhance the tracking performance of the system. The estimation errors can achieve the origin within a finite time independent of the initial conditions. On the basis of the FDO, in the context of fixed-time sliding mode manifold, a novel nonsingular fixed-time terminal sliding mode (NFTSM) scheme is formulated, by which MSVs can track the reference trajectory with all states globally stabilized in a fixed time. The effectiveness of the developed scheme is validated by numerical simulation results.

Temperature sensitivity of soil respiration (Q10) is an important mechanism for the possible feedback between global carbon cycle and climate system. Knowledge of how crop types and nitrogen (N) fertilization affect Q10 is critical for estimating soil respiration and carbon cycling in agro-ecosystem. A two-year field experiment was conducted with cold-resistant (winter wheat; Triticum aestivum L.) and thermophilic (spring maize; Zea mays L.) crops at two N fertilization levels (no fertilization (CK) and 160 kg N hm−1) from October 2013 to September 2015 in semi-arid Loess Plateau. Annual mean soil respiration and Q10 in maize were 20% (1.85 vs. 1.54 μmol m−2 s−1) and 36% (2.49 vs. 1.83) higher than that in wheat. Nitrogen fertilization resulted in a 35% increase in annual mean soil respiration (1.95 vs. 1.44 μmol m−2 s−1) and a 11% decrease in Q10 (2.05 vs. 2.28) compared with the CK treatment. Soil respiration was positively related to root biomass, whereas no significant relationship was found between root biomass and Q10. Therefore, it can be concluded that soil respiration and temperature sensitivity of soil respiration are significantly influenced by crop types and N fertilization regimes, which should be considered in calculating carbon budget in agro-ecosystem using carbon models.

Thermoplastic polyester elastomer (TPEE) blends with poly(butylene terephthalate) (PBT) were prepared by melt compounding for the phase morphology and mechanical property studies. Although PBT is immiscible with the continuous soft poly(tetramethylene glycol) (PTMEG) phase of TPEE, it is miscible with the discrete hard PBT one of TPEE. Therefore, PBT and TPEE are compatible and their blends reveal very low level of interfacial tension and very small size of discrete domains, as well as good interfacial adhesion between two phases, which provide high possibility to prepare TPEE alloys with controllable properties. Mechanical test results reveal that both the modulus and yield and tensile strengths increase with increasing weight ratios of PBT. The increased system rigidity and decreased system plasticity are further confirmed by the cyclic tensile tests. The main objective of this work is to provide useful information on the structure and property control of TPEE by simple mixing with aromatic polyesters.

Graphene nanosheets (GNS) with and without surface functionalization were used as the reinforcements to prepared the composites with thermoplastic polyester elastomer (TPEE) by melting mixing. The results show that the presence of GNS improves modulus, yield and tensile strengths of TPEE, and the surface functionalization of GNS further improves its reinforcing effect because of enhanced interfacial interactions. However, the elongation levels also increase in the presence of GNS, which indicates the increased elastoplasticity and viscoplasticity of system. This is because the discrete hard poly(butylene terephthalate) domains of TPEE are enriched on the surface of GNS and form ‘ball bearing’ structure in composites, leading to increased deformation ability of soft continuous poly(tetramethylene glycol) of TPEE during large-scale deformation. Thus, the composites show more amounts of tensile cycles with shorter true strain plateau associated with onset of chain disentangling during cyclic tensile tests. This ‘bearing ball’ effect, however, is not evident in small-scale viscoelastic deformation because the presence of GNS restrains creep of TPEE. In this case, the impeding effect of GNS on the deformation of TPEE chain coils is the dominant role. This work provides useful information on structure design and control of the GNS filled thermoplastic elastomer composites.