Path planning for autonomous ships: A hybrid approach based on improved apf and modified vo methods

In this research, a hybrid approach for path planning of autonomous ships that generates both global and local paths, respectively, is proposed. The global path is obtained via an improved artificial potential field (APF) method, which makes up for the shortcoming that the typical APF method easily falls into a local minimum. A modified velocity obstacle (VO) method that incorpo-rates the closest point of approach (CPA) model and the International Regulations for Preventing Collisions at Sea (COLREGS), based on the typical VO method, can be used to get the local path. The contribution of this research is two-fold: (1) improvement of the typical APF and VO methods, making up for previous shortcomings, and integrated COLREGS rules and good seamanship, making the paths obtained more in line with navigation practice; (2) the research included global and local path planning, considering both the safety and maneuverability of the ship in the process of avoiding collision, and studied the whole process of avoiding collision in a relatively entirely way. A case study was then conducted to test the proposed approach in different situations. The results indicate that the proposed approach can find both global and local paths to avoid the target ship.Safety and Security Scienc

A data-driven approach for ship-bridge collision candidate detection in bridge waterway

The consequences caused by bridge failures owing to the ship-bridge collision are always severe in terms of loss of life, economy, and environmental consequences to individuals and societies. The previous studies focused on the ship-bridge collision mainly concentrated on passive anti-collision, such as strengthening the bridge structure or setting anti-collision facilities. Compared with the previous research, the contribution of this work is to facilitate the reduction of collision risk of ship-bridge collision from the perspective of active anti-collision. A data-driven approach for ship-bridge collision candidate detection method in inland bridge waterways is proposed in this research. The approach is mainly divided into two steps: 1) The features (channel boundary, pier domain, and ship domain) of bridge waterways are identified using Kernel Density Estimation (KDE) method based on the historical AIS data; 2) Collision candidate detection with Velocity Obstacle (VO) method considering the identified features. This work can provide beneficial support for the ship-bridge active collision avoidance system.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Safety and Security Scienc

Study on the aging resistance of polyurethane precursor modified bitumen and its mechanism

As an environmentally friendly alternative for the production of high-performance modified asphalt by chemical reactions, a liquid-state polyurethane-precursor-based reactive modifier (PRM) was developed and employed in the asphalt modification. In contrast to the traditional solid bitumen modifier, for example, rubber and thermoplastic elastomers, the PRM as a liquid modifier has more significant advantages in reducing energy consumption and improving asphalt performance, which has attracted widespread attention. However, the aging resistance and its mechanism are not clear. In view of this, the aging performance of two PRM-modified bitumen (PRM-70 and PRM-90), under the short-term thermo-oxidative aging, long-term thermo-oxidative aging, and ultraviolet (UV) aging conditions, was investigated through chemical and mechanical methods. The results show that the PRM-90 is more susceptible to the thermos-oxidative aging and UV aging. The use of low-penetration-grade bitumen and ensuring an adequate reaction are beneficial to enhance the aging resistance of PRM-modified bitumen. The impact of aging on high-temperature performance of PRM-modified bitumen is great, followed by the low-temperature performance and the anti-fatigue performance. The mechanic-relevant rheological aging index (RAI) and fracture energy index (FEI) are recommended to evaluate aging properties for PRM-modified bitumen. This study not only provides support for further research on the relationship between the aging properties and mechanical performance of PRM-modified bitumen, but also provides a reference for conducting mechanism analysis.Pavement Engineerin

Putting precision and elegance in enzyme immobilisation with bio-orthogonal chemistry

The covalent immobilisation of enzymes generally involves the use of highly reactive crosslinkers, such as glutaraldehyde, to couple enzyme molecules to each other or to carriers through, for example, the free amino groups of lysine residues, on the enzyme surface. Unfortunately, such methods suffer from a lack of precision. Random formation of covalent linkages with reactive functional groups in the enzyme leads to disruption of the three dimensional structure and accompanying activity losses. This review focuses on recent advances in the use of bio-orthogonal chemistry in conjunction with rec-DNA to affect highly precise immobilisation of enzymes. In this way, cost-effective combination of production, purification and immobilisation of an enzyme is achieved, in a single unit operation with a high degree of precision. Various bio-orthogonal techniques for putting this precision and elegance into enzyme immobilisation are elaborated. These include, for example, fusing (grafting) peptide or protein tags to the target enzyme that enable its immobilisation in cell lysate or incorporating non-standard amino acids that enable the application of bio-orthogonal chemistry.BT/Biocatalysi

Influence of wheel polygonal wear on wheel-rail dynamic contact in a heavy-haul locomotive under traction conditions

For a heavy-haul locomotive within a wheel repairing period, wheel polygonal wear with different operating mileages is obtained by field testing. The test results show that the maximum radial runout of the wheel can increase to 0.87 mm and accompany with the typical damage of wheel tread shelling. Taking the wheel polygons as input excitation, the locomotive-track coupled dynamic model is established, which is verified by the comparisons of test and calculated wheelset vertical acceleration in time and frequency domains. The variable wheel-rail friction coefficient is introduced so as to consider the dry and wet rail conditions. The wheel-rail dynamic contact characteristics under the traction and dry-wet rail surface conditions are analysed simultaneously. It is found that the wheel polygon deteriorates the locomotive traction performance and induces the obvious wheel-rail slipping with large tangential stress, especially in wet rail condition. In dry condition, the wheel-rail could contact generally in the adhesion state. But the longitudinal creep forces fluctuate locally with some larger amplitudes closed to the adhesion force, which is mainly attributed to the excitation of serious wheel polygon. Comparing with the results of the newly repaired wheel, the maximum wheel-rail vertical force, longitudinal force, normal stress and tangential stress at the end of wheel repairing period can increase by 55 kN, 28 kN, 240 MPa and 470 MPa in sequence. The wheel-rail slipping and high-stress state in traction condition should be the dominant factors contributing to the wheel damage of tread shelling.Accepted author manuscriptMechanics and Physics of Structure

The hydro-mechanical interaction in novel polyurethane-bound pervious pavement by considering the saturation states in unbound granular base course

The pore-water pressure generated by intermittent dynamic vehicle loading under various saturation states is recognized as a critical factor influencing the behaviour of permeable pavement structures, especially the behaviour of UGB layer. However, the underlying mechanisms of hydro-mechanical interaction in the UGB layer and the influence on the pavement structure are still unclear. This study aims to characterize the changes in dynamic response in permeable pavement structures under various saturation conditions by considering the hydro-mechanical interaction within the UGB layer. To achieve this objective, a full-scale test track with a PUPM wearing course was constructed. Pressures and water distribution were characterized by embedded sensors within different layers of the test track when subjected to the accelerating pavement test. Based on the coupled SAME model, the water distribution and the dynamic response of UGB in the rainfall events were both characterised and solved by FEM. The results predicted by the proposed SAME model correspond to the field measurements, and the influence of the water content on the resilient modulus distribution within the UGB layer was then estimated. Based on the predictions for the stress state of the UGB layer, the sensitivity analysis was also proposed.Accepted Author ManuscriptPavement Engineerin

Asymmetric Sites on the ZnZrO_x Catalyst for Promoting Formate Formation and Transformation in CO₂ Hydrogenation

The role of formate species for CO2 hydrogenation is still under debate. Although formate has been frequently observed and commonly proposed as the possible intermediate, there is no definite evidence for the reaction of formate species for methanol production. Here, formate formation and conversion over the ZnZrOx solid solution catalyst are investigated by in situ/operando diffuse reflectance infrared Fourier transform spectroscopy-mass spectroscopy (DRIFTS-MS) coupled with density functional theory (DFT) calculations. Spectroscopic results show that bidentate carbonate formed from CO2 adsorption is hydrogenated to formate on Zn-O-Zr sites (asymmetric sites), where the Zn site is responsible for H2 activation and the Zr site is beneficial for the stabilization of reaction intermediates. The asymmetric Zn-O-Zr sites with adjacent and inequivalent features on the ZnZrOx catalyst promote not only formate formation but also its transformation. Both theoretical and experimental results demonstrate that the origin of the excellent performance of the ZnZrOx catalyst for methanol formation is associated with the H2 heterolytic cleavage promoted by the asymmetric Zn and Zr sites.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.ChemE/Inorganic Systems Engineerin

Constructing dataset of classified drainage areas based on surface water-supply patterns in High Mountain Asia

The High Mountain Asia (HMA) region, ranging from the Hindu Kush and Tien Shan in the west to the Himalaya in the south with an altitude between 2000 and 8844 m, holds the largest reservoir of glaciers and snow outside Earth Polar Regions. In the last decades, numerous glaciers and lake areas there have undergone tremendous changes with water redistribution. In order to increase understanding of the pattern of distribution of water resources, and their dynamic changes at the basin scale, a watershed classification based on the water replenishment patterns dataset was constructed. The input dataset are from the Randolph Glacier Inventory V.6.0 and the vector data of rivers and streams. Four datasets were thus obtained: Glacier-fed and Runoff-fed Drainage Area (GRDA), Glacier-fed and Runoff-free Drainage Area (GDA), Glacier-free and Runoff-fed Drainage Area (RDA), and the Glacier-free and Runoff-free Drainage Area (NGRDA), and the numbers of these four types of basins are 87, 107, 32, and 448 separately. The statistical results show GRDA has the largest surface area, accounting for 82.2% of the total basin area in HMA, mainly in the region of the basin with outflow rivers or streams. Dominated by small basins, the GDA area accounts for the smallest area, only 3.86% and the RDA accounts for 5.62%. For NGRDA, most are with small areas, accounting for 8.32%, and mainly distributes in the closed basin of the Qiangtang Plateau. This dataset provides a fundamental classified data source for research on water resources, climate, ecology, and environment in HMA. The published data are available at https://data.4tu.nl/download/uuid:d07d748f-d10b-4308-9626-199ef05cc9af/ and http://www.dx.doi.org/10.11922/sciencedb.923.Optical and Laser Remote Sensin

Optimization of mesa etch for a quasi-vertical gan schottky barrier diode (Sbd) by inductively coupled plasma (icp) and device characteristics

The optimization of mesa etch for a quasi-vertical gallium nitride (GaN) Schottky barrier diode (SBD) by inductively coupled plasma (ICP) etching was comprehensively investigated in this work, including selection of the etching mask, ICP power, radio frequency (RF) power, ratio of mixed gas, flow rate, and chamber pressure, etc. In particular, the microtrench at the bottom corner of the mesa sidewall was eliminated by a combination of ICP dry etching and tetramethylammonium hydroxide (TMAH) wet treatment. Finally, a highly anisotropic profile of the mesa sidewall was realized by using the optimized etch recipe, and a quasi-vertical GaN SBD was demonstrated, achieving a low reverse current density of 10−8 A/cm2 at −10 V.Electronic Components, Technology and Material

Triple-action self-healing protective coatings based on shape memory polymers containing dual-function microspheres

In this study, a new self-healing shape memory polymer (SMP) coating was prepared to protect the aluminum alloy 2024-T3 from corrosion by the incorporation of dual-function microspheres containing polycaprolactone and the corrosion inhibitor 8-hydroxyquinoline (8HQ). The self-healing properties of the coatings were investigated via scanning electron microscopy, electrochemical impedance spectroscopy, and scanning electrochemical microscopy following the application of different healing conditions. The results demonstrated that the coating possessed a triple-Action self-healing ability enabled by the cooperation of the 8HQ inhibitor, the SMP coating matrix, and the melted microspheres. The coating released 8HQ in a pH-dependent fashion and immediately suppressed corrosion within the coating scratch. After heat treatment, the scratched coating exhibited excellent recovery of its anticorrosion performance, which was attributed to the simultaneous initiation of scratch closure by the shape memory effect of the coating matrix, sealing of the scratch by the melted microspheres, and the synergistic effect of corrosion inhibition by 8HQ.(OLD) MSE-