A Design of an Unmanned Electric Tractor Platform

The tractor is a vehicle often used in agriculture. It is mainly used to tow other unpowered agricultural machinery for farming, harvesting, and seeding. They consume a lot of fuel with emissions that often contain a large amount of toxic gases, which seriously jeopardize human health and the ecological environment. Therefore, the electrical tractor is bound to become a future trend. The objective of this study is to design and implement a lightweight, energy-saving, and less polluting electric tractor, which meets the requirements of existing smallholder farmers, equipped with unmanned technology and multi-functions to assist labor and to provide the potential for unmanned operation. We reduced the weight of the tractor body structure to 101 kg, and the bending rigidity and torsional rigidity reached 11,579 N/mm and 4923 Nm/deg, respectively. Two 7.5 kW induction motors driven by lithium batteries were applied, which allows at least 3.5 h of working time.

Tiling a tubule: How increasing complexity improves the yield of self-limited assembly

The ability to design and synthesize ever more complicated colloidal particles opens the possibility of self-assembling a zoo of complex structures, including those with one or more self-limited length scales. An undesirable feature of systems with self-limited length scales is that thermal fluctuations can lead to the assembly of nearby, off-target states. We investigate strategies for limiting off-target assembly by using multiple types of subunits. Using simulations and energetics calculations, we explore this concept by considering the assembly of tubules built from triangular subunits that bind edge to edge. While in principle, a single type of triangle can assemble into tubules with a monodisperse width distribution, in practice, the finite bending rigidity of the binding sites leads to the formation of off-target structures. To increase the assembly specificity, we introduce tiling rules for assembling tubules from multiple species of triangles. We show that the selectivity of the target structure can be dramatically improved by using multiple species of subunits, and provide a prescription for choosing the minimum number of subunit species required for near-perfect yield. Our approach of increasing the system’s complexity to reduce the accessibility of neighboring structures should be generalizable to other systems beyond the self-assembly of tubules.

Thermally Fluctuating, Semiflexible Sheets in Simple Shear Flow

We perform Brownian dynamics simulations of semiflexible colloidal sheets with hydrodynamic interactions and thermal fluctuations in shear flow. As a function of the ratio of bending rigidity to shear energy...

Graphene coated cotton nonwoven for electroconductive and UV protection applications

The functional properties and applications of graphene coated textiles depend on the magnitude of graphene add-on which in turn is influenced by the type of substrate and the dipping conditions. In the present study, optimized GO (graphene oxide) dipping conditions are identified for the preparation of cost-effective and scalable rGO (reduced graphene oxide) coated cotton nonwoven for electroconductive and UV (ultraviolet) blocking applications. To understand the influence of GO dipping variables on rGO add-on and electrical resistivity of cotton, batch adsorption studies are carried out in loose fibre form to eliminate the structural influence of yarn or fabric. Batch adsorption studies suggest that GO concentration, pH of GO solution and sodium dithionite (reductant) concentration are the most influencing dipping variables and these dipping variables are optimized for cotton nonwoven fabric using Box–Behnken response surface design to achieve minimum surface resistivity. The rGO coated cotton nonwoven fabric shows excellent UV blocking properties (UV protection factor = 89.38) at the optimized GO dipping conditions. Physical properties of cotton nonwoven fabric such as GSM, thickness, stiffness, breaking strength and elongation are analysed at different dipping cycles. After the rGO coating, bending rigidity, bending modulus and breaking elongation of the cotton nonwoven fabric decrease, whereas the breaking strength increases. rGO coated cotton fabric exhibits excellent stability towards multiple washing and rubbing. The graphene coated cotton is characterised by FT-IR, XRD, Raman, TGA, FESEM and LEICA image analyser.

Experimental and Computational Modeling of Microemulsion Phase Behavior

The phase behavior of microemulsions formed in a surfactant-brine-oil system for a chemical Enhanced Oil Recovery (EOR) application is complex and depends on a range of parameters. Phase behavior indicates a surfactant solubilization. Phase behavior tests are simple but time-consuming especially when it involves a wide range of surfactant choices at various concentrations. An efficient and insightful microemulsion formulation via computational simulation can complement phase behavior laboratory test. Computational simulation can predict various surfactant properties, including microemulsion phase behavior. Microemulsion phase behavior can be predicted predominantly using Quantitative Structure-Property Relationship (QSPR) model. QSPR models are empirical and limited to simple pure oil system. Its application domain is limited due to the model cannot be extrapolated beyond reference condition. Meanwhile, there are theoretical models based on physical chemistry of microemulsion that can predict microemulsion phase behavior. These models use microemulsion surface tension and torque concepts as well as with solution of bending rigidity of microemulsion interface with relation to surface solubilization and interface energy.

Corner Strengthening by Local Thickening and Ausforming Using Planar Compression in Hot Stamping of Ultra-High Strength Steel Parts

Hot-stamped products are widely used for the body-in-white of an automobile as they are lightweight and improve crashworthiness. A hot-stamping process using planar compression was developed to strengthen corners of ultra-high strength parts by local thickening and hardening. In this process, the corners are thickened by compressing the blank in the planar direction with the upper and lower dies while blocking the movement of both edges with stoppers in the latter stage of forming. Thickening of the corners largely heightens the strength of the formed parts. Not only the thickness but also the hardness of the corner was increased by large plastic deformation and die quenching. For a hot hat-shaped part, a 30% increase in thickness and a 530 HV20 hardness around the corners were attained. The bending rigidity and strength of the formed parts thickened by 30% in the corners increased by 25% and 20%, respectively. In addition, the improvements of the part shape accuracy and the sidewall quenchability were obtained.

Radial dynamics of an encapsulated microbubble with interface energy

In this work a mathematical model based on interface energy is proposed within the framework of surface continuum mechanics to study the dynamics of encapsulated bubbles. The interface model naturally induces a residual stress field into the bulk of the bubble, with possible expansion or shrinkage from a stress-free configuration to a natural equilibrium configuration. The significant influence of interface area strain and the coupled effect of stretch and curvature is observed in the numerical simulations based on constrained optimization. Due to the bending rigidity related to additional terms, the dynamic interface tension can become negative, but not due to the interface area strain. The coupled effect of interface strain and curvature term observed is new and plays a dominant role in the dominant compression behaviour of encapsulated bubbles observed in the experiments. The present model is validated by fitting the experimental data of $1.7\,\mathrm {\mu }$ m, $1.4\,\mathrm {\mu }$ m and $1\,\mathrm {\mu }$ m radii bubbles by calculating the optimized parameters. This work also highlights the role of interface parameters and natural configuration gas pressure in estimating the size-independent viscoelastic material properties of encapsulated bubbles with interesting future developments.

An Atomistic-Based Nonlinear Plate Theory for Hexagonal Boron Nitride

Through the continuity of the DREIDING force field, we propose, for the first time, the finite-deformation plate theory for the single-layer hexagonal boron nitride (h-BN) to clarify the atomic source of the structure against deformations. Divergent from the classical Föppl-von Karman plate theory, our new theory shows that h-BN’s two in-plane mechanical parameters are independent of two out-of-plane mechanical parameters. The new theory reveals the relationships between the h-BN’s elastic rigidities and the atomic force field: (1) two in-plane elastic rigidities come from the bond stretching and the bond angle bending; (2) the bending rigidity comes from the inversion angle and the dihedral angle torsion; (3) the Gaussian rigidity only comes from the dihedral angle torsion. Mechanical parameters obtained by our theory align with atomic calculations. The new theory proves that two four-body terms in the DREIDING force field are necessary to model the h-BN’s mechanical properties. Overall, our theory establishes a foundation to apply the classical plate theory on the h-BN, and the approach in this paper is heuristic in modelling the mechanical properties of the other two-dimensional nanostructures.