Analysis of road network pattern considering population distribution and central business district.

This paper proposes a road network growing model with the consideration of population distribution and central business district (CBD) attraction. In the model, the relative neighborhood graph (RNG) is introduced as the connection mechanism to capture the haracteristics of road network topology. The simulation experiment is set up to illustrate the effects of population distribution and CBD attraction on the characteristics of road network. Moreover, several topological attributes of road network is evaluated by using coverage, circuitness, treeness and total length in the experiment. Finally, the suggested model is verified in the simulation of China and Beijing Highway networks

Modeling and Motion Control of a Liquid Metal Droplet in a Fluidic Channel

© 1996-2012 IEEE. As an emerging multifunctional material, Gallium-based room temperature liquid metal has attracted a lot of attention for a variety of applications due to its mobility and deformability. However, controlling the motion of a liquid metal droplet accurately still remains unrevealed, which restricts its application in many fields. In this article, we propose a hybrid framework that would control the motion of a liquid metal droplet in a one-dimensional (1-D) fluidic channel. A dynamic model of a liquid metal droplet immersed in the electrolyte when an electrical field is applied to each end of the channel is discussed first, followed by a setpoint controller designed to calculate the current input needed to drive the liquid metal droplet to its destination with vision feedback. To obtain the desired high-resolution current output, a fast and high-resolution current output power supply will be established by integrating a fast PID controller and a simple programmable dc power supply. The effectiveness of this proposed approach will be verified by controlling a liquid metal droplet so that it reaches its destination inside the polymethyl methacrylate channel. In this article, the proposed approach may lead to the development of tiny soft robots, or microfluidic systems that can be driven accurately by the liquid metal droplets

Postprocessing Study for the Controllable Structures of Ceramic Green Parts Realized by a Flexible Binder Jetting Printing (BJP) Solution

For indirect ceramic additive manufacturing (AM), green parts’ initial densities are low, limiting the postprocessing strengthening under atmospheric pressure. This study employed binder jetting printing (BJP) based on the polycondensation curing of urea-formaldehyde resin to produce series of Al2O3 green specimens with controllable structures. Further, an integrated postprocessing procedure, including the sequential stages of presintering, ceramic slurry infiltration, and final sintering, was conducted on these green specimens with designed structural characteristics for verifying strengthening mechanism. Using a self-developed BJP machine system and the related material which are flexible in process, this study printed green specimens with strong bonding (flexural strength above 6.84 MPa), additionally can regulate their initial densities within the wide range between 21.7%∼43.9%. Infiltrated with ceramic slurry, low-density green specimens were significantly strengthened via final sintering, realizing final densities, flexural strength, and compressive strength of 73.2%, 43.15 MPa, and 331.17 MPa, respectively. In comparison, high-density specimens performing poor infiltration obtained limited density increment after final sintering, but better mechanical properties and surface strengthening were realized, exhibiting final densities, flexural strength, comprehensive strength, surface roughness Ra, and Vickers hardness of 70.1%, 63.22 MPa, 450.18 MPa, 9.73 μm, and 4.58 GPa, respectively. In summary, this study is helpful to provide the technical reference for custom AM ceramic green parts and the postprocessing optimization

Effects of Li on microstructure and friction and wear behavior of 7075 aluminum alloy for drill pipe

7075-(0%, 0.5%, 1%, 2%, mass fraction)Li alloy was prepared by hot pressing sintering, and the effects of Li on microstructure and friction and wear behavior of 7075 Al alloy were investigated. The results show that the density of 7075-0.5Li alloy reaches above 99% at sintering pressure of 60 kN. Al alloy consists of α-Al, η and S' phases. With the increase of Li content to 2%, the η phase decreases, δ' and δ phases increase, but α-Al is still the main phase. The hardness and wear rate of Al alloy are 71.25HV and 3.50×10-3 mm3·N-1·m-1, respectively. As the Li content increases, the hardness of Al-Li alloy decreases and the wear rate increases. However, 7075-0.5Li exhibits higher hardness and lower wear rate than those of Al alloy. Both oxidation wear and adhesion wear occurs in 7075-Li alloy. With the increase of Li content, the η phase is reduced, the hardness decreases, the brittleness of Al2O3 is high which has a weak bonding with the matrix, and the dendrite spacing of microstructure widens, resulting in the transition from the abrasive wear to adhesive wear of the alloy, and therefore the wear resistance gradually decreases. Compared with Al alloy, 7075-0.5Li alloy prepared by hot pressing sintering shows a better wear resistance

Modelling and motion control of a liquid metal droplet in a fluidic channel

© 1996-2012 IEEE. As an emerging multifunctional material, Gallium-based room temperature liquid metal has attracted a lot of attention for a variety of applications due to its mobility and deformability. However, controlling the motion of a liquid metal droplet accurately still remains unrevealed, which restricts its application in many fields. In this article, we propose a hybrid framework that would control the motion of a liquid metal droplet in a one-dimensional (1-D) fluidic channel. A dynamic model of a liquid metal droplet immersed in the electrolyte when an electrical field is applied to each end of the channel is discussed first, followed by a setpoint controller designed to calculate the current input needed to drive the liquid metal droplet to its destination with vision feedback. To obtain the desired high-resolution current output, a fast and high-resolution current output power supply will be established by integrating a fast PID controller and a simple programmable dc power supply. The effectiveness of this proposed approach will be verified by controlling a liquid metal droplet so that it reaches its destination inside the polymethyl methacrylate channel. In this article, the proposed approach may lead to the development of tiny soft robots, or microfluidic systems that can be driven accurately by the liquid metal droplets

Microstructure and Corrosion Behavior of Laser-Cladding CeO2-Doped Ni-Based Composite Coatings on TC4

Laser-cladding CeO2-doped Ni-based composite coatings were prepared on the surface of a titanium alloy, and the effects of CeO2 addition on the microstructure, microhardness, and corrosion resistance of the prepared coatings were studied. The results showed that TiC, NiTi, Ni3Ti, and Ti2Ni phases were formed on the prepared coatings. Moreover, the addition of CeO2 in laser-cladding coatings effectively refined the microstructure and reduced the number of cracks generated in the laser-cladding process. When the amount of CeO2 was 2%, the number of cracks in the laser-cladding coating was significantly reduced compared with that of 0%. When the content of CeO2 was 2% or 3%, the microhardness of laser-cladding coatings reached the maximum value. At the same time, it was found that the appropriate addition of CeO2 was helpful to improve the corrosion resistance of the laser-cladding coating. However, excessive CeO2 addition could reduce the corrosion resistance of the laser-cladding coating

Liquid metal droplet robot

2020 Elsevier Ltd Liquid metal (LM) droplets made from gallium-based alloys exhibit excellent biomimetic locomotion and deformation capabilities under external stimulating fields and have presented potentials in a variety of applications. However, its application in robotics is presently hampered by limited maneuverability in two-dimensional (2D) space and weak cargo carrying capacity. Here, we propose a composite liquid metal droplet robot (LMDR) which appears as a LM droplet but exhibits an extraordinary actuating performance in 3D space. The LMDR is fabricated by assembling a hollow and spherical-shaped magnetic internal framework (IF) into a LM droplet, and the IF can be disassembled from the LM droplet with the application of an external magnetic field. The maneuver of the LMDR is realized using the interplay of electric and magnetic fields, and complex actuation especially jumping to avoid obstacles, climbing steep slopes, and rotating its body to the desired posture can be achieved. The hollow IF within the LMDR has a cargo carrying capacity and we demonstrate a proof-of-concept experiment to show the transportation and controlled release of a chemical indicator using the LMDR. More importantly, an in vitro targeted drug delivery and therapy trial to treat breast cancer cells (4T1) with a drug loaded LMDR is also successfully performed. The demonstrated capabilities of the LMDR present a promising potential in developing future targeted drug delivery and soft robotic systems with high controllability and multi-functionalities