In this study, in effort to improve the sliding wear resistance of gray cast iron under wet lubrication conditions, specimens with different bionic units were manufactured and modified according to bionic theory. Inspired by the structure and appearance of biological wear-resistant skin, two kinds of bionic units were processed by laser on the specimen surfaces. We investigated the wear resistance properties of the samples via indentation method and then observed the wear surface morphology of specimens and the stress distributions. The results indicated that coupling the bionic units enhanced the wear resistance of the cast iron considerably compared to the other samples. We also determined the mechanism of wear resistance improvement according to the results.
Articulated caterpillar robot has various locomotion patternswhich make it adaptable to different tasks. Generally, the researchers have realized undulatory (transverse wave) and simple rolling locomotion. But many motion patterns are still unexplored. In this paper, peristaltic locomotion and various additional rolling patterns are achieved by employing sinusoidal oscillator with fixed phase difference as the joint controller. The usefulness of the proposed method is verified using simulation and experiment. The design parameters for different locomotion patterns have been calculated that they can be replicated in similar robots immediately.
The paper introduces a new type underwater vehicle propelled by multiple undulatory fins, which propulsion control system is made up of four isomorphic bionic undulatory fins configured according to the crisscross orthogonal structure. The fixed-depth control of this vehicle is the mainly studied by the paper. Aiming at its structure and dynamics, a dual-loops control structure based the fuzzy PID in series is proposed to design the fixed-depth control system of this vehicle. The pitching controller designed according to fuzzy adaptive PID method acts as the inner-loop controller. As the outer-loop controller, the task decomposing module transforms the depth control objective to the pitching channel's objective adopting the expert PID control strategy. The paper studies the structure, strategy and parameter design method of the fixed-depth control system in detail, builds a simulation model, and then primarily verified the validities of the control system structure and control strategy proposed by this paper through simulation.
Multiple sclerosis (MS) is an autoimmune disease and leads to many inflammations. Cause of this disease is autoreactive T cells invade the blood-brain-barrier and attack the myelin sheath. Because MS infringes upon young human and has gradual loss of bodily functions, the disease has a burden on society and economy. Traditional treatment is to use immune-suppressant, but it has many side effects. Currently, the most effective treatment of MS is to use Natalizumab. Target molecule of this agent is α4-integrin of T cells. The mechanism is to prevent invasion of activated lymphocytes across the blood-brain-barrier. However, this agent affects the overall immune response and easily generates side effects of progressive multifocal leukoencephalopathy (PML). Transwall systems are often used to investigate cell invasion, but there is no specific protein immobilizing on the isolation membrane of these systems. In this work, we have successfully developed a bionic invasion membrane for the study of MS. Different chemokines were applied to the system for the demonstration of drug screening application. The bionic invasion membrane was a PP/PTEE membrane coated with VCAM-1 protein. Jurkat T cell was used to evaluate the feasibility of using the membrane for the study of MS. Results indicated that the invasion ability of T cells was reduced by VCAM-1 protein. The current work provides bionic invasion membrane for the study of MS in vitro.
The method of Multiple Stress Concentration Regions (MSCRs) on the surface of MEMS Silicon micro-structure is introduced in order to enhance the sensibility of the hair vector hydrophone without reducing the working bandwidth. The MSCRs with the thickness and width smaller than the rest of the cantilever can produce localized stress concentration when constant force is applied on the structure. ANSYS software has been used as a tool to analyze the effect of different shapes and dimensions on the performance of the micro-structure. The optimum MSCR has been obtained. Results show that compared with the ordinary structure, the sensitivity of the micro-structure with MSCR can be increased by 1.5 times, and the upper limit of bandwidth can be improved from 337Hz to 500Hz. This paper provides a new method to resolve contradiction between the sensitivity and working bandwidth.
Myoelectric hand prostheses are usually controlled with two bipolar electrodes located on the flexor and extensor muscles of the residual limb. With clinically established techniques, only one function can be controlled at a time. This is cumbersome and limits the benefit of additional functions offered by modern prostheses. Extensive research has been conducted on more advanced control techniques, but the clinical impact has been limited, mainly due to the lack of reliability in real-world conditions. We implemented a regression-based control approach that allows for simultaneous and proportional control of two degrees of freedom and evaluated it on five prosthetic end users. In the evaluation of tasks mimicking daily life activities, we included factors that limit reliability, such as tests in different arm positions and on different days. The regression approach was robust over multiple days and only slightly affected by changing in the arm position. Additionally, the regression approach outperformed two clinical control approaches in most conditions.