Search

Carbon nanomaterials are ideal fillers in composites for electrothermal applications due to their ultrahigh electrical conductivity, thermal conductivity, and excellent mechanical property. In this study, high-performance electrothermal laminate films were prepared by a layer-by-layer process, which used tannic acid-functionalized multiwalled carbon nanotubes as filler and thermoplastic polyurethane as substrate. The prepared electrothermal laminate films exhibit excellent mechanical property, electrical heating property, and high electrothermal performance, which can reach steady-state temperature in about 120 s. Additionally, the maximum steady-state temperature can reach ∼150 °C at 20 V. During 10 different cycles of experiments and 5 h aging time, no significant change in temperature was observed. Moreover, from the results, it is clear that the performance of the samples is related to the amount of filler added and the applied voltage, and we can precisely control the sample performance by regulating the amount of filler addition and applied voltage. We believe that these electrothermal laminate films could be widely used in wearable heating cotton fabric, controllable electric heating module, floor heating, and deicing devices.

Because of an unfortunate mistake during the production of this article, the initial printed versions and the online PDF had incorrect DOI numbers. The DOI has now been corrected and synchronized with the correct DOIs of the HTML versions.

A simple and efficient protocol was developed for the preparation of challenging α-aryl primary amides. This metal-free coupling process was triggered by TfOH-promoted electrophilic activation of α-silyl nitrile to generate keteniminium ion species, followed by reaction with aryl sulfoxide through [3,3]-sigmatrophic rearrangement to provide the target product. To the best of our knowledge, α-silyl nitrile has been rarely used as a pro-electrophilic reagent. Computational investigations confirmed the transient existence of a highly electrophilic keteniminium intermediate.

Carbon nanotubes (CNTs) and graphene (Gr) are promising materials for flexible transparent conductive films (TCFs) in optoelectronic application because of their exceptional electrical, optical, and mechanical properties. Here, high-quality graphene nanosheets were synthesized by the one-step green method which using natural polyphenols-gallic acid (GA) as the exfoliation medium through high-pressure homogenization; besides, GA molecules can also be used as a non-covalent modifier to obtain GA modified CNTs (GCNTs). Then, the Au decorated Gr/GCNT-PET (Au-Gr/GCNT-PET) TCFs were obtained by a simple spray-coating process. The TCFs exhibited an excellent optoelectronic performance (Rs = 45.6 Ω/sq., T = ca. 80% at 550 nm), relatively flat surface (roughness = 12.43 nm), good bending resistance (the ΔR Au-Gr/GCNT-PET TCF/R0 was 0.07 after 1000 times bending tests) and strong adhesion (the fT of all Au-Gr/GCNT PET films was higher than 0.8). Finally, the Au-Gr/GCNT-PET films were used as an anode to prepare flexible green-light OLED devices; the maximum luminance of the Au-Gr/GCNT-PET device was 6554.1 cd/m2 at 15V, and the maximum current efficiency was 4.03 cd/A. It confirmed that this type of TCFs has considerable potential application in photovoltaic devices.

Polyaniline nanofibers were facially synthesized by the chemical polymerization with binary oxidant containing ammonium persulfate and ferric chloride at the presence of para-phenylenediamine. For a better comparison, the polymerization with single oxidant was also carried out. The effect of binary oxidant on the morphology and structure was systematically investigated for better understanding the role of oxidant in the formation of nanostructures. The morphology, chemical structure as well as crystalline and thermal property were characterized by field emission scanning electron microscopy, ultraviolet-visible absorption spectroscopy, Fourier transform infrared and Raman spectroscopy, X-ray diffraction and thermogravimetric analysis.

To achieve rapid disengagement and smooth engagement of clutch in automated manual transmission systems, servo control of an electro-pneumatic clutch actuator controlled by solenoid on–off valves is considered. Nevertheless, realization of high-accuracy servo control usually depends on model-based non-linear control technologies requiring full-state knowledge of the system. Pressure sensors are not used in automated manual transmission systems owing to cost considerations. Thus, the pressure states in the chambers are unknown. To address this issue, non-linear pressure observers taking the place of pressure sensors were proposed in this paper. It is stable in the sense of the Lyapunov theory and independent of the load. Furthermore, the pressure observer’s polytropic exponent was analysed and then determined experimentally. Finally, a compound sliding-mode controller with pressure observers was presented. Extensive experiments demonstrated the feasibility and the effectiveness of the proposed pressure-observer-based controller.

The system considered in this work consists of a cylinder which is controlled by a pair of three-way servo valves rather than a four-way one. Therefore, the cylinder output stiffness is independently controllable of the output force. A discontinuous projection based adaptive robust controller (ARC) was constructed to achieve high-accuracy output force trajectory tracking for the system. In ARC, on-line parameter adaptation method was adopted to reduce the extent of parametric uncertainties due to the variation of friction parameters, and sliding mode control method was utilized to attenuate the effects of parameter estimation errors, unmodelled dynamics and disturbance. Furthermore, output stiffness maximization/minimization was introduced to fulfill the requirement of many robotic applications. Extensive experimental results were presented to illustrate the effectiveness and the achievable performance of the proposed scheme. For tracking a 0.5 Hz sinusoidal trajectory, maximum tracking error is 4.1 N and average tracking error is 2.2 N. Meanwhile, the output stiffness can be made and maintained near its maximum/minimum.

A new-type frictionless pneumatic cylinder with an aerostatic bearing as its piston can decrease the friction significantly. The stability and the leakage of this cylinder mostly depend on the radial load carrying capacity(RLCC) and the air consuming of the bearing. In order to make a better use of this cylinder in pneumatic servo systems, a simulation study on the influence of the structural parameters and time-varying surrounding parameters to this cylinder was carried out on the basis of a numerical solution method based on finite element method(FEM) which was constructed to solve Reynolds equations in this paper. Simulation shows that introducing a recess chamber at the end of the orifice hole can increase the RLCC significantly and smooth the sharp distribution of the pressure around the orifices in the air film, which makes the bearing working more stable; the time-varying parameters have a combined effects on the performance characteristics of the bearing.

For the stick-slip phenomenon encountered in the pneumatic cylinder motion in practical application, the stick-slip mechanism was analyzed and an nonlinear mathematical model based on the improved LuGre model of pneumatic cylinder movement was established. The movement of the piston and the pressure of the rodless chamber in the pneumatic cylinder based on meter-in circuit were obtained through solving the differential equations by four-order variable-step Runge-Kutta method. The comparison between simulation and experimental results shows that the established mathematical model can describe the stick-slip motion of pneumatic cylinder with a relatively good accuracy.