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To alleviate the performance deterioration caused by dynamic stall of a wind turbine airfoil, the flow control by a microsecond-pulsed dielectric barrier discharge (MP-DBD) actuator on the dynamic stall of a periodically pitching NACA0012 airfoil was investigated experimentally. Unsteady pressure measurements with high temporal accuracy were employed in this study, and the unsteady characteristics of the boundary layer were investigated by wavelet packet analysis and the moving root mean square method based on the acquired pressure. The experimental Mach number was 0.2, and the chord-based Reynolds number was 870 000. The dimensionless actuation frequencies F + were chosen to be 0.5, 1, 2, and 3, respectively. For the light dynamic regime, the MP-DBD plasma actuator plays the role of suppressing flow separation from the trial edge and accelerating the flow reattachment due to the high-momentum freestream flow being entrained into the boundary layer. Meanwhile, actuation effects were promoted with the increasing dimensionless actuation frequency F +. The control effects of the deep dynamic stall were to delay the onset and reduce the strength of the dynamic stall vortex due to the accumulating vorticity near the leading edge being removed by the induced coherent vortex structures. The laminar fluctuation and Kelvin–Helmholtz (K–H) instabilities of transition and relaminarization were also mitigated by the MP-DBD actuation, and the alleviated K-H rolls led to the delay of the transition onset and earlier laminar reattachment, which improved the hysteresis effect of the dynamic stall. For the controlled cases of F + = 2, and F + = 3, the laminar fluctuation was replaced by relatively low frequency band disturbances corresponding to the harmonic responses of the MP-DBD actuation frequency.

To alleviate the deterioration in wind turbine performance caused by dynamic stall, the flow control of a pitching NACA0012 airfoil is investigated through numerical simulation of an alternating current dielectric barrier discharge (AC-DBD) plasma actuator at a Reynolds number Re = 135 000. To avoid the harmonic oscillations of aerodynamic force caused by unsteady DBD actuation, this work focuses on improving the control potential for steady actuation. The control mechanisms of actuators at various positions are investigated using five groups of actuators mounted at 0%, 3%, 10%, 45%, and 80% chord lengths c above the upper surface of an airfoil. The actuator at 80% c performs more efficiently in terms of lift enhancement in the initial upstroke and the final downstroke. The actuator at 0% c suppresses the growth of the leading-edge vortex and maintains the suction of the dynamic stall vortex (DSV). After the shedding of the DSV, it suppresses the secondary separation to delay the onset of dynamic stall. At the flow reattachment stage, the actuators at 3% c and 10% c accelerate the boundary layer reattachment by momentum injection. From these results, a multi-DBD control strategy is proposed. The scheme selects the optimal actuator in operation at a certain stage of dynamic stall and takes advantage of actuators at different positions to enhance the average and maximum aerodynamic force, delay the onset of dynamic stall, accelerate flow reattachment, and avoid excessive energy consumption.

This paper considers the constrained leader-following consensus problem of second-order multi-agent networks with nonconvex input constraints, where the leader moves with a constant velocity. It is assumed that each agent can only perceive its own nonconvex constraint set and the joint communication graph has a directed spanning tree whose root is the leader. By introducing the constraint operator and the estimator of the leader, a new distributed algorithm is designed. Then, it is proved that the leader-following consensus can be reached under some mild conditions by constructing some auxiliary functions. Finally, a simulation example is given to examine the effectiveness of our results.

High-sensitivity pressure sensors are crucial for the ultrasensitive touch technology and E-skin, especially at the tiny-pressure range below 100 Pa. However, it is highly challenging to substantially promote sensitivity beyond the current level at several to 200 kPa–1 and to improve the detection limit lower than 0.1 Pa, which is significant for the development of pressure sensors toward ultrasensitive and highly precise detection. Here, we develop an efficient strategy to greatly improve the sensitivity near to 2000 kPa–1 using short-channel coplanar device structure and sharp microstructure, which is systematically proposed for the first time and rationalized by the mathematic calculation and analysis. Significantly, benefiting from the ultrahigh sensitivity, the detection limit is improved to be as small as 0.075 Pa. The sensitivity and detection limit are both superior to the current levels and far surpass the function of human skin. Furthermore, the sensor shows fast response time (50 μs), excellent...

Silica is one of the most commonly used materials for dielectric layer in organic thin-film transistors due to its excellent stability, excellent electrical properties, mature preparation process, and good compatibility with organic semiconductors. However, most of conventional preparation methods for silica film are generally performed at high temperature and/or high vacuum. In this paper, we introduce a simple solution spin-coating method to fabricate silica thin film from precursor route, which possesses a low leakage current, high capacitance, and low surface roughness. The silica thin film can be produced in the condition of low temperature and atmospheric environment. To meet various demands, the thickness of film can be adjusted by means of preparation conditions such as the speed of spin-coating and the concentration of solution. The p-type and n-type organic field effect transistors fabricated by using this film as gate electrodes exhibit excellent electrical performance including low voltage and high performance. This method shows great potential for industrialization owing to its characteristic of low consumption and energy saving, time-saving and easy to operate.

Inspired by the gas exfoliation of graphite oxide, a novel airflow sensor is demonstrated with an ultrathin (about 2 nm) reduced graphene oxide (RGO) film with tunable interlayer gaps. The airflow on/off reversibly switches the interlayer gaps of the RGO sheets, and thus changes the electrical conductivity of the RGO film. Remarkably, by virtue of the atomic-scale thickness of the sensing component, RGO sensors show high sensitivity, a wide detection range (tens of mm s−1 to several m s−1), and a low detection limit (26 mm s−1). Such performance is better than that of most of the traditional sensors and near to the capacity of some living beings.

Surface-grafting conducting polymer has advantage to circumvent the difficulty in patterning as well as the weak interface adhesion on substrate of the conventional conducting polymer, which would be desirable for its application as electrodes in electronic devices. In this work, the patterned surface-grafting polypyrrole (PPY) is used as electrode, which shows merits such as strong interface adhesion, robustness against solvent treatment, easy scaling-up, and good conductivity. Remarkably, the surface-grafting PPY electrodes can efficiently drive both p-type and n-type organic field-effect transistors. By combining p-/n-type transistors, organic complementary inverters are constructed with PPY electrodes, which exhibit low operational voltage ( V dd with a high noise margin (>70% of 0.5 V dd ). Dynamic switching measurements indicate that the inverter has an operational frequency of about 3.3 kHz. This is the first report on kilohertz organic complementary inverter driven with surface-grafting conducting polymer electrodes. High device performance, together with the facile patternability and other merits, may promote the application of surface-grafting conducting polymer electrode in the field of organic electronics.

The relationship between fatigue strength and tensile properties has drawn widespread concern in recent decades. It is gradually recognized that the fatigue strength is dependent on the strength of the weakest zone in materials, while the regular tensile test could only obtain the global strength. The present study, for the first time, constructed a fast evaluation method, in which extremely slender specimens were employed. It is found that, when the specimen is slender enough, i.e., the soft oriented grain could occupy the whole section of the specimen, the strength of the soft domain could be related to the fatigue strength. In the 18Ni maraging steels, the fatigue crack would nucleate in the precipitate free zone (PFZ), which is the soft domain. Furthermore, the fatigue strength of fully reversed loading test nearly equals to the yield strength of the PFZ measured by the slender tensile test. This founding may shed light on the fast evaluation of fatigue strength, which could bring great economic benefits and save invaluable time.

The piezoresistive pressure sensor, a kind of widely investigated artificial device to transfer force stimuli to electrical signals, generally consists of one or more kinds of conducting materials. Here, a highly sensitive pressure sensor based on the semiconductor/conductor interface piezoresistive effect is successfully demonstrated by using organic transistor geometry. Because of the efficient combination of the piezoresistive effect and field-effect modulation in a single sensor, this pressure sensor shows excellent performance, such as high sensitivity (514 kPa-1 ), low limit of detection, short response and recovery time, and robust stability. More importantly, the unique gate modulation effect in the transistor endows the sensor with an unparalleled ability-tunable sensitivity via bias conditions in a single sensor, which is of great significance for applications in complex pressure environments. The novel working principle and high performance represent significant progress in the field of pressure sensors.

Electrode materials and geometry play a crucial role in the charge injection efficiency in organic transistors. Reduced graphene oxide (RGO) electrodes show good compatibility with an organic semiconductor from the standpoint of energy levels and ordered growth of the organic semiconductor, both of which are favourable for charge injection. However, the wide electrode edge (>10 nm) in commonly-used RGO electrodes is generally detrimental to charge injection. In this study, ultrathin (about 3 nm) RGO electrodes are fabricated via a covalency-based assembly strategy, which has advantages such as robustness against solvents, high conductivity, transparency, and easy scaling-up. More remarkably, the ultrathin electrode fabricated in this study has a narrow edge, which may facilitate the diffusion and assembly of organic semiconductors and thus form a uniform semiconductor film across the electrode/channel junction area. As a result, the minimized electrode edge may significantly improve the charge injection in organic transistors compared with thick electrodes.

Flexible and light-weight photovoltaics are desirable for applications that involve their integration with flexible electronics. In this study, we demonstrate efficient flexible perovskite solar cells with a novel device architecture (that is indium-tin-oxide (ITO) free and top-illuminated) using a low-temperature processed doped fullerene as the electron-transporting layer. Silver is used as the bottom electrode, and a transparent conducting polymer electrode is used as the top electrode for light illuminating through to the active layer. Stearyldimethylbenzylammonium chloride (SDBAC)-doped [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) was the electron-transporting layer wherein SDBAC could enhance the conductivity by three orders of magnitude and therefore enhance the solar cell performance. The ITO-free flexible perovskite solar cells display power conversion efficiency of 11.8% on a polyethersulfone substrate and can maintain 84% of the initial PCE after 1000 bending cycles at a bending radius of 6 mm.

Electrical hysteresis in carbon nanotube thin-film transistor (CNTTFT) due to surface adsorption of H2O/O2 is a severe obstacle for practical applications. The conventional encapsulation methods based on vacuum-deposited inorganic materials or wet-coated organic materials have some limitations. In this work, we develop a general and highly efficient dry-laminating encapsulation method to reduce the hysteresis of CNTTFTs, which may simultaneously realize the construction and encapsulation of CNTTFT. Furthermore, by virtue of dry procedure and wide compatibility of PMMA, this method is suitable for the construction of CNTTFT on diverse surface including both inorganic and organic dielectric materials. Significantly, the dry-encapsulated CNTTFT exhibits very low or even negligible hysteresis with good repeatability and air stability, which is greatly superior to the nonencapsulated and wet-encapsulated CNTTFT with spin-coated PMMA. The dry-laminating encapsulation strategy, a kind of technological innovation...

The modification of dielectric surface with a self-assembled monolayer (SAM) such as octadecyltrichlorosilane (OTS) is a widely used method to tune the electrical property of diverse electronic devices based on organic semiconductors, graphene, transition metal dichalcogenides (TMDs), and so forth. The surface roughness of self-assembled OTS monolayer is a key factor in determining its effect on device performance, but the preparation of an ultrasmooth OTS monolayer is a technologically challenging task. In this work, an ultrasmooth OTS monolayer is prepared via a facile peeling method, which may serve as a postremedy strategy to remove the protuberant aggregates. Such a method has not been reported before. With organic semiconductors as a testing model, ultrasmooth OTS may significantly improve the charge mobility of organic field-effect transistors (OFETs). P-type dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) OFET with an ultrasmooth OTS monolayer yields good reproducibility and unprecendented maximum mobility of 8.16 cm(2) V(-1) s(-1), which is remarkably superior to that of the OFET with a pristine OTS monolayer. This work develops a simple method to resolve the common and significant problem of the quality of OTS modification, which would be highly promising for electronic applications as well as other fields such as surface and interface engineering.

Ultrathin film with thickness below 15 nm of organic semiconductors provides excellent platform for some fundamental research and practical applications in the field of organic electronics. However, it is quite challenging to develop a general principle for the growth of uniform and continuous ultrathin film over large area. Dip-coating is a useful technique to prepare diverse structures of organic semiconductors, but the assembly of organic semiconductors in dip-coating is quite complicated, and there are no reports about the core rules for the growth of ultrathin film via dip-coating until now. In this work, we develop a general strategy for the growth of ultrathin film of organic semiconductor via dip-coating, which provides a relatively facile model to analyze the growth behavior. The balance between the three direct factors (nucleation rate, assembly rate, and recession rate) is the key to determine the growth of ultrathin film. Under the direction of this rule, ultrathin films of four organic semiconductors are obtained. The field-effect transistors constructed on the ultrathin film show good field-effect property. This work provides a general principle and systematic guideline to prepare ultrathin film of organic semiconductors via dip-coating, which would be highly meaningful for organic electronics as well as for the assembly of other materials via solution processes.

Phages also known as bacteria viruses, are recognized as the most abundant and diverse microbes. This diversity is adapting to the selective pressures such as the prevalence of the phage resistance mechanisms of bacteria. Phages invade and lyse bacterial through six steps (adsorption, injection, replication, transcription translation, assemble, release). Bacteria evolve to many anti-phage mechanisms to avoid phage infection and lysis. This paper focus on a variety of anti-phage mechanisms of bacteria.

The bacteriophage LSPA1 was isolated from hospital sewage (Kunming, China), and lytic activity was demonstrated against the Salmonella enterica serovar Paratyphi A CMCC50973 strain. This bacteriophage has a 41,880-bp double-stranded DNA (dsDNA) genome encoding 58 coding sequences (CDSs) and belongs to the family Siphoviridae.

In order to pick up the low-frequency gravity anomaly from airborne gravity data, a finite impulse response (FIR) low-pass digital filter with the Chebyshev approximation theorem was designed, and the filtering effects of three design parameters were studied. Results show that the filter order may amplify the passband section and affect the stopband attenuation; the passband and stopband edge frequency have similar effects on transition band but opposite effects on stopband. Compared with the commercial software results, the standard deviations of the filtered gravity anomalies using the optimal parameters are within 1mGal, and the internal accord accuracy of four survey lines after level adjusting is 0.585mGal.