Combining the best features of both inorganic quantum dots and i-motif DNA, a dynamic pH-driven modulation system of photoelectric conversion was realized by making use of their conjugates immobilized on a Au electrode.

Purpose The paper aims to develop a cownose ray-inspired robotic fish which can be propelled by oscillating and chordwise twisting pectoral fins. Design/methodology/approach The bionic pectoral fin which can simultaneously realize the combination of oscillating motion and chordwise twisting motion is designed based on analyzing the movement of cownose ray’s pectoral fins. The structural design and control system construction of the robotic fish are presented. Finally, a series of swimming experiments are carried out to verify the effectiveness of the design for the bionic pectoral fin. Findings The experimental results show that the deformation of the bionic pectoral fin can be well close to that of the cownose ray’s. The bionic pectoral fin can produce effective angle of attack, and the thrust generated can propel robotic fish effectively. Furthermore, the tests of swimming performance in the water tank show that the robotic fish can achieve a maximum forward speed of 0.43 m/s (0.94 times of body length per second) and an excellent turning maneuverability with a small radius. Originality/value The oscillating and pitching motion can be obtained simultaneously by the active control of chordwise twisting motion of the bionic pectoral fin, which can better imitate the movement of cownose ray’s pectoral fin. The designed bionic pectoral fin can provide an experimental platform for further study of the effect of the spanwise and chordwise flexibility on propulsion performance.

An experimental investigation was conducted to study the transient behavior of the flow separation on a NASA low-speed GA (W)-1 airfoil at the chord Reynolds numbers of 68,000. A high-resolution PIV system was used to make detailed flow field measurements in addition to the surface static pressure distribution mapping around the airfoil. The measurement results visualized clearly that a separation bubble would be generated on the airfoil upper surface if the adverse pressure gradient is adequate. The length of the separation bubble could be up to 20% of airfoil chord length and its height only about 1% of the cord length. The transient behavior of the flow separation on the airfoil, which includes the "taking-off" of the laminar boundary layer from the airfoil surface at the separation point, the generation of unsteady Kelvin-Helmholtz vortex in the separated boundary layer, the rapid transition of the separated laminar boundary layer to turbulent flow, the reattachment of the turbulent flow to the airfoil surface to form separation bubble, and the burst of the separation bubble to cause airfoil stall, were elucidated clearly and quantitatively from the detailed flow field measurements.

We examined the mediating role of Chinese adolescents' core self-evaluations in the relationship between mindfulness and their life satisfaction. The participants (N = 436) completed the Mindful Attention Awareness Scale, the Core Self-Evaluations Scale, and the Satisfaction with Life Scale. The results suggested that greater life satisfaction was associated with higher levels of mindfulness and more positive core self-evaluations, and core selfevaluations were positively correlated with life satisfaction. The results of mediation analysis suggested that core self-evaluations partially mediated the relationship between mindfulness and life satisfaction of Chinese adolescents, implying that a higher level of mindfulness was correlated with more positive core self-evaluations, which were finally associated with greater life satisfaction. Together these results imply that enhancing the levels of mindfulness and encouraging positive core self-evaluations of adolescents will exert a significantly positive effect in promoting their well-being.

No abstract

The surface effect is becoming apparently significant as the miniaturization of fluidic devices. In the micro/nanochannel fluidics, the electrode surface effects have the same important influence on the current signals as the channel surface effects. In this paper, when aqueous solution are driven with non-continuous DC electric field force, the characteristics of current signals of the fluid transferring through microfluidic channel are systematically studied. Six modes of current signal are summarized, and some new significant phenomena are found, e.g. there exists a critical voltage at which the steady current value equals to zero; the absolute value of the steady current decreases at first, however, it increases with the external voltage greater than the critical voltage as the electrode area ratio of cathode and anode is 10 and 20; the critical voltage increases with the enhancing of electrode area ratio of cathode and anode and solution pH, while it decreases with the raising of ion concentration. Finally, the microscopic mechanism of the electrode surface charge effects is discussed preliminarily. The rules will be helpful for detecting and manipulating single biomolecules in the micro/nanofluidic chips and biosensors.

The phenomenon of hot gas ingestion at the rim seal section of turbines has been investigated for the front cavity and inside the sealing gap of an 1.5-stage turbine. This paper presents velocity distributions in and inside the rim seal. The experiments were performed using an unsteady 2D Laser Doppler Velocimetry system with a high local and time-based resolution. The hot gas ingestion has been examined for different parameters such as the non-dimensional seal flow rate and includes measurements at 17 circumferential positions with each 5 axial positions at dimensionless radii of 0.985 and 0.952. It is shown that the flow field inside the gap is influenced by the rotor blades as well as by secondary phenomena originating from the guide vanes. The location of hot gas ingestion is moving with the rotor blades and its strength is depending on the amount of seal flow rate. Unsteady interactions between rotor and stator blades have been investigated.

Effective foundation reinforcement treatment is essential for modern large and complex infrastructure, while it is significant for developing new green high-performance materials for foundation reinforcement. This study investigates a new green concrete by using high volume fly-ash and coal gangue aggregates, which is expected to apply for foundation treatment of modern infrastructure with high loading-bear ability. In this experiment, 12 mix proportions of fly ash coal gangue mixture (the material name, abbreviated FGM) were designed, and its mechanical properties and durability performance were investigated. The mechanical properties of FGM include compressive strength, dynamic elastic modulus, dynamic shear modulus, Poisson’s ratio, and the stress–strain behaviors. The durability performance was evaluated by the parameters of acid resistance, which simulated an acid circumstance. After that, the environmental effects about carbon emission of this material were also investigated. Results show that the FGM with 84.6% wastes utilizing rate is a cost-effective material for foundation reinforcing treatment. Its compressive strength at 28 days and 60 days can reach more than 8 MPa and 10 MPa, respectively. After being immersed in the acid environment for 140 days, the mass loss (%) of the material could be under 3.5%. The greenness shows that the e-CO2 indices of FGM are lower than 20 kg/MPa·m3, and the e-energy indices are at below 150 MJ/MPa·m3. FGM has the advantages of acid resistance, waste recycling, and lower carbon emissions than the previous methods for foundation improvement.