Transient effects during transitions of bio-inspired flapping foils between two different schooling configurations

Recently, there has been considerable interest in developing novel energy-saving vehicles that use flapping foils propulsion systems inspired by biology. Facing increasingly complex application tasks, the coordination of multiple vehicles will be a hot issue in the future this research field. We are inspired by changes in configurations of biological collective behavior (known as schooling) in nature, focused on studying transient effects during transitions of three-dimensional bio-inspired flapping foils between two different bionic schooling configurations. Numerical simulations employing the immersed boundary-lattice Boltzmann method (IB-LBM) for unsteady hydrodynamics of flapping foils in schooling transitions were performed. Effects of different mutual transition modes between tandem and diamond schooling configurations on their thrust performance were investigated. Meanwhile, we present hydrodynamics of flapping foils in a schooling with different downstream flapping frequencies under the best transition mode. The results show that during transitions between two schooling configurations, there is an optimal energy-saving transition mode. It has nothing to do with the length of transition distance. Different downstream flapping frequencies will affect the interacting vortices between fluid and structure and then affect transient effects during schooling transition. Although the transition modes were specified, our research takes the transients effects of schooling transitions as an influencing factor to be considered for formations changes, which will provide a new idea for the design bio-inspired vehicle cluster formation.

Assessment of the stability of the gas-diesel automatic control system

Any steady-state operation of the engine is evaluated by qualitative and quantitative parameters. For internal combustion engines, the qualitative parameter is the speed of the crankshaft, and the quantitative parameter is the engine torque. There are functional dependencies between these parameters, the graphical representation of which is called speed characteristics. However, the transition modes of engines are much more complex than the established ones, especially in gas-diesel engines, where the relationship between the parameters of the engine and the characteristics of the gas supply units is quite complex, and the transition process is accompanied by a change in the parameters of its working process over time and is a dynamic mode.

RPnet: A Reverse Projection Based Neural Network for Coarse-graining Metastable Conformational States for Protein Dynamics

Markov State Model (MSM) is a powerful tool for modeling the long timescale dynamics based on numerous short molecular dynamics (MD) simulation trajectories, which makes it a useful tool for elucidating the conformational changes of biological macromolecules. By partitioning the phase space into discretized states and estimate the probabilities of inter-state transitions based on short MD trajectories, one can construct a kinetic network model that could be used to extrapolate long time kinetics if the Markovian condition is met. However, meeting the Markovian condition often requires hundreds or even thousands of states (microstates), which greatly hinders the comprehension of conformational dynamics of complex biomolecules. Kinetic lumping algorithms can coarse grain numerous microstates into a handful of metastable states (macrostates), which would greatly facilitate the elucidation of biological mechanisms. In this work, we have developed a reverse projection based neural network (RPnet) method to lump microstates into macrostates, by making use of a physics-based loss function based on the projection operator framework of conformational dynamics. By recognizing that microstate and macrostate transition modes can be related through a projection process, we have developed a reverse projection scheme to directly compare the microstate and macrostate dynamics. Based on this reverse projection scheme, we designed a loss function that allows effectively assess the quality of a given kinetic lumping. We then make use of a neural network to efficiently minimize this loss function to obtain an optimized set of macrostates. We have demonstrated the power of our RPnet in analyzing the dynamics of a numerical 2D potential, alanine dipeptide, and the clamp opening of an RNA polymerase. In all these systems, we have illustrated that our method could yield comparable or better results than competing methods in terms of state partitioning and reproduction of slow dynamics. We expect that our RPnet holds promise in analyzing conformational dynamics of biological macromolecules.

Design of impact dampers for transporting cargoes by two-link vehicles

This paper considers the influence of the transitional modes of movement (acceleration, braking) of a multi-link vehicle on the vibration protection of transported non-fixed or partially fixed cargoes. The impact phenomenon, in this case, can be strengthened by the existence of coupling mechanisms between the links of a multi-link vehicle. To reduce such horizontal impact loads, it is advisable to use elements with viscoelastic damping in the coupling devices of a multi-link vehicle. To study the actual impact phenomena during the transportation of non-fixed or partially fixed cargoes under the extreme modes of movement of two-link vehicles, it is proposed to use a flat two- and three-mass dynamic model with viscoelastic damping. At the same time, the theory of elastic impact has been applied while the elastic-damping characteristics of vehicles' suspensions were not taken into consideration. It has been shown that the reported research results make it possible to estimate the approximate values of the mechanical parameters for restrictive devices that protect non-fixed or partially fixed cargoes from impact, during the transition modes of transportation, depending on the conditions of motion. This practically makes it possible to select the rational design parameters for the elements of viscoelastic restrictive devices, in particular elastic elements and dampers, in order to reduce impact loads on non-fixed heavy cargoes during transportation under extreme modes of movement. Based on this study, a procedure of vibration protection of non-fixed or partially fixed cargoes in the body of a two-link vehicle during its uneven movement has been proposed, which implies determining the maximum dynamic loads on these cargoes as well as the possibility of choosing the rational design parameters for restrictive devices in order to prevent or reduce the impact of these cargoes hitting the restrictive devices

Off-Resonant Absorption Enhancement in Single Nanowires via Graded Dual-Shell Design

Single nanowires (NWs) are of great importance for optoelectronic applications, especially solar cells serving as powering nanoscale devices. However, weak off-resonant absorption can limit its light-harvesting capability. Here, we propose a single NW coated with the graded-index dual shells (DSNW). We demonstrate that, with appropriate thickness and refractive index of the inner shell, the DSNW exhibits significantly enhanced light trapping compared with the bare NW (BNW) and the NW only coated with the outer shell (OSNW) and the inner shell (ISNW), which can be attributed to the optimal off-resonant absorption mode profiles due to the improved coupling between the reemitted light of the transition modes of the leak mode resonances of the Si core and the nanofocusing light from the dual shells with the graded refractive index. We found that the light absorption can be engineered via tuning the thickness and the refractive index of the inner shell, the photocurrent density is significantly enhanced by 134% (56%, 12%) in comparison with that of the BNW (OSNW, ISNW). This work advances our understanding of how to improve off-resonant absorption by applying graded dual-shell design and provides a new choice for designing high-efficiency single NW photovoltaic devices.

Off-Resonant Absorption Enhancement in Single Nanowires via Graded Dual-Shell Design

Single nanowires (NWs) are of great importance for optoelectronic applications, especially solar cells serving as powering nanoscale devices. However, weak off-resonant absorption can limit its light-harvesting capability. Here, we propose a single NW coated with the graded-index dual shells (DSNW). We demonstrate that with appropriate thickness and refractive index of the inner shell, the DSNW exhibits significantly enhanced light trapping compared with the bare NW (BNW), and the NW only coated with the outer shell (OSNW) and the inner shell (ISNW), which can be attributed to the optimal off-resonant absorption mode profiles due to the improved coupling between the reemitted light of the transition modes of the leak mode resonances of the Si core and the nanofocusing light from the dual shells with the graded refractive index. We found that the light absorption can be engineered via tuning the thickness and the refractive index of the inner shell, the photocurrent density is significantly enhanced by 134% (56%, 12%) in comparison with that of the BNW (OSNW, ISNW). This work advances our understanding of how to improve off-resonant absorption by applying graded dual-shell design and provides a new choice for designing high-efficiency single NW photovoltaic devices.

BEHAVIOR OF THE Ti-Zr-Ni THIN FILM CONTAINING QUASICRYSTALLINE AND APPROXIMANT PHASES UNDER RADIATIVE-THERMAL ACTION IN TRANSITION MODES

X-ray diffraction and SEM microscopy were used to study the structural and phase changes in a thin film obtained by magnetron sputtering of a Ti52Zr30Ni18 target (at.%) on a steel substrate under the radiation-thermal influence of pulsed hydrogen plasma on an QSPA Kh-50 accelerator. A technique has been worked out for the formation of the quasicrystalline and crystal-approximant phases as a result of high-speed quenching using pulsed action with a heat load of 0.6 MJ/m2. The changes in the contents of these phases as well as in their structure and substructure parameters were studied during isothermal vacuum annealing at a temperature of 550 °C and also as a result of irradiation with 5 plasma pulses in the range of heat load from 0.1 to 0.4 MJ/m2. The quasicrystalline phase was found to be resistant to irradiation with hydrogen plasma.