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Exploration of flexible tactile sensors with high sensitivity that can imitate the perception functions (tactile sensing and pain sensing) of human skin is the main force in the realization of electronic skin. The research of electronic skin with the function of pain perception is of great significance in the field of biomimetic robot and treatment of patients losing the pain sensation ability of their skin. Herein, to broaden the application field of traditional electronic skin, we demonstrate a biomimetic and highly sensitive tactile sensor for realization of sensory functionalities of human skin. The structure of our sensor mimics the surface of the tentacles of tentacled snakes, which are strikingly sensitive mechanoreceptors. We design a tentacle-inspired flexible sensor by sandwiching the convex dielectric layer of PDMS/MXene microarrays between two flexible electrodes. It is found that the bioinspired sensor exhibits a high sensitivity of 3.61 kPa−1, a fast response time of 29 ms and a satisfactory stability, ensuring the ability in monitoring physiological signals. Finally, we present the application of the sensor for finger bending, international Morse code detection, and artery pulse detection. By presetting the pain thresholds of different areas of skin in a program, the sensor can identify and distinguish pressure data that exceed the pain threshold, realizing the detection of pain. In addition, it can be further applied on robot skins to assess the risk level of the working environment by monitoring its pressure data.

Copyright © 2021 The Author(s). It is difficult to consider the heterogeneity and discontinuity of rock and soil in conventional slope stability analysis. This paper proposes an efficient slope stability analysis method based on discrete element method (DEM) and Monte Carlo simulations(MCS). The analysis employed the stacking models with multiple slopes and the element displacement to achieve rapid analysis of slope stability. Using on the high-performance discrete element software MatDEM, a stacking model containing 100 2D slopes and a total of more than 800,000 elements was generated. The element tensile strength F and friction coefficient μ p were set as random variables to consider the material heterogeneity and uncertainty. We performed the stability analyses of 40,000 slopes for 28 hours. The numerical results show that the slopes were instable when a sudden displacement and penetrating sliding surface occurred. The coefficient of variation COVPf of slope failure probability is greatly meets the target accuracy requirements of MCS, which shows the method can be applied to the refined analysis of slopes with high-precision requirements and multiple random variables.

The increasing amount of defect images in semiconductor manufacturing process imposes the demand of classifying these images in real-time. In this paper we adopt a two-step deep learning based Convolutional Neural Network (CNN) to detect and classify the defect images from clean ones. The proposed method integrates the detection and classification process into one forward step, which takes image-level feature as well as empirical defect classification rules into account. In practice, the Real-Time Automated Defect Classification (RT-ADC) system was deployed in inline production process, which brings high efficiency; better wafer analysis and root cause determination for yield enhancement.

The remarkably high theoretical energy densities of Li–O2 batteries have triggered tremendous efforts for next-generation conversion devices. Discovering efficient oxygen reduction reaction and oxygen evolution reaction (ORR/OER) bifunctional catalysts and revealing their internal structure-property relationships are crucial in developing high-performance Li–O2 batteries. Herein, we have prepared a nanoflower-like Ni5P4@NiSe2 heterostructure and employed it as a cathode catalyst for Li–O2 batteries. As expected, the three-dimensional biphasic Ni5P4@NiSe2 nanoflowers facilitated the exposure of adequate active moieties and provide sufficient space to store more discharge products. Moreover, the strong electron redistribution between Ni5P4 and NiSe2 heterojunctions could result in the built-in electric fields, thus greatly facilitating the ORR/OER kinetics. Based on the above merits, the Ni5P4@NiSe2 heterostructure catalyst improved the catalytic performance of Li–O2 batteries and holds great promise in realizing their practical applications as well as inspiration for the design of other catalytic materials.

Lunar dust is one of the most threatening problems confronting the return of human beings to the moon. In this work we studied the spatial distribution behavior of charged lunar dust in the solar wind plasma environment in the south polar region of the moon and considered the influence of a mini-crater using Spacecraft Plasma Interactions Software. The distribution of dust and plasma at low solar altitude angles of 20° and 0° was studied, and the spatial density of lunar dust was ∼ 1010.4 m−3 and ∼ 1011.5 m−3, respectively. This is because a higher surface potential will result in transportation of small dust particles and photoelectrons can also neutralize positively charged lunar dust. The dust density in the plasma void region created by a mini-crater with a 5 m high wall was studied. We obtained a quasi-neutral electric environment in the plasma void region of the mini-crater, and the dust density was about a magnitude lower than that in other regions. The dust risk to a spacesuit is much lower on the nightside than on the dayside, but there is severe charged lunar dust transport in the region between light and shade, which is dominated by the difference in surface and plasma potential caused by photoelectrons.

In order to understand our previous numerical finding that steady-state entanglement along the instability boundary remains unchanged in a three-mode optomechanical system [Phys. Rev. A 101 023838 (2020)], we investigate in detail the boundary entanglement in a simpler two-mode optomechanical system. Studies show that both the mechanism to generate entanglement and the parameter dependence of boundary entanglement are quite similar in these two models. Therefore, the two-mode system has captured the main features in the three-mode system. With the help of analytical calculations and discussing in a much bigger parameter interval, we find that the unchanging behavior previously discovered is actually an extremely slow changing behavior of the boundary entanglement function, and most importantly, this nearly invariant boundary entanglement is a general phenomenon via parametric down conversion process in the weak dissipation regime. This is by itself interesting as threshold quantum signatures in optomechanical phonon lasers, or may have potential value in related applications based on boundary quantum properties.

We present a numerical study of horizontal convection using both step and linear forcing profiles as the imposed surface thermal driving, the former of which is commonly used in many studies but the latter is closer to the real ocean. Our investigation focuses on how forcing profiles can affect the theoretical and experimental results previously obtained based on the step forcing profile. We show that both types of forcing profiles exhibit similar behaviors in terms of global heat transfer (Nu ), mean flow strength (Re ), and boundary layer thickness. However, these two forcing profiles show significant differences for some other physical quantities, such as the generation rate of available potential energy G APE and global thermal dissipation rate, for which exact relationships with Nu can be derived for the step forcing profile but not for linear forcing. We show that a relationship between Nu and G APE can be developed for linear forcing by defining an effective forcing area, and such area is found to be approximately constant. We further derive an approximate relationship between Nu and the global thermal dissipation rate for linear forcing by assuming that the boundary heat flux is proportional to the local temperature deviation from the mean, which works best under the condition of moderate plume emissions. Differences are also found for the viscous dissipation rate; however, these differences diminish for sufficiently high Ra . Though step forcing is obviously less appropriate for modeling ocean circulations, we show that most differences arising from the forcing profile difference can be reconciled. Considering its convenience in experiment control and theoretical analysis, step forcing is a good configuration for most problems, but one should also be aware of the differences between step and other forcing types in quantities like the global thermal dissipation rate when extrapolating the results to more general situations.

In this paper, we study the evolution of the ionization fraction x e(z) during the epoch of reionization by using the dispersion measurements (DMs) of fast radio bursts (FRBs). Different from the previous studies, here we turn to consider the large-scale clustering information of observed DMs of FRB catalog, which only needs the rough redshift distribution, instead of the exact redshift information of each FRB. Firstly, we consider the instantaneous “tanh” model for x e(z) and find that including the auto-correlation information of the mock catalog, about 104 FRBs with the intrinsic DM scatter of 100 pc/cm3 spanning 20% of all sky, could significantly improve the constraint on the width Δz of the model, when comparing with that from the CMB data alone. The evolution shape of the ionization fraction will be tightly narrowed, namely the duration of the epoch of reionization has been shrunk, z dur < 2.24 (95% C.L.). Furthermore, we also use another redshift-asymmetric reionization model and obtain that the FRB mock catalog could measure the ionization fraction at z = 6 precisely with the 1σ error Δ x e (z = 6) = 0.012, which means that the large-scale clustering information of observed DMs of FRB catalog is very sensitive to the ionization fraction of the end of reionization epoch. We conclude that the observation of high-redshift FRBs could be a complementary probe to study the reionization history in the future.

This study investigates the effects of long-period stacking order (LPSO) phases on the dynamic recrystallization (DRX) process. By comparing Mg-Gd-Y-Zn-Zr (GWZ) alloy and Mg-Gd-Y-Zr (GW) alloy deformed by 4 passes of Isothermal Reciprocating Upsetting-Extrusion (RUE), the initial alloy grain sizes are 113.4 μm and 88.2 μm, respectively, after 4 passes, the grain size becomes 3.5 μm and 4.8 μm, and the grain refinement of GWZ is greater. After 1 pass, the DRX volume fraction of GWZ alloy is 83% and 15%, which is related to the LPSO phases contained in the GWZ alloy. The texture strength of the GWZ alloy ranges from 8.5 of 1 pass to 2.2 of 4 passes, while the GW alloy is from 5.9 of 1 pass to 2.8 of 4 passes, mainly due to the DRX grain volume fraction. The tensile test results at room temperature (RT) showed that the ultimate tensile strength (UTS) and tensile yield strength (TYS) of GWZ alloy are higher than that of GW alloy, and the elongation is lower than that of GW alloy.

To determine the reasonable gas injection and production quantity and to minimize the influence of water invasion on the operation of underground gas storage is one of the key factors to decide whether the water drive gas storage can fully exert its peak shaving ability. At present, gas reservoir engineering method is mainly used in China, which mainly reflects the operation of underground gas storage under the condition of less water invasion at the end of gas production, it cannot really reflect the influence of water invasion on the operation of underground gas storage under the condition of large injection-production volume. Through the numerical simulation and the research of the injection-production performance, it is clear that the main geological factors affecting the reasonable injection-production rate of the gas storage are the pressure of the gas storage, the properties of the reservoir, the distribution of gas and water and the radius of well control. Based on the reservoir changes of pressure, water yield, gas-water ratio, gas-water interface and saturation, and according to the influence of multi-period water invasion on the operation of gas storage, the optimization technology of peak shaving capacity of water drive gas reservoir is established, which successfully guides the optimization of injection-production operation of an underground gas storage in China. The result shows that after 5 cycles of operation, the gas injection displacement effect is successful, the gas production capacity is improved gradually, and the peak shaving capacity is 6.85 X 108m3 in 2019. The conclusion is that the optimization technology of peak shaving capacity is applicable to some extent, which provides theoretical basis and operating experience for the design of injection-production operation of the same type gas storage in China.

In our previous work (Meng et al 2020 Phys. Rev. A 101 023838), we discover the phenomenon that the quantum entanglement on the driving threshold line remains a constant in a three-mode optomechanical phonon laser system. In this paper, to find the conditions under which the constant boundary entanglement shows up, we explicitly study how this boundary entanglement depends on various parameters through numerical integrations. The results show that the necessary and sufficient condition is a resonant frequency match between the optical frequency difference and the mechanical vibrational frequency, and this constant value is proportional to the multiplication of the square of the optomechanical coupling strength and the resonant driving threshold power.

The issue of campus energy and environment has become one of our increasing concerns. Environmental issues have become an important assessment index restricting the development of schools and students’ self-improvement. Only the sustainable development of the environment can ensure the smooth implementation of school education. For this reason, the development of an efficient energy environment monitoring system based on computer networks is imperative. Based on this research background, the paper analyses the needs of an efficient micro-energy environment monitoring system, and discusses the functions of the monitoring system and related hardware and software. Finally, the system was tested to verify the feasibility of the system.

The problem of the network node and the complex constrain in the path planning has become a difficulty in forest fire logistics support. The traditional ant colony algorithm is improved. We establish two objective functions for the distance between nodes and the time required to finish task. We optimize the two objective functions. We redesigned the calculation method of heuristic information and the update function of pheromone. We set a time window to limit the time to complete urgent tasks. Finally, an example is given for verification. The results show that the improved algorithm can solve the problem of logistics support path planning model of forest fire. The results are more close to the actual situation.

As an ecological material, Grass-planting concrete has been increasingly used in constructing bank revetment of the rivers, and the studies on the physical and mechanical properties of the concrete is key for more efficient application. This paper describes the physical and mechanical properties of the concrete through analyzing the relationship among cementitious materials, dry bulk density, compressive strength and porosity. The results indicated the grass-planting concrete could meet the requirements for the strength and plant growth of ecological bank protection of small and medium-sized rivers when the total amount of cementitious materials was greater than 526 kg/m3 or the dry bulk density was greater than 1700 kg/m3. There is a negative correlation between the compressive strength and the porosity. This work provides excellent technical support for the popularization and application of grass-planting concrete.

We consider a three-mode optomechanical system where two cavity modes are coupled to a common mechanical oscillator. We focus on the resolved sideband limit and illustrate the relation between the significant parameters of the system and the instantaneous-state mean phonon number of the oscillator cooled to the ground state, particularly at the early stage of the evolution. It is worth noting that the optical coupling sets up a correlation between the two cavity modes, which has significant effect on the cooling process. Using numerical solutions, we find that the inter-cavity coupling will decrease the cooling effect when both cavities have the same effective optomechanical coupling. However, when the effective optomechanical couplings are different, the cooling effect will be strongly improved by selecting appropriate range of inter-cavity coupling.

In order to improve the push precision and user satisfaction of the service platform, this paper proposes an intelligent directional push model based on the existing problems of the intelligent search model and the actual characteristics of the service platform. Firstly, use data preparation method to finish collecting, integrating, cleaning, conversion and protocol of the user association data in the service platform. Then deep learning model is used to build a local service platform semantic library. Thirdly, use jieba algorithm to match the user-associated data with the local service platform semantic library, set the weights of input data based on its importance, use the normalization algorithm to obtain the access matching matrix of the target users. Finally the collaborative filtering algorithm is used to calculate the user matching degree. The case analysis proves that the model in this paper has higher accuracy.

We report on the performance of silicon photomultiplier (SiPM) light sensors operating in electric field strength up to 30 kV/cm and at a temperature of 149K, relative to their performance in the absence of an external electric field. The SiPM devices used in this study show stable gain, photon detection efficiency, and rates of correlated pulses, when exposed to external fields, within the estimated uncertainties. No observable physical damage to the bulk or surface of the devices was caused by the exposure., Comment: 16 pages, 12 figures, 2 tables and two conferences (INPC2016 and TIPP2017)

A controllable entanglement scheme of two mechanical oscillators is proposed in a composite optomechanical system. In the case of strong driving and high dissipation, the dynamics of the movable mirror of the optomechanical cavity is characterized by an effective frequency in the long-time evolution of the system. Considering the classical nonlinear effects in an optomechanical system, we investigate the relationship between the effective frequency of the movable mirror and the adjustable parameters of the cavity. It shows that the effective frequency of the movable mirror can be adjusted ranging from ω m (the resonance frequency of the coupling oscillator) to −ω m . Under the condition of experimental realization, we can generate and control steady-state entanglement between two oscillators by adjusting the effective frequency of the movable mirror and reducing the effective dissipation by selecting the parameter of the cavity driving laser appropriately. Our scheme provides a promising platform to control the steady-state behavior of solid-state qubits using classical manipulation, which is significant for quantum information processing and fundamental research.

In this paper, we present a scheme to generate an entangled coherent state by considering a three-level \Lambda - type atom interacting with a two-mode cavity driven by classical fields. The two-mode entangled coherent state can be obtained under large detuning conditions. Considering the cavity decay, an analytical solution is deduced., Comment: 3 figures

Trichel pulse of negative corona discharge in atmospheric air is investigated numerically using a 2D fluid model. The model consists of a hyperbolic cathode tip and a plane anode, and considers 11 kinds of particles and the most important interactions among them. The spatio-temporal evolution of charged species and the electric field are evaluated during the pulse process. During the pulse rising edge, the positive ions accumulate ahead of the tip forming the temporal cathode sheath, significantly enhancing the local field. In the pulse decay edge, the temporal sheath collapses and the discharge falls back to a low-current mode. In the pulse interval, the discharge does not cease but sustains weakly until the next pulse. The location of the temporal sheath is independent of the averaged value during the Trichel pulse regime and also the same with that in a normal glow regime, which determines a nearly constant pulse rising time at given configurations. However, a smaller tip radius will lead to their decrease. The effect of negative ions on the pulse process is studied by adjusting the attachment rates. It indicates that the negative ions are actually not necessary in the Trichel pulse process, but will influence the pulse waveform significantly.

We propose a system for achieving some adjustable quantum coherence effects, including the normal-mode splitting (NMS), the optomechanically induced transparency (OMIT), and the optomechanically induced absorption (OMIA). In this system, two tunnel-coupled optomechanical cavities are each driven by a coupling field and coupled to an atomic ensemble. Besides, one of the cavities is also injected with a probe field. When the system works under different conditions, we can obtain the NMS, the OMIT, and the OMIA, respectively. These effects can be flexibly adjusted by the tunnel coupling between the two cavities, the power of the coupling lasers, and the coupling strength between the atomic ensembles and the cavity fields. Furthermore, we can realize the OMIT even if the oscillating mirrors have relatively larger decay rates.

A ZrOx switching layer with different oxygen content for TiN/ZrOx/Pt resistive switching (RS) memory was prepared by magnetron sputtering in different atmospheres such as N2/Ar mixture, O2/Ar mixture as well as pure Ar. The morphology, structure and RS characteristics were systemically investigated and it was found that the RS performance is highly dependent on the sputtering atmosphere. For the memory device sputtered in N2/Ar mixture, with 8.06% nitrogen content in the ZrOx switching layer, the highest uniformity with smallest distribution of V set and high resistance states (HRS)/low resistance states (LRS) values were achieved. By analyzing the current conduction mechanisms combined with possible RS mechanisms for three devices, we deduce that for the device with a ZrOx layer sputtered in N2/Ar mixture, oxygen ions (O2−), which are decisive to the disruption/formation of the conductive filament, will gather around the tip of the filament due to the existence of doping nitrogen, and lead to the reduction of O2− migration randomness in the operation process, so that the uniformity of the N-doped ZrOx device can be improved.

We investigate the primordial gravitational waves (PGWs) in the general scenario where the inflation is preceded by a pre-inflationary stage with the effective equation of state $w$. Comparing with the results in the usual inflationary models, the power spectrum of PGWs is modified in two aspects: One is the mixture of the perturbation modes caused by he presence of the pre-inflationary period, and the other is the thermal initial state formed at the Planck era of the early Universe. By investigating the observational imprints of these modifications on the B-mode polarization of cosmic microwave background (CMB) radiation, we obtain the constraints on the conformal temperature of the thermal gravitational-wave background $T63.5$ for the model with $w=1/3$, and $N>65.7$ for that with $w=1$. By taking into account various noises and the foreground radiations, we forecast the detection possibility of the thermal gravitational-wave background by the future CMBPol mission, and find that if $r>0.01$, the detection is possible as long as $T>1.5\times 10^{-4}$Mpc$^{-1}$. However, the effect of different $w$ is quite small, and it seems impossible to determine its value from the potential observations of CMBPol mission., 12 pages, 4 figures, JCAP accepted

We have done an experimental study of turbulent thermal convection in water using a cell with a baffle placed at its mid-height, over a range of Ra that spans from 2 × 108 to 2 × 1010. It was found that in this case the large-scale circulation is not able to advect heat between the top and bottom plates and heat has to be carried across the baffle mainly by thermal plumes. Furthermore, the measured Nu still scales with Ra with an exponent consistent with "2/7" for Ra > 1 × 109. For Ra below this value, the scaling of Nu with Ra is more consistent with an exponent of "1/3". The measured temperature PDFs also show signatures of "soft" and "hard" turbulence below and above Ra 1 × 109, respectively.

We perform a forecast analysis on how well a Euclid-like photometric galaxy cluster survey will constrain the total neutrino mass and effective number of neutrino species. We base our analysis on the Monte Carlo Markov Chains technique by combining information from cluster number counts and cluster power spectrum. We find that combining cluster data with CMB measurements from Planck improves by more than an order of magnitude the constraint on neutrino masses compared to each probe used independently. For the LCDM+m_nu model the 2 sigma upper limit on total neutrino mass shifts from M_nu < 0.35 eV using cluster data alone to M_nu < 0.031 eV when combined with CMB data. When a non-standard model with N_eff number of neutrino species is considered, we estimate N_eff, 26 pages 9 figure

The development of solution strategies for Zinc oxide (ZnO) quantum dots provides a pathway to utilizing ZnO nanocrystal thin films in optoelectronic devices. In this work, quasi-spherical ZnO quantum dots with a diameter of 5 nm are synthesized by using ethanol as a solvent. ZnO nanocrystal thin film is obtained by spin-coating ZnO quantum dots on a Au interdigital electrode (IDE)/Al2O3 substrate and annealing at different temperatures in order to yield the optimal photosensitive on/off ratio of ZnO. For further enhancing the responsivity, ion sputtering is utilized to deposit Pt nanoparticles on the surface of ZnO nanocrystal thin film, the responsivity of the ZnO/Pt bilayer nanostructure increases from 0.07 A/W to 54 A/W, showing that the metal/inorganic nanocrystal bilayer nanostructure can be used to improve the performance of optoelectronic devices. The excellent properties of ZnO/Pt bilayer nanostructure have important applications in future electronic and optoelectronic devices.