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The monitoring of bolt looseness is crucial to ensure the safety and reliability of structures. Prior studies have demonstrated that the vibro-acoustic modulation (VAM) method based on the nonlinear ultrasonic theory is sensitive to the early looseness of bolted connections. However, one limitation of the traditional VAM method is that the low frequency (LF) and high frequency (HF) for excitation should be specified in advance. The resonant frequency of the bolted structures changes after loosening, leading to inaccuracies in monitoring results if pre-specified excitation frequencies are used and not adapted to the new situation. To address this limitation, this paper improves the VAM method by using swept sine signals for both LF and HF excitations and relying on the bispectrum energy of the measured response to indicate the bolt pre-load. A steel bolted connection was fabricated and loaded on a universal testing machine to simulate different bolt pre-loads. Three low-cost lead zirconate titanate patches served as the LF actuator, HF actuator and sensor in the experiment. The experimental results demonstrate that the improved VAM method can evaluate the bolt looseness with better efficiency and robustness than the traditional VAM methods which use fixed frequencies as excitations. Therefore, the proposed method in this paper can potentially monitor the damages in complex structures based on nonlinear ultrasound theory.

We study the strong nonlinear optical dynamics of nanosecond pulsed Laguerre–Gaussian laser beams of high-order radial modes with zero orbital angular momentum propagating in the fullerene C60 molecular medium. It is found that the spatiotemporal profile of the incident pulsed Laguerre–Gaussian laser beam is strongly reshaped during its propagation in the C60 molecular medium. The centrosymmetric temporal profile of the incident pulse gradually evolves into a non-centrosymmetric meniscus shape, and the on-axis pulse duration is clearly depressed. Furthermore, the field intensity is distinctly attenuated due to the field-intensity-dependent reverse saturable absorption, and clear optical power limiting behavior is observed for different orders of the input pulsed Laguerre–Gaussian laser beams before the takeover of the saturation effect; the lower the order of the Laguerre–Gaussian beam, the lower the energy transmittance.

Due to the unavoidable interaction between the quantum channel and its ambient environment, it is difficult to generate and maintain the maximally entanglement. Thus, the research on multiparty information transmission via non-maximally entangled channels is of academic value and general application. Here, we utilize the non-maximally entangled channels to implement two multiparty remote state preparation schemes for transmitting different quantum information from one sender to two receivers synchronously. The first scheme is adopted to transmit two different four-qubit cluster-type entangled states to two receivers with a certain probability. In order to improve success probabilities of such multicast remote state preparation using non-maximally entangled channels, we put forward the second scheme, which deals with the situation that is a synchronous transfer of an arbitrary single-qubit state and an arbitrary two-qubit state from one sender to two receivers. In particular, its success probability can reach 100% in principle, and independent of the entanglement degree of the shared non-maximally entangled channel. Notably, in the second scheme, the auxiliary particle is not required.

Regarding a phase-only Fourier hologram, coherent illumination is required in its optical reconstruction. However, this requirement faces a challenge in lensless Fourier-transform correlated imaging with thermal sources. In this research, a correlated reconstruction scheme for the phase-only Fourier hologram with spatially incoherent illumination by utilizing intensity fluctuation correlation measurements is proposed. Numerical simulation and optical experiments were conducted to verify the feasibility of the correlated reconstruction scheme. Because the proposal requires neither a coherent light source nor a lens, holographic reconstruction can circumvent the limitation of the spatial coherence light source and the influence of lens aberrations.

Automobile braking system is an important guarantee for automobile driving safety, and improving automobile braking performance is an important task in automobile development. ESP system can effectively reduce the accident rate and improve driving safety. This paper systematically introduces the development of vehicle stability control technology from four aspects: dynamic modeling, state observation, control strategy and industrialization. It mainly introduces the state observation and control strategy.

Using a portable manipulator to take out the recovery crucible from the rare earth redox bath, its reliability is one of the bottlenecks restricting production automation. According to the production process of praseodymium and neodymium alloy, determine the mechanism design, and analyze the force to determine the motor selection. The manipulator model is established in the SolidWorks environment, the communication interface is compatible, and the adams software is imported to conduct dynamic simulation analysis of the manipulator mechanism. The manipulator opens and closes smoothly, and the output clamping force meets the theoretical value requirements. The motor is selected to meet the requirements of use.

Due to the continuous upgrading and optimization of fishing technology and tools, and the diversification of fishing vessel operation methods, marine fishery resources are continuously depleted. Precise prediction of the operation methods of marine fishing vessels is helpful to realize effective supervision of fishing behavior of fishing vessels. In order to improve the prediction accuracy, when doing feature engineering, this paper uses a vector encoding scheme based on trajectory sequence, and uses text vectors to train the word2vec model to calculate the embedding features of each position. At present, the single method needs to be improved in terms of forecasting accuracy. This paper proposes a forecasting method based on Stacking model fusion in order to further improve the forecasting accuracy of marine fishing vessel operations. The experimental results show that the Stacking fusion model using the vector coding scheme based on the trajectory sequence has a greater improvement in prediction accuracy than a single model.

We investigate the quantum dynamics of two defect centers in solids, which are coupled by vacuum-induced dipole–dipole interactions. When the interaction between defects and phonons is taken into account, the two coupled electron–phonon systems make up two equivalent multilevel atoms. By making Born–Markov and rotating wave approximations, we derive a master equation describing the dynamics of the coupled multilevel atoms. The results indicate the concepts of subradiant and superradiant states can be applied to these systems and the population transfer process presents different behaviors from those of the two dipolar-coupled two-level atoms due to the participation of phonons.

Chirp signal is widely used in communication, radar, sonar and ultrasonic systems. The impulse response of channel must be estimated in PSK chirp spread spectrum modulation systems which is a chirp signal multiplied by the PSK modulated signal. Due to the influence of filters and multipath channel, the received signal of current symbol will be affected by the interference of the previous symbol and the next symbol, the interference which is called inter-symbol interference (ISI) can degrade the performance of channel estimation and demodulation. In this paper, based on BPSK chirp spread spectrum modulation system, we describe the received model, the channel estimation based on FFT and channel estimation of matched filtering, analyze the impacts of ISI on channel estimation. And we simulate the MSE of channel estimation and the simulation results are consistent with the analysis, then an improved method of channel estimation is proposed based on the analysis of the impact of ISI on channel estimation.

Quantum sensing has been receiving researcher’s attention these years due to its ultrahigh sensitivity and precision. However, the bandwidth of the sensors may be low, thus limiting the scope of their practical applications. The low-bandwidth problem is conquered by feedback control methods, which are widely utilized in classic control fields. Based on a quantum harmonic oscillator model operating near the resonant point, the bandwidth and sensitivity of the quantum sensor are analyzed. The results give two important conclusions: (a) the bandwidth and sensitivity are two incompatible performance parameters of the sensor, so there must be a trade-off between bandwidth and sensitivity in practical applications; (b) the quantum white noise affects the signal to be detected in a non-white form due to the feedback control.

The validity of the transformer area’s file in the Power information acquisition system is very important, the man-made way is time-consuming, and the cost of relying on the equipment is high. In order to provide efficient, convenient and economical identification technology of the transformer area archives, this paper proposes a low voltage topology recognition method based on differential Lasso, which can complete automatic topology recognition only by using the power consumption information of the transformer area. First of all, the statistical model of Lasso is established for the data of electricity consumption. According to the characteristics of the meter in the meter box belonging to the same area, the differential Lasso model is further constructed. The regression coefficient based on the differential lasso can be calculated for each transformer area in turn by polling, and select the meter according to the threshold. The method of this paper is used to analyze the field collected electricity data. The results of topology recognition show the effectiveness of the proposed method.

The magnetic phase diagram of rare-earth perovskite compound, GdScO3, has been investigated by magnetization and heat capacity. The system undergoes an antiferromagnetic phase transition at T N = 2.6 K, with an easy axis of magnetization along the a axis. The magnetization measurements show that it exists a spin-flop transition around 0.3 T for the applied field along the a axis. The critical magnetic field for the antiferromagnetic-to-paramagnetic transition is near 3.2 T when temperature approaches zero. By scaling susceptibilities, we presume this point (B = 3.2 T, T = 0 K) might be a field-induced quantum critical point and the magnetic critical fluctuations can even be felt above T N.

In this paper, we demonstrate a three-axis atomic magnetometer based on parametric oscillations, which can measure the three magnetic field components simultaneously and independently. A circularly polarized pump beam is applied to create the spin polarization, and another linearly polarized probe beam is used to detect the dynamics of the polarized spin under a magnetic field. With a closed-loop system to keep the magnetic field in resonance with the atoms, three components of magnetic field are measured by their feedback signals. We achieve a magnetometer sensitivity of 6 pT ()−1, 25 pT ()−1, and 60 pT ()−1 along three axes in the frequency range from 100 Hz to 1 kHz with a bandwidth better than 1 kHz under an unshielded environment. Furthermore, this magnetometer is free of optical modulation, which reduces the complexity of experimental setups. The methods we present here provide a prototype all-electrical three-axis atomic magnetometer.

Si has been considered as one of the most potential new-generation anode materials for high-capacity lithium-ion batteries. However, the lithiation and delithiation of lithium ions during the charge-discharge processes of the Si electrode would give rise to almost four-fold volume expansion, causing structural changes and cracks of the conductive network, limiting the application of Si-based anode material. In this paper, the lithium ions inserting into Si material at various positions and at different doping concentrations of lithium ions was studied by first-principles method. The stability of different insertion sites, the structural changes, band structures and density of States after Li insertion were analyzed. It has been found that the lithium ions doping is an interstitial doping rather than a substitutional one and the tetrahedral center (Td) site is the most stable insertion position. From the band structure analysis, it can be seen that the Si material with the insertion of lithium ions becomes metal-like, and as the concentration changes, silicon changes from an indirect gap semiconductor to a direct gap semiconductor. When the concentration reaches 12.5%, the structural expansion rate increases obviously. This work provides a strategy for the improvement of the Si based anode material used in high-capacity lithium-ion batteries.

Atomic magnetometers are becoming the most sensitive sensors for magnetic field detections and have found applications in various fields. In nuclear magnetic resonance gyroscope (NMRG), researchers usually use an embedded atomic magnetometer to sense the transverse magnetic fields generated by the precessing nuclear spins. The additional spin-exchange and spin-destruction collisions between alkali-metal and inert gas atoms reduce the coherence time $\tau$ of the alkali-metal atom spins. In addition, in order to achieve an NMRG of high sensitivity, a relatively small bias magnetic field needs to be applied, thus giving a low Larmor frequency $\omega_{0}$ of the alkali-metal atom spins. These two factors violate the condition $\omega_{0}\tau\gg1$. In this paper, we systematically study the performance of this embedded atomic magnetometer when the product $\zeta=\omega_{0}\tau$ is on the order of unity. We demonstrate that the sensitivity of the magnetometer depends on two dimensionless parameters $\zeta$ and the modulation depth $\eta$ when the system is on resonance.a#13; We then find the key factor to achieve the best sensitivity of the magnetometer is to choose an optimized $\eta$ value. As an application of our results, we consider the demodulation phase in NMRG, where the Lamror frequency of the nuclear spins is to be determined by the magnetometer. We give an analytical expression of the demodulation phase, with which one can get maximal nuclear magnetic resonance signals.

As a major way to consume new energy, energy transmission across provinces and regions has increased rapidly in recent years. It is of great importance for the construction of the spot market to study the impact of different uncertainty of the outside power on the joint energy and reserve market. Firstly, this paper establishes a joint energy and reserve market equilibrium model that takes into account the uncertainty of the outside power which leads to additional reserve demand. Secondly, a game equilibrium algorithm is proposed to solve the market final equilibrium. The simulation results show that the uncertainty of the outside power will not only reduce market efficiency but also damage the interests of the outside new energy generator itself.

Ambient mechanical energy is one of the most abundant energy sources around us. It is a promising approach to solve the problem of energy and environment by harvesting such energy due to its cost-effectiveness, environmental friendliness and sustainability. Recently, triboelectric nanogenerator (TENG) has been proposed as an effective and promising technology for harvesting ambient mechanical energy. Herein, a coaxial rotatory-freestanding TENG (CRF-TENG) was developed and its theoretical model was constructed. An approximate V–Q–α relationship was derived and the explicit analytical solutions of the transferred charge, output current, voltage and average power are obtained from numerically calculation. Finally, to verify the theoretical results, the real output performances of as-fabricated CRF-TENG were measured. The experimental results are consistent with the theoretical ones. The newly developed TENG mode greatly expands the applicability of TENGs for harvesting energy from ambient rotating mechanical motion.

Recently, silver nanoparticles decorated with graphene and graphene oxide (GO) sheets can be employed as surface-enhanced Raman scattering (SERS) substrates. However, their SERS activity on macromolecular compound detection is all one-time process. In order to solve this issue and decrease the cost of routine SERS detection, silver/silver chloride (Ag/AgCl) with photocatalytic activity under visible light was introduced. In this study, a novel, simple and clean approach is carried out for synthesis of the Ag/AgCl/GO composite. The Ag/AgCl colloidal solution is obtained by hydrothermal method and then mixed with GO solution to obtain the Ag/AgCl/GO composite using a facile electrostatic self-assembly method. Results showed that the Ag/AgCl/GO composite has the optimized SERS activity to Rhodamine 6G molecules with the maximum enhancement factor value of 3.8×107. Furthermore, the Ag/AgCl particles with high efficient and stable photocatalytic activity under visible light lead to an outstanding self-cleaning property of the Ag/AgCl/GO composite.

We investigate the enhanced electric dipole-dipole interaction by surface plasmon polaritons (SPPs) supported by the planar metal film waveguide. By taking two nitrogen-vacancy (NV) center electric-dipoles in diamond as an example, both the coupling strength and collective relaxation of two dipoles are studied with numerical Green Function method. Compared to the two-dipole coupling on planar surface, metal film provides stronger and tunable coupling coefficients. Enhancement of the interaction between coupled NV center dipoles could have applications in both quantum information and energy transfer investigation. Our investigation provides a systematical result for experimental applications based on dipole-dipole interaction mediated with SPPs on planar metal film., 8 pages, 7 figures

With the explosive growth of network services, the reasonable traffic scheduling and efficient configuration of network resources have an important significance to increase the efficiency of the network. In this paper, an adaptive traffic scheduling policy based on the priority and time window is proposed and the performance of this algorithm is evaluated in terms of scheduling ratio. The routing and spectrum allocation are achieved by using the Floyd shortest path algorithm and establishing a node spectrum resource allocation model based on greedy algorithm, which is proposed by us. The fairness index is introduced to improve the capability of spectrum configuration. The results show that the designed traffic scheduling strategy can be applied to networks with multicast and broadcast functionalities, and makes them get real-time and efficient response. The scheme of node spectrum configuration improves the frequency resource utilization and gives play to the efficiency of the network.

Analysis in 27 cities across China shows that surface solar irradiance (SSI) and wind speed track similar decadal trends in 1961–2011, suggesting wind speed as a possible regulator of SSI. This assumption is further confirmed by the continuously widening gap in annually averaged daily SSI between windy and windless clear-sky days with worsening air pollution. Wider gaps are noted for more polluted cities and seasons. The gap in SSI between windy and windless conditions could therefore serve as a good indicator for air quality. The regulatory effect of wind speed on SSI starts to be important when air pollution index exceeds the boundary of 125. A plausible mechanism of wind speed regulating SSI through interactions with aerosols is proposed. There are two cut-off points of 2.5 m s−1 and 3.5 m s−1 wind speeds. Winds

This paper presents a novel in-plane photonic crystal channel drop filter. The device is composed of a resonant cavity sandwiched by two parallel waveguides. The cavity has two resonant modes with opposite symmetries. Tuning these two modes into degeneracy causes destructive interference in bus waveguide, which results in high forward drop efficiency at the resonant wavelength. From the result of numerical analysis by using two-dimensional finite-difference time-domain method, the channel drop filter has a drop efficiency of 96% and a Q value of over 3000, which can be used in dense wavelength division multiplexing systems.

Exciton levels and fine-structure splitting in laterally coupled quantum dot molecules are studied. The electron and hole tunnelling energies as well as the direct Coulomb interaction are essential for the exciton levels. It is found that fine-structure splittings of the two lowest exciton levels are contributed by the intra- and interdot exchange interactions which are greatly influenced by the symmetry and tunnel-coupling between the two dots. As the interdot separation is reduced, fine-structure splitting of the exciton ground state is largely increased while those of the second and fourth states are decreased. Moreover, the dependence of the fine-structure splitting in quantum dot molecules on the Coulomb correlation is clearly clarified.