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Gas steam boilers are special equipment subjected to high temperature and pressure, it is particularly important to detect and deal with operation faults in time. Against the 4 types of common fault of gas steam boilers, the fault diagnosis model was established based on deep neural networks (DNN), and the model parameters were optimized and verified by experiments. The results show that the fault diagnosis model performs the best as Tanh of the activation function, 100 of Batch_Size, Adam of Optimizer, 10-5 of learning rate and 0.2 of Dropout since the output accuracy is above 92% and the model begins to converge with iterative times of 12. The accuracy of fault identification of reaches 100% in verification experiments and the model can still effectively recognize the dataset from the early stage which suggests that the fault diagnosis based on deep neural networks has high accuracy and provides a reliable solution for the safety supervision of special equipments.

The first-order phase transitions in coupled oscillators have been widely studied because of their discontinuity and irreversibility. In previous research, the designed coupling mechanisms between each pair of oscillators can cause the first-order phase transitions occur stably. In the present study, we propose a new mechanism which requires the existence of an inversely proportional relationship between the natural frequencies and the intrinsic amplitudes in the homogeneously coupled oscillators. Based on two classical oscillator models, i.e., the Poincaré model and the Stuart–Landau model, the emergence of explosive oscillation death is independent of the frequency distributions. Our findings indicate that the first-order phase transitions can be induced by the frequency-amplitude correlation for the first time. Therefore, it provides a novel perspective to understand explosive phenomena in coupled oscillators.

The increasing occurrence of flash droughts with rapid onsets poses a great threat to food security and ecosystem productivity. While temporal trends in flash droughts have been extensively studied, the contributions of climate warming, vegetation greening, and the physiological effect of rising CO2 to trends in flash drought characteristics remain unclear. Here we show there are significant increasing trends in flash drought frequency, duration, and intensity for most of China during 1961–2016. Warmer temperatures and vegetation greening increase evapotranspiration and decrease soil moisture, and explain 89% and 54% of the increasing frequency of flash drought respectively. Rising CO2 concentrations reduce stomatal conductance, which acts to decelerate the increasing drought frequency trend by 18%, whereas the physiological effects of rising CO2 on flash drought duration and intensity are smaller. Warming also outweighs vegetation greening for the increasing trends of flash drought duration and intensity over most of China, except North China. Our study highlights the role of climate warming in increasing the risk of flash droughts.

Based on the multivariable dynamic matrix control algorithm, there are many similarities between the dynamic matrix control algorithm and LQR in the form of state equation, state variable and objective function. We can use the objective function of LQR to improve the objective function of DMC and improve the control effect of the system. Using the given mathematical model, the terminal weighting matrix of LQR is applied to DMC algorithm, and the optimized multivariable dynamic matrix control algorithm is simulated. The results show that the algorithm can effectively reduce the response time of the system, make the system sink faster and reach the given value faster.

The sand casting process of 18CrNiMo7-6 gate valve casting was designed in this paper. The molding and core making methods of castings are sodium silicate CO2 method and self hardening cold box method respectively. The technological parameters of the casting were determined. The middle pouring system and top riser were designed. Using software to draw the assembly and 3D entity of gate valve casting. ProCAST simulation software is used to realize the numerical simulation task of the gate valve casting process. Shrinkage and porosity are the main research objects. It is found that the defects mainly appear in the thick part of the casting and the flange through the simulation experiment feedback parameters. In this paper, from the point of view of reducing and avoiding defects, the casting process is improved and improved. Finally, according to the experimental results, S2 (with chill) is determined as the final scheme.

With the gradual deepening of power market reform, the top-level design of the market has been basically completed. According to the requirement of "Deepening Design Of National Unified Power Market", the ultimate goal of the power market in China is to establish a national unified operation mechanism of power market, so as to break down inter-provincial barriers, and finally realize the optimize configuration of power resources in a wider range. In this paper, based on the simplified model of national power grid, an optimal clearing model of the unified national power market with the province as the agent is established, and the validity of the proposed model based on practical scenario is verified.

At present, UAV photogrammetry technology is gradually applied in the field of Airport project survey, which improves the efficiency and accuracy of measurement, and ensures the overall effect of airport construction. The traditional manual measurement method is inefficient and easy to be interfered by other factors, so it is difficult to meet the needs of large-scale, high-efficiency and high-precision measurement of airport construction. UAV photogrammetry improves the efficiency and accuracy of measurement, which can provide important reference for airport construction.

This paper introduces the abnormal natural frequency at the end of a large-scale air-cooled generator in a power generation company, analyzes the abnormal vibration frequency data at the end of the generator, and solves them successfully, which provides a reference for the state analysis of new high power phase modifier.

As a research hotspot, wireless sensor network (WSN) has a wide range of application prospect. The non-line of sight (NLOS) localization is one of the most basic techniques. In order to mitigate the NLOS influence and increase the localization accuracy, we proposes an improved VB-AKF algorithm in this paper. Firstly, the propagation state of the signal is identified. Then, for the LOS and NLOS mix environments, we reduce the NLOS error by changing the attenuation coefficient. And the maximum likelihood (ML) method is used for localization. Finally, the simulation results show that our method can effectively obtain higher localization accuracy.

According to the requirements of relevant national standards, large photovoltaic grid connected inverters need to have zero voltage ride through (ZVRT) capability to prevent low voltage automatic disconnection, thus affecting the normal and stable operation of power system. On the basis of analyzing the ZVRT standard of PV grid connected inverter, the key technologies of inverter realizing ZVRT are discussed in detail, including grid voltage positive and negative sequence separation and phase locking, active and reactive current control of inverter, system control under unbalanced grid voltage and so on. On this basis, it is further proposed that the grid voltage feed forward component phase lead compensation link should be introduced into the system current loop, so as to improve the transient overshoot of grid connected fault. Finally, the correctness and effectiveness of the ZVRT control strategy of the PV grid connected inverter is verified by the experimental results of RTDS and a 500 kW prototype.

In this paper, we propose a novel concept, stochastic basin stability, to investigate the stability of dynamical systems under random noises. By this concept, we investigate synchronization of multistable second-order Kuramoto models under continuously acting perturbations in complex networks. By a mean-field approach and the Fokker-Planck equation, we derive formulas of the density functions of both phase and frequency. Based on them, we provide an analytical treatment of stochastic basin stability and illustrate that the theoretical results are in good agreement with numerical simulations. This proposed concept integrates the perturbations of both initial condition and random intervention, and paves a general and efficient approach for analytically and numerically investigating stability of stochastic dynamical systems.

We present here an adaptive control scheme with a feedback delay to achieve elimination of synchronization in a large population of coupled and synchronized oscillators. We validate the feasibility of this scheme not only in the coupled Kuramoto's oscillators with a unimodal or bimodal distribution of natural frequency, but also in two representative models of neuronal networks, namely, the FitzHugh–Nagumo spiking oscillators and the Hindmarsh–Rose bursting oscillators. More significantly, we analytically illustrate the feasibility of the proposed scheme with a feedback delay and reveal how the exact topological form of the bimodal natural frequency distribution influences the scheme performance. We anticipate that our developed scheme will deepen the understanding and refinement of those controllers, e.g. techniques of deep brain stimulation, which have been implemented in remedying some synchronization-induced mental disorders including Parkinson disease and epilepsy.

A compact diode-end-pumped passively Q-switched Nd3+:GdVO4/Cr4+:YAG self-Raman laser at 1176?nm is demonstrated. When the T0 = 80% Cr4+:YAG saturable absorber is inserted into the cavity, the maximum Raman laser output reaches 175?mW with 3.8?W incident pump power. The optical conversion from incident to the Raman laser is 4.6% and the slope efficiency is 6.5%. The pulse energy, duration, and repetition frequency of the first stokes laser are 4.5??J, 1.8?ns, and 38.5?kHz, respectively. There is strong blue emission (about 350?400?nm) can be observed in the Nd3+:GdVO4 crystal when the process of stimulated Raman scattering occurs, which is induced by the upconversion of the Nd3+ ions.

A compact low-threshold Raman laser at 1178 nm is experimentally realized by using a diode-end-pumped actively Q-switched Nd3+:YVO4 self-Raman laser. The threshold is 370 mW at a pulse repetition frequency of 5 kHz. The maximum Raman laser output is 182 mW with the pulse duration smaller than 20 ns at a pulse repetition frequency of 30 kHz with 1.8 W incident power. The optical efficiency from the incident power to the Raman laser is 10% and the slope efficiency is 13.5%.

Based on the basin of attraction, the basin stability is quantified to measure a system's ability to regain an equilibrium state subjected to even large perturbations. In this letter, we demonstrate a novel phenomenon uncovered by the basin stability that in complex networks of second-order Kuramoto models successively undergoes two first-order transitions: an onset transition from an unstable to a locally stable synchronous state, and a suffusing transition from a locally stable to a globally stable synchronous state; we call this sequence onset-suffusing transitions. We provide an analytical treatment of basin stability by a mean-field analysis. Our findings are in good agreement with simulations and fundamentally deepen the understanding of stability of microscopic mechanisms towards synchronization.

Large-area, seamless synthetic aperture radar (SAR) mosaics can reflect overall environmental conditions and highlight general trends in observed areas from a macroscopic standpoint, and effectively support research at the global scale, which is in high demand now across scientific fields. The SAR China Land Mapping Project (SCLM), supported by the Digital Earth Science Platform Project initiated and managed by the Center for Earth Observation and Digital Earth, Chinese Academy of Sciences (CEODE), is introduced in this paper. This project produced a large-area SAR mosaic dataset and generated the first complete seamless SAR map covering the entire land area of China using EnviSat-ASAR images. The value of the mosaic map is demonstrated by some potential applications in studies of urban distribution, rivers and lakes, geologic structures, geomorphology and paleoenvironmental change.

A simpler and refined version of effective-medium theory is adopted to calculate the fundamental energy properties of single helium atom in some metals. In this version, the relaxation effects of lattice have been taken into account. The calculated results of some typical energy values agree well with available experimental and other theoretical values.