Abstract: A method and a system for determining a safe under keel clearance of an ultra-large ship are provided. The method comprises: acquiring operation parameter values of the ship; obtaining fluid pressure according to the values; obtaining a squat force and a trim moment of the ship according to the pressure; establishing a mirror image model based on speed potential to establish a squat clearance calculation model for the ship; determining a half-wave rising height with above calculation model; obtaining draught and trim changes according to the squat force and the trim moment, to determine a maximum squat clearance of the hull; determining the safe under keel clearance; and controlling the squat clearance of the ship according to the safe under keel clearance of the ship, to avoid navigation dangers, and improve the loading rate.

Abstract: The invention provides a method for purifying silicon by means of a phase separation dealloying reaction, including: mixing a silicon raw material containing metallic or non-metallic impurities with magnesium powder first and then fully reacting under an inert atmosphere so as to obtain a first product; placing the first product in a nitrogen-containing atmosphere to undergo a nitriding reaction to form three-dimensional porous silicon and magnesium nitride distributed in pore channels thereof so as to obtain a second product, the impurities further being separated during the precipitation and crystallization of silicon, and being dissolved in the liquid-phase magnesium nitride; treating the second product by using acid-pickling, the magnesium nitride and impurities being dissolved and converted into a solution, and a solid product being high-purity porous silicon.

Abstract: The present disclosure provides a method for determining free radicals of CaO—Al2O3 series oxide melts. The method includes dividing the CaO—Al2O3 series oxide powder to into two aliquots by mass, putting into two identical corundum crucibles and tamping. The method also includes heating the two aliquots at the same high temperature in furnaces with and without a static magnetic field, respectively. Cylindrical samples with the same diameter and height, and only containing the melt at the bottom of the crucible and the slag reaction interface are drilled out from said two crucibles and ground into powder samples. The free radical relative content of the CaO—Al2O3 series oxide melts can be calculated from a ratio between the difference of the reaction mass contents of CaO in the two powder samples and the total mass content of CaO.

Abstract: The present invention provides a method for synergistically vitrifying medium and low-level radioactive glass fibers and combustible solid nuclear waste incineration ashes. According to the chemical composition characteristics of incineration ashes of combustible solid wastes such as glass fibers, cotton, plastic, rubber and absorbent paper produced during the operation of nuclear facilities, the present invention takes the glass fibers as a glass matrix of combustible waste incineration ashes and minimizes the addition of an additive by a combination in different proportions through a synergistic treatment method. A vitrified form provided by the present invention meets the requirements of uniformity, density, impact resistance, chemical durability and the like of radioactive waste vitrified forms.

Abstract: The present invention discloses a distributed pulsed light amplifier based on optical fiber parameter amplification, comprising a pump pulsed light source, a sensing pulsed light source, a synchronization device, a two-in-one optical coupler, an optical circulator, a parameter amplification optical fiber, a first optical filter, a photoelectric detector and a signal acquisition device. According to the distributed pulsed light amplifier, high-power pulsed light is used as pump light to generate an optical fiber parameter amplification effect near a zero-dispersion wavelength of an optical fiber, thereby amplifying a power of another sensing pulsed light. Meanwhile, due to the fact that effective optical fiber parameter amplification cannot be achieved through low-power light leakage outside a duration interval of the pump pulsed light, leaked light from the sensing pulsed light cannot be amplified, and the effect of amplifying a pulse extinction ratio can be achieved at the same time.

Abstract: A nonlinear resonance model-based active filtering crane steel rope resonance elimination control method, including: constructing a two-dimensional dynamic model of a bridge crane according to a Lagrange's equation; constructing a steel wire rope-motor nonlinear resonance model to detect a harmonic; and eliminating the harmonic by means of active filtering. The present disclosure makes in-depth study on positioning of a crane and intelligent control of an anti-swing and resonance elimination control system and uses active filtering to eliminate resonance between a heavy object and the steel wire rope, thereby reducing a swinging angle and achieving the rapid resonance elimination and anti-swing effect. The active filtering technology can quickly and effectively detect a resonance current so as to effectively suppress resonance between the heavy object and the steel wire rope, and further helps a controller quickly and accurately position a trolley to further improve anti-swing performance.

Abstract: A method and a system for diagnosing a fault of a three-phase three-level rectifier are relate to the technical field of fault diagnosis of power electronic equipment, and provided to implement identification and location of an open-circuit fault of a power switching device thereof. A deviation between an expected value and an actual value of a phase-to-phase voltage is adopted as a diagnosis variable. The diagnosis variable is calculated by adopting a screening technique, thereby reducing calculation error to ensure accuracy of diagnosis. Only existing voltage current signals in a control system of the rectifier are required to calculate the diagnosis variable, so no additional hardware is required and low-cost fault diagnosis can be implemented. Different voltage thresholds are adopted for different fault characteristic sections, and the voltage thresholds are updated in real time according to a direct current side voltage, which improves diagnosis speed while ensuring higher robustness.

Abstract: A transformer fault diagnosis and positioning system based on a digital twin is provided and includes the following. A communication sensing module, which is configured to transmit bottom-level monitoring data obtained from a device entity to a system support module. The system support module, which is configured to receive and preprocess bottom-level monitoring data, and store various data, models and expert systems. A dynamic twin module, which is configured to analyze a multi-dimensional probability status of a device fault, construct a dynamic degradation model of different health states, and realize model correction through human-computer interaction, real-time measurement, and dynamic update subsequently. A decision-making diagnosis module, which is configured to construct a digital twin of data to be diagnosed, to realize diagnosis and positioning of the health state.

Abstract: A method for laser-induced growth of nano-units to form oriented, chiral, and complex structures is provided. Through a laser-induced photochemical reaction, a metal precursor undergoes photolysis to produce inorganic nanoparticles, and these nanoparticles are orientally deposited on a substrate along a polarization direction in a linearly polarized laser to form fusiform nano-units. Through mixed polarized light generated by a vortex plate, the nano-units can grow rapidly and form a specific arrangement to obtain special three-dimensional (3D) nanostructures with chiral features and complex patterns. This method can be implemented in a room temperature environment, has the characteristics of simple operation, short reaction time, high repeatability, long storage time, low cost, and controllable orientations and sites, and shows promising application prospects in the fields of optical devices, chiral catalysis, sensing, integrated circuits, and the like.

Abstract: The invention discloses a calcium-alumino-silicate-hydrate nano-seeds suspension and preparation method thereof. The preparation method of calcium-alumino-silicate-hydrate nano-seeds suspension includes the following steps: dropwise adding the aqueous solution of calcium source, the aqueous solution of silicon source and the aqueous solution of aluminum source to the solution of polycarboxylate superplasticizer, and adjusting the pH value to 10.0˜13.5, and continuously stirring to obtain the calcium-alumino-silicate-hydrate nano-seeds suspension. The beneficial effect in the present invention is: the calcium-alumino-silicate-hydrate nano-seeds has small particle size, good dispersion stability, and it can effectively improve the early hydration and mechanical performance of cement-based materials, and has good application prospects; the preparation process is simple, without washing, drying, ultrasonic dispersion and other subsequent processes, suitable for large-scale production.

Abstract: An optical fiber grating sensing method applied to small-scale fire source monitoring are provided, distinguishing two concepts of a spatial resolution and a perception resolution, under the premise of ensuring the spatial resolution of a traditional fiber Bragg grating sensing system, only increase the number of fiber Bragg gratings covered by a single pulsed optical signal without changing a pulse width of a pulsed optical signal, so as to improve the perception resolution of the system without increasing the requirements for a hardware circuit, and truly shorten an interval between adjacent fiber Bragg gratings. Improving the perception resolution of the system, which not only ensures the spatial resolution of the system, but also realizes the monitoring of small-scale fire sources; by adopting a simple feature extraction algorithm to obtain fire temperature information in different areas, the temperature detection speed of the system is fast.

Abstract: A low-complexity precoding method for large-scale MIMO fast convergence is provided. The method includes the following steps: in step 1, starting a precoding procedure to initialize relevant parameters of an MIMO transmitting antenna; in step 2, accelerating a symmetric successive over-relaxation algorithm through a Chebyshev semi-iterative algorithm to complete a precoding inversion process according to the initialized parameters; and in step 3, generating a signal to be transmitted of the MIMO transmitting antenna according to a result of the iterative algorithm and ending the precoding procedure. Herein, the step of initializing the parameters includes parameter initialization and setting a number of transmitting antennas, a number of single-antenna users, and a channel transmission matrix.

Abstract: A reliability evaluation method and system for a microgrid inverter IGBT based on segmented long short-term memory (LSTM) is disclosed, including steps as follows. An electrothermal coupling model is constructed to obtain real-time junction temperature data. The original LSTM algorithm is improved to obtain a segmented LSTM prediction network for the aging characteristics of the IGBT. The monitoring value of the IGBT aging parameter is used to perform segmented LSTM prediction to obtain the predicted aging process, and the threshold values of different aging stages are categorized. An aging correction is performed on the aging parameter of the electrothermal coupling model to ensure the accuracy of the junction temperature data. Rainflow-counting algorithm is used to calculate real-time thermal stress load distribution of the IGBT. The fatigue damage theory and the Lesit life prediction model are combined to calculate the real-time cumulative damage and predicted life of the IGBT.

Abstract: A method and a system for vector-raster overlay analysis of a ground surface image area based on edge clipping are provided. A large amount of computing resources is required during the calculation of extracting a ground surface image area using the vector-raster overlay analysis and a loss of accuracy is resulted when vector data is converted into raster data, thereby leading to the issue of calculation error of a polygon surface area. The disclosure adopts the vector-raster overlay analysis method while cropping an edge vector polygon of the ground surface image to be measured and allocating an attribute value of the image according to a pixel, so as to accurately calculate the ground surface image area without drastically increasing the amount of calculation, thereby achieving the function of improving the accuracy and efficiency of calculating the ground surface image area.

Abstract: A method and a system of identifying and estimating a complex analog circuit failure, belonging to the field of power electronic circuit failure prediction. The method includes the following steps: building a degradation simulation model of an analog circuit to be diagnosed, performing a parameter aging simulation experiment on different devices; extracting a time domain feature of each of output signals by using a time-series transformation method, building a health index of each of the devices based on angle similarity; identifying whether the analog circuit to be diagnosed is degraded and a starting point of degradation by combining a time moving window and a convolutional neural network; multiplexing part of hidden layers of the convolutional neural network and a long short term memory-recurrent neural network to estimate a health state of a degraded analog circuit; and evaluating prediction accuracy.

Abstract: The present disclosure relates to a magnesium-based raw material with low thermal conductivity and low thermal expansion and a preparation method thereof. According to the technical solution, 40-60 wt % fused magnesia particles, 30-40 wt % fine monoclinic zirconia powder, 5-20 wt % fine zirconium oxychloride powder, 0.5-1.5 wt % calcium hydroxide nanopowder, 0.2-0.5 wt % calcium hydroxide nanopowder, and 0.1-0.3 wt % maleic acid are stirred for 15 min to mix well in a high-speed mixing mill at a constant temperature of 25° C. to obtain a mixed powder; and the mixed powder is mixed through a ball mill at a constant temperature of 25° C. for 3 min, roasted in a high temperature furnace at 250-400° C. for 0.5-3 h, and finally cooled to room temperature. The magnesium-based refractory material prepared has the advantages of relatively low thermal conductivity, low thermal expansion coefficient, excellent dispersibility, and strong resistance to slag penetration and erosion.

Abstract: A method, including: 1) inputting a multi-story point cloud, and segmenting a story and an inter-story connection region based on an elevation histogram of the point cloud in a vertical direction; 2) segmenting rooms for each story based on a grid map projected onto an XOY plane respectively, wherein the XOY plane is parallel to a flooring; 3) segmenting indoor space cells for each story based on a vector wall line respectively; constructing a vector indoor plan based on superimposition of the vector and the grid for each story respectively; and 5) establishing a three-dimensional model of a multi-story structure by deleting an overlapping surface between the story and the connection region according to the Boolean intersection.

Abstract: The disclosure discloses a multi-time-scale reliability evaluation method of a wind power IGBT considering fatigue damage and a system thereof. Lifetime information of a power device is comprehensively extracted by using multiple time scales. An electro-thermal coupling model of an IGBT module is established to obtain a junction temperature data. A steady-state junction temperature database of the IGBT in different aging states is established. Based on a SCADA monitoring data, the junction temperature data is outputted in real-time through the electro-thermal coupling model and a real-time thermal stress cycle number is calculated in a short-term time-scale profile, and a wind speed probability distribution curve is obtained in a long-term time-scale profile. A maximum thermal stress cycle number that the IGBT can withstand in different aging stages is obtained in advance and a cumulative damage degree and an estimated lifetime of the IGBT of the wind power converter are calculated.

Abstract: The invention discloses an artificial nacre material with layered structure and preparation method thereof. The preparation method includes the following steps: uniformly mixing a carbonated cementitious material and water at a water-solid ratio of 0.3 to 1.2 to obtain a carbonated cementitious material suspension; treating the carbonated cementitious material suspension by a freeze-casting process to obtain a carbonated cementitious material coagulation with layered structure; treating the carbonated cementitious material coagulation with the layered structure by a freeze-drying process to obtain a carbonated cementitious material with layered structure; treating the carbonated cementitious material with layered structure by a carbonization process to obtain an artificial nacre material with layered structure.

Abstract: A method of preparing a cement hydration product nano-thin film, the method including: (1) preparing a cement hydration product; (2) preparing a water sacrificial layer film; (3) depositing the cement hydration product obtained in (1) on the surface of the water sacrificial layer film obtained in (2) to obtain a cement hydration product film; and (4) immersing the cement hydration product film in a saturated aqueous solution of calcium hydroxide to dissolve the water sacrificial layer film to obtain a nano-thin film of the cement hydration product.