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During the process of cloud-to-ground lightning connection, the propagation of downward leader to the near-ground area can elevate the electric field at one or several points on the surface of ground tip object to the breakdown threshold of surrounding air, initiating one or more upward leaders, which are known as multiple upward leaders. The emergence of tall buildings has led to an increase in the number of observations of upward lightning strikes on different buildings or the same building. The presence of multiple upward leaders means that multiple parts of the building may be struck. Conducting simulation experiments to study the mechanism of the multiple upward leader phenomenon is of great significance for developing lightning protection. The relative velocity ratio of the downward and upward leaders may be one of the key factors in the lightning connection process. The relative speed ratio of leader propagation in random lightning connection mode cannot accurately describe the relative distance ratio of downward and upward leader propagation. Taking into account the optical observation facts and the electric field environment during thunderstorms, the background electric field module setting is improved on the basis of the existing three-dimensional random mode for multiple upward leaders. It also incorporates a relative propagation speed module for the downward negative and upward positive leaders, establishing the relative propagation speed of leaders according to their propagation distance. Applying the new model to simulate multiple upward leader phenomena triggered by a flat-roofed single building, compared with the previous version, parameters of the new model, such as flash distance and upward leader length, show better consistency with natural lightning. On this basis, the lightning connection process on the high-rise buildings in the Pearl River New Town is simulated, and the improved model can more accurately replicate the lightning occurrence patterns of complex buildings. Characteristic parameters of lightning strikes on urban building clusters are mainly determined by factors such as the shape characteristics, relative position, and relative height of each building. The distance at which lightning strikes buildings is positively correlated with their height. The probability of lightning strikes, the distance of lightning strikes, and other parameters of buildings with similar shapes in the same building group are relatively consistent during ground lightning activities. However, there are still special events that occur when a branch of the downward leader is in close spatial proximity to the building, causing the upward leader to initiate at the top of the building and connect to it.

Tall buildings distort the electric field of the surrounding environment, resulting in a relatively strong electric field at top corners, which affects the lightning strike process, and the protection effect that short buildings receive from tall buildings varies with the distance between them. A three-dimensional fine-resolution lightning attachment model with multiple upward leaders (LAMM) is used to simulate protection effect of a tall building and a short building with different height and distance, with an isolated building set as a control group. Experimental results show that when there is a tall building with a short building in the space and two buildings are close to each other, the distortion range of the tall building almost completely contains the distortion range of the short building, the development of downward leader is completely affected by the tall building, and the shielding effect of the tall building on the short building is significant. With the increase of the building distance, the shielding effect of the tall building on the short building decreases exponentially. When tall building is 250 m high and the short building is 150 m high, probabilities of lightning strikes on short building with distance from 50 m to 600 m with interval of 50 m are 8.3%, 15.0%, 26.5%, 36.7%, 39.5%, 47.5%, 58.9%, 57.0%, 56.0%, 57.2%, 61.0%, and 62.5%. When there is a cut-off point where the increasing trend of the probability of lightning strikes on short buildings appears to slow down significantly, the probability of lightning strikes on short building differs from its probability of lightning strikes in isolation by only 3.6%. Comparing the lightning strike results for different building distance and isolated building, the difference in lightning strike results caused by the presence of tall building decreases from 44.5% to 22.7% when the horizontal distance between tall and short buildings is increased from 400 m to 600 m. Given the height of tall building, the probability of lightning strikes on short building with different heights follows a similar trend from a large increase to a flat increase with an inflection point. Corresponding to short building height from 50 m to 200 m, the horizontal distances reaching cut-off point are 300, 450, 550 m and 600 m, respectively. When two buildings are far separated, the effect of tall building on the probability of lightning strikes on short building is weaker, and it can be assumed that there is a state when tall building have no effect on the lightning attachment process.

The scraper conveyor chain transmission system is prone to frequent faults due to its complex load bearing capacity. However, traditional fault diagnosis requires a large amount of prior knowledge and subjective intervention, which requires high technical personnel. In order to achieve the autonomy, accuracy, and efficiency of fault warning for the scraper conveyor chain transmission system, a fault warning method for the scraper conveyor chain transmission system based on LSTM-Adam is proposed using the powerful data mining capability of deep learning. Firstly, a monitoring system for the working conditions of the scraper conveyor is built based on configuration technology. The system collects real-time operating data of the scraper conveyor, such as the torque and speed of the output shaft of the reducer, the pressure of the middle groove plate, the vibration acceleration in the vertical direction of the scraper, and the strain in the running direction of the scraper chain. The data is cleaned and normalized in min-max to provide data support for fault warning. Secondly, a prediction model is built based on LSTM and trained and optimized using the Adam optimization algorithm to obtain the optimal LSTM Adam prediction model. Finally, the real-time operating data of the scraper conveyor is imported into the LSTM-Adam prediction model to obtain the predicted values of the scraper conveyor operating parameters. The sliding weighted average method is used to calculate the residual between the predicted value and the true value. The maximum residual of the same type of data under normal operating conditions is used as the warning threshold. When the residual exceeds the warning threshold, an early warning is given. The experimental results show that the LSTM-Adam prediction model can accurately predict the trend of strain data of the scraper chain and provide accurate warnings for stuck chain and broken chain faults.

The straightness problem is one of the neck problems in the intelligent construction of the fully mechanized working face. The key to solve this problem is to obtain the position and posture of the scraper conveyor or hydraulic support group. At present, most of the research on the straightness of fully mechanized working face is to discuss the straightness of hydraulic support and scraper conveyor separately. There are problems such as high cost and difficulty in implementation. In order to solve this problem, based on virtual reality(VR) and digital twin(DT) technology, the method to solve the straightness problem of the fully mechanized working face is explored. The hydraulic support, floating connection mechanism and scraper conveyor are considered as a whole system. The straightness solution framework of the fully mechanized working face is built. There are mainly five steps: mechanism analysis, model construction, fusion deduction, reconstruction monitoring and predictive control. It is pointed out that the key to the analysis of the relative position relationship of the fully mechanized supporting equipment is the floating connection mechanism connecting the hydraulic support base and the scraper conveyor. According to the motion characteristics of the floating connection mechanism, it is simplified into a robot model and solved by forward and reverse motion. According to the real coal seam environment, the motion simulation model of fully mechanized mining support equipment based on joints is established in Unity3D, and the VR scene is constructed to realize virtual and real mapping. Through non-contact visual sensor, virtual sensor, virtual-real fusion and other technologies, the information of sensor and point cloud are fused to perform the position and posture deduction of support equipment. Using the technology of virtual and reality interaction, combined with a real physical scenario, a DT system is constructed to achieve virtual monitoring of the fully mechanized working face. The travel distance required to ensure straightness is predicted in the virtual scene and fed back to the physical scene for straightness control.

Perovskite solar cells (PSC) offer a promising solution for building integrated photovoltaics (BIPVs) due to its high photoelectric conversion efficiency (PCE). However, increasing the transparency of their functional layers dramatically decreases the PCE. Here, a computer controlled laser patterning method was proposed to directly turn PSC modules into semitransparent and with aesthetic artificial pattern, without additional complexities to the conventional PSCs fabrication process. A structured ST-PSC achieving a champion PCE of 17.5% with average visible transparency (AVT) of 18.2%, and a mini-module with 5 × 5 cm2 delivering a PCE of 9.1% with AVT of 37.7% were demonstrated. Rationally designed aesthetic patterns were imprinted on mini-modules, achieving a PCE of 14.4%. These results reveal a new route for low-cost facile fabricating high performance large-area aesthetic BIPV modules, and represent a big step forward toward the fabrication of solar cells with high efficiency and high transparency.

In view of problems of low efficiency, poor accuracy and difficulty in reusing and sharing diagnostic knowledge of traditional fault diagnosis methods of mine hoist, a fault diagnosis method for mine hoist spindle system based on ontology was proposed. In view of diversification of fault causes of mine hoist spindle system, a three-dimensional coordinate method is proposed to summarize various fault phenomena and their causes, and the problems such as incomplete fault summary and unreasonable reason analysis are solved; fault diagnosis ontology library is established through Protégé4.3, and fault phenomenon, fault causes and their corresponding logical relationship are stored in ontology library as knowledge, which solves problems of knowledge sharing and reuse of fault diagnosis, and improves efficiency of fault diagnosis; SQL Server 2008 database is used to access monitoring data of the spindle system, and Java persistence layer application program interface JPA and Java application program interface Jena are used to establish mapping between ontology library and database, so as to realize dynamic data exchange of database and ontology library; finally the monitoring data is analyzed through ontology library to determine fault causes and locate fault sources, and then fault diagnosis is realized. The example analysis results show that the fault diagnosis method for mine hoist spindle system based on ontology improves efficiency and accuracy of fault diagnosis, and has high reliability.

Aiming at problem of inaccurate measurement results of existing horizontal shape detection methods for scraper conveyor, a horizontal shape detection method for scraper conveyor was proposed which was based on cooperative position and attitude calculation of shearer and scraper conveyor. Firstly, information of strapdown inertial navigation system was calculated by use of Rodrigues parameter method according to coupling relationship between shearer and scraper conveyor in running process, so as to obtain position and attitude information of shearer when running on scraper conveyor. Then the calculated position and attitude information of shearer and the known heading angle of middle trough of scraper conveyor were substituted into mathematical model of horizontal shape detection for scraper conveyor, thus each heading angle of middle trough of scraper conveyor was calculated, so as to obtain horizontal shape of scraper conveyor. The test results show that detection error of the method is 0-1.5° to heading angle of middle trough of scraper conveyor, and the maximum detection error of horizontal shape of scraper conveyor is 30.70 mm, which meets horizontal shape detection requirements of scraper conveyor.

This article reviews recent progress leading to the generation of optical vortex beams. After introducing the basics of optical vortex beams and their promising applications, we summarized different approaches for optical vortex generation by discrete components and laser cavities. We place particular emphasis on the recent development of vortex generation by the planar phase plates, which are able to engineer a spiral phasefront via dynamic or geometric phase in nanoscale, and highlight the independent operation of these two different phases which leads to a multifunctional optical vortex beam generation and independent spin-orbit interaction. We also introduced the recent progress on vortex lasing, including vortex beam generation from the output of bulk lasers by modification of conventional laser cavities with phase elements and from integrated on-chip microlasers. Similar approaches are also applied to generate fractional vortex beams carrying fractional topological charge. The advanced technology and approaches on design and nanofabrications enable multiple vortex beams generation from a single device via multiplexing, multicasting, and vortex array, open up opportunities for applications on data processing, information encoding/decoding, communication and parallel data processing, and micromanipulations.

For problems of inaccurate shearer position and attitude adjustment, a shearer position and attitude adjustment method based on strapdown inertial navigation system was researched on the ground with slowly varied angle. Firstly, shearer position technology was introduced, namely strapdown inertial navigation system obtained motion parameters of shearer for further processing by Euler angle method, so as to complete attitude solution and real-time position of shearer. Then, an attitude adjustment method based on strapdown inertial navigation system was introduced by taking cutting height adjustment of shearer as an example, and relation between cutting height and body dip angle of shearer was derived under different shearer cutting conditions. Finally, shearer position and cutting height adjustment experiments were carried out by use of a shearer model. The experimental results show that the shearer position and attitude adjustment method based on strapdown inertial navigation system can effectively improve position and attitude adjustment accuracy of shearer.

Existing hydraulic support monitoring methods can only monitor single support without fusion analysis of monitoring data of united hydraulic supports and have low utilization ratio of monitoring data. For above problems, a memory attitude monitoring method for hydraulic support based on grey theory was proposed. The method calculates predictive value of related memory attitude parameters according to monitored value of memory attitude of hydraulic support by use of grey theory. It can predict attitude of the next hydraulic support according to actual attitude of previous hydraulic supports in the same monitoring cycle, so as to realize horizontal cycle monitoring, and also predict attitude of a hydraulic support in the next monitoring cycle according to actual attitude of the hydraulic support in the last few cycles, so as to realize longitudinal cycle monitoring. The support height of hydraulic support monitoring test results show that predictive value of memory attitude of hydraulic support is similar to the actual value, which verifies the validity of the method.

Finger millet is a key food security crop widely grown in eastern Africa, India and Nepal. Long considered a 'poor man's crop', finger millet has regained attention over the past decade for its climate resilience and the nutritional qualities of its grain. To bring finger millet breeding into the 21st century, here we present the assembly and annotation of a chromosome-scale reference genome. We show that this ~1.3 million years old allotetraploid has a high level of homoeologous gene retention and lacks subgenome dominance. Population structure is mainly driven by the differential presence of large wild segments in the pericentromeric regions of several chromosomes. Trait mapping, followed by variant analysis of gene candidates, reveals that loss of purple coloration of anthers and stigma is associated with loss-of-function mutations in the finger millet orthologs of the maize R1/B1 and Arabidopsis GL3/EGL3 anthocyanin regulatory genes. Proanthocyanidin production in seed is not affected by these gene knockouts.

Under various power ratios and temperatures, Inxga1-xN films with different indium composition x were grown on Si(111) substrates by reactive magnetron sputtering, and then annealed at ammonia atmosphere around 700°C for 2 hours. The indium composition x can be adjusted by the growth temperature over the range of 600~800°C. There is no InN phase and In droplet formation in the Inxga1-xN films due to the low-temperature advantages of reactive magnetron sputtering. The rich In composition in Inxga1-xN films is caused by the higher sputtering yield of In2O3 target than Ga2O3 target. Raman scattering analysis revealed that the Inxga1-xN films obtained at different temperatures were wurtzite structure, and the compositional inhomogeneity is caused by the relaxation of momentum conservation and increase of lattice disorder.