Abstract:In this paper, we study global dynamics of a cubic non-symmetric Lienard system with global parameters, i.e., parameters are not required to be sufficiently small. After analyzing qualitative properties of all the equilibria and discussing the existence of limit cycles and heteroclinic orbits, we give a complete classification of the global phase portraits in the Poincare disc. Finally, associated with the previous results we obtain the bifurcation diagram in the parameter space.

Abstract:This paper mainly studies the numerical solution and parameter estimation of a multi-interface heat conduction equation. Firstly, the heat conduction equation and interface conditions are discretized to tridiagonal linear equations by using the finite difference method. Then a chasing algorithm is used to obtain the numerical solution. Furthermore, an adaptive Particle Swarm Optimization (PSO) algorithm is proposed for the parameter estimation. This algorithm adopts an adaptive nonlinear decreasing adjustment strategy for the inertia factor in order not to sink into the local extreme values prematurely and thus improve the optimization accuracy. Finally, the performance of the proposed algorithm is compared to the standard PSO algorithm and some classical nonlinear optimization algorithms such as Active Set ( AS ), Interior Point ( IP ) and SQP by using a numerical example.

Abstract:An energy-preserving mixed finite element is constructed to solve the Maxwell"s equations with nonlinear conductivity. This finite element is obtained by discretizing the first order formulation of the Maxwell"s equations in space based on the finite element exterior calculus as well as the continuous time Galerkin method, which can be viewed as a modification of the Crank-Nicolson method, is used to discretize the time. Then we obtain a full discrete scheme preserving the total energy exactly when the source term vanishes. The mixed finite element method can preserve the magnetic Gauss law exactly. Based on a projection-based quasi-interpolation operator, the optimal order convergence of the method is established. Finally, numerical examples are presented to exemplify the theoretical results.

Abstract:The main concern of this paper is the cooperative jamming problem of UAV cluster. A global space UAV platform distribution optimization model is proposed based on the 3D pattern function. Then the model is solved based on the genetic algorithm. Simulation results show that, compared with the traditional spherical or cylindrical distribution, the peak sidelobe level of the main beam pattern of the model is better. Finally, combined with concrete application backgrounds, the position deviation, damage, cluster capacity, minimum spacing in cluster and the cluster distribution range of UAV are considered, the dependence of the jamming effect of UAV cluster on the error conditions and model parameters is investigated.

Abstract:Correlation functions play a key role in the statistical description of chaotic maps. The main concern of this paper is the calculation of correlation functions of the Tchebyscheff maps, which is traditionally handled by using the graph theoretical method introduced by Beck in 1991. However, this method has poor efficiency when the orders of map and correlation function are large. To overcome this problem, we introduce a number theoretical method based on the definition of correlation functions of the Tchebyscheff maps. In this method, the calculation is transformed into solving a class of Diophantine equations with strictly increasing exponentials, which can be solved in a hierarchical way. Then we obtain all non-vanishing correlation functions with an order not more the order of map and show that the value of non-vanishing correlation functions is independent of the order of map as well as the number of non-vanishing correlation functions is closely related to the Stirling numbers of the second kind. As an application, we calculate all non-vanishing 12-order correlation functions of the Tchebyscheff maps with an order no less than 12.

Abstract:Lightweight nodes in blockchain have the limitation that they cannot participate in the blockchain verification process because they cannot store a complete copy of the blockchain, which weakens the distributed characteristics of the blockchain. The verification ability can be enhanced by compressing the copy of the blockchain stored in the lightweight node to reduce storage overhead. The Blockchain Selective Compression (BSC) algorithm, which is based on the Hyperledger Fabric blockchain architecture, is proposed. In the proposed BSC algorithm, the check chain is first generated by the blockchain main chain, the two chains are linked through the hash pointers, and the hash root path is used to verify the integrity of the main chain blocks which stores in the check chain; secondly, the checkpoints in the check chain is merged and updated to reduce the storage overhead of the check chain; finally, the blocks in the main chain are selectively retained and the hash pathes are calculated for verifying the integrity of the main chain, which reduce the storage overhead of the main chain. The simulation results show that, comparing with the EPBC algorithm and the Snapshot algorithm, the BSC algorithm has a better performance in storage overhead and verification capabilities.

Abstract:In the field of glass ampoule packaging integrity detection，high voltage discharge method is commonly used to detect micron-level leaky hole defects. In view of the existing methods，it is difficult to find appropriate filtering mode，discrimination thresholds depend on manual design， and detection accuracy is low，a microhole detection method based on improved GoogLeNet is proposed. For the original discharge current data，through the wavelet transform (WT)，and using the generalized Morse wavelet function (GMW) as the basic wavelet，transform the one-dimensional current time series into a two-dimensional time-frequency index graph to present the complete details of the data. On the basis of GoogLeNet prototype， Relu activation function is introduced to reduce overfitting，the input convolution is reduced to 1 layer，and then Inception module cutting at three different levels is carried out. Comparative analysis shows that when only the first 6 Inception modules are used and the proportion of large-size convolution kernels is increased for Inception(4D)，the model can also achieve a better effect of microhole discrimination with fewer parameters.In the industrial computer of production site， the trained model was used to replace the original algorithm，and 1000 positive and negative samples were tested. The results show that the accuracy of the algorithm is 99.15%，and the positive sample missing rate is only 08%，which is better than the 96.45% accuracy rate and 5.3% missing rate of the existing method.

Abstract:Idiom cloze test is a subtask in Machine Reading Comprehension (MRC), which aim to test the model's ability to understand and apply idioms in Chinese text. The existing idiom cloze algorithms ignore the fact that the idiom embeddings suffer from representational collapse, which leads to low accuracy and poor generalization performance on out-of-domain data. In this paper, the authors propose the NeZha-CLofTN, which consists of four parts: embedding layer, fusion coding layer, graph attention subnetwork, and prediction layer. The fusion coding layer uses contrastive learning to force the network to change the feature extraction that avoids the network outputting a constant embedding vector, thus preventing the representational collapse. The prediction layer combines the output of multiple synonym subgraphs to obtain better prediction than a single subgraph and to enhance the generalization performance of the model. NeZha-ClofTN is used in the ChID-Official and ChID-Competition datasets with accuracy of 80.3% and 85.3%, and the effectiveness of each module was demonstrated by ablation experiments.

Abstract:Aiming at the problem of equipment layout in multi-region single-row and double-row workshops, the workshop and equipment are parameterized by using the workshop's two-dimensional plane coordinate system to construct a mathematical model of multi-region single and double-row equipment layout, and a combination of SLP and improved genetic algorithm is proposed. The SLP improved genetic algorithm. The algorithm aims at minimizing the logistics distance of the workshop, adopts a staged algorithm idea, introduces an adaptive crossover operator, and uses a mixed population initialization method. Experimental results show that the algorithm can converge to a better solution at a faster speed when solving the equipment layout problem of multi-region single and double-line workshops.

Abstract:In view of the problems of low detection accuracy, poor real-time and robustness of existing target detection algorithms in vehicle target detection in autonomous driving fields, a vehicle target detection method based on YOLOv5 is proposed. With the framework of YOLOv5s network model, a one-shot aggregation (OSA) module is introduced to optimize the backbone network structure and improve the network feature extraction capability. Non-local attention mechanism is used for feature enhancement. At the same time, the weighted non--maximum suppression method is used to filter the detection frame. The experimental results show that compared with the original YOLOv5s model, the mAP of the improved network model is improved by 3%, and the AP of different target detection classes is improved, and the detection speed meets the real-time requirements. For dense vehicles and under different illumination conditions, vehicle target detection can be better achieved.

Abstract:The explosive growth of Android malware has put forward more efficient and accurate requirements for malware detection methods. In the early years, detection methods were mainly based on features such as permissions and opcode sequences. However, these methods did not fully mine the structural information of programs. The method based on API call graph is one of the mainstream methods. It focuses on capturing structural information and can accurately predict the possible behavior of the application. This paper proposes an Android malware detection method based on graph attention network. The method constructs an API call graph through static analysis to initially characterize the APK, and then introduces the SDNE graph embedding algorithm to learn structural and content features from the API call graph. The attention network fully fuses the neighbor node feature vectors, and then forms the graph embedding for the detection task. The experimental results on the AMD dataset show that the proposed method can effectively detect malware with an accuracy of 97.87% and an F1 score of 97.40%.

Abstract:Among the information contained in cyber threat intelligence, the tactics, techniques, and procedures (TTPs) associated with cyber attacks are the key information that best portrays organisational behaviour. However, TTPs information has a high level of abstraction and is often found in cyber threat intelligence texts with irregular grammatical structures. This makes it difficult for traditional manual analysis methods and feature engineering-based machine learning methods to quickly and effectively classify TTPs from them, and the use of a single deep learning feature extractor leads to low accuracy in TTP classification because it cannot extract the complete neighbourhood features and sequence features in the text semantics. To address these problems, this paper proposes a deep learning model based on attention mechanism and feature fusion: ACRCNN, for the classification of TTPs and techniques in cyber threat intelligence. The model extracts the neighbourhood and sequence information in the cyber threat intelligence text by convolutional and recurrent neural networks simultaneously, and then completes deep feature extraction and dimensionality reduction by convolutional and pooling layers to complete feature fusion. Then, feature weighting is completed by the attention layer, and finally the classification of tactics and techniques is completed by the fully connected layer. The experimental results show that ACRCNN performs well in tactical and technical classification tasks, achieving 91.91% and 83.86% in F1 metrics, which is an improvement of 2.46% and 4.94%, respectively, compared with existing models.

Abstract:The hydrogen storage properties of defective blue phosphorene monolayer decorated by alkali metal Li were systematically investigated by using first-principles calculations. The results show that the interaction between Li atom and blue phosphorene monolayer can be enhanced by introducing the double -vacancy defect DV2, thus hindering effectively aggregation of Li on the surface of the blue phosphorene monolayer. Three H2 molecules can be absorbed by a Li atom with the average adsorption energy of 0.248 eV/H2. Both the polarization mechanism of H2 molecules and the weaker hybridization of Li-s/p orbitals with H-s orbitals are responsible for the adsorption of H2 molecules. The effect of temperature and pressure on the hydrogen storage performance is also investigated, and the results indicate that the H2 storage systems can be stable at room temperature and low pressure, and thus the practical reversible hydrogen storage can be achieved at room temperature.

Abstract:In this paper, the wettability and corrosion behavior of liquid tin (Sn) on tungsten-based capillary porous meshes structure (CPS) under static high temperature and high density hydrogen plasma were investigated by vacuum tube furnace and Sichuan University plasma-material surface interaction platform (SCU-PSI). The experimental results show that the threshold temperature of liquid Sn wetted tungsten mesh (four layers 150 mesh) is 950 ℃ under static high temperature environment, and the wetting effect becomes better with the increase of experimental temperature. When the experimental temperature reached 1050 ℃, a large number of stannic oxide rod-like structures were observed on the surface of the tungsten screen. This rod-like structure may be due to the presence of a small amount of oxygen in the tubular furnace. Sn reacts with oxygen at high temperature to form SnO2 nanocrystals. When the liquid Sn-CPS structure was irradiated again by hydrogen plasma with an ion flux of 7.71×1022 m-2*s-1 and a heat load of 54.55 kW*m-2, a large area of fracture occurred in the tungsten sieve and a filamentous structure was formed. However, no similar damage occurred on the surface of the tungsten sieve without liquid Sn wetting. It is suggested that under the high density hydrogen plasma irradiation, the synergistic action of hydrogen plasma and SnO2 may aggravate the damage of tungsten screen, resulting in tungsten wire hardening and fracture. The experimental results provide a theoretical basis for the future application of liquid Sn-CPS in fusion devices.

Abstract:The wet multi-disk brakes are important braking components of automotive and off-highway drivetrains, which have a crucial influence on the safety of heavy-duty vehicles. The energy equation is proposed in steady laminar flow of the automotive transmission fluid (ATF) through an integral method, considering the disengaged drag torque condition owing to hydroviscous drive (HVD). The closed-form analytical solutions for the three-dimensional (3D) temperature and convective heat flux fields, together with those of the temperature rises of separator and friction plates, are obtained for ATF, respectively, which can satisfy all the boundary conditions for both radial and axial directions of oil film. The analytical expressions of the radial velocity and pressure of ATF are also obtained based on the simplified Navier-Stokes equation and the approximation of cubic polynomial distribution. By comparing the theoretical model of fluid pressure and temperature with previous experiments, we find that the analytical solution is in good agreement with the experimental results. The analytical methods of 3D velocity, temperature and heat flux proposed might have the potentials to be extended to predict those of HVD devices such as wet clutches and dynamometers.

Abstract:Dephosphorization has always been a high concern in the metallurgical industry. The melting temperature has a great impact on dephosphorization. Exploring the influence of main components in liquid steel on the melting temperature and the influence of different component contents on the liquid phase zone have laid a theoretical foundation for further optimizing dephosphorization process parameters. Therefore, this paper combines dephosphorization theory with factsage software for simulation calculation, the effects of CaO, SiO2, P2O5, MgO and FeO contents on the melting temperature are studied, and finds the best slag content combination through single factor analysis, orthogonal experimental analysis, analysis of variance and phase diagram analysis. The experimental results show that the melting temperature decreases with the increase of SiO2 concentration, the melting temperature increases with the increase of CaO concentration, the complete melting temperature decreases when MgO is between 3%~7.5%, and the melting temperature decreases with the increase of P2O5 concentration. CaO has the greatest influence on the initial melting temperature, and SiO2 and FeO have the greatest influence on the complete melting temperature. At the lowest initial melting temperature, the lowest values of various factors are: CaO=26%, SiO2=24%, FeO=21%, P2O5=9.8%, MgO=9%, and at the lowest complete melting temperature they are: CaO=38%, SiO2=22.5%, FeO=18%, P2O5=5.3% and MgO=3%. The effects of CaO content on FeO-SiO2-P2O5 phase diagram, FeO content on CaO-SiO2-P2O5 phase diagram and SiO2 content on the liquid phase region of CaO-FeO-P2O5 phase diagram are analyzed and compared. The results show that with the increase of CaO content, the temperature of liquid phase region in FeO-SiO2-P2O5 system increases, and the liquid phase region at 1800 ℃ expands. The increase of FeO content has an obvious effect on the liquid phase region of CaO-FeO-P2O5 system, especially in the range of 15%~18%, the temperature range of 1600 ℃ continues to expand, and the temperature range of 1400 ℃ and 1600 ℃ increases. The increase of SiO2 content has the least effect on the liquid phase range of CaO-FeO-P2O5 system, that is, it increases the melting temperature, which reduces the content of P2O5 in the slag and is conducive to dephosphorization.

Abstract:S-nitroso-N-acetyl-DL-penicillamine (SNAP), a nitric oxide donor, has a significant inhibitory effect on the growth of microorganisms. In order to further verify the antibacterial effect of SNAP on microorganisms, SNAP solids were first prepared through nitrification in this paper, and their antibacterial properties were verified based on different SNAP concentrations. The results showed that: (1) SNAP has been successfully prepared by 1H NMR and UV characterization; (2) SNAP has obvious inhibitory effects on Escherichia coli, Staphylococcus aureus (resistant/non-resistant) and Neisseria gonorrhoeae, and the inhibitory effect is concentration-dependent. The results indicates that SNAP has broad-spectrum antibacterial properties. With excellent antibacterial properties SNAP and nitric oxide donors have broad application prospects in the antibacterial field.

Abstract:In this work, the graphite intercalation compounds with different oxidation degrees are prepared via a chemical oxidation method, using the peracetic acid as a preoxidant and the concentrated sulfuric acid as an intercalating agent. Further, expanded graphite is prepared by microwave-heating expansion. SEM, XRD, and FT-IR are used to characterize the morphology, structure, and changes of oxygen-containing functional groups of graphite intercalation compounds and expanded graphite. Furthermore, the effect of pre-oxidation time on the expansion volume and electrical conductivity of expanded graphite is studied. The results show that when the preoxidation time is 20 min, the intercalation expansion is the best, the expansion volume of the obtained expanded graphite reaches 275 mL/g, and the electrical conductivity of the prepared flexible graphite foil reaches 2000 S/m, showing excellent performance. Electrical conductivity. This work provides an idea for the green preparation of expanded graphite with high expansion volume. The results show that the intercalation expansion is the best when the pre-oxidation reaction time is 20 min, and the expansion volume of expanded graphite reaches the maximum of 275 mL/g. Under the optimal expansion effect, the conductivity of the prepared flexible graphite foil reaches 2000 S/m, showing excellent electrical conductivity. This work provides an idea for the green preparation of expanded graphite with high expansion volume.

Abstract:In southwest China, there are a large number of traditional bamboo and wood residential buildings with national characteristics, which are of great historical and cultural value. However, due to the flammability and susceptibility to the fungal attack of wood, it has a great potential safety hazard in daily life. Using fire-retardant coatings and preservatives has endowed wood with significantly improved safe performances, but the effects of dual treatments on the fire-retardant and smoke-suppression behavior of wood remain to be revealed. In this paper, a two-step treatment of wood with copper/boron composite preservatives (CBCP) and fire-resistant coatings was performed, and the flame-retardant and smoke-suppressive behaviors of treated wood were investigated. The results show that CBCP can suppress the release of heat and smoke by promoting the charring reaction to form a physical barrier on the wood surface. More importantly, the dual-treated wood has better flame retardant, thermal insulation properties and less smoke emission than the single fire treated wood, indicating that CBCP and fire-retardant coatings have a synergistic effect on improving wood fire safety.

Abstract:To elucidate the molecular mechanism of DNA topoisomerase Ⅱ binding protein 1 (TopBP1) involved in DNA damage repair response, this study found several potential phosphorylation sites (T860, S887, T1104 and T1167) of TopBP1 through bioinformatics analysis. The TopBP1 was amplified from the human cDNA library and cloned into plasmid via molecular biology,and the above phosphorylation site was mutant to alanine to observe the response of the cells transfected with the mutant plasmid to DNA damage repair. Results showed that TopBP1 protein with the 1104th alanine mutation (T1104A) significantly reduced the phosphorylation level of pRPA32-S33 and inactivated the cell cycle checkpoint after the irradiation or chemotherapy drug treatment, which severely blocked DNA stress response. This study confirms that T1104 is the key activity site of TopBP1 involved in DNA damage repair.

Abstract:To establish and optimize the extraction method of carotenoids from Kiwifruit， carotenoids were extracted from the flesh of yellow kiwifruit "Jinshi 1" by ultrasound-assisted extraction method. Combined with a single factor test, the OD450 value was used as the detection wavelength to optimize the extraction conditionsof carotenoids in kiwifruit flesh by response surface methodology. The results showed that the optimal extraction process parameters of carotenoid from kiwifruit were as follows: extraction solvent ethanol-acetone mixed solvent (volume fraction: 2∶1), extraction time: 33 min, extraction temperature: 55 ℃, liquid/solid ratio: 16∶1 (mL∶g). Under these conditions, the extraction content of carotenoids from kiwifruit was 70.04±0.66 (μg/g). The process is simple, fast, stable and reliable, and can be used for the extraction of carotenoids from kiwifruit.

Abstract:To explore the functions of miRNA in flower organ development, silique and seed development in Brassica napus, a novel miRNA named Bna-novel-miR432 was screened by analyzing the small RNA sequencing data of Brassica napus silique and seed at a different developmental stage. Then the miRNA was overexpressed in the Arabidopsis thaliana for functional analysis. The results showed that the flowering time of the stably transformed plants overexpressing Bna-novel-miR432 was significantly advanced, and the observation of flower development showed that there were defects in stamen development, resulting in incomplete pollination of the pistils. we further tested pollen fertility and found that the pollen fertility decreased significantly. The statistics of silique development showed that the length of silique in the overexpressed Arabidopsis lines was shorter, the number of seeds was significantly reduced and some of them were aborted. And the statistics on seeds development also showed that the development of the embryo was delayed. Therefore, Bna-novel-miR432 is involved in the regulation of flowering time, the development of stamens and pollen, and the development of fruit.

Abstract:To investigate the occurrence of viral diseases, the outbreak regularity and virus diversity in Panax notoginseng planting areas in Yunnan province, Sichuan province, and Chongqing municipality, the suspected disease samples collected in the fields were detected by reverse transcription polymerase chain reaction (RT-PCR) / PCR. The results showed that viral diseases occurred in all Panax notoginseng planting areas, and the detection rate of the virus showed an upward trend year by year. Among them, the positive detection rate of CMV and PnVA was 51.04% and 63.54%, respectively, and the combined infection rate of the two viruses was 32.29%. Then, the sequence alignment and phylogenetic analysis of coat protein gene (CP) of cucumber mosaic virus (CMV) and panax notoginseng virus A (PnVA) were carried out. The results showed that there were differences in the CP gene of virus isolates from different Panax notoginseng planting areas.

Abstract:The risk of resource loss caused by exports is a hot topic nowadays. This paper focuses on resource flow, analyzes contribution rates of influencing factors to changes in resource flow dynamically, and then offers optimized export restructure strategies during the period from 2018 to 2022. In the analytic framework, firstly, the economic input-output table and energy-water consumption data are used to calculate the direct and complete consumption coefficients of water and energy; Secondly, to provide a reference for scenario definition and future export restructure, the authors use the structural decomposition analysis model to identify the main reasons for the variation of the resources flow. Besides, the authors use clustering analysis to identify sectoral water and energy consumption disparity and the potential for resource-saving. At last, this paper uses a bi-objective optimization model to optimize the export structure. The empirical analysis indicates that the volume of exports is found as the primary contributor to resource flow; direct energy consumption intensity helps to reduce energy outflow caused by export, while the reduction of total water consumption intensity greatly reduces the risk of resource loss, which is consistent with the reality. Cluster analysis offers the improving directions, and the optimization result shows that faced with the extension of export, reducing the energy-water coefficient helps to achieve resources conservation. Besides, this paper argues that the marginal output derived from technological improvement shows a gradually increasing effect.

Abstract:To discuss the influence of different subsidy modes on the airline networks of multi-airport systems, this paper constructs a dynamic game model between airports, airlines, and passengers.The Nash equilibrium is obtained by analyzing the payoff matrix.The result shows: (1) Different subsidy modes have an important impact on the multi-airport airline network, and the low subsidy promotes the multi-airport system to form a point-to-point network; on the contrary, in the high subsidy mode, the multi-airport system is easy to form a hub-spoke network.(2) If the total operating costs of air-HSR cooperation are relatively low, subsidy competition makes carriers choose large airports in the system as the hub; conversely, if the total operating costs of air-HSR cooperation are relatively high, subsidy competition makes carriers choose small airports as the hub.(3) With the increase in fixed flight costs and total operating costs of air-HSR cooperation, the probability of large airports as hub nodes will gradually decrease, while the probability of small airports being selected as hub nodes will gradually increase.At the same time, as the proportion of the population in large airports increases, the probability of carriers choosing a point-to-point network decreases.The research conclusions can provide a decision-making basis for the industry management department to scientifically formulate and apply the route subsidy policy.