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SiC is the ideal material for RF devices and power devices. Resistance-heated physical vapor transport method is considered a promising way to grow large size (especially 6 and 8 inch) SiC crystals due to its temperature uniformity. In recent years, the introduction of new technique such as the use of porous graphite improved the SiC crystal quality and yield, while there are only a few relatively comprehensive studies on its mechanism. This paper made comprehensive research on the influence of porous graphite on SiC growth system by means of numerical simulation. The crystal growth experiments under numerical simulation conditions have been carried out accordingly. The numerical simulation results show that the porous graphite raises the temperature and temperature uniformity within the powder area, which can strengthen the sublimation of powder. The temperature difference between the powder and the seed inside the crucible is improved and a greater growth driving force is obtained. The effect of decrease of the re-crystallization at powder surface has also been proved. Besides, the porous graphite improves the flow stability across the whole growth process, and assures a stable crystal growth. The C/ Si ratio has been increased under the influence of porous graphite, and thus reduces the probability of phase transition. The crystal shape has also been improved. The subsequent growth experiments verified the conclusions of numerical simulations such as the improvement of flow uniformity, decrease of poly-type transition probability, improvement of crystal shape, etc. The results of this paper have practical significance on comprehending the effecting mechanism of porous graphite and improving the SiC crystal growth conditions for better crystal quality. [ABSTRACT FROM AUTHOR]

In wireless communication system, buildings or active eavesdroppers by illegal devices can block the communication link between the transmitter and receiver. Utilizing the flexible mobility of unmanned aerial vehicle (UAV) and the intelligent controllable characteristic of intelligent reflective surface (IRS) in wireless environment, this paper proposed a safe transmission scheme of physical layer for IRS assisted UAV to maximize the averaged secrecy rate of the legitimate link. The scheme firstly utilized block coordinate descent method to decompose the average secrecy rate maximization problem of the system into three sub-problems: UAV-IRS flight trajectory optimization, IRS phase shift optimization and transmission power optimization. And then, this scheme transformed each subproblem into a convex optimization subproblem by utilizing relaxation variables, phase alignment and successive convex approximation methods, respectively. Furthermore, this paper used the alternating optimization method to obtain the maximum average secrecy rate of the system. Numerical simulation results show that the transmission power of the source node, the flight position and altitude of UAV-IRS and the number of IRS reflective elements are the main factors for improving the averaged secrecy rate of the legitimate link. The proposed scheme can effectively improve the average secrecy rate of the system with good convergence by comparing with the other two benchmark schemes. [ABSTRACT FROM AUTHOR]

In order to solve the problems of inadequate global search and easy to fall into local extremum, this paper proposed a multi-strategy fusion improved adaptive tunicate swarm algorithm（MITSA）. Firstly, this paper used the best point set strategy to improve population diversity during initialization. Secondly, it offered a multi-elite cooperative guidance mechanism to optimize the tunicates’ location information, and enhance the global exploration ability of the algorithm by increasing the exploration possibility of unknown search area. Then, the algorithm achieved dynamic global and local search balance by introducing adaptive weight factors into the group behavior stage. Meanwhile, probabilistic wavelet variation strategy promoted individual dynamic fine-tuning to enhance the anti-stagnation ability of the algorithm, while using the greedy principle to retain excellent information to help the population to the food source. Finally, this paper proved the global convergence of the improved algorithm based on Markov chain theory. Through the numerical simulation of the benchmark test function and CEC2014 complex function, the experimental results and Wilcoxon rank sum test results comprehensively verify MITSA’s excellent convergence accuracy, robust robustness and high-dimensional scalability. [ABSTRACT FROM AUTHOR]

This paper fused the characteristics of cloud security and the point-to-group networks, proposed a new malware propagation model based on cloud-edge combination, namely, cloud security environment and point-to-group information sharing networks, and formed the cloud-edge combination defense against malicious code. Firstly, this paper introduced cloud security node based on the classical susceptibility-infection-immune propagation model, and added additional immune pathways of nodes in cloud security environment. Secondly, this paper analyzed the dynamics of the new model, and calculated the equilibrium point and propagation threshold of the model, and proved the local stability and global stability of the equilibrium point. Finally, the results of numerical simulation and simulation experiments show that, the malware propagation model based on cloud-edge joint defense can better curb the spread of malware in the network, and with the improvement of node detection and feedback ability, the containment effect of malware will be better. [ABSTRACT FROM AUTHOR]

The BET (Brunauer-Emmett-Teller) theory of multimolecular adsorption is abstract yet widely applicable, and its equation involves complex mathematical derivations that are often difficult for students to grasp. Consequently, students may struggle to correctly interpret adsorption-desorption isotherms and specific surface area data generated by automated specific surface analyzers, leading to unsatisfactory educational outcomes. This paper introduces the use of computer simulations to model the adsorption-desorption process of gas molecules on solid surfaces. By adjusting the adsorption-desorption constants, the simulations can generate Type I, II, and III adsorption isotherms. The real-time visualization allows students to intuitively understand the dynamics of gas molecule adsorption and desorption on solid surfaces, thereby enhancing their comprehension of BET theory. The incorporation of computer simulation into teaching not only enlivens the classroom environment but also fosters an interactive teaching-learning experience, stimulating students' curiosity and research interest while improving the overall quality of education. [ABSTRACT FROM AUTHOR]

With non-toxic nature, wide bandgap, and thermal stability, Sn-based perovskite materials have become a hot topic in the field of perovskite solar cell research. In this paper, the SCAPS-1D software was used to construct the FTO/TiO2/CH3NH3SnI3/Spiro-OMeTAD/ Ag perovskite solar cells and the performances of the constructed cells were calculated. The effects of the thickness of absorption and hole buffer layer, the surface defects between hole buffer layer and absorption layer, and the operating temperature on the device performance were studied, then the device performance was optimized. The photoelectric conversion efficiency of the optimized perovskite solar cell is 30. 955%. The theoretical analysis suggests a new approach for enhancing the photoelectric conversion efficiency of perovskite solar cells. [ABSTRACT FROM AUTHOR]

In order to study the evolution of aircraft wake vortices more deeply and precisely, and to ensure the safe operation of aircraft, the dissipation law of A330‑300 aircraft wake at different temperature vertical decreasing rates is studied in this paper by numerical simulation. The shear stress transport (SST) k‑ω turbulence model is chosen for the numerical simulation. The temperature field under five different temperature vertical decreasing rates is constructed, and the A330‑300 aircraft wake flow field is compiled within the temperature field to realize the calculation under different temperature vertical decreasing rates. The reliability of the numerical simulation method is verified by comparing the numerical simulation results with the radar detection data. The results show that for general turbulence intensities, different rates of vertical decreases in temperature act mainly on the decay phase of the wake, affecting the evolution of the wake by changing the temperature inside and outside the wake.The smaller the temperature vertical decreasing rate is, the larger the rate of decrease of circulation in the wake vortex decay region is. The larger the vertical rate of temperature decreases, the larger the rate of tail vortex sinking is and the larger the distance between vortex cores after rapid dissipations is. [ABSTRACT FROM AUTHOR]

The spread of epidemics poses a significant threat to the entire human community. Therefore, it is critical to identify the sources of transmission quickly and take timely control measures. However, the diversity of epidemic transmission processes and information uncertainty makes it challenging to identify the sources of transmission quickly and accurately. This paper proposed a new algorithm for identifying transmission sources in a metapopulation network by combining the reverse infection algorithm and Markov chain theory. The algorithm first uses a Markov chain to initially estimate the time when a subpopulation is infected, and the infected subpopulation obtains its own identity information based on the infection time. Then, it traverses all subpopulations that obtain the identity information of the infected subpopulation and spreads the collected identity information of the infected subpopulation to all its neighbors. Finally, the spreading source of the metapopulation network can be inferred based on the temporal order in which all the identity information of the infected subpopulation is obtained. Simulation experiments conducted on real airports networks and artificial networks show that the accuracy of this algorithm is significantly improved compared to other algorithms, regardless of whether all or partial of the infection snapshots are known. This algorithm is well-suited for metapopulation networks such as aviation networks and is also useful for real-world epidemic transmission tracing and control. [ABSTRACT FROM AUTHOR]

As the reinforcing phase of the composites, the preform determines the performance of the composites. The performance of the precast often depends on the spatial structure of the yarn. To reflect the spatial configuration and micro-geometric structure of the yarn inside the fabric, through the discretization of the yarn, the weaving process is simulated by numerical simulation and simulation methods. We review the progress on digital element method simulation of the weaving process of composite preforms. In terms of micro-geometric structure, this paper details the development process of digital element method research from theory to application and introduces the advanced digital element modeling method. It points out that the current model is idealized for the digital element method to simulate the textile process, and does not consider the bending stiffness of the fiber, the air damping effect and the energy loss caused by lateral compression, etc. This paper also points out that the digital element method can be further optimized in future research and parametric modeling can be realized, and that the deformation mechanism of the fiber bundle is studied to obtain a more realistic micro-geometric structure model. [ABSTRACT FROM AUTHOR]

In order to further master the tunneling technology ol mining small coal pillars along the gob and improve the resource recovery rate. According to the specific production geological conditions, this paper analyzes the distribution characteristics and inlluence ol small coal pillar support stress in small coal pillar roadway excavation, working lace advance and secondary mining by means ol ground pressure monitoring and numerical simulation. The results show that: 1)During roadway excavation, the pressure in the first 50 meters ol the roadway is large, especially the two sides of the roadway move closer, and the maximum distance ol the two sides is about 200 mm. 2) During the roadway excavation stage and the mining inlluence period, a 5 m coal pillar is lelt between the return air chute and the upper transportation chute, lorming a large stress concentrathe maximum vertical stress in the coal pillar is 21. 38 MPa. The vertical stress in the coal wall behind the Iront of the work is about 30 MPa, the stress concentration lactor is about 3, the inlluence range is about 84 m, and the maximum vertical stress ol the coal pillar is 41 MPa. 3) Allected by the secondary mining, the stress in the coal pillar is basically about 40 MPa, which changes little compared with the primary mining, while the peak stress appears in the triangle area in Iront ol the working lace, up to 57. 4 MPa, indicating that this area is the locus ol prevention and control during the mining ol the working face. The results of ground pressure monitoring and numerical simulation are relatively consistent, which further proved the reliability ol the research results. [ABSTRACT FROM AUTHOR]

Harbors located in swell dominated seas may encounter problems such as inefficient performance of breakwaters and harbor oscillations. Taking a specific sea port in Chancay Bay, Peru, as an example, the performance of a breakwater and the characteristics of harbor oscillations are analyzed by numerical simulations. The results show that the breakwater is capable of providing protection against swell and the ratio of the wave heights inside and outside the harbor is approximately 0.15. The operational efficiency and safety at berth are guaranteed according to the tolerable wave height of short waves. The reduction of infragravity (IG) waves after they propagate into the harbor is negligible. Considerable downtime may be expected according to the tolerable IG waves. Therefore, IG waves should be taken into consideration during the design of harbor layouts and mooring systems and particularly, the natural periods of the mooring systems should not be close to the periods of IG waves inside the harbor. The results of the study presented in this paper may offer reference for the design of harbour layout and mooring system. [ABSTRACT FROM AUTHOR]

Objective The post-accident analysis of major hazards is a very complicated research work in oil field drilling site. The key parameters of the accident and its influence rule are studied by numerical simulation. Methods The fuzzy boundary condition is solved by the boundary condition hypothesis and trial calculation method on the premise that the specific parameters cannot be obtained. This paper mainly uses the well loss calculation model and field data to invert the well loss process to determine the leading parameters required for kick simulation, and studies the change law of bottom hole pressure when the string is falling. Results The downhole drilling string of a certain well is 4 500 meters long, generating more than 20 MPa surge pressure, and the cumulative loss for 7-8 minutes can reach more than 20 m³, which has a great impact on field operations and a short response time. The falling of short drill pipe produces less surge pressure and lower risk. The results show that under the condition of large fracture (more than 10 mm), the large surge pressure can instantly produce more than tens of cubic meters of leakage, which can not be controlled. In the case of narrow fracture (1 mm), the accumulated leakage amount reaches 20 m³ in about 6 minutes. In the case of micro-fracture (0.25 mm), the accumulated loss in 10 hours is only 20 m³. Conclusions The long drill string drop produces a larger surge pressure, which is the main sensitive parameter of loss and the main reason of blowout. The well shut-in measures should be taken as soon as possible. [ABSTRACT FROM AUTHOR]

The wear of conveying steel pipes has always been one of the key issues for research in the dredging industry. In this paper, the wear of the straight section of a pipe of Q235 with a diameter of DN50 and a length of 300 mm under 40%volume concentration of coarse sand, and the wear of coarse sand are studied experimentally. The results show that the wear rate of the same batch of coarse sand at a flow rate of 4.2 m/s decreased with time. The wear rate in the first 8 h was 1.875 g/(h·m)while the wear rate in the last two 16 h was only 0.52 g/(h·m)and 0.42 g/(h·m). After 40 hours of wear, the median particle size of coarse sand decreased from 0.82 mm to 0.75 mm. At the flow rate of 4.2 m/s, the wear amount of different batches of coarse sand in the straight pipe section is linear with time every 8 h and the slope is about 0.518 8, with an average wear rate of about1.736 g/(h·m), and the median particle size of coarse sand was basically unchanged during the experiment. The wear rate of coarse sand on the straight pipe section increased with the increase of flow rate. The wear rates at the flow rates of 2.2 m/s, 3.2m/s and 4.2 m/s were 0.625 g/(h·m), 1.25 g/(h·m)and 1.875 g/(h·m), respectively, showing a linear relationship. The median particle size of coarse sand during the experiment was basically unchanged, but at the flow rate of 5.2 m/s, the wear rate of the straight pipe section increased sharply to 3.54 g/(h·m), and the median particle size of coarse sand decreased from 0.82 mm to0.72 mm. This study results can provide experimental data support for pipeline wear estimation and numerical simulation of pipeline wear [ABSTRACT FROM AUTHOR]

Considering that the contacts between travelers promote the epidemic spreading, this study constructed a spreading model with non-Markovian travel process and used computer simulation technology to simulate the epidemic spreading, where the time delay travel process and the infection and recovery during travel were considered on the metapopulation network. Based on the microscopic Markovian chain approach（MMCA）, this paper developed a theoretical framework to predict the epidemic threshold. Simulation results indicate that the travel infection promotes the infection in travel but inhibits the infection within the subpopulations, and the travel time and the travel contact rate may change the time evolution of prevalence. These results help to understand the influence of travel infection on epidemic spreading. [ABSTRACT FROM AUTHOR]

The support of complex and fractured surrounding rock tunnels is one of the challenges that should be dealt with urgently during the development process of deep gold resources. At present, mines often use joint support methods with steel arch frames and wood. However, due to the inflammable and easily corrosible properties of wood, it is not applicable for permanent underground mine support. Therefore, based on the numerical simulation study, this paper proposes to use new type of support materials with lightweight energy-absorbing characteristics as the lining to replace the wood in the support of tunnels.The theoretical analysis shows that the new type of support materials has obvious energy absorption and pressure relief effects and is more suitable for the pressure relief support system for complex and fractured tunnels. [ABSTRACT FROM AUTHOR]

Based on the deep foundation pit project of Yellow River Tunnel in Jinan, this paper studied the deformation rules of ultra-deep foundation pit in considering seepage and not seepage. The numerical simulation results were compared with the field measured data, and the final seepage hazard mode to the excavation of the ultra-deep foundation pit in the silty clay formation was mastered. Mohr-Coulomb model was modified for soft clay and clay. For soil with higher friction coefficient like sand, the Mohr-Coulomb model was adopted. The main 15 stages of foundation pit excavation under seepage were simulated, and the influence of foundation pit excavation on the surface settlement, the horizontal displacement of the underground continuous wall, and the influence on the bottom uplift of the foundation pit were finally analyzed. It was found that the seepage greatly affected the deformation of the foundation pit, which was greater than the posterior deformation value when the seepage was not considered. In the site construction, if the deep foundation pit design was conducted without considering the seepage action, it would cause great judgment error and make the project have great safety risks. The study in this paper provides empirical guidance for similar engineering. [ABSTRACT FROM AUTHOR]

In this paper, the evolution of thermocapillary convection in melt of half-floating zone liquid bridge under the condition of zero gravity was studied by means of numerical simulation. Under the condition that the height L of the liquid bridge and the temperature difference ΔT remain unchanged, the aspect ratio (Ar = L / R) of the liquid bridge can be changed by changing the radius R of the liquid bridge. The convection in the liquid bridge exhibits various flow characteristics with the change of the aspect ratio Ar. Thermocapillary convection is in a three-dimensional steady state when Ar = 0. 5. The flow field and temperature field change from the steady state mode to the unsteady periodic multi-frequency oscillation mode satisfying the frequency doubling relationship (f n = nf 1) when Ar = 1. When Ar = 1. 25, the velocity oscillation frequency of the monitoring point increases, showing a smaller amplitude oscillation mode, and the temperature oscillation disappears. [ABSTRACT FROM AUTHOR]

This paper proposes a closed⁃loop homing guidance law with the constraints of the impact time and angle for the intercepting a constant⁃velocity target. In order to achieve the required terminal constraints，the line⁃of⁃sight （LOS） profile of the missile is modeled as a polynomial with one tuning parameter that is selected via an online optimization routine. Then，a terminal sliding mode guidance law is developed to nullify the tracking error within a fixed time. The key feature of the proposed guidance law is that it does not require the information of time⁃to⁃go estimation and the predictive intercept point. Numerical simulations are conducted to demonstrate the effectiveness and robustness of the proposed guidance law. [ABSTRACT FROM AUTHOR]

Seismic performance of a structure is an important indicator of its safety and stability. The environment where the immersed tube structure in the Dalian Bay Subsea Tunnel project is built is complex, and the analysis of the safety of the immersed tube structure under the action of seismic hazards is of great practical significance for the design, construction and operation of the project. In this paper, the seismic performance of the immersed tube tunnel structure is analyzed by numerical simulation and load tests respectively. The results show that the existing engineering design has good seismic performance and can ensure the stability and safety of the tunnel structure under complex stresses. [ABSTRACT FROM AUTHOR]

The discovery of marginal ore body in Fankou lead-zinc mine makes the current filling system of the mine unable to meet the increasing demand of backfilling. According to the position of the newly proved ore bodies and the filling stations in Fankou, this paper puts forward two kinds of pipeline layout schemes: the construction of new filling boreholes and the use of original filling boreholes. The maximum allowable stowing gradients of graded tailings and fine tailings transported by ground filling pipeline are calculated to be 8. 56 and 3. 47. According to the theoretical calculation and numerical simulation results, it is considered that when the graded tailings and fine tailings are transported at the surface stage of filling pipeline, both schemes need to be transported by pumping. In the underground stage of filling pipeline, the graded tailings filling slurry can be transported by flow. When the filling times line drops below 3, fine tailings can be transported by flow. The calculation results of pumping pressure show that the filling system needs to be equipped with a filling pump with the maximum pumping capacity of not less than 12 MPa to meet the demand of filling slurry transportation in the mine. [ABSTRACT FROM AUTHOR]

In order to evaluate the dynamic response of common continuous girder bridges under vehicle-bridge coupling in detail, this paper uses numerical simulation method to establish the finite element model of five-span continuous girder bridges with general drawings of bridges and culverts, and analyzes its dynamic responses under vehicle loads: deflection, stress. The corresponding dynamic amplification factor is calculated, and the variation law of dynamic amplification factor under the influence of vehicle frequency, bridge frequency and disturbance frequency is compared. The research shows that the fundamental frequency of the continuous beam bridge in the general drawing is 4. 44 Hz. When the vehicle frequency is close to the fundamental frequency of the bridge, the resonance effect will be produced and a larger dynamic amplification factor will be produced. The variation law and numerical value of the dynamic amplification factor at the middle position of the middle span and the middle position of the secondary side span obtained from the calculation are close to each other, but there are some differences with the dynamic amplification factor at the middle position of the side span, which shows that the structure with one end simply supported at the side span has a great influence on the dynamic amplification factor here. Vehicle frequency, bridge frequency and driving disturbance frequency all affect the dynamic amplification factor, so the impact coefficient in the bridge specification is only a function of the fundamental frequency of the bridge, which is far from the reality and needs to be improved. [ABSTRACT FROM AUTHOR]

To improve the throughput and energy efficiency of wireless sensor network ( WSN) in intelligent transportation system (ITS), this paper proposed a cooperative multiple input multiple output automatic repeat request protocol with spatial modulation( CMIMO-SM-ARQ). It considered a four-node WSN with dual sending nodes and dual receiving nodes, in which both receiving nodes could act as relays to each other to assist the sender transmitting data, to reduce the probability of system outage. The paper established the discrete time Markov chain ( DTMC) model of CMIMO-SM-ARQ protocol with 3L + 1 states and gave the state space. Based on the outage probability of WSN and the one-step state transition probability matrix, it derived the analytical expressions of throughput, energy efficiency and delay of CMIMO-SM-ARQ protocol. Numerical simulation results show that the outage probability and energy efficiency of the proposed protocol are better than the single input single output automatic repeat request ( SISO-ARQ) protocol, and the CMIMO-SM-ARQ protocol has a higher throughput and lower delay when transmitting information at medium and long distances( over 67 m). [ABSTRACT FROM AUTHOR]

This paper analyzed the security of an image encryption algorithm based on compound chaotic sequence, the proposed algorithm adopted three-level encryption structure of permutation-forward diffusion-reverse diffusion. Due to the forward diffusion and the reverse diffusion used the same one-dimensional diffusion sequence, therefore, this paper simplified the two level encryption structure of the forward diffusion and reverse diffusion to one-level diffusion encryption structure, further, simplified the three-level encryption structure of permutation-forward diffusion-reverse diffusion to two-level encryption structure of permutation and diffusion. Moreover, the chaotic sequences generated by the encryption algorithm were independent of the plaintext images or ciphertext images, consequently, it could crack the corresponding equivalent diffusion keys and equivalent permutation keys by chosen-plaintext attack. Theoretical analysis and numerical simulation experiment results verify the effectiveness of the analytical method. Finally, this paper proposed some improved suggestions for the original encryption algorithm to promote the security. [ABSTRACT FROM AUTHOR]

Aiming at the shortcomings of aquila optimization algorithm（AO）, this paper proposed an aquila optimization algorithm using hybrid search strategy. Firstly, the algorithm introduced dynamic adjustment function to balance global exploration and local exploitation; Secondly, it introduced chaotic adaptive weights to enhance the global search capability of the algorithm and accelerate the convergence speed of the algorithm; Thirdly, it introduced a new individual mutation probability coefficient and an improved differential mutation strategy, and used individuals with better fitness values to lead other individuals in the population to carry out search activities, which maintained the diversity of the population and enhanced the ability of the algorithm to jump out of the local optimum. Through the numerical experiment simulation of 8 benchmark test functions, 10 CEC2019 test functions and 1 engineering application problem, The experimental results show that the algorithm has a significant improvement in global convergence speed and optimization accuracy, and has a better ability to jump out of the local optimum. [ABSTRACT FROM AUTHOR]

The mist entrainment even flooding would unavoidably occur in traditional towers .Therefore,swirl bubble-cap is proposed,which would be expected to reduce the mist entrainment based on the principle of swirl coalescence and centrifugal sedimentation .In this paper,CFD numerical simulation is used to explore the hydrodynamic performance of swirl bubble-cap,including pressure drop and phase separation performance .The coalescence effect of the ratio of the average particle size at the outlet to the inlet is used to evaluate the phase separation performance .Firstly,the reliability of the simulation was verified with the pressure drop data tested .The RNGk-εmodel was used to deal with turbulence,the Euler-Euler model to deal with gas-liquid two-phase flow,the PBM model to consider the coalescence and breakage of droplets .Results showed that the pressure drop increased with the increase in feed flowrate,the coalescence effect increased with the increase in feed flowrate and then leveled off with further increase in feed flowrate,increased with the increase in droplet concentration and decreased with the increase in droplet size . [ABSTRACT FROM AUTHOR]

Due to the increasing demand for rich multimedia services, Internet of vehicles needs to provide massive equipment connections to meet the needs of high spectrum efficiency and low delay. Software Defined Network (SDN), caching and Non-Orthogonal Multiple Access (NOMA) technologies are considered as potential solutions to effectively solve these key challenges. Therefore, this paper proposed a cache aided NOMA power allocation scheme for software defined vehicular network. Firstly, according to the characteristics of vehicles always moving at high speed in Internet of vehicles, the scheme proposed a new cluster head selection algorithm. The arriving road traffic will be predicted with the help of SDN to realize adaptive vehicle clustering. Secondly, the scheme introduced a cache aided NOMA strategy. Each vehicle uses NOMA principle to cache and request files in the file cache stage. Thirdly, for the two cluster head vehicle communication scenarios under the condition of double Nakagami-m fading, the scheme proposed an optimal power allocation strategy. The optimization problem is formulated as finding the optimal power curve of each vehicle, so as to maximize the probability of successfully decoding the target file on each vehicle. Finally, numerical simulation and theoretical analysis show that the performance of the proposed cache aided NOMA power allocation scheme is significantly better than the conventional NOMA and cache aided Orthogonal Multiple Access（OMA). [ABSTRACT FROM AUTHOR]

This paper proposed an event-triggered mechanism based on cooperative control algorithm for the stability of autonomous vehicle platoon system,which could deal with the disturbance in the communication process and reduce the information redundancy and resource waste in the platoon control.Firstly,this paper designed a vehicle platoon algorithm for the directed topology on the basis of event-triggered mechanism.Even if there was disturbance,the follower autonomous vehicles could be consistent with the speed of leader autonomous vehicle,and each two consecutive autonomous vehicles could keep the desired safe distance.In addition,it constructed a Lyapunov function and gave the analysis of Zeno behavior to testify the validity and security of the proposed algorithm.Finally,the numerical simulation proves the correctness of the control algorithm. [ABSTRACT FROM AUTHOR]

Aiming at the shortcomings of crow search algorithm ( CSA), this paper proposed a crow search algorithm using multi-mode flight ( MFCSA) . Based on the strength of foraging ability, the algorithm divided the population into two groups: strong and weak foraging ability. Those with strong foraging ability adopted the strategy of trailing and tracking the optimal target of the current group, and flied to the vicinity of the current optimal position of the group under the guidance of the group information to carry out search activities, which enhanced the local exploitation ability of the algorithm. Those with weaker foraging ability adopted the two strategies of observing and learning the foraging methods of the strong, and flying away quickly when encountering danger, the former could improve the global exploration ability of the algorithm, and the latter could maintain the diversity of the population. Through the numerical experiment simulation of 15 benchmark test functions and 2 engineering application problems, the results show that the MFCSA has better performance in optimization accuracy, convergence speed, etc., enhances the ability to avoid falling into the local optimum, and has better stability. [ABSTRACT FROM AUTHOR]

To improve the delay and throughput performance of wireless sensor network ( WSN), this paper proposed a dualhop, multi-source and multi-relay cooperative automatic repeat request ( DH-MSMR-CARQ) protocol. The paper established the Markov chain models of DH-MSMR-CARQ protocol with two different relay selections under maximum ratio combining ( MRC) and gave the state spaces respectively. Based on truncation, this paper derived analytical expressions of average transmission delay and throughput according to their respective average packet error rate and state transition probability matrix. The numerical simulation results show that the number of source nodes, packet length and the packet error rate from the best relay node to destination node are the key factors affecting the average transmission delay, and the first relay selection method has higher throughput. In addition, the DH-MSMR-CARQ protocol has higher throughput than the direct SSSR-CARQ, MSSRCARQ and MSSR-CARQ protocols in non-extreme channel environment ( the packet error rates between source nodes and relay nodes are less than 0. 8). [ABSTRACT FROM AUTHOR]

Taking the medium deep hole mining in steeply narrow vein of a gold mine in Inner Mongolia as the engineering background, through empirical analogies, numerical simulation and field tests methods, the evolution law of cracks in narrow veins of deep hole blasting under different blasting parameters was analyzed, and the relationship between the blasting parameters and the over-under-excavation percentage of blasting, the density of blasting cracks and the vibration velocity of the surrounding rock particles is obtained. The results show that: when the hole spacing is 1. 2 - 1. 4 m, the over-under-excavation blasting area tends to be zero. When the burdern is 0. 8 - 1. 0 m, the blasting fragmentation is more uniform. A burden of 1. 0 m and a hole spacing of 1. 2 m can be taken as optimal parameters during deep hole blasting. The field blasting test also verifies the research results of this paper. [ABSTRACT FROM AUTHOR]

China􀆳s onshore oil fields have entered the late stage of development, while the reserves of thin-poor layers account for a large proportion of the remaining recoverable reserves. The development of thin-poor reservoirs has become an important potential for tapping potential. In this paper, the numerical simulation method is used to optimize the crack radius corresponding to the fracturing of the thin-poll injection-production system. The optimization results show that the fracture radius of the well has a greater impact on the final cumulative oil production and recovery when the fracture radius does not break the permeability boundary for a thin reservoir with a fracture penetration ratio of water and oil wells between 35% and 45%. When the oil well is in the high permeability area and the water well is in the low permeability area, the fracture radius of the well and the surrounding area of the oil well are used. The situation has a greater impact on the final oil production. [ABSTRACT FROM AUTHOR]

Iterative learning control problem is studied for a class of discrete nonlinear partial difference systems where the trial lengths vary randomly in this paper. The considered systems are composed of parabolic partial difference equations. Firstly, for the trial lengths vary randomly in systems, a stochastic variable satisfying Bernoulli distribution is introduced. Then, according to the properties of partial difference systems and P-type distributed update schemes, iterative learning controller is designed. Through rigorous theoretical analysis, the convergence sufficient condition of output error under λ norm and contractive mapping principle is established to ensure the convergence of tracking error in the sense of norm. The convergence speed of the algorithm is faster than the classical iterative learning algorithm. Finally, the effectiveness of the algorithm is verified by the numerical simulation. [ABSTRACT FROM AUTHOR]

This paper proposed two containment control algorithms for first-order/second-order multi-agent systems for discrete-time flocking motion problems. By using modern control theory, algebraic graph theory and linear matrix inequalities to analyze the proposed control algorithm, this paper obtained convergence conditions in a finite time for flocking motion of multiagent systems with interference under discrete-time conditions. Finally, by using the LMI toolbox in numerical simulation, it determined the range of positive definite matrices. The simulations illustrate the correctness of the conclusion. [ABSTRACT FROM AUTHOR]

In this paper, a transient numerical calculation method is established based on ANSYS CFX software and user-defined program, which can simulate the power-off runaway transient characteristics of a centrifugal pump. The variation rule of external characteristic parameters with time can be obtained through numerical calculations and compared with experimental data. The comparison of results show that the simulation results agree well with experimental results, the proposed numerical method has been therefore validated. During the power-off runaway transient process, the centrifugal pump system will successively undergo the pump condition, braking condition, turbine condition and runaway condition, with external characteristic varying significantly during the process. Internal flow structure is closely related to external characteristic and affects each other. The hydraulic loss due to friction and unstable flow patterns in the pump causes a drop in hydraulic efficiency. The traditional method for analyzing the hydraulic loss is by evaluating the total pressure drop, which has certain limitations and cannot determine the exact locations at which the high hydraulic loss occurs. In this study, entropy production theory has been adopted to obtain a detailed distribution of the hydraulic loss in the centrifugal pump. Through the use of the entropy production theory, the variation of the entropy production was obtained. The distribution of energy loss of flow components during this process is obtained by using the entropy generation theory, and the energy loss is analyzed. The results show that there is a clear correlation between the entropy production and the external characteristics of the centrifugal pump during the entire runaway process. The entropy production also undergoes dramatic changes at the moment of sudden changes in flow rate, rotational speed and torque. The main losses of the impeller, guide vanes and suction pipe are caused by turbulent dissipation, and the wall entropy production accounts for about 10%–15% of this total entropy production, which means the wall effect could not be ignored. However, the loss of the volute is mainly due to the strong wall effect in the near wall region, which is different from other three flow components, denoting the main loss generation mechanism is different. In addition, it is found that both the energy loss and variation range of the impeller and guide vanes are relatively larger than those of other flow components in the whole process. By analyzing the distribution of the local entropy production of the impeller and the vanes at different stages, it is intuitively obtained from the energy point of view that the high loss region of the internal flow field is the largest in the braking condition, and the high loss area fills the entire impeller flow path when the rotational speed drops to 0. The results obtained in this paper can improve the understanding of transient characteristics of a centrifugal pump during the power-off transient condition. [ABSTRACT FROM AUTHOR]

In view of the needs of the training IoT engineering professionals, the paper deeply researched OPNET, SoftRadio, Qemu,Proteus,Docker and other software, and built a comprehensive IoT virtual simulation experiment teaching platform. The paper focused on the experimental simulation teaching of computer network, wireless network, embedded IoT gateway and others coursed in the network layer and embedded gateway layer. The basic experimental project and comprehensive experimental project of related courses were designed. The experimental project runs through the serial port, communication programming, network communication programming and database programming expertise. It better solves the problems of " communication, storage, use" in the design and implementation of IoT application systems. Practice has proved that the virtual simulation experimental teaching platform provides better support for the experimental teaching of the network layer of the IoT and the embedded gateway layer. [ABSTRACT FROM AUTHOR]

This paper is concerned with the finite time synchronization of quaternion-value neural networks with time delays. Based on finite time control technique, the protocol of adaptive control is first proposed. Then by utilizing Lyapunov function method and inequalities skills, some sufficient conditions are derived to ensuring master systems and slave systems achieved synchronization in finite time, the settling time can also be theoretically given. Finally, the numerical simulation on quaternion-value neural networks with time delays is included to show the effectiveness of the theorem. [ABSTRACT FROM AUTHOR]

To reveal the evolutional characteristics of a stream-groundwater system, this paper takes the seasonal losing stream-groundwater system with stratified sediments as the research object. The criterion for the hydraulic connected states and the mechanism of the seepage in the system are analyzed. The variation types and mechanism of hydraulic connected states are clarified. A theoretical framework of stream-groundwater system hydraulic connected states is developed, and six stream-groundwater system models with different stratified sediment types are constructed. The evolution and variation of hydraulic connected states of the six stream-groundwater models are simulated by numerical simulations, and the results show that the wetting front curve and saturation front curve are of great importance to describe the evolutional process of the hydraulic connected states and can be regarded as characteristic curves for analysis. The difference of permeability and capillary force caused by different types of sediments is the fundamental driving force for the variation of the evolutional process. The variation types of wetting front curve include steep, gentle slope or alternate between steep and gentle slopes, and the variation types of saturation front curve include backward, forward, or alternate between backward and forward. The results of this study provide theoretical support for further research on water quantity assessment, mass transport and energy transfer in stream-groundwater systems. [ABSTRACT FROM AUTHOR]

Aiming at the problem that unmanned aerial vehicles（UAVs）are easy to overstep the boundary when rolling around the velocity vector axis，an adaptive sliding mode-based boundary protection control scheme is studied in this paper. Firstly，the attainable equilibrium set is improved based on dichotomy，and the command limitation method is introduced to realize online boundary solution and limited command generation. Then，to restrain the adverse impacts of uncertainties and disturbances to the closed-loop-system， a radial basis function（RBF）neural network is used to approximate the system uncertainties，and a nonlinear second-order disturbance observer is used to estimate the complex disturbances. Accordingly，an adaptive sliding mode-based boundary protection control law is designed to ensure the UAV’s safety and simultaneously realize the attitude tracking. Finally，the effectiveness of the adaptive sliding mode-based boundary protection control method is verified by numerical simulation. [ABSTRACT FROM AUTHOR]

This paper developed an opportunistic maintenance strategy model of multi-component equipment based on disassembly sequence for the problem that disassembly is not considered in the maintenance of multi-component equipment. Firstly, it represented the disassembly sequence by the disassembly mixture diagram, and then obtained the disassembly time and cost of each component. It described the failure characteristics of each component by combining the mixed failure rate of decreasing service age factor and increasing failure rate factor according to the decline process of each component. Secondly, on this basis, it solved the optimal preventive maintenance plan with the equipment opportunity window as the decision variable and the lowest maintenance cost as the goal under the condition that the equipment met certain availability. Finally, through numerical simulation analysis, it verified the effectiveness of the proposed multi-component opportunistic maintenance strategy. [ABSTRACT FROM AUTHOR]

Type-reduction is the key block in general type-2 fuzzy logic systems. This paper compares and analyzes the sum operation in discrete enhanced Karnik-Mendel (EKM) algorithms and the integral operation in continuous enhanced Karnik-Mendel (CEKM) algorithms. Based on the alpharepresentation theory of general type-2 fuzzy sets, EKM algorithms are extended to perform the centroid type-reduction of general type-2 fuzzy logic systems. While computing the centroid type-reduced sets and the defuzzified values of general type-2 fuzzy logic systems, two computer simulation examples show that the calculation results of EKM algorithms can accurately approximate the CEKM algorithms, when the number of sampling of primary variables of centroid output GT2 FSs increases appropriately. [ABSTRACT FROM AUTHOR]

The Interaction between magnetohydrodynamic (MHD) instabilities and energetic-ions in in Tokamak plasmas is one of the key issues, which is crucial for the steady-state long pulse operation of future reactors.HL-2A is the first magnetic confined fusion experiment research tokamak device with the non- circular cross-section and advanced divertor configuration in China. Tearing mode is one kind of fundamental resistive MHD in stability that can change the topology of the magnetic field, induce a shortcut in transport and even trigger major disruptions. Energetic-ions are inevitably produced in burning plasmas and various external auxiliary heating processes. There are still some critical problems on debate, such as the resonance condition between tearing mode and energetic-ions, the mechanism of energetic-ions loss induced by this resonant interaction. So farthere is still not acomplete simulation work with respect to the resonant interaction between tearing mode and energetic-ions in the magnetically confined plasmas. Hence, this review paper focuses on the following three aspects. Firstly, we retrospect the history o f the interaction between tearing mode and energetic-ion s. Secondly, based on HL-2A experiments, the numerical simulation results with respect to the resonant interaction be tween energetic-ions and t earing modes and the loss mechanism of energetic-ions are introduced. Finally, the prospects of the resonant interaction between energetic-ions and t earing mode in future reactors are made. [ABSTRACT FROM AUTHOR]

In this paper, numerical simulation is used to analyze the effect of the trailing edge of the stationary blade sawtooth on the 3.5-stage compressor, and the influences of shape and positions of the sawtooth on the compressor speed. The results show that the full blade with high opening on the trailing edge of the inlet guide blade can broaden the stable range of the compressor at 90% speed, and barely impact the pressure ratio and efficiency. But it has little effect the compressor at 100% speed. In this study, a sawtooth with a small tooth width is better than that with a large tooth width, and a sawtooth with full high-opening blades is better than that with partial opening tip. This study deepens the understanding of the effect of serrated trailing edge blades on compressor performance, and provides a reference for research on improving compressor stability. [ABSTRACT FROM AUTHOR]

The study of the interaction between wave and floating breakwater plays an important role in the performance optimization of the breakwater. In this paper, a new combined capsule type floating breakwater was proposed, and the wave dissipation performance of this structure was explored. By numerical calculation using Flow-3D, the influence of relative width and relative draft on the wave dissipation performance was discussed. The internal forces of the mooring system and the sway, heave and roll motion responses of the whole structure were analyzed. Results show that when D/d >0.5 or B/L >0.3, the transmission coefficient of the combined capsule type floating breakwater can reach 50%. Increasing the relative width and the relative draft can both improve the wave dissipation performance of the breakwater. During the movement of the structure, the force of the flexible connection between floating capsules is greater than the mooring force between floating capsules and ground. The sway, heave and roll motion of the structure is very stable, which shows that the overall stability is good. [ABSTRACT FROM AUTHOR]

Tires are very important on the performance of automobiles. The tread structure guarantees that the vehicle and the road surface have a good grasp, so as to play the traction performance and braking effect of the vehicle. The paper based on Reverse Engineering technology, the characteristic structure of reindeer feet was applied to the design of tread element structure, which could effectively improve the passing performance of tires on ice. In order to improve the anti-skid performance of tire, based on the mathematical model of reindeer’s plantar morphology, the bionic ribbed tread element and bionic non-ribbed tread element were designed by engineering bionics technology. Based on reverse engineering, the inner and outer edge curve of reindeer sole was simplified as a mathematical function of characteristic curve, and the reconstructed model of convex crown was transformed into a 3-dimensional model. 2 bionic anti-skid tread elements and herringbone tread elements were established in Solidworks software, combining with the microstructure of convex crown. The adhesion test of tread element and ice was carried out on UTM (QT-1090) linear friction tester. The thermo-mechanical coupling between tread element and ice was established by finite element analysis software ABAQUS. Moreover, the ice surface temperature of 3 tread elements under low pressure of 0.02 MPa and temperature of -11°C was analyzed. The anti-skid performance of bionic trad elements were analyzed by ice adhesion test and Finite Element Method (FEM), compared with the same size conventional herringbone tread element. Under the condition of low pressure (pressure≤0.02 MPa), the 3 kinds of tread elements with self-made ice block was tasted through the ice adhesion test. The result showed that the Dynamic Coefficient of Friction (DCOF) of bionic non-ribbed tread element was the highest at the same velocity, temperature and pressure. It was 1.04-1.26 times herringbone tread element. Through the finite element analysis, it was found that under the low pressure (pressure=0.02 MPa), the ice surface temperature of bionic ribbed tread element, bionic non-ribbed tread element and herringbone tread element increased by 0.21, 0.66 and 0.54 °C relative to the initial temperature, respectively. The ice temperature of bionic non-ribbed tread element increased the highest. The results showed that the anti-slip performance of bionic non-ribbed tread element was the best under low pressure. At high pressure (pressure = 2 MPa), finite element analysis showed that the ice surface temperature under bionic ribbed tread element, bionic non-ribbed tread element and herringbone tread element increased by 7.76, 4.07 and 3.39 °C relative to the initial temperature, respectively. The ice temperature of bionic ribbed tread element increased the highest. The results showed that the anti-slip performance of bionic ribbed tread element was the best under high pressure. Therefore, the bionic non-ribbed tread element and the bionic ribbed tread element had good anti-skid performance under low pressure and high pressure, respectively. The tire slippage caused by ice effect was solved effectively. This paper will provide research direction and theoretical basis for anti-slip design of tread element on ice ground. [ABSTRACT FROM AUTHOR]

The performance of greenhouse wall thermal storage and release capacity depends on the characteristics of the wall material and the thickness of the thermal storage layer. Determining the thickness of the solar greenhouse thermal storage layer is of great significance for promoting the improvement of the solar greenhouse wall. Parametric model according to the actual size and correlation of the test greenhouse was created based on the solar radiation and air temperature. Thickness of the wall thermal storage layer in different months was simulated in this study. In this paper, January 9th, February 9th, March 6th, and April 6th, 2018 in Urumqi was selected as typical sunny days. The solar radiation on the greenhouse floor and wall surface were used as the input condition, and the outdoor air temperature was the boundary conditions. The internal temperature field including each depth of 0, 10, 20, 30, 40, 50 cm of the greenhouse wall from 9:00 to next day 9:00 were simulated by using Autodesk CFD software. In order to ensure the consistency of CFD geometric models within one day and full release of heat from the greenhouse wall at night, no covering insulation quilt was carried out during the greenhouse test. The accuracy of simulated values was verified by comparing with the measured values. The results showed that the simulation results of the greenhouse wall were agreed well with the test results. The average error of each layer on January 9th, February 9th and March 6th was below 1.5 °C. The error and simulated results lags between the test results and the simulated results on April 6th is large. The trend becomes more pronounced as the depth and wall temperature increased. Under the combined influence of greenhouse wall materials, structures, and light and temperature environments, greenhouse wall heat transfer is a complex unsteady process. The brick wall greenhouse was similar to the soil wall greenhouse. The wall could be divided into “insulation layer, stable layer and heat storage layer”. The thickness of each layer was related to the thermal properties of the wall heat storage material and insulation material. The wall temperature fluctuation was more obvious in the depth range of 0-30 cm according to the temperature field of the wall, the temperature attenuation factor of each layer and the delay time. When the wall depth was more than 30 cm, the greenhouse wall temperature fluctuations was relatively flat and the amplitude is small. As the temperature rose, the internal temperature of the greenhouse wall increased overall, and the temperature fluctuations of the various layers were small. The thickness and fluctuation of the greenhouse heat storage layer were less affected by the external light and temperature environment in the case of the greenhouse structure and insulation performance unchanged. In summary, it was feasible to simulate the change of greenhouse wall temperature field. It was reliable that the thickness of greenhouse wall thermal storage layer determined according to the temperature field variation of greenhouse wall. Solar greenhouse temperature environment dynamic simulation model based on greenhouse structure parameters and environmental parameters also could be established in other regions through the methods provided in this paper. It can provide basis and reference for the improvement and optimization of greenhouse wall structure. [ABSTRACT FROM AUTHOR]

In order to solve the problem, that the hard rock fault with a large throw hinders the advance of a fully mechanized mining face, this paper analyzes the disadvantages of the traditional method for passing through the fault and the existing technologie. Also, the paper carries out a systematic study on the deep hole pre-splitting blasting tech-nology for passing through the fault with a large throw. Aiming at the problems of unclear occurrence of fault with a large throw and inaccurate designed path for passing through fault, it puts forward fault occurrence detection technology and the optimized layout for fault detection roadway. Based on the revealed information, the fault strike calculation model is established. Aiming at the problem that deep hole blasting technology is not suitable for working face and groove, it studies the key technology of pre-excavation blasting roadway, and puts forward the layout principle and calculation method of layout parameters of blasting roadway. It determines the scheme of deep hole pre-splitting blasting in blasting roadway, designs the construction method of ear chamber, and solves the problem of concentrated blasting with large amount of explosive. Based on the theory of rock blasting, combined with the characteristics of fault engineering with large throw difference, the blasting parameter selection and calculation method are completed by designing the hole diameter, hole depth, charge mass, plugging length, hole layout and blasting vibration safety control. The underground roadway of 2302 N working face at Xinjulong Coal Mine reveals a hard rock fault with a comprehensive drop 12. 5 m. Through the exposure points of lower roadway and six detection holes arranged in sequence, the initial strike of the fault extending to the working face is verified, and the vertical strike of the fault, the driving scheme along the floor of the coal seam and the driving scheme along the floor of the coal seam under the fault are designed. Based on the measured information, it plans the path through the fault. According to the change of fault occurrence in the path, it divides eight blasting regions, designs the blasting layout parameters in each region, and predicts and analyzes the blasting effect by means of numerical simulation. The application results show that the blasting fissure penetration effect is good, the consumption of shearer picks through the fault is reduced by 40%-50%, and the time is reduced to half compared with the time using traditional method through the fault. The technology for passing large throw fault have been successfully applied in many working faces in Xinjulong coal mine. It has achieved good results in ensuring high efficiency continuous mining, reducing the cost of passing through fault and ensuring blasting safety. The practice has proved that this technique is widely applicable in dealing with large throw fault at a fully mechanized mining face. [ABSTRACT FROM AUTHOR]

Automatic poppet valve is a key component of reciprocating pump, which directly influences its performance and lifespan by controlling flow direction of fluid. Many researchers focus mainly on constant stiffness coefficient springs, due to its widespread application in the automatic poppet valve. Previous research already proves that spring plays an important role in the dynamic properties of poppet valve. The main function of spring is to balance inertia force. Studies also suggest that impact velocity and lag height gradually decreases with the increases of stiffness coefficient and preload. However, the increases of stiffness and preload makes head loss rise. Therefore, only by adjusting different combinations of spring stiffness and preload, it is difficult to reduce impact velocity and lag height while reducing head loss. This contradiction restricts the further improvement of reciprocating pump performance. In addition, the determination of the preload and stiffness of spring is often based on empirical formulas in the design process about constant stiffness coefficient spring. To solve these problems, application of variable stiffness coefficient spring on the pump valve was proposed in this paper. In the meantime, a new optimization design method for it was established. The main research contents of this paper included: (i) A mathematical model on the motion properties of valve disc was established under the condition which spring stiffness coefficient was variable. In this model, dynamics differential equation of valve disc motion, continuous flow equation of fluid between valve gaps and initial condition were all considered about. Based on above mathematical model, a computer simulation program was compiled to solve this simulation model by using of Runge-Kutta method. (ii) In order to verify accuracy of simulation model, two contrast tests were carried out. Firstly, lift of valve disc was compared between simulation results and measured results when stroke frequency was 74 min-1. In the process of measurement, the lift of valve disc was measured by lift sensor and pressure in the liquid cylinder was measured by semiconductor pressure transducers. The contrast result showed that the error was less than ±8％. Secondly, by changing parameter of stroke frequency, maximum lift was compared under different stroke frequencies, the error was less than ±10％. In summary, the above comparison showed that simulation model met the requirement of precision. (iii) According to above simulation model, we selected many different combinations of stiffness and preload for the constant stiffness coefficient spring for simulation comparison. After calculation, there was a mutual contradiction between impact velocity, lag height and head loss. In other words, impact velocity and lag height would increase with head loss reduced. Subsequently, in response to above deficiencies, three common types of spring: stiffness decreasing type, stiffness increasing type and stiffness constant type were chosen in the simulation. By comparing with curves of lift, velocity and head loss, it was demonstrated that stiffness decreasing type can improve the suction performance of reciprocating pump, while impact velocity and lag height were not significantly increased. (iv) Based on the numerical simulation model of valve disc motion properties, optimization simulation model of variable stiffness spring parameters was established. In this optimization model, the objective function was that maximum head loss was minimum. The constraint condition was that impact velocity satisfied the theory of no impact. Genetic algorithm and pattern search were used to solve this optimization model. In the end, compared with the constant stiffness coefficient spring, the maximum head loss for variable stiffness spring was reduced by 20.85%. In conclusion, variable stiffness coefficient spring can be used for improving suction performance of reciprocating pump and alleviating the occurrence of cavitation. Besides, this optimization method has a certain guiding significance for guiding design process of spring parameters on the pump valve. [ABSTRACT FROM AUTHOR]

Focused on the problems that low-precision and easily to fall into local optimum result in the high-dimensional space by the longhorn search algorithm,this paper proposed a new optimization algorithm of the short-lived beetles-the shortlived search algorithm based on quadratic interpolation which was called QIBAS.The algorithm took tentacle’s left and right tentacles as interpolation coordinate points after the beetle moved.And it generated new solution with a second interpolation,then compared to the current optimal solution and the global optimal solution with the fitness of interpolation solution.At the same time to update the global optimal solution,it performed numerical simulation tests on multiple unimodal and multimodal functions,and their dimensions took as 100,500,1 000,5 000 and 10 000.The simulation results show that the introduction of quadratic interpolation effectively improves the ability of the BAS algorithm to jump out of the local optimum.When QIBAS solves the optimal value,its solution accuracy is greatly improved,and the convergence speed is also significantly improved.The effectiveness of the improved algorithm is verified. [ABSTRACT FROM AUTHOR]

For the detection blind zone problem of interference suppression method based on block matrix, this paper proposed a post-processing method of interference suppression based on local transform processing. Firstly, the method used linear trans-- form synthesize a set data on the interference suppression azimuth. Secondly, it obtained the corresponding spatial spectrum of each spatial azimuth by spatial spectrum synthesis method. Then, it extracted the base change value of spatial spectral by local transformation. Finally, it equalized the spatial spectrum by the base change value of spatial spectrum and reduced the detection blind wne. The numerical simulation and data processing results show that, this method reduces the change value of spatial spectrum base through local nonlinear equalization of spatial spectrum after interference suppression, reduces detection blind zone within 3°, and improves interference suppression method based on block matrix. [ABSTRACT FROM AUTHOR]

In view of the characteristics of the small-scale unmanned helicopter system which is highly nonlinear, strongly coupled and susceptible to internal and external disturbance, this paper proposed a control strategy combining nonlinear block back-stepping control with generalized proportional integral observer. In this method, at first, it used a generalized proportional integral observer to construct a multi-order observation loop and to estimate the system state variables, disturbances and the multi-order derivatives of disturbances, and then it added the estimated value of disturbance into the helicopter system model and adapted back-steeping method to obtain the tracking flight controller of the helicopter. Numerical simulation results of step signal and complex trajectory tracking show that, the designed controller has an ideal dynamic response performance, tracking capability and disturbance attenuation ability under the influence of various internal and external disturbances. Compared with the nonlinear disturbance observer, the generalized proportional integral observer has a higher estimation accuracy for high order and fast time-varying disturbances and achieves better disturbance suppression effects. [ABSTRACT FROM AUTHOR]