Integrated hazard assessment of rockfall incidents in the Cap Aokas Cliff Region

Rock fall accidents in mountainous cliff areas have significant consequences for human life and transportation.This study aimed to evaluate the rockfall hazard in the Cap Aokas cliff region located along the northeast coast of Algeria by identifying the key factors contributing to rockfall occurrence.We employed a combination of kinematic analysis,Matterocking method,and 3D trajectory simulations to determine zones that are susceptible to rockfall mobilization.By using a probabilistic and structural approach in conjunction with photogrammetry,we identified the controlling factors.The kinematic analysis revealed the presence of five discontinuity families,which indicated both plane and wedge failure modes.The 3D trajectory simulations demonstrated that the falling blocks followed the stream direction.We then validated the susceptibility maps generated from the analysis using aerial photos and historical rockfall events.The findings of this study enhance our understanding of rockfall phenomena and provide valuable insights for the development of effective strategies to mitigate rockfall hazards.

Trajectory design and simulation in injection phase for hyper-velocity kinetic energy missile

A movement law of laser beam facula is designed for the injection trajectory of hyper-ve- locity kinetic energy missile to eliminate the influence of motor exhaust smoke on laser signal trans mission. Taking guidance loop of hyper velocity kinetic energy missile as plant, a closed loop control system with desired step response characteristics is constructed and the movement law of laser beam facula for the missile injection trajectory is designed based on the output signal of the closed loop controller under a step input. Six degree of freedom trajectory simulations show that by the guidance of the laser beam facula moving with designed law, the missile can finish transition from the initial trajectory to a stable tracking trajectory without overshoot within the required time.

Diagnostic Analysis of Rainstorm and Backward Trajectory Simulation of Water Vapor in Jilin Province in July,2010

[Objective] The research aimed to analyze the rainstorm process and backward trajectory simulation of water vapor condition in Jilin Province in July,2010.[Method] Based on the actual situation data of routine weather chart,NCEP (2.5°×2.5°) reanalysis data per 6 h and GBL data of NOAA,the rainstorm process was carried out the diagnostic analysis of physical quantity in Jilin Province in July,2010.Moreover,HYSPLIT backward trajectory mode was used to simulate the water vapor source.[Result] The coexistence of upper-level divergence and low-level convergence generated the ascending motion,which was the dynamic condition of rainstorm appearance.The unstable energy induced by the low-level shear promoted the generation of heavy rainstorm.The water vapor source of precipitation process was divided into the water vapor in the southern sea area,northern high-altitude water vapor transportation and local water vapor source.[Conclusion] The research provided some reference basis for the forecast and analysis of rainstorm.

Spacecraft aerodynamics and trajectory simulation during aerobraking

This paper uses a direct simulation Monte Carlo （DSMC） approach to simulate rarefied aerodynamic characteristics during the aerobraking process of the NASA Mars Global Surveyor （MGS） spacecraft. The research focuses on the flowfield and aerodynamic characteristics distribution under various free stream densities. The vari- ation regularity of aerodynamic coefficients is analyzed. The paper also develops an aerodynamics-aeroheating-trajectory integrative simulation model to preliminarily calculate the aerobraking orbit transfer by combining the DSMC technique and the classical kinematics theory. The results show that the effect of the planetary atmospheric density, the spacecraft yaw, and the pitch attitudes on the spacecraft aerodynamics is significant. The numerical results are in good agreement with the existing results reported in the literature. The aerodynamics-aeroheating-trajectory integrative simulation model can simulate the orbit transfer in the complete aerobraking mission. The current results of the spacecraft trajectory show that the aerobraking maneuvers have good performance of attitude control.

Fragmentation dynamics of electron-impact double ionization of helium

We study the double ionization dynamics of a helium atom impacted by electrons with full-dimensional classical trajectory Monte Carlo simulation. The excess energy is chosen to cover a wide range of values from 5 e V to 1 ke V for comparative study. At the lowest excess energy, i.e., close to the double-ionization threshold, it is found that the projectile momentum is totally transferred to the recoil-ion while the residual energy is randomly partitioned among the three outgoing electrons, which are then most probably emitted with an equilateral triangle configuration. Our results agree well with experiments as compared with early quantum-mechanical calculation as well as classical simulation based on a two-dimensional Bohr's model. Furthermore, by mapping the final momentum vectors event by event into a Dalitz plot,we unambiguously demonstrate that the ergodicity has been reached and thus confirm a long-term scenario conceived by Wannier. The time scale for such few-body thermalization, from the initial nonequilibrium state to the final microcanonical distribution, is only about 100 attoseconds. Finally, we predict that, with the increase of the excess energy, the dominant emission configuration undergoes a transition from equilateral triangle to T-shape and finally to a co-linear mode. The associated signatures of such configuration transition in the electron–ion joint momentum spectrum and triple-electron angular distribution are also demonstrated.

Study on Overall Concept Planning of Terminal Correction Mortar Projectiles

The system composition, the operational principle of terminal correction mortar projectiles （TCMP） and the concept planning design of TCMP are researched in this paper. An overall design and aerodynamic configuration layout for TCMP are made in this paper, and its aerodynamic coefficients are calculated by using computational fluid dynamics （CFD） software. Test results of TCMP simulated ballistic projectiles indicate the designed TCMP can satisfy the interior ballistic demand and has a fine flight stability. The drag coefficients identified from the radar velocity-time data are in accord with the CFD computed results. According to the exposure frequency of the ground laser designator, a four-quadrant impulse correction scheme and a high exposure frequency impulse correction scheme are brought. The latter can calculate the target azimuth angle by counting the times of the facula passing through one quadrant. Simulation results also show that the guidance precision of the velocity pursuit is higher than that of the body pursuit, and the detector axis is less circuitous. Researches on the typical trajectory indicate that the terminal impulse correction can improve the hit precision of TCMP remarkably.

A new calibration algorithms of spinning projectile aerodynamic parameters

This paper demonstrates that the application of calibration algorithms of aerodynamic parameters for the trajectory of spinning projectile is successful. First, from the point of view of the trajectory simulation, a general summary of well-known trajectory models is given. A five degrees of freedom （5 DOF） model is developed that can match the projectile motion essentially in the vertex region, and the results obtained by 5 DOF model are in close agreement with those of a more sophisticated 6 DOF model for elevation angles above 45 degrees. Secondly, the calibration algorithms have been developed and are summarized. The methods of calibrating the flight trajectory models are compared, and these methods are shown to be effective in the representative cases. In addition, the method of Math number calibration （MNC） is presented; some possible areas in MNC for further investigation are indicated together with benefits to be gained. The utilization of MNC schemes not only allow a worthwhile reduction of calibration rounds firing in range and accuracy （R＆A） trial and production of firing tables （PFT） test, but also make PFT and fire control data （FCD） more cost effective.

An Improved Underwater Confrontation Simulation Method of Naval Amphibious Operational Training System

This paper described an improved underwater confrontation simulation method of naval amphibious operational training system. The initial position of submarine forces on the enemy is generated automatically, and the attacking distance model of torpedoes is established based on the kinematics theory, which is more flexible and reasonable to judge the launch condition compared to traditional method. The two kinds of confrontation behavior models on the enemy submarine are created to depict its tactical action from the defensive to the offensive as well as the contrary, ensuring that operational style is simulated more comprehensively and properly. The existing motion trajectory estimation and collision detection algorithms on operational platforms are also improved to reduce the iteration error and further enhance the detection accuracy of target hit.

Trajectory planning and motion control of full-row seedling pick-up arm

Frequent start-stops of automatic seedling transplanters would lengthen the seedling picking time due to alternating movement of the motor,and cause positioning errors and frequent motor vibrations when starting the machine.To solve these problems and ensure the pick-up continuity of automatic transplanters,in this study the smooth circular arc interpolation algorithm and the least square method for multinomial curve fitting were used to conduct the trajectory planning of automatic transplanter based on the movement of the pick-up arm of the transplanter.Velocity and time curves were fitted in segments to acquire motion control parameters and further tracking control was conducted.The mathematical model of the control system was established using Simulink,and simulation analysis and system debugging test were performed.Experiments show that the trajectory curves obtained by MATLAB’s data processing can realize the continual and smooth motion trajectory of the pick-up arm;stepper motor velocity control can effectively track the planning curve and improve the seedling pick-up efficiency.The pick-up and pushing time of each motion of the planned plug seedling transplanter reduced by 1.0678 s and the start-stop times reduced from 6 to 1,which solved the frequent motor vibrations when starting the machine and improved the stability of the system.In addition,overstep and out-of-step of the motor at the start-stop moment were avoided and displacement error was reduced.

Stratospheric entry point for upper-tropospheric air within the Asian summer monsoon anticyclone

The Asian summer monsoon(ASM) anticyclone isolates upper-tropospheric air within the interior of the anticyclone from the outside. Forward trajectory simulations in previous studies have shown that much of the air within the ASM anticyclone can be trapped for up to two or three weeks, not only laterally but also vertically. Here, we investigate the locations of exit points for upper-tropospheric air trapped within the ASM anticyclone, especially the preferred tropopause-crossing locations, using a 3-dimensional trajectory model. Forward trajectory calculations show two-thirds of the air crosses the tropopause at the southern part of the anticyclone via upward diabatic transport. Furthermore, some air crosses at northern and eastern parts via isentropic shedding, but air crosses rarely through the center of the anticyclone. However, calculations also show that many stratospheric parcels within the anticyclone are traceable from the upper-tropospheric anticyclone. This implies they cannot break through the tropopause directly overhead but instead enter the stratosphere via other entry points.