An Operational Modal Analysis Experimental Technique for Self-propelled Gun

The experimental modal analysis of the selected self-propelled gun was completed to obtain its modal frequency distribution and modes by using an operational modal analysis experimental technique.The result obtained by the method was compared with that obtained by the traditional method.It indicates that the two results are in good agreement.

Self-propelled Leidenfrost droplets on femtosecond-laser-induced surface with periodic hydrophobicity gradient

The controllable transfer of droplets on the surface of objects has a wide application prospect in the fields of microfluidic devices,fog collection and so on.The Leidenfrost effect can be utilized to significantly reduce motion resistance.However,the use of 3D structures limits the widespread application of self-propulsion based on Leidenfrost droplets in microelectromechanical system.To manipulate Leidenfrost droplets,it is necessary to create 2D or quasi-2D geometries.In this study,femtosecond laser is applied to fabricate a surface with periodic hydrophobicity gradient(SPHG),enabling directional self-propulsion of Leidenfrost droplets.Flow field analysis within the Leidenfrost droplets reveals that the vapor layer between the droplets and the hot surface can be modulated by the SPHG,resulting in directional propulsion of the inner gas.The viscous force between the gas and liquid then drives the droplet to move.

Passive particles driven by self-propelled particle:The wake effect

This work focuses on numerically studying hydrodynamic interaction between a passive particle and a self-propelled particle,termed a squirmer,by using a two-dimensional lattice Boltzmann method(LBM).It is found that the squirmer can capture a passive particle and propel it simultaneously,provided the passive particle is situated within the squirmer's wake.Our research shows that the critical capture distance,which determines whether the particle is captured,primarily depends on the intensity of the squirmer's dipolarity.The stronger dipolarity of squirmer results in an increased critical capture distance.Conversely,the Reynolds number is found to have minimal influence on this interaction.Interestingly,the passive particle,when driven by the squirmer's wake,contributes to a reduction in the squirmer's drag.This results in a mutual acceleration for both particles.Our findings can provide valuable perspectives for formulating the principles of reducing the drag of micro-swimmers and help to achieve the goal of using micro-swimmers to transport goods without physical tethers.

Investigation and Research on Auto-Aiming of Self-Propelled Gun

This paper analyses the automatic adjusting of the aim angle because of self-propelledgun’s platform sloping with ground plane caused by self-propelled gun movement, sets up adjustingmethod and model, and presents the corresponding algorithm.

An internal ballistic model of electromagnetic railgun based on PFN coupled with multi-physical field and experimental validation

To accelerate the practicality of electromagnetic railguns,it is necessary to use a combination of threedimensional numerical simulation and experiments to study the mechanism of bore damage.In this paper,a three-dimensional numerical model of the augmented railgun with four parallel unconventional rails is introduced to simulate the internal ballistic process and realize the multi-physics field coupling calculation of the rail gun,and a test experiment of a medium-caliber electromagnetic launcher powered by pulse formation network(PFN)is carried out.Various test methods such as spectrometer,fiber grating and high-speed camera are used to test several parameters such as muzzle initial velocity,transient magnetic field strength and stress-strain of rail.Combining the simulation results and experimental data,the damage condition of the contact surface is analyzed.

Mussel-inspired PTW@PDA composites for developing high-energy gun propellants with reduced erosion and enhanced mechanical strength

The severe erosion and inadequate mechanical strength are prominent challenges for high-energy gun propellants.To address it,novel PTW@PDA composites was prepared by polydopamine(PDA)-modifying onto potassium titanate whisker(PTW,K_(2)Ti_(6)O_(13)),and after was incorporated into gun propellant as erosion-reducing and mechanical-reinforcing fillers.The interfacial characterizations results indicated that as-prepared PTW@PDA composites exhibits an enhanced surface compatible with propellant matrix,thereby facilitating their dispersion into propellants more effectively than raw PTW materials.Compared to original propellants,PTW@PDA-modified propellants exhibited significant less erosion,with a Ti-Kbased protective coating being detected on the eroded steel.And 0.5 wt%and 1.0 wt%addition of PTW@PDA significantly improved impact,compressive and tensile strength of propellants.Despite the inevitably reduction in relative force,PTW@PDA slightly increase propellant burning rate while exerting little adverse impact on propellant dynamic activity.This strategy can provide a promising alternative to develop high-energy gun propellant with less erosion and more mechanical strength.

Classifying wakes produced by self-propelled fish-like swimmers using neural networks

We consider the classification of wake structures produced by self-propelled fish-like swimmers based on local measurements of flow variables.This problem is inspired by the extraordinary capability of animal swimmers in perceiving their hydrodynamic environments under dark condition.We train different neural networks to classify wake structures by using the streamwise velocity component,the crosswise velocity component,the vorticity and the combination of three flow variables,respectively.It is found that the neural networks trained using the two velocity components perform well in identifying the wake types,whereas the neural network trained using the vorticity suffers from a high rate of misclassification.When the neural network is trained using the combination of all three flow variables,a remarkably high accuracy in wake classification can be achieved.The results of this study can be helpful to the design of flow sensory systems in robotic underwater vehicles.

Where is the rudder of a fish?:the mechanism of swimming and control of self-propelled fish school

Numerical simulation and control of self- propelled swimming of two- and three-dimensional biomimetic fish school in a viscous flow are investigated. With a parallel computational fluid dynamics package for the two- and three-dimensional moving boundary problem, which combines the adaptive multi-grid finite volume method and the methods of immersed boundary and volume of fluid, it is found that due to the interactions of vortices in the wakes, without proper control, a fish school swim with a given flap- ping rule can not keep the fixed shape of a queue. In order to understand the secret of fish swimming, a new feedback con- trol strategy of fish motion is proposed for the first time, i,e., the locomotion speed is adjusted by the flapping frequency of the caudal, and the direction of swimming is controlled by the swinging of the head of a fish. Results show that with this feedback control strategy, a fish school can keep the good order of a queue in cruising, turning or swimming around circles. This new control strategy, which separates the speed control and direction control, is important in the construction of biomimetic robot fish, with which it greatly simplifies the control devices of a biomimetic robot fish.

Comparison of Microbubble and Air Layer Injection with Porous Media for Drag Reduction on a Self-propelled Barge Ship Model

Ship resistance issues are related to fuel economy,speed,and cost efficiency.Air lubrication is a promising technique for lowering hull frictional resistance as it is supposed to modify the energy in the turbulent boundary layer and thereby reduce hull friction.In this paper,the objective is to identify the optimum type of air lubrication using microbubble drag reduction(MBDR)and air layer drag reduction(ALDR)techniques to reduce the resistance of a 56-m Indonesian self-propelled barge(SPB).A model with the following dimensions was constructed:length L=2000 mm,breadth B=521.60 mm,and draft T=52.50 mm.The ship model was towed using standard towing tank experimental parameters.The speed was varied over the Froude number range 0.11–0.31.The air layer flow rate was varied at 80,85,and 90 standard liters per minute(SLPM)and the microbubble injection coefficient over the range 0.20–0.60.The results show that the ship model using the air layer had the highest drag reduction up to a maximum of 90%.Based on the characteristics of the SPB,which operates at low speed,the optimum air lubrication type to reduce resistance in this instance is ALDR.

A comparative study of the self-propelled jumping capabilities of coalesced droplets on RTV surfaces and superhydrophobic surfaces

Understanding the mechanism of coalescence-induced self-propelled jumping behavior provides distinct insights in designing and optimizing functional coatings with self-cleaning and anti-icing properties.However,to date self-propelled jumping phenomenon has only been observed and studied on superhydrophobic surfaces,other than those hydrophobic surfaces with weaker but fairish water-repellency,for instance,vulcanized silicon rubber(RTV) coatings.In this work,from the perspective of thermodynamic-based energy balance aspect,the reason that self-propelled jumping phenomenon does not happen on RTV coatings is studied.The apparent contact angles of droplets on RTV coatings can be less than the theoretical critical values therefore cannot promise energy surplus for the coalesced droplets onside.Besides,on RTV and superhydrophobic surfaces,the droplet-size dependent variation characteristics of the energy leftover from the coalescence process are opposite.For the droplets coalescing on RTV coatings,the magnitudes of energy dissipations are more sensitive to the increase in droplet size,compared to that of released surface energy.While for superhydrophobic coatings,the energy generated during the coalescence process can be more sensitive than the dissipations to the change in droplet size.

One-step green method to prepare progressive burning gun propellant through gradient denitration strategy

Gradiently denitrated gun propellant(GDGP)prepared by a“gradient denitration”strategy is obviously superior in progressive burning performance to the traditional deterred gun propellant.Currently,the preparation of GDGP employed a tedious two-step method involving organic solvents,which hinders the large-scale preparation of GDGP.In this paper,GDGP was successfully prepared via a novelty and environmentally friendly one-step method.The obtained samples were characterized by FT-IR,Raman,SEM and XPS.The results showed that the content of nitrate groups gradiently increased from the surface to the core in the surface layer of GDGP and the surface layer of GDGP exhibited a higher compaction than that of raw gun propellant,with a well-preserved nitrocellulose structure.The denitration process enabled the propellant surface with regressive energy density and good progressive burning performance,as confirmed by oxygen bomb and closed bomb test.At the same time,the effects of different solvents on the component loss of propellant were compared.The result showed that water caused the least component loss.Finally,the stability of GDGP was confirmed by methyl-violet test.This work not only provided environmentally friendly,simple and economic preparation of GDGP,but also confirmed the stability of GDGP prepared by this method.

Development and simulation of a gridded thermionic cathode electron gun for a high-energy photon source

A gridded thermionic cathode electron gun was developed for the linear accelerator of the High Energy Photon Source(HEPS).An electron gun should provide a large maximum bunch charge with a wide adjustable range.To satisfy these requirements,the shape of the electrode was optimized using a multi-objective genetic algorithm.A large bunch charge with an adjustable range was achieved using the grid-limited gun,the flow of which was analyzed using 3-D simulations.The electron gun has been manufactured and tested,and the measured data of the grid-limited current and simulation results are compared and discussed in this study.

Ratchet transport of self-propelled chimeras in an asymmetric periodic structure

We studied the rectified transport of underdamped particles subject to phase lag in an asymmetric periodic structure.When the inertia effect is considered,it is possible to observe reversals of the average velocity with small self-propelled force,whereas particles always move in the positive direction with large self-propelled force.The introduction of phase lag leads particles to follow circular orbits and suppress the polar motion.In addition,this can adjust the direction of particle motion.There exists an optimal value of polar interaction strength at which the rectification is maximal.These results open the way for many application processes,such as spatial sorting of particles mixture and separation based on their physical properties.

Nonvanishing optimal noise in cellular automaton model of self-propelled particles

A minimal cellular automaton model is introduced to describe the collective motion of self-propelled particles on two-dimensional square lattice. The model features discretization of directional and positional spaces and single-particle occupation on one lattice site. Contrary to the Vicsek model and its variants, our model exhibits the nonvanishing optimal noise. When the particle density increases, the collective motion is promoted with optimal noise strength and reduced with noise strength out of optimal region. In addition, when the square lattice undergoes edge percolation process, no abrupt change of alignment behaviors is observed at the critical point of percolation.

Dynamics of a self-propelled particle under different driving modes in a channel flow

In this paper, a model that combines the lattice Boltzmann method with the singularity distribution method is proposed to simulate a self-propelled particle swimming（exhibiting translation and rotation） in a channel flow. The results show that the velocity distribution for a self-propelled particle swimming deviates from a Maxwellian distribution and exhibits highvelocity tails. The influence of an eccentric potential doublet on the translation velocity of the particle is significant. The velocity decay process can be described using a double exponential model form. No large differences in the velocity distribution were observed for different translation Reynolds numbers, rotation Reynolds numbers, or regular intervals.

Effect of the structure of backward orifices on thejet performance of self-propelled nozzles

Self-propelled nozzle is a critical component of the radial jet drilling technology.Its backward orifice structure has a crucial influence on the propulsive force and the drilling performance.To improve the working performance of the nozzle,the numerical simulation model is built and verified by the experimental results of propulsive force.Then the theoretical model of the energy efficiency and energy coefficient of the nozzle is built to reveal the influence of the structural parameters on the jet performance of the nozzle.The results show that the energy efficiency and energy coefficient of the backward orifice increase first and then decrease with the angle increases.The energy coefficient of forward orifice is almost constant with the angle increases.With the increase in the number and diameter,energy efficiency and energy coefficient of the forward orifice gradually decrease,but the backward orifice energy coefficient first increases and then decreases.Finally,it is obtained that the nozzle has better jet performance when the angle of backward orifice is 30°,the number of backward orifice is 6,and the value range of diameter is 2-2.2 mm.This study provides a reference for the design of efficiently self-propelled nozzle for radial jet drilling technology.

Traction Potential Analysis of Self-Propelled Seafloor Trencher Based on Mechanical Measurements in Bentonite Soil

Shear stress-displacement relationship model of soil is very important to predict the tractive performance of tracked vehicle. Most shear stress-displacement models were proposed for terrestrial field.However,they are not suit for soft seafloor with flow surface and high water content. Based on comprehensive analysis of seafloor soil shear deformation and track segment shear tests,a new empirical model of shear stressdisplacement relationship for saturated soft-plastic soil(SSP model) was proposed. To validate the SSP model and evaluate potential tractive force of self-propelled seafloor trencher,a test platform,where track segment shear test and drawbar pull test can be performed in seafloor soil substitute(bentonite water mixture),was built. Series of shear tests were carried out. Test results show that the SSP model can describe the mechanical behavior of track segment in seafloor soil substitute with good approximation. Through analyzing the main external forces,including environmental loads from seafloor soil and sea current applied to seafloor tracked trencher during the trenching process in a straight line,drawbar pull analysis model was deduced with the SSP model. A scale test model of seafloor tracked trencher was built,and the verification tests for drawbar pull analysis model were designed and carried out. Results of verification tests indicate that the drawbar pull analysis model was feasible and effective. The drawbar pull tests also indicated that the SSP model is valid from another side.

Going in Homer:The Role of Verb-Inherent Actionality Within Self-Propelled Motion-Event Encoding

The paper aims at investigating the encoding of self-propelled motion events in Homeric Greek in the light of the typology of motion events,taking into account the case of to go.The verbal class of the self-propelled motion refers to those verbs expressing the idea of a simple translational motion,such as to go,to move,without any information about the manner of motion(see,by contrast,the class of the manner-of-motion verbs,such as to run,to swim)or about the path of motion(see,by contrast,the class of the path verbs,such as to enter,to exit).According to Talmy(2000),world languages can be distinguished depending on whether they prototypically express the semantic component of Path in or outside the motion verb.Languages belonging to the S(atellite)-Framed type tend to convey Path outside the motion verb,in a satellite element,such as a particle,an adposition(adpositional phrase),a preverb,an adverb(ial),a nominal case marker.The prototypical encoding pattern of the S-Framed languages,such as Homeric Greek,involves a motion verb conveying Manner and a satellite conveying Path,i.e.,[manner-of-motion verb+Path-satellite].Nonetheless,another pattern is used by this type of languages,albeit less prototypical,which involves a motion verb conveying only Motion and a satellite conveying Path,i.e.,[self-propelled motion verb+Path-satellite].Verb-inherent actionality,namely telicity,turns out to be a strong feature within the ancient Indo-European languages,such as Homeric Greek,playing a role not only in the development of aspectual/tense morphology,but also in the encoding of motion events,at least with reference to manner-of-motion verbs.The present paper aims at verifying the role of inherent telicity within self-propelled motion verbs,through the analysis of Homeric verbs for go.The study takes into account the Homeric suppletive paradigm for go,focusing on ερχομαι“go;come”and ηλθον(aorist)“go;come”(also with reference to the unclear actional opposition between ερχομαι and ειμι“go;come”).From the textual analysis of all the occurrences of both ερχομαι and ηλθον,as well as their co-occurring Path-encoding elements in the Iliad and the Odyssey,data show to what extent verbal inherent telicity plays an important role in motion event encoding also within the class of self-propelled motion verbs.

Deployment of Self-Propelled Modular Transporter for Vessel Installation

The traditional way of installing large vessels has always been to employ the use of cranes. The Water Handling Debottlenecking Project team has, instead, made use of a different technology—employing a Self-Propelled Modular Transporter (SPMT) to install nine vessels in situ. These SPMT units have many advantages over crane installations, such as safety and efficiency, not to mention lower costs due to their self-propelled capabilities.

Development and Evaluation of Self-propelled Cabbage/Cauliflower Harvester

In the present study,self-propelled cabbage/cauliflower harvester was designed,developed and evaluated.The machine consisted of different components like engine,frame,shearing(cutting)unit and power transmission unit.The power transmission unit consisted of main clutch,shearing blade operating clutch,belt drive unit,chain and sprocket drive,universal joint and cutter blade assembly.The main working principle of harvester is based on shearing of crop stem against high-speed rotating blade.The power from the engine is transmitted by belt-pulley drive unit to transmission shaft on which chain and sprocket is mounted on one side and then power is transmitted to shearing blade coupling with the help of a stationary pulley and fixed socket.Average mean head diameter of the selected cabbage and cauliflower was 89.5±15.24 mm and 107.5±15.24 mm,respectively.Average mean stem(plant)diameter of the selected cabbage and cauliflower was 18±4.85 mm and 21.5±3.08 mm,respectively.The shearing force increased with increase in diameter of stem.The optimum performance of the machine was achieved when it was operated at 1.5 km/h forward speed and the shearing blade moving at speed of 147 rpm.The mean field capacity for developed prototype was observed as 0.063 ha/h and 0.053 in case of cabbage and cauliflower,respectively with field efficiency of 91.97 and 90.48%.The average head damage was negligible(0.15%)for both the crops.The average untrimmed percentage with developed harvester was 3.2 and 3.0%in case of cabbage and cauliflower crop,respectively.The developed machine helps to increase the field capacity in cabbage/cauliflower harvesting due to 7-times more capacity and 50%cheaper compared to traditional method of cabbage/cauliflower harvesting.At the operating condition of forward speed(1.5 km/h)and shearing blade speed(147 rpm),the machine could harvest 0.5 ha of cabbage and 0.42 ha of cauliflower farm per day of 8-h.This same task would have required between 15 labour per day if entirely done manually.