In this paper,to study the mechanical responses of a solid propellant subjected to ultrahigh acceleration overload during the gun-launch process,specifically designed projectile flight tests with an onboard measuremen...
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In this paper,to study the mechanical responses of a solid propellant subjected to ultrahigh acceleration overload during the gun-launch process,specifically designed projectile flight tests with an onboard measurement system were *** projectiles containing dummy HTPB propellant grains were successfully recovered after the flight tests with an ultrahigh acceleration overload value of 8100 *** onboard-measured time-resolved axial displacement,contact stress and overload values were successfully obtained and *** compression tests of the dummy HTPB propellant used in the gunlaunched tests were carried out at low and intermediate strain rates to characterize the propellant's dynamic properties.A linear viscoelastic constitutive model was employed and applied in finite-element simulations of the projectile-launching *** the launch process,the dummy propellant grain exhibited large deformation due to the high acceleration overload,possibly leading to friction between the motor case and propellant *** calculated contact stress showed good agreement with the experimental results,though discrepancies in the overall displacement of the dummy propellant grain were *** dynamic mechanical response process of the dummy propellant grain was analysed in *** results can be used to estimate the structural integrity of the analysed dummy propellant grain during the gun-launch process.
With the future substantial increase in coverage and network heterogeneity,emerging networks will encounter unprecedented security *** communication is considered a potential enhanced security and privacy solution for...
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With the future substantial increase in coverage and network heterogeneity,emerging networks will encounter unprecedented security *** communication is considered a potential enhanced security and privacy solution for safeguarding future wireless networks,as it can enable monitors to detect the transmitter's transmission behavior with a low probability,thereby ensuring the secure trans-mission of private *** to its favorable security,it is foreseeable that covert communication will be widely used in various wireless communication settings such as medical,financial,and military ***,existing covert communication methods still present many challenges toward prac-tical *** particular,it is difficult to guarantee the effectiveness of covert schemes based on the randomness of eavesdropping environments,and it is challenging for legitimate users to detect weak cov-ert *** that emerging artificial-intelligence-aided transmission technologies can open up entirely new opportunities to address the above challenges,we provide a comprehensive review of recent advances and potential research directions in the field of intelligent covert communications in this ***,the basic concepts and performance metrics of covert communications are ***,exist-ing effective covert communication techniques in the time,frequency,spatial,power,and modulation domains are ***,this paper discusses potential implementations and challenges for intel-ligent covert communications in future networks.
Many shared mobility services, such as electric scooters and bicycles, are available for outdoor use. However, finding a suitable shared mobility vehicle for indoor environments still presents a significant challenge....
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Although post-installed anchors are used for seismic reinforcement and installation of equipment, there is concern that the anchorage performance of anchor bolts anchored to base concrete with a surface layer that has...
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In this study,the mechanical behavior of crystal group of hexagonal close-packed(hcp;αphase)and body-centered cubic(bcc;βphase)during tensile loading was investigated to elucidate the mechanism from elastic to plast...
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In this study,the mechanical behavior of crystal group of hexagonal close-packed(hcp;αphase)and body-centered cubic(bcc;βphase)during tensile loading was investigated to elucidate the mechanism from elastic to plastic deformation transition of the rolled LZ91 Mg alloy using transmission-X-ray diffraction(transmission-XRD)measurement,transmission electron microscopy(TEM),scanning transmission electron microscopy(STEM),energy dispersive X-ray spectroscopy(EDS).The approximate proof stress of the LZ91 Mg alloy sample was found that the lattice strain retained the expanded state from 0.6%nominal strain,and the transmission-XRD measurement characterized the crystalline behavior during the transition by the integrated intensity of crystal group hcp(100).The lattice strain of bcc(110)decreased from the 0.6%nominal strain due to dislocation activity,which occurred nearβ/βgrain *** addition,we performed the analyses of electron energy loss spectroscopy(EELS)modes,the Li-K peak disappeared from the segregated Li regions of 10–60 nm nearβ/βgrain boundary at the nominal strain of 0.8%.Understanding this mechanical behavior during the elastic to plastic deformation transition by transmission-XRD is crucial for the development of Mg-Li alloys.
There has been renewed interest in commercial supersonic air travel in recent years with new concepts currently being advertised for a potential comeback within the next decade. Current regulations do not permit overl...
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The objective of this paper is to investigate the dynamic behavior of cloud cavitating flow around a flexible hydrofoil with experimental and numerical *** tightly coupled fluid-structure interaction(FSI)modeling is a...
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The objective of this paper is to investigate the dynamic behavior of cloud cavitating flow around a flexible hydrofoil with experimental and numerical *** tightly coupled fluid-structure interaction(FSI)modeling is applied and validated with the experimental *** Q-criterion andω-criterion are applied to illustrate the interaction between the vortex structures and *** flexibility is seen to result in nose-up twist deformation,causing a reduction of the shedding frequency from an increase in the attached cavity *** to the flexibility,the fluctuation of load coefficients of the flexible hydrofoil is larger than that of the rigid ***,the re-entrant jet propagation speed of the flexible hydrofoil is greater than that of the rigid *** shed cloud cavity is observed to be uniform along the flexible hydrofoil span under the combined influence of the strong vibration and the gap flow.
The economy of a country is directly impacted by agricultural productivity. If proper precautions are not taken in this area, plants suffer serious consequences, which have an impact on the quality, quantity, or produ...
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Signal parameters such as amplitude, frequency, decay constant, and phase play an important role in identifying the signal’s origin in many real-life applications. Standard gradientbased curve-fitting approaches are ...
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This study aims to achieve uniformity in heat history by mitigating heat gradients during the production of overhang structures using the metal powder melting process. Specimens with a 30-degree overhang angle were cr...
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