Topological optimization of ballistic protective structures through genetic algorithms in a vulnerability-driven environment

Reducing the vulnerability of a platform,i.e.,the risk of being affected by hostile objects,is of paramount importance in the design process of vehicles,especially aircraft.A simple and effective way to decrease vulnerability is to introduce protective structures to intercept and possibly stop threats.However,this type of solution can lead to a significant increase in weight,affecting the performance of the aircraft.For this reason,it is crucial to study possible solutions that allow reducing the vulnerability of the aircraft while containing the increase in structural weight.One possible strategy is to optimize the topology of protective solutions to find the optimal balance between vulnerability and the weight of the added structures.Among the many optimization techniques available in the literature for this purpose,multiobjective genetic algorithms stand out as promising tools.In this context,this work proposes the use of a in-house software for vulnerability calculation to guide the process of topology optimization through multi-objective genetic algorithms,aiming to simultaneously minimize the weight of protective structures and vulnerability.In addition to the use of the in-house software,which itself represents a novelty in the field of topology optimization of structures,the method incorporates a custom mutation function within the genetic algorithm,specifically developed using a graph-based approach to ensure the continuity of the generated structures.The tool developed for this work is capable of generating protections with optimized layouts considering two different types of impacting objects,namely bullets and fragments from detonating objects.The software outputs a set of non-dominated solutions describing different topologies that the user can choose from.

Editorial: Special subject on the mechanical behavior of thermal protection materials and structures

The thermal protection materials and structures are widely used in hypersonic vehicles for the purpose of thermal insulation, and their mechanical behavior is one of the key issues in design and manufacture of hypersonic vehicles. It is our great pleasure to present the seven papers in this special subject of Theoretical ＆ Applied Mechanics Letters （TAML） and introduce the recent progresses on the mechanical behavior of thermal protection materials and structures by the authors.

Seismic protection of frame structures via semi-active control:modeling and implementation issues

Theoretical and practical issues concerning the multi-faceted task of mitigating the latero-torsional seismic response of a prototypal frame structure with asymmetric mass distribution are approached, Chevron braces with embedded magnetorheological dampers acting on the interstory drift are used to ensure additional energy dissipation. The semi-active control strategy employed to govern the modification of the damper characteristics via feedback is based on the selection of optimal forces according to a H2/LQG criterion, with respect to which the actual forces are regulated by a clipped-optimal logic. A dynamic observer is used to estimate the state through a non-collocated placement of the acceleration sensors. Several aspects to be addressed throughout the complex process including the design, modelization, and implementation phases of semi-active protection systems are discussed. Finally, experimental results obtained to mitigate the motion induced by ground excitation in a large-scale laboratory prototype, simulating the seismic response of a two-story building, are summarized.

Trust Model Based on Structured Protection for High Level Security System

In order to ensure the security of information systems, it's essential to make sure that system behaviors are trusted. By analyzing threats that exist in executing procedures, a trust model based on structured protection is proposed. We consider that functional components, system actions and message flows between components are three key factors of information systems. Structured protection requirements on components, connections and action parameters are also provided. Four trusted properties of the model are deducted through formal analysis, and trusted system behavior is defined based on these properties. Furthermore, decision theorem of trusted system behavior is proved. The developed prototype system indicates the model is practical. It is a general theory model built on logic deduction and independent on specific environment and the behaviors of the system designed and implemented following the model are trusted.

Some aspects affecting the response of RC compartment structures subjected to internal blast loads

Protective compartments are typically used to protect some specific structures from internal explosions,such as industrial buildings that contain devices that may explode in certain circumstances.This research investigates how the response of reinforced concrete(RC)compartment structures subjected to internal blast loads are affected by the following aspects:introduction of material nonlinearity in the analysis,reinforcement ratio,and aspect ratio of the compartment.To achieve this goal,a calibrated and sophisticated FE numerical model is introduced,and a parametric study for the intended aspects is carried out.A discussion of the results and conclusions are offered,which show the role of each aspect in the dynamic performance of the compartment structures.The main conclusions are as follows:introduction of material nonlinearity in this type of analysis and for these structures is very important and significant in obtaining accurate outputs that are similar to actual behavior;the reinforcement ratio has a significant effect on the response and its effect varies depending on the thickness of the compartment;in general,increasing the reinforcement ratio enhances the behavior and reduces the stresses in the compartment;and the aspect ratio of the compartment does not show a clear pattern on the response of such structures under internal blast loads.

The Use of Underground Metro Stations and Tunnels as Protective Structures in Case of Nuclear Emergencies

This paper discusses the use of Underground Metro stations and tunnels as protective structures in case of nuclear emergencies. Six lines are taken as a case study to investigate the use of their underground stations and tunnels. The research explains the structural design of Underground Metro and the necessary needs for hidden people inside Underground Metro used as shelters. The research investigates the calculations of the number of hidden persons inside Underground Metro used as shelters. A field study has been conducted to an Underground Metro station to detemaine the peaceful use and the emergency use of all basements of the station. Also, the field study aims to determine the existing spaces and the needed spaces of the Underground Metro station to dual--used as a nuclear shelter. Three Underground Metro stations have been selected and a field study has been conducted to determine the usages of these basements, the planning, general and design features for each one of them, and whether they can be used as protective structures for citizens in emergencies. These basements were compared for their protective factors. Also, their capacities for sheltering were calculated.

Effects of Protective Structures in Morpho-Sedimentological Changes： A Case Study of Rufisque＇s Coast, Petite C6te, Senegal

Protective structures, built in the 1980＇s in order to reduce or stop coastal erosion in Rufisque, involved a modification of the coastal morpho-sedimentary landscape and have intensified the coastal dynamics. The diachronic study of beach profiles, before and after the seawalls construction showed that these protective structures accentuated the coastal erosion, with more important sedimentary deficits at the ends of the structures. Today, the Rufisque coast is characterized by a set of sedimentary cells whose morphological evolution and annual sedimentary dynamics are controlled by seasonal forcing： sedimentary deposits in dry season and erosion in wet season. However, this alternation of deposits and erosion phase shows spatiotemporal disparities. These disparities are very marked between a northwestern area characterized by concave profiles and a southeastern area （the bay of Rufisque） characterized by convex profiles and a much more important sedimentary deficit. The results also showed that these methods of shoreline protection are not durable measurements （degradation of the structures） and have exacerbated the vulnerability to coastal erosion as well as those of the coastal populations.

Investigation on the Mechanical Properties and Shape Memory Effect of Landing Buffer Structure Based on NiTi Alloy Printing

With the deepening of human research on deep space exploration,our research on the soft landing methods of landers has gradually deepened.Adding a buffer and energy-absorbing structure to the leg structure of the lander has become an effective design solution.Based on the energy-absorbing structure of the leg of the interstellar lander,this paper studies the appearance characteristics of the predatory feet of the Odontodactylus scyllarus.The predatory feet of the Odontodactylus scyllarus can not only hit the prey highly when preying,but also can easily withstand the huge counter-impact force.The predatory feet structure of the Odontodactylus scyllarus,like a symmetrical cone,shows excellent rigidity and energy absorption capacity.Inspired by this discovery,we used SLM technology to design and manufacture two nickel-titanium samples,which respectively show high elasticity,shape memory,and get better energy absorption capacity.This research provides an effective way to design and manufacture high-mechanical energy-absorbing buffer structures using bionic 3D printing technology and nickel-titanium alloys.

Seismic dip estimation based on the twodimensional Hilbert transform and its application in random noise attenuation

In seismic data processing, random noise seriously affects the seismic data quality and subsequently the interpretation. This study aims to increase the signal-to-noise ratio by suppressing random noise and improve the accuracy of seismic data interpretation without losing useful information. Hence, we propose a structure-oriented polynomial fitting filter. At the core of structure-oriented filtering is the characterization of the structural trend and the realization of nonstationary filtering. First, we analyze the relation of the frequency response between two-dimensional（2D） derivatives and the 2D Hilbert transform. Then, we derive the noniterative seismic local dip operator using the 2D Hilbert transform to obtain the structural trend. Second, we select polynomial fitting as the nonstationary filtering method and expand the application range of the nonstationary polynomial fitting. Finally, we apply variableamplitude polynomial fitting along the direction of the dip to improve the adaptive structureoriented filtering. Model and field seismic data show that the proposed method suppresses the seismic noise while protecting structural information.

Design and test of a protective structure for the double vertical explosive welding of large titanium/steel plate

A comprehensive protective structure with rigidity and flexibility was put forward and designed in view of the quality and safety problems for the double vertical explosive welding of large titanium/steel cladding plate.The movement speed and displacement of the protective structure was calculated by establishing its physics model.The dynamics and stabilization properties were analyzed,and the protective structure parameters were optimized and devised.The comprehensive protective structure,which is composed of rigidity unit and flexibility wall,can bear the impact of detonation wave and the high-speed movement of the cladding plate.There are no damage and deformation in the protective structure and the cladding plate.The protective structure can be used many times.The bonding rate of the Ti/steel plate obtained was nearly 100%,and there is no deformation,surface cracks,and big wave and micro-defects.Therefore,the protective problems of the double vertical explosive welding can be solved effectively by the protective structure.

Experimental study on anti-penetration mechanism of bolted composite protective structure with limited span under impact of low-velocity projectile

In order to study the influence of the bolt joint mode on low-velocity projectiles penetrating the composite protective structure,two bolt joint models which connect the composite target to the fixed frame were designed,the ballistic test of the bolted composite protective structure with limited span was carried out,and the bearing and failure characteristics of the bolted region,as well as the energy dissipation of each part of the structure,were analyzed.The results show that in the condition of lowvelocity impact,there are three failure modes for the bolted composite protective structure subjected to projectile penetration,including failure of the impact point of the composite target,failure of protective structure connecting components and failure of the holes in the bolted region of the composite target;the failure mode of bolt holes in the bolted region has a great influence on the protection performance,and the allowable value of the bearing capacity of the bolted region depends on the sum of the minimum failure load in the failure modes and the friction force;shear-out failure occurring in the bolt holes in the bolted region exerts the greatest effect on ballistic performance,which should be avoided;When simultaneous failure occurs in the bolted region and the free deformation region of the composite protective structure,the energy absorption per unit surface density of the composite protective structure reaches the maximum,which can give full play to its anti-penetration efficiency.

A Study on Some Causes of Rubble Mound Breakwater Failure

Rubble mound breakwater, one of the protection structures, has been widely used in coastal and port engineering. Block stones were first used as its armor layer, and its use was limited to shallow sea areas where there is no large waves. Since the specially-shaped armor unit was developed, the rubble mound breakwater has become the main sort of the protection structures, which can be used in deep water zones where storm sometimes occurs. Owing to severe and complex surrounding conditions, the rubble mound breakwater failure sometimes occurs, thus the study on the causes of failure is of great importance. In the present study some breakwater failures at home and abroad are illustrated and the causes of failure are investigated from the point of view of design, test, construction and maintenance.

A Survey on Working under Trees with an Agricultural Narrow Tractor in Italy

To protect the driver in case of a tractor overturn,narrow-track tractors,mainly used for working under trees or in vineyards,can be equipped with a foldable roll-over protective structure(FROPS)generally consisting of a two-pillar front-mounted foldable rollbar.FROPSs have been mainly developed to offer greater mobility when working in low overhead clearance zones(CZs)and more storage options.However,many fatalities and serious injuries in Italy are due to overturn of narrow tractors with FROPS not in safety configuration.The reason lies on that lowering and raising a conventional FROPS is a time-consuming and strenuous process.After operators fold down FROPS to pass a low overhead CZ,some prefer to leave it in the folded or inoperative position,increasing the risk of a roll-over fatality.Italian Workers Compensation Authority(Inail)collects injury reports of workers covered by compulsory accident insurance.However,for agricultural sector Inail set up in 2008 a national observatory to add data and information on fatalities in agriculture covering workers,even those not Inail insured.From these data it appears that about 10 fatalities per year occur in Italy involving folded ROPS.The aim of the analysis in this article is to make a survey on the FROPS issue considering both what is required by Mother Regulation(Regulation(EU)167/2013)for new tractors and the achievable technical solutions to be applied on old tractors for reducing the misuse of FROPS.

Seismic airgun exploration of continental crust structures

The active sources generate seismic waves transmitting appropriate through the deep is underground key and can be used to image Abstract high-resolution subsurface structures.Therefore,an seismic source the factor to active source exploration.In order to study the structure of continental crust and its temporal variations,we selected an artificial seismic source generated from releasing air bubbles in water(airgun source hereinafter)out of a variety and of artificial sources like the is explosion,new electronic sparkers,source hammering,eccentric proven vibration,be heavy-duty train vibration,vibroseis etc.Airgun Three source Fixed a type of artificial that have been to environmentally friendly,safe,and highly efficient.Airgun western Signal China Transmission and Stations(FASTS)have been for built a few years ago in Yunnan,Xinjiang,and Gansu provinces in have been continuously them running several years.Seismic waves generated away by the the airgun sources are highly seismic reproducible waves and stacking in of can produce can good seismograms on 1300 stations km far from source,for instance,an produced Xinjiang FASTS be well about recorded 60 nearly away after 5000 stacking,China covering area of 6 million km2 and penetrating down to of a depth of km.Establishing about 10 FASTSs in would enable long-term illuminate continuous subsurface underground structures,monitoring can all 9.6 million km2 of land area.Treating from airgun sky active sources as lanterns to we achieve the situation with"Beidou surveys the and lantern illuminates underground".

Recent progress of sugar amino acids: Synthetic strategies and applications as glycomimetics and peptidomimetics

In order to meet the increasing demands for the development of large varieties of new molecules for discovering new drugs and materials, organic chemists are developing many novel multifunctional building blocks, which are assembled rationally to create ‘nature-like＇ and yet unnatural organic molecules with well-defined structures and useful properties. Sugar amino acids（SAAs）, the carbohydrate derivatives bearing both amino and carboxylic acid functional groups, are important ones of these multifunctional building blocks, which can be used to create novel materials with potential applications as glycomimetics and peptidomimetics. This review will focus on recent synthetic strategies of SAAs and their applications in creating large number of structurally diverse glycomimetics and peptidomimetics.