Showing papers in "Defence Science Journal in 2018"
TL;DR: The threat models for Machine Learning systems and the various techniques to attack and defend them are explored and privacy issues in these models are presented and a cyber-warfare test-bed is described to test the effectiveness of the various attack-defence strategies.
Abstract: The changing nature of warfare has seen a paradigm shift from the conventional to asymmetric, contactless warfare such as information and cyber warfare. Excessive dependence on information and communication technologies, cloud infrastructures, big data analytics, data-mining and automation in decision making poses grave threats to business and economy in adversarial environments. Adversarial machine learning is a fast growing area of research which studies the design of Machine Learning algorithms that are robust in adversarial environments. This paper presents a comprehensive survey of this emerging area and the various techniques of adversary modelling. We explore the threat models for Machine Learning systems and describe the various techniques to attack and defend them. We present privacy issues in these models and describe a cyber-warfare test-bed to test the effectiveness of the various attack-defence strategies and conclude with some open problems in this area of research.
55 citations
TL;DR: A model which combines fractal theory, Dempster-Shafer evidence theory and analytic hierarchy process to classify objects with incomplete information is proposed, which takes the advantage of not only efficient modelling of uncertain information, but also efficient combination of uncertainty information.
Abstract: Target recognition in uncertain environments is a hot issue, especially in extremely uncertain situation where both the target attribution and the sensor report are not clearly represented. To address this issue, a model which combines fractal theory, Dempster-Shafer evidence theory and analytic hierarchy process (AHP) to classify objects with incomplete information is proposed. The basic probability assignment (BPA), or belief function, can be modelled by conductivity function. The weight of each BPA is determined by AHP. Finally, the collected data are discounted with the weights. The feasibility and validness of proposed model is verified by an evidential classifier case in which sensory data are incomplete and collected from multiple level of granularity. The proposed fusion algorithm takes the advantage of not only efficient modelling of uncertain information, but also efficient combination of uncertain information.
52 citations
TL;DR: This paper presents mainly the developments in Transmit/Receive (T/R) Module technology, which assimilates various stages of the technological evolution - past, current and futuristic, and discusses how these technologies contribute towards the improvement of efficiency, miniaturization and reliability without compromising its performance parameters.
Abstract: Worldwide, defense technologies are rapidly evolving and are currently aiming at integrating diverse functionalities like Radar, Electronic Warfare, Communications, etc., on a singular miniaturized platform. Hence, it cannot be denied that the advancements in modern Active Phased Array Radar technologies assume a critical role towards the achievement of this goal. A typical Active Phased Array Radar comprises of an Active Antenna Array Unit (AAAU) consisting of a large number of radiating elements, Transmit/Receive (T/R) Modules with other associated RF and digital circuitry and power electronics. This paper presents mainly the developments in Transmit/Receive (T/R) Module technology, which assimilates various stages of the technological evolution - past, current and futuristic. It discusses how these technologies contribute towards the improvement of efficiency, miniaturization and reliability without compromising its performance parameters.
26 citations
TL;DR: In this article, the role of tool tilt angle on material flow and defects in friction stir welding (FSW) has been investigated and the impact of different tool tilt angles on the material flow strain rate was found to be responsible for material flow in the weld.
Abstract: Heat treatable aluminium alloy AA2219 is widely used for aerospace applications, welded through gas tungsten and gas metal arc welding processes Welds of AA2219 fabricated using a fusion welding process suffers from poor joint properties or welding defects due to melting and re-solidification Friction stir welding (FSW) is a solid-state welding process and hence free from any solidification related defects However, FSW also results in defects which are not related to solidification but due to improper process parameter selection One of the important process parameters, ie, tool tilt angle plays a critical role in material flow during FSW, controlling the size and location of the defects Effect of tool tilt angle on material flow and defects in FSW is ambiguous A study is therefore taken to understand the role of tool tilt angle on FSW defects Variation in temperature, forces, and torque generated during FSW as a result of different tool tilt angles was found to be responsible for material flow in the weld, controlling the weld defects An intermediate tool tilt angle (1o-2o) gives weld without microscopic defect in 7 mm thick AA2219 for a given set of other process parameters At this tool tilt angle, x-force, and Z- force is balanced with viscosity and the material flow strain rate sufficient for the material to flow and fill internal voids or surface defects in the weld
22 citations
TL;DR: Taguchi’s design of experiments based parameter tuned genetic algorithm (GA) is developed for generalised task allocation of single-task robots to multi-robot tasks and shows good convergence and found that the precedence constraints affect the optimal number of robots required for a particular task level.
Abstract: Efficacy of the multi-robot systems depends on proper sequencing and optimal allocation of robots to the tasks. Focuses on deciding the optimal allocation of set-of-robots to a set-of-tasks with precedence constraints considering multiple objectives. Taguchi’s design of experiments based parameter tuned genetic algorithm (GA) is developed for generalised task allocation of single-task robots to multi-robot tasks. The developed methodology is tested for 16 scenarios by varying the number of robots and number of tasks. The scenarios were tested in a simulated environment with a maximum of 20 robots and 40 multi-robot foraging tasks. The tradeoff between performance measures for the allocations obtained through GA for different task levels was used to decide the optimal number of robots. It is evident that the tradeoffs occur at 20 per cent of performance measures and the optimal number of robot varies between 10 and 15 for almost all the task levels. This method shows good convergence and found that the precedence constraints affect the optimal number of robots required for a particular task level.
20 citations
TL;DR: In this article, a planar cavity-backed bow-tie-complementary-ring-slot antenna is proposed, and a new approach for bandwidth enhancement using a shorted-via is introduced.
Abstract: In this study, a planar cavity-backed bow-tie-complementary-ring-slot antenna is proposed, and a new approach for bandwidth enhancement using a shorted-via is introduced. A shorted-via concept overcomes the narrow impedance bandwidth of a conventional substrate integrated waveguide cavity-backed antenna. By adjusting the location of the shorted-via (placed just above the centroid of the radiating slot), the individual bandwidth of the lower and higher order resonances has been tuned below -10 dB criterion, which results in the broadening of the bandwidth. Finally, the antenna is proficient to operate for an impedance bandwidth of 15.71 per cent, ranging from 12.02~14.07 GHz. The proposed antenna shows a gain of better than 4 dBi within the operating band with less than 0.5 dBi variation. Moreover, the antenna preserves good radiation characteristics, which is similar to that of the conventional metallic counterpart. To validate the simulated results, an antenna is fabricated and tested. The simulated results in terms of the reflection coefficient, gain, and radiation patterns are in good agreement with the measured results.
20 citations
TL;DR: The efficacy of the identified model and proposed neural derivative method is demonstrated using real time flight data of ATTAS aircraft and the results from the proposed approach compare well with those from the other.
Abstract: Aerodynamic parameter estimation involves modelling of force and moment coefficients and computation of stability and control derivatives from recorded flight data. This problem is extensively studied in the past using classical approaches such as output error, filter error and equation error methods. An alternative approach to these model based methods is the machine learning such as artificial neural network. In this paper, radial basis function neural network (RBF NN) is used to model the lateral-directional force and moment coefficients. The RBF NN is trained using k-means clustering algorithm for finding the centers of radial basis function and extended Kalman filter for obtaining the weights in the output layer. Then, a new method is proposed to obtain the stability and control derivatives. The first order partial differentiation is performed analytically on the radial basis function neural network approximated output. The stability and control derivatives are computed at each training data point, thus reducing the post training time and computational efforts compared to hitherto delta method and its variants. The efficacy of the identified model and proposed neural derivative method is demonstrated using real time flight data of ATTAS aircraft. The results from the proposed approach compare well with those from the other.
18 citations
TL;DR: In this article, the design and fabrication of gate/source connected multi-finger field plate structures using TCAD ATLAS simulation software is presented, which are fabricated on indigenous AlGaN/GaN HEMT devices.
Abstract: The design and fabrication of gate/source connected multi-finger field plate structures using TCAD ATLAS simulation software is presented. The designed field plate structures are fabricated on indigenous AlGaN/GaN HEMT devices. AlGaN/GaN HEMT devices with field plate structures exhibit about three times improvement in breakdown voltage of device and are in close agreement with the simulation results. Integration of field plates in device have resulted in higher VDS (drain to source voltage) operation and improvement in output power of AlGaN/GaN HEMT devices. Incorporation of field plates also decrease the reverse leakage current of HEMT devices.
17 citations
TL;DR: The aim of this paper is to emphasise the importance of developing new scientific fields for countering UAVs, and hence it is directed firstly on the scientific audience.
Abstract: Unmanned aerial vehicles (UAVs) are massively seeping into a wide range of human activities Along with other remotely controlled or automatic devices, they have entered many aspects of human activities and industry While the majority of researchers have been working on the construction, deployment and non-military use of UAVs, the protection against UAVs remained on the edge of their interest Nowadays, the situation is rapidly changing The risk of misuse of UAVs by criminals, guerrillas or terrorists has compelled authorities, scientists and defence industry to face this threat Organisations have launched crucial infrastructure defence programs to cope with UAV threat To solve this problem, it is necessary to develop disciplines improving the air space surveillance and UAVs elimination techniques The substantial aspects of the UAVs detection and elimination were analysed, being supported by a number of conferences, workshops and journals articles The contribution of the study in the Counter–UAV area consists particularly in generalisation and evaluation of the main technical issues The aim of this paper is to emphasise the importance of developing new scientific fields for countering UAVs, and hence it is directed firstly on the scientific audience
16 citations
TL;DR: Fuzzy based AEKF algorithm has the capability to mitigate ionospheric scintillations under both geomagnetic quiet and disturbed conditions.
Abstract: Designing robust carrier tracking algorithms that are operable in strident environmental conditions for global navigation satellite systems (GNSS) receivers is the discern task. Major contribution in weakening the GNSS signals are ionospheric scintillations. The effect of scintillation can be known by amplitude scintillation index S 4 and phase scintillation index sf parameters. The proposed fuzzy logic based adaptive extended Kalman filter (AEKF) method helps in modelling the signal amplitude and phase dynamically by Auto-Regressive Exogenous (ARX) analysis using Sugeno fuzzy logic inference system. The algorithm gave good performance evaluation for synthetic Cornell scintillation monitor (CSM) data and real-time strong scintillated PRN 12 L1 C/A data on October 24 th , 2012 around 21:30 h, Brazil local time collected by GNSS software navigation receiver (GSNR’x). Fuzzy logic algorithm is implemented for selecting the ARX orders based on estimated amplitude and phase ionospheric scintillation observations. Fuzzy based AEKF algorithm has the capability to mitigate ionospheric scintillations under both geomagnetic quiet and disturbed conditions.
12 citations
TL;DR: The experimental results show that indoor scene recognition algorithm employing SVM with enhanced GIST descriptors produces very high recognition rates, compared to kNN and Naive Bayes classifiers, and is suitable for real-time operations.
Abstract: An indoor scene recognition algorithm combining histogram of horizontal and vertical directional morphological gradient features and GIST features is proposed in this paper. New visual descriptor is called enhanced-GIST. Three different classifiers, k-nearest neighbour classifier, Naive Bayes classifier and support vector machine, are employed for the classification of indoor scenes into corridor, staircase or room. The evaluation was performed on two indoor scene datasets. The scene recognition algorithm consists of training phase and a testing phase. In the training phase, GIST, CENTRIST, LBP, HODMG and enhanced-GIST feature vectors are extracted for all the training images in the datasets and classifiers are trained for these image feature vectors and image labels (corridor-1, staircase-2 and room-3). In the test phase, GIST, CENTRIST, LBP, HODMG and enhanced-GIST feature vectors are extracted for each unknown test image sample and classification is performed using a trained scene recognition model. The experimental results show that indoor scene recognition algorithm employing SVM with enhanced GIST descriptors produces very high recognition rates of 97.22 per cent and 99.33 per cent for dataset-1 and dataset-2, compared to kNN and Naive Bayes classifiers. In addition to its accuracy and robustness, the algorithm is suitable for real-time operations.
TL;DR: This paper introduces motifs as the basic unit of configuration and proposes a motif-based mission planning method considering dynamic reconfiguration and incorporates order preserved operators with NSGA-III algorithm to find Pareto front solutions of all possible mission planning schemes.
Abstract: Influenced by complex terrain conditions of combat environments and constrained by the level of communication technology, communication among unmanned aerial vehicles (UAV) is greatly restricted. In light of this situation, mission planning for UAV swarms under limited communication has become a difficult problem. This paper introduces motifs as the basic unit of configuration and proposes a motif-based mission planning method considering dynamic reconfiguration. This method uses multidimensional dynamic list scheduling algorithm to generate a mission planning scheme based on the motif-based swarm configuration solution. Then it incorporates order preserved operators with NSGA-III algorithm to find Pareto front solutions of all possible mission planning schemes. The feasibility of this mission planning method is validated through a case study.
TL;DR: In this article, the effect of ODS on the microstructure and tensile properties of tungsten heavy alloys is investigated, and the results show that ODS has been considered as a promising processing technique for improving the micro-structural features of Tungsten alloys.
Abstract: Tungsten heavy alloys are considered as two phase composites with 88 to 97 wt% tungsten interspersed in a matrix of relatively low melting elements such as nickel, iron and cobalt The mechanical properties of these alloys are greatly influenced by the microstructural features such as tungsten grain size, tungsten-tungsten contiguity and matrix volume fraction Oxide dispersion strengthening (ODS), refinement of tungsten grain size, cyclic heat treatment, addition of alloying elements like Cr, Mo, and Co are some of the methods investigated to improve the microstructural features and thereby the mechanical properties of tungsten heavy alloys Among these methods ODS has been considered as a promising processing technique since the tungsten grain size observed in ODS alloys is finer compared to the conventional alloys and more importantly the dynamic fracture mode changes from adiabatic shear band to brittle fracture The present study is mainly focused on investigating the effect of 03 wt% yttrium oxide (Y2O3) dispersion on the microstructure and consequently the tensile properties of 90W-6Ni-2Fe-2Co alloy With 03 wt%Y2O3, the ODS alloy (897W-6Ni-2Fe-2Co-03Y2O3) is processed by two-stage sintering with subsequent thermo-mechanical treatment which includes vacuum heat treatment and swaging ODS alloy and the conventional alloy (without oxides) are compared based on the microstructures and tensile properties obtained after liquid phase sintering and after final processing
TL;DR: A novel algorithm is developed which simultaneously takes care of video stabilisation and target tracking, and accurate tracking results have been obtained in destabilised videos.
Abstract: Visual tracking is performed in a stabilised video. If the input video to the tracker algorithm is itself destabilised, incorrect motion vectors will cause a serious drift in tracking. Therefore video stabilisation is must before tracking. A novel algorithm is developed which simultaneously takes care of video stabilisation and target tracking. Target templates in just previous frame are stored in positive and negative repositories followed by Affine mapping. Then optimised affine parameters are used to stabilise the video. Target of interest in the next frame is approximated using linear combinations of previous target templates. Proposed modified L1 minimisation method is used to solve sparse representation of target in the target template subspace. Occlusion problem is minimised using the inherent energy of coefficients. Accurate tracking results have been obtained in destabilised videos.
TL;DR: In this paper, an attempt was made to fabricate polymeric syntactic foams of epoxy containing hollow glass microballoon at varying loading (40 % - 60 %) and explore their potential towards blast mitigation.
Abstract: Polymeric syntactic foams refer to a class of cellular material created using preformed hollow spheres bound together with a polymeric matrix. These cellular materials possess exceptional ability to respond against high impact dynamic loads. This paper is an attempt to fabricate polymeric syntactic foams of epoxy containing hollow glass microballoon at varying loading (40 % - 60 %) and explore their potential towards blast mitigation. The tensile, compressive and flexural strength were found to be inversely proportional to the microballoon loading in the quasi-static regime. The strain rate sensitivity of the foams was confirmed by performing high strain rate studies using split hopkinson pressure bar. The flow stress of these foams was found to increase with increasing strain rates. The syntactic foams were subjected to controlled transient blast loadings using a shock tube. The samples remained intact and no strain was observed on the strain gauge, even under a blast load of ~ 90 psi, which clearly highlight their potential as core materials for blast mitigating applications.
TL;DR: In this paper, transition metal salt, manganese chloride was incorporated into polyvinyl alcohol (PVA) to prepare metal salt filled polymer material (M-PVA), and their optical properties were evaluated.
Abstract: Transition metal salt, manganese chloride was incorporated into polyvinyl alcohol (PVA) to prepare metal salt filled polymer material (M-PVA) and their optical properties were evaluated. XRD, UV-vis, and FTIR analyses reveal that there is strong interaction between PVA and the manganese chloride salt. From XRD analysis, the inter-chain separation in pristine PVA and M-PVA was found to be 5.62 Ǻ and 4.70 Ǻ, respectively; thus indicating that the packing of polymer chains is more compact under the influence of manganese chloride. Optical band gap of PVA was found as 5.06 eV but such band gap was reduced on incorporation of manganese chloride into the PVA matrix system with corresponding increase in optical conductivity. Spectral evaluation indicates that refractive index of M-PVA decreases faster than that of PVA in the visible range. Abbe Number was found to have decreased on incorporation of manganese chloride into the PVA matrix system indicating increase in optical dispersion in conformity with the trend of increase in dispersion energy (Ed). The average interband oscillator wavelength was found close to the respective values of absorption edges.
TL;DR: This work adopts sum of squared error (SSE) approach and Dunn index to measure the quality of clusters and performs the experimentation on real world crime data to identify spatiotemporal crime clusters.
Abstract: The various sources generate large volume of spatiotemporal data of different types including crime events. In order to detect crime spot and predict future events, their analysis is important. Crime events are spatiotemporal in nature; therefore a distance function is defined for spatiotemporal events and is used in Fuzzy C-Means algorithm for crime analysis. This distance function takes care of both spatial and temporal components of spatiotemporal data. We adopt sum of squared error (SSE) approach and Dunn index to measure the quality of clusters. We also perform the experimentation on real world crime data to identify spatiotemporal crime clusters.
TL;DR: In this article, photoacoustic spectra of various trace molecules in the mid-infrared spectral band 7 μm - 9 μm have been recorded in vapor, aerosol, liquid forms as well as samples adsorbed on surfaces such as plastic and cloth.
Abstract: Standoff photoacoustic spectroscopic technique has been studied for the detection of hazardous molecules adsorbed on surfaces and in vapour/aerosols form in open air. Detection and identification of components in explosive mixtures in trace amounts is very challenging by any point or standoff spectroscopic detection technique. Discusses detection and identification of such components using standoff laser photoacoustic spectroscopic technique. Laser photoacoustic spectra of various trace molecules in the mid-infrared spectral band 7 μm - 9 μm have been recorded in vapor, aerosol, liquid forms as well as samples adsorbed on surfaces such as plastic and cloth. Pulsed quantum cascade laser is modulated at a frequency of 42 kHz resonant with that of microphone. Hazardous chemicals/explosives adsorbed on plastic and cloths surfaces were detected from a standoff distance up to 1.5 m. The sensitivities were found to be 20 μg/cm2, 20 μl liquid and 1.0 ppm corresponding to solid, liquid and vapour phases respectively. The chemicals/explosives used in the study were PETN, DNT, Acetone, and DMMP. Our study suggests that the photoacoustic technique has high selectivity and sensitivity for the trace detection and be used for screening of suspicious objects for security applications as a handy product.
TL;DR: In this paper, Paraffin wax microspheres were first synthesized and then encapsulated with silver through in situ chemical reduction, and the thermal properties were investigated under differential scanning calorimeter and thermogravimetric analyser.
Abstract: Microencapsulation of phase change materials (PCMs) with metallic shell materials is a very innovative and challenging task. This can mitigate the problems related to thermal barrier for conventional nonconductive shell materials as well as enhance mechanical properties of PCM microcapsules. Such microcapsules can be integrated into microelectronic devices for their intermittent thermal management in mission critical components. The present work is aimed at developing a new method to synthesise phase change material encapsulated with metallic shell material and characterising the same. Paraffin wax microspheres were first synthesised and then encapsulated with silver through in situ chemical reduction. Further more, a new set of experiments were identified to analyse the quality of encapsulation. The thermal properties were investigated under differential scanning calorimeter and thermogravimetric analyser. The average diameter of paraffin wax microspheres (PW) is found to be ±329 μm. It reveals from DSC analysis that the enthalpy of fusion is minimum for PW@Ag-PVA amongst all others. Accordingly, higher deposition of Ag is possible for PW@Ag-PVA. This is also supported by TGA results where PW@Ag-PVA has only 40 per cent mass loss and the remaining samples have 100 per cent. However, even for PW@Ag-PVA the encapsulation is found incomplete. The present work provides knowhow of the difficulties associated with encapsulation of PCMs with metallic shell material.
TL;DR: In this article, a generalised model has been developed for theoretical prediction of short start pressure (SSP) for rifled gun system using dimensional analysis approach, which has been validated by data available from the open literature.
Abstract: Determination of short start pressure (SSP) for gun system has always been of paramount interest for gun designers. In this paper, a generalised model has been developed for theoretical prediction of SSP for rifled gun system using dimensional analysis approach. For this, parameters affecting the SSP of the gun like rifling dimensions, driving band dimensions, material properties of driving band, projectile mass and diameter are taken into consideration. For a particular case of large caliber rifled gun system, the model is established using linear relations among dimensionless groups of parameters. The model has been validated by data available from the open literature.
TL;DR: In this article, the porosity of PZT-based piezoelectric ceramics was investigated using Field Emission Scanning electron microscopy (FESEM) studies.
Abstract: Ultimate properties of a porous ceramic is highly process dependent. In this study, prevalent porous ceramics fabrication methods (Freeze casting, Foam reticulation and Burnable Plastic Sphere (BURPS) method) have been compared by fabricating the porous lead zirconate titanate (PZT) based piezoelectric ceramics. Field Emission Scanning electron microscopy (FESEM) studies were carried out to study the pore size and distribution of the ceramics. Hydrostatic co-efficients increased tremendously on incorporation of porosity which led to Hydrostatic Figure of Merit of 7480 in Foam reticulation samples (porosity 86%). The three dimensionally interconnected networks in the freeze casted samples led to lowest acoustic impedance (6 MRayls) despite not having the lowest density.
TL;DR: A new design for testability methodology for the detection of stuck-at faults in multiple controlled Toffoli based reversible circuits with a reduction up to $50.58\% in operating costs as compared to the existing work implemented on the same platform.
Abstract: Testability leads to a large increment in operating costs from their original circuits which drastically increases the power consumption in logic circuits. This paper presents a new design for testability methodology for the detection of stuck-at faults in multiple controlled Toffoli based reversible circuits. The circuit is modified in such a manner that the applied test vector reaches all the levels without any change in values on the wires of the circuit. An (n+1) dimensional general test set containing only two test vectors is presented, which provide full coverage of single and multiple stuck-at faults in the circuit. The work is further extended to locate the occurrence of stuck-at faults in the circuit. Deterministic approaches are described and the modification methodology is experimented on a set of benchmarks. The present work achieved a reduction up to $50.58\%$ in operating costs as compared to the existing work implemented on the same platform.
TL;DR: In this paper, an analytical model for calculating MB efficiency, MB force and weapon recoil force for MBs of two, three and four chambers has been established, which is then used in combination with design of experiment (DOE) and Response Surface Method (RSM) statistical techniques to develop a smooth response function which can be efficiently used in optimisation formulation.
Abstract: Muzzle brakes (MBs) have a great effect on reducing the recoil force of weapons during firing In this paper, optimum MB efficiency, MB force and recoil force for (12,7 x 99 mm) sniper rifle have been studied The objective is to obtain the optimum area of side openings, inclination angle and number of chambers for the MB in order to increase the MB efficiency and MB force and thereby to decrease their coil force of the weapon An analytical model for calculating MB efficiency, MB force and weapon recoil force for MBs of two, three and four chambers has been established This Model is then utilised in combination with design of experiment (DOE) and Response Surface Method (RSM) statistical techniques to develop a smooth response function which can be efficiently used in optimisation formulation Finally, multi objectives generic algorithm (MOGA) optimisation method has been employed to find the optimum MB design parameters The optimisation results show that the three or four chambers MBs have no significant effect on reducing the weapon recoil force compared with the two chamber MB for this sniper rifle
TL;DR: This paper presents a computing based integrated design approach for a flexible buoyancy system (FBS) aimed towards the applications in autonomous underwater vehicles and gliders.
Abstract: Modern design approaches are conceived and utilised in an integrated loop covering system statics, dynamics, optimisation, and others. In this regard this paper presents a computing based integrated design approach for a flexible buoyancy system (FBS) aimed towards the applications in autonomous underwater vehicles and gliders. The primary design alternatives for the FBS are: piston and pump driven and both are investigated. The primary design of autonomous underwater vehicles and gliders is computed from first principle of mechanics and defined in the computer aided design model and it is implemented in the Matlab*TM. Lastly, to show the application of the present approach, a design example is presented for a water depth of 6000 m.
TL;DR: The quantitative method of the assessment of invisible areas and military objects in mountainous terrain is developed and offered by using Unmanned Aerial Vehicle and the probabilities of detection of invisible area or enemy object by using 1 and n UAVs are calculated.
Abstract: During war activities, the evaluation of invisible areas and military armors in mountainous terrain is very important for assessment of operational-tactical situation in battlefield This information can be used for prevention of an enemy sudden attack In given paper, the quantitative method of the assessment of invisible areas and military objects in mountainous terrain is developed and offered by using Unmanned Aerial Vehicle The probabilities of detection of invisible area or enemy object by using 1 and n UAVs are calculated Previously obtained data by ArcGIS software (GIS technology) have been used for calculations and evaluations the number of invisible areas and military objects The analysis of the dependence of effectiveness of revealing and localization areas and military objects on UAV number has been carried out It was established that for quantitative analysis of invisible areas it is more efficiently to use one UAV, but for detection of armored vehicles and military objects it is more efficiently to use several UAV Our experiments in mountainous conditions had shown that at flight height 300 m and battle-front 2,5 km putting 3-5 UAVs is real In this case, all of them perform operational mission and return to base
TL;DR: In this paper, a full-scale experimental program consisting of six reinforced concrete slabs with compressive strengths of 60 MPa, 50 MPa and 40 MPa was conducted in blast test area of Science and Technology Aerospace Department (Brazilian Air Force).
Abstract: Explosions emanating from terrorist attacks or military weapons cause damage to civilian and military facilities. Understanding the mechanical behaviour of reinforced concrete structures subjected to blast is of paramount importance for minimizing the possible blast damage. A full-scale experimental program consisting of six reinforced concrete slabs with compressive strengths of 60 MPa, 50 MPa and 40 MPa, measuring 1.0 m × 1.0 m × 0.08 m, and subjected to 2.7 kg of non-confined plastic bonded explosive, was conducted in blast test area of Science and Technology Aerospace Department (Brazilian Air Force). This paper compares experimentally measured peak displacement values with theoretical values. Theoretical analysis was carried out using single degree of freedom (SDOF) models. The comparison showed that SDOF analysis worked very well in predicting the reinforced concrete slab peak displacement against blast effects. Qualitative analysis after the experiments showed that the blast wave shape generated by the cylindrical explosive was not uniformly distributed on the slabs for the standoff distance of 0.927 m∕kg1/3.
TL;DR: In this article, the radial layered PELE produced massive fragments with transverse velocity component when impacting the 45# steel plate with 5 mm thickness under the impact velocity of 657.2 m/s.
Abstract: The fragmentation mechanism of the penetrator with lateral effect (PELE) after perforating a thin target plate has been summarised and analysed firstly. Then the fragmentation of radial layered PELE was analysed qualitatively and verified by experiment. In the experiment, the target plates were made of 45# steel and 2A12 aluminium respectively. Qualitative analysis and experimental results show that: for normal PELE without layered, after perforating the thin metal target plate, from the bottom to the head of the projectile, the number of fragments formed by the jacket gradually increases, and the mass of the fragment decreases correspondingly. Compared with the normal PELE without layered, the radial layered PELE is less likely to break into fragments, when impacting the thin metal target plate with the same material and thickness under the same impact velocity. However, from the mechanism of the PELE, when the resistance of the target plate is large enough, and the duration of pressure is long enough, the radial layered PELE also can break into fragments with transverse velocity component. The resistance of the target plate plays an important role in the fragmentation of radial layered PELE. The radial layered PELE produced massive fragments with transverse velocity component when impacting the 45# steel plate with5 mm thickness under the impact velocity of 657.2 m/s.
TL;DR: In this article, the effect of sand temperature on the ricochet of sphere projectiles was investigated through experiments and FEM, by measuring the shear stress and internal friction angle when the sand temperature increases.
Abstract: The debris generated by the explosion of a building or ammunition is flown far away through the ricochet phenomenon. The debris contains a very large amount of energy, and a risk factor surrounding it may be applied. The safety distance from debris is set from experiments or FEM analysis. The ricochet of debris is affected not only by the initial conditions of the debris, but also by the conditions of the medium. In this paper, the effect of sand temperature on the ricochet of sphere projectiles was investigated through experiments and FEM, by measuring the shear stress and internal friction angle when the sand temperature increases. As the temperature of the sand increases, the shear stress and the internal friction angle decrease, and the penetration depth of the projectile increases. As the depth of penetration becomes longer, the kinetic energy is lost more by the friction force with the sand and, the sphere projectile speed decreases more. This is mainly caused by the energy loss of the projectile, so the kinetic energy of the ricocheted projectile is reduced. Therefore, when setting the optimized inhabited building distance (IBD), the conditions of the medium should be taken into account.
TL;DR: The dynamic behaviour of gun/projectile system is discussed and then the design recommendations for the main gun components such as bearings, gun barrel, recoil system etc. to achieve higher first shot hit probability are reviewed.
Abstract: Fire power for a main battle tank is one of the most important performance parameters like survivability and mobility. Fire power effectiveness is directly related to the first shot hit probability, performance of main gun, second armament, gun and turret drive system, fire control system, automatic target tracker, commander and gunner sight etc. First shot hit probability (a measure of cumulative effects of errors) is affected by the variations of the projectile parameters, the main gun structure uncertainties, fire control system errors, interaction between the projectile and the gun barrel and the unpredictable environmental changes. These errors and variations can be eliminated or minimised by understanding and simulating the firing event properly, manufacturing the related parts in high precision, using advanced fire control algorithms, and accurate sensors. In this review study, the effects of main gun structural components on the first shot hit probability are investigated taking into account all of the associated error sources. In order for a main battle tank to have both high and repetitive first shot hit probability under all battlefield conditions the gun structure should respond in a similar manner in successive firings without causing any abrupt change in performance. In this study, first the dynamic behaviour of gun/projectile system is discussed and then the design recommendations for the main gun components such as bearings, gun barrel, recoil system etc. to achieve higher first shot hit probability are reviewed.
TL;DR: In this paper, the impact strength of an aluminum plate is investigated using smoothed particle hydrodynamics (SPH) method, and the results show that the maximum error percentage of SPH method in compared with Rosenberg analytical model is within an acceptable range.
Abstract: Performing various experimental, theoretical, and numerical investigations for better understanding of behavioural characteristics of metals under impact loading is of primary importance. In this paper, application of smoothed particle hydrodynamics (SPH) method in impact mechanics is discussed and effective parameters on impact strength of an aluminum plate are investigated. To evaluate the accuracy of smoothed particle hydrodynamics method for simulating impact, Recht and Ipson model is first provided thoroughly for both Rosenberg analytical model and smoothed particle hydrodynamics method, and then plots of initial velocity-residual velocity and initial velocity-absorbed energy for target of aluminum 6061-T651 are presented. The derived information and simulation results expresses that the maximum error percentage of smoothed particle hydrodynamics method in compared with Rosenberg analytical model is within an acceptable range. Therefore, the results of smoothed particle hydrodynamics method verify the Rosenberg analytical model with high accuracy. Results reveal that higher initial impact velocity decreases the time of projectile penetration, and so penetration depth and length as well as the local damage rate of plate increases.