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Epoxy-glass Microballoon Syntactic Foams for Blast Mitigating Applications
Get PDFPolymeric 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
Ultrasonic Standoff Photoacoustic Sensor for the Detection of Explosive and Hazardous Molecules
Get PDFStandoff 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
A Field Study on Concurrent Spare Parts Recommendation in an Airborne Weapon System
Get PDFAs the complexity of weapon systems has grown exponentially during the past few years, initial operation capability has been a crucial factor for military forces. Concurrent spare parts (CSPs) is the quantity of spare parts ensuring initial operating period specified by demanding forces acquiring newly deployed weapon systems. Because of the growth of system complexity, recommending precise CSP is not trivial. The Republic of Korea developed an improved CSP recommendation system and deployed the system for naval weapon systems. In this paper, we increase the prediction accuracy of CSP up to 23.1 per cent and 7.16 per cent higher in terms of budget constraint and operational availability (Ao) constraint. The main improvement is achieved by facilitating simulations using the real field data from Korean air force. Also, we propose two validation approaches and show the possibility of extension to the general weapon systems. From the experimental study, we show that the CSP recommendation system can be deployed for navy and air forces
Ricochet of Spheres on Sand of Various Temperature
Get PDFThe 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
Small-Caliber Grenade Projectile Applicable to Individual Grenade Launchers
Get PDFAn overview of development of grenade types for individual grenade launcher is presented. Considering historical and current research programs, a new type of projectile is proposed. Results of initial experiment which verifies chosen approach are included herein. It is said, based on obtained results, that showed new design can be applied in different applications without negative impact on combat capabilities – it even increases some crucial criteria. Current study indicates nearly 30 per cent increase of the effective exit velocity, however there is a design space where further investigation and optimisation can provide additional profits
Indoor Scene Recognition for Micro Aerial Vehicles Navigation using Enhanced-GIST Descriptors
Get PDFAn 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, Naïve 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 Naïve Bayes classifiers. In addition to its accuracy and robustness, the algorithm is suitable for real-time operations
A Triangular-shaped Quarter-mode Substrate Integrated Waveguide based Antenna for WBAN Applications
Get PDFIn this study, a compact quarter-mode substrate integrated waveguide (QMSIW) based dual-band antenna is proposed for wireless body area network applications. A QMSIW resonator is realised by splitting the full-mode substrate integrated waveguide cavity along the perfect magnetic conductor walls. The proposed antenna preserves the fundamental mode TE110 and the third order mode TE220 of the square SIW cavity. The proposed antenna is linearly polarised in the lower band at 2.45 GHz and circularly polarised in the higher frequency band at 5.8 GHz. The on-body performance of the antenna is validated on a piece of pork muscle tissue and it has been found to be stable with respect to surroundings. The proposed antenna covers the ISM bands 44 MHz (2.445 GHz - 2.489 GHz) and 225 MHz (5.730 GHz - 5.955 GHz) at 2.45 GHz and 5.8 GHz, respectively. The measured gain of the antenna on pork tissue is 1.87 dBi and 5.5 dBi at two bands. In addition, the specific absorption rate is obtained of 0.65 mW/g and 1.51 mW/g at two bands (wext = 2 mm), averaged over 1 g of muscle with 100mW input power. Moreover, the simulated and experimental results demonstrate a good agreement
Fuzzy Logic-based Adaptive Extended Kalman Filter Algorithm for GNSS Receivers
Get PDFDesigning 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 S4 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 24th, 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
Construction of Dual Cyclic Codes over {F}_{2}[u,v]/ < u^2, v^2 - v, uv - vu > for DNA Computation
Get PDFHere, we assume the construction of cyclic codes over ℜ={F}_{2}[u,v]/ < u^2, v^2 - v, uv - vu >. In particular, dual cyclic codes over ℜ= {F}_{2}[u]/ <u^2> with respect to Euclidean inner product are discussed. The cyclic dual codes over ℜ are studied with respect to DNA codes (reverse and reverse complement). Many interesting results are obtained. Some examples are also provided, which explain the main results. The GC-Content and DNA codes over ℜ are discussed. We summarise the article by giving a special DNA table