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Optimized Mosaic Method for Accurate Measurement of Soot Concentration Indirect Method
Full text linkGlobal air pollution poses health risks. Soot is a major contributor to warming and pollution. Measuring soot is key to mitigating emissions. This study proposes an empirical method using markers to indirectly gauge soot levels. The Mosaic method was tested against conventional techniques with over 50 samples. This method utilizes markers to collect impurities in the air, employing the µ/m³, m(g), and the newly devised Mosaic method. All results underwent standard statistical processing, enabling a comparison between the new method (Mosaic) and conventional techniques used
Response of a Stretched String Subjected to a Moving Mass
Full text linkIn this paper, the dynamics of a taut horizontal string with a constant velocity moving mass including its rotary inertia, is modelled. The equation of motion is solved using Galerkin’s approach, employing appropriate comparison functions. A discontinuity or jump in the trajectory of the mass has been established when the mass is about to leave the string. The consideration of rotary inertia in the model is found to affect the spatial location of the jump in the trajectory of the moving mass
Investigation of Multi layered Mitigation Systems for Protection from 120mm Mortar HE Top Attacks
Full text linkThis paper investigates the protection of reinforced concrete (RC) structures from the Mortar 120mm HE (high explosive) top attacks. Two multi-layered mitigation systems are proposed to be added on RC structures' roofs to achieve full protection against the Mortar 120mm destroying effects (i.e. ballistic penetration and explosion effects). The proposed mitigation systems combine relatively high-strength materials, to stop or slow down the projectile, with lightweight porous materials, to attenuate the explosion shock wave. Another function of the porous materials is to increase the thickness of the proposed mitigation systems and hence increasing the explosion stand-off distance. Traditional construction materials, steel and RC, were used as cheap high-strength materials, whereas commercial rigid polyurethane foam and light-weight brick were examined as shock wave absorbers. Two firing tests of the 120mm bomb from cannon barrels against one-story RC structures strengthened with the proposed protection systems were executed. A numerical simulation of the real firing tests was performed via Autodyn hydrocode to further analyze the performance of the constituting components in alleviating the round effects. The current study demonstrated that the proposed mitigation systems, which are based on the multi-layering concept, are efficient and have their merits in defeating the Mortar 120mm HE attacks
High Speed Coding Unit Depth Identification Based on Texture Image Information Using SVM
Full text linkHigh-Efficiency Video Coding (HEVC/H.265) is a new video coding standard with half the bit rate of its predecessor, Advanced Video Coding (AVC/H.264). AVC/H.264 uses macroblocks, processing units between 4×4 and 16×16 pixels in size. H.265 uses Coding Tree Units (CTUs), a more complicated block structure that lets images be as large as 64×64 pixels. However, changing from macroblocks to coding tree units is essential for H.265 to become more efficient. Using the quadtree structure to divide the Coding Unit (CU) makes it harder for HEVC to find the optimal rate distortion. This paper presents a Support Vector Machine (SVM)-based method for finding the fastest coding unit division in intra-prediction HEVC without compromising compression efficiency. All partitions of CTU are assessed using five characteristics: Standard Deviation (SD), Root Mean Square Error (RMSE), Sub CU Complexity Difference (SCCD), Directional Complexity (DC), and Quantization Parameter (QP) to optimize the intra-prediction of HEVC in all intra-configurations. Simulations have been carried out to estimate the performance of the proposed machine learning-based algorithm using test sequences with different resolutions. Simulation results have shown that combining directional complexity and standard deviation gives a more accurate classification. SVM has been used to separate split-unsplit samples, and the standard rate-distortion optimization technique has been used to separate samples that are hard to separate. The results have shown a reduction of 67.44% in encoding time with a slight increase in bit rate
Comparison of Response Surface Based Preliminary Design Methodologies for a Gas Turbine Combustor
Full text linkPreliminary design of gas turbine combustor is a multi-objective optimization problem. The methodology to be used at the preliminary design stage depends on the freedom of design choices available. In this article, we explore three preliminary design methodologies for gas turbine combustor - M1: combustion liner design for a given casing; M2: combustion liner design without the casing and M3: coupled design of combustion liner and casing. A workflow for the automated design space exploration of gas turbine combustor using response surface methodology is presented. Computational fluid dynamics studies along with central composite design for design of experiments and genetic aggregation for response surface generation are used to quantify the combustor performance in design space. Comparison of three different design methodologies (M1, M2 and M3) is made to show how the choice of design methodology changes the available design space and limits/expands combustor performance. Candidate optimal designs and associated trade-offs from the optimization study are also presented. This study can aid combustor design engineers choose the most suitable preliminary design methodology for their specific use case
Investigations on Penta Band High Isolation MIMO Antenna for 5G NR Bands and HIPERLAN Applications Using TCMA
Full text linkThe present article proposes a penta band Multiple Input Multiple Output (MIMO) antenna for 5G New Radio (NR) bands and HIPERLAN applications using Characteristic Mode Analysis (CMA). The design is obtained and optimised in step-by-step procedure using novel CMA approach and by perturbing the conventional rectangular structure with slots on the patch (left and right sides) and the ground plane (wide slot + narrow slots) for enhancing the isolation at multi bands. The MIMO configuration has a total dimension of 0.58 l0 × 0.35 l0 × 0.01 l0 mm3 with an optimum element separation of 0.05 l0 (l0 is the lowest frequency operating wavelength). Multiband resonance is produced at 2.2, 4.2, 7.2, 16, 17.5 GHz. The radiating elements can excite various characteristic modes that support wider bandwidth. The -10 dB impedance bandwidth at working region are 0.2, 0.2, 0.38, 3.6, 2 GHz respectively. The suggested design yields a gain of 2.1, 5.7, 3.5, 3.5, 5.2 dBi and consistent radiation patterns at the working frequencies. The analysis of the diversity performance considers the Diversity Gain (DG) and Envelope Correlation Coefficient (ECC), whose values are near 9.9 dB and 0, respectively. Additionally, the assessed parameters are the CCL and TARC. The structure prototype has been developed, and the observed findings are highly coherent with the simulated results, making it appropriate for use in 5G NR bands, HIPERLAN, and IoT applications
Study of Aging Characteristics for Metalized HTPB Based Composite Solid Propellants Stored in Ambient Conditions
Full text linkThe aging of any propellant is defined as the change in the physical, chemical, and performance parameters of solid rocket propellants. The propellant’s service life and aging properties are important parameters of the study, especially for missiles and other defense applications. Hydroxyl-terminated polybutadiene (HTPB) based composite solid propellants with ammonium perchlorate (AP) are the most prominently used propellants in the operations of solid rocket motors in the defense and space sectors. Thus, studying this composite solid propellant is of essential when determining ambient service life. Performance parameters studied in this research are burn rate under high-pressure conditions in Crawford bomb setup, Thermogravimetric Analysis, and Fourier Transform Infrared Spectroscopy (FTIR). SEM and X-ray diffraction (XRD) analysis of the aged sample were also conducted to ascertain the chemical composition and morphological changes in the samples. Naturally aged propellant strands manufactured in different years have been compared with freshly prepared ones to establish a trend for deriving conclusions. The results from different analysis techniques, FTIR, XRD, and FESEM, depicted that oxidation of metals happens while aging of propellant due to atmospheric moisture, and the metal oxides prominently affect the propellant chemical composition and decomposition process of the propellant samples. The ballistic properties of the aluminium added samples showed an increment in burn rate. In contrast, the bimetal addition of aluminium and magnesium combined as an additive decreased the ballistic burn rate
Terramechanics Models for Tracked Vehicle Terrain Interaction Analysis A Review
Full text linkEfficient manoeuvrability of off-road tracked vehicles such as military tanks and rovers is essential in ensuring the success of military/extra-terrestrial operations. To achieve this, in-depth research on vehicle-terrain interaction is crucial. This manuscript deals with reviewing the ways to study terramechanics viz. theoretical, empirical, and field tests, and proposing the merits and demerits of each method. Under the theoretical approach, empirical, numerical, and semi-empirical methods are discussed. Under the empirical approach, the method based onthe vehicle cone index for tracked and wheeled vehicles is discussed. Under the numerical approach, advantages and disadvantages of Finite Element Method (FEM) and Discrete Element Method (DEM) are discussed. Semi-empirical method, based upon a combination of the best features of numerical and empirical approaches discusses terrain response to normal repetitive loads and shear repetitive loads for tracked as well as wheeled vehicles. Pressure sinkage relationship for terrains at various loading conditions and shear stress displacement relationship for different terrains obtained through penetration and shear tests are discussed to determine the vehicle’s mobility parameters under a semi-empirical approach. Further, the Super element model, multi-body simulation model, and ride and cornering vibration model are discussed under computer simulation models. A detailed review of various models customized towards tracked vehicle-terrain interaction discussed in this manuscript helps the authors set up a laboratory for terramechanics at DIAT. Preliminary analysis along with conceptual design of the experimental setup is also discussed. In a nutshell, this paper attempts to summarize the research that has been carried out in the field of tracked vehicle-terrain inter action comprising of VCI, MMP, FEM, DEM, Super element model, Multibody technique, and Semi-empirical methods helping the authors to establish a laboratory of terramechanics for their M. Tech. program on Armament and Combat Vehicles at DIAT Pune
A High Performance Parallel Approach to Delay Sum Beamformer in a Homogeneous Multicore Environment
Full text linkA Cache-Aware Beamformer (CABF) algorithm for the DAS beamformer in a homogeneous multicore processor environment is presented. The context of the proposed algorithm is established by discussing the case for a refined multicore implementation of the beamformer algorithm for a sonar application. The algorithm is designed, implemented, and compared to a regular pthread multicore implementation and a standard OpenMP-based implementation, using arithmetic intensity as the metric. FMA implementations of the algorithms are carried out, and the CABF algorithm is shown to achieve a better arithmetic intensity. A 6000-element array is designed with a simultaneous forming of 200 beams to test the efficacy of cabf in a multicore platform. The results show a 73 % increase in GFLOPS for FMA operations. The performance of the beamformer algorithm for different data sizes is studied, and on average, a 36 % improvement in computational performance is achieved compared to the OpenMP-based implementation
Numerical Estimation of Convective Heat Transfer Coefficient and Heat Flux for a Supersonic Rocket Nozzle
Full text linkRocket nozzles are often cooled by passing liquid propellants through channels in the nozzle walls. Estimating heat transfer to the wall from the hot gases in the nozzle is essential in deciding on the coolant flow requirements. The present work examines the computational estimation of convection heat transfer to the nozzle walls for compressible turbulent flows. Computations were performed using the rhoPimpleFoam solver in OpenFOAM® with two different turbulence models. We simulate the supersonic flow over a flat plate and validate the heat flux calculation method and turbulence model characteristics. We compare two methods of calculating convection heat transfer in the context of the nozzle flow case presented by Back & Massier. We find that the realizablek-ε turbulence model works well in estimating the heat transfer coefficient