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    7122 research outputs found

    Feasibility analysis of convolution neural network models for classification of concrete cracks in Smart City structures

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    Cracks are one of the forms of damage to concrete structures that debase the strength and durability of the building material and may pose a danger to the living being associated with it. Proper and regular diagnosis of concrete cracks is therefore necessary. Nowadays, for the more accurate identification and classification of cracks, various automated crack detection techniques are employed over a manual human inspection. Convolution Neural Network (CNN) has shown excellent performance in image processing. Thus, it is becoming the mainstream choice to replace the manual crack classification techniques, but this technique requires huge labeled data for training. Transfer learning is a strategy that tackles this issue by using pre-trained models. This work first time strives to classify concrete surface cracks by re-training of six pre-trained deep CNN models such as VGG-16, DenseNet-121, Inception-v3, ResNet-50, Xception, and InceptionResNet-v2 using transfer learning and comparing them with different metrics, such as Accuracy, Precision, Recall, F1-Score, Cohen Kappa, ROC AUC, and Error Rate in order to find the model with the best suitability. A dataset from two separate sources is considered for the retraining of pre-trained models, for the classification of cracks on concrete surfaces. Initially, the selective crack and non-crack images of the Mendeley dataset are considered, and later, a new dataset is used. As a result, the re-trained classifier of CNN models provides a consistent performance with an accuracy range of 0.95 to 0.99 on the first dataset and 0.85 to 0.98 on the new dataset. The results show that these CNN variants can produce the best outcome when finding cracks in the real situation and have strong generalization capabilities

    Kinematic Synthesis and Optimization of a Double-Slotted Fowler Flap Mechanism

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    A double-slotted Fowler flap in transport aircraft has more complexities in kinematic synthesis and design. The present research work presents a combination of six-bar mechanism, four-bar mechanism and a double-slotted mechanism configured for deployment of a Fowler flap arrangement. The mechanism is synthesized for cruise, take-off and landing conditions. A novel procedure for dimensional synthesis and optimization of the mechanism is developed for synchronizing flap and aft-flap positions. The complete synthesis, optimization procedures and parametric analysis are coded into MATLAB program. The results of the synthesis procedure are verified with 2D planar kinematic models and 3D solid models using SolidWorks. Also the novel kinematic synthesis procedure is validated by developing a prototype model of the mechanism using 3D printing technology

    Unmanned Aerial Vehicle-Based Multispectral Remote Sensing for Commercially Important Aromatic Crops in India for Its Efficient Monitoring and Management

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    Aromatic plants cultivation, processing and marketing is an upcoming agro-industry. The yields from these plants are generally governed by its good management practices of timely, suitable and precise actions against damaging factors. Remote sensing in agriculture is not a new phenomenon anymore, but using unmanned aerial vehicle (UAV, commonly known as drones) for the same is a pertinent topic these days, especially in India. Therefore, the study seeks to perform UAV-based airborne data acquisition, processing and analysis for modernised agricultural practices, finding of which may lead to generate rapid and on-demand real-time remotely sensed data for precision agriculture of commercial crops, which require more care and timely inputs as compared to conventional crops. The UAV high-resolution (1.5 cm/pixel) data were acquired from Mica Sense Altum, a 6 bands multispectral sensor, mounted over an indigenous Quad-copter (< 5 kg). With the help of processed orthoimage, the 22 plots of Rosa damascena (Damask Rose) were precisely (95% accuracy) classified into 03 categories, i.e., rose canopy, weed and open soil areas. We have also estimated digital plant count, plant height derived from canopy height model (CHM), canopy temperature and the topographic conditions of the crop plots. The digital plant counting for R. damascena planted in 4323 m2 area took 1.2 h as compared to manual 5.94 h counting. Average plant height values derived from CHM ranged from 23–68 cm as compared to 28–71 cm manually measured heights. Results were compared with ground sampling data, with which high correlation was found in digital plant count (R2 = 0.99) and plant height (96.69% accuracy). The derived average moderate slopes and northeast aspect suggested suitable topographic conditions required for R. damascena cultivation. The image-derived canopy temperature was compared to the relative ground-based measurements, obtaining accuracy percent of 98.54%. The outcomes are encouraging and have potential to be applied for future UAV grounded applications by farmhands

    Kinematic and Dynamic Analysis of Primary FCS Circuits of Typical 25 Seater Transport Aircraft

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    his research work presents kinematic and dynamic analysis of primary flight control surface actuation mechanisms including aileron, elevator and rudder of typical mechanically controlled transport aircraft. The 3D CAD models of the actuation mechanisms are constructed using SolidWorks. The circuit assemblies are exported to MSC ADAMS for detailed kinematic and force analysis. An elaborate simulation model is built in MSC ADAMS to understand the kinematic relations and to estimate the forces acting on all links, brackets and joints under the action of aerodynamic loads on the control surfaces. Analytical formulations are developed to verify the results of the force analysis. Further, the effect of inertia of control surfaces on the pilot forces is studied in detail and discussed

    Separation and flow unsteadiness control in a compression corner induced interaction using mechanical vortex generators: Effects of vane size and inter-device spacing

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    An experimental investigation was conducted to control separation characteristics of a 24° compression corner induced interaction in a Mach 2.0 flow using an array of mechanical vortex generators (VGs) with rectangular vanes (RRV) placed 6.8δ upstream of the interaction. The objective was to study the effect of (i) inter-VG spacing (s/h = 12, 9.5, 8.0, 6.1, 5.7, 5.5, 4.9, and 4.7), (ii) vane chord length (c/h = 7.2, 4.2, and 3.0), and (iii) vane angle (α = 24°, 20°, 18°, and 16°) in controlling the interaction and on the surface flow topology. These modifications reduce the projected area of VGs in the array from the conventional VG design of RRV2 (c/h = 7.2 and s/h = 9.5) to RRV8 (c/h = 3.0 and s/h = 4.7) by 41%. Reducing s/h also reduces the inter-VG region of the separation significantly that helps to achieve maximum reduction in the streamwise extent of separation up to 83% and in the peak rms value up to 80%. The former improves the overall pressure recovery from 3.0 to 3.4, thereby moving closer toward the inviscid value of 3.8. Surface flow topology shows that the VG array splits a single large spanwise separation bubble for no control into multiple smaller scale individual separation cells placed side-by-side all along the span of the interaction. This helps to reduce the magnitude of mass exchange imbalance across each individual separation cell and, hence, stabilizes the overall interaction relative to no control. The best VG configuration of RRV8 shifts the dominant frequency of fluctuations to approximately 2 kHz or St = 0.19, which is nearly an order of magnitude higher than that for no control

    Influence of particle size on magnetic and electromagnetic properties of hexaferrite synthesised by sol-gel auto combustion route

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    Magnetoplumbite barium hexaferrite (BaFe11.8Co0.2O19) is synthesised through sol-gel auto-combustion method under two pH conditions of precursor solutions (acidic i.e. pH < 1 and neutral i.e. pH = 7). The XRD analysis followed by Reitveld refinement indicates the formation of phase pure samples in both cases but the barium hexaferrite obtained from acidic precursor solution has smaller crystallite sizes. The Transmission Electron Microscopy (TEM) analysis followed by High Resolution Transmission Electron Microscopy (HRTEM) confirms a lower particle size of ∼20 nm for barium hexaferrite synthesised from acidic pH precursor solution. The shift in Raman peak (520-540 cm−1) by 20 cm−1, represents the whole structural block and further confirms the differences in the distribution of particle sizes due to the method of synthesis. The magnetic studies display a lower coercive field for the samples with smaller particle sizes. This is due to the crystalline size-induced microstrain that controls the magneto-crystalline anisotropy, shape anisotropy and stress anisotropy. The electromagnetic characterisation confirms broader absorption in the range of 8–18 GHz (X-band) with RL ≤ −7 db for the entire range for the samples with smaller particle sizes

    Nonlinear damping model for supersonic air-intake buzz

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    Air-intake buzz was initiated at Mach number of 3.0 on a two-dimensional isolated air-intake model in a wind tunnel by throttling the exit area. Schlieren images of shock oscillation around the intake entry during buzz were recorded using a high-speed camera. The recordings show a strong coupling between the bow-shock at the cowl lip and the oblique shock from the ramp. Image analyses were carried out, considering each image as a matrix of pixels and the change of intensity of light analyzed. A dominant frequency of 103.8 Hz (Strouhal no = 0.008 based on throat height) associated with the shock oscillations and harmonics of the shock oscillations are indicated. Phase-plots of the intensity and the rate of change of intensity show nearly perfect ellipse after filtering at the dominant frequency. Thus, the buzz phenomenon is associated with a limit-cycle oscillation as in a nonlinear Van-Der Pol oscillator. The computed damping factor synchronizes with the amplitude at all times, establishing that buzz is a stable and self-sustained oscillation with equilibrium between inertial and damping forces. It is proposed that a control scheme based on feed-forward control system using a suitable forcing function could be mathematically developed to suppress supersonic air-intake buzz

    On the structural changes, mechanism and kinetics of stabilization of lignin blended polyacrylonitrile copolymer fiber

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    Polyacrylonitrile(PAN)/lignin blend fiber prepared by continuous wet spinning process in dimethylsulfoxie(DMSO) was thermally stabilized under oxygen atmosphere in a continuous multizone oven at different heating temperature. The thermal behaviour of PAN/lignin fiber (PL fiber) stabilized were characterized by differential scanning calorimetry(DSC) under nitrogen atmosphere. The cyclization kinetics parameters such as activation energy(Ea), rate constant(k), pre-exponential factor(A) and extent of oxidation reaction (EOR) at different temperature were calculated from Kissinger and Ozawa method. FTIR analysis was used to investigate the structural changes and calculate the cyclization index and dehydrogenation index of stabilized PL fiber. The cyclization index values for the temperature of stabilization from 235 °C to 265 °C varied from 40 to 85%. The variation in density, elemental composition and mechanical properties of PL fiber stabilized at different temperature was determined. The density of the stabilized fiber varied from 1.225 to 1.385 g/cc as the stabilization temperature increased from 235 to 265 °C. The mechanism of thermal stabilization of and a set of temperature profile for a complete stabilization of PL fiber has been deduced from the various characterization

    High d 33 Lead-Free Piezoceramics: A Review

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    Over the past two decades, lead-free piezoceramics have been developed aiming to replace toxic lead-bearing lead zirconate titanate (PZT). A large number of lead-free piezo systems were explored during this period as evidenced from the huge number of publications. At this juncture, it was felt necessary to publish a review article focusing on material systems and processes delivering high d33 in order to give direction to future research for its further improvement equivalent to or higher than the d33 level delivered by PZT. The important lead-free piezo systems under consideration are: modified barium titanates such as barium calcium titanate zirconate (BCTZ), barium calcium tin titanate (BCSnT), barium calcium hafnium titanate (BCHfT), and potassium sodium niobate (KNN). In this article, an effort has been made to review the high piezoelectric properties achieved on the above lead-free piezo systems explaining the reasons and mechanisms behind high piezo properties and possible future directions of the research for further enhancement of properties

    Flutter Reliability Analysis of an Aircraft Wing: A Comparative Study

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    In this paper, a comparative flutter reliability study is presented for various types of limit state functions using first-order second moment (FOSM) method and the same is compared with Monte Carlo simulation (MCS). For the reliability study, a straight cantilever wing is considered in low subsonic flow, where aerodynamic modeling is based on Theodorsen’s aerodynamic-based strip theory, and for structure, finite element method (FEM) is used. Various parameters such as dimensionless static unbalance, mass moment of inertia, bending stiffness, and torsional stiffness are considered as independent Gaussian random variables. Results show that the probability density functions (PDFs) of various types of limit state function change with parameters, and also for some parameters, the distributions are not unique. The cumulative distribution function (CDF) of flutter velocity among different forms of limit state function obtained from FOSM method is best represented by flutter margin-based limit state function. Among various parameters considered, the most sensitive parameter is torsional stiffness and the least is bending stiffness


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