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Effect of Environment on Underwater Acoustic Communication Data Rates
Get PDFUnderwater acoustic communication has several applications for civilians and defence. It is a challenging engineering problem, where large variability of ambient noise and highly variable channel characteristics limits the performance of communication system. In addition horizontal transmissions in shallow water is considered very challenging due to time varying delay spread and significant Doppler spread. An experiment was conducted to study the diurnal variability of underwater acoustic communication channel properties of the south west coast of India. Time spread and bit error rate for different ranges and depths are compared in this paper. Influence of prevailing sound speed profile on acoustic communication link is also discussed
Development of a Fuel Quantity based Engine Control Unit Software Architecture
Get PDF Conventionally diesel engines are controlled in open loop with maps based on engine speed and throttle position wherein fuel quantity is indirectly fixed using the rail pressure and injection duration maps with engine speed and throttle position as the independent variables which are measured by the respective sensors. In this work an engine control unit (ECU) software architecture where fuel quantity is directly specified in relation to the driver demand was implemented by modifying the control logic of a throttle position based framework. A desired fuel quantity for a given engine speed and throttle position was mapped from base line experiments on the reference engine. Injection durations and rail pressure required for this quantity was mapped on a fuel injector calibration test bench. The final calculation of injection duration in the new architecture is calculated using the fuel injector model. This enables determination of fuel quantity injected at any moment which directly indicates the torque produced by the engine at a given speed enabling smoke limited fuelling calculations and easing the implementation of control functions like all-speed governing
An Intelligent Gain based Ant Colony Optimisation Method for Path Planning of Unmanned Ground Vehicles
Get PDF In many of the military applications, path planning is one of the crucial decision-making strategies in an unmanned autonomous system. Many intelligent approaches to pathfinding and generation have been derived in the past decade. Energy reduction (cost and time) during pathfinding is a herculean task. Optimal path planning not only means the shortest path but also finding one in the minimised cost and time. In this paper, an intelligent gain based ant colony optimisation and gain based green-ant (GG-Ant) have been proposed with an efficient path and least computation time than the recent state-of-the-art intelligent techniques. Simulation has been done under different conditions and results outperform the existing ant colony optimisation (ACO) and green-ant techniques with respect to the computation time and path length
Ground penetrating Radar Clutter Removal via 1D Fast Sub band Decomposition
Get PDFTarget detection performance in ground-penetrating radar (GPR) deteriorates highly in the presence of clutter. Multi-scale (wavelet transform) or the recently proposed multi-scale and multi-directional decomposition based methods can efficiently remove the clutter, however they have high computational complexity. In this paper, we propose a new multi-scale method which requires only 1D fast subband decomposition of the rows of the GPR image. The resulting detail layers directly provide the clutter-free target component of the GPR image. The proposed method is compared to the state-of-art clutter removal methods both visually and quantitatively using a realistic simulated dataset which is constructed by the gprMax simulation software. The results show that the proposed 1D subband decomposition scheme approximates the classical 2D wavelet decomposition successfully and even presents a performance increase as well as a complexity decrease for fast decomposition methods based on lifting wavelet transform and a trous wavelet transform
Effect of Type of Carbon Matrix on Tribological Properties of C C Aircraft Brake Discs
Get PDFFour type of Carbon/Carbon (C/C) composite brake discs (A, B, C, D) were manufactured using different process routes, using spun yarn graphitised carbon fabric as reinforcement. These discs were densified with different types of carbon matrices derived from different precursor materials. C/C brake disc of type A is having carbon matrix derived from pitch precursor, type B has a mixture of resin and pitch derived carbon matrices, type C has a combination of resin derived, pyro and pitch derived carbons and type D has pyro and pitch derived carbon matrices. Friction and wear performance of these brake discs were studied by simulating aircraft landing braking energies (normal and over load) corresponding to one interface using disc-on-disc dynamometer. It was found that the type of carbon matrix influences the nature of friction film formed, which in turn affects the wear rate of C/C brake discs. It was also discussed how the matrix characteristics affected the mechanical properties and the friction film formed affect the coefficient of friction of each type of disc
Simulation of Fragmentation Characteristics of Projectile Jacket Made of Tungsten Alloy after Penetrating Metal Target Plate using SPH Method
Get PDFA smooth particle hydrodynamics (SPH) model was used to simulate the fragmentation process of the jacket during penetrator with lateral efficiency (PELE) penetrating the metal target plate to study the fragmentation characteristics of PELE jacket made of tungsten alloy. The validity of the SPH model was verified by experimental results. Then the SPH model was used to simulate the jacket fragmentation under different impact velocity and thickness of target plate. The influence of impact velocity and thickness of target plate on the jacket fragmentation was obtained by analysing the mass distribution and quantity distribution of the fragments formed by the jacket. The results show that the dynamic fragmentation of tungsten alloy can be simulated effectively using the SPH model, Johnson-Cook strength model, maximum tensile stress failure criterion and stochastic failure model. When the thickness of target plate is fixed, the greater the impact velocity, the greater the pressure produced by the projectile impacting the target plate; with the increase of impact velocity, the mass of residual projectile decreases, the number of fragments formed by fragmentation of jacket increases linearly, and the average mass of fragments decreases exponentially. When the impact velocity is constant, the greater the thickness of the target plate, the longer the pressure duration by the projectile impacting the target plate; with the increase of the thickness of target plate, the mass of residual projectile decreases, the number of fragments formed by fragmentation of jacket increases linearly, and the average mass of fragments decreases exponentially. The numerical calculation model and research method adopted in this paper can be used to study the impact fragmentation of solid materials effectively
Intra annual Variability of the Arabian Sea high salinity water mass in the South Eastern Arabian Sea during 2016 17
Get PDFIntra-annual variability of the Arabian Sea high salinity water mass (ASHSW) in the South Eastern Arabian Sea (SEAS) and Gulf of Mannar (GoM) are addressed in this paper by utilisng the monthly missions carried out onboard INS Sagardhwani during 2016-17. Our observations revealed that the ASHSW was evident along the SEAS irrespective of seasons, whereas in the GoM the presence of ASHSW was observed during winter. The processes such as downwelling/up-welling, coastal currents, intrusion of low saline waters, stratification are clearly affects the spreading of the ASHSW. The characteristics such as core salinity value, depth and thickness of ASHSW exhibited remarkable spatio-temporal variability. Lateral mixing with the low saline waters in the region during winter reduces its core salinity. The intrusion of low saline waters was clearly seen upto 15 ON but the intrusion of low saline waters is not flowing through the GoM. The interface between the ASHSW and the prevailing low saline waters showed strong horizontal gradients of salinity. The presence of the ASHSW makes difference in the SLD and the below layer gradient which is sufficient to complicate or influence sound transmission. The spatio temporal variability of the ASHSW and its acoustic relevance are documented in this paper
Onset and Evolution of Upwelling along the West Coast of India
Get PDFTo describe the onset and evolution of upwelling along the south west coast of India, authors collected a series of conductivity temperature depth measurements on board INS Sagardhwani extending from 7 °N – 15 °N during the period extending from February 2017 - October 2017. In this paper we utilised the undulations of the 23 °C isotherm as a proxy to study the upwelling phenomenon. The upward movement of the waters at the southern tip off India (77.5 °E) in the subsurface levels was observed to commence from late February 2017 in depths around 80 m and by the end of May 2017, it is observed to rise rapidly to the surface. The upwelled waters reach the surface during the 2nd week of July all along the Indian coast, and then intensified during August 2017. Beyond 12 °N maximum upwelling is seen in July and thereafter in early August 2017 upwelling was intense till October 2017
THz Communication Technology in India Present and Future
Get PDFAs the communication industry is currently undergoing a major overhaul to accommodate greater bandwidth and higher data-rate to meet the rapidly growing data demand; terahertz range of frequencies from 100 GHz to 3 THz are being investigated as a possible replacement of the conventional mm-wave technology. In this paper, we have examined the technology readiness of Indian research community in this specific direction and have discussed the research development strategies that are required to gain momentum towards achieving a viable technology standard in THz communication in India. Moreover, we have presented a collection of technology recommendations towards product development required for initiation and advancement in THz communication. We have also introduced a design of a short-range THz communication configuration in conclusion, based on recent reports of successful realization of THz communication which could be utilized for immediate realization using commercially available resources
Correlates of Professional Obsolescence among Researchers
Get PDFObsolescence setting in the employees of the organisations significantly hampers the organisational productivity. An empirical investigation of the associated factors and the efforts to minimise them help in designing strategies to deal with obsolescence and maintain optimum effectiveness of the organisation. As an attempt in this direction, the present study aimed at exploring the role of literature-suggested correlates of obsolescence in case of researchers in an Indian government organisation. The sample included 200 participants (146 males and 54 females) working as researchers in government scientific institutions with service experience ranging from two to 30 years. The participants were administered with standardised measures of obsolescence, work engagement, work motivation, resistance to change, organisational climate, human resource management (HRM) Policies and Practices, and Self Esteem. The obtained data were analysed with correlation and regression analyses. The findings revealed that in the target population obsolescence due to both organisational and individual level factors was found significantly and positively correlated with amotivation and resistance to change; whereas, negatively correlated with work engagement, organisational climate, HRM policies and practices, intrinsic motivation, and self-esteem. Regression analyses indicated that adequate recognition of efforts, better training and development, qualitative work availability (pressure), and enhanced concern to optimally maintain the intrinsic motivation and dedication of employees are significant factors for keeping check on obsolescence. The findings are explained and discussed in details