Bhagalpur College of Engineering

This study utilizes the effectiveness of machine learning techniques, namely multilayer perceptron (MLP), radial basis function neural network (RBFNN), and long short-term memory (LSTM) for predicting the undrained shear strength of clay (SU). 400 datasets were generated using seven inputs, viz., water content, specific gravity, void ratio, liquid limit, plastic limit, height of the clay layer, and water table position. Performance parameters, including coefficient of determination (R2), variance account factor (VAF), Legate and McCabe index (LMI), root mean square error (RMSE), maximum absolute error (UAE), and expanded uncertainty (U95), were used to assess the model’s performance. Among three models, LSTM outperformed in all the three phases due to highest value of R2 (Train = 0.995, Test = 0.992 and Validation = 0.986), VAF (Train = 99.644, Test = 99.405 and Validation = 98.80), LMI (Train = 0.931, Test = 0.911 and Validation = 0.875) and lowest value of RMSE (Train = 0.014, Test = 0.017 and Validation = 0.016), UAE (Train = 0.040, Test = 0.060 and Validation = 0.030) and U95 (Train = 0.386, Test = 0.370 and Validation = 0.270). The model’s performance was also assessed using the convergence curve, reliability index, regression plot, William’s plot, external validation, and comparative analysis.

Antenna systems having small size, higher efficiency and stable radiation behaviour at terahertz frequencies are need for today's scenario for sustainable energy communication network. Proposed work suggests the design and optimization of DRA antenna for THz microwave frequency which is based on the parameters like voltage standing wave ratio (VSWR), axial ratio, and total efficiency. The optimized DRA possesses a value of VSWR that is less than 2.0 at the entire operating frequency that makes it an ideal match of the impedance. The antenna axial ratio is approximately 1.2 dB, which ensures the stability of circular polarization, suitable to the capacity of wireless connections of high capacity. Moreover, the design will achieve a maximum overall efficiency of about 85, which is very optimum in the context of energy conscious and low loss communication systems. Because of these features, the proposed THz DRA can be applied in smart grid successfully. Sustainable wireless, IoT devices which are energy-efficient and communication.

Volumetric heat capacity (VHC) is a key thermophysical property governing the thermal storage performance of backfill materials. Bentonite-granular soil mixtures are commonly used as heat transfer media due to their favorable thermal and hydraulic properties. The VHC of these mixtures is strongly affected by several geotechnical properties. The effect of additives such as sand and fly ash on the VHC of bentonite-based backfills remain insufficiently understood. This study presents a comprehensive experimental dataset comprising 219 VHC measurements of bentonite-based backfill mixtures using a KD2-Pro dual-probe system under controlled laboratory conditions. The sample was compacted to 80-95% of the maximum dry density and the water content was varied up to near-saturation. Pure bentonite exhibited the highest VHC (approximate to 3.00 MJ/m3 & sdot;K) compared with sand (1.71 MJ/m3 & sdot;K) and fly ash (2.24 MJ/m3 & sdot;K). Bentonite-fly ash mixtures showed slightly higher VHC (3.2-3.4 MJ/m3 & sdot;K) than bentonite-sand mixtures (3.0-3.2 MJ/m3 & sdot;K) for additive contents up to 40%. Micro-structural observations suggest that flocculated bentonite initially encapsulates granular particles, forming continuous heat-transfer pathways, which diminish as additive content increases. Furthermore, predictive models namely genetic programming (GP) and multivariate adaptive regression splines (MARS) were developed to simulate the VHC. The MARS model achieved superior performance (R2 = 0.9532 for training and 0.9517 for testing). Global sensitivity analysis identified water content as the most influential parameter affecting VHC, followed by dry density and clay content. Beyond improved accuracy, these models significantly reduce laboratory time and cost, minimize human error in testing, and enable faster, optimized mix design development.

Abstract This article proposes the harmonic-power calculation for a symmetrically arranged 2 N -element time-modulated antenna array by exploiting single-pole-double-throw-based (SPDT) time sequences. The SPDT sequence can improve the overall efficiency of time-modulated arrays by overcoming the challenges of the simple ON–OFF scheme implemented using single-pole-single-throw networks (SPST). Time-modulated arrays are an unconventional alternative to phased antennas, in which amplitude and phase tapering can be achieved by appropriately controlling the ON-time periods and instants. In this work, for the first time, a closed-form derivation of the side-beam power calculation for a 2 N -element symmetric timed-modulated array is presented. The array is then exploited with appropriately designed SPDT time schemes for monopulse radar beamforming with sidelobe suppression. Monopulse is targeted with a bidirectional phase-center motion-based (BPCM) switching scheme that controls a clustered subarray of M elements within the 2 N -element array. Further, sidelobe suppression is achieved using a Chebyshev distribution. Monopulse generation and sidelobe suppression can be viewed as two distinct scenarios in which phase and amplitude tapering are addressed using SPDT switching schemes. To demonstrate that the proposed SPDT schemes are more power-efficient than conventional methods, a detailed comparison with SPST switching frameworks is also presented. The comparison is also carried out using other performance metrics, such as realized gain, instantaneous gain, and directivity. The proposed research is a cost-efficient alternative to the conventional phased arrays, offering sidelobe and sideband cancellation, beam steering, and beam scanning capabilities beneficial for radars.

The design of an effective sidelobe-suppressed beamformer array antenna using ‘time modulation’ is proposed in this research for beam scanning and anti-jamming applications in radar. Time-modulated array (TMa) is the substitute of traditional phased antenna array, where the impinging signal’s phases are controlled by managing the ON and OFF timings of the array radiators. This research aims an optimal TMa beam scanner, targeting a wide scanned region of 90° in the broadside. The scanning patterns are created using delta potential well-based quantum-optimized timing sequences, and the ON durations of the radiators are optimized to create sidelobe-suppressed radiation properties. The beamformer is developed in an 8-element TMa, and the inclusion of modulated schemes enables simultaneous scanned beams over the desired sector. The scanning patterns with suppressed sidelobes are then managed to place strategic nulls pointing to the jamming signal’s directions. The beamformer is developed to point single nulls and multi-nulls in prespecified sectors for anti-jammer purposes, which shows the efficiencies, adaptiveness, and robustness of the TMa beamformer. The directional optimized anti-jammer method is also investigated in terms of convergence speed. The sidelobe-suppressing beamformer demonstrates decent performance, minimizing the sidelobes of the main beams and scanned beams around − 35 dB and − 25 dB, respectively, for all cases. The uniquely designed objective function (OFN) helps to mitigate the unwanted interferences and suppressed higher-order sidebands below − 20 dB. The proposed beamformer also creates deep nulls around − 75 dB and − 60 dB for single-point and multi-point anti-jamming applications, respectively. The radiation efficiencies are maintained above 70