Faculty Publications
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Item Implementation of Acoustic Emission Testing to Study the Type of Cracking in Reinforced Concrete Beams(Springer Science and Business Media Deutschland GmbH, 2021) Ghosh, S.; Agrawal, R.; Vidya Sagar, R.In this experimental study, crack classification in reinforced concrete (RC) beams was carried out using acoustic emission (AE) testing. Two types of under reinforced RC beams were tested in laboratory subjected to four-point bending, and monotonically increased load was applied. The first type of RC beam had shear reinforcement (steel stirrups), and the second type of RC beam had no shear reinforcement. The generated AE during the fracture process in the tested RC beams were used for the crack classification analysis. Gaussian mixture modeling (GMM) of acoustic emission signals was performed. It was observed that the RC beam without shear reinforcement failed suddenly (brittle nature). However, the RC beam with shear reinforcement failed gradually thereby exhibiting ductile nature. In both the RC beams, considerable AE related to shear cracking appeared at a 20–30% peak load. In the case of the RC beam with shear reinforcement, initially, tensile cracks were developed at the bottom of the beam and slowly started widening upward. Diagonal shear cracks started forming near to the supports when the test specimen reaching to collapse. In the case of the RC beam with no shear stirrups, tensile cracks originated at the bottom of the beam. But in this case, the influence of shear cracks developed near to the supports was more pronounced as it propagated rapidly. By comparing the different AE parameters, a steady increase in the number of hits till failure was observed in the case of the RC beam with shear reinforcement. But on the other hand, an abrupt increase in the number of hits was observed after 50% of peak load in the case of the RC beam with no shear reinforcement. The results are useful to study the sensitivity of AE to the shear reinforcement present in the RC beams. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item A new probabilistic rekeying method for secure multicast groups(2010) Pais, A.R.; Joshi, S.The Logical Key Hierarchy (LKH) is the most widely used protocol in multicast group rekeying. LKH maintains a balanced tree that provide uniform cost of O(log N) for compromise recovery, where N is group size. However, it does not distinguish the behavior of group members even though they may have different probabilities of join or leave. When members have diverse changing probabilities, the gap between LKH and the optimal rekeying algorithm will become bigger. The Probabilistic optimization of LKH (PLKH) scheme, optimized rekey cost by organizing LKH tree with user rekey characteristic. In this paper, we concentrate on further reducing the rekey cost by organizing LKH tree with respect to rekey probabilities of members using new join and leave operations. Simulation results show that our scheme performs 18 to 29% better than PLKH and 32 to 41% better than LKH. © 2010 Springer-Verlag.Item A comprehensive framework for Double Spatial Modulation under imperfect channel state information(Elsevier B.V., 2017) G.D., G.S.; Koila, K.; Raghavendra, R.; Shripathi Acharya, U.The essential requirement for a 5G wireless communication system is the realization of energy efficient as well as spectrally efficient modulation schemes. Double Spatial Modulation (DSM) is a recently proposed high rate Index Modulation (IM) scheme, designed for use in Multiple Input Multiple Output (MIMO) wireless systems. The aim of this scheme is to increase the spectral efficiency of conventional Spatial Modulation (SM) systems while keeping the energy efficiency intact. In this paper, the impact of imperfect channel knowledge on the performance of DSM system under Rayleigh, Rician and Nakagami-m fading channels has been quantified. Later, a modified low complexity decoder for the DSM scheme has been designed using ordered block minimum mean square error (OB-MMSE) criterion. Its performance under varied fading environments have been quantified via Monte Carlo simulations. Finally, a closed form expression for the pairwise error probability (PEP) for a DSM scheme under conditions of perfect and imperfect channel state information has been derived. This is employed to calculate the upper bound on the average bit error probability (ABEP) over aforementioned fading channels. It is observed that, under perfect and imperfect channel conditions DSM outperforms all the other variants of SM by at least 2dB at an average bit error ratio (ABER) of 10?5. Tightness of the derived upper bound is illustrated by Monte Carlo simulation results. © 2017 Elsevier B.V.Item Performance Analysis of Hybrid RF/FSO System Using BPSK-SIM and DPSK-SIM Over Gamma-Gamma Turbulence Channel With Pointing Errors for Smart City Applications(Institute of Electrical and Electronics Engineers Inc., 2018) Krishnan, P.The flourishing technology in wireless communication-free space optics (FSO) offers lots of merits over radio frequency (RF) links due to its license free bandwidth, ease of installation, high security features, and viable cost for short distance communication. It's high speed data rate and immunity against electromagnetic interference makes FSO the emerging technology of today. But, FSO is not always reliable especially during atmospheric conditions, such as fog, rain, mist, and snow. Hence, in account a new technique of hybrid FSO/RF, this includes advantages of both FSO and RF technologies. Through this paper intend to perform an extensive analysis of the error and misalignment effects encountered in line of sight communication. Pointing error and turbulence effects are the main drawback parameters for our analysis. For this purpose I have taken into consideration different modulation techniques-binary phase shift keying-subcarrier intensity modulation, differential phase shift keying-subcarrier intensity modulation communication system with reference to on-off keying (OOK) modulation. The novel expressions for outage probability and BER for both FSO and RF system are derived which uses Rician channel and 16QAM modulation scheme alongside hybrid FSO/RF system for weak, moderate, and strong turbulence regimes using Meijer-G function. © 2013 IEEE.Item Time synchronization problem of wireless sensor network using maximum probability theory(Springer, 2018) Upadhyay, D.; Dubey, A.K.; Santhi Thilagam, P.S.Synchronizing time between the sensors of wireless sensor network has vital importance. It helps in maintaining a consistent and reliable frame of time across the network. Two clocks are stated to be synchronized when their frequency source runs with equal rate and their offsets are set identical. Basically, due to the manufacturing difference there is slight variation in their clock oscillator which affects the degree of frequency source and accuracy. Therefore this leads to the problem of synchronizing time between the sensor clocks. To attain time synchronization in a network typical contention-based message passing techniques are used. In this paper two-way message passing scheme is utilized. It proposes a statistical tool based on the maximum probability theory for selecting the reference clock offset for time synchronization protocols. It also proposes a subset selection algorithm to support the proposed statistical tool. The results obtained consist of the selection of most probable estimate for clock offset. The proposed algorithm utilizes the two-way message passing scheme for the exchange of timing messages within the network. The proposed algorithm is compared with the existing algorithms for estimation of clock offset. It was observed that the proposed works gives better results in terms of efficiency i.e. 99.8% efficient. © 2018, The Society for Reliability Engineering, Quality and Operations Management (SREQOM), India and The Division of Operation and Maintenance, Lulea University of Technology, Sweden.Item A statistical tool for time synchronization problem in WSN(Bentham Science Publishers P.O. Box 294 Bussum 1400 AG, 2019) Upadhyay, D.; Dubey, A.K.; Santhi Thilagam, P.S.Background: In recent research, time synchronization has a great importance in the various application of wireless sensor network. Localization, tracking, message passing using contention-based schemes and communication are some of the fields where synchronization between sensor clocks is highly required. Therefore, several algorithms were designed to achieve a rational and reliable frame of time within the wireless sensor network. Patents related to time synchronization in WSN were also analyzed. Methods: This paper discusses the powerful statistical tool using maximum probability theory for synchronizing the time within the sensor's clock. In this paper, maximum probability theory is applied to estimate the best value of clock offset between two sensor clocks. The proposed algorithm is analyzed by exchanging timing messages between nodes using two-way message exchange schemes. Results: The proposed algorithm is also implemented along with a Time-Sync Protocol for Sensor Network. It reduces error deviation from 2.32 to 0.064 ms as compared with Time-Sync Protocol for Sensor Network without proposed works. Conclusion: It was observed that for a small network, proposed work gives better and efficient results with Time-Sync Protocol for Sensor Network. © 2019 Bentham Science Publishers.Item A Probabilistic Model of Clock Offset Estimator (PMCOE) for Clock Synchronization in Wireless Sensor Network(Springer New York LLC barbara.b.bertram@gsk.com, 2019) Upadhyay, D.; Dubey, A.K.; Santhi Thilagam, P.Synchronization of clock within a wireless sensor network epitomizes crucial problems in the efficient and reliable operation of the sensors. This paper discusses a novel probability theory based clock offset estimator for various clock synchronization schemes of wireless sensor networks is proposed. The motivation is to utilize local clock timing for achieving the global clock synchronization. It presents a probabilistic model to estimate the most expected value of clock offset for sensor nodes. This model uses a statistical tools based on dispersion and central tendency. The proposed model was compared with the existing clock offset estimating models. It was observed that the proposed model gives better results with 1.008% accuracy, 0.065% precision and 99.8% efficiency. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.Item Characterization of climatic parameters in the perspective of irrigated agriculture in Uttar Kannada district of Karnataka, India(India Meteorological Department mausamps@gmail.com, 2020) Yallurkar, S.; Nayak, S.; Nandagiri, L.A rainfall and potential evapotranspiration characteristics together determine the agro-meteorological regime of a region and influences decision concerning the magnitudes and timing of irrigation application. In the present study, historical rainfall and climate data pertaining to the study area, Uttar Kannada district, Karnataka, was analyzed with a view to characterizing irrigation water requirements. In addition to rainfall input, an important aspect of the water balance model is the crop evapotranspiration (ETcrop), which is the main factor in determining the irrigation schedule. ETcrop could be estimated by reference evapotranspiration (ET0) and crop coefficient. Atmospheric demand for water is represented by ‘potential evapotranspiration’ (PET) and calculated from climatic variables which is crucial for irrigation planning. It has been reported that the Penman-Monteith method gives more consistently correct ET0 estimates to other ET0 methods. While recognizing the importance of both rainfall and PET, an effective measure is known as the ‘Moisture Availability Index’ (MAI), which is computed as the ratio of 75% dependable rainfall and potential evapotranspiration. An MAI value of 1.00 indicates that dependable precipitation is equal to potential evapotranspiration. An MAI value of 0.33 or less for one month during the crop growing season is considered to be a signal of water deficit resulting reduction in crop yield. The findings of this study on MAI are used to decide the selection of the sowing period of crops so as to avoid water stress during the critical harvesting period. © 2020, India Meteorological Department. All rights reserved.Item Index modulation aided multi carrier power line communication employing rank codes from cyclic codes(Elsevier B.V., 2020) Raghavendra, M.A.N.S.; Shripathi Acharya, U.In a multi-carrier power line communication (mPLC) with dominant Narrowband and Impulse noise, crisscross errors can be clearly observed. In this work, mPLC employing Rank codes with Index modulation (mPLC-IM) has been considered to provide a reliable high data rate communication over the powerline channel. The rank codes required for this implementation have been derived from cyclic codes over GF(qm) viewed as m×n matrices over GF(q). Encoding has been performed by employing the Galois Field Fourier Transform (GFFT) domain description of cyclic codes. This scheme is able to correct a variety of crisscross errors in mPLC-IM The GFFT approach provides an additional degree of freedom that is offered by choice of free transform component indices. It can be used to design an index key scheme which can enhance the physical layer security of an mPLC system. In the absence of knowledge of the index key, it is observed that the probability of error reaches an error floor of ?10?2, highlighting the need for index key for appropriate decoding. Further, a novel check matrix construction is proposed and used in devising a decoding strategy. It is observed that the proposed decoder is capable of correcting any errors of rank ??m?12?. In mPLC-IM with OFDM, the proposed codes over GF(24) provide an asymptotic gain of approximately 3 dB when compared to the uncoded system. For mPLC-IM with multi-tone Frequency Shift Keying (FSK), the proposed RC over GF(24) provides a 25% improvement in symbol error rate (SER) at lower values of p (probability of occurrence of narrowband noise) when compared to Reed-Solomon (RS) based Constant Weight (CW) CW(13,6,5)2?RS[15,14,2]16 codes. Further, a SER improvement of around 30% is achieved using rank codes (RCs) over GF(28) when compared with CW(9,4,4)2?RS[15,14,2]16. In the presence of dominant background noise, the BER graphs show that the proposed codes are equivalent (slightly superior) in performance as that of Low Rank Parity Check (LRPC)/Gabidulin based designs. In the presence of dominant impulse noise, the proposed system is providing significant gain when compared with the Linearly Pre-coded Orthogonal Frequency Division Multiplexing (LP-OFDM) system and LRPC based scheme. Additionally, simulation results show that, in the absence of an index key, the probability of error reaches the error floor, highlighting the need for index key for appropriate decoding. This can be viewed as the code capable of providing an additional layer of security. © 2019 Elsevier B.V.Item Diverse interactions of aggregated insulin with selected coumarin dyes: Time dependent fluorogenicity, simulation studies and comparison with thioflavin T(Elsevier Ltd, 2021) Dalal, S.; Das, B.K.; Saini, M.; Chakraborty, D.; Sadhu, K.K.In this study, we have compared neutral coumarin based well-known commercially available probes C6, C7 and C545T for fluorogenic response from the aggregated insulin. The immediate fluorogenic responses were comparatively poor from all the three probes with respect to the previously reported response from thioflavin T (ThT) in the presence of aggregated insulin. Interestingly C6 among the three neutral coumarin derivative showed a significant steady increase of fluorescence intensity with time up to 6 h before reaching the saturation limit. Similar time dependent fluorogenic experiment with C7, C545T and ThT showed comparatively fast saturation within few minutes to 2 h. The molecular docking and simulation studies showed that these neutral probes could be stabilized in the aggregated form of the insulin predominantly by non-covalent weak interactions such as hydrogen bonding, ?-? and cation-? interactions. The probability distributions of the dihedral angles between two heterocyclic parts in C6 showed maximum probability of occurrence at 0° and 180°. These probability distributions of the dihedral angles between two heterocyclic parts within all the four fluorophores provided the justification of selective time dependent fluorescence enhancement from C6 in presence of insulin aggregate. The overall fluorogenic enhancement from C6 was comparable to the fluorogenic response from ThT and theoretical study confirmed distinctly different origin of this associated slow time dependent fluorogenic response. © 2020 Elsevier Ltd