An Approach to Transit Path Design Using GIS

S.V.C. Sekhar, Wen Long Yue, M.A.P.Taylor 서울시립대학교 도시과학연구원 2004 International journal of urban sciences (IJUS) Vol. No.

The design of public transportation networks is complex and can include conflicting objectives. Networks designed to minimise travel time may not fulfil the requirement of maximum coverage and accessibility. In this context, a multi-criteria approach for transit alignment design has been developed to maximise a range of objectives using census data. Whenever a subdivision is developed in a suburban region of a medium sized city, transit operators often receive requests to link the city centre with the new locality via new routes. Traditionally, implementation of routing a new bus service is based on a ‘common sense’approach. This can lead to the development of an irrational network of public transport routes. This research offers an alternative approach, which essentially optimises ulticriteria for planning transit routes. This research has proved that it is worth considering such options for connecting origin-destination zones with a new bus service.

Ferroelectric switching behavior of pulsed laser deposited Ba0.8Sr0.2TiO3 thin films

José P.B. Silva,Koppole C. Sekhar,Sofia A.S. Rodrigues,Anatoli Khodorov,Javier Martín-Sanchez,Mário Pereira,Maria J.M. Gomes 한국물리학회 2012 Current Applied Physics Vol.12 No.4

The effect of pulse amplitude on the ferroelectric and switching properties of pulsed laser deposited Ba0.8Sr0.2TiO3 thin films has been studied. The structural and morphological analysis revealed that the films had a well crystallized perovskite phase and grain size of about 30e40 nm. A well saturated PeE hysteresis loop was observed with a remnant polarization (Pr)z4.8 mC/cm2 and a coercive fieldz100 kV/cm at a frequency of 1 kHz. The Pr has been found to be decreased only 4.3% after passing 8.0 × 108 cycles. The analysis of switching response with nucleation limited switching model reveals that characteristic switching time (t0) variance is due to the random distribution of the local electric fields. The peak value of polarization current and t0 exhibits exponential dependence on reciprocal of pulse amplitude. The effect of pulse amplitude on the ferroelectric and switching properties of pulsed laser deposited Ba0.8Sr0.2TiO3 thin films has been studied. The structural and morphological analysis revealed that the films had a well crystallized perovskite phase and grain size of about 30e40 nm. A well saturated PeE hysteresis loop was observed with a remnant polarization (Pr)z4.8 mC/cm2 and a coercive fieldz100 kV/cm at a frequency of 1 kHz. The Pr has been found to be decreased only 4.3% after passing 8.0 × 108 cycles. The analysis of switching response with nucleation limited switching model reveals that characteristic switching time (t0) variance is due to the random distribution of the local electric fields. The peak value of polarization current and t0 exhibits exponential dependence on reciprocal of pulse amplitude.

Dysarthric-Speech Detection Using Transfer Learning With Convolutional Neural Networks

S R Mani Sekhar,Gaurav Kashyap,Akshay Bhansali,Andrew Abishek A.,Kushan Singh 한국통신학회 2022 ICT Express Vol.8 No.1

Speech Dysarthria is a disorder in which speech muscles become weak, and it becomes difficult to articulate otherwise linguistically normal speech. This work is based on detection of speech dysarthria and how it can assist physicians, specialists, and doctors in its detection. The proposed work achieves higher accuracies on the TORGO dataset by using a transfer learning based convolutional neural network model (TL-CNN) and by converting the audio samples to Mel-spectrograms. The proposed work TL-CNN achieved better accuracy when compared with other machine learning models.

Damping identification in rotors from run-up beat responses using Hilbert transforms

N. Harish Chandra,A. S. Sekhar 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.2

In a rotor bearing system operating with constant angular acceleration, after passing through the critical speed, typical beat characteristics are observed because the transverse vibration response contains both excited and natural motion, and shortly after passing resonance, vibrations with close frequencies appear. The present study explains a method for estimating damping of rotor bearing systems from transient beat vibration signals observed during run up stage. A mathematical derivation to prove that a part of run-up vibration of the rotor system consists of beat phenomenon when the system crosses critical speed. It is also observed from the mathematical model that the beat vibrations depend on the damping in the system. This beat response is considered for Hilbert analysis and the damping is estimated. Increase in angular acceleration of the rotor will increase the damping. This paper investigates how the damping varies with respect to different angular acceleration values of the rotor bearing system. Experimental validation of the beat phenomenon and damping estimation are done for the rotor system. The proposed method is validated by using half-power band width method applied to run-up response.

Influence of combined radial location and growth on the leakage performance of a rotating labyrinth gas turbine seal

Sivakumar Subramanian,A. S. Sekhar,B. V. S. S. S. Prasad 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.6

Leakage characteristics, influenced by centrifugal and thermal radial growth are determined computationally for a generic rotating labyrinthseal used in the gas turbine secondary air system. Three seal locations, namely, R25, R50 and R75 are represented by means ofvarying the rotor radius mimicking different radial positions of the seal from the shaft axis. The combined influence of seal location andits radial (Centrifugal and thermal) growth on the leakage performance is investigated for a wide-ranging speeds from 1000 to 3000 rad/s,temperatures ranging from 200 to 450 oC and pressure ratios varying from 1.1 to 2.5, for a chosen initial clearance of 500 micron. Acomparison of the effect of rotation and temperature gradient among different rotors shows that the radial growth and leakage flow ratessignificantly vary with the increasing radius.

Life estimation of shafts using vibration based fatigue analysis

Sagi Rathna Prasad,A. S. Sekhar 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.9

Many rotating machinery components fail due to fatigue when subjected to continuous fluctuating stresses. Hence, estimation of fatigue crack initiation life is essential to avoid catastrophic failure. Effective vibration based fatigue life analysis requires measurement of accurate time varying signal. In this study, experimentally observed fatigue lives of rotating shaft, for three different notch configurations, are compared with fatigue lives estimated using two approaches based on an acquired vibration signal. The first one is time domain approach (based on Rainflow cycle counting) while the second one is frequency domain approach (based on power spectral density moments). In the frequency domain approach, fatigue life is estimated using the narrow-band approximation and Dirlik’s empirical solution. The performance of two approaches in estimating fatigue life for the same signal length taken at different time intervals from the total signal acquired is also discussed. In addition, experimental uncertainty analysis is performed and discussed in this study. A good correlation is found between the estimated fatigue life using Dirlik’s rainflow range probability density function and experimental life. Therefore, this study concludes that the Dirlik’s approach can be considered as preferable method for estimating fatigue life of rotating shaft.

Solvent Free Microwave Accelerated Synthesis of Heterocyclic Thiazolidin-4-ones as Antimicrobial and Antifungal Agents

Kondapalli Venkata Gowri Chandra Sekhar,Vajja Sambasiva Rao,Aravalli Satish Reddy,Ravada Sunandini,V S A Kumar Satuluri 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.5

A simple and efficient method has been developed for conversion of arenecarbaldehyde-3-methylquinoxalin-2-ylhydrazones to 3-(2-methylquinoxalin-3-yl)-2-(substitutedphenyl)thiazolidin-4-ones in good yields using microwave irradiation technique on silica as solid support under solvent free conditions. The synthesized compounds were characterized by elemental microanalysis, infrared spectroscopy, 1H NMR, and mass spectroscopy. All the synthesized thiazolidinones were investigated for their antimicrobial and antifungal activities. The results of the biological activities revealed that the compounds 3b, 3d, 3f and 3h exhibited excellent antibacterial activities while 3d and 3h exhibited good antifungal activity.

Solvent Free Microwave Accelerated Synthesis of Heterocyclic Thiazolidin-4-ones as Antimicrobial and Antifungal Agents

Sekhar, Kondapalli Venkata Gowri Chandra,Rao, Vajja Sambasiva,Reddy, Aravalli Satish,Sunandini, Ravada,Satuluri, V S A Kumar Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.5

A simple and efficient method has been developed for conversion of arenecarbaldehyde-3-methylquinoxalin-2-ylhydrazones to 3-(2-methylquinoxalin-3-yl)-2-(substitutedphenyl)thiazolidin-4-ones in good yields using microwave irradiation technique on silica as solid support under solvent free conditions. The synthesized compounds were characterized by elemental microanalysis, infrared spectroscopy, $^1H$ NMR, and mass spectroscopy. All the synthesized thiazolidinones were investigated for their antimicrobial and antifungal activities. The results of the biological activities revealed that the compounds 3b, 3d, 3f and 3h exhibited excellent antibacterial activities while 3d and 3h exhibited good antifungal activity.

New Efficient Synthesis of 3-Carboxylquinolines

Kirankumar, S.,Rambabu, D.,Sekhar, N. Chandra,Prasad, A.S.G.,Rao, M.V. Basaveswara Korean Chemical Society 2012 대한화학회지 Vol.56 No.3

Rapid and efficient synthesis of substituted 3-carboxylquinoline derivatives from 4-chloro-3-formylcoumarin and substituted anilines using 30% $H_2SO_4$ in methanol at room temperature within the duration of 5-30 min., through domino condensation-cyclization-ring opening reaction.

Role of Composition in Enhancing Heat Transfer Behavior of Carbon Nanotube‑Ethylene Glycol Based Nanofluids

N. Bindushree,A. Dhabale,M. S. Dhanush,A. Honakeri,A. Ankit,M. K. Anusha,R. Kumar,H. K. Choudhary,V. Khopkar,K. Chandra Sekhar,B. Sahoo 대한금속·재료학회 2020 ELECTRONIC MATERIALS LETTERS Vol.16 No.6

We report the method of tuning the thermal conductivity through the composition of multiwall carbon nanotube (MWCNT)dispersed ethylene glycol based nanofluids. The structure and properties of the MWCNTs were characterized by scanningelectron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy and thermogravimetric analysis. A parallel plate thermal conductivity (PPTC) set up was fabricated and used for measurement of thermal conductivityof the nanofluids. We have prepared ethylene glycol based nanofluids containing 0.05, 0.1, 0.15, 0.20, 0.25 and 0.35 wt%of MWCNTs. The thermal conductivities of these fluids were measured by keeping them between the two (parallel) plates,referred as the hot and the cold plates, of the sample holder in the PPTC apparatus. The lower plate was water-cooled andthe upper plate was heated. The temperature of the hot plate was varied between 35 and 80 °C. The thermal conductivityof the fluids was calculated using the one-dimensional heat conduction equation. According to our observation, an efficientheat transfer occurs through the nanofluids with an optimum concentration of 0.20 wt% of CNTs. Our work demonstrates the importance of the composition of the nanofluids and their structural defects in heat transfer.