Journal Articles
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/19884
Browse
216 results
Search Results
Item State-of-the-art review on automated lumen and adventitial border delineation and its measurements in carotid ultrasound(Elsevier Ireland Ltd, 2018) Kumar, P.K.; Araki, T.; Rajan, J.; Laird, J.R.; Nicolaïdes, A.; Suri, J.S.Background and objective: Accurate, reliable, efficient, and precise measurements of the lumen geometry of the common carotid artery (CCA) are important for (a) managing the progression/regression of atherosclerotic build-up and (b) the risk of stroke. The image-based degree of stenosis in the carotid artery and the plaque burden can be predicted using the automated carotid lumen diameter (LD)/inter-adventitial diameter (IAD) measurements from B-mode ultrasound images. The objective of this review is to present the state-of-the-art methods and systems for the measurement of LD/IAD in CCA based on automated or semi-automated strategies. Further, the performance of these systems is compared based on various metrics for its measurements. Methods: The automated algorithms proposed for the segmentation of carotid lumen are broadly classified into two different categories as: region-based and boundary-based. These techniques are discussed in detail specifying their pros and cons. Further, we discuss the challenges encountered in the segmentation process along with its quantitative assessment. Lastly, we present stenosis quantification and risk stratification strategies. Results: Even though, we have found more boundary-based approaches compared to region-based approaches in the literature, however, the region-based strategy yield more satisfactory performance. Novel risk stratification strategies are presented. On a patient database containing 203 patients, 9 patients are identified as high risk patients, whereas 27 patients are identified as medium risk patients. Conclusions: We have presented different techniques for the lumen segmentation of the common carotid artery from B-mode ultrasound images and measurement of lumen diameter and inter-adventitial diameter. We believe that the issue regarding boundary-based techniques can be compensated by taking regional statistics embedded with boundary-based information. © 2018 Elsevier B.V.Item Challenges in Design, Data Placement, Migration and Power-Performance Trade-offs in DRAM-NVM-based Hybrid Memory Systems(Taylor and Francis Ltd., 2023) Rai, S.; Talawar, B.DRAM-NVM-based hybrid memory opens up a varied range of power-performance-area operational configurations through page migration between the high-performance DRAM and the reliable NVM. The amalgamation of two technologies requires various modifications for the existing monolithic DRAM-based systems. This paper summarizes the current research work in the areas of data placement and page migration in hybrid memories. The challenges and design solutions from a range of NVMs-PCM, STT-RAM, ReRAM is presented. This paper also identifies several research challenges in these areas. © 2023 IETE.Item A comprehensive review on evaporative cooling systems(Elsevier B.V., 2023) Kapilan, N.; Isloor, A.M.; Karinka, S.The evaporative cooling system (ECS) is one of the cheapest and oldest cooling technologies. The conventional single stage ECS is most widely used in domestic application, particularly in hot and dry regions. However, in this system, the temperature of the air cannot be reduced below the wet bulb temperature of the air. The multistage ECS system helps to overcome this problem. The combination of direct and indirect ECS helps to reduce the temperature of the air below its wet bulb temperature. The further reduction in air temperature may be achieved with the help of the cooling coil driven by vapour compression system. The energy consumed by the ECS is lower as compared to vapour compression refrigeration system. The ECS can be driven with the help of solar power. The conventional cooling pad used in ECS can be replaced with locally available natural fibers to reduce initial cost and to reduce dependence on import of cooling pads. The performance of the ECS can be improved with the help of heat pipe. Various techniques are used to enhance ECS's performance. The performance of the vapour compression refrigeration system can be improved with the help of ECS. This paper discusses basics and types of ECS, methods used to increase the performance of ECS, types of natural fiber cooling pad material, process variables affecting ECS, recent technical advancements, challenges and opportunities. © 2023 The AuthorsItem A laboratory investigation on single row suspended porous pipes was conducted in a two-dimensional regular wave flume to study their hydraulic performance. The effects of porosity, water depth, incident wave steepness and relative wave height on transmission and reflection coefficients were studied. It was found that (a) as incident wave steepness increases transmission coefficient Kt decreases and reflection coefficient Kt increases; (b) water depth has insignificant effect on Kt and Kt for porous pipes; (c) as porosity decreases Kt decreases and Kt increases; and (d) the range of variables studied, as the relative wave height increases Kt increases and Kr decreases.(Performance of single row of suspended porous pipe breakwater) Rao, S.; Rao, N.B.S.; Reddy, Y.V.B.2001Item Long haul, repeaterless, coherent optical multichannel communication systems employing hybrid multiplexing schemes wherein Wavelength Division Multiplexing (WDM) and Optical Code Division Multiplexing (OCDM) are combined is analyzed in the presence of performance limiting factors such as Inter Channel Interference (ICI), Stimulated Raman Scattering (SRS) and detector shot noise. Error control coding techniques in the form of rate 1/2 convolutional codes are employed in the system to counter these performance limiting factors. It is seen that the use of error control coding technique can enhance the system performance to such an extent that a Bit Error Rate (BER) performance of less than 10-8 is achievable without crossing the SRS power threshold for as many as 1000 to 1200 channels. Advantages of the hybrid multiplexed system over systems relying solely on WDM or OCDM are also discussed along with the advantages of using error control coding compared to optical amplification in countering the performance degrading factors.(Fachverlag Schiele und Sohn GmbH, Coding to enhance performance of hybrid multiplexed coherent optical communication systems in the presence of ICI and SRS) Kumar, M.S.; Bhat, K.N.H.; Umesh, G.2003Item A multichannel reservation-based channel-access protocol is investigated in this paper. The available system bandwidth is divided into distinct frequency channels. Under the protocol, one channel (the control channel) is used to exchange reservation messages and the remaining channels (the traffic channels) are used for information-bearing traffic. The performance of this scheme is compared to that of a single-channel reservation-based protocol. A simple contention-based slotted-Aloha protocol is also considered. Performance results take into account the effects of multiple-access interference on acquisition and packet errors. Results show that the reservation-based approach is advantageous under conditions of high traffic. In addition, a pacing mechanism that mitigates multiple-access interference and promotes fairness is described, and results are presented that demonstrate its effectiveness.(Baltzer Sci Publ, Unslotted multichannel channel-access protocol for distributed direct-sequence networks) Raghavan, A.R.; Baum, C.W.2004Item Performance of major ports using performance appraisal index(2007) Yaragal, S.C.; Nagaraj, M.K.Infrastructure plays a very important role in the economic progress of the nation. 90% of the international cargo is transported by the ships. In this view, the performance of ports plays an important role. The performance of the port should be assured based on multiple parameters. Such a study helps not only in comparing different ports based on performance, but also helps in corrective measures, identifying weakness areas and strengthening of key parameters. In the present study, a performance appraisal index for major ports is evolved using different parameters, to compare the efficiency of major ports in India. Important parameters are selected from the statistics of major ports in India. Sensitivity analyses are also performed, to evolve strategies for productive decision making for better performance.Item Comparison of performance of biodiesels of mahua oil and gingili oil in dual fuel engine(Serbian Society of Heat Transfer Engineers, 2008) Nadar, K.N.; Reddy, R.P.; Anjuri, E.R.In this work, an experimental work was carried out to compare the performance of biodiesels made from non edible mahua oil and edible gingili oil in dual fuel engine. A single cylinder diesel engine was modified to work in dual fuel mode and liquefied petroleum gas was used as primary fuel. Biodiesel was prepared by transesterification process and mahua oil methyl ester (MOME) and gingili oil methyl ester (GOME) were used as pilot fuels. The viscosity of MOME is slightly higher than GOME. The dualfuel engine runs smoothly with MOME and GOME. The test results show that the performance of the MOME is close to GOME, at the pilot fuel quantity of 0.45 kg/h and at the advanced injection timing of 30 deg bTDC. Also it is observed that the smoke, carbon monoxide and unburnt hydro carbon emissions of GOME lower than the MOME. But the GOME results in slightly higher NOx emissions. From the experimental results it is concluded that the biodiesel made from mahua oil can be used as a substitute for diesel in dual fuel engine.Item Combustion and emission characteristics of a dual fuel engine operated with mahua oil and liquefied petroleum gas(Serbian Society of Heat Transfer Engineers, 2008) Nadar, K.N.; Reddy, R.P.For the present work, a single cylinder diesel engine was modified to work in dual fuel mode. To study the feasibility of using methyl ester of mahua oil as pilot fuel, it was used as pilot fuel and liquefied petroleum gas was used as primary fuel. In dual fuel mode, pilot fuel quantity and injector opening pressure are the few variables, which affect the performance and emission of dual fuel engine. Hence, in the present work pilot fuel quantity and injector opening pressure were varied. From the test results, it was observed that the pilot fuel quantity of 5 mg per cycle and injector opening pressure of 200 bar results in higher brake thermal efficiency. Also the exhaust emissions such as smoke, unburnt hydrocarbon and carbon monoxide are lower than other pressures and pilot fuel quantities. The higher injection pressure and proper pilot fuel quantity might have resulted in better atomization, penetration of methyl ester of mahua oil and better combustion of fuel.Item Thermodynamic simulation of ammonia-water absorption refrigeration system(Serbian Society of Heat Transfer Engineers, 2008) Sathyabhama, A.; Ashok Babu, T.P.The ammonia-water absorption refrigeration system is attracting increasing research interests, since the system can be powered by waste thermal energy, thus reducing demand on electricity supply. The development of this technology demands reliable and effective system simulations. In this work, a thermodynamic simulation of the cycle is carried out to investigate the effects of different operating variables on the performance of the cycle. A computer program in C language is written for the performance analysis of the cycle.