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Gopakumar S.,Sree Renga Raja T. 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.4
Transformer defects are defined by their severity which is the intrinsic property of the transformer. Several approaches for identifying the severity of Power Transformer (PT) problems have previously been proposed; however, most published research does not incorporate Gas Level (GL), Gas Rate (GR), and DGA interpretation into a unified strategy. A novel technique in the form of fuzzy logic (FL) has been offered as a new way to assess faults’ severity by utilizing the combination of GL, GR, and DGA interpretation from the Duval Pentagon Method (DPM) to increase the reliability of the faults’ severity evaluation of PT. Based on the local population, a four-level typical concentration and rate were created. A Deep Learning (DL) oriented Convolutional Neural Network (CNN) based DPM and Harris Hawks Optimization (HHO) method with a high agreement to that same graphical DPM has also been devised to enable the evaluation of hundreds of PT information easy. The proposed method was applied to 448 PTs, and it was then used to assess the severity of problems in PTs using historical DGA data. Due to the integration of GL, GR, and DGA interpretation results in one technique, this novel strategy yields good agreement with earlier methods, but with better sensitivity. Transformer defects are defi ned by their severity which is the intrinsic property of the transformer. Several approaches for identifying the severity of Power Transformer (PT) problems have previously been proposed; however, most published research does not incorporate Gas Level (GL), Gas Rate (GR), and DGA interpretation into a unifi ed strategy. A novel technique in the form of fuzzy logic (FL) has been off ered as a new way to assess faults’ severity by utilizing the combination of GL, GR, and DGA interpretation from the Duval Pentagon Method (DPM) to increase the reliability of the faults’ severity evaluation of PT. Based on the local population, a four-level typical concentration and rate were created. A Deep Learning (DL) oriented Convolutional Neural Network (CNN) based DPM and Harris Hawks Optimization (HHO) method with a high agreement to that same graphical DPM has also been devised to enable the evaluation of hundreds of PT information easy. The proposed method was applied to 448 PTs, and it was then used to assess the severity of problems in PTs using historical DGA data. Due to the integration of GL, GR, and DGA interpretation results in one technique, this novel strategy yields good agreement with earlier methods, but with better sensitivity.
Harishankar Gopakumar,Ishaan Vohra,Srinivas Reddy Puli,Neil R Sharma 대한소화기내시경학회 2024 Clinical Endoscopy Vol.57 No.1
Background/Aims: Scissor-type endoscopic submucosal dissection (ST-ESD) knives can reduce the adverse events associated with ESDs. This study aimed to compare ST-ESD and non-scissor-type (NST)-ESD knives. Methods: We identified ten studies that compared the performance characteristics and safety profiles of ST-ESD and NST-ESD knives. Fixed- and random-effects models were used to calculate the pooled proportions. Heterogeneity was assessed using the I2 test. Results: On comparing ST-ESD knives to NST-ESD knives, the weighted odds of en bloc resection was 1.61 (95% confidence interval [CI], 0.90–2.90; p=0.14), R0 resection was 1.10 (95% CI, 0.71–1.71; p=0.73), delayed bleeding was 0.40 (95% CI, 0.17–0.90; p=0.03), perforation was 0.35 (95% CI, 0.18–0.70; p<0.01) and ESD self-completion by non-experts was 1.89 (95% CI, 1.20–2.95; p<0.01). There was no heterogeneity, with an I2 score of 0% (95% CI, 0%–54.40%). Conclusions: The findings of reduced odds of perforation, a trend toward reduced delayed bleeding, and an improvement in the rates of en bloc and R0 resection with ST-ESD knives compared to NST-ESD knives support the use of ST-ESD knives when non-experts perform ESDs or as an adjunct tool for challenging ESD procedures.
Experimental investigation of dynamic trim control devices in fast speed vessel
Kwang-Cheol Seo,Nithin Gopakumar,Mehmet Atlar 한국항해항만학회 2013 한국항해항만학회지 Vol.37 No.2
The displacement Deep-V catamaran concept was developed in Newcastle University(UNEW) through development of the systematic Deep-V catamaran series. One of the most important Deep-V catamaran launched to date is Newcastle University’s own multi-purpose research vessel, The Princess Royal. The vessel was launched in 2011 and enhanced the Deep-V catamaran concept further with the successful adoption of a novel anti-slamming bulbous bow and tunnel stern for improved efficiency. It was however identified that the vessel has substantial amount of dynamic trim that limited the visibility of the captain. The dynamic trim also increased the wave-making resistance thereby preventing the vessel from attaining its maximum speed in certain sea states. This paper therefore presents the application of devices such as Trim Tabs, Interceptors, Transom Wedges and Integrated Transom Wedges-Tabs to control the dynamic trim and improvement of fuel efficiency of the vessel. All of these energy saving devices were fitted into a model for tests in Newcastle University’s Towing Tank. Model test verification confirmed that the optimum appendage was the interceptors, they produced a 5 % power saving and 1.2 degree trim reduction at 15 knots, and investigations of full scale trials will be scheduled with and without application of device to compare the improvement of performance.
Progress of renewable energy in India
Kar, Sanjay Kumar,Gopakumar, K. Techno-Press 2015 Advances in energy research Vol.3 No.2
Energy holds key to economic growth and prosperity of India. Currently, India has very high-energy import dependence, especially in the case of crude oil (80%) and natural gas (40%). Even coal import has been increasing over the years. Considering India's population growth, emphasis on manufacturing, production, and service industry, energy consumption is bound to increase. More fossil energy consumption means greater dependence on energy import leading to widening trade deficit and current account deficit. Therefore, exploitation of indigenous renewable energy production is necessary. The paper reviews the progress and growth of renewable energy production, distribution, and consumption in India. The paper highlights some of the enablers of renewable energy in India. The authors discuss the opportunities and challenges of increasing share of renewable energy to reduce energy import and address issues of energy security in India. The findings suggest that India is ready for a quantum leap in renewable production by 2022.
Experimental investigation of dynamic trim control devices in fast speed vessel
Seo, Kwang-Cheol,Gopakumar, Nithin,Atlar, Mehmet Korean Institute of Navigation and Port Research 2013 한국항해항만학회지 Vol.37 No.2
The displacement Deep-V catamaran concept was developed in Newcastle University(UNEW) through development of the systematic Deep-V catamaran series. One of the most important Deep-V catamaran launched to date is Newcastle University's own multi-purpose research vessel, The Princess Royal. The vessel was launched in 2011 and enhanced the Deep-V catamaran concept further with the successful adoption of a novel anti-slamming bulbous bow and tunnel stern for improved efficiency. It was however identified that the vessel has substantial amount of dynamic trim that limited the visibility of the captain. The dynamic trim also increased the wave-making resistance thereby preventing the vessel from attaining its maximum speed in certain sea states. This paper therefore presents the application of devices such as Trim Tabs, Interceptors, Transom Wedges and Integrated Transom Wedges-Tabs to control the dynamic trim and improvement of fuel efficiency of the vessel. All of these energy saving devices were fitted into a model for tests in Newcastle University's Towing Tank. Model test verification confirmed that the optimum appendage was the interceptors, they produced a 5% power saving and 1.2 degree trim reduction at 15 knots, and investigations of full scale trials will be scheduled with and without application of device to compare the improvement of performance.
Plasmon Enhanced Terahertz Emission from Single Layer Graphene
Bahk, Young-Mi,Ramakrishnan, Gopakumar,Choi, Jongho,Song, Hyelynn,Choi, Geunchang,Kim, Yong Hyup,Ahn, Kwang Jun,Kim, Dai-Sik,Planken, Paul C. M. American Chemical Society 2014 ACS NANO Vol.8 No.9
<P>We show that surface plasmons, excited with femtosecond laser pulses on continuous or discontinuous gold substrates, strongly enhance the generation and emission of ultrashort, broadband terahertz pulses from single layer graphene. Without surface plasmon excitation, for graphene on glass, ‘<I>nonresonant laser-pulse-induced photon drag currents</I>’ appear to be responsible for the relatively weak emission of both <I>s</I>- and <I>p</I>-polarized terahertz pulses. For graphene on a discontinuous layer of gold, only the emission of the <I>p</I>-polarized terahertz electric field is enhanced, whereas the <I>s</I>-polarized component remains largely unaffected, suggesting the presence of an additional terahertz generation mechanism. We argue that in the latter case, ‘<I>surface-plasmon-enhanced optical rectification</I>’, made possible by the lack of inversion symmetry at the graphene on gold surface, is responsible for the strongly enhanced emission. The enhancement occurs because the electric field of surface plasmons is localized and enhanced where the graphene is located: at the surface of the metal. We believe that our results point the way to small, thin, and more efficient terahertz photonic devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-9/nn5025237/production/images/medium/nn-2014-025237_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn5025237'>ACS Electronic Supporting Info</A></P>