Effect of barrier growth temperature on morphological evolution of green InGaN/GaN multi-quantum well heterostructures

Senthil Kumar, M,Park, J Y,Lee, Y S,Chung, S J,Hong, C-H,Suh, E-K Institute of Physics [etc.] 2007 Journal of Physics. D, Applied Physics Vol.40 No.17

<P>Surface morphology of green InGaN/GaN multi-quantum wells (MQWs) on a sapphire substrate with various high temperature grown GaN barriers has been evaluated. Keeping the InGaN well growth temperature constant at 740 °C, a series of MQWs were grown with GaN barrier temperatures varied up to 910 °C. GaN barriers grown below 800 °C lead to the generation of a high density of V-defects and inclusions embedded within V-defects as observed by atomic force microscopy. Scanning electron microscopy and cathodoluminescence (CL) studies revealed that the embedded inclusions are of two kinds: one of them appears as bright spots in CL mapping while the other appears as the surrounding region. Temperature ramping and subsequent interruption for GaN barrier growth suppresses both kinds of inclusion defects and also significantly reduces the V-defect density. An inclusion-free smooth surface is obtained for green emitting InGaN/GaN MQWs with the GaN barrier grown at 910 °C.</P>

Effects of High-energy Ni-ion Irradiation in the InAlGaN/GaN Heterostructure

M.Senthil Kumar,Y.S. Lee,S.J. Chung,C.-H. Hong,E.-K. Suh 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.2

We report the effects of high-energy Ni-ion irradiation on the properties of the InAlGaN/GaN heterostructure grown on c-plane sapphire substrates by using a low-pressure metal organic chemical vapor deposition system. The heterostructure was irradiated with 100 MeV Ni ions for a fluence of 5 × 1012 cm−2 at room temperature. The X-ray rocking curve (0002) full width at half maximum (FWHM) value of the as-grown InAlGaN layer was measured to be 250 arcsec and was not affected by Ni-ion irradiation. However, the PL peak intensity of the heterostructure was completely quenched after ion irradiation, and its electrical properties turned to be highly insulating due to irradiation-induced defects. These results indicate that optical and electrical isolation is feasible in InAlGaN/GaN devices without damaging the crystalline quality by using the Ni-ion irradiation. The thermal annealing process could partly recover the optical and electrical properties of the heterostructure whereas, the junction properties of Schottky contacts fabricated on InAlGaN layer could not be restored. We report the effects of high-energy Ni-ion irradiation on the properties of the InAlGaN/GaN heterostructure grown on c-plane sapphire substrates by using a low-pressure metal organic chemical vapor deposition system. The heterostructure was irradiated with 100 MeV Ni ions for a fluence of 5 × 1012 cm−2 at room temperature. The X-ray rocking curve (0002) full width at half maximum (FWHM) value of the as-grown InAlGaN layer was measured to be 250 arcsec and was not affected by Ni-ion irradiation. However, the PL peak intensity of the heterostructure was completely quenched after ion irradiation, and its electrical properties turned to be highly insulating due to irradiation-induced defects. These results indicate that optical and electrical isolation is feasible in InAlGaN/GaN devices without damaging the crystalline quality by using the Ni-ion irradiation. The thermal annealing process could partly recover the optical and electrical properties of the heterostructure whereas, the junction properties of Schottky contacts fabricated on InAlGaN layer could not be restored.

Correction: A Review of Energy-Efficient Secured Routing Algorithm for IoT-Enabled Smart Agricultural Systems

Kumar C. Senthil,Anand R. Vijay 한국농업기계학회 2024 바이오시스템공학 Vol.49 No.1

Correction to: A Review of Energy-Efficient Secured Routing Algorithm for IoT-Enabled Smart Agricultural Systems

C Senthil kumar,R Vijay Anand 한국농업기계학회 2023 바이오시스템공학 Vol.48 No.4

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A Review of Energy-Efficient Secured Routing Algorithm for IoT-Enabled Smart Agricultural Systems

Kumar C. Senthil,Anand R. Vijay 한국농업기계학회 2023 바이오시스템공학 Vol.48 No.3

Purpose Food security is the most concerning term nowadays with the increase in world population. The increase in population leads to the conversion of farmland into houses, and unpredictable natural disasters bring down the production of food. This might have increased the usage of smart agriculture with the employment of the Internet of Things (IoT) and big data solutions. Methods Traditional agriculture methods are being migrated by requiring smart IoT technologies. Monitoring, maintenance performance, and cost are controlled using modern technologies. In modern agriculture, aerial imagery and satellites play a significant role. The agriculture-related information, such as water level, soil nutrition levels, soil PH, humidity, and temperature, is measured via an accurate agriculture sensor monitoring network in which the computers and phones remotely monitor their crop, and the details are updated to the farmers. This smart agriculture might have increased productivity and operational efficiency to a great extent. The IoT combines most of the traditional technologies and thus increases productivity. Results In this paper, we present the literature review of an IoT-based energy-efficient secured routing protocol applied to the smart agriculture field. We have taken papers from different publishers like IEEE, Springer, Elsevier, and others and reviewed their limitations and advantages. The reviewed papers include protocols such as MAC, cross-layer, LEACH, multihop, and artificial intelligence (AI). Conclusions This study will help guide the researchers to contribute their works to this most trending and needed topic to enhance the productivity and energy efficiency of agricultural products securely for a sustainable future.

Multiobjective optimization process of Ti6Al4V alloy using MWCNTs dispersed cutting fluid in turning operation

Senthil Kumar L,Savadamuthu L,Manivel C 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.4

Turning is one of the precise machining processes, which are widely used at present for many industrial applications. Titaniumalloy Ti6Al4V is widely implemented in the field of aerospace, structural, automotive and biomedical applications. In thisstudy, the most significant factor of Cutting Force, Cutting Temperature and Material Removal Rate is considered the mostresponsible for determining the desirable input factors to the titanium Ti6Al4V alloy in the turning process. Initially, the designof the experiment was conducted for speed, cutting feed, axial depth of cut and the environmental eco-friendly coolant oilconcentration of Multi-Walled Carbon Nanotubes nano-fluid are input parameters of machining process were studied inturning of titanium Ti6Al4V alloy to achieve sustainable production. Desirability Function Analysis was used to predict themathematical model and ANOVA was used to analyze the contribution percentages of the machining parameters. Since theinfluence of the machining parameters of the Cutting Force, Tool Temperature and Material Removal Rate are conflicting innature; the problem was considered a Multi-objective evaluator algorithm-based analysis of the problem. Hence, DesirabilityFunction Analysis was adapted to predict the optimal set of input parameters. The interactive plots reveal that MWCNT’snanofluid improves the result in terms of the maximum rate of removed material with minimum cutting force and cuttingtemperature. Based on multi-objective optimizations of RSM based DFA the optimal results confirm that 1% of MWCNT’sconcentration reduces the cutting temperature and improves the removal of material when MWCNTs are used as cutting fluid.

Experimental investigation of weld characteristics on submerged friction stir welded 6061-T6 aluminum alloy

C. Rathinasuriyan,V. S. Senthil Kumar 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.8

Mechanical properties such as fatigue life, corrosion resistance, brittle fracture, hardness and dimensional stability mainly depend on the residual stresses of the welded sample. The main purpose of the research work is measuring the residual stress at different rotational speeds and water heads and correlates the results with its microhardness and its grain size. In the present study, submerged friction welding was conducted at different rotational speeds of 800, 1000 and 1200 rpm and water heads of 10 and 20 mm, respectively, while the welding speed and axial load were maintained constant. Residual stress was evaluated at the center of the nugget zone on the welded samples using the nondestructive of X-ray diffraction method. Normal friction stir welding (without water head) experiments were carried out later at various rotational speeds of 800, 1000 and 1200 rpm for comparing with the results of the SFS welded samples. The results indicate that the value of d-spacing, lattice parameter and residual stress of submerged friction stir welded sample as higher than that of the normal FS welded sample. The grain size of the SFS welded samples is compared with those of FS welded samples using a scanning electron microscopy. SFSW samples exhibit smaller grain sizes compared to the normal FSW.

Applications of proportional odds ordinal logistic regression models and continuation ratio models in examining the association of physical inactivity with erectile dysfunction among type 2 diabetic patients

( Anil C. Mathew ),( Elbin Siby ),( Amal Tom ),( Senthil Kumar R ) 한국운동영양학회 2021 Physical Activity and Nutrition (Phys Act Nutr) Vol.25 No.1

[Purpose] Many studies have observed a high prevalence of erectile dysfunction among individuals performing physical activity in less leisure-time. However, this relationship in patients with type 2 diabetic patients is not well studied. In exposure outcome studies with ordinal outcome variables, investigators often try to make the outcome variable dichotomous and lose information by collapsing categories. Several statistical models have been developed to make full use of all information in ordinal response data, but they have not been widely used in public health research. In this paper, we discuss the application of two statistical models to determine the association of physical inactivity with erectile dysfunction among patients with type 2 diabetes. [Methods] A total of 204 married men aged 20-60 years with a diagnosis of type 2 diabetes at the outpatient unit of the Department of Endocrinology at PSG hospitals during the months of May and June 2019 were studied. We examined the association between physical inactivity and erectile dysfunction using proportional odds ordinal logistic regression models and continuation ratio models. [Results] The proportional odds model revealed that patients with diabetes who perform leisure time physical activity for over 40 minutes per day have reduced odds of erectile dysfunction (odds ratio=0.38) across the severity categories of erectile dysfunction after adjusting for age and duration of diabetes. [Conclusion] The present study suggests that physical inactivity has a negative impact on erectile function. We observed that the simple logistic regression model had only 75% efficiency compared to the proportional odds model used here; hence, more valid estimates were obtained here.

Glycolate Oxidase Modulates Reactive Oxygen Species-Mediated Signal Transduction during Nonhost Resistance in Nicotiana benthamiana and Arabidopsis

Rojas, C.M.,Senthil-Kumar, M.,Wang, K.,Ryu, C.-M.,Kaundal, A.,Mysore, K.S. AMERICAN SOCIETY OF PLANT BIOLOGISTS 2012 The Plant cell Vol.24 No.1

Improved Thermal Stability of Green InGaN/GaN Multiple-Quantum-Well Light-Emitting Diodes with an AlGaN/GaN Short-Superlattice-Inserted Structure

Y. S. Lee,M. Senthil Kumar,T. V. Cuong,J. Y. Park,J. H. Ryu,S. J. Chung,E.-K. Suh,C.-H. Hong 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1

We report an amelioration of the electrical, thermal and optical performances of green InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) with AlGaN/GaN short- superlattice (SSL)-inserted structure grown using metal-organic chemical vapor deposition. Ac- cording to an atomic force microscopic study, the GaN template with the SSL-inserted structure shows a signicant reduction in pit density compared to the conventionally-grown template. The insertion of the SSL is also found to alleviate the eect of threading dislocations on the degradation of the electrical performance and promotes the stability of the K-factor and a low thermal resis- tance under a long-term acceleration test. A relatively higher optical output power is obtained for SSL-inserted InGaN/GaN green LEDs at high injection currents. We report an amelioration of the electrical, thermal and optical performances of green InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) with AlGaN/GaN short- superlattice (SSL)-inserted structure grown using metal-organic chemical vapor deposition. Ac- cording to an atomic force microscopic study, the GaN template with the SSL-inserted structure shows a signicant reduction in pit density compared to the conventionally-grown template. The insertion of the SSL is also found to alleviate the eect of threading dislocations on the degradation of the electrical performance and promotes the stability of the K-factor and a low thermal resis- tance under a long-term acceleration test. A relatively higher optical output power is obtained for SSL-inserted InGaN/GaN green LEDs at high injection currents.