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Combustion Synthesis of Advanced Materials : Fundamentals and Applications
Varma, Arvind,Mukasyan, Alexander S. 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.2
The combustion synthesis(CS) of materials is an advanced approach in powder metallurgy. The number of products synthesized by CS has increased rapidly during recent years and currently exceeds 1,000 different compounds. The same features, such as high temperatures and rates, self-sustained manner of microstructure formation in non-equilibrium conditions, that make CS an attractive technology also define difficulties to study the nature and mechanism of this process, which in turn are essential to control the properties of the synthesized materials. In this survey paper, we present results of our recent work both in fundamental studies of mechanisms for rapid reaction wave propagation in heterogeneous media and in using the CS approach to synthesized different types of advanced materials, including bio-alloys and nano-sized powders.
A review on numerical models and controllers for biped locomotion over leveled and uneven terrains
Varma, Navaneeth,Jolly, K.G.,Suresh, K.S. Techno-Press 2018 Advances in robotics research Vol.2 No.2
The evolution of bipedal robots was the foundation stone for development of Humanoid robots. The highly complex and non-linear dynamic of human walking made it very difficult for researchers to simulate the gait patterns under different conditions. Simple controllers were developed initially using basic mechanics like Linear Inverted Pendulum (LIP) model and later on advanced into complex control systems with dynamic stability with the help of high accuracy feedback systems and efficient real-time optimization algorithms. This paper illustrates a number of significant mathematical models and controllers developed so far in the field of bipeds and humanoids. The key facts and ideas are extracted and categorized in order to describe it in a comprehensible structure.
Varma, Chejerla Mohan Kumar,Gouda, Patil Kalmeshwer,Saikumar, Surapaneni,Shenoy, Vinay,Shashidhar, Halagappa Eshwarappa,Neelamraju, Sarla 한국작물학회 2012 Journal of crop science and biotechnology Vol.15 No.3
Wild species of the genus Oryza are a good source of beneficial alleles for enhancing rice yield under normal and adverse conditions. $Bc_2F_3$ population was derived from a cross between Oryza sativa IR58025B and Oryza meridionalis Ng. (2n = 24, AA) a heat tolerant wild species to evaluate 12 yield traits under irrigated and aerobic conditions. Analysis of variance and genetic estimates indicated there is substantial genetic variation among progenies under both conditions. Grain yield had high heritability (61.9%) and genetic advance (36.4%) under irrigated conditions but moderate heritability (49.6%) and genetic advance (13.3%) under aerobic conditions indicating that selection for yield will be effective under both conditions. Panicle number, grain number, spikelet fertility, and test weight showed significant positive correlation with grain yield under both conditions. Families out-performing IR58025B for yield under both conditions were obtained providing evidence that phenotypically inferior O. meridionalis contributed to yield increase. This species can be a novel source of natural genetic variation for the improvement of rice under irrigated as well as under aerobic condition.
Thulasi-Varma, Chebrolu Venkata,Rao, S. Srinivasa,Ikkurthi, Kanaka Durga,Kim, Soo-Kyoung,Kang, Tae-Su,Kim, Hee-Je The Royal Society of Chemistry 2015 Journal of Materials Chemistry C Vol.3 No.39
<▼1><P>This study describes the synthesis of monodispersed PbS nanocrystals by a facile chemical bath deposition and cost-effective approach.</P></▼1><▼2><P>This study describes the synthesis of monodispersed PbS nanocrystals by a facile chemical bath deposition and cost-effective approach. PbS counter electrodes (CEs) were used to grow high-quality thin films containing cube-shaped nanocrystals or nanodendrites. The size and shape of the PbS nanocrystals can be easily controlled by varying the deposition time. Quantum dot-sensitized solar cells (QDSSCs) were made and showed improved performance using the PbS CEs obtained with a deposition time of 2 h. The nanocrystal structured PbS CE in QDSSCs under one-sun illumination (AM 1.5, 100 mW cm<SUP>−2</SUP>) yielded a high short circuit current density (<I>J</I>sc) of 11.20 mA cm<SUP>−2</SUP>, an open circuit voltage (<I>V</I>oc) of 0.560 V, a fill factor (FF) of 0.55, and a power conversion efficiency (<I>η</I>) of 3.48%. These values are much higher than those of the Pt CE (<I>J</I>sc = 79.29 mA cm<SUP>−2</SUP>, <I>V</I>oc = 0.604, FF = 0.28, and <I>η</I> = 1.58%). The concentration of acetic acid plays an important role in deciding the size and shape of the PbS nanocrystals in the nucleation and growth process. The PbS strongly adhered to the FTO substrate due to the acetic acid, which acts as a stabilizer and a strong reagent in this one-step preparation. The performance of the PbS CE was improved by the surface morphology, which enables rapid electron transport and a lower electron recombination rate for the polysulfide electrolyte redox couple. Electrochemical impedance spectroscopy and Tafel-polarization measurements were used to investigate the electrocatalytic activity of the PbS and Pt CEs.</P></▼2>