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Binder burnout and sintering kinetic study of alumina ceramics shaped using methylcellulose
K. Rajeswari,S. Chaitanya,P. Biswas,M. Buchi Suresh,Y.S. Rao,Roy Johnson 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.1
Ceramic components are generally processed by the techniques such as compaction, extrusion, injection molding, casting etc., and the selection of forming method is generally based on the complexity of the shapes. Additives such as binders, plasticizers, surfactants and lubricants, which are generally organic in nature, play a significant role to ensure the flowability of the mass which is critical in shaping of ceramics. Alumina (α-Al2O3) powder was subjected to torque rheometric studies to identify Critical Volume Binder Concentrations (CBVC) corresponding to specific processing regimes. An initial torque value of 3-4Nm for compaction followed by 6-7N-m for extrusion and 2-3N-m for casting regimes were observed. Viscosities of the pre-mixes prepared by the addition of methyl cellulose (C6H7O2 (OH)x(OCH3)y, (where x = 1.0-1.5 and y = 2-1.45) as a binder were also found to exhibit a similar trend in viscosity, corresponding to CBVC torque values and are shaped into green specimens. Green strength of the standard specimens (45 × 4 × 3 mm) was estimated through 3-point bend tests and exhibited a good correlation with the binder content. Binder burnout characteristics were also elucidated by TG/DSC technique and activation energy estimated is 75-110 kJ/mol for the thermal degradation of methylcellulose binder. Activation energy of 883 ± 45 kJ/mol was estimated through kinetic analysis of sintering by the construction of the Master Sintering Curves (MSC).
지속시간이 긴 저주파 발파진동과 주거 구조물에 미치는 영향
Roy M. P.,Sirveiya A. K.,Singh P. K. 대한화약발파공학회 2005 화약발파 Vol.23 No.2
A major concern with blasting at surface mines is generation of ground vibration, air blast, flyrock, dust & fume and their impact on nearby structures and environment. A study was conducted at a coal mine in India which produces 10 million tonne of coal and 27 million cubic meter of overburden per annum. Draglines and shovels with dumpers carry out the removal of overburden. Detonation of 100 tonnes of explosives in a blasting round is a common practice of the mine. These large sized blasts often led to complaints from the nearby inhabitants regarding ground vibrations and their affects on their houses. Eighteen dragline blasts were conducted and their impacts on nearby structures were investigated. Extended seismic arrays were used to identify the vibration characteristics within a few tens meters of the blasts and also as modified by the media at distances over 5 km. 10 to 12 seismographs were deployed in an array to gather the time histories of vibrations. A signature blast was conducted to know the fundamental frequency of the particular transmitting media between the blast face and the structures. The faster decay of high frequency components was observed. It was also observed that at distances of 5km, the persistence of vibrations in the structures was substantially increased by more 10 seconds. The proximity of the frequency of the ground vibration to the structure's fundamental frequencies produced the resonance in the structures. On the basis of the fundamental frequency of the structures, the delay interval was optimized, which resulted into lower amplitude and reduced persistence of vibration in the structures.
Vibrational predissociation of aniline(water)<sub>n</sub><sup>+</sup> (n=1-12)
Roy, M.,Kim, K.K.,Song, J.K.,Choe, J.C.,Park, S.M. North Holland 2016 Chemical physics letters Vol.651 No.-
<P>Vibrational predissociation dynamics of aniline(water)(n)(+) cluster ions formed via resonance two photon ionization followed by the absorption of single infrared photon was investigated. A linear tandem time of flight mass spectrometer designed for this research was tested by the dissociation of aniline* at 266 nm and observed decay constant matched well with the previous result. The rate of dissociation of aniline(water)(n)(+) cluster increased with internal energy, whereas decreased with increasing the size of cluster, manifesting that the intramolecular vibrational energy redistribution precedes VP. The internal energies of the cluster ions were estimated from comparing the experimental and Rice-Ramsperger-Kassel-Marcus calculation results. (C) 2016 Elsevier B.V. All rights reserved.</P>
A Non-Linear Exponential(NLINEX) Loss Function in Bayesian Analysis
Islam, A.F.M.Saiful,Roy, M.K.,Ali, M.Masoom The Korean Data and Information Science Society 2004 한국데이터정보과학회지 Vol.15 No.4
In this paper we have proposed a new loss function, namely, non-linear exponential(NLINEX) loss function, which is quite asymmetric in nature. We obtained the Bayes estimator under exponential(LINEX) and squared error(SE) loss functions. Moreover, a numerical comparison among the Bayes estimators of power function distribution under SE, LINEX, and NLINEX loss function have been made.
Nayak, Akshata,Chandra, Girish,Hwang, Inah,Kim, Kyunglim,Hou, Xiyan,Kim, Hea Ok,Sahu, Pramod K.,Roy, Kuldeep K.,Yoo, Jakyung,Lee, Yoonji,Cui, Minghua,Choi, Sun,Moss, Steven M.,Phan, Khai,Gao, Zhan-Guo American Chemical Society 2014 Journal of medicinal chemistry Vol.57 No.4
<P/><P>Truncated <I>N</I><SUP>6</SUP>-substituted-(<I>N</I>)-methanocarba-adenosine derivatives with 2-hexynyl substitution were synthesized to examine parallels with corresponding 4′-thioadenosines. Hydrophobic N<SUP>6</SUP> and/or C2 substituents were tolerated in A<SUB>3</SUB>AR binding, but only an unsubstituted 6-amino group with a C2-hexynyl group promoted high hA<SUB>2A</SUB>AR affinity. A small hydrophobic alkyl (<B>4b</B> and <B>4c</B>) or <I>N</I><SUP>6</SUP>-cycloalkyl group (<B>4d</B>) showed excellent binding affinity at the hA<SUB>3</SUB>AR and was better than an unsubstituted free amino group (<B>4a</B>). A<SUB>3</SUB>AR affinities of 3-halobenzylamine derivatives <B>4f</B>–<B>4i</B> did not differ significantly, with <I>K</I><SUB>i</SUB> values of 7.8–16.0 nM. <I>N</I><SUP>6</SUP>-Methyl derivative <B>4b</B> (<I>K</I><SUB>i</SUB> = 4.9 nM) was a highly selective, low efficacy partial A<SUB>3</SUB>AR agonist. All compounds were screened for renoprotective effects in human TGF-β1-stimulated mProx tubular cells, a kidney fibrosis model. Most compounds strongly inhibited TGF-β1-induced collagen I upregulation, and their A<SUB>3</SUB>AR binding affinities were proportional to antifibrotic effects; <B>4b</B> was most potent (IC<SUB>50</SUB> = 0.83 μM), indicating its potential as a good therapeutic candidate for treating renal fibrosis.</P>
Roy, G.M.,Kumar, S.,Kanuajia, B.K.,song, H. Mackintosh Publications] 2017 Microelectronics journal Vol.67 No.-
<P>This work concerns on CMOS based trans-impedance amplifier (TIA) where enhancing the bandwidth by using optimized on-chip T-network for biomedical diagnosis applications. The proposed TIA consists of inductive peaking components as an input stage, distributed amplifier with feedback loop as middle stage while output as T-network. The proposed TIA with T-network achieves much wide band operation within range of 4.8-19.6 GHz. As compared to conventional TIA, additional trans-impedance bandwidth of 1.4 GHz in the lower band while 9.1 GHz in higher band are able to achieve for the proposed design. The proposed architectures are implemented into ADS platform using commercial 65 nm TSMC process. With this proposed technique, TIA also succeeds lower bit error rate (BER) for high speed data transmission in optical receiver i.e. beneficial towards the biomedical diagnosis. Chip fabrication of proposed TIA consuming less power of 10.8 mW from the power supply of 1.6 V. Measured and simulated data exhibits a wide bandwidth operation with trans-impedance gain of 55dBOand made good correlation with each other. Moreover, experimental BER demonstrates less than 10-11 by providing pseudorandom bit sequence at 6-11 Gb/s within desired band of operation in TIA. The optimized on-chip T-network occupies only 10% of the whole chip area of 0.4 mm(2).</P>
EFFECT OF Mn DOPING ON MICROSTRUCTURE AND OPTICAL PROPERTIES OF NANOCRYSTALLINE ZnO
M. KARMAKAR,O. MONDAL,B. ROY,P. K. PAUL,M. PAL 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2013 NANO Vol.8 No.6
Mn-doped ZnO has emerged as the most studied system for prototype applications in spintronics devices because of its interesting magnetic properties. In this report, nanocrystalline ZnO doped with various concentration of Mn have been synthesized from different precursors using modified ceramic route. Samples are characterized by using X-ray diffractometer (XRD), high resolution transmission electron microscopy (HRTEM) and UV-Vis spectrophotometer. XRD and HRTEM studies confirm the growth of single phase, well crystallized Mn-doped ZnO nanoparticles. Particle size estimated from Rietveld analysis as well as TEM images show a decreasing tendency with the increase in Mn concentration. We observe both band bowing and red shift in optical bandgap by varying the concentration of Mn and precursors. This study demonstrates that Mn concentration is not the only factor but precursors have a definite role on the variation of optical bandgap.
Kim, K.B.,Das, J.,Lö,ser, W.,Lee, M.H.,Kim, D.H.,Roy, S.K.,Eckert, J. Elsevier 2007 Materials science & engineering. properties, micro Vol.449 No.-
<P><B>Abstract</B></P><P>Zr<SUB>73.5</SUB>Nb<SUB>9</SUB>Cu<SUB>7</SUB>Ni<SUB>1</SUB>Al<SUB>9.5</SUB> (numbers indicate at.%) nanostructure-dendrite composites were fabricated using three different casting techniques: suction casting, centrifugal casting and arc-melting. The microstructure of the suction casting sample consists of micrometer-scale dendrites in a nanostructured matrix. However, some areas in the matrix contain nano-scale crystals together with an amorphous phase revealing an inhomogeneity of the specimen. On the contrary, the microstructures of the centrifugally-cast and the arc-melted samples are overall homogeneous, consisting of micrometer-scale dendrites that are homogeneously distributed in a nanostructured matrix. The dendrites correspond to a body centered cubic (bcc) β-Zr phase, whereas the nanostructured matrix consists of body centered tetragonal (bct) Zr<SUB>2</SUB>Cu-type and hexagonal close-packed (hcp) MgZn<SUB>2</SUB>-type phases. The comparison of the microstructures of these two alloys reveals that the formation of nano-scale twins and a disordered ω-phase in the β-Zr dendrites only happens in the centrifugally-cast sample. The differences in the phases and the microstructures between the differently prepared samples significantly influence the corresponding mechanical properties of the specimens.</P>