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Characterization of (ZnO)_(1-x)(AlN)_x/ZnO junction for optoelectronic applications
N. Gopalakrishnan,L. Balakrishnan,V. Senthamizh Pavai,J. Elanchezhiyan,T. Balasubramanian 한국물리학회 2011 Current Applied Physics Vol.11 No.3
We report the characterization of ZnO homojunction fabricated with undoped (n-ZnO) and AlN codoped ZnO (p-ZnO) films by RF magnetron sputtering. We directly doped (codoped) AlN into ZnO to obtain p-ZnO instead of conventional codoping method. The Current-Voltage characteristics of the fabricated p-n junction show a typical rectification behavior. The junction parameters such as ideality factor (11.85),barrier height (0.782 eV) and series resistance (33 kΩ) have been determined using Cheung’s method. The barrier height (0.805 eV) determined by Norde’s method is also in good agreement with Cheung’s method.
Ahad Jamalizadeh,H. Mahmoodian,A. Pourdarvish,N. Balakrishnan 한국통계학회 2012 Journal of the Korean Statistical Society Vol.41 No.2
In this paper, by considering a (k + n)-dimensional random vector XT , YT T , X ∈ Rk and Y ∈ Rn, having a multivariate elliptical distribution, we derive the exact distribution of AX + LY (n), where A ∈ Rp×k, L ∈ Rp×n, and Y(n) = Y(1), Y(2), . . . , Y(n)T denotes the vector of order statistics from Y. Next, we discuss the distribution of aTX+bY(r), for r = 1, . . . ,n, a =(a1, . . . , ak)T ∈ Rk and b ∈ R. We show that these distributions can be expressed as mixtures of multivariate unified skew-elliptical distributions. Finally, we illustrate an application of the established results to stock fund evaluation.
Microindentation fracture behavior of surface modified alumina ceramic using glass infiltration
Balakrishnan, A.,Panigrahi, B.B.,Chu, M.C.,Kim, T.N.,Cho, S.J. Elsevier 2009 Journal of materials processing technology Vol.209 No.4
This study investigates the effect of a low expansion glass (Mg<SUB>3</SUB>Al<SUB>2</SUB>Si<SUB>6</SUB>O<SUB>18</SUB>) treatment on the surface fracture toughness of sintered alumina. The surface fracture toughness was determined by direct indentation method (Vickers indentations), carried out at different loads ranging from 9.8 to 196N. The crack lengths on the surface at each load were found to be decreased (8-12%) by glass treatment and the corresponding crack resistance values increased by about 17-20%. Both sintered and glass treated specimens showed rising trend in crack resistance values as the indentation load was increased. There was also a significant increase in the Weibull modulus value of crack resistance. Improved properties of glass treated sample were attributed to the formation of a relatively larger process zone surrounding the crack, crack arrest behavior due to the compressive stresses and the crack bridging phenomena. The compressive stresses were generated from the thermo-elastic properties mismatch: (a) between the glass and the ceramic in the glass infiltrated zone, and (b) the glass-ceramic composite layer and the ceramic substrate.
Balakrishnan, A.,Panigrahi, B.B.,Sanosh, K.P.,Chu, Min-Cheol,Kim, T.N.,Cho, Seong-Jai Elsevier 2009 Journal of materials processing technology Vol. No.
<P><B>Abstract</B></P><P>This work attempts to improve the mechanical properties of alumina-10wt% zirconia (3mol% yttria stabilized) composite by infiltrating a glass (magnesium aluminum silicate glass) of lower thermal expansion on the surface at high temperature. The glass improved the strength of the composite at room temperature as well as at higher temperatures. There was a significant improvement in the Weibull modulus after the glass infiltration. Glass-infiltrated samples showed better thermal shock resistance. The magnitude of strength increment was found to be in the order of the surface residual stress generated by thermo-elastic properties mismatch between the composite and the infiltrated glass.</P>
Facile Synthesis of Hydroxyapatite by Hydrothermal and Solvent Combustion Methods
Bramhe, Sachin N,Lee, Hyun Chul,Chu, Min Cheol,Ryu, Jae-Kyung,Balakrishnan, Avinash,Kim, Taik Nam Materials Research Society of Korea 2015 한국재료학회지 Vol.25 No.9
Hydroxyapatite (HA), which is an important calcium phosphate mineral, has been applied in orthopedics, dentistry, and many other fields depending upon its morphology. HA can be synthesized with different morphologies through controlling the synthesis method and several parameters. Here, we synthesize various morphologies of HA using two simple methods: hydrothermal combustion and solution combustion. The phase purity of the synthesized HA is confirmed using X-ray diffractometry. It demonstrates that pure phased hydroxyapatite can be synthesized using both methods. The morphology of the synthesized powder is examined using scanning electron microscopy. The effects of pH and temperature on the final powder are also investigated. At $140^{\circ}C$, using the hydrothermal method, nano-micro HA rods with a hexagonal crystal structure can be synthesized, whereas using solution combustion method at $600^{\circ}C$, a dense cubic morphology can be synthesized, which exhibits monoclinic crystal structures.
Distribution-free prediction intervals for order statistics based on record coverage
Jafar Ahmadia,N. Balakrishnan 한국통계학회 2011 Journal of the Korean Statistical Society Vol.40 No.2
In this paper, based on the largest and smallest observations at the times when a new record of either kind (upper or lower) occurs, we discuss the prediction of future order statistics. The proposed prediction intervals are distribution-free in that the corresponding coverage probabilities are known exactly without any assumption about the parent distribution other than that it being continuous. An exact expression for the prediction coefficient of these intervals is derived. Similarly, prediction intervals for future records based on observed order statistics are also obtained. Finally, two real-life data, one involving the average July temperatures in Neurenburg, Switzerland, and the other involving the amount of annual rainfall at the Los Angeles Civic Center, are used to illustrate the procedures developed here.