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Measurement method of complex viscoelastic material properties
Boiko, A.V.,Kulik, V.M.,Seoudi, B.M.,Chun, H.H.,Lee, I. Pergamon Press ; Elsevier Science Ltd 2010 International journal of solids and structures Vol.47 No.3
A measurement technique of viscoelastic properties of polymers is proposed to investigate complex Poisson's ratio as a function of frequency. The forced vibration responses for the samples under normal and shear deformation are measured with varying load masses. To obtain modulus of elasticity and shear modulus, the present method requires only knowledge of the load mass, geometrical characteristics of a sample, as well as both the amplitude ratio and phase lag of the forcing and response oscillations. The measured data were used to obtain the viscoelastic properties of the material based on a 2D numerical deformation model of the sample. The 2D model enabled us to exclude data correction by the empirical form factor used in 1D model. Standard composition (90% PDMS polymer+10% catalyst) of silicone RTV rubber (Silastic<SUP>(</SUP>R) S2) were used for preparing three samples for axial stress deformation and three samples for shear deformation. Comprehensive measurements of modulus of elasticity, shear modulus, loss factor, and both real and imaginary parts of Poisson's ratio were determined for frequencies from 50 to 320Hz in the linear deformation regime (at relative deformations 10<SUP>-6</SUP> to 10<SUP>-4</SUP>) at temperature 25<SUP>o</SUP>C. In order to improve measurement accuracy, an extrapolation of the obtained results to zero load mass was suggested. For this purpose measurements with several masses need to be done. An empirical requirement for the sample height-to-radius ratio to be more than 4 was found for stress measurements. Different combinations of the samples with different sizes for the shear and stress measurements exhibited similar results. The proposed method allows one to measure imaginary part of the Poisson's ratio, which appeared to be about 0.04-0.06 for the material of the present study.
Laminar-Turbulent Transition Research and Control in Near-wall Flow
Boiko A.V.,Chun H.H. The Society of Naval Architects of Korea 2004 Journal of ship and ocean technology Vol.8 No.4
A response of a swept wing boundary layer to a single free-stream stationary axial vortex of a limited spanwise extent is considered as an example of typical problems that one can find in laminar-turbulent transition research and control. The response is dominated by streamwise velocity perturbations that grow quasi-exponentially downstream. It is shown that the formation of the boundary layer disturbance occurs for the most part close to the leading edge. The disturbance represents itself a wave packet consisted of the waves with characteristics specific for cross-flow instability. However, an admixture of growing disturbances whose origin can be attributed to transient effects and to a distributed receptivity mechanism is also identified.
Alpha particle detection with GaN Schottky diodes
Polyakov, A. Y.,Smirnov, N. B.,Govorkov, A. V.,Markov, A. V.,Kozhukhova, E. A.,Gazizov, I. M.,Kolin, N. G.,Merkurisov, D. I.,Boiko, V. M.,Korulin, A. V.,Zalyetin, V. M.,Pearton, S. J.,Lee, I.-H.,Dabir American Institute of Physics 2009 JOURNAL OF APPLIED PHYSICS - Vol.106 No.10
So, J. H.,Kim, H. J.,Alenkov, V. V.,Annenkov, A. N.,Bhang, H.,Boiko, R. S.,Buzanov, O. A.,Chernyak, D. M.,Choi, J. H.,Choi, S.,Danevich, F. A.,Efendiev, K. V.,Gangapshev, A. M.,Gavryluk, Y. M.,Gezhaev IEEE 2012 IEEE transactions on nuclear science Vol.59 No.5
<P>Scintillation properties and radioactive contamination of calcium molybdate scintillating crystals depleted in <SUP>48</SUP>Ca and enriched in <SUP>100</SUP>Mo (<SUP>40</SUP>Ca<SUP>100</SUP>MoO<SUB>4</SUB> ) have been studied to prepare a <SUP>100</SUP>Mo-based neutrinoless double beta decay experiment. The prospects of a neutrinoless double beta decay experiment using <SUP>40</SUP>Ca<SUP>100</SUP>MoO<SUB>4</SUB> crystals are discussed.</P>
Lee, J. Y.,Alenkov, V.,Ali, L.,Beyer, J.,Bibi, R.,Boiko, R. S.,Boonin, K.,Buzanov, O.,Chanthima, N.,Cheoun, M. K.,Chernyak, D. M.,Choi, J.,Choi, S.,Danevich, F. A.,Djamal, M.,Drung, D.,Enss, C.,Fleisc IEEE 2016 IEEE transactions on nuclear science Vol.63 No.2
<P>A calcium molybdate (CaMoO4) crystal scintillator, with molybdenum enriched in Mo-100 and calcium depleted in Ca-48 ((CaMoO4)-Ca-40-Mo-100), was developed by the Advanced Molybdenum based Rare process Experiment (AMoRE) collaboration to search for a neutrinoless double beta (0 nu beta beta) decay of Mo-100. We are planning to use about 10 kg of (CaMoO4)-Ca-40-Mo-100 crystals as cryogenic bolometers for the first phase of the experiment (AMoRE-I) at the Yang Yang underground laboratory (Y2L) in Korea. This experiment calls for an extremely low level of radioactive contamination in detectors, particularly by thorium, uranium, and radium decay chains. We measured scintillation properties and radioactive contamination of CaMoO4 and (CaMoO4)-Ca-40-Mo-100 crystals at the Y2L. We also estimated the acceptable level of internal radioactive background using Monte Carlo simulation for the AMoRE-I.</P>
Viscoelastic properties of silicone rubber with admixture of SiO<sub>2</sub> nanoparticles
Kulik, V.M.,Boiko, A.V.,Bardakhanov, S.P.,Park, H.,Chun, H.H.,Lee, I. Elsevier 2011 Materials science & engineering. properties, micro Vol.528 No.18
<P><B>Highlights</B></P><P>► SiO<SUB>2</SUB> nanoparticles were used as an additive to silicone rubber. ► Dynamic viscoelastic properties of the silicone rubber changed significantly. ► The modulus of elasticity is increased, while the loss factor is decreased. ► The new method of measurements enabled determination of the dynamic Poisson's ratio.</P> <P><B>Abstract</B></P><P>Measurements have been carried out to investigate the change of dynamic viscoelastic properties of silicone rubber with the admixture of small amount SiO<SUB>2</SUB> nanoparticles. A novel measurement method for the dynamic viscoelastic properties including the modulus of elasticity, the loss factor and the Poisson's ratio is employed. It was found that an admixture of rather small amount of SiO2 nanoparticles can substantially affect the viscoelastic properties of the silicone rubber. It is observed that the modulus of elasticity is increased, while the loss factor and the Poisson's ratio are reduced.</P>