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Experiments and numerical analyses for composite RC-EPS slabs
Ł. Skarżyński,J. Tejchman,I. Marzec 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.20 No.6
The paper presents experimental and numerical investigations of prefabricated composite structural building reinforced concrete slabs with the insulating material for a residential building construction. The building slabs were composed of concrete and expanded polystyrene. In experiments, the slabs in the full-scale 1:1 were subjected to vertical concentrated loads and failed along a diagonal shear crack. The experiments were numerically evaluated using the finite element method based on two different constitutive continuum models for concrete. First, an elasto-plastic model with the Drucker-Prager criterion defined in compression and with the Rankine criterion defined in tension was used. Second, a coupled elasto-plastic-damage formulation based on the strain equivalence hypothesis was used. In order to describe strain localization in concrete, both models were enhanced in the softening regime by a characteristic length of micro-structure by means of a non-local theory. Attention was paid to the formation of critical diagonal shear crack which was a failure precursor.
Highly amorphous PbO2 as an electrode in hybrid electrochemical capacitors
K. Kopczynski,Ł. Kolanowski,M. Baraniak,K. Lota,A. Sierczynska,G. Lota 한국물리학회 2017 Current Applied Physics Vol.17 No.1
This paper presents a synthesis and characterizes highly amorphous lead dioxide and its use in hybrid electrochemical capacitor C/PbO2. Highly amorphous lead dioxide with a small amount of b-PbO2 was synthesized by galvanostatic deposition from acetate solution. The hybrid supercapacitor was constructed with PbO2 as the positive electrode whereas activated carbon as the negative electrode. The morphology of materials was examined by scanning electron microscopy and their structure was characterized by means of an X-ray diffraction technique. The electrochemical performance of hybrid electrochemical capacitor with synthesized PbO2 was studied by cyclic voltammetry, galvanostatic charge/ discharge and electrochemical impedance spectroscopy. To indicate that the amorphous form of lead dioxide was predominant, results were compared to highly crystalline b-PbO2. The hybrid electrochemical capacitor with synthesized material exhibits a much greater specific capacitance, higher specific energy and power than the highly crystalline one. The specific capacitance values obtained for the supercapacitor rose more than twice in favour of amorphous PbO2. Also, long cycling did not influence any of the electrochemical properties of this hybrid electrochemical capacitor, which makes it an interesting energy storage device.
Aluminium and titanium alloys surface behaviour under argon and helium ion exposure
Bizyukov, I.,Girka, O.,Kaczmarek, Ł.,Klich, M.,Myroshnyk, M.,Januszewicz, B.,Owczarek, S. Elsevier 2018 Nuclear instruments & methods in physics research. Vol.436 No.-
<P><B>Abstract</B></P> <P>Samples of aluminium alloy 2024 and titanium alloy Ti-6Al-4V are irradiated with 2 keV helium (He) and argon (Ar) ion fluxes using FALCON ion source. Cone-like structures are found to be formed on the surface of two Al(2024) samples due to both irradiation conditions: Ar and He ions exposure reaching total fluence 9.75 × 10<SUP>25</SUP> m<SUP>−2</SUP> and total charge 150 Coulomb per sample. Ar ions exposure of Ti-6Al-4V causes cones formation, while exposure for He ions causes only physical sputtering morphology at the same fluence. Chemical composition of grown structures is obtained from energy dispersive spectroscopy (EDS). Surface roughness and roughness profile are investigated with confocal microscope. Hardness of irradiated surfaces is obtained from results of Vickers hardness test. Residual stresses after irradiation and phase composition are measured by X-ray Diffraction spectroscopy (XRD). The mechanisms of cones growth on alloys surface are surface radiation-stimulated diffusion and ion induced collision cascades evolution.</P>
Electrochemical properties of modified negative electrode for Ni-MH cel
K. Lota,P. Swoboda,I. Acznik,A. Sierczyńska,R. Mańczak,Ł. Kolanowski,G. Lota 한국물리학회 2020 Current Applied Physics Vol.20 No.1
This study discusses the influence of different composition of negative electrode material on the performance of Ni-MH cells. Two major groups of multicomponent alloys were used during the experiments: AB5 and AB2 types. The best capacity was observed for the AB5-type alloy with the highest content of Co in its structure. The presence of Co in the alloy increased the capacity of the negative electrode most likely as a result of hydriding/ dehydriding processes or Faradaic reaction following the dissolution-precipitation mechanism. The influence of different amounts of nickel (0–20 wt%) was determined. The presence of nickel in the electrode materials increased the current density as well as the diffusion of hydrogen into the bulk of alloys. Moreover, the carbon materials have been used as an additive for negative electrode grains in order to increase the conductivity and hydrogen sorption properties.
An improvement of Ozaki’s P-valent conditions
Nunokawa, M.,Cho, N. E.,Kwon, O. S.,Sokó,ł, J. Springer Business + Business Media 2016 Acta mathematica Sinica. English series Vol.32 No.4
<P>The old result due to [Ozaki, S.: On the theory of multivalent functions II. Sci. Rep. Tokyo Bunrika Daigaku Sect. A, 45-87 (1941)], says that if f(z) = z(p) + Sigma(infinity)(n=p+1) a(n)z(n) is analytic in a convex domain D and for some real alpha we have Re{exp(i alpha)f((p))(z)} > 0 in D, then f(z) is at most p-valent in D. In this paper, we consider similar problems in the unit disc D = {z is an element of C : vertical bar z vertical bar < 1}.</P>