564 research outputs found
Effects of impregnation with boron compounds on the surface adhesion strength of varnishes used woods
The aim of this study was to determine the effects of impregnation with boron compounds on the surface adhesion strength of varnishes used woods. For this purpose, the test specimens prepared from Oriental beech (Fagus orientalis Lipsky) and European oak (Quercus petreae (Matt.) Liebl.) which met the requirements of ASTM D 358 were impregnated according to ASTM D 1413 with boric acid (Ba) and borax (Bx) by vacuum technique. After impregnation, surfaces were coated with cellulosic, synthetic, polyurathane, water-based, acrylic and acid hardening varnishes in accordance with ASTM D 3023 standards. According to ASTM D 4541 standards, the surface adhesion strength of specimens after varnishing process was determined. Considering the interaction of wood type, impregnation material and varnish type, adhesion strength values were found the highest in Oriental beech + boric acid + synthetic varnish (6.240 Mpa) and the lowest values in European oak + borax + cellulosic varnish (2.080 Mpa). Consequently, impregnation of wood material with boron compounds (boric acid: 3.677 Mpa and borax : 3.732 Mpa) showed increasing impact on the surface adhesion strength of cellulosic, synthetic, polyurathane, water-based, acrylic and acid hardening varnishes.Key words: Adhesion strength, impregnation, boric acid, borax, varnishes, finishing, wood
Application of Differential Transform Method for El Nino Southern Oscillation (ENSO) Model with compared Adomian Decomposition and Variational Iteration Methods
We consider two nonlinear El Nino Southern Oscillation (ENSO) model to obtain
approximate solutions with differential transform method for the first time.
Efficiency, accuracy and error rates of solutions are compared with analytic
solution, variational iteration and adomian decomposition solutions on the
given tables and figures.Comment: 12 pages, 10 figure
Microscopic description of Gamow-Teller transitions in middle pf--shell nuclei by a realistic shell model calculation
GT transitions in nuclei are studied in terms of a large-scale
realistic shell-model calculation, by using Towner's microscopic parameters.
values to low-lying final states are reproduced with a reasonable
accuracy. Several gross properties with respect to the GT transitions are
investigated with this set of the wavefunctions and the operator. While the
calculated total GT strengths show no apparent disagreement with the
measured ones, the calculated total GT strengths are somewhat larger than
those obtained from charge-exchange experiments. Concerning the Ikeda sum-rule,
the proportionality of to persists to an excellent
approximation, with a quenching factor of 0.68. For the relative GT
strengths among possible isospin components, the lowest isospin component
gathers greater fraction than expected by the squared CG coefficients of the
isospin coupling. It turns out that these relative strengths are insensitive to
the size of model space. Systematics of the summed values are
discussed for each isospin component.Comment: IOP-LaTeX 23 pages, to appear in J. Phys. G., 5 Postscript figures
available upon reques
Harmonic behavior of metallic glasses up to the metastable melt
In two amorphous alloys ZrTiCuNiBe and ZrAlNiCu coherent neutron scattering has been measured over five decades in energy, including measurements in the metastable melt of a metallic alloy more than 80 K above Tg. In the vibrational spectra a pronounced "boson" peak is found: Even in crystallized samples the density of states exceeds the Debye ω2 model, and in the amorphous state low-frequency vibrations are further enhanced. The peak position shows no dispersion in q, while intensities are strongly correlated with the static structure factor. Over the full energy range the temperature dependence is strictly harmonic. From high-energy resolution measurements we establish lower bounds for the temperatures at which structural α and fast β relaxation become observable
Cultivation of Agaricus bisporus on wheat straw and waste tea leaves based compost formulas using wheat chaff as activator material
This study was designed to determine the pin head formation time and yield values of Agaricus bisporus on some casing materials. Composts were prepared basically from wheat straw and waste tea leaves by using wheat chaff as activator substance. Temperatures of the compost formulas were measured during composting at various depths in order to determine the compostability level. Results showed that in both compost types, maximum temperature values were recorded in the second turning stage. Composting was completed in 21 days for both composts. While the fastest pin head formation (12.50 days) was obtained on wheat straw based compost using peat of Bolu (PB) and peat of Agacbasi (PA) (50+50; in volume); waste tea leaves based compost using peat of Caykara (PC) and forest soil (FS) mixture (50+50; in volume) as casing material gave the fastest pin head formation (13.25 days). In terms of yield, a mixture of peat of Bolu and peat of Agacbasi (PA) (50+50; in volume) gave the highest yieldfor wheat straw based compost, a mixture of peat of Agacbasi and perlite (P) (80+20; involume) had the highest yield for waste tea leaves based compost
Cultivation of Agaricus bisporus on wheat straw and waste tea leaves based composts using poplar leaves as activator material
This study was carried out to determine pin head formation time and mushroom yield of Agaricus bisporus on some casing materials. Composts were prepared basically from wheat straw and waste tealeaves using poplar leaves as activator material. In this study, moreover, in order to follow the evolution of the composting process, daily temperature measurements were taken. According to the results of the study, in both compost types, maximum temperature values were observed in the second turning stage. While in the first and second turning stages, inner-pile temperature of the compost was in atendency of exhibiting steady increase, they are prone to decrease in the following turning stages. In both composts, the period of composting has finished in 19 days. While the fastest pin head formation(13 days) was obtained on wheat straw based compost using peat of Caykara (PC) and forest soil (FS) (50+50; in volume); waste tea leaves based compost using peat of Bolu (PB) and peat of Caykara (PC)mixture (50+50; in volume) as casing material gave the fastest pin head formation (13.30 days). While, a mixture of peat of Agacbasi (PA) and perlite (P) gave the highest yield for wheat straw based compost,peat of Bolu shows the highest yield for waste tea leaves based compost
Composite Polarons in Ferromagnetic Narrow-band Metallic Manganese Oxides
A new mechanism is proposed to explain the colossal magnetoresistance and
related phenomena. Moving electrons accompanied by Jahn-Teller phonon and
spin-wave clouds may form composite polarons in ferromagnetic narrow-band
manganites. The ground-state and finite-temperature properties of such
composite polarons are studied in the present paper. By using a variational
method, it is shown that the energy of the system at zero temperature decreases
with the formation of composite polaron; the energy spectrum and effective mass
of the composite polaron at finite temperature is found to be strongly
renormalized by the temperature and the magnetic field. It is suggested that
the composite polaron contribute significantly to the transport and the
thermodynamic properties in ferromagnetic narrow-band metallic manganese
oxides.Comment: Latex, no figur
Waste hemp hurd as a sustainable precursor for affordable and high-rate hard carbon-based anodes in sodium-ion batteries
The present study reports the promising potential of waste hemp-hurd-derived carbons as anodes in sodium-ion batteries (SIBs). Carbons were produced through an easily scalable process consisting of pyrolysis of raw biomass at 500 °C followed by mild chemical activation of the resulting char through wet impregnation with K2CO3 and subsequent heating of the solid phase (after filtration and drying) up to 700 or 800 °C under nitrogen. The best electrochemical performance was observed for the hard carbon activated at a char-K2CO3 mass ratio of 1:4 and heated up to 800 °C, which exhibited an excellent initial coulombic efficiency (73%) and achieved reversible charge capacities of 267 and 79 mAh g–1 at 0.03 and 1 A g–1, respectively. This material also exhibited an impressive cyclic stability and rate capability, with a capacity retention of 96% after 300 cycles at a current density of 2 A g–1. This more than satisfactory performance could be related to the textural and structural features of the hard carbon, which include moderate interconnected microporosity (with pore sizes below 1 nm), an appropriate concentration of defects in the carbon structure, relatively large interplanar distances, and a certain number of closed pores
A single hollow beam optical trap for cold atoms
We present an optical trap for atoms that we have developed for precision
spectroscopy measurements. Cold atoms are captured in a dark region of space
inside a blue-detuned hollow laser beam formed by an axicon. We analyze the
light potential in a ray optics picture and experimentally demonstrate trapping
of laser-cooled metastable xenon atoms.Comment: 12 pages, 8 figure
Atomic Transport in Dense, Multi-Component Metallic Liquids
Pd43Ni10Cu27P0 has been investigated in its equilibrium liquid state with
incoherent, inelastic neutron scattering. As compared to simple liquids, liquid
PdNiCuP is characterized by a dense packing with a packing fraction above 0.5.
The intermediate scattering function exhibits a fast relaxation process that
precedes structural relaxation. Structural relaxation obeys a time-temperature
superposition that extends over a temperature range of 540K. The mode-coupling
theory of the liquid to glass transition (MCT) gives a consistent description
of the dynamics which governs the mass transport in liquid PdNiCuP alloys. MCT
scaling laws extrapolate to a critical temperature Tc at about 20% below the
liquidus temperature. Diffusivities derived from the mean relaxation times
compare well with Co diffusivities from recent tracer diffusion measurements
and diffsuivities calculated from viscosity via the Stokes-Einstein relation.
In contrast to simple metallic liquids, the atomic transport in dense, liquid
PdNiCuP is characterized by a drastical slowing down of dynamics on cooling, a
q^{-2} dependence of the mean relaxation times at intermediate q and a
vanishing isotope effect as a result of a highly collective transport
mechanism. At temperatures as high as 2Tc diffusion in liquid PdNiCuP is as
fast as in simple liquids at the melting point. However, the difference in the
underlying atomic transport mechanism indicates that the diffusion mechanism in
liquids is not controlled by the value of the diffusivity but rather by that of
the packing fraction
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