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Central leader and vase form tree models were built using Finite Element Modelling (FEM). Their main characteristics were chosen to be the same. To get comparable results to real values, acceleration versus time curves of the two types of real trees were processed using FFT method to determine their natural frequencies. The natural frequencies measured on real trees and calculated for the models have shown good similarity. The models were virtually exposed to the effect of horizontal forced vibration in the frequency range of 0–20 Hz. Acceleration-frequency curves were calculated and drawn to find the best frequency values for the highest accelerations and also to see their differences in the limb. For the same purpose, the direction of shaking was also changed. It was found that for the central leader limb shape multidirectional shaking would bring uniform detachment, while for the vase form trees, even the unidirectional shakers are appropriate. Real trees were also shaken and their acceleration-frequency curves were compared with the values of the FEMs. The resultant good similarity proves the ability of the models. The acceleration values achieved in the vase form models were much higher than for the central leader type. The acceleration-frequency curve of the shaker unit can be used to find the best frequency for shaking.

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Abstract  

A non-ionic polymer (poly(vinyl alcohol) (PVA)) has been incorporated into the inorganic layers of calcium silicate hydrate (C–S–H) during precipitation of quasicrystalline C–S–H from aqueous solution. C–S–H and a C–S–H-polymer nanocomposite (C–S–HPN) material were synthesized and characterized by X-ray fluorescence (XRF), energy dispersive spectroscopy (EDS), 29Si magic angle spinning nuclear magnetic resonance (29Si MAS NMR) and 13C cross-polarization nuclear magnetic resonance (13C CP NMR) spectroscopy, atomic force microscopy (AFM), thermal conductivity, thermogravimetric analysis (TG) and differential thermal analysis (DTA). Thermal conductivity of PVA, C–S–H and C–S–HPN material was studied in the temperature range 25–50°C. C–S–HPN materials exhibited the highest thermal conductivity at 25 and 50°C. The thermal conductivity increases from 25 to 50°C are 7.03, 17.46 and 14.85% for PVA, C–S–H and C–S–HPN material, respectively. Three significant decomposition temperature ranges were observed on the TG curve of C–S–HPN material.

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Abstract  

Electrochemical measurements and Mössbauer spectroscopy were used to study a rapidly quenched Ni80 57Fe1P19 amorphous alloy solution treated between 920 and 1500 °C. Different short range orderings were shown in amorphous alloys solution treated at different temperatures. This finding can be associated with phase separation occurring in the liquid state. This phase separation can be inherited in slightly relaxed amorphous state.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
J. Kučera
,
J. Novák
,
K. Kranda
,
J. Poncar
,
I. Krausová
,
L. Soukal
,
O. Cunin
, and
M. Lang

Abstract  

We determined 35 major, minor and trace elements in sandstone samples taken from building blocks of 19 Angkor temples and from an old and a new quarry using INAA. We also characterized the sandstone samples with conventional microscopy and electron microprobe analysis. Using cluster analysis, we found no straightforward correlation between the chemical/petrological properties of the sandstones and a presumed period of individual temples construction. The poor correlation may result either from the inherent inhomogeneity of sandstone or just reflect the diversity of quarries that supplied building blocks for the construction of any particular temple.

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Abstract  

The influence of aqueous silica of two different physical forms (dissolved ions and SiO2 colloid) on the dissolution of UO2 nuclear fuel material was investigated at 95 °C temperature in autoclaves. It was tested that SiO2 colloids can contribute to the surface degradation or act as carrier for uranium ions during a near field geochemical dissolution process. In the presence of colloids, well-crystallized secondary phases containing U and Si were formed on the surfaces, the latter attacked by the treatment. This was not the case when dissolved Si was used. SiO2 colloids were partly found in their original form on the surfaces after 1000 hours at 95 °C. A surface charge model suggests that this different effects are due to the development of electrostatic interactions between the UO2 and SiO2 surfaces.

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This paper develops an instrumental analytical approach for detection of fourteen polycyclic aromatic hydrocarbons (PAHs) in edible oil samples using gel permeation chromatography (GPC) and ultra-high performance liquid chromatography (UHPLC) coupled with diode array detector (DAD), and fluorescence detector (FLD). The GPC was used to remove triglycerides from edible oil samples. The extracted samples were then detected using UHPLC—DAD—FLD. In order to obtain good separation and high reproducibility, the UHPLC—DAD—FLD experimental condition was optimized. The PAHs including three groups of isomeric PAHs can be separated completely in 12 min using BEH Shield RP 18 column with a suitable gradient elution program. The mean recoveries were in the range of 73–110% with an acceptable reproducibility (RSD < 10%, n = 3). During real sample analysis, the method can decrease the chance of false positives with both DAD and FLD being used simultaneously. The results indicate that the approach is simple, easy, and acceptably reproducible, thereby showing great potential as a method for detection of fourteen PAHs contained in edible oil samples.

Open access
Journal of Thermal Analysis and Calorimetry
Authors:
M. Donaldson
,
Rebecca Stevens
,
B. E. Lang
,
Juliana Boerio-Goates
,
B. F. Woodfielda
,
R. L. Putnam
, and
Alexandra Navrotsky

Summary As part of a larger study of the physical properties of potential ceramic hosts for nuclear wastes, we report the molar heat capacity of brannerite (UTi2O6) and its cerium analog (CeTi2O6) from 10 to 400 K using an adiabatic calorimeter. At 298.15 K the standard molar heat capacities are (179.46±0.18) J K-1 mol-1 for UTi2O6  and (172.78±0.17) J K-1 mol-1 for CeTi2O6. Entropies were calculated from smooth fits of the experimental data and were found to be (175.56±0.35) J K-1 mol-1 and (171.63±0.34) J K-1 mol-1 for UTi2O6 and CeTi2O6, respectively. Using these entropies and enthalpy of formation data reported in the literature, Gibb’s free energies of formation from the elements and constituent oxides were calculated. Standard free energies of formation from the elements are (-2814.7±5.6) kJ mol-1 for UTi2O6 and (-2786.3±5.6) kJ mol-1 for CeTi2O6. The free energy of formation from the oxides at T=298.15 K are (-5.31±0.01) kJ mol-1 and (15.88±0.03) kJ mol-1 for UTi2O6 and CeTi2O6, respectively.

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