198 research outputs found
Neutron Activation Analysis of Traces of Palladium, Gold, and Iridium in Supernates from the Refining of Precious Metals
In the refining of precious metals it is desirable to be able
to determine amounts \u27of the elements remaining in solution after
various precipitations. Neutron-activation analysis can be used
advantageously in this field, and in the present report the application
of the method for the determination of traces of palladium,
gold and iridium is described. The nuclear reactor BEPO at
Harwell was used as the source of neutrons and each of the three
elements could be determined wHh high sensitivity in a 0.5-ml
aliquot of a sample solution. Results of analyses of microgram and
submicrogram quantities of palladium, gold and iridium in the
solutions under investigation showed good precision
Symmetric and antisymmetric exchange anisotropies in quasi-one-dimensional CuSeO as revealed by ESR
We present an electron spin resonance (ESR) study of single-crystalline spin
chain-system CuSeO in the frequency range between 9 GHz and 450 GHz. In
a wide temperature range above the N\'{e}el temperature K we observe
strong and anisotropic frequency dependence of a resonance linewidth. Although
sizeable interchain interaction ( is the intrachain
interaction) is present in this system, the ESR results agree well with the
Oshikawa-Affleck theory for one-dimensional Heisenberg antiferromagnet.
This theory is used to extract the anisotropies present in CuSeO. We
find that the symmetric anisotropic exchange and the
antisymmetric Dzyaloshinskii-Moriya (DM) interaction are
very similar in size in this system. Staggered-field susceptibility induced by
the presence of the DM interaction is witnessed in the macroscopic
susceptibility anisotropy.Comment: 8 pages, 7 figures, 2 tables, published in Phys. Rev.
Linear compression behaviour of oil palm empty fruit bunches
Received: January 29th, 2021 ; Accepted: April 8th, 2021 ; Published: May 20th, 2021 ; Correspondence: [email protected] study describes the mechanical behaviour of oil palm empty fruit bunches (EFB)
as a promising product for pyrolysis production. The EFB samples mixture of moisture content
6.3 ± 0.3 (% d.b.) were grouped into different fraction sizes of 10, 20, 40 and 100 mm. The initial
pressing height of each fraction size was measured at 60 mm and compressed at a maximum force
of 4,500 N and speed of 10 mm min-1
to obtain the force-deformation dependencies using the
universal compression machine and pressing vessel of diameter 60 mm with a plunger.
Deformation, deformation energy, volume energy and strain were calculated. While deformation
decreased with fraction sizes, deformation energy increased. The deformation energies at fraction
sizes from 10 mm to 100 mm indicated energy savings of approximately 23%. The optimal
fraction size in relation to energy efficiency was observed at 10 mm. The tangent model
accurately described the mechanical behaviour of the EFB samples mixture. The results provide
useful information for the design of optimal technology for processing EFB for energy purposes
3D image analysis of the shapes and dimensions of several tropical fruits
ArticleT
hree dimension virtual models of Avocado
(
Persea americana
)
, Salak
(
Salacca
zalacca
)
, Dragon fruit
(
Hylocereus undatus
)
, Mango
(
Mangifera indica
)
, Coconut
(
Cocos
nucifera
)
using
3D scanner Intel RealSense
were determined. C
alculated models based on
arithmetic and geometric diameter were also determined.
From statistically analysis implies that
virtual models on significance level 0
.05 are significantly different with calculated values based
on arithmetic or geometric diameter
Utilization of image analysis for description of drying characteristics of selected tropical fruits
ArticleThis study is focused on the utilization of image analysis for description of dimensions,
and colours changes of fruits during drying process. Selected tropical fruits such are banana
(Musa acuminata), mango (Magnifera indica) and pineapple (Ananas comosus) originally from
North Sumatera in Indonesia were used in this experiment. Sliced pieces of the fruits were dried
in experimental oven under temperature 90 °C for period of time 180 min and image of fruits
samples were recorded by digital camera with HD resolution continuously throughout drying
process. With aid of image analysis using Image J software and regarding to drying characteristics
the colours and dimensions of the samples were analysed
Theoretical analysis of force, pressure and energy distributions of bulk oil palm kernels along the screwline of a mechanical screw press FL 200
ArticleThe present study is a follow-up of the previously published study on the mathematical
description of loading curves and deformation energy of bulk oil palm kernels under compression
loading, aimed at determining theoretically the amounts of force, pressure and energy along the
screw lamella positions of the screw press FL 200 by applying the tangent curve
mathematical model and the screwline geometry parameters (screw shaft diameter, screw inner
and outer diameters, screw pitch diameter and the screw thickness). The fitting curve value of
the tangent mathematical model was further examined at = 2 and = 3 by identifying the
force, deformation, stress and compression coefficients at varying vessel diameters and initial
pressing heights of the bulk oil palm kernels. Based on the results of the stepwise regression
analysis, the amounts of the theoretical deformation energy in linear pressing as well as the
theoretical force
, pressure and energy of the screw press FL 200 were statistically
significant (P-value significance F) in relation to the predictors (
,
,
and ). The coefficient of determination (R2
) values between 61 and 86 % were observed for
the determined regression models indicating that the responses ,
, and can accurately
be predicted by the corresponding predictors. The normal probability plots of the responses
approximately showed a normal distribution
Mathematical description of loading curves and deformation energy of bulk oil palm kernels
ArticleThe study aimed at describing the experimental and theoretical relationships between
t
he force and deformation curves as well as the deformation energy of bulk oil palm kernels under
compression loading. V
essel diameters of 60, 80 and 100
mm
with initial pressing heights of the
bulk kernels measured at 40, 60 and 80
mm
were examined
by appl
ying
a maximum compressive
force of 200
kN and a speed of 5
mm
min
-
1
. For the theoretical description of the force and
deformation curves, the tangent curve mathematical model was applied using the MathCAD
14
software where the force coefficient of mechani
cal behaviour,
A
(kN), the deformation coefficient
of mechanical behaviour,
B
(mm
-
1
) and the fitting curve function exponent,
n
(
-
)
were
determined
respectively. The determined coefficients in addition to the maximum deformation values
obtained from the co
mpression test were used for the estimation of the theoretical or analytical
deformation energy. The determined
regression models expressing the deformation, numerical
energy and theoretical energy as well as the tangent model coefficients
A
and
B
dependen
t on the
vessel diameter and pressing height were
statistically significant (
P
<
0.05) or (
F
-
ratio
>
F
-
critical)
.
Improving the mechanical pressing of oil extraction for both domestic and industrial
applications still remain a concer
n of researchers and en
gineers
Simulating H/V spectral ratios (HVSR) of ambient vibrations: a comparison among numerical models
The use of H/V spectral ratios (HVSR) of ambient vibrations to constrain the local seismo-stratigraphical configuration relies on numerical forward models able to connect observations with subsoil seismic properties. Several models were proposed to this purpose in the last decades, which are based on different assumptions about the nature of the ambient vibration wavefield. Performances of nine numerical tools implementing these models have been checked by considering 1600 realistic 1-D subsoil configurations mostly relative to A, B and C Eurocode8 soil classes. Resultant HVSR curves predicted by the models are quite similar both in their general shape and in predicting the resonant soil frequencies, possibly because all of them share the same basic representation of the subsoil as a 1-D stack of flat uniform viscoelastic layers. The common sensitivity to transmission/reflection matrices resulting from that representation explains the well-known correspondence of HVSR maxima to 1-D resonance frequency estimates, regardless of the physical assumptions (about source distribution, radiation pattern, dominating seismic phases, etc.) behind the computational model adopted for simulating HVSR curves. On the other hand, the computational models here considered provide quite different amplitudes for HVSR values corresponding to the resonance frequencies. However, since experimental HVSR amplitudes at the same site are affected by an inherent variability (e.g. due to the possible lack of ergodicity of the ambient vibration stochastic wavefield, non-ideal experimental settings, etc.) and uncertainty about the local seismo-stratigraphical profile (attenuation, 2-D/3-D effects, etc.) observations cannot be used for general scoring of the considered computational models on empirical basis. In this situation, the ‘optimal’ numerical tool to be considered for the forward HVSR modelling must be defined case by case
Site-selective quantum correlations revealed by magnetic anisotropy in the tetramer system SeCuO3
We present the investigation of a monoclinic compound SeCuO3 using x-ray
powder diffraction, magnetization, torque and electron-spin-resonance (ESR).
Structurally based analysis suggests that SeCuO3 can be considered as a 3D
network of tetramers. The values of intra-tetramer exchange interactions are
extracted from the temperature dependence of the susceptibility and amount to
~200 K. The inter-tetramer coupling leads to the development of long-range
antiferromagnetic order at TN = 8 K. An unusual temperature dependence of the
effective g-tensors is observed, accompanied with a rotation of macroscopic
magnetic axes. We explain this unique observation as due to site-selective
quantum correlations
- …