304 research outputs found
Understanding Caking Phenomena in Industrial Fertilizers: A Review
One of the most important problems of the fertilizer industry is that fertilizers show caking tendency during transportation and storage. Caking occurs as a result of interaction at the contact points formed between solid fertilizer particles. These interactions, also called contact mechanisms, are activated by a number of properties that fertilizers have and by environmental conditions. Prevention of caking mechanism is a substantial research subject that directly affects the quality and financial value of the final product and ensures its applicability. Fertilizer in good quality can provide ease in agricultural applications, and directly affect plant nutrition and crop productivity. At this point, there are various promoter practices for obtaining the free-flowing property in fertilizers that can be maintained or suggested during or after production, both in industry and in R&D studies. In order to develop new process control points in the industry, it is important to understand the factors that cause caking and the mechanism of physicochemical interactions that progress depending on these factors. In addition, it is essential to improve the storage conditions of the fertilizer, as well as to maintain its quality until end-use. This paper focuses on the caking behavior of fertilizers in detail, giving brief information about the prevention of caking and various types of anticaking agents.
This work is licensed under a Creative Commons Attribution 4.0 International License
Elastic and quasi-elastic and scattering in the Dipole Model
We have in earlier papers presented an extension of Mueller's dipole cascade
model, which includes sub-leading effects from energy conservation and running
coupling as well as colour suppressed saturation effects from pomeron loops via
a ``dipole swing''. The model was applied to describe the total and diffractive
cross sections in and collisions, and also the elastic cross
section in scattering.
In this paper we extend the model to describe the corresponding quasi-elastic
cross sections in , namely the exclusive production of vector mesons
and deeply virtual compton scattering. Also for these reactions we find a good
agrement with measured cross sections. In addition we obtain a reasonable
description of the -dependence of the elastic and quasi-elastic
cross sections
Fluctuations, Saturation, and Diffractive Excitation in High Energy Collisions
Diffractive excitation is usually described by the Good--Walker formalism for
low masses, and by the triple-Regge formalism for high masses. In the
Good--Walker formalism the cross section is determined by the fluctuations in
the interaction. In this paper we show that by taking the fluctuations in the
BFKL ladder into account, it is possible to describe both low and high mass
excitation by the Good--Walker mechanism. In high energy collisions the
fluctuations are strongly suppressed by saturation, which implies that pomeron
exchange does not factorise between DIS and collisions. The Dipole Cascade
Model reproduces the expected triple-Regge form for the bare pomeron, and the
triple-pomeron coupling is estimated.Comment: 20 pages, 12 figure
Effectiveness of seismic retrofitting of a historical masonry structure: Kutahya Kursunlu Mosque, Turkey
"Accepted manuscript"A seismic performance assessment of historical Kutahya Kurunlu Mosque in Turkey is presented before and after it has been retrofitted. Site investigations were carried out to identify structural conditions, in which severe cracks, especially on the dome, were mapped. Regarding damage conditions, the Mosque has undergone several interventions, including retrofitting actions, in order to improve its seismic performance and global structural behavior. Effectiveness of seismic retrofitting of the Mosque was investigated by using the finite element method. Two representative structural models of the Mosque, namely non-retrofitted and retrofitted, were generated as a three-dimensional finite element model using an advanced structural analysis software. Ambient vibration measurements were performed to identify modal properties of the Mosque. Thus, the finite element model was calibrated and improved according to the experimental modal data. Nonlinear pushover and dynamic analyses were conducted to evaluate the seismic performance of the historical Mosque. This paper aims to demonstrate the effectiveness of the adopted retrofitting by comparing the models (before and after retrofitting) and, also, to validate the nonlinear behavior of the model by comparing it with the existing damage on the Mosque
Finite element modeling and operational modal analysis of a historical masonry mosque
Finite Element Modeling (FEM) and Operational Modal Analysis (OMA) is herein presented for the historical masonry Kütahya Kurşunlu Mosque within the framework of its seismic performance assessment. The historical structure is located in Turkey which has a high-level seismic activity. A FEM strategy was adopted to construct a numerical model of the structure considering a simplified three-dimensional geometry and a macro-modeling approach for the masonry. A representative numerical model of the existing structure was calibrated and improved according to the OMA results obtained from ambient vibration measurements, performed in-situ. The ambient vibration measurements were operated by using two triaxial accelerometers, that one of the accelerometers was regulated as a reference station whereas the other accelerometer was relocated to seven different points on the top of the walls. Identification of the experimental modal parameters was achieved by performing two different signal processing methodologies, namely the Enhanced Frequency Domain Decomposition (EFDD) and the Stochastic Subspace Identification - Unweighted Principal Components (SSI-UPC). Results obtained from both methods were compared in terms of the Modal Assurance Criterion (MAC) which considers the mode shapes derived in a specific range of frequency. The SSI-UPC method was employed in achieving the experimental modal response of the structure and the results were compared with the eigenvalue analysis results of the preliminary numerical model. A calibration process was carried out in terms of minimizing the difference between the experimental and numerical modal response by a trial and error approach and an average error of 4.9% was calculated for the modal frequencies of the first four global modes of vibration
Next-to-leading and resummed BFKL evolution with saturation boundary
We investigate the effects of the saturation boundary on small-x evolution at
the next-to-leading order accuracy and beyond. We demonstrate that the
instabilities of the next-to-leading order BFKL evolution are not cured by the
presence of the nonlinear saturation effects, and a resummation of the higher
order corrections is therefore needed for the nonlinear evolution. The
renormalization group improved resummed equation in the presence of the
saturation boundary is investigated, and the corresponding saturation scale is
extracted. A significant reduction of the saturation scale is found, and we
observe that the onset of the saturation corrections is delayed to higher
rapidities. This seems to be related to the characteristic feature of the
resummed splitting function which at moderately small values of x possesses a
minimum.Comment: 34 page
Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes
Two-dimensional materials offer new opportunities for both fundamental
science and technological applications, by exploiting the electron spin. While
graphene is very promising for spin communication due to its extraordinary
electron mobility, the lack of a band gap restricts its prospects for
semiconducting spin devices such as spin diodes and bipolar spin transistors.
The recent emergence of 2D semiconductors could help overcome this basic
challenge. In this letter we report the first important step towards making 2D
semiconductor spin devices. We have fabricated a spin valve based on ultra-thin
(5 nm) semiconducting black phosphorus (bP), and established fundamental spin
properties of this spin channel material which supports all electrical spin
injection, transport, precession and detection up to room temperature (RT).
Inserting a few layers of boron nitride between the ferromagnetic electrodes
and bP alleviates the notorious conductivity mismatch problem and allows
efficient electrical spin injection into an n-type bP. In the non-local spin
valve geometry we measure Hanle spin precession and observe spin relaxation
times as high as 4 ns, with spin relaxation lengths exceeding 6 um. Our
experimental results are in a very good agreement with first-principles
calculations and demonstrate that Elliott-Yafet spin relaxation mechanism is
dominant. We also demonstrate that spin transport in ultra-thin bP depends
strongly on the charge carrier concentration, and can be manipulated by the
electric field effect
Electronic Spin Transport in Dual-Gated Bilayer Graphene
The elimination of extrinsic sources of spin relaxation is key in realizing
the exceptional intrinsic spin transport performance of graphene. Towards this,
we study charge and spin transport in bilayer graphene-based spin valve devices
fabricated in a new device architecture which allows us to make a comparative
study by separately investigating the roles of substrate and polymer residues
on spin relaxation. First, the comparison between spin valves fabricated on
SiO2 and BN substrates suggests that substrate-related charged impurities,
phonons and roughness do not limit the spin transport in current devices. Next,
the observation of a 5-fold enhancement in spin relaxation time in the
encapsulated device highlights the significance of polymer residues on spin
relaxation. We observe a spin relaxation length of ~ 10 um in the encapsulated
bilayer with a charge mobility of 24000 cm2/Vs. The carrier density dependence
of spin relaxation time has two distinct regimes; n<4 x 1012 cm-2, where spin
relaxation time decreases monotonically as carrier concentration increases, and
n>4 x 1012 cm-2, where spin relaxation time exhibits a sudden increase. The
sudden increase in the spin relaxation time with no corresponding signature in
the charge transport suggests the presence of a magnetic resonance close to the
charge neutrality point. We also demonstrate, for the first time, spin
transport across bipolar p-n junctions in our dual-gated device architecture
that fully integrates a sequence of encapsulated regions in its design. At low
temperatures, strong suppression of the spin signal was observed while a
transport gap was induced, which is interpreted as a novel manifestation of
impedance mismatch within the spin channel
Energy dependence of the saturation scale and the charged multiplicity in pp and AA collisions
A natural framework to understand the energy dependence of bulk observables
from lower energy experiments to the LHC is provided by the Color Glass
Condensate, which leads to a "geometrical scaling" in terms of an energy
dependent saturation scale Q_s. The measured charged multiplicity, however,
seems to grow faster (~\sqrt{s}^0.3) in nucleus-nucleus collisions than it does
for protons (~\sqrt{s}^0.2), violating the expectation from geometric scaling.
We argue that this difference between pp and AA collisions can be understood
from the effect of DGLAP evolution on the value of the saturation scale, and is
consistent with gluon saturation observations at HERA.Comment: RevTeX, 8 pages, 4 figures. V2: modified discussion of fragmentation,
published in EPJ
Spin Relaxation in Single Layer Graphene with Tunable Mobility
Graphene is an attractive material for spintronics due to theoretical
predictions of long spin lifetimes arising from low spin-orbit and hyperfine
couplings. In experiments, however, spin lifetimes in single layer graphene
(SLG) measured via Hanle effects are much shorter than expected theoretically.
Thus, the origin of spin relaxation in SLG is a major issue for graphene
spintronics. Despite extensive theoretical and experimental work addressing
this question, there is still little clarity on the microscopic origin of spin
relaxation. By using organic ligand-bound nanoparticles as charge reservoirs to
tune mobility between 2700 and 12000 cm2/Vs, we successfully isolate the effect
of charged impurity scattering on spin relaxation in SLG. Our results
demonstrate that while charged impurities can greatly affect mobility, the spin
lifetimes are not affected by charged impurity scattering.Comment: 13 pages, 5 figure
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