Abstract: Aluminothermic rail welding was from the beginning
a great success because its low price even in 1895 in Germany. This
method is now, widely used all over the world for the railways
construction, maintenance and modernization. Instructions give you
guidelines for preparing papers for conferences or journals.
After 1989, the welding needs of the potentials beneficiaries
(Romanian Railways, Urban Transportation Companies) keep raise
because of the railways maintenance and modernization necessity.
The main materials that determine the Thermit (T) composition
result from manufacturing scraps all over the country. This can help
the environment by consuming these scraps.
The Romanian need for alumino-thermic welding is now by 11300
per year, and in a favourable economical environment, this amount
can reach 30000 units.
This paper tries to show the effect of two types of modifiers
introduced in the T composition on the structure and properties of an
alumino-thermic welding.
Abstract: This work relates the development of an optical fiber
(OF) sensor for the detection and quantification of single walled
carbon nanotubes in aqueous solutions. The developed OF displays a
compact design, it requires less expensive materials and equipment
as well as low volume of sample (0.2 mL). This methodology was
also validated by the comparison of its analytical performance with
that of a standard methodology based on ultraviolet-visible
spectroscopy. The developed OF sensor follows the general SDS
calibration proposed for OF sensors as a more suitable calibration
fitting compared with classical calibrations.
Abstract: The use of un-activated bentonite, and un-activated
bentonite blended with limestone for the treatment of acid mine
drainage (AMD) was investigated. Batch experiments were
conducted in a 5 L PVC reactor. Un-activated bentonite on its own
did not effectively neutralize and remove heavy metals from AMD.
The final pH obtained was below 4 and the metal removal efficiency
was below 50% for all the metals when bentonite solid loadings of 1,
5 and 10% were used. With un-activated bentonite (1%) blended with
1% limestone, the final pH obtained was approximately 7 and metal
removal efficiencies were greater than 60% for most of the metals.
The Langmuir isotherm gave the best fit for the experimental data
giving correlation coefficient (R2) very close to 1. Thus, it was
concluded that un-activated bentonite blended with limestone is
suitable for potential applications in removing heavy metals and
neutralizing AMD.
Abstract: The influence of extrusion parameters on surface
quality and properties of AA6061+x% vol. SiC (x = 0; 2,5; 5; 7,5;10)
composites was discussed in this paper. The averages size of
AA6061 and SiC particles were 10.6 μm and 0.42 μm, respectively.
Two series of composites (I - compacts were preheated at extrusion
temperature through 0.5 h and cooled by water directly after process;
II - compacts were preheated through 3 hours and were not cooled)
were consolidated via powder metallurgy processing and extruded by
KoBo method. High values of density for both series of composites
were achieved. Better surface quality was observed for II series of
composites. Moreover, for these composites lower (compared to I
series) but more uniform strength properties over the cross-section of
the bar were noticed. Microstructure and Young-s modulus
investigations were made.
Abstract: The present article comprises a theoretical study of
structures Performat radical (HCO3) with H2O molecule. We make
use of ab initio quantum chemical methods. Unrestricted Hartee-Fock
(UHF) with the basis set6-311+g(2df,2p) and density functional
theory (B3LYP) with the basis set 6-311+g(2df,2p) and also we done
atoms in molecules (AIM) theory for them. We have found four
stable geometries the PerformatRadical(HCO3) with H2O.
Abstract: Inorganic nanoparticles filled polymer composites
have extended their multiple functionalities to various applications,
including mechanical reinforcement, gas barrier, dimensional
stability, heat distortion temperature, flame-retardant, and thermal
conductivity. Sodium stearate-modified calcium carbonate (CaCO3)
nanoparticles were prepared using surface modification method. The
results showed that sodium stearate attached to the surface of CaCO3
nanoparticles with the chemical bond. The effect of modified CaCO3
nanoparticles on thermal properties of polypropylene (PP) was
studied by means of differential scanning calorimetry (DSC) and
Thermogravimetric analysis (TGA). It was found that CaCO3
significantly affected the crystallization temperature and
crystallization degree of PP. Effect of the modified CaCO3 content on
mechanical properties of PP/CaCO3 nanocomposites was also
studied. The results showed that the modified CaCO3 can effectively
improve the mechanical properties of PP. In comparison with PP, the
impact strength of PP/CaCO3 nanocomposites increased by about
65% and the hardness increased by about 5%.
Abstract: The production of devices in nanoscale with specific
molecular rectifying function is one of the most significant goals in
state-of-art technology. In this work we show by ab initio quantum
mechanics calculations coupled with non-equilibrium Green
function, the design of an organic two-terminal device. These
molecular structures have molecular source and drain with several
bridge length (from five up to 11 double bonds). Our results are
consistent with significant features as a molecular rectifier and can be
raised up as: (a) it can be used as bi-directional symmetrical rectifier;
(b) two devices integrated in one (FET with one operational region,
and Thyristor thiristor); (c) Inherent stability due small intrinsic
capacitance under forward/reverse bias. We utilize a scheme for the
transport mechanism based on previous properties of ¤Ç bonds type
that can be successfully utilized to construct organic nanodevices.
Abstract: Adsorption of methanol and ethanol over mesoporous
siliceous material are studied in the current paper. The pure
mesoporous silica is prepared using tetraethylorthosilicate (TEOS) as
silica source and dodecylamine as template at low pH. The prepared
material was characterized using nitrogen adsorption,nX-ray
diffraction (XRD) and scanning electron microscopy (SEM). The
adsorption kinetics of methanol and ethanol from aqueous solution
were studied over the prepared mesoporous silica material. The
percent removal of alcohol was calculated per unit mass of adsorbent
used. The 1st order model is found to be in agreement with both
adsorbates while the 2nd order model fit the adsorption of methanol
only.
Abstract: Titanium alloys like the modern alloy Ti 6Al 2Sn 4Zr 6Mo (Ti-6246) combine excellent specific mechanical properties and corrosion resistance. On the other hand,due to their material characteristics, machining of these alloys is difficult to perform. The aim of the current study is the analyses of wear mechanisms of coated cemented carbide tools applied in orthogonal cutting experiments of Ti-6246 alloy. Round bars were machined with standard coated tools in dry conditions on a CNC latheusing a wide range of cutting speeds and cutting depths. Tool wear mechanisms were afterwards investigated by means of stereo microscopy, optical microscopy, confocal microscopy and scanning electron microscopy. Wear mechanisms included fracture of the tool tip (total failure) and abrasion. Specific wear features like crater wear, micro cracks and built-up edgeformation appeared depending of the mechanical and thermal conditions generated in the workpiece surface by the cutting action.
Abstract: This paper presents a critical study about the
application of Neural Networks to ion-exchange process. Ionexchange
is a complex non-linear process involving many factors
influencing the ions uptake mechanisms from the pregnant solution.
The following step includes the elution. Published data presents
empirical isotherm equations with definite shortcomings resulting in
unreliable predictions. Although Neural Network simulation
technique encounters a number of disadvantages including its “black
box", and a limited ability to explicitly identify possible causal
relationships, it has the advantage to implicitly handle complex
nonlinear relationships between dependent and independent
variables. In the present paper, the Neural Network model based on
the back-propagation algorithm Levenberg-Marquardt was developed
using a three layer approach with a tangent sigmoid transfer function
(tansig) at hidden layer with 11 neurons and linear transfer function
(purelin) at out layer. The above mentioned approach has been used
to test the effectiveness in simulating ion exchange processes. The
modeling results showed that there is an excellent agreement between
the experimental data and the predicted values of copper ions
removed from aqueous solutions.
Abstract: Copolymerization of ethylene with 1-hexene was
carried out using two ansa-fluorenyl titanium derivative complexes.
The substituent effect on the catalytic activity, monomer reactivity
ratio and polymer property was investigated. It was found that the
presence of t-Bu groups on fluorenyl ring exhibited remarkable
catalytic activity and produced polymer with high molecular weight.
However, these catalysts produce polymer with narrow molecular
weight distribution, indicating the characteristic of single-site
metallocene catalyst. Based on 13C NMR, we can observe that
monomer reactivity ratio was affected by catalyst structure. The rH
values of complex 2 were lower than that of complex 1 which might
be result from the higher steric hindrance leading to a reduction of 1-
hexene insertion step.
Abstract: The main objective of this study was to remove and recover Ni, Cu and Fe from a mixed metal system using sodium hypophosphite as a reducing agent and nickel powder as seeding material. The metal systems studied consisted of Ni-Cu, Ni-Fe and Ni-Cu-Fe solutions. A 5 L batch reactor was used to conduct experiments where 100 mg/l of each respective metal was used. It was found that the metals were reduced to their elemental form with removal efficiencies of over 80%. The removal efficiency decreased in the order Fe>Ni>Cu. The metal powder obtained contained between 97-99% Ni and was almost spherical and porous. Size enlargement by aggregation was the dominant particulate process.
Abstract: A double module hollow fiber supported liquid
membrane (HFSLM) was applied to selectively separate lead and
mercury ions from dilute synthetic produced water. The experiments
were investigated on several variables: types of extractants
(D2EHPA, Cyanex 471, Aliquat 336, and TOA), concentration of the
selected extractant and operating time. The results clearly showed
that the double module HFSLM could selectively separate Pb(II) and
Hg(II) in feed solution at a very low concentration to less than the
regulatory discharge limit of 0.2 and 0.005 mg/L issued by the
Ministry of Industry and the Ministry of Natural Resource
Environment, Thailand. The highest extractions of lead and mercury
ions from synthetic produced water were 96% and 100% using 0.03
M D2EHPA and 0.06 M Aliquat 336 as the extractant for the first
and second modules.
Abstract: Environmental awareness and depletion of the
petroleum resources are among vital factors that motivate a number
of researchers to explore the potential of reusing natural fiber as an
alternative composite material in industries such as packaging,
automotive and building constructions. Natural fibers are available in
abundance, low cost, lightweight polymer composite and most
importance its biodegradability features, which often called “ecofriendly"
materials. However, their applications are still limited due
to several factors like moisture absorption, poor wettability and large
scattering in mechanical properties. Among the main challenges on
natural fibers reinforced matrices composite is their inclination to
entangle and form fibers agglomerates during processing due to
fiber-fiber interaction. This tends to prevent better dispersion of the
fibers into the matrix, resulting in poor interfacial adhesion between
the hydrophobic matrix and the hydrophilic reinforced natural fiber.
Therefore, to overcome this challenge, fiber treatment process is one
common alternative that can be use to modify the fiber surface
topology by chemically, physically or mechanically technique.
Nevertheless, this paper attempt to focus on the effect of
mercerization treatment on mechanical properties enhancement of
natural fiber reinforced composite or so-called bio composite. It
specifically discussed on mercerization parameters, and natural fiber
reinforced composite mechanical properties enhancement.
Abstract: Team distillation assisted by microwave extraction
(SDAM) considered as accelerated technique extraction is a
combination of microwave heating and steam distillation, performed
at atmospheric pressure. SDAM has been compared with the same
technique coupled with the cryogrinding of seeds (SDAM -CG).
Isolation and concentration of volatile compounds are performed by a
single stage for the extraction of essential oil from Cuminum
cyminum seeds. The essential oils extracted by these two methods for
5 min were quantitatively (yield) and qualitatively (aromatic profile)
no similar. These methods yield an essential oil with higher amounts
of more valuable oxygenated compounds, and allow substantial
savings of costs, in terms of time, energy and plant material. SDAM
and SDAM-CG is a green technology and appears as a good
alternative for the extraction of essential oils from aromatic plants.
Abstract: The present work consecutively on synthesis and
characterization of composites, Al/Al alloy A 384.1 as matrix in
which the main ingredient as Al/Al-5% MgO alloy based metal
matrix composite. As practical implications the low cost processing
route for the fabrication of Al alloy A 384.1 and operational
difficulties of presently available manufacturing processes based in
liquid manipulation methods. As all new developments, complete
understanding of the influence of processing variables upon the final
quality of the product. And the composite is applied comprehensively
to the acquaintance for achieving superiority of information
concerning the specific heat measurement of a material through the
aid of thermographs. Products are evaluated concerning relative
particle size and mechanical behavior under tensile strength.
Furthermore, Taguchi technique was employed to examine the
experimental optimum results are achieved, owing to effectiveness of
this approach.
Abstract: The aim of this work was to study the in vitro effects
of δ-lactam 1 and its 4-chlorophenyl derivative 2, on the proliferative
responses of human lymphocytes and Th1 and Th2 cytokine
secretion. The possible protective role of vitamin E on intracellular
stress oxidative induced by these compounds was also investigated.
Peripheral blood lymphocytes were isolated using differential
centrifugation on a density gradient of Histopaque. They were
cultured with mitogen concanavalin A, vitamin E (10 μM) and with
different concentrations of the compounds 1 and 2 (0.1 to 10 μM).
Proliferation (MTT assay), IL-2, INFγ and IL-4 (Elisa kits),
intracellular superoxide anion were determined. 1 and 2 were
immunostimulant and increased cytokine secretion with a shift away
from Th1 response to Th2. These properties were however
accompanied by an increase in intracellular oxidative stress. The
presence of vitamin E exhibited protective effects by reducing δ-
lactam-induced superoxide anion generation in lymphocytes.
Abstract: The results of the two-phase gas-solid jet in pneumatic
powder injection process analysis were presented in the paper. The
researches were conducted on model set-up with high speed camera
jet movement recording. Then the recorded material was analyzed to
estimate main particles movement parameters. The values obtained
from this direct measurement were compared to those calculated with
the use of the well-known formulas for the two-phase flows
(pneumatic conveying). Moreover, they were compared to
experimental results previously achieved by authors. The analysis led
to conclusions which to some extent changed the assumptions used
even by authors, regarding the two-phase jet in pneumatic powder
injection process. Additionally, the visual analysis of the recorded
clips supplied data to make a more complete evaluation of the jet
behavior in the lance outlet than before.
Abstract: Graphene-metal contact resistance limits the performance of graphene-based electrical devices. In this work, we have fabricated both graphene field-effect transistors (GFET) and transfer length measurement (TLM) test devices with titanium contacts. The purpose of this work is to compare the contact resistances that can be numerically extracted from the GFETs and measured from the TLM structures. We also provide a brief review of the work done in the field to solve the contact resistance problem.
Abstract: In this study a neural network (NN) was proposed to
predict the sorption of binary mixture of copper-cobalt ions into
clinoptilolite as ion-exchanger. The configuration of the
backpropagation neural network giving the smallest mean square
error was three-layer NN with tangent sigmoid transfer function at
hidden layer with 10 neurons, linear transfer function at output layer
and Levenberg-Marquardt backpropagation training algorithm.
Experiments have been carried out in the batch reactor to obtain
equilibrium data of the individual sorption and the mixture of coppercobalt
ions. The obtained modeling results have shown that the used
of neural network has better adjusted the equilibrium data of the
binary system when compared with the conventional sorption
isotherm models.