bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal conductivity of CO2 + R1234yf and CO2 + R1234ze(Z) binary gaseous mixtures at low pressure
Authors: Laptev Ya A , Tsvetkov O B , Pyatakov G L , Zainullina E R 
Published: November 2019

Abstract
Chlorofluorocarbons (CFCs) have been phased out under Montreal Protocol of 1987 as a result of ozone depleting potential (ODP). Carbon dioxide owing to the environmental benefits zero ODP, low global warming potential (GWP), no flammability was expected to replace the principal classes of refrigerants. The use of CO2 may require a total redesign of refrigeration units. Hydrofluoroolefins (HFOs) especially R1234yf and R1234ze(Z) has recently proposed as new generation alternative refrigerants. Because of their mildly flammability the mixing of CO2 and HFOs may offer a good alternative to meet the requirement of high cycle efficiency and not dangerous for human beings. A representation for the thermal conductivity of the mixtures of CO2+HFO’s at atmospheric pressure is developed. The thermal conductivity concerning the mixtures was estimated by Sutherland equation type and by Wassiljeva relation modified by Lindsey and Bromley. To apply this procedure the viscosity and thermal conductivity of pure HFC’s substances were established. To obtain these properties the theoretical approach by Mason, Monchick, Filippov and Golubev were used. The data were obtained at temperatures from 250 K to 360 K. The proposed technique was checked by the comparison with the experi-mental thermal conductivity data for the binary mixtures of R134a and R32 and for the triple zeotrop R407C. The agreement is satisfactory.
Analysis of thermochemical data of fatty acids and acetates on their base
Authors: Ovchinnikov V V , Kulakov A A , Maltseva S A 
Published: November 2019

Abstract
The heat of vaporization, combustion, formation, entropy in different phases and the heat of capacity of fatty carbonic acids and their acetates were analyzed and was determined that all functions of these types of compounds depend from the number of valence electrons N from which is excluded the sum of lone electron pairs g as represented in equations Δvap,f,c

H° = i ± f (N – g) and S° (Cp
) = i ± f (N – g). The coefficients f in the first equations is in the range 108 – 109 kJ⋅mol−1 electron−1, that corresponds to the same values f in the equations, which are related to combustion processes. Other coefficient i is different for each type of compounds. The received new seven equations can be used for the calculation of the same thermodynamic functions for other organic and especially bioorganic substances with fatty radicals.
A generalized model of the Kapitza resistance
Authors: Khvesyuk V I 
Published: November 2019

Abstract
This work devoted to a new generalized model of Kapitza conductance. At present, the problem of the development of the theory of contact resistances between solids is particularly relevant due to growth of nanotechnology, where it plays an important and sometimes main role in the heat transport. Presented model takes into all specified properties of acoustic waves. First of all, it is refraction and reflection of acoustic waves that caused simultaneously both longitudinal and transverse waves. Secondly, it is considered the phenomenon of total internal reflection, which makes a significant contribution to the Kapitza resistance. These facts totally change the formulation of the problem, especially, the boundary conditions on the contact surface (interface). Results shows a good agreement with the experimental data, better than in previous works.
Investigation of the diffusion of alloying elements in multicomponent alloy using the photometric analysis of the radiation brightness spectrum
Authors: Ermishkin V A , Mikhaylov D L , Minina N A , Belousov O K , Palyi N A 
Published: November 2019

Abstract
In this paper we consider the results of studying the diffusion of molubdenum and boron in the alloy G 35 (USA), in the chemical composition of which there were 12 elements, with the help of the method of photometric analysis of structural images (PHASI), developed in IMET RAS. PHASI method is based on comparison according to the differential scheme of the spectra of the brightness of the reflection of visible light from the fragments of the surface of the object under study and their images before, during and after heating. The study was performed in situ in a high temperature metallographic microscope. The digital camera allowed in a periodic mode to register the image of the investigated fragment of the sample surface. Analysis of the data obtained by the PHASI method made it possible to establish the time and radial dependencies of the partial derivatives of the concentrations of the first and second order alloying elements that appear in the diffusion equation. A complete analysis of the obtained experimental data made it possible to obtain temperature dependencies of the diffusion coefficients of chromium and boron.
Comparing different force fields by viscosity prediction for branched alkane at 0.1 and 400 MPa
Authors: Kondratyuk N D 
Published: November 2019

Abstract
Shear viscosity is one of the key subjects of molecular modeling studies since this quality is used in the development of lubricants. In this paper, molecular dynamics methods are used to compute viscosity at 298 K and 0.1 MPa, 400 MPa for 2,2,4-trimethylpentane for which experimental data are available. Three different force fields are compared by the ability to predict the shear viscosity coefficient at these two pressures.
Melting properties of sodium halides: molecular dynamics simulation
Authors: Zakiryanov D O , Kobelev M A , Tkachev N K 
Published: November 2019

Abstract
Molecular dynamics was used to calculate the melting phase transition properties in classical ionic systems. A simplified model of pair potential is considered, with only two terms the Born-Mayer repulsion and the Coulomb interaction. Preliminary ab initio calculation of the potential parameters was carried out for sodium halides. Regularities in changes of temperature, enthalpy and entropy of melting have been analyzed by direct heating method. It was found that the calculated values of the enthalpy of melting differ from the experimental data less than 5%.
Phase transitions and critical properties of 1-propanol–n-hexane system
Authors: Bazaev E A , Bazaev A R 
Published: November 2019

Abstract
By using experimental data on p, T, x and p, T, ρ, x - relations of 1-propanol- n-hexane mixtures (0.2, 0.5, 0.8 and 0.9 mol. fraction of n-hexane x) and the method of isochore fracture p = f (T)
ρ,x
at two-phase (liquid-gas), one-phase (liquid, gas), near-critical and supercritical region liquid ↔ gas (ps
, ρs
, Ts
) phase transition parameters are determined. And parameters of critical points (pc
, ρs
, Tc
) are determined by the grapho-analytical method combining with scaling behavior. The dependence of pressure from temperature, density and composition along the phase coexistence curve is described by three parameter polynomial represented by expansion of the compressibility factor Z = p/RTρ into a power series of density ω = ρ/ρk
and temperature

τ
=
T
/

T
k

:
Z
=

p

R
T

ρ
m

=
1
+

∑

i
=
1

m

∑

j
=
0

n

∑

k
=
0

a

a

i
j
k

ω
i

x
k

/

τ
j

, and

p
=
R
T

ρ
m

[

1
+

∑

i
=
1

m

∑

j
=
0

n

∑

k
=
0

a

a

i
j
k

ω
i

x
k

/

τ
j

]

.
The average relative deviation of calculated values of pressure from experimental ones is 1%. The dependence of temperature from density along the liquid ↔ gas phase coexistence curve is described by equations: far from critical points ρ = ρk
(1 ± B
0
τ

β
0
+ B
1
τ

β
1
± B
2
τ
β2
+ …), and in the symmetrical part of equilibrium curve (ρf – ρg)/2ρk
= B
0
τ

β
0
+ B
2
τ

β
2
+ B
4
τ

β
4
+ …, where τ = (T – Tk
)/Tk
and ω = (ρ – ρk
)/ρk
. Average relative error is 1.47%.
Features of heat transfer to hydrocarbon fuel at bubble and film boiling
Authors: Zhukov S A , Yanovskiy L S , Molokanov A A 
Published: November 2019

Abstract
The article presents the results of a study of heat transfer from a heater to a RT grade hydrocarbon fuel. A number of features of heat transfer during boiling of hydrocarbon fuel in bubble and film modes were discovered. The presence of self-oscillations occurring during heat transfer is noted.
The effect of water traces on heat transfer in liquid hydrocarbons under pulse heating mode
Authors: Lukianov K V , Kotov A N , Starostin A A , Skripov P V 
Published: November 2019

Abstract
The peculiarities of heat transfer and spontaneous boiling-up of pure hydrocarbons (n-hexane, n-decane, and n-hexadecane) and those with water traces have been studied under the pulse heating mode. The pulse lengths were from 5 to 25 ms; the pressure was elevated up to the critical one. The phenomenon of strong sensitivity of heat transfer intensity to the presence of water traces has been revealed in the vicinity of spontaneous boiling-up temperature. The hypothesis on the initiating action of water traces on macroscopic phase transitions is assumed.
Thermodynamic fundamentals of extraction of hydrocarbons from oil sludge with the use of supercritical propane-butane mixture
Authors: Khairutdinov V F , Gumerov F M , Zaripov Z I , Farakhov M I 
Published: November 2019

Abstract
Current paper represents the results of the study on phase equilibrium characteristics and thermal conductivity of some thermodynamic systems involved in the extraction of hydrocarbons from oil sludge with the use of propane-butane mixture in both liquid and supercritical (SC) states. Phase equilibria have been studied for such previously unexplored binary systems as: “naphthalene – propane/butane”, “sulfur – propane/butane”, “water – propane/butane”. The studies have been carried out with the traditional version of the static method, as well as by using an optical cell for phase equilibrium studies, designed for high pressures. Thermal conductivity of water-oil emulsion at a pressure of 0.098 MPa in the temperature range of 290 – 360 K has been investigated using the hot-wire method.
Desalination of seawater using an electrode modified with poly(3,4-ethylenedioxythiophene)
Authors: Salgado R , Arteaga G C , Romero M , Martínez J , Ramos A , Burgos R , García C 
Published: November 2019

AbstractThe procedure for obtaining electrodes modified with poly(3,4-ethylenedioxythiophene) has been widely studied for its multiple applications. This study evaluates the potential contribution of electrodes modified with poly(3,4-ethylenedioxythiophene) for desalination of seawater. Potentiostatic electropolymerization of 3,4-ethylenedioxythiophene was conducted on 6 cm2steel electrodes by using a supporting electrolyte consisting of lithium perchlorate in acetonitrile. This modified electrode was used in the extraction of anions and cations from samples of synthetic seawater by means of 20 extraction cycles (optimal cycles) and using a combination of p-type and n-type doping. A total of 140 extractions (number of optimal extractions) were carried out, which led to desalination of synthetic seawater by about 80-90%, as evidenced by the decrease in the conductivity of the solution containing the ions. Therefore, this procedure could become an alternative for seawater desalination.
Graphene deposit in direct current abnormal glow discharge
Authors: Alvarez B , Sarmiento-Santos A , Hernández Y 
Published: November 2019

Abstract
With the advent of nanotechnology, graphene has gained relevance in the last two decades, due to its exceptional mechanical, electrical and thermal properties. This material being one of the thinnest existing, has at the same time great mechanical strength, flexibility, is transparent, in addition to very good conductor of electricity, much better than copper or any other known material. These properties are due to its structure constituted by a flat monoatomic sheet of carbon atoms arranged cyclically with the same structure of benzene. Several layers (>10) of superimposed graphene constitute the well-known graphite structure. To obtain it, among other methods, plasma enhanced chemical vapor deposition has been used, which uses electric discharges in the radiofrequency regime. In this work, the formation of graphene in the plasma of the abnormal glow discharge of direct current is reported. For this purpose, a mixture of 60% Ar, 5% C2H2 and 35% H2 is used as gas atmosphere, at a pressure of 2.0 torr. Electrolytic copper sheets were used as substrate. Temperature of the process was 600 °C and the formation time was 5 s. Deposits characterization was made by infrared spectroscopy and Raman spectroscopy.
Corrosion resistance hydroxyapatite assessment and tricalcium beta phosphate coating, deposited on stainless steel low carbon vacuum melted
Authors: Rojas C , Vera E , Aperador W 
Published: November 2019

Abstract
316 stainless steel low carbon vacuum melted, used for surgical implants, has good corrosion resistance, but it is degraded in the body fluids presence, generating problems for the receiver, therefore it is necessary to apply coatings that improve their biocompatibility. In the current work hydroxyapatite and tricalcium beta phosphate coatings were applied on 316 stainless steel substrates, by the radio frequency magnetron sputtering technique, with a 2 m thickness for possible biomedical applications. The coatings characterization was performed, using scanning electron microscopy, found the Ca/P ratio of 1.639 for hydroxyapatite and 1.515 for phosphate, the friction coefficient was additionally evaluated by pin on disk tribometer, with a lower coefficient of beta tricalcium phosphate in relation to hydroxyapatite. The corrosion evaluation was carried out using the electrochemical polarization technique Tafel, in Ringer lactate, as simulated biological fluid. It was observed that the coatings improve the steel electrochemical behavior and between the two coatings the one that best behaves is the tricalcium beta phosphate, with a corrosion low rate.
Effects of increasing the concentration of Cr in the alloys Nb1-xCrxN
Authors: Ortega López C , Murillo G J F , Espitia Rico M J 
Published: November 2019

Abstract
We investigate the effects of increasing in the concentration of Cr atoms on the structural and electronic properties of Nb1-xCrxN alloys in the concentrations (x = 0.0,0.125,0.25,0.50,0.75 and 1.0) in the NiAs phase. For NbN and CrN in all concentrations, the calculations were carried out using the Quantum ESPRESSO code through the pseudopotential method within the framework of density functional theory. Regarding the structural properties, it was found that the lattice constant of the alloys decreases while the concentration of Cr increases. The bulk modulus of the alloys changes slightly compared to the bulk modulus of the binary NbN compound. Furthermore, the density of states calculations shows that the incorporation of Cr into the NbN matrix gives magnetic properties to the NbN. All the alloys have a metallic-ferromagnetic character.
Mechanical response to tensile stress of a composite material reinforced with sugar cane fibers
Authors: Vega H F , Bohórquez O , Pertuz A , Sánchez Acevedo H G , González-Estrada O A 
Published: November 2019

Abstract
Composite materials reinforced with organic fibers have attracted great interest in the area of mechanical engineering in recent decades due to the wide variety of industrial applications where these materials can be used, and the low impact on the environment, compared with traditional materials. In this work, experimental and numerical tests are carried out to investigate the mechanical response to a tensile load of a composite material with an epoxy matrix, reinforced with sugar cane fibers. Mechanical tests under the ASTM standard for tensile loads were performed. Then, a numerical model to investigate the mechanical response of the composite is done by finite element analysis. Results indicate that this composite material has good performance under axial loading conditions, and can be used for structural applications.
Adsorbent materials obtained from palm waste and its potential use for contaminants removal from aqueous solutions
Authors: Giraldo S , Ramirez A P , Flórez E , Acelas N Y 
Published: November 2019

Abstract
This work reports the production of an adsorbent material obtained by H3PO4 chemical activation of oil palm waste (fiber). The experiments were carried out to explore methylene blue uptake by this adsorbent. The influence of initial dye concentration and adsorbent dosage was investigated. The adsorption equilibrium data of methylene blue onto the adsorbent material were best fitted to the Langmuir model. The maximum adsorption capacity monolayer was of 20.85 mg g−1, which showed to be high compared to other adsorbent materials reported in the literature. Adsorption of methylene blue onto adsorbent material followed pseudo-second order model. The structural and chemical characterization of the adsorbent material was carried out by using various analytical techniques. FTIR showed the formation of oxygenated functional groups on the surface, which are very important for adsorption applications because they act as active sites capable of interacting with dye molecules.
Removal of rhodamine B in wastewater from the textile industry using geopolymeric material
Authors: Pinto L F , Montaño A M , González C P , Barón G C 
Published: November 2019

Abstract
In this work a geopolymeric material was synthesized by alkaline activation of calcined coal gangue at 700 °C using a solution 1:9 of NaOH:Na2SiO3, as a sorbent to remove rhodamine B from aqueous solutions. X-ray diffraction, fourier-transform infrared spectroscopy and scanning electron microscopy were used to characterize the material structurally and morphologically; removal efficiency and rhodamine B sorption capacity were evaluated by using ultraviolet-visible spectrophotometry. Sorption tests were performed to evaluate the effect of the dose of geopolymeric material and the contact time of this material with rhodamine B solution in a range from 0.5 to 30 hours, interval in which the best sorption was observed. Removal efficiencies and sorption capacity to 80.4% and 1.035 mg/g respectively were found, these values show the usefulness of the material for the removal of rhodamine B in aqueous solution, making it an interesting alternative for water decontamination and object of study for future works. Removal efficiency increased by increasing geopolymer dosage and contact time.
Sintering of a metal matrix composite Cu-Ti-TiC assisted by abnormal glow discharge
Authors: Bohórquez C D , Pérez S , Sarmiento A , Mendoza M 
Published: November 2019

Abstract
A metal matrix composite based copper with ceramic reinforcement at 1% w/w of titanium carbide had been studied under variable titanium at 10%, 15% and 20%, in order to evaluate the microstructure and tribological properties (coefficient of friction and wear rate) in the composite material after abnormal glow discharge sintering. The metal matrix composite was manufactured by powder metallurgy process that included: mechanical and ultrasonic mixing in a suspension of 2-propanol, compaction at 200 MPa and sintering by abnormal glow discharge in an atmosphere of 10% nitrogen and 90% argon. As a result, a differentiation in the morphology and properties had been found due to the temperature, this effect was related with diffusion phenomena and energy provide by the plasma process. The final porosity of the samples at 750 °C decreases with titanium increments, reach to 2.6% with 20%. Additionally, in the grain limits of the titanium particles were detected CuTi and CuTi2 phases. On the other hand, at 850 °C the porosity increased with concentration of titanium, a value of 16.8% was shown at 20%. Furthermore, intermetallic phases as Cu3Ti, Cu4Ti, CuTi2 had been identified in the sintered at 850°C. Tribological properties had evidenced that the samples at 750 °C with Ti contents of 20% presented a wear rate value of 7.2x10−8 mm3.N−1.m−1, despite the porous morphology of the compound at 850 °C was estimated in 2.0x10−8 mm3.N−1.m−1 with concentration of 20%.
Carbides formation in weld metal produced by recycling of titanium machining swarf
Authors: Fagundes J G , Ventrella V A , Gallego J , Moreno A M , Jácome J L , Bracarense A Q 
Published: November 2019

Abstract
Application of titanium alloys for orthodontic implants have increase in last years and it has generated a great amount of titanium chips which are disposed as metal scrap. Titanium carbide has high hardness and can be applied as coating reinforcement against wear. Chips of titanium alloys were processed and used in the fabrication of experimental hardfacing consumables for improving the resistance of wear of mechanical components. Coatings were produced in cast steel specimens using the gas tungsten arc welding process. Microstructure was investigated by means of scanning electron microscopy. Microhardness of the coatings was analyzed by a dynamic ultra-micro hardness tester. The microstructure of the welding metal was composed of circular particles of titanium carbide surrounded by a ferritic matrix. The measures made by electron dispersive spectroscopy showed a variation in titanium amount trough the weld, where larger contents of titanium were found, and the matrix. The crystallographic analyses reinforced the formation of titanium carbides embedded in a ferrite matrix into welding metal.
Technological characterization of Colombian clay during the stages of the production process
Authors: García-León R A , Quintero-Quintero W , Espinel-Blanco E 
Published: November 2019

Abstract
Clays are of great importance at the industrial level because they can be used to make masonry products such as blocks, roof tiles, bricks, and tiles, among others. Currently, many companies in the ceramic sector get a lot of waste due to the lack of technical analysis of the raw material to forecast the behavior of the ceramic mixtures and to improve the quality of the final product. In this paper, the physical and chemical characterization of the clay used in one of the companies dedicated to the manufacture of masonry products for construction in Ocaña, Norte de Santander, Colombia was conducted. The development of the investigation was achieved by means of the execution of physical and chemical tests to the sample of selected clay from different points of the production process with which the granulometry, index of plasticity and the mineralogical composition were determined. The results obtained show that the clays currently used by the company are at a low level for masonry products for construction. This is why the addition of other clays is considered, with which an optimum mixture is achieved with which can meet the requirements of the current regulations in force. It is essential to technologically characterize the clays to optimize the mix and thus avoid defective products. It will obviously improve the company’s environmental and economic resources.