Academic Journals

Electron diffraction analysis of quenched Fe–C martensite

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

Martensite has a body-centered tetragonal (bct) structure in high carbon steels. However, body-centered cubic (bcc) {112} 〈111〉-type twins instead of bct twins always be observed as the substructure of martensite in high carbon steels. In this paper, martensitic substructure in a quenched high carbon Fe-1.4C (wt%) alloy has been investigated in detail using selected area electron diffraction (SAED) technique in a conventional transmission electron microscopy. The reciprocal lattice of martensite has been built based on the experimental SAED patterns. Two sets of diffraction spots (one face-centered cubic lattice and one hexagonal lattice) in the built reciprocal lattice suggest that two crystalline phases with bcc (or α-Fe) and hexagonal (ω-Fe) structure actually coexist in the twinned martensite. The two-phase diffraction spot patterns from the reciprocal lattice can match perfectly with the experimental results. The fact that the {0001}ω diffraction spot at the 1/3{222}α position and the {0002}ω at 2/3{222}α can support the ω-Fe existence in the twinned martensite.

Categories: Academic Journals

Solidification loops in the phase diagram of nanoscale alloy particles: from a specific example towards a general vision

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

Interface contributions as well as size confinement effects need to be taken into account into the description of phase equilibria and phase transformations in nanoscale systems. Here, a modified Gibbsian thermodynamic approach has been suggested to describe the solidification of a nano-sized liquid alloy droplet and the equilibrium states in the two-phase region of the phase diagram. Cu–Ni has been chosen as a model system due to the availability of thermodynamic data. This description shows for the first time the occurrence of solidification loops at the size-dependent temperature–composition phase diagram for the isolated Cu–Ni nano-droplet, showing two-phase equilibrium states for droplet radii of 25 and 40 nm, i.e. well within the size domain of nanoparticles that are, for example, used for applications in additive manufacturing. Furthermore, the current results show quantitatively that these equilibrium loops that are specific for the nano-sized systems do not coincide with the solubility curve. It leads to the new “solidification loop” concept concerning the phase diagram introduced in the paper. The isolated liquid Cu–Ni nanoscale droplet can actually crystallize along different trajectories, whereas the dominant transition type is comparable to homogeneous nucleation that proceeds from the inner part of the droplet towards the surface: the newly formed phase after initial nucleation is a Ni-rich crystal with a Cu-rich liquid shell. The decrease in the nanoparticle size causes the decrease in the solidification temperature and the temperature width of the phase transition, the increase in the solubility limit and the concentration width of the solidification loop as well as a change in the shape and slope of the equilibrium curves of the two-phase region of the phase diagram. For larger droplets, the size-dependent phase diagram approaches the well-known bulk phase diagram.

Categories: Academic Journals

Transformation from non-isothermal to isothermal tempering of steel based on isoconversional method

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

The microstructural evolution of martensitic AISI 52100 steel during non-isothermal tempering under a series of constant heating rates was investigated through differential scanning calorimetry and dilatometry. The kinetic parameters for different tempering stages during heating were studied using the differential isoconversional method and also the Kissinger method as comparison. It is found that the activation energies obtained by both methods coincided with the literature. The activation energies obtained by the Kissinger method were constant, while those obtained by the isoconversional method varied with the fraction converted and presented respective variation trends. The kinetics of phase transformation during isothermal tempering was then simulated based on the Johnson–Mehl–Avrami–Kolmogorov (JMAK) theory. The calculated isothermal kinetics coincided with the experimental data from the literature. The Vickers hardness of samples with the same fraction converted under non-isothermal tempering at 0.33 K s−1 and isothermal tempering at both 373 and 473 K was measured to verify the applicability of non-isothermal to isothermal transformation. Increasing the isothermal tempering temperature accelerated the reduction of hardness when compared with non-isothermal tempering. Mechanisms for the differences in hardness between these two types of tempering were discussed.

Categories: Academic Journals

Nitrogen-doped porous carbon using ZnCl 2 as activating agent for high-performance supercapacitor electrode materials

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

A facile method for synthesising porous carbon materials with high nitrogen content is employed in this study using 1H-Benzotriazole (BTA) as carbon precursor and ZnCl2 as active agent at 600–800 °C for 2 h under N2 atmosphere. Pure BTA completely degrades even at low temperature (270 °C) under inert gas, but ZnCl2 can convert the more organics to carbon because of its dehydration. The obtained NC-2-700 sample possesses a high specific surface area (1228 m2·g−1) and a nitrogen content up to 10.27 wt%. Moreover, the N-doped carbon exhibits a good electrochemical property (with a specific capacitance of 332 F·g−1 at the current density of 0.5 A·g−1), as well as an outstanding cycle stability (96.5% of the initial specific capacitance is maintained after 5000 cycles at 1 A·g−1). In addition, this obtained symmetric ultra-capacitor prepared from the NC-2-700 sample exhibits a highest energy density of 12.94 Wh·kg−1 with a power density of 375 W·kg−1 at a current density of 1 A·g−1. And even this NC-2-700//NC-2-700 supercapacitor gives 5.43 Wh·kg−1 with a power density of 3750 W·kg−1 at a high current density of 10 A·g−1. Consequently, these experimental results confirm that the porous carbon materials with high nitrogen content can be a prospective electrode material for supercapacitors.

Categories: Academic Journals

Fabrication of lead-free piezoelectric (Bi 0.5 Na 0.5 )TiO 3 –BaTiO 3 ceramics using electrophoretic deposition

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

Electrophoretic deposition (EPD) process has certain advantages such as it can be applied for a mass production and also can be combined with magnetic crystal alignment technique. In this work, we prepared lead-free 85(Bi0.5Na0.5)TiO3–15BaTiO3 (85BNT–15BT) piezoelectric ceramics by conventional uniaxial pressing and EPD process. Various conditions were optimized such as suspension media, applied electrical field, and deposition time in order to yield dense green ceramics of 85BNT–15BT composition using EPD process. 85BNT–15BT ceramics prepared using EPD process revealed the Curie temperature of about 250 °C, coercive field of about 30 kV/cm, and piezoelectric constant (d 33) of 75 pC/N. The EPD-processed samples exhibited structural and electrical properties similar to that of the conventionally processed one suggesting the successful fabrication of 85BNT–15BT piezoelectric ceramics by EPD method without composition deviation. This study lays a foundation on the fabrication of Bi-based lead-free piezoelectric ceramics by an alternative route other than the conventionally practiced solid-state reaction method maintaining the similar chemical composition, moreover, leaving a large space to explore more in the future.

Categories: Academic Journals

Photoluminescence properties of N-doped carbon dots prepared in different solvents and applications in pH sensing

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

Two kinds of nitrogen-doped carbon dots (N-CDs) were synthesized by choosing citric acid, l-serine and monoethanolamine as the precursors, respectively, in organic solvent N,N-dimethylformamide (DMF) and deionized water. The FTIR, UV–Vis, HRTEM and XRD were used to characterize the surface molecular structures of these two N-CDs. It was found that different reaction systems made the as-prepared N-CDs possess varied surface states and thus exhibit distinctive photoluminescence features. For the N-CDs prepared in DMF, its fluorescent property showed pH dependent and color-switchable in visible light and could be reversibly changing over in both alkaline and acidic environments due to the protonation and de-protonation of the carboxyl groups on the surface of the N-CDs. Also, its fluorescence intensity exhibited a linear fashion over the pH range from 1.5 to 7.5, indicating its potential applications in pH quantitative detection under acidic condition.

Categories: Academic Journals

Electron diffraction analysis of quenched Fe–C martensite

The Behavior Analyst - Thu, 02/01/2018 - 00:00
Abstract

Martensite has a body-centered tetragonal (bct) structure in high carbon steels. However, body-centered cubic (bcc) {112} 〈111〉-type twins instead of bct twins always be observed as the substructure of martensite in high carbon steels. In this paper, martensitic substructure in a quenched high carbon Fe-1.4C (wt%) alloy has been investigated in detail using selected area electron diffraction (SAED) technique in a conventional transmission electron microscopy. The reciprocal lattice of martensite has been built based on the experimental SAED patterns. Two sets of diffraction spots (one face-centered cubic lattice and one hexagonal lattice) in the built reciprocal lattice suggest that two crystalline phases with bcc (or α-Fe) and hexagonal (ω-Fe) structure actually coexist in the twinned martensite. The two-phase diffraction spot patterns from the reciprocal lattice can match perfectly with the experimental results. The fact that the {0001}ω diffraction spot at the 1/3{222}α position and the {0002}ω at 2/3{222}α can support the ω-Fe existence in the twinned martensite.

Categories: Academic Journals

Solidification loops in the phase diagram of nanoscale alloy particles: from a specific example towards a general vision

The Behavior Analyst - Thu, 02/01/2018 - 00:00
Abstract

Interface contributions as well as size confinement effects need to be taken into account into the description of phase equilibria and phase transformations in nanoscale systems. Here, a modified Gibbsian thermodynamic approach has been suggested to describe the solidification of a nano-sized liquid alloy droplet and the equilibrium states in the two-phase region of the phase diagram. Cu–Ni has been chosen as a model system due to the availability of thermodynamic data. This description shows for the first time the occurrence of solidification loops at the size-dependent temperature–composition phase diagram for the isolated Cu–Ni nano-droplet, showing two-phase equilibrium states for droplet radii of 25 and 40 nm, i.e. well within the size domain of nanoparticles that are, for example, used for applications in additive manufacturing. Furthermore, the current results show quantitatively that these equilibrium loops that are specific for the nano-sized systems do not coincide with the solubility curve. It leads to the new “solidification loop” concept concerning the phase diagram introduced in the paper. The isolated liquid Cu–Ni nanoscale droplet can actually crystallize along different trajectories, whereas the dominant transition type is comparable to homogeneous nucleation that proceeds from the inner part of the droplet towards the surface: the newly formed phase after initial nucleation is a Ni-rich crystal with a Cu-rich liquid shell. The decrease in the nanoparticle size causes the decrease in the solidification temperature and the temperature width of the phase transition, the increase in the solubility limit and the concentration width of the solidification loop as well as a change in the shape and slope of the equilibrium curves of the two-phase region of the phase diagram. For larger droplets, the size-dependent phase diagram approaches the well-known bulk phase diagram.

Categories: Academic Journals

Transformation from non-isothermal to isothermal tempering of steel based on isoconversional method

The Behavior Analyst - Thu, 02/01/2018 - 00:00
Abstract

The microstructural evolution of martensitic AISI 52100 steel during non-isothermal tempering under a series of constant heating rates was investigated through differential scanning calorimetry and dilatometry. The kinetic parameters for different tempering stages during heating were studied using the differential isoconversional method and also the Kissinger method as comparison. It is found that the activation energies obtained by both methods coincided with the literature. The activation energies obtained by the Kissinger method were constant, while those obtained by the isoconversional method varied with the fraction converted and presented respective variation trends. The kinetics of phase transformation during isothermal tempering was then simulated based on the Johnson–Mehl–Avrami–Kolmogorov (JMAK) theory. The calculated isothermal kinetics coincided with the experimental data from the literature. The Vickers hardness of samples with the same fraction converted under non-isothermal tempering at 0.33 K s−1 and isothermal tempering at both 373 and 473 K was measured to verify the applicability of non-isothermal to isothermal transformation. Increasing the isothermal tempering temperature accelerated the reduction of hardness when compared with non-isothermal tempering. Mechanisms for the differences in hardness between these two types of tempering were discussed.

Categories: Academic Journals

Nitrogen-doped porous carbon using ZnCl 2 as activating agent for high-performance supercapacitor electrode materials

The Behavior Analyst - Thu, 02/01/2018 - 00:00
Abstract

A facile method for synthesising porous carbon materials with high nitrogen content is employed in this study using 1H-Benzotriazole (BTA) as carbon precursor and ZnCl2 as active agent at 600–800 °C for 2 h under N2 atmosphere. Pure BTA completely degrades even at low temperature (270 °C) under inert gas, but ZnCl2 can convert the more organics to carbon because of its dehydration. The obtained NC-2-700 sample possesses a high specific surface area (1228 m2·g−1) and a nitrogen content up to 10.27 wt%. Moreover, the N-doped carbon exhibits a good electrochemical property (with a specific capacitance of 332 F·g−1 at the current density of 0.5 A·g−1), as well as an outstanding cycle stability (96.5% of the initial specific capacitance is maintained after 5000 cycles at 1 A·g−1). In addition, this obtained symmetric ultra-capacitor prepared from the NC-2-700 sample exhibits a highest energy density of 12.94 Wh·kg−1 with a power density of 375 W·kg−1 at a current density of 1 A·g−1. And even this NC-2-700//NC-2-700 supercapacitor gives 5.43 Wh·kg−1 with a power density of 3750 W·kg−1 at a high current density of 10 A·g−1. Consequently, these experimental results confirm that the porous carbon materials with high nitrogen content can be a prospective electrode material for supercapacitors.

Categories: Academic Journals

Fabrication of lead-free piezoelectric (Bi 0.5 Na 0.5 )TiO 3 –BaTiO 3 ceramics using electrophoretic deposition

The Behavior Analyst - Thu, 02/01/2018 - 00:00
Abstract

Electrophoretic deposition (EPD) process has certain advantages such as it can be applied for a mass production and also can be combined with magnetic crystal alignment technique. In this work, we prepared lead-free 85(Bi0.5Na0.5)TiO3–15BaTiO3 (85BNT–15BT) piezoelectric ceramics by conventional uniaxial pressing and EPD process. Various conditions were optimized such as suspension media, applied electrical field, and deposition time in order to yield dense green ceramics of 85BNT–15BT composition using EPD process. 85BNT–15BT ceramics prepared using EPD process revealed the Curie temperature of about 250 °C, coercive field of about 30 kV/cm, and piezoelectric constant (d 33) of 75 pC/N. The EPD-processed samples exhibited structural and electrical properties similar to that of the conventionally processed one suggesting the successful fabrication of 85BNT–15BT piezoelectric ceramics by EPD method without composition deviation. This study lays a foundation on the fabrication of Bi-based lead-free piezoelectric ceramics by an alternative route other than the conventionally practiced solid-state reaction method maintaining the similar chemical composition, moreover, leaving a large space to explore more in the future.

Categories: Academic Journals

Photoluminescence properties of N-doped carbon dots prepared in different solvents and applications in pH sensing

The Behavior Analyst - Thu, 02/01/2018 - 00:00
Abstract

Two kinds of nitrogen-doped carbon dots (N-CDs) were synthesized by choosing citric acid, l-serine and monoethanolamine as the precursors, respectively, in organic solvent N,N-dimethylformamide (DMF) and deionized water. The FTIR, UV–Vis, HRTEM and XRD were used to characterize the surface molecular structures of these two N-CDs. It was found that different reaction systems made the as-prepared N-CDs possess varied surface states and thus exhibit distinctive photoluminescence features. For the N-CDs prepared in DMF, its fluorescent property showed pH dependent and color-switchable in visible light and could be reversibly changing over in both alkaline and acidic environments due to the protonation and de-protonation of the carboxyl groups on the surface of the N-CDs. Also, its fluorescence intensity exhibited a linear fashion over the pH range from 1.5 to 7.5, indicating its potential applications in pH quantitative detection under acidic condition.

Categories: Academic Journals

Designing an air-to-air heat exchanger dedicated to single room ventilation with heat recovery

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

The present paper focuses on the development steps of heat exchangers dedicated to single room ventilation unit with heat recovery (SRVHR) by proposing a numerical approach. A methodology is suggested in order to determine the best trade-off between hydraulic and thermal performance given a specific geometry. The methodology consists in a mapping of the coefficient of performance (COP) of the unit. The latter is defined as the ratio between recovered heat and the fan energy use, given a specific indoor/outdoor temperature difference. However, the energy performance should not be the only criterion to be taken into account in the frame of the design steps of a heat recovery exchanger: technical, economic and acoustic aspects should also be considered. This numerical methodology is illustrated by means of a real example of a newly developed heat exchanger dedicated to a SRVHR. The optimization is first performed while using a semi-empirical model (based on the use of correlations and on a spatial division of the studied heat exchanger). The semi-empirical model allows for the creation of a COP map in order to identify the most effective geometry parameters for the heat exchanger. The decision concerning the final geometry is made accounting for the so-called technical, economic and acoustic considerations. A discussion on some parameters needed for the COP establishment is also proposed.

Categories: Academic Journals

Designing an air-to-air heat exchanger dedicated to single room ventilation with heat recovery

The Behavior Analyst - Thu, 02/01/2018 - 00:00
Abstract

The present paper focuses on the development steps of heat exchangers dedicated to single room ventilation unit with heat recovery (SRVHR) by proposing a numerical approach. A methodology is suggested in order to determine the best trade-off between hydraulic and thermal performance given a specific geometry. The methodology consists in a mapping of the coefficient of performance (COP) of the unit. The latter is defined as the ratio between recovered heat and the fan energy use, given a specific indoor/outdoor temperature difference. However, the energy performance should not be the only criterion to be taken into account in the frame of the design steps of a heat recovery exchanger: technical, economic and acoustic aspects should also be considered. This numerical methodology is illustrated by means of a real example of a newly developed heat exchanger dedicated to a SRVHR. The optimization is first performed while using a semi-empirical model (based on the use of correlations and on a spatial division of the studied heat exchanger). The semi-empirical model allows for the creation of a COP map in order to identify the most effective geometry parameters for the heat exchanger. The decision concerning the final geometry is made accounting for the so-called technical, economic and acoustic considerations. A discussion on some parameters needed for the COP establishment is also proposed.

Categories: Academic Journals

Optimal sidewall functionalization for the growth of ultrathin TiO 2 nanotubes via atomic layer deposition

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

One of the most suitable approaches for the production of inorganic nanotubes is by means of carbon nanotube (CNT) templates coated by atomic layer deposition (ALD). This approach is attractive because it has the potential of controlling the wall thickness down to the Angstroms level. However, it is a recognized fact that the chemistry of the substrate surface can delay the full coverage at the initial stages of the ALD coating process, mainly due to nucleation issues. This is an important issue that might restrict laying down homogeneous coatings within the ultrathin range, which is the foundation for producing self-supported inorganic nanotubes. Here, we explore the early stage of the TiO2 nucleation on CNT templates systematically functionalized with different chemical groups (COOH, OH) or N-doped. The effects of the functionalization on the nucleation process from tetrakis (dimethylamino) titanium and water were meticulously studied by means of transmission electron microscopy. Observations revealed grain-like growth of TiO2 over pristine, purified and –OH-functionalized CNTs. In contrast, COOH functionalization yielded good conformality, which was improved on N-doped CNTs. Results were confirmed by X-rays photoelectron spectroscopy analysis. We recommend either COOH or N-doped CNTs for the production of ultrathin TiO2 nanotubes.

Categories: Academic Journals

Helical gold nanotube film as stretchable micro/nanoscale strain sensor

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

A micro/nanoscale strain sensor based on helical gold nanotube films (GNTFs) is proposed, which is prepared by magnetron sputtering using carbon nanocoils (CNCs) as templates. The gauge factor of the sensor reaches 5, while the stretch of it can achieve more than 10% owing to the helical geometries. The resistance increase of GNTFs with temperature decreasing from 300 to 4 K indicates a thermal activation tunneling model for electron transport. With thicknesses increasing from 16 to 32 nm, the GNTFs show a structural transition from discontinuous to quasi-continuous film. In this transition region, the conductive path of GNTFs increases rapidly, resulting in a rapid resistance decrease of CNC–GNTF composite structure. When a helical GNTF is stretched, the resistance is increased. The helical GNTFs in the transition region exhibit the highest response sensitivity, which owes to the special torsion-dominated strains of this helical structure to some extent. The unique helical morphology gives the sensor great stretchability and special electrical response. Choosing appropriate CNCs and GNTFs with suitable thickness, the helical GNTFs can be used as micro/nanostretchable strain sensors, stretchable electrodes or connects, resonators in micro/nanoelectromechanical system.

Categories: Academic Journals

A high-performance aromatic co-polyimide fiber: structure and property relationship during gradient thermal annealing

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

A high-performance aromatic co-polyimide (co-PI) fiber was prepared by thermal treating the polyamic acid (PAA) precursor fiber produced through a wet spinning technique. A gradient thermal treatment protocol, which was selected based on the thermogravimetric analysis of PAA fibers, was employed for achieving the best structure and fiber performance. The structural and morphological variations of fibers at different thermal treatment stages were verified by Fourier transform infrared spectroscopy, sonic orientation detection, wide-angle X-ray diffraction and scanning electronic morphology. Thermal treatment cycloimidizes the PAA precursor into PI fibers with the concomitant development of a laminar orientation structure expanded from outer to inner layers of the fiber. The ordered chain repeat length is calculated to be 1.62 nm in the meridian direction. Mechanical measurements indicate that the synthesized co-PI fiber achieves optimum fracture strength and initial modulus up to 3.56 and 101 GPa, respectively. Thermal characterization results indicate a 5% weight loss temperature under nitrogen up to 591 °C and a glass transition temperature at 340 °C.

Categories: Academic Journals

Broad-spectrum antimicrobial activity of bacterial cellulose silver nanocomposites with sustained release

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

Bacterial cellulose-based antifouling materials have been produced by incorporation of silver nanoparticles for broad-spectrum antimicrobial activity. Three variations of silver nitrate (AgNO3) to reducing agent concentrations have been tried to vary the silver nanoparticle dimension. The formation of silver nanoparticles was also evidenced by the X-ray diffraction, and the crystallite size was found to decrease with increase in NaBH4 concentration. AgBC composites having < 2% (W/W) of silver exhibited 99.9% antimicrobial activity which was sustained up to 72 h against spoiled food derived mixed microbial culture. On the other hand, only 90% activity was observed with colloidal AgNPs due to aggregate formation. Composites displayed superior antimicrobial activity than colloid with equivalent amount of silver. Food stuff was protected from microbial spoilage for 30 days when stored in AgBC nanocomposites, whereas spoilage was noticed within 15 days for food stuff stored in regular polythene bag. Therefore, the AgBC composite having < 2% silver can be used as a lining of regular food packaging material to extend shelf life till 30 days. Toxicity due to high amount of silver can be prevented with these composites and can be safely used in healthcare applications such as food packaging, wound dressing, hospital bed lining and surgical apparels.

Categories: Academic Journals

Synthesis of green phosphors from highly active amorphous silica derived from rice husks

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

In this work, high purity amorphous silica derived from rice husk (RH) biomass was used to prepare green phosphor (Zn2SiO4:Mn2+). Based on the solid phase reaction under high temperature, the optimum doping concentration and reaction temperature were identified. The overall performance in terms of photoluminescence intensity and quantum yield of the RH-derived phosphor was superior to the one derived from commercial silica and close to the one made from silicic acid. The results showed that the phosphor derived from RH silica could serve as an alternative to commercial phosphor because of its decent properties and inexpensive green resource.

Categories: Academic Journals

Electric properties of MnZn ferrite/polyaniline composites: the implication of polyaniline morphology

The Psychological Record - Thu, 02/01/2018 - 00:00
Abstract

(Di)electric properties of MnZn ferrite particles coated by conductive (emeraldine salt) and non-conductive (emeraldine base) forms of PANi were measured and discussed in relation to properties of individual components of such composite. The electric response in a wide frequency (0.1 Hz–10 MHz) and temperature (−150 to 100 °C) range was determined. Recorded relaxation processes were identified as a result of hopping charge carriers, which either only polarize or give rise to DC conductivity. Temperature dependence of conductivity modelled by variable range hopping model indicated different system dimensionality: 3D in PANi bulk and 1D in PANi film, that is result of PANi morphology variation. AC conductivity frequency spectra were well approximated by power law model, and temperature evolution of its exponent was related to the type of charge involved in the charge transport. Altogether, the overlayer of conductive PANi increases by two orders of magnitude the electrical conductivity of ferrite/PANi composite compared to pristine ferrite, whereas non-conductive PANi reduced it by three orders of magnitude. Therefore, the electrical properties of ferrite/PANi composites are determined by electrical properties of PANi, which in turn depend upon mesoscale charge transport in PANi.

Categories: Academic Journals

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