Pradeep Sahoo - Academia.edu (original) (raw)

Papers by Pradeep Sahoo

Astrophysics and Space Science, 2003

A class of exact solutions of Eistein's field equations with attractive massive scalar field in L... more A class of exact solutions of Eistein's field equations with attractive massive scalar field in LRS Bianchi type I space time is obtained. It is shown that how the dynamical importance of the scalar field and the shear change in the course of evolution.

Hvac&r Research, 2008

An experimental investigation was carried out to evaluate the flow characteristics of refrigerant... more An experimental investigation was carried out to evaluate the flow characteristics of refrigerant R-134a through an adiabatic helically coiled capillary tube. The effect of various physical parameters like diameter and length of capillary tube, coil pitch, and inlet subcooling on the mass flow rate of R-134a was investigated. Moreover, the refrigerant mass flow rate through an instrumented capillary tube was also compared to that through a noninstrumented capillary tube. It was found that the provision of taps for pressure measurement on the capillary tube surface has a negligible effect on the mass flow rate of R-134a. Further, the coil pitch had a significant effect on the performance of the adiabatic helically coiled capillary tube. It was established that the coil pitch significantly influenced the mass flow rate through the adiabatic helically coiled capillary tube. It was concluded that the effect of coiling of the capillary tube reduces the mass flow rate by 5% to 15%, as compared to those of the straight capillary tube operating under similar conditions. The data obtained from the experiments were analyzed, and a semi-empirical correlation was developed. Almost 97% of the mass flow rate predicted by the proposed correlation lies in the error band of ±10%.

International Journal of Refrigeration-revue Internationale Du Froid, 2009

Hvac&r Research, 2008

This paper presents the performance of R-134a through a diabatic capillary tube with lateral conf... more This paper presents the performance of R-134a through a diabatic capillary tube with lateral configuration. The paper is divided into two sections: (1) an experimental investigation of straight and helical diabatic capillary tubes and (2) a numerical investigation of the straight diabatic capillary tube. In the experimental investigation, the effects of parameters such as capillary tube diameter, capillary tube length, coil pitch, and inlet subcooling on the refrigerant mass flow rate through a diabatic capillary tube were studied. In addition to the parameters mentioned above, the mass flow rate through a diabatic helical capillary tube was also found to be a function of suction-line inlet superheat and heat exchange length. The suction-line inlet superheat in the present investigation is not a controlled parameter. A comparison of the results of diabatic helical capillary and adiabatic helical capillary tubes was also made. On the basis of acquired experimental data, a correlation to predict the refrigerant mass flow rate was proposed. It was found that the predictions of the proposed correlation are within ±5% agreement with the experimental data.In the numerical investigation, a mathematical model was developed by applying laws of conservation of mass, momentum, and energy to a straight diabatic capillary tube. These differential equations were solved numerically using a finite difference method. The developed model was validated with experimental data from previous and present research. Further, a comparison was also made between the proposed model and the models of Sinpiboon and Wongwises (2002) and Valladares (2007).

Hvac&r Research, 2007

An analytical model has been developed to predict the length of adiabatic capillary tubes used in... more An analytical model has been developed to predict the length of adiabatic capillary tubes used in domestic refrigerators and low-capacity residential air conditioners. The model predicts the length of two types of tubes—straight and spiral adiabatic capillary tubes. The proposed model is based on the homogenous two-phase flow model, which predicts the length of the adiabatic capillary tubes as a function of refrigerant mass flow rate, capillary tube diameter, degree of subcooling at capillary inlet, internal surface roughness, and the pitch of the Archimedean spiral. The existence of subcooled liquid at the entry of the capillary tube requires the computation of single-phase and then two-phase lengths of the tube. The McAdams et al. (1942) viscosity correlation has been used to evaluate the two-phase viscosity of the expanding refrigerant in the latter part of the capillary tube. All the thermophysical and transport properties of the refrigerants are evaluated by the REFPROP Version 7 database, which is based on the Carnahan-Starling-DeSantis equation of state. The simulation results are validated with the experimental findings of previous researchers. The performance of the above two geometries of adiabatic capillary tube is compared, and it is established that for the same state of refrigerants at the inlet and exit of the adiabatic capillary, spiral capillary is found to have a shorter length. Parametric study of the adiabatic capillary tubes is also carried out. Further, the effect of geometric and physical parameters has been presented in detail. A much smaller capillary tube is required when the eco-friendly refrigerants R-134a and R-152a are used in place of refrigerant R-12 for similar conditions across the adiabatic spiral capillary tube.

Applied Thermal Engineering, 2009

A comprehensive review of the literature on the flow of various refrigerants through the capillar... more A comprehensive review of the literature on the flow of various refrigerants through the capillary tubes of different geometries viz. straight and coiled and flow configurations viz. adiabatic and diabatic, has been discussed in this paper. The paper presents in chronological order the ...

International Journal of Refrigeration-revue Internationale Du Froid, 2008

Capillary Adiabatic Flow Pitch Correlation a b s t r a c t This paper presents an experimental in... more Capillary Adiabatic Flow Pitch Correlation a b s t r a c t This paper presents an experimental investigation for the flow of R-134a inside an adiabatic spirally coiled capillary tube. The effect of various geometric parameters like capillary tube diameter, length and coil pitch for different capillary tube inlet subcoolings on the mass flow rate of R-134a through the spiral capillary tube geometry has been investigated.

Applied Surface Science, 2006

In the course of a systematic investigation of dynamic, chemical, and laser-induced solid phase e... more In the course of a systematic investigation of dynamic, chemical, and laser-induced solid phase epitaxy of a-quartz after ion implantation, we have studied epitaxy and cathodoluminescence emission after 250 keV Cs-ion implantation and subsequent pulsed excimer laser treatment in air. Rutherford backscattering channelling analysis showed partial epitaxy for all the laser-irradiated samples; however, no full epitaxy was achieved. The optical properties of these samples were analyzed using cathodoluminescence spectroscopy, giving evidence of five emission bands at 2.42, 2.79, 3.25, 3.65, and 4.30 eV photon energy. Their intensity relation to the laser power and retained Cs-ion fraction are discussed and the present results will be compared with those obtained after chemical and dynamic epitaxy of quartz after alkali-ion, Ge, and Ba implantation. #

Applied Physics B-lasers and Optics, 2006

Implanting photoactive ions into quartz or silica is a simple and efficient way to tune the lumin... more Implanting photoactive ions into quartz or silica is a simple and efficient way to tune the luminescence light used for various optoelectronic applications. However, such ion implantation damages or even destroys the crystalline order in quartz. We report here on cathodoluminescence of α-quartz after 175 keV Rb-ion implantation and epitaxial growth when annealing the samples in air or 18O 2. In the cathodoluminescence spectra taken at room temperature, five bands were identified. In addition to three intrinsic bands at 2.40, 2.79, and 4.30 eV, which are related to the quartz and/or silica matrix, two strong violet sub-bands at 3.25 and 3.65 eV were observed, which appear to be strongly correlated with the presence of alkali ions and/or the degree of epitaxy of the matrix. Their properties and origin are discussed in relation to similar bands observed after Ba, Ge, and Na ion implantation.

Physica B-condensed Matter, 2007

Ion implantation is a promising route for doping quartz with luminescent impurity atoms and growi... more Ion implantation is a promising route for doping quartz with luminescent impurity atoms and growing photoactive nanoparticles of them. The present work focuses on cathodoluminescence (CL) and epitaxy during or after Na, Rb, Cs, Ge, and Ba ion implantation as well as Rb/Ge double implantation in crystalline alpha-quartz, under the conditions of dynamic, chemical or laser epitaxy. In addition to the known intrinsic sub-bands in the CL spectra, which have been associated with specific defects in the silica matrix, very intense blue or violet bands were found. They are correlated with the implanted ion species and follow their thermal behaviour. The quantum efficiency and possible origins of the blue/violet CL emission for various ions and processing treatments will be discussed. The case of double Rb/Ge implantation appears to be very promising with respect to a combination of a high CL output and full chemical epitaxy.

Journal of Non-crystalline Solids, 2006

Even at low fluences doping of quartz by ion implantation results in amorphization. Here we repor... more Even at low fluences doping of quartz by ion implantation results in amorphization. Here we report on the measurement of cathodoluminescence and surface structures during solid phase epitaxy in Na-implanted a-quartz annealed in 18 O 2 atmosphere. Complete epitaxy was achieved under appropriate conditions of ion fluence, annealing temperature and time. The crystalline structure of the samples was studied by Rutherford backscattering channelling spectroscopy and the 18 O-16 O exchange between the matrix and 18 O 2 annealing gas by elastic recoil detection analysis. In the cathodoluminescence spectra taken at room temperature, five bands were identified and assigned to various defect centres. Two of the bands in the violet region at 3.25 and 3.65 eV strongly vary in intensity at 843-1173 K annealing temperature and appear to be intimately correlated with the presence of Na-ions in the implanted region of the matrix. Finally, atomic force microscopy enabled, for the first time, the observation of the correlation of surface structures and epitaxy.

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2005

The luminescence properties of ion-beam doped silica and quartz sensitively depend on the ion spe... more The luminescence properties of ion-beam doped silica and quartz sensitively depend on the ion species and fluence and the thermal processing during or after ion implantation. While no epitaxy, but a high cathodoluminescence (CL) output can be reached after dynamic Ge-ion implantation in quartz, full planar epitaxy is achieved after alkali-ion implantation (Na, Rb, Cs) under appropriate ion and annealing conditions. Now for the first time we achieved high luminescence intensity and (partial) recrystallization of a-quartz by double Ge/Rb-ion implantation. Pure synthetic a-quartz samples were irradiated with 175 keV Rb-ions and subsequently with 120 keV Ge-ions and post-annealed at 1170 K in vacuo, air or 18 O 2 gas. A comparative analysis of the epitaxy (via RBS-Channeling) and cathodoluminescence was carried out, the latter showing three dominant emission bands in the blue/violet region at 2.95, 3.25 and 3.53 eV, which were assigned to Rb-or Ge-implantation. For increasing CL temperature, a shift of the predominant peak from 2.95 to 3.25 eV was noted after air-annealing, accompanying partial chemical epitaxy.

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2004

... Appl. Phys. Lett., 53 (1988), p. 89. [2] BG Yacobi and DB Holt. J. Appl. Phys., 59 (1986), p.... more ... Appl. Phys. Lett., 53 (1988), p. 89. [2] BG Yacobi and DB Holt. J. Appl. Phys., 59 (1986), p. R1. ... [5] MAS Kalceff. Phys. Rev. B, 57 (1998), p. 5674. [6] J. Von Borany, R. Grötzschel, KH Heinig, A. Markwitz, W. Matz, B. Schmidt and W. Skorupa. Appl. Phys. Lett., 71 (1997), p. 3215. ...

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2006

Modifications of Ni/Si and Fe/Si bilayers induced by swift heavy ions were studied in the regime ... more Modifications of Ni/Si and Fe/Si bilayers induced by swift heavy ions were studied in the regime of pure electronic stopping. Polycrystalline films, 65-75 nm thick, were deposited via electron evaporation (Ni) or pulsed laser deposition (Fe) onto Si wafers and irradiated at 6300 K with 350-MeV Au 26+ ions to fluences of up to 5 · 10 15 ions/cm 2 . The samples were analyzed by Rutherford backscattering spectroscopy, X-ray diffraction and the magneto-optical Kerr effect. In the Fe/Si samples, a 20 nm 57 Fe layer was interlayed between nat Fe and Si in order to monitor interface mixing and phase formation by means of Moessbauer spectroscopy. In both systems, a high mixing rate of %60 nm 4 was found, correlated with relaxation of the as-deposited stress and uniaxial magnetic anisotropy. At higher fluences, full interdiffusion gives rise to amorphous silicide phases, build-up of stress and loss of magnetic texture.

Astrophysics and Space Science, 2003

A class of exact solutions of Eistein's field equations with attractive massive scalar field in L... more A class of exact solutions of Eistein's field equations with attractive massive scalar field in LRS Bianchi type I space time is obtained. It is shown that how the dynamical importance of the scalar field and the shear change in the course of evolution.

Hvac&r Research, 2008

An experimental investigation was carried out to evaluate the flow characteristics of refrigerant... more An experimental investigation was carried out to evaluate the flow characteristics of refrigerant R-134a through an adiabatic helically coiled capillary tube. The effect of various physical parameters like diameter and length of capillary tube, coil pitch, and inlet subcooling on the mass flow rate of R-134a was investigated. Moreover, the refrigerant mass flow rate through an instrumented capillary tube was also compared to that through a noninstrumented capillary tube. It was found that the provision of taps for pressure measurement on the capillary tube surface has a negligible effect on the mass flow rate of R-134a. Further, the coil pitch had a significant effect on the performance of the adiabatic helically coiled capillary tube. It was established that the coil pitch significantly influenced the mass flow rate through the adiabatic helically coiled capillary tube. It was concluded that the effect of coiling of the capillary tube reduces the mass flow rate by 5% to 15%, as compared to those of the straight capillary tube operating under similar conditions. The data obtained from the experiments were analyzed, and a semi-empirical correlation was developed. Almost 97% of the mass flow rate predicted by the proposed correlation lies in the error band of ±10%.

International Journal of Refrigeration-revue Internationale Du Froid, 2009

Hvac&r Research, 2008

This paper presents the performance of R-134a through a diabatic capillary tube with lateral conf... more This paper presents the performance of R-134a through a diabatic capillary tube with lateral configuration. The paper is divided into two sections: (1) an experimental investigation of straight and helical diabatic capillary tubes and (2) a numerical investigation of the straight diabatic capillary tube. In the experimental investigation, the effects of parameters such as capillary tube diameter, capillary tube length, coil pitch, and inlet subcooling on the refrigerant mass flow rate through a diabatic capillary tube were studied. In addition to the parameters mentioned above, the mass flow rate through a diabatic helical capillary tube was also found to be a function of suction-line inlet superheat and heat exchange length. The suction-line inlet superheat in the present investigation is not a controlled parameter. A comparison of the results of diabatic helical capillary and adiabatic helical capillary tubes was also made. On the basis of acquired experimental data, a correlation to predict the refrigerant mass flow rate was proposed. It was found that the predictions of the proposed correlation are within ±5% agreement with the experimental data.In the numerical investigation, a mathematical model was developed by applying laws of conservation of mass, momentum, and energy to a straight diabatic capillary tube. These differential equations were solved numerically using a finite difference method. The developed model was validated with experimental data from previous and present research. Further, a comparison was also made between the proposed model and the models of Sinpiboon and Wongwises (2002) and Valladares (2007).

Hvac&r Research, 2007

An analytical model has been developed to predict the length of adiabatic capillary tubes used in... more An analytical model has been developed to predict the length of adiabatic capillary tubes used in domestic refrigerators and low-capacity residential air conditioners. The model predicts the length of two types of tubes—straight and spiral adiabatic capillary tubes. The proposed model is based on the homogenous two-phase flow model, which predicts the length of the adiabatic capillary tubes as a function of refrigerant mass flow rate, capillary tube diameter, degree of subcooling at capillary inlet, internal surface roughness, and the pitch of the Archimedean spiral. The existence of subcooled liquid at the entry of the capillary tube requires the computation of single-phase and then two-phase lengths of the tube. The McAdams et al. (1942) viscosity correlation has been used to evaluate the two-phase viscosity of the expanding refrigerant in the latter part of the capillary tube. All the thermophysical and transport properties of the refrigerants are evaluated by the REFPROP Version 7 database, which is based on the Carnahan-Starling-DeSantis equation of state. The simulation results are validated with the experimental findings of previous researchers. The performance of the above two geometries of adiabatic capillary tube is compared, and it is established that for the same state of refrigerants at the inlet and exit of the adiabatic capillary, spiral capillary is found to have a shorter length. Parametric study of the adiabatic capillary tubes is also carried out. Further, the effect of geometric and physical parameters has been presented in detail. A much smaller capillary tube is required when the eco-friendly refrigerants R-134a and R-152a are used in place of refrigerant R-12 for similar conditions across the adiabatic spiral capillary tube.

Applied Thermal Engineering, 2009

A comprehensive review of the literature on the flow of various refrigerants through the capillar... more A comprehensive review of the literature on the flow of various refrigerants through the capillary tubes of different geometries viz. straight and coiled and flow configurations viz. adiabatic and diabatic, has been discussed in this paper. The paper presents in chronological order the ...

International Journal of Refrigeration-revue Internationale Du Froid, 2008

Capillary Adiabatic Flow Pitch Correlation a b s t r a c t This paper presents an experimental in... more Capillary Adiabatic Flow Pitch Correlation a b s t r a c t This paper presents an experimental investigation for the flow of R-134a inside an adiabatic spirally coiled capillary tube. The effect of various geometric parameters like capillary tube diameter, length and coil pitch for different capillary tube inlet subcoolings on the mass flow rate of R-134a through the spiral capillary tube geometry has been investigated.

Applied Surface Science, 2006

In the course of a systematic investigation of dynamic, chemical, and laser-induced solid phase e... more In the course of a systematic investigation of dynamic, chemical, and laser-induced solid phase epitaxy of a-quartz after ion implantation, we have studied epitaxy and cathodoluminescence emission after 250 keV Cs-ion implantation and subsequent pulsed excimer laser treatment in air. Rutherford backscattering channelling analysis showed partial epitaxy for all the laser-irradiated samples; however, no full epitaxy was achieved. The optical properties of these samples were analyzed using cathodoluminescence spectroscopy, giving evidence of five emission bands at 2.42, 2.79, 3.25, 3.65, and 4.30 eV photon energy. Their intensity relation to the laser power and retained Cs-ion fraction are discussed and the present results will be compared with those obtained after chemical and dynamic epitaxy of quartz after alkali-ion, Ge, and Ba implantation. #

Applied Physics B-lasers and Optics, 2006

Implanting photoactive ions into quartz or silica is a simple and efficient way to tune the lumin... more Implanting photoactive ions into quartz or silica is a simple and efficient way to tune the luminescence light used for various optoelectronic applications. However, such ion implantation damages or even destroys the crystalline order in quartz. We report here on cathodoluminescence of α-quartz after 175 keV Rb-ion implantation and epitaxial growth when annealing the samples in air or 18O 2. In the cathodoluminescence spectra taken at room temperature, five bands were identified. In addition to three intrinsic bands at 2.40, 2.79, and 4.30 eV, which are related to the quartz and/or silica matrix, two strong violet sub-bands at 3.25 and 3.65 eV were observed, which appear to be strongly correlated with the presence of alkali ions and/or the degree of epitaxy of the matrix. Their properties and origin are discussed in relation to similar bands observed after Ba, Ge, and Na ion implantation.

Physica B-condensed Matter, 2007

Ion implantation is a promising route for doping quartz with luminescent impurity atoms and growi... more Ion implantation is a promising route for doping quartz with luminescent impurity atoms and growing photoactive nanoparticles of them. The present work focuses on cathodoluminescence (CL) and epitaxy during or after Na, Rb, Cs, Ge, and Ba ion implantation as well as Rb/Ge double implantation in crystalline alpha-quartz, under the conditions of dynamic, chemical or laser epitaxy. In addition to the known intrinsic sub-bands in the CL spectra, which have been associated with specific defects in the silica matrix, very intense blue or violet bands were found. They are correlated with the implanted ion species and follow their thermal behaviour. The quantum efficiency and possible origins of the blue/violet CL emission for various ions and processing treatments will be discussed. The case of double Rb/Ge implantation appears to be very promising with respect to a combination of a high CL output and full chemical epitaxy.

Journal of Non-crystalline Solids, 2006

Even at low fluences doping of quartz by ion implantation results in amorphization. Here we repor... more Even at low fluences doping of quartz by ion implantation results in amorphization. Here we report on the measurement of cathodoluminescence and surface structures during solid phase epitaxy in Na-implanted a-quartz annealed in 18 O 2 atmosphere. Complete epitaxy was achieved under appropriate conditions of ion fluence, annealing temperature and time. The crystalline structure of the samples was studied by Rutherford backscattering channelling spectroscopy and the 18 O-16 O exchange between the matrix and 18 O 2 annealing gas by elastic recoil detection analysis. In the cathodoluminescence spectra taken at room temperature, five bands were identified and assigned to various defect centres. Two of the bands in the violet region at 3.25 and 3.65 eV strongly vary in intensity at 843-1173 K annealing temperature and appear to be intimately correlated with the presence of Na-ions in the implanted region of the matrix. Finally, atomic force microscopy enabled, for the first time, the observation of the correlation of surface structures and epitaxy.

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2005

The luminescence properties of ion-beam doped silica and quartz sensitively depend on the ion spe... more The luminescence properties of ion-beam doped silica and quartz sensitively depend on the ion species and fluence and the thermal processing during or after ion implantation. While no epitaxy, but a high cathodoluminescence (CL) output can be reached after dynamic Ge-ion implantation in quartz, full planar epitaxy is achieved after alkali-ion implantation (Na, Rb, Cs) under appropriate ion and annealing conditions. Now for the first time we achieved high luminescence intensity and (partial) recrystallization of a-quartz by double Ge/Rb-ion implantation. Pure synthetic a-quartz samples were irradiated with 175 keV Rb-ions and subsequently with 120 keV Ge-ions and post-annealed at 1170 K in vacuo, air or 18 O 2 gas. A comparative analysis of the epitaxy (via RBS-Channeling) and cathodoluminescence was carried out, the latter showing three dominant emission bands in the blue/violet region at 2.95, 3.25 and 3.53 eV, which were assigned to Rb-or Ge-implantation. For increasing CL temperature, a shift of the predominant peak from 2.95 to 3.25 eV was noted after air-annealing, accompanying partial chemical epitaxy.

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2004

... Appl. Phys. Lett., 53 (1988), p. 89. [2] BG Yacobi and DB Holt. J. Appl. Phys., 59 (1986), p.... more ... Appl. Phys. Lett., 53 (1988), p. 89. [2] BG Yacobi and DB Holt. J. Appl. Phys., 59 (1986), p. R1. ... [5] MAS Kalceff. Phys. Rev. B, 57 (1998), p. 5674. [6] J. Von Borany, R. Grötzschel, KH Heinig, A. Markwitz, W. Matz, B. Schmidt and W. Skorupa. Appl. Phys. Lett., 71 (1997), p. 3215. ...

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2006

Modifications of Ni/Si and Fe/Si bilayers induced by swift heavy ions were studied in the regime ... more Modifications of Ni/Si and Fe/Si bilayers induced by swift heavy ions were studied in the regime of pure electronic stopping. Polycrystalline films, 65-75 nm thick, were deposited via electron evaporation (Ni) or pulsed laser deposition (Fe) onto Si wafers and irradiated at 6300 K with 350-MeV Au 26+ ions to fluences of up to 5 · 10 15 ions/cm 2 . The samples were analyzed by Rutherford backscattering spectroscopy, X-ray diffraction and the magneto-optical Kerr effect. In the Fe/Si samples, a 20 nm 57 Fe layer was interlayed between nat Fe and Si in order to monitor interface mixing and phase formation by means of Moessbauer spectroscopy. In both systems, a high mixing rate of %60 nm 4 was found, correlated with relaxation of the as-deposited stress and uniaxial magnetic anisotropy. At higher fluences, full interdiffusion gives rise to amorphous silicide phases, build-up of stress and loss of magnetic texture.