The Experts below are selected from a list of 2079 Experts worldwide ranked by ideXlab platform
Ribal Georges Sabat - One of the best experts on this subject based on the ideXlab platform.
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laser induced controllable chirped pitch Circular Surface relief diffraction gratings on azo glass
Photonics Research, 2015Co-Authors: James Leibold, Ribal Georges SabatAbstract:Chirped-pitch nanoscale Circular Surface-relief diffraction gratings were photoinscribed on thin films of a Disperse Red 1 functionalized material using a holographic technique. A truncated conical mirror splits and redirects a converging or diverging laser beam, resulting in an interference pattern of concentric circles with a chirped pitch that can be controlled by varying the wavefront curvature. The resulting Circular gratings have a diameter of 12 mm and have the advantage of being produced in a fast, single-step procedure with no requirement for a master grating, photomask, or milling equipment.
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Photo-induced large-scale Circular Surface-relief diffraction gratings on azo-glass
Alternative Lithographic Technologies VII, 2015Co-Authors: James Leibold, Ribal Georges SabatAbstract:Novel metallic light-interfering fixtures were designed and fabricated in order to achieve a laser interference pattern of constant-pitch, concentric and sinusoidal light variations. These fixtures consisted of annular rings with the inner diameter shaped conically. Azobenzene-containing solid thin-films were subsequently placed behind the fixture and Circular Surface-relief diffraction gratings were inscribed due to the azo molecules photochemical isomerization process. Gratings pitches were dependent on the fixture dimensions and ranged from 600 to 1400 nm with depths up to 250 nm.
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design and fabrication of constant pitch Circular Surface relief diffraction gratings on disperse red 1 glass
Optics Letters, 2014Co-Authors: James Leibold, Peter Snell, Olivier Lebel, Ribal Georges SabatAbstract:Circular Surface-relief diffraction gratings with a constant pitch were photo-inscribed on thin films of a disperse red 1 functionalized glass-forming compound using a novel holographic technique. Various light-interfering metallic fixtures, which consisted of annular rings with a sloped and polished inner Surface, were designed and fabricated. Each of them allowed the inscription of stable and high-quality Circular diffraction gratings with pitches ranging from approximately 600–1400 nm and depths up to 250 nm. This was accomplished by exposure to a collimated laser beam with an irradiance of 604 mW/cm2 for 350 s. The resulting gratings had a diameter of 11.4 mm and had the advantage of being produced in a simple single-step procedure with no postprocessing or specialized equipment. The pitch and diameter of these Circular gratings were dependent on the fixture geometry, while the depth was related to the exposure time.
Bimlesh Kumar - One of the best experts on this subject based on the ideXlab platform.
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Parameter optimization of unbaffled Circular Surface aeration tank.
Journal of environmental science & engineering, 2011Co-Authors: Bimlesh Kumar, Achanta Ramakrishna Rao, Ajey Kumar PatelAbstract:The efficiency of the Surface aeration systems is generally governed by the geometric and dynamic parameters. The geometry is important because successful translation of the laboratory finding can be scaled up to field installations. Experimental optimization of the geometrical parameters (classical approach of one parameter variations at a time) has certain limitations, because it assumes a linear relationship among the various geometric parameters. In the real experimental process, it is not possible to vary all the parameters simultaneously. In such a case, the model of the system is built through computer simulation, assuming that the model will result in adequate determination of the optimum conditions for the real system. In this paper, two approaches have been used to model the phenomena in unbaffled Circular Surface aerators: i) Multiple regression and ii) Neural network. It has been found that neural network approach is showing better predictability compared to the multiple regression approach. In process of optimization, the pertinent dynamic parameter is divided into a finite number of segments over the entire range of observations. For each segment of the dynamic parameter, the neural network model is optimized for the geometrical parameters spanning over the entire range of observations. Thus each segment of the dynamic parameter has its set of optimal geometrical conditions. Results obtained are having less variation among them and they are very nearer to the experimental optimal conditions. Input parameter significance test of neural network model reveals that blade width of the rotor is the most significant geometric parameter for the aeration process.
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Economizing the Energy Consumption in Circular Surface Aerator
Survival and Sustainability, 2010Co-Authors: Achanta Ramakrishna Rao, Bimlesh KumarAbstract:Oxygen transfer and power requirement with rotor speed has always been a central topic for design and scale-up of Surface aerators. Present study develops design curves correlating the oxygen transfer coefficient, power per unit volume and rotor speed. Based on the design curves, energy conservation by using right sized Circular tank Surface aerators has been discussed and demonstrated that it is economical to use a big sized Circular tank Surface aerator rather than using multiple numbers of smaller sized Circular tank to aerate the same volume of water.
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Oxygen transfer in Circular Surface aeration tanks
Environmental technology, 2009Co-Authors: Achanta Ramakrishna Rao, Ajey Kumar Patel, Bimlesh KumarAbstract:Surface aeration systems employed in activated sludge plants are the most energy-intensive units of the plants and typically account for a higher percentage of the treatment facility's total energy use. The geometry of the aeration tank imparts a major effect on the system efficiency. It is said that at optimal geometric conditions, systems exhibits the maximum efficiency. Thus the quantification of the optimal geometric conditions in Surface aeration tanks is needed. Optimal geometric conditions are also needed to scale up the laboratory result to the field installation. In the present work, experimental studies have been carried out on baffled and unbaffled Circular Surface aeration tanks to ascertain the optimal geometric conditions. It is found that no optimal geometric conditions exist for the liquid/water depth in Circular Surface aeration tanks; however, for design purposes, a standard value has been assumed. Based on the optimal geometric conditions, a scale-up equation has been developed for the baffled Circular Surface aeration tanks.
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Resistance characteristics of Surface aerators.
Journal of Hydraulic Engineering, 2009Co-Authors: Achanta Ramakrishna Rao, Bimlesh KumarAbstract:The resistance characteristics in terms of power consumption, interpreted in terms of Power number (P-0), of unbaffled Surface aeration systems consisting of flat bladed impellers, were studied in two shapes of Surface aerations tanks: square and Circular. Experiments were conducted in three different sizes in each of the geometrically similar unbaffled square and Circular Surface aerators. Results have shown that the P-0 cannot be simulated singularly either with Reynolds number R or with Froude number as there are scale effects; hence there appears to be a need for incorporating the effects of both R and F. It is found that P-0 is uniquely related to a parameter X (=(FR1/3)-R-4/3), which is defined as a parameter governing the theoretical power per unit volume for both shapes of aeration tanks; however, such relationships are different for both shapes of aerators. Interestingly P-0 values are always higher in square Surface aerators than in Circular Surface aerators, which suggests that the Circular Surface aerators require less power input than the square Surface aerators. The usefulness of such correlations was demonstrated in estimating the power requirement while achieving a required oxygen transfer coefficient in Surface aerators.
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The use of Circular Surface aerators in wastewater treatment tanks
Journal of Chemical Technology & Biotechnology, 2006Co-Authors: Achanta Ramakrishna Rao, Bimlesh KumarAbstract:Aeration experiments were conducted in different sized baffled and unbaffled Circular Surface aeration tanks to study their relative performance on oxygen transfer process while aerating the same volume of water. Experiments were carried out with the objective of ascertaining the effect of baffle on oxygen transfer coefficient k. Simulation equations govern the oxygen transfer coefficient with the theoretical power per unit volume, X and actual power per unit volume, P-V. It has been found that, for any given X, Circular tanks with baffle produce higher values of k than unbaffled Circular tanks, but in terms of actual power consumption unbaffled tanks consume less power when compared to baffled Circular tanks to achieve the same value of k. It has been found that in terms of energy consumption, epsilon, baffled tanks consume more energy than unbaffled tanks at any value of X. This suggests that the unbaffled Circular tank gives a better performance as far as energy consumption is concerned and hence better economy. An example illustrating the energy conservation to aerate the same volume of water in both types of aerators is given. (c) 2007 Society of Chemical Industry.
James Leibold - One of the best experts on this subject based on the ideXlab platform.
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laser induced controllable chirped pitch Circular Surface relief diffraction gratings on azo glass
Photonics Research, 2015Co-Authors: James Leibold, Ribal Georges SabatAbstract:Chirped-pitch nanoscale Circular Surface-relief diffraction gratings were photoinscribed on thin films of a Disperse Red 1 functionalized material using a holographic technique. A truncated conical mirror splits and redirects a converging or diverging laser beam, resulting in an interference pattern of concentric circles with a chirped pitch that can be controlled by varying the wavefront curvature. The resulting Circular gratings have a diameter of 12 mm and have the advantage of being produced in a fast, single-step procedure with no requirement for a master grating, photomask, or milling equipment.
-
Photo-induced large-scale Circular Surface-relief diffraction gratings on azo-glass
Alternative Lithographic Technologies VII, 2015Co-Authors: James Leibold, Ribal Georges SabatAbstract:Novel metallic light-interfering fixtures were designed and fabricated in order to achieve a laser interference pattern of constant-pitch, concentric and sinusoidal light variations. These fixtures consisted of annular rings with the inner diameter shaped conically. Azobenzene-containing solid thin-films were subsequently placed behind the fixture and Circular Surface-relief diffraction gratings were inscribed due to the azo molecules photochemical isomerization process. Gratings pitches were dependent on the fixture dimensions and ranged from 600 to 1400 nm with depths up to 250 nm.
-
design and fabrication of constant pitch Circular Surface relief diffraction gratings on disperse red 1 glass
Optics Letters, 2014Co-Authors: James Leibold, Peter Snell, Olivier Lebel, Ribal Georges SabatAbstract:Circular Surface-relief diffraction gratings with a constant pitch were photo-inscribed on thin films of a disperse red 1 functionalized glass-forming compound using a novel holographic technique. Various light-interfering metallic fixtures, which consisted of annular rings with a sloped and polished inner Surface, were designed and fabricated. Each of them allowed the inscription of stable and high-quality Circular diffraction gratings with pitches ranging from approximately 600–1400 nm and depths up to 250 nm. This was accomplished by exposure to a collimated laser beam with an irradiance of 604 mW/cm2 for 350 s. The resulting gratings had a diameter of 11.4 mm and had the advantage of being produced in a simple single-step procedure with no postprocessing or specialized equipment. The pitch and diameter of these Circular gratings were dependent on the fixture geometry, while the depth was related to the exposure time.
Mool C Gupta - One of the best experts on this subject based on the ideXlab platform.
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ultrafast laser induced self organized conical micro nano Surface structures and their origin
Optics and Lasers in Engineering, 2010Co-Authors: Barada K Nayak, Mool C GuptaAbstract:Abstract We have investigated the origin and subsequent evolution of self-organized conical micro/nano structures in silicon Surface upon irradiation of multiple ultrafast laser pulses in the gaseous environments of SF 6 and He. Localized Circular Surface waves are observed in ultrafast laser exposed regions under various states of polarization. These localized Circular Surface waves interfere with each other to produce scattering sites for subsequent pulses. Additional exposure gives rise to ripples. The period of the ripple structures is usually on the order of the wavelength of the irradiating laser pulse (800 nm) in the central region of the laser spot while towards the edge of the spot, ripple periods are much smaller (∼500 nm). Also, we have observed that the period of the localized Circular Surface wave appear to be unrelated to the laser wavelength. With further laser exposure, the initial ripple structure breaks down into Surface roughness due to further formation of localized Circular Surface waves on already produced ripples. This initial Surface roughness evolves into sharp and regular array of self-organized conical micro/nano Surface structures due to self-masking phenomenon. We have also demonstrated that for laser assisted conical micro/nano structure formation in silicon, presence of a reactive gas is not necessary, although it enhances the etching process as well as makes the structures sharper.
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Ultrafast laser-induced self-organized conical micro/nano Surface structures and their origin
Optics and Lasers in Engineering, 2010Co-Authors: Barada K Nayak, Mool C GuptaAbstract:Abstract We have investigated the origin and subsequent evolution of self-organized conical micro/nano structures in silicon Surface upon irradiation of multiple ultrafast laser pulses in the gaseous environments of SF 6 and He. Localized Circular Surface waves are observed in ultrafast laser exposed regions under various states of polarization. These localized Circular Surface waves interfere with each other to produce scattering sites for subsequent pulses. Additional exposure gives rise to ripples. The period of the ripple structures is usually on the order of the wavelength of the irradiating laser pulse (800 nm) in the central region of the laser spot while towards the edge of the spot, ripple periods are much smaller (∼500 nm). Also, we have observed that the period of the localized Circular Surface wave appear to be unrelated to the laser wavelength. With further laser exposure, the initial ripple structure breaks down into Surface roughness due to further formation of localized Circular Surface waves on already produced ripples. This initial Surface roughness evolves into sharp and regular array of self-organized conical micro/nano Surface structures due to self-masking phenomenon. We have also demonstrated that for laser assisted conical micro/nano structure formation in silicon, presence of a reactive gas is not necessary, although it enhances the etching process as well as makes the structures sharper.
Achanta Ramakrishna Rao - One of the best experts on this subject based on the ideXlab platform.
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Parameter optimization of unbaffled Circular Surface aeration tank.
Journal of environmental science & engineering, 2011Co-Authors: Bimlesh Kumar, Achanta Ramakrishna Rao, Ajey Kumar PatelAbstract:The efficiency of the Surface aeration systems is generally governed by the geometric and dynamic parameters. The geometry is important because successful translation of the laboratory finding can be scaled up to field installations. Experimental optimization of the geometrical parameters (classical approach of one parameter variations at a time) has certain limitations, because it assumes a linear relationship among the various geometric parameters. In the real experimental process, it is not possible to vary all the parameters simultaneously. In such a case, the model of the system is built through computer simulation, assuming that the model will result in adequate determination of the optimum conditions for the real system. In this paper, two approaches have been used to model the phenomena in unbaffled Circular Surface aerators: i) Multiple regression and ii) Neural network. It has been found that neural network approach is showing better predictability compared to the multiple regression approach. In process of optimization, the pertinent dynamic parameter is divided into a finite number of segments over the entire range of observations. For each segment of the dynamic parameter, the neural network model is optimized for the geometrical parameters spanning over the entire range of observations. Thus each segment of the dynamic parameter has its set of optimal geometrical conditions. Results obtained are having less variation among them and they are very nearer to the experimental optimal conditions. Input parameter significance test of neural network model reveals that blade width of the rotor is the most significant geometric parameter for the aeration process.
-
Economizing the Energy Consumption in Circular Surface Aerator
Survival and Sustainability, 2010Co-Authors: Achanta Ramakrishna Rao, Bimlesh KumarAbstract:Oxygen transfer and power requirement with rotor speed has always been a central topic for design and scale-up of Surface aerators. Present study develops design curves correlating the oxygen transfer coefficient, power per unit volume and rotor speed. Based on the design curves, energy conservation by using right sized Circular tank Surface aerators has been discussed and demonstrated that it is economical to use a big sized Circular tank Surface aerator rather than using multiple numbers of smaller sized Circular tank to aerate the same volume of water.
-
Oxygen transfer in Circular Surface aeration tanks
Environmental technology, 2009Co-Authors: Achanta Ramakrishna Rao, Ajey Kumar Patel, Bimlesh KumarAbstract:Surface aeration systems employed in activated sludge plants are the most energy-intensive units of the plants and typically account for a higher percentage of the treatment facility's total energy use. The geometry of the aeration tank imparts a major effect on the system efficiency. It is said that at optimal geometric conditions, systems exhibits the maximum efficiency. Thus the quantification of the optimal geometric conditions in Surface aeration tanks is needed. Optimal geometric conditions are also needed to scale up the laboratory result to the field installation. In the present work, experimental studies have been carried out on baffled and unbaffled Circular Surface aeration tanks to ascertain the optimal geometric conditions. It is found that no optimal geometric conditions exist for the liquid/water depth in Circular Surface aeration tanks; however, for design purposes, a standard value has been assumed. Based on the optimal geometric conditions, a scale-up equation has been developed for the baffled Circular Surface aeration tanks.
-
Resistance characteristics of Surface aerators.
Journal of Hydraulic Engineering, 2009Co-Authors: Achanta Ramakrishna Rao, Bimlesh KumarAbstract:The resistance characteristics in terms of power consumption, interpreted in terms of Power number (P-0), of unbaffled Surface aeration systems consisting of flat bladed impellers, were studied in two shapes of Surface aerations tanks: square and Circular. Experiments were conducted in three different sizes in each of the geometrically similar unbaffled square and Circular Surface aerators. Results have shown that the P-0 cannot be simulated singularly either with Reynolds number R or with Froude number as there are scale effects; hence there appears to be a need for incorporating the effects of both R and F. It is found that P-0 is uniquely related to a parameter X (=(FR1/3)-R-4/3), which is defined as a parameter governing the theoretical power per unit volume for both shapes of aeration tanks; however, such relationships are different for both shapes of aerators. Interestingly P-0 values are always higher in square Surface aerators than in Circular Surface aerators, which suggests that the Circular Surface aerators require less power input than the square Surface aerators. The usefulness of such correlations was demonstrated in estimating the power requirement while achieving a required oxygen transfer coefficient in Surface aerators.
-
The use of Circular Surface aerators in wastewater treatment tanks
Journal of Chemical Technology & Biotechnology, 2006Co-Authors: Achanta Ramakrishna Rao, Bimlesh KumarAbstract:Aeration experiments were conducted in different sized baffled and unbaffled Circular Surface aeration tanks to study their relative performance on oxygen transfer process while aerating the same volume of water. Experiments were carried out with the objective of ascertaining the effect of baffle on oxygen transfer coefficient k. Simulation equations govern the oxygen transfer coefficient with the theoretical power per unit volume, X and actual power per unit volume, P-V. It has been found that, for any given X, Circular tanks with baffle produce higher values of k than unbaffled Circular tanks, but in terms of actual power consumption unbaffled tanks consume less power when compared to baffled Circular tanks to achieve the same value of k. It has been found that in terms of energy consumption, epsilon, baffled tanks consume more energy than unbaffled tanks at any value of X. This suggests that the unbaffled Circular tank gives a better performance as far as energy consumption is concerned and hence better economy. An example illustrating the energy conservation to aerate the same volume of water in both types of aerators is given. (c) 2007 Society of Chemical Industry.