The Experts below are selected from a list of 228 Experts worldwide ranked by ideXlab platform
Saim Suratman - One of the best experts on this subject based on the ideXlab platform.
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Modelling contaminant transport for Pumping wells in riverbank filtration systems
Journal of environmental management, 2015Co-Authors: Shaymaa Mustafa, Arifah Bahar, Zainal Abdul Aziz, Saim SuratmanAbstract:Analytical study of the influence of both the Pumping well discharge rate and Pumping Time on contaminant transport and attenuation is significant for hydrological and environmental science applications. This article provides an analytical solution for investigating the influence of both Pumping Time and travelling Time together for one-dimensional contaminant transport in riverbank filtration systems by using the Green's function approach. The basic aim of the model is to understand how the Pumping Time and Pumping rate, which control the travelling Time, can affect the contaminant concentration in riverbank filtration systems. Results of analytical solutions are compared with the results obtained using a MODFLOW numerical model. Graphically, it is found that both analytical and numerical solutions have almost the same behaviour. Additionally, the graphs indicate that any increase in the Pumping rate or simulation Pumping Time should increase the contamination in groundwater. The results from the proposed analytical model are well matched with the data collected from a riverbank filtration site in France. After this validation, the model is then applied to the first pilot project of a riverbank filtration system conducted in Malaysia. Sensitivity analysis results highlight the importance of degradation rates of contaminants on groundwater quality, for which higher utilization rates lead to the faster consumption of pollutants.
Shaymaa Mustafa - One of the best experts on this subject based on the ideXlab platform.
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Analytical Modeling of Well Design in Riverbank Filtration Systems.
Ground Water, 2019Co-Authors: Shaymaa Mustafa, Mohamad Darwish, Arifah Bahar, Zainal Abdul AzizAbstract:: Analytical studies for well design adjacent to river banks are the most significant practical task in cases involving the efficiency of riverbank filtration systems. In Times when high pollution of river water is joined with increasing water demand, it is necessary to design Pumping wells near the river that provide acceptable amounts of river water with minimum contaminant concentrations. This will guarantee the quality and safety of drinking water supplies. This article develops an analytical solution based on the Green's function approach to solve an inverse problem: based on the required level of contaminant concentration and planned Pumping Time period, the shortest distance to the riverbank that has the maximum percentage of river water is determined. This model is developed in a confined and homogenous aquifer that is partially penetrated by the stream due to the existence of clogging layers. Initially, the analytical results obtained at different Pumping Times, rates and with different values of initial concentration are checked numerically using the MODFLOW software. Generally, the distance results obtained from the proposed model are acceptable. Then, the model is validated by data related to two Pumping wells located at the first riverbank filtration pilot project conducted in Malaysia.
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Modelling contaminant transport for Pumping wells in riverbank filtration systems
Journal of environmental management, 2015Co-Authors: Shaymaa Mustafa, Arifah Bahar, Zainal Abdul Aziz, Saim SuratmanAbstract:Analytical study of the influence of both the Pumping well discharge rate and Pumping Time on contaminant transport and attenuation is significant for hydrological and environmental science applications. This article provides an analytical solution for investigating the influence of both Pumping Time and travelling Time together for one-dimensional contaminant transport in riverbank filtration systems by using the Green's function approach. The basic aim of the model is to understand how the Pumping Time and Pumping rate, which control the travelling Time, can affect the contaminant concentration in riverbank filtration systems. Results of analytical solutions are compared with the results obtained using a MODFLOW numerical model. Graphically, it is found that both analytical and numerical solutions have almost the same behaviour. Additionally, the graphs indicate that any increase in the Pumping rate or simulation Pumping Time should increase the contamination in groundwater. The results from the proposed analytical model are well matched with the data collected from a riverbank filtration site in France. After this validation, the model is then applied to the first pilot project of a riverbank filtration system conducted in Malaysia. Sensitivity analysis results highlight the importance of degradation rates of contaminants on groundwater quality, for which higher utilization rates lead to the faster consumption of pollutants.
Zainal Abdul Aziz - One of the best experts on this subject based on the ideXlab platform.
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Analytical Modeling of Well Design in Riverbank Filtration Systems.
Ground Water, 2019Co-Authors: Shaymaa Mustafa, Mohamad Darwish, Arifah Bahar, Zainal Abdul AzizAbstract:: Analytical studies for well design adjacent to river banks are the most significant practical task in cases involving the efficiency of riverbank filtration systems. In Times when high pollution of river water is joined with increasing water demand, it is necessary to design Pumping wells near the river that provide acceptable amounts of river water with minimum contaminant concentrations. This will guarantee the quality and safety of drinking water supplies. This article develops an analytical solution based on the Green's function approach to solve an inverse problem: based on the required level of contaminant concentration and planned Pumping Time period, the shortest distance to the riverbank that has the maximum percentage of river water is determined. This model is developed in a confined and homogenous aquifer that is partially penetrated by the stream due to the existence of clogging layers. Initially, the analytical results obtained at different Pumping Times, rates and with different values of initial concentration are checked numerically using the MODFLOW software. Generally, the distance results obtained from the proposed model are acceptable. Then, the model is validated by data related to two Pumping wells located at the first riverbank filtration pilot project conducted in Malaysia.
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Modelling contaminant transport for Pumping wells in riverbank filtration systems
Journal of environmental management, 2015Co-Authors: Shaymaa Mustafa, Arifah Bahar, Zainal Abdul Aziz, Saim SuratmanAbstract:Analytical study of the influence of both the Pumping well discharge rate and Pumping Time on contaminant transport and attenuation is significant for hydrological and environmental science applications. This article provides an analytical solution for investigating the influence of both Pumping Time and travelling Time together for one-dimensional contaminant transport in riverbank filtration systems by using the Green's function approach. The basic aim of the model is to understand how the Pumping Time and Pumping rate, which control the travelling Time, can affect the contaminant concentration in riverbank filtration systems. Results of analytical solutions are compared with the results obtained using a MODFLOW numerical model. Graphically, it is found that both analytical and numerical solutions have almost the same behaviour. Additionally, the graphs indicate that any increase in the Pumping rate or simulation Pumping Time should increase the contamination in groundwater. The results from the proposed analytical model are well matched with the data collected from a riverbank filtration site in France. After this validation, the model is then applied to the first pilot project of a riverbank filtration system conducted in Malaysia. Sensitivity analysis results highlight the importance of degradation rates of contaminants on groundwater quality, for which higher utilization rates lead to the faster consumption of pollutants.
Arifah Bahar - One of the best experts on this subject based on the ideXlab platform.
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Analytical Modeling of Well Design in Riverbank Filtration Systems.
Ground Water, 2019Co-Authors: Shaymaa Mustafa, Mohamad Darwish, Arifah Bahar, Zainal Abdul AzizAbstract:: Analytical studies for well design adjacent to river banks are the most significant practical task in cases involving the efficiency of riverbank filtration systems. In Times when high pollution of river water is joined with increasing water demand, it is necessary to design Pumping wells near the river that provide acceptable amounts of river water with minimum contaminant concentrations. This will guarantee the quality and safety of drinking water supplies. This article develops an analytical solution based on the Green's function approach to solve an inverse problem: based on the required level of contaminant concentration and planned Pumping Time period, the shortest distance to the riverbank that has the maximum percentage of river water is determined. This model is developed in a confined and homogenous aquifer that is partially penetrated by the stream due to the existence of clogging layers. Initially, the analytical results obtained at different Pumping Times, rates and with different values of initial concentration are checked numerically using the MODFLOW software. Generally, the distance results obtained from the proposed model are acceptable. Then, the model is validated by data related to two Pumping wells located at the first riverbank filtration pilot project conducted in Malaysia.
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Modelling contaminant transport for Pumping wells in riverbank filtration systems
Journal of environmental management, 2015Co-Authors: Shaymaa Mustafa, Arifah Bahar, Zainal Abdul Aziz, Saim SuratmanAbstract:Analytical study of the influence of both the Pumping well discharge rate and Pumping Time on contaminant transport and attenuation is significant for hydrological and environmental science applications. This article provides an analytical solution for investigating the influence of both Pumping Time and travelling Time together for one-dimensional contaminant transport in riverbank filtration systems by using the Green's function approach. The basic aim of the model is to understand how the Pumping Time and Pumping rate, which control the travelling Time, can affect the contaminant concentration in riverbank filtration systems. Results of analytical solutions are compared with the results obtained using a MODFLOW numerical model. Graphically, it is found that both analytical and numerical solutions have almost the same behaviour. Additionally, the graphs indicate that any increase in the Pumping rate or simulation Pumping Time should increase the contamination in groundwater. The results from the proposed analytical model are well matched with the data collected from a riverbank filtration site in France. After this validation, the model is then applied to the first pilot project of a riverbank filtration system conducted in Malaysia. Sensitivity analysis results highlight the importance of degradation rates of contaminants on groundwater quality, for which higher utilization rates lead to the faster consumption of pollutants.
S. N. Tsyranov - One of the best experts on this subject based on the ideXlab platform.
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Effect of space charge on subnanosecond current cutoff in powerful semiconductor diodes
Technical Physics, 2009Co-Authors: S. N. Rukin, S. N. TsyranovAbstract:High-density current cutoff in an SOS diode is studied with a physicomathematical model including the space-charge effect. If the depth of the p-n junction exceeds 180 µm, the forward Pumping Time is less than 60 ns, and the backward Pumping Time is shorter than 20 ns, the subnanosecond cutoff of current with a density of several kiloamperes per square cenTimeter takes place. The cutoff mechanism is associated with the origination of three high-field zones at the stage of current cutoff: two zones on the p-side, which expand with a velocity close to the saturation value, and one on the n-side, which expands slowly. Taking the space charge into account reduces the role of avalanche multiplication and, as a consequence, improves the switching properties of the diode. It is found that a set of conditions for the electric circuit parameters that specify the Pumping current duration and density and for the dopant profile in the semiconductor must be met for subnanosecond current cutoff to occur. The results are compared with experimental data and a model using a quasi-neutral approximation.
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Operation of a Semiconductor Opening Switch at the Pumping Time of a Microsecond and Low Current Density
Semiconductors, 2009Co-Authors: P. V. Vasiliev, S. K. Lyubutin, A. V. Ponomarev, S. N. Rukin, B.g. Slovikovsky, S. N. Tsyranov, S. O. CholakhAbstract:The mechanism of operation of a semiconductor opening switch (a SOS diode) at the forward-Pumping Time of a microsecond and low current density was studied. The current’s cutoff Time shorter than 10 ns at the voltage across the SOS diode as high as 80 kV was obtained experimentally at the reverse-Pumping Time ∼200 ns and the cutoff-current density of about 120 A/cm2. These are the results of numerical simulation of processes in the dynamics of the electron-hole plasma in the diode at the stages of Pumping and current cutoff. It is shown that the stage of the current cutoff is similar to the conditions of the SOS effect observed at a high current density and is also related to motion of the concentration front of excess plasma along the heavily doped p-type region of the structure. In spite of the low density of current in the course of its cutoff, the switching process takes several nanoseconds. The reason is that the low current density is compensated by a low concentration of the excess plasma at the front, which retains the high velocity of motion of this front at the stage of the current cutoff.
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Subnanosecond breakage of current in high-power semiconductor switches
Technical Physics Letters, 2000Co-Authors: S. N. Rukin, S. N. TsyranovAbstract:The process of high-density current breakage in an SOS diode structure was studied using a corresponding theoretical model. For a p-n junction depth of ∼200 μm, a forward Pumping Time shorter than 60 ns, and a reverse Pumping Time of ∼10–15 ns, the structure studied exhibits a subnanosecond breakage of a current with a density of up to 103–104 A/cm2. The mechanism of current breakage involves the formation of two spatially separated domains featuring strong electric field build-up on the p side of the diode structure, which expand during the current breakage at a velocity close to the carrier velocity saturation level.
