The Experts below are selected from a list of 18123 Experts worldwide ranked by ideXlab platform
Mahmoud M. El-halwagi - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and Scheduling of Optimal Batch Water-recycle Networks
Chinese Journal of Chemical Engineering, 2008Co-Authors: Arwa H. Rabie, Mahmoud M. El-halwagiAbstract:Abstract This work develops an optimization-based methodology for the design and scheduling of batch water recycle networks. This task requires the identification of network configuration, fresh-water usage, recycle assignments from Sources to sinks, wastewater discharge, and a scheduling scheme. A new Source-Tank-sink representation is developed to allow for storage and dispatch Tanks. The problem is solved in stages by first eliminating scheduling constraints and determining minimum usage of fresh water and wastewater discharge. An iterative procedure is formulated to minimize the total annual cost of the system by trading off capital versus operating costs. The work overcomes limitations in previous literature work including restricted recycle within the same cycle, lumped balances that may not lead to feasible solutions, and unrealistic objective functions. A case study is solved to illustrate the usefulness of the devised procedure.
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Simultaneous synthesis of property-based water reuse/recycle and interception networks for batch processes
AIChE Journal, 2008Co-Authors: Dominic C.y. Foo, Arwa H. Rabie, Mahmoud M. El-halwagiAbstract:A systematic technique is introduced for the synthesis of cost-effective batch water networks with the placement of interception devices. Utilizing the new concept of property integration, a property-based approach is adopted. The water streams (Sources) are characterized by a number of key properties, and water-using units (sinks) are bound with property constraints. The problem also considers a number of interception devices that can be used to modify the properties of the streams to optimize the reuse/recycle of process streams and minimize fresh reSources. A Source-Tank-interception-Tank-sink representation is developed. Storage Tanks are used throughout the network to enable mixing, storage, and dispatch of the reused/recycled water streams. The procedure is supported by an optimization formulation whose solution identifies optimal allocation of Sources to Tanks, interception devices, and sinks. The solution also determines an optimal policy for operating the water network. A case study is solved to illustrate the important aspects of the devised procedure. © 2008 American Institute of Chemical Engineers AIChE J, 2008
Dominic C.y. Foo - One of the best experts on this subject based on the ideXlab platform.
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Simultaneous synthesis of property-based water reuse/recycle and interception networks for batch processes
AIChE Journal, 2008Co-Authors: Dominic C.y. Foo, Arwa H. Rabie, Mahmoud M. El-halwagiAbstract:A systematic technique is introduced for the synthesis of cost-effective batch water networks with the placement of interception devices. Utilizing the new concept of property integration, a property-based approach is adopted. The water streams (Sources) are characterized by a number of key properties, and water-using units (sinks) are bound with property constraints. The problem also considers a number of interception devices that can be used to modify the properties of the streams to optimize the reuse/recycle of process streams and minimize fresh reSources. A Source-Tank-interception-Tank-sink representation is developed. Storage Tanks are used throughout the network to enable mixing, storage, and dispatch of the reused/recycled water streams. The procedure is supported by an optimization formulation whose solution identifies optimal allocation of Sources to Tanks, interception devices, and sinks. The solution also determines an optimal policy for operating the water network. A case study is solved to illustrate the important aspects of the devised procedure. © 2008 American Institute of Chemical Engineers AIChE J, 2008
Arwa H. Rabie - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and Scheduling of Optimal Batch Water-recycle Networks
Chinese Journal of Chemical Engineering, 2008Co-Authors: Arwa H. Rabie, Mahmoud M. El-halwagiAbstract:Abstract This work develops an optimization-based methodology for the design and scheduling of batch water recycle networks. This task requires the identification of network configuration, fresh-water usage, recycle assignments from Sources to sinks, wastewater discharge, and a scheduling scheme. A new Source-Tank-sink representation is developed to allow for storage and dispatch Tanks. The problem is solved in stages by first eliminating scheduling constraints and determining minimum usage of fresh water and wastewater discharge. An iterative procedure is formulated to minimize the total annual cost of the system by trading off capital versus operating costs. The work overcomes limitations in previous literature work including restricted recycle within the same cycle, lumped balances that may not lead to feasible solutions, and unrealistic objective functions. A case study is solved to illustrate the usefulness of the devised procedure.
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Simultaneous synthesis of property-based water reuse/recycle and interception networks for batch processes
AIChE Journal, 2008Co-Authors: Dominic C.y. Foo, Arwa H. Rabie, Mahmoud M. El-halwagiAbstract:A systematic technique is introduced for the synthesis of cost-effective batch water networks with the placement of interception devices. Utilizing the new concept of property integration, a property-based approach is adopted. The water streams (Sources) are characterized by a number of key properties, and water-using units (sinks) are bound with property constraints. The problem also considers a number of interception devices that can be used to modify the properties of the streams to optimize the reuse/recycle of process streams and minimize fresh reSources. A Source-Tank-interception-Tank-sink representation is developed. Storage Tanks are used throughout the network to enable mixing, storage, and dispatch of the reused/recycled water streams. The procedure is supported by an optimization formulation whose solution identifies optimal allocation of Sources to Tanks, interception devices, and sinks. The solution also determines an optimal policy for operating the water network. A case study is solved to illustrate the important aspects of the devised procedure. © 2008 American Institute of Chemical Engineers AIChE J, 2008
Inayatullah Shah Sayed - One of the best experts on this subject based on the ideXlab platform.
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Effects of Copper 0.127 mm Thick Flat Sheet on Uniform and Hot Region Images as A Material Filter for Scatter Correction in Tc-99m SPECT
2016Co-Authors: Inayatullah Shah Sayed, Siti Zawani HarunAbstract:In the SPECT image data, presence of scatter component leads to poor image quality. Consequently, inaccuracy in the diagnosis of disease occurs. This study aims to improve the image quality by reducing some fraction of scattered gamma photons prior to detection using a material filter technique. Data were acquired by scanning a cylindrical Source Tank with hot/cold regions insert filled with water and uniformly distributed Tc-99m radionuclide. Philip ADAC Forte dual head gamma camera with LEHR collimator was used. Material filter, a flat sheet of Cu 0.127mm thick was attached on the outer surface of the collimator. SPECT data were acquired without and with material filter. Filtered back projection technique was applied. Images were visually examined in order to observe the improvement in image quality of uniform and hot regions as well as the detectability of hot regions. Standard deviation in the count density of uniform region and contrast of hot region images was calculated. Findings of the study reflect an overall enhancement in the image uniformity, hot regions detectability and contrast with material filter. It is concluded that, material filter technique need further investigations for applicability in clinical studies by scanning other phantoms mimicking human organs.
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Use of a tin (Sn) flat sheet as a material filter for reduction of scattered gamma photons and enhancement of cold regions image quality in Tc-99m SPECT
2016Co-Authors: Inayatullah Shah SayedAbstract:The presence of scattered gamma photons in SPECT data degrade the quality of reconstructed images. In this work, a material filter was employed in order to improve cold regions detectability and overall image quality by pre-filtering of some fraction of scattered gamma photons. Material filter was constructed from a 300x300mm flat sheet of tin (Sn) 0.25mm thick. It was installed on the outer surface of LEGP collimator of a gamma camera. Tc-99m spectra were plotted from the count rates recorded without and with material filter by scanning a cylindrical Source Tank in contiguous 10 keV energy windows (55-65, 65-75,……155-165 keV). SPECT image data of R. A. Carlson’s phantom with cold regions insert (placed into the cylindrical Tank) were gathered without and with material filter by setting 20% energy window centered at 140 keV. Images were reconstructed by applying filtered back projection method. Tc-99m spectra show the reduction in count rate with material filter from the lower part of the photopeak region
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Effect of Cut-Off Frequency of Butterworth Filter on Detectability and Contrast of Hot and Cold Regions in Tc-99m SPECT
International Journal of Medical Physics Clinical Engineering and Radiation Oncology, 2016Co-Authors: Inayatullah Shah Sayed, Nor Syahirah Mohamed NasrudinAbstract:In SPECT, noise is one of the major limitations that degrade image quality. To suppress the noisy signals in an image, digital filters are most commonly applied. However, in SPECT image reconstruction, selection of an appropriate filter and its functions has always remained a difficult task. In this work an attempt was made to investigate the effects of varying cut-off frequencies and in keeping the order of Butterworth filter constant on detectability and contrast of hot and cold re-gions images. A new insert simulating hot and cold regions which provides similar views in a reconstructed image was placed in the phantom’s cylindrical Source Tank and imaged. Tc-99m radionuclide was distributed uniformly in the phantom. SPECT data were collected in a 20% energy window centered at 140 keV by a Philips ADAC Forte dual head gamma camera mounted with a LEHR collimator. Images were generated by using the filtered backprojection technique. A Butterworth filter of order 5 with cut-off frequencies 0.35 and 0.45 cycles·cm-1 was applied. Images were examined in terms of hot and cold regions, detectability and contrast. Results show that the hot and cold regions’ detectability and contrast vary with the change of cut-off frequency. With a 0.45 cycles·cm-1 cut-off frequency, a significant enhancement in contrast of cold regions was achieved as compared to a 0.35 cycles·cm-1 cut-off frequency. Furthermore, the detectability of hot and cold regions improved with the use of a 0.45 cycles·cm-1 cut-off frequency. In conclusion, image quality of hot and cold regions affected in a different way with a change of cut-off frequency. Thus, care should be taken in selecting the filter cut-off frequency prior to reconstruction of images; particularly, when both types of regions are expected in the reconstructed image.
Vasilios I. Manousiouthakis - One of the best experts on this subject based on the ideXlab platform.
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Gas Tank fill-up in globally minimum time: Theory and application to hydrogen
International Journal of Hydrogen Energy, 2014Co-Authors: Fernando Olmos, Vasilios I. ManousiouthakisAbstract:Abstract The process of filling-up high-pressure gas storage vessels consists of a gas Source Tank, an isenthalpic (Joule–Thomson or J–T) valve, a cooling system, and a gas storage vessel. These units are assumed to be thermally insulated. The fill-up process is formulated as a minimum time optimal control problem. Despite the nonlinear nature of the aforementioned optimal control problem, its global solution is obtained analytically. A novel transformation technique is employed, to decompose the problem into a process simulation problem independent of time, and a simpler minimum time control problem that only depends on the final molar density value and the maximum allowable feed mass flowrate. The feasibility of the fill-up is uniquely determined by the process simulation problem, and upon fill-up feasibility, the minimum time control problem is then globally solved. Two fill-up case studies, involving two different system configurations are analyzed. In Case 1, the fill-up process has a constant molar enthalpy feed, and no cooling system. Case 2 considers a fill-up process with a constant temperature feed, delivered by an efficient cooling system. It was demonstrated that the optimal control strategy to achieve minimum fill-up time is to have the mass flowrate at its maximum allowable value during the entire duration of the fill-up. The presented problem formulation is general and can be applied to the fill-up of other gases, such as compressed natural gas.